Evaluierung zellulärer Marker zur Charakterisierung der Schutzleistung von Sonnenschutzprodukten

Abstract

Summary: Great importance is attributed globally to the protection against UV radiation and the resulting short and/or long-term damaging effects on the human skin. Increasing skin-cancer rates demonstrate the urgency of a broad-spectrum protection of the skin against sunlight and an extensive information and behavioural training for the population. Unlike earlier formulations (between 1985 and 2000), current sunscreen products contain UV filter combinations, with broader protection in the UVB and UVA range of the solar spectrum. The efficacy of the products is expressed by the sun protection factor (SPF) (in vivo determination), which is a measure of the protection against the development of erythema. However, SPF only characterises the protective performance in the UVB range. Determination of SPF is performed exclusively on humans, is time-consuming and expensive and is accompanied by the damaging of the skin of volunteers. Additionally the link between erythema and the development of skin cancer is not completely understood. The UVA protection capacity of a sun protection product can also be determined and the compliance with all requested EU recommandations is indicated with the UVA logo. The UVA protection factor (UVA-PF) can be determined with an accepted in vitro method. There is a worldwide research for additional parameters for characterizing the protective performance of sunscreen products. The objective of the present work was the development of an in vitro test system to characterize the protective performance of formulations already during the development phase. In this context, markers suitable for the characterization of UV-induced damage are evaluated at cellular levels. Different cellular localisations, such as extracellular matrix, cytoplasmic range and nucleic region should be considered in the selection of potential cell damage markers. Cytokines (interleukin 1a and interleukin 8), p38-MAPK, p53, and cyclobutane pyrimidine dimers (CPD) have been analysed experimentally as potential markers. Normal human keratinocytes (HNK) and immortalised HaCaT cells served as models and were exposed to UV radiation. Assay techniques such as ELISA and/or flow cytometry (FACS) were used for read-out evaluation. The kinetics and dose-response relationships were determined for each marker in individual preliminary tests. Two of the five markers tested, delivered no reproducible results. The experiments performed with cytokines as potential cell damage markers were regarded as unsuitable due to the high divergence in the measurement values, and were not followed up. In order to evaluate the selected test systems, different sunscreen products (SPF 5 to 50+) were analyzed. The products were applied to PMMA platelets and the latter were attached to the cell culture dishes. Following UV exposure the markers were quantified. In the case of p38-MAPK, after exposure to a dose of 200 mJ/cm2 UVB and subsequent incubation period of 30 minutes, the maximal activation of p38 was 2.2 ± 0.29. The protective performance of…