Dan Keller: Hello, and welcome to Episode Thirty-six of Multiple Sclerosis Discovery, the podcast of the MS Discovery Forum. I’m your host, Dan Keller.
This week’s podcast features an extended interview with Jenny Ting, an immunologist who studies the inflammasome, a multi-protein oligomer that’s part of the innate immune system. But to begin, we’d like to tell you something about why we started the MS Discovery Forum.
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Now to the interview. Dr. Jenny Ting is Professor of Microbiology in the Institute for Global Health & Infectious Diseases at the University of North Carolina at Chapel Hill School of Medicine. In addition to MS, Dr. Ting’s research interests include the role of the immune system in infection, inflammation, and cancer. Science Journalist Carol Morton caught up with Dr. Ting at a recent Keystone meeting.
Carol Morton: I appreciate your taking time out to talk to MS Discovery Forum. So we’re at the Keystone meeting on Neuroinflammation in Taos, New Mexico, and you gave a very interesting talk today.
Jenny Ting: Thank you.
Morton: So can you tell us what you’re talking about when you’re talking about the inflammasome and the particular proteins that you’ve been looking at.
Ting: The groups of proteins that we work on are cytokines, and cytokines are made by immune cells. And they have a tremendous impact on inflammatory responses. As you know, in MS there is a big immune component, so these cytokines will influence it. And in most cases cytokines activate the immune system. One of the key cytokines that we’ve studied is called IL-1, interleukin-1 beta; this is the one, for example, that causes fever, inflammation, and so forth. So it’s called interleukin-1 because it was the first one discovered, and it turns out it’s probably one of the most important ones.
So because it’s a master cytokine, and once it goes it kicks off all the other cytokines, so there’s a cascade that goes on. So it could activate other cells to make other cytokines, so it’s like a vicious cycle. Obviously, this becomes a pretty important target to think about. The process that causes this cytokine to be produced is a very big molecule that’s comprised of different proteins. And these different proteins, they are, together, called the inflammasome for inflammation large complex because “some” means large complex. Inflam- is inflammation, as in inflammasome. It’s the name given by Jürg Tschopp.
And so this process where you have this big complex, and as a result you get the cytokine called interleukin-1 beta, what happens is that interleukin-1 beta has now been implicated in so many diseases including arthritis, very rare diseases that causes a lot of inflammatory responses. It’s involved in skin allergies. It’s involved in colitis, you name it, and it’s involved in smoke-induced chronic obstructive pulmonary disease, COPD, that we see advertised on TV. So all of these have this component of this molecule.
Morton: So anything that releases IL-1 beta, inside the cell there’s a cluster of proteins that have to come together to make it.
Morton: And then it gets secreted and does its job.
Ting: Yes. And as we learned today, and actually it’s been published, but may be new to some of the audience, is that this whole complex can also be excreted in some ways into the cell, you know, pushed outside of cells so it can go from perhaps one cell to the other. So we have previously found that this can be a complex that’s membrane bound, and that’s called an exosome. So it’s both just like a minicell that goes from one cell to the next and make the next cell inflammatory as well. The speaker today showed that, in addition to that, it can also go out as a complex, perhaps naked. It seems like they are not really membrane bound, so that’s a different form. So it could be different forms that goes out from one cell to the next causing inflammasomal activation in the next cell and therefore perpetuates this IL-1 process.
Obviously, in normal hosts there must be a way to turn off this process, otherwise we would be, you know, a little ball of pus sitting on a chair. So obviously these don’t go on forever. The problem with chronic inflammatory diseases is many of these things, they don’t go on probably all the time, but they do increase. So what we did is really look at mice lacking genes that can make these proteins. This complex is usually comprised of at least three components; you knock out one and you can’t make IL-1 anymore. Actually, I should say five components. So we did that, and what we found was that if you take this out, the models of MS suggests the well-known mouse model, EAE, and another model that we’ve been really pushing, although it was initially worked on in the late 1960s and early 70s, this model of neurotoxicant-induced demyelination. In both of those models this process of inflammasome/IL-1 turned out to be bad.
So if you remove this process, the disease is much more attenuated. So that’s one of the really interesting parts about what we had found is that potentially this could be a target. And the good thing is that there is certainly some companies that have successfully made anti-IL-1s. So there is an IL-1 receptor antagonist that inhibits this process. There is an antibody against IL-1 that will inhibit this process. So certainly there are therapies, if this is true, that this is part of the MS problem that this could be used as a therapy.
The other thing we have found, which I didn’t get a chance to talk about, is that we did look at the remyelination phase and found out that, for example, IL-18 is not very good for remyelination. Of course, remyelination is what everybody would like to have, is a reparative process. And so one possibility is, can we block the IL-18 pathway, and can we get better remyelination processes. So those are some of the thoughts that we have.
Morton: So have you examined a number of the ILs from 1 to 18 or…?
Ting: No, because 18 is the product. So this inflammasome actually has many different targets. One of them is IL-1 beta; that’s the key one. Another one is IL-18. So we went from there to look at what’s downstream of the inflammasome and found out that IL-18 actually has a role both in making MS disease models worse and in reducing the extent of remyelination. So it doesn’t look like it’s a great protein to have around. So the question is can we try to inhibit this molecule.
Morton: Just to make sure that I’m clear on that: the inflammasome is a cluster of proteins that come together in an immune cell, like a T-cell, or a…
Ting: Usually it’s a macrophage or a microglia or an astroglia.
Morton: A macrophage or a microglia. And then that makes the IL…
Ting: So what you have is – I don’t know if the audience might be familiar with the coagulation pathway where you have one protein that has to be cleaved into a smaller protein. Then this protein B goes and cleaves a second protein from a bigger form to a smaller form. And the smaller form, in every case, is the mature protein that has activity. The bigger protein is the inactive form that doesn’t do anything. So this exactly the same. Pro-IL-1 has to be cleaved into IL-1. Pro-IL-18 has to be cleaved into IL-18. And what that cleavage process is this inflammasome complex producing an enzyme that will cleave these proteins.
Morton: So the inflammasome is like Edward Scissorhands running around cutting proteins making them active.
Ting: Yes, that’s a great analysis. So it’s just exactly like that. The inflammasome produces this – like you said – Edward Scissorhand that then this guy can go and prune the roses and prune the bushes, and they’re different, and they have different functions.
Morton: And it’s the starting block for the activity of the IL-1 and IL-18.
Ting: Right, so the bushes are like – if the roses are the IL-1, you can decorate it; you can give it to somebody; you can make it into a bouquet. So that’s the kind of idea. And then if you have a bush, you know, you can potentially do other things with it. Or if he’s cutting some edible plants you can use that for cooking. So that’s the whole idea. Whatever you produce has different effects. And it turns out IL-18, in our hands, looked like it’s not a good molecule. We have previously found that a cytokine called TNF, which has different roles depending on what it binds. So if it binds to TNF receptor 1, then it’s not so good. If it binds to TNF receptor 2, it actually enhances remyelination, so again, something you want.
And there’s recent talks and there are small molecules where people tried to activate the TNF receptor 2 pathway, and they found that that really enhances the remyelination process. It’s kind of really neat; if you can dissect these pathways well enough, then you might be able to use drugs to target MS.
Morton: So what are the next questions that you’re asking? Where are you going from here?
Ting: So we have a number of directions. Certainly, like I say, I raised the concept of IL-18; so can we target that molecule? In our own lab we’re also looking at several other pathways. So we have found a pathway that’s really important for cell-cell interaction that’s important for MS activation. And the molecules are called plexins and semaphorins. And this is a pair of proteins that seems to activate the immune system especially during MS. So we’ve done that in disease models, and we actually produce a blocker of that pathway. And we have treated mice, and they look much better. We showed that when they’re going through relapse, we can actually prevent them from coming back with a relapse.
So, very similar to some other MS drugs that are on the market, we’d like to think about this as additional possibilities. So those are some of the things that we’re doing.
Morton: What cells are these on?
Ting: These are T-cells and dendritic cells so they’re…
Morton: They’re talking to each other.
Ting: Yes, exactly, they’re talking to each other. And in an MS situation they talk to each other, they activate T-cells, which destroys the myelin. So if you can block that interaction, many of the drugs that are used for MS actually are targeting exactly that interaction pathway. For example, Tysabri is one that’s not so much dendritic cells and T-cells, but it reduces T-cell migration through the vasculature into the blood brain barrier. So that’s one of them where they block T-cell activation. So we are trying to block T-cell activation as well, but at the face of these two cell types.
Morton: If the inflammasomes, if they were superheroes or characters in an Oscar-winning movie, what would their personalities be, do you think?
Ting: I think they would be very powerful because they impact a lot of disease processes, yet they have very strong roles so that, when they’re used properly, they can defend against all sorts of stuff. Whey they’re used improperly, they can really cause a lot harm. So if they’re a superhero, people always say Batman has a dark side, right, a really dark side and a really good side. Maybe that’s what they are.
Morton: That’s a good analogy.
Ting: They’re not like Superman because Superman seems like all good.
Keller: Thank you for listening to Episode Thirty-Six of Multiple Sclerosis Discovery. This podcast was produced by the MS Discovery Forum, MSDF, the premier source of independent news and information on MS research. MSDF’s executive editor is Robert Finn. Msdiscovery.org is part of the non-profit Accelerated Cure Project for Multiple Sclerosis. Robert McBurney is our President and CEO, and Hollie Schmidt is vice president of scientific operations.
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