Marina Picciotto, PhD, Acetylcholine signaling in hippocampus: implications for anxiety and depression

Transcript

• 00:00Hi everyone, welcome to the Yale Psychiatry
• 00:03and Child Study center datablitz.
• 00:06I'm happy to share with you some of
• 00:08my work on Astral cooling signaling
• 00:11and how it affects behaviors related
• 00:13to stress in mice and how that's
• 00:16translatable to human subjects.
• 00:19I'm going to share my screen now
• 00:21and show you some of the work
• 00:23that's going on in my lab.
• 00:25Our laboratory is interested in
• 00:26the receptors for nicotine in the
• 00:29brain and how those affect behaviors
• 00:31in typical situations and also
• 00:33related to psychiatric illness.
• 00:35One thing we know is that smoking
• 00:37anxiety and depression are highly
• 00:39correlated in human subjects.
• 00:41We know that major depressive
• 00:43disorder is a chronic, debilitating,
• 00:45relapsing illness.
• 00:46The huge cost to the individual
• 00:48to families and to society,
• 00:50and there's a bidirectional
• 00:51relationship with smoking.
• 00:53People who are depressed or
• 00:55more likely to smoke.
• 00:56And people who smoke are
• 00:58more likely to be depressed,
• 01:00so about 40 to 60% of patients with
• 01:02depression smoke versus now much less
• 01:04than 20% of the general population.
• 01:07So can we identify the neurobiological
• 01:10mechanisms underlying this comorbidity?
• 01:12Where should tell you that the primary
• 01:15targets for nicotine in the brain or
• 01:17the nicotinic acetylcholine receptors?
• 01:19These are a family of receptors
• 01:20that respond to the endogenous
• 01:22neurotransmitter acetal choline and
• 01:24there are two families of Astle calling
• 01:26receptors nicotinic and muscarinic.
• 01:28And I'm going to tell you about the
• 01:31relationship between the nicotinic
• 01:32receptors and Astle calling signaling.
• 01:34Today we have projects and muscarinic
• 01:36receptors as well as still calling
• 01:38neurons in the brain project very widely.
• 01:41Their cell bodies in the basil.
• 01:43Or bring complex and in the brainstem
• 01:46project pretty much everywhere in the brain,
• 01:48and in addition number of studies have shown,
• 01:51and here's one from the 1990s.
• 01:53That stress induces us to cooling
• 01:56release in many different brain areas.
• 01:58And so you can see here that
• 02:00using microdialysis, restraint,
• 02:02stress results in elevations of Astle
• 02:04calling signaling throughout the brain,
• 02:06including the hippocampus for as long
• 02:09as that restraint stress is applied.
• 02:12So what we've done is to use biochemical
• 02:14and molecular biological techniques
• 02:16to manipulate Astle calling signaling,
• 02:18and in this experiment from 2013,
• 02:21what we did was to block Astle
• 02:23calling breakdown throughout the
• 02:25brain and body by using the
• 02:28pharmacological antagonist Astle.
• 02:29Colon especial cholinesterase antagonist,
• 02:30physostigmine,
• 02:31and what we saw was that there was
• 02:34more immobility in this one test.
• 02:36We used many,
• 02:38but I'm showing you the tail
• 02:40suspension here as an example.
• 02:43You got more reactivity to stress
• 02:45as we increase the dose of this
• 02:47Astle cholinesterase blocker,
• 02:49which means as overall levels
• 02:51of actual calling increased,
• 02:52we got more stress related behaviors.
• 02:55These could be reversed by blockers
• 02:57of either nicotinic, muscarinic,
• 02:58or both families of astral choline
• 03:01receptors and that makes sense
• 03:03because that means that this increase
• 03:05in national calling resulted in
• 03:07behaviors that were sensitive
• 03:09to colon estel choline receptor
• 03:10blockers and you can see that.
• 03:13The behavior actually
• 03:14went down below baseline,
• 03:16with these blockers,
• 03:17suggesting that there's hostile
• 03:19calling tone that that is responsible
• 03:21for the baseline immobility.
• 03:23In this in this test.
• 03:26And this was also reversible by
• 03:28giving the SSRI fluoxetine Prozac.
• 03:30So first here's the increase in
• 03:32immobility that we see when we increase
• 03:35Estel coin signaling and that can also
• 03:37be reversed by this antidepressant
• 03:40that's widely prescribed in humans,
• 03:42suggesting that the model that we're
• 03:44looking at is more broadly relevant
• 03:46to depression related behaviors
• 03:48than just to the cholinergic system.
• 03:51And this is related to experiments
• 03:53done back in the 70s and 80s.
• 03:56By David Chrzanowski and his colleagues
• 03:58who gave the same drug Pfizer
• 04:00stigma to humans and saw depressive
• 04:02symptomatology even in human subjects,
• 04:04had never had a history of depression,
• 04:06suggesting that what we're looking
• 04:08at in mice is translatable to humans.
• 04:10Where in the brain is this
• 04:12happening where we were able to
• 04:14use molecular genetics to block,
• 04:16to downregulate Astle?
• 04:17Cholinesterase activity only locally
• 04:18in the hippocampus?
• 04:19I won't walk through all of this
• 04:21for the met up for reasons of time,
• 04:24but what you can see is that when
• 04:27we knocked down.
• 04:28Ask for cholinesterase only in
• 04:30the hippocampus.
• 04:31We see the same phenotype that we
• 04:33see when we pharmacologically block
• 04:34it everywhere and we can rescue
• 04:37that by expressing a human Estel
• 04:40cholinesterase transcript that can't
• 04:42be knocked down in here I'm showing
• 04:45you three different paradigms,
• 04:46both 2 models of immobility but one
• 04:49model of amorphism or ethologically.
• 04:51Relevant stressors.
• 04:52Social defeat stress where we give
• 04:55a subthreshold social defeat and
• 04:57now we see a very potent avoidance.
• 04:59After that social defeat by knocking
• 05:02down Astral cholinesterase only
• 05:04in the hippocampus.
• 05:05So I've shown you some data from our
• 05:08historical experiments showing the
• 05:10increasing Astle calling signaling
• 05:12in hippocampus by decreasing its
• 05:14breakdown increases stress related
• 05:15behaviors in mice to changes in
• 05:18Astral calling signaling than
• 05:19occur and oppressed human subjects.
• 05:21I'm going to show you some data
• 05:23that was gathered by our clinical
• 05:26colleagues in which we collaborated
• 05:28and it was using a tracer of this
• 05:31nicotinic acetylcholine receptor
• 05:32that was competitive for Astle
• 05:35choline at its binding site.
• 05:37And now what would we expect to see
• 05:39if human subjects who are depressed
• 05:41have more Astle calling signaling
• 05:43when we use this competitive tracer,
• 05:45well,
• 05:45there's going to be some astral
• 05:47calling in the brain that binds
• 05:49to these nicotinic receptors,
• 05:50and so when that radiotracers introduced,
• 05:52there are going to be others
• 05:54binding sites that it can bind to,
• 05:57and we will see changes in receptor
• 05:59availability when this tracer
• 06:00is administered.
• 06:01How about in patients or in subjects
• 06:03who might have elevated Astle calling,
• 06:05signaling they'll have more
• 06:06occupancy of their receptors.
• 06:08And now when the tracers introduced,
• 06:10they'll be fewer binding sites,
• 06:11and that's exactly what we see in the
• 06:14brains of depressed human subjects.
• 06:16So here's just an example.
• 06:17Human subject has to be a non
• 06:19smoker because This site is also
• 06:22competitive with nicotine.
• 06:23You can see the heat map of binding and
• 06:25that binding is decreased in a depressed
• 06:28and actively depressed nonsmoker.
• 06:29And when we do this in a large group
• 06:32of human subjects you can see that
• 06:34that decrease in availability is
• 06:36obvious throughout many cortical areas,
• 06:38but also through deeper.
• 06:40Brain structures.
• 06:41This could also have been due
• 06:43to decreases in the receptor
• 06:45itself and not to competition,
• 06:47and so that we were able to do
• 06:49was to take postmortem human brain
• 06:51tissue washout Astle calling and
• 06:53show that there is absolutely no
• 06:56change in the receptor number and
• 06:58what our colleague Irene Esther List
• 07:00was able to do was to reproduce the
• 07:03challenge study that Janowsky did
• 07:05and show that in the same person
• 07:07who at baseline had a relatively
• 07:09high level of Astle choline binding.
• 07:11Sites available after five cystic
• 07:13mean administration.
• 07:14The number of those bindings,
• 07:16the availability of those binding
• 07:17sites goes down just as you would
• 07:20expect with a competitive tracer,
• 07:21and this is allowed us to go back and
• 07:24forth between mouse models in human
• 07:26subjects and test our hypothesis
• 07:27generated from these pharmacological
• 07:29and molecular biology experiments
• 07:31in human subjects.
• 07:32So now can we use this mass model
• 07:34of an anxiety and depression like
• 07:36state to identify sites and receptors
• 07:38of cholinergic signaling?
• 07:40Important for these behaviors?
• 07:41I'm going to show you just a couple
• 07:44slides of ongoing experiments that
• 07:45are not yet published to show you
• 07:47a flavor of what we're doing.
• 07:48First of all,
• 07:50here's a diagram of the cholinergic
• 07:52innervation of the hippocampus,
• 07:54in particular the medial septum
• 07:56provides a large projection to
• 07:58the hippocampus.
• 07:59And what we've been able to do is to
• 08:02use designer receptors exclusively
• 08:04access activated by designer drugs,
• 08:07dreads that are targeted.
• 08:09Only two Astle choline neurons by
• 08:12infusing them into mice in which a
• 08:14recombinase is driven by the promoter
• 08:17for choline acetyl transferase,
• 08:19the synthetic enzyme for astral cooling,
• 08:22and to then direct these dreads
• 08:25locali to the hippocampus by
• 08:27infusing them into the hippocampus.
• 08:29Packaged in a virus that infects
• 08:32terminals of neurons and goes
• 08:33back to their cell bodies.
• 08:35So what does that look like?
• 08:37We infuse the retrograde dread
• 08:39here into the hippocampus.
• 08:40It goes back to the medial septum,
• 08:43and now when we give the chemical
• 08:45activator of this dread,
• 08:46we can exclusively activate this
• 08:48pathway in the brain and ask,
• 08:50does that also change behavior
• 08:52in ways relevant distress?
• 08:53And that's exactly what we see in a
• 08:56number of tests that I'm diagramming here.
• 08:59The light dark box,
• 09:00which is sensitive to anxiolytic
• 09:02medications that.
• 09:02Forced women tail suspension tests that
• 09:05are sensitive to acute administration
• 09:07of anti depressants and the social
• 09:09defeat test which is sensitive to
• 09:12chronic administration of antidepressants.
• 09:14All show changes in behavior
• 09:16when this dread activates the
• 09:18hippocampus that choline the astral.
• 09:20Colleen inputs to the big campus
• 09:22that are relevant that are consistent
• 09:25with the idea that increased
• 09:27hippocampal Estel cooling system
• 09:29signaling increases behaviors.
• 09:31Relevant distress, and we've now done.
• 09:33A number of experiments to show that this is
• 09:37actually mediated by Astle choline, not Co.
• 09:41Released neurotransmitters because if we
• 09:43locally infused and nicotinic antagonist
• 09:45mecamylamine into the hippocampus,
• 09:47we can reverse these effects of the dread.
• 09:51So here's the control plus
• 09:54Mecamylamine compared to the Dread
• 09:56activation in three different tests.
• 09:59So that means that.
• 10:01We can actually increase Astle calling
• 10:03signaling using this thread and reverse it
• 10:06using a nicotinic acetylcholine antagonist.
• 10:08So we have a number of studies that
• 10:10are dissecting the signaling of
• 10:12Astle calling in brain structures
• 10:14in addition to the hippocampus.
• 10:16For example, the amygdala,
• 10:18the prefrontal cortex,
• 10:19and then locally the basil forebrain
• 10:21complex where the cell bodies of
• 10:23those Astle calling neurons reside,
• 10:25and altogether what we are building
• 10:28is an integrated picture of how Astle
• 10:30calling signaling sets the threshold
• 10:32for behaviors relevant to stress.
• 10:34In mice and how we might translate
• 10:36those to understanding how I still
• 10:38calling signaling is affecting
• 10:40behavior in depressed human subjects,
• 10:41I want to thank the lab members
• 10:44who are contributing to this work.
• 10:46Particularly young men are a
• 10:47research scientist in the lab who's
• 10:49worked with me for many years.
• 10:51Thank you everybody for listening.
• 10:53I really enjoyed presenting
• 10:54this glimpse of the work.
• 10:56Please contact me if you'd
• 10:58like more information about
• 10:59the work going on in my lap.
• 11:02Bye bye.