Kang Y James, Li Yan, Sun Xichun, Sun Xiuhua
Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA.
Am J Pathol. 2003 Oct;163(4):1579-86. doi: 10.1016/S0002-9440(10)63514-6.
Previous studies using a cardiac-specific metallothionein (MT)-overexpressing transgenic mouse model have demonstrated that MT inhibits ischemia/reperfusion-induced myocardial injury. The present study was undertaken to test the hypothesis that the MT inhibition is associated with suppression of apoptosis mediated by mitochondrial cytochrome c release and caspase-3 activation. An open-chest coronary artery occlusion and reperfusion procedure to produce ischemia/reperfusion-induced left ventricle infarction was used in MT-overexpressing transgenic mice and non-transgenic controls. After 30 minutes of ischemia, the left ventricle was reperfused to allow blood flow through the previously occluded coronary artery bed. Myocardial infarction produced after reperfusion for 4 hours was significantly reduced in the MT transgenic mice. This inhibition correlated with the antiapoptotic effect of MT, as determined by a terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick-end labeling assay, mitochondrial cytochrome c release and caspase-3 activation. Ischemia/reperfusion-induced lipid peroxidation was also significantly inhibited in the MT-transgenic heart. Dimethylsulfoxide, a chemical scavenger for reactive oxygen species, was used to confirm the antioxidant effect of MT and found to suppress myocardial infarction and lipid peroxidation just as MT did. This study thus demonstrates that MT suppresses ischemia/reperfusion-induced myocardial apoptosis through, at least in part, the inhibition of cytochrome c-mediated caspase-3 activation pathway. The antiapoptotic effect of MT likely results from the suppression of oxidative stress and correlates with the inhibition of myocardial infarction.
先前使用心脏特异性金属硫蛋白（MT）过表达转基因小鼠模型的研究表明，MT可抑制缺血/再灌注诱导的心肌损伤。本研究旨在验证MT的抑制作用与抑制线粒体细胞色素c释放和半胱天冬酶-3激活介导的细胞凋亡有关这一假说。在MT过表达转基因小鼠和非转基因对照小鼠中，采用开胸冠状动脉闭塞和再灌注程序来产生缺血/再灌注诱导的左心室梗死。缺血30分钟后，对左心室进行再灌注，以使血液流过先前闭塞的冠状动脉床。MT转基因小鼠再灌注4小时后产生的心肌梗死明显减少。如通过末端脱氧核苷酸转移酶介导的脱氧尿苷5-三磷酸缺口末端标记试验、线粒体细胞色素c释放和半胱天冬酶-3激活所确定的，这种抑制作用与MT的抗凋亡作用相关。缺血/再灌注诱导的脂质过氧化在MT转基因心脏中也受到显著抑制。二甲基亚砜是一种活性氧的化学清除剂，用于证实MT的抗氧化作用，发现其与MT一样能抑制心肌梗死和脂质过氧化。因此，本研究表明MT至少部分地通过抑制细胞色素c介导的半胱天冬酶-3激活途径来抑制缺血/再灌注诱导的心肌细胞凋亡。MT的抗凋亡作用可能源于氧化应激的抑制，并且与心肌梗死的抑制相关。
