Effect of cyclosporin A on melanogenesis in cultured human melanocytes

Cyclosporin A (CsA) is a widely used immunosuppressant. Reports on the effect of CsA on hyperpigmentation in patients appear inconsistent, and the effect of CsA on skin pigment cells (melanocytes) in vitro is unknown. We examined the effect of CsA on human melanocyte proliferation and melanogenesis in vitro. Melanocyte proliferation was dose-dependently inhibited by 0.1-10 microM CsA, with no effect on cell viability. Melanocytes incubated with 10 microM CsA for 6 days showed decreased pigmentation and tyrosinase activity. Western blot analysis using an anti-tyrosinase antibody revealed that CsA (0.1-10 microM) decreased tyrosinase protein levels in a dose-dependent manner. Northern blot analysis showed similar effects on tyrosinase mRNA levels. These effects of CsA on melanogenesis in vitro are not consistent with suggestions that systemic CsA therapy causes patient skin hyperpigmentation.