Ng Li Fang, Ng Li Theng, van Breugel Michiel, Halliwell Barry, Gruber Jan
Ageing Research Laboratory, Science Division, Yale-NUS College, Singapore, Singapore.
Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
Front Genet. 2019 Apr 12;10:311. doi: 10.3389/fgene.2019.00311. eCollection 2019.
The mitochondrial free radical theory of aging (mFRTA) proposes that accumulation of oxidative damage to macromolecules in mitochondria is a causative mechanism for aging. Accumulation of mitochondrial DNA (mtDNA) damage may be of particular interest in this context. While there is evidence for age-dependent accumulation of mtDNA damage, there have been only a limited number of investigations into mtDNA damage as a determinant of longevity. This lack of quantitative data regarding mtDNA damage is predominantly due to a lack of reliable assays to measure mtDNA damage. Here, we report adaptation of a quantitative real-time polymerase chain reaction (qRT-PCR) assay for the detection of sequence-specific mtDNA damage in and apply this method to investigate the role of mtDNA damage in the aging of nematodes. We compare damage levels in old and young animals and also between wild-type animals and long-lived mutant strains or strains with modifications in ROS detoxification or production rates. We confirm an age-dependent increase in mtDNA damage levels in but found that there is no simple relationship between mtDNA damage and lifespan. MtDNA damage levels were high in some mutants with long lifespan (and ). We next investigated mtDNA damage, lifespan and healthspan effects in nematode subjected to exogenously elevated damage (UV- or γ-radiation induced). We, again, observed a complex relationship between damage and lifespan in such animals. Despite causing a significant elevation in mtDNA damage, γ-radiation did not shorten the lifespan of nematodes at any of the doses tested. When mtDNA damage levels were elevated significantly using UV-radiation, nematodes did suffer from shorter lifespan at the higher end of exposure tested. However, surprisingly, we also found hormetic lifespan and healthspan benefits in nematodes treated with intermediate doses of UV-radiation, despite the fact that mtDNA damage in these animals was also significantly elevated. Our results suggest that within a wide physiological range, the level of mtDNA damage does not control lifespan in .
线粒体衰老自由基理论（mFRTA）提出，线粒体中大分子的氧化损伤积累是衰老的一种致病机制。在这种情况下，线粒体DNA（mtDNA）损伤的积累可能特别值得关注。虽然有证据表明mtDNA损伤存在年龄依赖性积累，但将mtDNA损伤作为长寿决定因素的研究数量有限。缺乏关于mtDNA损伤的定量数据主要是由于缺乏可靠的检测方法来测量mtDNA损伤。在这里，我们报告了一种定量实时聚合酶链反应（qRT-PCR）检测方法的改进，用于检测[具体生物]中序列特异性的mtDNA损伤，并应用该方法研究mtDNA损伤在线虫衰老中的作用。我们比较了老年和幼年动物之间以及野生型动物与长寿突变株或ROS解毒或产生速率发生改变的菌株之间的损伤水平。我们证实了[具体生物]中mtDNA损伤水平随年龄增长而增加，但发现mtDNA损伤与寿命之间没有简单的关系。一些长寿突变体（[具体突变体1]和[具体突变体2]）的mtDNA损伤水平很高。接下来，我们研究了受到外源损伤（紫外线或γ辐射诱导）的线虫的mtDNA损伤、寿命和健康寿命影响。我们再次观察到这些动物的损伤与寿命之间存在复杂的关系。尽管γ辐射导致mtDNA损伤显著增加，但在所测试的任何剂量下，γ辐射都没有缩短线虫的寿命。当使用紫外线辐射使mtDNA损伤水平显著升高时，线虫在较高的测试暴露水平下确实寿命缩短。然而，令人惊讶的是，我们还发现，用中等剂量紫外线辐射处理的线虫具有促寿命和促健康寿命的益处，尽管这些动物的mtDNA损伤也显著增加。我们的结果表明，在广泛的生理范围内，mtDNA损伤水平并不控制[具体生物]的寿命。
