缺氧过程中大鼠脑mtDNA编码12S rRNA和COXⅠ mRNA表达的变化

Changes of expression levels of 12S rRNA and COXⅠ mRNA encoded by mtDNA in rat brain during hypoxic exposure

目的 探讨大鼠经不同时间低压缺氧暴露后脑皮质mtDNA编码 12SrRNA和细胞色素氧化酶 (Cytochromeoxi dase ,COX)亚基ⅠmRNA表达的变化。方法 健康雄性Wistar大鼠在模拟海拔 5 0 0 0m高原低压舱内每天缺氧暴露 2 3 5h ,分别连续缺氧 2、5、15、3 0d ,对照组不做缺氧处理。断头活杀后取脑皮质 ,提取组织总RNA ,以 β actin为内参照 ,反转录PCR法分析 12SrRNA和COXⅠmRNA的表达量。结果 缺氧 2d ,12SrRNA的表达比对照组显著升高 5 7%(P <0 0 5 ) ,缺氧 5d以后恢复至正常对照组水平 (P >0 .0 5 ) ;COX亚基ⅠmRNA表达在缺氧 2d和 5d显著升高 (P <0 .0 1) ,分别比对照组升高 5 5 %和 10 6%,缺氧 15d和 3 0d恢复至正常 ,与对照组无显著性差异 (P >0 .0 5 )。结论 缺氧暴露可同时影响mtD NA蛋白编码基因和核糖体基因的表达 ,提示缺氧可在转录与翻译两个水平上影响氧化磷酸化基因的表达 ,且其变化与缺氧暴露时间有关。

Objective To explore the changes of expression levels of 12S rRNA and cytochrome oxidase subunit Ⅰ (COXⅠ) mRNA encoded by mtDNA in rat cerebral cortex after rat exposure to hypobaric hypoxia for different days. Methods Healthy male Wistar rats were exposed to hypobaric chamber simulating 5 000 m above sea level (23 5 h/day) for 2, 5, 15 and 30 d. Rats in the control group were not exposed to hypoxia. Rats were sacrificed by decapitation. Total RNA in cerebral cortex was extracted using a standard program. Transcriptional levels of 12S rRNA and COXⅠ mRNA were determined by reverse transcription polymerase chain reaction (RT PCR). Results Compared with that in the control, the expression of 12S rRNA increased by 57% after hypoxic exposure for 2 d ( P <0 05), but restored to the level in the control group after hypoxic exposure for 5 d ( P >0 05). Compared with that in the control group, the expression of COXⅠ mRNA increased significantly by 55% and 106% after hypoxic exposure for 2 and 5 d ( P <0 01), but restored to the level in the control group after hypoxic exposure for 15 and 30 d ( P >0 05). Conclusion Hypoxic exposure may have effect on both protein gene and ribosome gene expression encoded by mtDNA, and the expression changes in a hypoxic exposure time dependent manner. This suggests that hypoxia can have effect on mitochondrial oxidative phosphorylation gene expression at both mitochondrial transcriptional and translational levels.