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Sunscreen Protection Against Ultraviolet Radiation‐induced Pyrimidine Dimers in Mouse Epidermal DNA

1997; Wiley; Volume: 65; Issue: 6 Linguagem: Inglês

10.1111/j.1751-1097.1997.tb07961.x

1751-1097

Ronald D. Ley, Anny Fourtanier,

Olfactory and Sensory Function Studies

ABSTRACT Pyrimidine dimers were measured in epidermal DNA of SKH:HRI mice following exposure to solar‐simulated UV radiation (SSUV, 290–400 nm) or to UVA (320–400 nm). Mice were exposed to SSUV or UVA after topical application (2 mg/cm 2 ) of vehicle, a UVB absorber (5% 2‐ethylhexyl p‐methoxycinnamate [2‐EHMC]), or a broad‐spectrum UVA absorber (5% Mexoryl®SX). The rates of induction of pyrimidine dimers in untreated animals were 5.4 ± 0.57 times 10 ‐4 (mean ± SEM) and 7.6 ± 0.95 times 10 ‐6 dimers per 10 8 Da of epidermal DNA per J/m 2 of SSUV and UVA, respectively. Topical application of Mexoryl®SX reduced the rate of induction of pyrimidine dimers in SSUV‐exposed animals to 4.7 ± 0.44 times 10 ‐5 dimers per 10 8 Da per J/m 2 for a dimer induction protection factor (PF) of 11.5 (5.4 times 10 4 /4.7 times 10 ‐5 ). The rate of dimer induction in Mexoryl®SX‐treated, UVA‐ex‐posed mice was 0.95 ± 0.2 times 10 ‐6 dimers per 10 8 Da per J/m 2 (PF = 8.0). The 2‐EHMC at a concentration of 5% (wt/wt) was significantly less effective than Mexoryl®SX in preventing the induction of pyrimidine dimers in animals exposed to either SSUV or UVA. The rates of dimer induction in 2‐EHMC‐treated mice were 8.2 ± 1.1 times 10 ‐5 and 3.8 ± 0.33 times 10 ‐6 dimers per Da per J/m 2 of SSUV (PF = 6.6) and UVA (PF = 2.0), respectively. Upon normalizing to the efficacy for edema induction, UVA induced approximately one‐fourth the number of pyrimidine dimers per equivalent edematous response when compared to SSUV.