Yale Psychiatry Grand Rounds: "The Metabotropic Glutamatergic Receptor 5: What is its Role in Psychiatry?"

November 17, 2023

"The Metabotropic Glutamatergic Receptor 5: What is its Role in Psychiatry?"

Irina Esterlis, PhD, Associate Professor of Psychiatry, Yale School of Medicine

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00:00OK.
00:05Yeah. Thank you so much,
00:06Jerry, for the introduction.
00:09And this work with Anglo 5 I've been
00:12doing for I think about 15 years.
00:14And it actually started in
00:16collaboration with Jerry.
00:17Jerry was my mentor on my
00:20first imaging study with this.
00:22I will not be talking about
00:24synaptic density much today,
00:26but I'd be happy to come back and another
00:29grand rounds and talk about that.
00:32So if you guys know it takes
00:35an army to do this work,
00:37this is some of the army that
00:39has helped me do this work.
00:40And I just want to just show all the
00:43people now in case we run out of time.
00:45And these are the acknowledgements
00:48on the translational brain imaging
00:50program with Nicole de La Jolla and
00:53Sarah Davanni have been doing a lot
00:55of help with recruitment of subjects
00:57and identification of subjects.
00:59And then Rich Carson has been my
01:01mentor from when I started doing PET.
01:03And then Chrissy de Lorenzo
01:05has done a lot of ketamine.
01:06I'm go 5 work with me and Jane Taylor,
01:09Hilary Bloomberg and Jerry Sinacor
01:11have really helped a lot through
01:13for clinical and clinical studies.
01:16And I don't have any relevant
01:19financial disclosures.
01:20And so why did I decide to study
01:23glutamate besides the fact that we
01:25can actually image glutamatergic
01:27system in the brain in humans?
01:29Well,
01:30glutamate is the most common
01:31neurotransmitter in the brain with 80
01:34to 90% of synapses being glutamatergic.
01:36And so if you think about it,
01:38whatever system you're studying,
01:40whatever disorder you're studying,
01:42glutamate dysfunction is going to
01:43be implicated in that disorder.
01:45There are two types of receptors.
01:48Bionotropic receptors are responsible
01:50for fast excitatory transmission.
01:52Emmetabotropic have more of a
01:54modulatory role in the central nervous
01:57system and so I'm studying Amglu 5.
02:00It's AG protein coupled receptor.
02:02It is located mostly post
02:04synaptically everywhere in the
02:06brain and the peripheral tissue.
02:08It is involved in everything that
02:09we do including learning, memory,
02:11anxiety and perception of pain.
02:13Probably sleeping cycle as well and
02:16allosteric modulation of the system
02:18contributes to cognitive function,
02:20anxiety, pain.
02:20A lot of this work has been done in
02:23animal models and then I'll show you
02:25some work that we've done in human.
02:28And so the way I study Anglo 5 is
02:30through positron emission tomography or PET.
02:33I'll just show you a few slides on
02:36what we actually study and how PET
02:39works so that you can understand better
02:41what it is that I'm studying and
02:43the data that I will show you later.
02:45And so for PET, we need a cyclotron,
02:47which is a large machine that
02:49makes radioactive particles such
02:50as carbon 11 and F18,
02:53which we then bind to whatever target
02:56you're sending into the brain to bind
02:58to the enzyme neurotransmitter receptor,
03:00whatever it is you're trying to study.
03:03And this composite is called the
03:05radio pharmaceutical or radio
03:07ligand or radio tracer.
03:08We use those terms interchangeably.
03:11I also short and sometimes
03:13I'll say ligand or tracer
03:15and it all means the same thing.
03:17We inject this into the subject as
03:19a bolus over a one minute push or
03:22bolus plus injection over could be
03:23an hour a couple hours depending
03:25on the system that we're studying.
03:28And then we acquire images.
03:30And this is just an example of a PET scanner.
03:33This is an outdated picture,
03:34but it gives you an idea of a brain.
03:37Dedicated PET scanner has a short
03:39bore where only the subject's head
03:42is positioned and so people with
03:44claustrophobia really have an easier
03:47time participating in PET scans.
03:48Now we have different scanners
03:50with where the bore is larger and
03:52the whole body needs to go in.
03:54So we do account for claustrophobia.
03:57And so as Jerry mentioned,
03:58I'm a neuropsychologist by training.
04:02And so for me when I found PET,
04:04I was super excited.
04:07And I'm really honoured to be able
04:09to do these studies where I can look
04:10at what's going on in the brain and
04:12I can ask people how do they feel,
04:14measure their cognition, etcetera, etcetera.
04:16So I can, you know,
04:17unite the human and neuroscience.
04:21And so this is an example of
04:24participation in the study by a subject.
04:27So first we collect MRI images
04:29to guide placements of regions
04:31of interest for PET and to make
04:34sure there are no abnormalities.
04:35Sometimes we see people have tumors
04:38or hemorrhage and we of course report
04:40that and then the radio chemist
04:43synthesize the radio tracer when the
04:45subjects show up at the PET scan.
04:47So it is not something that we
04:49can do ahead of time.
04:50The radio tracers have a half
04:53life of some 20 minutes,
04:54some 110 minutes.
04:55And so it's not something that can
04:58be done in batches and distributed
05:00throughout the day or week.
05:02And then we collect bloods for metabolism
05:04and protein binding of the radio tracer.
05:07Since everybody you know works,
05:08their systems work differently.
05:10And then we inject the radio
05:12tracer and collect PET images.
05:15And so this is an example of
05:17a PET image and Amar image.
05:20And so for pet outcome measures we have,
05:23we have several,
05:24but I'll be talking about two.
05:26One is BPNT, which is a binding potential.
05:29It's how much radioactivity we have in
05:31a region that you're trying to study
05:34versus how much radioactivity is in
05:35the region that has nothing of what
05:38it is that you're trying to study.
05:40So it has negligible specific binding.
05:42Sometimes for some systems,
05:44we don't have that and so we
05:46have to measure blood.
05:48And so we look at how much
05:50radioactivity is in the brain and the
05:52tissue that you're trying to study
05:54versus how much is in the blood.
05:57And so the first one is called BPNT
05:59and the second one is called BT.
06:00And I as I go through,
06:02I will tell you which one I used.
06:05We have two radio ligands that most
06:08commonly used to study Onglu 5 in human
06:11in vivo and I have used both of these.
06:15One is F18 FPEB, it has very high
06:17affinity and specificity for the
06:19receptor has slower kinetics of
06:22110 minute half life and and that
06:25sorry half life's 110 minutes.
06:27And we think because of its high
06:30specificity it's well suited
06:31to study between group changes.
06:33So even if the differences between
06:35groups are really, really small,
06:36we can detect it with FBEB.
06:39AEP 688 is also high affinity,
06:41not as good as FBEB but because
06:43of its short half life we can do
06:45challenge studies on the same
06:47day we can administer this radio
06:49tracer even three times.
06:50They're both negative ballasteric modulators,
06:53which means they bind on the receptor
06:55on a site different from where they're
06:58endogenous neurotransmitter binds.
07:00And I will explain that to you in a minute.
07:04So first I wanted to show you
07:06what typically happens in the
07:08brain when we measure receptors,
07:10and then I will show you
07:12what happens with Anglo 5.
07:14So this was published by Mark Laurel,
07:16who was a trainee here a few decades ago.
07:20Then he was here again for a few months,
07:23maybe a decade ago, and he explained
07:25really well the classical occupancy model.
07:28So the gap, the little Y shapes are,
07:32for example, D2 dopamine receptors,
07:35the the black triangles is dopamine,
07:39the endogenous neurotransmitter
07:41or endogenous ligand,
07:43and the Pentagon shapes are rocklopride,
07:45our radio tracer.
07:46So in the typical situation
07:49in the middle here,
07:51some of the receptors are going to
07:52be occupied by dopamine, not all.
07:54And so the radio ligand can
07:56occupy the other receptors.
07:58So the endogenous neurotransmitter has higher
08:01affinity or higher ligand for the receptor,
08:04so it's going to the radio
08:06ligand cannot kick them off.
08:08So whatever dopamine does not
08:10occupy is what rectified can occupy.
08:12And so this is called receptor availability.
08:15When we have a situation where
08:17we have too much dopamine,
08:19for example,
08:20we gave subjects
08:23a medication that induces dopamine
08:25relief or a dopamine release or we have a
08:28condition where there's too much dopamine,
08:30we don't have as many receptors
08:32for the radioligand to occupy.
08:33So now we're measuring
08:35low receptor availability.
08:36And then on the left here is the opposite.
08:38When there's either dopamine
08:39depletion by tryptophan or a situation
08:42where the subject has too little
08:44dopamine because of an illness,
08:46we have more receptors available
08:48and so high receptor availability
08:50is going to be measured.
08:52Unfortunately, in my case,
08:54Anglu 5 works a bit differently.
08:57So the endogenous ligand glutamate is
09:01going to bind in the extrasynaptic space,
09:04but the radioligand binds in
09:06the membrane space.
09:07So there's no direct competition
09:10between the endogenous ligand and the
09:13neurotransmitter and the radio ligand.
09:16So whatever happens at the glutamate site
09:19may not influence the radio ligand site.
09:24And I was really trying hard to
09:26understand that concept and some other
09:28concepts that I will show you later.
09:31And at the same time I was doing my In
09:33Vivo work, Jonathan Jovic at Columbia,
09:35I was doing some hexel work showing these
09:40similar phenomenon and explaining how
09:42Anglo 5 ligands really work in brain.
09:45So in one study he administered glutamate
09:51and he saw that it did not influence
09:54the binding of the radioligand so again,
09:56as I showed you before,
09:57there's no drug competition
09:59between ligand and glutamate.
10:03However,
10:04when he administered an agonist,
10:08however, sorry,
10:08he was trying to also measure
10:10internalized receptors.
10:11And he could not measure internalized
10:14receptors without administering
10:16something that's going to permealize the
10:18membrane and let the radio ligand in.
10:21So here we see that the radio ligand cannot
10:24cross the membrane and bind to Homer cells.
10:27But when they permealize the membrane,
10:30the radio ligand can bind and
10:33same thing here.
10:34And blue is the typical binding,
10:37in red is just sending the
10:39radioligand in it cannot cross the
10:42and bind to internalized receptors.
10:44And in purple when we make little holes
10:46in the membrane with the detergent,
10:49it can cross the membrane and
10:51bind to internalized receptors.
10:52So this is really second really
10:55important concept that our radioligands
10:57cannot bind to internalized
10:59receptors unless they get help.
11:02And so I was really excited to see that
11:04because it really explains some of my work.
11:06However,
11:06when I presented my data conferences
11:09or was trying to publish papers,
11:11people said,
11:12well,
11:12how come your radioligand passes
11:14through the the vein barrier but
11:17cannot pass through the membrane.
11:19So I went back to Jonathan and he showed you.
11:21So this is what I just showed you before.
11:24He showed that the radioligand these
11:28MGO 5 ligands actually cannot on
11:31their own pass the DVB that they
11:33need a transporter to get them
11:35through the blood brain barrier.
11:37So this is again really important
11:39because a lot of the other
11:41ligands that we study can actually
11:43measure internalized receptors.
11:45And so the explanation of what
11:47it is that we're
11:48seeing is going to be different.
11:50And then the third caveat of
11:53studying Mglo Five came initially
11:55from studies by Chrissy de Lorenzo,
11:57who was at Columbia when she did
12:00this first study and then she did
12:02the second study here at Yale.
12:04So when we bring up new radio ligands,
12:07we go through different processes
12:09of studying them in cells and
12:12animal models and then human.
12:14And to study in human,
12:16we need to do test, retest studies.
12:18So we administer the ligand in the morning,
12:20then we give the subjects a break
12:22and minister in the afternoon
12:24and we want to make sure that the
12:26test retest is within 10 to 15%.
12:28So that every time that you measure,
12:31whatever it is you're trying to measure,
12:32it is the same thing that you're measuring,
12:35that there are no significant differences.
12:38And so back in the day,
12:39these studies were done only
12:40in male subjects.
12:41So Chrissy had nine subjects participate.
12:44They were all new to PET scanning
12:47and contrary to the 1015 plus minus
12:51test 3 test that we typically see,
12:54Chrissy showed about 20 to 40% plus.
12:57So in the morning,
12:59subjects were scanned and then their
13:02receptor availabilities appeared to
13:04go up in the afternoon by 20 to 40%.
13:06And so this was really puzzling.
13:08And we were trying to figure out,
13:09is it because people were anxious because
13:11I've never had a PET scan before,
13:13so they're anxious in the morning and
13:14then in the afternoon they're not so anxious.
13:17Or was there something else?
13:18Was there heart rate, you know,
13:20or blood pressure higher in the
13:21morning or like, what was going on?
13:23And in the meantime,
13:25we all thought this was AVP 688.
13:27We all thought that this was a bad lag.
13:28And so I was doing test retest
13:30studies on the same day with FBAB.
13:32But Chrissy was persistent,
13:34and she did test,
13:35retest again,
13:36this time at Yale with female
13:39participants as well.
13:41And so this is AVP 688 showing
13:44increases in the afternoon scan
13:46binding in male and female subjects.
13:50And then this is FBEB showing
13:52increases in the afternoon scan
13:54in female and male subjects.
13:57And if you see here,
13:59so the females are in red and
14:01the males are in blue.
14:02Females showed a greater increase in the
14:06afternoon scan as compared to males.
14:09And so we started you know,
14:10reading literature.
14:11We also took people's heart rates
14:13and blood pressure and their
14:15anxiety levels etcetera, etcetera.
14:17But nothing could really well explain this,
14:19you know 20 to like 80% increase in
14:23receptor availability over a few hours.
14:26And we read some animal work,
14:28some medication development work.
14:29And what became apparent to us was
14:32that we weren't studying test retest.
14:34We were studying during our variation.
14:37So for those of you who are not
14:39familiar with the cortisol system,
14:41cortisol levels in humans increase
14:43overnight and in the morning we wake
14:45up because of higher cortisol levels.
14:47We're more alert. We're ready to go
14:49maybe a little chocolate or caffeine,
14:51but you know, we're ready to start
14:53the day and get to work and do stuff.
14:55And then over the afternoon our corisol
14:59levels decrease and we get more tired,
15:01a bit more lethargic.
15:02We're kind of done with the day and by
15:05evening they're the lowest and that's
15:07when we are ready to go to sleep.
15:08And then the cycle continues.
15:10Well, animal literature shows that
15:12administration of cortisone actually
15:14decreases Anglo 5 S increases in Corso
15:17levels decrease Anglo 5 availability.
15:20So what we think is happening in our
15:23test retest scanning is that in the
15:25morning when Corso levels are highest,
15:28we're observing lower Anglo 5 availability.
15:30In the afternoon when the Corso levels
15:33are much lower for observing greater
15:36or higher amplified availability.
15:38So in so the test retest studies
15:41were really are not accurate but are
15:44measuring journal variation which
15:46actually was something interesting.
15:47And based on these data,
15:48Chrissy got an RO one to study circadian
15:51rhythm and sleep wake cycle in people
15:54who are controls and who have depression.
15:58And so these were the many caveats
16:00of studying amplified in Viva.
16:04And now I'll show you our work in psychiatry.
16:08So this was maybe in 2008 or 2010
16:12long time ago that we decided to
16:14study Anglu 5 in unipolar depression.
16:17And I showed you that Anglu 5 is
16:20important to our daily functioning.
16:22And at that time, a lot of pharma
16:24studies were studying Anglu 5 agent
16:27agents for treatment of depression.
16:29But there was no work in human,
16:31a lot of the work was done in animal studies.
16:34And so we thought that it would be good
16:36to to invivo human work and see if Mglu
16:395 actually plays a role in depression.
16:41At the same time as I was writing that grant,
16:44this was a Dana grant.
16:46There was a preliminary study published
16:48by Gregor Hessler's group showing in
16:5111 people with depression and then
16:53they also had postmortem group that
16:56MGLU 5 availability is lower and lower
17:00angulified availability was in their
17:03group associated with anxiety symptoms.
17:06And so I had the opportunity to
17:09study a much larger group of people.
17:12And so we scanned 30 subjects with MDD,
17:15which for PET is quite a large study.
17:18They were all unmedicated 35 years
17:21of age on average.
17:22Average depression scores we
17:24measured with PDI,
17:25modulus and AMD and then we had 35
17:29healthy controls who were matched by sex,
17:31age and smoking status.
17:33None of them had significant personal
17:37psychiatric history or first degree
17:39relative with psychiatric history,
17:42and subjects did PET scan, Mrs.
17:44and MRI,
17:46and Mrs.
17:47stands for magnetic resonance spectroscopy.
17:49This part of the study was done in
17:52collaboration with Graham Mason.
17:53We use a magnet to study metabolic
17:56changes in the brain.
17:57All the measurements are in tissue
17:59and when when we get the data,
18:01it's put into a spectrum and each metabolite
18:03has its own peak in the spectrum.
18:05And so this was back back in
18:08the day when we couldn't really
18:10separate glutamate and GLN too well.
18:14So we studied GLX,
18:15which is the sum of glutamate and glutamine.
18:20And the other caveat with Mrs. is that,
18:23especially when I started doing this,
18:25we could only do one voxel at a time because
18:28it took us about two hours to do 1 scan.
18:30And as you can imagine, the subjects
18:32were not going to be in the scanner
18:34for four hours for us to get 2 voxels.
18:35And so we decided to study the
18:38anterior singular cortex given its
18:39role in mood and cognitive processes.
18:43And so this is our main outcome.
18:46So the healthy controls are in diamonds
18:48and people with depression are in circles.
18:51We did not see any differences between groups
18:53in any of the regions that we assessed.
18:55And with that you can look across
18:58the whole brain and we saw nothing
19:00across the whole brain.
19:02The previous study used a reference
19:06region to calculate their outcomes.
19:08So even though Anglo fives
19:10are everywhere in the brain,
19:11I decided to try that too,
19:14because maybe that was the difference of
19:16why would it not see significant findings.
19:19And again, whether we use blood
19:22or cerebellum as a reference,
19:24we did not see difference between groups.
19:26However,
19:27if you go back and look at the literature,
19:29we're actually not an odd duck.
19:31So there's a postmortem study
19:33showing no differences between
19:35controls and people with depression,
19:36with psychosis or no psychosis,
19:39and amplified availability.
19:40And then we did our own autobadiography
19:43study was showing no differences between
19:46people with depression as compared
19:48to controls in Anglo 5 availability,
19:50although there's a little more
19:53variability in the MDT group.
19:55The novel part is that we of course did Mrs.
19:59with PET and so we saw higher glutamate,
20:04glutamine and GLX levels in people
20:06with depression as compared to
20:08controls and when we looked at
20:10relationship between glutamate.
20:12Or G glutamine or GLX and
20:17receptor availability,
20:18we saw that people who had
20:21greater glutamate levels,
20:22et cetera had low receptor availability.
20:25So this really makes sense that
20:27higher endogenous neurotransmitter
20:29would down regulate receptors which
20:33would then in turn internalize.
20:35But this has never been shown
20:37in human in the vivo.
20:38We've hypothesized for years that
20:41too much glutamate is excited,
20:43toxic,
20:43but that's the first time we
20:44were able to show it in vivo,
20:46and this was really exciting.
20:49So this work has been published and
20:54has given the rise to a lot of other
20:57work that I won't now show you,
20:59some of which has now been published.
21:01So my first R1 was actually looking
21:04at Anglo 5 as a marker to help us
21:08differentiate depression during bipolar
21:10disorder versus in unipolar disorder.
21:13And this work was done in
21:15collaboration with Hilary Blumberg.
21:18And so we recruited people who are controls,
21:21people who have bipolar depression,
21:23people who have bipolar euthymia,
21:25and then people who have unipolar depression.
21:28And although the grant did
21:30not call for bipolar Euthymia,
21:32but when we recruited people and
21:34we did their screening and then
21:36they showed up for PET scans,
21:38they were in whatever mood episode,
21:40you know, because people depression cycle
21:42with bipolar disorder cycle quite a bit.
21:45So we amended our protocol and let people
21:48with any mood state participate in the study.
21:53So there are no differences
21:54between subjects and age,
21:55sex, smoking status, etcetera,
21:58except for depression status.
22:00So people with bipolar disorder who
22:02are depressed and unipolar disorder
22:04who are depressed or more significantly
22:06depressed than any other group,
22:07another group was depressed.
22:11And so these are our data that
22:13were recently published with Sophie
22:15Holmes and Booth Ashe leading
22:17the writing of the manuscript.
22:19And so we see that people who
22:21are controls aren't grey,
22:23people with unipolar depression
22:25aren't orange.
22:26Again,
22:26there's no difference receptor
22:27availability between these two
22:29groups as we showed previously.
22:31And then people bipolar disorder
22:34who are depressed or in purple and
22:36who are euthymic are in turquoise
22:40and both of these groups are lower
22:42in their receptor availability
22:43as compared to controls and are
22:46unipolar depressed.
22:47And this was across brain regions.
22:49The prefrontal cortical regions
22:51were my main hypothesis,
22:52but this was across the brain and
22:56what was really interesting as well
23:00is not only is Amglo 5 availability
23:03different between people bipolar
23:04disorder versus unipolar disorder,
23:06but its relationship to mood and
23:10cognitive functioning was also different.
23:14So this shows us that Amglo 5 can help
23:17potentially to differentiate to disorders,
23:19but may also be treatment targets
23:22specifically for bipolar disorder.
23:24And we also collected BOLD fMRI and
23:30during an emotional processing task that
23:33Hillary has extensively published on.
23:35And so in this task,
23:36people are oriented to happy,
23:40neutral or fearful faces.
23:42And our data are currently under review.
23:45Biological Psychiatry with Ruth
23:47Ash being the lead author.
23:49And we have people who are controls in black,
23:52people with bipolar disorder
23:54across smooth states in brown,
23:57and then people who are who have
23:59unipolar depression in blue.
24:01And you can see that the response
24:03and the fear task is the same between
24:06controls and people with MDD.
24:09But people with bipolar disorder
24:11have an upregulated response across
24:13various clusters in the brain.
24:16And when we correlate this response
24:19with anglify availability,
24:20we also see significant findings
24:22in the bipolar group only.
24:25So we here,
24:26we're seeing that Anglo 5 potentially
24:28can help but differentiate BD
24:30from MDD across mood,
24:34cognitive and bold response measures.
24:38And currently,
24:39I'm evaluating Anglo 5 to see if it
24:42can help us differentiate suicidality
24:46in people with bipolar disorder specifically.
24:49And this RO one started right before COVID.
24:52And so we've not been as successful
24:55in these previous studies,
24:57but the data collection's ongoing.
24:58I'll be happy to present our data
25:00in a couple of years,
25:01but right now I will switch gears
25:04and talk about PTSD.
25:06So a few years ago,
25:08I was asked to incorporate PTSD and
25:12get the PTSD molecular imaging program
25:15growing at Yale and in collaboration
25:18with the National Center for PTSD.
25:20And so I wanted to see if Amglu 5
25:23availability again can help us
25:26differentiate people who have PTSD
25:28versus MDD or bipolar etcetera,
25:30etcetera in in terms of helping
25:34them get better treatment.
25:35And so PTSD is one of the
25:38newer disorders in the DSM.
25:40It was established as a diagnosis in 1980,
25:42and it is the only disorder
25:44that we know the etiology for.
25:46There has to have been a traumatic event,
25:48a criterion, a event that has led
25:51to this to development of PTSD.
25:54About 8% of Americans suffer from
25:57PTSD and this number varies between
25:59a few different publications.
26:02It is more prevalent in women,
26:03more prevalent in veterans,
26:05and it is the only anxiety disorder
26:08which predicts anxiety related
26:10disorder which predicts suicidality
26:13independent of other comorbidities.
26:16Unfortunately, there are only two
26:18FDA approved treatments for PTSD.
26:21They're both SSRIs and they're both
26:24developed for the treatment of depression.
26:27So they have modest efficacy,
26:29about 10% difference as compared to placebo,
26:33smaller effect size than psychotherapy
26:36and unclear synergy with psychotherapy.
26:39They are slow to response typical to any
26:43SSRIs of about, you know, two months.
26:47And so you know,
26:48we don't think that that's good enough,
26:50right.
26:50If somebody has severe symptoms,
26:52they cannot sleep,
26:53they cannot work etcetera,
26:54etcetera.
26:55You want to be able to help them right away.
26:58And so there is a lot of data in
27:00the literature showing that Anglo
27:035 is anxiolytic and could actually
27:06participate in symptomatology of PTSD.
27:08And all these data come
27:10from preclinical models.
27:11There are no data in human before
27:14we started publishing this.
27:15So we see that fear conditioning
27:18is associated with increased
27:20expression of Anglo 5.
27:22Anglo 5 activity leads to enhancement
27:24of contextual fear after stress.
27:27Studies have shown that administration of
27:30a negative Alastric modulator immediately
27:32post trauma inhibits memory consolidation.
27:35Our blockaded knockout of Anglo 5
27:38interferes with fear extinction.
27:39So these some of these seem against
27:43each other And so we have to be
27:45really careful of when we give
27:46Anglo 5 to people with PTSD,
27:48if we give it and whether we would
27:51give agents directly targeting Anglo
27:545 or modulate via different pathway.
27:57And so this is the first study that we did.
28:01We recruited 16 individuals with PTSD.
28:04They were all unmedicated, 16 age,
28:07sex and smoking status match controls.
28:11We did a lot of measures
28:14including CAPS and and PCL,
28:16which measured PTSD specifically.
28:18And then all participants did a PET scan
28:22to measure and glorify availability.
28:25And so our sample was pretty chronic PTSD,
28:27about 20 years.
28:29On average,
28:30nine met criteria for comorbid MDD,
28:32which tells you that a lot of
28:35these individuals were more severe
28:37in their PTSD symptomatology.
28:39It was a mixed trauma sample with some
28:43civilians and some combat veterans.
28:45And then we had six people with
28:47passive suicidal ideations at
28:49the time of pet scanning,
28:51and four reported at least
28:53one suicide attempt.
28:54And so these are outcome data.
28:56So the top panel is the
28:59PTSD group and the bottom
29:02is our healthy control group.
29:04And so we look at, if you look at red,
29:07orange, yellow areas,
29:08these are quote UN quote hot areas.
29:10So these are the areas where we see
29:12the greatest density of whatever it is
29:14that you're trying to study in PET.
29:15And you can visually see higher
29:17receptor availability in people
29:19with PTSD as compared to controls.
29:20And that won't lie that we actually
29:23expected low receptor availability
29:25given the previous MDD study that
29:28was published and also thinking in
29:31terms of synaptic density and that
29:34it should be lower under stress
29:36disorders and so there should be
29:38less places from Glow 5 to sit.
29:40And so it would measure
29:42low receptor availability,
29:44but we showed crater across brain regions.
29:47And again prefrontal cortical
29:49regions were our main outcomes,
29:52but we saw this across the whole brain.
29:55And Sophie Holmes led the publication of
29:58this study and when she ran some correlation,
30:01she saw that high Anglo 5
30:03availability was associated with
30:05great avoidance symptoms in PTSD.
30:07So it's it's really interesting to see
30:09differences in the brains between groups,
30:12but it's actually much more interesting
30:14to see that there's clinical relevance.
30:17And this finding is really,
30:19really important because avoidance
30:22is something that
30:26prevents people from overcoming
30:28their PTSD symptoms.
30:29So if we avoid places, people, time,
30:31etcetera that remind us of the event,
30:34we cannot overcome the PTSD.
30:37And maybe on below 5 agents
30:38could help us with therapy,
30:40maybe we can give it prior to
30:42exposure therapy, etcetera.
30:43And again, I told you that I was
30:46kind of surprised by these findings.
30:50And so I had been collaborating with
30:53the late Ron Duman for some other work.
30:55And I had asked him if he could look
30:58at the postmortem brain tissue and
30:59people with PTSD that he had from
31:02National Center Brain Bank and see if
31:04there were Anglo 5 related proteins
31:06or stress related proteins that
31:08could help us explain his findings.
31:11And so Ron was kind to run some
31:14analysis for us and he showed that
31:16F KB P5 was 3 1/2 times lower and
31:19people with PTSD in the postmortem
31:21sample as compared to controls.
31:23And FKBP 5 is a glucocorticoid
31:26regulating protein.
31:27And there's some hypothesis that there's
31:30hypochlorosolamia in people with PTSD.
31:33So this would go along with just reduced
31:36cortisol tone in people with PTSD.
31:38And then he showed that Shank protein,
31:40but not Anglo 5 gene expression
31:43were higher in people with PTSD.
31:46And so again,
31:47what we're showing is lower
31:49cortisol protein but higher Anglo
31:525 related trafficking protein.
31:53And So what we think is happening
31:56in the healthy brain,
31:58there's so many receptors,
31:59some of them are internalized,
32:01some of them are in the synaptic space.
32:04And so our radioligand as I told you
32:06can only bind to the places that to the
32:09receptors that are the synaptic space.
32:11In PTSD,
32:12we think that they're increased
32:14Shank levels which traffic Anglo
32:165 to the synaptic space.
32:18Now the radioligand has more places
32:21to bind and so we're measuring
32:23receptor availability that is higher.
32:24So the number of receptors did not change,
32:27but their location changed and this location,
32:30this change in location appears to
32:33contribute to the avoided symptomatology.
32:36And so,
32:37given the higher rates of
32:39suicidality in this group as well,
32:41we proceeded with another study
32:42that was led by Maggie Davis.
32:45And we have people with who
32:48are healthy controls in grey,
32:50people with depression and purple.
32:52The light purple is people with
32:53depression who did not have suicidality
32:55at the time of pet scanning.
32:57And then the darker purple are people who
33:00had suicidality at the time of scanning.
33:02And then in below are people
33:04with PTSD and light.
33:05No suicidality time of scanning and
33:08then dark suicidality time of scanning.
33:10And so here I just wanted to
33:11show you our pretty images.
33:13So the top panel people with PTSD
33:15with suicidality and you can see
33:18significantly higher receptor
33:20availability in our graph and
33:22in this panel as compared to any
33:24other group in PTSD suicidality.
33:27And what was critically important
33:29is the correlation between
33:34and mood symptoms in people with
33:38depression as compared people with
33:40PTSD as compared to people with
33:42with depression were different.
33:43So people with PTSD who had
33:45greater receptor availability also
33:47had greater number of symptoms,
33:49but people with depression who
33:51had greater receptor availability
33:53had actually lower symptoms.
33:55So here again,
33:57we're using Anglo 5 to help us
34:00differentiate some stress disorders
34:02that may overlap in symptomatology
34:05and show that they really potentially
34:07need to be treated differently.
34:10But what I really was confused about and
34:13still wasn't explaining about these data was,
34:17is Anglo 5A regulation A
34:20predisposition to developing a PTSD?
34:22So are people who are born with high
34:25Anglo 5 levels are more likely to
34:28develop PTSD upon a traumatic event?
34:31Or is Anglo 5A regulation
34:33A consequence of PTSD?
34:35Because a lot of people have
34:38significant trauma in their life,
34:40but not all of them or most of
34:43them will develop PTSD symptoms.
34:46And so we collaborated with Jane
34:48Taylor and Ralph de Leon in
34:52Molecular Psychiatry and Ruth Ashe
34:54led the studies in animal models.
34:57They tried to do this in human,
34:58but it provided impossible to identify
35:00an emergency room people who had a
35:02traumatic event and then followed
35:03them for months to see if they would
35:06develop PTSD and scan everybody.
35:07And so Ruth took on the study in
35:11rats and we administered stress
35:13enhanced fear learning paradigm.
35:16And so after the animal survived,
35:18they acclimated for a bit.
35:20Then they participate in pet scanning,
35:23daily handling and then Ruth
35:26did behavioral testing and then
35:29more pet scanning.
35:31And so on the first day
35:33the animals were shocked
35:37and then the next day there was no shock
35:39in animals and they were shocked again
35:41the 3rd day and no shock on the 4th day.
35:43And so this is encephal paradigm
35:46where the shock is not,
35:49the number of shocks is not to
35:51the extent that all animals are
35:52going to develop PTC type symptoms,
35:54there's going to be a spread
35:56like just like in humans.
35:57So some animals are going to be resilient
36:00and some animals are going to be vulnerable.
36:03And we started seeing sex differences between
36:06behaviours in animals who were shocked.
36:11And then Ruth also divided the animals
36:14who were low responsers or resilient
36:17versus high responders or vulnerable after
36:21their shock in the in their freezing.
36:24And she saw sex differences
36:26in those groups as well.
36:28And then in PET scanning,
36:30we saw that actually receptor
36:32availability was not different
36:35between control groups and groups
36:37who were vulnerable or groups
36:40who develop PTSD type symptoms.
36:42So ANGLE 5 availability does not
36:45predispose to development of PTSD,
36:47at least in this work,
36:48but did increase in animals
36:51as a consequence of
36:55of foot shock of stress.
36:57And again we saw some stress sex
37:00differences And the freezing on day
37:022 on the day that animals were not
37:05shocked is related to fear memory.
37:07So it's after the traumatic event when
37:10the animals are being put back in the
37:12context of where they were stressed and
37:14how do they behave there and how much
37:16freezing are they participating in.
37:18And so the greater the freezing behavior,
37:20the greater receptor availability and
37:23again some sex differences in that.
37:26And so looking at some more recent literature
37:31and back at some other literature,
37:33there is some evidence to support Anglo 5
37:36of regulation in response to PTSD events.
37:38And so this work was done right
37:41around the time that we published
37:43our work only in male models,
37:46but also showing that freezing
37:49behaviour is more prevalent in animals
37:52who develop PTSD type symptoms.
37:55But MPEP, which is Mglu 5 negative
37:58elastaric modulators,
37:58blocked this response,
38:00this freezing response.
38:02And actually animals also who had
38:06greater PTSD symptoms had developed more,
38:09had greater Mglu 5 availability upon retest.
38:12But MPEP had blocked this effect.
38:15So the study actually,
38:16you know,
38:17did some treatment and showed
38:20that treatment with Mglu 5 NAMM
38:23could actually be beneficial.
38:25And so we also did our own work
38:28to modulate Mglo 5 to see we'll
38:31change symptomatology in human.
38:36And we did this a while ago
38:38via administration of ketamine.
38:41And why we administered ketamine is we
38:45wanted to modulate Mglo 5 not directly,
38:48but via modulation of glutamate.
38:51And I think all of you know at this
38:54point that 7 acetic doses of ketamine
38:56lead to a large surge in glutamate.
38:59This was replicated many, many times,
39:01but anaesthetic doses do not
39:02lead to a surge in glutamate.
39:05And there were studies done with Mrs.
39:08showing this is proton, Mrs.
39:10showing that administration of ketamine
39:12leads to increases in glutamate in human.
39:15And then Jerry Senecora and his
39:18group did a study with carbon 13 Mrs.
39:21showing increases in glutamate
39:23levels after anesthetic doses
39:26of ketamine in animal models.
39:29And so this was our study day,
39:31our study design, sorry.
39:33So we screened subjects and they
39:35participate in MRI scanning and
39:36then we do a baseline scan and
39:38a ketamine scan the same day.
39:40And then we invited people 24 hours
39:42later to participate in another
39:44scan and we picked the 24 hour
39:46time point is because that's the
39:48greatest antidepressant response
39:50of ketamine administration.
39:52And so we thought that administration
39:54of ketamine would lead to a
39:57glutamate surge which would down
39:59regulate and Glu fives immediately.
40:01But that would lead to an up
40:04regulation of Glu 524 hours later
40:06because there will be more synapses.
40:08Given Ron's work of increased synaptogenesis,
40:11there will be more synapses.
40:14More places for Anglo 5 to sit on
40:16and so there will be greater angle 5
40:18availability and it will be related
40:20to instepressing response and so on.
40:22The ketamine day subjects
40:24participating to PET scans.
40:26That radio tracer was
40:27administered as a bolus,
40:28People are scanned for 90 minutes,
40:31they had a break and then we administered
40:33the radio tracer followed by ketamine
40:36bolus plus infusion paradigm.
40:37So this administration gives a
40:40bit more ketamine than the quote
40:43typical antidepressant 40 minute
40:46just infusion administration.
40:48But we really given the expense of pet,
40:51the need for a line,
40:53the radiation we give the subjects the
40:55time the subjects contribute to our studies.
40:58We really wanted to make sure that
41:00we're going to see significant findings
41:02if there were significant findings.
41:04So we gave a bit of a higher dose.
41:06So we had 13 people with
41:10depression participate.
41:11They you can see that they're
41:13depression scores were a bit lower
41:15than the typical depression group
41:17that we recruit but we were excluding
41:18people with any suicidality.
41:20We were really, really,
41:21really careful about making sure
41:23that people who are participating
41:25in the study given there was a
41:27research study with only one dose of
41:29ketamine and no treatment after that.
41:31We followed subjects but we did not
41:34provide treatment pharmacological treatment.
41:36We really wanted to make sure that
41:39these were subjects who could be
41:41able to complete the study without
41:43adverse events and then we have
41:4513 match controls as typical.
41:47And so this is our preliminary,
41:51our first study.
41:52This was only in healthy controls that
41:54Chrissy published in Biological Psychiatry.
41:57And so the top panel is MRI scans,
42:00the middle panel is our baseline PET and
42:03the bottom panel is our ketamine study.
42:06And you can see significant
42:07decrease in receptor availability
42:09after administration of ketamine.
42:11And if you think back to slide maybe
42:138 or 9 where I showed you there are no
42:17variation of Unglu 5 and that in the
42:20afternoon Unglu 5 levels are lower as it is.
42:23Given that we were measuring
42:24this in the afternoon,
42:25we're likely sub estimating how much display,
42:30how much change there was after
42:33administration of ketamine.
42:34So this 20 to 40% change the way measured,
42:37it's probably even greater.
42:38And this was across all brain regions
42:41including the cerebellum where
42:43people use as a reference tissue,
42:45again providing evidence that there
42:47is really indeed no reference tissue
42:50for measuring anglify availability.
42:53And contrary to our initial hypothesis,
42:58the 24 hour PET scan here in Gray,
43:00we're showing persistent lower Anglify
43:04availability and people with who are
43:07controls and and people who are depressed.
43:10And so again we were surprised and
43:14given that we expected increases
43:17in Anglophile availability and
43:19all of the initial studies,
43:22the mechanistic studies that I showed you
43:24helped us understand what is going on.
43:27And so on the left we have a typical
43:30situation where person has had no drug.
43:33Some of the receptors are
43:34the extrasynaptic space.
43:35There's so much glutamate and we're measuring
43:38receptors that are here on the cell surface.
43:41However,
43:42after administration of ketamine,
43:43we think there's greater glutamate release
43:45which is going to down regulate on Glu fives.
43:49So now more on Glu fives are
43:50going to be an internal space.
43:52Given that the radio ligand cannot
43:54measure internalized receptors,
43:55we're measuring low receptor availability.
43:58So we're thinking that this low
44:01receptor availability is indeed
44:03receptor trafficking to the
44:05internalized space and potentially is
44:08associated with changes in hematology.
44:11And so of course they told you
44:13to me it's really,
44:14really important to understand the
44:16link between what we're seeing
44:18in the brain to symptoms.
44:20And we saw a significant association
44:23between decreased and Angle 5 availability
44:26and decrease in symptomatology in
44:28specific in the psychic anxiety symptoms.
44:31And we also saw a decrease in suicidality
44:35in individuals who had greater
44:38decrease in Angle 5 availability.
44:41And so between the PTSD study
44:45and this ketamine study,
44:48we are seeing the Anglo 5 May
44:51not only help us differentiate
44:53between different disorders,
44:55but potentially has a role in suicidality.
44:57And I'm also seeing some of this
44:59in my bipolar work that I'm not
45:01ready to present yet.
45:03But going back to the literature,
45:05there's some
45:08support for alterations in Homer which is
45:11another trafficking protein for Anglo 5
45:13which is associated with suicide attempt.
45:15Higher PSD and 95 levels which is a
45:19post synaptic protein is a is increased
45:23in people with who died by suicide.
45:26Both ketamine and lithium exert
45:28into suicidal actions via influences
45:30and glutamatergic system.
45:32And now we're having evidence from our
45:34group showing that greater extent of
45:37Glu 5 down regulation is supporting
45:40greater relief from suicidal thinking.
45:43And so I truly believe that M Glu
45:465 is an important agent to study in
45:49helping us alleviate mental illness
45:52in various populations and there
45:54could be differentially expressed
45:56and differentially important across
45:59different populations.
46:00And this is all I have to show
46:03in terms of my large data,
46:05but I did want to show you a couple,
46:08just a couple more slides that have been,
46:12this is secondary analysis from what
46:14we've been doing and I'm looking
46:17for some collaborators especially
46:18in the studies of pain.
46:21So a lot of, you know,
46:24you know,
46:25there's interplay between pain and
46:27mood symptoms,
46:28but also between pain and suicidality.
46:30And what we're seeing with our Angular
46:335 work in people is higher receptor
46:36availability across diagnostic
46:38groups in people who reported chronic
46:41pain at the time of PET scanning.
46:44So they're in the top panel as
46:45compared to healthy control groups.
46:47And I just showed you that suicidality
46:50is associated with higher angular
46:525 availability as well.
46:53And so, you know, I'm,
46:56I'm trying to see if I can study
46:58pain and suicidality simultaneously,
47:00potentially cross diagnosis.
47:01And if anybody's interested,
47:03please let me know.
47:05But what is also really important
47:07is our pilot data showing higher
47:10Anglo 5 levels in people who use
47:13cannabis as compared to people
47:14who do not use cannabis.
47:16And I know a lot of people use
47:17cannabis and report using cannabis.
47:19And again, this is across stress groups.
47:23People call us and they say they
47:25use cannabis to relieve their
47:26PTSD symptoms or their anxiety
47:28symptoms or whatever symptoms,
47:29their pain symptoms.
47:30But it appears that use of cannabis
47:33is actually up regulating MGULA 5,
47:35which may potentially put these
47:37people at higher risk for suicidality.
47:39So I just wanted to show this,
47:41it's all preliminary data that
47:44we we're playing around with to
47:45see what we're going to do next.
47:47And if anybody wants to work
47:49together to collaborate, let me know.
47:50And thank you so much for your attention.
48:00Thanks, Irena.