1-Methyl-4-phenylpyridinium (MPP(+)) ion, a toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, is produced by monoamine oxidase B in astrocytes. MPP(+) causes a selective dopaminergic neurodegeneration, the pathophysiologic hallmark of Parkinson disease. However, the toxic effect of MPP(+) on astrocytes remains unclear. Here, we examined the effect of MPP(+) on human astrocytoma U373MG cells, with particular attention to the temporal interaction of glutathione (GSH) and reactive oxygen species (ROS) (H2O2 and O). MPP(+) induced astrocyte apoptosis in a dose-dependent manner 48 hr after treatment. Distinctive early (<6 hr) and late (24-48 hr) responses were observed. ROS production and the oxidized GSH (GSSG)/GSH ratio, indicators of oxidative stress, rose dramatically after 24 hr of MPP(+) exposure, whereas the H2O2 level transiently decreased at 6 hr. ROS overproduction and GSH dysfunction were concomitantly associated with caspase-3 activation and finally led to cell apoptosis. Moreover, GSH depletion by diethyl maleate, but not buthionine sulfoximine, caused cells to die quickly and potentiated the cytotoxicity of MPP(+). Co-treatment with melatonin, a known antioxidant secreted by the pineal gland, significantly prevented cell apoptosis by inhibiting oxidative stress and caspase-3 activation, but it did not affect that the early changes due to MPP(+) treatment. Our results demonstrate that in astrocytes, GSH is involved in the early decrease and late increase in ROS levels induced by MPP(+) treatment. Melatonin remedies the dysfunction of GSH system to block caspase-3 activation and cell apoptosis induced by oxidative stress during the long-term exposure of MPP(+).

中文翻译：

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褪黑素对人星形细胞瘤U373MG细胞中MPP（+）处理后活性氧和谷胱甘肽的时间变化的影响。

1-甲基-4-苯基吡啶鎓（MPP（+））离子是单胺氧化酶B在星形胶质细胞中产生的1-甲基-4-苯基-1,2,3,6-四氢吡啶的有毒代谢产物。MPP（+）导致选择性多巴胺能神经退行性变，这是帕金森氏病的病理生理学标志。但是，MPP（+）对星形胶质细胞的毒性作用仍不清楚。在这里，我们检查了MPP（+）对人星形细胞瘤U373MG细胞的影响，特别注意谷胱甘肽（GSH）和活性氧（ROS）（H2O2和O）的时间相互作用。治疗后48小时，MPP（+）以剂量依赖性方式诱导星形胶质细胞凋亡。观察到明显的早期（<6小时）和晚期（24-48小时）响应。暴露于MPP（+）24小时后，ROS的产生和氧化的GSH（GSSG）/ GSH比率（氧化应激的指标）急剧上升，而H2O2水平在6小时时短暂下降。ROS过量生产和GSH功能异常与caspase-3活化相关，并最终导致细胞凋亡。此外，马来酸二乙酯对GSH的消耗，但对丁硫氨酸亚砜胺却没有，导致细胞迅速死亡并增强了MPP（+）的细胞毒性。与褪黑激素（一种由松果体分泌的已知抗氧化剂）共同处理可通过抑制氧化应激和caspase-3活化来显着阻止细胞凋亡，但它并不影响MPP（+）处理引起的早期变化。我们的结果表明，在星形胶质细胞中，GSH参与了MPP（+）治疗诱导的ROS水平的早期降低和晚期升高。