Oxidative stress and in vivo chemiluminescence in mouse skin exposed to UVA radiation

Mouse skin was exposed to UVA radiation (320-400 nm). The in vivo chemiluminescence of the skin was measured after irradiation. Chemiluminescence showed a maximum 13-fold increase (control emission, 10+/-1 cps cm(-2)) after 45-60 min of exposure to UVA, with no further increase with 60 min additional exposure. Spectral analysis of the emitted chemiluminescence showed that the principal species emitted in the 400-500 nm range. Topical application with alpha-tocopherol (10% v/w) and beta-carotene (1 mM) greatly reduced the UVA-induced skin chemiluminescence. Thiobarbituric acid reactive substance (TEARS) levels were increased by 130% in skin homogenates after 2 h of exposure to UVA (control value, 77 +/- 14 nmol malonaldehyde equivalents (g tissue) (-1)). The activities of antioxidant enzymes in skin homogenates were decreased after 2 h of irradiation: the superoxide dismutase (SOD) activity (control value, 181+/-10 U SOD (g tissue)(-1)) was decreased by 40% and the catalase activity (control value, 1.34+/-0.14 pmol (g tissue)(-1)) was decreased by 45%. In vivo chemiluminescence appears to be a suitable method for following the kinetics of the skin oxidative stress processes and for testing the effect of topical application with antioxidants and photoprotective agents. (C) 1997 Elsevier Science S.A.