Taurine Chloramine Inhibits Osteoclastic Differentiation and Osteoclast Marker Expression in RAW 264.7 Cells

Taurine is an abundant sulfur-containing amino acid in myeloid cells. It undergoes halogenation in activated phagocytes and is converted to taurine chloramine (TauCl) and taurine bromamine. Bone homeostasis is mediated by the balance between bone-forming osteoblasts and bone-resorbing osteoclasts. Osteoclasts are bone-resorbing multinucleated cells differentiated from monocyte/macrophage precursor cells in response to receptor activator of NF-κB ligand (RANKL). In this study, we investigated the effect of TauCl on RANKL-induced osteoclastogenesis from RAW 264.7 macrophages. TauCl inhibited the formation of multi-nucleated osteoclast and the activity of tartrate-resistant acid phosphatase (TRAP). TauCl decreased the mRNA expression of osteoclast markers, such as TRAP, cathepsin K, and calcitonin receptor. TauCl also inhibited expression of the transcription factors, c-Fos and nuclear factor of activated T cells, which are important for osteoclast differentiation. These results suggest that TauCl might be used as a therapeutic agent to treat bone diseases associated with excessive bone resorption.