Podcasts about camkii

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.08.01.549180v1?rss=1 Authors: Jain, A., Nakahata, Y., Watabe, T., Rusina, P., South, K. E., Adachi, K., Yan, L., Simorowski, N., Furukawa, H., Yasuda, R. Abstract: Behavioral time scale plasticity (BTSP), is a form of non-Hebbian plasticity induced by integrating pre- and postsynaptic components separated by behavioral time scale (seconds). BTSP in the hippocampal CA1 neurons underlies place cell formation. However, the molecular mechanisms underlying this behavioral time scale (eligibility trace) and synapse specificity are unknown. CaMKII can be activated in a synapse-specific manner and remain active for a few seconds, making it a compelling candidate for the eligibility trace during BTSP. Here, we show that BTSP can be induced in a single dendritic spine using 2-photon glutamate uncaging paired with postsynaptic current injection temporally separated by behavioral time scale. Using an improved CaMKII sensor, we saw no detectable CaMKII activation during this BTSP induction. Instead, we observed a dendritic, delayed, and stochastic CaMKII activation (DDSC) associated with Ca2+ influx and plateau 20-40 s after BTSP induction. DDSC requires both pre-and postsynaptic activity, suggesting that CaMKII can integrate these two signals. Also, optogenetically blocking CaMKII 30 s after the BTSP protocol inhibited synaptic potentiation, indicating that DDSC is an essential mechanism of BTSP. IP3-dependent intracellular Ca2+ release facilitates both DDSC and BTSP. Thus, our study suggests that the non-synapse specific CaMKII activation provides an instructive signal with an extensive time window over tens of seconds during BTSP. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.22.550175v1?rss=1 Authors: Trewin, A. J., Weeks, K. L., Wadley, G. D., Lamon, S. Abstract: Cardiomyocyte calcium homeostasis is a tightly regulated process. The mitochondrial calcium uniporter (MCU) complex can buffer elevated cytosolic Ca2+ levels and consists of pore-forming proteins including MCU, and various regulatory proteins such as mitochondrial calcium uptake proteins 1 and 2 (MICU1/2). The stoichiometry of these proteins influences the sensitivity to Ca2+ and activity of the complex. However, the factors that regulate their gene expression remain incompletely understood. Long non-coding RNAs (lncRNAs) regulate gene expression through various mechanisms, and we recently found that the lncRNA Tug1 increased the expression of Mcu and associated genes. To further explore this, we performed antisense LNA knockdown of Tug1 (Tug1 KD) in H9c2 rat cardiomyocytes. Tug1 KD increased MCU protein expression, yet pyruvate dehydrogenase dephosphorylation, which is indicative of mitochondrial Ca2+ uptake was not enhanced. However, RNA-seq revealed that Tug1 KD increased Mcu along with differential expression of greater than 1000 genes including many related to Ca2+ regulation pathways in the heart. To understand the effect of this on Ca2+ signalling, we measured phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and its downstream target cAMP Response Element-Binding protein (CREB), a transcription factor known to drive Mcu gene expression. In response a Ca2+ stimulus, the increase in CaMKII and CREB phosphorylation was attenuated by Tug1 KD. Inhibition of CaMKII, but not CREB, partially prevented the Tug1 KD-mediated increase in Mcu. Together, these data suggest that Tug1 modulates MCU expression via a mechanism involving CaMKII and regulates cardiomyocyte Ca2+ signalling which could have important implications for cardiac function. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Kanazawa University NanoLSI Podcast: Experiments provide insights into the molecular mechanism for memory and learning Transcript of this podcastHello and welcome to the NanoLSI podcast. Thank you for joining us today. In this episode we feature the latest research by Mikihiro Shibata at the Kanazawa University NanoLSI alongside Hideji Murakoshi at The Graduate University for Advanced Studies and the National Institute for Physiological Sciences, and their colleagues.The research described in this podcast was published in Science Advances in June 2023Kanazawa University NanoLSI websitehttps://nanolsi.kanazawa-u.ac.jp/en/Experiments provide insights into the molecular mechanism for memory and learning Researchers at Kanazawa University report in Science Advances  high-speed atomic force microscopy experiments that show the structural and chemical changes in an enzyme thought to play a vital role in modulating the strength of neural connections.Synapses connect neurons allowing the transmission of signals around the neural network. The strength of these connections varies – for instance strengthening or weakening depending on the signals received and how. This synaptic “plasticity” underlies learning and memory and the Ca2+/calmodulin-dependent protein kinase II (CaMKII) is known to play a key role. Previous studies have provided some clues to the mechanisms of CaMKII protein activity in these functions but no-one had seen these proteins in action. Now Hideji Murakoshi at the Graduate University of Advanced Studies and the National Institute for Physiological Sciences and Mikihiro Shibata at Kanazawa University and their colleagues have used high speed atomic force microscopy (HS-AFM) to observe the structural dynamics of these proteins for the first time, not only in various states but in three different species.CaMKII is common to a vast range of species from mammals like rats to older, non-mammalian species like the roundworms (C. elegans) and hydra. In particular, certain structural features of the protein are particularly well preserved, including the kinase domain, the regulatory segment that inhibits the activity of the kinase domain and the hub domain. In addition, the protein has binding sites, phosphorylation sites and linker regions – however, the linker region shows a little more variability across species suggesting that its function and activation mechanisms are more bespoke for the different species.So what did we know about how this protein works? (3min)Previous studies had suggested that the regulatory segment's inhibition of the kinase domain is released when Ca2+/calmodulin binds to the regulatory segment. The activated kinase domains then phosphorylate each other, activity that persists even after the Ca2+/calmodulin becomes dissociated, which has been “hypothesized to be a form of molecular memory”, as the researchers describe in their report.Murakoshi, Shibata and their colleagues studied the protein using atomic force microscopy, which feels topologies using a nanoscale tip like a needle reading a vinyl record, raster scanning the image plane to build up a picture of the sample structure. With HS-AFM, these images are collected quickly enough to record movies of how these structures change. The researchers noted various measures of the proteins size and motion – the gyrus of rotation – as well as reactions such as kinase domain oligomerization (that is, where there is a limited level of polymerization to join molecules into chains) and phosphorylation – the addition of a phosphoryl group (PO3), which can activate enzymes like kinase.They found that the kinase domain was quite mobile, although this decreased with Ca2+/calmodulin binding. ThNanoLSI Podcast website

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.09.548255v1?rss=1 Authors: Li, G., McLaughlin, D. W., Peskin, C. S. Abstract: Synaptic plasticity (long term potentiation/depression (LTP/D)), is a cellular mechanism underlying learning. Two distinct types of early LTP/D (E-LTP/D), acting on very different time scales, have been observed experimentally -- spike timing dependent plasticity (STDP), on time scales of tens of ms; and behavioral time scale plasticity(BTSP), on time scales of seconds. BTSP is a candidate for the mechanism for rapid learning of spatial location by hippocampal place cells. Here a computational model of the induction of E-LTP/D at a spine head of a synapse of a hippocampal pyramidal neuron is developed. The single compartment model represents two interacting biochemical pathways for the activation (phosphorylation) of the kinase (CaMKII) with a phosphatase, with Ion inflow described by NMDAR, CaV1, and Na channels. The biochemical reactions are represented by a deterministic system of differential equations. This single model captures realistic responses (temporal profiles with the differing timescales) of STDP and BTSP and their asymmetries for each (STDP or BTSP) signaling protocol. The simulations detail several mechanisms underlying both STDP and BTSP, including i) the flow of Ca^2+ through NMDAR vs CaV1 channels, and ii) the origin of several time scales in the activation of CaMKII. The model also realizes a priming mechanism for E-LTP that is induced by Ca^2+ flow through CaV1.3 channels. Once in the spine head, this small additional Ca^2+ opens the compact state of CaMKII, placing CaMKII "in the ready" for subsequent induction of LTP. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.04.29.537929v1?rss=1 Authors: Kon, K., Ode, K. L., Mano, T., Fujishima, H., Tone, D., Shimizu, C., Shiono, S., Yada, S., Garcon, J. Y., Kaneko, M., Shinohara, Y., Takahashi, R. R., Yamada, R. G., Shi, S., Sumiyama, K., Kiyonari, H., Susaki, E. A., Ueda, H. R. Abstract: Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.04.18.537377v1?rss=1 Authors: Xiao, K., Li, Y., Chitwood, R. A., Magee, J. C. Abstract: Behavioral timescale synaptic plasticity (BTSP) is a type of non-Hebbian synaptic plasticity reported to underlie place field formation in the hippocampal CA1 neurons. Despite this important function, the molecular mechanisms underlying BTSP are poorly understood. The Calcium-calmodulin-dependent protein kinase II (CaMKII) is activated by synaptic transmission-mediated calcium influx and its subsequent phosphorylation is central to synaptic plasticity. Because the activity of CaMKII is known to outlast the event triggering phosphorylation, we hypothesized it could be involved in the extended timescale of the BTSP process. To examine the role of CaMKII in BTSP, we performed whole-cell in-vivo and in-vitro recordings in CA1 pyramidal neurons from mice engineered to have a point mutation at the autophosphorylation site (T286A) causing accelerated signaling kinetics. Here we demonstrate a profound deficit in synaptic plasticity, strongly suggesting that CaMKII signaling is required for BTSP. This study elucidates part of the molecular mechanism of BTSP and provides insight into the function of CaMKII in place cell formation and ultimately learning and memory. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.20.529299v1?rss=1 Authors: Rivero-Rios, P., Tsukahara, T., Uygun, T., Chen, A., Chavis, G. D., Giridharan, S. S. P., Iwase, S., Sutton, M. A., Weisman, L. S. Abstract: Trafficking of cell-surface proteins from endosomes to the plasma membrane is a key mechanism to regulate synaptic function. In non-neuronal cells, proteins recycle to the plasma membrane either via the SNX27-Retromer-WASH pathway, or via the recently discovered SNX17-Retriever-CCC-WASH pathway. While SNX27 is responsible for the recycling of key neuronal receptors, the roles of SNX17 in neurons are less understood. Here, using cultured hippocampal neurons, we demonstrate that the SNX17 pathway regulates synaptic function and plasticity. Disruption of this pathway results in a loss of excitatory synapses and prevents structural plasticity during chemical long-term potentiation (cLTP). cLTP drives SNX17 recruitment to synapses, where its roles are in part mediated by regulating surface expression of {beta}1-integrin. SNX17 recruitment relies on NMDAR activation, CamKII signaling, and requires binding to the Retriever and PI(3)P. Together, these findings provide molecular insights into the regulation of SNX17 at synapses, and define key roles for SNX17 in synaptic maintenance and in regulating enduring forms of synaptic plasticity. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.13.528397v1?rss=1 Authors: Ko, T., Jou, C., Grau-Perales, A., Reynders, M., Fenton, A., Trauner, D. Abstract: Hundreds of proteins determine the function of synapses, and synapses define the neuronal circuits that subserve myriad brain, cognitive, and behavioral functions. It is thus necessary to precisely manipulate specific proteins at specific sub-cellular locations and times to elucidate the roles of particular proteins and synapses in brain function. We developed PHOtochemically TArgeting Chimeras (PHOTACs) as a strategy to optically degrade specific proteins with high spatial and temporal precision. PHOTACs are small molecules that, upon wavelength-selective illumination, catalyze ubiquitylation and degradation of target proteins through endogenous proteasomes. Here we describe the design and chemical properties of a PHOTAC that targets Ca2+/calmodulin-dependent protein kinase II alpha (CaMKII), which is abundant and crucial for baseline synaptic function of excitatory neurons. We validate the PHOTAC strategy, showing that the CaMKII-PHOTAC is effective in mouse brain tissue. Light activation of CaMKII-PHOTAC removed CaMKII from regions of the mouse hippocampus only within 25 m of the illuminated brain surface. The optically-controlled degradation decreases synaptic function within minutes of light activation, measured by the light-initiated attenuation of evoked field excitatory postsynaptic potential (fEPSP) responses to physiological stimulation. The PHOTACs methodology should be broadly applicable to other key proteins implicated in synaptic function, especially for evaluating their precise roles in the maintenance of long-term potentiation and memory within subcellular dendritic domains. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.10.528087v1?rss=1 Authors: Zhou, Z., Kakegawa, W., Fujimori, K., Sho, M., Shimamura, R., Supakul, S., Yoshimatsu, S., Kohyama, J., Yuzaki, M., Okano, H. Abstract: Cortical excitatory neurons (Cx neurons) are the most dominant neuronal cell type in the cerebral cortex and play a central role in cognition, perception, intellectual behavior, and emotional processing. Robust in vitro induction of Cx neurons may facilitate as a tool for the elucidation of brain development and the pathomechanism of the intractable neurodevelopmental and neurodegenerative disorders, including Alzheimers disease, and thus potentially contribute to drug development. Here, we report a defined method for the efficient induction of Cx neurons from the feeder-free-conditioned human embryonic stem cells (ES cells) and induced pluripotent stem cells (iPS cells). Using this method, human ES/iPS cells could be differentiated into ~99% MAP2-positive neurons by three weeks, and these induced neurons displayed several characteristics of mature excitatory neurons within 5 weeks, such as strong expression of glutamatergic neuron-specific markers (subunits of AMPA and NDMA receptors and CAMKII), highly synchronized spontaneous firing and excitatory postsynaptic current (EPSC). In addition, the Cx neurons showed susceptibility to A{beta} oligomer toxicity and excessive glutamate excitotoxicity, which is another advantage for toxicity testing and searching for therapeutic agent discovery. Taken together, this study provides a novel research platform for studying neural development and degeneration based on the feeder-free human ES/iPS cell system. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.26.524131v1?rss=1 Authors: Song, I., Kuznetsova, T., Baidoe-Ansah, D., Mirzapourdelavar, H., Senkov, O., Hayani, H., Mironov, A., Kaushik, R., Druzin, M., Johansson, S., Dityatev, A. Abstract: Our previous studies demonstrated that enzymatic removal of highly sulfated heparan sulfates with heparinase 1 impaired axonal excitability and reduced expression of ankyrin G at the axon initial segments in the CA1 region of the hippocampus ex vivo, impaired context discrimination in vivo, and elevated Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity in vitro. Here, we show that in vivo delivery of heparinase 1 in the CA1 region of the hippocampus elevated autophosphorylation of CaMKII 24 hours after injection in mice. Patch-clamp recording in CA1 neurons revealed no significant heparinase effects on the amplitude or frequency of miniature excitatory and inhibitory postsynaptic currents, while the threshold for action potential generation was increased and fewer spikes were generated in response to current injection. Delivery of heparinase on the next day after contextual fear conditioning induced context overgeneralization 24 hours after injection. Co-administration of heparinase with the CaMKII inhibitor (autocamtide-2-related inhibitory peptide) rescued neuronal excitability and expression of ankyrin G at the axon initial segment. It also restored context discrimination, suggesting a key role of CaMKII in neuronal signaling downstream of heparan sulfate proteoglycans and highlighting a link between impaired CA1 pyramidal cell excitability and context generalization during recall of contextual memories. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.23.523316v1?rss=1 Authors: Rumian, N. L., Brown, C. N., Hendry-Hofer, T. B., Rossetti, T., Orfila, J. E., Tullis, J. E., Dwoskin, L. P., Asfaha, O., Lisman, J. E., Quillinan, N., Herson, P. S., Bebarta, V. S., Bayer, K. U. Abstract: The Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a central regulator of learning and memory, which poses a problem for targeting it therapeutically. Indeed, our study supports prior conclusions that long-term interference with CaMKII signaling can erase pre-formed memories. By contrast, short-term pharmacological CaMKII inhibition with tatCN19o interfered with learning in mice only mildly and transiently (for less than 1 h) and did not at all reverse pre-formed memories. This was at greater than or equal to 500fold of the dose that protected hippocampal neurons from cell death after a highly clinically relevant pig model of transient global cerebral ischemia: ventricular fibrillation followed by advanced life support and electrical defibrillation to induce return of spontaneous circulation. Of additional importance for therapeutic development, cardiovascular safety studies in mice and pig did not indicate any concerns with acute tatCN19o injection. Taken together, even though prolonged interference with CaMKII signaling can erase memory, acute short-term CaMKII inhibition with tatCN19o did not cause such retrograde amnesia that would pose a contraindication for therapy. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.10.523378v1?rss=1 Authors: Tsujioka, S., Sumino, A., Nagasawa, Y., Sumikama, T., Flechsig, H., Puppulin, L., Tomita, T., Baba, Y., Kakuta, T., Ogoshi, T., Umeda, K., Kodera, N., Murakoshi, H., Shibata, M. Abstract: Ca2+/calmodulin-dependent protein kinase II (CaMKII) has long been central in synaptic plasticity research. CaMKII is a dodecameric serine/threonine kinase that has been essentially conserved across metazoans for over a million years. While the mechanisms of CaMKII activation are well studied, its "behavior" at the molecular level has remained unobserved. Here, high-speed atomic force microscopy was used to visualize the activity-dependent structural dynamics of rat/hydra/C. elegans CaMKII in various states at nanometer resolution. Among the species, rat CaMKII underwent internal kinase domain aggregation in an activity-dependent manner and showed a higher tolerance to dephosphorylation by phosphatase. Our findings suggest that mammalian CaMKII has evolutionarily acquired a new structural form and a tolerance to phosphatase to maintain robust CaMKII activity for proper neuronal function. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.12.30.522289v1?rss=1 Authors: Zhao, Z., Liu, Z., Chen, L., Chen, W., Guo, H., Wang, J., Mai, Y., Wei, X., Ding, J., Ge, F., Fan, Y., Guan, X. Abstract: Adolescent cocaine exposure (ACE) induce anxiety and higher sensitivity to drug addiction in adulthood. Here, we show that the claustrum is crucial for control of these two distinct psychiatric disorders in ACE mice. In the process of anxiety test, the CaMKII-positive neurons in median portion of claustrum (MClaustrum) were obviously triggered, and chemogenetic suppressing these neurons efficiently reduced ACE-induced anxiety in adulthood. While, the CaMKII-positive neurons in anterior portion of claustrum (AClaustrum) were obviously activated in response to cocaine-induced conditioned place preference (CPP), and chemogenetic suppressing these neurons efficiently blocked cocaine CPP in ACE mice during adulthood. Our findings dissociating specific sub-portions of claustrum for drug-related anxiety and susceptibility of addiction, extending our understanding to diverse functions of claustrum subregions. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.28.514232v1?rss=1 Authors: Thomas, J. R., Spiess, K. L., Colbran, R. J. Abstract: Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a key modulator of excitatory synaptic transmission, gene expression, learning and memory. Mutations in the CAMK2A gene, which encodes CaMKII alpha and is highly expressed in multiple regions in the forebrain, have been recently linked to neurodevelopmental disorders such as autism spectrum disorder (ASD) and intellectual disability (ID). Our lab generated and characterized a knock-in (KI) mutant mouse with a glutamate-183 to valine (E183V) CaMKII alpha mutation detected in several children diagnosed with ASD or ID. The E183V mutation reduces CaMKII activity and expression levels but the contributions of these two changes to the ASD-related behavioral phenotypes of these mice are unclear. Therefore, we performed side-by-side comparisons of the behavioral phenotypes of CaMKII alpha E183V-KI mice with two other mutant mouse lines with either a complete loss of CaMKII alpha expression (CaMKII alpha Null mice) or reduced kinase activity (due to a threonine-286 to alanine mutation that abrogates autophosphorylation at this site) with no significant change in expression levels (CaMKII alpha T286A-KI mice). In all three lines, homozygous mutant mice displayed increased stereotypic jumping behavior and hyperactivity, without alterations in anxiety or social interactions. Interestingly, homozygous mutant mice in all three lines also displayed a substantial reduction in tactile sensitivity using the Von Frey filament test. Together, these data suggest that reductions of either CaMKII alpha expression or activity in mice disrupted normal motor and sensory functions. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.18.512685v1?rss=1 Authors: Chen, L., Liu, Z., Zhao, Z., Pan, W., Hu, T., Wei, X., Nie, J., Ge, F., Ding, J., Fan, Y., Kim, H. Y., Guan, X. Abstract: Adolescent cocaine exposure (ACE) increases the risk of suffering psychiatric disorders including anxiety in later life, which is a big public health concern with limited treating options. Consistent with our previous study, we found that ACE mice exhibited obvious anxiety-like behaviors in their adulthood, which was efficiently suppressed by electro-acupuncture (EA) at acupoints of Baihui (GV 20) and Yintang (GV 29) with stimulus of a mixed frequency of 2/100 Hz for 28 withdrawal days. In the claustrum (CL) of ACE mice, more CaMKII-positive neurons (CaMKIICL) were activated, accompanied with increased expression of dopamine receptor 1 (D1R) on them (D1RCaMKII) and phosphorylated-EKR (p-ERK), p-CREB, and BDNF protein levels. Local blockade of CL D1R by SCH23390 or specific knockdown of CL D1RCaMKII by virus suppressed both anxiety-like behaviors and CaMKIICL activity in ACE mice of adulthood, indicating the critical role of CL D1RCaMKII in ACE-enhanced anxiety. Importantly, EA treatment suppressed CaMKIICL activity and D1RCaMKII staining, along with attenuated levels of p-CREB and BDNF in CL of ACE mice. Collectively, our study for the first time identified a novel molecular mechanism of CL D1RCaMKII and CaMKIICL activity in the process of ACE-increased anxiety in adulthood. Further, by targeting CL D1RCaMKII, EA at acupoints of GV 20 and GV 29 serves as preventative strategy to adolescent drugs exposure-induced anxiety in the later life. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.09.02.506383v1?rss=1 Authors: Ghane, M. A., Allen, Z. D., Miller, C. L., Dong, B., Fang, N., Yang, J. J., Mabb, A. M. Abstract: Synaptic plasticity relies on rapid, yet spatially precise signaling to alter synaptic strength. Arc is a brain enriched protein that is rapidly expressed during learning-related behaviors and is essential for regulating metabotropic glutamate receptor-mediated long-term depression (mGluR-LTD). We previously showed that disrupting the ubiquitination capacity of Arc enhances mGluR-LTD; however, the mechanism by which this occurs and its consequences on other mGluR-mediated signaling events is unknown. Here we show that disrupting Arc ubiquitination on key amino acid residues leads to derangements in Ca2+ release from the endoplasmic reticulum (ER) during pharmacological activation of Group I mGluRs. These alterations were observed in all neuronal subregions except secondary branchpoints. Deficits in Arc ubiquitination increased Arc self-association and enhanced its interaction with calcium/calmodulin-dependent protein kinase IIb (CaMKIIb) and constitutively active forms of CaMKII. Notably, these interactions were also excluded at secondary branchpoints. Finally, disruptions in Arc ubiquitination were found to increase Arc interaction with the integral ER protein Calnexin. These results suggest a previously unknown role for Arc ubiquitination in the fine tuning of ER-mediated Ca2+ signaling that is needed for mGluR-LTD, which, in turn, regulates CaMKII-dependent regulation of Arc. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

Emily Agnello explains the lab procedures used to study CaMKII, a protein in your brain that helps create and store memories. In order of appearance: Laura Fattaruso, Emily Agnello, Laura Patrick, Meg Stratton.

This month on Episode 32 of Discover CircRes, host Cynthia St. Hilaire highlights four original research articles featured in the January 7 and January 21 issues of Circulation Research. This episode also features a conversation with Ms Natalie Harris and Dr Kathleen Caron from the University of North Carolina Chapel Hill about their study, VE-Cadherin Is Required for Cardiac Lymphatic Maintenance and Signaling.   Article highlights:   Carlson, et al. AKAP18δ Controls CaMKIIδ Activity   Gan, et al. sEV and Adipocyte ER Stress Following MI/R   Khan, et al. Long-term Risk Prediction of Heart Failure   Awan, et al. Wnt5a Is Essential for Cholesterol Homeostasis   Cindy St. Hilaire:        Hi, and welcome to Discover CircRes, the podcast of the American Heart Association's journal Circulation Research. I'm your host, Dr Cindy St. Hilaire from the Vascular Medicine Institute at the University of Pittsburgh. Today, I'm going to be highlighting the articles from our January issues of Circulation Research. I'm also going to speak with Ms Natalie Harris and Dr Kathleen Caron from the University of North Carolina Chapel Hill about their study, VE-Cadherin Is Required for Cardiac Lymphatic Maintenance and Signaling.   Cindy St. Hilaire:        The first article I want to share is titled AKAP18δ Anchors and Regulates CaMKII Activity at Phospholamban-SERCA2 and Ryanodine Receptors. The first and corresponding author for this article is Cathrine Carlson, and the study was conducted at University of Ohio. In cardiac muscle cells, calcium is continuously released and taken up by the sarcoplasmic reticulum to drive alternating contractions and relaxations. The kinase, CaMKII, regulates this calcium signaling via phosphorylation of the sarcoplasmic reticulum proteins ryanodine receptors also called RYR.   Cindy St. Hilaire:         These receptors promote calcium release, and phospholamban promotes calcium uptake via the transporter SERCA, but how CaMKII localizes to and associates with these sarcoplasmic reticulum factors was unclear. Because AKAP18 delta enables phosphorylation of phospholamban and calcium uptake into the sarcoplasmic reticulum, this group suspected it might be involved. The team's immuno precipitation and functional experiments in rodent cardiomyocytes show that AKAP18 delta associates with CaMKII and phospholamban SERCA2 as well as with CaMKII and ryanodine receptors, and that these interactions are linked to CaMKII activity.   Cindy St. Hilaire:         The team identified two separate CaMKII binding domains within the AKAP18 delta protein, one that inhibits the kinase and one that actuates it, suggesting they may somehow serve to fine tune CaMKII activity. While such regulatory details remain to be resolved, the isolated domains may be utilized as tools for studying calcium handling in cardiomyocytes, and for developing therapeutic CaMKII regulating reagents for treating arrhythmia.   Cindy St. Hilaire:         The second article I want to share is titled Ischemic Heart-Derived Small Extracellular Vesicles Impair Adipocyte Function. The first author is Lu Gan, and the corresponding authors are Yajing Wang and Yu Cao from Thomas Jefferson University. While diabetes and obesity increase a person's risk of myocardial infarction, suffering a myocardial infarction itself can lead to metabolic dysfunction. One of the main regulators of systemic metabolic homeostasis is the body's adipose tissue, but whether and how an injured heart communicates with adipocytes was unclear.   Cindy St. Hilaire:         The infarcted heart is known to release microRNA containing extracellular vesicles, also called EVs, and so this group hypothesized that these EVs might constitute a heart-to-fat communication system. They isolated circulating EVs before and after myocardial infarction in mice, and incubated these vesicles with cultured adipocytes. After 24 hours, differences in adipocyte gene and protein expression were apparent. Notably, a key cardioprotective metabolic factor called adiponectin was downregulated in cells treated with the extracellular vesicles from myocardial infarcted mice, while genes involved in endoplasmic reticulum stress were increased.   Cindy St. Hilaire:         Analysis of the myocardial infarction extracellular vesicle content showed an increased abundance of specific microRNAs, and the team went on to show that inhibiting production of these microRNAs or the EVs themselves, prevented adipocyte ER stress and adiponectin production in mice after myocardial infarction. Together, these data hints that such microRNA inhibition may be a clinical strategy that can be used to prevent infarction-associated metabolic dysfunction in humans.   Cindy St. Hilaire:         The next article I want to share is titled Development and Validation of A Long-Term Incident Heart Failure Risk Model. The first and corresponding author of this study is Sadiya Khan from Northwestern University. Heart failure contributes to approximately 1.2 million hospitalizations, and 300,000 deaths in the U.S. annually. Heart failure also has an estimated healthcare cost of over $10 billion. With both the incident rates and costs expected to rise in the future, a method for predicting an individual's heart failure risk would enable preventative interventions such as diet and blood pressure treatments to be initiated early, thus prolonging the number of healthy years.   Cindy St. Hilaire:         To develop such a prediction tool, this group studied decades of health data from over 24,000 individuals that was collected as part of five separate, long-running national heart, lung and blood institute studies. The individuals included in the model for development were at baseline aged between 20 and 59 years old, and had no cardiovascular disease diagnosis at that time. Analysis of their body mass indices, blood pressures, total cholesterol levels, high density lipoprotein levels, smoking statuses, diabetes diagnoses, and other cardiovascular health data over several decades enabled the team to develop an equation for predicting an individual's likelihood of developing heart failure in the next 30 years. The hope is such personalized risk assessments will help to guide patient-doctor discussions regarding cardiovascular health, lifestyle choices and medical interventions.   Cindy St. Hilaire:        The last article I want to share is titled Wnt5a Promotes Lysosomal Cholesterol Egress and Protects Against Atherosclerosis. The first authors are Sarah Awan and Magalie Lambert, and the corresponding author is Philippe Boucher from the University of Strasbourg. The Wnt family of signaling proteins drives many developmental processes, such as cell fate determination, proliferation and migration. Recently, Wnt signaling has been implicated in lipid homeostasis. Mutations that impair Wnt signaling have been shown to cause hyperlipidemia in mice, and in humans, decreased Wnt signaling activity inversely correlates with atherosclerosis severity.   Cindy St. Hilaire:        Because the protein Wnt5a in particular has been shown to inhibit cholesterol accumulation in cells, this group investigated the role of Wnt5a protein in mice and human cells. Mice whose vascular smooth muscle cells lacked Wnt5a developed more severe atherosclerosis compared to control animals, and human smooth muscle cells lacking Wnt5a accumulated far greater amounts of cholesterol in the lysosomes than did cells with normal levels of Wnt5a. The group then showed that Wnt5a normally associates with lysosomes, where it promotes the catabolism of lysosomal cholesterol via activating lysosomal lipase, and promoting cholesterol egress via the endoplasmic reticulum. In revealing how cholesterol efflux is trafficked by Wnt5a, these findings may help to inform future cholesterol regulating therapies.   Cindy St. Hilaire:         Today, Natalie Harris and Dr Kathleen Caron from the University of North Carolina Chapel Hill are here with me to discuss their study, VE-Cadherin Is Required for Cardiac Lymphatic Maintenance and Signaling, which is featured in our January 7th issue of Circulation Research. Thank you both for joining me today.   Kathleen Caron:          Thanks, Cindy, for having us. We're really honored and excited to talk with you.   Cindy St. Hilaire:         I'm excited too, because I think this is my first lymphatic paper I'm talking about. That's where I'm going to start my questions. Your study is investigating cardiac lymphatics. But like I said, I haven't talked a lot about lymphatics here, so I was wondering if you could at least give a little bit of background about what the role is of the lymphatic system, especially because I feel like it's the unappreciated member of the circulation, and also give us a little bit of background on what cardiac lymphatics are.   Kathleen Caron:          That's a really great question. We sometimes talk about lymphatic vessels as the third vascular system or the understudied vascular system. I'm hoping that that's not the case so much anymore, because the lymphatic field has really boomed in the past 15 years or so. I think where we are right now in the field is in early days, we and others had discovered key signaling molecules, and transcription factors, and growth factors that are important and specific to the lymphatic vasculature as compared to blood endothelial cells. Through those unique tools, now, the field has fast forwarded where we're starting to look into organ-specific functions of lymphatics.   Kathleen Caron:          We're appreciating that perhaps a little unlike the blood vascular system, which has one main function of delivering blood, lymphatics actually have very different functions depending on the organ that they're in. Some of the more common ones that you'll read about in textbooks in about a paragraph in a medical textbook are that lymphatics are important for immune cell trafficking through the lymph nodes, so they're the major route of trafficking for immune cells and for their maturation. Lymphatics are also important for draining interstitial fluid, and maintaining the homeostasis of tissue fluid balance.   Kathleen Caron:          A third really big one, which is sometimes underappreciated, is that lymphatics are the key vessels within the intestine that absorb lipid, and so all of our dietary lipids are absorbed through lymphatic vessels as opposed to the blood vasculature. Those three hallmark functions of lymphatics are the cornerstone of what they do throughout our body. But when you start to look into different organs and recognizing the different extrinsic and intrinsic forces that govern the function of these endothelial cells and different organs, you start to realize that they're even more complex, and that brings us to the heart.   Kathleen Caron:          The heart just has this beautiful network of lymphatic vessels that begin in the subendocardial space, and then project out and cover the subepicardial surface of the heart. And because the heart is always pumping, and because lymphatic vessels don't have an intrinsic mechanism for the flow of fluid through them, they rely on the movement of the tissue that they're in to help propel the fluid. So, this really raises the question of how are lymphatics functioning physically within a myocardium that is pumping with a very strong extrinsic force, and what is the function of those vessels if the heart is a very dense, thick organ that is not necessarily prone to edema necessarily as maybe our peripheral tissue and our skin is? Kathleen Caron:          We've been studying this for many years now, and we've had several studies exploring genetic factors that are important for the growth and development of cardiac lymphatics. That's the focus of this paper today. They're quite unique and very different vessels.   Cindy St. Hilaire:         Reading your paper, I definitely learned a lot about lymphatics in general. One of the things I was thinking about, obviously, you're looking at VE-Cadherin, which is an endothelial cell marker. When I think of VE-Cadherin, and when I think of endothelial cells, my mind goes primarily to those that are in arteries and veins. In those conduits, their role is to really keep a tight seal to keep things out. But in the lymphatic system, it's very different, so how exactly different are the endothelial cells in the lymphatic tissue, and are they different, say, in the cardiac lymphatics versus, like you said, the mesenteric lymphatic?   Kathleen Caron:          Lymphatics are very different than the blood vasculature. First of all, the lymphatic vasculature has key differences in terms of its architecture and structure. The lymphatic endothelial cells themselves, as they exist in vessels, don't put down a basement membrane, and in general, the dermal capillaries or the initial collector lymphatics that are the ones that are taking in fluid also don't have smooth muscle cells surrounding them like our typical vasculature does. All of this is guided and precedented by the differences in gene expression patterns of these very specialized endothelial cells.   Kathleen Caron:          They also have very different cell-cell junctions. So when we think of a blood endothelial cell, we typically think of these tight junctions that bring them together, but the lymphatic endothelial cells have oak leaf shaped overlapping junctions. They're really beautiful to see on an EM, and they're very different than the blood vasculature, because, Cindy, as you mentioned, the function is very different. You're supposed to let things leak out, and big things too, right, like immune cells and large proteins.   Cindy St. Hilaire:         One of the neat things that really made your study possible is this really nice PROX1 inducible CRE that you crossed with the flox-cadherin5 gene. I was wondering a little bit about that protein. Is that one of these, I guess, markers that allows lymphatic EC to be a lymphatic EC, and how specific is that protein for those specific ECs?   Natalie Harris:            The PROX1 CRE that we use is based off of the PROX1 transcription factor, which we consider to be one of the master transcription factors of lymphatics. In fact, that was one of the very first lymphatic specific transcription factors that help maintain the lymphatic identity. So in this case, PROX1 turns on from blood endothelial cells, because many lymphatics are of venous origin, so actually, PROX1 turning on is a hallmark of them becoming a lymphatic endothelial cell.   Natalie Harris:            Those are really great CRE specifically to look at lymphatics in this case, and it actually is a perfect model system because VE-Cadherin itself is only expressed in lymphatics and blood vessels, and then we have PROX1 as our free driver. Therefore, it will only be lymphatic, so it's a very specific lymphatic knockout of VE-Cadherin.   Cindy St. Hilaire:         That's so wonderful when we discover things that are so specific like that. So using this really nice model that's also Tamoxifen inducible, you then have control to look at things temporally. One of the neat things that you did was you looked at this in terms of an embryonic level knockout, but then another one postnatally, and then another one, it was an adult mouse, which not a lot of people do that intricate, temporal spacing of things. So I was wondering if you could just share with us what you were thinking behind doing that, and then really importantly, what those different models actually taught you about the cardiac lymphatics?   Kathleen Caron:          That's a great question, Cindy. It would take me 20 minutes to answer. It really represents work by all of the co-authors. Really, it's the first effort to look at the different stages. That's because the growth and development of lymphatics, particularly within the myocardium, differs a lot during embryogenesis, and then the vessels themselves are quiescent in an adult animal. Then of course, we were interested in seeing what might happen in an injured myocardium, and that was also part of the study.   Kathleen Caron:          We felt that it was important to address the changing and dynamic role of this protein in a developing lymphatic, because it's growing and forming these nascent vessels, and then as it's starting to remodel an early life, and then in adulthood when it's in a quiescence state. That was the rationale for looking at this. It was also... Sometimes, science just takes you where it takes you, and it was a co-author of ours, and collaborator of ours, who had noted a phenotype in the hearts of these animals that he generated and suggested that maybe it would be a good idea to look early in development. Then as one thing leads to another, you start looking later in development and so on and so forth, so the science just kind of…   Cindy St. Hilaire:         Sometimes tells you where to go on its own.   Kathleen Caron:          Exactly. It was a long project.   Natalie Harris:            Part of the reason too is that the cardiac lymphatics have been shown to have a little bit of a different development and maintenance and pruning cycle than some of the other lymphatics. Some other lymphatics are totally fully formed in embryonic development, but the cardiac lymphatics have been shown to develop through birth and a little bit postnatally as well. That makes them a little bit unique in the sense that their maturation is very prolonged, so that's part of the reason as well we wanted to look both in embryonic development as well as that postnatal period.   Cindy St. Hilaire:         That's so interesting. There are a lot of little nuggets that my antennas would perk up as I read your paper, really neat observations. One of them was that I think it was the postnatal and the adults. There was lymphatic endothelial cells in the cardiac tissue were disrupted. They were discontinuous and fragmented, yet there was no cardiac edema. I thought that was interesting because normally, you'd think about any of these mice with lymphatic issues. You think of edema. You think of swelling, and yet it wasn't happening in the heart. What do you think that means either about the lymphatic system in the heart or in lymphatics as a whole?   Kathleen Caron:          That's a really great question, and one that we think about all the time. I think it goes back to the first question or the first comment about the really remarkable differences in the functions of lymphatics and different tissues, right? And within the myocardium, because it is continuously moving and pumping with great force, the extrinsic forces within that tissue will help to mitigate the formation of edema. This is not to say that you can't get myocardial edema, and we've actually developed surgical models in our lab to form myocardial edema in mice.   Kathleen Caron:          It is a very common clinical condition in humans as well, but the lymphatics themselves being fully invested within this myocardium probably are being regulated differently in their function in draining fluid than, for example, the lymphatics that you might have in the skin or in your thigh or in other organs in your body. The fact that there wasn't edema, even though you had leaky vessels, didn't alarm us too much because we knew and sensed that with this constant pressure and pumping of the myocardium, that in itself helps to keep the tissue fluid balanced.   Natalie Harris:            That might be another reason why we're not seeing such extremes in edema, and then going back to what Kathrine said, again, because lymphatics have multiple functions, perhaps it's more in the immune cell realm or even other functions we haven't uncovered yet.   Cindy St. Hilaire:         One of the other neat observations you had was that you were doing a myocardial infarction model on the adult animals, and you noticed that the infarct size and the fibrosis was indeed larger in the knockouts, but the cardiac function wasn't exactly affected. What does this mean, and were you surprised by this?   Kathleen Caron:          Yeah, we were surprised. We absolutely were surprised, and we think that's actually one of the key big reveals for the field. To balance this, to counterbalance the absence of a phenotype, that was really remarkable to us, and I hope to many others as well, is that other studies including work from our lab and Paul Riley's lab and Eva Brackinham's lab have very convincingly shown in multiple different ways that if you stimulate lymphangiogenesis after injury, if you have a model, either genetic or induced, where there are more lymphatics for whatever reason, that's a beneficial thing. That's a great thing, and having more lymphatics is positive and beneficial to improving heart repair, and mitigating heart injury, and helping in the context of myocardial infarction.   Kathleen Caron:          Of course, it was really surprising that now we have a mouse model where we essentially have little to no lymphatics with very little to no function, and yet the ejection fractional shorting of the heart was doing just fine. I think that was a big moment and a big discovery for us, but very convincing. Then I think it leads us to really asking while more might be better, what really could be the critical function of the lymphatics in an injured myocardium? As Natalie just mentioned previously, it might be related to immune cell trafficking. Paul Riley's group has made some really seminal discoveries in that regard.   Natalie Harris:            It's just very interesting, because it's really against everything that you would expect from, again, all the previous studies. It just goes to show again that the lymphatics are so heterogeneous in their organ level function that that's really worth exploring more, because maybe if you can figure out strategies to selectively target certain beds, you can really do a treat on the disease by disease, organ by organ basis. That makes the lymphatics just really cool in my opinion, because they are so different, but it's all the same system, so it's just a very interesting organ, in my opinion.   Kathleen Caron:          I should also say serendipitously or right about a few months ago... Shout out to Mark Kahn's lab at University of Pennsylvania. They had a recent paper, I believe, in JCI that had a similar finding to ours. It's always gratifying when another lab says, "Oh, wow, really?" Their study was very different than ours and on a different series of signaling molecules, but similarly, they ablated or reduced cardiac lymphatics through different mechanisms, and then had an injury model. Also, were rather surprised to see that it didn't have this negative effect.   Cindy St. Hilaire:        It's so neat. The whole observations that you saw with these knockouts was a paper in itself, but the next half of the paper, you dig into the mechanism, which is also interesting. Can you share a little bit about the links that you found between VE-Cadherin and the VEGF receptor signaling, and is your mechanism you think specific to all lymphatic ECs or even all ECs, or is it specific just to the cardiac lymphatic ECs?   Kathleen Caron:          Yes, the mechanism, I find one of the funnest parts of this paper, because I think it really synergizes a lot of the key signaling molecules within our field. Also, I think it bridges together a G-protein-coupled-receptor signaling pathway that my lab has been interested in for decades now, and that is a pathway with the VEGFR3 signaling pathway. I think that's been a big open question in the field. How do these two critical requisite signaling paradigms for lymphatics converge together to maintain lymphatic function development?   Kathleen Caron:          I think we've really made some really great inroads in the study, and VE-Cadherin is central to that because it forms a structural scaffold to keep a GPCR signaling pathway in register with the receptor tyrosine kinase signaling pathway, and basically allow for the transactivation of these two really powerful pathways. The mechanism really is gratifying to be able to finally pull how these molecules all interface together and regulate one another.   Natalie Harris:            It's very interesting in the fact that VE-Cadherin, it's not necessarily like a lymphatic-specific molecule, but a lot of work in terms of VE-Cad has been more in studying mechanosensing and mechanotransductions. That's where a lot of little nuggets about maybe our mechanism has occurred that we know from really just on protein level studies that VE-Cadherin does interact with VEGFR2 and VEGFR3 by the transmembrane domain interaction. That was clue number one, and then clue number two is that we know that a lot of different mechanical signals that might affect VEGFR3 happened in the presence of VE-Cad.   Natalie Harris:            So in a sense, this particular paper is just piecing together a lot of these nuggets of information, and it all makes sense. One thing that you were saying in terms of maybe specific to the heart, going back to some of the earlier studies on these papers on these mice, that we found very vessel-bed-specific effects. One of the vessel beds that is really impacted is the lacteals and the mesentery, so the gut lymphatics. We do know that these lymphatic beds are very sensitive to VEGFC. In fact, they require constant VEGFC signaling. So if you're not having VEGFR3 stable at the membrane to receive these signals, it makes sense if you would have really extreme effects. That might be, again, some of the case in the heart as well. We do know after a cardiac injury, we do see an increase in things like adrenomedullin, and an increase in VEGFC has been shown to increase lymphangiogenesis, so perhaps also the heart, the gut lymphatics also has a special requirement for VEFGR3 signaling.   Cindy St. Hilaire:         So in terms of, I guess, the future of this line of research and maybe thinking about translation, what do you see as maybe a role for this in terms of developing therapeutic strategies or even preventative measures, I guess, specifically in the cardiac lymphatic area?   Natalie Harris:            Like we mentioned earlier, there's been a lot of studies in mice that have looked at increasing lymphangiogenesis post-injury, so it would be interesting to see more when those hit the clinical end, and if you're seeing similar effects. Then the other thing that's interesting about lymphatics, you can think of them as both a target and also as a drug delivery route. There's a huge, huge field totally dedicated to using the lymphatics to deliver drugs like nanoparticles. That's very big in the cancer realm, and pretty much for any kind of drug delivery, if you can imagine using that as a super highway to deliver drugs as well.   Natalie Harris:            That could be a potential avenue in terms of the heart as well, getting a more specific administration of cardiovascular drugs to the heart. So whether or not we're thinking of them as being modulated by disease, we can also use them to modulate the disease itself by delivering drugs as well, so it's interesting. You can think of the lymphatics as a therapeutic target and as a therapeutic administrator. That's going to be really interesting to see where the field goes.   Cindy St. Hilaire:         I like that, a new super highway to deliver drugs. Thank you so much, soon to be Dr Harris and Dr Caron from UNC Chapel Hill. This was a wonderful conversation and a beautiful paper. Congratulations on all the hard work. Kathleen Caron:          Well, thanks so much, Cindy, and to the whole Circ Research team. We really appreciate your advocacy for our work and giving us this wonderful opportunity.   Natalie Harris:            Thank you so much.   Cindy St. Hilaire:         That's it for the highlights from our January issues of Circulation Research. Thank you for listening. Please check out the CircRes Facebook page, and follow us on Twitter and Instagram with the handle @CircRes and #DiscoverCircRes. Thank you to our guests, Natalie Harris and Dr Kathleen Caron. This podcast was produced by Ashara Ratnayaka, edited by Melissa Stoner, and supported by the editorial team of Circulation Research. Some of the copy text for highlighted articles was provided by Ruth Williams. I'm your host, Dr Cindy St. Hilaire, and this is Discover CircRes, your on-the-go source for the most up-to-date and exciting discoveries in basic cardiovascular research.   Cindy St. Hilaire:         This program is copyright of the American Heart Association, 2022. The opinions expressed by speakers on this podcast are their own and not necessarily those of the editors or of the American Heart Association. For more information, visit ahajournals.org.  

SHR # 2759:: Muscle Protein That Makes Vertebrates Fit Linked to Limiting Lifespan plus HRT For Dogs Improves Health - Dr. Gabriel Bever, Ph.D. - Dr. Qinchuan Wang, PH.D. - Linda Brent Ph.D. - Antagonistic pleiotropy is a foundational theory that predicts aging-related diseases are the result of evolved genetic traits conferring advantages early in life. Here we examine CaMKII, a pluripotent signaling molecule that contributes to common aging-related diseases, and find that its activation by reactive oxygen species (ROS) was acquired more than half-a-billion years ago along the vertebrate stem lineage. Functional experiments using genetically engineered mice and flies reveal ancestral vertebrates were poised to benefit from the union of ROS and CaMKII, which conferred physiological advantage by allowing ROS to increase intracellular Ca 2+and activate transcriptional programs important for exercise and Immunity. Enhanced sensitivity to the adverse effects of ROS in diseases and aging is thus a trade-off for positive traits that facilitated the early and continued evolutionary success of vertebrates. PLUS The practice of castration and ovariectomization is commonplace among veterinarians today. Dogs are spayed and neutered at very young ages removing all sex hormones which have important roles in the health and immune systems of dogs. We look at castrated male dogs who received testosterone replacement after being neutered to identify is any health advantages were conferred.

SHR # 2759:: Muscle Protein That Makes Vertebrates Fit Linked to Limiting Lifespan plus HRT For Dogs Improves Health - Dr. Gabriel Bever, Ph.D. - Dr. Qinchuan Wang, PH.D. - Linda Brent Ph.D. - Antagonistic pleiotropy is a foundational theory that predicts aging-related diseases are the result of evolved genetic traits conferring advantages early in life. Here we examine CaMKII, a pluripotent signaling molecule that contributes to common aging-related diseases, and find that its activation by reactive oxygen species (ROS) was acquired more than half-a-billion years ago along the vertebrate stem lineage. Functional experiments using genetically engineered mice and flies reveal ancestral vertebrates were poised to benefit from the union of ROS and CaMKII, which conferred physiological advantage by allowing ROS to increase intracellular Ca 2+and activate transcriptional programs important for exercise and Immunity. Enhanced sensitivity to the adverse effects of ROS in diseases and aging is thus a trade-off for positive traits that facilitated the early and continued evolutionary success of vertebrates. PLUS The practice of castration and ovariectomization is commonplace among veterinarians today. Dogs are spayed and neutered at very young ages removing all sex hormones which have important roles in the health and immune systems of dogs. We look at castrated male dogs who received testosterone replacement after being neutered to identify is any health advantages were conferred.

This month on Episode 23 of Discover CircRes, host Cindy St. Hilaire highlights the topics covered in the April 2nd Compendium on Hypertension issue, as well as discussing two articles from the April 16 issue of Circulation Research. This episode also features an in-depth conversation with Dr Kathryn Moore from the New York University School of Medicine, discussing her study, miR-33 Silencing Reprograms the Immune Cell Landscape in Atherosclerotic Plaques.   Article highlights:   Compendium on Hypertension   Mustroph, et al. CASK Regulates Excitation-Contraction Coupling   Ward, et al. NAA15 Haploinsufficiency and CHD   Cindy St. Hilaire:         Hi, and welcome to Discover CircRes, the podcast of the American Heart Association's journal, Circulation Research. I'm your host, Dr Cindy St. Hilaire from the Vascular Medicine Institute at the University of Pittsburgh. Cindy St. Hilaire:         Today, I'm going to be highlighting the topics presented in our April 2nd Compendium on Hypertension, as well as two articles from the April 16th issue of Circ Res. I also will speak with Dr Kathryn Moore from New York University School of Medicine about her study, miR-33 Silencing Reprograms the Immune Cell Landscape in Atherosclerotic Plaques. So the April 16th issue of Circulation Research is a compendium on hypertension. As introduced by Rhian Touyz and Ernesto Schiffrin, there are over 10,000 articles in PubMed related to hypertension. Hypertension is a major cause of morbidity and mortality worldwide, and data trends suggest that fewer and fewer patients are able to control their blood pressure medically. Further, the recent Sprint trial showed us that lowering blood pressure to levels below previously recommended values strongly correlated with significantly reduced rates of cardiovascular events and risk of death. Cindy St. Hilaire:         As such, the April 2nd issue of Circ Res provides an extensive and expansive review on the current knowledge in the field. The series starts with an article on hypertension in low and middle-income countries by Aletta Schutte and colleagues. There they present the stark differences in the trajectory, healthcare, inequality, and established and emerging risks that are specific to low and middle-income countries. Cindy St. Hilaire:         Robert Carey and colleagues present an evidence-based update in their article titled Guideline-Driven Management of Hypertension. In Pathophysiology of Hypertension, David Harrison and colleagues present the concept of the mosaic theory of hypertension originally proposed by Dr Irvine Page in the 1940s, which proposes that hypertension is the result of multiple factors that in some, raise blood pressure and induce end-organ damage. This article further refines this theory by incorporating what is known regarding the role of things like oxidative stress, inflammation, genetics, sodium homeostasis, and the microbiome in hypertension pathogenesis. Cindy St. Hilaire:         Phil Chowienczyk and Jay Humphrey and colleagues cover the contribution of Arterial Stiffness and Cardiovascular Risk in Hypertension and identify steps required for making arterial stiffness measurements a keystone in hypertension management, and cardiovascular disease prevention as a whole. In Renin Cells, The Kidney, And Hypertension, Maria Luisa Sequeira Lopez and Ariel Gomez cover the major mechanisms that control the differentiation and fate of renin cells, the chromatin events that control the memory of the renin phenotype, and the major pathways that determine the cells’ plasticity. Cindy St. Hilaire:         Meena Madhur and Annet Kirabo and colleagues penned the article, Hypertension: Do Inflammation and Immunity Hold the Key to Solving this Epidemic? In this Teview, they covered the emerging concepts of how environmental, genetic, and microbial-associated mechanisms promote both innate and adaptive immune cell activation and help lead to hypertension. Cindy St. Hilaire:         In the article, The Gut Microbiome in Hypertension. Dominik N. Müller and colleagues present insights into the host-microbiome interaction and summarize the evidence of its importance in the regulation of blood pressure and provide recommendations for ongoing and future research. Cindy St. Hilaire:         Paul Cohen, James Sowers, and colleagues cover Obesity, Adipose Tissue, and Vascular Dysfunction in which they discuss the abnormal remodeling of specific adipose tissue depots during obesity and how this contributes to the development of hypertension, endothelial dysfunction, and vascular stiffness. Cindy St. Hilaire:         Clinton Webb, Satoru Eguchi, Rita Tostes, and colleagues cover Vascular Stress Signaling in Hypertension. In this Review, they discuss common adaptive signaling mechanisms against stresses, including the unfolded protein response, antioxidant response element signaling, autophagy, mitophagy, mitochondrial fission and fusion, STING-mediated responses, and activation of pattern recognized receptors. And how all of these responses contribute to vascular stress and ultimately hypertension. Cindy St. Hilaire:         Rhian Touyz and colleagues then specifically dig into the topic of Oxidative Stress and Hypertension, focusing in on recent advances in delineating the primary and secondary sources of reactive oxygen species, the posttranslational oxidative stress modification ROS induces on protein targets important for redox signaling, their interplay between ROS and endogenous antioxidant systems, and the role of inflammation activation and endoplasmic reticular stress in the development of hypertension. Cindy St. Hilaire:         Curt Sigmund and then colleagues cover the Role of the Peroxisome Proliferator Activated Receptors in Hypertension. In this Review, they discuss the tissue- and cell-specific molecular mechanisms by which PPARs in different organ systems modulate blood pressure and related phenotypes, such as endothelial cell dysfunction. Importantly, they also discuss the role of placental PPARs in preeclampsia which is a life-threatening form of hypertension that accompanies pregnancy. Cindy St. Hilaire:         Daan van Dorst, Stephen Dobbin, and colleagues provide the Review, Hypertension and Prohypertensive Antineoplastic Therapies in Cancer Patients. Many cancer therapies have prohypertensive effects. And this Review covers some of the mechanisms by which these antineoplastic agents lead to hypertension and details the current gaps in knowledge that future clinical studies must investigate, to identify the exact pathophysiology and the optimal management of hypertension associated with anticancer therapy. Cindy St. Hilaire:         In Hypertension, a Moving Target in COVID-19, Massimo Volpe, Reinhold Kreutz, and Carmine Savoia, review available data on the role of hypertension and its management in COVID-19. Cindy St. Hilaire:         Melvin Lobo and colleagues review Device Therapy of Hypertension. In this Review, they discussed the newer technologies, which are predominantly aimed at neuromodulation of peripheral nervous system targets, and discuss the preclinical data that underpin their rationale and the human evidence that supports their use. Cindy St. Hilaire:         Last but not least, in Artificial Intelligence in Hypertension: Seeing Through a Glass Darkly, Anna Dominiczak and colleagues cover a clinician-centric perspective on artificial intelligence and machine learning as applied to medicine and hypertension. In this Review, they focus on the main roadblocks impeding implementation of this technology in clinical care and describe efforts driving potential solutions. Cindy St. Hilaire:         This is an expansive set of Reviews written by the leading experts in the field and provides an up-to-date assessment of all aspects of hypertension. The graphics, and the articles are absolutely beautiful. And I'm sure we will be seeing a lot of them in upcoming presentations. Hopefully at AHA and the other sub-meetings when we're all back in person. Cindy St. Hilaire:         In the April 16th issue, I want to highlight the article, Loss of CASK Accelerates Heart Failure Development. The first author is Julian Mustroph, and the corresponding authors are Lars Maier and Stefan Wagner from the University Medical Center in Regensburg, Germany. Despite advances in cardiovascular medicine, heart failure takes the lives of tens of thousands of Americans each year. To develop novel treatments, a better understanding of the conditions of molecular pathology is needed. One contributing factor in heart failure is increased activity of the Ca/calmodulin-dependent kinase II (CaMKII). Cindy St. Hilaire:         In this paper, the authors suggest a way to get CaMKII levels under control. Ca/CaM-dependent serine protein kinase or CASK, suppresses CaMKII neurons and the team showed that CASK is also expressed in human heart cells, where it associates with CaMKII. Next, they engineered mice to CASK specifically in cardiomyocytes, finding that when these animals are subjected to beta-adrenergic stimulation, cardiomyocyte like CaMKII activity was significantly greater than that seen in control animals. Calcium spark frequency and the propensity for arrhythmia were also increased. Furthermore, in a mouse model of heart failure, mice lacking CASK fared worse and had reduced survival compared to the wild type control animals while boosting CASK expression in wild type animals reduced the elevated CaMKII activity and calcium sparks associated with heart failure. The author suggests that increasing CASK activity might be a heart failure treatment strategy worthy of further study. Cindy St. Hilaire:         The last article I want to share from the April 16th issue is titled, Mechanisms of Congenital Heart Disease Caused by NAA15 Haploinsufficiency. The first author is Tarsha Ward, and the co-senior authors are Kris Gevaert, Christine Seidman, and JG Seidman from Harvard University in Boston, Massachusetts. A number of genetic variants are associated with congenital heart disease, including loss of function variants of the gene encoding NAA15,  a sub N-terminal acetyltransferase complex called NatA, which acetylates a large portion of newly forming proteins. To find out how these variants contribute to defective heart development, the authors performed genome editing on human pluripotent stem cells to convert one or both copies of NAA15 gene into congenital heart disease linked to variants. The team then examined cardiomyocyte differentiation, protein acetylation, and protein expression in the edited and unedited cells. Cindy St. Hilaire:         They found that while NAA15 haploinsufficiency cells were able to develop into cardiomyocytes seemingly normally, the cell's contractile ability was significantly impaired. Cells homozygous for NAA15 variants failed to differentiate and had poor viability. The team also found that while only a small number of proteins had reduced end terminal acetylation in NAA15 haploinsufficiency cells, over 500 proteins had altered expression levels, four of which were encoded by congenital heart disease-linked genes. This work provides the first insights into the effects of NAA15 variants in human cells and sets the stage for analyzing other congenital heart disease-linked variants in this manner. Cindy St. Hilaire:         Today, Dr Kathryn Moore from NYU School of Medicine is with me to discuss her study, miR-33 Silencing Reprograms the Immune Cell Landscape in Atherosclerotic Plaques, which is in our April 16th issue of circulation research. So thank you so much for joining me today, Kathryn. Kathryn Moore:          My pleasure. Cindy St. Hilaire:         Atherosclerosis is the result of lipid-induced chronic inflammation, and while lipids are kind of thought to be an initial driver, therapies that target lipids alone, such as statins, they're not sufficient. They can obviously bring things down and improve things a lot, but a lot of research now is focused on uncovering the nuances of the inflammatory component of atherosclerosis to help identify new targets for therapies. One specific arm of this research has focused on resolving atherosclerotic inflammation. And my first question to you is, what exactly does resolving inflammation mean in the context of an atherosclerotic plaque? And maybe could you give us a little primer on some of those key cell types or processes involved in that. Kathryn Moore:          I'm really fascinated by the resolution of inflammation and in particular, in the atherosclerotic plaques. So inflammation used to be thought of as an active process, almost a one-way process, which in order to resolve had to stop. But actually, the pro-inflammatory and anti-inflammatory responses are a continuum. And so inflammation resolution, we now recognize is an active process, and it's not just a matter stopping the influx of immune cells but these cells take on new phenotypes and different functions. And the immune cells themselves are required for resolution of inflammation and tissue repair. And so we're really interested in looking at what those pathways are, that tip the balance between pro-inflammatory responses and pro-resolving responses and how to incite them in the plaque so that you can start to remodel the plaque to be more stable or have a more favorable phenotype, or even to regress the plaque, to shrink the plaque in size. Cindy St. Hilaire          This study specifically focused on microRNA-33, and I believe your lab was one of the very first to look at this specific, but also other micro RNAs in atherosclerosis. And the prior research that you and others have shown is that this microRNA modulates a variety of genes that control lipid metabolism. You found this in mice, but also in monkeys. And really by using anti-miRs against this microRNA, you can induce cholesterol efflux and that cholesterol will leave the liver and the macrophage cells, and it's incorporated into the protective HDL particles and excreted. Cindy St. Hilaire:       And so it has this really nice protective effect. However, the effects seen in these animal studies were suggested that microRNA-33 had HDL independent action, which I think is where your story starts. So could you tell us some of the premises or the gaps in knowledge between those first initial findings of miR-33 that led you to conduct this study and then kind of what the design of the study was? Kathryn Moore:          So, as you mentioned, we discovered miR-33 as an inhibitor of cholesterol efflux and the pathways that lead to the generation of HDL, the so-called good cholesterol. And when you inhibit miR-33 in mice and monkeys, you can raise plasma levels of HDL. But we also saw that in mice that had been fed a Western diet continuously, we saw favorable changes in the atherosclerotic plaque under conditions where we didn't see the increase in HDL. So if the mice are on a Western diet, the levels of miR-33 in the liver are very low, and inhibiting it doesn't cause the increase in HDL cholesterol. But we still saw this 25% regression in atherosclerotic plaques. And that got us thinking about the other things that miR-33 could be doing and around the same time, I was also very interested in immunometabolism and how the metabolic state of macrophages influences their function. Kathryn Moore:          And Mihail Memet, who is a former postdoc in my lab made the discovery that miR-33 could inhibit fatty acid oxidation in macrophages and that this polarized the cells to a more inflammatory phenotype. So when we give the miR-33 inhibitors, we're raising a level of fatty acid oxidation in the macrophages and they become more tissue reparative. And so we suspected that could be the mechanism going on in the plaque but those studies, those initial studies were done over five years ago. And that was before the advent of single-cell technologies, which have really revolutionized how we're studying the atherosclerotic plaque. So in this study, we were able to apply some of these more high dimensional analyses of all of the immune cells in the plaque. And really look at how inhibiting miR-33 was altering their transcriptome and their phenotype. Cindy St. Hilaire:         Yeah, so that is a perfect segue to my next question, which is you're doing this single-cell RNA-sequencing on tissue, but it's not just any tissue. It's not like a nice spleen that you can kind of pop open and all the cells fall out nicely and you can fax them or whatever. This is from an aorta, which itself is fibrous and tough on top of the atherosclerotic plaque, which is also difficult. So can you discuss maybe some of the challenges regarding doing this exact kind of analysis with this tissue and maybe some of the limitations or controls that you used to help really refine your result? Kathryn Moore:           It is a little bit challenging to learn how to digest the aorta to release the immune cells, so to isolate the CD45+ immune cellsthat then go on to the sequence that takes some trial and error to get the right conditions. But actually, once you've done that a couple of times, it's not as difficult as it seems but I think that one of the challenges of doing these types of studies is integrating the results that we get from the single-cell RNA-sequencing with the other technologies that we've used in the past to analyze atherosclerosis. Kathryn Moore:          So, previously when we were analyzing atherosclerotic plaque size or immune cell content, we are doing this through histology and immunostaining. And single-cell RNA-sequencing has identified all these new immune cell subsets based on transcriptomic signatures. And they don't really match up nicely with the protein signatures that we've used in the past. Cindy St. Hilaire:         Yeah. Kathryn Moore:          I saw this as a great opportunity to try to integrate all these techniques. And see if we could come to some middle ground. To understand how maybe the new subsets that we're identifying with single-cell RNA-seq from the aortic immune cells matched some of the things that we were able to do by looking at histology and tracing monocytes and macrophage entry and retention in the plaque. Cindy St. Hilaire:         How did it line up? What's the nice Venn diagram of this study and what we've all been doing previously? Kathryn Moore:          Well, it's a challenge, but what I thought was really really fascinating was we did monocyte-macrophage tracing experiments. Because one of the things we find when we inhibit miR-33 is we have a 50% decrease in the macrophage content of the plaque, but how is that happening? And what we found was there was an increase in the recruitment of monocytes into the plaque which may sound surprising if the plaque is shrinking, but they are the cells that are needed. They're the cleanup crew that are being introduced. But we saw a decrease in retention of macrophages and a decrease in proliferation and an increase in macrophage death and clearance of the apoptosis cells. And then through the single-cell RNA-sequencing, we were able to look at the different macrophage subsets. We had resident macrophages, Trem2hi metabolic macrophages, and MHCIIhi inflammatory macrophages. Kathryn Moore:          We were able to look at their transcriptomes and say, "Which of these subsets are most likely to be performing those functions that we saw before?" And that was fun because that was like piecing together a puzzle. And what we saw, what it leads us to believe is that the Trem2hi metabolic macrophages are the ones that are undergoing aptosis. They have an increase in aptosis genes and eat-me signals and the MHCIIhi, having an increase in athoscoertic genes like mirTK that will help them clear the dying cells and the MHCIIhi macrophages also have decreased markers of proliferation. So although we used to think about macrophages as this one big pool, now we're able to say that these different subsets are performing different functions. And to me that's really exciting. Cindy St. Hilaire:        Oh, that is exciting. And it's also extremely complicated because I was having enough trouble with just the two types of macrophages of a couple of years ago. The study showed that inhibiting this miR-33 using these anti-miR-33 oligos, and you're just kind of injecting oligos against it. And you're doing this in mice with established atherosclerosis. This helped to alter these monocyte and macrophage populations in the plaque itself. Cindy St. Hilaire:        Do you think a function of the success of this study and essentially this therapy in the mouse is really dependent on the fact that it's targeting these circulating cells that are then going to the plaque? And I guess part of that question is, do you think part of this is because it's a circulating cell that can take it up, and then change and be delivered to the location it's going to, as opposed to that oligo targeting the plaque itself and the cells that are already residing there. Do you have any sense of that? Kathryn Moore:          So it's interesting because one of the things that we did with our single-cell RNA-seq was to look at all immune cells in the plaque and say, "How many miR-33 target genes are changing in the ones from the treated mice?" And in the monocytes, you see very little change in miR-33 target genes. And that's consistent with what we know from Regulus Therapeutics who designed the anti-miR-33 antisense oligonucleotides. So we don't think that the ASO are being taken up in the circulation. I think they're actually being taken up by the macrophages in the plaque. And one of the great things about trying to target macrophages is they're very phagocytic. So they're going to be the ones that take up these ASOs, and the single-cell really allowed us to see whether it was just macrophages that were being affected or whether there were other immune cell populations that also seemed to have miR-33 induce changes. And of course it's hard from the single-cell to infer whether this is direct or indirect. Cindy St. Hilaire:         Yeah. Kathryn Moore:          But it seemed as if T-cells also were targeted by the anti-miR-33, definitely macrophages. We saw some changes in dendritic cells, very little changes in K cells, for example. And no changes in monocytes. And so it also begins to tell us how many different cell types are being affected and who's driving the bus when it comes to these changes. But by far the most miR-33 target genes change were the macrophage populations. And I think that's really due to their phagocytic ability. Cindy St. Hilaire:         So I know there's a great divergence generally in microRNAs between mice and humans or really any species, but there are homologs to this in humans. What is the same and what is different between, I guess, this particular targeting micro RNA or what we know about it in mice and humans? Kathryn Moore:          So mice have only one copy of miR-33, whereas humans and monkeys have two copies but those two copies are very similar in sequence. They differ only by two nucleotides. So you can use the same antisense oligonucleotides to target in mice and in non-human primates, for example. It's never been tried in humans. Cindy St. Hilaire:         Yeah, of course. Not yet. Kathryn Moore:          But it has been tried in monkeys, and we were able to effectively inhibit both miR-33a and miR-33b in the non-human primates. But the different variants of miR-33 have different transcriptional regulation. So they're induced under different conditions. And I think that's one way that mice and humans will really differ-the conditions where you'd have high levels of miR-33 will be different. Cindy St. Hilaire:         Got it. Yeah. And the mice has that in the SREBP gene and humans. Kathryn Moore:          And miR-33a is an SREBP-2 gene, which is SREBF2. And in humans there's an additional copy, which is SREBF. So it's in both of the SREBP genes in humans. Cindy St. Hilaire:         Interesting. So I wonder, we need to ask the evolutionary biologist. Did they segregate together? I mean, I guess they must have. That's really interesting. That's cool. Kathryn Moore:          One of the things that I love about miR-33 is that the SREBP-2 gene is turned on when cholesterol levels are low and it acts to increase the pathways involved in cholesterol synthesis and uptake. And miR-33 is transcribed at the same time. And what it does is it blocks the exits for cholesterol from the cell and from the body. And so it's just this hidden gem in the locus that sort of boosts SREBP-2 function. Cindy St. Hilaire:         Its amazing stuff works out like that. I love it. So if we were going to leverage this inflammation resolution as atherosclerotic therapy, wherein the continuum of the disease, should we target? You know, we have obviously atherosclerotic plaque does not happen overnight. Teenagers can even have evidence of a fatty streak. If we were going to leverage antisense oligos as therapy, especially specifically against miR-33, where do you think would be a good place to target? And do we know, or have the kind of imaging capabilities to maybe identify that window right now in patients? Kathryn Moore:          That's an interesting question. So lipid-lowering therapies will remain the first line of treatment for atherosclerosis, but lipid-lowering alone is insufficient to regress the plaque. It can stabilize plaques, but it doesn't really cause them to shrink. And when you think about the patient population that presents with cardiovascular disease, it's adults, for the most part. These are people in their fifties and sixties, and we've missed the chance to stop the early events. And so those are the majority of the people that are being treated. And I think there is room there to treat inflammation at the same time in the hopes of tipping that balance between pro-inflammatory events and then inflammation resolution. So we know surprisingly little about that tipping point. And now I think when miR-33 inhibition is fascinating in that it can affect both lipid metabolism and inflammation. And so I think that as an add-on therapy with lipid-lowering, it would be interesting, but of course, I'm not ready. Cindy St. Hilaire:         We're not there yet. Cindy St. Hilaire:         So I guess what's next for this line of research? What are kind of the next questions that the single-cell RNA-seq discovered for you? Was there anything kind of surprising or really exciting that you want to pursue next? Kathryn Moore:          One of the things that I thought was really interesting was that the different macrophage subpopulations had different miR-33 target genes being de repressed. And that's probably not surprising, but I didn't initially think that would happen, but of course, the subpopulations are identified based on their unique transcriptomes. So they're not all the same, which means that they'll have different levels of miR-33, and they'll have different levels of the miR-33 target genes. And so Abca1, which we think about all the time as a miR-33 target gene that's involved in cholesterol efflux, it went up in Trem2hi macrophages and the resident macrophage population, but not in the MHCIIhi. The target genes and the MHCIIhi were different than the other two populations. And I think this now gives us a chance to sort that out. Kathryn Moore:          And some of the targets in the MHCIIhi macrophages were ones that are involved in chromatin reorganization- Cindy St. Hilaire:         Oh, interesting. Kathryn Moore:          ... and inscriptional regulation. And when I looked across the other subsets, I could see that common pattern in T-cells and B-cells that were changing. And I think that's one way that miR-33 could have a broad impact. MiR-33 is a little bit of a unique microRNA. It has a very potent impact on these pathways. Other microRNAs often can change gene expression by 10 to 20%, but miR-33, when we inhibit it, we see really powerful effects. And I think that if it is involved in targeting genes that mediate chromogenic reorganization or transcriptional complex formation, that gives us a hint of how it could be having additional impact. Cindy St. Hilaire:         That's really cool. And this was an absolutely beautiful story, not only in kind of dissecting out the mechanisms at play, but you know, those beautiful tisney plots and the nice graphics of the single-cell stuff. Kathryn Moore:          The first author of the paper, Milessa Afonso, is a postdoc that just left the lab, and she worked so hard on this and did such a beautiful job. Cindy St. Hilaire:         Well, it's a wonderful story and I'm really happy we were able to publish it. So, Dr Moore, thank you so much for joining me today. Kathryn Moore:                      My pleasure. Thank you. Cindy St. Hilaire:        That's it for the highlights from the April 2nd and 16th issues of Circulation Research. Thank you so much for listening. Please check out the CircRes Facebook page and follow us on Twitter and Instagram with the handle @circres and hashtag DiscoverCircRes. Thank you to our guest, Dr Kathryn Moore. This podcast is produced by Ashara Ratnayaka, edited by Melissa Stoner, and supported by the Editorial Team of Circulation Research. Copy text for the highlighted articles was provided by Ruth Williams. I'm your host, Dr Cindy St. Hilaire and this is Discover CircRes, your on-the-go source for the most exciting discoveries in basic cardiovascular research.    

Gary Null Show Notes 02/08/21 CDC: Over 500 Deaths Now Following mRNA Experimental Injections – “Vaccine Hesitancy” Increasing Invasive Insects and Diseases Are Killing Our Forests How ExxonMobil Uses Divide and Rule to Get Its Way in South America How the Pandemic Left the $25 Billion Hudson Yards Eerily Deserted Bayer makes new $2 billion plan to head off future Roundup cancer claims Billionaire capitalists are designing humanity’s future. Don’t let them Citizen scientists are filling research gaps created by the pandemic After COVID, Davos Moves to The “Great Reset” COVID-19: Here’s why global travel is unlikely to resume ‘till 2024     The Acute and Chronic Cognitive Effects of a Sage Extract: A Randomized, Placebo Controlled Study in Healthy Humans Northumbria University (UK), January 31, 2021 The sage (Salvia) plant contains a host of terpenes and phenolics which interact with mechanisms pertinent to brain function and improve aspects of cognitive performance. However, previous studies in humans have looked at these phytochemicals in isolation and following acute consumption only. A preclinical in vivo study in rodents, however, has demonstrated improved cognitive outcomes following 2-week consumption of CogniviaTM, a proprietary extract of both Salvia officinalis polyphenols and Salvia lavandulaefolia terpenoids, suggesting that a combination of phytochemicals from sage might be more efficacious over a longer period of time. The current study investigated the impact of this sage combination on cognitive functions in humans with acute and chronic outcomes. Participants (n = 94, 25 M, 69 F, 30–60 years old) took part in this randomised, double-blind, placebo-controlled, parallel groups design where a comprehensive array of cognitions were assessed 120- and 240-min post-dose acutely and following 29-day supplementation with either 600 mg of the sage combination or placebo. A consistent, significant benefit of the sage combination was observed throughout working memory and accuracy task outcome measures (specifically on the Corsi Blocks, Numeric Working Memory, and Name to Face Recall tasks) both acutely (i.e., changes within day 1 and day 29) and chronically (i.e., changes between day 1 to day 29). These results fall slightly outside of those reported previously with single Salvia administration, and therefore, a follow-up study with the single and combined extracts is required to confirm how these effects differ within the same cohort. In conclusion, we have observed a consistent significant benefit of a sage combination intervention  in healthy adult humans on working memory and accuracy of performance cognitive domains. This significant activity was observed both acutely (after just 2 h following consumption) and chronically (after 29 days of administration). The pattern and magnitude of significance points towards an increase in product efficacy over the administration period and, taken together, suggests that future trials should focus on disentangling the working and spatial memory effects of this intervention in humans with an extended timeframe of perhaps several months. Validating the CaMKII mechanism in humans would also be advantageous. Blink! The link between aerobic fitness and cognition University of Tsukuba (Japan), February 3, 2021 Although exercise is known to enhance cognitive function and improve mental health, the neurological mechanisms of this link are unknown. Now, researchers from Japan have found evidence of the missing link between aerobic fitness and cognitive function. In a study published in Medicine & Science in Sports & Exercise, researchers from the University of Tsukuba revealed that spontaneous eye blink rate (sEBR), which reflects activity of the dopamine system, could be used to understand the connection between cognitive function and aerobic fitness. The dopaminergic system is known to be involved in physical activity and exercise, and previous researchers have proposed that exercise-induced changes in cognitive function might be mediated by activity in the dopaminergic system. However, a marker of activity in this system was needed to test this hypothesis, something the researchers at the University of Tsukuba aimed to address. “The dopaminergic system is associated with both executive function and motivated behavior, including physical activity,” says first author of the study Ryuta Kuwamizu. “We used sEBR as a non-invasive measure of dopaminergic system function to test whether it could be the missing link between aerobic fitness and cognitive function.” To do this, the researchers asked healthy participants to undergo a measure of sEBR, a test of cognitive function, and an aerobic fitness test. They also measured brain activity during the cognitive task using functional near-infrared spectroscopy. “As expected, we found significant correlations between aerobic fitness, cognitive function, and sEBR,” explains Professor Hideaki Soya, senior author. “When we examined these relationships further, we found that the connection between higher aerobic fitness and enhanced cognitive function was mediated in part by dopaminergic regulation.” Furthermore, activity in the left dorsolateral prefrontal cortex (l-DLPFC) during the cognitive task was the same or lower in participants with higher sEBR compared with lower sEBR, even though those with higher sEBR appeared to have greater executive function, and thus higher neural efficiency. “Although previous studies have indicated that aerobic fitness and cognitive function are correlated, this is the first to provide a neuromodulatory basis for this connection in humans. Our data indicate that dopamine has an essential role in linking aerobic fitness and cognition,” says first author Kuwamizu. Given that neural efficiency in the l-DLPFC is a known characteristic of the dopaminergic system that has been observed in individuals with higher fitness and executive function, it is possible that neural efficiency in this region partially mediates the association between aerobic fitness and executive function. Furthermore, physical inactivity may be related to dopaminergic dysfunction. This information provides new directions for research regarding how fitness affects the brain, which may lead to improved exercise regimens. For instance, exercise that specifically focuses on improving dopaminergic function may particularly boost motivation, mood, and mental function. Vegan diet better for weight loss and cholesterol control than Mediterranean diet Physicians Committee for Responsible Medicine, February 5, 2021 A vegan diet is more effective for weight loss than a Mediterranean diet, according to a groundbreaking new study that compared the diets head to head. The randomized crossover trial, which was published in the Journal of the American College of Nutrition, found that a low-fat vegan diet has better outcomes for weight, body composition, insulin sensitivity, and cholesterol levels, compared with a Mediterranean diet. The study randomly assigned participants–who were overweight and had no history of diabetes–to a vegan diet or a Mediterranean diet in a 1:1 ratio. For 16 weeks, half of the participants started with a low-fat vegan diet that eliminated animal products and focused on fruits, vegetables, whole grains, and legumes. The other half started with the Mediterranean diet, which followed the PREDIMED protocol, which focuses on fruits, vegetables, legumes, fish, low-fat dairy, and extra virgin olive oil, while limiting or avoiding red meat and saturated fats. Neither group had a calorie limit, and participants did not change exercise or medication routines, unless directed by their personal doctors. As part of the crossover design, participants then went back to their baseline diets for a four-week washout period before switching to the opposite group for an additional 16 weeks. The study found that within 16 weeks on each diet: Participants lost an average of 6 kilograms (or about 13 pounds) on the vegan diet, compared with no mean change on the Mediterranean diet. Participants lost 3.4 kg (about 7.5 pounds) more fat mass on the vegan diet. Participants saw a greater reduction in visceral fat by 315 cm3 on the vegan diet. The vegan diet decreased total and LDL cholesterol levels by 18.7 mg/dL and 15.3 mg/dL, respectively, while there were no significant cholesterol changes on the Mediterranean diet. Blood pressure decreased on both diets, but more on the Mediterranean diet (6.0 mm Hg, compared to 3.2 mmHg on the vegan diet). “Previous studies have suggested that both Mediterranean and vegan diets improve body weight and cardiometabolic risk factors, but until now, their relative efficacy had not been compared in a randomized trial,” says study author Hana Kahleova, MD, PhD, director of clinical research for the Physicians Committee. “We decided to test the diets head to head and found that a vegan diet is more effective for both improving health markers and boosting weight loss.” The authors note that the vegan diet likely led to weight loss, because it was associated with a reduction in calorie intake, increase in fiber intake, decrease in fat consumption, and decrease in saturated fat consumption. “While many people think of the Mediterranean diet as one of the best ways to lose weight, the diet actually crashed and burned when we put it to the test,” says study author Neal Barnard, MD, president of the Physicians Committee. “In a randomized, controlled trial, the Mediterranean diet caused no weight loss at all. The problem seems to be the inclusion of fatty fish, dairy products, and oils. In contrast, a low-fat vegan diet caused significant and consistent weight loss.” “If your goal is to lose weight or get healthy in 2021, choosing a plant-based diet is a great way to achieve your resolution,” adds Dr. Kahleova. Study finds childhood diet has lifelong impact University of California at Riverside, February 3, 2021 Eating too much fat and sugar as a child can alter your microbiome for life, even if you later learn to eat healthier, a new study in mice suggests. The study by UC Riverside researchers is one of the first to show a significant decrease in the total number and diversity of gut bacteria in mature mice fed an unhealthy diet as juveniles. “We studied mice, but the effect we observed is equivalent to kids having a Western diet, high in fat and sugar and their gut microbiome still being affected up to six years after puberty,” explained UCR evolutionary physiologist Theodore Garland. A paper describing the study has recently been published in the Journal of Experimental Biology. The microbiome refers to all the bacteria as well as fungi, parasites, and viruses that live on and inside a human or animal. Most of these microorganisms are found in the intestines, and most of them are helpful, stimulating the immune system, breaking down food and helping synthesize key vitamins. In a healthy body, there is a balance of pathogenic and beneficial organisms. However, if the balance is disturbed, either through the use of antibiotics, illness, or unhealthy diet, the body could become susceptible to disease. In this study, Garland’s team looked for impacts on the microbiome after dividing their mice into four groups: half fed the standard, ‘healthy’ diet, half fed the less healthy ‘Western’ diet, half with access to a running wheel for exercise, and half without. After three weeks spent on these diets, all mice were returned to a standard diet and no exercise, which is normally how mice are kept in a laboratory. At the 14-week mark, the team examined the diversity and abundance of bacteria in the animals. They found that the quantity of bacteria such as Muribaculum intestinale was significantly reduced in the Western diet group. This type of bacteria is involved in carbohydrate metabolism. Analysis also showed that the gut bacteria are sensitive to the amount of exercise the mice got. Muribaculum bacteria increased in mice fed a standard diet who had access to a running wheel and decreased in mice on a high-fat diet whether they had exercise or not. Researchers believe this species of bacteria, and the family of bacteria that it belongs to, might influence the amount of energy available to its host. Research continues into other functions that this type of bacteria may have. One other effect of note was the increase in a highly similar bacteria species that were enriched after five weeks of treadmill training in a study by other researchers, suggesting that exercise alone may increase its presence. Overall, the UCR researchers found that early-life Western diet had more long-lasting effects on the microbiome than did early-life exercise. Garland’s team would like to repeat this experiment and take samples at additional points in time, to better understand when the changes in mouse microbiomes first appear, and whether they extend into even later phases of life. Regardless of when the effects first appear, however, the researchers say it’s significant that they were observed so long after changing the diet, and then changing it back. The takeaway, Garland said, is essentially, “You are not only what you eat, but what you ate as a child!” Turns Out Maple Syrup Is Anticarcinogenic Kindai University (Japan), February 2, 2021 Darker coloured syrup is suggested as healthier than lightly coloured syrup. Maple syrup is a classic natural sweetener that has been making a comeback recently as an alternative to refined sugar. The syrup is tapped from different species of maple trees, with the Canadian province of Quebec being a top producer. Along with a rich and complex flavor, maple syrup offers an abundance of amino acids, manganese and zinc, as well as phenolic compounds, including lignans and coumarin. A new study called “Inhibitory effect of maple syrup on the cell growth and invasion of human colorectal cancer cells” was guided by Dr. Tetsushi Yamamoto, a molecular and cell biologist from the Faculty of Pharmacy at Kindai University in Osaka, Japan. The research evaluated the effect of three different types of maple syrup. The main objective was to identify if maple syrup could be used as a phytomedicine within cancer treatment. Dr. Yamamoto and his research team classified the different types of maple syrup according to colour, as well as cell proliferation, and migration and invasion capability for colorectal cell cancer (CRC). Results showed that CRC cells administered maple syrup showed lower rates of carcinogenic cells when compared with cells administered only sucrose. Additionally, the study suggests that maple syrup should not only be classified by its sugar content, but also according to its nutritional and physiochemical components. This study showed that maple syrup, particularly when coloured darker, might be suitable as a phytomedicine, which may offer a more gentle alternative to traditional chemotherapy. This outstanding revelation is in contrast to other studies, which support the idea that sugar perpetuates cancer and other chronic diseases. However, this disparity might concern diverse types of sugar, including sucrose, fructose and glucose. Also, sugar behaves differently when consumed in diverse nutritional contexts. In this context, researchers experimented with different sucrose concentrations, ranging from 0.1% to 10%. Results showed that only maple syrup with a 10% concentration of sucrose inhibited colorectal cancer cell growth. The study explained that this is because higher concentrations might have cytotoxic effects due to high osmotic pressure. Brains are more plastic than we thought McGill University, January 31, 2021 Practice might not always make perfect, but it’s essential for learning a sport or a musical instrument. It’s also the basis of brain training, an approach that holds potential as a non-invasive therapy to overcome disabilities caused by neurological disease or trauma. Research at the Montreal Neurological Institute and Hospital of McGill University (The Neuro) has shown just how adaptive the brain can be, knowledge that could one day be applied to recovery from conditions such as stroke. Researchers Dave Liu and Christopher Pack have demonstrated that practice can change the way that the brain uses sensory information. In particular, they showed that, depending on the type of training done beforehand, a part of the brain called the area middle temporal (MT) can be either critical for visual perception, or not important at all. Previous research has shown the area MT is involved in visual motion perception. Damage to area MT causes “motion blindness”, in which patients have clear vision for stationary objects but are unable to see motion. Such deficits are somewhat mysterious, because it is well known that area MT is just one of many brain regions involved in visual motion perception. This suggests that other pathways might be able to compensate in the absence of area MT. Most studies have examined the function of area MT using a task in which subjects view small dots moving across a screen and indicate how they see the dots moving, because this has been proven to activate area MT. To determine how crucial MT really was for this task, Liu and Pack used a simple trick: They replaced the moving dots with moving lines, which are known to stimulate areas outside area MT more effectively. Surprisingly, subjects who practiced this task were able to perceive visual motion perfectly even when area MT was temporarily inactivated. On the other hand, subjects who practiced with moving dots exhibited motion blindness when MT was temporarily deactivated. The motion blindness persisted even when the stimulus was switched back to the moving lines, indicating that the effects of practice were very difficult to undo. Indeed, the effects of practice with the moving dot stimuli were detectable for weeks afterwards. The key lesson for brain training is that small differences in the training regimen can lead to profoundly different changes in the brain. This has potential for future clinical use. Stroke patients, for example, often lose their vision as a result of brain damage caused by lack of blood flow to brain cells. With the correct training stimulus, one day these patients could retrain their brains to use different regions for vision that were not damaged by the stroke. “Years of basic research have given us a fairly detailed picture of the parts of the brain responsible for vision,” says Christopher Pack, the paper’s senior author. “Individual parts of the cortex are exquisitely sensitive to specific visual features – colors, lines, shapes, motion – so it’s exciting that we might be able to build this knowledge into protocols that aim to increase or decrease the involvement of different brain regions in conscious visual perception, according to the needs of the subject. This is something we’re starting to work on now.” Higher Fiber Intake May Improve Lung Function   University of Nebraska, January 28, 2021 Eating a fiber-rich diet may help protect you against lung disease, a new study suggests. “Lung disease is an important public health problem, so it’s important to identify modifiable risk factors for prevention,” study author Corrine Hanson, an associate professor of medical nutrition at the University of Nebraska Medical Center, said in a journal news release. “However, beyond smoking very few preventative strategies have been identified. Increasing fiber intake may be a practical and effective way for people to have an impact on their risk of lung disease,” she added. The findings were published recently in the Annals of the American Thoracic Society. Researchers looked at federal government data from almost 2,000 American adults. They were between 40 and 79 years old. The researchers found that 68 percent of those who had the highest fiber consumption (about 18 grams or more daily) had normal lung function compared to 50 percent for those with the lowest fiber intake. And, only 15 percent of those who ate a lot of fiber had airway restriction, but 30 percent of those with the lowest fiber intake did, the study showed. People with the highest fiber consumption also did better on two important breathing tests. They had larger lung capacity and could exhale more air in one second, the study said. Although the study found a link between fiber consumption and better lung health, it wasn’t designed to prove a cause-and-effect relationship. But, if the findings are confirmed in future studies, public health campaigns may one day “target diet and fiber as safe and inexpensive ways of preventing lung disease,” Hanson said. Previous research has suggested a diet high in fiber protects against heart disease and diabetes, and that fiber reduces inflammation in the body, the researchers said.

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.04.368571v1?rss=1 Authors: Blackwell, K. T., Miningou, N. Abstract: Long lasting long-term potentiation (L-LTP) is a cellular mechanism of learning and memory storage. Studies have demonstrated a requirement for the extracellular signal-regulated kinase (ERK) activation in L-LTP produced by a diversity of temporal stimulation patterns. Multiple signaling pathways converge to activate ERK, with different pathways being required for different stimulation patterns. We addressed the critical questions of whether maximal activation of ERK requires multiple pathways, and whether different temporal patterns select different signaling pathways for ERK activation. We developed a computational model of five signaling pathways (including two novel pathways) leading to ERK activation during L-LTP. Simulations show that calcium and cAMP work synergistically to activate ERK, and that stimuli given with large inter-trial intervals activate more ERK than shorter intervals, a temporal sensitivity similar to PKA but contrary to CaMKII. These results suggest that signaling pathways with different temporal sensitivity facilitate ERK activation to diversity of temporal patterns. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.25.354241v1?rss=1 Authors: Ozden, C., Sloutsky, R., Santos, N., Agnello, E., Gaubitz, C., Esposito, E. A., Lapinskas, E., Kelch, B. A., Garman, S. C., Hayashi, Y., Stratton, M. Abstract: Ca2+/calmodulin dependent protein kinase II (CaMKII) is a signaling protein that is required for successful long-term memory formation. Ca2+/CaM activates CaMKII by binding to its regulatory segment, thereby making the substrate binding pocket available. One exceptional feature of this kinase is that two binding partners have been shown persistently activate CaMKII after the Ca2+ stimulus dissipates. The molecular details of this phenomenon are unclear. Despite having a large variety of interaction partners, the specificity of CaMKII has not been structurally well-characterized. To this end, we solved X-ray crystal structures of the CaMKII kinase domain bound to four different binding partners: a peptide substrate, a substrate/activator, a substrate/binding partner, and an inhibitor (AMPA-type glutamate receptor, NMDA-type glutamate receptor, Tiam1, and Densin-180). We show that all four binding partners use similar interactions to bind across the substrate binding pocket of the CaMKII active site. We generated a sequence alignment based on our structural observations, which revealed conserved interactions across these binding partners. The structures presented here shed much-needed light on the interaction between CaMKII and its binding partners. These observations will be crucial in guiding further biological experiments. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.08.331827v1?rss=1 Authors: Jones, S. K., Rha, J., Kim, S., Morris, K. J., Omotade, O. F., Moberg, K. H., Myers, K. R., Corbett, A. H. Abstract: ZC3H14 (Zinc finger CysCysCysHis domain-containing protein 14), an evolutionarily conserved member of a class of tandem zinc finger (CCCH) polyadenosine (polyA) RNA binding proteins, is associated with a form of heritable, nonsyndromic autosomal recessive intellectual disability. Previous studies of a loss of function mouse model, Zc3h14{triangleup}ex13/{triangleup}ex13, provide evidence that ZC3H14 is essential for proper brain function, specifically for working memory. To expand on these findings, we analyzed the dendrites and dendritic spines of hippocampal neurons from Zc3h14{triangleup}ex13/{triangleup}ex13 mice, both in situ and in vitro. These studies reveal that loss of ZC3H14 is associated with a decrease in total spine density in hippocampal neurons in vitro as well as in the dentate gyrus of 5-month old mice analyzed in situ. This reduction in spine density in vitro results from a decrease in the number of mushroom-shaped spines, which is rescued by exogenous expression of ZC3H14. We next performed biochemical analyses of synaptosomes prepared from whole wild-type and Zc3h14{triangleup}ex13/{triangleup}ex13 mouse brains to determine if there are changes in steady state levels of postsynaptic proteins upon loss of ZC3H14. We found that ZC3H14 is present within synaptosomes and that a crucial postsynaptic protein, CaMKII, is significantly increased in these synaptosomal fractions upon loss of ZC3H14. Together, these results demonstrate that ZC3H14 is necessary for proper dendritic spine density in cultured hippocampal neurons and in some regions of the mouse brain. These findings provide insight into how a ubiquitously expressed RNA binding protein leads to neuronal-specific defects that result in brain dysfunction. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.28.310474v1?rss=1 Authors: Leurs, U., Klein, A. B., McSpadden, E. D., Griem-Krey, N., Solbak, S. M., Houlton, J., Villumsen, I. S., Vogensen, S. B., Hamborg, L., Gauger, S. J., Palmelund, L. B., Larsen, A. S. G., Shehata, M. A., Kelstrup, C. D., Olsen, J. V., Bach, A., Burnie, R. O., Kerr, D. S., Gowing, E. K., Teurlings, S. M. W., Chi, C. C., Gee, C. L., Frolund, B., Kornum, B. R., van Woerden, G. M., Clausen, R. P., Kuriyan, J., Clarkson, A. N., Wellendorph, P. Abstract: Ca2+/calmodulin-dependent protein kinase II alpha (CaMKII) is an abundant neuronal signaling protein involved in synaptic plasticity and memory formation1,2. The central hub domain regulates the activity of CaMKII by organizing the holoenzyme complex into functional oligomers3-6. Recent findings have suggested that the hub is also an allosteric determinant of kinase activity7, and is thus an emerging target for therapies to correct CaMKII dysregulation8,9. However, pharmacological modulation of the hub domain has never been demonstrated. Here we show that stabilization of the CaMKII hub domain confers neuroprotection. By combining photoaffinity labeling and chemical proteomics using small molecule analogs of the natural metabolite {gamma}-hydroxybutyrate (GHB)10, we reveal that CaMKII is the selective target for GHB. We further find that these GHB analogs bind to the hub interior by solving a 2.2 [A] crystal structure of CaMKII with bound ligand. Using differential scanning fluorimetry, we show that binding of ligands to the hub interior increases the thermal stability of hub oligomers in a concentration-dependent manner. Moreover, we demonstrate the functional significance of this hub stabilization by showing substantial neuroprotective effects in cellular excitotoxicity assays and in a mouse model of cerebral ischemia. Together, our results reveal that CaMKII hub stabilization is the mechanism by which GHB provides endogenous neuroprotection and that small-molecule CaMKII-selective ligands have therapeutic potential. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.26.314856v1?rss=1 Authors: Smolen, P. D., Baxter, D. A., Byrne, J. H. Abstract: A fundamental problem in neuroscience is how memories are maintained from days to a lifetime, given turnover of proteins that underlie expression of long-term synaptic potentiation (LTP) or tag synapses as eligible for LTP. One likely solution relies on synaptic positive feedback loops, prominently including persistent activation of Ca2+/calmodulin kinase II (CaMKII) and self-activated synthesis of protein kinase M {zeta} (PKM{zeta}). Recent studies also suggest positive feedback based on recurrent synaptic reactivation within neuron assemblies, or engrams, is necessary to maintain memories. The relative importance of these feedback mechanisms is controversial. To explore the likelihood that each mechanism is necessary or sufficient to maintain memory, we simulated maintenance of LTP with a simplified model incorporating persistent kinase activation, synaptic tagging, and preferential reactivation of strong synapses, and analyzed implications of recent data. We simulated three model variants, each maintaining LTP with one feedback loop: autonomous, self-activated PKM{zeta} synthesis (model variant I); self-activated CamKII (model variant II); and recurrent reactivation of strengthened synapses (model variant III). Variant I requires and predicts that, for successful maintenance, PKM{zeta} must contribute to synaptic tagging. Variant II maintains LTP and suggests persistent CaMKII activation could maintain PKM{zeta} activity, a feedforward interaction not previously considered. However we note data challenging this feedback loop. In Variant III synaptic reactivation drives, and thus predicts, recurrent or persistent activity elevations of CamKII and other necessary kinases, plausibly contributing to empirically persistent elevation of PKM{zeta} levels. Reactivation is thus predicted to sustain recurrent rounds of synaptic tagging and incorporation of plasticity-related proteins. We also suggest (model variant IV) that synaptic reactivation and autonomous kinase activation could synergistically maintain LTP. We propose experiments that could discriminate these maintenance mechanisms. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.19.304550v1?rss=1 Authors: Malfatti, T., Ciralli, B., Hilscher, M. M., Edwards, S. J., Kullander, K., Leao, R. N., Leao, K. E. Abstract: The dorsal cochlear nucleus (DCN) is the first auditory region that integrates somatosensory and auditory inputs. The region is of particular interest for auditory research due to the large incidence of somatic tinnitus and increased aberrant activity in other forms of tinnitus. Yet, the lack of useful genetic markers for in vivo manipulations hinders the elucidation of the DCN contribution to tinnitus pathophysiology. In this work, we assessed whether adeno-associated viral vectors (AAV) containing the calcium/calmodulin-dependent protein kinase 2 alpha (CaMKII) promoter and our mouse line of nicotinic acetylcholine receptor alpha 2 subunit (Chrna2)-Cre can be used to target specific DCN populations. The CaMKII promoter is usually applied in studies of principal neurons of neo and paleocortex while Chrna2-cre mice express Cre recombinase in cortical dendrite inhibiting interneurons. We found that CaMKII cannot be used to specifically target excitatory fusiform DCN neurons. EYFP expression driven by the CaMKII promoter was stronger in the fusiform layer but labelled cells showed a diverse morphology indicating that they belong to different classes of DCN neurons. Light stimulation after driving Channelrhodopsin2 (ChR2) by the CaMKII promoter generated spikes in some units but firing rate decreased when light stimulation coincide with sound presentation. Expression and activation of eArch3.0 (CaMKII driven) in the DCN produced spike inhibition in some units but, most importantly, sound-driven spikes were delayed by concomitant light stimulation. We explored the existence of Cre+ cells in the DCN of Chrna2-Cre mice by hydrogel embedding technique (CLARITY). There were almost no Cre+ cell bodies in the DCN; however, we observed profuse projections arising from the ventral cochlear nucleus (VCN). Anterograde labeling Cre dependent AAV injected in the VCN revealed two main projections: one arising in the ipsilateral superior olive and the contralateral medial nucleus of the trapezoid body (bushy cells) and a second bundle terminating in the DCN, suggesting the latter to be excitatory Chrna2+ T-stellate cells). Stimulating ChR2 expressing terminals (light applied on the DCN) of VCN Chrna2+ cells increased firing of sound responding and nonresponding DCN units. This work shows that molecular tools intensively used in cortical studies may be useful for manipulating the DCN especially in tinnitus studies. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.19.258269v1?rss=1 Authors: Stein, I. S., Park, D. K., Claiborne, N., Zito, K. Abstract: Experience-dependent refinement of neuronal connections is critically important for brain development and learning. Here we show that ion flow-independent NMDAR signaling is required for the long-term dendritic spine growth that is a vital component of brain circuit plasticity. We found that inhibition of p38 MAPK, shown to be downstream of non-ionotropic NMDAR signaling in LTD and spine shrinkage, blocked LTP-induced spine growth but not LTP. We hypothesized that non-ionotropic NMDAR signaling drives the cytoskeletal changes that support bidirectional spine structural plasticity. Indeed, we found that key signaling components downstream of non-ionotropic NMDAR function in LTD-induced spine shrinkage also are necessary for LTP-induced spine growth. Furthermore, NMDAR conformational signaling with coincident Ca2+ influx is sufficient to drive CaMKII-dependent long-term spine growth, even when Ca2+ is artificially driven through voltage-gated Ca2+ channels. Our results support a model in which non-ionotropic NMDAR signaling gates the bidirectional spine structural changes vital for brain plasticity. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.11.247270v1?rss=1 Authors: Cao, X., An, S., Wang, J., Zhang, X., Duan, Y., Lv, J., Wang, D., Zhang, H., Richter-Levin, G. Abstract: Impaired fear extinction is one of the hallmark symptoms of post-traumatic stress disorder (PTSD). The roles of CaMKII have been not extensively studied in fear extinction and LTD. Here, we found PTSD susceptible mice exhibited significant up-regulation of CaMKII in the lateral amygdala (LA). Consistently, increasing CaMKII in LA profoundly not only caused PTSD-like symptoms such as impaired fear extinction and anxiety-like behaviors, but also attenuated NMDAR-dependent LTD at thalamo-LA synapses, reduced GluA1-Ser845/Ser831 dephosphorylation and AMPAR internalization. Suppressing the elevated CaMKII to normal level could completely reverse both PTSD-like symptoms and the impairments in LTD, GluA1-Ser845/Ser831 dephosphorylation, and AMPAR internalization. Intriguingly, deficits in AMPAR internalization and GluA1-Ser845/Ser831 dephosphorylation were detected not only after impaired fear extinction, but also after attenuated LTD Our results demonstrate for the first time GluA1-Ser845/Ser831 dephosphorylation and AMPAR internalization are molecular links between LTD and fear extinction, and suggest CaMKII may be a potential molecular determinant of PTSD. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.06.08.136762v1?rss=1 Authors: Park, P., Georgiou, J., Sanderson, T. M., Ko, K.-H., Kang, H., Kim, J.-i., Bradley, C. A., Bortolotto, Z. A., Zhuo, M., Kaang, B.-K., Collingridge, G. L. Abstract: Long-term potentiation (LTP) at hippocampal CA1 synapses can be expressed by an increase either in the number (N) of AMPA (-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors or in their single channel conductance ({gamma}). Here we have established how these distinct synaptic processes contribute to the expression of LTP in hippocampal slices obtained from young adult rodents. LTP induced by compressed theta burst stimulation (TBS), with a 10 s inter-episode interval, involved purely an increase in N (LTPN). In contrast, either a spaced TBS, with a 10 min inter-episode interval, or a single TBS, delivered when PKA was activated, resulted in LTP that was associated with a transient increase in {gamma} (LTP{gamma}). This {gamma} increase was due to the insertion of calcium-permeable (CP)-AMPA receptors. Activation of CaMKII was necessary and sufficient for LTPN whilst PKA was additionally required for LTP{gamma}. Thus, two mechanistically distinct forms of LTP co-exist at these synapses. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.30.124958v1?rss=1 Authors: Acuna-Hinrichsen, F., Covarrubias-Pinto, A., Ishizuka, Y., Stolzenbach, M. F., Martin, C., Salazar, P., Castro, M. A., Bramham, C., Otth, C. Abstract: Herpes simplex virus type 1 (HSV-1) is a widespread neurotropic virus. The primary infection in facial epithelium leads to retrograde axonal transport to the central nervous system (CNS) where it establishes latency. Under stressful conditions, the virus reactivates, and new progeny is transported anterogradely to the primary site of infection. In late stages of neuronal infection, axonal damage is known to occur. However, the impact of HSV-1 infection on morphology and functional integrity at earlier stages of infection in neuronal dendrites is unknown. Previously, we demonstrated that acute HSV-1 infection in neuronal cell lines selectively enhances the expression of Arc protein - a major regulator of long-term synaptic plasticity and memory consolidation, known for being a protein-interaction hub in the postsynaptic dendritic compartment. Thus, HSV-1 induced Arc may alter the functionality of the infected neurons having an impact on dendritic spine dynamics. In this study we demonstrated that HSV-1 infection causes structural disassembly and functional deregulation in cultured cortical neurons, through protein homeostasis alteration with intracellular accumulation of Arc, and decreased expression of spine scaffolding-like proteins such as PSD-95, Drebrin and CaMKII{beta}. Our findings reveal progressive deleterious effects of HSV-1 infection on excitatory neuronal synapse function and dendritic morphology, supporting the thesis of the infectious origin of neurodegenerative processes. Key words: HSV-1, neurotropic virus, Arc, PSD-95, Drebrin, CaMKII{beta}, dendritic spines, neuronal infection, neurodegeneration. Copy rights belong to original authors. Visit the link for more info

This month on Episode 12 of the Discover CircRes podcast, host Cindy St. Hilaire highlights three featured articles from the May 8 issue of Circulation Research and gives listeners an inside scoop of the cutting edge ideas in the May 22nd Compendium on Obesity. This episode also features an in-depth conversation with Dr Eduardo Marbán concerning COVID-19 and its effects on the heart.   Article highlights:   Roberts et al.  LYN Regulates Monocyte Heterogeneity and Lifespan Lu, et al. Acute Hyperglycemia Activates CaMKII-ROS Pathway Yan, et al. Epicardium and Atrial Cardiomyopathy Transcript Dr Cindy St. Hilaire: Hi. Welcome to Discover CircRes, the podcast of the American Heart Association's journal, Circulation Research. I'm your host, Dr Cindy St. Hilaire, from the Vascular Medicine Institute at the University of Pittsburgh. Today, I'm going to share with you articles selected from the May 8th issue of Circulation Research as well as give you a hint at the cutting-edge ideas in the May 22nd Compendium on Obesity. We'll also have discussion with Dr Eduardo Marbán from the Smidt Heart Institute at Cedar Sinai Medical Center about his Review on COVID-19 and its effects on heart. So, first the highlights. The first article I'm sharing with you is titled Deep Phenotyping by Mass Cytometry and Single Cell RNA Sequencing reveals LYN Regulated Signaling Profiles Underlying Monocyte Subset Heterogeneity and Lifespan. The first authors are Morgan Roberts and Maunish Barvalia and the corresponding author is Kenneth Harder and they're from the University of British Columbia. Monocytes can be separated into two main groups, conventional monocytes which enter tissues from the bloodstream and differentiate into macrophages, and patrolling monocytes, which developed from conventional monocytes but tend to remain in the blood vessel walls where they can scavenge cells and tissue debris. It's thought that patrolling monocytes help to prevent a range of diseases like atherosclerosis by helping to clean up the vessel walls. Studies in mice harboring genetic mutations in a gene called Nr4a1 cause mice to have less than normal numbers of patrolling monocytes. In these mice, the development of atherosclerosis is exacerbated. In addition to Nr4a1, this group has now identified another factor regulating the survival of patrolling monocytes, the tyrosine kinase LYN, L-Y-N. Genetic deficiency of LYN caused the upregulation of Nr4a1 and other genes involved in patrolling monocytes development and survival. This in turn led to the accumulation of patrolling monocytes in the blood, also in the bone marrow, spleen, and the aorta. Loss of LYN was also protective against atherosclerosis in mouse models of this disease. These results not only provide novel insights into patrolling monocyte biology, but also suggest that targeting LYN could offer novel treatments for diseases like atherosclerosis, where boosting the patrolling monocyte numbers could be beneficial. The second article I want to highlight is titled Hyperglycemia Acutely Increases Cytosolic Reactive Oxygen Species via O-linked GlcNAcylation and CaMKII Activation in Mouse Ventricular Myocytes. The first author is Shan Lu and the corresponding author is Don Bers, and they're from the University of California, Davis. Diabetes affects more than 400 million people worldwide and puts these individuals at a higher risk for developing heart failure. When heart failure does occur, the outcomes for these patients with diabetes are likely to be far worse than for individuals without the diabetic condition. Both heart failure and diabetes have been associated with excessive production of reactive oxygen species and also with increased activation of a protein kinase in the cells of the heart called CaMKII. Both ROS and CaMKII are induced by hypoglycemia, where there is an increased amount of extracellular glucose levels in the blood. This study shows that reactive oxygen species in CaMKII are causally linked. When CaMKII was inhibited or genetically deleted in mouse cardiomyocytes, high extracellular glucose levels were unable to induce reactive oxygen species production, which is what would normally occur. The team also discovered that O-GlcNAcylation post-translational modification of CaMKII is induced by the extracellular glucose and this modification is necessary for the enzyme's reactive oxygen species- boosting effects. Lastly, they found that the enzyme NADPH oxidase 2 or NOX2 was the source of this CaMKII induced reactive oxygen species. This work uncovers the molecular pathway linking hyperglycemia, cardiomyocyte-damaging reactive oxygen species production, and it helps explain why heart failure pathology is exacerbated in diabetic patients. The next article I want to share with you is Reactivation of the Epicardium at the Origin of Myocardial Fibro-Fatty Infiltration During the Atrial Cardiomyopathy. The first author is Nadine Suffee and the corresponding author is Stéphane Hatem and they're from Inserm in Montpellier, France. Fatty tissue surrounding the heart is linked to an increased risk for atrial fibrillation, which is the most common form of arrhythmia. It seems that a combination of fat cells, which are called adipocytes and the fibroblast localized within the heart's epicardium, builds up and expand into the subepicardial layers, and this is a feature that is called fibro-fatty infiltration. These fibro-fatty infiltrations cause disturbances to the electrical rhythms that regulate the heart beating. Although generally quiescent in the adult heart, epicardial cells possess the ability to proliferate and have been shown that they harbor the ability to differentiate into adipocytes and fibroblast. This team hypothesized that the epicardial cells were the source of the damaging fibro-fatty infiltrations. Sure enough, when they looked at human heart sections, they found that within the epicardial layer, there were cells that were expressing fibroblast and adipocyte progenitor cell markers. In culture, these epicardial cells with fibroblast progenitor markers could be differentiated into fibroblasts by treatment with angiotensin II and cells with the adipocyte progenitor markers could be differentiated into adipocytes by treatment with atrial natriuretic peptide. The team also showed that these epicardial fibro-fatty infiltrations occurred in a mouse model of atrial cardiomyopathy. Together this work highlights the pathogenesis of epicardial fibro-fatty infiltrations and suggest a novel model in which to study its progression to AFib. The last thing I want to share with you before we switch to our interview with Dr Marbán is that the May 22nd issue of Circulation Research is our Obesity Compendium. Obesity is a major threat to cardiovascular health worldwide. While early studies focused on body mass index as a generalized measure of obesity and focused on the BMIs relation to cardiovascular disease, studies within the last decade have now tried to more fully understand adipose tissue physiology and the overall impact of obesity on cardiovascular disease. The articles in this compendium are obesity phenotypes, diabetes and cardiovascular diseases, basic mechanisms of diabetic heart disease, leukocyte heterogeneity and adipose tissue including obesity, an eclectic cast of cellular actors orchestrates innate immune responses and the mechanisms driving obesity and the metabolic perturbation, metabolic inflammation and insulin resistance in obesity, genetic insights into the relationship between Type 2 diabetes and coronary heart disease, metabolomics and proteomics in Type 2 diabetes, metabolic and molecular imaging in diabetic cardiomyopathy and treatment of obesity and mitigating metabolic risk. This compendium reflects the collective work of leading investigators in the space of diabetes, cardiometabolic disease, and cardiovascular disease with the ultimate goal of providing a summary of selected aspects of obesity and metabolic physiology central to cardiovascular disease development. So, I have with me here today, Dr Eduardo Marbán, the founder of the Smidt Heart Institute at Cedars-Sinai Medical Center in Los Angeles, California. He's a leading physician scientist in the fields of electrophysiology, cardiac progenitor cells, and next generation cell-free therapeutics. Dr Marbán, thank you very much for taking the time out of your busy schedule to speak with us today about your article COVID-19 and the Heart, which is now freely available on the Circulation Research webpage. Dr Eduardo Marbán: It's my pleasure to talk to you Cynthia. Dr Cindy St. Hilaire: First off, how are you and how are things at your hospital center in LA? Dr Eduardo Marbán: We seem to have dodged the bullet here in the sense that we were pretty progressive in terms of quarantine and stay at home orders. Given that, we seem to have peaked at a level that is very manageable in terms of our surge capacity. So, we feel for those who are worse off, but at least knock on wood here, we seem to be surviving so far. Dr Cindy St. Hilaire: Yeah, that's similar to how we are in Pittsburgh. We shut down about the same time that Philadelphia, who was already surging was shutting down. So, we are feeling safe but still prepared. So, I was extremely excited to read this article because as we know, cardiac injury is happening in between 20% to 30% of the COVID-19 patients and cardiac injury is also the cause of about 40% of the COVID-19 related deaths. So, my first question is, what are the types of cardiac injuries or events that you're seeing in these COVID-19 patients and are there any particular characteristics that the subpopulation of patients shares that's different from non-cardiac injury COVID patients? Dr Eduardo Marbán: What seems to be extremely common in COVID-19 patients is elevations of circulating biomarkers, things like troponin I, troponin T, BNP as an indicator of heart failure, but what's much less certain is whether these biomarker elevations have any clinical significance. At the level of isolated case reports, there's fulminant myocarditis, ventricular tachycardia, arrhythmias, occasional acute coronary syndromes, but there seems to be a disconnect between the almost ubiquitous nature of the circulating biomarker elevations and the relative rarity of clinical events. Dr Cindy St. Hilaire: So, do these patients, do a majority of them have a history of cardiovascular disease or is this all new developments? Do we know? Dr Eduardo Marbán: Underlying cardiovascular disease, diabetes, hypertension, and recently obesity and, of course age, have all been implicated as general risk factors for being critically ill with COVID, but there's no specific indication epidemiologically yet that those with underlying cardiovascular disease have a particular predilection to manifesting worse heart symptoms or signs during COVID-19. It makes sense that that would be the case, but so far, the epidemiology is somewhat more general. Dr Cindy St. Hilaire: When you were first writing this article, I'm sure between then and now we even have more epidemiological data points that are constantly changing. Dr Eduardo Marbán: Since the article was published online on April 7th, I've given four updated versions of the webinar to various audiences. Every time we do so, the slides need to change subtly. It's a very rapidly evolving field. Dr Cindy St. Hilaire: Yeah, that's amazing. In the first SARS outbreak, which was in 2002-2003, scientists discovered that this type of Coronavirus enters the cell by binding to angiotensin converting enzyme II as a receptor. So, ACE2 as it's called. It's not a receptor in the canonical sense of the word, but it's a cell surface enzyme and it's involved in the renin angiotensin aldosterone system, which regulates a handful of cardiovascular homeostatic processes and is quite frankly, rather complicated. So, I don't want to talk specifically about that, but I'm wondering if you could tell us a little bit about what ACE2 is, what cells it's found on, and what that might mean for the implications of this virus and its effects on the cardiovascular system? Dr Eduardo Marbán: Well as you correctly stated, ACE2 is central to cardiac physiology in the sense that it creates the bioactive form of angiotensin. In so doing, its regulation is central to that of blood pressure, human dynamics. What is less appreciated and to me was a bit of a revelation is the fact that it's expressed fairly richly on the surface of epithelial cells of the lung and the SARS-CoV virus family seems to have co-opted the presence of that in order to create a handy sort of hook to get into the cells in the first place. Whether there are broader ranging implications of ACE2 other than the particular mode of entry into the cell for a viral infection is a topic of great speculation at this point. Dr Cindy St. Hilaire: Yeah. In some of my preparation for this and also just my curiosity regarding this virus and the vascular system, when you look at things like the human protein atlas, you can see that ACE2 is highly expressed, not only on the lung epithelial like you say, but they're also expressed on cardiovascular cells in nearly all of the tissue. I'm thinking of cells like the smooth muscle cell and the endothelial cell. Is the virus binding to ACE2 positive cells part of the reason for the cardiac events or these cardiac events secondary to systemic toxicity? So, I guess the real question is, do we know anything about the direct versus the indirect effects of the virus on the heart? Dr Eduardo Marbán: No question in vitro that SARS-CoV can infect cardiac myocytes and most surely almost any other cell that expresses these two on its surface. In vivo, how frequently that happens as opposed to triggering secondary cardiac damage due to the systemic inflammation is uncertain, but I can tell you from the various case reports that have actually analyzed human tissue either at autopsy or an endomyocardial biopsy in cases of fulminant myocarditis, the frequency of direct viral infection seen either by culturing viral particles or more frequently by electron microscopy and visualization of inclusion bodies within cells points to perhaps a third of the cases being due to direct infection and two thirds of the cases likely being due to some bystander effect of systemic inflammation. Dr Cindy St. Hilaire: Interesting. So, are the phenotypes different between those patients where it seems to be direct versus indirect? Does the myocarditis appear similar or the cytokine profiles, anything like that? Dr Eduardo Marbán: There are too few patients to make really good conclusions about whether or not the phenotypes differ greatly when there's direct versus indirect cardiac involvement, but certainly from the literature as it exists now, there's no reason to believe that we could outsmart the clinical picture. They all look pretty much the same from the bedside. Dr Cindy St. Hilaire: So from the first SARS outbreak, do we know anything about the long-term effects of this type of viral infection on the cardiovascular system or on the heart specifically? Dr Eduardo Marbán: Yeah. COVID-19 of course the follow-up is limited to a few months since the first cases probably didn't emerge until late October early November and weren't really recognized as such until late '19 early 2020, but for SARS from the 2002-2003 epidemic, some of the long lasting sequelae are unanticipated and include hypertension, hyperlipidemia, pulmonary fibrosis, avascular necrosis. So, it seems that even when a patient is out of the woods, perhaps they're not really out of the woods in terms of long-term sequelae. We need to be watchful for long-term sequelae in COVID-19 survivors. They're going to be many more of them than there were from the SARS epidemic. Dr Cindy St. Hilaire: So, one of the things that's come out recently, which I've been really mulling about because my background is vascular biology and specifically smooth muscle cells and endothelial cells, but one of the findings is about the later stage or more sick patients. These are patients who are going on ventilators and about 50% of them going on the ventilators are dying and/or just not responding to ventilator therapy as doctors expect. So, just to give a little background about ventilators, they're normally used when a patient's blood oxygen level drops too low. So, normal levels are between 95% and 100%. However, patients with pneumonia or acute respiratory symptoms are put on ventilators sometimes when their oxygen drops below 90%, but some of the COVID-19 patients are exhibiting blood oxygen levels at 70% or sometimes even lower, but they don't have outward signs of distress and they can still hold conversations. So, I'm wondering if you can give me any insight into possibly what's going on there with the lens of vascular remodeling, what might be happening to the vasculature in the lung that is unique to this ventilator response and COVID response? Dr Eduardo Marbán: The observation you described is common that sometimes a patient will be profoundly hypoxemic but chatting away or surfing the internet as if nothing were happening. We're not used to seeing this in other cases of ARDS or viral sepsis where the patient usually is in extremis by the time the blood oxygen levels get that low. It begs the question as to whether perhaps there's something about the cerebral circulation, and this is complete and rampant speculation. Whether there's something about the cerebral circulation that makes it somewhat resistant to the effects of systemic hypoxia, perhaps there's a compensatory vasodilation that occurs that compensates for the otherwise deadly systemic hypoxemia. It would be quite interesting to monitor oxygen tensions within the cerebral parenchyma to test that, but all I can say with any certainty right now is that the clinical observation is robust. We see this not infrequently in patients who in the sort of clinical jargon have no right to look that good. Dr Cindy St. Hilaire: Yeah. Yeah. It's like your numbers, you really have those numbers? Yeah. There's just so many questions. It's really unprecedented. So, I guess we've been talking a lot about the disease itself and the symptoms and the pathogenesis, but I want to switch to ask about potential therapies. There's been several therapies that have been suggested by a variety of people and there's, I don't even know how many clinical trials. I looked a week ago and there's really a great response of pharmaceutical companies and university hospital systems trying what they can with the tools they have. So, things like antivirals, HIV protease inhibitors, inhibitory antibodies, and even antimalarial drugs have been suggested that they could possibly work. So, I'm wondering if you could give us some insight from a cardiovascular standpoint, what are the potential implications or potential adverse side effects of using these different therapies off label and what might that mean for the heart in addition to treating the viral infection? Dr Eduardo Marbán: You're correct in the explosion of clinical trials in this area or at least, clinical interventions. At our IRB, as of today, there are 56 active COVID protocols. Imagine nobody even cared about COVID until mid-February, right? Dr Cindy St. Hilaire: That's just at Cedars-Sinai. Dr Eduardo Marbán: Yeah. Now, we have 56 active protocols. So, not all of those are interventional. Some of them are epidemiological or biomarker studies, but still there's an incredible plethora. You're right, the approaches of targeted anything from the viral infection to the viremia to the downstream consequences of viral infection including the hyper inflammation and cytokine storm. The rationale for anti-malarials is actually fairly thin and resides on in vitro observations that actually were just from February that SARS-CoV-2 infection in vitro is somewhat retarded by exposure to hydroxychloroquine. This didn't come out of the blue. There had been an extensive literature and quite controversial literature, I should say, that anti-malarials might be useful in influenza and other infections. In a very general sense, there was a lot of hype created by early in vitro studies, which turned out to be neutral or in some cases even harmful clinically, but this has led to an almost universal adoption of hydroxychloroquine in patients with COVID-19 coupled sometimes with the antibacterial agent azithromycin for which the rationale is even thinner. There's no reason to believe that an antibacterial per se would help in a viral infection, but azithromycin is said to have antioxidant properties, which may or may not potentiate the effects of hydroxychloroquine, but for sure what they do together is prolong repolarization of the heart and lead to a clinical syndrome known as prolonged QT, which is a known substrate for toxic arrhythmias like polymorphic ventricular tachycardia. So, in prescribing some of these agents, one needs to weigh the uncertain benefits against the very certain risk that they entail. Dr Cindy St. Hilaire: Yeah. I think that's a really important point. I think one of the scary things that has the potential of happening during this crisis is too quick of a jump to conclusions. While there is a need for as rapid a response as possible, we still need to make sure that we're taking in all the scientific information we have and that that science is good and strong. I think one of the things that you mentioned in the Review is the lack of power in some of those initial anti-malarial studies. I think it's really important thing I want to emphasize that it's an emergency, but we still need to make proper good scientific decisions. Dr Eduardo Marbán: Well, one of the problems is that hydroxychloroquine and other agents in some cases, remdesivir and you know, you choose, have gotten so popular and hyped that there's almost no possibility of being an ethical clinical trial because the patients want to be on them. So, it may be easier in some settings than in others, but it's certainly not going to be a trivial thing to sort out the true risk benefit ratio of these drugs in this illness. Dr Cindy St. Hilaire: So right now, doctors and scientists, we're all in crisis mode, but once things settled down, we could really start to sit down and think about more mechanistic questions that might be able to be tested that will really help us flush out our understanding of COVID-19 disease pathogenesis and its effects on the cardiovascular system. So, what do you see after this initial crisis is under control, what do you see as the immediate next questions that basic scientists and translational scientists need to address that can help the next time that this comes again? Dr Eduardo Marbán: First of all, it's quite clear that we've all become consumed by COVID-19 and SARS-CoV-2. We can't think of anything else often. It's really hard to even focus on work from the laboratory that doesn't have to do with SARS-CoV-2 and COVID. It's so ubiquitous in public perception and the way we're living our lives that it just makes it incredibly difficult to think about anything else. I think there's going to be a correction in which we're going to get frankly tired of SARS-CoV-2 and COVID and want to think about other things, but among the lasting questions and the ones that will have greater biological merit above and beyond how to deal with this particular virus and this particular pandemic are the following. What is the role of ACE2 in human biology? Clearly here, there's an experiment of nature in which this surface enzyme has been co-opted for viral entry and a tremendous amount of speculation surrounds the question of whether high ACE2 values are protective and detrimental and ACE inhibitors and angiotensin receptor blockers might be detrimental or beneficial. All of these fundamental mechanisms need to be sorted out and now there's motivation to do so because of the epidemic. Some of this work is easier than others and those institutions that happen to have a BSL-3 level facility for being able to directly study the effects of the virus on various tissues should do so with alacrity because it's a limited resource right now where the number of questions really far exceed the ability to answer them just physically. Another question which I think is going to be motivated by our experience with COVID-19 is that of the mechanisms of cytokine storm and hyper thrombotic states. These are things that characterize the critically ill patient with COVID-19. Dr Cindy St. Hilaire: Can you just explain what is a cytokine storm? What does that exactly mean? Dr Eduardo Marbán: So, patients who are critically ill with COVID-19 manifest a late stage of the illness, which is often fatal, in which circulating levels of various inflammatory biomarkers, interleukin 6, C-reactive protein, ferritin being among them, but basically anything that goes up in an inflammatory state. And some of these appeared not to just be markers of inflammation. Something like C-reactive protein is probably just a biomarker of inflammation, but interleukin 6 for example, is a highly bioactive cytokine that itself probably causes tremendous tissue injury and there's some enthusiasm for the use of anti IL6 antibodies and anti IL6 receptor antibodies to treat the critically ill with some anecdotal dramatic success I should say. So perhaps the cytokine storm isn't just a marker of those who are critically ill, perhaps it's causative. If that presumption is real, then it makes good sense to target the cytokine storm, but from a scientific point of view, what causes it in the first place? How does a viral infection lead to massive production of cytokines and inflammatory biomarkers and how can that be mitigated? One of the ways of dealing with that is by understanding precisely how it happens in the first place and there's not that much literature on it. There's a recent study which I found quite provocative that glucose metabolism and the whole process known as O-GlcNAcylation might actually be a trigger in the production of cytokines during viral infections like COVID-19, but I think understanding how it happens will lead to much more targeted therapeutics and perhaps enable us to eventually divorce the infection from the overreaction. Really what's happening is friendly fire. The body's immune system is turning against itself in a sort of vain effort to control the virus. Sometimes the viremia is actually almost gone by the time that these inflammatory biomarkers increase, and the cytokine storm surges. Dr Cindy St. Hilaire: So, it's almost like the inflammatory response reaches some point beyond which it doesn't need virus anymore. It is just full force feeding forward and causing more damage by itself. Dr Eduardo Marbán: Yeah, exactly. It's almost as if there's an eroding cliff and even though the river may be back down to normal levels, the cliff is still unstable and the whole hillside could come crashing down. Dr Cindy St. Hilaire: Are there long terms effects of that? I wonder how long that would last after the infection or is it only during a viral titer in the system? Dr Eduardo Marbán: Well, you raised yet another interesting question to the extent that patients who have survived SARS- CoV-2 infection develop long-term sequelae, what's the mechanism of those long-term sequelae? Why should patients who are previously well develop hyperlipidemia and hypertension after the infection, if in fact they do, so are any of these related to micro thrombotic events? It's quite conceivable. Dr Cindy St. Hilaire: Great. Well, thank you so very much for taking the time to speak with me today. I don't think I found a ton of answers. I found a lot more questions, but hopefully as this develops and we get it under control, maybe we can talk again and talk about some of those new mechanistic findings and potential therapies. Dr Eduardo Marbán: Absolutely. You're welcome, and I hope you and all the listeners stay safe during this pandemic. Dr Cindy St. Hilaire: You too, and your clinical team. That's it for highlights from the May 10th and May 22nd Obesity Compendium issues of Circulation Research. Thank you so much for listening. Please check out the Circulation Research Facebook page and follow us on Twitter and Instagram with the handle @CircRes and #DscoverCircRes. Thank you to our guest, Dr Eduardo Marbán. This podcast is produced by Rebecca McTavish, edited by Melissa Stoner, and supported by the editorial team of Circulation Research. Some of the copy text for highlighted articles is provided by Ruth Williams. I'm your host, Dr Cindy St. Hilaire, and this is Discover CircRes, your on-the-go source for the most up-to-date and exciting discoveries in basic cardiovascular research.  

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.05.078543v1?rss=1 Authors: Tong, R., Emptage, N. J., Goda, Y. Abstract: Dendrites are crucial for integrating incoming synaptic information. Individual dendritic branches are thought to constitute a signal processing unit, yet how neighbouring synapses shape the boundaries of functional dendritic units are not well understood. Here we addressed the cellular basis underlying the organization of the strengths of neighbouring Schaffer collateral-CA1 synapses by optical quantal analysis and spine size measurements. Inducing potentiation at clusters of spines produced NMDA receptor-dependent heterosynaptic plasticity. The direction of postsynaptic strength change showed distance-dependency to the stimulated synapses where proximal synapses predominantly depressed whereas distal synapses potentiated; potentiation and depression were regulated by CaMKII and calcineurin, respectively. By contrast, heterosynaptic presynaptic plasticity was confined to weakening of presynaptic strength of nearby synapses, which required CaMKII and the retrograde messenger nitric oxide. Our findings highlight the parallel engagement of multiple signalling pathways, each with characteristic spatial dynamics in shaping the local pattern of synaptic strengths. Copy rights belong to original authors. Visit the link for more info

  This month on Episode 10 of the Discover CircRes podcast, host Cindy St. Hilaire highlights four featured articles from the February 28 and March 13, 2020 issues of Circulation Research and talks with Dr Mary McDermott about her article Cocoa to Improve Walking Performance in Older People With Peripheral Artery Disease: The Cocoa-Pad Pilot Randomized Clinical Trial.   Article highlights:   Rykaczewska, et al. PCSK6 Is a Key Protease in Vascular Injury   Lebek, et al. SDB Induces Arrhythmias via CaMKII and Late Ina   Mueller, et al. Brain Damage With Heart Failure Napierski, et al. Cut and Paste of cMyBP-C Domains In Situ Transcript Cindy St. Hilaire: Hi. Welcome to Discover CircRes, the podcast of the American Heart Association's journal Circulation Research. I'm your host, Dr Cindy St. Hilaire, and I'm from the Vascular Medicine Institute at the University of Pittsburgh. Today I'm going to share with you four articles selected from the February 28th and the March 13th issues of Circulation Research as well as have an in-depth discussion with Dr Mary McDermott, who is the corresponding author of the study COCOA-PAD Pilot Randomized Clinical Trial. So first, the highlights. The first article I'm sharing with you is titled PCSK6 Is a Key Protease in the Control of Smooth Muscle Cell Function in Vascular Remodeling. The first authors are Urszula Rykaczewska, Bianca Suur, Samuel Röhl, and the corresponding author is Ljubica Matic from the Karolinska Institute in Stockholm, Sweden. The family of proprotein convertase subtilisins/kexins, or PCSKs case for short, are a group of proteases whose role in vascular disease was only recently recognized. Humans with gain- and loss-of-function mutations in PCSK9 exhibit very high or very low levels of cholesterol, respectively, and this information was leveraged for the development of novel, albeit extremely expensive, drugs for regulating cholesterol. However, the role of other members of the PCSK family in cardiovascular disease is not known. This group previously found that PCSK6 was one of the most enriched molecules in human carotid artery plaques as compared to normal arteries, while other PCSK family members did not show the same trend. This prompted the group to further explore the role of PCSK6 in vascular disease. They used a very integrative approach drawing from several independent human biobanks for genetic information, conducting in situ functional investigations using human tissue, also conducting in vivo animal models of vascular injury, including using the PCSK6 knockout mice, as well as ex vivo and in vitro mechanistic studies. And they found that PCSK6 was a key modulator of smooth muscle cell function in vascular remodeling and atherosclerosis through a very novel mechanism implicating MMP14 and MMP2 activation upon cytokine stimulation. Future studies will investigate the role of PCSK6 on atherosclerotic plaque remodeling and instability because, as we know, plaque rupture can have devastating consequences. The second article I will highlight is titled Enhanced CaMKII-Dependent Late I Na Induces Atrial Pro-Arrhythmic Activity in Patients with Sleep-Disordered Breathing. The first author is Simon Lebek, and the corresponding author is Stefan Wagner, from the University Hospital Regensburg in Regensburg, Germany. Sleep-disordered breathing is an umbrella term for any chronic condition involving the complete or partial interruption of breathing during sleep, and this is commonly called sleep apnea. Aside from daytime sleepiness, people with sleep-disordered breathing run the risk of developing arrhythmia, such as atrial fibrillation. Arrhythmias are an electrical problem as opposed to a mechanical one. And at the cellular level, arrhythmias are associated with increased activity of the enzyme calcium/calmodulin-dependent protein kinase 2, or CaMKII, and this protein regulates cellular electrophysiology. Despite the role of CaMKII in propagating electrical signals in the heart, its activity has not been investigated in sleep-disordered breathing patients. This group now shows in a study that used 113 patients undergoing heart surgery that those with sleep-disordered breathing have higher CaMKII in biopsied myocardium than those without the condition. Furthermore, this CaMKII increase was associated with other pro-arrhythmic alterations to the tissue, including increased reactive oxygen species production, enhanced phosphorylation of a major sodium channel, and consequent late firing of sodium currents. Importantly, these alterations could be prevented by pharmacological inhibition of CaMKII, suggesting that such an inhibitor could be a novel treatment strategy for patients with sleep-disordered breathing to reduce their arrhythmia risk. The next article I want to share with you is titled Brain Damage with Heart Failure: Cardiac Biomarker Alterations and Gray Matter Decline. The first authors are Karsten Mueller and Friederike Thiel, and the corresponding author is Matthias Schroeter, and the work was completed at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany. Heart failure leads to decreased blood flow due to a reduced pumping efficiency of the heart, and as a consequence, this can cause insufficient oxygen supply to the tissues, including the brain. Cardiovascular insults, including heart failure, increase the risk for the development of neurological diseases later in life, such as vascular dementia and Alzheimer's disease. Patients with heart failure can show neurological symptoms such as fatigue, nausea, and dizziness. However, the long-term consequences of the effects of heart failure on brain integrity are not well understood. However, several studies suggest that structural changes in the gray matter can occur. This study sought to identify correlations between cardiovascular biomarkers and structural gray matter changes in the brain. They found that patients who suffered from heart failure undergo detrimental brain structural changes. Reduced gray matter density in several regions of the brain correlated with decreased ejection fraction at baseline and increased NT-proBNP, which is a heart failure biomarker. While these observations might reflect structural brain damage in areas that are related to cognition, whether these structural changes facilitate the development of cognitive alterations will need to be proven in future longitudinal studies. The last article I want to share with you before we switch to our interview is titled A Novel "Cut And Paste" Method for In Situ Replacement of Cardiac Myosin Binding Protein C Reveals a New Role for This Protein in the Regulation of Contractile Oscillations. The first author is Nathaniel Napierski, and the corresponding author is Samantha Harris, and they're from the University of Arizona. Actin and myosin are the respective thin and thick filament proteins that allow for muscle contraction, including in the cardiomyocytes, the muscle cells of the heart. Cardiac myosin binding protein C is a critical protein that regulates heart contraction, but the mechanisms by which this protein affects actin and myosin are only partially understood. One reason for this is that cardiac myosin binding protein C localization on the thick filaments may be a key component of contraction, but most in vitro studies cannot spatially replicate arrangements of cardiac myosin binding protein C within the sarcomere. To address this technical gap, this group created a novel hybrid genetic/protein engineering approach that allows for rapid manipulation of cardiac myosin binding protein C in sarcomeres of permeabilized myocytes isolated from genetically engineered Spy-C mice in situ. So essentially, they can do some gene editing in tissue in situ. Using this approach, they were able to rapidly remove and replace cardiac myosin binding protein C. Deletion of this protein fully recapitulates effects obtained using traditional knockout and transgenic mouse models of cardiac myosin binding protein C. However, the ability to rapidly remove and replace this protein identified a new regulatory role for cardiac myosin binding protein C where it functions to dampen contractile oscillations. The novel cut and paste approach should be very useful in testing these new hypotheses of the role of cardiac myosin binding protein C function as well as in defining the role of how spontaneous contractile oscillations affect cardiac contractility during both health and disease. Okay. Now we're going to switch over to the interview portion of the podcast. I have with me Dr Mary McDermott from the Departments of Medicine and Preventative Medicine at Northwestern University's Feinberg School of Medicine. And today we're going to be discussing her manuscript titled Cocoa to Prevent Walking Performance in Older People With Peripheral Artery Disease: The COCOA-PAD Pilot Randomized Clinical Trial. Thank you for joining me. Mary McDermott: Oh, it's a pleasure to be here. Cindy St. Hilaire: Before we dig into the details and the nitty-gritty of the study, could you maybe first explain to us what peripheral artery disease is and perhaps maybe why it's so pernicious? Mary McDermott: Sure. So peripheral artery disease is atherosclerosis of the arteries that supply the legs, and it is a problem because it causes great difficulty with walking. People with peripheral artery disease, or PAD, can typically walk only at one or two blocks before they have to stop because of symptoms or weakness or pain or tightness in their lower extremities, in their legs. And it's also difficult to treat because we have very few medical therapies available that are effective. Cindy St. Hilaire: So this is really something that you only know it's there until you're feeling the adverse symptoms. Mary McDermott: That's correct. Cindy St. Hilaire: That sounds very difficult to treat clinically. This study was called the COCOA-PAD study, and it was a double-blind pilot, randomized clinical trial, and it was designed to test the hypothesis that daily cocoa consumption for about six months improves or prevents the decline in something called the six-minute walk distance test. So my first burning question is, is it okay to eat a lot of chocolate every day? And then my second question is, what is the significance of the six-minute walk test? And maybe you could tell us a little bit about this trial's design. Mary McDermott: Sure. Maybe I'll go in reverse order for those questions. Cindy St. Hilaire: Sure. Mary McDermott: So the trial design, it was a randomized clinical trial. 44 participants with peripheral artery disease were randomized to receive either the cocoa beverages, we asked them to take three a day, or a placebo control, which was very much like the intervention except that the placebo did not have cocoa or cocoa flavanols. And participants were followed for six months, and at baseline and six-month follow-up, we measured the six-minute walk test, and we also did muscle biopsy on those who consented to that, and we also measured lower extremity perfusion with MRI. Now, the six-minute walk test is a test that's very well-validated in patients with peripheral artery disease, and it's really a measure of walking endurance. The way you conduct it is you need a hundred-foot hallway. We use standardized instructions. We actually use a script where the research assistant reads the script with the instructions, and the goal of the test is for the participant to walk as many lengths as they can in the six minutes. And often what you see in people with peripheral artery disease is they start out fine, but after maybe a few hundred-foot lengths, they start to slow down or they start to limp, and many of them cannot finish the six-minute walk without having to stop and rest. If they need to stop, then they can start walking again. Cindy St. Hilaire: That's interesting. Is it a fatigue or is it a pain, or what is prompting them to stop? Mary McDermott: It's symptoms in the legs or the hips classically, and it can be either of those symptoms that you mentioned. It may be a fatigue or a weakness. Some people will say, "I don't have pain. My legs just get weak, and I can't keep walking." Others will have pain. Many will have tightness or burning. And it's interesting, some people will get symptoms mainly in their feet or ankles, others will get it classically in the calves, but many will get it in the hips. And the location depends in part on the location of the atherosclerosis and where they're experiencing the ischemia. Cindy St. Hilaire: Interesting. And so ultimately this is due to the atherosclerotic plaque blocking blood flow? Mary McDermott: Exactly. Right. So when they go to walk, their muscles are not getting an adequate oxygen supply, and that causes these symptoms or weakness in the legs. Cindy St. Hilaire: Interesting. What's so special about cocoa, and what are these flavonoids that you mentioned? Mary McDermott: Sure. Cocoa actually comes from the cacao plant, and in that plant there's cocoa, but also something called cocoa flavonoids, and this is a nutritional substance. And there's a variety, but in cocoa, epicatechin is the most prevalent flavonoid. And flavonoids have health benefits that include improving blood flow by causing dilation of vessels, but also, they've been shown to have favorable effects on muscles, skeletal muscle. And so this is particularly potentially helpful in peripheral artery disease because, obviously, patients with PAD have difficulty with blood flow because of those atherosclerotic blockages, but also they've been shown to have skeletal muscle abnormalities, probably because their leg muscles aren't getting enough oxygen. So they develop loss of muscle mass, they develop mitochondrial dysfunction and other abnormalities in their muscle that also make it hard for them to walk. So cocoa and cocoa flavonoids are an attractive therapy in PAD because they both can improve blood flow and improve the health of the skeletal muscle in the legs. Cindy St. Hilaire: Interesting. So it's kind of a two-pronged approach to possibly helping these patients. What was the scientific evidence out there that the flavonoids or maybe even just dark chocolate may be beneficial, and how was your study different from other studies? Mary McDermott: Some of the evidence comes from animal studies where it's clearly been shown to improve skeletal muscle mitochondrial activity and muscle growth and also blood flow. But there were also some preliminary studies in humans, a couple of them really small sample sizes of patients with heart failure, showing improvements in skeletal muscle health. But there was one trial published about five years ago in patients with PAD where the PAD patients were given one dose of dark chocolate or one dose of milk chocolate, and that one dose helped them achieve increased walking distance on a treadmill about two to three hours later. But to our knowledge, no prior studies had tested whether a daily dose of cocoa could improve six-minute walk or improve skeletal muscle or blood flow. Cindy St. Hilaire: So should I eat chocolate every day? Mary McDermott: Well, there's a couple of important things about chocolate. First of all, most of the chocolate that you can buy at the store is not the type we used in our study. Oftentimes chocolate is alkalized, and what that does is it makes it taste better, but it also removes some of those cocoa flavonoids that are thought to be responsible for the health benefits. The cocoa that we studied was rich in the cocoa flavanols. It had not been alkalized, and it was more of the dark chocolate. So if you want to eat it for health benefits, you need to read the label, and it should tell you whether the chocolate has been alkalized. The other thing to take note of is, of course, many forms of chocolate come with a lot of calories or sugars, so that can be problematic if it leads to weight gain. The chocolate that we used in our study and the placebo added about 180 calories per day to the diet, and prior to starting the study we did a little bit of diet counseling with all the participants, and we helped them identify drinks or foods they were eating that maybe could be removed so that they could take the 180 calories without gaining weight. And we did not find weight gain in either group in this study. Cindy St. Hilaire: That's good. That's good. One of your results I found interesting was that it showed that this daily supplementation of cocoa in the diet improved the six-minute walk test at a timeframe that was shortly after the chocolate dosing, but not 24 hours after. Can you maybe talk about that result and what the implications for that mean? Mary McDermott: Sure. Because of that prior trial that I mentioned, which indicated that cocoa had an acute effect, we were interested in separating out the acute and the chronic effects. So we did two six-minute walk tests at six-month follow-up. The first was performed two and a half hours after the final cocoa dose, and the second was performed 24 hours later. And we saw the biggest benefit at the time point that was two and a half hours after the final cocoa dose. The benefit was about 42 meters favoring the cocoa intervention. When participants came back 24 hours later, the difference between the intervention and the placebo was only 18 meters, and that didn't quite achieve statistical significance in our primary analyses. Now, we were a little surprised by the difference in those findings. One possible explanation is that cocoa has both the chronic and acute benefit and that first measurement reflected both the acute and the chronic benefits. So that's one possible explanation. Another is, interestingly, we found that the placebo group had a bit of a learning effect between the two-and-a-half-hour time point and the 24-hour time point, and it's possible that that explained the diminishment in the difference of the 24-hour time point. But we didn't see that learning effect in the cocoa group, so that didn't quite make sense. In my mind, the best explanation is there may be both an acute and a chronic effect, and we saw the benefit of both of those at that first time point. Cindy St. Hilaire: Interesting. And a learning effect, by that you just mean the patients just learned to do the test better? Mary McDermott: Yeah. So they got more comfortable with it between the first and the second measurement, which were just 24 hours apart. Prior study in peripheral artery disease patients has not shown a learning effect. But in the prior study, the six-minute walk tests were performed one or two weeks apart. And to my knowledge, no one's ever tested it just 24 hours apart. Cindy St. Hilaire: Interesting. Very interesting. What was really the most challenging aspect of  this study? Can you talk about some of the limitations also? Mary McDermott: Sure. I'd say the biggest limitation was the sample size. This was a pilot study. It's not a definitive result. There were 44 people, so that is certainly a limitation. And perhaps related to that, we did see some imbalances at baseline between the two groups in terms of BMI and prevalence of African-Americans between the two groups. Our analyses do adjust for those differences to try to overcome that potential difference. With regard to challenges, well, recruiting for studies of peripheral artery disease is always a challenge because the patients are limited in their own mobility, and it can be hard for them to come in for the study visits. A study like this requires multiple visits at baseline and follow-up. Another potential challenge is that the adherence rate was about 64% in the intervention group versus closer to 80% in the placebo group. We don't know- Cindy St. Hilaire: Oh, interesting. What do you think that is? Mary McDermott: We don't know exactly why. It's possible that the cocoa intervention had a different taste and maybe was not as palatable, but since participants only had their own drink, we didn't ask them to compare, and we can't say that for sure. That could've been just due to chance. Cindy St. Hilaire: Sure. Wow. Well, hopefully, a future study can help figure that out. Speaking of that, what would be next really in terms of kind of translating this study into either a bigger study or really translating it to the clinic? What do you see for this moving forward? Mary McDermott: Well, couple things. I think most immediately, because there are so few therapies for peripheral artery disease and because cocoa has essentially no side effects with the caveat being the potential for weight gain, that it would be reasonable to recommend it to patients who are really symptomatic and can't seem to get better with standard options such as exercise or maybe in addition to exercise. But I do think before we can reach a definitive conclusion, a definitive trial is needed. We have applied, we have submitted a grant application to obtain funding to do a larger study, but we'll need to wait and see how that goes. Cindy St. Hilaire: Well, hopefully, that gets funded because I would love any excuse to eat a little more chocolate, even if it's non-alkalized. Well, great. Well, thank you so much for joining me today, Dr McDermott. This is a wonderful study, and I wish you the best of luck on that next funding to do a larger study. Mary McDermott: Well, thank you so much. I really appreciate your interest in this work. Thank you. Cindy St. Hilaire: That's it for highlights from the February 28th and March 13th issues of Circulation Research. Thank you so much for listening. This podcast is produced by Rebecca McTavish, edited by Melissa Stoner, and supported by the editorial team of Circulation Research. Some of the copy text for highlighted articles was provided by Ruth Williams. Thank you to our guest, Dr Mary McDermott. I'm your host, Dr Cindy St Hilaire, and this is Discover CircRes, your source for the most up-to-date and exciting discoveries in basic cardiovascular research.  

On this episode we chat with recent graduate Emily Agnello and Dr. Meg Stratton of the Stratton Lab in the Biochemistry Dept. at UMass. They study a protein in the brain, CaMKII, that is critical for memory. While scientists know that CaMKII affects memory, they don't yet know exactly how or why... and that's what the Stratton Lab wants to figure out. Comedian Laura Patrick, founding member of the improv troupe The Ha Ha's joins as co-host.

Dr. Paul Wang:           Welcome to the monthly podcast On the Beat for Circulation Arrhythmia and Electrophysiology. I'm Dr Paul Wang, editor-in-chief, with some of the key highlights for this month's issue. We'll also hear from Dr. Suraj Kapa reporting on new research from the latest journal articles in the field.                                                 In our first article, Barry Maron associates report on the long term clinical course of hypertrophic cardiomyopathy patients following ICD therapy for ventricular arrhythmias. They studied a cohort of 486 high-risk hypertrophic cardiomyopathy patients with ICDs from eight international centers. Of these 486 patients over 6.4 years, 94 patients or 19% experienced appropriate ICD interventions, terminating VT or VF. Of the 94 patients receiving appropriate ICD therapy, 87 were asymptomatic or only mildly symptomatic at the time of appropriate ICD interventions. Of these 87 patients, 74 or 85% remained in classes one or two without significant change in clinical status of the subsequent 5.9 years up to 22 years. Among the 94 patients, there was one sudden death in three patients who died from non arrhythmic hypertrophic cardiomyopathy related processes. Post ICD intervention, freedom from hypertrophic cardiomyopathy, mortality was 100% at one year, 97% at five years, and 92% at 10 years, distinctly lower than the risk of ischemic or non ischemic cardiomyopathy in ICD trials.                                                 Hypertrophic cardiomyopathy patients with ICDs interventions reported the heightened anxiety and expectation of future shocks. However, they did not affect general psychological well-being or quality of life. The authors concluded that in hypertrophic cardiomyopathy, unlike ischemic heart disease, prevention of sudden death with ICD therapies unassociated with a significant increase in cardiovascular morbidity and mortality, nor transformation into heart failure deterioration, ICD therapy does not substantially impair overall psychological and physical well-being. In our next article, Abdulla Damluji and associates examined the cost of hospitalizations for cardiac arrest using the US nationwide inpatient sample from 2003 to 2012. Using the log transformation of inflation adjusted costs the authors examined 1,387,396 patients who were hospitalized after cardiac arrest. They had a mean age of 66 years. Inpatient procedures included coronary angiography in 15%, PCI in 7%, intra-aortic balloon pump in 4.4%, therapeutic hypothermia in 1.1%, and mechanical circulatory support in 0.1% of patients.                                                 Notably the rates of therapeutic hypothermia increased from 0 in 2003 to 2.7 in 2012, p less than 0.001. Both hospital charges inflation adjusted costs linear increased over time. In a multi-variant analysis predictors of inflation adjusted costs included large hospitals size, urban teaching hospital, and length of stay. Among co-morbidities, atrial fibrillation or fluid and electrolytes imbalance were the most common associated with cost. The authors found that during the period between 2003 and 2012 post cardiac arrest, hospitalizations had a steady rise and associated healthcare costs likely related to increase length of stay, medical procedures and systems of care.                                                 In our next paper, Peter Huntjens and associates examined intrinsic interventricular dyssynchrony as a predictor of human dynamic response to cardiac resynchronization. The authors use a cardiovascular computational model CircAdapt to characterize the isolated effect of intrinsic interventricular or intraventricular activation on resynchronization therapy response that is the change in LV dP/dt max. The simulated change in LV dP to dt max had a range of 1.3 to 26.5% increased considerably with increasing inter ventricular dyssynchrony. In contrast, the isolated effect of intra ventricular dyssynchrony was limited with the change in the LV dP/dt max range and the left ventricle from 12.3 to 18.3% in the right ventricle from 14 to 15.7%.                                                 Secondly, electrocardiographic imaging derived activation characteristics of 51 CRT candidates were used to create individual models of ventricular activation in CircAdapt. The model predicted change in LV dP/dt max was close to the actual value in left bundle branch block patients with 2.7% difference between measured and simulated when only intrinsic interventricular dyssynchrony was personalized. Among non left bundle branch block patients a change in LV dP/dt max was systematically over predicted by CircAdapt with a 9.2% difference between measured and simulated. Adding intra ventricular activation to the model did not improve the accuracy of response prediction. The authors found that computer revealed intrinsic interventricular dyssynchrony is the dominant component of the electrical substrate driving the response to CRT.                                                 In the next paper Kenji Kuroki and associates examined the use of voltage limit adjustment of substrate mapping and fast Fourier transform analysis of local ventricular bipolar electrograms during sinus rhythm to predict VT isthmuses. They performed these studies and nine post infarction patients who underwent catheter ablation for total of 13 monomorphic ventricular tachycardias. Relatively higher voltage areas on electroanatomical map or defined as high voltage channels, which were further classified as full or partial if the entire or more than 30% of the high voltage channel was detectable. 12 full high voltage channels were identified in seven of nine patients. Relatively higher fast Fourier transform areas were defined as high frequency channels, which were located on seven of 12 full high voltage channels. Five VT isthmuses or 71% were included in the seven full high voltage channels positive in high frequency channel positive sites.                                                 While no VT isthmuses were found in five full high voltage channel positive but high frequency channel negative sites, high frequency channels were identical to 9 out of 16 partial high voltage channels. Eight VT isthmuses or 89% were included in nine partial high voltage channel positive in high frequency channel positive sites, whereas no VTs isthmuses were found in the seven partial high voltage channel positive and high frequency channel negative sites.                                                 All high voltage channel positive in high-frequency channel positive sites predicted VT isthmus with a sensitivity of 100% and specificity of 80%. The authors concluded that based on this small series that combined use of voltage, limited adjustment and fast Fourier transform analysis may be useful method to detect VT isthmuses.                                                 In the next study, John Whitaker and associates examined the use of lesion index, LSI index, a proprietary algorithm combining contact force, radio-frequency application duration, and RF current. Cardiac CT was used to assess atrial tissue thickness. Ablation lines two to three per animal were created in the right atrium in seven mini pigs with point lesions using 25 watts of energy. Two weeks after the ablation, serial sections of targeted atrial tissue or examine histologically to identify gaps and transmural ablation. LSI guidelines had a lower incidence of histological gaps. Four gaps in the 69 catheter moved or 5.8% compared to ablation using LSI plus two millimeter lines in which there is seven gaps in 33 catheter moves or 21.2% and using LSI plus four millimeter lines in which there are 15 gaps in 23 moves or 65.2% p less than 0.0. The change in LSI was calculated retrospectively is a distance between two adjacent lesions above the mean LSI of the two lesions. Changing LSI values of 1.5 or less were associated with no gaps in transmural ablation.                                                 The authors concluded that in this mod of chronic atrial ablation delivery of uninterrupted transmural linear lesions may be facilitated using LSI to guide catheter movement. When change in LSI between adjacent legions is 1.5 millimeters or lower, no gaps in atrial linear lesions should be expected.                                                 In our next paper, Matthew Bennett and associate examined whether their response to antitachycardia pacing in patients with ICD could further discriminate ventricular from super ventricular arrhythmias in patients receiving ATP in the RAFT trial. The RAFT trial randomized 1,798 patients with New York Heart Association class two or three heart failure, left ventricular ejection fraction less than or equal to 30%, in QRS duration 120 millisecond or greater, to an ICD plus or a minus cardiac resynchronization. Beginning with 10,916 ATP attempts for 8,150 tachycardia episodes in 924 patients, the author's excluded tachycardias where ATP terminated the episode or were the specific etiology tachycardia was uncertain. In this study, they analyzed 3,676 ATP attempts delivered to 2,046 tachycardia episodes in 541 patients. The authors found that a shorter difference between the post pacing interval is PPI minus TCL, was more likely to be associated with VT than SVT, mean of 138.1 milliseconds for VT and 277.4 milliseconds for SVT p, less than 0.001. A PPI minus TCL value of less than or equal to 300 milliseconds had a sensitivity in 97.4% and a specificity of 28.3% for VT.                                                 The authors concluded that specifically the PPI minus TCL following antitachycardia pacing may help distinguish ventricular from supraventricular arrhythmias.                                                 In the next study, Shailee Shah and Amr Barakat and associates examined the outcomes after repeat AF ablation. The authors examined 137 patients out of a total of 10,378 patients undergoing Afib ablation who had had initial long-term success defined from recurrent arrhythmias for greater than 36 months off anti-arrhythmic drugs in subsequent underwent repeat ablation for recurrent atrial fibrillation. The median arrhythmia free period that define long-term success was 52 months. In redo-ablations reconnection of at least one of the pulmonary veins was found in 111 or 81% of patients. Additional non PV ablations were performed in 127 or 92.7% of patients. After a mean follow-up of 17 months, 103 patients or 75% were arrhythmia-free, 79 off anti-arrhythmics, and 24 on arrhythmics. The authors found that repeat ablations with re-isolation to the point of veins and modifying the atrial substrate had a good success rate.                                                 In the next article Qiongling Wang and associates hypothesized that genetic inhibition of CaMKII oxidation in a mouse model of Duchenne muscular dystrophy can alleviate abnormal calcium homeostasis thus preventing ventricular arrhythmias. The authors tested whether the selective loss of oxidation of the CaMKII effects ventricular arrhythmias in the mouse model of Duchenne muscular dystrophy. Genetic inhibition of ox-CaM kinase II by knocking replacement of the regulatory domain methionines with valines, which we'll call MMVV, prevented ventricular tachycardia in the mdx mice. Confocal calcium imaging of ventricular myocytes, isolated from the mdx MMVV mice revealed normalization of intra-calcium release events compared to myocytes from the mdx mice. Abnormal action potentials as assessed by optical mapping mdx were also alleviated by genetic inhibition of ox-CaMK II. Knockout of the NADPH oxidase regulatory sub-unit P 47 Fox normalized elevated ox-CaMK II, repaired intracellular calcium hemostasis and rescued inducible ventricular arrhythmias in the mdx mice. The authors concluded that inhibition of ROS or ox-CaMK II protects against pro-arrhythmic intracellular calcium handling, preventing ventricular arrhythmias in a mouse model of Duchenne muscular dystrophy.                                                 In the next article, Kyohei Marume and Teruo Noguchi and associates examined whether the combination of QRS duration of 120 milliseconds or greater in late gadolinium enhancement is a precise prognostic indicator for the primary endpoint of all cause death and a composite of sudden cardiac death or aborted sudden cardiac death in 531 patients with dilated cardiomyopathy. They also analyzed the association between the combination of late gadolinium enhancement and increased QRS duration in these end points among patients with a class one indication for implantable defibrillator. The author's divided study patients in three groups according to late gadolinium enhancement in QRS duration. Two negative indices that is late gadolinium enhancement negative and narrow QRS, one positive index with either late gadolinium enhancement positive or wide QRS or two positive indices late gadolinium positive and wide QRS and followed them for 3.8 years. Multiple variable Cox regression analysis identified to positive indices as significant predictors of all cause death. A hazard ratio of 4.29 p equals 0.026. Among the 317 patients with a class one indication for ICD, the five year event rate of sudden cardiac death or aborted sudden cardiac death was lowest in the two negative indices groups, 1.4%. With propensity score matching cohorts the two negative indices group had a significant lower event rate of sudden cardiac death or aborted sudden cardiac death than to two other groups hazard ratio 0.2, p equals 0.046.                                                 The authors concluded that the combination of late gadolinium enhancement in wide QRS provides additional prognostic stratification compared to late gadolinium enhancement status alone.                                                 In the next study, Matthew Sulkin and associates examined whether a novel local impedance measurement on an ablation catheter identifies catheter tissue coupling and is predictive of lesion formation. The author's first studied explanted hearts, 10 swine, and then in vivo 10 swine, using an investigational electro anatomical mapping system that measures impedance from an ablation catheter with mini electrodes incorporated into the distal electrode. Rhythmia and Intellanav, Boston Scientific.                                                 Explanted tissue was placed in a warmed 37 degree celsius saline bath mounted on a scale, and the local impedance was measured 15 millimeters away from the tissue to five millimeters of catheter tissue compression at multiple catheter angles. Lesions were created for 31 and 50 watts from 5 to 45 seconds for an N of 70. During in vivo valuation of the local impedance measurements of the myocardium 90 and blood pool 30 were guided by intracardiac ultrasound while operators were blinded to the local impedance data. Lesions were created with 31 and 50 watts for 45 seconds in the ventricle with an n of 72. The local impedance of myocardium, which was 119.7 ohms, was significantly greater than in blood pool 67.6 ohms the p of less than 0.01. Models that incorporate local impedance drop to predict lesion size had better performance that models incorporate force time integral r squared of 0.75 versus r squared of 0.54 and generator impedance drop r squared of 0.2 versus r squared of 0.58. Steam pops displayed a significantly higher starting local impedance and a larger change in local impedance compared to successful RF applications, p less than 0.01.                                                 The authors concluded that local impedance recorded for miniature electrodes provides a valuable measure of catheter tissue coupling and the change in local impedance is predictive of lesion formation during RF ablation.                                                 In the next paper, Boaz Avitall and associates found that the rising impedance recorded from a ring electrode placed two millimeters from the cryoballoon signifies ice formation covering the balloon surface and indicates ice expansion. The authors studied 12 canines in a total of 57 pulmonary veins, which were targeted for isolation. Two cryoapplications were delivered per vein with a minimum of 90 and a maximum 180 second duration. Cryoapplications was terminated upon reaching a 500 ohm change from baseline. Animals recovered 38 plus or minus six days post procedure, and the veins were assessed electrically for isolation. Heart tissue was histological examined. Extra cardiac structures were examined for damage. Pulmonary vein isolation was achieved in 100% of veins if the impedance reached 500 ohms in 90 to 180 seconds. When the final impedance was between 200 and 500 ohms within 180 seconds of freeze time, pulmonary vein isolation was achieved in 86.8%. For impedance of less than 200 ohms pulmonary vein isolation was achieved in 14%. No extra cardiac damage was recorded. The authors found that impedance rise of 500 ohms at less than 90 seconds with a freeze time of 90 seconds resulted in 100% pulmonary vein isolation.                                                 In our final papers Sally-Ann Clur and associates examined left ventricular isovolumetric relaxation time as the potential diagnostic marker for fetal Long QT Syndrome. Left ventricular isovolumetric contraction time, ejection time, left ventricular isovolumetric relaxation time, cycle length, and fetal heart rate were measured using pulse doppler wave forms in fetuses. Time intervals were expressed as percentage of cycle length, and the left ventricular myocardium performance index was calculated. Single measurements were stratified and compared between Long QT Syndrome fetuses and controls. Receiver operator curves were reformed for fetal heart rate in normalized left ventricular isovolumetric relaxation time. A linear mixed effect model including multiple measurements was used to analyze fetal heart rate, the left ventricular iso volume metric relaxation time, and the left ventricular myocardial performance index. There were 33 Long QT fetuses in 469 controls. In Long QT fetuses the left ventricular isovolumetric relaxation time was prolonged in all groups, p less than 0.001, as was the left ventricular isovolumetric relaxation time.                                                 The best cutoff to diagnose Long QT syndrome was the normalized left ventricular isovolumetric relaxation time greater than equal to 11.3 at less than or equal to 20 weeks, giving a sensitivity in 92% and a specificity of 70%. Simultaneous analysis of the normalized left ventricular isovolumetric relaxation time and fetal heart rate improved the sensitivity and specificity of Long QT Syndrome, AUC of 0.96. The normalized left ventricular isovolumetric relaxation time, the left ventricular myocardial performance index, and fetal heart rate trends differed significantly between Long QT Syndrome fetuses and controls throughout gestation.                                                 The authors concluded that left ventricular volumetric relaxation time is Prolonged QT fetuses. Findings of a prolonged normalize left ventricular isovolumetric relaxation time, and sinus bradycardia can improve the prenatal detection of fetal Long QT Syndrome.                                                 That's it for this month, but keep listening. Suraj Kapa will be surveying all journals for the latest topics of interest in our field. Remember to download the podcasts On the Beat. Take it away Suraj. Suraj Kapa:                          Thank you, Paul and welcome back to On the Beat were we will be summarizing hard-hitting articles across the entire electrophysiologic literature. Today we'll be starting within the realm of atrial fibrillation where we're review an article within the realm of anticoagulation and stroke prevention. Quon et al. published in last month's issue of JACC cardiac electrophysiology on anticoagulant use and risk of ischemic stroke and bleeding in patients with secondary atrial fibrillation. It is well known that use of anticoagulation in atrial fibrillation can reduce overall thromboembolic outcomes. However, its role in secondary atrial fibrillation is unclear. Thus, the authors sought to evaluate the effects anticoagulant use on stroke and bleeding risk. Amongst those where atrial fibrillation occurred in the setting of acute coronary syndrome, pulmonary disease, or sepsis. Amongst around 2300 patients evaluated retrospectively there was no evidence of a lower incidence of ischemic stroke among those treated with anticoagulants compared to those who are not.                                                 However, anticoagulation was associated with a higher risk of bleeding in those with new onset AF associated with acute pulmonary disease. The authors suggest as a result that there is unclear overall benefit for long-term anticoagulation in patients with presumed secondary atrial fibrillation. The difficulty in assessing this is how to define secondary atrial fibrillation. However, in many studies patients who developed in the setting of acute illness still had a high risk of developing quote unquote clinically significant AF in long-term follow-up. However, this was not necessarily absolute as many patients not necessarily develop AF that could be considered clinically significant. Thus, the clinical question that arises is: how long should we treat a patient with anticoagulation when they have presumed secondary atrial fibrillation. These data seem to suggest that there may be no net overall benefits. In other words, all-comers with secondary atrial fibrillation should not necessarily be forever treated with anti-coagulation. However, this slightly requires clinical trials to evaluate further.                                                 Next we delve into the realm of cardiac mapping and ablation where we view an article by Gaita et al. entitled 'Very long-term outcome following transcatheter ablation of atrial fibrillation. Are results maintained after 10 years of follow-up?', published in Europace last month. While pulmonary vein isolation is a widely accepted approach for treatment of atrial fibrillation, most reported studies review outcomes in terms of freedom of AF over a relatively short time period, generally two to five years. However longer term follow up is inconsistently reported. Gaita et al. sought to review 10 year outcomes amongst 255 patients undergoing ablation in a single center. They noted 52% remainder arrhythmia-free amongst a mixed cohort of both paroxysmal and persistent patients while 10% progressed to permanent atrial fiBrillation. They found that absence of increases in blood pressure, BMI, and fasting glucose was protective against an arrhythmia recurrence.                                                 These findings suggest that in a relatively small cohort of patients limited to a single center that even long-term outcomes after pulmonary vein isolation are generally quite good, exceeding 50%. However, future freedom from atrial fibrillation is heavily tied to control of other risk factors. In other words, if a patient is going to have poor control of diabetes, blood pressure, or gain weight, the benefit of their pulmonary vein isolation over long-term follow-up is likely less. These data thus highlight both the potential long-term benefit of PVI, but also the importance of counseling patients regarding the need for continued management and control of future and existing risk factors.                                                 Staying within the realm of atrial fibrillation we next review an article by Weng et al. entitled 'Genetic Predisposition, Clinical Risk Factor Burden, and Lifetime Risk of Atrial Fibrillation' published in last month's issue of circulation. The probability of detecting atrial fibrillation in patients based on clinical factors and genetic risk is unknown. Weng et al. sought to clarify whether a combination of clinical and polygenic risk scores could be used to predict risk of developing atrial fibrillation over long-term followup in the Framingham Heart Study. Amongst 4,600 individuals, 580 developed incident atrial fibrillation and had an overall lifetime risk of developing atrial fibrillation of 37%. Those are the lowest risk tertile based on clinical risk factor burden and genetic predisposition had a lifetime risk of 22% versus 48% in the highest. Furthermore, a lower clinical risk factor burden was associated with delayed atrial fibrillation onset. In order to identify patients with atrial fibrillation, before negative sequelae such as stroke occur, patient and physician understanding of risk and monitoring needs is necessary. The fact is that it will be great to identify every single patient who has atrial fibrillation before they have a negative sequela of that atrial fibrillation such as ischemic stroke.                                                 However, performing continuous monitoring of all patients with potential negative sequelae of atrial fibrillation is extraordinarily difficult. The reason is it's excessively costly. We cannot monitor the entire population irrespective of whatever the risk factors are. However, if we're able to identify the highest risk cohorts early on before the atrial fibrillation onsets, this may offer opportunities for use of newer cheaper monitors. The work by Weng et al. suggests one such possible approach combines clinical and polygenic risk scores. Actionability of these data, however, remains to be seen and further validation other cohorts is necessary to clarify generalized ability.                                                 The next article we review is published in last month's issue of the Journal of American College of Cardiology by Lopes at al. entitled 'Digoxin and Mortality in Patients With Atrial Fibrillation. Lopes et al. sought to evaluate the impact of the Digoxin on mortality in patients with atrial fibrillation and the association with the Digoxin serum concentration and heart failure status. They value this association in over 17,000 patients. At baseline 32% were receiving Digoxin. Baseline Digoxin use did not associate with risk of death, but even in these patients a serum concentration of greater than 1.2 nanograms per milliliter was associated with a 56% increase in mortality risk. For each .5 nanogram per milliliter increase in oxygen concentration the hazard ratio increased by 19% for overall mortality. This was irrespective of heart failure status. Furthermore, in patients who are newly started in Digoxin over the follow-up period, the risk and death and sudden death was higher. These data suggests a significant risk associated with Digoxin use for management of atrial fibrillation irrespective of heart failure status. Furthermore, serum valleys above 1.2 require close consideration of dose de-escalation. Whether there is any optimal dose, however, from the study is unclear. These data amongst a host of prior data strongly suggest again strategic use of Digoxin  principally for the management of atrial fibrillation.                                                 Moving on within the realm of atrial fibrillation, we review an article published in last month's issue of Circulation Research by Yan et al. entitled Stress Signaling JNK2 Crosstalk with CaMKII Underlies Enhanced Atrial Arrhythmogenesis. In this more acellular based study the mechanism underlying atrial arrhythmogenesis associated with aging was evaluated. Yan et al. sought to figure out whether the stress response JNK in calcium mediated arrhythmias might contribute to atrial arrhythmogenesis in aged transgenic mouse models. They demonstrated significant increased activity of JNK2 and aging atria, those furthermore associated with rhythmic remodeling. This association was mediated through CaMKII and ryanodine receptor channel function, with activation of the former leading to increased calcium leak mediated by the ladder. This in turn related to increase atrial fibrillation likelihood. Identifying novel targets for atrial fibrillation therapy is critical. Given atrial fibrillation is a complex disease process related to a multitude of risk factors it can be assumed that the contribution of any single factor may be mediated through distinct mechanisms.                                                 Aging in particular as well regarded, but considered to be non-modifiable risk factor for atrial fibrillation. Identifying genes or pathways, the immediate aging associated fibrillation, may take the risk of aging as no longer a non-modifiable thing. The finding of the significance of JNK2 and associate downstream effects with AF risks and aging hearts may hold potential in offering unique therapeutic targets.                                                 Finally, within the realm of atrial fibrillation, we're viewing article by Chen et al. in last month's issue of the Journal of the American Heart Association entitled Association of Atrial Fibrillation With Cognitive Decline and Dementia Over 20 Years: The ARIC-NCS Study. Multiple studies have suggested a significant association between atrial fibrillation risk of dementia. However, these studies have limited time follow-up and were often done and predominantly white patients. Thus, the authors sought to use the data from ARIC, the Atherosclerosis Risk in Communities Neurocognitive Study, to assess the risk of cognitive decline associated with atrial fibrillation. Amongst over 12,000 participants, a quarter of whom are black and half of whom are white, they noted 2100 patients developed atrial fibrillation and 1,150 develop dementia over a 20 year follow up period.                                                 There was a significantly greater risk of cognitive decline amongst those who developed atrial fibrillation. In turn incident atrial fibrillation for the follow-up period was associated with a higher risk of dementia even after adjusting for other clinical and cardiovascular risk factors such as incidents that ischemic stroke. These data further strengthened prior evidence of a direct link between atrial fibrillation and risk of cognitive decline and dementia. Understanding this long-term risk raises the need to additionally identify approaches to prevent this occurrence, which in turn is dependent on understanding the underlying mechanisms. The finding that the risk of cognitive decline dementias independent of ischemic stroke events raises concern that either subclinical micro-embolic events or other factors may be playing a role in this risk and in turn raises question as to how best to prevent them. Until better understood, however, the question of whether the association is causal remains to be seen.                                                 Changing gears yet again, we now delve into the realm of ICDs, pacemakers and CRT. Published in last month, issue of Heart Rhythm Tarakji et al. published a paper entitled 'Unrecognized venous injuries after cardiac implantable electronic device transvenous lead extraction.' Overall risk of transvenous lead extraction includes that of potentially fatal venous laceration. The authors sought to evaluate the incidence of venous injury that may be unrecognized based on microscopic study of extracted leads. Amongst 861 leads obtained from 461 patients they noted 80 leads or almost 9%. Amongst 15% of patients showed segments vein on the lead body, most of which were transmural including the tissue layer. However, in terms of clinical significance, only 1% had need for emergent surgical intervention for clinically significant venous laceration. Risk factors for having the entire vein on the lead included age of lead, ICD leads, and the use of the laser sheath.                                                 These findings suggest that there may be a high incidence of subclinical venous injury after lead extraction though rarely resulting clinically apparent sequelae. As would be expected, venous injury, including transmural removal of portions of the vein traversed by the lead, was more common amongst older leads, which generally more often require laser sheets and ICD leads. The question is however, whether this carries any direct clinical implications. One they may be considered is the potential additive risk of an advancing new lead through the same venous channel, particularly in the setting of potential transmural venous injury that already exists.                                                 Next in last month's issue of Heart Rhythm we review an article by Sharma at al. entitled 'Permanent His-bundle pacing as an alternative to biventricular pacing for cardiac resynchronization therapy: A multicenter experience.' The use of resynchronization therapy for treatment of patients with heart failure and wide QRS has been shown to offer morbidity and mortality benefits. However, many patients maybe non-responders, and recent studies on His bundle pacing of suggested potential clinical benefits. His bundle pacing essentially only requires one pacing catheter attached within the region of the His bundle Sharma et al. sought to evaluate the safety and success rates of His bundle pacing for patients who have either failed standard resynchronization therapy or in whom most tried as a primary intervention. They noted His bundle pacing was successful in 90% of patients with reasonable myocardial and His bundle capture thresholds. Patients in both groups exhibits significant narrowing of QRS morphology and improvement in left ventricular ejection fraction from a mean of 30 to 43%. However, a total of seven patients had lead related complications.                                                 These database on a retrospective analysis of two types of patients, those failing standard biventricular therapy, and those on whom his bundle pacing was attempted as a primary modality suggest overall safety and efficacy in a handful of experienced centers. The promise of His bundle pacing is that a may allow for more effective resynchronization than standard approaches. The high rate of success suggests that His bundle pacing maybe both safe and reasonable to pursue. However randomized trials across more centers are needed to fully prove its benefit, particularly as a primary modality of treatments.                                                 Next we review ICDs and chronic kidney disease. In last month's issue of JAMA cardiology by Bansal at al. entitled 'Long-term Outcomes Associated With Implantable Cardioverter Defibrillator in Adults With Chronic Kidney Disease.' While the benefit of ICDs in patients with low EF is widely recognized, modifying factors that may increase risk of death are not as well defined. These include things like advanced age and chronic kidney disease. Bansal et al. sought to evaluate long-term outcomes and ICD therapy in patients with chronic kidney disease. In retrospective study of almost 5,900 ambulatory patients amongst whom 1550 had an ICD, they found no difference in all cause mortality. However, ICD placement was associated with an increased risk of subsequent hospitalization due to heart failure or any cause hospitalization.                                                 In light of recent studies such as DANISH the robust sense of ICD benefit is being questioned. One of the thoughts for the absence of similar benefit to prior studies lies in the improving care of ambulatory heart failure patients. In patients with chronic kidney disease several questions rises to the risk with ICD, including infectious risk in dialysis patients and the concomitant mortality risk with renal dysfunction. The author suggested in retrospective study, no incremental benefit of ICDs in patients with chronic kidney disease and perhaps some element of added risk is related to hospitalization. However, this study has several limitations. It is retrospective and many patients received ICDs may have been perceived to be sicker in some way. Thus care must be taken in interpretation, but consideration of randomized studies to adjudicate benefit are likely necessary.                                                 Finally, within the realm of devices, we reviewed an article by Tayal et al. entitled "Cardiac Resynchronization Therapy in Patients With Heart Failure and Narrow QRS Complexes.' publishing the Journal of American College of Cardiology last month. Several parameters have been stressed to identify benefit of resynchronization therapy in patients with wide QRS include cross correlation analysis with tissue doppler imaging. However, many patients may have evidence in mechanical dyssynchrony even in the absence of an apparent wide QRS thus Tayal et al. sought to evaluate the benefit of resynchronization therapy amongst 807 patients with heart failure and a narrow QRS mean criteria in a randomized study. Of the 807 46% had delayed mechanical activation. Those without delay mechanical activation had underwent we standardization therapy and were associated with worse overall outcomes likely due to new delayed mechanical activation potentially related to CRT pacing. These data support the absence of a role for resynchronization therapy in patients with a narrow QRS. This is expected as resynchronization therapy likely offers the most benefit in patients with mechanical dyssynchrony that results from electrical dyssynchrony.                                                 Since by its very nature resynchronization therapy relies on non physiologic cardiac pacing thus compared to normal cardiac activation the nature of resynchronization pacing is desynchronization. These data support the absence of a role for resynchronization therapy in patients with heart failure and narrow QRS complexes.                                                 Moving on to cellular electrophysiology we review an article by Kozasa et al. published in last month's issue of Journal of Physiology entitled 'HCN4 pacemaker channels attenuate the parasympathetic response and stabilize the spontaneous firing of the sinoatrial node.' Heart rate is controlled by an interplay between sympathetic and parasympathetic components. In turn HCN4 abnormalities have been implicated in congenital sick sinus syndrome. The authors sought to clarify the contribution of HCN4 to sinus node autonomic regulation. They created a novel gain-of-function mouse where the HCN4 activity could be modulating from zero to three times normal. They then evaluated ambulatory heart-rate variability and responsive heart rate to vagus nerve stimulation. They found HCN4 over-expression did not increase heart rate, but attenuated heart-rate variability. It also attenuated bradycardic response to vagus nerve stimulation. Knockdown of HCN4 in turn lead to sinus arrhythmia and enhanced parasympathetic response. These data suggest HCN4 attenuates sinus node response to vagal stimuli thus stabilizing spontaneous firing of the node. The clinical application of this remain to be seen but are maybe important in that they highlight a mechanism for a heretofore poorly understood mechanism for how exactly HCN4 abnormalities may lead to sick sinus syndrome.                                                 Within the realm of ventricular arrhythmias we highlighted a number of articles published this past month. The first article we review was published in last month's issue of JACC clinical electrophysiology, entitled characterization of the electrode atomic substrate and cardiac sarcoidosis: correlation with imaging findings of scarring inflammation published by [inaudible 00:41:40] et al. In patients with cardiac sarcoidosis one of the questions is how to define the electronic atomic substrate, particularly before we entered the electrophysiology laboratory. Both active inflammation and replacement fibrosis maybe be seen in patients. The authors evaluated in 42 patients with cardiac sarcoidosis, the association between an abnormal electrograms and cardiac imaging findings including PET and Computed Tomography, as well as Cardiac MRI. They noted that amongst these 40 patients, a total of 21,000 electrograms were obtained, and a total of 19% of these were classified as abnormal. Most of the abnormalities occurred in the basal paravalvular segments and intraventricular septum. They further noted that many of these abnormalities in terms of electrograms were located outside the low voltage areas, particularly as it relates to fractionation. In about 90% of patients they notice late gadolinium enhancements and they noted abnormal FDG uptakes suggesting active inflammation in about 48%.                                                 However, it should be noted that only 29 of the 42 patients underwent cardiac imaging. Segments with abnormal electrograms tended to have more late gadolinium enhancement evidence scar transmurality, and also they noted that the association of abnormal PET scan did not necessarily occur with abnormal electrograms. Thus, they concluded that in patients with cardiac sarcoidosis and ventricular tachycardia pre-procedural imaging with cardiac MRI could be useful in detecting electroanatomic map abnormalities that may in turn be potential targets for substrate ablation. However, they were more likely associated with more scar transmurality and lower degrees of inflammation on PET scanning. These data are important in that they highlight potential non-invasive means by which to understand where substrate might occur in patients with the cardiac sarcoidosis. It is well recognized that cardiac sarcoidosis is associated with increased risk of ventricular arrhythmias. These risks have increased ventricular arrhythmias, might be targetable with ablation. Newer therapies might even offer non invasive means by which to perform ablation in patients best. Thus if we could identify non based on mechanisms of identifying the substrate, this will be even more critical.                                                 The critical findings of this particular paper lie in noting that most of the abnormalities still is in intra ventricular sePtum in basal segments, and also that it is MRI in late gadolinium enhancement and associates more with the abnormal electrograms. Interestingly, the absence of inflammation correlating with the presence of more abnormal electrograms suggests that it is not so much the act of inflammation as being reflected in the endocardial map, but the existence of scar.                                                 Next, again within JACC clinical electrophysiology we review an article by Porta-Sánchez et al. entitled 'Multicenter Study of Ischemic Ventricular Tachycardia Ablation With Decrement Evoked Potential Mapping With Extra Stimulus.' The authors sought to conduct a multicenter study of decrement evoked potential base functional tech ventricular tachycardia substrate modification to see if such mechanistic and physiologic strategies could result in reduction in VT burden. It is noted that really only a fraction of the myocardium in what we presume to be substrate based on the presence of low voltage areas are actually involved in the initiation and perpetuation of VT. Thus if we can identify the critical areas within the presumed substrate for ablation, this would be even a better way of potentially honing in on our targets. They included 20 consecutive patients with ischemic cardiomyopathy. During substrate mapping fractionated late potentials were targeted and an extra stimulus was provided to determine which display decrements. All patients underwent DEEP focus ablation with elimination being correlated with VT non-inducibility after radio-frequency ablation. Patients were predominantly male, and they noted that the specificity of these decrement evoked potentials to detect the cardiac isthmus for VT was better than that of using late potentials alone. They noted 15 of 20 patients were free of any VT after ablation of these targets over six months of follow-up, and there was a strong reduction in VT burden compared to six months pre ablation.                                                 They concluded that detriment evoked potential based strategies towards ablation for ventricular tachycardia might identify the functional substrate and those areas most critical to ablation. They in turn regarded that by its physiologic nature it offers greater access to folks to ablation therapies.                                                 This publication is important in that it highlights another means by which we can better hone in on the most critical regions for substrate evaluation in patients with ventricular tachycardia. The fact is more extensive ablation is not necessarily better and might result in increased risk of harm if we think about the potential effects of longer ablations or more ablation lesions. Thus if we could identify ways of only targeting those areas that are most critical to the VT circuits, we could perhaps short and ablation procedural time, allow for novel ways of approaching targeted ablation with limited amounts of ablation performed, or perhaps even improve overall VT outcomes by knowing the areas that are most critical to ensure adequate ablation therapy provided. However, we need to understand that this is still a limited number of patients evaluated in a non randomized manner. Thus whether or not more extensive ablation performed might have been better is as of yet unclear                                                 Staying within the realm of ventricular tachycardia we review an article published in last month's issue of Heart Rhythm by Winterfield et al. entitled the 'Impact of ventricular tachycardia ablation on healthcare utilization.' Catheter ablation of atrial tachycardia has been well accepted to reduce recurrent shocks in patients with ICDs. However, this is a potentially costly procedure, and thus effect on overall long-term health care utilization remains to be seen. The authors sought to evaluate in a large scale real world retrospective study the effect of VT ablation on overall medical expenditures in healthcare utilization. A total 523 patients met study inclusion criteria from the market scan database. After VT ablation median annual cardiac rhythm related medical expenditures actually decreased by over $5,000. Moreover the percentage of patients with at least one cardiac rhythm related hospitalization an ER visit decreased from 53 and 41% before ablation respectively, to 28 and 26% after ablation. Similar changes we're seeing in number of all cause hospitalizations and ER visits. During the year before VT ablation interestingly there was an increasing rate of healthcare resource utilization, but a drastic slowing after ablation.                                                 These data suggests that catheter ablation may lead to reduced hospitalization in overall healthcare utilization. The importance of these findings lies in understanding why we do the things we do. We can provide a number of therapies to patients, but we seek two different effects. One is the individual effect of improving their particular health. The second thing is trying to avoid increasing healthcare expenditures on a population level and making sure resources are utilized. If we can reduce recurrent hospitalizations and overall healthcare expenditure in patients by providing a therapy in addition to provide individual benefit, this is the optimal situation. These data suggests that VT ablation might provide such a benefits, that in fact it reduces overall healthcare utilization while improving overall outcomes.                                                 Next and finally within the realm of ventricular arrhythmias, we review more on the basic side the role of Titin cardiomyopathy leads to altered mitochondrial energetics, increased fibrosis and long-term life-threatening arrhythmias, published by Verdonschot et al. in last month's issue of European Heart Journal. It is known now that truncating Titin variants might be the most prevalent genetic cause of dilated cardiomyopathy. Thus, the authors sought to study clinical parameters and long term outcomes related to Titin abnormalities in dilated cardiomyopathy. They reviewed 303 consecutive and extensively phenotype dilated cardiomyopathy patients who underwent cardiac imaging, Holter monitoring, and endomyocardial biopsy and in turn also underwent DNA sequencing of 47 cardiomyopathy associated genes. 13% of these patients had Titin abnormalities. Over long-term followup they noted that these patients had increased ventricular arrhythmias compared to other types of dilated cardiomyopathy, but interestingly, they had similar survival rates. Arrhythmias in those Titin abnormal patients were most prominent in those who were subjected to an additional environmental trigger, including viral infection, cardiac inflammation, other systemic disease or toxic exposure. They also noted the cardiac mass was relatively reduced in titan admirable patients.                                                 They felt that all components of the mitochondrial electron transport chain we're simply up-regulated in Titin abnormal patients during RNA sequencing and interstitial fibrosis was also augmented. As a result, they concluded that Titin variant associated dilated cardiomyopathy was associated with an increased risk of ventricular arrhythmias, and also with more interstitial fibrosis. For a long time we have reviewed all non ischemic cardiomyopathy as essentially equal. However, more recent data has suggested that we can actually hone in on the cause. In turn, if we hone in on the cause, we might be able to understand the effects of specific therapies for ventricular arrhythmias based on that underlying cause. Patchy fibrosis might not be as amenable, for example, to ablation as discreet substrate that we might see in infarct related VT. Understanding the relative benefit in very specific types of myopathies might hold benefit in understanding how to, one, risk stratify these patients, and two, understand what type of therapy, whether pharmacologic or ablative, might result in greatest benefit to the patients.                                                 Changing gears entirely now to the role of genetics, we review multiple articles in various genetic syndromes published this past month. First, we reviewed an article by Providência et al. published in the last month's issue of heart entitled 'Impact of QTc formulae in the prevalence of short corrected QT interval and impact on probability and diagnosis of short QT syndrome.' The authors sought to assess the overall prevalence of short corrected QT intervals and the impact on diagnosis of short QT syndrome using different methods for correcting the QT interval. In this observational study they reviewed the sudden cardiac death screening of risk factors cohorts. They then applied multiple different correction formulae to the ECGs. They noted that the prevalence of individuals with the QTc less than 330 and 320 was extremely low, namely less than .07 and .02% respectively. They were also more frequently identified using the Framingham correction. The different QTc correction formulae could lead to a shift of anywhere from 5 to 10% of individuals in the cohort overall.                                                 They further noted, that based on consensus criteria, instead of 12 individuals diagnosed with short gut syndrome using the Bazett equation, a different number of individuals would have met diagnostic criteria with other formulae, 11 using Fridericia, 9 with Hodges, and 16 using the Framingham equation. Thus, they noted that overall the prevalence of short QT syndrome exceedingly low and an apparently healthy adult population. However, reclassification as meeting criteria might be heavily dependent on which QT correction formula is used. The importance of these findings is that not all QTs are created equal.                                                 Depending on how you compute the QT interval in which formula to use may affect how you actually risk characterize a patient. Unfortunately, these data do not necessarily tell us which is the right formula, but this highlights that it might be relevant to in the future evaluate the role of different formulae and identifying which is the most necessary to classify a patient.                                                 Moving on to an article published in last month's issue of the journal of clinical investigation by Chai et al. we review an article entitled 'Physiological genomics identifies genetic modifiers of Long QT Syndrome type 2 severity.' Congenital Long QT Syndrome is a very well recognized, inherited channelopathy associated life-threatening arrhythmias. LQTS type 2 is specifically caused by mutations in casein to encoding the potassium channel hERG. However, even with the mutation not all patients exhibit the same phenotype. Namely some patients are more at risk of life threatening arrhythmias in spite of having the same mutation as others who do not exhibit the same severity phenotype. The authors sought to evaluate whether specific modifiable factors within the remaining genetic code might be modifying the existing mutation. Thus, they sought to identify contributors to variable expressivity in an LQT 2 family by using induced pluripotent stem cell derived cardiomyocytes and whole exome sequencing in a synergistic manner.                                                 They found that patients with severely effected LQT 2 displayed prolonged action potentials compare to sales from mildly effected first-degree relatives. Furthermore, stem cells derived from patients were different in terms of how much L-type calcium current they exhibited. They noted that whole exome sequencing identified variants of KCNK17 and the GTP-binding protein REM2 in those patients with more severe phenotypes in whom greater L-type calcium current was seen. This suggests that abnormalities or even polymorphisms in other genes might be modifying the risk attributed to by mutations in the primary gene. This showcases the power of combining complimentary physiological and genomic analysis to identify genetic modifiers and potential therapeutic targets of a monogenic disorder. This is extraordinarily critical as we understand on one level that when we sequence a monogenic disorder that there might exist variants of uncertain significance, namely they have not been classified as disease causing, but could be. In turn, we also recognize that mutations in a family might effect different relatives differently. However, why this is has been relatively unclear.                                                 If we can understand and identify those patients who are most at risk of dangerous abnormal rhythms, this will be useful in how much to follow them, and what type of therapy to use in them. The fact that other genes might modify the risk even in the absence of specific mutations, suggests that novel approaches to characterizing the risk might help for the risk modified patients classification in general. Clinical use, however, remains to be seen.                                                 Moving on from long QT, we evaluate 'The Diagnostic Yield of Brugada Syndrome After Sudden Death With Normal Autopsy' noted in last month's issue of the Journal of American College of Cardiology and published by Papadakis et al. It is well known, the negative autopsies are not uncommon in patients, however, families might be wondering how at risk they are. Thus, the authors sought to assess the impact of systematic ajmaline provocation testing using high right precordial leads on the diagnostic yield Brugada syndrome in a large cohort of Sudden Arrhythmic Death syndrome families. Amongst 303 families affected by Sudden Arrhythmic Death Syndrome evaluation was done to determine whether or not there was a genetic inherited channelopathy cause. An inherited cardiac disease was diagnosed in 42% of the families and 22% of relatives Brugada syndrome was the most prevalent diagnosis overall amongst 28% of families. Ajmaline testing was required, however, to unmask the Brugada Syndrome in 97% of diagnosed individuals. Furthermore, they use of high right precordial leads showed a 16% incremental diagnostic yield of ajmaline testing for diagnosing Brugada syndrome.                                                 They further noted that a spontaneous type 1 regard or pattern or a clinically significant rhythmic event developed in 17% of these concealed regardless syndrome patients. The authors concluded the systematic use of ajmaline testing with high right precordial leads increases the yield of Brugada Syndrome testing in Sudden Arrhythmic Death Syndrome families. Furthermore, they noted that assessments should be performed in expert centers or patients could also be counseled appropriately. These findings are important and one of the big questions always becomes how aggressively to test family members of patients or of deceased individuals who experienced sudden arrhythmic death. Many of these patients have negative autopsies, and genetic autopsy might not be possible due to lack of tissue or blood products that can be adequately tested.                                                 The data here suggest that amongst a group of 303 sudden arrhythmic death, families that Brugada Syndrome is by far the most frequent diagnosis. If an inherited cardiac disease was identified. In turn, it is not ECG alone or echo alone that helps identify them, but requires drug provocation testing in addition to different electrode placements. Whether or not this will consistently offer benefit in patients in general or my result in overcalling remains to be seen next within the realm of genetic predisposition.                                                 We view an area where we don't know if there's a genetic predisposition in article published by Tester et al. entitled Cardiac Genetic Predisposition in Sudden Infant Death Syndrome in last month's issue of the journal of american college of cardiology. Sudden Infant Death Syndrome is the leading cause of post-neonatal mortality and genetic heart diseases might underlie some cases of SIDS. Thus the authors sought to determine the spectrum and prevalence of genetic heart disease associated mutations as a potential monogenic basis for Sudden Infant Death Syndrome. They study the largest cohort to date of unrelated SIDS cases, including a total of 419 individuals who underwent whole exome sequencing and targeted analysis for 90 genetic heart disease susceptibility genes. Overall, 12.6% of these cases had at least one potentially informative genetic heart disease associated variants. The yield was higher in those mixed European ancestry than those of European ancestry.                                                 Infants older than four months were more likely to host a potentially informative gene. Furthermore, they noted that only 18 of the 419 SIDS cases hold a [inaudible 01:01:26] or likely pathogenic variant. So in other words, only 4% of cases really had a variant that they could say was distinctly pathogenic or likely pathogenic. Thus, overall, the minority of SIDS cases have potentially informative variant in genetic heart disease susceptibility gene, and these individuals were mostly in the 4 to 12 month age group. Also, only 4% of cases had immediately clinically actionable variance, namely a variant, which is well recognized as pathogenic and where we could actually say that a specific therapy might have had some effect. These findings can have major implications for how best to investigate SIDS cases in families. It might suggest that SIDS cases where the individual was older, nearly 4 to 12 months of age might have a greater yield in terms of identifying variance.                                                 While this might not affect the deceased in fit, it might affect, families are planning on having another child in whom a variant can be identified.                                                 Finally, within the realm of genetics, we review an article published in last month's issue of Science Advances by Huang. et al. entitled 'Mechanisms of KCNQ1 Channel Dysfunction in Long QT Syndrome Involving Voltage Sensor Domain Mutations'. Mutations that induce loss of function of human KCNQ1 underlie the Long QT Syndrome type 1. While hundreds of mutations have been identified the molecular mechanism by which they result in impaired function are not as well understood. The authors sought to investigate impact of 51 specific variants located within the voltage sensor domain and emphasized effect on cell surface expression, protein folding, and structure. For each variant efficiency of trafficking of the plasma membrane, impact of proteasome inhibition, and protein stability were evaluated. They noted that more than half of the loss of function mutations were seen to destabilized structure of the voltage sensor domain, generally accompanied by mistrafficking and degradation by the proteasome.                                                 They also noted that five of the folding defective Long QT Syndrome mutant sites were located in the S0 helix, where they tend to interact with a number of other loss of function mutation sites in other segments of the voltage sensor domain. They suggested these observations reveal a critical role for the S0 helix as a central scaffold to help organize and stabilized KCNQ1 overall. They also note the importance of these findings is that mutation-induced destabilization of membrane proteins may be a more common cause of disease functioning in humans. The importance of these findings lies in better understanding why specific mutations lead to appa

Dr Wong:             Welcome to the monthly podcast, "On The Beat, for Circulation: Arrhythmia, and Electrophysiology." I'm doctor Paul Wong, editor in chief, with some of the key highlights from this month's issue. We'll also here from Dr. Suraj Kapa reporting on new research from the latest journal articles in the field.                                 In our first article, Mathew Daly and associates examine whether a high-resolution, 9 French, infrared thermography catheter can continuously image esophageal temperatures during atrial fibrillation catheter ablation. The infrared temperature catheter was inserted nasally or orally into the esophagus, adjacent to the left atrium. Endoscopy was performed within 24 hours to document esophageal injury. Thermal imaging showed that 10 out of 16 patients experienced one or more events where the peak esophageal temperature was greater than 40 degrees centigrade. Three patients experienced temperatures greater than 50 degrees centigrade and one experienced greater than 60 degrees centigrade. Analysis of temperature data from each subject's maximal thermal event revealed high radius, 2.3 degrees centigrade per millimeter and rates of change 1.5 degrees centigrade per second, with an average length of esophageal involvement of 11.0 millimeters.                                 Endoscopy identified three distinct thermal lesions, all in patients with temperatures greater than 50 degrees centigrade, all resolving within two weeks. The authors concluded that infrared thermography, high-resolution mapping of esophageal temperatures during catheter ablation may be performed. Esophageal thermal injury occurs with temperatures greater than 50 degrees centigrade, and was associated with large spacial-temporal gradients.                                 In our next article, Nitesh Sood and associates reported on the real-world incidence and predictors of perioperative complications in transvenous lead extractions involving ICD leads in the NCDR ICD registry. Lead extraction was defined as removal of leads implanted for greater than one year. Predictors of major perioperative complication for all extraction procedures, 11,304, and for high voltage leads, 8,362, or 74% across 762 centers were analyzed, using univariate and multivariate logistic regression. Major complications occurred in 258, or 2.3% of the extraction procedures. Of these, 258 procedures with a complication, 41 or 16% required urgent cardiac surgery. Of these, 14 or 34% died during surgery. Among the total 98, or 0.9% deaths reported, 18 or 0.16% of the total occurred during extraction.                                 In multivariate, logistic regression analysis of all extractions, female sex, admission other than electively for the procedure, three or more leads extracted, longer implant duration, dislodgement of other leads, patients' clinical status, requiring lead extraction, such as infection or perforation, were associated with increased risk of complications. For high voltage leads, smaller lead diameter, a flat versus round coil shape, in greater proximal surface coil area, were multivariate predictors of major perioperative complications.                                 The rate of major complications and mortality with transvenous lead extraction is similar in the real world compared to single center studies from high volume centers. There remains a significant risk of urgent cardiac surgery with a very high mortality, and planning for appropriate cardiothoracic surgical backup is imperative.                                 In our next paper, Bence Hegyi and associates, have reported on the repolarization reserve in failing rabbit ventricular myocytes, and the role of calcium and beta-adrenergic effects on delayed and inward rectifier potassium currents. The authors measured the major potassium currents, IKr, IKs, IK1, and their calcium and beta-adrenergic dependence in rabbit ventricular myocytes, in chronic pressure, in volume overload, induced heart failure, and compared them to age-matched controls.                                 The authors made a number of observations. One, action potential duration was significantly prolonged only at lower pacing rates, 0.2 to 1 Hertz, in heart failure under physiological ionic conditions and temperature. Two, beat to beat variability of action potential duration was also significantly increased in heart failure. Three, both IKr and IKs were significantly regulated in heart failure under action potential clamp but only when cytosolic calcium was not buffered. Four, CaMKII inhibition abolished IKs upregulation in heart failure, but did not affect IKr. Five, IKs response to beta-adrenergic stimulation was also significantly diminished in heart failure, and, six, IK1 was also decreased in heart failure regardless of calcium buffering, CaMKII inhibition or beta-adrenergic stimulation.                                 These observations changed when cytosolic calcium was buffered. The action potential prolongation in heart failure was also significant in higher pacing rates. The authors concluded that in heart failure, calcium dependent up regulation of IKr and IKs counter-balances the reduced IK1, maintaining the repolarization reserve, especially at higher heart rates. In physiologic conditions, unlike conditions of strong cytosolic calcium buffering. Under beta-adrenergic stimulation, reduced IKs responsiveness, severely limits the integrated repolarizing potassium current in repolarization reserve in heart failure, increasing the arrhythmia propensity.                                 In the next paper, Christopher Piorkowski and associates report on the feasibility of a combined endo-epicardial catheter approach for mapping the ablation of atrial fibrillation. The authors studied 59 patients with permanents pulmonary veins isolation and had further symptomatic recurrences of paroxysmal atrial fibrillation, persistent atrial fibrillation, or atrial tachycardia. These patients underwent repeat ablation using bi-atrial endo- and epicardial mapping and ablation. Identification of arrhythmia substrates and selection of ablation strategy were based on sinus rhythm voltage mapping. In all patients, endo-epicardial mapping ablation were feasible using standard technologies of catheter access, three dimensional mapping, and radiofrequency ablation.                                 Epicardial mapping and ablation did not add procedural risk. Exclusively, epicardial low voltage substrate were found in 14% of patients. For the first time, novel epicardial conduction abnormalities located in the epicardial fiber network were described in human patients, 19% of the cohort. Epicardial ablation was needed in 80% of the patients. Over 23 months of follow up, freedom from arrhythmia recurrence was 73%. The authors used continuous monitoring and three months blanking period. Freedom from ATR of greater than two minutes was defined as the primary end-point.                                 The authors concluded that endo-epicardial mapping ablation was feasible and safe. Epicardial ablation increases transient mortality of ablation lesions. Further studies will be needed to demonstrate reproducibility and long-term outcomes, and how the technique compares to other methods.                                 In the next article, Michael Wolf and associates examined the long-term results of substrate modification for ablation of ventricular tachycardia using substrate elimination, targeting local, abnormal ventricular activities, or LAVA, post-myocardial infarction. They reported on 159 consecutive patients undergoing first ablation, age 65, 92% with ICDs, 54% with storms, and 73% with appropriate shocks. LAVA were identified in 92% and VT was inducible in 73%. Complete LAVA elimination after ablation was achieved in 64% and non-inducibility was achieved in 85%. During a median follow-up of 47 months, single procedure, ventricular free survival was 55%, 10% storms, and 19% shocks. The ventricular arrhythmia free survival was 73% after one year and 49% after five years.                                 Complete LAVA elimination was associated with improved outcomes, ventricular arrhythmia free survival of 82% at one year and 61% at five years. The subgroup treated with multi-electrode mapping and real-time image integration had improved ventricular arrhythmia free survival, 86% at one year and 65% at four years. Repeat procedures were also performed in 18% of patients. The outcomes improved, 69% ventricular arrhythmia free survival during a median follow-up of 46 months.                                 In a single center study, substrate modification, targeting LAVA for post myocardial infarction ventricular tachycardia resulted in a substantial reduction in ventricular tachycardia storm and ICDs shocks with up to 49% of patients free of arrhythmias at five years after a single procedure. Complete LAVA elimination, multi-electrode mapping, and real-time integration were associated with improved ventricular arrhythmia free survival.                                 In the next paper, Jean-Baptiste Gourraud and associates examined the safety and feasibility of transvenous lead extraction in adults with congenital heart disease over a 20 year period at a single center. The authors reported on 71 transvenous lead extraction procedures in 49 patients with adult congenital heart disease, mean age 38 years in which a total of 121 leads were extracted. The primary indication for extraction were infection in 48%, lead failure in 31%. A laser sheath was required in 46% and a femoral approach in 8%. Complete transvenous lead extraction was achieved in 92% of the leads. 49% of the patients had transposition of the great arteries. In multivariate analysis, lead duration was predictive of transvenous lead extraction failure. No perioperative death or pericardial effusion was observed. Subpulmonary, atrioventricular valve regurgitation increased in eight patients, five of whom had TGA and were independently associated with ICD leak or valvular vegetation.                                 After a median of 54 months of follow up after the first lead extraction, three deaths occurred independently from lead management. The authors concluded that despite complex anatomical issues, transvenous lead extraction can be achieved successfully in most adult congenital heart disease patients using advanced extraction techniques. Subpulmonary AV valve regurgitation is a prevalent complication, particularly in patients with transposition of the great arteries.                                 In the next paper, Gabriela Orgeron and associates examined the incidence of ventricular arrhythmias and follow-up in ARVC patients grouped by the level of indication for ICD placement, based on the 2015 International Task Force Consensus Statement Risk Stratification Algorithms for ICD Placement in arrhythmogenic right ventricular dysplasia/cardiomyopathy. In 365 of arrhythmogenic right ventricular dysplasia/cardiomyopathy patients, the authors found that the algorithm accurately differentiates survival from any sustained VT/VF among the four risk groups, p < 0.001. Patients with a Class I indication had significantly worst survival from VT/VF than patients with a Class IIa indication or a Class IIb. However, the algorithm did not differentiate survival free from VF or V flutter between patients with Class I and Class II indications. Adding Colter results, less than 100 PVCs per 24 hours to the classification, helps differentiate the risk.                                 Patients with a high PVCs burden, greater than 1000 PCVs per 24 hours had a poor survival from both VT/VF and VF and V flutter.                                 In the next paper, Takeshi Kitamura and associates studied eight patients that had bi-atrial tachycardia, a rare form of atrial macroreentrant tachycardia, in which both atria form a critical part of the circuit and were mapped using an automatic, high resolution, mapping system. 708 patients had a history of persistent atrial fibrillation, including septal or anterior left atrial ablation before developing bi-atrial tachycardia. One of the patients had a history of atrial septal path closure with a massively enlarged right atrium. The authors found that 9 atrial tachycardias, with a median cycle length of 334 milliseconds had three different types. Three were peri-mitral and peri-tricuspid reentrant circuit, three utilized the right atrial septum in a peri-mitral circuit, and three utilized only the left atrium and the left right atrial septum.                                 Catheter ablation successfully terminated eight of the nine bi-atrial tachycardias. The authors found that all patients who developed bi-atrial tachycardia had an electrical obstacle on the intraseptal left atrium, primarily from prior ablation lesions.                                 In our next paper, Kwang-No Lee and associates randomized 500 patients with paroxysmal atrial fibrillation to one of two strategies after pulmonary vein isolation. One, elimination of non-PV triggers in 250 patients, group A, or, two, step-wise substrate modification using complex fractionated atrial electrogram or linear ablation until non-inducibility of atrial tachyarrhythmias was achieved, 250 patients in group B. Recurrence of atrial tachyarrhythmias was higher in group B compared to group A. 32% of patients in group A experienced at least one episode of recurrent atrial tachyarrhythmia after the single procedure, compared to 43.8% in group B. P-value of 0.012 after a median follow-up of 26 months. Competing risk analysis showed that the cumulative incidence of atrial tachycardia was significantly higher in group B compared to group A (p= 0.007).                                 The authors concluded that elimination triggers as the end-point of ablation in paroxysmal atrial fibrillation patients decreased long-term recurrence of atrial tachyarrhythmias compare to non-inducibility approach achieved by additional empiric ablation.                                 In our final paper of the month, Roland Tilz and associates reported on 10 year outcome after circumferential pulmonary vein isolation using a double lasso and three dimensional electro anatomic mapping technique. From 2003 to 2004, 161 patients with symptomatic drug refractory paroxysmal atrial fibrillation underwent electro-anatomical mapping guided circumferential pulmonary vein isolation. The procedure end-point was absence of pulmonary vein spikes thirty minutes after isolation, after a single procedure and a median follow up of 129 months, stable sinus rhythm was present in 32.9% of patients based on Holter-ECGs and telephonic interviews. After multiple procedures, mean 1.73 and median follow up of 123.4 months, stable sinus rhythm was seen in 62.7% of patients. Progression towards persistent atrial fibrillation was observed in 6.2%.                                 The authors concluded that although the 10-year single procedure outcome in patients with paroxysmal atrial fibrillation was low, 32.9%, it increased to 62.7% after multiple procedures and the progression rate to persistent atrial fibrillation was remarkably low.                                 That's it for this month but keep listening. Suraj Kapa will be surveying all journals for the latest topics of interest in our field. Remember to download the podcast, "On the beat." Take it away Suraj. Dr Kapa:               Thank you Paul, and welcome back everybody to Circulation’s “On the Beat”, where we'll be discussing hard hitting articles across the electrophysiology literature.                                 Today, we'll be reviewing 22 separate articles of particular interest, published in January 2018. The new year saw plenty of articles that are of particular interest either for the future of our field of for present management of our patients. First, within the realm of atrial fibrillation, we'll review several articles within the realm of anticoagulation and left atrial appendage occlusion.                                 The first article we'll review is by Yong et al in the American Heart Journal, volume 195, entitled "Association of insurance type with receipt of oral anticoagulation in insured patients with atrial fibrillation: A report from the American College of Cardiology NCDR PINNACLE registry." In this publication, the author sought to evaluate the effect of insurance type on the appropriate receipt of anticoagulant therapy, specifically looking at warfarin versus NOACs. They reviewed retrospectively over 360,000 patients and found significant differences in appropriate prescription of anticoagulants, irrespective of which anticoagulant was considered. Medicaid patients received less appropriate anticoagulant prescription than those who were privately insured on Medicare or military insured. Furthermore, those on military or private insurances had a higher rate of NOAC prescription than those with Medicare.                                 Furthermore, there was an even wider disparity in NOAC use than warfarin use amongst differently insured patients. These data are important in that they highlight potential variability in appropriate management of patients based on insurance type. Of course, there are many issues that might impact this, such as health care access or available pharmacy coverage of specific medications. Furthermore, the authors do not dive into the impact on outcomes based on the therapy availability.                                 The next article we'll review is by Jazayeri et al, entitled "Safety profiles of percutaneous left atrial appendage closure and lysis: An analysis of the Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE) database from 2009 to 2016" published in the Journal of Cardiovascular Electrophysiology in volume 29 issue 1. Here, the authors sought to evaluate the overall safety profiles of procedures performed with different percutaneous left atrial appendage occlusion devices, including LARIAT and WATCHMAN. They review 356 unique reports and compared outcomes pre- and post- approval of the WATCHMAN device. The look at the specific composite outcome of stroke, TIA, pericardiocentesis, cardiac surgery, and death. They noted that this composite outcome occurred more frequently with WATCHMAN than with LARIATs, and this is irrespective of pre- or post- approval status.                                 These findings highlight the importance of postoperative monitoring in evaluation of overall outcomes. The reason by which there was more frequent negative outcomes in the WATCHMAN than LARIATs need to be considered. Obviously there's several limitations in the MAUDE database, similar with all large databases. However, it does highlight the importance of considering the mechanisms or sure decision making necessary, not just amongst patients and their providers but amongst operators of the staff or amongst physicians and industry executives. To determine how to optimize devices going forward.                                 Speak of left atrial appendage occlusion devices and the potential future of these, we next review an article by Robinson et al, entitled "Patient-specific design of a soft occluder for the left atrial appendage" published in nature biomedical engineering, in volume two in the year 2018. Robinson et al used 3D printing to create a soft, immunocompatible, biocompatible, endocardial implant to occlude the left atrial appendage. They use the individual CT of an in vivo pig to three D print using a specialized material, a left atrial appendage occlusion device, and demonstrated feasibility of achieving adequate occlusion. This paper is important and is one of the initial [inaudible 00:22:03] to how three D printing may be used to optimize patient care. In fact, three D printing has the potential to overturn medical manufacturing and device development.                                 Anatomy tends to be more often patient-specific than not. That's one size fits all implant designs may not be optimal, and resulting exclusion or inadequate occlusion amongst many patients. Decide of three D printable patient specific rapidly prototype soft devices that are biocompatible and hemocompatible, holds the potential to revolutionize the occlusion.                                 Staying in the field of left atrial appendage occlusion, we next review an article by Lakkireddy et al entitled "left atrial appendage closure and systemic homeostasis: The LAA homeostasis study" published in JACC. The authors sought to evaluate the effect of epicardial-versus endocardial left atrial appendage occlusion on systemic homeostasis, including effects on neuro-hormonal profiles of patients. They performed a prospective, single center, observational study, including 77 patients, about half of whom received endocardial versus epicardial device. Interestingly, they noted that the epicardial left atrial appendage occlusion cohort exhibited significant decrease in blood adrenaline, noradrenaline and aldosterone levels. Those are not seen with endocardial devices. Internal epicardial devices are associated with increases in adiponectin and insulin levels as well as a decrease in free fatty acids and consistently lower systemic blood pressure.                                 These data suggest a significant difference in the effect of epicardial versus endocardial closure left atrial appendage on neurohormonal profile. The authors propose several mechanisms for these findings but not the exact mechanisms as yet unclear. Several factors potentially could lead to these findings. One is that epicardial ligation may result in more total ischemia of the left atrial appendage than endocardial closure. Another potential mechanism maybe that the presence for material in the pericardial space versus in the bloodstream may have different effects on neuro-hormonal profile. However, these significant differences in outcomes highlight the importance of considering whether all approaches of left atrial appendage occlusion are considered equal. Many flaws of this study is that it's observational and not randomized. Does it possible those receiving epicardial closure may have been perceived to be lower risk for epicardial puncture, in this, as result, had better long-term outcomes.                                 Changing gears now but staying within the realm of atrial fibrillation, we next review elements for cardiac mapping and ablation. The first article we review is one that has received significant press, published by Marrouche et al entitled "Catheter ablation for atrial fibrillation with heart failure" in the New England Journal of Medicine, volume 378. It is well recognized that morbidity and mortality are higher in heart failure patients who also have atrial fibrillation. Marrouche et al published the results of the CASTLE-AF trial, which attempted to determine if catheter ablation [inaudible 00:24:46] better outcomes among patients with heart failure and atrial fibrillation. They randomized 179 patients to ablation and 184 to medical therapy, which consisted of either rate or rhythm control. Inclusion criteria were those with NYHA class II to IV heart failure, LVEF of 35% or less, and an ICD.                                 The primary endpoint was a composite where the death from many causes or hospitalizations for worsening heart failure. They noted over a median of three as a follow up, the end-point was reached in 28.5% of the ablation group and 44.6% of the medical therapy group, accounting for a significant hazard ratio of 0.62. Furthermore, fewer patients that in the ablation group died from any cause, were hospitalized for worsening heart failure, or died from cardiac causes. These data made a big splash because they're highly supportive of the premise that catheter ablation may be beneficial in some patients with atrial fibrillation and heart failure, often beyond that of medical therapy alone.                                 One major strength of this paper is that the actual AF burden was tracked by the ICD, so we know for sure whether or not the procedure was successful and how controlled the atrial fibrillation was. One thing to note however, is that subgroup analysis suggest that those with more symptomatic heart failure, namely NYHA class III to IV, not benefit as much from ablation. Furthermore, it's also important to note that the five years expected mortality in patients was higher than predicted in the CASTLE-AF trial, however overall these trials highly suggest that the potential benefit that ablation may hold over conventional medical therapy. Extrapolation to comparison with the utility of interventions such as biventricular pace with AV node ablation, however, remains to be considered.                                 Next, we review an article by Chugh et al entitled "Spectrum of atrial arrhythmias using ligament of Marshall in patients with atrial fibrillation" published in Heart Rhythm volume 15, issue 1. They reviewed the spectrum of presentations associated with arrhythmogenesis attributed to the ligament of Marshall, amongst patients with atrial fibrillation. They demonstrate that nearly a third of those patients, ligament of Marshall associated arrhythmias had a pulmonary vein ligament connection, that variously required ablation, the left lateral ridge, the mitral annulus, or alcohol ablation. In addition, they noted about a quarter of patients had atrial tachycardia attributable to the ligament, and the remaining had periatrial reentry requiring either ablation or alcohol injection of the ligament to attain a conduction block.                                 The relevance of this publication, albeit it is of a small number of patients and a small center, lies in highlighting on the right mechanisms by which the ligament of Marshall may contribute to arrhythmogenesis. Namely, can include direct venous connections, inhibition to inaudibility to attain mitral block, and directly attributed atrial arrhythmias. Recognition of the various ways and situations under which the ligament of Marshall may play a role in arrhythmogenesis in atrial fibrillation patients, may optimize physician decisions to look for identify and target the ligaments. What is not as well understood however is the frequency with which ligament of Marshall plays a significant role in arrhythmogenesis in atrial fibrillation.                                 Moving gears, we next review an article by Pathik et al entitled "Transient rotor activity during prolonged three-dimensional phase mapping in human persistent atrial fibrillation" published in a special issue of JACC Clinical Electrophysiology, that focus on atrial fibrillation specifically, in volume 4 issue 1. Pathik et al sought to validate three-dimensional phase mapping system for persistent atrial fibrillation. Commercially available rotor mapping systems project the heart into two dimensions based on a three-dimensional catheter. Instead, Pathik et al used a combination of basket catheters along with the non-left atrial surface geometry to construct three D representations of phase progression. Amongst 9 out of 14 patients, they identified 34 rotors, with all these rotors being transients. Of particular interest, the rotors were only seen in areas of high electric density, where internal electric distances were shorter. They also noted the single wave front is also the most common propagation pattern. The importance of this publication lies in considering two things. First is the three dimensional representation of rotor position and the feasibility of this, and the second is really the high electro-density necessary to observe for others.                                 This has been one of the main problems in rotor analysis, namely what the spacial and temporal density is, that is required to identify rotors, especially given how transient they often are. The presence of rotors does not necessarily mean they're ablation targets in all patients. However, the question still remains regarding the optimal approach to mapping rotors, it needs to be remembered that rotors actually are meant to represent three dimensional scrollway phenomena, that cannot necessarily always be reflected in traditional two D mapping schema. Furthermore, to be remembered that when we claim three-dimensional mapping, this just reflects a two-dimensional surface being wrapped in three dimensions to reflect overall internal surface geometry but it does not take into account transmural activation.                                 Thus, taking into account all these elements it should be remembered as sometimes, it is possible that a rotor might exist but it's just not evident based on the two-dimensional representation or a two-dimensional representation that looks like a rotor may in fact not be a rotor when you consider it in a three-dimensional media.                                 Our last article within the realm of cardiac mapping and ablation we will consider is by Zghaib et al, entitled "Multimodal examination of atrial fibrillation substrate: Correlation of left atrial bipolar voltage using multielectrode fast automated mapping, point by point mapping, and magnetic resonance imaging intensity ratio", published in JACC Clinical Electrophysiology, in the same volume as the previous article. The authors sought to compare fast automated mapping with multiple electrodes versus point by point mapping and correlate with weighed gadolinium enhancement as seen by MRI, termed the image intensity ratio.                                 We all recognize that bipolar voltage is critical to recognizing and evaluating substrate. It's traditionally used in decay regions of substrate in both the atrium and ventricles. However, whether a newer automated approach used to characterize substrate perform equally well in comparison with traditional point to point mapping is still unknown. Thus, the authors in 26 patients perform cardiac MRI and mapping endocardial using both voltage mapping techniques. They noted that for each unit increase in image intensity ratio on MRI, in other words, increasing late enhancement, there was 57% reduction of bipolar voltage. They also noted that the bipolar voltage using other fast elevating mapping or point by point was significantly related with actual differences in calculated voltage, becoming more dissimilar in the extreme of high and low voltage areas.                                 The relevance of this publication is highlight in the potential utility of fast automated mapping in creating accurate voltage maps. The correlation of voltage values with image-intensity ratios suggest the utility of either approach. In turn, correlation with MRI suggest a pathologic correlate for all of these findings. However, whether substrate characterization guide ablation carries incremental benefit remains to be seen.                                 Changing gears but staying in the realm of atrial fibrillation, we next review elements of risk stratification and management. The first article we review is by Friedman et al, entitled "Association of left atrial appendage occlusion and readmission for thromboembolism amongst patients with atrial fibrillation undergoing concomitant cardiac surgery", published in JAMA, volume 319, issue four. Friedman et al sought to evaluate whether surgical left atrial appendage occlusion let to a reduction in long-term thromboembolic risk in a large database of Medicare recipients. They included the primary outcome as readmission for thromboembolism, including stroke, TIA, or systemic embolism, in up to three years of follow-up. With secondary end-points including hemorrhagic stroke, all-cause mortality, and a composite end-point of all outcomes.                                 Amongst more than 10,000 patients, there were almost 4,000 patients receiving surgical occlusion of left atrial appendage. Surgical occlusion was associated with a reduction in thromboembolic risk, OR of 6%, all cause mortality, 17 versus 24%, and the composite end-point, 21 versus 29%. However, interestingly, surgical occlusion was only associated with reduction in thromboembolic risk compared with no occlusion amongst those discharged without anticoagulation and those discharge with it. Namely, the thromboembolic risk reduction was primarily seen in those where the surgical occlusion, those who were sent home without any sort of anticoagulation. These data suggest that surgical occlusion leads to reduction of thromboembolic risk overall. As any large database based study, there are massive flaws in the database itself. Namely, we're relying on the coding of hospitals and operators. To know exactly what was done and what happens latter.                                 However, these data are hypothesis generating. One key element is the fact that surgical left atrial appendage occlusion was only superior in reducing thromboembolic risk amongst those discharged without anticoagulation. This raises the question as why. Was left atrial appendage completely closed in these patients? In which case, they may be at further increased risk or that the operators felt that there is a high risk for other reasons that cannot be cleaned from an administrative datasets? While the data support consideration of the benefit of left atrial appendage occlusion in a surgical manner, a kin to what has been seen in papers on WATCHMEN and other approaches, and how is the critical nature of randomized trials in this regard.                                 We next review an article published in JAMA Cardiology, volume three issue one by Inohara et al, entitled "Association of atrial fibrillation clinical phenotypes with treatment patterns and outcomes: A multicenter registry study." Traditionally classification of AF has depended largely on factors such as the nature of AF, paroxysmal versus persistent, LA size, and other factors such as extend of the late enhancement. Inohara et al sought to evaluate whether cluster analysis could better define heterogeneity of AF in the population. They included an observational cohort of almost 10,000 patients admitted to 124 sites in the United States in the ORBIT-AF registry.                                 Outcome was a composite major address cardiovascular and neurological events or major bleeding. Amongst these patients, they identified four clusters, including one those with lower rates of risk factors and comorbidities than other clusters, two, those with AF at younger ages and with comorbid behavior disorders. Three, those with AF with tachycardia-bradycardia type syndromes and had devices for sinus node dysfunction, and four, those with AF with other risk factors such as a coronary disease. Those in the first cluster had significantly lower risks of major events. All clusters were noted to have symptom dissociation to specific clinical outcomes.                                 These data are interesting and highlight the highly heterogeneous nature of classifying risk attributable to atrial fibrillation. When broad datasets associated atrial fibrillation with specific outcomes. Maybe suggest an attribution to all patients with atrial fibrillation. However, this single relationship was specific to the outcomes suggest the limitation of applying outcome as approach to understand atrial fibrillation impacts and outcomes, namely depending on clusters that may take into account patient age or comorbidities, it may be irrelevant in discriminating patient outcomes than the traditional paradigm in the same paroxysmal versus persistent or depending on the left atrial size.                                 These data also highlight the importance of considering the inclusion criteria in randomized trials of atrial fibrillation before stripling real world outcomes to patients who don't fit within that trial.                                 Next, we will be reviewing an article by Chou et al entitled "Relationship of aging and incident comorbidities to stroke risk in patients with atrial fibrillation," published in JACC, volume 71 issue two. Chou et al sought to evaluate the effect of aging and evolving instant comorbidities to stroke risk in patients with atrial fibrillation. Many large database studies or trials where added baseline CHADSVASC score and the then ensuing follow up period to define risk over time of ischemic stroke.                                 The authors hypothesized that as patients age, develop new comorbidities that would change the score, may be more predictable of long-term outcomes than the score itself. They included over 31,000 patients who do not have comorbidities to CHADSVASC aside from age and sex but had atrial fibrillation. They didn't calculate a delta score defined as the difference between the baseline and follow up scores. The mean baseline score was 1.29 with an increase in 2.3 during follow up, with an average delta of one. The score may not change over follow up in 41% of patients. Interestingly, significantly more patients had a delta CHADSVASC of one or more and develop ischemic stroke than non-ischemic stroke. The delta CHADSVASC was shown to better predictor of ischemic stroke than either baseline or follow up CHADSVASC score. This data suggest that additive shifts in the CHADSVASC score over time may be more predictive of stroke risk than the actual score itself.                                 These findings are thoughtful and logical. They indicate the potential impact of continued aging or acquisition identification of new comorbidities. In some patients, potential discovery or new comorbidities or follow-up; for example, hypertension and coronary artery disease may lead to reclassification of stroke risk. That is important to maintain close follow up of atrial fibrillation patients, and not to show a continued need or lack of need of anticoagulation on the basis of a baseline evaluation. This also holds relevance single center long-term outcomes in patients specific scores. Whether is acquisition of new comorbidities or presence of baseline comorbidities or predict a long-term score, should we consider when assessing the need for anticoagulation, particularly in perceived initially low risk cohorts who go on to develop ischemic stroke.                                 Lastly, within the realm of atrial fibrillation, we review an article by Hussain et al, entitled "Impact of cardiorespiratory fitness on frequency of atrial fibrillation, stroke, and all-cause mortality" published in the American Journal of Cardiology, volume 121 issue one. Hussain et al review the effect of cardiorespiratory fitness on overall outcomes and incidence of atrial fibrillation and outcomes amongst patients with atrial fibrillation. Amongst over 12,000 individuals prospectively followed up after treadmill exercise test, they noted 1,222 had a incidence of AF, 1,128 developed stroke, and 1,580 died. For every 10% increase in functional layover capacity, there was a 7% decrease in risk of incident AF, stroke, or death.                                 Similarly, in those who developed AF, stroke was lower in those with higher functional aerobic capacity. These findings support the notion known to other areas of cardiovascular disease that better cardiorespiratory fitness is associated with better outcomes, in this case to stroke, incident AF, or mortality. Furthermore, even on the presence of AF, those with better functional capacity had a lower risk of stroke. These data highlight the continued importance of counseling patients on the benefits of physical fitness even in the setting of already present AF.                                 Moving on to a different area of electrophysiology, we review the realm of ICD pacemakers and the CRT.                                 The first article review is by Sze et al entitled "Impaired recovery of left ventricular function in patients with cardiomyopathy and left bundle branch block" published in JACC volume 71 issue 3. Patients with left bundle branch block and cardiomyopathy are known to respond to CRT therapy. Thus the investigators sought to evaluate whether guideline medical therapy in patients with reduced LVEF and left bundle branch block, afford a beneficial first line approach therapy. The reason for this currently guidelines suggest waiting at least three months before consideration of CRT has had as some patients may recover on guideline directed medical therapy without the need for device implantation.                                 They review patients with a LVEF of less or equal than 35% and baseline ECG showing left bundle branch block. In evaluating left ventricular ejection fraction at follow up of three to six months. They excluded patients with severe valvular disease, and already present cardiac device, an LVAD, or heart transplant. Among 659 patients meeting criteria, they notice 74% had a narrow QRS duration of less than 120 whereas 17% had QRS duration greater than 120, and the remainder had a QRS duration greater 120 but was not left bundle branch block. The mean increase in the left ventricular ejection fraction on guideline directed medical therapy was in those with a narrow QRS duration and least in those with left bundle branch block, 8.2%.                                 Furthermore, when comparing mean LVEF improvement, those with on versus non-on guideline directed medical therapy, there was virtually no difference in rates of recovery. Furthermore, composite end-point of heart failure hospitalization mortality was highest in those with left bundle branch block. These data suggest that those with bundle branch block and cardiomyopathy received less overall benefit from guideline directed medical therapy over the three to six months follow up period. Whether this is due to already more severe myopathic process to start with or due to the CRT is unclear. However, it may suggest that in some patients, left bundle branch block may benefit from inclusion of CRT early in their disease course as known the significant number of patients up to three to six months guideline directed medical therapy with insufficient DF recovery may then benefit from CRT. As well as intervening earlier may result in better outcomes, especially knowing the high and term raise mortality in heart failure hospitalization remains to be seen.                                 A trial studying early implantation of CRT on these patients may be relevant.                                 The next article review is by Gierula et al entitle "Rate-response programming tailored to the force-frequency relationship improves exercise tolerance in chronic heart failure" published in JACC Heart Failure, in volume six, issue two. The authors sought to evaluate whether tailored rate-response programming improved exercise tolerance in chronic heart failure. The double blinded, randomized, control, crossover study, they compared the effects of tailored programming on the basis of calculated force-frequency relationship, defined as including critical heart rate, peak contractility, and the slope, multidimensional programming and exercise time and maximal oxygen consumption. They demonstrate amongst 98 enrolled patients that rate-response settings limiting heart rate raise to below the critical heart rate led to create exercise timing and higher peak oxygen consumption.                                 These data suggest that personalizing rate-response therapies may improve exercise time and oxygen consumption values in patients with heart failure and pacing devices. The main limitation of the study is that the number of patients was small, 90, and then the number of patients crossing over was even smaller, 52. However, highlights the potential of working closely between device programmers and consideration of individual's characteristics and their exercise needs in determining optimal programming strategy.                                 Finally, within the realm of devices, we review an article by Hawkins et al, entitled "Long-term complications, reoperations, and survival following cardioverter defibrillator implant" published in Heart, volume 104 issue three. Hawkins et al sought to evaluate the long-term complications and risk of reoperation associated with defibrillator implantations in a large [inaudible 00:41:56] population of 300,410 patients, they noted over a 30-month follow up period there was a 12% reoperation rate within the year of implant. This is most prominent for CRT devices, with a risk of 18% in one year post-implant. Furthermore, CRT had the highest rate of early complications, with device complexity, age, or the presence of atrial fibrillation being significantly associated with complication risk.                                 Mortality also increased over time from 5% within the first year to nearly a third after five years. However, younger patients exhibited five years survival similar to the general population with a progressive decline of this as older patients were considered. These findings highlight several critical issues. First, they report a high one year reoperation rate for a variety of reasons. This finding highlights the importance of considering protocols to minimize the need for reoperation. Furthermore, they note the higher rate amongst CRT patients, with seems logical given the likely longer associated procedural risk and need for more leads. Finally, the impact of age on expectant survival are to be taken into consideration with the device and the life-saving potential of the defibrillator.                                 Moving on to cellular electrophysiology, review one article by Zhang et al, entitled "Reduced N-type calcium channels in atrioventricular ganglion neuron are involved in ventricular arrhythmogenesis" published at the journal of the American Heart Association, in volume seven issue two. Zhang et al reported a rat model of ventricular arrhythmogenesis and characterized the role of atrioventricular ganglion neurons in risk of arrhythmogenesis as well as the mechanism for this risk this model relates in humans to the attenuated cardiac vagal activity in heart failure patients, which is known to relate to their arrhythmic risk. The demonstrated reduced N-type calcium channel in these AV ganglion neurons, which project innervating systems to the myocardium, resulting in increased risk of PVCs, and increased susceptibility to induction of ventricular arrhythmias with programmed stimulation.                                 The relevance of the intrinsic cardiac nervous system arrhythmogenesis has become increasingly prominent as methods to study it have improved. Understanding the direct and most relevant inputs may facilitate better understanding of risk of arrhythmias in patients. In the case of this study by Zhang et al, the critical finding is that disorder of the atrioventricular ganglion neurons may lead to increased susceptibility for ventricular arrhythmogenesis. Clinical relevance includes consideration of effects on this specific ganglion when performing ablation on for other conditions, and potential long-term effect on arrhythmogenic risk, as well as potentially relevant functional explanations for arrhythmogenesis.                                 Moving on to the genetic channelop, these are considered two separate articles. The first one by Bilmayer et al, entitled "ExomeChip-Wide analysis of 95,626 individuals identified ten novel loci associated QT and JT intervals" published in Circulation: Genomic and Precision Medicine, in volume 11 issue 1. This whole exome study reviewed several novel loci that modified the QT and JT intervals. They include over 100,000 individuals and identified ten novel loci not previously reported in the literature. This increases the number of known loci that impact from ventricular portal adjacent by nearly one third. These loci appear to be responsible for myocyte and channel structure and interconnections that internally impact the ventricular repolarization.                                 While long QT syndrome be characterized amongst the known genes in 75% of affected individuals, that also means one fourth long QT syndrome cannot be characterized based on known genes impacting ventricular repolarization. The identification of novel loci or novel that may be affect repolarization kinetics to unique means are critical to define novel therapies as well as in genetic counseling the patients in potential effects on family members when screening them for potential disease risk. These findings should assess an opportunity for further studying the mechanisms by which these loci modulate QT and JT intervals and the potential contribution to phenotypic risk.                                 The second paper within this realm we review is by Zumhagen et al, entitled "Impact of presynaptic sympathetic imbalance on long QT syndrome by positron emission tomography" published in Heart, volume 104. The authors sought to evaluate by a PET scan the impact of sympathetic heterogeneity on long-QT syndrome risk. Amongst 25 patients with long-QT syndrome, including long-QT type I and II, and 20 ostensibly healthy controls, they noted that regional retention in disease were similar between affected patients and controls. However, regional washout rates were higher in the lateral left ventricles in patients with long-QT syndrome. Internal global washout rates were associated with greater frequency of clinical symptoms. That's there seem to be some relationship between regional and global sympathetic heterogeneity, particularly during washout, with overall risk in long-QT syndrome patients.                                 These findings report the notion for sympathetic imbalance, partly mediating the risk attributable to long-QT syndrome. The findings on PET suggest regional imbalance of presynaptic cathecholamine and reuptake and release, being one mechanisms. This was most prominent in long-QT I patients who also often drive most benefit from left sided sympathectomy. The novelty of these findings is in the potential role of imaging to determine basic contributors to congenital long-QT syndrome in given patients. The larger prospect of size would really need to be evaluated this further.                                 Moving on to the realm of ventricular arrhythmias, we review three different articles. The first one, by Hamon et al, entitled "Circadian variability patterns predict and guide premature ventricular contraction ablation, procedural disability, and outcomes" published in Heart Rhythm, volume 15 issue one. Hamon et al sought to evaluate whether circadian variability of PVC frequency can predict optimal drug response intraprocedurally during PVC ablation. One of the main problems of PVC ablation is when PVC are infrequent and tend to disappear during the procedure, achieving procedural success or attaining sufficient frequencies of PVCs to map becomes very difficult. Next, they use Holter monitoring in the ambulatory stripe to define three groups. Those of higher PVC burden during faster heart rates, those with higher PVC burden during slower heart rates, and those with no correlation between their PVCs burden and their heart rate.                                 More than half the one hundred and one patients included a high burden of PVCs at fast rate while 40% had no correlation between the two and 10% had higher burden in slower heart rates. Almost one third of patients taken for ablation have infrequent PVCs during a procedure, while the best predictor of this being a low ambulatory PVC burden of less than 120 per hour. Isoproterenol infusion was only useful in lessening PVCs in those with PVCs associated with fast heart rates. The isoproterenol washout or phenylephrine where used with those associated with slower heart rates.                                 Interestingly, not a single drug was effective in inducing PVCs in those with infrequent PVCs that have not heart rate correlation in the ambulatory stages. They noted that outcomes ablates were similar amongst those with higher heart rate associated PVCs and non-heart rate correlated PVCs previously responded to a drug. But, [inaudible 00:48:08] noted only a 15% success rate from ablation in infrequent PVCs in patients who lacked correlation between PVC burden and heart rate and who were unresponsive to drug previously. These data are important highlighting the potential for further defining idiopathic PVC ablation needs and likelihood of success based on ambulatory data, by correlating PVC burden with heart rate and their circadian variability, it's possible to predict likelihood specific intraoperative drugs working when dealing with infrequent intraprocedural PVCs.                                 Furthermore, the finding of lack of correlation with slower or fast heart rate in terms of PVC burden is associated with the poor success rate unless those PVCs are drug responsive. Highlights the potential benefit of performing preoperative antiarrhythmic drug testing to get likelihood of ablation success in this patients.                                 The next article we review is by Lee et al, entitled "Incidence and significance of the lesions encountered during epicardial mapping and ablation of ventricular tachycardia in patients with no history of prior cardiac surgery or pericarditis" published in Heart Rhythm, volume 15 issue one. Lee et al sought to determine the frequency of pericardial lesions, impeding mapping in patients without prior surgery, operative procedure, or pericarditis, in other words virgin hearts. Amongst 155 first time attempts of access, 8% had pericardial lesions. The only clinical predictor was the presence of severe renal impairment.                                 In addition, no patients with supposedly normal hearts had a lesions. Notably, those with a lesion had more frequent impairment in mapping and lower overall success rates; there were similar complication rates as those without the lesions. These data are relevant in highlighting the ease of mapping of pericardial access may not always be present, even when dealing with inversion of pericardial space. A lesion may be present in patients, particularly with severe renal disease. Advising patients of this possibility prior to the procedure and considering that epicardial access may be impaired in a fair number of patients, even the absence of prior history of surgery, epicardial access or pericarditis isn't important.                                 The final article we'll review within the realm of ventricular arrhythmias is by Kumar et al, published in Journal of Cardiovascular Electrophysiology, volume 29 issue one, entitled "Right ventricular scar-related ventricular tachycardia in nonischemic cardiomyopathy: Electrophysiological characteristics, mapping, and ablation underlying heart disease." Kumar et al sought to evaluate the substrate and outcomes associated with right ventricle scar related ventricular tachycardia ablation in nonischemic patients at large, but particularly in those with neither stroke or coronary artery disease as potential explanations for this scar. They reviewed 100 patients consecutively over half of whom had ARVC and the remainder was sarcoid or RV scar of unclear origin. Those with RV scar of unknown origin tend to be older compared to the ARVC patients, and had more severe LV dysfunction compared with saroid patients.                                 However, the scar distribution extend was similar within all these groups. Furthermore VT/VF survival was higher in those with RV scar of unknown origin. The velocity of survival free or death or cardiac transplant and VT/VF survival seen in sarcoid patients. These data suggest that close to one third of patients, RV scar related VT may have VT of unknown cause. Total outcome was superior overall to those with defined myopathic processes. What's most interesting is, over follow up, none of those with RV scar of unknown origin develop any further findings to reclassify them as sarcoid or ARVC. It is possible this group reflects some mild form of either disease however. Again, the exact pathophysiologic process remains unclear. These findings may help in counseling patients who are in long-term expected outcomes from ablation intervention.                                 The final article we'll review this month is within the realm of other EP concepts that may be broadly applicable, published by van Es et al, entitled "Novel methods for electrotissue contact measurement with multielectrode catheters", published in Europace, volume 20 issue one. In this publication, the authors sought to evaluate the potential utility of a novel measure on evaluating electro tissue contact. With multielectrode catheters it is known that one of the problems with assessing contact is a contact force that cannot be used. Electro with coupling index is often used but even this has fragile problems, especially when you get into high impedance areas, that can be affected by surrounding ion impedance structures. Due to the fact that measuring contacts forces challenging in such multielectrode catheters, the authors measure electric interface resistance by applying a low level electrical field, pushing neighboring electrodes. They compared the effectiveness of assessing contact by this approach without using contact force in a poor side model.                                 They know that this measure was directly correlated with contact force in measuring tissue contacts. These findings support a role for aversion of an active electrode location and determining tissue proximity and contact-based on the coupling between the electrodes on multipolar catheters in the tissue. These findings may be highly useful when there is a variety of catheters where contact force cannot be implemented. Further studies on the methods and cutoff to establish tissue proximity on the end of contact will be also needed.                                 To summarize, however, as a term was brilliant here that was not well explained, active electrical location is actually a phenomenon that occurs in nature. This is seen in deep sea fish, which actually have multiple electrodes oriented around its body. They emit a small electrical field that results in a general impedance field surrounding the fish. This essentially is the way of visualizing the world around them. Perturbations based on proximity to different structures, whether they are live or death, and based on whether they are live or death, results in changes in the perturbations of this resistive fields, resulting in proximity determination by the fish. Several individuals are looking into potential applications of this to understanding tissue proximity when using catheters in the body. This consideration of impedance is fundamentally different than the traditional measure impedance were used by traditional generator.                                 I appreciate everyone's attention to this key and hardening articles that we've just focus on or this past month of cardiac electrophysiology across literature. Thanks for listening. Now back to Paul. Dr Wong:             Thanks Suraj, you did a terrific job surveying all journals for the latest articles on topics of interesting in our field. There's not an easier way of staying in touch with the latest advances. These summaries and the list of all major articles in our field for month can be downloaded from the Circulation: Arrhythmia and Electrophysiology website. We hope that you find the journal to be the go to place for everyone interested in the field.                                 See you next month.  

  Dr. Lam: Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. I'm Dr. Carolyn Lam, associate editor from the National Heart Center in Duke National University of Singapore.     Today we will be discussing the first multinational study looking at per-cutaneous device closure of peri-valvular leaks, a topic I'm certain you'll recognize as rapidly developing in cardiology, but first, let me fill you in on the highlights of this week's journal.     The first paper is a translational study telling us that when transfusing stored red blood cells for hemorrhagic shock, cold transfusing hemopexin and heptoglobin may be beneficial. This study is from first author Dr. Graw, and corresponding author Dr. Zapol and colleagues from the anesthesia center for critical care research at Massachusetts General Hospital and Harvard Medical School.     These authors reasoned that erythrocytes undergo progressive deleterious changes during storage. Such that, the transfusion of long-stored, packed red blood cells increases plasma levels of cell-free hemoglobin and heme. These are toxic breakdown products of hemolyzed erythrocytes.     Now, mammals usually synthesize the scavenger proteins: heptoglobin and hemopexin, which bind these toxic extracellular hemoglobin and heme, respectively. The authors therefore, tested the concept of cold transfusion of heptoglobin and hemopexin along with stored red blood cells in their murine remodel of hemorrhagic shock.     They first showed that resuscitation with long-stored, packed red blood cells produced a higher mortality, higher plasma hemoglobin levels, hemoglobinuria, kidney injury and diffused tissue inflammation, compared to resuscitation with fresh, packed red blood cells. However, when resuscitating hemorrhagic shock with stored red blood cells co-infused with either exogenous human hemopexin or heptoglobin, there was an increased survival and decreased tissue inflammation. Furthermore, co-infusion of heptoglobin with the stored red blood cells, prevented hemoglobinuria and kidney injury. These animal model data warrant further assessment in clinical conditions of severe hemolysis.     The next study suggests that sickle cell disease, although primarily a blood disease, may also be considered a vascular disease. This is a paper from co-authors Dr. Ranque and Menet from the University Paris Descartes in France, and describe results from the CADRE study. That is, the heart arteries and sickle cell study, which is the World's largest ongoing cohort of sickle cell disease that prospectively recruited more than 3,700 patients with sickle cell disease and 950 healthy controls from Cameroon, Ivory Coast, Gabon, Mali, and Senegal.     The authors found that mean carotid femoral pulse wave velocity was lower in patients with sickle cell disease, compared to controls and lower in specific hemoglobin phenotypes compared to others. Augmentation index, corrected for heart rate, also increased more rapidly with age in the patients with sickle cell disease, compared to controls, and was higher in patients than in controls. Both carotid femoral pulse wave velocity and augmentation index were independently associated with the glomerular filtration rate and osteonecrosis.     Augmentation index was also associated with stroke, pulmonary hyper-tension and priapism. Whereas, carotid femoral pulse wave velocity was also associated with microalbuminuria. These findings really under-score the association between sickle cell disease and vascular abnormalities and complications. The prognostic value of these vascular indexes will be assessed during the follow-up of these patients.     The next paper is a basic science paper suggesting that after sudden cardiac arrest, normalizing calcium cycling, may be a novel approach to improved post-arrest myocardial function. This paper is from co-corresponding authors Dr. Woods, from the Palo Alto Medical Foundation and Dr. Ashley from Stanford University in California.     These authors developed a rodent model of cardiac arrest using ECMO resuscitation. They used a genetically encoded calcium sensor in a novel fiber optic catheter imaging system to observe calcium-induced calcium release in-vivo before and after resuscitation. They then isolated cardiomyocytes from this model and assessed a mechanical load and calcium cycling simultaneously, using the micro-fiber carbon technique.     The main finding was of potentiation of calcium-induced calcium release in the post-arrest situation that began in-vivo and was mediated by activation of the calcium calmodulin kinase 2 or CaMKII. Since they also observed that oxidated stress and aldehydic adduct formation were high post arrest, they further tested a small molecule activator of aldehyde dehydrogenase type 2, known as Alda-1, which reduced oxidative stress, restored calcium and c CaMKII homeostasis and improved cardiac function in post-arrest outcomes in-vivo.     These findings are significant for their potential translational application in post-sudden cardiac arrest, a condition which is really known to have a high mortality.     The next study reports the results of the DOCTORS Study, standing for Does Optical Coherence Tomography Optimized Results of Stenting. This paper is from Dr. Meneveau from the University Hospital Jean Minjoz and colleagues. The DOCTORS Study is the first randomized control trial testing optical coherence tomography via OCT guided PCI to standard fluoroscopy guided PCI in 240 patients with non-ST-elevation and acute coronary syndromes.     The first finding was that OCT results directly impacted physician decision making, leading to a change in procedural strategy in half of the cases in the OCT guided group. The primary end-point of functional results of PCI, as assessed by post-PCI, FFR, was modestly improved in the OCT guided group compared to fluoroscopy alone. This improvement appeared to be explained mostly by optimization of the stent expansion. The benefit was obtained at the cost of a longer procedural and fluoroscopy time and more contrast use, but without an increase in peri-procedural myocardial infarction or kidney dysfunction.     These findings of the DOCTORS study add to the accumulating body of evidence supporting a potential benefit of OCT to guide PCI procedures in acute coronary syndrome. Additional prospective studies with clinical endpoints are warranted. These issues are discussed in an excellent accompanying editorial by Dr. Wijns and Dr. Pyxaras.     This brings us to the end of our summaries. Now for our feature paper.     Our featured paper today discusses a problem that we've actually created and that is para-valvular leaks following surgical valve replacement, and we're specifically discussing the role of percutaneous device closure exploring the first multi-national experience form the United Kingdom and Ireland and I'm here with first author, corresponding author as well, Dr. Patrick Calvert from Papworth Hospital in the United Kingdom. Welcome Patrick.   Dr. Calvert: It's a great pleasure to be here, thank you for inviting me.   Dr. Lam: Joining us also is Dr. Dharam Kumbhani, associate editor from UT Southwestern, hi.   Dr. Kumbhani: Hi Carolyn, thanks for having me.   Dr. Lam: Let's get straight into this. It's a problem we've created. How common is it? Why should we care about talking about perivalvular leaks?   Dr. Calvert: You know Carolyn, this is actually quite a common problem. The series we know from previous publications around 5-17% of surgical valves develop leaks. We know in the early experience of TAVR that there was quite a problem with leak, although more recent iterations that's less of a problem. There's a lot of patients out there that have this problem. It's a difficult problem to treat because these are, by definition, high-risk patients and re-operation is not such an inviting thought for them to have. This is something that needs may be a different solution than re-operation.   Dr. Lam: Could you tell us what makes your series special?   Dr. Calvert: Yes, so let's talk about the other series first of all. We had a fabulous series published in 2001 from the Mayo Clinic. That was a single center of excellence where they are really great at doing the procedure, but they gave us great insight of a master class, really if you like, if I had to do the procedure. What is different about our paper is that it's like a real-world experience. It's all the centers that contributed in the United Kingdom and Ireland. It's 20 centers over an 11 year period, in total 308 procedures. It's, if you like, a warts-and-all approach to it. It think that's one way it's a little different.     I think another way that it definitely stands out is that we are fortunate enough in Europe to have licensed or CE-mark, a number of oblong devices that are a little different in shape. What we do know about these holes is, they tend to be crescentic in shape or at least longer then they are wide. The problem is, if you try to put a circular device in an oblong hole, it's not going to work.   Dr. Lam: Which types of perivalvular leak are you talking about here?   Dr. Calvert: We have approximately 50/50 split between the aortic surgical valve and the micro-surgical valve. Then, about 5% were TAVIs or TAVRs. Then we had a small number of pulmonic valves and one or two around angioplastic rings, so that's the proportions. We had about 57% mechanical valves and 37% bio-prosthetic valves.   Dr. Lam: Wow, first congratulations. That is really important information. I can already imagine. I see those patients too. Dharam, as an interventional cardiologist. What is your take on it. Especially this mention of the oblong devices? They are not FDA approved, so they won't be in the United States, but what did you think of that, managing this paper?   Dr. Kumbhani: I think this is a very tricky subset of patients to treat. As Patrick and his group have shown, that the rates of success can be very high. As you point out, we don't have all the devices that they have in the U.S. A lot of us who do this use more circular devices but they're flexible. The feeling is that they tend to fit in with whatever geometry of the leak is. I do think it would be interesting, and probably more appropriate to have devices that are shaped like these holes are. As Patrick mentioned, they're usually crescentic, or certainly not round.   Dr. Lam: As a non-interventional cardiologist, I didn't realize it was very intricate. Tell us about your main findings.   Dr. Calvert: Our principle findings, and what I think is the most important thing is that, if you're going to do this procedure, you have to achieve a leak at the end of the procedure, or at least in the months that follow-up, that is mild or less. In our series, we showed that those patients that had that, they were independently associated with less deaths and less major adverse cardiovascular events. It's a very clear dichotomy between those groups.     Of course there's all sorts of reasons why you might be able to achieve a good result in a patient, but we know that if you can do it, those patients will be very much better than the others. In our paper we achieved that in around 75% of patients and they did much better than the others. That is a principle finding. There were another of other factors that were associated independently with death and those also included NYHA classification at follow up, but also creatinine baseline. As I've already eluded to, this is a high-risk chord of patients and there are conventional risk factors that will pre-dispose whether someone's going to do well or not. That's what came out in the multi-variable analysis.   Dr. Lam: Very important clinically. Take home message from your point?   Dr. Kumbhani: I think one of the interesting findings was that only 16% of these PVLs were closed for hemolysis. The vast majority of them were done for symptomatic causes. That probably speaks to the dictum that it's the smaller PVLs that cause hemolysis. I don't know if you have a handle, based on your experience, on that?   Dr. Calvert: When we designed the series, a number of years ago ... When you design a registry you look at the things you're going to collect. Then when you've written the paper you think, "I just wish I had collected some more data." That's one of those things we really wish we looked ... It's fascinating. We do this procedure together and one of the things we're terrified about is taking a big leak, getting rid of heart failure and creating hemolysis.   Dr. Kumbhani: Exactly.   Dr. Calvert: We all have had personal experiences of that happening.   Dr. Kumbhani: Yes.   Dr. Calvert: The data we collected, collected patients who had new hemolysis, requiring transfusion. Therefore, all I can tell you from our series is, that was really quite a small ... It was only 2 or 3% of people who had new hemolysis.   Dr. Kumbhani: After the closure?   Dr. Calvert: After the closure. Of course, about 16 or 17% had hemolysis going into it. It doesn't really tell us any information about what happened to those, unfortunately.   Dr. Kumbhani: One other interesting thing that I wanted to point out. If you look at the PCIs registry, all of, there are about 120 hospitals in it. Is that correct?   Dr. Calvert: That's approximately correct, yes.   Dr. Kumbhani: You had 20 centers that were doing this?   Dr. Calvert: Yes.   Dr. Kumbhani: 1 in 6 is doing these in a competent fashion, the PVL closures. I think, as you pointed out, the series are usually single institutions that really specialize in this in the U. S. I think the experience may be a little more consolidated. If you want to just comment on that finding alone?     The second thing is, is there something different about the intervention training procedure in the U.K. that allows for more interventionists to be comfortable doing this?   Dr. Calvert: I think that's a really great question. I think there's a little to pick apart behind that. I think the first thing to say is that, although there were 20 centers that contributed cases, some of those centers would have definitely had proctors come in to do the cases. This is the entire learning curve. This is every case that has contributed in the U.K. It's watching our learning curve and the lot. There will be a number of centers that have been heavily proctored coming in.     One thing that's really nice about the U.K., it's a small country. Particularly in this structural community, most people know each other. If you've got a problem, you ring up your friend down the road and say, "You've done a few of these, come and give us a hand." We get that and I do that too, so that's great.     I think the second thing to say, and I think it's important to say this, our cousins in America are fantastic at doing this procedure. I think they have to be because although the devices are malleable, and they will squash because as we both know, it doesn't matter what the device looks like at the end provided it plugs the hole and is not interfering with the leaflets and it's not falling out. That's fine. I do believe that the oblong devices are more likely to get a good closure. I think therefore, you're less likely to be having to put in 2 or 3 devices in the same sitting. I think that's technically demanding for ... I think it probably is a little more straight forward with the oblong devices.     I think it is important to say for the record, that there's nothing in this paper that is scientifically proven the oblong devices are better. They trend in their right but, it is a fact of the series of oblong devices. Once they're available, it was 72% and for the total it's about 2/3. It's not a scientific comparison but, we've got these good results with these devices.   Dr. Kumbhani: It would not be a fair comparison but in your database, are you able to do some kind of propensity analysis looking at the oblong versus the other devices? Comparing ventricle leak for example or hemolysis?   Dr. Calvert: We don't have enough breakdown data on hemolysis unfortunately. I think I just need to be careful what I say because a lot of the authors came up with hypotheses about things. I looked at the data and I think when we subgroup too much, it became too small to read to give any careful answers.   Dr. Kumbhani: I see.   Dr. Calvert: I think what would be really fascinating, is when we pool data with other countries because I know there are other countries that are looking at this as well. We might get more information, but that's something we have on the horizon so what this space.   Dr. Kumbhani: That's good.   Dr. Lam: That is fantastic. Thank you Patrick. Thank you Darrin. Seriously, I'm floored. I learned so much from this and I really enjoyed this conversation.     Thank you very much, and to the listeners out there, don't forget you've been listening to Circulation on the Run. Join us next week for more highlights and features.    

Thursday, March 1, 2012 Neal Waxham (Professor, Dept of Neurobiology & Anatomy, UT Medical School at Houston) discusses molecular dynamics at the PSD, including CaMKII as a structural molecule, molecular trapping at the spine, and the potential modularity of the post synaptic density. Duration: 45 minutes Discussants:(in alphabetical order) Fidel Santamaria (Asst Prof, UTSA) Salma Quraishi (Res Asst Prof, UTSA) acknowledgement: JM Tepper for original music.

The success of acrosomal exocytosis, a complex process with a variety of inter-related steps, relies on the coordinated interaction of participating signaling molecules. Since the acrosome reaction resembles Ca(2+)-regulated exocytosis in neurons, we investigated whether cognate neuronal binding partners of the multi-PDZ domain protein MUPP1, which recruits molecules that control the initial tethering and/or docking between the acrosomal vesicle and the plasma membrane, are also expressed in spermatozoa, and whether they contribute to the regulation of acrosomal secretion. We observed that CaMKIIalpha colocalizes with MUPP1 in the acrosomal region of epididymal spermatozoa where the kinase selectively binds to a region encompassing PDZ domains 10-11 of MUPP1. Furthermore, we found that pre-treating mouse spermatozoa with a CaMKII inhibitor that directly blocks the catalytic region of the kinase, as well as a competitive displacement of CaMKIIalpha from PDZ domains 10-11, led to a significant increase in spontaneous acrosomal exocytosis. Since Ca(2+)-calmodulin releases CaMKIIalpha from the PDZ scaffolding protein, MUPP1 represents a central signaling platform to dynamically regulate the assembly and disassembly of binding partners pertinent to acrosomal secretion, thereby precisely adjusting an increase in Ca(2+) to synchronized fusion pore formation.

Um eine Parthenogenese zu verhindern, arretieren reife Oozyten von Wirbeltieren in der Metaphase der Meiose II. Diese biochemische Aktivität wurde 1971 als Zytostatischer Faktor (engl. Cytostatic Factor; CSF) beschrieben. Einzelne wichtige Komponenten wurden im Laufe der Zeit identifiziert, aber deren Zusammenspiel noch nicht aufgeklärt. Eine wichtige Rolle spielt dabei der Anaphase Fördernder Komplex (engl.Anaphase promoting complex/Cyclosome;APC/C), eine Ubiquitin-Ligase welche Zellzyklus regulierende Proteine dem Abbau zuführt und somit den Beginn der Anaphase ermöglicht. Der APC/C ist in reifen Oozyten inaktiv und wird nach der Befruchtung aktiviert, so dass der Arrest aufgehoben wird. Des Weiteren sind für den Eintritt in die Anaphase II die Aktivitäten zweier Kinasen nötig. Erstens erfolgt während der Befruchtung ein Anstieg der Konzentration des intrazellulären Calciums, dies führt zur Aktivierung der Calmodulin-abhängigen-kinase-II (CaMKII). Allerdings waren die Substrate dieser Kinase bis jetzt unbekannt. Zweitens ist die Polo-like-kinase-1 (Plk1) essentiell für die Aufhebung des Metaphase II - Arrests. In Xenopus Eiextrakt konnte gezeigt werden, dass die Aktivität der Xenopus Plk1 (Plx1) essentiell für den Eintritt in die Anaphase ist. Kürzlich wurde ein Inhibitor des APC/C in einem Yeast-Two-Hybrid-Screen mit inaktiver Plx1 als bait gefunden – Xenopus-Emi1-verwandtes-Protein-1 (engl. Xenopus-Emi1-related protein-1; XErp1). Die Depletion dieses Proteins in Xenopus-Ei-Extrakt führt zu einem verfrühten Eintritt in die Anaphase. Im Rahmen meiner Doktorarbeit konnte gezeigt werden, dass CaMKII und Plx1 kooperieren, um XErp1 nach der Befruchtung zu inaktivieren, indem sie XErp1 für den Abbau markieren. Auch das humane Protein wurde kloniert und es wurde damit begonnen Versuche in Säugetierzelllinien durchzuführen. Erste Hinweise lassen darauf schließen, dass das humane Protein in gleicher Weise reguliert wird wie XErp1.