胰岛素样生长因子I通过改善线粒体功能保护新生大鼠心肌细胞免于凋亡

 目的：探讨线粒体机制在胰岛素样生长因I(IGF-I)保护心肌细胞中的作用。方法：体外培养新生大鼠心肌细胞，过氧化氢处理诱导凋亡，JC-1线粒体膜电位检测法和透射电镜观察心肌细胞线粒体膜电位和形态的改变，Annexin V-FITC/PI双染色法、caspase-3活性测定、DNA-ladder分析和Hoechst 33258染色方法观察心肌细胞凋亡的情况。结果：过氧化氢可诱导心肌细胞凋亡，siRNA下调Kruppel 样因子9（KLF9）48 h后，心肌细胞线粒体膜电位下降率明显降低，由对照组的(24.0±1.6)%，降为IGF-I处理组的(18.3±1.2)%和KLF9下调组的(15.2±1.2)%；线粒体形态明显改善；DNA片段化改善；caspase-3活性降低，与对照组相比IGF-I处理组降低(1.30±0.28)倍，KLF9下调组降低(1.31±0.43)倍；Annexin V-FITC/PI双染法显示细胞凋亡率对照组为（42.5±1.8）%，IGF-I处理组为（22.4±4.2）%，KLF9下调组为（32.5±3.5）%；Hoechst 33258染色结果显示凋亡小体减少，KLF9下调组与IGF-I的抗心肌细胞凋亡效果相似。结论：IGF-I通过下调KLF9表达改善线粒体功能，保护心肌细胞免于凋亡。

Insulin-like growth factor I protects neonatal rat cardiomyocytes from apoptosis through improvement of mitochondrial function

AIM：To investigate whether mitochondrial mechanism is involved in the anti-apoptotic effect of insulin-like growth factor I (IGF-I) on cardiomyocytes. METHODS：Primary neonatal rat cardiomyocytes (NRCMs) were cultured and treated with 200 μmol/L hydrogen peroxide (H2O2) to induce apoptosis. Kruppel-like factor 9 (KLF9)-specific siRNA was transfected into the cells by Lipofectamine 2000. The mitochondrial function was measured by JC-1 mitochondrial membrane potential (MMP) assay. The mitochondrial morphology was observed by transmission electron microscopy. Myocardial cell apoptosis was detected by Annexin V-FITC/PI dual staining, caspase-3 activity assay, DNA-ladder analysis and Hoechst 33258 staining. RESULTS：The apoptosis of NRCMs was induced by H2O2, with MMP decreased by (24.0±1.6)% compared with control group. The fall rates of MMP in IGF-I group and KLF9 siRNA group were (18.3±1.2)% and (15.2±1.2)%, respectively (both P<0.01 vs H2O2 group), and improved mitochondrial morphology, decreased caspase-3 activity, attenuated DNA fragmentation and reduced apoptotic bodies were also observed in these two groups. The apoptotic rates of NRCMs in IGF-I group and KLF9 siRNA group were (22.4±4.2)% and (32.5±3.5)%, respectively, both lower than that in H2O2 group ［(42.5±1.8)%, P<0.01］. The anti-apoptotic effect of KLF9 silencing on NRCMs was consistent with that of IGF-I treatment. CONCLUSION：IGF-I protects NRCMs from apoptosis through down-regulating KLF9 expression and improving mitochondrial function.