Time- and Concentration-Dependent Stimulation of Oxidative Stress in Chondrocytes by Intracellular Soluble Urate

Background: Gout could result in irreversible bone erosion, and chondrocyte might be involved in the process. Increased soluble urate is the early stage of gout and is strongly oxidative.Objective: To explore the effect of intracellular urate on the oxidative status of chondrocytesMethods: A chondrocyte model was used. Serial concentrations of exogenous urate were incubated with chondrocytes for increasing amounts of time. Reactive oxygen species (ROS), oxidant, and anti-oxidant molecules were measured with biochemical assays, rt-PCR, and western blot. A urate transport inhibitor and oxidative inhibitors were used to confirm the effect of exogenous urate.Results: All concentrations of exogenous urate stimulated the production of ROS in a time- and concentration-dependent manner, as well as oxidant molecules, including hydrogen peroxide (H2O2), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, nitric oxide (NO) inducible nitric oxide synthase (iNOS), and these effects, could be inhibited by oxidant inhibitors. However, anti-oxidant molecules, including acidic leucine-rich nuclear phosphoprotein-32A (ANP32A), ataxia-telangiectasia mutated (ATM), heme oxygenase-1 (HO-1), and the transcription factor nuclear factor erythroid 2 (NF-E2)-related (Nrf2), was decreased by high concentrations of exogenous urate after prolonged incubation, but not by low to medium concentrations of exogenous urate. By inhibiting soluble urate trafficking, benzbromarone significantly suppressed the effect of urate stimulus on the oxidant and anti-oxidant molecules.Conclusion: Intracellular soluble urate could regulate chondrocyte redox balance in a time and concentration-dependent manner, and would be a target for regulating and protecting chondrocyte function in the early gout stage.