Abstract. The aim of the present study was to investigate the effect of bavachin treatment on A375 cells and the regulation of melanin synthesis. The cultured A375 cells in vitro were treated with bavachin; and the effect of bavachin on cell activity, tyrosinase (TYR) activity and melanin synthesis were respectively tested by the MTT assay, L-dopa oxidation assay and the NaOH lysis assay. The expression levels of TYR and c-Jun N-terminal kinases (JNK) proteins were tested by western blot analysis. The expression levels of TYR, tyrosinase-related protein-1 (TRP-1), TRP-2, extracellular signal-regulated kinase 1 (ERK1), ERK2 and JNK2 mRNA were tested by the reverse transcription-polymerase chain reaction assay. Simultaneously, the effect of estrogen receptor inhibitor (ICI182780) and ERK pathway inhibitor (U0126) was also tested on A375 cells following bavachin. The safe dose of bavachin significantly inhibited melanin synthesis and TYR activity. Bavachin (10 ”mol/l) inhibited the expression of TYR and JNK proteins, and the expression of TYR, TRP-1, TRP-2, ERK1, ERK2 and JNK2 mRNA in A375 cells. ICI182780 and U0126 could significantly reverse the bavachin treatment on the protein expression levels and the mRNA expression of TYR, TRP-1, TRP-2, ERK1, ERK2 and JNK2. In conclusion, bavachin inhibited the synthesis of melanin on A375 cells by inhibiting the protein and mRNA expression of TYR, TRP-1, TRP-2, ERK1, ERK2 and JNK2.
IntroductionPsoralea coryfolia is a traditional tonifying drug, which can tonify renal function and is antidiarrheal. A previous study illustrated that Psoralea coryfolia has estrogen-like effects (1). For adult ovariectomized female-mice, Psoralea coryfolia could not only increase keratinization of vaginal epithelial cells and enhance the weight of the uterus, but it also has an influence on their estrous cycles, which demonstrate the estrogen effects of Psoralea coryfolia (2). Bavachin is one of the classic flavonoid phytoestrogens extracted from Psoralea coryfolia (3-5). Phytoestrogens are one of the selective estrogen receptor (ER) modulators extracted from plants with a structure similar to estrogen, which may have an important role in the treatment of skin disease as a substitute of estrogen, due to its estrogen-like effects but mild estrogen-like side effects (6). Previously, certain studies have shown that Psoralea coryfolia and certain phytoestrogens extracted from Psoralea coryfolia that exhibit estrogen-like effects were closely connected with melanin synthesis. Psoralea coryfolia combined with psoralen combined with ultraviolet A (UVA) treatment could increase the activity of melanocytes, and reduce the degeneration of melanocytes and keratinocytes (7). Bakuchiol, bavachin and isobavachalcone can inhibit melanin synthesis in B16 mouse melanoma cells (8). Phytoestrogen can regulate melanin synthesis of melanocytes through the mitogen-activated protein kinase (MAPK) signaling pathway initiated by binding of phytoestrogen to the ER. Thus, bavachin may regulate melanin synthesis of A375 c...