Li Hailan, Min Young Sil, Park Kyoung-Chan, Kim Dong-Seok
Department of Biochemistry, Chung-Ang University College of Medicine, Seoul, Republic of Korea.
Biosci Biotechnol Biochem. 2012;76(4):767-71. doi: 10.1271/bbb.110894. Epub 2012 Apr 7.
Xanthium strumarium L. (Asteraceae) is traditionally used in Korea to treat skin diseases. In this study, we investigated the effects of a X. strumarium stem extract on melanin synthesis. It inhibited melanin synthesis in a concentration-dependent manner, but it did not directly inhibit tyrosinase, the rate-limiting melanogenic enzyme, and instead downregulated microphthalmia-associated transcription factor (MITF) and tyrosinase expression. MITF, the master regulator of pigmentation, is a target of the Wnt signaling pathway, which includes glycogen synthase kinase 3β (GSK3β) and β-catenin. Hence, the influence of X. strumarium stem extract on GSK3β and β-catenin was further investigated. X. strumarium induced GSK3β phosphorylation (inactivation), but the level of β-catenin did not change. Moreover, a specific GSK3β inhibitor restored X. strumarium-induced melanin reduction. Hence, we suggest that X. strumarium inhibits melanin synthesis through downregulation of tyrosinase via GSK3β phosphorylation.
苍耳（菊科）在韩国传统上用于治疗皮肤病。在本研究中，我们研究了苍耳茎提取物对黑色素合成的影响。它以浓度依赖性方式抑制黑色素合成，但它并不直接抑制酪氨酸酶（黑色素生成的限速酶），而是下调小眼畸形相关转录因子（MITF）和酪氨酸酶的表达。MITF是色素沉着的主要调节因子，是Wnt信号通路的一个靶点，该信号通路包括糖原合酶激酶3β（GSK3β）和β-连环蛋白。因此，进一步研究了苍耳茎提取物对GSK3β和β-连环蛋白的影响。苍耳诱导GSK3β磷酸化（失活），但β-连环蛋白水平没有变化。此外，一种特异性GSK3β抑制剂恢复了苍耳诱导的黑色素减少。因此，我们认为苍耳通过GSK3β磷酸化下调酪氨酸酶来抑制黑色素合成。
