ROLE OF OXYGEN RADICALS AND XANTHINE OXIDASE IN STROKE

氧自由基和黄嘌呤氧化酶在中风中的作用

• 批准号: 3408828
• 负责人: JOSEPH S BECKMAN
• 金额: $ 9.61万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-08-01 至 1991-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3408828
• 关键词: antioxidants; brain edema; carotid artery; catalase; cerebral ischemia /hypoxia; cerebrovascular occlusions; disease /disorder model; enzyme inhibitors; free radicals; histopathology; hydrogen peroxide; laboratory rat; liposomes; molybdenum; neurochemistry; neutrophil; stroke; superoxide dismutase; xanthine dehydrogenase

Mortality within the first 24 hours after stroke frequently results from cerebral edema for which no effective treatment is available. Injury to endothelium by oxygen radicals in a well- recognized cause of edema formation in the lung and other organs but its role in cerebral ischemia is poorly defined. We show that enzymatic oxygen radical scavengers can reduce infarct volume in a rat focal stroke model and hypothesize that xanthine oxidase (XO) is an important source of these oxygen radicals. Evidence is presented to show that cerebral ischemia induces the conversion of a normally benign enzyme, xanthine dehydrogenase (XDH), to a free radical-producing oxidase which reduces molecular oxygen to the toxic intermediates, superoxide and H2O2. Most of the brain XDH and XO is localized within the endothelium, putting the blood-brain barrier at risk of oxygen radical injury. In this proposal, the role of cytotoxic oxygen free radicals will be investigated in early post-ischemic changes in cerebral blood flow, edema formation, neutrophil influx and infarction in a focal stroke model in the rat. The stroke is induced by occluding the right middle cerebral artery (MCA) and transiently clamping both carotid arteries for up to 90 minutes, which yields a reproducible, quantifiable infarct restricted to the right cortex and ideal for examining pharmacological efficacy. The effects of treatment with specific enzymatic radical scavengers on the development of cytotoxic and vasogenic edema, changes in cerebral blood flow and histologic injury after the MCA-carotid occlusion will be evaluated. To optimize delivery to sites of free radical production, the oxygen radical scavenging enzymes, superoxide dismutase and catalase, will be either conjugated to polyethylene glycol or entrapped in liposomes, which increases their circulatory half-life and cell entry. The contribution of ischemia-induced XDH conversion of XO to injury will be examined by depleting XDH/XO activity in rats by three independent methods and measuring the effects on infarct volume, edema formation, cerebral blood flow and histologic injury after the MCA-carotid procedure. Rates of oxygen radical production in vivo will be measured after treatment with free radical scavengers and xanthine oxidase inhibitors. These studies will help define the role of oxygen radicals in cerebral ischemia and may lead to new therapeutic approaches in the treatment of stroke.

中风后 24 小时内经常导致死亡 脑水肿，目前尚无有效治疗方法 可用的。 氧自由基对内皮细胞的损伤 肺和其他器官水肿形成的公认原因 但其在脑缺血中的作用尚不清楚。 我们表明 酶促氧自由基清除剂可以减少梗塞体积 大鼠局灶性中风模型并假设黄嘌呤氧化酶 (XO)是这些氧自由基的重要来源。 证据是 表明脑缺血可诱导转化 一种通常良性的酶，黄嘌呤脱氢酶 (XDH)， 产生自由基的氧化酶，将分子氧还原为 有毒中间体超氧化物和H2O2。 大部分大脑 XDH 和 XO 位于内皮细胞内，使 血脑屏障面临氧自由基损伤的风险。 在这个 建议，细胞毒性氧自由基的作用将是 研究脑缺血后早期的变化 血流、水肿形成、中性粒细胞流入和局灶性梗死 大鼠中风模型。 中风是由于闭塞引起的 右大脑中动脉 (MCA) 并短暂夹紧两者 颈动脉长达 90 分钟，产生可重复的、 可量化的梗死仅限于右侧皮质，非常适合 检查药理功效。 治疗效果 与特定的酶自由基清除剂的发展 细胞毒性和血管源性水肿，脑血流量的变化 MCA-颈动脉闭塞后的组织学损伤将 评价。 优化向自由基位点的递送 生产、氧自由基清除酶、超氧化物 歧化酶和过氧化氢酶，将与聚乙烯缀合 乙二醇或包埋在脂质体中，这会增加它们的循环 半衰期和细胞进入。 缺血引起的贡献 XO 到损伤的 XDH 转化将通过消耗进行检查 通过三种独立方法测定大鼠 XDH/XO 活性 测量对梗塞体积、水肿形成的影响， MCA-颈动脉术后脑血流量和组织学损伤 程序。 体内氧自由基的产生速率为 用自由基清除剂处理后测量 黄嘌呤氧化酶抑制剂。 这些研究将有助于定义 氧自由基在脑缺血中的作用并可能导致新的 治疗中风的治疗方法。