Department of Clinical Laboratory, Xuanwu Hospital, Capital Medical University, Beijing, 100053, People's Republic of China.
Mol Biol Rep. 2012 Jan;39(1):233-41. doi: 10.1007/s11033-011-0731-4. Epub 2011 May 10.
Aging is associated with a reduction in the DNA repair capacity under oxidative stress. However, whether the DNA damage and repair capacity can be a biomarker of aging remains controversial. In this study, we demonstrated two cause-and-effect relationships, the one is between the DNA damage and repair capacity and the cellular age, another is between DNA damage and repair capacity and the level of oxidative stress in human embryonic lung fibroblasts (2BS) exposed to different doses of hydrogen peroxide (H2O2). To clarify the mechanisms of the age-related reduction in DNA damage and repair capacity, we preliminarily evaluated the expressions of six kinds of pivotal enzymes involved in the two classical DNA repair pathways. The DNA repair capacity was observed in human fibroblasts cells using the comet assay; the age-related DNA repair enzymes were selected by RT-PCR and then verified by Western blot in vitro. Results showed that the DNA repair capacity was negatively and linearly correlated with (i) cumulative population doubling (PD) levels only in the group of low concentration of hydrogen peroxide treatment, (ii) with the level of oxidative stress only in the group of young PD cells. The mRNA expression of DNA polymerase δ1 decreased substantially in senescent cells and showed negative linear-correlation with PD levels; the protein expression level was well consistent with the mRNA level. Taken together, DNA damage and repair capacity can be a biomarker of aging. Reduced expression of DNA polymerase δ1 may be responsible for the decrease of DNA repair capacity in senescent cells.
衰老是与氧化应激下 DNA 修复能力下降有关。然而，DNA 损伤和修复能力是否可以作为衰老的生物标志物仍然存在争议。在这项研究中，我们证明了两种因果关系，一种是 DNA 损伤和修复能力与细胞年龄之间的关系，另一种是 DNA 损伤和修复能力与暴露于不同浓度过氧化氢（H2O2）的人胚肺成纤维细胞（2BS）中氧化应激水平之间的关系。为了阐明与年龄相关的 DNA 损伤和修复能力下降的机制，我们初步评估了参与两种经典 DNA 修复途径的六种关键酶的表达。使用彗星试验在人成纤维细胞中观察 DNA 修复能力；通过 RT-PCR 体外选择与年龄相关的 DNA 修复酶，然后通过 Western blot 进行验证。结果表明，DNA 修复能力与（i）仅在低浓度过氧化氢处理组中与累积倍增水平呈负线性相关，（ii）仅在年轻 PD 细胞组中与氧化应激水平呈负线性相关。衰老细胞中 DNA 聚合酶 δ1 的 mRNA 表达显著降低，与 PD 水平呈负线性相关；蛋白表达水平与 mRNA 水平很好地一致。总之，DNA 损伤和修复能力可以作为衰老的生物标志物。DNA 聚合酶 δ1 的表达减少可能是衰老细胞中 DNA 修复能力下降的原因。
