Laboratory of Integrative Physiology in Veterinary Sciences, Osaka Prefecture University, 1-58, Rinku-Ourai Kita, Izumisano, Osaka 598-8531, Japan.
Neurochem Res. 2013 Jan;38(1):32-41. doi: 10.1007/s11064-012-0882-2. Epub 2012 Sep 15.
Under some pathological conditions in brain, a large amount of superoxide anion (O(2)(-)) is produced, causing various cellular damages. Among three isozymes of superoxide dismutase (SOD), extracellular (EC)-SOD should play a role to detoxify O(2)(-) in extracellular space; however, a little is known about EC-SOD in brain. Although dopamine (DA) stored in the synaptic vesicle is stable, the excess leaked DA is spontaneously oxidized to yield O(2)(-) and reactive DA quinones, causing damages of dopaminergic neurons. In the present study, we examined the effects of DA on SOD expression in cultured rat cortical astrocytes. By means of RT-PCR, all mRNA of three isozymes of SOD could be detected; however, only EC-SOD was increased by DA exposure for 24 h, dose-dependently. The expression of EC-SOD protein and the cell-surface SOD activity in astrocytes also increased with 100 μM DA exposure. The increase of EC-SOD mRNA by DA was inhibited by a DA transporter inhibitor, GBR12909, whereas it was not changed by DA receptor antagonists, SKF-83566 (D1) and haloperidol (D2). Furthermore, a monoamine oxidase inhibitor, pargyline, and antioxidants, N-acetyl-L-cysteine and glutathione, also did not affect the DA-induced expression of EC-SOD mRNA. On the other hand, an inhibitor of nuclear factor kappaB (NF-κB), ammonium pyrrolidine-1-carbodithioate, suppressed the DA-induced expression of EC-SOD mRNA. These results suggest that DA incorporated into the cells caused the induction of EC-SOD mRNA followed by the enhancements of EC-SOD protein level and the enzyme activity, and that NF-κB activation is involved in the mechanisms of the EC-SOD induction. The regulation of EC-SOD in astrocytes surrounding dopaminergic neurons may contribute to the defensive mechanism against oxidative stress in brain.
在大脑的某些病理条件下，会产生大量超氧阴离子（O2(-)），导致各种细胞损伤。在三种超氧化物歧化酶（SOD）同工酶中，细胞外（EC）-SOD 应该在细胞外空间中发挥解毒 O2(-)的作用；然而，关于大脑中的 EC-SOD 知之甚少。虽然突触小泡中储存的多巴胺（DA）是稳定的，但过量泄漏的 DA 会自发氧化生成 O2(-)和反应性 DA 醌，导致多巴胺能神经元损伤。在本研究中，我们研究了 DA 对培养的大鼠皮质星形胶质细胞中 SOD 表达的影响。通过 RT-PCR，可以检测到三种同工酶的所有 SOD mRNA；然而，只有 DA 暴露 24 小时后，EC-SOD 的表达才会增加，呈剂量依赖性。星形胶质细胞中 EC-SOD 蛋白的表达和细胞表面 SOD 活性也随着 100μM DA 的暴露而增加。DA 转运蛋白抑制剂 GBR12909 可抑制 DA 诱导的 EC-SOD mRNA 增加，而 DA 受体拮抗剂 SKF-83566（D1）和氟哌啶醇（D2）则不会改变。此外，单胺氧化酶抑制剂帕吉林、抗氧化剂 N-乙酰-L-半胱氨酸和谷胱甘肽也不会影响 DA 诱导的 EC-SOD mRNA 表达。另一方面，核因子 kappaB（NF-κB）抑制剂铵吡咯烷-1-碳二硫代氨基甲酸酯可抑制 DA 诱导的 EC-SOD mRNA 表达。这些结果表明，进入细胞的 DA 导致 EC-SOD mRNA 的诱导，随后 EC-SOD 蛋白水平和酶活性增强，NF-κB 激活参与了 EC-SOD 诱导的机制。多巴胺能神经元周围星形胶质细胞中 EC-SOD 的调节可能有助于大脑中氧化应激的防御机制。
