Epigallocatechin-3-gallate suppresses NF-κB activation and phosphorylation of p38 MAPK and JNK in human astrocytoma U373MG cells

Epigallocatechin-3-gallate (EGCG) is the major polyphenol component of green tea and is primarily responsible for the green tea effect. EGCG possesses two triphenolic groups in its structure. These groups are reported to be important with respect to anticarcinogenic and antioxidant effects. However, the anti-inflammatory effect of EGCG on Alzheimer's disease (AD) is still not fully understood. In this study, we investigated the effects of EGCG in attenuating the inflammatory response induced by interleukin (IL)-1 beta+beta-amyloid (25-3 5) fragment (A beta) in human astrocytoma, U373MG cells. EGCG significantly inhibited the IL-1 beta+A beta (25-35)-induced IL-6, IL-8, vascular endothelial growth factor (VEGF) and prostaglandin (PG)E-2 production at 24 h (P <.01). The maximal inhibition rate of IL-6, IL-8, VEGF and PGE(2) production by EGCG was approximately 54.40%, 56.01%, 69.06% and 47.03%, respectively. EGCG also attenuated the expression of cyclooxygenase-2 and activation of nuclear factor-kappa B induced by IL-1 beta+A beta(25-35). We demonstrated that EGCG suppresses IL-1 beta+A beta (25-35)-induced phosphorylation of the mitogen-activated protein kinase p38 and the c-Jun N-terminal kinase. In addition, EGCG induced the expression of mitogen-activated protein kinase phosphatase-1. These results provide new insight into the pharmacological actions of EGCG and its potential therapeutic application to various neurodegenerative diseases such as AD. (c) 2007 Elsevier Inc. All rights reserved.