The efficacy of a broad-spectrum sunscreen to protect engineered human skin from tissue and DNA damage induced by solar ultraviolet exposure

Sunscreens are known to protect against sunlight-induced erythema and sunbu rn, but their efficiency at protecting against skin cancer is still a matte r of debate. Specifically, the capacity of sunscreens to prevent or reduce tissue and DNA. damage has not been thoroughly investigated. The present st udy was undertaken to assess the ability of a chemical broad-spectrum sunsc reen to protect human skin against tissue and DNA damage after solar UV rad iation. Engineered human skin was generated and either treated or not with a broad-spectrum SPF 30 sunscreen and exposed to increasing doses of simula ted sunlight (SSL), Immediately after irradiation, histological, immunohist ochemical, and molecular quantitative analyses were performed. The unprotec ted irradiated engineered human skin showed significant epidermal disorgani zation accompanied by a complete absence of laminin deposition. The sunscre en prevented SSL-induced epidermal damage at low doses and allowed laminin deposition at almost all SSL doses tested. The frequencies of cyclobutane p yrimidine dimers, pyrimidine (6-4) pyrimidone photoproducts, and photooxida tive lesions measured by alkaline gel electrophoresis and radioimmunoassay were significantly reduced by the sunscreen. Thus, tissue and DNA damage ma y provide excellent quantitative end points for assessing the photoprotecti ve efficacy of sunscreens.