FK506 increases pigmentation and migration of human melanocytes.

BACKGROUND

Topical tacrolimus (FK506) is a potential therapeutic option for vitiligo management. Despite its clinical efficacy, the underlying mechanism of how topical tacrolimus induces repigmentation in vitiligo has scarcely been investigated.

OBJECTIVES

To investigate the direct effects of FK506 on pigmentation and migration of human melanocytes.

METHODS

Cell proliferation was measured using a Coulter counter. The effects on pigmentation were investigated by measuring melanin contents, tyrosinase activity and tyrosinase expression. To determine the effects of FK506 on cell migration, we performed scratch assays and Boyden chamber assays.

RESULTS

FK506 treatment increased melanin contents, although there was an inhibitory effect on growth of melanocytes. The increase of pigmentation was due to the result of the stimulatory action of FK506 on tyrosinase activity and its expression, which eventually led to melanin biosynthesis. Furthermore, cell migration was enhanced by FK506 treatment.

CONCLUSIONS

These findings provide in vitro evidence demonstrating direct effects of FK506 on pigmentation and melanocyte migration and may provide a possible mechanism for the effect of tacrolimus in vitiligo.