The protective mechanism of quercetin-3-O-beta-d-glucuronopyranoside (QGC) in H2O2-induced injury of feline esophageal epithelial cells

Abstract

Quercetin-3-O-beta-d-glucuronopyranoside (QGC) is a flavonoid glucoside extracted from Rumex Aquaticus. Recent studies have shown that QGC exhibits anti-inflammatory, anti-oxidateve effect in vivo and cytoprotective effect in vitro. Reactive oxygen species (ROS), at low concentration, play role as a primary signal or second messenger, however, at high concentration, ROS are cytotoxic. In this study, we investigated the protective mechanism of QGC in H2O2-induced injury of Feline Esophageal Epithelial Cells. Primary-cultured feline esophagus cells were identified by an indirect immunofluorescent staining method using a cytokeratin monoclonal antibody. Cell viability was determined by the conventional MTT reduction assay. Western blot analysis was performed with specific antibodies to investigate the activation of MAPKs, NF-kappa B, and I kappa B-alpha, and the expression of COX-2. When the cells were exposed to 600 mu M H2O2 medium for 24 h, cell viability decreased to 54 %. However, when cells were pretreated with 50-150 mu M QGC for 12 h, the viability of cells exposed to H2O2 significantly increased in the dose dependent manner. QGC (50 mu M, 12 h) also inhibited the expression of COX-2 induced by 10 mu M H2O2 for 24 h. We found that treatment of H2O2 activated p38 MAPK and JNK, but not ERK. However QGC inhibited the H2O2-induced p38 MAPK and JNK phosphorylation. In addition, NF-kappa B was activated by H2O2 and translocated into the nucleus, but QGC inhibited the activation of NF-kappa B by blocking degradation of I kappa B. These data suggest that QGC reduces H2O2-induced COX-2 production by modulating the p38 MAPK, JNK, NF-kappa B signal pathway in feline esophageal epithelial cells.