Lee H S, Park C W, Kim Y S
Department of Pharmacology, College of Medicine, Seoul National University, 28 Yongon-Dong, Chongo-Gu, Seoul, Korea.
Exp Neurol. 2000 Sep;165(1):164-71. doi: 10.1006/exnr.2000.7460.
MPP(+), an active metabolite of MPTP, causes a dopaminergic neuronal degeneration similar to that observed in Parkinson's disease. Current data suggest that MPP(+)-induced cytotoxicity may be mediated by oxygen free radicals. To evaluate this hypothesis, we first investigated whether MPP(+) could cause oxidative stress by producing oxygen free radicals in the SH-SY5Y, human neuroblastoma cell line. MPP(+) was toxic to the cells dose-dependently but did not increase the level of lipid peroxidation at toxic concentrations. Second, we examined the effects of various antioxidants and an inhibitor of nitric oxide synthase (NOS) on the development of MPP(+) cytotoxicity. Pretreatment with antioxidants such as ascorbic acid, Trolox, phenyl-tertiary-butyl-nitrone (PBN), which show protective effects on tert-butyl hydroperoxide (tBOOH) toxicity did not attenuate MPP(+) cytotoxicity. Similarly, the combination of antioxidant enzymes, SOD and catalase (50 U/ml, respectively), did not protect the cells from the toxic action of MPP(+). Also N-nitro-l-arginine methyl ester (NAME), a competitive inhibitor of NOS, and combined incubation with NAME and antioxidant enzymes failed to attenuate MPP(+) cytotoxicity. On the other hand, a sublethal dose of MPP(+) potentiated iron and H(2)O(2)-induced cytotoxicity. These results suggest that oxygen free radicals may not be a primary cause of MPP(+)-induced cell death but that MPP(+) increases the vulnerability of cells to oxidative stress.
MPP(+)是MPTP的一种活性代谢产物，可导致类似于帕金森病中观察到的多巴胺能神经元变性。目前的数据表明，MPP(+)诱导的细胞毒性可能由氧自由基介导。为了评估这一假设，我们首先研究了MPP(+)是否能通过在人神经母细胞瘤细胞系SH-SY5Y中产生氧自由基来引起氧化应激。MPP(+)对细胞具有剂量依赖性毒性，但在毒性浓度下并未增加脂质过氧化水平。其次，我们研究了各种抗氧化剂和一氧化氮合酶（NOS）抑制剂对MPP(+)细胞毒性发展的影响。用对叔丁基过氧化氢（tBOOH）毒性具有保护作用的抗氧化剂如抗坏血酸、Trolox、苯基叔丁基硝酮（PBN）预处理，并未减弱MPP(+)的细胞毒性。同样，抗氧化酶超氧化物歧化酶（SOD）和过氧化氢酶（分别为50 U/ml）的组合也不能保护细胞免受MPP(+)的毒性作用。此外，NOS的竞争性抑制剂N-硝基-L-精氨酸甲酯（NAME）以及NAME与抗氧化酶的联合孵育也未能减弱MPP(+)的细胞毒性。另一方面，亚致死剂量的MPP(+)增强了铁和H₂O₂诱导的细胞毒性。这些结果表明，氧自由基可能不是MPP(+)诱导细胞死亡的主要原因，但MPP(+)增加了细胞对氧化应激的易感性。
