Effects of UV irradiation on the sebaceous gland and sebum secretion in hamsters

Background: Although an understanding of the photobiology of the skin has been extensively advanced recently, the effect of ultraviolet (UV) radiation on sebaceous glands is not well known. Objective: In this study, we examined the direct effect of UV radiation on cultured sebocytes from hamsters in vitro experimental system. Moreover, we examined whether UV-induced peroxidation of skin surface lipids may affect barrier function of horney layer. Methods: We irradiated cultured sebocytes from hamsters, which have similar biological characteristics to the human sebocytes, with UV radiation. Moreover, transepidermal water toss (TEWL) was examined after topical application of cholesterol or triglyceride (TG) and UV exposures on the back of hamsters. Results: The number of sebocytes were increased significantly (120-140%) after 4 days as compared with the non-irradiated controls. Lipid production in sebocytes was also increased on day 7 in an irradiation-dependent manner up to 4.1 times of the pre-irradiated level. When UVB was irradiated to TG- or cholesterol-applied skin at the minimum ear-swelling dose, TEWL increased twice or more as compared with UVB irradiation to unapplied sites. When in vitro-irradiated TG, in vitro-irradiated cholesterol, TG-peroxide (TG-OOH), and cholesterol-peroxide (CHO-OOH) were applied to the skin, TEWL increased significantly. Conclusion: These results suggest that UVB may directly activate the functions of the sebaceous gland in vivo to produce increased amounts of sebum, which may undergo peroxidation by UV light and damage the barrier functions of the skin. (C) 2003 Japanese Society for Investigative Dermatology. Published by Elsevier Science Ireland Ltd. All rights reserved.