Time-course of mitochondrial gene expressions in mice brains:: implications for mitochondrial dysfunction, oxidative damage, and cytochrome c in aging
Time-course of mitochondrial gene expressions in mice brains:: implications for mitochondrial dysfunction, oxidative damage, and cytochrome c in aging
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DOI：
10.1111/j.1471-4159.2004.02884.x
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发表时间：
2005-02-01
影响因子：
4.7
通讯作者：
Reddy, PH
中科院分区：
文献类型：
--
作者：
Manczak, M;Jung, YS;Reddy, PH
对衰老的研究对于更好地了解许多与年龄相关的疾病是至关重要的。衰老假说中的自由基学说认为，在衰老过程中，线粒体中的活性氧增加，导致线粒体DNA发生突变，损伤线粒体成分，从而导致衰老。了解线粒体基因表达谱及其与线粒体功能的关系成为了解衰老的重要一步。本研究的目的是测定4个年龄段(2、12、18和24月龄)C57BL6小鼠脑片中线粒体编码基因的mRNA表达，并确定这些改变如何影响与年龄相关的变化，包括氧化损伤和细胞色素c在细胞凋亡中的作用。采用Northern杂交、原位杂交和免疫荧光分析等方法，分析了C57BL6小鼠大脑皮质线粒体基因、氧化损伤标志物8-羟基鸟苷(8-OHG)和细胞色素c基因的表达变化。我们的Northern印迹分析显示，与2个月大的小鼠相比，12和18个月大的C57BL6小鼠呼吸链复合体I、III、IV和V中线粒体编码基因的表达增加，这表明一种代偿机制，允许产生参与电子传递链的蛋白质。与12月龄和18月龄C57BL6小鼠线粒体基因表达上调相反，24月龄C57BL6小鼠mRNA表达下降，提示上调基因维持的代偿是不可持续的，表达下调导致衰老后期。我们对海马区和大脑皮层线粒体基因的原位杂交分析显示，线粒体基因过度表达，这表明这些脑区对线粒体功能至关重要。我们对8-OHG和细胞色素c的免疫荧光分析显示，12月龄C57BL6小鼠的8-OHG和细胞色素c增加，表明与年龄相关的线粒体氧化损伤和细胞凋亡与线粒体功能障碍有关。我们对ATPase 6原位杂交的双标记分析和我们对8-OHG的免疫荧光分析表明，特定的神经元群体经历了氧化损伤。此外，ATPase 6原位杂交的双标记分析和细胞色素c的免疫荧光分析表明，细胞色素c的释放与衰老的C57BL6小鼠脑内线粒体功能障碍有关。这项研究还表明，这些线粒体基因表达的变化可能与线粒体功能障碍、氧化损伤和细胞色素c在衰老以及阿尔茨海默病和帕金森病等与年龄相关的疾病中的作用有关。
The study of aging is critical for a better understanding of many age-related diseases. The free radical theory of aging, one of the prominent aging hypotheses, holds that during aging, increasing reactive oxygen species in mitochondria causes mutations in the mitochondrial DNA and damages mitochondrial components, resulting in senescence. Understanding a mitochondrial gene expression profile and its relationship to mitochondrial function becomes an important step in understanding aging. The objective of the present study was to determine mRNA expression of mitochondrial-encoded genes in brain slices from C57BL6 mice at four ages (2, 12, 18, and 24 months) and to determine how these altered mitochondrial genes influence age-related changes, including oxidative damage and cytochrome c in apoptosis. Using northern blot analysis, in situ hybridization, and immunofluorescence analyses, we analyzed changes in the expression of mitochondrial RNA encoding the mitochondrial genes, oxidative damage marker, 8-hydroxyguanosine (8-OHG), and cytochrome c in brain slices from the cortex of C57BL6 mice at each of the four ages. Our northern blot analysis revealed an increased expression of mitochondrial-encoded genes in complexes I, III, IV, and V of the respiratory chain in 12- and 18-month-old C57BL6 mice compared to 2-month-old mice, suggesting a compensatory mechanism that allows the production of proteins involved in the electron transport chain. In contrast to the up-regulation of mitochondrial genes in 12- and 18-month-old C57BL6 mice, mRNA expression in 24-month-old C57BL6 mice was decreased, suggesting that compensation maintained by the up-regulated genes cannot be sustained and that the down-regulation of expression results in the later stage of aging. Our in situ hybridization analyses of mitochondrial genes from the hippocampus and the cortex revealed that mitochondrial genes were over-expressed, suggesting that these brain areas are critical for mitochondrial functions. Our immunofluorescence analysis of 8-OHG and cytochrome c revealed increased 8-OHG and cytochrome c in 12-month-old C57BL6 mice, suggesting that age-related mitochondrial oxidative damage and apoptosis are associated with mitochondrial dysfunction. Our double-labeling analysis of in situ hybridization of ATPase 6 and our immunofluorescence analysis of 8-OHG suggest that specific neuronal populations undergo oxidative damage. Further, double-labeling analysis of in situ hybridization of ATPase 6 and immunofluorescence analysis of cytochrome c suggest cytochrome c release is related to mitochondrial dysfunction in the aging C57BL6 mouse brain. This study also suggests that these mitochondrial gene expression changes may relate to the role of mitochondrial dysfunction, oxidative damage, and cytochrome c in aging and in age-related diseases such as Alzheimer's disease and Parkinson's disease.