Photoallergy can be considered a special type of contact hypersensitivity, in which UV light activates the allergen and, therefore, the physiological mechanisms involved in the development of symptoms. In the case of pharmaceuticals, preclinical trials should include phototoxicity and photoallergy assays to ensure their safety. However, nowadays there is still a lack of non-animal methods to predict potential photoallergic reactions. Knowledge of the pathophysiological mechanisms of photoallergic contact dermatitis at different levels, such as molecular and cellular ones, is thus an important field of research. In this sense, this work explores the use of a cell line of skin keratinocytes to develop a vitro assay to identify phototoxic molecules and discriminate between phototirritant and photoallergic by differential secretion of humoral molecules. To achieve this goal, keratinocytes have been exposed to different chemicals at various concentrations with well-known phototoxic potential concomitantly with 4 J/cm² UVA or maintained in dark. The chemicals assayed were Chlorpromazine (photoirritant and photoallergen); 8-methoxypsoralen (photoirritant); Benzophenone (photoallergen) and p-phenilendyamine (allergen). After 24 hours post-incubation cell viability was determined and the concentration that induces an 80% of cell viability in dark and UVA conditions was calculated. Then, the secretion of different metalloproteinases (10) and inflammatory cytokines (40) in supernatant was evaluated by semi-quantitative arrays (RayBiotech). Our results indicate that MMP-1 and IL-6 are potential biomarkers to discriminate between photoirritant and photoallergic reactions. Next step includes to evaluate the release of both biomarkers with a more quantitively assay as ELISA and increasing the number of chemicals studied.

Acknowledgement: Grant PID2020-113186RB-I00 funded by MCIN/AEI/10.13039/501100011033