OXYGEN RADICAL TOXICITY AND CHRONIC NEURONAL LOSS

氧自由基和其他自由基对细胞有毒，最常见的是 通过破坏膜脂和DNA。单元格具有多个级别的 抗氧化防御，而超氧化物歧化酶是第一级的 防御超氧阴离子自由基。认为逐渐减少的概念 可能在衰老或神经退行性变中起作用 多年来，人们一直在考虑疾病，但一直存在争议。 铜锌超氧化物歧化基因突变的最新发现 家族性肌萎缩侧索硬化症中的歧化酶(SOD1)提供了第一个很好的证据 抗氧化剂防御中的特定缺陷可能是导致 神经退行性疾病。 确定超氧化物歧化酶活性降低是否与运动有关 神经元丢失，我们打算建立脊髓SOD1慢性丢失的模型 器官培养，然后用这个模型来研究各种 神经保护策略： (1)毒性模型：建立慢性氧化毒性模型 在器官型脊髓培养中。是对超氧化物的慢性抑制 对脊髓运动神经元有毒性的歧化酶：我们将开发一种 啮齿动物脊髓器官型培养系统，然后定义易感性 大的胆碱能前角细胞对急慢性暴露的影响 至SOD1抑制。 意义：体外模型的建立允许进行实验 控制和药物操纵，这是不可能的 病人。 (2)使用慢性氧化损伤模型，运动神经元丢失 被抗氧化剂和其他潜在的神经保护剂阻止： 意义：目前对生物化学级联反应的了解 程序性细胞死亡提示神经元毒性诱导 通过氧化应激可能被抗氧化剂和 神经营养因子。这些研究将提供哪些数据 一类药物可能是最有益的，对 肌萎缩侧索硬化症运动神经元死亡的预防 (3)天然抗氧化剂Bc l-2家族：BCL-2原-能不能- 癌基因保护慢性氧化应激的神经毒性？ 从转基因小鼠制备的器官型脊髓培养物 BCL-2要么被敲除要么过度表达将用于研究 这一假定的抗氧化途径的介体作为天然的 抗氧化剂或神经保护剂。 意义：bcl-2是一种独特的内源性蛋白，可以阻断 凋亡性死亡。作为一种天然抗氧化剂，它可以起到 防止氧化应激引起的慢性神经变性。 (4)特异性：谷氨酸毒性是否参与选择性 氧化应激模型中的运动神经元靶向？ 意义：选择性细胞死亡是理解 肌萎缩侧索硬化症及其他神经退行性变的发病机制 流程。 这些实验将检验长期过量的总体假设 氧自由基在运动神经元中的重要病理生理作用 死亡。如果这是真的，它将对我们的 对慢性氧化侮辱在神经退行性变中的认识 障碍和衰老，以及如何从神经药理学的角度处理这些问题。

Oxygen radicals and other radical species are toxic to cells, most often by damaging membrane lipids and DNA. Cells have multiple levels of antioxidant defenses, and superoxide dismutase is the first level of defense against superoxide radicals. The notion that a gradual decrease in these defenses might play a role in aging or neurodegenerative diseases has been considered for years, but has remained controversial. The recent discovery of mutations in the gene for Cu/Zn superoxide dismutase (SOD1) in familial ALS provides the first good evidence that a specific defect in antioxidant defenses could be responsible for a neurodegenerative disease. To determine whether decreased SOD activity could contribute to motor neuron loss, we intend to model the chronic loss of SOD1 in spinal cord organotypic cultures and then to use this model to investigate various neuroprotective strategies: (1) Toxicity Model: To develop a model of chronic oxidative toxicity in organotypic spinal cord cultures. Is chronic inhibition of superoxide dismutase toxic to motor neurons in spinal cord: We will develop a rodent spinal cord organotypic culture system, then define susceptibility of large cholinergic anterior horn cells to acute and chronic exposure to SOD1 inhibition. Significance: Creation of in vitro models allows for experimental control and pharmacologic manipulation that is impossible in patients. (2) Using a model of chronic oxidative injury, can motor neuron loss be prevented by antioxidants and other potential neuroprotectants: Significance: Current knowledge of biochemical cascades operant in programmed cell death suggest that neuronal toxicity induced by oxidative stress might be blocked with both antioxidants and neurotrophic factors. These studies will provide data on which class of drugs might be most beneficial and specific to the prevention of motor neuron death in ALS. (3) The Bcl-2 family of natural antioxidants: Can the bcl-2 proto- oncogene protect against the neurotoxicity of chronic oxidative stress? Organotypic spinal cord cultures prepared from transgenic mice in which Bcl-2 has either been knocked out or over-expressed will be used to study the role of this putative mediator of antioxidant pathways as a natural antioxidant or neuroprotectant. Significance: Bcl-2 is a unique endogenous protein that can block apoptotic death. As a natural antioxidant, it could function to prevent chronic neural degeneration due to oxidative stress. (4) Specificity: Does glutamate toxicity participate in the selective targeting of motor neurons in models of oxidative stress? Significance: Selective cell death is central to understanding the pathogenesis of ALS as well as other neurodegenerative processes. These experiments will test the overall hypothesis that chronic excess oxygen radical play an important pathophysiologic role in motor neuron death. If this were true it would have fundamental consequences for our understanding on chronic oxidative insults in neural degenerative disorders and aging, and how to approach them neuropharmacologically.