Establishment of an in vitro biological photoassay to identify chemical photosensitizer

Abstract

Over the last few years, there has been an increase on the incidence of cases of individuals with skin problems, which has led to an accentuation of studies on medicines, cosmetics, or pharmaceutical products, with the aim of preventing or predicting the behaviour of these chemicals when they meet the skin simultaneously with solar radiation. In addition, the limitations that have emerged on the use of animal models and the tightening of the ethical aspects involved in working with them have caused an increase in the development of alternative methods including the in vitro techniques, which ensure the integrity and welfare of the animals. For this reason, the aim of this project is to carry out an in vitro photobiological test in order to be able to identify chemical products with photosensitising properties. In this study, we focus on the role of keratinocytes, as these cells can help to activate photoallergic and phototoxic reactions. Specifically, we will work with the commercial cell line of human keratinocytes called HaCaT and we will evaluate the phototoxic behaviour of compounds of different characteristics such as Chlorpromazine (CPZ), Sodium Dodecyl Sulphate (SDS). We perform a cytotoxic study as a previous step of the phototoxic assessment. The establishment of UVA irradiation dose conditions (J/cm2) that should be applied to the cells has been set up and, thus, we have been able to evaluate the phototoxic potential of the chemicals studied. This potential is determined by calculating a photoirradiation factor (PIF) with the concentration that reduced cell viability 50% (IC50) in irradiated and non-irradiated conditions and applying a prediction model. From our results, CPZ shows a very high PIF, indicating a phototoxic behaviour, whereas SDS shows similar cytotoxic activity in both situations. In conclusion, our assay shows that can identify properly CPZ as a phototoxic chemical and SDS as a non-phototoxic one. Further chemicals with well-known phototoxic behaviour must be tested to validate the present assay