Prochlorperazine interaction with melanin and melanocytes

Prochlorperazine is a phenothiazine-class antipsychotic drug usually used to treat nausea, vomiting and schizophrenia. Phenothiazine derivatives have been known to cause serious side effects, like extrapyramidal symptoms, but also skin disorders which mechanism has not been fully established. The aim of this study was to examine the interaction between prochlorperazine and melanin as well as to estimate the effect of prochlorperazine on cell viability, melanogenesis and antioxidant defense system in normal human melanocytes. We have demonstrated that prochlorperazine forms stable complexes with melanin, characterized by two classes of independent binding sites with the association constants K1∼106 M-1 and K2∼102 M-1. It has been shown that prochlorperazine induces concentration-dependent loss in cell viability. The value of EC50 was calculated to be 18.49 μM. Prochlorperazine in a concentration of 0.001 μM stimulated melanogenesis, while in concentrations 1.0 and 10.0 μM melanization process was inhibited. Furthermore, the drug in concentrations of 0.1, 1.0 and 10.0 μM caused changes in cellular antioxidant defense system, what indicated the induction of oxidative stress. The observed changes in cell viability, melanization and antioxidant defense system in normal human melanocytes after prochlorperazine treatment may explain a potential role of melanin, oxidative stress and melanocytes in mechanisms of undesirable side effects after accumulation of this drug in pigmented tissues.