IN-VIVO ANTIOXIDANT STATUS, DNA-DAMAGE, MUTATION AND DNA-REPAIR CAPACITY IN CULTURED LYMPHOCYTES FROM HEALTHY 75 TO 80-YEAR-OLD HUMANS

The accumulation of damage to cellular biomolecules, including DNA, ov er time may play a significant role in the aetiology of the ageing pro cess. We have previously quantified DNA damage and mutation within cul tured lymphocytes from healthy human male subjects in three different age groups (35-39, 50-54 and 65-69 years). The results of that study s howed an age-related increase in DNA damage and mutations in lymphocyt es. In addition, an age-related decrease in the capacity of the lympho cytes to repair H2O2-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 fre quency at the hypoxanthine phosphoribosyltransferase (hprt) gene locus (for 16 subjects) within cultured lymphocytes. In addition, in vivo a ntioxidant status (for all study subjects) and the capacity of lymphoc ytes to repair H2O2-induced DNA damage (for 18 subjects) were also ass essed. The results obtained showed: that the mean basal level of DNA d amage 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 differen ce between log mean mutant frequency at the hprt gene locus in lymphoc ytes from the 75- to 80-year age group (0.31 +/- 0.33) compared to tha t 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 per oxidase (GPx EC 1.11.1.9), catalase (CAT; EC 1.11.1.6) and caeruloplas min (CPL; EC 1.16.3.1) were significantly elevated in the 75- to 80-ye ar age group, compared to the 35- to 39-, 50- to 54- and 65- to 69-yea r age groups. Levels of bilirubin (BR) were reduced in the 75- to 80-y ear 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 treatme nt of lymphocytes with H2O2, we did not find any difference in the sus ceptibility of lymphocytes to DNA damage in the 75- to 80-year age gro up, compared to the other age groups. The DNA repair capacity in lymph ocytes 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. T hese results highlight the importance of DNA repair processes and anti oxidant defence systems for maintaining genomic stability in vivo.