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扮演着一种 在精神分裂症病因学中的重要作用。一直以来 假设儿茶酚胺神经元长期暴露于 过量的多巴胺或多巴胺的氧化代谢产物可能 造成神经元损伤，细胞死亡，并对 精神分裂症的一些负面症状。儿茶酚胺一直是 显示对去甲肾上腺素和多巴胺神经元有神经毒性 培养(神经科学杂志26：428,1990；药理实验杂志262：1274， (1992年)。我们正在评估多巴胺的神经毒性效应。 Chikaraishi和他的同事(J Neurosci)建立的克隆细胞系 13：1280,1993)。该细胞系来源于一种酪氨酸羟化酶。 从携带SV的转基因小鼠的中枢神经系统获得阳性肿瘤 大鼠转录调控下的40T抗原癌基因 酪氨酸羟基酶基因。我们发现CATH.a细胞与 多巴胺引起时间和剂量依赖性的细胞死亡增加。细胞 用儿茶酚胺治疗后也发生死亡，L-二羟基- 苯丙氨酸、去甲肾上腺素、肾上腺素和异丙肾上腺素 作为神经毒性化合物，6-羟基多巴胺。没有出现细胞死亡 是受体介导的，因为选择性去甲肾上腺素和多巴胺能 受体激动剂对CATH.a细胞活力无影响。多巴胺 DNA片段化检测显示可诱导细胞凋亡 凝胶电泳法和流式细胞仪分析。细胞凋亡 似乎是由多巴胺自氧化产生的，因为细胞内 多巴胺治疗后过氧化物量增加，细胞死亡 被过氧化氢酶和N-乙酰半胱氨酸抑制。生产N-乙酰半胱氨酸 剂量依赖性(100-1250 mM)减少多巴胺诱导的细胞死亡 这与过氧化氢形成的减少有关。此外, 对抗氧化蛋白Bc l-2的反义作用增加了敏感性 对多巴胺诱导的细胞死亡有明显的抑制作用。这些发现表明 多巴胺的氧化产物通过 细胞凋亡。

Overactive dopaminergic neurons in the brain are thought to play 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, cell death, and be partially responsible for some of the negative symptoms of schizophrenia. Catecholamines have been shown to be neurotoxic to norepinephrine and dopamine neurons in primary culture (J Neurosci Res 26:428, 1990; J Pharmacol Exp Ther 262:1274, 1992). We are evaluating the neurotoxic effects of dopamine by using a clonal cell line developed by Chikaraishi and co-workers (J Neurosci 13:1280, 1993). This cell line was derived from a tyrosine hydroxylase positive tumor obtained from the CNS of transgenic mice carrying the SV 40 T antigen oncogene under the transcriptional control of the rat tyrosine hydroxylase gene. We found that incubation of CATH.a cells with dopamine produced a time and dose dependent increase in cell death. Cell death also occurred after treatment with the catecholamines, l-dihydroxy- phenylalanine, norepinephrine, epinephrine, and isoparoterenol, as well as the neurotoxic compound, 6-hydroxydopamine. Cell death did not appear to be 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 peroxides increase after dopamine treatment and cell death can be inhibited by catalase and n-acetylcysteine. N-acetylcysteine produced a dose dependent (100-1250 mM) decrease in dopamine-induced cell death and this correlated with a decrease in peroxide formation. In addition, antisense to the antioxidant protein, Bcl-2, increases the sensitivity of CATH.a cells to dopamine induced cell death. These findings indicate that the oxidative products of dopamine cause neurotoxicity through apoptosis.