DOPAMINE INDUCED NEUROTOXICITY IN A CATECHOLAMINERGIC CELL LINE

大脑中过度活跃的多巴胺能神经元被认为计划了一个 在精神分裂症病因学中的重要作用。 已经 假设，长期暴露于儿茶酚胺神经元， 过量的多巴胺或多巴胺的氧化代谢物 可能导致神经元损伤和细胞死亡， 精神分裂症的一些阴性症状 我们正在评估 多巴胺的神经毒性作用，通过使用一个克隆的儿茶酚胺能 从小鼠CNS分离的细胞系（CATH. a细胞）。 多巴胺 在CATH中产生细胞死亡的时间和剂量依赖性增加。 细胞 细胞死亡也发生在用其他药物治疗后。 儿茶酚胺，以及神经毒性化合物，6-羟基多巴胺 和一氧化氮 细胞死亡不是受体介导的， 去甲肾上腺素能和多巴胺能受体激动剂对CATH无影响。 细胞活力 多巴胺诱导凋亡性细胞死亡，如 通过凝胶电泳和流式细胞术测量DNA片段化 分析. 细胞凋亡似乎由多巴胺自氧化产生， 由于多巴胺处理后细胞内周期增加， 过氧化氢酶可抑制过氧化物增加和细胞死亡 和N-乙酰半胱氨酸。 超氧化物歧化酶似乎在 多巴胺的氧化代谢物的解毒， 这种酶的抑制剂，二乙基氨基甲酸酯， 诱导的细胞死亡和由超氧化物发生器产生的细胞死亡， 二羟富马酸盐 多巴胺还降低了一些 帮助保护细胞免受自由基侵害的细胞成分， 包括超氧化物歧化酶、谷胱甘肽和抗氧化蛋白， bcl-2基因。 此外，bcl-2反义核酸增加了 CATH. a细胞对多巴胺诱导的细胞死亡。 为了定义 在CATH. a细胞中多巴胺诱导细胞死亡的细胞途径，我们 发现了一个选择性的线粒体膜电位下降， CATH. a细胞在加入多巴胺后4小时内， 媒体 这些发现表明，如果多巴胺 通过CATH. a细胞系中的细胞凋亡引起神经毒性， 可能是通过对线粒体的选择性作用。

Overactive dopaminergic neurons in the brain are thought to plan an important role in the etiology of schizophrenia. It has been hypothesized that prolonged exposure of catecholamine neurons to excessive levels of dopamine or the oxidative metabolites of dopamine may produce neuronal damage and cell death and be partially responsible for some of the negative symptoms of schizophrenia. We are evaluation the neurotoxic effects of dopamine by using a clonal catecholaminergic cell line isolated from the CNS of the mouse (CATH.a cells). Dopamine produces a time and dose dependent increase in cell death in CATH.a cells. Cell death also occurred after treatment with other catecholamines, as well as the neurotoxic compounds, 6-hydroxydopamine and nitric oxide. Cell death is not receptor mediated since selective noradrenergic and dopaminergic receptor agonists had no effect on CATH.a cell viability. Dopamine induces apoptotic cell death as indicated by DNA fragmentation measured by gel electrophoresis and by flow cytometric analysis. Apoptosis appears to be produced by dopamine autoxidation, since intracellular perodixes increase after dopamine treatment and this increase in peroxides and cell death can both be inhibited by catalase and n-acetylcysteine. Superoxide dismutase appears to be important in the detoxification of dopamine's oxidative metabolites since an inhibitor of this enzyme, diethycarbamate, potentiates both dopamine induced cell death and cell death produced by the superoxide generator, dihydroxyfumarate. Dopamine also decreased the levels of a number of cellular components that help protect cells from free radicals, including superoxide dismutase, glutathione and the antioxidant protein, bcl-2. In addition, antisense to bcl-2 increased the sensitivity of CATH.a cells to dopamine induced cell death. In an attempt to define the cellular pathway for dopamine-induced cell death in CATH.a cells, we found a selective decrease in the mitochondrial membrane potential in CATH.a cells within four hours after the addition of dopamine to the media. These findings indicate that the oxidative products if dopamine cause neurotoxicity through apoptosis in the CATH.a cell line and this may be through a selective action on mitochondria.