Reduction of oxidative stress in cultured renal tubular cells and preventive effects on renal stone formation by the bioflavonoid quercetin

Purpose: We investigated the effects of quercetin on renal tubular cell injury induced by oxalate and the inhibitory effects of quercetin on urinary crystal deposit formation in an animal model. Materials and Methods: MDCK cells (American Type Culture Collection, Manassas, Virginia) were incubated with different concentrations of oxalate with and without quercetin. MTT (Sigma (R)) assays for cell viability, malondialdehyde and catalase activity were measured to investigate the antioxidant effect of quercetin. Male Sprague-Dawley rats were divided into 3 groups. Group 1 was fed standard rat chow. Groups 2 and 3 rats were fed standard chow supplemented with 3% sodium oxalate for 4 weeks. For the first 8 days in 4 weeks each rat in groups 2 and 3 also received gentamicin intramuscularly. Additionally, group 3 rats were administered quercetin for 4 weeks. Rats were sacrificed after 4 weeks, after which 24-hour urine collections and kidney removal were performed. In the renal tissue malondialdehyde, superoxide dismutase and catalase activity was measured. Bisected kidneys were examined under microscopy to determine the number of crystals. Results: The viability of MDCK cells significantly decreased and malondialdehyde production increased in the presence of oxalate. However, co-exposure to quercetin inhibited the decrease in cell viability and inhibited the lipid peroxidation production induced by oxalate. In the animal study malondialdehyde production in group 3 significantly decreased compared to that in group 2. Catalase and superoxide dismutase activity was increased in group 3 compared to that in group 2. The number of crystals in kidneys in group 3 was decreased significantly compared to that in group 2. Conclusions: Quercetin has an inhibitory effect on urinary crystal deposit formation.