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

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. HO (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 HO 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). The cell viability weakened in the HO 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 HO group. Quercetin treatment significantly enhanced the expression levels of them as compared to the HO group. HO 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. Quercetin prevents the loss of tight junction proteins by upregulating autophagy after oxidative stress in ARPE-19 cells.