Abstract 1317: The 2-phenylbenzimidazole-5-sulfonic acid sunscreen agent photosensitizes oxidized guanines following UVA or UVB exposure

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC The 2-phenylbenzimidazole-5-sulfonic acid (PBSA) is a sunscreen agent widely used in the cosmetic industry because it absorbs strongly at UVB wavelengths providing a good protection against the cyclobutane pyrimidine dimer (CPD) generation. Previous studies have shown that PBSA oxidize guanine bases in vitro (isolated DNA). Due to its potential phototoxic effect, it is of great interest to determine whether PBSA can play the role of a photosensitizer in cellulo. For this purpose, we investigated in vitro and in cellulo (in fibroblasts) the effect of 0 to 4 mM PBSA on DNA damage formation after UVA or UVB irradiation. In order to monitor oxidized bases and CPD formation, DNA was digested with either endonuclease III and FaPy-DNA glycosylase or T4 endonuclease V and photolyase, then analyzed by means of glyoxal gel electrophoresis and ligation-mediated polymerase chain reaction (LMPCR). We found that in cellulo and in vitro, PBSA provided a good protection against CPD formation, but induced oxidative damage and DNA-strand breaks. Moreover, with the LMPCR technology we were able to determine that oxidative damage were preferentially formed at guanine sites. Our results indicate that PBSA has the potential to act as a double-edged sword toward DNA, on one hand it blocks the formation of CPDs after UVB and on the other hand increase the formation of oxidized guanines upon UVA and UVB irradiation. This raises major concern regarding its suitability for sunscreen applications. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1317.