A comparative evaluation of photo-toxic effect of fractionated melanin and chlorpromazine hydrochloride on human (dermal fibroblasts and epidermal keratinocytes) and mouse cell line/s (fibroblast Balb/c 3T3)

Fractionated melanin (Mel-HEV), a bleached version of natural melanin, offers protection against the high energy visible (HEV/UVA) and ultraviolet (specifically UVA) irradiation making it a potential compound to be added to skin care and sunscreen formulations and other cosmetic and personal care products. Chlorpromazine (CPZ) has been shown to exhibit photosensitivity and phototoxicity reaction in vitro and in vivo. Comparative evaluation of chemotoxicity and phototoxicity using Mel-HEV and CPZ (as positive control) was performed on mouse fibroblast cell line 'Balb/c 3T3'. This is the recommended method for evaluating the phototoxic potential of compounds under the European Center of Validation of Alternative Methods (ECVAM) guidelines (OECD, 2004). This study was expanded from a mouse cell line - Balb 3T3/c to two human cell lines - HDF and HEKn for two reasons: to compare the difference between the sensitivity and behavior of two fibroblast cell lines (Balb/c 3T3 vs. HDF) and to compare the differences between two fibroblast cell lines with the keratinocyte cell line (HDF & Balb/c 3T3 vs. HEKn). It was found that Balb/c 3T3 and HEKn were both sensitive to the phototoxic potential of CPZ. However, HDF showed insensitivity to phototoxic evaluation. The test compound, Mel-HEV, was found to be non-phototoxic. The mean toxic concentration (MTC) for CPZ during HEV and UVA exposure conditions was found to be similar using Balb/c 3T3 (36.25 μg/ml) and HEKn (39.99 μg/ml) showing that cells exhibit similar responses at HEV/UVA− conditions. However, Balb/c 3T3 showed more sensitivity to CPZ at HEV/UVA+ condition (MTC = 0.87 μg/ml; mean PIF = 55.33; MPE = 0.395) than HEKn (MTC = 5.35 μg/ml; PIF = 7.61; MPE = 0.276) making it the preferred cell line for phototoxicity evaluations.