Cellular and molecular mechanisms of 17β-estradiol postconditioning protection against gastric mucosal injury induced by ischemia/reperfusion in rats

Aims: To investigate the protective effects of 17 beta-estradiol postconditioning against ischemia/reperfusion (I-R)induced gastric mucosal injury in rats. Main methods: The animal model of gastric ischemia/reperfusion was established by clamping of the celiac artery for 30 min and reperfusion for 30 min, 1 h, 3 h, 6 h, 12 h or 24 h. 17 beta-estradiol at doses of 5,50 or 100 mu g/kg (rat) was administered via peripheral veins 2 min before reperfusion. In a subgroup of rats, the estrogen receptor antagonist fulvestrant (Ful, 2 mg/kg) was intravenously injected prior to 17 beta-estradiol administration. Histological and immunohistochemical methods were employed to assess the gastric mucosal injury index and gastric mucosal cell apoptosis and proliferation. The malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, xanthine oxidase (XOD) activity and hydroxyl free radical (-OH) inhibitory ability were determined by colorimetric assays. Subsequently, the expression of Bcl-2 and Bax in rat gastric mucosa was examined by western blotting. Key findings: 17 beta-estradiol dose-dependently inhibited gastric I-R (GI-R) injury, and 17 beta-estradiol (50 mu g/kg) markedly attenuated GI-R injury I h after reperfusion. 17 beta-estradiol inhibited gastric mucosal cell apoptosis and promoted gastric mucosal cell proliferation in addition to increasing SOD activity and -OH inhibitory ability and decreasing the MDA content and XOD activity. The Bax protein level increased 1 h after GI-R and was markedly reduced by intravenous administration of 17 beta-estradiol. In contrast, the level of Bcl-2 protein decreased 1 h after GI-R and was restored to normal levels by intravenous administration of 17 beta-estradiol. These effects of 17 beta-estradiol were inhibited by pretreatment with fulvestrant. Significance: 17 beta-estradiol postconditioning should be investigated further as a possible strategy against gastric mucosal injury. (C) 2009 Elsevier Inc. All rights reserved.