Low-dose alcohol consumption protects against transient focal cerebral ischemia in mice: possible role of PPARγ.

BACKGROUND: We examined the influence of low-dose alcohol consumption on cerebral ischemia/reperfusion (I/R) injury in mice and a potential mechanism underlying the neuroprotective effect of low-dose alcohol consumption. METHODOLOGY/PRINCIPAL FINDINGS: C57BL/6 J mice were fed a liquid diet without or with 1% alcohol for 8 weeks, orally treated with rosiglitazone (20 mg/kg/day), a peroxisome proliferator-activated receptor gamma (PPARγ)-selective agonist, or GW9662 (3 mg/kg/day), a selective PPARγ antagonist, for 2 weeks. The mice were subjected to unilateral middle cerebral artery occlusion (MCAO) for 90 minutes. Brain injury, DNA fragmentation and nuclear PPARγ protein/activity were evaluated at 24 hours of reperfusion. We found that the brain injury and DNA fragmentation were reduced in 1% alcohol-fed mice compared to nonalcohol-fed mice. Rosiglitazone suppressed the brain injury in nonalcohol-fed mice, but didn't alter the brain injury in alcohol-fed mice. In contrast, GW9662 worsened the brain injury in alcohol-fed mice, but didn't alter the brain injury in nonalcohol-fed mice. Nuclear PPARγ protein/activity at peri-infarct and the contralateral corresponding areas of the parietal cortex was greater in alcohol-fed mice compared to nonalcohol-fed mice. Using differentiated catecholaminergic (CATH.a) neurons, we measured dose-related influences of chronic alcohol exposure on nuclear PPARγ protein/activity and the influence of low-dose alcohol exposure on 2-hour oxygen-glucose deprivation (OGD)/24-hour reoxygenation-induced apoptosis. We found that low-dose alcohol exposure increased nuclear PPARγ protein/activity and protected against the OGD/reoxygenation-induced apoptosis. The beneficial effect of low-dose alcohol exposure on OGD/reoxygenation-induced apoptosis was abolished by GW9662. CONCLUSIONS/SIGNIFICANCE: Our findings suggest that chronic consumption of low-dose alcohol protects the brain against I/R injury. The neuroprotective effect of low-dose alcohol consumption may be related to an upregulated PPARγ

Role of nitric oxide synthases in early blood-brain barrier disruption following transient focal cerebral ischemia.

The role of nitric oxide synthases (NOSs) in early blood-brain barrier (BBB) disruption was determined using a new mouse model of transient focal cerebral ischemia. Ischemia was induced by ligating the middle cerebral artery (MCA) at its M2 segment and reperfusion was induced by releasing the ligation. The diameter alteration of the MCA, arterial anastomoses and collateral arteries were imaged and measured in real time. BBB disruption was assessed by Evans Blue (EB) and sodium fluorescein (Na-F) extravasation at 3 hours of reperfusion. The reperfusion produced an extensive vasodilation and a sustained hyperemia. Although expression of NOSs was not altered at 3 hours of reperfusion, L-NAME (a non-specific NOS inhibitor) abolished reperfusion-induced vasodilation/hyperemia and significantly reduced EB and Na-F extravasation. L-NIO (an endothelial NOS (eNOS) inhibitor) significantly attenuated cerebral vasodilation but not BBB disruption, whereas L-NPA and 7-NI (neuronal NOS (nNOS) inhibitors) significantly reduced BBB disruption but not cerebral vasodilation. In contrast, aminoguanidine (AG) (an inducible NOS (iNOS) inhibitor) had less effect on either cerebral vasodilation or BBB disruption. On the other hand, papaverine (PV) not only increased the vasodilation/hyperemia but also significantly reduced BBB disruption. Combined treatment with L-NAME and PV preserved the vasodilation/hyperemia and significantly reduced BBB disruption. Our findings suggest that nNOS may play a major role in early BBB disruption following transient focal cerebral ischemia via a hyperemia-independent mechanism

Exercise training restores impaired dilator responses of cerebral arterioles during chronic exposure to nicotine

Our goal was to determine whether exercise training (ExT) alleviates impaired nitric oxide synthase (NOS)-dependent dilation of pial arterioles during chronic exposure to nicotine. We measured dilation of cerebral (pial) arterioles in sedentary and exercised control and nicotine-treated (2 mg·kg−1·day−1 for 4 wk via an osmotic minipump) rats to an endothelial NOS (eNOS)-dependent (ADP), a neuronal NOS (nNOS)-dependent [N-methyl-d-aspartic acid (NMDA)], and a NOS-independent (nitroglycerin) agonist. In addition, we harvested brain tissue from sedentary and exercised control and nicotine-treated rats to measure the production of superoxide anion and measured superoxide dismutase-1 (SOD-1) protein in cerebral microvessels using Western blot. We found that eNOS-and nNOS-dependent, but not NOS-independent, vasodilation was impaired in nicotine-treated compared with control rats. In addition, the production of superoxide anion (lucigenin chemiluminescence) was increased, and SOD-1 protein decreased, in rats treated with nicotine compared with control rats. Further, although ExT did not significantly affect eNOS- or nNOS-dependent vasodilation in control rats, ExT restored impaired eNOS- and nNOS-dependent responses in nicotine-treated rats. In addition, the increase in superoxide anion production observed in nicotine-treated rats was reduced by ExT, and SOD-1 protein was increased in nicotine-treated rats by ExT. We suggest that ExT restores impaired NOS-dependent dilation of pial arterioles during chronic exposure to nicotine by a mechanism related to the formation of superoxide anion

Dose-related influences of chronic alcohol exposure on nuclear protein expression (A) and DNA-binding activity (B) of PPARγ in CATH.a neurons.

<p>Values are means ± SE for 6 wells in each group. *P<0.05 vs. 0 mM alcohol.</p

Total infarct volume (A) and neurological score (B) at 24 hours of reperfusion after a 90-minute MCAO in nonalcohol-fed and 1% alcohol-fed mice treated without and with rosiglitazone or GW9662.

<p>Values are means ± SE for 6 mice in each group. *P<0.05 vs. Nonalcohol. #P<0.05 vs. Without Treatment.</p

Effect of chronic exposure of 1 mM alcohol on apoptosis in CATH.a neurons following a 2-hour OGD/24-hour reoxygenation.

<p>Values are means ± SE for 6 wells in each group. *P<0.01 vs. Without OGD/reperfusion. *P<0.05 vs. Nonalcohol.</p

Nuclear protein expression (A) and DNA-binding activity (B) of PPARγ in parietal cortex punched at the peri-infarct and the contralateral corresponding areas of nonalcohol-fed and 1% alcohol-fed mice following a 90-minute MCAO/24-hour reperfusion.

<p>Values are means ± SE for 6 mice in each group. *P<0.001 vs. Nonalcohol. #P<0.001 vs. Without MCAO/reperfusion.</p