大鼠脑缺血诱导的细胞色素c的释放和Bcl-2表达的上调

利用全脑缺血模型,采用免疫印迹和免疫沉淀方法,探讨N-甲基-D-天冬氨酸受体和L-型电压门控钙通道拮抗剂对细胞色素c从线粒体中的释放和Bcl-2的表达变化影响。缺血／复灌后24h,线粒体中细胞色素c明显降低而胞浆中细胞色素c的成分相应增加。Bcl-2的表达呈时间依赖性,其表达在缺血／复灌后6h达到最大。在所有样品中,线粒体呼吸链蛋白细胞色素氧化酶没有变化,表明线粒体的制备方法是可靠的。线粒体中Bcl-2的表达减少和细胞色素c的释放可以被NMDA受体拮抗剂氯胺酮和L-型电压门控钙通道拮抗剂尼氟地平抑制。结果表明,N-甲基-D-天冬氨酸受体和L-型电压门控钙通道可能介导了脑缺血后细胞色素c从线粒体中的释放和Bcl-2的上调表达。缺血诱导的细胞色素c释放具有损伤作用而Bcl-2的上调表达则对脑缺血具有一定的保护作用。

Ischemia-induced release of cytochrome c from mitochondria and up-regulation of Bcl-2 expression in rat hippocampus

To evaluate the effects of different antagonists on the release of cytochrome c from mitochondria to cytosol and the expression of Bcl-2 in mitochondria in rat hippocampus after ischemia, we examined Bcl-2 and cytochrome c expression by immunoblotting using 4-vessel occlusion (4-VO) as brain ischemia model. The results showed that after 24 h ischemia/reperfusion (I/R) cytochrome c decreased markedly in mitochondria, which was correspondingly increased in the cytosolic fraction. Bcl-2 expression was time-dependent, reaching its peak level after 6 h I/R. In all those samples, there were no alterations in the subcellular distribution of cytochrome oxidase, a mitochondrial respiratory chain protein. The decreases in Bcl-2 and cytochrome c in mitochondria were restored by pretreatment with non-competitive NMDA receptor antagonist ketamine or L-type voltage-gated Ca2+ channel (L-VGCC) antagonist nifedipine at 20 min prior to ischemia. The results demonstrate that the release of cytochrome c from mitochondria to cytosol and the up-regulation of Bcl-2 are possibly mediated by NMDA receptors or L-VGCC following brain ischemia. Cytochrome c release may be injurious while Bcl-2 up regulation may be protective to ischemic hippocampus.