Antioxidant Activity of 5,6,7,8-Tetrahydrobiopterin (BPH4) and Its Effect on Brain Damages

研究了5，6，7，8-四氢生物蝶呤（BPH 4）的体外抗氧化活性及其对脑损伤的可能作用，BPH 4在黄嘌呤/黄嘌呤氧化酶和大鼠巨噬细胞/佛波醇肉豆蔻酸酯自由基产生系统中均表现出极强的清除超氧阴离子自由基的活性。通过自旋捕集-ESR谱证实了BPH 4对超氧阴离子和羟基自由基的抗氧化活性。BPH 4对百草枯诱导的大鼠肝细胞乳酸脱氢酶（LDH）释放的升高有剂量依赖性的抑制作用。此外，BPH 4还能抑制MPTP引起的细胞损伤，并观察了BPH 4对缺血性神经元损伤的影响。用Fischer 344大鼠双侧颈总动脉夹闭60分钟造成脑缺血，导致海马CA 1区神经元延迟性死亡。BPH 4预处理可减轻海马神经元的损伤。最后，在PC-12细胞中观察了BPH 4对DOPA诱导的细胞毒性的影响。SOD和BPH 4基本上消除了DOPA的毒性，而过氧化氢酶则减轻了DOPA的毒性。提示BPH 4保护PC-BPH_4可能通过其抗氧化活性抑制多巴胺神经元的变性，提示BPH_4还可能通过其抗氧化活性抑制多巴胺神经元的变性，具有治疗多种其它疾病如帕金森病的潜力，其中活性氧自由基参与发病机制。

The in vitro antioxidative activity of 5,6,7,8-tetrahydrobiopterin (BPH4) and its possible efficacy to brain damages were examined.BPH4 showed an extremely strong superoxide anion radical-scavenging activity in both xanthine/xanthine oxidase and rat macrophage/phorbol myristate acetate radical-generating systems. The antioxidative activity of BPH4 against both superoxide anion and hydroxyl radicals were confirmed by spin trapping-ESR spectrometry. BPH4 also protected rat brain homogenate against autooxidation.The paraquat-induced elevation of the release of lactate dehydrogenase (LDH) in cultured rat hepatocytes was suppressed by BPH4 in a dose-dependent manner. Besides, BPH4 suppressed the cell damages caused by MPTP.The effect of BPH4 on ischemic neuronal damage was examined. Cerebral ischemia was produced in the Fischer 344 rat by bilateral common carotid arteries occlusion for 60 min, which resulted in delayd neuronal death in the CA1 region of the hippocampus. Pretreatment with BPH4 reduced hippocampal neuronal damage.Finally, the effect of BPH4 on DOPA-induced cytotoxicity was examined in PC-12 cells.The toxicity of DOPA was essentially abolished by SOD and BPH4, and ameliorated by catalase, suggesting that BPH4 protects PC-12 cells from damage induced by DOPA and may inhibit the degeneration of dopamine neurons through its antioxidative activity.It is concluded that BPH4 may also have therapeutic potentials against various other diseases such as Parkinson's disease, where active oxygen radicals are involved in the pathogenesis.