Leucine-rich glioma inactivated 3 is a melanogenic cytokine in human skin.

Recently, we demonstrated that leucine-rich glioma inactivated 3 (LGI3) is expressed in human skin. However, the effects of LGI3 on melanocytes remain unknown. The present study demonstrated that LGI3 can serve to stimulate melanogenesis without affecting cell viability. To determine the effects of LGI3 on melanin synthesis, normal human melanocytes and Mel-Ab cells were treated with recombinant LGI3 and melanin content was measured. Our results showed that LGI3 promoted melanin synthesis in both cell types. Moreover, upregulation of microphthalmia-associated transcription factor (MITF) and tyrosinase was observed at both the mRNA and protein levels via RT-PCR and Western blotting, respectively. Furthermore, immunohistochemical staining showed that the expression of LGI3 increased in the basal layer of melasma skin samples, whereas it decreased slightly in vitiligo samples. These results suggest that LGI3 may play a role as a melanogenic cytokine in human skin.