Reconstructed human epidermis as an efficient tool in the evaluation of the effects of UV irradiation and of the photoprotective capacities of a sunblock

Abstract

Solar or UVA (ultraviolet A) irradiation of the skin causes biological damage, including apoptosis, which is evident in the form of sunburn cells and the overexpression of p53. These two parameters, as well as the measurement of cellular viability, were used to evaluate the effects of UV irradiation on a reconstructed human epidermis (RHE) model, with and without the photoprotection of a broad spectrum sunblock. Reconstructed epidermis models were irradiated by solar spectrum (420 mJ cm –2 ) or UVA (20 J cm –2 ). In the absence of irradiation, and with irradiation doses of 420 mJ cm –2 and 20 J cm –2 , viability was estimated at 95, 12 and 70% respectively. Sunburn cells per cm were evaluated at 0, 41 and 22, respectively under these same conditions. The apoptotic response was studied through the expression of p53, which increased at first and was then followed by a specific cleavage, 24 h after irradiation at 420 mJ cm –2 . However, in the presence of a broad spectrum sunblock preparation (a combination of OMC, MBTBP, TiO 2 and ZnO) and after irradiation at 420 mJ cm –2 and 20 J cm –2 , viability increased to 40 and 85% respectively. The number of sunburn cells (SBC) per cm fell to 12 and nine respectively. The photoprotection provided by the sunblock limited the increase in the expression of p53 and resulted in the total disappearance of the cleavage. This study shows that human reconstructed epidermis is a valid skin model for use in the evaluation of the effects of solar and UVA irradiation, as well as in the testing of the efficacy of sunfilters.