Dioscorin, patatin, and extract of Phellinus liteus (PL-H) activate Toll-like receptor 4-signaling pathways and induce cytokine expression in macrophages

• Main Authors: Pei-Yeh Lee, 李佩曄
• Other Authors: Shu-Ling Fu
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/38563240366386590203

碩士 === 國立陽明大學 === 傳統醫藥學研究所 === 93 === Abstract Toll-like receptor 4 (TLR4) is crucial for both innate and adaptive immunity and is considered as a molecular target for immune-modulating drugs. Certain TLR4 agonists were found to be of great anti-cancer potential. Indeed, several immune-modulating natural compounds/medicinal plants were recently reported to act via TLR4-dependent pathways. Stimulation of TLR4 triggers NF-kappaB activity via either MyD88-dependent or MyD88-independent signaling pathway. Based on this fact, we first performed a screening procedure to systematically identify medicinal plants/nature compounds that act via NF-kappaB. These NF-kappaB activators were then tested in bone marrow-derived cells from C3H/HeN (TLR4-functional) or C3H/HeJ (TLR4-defective) mice to determine whether they are TLR4 ligands. The effects of TLR4-activating natural products on TLR4-downstream signaling pathway and cytokine expression were further characterized in RAW 264.7 macrophages. Natural product-mediated TLR4-downstream cytokine expression was determinated by RT-PCR. Effects of natural products on NF-kappaB activity were determinated by luciferase reporter gene assay, and ERK, JNK and p38 activity were determinated by Western blot. The effects of inhibitors on natural product-mediated pathways were determinated by ELISA. To exclude the possible LPS contamination in these natural products, they were treated with a LPS-inhibitor, polymyxin B. In this study, we found dioscorin, patatin and herbal extracts of Phellinus liteus （PL-H） acted in a TLR4-dependent manner. Dioscorin, patatin, and PL-H activated NF- kappaB and induced expression of cytokines (TNF-alpha, IL-1beta, IL-6) and iNOS in RAW 264.7 cells. Dioscorin and patatin also activated ERK, JNK and p38. Furthermore, induction of TNF-alpha by dioscorin, patatin or PL-H was abolished by inhibitors PD98059, SP600125, SB203580, and PDTC, suggesting that ERK, JNK, p38 and NF-kappaB-mediated pathways are all required for dioscorin, patatin and PL-H -mediated TNF-alpha production. Take together, dioscorin, patatin and PL-H can trigger TLR4-signaling pathway and induce macrophage activation. The therapeutic potential of these TLR4 activators is worthy of further exploring.