Figure 2.

Quercetin attenuated IL-1β-induced inflammation and the apoptosis of rat chondrocytes. Rat chondrocytes were treated with 8 μM quercetin for 2 h, followed by stimulation with IL-1β. (A) IC50 of OA chondrocytes to quercetin. (B) Chondrocyte viability was analyzed by the CCK-8 assay. (C and D) The levels of pro-inflammatory cytokines (IL-18 and TNF-α) were determined by ELISA. (E) Cell apoptosis was evaluated by flow cytometry analysis performed with an Annexin V-FITC/propidium iodide (PI) apoptosis kit. (F) Hoechst 33342 staining was performed. Apoptotic cells exhibited morphological changes in the nuclei typical of apoptosis. Images were captured under a fluorescence microscope. (G) The levels of NLRP3, ASC, and IRAK1 proteins were examined by Western blotting. (H) NLRP3 immunofluorescence staining. Markedly increased red bright puncta indicate the upregulated expression of NLRP3 (bar: 20 μm). Data represent a mean value ± standard deviation. *p <0.05, **p < 0.01, ***p < 0.001, compared with blank; ^#p < 0.05, ^##p < 0.01, ^###p < 0.001, compared with IL-1β. ^$$p < 0.01, compared with IL-1β + quercetin + vector.

Abbreviation: NS, No significance.