Mazzio Elizabeth A, Soliman Karam F A
College of Pharmacy and Pharmaceutical Sciences, Florida A and M University, Tallahassee, FL 32307, USA.
J Appl Toxicol. 2004 Mar-Apr;24(2):99-106. doi: 10.1002/jat.954.
The pathology of Parkinson's disease involves oxidative damage to dopaminergic neurons of the substantia nigra. Oxidation of the dopamine (DA) neurotransmitter itself may contribute to the generation of a reactive oxygen species (ROS) and subsequent neurodegeneration. Glia cells can either exacerbate injury or exert protective properties on local neurons in the brain. We investigate glial antioxidant enzyme systems relative to ROS generated during cytokine activation, monoamine oxidase (MAO) activity and autoxidation of DA in glioma cells. Rat C6 glioma cells stimulated with lipopolysaccharide Escherichia coli 0111:B4 and interferon gamma (LPS/IFN-g) produced high levels of nitric oxide (241 nmol mg(-1) protein 24 h(-1)) but not superoxide (O(-) (2)) or hydrogen peroxide (H(2)O(2)). Basal C6 cells exhibited a rapid and robust capacity to remove exogenous H(2)O(2) within minutes. Preincubation with sodium azide but not buthionine-[S, R]-sulfoximine attenuated this response, indicating catalase as the primary enzyme responsible for this effect. The glioma catalase reaction rate was slightly attenuated by exposure to LPS/IFN-g for 24 h. However, the reduction in catalase activity was not due to nitric oxide, because both the supernatant and sodium nitroprusside had no effect on isolated catalase enzyme activity. Hydrogen peroxide was produced only through substrate-driven MAO activity in prepared lysate. However, the quantity of H(2)O(2) produced per unit time (0.46 nmol mg(-1) protein min(-1)) was negligible compared with the enormous capacity for its removal by catalase (213.9 nmol mg(-1) protein min(-1)) (> or =462 x greater). Similarly, H(2)O(2) generated by DA autoxidation per unit time (0.28 nmol mg(-1) protein equiv. min(-1)), was rapidly dissolved by glioma cells at high capacity (> or =750 x greater). In conclusion, C6 cells produce nitric oxide under cytokine/endotoxin-stimulated conditions. Moreover, C6 cells exhibit a dynamic H(2)O(2) scavenging capacity, with ample facility to dispose of the peroxide generated by both MAO activity and spontaneous DA autoxidation.
帕金森病的病理学涉及黑质多巴胺能神经元的氧化损伤。多巴胺（DA）神经递质本身的氧化可能导致活性氧（ROS）的产生及随后的神经退行性变。神经胶质细胞可加重脑内局部神经元的损伤或发挥保护作用。我们研究了与细胞因子激活、单胺氧化酶（MAO）活性以及胶质瘤细胞中DA自氧化过程中产生的ROS相关的神经胶质抗氧化酶系统。用脂多糖大肠杆菌0111:B4和干扰素γ（LPS/IFN-γ）刺激大鼠C6胶质瘤细胞，可产生高水平的一氧化氮（241 nmol mg⁻¹蛋白24 h⁻¹），但不产生超氧阴离子（O₂⁻）或过氧化氢（H₂O₂）。基础状态的C6细胞在数分钟内表现出快速且强大的清除外源性H₂O₂的能力。用叠氮化钠而非丁硫氨酸-[S,R]-亚砜亚胺预孵育可减弱这种反应，表明过氧化氢酶是负责此效应的主要酶。胶质瘤细胞的过氧化氢酶反应速率在暴露于LPS/IFN-γ 24小时后略有减弱。然而，过氧化氢酶活性的降低并非由一氧化氮引起，因为上清液和硝普钠对分离出的过氧化氢酶活性均无影响。仅通过制备的裂解物中底物驱动的MAO活性产生过氧化氢。然而，与过氧化氢酶巨大的清除能力（213.9 nmol mg⁻¹蛋白min⁻¹）（≥462倍更高）相比，单位时间内产生的H₂O₂量（0.46 nmol mg⁻¹蛋白min⁻¹）可忽略不计。同样，DA自氧化单位时间内产生的H₂O₂（0.28 nmol mg⁻¹蛋白当量min⁻¹）也被胶质瘤细胞以高能力快速清除（≥750倍更高）。总之，C6细胞在细胞因子/内毒素刺激条件下产生一氧化氮。此外，C6细胞表现出动态的H₂O₂清除能力，有充足的能力处理由MAO活性和DA自发自氧化产生的过氧化物。
