Peroxynitrite-Induced Oxidative Damage in TBI

描述(由申请人提供)：现在有大量证据支持这样的概念，即活性氧基(ROS)介导的对脂质、蛋白质和核酸的氧化损伤在创伤性脑损伤(TBI)的急性病理生理中起主要作用，抑制这种损伤的抗氧化剂将减少继发性脑损伤并促进神经恢复。然而，对创伤性脑损伤的抗氧化剂治疗的优化设计需要更全面地了解ROS的来源和特征。最近的研究表明，当线粒体功能失调时，线粒体可以成为ROS的重要来源，这是由于脑损伤导致细胞内钙(Ca++)升高。其他研究表明，线粒体形成的一个关键ROS是过氧亚硝酸盐(PON)。PON衍生的二氧化氮(NO2)、碳酸盐(CO3)和羟基(OHO)自由基可引起线粒体脂质(脂质过氧化)和蛋白质(羰化、硝化)的氧化损伤，加剧细胞内钙超载，引发Calain介导的细胞骨架降解和神经变性。这一建议的具体目的是检验以下假设：1)弥漫性和局灶性脑损伤的创伤后氧化损伤都是由PON介导的，PON介导的脂质和蛋白质损伤的时间进程先于Calain介导的细胞骨架损伤和神经变性；2)线粒体功能障碍是PON的主要来源，线粒体是脂质和蛋白质氧化损伤的起始部位。3)药物清除剂PON或PON衍生的氧自由基能保护离体脑线粒体免受氧化损伤和功能障碍；4)药物清除PON或PON产生的氧自由基可有效抑制脑创伤后线粒体的氧化损伤和功能障碍，减轻下游细胞骨架的降解和神经退行性变。实验将在中度和重度弥漫性和局灶性脑损伤模型中进行。系统研究PON在急性颅脑损伤中的作用，以及仔细研究PON形成后清除PON或阻断PON引起的氧化损伤的化合物的神经保护效果，有望为临床提供一种有效和实用的抗氧化剂神经保护策略。

DESCRIPTION (provided by applicant): Extensive evidence now supports the concept that the reactive oxygen species (ROS)-mediated oxidative damage to lipids, proteins and nucleic acids plays a major role in the acute pathophysiology of traumatic brain injury (TBI), and that antioxidant drugs which inhibit this damage will reduce secondary brain injury and improve neurological recovery. However, the optimal design of antioxidant treatment for TBI requires a more complete understanding of the source and characteristics of ROS formation. Recent work indicates that mitochondria can become an important source of ROS when they become dysfunctional as a result of the massive TBI-induced rise in intracellular calcium (Ca++). Other work suggests that a key ROS formed by mitochondria is peroxynitrite (PON). PON-derived nitrogen dioxide (,NO2), carbonate (,CO3) and hydroxyl (,OH) radicals can cause oxidative damage to mitochondrial lipids (lipid peroxidation) and proteins (carbonylation, nitration) exacerbating intracellular Ca++ overload and triggering calpain-mediated cytoskeletal degradation and neurodegeneration. The specific aims of this proposal are to test the following hypotheses: 1) that post-traumatic oxidative damage in both diffuse and focal TBI is mediated by PON and that the time course of PON-mediated damage to lipids and proteins precedes calpain-mediated cytoskeletai damage and neurodegeneration, 2) that mitochondrial dysfunction is a major source of PON, and that mitochondria are an initial site of lipid and protein oxidative damage, 3) that pharmacological scavengers of PON or PON-derived oxygen radicals can protect isolated brain mitochondria from oxidative damage and dysfunction and 4) that pharmacological scavenging of PON or PON-dedved oxygen radicals will effectively inhibit post-TBI oxidative damage and dysfunction in brain mitochondria and attenuate downsteam cytoskeletal degradation and neurodegeneration. Experiments will be carried out in models of moderate and severe diffuse and focal TBI. A systematic investigation of the role of PON in acute TBI, and a careful examination of the neuroprotective efficacy of compounds which scavenge it after it is formed or that block PON-induced oxidative damage is expected to lead to a clinically effective and practical antioxidant neuroprotective strategy for acute TBI.