How do psychiatric drugs work?

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1. Statement of the problem: Antispychotics, Antidepressants, Bipolar drugs

2. Lessons from nAChRS; 3. Pharmacokinetics

4. Detailed hypotheses: Antipsychotic drugs SSRI Antidepressant drugs “Fast” NMDA blocker antidepressants

5. Tests of “inside-out” mechanisms for psychiatric drugs

Psychiatric drugs bind to classical targets within early exocytotic pathways: Therapeutic effects

Biological Psychiatry, Dec 2012 Henry A. Lester, Julie M. Miwa, and Rahul Srinivasan

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Disclaimer

This session deals with psychiatric disease.

Henry Lester is not a psychiatrist--not even a physician.

Don’t change any medical treatment that you might now be receiving on the basis of these lectures.

Don’t give any medical advice based on these lectures or problem sets.

0 2 4 6 8 10 12

Percent of Total

Disease Burden by Illness - Disability Adjusted Life Years

United States, Canada and Western Europe, 200015-44 year olds

Unipolar depressive disorders

Alcohol use disorders

Schizophrenia

Iron-deficiency anemia

Bipolar affective disorder

Hearing loss, adult onset

HIV/AIDS

Chronic OPD

Osteoarthritis

Road traffic accidents

0 2 4 6 8 10 16

Source: WHO – World Health Report, 2001

1. “The mood-elevating effects of fluoxetine [Prozac] are not evident after initial exposure to the drug but require its continued use for several weeks. This delayed effect suggests that it is not the inhibition of serotonin transporters per se, but some adaptation to sustained increases in serotonin function that mediates the clinical actions of fluoxetine. However, where these adaptations occur in the brain, and the nature of the adaptations at the molecular level, have yet to be identified with certainty.”

2. “All current antipsychotic drugs exert their full therapeutic actions over weeks, suggesting that, like lithium and antidepressants, slowly developing adaptations (in this case to initial D2 dopamine receptor blockade) are required for their antipsychotic effects.”

S. E. Hyman, E. Nestler, R. Malenka, 2008Molecular Neuropharmacology : A Foundation for Clinical Neuroscience, 2nd Edition

How do psychiatric drugs work?

4

Some psychiatric drugs, their targets, logP values, and half lives

fluoxetine (Prozac)

serotonin transporter logP 3.4, 24-72 hr

clozapine (Clozaril)5-HT2A serotonin receptor, GPCR

logP 3.2, 8-12 hr

ketamine (“special K”)

NMDA glutamate receptor logP 2.2, 3-5 hr

chlorpromazine (Thorazine)

dopamine D2 receptor, GPCRlogP 5.2, 16-30 hr

nicotine acetylcholine receptor

logP 1.2, 0.5 -2 hr

recreational / abused / addictive

antipschizophrenic antidepressant

5

6

Population of US Public Mental Insitutions

0

100

200

300

400

500

600

1800 1850 1900 1950 2000 2050

yearth

ousa

nds

Each “advance” in biology has been tried out on schizophrenia.

Early 20th century, German classification & Nazi genetics

1950’s American psychiatrists (including Bettelheim) reacted with “schizogenic mother”

or “refrigerator mother” hypothesis

1950, Linus Pauling fractionated urine; 1968 “Orthomolecular Psychiatry” in Science

1955, chlorpromazine dopamine theories

1970, glutamate theories

1995, growth factors, development, migration

2000, genetics & genomics

2003, interneuron diversity

2005, inflammation

There is no satisfactory explanation yet.

Schizophrenia Pathophysiology

In general, modern theories of schizophrenia emphasize abnormal balance among

neuronal circuits or pathways, rather than individual neurons that either(a) degenerate or (b) fire too much or too little

Clinical potency of

“classical” or “typical”

antipsychotic drugs

correlates best

with

dopamine D2 receptor blocking dose

(Nestler, 16-6)

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Clinical potency of “classical” or “typical” antipsychotic drugs correlates with dopamine D2 receptor blocking dose . . .

. . . . but modern “atypical” antipsychotics also block other GPCRs (Nestler, 16-8)

Haloperidol Clozapine Quetiapine

Risperidone Olanzapine Sertindole

Affinity

D1 dopaminergic

D2 &D3 dopaminergic

Muscarinic cholinergic

5HT2A serotonergic

α1 adrenergic

α2 adrenergic

H1 histaminergic

Conventionals:

8

Terrible side effects:

tardive dyskinesia (mesostriatal pathway) weight gain, agranulocytosis

Atypicals:

Major DepressionI. Symptoms: Depression is defined as the affective state of sadness that

occurs in response to a variety of human situations such as loss of a loved one, failure to achieve goals, or disappointment in love. Major depression differs only in intensity and duration or quality of the emotional state.

From Berton and Nestler, Nature Reviews Neuroscience, 7: 137, 2006

(“Anhedonia”)

II. Characteristics of Major DepressionA. Untreated episodes of major depression usually last from 7 - 14

months.B. Major depression is a recurring disorder, usually worsening with

age if not treated.C. The reported incidence of depression is 3 times higher in women

than in men.

Along with changes in mood, the symptoms of Major Depression include disruption of basic drives (eating and sleeping), as well as cognitive disturbances (ruminations, guilt, indecisiveness, persistent thoughts of suicide).

This constellation of symptoms suggest involvement of cortical structures, a number of limbic brain structures, including the hippocampus, amygdala, and mesolimbic dopamine neurons (“reward centers”), and also midbrain structures controlling appetite.

Depression involves dysfunction of many brain areas

From Berton and Nestler, Nature Reviews Neuroscience, 7: 137, 2006

Brain Areas that Regulate Mood

FC: Frontal cortex (esp. prefrontal and cingulate) - cognitive function, attention

HP: Ventral Hippocampus - cognitive function, memory

NAc: Nucleus Accumbens (ventral striatum) - reward and aversion

Amy: Amygdala - mediates responses to emotional stimuli

HYP: Hypothalamus regulates sleep, appetite, energy, sex

VTA: Ventral Tegmental Area - Sends dopaminergic projections to other areas

DR: Dorsal Raphe nuclei - send serotonergic input to other areas

LC: Locus Coeruleus - sends noradrenergic input to other areas.

I. The most successful medicines for treatment of Major Depression in recent years have been the selective serotonin reuptake inhibitors (SSRI’s)

II. SSRI’s include Prozac, Zoloft, Celexa, Paxil… These drugs inhibit the specific serotonin transporters that take up serotonin after it is released. Thus, the drugs are believed to increase serotonin levels in the brain.

III. Depression also is accompanied by misregulation of other neurohormonal pathways, for example the ACTH (pituitary) /cortisol (adrenal gland) pathway. NE and DA systems may also be misregulated.

IV. The SSRI’s are not effective for about half of cases of depression. Thus, we have much more to learn about the various causes of depression.

SSRI’s

Serotonergic systems in the brain

The midbrain Raphe nuclei

from Feldman et al., Principles of Neuropsychopharmacology, Sinauer, 1997

Rostral System

Caudal System

B6 and B7 are the Dorsal Raphe nuclei, which contain 5-HT neurons whose endings branch profusely and do not make “conventional” synapses. This fiber system is called the D-system.

B5 and B8 are the Median Raphe nuclei, which contain 5-HT neurons whose endings form repeated, more conventional synapses. This fiber system is called the M system.

Rostral System

from Feldman et al., Principles of Neuropsychopharmacology, Sinauer, 1997

B9 is also called the supralemniscal nucleus (SLN).

Two Serotonergic Fiber Types in the Forebrain Demonstrated by Immunocytochemical Labeling

D-System - small arrowsM-System - large arrows

Scale bar = 10 µm

from Tork, Ann. N.Y. Acad. Sci., 1990

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Bipolar Disease

1. Clinical description

2. Genetics

3. Possible causes

4. Heterozygote advantage?

5. Therapeutic approaches

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Bipolar disorder affects 1-1.5% of the

population in most modern societies.

Like depression, bipolar disorder is a

mood disorder. It was formerly termed

manic-depressive disorder, because

patients have one or more manic or nearly

manic episodes, alternating with major

depressive episodes.

1st episode often in mid-20’s.

Bipolar disorder often leads to suicide.

1. Clinical description, based on DSM-IV.

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From DSM-IV

Summary description of a manic episode

Manic Episode is defined by a distinct period during which there is an abnormally and persistently elevated, expansive, or irritable mood. This period of abnormal mood must last at least 1 week (or less if hospitalization is required).

The mood disturbance must be accompanied by at least three additional symptoms from this list:

-inflated self-esteem or grandiosity,

-decreased need for sleep,

-pressure of speech,

-flight of ideas,

-distractibility,

-increased involvement in goal-directed activities or psychomotor agitation, and

Excessive involvement in pleasurable activities with likelihood of painful consequences

If the mood is irritable (rather than elevated or expansive), at least four of the above symptoms must be present . . . .

The disturbance must be sufficiently severe to cause marked impairment in social or occupational functioning or to require hospitalization, or it is characterized by the presence of psychotic features . . . . .

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No single gene causes bipolar disorder.

Data for concordance among twins in bipolar disorder:

“narrow”

definition

“broad”

definition

monozygotic

(n = 55)79% 97%

monozygotic,

reared apart

(n = 12)

69%

dizygotic

(n = 52)24% 38%

2. Genetics

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Each new advance in neuroscience has been tried out on bipolar disorder--

as for schizophrenia.

There is no satisfactory explanation yet.

As for schizophrenia, present theories invoke:

circuit properties

early developmental events

rather than individual neurotransmitter systems.

3. Possible causes of bipolar disease

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Touched With Fire : Manic Depressive Illness and the Artistic Temperamentby Kay Redfield Jamison

"This is meant to be an illustrative rather than a comprehensive list . . .Most of the

writers, composers, and artists are American, British, European, Irish, or Russian; all

are deceased . . . Many if not most of these writers, artists, and composers had other

major problems as well, such as medical illnesses, alcoholism or drug addiction, or

exceptionally difficult life circumstances. They are listed here as having suffered from

a mood disorder because their mood symptoms predated their other conditions,

because the nature and course of their mood and behavior symptoms were

consistent with a diagnosis of an independently existing affective illness, and/or

because their family histories of depression, manic-depressive illness, and suicide--

coupled with their own symptoms--were sufficiently strong to warrant their inclusion."

4. Heterozygote advantage?

autobiography:An Unquiet Mind by Kay Redfield Jamison

23

from JamisonKEY:H= Asylum or psychiatric hospital; S= Suicide; SA = Suicide Attempt

Writers Hans Christian Andersen, Honore de Balzac, James Barrie, William Faulkner (H), F. Scott Fitzgerald (H), Ernest Hemingway (H, S), Hermann Hesse (H, SA), Henrik Ibsen, Henry James, William James, Samuel Clemens (Mark Twain), Joseph Conrad (SA), Charles Dickens, Isak Dinesen (SA), Ralph Waldo Emerson, Herman Melville, Eugene O'Neill (H, SA), Mary Shelley, Robert Louis Stevenson, Leo Tolstoy, Tennessee Williams (H), Mary Wollstonecraft (SA), Virginia Woolf (H, S)

Composers Hector Berlioz (SA), Anton Bruckner (H), George Frederic Handel, Gustav Holst, Charles Ives, Gustav Mahler, Modest Mussorgsky, Sergey Rachmaninoff, Giocchino Rossini, Robert Schumann (H, SA), Alexander Scriabin, Peter Tchaikovsky

Nonclassical composers and musicians Irving Berlin (H), Noel Coward, Stephen Foster, Charles Mingus (H), Charles Parker (H, SA), Cole Porter (H)

Poets William Blake, Robert Burns, George Gordon, Lord Byron, Samuel Taylor Coleridge, Hart Crane (S) , Emily Dickinson, T.S. Eliot (H), Oliver Goldsmith, Gerard Manley Hopkins, Victor Hugo, Samuel Johnson, John Keats, Vachel Lindsay (S), James Russell Lowell, Robert Lowell (H), Edna St. Vincent Millay (H), Boris Pasternak (H), Sylvia Plath (H, S), Edgar Allan Poe (SA), Ezra Pound (H), Anne Sexton (H, S), Percy Bysshe Shelley (SA), Alfred, Lord Tennyson, Dylan Thomas, Walt Whitman

Artists Richard Dadd (H), Thomas Eakins, Paul Gauguin (SA), Vincent van Gogh (H, S), Ernst Ludwig Kirchner (H, S), Edward Lear, Michelangelo, Edvard Meunch (H), Georgia O'Keeffe (H), George Romney, Dante Gabriel Rossetti (SA)

24

People with bipolar disorder are often fascinating in the early stages.

25

1887 1887-88

Vincent Van Gogh 1853-1890750 paintings; 1600 drawings; 700 letters

Life history: born and raised in the NetherlandsParis 1886-88Arles 1888 (1st episode; cut off his own ear)hospitalized 1888-1890Auvers-sur-Oise 3 months. Shot himself 7/27/1890

1886

26

I should like to do portraits which will appear as

revelations to people in a hundred years' time.

-- Letter to his sister Wil, 3 June 1890

Early 1889

Dr. GachetJune 1890

27

July 1890

28

29

30

Surgery to remove large portions of the brain (1950’s-60’s)

Electroconvulsive shock therapy (ECT).

Now administered under anesthesia.

Various electrode placements, pulse widths, and frequencies

“In situations where medication, psychotherapy, and the combination of these

interventions prove ineffective, or work too slowly to relieve severe symptoms

such as psychosis (e.g., hallucinations, delusional thinking) or suicidality,

electroconvulsive therapy (ECT) may be considered. ECT is a highly effective

treatment for severe depressive episodes.“

-- National Institute of Mental Health

Over a hundred theories have been offered to account for the efficacy of ECT.

http://www.acnp.org/G4/GN401000108/CH106.html

5. Therapeutic approaches to bipolar disorder

Surgical and electrical intervention

31

Li+ ion

Therapeutic effects begin in ~ 5 d, require several wk.

Li+ is quite poisonous at higher doses.

Valproic acid and other anticonvulsants

These also require several wk for full effects.

Therapeutic approaches to bipolar disorder

Drugs(upper left-hand regionof the periodic table)

32

1. We don’t know, but there are now some good guesses.

2. All ideas about Li+ assume an intracellular target.

Li+ enters cells freely through several channels and ion-coupled transporters

that normally serve for Na+.

Intracellular concentrations of Li+ are probably several mM.

3. Most ideas about Li+ involve enzyme inhibition.

Most of the suspected enzymes manipulate high-energy phosphate bonds.

How does Li+ act?

Three exemplar patients in the early days of Li+

Contemporary ideas about psychiatric drugshave emphasized binding to

the classical targets at synapses. . .

“Inside-out” mechanisms emphasize binding to the same classical targets, but within the

endoplasmic reticulum and cis-Golgi

BloodLungs

H+

Like most drugs, nicotine is a weak base.Its neutral form passes through 6 plasma membranes in ~ 20 s

logP = 1.1 = log (solubility in octanol / water) 34

NH+

N

N

N

N

N

CSF

Alvelolarepithelium

Brain capillary

35Nucleus

UPRE

PlasmanACh

R

Nicotine in CSF

Classical Pathway:Channel activation & desensitization

→ Do neurons survive Despite stressors?

Unfolded protein response

membrane

COPII vesicleSec 13/31

Sar1Sec24Sec23

ATF6

Golgi

PharmacologicalChaperoning→ upregulation

M3-M4 loop

H+ +

ERBiP

PERKIRE1

Clathrin

Secretory vesicle

COPII

Golgi complex

COPI

Early endosome

COPI

Lysosome

Ca2+

Na+

“Inside-out” Drug Action by Nicotine at α4β2 nAChRs

NH+

N

H+

N

N

Endoplasmic reticulum

nAChR

ATF6

IRE1

XBP1

eIF2α

PERK

ATF4

1. Agonist binding eventually favors stable, high-affinity states (a “chaperone”)

106

channels

nicotine20 sec

Three possible results of nicotine-nAChR binding in the endoplasmic reticulum

“closed”

AC Highest affinity

Fre

e E

ne

rgy

Reaction Coordinate

“activated”

“desensitized”

Bound states with increasing affinityunbound

agonist

?

2. Nicotine binding at subunit interface favors assembled nAChRs (a “matchmaker”)

3. Nicotine may displace lynx, directing nAChRs toward cholesterol-poor domains (an “escort”)

nicotine

lynx

36

R. L. Wiseman, C. M. Haynes, D. Ron Cell 2010

The three arms of the ER stress / unfolded protein response pathway

37

38

During chronic exposure to nicotine, α4β2 nAChRs are selectively upregulated.

Pharmacological chaperoning is necessary but not sufficient for upregulation.

Other sequelae of chaperoning: changed stoichiometry, reduced ER stress and reduced UPR.

Upregulation proceeds similarly in clonal cells, rodent brains, and smokers’ brains.

Inside-out Pharmacology of Nicotine Effects at α4β2 nAChRs

Now we’re assessing gene expression in identified neurons chronically exposed to nicotine.

Inside-out pharmacology is a powerful concept for nearly all CNS drugs:They are all membrane-permeant weak bases.

The discovery criteria for psychiatric drugs lead to excellent intracellular chaperoning

1. High bioavailability implies high membrane permeationAll psychiatric drugs have logP > 2

2. Good stability in the body implies simple or little enzymatic breakdown.Half-life is ~ 1 day.

3. Good selectivity, few off-target effects imply high-affinity binding to the targetKd < 1 μM, often ~ 10 nM

a. “Chaperoning”: (i) Transporter ligands are

organic substratesions,or antagonists,

They favor two major binding states, “inward” vs “outward”.

(ii) GPCR ligands (see next slide): agonistsantagonistsallosteric modulators“inverse” agonists

b. “Matchmaking”:(i) Neurotransmitter transporters must homodimerize before leaving the ER(ii) GPCRs homo- and heterodimerize, in some cases required for ER export,

in some cases favored by ligands 39

Pharmacological chaperoning of GPCRs

40

receptor mutant /WT drug class reference

adenosine A1 mutant agonists; antagonists (Malaga-Dieguez et al., 2010)

dopamine D4 bothtransported dopamine; quinpirole; antagonists

(Van Craenenbroeck et al., 2005

)gonadotropin-

releasing hormonemutant antagonists

(Conn and Ulloa-Aguirre, 2011

)

histamine H2 both agonist, inverse agonist (Alewijnse et al., 2000)

opsin mutant -- (Noorwez et al., 2008)

δ-opioid mutant antagonist (Leskela et al., 2012)

μ-opioid mutant agonists, antagonists (Chaipatikul et al., 2003)

melanin conc. hormone

mutant antagonist (Fan et al., 2005)

melanocortin-4 both antagonist, inverse agonist (Tao, 2010)vasopressin V1a both antagonist (Hawtin, 2006)

vasopressin V1b/V3 both antagonist (Robert et al., 2005)vasopressin V2 both antagonists (Wuller et al., 2004)

Enzyme or

channel

Transcription factors

Nucleus

Intracellular messenger

kinase cascade

Drug

+ In CSF

+

Endoplasmic reticulum

GolgiH+

ATF6,

CREB-H

IRE1

XBP1

p-eIF2α

PERK

ATF4

NucleusUPRE

Drug

+ in CSF

Transcription factors

ATF6

+ +

Neutral permeant drug

+

+ +

+

BiP

PERKIRE1

++

H+

ER

Golgi

β-arrestin

A. Inhibition of plasma membrane GPCR , and downstream effects

B. Intracellular pharmacological chaperoning of GPCR, and downstream effects

Most papers suggest . . . We suggest . . .

Two mechanisms for gene activation downstream from antipsychotic drugs

“Nearly” cell-autonomous actions of SSRI antidepressant treatment

Kellermann group 42

43

Other diagrams

Samuels & Hen, Eur J. Neurosci, 2011

Adult Neurogenesis

Inside-out actions would occur here

Gene activation is too brief to account for the “therapeutic lag”

Axonal transport provides a natural delay in the “inside-out” mechanism.

Speed: ~ 1 mm / day.

Suggests that equivalent effects would require briefer delays in animals with shorter axons

44

Marks et al, 1985

Dendritically localized events

Days of nicotine infusion

Mouse hippocampus

45

How does acute ketamine produce antidepressant effects within 2 hr?

Monteggia & Duman groups suggest . . .

(1) involve BDNF synthesis & release, (2) occur in the dendrites,(3) require protein synthesis, (4) do not require gene activation.

The effects

NMDA Receptor

kinases↓

BDNFsecretion

BDNF mRNA

BDNF↑

Dendritic Golgi

Outside-in

Ca2++

Decreased Ca2+ flux

DendriticER

COPII

BDNF mRNA

p-eIF2α↓

pPERK↓

Escorting

BDNF secretion

BDNF↑

Inside-out

BiP

PERKIRE1

H+

+

ER

+ +

+

+ +

NMDA Receptor

NH2+

H3C

H+

O

Cl

NHH3C

O

Cl

We suggest . . .

“Acid trapping” of nicotine might1.keep nAChRs

desensitized untilthey are exocytosed;

2.serve as a reservoir for nicotine

Cell nACh

R membrane

Clathrin

Endoplasmic reticulum

nAChR

Secretory vesicle

COPII

Golgi complex

COPI

Early endosome

COPI

Lysosome

pH

5.2 100

6.0 30

6.7 3

6.3 20

6.5 10

7.2 1

nic+

nicCSF

Nicotine in CSF

NH+

N

H+

N

N

See detailed calculations for antipsychotics:Tischbirek et al, Neuron 2012

7.2 1 &

What knowledge do we need next?

As usual, we need cell biology & biochemistry

1. Reconstituted, cell-free systems for ER exit and retrieval

2.Better real-time markers for compartmentalized receptors and transportersa. Imaging mass spectrometryb. Plasma membrane binding only? Possible with impermeant derivativesc. ER binding only? More challenging, especially for antagonists.

3.Better measurements of pathway-specific gene activation (RNA-Seq)

4.Analyze newly synthesized proteins

47

Contemporary ideas about psychiatric diseaseshave emphasized synaptic and signaling deficits . . .

“Inside-out” mechanisms emphasize that ~30% of a cell’s proteins enter the ER,

and additional nuclear and cytoplasmic proteins control their synthesis & trafficking.

49

Polygenicthe disease occurs only if several genotypes are present together

Genetically Multifactorialseveral distinct genes (or sets of genotypes) can independently cause the disease

Partially penetrantnongenetic or epigenetic factors are required, or the disease is inherently stochastic

PolygenicGenetically Multifactorial

PartiallyPenetrant

Three concepts used in describing complex diseases such a schizophrenia

50

Concordance for Lifetime Risk of Schizophrenia

0% 10% 20% 30% 40% 50%

general population

1st cousins

uncles/aunts

nephews/nieces

grandchildren

half siblings

parents

siblings

children

fraternal twins

identical twins

shared DNA

100%

50%(1st-degree relatives)

25%

12.5%

Like Kandel Figure 60-3

48%17%

1% (independent of culture)

Genetics(David Helfgott’s father; John Nash’s son)

51

GABAergic “chandelier cell” in human cerebral cortex hasmany large axon terminals . . .

DeFelipe, Brain (1999) 122, 1807 (Cajal Institute, Madrid)

PyramidalCells

Ch terminals

~ 100 μm

Ch terminals

Ch axon

. . . and plentiful somatic ER

Jones, J. Comp. Neurol., 1984

End of session

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