Oxidatively damaged DNA in aging dyslipidemic ApoE-/- and wild-type mice.

The free radical theory of aging depicts an accumulation of cellular oxidatively damaged DNA. In this study, we investigated this theory in mice with knocked-out apolipoprotein E gene (ApoE(-/-)), which develops atherosclerosis and wild-type counterparts. The level of oxidatively damaged DNA was investigated as strand breaks, endonuclease III- and formamidopyrimidine DNA glycosylase-sensitive sites by the comet assay. The level of DNA damage was mainly increased with age in the liver of ApoE(-/-) mice, whereas no increase was observed in the aorta or lung of the mice. This suggests that the accumulation of oxidized DNA in the liver of dyslipidemic ApoE(-/-) mice could be secondary to dysfunction of the lipid metabolism. Visually, the aortas of the ApoE(-/-) mice were clearly atherosclerotic as indicated by rigid texture and yellowish in color. However, the unaltered levels of oxidized DNA in severely atherosclerotic aortas of old ( approximately 70 weeks) ApoE(-/-) mice indicate that oxidative stress may not be a generalized phenomenon, but rather related locally to the individual plaques. In conclusion, the results of this study suggest that dyslipidemic ApoE(-/-) mice suffer from hepatic oxidative stress in terms of oxidized DNA, and this effect could be due to the dysfunction of lipid metabolism.