Offen D, Ziv I, Sternin H, Melamed E, Hochman A
Department of Neurology, Beilinson Medical Center, Petah-Tiqva, Israel.
Exp Neurol. 1996 Sep;141(1):32-9. doi: 10.1006/exnr.1996.0136.
We have recently shown that dopamine (DA) can trigger apoptosis, an active program of cellular self-destruction, in various neuronal cultures and proposed that inappropriate activation of apoptosis by DA and or its oxidation products may initiate nigral cell loss in Parkinson's disease (PD). Since DA toxicity may be mediated via generation of oxygen-free radical species, we examined whether DA-induced cell death in PC12 cells may be inhibited by antioxidants. We have found that the thiol containing compounds, reduced glutathione (GSH), N-acetyl-cysteine (NAC), and dithiothreitol (DTT) were markedly protective, while vitamins C and E had lesser or no effect. The thiol antioxidants and vitamin C but not vitamin E, prevented dopamine autooxidation and production of dopamine-melanin. Their protective effect has also manifested by inhibiting DA-induced apoptosis; DNA fragmentation was prevented as was shown histochemically by the in situ end-labeled DNA technique (TUNEL). Intracellular GSH and other thiols constitute an important natural defense against oxidative stress. We have found that depletion of cellular GSH by the addition of phoron, a substrate of glutathione transferase, and buthionine sulfoximine (BSO), an inhibitor of gamma-glutamyl transpeptidase, significantly enhanced DA toxicity. Cotreatment with NAC rescued the cells from the toxic effect of BSO+DA, and phoron+ DA, while addition of GSH provided only partial protection from BSO+DA toxicity. Our data indicate that the thiol family of antioxidants, but not vitamins C and E, are highly effective in rescuing cells from DA-induced apoptosis. Further study of the mechanisms underlying the unique protective capacity of thiol antioxidants may lead to the development of new neuroprotective therapeutic strategies for PD.
我们最近发现，多巴胺（DA）可在多种神经元培养物中引发细胞凋亡，即细胞自我毁灭的主动过程，并提出DA及其氧化产物不适当激活细胞凋亡可能引发帕金森病（PD）中的黑质细胞丢失。由于DA毒性可能通过氧自由基的产生介导，我们研究了抗氧化剂是否可抑制PC12细胞中DA诱导的细胞死亡。我们发现，含硫醇的化合物，还原型谷胱甘肽（GSH）、N-乙酰半胱氨酸（NAC）和二硫苏糖醇（DTT）具有显著的保护作用，而维生素C和E的作用较小或无作用。硫醇抗氧化剂和维生素C而非维生素E可防止多巴胺自氧化和多巴胺-黑色素的产生。它们的保护作用还表现为抑制DA诱导的细胞凋亡；通过原位末端标记DNA技术（TUNEL）组织化学显示，DNA片段化得到了预防。细胞内GSH和其他硫醇构成了对抗氧化应激的重要天然防御。我们发现，通过添加谷胱甘肽转移酶的底物磷酰胺和γ-谷氨酰转肽酶的抑制剂丁硫氨酸亚砜胺（BSO）消耗细胞内GSH，可显著增强DA毒性。与NAC共同处理可使细胞免受BSO+DA和磷酰胺+DA的毒性作用，而添加GSH仅能部分保护细胞免受BSO+DA毒性。我们的数据表明，抗氧化剂的硫醇家族而非维生素C和E在挽救细胞免受DA诱导细胞凋亡方面非常有效。进一步研究硫醇抗氧化剂独特保护能力的潜在机制可能会导致开发针对PD的新神经保护治疗策略。
