TLR 4 Signaling Inhibitory Pathway Induced by Green Tea Polyphenol Epigallocatechin-3-Gallate through 67-kDa Laminin Receptor

ABSTRACT: Epigallocatechin-3-gallate (EGCG), a major active polyphenol of green tea, has been shown to downregulate inflammatory responses in macrophages; however, the underlying mechanism has not been understood. Recently, we identified the 67-kDa laminin receptor (67LR) as a cell-surface EGCG receptor that mediates the anti-cancer action of EGCG at physiologically relevant concentrations (0.1-1 mM). Here we show the molecular basis for the downregulation of TLR4 signal transduction by EGCG at 1 mM in macrophages. Anti-67LR antibody treatment or RNAi-mediated silencing of 67LR resulted in abrogation of the inhibitory action of EGCG on LPS-induced activation of downstream signaling pathways and target gene expressions. Additionally, we found that EGCG reduced the TLR4 expression through 67LR. Interestingly, EGCG induced a rapid upregulation of Tollip protein, a negative regulator of TLR-signaling, and this EGCG action was prevented by 67LR silencing or anti-67LR antibody treatment. RNAi-mediated silencing of Tollip impaired the TLR4 signaling inhibitory activity of EGCG. Taken together, these findings demonstrate that 67LR plays a critical role in mediating anti-inflammatory action of a physiologically relevant EGCG and Tollip expression could be modulated through 67LR. These results provide a new insight into the understanding of negative regulatory mechanisms for TLR4 signaling pathway and consequent inflammatory responses which are implicated in the development and progression of many chronic diseases. We quantified expression profile of 210 inflammatory-relating genes in the 67LR-downregulated cells treated with LPS or/and EGCG by microarray

ORGANISM(S): Mus musculus

SUBMITTER: kenjiro ikuta 

PROVIDER: E-GEOD-21320 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress