T-614 Promotes Osteoblastic Cell Differentiation by Increasing Dlx5 Expression and Regulating the Activation of p38 and NF-κB

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease characterized by bone loss. Degree of inflammation has been identified as an important initiator of skeletal damage in RA. Iguratimod (T-614) is an anti-inflammatory agent which has been reported to show the inhibitory effect of bone destruction in RA. However, the role of T-614 in osteoblast differentiation is still not clear. In this study, we intended to find the effect of T-614 on the osteogenesis process. We detected osteogenesis markers and transcription factors associated with osteoblastic lineage and bone formation in the culture of mesenchymal stem cells which differentiate osteoblast. The contents and activity of alkaline phosphatase, levels of collagen type I and bone gla protein, and calcium nodule formation were increased significantly after T-614 treated. Meanwhile, the mRNAs expressions of Osterix and Dlx5 were also found to be increased significantly by real-time PCR. The changes of levels of phosphorylation of p38 and NF-κB were also detected by Western blot. The results showed that T-614 promotes osteoblastic differentiation by increasing the expression of Osterix and Dlx5 and increasing the activation of P38. T-614 could advance the ectopic expression of NF-κB to suppress inflammation, which indirectly inhibits the damage of the osteoblasts.