钙调神经磷酸酶的抑制参与大鼠心脏缺血后处理的保护作用

Inhibition of calcineurin is involved in cardioprotection induced by ischemic postconditioning in rats

目的:研究缺血后处理(I-postC)对缺血/再灌注(I/R)大鼠心肌钙网蛋白(CRT)及其下游钙调神经磷酸酶(CaN)信号转导途径的影响,探讨I-postC保护I/R心脏的机制。方法:采用Wistar大鼠在体心脏I/R模型,检测血流动力学及血浆乳酸脱氢酶(LDH)和肌酸激酶(CK-MB)含量,以TTC法和TUNEL法分别检测心肌梗死面积和细胞凋亡,发色底物法测定心肌CaN活性,免疫印迹法检测心肌组织CaN和CRT蛋白表达。结果:CaN抑制剂环孢霉素A显著缩小I/R所致的心肌梗死面积(P<0.05),抑制细胞凋亡(P<0.01),但对心功能无明显改善(P>0.05);与I/R组比较,I-postC组心功能改善(P<0.01),心肌梗死范围缩小(P<0.01),LDH和CK-MB漏出减少(P<0.01),细胞凋亡率降低(P<0.01),并显著抑制I/R诱导的心肌组织CaN活性升高(P<0.05)及CaN和CRT表达上调(P<0.05),与缺血预处理组比较差异无显著,但对I/R心肌的保护作用强于单纯环孢霉素A组。结论:I-postC至少部分通过抑制CRT-CaN信号途径,减轻大鼠心肌I/R损伤。

AIM： To demonstrate the mechanisms underlying eardioproteetion induced by isehemie postconditioning （I -postC） via studying the alteration of ealretieulin （CRT）/ealeineurin （CaN） signaling pathway in rat heart subjected to ischemia/reperfusion （I/R）. METHODS： The model of myocardial I/R injury in vivo was made by occluding the left anterior descending artery for 45 min followed by 24 h of reperfusion in Wistar rats. Hemodynamics and activity of lactate dehydrogenase （LDH） and creatine kinase - MB （ CK - MB） in plasma were measured. Myocardial infarct size was measured by 2,3,5 - triphenyhetrazolium chloride （TTC） staining and cardiomyocyte apoptosis was detected using in situ TDT- mediated dUTP nick end labeling （TUNEL）. The activity of CaN, the expressions of CaN and CRT in myocardium were detected by enzyme reaction phosphorus measurement and Western blotting analysis, respectively. RESULTS： Cyclosporin A, the inhibitor of CaN, limited significantly myocardial infarct size and cardiomyocyte apoptosis induced by I/R, but had no significant effect on cardiac function. I - postC ameliorated significantly the cardiac dysfunction induced by I/R. Compared with those in I/R group, the myocardial infarct size, the LDH and CK - MB activities in plasma and the cardiomyocyte apoptotic index were significantly reduced in I -postC group. In addition, I/R -induced upregnlation of CaN activity, CaN and CRT expression were relieved by I - postC. No significant difference was found between I - postC and ischemic preconditioning groups. I - postC had stronger protective effect on the reperfused heart compared with cyclos- porin A. CONCLUSION： The findings indicate that I - postC protects myocardium against I/R injury, at least in part, via inhibiting the CRT/CaN signaling pathway.