钠钙交换体激活 CaMKII 介导大鼠离体心脏缺血再灌注损伤

目的：探讨钠钙交换体(Na+/Ca2+ exchanger，NCX)在离体心脏缺血再灌注损伤中的作用及其可能机制。 方法：40只大鼠随机分为4组：正常对照组(Control组)、10 μmol/L KB-R7943药物对照组(KB-R7943组)、缺血再 灌注(ischemia reperfusion，IR)组和10 μmol/L KB-R7943干预缺血再灌注组(KB-R7943+IR组)。采用Langendorff灌流 装置建立离体心脏缺血再灌注模型；以再灌注末心肌纤维形态的变化、左室发展压(LVDP)比值、左室舒张末压 (LVEDP)、冠状动脉流出液中乳酸脱氢酶(lactate dehydrogenase，LDH)活性、心肌梗死面积及细胞色素c和cleaved caspase-3蛋白的变化评价心肌损伤程度；Western印迹检测磷酸化钙/钙调蛋白依赖的蛋白激酶II(Ca2+/calmodulin- dependent protein kinase II，CaMKII)和受磷蛋白(phospholamban，PLN)苏氨酸17位点磷酸化(pThr17)水平的变化。 结果：与Control组相比，IR组再灌注末心肌纤维排列紊乱，断裂明显，心肌梗死面积、LVEDP和冠状动脉流出 液中LDH活性明显增加，LVDP比值降低，细胞色素c、cleaved caspase-3、磷酸化CaMKII及pThr17-PLN水平均上调 (P<0.01)；KB-R7943+IR组心肌梗死面积明显减小，LVEDP降低，LVDP比值明显改善，LDH活性明显降低，细胞色素 c和cleaved caspase-3蛋白水平明显降低，磷酸化CaMKII和pTh r17-PLN水平也明显下调(P<0.01)。结论：NCX可通过激活 CaMKII启动细胞凋亡和坏死，进而诱导心肌缺血再灌注损伤。

Na+/Ca2+ exchanger mediates ischemia-reperfusion injury by activation of CaMKII in isolated rat heart

Objective: To investigate the role of Na+/Ca2+ exchanger (NCX) in myocardial ischemia- reperfusion injury and the underlying mechanisms. Methods: Forty Sprague-Dawley rats were divided into 4 groups randomly: a control group, a KB-R7943 group, an ischemia-reperfusion group (IR group), and an IR plus KB-R7943 group (KBR7943+ IR group). Isolated Sprague Dawley male rat hearts underwent Langendorff perfusion. The ratio of left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), the infarct size of myocardium, and the lactate dehydrogenase (LDH) activity in the coronary flow was determined. HE staining was used to assess the change of myocardial morphology. Western blot was used to determine the levels of cleaved caspase-3, cytochrome c and the phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and the Thr17 site of phospholamban. Results: Compared with the control group, IR group significantly induced an enlarged infarct size, reduction of the ratio of LVDP, up-regulation of cytochrome c, cleaved caspase-3, p-CaMKII and p-phospholamban, and increased in the activity of LDH, the level of LVEDP (P<0.01) and the disordered myocardial morphology. These effects were significantly attenuated in the presence of KB-R7943 treatment (10 μmol/L). Conclusion: NCX mediates myocardial ischemia-reperfusion-induced cell apoptosis and necrosis through activation of CaMKII.