Aging of the dog brain : molecular pathological study on the mechanism of biometal (iron) accumulation

研究目的：对自由基中毒引起的狗脑神经元变性进行病理学研究。本研究主要包括铁蓄积与神经退行性变的关系及铁在脑内蓄积的机制。1.分布与年龄相关的形态学变化，积累铁（细胞种类，电镜调查），2。铁相关蛋白质（铁蛋白，转铁蛋白）的证明，3。8-OHdG和4-HNE表达作为自由基诱导的细胞损伤的标志物，4.金属硫蛋白表达（免疫组化，生化分析）。铁在胶质细胞（少突胶质细胞）的胞浆中有明显的蓄积，这是铁在胶质细胞中蓄积的证据.铁蛋白在胶质细胞胞浆中的分布与铁积累相似，随年龄增长，铁蛋白免疫反应增强. 8-OHdG和4-HNE表达作为自由基诱导的细胞损伤的标志物，随着年龄的增长而增加，提示氧自由基可能是脑老化的部分原因.随着年龄的增长，灰质和白色物质中总金属硫蛋白的水平均下降，表明抗过氧化蛋白的缺乏可能是脑老化的部分原因。

Purpose of the studyAge-related changes of the brain of dogs including neuronal degeneration induced by the free radical intoxication were pathologically studied. The study included relationship between the iron accumulation and neuronal degenerative changes and mechanism of the iron accumulation in the brain. 1. Distribution of the age-related morphological changes, accumulated iron (cell species, electron microscopic investigation), 2. Demonstration of iron-related proteins (ferritin, transferrin), 3. 8-OHdG and 4-HNE expression as a marker of cell injury induced by free radicals, 4. Metallothionein expression (immunohistochemical, biochemical analysis).Summarized findings and conclusion1. Iron accumulation was demonstrated in the cytoplasm of glial cells (oligodendroglia), some evidence of iron accumulation in the mitochondria.2. Ferritin distribution was similar to that of iron accumulation in the cytoplasm of glial cells ; ferritin immunoreactivity became strong with age.3. 8-OHdG and 4-HNE expression as a marker of cell injury induced by free radicals, increased with age suggesting that oxygen radicals would, in part, be responsible for brain aging.4. Level of total Metallothionein decreased with age in both gray and white matter, indicating that shortage of the anti-peroxidization protein would be, in part, responsible for the brain aging.