Targeting eNOS Targeting eNOS for for

stroke protectionstroke protection

Li-ping WuLi-ping Wu

2004-10-132004-10-13

BackgroundBackground

nitric oxide synthasenitric oxide synthase (NOS)(NOS)

nitric oxide synthasenitric oxide synthase (NOS)(NOS)

L-arginineL-arginine

NONO

Neuroprotective:increasing cerebral Blood flow during brain ischemia

VasodilatoryAnti-inflammatoryAntithromboticAntiproliferative

eNOSeNOS

In vascular diseases

Main isomers of NOSMain isomers of NOS

cNOScNOSconsitutive formconsitutive form

iNOSiNOSinducible forminducible form

Constitutively expressed Calcium-dependent Including:

Induced in inflammatory and other cell types by stimuli such as endotoxin and proinflammatory cytokines Calcium-independent

Neuronal (nNOS)Neuronal (nNOS) Endothelial (eNOS)

eNOS: neuroprotectiveeNOS: neuroprotective

eNOS

nNOScerebral infarction

regional cerebral blood flow

(knocked out)

eNOS: neuroprotectiveeNOS: neuroprotective

L-NAME

eNOS

nNOScerebral infarction

regional cerebral blood flow

(lacking)

(inhibiting activity)

eNOSeNOS

nNOSnNOS

L-arginine

cerebral infarction

regional cerebral blood flow

(enhancing NO production)

eNOS: neuroprotectiveeNOS: neuroprotective

eNOS: neuroprotectiveeNOS: neuroprotective

Enhanacing eNOS function

Increase the number of circulating Increase the number of circulating Endothelial Progenitor cells (EPCs)Endothelial Progenitor cells (EPCs)

Contribute to neovasularization after ischemia stroke

Janus effect of NO in the brainJanus effect of NO in the brain

brain ischemia

nNOS

NO

toxic to surrounding neurons

iNOS

secondary damage

eNOS

neuroprotective

?What we should doWhat we should do

eNOS

nNOS

iNOS

upregulate and/or activate

inhibit

how

How to upregulate/activate eNOSHow to upregulate/activate eNOS

Statins

Steroid hormones

Physical activity

Nutrients

StatinsStatins

Statins:

cholesterol lowering inhibitors of

hydroxymethylglutaryl coenzyme A

(HMG-CoA) reductase

StatinsStatins

Indirectly: by reducing cholesterol levels

Directly: by stability of eNOS mRNA

by activating the pathway involving

phosphoinositide 3-kinase (PI3K)

and PKB/Akt

Mechanism:

Steroid hormonesSteroid hormones

corticosteroids

oestrogen

Directly activate eNOS

corticosteroids

Transcriptional effect: modulation of target genes by glucocorticoid receptor (GR)

PI3K and PKB/Akt

NO bioavailability

Non-nuclear effect: eNOS activation

corticosteroids

GR

Mechanism:

corticosteroids

Depending on the dose and duration of

corticosteroid administration

In clinical practice:

not good

Hyperglycemia (lactate acidosis)

Ten times higher dose

In animal models:

oestrogen

Genomic effects: an interaction between oestrogen receptor and regulatory subunit of PI3K

Nontranscriptional effects: direct binding of the oestrogen

receptor isoform to PI3K

eNOS activity

Mechanism:

oestrogen

Strongly neuroprotective effect in animal models of stroke

No effect in clinical trials of primary prevention

Physical activityPhysical activity

Regular physical activity

Mechanism: relating to alterations in blood flow increasing the number of circulating EPCs increasing neovascularization

NutrientsNutrients

Red wine and diets rich in flavonoids and plant polyphenols

Mechanism: ?

Uncoupling of eNOSUncoupling of eNOS

eNOS

enhancing ROS productionL-arginine

BH4

superoxide

NO

NADPH oxidase Vascular damage

eNOS uncoupling

eNOS – protect against stroke in human?eNOS – protect against stroke in human?

preventive approaches

chronic eNOS upregulation

regular physical activity

moderate consumption of red wine

chronic statin treatment high risk patients (high dose)

primary and secondary prevention

eNOS – protect against stroke in human?eNOS – protect against stroke in human?

acute approaches

eNOS activation

PI3K-Akt-mediated eNOS activation can be achieved administration of statins,corticosteroids and oestrogensL-arginine could be directly administered intravenously to increase NO production

Concluding remarksConcluding remarks

Although several important caveats, such as eNOSuncoupling and the dual role of NO in brain ischemia have to beconsidered

However statins, physical activity, steroid hormonesand nutrients can Lead to eNOS upregulation or activation, which protects from brain ischemic stroke

Thus eNOS targeting is an attractive approach to prevent and treat stroke in humans

ThankThank yyoouu