Pyridone 6 suppresses OSM-induced JAKs/STATs activation in RA-FLS; Pyridone 6 suppresses OSM-induced IL-6 synthesis in RA-FLS. (a) Quiescent RA-FLS were pretreated with vehicle (DMSO -) or pyridone 6 for 2 hours, then stimulated with OSM (20 ng/ml) for 20 minutes. Cellular lysates were subjected to Western blotting using phospho-specific antibodies against JAK1, JAK2, JAK3, STAT1, STAT3 and STAT5. Two experiments were performed using different RA-FLS and a representative result is shown. (b) Quiescent RA-FLS were pretreated with vehicle (DMSO, -) or pyridone 6 for two hours, then stimulated with OSM (20 ng/ml) for 24 hours. IL-6 protein in the conditioned media was determined by ELISA. The data were expressed as the mean ± SD of two independent experiments. *P < 0.05 compared to OSM-treated RA-FLS. **P < 0.01 compared to OSM-treated RA-FLS.