Department of Brain Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
Glia. 2011 Mar;59(3):435-51. doi: 10.1002/glia.21112. Epub 2010 Dec 29.
Our previous studies demonstrated the involvement of quinone formation in dopaminergic neuron dysfunction in the L-DOPA-treated parkinsonian model and in methamphetamine (METH) neurotoxicity. We further reported that the cysteine-rich metal-binding metallothionein (MT) family of proteins protects dopaminergic neurons against dopamine (DA) quinone neurotoxicity by its quinone-quenching property. The aim of this study was to examine MT induction in astrocytes in response to excess DA and the potential neuroprotective effects of astrocyte-derived MTs against DA quinone toxicity. DA exposure significantly upregulated MT-1/-2 in cultured striatal astrocytes, but not in mesencephalic neurons. This DA-induced MT upregulation in astrocytes was blocked by treatment with a DA-transporter (DAT) inhibitor, but not by DA-receptor antagonists. Expression of nuclear factor erythroid 2-related factor (Nrf2) and its binding activity to antioxidant response element of MT-1 gene were significantly increased in the astrocytes after DA exposure. Nuclear translocation of Nrf2 was suppressed by the DAT inhibitor. Quinone formation and reduction of mesencephalic DA neurons after DA exposure were ameliorated by preincubation with conditioned media from DA-treated astrocytes. These protective effects were abrogated by MT-1/-2-specific antibody. Adding exogenous MT-1 to glial conditioned media also showed similar neuroprotective effects. Furthermore, MT-1/-2 expression was markedly elevated specifically in reactive astrocytes in the striatum of L-DOPA-treated hemi-parkinsonian mice or METH-injected mice. These results suggested that excess DA taken up by astrocytes via DAT upregulates MT-1/-2 expression specifically in astrocytes, and that MTs or related molecules secreted specifically by astrocytes protect dopaminergic neurons from damage through quinone quenching and/or scavenging of free radicals.
我们之前的研究表明，醌的形成参与了 L-DOPA 治疗的帕金森病模型中的多巴胺能神经元功能障碍和 methamphetamine（METH）神经毒性。我们进一步报道，富含半胱氨酸的金属结合金属硫蛋白（MT）家族蛋白通过其醌猝灭特性保护多巴胺能神经元免受多巴胺（DA）醌神经毒性。本研究旨在研究星形胶质细胞中过量 DA 诱导的 MT 诱导及其对 DA 醌毒性的星形胶质细胞衍生 MT 的潜在神经保护作用。DA 暴露显著上调了培养的纹状体星形胶质细胞中的 MT-1/-2，但对中脑神经元没有影响。这种 DA 诱导的星形胶质细胞 MT 上调被 DA 转运蛋白（DAT）抑制剂阻断，但不受 DA 受体拮抗剂的影响。DA 暴露后，星形胶质细胞中核因子红细胞 2 相关因子（Nrf2）的表达及其与 MT-1 基因抗氧化反应元件的结合活性显著增加。DAT 抑制剂抑制 Nrf2 的核易位。用 DA 处理的星形胶质细胞条件培养基预孵育可改善 DA 暴露后中脑 DA 神经元的醌形成和减少。这些保护作用被 MT-1/-2 特异性抗体所阻断。向神经胶质细胞条件培养基中添加外源性 MT-1 也显示出类似的神经保护作用。此外，在 L-DOPA 治疗的半帕金森病小鼠或 METH 注射小鼠的纹状体中，反应性星形胶质细胞中 MT-1/-2 的表达明显升高。这些结果表明，星形胶质细胞通过 DAT 摄取的过量 DA 特异性地上调 MT-1/-2 的表达，并且星形胶质细胞特异性分泌的 MT 或相关分子通过醌猝灭和/或自由基清除来保护多巴胺能神经元免受损伤。
