Effect of topical application of antioxidants and free radical scavengers on protection of hairless mouse skin exposed to chronic doses of ultraviolet B.

BACKGROUND/AIMS: Within the past three decades, there has emerged a greater awareness of the molecular effects of solar rays especially ultraviolet radiation (UV-R), to the extent that the harmful effects of solar radiation are recognized not only by molecular biologists and physicians, but also by the general public (1). Various sunscreen molecules that effectively block the UVB component of the sun are available; however, a large part of Western populations elicits adverse reactions against chemical sunscreens (2). This study was designed to observe the protective effect of antioxidants against the damaging effects of chronic UVB exposure of skin in an attempt to introduce antioxidants and free radical scavengers as topical sun protective agents.

METHODS: Jackson hairless mice were exposed to suberythemal doses of UVB, three times a week, and topically treated with a cream containing the anti-oxidants vitamin E, butylated hydroxy-toluene, nordihydroguaradinic acid and vitamin C.

RESULTS: Treatment with vehicle alone along with UVB exposure resulted in an increase in epidermal thickness showing a 38%, 77% and 112% increase after 4 weeks, 8 weeks and 12 weeks, respectively. Chronic UVB exposed skin treated with the material containing free radical scavengers and antioxidants mix (AO mix) exhibited 39%, 73% and 124% thicker epidermis than the un-treated control after, respectively, 4 weeks, 8 weeks and 12 weeks of treatment. The vehicle did not appear to protect skin against UV irradiation, since there appeared to be more (16%) sunburn cells in vehicle treated skin than the untreated, UV exposed skin after 4 weeks of treatment. After 8 weeks and 12 weeks, there were 33% and 36% less sunburn cells in the vehicle treated skin than the untreated, UV exposed skin. The antioxidant mix was significantly effective (P=<0.001) in protecting against UVB irradiation, having 63%, 71 % and 79% fewer sunburn cells than the untreated, UV exposed skin after 4 weeks, 8 weeks and 12 weeks of treatment, respectively.

CONCLUSION: Data from these studies suggest that low level chronic exposures to UV can lead to alteration of the skin, like epidermal thickening and appearance of sunburn cells. The data also indicates that a mix of common antioxidants and free radical scavengers are photoprotective against chronic skin damage in the hairless mouse skin model.