EGCG suppresses NF-κB activation induced by gastroesophageal reflux contents in human esophageal epithelial cells

Background and aims: Epigallocatechin-3-gallate (EGCG) is a natural component of green tea that has been shown to have inhibitory effects against the inflammation-induced onset and the development of carcinogen-induced tumors in animal models at different organ sites, including the esophagus. This study investigates the effect of mixed refluxate (acid, bile acids and trypsin) on the expression of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappa B) signaling pathway in normal human esophageal epithelial cells (HEECs) and the effect of EGCG pretreatment of cells on activation of NF-kappa B induced by the mixed refluxate. Methods: HEECs were cultured in vitro and treated with varying concentrations of EGCG in the absence or presence of GER contents. NF-kappa B DNA-binding activity was examined using an electrophoretic mobility shift assay (EMSA) and intracellular levels of NF-kappa B were evaluated using an ELISA. NF-kappa B reporter gene activity was measured using a luciferase reporter gene assay. The expression levels of NF-kappa B/p65, p-NF kappa B/p65, I kappa B alpha, p-I kappa B alpha, p-IKK alpha and proinflammatory cytokines, such as IL-6, IL-8, iNOS and COX-2 proteins, were examined using Western blot analysis. Results: Exposure of GER to HEECs results in a significant increase in NF-kappa B DNA-binding activity, intracellular levels of NF-kappa B and luciferase reporter activity compared to the control group. GER also induced the activation and nuclear translocation of NF-kappa B/p65, phosphorylation of I kappa B alpha and IKK alpha, and upregulated the expression of NF-kappa B-regulated proteins IL-6, IL-8, COX-2 and iNOS all of which were significantly downregulated by EGCG pretreatment. Conclusions: Our data suggest that EGCG can suppress GER-induced NF-kappa B activation and can downregulate the expression of NF-kappa B-regulated proteins in HEECs.