The sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid photosensitizes the formation of oxidized guanines in cellulo after UV-A or UV-B exposure.

The sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid (PBSA) is water soluble and is widely used in the cosmetic industry because it absorbs strongly at UV-B wavelengths. Previous studies have shown that PBSA, photoexcited by UV-B, oxidizes guanine bases in vitro. Because of its potential phototoxic effect, it is important to determine whether PBSA photosensitizes in cellulo the formation of oxidatively generated DNA damage on UV exposure. For this purpose, we investigated, in vitro and in cellulo, the effect of PBSA on DNA bases after UV-A or UV-B irradiation. To monitor the formation of oxidized bases and cyclobutane pyrimidine dimers (CPDs), DNA was digested either with FaPy-DNA glycosylase and endonuclease III or with T4 endonuclease V and photolyase, then analyzed by means of neutral- and glyoxal-agarose gel electrophoresis and ligation-mediated PCR. In cellulo, we found that PBSA provided good protection against CPD formation after UV-B exposure. However, PBSA also photosensitized oxidized guanines on UV-A and UV-B irradiation. Our results indicate that PBSA has the potential to function as a double-edged sword toward DNA and question its suitability for sunscreen applications.