Photoprotective Effect of Various Sunscreens Against Ultraviolet B - induced Chronic Skin Damage

Choi, Hyun Joo; Hann, Seung Kyung; Park, Yoon Kee

Abstract

BACKGROUND: Chronic exposure to ultraviolet radiation(UVE) nduces photoaging characterized by dry, deeply wrinkled, inelastic, leathery, and irregulaity pigmented skin. UVR also induces solar keratosis and carcinoma, and is a contributing factor in melanoma. Sunscreens are used to prevent solar damage to skin and, if used on a daily lass should significantly reduce the incidence of the chronie photodamaging events.
OBJECTIVE
We tried to evaulate the photoaging effects of UVR in the skin and the photoprotective effect of sunscreens. METHOD: We examined the gross and microscopic changes skin of albino hairless Skh : HR-1 mice exposed chronically to ultraviolet B(UVB) and suncreen-treated mice.
RESULTS
The skin of the UVB-irradiated mouse shows chear, cteristic signs of photoaging, such as deep wrinkles across the back, and thickened and a hery skin. Histologically, the photoaged skin shows increased epidermal thickness, numeross fibroblasts and inflammatory cell infiltration in the upper dermis, and many enlarged keratering cysts in the lower dermis. By the 20th week, seven of the total of 9 mice(78%) in UVB irradiated mice developed at least one tumor. Histologically, the tumor is a papilloma, but the he are many dyskeratotic cells and loss of polarity in epidermis. Octyl methoxycinnamate or TiO ZnO Talc-treated mic show a significantly decreased wrinkling score, mimmal epidermal hyperplasia, slightly increased dermal cellularity, and lack of proliferation of cysts. The octyl dimethyl PABA-treatd mice shows significantly increased wrinkling score and marked inflammatory infiltration dermis. By the 20th week, only one mouse had developed a tumor in the octyl methoxy irmamate-treated group and no evidence of tumor was seen in the TiO ZnO Talc-treated group. In the octyl dimethyl PABA-treated group, five of 7 mice(71%) developed at least one tumor.
CONCLUSION
The skin which is chronically exposed to UVB is subject to photoaging and photocarcinogenesis and regular use of an adequate sunscreen would prevent these photodamaging effects of UVB.