Glycogen synthase kinase-3β/β-catenin promotes angiogenic and anti-apoptotic signaling through the induction of VEGF, Bcl-2 and survivin expression in rat ischemic preconditioned myocardium

Ischemic preconditioning (IP) enhances vascular endothelial growth factor (VEGF), Bcl-2 and survivin expression after myocardial infarction (MI). Mechanisms of angiogenic and anti-apoptotic effects due to IP still remain unclear. The present study attempts to address whether GSK-3β-β-catenin signaling in turn interacts with T-cell transcription factor/lymphoid-enhancer binding factor (TCF/LEF) and regulates these genes in the ischemic preconditioned myocardium. In a rat MI model with permanent occlusion of left anterior descending coronary artery (LAD), IP (four cycles of 4-min of ischemia and 4-min of reperfusion) significantly phosphorylated and inhibited GSK-3β and accumulated β-catenin in the cytosol and nucleus. Wortmannin, a PI-3 kinase inhibitor, repressed this effect in our model. We examined whether pretreatment with GSK-3β inhibitor lithium or SB216763, mimicked IP-mediated angiogenesis and cardioprotection. Lithium- or SB216763- treated rats revealed accumulation of cytosolic and nuclear β-catenin. This was followed by increased TCF/LEF transcriptional activity and the upregulation of VEGF, Bcl-2 and survivin mRNA expression accompanied by reduction of apoptotic cardiomyocytes and endothelial cells and increased capillary density after MI. The results of this study demonstrate, first time that inhibition of GSK-3β followed by accumulation of β-catenin in the cytosol and nucleus has potent anti-apoptotic and angiogenic effects after MI and that the PI3-kinase/GSK-3β/β-catenin signaling pathway plays an important role in IP.