Social Stress Induces Oxidative DNA Damage in Mouse Peripheral Blood Cells

We investigated whether or not social stress (isolation, 1 mouse per cage) increases oxidative DNA damage in mouse peripheral blood cells. Male BALB/c mice (4 weeks old) were housed 5 per cage for 10 days. After acclimatization, mice were exposed to isolation stress for 7 and 30 days. Control mice were housed 5 per cage. Serum levels of corticosterone, which is a well known stress marker, and antioxidant compounds, ascorbic acid and a-tocopherol, were determined by liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) and ESACoul Array analysis, respectively. Single cell gel electrophoresis (comet assay) using formamidopyrimidine DNA glycosylase (FPG) was done to determine oxidative DNA damage in mouse peripheral blood cells. The significant increases of plasma level of corticosterone were observed in mice exposed to isolation stress for 7 days and 30 days. Although no significant differences in plasma concentration of ascorbic acid and a-tocopherol were observed between the control mice and the isolated mice, oxidative DNA damage was induced in the isolated mice for 7 days and 30 days. These results suggest that social stress, isolation, causes mild oxidation in mice. Key words: social stress, isolation, oxidative DNA damage, comet assay.