ISCHEMIC POSTCONDITIONING MEDIATES CARDIOPROTECTION VIA PI3K/GSK-3β/β-CATENIN SIGNALING PATHWAY IN ISCHEMIC RAT MYOCARDIUM

Previous studies have shown that PI3K/GSK-3 beta/beta-catenin signaling pathway plays a vital role in ischemic preconditioning. The present study attempts to evaluate whether PI3K/GSK-3 beta/beta-catenin signaling pathway might be responsible for the cardioprotection in ischemic postconditioning. Male Sprague-Dawley rats underwent 30 min of left anterior descending coronary artery occlusion and 2 h of reperfusion. One hundred twenty rats were randomized into six groups: sham, ischemia/reperfusion (I/R), ischemic postconditioning (Post), 15 mu g . kg(-1) wortmannin (PI3K inhibitor) plus ischemic postconditioning (Wort + Post), wortmannin plus I/R (Wort + I/R), and 0.6 mg . kg(-1) SB216763 (GSK-3 beta inhibitor) plus I/R (SB + I/R). Wortmannin and SB216763 were administered, respectively, 10 and 5 min before reperfusion. Myocardial infarct size; number of apoptotic cardiomyocytes; total Akt, GSK-3 beta; phosphorylated Akt, GSK-3 beta; beta-catenin in cytosol and nucleus; and Bcl-2 protein were assessed. It was found that Post and SB + I/R reduced infarct size (32.3% [SD, 2.8%], 32.7% [SD, 2.1%], vs. 53.4% [SD, 3.2%], respectively, P < 0.05) and apoptotic index of cardiomyocytes (23.2% [SD, 1.8%], 23.8% [SD, 1.8%], vs. 47.3% [SD, 5.8%], respectively, P < 0.05); compared with I/R, wortmannin abolished the cardioprotection of ischemic postconditioning. Post and SB + I/R increased phosphorylated Akt, phosphorylated GSK3 beta, beta-catenin in cytosol and nucleus, and Bcl-2 expression versus I/R. These results indicate that ischemic postconditioning could induce myocardial protection via PI3K/GSK-3 beta/beta-catenin signaling pathway, activation of which results in accumulation of beta-catenin and upregulation of its target genes Bcl-2.