Epimedin B exhibits pigmentation by increasing tyrosinase family proteins expression, activity and stability

Abstract

Background and Purpose: Epimedii Folium is a traditional herb widely-utilized in China. Recently, our study discovered that Epimedin B (EB), as a high-content, low-toxicity flavonoid compound in Epimedii Folium extract, strongly showed melanogenesis and tyrosinase activation effect. However, there are no studies of EB in pigment synthesis and regulation mechanism. This study aims to evaluate the pigmentation effect of EB and elucidate the melanogenic mechanism. Experimental Approach: Melanin contents in melanoma cells, primary human melanocytes, human skin tissues, and intracellular melanosomes changes were determined to evaluate the melanogenic effect of EB. The influence of TYRs expression was determined by RNA sequencing and mRNA/proteins changes. The tyrosinase activity were tested on mushroom tyrosinase, depigmented models of melanoma cells, zebrafishes and C57BL/6 mice. The stability of TYRs were investigated by monobenzone-induced TYRs degradation on melanoma cells, skin tissues and C57BL/6 mice, analyzed by cellular ubiquitin, chaperone co-expression, and endoplasmic reticulum/ proteasome co-localization assays. Key Results: EB increased TYRs expression through MITF-mediated pathways, then to promote melanosome number and maturation for melanogenesis. Additionally, EB exerted repigmentation through activating tyrosinase activity in multiple tyrosinase inhibitive models. Furthermore, EB could protect monobenzone-induced TYRs degradation and repigmentation in vitro and in vivo, enhance TYRs stability via inhibiting misfolded tyrosinase, TYR-related protein 1 formation, retention in endoplasmic reticulum, and ubiquitin-proteasome system. Conclusion and Implications: These data conclude that EB can target TYRs from expression, catalytic activity and stability approaches to exhibit pigmentation function, which might provide a novel rational strategy for hypopigmentation in pharmaceutical and cosmetic industries.