autonomic neuroscience from bench to bedside

Autonomic Neuroscience from Bench to Bedside

Ann Arbor

May 14, 2004

Mentoring Advice

• Become a skilled clinician

• Use the best methodology

• Know everything about something

• Work hard

– John B. Youmans, John A. Oates and Victor A. McKusick

How Dysautonomias Teach Us

Amplification of Signal

Unique Pathophysiologic Modelsafferent lesion (BF)efferent lesion (AF)central lesion (MSA/SDS)gene-specific disorders

Phenomena

Mechanisms

Top 7 Lessons: A Personal Perspective

LBP POTS NormotensionLabileHBP

HBP

Cardiovascular Continuum

Orthostatic tachycardia

Orthostatic hypotension

~500,000 Americans

~100,000 Americans

NMS

Bradycardia/hypotension~500,000 Americans

Top 7 Lessons From Dysautonomias

• You can live without norepinephrine (NE)

• Dopamine can be important in BP control

• Baroreflex failure (BF) can present as Pheo

• BF can present as malignant vagotonia

• Food and water powerfully affect BP

• Orthostatic tachycardia (POTS) is common

• Too much NE can be bad for you

DBH Deficiency

• Severe orthostatic hypotension• Ptosis of the eyelids• Complicated perinatal course

– Shock– Hypoglycemia– Hypothermia

• Nasal stuffiness• Retrograde ejaculation

Are pressor reflexes intact ?

-5

0

5

10

15

20

25

30

NL PT

cold pressormm Hg

Noradrenergic system is nonfunctional

Are Adrenergic Receptors Present?(Phenylephrine)

0

20

40

60

80

100

120

140

160

180

NL PT

Phe25

Adrenergic receptors are functional

Are Sympathetic Nerves Present?

0

5

10

15

20

25

30

35

40

45

50

NL PT

MSNAbursts/min

Noradrenergic nerves are electrically active

Is Plasma Norepinephrine Present?

0

50

100

150

200

250

NL PT

NEpg/ml

No Norepinephrine

Catecholamine SynthesisCatecholamine Synthesis

E P I

N O R E P I

D A

D O P A

TY R

Is Plasma Dopamine Present?

0

50

100

150

200

250

NL PT

dopamine

Dopamine is greatly increased

pg/ml

Plasma DA >> NE

0

50

100

150

200

250

NL PT

DANEpg/ml

DA replacing NE ?

Catecholamine SynthesisCatecholamine Synthesis

E P I

N O R E P I

D A

D O P A

TY R

DBH

DBH Deficiency Genetics

• IVS1+2T>C is causative in both patients.

• Missense mutation in exon 2.

• Missense mutations in exons 1 and 6.

Kim K-S, Am J Hum Gen 2002; 108: 140

...GACACTGCCTATTTTGCG GACGCCTGGAGTGACCAG... D T A Y F A D A W S D Q

Exon1 Exon2

Exon 1 Exon 2

…GACACTGCCTATTTTGCG gcgagt-108bp-gtttga-380bp-agcag GACGCCTGGAGTGACCAG D T A Y F A A S ------- V stop

Exon 1 Intron 1

1,018

517

396

298

220

Exon 2

Exon1 Exon2

B

Effect of the mutation IVS1+2T on DBH splicing

No

rma

l

Mu

tan

t

AExon1 Exon2 Exon3 Exon4

CMV promoter

Normal

Mutant

DDH-DeficiencyH-Deficiency

DOPS TherapyDOPS Therapy

DOPSDOPSDOPS

NE

NE

DOPS* Restores NE to Normal

0

100

200

300

400

500

600

Placebo DOPS

DANEStand Time

pg/ml orseconds

*Norepinephrine-COOH

Catechols in DBH Deficiency

• ‘Normal’ cognitive and psychiatric faculties• Completely absent in blood, CSF, urine:

– Norepinephrine– Epinephrine– Normetanephrine– Metanephrine– DHPG– VMA

• “Why is BP low in DBH Deficiency ? – because NE is absent ?– or because DA is raised ?”

…..Otto Kuchel, Montreal

Metyrosine blocks tyrosine hydroxylase causing hypotension by lowering NE

The TH-antagonist metyrosine lowers DA and raises BP

0

50

100

150

200

250

Placebo MET

NEDABP

pg/ml ormm Hg

Weight rose 1 kg: DA was an endogenous diuretic

Normal Baroreflex

Baroreflex Failure

Resting quietly Excitation

Selective Baroreflex Failure

Resting Quietly ExcitationJens Jordan et al, Hypertension 1997;30:1072

Water and BP in Autonomic Failure

Jens Jordan et al. Circulation 2000;101:504

Effect of Nn-Nicotinic Blockade (Trimethaphan) on Water’s Pressor

Action

0

5

10

15

20

25

30

35

40

45

No Trim Trim

BP RisemmHg

Autonomic Function Necessary for Pressor Action

500 ml Oral vs Intravenous Fluid

0

5

10

15

20

25

30

35

40

45

Oral H2O IV D5W

BP Rise

The oral route is key to water’s pressor effect

mmHg

Does Oral Water Suppress Sympathetic Activity

36

37

38

39

40

41

42

43

44

45

Before H2O After H2O

MSNAbursts/min

Water increases sympathetic activity

Water and BP: Many questions

• Pressor when baroreflex fails

• Must be oral for effect

• Causes increased sympathetic activity

Water in normal subjects

• Water raises BP ~11 mmHg in older normal subjects

Is water ingestion a source of noise in clinic BP determinations?

Water

No Water

Water Improves Tolerance of Head-Up Tilt

Time (min)

50403020100

Cu

mu

lati

ve S

urv

ival

of

Tilt

Te

sti

ng

1.0

0.8

0.6

0.4

P = 0.007

n=22 normal subjects

Postural Tachycardia Syndrome(POTS)

• Symptoms of sympathetic activation x 6 mo

• Orthostatic tachycardia > 30 bpm

• No orthostatic hypotension (BP > 20/10)

• Plasma NE > 600 pg/ml

Postural Tachycardia Syndrome:Many Names

Orthostatic Intolerance (OI)Effort SyndromeHyperdynamic ß-Adrenergic StateIdiopathic HypovolemiaIrritable HeartMitral Valve Prolapse SyndromeNeurocirculatory AstheniaOrthostatic Tachycardia SyndromeSoldier’s HeartVasoregulatory Asthenia

Postural Tachycardia (POTS)

Not a disease !

A syndrome

Like “anemia” or “fever”

Proband with POTSProband with POTS

• Palpitations

• Dizziness or lightheadedness

• Slowed thinking on standing

• Reduced exercise capacity

• Fatigue

• Near-fainting often and rarely fainting

John R. Shannon NEJM 2000;342:541

Plasma NE and Sympathetic Plasma NE and Sympathetic Activity (SA)Activity (SA)

050

100150200250300350400450

SA NE SA NE

Normal Patient

supineupright

% ofsupine value

An electrical/chemical dissociation ?

Tritiated NE ClearanceTritiated NE Clearance

0

0.5

1

1.5

2

2.5

L/min

NL PT

NE Clearance

NE clearance is impaired

Evidence of NET DeficiencyEvidence of NET Deficiency

• NE/MSA Dissociation

• Impaired NE Clearance

• Tyramine Insensitivity

• Yohimbine Hypersensitivity

• Low DHPG/NE Ratio

NET DeficiencyNET Deficiency

.

P

P P P

P

S-S

P

V69I

T99I

V245I

V449I

G478SA457P

N292T

V356L

A369P N375S

K463R

F528C

Y548H

Identified Coding Variants in the Human Norepinephrine Transporter

[3H

]NE

Up

take

(p

erce

nt

hN

ET

wt)

0.00

20.00

40.00

60.00

80.00

100.00

120.00

CHO LLC-PK1 HEK-293 COS-7

A457P

wt

The A457P Mutant Fails to Demonstrate NE Uptake in Several Heterologous

Expression Systems

How dysfunctional is A457P ?

• A457P has virtually no NE transport function.

• Little A457P actually gets into the cell surface.

• A457P interferes with WT NET getting to surface.

Conclusions

• Autonomic disorders lead us to discovery of both phenomena and mechanisms.

• Autonomic disorders like POTS are heterogeneous and will lead to discovery of many new genetic and acquired pathophysiologies.

• These discoveries will be enabled by bedside interventions and imaging capabilities which allow us to visualize physiology in real time.

Tyramine ResponsivenessTyramine Responsiveness(NE release into plasma)(NE release into plasma)

0

10

20

30

40

50

60

pg/ml

NL PT

NE Increase

Impaired tyramine release

Yohimbine (Yohimbine (22-antagonist)-antagonist)

0

10

20

30

40

50

60

70

80

NLNL+TCAPT

Therapy of Severe Dysautonomias

FIRST LINE:1. Water (+40 mmHg!)2. Food (-30mmHg!)

SECOND LINE:1. Physical Maneuvers2. Exercise (in water)

THIRD LINE:1. Fludrocortisone + Salt2. Pressor Drugs (midodrine)

Audience Question

I wondered if you’d comment on the other major pressor system, “rigination” intensive system, either in the DBH defiency or during the water “logging”?

Audience Question

There’s another system that involves anti-diuretic hormone… is there some sort of paradoxical DBH response to water in these individuals?

Audience Question

I was kind of puzzled about the fact that the absence of norepinephrine has little effects on brain function and also knowing that norepinephrine plays a significant role on appetite regulation because some of the anorexgenic drugs actually cause an increase in norepinephrine or norepinephrine “???” inhibitors. Was there any subtle effects that you could see whether these people tested by cognitive function or some other way?

Audience Question

So other neurotransmitters must be compensated for the absence of norepinephrine?

Audience Question

There has been a lot of interest in the pain field very recently in the COMT enzyme and that polymorphisms might be responsible for differences in pain sensitivity. But I am not aware of works that been done looking at the consequences on classic text of autonomic function. Are any of those polymorphisms associated with differences in autonomic function as we know it?

Audience Question

It’s always striking to me that patience with the “??????????” dysfunction are not orthostatic at all as compared to the “puromotic” failure. Do you have good explanations for the clinical evidence for the no orthostatis whatsoever in these patience?

autonomic neuroscience from bench to bedside

Documents

norepinephrine nedopamine

bp low

bporthostatic tachycardia

malignant vagotoniafood

bp pgml ormm hgweight

exon 2exon1exon2beffect

w s d q exon1exon2exon

dbh deficiencynormal