p53 induction in normal human skin in vitro following exposure to solar simulated UV and UV-B irradiation

Exposure of normal human breast skin ex vivo to physiological levels of UV- B and solar simulated UV results in a UV dose- and time-dependent increase in epidermal p53, as determined by PAGE analysis. Peak p53 levels are detec ted 12 to 24 h post irradiation with UV-B (470-1410 mJ cm(-2)) and solar si mulated UV (5-12 minimal erythema dose (MED) equivalents). Irradiation with an FS20 UV-B lamp, contaminated with UV-A and UV-C (74-1111 mJ cm(-2)), al so induces peak levels after 12 h incubation at 37 degrees C but these leve ls persist to 36 h post UV irradiation. In all cases p53 levels start to re turn to normal by 48 h culture. A significant positive correlation is demon strated between UV-B dose (47-1645 mJ cm(-2)) and p53 level (p < 0.01, R > 0.977) in explants cultured for 24 h at 37 degrees C post irradiation. The FS20 induces a 'UV-B' dose-dependent increase in p53 to a maximum from 370 to 1111 mJ cm(-2). Similarly, solar simulated UV induces a plateau of peak p53 induction between 5 and 15 MED equivalents. Immunohistochemical analysi s using microwave retrieval on 5 mu m sections shows the same pattern of p5 3 staining with UV-B and solar UV insult, but proves unreliable as a method of quantification. These results suggest that the skin explant model may b e a useful tool in the evaluation of UV-induced epidermal cell damage, prov iding a valuable alternative to in vivo studies. (C) 1999 Elsevier Science S.A. All rights reserved.