Lack of correlation between apoptosis and DNA single-strand breaks in X-irradiated human peripheral blood mononuclear cells in the course of ageing

Abstract The dependence on age of both the basal and the X-radiation-induced levels of apoptosis was examined in human peripheral blood mononuclear cells (PBMC). In the same samples, the base value and the extent of induced DNA single-strand breaks were determined, using a sensitive and fast microplate assay. PBMC were isolated from blood of donors of various age groups (20–30, 40–60 and >70 years of age) and X-irradiated ex vivo using a 6 MV linear accelerator to give a total exposure of 4 Gy. The mean basal levels of apoptosis in PBMC from donors in the 40–60 year age group and the >70 year age group were found to be only slightly higher (by 20–10%) compared to that of the 20–30 year age group, whereas the extent of DNA damage strongly and significantly ( P 70), compared to age group 20–30. The results show that X-ray-induced apoptosis and DNA damage in PBMC are not correlated during ageing.