Exosomal miR-365b-5p derived from keratinocyte promotes melanogenesis by directly targeting GLI2

In previous studies, we analyzed that exosomal microRNA (miRNA) secreted by keratinocytes exposed to Ultraviolet B(UVB) light regulate melanogenesis in melanocytes. Through functional experiments, it was determined that a subgroup of exosomal miRNAs had distinct impacts on melanogenesis. In the current study, we focused on hsa-miR-365b-5p which founded upregulated in UVB-irradiated keratinocyte exosomes and confirmed to exert enhancing effects on melanogenesis in human melanocyte. Hsa-miR-365b-5p is a specific, mature microRNA derived from the precursor hsa-miR-365. We demonstrated that the overexpression of hsa-miR-365b-5p in normal human epidermal melanocytes (NHEM) resulted in an approximate 50% increase in melanin content relative to the control group. Furthermore, treatment with an inhibitor of hsa-miR-365b-5p substantiated its specific regulatory role in melanogenesis, as inhibition resulted in a nearly 90% reduction in melanin production. Notably, hsa-miR-365b-5p upregulates the expression of genes associated with melanogenesis, including MITF, TYR, TRP1, and TRP2. Additionally, we established that GLI Family Zinc Finger 2 (GLI2) functions as a repressor of MITF, with its inhibition via siRNA leading to increased melanogenesis. Moreover, we constructed a luciferase reporter vector containing the 3' UTR of GLI2, confirming that hsa-miR-365b-5p specifically targets GLI2, a known repressor of MITF. These findings elucidate the regulatory pathways governing melanogenesis and underscore the significant role of hsa-miR-365b-5p in this biological process.