亚硒酸钠诱导NB4细胞中细胞色素c氧化酶亚基IV的下调机制

目的 探讨亚硒酸钠诱导NB4细胞凋亡的过程中,细胞色素c氧化酶亚基IV(COX IV)表达的变化情况及其机制和意义.方法 用20μmol/L亚硒酸钠作用NB4细胞不同时间,Western blot和RT-PCR分别检测COX IV蛋白和mRNA表达的变化.活性氧清除剂预处理细胞后Western blot检测COX IV蛋白表达的变化以及caspase-3的激活.caspase-3抑制剂预处理细胞后Western blot检测COX IV蛋白表达的变化.瞬时转染干扰NB4细胞中COX IV表达后,流式细胞术检测细胞凋亡.结果 亚硒酸钠诱导NB4细胞COX IV蛋白表达显著下调,但mRNA表达水平无变化.活性氧清除剂能完全逆转亚硒酸钠引起的COX IV表达下调与caspase-3激活.caspase-3抑制剂能部分逆转亚硒酸钠引起的COX IV表达下调.干扰COX IV表达后,亚硒酸钠诱导的细胞凋亡显著增加.结论 在亚硒酸钠诱导NB4细胞凋亡过程中,COX IV在蛋白水平显著下调.活性氧介导COX IV下调与caspase-3激活,caspase-3在一定程度上参与COX IV表达下调,抑制COX IV能显著提高NB4细胞对亚硒酸钠诱导凋亡的敏感性.

Machanism for Downregulation of Cytochrome c Oxidase Subunit IV in NB4 Cells Induced by Sodium Selenite

Objective To explore the mechanism and significance of cytochrome c oxidase subunit IV (COX IV) downregulation during apoptosis of NB4 cells induced by sodium selenite. MethodsNB4 cells were treated with 20 μmol/L sodium selenite at different time points. COX IV protein and mRNA were detected by Western blot and RT-PCR, respectively. NB4 cells were pretreated with reactive oxygen species (ROS) scavenger before selenite exposure, and then COX IV protein expression and caspase-3 activation were detected by Western blot. NB4 cells were pretreated with caspase-3 inhibitor before selenite exposure, and then COX IV protein expression was detected by Western blot. NB4 cells were transiently transfected with vectors to interfere with the expression of COX IV, and then the apoptosis induced by selenite was analyzed by flow cytometry. ResultsSodium selenite induced evident downregulation of COX IV protein in NB4 cells, while its mRNA level was almost unchanged. ROS scavenger completely reversed selenite-induced COX IV downregulation and caspase-3 activation. Caspase-3 inhibitor partially reversed selenite-induced COX IV downregulation. Interference with COX IV expression dramatically enhanced selenite-induced apoptosis of NB4 cells. ConclusionsCOX IV is remarkaly downregulated during selenite-induced apoptosis of NB4 cells. ROS mediates COX IV downregulation and caspase-3 activation, while caspase-3 is partially involved in COX IV downregulation. COX IV interference markedly increases the sensitivity of NB4 cells to selenite-induced apoptosis.