AN IN-VITRO STRATEGY TO EVALUATE THE PHOTOTOXICITY OF SOLAR UV AT THEMOLECULAR AND CELLULAR-LEVEL - APPLICATION TO PHOTOPROTECTION ASSESSMENT

Skin cancers are among the most common human cancers and have an incre asing incidence. The ultraviolet radiation components of sunlight play a major role in skin tumor induction and development. Cellular DNA ha s been identified as a target for most of the biological effects of UV , and the induction of photodamage is considered as the initiating ste p of photocarcinogenesis. Thus, effective photoprotection of DNA again st harmful overexposure to solar UV is a critical issue. The efficienc y of a sunscreen is usually tested with respect to its ability to prev ent skin erythema, but conceivably, more data are required at the mole cular and cellular level in order to ascertain protection against phot ocarcinogenic risk. In the present study, we define a strategy based o n the use of various in vitro models and solar-simulated light to eval uate photodamage and photoprotection: Supercoiled circular plasmid DNA for detection of structural alterations. The yeast Saccharomyces cere visiae to evaluate cytotoxicity and genotoxicity. The single-cell gel electrophoresis or comet assay to determine DNA damage and DNA repair in human keratinocytes. p53 expression as a hallmark for genotoxic str ess. Induction of pigmentation in human melanocytes. In conditions whe re light source, spectrum and control of radiation delivery were preci sely defined, we have demonstrated that the wide spectrum WA sunscreen Mexoryl(R) SX protects from the cytotoxicity and genotoxicity of sola r UV.