Pursuing Deeper Understanding of Inflammation with Murali Prakriya, PhD

“We're on the cusp of potentially being able to develop … a new line of therapeutics to regulate inflammation. Whether it be inflammation in the brain, whether it be inflammation in the lung, there's an opportunity here to approach this problem from a completely different angle, in the sense that we're targeting a very specific pathway that has never been considered before.”  — Murali Prakriya, PhD 

• Magerstadt Professor of Pharmacology 
• Professor of Pharmacology and of Medicine in the Division of Allergy and Immunology 
• Member of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University 

Prakriya has spent the last two decades researching the ORAI gene and its relationship to calcium signaling and brain inflammation. Now on its way to human clinical trials, this breakthrough discovery will hopefully lead to a new line of therapeutics for inflammation.  

• Prakriya began his education in engineering before pursuing biomedical research. He ultimately earned a PhD in neuroscience at Washington University where he studied calcium signaling and trained as a biophysicist with a highly respected ion channel biologist, Dr. Chris Lingle.  
• In 2006 when he had just joined Northwestern, Prakriya worked with colleagues at Harvard and Stanford to identify the ORAI proteins as the molecules encoding CRAC channels. This work came from analysis of the T-cells of children suffering from a severe immunodeficiency. CRAC channels are critical for the function of many immune cells including T-cells and mast cells and this important discovery opened a new understanding of the mechanisms of inflammation and immunity. 
• This breakthrough catalyzed Prakriya’s research efforts over the next 18 years on the mechanisms of ORAI channels operation and their physiological contributions for immunity, brain function and lung inflammation.
• Prakriya’s current research is focused on addressing the relationship between the ORAI calcium pathway and uncontrolled inflammation, which frequently shows up in many brain disorders, causing significant damage beyond the disease itself. 
• Prakriya’s team has discovered that two glial cell types in the brain — astrocytes and microglia — drive neuroinflammation associated with neuropathic pain and depression in large part due to excessive activation of the ORAI calcium pathway, causing excessive production of damaging inflammatory cytokines.   
• Inhibiting the ORAI pathway in astrocytes or microglia by pharmacology or gene silencing mitigates the damaging neuroinflammation.
• Prakriya expects that a therapeutic window will be identified to safely inhibit ORAI activity in inflammatory syndromes and is hopeful that the ongoing human clinical trials will yield a new line of therapeutics targeting ORAI channels to dampen damaging inflammation in brain and lung disorders.   

Additional Reading 

• Find out more about an earlier paper, published in Science Signaling, that laid groundwork for this latest advance 
• Read an article published in Science Advances by Prakriya’s lab that identifies how specific calcium channels help regulate sex differences in the functioning of immune cells for neuroinflammation and overall neuropathic pain 
• Explore Prakriya’s lab 

Recorded on December 7, 2023.

Target Audience

Academic/Research, Multiple specialties

Learning Objectives

At the conclusion of this activity, participants will be able to:

1. Identify the research interests and initiatives of Feinberg faculty.
2. Discuss new updates in clinical and translational research.

Accreditation Statement

The Northwestern University Feinberg School of Medicine is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

Credit Designation Statement

The Northwestern University Feinberg School of Medicine designates this Enduring Material for a maximum of 0.50 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

American Board of Surgery Continuous Certification Program

Successful completion of this CME activity enables the learner to earn credit toward the CME requirement(s) of the American Board of Surgery’s Continuous Certification program. It is the CME activity provider's responsibility to submit learner completion information to ACCME for the purpose of granting ABS credit.

All the relevant financial relationships for these individuals have been mitigated.

Disclosure Statement

Murali Prakriya, PhD, has nothing to disclose. Course director, Robert Rosa, MD, has nothing to disclose. Planning committee member, Erin Spain, has nothing to disclose. FSM’s CME Leadership, Review Committee, and Staff have no relevant financial relationships with ineligible companies to disclose.

[00:00:00] Erin Spain, MS: This is Breakthroughs, a podcast from Northwestern University Feinberg School of Medicine. I'm Erin Spain, host of the show. Inflammation is a common feature of many neurological and lung diseases. Northwestern Medicine investigators have identified how a calcium channel contributes to such inflammation and could aid in the quest to find new types of therapeutics for inflammation-related diseases and conditions. Joining me to discuss this work is Dr. Murali Prakriya, a professor of pharmacology and a professor of medicine in the Division of Allergy and Immunology at Northwestern University Feinberg School of Medicine. Welcome to the show.  

[00:00:55] Murali Prakriya, PhD: Thank you, Erin. I'm glad to chat with you.  

[00:00:58] Erin Spain, MS: I want to talk about your background and the work that you have been doing in this specific calcium channel. This has been decades of work. Take us back and tell me the story about how all of this began.  

[00:01:10] Murali Prakriya, PhD: Sure. Let me just go way back. I'm actually an engineer by training in terms of my undergraduate education, and ended up pursuing biomedical research in a somewhat circuitous fashion, getting a master's in engineering along the way as well and then switching to neuroscience for my PhD at Washington University, where I studied calcium signaling with one of the giants in the field of ion channels and calcium signaling at that time. His name is Chris Lingle. And I was trained as a biophysicist where I was able to apply my engineering skills and engineering principles to understand how these molecules work by looking at their single molecule behavior using an approach called patch clamp electrophysiology. After that, I kind of continued my interest in understanding calcium signaling by doing a postdoctoral fellowship with Dr. Richard Lewis at Stanford University. And it is here that I really got involved in working on the topic that I continue to work on today, which is these ORAI family of calcium channels. And the way we got into the field at the time was that my postdoc mentor, Richard Lewis, was one of the first, if not the first, actually to record electrophysiologically the activity of the calcium channel that we now call ORAI. But at that point of time, the gene or the protein that encodes that calcium channel, its identity was unknown. So, I teamed up with another postdoc at Harvard at the time by the name of Stefan Feske, and the two of us with our respective mentors started working on trying to identify the molecular basis of this pathway, this calcium channel pathway, which was beginning to be appreciated as being really critical and important for the immune system and for immune cell activation. So this was a pathway that the field at the time, the calcium pathway that the field called the CRAC Channel Pathway, which stands for Calcium Release Activated Calcium Channel.  

 [00:03:11] Erin Spain, MS: It was during this time that there were many people who were really on the hunt to understand the molecular basis of this CRAC channel. Why is that? 

[00:03:21] Murali Prakriya, PhD: So this CRAC channel which was beginning to be appreciated as being essential for activation of the immune system, especially in cell types like T cells and B cells where genetic evidence and some pharmacology was accumulating that if you block the activity of this CRAC channel, you can basically shut down the T cell and B cell part of the immune system. Very powerful and very important, obviously, for human immunity. So, my friend and colleague, Stefan Feske, trained in Germany as a physician, and he was following these children who were suffering from an unknown form of immunodeficiency. And it was not clear what the mechanistic basis of this immunodeficiency was, and working with his mentor at the time who was an immunodeficiency expert, they came to the conclusion that the immunodeficiency in that family, these were kids at that point was caused by lack of activation of T cells when they're challenged with an antigenic or a pathogenic stimulus. So subsequent work then identified that this was, in fact, a defect in the calcium signaling. Now it turns out that calcium is a very important signaling molecule or a signal transduction molecule. It works as a switch to turn on or turn off pathways, effector cell responses in immune cells, in the muscle, in the heart, in the brain, and so forth. And the way that typically works is that there are these signals, calcium signals, the concentrations of calcium go up and down within cells, encode information in a sort of like a biological Morse code, if you will. The cell has ways of decoding those rises and falls in calcium signals to then drive or activate downstream biological responses, like muscle contraction in the case of muscle, neuronal communication in the brain or generation of inflammatory mediators by immune cells and by many other types of cells as well. So, it turned out that we found that these children in this particular family had a mutation that caused the CRAC channel activity to be lost, to be completely lost, and that was a very exciting finding because that was the very first time that we were able to have essentially a null background. And if we could figure out what was causing that null functional background, then we might be able to identify the gene and the protein that encodes this particular channel.  

[00:05:54] Erin Spain, MS: So that was really a breakthrough in a lot of ways and set the stage for the work that you would do for the next nearly 20 years.  

[00:06:01] Murali Prakriya, PhD: For 20 years. Yeah, exactly. So, we undertook a collaboration where we then analyzed the cells from this patient, because basically by analyzing the inheritance form, inheritance of the disease, and of the calcium phenotype in the extended family, you can basically zero in on at least a region of the chromosome, and then ultimately we arrived at this particular gene that was annotated as a gene of unknown function in the Human Genome Database at that point. This is back in 2005 and 2006. And this gene was called ORAI, and there are three ORAIs in humans, ORAI1, ORAI2, ORAI3. And these form the highly calcium selective channels whose loss of function led to the immunodeficiency. The immunodeficiency is very severe, and it usually results in these individuals passing away within the first year after birth because of opportunistic bacterial and viral infections. So, that sort of set the stage for now, trying to understand, now that we have a gene and we have a protein, we could then begin to understand how the pathway works, because at that point, we had no idea how the channel was activated. So we, along with many other labs, by "we" I mean, you know, not just my lab, but along with many other labs. I joined Northwestern University in 2005, right at the time when this discovery was made. So basically we were in a very strong position to leverage the discovery, take it up to the next level. And we spent about 15 years, my lab spent about 15 years or so trying to understand, you know, how is the channel activity controlled, how is it activated by environmental stimuli, what happens in disease causing mutations that eliminate channel activity, and how is that then linked to the phenotypes, the immunodeficiencies, and other immune disorders. The most prominent disorder of loss of function mutations in this particular channel is the lack of immune system activation. And so that immediately clued us in that an important way of perhaps dampening down immune system activation may be to decrease, maybe not entirely kill, but decrease channel activity into a sweet spot where it might then be exploited potentially for therapeutic applications related to runaway and uncontrolled inflammation. And that's the angle that we've been pursuing in the last few years.  

[00:08:25] Erin Spain, MS: Tell me more about this critical balance required in managing inflammation. 

[00:08:30] Murali Prakriya, PhD: So even though the role of this particular pathway in the immune system has been fairly well established, that this is essential for host defense, for human immunity, and for triggering inflammation in a good way. And that is necessary to fight pathogens and to fight infections. Now, that said, uncontrolled and runaway inflammation is frequently seen in many disorders, many brain disorders, for example, or it's thought that there is a pretty substantial inflammatory component. Depression is one of these. Another is the neuropathic pain that develops chronic pain that develops after, for example, nerve injury or some other syndrome. And there are many other situations where uncontrolled inflammation is not a desirable endpoint. And this is exactly also true in the lung where inflammation that arises after COVID pneumonia, for example, can be quite dangerous. And if it is not properly dampened, it's not really the bug that does most of the damage after a certain point. It's actually your own immune system that's attacking and damaging delicate cells and delicate organ systems. So it's important to figure out ways to dampen that. And historically the way the approach has been to use very broad spectrum inhibitors that affect a lot of different pathways and cell types. Steroids are a frontline mechanism for controlling lung inflammation. For example, in asthma patients and other inflammatory diseases. Steroids are also used in certain other inflammatory conditions affecting the brain and other parts of the body. Anti-inflammatories that inhibit COX enzymes like ibuprofen, for example, have been shown to be potentially useful in certain types of brain inflammatory diseases. But these are not, I would say that these are not optimal therapeutic approaches. And that's because we don't know how to use a fine approach. The toolkit is somewhat limited at this point in terms of what molecules can be manipulated to dampen inflammation.  

[00:10:34] Erin Spain, MS: So that's led your group to this particular channel, and you've been exploring this angle and the brain focusing on two cell types that really play an outsized role in driving brain inflammation. You've published about this work. Can you tell me more about this?  

[00:10:51] Murali Prakriya, PhD: One of these cell types is called the astrocyte and the other cell type is called the microglia. Now, both of these cell types form a set of non-neuronal cells in the brain that are broadly referred to as glia. Their origins are actually quite different, but both are referred to as glial cells. And what they do is, in addition to some of the other functions that they might facilitate, like neural development, stabilizing connections between neurons, and so forth in the brain, these cells also play a very important role in causing inflammation. They're essentially, you can consider them to be innate immune cells. They have the ability to produce large quantities of inflammatory cytokines, like interferons, for example, or IL 6 which If not properly regulated, it can cause tissue damage and even neuronal death. That's not a desirable end point. And so what we have been exploring is, can you dampen brain inflammation in certain inflammatory conditions? For example, after nerve injury or inflammation induced depression, by genetically ablating this channel just in those cell types, either in astrocytes or in microglia, because that gives us a very fine and precise way of manipulating the activity of a particular cell type, because the channel exists in nearly every cell in our body. And can that selectivity then be used to understand, number one, the role of those cells, those astrocytes in the microglia, in driving brain inflammation, because that itself is not very well established. And number two, could it give us clues for the use of small molecule compounds, ultimately to develop a new line of therapeutics? Not the ones that are currently out there, but a new line of therapeutics that targets ORAI channels for regulating either brain inflammation for the conditions that I talked about, or lung inflammation in situations where excess inflammation is undesirable.  

[00:12:47] Erin Spain, MS: You're doing these studies in mice right now, but there are some opportunities to do this in humans as well. Tell me a little bit about the work that you're doing with mice that is featured in these recent studies, and then also what you're able to do right now in some human trials.  

[00:13:04] Murali Prakriya, PhD: The mouse studies are useful and important because they provide the preclinical foundation, the mechanistic foundation for understanding how this ORAI signaling pathway is controlled, regulated, and what are its potential physiological functions. You can, for example, manipulate this pathway in the way we want to in higher animals, and there's extensive genetics available. There are genetic approaches where we can use to selectively eliminate this particular pathway in either astrocytes or in microglia or in neurons. And among neurons, we can eliminate it in a subtype specific way in excitatory neurons or inhibitory neurons or so forth. And we've done all of that. We have ablated this channel in nearly every brain cell type that you can imagine. And there are phenotypes, and so the mouse studies were very useful in basically establishing the physiological role of ORAI channels in astrocytes, for example, where they're highly expressed, as well as in microglia. And we showed that in the cell types ORAI channels, ORAI1 channels in particular, are a major, in fact, the primary mechanism for calcium entry across the plasma membrane, and they're necessary to produce the sustained calcium signals that are then connected to these downstream inflammatory functions. So that's the first thing it establishes, the presence and the identity. And it's at a mechanistic level, its connection to downstream physiological functions in that particular cell type. And that in itself is an important discovery because the role of calcium signaling, and more broadly, astrocytes and regulating different brain functions is also not that well understood. So it's not just that we are focusing on ORAI, but we are using ORAI as a way to try to understand what is it that astrocytes are doing for brain inflammation. And that's the broader question. Same thing for microglia. What is it that microglia are doing for brain inflammation? And what we find is that by silencing a particular pathway in those particular cell types, we have, number one, found that those cell types are actually very important for driving inflammatory phenotypes connected to neuropathic pain or connected to depression, for example. Number two, we have identified this channel as an important mechanistic link in causing astrocyte mediated brain inflammation. And so now we have the preclinical foundation then to basically ask, if you now come in with a drug, which is not going to just only hit astrocytes, but it'll hit multiple different cell types, including microglia and of course the neurons, not to speak of all the other organ systems in the body, what is the therapeutic window that we can leverage to where we can safely dampen the activity of this channel in astrocytes, in microglia to get a beneficial effect on a transient, on a temporary basis without causing, for example, immunodeficiency, which is undesirable because we know that if you eliminate the channel altogether, then you end up with an immunodeficient patient. And that's not what we want. What we want is a much more targeted beneficial endpoint. And so there's some distance to go before we can get there. But the good news is that there are small molecule drugs that are now in clinical trials. And Northwestern itself is actually the hospital here is a part of a multi center clinical trial that's using an ORAI1 channel blocker for dampening down inflammation in the lung in this particular trial that is caused by COVID to prevent COVID pneumonia and to dampen down airway inflammation in that particular endpoint. The drug appears to be safe. It has completed the phase one and phase two trials, and so that's very promising, and if it shows efficacy, which it very well might given its safety profile, it's possible that other applications of the drug could emerge on the horizon for dampening down inflammation and other contexts like in depression, for example.  

[00:17:09] Erin Spain, MS: I mean, this is a point in research that a lot of folks never get to see actually going into human clinical trials. And you seem very hopeful there could be new therapies on the horizon. Would you agree? 

[00:17:21] Murali Prakriya, PhD: Oh, I'm extremely excited and extremely hopeful, because it appears that there is a therapeutic window that, in fact, can be exploited safely without causing dangerous side effects and dangerous endpoints. Even though the channel exists in multiple cell types, its connection to physiological functions in different cell types, they're not all equal. So for example, in immune cells you can target, you can block this pathway in particular types of immune cells and dampen down their ability to synthesize excess amounts of dangerous inflammatory mediators like interferons, for example, or cytokines, without really affecting a certain amount of inhibition the activity of other cell types. And so that's where the therapeutic window becomes important. And a lot of this is empirical. And what we're finding is that you can, in fact, there is a safety margin that can be exploited without shutting down all cells. 

[00:18:23] Erin Spain, MS: How exciting. You know, you've been recognized for your work. The American Association for the Advancement of Science named you a fellow in 2022. And there have been other folks who have been recognizing this work. Just tell me what it's like to be at this point in your research and your career where these honors and these different associations have been recognizing your work.  

[00:18:44] Murali Prakriya, PhD: Yes, that was very gratifying to see and I greatly appreciate the recognition from my peers and from my colleagues and from the broader community. That's important. It's really a recognition of the work and the motivation and efforts of the people in my lab, the students and the amazing postdocs that really worked hard. I've been really fortunate in having amazing graduate students, PhD students, and MD-PhD students, over 10 of them in the lab in the last 18 years that I've been here at Northwestern, and an equal number of postdocs. Certainly grateful to my mentors, former mentors, and my current chair, who has been extremely supportive and nominated me for this award. So it's really a tribute to the lab trainees and the lab postdocs and students who push this work.  

[00:19:35] Erin Spain, MS: As we wrap up today, what's the number one thing you would like listeners to walk away with understanding about your research. 

[00:19:43] Murali Prakriya, PhD: This ORAI pathway that we are studying is very poorly understood in the brain. So at the outset, it's important to state that even though it is understood in the peripheral immune system, in T cells, B cells, for example, the physiology and the physiological roles, and the pathophysiological roles of this pathway in the brain, these are extremely early days right now. I mean, and I would say that, you know, my lab is really at the forefront of trying to understand what this pathway is doing in the brain. There's not very many labs that are studying this, and for a very long time, this pathway was ignored in the nervous system. And what we're finding is that through these genetic studies, is that nearly in every cell type where we are looked at in the brain, this pathway is playing a very important role.  It's playing an important role in astrocyte mediated inflammation and microglial mediated inflammation. It's playing a very important role in neurons in regulating process called synaptic plasticity which is very important for learning and memory and cognitive functions. So the bigger story here is that, you know, we are trying to understand the role of this signal transduction pathway in the nervous system and its potential links to a variety of neurological diseases, including neurodegenerative diseases, for example, like Alzheimer's disease. I think we are at a point now where we're on the cusp of potentially being able to develop --by we I mean not just my lab per se, but the broader field-- a new line of therapeutics to regulate inflammation. Whether it be inflammation in the brain, whether it be inflammation in the lung, there's an opportunity here to approach this problem from a completely different angle, you know, in the sense that, we're targeting a very specific pathway that has not, never been considered before. And so that's the exciting part. It appe ars that this is a pathway that can be exploited for therapeutics potentially as much safety as the currently available therapeutics. And the genetic evidence bears it out, and I think increasingly the pharmacological evidence also is bearing that out, and I think this could be another tool in the toolkit because of the diversity of patient population, you can never really rely on one particular drug to have a beneficial effect in the entire population. If you take steroids, for example, for asthma, about 30 percent of the patients, they never respond to steroids. They don't benefit from the inhaled steroids that have been a game changer for dampening down the inflammation. And because this is a pathway that's at the top of the chain of events that drives inflammation, we think that this could be at least as powerful, if not more powerful than some of those powerful anti-inflammatory agents that are being used for airway inflammation and other endpoints. So I think we are at an exciting phase. The next five years, in my opinion, are gonna be critical in revealing whether or not this is going to be possible . 

[00:22:48] Erin Spain, MS: Well, thank you so much for coming on the show and talking about really your decades of research and these exciting discoveries that have recently been made. Thank you so much for your time.  

[00:22:58] Murali Prakriya, PhD: Thank you, Erin.  

[00:22:59] Erin Spain, MS: Thanks for listening and be sure to subscribe to this show on Apple Podcasts or wherever you listen to podcasts and rate and review us. Also for medical professionals, this episode of Breakthroughs is available for CME credit. Go to our website, feinberg. northwestern. edu and search CME.