活性氧激活线粒体凋亡通路是亚硒酸钠诱导NB4细胞凋亡的重要机制

目的 探讨亚硒酸钠诱导NB4细胞凋亡过程中,活性氧引起的线粒体膜电位丧失及凋亡作用的相关机制。方法 用活性氧荧光探针DCFH-DA探测经亚硒酸钠诱导的NB4细胞内活性氧的含量。流式细胞术检测细胞凋亡率及线粒体膜电位变化。Westem blot检测胞浆中细胞色素C含量的变化及细胞总蛋白中Bcl-xl、Bax和Bid的含量变化及切割行为。同时应用活性氧清除剂MnTmPy及活性氧激活剂BSO预处理细胞,观察Bid及凋亡的变化。结果 活性氧清除剂MnTmPy可有效抑制亚硒酸钠诱导的NIM细胞凋亡、线粒体膜电位丧失及Bid的切割;而BSO可促进线粒体膜电位丧失。结论 亚硒酸钠诱导NIM细胞凋亡的可能机制是通过刺激细胞产生活性氧,一方面下调抗凋亡蛋白Bcl-xl,另一方面激活线粒体打孔蛋白Bax和Bid,损伤线粒体使膜电位降低,促使线粒体释放细胞色素C。

Mitochondrial transmembrane potential loss caused by reactive oxygen species plays a major role in sodium selenite-induced apoptosis in NB4 cells

OBJECTIVE: To investigate the role of reactive oxygen species (ROS) and ROS-caused mitochondrial transmembrane potential loss in sodium selenite-induced apoptosis in NB4 cells. METHODS: ROS production was measured by ROS-specific probe DCFH-DA. Sodium selenite mitochondrial transmembrane potential loss was evaluated by flow cytometry with Rh123 staining. Protein levels of cytochrome C, Bid, Bcl-xl, and Bax were measured by Western blot using protein-specific antibodies. NB4 cells were pre-incubated by MnTmPy or BSO before selenite treatment to further confirm the effects of ROS on NB4 cells. RESULTS: 20 micromol/L sodium selenite induced ROS production and mitochondrial transmembrane potential loss in NB4 cells time-dependently. Cytochrome C accumulated in cytoplasm after selenite treatment. Sodium selenite also downregulated Bcl-xl and activated Bax and Bid at protein level. Pretreatment with antioxidant MnTmPy almost fully abrogated the proapoptotic effect of sodium selenite prevented the cleavage of Bid protein and in turn the mitochondrail transmembrane potential loss. On the contrary, pretreatment with BSO intensified the mitochondrail transmembrane potential loss induced by sodium selenite. CONCLUSIONS: Sodium selenite may induce apoptosis by inducing ROS production in NB4 cells, which leads to the downregulation of Bcl-xl, upregulation of Bax, and cleavage and activation of Bid. Bax and tBid then agregate on mitochondrial membrane, which in turn causes a decrease of mitochondrial transmembrane potential and release of cytochrome C into cytoplasm.