衰老小鼠脑老化过程中线粒体结构功能与mtDNA缺失的生物学规律

Biological rule of mitochondrial structure and function in relation to mtDNA deletion during brain aging of senescent mice

目的:研究小鼠脑老化过程中线粒体的生物学变化规律,探讨衰老的机制。方法:实验于2002-01/2003-04在广州体育学院科学实验中心及中山大学医学院完成。利用电镜对线粒体进行观察计数,Clark氧电极法测定线粒体呼吸链细胞色素C氧化酶及NADH脱氢酶活性,分光光度法测定抗氧化酶活性,聚合酶链反应检测mtDNA3866bp片段缺失率。结果:与5月龄小鼠比较,20月龄的老年小鼠脑线粒体数量减少、体积增大,线粒体呼吸控制率减小,而ADP/O比值无显著性差异,呼吸链NADH脱氢酶、细胞色素C氧化酶活性下降,mtDNA3866bp片段缺失率增加,而抗氧化酶活性却增大。通过各指标间的相关分析发现呼吸控制率与mtDNA缺失率显著相关(r=0.739,P<0.01),NADH脱氢酶、细胞色素C氧化酶活性与mtDNA缺失率亦显著相关(r=0.582,P<0.05,r=0.810,P<0.01),但抗氧化酶活性与mtDNA缺失率无相关性(r=0.256,P>0.05)。结论:推测衰老时mtDNA的损伤积累可引起呼吸链酶复合物活性下降,导致呼吸链功能减退致生物衰老。

AIM:To study the changes of mitochondria isolated from the brain of aged mice,and probe into the senescent mechanism. METHODS:The experiment was finished in the Scientific Experiment Center of Guangzhou Physical Education and Medical College of Sun Yat-sen University from January 2002 to April 2003.Morphometric quantitative study of mitochondria in myocardium was investigated with electron microscopy,the activities of cytochrome C oxidase and activities of nicotinamide-adenine dinucleotide(NADH) dehydrognase in respiratory chain were measured with Clark oxygen electrode,the activities of antioxidant enzyme were measured with spectrophotography, the levels of mtDNA 3 866 bp deletion were determined with polymerase chain reaction(PCR). RESULTS:The decreased quantity of mitochondrion,RCR,activities of NADH dehydrognase and cytochrome oxidase and increased volum of brain mitochondria and activities of antioxidant enzyme were found in 20-month aged mice as compared with 5-month mice, meanwhile,the mtDNA 3 866 bp deletion was increased, and there was no significant difference in ADP/O.Correlated analysis to all indexes,it was found that RCR and mtDNA deletion were significantly correlated(r =0.739, P < 0.01),and so between the NADH dehydrognase, activities of cytochrome C oxidase and mtDNA deletion(r=0.582, P< 0.05, r=0.810, P < 0.01), but it was not between antioxidant enzyme and mtDNA deletion(r =0.256, P >0.05). CONCLUSION:These observations suggest that accumulation of mtDNA damage causes the decreased activities of enzyme compound,hypofunction of respiratory chain when senility,and those may be the foundation of onset of aging regressive disease and organism senility.