左卡尼汀通过抑制钙/钙调素依赖蛋白激酶Ⅱ信号通路抑制过氧化氢诱导的大鼠心肌细胞凋亡

 目的： 观察左卡尼汀对过氧化氢（H2O2）诱导的大鼠心肌细胞凋亡的保护作用及其机制。方法：利用200 μmol/L H2O2刺激12 h，建立体外原代培养新生乳鼠心肌细胞凋亡模型。Ca2+螯合剂1,2-双(2-氨基苯氧基)乙烷-N, N, N′, N′-四乙酸(BAPTA)、钙调素依赖蛋白激酶II (CaMKII)特异性抑制剂KN93及左卡尼汀分别于加入H2O2前30 min或1 h加入，以检测这3种药物对H2O2刺激下心肌细胞活力、细胞凋亡、细胞内静息钙浓度（［Ca2+］i）及磷酸化CaMKII (p-CaMKII)表达的影响。利用MTT比色法检测心肌细胞活力；流式细胞仪检测细胞凋亡率；利用激光共聚焦扫描检测［Ca2+］i；蛋白质免疫印迹法检测cleaved caspase-3及p-CaMKII的表达。结果：模型组经200 μmol/L H2O2作用12 h后，细胞活力显著下降，细胞凋亡率显著增加。BAPTA、KN93及左卡尼汀预处理显著抑制上述细胞损伤。进一步研究发现，H2O2 诱导的 ［Ca2+］i水平升高、cleaved caspase-3及p-CaMKII的表达增加均可被上述3种药物不同程度地抑制。结论：左卡尼汀可抑制H2O2所致的心肌细胞凋亡，该心肌保护作用可能与其抑制Ca2+/CaMKⅡ信号通路有关。

L-carnitine inhibits H2O2-induced rat cardiomyocyte apoptosis through suppressing Ca2+/CaMKII signaling pathway

AIM：To examine the inhibitory effect of L-carnitine on hydrogen peroxide (H2O2)-induced apoptosis of rat cardiomyocytes and to further explore the underlying mechanisms. METHODS：Primarily cultured neonatal rat myocardial cells were prepared and challenged by 200 μmol/L H2O2 to induce cell apoptosis. In order to evaluate the effects of Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N, N, N′, N′-tetraacetic acid (BAPTA), calmodulin-dependent protein kinase II (CaMKII) inhibitor KN93 and L-carnitine on cell viability, apoptosis, resting intracellular free Ca2+ concentration (［Ca2+］i) and phospho-CaMKII (p-CaMKII) expression, these three agents were added 30 min or 1 h prior to H2O2 stimulation. Cell viability was measured by MTT assay and apoptosis was determined by flow cytomertry. The ［Ca2+］i was measured by laser confocal scanning. Cleaved caspase-3 and p-CaMKII expression was detected using Western blotting. RESULTS：Upon 200 μmol/L H2O2 stimulation for 12 h， cell viability decreased and apoptotic rate increased significantly compared with control．Pretreament with L-carnitine, BAPTA and KN93 significantly increased cell viability and decreased apoptosis．Furthermore, intracellular Ca2+ overload triggered by H2O2 could be greatly relieved by L-carnitine and BAPTA pretreatment, but not affected by KN93. H2O2-stimulated cleaved caspase-3 and p-CaMKII expression was also significantly inhibited by all these three agents. CONCLUSION：L-carnitine inhibits H2O2-induced rat cardiomyocyte apoptosis possibly via suppressing Ca2+/CaMKII signaling pathway.