Quercetin Regulates Inflammatory Response of Retinal Ganglion Cells by Affecting the Tumor Necrosis Factor Receptor Associated Factor 6/Transforming Growth Factor-β-Activated Kinase-1 Signaling Pathway

Abstract

To investigate the protective effect of quercetin on the lipopolysaccharide-induced inflammatory response of retinal ganglion cell line 5 cells and to explore its possible molecular mechanism. Retinal ganglion cell line 5 cells were cultured in vitro and assigned into blank control group, lipopolysaccharide (1.0 μg/ml) induction group, lipopolysaccharide+low dose (0.25 μg/ml) quercetin group, lipopolysaccharide+medium dose (0.5 μg/ml) quercetin group and lipopolysaccharide+high dose (1.0 μg/ml) quercetin group. The relative survival rate of retinal ganglion cell line 5 cells was determined by cell counting kit-8 assay and the levels of inflammatory factors interleukin-6 and tumor necrosis factor-alpha were detected using enzymelinked immunosorbent assay kits. In addition, the levels of tumor necrosis factor receptor-associated factor 6, phosphorylation-transforming growth factor-beta-activated kinase 1 and transforming growth factorbeta- activated kinase 1 were measured by western blotting. The results of cell counting kit-8 assay revealed that quercetin could dramatically elevate the relative survival rate of retinal ganglion cell line 5 cells. The levels of inflammatory factors interleukin-6 and tumor necrosis factor-alpha in different quercetin groups were significantly lower than those in lipopolysaccharide induction group and the levels of interleukin-6 and tumor necrosis factor-alpha in cell supernatant declined with the increase of quercetin concentration in a concentration-dependent manner. In addition, the expression levels of tumor necrosis factor receptorassociated factor 6 and phosphorylation-transforming growth factor-beta-activated kinase 1 in different quercetin groups were remarkably lower than those in lipopolysaccharide induction group and they also declined with the increase of quercetin concentration in a concentration-dependent manner. Quercetin displays a protective effect against the lipopolysaccharide-induced inflammatory response of retinal ganglion cell line 5 cells and its mechanism is related to suppression of the activation of the tumor necrosis factor receptor-associated factor 6/transforming growth factor-beta-activated kinase 1 signaling pathway.