Melanocyte melanin augments sparfloxacin-induced phototoxicity.

Quinolone has become one of the common causative agents of drug-induced photosensitive dermatitis, and its phototoxicity has now become a clinical issue. The mechanisms of long-lasting phototoxicity induced by sparfloxacin (SPFX) were investigated using melanotic and amelanotic melanoma cell lines. The sensitivities to SPFX and UVA irradiation up to 6 J/cm2 of both cells were not significantly different. However, the melanotic melanoma cell cultured with 1-150 microg/ml of SPFX showed significantly higher sensitivity to UVA irradiation compared with that of the amelanotic melanoma cell. By pulse culture with SPFX, the bound SPFX level of melanotic cell line was 10-20 times higher than that of the amelanotic cell line. These data strongly suggest that the melanin in melanocytes and keratinocytes accumulates the antibacterial quinolone and increases its tissue concentration in the basal epidermis and contributes to the long-lasting photo-injury and liquefaction degeneration of the basal cells in antibiotic quinolone phototoxic dermatitis.