In vivo antioxidant status, DNA damage, mutation and DNA repair capacity in cultured lymphocytes from healthy 75- to 80-year-old humans

Abstract

The accumulation of damage to cellular biomolecules, including DNA, over time may play a significant role in the aetiology of the ageing process. We have previously quantified DNA damage and mutation within cultured lymphocytes from healthy human male subjects in three different age groups (35–39, 50–54 and 65–69 years). The results of that study showed an age-related increase in DNA damage and mutations in lymphocytes. In addition, an age-related decrease in the capacity of the lymphocytes to repair H 2O 2-induced DNA damage was found. In this article, we report the findings of an extension to the earlier study. Thirty-one generally healthy male and female subjects between the ages of 75 and 80 years were recruited. Using a number of bioassays, we were able to determine; basal levels of DNA damage (for 18 subjects) and mutant frequency at the hypoxanthine phosphoribosyltransferase ( hprt) gene locus (for 16 subjects) within cultured lymphocytes. In addition, in vivo antioxidant status (for all study subjects) and the capacity of lymphocytes to repair H 2O 2-induced DNA damage (for 18 subjects) were also assessed. The results obtained showed: that the mean basal level of DNA damage in lymphocytes from subjects in the 75- to 80-year age group (12.6±4.7%) was similar to that of the 35- to 39-year age group (13.3±3.3%), p=0.42 (Mann–Whitney); there was no significant difference between log mean mutant frequency at the hprt gene locus in lymphocytes from the 75- to 80-year age group (0.31±0.33) compared to that observed in the 35- to 39-year age group (0.24±0.21; Student's t-test, t=0.68, p>0.05). Levels of the antioxidants glutathione peroxidase (GPx EC 1.11.1.9), catalase (CAT; EC 1.11.1.6) and caeruloplasmin (CPL; EC 1.16.3.1) were significantly elevated in the 75- to 80-year age group, compared to the 35- to 39-, 50- to 54- and 65- to 69-year age groups. Levels of bilirubin (BR) were reduced in the 75- to 80-year age group, the decrease being contributed by the female subjects. No differences in levels of superoxide dismutase (SOD; EC 1.15.1.1) or uric acid (UA) were found between the 4 age groups. Following treatment of lymphocytes with H 2O 2, we did not find any difference in the susceptibility of lymphocytes to DNA damage in the 75- to 80-year age group, compared to the other age groups. The DNA repair capacity in lymphocytes from individuals in the 75- to 80-year age group was similar to that of the 35- to 39-year age group, for all time points assessed. These results highlight the importance of DNA repair processes and antioxidant defence systems for maintaining genomic stability in vivo.