Discover CircRes

Monthly summary & in-depth analysis of the research published in the Circulation Research journal

Discover CircRes April 2025 04/17/2025

Discover CircRes March 2025 03/20/2025

Discover CircRes February 2025 02/20/2025

Discover CircRes January 2025 01/16/2025

Discover CircRes December 2024 12/19/2024

Discover CircRes November 2024 11/21/2024

October 2024 Discover CircRes 10/17/2024

September 2024 Discover CircRes 09/19/2024

August 2024 Discover CircRes 08/15/2024

July 2024 Discover CircRes 07/18/2024

June 2024 Discover CircRes 06/20/2024

May 2024 Discover CircRes 05/16/2024

April 2024 Discover CircRes 04/18/2024

March 2024 Discover CircRes 03/21/2024

February 2024 Discover CircRes 02/15/2024

January 2024 Discover CircRes 01/18/2024

December 2023 Discover CircRes 12/21/2023

November 2023 Discover CircRes 11/16/2023

October 2023 Discover CircRes 10/19/2023

September 2023 Discover CircRes 09/21/2023

August 2023 Discover CircRes 08/17/2023

July 2023 Discover CircRes 07/20/2023

June 2023 Discover CircRes 06/15/2023

May 2023 Discover CircRes 05/18/2023

May 2023 Discover CircRes This month on Episode 48 of Discover CircRes, host Cynthia St. Hilaire highlights three original research articles featured in the April 28th issue of Circulation Research. This Episode also includes a discussion between Dr Mina Chung, Dr DeLisa Fairweather and Dr Milka Koupenova, who all contributed to manuscripts to the May 12th Compendium on Covid-19 and the Cardiovascular System. Article highlights: Heijman, et al. Chen, et al. Enzan, et al. Cindy St. Hilaire: Hi, and welcome to Discover CircRes, the podcast of the American Heart Association's journal, Circulation Research. I'm your host, Dr Cindy St. Hilaire, from the Vascular Medicine Institute at the University of Pittsburgh. Today, I'm going to be highlighting articles from our April 28th and May 12th issues of Circulation Research. I'm also going to have a chat with Dr Mina Chung, Dr DeLisa Fairweather and Dr Milka Koupenova, who all contributed to articles in the May 12th COVID Compendium. But before we have that interview, let's first talk about some highlights. The first article I want to present is titled Enhanced Calcium-Dependent SK-Channel Gating and Membrane Trafficking in Human Atrial Fibrillation. This article is coming from the University of Essen by Heijman and Zhou, et al. Atrial fibrillation is one of the most common forms of heart arrhythmia in humans and is characterized by irregular, often rapid heartbeats that can cause palpitations, dizziness and extreme fatigue. Atrial fibrillation can increase a person's risk of heart failure, and though treatments exist such as beta blockers, blood thinners and antiarrhythmia medications, they can have limited efficacy and side effects. A new family of drugs in development are those blocking small-conductance calcium-activated potassium channels called SK channels, which exhibit increased activity in animal models of AF and suppression of which attenuates the arrhythmia. In humans however, the relationship between SK channels and atrial fibrillation is less clear, at least in terms of SK channel mRNA levels. Because mRNA might not reflect actual channel activity, this group looked at just that and they found indeed that channel activity was increased in cardiomyocytes from atrial fibrillation patients compared to those from controls even though the mRNA and protein levels themselves were similar. The altered currents were instead due to changes in SK channel trafficking and membrane targeting. By confirming that SK channels play a role in human atrial fibrillation, this work supports the pursuit of SK channel inhibitors as possible new atrial fibrillation treatments. The next article I want to present is titled IL-37 Attenuates Platelet Activation and Thrombosis Through IL-1R8 Pathway. This article comes from Fudan University by Chen and Hong, et al. Thrombus formation followed by the rupture of a coronary plaque is a major pathophysiological step in the development of a myocardial infarction. Understanding the endogenous antithrombotic factors at play could provide insights and opportunities for developing treatments. With this in mind, Chen and Hong, et al. investigated the role of interleukin-1 receptor 8, or IL-1R8, which suppresses platelet aggregation in mice, and of IL-37, a newly discovered human interleukin that forms a complex with IL-1R8 and is found at increased levels in the blood of patients with myocardial infarction. Indeed, the amount of IL-37 in myocardial infarction patients negatively correlates with platelet aggregation. They also show that treatment of human platelets in vitro with IL-37 suppresses the cell's aggregation and does so in a concentration-dependent manner. Moreover, injection of the protein into the veins of mice inhibits thrombus development and better preserves heart function even after myocardial infarction. Such effects were not seen in mice lacking IL-1R8. This suggests IL-37's antithrombotic action depends on its interaction with the receptor. Together, the results suggest IL-37 could be developed as a antithrombotic agent for use in MI patients or indeed perhaps other thrombotic conditions. The last article I want to present before our interview is titled ZBP1 Protects Against Mitochondrial DNA-Induced Myocardial Inflammation in Failing Hearts. This article is coming from Kyushu University and is by Enzan, et al. Myocardial inflammation is a key factor in the pathological progression of heart failure and occurs when damaged mitochondria within the stricken cardiomyocyte release their DNA, triggering an innate inflammatory reaction. In a variety of cells, DNA sensors such as Z-DNA-binding protein 1 or ZBP1 are responsible for such mitochondrial DNA-induced inflammation. In theory then, it's conceivable that therapeutic suppression of ZBP1 might reduce myocardial inflammation in heart failure and preserve function. But as Enzan and colleagues have now discovered to their surprise, mice lacking ZBP1 exhibited worse, not better heart inflammation and more failure after induced myocardial infarction. Indeed, the test animals' hearts had increased infiltration of immune cells, production of inflammatory cytokines and fibrosis together with decreased function compared with the hearts of mice with normal ZBP1 levels. Experiments in rodent cardiomyocytes further confirmed that loss of ZBP1 exacerbated mitochondrial DNA-induced inflammatory cytokine production while overexpression of ZBP1 had the opposite effect. While the reason behind ZBP1's opposing roles in different cells is not yet clear, the finding suggests that boosting ZBP1 activity in the heart might be a strategy for mitigating heart inflammation after infarction. Cindy St. Hilaire: The May 12th issue of Circulation Research is our COVID compendium, which consists of a series of 10 reviews on all angles of COVID-19 as it relates to cardiovascular health and disease. Today, three of the authors of the articles in this series are here with me. Dr Mina Chung is a professor of medicine at the Cleveland Clinic. She and Dr Tamanna Singh and their colleagues wrote the article, A Post Pandemic Enigma: The Cardiovascular Impact of Post-Acute Sequelae of SARS-CoV-2. Dr DeLisa Fairweather, professor of medicine, immunology and clinical and translational science at the Mayo Clinic, and she and her colleagues penned the article, COVID-19 Myocarditis and Pericarditis. Dr Milka Koupenova is an assistant professor of medicine at the UMass Chan School of Medical and she led the group writing the article, Platelets and SARS-CoV-2 During COVID-19: Immunity, Thrombosis, and Beyond. Thank you all for joining me today. DeLisa Fairweather: Thank you so much for having us. Mina Chung: Thank you. Milka Koupenova: Thank you for having us, Cindy. Cindy St. Hilaire: In addition to these three articles, we have another seven that are on all different aspects of COVID. Dr Messinger's group wrote the article, Interaction of COVID-19 With Common Cardiovascular Disorders. Emily Tsai covered cell-specific mechanisms in the heart of COVID-19 patients. Mark Chappell and colleagues wrote about the renin-angiotensin system and sex differences in COVID-19. Michael Bristow covered vaccination-associated myocarditis and myocardial injury. Jow Loacalzo and colleagues covered repurposing drugs for the treatment of COVID-19 and its cardiovascular manifestations. Dr Stephen Holby covered multimodality cardiac imaging in COVID, and Arun Sharma covered microfluidic organ chips in stem cell models in the fight against COVID-19. Cindy St. Hilaire As of today, worldwide, there have been over six hundred million individuals infected with the virus and more than six and a half million have died from COVID-19. In the US, we are about a sixth of all of those deaths. Obviously now we're in 2023, the numbers of individuals getting infected and dying are much, much lower. As my husband read to me this morning, one doctor in Boston was quoted saying, "People are still getting wicked sick." In 75% of deaths, people have had underlying conditions and cardiovascular disease is found in about 60% of all those deaths. In the introduction to the compendium, you mentioned that the remarkable COVID-19 rapid response initiative released by the AHA, which again is the parent organization of Circ Research and this podcast, if I were to guess when that rapid response initiative started, I would've guessed well into the pandemic, but it was actually March 26th, 2020. I know in Pittsburgh, our labs have barely shut down. So how soon after we knew of SARS-CoV-2 and COVID, how soon after that did we know that there were cardiovascular complications? Mina Chung: I think we saw cardiovascular complications happening pretty early. We saw troponin increases very early. It was really amazing what AHA did in terms of this rapid response grant mechanism. You mentioned that the RFA was announced, first of all, putting it together by March 26th when we were just shutting down in March was pretty incredible to get even the RFA out. Then the grants were supposed to be submitted by April 6th and there were 750 grants that were put together and submitted. They were all reviewed within 10 days from 150 volunteer reviewers. The notices were distributed April 23rd, less than a month out. Cindy St. Hilaire: Amazing. Mina Chung: So this is an amazing, you're right, paradigm for grant requests and submissions and reviews. DeLisa Fairweather: For myocarditis, reports of that occurred almost immediately coming out of China, so it was incredibly rapid. Cindy St. Hilaire: Yeah, and that was a perfect lead up to my next question. Was myocarditis, I guess, the first link or the first clue that this was not just going to be a respiratory infection? DeLisa Fairweather: I think myocarditis appearing very early, especially it has a history both of being induced by viruses, but being strongly an autoimmune disease, the combination of both of those, I think, started to hint that something different was going to happen, although a lot of people probably didn't realize the significance of that right away. Cindy St. Hilaire: What other disease states, I guess I'm thinking viruses, but anything, what causes myocarditis and pericarditis normally and how unique is it that we are seeing this as a sequelae of COVID? DeLisa Fairweather: I think it's not surprising that we find it. Viruses around the world are the primary cause of myocarditis, although in South America, it's the parasite Trypanosoma cruzi. Really, many viruses that also we think target mitochondria, including SARS-CoV-2, have an important role in driving myocarditis. Also, we know that SARS-CoV-1 and MERS also reported myocarditis in those previous infections. We knew about it beforehand that they could cause myocarditis. Cindy St. Hilaire: Is it presenting differently in a COVID patient than say those South American patients with the... I forget the name of the organism you said, but does it come quickly or get worse quickly or is it all once you get it, it's the same progression? DeLisa Fairweather: Yeah. That's a good question. Basically, what we find is that no matter what the viral infection is, that myocarditis really appears for signs and symptoms and how we treat it identically and we see that with COVID-19. So that really isn't any different. Cindy St. Hilaire: Another huge observation that we noticed in COVID-19 patients, which was the increased risk of thrombic outcomes in the patients. Dr Koupenova, Milka, you are a world expert in platelets and viruses and so you and your team were leading the writing of that article. My guess is knowing what you know about platelets and viruses, this wasn't so surprising to you, but could you at least tell us the state of the field in terms of what we knew about viruses and platelets before COVID, before Feb 2020? Milka Koupenova: Before Feb 2020, we actually knew that influenza gets inside in platelets. It leads to not directly prothrombotic events, but it would lead to release of complement 3 from them. That complement 3 would actually increase the immunothrombosis by pushing neutrophils to release their DNA, forming aggregates. In cases when you have compromised endothelium and people with underlying conditions, you would expect certain thrombotic outcomes. That, we actually published 2019 and then 2020 hit. The difference between influenza and SARS-CoV-2, they're different viruses. They carry their genome in a different RNA strand. I remember thinking perhaps viruses are getting inside in platelets, but perhaps they do not. So we went through surprising discoveries that it seemed like it is another RNA virus. It also got into platelets. It was a bit hard to tweak things surrounding BSL-3 to tell you if the response was the same. It is still not very clear how much SARS or rather what receptor, particularly when it gets inside would induce an immune response. There are some literature showing the MDA5, but not for sure, may be responsible. But what we found is that once it gets in platelets, it just induces this profound activation of programmed cell death pathways and release of extracellular vesicles and all these prothrombotic, procoagulant form of content that can induce damage around, because platelets are everywhere. So that how it started in 2019 and surprisingly progressed to 2021 or 2020 without the plan of really studying this virus. Cindy St. Hilaire: How similar and how different is what you observe in platelets infected, obviously in the lab, so I know it's not exactly the same, but how similar and how different is it between the flu? Do you know all the differences yet? Milka Koupenova: No offense here, they don't get infected. Cindy St. Hilaire: Okay. Milka Koupenova: Done the proper research. The virus does not impact platelets, but induces the response. Cindy St. Hilaire: Okay. Milka Koupenova: That goes back to sensing mechanism. Thank goodness platelets don't get infected because we would be in a particularly bad situation, but they remove the infectious virus from the plasma from what we can see with function. Cindy St. Hilaire: Got it. So they're helping the cleanup process and in that cleaning up is where the virus within them activates. That is a really complicated mechanism. Milka Koupenova: Oh, they're sensing it in some form to alert the environment. It's hard to say how similar and how different they are unless you study them hint by hint next to each other. All I can tell is that particularly with SARS-C, you definitely see a lot more various kinds of extracellular vesicles coming out of them that you don't see the same way or rather through the same proportion with influenza. But what that means in how platelet activates the immune system with one versus the other, and that goes back to the prothrombotic mechanisms. That is exactly what needs to be studied and that was the call for this COVID compendium is to point out how much we have done as a team. As scientists who put heads together, as Mina said, superfast response, it's an amazing going back and looking at what happened to think of what we achieved. There is so much more, so much more that we do not understand how one contributes to all of these profound responses in the organs themselves, such as myocarditis. We see it's important and that will be the problem that we're dealing from here on trying to figure it out and then long COVID, right? Cindy St. Hilaire: Yeah. Related to what you just said about the mechanism, this cleanup by the platelets or the act of cleaning up helps trigger their activation, is that partly why the antiplatelet and anticoagulant therapies failed in patients? Can you speculate on that? I know the jury's still out and there's a lot of work to be done, but is that part of why those therapies weren't beneficial? Milka Koupenova: The answer to that in my personally biased opinion is yes. Clearly, the antiplatelet therapies couldn't really control the classical activation of a platelet. So what I think we need to do from here on is to look at things that we don't understand that non-classically contribute to the thrombotic response downstream. If we manage to control the immune response in some way or the inflammation of the infection or how a platelet responds to a virus, then perhaps we can ameliorate a little bit of the downstream prothrombotic effect. So it's a lot more for us to trickle down and to understand in my personal opinion. DeLisa Fairweather: There is one thing that was really remarkable to me in hearing your experience, Milka, is that I had developed an autoimmune viral model of myocarditis in mice during my postdoc. So I've been studying that for the last 20 years. What is unique about that model is rather than using an adjuvant, we use a mild viral infection so it doesn't take very much virus at all going to the heart to induce it. I also, more recently, started studying extracellular vesicles really as a therapy, and in doing that, inadvertently found out that actually, the model that I'd created where we passage the virus through the heart to induce this autoimmune model, we were actually injecting extracellular vesicles into the mice and that's what was really driving the disease. This is really brought out. So from early days, I did my postdoc with Dr Noel Rose. If you've heard of him, he came up with the idea of autoimmune disease in the '50s. We had always, in that environment, really believed that viruses were triggering autoimmune disease and yet it took COVID before we could really prove that because no one could identify them. Here we have an example and I think the incidence rates with COVID were so high for myocarditis because for the first time, we had distinguished symptoms of patients going to the doctor right at the beginning of their infection having an actual test to examine the virus, knowing whether it's present or not, whether PCR or antibody test, and then being able to see when myocarditis happened. Cindy St. Hilaire: Yeah. I think one thing we can all appreciate now is just some of the basic biology we've learned on the backend of this. Actually, those last comments really led well to the article that your team led, Dr Chung, about what we call long COVID, which I guess I didn't realize has an actual name, post-acute sequelae of SARS-CoV-2 or PASC is the now more formal name for... /episode/index/show/circresearch/id/26870553

April 2023 Discover CircRes 04/20/2023

April 2023 Discover CircRes This month on Episode 47 of Discover CircRes, host Cynthia St. Hilaire highlights three original research articles featured in the March 31 issue of Circulation Research. We’ll also provide an overview of the Compendium on Increased Risk of Cardiovascular Complications in Chronic Kidney Disease published in the April 14 issue. Finally, this episode features an interview with Dr Elizabeth Tarling and Dr Bethan Clifford from UCLA regarding their study, RNF130 Regulates LDLR Availability and Plasma LDL Cholesterol Levels. Article highlights: Shi, et al. Chen, et al. Subramaniam, et al. 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, and today I'm going to share three articles selected from our March 31st issue of Circulation Research and give you a quick summary of our April 14th Compendium. I'm also excited to speak with Dr Elizabeth Tarling and Dr Bethan Clifford from UCLA regarding their study, RNF130 Regulates LDLR Availability and Plasma LDL Cholesterol Levels. So first the highlights. The first article we're going to discuss is Discovery of Transacting Long Noncoding RNAs that Regulates Smooth Muscle Cell Phenotype. This article's coming from Stanford University and the laboratory of Dr Thomas Quertermous. Smooth muscle cells are the major cell type contributing to atherosclerotic plaques. And in plaque pathogenesis, the cells can undergo a phenotypic transition whereby a contractile smooth muscle cell can trans differentiate into other cell types found within the plaque, such as macrophage-like cells, osteoblast-like cells and fibroblast-like cells. These transitions are regulated by a network of genetic and epigenetic mechanisms, and these mechanisms govern the risk of disease. The involvement of long non-coding RNAs, or Lnc RNAs as they're called, has been increasingly identified in cardiovascular disease. However, smooth muscle cell Lnc RNAs have not been comprehensively characterized and the regulatory role in the smooth muscle cell state transition is not thoroughly understood. To address this gap, Shi and colleagues created a discovery pipeline and applied it to deeply strand-specific RNA sequencing from human coronary artery smooth muscle cells that were stressed with different disease related stimuli. Subsequently, the functional relevancy of a few novel Lnc RNAs was verified in vitro. From this pipeline, they identified over 4,500 known and over 13,000 unknown or previously unknown Lnc RNAs in human coronary artery smooth muscle cells. The genomic location of these long noncoding RNAs was enriched near coronary artery disease related transcription factor and genetic loci. They were also found to be gene regulators of smooth muscle cell identity. Two novel Lnc RNAs, ZEB-interacting suppressor or ZIPPOR and TNS1-antisense or TNS1-AS2, were identified by the screen, and this group discovered that the coronary artery disease gene, ZEB2, which is a transcription factor in the TGF beta signaling pathway, is a target for these Lnc RNAs. These data suggest a critical role for long noncoding RNAs in smooth muscle cell phenotypic transition and in human atherosclerotic disease. Cindy St. Hilaire: The second article I want to share is titled Destabilization of Atherosclerotic Plaque by Bilirubin Deficiency. This article is coming from the Heart Research Institute and the corresponding author is Roland Stocker. The rupture of atherosclerotic plaque contributes significantly to cardiovascular disease. Plasma concentrations of bilirubin, a byproduct of heme catabolism, is inversely associated with risk of cardiovascular disease, but the link between bilirubin and atherosclerosis is unknown. Chen et el addressed this gap by crossing a bilirubin knockout mice to a atherosclerosis prone APOe knockout mouse. Chen et el addressed this gap by crossing the bilirubin knockout mouse to the atherosclerosis-prone APOE knockout mouse, and used the tandem stenosis model of plaque instability to address this question. Compared with their litter mate controls, bilirubin-APOE double knockouts showed signs of increased systemic oxidative stress, endothelial dysfunction, as well as hyperlipidemia. And they had higher atherosclerotic plaque burden. Hemeatabolism was increased in unstable plaques compared with stable plaques in both of these groups as well as in human coronary arteries. In mice, the bilirubin deletion selectively destabilized unstable plaques and this was characterized by positive arterial remodeling and increased cap thinning, intra plaque hemorrhage, infiltration of neutrophils and MPO activity. Subsequent proteomics analysis confirmed bilirubin deletion enhanced extracellular matrix degradation, recruitment and activation of neutrophils and associated oxidative stress in the unstable plaque. Thus, bilirubin deficiency generates a pro atherogenic phenotype and selectively enhances neutrophil-mediated inflammation and destabilization of unstable plaques, thereby providing a link between bilirubin and cardiovascular disease risk. Cindy St. Hilaire: The third article I want to share is titled Integrated Proteomics Unveils Regulation of Cardiac Monocyte Hypertrophic Growth by a Nuclear Cyclic AMP Nano Domain under the Control of PDE3A. This study is coming from the University of Oxford in the lab of Manuela Zaccolo. Cyclic AMP is a critically important secondary messenger downstream from a myriad of signaling receptors on the cell surface. Signaling by cyclic AMP is organized in multiple distinct subcellular nano domains, regulated by cyclic AMP hydrolyzing phosphodiesterases or PDEs. The cardiac beta adrenergic signaling has served as the prototypical system to elucidate this very complex cyclic AMP compartmentalization. Although studies in cardiac monocytes have provided an understanding of the location and the properties of a handful of these subcellular domains, an overview of the cellular landscape of the cyclic AMP nano domains is missing. To understand the nanodynamics, Subramanian et al combined an integrated phospho proteomics approach that took advantage of the unique role that individual phosphodiesterases play in the control of local cyclic AMP. They combined this with network analysis to identify previously unrecognized cyclic AMP nano domains associated with beta adrenergic stimulation. They found that indeed this integrated phospho proteomics approach could successfully pinpoint the location of these signaling domains and it provided crucial cues to determine the function of previously unknown cyclic AMP nano domains. The group characterized one such cellular compartment in detail and they showed that the phosphodiesterase PDE3A2 isoform operates in a nuclear nano domain that involves SMAD4 and HDAC1. Inhibition of PDE3 resulted in an increased HDAC1 phosphorylation, which led to an inhibition of its deacetylase activity, and thus derepression of gene transcription and cardiac monocyte hypertrophic growth. These findings reveal a very unique mechanism that explains the negative long-term consequences observed in patients with heart failure treated with PDE3 inhibitors. Cindy St. Hilaire: The April 14th issue is our compendium on Increased Risk of Cardiovascular Complications in Chronic Kidney Disease. Dr Heidi Noels from the University of Aachen is our guest editor of the 11 articles in this issue. Chronic kidney disease is defined by kidney damage or a reduced kidney filtration function. Chronic kidney disease is a highly prevalent condition affecting over 13% of the population worldwide and its progressive nature has devastating effects on patient health. At the end stage of kidney disease, patients depend on dialysis or kidney transplantation for survival. However, less than 1% of CKD patients will reach this end stage of chronic kidney disease. Instead, most of them with moderate to advanced chronic kidney disease will prematurely die and most often they die from cardiovascular disease. And this highlights the extreme cardiovascular burden patients with CKD have. The titles of the articles in this compendium are the Cardio Kidney Patient Epidemiology, Clinical Characteristics, and Therapy by Nicholas Marx, the Innate Immunity System in Patients with Cardiovascular and Kidney Disease by Carmine Zoccali et al. NETs Induced Thrombosis Impacts on Cardiovascular and Chronic Kidney disease by Yvonne Doering et al. Accelerated Vascular Aging and Chronic Kidney Disease, The Potential for Novel Therapies by Peter Stenvinkel et al. Endothelial Cell Dysfunction and Increased Cardiovascular Risk in Patients with Chronic Kidney Disease by Heidi Noels et al. Cardiovascular Calcification Heterogeneity in Chronic Kidney Disease by Claudia Goettsch et al. Fibrosis in Pathobiology of Heart and Kidney From Deep RNA Sequencing to Novel Molecular Targets by Raphael Kramann et al. Cardiac Metabolism and Heart Failure and Implications for Uremic Cardiomyopathy by P. Christian Schulze et al. Hypertension as Cardiovascular Risk Factor in Chronic Kidney Disease by Michael Burnier et al. Role of the Microbiome in Gut, Heart, Kidney crosstalk by Griet Glorieux et al, and Use of Computation Ecosystems to Analyze the Kidney Heart Crosstalk by Joachim Jankowski et al. These reviews were written by leading investigators in the field, and the editors of Circulation Research hope that this comprehensive undertaking stimulates further research into the path flow of physiological kidney-heart crosstalk, and on comorbidities and intra organ crosstalk in general. Cindy St. Hilaire: So for our interview portion of the episode I have with me Dr Elizabeth Tarling and Dr Bethan Clifford. And Dr Tarling is an associate professor in the Department of Medicine in cardiology at UCLA, and Dr Clifford is a postdoctoral fellow with the Tarling lab. And today we're going to be discussing their manuscript that's titled, RNF130 Regulates LDLR Availability and Plasma LDL Cholesterol Levels. So thank you both so much for joining me today. Elizabeth Tarling: Thank you for having us. Bethan Clifford: Yeah, thanks for having us. This is exciting. Cindy St. Hilaire: I guess first, Liz, how did you get into this line of research? I guess, before we get into that, I should disclose. Liz, we are friends and we've worked together in the ATVB Women's Leadership Committee. So full disclosure here, that being said, the editorial board votes on these articles, so it's not just me picking my friends. But it is great to have you here. So how did you enter this field, I guess, briefly? Elizabeth Tarling: Yeah, well briefly, I mean my training right from doing my PhD in the United Kingdom in the University of Nottingham has always been on lipid metabolism, lipoprotein biology with an interest in liver and cardiovascular disease. So broadly we've always been interested in this area and this line of research. And my postdoctoral research was on atherosclerosis and lipoprotein metabolism. And this project came about through a number of different unique avenues, but really because we were looking for regulators of LDL biology and plasma LDL cholesterol, that's sort of where the interest of the lab lies. Cindy St. Hilaire: Excellent. And Bethan, you came to UCLA from the UK. Was this a topic you were kind of dabbling in before or was it all new for you? Bethan Clifford: It was actually all completely new for me. So yeah, I did my PhD at the same university as Liz and when I started looking for postdocs, I was honestly pretty adamant that I wanted to stay clear away from lipids and lipid strategy. And then it wasn't until I started interviewing and meeting people and I spoke to Liz and she really sort of convinced me of the excitement and that the interest and all the possibilities of working with lipids and well now I won't go back, to be honest. Cindy St. Hilaire: And now here you are. Well- Bethan Clifford: Exactly. Cindy St. Hilaire: ... congrats on a wonderful study. So LDLR, so low density lipoprotein receptor, it's a major determinant of plasmid LDL cholesterol levels. And hopefully most of us know and appreciate that that is really a major contributor and a major risk for the development of atherosclerosis and coronary artery disease. And I think one thing people may not really appreciate, which your study kind of introduces and talks about nicely, is the role of the liver, right? And the role of receptor mediated endocytosis in regulating plasma cholesterol levels. And so before we kind of chat about the nitty-gritty of your study, could you just give us a brief summary of these key parts between plasma LDL, the LDL receptor and where it goes in your body? Elizabeth Tarling: Yeah. So the liver expresses 70% to 80% of the body's LDL receptor. So it's the major determinant of plasma lipoprotein plasma LDL cholesterol levels. And through groundbreaking work by Mike Brown and Joe Goldstein at the University of Texas, they really define this receptor mediated endocytosis by the liver and the LDL receptor by looking at patients with familial hypercholesterolemia. So those patients have mutations in the LDL receptor and they either express one functional copy or no functional copies of the LDL receptor and they have very, very large changes in plasma LDL cholesterol. And they have severe increases in cardiovascular disease risk and occurrence and diseases associated with elevated levels of cholesterol within the blood and within different tissues. And so that's sort of how the liver really controls plasma LDL cholesterol is through this receptor mediated endocytosis of the lipoprotein particle. Cindy St. Hilaire: There's several drugs now that can help regulate our cholesterol levels. So there's statins which block that rate limiting step of cholesterol biosynthesis, but there's this new generation of therapies, the PCSK9 inhibitors. And can you just give us a summary or a quick rundown of what are those key differences really? What is the key mechanism of action that these therapies are going after and is there room for more improvement? Bethan Clifford: Yeah, sure. So I mean I think you've touched on something that's really key about the LDR receptor is that it's regulated at so many different levels. So we have medications available that target the production of cholesterol and then as you mentioned this newer generation of things like PCSK9 inhibitors that sort of try and target LDL at the point of clearance from the plasma. And in response to your question of is there room for more regulation, I would say that given the sort of continual rate of increased cholesterol in the general population and the huge risks associated with elevated cholesterol, there's always capacity for more to improve that and sort of generally improve the health of the population. And what we sort of found particularly exciting about RNF130 is that it's a distinct pathway from any of these regulatory mechanisms. So it doesn't regulate the level of transcription, it doesn't regulate PCSK9. Or in response to PCSK9, it's a completely independent pathway that could sort of improve or add to changes in cholesterol. Cindy St. Hilaire: So your study, it's focusing on the E3 ligase, RNF130. What is an E3 ligase, and why was this particular one of interest to you? How did you come across it? Elizabeth Tarling: is predTates Bethan joining the lab. This is, I think, again for the listeners and those people in training, I think it's really important to note this project has been going in the lab for a number of years and has really... Bethan was the one who came in and really took charge and helped us round it out. But it wasn't a quick find or a quick story. It had a lot of nuances to it. But we were interested in looking for new regulators of LDL cholesterol and actually through completely independent pathways we had found the RNF130 locus as being associated with LDL cholesterol in animals. And then it came out in a very specific genome-wide association study in the African American care study, the NHLBI care study. And so really what we started looking at, we didn't even know what it was. Elizabeth Tarling: So we asked ourselves, well what is this gene? What is this protein? And it's RNF, so that's ring finger containing protein 130 and ring stands for really interesting new gene. Somebody came up with the glorious name. But proteins that contain this ring domain are very characteristic and they are E3 ubiquitin ligases. And so they conjugate the addition of ubiquitin to a target protein and that signals for that protein to either be internalized and/or degraded through different decorative pathways within the cell. And so we didn't land on it because we were looking at E3 ligases, we really came at it from an LDL cholesterol perspective. And it was something that we hadn't worked on before and the study sort of blossomed from there. Cindy St. Hilaire: That's amazing and a beautiful, but also, I'm sure, heartbreaking story because these long projects are just... They're bears. So what does this RNF130 do to LDLR? What'd you guys find? Bethan Clifford: As Liz said, this is a long process, but one of the key factors of RNF130 is it's structurally characteristically looked like E3 ligase. So the first thing that Liz did and then I followed up with in the lab is to see is this E3 ligase ubiquitinating in vitro. And if it is going to ubiquitinate, what's it likely to regulate that might cause changes in plasma cholesterol that would explain these human genetic links that we saw published at the same time. And so because the LDL cholesterol is predominantly regulated by the LDL receptor and the levels of it at the surface of the parasites in the liver, the first question we wanted to see is does RNF130 interact in any way with that pathway? And I'm giving you... /episode/index/show/circresearch/id/26591421

March 2023 Discover CircRes 03/16/2023

March 2023 Discover CircRes This month on Episode 46 of Discover CircRes, host Cynthia St. Hilaire highlights four original research articles featured in the March 3 and March 17th issues of Circulation Research. This episode also features an interview with Dr Andrew Hughes and Dr Jessilyn Dunn about their review, Article highlights: Delgobo, et al. Sun, et al. Sun, et al Johnson, et al. 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, and today I'm going to share four articles selected from the March 3rd and March 17th issues of CircRes. I'm also going to have a discussion with Dr Andrew Hughes and Dr Jessilyn Dunn about their review, Wearable Devices in Cardiovascular Medicine. And the Review is also featured in our March 3rd issue. Cindy St. Hilaire: First, the highlights. The first article I'm going to present is Myocardial Milieu Favors Local Differentiation of Regulatory T-Cells. The first author is Murilo Delgobo and the corresponding author is Gustavo Campos Ramos. After myocardial infarction, the release of autoantigens from the damaged heart cells activates local and infiltrating immune cells such as the T-cell. Studies in mice have shown that fragments of the muscle protein myosin can act as autoantigens, and these myosin fragments are the dominant driver of the T-cell response. But how do these myosin specific T-cells behave in the damaged heart to drive inflammation and repair is unknown. To find out, Delgobo and colleagues studied endogenous myosin specific T-cells, as well as those transferred into recipient mice. They found, whether exogenously supplied or endogenously created, the myosin specific T-cells that accumulated in the animals' infarcted hearts tended to adopt an immunosuppressive T-regulatory phenotype. Strikingly, even if the exogenous cells were differentiated into inflammatory TH-17 cells prior to transfer, a significant proportion of them were still reprogrammed into T-regs within the heart. Although cells pre-differentiated into an inflammatory TH-17 phenotype were less inclined to change after the transfer, the results nevertheless indicate that, by and large, the infarcted heart promotes T-cell reprogramming to quell inflammation and drive repair. Yet exactly how the heart does this is a question for future studies. Cindy St. Hilaire: The next article I'm going to present is titled Inhibition of FAP Promotes Cardiac Repair by Stabilizing BNP. The first authors of the study are Yuxi Sun and Mengqiu Ma, and the corresponding author is Rui Yue, and they are from Tongji University. After myocardial infarction, there needs to be a balance of recovery processes to protect the tissue. Fibrosis, for example, acts like an immediate bandaid to hold the damaged heart muscle together, but fibrosis can limit contractile function. Similarly, angiogenesis and sufficient revascularization is required to promote survival of cardiomyocytes within the ischemic tissue and protect heart function. To better understand the balance between fibrotic and angiogenic responses, Sun and colleagues examined the role of fibroblasts activated protein, or FAP, which is dramatically upregulated in damaged hearts, and brain natriuretic peptide, or BNP, which promotes angiogenesis in the heart. In this study, they found that genetic deletion or pharmacological inhibition of FAP in mice reduces cardiac fibrosis and improves angiogenesis and heart function after MI. Such benefits are not seen if BNP or its receptor, NRP-1, are lacking. The in vitro experiments revealed that FAP's protease activity degrades BNP, thus inhibiting the latter's angiogenic activity. Interestingly, while FAP is upregulated in the heart, its levels drop in the blood, showing that BNP inhibition is localized. Together, these results suggest that blocking FAP's activity in the heart after MI could be a possible strategy for protecting the muscle's function. Cindy St. Hilaire: The next article I want to present is Hypoxia Sensing of Beta-Adrenergic Receptor is Regulated by Endosomal PI-3 Kinase Gamma. The first author of this study is Yu Sun, and the corresponding author is Sathyamangla Naga Prasad. Hypoxia is the most proximate acute stress encountered by the heart during an ischemic event. Hypoxia triggers dysfunction of the beta-adrenergic receptors, beta-1AR and beta-2AR, which are critical regulators of cardiac function. Under normoxic conditions, activation of PI3K-gamma by beta-adrenergic receptors leads to feedback regulation of the receptor by hindering its dephosphorylation through inhibition of protein phosphatase 2A or PP2A. Although it is known that ischemia reduces beta-adrenergic receptor function, the impact of hypoxia on interfering with this PI3K feedback loop was unknown. Using in vitro and in vivo techniques, this group found that activation of PI3K-gamma underlies hypoxia sensing mechanisms in the heart. Exposing PI3K-gamma knockout mice to acute hypoxia resulted in preserved cardiac function and reduced beta-adrenergic receptor phosphorylation. And this was due to a normalized beta-2AR associated PP2A activity, thus uncovering a unique role for PI3K-gamma in hypoxia sensing and cardiac function. Similarly, challenging wild-type mice post hypoxia with dobutamine resulted in an impaired cardiac response that was normalized in the PI3K-gamma knockout mice. These data suggests that preserving beta-adrenergic resensitization by targeting the PI3K-gamma pathway would maintain beta-adrenergic signaling and cardiac function, thereby permitting the heart to meet the metabolic demands of the body following ischemia. Cindy St. Hilaire: The last article I want to highlight is Systemic Hypoxia Induces Cardiomyocyte Hypertrophy and Right Ventricle Specific Induction of Proliferation. First author of this study is Jaslyn Johnson, and the corresponding author is Steven Houser, and they're at Temple University. The cardiac hypoxia created by myocardial infarction leads to the death of the heart tissue, including the cardiomyocytes. While some procedures such as reperfusion therapy prevent some cardiomyocyte death, true repair of the infarcted heart requires that dead cells be replaced. There have been many studies that have attempted new approaches to repopulate the heart with new myocytes. However, these approaches have had only marginal success. A recent study suggested that systemic hypoxemia in adult male mice could induce cardiac monocytes to proliferate. Building on this observation, Johnson and colleagues wanted to identify the mechanisms that induced adult cardiomyocyte cell cycle reentry and wanted to determine whether this hypoxemia could also induce cardiomyocyte proliferation in female mice. Mice were kept in hypoxic conditions for two weeks, and using methods to trace cell proliferation in-vivo, the group found that hypoxia induced cardiac hypertrophy in both the left ventricle and the right ventricle in the myocytes of the left ventricle and of the right ventricle. However, the left ventricle monocytes lengthened while the RV monocytes widened and lengthened. Hypoxia induced an increase in the number of right ventricular cardiomyocytes, but did not affect left ventricular monocyte proliferation in male or in female mice. RNA sequencing showed upregulation of cell cycle genes which promote the G1 to S phase transition in hypoxic mice, as well as a downregulation of cullen genes, which are the scaffold proteins related to the ubiquitin ligase complexes. There was significant proliferation of non monocytes in mild cardiac fibrosis in the hypoxic mice that did not disrupt cardiac function. Male and female mice exhibited similar gene expression patterns following hypoxia. Thus, systemic hypoxia induced a global hypertrophic stress response that was associated with increased RV proliferation, while LV monocytes did not show increased proliferation. These results confirm previous reports that hypoxia can induce cardiomyocyte cell cycle activity in-vivo, and also show that this hypoxia induced proliferation also occurs in the female mice. Cindy St. Hilaire: With me today for our interview, I have Dr Andrew Hughes and Dr Jessilyn Dunn, and they're from Vanderbilt University Medical Center. And they're here to discuss the review article that they helped co-author called Wearable Devices in Cardiovascular Medicine. And just as a side note, the corresponding author, Evan Brittain, unfortunately just wasn't able to join us due to clinical service, but they're going to help dissect and discuss this Review with us. Thank you both so much for joining me today. Andy, can you just tell us a little bit about yourself? Andy Hughes: Yeah, thank you, Cindy. I'm Andy Hughes. I'm a third year medicine resident at Vanderbilt University who is currently on an NIH supported research year this year. And then will be applying to cardiology fellowships coming up in the upcoming cycle. Cindy St. Hilaire: Great, thank you. And Jessilyn, I said you are from Vanderbilt. I know you're from Duke. It was Evan and Andy at Vanderbilt. Jessilyn, tell us about yourself. Jessilyn Dunn: Thanks. I am an Assistant Professor at Duke. I have a joint appointment between biomedical engineering and biostatistics and bioinformatics. The work that my lab does is mainly centered on digital health technologies in developing what we call digital biomarkers, using data from often consumer wearables to try to detect early signs of health abnormalities and ultimately try to develop interventions. Cindy St. Hilaire: Thank you. We're talking about wearable devices today, and obviously the first thing I think most of us think about are the watch-like ones, the ones you wear on your wrists. But there's really a whole lot more out there. It's not just Apple Watches and Fitbits and the like. Can you just give us a quick summary of all these different types of devices and how they're classified? Jessilyn Dunn: Yeah, absolutely. We have a wide variety of different sensors that can be useful. A lot of times, we like to think about them in terms of the types of properties that they measure. So mechanical properties like movement, electrical properties like electrical activity of the heart. We have optical sensors. And so, a lot of the common consumer wearables that we think about contain these different types of sensors. A good example that we can think about is your consumer smartwatch, like an Apple Watch or a Fitbit or a Garmin device where it has something called an accelerometer that can measure movement. And oftentimes, that gets converted into step counts. And then it may also have an optical sensor that can be used to measure heart rate in a particular method called PPG, or photoplethysmography. And then some of the newer devices also have the ability to take an ECG, so you can actually measure electrical activity as well as the optical based PPG heart rate measurement. These are some of the simpler components that make up the more complex devices that we call wearables. Cindy St. Hilaire: And how accurate are the measurements? You did mention three of the companies, and I know there's probably even more, and there's also the clinical grade at-home ECG machines versus the one in the smartwatch. How accurate are the measurements between companies? And we also hear recent stories about somebody's Apple Watch calling 911 because they think they're dead, things like that. Obviously, there's proprietary information involved, but how accurate are these devices and how accurate are they between each other? Jessilyn Dunn: This is a really interesting question and we've done quite a bit of work in my lab on this very topic, all the way from what does it mean for something to be accurate? Because we might say, "Well, the more accurate, the better," but then we can start to think about, "Well, how accurate do we need something to be in order to make a clinical decision based off of that?" And if it costs significantly more to make a device super, super accurate, but we don't need it to be that accurate to make useful decisions, then it actually might not be serving people well to try to get it to that extreme level of accuracy. So there are a lot of trade-offs, and I think that's a tough thing to think about in the circumstances, is these trade-offs between the accuracy and, I don't know, the generalizability or being able to apply this to a lot of people. That being said, it also depends on the circumstances of use. When we think about something like step counts, for example, if you're off by a hundred step counts and you're just trying to get a general view of your step counts, it's not that much of a problem. But if we're talking about trying to detect an irregular heart rhythm, it can be very bad to either miss something that's abnormal or to call something abnormal that's not and have people worried. We've been working with the Digital Medicine Society to develop this framework that we call V3, which is verification, analytic validation and clinical validation. And these are the different levels of analysis or evaluation that you can do on these devices to determine how fit for purpose are they. Given the population we're trying to measure in and given what the goal of the measurement is, does the device do the job? And what's also interesting about this topic is that the FDA has been evolving how they think about these types of devices because there's, in the past, been this very clear distinction between wellness devices and medical devices. But the problem is that a lot of these devices blur that line. And so, I think we're going to see more changes in the way that the FDA is overseeing and potentially regulating things like this as well. Cindy St. Hilaire: These consumer-based devices have started early on as the step counters. When did they start to bridge into the medical sphere? When did that start to peak the interest of clinicians and researchers? Jessilyn Dunn: Yeah, sure. What's interesting is if we think back to accelerometers, these have been used prior to the existence of mobile phones. These really are mechanical sensors that could be used to count steps. And when we think about the smartwatch in the form that we most commonly think of today, probably looking back to about 2014 is when ... maybe between 2012, 2014 is when we saw these devices really hitting the market more ... Timing for when the devices that we know as our typical consumer smartwatch today was around 2012 to 2014. And those were things that were counting steps and then the next generation of that added in the PPG or photoplethysmography sensor. That's that green light when we look on the back of our watch that measures heart rate. And so, thinking back to the early days, probably Jawbone, there was a watch called Basis, the Intel Basis watch. Well, it was Basis and then got acquired by Intel. Fitbit was also an early joining the market, but that was really the timing. Cindy St. Hilaire: How good are these devices at actually changing behavior? We know we're really good at tracking our steps now and maybe monitoring our heartbeat or our oxygen levels. How good are they at changing behavior though? Do we know yet? Andy Hughes: Yeah, that's a great question and certainly a significant area of ongoing research right now with physical activity interventions. Things that we've seen right now is that simple interventions that use the wearable devices alone may not be as effective as multifaceted interventions. And what I mean by that is interventions that use the smartwatch but may be coupled with another component, whether that is health education or counseling or more complex interventions that use gamification or just in time adaptive interventions. And gamification really takes things to another level because that integrates components, competition or support or collaboration and really helps to build upon features of behaviors that we know have an increased likelihood of sustaining activity. With that being said, that is one of the challenges of physical activity interventions, is the sustainability of their improvements over the course of months to years. And something that we have seen is the effects do typically decrease over time, but there is work on how do we integrate all of these features to develop interventions that can help to sustain the results more effectively. So we have seen some improvement, but finding ways to sustain the effects of physical activity is certainly an area of ongoing research. Cindy St. Hilaire: I know it's funny that even as adults we love getting those gold stars or the circle completions. All of these devices, whether it's smartwatches like we're just talking about, or the other things for cardiac rehabilitation, they're generating a ton of data. What is happening with all this data? Who's actually analyzing it? How is it stored and what's that flow through from getting from the patient's body to the room where their physician is looking at it? Andy Hughes: And that is certainly a challenge right now that is limiting the widespread adoption of these devices into routine clinical care is, as Jessilyn mentioned. The wearables generate a vast amount of data, and right now, we need to identify and develop a way as clinicians to sort through all of the noise in order to be able to identify the information that is clinically meaningful and worthy of action without significantly increasing the workload. And a few of the barriers that will be necessary in order to reach that point is, one, finding ways to integrate the wearables' data into the electronic health record and also developing some machine learning algorithms or ways with which we can use the computational power of those technologies to be able to identify when there is meaningful data within all of the vast data that comes from wearables. So it's somewhere that certainly we need to get to for these devices to reach their full clinical potential, but we are limited right now by a few of those challenges. Jessilyn Dunn: I was just going to say, I will add on to what Andy was saying about this idea behind digital biomarkers because this fits really nicely with this idea that giving people this huge data deluge is not helpful, but if we had a single metric where we can say, "Here's the... /episode/index/show/circresearch/id/26239170

February 2023 Discover CircRes 02/16/2023

February 2023 Discover CircRes This month on Episode 45 of Discover CircRes, host Cynthia St. Hilaire highlights four original research articles featured in the February 3rd and February 17th issues of Circulation Research. This episode also features an interview with Dr Hind Lal and Dr Tousif Sultan from the University of Alabama at Birmingham about their study Article highlights: Pi, et al. Carnevale, et al. Cai, et al. Koide, et al. 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 Cynthia St. Hilaire from the Vascular Medicine Institute at the University of Pittsburgh, and today I'm going to be highlighting the articles from our February 3rd and 17th issues of Circulation Research. I'm also going to have a chat with Dr Hind Lal and Dr Tousif Sultan from the University of Alabama at Birmingham about their study, Ponatinib Drives Cardiotoxicity by S100A8/A9-NLRP3-IL-1β Mediated Inflammation. But before I get to the interviews, here are a few article highlights. Cindy St. Hilaire: The first article I want to highlight comes from the laboratory of Dr Peter Leary at the University of Washington, and the title is Metabolomic Signatures Associated With Pulmonary Arterial Hypertension Outcomes. Pulmonary Arterial Hypertension or PAH is a rare but life-threatening disease in which progressive thickening of the walls of the lung’s blood vessels causes increased blood pressure and that increased blood pressure ultimately damages the heart's right ventricle. Interestingly, progression to heart failure varies considerably among patients, but the reasons why there is variability are not well understood. To find out, this group turned their attention to patient metabolomes, which differ significantly from those of healthy people and thus may also change with severity. Blood samples from 117 PAH patients were analyzed for more than a thousand metabolites by mass spectrometry and the patient's progress was followed for the next three years. 22 patients died within a three-year period and 27 developed significant right ventricle dilation. Other measures of severity included pulmonary vascular resistance, exercise capacity and levels of BNP, which is a metric of heart health. Two metabolic pathways, those relating to polyamine and histidine metabolism, were found to be linked with all measures of severity suggesting a key role for them in disease pathology. While determining how these pathways influence disease as a subject for further study, the current findings may nevertheless lead to new prognostic indicators to inform patient care. Cindy St. Hilaire: The next article I want to discuss is coming from our February 3rd issue of Circulation Research and this is coming from the laboratory of Dr Francisco Violi at the University of Rome and the title is Toll-Like Receptor 4-Dependent Platelet-Related Thrombosis in SARS-CoV-2 Infection. Thrombosis can be a complication of COVID-19 and it is associated with poor outcomes, including death. However, the exact mechanism by which the virus activates platelets, which are the cells that drive thrombosis, is not clear. For one thing, platelets do not appear to express the receptor for SARS-CoV-2. They do however, express the TLR4 receptor and that's a receptor that mediates entry of other viruses as part of the immune response. And TLR4 is ramped up in COVID-19 patient platelets. This group now confirms that, indeed, SARS-CoV-2 interacts with TLR4, which in turn triggers thrombosis. The team analyzed platelets from 25 patients and 10 healthy controls and they found that the platelet activation and thrombic activity were both boosted in the patient samples and could not be blocked using a TLR4 inhibitor. Additionally, immunoprecipitation and immunofluorescent experiments further revealed colocalization between the virus protein and the TLR4 receptor on patient platelets. The team went on to show that the signaling pathway involved reactive oxygen species producing factors p47phox and Nox2, and that inhibition of phox 47, like that of the TLR4 receptor itsel,f could prevent platelet activation. As such, this study suggests that inhibiting either of these proteins may form the basis of an antithrombotic treatment for COVID-19. Cindy St. Hilaire: The third article I want to highlight is coming from the lab of Shi-You Chen at University of Missouri and the title of this article is ADAR1 Non-Editing Function in Macrophage Activation and Abdominal Aortic Aneurysm. Macrophage activation plays a critical role in abdominal aortic aneurysm development, or AAA development. Inflammation is a component of this pathology; however, the mechanisms controlling macrophage activation and vascular inflammation in AAA are largely unknown. The ADAR1 enzyme catalyzes the conversion of adenosine to inosine in RNA molecules and thus this conversion can serve as a rheostat to regulate RNA structure or the gene coding sequence of proteins. Several studies have explored the role of ADAR1 in inflammation, but its precise contribution is not fully understood, so the objective of this group was to study the role of ADAR1 in macrophage activation and AAA formation. Aortic transplantation was conducted to determine the importance of nonvascular ADAR1 in AAA development and dissection and angiotensin II infusion of ApoE knockout mice combined with a macrophage specific knockout of ADAR1 was used to study the role of ADAR1 macrophage specific contributions to AAA formation and dissection. Allograft transplantation of wild type abdominal aortas to ADAR1 haploinsufficient recipient mice significantly attenuated AAA formation. ADAR1 deficiency in hematopoietic stem cells also decreased the prevalence and the severity of AAA and it also inhibited macrophage infiltration into the aortic wall. ADAR1 deletion blocked the classic macrophage activation pathway. It diminished NF-κB signaling and it enhanced the expression of a number of anti-inflammatory microRNAs. Reconstitution of ADAR1 deficient but not wild type human monocytes to immunodeficient mice blocked the aneurysm formation in transplanted human arteries. Together these results suggest that macrophage ADAR1 promotes aneurysm formation in both mouse and human arteries through a novel mechanism of editing the microRNAs that target NF-κB signaling, which ultimately promotes vascular inflammation in AAA. Cindy St. Hilaire: The last article I want to highlight is also from our February 17th issue of Circulation Research and it is coming from the lab of Shintaro Mandai at Tokyo Medical and Dental University and the title of the article is Circulating Extracellular Vesicle Propagated MicroRNA signatures as a Vascular Calcification Factor in Chronic Kidney Disease. Chronic Kidney Disease or CKD accelerates vascular calcification in part by promoting the phenotypic switching of vascular smooth muscle cells to osteoblast like cells. This study investigated the role of circulating small extracellular vesicles or SUVs from the kidneys in promoting this osteogenic switch. CKD was induced in rats and in mice by an adenine induced tubular interstitial fibrosis and serum from these animals induced calcification in in vitro cultures of A-10 embryonic rat smooth muscle cells. Intraperitoneal administration of a compound that prevents SEV biosynthesis and release inhibited thoracic aortic calcification in CKD mice under a high phosphorus diet. In Chronic Kidney Disease, the microRNA transcriptome of SUVs revealed a depletion of four microRNAs and the expression of the microRNAs inversely correlated with kidney function in CKD patients. In vitro studies found that transected microRNA mimics prevented smooth muscle cell calcification in vitro. In silico analyses revealed that VEGF-A was a convergent target of all four microRNAs and leveraging this, the group used in vitro and in vivo models of calcification to show the inhibition of the VEGF-A, VEGFR-2 signaling pathway mitigated calcification. So in addition to identifying a new potential therapeutic target, these SUV propagated microRNAs are a potential biomarker that can be used for screening patients to determine the severity of CKD and possibly even vascular calcification. Cindy St. Hilaire: Today I have with me Dr Hind Lal who's an associate professor of medicine at the University of Alabama Birmingham and his post-doctoral fellow and the lead author of the study Dr Tousif Sultan. And their manuscript is titled Ponatinib Drives Cardiotoxicity by S100A8/A9-NLRP3-IL-1β Mediated Inflammation. And this article is in our February 3rd issue of Circulation Research. So thank you both so much for joining me today. Tousif Sultan: Thank you. Hind Lal: Thank you for taking time. Cindy St. Hilaire: So ponatinib, it's a tyrosine kinase inhibitor and from my understanding it's the only treatment option for a specific group of patients who have chronic myelogenous leukemia and they have to harbor a specific mutation. And while this drug helps to keep these patients alive essentially, it's extremely cardiotoxic. So cardiotoxicity is somewhat of a new field. So Dr Lal, I was wondering how did you get into this line of research? Hind Lal: So I was fortunate enough to be in the lab of Dr Tom Force and he was kind of father of this new area, now is very developed, it's called cardio-oncology. On those days there were basically everything started in cardio-oncology. So I just recall the first tyrosine kinase approved by FDA was in 2000 and that was... Imagine and our paper came in Nature Medicine 2005 and discovering there is... so to elaborate it a little bit, the cancer therapy broadly divided in two parts. One is called non-targeted therapy like chemotherapy, radiations, et cetera, and then there are cytotoxic drugs. So those cytotoxic drugs because they do not have any targeted name on it so they are, cardiotoxic are toxic to any organ was very obvious and understanding. When these targeted therapy came, which is mainly kinase inhibitor are monoclonal antibodies. So these are targeted to a specific pathway that is activated only in the cancer cells but not in any other cells in the body so they were proposed as like magic bullets that can take off the cancer without any cardiotoxity or minimal side effects. But even in the early phase like 2005 to 2010, these came out, these so-called targeted, they are not very targeted and they are not also the magic bullets and they have serious cardiotoxicity. Cindy St. Hilaire: And so what's the mechanism of action of ponatinib in the leukemia and how does that intersect with the cardiovascular system? Hind Lal: Yeah, so this is very good question I must say. So what we believe at this point because, so leukemia if you know is driven by the famous Philadelphia chromosome, which is a translicational gene, one part of human chromosome nine and one part of human chromosome 22 and they translocate make a new gene which is BCR-ABL gene. And because it was discovered in Philadelphia UPENN, is named that Philadelphia chromosome, which is very established mechanism, that's how CML is driven. But what we have discovered that the cardiotoxicity driven by totally, totally different from the ponatinib is one of the inflammatory So it's kind of goodening. So this question is so good. One kind of toxicity is called on-target, when toxicity is mediated by the same mechanism, what is the mechanism of the drug to cure the cancer? So in that case your absolute is minimal because if you manipulate that, the drug's ability to cure the cancer will be affected but if the toxicity and the efficacy is driven by two different mechanism, then as in case of ponatinib seems like it's NLRP3 and inflammasome related mechanism. So this can be managed by manipulating this pathway without hampering the drug efficacy on the cancer. Cindy St. Hilaire: So what exactly is cardiotoxicity and how does it present itself in these patients? Hind Lal: So these drugs like ponatinib, they call broader CVD effects. So it's not just cardiac, so they also in hypertensives and atherosclerosis and thrombosis, those kind of thing. But our lab is primarily focused on the heart. So that's why in this paper we have given impresses on the heart. So what we believe at this point that ponatinib lead to this proinflammatory pathway described in this paper, which is just 108A9-NLRP3-IL-1β and this inflammatory pathway lead to a cytokine storm very much like in the COVID-19 and these cytokine storms lead to excessive myocarditis and then finally cardiac dysfunction. Cindy St. Hilaire: Is the cytokine storm just local in the cardiac tissue or is it also systemic in the patients? Is cardiotoxicity localized only or is it a more systemic problem? Tousif Sultan: I would like to add in this paper we have included that we look this cytokine things and explain blood circulation, bone marrow. So the effect is everywhere, it's not local. So we didn't check other organs, maybe other organs also being affected with the ponatinib treatment. Cindy St. Hilaire: And what's the initial phenotype of a patient has when they start to get cardiotoxicity, what's kind of like a telltale symptom? Hind Lal: So good thing that in recent years cardio-oncology developed. So initially the patient that were going for cancer treatment, they were not monitored very closely. So they only end up in cardiology clinic when they are having some cardiac events already. So thanks to the lot of development and growth in the cardio-oncology field, now most patients who going for a long-term cancer treatment, they are closely monitored by cardiology clinics. Cindy St. Hilaire: Got it. So they can often catch it before a symptom or an event. That's wonderful. Hind Lal: Yeah, so there's a lot of development in monitoring. Cindy St. Hilaire: Wonderful. So you were really interested in figuring out why ponatinib induces cardiotoxicity and you mentioned that really up until now it's been very difficult to study and that's because of the limitation of available murine models. If you just inject a wild type mouse with ponatinib, nothing happens really. So what was your approach to finding relatively good murine models? How did you go about that? Hind Lal: So this is the top scientific question you can ask. So like science, the field is try and try again. So initially this is the first paper with the ponatinib toxicity using the real in vivo models. Any paper before this including ours studies published, they were done on the cellular model in hiPSC, that isolated cardiomyocytes. So you directly putting the ponatinib directly the isolated cells. So this is first case when we were trying to do in vivo, maybe other attempt in vivo but at least not published. So first we also treated the animals with ponatinib and that failed, we don't see any cardiotoxic effect. And then when we going back to the literature, the clinical data is very, very clear from pharmacovigilance that ponatinib is cardiotoxic in humans. So when we're not able to see any phenotype in mouse, we realize that we are not mimicking what's happening in the humans. So we certainly missing something. Now once again I quote this COVID-19, so many people get infected with COVID-19 but people are having preexisting conditions are on high risk to developing CVD. So there was some literature on that line. So we use this very, very same concept that if there is preexisting conditions, so likely who'd have developing future cardiac event will be more. So we use two model in this paper one atherosclerosis model which is APoE null mice mice, another is tag branding which is pressure overload model for the heart and as soon as we start using what we call comorbidity model like patient is having some preexisting conditions and we very clearly see the robust defect of ponatinib on cardiac dysfunction. Cindy St. Hilaire: Yeah, it's really, really well done and I really like that you use kind of two different models of this. Do you think it's also going to be operative in maybe like the diabetic mirroring models? Do you think if we expand to other comorbidities, you might also recapitulate the cardiotoxicity? Hind Lal: So you got all the best questions. Cindy St. Hilaire: Thank you. I try. Hind Lal: So because this is CML drug and lot of the risk factor for cardiovascular and cancer are common and even metabolic disease. So most of the time these patients are elderly patients and they're having metabolic conditions and most of the time they have blood pressure or something CVD risk factors. So I agree with you, it'll be very relevant to expand this to the diabetes or metabolic models, but these were the first study, we put all our focus to get this one out so news is there then we can expand the field adding additional models et cetera. But I agree with you that will be very logical next step to do. Cindy St. Hilaire: Yeah. And so I guess going back to what you know from the human study or the clinical trials or the human observations, are different populations of patients with CML more predisposed to cardio toxicity than others or is that not known yet? Hind Lal: So one other area called pharmacovigilance. So what pharmacovigilance does patient all over the world taking these drugs. So WHO have their own vigilance system and FDA have their own, so it's called BG-Base for the WHO and it's called the FAERS for the FDA. So one can go back in those data sets and see if X patient taking this Y drug and what kind of... /episode/index/show/circresearch/id/25951446

January 2023 Discover CircRes 01/19/2023

January 2023 Discover CircRes This month on Episode 44 of Discover CircRes, host Cynthia St. Hilaire highlights four original research articles featured in the January 6th and January 20th issue of Circulation Research. This episode also features an interview with Dr Timothy McKinsey and Dr Marcello Rubino about their study, Article highlights: Prasad, et al. Cui, et al. Li, et al. Luo, et al. 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. And today I'm going to be highlighting articles from our January 6th and January 20th issues of Circulation Research. I'm also going to have a chat with Dr Timothy McKinsey and Dr Marcello Rubino about their study, Inhibition of Eicosanoid Degradation Mitigates Fibrosis of the Heart. But before the interview, I want to get to a few articles to highlight. Cindy St. Hilaire: The first article is titled, Maintenance of Enteral ACE2 Prevents Diabetic Retinopathy in Type 1 Diabetes. The first authors are Ram Prasad and Jason Floyd, and the corresponding author is Maria Grant, and they are from the University of Alabama. Type 1 Diabetes has a complex etiology and pathology that are not entirely understood. In addition to the destruction of insulin-producing cells, a recently discovered feature of the disease in both humans and in rodent models is that the levels of angiotensin converting enzyme 2 or ACE2 can be unusually low in certain tissues. ACE2 is a component of the renin angiotensin system controlling hemodynamics and interestingly, genetic deficiency of ACE2 in rodents exacerbates aspects of diabetes such as gut permeability, systemic inflammation and diabetic retinopathy, while boosting ACE2 has been shown to ameliorate diabetic retinopathy in mice. This study shows that ACE2 treatment also improves gut integrity and systemic inflammation as well as retinopathy. Six months after the onset of diabetes in a mouse model, oral doses of a bacteria engineered to express humanized ACE2 led to a reversal of the animal's gut barrier dysfunction and its retinopathy. Humans with diabetic retinopathy also displayed evidence of increased gut permeability in low levels of ACE2. This study suggests they may benefit from a similar probiotic treatment. Cindy St. Hilaire: The next article I want to highlight is titled, Epsin Nanotherapy Regulates Cholesterol Transport to Fortify Atheroma Regression. The first authors are Kui Cui, Xinlei Gao and Beibei Wang, and the corresponding authors are Hong Chen and Kaifu Chen and they're from Boston Children's Hospital. Epsins are a family of plasma membrane proteins that drive endocytosis. They're expressed at varying levels throughout the tissues of the body, and recent research shows that they are unusually abundant on macrophages within atherosclerotic lesions. In mice, macrophage specific Epsin loss results in a reduction in foam cell formation and atherosclerotic plaque development. This study now shows that this effect on foam cells is because Epsins normally promote the internalization of lipids into macrophages through their endosytic activity. But that's not all. The proteins also impede cholesterol efflux from macrophages to further exacerbate lipid retention. It turns out out Epsins regulate the endocytosis and the degradation of a cholesterol efflux factor called ABCG1. Importantly, these pro atrogenic activities of Epsins can be stopped. Using macrophage targeted nanoparticles carrying Epson specific silencing RNA, the team could suppress reduction of the protein in cultured macrophages and could reduce the size and number of plaques in atherosclerosis prone mice. Together these results suggest blocking Epsins via nanotherapy or other means could be a therapeutic approach to stopping or slowing atherosclerotic plaque progression. Cindy St. Hilaire: The third article I want to highlight is coming from our January 20th issue of Circ Res and is titled, Hydrogen Sulfide Modulates Endothelial-Mesenchymal Transition in Heart Failure. The first author is Zhen Li, and the corresponding author is David Lefer and they're from Cedars-Sinai. Hydrogen sulfide is a critical endogenous signaling molecule that exerts protective effects in the setting of heart failure. Cystathionine γ-lyase, or CSE, is one of the three hydrogen sulfide producing enzymes, and it's predominantly localized in the vascular endothelium. Genetic deletion of CSE, specifically in the endothelium, leads to reduced nitric oxide bioavailability, impaired vascular relaxation and impaired exercise capacity, while genetic over-expression of PSE in endothelial cells improves endothelial cell dysfunction, and attenuates myocardial infarction following myocardial ischemia-reperfusion injury. In this study, endothelial cell specific CSE knockout mice and endothelial cell specific CSE overexpressing transgenic mice were subjected to transverse aortic constriction to induce heart failure with reduced ejection fraction. And the goal was to investigate the contribution of the CSE hydrogen sulfide access in heart failure. Endothelial specific CSE knockout mice exhibited increased endothelial to mesenchymal transition and reduced nitric oxide bioavailability in the myocardium. And this was associated with increased cardiac fibrosis, impaired cardiac and vascular function, and it worsened the vascular performance of these animals. In contrast, genetic overexpression of CSE in endothelial cells led to increased myocardial nitric oxide, decreased EndoMT and decreased cardiac fibrosis. It also improved exercise capacity. These data demonstrate that endothelial CSE modulates endothelial mesenchymal transition and ameliorated the severity of pressure overload induced heart failure , in part through nitric oxide related mechanisms. This data further suggests that endothelium derived hydrogen sulfide is a potential therapeutic for the treatment of heart failure with reduced ejection fraction. Cindy St. Hilaire The last article I want to highlight is titled, Flavonifractor plautii Protects Against Elevated Arterial Stiffness. The first authors are Shiyun Luo and Yawen Zhao, and the corresponding author is Min Xia, and they are at Sun Yat-sen University. Dysbiosis of gut microbiota contributes to vascular dysfunction and gut microbial diversity has been reported to be inversely correlated with arterial stiffness. However, the causal role of gut microbiota in the progression of arterial stiffness and the specific species along with the molecular mechanisms underlying this change remain largely unknown. In this study, the microbial composition in metabolic capacities were compared in participants with elevated arterial stiffness and in normal controls free of medication. And these groups were age and sex match. Human fecal metagenomic sequencing identified a significant presence of Flavonifractor plautii or F. plautii in normal controls, which was absent in the subjects with elevated arterial stiffness. The microbiome of normal controls exhibited an enhanced capacity for glycolysis and polysaccharide degradation, whereas individuals with increased arterial stiffness exhibited increased biosynthesis of fatty acids and aromatic amino acids. Additionally, experiments in the angiotensin II induced and humanized mouse model show that replenishment with F. plautii or its main effector cis-aconitic acid or CCA improved elastic fiber network and reversed increased pulse wave velocity through the suppression of matrix metalloproteinase-2 and through the inhibition of monocyte chemoattractant protein-1. And this was seen in both the angiotensin II induced and humanized models of arterial stiffness. This study now identifies a novel link between F. plautii and arterial function and raises the possibility of sustaining vascular health by targeting the gut microbiota. Cindy St. Hilaire: Today with me I have Dr Tim McKinsey and Dr Marcello Rubino from the University of Colorado Anschutz Medical Campus, and we're here to talk about their paper Inhibition of Eicosanoid Degradati`on Mitigates Fibrosis of the Heart. And this article is in our January 6th issue of Circulation Research, so thank you both so much for joining me today. Timothy McKinsey: Thank you for inviting us. Marcello Rubino: Yeah, thank you for the opportunity. Cindy St. Hilaire: And so Dr McKinsey, you're a professor at the University of Colorado. How long have you been investigating cardiac fibrosis? Timothy McKinsey: Oh, a long time. Before I started the lab here in 2010, I was in industry working in biotech with Myogenic Gilead, and we were very interested in cardiac fibrosis all the way back then. Cindy St. Hilaire: Oh wow, so you actually made an industry to academia transfer. Timothy McKinsey: Yes. Cindy St. Hilaire: Good topic for another podcast. That is really great. Timothy McKinsey: Yeah, it's of interest to a lot of people, including trainees. Cindy St. Hilaire: Yeah, I bet. Dr Rubino, you were or are a postdoc in the McKinsey lab? Marcello Rubino: Yeah, I was a postdoc in Timothy McKinsey lab. I spent four years in Tim's lab. It was my first time studying cardio fibrosis, so it was a little bit difficult at the end, but I think I was right choosing Tim, so I'm really happy now. Cindy St. Hilaire: Nice and are you sticking with fibrosis or are you moving on? Marcello Rubino: Yeah, so now I'm back in Milan where I did my PhD student and postdoc. I am like an independent researcher, but it's still not a principal investigator, so I want to become one of the that, studying cardiac fibrosis. Yeah. And inflammation and epigenetics, so yeah, I'm going try to go to my way, thanks to Tim, I think that I find my own way. Cindy St. Hilaire: I'm sure you will. I mean, based on the great work in this study, right. Building upon that, I'm sure you'll be a success. Timothy McKinsey: No doubt about it. Cindy St. Hilaire: So your manuscript, this study, it's investigating whether eicosanoid availability can attenuate fibrosis in the heart. But before we kind of jump into this study, why is fibrosis in the heart a bad thing? Is it always detrimental? Is there some level of fibrosis that's necessary or even helpful? Timothy McKinsey: I mean, a certain level of extracellular matrix is deposited in your heart and that maintains the structure of the heart. Fibrosis can also be good after you have a myocardial infarction and a big piece of the muscle of your heart has died, it needs to be replaced with a fibrotic scar, essentially to prevent rupture of the ventricle. So fibrosis isn't always bad, but chronic fibrosis can be really deleterious to the heart and contribute to stiffening of the heart and cause diastolic dysfunction. It can create substrates for arrhythmias and sudden cardiac death. So we're really trying to block the maladaptive fibrosis that occurs in response to chronic stress. Cindy St. Hilaire: Yeah, yeah. And what about eicosanoids? What are they and what role do they play in cardiac fibrosis or what was known about their role in this process before your study? Timothy McKinsey: Eicosanoids are lipids, they're basically fatty acids, 20 carbon in length and a lot is known about them. It's a very complex system. There are many different eicosanoids, but they're produced from arachidonic acid through the action of cyclooxygenase enzymes like COX-2. And so you're probably familiar with the literature showing that non-steroidal anti-inflammatory drugs that target the COX enzymes can actually increase the risk of cardiac disease, so there was a lot known about what produces eicosanoids in the heart, but our study is really the first to address how they're degraded and how that controls cardiac fibrosis. Cindy St. Hilaire: What I thought you did really well in the introduction and what I guess I didn't really fully appreciate until I had read your study, was that your goal was to identify compounds that could attenuate fibrosis. And you spent some time emphasizing the differences between a targeted small molecule screen and a phenotype based screen. And I was wondering if you could just expand on this difference for the audience and maybe just explain why in your case you went with the latter. Timothy McKinsey: Well, we wanted to use an unbiased approach and some people call this a chemical biology approach where we took a targeted library, meaning we took compounds with known activities, meaning compounds that with known targets and we screened that library using a phenotypic assays that we developed in the lab. And the phenotypic assay is an unbiased assay, right? We're just screening for compounds that have the ability to block the activation of fibroblasts. And we monitor activation by looking at markers of fibroblast activation such as alpha smooth muscle Actin. And we can do this in a very quantitative and high throughput manner using this imaging system, high content imaging system that we have in the lab. It was an unbiased screen looking for inhibitors of fibroblasts activation across organ systems. We not only studied cardiac fibroblasts, but we also studied lung and renal fibroblasts looking for compounds with a common ability to block the activation state of each of those cell types. One of the things that I get asked frequently is how do we maintain the cardiac fibroblasts in a quiescent state? Because you may know this, but when fibroblasts are plated on cell culture plastic, which has a very high 10 cell strength, they tend to spontaneously activate, so we actually spent a couple of years working out the conditions to maintain the cells in quiescent state, and I think that will also be of great interest to the field. Cindy St. Hilaire: Probably even the smooth muscle cell biology field where I hang out and even valve interstitial cells that we study. All of those, I guess basic things related to cell culture, we have taken for granted that plastic is not physiological. Timothy McKinsey: Right. Cindy St. Hilaire: And so I think with this really nice phenotypic or chemical screen that you conducted, you first identified nine compounds, but what made you zero in on this one, SW033291? Timothy McKinsey: When we got the hits, we were intrigued by the SW compound SW033291 because there was only one paper describing its action and there was a paper published in Science showing that SW or inhibition of this enzyme 15-PGDH could enhance organ regeneration. Cindy St. Hilaire: Oh, okay. Timothy McKinsey: And there's a very interesting interplay between fibrosis and organ regeneration where fibrosis inhibits regeneration and if you can stimulate regenerative pathways, they can actually block fibrosis, so there's this back and forth. And so that's really the main reason we were interested in pursuing SW just because of the novelty and the potential. And also it was a compound that behaved beautifully in our cell culture models with beautiful dose-dependent inhibition of each of the fibroblast types. Cindy St. Hilaire: It's kind of like the cleanest thing to start with. Also, if there's nothing known, it's ripe for investigation, so that's great. You just said this SW compound acts on 15-PGDH, so what is the role of that protein in fibroblasts and what if any known effects are there on this protein's inhibition in other cell types or disease states? Marcello Rubino: In fibroblasts team, I would like to say that this was really the first article that was published. Maybe there was just one published in Pulmonary Fibrosis, but like last year, but I didn't really talk about 15-PGDH, so you need to consider that 15-PGDH is an inhibitor, an enzyme that degrades prostaglandin, so if you inhibit the inhibitor, the release increase production, a lot of prostaglandin. And so a lot of paper were talking about this effect, so they will see we are just using SW in order to increase Prostaglandin E2 level and that was why we had this like anti-inflammatory or whatever effect. I would like to say that until now, maybe this can be the first really paper talking about no more than not just prostaglandin but 15-PGDH. Its action total level, a global level at particularly on fibroblasts. To answer your question, I would like to say that this was also our question first and we checked by level other browser to try to find the answer to your question. We figured out that it was known that 15-PGDH was increasing a pathology condition in different organ, not just related by fibroblasts, not just related to cardiac disease, about the function with discover a function in macrophage that interested us because it can regulate maybe the polarization macrophage, so still involving the prostaglandin production inflammation, so that's why also we decide to take a look because it was still novel in fibrolbasts and we still know that it was doing something important and we were trying not to put the piece together and find something new in that we were lucky for this. Timothy McKinsey: 15-PGDH is actually expressed at very low levels in fibroblasts. It's much more highly expressed in macrophage, just as Marcello pointed out, so in the future we're very interested in knocking out or inhibiting 15-PGDH in different cell types to see how that contributes to inhibition of cardiac fibrosis. Cindy St. Hilaire: Really interesting. Related to that, you used a couple different animal models for fibrosis. They're all different or special in their own way. How well did these recapitulate what we observe in humans. Are there any limitations of benefits? Timothy McKinsey: They're always limitations to animal models. We started out with a very robust commonly used model of cardiac fibrosis, which relies on Angiotensin II infusion in mice. We like that model because it's robust and quick so we can get answers quickly. And then we transitioned into a model of diastolic dysfunction that we've been working with in a lab where we remove a kidney from a mouse and we implant something called DOCA, which is an aldosterone memetic. And so the animals develop hypertension that leads to a mild but significant diastolic dysfunction with preserved ejection fraction. And that's a model that we like a lot. It has something that we call hidden fibrosis, so if you just do standard histochemical... /episode/index/show/circresearch/id/25648197

December 2022 Discover CircRes 12/15/2022

December 2022 Discover CircRes This month on Episode 43 of Discover CircRes, guest host Nicole Purcell highlights two original research articles featured in the December 2 issue of Circulation Research. This episode also features an interview with Drs Aaron Phillips and Kevin O'Gallagher about their study, The Effect of a Neuronal Nitric Oxide Synthase Inhibitor on Neurovascular Regulation in Humans. Article highlights: Akerberg, et al. Lv, et al. Nicole Purcell: Hi and welcome to Discover CircRes, the podcast of the American Heart Association's Journal, Circulation Research. I am your host, Dr Nicole Purcell, from the Huntington Medical Research Institutes in Pasadena, California, and today I will be highlighting two articles from our December 2 issue of Circulation Research. I'll also have a chat with Drs Aaron Phillips and Kevin O'Gallagher about their study, The Effect of a Neuronal Nitric Oxide Synthase Inhibitor on Neurovascular Regulation in Humans. Nicole Purcell: But before I get to the interview, here are a few article highlights. The first article we're going to highlight is RBPMS2 Is a Myocardial Enriched Splicing Regulator Required for Cardiac Function. This comes from Boston Children's Hospital with first author Dr Alexander Akerberg, and corresponding author Dr Jeffrey Burns. RNA splicing, along with transcription control and post-translational modifications, is a mechanism for fine tuning the expression of a gene for a particular purpose in a particular tissue. Factors that control splicing are thus often enriched in certain cell types. The factor, RBPMS2, for example, is enriched in the myocytes of amphibians, fish, birds and mammals. This conserve tissue specificity suggesting essential role of RBPMS2 in heart function. Akerberg and colleagues now confirm this is indeed the case. They generated zebra fish embryos and human cardiomyocytes lacking RBPMS2, and found the fish suffered early cardiac dysfunction by 48 hours post fertilization. The animal's hearts had reduced ejection fractions, compared with the hearts of controlled fish. At the cellular level, the RBPMS2 lacking fish cardiomyocytes displayed malformed sarcomere fibers and disrupted calcium handling, both of which were also seen in the RBPMS2 deficient human cardiomyocytes. Furthermore, RNA sequencing experiments revealed a conserve set of 29 genes in the RBPMS2-lacking fish and human cells that were incorrectly spliced. In revealing the essential cardiac role of RBPMS2 and its RNA targets, the work provides new molecular details for understanding vertebrate heart function and disease, say the team. Nicole Purcell: Our second article being highlighted is Blocking MG53 Serine 255 Phosphorylation Protects Diabetic Heart from Ischemic Injury. This comes from Peking University with first authors, Fengxiang L, Yingfan Wang and Dan Shan, as well as corresponding author Dr Rui-Ping Xiao. Midsegment 53, or MG53, is a recently discovered muscle-specific protein that is an essential component of the cell membrane repair machinery with cardioprotective effects. MG53 thus has therapeutic potential, but for patients whose heart disease is linked to type 2 diabetes, there's a problem. MG53 also tags certain cellular proteins for destruction, including the insulin receptor and the insulin signaling factor, IRS1. Loss of these factors could worsen insulin resistance. lev and colleagues therefore investigate whether MG53 could be tweaked to provide protection without the diabetes downside. Nicole Purcell: They discovered the phosphorylation of MG53 at serine 255 is required for its role in protein destruction, and that a mutant version of MG53, incapable of this phosphorylation, MG53 serine to 255 alanine mutant, could still promote cardiomyocyte survival, and protect the cells from membrane damaging insults. Importantly, when a diabetic mouse model was injected with MG53 serine 255 to alanine mutant, the protein better protected the animals against myocardial infarction than injection with the wild type MG53, recipients of which had poor insulin sensitivity. Based on these findings, the authors suggest MG53 serine 255 alanine mutant could be developed into a heart protective drug, for use in diabetic and non-diabetic patients alike. Nicole Purcell: Today, Dr Aaron Phillips and Dr Kevin O'Gallagher from University of Calgary are with me to discuss their study, the Effect of a Neuronal Nitric Oxide Synthase Inhibitor on Neurovascular Regulation in Humans in our December 2 issue of Circulation Research. Thank you for joining me today. Kevin O'Gallagher: Hello, my name's Dr Kevin O'Gallagher. I'm a British Heart Foundation clinician scientist and interventional cardiologist at Kings College London and Kings College Hospital NHS Foundation Trust. Aaron Phillips: Hello, my name's Dr Aaron Phillips. I'm an associate professor in physiology, pharmacology, cardiac sciences, biomedical engineering and clinical neurosciences at the University of Calgary in the Hotchkiss Brain Institute and Libin Cardiovascular Institute. I am also the director of the Restore Network, which is a large platform at the University of Calgary spanning all these groups, developing new tools and techniques for translational research into neurological conditions. Nicole Purcell: There are a lot of authors involved in this study. While all could not join us, I appreciate you taking the time to discuss your findings today. Your paper deals with looking at neurovascular control in humans. Two primary regulatory pathways are neurovascular coupling, or NVC, and dynamic cerebral autoregulation. Dr Phillips, can you explain what NVC to our audience, and what does dysregulation lead to? Aaron Phillips: Yeah, thanks Nicole and I'm happy to be here. Thank you for the invitation. NVC, or neurovascular coupling, we've been studying it for about 15 years. At its fundamental level, it's kind of this elegant interplay between neurons, which unfortunately have very limited capacity for substrate storage. The brain has very limited substrate storage capacity, and so neurons need to very rapidly match their metabolic activity to the blood flow that's being delivered to them, and that needs to happen locally, for areas of the brain that have greater metabolic needs as opposed to other areas. What happens, in terms of dysregulation or conditions that are associated with dysregulation, it's an interesting story because we still really need to understand the mechanisms fully, in order to suss out what clinical conditions should have dysfunction of this unit. We know that certain conditions, such as vascular cognitive impairment, even spinal cord injury, we've done some work in stroke patients, it seems to be dysfunctional in all of these conditions, but understanding exactly why it's dysfunctional, we're still establishing that. Nicole Purcell: Great. You were talking about how it's the connection or interplay between blood flow, so we're talking about altered blood pressure seems to play a key role in neurovascular coupling. So, for those listeners not familiar with this field, can you explain how nitric oxide synthase and its isoforms, how this relates to NVC? Aaron Phillips: Well, nitric oxide synthase is an enzyme that produces nitric oxide that's expressed primarily in neurons. Nitric oxide is a powerful vasodilator. It actually works on quite a rapid time course. So, we surmised, we suspected, and there were some preclinical work before our human study, that neuronal sources of nitric oxide, being that nitric oxide is a potent vasodilator, we thought that would be likely to be mediating a large part of the neurovascular coupling response. Nicole Purcell: Great. So, Dr O'Gallagher, based on that, what was your main objective or hypothesis of this study, and how is your study novel from those that have already just suggested, looked at NOS regulation for cerebral blood flow? Kevin O'Gallagher: Thanks very much for the invite to talk. I mean, we hypothesized that nNOS would have a role in regulating neurovascular coupling. I think the novelty of our study is that although people have been interested in NOS and its regulation of cerebral vascular and cardiovascular blood flow, it's only relatively recently that there has become an agent available that will specifically inhibit nNOS, and therefore give us an idea of what it is doing, rather than previous inhibitors which just inhibit all of the three NOS isoforms. It was really that the development of the agent was what allowed us to do this study. I think it was really through that, that makes this an interesting finding that nNOS does play a role in neurovascular coupling, and really pushes the field forward ever so slightly. Nicole Purcell: Great. So, as you pointed out, this is a specific nNOS inhibitor, which is known as SMTC. It's a synthetic L-Arginine analog, right? That's really what sets your study apart. Can you tell us a little bit the audience, whether that be you, Dr Phillips or Dr O'Gallagher, about what your study was and what did you find, and how did an ambition of using this SMTC to inhibit nNOS affect systemic hemodynamic changes and NVC? Aaron Phillips: Yeah, I think both of us can probably speak to this interchangeably and add in different elements of the experiment. This is kind of a summary of the study, I guess. In advance of this, adding on what Kevin had just said in terms of the novelty of the study and the importance, we had done a lot of work previous to this paper where we were one of the groups that helped establish neurovascular coupling as a measure that could be tested in humans. This involved kind of understanding metabolism of the eye, how that's coupled to the visual cortex, and how to measure blood flow on a high temporal resolution in the visual cortex in response to visual input. That's why we used very well standardized perturbations involving tracking an eye, tracking a dot on a screen at a known one rate and a known one amplitude of movement, while also measuring the hyperemic response in the posterior brain. Then we kind of went on and developed some new measures, developed some software that we're now proud is used in a few different labs around the world, that kind of automatically takes that input of repetitive eyes opening and closing and that hyperemic response, and it breaks it down into a single wave form. A single hyperemic response is superimposed of 10, 15, 20 cycles of those eyes open and eyes closed, and then when we superimpose all the wave forms together, we can generate different metrics from that hyperemic response that correspond to different elements. One of the ways where software can, I guess dice out the hyperemic response, is by timing. We can look at very specific unique time windows over that 30 seconds of eyes open, and we can also look at the slope of the response, as well as we recently did some dimensionality reduction techniques and looked at specific computed measures of that hyperemic response. We published that a few years ago. Those were some of the tools that enabled this study, along with a fantastically unique drug that really could isolate that neuron expression of NOS and the capacity of nNOS to mediate neurovascular coupling. Kevin O'Gallagher: Obviously, we're going to use a systemic infusion of SMTC, the study drug, and we've used that before and shown it to be safe. But because a systemic infusion of SMTC through peripheral and systemic nNOS inhibition does cause an increase in systemic vascular resistance, and therefore an increase in mean arterial pressure of around about 7 mm of mercury, in addition to a cline placebo control condition, we also felt the need to have a pressure control condition. For that, we used phenylephrine to match the rise in mean arterial pressure that we anticipated we'd see with SMTC. We ended up with 12 healthy volunteers who attended on three separate visits, and so we had a party randomized double blinded intervention study where we measured the neurovascular coupling metrics, both before and after an infusion of one of the three conditions on each particular visit. Aaron Phillips: I just wanted to add into that, we had found previously that mean arterial pressure does have an effect on the hyperemic response. This was actually classically found by 1960s by Harper and Glass in a dog study, but we've repeated that in humans and kind of found that the ability of the brain to kind of... It's reserve for further vasodilation is dependent on pressure. As you drop it, neurovascular coupling will go away, and as you increase it, neurovascular coupling will increase partially, so it's important to standardize the mean arterial pressure levels. I always liken it to your water pressure in your house. You can't turn on a faucet with a given pressure unless you have that in the system upstream. That was a really important aspect of the study. Nicole Purcell: That was quite unique for your study, too. Not a lot of people have control for pressure. Aaron Phillips: Correct. Kevin O'Gallagher: I think it reflects the challenges of these healthy volunteer studies where you're trying to look at one particular part of the cardiovascular system, because as a cardiologist, if we were doing a study like this, looking at cardiovascular regulation, we would put a catheter into the coronary arteries in patients who had come for angiograms, and we'd give a local infusion of SMTC, as we've done in studies before. But with healthy volunteers, and ethically it really demanded a systemic infusion, so it was a really nice workaround to have that pressure control condition. Nicole Purcell: So, can you tell us a little bit about what your findings were? Kevin O'Gallagher: I think testament to the study design and the rigorous methodology that we employed, we did find with the resting steady state hemodynamics that SMTC condition performed as we would expect, and as we've seen in prior studies where we've given a systemic dose in that compared to both placebo and pressure control conditions, SMTC decreased cardiac output, and it decreased stroke volume, and also increased systemic vascular resistance, so very much as expected the resting hemodynamic conditions. Aaron Phillips: Yeah, thanks. Just adding onto that, moving on into some of the cerebral vascular measures. So again, we were measuring posterior cerebral artery velocity, blood velocity and specific responsiveness that it has to a visual stimuli. Between conditions, we didn't see a change in resting posterior cerebral artery velocity, so that was consistent between the conditions. Where we saw most of our change actually was in this very early period, the first five seconds of what we're going to call the hyperemic response, or the first five seconds of the neurovascular coupling response. That's where we saw our primary effect. We didn't see an effect in almost any of the neurovascular coupling measures that we generated in the actual sustained period after that initial rise, so that's where we saw our key inhibition with nNOS inhibition. What permitted that was the phenylephrine control group, again, allowing us to really look at apples and apples, not apples and oranges. Nicole Purcell: Great. So that early transient change that you saw, that as you said, hyperemic response, what therapeutic implications does this have for the field? Kevin O'Gallagher: Well, certainly there are conditions in which nNOS dysfunction, nNOS may be implicated, we mentioned a couple in the paper, some neurodegenerative diseases. But also, I think the field is now open for any vascular mediated headache syndrome, such as migraine, to investigate the potential role of nNOS from that angle. Then we haven't touched on already, but as well as dysfunctional, so decreased nNOS activity, there's also some conditions in which there's dysregulation or abnormally increased nNOS function. Again, we've highlighted this kind of study methodology is a tool that could be used to investigate those types of conditions. Aaron Phillips: These are all terrific points, and I think there's a lot of conditions where neurovascular coupling is impaired, and it's worth exploring them and understanding the specific role where nNOS might be a part of it. I also think there's a lot of interesting basic science surrounding this, in terms of the mechanisms. What was really interesting in this study, which is still kind of wracking my brain, is why didn't more of the neurovascular coupling response go away? This is a highly selective inhibitor for what was potentially thought by some groups to be a large mediator, this response. It was a relatively small inhibitory effect, and isolated to a small part of the neurovascular coupling response, just that early phase. So, still lots of work to do to kind of dice out the other pathways. They're probably highly redundant. This is such a critical mechanism in the central nervous system. Getting at it and humans is going to be tricky, but we're excited about the future and exploring some of those other avenues on the mechanistic cascade. Nicole Purcell: Based on the fact that you just had 12 healthy individuals, what do you see as some of the limitations of your study going forward, thinking about what you did? Kevin O'Gallagher: I think you've just hit on a key limitation. It was a small number of volunteers. They were all healthy, so we can't extrapolate these findings to conditions such as hypertension, where we know from other studies that cardiovascular responses, nNOS responses are impaired Also, this was a noninvasive study. We looked at the blood flow through Doppler, but we don't really know the effect of SMTC on cerebral artery diameter or other markers like that, so I think those are important limitations to mention. Nicole Purcell: I know I didn't ask this, and I know it was mentioned in the paper, but for our audience, and it was a small sample size, but did you see any sex differences between your male and female cohort? Kevin O'Gallagher: No. We did analyze for that and there were no sex... /episode/index/show/circresearch/id/25341690

November 2022 Discover Circ Res 11/17/2022

November 2022 Discover Circ Res This month on Episode 42 of Discover CircRes, host Cynthia St. Hilaire highlights four original research articles featured in the October 28 and November 11th issues of Circulation Research. This episode also features an interview with Dr Miguel Lopez-Ramirez and undergraduate student Bliss Nelson from University of California San Diego about their study, Neuroinflammation Plays a Critical Role in Cerebral Cavernous Malformations. Article highlights: Jia, et al. Rammah, et al. Wang, et al. Katsuki, et al. 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, and today, I'm going to be highlighting articles from our October 28th and our November 11th issues of Circ Res. I'm also going to have a chat with Dr Miguel Lopez-Ramirez and undergraduate student Bliss Nelson, about their study, Neuroinflammation Plays a Critical Role in Cerebral Cavernous Malformations. But, before I get into the interviews, here are a few article highlights. Cindy St. Hilaire: The first article is from our October 28th issue, and the title is, PHB2 Maintains the Contractile Phenotype of Smooth Muscle Cells by Counteracting PKM Splicing. The corresponding author is Wei Kong, and the first authors are Yiting Jia and Chengfeng Mao, and they are all from Peking University. Insults to blood vessels, whether in the form of atherosclerosis, physical injury, or inflammation, can trigger vascular smooth muscle cells to transition from a contractile state to a proliferative and migratory one. Accompanying this conversion is a switch in the cells' metabolism from the mitochondria to glycolysis. But what controls this switch? To investigate, this group compared the transcriptomes of contractile and proliferative smooth muscle cells. Among the differentially expressed genes, more than 1800 were reciprocally up and down regulated. Of those, six were associated with glucose metabolism, including one called Prohibitin-2, or PHB2, which the team showed localized to the artery wall. In cultured smooth muscle cells, suppression of PHB2 reduced expression of several contractile genes. While in rat arteries, injury caused a decrease in production of PHB2 itself, and of contractile markers. Furthermore, expression of PHB2 in proliferative smooth muscle cells could revert these cells to a contractile phenotype. Further experiments revealed PHB2 controlled the splicing of the metabolic enzyme to up-regulate the phenotypic switch. Regardless of mechanism, the results suggest that boosting PHB2 might be a way to reduce adverse smooth muscle cell overgrowth and conditions such as atherosclerosis and restenosis. Cindy St. Hilaire: The second article I'm going to highlight is also from our October 28th issue, and the first authors are Mayassa Rammah and Magali Theveniau-Ruissy. And the corresponding authors are Francesca Rochais and Robert Kelly. And they are all from Marseille University. Abnormal development of the heart's outflow track, which ultimately forms the bases of the aorta and the pulmonary artery, accounts for more than 30% of all human congenital heart defects. To gain a better understanding of outflow tract development, and thus the origins of such defects, this group investigated the role of transcription factors thought to be involved in specifying the superior outflow tract, or SOFT, which gives rise to the subaortic myocardium, and the inferior outflow tract, which gives rise to the subpulmonary myocardium. Transcription factor S1 is over-expressed in superior outflow tract cells and the transcription factors, TBX1 and PPAR gamma, are expressed in inferior outflow tract cells. And now this group has shown that TBX1 drives PPAR gamma expression in the inferior outflow tract, while Hess-1 surpasses PPAR gamma expression in the superior outflow tract. Indeed, in mouse embryos lacking TBX1, PPAR gamma expression was absent in the outflow tract. While in mouse embryos lacking Hess-1, PPAR gamma expression was increased and PPAR gamma positive cells were more widespread in the outflow tract. The team also identified that signaling kinase DLK is an upstream activator of Hess-1 and a suppressor of PPAR gamma. In further detailing the molecular interplay regulating outflow tract patterning, the work will shed light on congenital heart disease etiologies, and inform potential interventions for future therapies. Cindy St. Hilaire: The third article I want to highlight is from our November 11th issue of Circulation Research, and the title is Histone Lactylation Boosts Reparative Gene Activation Post Myocardial Infarction. The first author is Jinjin Wang and the corresponding author is Maomao Zhang, and they're from Harbin Medical University. Lactylation of histones is a recently discovered epigenetic modification that regulates gene expression in a variety of biological processes. In inflammation, for example, a significant increase in histone lactylation is responsible for switching on reparative genes and macrophages when pro-inflammatory processes give way to pro-resolvin ones. The role of histone lactylation in inflammation resolution has been shown in a variety of pathologies, but has not been examined in myocardial infarction. Wang and colleagues have now done just that. They isolated monocytes from the bone marrow and the circulation of mice at various time points after induced myocardial infarctions, and examined the cells' gene expression patterns. Within a day of myocardial infarction, monocytes from both bone marrow and the blood had begun upregulating genes involved in inflammation resolution. And, concordant with this, histone lactylation was dramatically increased in the cells, specifically at genes involved in repair processes. The team went on to show that injection of sodium lactate into mice boosted monocyte histone lactylation and improved heart function after myocardial infarction, findings that suggest further studies of lactylation's pro-resolving benefits are warranted. Cindy St. Hilaire: The last article I want to highlight is titled, PCSK9 Promotes Macrophage Activation via LDL Receptor Independent Mechanisms. The first authors are Shunsuke Katsuki and Prabhash Kumar Jha, and the corresponding author is Masanori Aikawa, and they are from Brigham and Women's Hospital in Harvard. Statins are the go-to drug for lowering cholesterol in atherosclerosis patients. But the more recently approved PCSK9 inhibitors also lower cholesterol and can be used to augment or replace statins in patients where these drugs are insufficient. PCSK9 is an enzyme that circulates in the blood and destroys the LDL receptor, thereby impeding the removal of bad cholesterol. The enzyme also appears to promote inflammation, thus potentially contributing to atherosclerosis in two ways. This group now confirms that PCSK9 does indeed promote pro-inflammatory macrophage activation and lesion development, and does so independent of its actions on the LDL receptor. The team assessed PCSK9-induced lesions in animals with saphenous vein grafts, which are commonly used in bypass surgery but are prone to lesion regrowth. They found that LDL receptor lacking graft containing mice had greater graft macrophage accumulation and lesion development when PCSK9 activity was boosted than when it was not. The animal's macrophages also had higher levels of the pro-inflammatory factor expression. Together, this work shows that PCSK9 inhibitors provide a double punch against atherosclerosis and might be effective drugs for preventing the all too common failure of saphenous vein grafts. Cindy St. Hilaire: So, today with me I have Dr Miguel Lopez-Ramirez and undergraduate student Bliss Nelson from the University of California in San Diego, and we're going to talk about their study, Neuroinflammation Plays a Critical Role in Cerebral Cavernous Malformation Disease, and this article is in our November 11th issue of Circulation Research. Thank you both so much for joining me today. Before we talk about the science, want to just maybe tell me a little bit about yourselves? Bliss Nelson: My name is Bliss Nelson. I'm a member of Miguel Lopez-Ramirez's lab here at UC San Diego at the School of Medicine. I'm an undergraduate student here at UC San Diego. I'm actually a transfer student. I went to a community college here in California and I got involved in research after I transferred. Cindy St. Hilaire: What's your major? Bliss Nelson: I'm a cognitive science major. Cindy St. Hilaire: Excellent. You might be the first undergrad on the podcast, which is exciting. Bliss Nelson: Wow. What an honor. Thank so much. Cindy St. Hilaire: And Miguel, how about you? Miguel Lopez-Ramirez: Yes, thank you. Well, first thank you very much for the opportunity to present our work through this media. It's very exciting for us. My name is Miguel Alejandro Lopez-Ramirez, and I'm an assistant professor in the Department of Medicine and Pharmacology here at UCSD. Cindy St. Hilaire: Wonderful. I loved your paper, because, well, first, I don't think I've talked about cerebral cavernous malformations. So what are CCMs, and why are they so bad? Bliss Nelson: Cerebral cavernous malformations, or CCMs for short, are common neurovascular lesions caused by a loss of function mutation in one of three genes. These genes are KRIT1, or CCM1, CCM2 and PDCD10, or CCM3, and generally regarded as an endothelial cell autonomous disease found in the central nervous system, so the brain and the spinal cord. The relevance of CCMs is that it affects about one in every 200 children and adults, and this causes a lifelong risk of chronic and acute hemorrhaging. CCMs can be quiescent or dynamic lesions. If they are dynamic, they can enlarge, regress, or behave progressively, producing repetitive hemorrhaging and exacerbations of the disease. Other side effects of the disease could be chronic bleedings, focal neurological deficits, headaches, epileptic seizures and, in some cases, death. There's no pharmacological treatment for CCMs. There's only one type of option some patients may have, which would be to have surgery to cut out the lesions. But of course this depends on where the lesion or lesions are in the central nervous system, if that's even an option. So sometimes there's no option these patients have, there's no treatment, which is what propels our lab to towards finding a pharmacological treatment or uncovering some of the mechanisms behind that. Cindy St. Hilaire: Do people who have CCM know that they have them or sometimes it not detected? And when it is detected, what are the symptoms? Bliss Nelson: Sometimes patients who have them may not show any symptoms either ever in their lifetime or until a certain point, so really the only way to find out if you were to have them is if you went to go get a brain scan, if you went to go see a doctor, or if you started having symptoms. But also, one of the issues with CCMs is that they're very hard to diagnose, and in the medical community there's a lack of knowledge for CCMs, so sometimes you may not get directed to the right specialist in time, or even ever, and be diagnosed. Miguel Lopez-Ramirez: I will just add a little bit. It is fabulous, what you're doing. I think this is very, very good. But yes, that's why they're considered rare disease, because it's not obvious disease, so sometimes most of the patient, they go asymptomatic even when they have one lesions, but there's still no answers of why patients that are asymptomatics can become symptomatics. And there is a lot in neuro study, this study that we will start mentioning a little bit more in detail. We try to explain these transitions from silent or, quiescent, lesion, into a more active lesion that gives the disability to the patient. Some of the symptoms, it can start even with headaches, or, in some cases, they have more neurological deficits that could be like weakness in the arms or loss of vision. In many cases also problems with the speech or balance. So it depends where the lesion is present, in the brain or in the spinal cord, the symptoms that the patient will experience. And some of the most, I will say, severe symptoms is the hemorrhagic stroke and the vascular thrombosis and seizure that the patients can present. Those would be the most significant symptoms that the patient will experience. Cindy St. Hilaire: What have been some limitations in the study of CCMs? What have been limitations in trying to figure out what's going on here? Bliss Nelson: The limitations to the disease is that, well, one, the propensity for lesions, or the disease, to come about, isn't known, so a lot of the labs that work on it, just going down to the basic building blocks of what's even happening in the disease is a major problem, because until that's well established, it's really hard to go over to the pharmacological side of treating the disease or helping patients with the disease, without knowing what's going on at the molecular level. Cindy St. Hilaire: You just mentioned molecular level. Maybe let's take a step back. What's actually going on at the cellular level in CCMs? What are the major cell types that are not happy, that shift and become unhappy cells? Which are the key players? Bliss Nelson: That's a great question and a great part of this paper. So when we're talking about the neuroinflammation in the disease, our paper, we're reporting the interactions between the endothelium, the astrocytes, leukocytes, microglia and neutrophils, and we've actually coined this term as the CaLM interaction. Cindy St. Hilaire: Great name, by the way. Bliss Nelson: Thank you. All props to Miguel. And if you look at our paper, in figure seven we actually have a great graphic that's showing this interaction in play, showing the different components happening and the different cell types involved in the CaLM interaction that's happening within or around the CCM lesions. Cindy St. Hilaire: What does a astrocyte normally do? I think our podcast listening base is definitely well versed in probably endothelial and smooth muscle cell and pericyte, but not many of us, not going to lie, including me, really know what a astrocyte does. So what does that cell do and why do we care about its interaction with the endothelium? Miguel Lopez-Ramirez: Well, the astrocytes play a very important role. Actually, there are more astrocytes than any other cells in the central nervous system, so that can tell you how important they are. Obviously play a very important role maintaining the neurological synapses, maintaining also the hemostasis of the central nervous system by supporting not only the neurons during the neural communication, but also by supporting the blood vessels of the brain. All this is telling us that also another important role is the inflammation, or the response to damage. So in this case, what also this study proposed, is that new signature for these reactive astrocytes during cerebral malformation disease. So understanding better how the vasculature with malformations can activate the astrocytes, and how the astrocytes can contribute back to these developing of malformations. It will teach us a lot of how new therapeutic targets can be implemented for the disease. This is part of this work, and now we extend it to see how it can also contribute to the communication with immune cells as Bliss already mentioned. Cindy St. Hilaire: Is it a fair analogy to say that a astrocyte is more similar to a pericyte in the periphery? Is that accurate? Miguel Lopez-Ramirez: No, actually there are pericytes in the central nervous system as well. They have different roles. The pericyte is still a neuron cell that give the shape, plays a role in the contractility and maintains the integrity of the vessels, while the astrocyte is more like part of the immune system, but also part of the supporting of growth factors or maintaining if something leaks out of the vasculature to be able to capture that. Cindy St. Hilaire: You used a handful of really interesting mouse models to conduct this study. Can you tell us a little bit about, I guess, the base model for CCM and then some of the unique tools that you used to study the cells specifically? Bliss Nelson: Yeah, of course. I do a lot of the animal work in the lab. I'd love to tell you about the mouse model. So to this study we use the animal model with CCM3 mutation. We use this one because it is the most aggressive form of CCM and it really gives us a wide range of options to study the disease super intricately. We use tamoxifen-regulated Cre recombinase under the control of brain endothelial specific promoter, driving the silencing of the gene CCM3, which we call the PDCD10 betco animal, as you can see in our manuscript. To this, the animal without the Cre system, that does not develop any lesions, that we use as a control, we call the PDCD10 plox. And these animals are injected with the tamoxifen postnatally day one, and then for brain collection to investigate, wcollected at different stages. So we do P15, which we call the acute stage, P50, which we term the progressive stage, and then P80, which is the chronocytes stage. And after enough brain collections, we use them for histology, gene expression, RNA analysis, flow cytometry, and different imaging to help us further look into CCMs. Cindy St. Hilaire: How similar is a murine CCM to a human CCM? Is there really good overlap or are there some differences? Miguel Lopez-Ramirez: Yes. So, actually, that's a very good question, and that's part of the work that we are doing. This model definitely has advantages in which the lesions of the vascular formations are in an adult and juvenile animals, which represent an advantage for the field in which now we will be able to test pharmacological therapies in a more meaningful, way where we can test different doses, different, again, approaches. But definitely, I mean, I think... /episode/index/show/circresearch/id/25039365

Discover CircRes

TOPICS