Modulation of reactive oxygen species production by IL-1β and high glucose. (a) Reactive oxygen species (ROS) production in normal and osteoarthritis (OA) chondrocytes treated with or without IL-1β 30 ng/ml for 1 hour (n = 4). (b) ROS production in normal and OA chondrocytes (n = 5) cultured in regular glucose medium (RGM) or in high glucose medium (HGM, 30 mM) for the periods indicated and then loaded with 5 μM 2',7'-dichlorodihydrofluorescein diacetate for 20 minutes at 37°C, as described in Materials and methods. Results expressed as the percentage relative to the respective control cells maintained in RGM. **P < 0.01 and ***P < 0.001 relative to the respective control cells maintained in RGM, §§§P < 0.001 between normal and OA chondrocytes exposed to the same glucose concentration for the same period. Bars = mean ± standard deviation.