MicroRNA-340 is involved in ultraviolet B-induced pigmentation by regulating the MITF/TYRP1 axis

Objective There is growing evidence that ultraviolet B (UVB) irradiation can change the expression profile of microRNAs (miRNAs) in immortalized human epidermal melanocytes (Pig-1). We aimed to investigate the effect of miR-340 on regulating UVB-induced pigmentation. Methods Real-time quantitative PCR (qRT-PCR) was used to evaluate the expression of miR-340 in Pig-1 cells. Immunoblotting analysis, qRT-PCR, and luciferase reporter assays were used to detect the potential target of miR-340. The sodium hydroxide dissolution assay was used to assess the effect of miR-340 on changes in melanin content. Results Expression of miR-340 was reduced in human Pig-1 cells after UVB irradiation. We found a negative correlation between miR-340 and melanocyte inducing transcription factor (MITF) in Pig-1 cells after UVB irradiation. Knockdown and overexpression of MITF in Pig-1 cells down- and upregulated melanogenesis, respectively. Overexpression of miR-340 inhibited MITF expression, reduced the amount of melanin, and suppressed expression of multiple key molecules involved in the pigment synthesis pathway, whereas knockdown of miR-340 showed the opposite results. Conclusions Our results showed that miR-340 inhibited melanogenesis by regulating the downstream molecules of MITF and its signaling pathways, suggested that miRNA-340 may be a new target for the clinical treatment of UVB-induced pigmentation.