TitleInhibition of gap junctional intercellular communication by the green tea polyphenol (-)-epigallocatechin gallate in normal rat liver epithelial cells.
Publication TypeJournal Article
Year of Publication2008
AuthorsKang, NJoo, Lee, KMi, Kim, JHun, Lee, BKyung, Kwon, JYeon, Lee, KWon, Lee, HJoo
JournalJ Agric Food Chem
Volume56
Issue21
Pagination10422-7
Date Published2008 Nov 12
ISSN1520-5118
KeywordsAnimals, Catechin, Cell Communication, Cells, Cultured, Connexin 43, Epithelial Cells, Flavonoids, Gap Junctions, Mitogen-Activated Protein Kinase 3, Phenols, Phosphorylation, Polyphenols, Rats, Tea
Abstract

(-)-Epigallocatechin gallate (EGCG), a polyphenolic compound found in green tea, is a promising chemopreventive agent against cancer due to its strong antiproliferative effects on cancer cells; however, its possible toxicity and carcinogenicity must be investigated before EGCG can be used as a dietary supplement for chemoprevention. The inhibition of gap junctional intercellular communication (GJIC) is strongly associated with carcinogenesis, particularly the tumor promotion process; thus, we investigated the effects of EGCG on GJIC in WB-F344 normal rat liver epithelial (RLE) cells. EGCG, but not (-)-epicatechin (EC), another polyphenol found in green tea, inhibited GJIC in a dose-dependent and reversible manner in RLE cells. EGCG also induced the phosphorylation of connexin 43 (Cx43), a major regulator of GJIC. The phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK1/2) was also observed in EGCG-treated RLE cells. The inhibition of GJIC and phosphorylation of Cx43 and ERK1/2 by EGCG were completely blocked by U0126, a pharmacological inhibitor of mitogen-activated protein kinase/ERK kinase. EGCG generated a larger amount of hydrogen peroxide than EC in a dose-dependent manner. Furthermore, catalase partially inhibited the EGCG-induced inhibition of GJIC and the phosphorylation of Cx43 and ERK1/2. These results indicated that EGCG inhibited GJIC mainly due to its prooxidant activity.

DOI10.1021/jf801981w
Alternate JournalJ. Agric. Food Chem.
PubMed ID18828601