Development of assays for the detection of photomutagenicity of chemicals during exposure to UV light. II. Results of testing three sunscreen ingredients

Abstract

Three sunscreen ingredients, derivatives of benzylidene camphor, were tested for photomutagenic potential. These were benzenesulfonic acid, 4-[(4,7,7,-trimethyl-3-oxo-bicyclo [2.2.1] hept-2-ylidene) methyl] (Mexoryl SL), 4-(2-oxo 3-bornylidenemethyl) phenyl trimethylammonium methyl sulphate (Mexoryl SO) and 3,3'-(1,4-phenylenedimethylidyne) bis [7,7-dimethyl-2-oxo-bicyclo [2.2.1] heptane-1-methanesulfonic acid] (Mexoryl SX). Two complementary assay systems were used, one involving the induction of reverse mutations in Escherichia coli strain WP2, the other measuring the induction of chromosome damage in Chinese hamster ovary (CHO) cells. Irradiation with UVA and/or UVB was provided by an Osram Ultra-Vitalux sunlamp. None of the three sunscreens, tested either to the limit of solubility or toxicity, gave any indication of photomutagenicity in either assay, under conditions in which the positive control compound, 8-methoxypsoralen, was extremely photomutagenic. It is concluded that Mexoryls SL, SO and SX can be exposed to UV light without producing photomutagenicity measurable using a bacterial reverse mutation or a mammalian chromosome aberration assay.

Photomutagenicity of cosmetic ingredient chemicals azulene and guaiazulene

“…For the positive control, in the presence of 10 g/plate of 8-MOP, the number of revertant bacteria colonies for TA102 increases steadily as the light dose increases before reaching a maximum number of about six times the revertant colonies of the spontaneous mutation. This result is comparable to the literature values [12][13][14][15].…”

“…Several European communities have recently published guidelines for testing chemicals with regard to photomutagenicity [12][13][14][15]. Although ideal photomutagenicity assay is to use the level of light only to photo-activate the chemicals that results in mutation, not to cause death of the bacteria.…”

Alternative methods to evaluate the protective ability of sunscreen against photo-genotoxicity

“…To avoid damage caused by prolonged exposure to the sun, the effective utilization of sunscreen should be further encouraged. On the other hand, Xu and Parsons have reported the cytotoxic effect of a sunscreen component in cultured human cells [29], although Dean et al showed no photomutagenicity of three sunscreen ingredients with UV light using bacterial reverse mutation and a mammalian chromosome aberration assay [30]. The Drosophila systems used in this study could also be used to examine the genotoxicity of the sunscreen itself, with an investigation of the effects of direct contact of sunscreen with larvae being one approach.…”

Mexoryl: Broad-Spectrum Ultraviolet a Photoprotection

“…7,8,[10][11][12][13][14][15][16][17][18] Skin Pigmentation E x p o s u re to solar UV irradiation generally causes increased pigmentation of the skin, known as tanning, as a result of increased melanin production. UVA radiation, in particular, plays a major role in the induction of longlasting pigmentation, which may persist from several months to 1 year.…”

“…Numerous in vitro and in vivo studies with Mexoryl SX and Mexoryl XL have demonstrated their efficacy in the prevention of UV radiation–induced damage, including skin pigmentation, photoaging, and skin photosensitivity reactions. 7,8,10–18…”