p53 labeling index in assessing the efficacy of a sunscreen in protection against UV-induced damage.
BACKGROUND
Sunscreen efficacy is currently evaluated by the estimation of the sun protection factor (SPF). Our objective was to determine the role of the p53 labeling index in assessing the effectiveness of a sunscreen in the prevention of UV-induced DNA damage.


METHODS
A broad-spectrum sunscreen (SPF15) was applied to two of four test areas on the backs of 20 volunteers. Two test areas (with and without prior sunscreen application) were then irradiated with two minimal erythemal doses (MEDs) of solar-simulated UV radiation (290-400 nm). At 24 h, suction blisters were raised from all four test areas using a vacuum technique, and immunohistochemical staining for p53 was performed.


RESULTS
In normal epidermis, nonirradiated without sunscreen, p53 was almost undetectable [0.5% positive cells per field (PC/F)]. In UV-exposed skin without sunscreen, p53 expression was 10.4% PC/F, whereas, in skin treated with sunscreen before UV irradiation, p53 expression was 0.3% PC/F. The mean positive labeling indices (x10(3)/microm) for UV-exposed skin with and without sunscreen were 0.002 and 0.059, respectively (P < 0.001).


CONCLUSIONS
In vivo assessment of the p53 labeling index using the suction blister method can serve as a sensitive endpoint in the evaluation of the effectiveness of a sunscreen in the prevention of UV-induced DNA damage.
Lens
Marko
M
Twin Research and Genetic Epidemiology Unit, King's College, London, UK. markolens@aol.com
Bielfeldt
S
S
Bataille
Veronique
V
Wilhelm
K P
KP
D000328:Adult; D004249:DNA Damage / Q000528:radiation effects; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D012867:Skin / Q000378:metabolism / Q000528:radiation effects*; D013473:Sunscreening Agents / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014466:Ultraviolet Rays
D013473:Sunscreening Agents; D016159:Tumor Suppressor Protein p53