Effect of quercetin on tight junction disruption induced by hydrogen peroxide

Abstract

Oxidative stress has been identify as a major cause of endothelium dysfunction and loss in vascular protective barrier against xenobiotics. Several studies showed that oxidative stress affected the expression and distribution of tight junction proteins, leading to tight junction disruption and increase in permeability. The proposed of this study were to investigate the effect of quercetin, a known antioxidant flavonoid, on the H2O2-mediated disruption of tight junction. ECV304 cells were pretreated with 10 µM quercetin for 30 min prior to the addition of 100 µM H2O2. After the incubation period of 4 hr, the integrity of tight junction was evaluated through an alteration of TEER values and paracellular permeability of phenol red. In addition, the expression and localization of tight junction proteins were determined with western blot and immunofluorescent techniques. In this study, exposure to 100 µM H2O2 for 4 hr markedly increased the paracellular permeability and decreased TEER value without an observable effect on cell viability. Pretreatment the cells with quercetin prevented H2O2-induced hyperpermeability as well as a loss of TEER value. The disruption of occludin and ZO-1 at the cell border was not observed in the quercetin pretreatment group. In addition, pretreatment with quercetin could significantly prevent the H2O2-induced reduction of expression of these two tight junction proteins, Furthermore, experiments with anti-MAP kinases activities revealed that the protective effect of quercetin against H2O2-induced tight junction disruption was involved with inhibition of phosphorylated p38 MAP activity along with NO production. In conclusion, quercetin could preserve the barrier integrity of ECV304 upon challenging with H2O2. The results suggested that quercetin was able to prevent the loss of tight junction protein expression as well as its assembly through the mechanisms involved with MAPK pathways.