Ultraviolet B irradiation induces the expression of hornerin in xenotransplanted human skin

Ultraviolet (UV) irradiation exerts numerous effects on the skin. Exposure of human skin to UVB at doses that induce mild sunburn reactions causes epidermal hyperproliferation and alterations in the expression of several epidermal differentiation markers. This study investigated the effects of UVB irradiation on the expression of hornerin, a member of the S100 fused-type protein family, using the xenotransplantation of normal human skin onto nude mice. Hornerin mRNA was detected in the UVB-irradiated skin on day 2 using RT-PCR. In accordance with the results of the RT-PCR, the expression of hornerin was induced in the granular layers of the UVB-exposed skin beginning two days after UVB irradiation and occurred in parallel with the expressions of cytokeratin 6 and Ki67. This finding suggests that hornerin induction in UVB-irradiated skin might be associated with epidermal hyperproliferation. This study demonstrated that hornerin is a protein whose expression is changed by UVB irradiation and suggests that the expression of hornerin might be a useful marker of acute UV damage in skin.