Glycyrrhizin, the main active compound in licorice, attenuates pro-inflammatory responses by interfering with membrane-dependent receptor signaling.

Biochem J. 2009 May 14; Schröfelbauer B, Raffetseder J, Hauner M, Wolkerstorfer A, Ernst W, Szolar OHThe triterpene glycoside glycyrrhizin (GL) is the main active compound in licorice. It is used as a herbal medicine owing to its anti-cancer, anti-viral, and anti-inflammatory properties. Its mode of action however remains widely unknown. In this study, we aimed to elucidate the molecular mechanism of GL in attenuating inflammatory responses in macrophages. Using microarray analysis, we found that GL caused a broad block in the induction of pro-inflammatory mediators induced by the toll-like receptor 9 (TLR9) agonist CpG-DNA in RAW 264.7 cells. Furthermore, we found that GL also strongly attenuated inflammatory responses induced by TLR3 and TLR4 ligands. The inhibition was accompanied by reduced activation not only of the NF-kappaB pathway but also of the parallel MAPKs signaling cascade upon stimulation with TLR9 and TLR4 agonists. Further analysis of upstream events revealed that GL treatment reduced cellular attachment and/or uptake of CpG-DNA and strongly impaired TLR4 internalization. Moreover, we found that the anti-inflammatory effects were specific for membrane-dependent receptormediated stimuli, as GL was ineffective in blocking Tnfa induction upon stimulation with phorbol myristate acetate (PMA), a receptor and membrane-independent stimulus. These observations suggest that the broad anti-inflammatory activity of GL is mediated by the interaction with the lipid bilayer thereby attenuating receptor-mediated signaling.

Effects of Bambusae caulis in Liquamen on the development of atopic dermatitis-like skin lesions in hairless mice.

J Ethnopharmacol. 2009 Jun 22; 123(2): 195-200Qi XF, Kim DH, Yoon YS, Li JH, Jin D, Deung YK, Lee KJETHNOPHARMACOLOGICAL RELEVANCE: Bambusae caulis in Liquamen (BCL) is a nutritious liquid extracted from heat-treated fresh bamboo stems. It is an important traditional herbal medicine used to treat coughs and asthma in East Asia. In recent years, it has been studied for its anti-inflammatory, anti-allergenic, and immune-regulating properties. AIM OF THE STUDY: To examine whether BCL suppresses the development of 2,4-dinitrochlorobenzene (DNCB)-induced atopic dermatitis (AD)-like skin lesions in hairless mice. MATERIALS AND METHODS: The effects of BCL were analyzed by measuring transepidermal water loss (TEWL), melanin content, and erythema in the skin, leukocyte numbers and IgE levels in the serum, and mRNA expression of relevant cytokines in the spleen. RESULTS: The transdermal administration of BCL to hairless mice inhibited the development of DNCB-induced AD-like skin lesions by suppressing TEWL, melanin production and erythema of skin, the number of leukocytes and the level of IgE in serum, and the mRNA expression of IL-4, IL-13, and TNF-alpha in the spleen. However, BCL administration increased the expression of IFN-gamma in the spleen. CONCLUSIONS: These findings indicate that BCL suppresses the development of DNCB-induced AD-like skin lesions in hairless mice, suggesting that BCL may be a potential therapeutic agent for AD in a clinical setting.