Quercetin protects retina external barrier from oxidative stress injury by promoting autophagy

Purpose: This study aimed to investigate the protective effects of quercetin on the tight junction proteins of human retinal pigment epithelial cells (ARPE-19 cells) suffering from oxidative stress injury and explore the possible mechanism.Methods: H₂O₂ (300 μM) was used to establish an oxidative stress model of ARPE-19 cells. ARPE-19 cells were pretreated with different concentrations (0-80 μM) of quercetin before H₂O₂ exposure. The expression and distribution of tight junction proteins and autophagy-related proteins were detected by Western blot and immunostaining. ARPE-19 cells were pretreated with 5 mM 3-methyladenine (3-MA).Results: The cell viability weakened in the H₂O₂ group compared with the control group. However, it was preserved after pretreatment with quercetin. It was observed that the expression levels of occludin, claudin-1 were decreased in the H₂O₂ group. Quercetin treatment significantly enhanced the expression levels of them as compared to the H₂O₂ group. H₂O₂ alone strongly decreased the Zonula occludens protein 1 (ZO-1) expression in the cytomembrane. Quercetin supplementation enhanced the accumulation of ZO-1 in ARPE-19 cells. The expression levels of Beclin-1 and Microtubule associated protein light chain 3 II (LC-3II) increased, and that of P62 decreased in the quercetin protection group. The appearance of LC-3II, which examined by immunofluorescence experiments, enhanced in the quercetin protection group as compared with the control group. The expression levels of beclin-1 and LC-3II increased, and that of P62 increased in the autophagy-inhibited group compared with the quercetin protection group. The levels of occludin and claudin-1 also decreased.Conclusion: Quercetin prevents the loss of tight junction proteins by upregulating autophagy after oxidative stress in ARPE-19 cells.