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Circulation on the Run


Sep 14, 2021

This week's episode features special Guest Host Mercedes Carnethon, as she interviews author Miriam Cortese-Krott and Associate Editor Charles Lowenstein as they discuss the article "Red Blood Cell and Endothelial eNOS Independently Regulate Circulating Nitric Oxide Metabolites and Blood Pressure."

Dr. Carolyn Lam:

Welcome to Circulation on the Run, your weekly podcast, summary, and backstage pass to the journal and its editors. We're your co-host I'm Dr. Carolyn Lam, associate editor from The National Heart Center in Duke National University of Singapore.

Dr. Greg Hundley:

And I'm Dr. Greg Hundley, associate editor, director of the Pauley Heart Center at VCU Health in Richmond, Virginia.

Dr. Carolyn Lam:

Greg, today's feature paper is one of those really, really landmark papers that really advance our understanding of Nitric oxide signaling. And it's about red blood cell and Endothelial eNOS, and how they independently regulate circulating nitric oxide, metabolites, and blood pressure. A real, real must, but let's go on and look at the other papers in this issue first. Greg, you want to go first?

Dr. Greg Hundley:

You bet, Carolyn. Better grab a cup of coffee. And my first paper is from professor Nathan Mewton from Hôpital Louis Pradel Hospices Civils de Lyon. Carolyn, these authors hypothesized that Colchicine a potent anti-inflammatory agent may reduce infarct size in left ventricular remodeling at the acute phase of STEMI. And so to address this hypothesis, they performed a double-blind multi-center trial and randomly assigned patients admitted for a first episode of STEMI referred for primary PTCA to receive oral Colchicine two-milligram loading dose followed by 0.5 milligrams twice a day, or matching placebo from admission to day five and the primary efficacy outcome was infarct size determined by cardiovascular magnetic resonance imaging at five days. And the relative left ventricular end-diastolic volume change at three months and infarct size at three months was also assessed by cardiac MRI. And these were secondary outcomes.

Dr. Carolyn Lam:

Nice. Okay. So what were the results?

Dr. Greg Hundley:

Right, Carolyn. So 192 patients were enrolled. 101 in the Colchicine group and 91 in the controls. And as a result of this trial, the oral administration of high dose Colchicine at the time of Reperfusion. And for five days thereafter did not reduce infarct size assessed by cardiac MRI. And so Carolyn, the clinical implications of these results suggest that other studies exploring the timing, pharma kinetics, and dose-response of Colchicine, as well as other anti-inflammatory agents are needed to identify an effective method to reduce infarct size and limit remodeling in this group of patients.

Dr. Carolyn Lam:

Wow, it's just such a rich field done with all this about Colchicine. Well, our next paper is a pre-specified sub-analysis of the randomized EAST-AFNET 4 Trial and the sub-analysis assess the effect of systematic early rhythm control therapy that is using Antiarrhythmic drugs or catheter ablation compared to usual care, which means allowing rhythm control therapy to improve symptoms in patients with heart failure. And this was defined in the sub-analysis as the presence of heart failure symptoms of New York Heart Association status two to three or a left ventricular ejection fraction of less than 50%.

Dr. Carolyn Lam:

Now, the authors led by Dr. Kirchhof at University Heart and Vascular Center UKE in Hamburg, Germany included 798 patients in this sub-analysis of whom 442 had HFpEF, 211 had heart failure with mid-range ejection fraction and 132 had HF-rEF over a median of 5.1 years of follow-up the composite primary outcome of cardiovascular death stroke or hospitalization for worsening heart failure, or for acute coronary syndrome occurred less often in patients randomized to early rhythm control therapy compared with patients randomized to usual care. And this was not altered by heart failure status with an interaction P-value of 0.6. Left ventricular function, symptoms, and quality of life improved equally in both treatment strategies.

Dr. Greg Hundley:

Wow, Carolyn, a lot of information here. So what can we take away from this?

Dr. Carolyn Lam:

Well, let's remember that this is a sub-analysis, albeit pre-specified of that randomized trial of the EAST-AFNET 4 Trial, but nonetheless, the data supports a treatment strategy of rhythm control therapy with Antiarrhythmic drugs or ablation within a year of diagnosing atrial fibrillation in patients with signs and symptoms of heart failure to reduce cardiovascular outcomes.

Dr. Greg Hundley:

Very nice, Carolyn. So, Carolyn, my next paper pertains to Alarmin Interleukin-1 Alpha, and it comes to us from Dr. Thimoteus Speer at Saarland University. So, Carolyn, Alarmin Interleukin-1 Alpha is expressed in a variety of cell types, promoting sterile systemic inflammation. And the aim of the present study was to examine the role of Alarmin Interleukin-1 Alpha in mediating inflammation in the setting of acute myocardial infarction and chronic kidney disease.

Dr. Carolyn Lam:

Wow, sterile inflammation. It's a really hot topic now. So what did these authors find?

Dr. Greg Hundley:

Right, Carolyn. So we're going to call Alarmin Interleukin-1 Alpha. Let's just call it IL-1 Alpha and so increased IL-1 Alpha surface expression on monocytes from patients with acute myocardial infarction in patients with chronic kidney disease was found to be associated with cardiovascular events. Next, IL-1 Alphas itself served as an adhesion molecule, mediating leukocyte-endothelial adhesion, and finally, abrogation of IL-1 alpha prevented inflammation after myocardial infarction and ameliorated chronic kidney disease in Vivo.

Dr. Carolyn Lam:

Wow. So what does this mean clinically?

Dr. Greg Hundley:

Right, Carolyn, so perhaps targeted therapeutic inhibition of IL-1 Alpha might represent a novel anti-inflammatory treatment strategy in patients with myocardial infarction and in patients with chronic kidney disease.

Dr. Carolyn Lam:

Amazing. Thanks, Greg. Well, in today's issue, there's also an exchange of letters between doctors Lother and Filippatos on Finerenone and risk of hyperkalemia in CKD and type two diabetes. There's an On My Mind paper by Dr. Sattler on the single-cell immunology and cardiovascular METs in, do we know yet what we don't know?

Dr. Greg Hundley:

And then Carolyn, from the mailbag, a Research Letter from Professor Wehrens entitled “Atrial Specific LK Beta One Knockdown Represents a Novel Mouse Model of Atrial Cardiomyopathy with Spontaneous Atrial Fibrillation.” Well, Carolyn, how about we turn our attention to those red blood cells and endothelial nitric oxide synthase.

Dr. Carolyn Lam:

Yeah. Can't wait.

Dr. Mercedes Carnethon:

Well, welcome to this episode of Circulation on the Run. Our podcasts, where we have an opportunity to speak with authors of important papers that are appearing in the journal of circulation. I'm pleased to introduce myself. My name is Mercedes Carnethon, professor and vice-chair of preventive medicine at the Northwestern University Feinberg School of Medicine. And I'm pleased today to invite our guest author, Miriam Cortese-Krott, who is the faculty of the University of Duesseldorf, and a guest professor at the Karolinska Institute in Stockholm. And we have with us as well the other associate editor who handled the piece for circulation, Dr. Charlie Lowenstein from Johns Hopkins University. So welcome to each of you this morning.

Miriam Cortese-krott:

Thank you.

Dr. Charles Lowenstein :

Thanks for having me.

Dr. Mercedes Carnethon:

Well, thank you. I'm really excited to jump right into this piece, Miriam, can you tell me a little bit about the rationale for carrying out the study, why you pursued it?

Professor Miriam Cortese-Krott:

The reason is because when I was working as a post-doc, I had to isolate an enzyme from red blood cells, which is a very, very difficult. And if you know, this enzyme is endothelial nitric oxide synthase, which produce nitric oxide, and actually, the red blood cell is full of the worst enemy of nitric oxide, which is hemoglobin. So actually, when I was talking about my project, everybody was asking, "Why are you doing that?" And I was actually able to isolate the enzyme and look at activity and be sure that the enzyme was fine, but the function of this enzyme was absolutely unknown.

Professor Miriam Cortese-Krott:

And the only way to study proteins in red blood cells is to make modification in the bone marrow of the mice. So in the Erythroid cells, because you can not, of course, if there are cells without nucleus you don't have any chance to modify them in culture, something like that. So the only way was to generate mice with modification specifically in the red blood cells. And I had the chance to create, to generate red cell-specific eNOS knockout mice. And of course, as a control endothelial-specific eNOS knockout mice by using the Cre-loxP technology. And with this technology, I could really understand what's happening to the physiology of the mouse if you remove this protein from the red blood cells. And so this was the whole idea.

Dr. Mercedes Carnethon:

Thank you so much. It was really exciting for me to read this piece. We are on opposite ends of the scientific inquiry spread as I'm an epidemiologist who does things at the population level, and you're identifying things at the basic science level. I thought the paper was extremely well-written and that encouraged people to dig in, even if you're unfamiliar, and in part that's because you provided such a great explanation of how your findings are used and how they're relevant to the process. Do you mind sharing a little bit about your findings and how you expect that they will be used by our scientific community?

Professor Miriam Cortese-Krott:

I think the main finding of this paper is that if you remove eNOS from the red blood cells if the mice are hypertensive, have hypertension, and this is completely something that you actually will not expect, as I told you that indeed red cells are full of the enemy of nitric oxide that remove it immediately. So you can ask yourself how it is possible. But I think the key finding here in this paper was that I also generated the opposite model. So I created the model a conditional eNOS Knockout model where you can decide in which tissue you want to have your enzyme. And of course, I applied for red blood cells. And what you see in this model is that you start from a global knockout mouse with hypertension, you reintroduce the eNOS just in the red blood cells, you have normal tension. So this means, this is the main finding. You have a switch in the red blood cells, which is the enzyme eNOS, which it's behaving in a completely different way clearly as compared to the vessel wall eNOS and still regulating blood pressure.

Dr. Mercedes Carnethon:

Well, thank you so much. I think this is the point at which I like to turn to the associate editor who handled the piece. Charlie, you and I don't get to talk as often given the diversity of work that we each pursue, but Charlie, tell me a little bit about what excited you about this piece?

Dr. Charles Lowenstein:

Thanks, Mercedes. So I love this piece. I thought Miriam, your article is so great. So a couple of thoughts. One is nitric oxide and nitric oxide synthase are so important in biology and medicine, nitric oxide regulates blood pressure. It regulates neurotransmission. It regulates inflammation. And this is true, not only in the lab, looking at cells in mice, but also in the human. So genetic variance in the endothelial nitric oxide synthase gene or NOS3 are associated with risks for diseases like coronary artery disease. So eNOS is just so important in biology and medicine. And now some ancient history. When I was a cardiology fellow, about a hundred years ago, I worked in the lab that first purified nitric oxide synthase proteins, and we cloned two of the nitric oxide synthase genes that was in the lab of Dr. Solomon Snyder at Johns Hopkins back in the 1700s.

Dr. Charles Lowenstein:

So when we cloned the nitric oxide synthase genes, when we and others did, we made a huge mistake. We chose the names for these isoforms from the tissue where they were first isolated. So we called the brain nitric oxide synthase nNOS, because it's a neurons, macrophages MCnos we called it MCnos and in endothelial cells, we called it the nitric oxide synthase eNOS or endothelial NOS. But in the last 20 years, lots of investigators have found these isoforms are in other cells, not just the original cells at discovery. And so Miriam's question is just so important, which cells make endothelial NOS also called NOS3. That's the history. Now what Miriam has discovered is just so important. I was so fascinated by her work because as she just said, she made two amazing discoveries. One, red blood cells make endothelial nitric oxide synthase.

Dr. Charles Lowenstein:

And that's been a controversy for a long time. Some people have said, "Yes." Some, "No." And Miriam made the definitive answer. Yes, red blood cells make eNOS, and secondly, she has discovered so much about the physiology of ENO coming from red blood cells, the nitric oxide that's made inside red blood cells regulates blood pressure. What a magical, interesting, and important finding. That's a little bit about the history. Nitric oxide and NOS are important in medicine. The people who originally cloned and purified the nitric oxide synthase isoforms named them after the tissue in which they discovered. And Miriam has made a major discovery that it's not only endothelial cells that make nitric oxide but also red blood cells.

Dr. Mercedes Carnethon:

Thank you so much for that summary. And I guess, I would have thought perhaps this was something of an Elixir of youth because if you've been working in this area for 200 plus years and Miriam, you started working on this as part of your dissertation work, you both have a lot of insight and background on where we've been and what the advances are. Miriam, can you tell me a little bit about how you'd like to see these findings used by the scientific community?

Professor Miriam Cortese-Krott:

I think I would like that the scientific community would use my mice first because I think, as Charles has said, it's not only red cells that express eNOS and it's not only endothelial cells. There are other cells producing eNOS and the function in the other cells is not known even in leukocytes, even when they have iNOS of course, but also have eNOS. So you can use my mice since it's a flux model. You can choose whatever you want, what cell you want, and then knock it in and knock it out. So this is one thing that I think the community could really do. I cannot do everything. So I'm happy to give my mice away.

Professor Miriam Cortese-Krott:

And the second thing is I would like too that in particular, the clinical community would see this link between Emathology and cardiovascular disease. This is something that was started, of course, there are studies looking at anemia and cardiovascular disease, but these studies have sometimes some issues I of course cannot speak as a basic scientist. I cannot speak about huge clinical trials, but I think this link exists and exists at the molecular level and it can be a target for pharmacological therapy. So I think this is what I would like to transport with this study to the clinical community and the basic science community.

Dr. Mercedes Carnethon:

Yeah. I think this is the point at which Charlie, I turn it to you because you really stand at the intersection of both of those communities. What questions do you have for Miriam going forward, as you think about spreading the word on this important work?

Dr. Charles Lowenstein:

So Miriam's discovery is just so important and she now has the tools to help answer really, really important questions. How is nitric oxide made in red blood cells? How is it stored in red blood cells? How is it transported throughout the body in red blood cells? What is the chemistry of nitric oxide, when it is stored, when it combines with oxygen when it forms nitrite and nitrate, how is it released from red blood cells? How is it targeted from a red blood cell to the vasculature? So there're these great basic science questions that Miriam and her colleagues are now poised to answer. So there's the science part of it. Then there's the medicine part of it because Miriam's mice and her great discovery have really huge implications for medicine. And so the question is, how can we use ENO? How can we deliver it? How can we target ENO to human tissues?

Dr. Charles Lowenstein:

How can we turn on erythrocyte, nitric oxide synthase? How can we turn it off? Because there are all these medical diseases where too much nitric oxide is bad, like in sepsis or inadequate amounts, don't protect the vasculature like atherosclerosis. Then there are all these other interesting questions. When we transfuse red blood cells, sometimes if you transfuse aged red blood cells, it's not good. You can harm people. Maybe we can load up or activate eNOS in stored red blood cells and then help deliver more ENO to patients who need red blood cells. So there are all these fascinating medical questions that we can look at based on Miriam's really important discovery.

Dr. Mercedes Carnethon:

Well, thank you so much. We're coming to the end of this wonderful and informative podcast. And I guess, I'd just ask Miriam, do you have anything else you'd like our listeners to know about your work and about the findings from this study?

Professor Miriam Cortese-Krott:

I would like people know that hard work help a lot, and that you have to believe in what you are doing and the quality of your science at the end would bring their true discoveries. So I think it's important specifically, for the young women in science that having this message too. So the science per se must be excellent and to proceed, you need a lot of work, but then the work goes to a good end.

Dr. Mercedes Carnethon:

Miriam, thank you so much for that inspirational note. The hard work that scientists need, the persistence across one's career and building from earlier discoveries, and bringing those forward through one's career are always critically important. And so I hope everyone has really enjoyed this episode and this opportunity to hear from Dr. Cortese-Krott. Miriam, you've done such wonderful work, and thank you as well, Charlie, for your insights about the intersection of this work with clinical care and basic science.

Professor Miriam Cortese-Krott:

Thank you.

Dr. Charles Lowenstein:

Thank you.

Dr. Mercedes Carnethon:

Thank you all very much for joining us today in this episode of Circulation on the Run.

Dr. Greg Hundley:

This program is copyright of the American Heart Association, 2021. The opinions expressed by speakers in this podcast are their own and not necessarily those of the editors or of the American Heart Association. For more, visit ahajournals.org.