New developments in photoprotection of human skin

Because of increased leasure time, the growing popularity of staying outdoors and of holidays in the sun, it has become more and more important to study the molecular and photobiological effects that ultraviolet (UV) radiation exerts on human skin. Information obtained from these studies is being used to constantly improve the quality of sunscreen preparations containing organic and inorganic filters. It is also fostering the development of antioxidants and active agents that can be used in combination with or in addition to UV filters to provide better photoprotection for human skin. In addition, these studies provide novel test models which allow to prove or disprove the efficacy of a given sunscreen preparation for biological endpoints that differ from the sunburn reaction and are of direct relevance for photocarcinogenesis and photoaging. In this review, two examples are given to illustrate this development: (1) the use of topically applied DNA repair enzymes to prevent UVB-radiation-induced damage and (2) the development of a novel assay that is based on the detection of UVA-radiation-induced mutations in mitochondrial DNA and can be used to study the efficacy of protective measures against photoaging of human skin.