Kaga Shigeaki, Zhan Lijun, Altaf Elham, Maulik Nilanjana
Molecular Cardiology Laboratory, Department of Surgery, University of Connecticut Health Center, 263, Farmington Avenue, Farmington, CT 06030-1110, USA.
J Mol Cell Cardiol. 2006 Jan;40(1):138-47. doi: 10.1016/j.yjmcc.2005.09.009. Epub 2005 Nov 9.
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-3beta-beta-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-3beta and accumulated beta-catenin in the cytosol and nucleus. Wortmannin, a PI-3 kinase inhibitor, repressed this effect in our model. We examined whether pretreatment with GSK-3beta inhibitor lithium or SB216763, mimicked IP-mediated angiogenesis and cardioprotection. Lithium- or SB216763- treated rats revealed accumulation of cytosolic and nuclear beta-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-3beta followed by accumulation of beta-catenin in the cytosol and nucleus has potent anti-apoptotic and angiogenic effects after MI and that the PI3-kinase/GSK-3beta/beta-catenin signaling pathway plays an important role in IP.
缺血预处理(IP)可增强心肌梗死(MI)后血管内皮生长因子(VEGF)、Bcl-2和生存素的表达。IP产生血管生成和抗凋亡作用的机制仍不清楚。本研究旨在探讨糖原合成酶激酶-3β(GSK-3β)-β-连环蛋白信号通路是否反过来与T细胞转录因子/淋巴增强因子结合因子(TCF/LEF)相互作用,并在缺血预处理的心肌中调节这些基因。在左冠状动脉前降支(LAD)永久闭塞的大鼠MI模型中,IP(4分钟缺血和4分钟再灌注的四个周期)显著使GSK-3β磷酸化并抑制其活性,使β-连环蛋白在细胞质和细胞核中积累。渥曼青霉素,一种PI-3激酶抑制剂,在我们的模型中可抑制这种作用。我们研究了用GSK-3β抑制剂锂或SB216763预处理是否能模拟IP介导的血管生成和心脏保护作用。锂或SB216763处理的大鼠显示细胞质和细胞核中β-连环蛋白积累。随后,TCF/LEF转录活性增加,VEGF、Bcl-2和生存素mRNA表达上调,同时MI后凋亡心肌细胞和内皮细胞减少,毛细血管密度增加。本研究结果首次证明,抑制GSK-3β后β-连环蛋白在细胞质和细胞核中积累,在MI后具有强大的抗凋亡和血管生成作用,且PI3激酶/GSK-3β/β-连环蛋白信号通路在IP中起重要作用。