In vitro melanogenesis inhibition by fluphenazine and prochlorperazine in normal human melanocytes lightly pigmented

PURPOSE: Fluphenazine and prochlorperazine as phenothiazine-class antipsychotic drugs are widely used to treat schizophrenia, however their use is associated with significant side effects such as extrapyramidal symptoms, as well as ocular and skin disorders. Our goal was to determine the effect of fluphenazine and prochlorperazine on cell viability and melanogenesis in lightly pigmented normal human melanocytes. METHODS: The viability of melanocytes was evaluated by the WST-1 colorimetric assay, while melanin content and tyrosinase activity were tested spectrophotometrically. RESULTS: It has been shown that both phenothiazines induce the concentration-dependent loss in cell viability. The EC(50) values were calculated to be 6.13 and 0.63 μM for fluphenazine and prochlorperazine, respectively. Fluphenazine in the concentration of 5.0 μM and prochlorperazine in concentrations of 0.5 and 0.75 μM decreased melanin content and tyrosinase activity. The observed inhibition of melanogenesis may be explained by the decrease of enzyme activity. CONCLUSIONS: The demonstrated changes in melanization process in lightly pigmented cells exposed to fluphenazine and prochlorperazine in vitro suggest a significant role of melanin and melanocytes in the mechanisms of undesirable side effects of these drugs in vivo. [Figure: see text]