MITOCHONDRIAL FREE RADICALS AND AGING

所提出的研究是基于细胞和器官 衰老在很大程度上是无氧的后果 自由基介导的线粒体老化或损伤导致的 线粒体DNA突变的积累。尽管间接 然而，目前还没有直接证据表明， 衰老假说然而，调节Mn的活性的能力 线粒体内的超氧化物歧化酶（MnSOD）通过遗传手段使 它可以评估的作用，氧自由基产生的 线粒体在衰老过程中的作用为了实现MnSOD的这种调节， 活性，突变小鼠完全缺乏MnSOD和小鼠与低 来自培育到MnSOD缺陷型中的转基因的MnSOD表达水平 库存将被使用。缺乏MnSOD的胎儿成纤维细胞的发现， 对大气中的氧气敏感，复制寿命较短 表明线粒体内超氧化物水平 MnSOD活性的变化也会影响其活性。突变小鼠缺乏 MnSOD迅速发展为扩张型心肌病和代谢性酸中毒 出生后10天内死亡。然而，在特定目标I中，嵌合体 由完全缺乏MnSOD的细胞和野生型细胞组成， 形成，并且MnSOD缺陷细胞的存活暴露于高浓度 将在几个器官和大脑中跟踪超氧化物的水平。 通过这种方式，将有可能评估 不同类型的细胞和大脑不同区域的细胞 自由基引起的线粒体损伤。在《具体目标二》中， 长期增加暴露于线粒体内超氧化物将是 在适当构建的转基因动物中研究， 正常MnSOD活性。这些动物的寿命将决定， 以及对线粒体DNA和电子 运输系统将进行评估。此外，行为研究将 以确定在大脑中观察到的任何变化 与行为的改变有关。这些研究表明， 新的和创新的办法，直接审查 氧自由基产生线粒体突变， 功能障碍，反过来，器官和有机体老化。证据表明 线粒体自由基确实参与了衰老过程 将构成寻找治疗方法的基础， 线粒体内氧自由基水平的调节。

The proposed studies are based on the hypothesis that cellular and organ aging are, to a significant degree, the consequences of oxygen free radical-mediated mitochondrial aging or impairment resulting from the accumulation of mitochondrial DNA mutations. Despite much indirect evidence, there is, as yet, no direct proof of the mitochondrial hypothesis of aging. However, the ability to modulate the activity of Mn superoxide dismutase (MnSOD) within mitochondria by genetic means makes it possible to assess the role of oxygen free radicals generated by the mitochondria in the aging process. To achieve this modulation of MnSOD activity, mutant mice completely lacking in MnSOD and mice with a low level of MnSOD expression from a transgene bred into the MnSOD deficient stock will be used. The finding that fetal fibroblasts lacking MnSOD are sensitive to atmospheric oxygen and have a shorter replicative life span than normal cells indicates that intramitochondrial superoxide levels can be affected by alteration of MnSOD activity. Mutant mice lacking MnSOD quickly develop a dilated cardiomyopathy and metabolic acidosis and die within 10 days after birth. However, in Specific Aim I, chimeras composed of cells completely lacking MnSOD and wild type cells will be formed, and the survival of the MnSOD-deficient cells exposed to a high level of superoxide will be followed in several organs and in the brain. In this manner it will be possible to assess the vulnerability of different types of cells and of different regions of the brain to free- radical induced mitochondrial damage. In Specific Aim II, the effects of chronically increased exposure to intra-mitochondrial superoxide will be studied in appropriately constructed transgenic animals with 10-30% of normal MnSOD activity. The longevity of these animals will determined, and the long term effects on mitochondrial DNA and the electron transport system will be assessed. In addition, behavioral studies will be carried out to determine whether any changes observed in the brain are correlated with alterations in behavior. These studies represent a new and innovative approach to the direct examination of the role of oxygen free radicals in producing mitochondrial mutations and dysfunction and, in turn, organ and organismal aging. Evidence that mitochondrial free radicals are indeed involved in the aging process would constitute a basis for searching for therapeutic approaches to the modulation of oxygen free radical levels within mitochondria.