Emodin isolated from Polygoni Multiflori Ramulus inhibits melanogenesis through the liver X receptor-mediated pathway.

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Kim MO, Park YS, Nho YH, Yun SK, Kim Y, Jung E, Paik JK, Kim M, Cho IH, Lee J

Emodin isolated from Polygoni Multiflori Ramulus inhibits melanogenesis through the liver X receptor-mediated pathway.

Chem Biol Interact. 2016 Apr 25;250:78-84. doi: 10.1016/j.cbi.2016.03.014. Epub 2016 Mar 10.

PubMed ID

26972667 [ View in PubMed

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Abstract

Melanogenesis is a physiological process that results in the synthesis of melanin pigments, which play a crucial protective role against skin photocarcinogenesis. We investigated the effects of a Polygoni Multiflori Ramulus extract on melanogenesis and isolated emodin from Polygoni Multiflori as an active compound. In addition, the possible mechanisms of action were examined. We found that emodin inhibited both melanin content and tyrosinase activity concentration and time dependently. Tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2 mRNA levels decreased following emodin treatment. However, while the mRNA levels of microphthalmia-associated transcription factor (MITF) were not affected by emodin, emodin reduced MITF protein levels. Furthermore, expression of the liver X-receptor (LXR) alpha gene, but not the LXR beta gene was upregulated by emodin. Moreover, emodin regulated melanogenesis by promoting degradation of the MITF protein by upregulating the LXR alpha gene. The emodin effects on MITF was found to be mediated by phosphorylation of p42/44 MAPK. Taken together, these findings indicate that the inhibition of melanogenesis by emodin occurs through reduced MITF protein expression, which is mediated by upregulation of the LXR alpha gene and suggest that emodin may be useful as a hyperpigmentation inhibitor.