Assessment of nitric oxide (NO)
The NO concentration in cell suspensions was measured with Griess reagent (Sigma, G4410). Chondrocytes were pretreated with empagliflozin at various concentrations (0, 1, and 5 μM) for 2 h and incubated with IL-1β (10 ng/ml) for 24 h, the NO levels in the cell culture medium were assessed with Griess reagent according to the manufacturer. The relative levels of NO were normalized to cell count.