Podcasts about caveolin

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.12.13.520222v1?rss=1 Authors: Girardello, R., Martin, E., Dittmar, G., Ludwig, A. Abstract: Caveolae play fundamental roles in mechanotransduction. Critical to caveolae function is their ability to flatten out in response to an increase in membrane tension, thereby acting as a membrane reservoir to buffer acute mechanical stress. Cycles of caveolae assembly and disassembly also regulate membrane tension at the rear of migrating cells via RhoA/ROCK-mediated actomyosin contractility. However, the molecular mechanisms that couple caveolae-mediated mechanotransduction to cortical actin dynamics are poorly understood. Here we used biotin-based proximity labelling and quantitative mass spectrometry to define a caveolae-associated interactome in migrating RPE1 cells at steady state and in response to an acute increase in membrane tension induced by hypo-osmotic shock. Our data reveal a dynamic caveolae-associated protein network composed of focal adhesion proteins and cortical actin regulators that is highly sensitive to changes in membrane tension. We show that membrane tension differentially controls the association of ROCK and the RhoGAP ARHGAP29 with caveolae and that ARHGAP29 regulates caveolin-1 Y14 phosphorylation, caveolae rear localisation and RPE1 cell migration. Caveolae in turn regulate ARHGAP29 expression, most likely through the control of YAP signalling. Taken together, our work uncovers a membrane tension-dependent functional coupling between caveolae and the rear-localised actin cytoskeleton, which provides a framework for dissecting the molecular mechanisms underlying caveolae-regulated mechanotransduction pathways. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Aging-US published a Special Collection on Eye Disease which included "HMGB1 and Caveolin-1 related to RPE cell senescence in age-related macular degeneration" and reported that AMD is a major unmet medical need as it is estimated that more than 20 million patients will be affected by 2050 in the US alone. STGD is the most common hereditary macular dystrophy, mostly affecting young patients aged between 6 and 15 years old with a prevalence of 1/8,000-1/10,000. It is formed by the reaction of 2 all-trans retinal molecules with phosphatidylethanolamine generating N-retinylidene-PE, as a detoxication mechanism of retinal isomers including all-trans and 11-cis-retinal. Indeed, it has been shown that as early as in 3-month-old Abca4-/- Rdh8-/- mice, the amplitudes of scotopic A and B waves and flicker ERG are reduced. Dr. Jin Yang and Dr. Xiaorong Li both from The Tianjin Medical University Eye Hospital said, "Age-related macular degeneration (AMD) is the leading cause of vision loss in older adults worldwide." AMD can be classified into early-stage or late-stage AMD. The latter is characterized by neovascularization, geographic atrophy, or both. Conversely, early-stage AMD is characterized by a limited amount of drusen, which is mainly caused by lipid and protein accumulation and thought to contribute to atrophic changes. As the disease progresses, neovascular changes or geographic atrophy involving the macular area can be present in patients for years. Therefore, the authors explored the relationship between dry AMD and RPE dysfunction and senescence using proteomic mass spectrometry to examine differential expression in induced pluripotent stem cell-derived RPE cell lines with and without A2E treatment. They have previously demonstrated that the iPSC-derived RPE is phenotypically and functionally similar to the native RPE. In addition, the young status of iPSC-RPE may provide an excellent means for observing changes in protein expression during the process of RPE cell aging. A2E photo-oxidation products can cause oxidative stress, membrane permeation, telomere dysfunction and accelerated RPE senescence. Although A2E is clearly present in the retina, there are rather different opinions regarding its distribution. Ablonczy et al. showed that levels of A2E decreased from the periphery to the centre region in aging tissue of macaques and humans but A2E was localized mainly in the centre region of young mouse retina. The Yang/Li Research Team concluded in their Aging-US Research Output, "upregulation of HMGB1 and Caveolin-1 caused RPE cell senescence and suppressed migration and invasion, and β-catenin and Zo-1 accumulation was enhanced by A2E in RPE cells. In particular, the results showed a change in expression of HMGB1 and Caveolin-1, which suggests that they are prime gatekeepers in RPE cell senescence. The above results indicate that stabilizing expression of HMGB1 and Caveolin-1 is a potential therapeutic target to prevent the progression of RPE cell senescence." Full Text - https://www.aging-us.com/article/102039/text Correspondence to: Jin Yang email: yangjinchina324@gmail.com and Xiaorong Li email: lixiaorong@tmu.edu.cn Keywords: A2E, HMGB1, Caveolin-1, RPE cell senescence, AMD About Aging-US Launched in 2009, Aging-US publishes papers of general interest and biological significance in all fields of aging research as well as topics beyond traditional gerontology, including, but not limited to, cellular and molecular biology, human age-related diseases, pathology in model organisms, cancer, signal transduction pathways (e.g., p53, sirtuins, and PI-3K/AKT/mTOR among others), and approaches to modulating these signaling pathways. To learn more about Aging-US, please visit http://www.Aging-US.com or connect with @AgingJrnl Aging-US is published by Impact Journals, LLC please visit http://www.ImpactJournals.com or connect with @ImpactJrnls Media Contact 18009220957x105 MEDIA@IMPACTJOURNALS.COM

This month on Episode 22 of the Discover CircRes podcast, host Cindy St. Hilaire highlights four featured articles from the March 5 and March 19 issues of Circulation Research. This episode also features an in-depth conversation with Norberto Gonzalez-Juarbe and Maryann Platt from the J. Craig Venter Institute to discuss their study, Influenza Causes MLKL-Driven Cardiac Proteome Remodeling During Convalescence.   Article highlights:   Carnicer, et al. BH4 Prevents and Reverses Diabetic LV Dysfunction   Kyryachenko, et al. Regulatory Profiles of Mitral Valve   Mangner, et al. Heart Failure Associated Diaphragm Dysfunction   Peper, et al. Identification of McT1 as Caveolin3 Interactor       Dr 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 will be highlighting four articles selected from our March 5th and March 19th issues of Circ Res. After the highlights Drs Norberto Gonzalez-Juarbe and Maryann Platt from the J. Craig Venter Institute are here to discuss their study, Influenza Causes MLKL-Driven Cardiac Proteome Remodeling During Convalescence Dr Cindy St. Hilaire:        The first article I want to share is titled, BH4 Increases nNOS Activity and Preserves Left Ventricular Function in Diabetes. The first author is Ricardo Carnicer, who is also corresponding author alongside Barbara Casadei and they're from University of Oxford in the UK. Cardiomyopathy and heart failure are common complications of diabetes, but the molecular pathology underlying this cardiac dysfunction is not entirely clear. Increased oxidative stress and reduced functioning of both mitochondria and nitric oxide synthase or nNOS have been implicated in diabetic cardiomyopathy. Tetrahydrobiopterin or BH4 is a co-factor necessary for nNOS activity. Dr Cindy St. Hilaire:        And in diabetic patients and animals oxidation of BH4 inactivates nNOS and induces vascular endothelial pathology. But, what happens in the cardiac tissue itself? This group shows that although boosting BH4 levels by genetic or pharmacological means prevented or reversed heart dysfunction in diabetic mice, the status of BH4 oxidation and nNOS function in the heart tissue of diabetic patients and mice, did not actually differ significantly from that of healthy controls. Instead through molecular analysis, they revealed that in diabetic mouse cardiomyocytes boosting BH4 promoted a nNOS dependent increase in glucose uptake, which then preserved the cell’s mitochondrial function. Regardless of the pathways involved, the fact that BH4 reversed diabetic associated cardiac dysfunction in mice suggests the potential for therapies that could be used to lower the risks of such complications in humans as well. Dr Cindy St. Hilaire:        The second article I want to share is titled, Chromatin Accessibility of Human Mitral Valves and Functional Assessment of MVP Risk Loci. The first authors are Sergiy Kyryachenko, Adrien Georges, and Mengyao Yu, and the corresponding author is Nabila Bouatia-Naji from Paris Cardiovascular Research Institute in France. The mitral valve opens and closes to direct a one-way flow of blood from the left atrium to the ventricle. If the mitral valve fails, as in the case of mitral valve prolapse or MVP, blood regurgitation, cardiac arrhythmia, and ultimately heart failure can occur. Dr Cindy St. Hilaire:        With 11 valves from MVP patients and 7 control patients, this group used a highly sensitive chromatin profiling technique called ATAC-Seq to identify regions of the genome with increased accessibility, which indicates transcriptional activity. They found that while diseased and healthy valves had similar chromatin profiles, they differed from those of other heart tissues. Valve specific open chromatin regions were enriched in binding sites for NFATC, a transcription factor known to regulate valve formation. And, specifically in MVP tissues, they found two potential causative sequence variants. These MVP-linked variants exhibited enhancer activity in cultured cells. And for one variant, the team identified the gene target of this variant. In providing the first mitral valve cell chromatin profiles and demonstrating their use and functional analysis of MVP-linked variants, this work supplies a valuable research for mitral valve prolapse evological studies. Dr Cindy St. Hilaire:        The third article I want to share is titled, Molecular Mechanisms of Diaphragm Myopathy in Humans with Severe Heart Failure. The first author is Norman Mangner, and the co-senior authors are Axel Linke and Volker Adams from Dresden University of Technology in Germany. The diaphragm is the primary muscle controlling a person's breathing. This muscle can become weakened during heart failure, which exacerbates symptoms and increases the risk of death. The pathological mechanisms underlying the diaphragm's demise are largely unclear. Studies in animals have pointed to increase reactive oxygen species as a contributing factor, but human studies have been limited. This group evaluated the histological and molecular features of human diaphragm biopsies from both heart failure patients and controls. Dr Cindy St. Hilaire:        The diaphragm samples were collected from 18 heart failure patients, who were undergoing implantation of left ventricular assist devices. And 21 control samples were obtained from patients not having heart failure bypass graft surgery. Compared with the controls, the heart failure diaphragms showed significantly reduced thickness, severe muscle fiber atrophy, increased oxidative stress in the form of protein oxidation, increased proteolysis, impaired calcium handling and mitochondrial abnormalities and dysfunction. Pathological measures also correlated with clinical severity. These data are the first insights into the pathology of heart failure related diaphragm weakness, and this work points to the molecular players that could be targeted for novel treatments. Dr Cindy St. Hilaire:        The last article I want to share before our interview is titled, Caveolin3 Stabilizes McT1-Mediated Lactate/Proton Transport in Cardiomyocytes. The first author is Jonas Peper and the corresponding author is Stephan Lehnart from the Heart Research Center, Göttingen in Germany. Caveolae are invaginations of the plasma membrane, and these structures are involved in endocytosis, signal transduction and other important cellular processes. Caveolin is the key protein component of caveolae and isoforms of Caveolin have been implicated in heart conditions. Mice lacking the isoform CAV1 develop heart failure and genome-wide association studies have been linked to human CAV1 variants with cardiac conduction disease and atrial fibrillation. Rare variants of CAV3 are known to cause hypertrophic cardiomyopathy. However, little is known about the normal or pathological actions of Caveolin in heart cells where caveolae are plentiful. To learn more, this group performed mass spectrometry, immunoprecipitation, and other analysis in cardiomyocyte, and uncovered novel CAV associated proteins, some of which turned out to be isoform specific. Dr Cindy St. Hilaire:        CAV1 interacted specifically with aquaporin while CAV3 was associated specifically with the lactate transporting McT1 protein and the iron transporting TFr1 protein. When the team knocked out the function of CAV3 in stem cells derived from human cardiomyocytes, they found that McT1 had reduced surface expression and function, and that the cells exhibited abnormal de-polarizations. Together the results set the stage for future studies of cardiomyocyte CAV biology, including how CAV variants might contribute to disease pathogenesis. Dr Cindy St. Hilaire:        Today I have with me Drs Norberto Gonzalez-Juarbe and Maryann Platt from the J. Craig Venter Institute, and they're here to discuss their study, Influenza Causes MLKL-Driven Cardiac Proteome Remodeling During Convalescence . And this is in our March 5th issue of Circulation Research. So thank you both for being with me today. Dr Maryann Platt:           Great to be here. Dr Norberto Gonzalez-Juarbe:    Thank you. Dr Cindy St. Hilaire:        So I want to start with influenza mediated cardiac complications. So what are these complications? How prevalent are they in people who catch influenza and who's most affected? Dr Norberto Gonzalez-Juarbe:    So for the last hundred years, we have known that every time there's an epidemic or pandemic from influenza, there's adverse cardiac events that come after you get the disease. During the 1918 pandemic, we could see myocardial damage and about 90% of all people that succumb to the infection, and in the latest epidemics that has been about 40% to 50%, suggesting that the more pandemic the strain of influenza is, the more virulent, the more of these adverse cardiac events we are going to see. So it seems that it is attached to severity of disease. The virus can get to the heart easy, the more severe your disease phenotype is, but it seems that some pandemic strains have a better way to get there of causing more damage than the common epidemic strengths. Dr Cindy St. Hilaire:        That was actually one of my other questions, how does it get to the heart? What's happening there? Do we know much about that? I guess, specifically for flu, but I'm sure in the back of everybody's mind, people are also thinking about SARS-CoV2 too. So how does that kind of pathway work or transportation work? Dr Norberto Gonzalez-Juarbe:    Circulation is going to be the main way it gets there for, for example, if we were to look at COVID then in the heart there's the same receptors for the epithelial cells that are in there, the ACE-2 receptor, that's also in the cardiac tissue and COVID-19 can actually infect cardiomyocytes through that receptor. In terms of influenza, it's basically similar. Some of these receptors are present on the epithelium in the lungs, are also present there and flu can actually infect cardiomyocytes. In our study we also look at some other cell types like endothelial cells and fibroblasts, and we show that there's actually some lower grade infection too. But that's why it's all of these, it starts in the severity of disease, that's the more virus is going to be in your bloodstream, the easier it's going to be to get there. And since the same receptors are present in the heart, so it's going to be easy for the virus to affect the cell. Dr Maryann Platt:           It's not necessarily dependent on age or race or anything it's dependent on how sick you are, for sure. Dr Cindy St. Hilaire:        And by sick, does that directly correlate with viral load of the patients or just their response, an overactive response or something like that? Do we know? Dr Norberto Gonzalez-Juarbe:    I think it's a double edged sword, so it's going to be related to viral load, but also the type of immune responses that you're going to be having, it's going to affect the role of the virus in their heart. In our case we studied way after you cleared the proof from the lungs. So most of the studies that have been out there for a while show, when you're really, really sick, what is happening, but that of your compounding because you have all of these immune responses happening, and the virus is doing its thing. But once you clear the virus from the lungs, your, kind of, immune system settles down. And in our study, we show that even if you clear it from the lungs, the virus is still present in the heart. Dr Cindy St. Hilaire:        So one of the mechanisms that you focused on in terms of how influenza was contributing or leading to cardiac complications, is this process called necroptosis? Can you just maybe give us a primer on what that is, and what it's doing specifically in the cardiomyocytes? Dr Maryann Platt:           Sure. So necroptosis, there's a couple of different ways that cells can die, either under normal circumstances, just maintaining the number of cells in your body or in the case of infection, trying to get rid of the infection. So most commonly, cells will undergo apoptosis, which is programmed cell death, not very inflammatory. And then necroptosis is another way that is highly inflammatory and driven by, initiated by, some of the same molecular cascades, but then affected by a different set of molecules. Dr Cindy St. Hilaire:        Interesting. And so it's really that inflammatory component that is driving pathogenesis in the cardiac tissue then. Dr Maryann Platt:           Yeah. Dr Norberto Gonzalez-Juarbe:    And evolutionarily necroptosis has been shown to help the host against viral infections. Specifically, influenza has proteins that can block apoptosis, which is kind of like the good way of dying. And then the cell has to undergo these other necrotic type of cell death to get rid of viral replication. But while some of these might interact with both pathways, necroptosis effect their molecule. MLKL is the last protein in the pathway. That's the one that actually rupture the cells. So we wanted to prevent that from happening to see if we can actually stimulate something protective by having all of the other good cascade-type molecules still there. Dr Cindy St. Hilaire:        ‘Good’in quotes (laughing). Dr Maryann Platt:           Still dying cells, less bad, not as inflammatory Dr Norberto Gonzalez-Juarbe:    Inflammatory since the heart is this type of organ that any injury will be, more or less, long lasting, and that will have detrimental effects throughout life. Dr Cindy St. Hilaire:        Got it. That's interesting. So can you maybe give us a summary of your experimental design and kind of the groups you were looking at, and a summary of the results? Dr Maryann Platt:           Sure. So we had four different groups of mice, two of them were wild type mice and two were MLKL, all knockout mice, which could not undergo necroptosis. And then each of those genotypes, we had uninfected mice or mice that were infected with flu. And then we monitored long viral titer to see how much infection was there at the lungs. And then after the infections subsided in the lungs, two days after a viral load was undetectable, we sacrificed those animals, collected their hearts. Dr Cindy St. Hilaire:        That's great. So that two day resolution, is that a similar time course with humans, in terms of a pathogenesis of developing cardiac complications? How similar, I mean, mice are never perfect models, but what's good and what's not good about using a mouse as for this model? Dr Norberto Gonzalez-Juarbe:    So, mice are not human right?. So, we are always thinking about that quote, but most of the cardiac events that occurred during these type of infections and similar things have been observed in, for example, pneumococcal infection, which is by streptococcus pneumonia. Most of these adverse cardiac events occur right after you leave the hospital. Those are a specific set of adverse cardiac events that are different from the ones that happen when you are severely infected in the hospital. And these can be arrhythmias and myocardial infarction, and some of these things that can happen up to 10 years after you recover from the pulmonary infection. Dr Norberto Gonzalez-Juarbe:    So our model was designed to see that step of the host trying to retcover. And if there was still something there in the heart, right after you get out of the hospital, that you receive your therapeutics, and you're thinking, 'Oh, I don't have any more flu in my lungs, and I'm recovering', that timeframe right after you get out, you might still have some other things happening in your body, that might determine what happens to your heart. Dr Cindy St. Hilaire:        Interesting. So you may actually be feeling pretty good, but your heart or even possibly other organs are still kind of under the weather, so to speak? Dr Norberto Gonzalez-Juarbe:    Exactly. Dr Maryann Platt:           Exactly. Dr Cindy St. Hilaire:        So in your proteomic analysis, I think you stated it was some, it was just under a hundred proteins were differentially regulated, and a majority were actually in kind of metabolic mitochondrial related pathways. Could you maybe tell us the importance about that? But then also, yes, that was a big chunk of it, but were there any other pathways that were either up or down, that were surprising in your findings? Dr Norberto Gonzalez-Juarbe:    The importance of the major mitochondrial proteins that we found, first that the MLKL knockout, so inhibiting these necrotic cell death actually promoted mitochondrial health. So that first was interesting, because that will suggest that this can be quite therapeutic target in the future. That innovation enhance some proteins that protect the mitochondria and aid in mitochondrial function. And if we think about the heart as our engine, we need energy for an engine to work and mitochondria is that energy resource that we have. And the heart is really relying on these, because if you have a metabolic breakdown in the heart, you get cardiac event. So most of the proteins that were changed upon infection had to do with these specific, important metabolic function of the heart. Some other proteins have to do with cellular signaling mechanisms and calcium homeostasis, all these other things that are important to maintaining homeostasis in the heart thus suggesting that the virus is inducing massive stress in their heart without actively replicating or causing inflammation. Dr Norberto Gonzalez-Juarbe:    And that was very important in our study that we didn’t see these antiviral effects, but at the same time, we saw all of these detrimental metabolic effects. So future studies might be also targeting what viral factors might be actually inducing these metabolic effects in the heart. But we also saw some molecules important for cell death mechanisms that were not necroptosis. Dr Norberto Gonzalez-Juarbe:    Marianne, you can describe some of those. Dr Maryann Platt:           So one third way that cells can die is called pyroptosis. And we actually saw that pyroptosis was also elevated in flu infected mice, in their hearts, suggesting that it might not just be necroptosis. All this inflammation coming from necroptosis is what's driving breakdown of heart function, but also possibly pyroptosis. Dr Cindy St. Hilaire:        The mitochondrial aspect is interesting. In heart failure normally there's the switch from fatty acid oxidation to glycolysis. Does that happen in a shorter or smaller way after flu? And in some patients they just don't recover? Is there a metabolic switch to an infected cardiomyocyte, that is more transient, and then in a subset it turns to permanent? Is that what's happening? Dr Norberto Gonzalez-Juarbe:    Yeah, that is something that we might need to follow up on, since our study was more of a snapshot of that specific time point. It will be good to do follow-up studies where we look at different time points post infection. And even maybe three months after infection, then six months after infection. We have done similar studies with pneumococcal pneumonia, and we have found that cardiac function and metabolic function, it is significantly remodeled, even three months after the pneumonia event. Dr Cindy St. Hilaire:        Interesting. So once it's actually cleared from the lungs, it's still… Dr Norberto Gonzalez-Juarbe:    The heart is still undergoing this injury recovery, which cause scarring process and these leads to reduced cardiac function. Dr Cindy St. Hilaire: So influenza actually, maybe a lot of people know this now, but it was somewhat new to me, I guess, at least a year ago when COVID first started. But influenza like SARS-CoV2 is an enveloped virus. It's a single strand RNA virus. So are these findings specific to this class of viruses, specific to RNA viruses? Or is this something that you think is operative in other types of viruses in terms of causing these cardiac complications? Dr Maryann Platt:           It's certainly possible. I'm not a virologist. (laughs). Dr Cindy St. Hilaire:        Not yet. (laughs). Dr Norberto Gonzalez-Juarbe:    Eventually you'll get there. Dr Maryann Platt:           Yeah, eventually probably. But you know, there have been reports of lots of adverse cardiac events in SARS-CoV too. So it's certainly not just unique to influenza, as far as other types of double stranded RNA viruses. I'm not sure. Dr Norberto Gonzalez-Juarbe:    Yeah, of course Coxsackieviruses viruses have shown inductionof cardiac events. And there's a Review in the New England Journal of Medicine about some of these other pneumonia causing agents, but also all other pathogens that can do some of these events, but it's all clinical observations. So, we think that our study and several others studies that are starting to come out, can induce a shift part of field to look at how some of these major respiratory viruses can induce these adverse cardiac events that we see are highly prevalent, right after the event, like during infection. And importantly, how all the pathogens may synergize. Some pathogens such as RSB, flu, COVID, have synergized with bacteria or other virus one enhancing the ability of the other to cause injury and disease. Dr Norberto Gonzalez-Juarbe:    For example, flu with pneumococcal disease, COVID with assorted grand negative pathogens, and actually influenza also has been shown to cause co-infection. So we don't know how some of these pathogens may synergize in the lungs, but also in other organs, to cause these injury that are going to be long lasting. So we are having the acute problem now with COVID and we had this with the 2009 pandemic flu, but in the next 10 years, five years, we're going to see this equivalent of disease damage, the damage associated with the disease, and we are going to have to explain why people are having these cardiac events, why people are having kidney events or liver damage problem. So we need to better understand not only how RNA viruses do this, and there's actually data shows that COVID is present in the cardiac tissue and can replicate in cardiac cells, but also how they may synergize to potentiate these effects. And how can we prevent all of these from happening? By action, therapies to antivirals, or any other way. Dr Cindy St. Hilaire:        That's a perfect segue to my last question I had. And that is, how can, what you found in the study regarding necroptosis, or even just the base proteins that are involved, is it able to be leveraged either for the development of therapies or perhaps even like a screening method, a biomarker to determine which flu patients might go on to develop cardiac phenotypes? Dr Norberto Gonzalez-Juarbe:    There might be a couple of avenues our study can help create these adjunct therapeutics to anti-virals. So one might be targeting the specific necrotic cell pathways to prevent that titrating that is long-lasting and these can be targeting necroptosis or pyroptosis, and there's FDA approved drugs that we may be able to repurpose to target some of these pathways that have these secondary effects, that can target these pathways. But also the very interesting part for me was that MLKL lesion increased this protein called NNT, which is a major factor of mitochondrial function and ATP production. So if we can improve the ability of the heart function and to protect their mitochondria, then we probably can have more roughly protective response against not only flu, but maybe COVID or other viruses that might also do similar things to the heart. Dr Cindy St. Hilaire:         Or even just other heart failures. That's pretty neat. Dr Norberto Gonzalez-Juarbe:    Exactly. Dr Maryann Platt:           Yeah, exactly. Dr Cindy St. Hilaire:        That's great. Drs Gonzalez-Juarbe and Platt. Thank you so much for joining me today. Congratulations on an excellent study and I'm really looking forward to your future, probably viral related, work. Dr Norberto Gonzalez-Juarbe:    Thank you very much. Dr Maryann Platt:           Thanks. Dr Cindy St. Hilaire:        That's it for our highlights from the March 5th and 19th 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 Circ. Thank you to our guests, Drs Norberto Gonzalez-Juarbe and Maryann Platt. The podcast is produced by Rebecca McTavish and Ashara Ratnayaka, edited by Melissa Stoner, and supported by the Editorial Team of Circulation Research. Some of the copy text for the 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 exciting discoveries in basic cardiovascular research.  

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.24.220129v1?rss=1 Authors: Wang, S., Leem, J., Podvin, S., Hook, V., Kleschevnikov, N., Savchenko, P., Dhanani, M., Zhou, K., Kelly, I., Zhang, T., Miyanohara, A., Kleschevnikov, A., Wagner, S., Trojanowski, J., Roth, D., Patel, H., Patel, P., Head, B. P. Abstract: AD presents with severe neurodegeneration which leads to cognitive deficits and dementia. Identifying the molecular signals that attenuate neurodegeneration in AD may be exploited as therapeutic targets. This study revealed that transgenic AD mice (PSAPP) exhibit decreased caveolin-1 (Cav-1), a membrane/lipid raft (MLR) scaffolding protein that organizes synaptic signaling components. Subcellularly, Cav-1 and full length (fl)-TrkB were significantly decreased in MLRs. We thus developed an in vivo gene therapy that re-expresses neuronal-targeted Cav-1 using the synapsin promoter (SynCav1). While AD mice showed significant learning and memory deficits at 9 and 11 months, AD mice that received hippocampal SynCav1 (AD-SynCav1) maintained normal learning and memory at 9 and 11 months respectively. Furthermore, AD-SynCav1 mice showed preserved hippocampal MLR-localized fl-TrkB, synaptic ultrastructure, dendritic arborization and axonal myelin content, all of which occurred independent of reducing amyloid deposit and astrogliosis. Thus, SynCav1 demonstrates translational potential to treat AD by delaying neurodegeneration. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.13.093336v1?rss=1 Authors: Chang, J.-H., Greene, C., Futter, C., Nichols, B. J., Campbell, M., Turowski, P. Abstract: The blood-brain barrier (BBB) is a multifactorial and multicellular vascular interface separating the systemic environment from the central nervous system (CNS). It gates cerebral penetration of circulating molecules and cells and is the principal reason for low accumulation of many therapeutics in the brain. Low dose methamphetamine (METH) induces fluid phase transcytosis across the BBB in vitro and could therefore be used to enhance CNS drug delivery. Here we show, that low dose intravascular METH induced significant leakage exclusively via caveolar transport at the intact BBB in rodents ex vivo. Notably, METH-induced leakage was suppressed at 4C and in Caveolin-1 (CAV1) knockout mice. Furthermore, METH strongly enhanced brain penetration of therapeutic molecules, namely doxorubicin (DOX), a small chemotherapeutic agent, and aflibercept (AFL), a ca. 100 kDA recombinant protein. Lastly, METH improved the therapeutic efficacy of DOX in a mouse model of human glioblastoma (GBM), as measured by a 25% increase in median survival time (p = 0.0024). Collectively, our data indicated that METH can facilitate preclinical assessment of novel experimental treatments and has the potential to enhance drug delivery to the diseased CNS. Copy rights belong to original authors. Visit the link for more info

Dr Carolyn Lam:                Welcome to Circulation on the Run, your weekly podcast summary and backstage pass to the journal and its editors. We're your co-hosts, I'm Dr Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore. Dr Greg Hundley:             And I'm Dr Greg Hundley: Hundley, Associate Editor from the Pauley Heart Center in Richmond, Virginia at VCU Health. Well Carolyn, our featured article this week addresses the age at which to initiate clinical screening of relatives for hypertrophic cardiomyopathy. Our guidelines suggest screening of relatives from age ten and onwards but data are lacking to substantiate this suggestion. I look forward to the authors' discussion of their findings regarding initiation of screening in children. For now though, do you have an article that you'd like to share? Dr Carolyn Lam:                You bet, Greg. So, the first paper I chose really demonstrates that patients inducible pluripotent stem cells or IPSC cardio derived myocytes can be used as a disease modeling platform to delineate the functional mechanisms that underlie cardiac hypertrophy and in this particular case they looked at Noonan Syndrome and showed that how these techniques can be subsequently used to identify novel molecular and genetic therapeutic targets. So, Greg, here's your quiz. The genetics of Noonan Syndrome. Dr Greg Hundley:             I remember it was on our board exam. Dr Carolyn Lam:                Let me tell you about it. So more than 90% of patients with Noonan Syndrome have a mutation in the hinge region CR2 domain of Raf-1 and they exhibit severe hypertrophic cardiomyopathy for which there is no treatment. Authors, Dr Jaffrey from Cornell University and Dr Kontaridis from Masonic Medical Research Institute in Utica in New York and their colleagues used Noonan Syndrome Raf-1 patient and CRISPR corrected IPSC cardiomyocytes to recapitulate the Noonan Syndrome cardiac phenotype.                                                 These Noonan Syndrome IPSC derived cardiomyocytes exhibited the same hypertrophy and myofibrillar disarray that's really observed in Noonan Syndrome patient hearts, so mechanistically the authors showed that activation of mitogen-activated protein kinase or mech-1 or -2, but not the extracellular regulated kinase, which is ERK1 or 2 triggered abnormal cardiomyocytes structure and conversely ERK5 mediated increased cell size in these Noonan Syndrome mutant IPSC derived cardiomyocytes.                                                 RNA sequencing further identified genes dysregulated in the Noonan Syndrome cardiomyocytes that may underlie hypertrophic cardiomyopathy downstream if the mech-1 or -2 and ERK5 genes. Dr Greg Hundley:             So, Carolyn, that's a lot of genetic information, so what can I take home as I think about this further and what may come down the line as we manage patients with Noonan Syndrome? Dr Carolyn Lam:                Thanks, Greg. The real take home message is that these pathways could serve as novel therapeutic targets to treat hypertrophic cardiomyopathy in patients with Noonan Syndrome and Raf-1 mutations. Overall, the elucidation of rare disease mechanism of hypertrophic cardiomyopathy may further unravel and reveal causes of other more common idiopathic congenital disorders and hypertrophic diseases. Dr Greg Hundley:             Oh, very good. Well, I'm going to switch gears and talk a little bit about infective endocarditis prophylaxis and this article comes from Pallavi Garg at the London Health Scientist Center. Carolyn, as you may recall, given the lack of proven efficacy and concerns about the perceived risks of antibiotic prophylaxis like development of antibiotic resistance, the American Heart Association in 2007 and the European Society of Cardiology in 2009 published revised guidelines recommending cessation of antibiotic prophylaxis prior to dental procedures for patients at moderate risk of infective endocarditis while continuing the practice in high risk patients. This Canadian study was conducted from 2002 to 2014 among all adults and those at high and moderate risk for infective endocarditis and they were stratified by age. Prescriptions for antibiotic prophylaxis were obtained from the Ontario Drug Benefit Database for adults 65 and older and outcomes regarding antibiotic prophylaxis prescription rates and the incidents of infective endocarditis related hospitalization were assessed. Dr Carolyn Lam:                 Ooh, interesting. What did they find? Dr Greg Hundley:             The authors found a sustained reduction in antibiotic prophylaxis prescriptions among individuals at moderate risk for infective endocarditis that coincided with the change in guidelines. In contrast, while there was a decreasing trend in antibiotic prophylaxis among individuals at high risk of infective endocarditis and a minimal drop following the guidelines released, the overall rates of prophylaxis prescribing in this group continued to climb since early 2007, and collectively, these findings suggest that appropriate uptake of the revised AHA guidelines occurred.                                                 Furthermore, over the thirteen-year study period, the authors identified an increase in hospitalizations for new episodes of endocarditis approximately three years after the AHA guidelines were revised. This timeline along with the rise of endocarditis incidents in both the high and moderate risk groups suggests that this observed increase in endocarditis is likely unrelated to the change in the prescribing practice of antibiotic prophylaxis. This conclusion is further supported by the overall decrease in endocarditis cases attributable to streptococcal infections over time, a finding contrary to what might be expected as a result of the reduction in antibiotic prophylaxis. Dr Carolyn Lam:                Oh, very interesting, Greg. At first a little bit scary and then after when you described it more, it does seem a little bit more reassuring. Very interesting. Well, thank you. My next paper deals with functional tricuspid regurgitation, which as you know is really common in heart failure with reduced ejection fraction or HFrEF and mostly consequent to pulmonary hypertension. However, what is the access mortality associate with functional tricuspid regurgitation in HFrEF? Well, this paper from Dr Maurice Serrano from Mayo Clinic and colleagues looked at all Mayo Clinic patients from 2003 to 2011 diagnosed with heart failure stage B and C and an ejection fraction less than 50% who had functional tricuspid regurgitation grading and systolic pulmonary artery pressure measured by Doppler echocardiography.                                                 Now among more than 13,000 patients meeting these inclusion criteria, functional tricuspid regurgitation was detected in 88%. Functional tricuspid regurgitation was independently associated with more dyspnea, more impaired kidney function, and lower cardiac output. For the long term outcomes, the higher the degree of functional tricuspid regurgitation compared with a group with trivial tricuspid regurgitation was independently associated with a higher mortality hazard. The five year survival was substantially lower with increasing severity of tricuspid regurgitation so it was 68% on average for trivial functional tricuspid regurgitation versus 34% for severe functional tricuspid regurgitation.                                                 Importantly, this access mortality observed with moderate or severe functional tricuspid regurgitation was independent of pulmonary hypertension and any other clinical characteristics. Dr Greg Hundley:             Hmm, interesting but Carolyn, wouldn't we expect this? Dr Carolyn Lam:                You know what, you may expect it, but this is really the largest series, I think, that has shown this and shown this in the systematic way that functional tricuspid regurgitation in and of itself may play an important pathophysiologic role and thus, may represent a potential therapeutic target in HFrEF. In other words, the present study really advocates for a trial to test treating functional tricuspid regurgitation in patients with HFrEF. Dr Greg Hundley:             Oh wow, you really put that in great perspective, Carolyn. Well, your reward is   going to be a quiz. Dr Carolyn Lam:                 Oh my gosh, Greg. Dr Greg Hundley:             We're going to talk about ... Dr Carolyn Lam:                 What now? Dr Greg Hundley:             Caveolin-1, an atherogenesis and nitric oxide and this is from Professor Carlos Fernandez Hernando at the Yale University School of Medicine. Okay, multiple choice. What are caveolae? Now I'm going to give you some choices, you get to pick A. Are they crypts within the walls of vessels. B. Crypts within the membranes of endothelial cells. Or C. Crypts within the border zones of infarcts. Dr Carolyn Lam:                Wait a minute, Greg. I'm not even sure we're pronouncing it the same. You're asking about caveolae like ... Potato potata. They're invaginations of cell membranes, that's all I know. Dr Greg Hundley:             Oh wow, fantastic. This study focused on the effect of Caveolin-1, a protein integral to the formation of caveolae. The investigators found in a series of mouse experiments that A. The athero-protection observed in mice lacking Caveolin-1 is independent of endothelial nitric oxide synthase activation and nitric oxide production. B. Endothelial Caveolin-1 controls lipoprotein infiltration in vascular inflammation in early stage atherosclerotic lesion. C. Endothelial Caveolin-1 promotes pro-atherogenic matrix deposition leading to endothelial cell activation in atheroprone regions of the aorta and finally, D. Atheroprone regions of the aorta are characterized by increased intracellular and basolateral caveolae distribution in endothelial cells compared to athero-resistant areas. Dr Carolyn Lam:                Wow, I like the way you broke that down into four points, but could you summarize what it means clinically? Dr Greg Hundley:             Yeah, so I think if you had to summarize all of this in a sentence, perhaps the suppression of Caveolin-1 expression in endothelial cells might prevent the progression and promote the regression of atherosclerosis so in the future perhaps an interesting target to treat atherosclerosis. Well, now Carolyn, I guess we should proceed to that talk with our featured discussion. Dr Carolyn Lam:                 Absolutely. Thanks, Greg.                                                 Hypertrophic cardiomyopathy is an inheritable myocardial disease with age-related penetrance. Current guidelines recommend that clinical screening of relatives start from the age of ten years onwards by the European Society of Cardiology and twelve years onwards by the American College of Cardiology or American Heart Association. There are of course caveats for earlier screening but the clinical value of this approach has really not been systematically evaluated. That is until today's feature paper and we are so pleased to be here discussing it. This is Greg Hundley and Carolyn Lam and we're your co-hosts for Circulation on the Run. So happy to welcome Dr Juan Pablo Kaski who's the corresponding author of today's feature paper from Great Ormand Street Hospital in London and we also have Dr Gerald Greil, Associate Editor from UT Southwestern.                                                 Welcome, everyone. Juan, if you don't mind, could you start by summarizing this very important study of yours? Dr Juan Pablo Kaski:        Thank you very much. Hypertrophic cardiomyopathy is a genetic muscle condition that is characterized by hypertrophy and is most commonly inherited as a dominant trait. Previous studies have suggested that in familial disease at least ventricular hypertrophy doesn't usually present until adolescence and this has led to the current guidelines which do not recommend routine screening of children below the age of twelve according to the American guidelines below the age of ten and the European guidelines for hypertrophy cardiomyopathy but own clinical experience was different and suggested that perhaps sarcomeric disease and familial disease could present in younger children, so what we aimed to do with this study was to assess the validity of this approach and tried to assess the yield of clinical screening in children from families of hypertrophic cardiomyopathy. Dr Juan Pablo Kaski:        We took our collective experience in our institution over a period of many years and recruited just on the 1,200 consecutive children all aged less than eighteen years at the time of initial assessment coming from just under 600 families and these were children who were referred for clinical screenings because a first degree relative had been diagnosed with hypertrophic cardiomyopathy. What we found was that in 5% of these children and in fact, in 8% of the families that we screened, we were able to pick up early phenotypic features of hypertrophic cardiomyopathy. In 72% of patients, we made a diagnosis before the age of twelve, so before current clinical screening guidelines we'd recommend and importantly, a third of these patients during follow up had a change in their management as a result of the diagnosis. Their medication was commenced, they underwent procedures or implantations of defibrillators. Dr Greg Hundley:             Juan, this is Greg Hundley and I was wondering when did the participants that were enrolled experience events? Did those that were say under fourteen or even under twelve, did they experience events relative to those that were a little older? Dr Juan Pablo Kaski:        The events that our participants experienced were relatively few. Many of these occurred during the childhood age but some occurred once the children had transitioned into the adult age. We did look to see whether there was any difference in terms of early diagnosis and subsequent events, but we didn't find anything, we didn't identify two separate populations in that respect. Dr Greg Hundley:             And then did you perform genetic analyses? I know you described phenotypic characterization of the patient population but how about genetically? What results did you find there? Dr Juan Pablo Kaski:        The main aim of the study really was to determine a yield of clinical screenings, so this is a reflection of a real-world practice where genetic testing may not necessarily be routinely available. Having said that, we did have genetic data in a third of our families and in fact, in maybe 70% of those children who made clinical diagnosis of hypertrophic cardiomyopathy was made and what we find in those individuals who have undergone genetic testing is that the vast majority of those had mutations in sarcomeric protein genes and pathogenic or likely pathogenic variants in sarcomeric genes in just under 70% and these were well characterized mutations that are very similar to those that are seen in adolescence or adult onset hypertrophic cardiomyopathy.                                                 I think what was interesting about these genetic results is that we seem to have identified a population of early onset sarcomeric disease that genetically appears to be indistinguishable from a sort of later onset adult disease but with the clinical presentation and natural history curve shifted somewhat to the left. Dr Greg Hundley:             Gerald, just switching over, can you tell us some of your thoughts about how the results of this study will impact clinical practice, both in the European countries as well as U.S.? Dr Gerald Greil:                 I mean, I was obviously delighted to see the study being submitted to circulation because there's a very important message particularly for pediatric cardiologists which is potentially influencing the guidelines and Dr Kaski may comment on this as well as the next step meaning that it seems like screening patients older than ten or twelve years and once again, there's a slight discrepancy between the European and U.S. guidelines, seems to be ... Can be questioned and potentially we should screen these patients earlier.                                                 Another amplification of this study is that we should think about how much genetic screening can be an essential tool in our methods in looking at these patients and I want to point out that because of these discrepancies we also initiated an editorial letter for this publication done by Dr Ommen and by Dr Mital kind of pointing out there needs a lot of work to be done maybe even including rewriting the current guidelines.                                                 There's another paper that came out recently in European Society Cardiology, the European Heart Journal about a similar topic so it's something which is very, very heavily discussed in our community. We think how we are looking at these patients and how we're following them up. Dr Greg Hundley:             What would you suggest are next steps for the world community in this space in regards to modifying those guidelines? Dr Gerald Greil:                 I think there's now enough literature around which suggests that we should look at these patients earlier and screen them earlier on both sides in European, in the U.S., in the Asian world, and ideally these two groups should sit together and write combined guidelines. It's still interesting that the European and U.S. guidelines are slightly different in that we're talking about a similar group of patients, so I'm very, very delighted to see that this is coming up in the national literature as a new topic and I think everything is open now to rethink this topic and rewrite these guidelines. Dr Greg Hundley:             Do you think prospective studies would be necessary because I believe, and Dr Kaski please weigh in here, this was a retrospective review, and do you think there could have been triggering circumstances that prompted early screening? I mean, would a next step be some sort of prospective registry? Dr Gerald Greil:                 I mean definitely that's the next step. I think we have enough data material around once again to rethink the strategy which age these patients should be looked at. A prospective registry and Dr Kaski can probably comment on it better than I can, I think that something which is a logical next step and there may be even something being on the way to make this happen. Dr Juan Pablo Kaski:        I agree. I think further validation and confirmation of these data from prospective studies would be extremely helpful. I think one of the things that we need to bear in mind is the potential cost implications of expending screening to ever increasing populations and so perhaps an additional further step would be to try to refine the screening tools so that we are able to identify clinical by a chemical of those individuals who are more likely to present in childhood and perhaps set a target screening towards that population.                                                 I can just go back to one of your sort of previous points also about a potential bias and it is true that these patients were referred for clinical screening at a time when clinical recommendations do not suggest that this is necessary and although we didn't specifically in this cohort look at those that would have fulfilled current early screening criteria, the vast majority of the patients were asymptomatic at the time that they were referred. We also looked to see whether there was any link between those individuals who had a family history of early onset disease and an early diagnosis, and that was the only factor that came up as potentially significant so perhaps the current guidelines that do recommend considering earlier screenings if there's a family history of childhood disease are still applicable. Dr Carolyn Lam:                That was just an amazing interview, by the way. I've learned so much and thank you so much for publishing this very important paper with us.                                                 You've been listening to Circulation on the Run. Don't forget to tune in again next week. This program is Copyright American Heart Association 2019.  

Dr. Paul Wong:                  Welcome to the monthly podcast, On The Beat, for Circulation: Arrhythmia and Electrophysiology. I'm Dr. Paul Wong, editor in chief, with some of the key highlights from 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, Ratika Parkash and associates examined whether the outcomes following escalated antiarrhythmic drug therapy, or catheter ablation, depended on whether ventricular tachycardia with amiodarone refractory or sotalol refractory in patients with prior myocardial infarction in the VANISH study. At baseline, 169, or 65%, were amiodarone refractory, while the remaining were sotalol refractory. Amiodarone refractory patients had more renal insufficiency; 23.7% versus 10%. Worse, new ARC Heart Association class, 82.3% versus 65.5% class II or III; and lower ejection fraction, 29% versus 35%. Within the amiodarone refractory group, ablation resulted in a reduction of any ventricular arrhythmias compared to escalated drug therapy, with a hazard ratio of 0.53, P = 0.02. Sotalol refractory patients had trends towards higher mortality in VT storm with ablation, with no effect on ICD shocks. Within the escalated drug arm, amiodarone refractory patients had a higher rate of composite endpoint, with a hazard ratio of 1.94 and a P value of 0.01. In a trend toward higher mortality, hazard ratio 2.4, P = 0.07. While mortality was not different between amiodarone and sotalol refractory patients within the ablation treatment group. In our next study, Junaid Zaman and associates examined 57 cases in which local ablation of persistent atrial fibrillation terminated to sinus rhythm or organized tachycardia. The authors analyze unipolar electrograms collected during atrial fibrillation from multi-polar basket catheters to reconstruct isochronal activation maps for multiple cycles, and computational modeling and phase analysis were used to study mechanisms of map variability. At all signs of atrial fibrillation termination, localized, repetitive activation patterns were observed, 21% with complete rotational activity, 46% with partial rotational circuits, and 33% with focal patterns. In computer simulations incomplete segments of partial rotations coincided with areas of slow conduction, characterized by complex, multi-component electrograms. In our next article, Matthew Kalscheur and associates sought to use a novel machine-learning approach to predict outcomes following resynchronization therapy in the companion trial. The random forest algorithm resulted in the best performing model. In 595 CRTD patients in the companion trial, 105 deaths occurred, with a median follow-up of 15.7 months. The survival difference across subgroups differentiated by bundle branch block morphology and cure restoration did not reach significance, P = 0.08. The random forest model, however, produced quartiles of patients with an eight-fold difference in survival between those with the highest and lowest predictive probability for events, hazard ratio 7.96 with a P value of less than 0.0001. The model also discriminated the risk of composite endpoint of all cause mortality, or heart failure hospitalization, better than subgroups based on bundle branch block morphology and cure restoration. Future studies are needed to validate this model in other populations. In our next paper, Amr Barakat and associates examined the clinical outcomes of trans-venous lead extraction for CIED infection based on renal function. The authors examined 1,420 consecutive patients undergoing trans-venous lead extraction of infected CIEDs over a 14 year period. Groups with normal renal function, Group 1, consisting of 1,159 patients, Group 2, 163 patients with renal dysfunction not requiring dialysis, and Group 3, 98 patients on dialysis. Complete procedural success rates were comparable in the three groups: 94%, 96%, and 94% in Groups 1, 2 and 3, respectively. This was not statistically significant. The mortality rates were significantly higher in dialysis patients at one month. The procedure-related complication was 12.2% in dialysis patients versus 6.5% in Group 1 and 6.1% in Group 2. Other factors associated with mortality were lead material retention, functional New York Heart Association Class, and occurrence of procedural complications. In our next paper, Eric Johnson and associates studied the contribution of the current ITO, two left ventricular re-polarization in the human heart, since the current has been shown to have an important role in animal models. The authors found that using whole-cell voltage clamp recordings from myocytes, isolated from the left ventricle, non-failing human hearts, that there were two, distinct transient currents, ITO fast and ITO slow. The two currents have significantly different rates of recovery from inactivation and pharmacological sensitivities. ITO fast recovers in about 10 milliseconds, 100 times faster than ITO slow, and it's selectively blocked by KV4 channel toxin SNX 482. Using current clamp experiments, they found that regional differences in action potential wave forms, with a notch in phase one in the left ventricular subepicardial myocytes. In failing, left ventricular subepicardial myocytes, ITO fast was reduced, while ITO slow was increased. In addition, the notch and plateau potentials were depolarized, and action potential durations were prolonged, both statistically significantly. Slowing ITO fast inactivation results in a dramatic action potential shortening. The authors concluded that remodeling of ITO fast in failing, human left ventricular subepicardial myocytes, attenuates transmural differences in action potential wave forms. In our next paper, Ravi Vaidyanathan and associates examine the interaction between Caveolin 3 domain in the inward rectifier potassium channels. Although the IK1 current is mainly composed of Kir2.1, there are Kir2.2 and Kir2.3 heterotetromerisoforms that occur and modulate the IK1 current, but these have not been studied. Kir2.x isoforms have unique, subcellular co-localization in human cardiomyoctyes and co-immunoprecipitate with Cav3. Using induced pluripotential stem-cell-derived cardiomyocytes, the LQT9 Cav3 mutation, F97CCav3 resulted in actual potential prolongation. Based on the technique FRET, which is Fluorescent Resonance Energy Transfer, the authors calculated the distance between KR2.2 and cath ray proteins to be 6.61 nanometers. LQT9 is caused by Cav3 mutations. Prior work has shown that F97CCav3 mutation increases the late sodium current, and decreases KR2.1 current density by distinctive mechanisms. This study extends the authors' previous observations on the impact of LQT9 Cav3 mutation on Kir2.1 current, by demonstrating that mutation affects the Kir2.2 current. LQT9 causing Cav3 mutation differentially regulates current density and cell surface expression of Kir2.x homomeric and heteromeric channels. The authors show that the mutation does not affect Kir2.3 current, but the heterotetromer Kir2.2-2.3 demonstrated loss of function. Using the Li-Rudy [inaudible 00:09:45] model and myocyte mathematical model, the authors' data suggest that both loss of IK1 and increased sodium L are required for arrhythmia generation in LQT9. In our next study, Christophe Teuwen and associates use high resolution epicardial mapping electrodes, 128 or 192, with an inter-electrode distance of 2.0mm of the entire atrial surface in 164 patients. These patients were undergoing open-chest cardiac surgery. This study was designed to examine the conduction of atrial extrasystoles. The authors found that a higher degree of aberrancy was associated with a higher instance of conduction disorders. Most conduction disorders were provoked by atrial systoles emerging as epicardial breakthroughs. Atrial extrasystoles cause most conduction disorders in patients with left atrial dilatation or diabetes mellitus. In our next paper, Yuki Komatsu and associates examine 31 patients with idiopathic ventricular arryhthmias, using a two french microcatheter placed in a communicating vein between the great cardiac vein and small cardiac venous system, which passes between the aortic and pulmonary annulae, and is located in close associated with the left ventricular summit. They found that 14 patients had summit ventricular arryhthmias. The remaining 17 patients control group had ventricular arryhthmias originate from the right ventricular outflow track in the aortic cusps.  In patients with summit ventricular arryhthmias, the earliest activation during ventricular arryhthmias in the summit, preceded to cure as onset by 34 milliseconds. The summit ventricular arryhthmias exhibited inferior axes, negative polarity in lead one, deeper Q wave in AVL than AVR, nonspecific bundle branch morphology with an RS ratio in lead V1 of 0.67, distinguishing them from arryhthmias originating from the right ventricular outflow track or right ventricular cusp. Overall, ablation success was achieved in 10, or 71% of patients with summit ventricular arryhthmias, and 88% in the control group, P = 0.24. In our final paper, Deepak Padmanabhan and associates examine differences in mortality in patients with non-MRI conditional CID undergoing brain MRI compared to controls. Patients with CIDs undergoing brain MRI were compared with three control groups matched for age, sex, imaging year, and type of CID. These groups included 1) no CID and brain MRI, 2) CID in brain-computed CT, and 3) no CID in brain CT. They estimated all cause mortality at five years for CID MRI group, was not significantly different from patients who underwent CT, with or without a device. There was a significant increase in the mortality between CIED versus no CID MRI groups, hazard ratio 1.46 with a P value of 0.04. That's it for this month, but keep listening. Saraj 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 Saraj. Saraj Kapa:                          Thank you Paul, and welcome back to On the Beats where this month we'll be focusing on articles that are particularly hard-hitting, published across the literature in December of 2017. It's my pleasure to introduce 20 different articles that seem to have either particular interest or might change the field in the future. First, within the area of atrial fibrillation, we'll focus within the area of anticoagulation and stroke prevention. In the Journal of the American College of Cardiology, Vivek Reddy et al published on the five-year outcomes after left atrial appendage closure, from the Prevail and Protect AF trials. They included a total of 1,114 patients, with a total of 4,343 patient years of follow-up, randomized two to one to closure versus Warfarin. While ischemic stroke and systemic embolism of [inaudible 00:14:32] were numerically higher with closure, this did not reach statistical significance in terms of hemorrhagic stroke, unexplained death, and post-procedure bleeding favor left atrial appendage closure. These findings further support a role for left atrial appendage closure in the specific groups of patients enrolled in the Protect and Prevail Studies. Of course, we always need to understand, that extrapolation to patients who may not have met inclusion criteria will be difficult. In particular, given both trials had their own fundamental limitations in the Prevail study. There was a relatively low rate of [inaudible 00:15:09] in the Warfarin arm. And in turn, there was a relatively high complication rate in Protect AF with left atrial appendage closure. Part of the differences might be due to the fact that, with more experience, complication rates might decrease. Furthermore, a comparison with more novel agents, such as the new oral anticoagulants, remains to be seen. Next, within the realm of cardiac mapping and ablation for atrial fibrillation, we review an article by Vlachos et al published in the Journal of Cardiovascular Electrophysiology entitled Low-Voltage Areas Detected by High-Density Electroanatomical Mapping for Recurrence of Ablation after a Paroxysmal Atrial Fibrillation. They presented the results from a series of 80 patients undergoing ablation for paroxysmal atrial fibrillation, performing high-density voltage mapping to characterize the total area involved by low voltage. They demonstrated, when low voltage areas, defined as less than 0.4 millivolts, were seen in greater than 10% of the left atrial surface area, this served as an independent predictor of atrial fibrillation recurrence. These data support prior research, including that of MRIs, suggesting the characterization of the atrial substrate may correlate with likelihood of ablation success. Identifying methods however, to accurately and reproduce will identify these patients with more atrial substrate prior to ablation, remains to be seen. The importance of this, however, is our ability to better counsel patients on the likelihood of treatment success. Next within the realm of atrial fibrillation, we review elements of risk stratification managements. First, in the December issue of the Journal of American College of Cardiology, Takimoto et al published on how Eplerenone may reduce atrial fibrillation burden without preventing atrial electrical remodeling. In a randomized controlled ovine atrial tachy pacing model of atrial fibrillation. The authors provided daily, oral Eplerenone and compared this with a placebo. They showed that Eplerenone significantly reduced the rate of left atrial dilatation, with less smooth muscle actin protein, atrial fibril [inaudible 00:17:17]. Furthermore, Eplerenone further prolonged the time to persist in atrial fibrillation in 26% of animals. However, interestingly, Eplerenone did not prevent AF-induced electrical remodeling.  These data suggest that Eplerenone, or other medications that can be used to prevent or reverse structural remodeling, may offer an upstream therapy to reduce atrial fibrillation burden, and decrease likely the persistent atrial fibrillation. Giving the ever-growing population of patients suffering from atrial fibrillation, identifying upstream approaches to prevent it will be critical. Of course, these need to be taken with due consideration, however. Specifically, the model used here, namely that of an atrial tachy pacing model, might not be applicable to all human atrial fibrillation. Thus, whether or not such therapies actually offer benefit in clinical models, is as of yet unclear. Finally, from the realm of atrial fibrillation, we review the article by Rowin et al published in circulation entitled Clinical Profile of Consequences of Atrial Fibrillation Hypertrophic Cardiomyopathy. In patients presenting with hypertrophic cardiomyopathy, atrial fibrillation is known to be a significant co-morbidity. However, the implications of atrial fibrillation in terms of worsening of heart failure status, or long-term morbidity mortality are less clear. Rowin et al reviewed the natural history of atrial fibrillation amongst 1,558 patients, prospectively followed at a single center. Nearly 20% of the population developed atrial fibrillation with the majority having symptomatic paroxysmal atrial fibrillation. However, atrial fibrillation was not associated with any increase in cardiovascular mortality or worsening of heart failure status. Furthermore, mortality that was directly related to atrial fibrillation was nearly exclusively related to thrombolic stroke. Anticoagulation [inaudible 00:19:13] reduced this risk. The traditional scoring systems fared poorly in assessing the stroke risk of this population. About 121 patients underwent invasive rhythm control approaches, including 72 patients undergoing maze and 49 catheter ablation. The success rate of maze was significantly greater at around 75%. These data are important when counseling hypertrophic cardiomyopathy patients presenting with new-onset atrial fibrillation. While it is clear that paroxysmal atrial fibrillation has a significant impact on symptoms and quality of life, it does not cause worsened, overall, long-term outcomes. However, it does highlight the importance of anticoagulation in this population, nearly irrespective of the underlying risk score. In terms of rhythm control options, it appears that rhythm control options can be successful in these patients. Finding that catheter ablation is associated with a 40 to 50% success rate is in keeping with prior published data. Thus, consideration of when a patient needs to be referred to maze, needs to be considered in the clinical inpatient context. Changing gears, we will next review articles within the realm of ICDs, pacemakers, and CRT. In the New England Journal of Medicine this past month, Nazarian et al published on their experience regarding the safety of magnetic resonance imaging in patients with cardiac devices. They performed a prospective non-randomized study of the safety of, specifically, 1.5 tesla-strength MRI scans on legacy. In other words, not MRI conditionally-safe pacemakers and defibrillators. A total of 2,103 scans were done among 1,580 patients. They demonstrated no long term clinically significant adverse events. Nine patients did experience a reset to a backup mode, though eight of which were transients. The most common change seen acutely was a decrease in PVA amplitude in one percent of patients, and in a long term follow-up, 4% of patients experiencing a decrease in PVA amplitude, increase in atrial catheter sheer threshold, or increase in right or left ventricular capture threshold. However, none of these events were considered clinically significant. Furthermore, there was not a good [inaudible 00:21:23] group to know if this long term change in amplitudes or thresholds might have been seen in patients who had devices that were not exposed to MRI. These findings are complimentary to multiple, prior, published reports, indicating the safety of performing MRIs under clinical protocol in legacy pacemakers and defibrillators. It calls into question whether MRI conditional devices truly offer an additional safety factor furthermore, over legacy devices. Next we review an article by Lakkireddy et al published in Heart Rhythm entitled A Worldwide Experience, the Management of Battery Failures and Chronic Device Retrieval of the Nanostim Leadless Pacemaker. Lakkireddy et al reported their large multi-center experience on the overall risk of battery failure. Amongst 1,423 implanted devices there were 34 battery failures occurring, on the average, three years after implants. Furthermore, about 73 patients underwent attempted device retrieval, and this was successful in 90%, with the seven failures of retrieval being due to either inaccessibility of the docking button, or dislodgement of the docking button in one patient, in whom it embolized to the pulmonary artery. An additional 115 patients interestingly received an additional pacemaker after release of the device advisory. These data suggest that there may be as high as an overall 2% risk of battery failure with the Nanostim device, even late after implants. This highlights the need for close follow-up, even if the battery appears relatively stable up to two year after implants. Furthermore, almost 10% of devices cannot be successfully retrieved. However, in those patients, even with re-implantation of a separate device, there was no device-device interaction seen. Further innovation will be needed to optimize device longevity, and close follow-up of all patients undergoing implantation will be critical to understand the overall long term efficacy and safety when compared to other traditional devices. Finally, within the realm of device care, we focus on an article by Kiehl et al, again published in Heart Rhythm this past month entitled Incidence and Predictors of Late Atrial Ventricular Conduction Recovery Among Patients Requiring Permanent Pacemaker for complete heart block after cardiac surgery. They reviewed the likelihood of recovery of conduction in their retrospective cohort of 301 patients. Interestingly, 12% of patients had recovery of AV conduction on average six months after surgery. Those who did not recover tended to more likely have preoperative conduction abnormalities. Saraj Kapa:                          Findings that suggested a higher likelihood of long term conduction recovery included female sex and the existence of transient periods of AV conduction postoperatively. These data highlight that recovery of AV conduction is possible in a significant number of patients undergoing cardiac surgery. However, being able to predict long term recovery may assist in device selection, to avoid more costly device implantations that may not be needed over chronic follow-up. Prospective studies amongst larger numbers of patients are needed to better understand mechanisms of block, mechanisms of recovery, an optimal device in patient selection. Changing focus, we will next review two articles within the realm of supraventricular tachycardias. First we read an article by Han et al published in JACC Clinical Electrophysiology, entitled Clinical Features in Sites of Ablation for Patients With Incessant Supraventricular Tachycardia From Concealed Nodofascicular and Nodoventricular Tachycardias. Han and group describe three cases of concealed nodovascicular, nodoventricular re-entrant tachycardias, and focus on the different mechanisms of proving their participation in tachycardia. In all cases, atrial ventricular re-entering tachycardia was excluded. Successful ablation for these tachycardias occurred either at the slow pathway region, the right bundle branch, or the proximal coronary sinus. This is the first described case of incessant, concealed tachycardias related to these pathways. The importance of this article highlights an understanding the mechanisms proving the contribution to tachycardia, and the importance of recognition when performing electrophysiology studies, and being unable to reveal traditional mechanisms, which exist in most patients, such as atrial tachycardia, AVNRT or AVRT. Next we review an article by Guo et al published in Europace entitled Mapping and Ablation of Anteroseptal Atrial Tachycardia in Patients With Congenitally Corrected Transposition of the Great Arteries: Implications of Pulmonary Sinus Cusps. They reviewed three separate cases of anteroseptal atrial tachycardias in the setting of congenitally corrected transposition. They demonstrated that in these cases, there was successful ablation performed with the pulmonary sinus cusps. The result is successful and durable suppression. The reason this article is important lies in the fact that it's critical to understand both cardiac anatomy and cardiac nomenclature. The pulmonary valve in CCTJ is affectively the systemic ventricular arterial valve, given that the right ventricle is the systemic ventricle. Thus, mapping in this region of CCTJ abides the same principles as mapping the aortic valve in structurally normal hearts for similar tachycardias. However, understanding the nomenclature and that despite the variant anatomy, the utility of similar approaches to mapping of the systemic outflow are important when matching these complex, congenital anatomy or arrhythmia patients. Changing gears yet again, we review an article within the realm of sudden death and cardiac arrest. Baudhuin et al published in Circulation and Genetics entitled Technical Advances for the Clinical Genomic Evaluation of Sudden Cardiac Death. Baudhuin et al reviewed the utility of formal and fixed paraffin-embedded tissue, which is routinely obtained in an autopsy, to perform post-mortem, genetic testing. One of the main limitations to advising family members who have had prior family history of sudden death in closely related relatives, is that blood is often not available to perform DNA screening late after death. DNA however is often degraded in the tissues that are commonly available at autopsy, namely the formal and fixed paraffin-embedded tissues. The authors sought to evaluate if your next generation techniques could make these types of tissue adequate for diagnosis. They demonstrated amongst 19 samples, that performance characteristics were similar between whole blood and these tissue samples, which could be as old as 15 years. It can be critical to identify disease-causing mutations in family members, as individuals who might not yet be affected, but at risk, need to know about that overall risk. Given that decision to sequence might also not be universally applied at all centers, or in all situations, oftentimes these paraffin-embedded tissues might be the only available option, sometimes over a decade after death. This represents the first report of using next-generation sequencing approaches to successfully and accurately sequence for specific mutations using paraffin-embedded tissue. This may offer additional options to help family members achieve diagnoses for sudden death-inducing conditions. Within the realm of cellular electrophysiology, we review an article by Lang et al published in Circulation Research entitled Calcium-Dependent Arrhythmogenic Foci Created by Weakly Coupled Myocytes in the Failing Heart. Lang et al reviewed the effect of cell-cell coupling on the likelihood of triggered arryhthmias. In a [inaudible 00:28:45] model, they demonstrated the myocytes that are poorly synchronized with adjacent myocytes were more prone to triggered activity due to abnormal calcium handling when compared to myocytes with normal connection to adjacent cells. Thus, adequate coupling leads to voltage clamping during calcium waves, thus preventing triggering arrhythmias. While poorly coupled myocytes aren't able to to this due to a weakened currency, making them more prone arrhythmogenesis. These data highlight another critical cellular basis for arrhythmogenesis. In heart failure, while the focus for clinical management is typically areas of scar, there's clearly a role at the cellular level where cell-cell coupling abnormalities can lead to dynamic changes that can increase tendencies to arrhythmogenesis. The role in understanding the varying, arrhythmogenic risk based on varying factors, is important, and might have importance in the future advances in mapping technologies. Changing gears, we review an article published in the Journal of the American College of Cardiology by Mazzanti et al within the realm of genetic channelopathies entitled Hydroxyquinoline Prevents Life-Threatening Arrhythmic Events in Patients With Short QT Syndrome. They reviewed a cohort of 17 patients and demonstrated that hydroxyquinoline resulted in a reduction of arrhythmic events from 40% to 0% of patients. QTc prolongation was seen in all patients. These data clearly demonstrate that hydroxyquinoline plays a role in lowering the incidence of arrhythmic events in patients suffering from short QT syndrome. However, it's important to note that in many markets, quinoline has been difficult to access. In the specific case of QT syndrome thus, there's clearly a role for hydroxyquinoline. However, it also must be noted, the comparative efficacy with more commonly available drugs still needs to be evaluated. This past month has been of particular interest in the realm of ventricular arrhythmias, with multiple, potentially ground-breaking articles. One of the well-recited articles published this past month already is by Cuculich et al entitled Noninvasive Cardiac Radiation for Ablation of Ventricular Tachycardia published in the New England Journal of Medicine. Cuculich et al reported the first in-human data on the use of stereotactic body radiation therapy to perform noninvasive ablation of ventricular arryhthmias. Using a combination of noninvasive electrocardiographic imaging curing ventricular tachycardia, and stereotactic radiation, patients were treated with a single fraction of 25 [inaudible 00:31:15] while awake. A total of five patients were included with a mean ablation time of only 14 minutes. During the three months prior to treatment, there was a total of 6,577 VT episodes seen, and during a six week post-ablation period, considered a blanking period, there were 680 episodes. After this blanking episodes, there were only four episodes of VT seen over the ensuing 46 patient months. This study is important because it reflects the first in-human proof of concept that noninvasive ablation using radiation therapy traditionally as for treatment of solid tumors, may be affective in targeting cardiac tissue. Furthermore, modern techniques such as noninvasive electrocardiographic imaging might allow for a fully noninvasive experience for the patients. This is a vast advance seen within the realm of cardiac electrophysiology. In the early days, all we could do was map invasively and then have to go to much more invasive, open-heart surgery to treat arryhthmogenic substrates. Since the advent of catheter and radiofrequency ablation, surgical ablation is relatively fallen by the wayside, to a less invasive approaches. A completely noninvasive approach to successfully targeting tissue is potentially ground-breaking. However, there are several limitations in this study that can only be ascertained by reading the actual article. When we actually review the patients included, the long term follow-up was limited to only four patients, as one patient actually died within the blanking period, and in fact, this patient suffered from the largest burden overall of VT. Furthermore, amongst the remaining four patients, one required a redo ablation within the blanking period, and one had to be restarted on amioderone after the blanking period was over. Thus further data is really needed to clarify efficacy, given the overall success rate appears to be less than 50% on a per patient basis. Though on an overall episode basis, there was significant reduction. The exact type of radiation to be used also needs to be considered, within the realm of solid oncology. Stereotactic radiation is considered an older modality, with proton beam, and more recently, carbon beams offer more directed therapy. Thus, a lot more data is required to identify the promise of radiation therapy. Though again, this is a significant advance. Next, within the realm of invasive electrophysiology, we review an article by Turagam et al published in the JACC Clinical Electrophysiology entitled Hemodynamic Support in Ventricular Tachycardia Ablation: An International VT Ablation Center Collaborative Group Study. The utility of hemodynamic support during VT ablation is relatively unclear. Studies have been variable and limited. This group included 1,655 patients who underwent 105 VT ablations using hemodynamic support with a percutaneous ventricular assist device. Those undergoing support overall tend to be sicker, including lower ejection fractions and [inaudible 00:34:07] classes, and more VT events, including ICD shocks and VT storm. Hemodynamic support use interestingly, was an independent predictor of mortality with a hazard ratio of 5, though there was no significant difference in VT recurrence rates irrespective of the subgroup considered. These data indicate that, while patients are receiving hemodynamic support were overall sicker, there was no clear incremental benefit in use of hemodynamic support in terms of long term outcomes. In the area of substrate ablation, whether use of hemodynamic support to facilitate mapping during VT, actually alters outcomes remains to be seen. This study highlights the potential importance of randomized clinical approaches to better evaluate whether hemodynamic support truly alters the long term outcomes of the VT ablation. Next, we review an article by Munoz et al that focuses more on prediction of those patients who might be at risk for ventricular arrhythmias, again published in the last edition of JACC Clinical Electrophysiology and entitled Prolonged Ventricular Conduction and Repolarization During Right Ventricular Stimulation Predicts Ventricular Arrhythmias and Death in Patients With Cardiomyopathy. Munoz et al reviewed the relationship between paced QRS and pace Qtc and long term risk. A total of 501 patients with mean ejection fractions of 33% were included. Longer paced ventricular QRS and Qtc was associated with a higher risk of ventricular arrhythmia, and all caused death or arrhythmia, irrespective or ejection fraction. A paced QRS duration of 190 milliseconds was associated with 3.6 fault higher risk of arrhythmia, and a 2.1 fault higher risk of death or arrhythmia. These data suggest that findings during [inaudible 00:35:47] pacing and otherwise normal rhythm, including paced QRS and QTc may independently result in elevation of overall risk of ventricular arrhythmia and death. Physiologically these data make sense. In light of the fact that longer cure restorations are probably related to a greater degree of myopathy. While these data offer a prognostic indication, whether they alter outcomes or decision making regarding ICM implantation, remains to be seen. Next, also published in JACC Clinical Electrophysiology, Vandersickel et al reviewed a more cellular basis for toursades in an article entitled Short-Lasting Episodes of Toursades de Pointes in the Chronic Atrial Ventricular Model Have Focal Mechanism While Longer-Lasting Episodes are Maintained by Reentry. Vandersickel et al reviewed the mechanisms underlying toursades, and demonstrated that both focal and reentry mechanisms may exist. In five canines they used broadly distributed neuro electrodes to simultaneously map across the heart. They demonstrated that initiation and termination was always focal, but longer and non-terminal episodes always had reentry mechanisms. These data suggest that the mechanisms underlying toursades actually reflect a spectrum of potentially dynamic, electrophysiologic phenomenon the heart, including both focal and reentry activity. Understanding these mechanisms, and the fact that focal mechanisms almost universally underlie initiation may bring into consideration the optimal treatments whether in the form of pacing and defibrillation techniques or medication techniques for toursades. Finally, in the realm of ventricular arrhythmia, we review an article published in the last month's edition of Heart Rhythm by Penela et al entitled Clinical Recognition of Pure Premature Ventricular Complex-Induced Cardiomyopathy at Presentation. As we know, it's sometimes difficult to recognize patients when they present with frequent PVCs and a depressed injection fraction in terms of, whose injection fractions are purely caused by the presence of PVCs, and whose PVCs are only exacerbated by the presence of an underlying myopathy. The group included 155 patients and excluded all patients who did not normalize their elevated ejection fraction, or who had previously diagnosed structural heart disease, leaving a total cohort under consideration, of 81 patients. About 50% were diagnosed as having a PVC-induced cardiomyopathy on the basis of normalization of elevated function after PVC suppression. While the remainder was considered to have PVC exacerbated cardiomyopathy on the basis that things did not entirely resolve, and thus had an independent mechanism for nonischemic myopathy. Characteristics that suggested patients with a lower likelihood of EF normalization included those with longer intrinsic QRSs, above 130 milliseconds, a lower PVC burden of baseline, considered less than 17%, and larger [inaudible 00:38:33] greater than 6.3 cm. PVCs as a cause of [inaudible 00:38:35] are obviously a well-recognized treatable cause of myopathy, however again, it might be difficult to differentiate. Those patients whose PVCs are a result of the underlying myopathy versus those whose PVCs are the cause, and for whom ablation or suppression may reverse the myopathic process. The work of Penela et at offers an initial attempt at helping differentiate these processes, however validation of larger cohort is necessary. Next we review an article within the realm of syncopy entitled Prohormones in the Early Diagnosis of Cardiac Syncopy by Badertscher et al published in the Journal of the American Heart Association this month. They review the utility of circulating prohormones [inaudible 00:39:14] autonomic dysfunction or neurohormonal abnormalities, to differentiate cardiac from non-cardiac causes of syncopy in the emergency departments. They measured four novel prohormones in a multi-center study. In the emergency departments there is a specific protocol used to determine the perceived likelihood of the cause of syncopy to be cardiac versus non-cardiac. In addition to this, the prohormones are drawn. After this, everyone's final diagnosis was reached. Two independent cardiologists reviewed the cases to determine if it was a truly cardiac or non-cardiac cause of syncopy. Among 689 patients included, 125 overall were adjudicated as cardiac syncopy. Measure of the specific marker MR-proANP in combination with emergency department suspicion of syncopy, performed better than suspicion alone, to differentiate cardiac causes of syncopy. A combination of a circulating MR-proANP, less than 77, picomoles per liter, an [inaudible 00:40:17] probability of cardiac syncopy could be less than 20%, had a very high sensitivity negative predictive value of 99%. The significant resources are often used to manage patients with syncopy presenting to the emergency departments, and it's often extremely difficult at this stage to differentiate cardiac from non-cardiac causes of syncopy. And the amount of evaluation that can be done in the emergency department is often limited. Cardiac caused of syncopy are not good to miss, however, since these can include ventricular arrhythmias, and transient AV block, that might result in death as well. As is well-recognized, emergency department evaluation in clinical [inaudible 00:40:49] are limited in terms of their utility. This raises the utility of objective measures to help differentiates. These data suggest that circulating prohormones [inaudible 00:40:59] your hormonal function drawn during your emergency department evaluation, may be a useful adjunct to differentiate cardiac from non-cardiac syncopy. Whether they can be used to prospectively differentiate those patients requiring inpatient admission or now, however, remains to be seen. The last two articles we'll choose to focus on will fall under the realm of broader, other EP concepts. The first article we will review is by Varghese et al published in Cardiovascular Research entitled Low-Energy Defibrillation With Nanosecond Electric Shocks. Varghese et al reviewed the potential of low-energy nanosecond duration shocks for defibrillation in rapid hearts. In induced fibrillation examples, the repeated defibrillated nanosecond impulses as low as three kilovolts demonstrated effective defibrillation. The energy required is significantly lower than from monophasic shocks and longer pulse durations. Furthermore, there was no detectable evidence of electroporation, namely cardiac or so injury after defibrillation. Using nanosecond impulses, it may be feasible to defibrillate the heart with significantly lower energies. The implications for patients experiencing defibrillation, for example pain, is unclear without in-human studies. However, the ability to use lower energies could have implications in battery life. Further [inaudible 00:42:11] studies will be critical to study ambulatory efficacy as this research is performed in [inaudible 00:42:19] hearts. Finally, we review an article published in Circulation entitled Mortality in Supravascular Events After Heart Rhythm Disorder Management Procedures by Lee et al. Amongst three centers, a retrospective cohort study regarding the mortality and risk of supravascular events, was performed. They included a variety of heart rhythm [inaudible 00:42:40] procedures, including defibrillation threshold testing, lead extraction, device implant, and invasive electrophysiology studies and ablation procedures. Amongst 48,913 patients, 62,065 procedures were performed and an overall mortality of .36% was seen. Supravascular [inaudible 00:42:58] was lower at .12%. Interestingly, and expectedly, the highest risk was seen with lead extraction patients, with an overall mortality risk of 1.9%. Less than half of the deaths seen, however, were directly attributable to the procedure itself. The most common cause of procedural death was cardiac tamponade, largely seen amongst device implant patients. This is critical, as the number of ablation and other invasive electrophysiology procedures performed, is increasing. These data provide a large, contemporary experience regarding the overall risk attributable to a variety of heart rhythm disorder procedures. Interestingly, half of the procedure related deaths were associated with device implantation procedures. With the predominant cause being tamponade, highlighting the importance of early recognition of this treatable complication. Tamponade may not always be considered as a major issue after device implantation, however these data clearly suggest that it is. In addition, extraction, as expected, carried the highest incident of both supravascular events and mortality. Though, this is likely related to the higher rate of core morbidity in this population, including active infection. In summary, this month, we have reviewed 20 articles in various areas of electrophysiology published across the literature. Particularly high impact articles range from those reviewing experience regarding left atrial appendage closure and the efficacy of this, to the utility of using atrial fibrillation to predict risk and long term morbidity and mortality in hypertrophic cardiomyopathy, to further evidence regarding the safety of magnetic resonance imaging in legacy pacemakers and defibrillators, and novel considerations regarding supraventricular tachycardias and there diagnosis and management, especially invasively. Other potential groundbreaking articles included evidence that we can successfully use formal and fixed paraffin-embedded tissue that can be as old as 15 years, to successfully identify genetic mutations that might be responsible for sudden death. And evidence that using novel techniques, we might be able to perform completely noninvasive therapies for arrhythmias by using radiation therapies. However questions were also raised such as regarding the role of hemodynamic support for VT ablation. How to better differentiate those patients who will have recovery of AV conduction from those who won't, as they meet class I indications post cardiac surgery? And whether other factors such as right ventricular pacing during [inaudible 00:45:28] study might further differentiate patients at risk for ventricular arrhythmias in spite of a low ejection fractions. Many of the papers had to deal with tranlational work that still remains to be proven in terms of value at a clinical level, such as demonstrating mechanisms underlying trousades de pointes. Or the potential value of low-energy defibrillation with nanosecond electric shocks. Clinical protocols involving the use of prohormones in the early diagnosis of cardiac syncopy. How to differentiate PVC induced from other causes of myopathy, and how to manage, in the long term, these devices. Also, likely requires further study. Finally, covering all areas of electrophysiology, we reviewed one large article focusing on mortality in supravascular events after heart rhythm management disorder procedures at large. This article highlights the importance of considering institutional experience and reporting it to use as a benchmark to help better optimize our counseling of patients, as well as our procedures and protocols. I appreciate everyone's attention to these key and hard-hitting articles that we just focused on from this past month of cardiac electrophysiology across the literature. Thanks for listening. Now, back to Paul. Dr. Paul Wong:                  Thanks Seraj. You did a terrific job surveying all journals for the latest articles on topics of interest in our field. There's not an easier way to stay in touch with the latest advance. These summaries, and a list of all major articles in our field each month, can be downloaded from the Circulation Arrhythmia and Electrophysiology website. We hope you'll find the journal to be the go-to place for everyone interested in the field. See you next month.  

Caveolin-1 (Cav1) is a scaffold protein and pathogen receptor in the mucosa of the gastrointestinal tract. Chronic infection of gastric epithelial cells by Helicobacter pylori (H. pylori) is a major risk factor for human gastric cancer (GC) where Cav1 is frequently down-regulated. However, the function of Cav1 in H. pylori infection and pathogenesis of GC remained unknown. We show here that Cav1-deficient mice, infected for 11 months with the CagA-delivery deficient H. pylori strain SS1, developed more severe gastritis and tissue damage, including loss of parietal cells and foveolar hyperplasia, and displayed lower colonisation of the gastric mucosa than wild-type B6129 littermates. Cav1-null mice showed enhanced infiltration of macrophages and B-cells and secretion of chemokines (RANTES) but had reduced levels of CD25+ regulatory T-cells. Cav1-deficient human GC cells (AGS), infected with the CagA-delivery proficient H. pylori strain G27, were more sensitive to CagA-related cytoskeletal stress morphologies ("humming bird") compared to AGS cells stably transfected with Cav1 (AGS/Cav1). Infection of AGS/Cav1 cells triggered the recruitment of p120 RhoGTPase-activating protein/deleted in liver cancer-1 (p120RhoGAP/DLC1) to Cav1 and counteracted CagA-induced cytoskeletal rearrangements. In human GC cell lines (MKN45, N87) and mouse stomach tissue, H. pylori down-regulated endogenous expression of Cav1 independently of CagA. Mechanistically, H. pylori activated sterol-responsive element-binding protein-1 (SREBP1) to repress transcription of the human Cav1 gene from sterol-responsive elements (SREs) in the proximal Cav1 promoter. These data suggested a protective role of Cav1 against H. pylori-induced inflammation and tissue damage. We propose that H. pylori exploits down-regulation of Cav1 to subvert the host's immune response and to promote signalling of its virulence factors in host cells.

Die Dysferlinopathie ist eine Erkrankung aus dem Formenkreis der Gliedergürtel-Muskel-dystrophien. Sie wird verursacht durch autosomal-rezessiv vererbte Mutationen, die drei klinisch heterogene Phänotypen verursachen können: Die Gliedergürtel-Muskeldystrophie Typ 2B (LGMD2B), die Miyoshi Myopathie (MM) und die distale anteriotibiale Myopathie (DMAT). Betroffen sind initial dementsprechend unterschiedliche Muskelgruppen. Um ein zuverlässiges Diagnosesystem zu etablieren und einen Beitrag zur klinischen und therapeutischen Bedeutung der molekularen Diagnostik sowie zum Verständnis der Pathophysiologie der Erkrankung zu leisten, wurden 17 Patienten untersucht. Bei sechs Patienten wurden bei der molekulargenetischen Diagnostik Mutationen des Dysferlin-Gens gefunden. Diese Ergebnisse wurden mit den Befunden von klinischen und technischen Untersuchungen sowie der Proteindiagnostik von Dysferlin und den möglichen Interaktionspartnern Caveolin-3 und Calpain-3 korreliert. Bei fünf dieser sechs Patienten konnte die Diagnose einer Dysferlinopathie gestellt werden, bei zehn Patienten wurde die Erkrankung ausgeschlossen, in zwei Fällen gelang weder der sichere Ausschluss noch der Nachweis einer Dysferlinopathie. Hinsichtlich der Proteininteraktionen des Dysferlin konnte im Rahmen der durchgeführten Proteindiagnostik ein deutlicher Hinweis für eine Interaktion mit den Proteinen Caveolin-3 und Calpain-3 erbracht werden. Welchen genauen Charakter die Interaktion zwischen Dysferlin und Caveolin-3 und Calpain-3 hat, muss noch weiter erforscht werden, denn feste "regelhafte" Auswirkungen der hier gefundenen Dysferlin-Mutationen z.B. auf den Phänotyp der Erkrankung konnten in dieser Arbeit nicht festgestellt werden. In diesem Kontext muss auch die Rolle von Mutationen noch weiter aufgeklärt werden, die in den C2-Domänen zu liegen kommen. Diesbezüglich können die hier dargestellten Ergebnisse zusammen mit den Daten zukünftiger Studien zur pathogenetischen Klärung beitragen. Es konnte die diagnostische Eignung der hier beschriebenen molekulargenetischen Untersuchung bei dieser heterogenen Erkrankung gesichert und darüber hinaus ein Beitrag zum pathophysiologischen Verständnis der Erkrankung hinsichtlich der Bedeutung der C2-Domänen des Dysferlins und der Proteininteraktionen geleistet werden. Die Ergebnisse bieten, neben der Bedeutung für den einzelnen Patienten, eine Grundlage für die weitere Erforschung der Dysferlinopathie.

In dieser Arbeit wurde die biologische Funktion der PTP-Meg2 in der zellulären Signaltransduktion untersucht. Analysen mittels c-DNA-Filter, „Real Time PCR” und Immunblot zeigen eine ubiquitäre Expression der PTP-Meg2 auf ähnlichem, jedoch geringem Niveau in fast allen untersuchten Krebszelllinien unterschiedlicher Gewebeherkunft, wobei die Expressions-stärke nicht in direktem Zusammenhang mit krebsrelevanten Eigenschaften wie Invasivität und Metastasierung steht. Die induzierte Differenzierung von MCF 7-Zellen durch Natriumbutyrat steigert die Meg2-Expression um das 5-fache, wogegen die Differenzierung von SW948- und SK-N- SH-Zellen mit TPA bzw. Retinolsäure die Meg2-Expression reprimiert. Zellfraktionierung und Immunfluoreszenz zeigen eine primär zytosolische, aber partiell auch vesikuläre bzw. strukturierte Lokalisation der PTP-Meg2, für welche die CRALBP-Domäne der PTP-Meg2 mitverantwortlich ist. Untersuchungen der endogenen Meg2-Aktivität nach Immunpräzipitation und in vitro Phosphatasetests zeigen eine erhöhte Phosphataseaktivität nach Stimulation von Zellen mit FCS, EGF und LPA, wogegen TPA stark inhibierenden wirkt. Aktivitätsstudien mit GST-Meg2-Fusionsproteinen zeigen, dass die CRALBP-Domäne die Meg2-Phosphataseaktivität negativ reguliert. Im Protein-Lipid-Overlay interagiert PTP-Meg2 mit PI(3)P, PI(4)P, PI(5)P und Phosphatidylserin. Eine Interaktion mit PI(4)P führt zu einer erhöhten Meg2 Aktivität. Pervanadat-Stimulation von Zellen führt zu einer Tyrosinphosphorylierung sowie einer Mobilitätsänderung der PTP-Meg2, was auch mit einer katalytisch inaktiven Meg2-Mutante beobachtet wurde. PTP-Meg2 interagiert in vitro und in Koexpressionsstudien mit dem EGF-Rezeptor in Abhängigkeit von dessen Aktivierung. Eine physiologische Relevanz konnte nicht gezeigt werden. Die Depletion der PTP-Meg2 durch spezifische siRNA führt zu einer erhöhten Tyrosinphosphorylierung einiger, noch zu identifizierender Proteine. PTP-Meg2 vermindert, die inaktive PTP-Meg2CS-Mutante erhöht die durch v-ErbB und EGF-Rezeptor, nicht aber die durch HER2 und v-Ki-Ras induzierte Transformation von NIH3T3-Zellen im Focusbildungstest. Zudem bewirkt PTP-Meg2CS, mit Ausnahme der v-Ki-Ras infizierten Zellen, eine leicht erhöhte ERK1/2-Aktivität. Ferner stimuliert PTP-Meg2 die Migration von NIH3T3-Zellen im Wundheilungsexperiment. Ein Einfluss auf die basale und durch Stimuli induzierte Proliferation von Zellen in Wachstumstests wurde nicht beobachtet. Ein durch siRNA-vermittelter Meg2- „knockdown“ führte zur Induktion bzw. Repression der Expression von Genen, wie z.B. einiger Liganden, Caveolin-2, Nck und Rock, was auf eine Beteiligung der PTP-Meg2 an der Regulation von Signalwegen kleiner GTPasen bzw. von endo- sowie exocytotischen Prozessen schließen lässt.