Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185, Republic of Korea.
Biochem Biophys Res Commun. 2012 Oct 5;426(4):480-5. doi: 10.1016/j.bbrc.2012.08.096. Epub 2012 Aug 29.
Epigallocatechin-3-gallate (EGCG), a major active polyphenol of green tea, has been shown to down-regulate inflammatory responses in dendritic cells (DCs); however, the underlying mechanism has not been understood. Recently, we identified the 67-kDa laminin receptor (67LR) as a cell-surface EGCG receptor. In this study, we showed the molecular basis for the down-regulation of toll-like receptor 4 (TLR4) signal transduction by EGCG in DCs. The expressions of CD80, CD86, and MHC class I and II, which are molecules essential for antigen presentation by DCs, were inhibited by EGCG via 67LR. In addition, EGCG-treated DCs inhibited lipopolysaccharide (LPS)-induced production of pro-inflammatory cytokines (tumor necrosis factor [TNF]-α, interleukin [IL]-1β, and IL-6) and activation of mitogen-activated protein kinases (MAPKs), e.g., extracellular signal-regulated kinase 1/2 (ERK1/2), p38, c-Jun N-terminal kinase (JNK), and nuclear factor κB (NF-κB) p65 translocation through 67LR. Interestingly, we also found that EGCG markedly elevated the expression of the Tollip protein, a negative regulator of TLR signaling, through 67LR. These novel findings provide new insight into the understanding of negative regulatory mechanisms of the TLR4 signaling pathway and consequent inflammatory responses that are implicated in the development and progression of many chronic diseases.
没食子儿茶素-3-没食子酸酯 (EGCG),一种绿茶中的主要活性多酚,已被证明可下调树突状细胞 (DC) 中的炎症反应;然而,其潜在机制尚未被理解。最近,我们鉴定出 67kDa 层粘连蛋白受体 (67LR) 是 EGCG 的细胞表面受体。在这项研究中,我们展示了 EGCG 在 DC 中下调 Toll 样受体 4 (TLR4) 信号转导的分子基础。CD80、CD86 和 MHC 类 I 和 II 的表达,这些分子是 DC 呈递抗原所必需的,被 EGCG 通过 67LR 抑制。此外,EGCG 处理的 DC 通过 67LR 抑制脂多糖 (LPS) 诱导的促炎细胞因子(肿瘤坏死因子 [TNF]-α、白细胞介素 [IL]-1β 和 IL-6)的产生和丝裂原活化蛋白激酶 (MAPKs) 的激活,例如细胞外信号调节激酶 1/2 (ERK1/2)、p38、c-Jun N 末端激酶 (JNK) 和核因子 κB (NF-κB) p65 易位。有趣的是,我们还发现 EGCG 通过 67LR 显著增加了 Toll 样受体信号负调节剂 Tollip 蛋白的表达。这些新发现为理解 TLR4 信号通路的负调控机制以及随后的炎症反应提供了新的见解,这些反应与许多慢性疾病的发展和进展有关。