Raspberry ketone glucoside suppresses melanin synthesis through IL6/JAK1/STAT3 signal pathway.

OBJECTIVE: This study aimed to evaluate the anti-melanogenic activity of raspberry ketone glucoside (RKG) and further explore the specific molecular mechanisms by which RKG affects melanogenesis.

MATERIALS AND METHODS: The B16F10 cells model, the mushroom tyrosinase model and the zebrafish model were used to assess the whitening activity of RKG. We subsequently identified possible pathways related to RKG inhibition of melanogenesis by RNA-seq analysis and qRT-PCR on the zebrafish model, and further explored the effects of key genes on the pathway on the melanogenic effect of RKG by using related pathway inhibitors and Tg [mpeg: EGFP] transgenic zebrafish line.

RESULTS: RKG could noticeably inhibit melanogenesis in B16F10 cells in vitro and on zebrafish in vivo. The RNA-Seq analysis and the qRT-PCR in zebrafish embryos indicated that the inhibition of melanogenesis by RKG could be achieved by activating JAK1/STAT3 signal pathway and inhibiting the expression levels of the MITFa, TYR, TYRP1a genes directly associated with melanogenesis. The inhibitor tests revealed that the inhibitory effect of the RKG on melanogenesis was restored by the IL6, JAK1/2, and STAT3 inhibitors, specifically STAT3 inhibitor. We further examine the relationship between the JAK1/STAT3 signal pathway and the MITFa. The achieved results indicate that the RKG could activate the zebrafish macrophages via the JAK1, but the inhibition of macrophage activation by loganin did not affect the anti-pigmentation effect of the RKG.

CONCLUSIONS: RKG showed remarkable whitening activity on both B16F10 cells in vitro and zebrafish model in vivo. Furthermore, RKG could inhibit melanogenesis by activating the IL6/JAK1/STAT3 pathway, inhibiting the transcriptional activity of MITFa, and its downstream expression levels of the TYR and TYRP1a genes.