A physical sunscreen protects engineered human skin against artificial solar ultraviolet radiation-induced tissue and DNA damage

Abstract

Sunscreens are known to protect against sunlight-induced erythema and sunburn, but their efficiency at protecting against skin cancer is still a matter of debate. Specifically, the capacity of physical sunscreens to prevent or reduce tissue and DNA damage has not been thoroughly investigated. Our objective was to assess the ability of a broad-spectrum sunscreen containing TiO₂ to protect human skin against tissue and DNA damage following ultraviolet radiation. For this purpose, engineered human skin (EHS) was generated and either treated or not treated with an SPF 28 physical sunscreen and exposed to increasing doses of simulated sunlight (SSL). Immediately after irradiation, histological, immunohistochemical and molecular analyses were performed. Cyclobutane pyrimidine dimers and pyrimidine (6–4) pyrimidone photoproducts were measured by radioimmunoassay, photooxidative lesions were measured by neutral glyoxal gel electrophoresis. The unprotected irradiated EHS showed significant epidermal disorganization accompanied by a complete absence of laminin deposition. The physical sunscreen prevented SSL-induced epidermal damage at low doses and allowed laminin deposition at almost all SSL doses tested. The frequencies of all 3 types of molecular photodamage were significantly reduced in the sunscreen-protected tissues. In conclusion, although, the level of protection against erythema offered by this sunscreen does not correlate with the level of protection against DNA damage, these results strongly suggest that an SPF 28 physical sunscreen significantly protected human skin against solar UV radiation. Thus, tissue and DNA damage may provide excellent quantitative endpoints for assessing the photoprotective efficiency of sunscreens.