Published Online
on June 28, 2007

A more recent version of this article appeared on August 1, 2007

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Submitted on January 23, 2007
Revised on February 13, 2007
Accepted on February 20, 2007

Neuroprotective Effects of Leptin Against Ischemic Injury Induced by Oxygen-Glucose Deprivation and Transient Cerebral Ischemia

Feng Zhang MD, PhD; Suping Wang MD; Armando P. Signore PhD; and Jun Chen MD^*

From the Departments of Neurology (F.Z., S.W., A.P.S., J.C.) and Pharmacology (J.C.), University of Pittsburgh, and the Geriatric Research, Educational and Clinical Center (J. C.), VA Pittsburgh Health Care System, Pittsburgh, Pa.

^* To whom correspondence should be addressed. E-mail: chenj2{at}upmc.edu.

Background and Purpose--Leptin is the major adipose hormone that regulates body weight and energy expenditure by activating leptin receptors in the hypothalamus. Leptin receptors are also present in other cell types, and a potent antiapoptotic effect for leptin has recently been reported. We investigated whether leptin was neuroprotective against ischemic brain injury.

Methods--In vitro ischemic injury was induced in rat primary neuronal culture by oxygen-glucose deprivation for 90 minutes. In vivo ischemic brain injury was induced by middle cerebral artery occlusion in mice for 60 minutes.

Results--Leptin receptors were detected in cultured rat cortical neurons, as well as in the mouse cortex, striatum, and hippocampus. In vitro results showed that leptin, 50 to 100 µg/mL, protected primary cortical neurons against death induced by oxygen-glucose deprivation in a concentration-dependent manner. In vivo studies in the mouse brain demonstrated that the intraperitoneal administration of leptin, 2 to 8 mg/kg, dose-dependently reduced infarct volume induced by middle cerebral artery occlusion. Leptin was effective when injected 5 minutes before or 30 to 90 minutes after reperfusion, but not 2 hours after reperfusion. Leptin improved animal body weight recovery and behavioral parameters after cerebral ischemia. Leptin enhanced the phosphorylation of extracellular signal-related kinase 1/2. Both extracellular signal-related kinase 1/2 activation and neuroprotection were abolished by the administration of PD98059 in vitro and in vivo.

Conclusions--Leptin is neuroprotective against ischemic neuronal injury. Our findings suggest that leptin is a legitimate candidate for the treatment of ischemic stroke.

Key words: brain ischemia • extracellular signal-related kinase 1/2 • leptin • oxygen-glucose deprivation

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