Assessment of the Phototoxic Potential of Compounds and Finished Topical Products Using a Human Reconstructed Epidermis

Abstract

The goal of this study was to design a model system for the assessment of phototoxic potential using a human reconstructed epidermis (HRE, SkinEthic Laboratories, Nice, France), by testing some representative phototoxic (P) and non-phototoxic (NP) compounds and finished topical products. The tissue response to 24-h application of 5-5000 microg/mL of the test agents in the presence and absence of UVA light was analyzed in terms of viability (Lactate Dehydrogenase release), pro-inflammatory activity (IL-8 release and mRNA expression) and morphology (histopathology). 8-Methoxypsoralen (P) and promethazin (P), but not sodium lauryl sulfate (NP) produced cytotoxicity concentration-response curves significantly different between irradiated and nonirradiated tissues. Only irradiated tissues showed morphological damage. Application of tetracyclin (P) in the culture medium, but not topically, induced similar signs of phototoxicity. 6-Methylcoumarine (weak P) was not cytotoxic, yet it increased IL-8 release and mRNA expression only following UVA irradiation. PUVA therapy creams containing 1% 8-Methoxy-psoralen (P) or coal tar (P) decreased viability and induced histologic damage in UVA-exposed tissues. In conclusion, the phototoxic potential of the tested agents was correctly predicted by using a tiered strategy that involves determining cytotoxicity, production of IL-8, and morphological damage following exposure of the HRE to the compounds and UVA light.

In vitro phototoxicity test using artificial skin with melanocytes

“…IL-1a has been known and is widely used as a useful parameter to identify the compounds inducing phototoxic responses (21). The release of IL-1a appeared to be in concordance with the cell mortality (2,17,19,21). IL-1b is produced mainly in the keratinocytes but its major activities are known to influence lymphocytes, langerhans cell and monocytes (19).…”

“…Increased melanization and activation of melanocytes in AS with melanocytes after UVA irradiation showed similar responses to native human skin in vivo (15, 16). Previous studies have demonstrated that the presence of epidermal differentiation (particularly stratum corneum) cannot exert an in vitro protective effect against UVA damage (2, 17), which leads to the conclusion that resistance to UVA exposure should be emphasized in in vitro phototoxicity models using artificial skins (2, 3). This AS with melanocytes is superior to other AS systems in this point.…”

“…These phototoxic reactions can be defined as inflammatory, non‐immunological reactions induced by the action of light, particularly ultraviolet A (UVA) on photoactive chemicals (1). The identification of phototoxic compounds is the main issue in the developmental fields of drugs and cosmetics, because it can be induced in almost all the individuals if they are exposed to adequate concentrations of phototoxic drugs and subsequent UVR (2, 3).…”

“…However, the main limitation of this fibroblast monolayer assay is that it cannot be used to evaluate non‐hydrosoluble compounds of solid or liquid formulation and finished products. In order to overcome this difficulty, several models of reconstructed epidermis or full‐thickness skin have been developed (1, 2). However, in vitro phototoxicity test using a reconstructed epidermis has not yet been established as a standardized method (6, 8, 9).…”

In Vitro Phototoxicity Testing: A Procedure Involving Multiple Endpoints

“…Several studies have reported their capacity to predict photoirritancy [64][65][66][67][68][69][70]. Several studies have reported their capacity to predict photoirritancy [64][65][66][67][68][69][70].…”