Evaluation of the Protection Efficacy of a Sunscreen by Measuring Tissue p53 Levels

Background. The protective efficacy of sunscreens is currently evaluated by the sun protection factor (SPF). It is thought that it is not a good indicator of protection against DNA damage and that other indicators may prove to be more useful. Objective. To study the p53 levels in the skin as a measure of the protective efficacy of sunscreens against ultraviolet light-induced (UV-induced) DNA damage. Patients and methods. For each of 20 volunteers included in the study, four test areas were specified; 2 treated with broad-spectrum sunscreen formulation with SPF 50 and 2 untreated. Two minimal erythema doses (MEDs) of broadband ultraviolet B (UVB) were then applied to one treated and one untreated areas, followed by 3 J/cm2 of ultraviolet A (UVA) without photosensitizers. After 48 hours, 3 mm punch biopsies were taken, homogenized, and p53 levels were measured using enzyme linked immuno sorbent assay (ELISA) technique.Results. p53 levels were significantly higher in irradiated than non-irradiated skin (mean 229.8 ± 76.1 and 91.1 ± 23.6 pg/mg protein, respectively). In addition, p53 levels in irradiated unprotected skin were significantly higher than in irradiated protected skin (mean 229.8 ± 76.1 and 160.7 ± 47.2 pg/mg protein, respectively). Conclusion. Measurement of p53 in skin homogenates by ELISA can be an in vivo assessment tool for the protective efficacy of a sunscreen against UV-induced DNA damage