The Effect of Cold Stress on UVB Injury in Mouse Skin and Cultured Keratinocytes

Abstract— The effect of cold stress on skin damage caused by UVB irradiation was investigated both in vivo and in vitro. Ear skin of mice that had been exposed to cold stress at 0°C for 20 min and at 5°C for 24 h was exposed to UVB radiation. Sunburn cell production was less in mice exposed to the lower temperature. In addition, the effect of cold stress on the survival rate of UVB-irradiated rat keratinocytes was examined in a cytotoxicity test, with the results showing that keratinocytes exposed to cold stress of 0°C had a higher survival rate than control cells. To pursue a promising clue for explaining the result, we examined metallothionein (MT) production in rat keratinocytes that had been exposed to cold stress at 0°C. Microfluorometric quantification showed a positive correlation between the time course and the intensity of immunofluorescence for MT, indicating that the molecule is inducible by exposure to cold stress in our experimental system. These results suggest that epidermal cells that have been exposed to cold stress maintain a higher resistance to UV radiation than nonexposed controls in vivo and in vitro , and that MT with radical-scavenging activity might contribute, at least in part, to photoprotection against UVB-induced oxidative damage in mammalian skin.