Endothelin-1 enhances the melanogenesis via MITF-GPNMB pathway

Endothelin-1 (ET-1) plays an indispensable role in epidermal pigmentation in hyperpigmentary disorders due to a central role in melanogenesis. Nevertheless, precise mechanism involved in ET-1-induced hyperpigmentation is still undefined. Glycoprotein (transmembrane) non-metastatic melanoma protein b (GPNMB) is a key element in melanosome formation. Therefore, we speculated that GPNMB was correlated with ET-1-induced pigmentation. After culturing with ET-1, melanin synthesis was significantly up-regulated, accompanying with increased expression of GPNMB and microphthalmia- associated transcription factor (MITF). Total number of melanosomes and melanin synthesis were sharply reduced via GPNMB-siRNA transfection, indicating ET-1-induced pigmentation by GPNMB-dependent manner. Furthermore, MITFsiRNA transfection strikingly inhibited GPNMB expression and the melanogenesis, and this suppression failed to be alleviated by ET-1 stimulation. All of these results demonstrated that ET-1 can trigger melanogenesis via the MITF-regulated GPNMB pathway. Taken together, these findings will provide a new explanation of how ET-1 induces hyperpigmentation, and possibly supply a new strategy for cosmetic studies.