Role of Chronic Inflammation in Risk for Neurodegenerative Disorders: Alzheimer’s Disease

Video Transcript

• 00:00 - 00:16: Hello, my name is Malu Tansey.
• 00:16 - 00:21: I’m a professor at the University of Florida College of Medicine in the Center for Translational
• 00:21 - 00:24: Research in Neurodegenerative Disease.
• 00:24 - 00:28: And today I’m going to talk to you about the role of chronic inflammation in neurodegenerative
• 00:28 - 00:33: disease and we’ll focus specifically on Alzheimer’s disease.
• 00:33 - 00:39: The objectives for today’s lecture are to understand the role of immune aging in the
• 00:39 - 00:42: risk for age-related neurodegeneration.
• 00:42 - 00:50: We’re going to try to outline and understand how genetic predisposition and chronic inflammation
• 00:50 - 00:57: may lead to innate immune dysfunction and describe an alternative view of Alzheimer’s
• 00:57 - 00:59: disease pathogenesis.
• 00:59 - 01:05: We’re also going to discuss and understand how targeting soluble tumor necrosis factor
• 01:05 - 01:11: could mitigate the effects of chronic inflammation that are associated with an obesogenic diet
• 01:11 - 01:18: and its effects on metabolic dysregulation and how it may lower the risk for development
• 01:18 - 01:21: of Alzheimer’s disease.
• 01:21 - 01:25: The road map specifically is here.
• 01:25 - 01:30: We’re going to talk about how the brain is really not an immune-privileged organ.
• 01:30 - 01:37: We’re going to talk about microglia, the brain resident immune cells, how immune aging is
• 01:37 - 01:40: kind of a two-headed monster.
• 01:40 - 01:47: We’ll talk about what the genetics tell us about Alzheimer’s disease and the current view
• 01:47 - 01:48: of Alzheimer’s.
• 01:49 - 01:56: Then we’ll flip to an alternate view of Alzheimer’s disease and the amyloid hypothesis.
• 01:56 - 02:02: Then I’ll discuss how targeting soluble tumor necrosis factor may be an alternative therapeutic
• 02:02 - 02:11: approach that may be very possible to couple with amyloid therapies to lower risk for Alzheimer’s
• 02:11 - 02:12: disease.
• 02:12 - 02:22: Finally, we’ll discuss how targeting microbiome and the triaccess of brain, gut, blood be
• 02:22 - 02:28: a beneficial way to lower risk for Alzheimer’s disease.
• 02:28 - 02:33: So I want to start out with this schematic that should dispel the myth that the brain
• 02:33 - 02:36: is an immune-privileged organ.
• 02:36 - 02:45: We all were told that the brain was immune-privileged and there was no way that immune cells or
• 02:45 - 02:49: immune attacks could happen in the brain.
• 02:49 - 02:51: That’s actually very far from the truth.
• 02:51 - 02:59: It turns out that immune function and immune system and the brain work very closely together.
• 02:59 - 03:05: This bi-directional communication between the brain and peripheral organs is critical
• 03:05 - 03:06: for brain health.
• 03:06 - 03:15: And Tony Wyss-Coray described this bi-directional communication in this review in 2012, where
• 03:15 - 03:23: he describes that at the cellular, at the tissue, and at the organismal level, you have
• 03:23 - 03:34: this communication between cytokines and cells and glia and neurons and tissues that is super
• 03:35 - 03:39: critical, not just for development, but for function.
• 03:39 - 03:45: And if this is disrupted at any point, then you can be prone to pathology.
• 03:45 - 03:52: And so when people talk about cytokines, they often discuss how detrimental they can be
• 03:52 - 04:00: to the brain and to tissues, but they very rarely appreciate the fact that these are
• 04:00 - 04:06: important for normal function, and it’s only when they’re overproduced or produced at the
• 04:06 - 04:11: wrong time or in the wrong place that they set you up for pathology.
• 04:11 - 04:16: So that’s the first thing that you need to appreciate, that this bi-directional communication
• 04:16 - 04:22: is very critical for health of the brain, as well as the health of peripheral organs.
• 04:22 - 04:29: So the microglia are the brain-resident immune cells, and they are tasked with surveilling the
• 04:30 - 04:34: environment, with keeping neurons healthy.
• 04:34 - 04:39: You can think of them as the parents of the environment.
• 04:39 - 04:41: They take care of neurons.
• 04:41 - 04:44: Without them, the neurons would probably die.
• 04:44 - 04:47: And so they provide trophic support.
• 04:47 - 04:50: They secrete cytokines and cytokines.
• 04:51 - 04:53: They move around.
• 04:53 - 05:00: They phagocytose, then they clean up debris, including amyloid, and they respond to a lot
• 05:00 - 05:05: of signals that the neurons give off, and they also touch the neurons.
• 05:05 - 05:11: So they function with the cell-to-cell communication set of ligands, as well as responding to ligands
• 05:11 - 05:18: that are secreted by the neurons, including ATP, which is the signal that neurons may be in trouble.
• 05:19 - 05:25: And so they’re basically the brain-resident vacuum cleaners, and they’re important for
• 05:25 - 05:29: keeping everything copasetic and homeostatic.
• 05:31 - 05:35: One important role of microglia is to present antigen.
• 05:35 - 05:41: And what this means is that when they engulf pathogens, or they engulf any kind of debris,
• 05:41 - 05:49: they chew it up, and then they decorate themselves or their surfaces with small bits and pieces of
• 05:49 - 05:57: this pathogen, or peptides, or protein, and they display it on their surface on a complex
• 05:57 - 06:02: of proteins called major histocompatibility complex, or MHC.
• 06:03 - 06:07: In humans, they’re called HLA, or histocompatibility leukocyte antigen, HLA.
• 06:08 - 06:16: And they are basically presented or shown to naive T-cells, and T-cells are part of
• 06:16 - 06:17: the adaptive immune system.
• 06:18 - 06:25: And when they present these bits and pieces of chewed up antigens, they basically cause
• 06:25 - 06:32: the adaptive immune arm of the immune system to become mature and differentiated.
• 06:32 - 06:35: And this is how they become activated.
• 06:35 - 06:37: This is how they grow up, if you will.
• 06:37 - 06:46: And so this antigen presentation is a key role of innate immune cells, microglia, monocytes,
• 06:46 - 06:47: dendritic cells.
• 06:47 - 06:53: And all these innate immune cells are therefore harmless to be able to activate the adaptive
• 06:53 - 06:59: immune arm, which is the more newer, in terms of evolution, arm of the immune cell, immune
• 06:59 - 07:00: system.
• 07:00 - 07:03: This is super critical for keeping you healthy.
• 07:03 - 07:08: This is the adaptive immune arm that generates memory in your body.
• 07:08 - 07:17: And so depending on what kind of T-cell you become, you become a helper cell, a regulatory
• 07:17 - 07:23: T-cell, and there’s all these transcription factors called STATs that allow these cells
• 07:23 - 07:24: to become specialized.
• 07:24 - 07:28: And they produce different interleukins, shown here.
• 07:28 - 07:34: And these interleukins will then allow these cells to become important for autoimmunity,
• 07:34 - 07:42: for inflammation, for making anti-inflammatory molecules like TGF-beta.
• 07:43 - 07:49: And so this orchestration of innate and adaptive immune function is super important, both in
• 07:49 - 07:50: the periphery as well as in the brain.
• 07:51 - 07:59: Now, what happens when you age is that there becomes a process that we call age-related
• 07:59 - 08:01: immunodeficiency.
• 08:01 - 08:06: So these T-cells, as well as the B-cells that we didn’t talk about, but they’re also part
• 08:06 - 08:11: of the adaptive immune system, there’s a shrinking of these naive T-cells and B-cells, right?
• 08:11 - 08:17: So the more antigen is presented to them, the less naive cells you have and the more
• 08:17 - 08:18: mature cells you have.
• 08:18 - 08:24: So obviously, as you’re growing up, you have less naive cells and more differentiated and
• 08:24 - 08:26: mature T-cells and B-cells.
• 08:26 - 08:30: So there’s a shrinking of the naive T and B-cell compartment.
• 08:30 - 08:35: There’s also a contraction in the T and B-cell receptor diversity.
• 08:35 - 08:40: In other words, they’ve seen a lot, because you’ve been around, you’re growing up, and
• 08:40 - 08:41: you’re aging.
• 08:41 - 08:47: And so now there’s less opportunity for them to be able to respond to new antigens, and
• 08:47 - 08:49: respond to new antigens.
• 08:49 - 08:53: So an example, the coronavirus, right?
• 08:53 - 08:59: It’s a new virus and they have to pull another trick out of their hat to be able to respond
• 08:59 - 09:06: to this novel thing, because the older you are, the more difficult it becomes to respond
• 09:06 - 09:07: to new things.
• 09:07 - 09:13: So perhaps children are able to do it better because they have a more naive repertoire
• 09:13 - 09:15: of adaptive immune cells.
• 09:15 - 09:21: Another thing that happens when you age is this decreased T-cell receptor sensitivity
• 09:21 - 09:23: to respond to stimuli.
• 09:23 - 09:30: So again, you have fewer naive cells, fewer receptor diversity, and the sensitivity, your
• 09:30 - 09:34: ability to really sense that stimulus is worsened.
• 09:34 - 09:38: So that’s what we call an age-related immunodeficiency, right?
• 09:38 - 09:43: Not quite HIV, because that’s an acquired thing, but as you’re aging, you’re kind of
• 09:43 - 09:46: becoming age-related immunodeficient.
• 09:46 - 09:48: This is why it’s harder to immunize older people.
• 09:51 - 09:54: The other thing that happens is an age-related inflammatory syndrome.
• 09:54 - 09:55: So what does that mean?
• 09:55 - 10:01: This means that as you’re aging, the myeloid cells, the myeloid cells like monocytes, right?
• 10:01 - 10:08: And those are the ones that are predominantly producing cytokines and inflammatory factors.
• 10:08 - 10:15: They take over, and then there’s more of them and fewer T-cells and B-cells, and you
• 10:15 - 10:22: actually end up becoming more inflamed because they’re producing more of the cytokines like
• 10:22 - 10:27: interleukin-6 and tumor necrosis factor, and they’re the granddaddies of inflammation.
• 10:27 - 10:31: So now you have more of those cells and more inflammatory factors.
• 10:31 - 10:38: The last thing that happens is that you now are less able to recognize self, and the ability
• 10:38 - 10:44: to recognize self is very important because that’s how you prevent autoimmune disease.
• 10:44 - 10:50: So autoimmune disease is when you take something that is you and you say, okay, this is me,
• 10:50 - 10:52: I should not attack it, right?
• 10:52 - 10:59: And so MS, as an example, is your body’s ability to not recognize self, and it attacks the
• 10:59 - 11:00: myelin in your body.
• 11:00 - 11:06: And so it destroys the myelin, and then you lose the ability to conduct nerve impulses,
• 11:06 - 11:08: and that’s how you get MS.
• 11:08 - 11:15: And so as you get older, we become a little bit less tolerant of self, and you start attacking
• 11:15 - 11:17: tissues that are yours.
• 11:17 - 11:23: And so together, you have this impaired adaptive immune response, this constitutive low-grade
• 11:23 - 11:27: inflammation, and you’re kind of autoimmune, right?
• 11:27 - 11:33: So this is the double-headed immune aging, immunodeficiency, and inflammation.
• 11:33 - 11:41: So why is this important for age-related immunodeficiency and age-related neurodegeneration?
• 11:41 - 11:50: Because we are humans evolving in a society that are hunters and gatherers, right?
• 11:50 - 11:56: There’s been strong evolutionary pressure for our genes to develop strong immune responses.
• 11:56 - 11:57: Why?
• 11:57 - 12:00: Because of infectious disease, right?
• 12:00 - 12:02: And coronavirus is a perfect example.
• 12:02 - 12:06: We hang out in groups, and because we hang out in groups, we’re likely to infect each
• 12:06 - 12:09: other with things that are around.
• 12:09 - 12:14: And so evolution said, well, you’ve got to have strong immune responses.
• 12:14 - 12:22: And so because of that, we have evolved a way to have strong immune responses, but only
• 12:22 - 12:25: until you can pass on your genes, right?
• 12:26 - 12:33: So we have strong immune responses, but only until the early 20s, mid-20s.
• 12:33 - 12:34: What does that mean?
• 12:34 - 12:39: That means that by the time you get to be in your 20s or 30s, that’s all she wrote,
• 12:39 - 12:41: because you’ve passed on your genes.
• 12:41 - 12:48: So because of increased longevity, we’ve lived a little bit too long, and the chronic
• 12:48 - 12:54: antigenic mode, because we continue to live past the age of reproductive aging, right?
• 12:54 - 12:59: We now have inflammation, too much low-grade inflammation.
• 12:59 - 13:01: Our immune cells are aging.
• 13:01 - 13:03: They’re becoming less tolerant.
• 13:03 - 13:05: They’re becoming less competent.
• 13:05 - 13:08: So we have loss of immunocompetence, and we have autoimmunity.
• 13:09 - 13:16: We’re here, we’re more inflamed, and our immune system is aging right along with us.
• 13:16 - 13:25: Therefore, we believe that this immune aging is one of the big important factors why we
• 13:25 - 13:27: have Alzheimer’s and Parkinson’s disease.
• 13:27 - 13:32: Aging is the number one risk factor for these diseases, and we believe it’s important for
• 13:32 - 13:37: researchers to acknowledge this and study it more to understand the causes of these
• 13:37 - 13:38: diseases.
• 13:39 - 13:41: So let’s talk about Alzheimer’s disease.
• 13:41 - 13:47: A current view of Alzheimer’s is that you have microglia, which are in the brain, and
• 13:47 - 13:52: they’re perfectly happy, and they’re just basically sitting around, quiescent in what
• 13:52 - 14:01: they call an M2 phenotype, and they’re very happy, and they’re neuroprotective, vacuuming
• 14:01 - 14:05: up stuff, being anti-inflammatory, making neurotrophic factors that we talked about.
• 14:06 - 14:11: And then something happens, and the neurons start overproducing the amyloid beta.
• 14:12 - 14:20: And when that amyloid beta becomes too accumulated, and the microglia have this adaptive
• 14:20 - 14:26: response, right, and then the amyloid gets to be too much, and then the microglia then
• 14:26 - 14:32: become dysfunctional, they can’t keep up, and they become pro-inflammatory, and they
• 14:32 - 14:38: make reactive oxygen species, and then you get this perpetuated amyloid pathology, chronic
• 14:38 - 14:40: inflammation, and then neuronal death.
• 14:40 - 14:47: So this current view of Alzheimer’s disease is amyloid first, and microglia activation
• 14:47 - 14:53: second, and microglia activation is a result of the amyloid, and so the targeted therapies
• 14:53 - 14:55: have gone towards amyloid, right?
• 14:55 - 14:57: That’s the chronology.
• 14:57 - 15:03: And therefore, we have focused on inflammation and Alzheimer’s disease as a consequence
• 15:03 - 15:09: of amyloid accumulation, we’ve looked at neurohistological outcomes, we’ve looked
• 15:09 - 15:15: at biofluids, we’ve looked at neuroimaging, and we’ve looked at epidemiology, all thinking
• 15:15 - 15:19: that inflammation is a result of amyloid accumulation.
• 15:19 - 15:26: But the genetics, very recently, tell us a different story, and this is a meta-analysis
• 15:26 - 15:32: of genetic genome-wide association studies, which I think is very interesting, because
• 15:32 - 15:42: what it tells you is that 60% of the genome-wide association hits are immune-specific, so
• 15:42 - 15:50: if somebody showed you this, you would say Alzheimer’s is an immunologic disease.
• 15:50 - 15:59: More than 50% of the genetic hits are associated with immune cells.
• 16:00 - 16:06: So we would like to propose an alternative view of inflammation and the role of inflammation
• 16:06 - 16:07: in Alzheimer’s disease.
• 16:08 - 16:17: What if what’s really happening is that the microglia, in fact, or other glial cells,
• 16:17 - 16:24: doesn’t just have to be microglia, it has to be an immune expression, immune cell, have
• 16:24 - 16:29: innate immune dysfunction for some reason, maybe it’s not one gene, it’s several genes,
• 16:29 - 16:35: it could be multifactorial, we just have to figure out how many and where, there’s innate
• 16:35 - 16:44: immune dysfunction, right, and they actually are unable to vacuum up and keep up with the
• 16:44 - 16:51: tau and the amyloid, and they’re not able to vacuum it up, and it accumulates.
• 16:52 - 16:58: And therefore, this is a microglia-driven amyloid tau pathology.
• 16:59 - 17:06: And now you have dysfunctional immune cells that perpetuate this chronic inflammation,
• 17:06 - 17:11: you have accumulation, and you have everything else that comes with it, right, synaptic
• 17:11 - 17:14: dysfunction, synaptic stripping, neuronal cell degeneration.
• 17:15 - 17:20: This chronology is innate immune dysfunction first, that maybe we haven’t focused on it
• 17:20 - 17:28: before, and then you have the accumulation of all other proteins, and the consequences
• 17:28 - 17:29: are more inflammation.
• 17:29 - 17:34: So if this is the view, then we need to think about it in a different way, and we need to
• 17:34 - 17:41: look for earlier signs of inflammation, immune dysfunction, and perhaps now there’s a way
• 17:41 - 17:47: to think about therapies that should start earlier, and maybe are not all amyloid-based.
• 17:48 - 17:54: So this schematic talks about potentially innate immune dysfunction being the root cause
• 17:54 - 18:01: of neurodegenerative diseases, maybe not in all people, but in a good fraction of them.
• 18:02 - 18:09: And then this being the source of the excitotoxicity, the reduced clearance of toxic debris,
• 18:09 - 18:11: the synaptic loss, et cetera.
• 18:12 - 18:16: And then we know it’s not all about genetics.
• 18:16 - 18:22: We know that there’s environmental factors and epigenetic causes that can synergize with
• 18:22 - 18:23: the genetics.
• 18:23 - 18:30: Perhaps there’s factors like infection, and diet, and stress, and lifestyle choices,
• 18:30 - 18:31: and of course, aging.
• 18:34 - 18:40: And to kind of support that argument, this is a paper from a colleague of mine that just
• 18:40 - 18:46: also moved to the University of Florida, with whom we’re collaborating, who basically showed
• 18:46 - 18:52: that the TRM2 variant, which is a risk factor for Alzheimer’s, and in fact, one of the
• 18:52 - 19:01: TRM2 variants, R47H, has an effect on the kinds of plaques that form in the human brain
• 19:01 - 19:04: when you have Alzheimer’s disease.
• 19:04 - 19:11: And in this paper, they very elegantly showed that TRM2 variant carriers have reduced plaque
• 19:11 - 19:16: associated microglia and increased neuritic plaques in tau.
• 19:17 - 19:22: And they did this analysis by looking at the microglia that were surrounding the plaques
• 19:22 - 19:28: using digital spatial profiling, not just looking at the numbers of microglia or the
• 19:28 - 19:35: shape of microglia, but the expression of proteins in the core, in the borders, and
• 19:35 - 19:40: with certain distance from the center of the plaque in a very elegant way.
• 19:41 - 19:47: And we’re planning to do this in much more deep analysis in other neurodegenerative diseases.
• 19:47 - 19:52: But this is the kind of information that we need to have to really understand the role
• 19:52 - 19:59: of immune dysfunction, innate and adaptive, in neurodegenerative diseases.
• 20:00 - 20:08: And it suggests that the genetics of the individual are going to really play a role
• 20:08 - 20:15: in telling you perhaps how early some of the dysfunction may start and how it could play
• 20:15 - 20:17: a role with some of the environmental factors.
• 20:18 - 20:20: Now, how do we know?
• 20:20 - 20:26: Is there any evidence that genetics really synergizes with an environmental component
• 20:26 - 20:27: of inflammation?
• 20:27 - 20:34: So this is a recent paper, very recent, in fact, in JAMA Network, where they looked at
• 20:34 - 20:37: the highest risk factor for Alzheimer’s disease, APOE.
• 20:38 - 20:43: And APOE4 is, of course, the highest genetic risk factor.
• 20:43 - 20:50: And what they did, circled here in the red, is they actually looked at APOE4 and APOE3
• 20:50 - 20:54: carriers, and they looked at chronic inflammation.
• 20:54 - 20:57: They looked at CRP, C-reactive protein levels.
• 20:57 - 20:59: And what they found was fascinating to us.
• 20:59 - 21:05: What they actually found was an association of chronic low-grade inflammation in the way
• 21:05 - 21:11: of CRP levels with the risk of Alzheimer’s disease, but only in APOE4 carriers.
• 21:11 - 21:18: And what they found is that, basically, that APOE4 was coupled with chronic low-grade
• 21:18 - 21:24: inflammation, and it was a CRP level of eight milligrams per liter or higher, was associated
• 21:24 - 21:30: with an increased risk for AD, especially in the absence of cardiovascular disease.
• 21:31 - 21:37: And this increased risk of earlier disease onset compared with APOE carriers with
• 21:37 - 21:38: that chronic inflammation.
• 21:38 - 21:43: So if you have chronic inflammation in APOE4, you had an increased risk for Alzheimer’s
• 21:43 - 21:51: disease, but this was not seen if you were an APOE3 or an APOE2 carrier with chronic
• 21:51 - 21:52: inflammation.
• 21:52 - 21:58: Therefore, APOE4 is a bad thing, and you layer chronic low-grade inflammation on top of that,
• 21:58 - 21:59: it’s even worse.
• 22:00 - 22:06: If you have lucky genetics, APOE3 or 2, and you have inflammation, then it’s not a double
• 22:06 - 22:07: whammy.
• 22:08 - 22:11: So let’s talk about the inflammation factors that come into this.
• 22:11 - 22:13: What kind of inflammation?
• 22:13 - 22:14: Is it all inflammation?
• 22:14 - 22:19: Well, microglia are making a lot of things, and we’ve been very interested in tumor necrosis
• 22:19 - 22:20: factor for a long time.
• 22:21 - 22:23: When I started my lab, we began targeting this.
• 22:23 - 22:29: I spent some time in the private sector developing ways to inhibit tumor necrosis factor.
• 22:29 - 22:35: And one of the reasons that it’s become very interesting is because tumor necrosis factor
• 22:35 - 22:39: inhibitors have been associated with lower incidence of Alzheimer’s disease.
• 22:39 - 22:42: And here’s sort of the interesting evidence.
• 22:43 - 22:48: If you look at the risk for Alzheimer’s disease in the general population, okay?
• 22:48 - 22:51: And you look at people with rheumatoid arthritis.
• 22:51 - 22:55: So this is one of the big autoimmune diseases in the population.
• 22:56 - 23:03: If you just look at the predicted risk for them, these are people that are essentially
• 23:03 - 23:04: not treated, right?
• 23:04 - 23:07: They just have a lot of inflammation in their joints and bodies.
• 23:08 - 23:16: Their risk for Alzheimer’s disease is 800% compared to the general population.
• 23:17 - 23:20: That seems to me to be super high.
• 23:21 - 23:28: If you look at those people and look at the ones that are treated with anti-TNF, so the
• 23:28 - 23:36: drugs like Enbrel, Remicade, their risk compared to the general population is minus 60%.
• 23:36 - 23:41: So that suggests, again, it’s an epidemiological comparison.
• 23:42 - 23:47: It suggests that something about the therapy may potentially lower the incidence of the
• 23:47 - 23:49: risk for Alzheimer’s disease.
• 23:49 - 23:55: And it compels some kind of question about, do anti-inflammatories potentially lower the
• 23:55 - 23:55: risk?
• 23:57 - 24:04: Now, when you look at the implication of the Pfizer findings, there were some debate about
• 24:04 - 24:11: whether Pfizer had some information about their drug and why they didn’t use it in people
• 24:11 - 24:14: with Alzheimer’s disease, why they didn’t take it to the clinic.
• 24:14 - 24:16: There was a lot of criticism.
• 24:16 - 24:22: And I think their argument was it was not the right drug to be taken to the clinic in
• 24:23 - 24:24: elderly individuals.
• 24:25 - 24:26: That was their argument.
• 24:26 - 24:30: And to be honest, one of the issues is that their drugs don’t cross into the brain.
• 24:30 - 24:35: And potentially, they felt like it really was not the right candidate.
• 24:35 - 24:41: Bottom line is that epidemiologically, there might have been some arguments that it might
• 24:41 - 24:41: have been helpful.
• 24:42 - 24:48: Potentially, the argument that I’m going to make for you is that not all anti-TNF drugs
• 24:48 - 24:49: are created equal.
• 24:50 - 24:56: And the Pfizer drug and the drugs that have been marketed to date have an interesting
• 24:56 - 24:59: biology in the way that they block TNF.
• 24:59 - 25:04: And perhaps, the mechanism of action is really important.
• 25:04 - 25:09: But the epidemiology does suggest, if you put it all together in this last schematic,
• 25:09 - 25:17: that anti-TNF does appear in a meta-analysis to be associated with lower dementia, right?
• 25:17 - 25:25: So the odds ratios do suggest that the Tenorcept, Infliximab, all these different drugs appear
• 25:25 - 25:28: to be associated with lower dementia.
• 25:29 - 25:35: So perhaps, the timing at which you take them, when you take them for rheumatoid arthritis
• 25:35 - 25:38: and other diseases may be important.
• 25:40 - 25:42: So when does it start?
• 25:42 - 25:47: And studies have shown, interestingly enough, I mentioned earlier, that it starts pretty
• 25:47 - 25:47: early.
• 25:47 - 25:49: It starts in your 30s.
• 25:49 - 25:54: And so this is a study that shows that TNF levels, TNF receptor levels actually start
• 25:54 - 25:56: going up in your 30s, right?
• 25:56 - 25:58: And why do TNF receptor levels go up?
• 25:58 - 26:04: Well, these are actually on the surface of cells and they are clipped.
• 26:05 - 26:13: They are basically clipped from cells because TNF is actually made on the surface of cells
• 26:13 - 26:17: and the receptors are also made on the surface of cells.
• 26:17 - 26:26: And when TNF is high, the TNF receptor 2 is clipped from the cell surface and it’s meant
• 26:26 - 26:28: to suck up the ligand.
• 26:28 - 26:31: And so it’s a response to inflammation.
• 26:32 - 26:37: Now, TNF, as I mentioned, is a membrane-associated ligand.
• 26:37 - 26:41: It is binding to two receptors.
• 26:41 - 26:46: It’s binding to TNF receptor 2 with a cell-to-cell contact.
• 26:46 - 26:51: And in this fashion, it’s very important for lymphoid organ development.
• 26:52 - 26:56: It’s important for myelination and it’s important to protect you against infection.
• 26:56 - 27:02: And in this manner, many papers have shown that it’s important for neuroprotective action.
• 27:04 - 27:12: And when it gets clipped from the membrane, tumor necrosis factor is actually doing a
• 27:12 - 27:14: different kind of biology.
• 27:14 - 27:21: It is preferentially now interacting with TNF receptor 1, which is on the surface of
• 27:21 - 27:22: cells as well.
• 27:22 - 27:30: But in this soluble form, TNF is now mediating pro-inflammatory pathology and it’s mediating
• 27:30 - 27:31: demyelination.
• 27:31 - 27:36: And many papers have shown that it’s mediating neurodegeneration.
• 27:37 - 27:39: So very interesting, right?
• 27:39 - 27:42: People tend to think of tumor necrosis factor as one ligand.
• 27:42 - 27:47: And in fact, it’s two ligands, the membrane-bound and the soluble form.
• 27:47 - 27:52: And based on what I’m telling you, in hundreds of papers, very different biology.
• 27:53 - 27:59: Now, the drugs I just mentioned block both because they’re antibodies or they’re decoy
• 27:59 - 28:05: receptors, which basically will bind and neutralize both forms of the ligand.
• 28:07 - 28:12: Now, when I was in the private sector, the colleagues that I worked with and I developed
• 28:13 - 28:19: a different kind of TNF inhibitor, which is basically a TNF mutant, right?
• 28:19 - 28:25: So the TNF mutant is basically a TNF that has two-point mutations.
• 28:26 - 28:33: And the idea here was to design a TNF mutant that could not bind its own receptors.
• 28:33 - 28:40: And what was done is a TNF mutant that had two-point mutations to disrupt the binding
• 28:40 - 28:41: to its own receptors.
• 28:41 - 28:47: And the actual outcome was to create a dominant negative TNF.
• 28:47 - 28:54: By disrupting the binding to its own receptors, you actually ended up with a TNF monomer that
• 28:54 - 28:58: could still heterotrimerize with itself.
• 28:58 - 29:06: So TNF is a trimer, shown here in white in the middle, and it will detrimerize long enough
• 29:06 - 29:13: to let in one of these TNF mutants with two-point mutations that basically see native soluble
• 29:13 - 29:15: TNF as itself.
• 29:15 - 29:21: And it will form these heterotrimers with the native soluble TNF.
• 29:21 - 29:25: And what it basically does is it stops them away from these blue receptors.
• 29:25 - 29:29: This is a bird’s eye view of TNF and its three blue receptors.
• 29:29 - 29:35: And by heterotrimerizing with soluble TNF, it cuts them away from the blue receptors.
• 29:35 - 29:42: Now, this heterotrimerization only happens when TNF is in its soluble form.
• 29:42 - 29:48: This heterotrimerization will not happen if TNF is tethered to the membrane.
• 29:49 - 29:58: So this action makes this dominant negative TNF a soluble TNF selective inhibitor, because
• 29:58 - 30:04: this heterotrimerization will never happen with the membrane-bound ligand.
• 30:04 - 30:10: So what this does is it allows us to target only the soluble arm that I just described
• 30:10 - 30:11: to you.
• 30:11 - 30:19: And it leaves the membrane-bound arm completely untouched, which allows them to not interfere
• 30:19 - 30:24: with function, not interfere with myelination, but only to block the pro-inflammatory site.
• 30:24 - 30:30: And as such, it became a great tool for my lab and hundreds of other investigators that
• 30:30 - 30:36: were able to put it in their preclinical models to figure out what was going on only
• 30:36 - 30:39: with soluble TNF without disrupting the other side.
• 30:40 - 30:48: And this targeting soluble TNF approach was shown in several models of Alzheimer’s disease
• 30:49 - 30:57: to attenuate the synaptic dysfunction in various models, to attenuate the cognitive impairment,
• 30:58 - 31:05: to reverse or prevent some of the immune dysfunction with activated myeloid cells,
• 31:05 - 31:09: with brain T cell infiltration, the microglia.
• 31:09 - 31:13: So some of the work was from my lab, and you can look it up.
• 31:13 - 31:15: Others was not from my lab.
• 31:15 - 31:23: And so there’s been several papers now that suggest that targeting soluble TNF is a good
• 31:24 - 31:27: potential intervention, at least in preclinical models.
• 31:28 - 31:35: There have been now probably more than 63 publications in 24 therapeutic areas,
• 31:35 - 31:38: lots of different disease indications.
• 31:39 - 31:44: Again, targeting soluble TNF as a mechanism, which is pretty interesting.
• 31:44 - 31:50: And again, the idea is that you want to target only the soluble arm, not the other one,
• 31:50 - 31:56: to be able to ask the question, does the mechanism involve soluble TNF inhibition?
• 31:57 - 32:03: And so shifting back to the chronic inflammation story, in terms of does chronic inflammation
• 32:03 - 32:07: play a role in this risk for Alzheimer’s disease and in neurodegeneration,
• 32:08 - 32:11: here’s the way that we thought about testing this idea.
• 32:11 - 32:17: We thought that there was enough evidence out there trying to link metabolic dysregulation,
• 32:17 - 32:20: diabetes, obesity to Alzheimer’s risk.
• 32:20 - 32:27: And we thought, perhaps the high fat diet, fructose sedentary lifestyle is leading to
• 32:27 - 32:28: a leaky gut.
• 32:29 - 32:36: And you may have the onset of dyslipidemia, diabetes, obesity, and this creates peripheral
• 32:36 - 32:43: inflammation, some hormonal dysregulation, reactive oxygen species, a leaky BBB.
• 32:44 - 32:50: And this then increases directly and indirectly neuroinflammation, peripheral inflammation,
• 32:50 - 32:56: and increases the risk for vulnerable populations for degeneration.
• 32:56 - 33:01: And so we set out to create basically a fatty liver model.
• 33:01 - 33:09: And Betty Rodriguez in my lab published a paper that suggested that if you fed black
• 33:09 - 33:16: six mice high fat, high fructose diets, you could very interestingly model metabolic
• 33:16 - 33:20: dysregulation, both in the periphery and in the brain.
• 33:20 - 33:24: You could get beautiful insulin resistance in the brain.
• 33:24 - 33:29: And many times Alzheimer’s has been called type three diabetes because you get insulin
• 33:29 - 33:30: resistance in the brain.
• 33:30 - 33:37: And she basically showed that you could get this really nice fatty liver shown here that’s
• 33:37 - 33:42: really kind of pink instead of being bright red and with oil red O that you could get
• 33:42 - 33:44: this fatty deposition.
• 33:44 - 33:51: And then she showed that if you targeted soluble TNF, you could reverse this metabolic
• 33:51 - 33:56: dysregulation that was induced by an obesogenic diet in wild type mice.
• 33:56 - 34:01: And this is just some of the data that you can look up since it’s been published.
• 34:01 - 34:09: This metabolome or metabolomic profile with high fat, high carbohydrate diet in the first
• 34:09 - 34:15: column is what you get with just the diet and some of the metabolic pathways.
• 34:15 - 34:19: In the middle is Expro, which is a soluble TNF drug by itself.
• 34:19 - 34:23: And in the far right column is what you get with both.
• 34:23 - 34:28: And hopefully you can see that the far right column is more like the middle than it is
• 34:28 - 34:29: like the diet.
• 34:29 - 34:35: And so we’re still diving more deeply into the data and what it means in the hopes of
• 34:35 - 34:41: understanding exactly what it is about targeting soluble TNF that allows you to restore the
• 34:41 - 34:47: metabolic profile of the mice when you induce this dysregulation.
• 34:49 - 34:55: So going back to this idea that you have innate immune dysfunction and that maybe that increases
• 34:55 - 35:01: your risk for neurodegeneration and how that might play a role in the risk for Alzheimer’s
• 35:01 - 35:07: disease through this gene environment interaction, we thought, how can we test that in a preclinical
• 35:07 - 35:11: model of Alzheimer’s disease using diet in Betty’s model?
• 35:12 - 35:21: How can we link this diet to an Alzheimer’s sort of genetically predisposed situation?
• 35:21 - 35:27: Again, thinking that microglia and the TNF story might give us an angle or an opportunity
• 35:27 - 35:32: to test that and give us a view and an entry into a therapeutic.
• 35:32 - 35:34: So this is the study design that we did.
• 35:34 - 35:44: And we’ve been playing with the idea of Alzheimer’s and diet and microbiome and the idea that
• 35:45 - 35:50: there’s an opportunity perhaps for targeting things through diet.
• 35:50 - 35:54: And so we took the 5X mice, which is in the pretty aggressive model of Alzheimer’s disease.
• 35:54 - 35:56: We recognize that.
• 35:56 - 35:59: We thought if the 5X mice can’t be helped, then nobody can be helped.
• 35:59 - 36:02: So we stacked the deck against us and went for that.
• 36:02 - 36:07: And so we took two-month-old female mice, transgenic or non-transgenic.
• 36:08 - 36:11: We fed them a high-fat, high-fructose diet like Betty’s.
• 36:11 - 36:18: And halfway through that, we started the soluble TNF inhibition, which is a sub-Q
• 36:18 - 36:20: injection every third day.
• 36:20 - 36:25: And in half of them, we just gave them saline.
• 36:25 - 36:33: And we then were collecting blood, and we’re collecting plasma by tick bleed and stool.
• 36:33 - 36:38: And we, at the end, looked at real-time PCR.
• 36:38 - 36:40: We looked at gut microbiome.
• 36:40 - 36:45: We did a lot of flow cytometry for immune populations in the brain, in the blood.
• 36:45 - 36:50: And at the end, we did histology, certainly to look for amyloid beta and for many other
• 36:50 - 36:51: things.
• 36:51 - 36:54: And these studies are still ongoing.
• 36:54 - 36:55: We have some data.
• 36:55 - 36:59: And I’m going to give you the punchline because it hopefully will soon be published.
• 36:59 - 37:03: And so it’s just to pique your interest in having you go look for the results.
• 37:05 - 37:12: But the punchline is, and in a very exciting way, that these young mice, two-month-old,
• 37:12 - 37:19: just in a short high-fat, high-fructose diet time course, developed earlier amyloid plaques,
• 37:19 - 37:19: right?
• 37:19 - 37:21: So that’s important.
• 37:23 - 37:27: The other thing that happened is that they definitely displayed abnormal immune cell
• 37:27 - 37:28: traffic into the brain.
• 37:28 - 37:31: And that probably is not a good thing.
• 37:31 - 37:35: We don’t know necessarily that that does play a role, but that did happen.
• 37:35 - 37:39: It is possible that that traffic was an adaptive response.
• 37:39 - 37:41: And that may be good, but we just don’t know.
• 37:42 - 37:47: We did describe that there was more leaky gut syndrome and there was more brain inflammation.
• 37:48 - 37:53: And one of the interesting things is that the gut microbiome was also shifted with
• 37:53 - 37:56: Expro in a very substantial way.
• 37:56 - 38:02: And Expro was able to reverse a lot of the phenotypes that we saw with the leaky gut,
• 38:02 - 38:08: the brain inflammation, and very importantly, the synaptic dysfunction that we saw that
• 38:08 - 38:11: was enhanced by the diet.
• 38:11 - 38:14: That was a collaboration with Chris Norris at the University of Kentucky.
• 38:14 - 38:22: So hopefully, we’ll be able to pinpoint what it is about the acceleration in a genetically
• 38:22 - 38:29: predisposed environment by the diet and understand what are the soluble TNF steps that are being
• 38:29 - 38:30: targeted.
• 38:31 - 38:39: So to summarize, we do believe that the obesogenic diet was able to enhance the amyloid pathology
• 38:39 - 38:41: in the hippocampus.
• 38:41 - 38:42: It was a modest increase.
• 38:42 - 38:46: And so we don’t really think that it’s all about amyloid.
• 38:46 - 38:50: We do think that amyloid plays a role and is exacerbated.
• 38:51 - 39:00: We know that the AD risk and the poor diet of the mice combined to exacerbate the cytotoxic
• 39:00 - 39:02: T cell infiltration into the brain.
• 39:02 - 39:07: We did have decreased T cell numbers in the blood, and we had increased hippocampal inflammation,
• 39:08 - 39:11: which we didn’t examine the behavior of the mice.
• 39:11 - 39:18: But potentially, that could have contributed to cognitive issues.
• 39:18 - 39:24: We saw that neutralization of soluble TNF mitigated the immune dysfunction and reversed
• 39:24 - 39:27: multiple effects of the obesogenic diet.
• 39:27 - 39:33: And the implications for the study is that in an obesogenic diet in humans, we know that
• 39:33 - 39:38: others have reported induced gut dysbiosis and a leaky gut.
• 39:38 - 39:46: And we feel that this is likely to increase blood-brain barrier leakiness and potentially
• 39:46 - 39:48: inflammation in the brain.
• 39:48 - 39:55: And all of these are likely to act in concert to enhance risk for cognitive decline and
• 39:55 - 39:55: MCI.
• 39:56 - 40:03: And so I want to end with sort of a schematic by my colleague, Brian, who is an expert in
• 40:03 - 40:04: gut microbiome.
• 40:04 - 40:11: And he makes a real compelling argument that we need to think about the microbiome as the
• 40:11 - 40:16: third partner in this relationship between the brain and the periphery, right?
• 40:16 - 40:22: We know that if you deplete the gut microbiome, you actually end up not just reprogramming
• 40:23 - 40:27: what’s in the blood, but what’s coming out of the bone marrow, what’s going into the
• 40:27 - 40:28: circulation.
• 40:28 - 40:37: And I think that by looking at the gut microbiome, it may be very important to harness that power
• 40:37 - 40:45: to approach several diseases, not just things like autism and anxiety and sickness behavior,
• 40:45 - 40:49: but including diseases like the ones we’re very interested in, like Alzheimer’s and
• 40:49 - 40:52: Parkinson’s and MS, stroke, TBI.
• 40:52 - 40:59: So a whole host of neurologic diseases may be very helped by being able to harness the
• 40:59 - 41:02: idea of the central and peripheral compartment.
• 41:03 - 41:10: And so, again, we need to think about the CNS periphery gut as this tripartite axis
• 41:10 - 41:16: where we know that there are lots of communication between this compartment, there are
• 41:16 - 41:25: molecules being made that increase the communication between neurons, microglia,
• 41:25 - 41:26: immune cells.
• 41:26 - 41:33: And it’s by understanding the functional relationship between these pathways that new
• 41:33 - 41:41: tools, new antibodies, new therapies will emerge that will allow us to really make a
• 41:41 - 41:47: dent in understanding and being able to cure and have therapies for these diseases.
• 41:48 - 42:01: Be happy to answer any questions.