Quercetin protects against diabetic retinopathy in rats by inducing heme oxygenase-1 expression

Quercetin is a widely-occurring flavonoid that protects against cancer, and improves memory and cardiovascular functions.However, whether quercetin exhibits therapeutic effects in diabetic retinopathy remains unclear.In this study, we established a rat model of streptozocininduced diabetic retinopathy.Seventy-two hours later, the rats were intraperitoneally administered 150 mg/kg quercetin for 16 successive weeks.Quercetin markedly increased the thickness of the retinal cell layer, increased the number of ganglion cells, and decreased the overexpression of the pro-inflammatory factors interleukin-1β, interleukin-18, interleukin-6 and tumor necrosis factor-α in the retinal tissue as well as the overexpression of high mobility group box-1 and the overactivation of the NLRP3 inflammasome.Furthermore, quercetin inhibited the overexpression of TLR4 and NF-κBp65, reduced the expression of the pro-angiogenic vascular endothelial growth factor and soluble intercellular adhesion molecule-1, and upregulated the neurotrophins brain-derived neurotrophic factor and nerve growth factor.Intraperitoneal injection of the heme oxygenase-1 inhibitor zinc protoporphyrin blocked the protective effect of quercetin.These findings suggest that quercetin exerts therapeutic effects in diabetic retinopathy possibly by inducing heme oxygenase-1 expression.This study was approved by the Animal Ethics Committee of China Medical University, China(approval No.2016 PS229K) on April 8, 2016.