Taurine Chloramine, a Taurine Metabolite from Activated Neutrophils, Inhibits Osteoclastogenesis by Suppressing NFATc1 Expression.

Abstract

AbstractTaurine is one of the most abundant free amino acids in inflammatory cells including neutrophils. Taurine chloramine (TauCl) is produced by the halide-dependent myeloperoxidase system in activated neutrophils during inflammation. TauCl protects cells against inflammatory injury by inhibiting the overproduction of inflammatory mediators and by increasing the production of antioxidant enzymes. Inflammatory molecules and cytokines regulate bone homeostasis which is mediated by bone-forming osteoblasts and bone-resorbing osteoclasts. In this study, we investigated the effect of TauCl on osteoclastogenesis. TauCl inhibited the differentiation of bone marrow-derived monocyte/macrophage precursor cells to osteoclasts, the expression of osteoclast markers, such as tartrate-resistant acid phosphatase (TRAP) and cathepsin K, and decreased TRAP activity. Furthermore, TauCl inhibited the expression of nuclear factor of activated T cell 1 (NFATc1), an essential transcription factor for osteoclastogenesis. These results indicate that TauCl produced endogenously as a result of a phagocytic oxidative burst during inflammation inhibits osteoclast formation by inhibiting NFATc1, which regulates TRAP and cathepsin K. These findings suggest that TauCl might be used to delay osteoclastogenesis and the progression of inflammatory bone diseases like rheumatoid arthritis and osteoporosis.KeywordsTaurine chloramineInflammationOsteoclastOsteoclastogenesisNeutrophilTartrate-resistant acid phosphatase (TRAP)Nuclear factor of activated T cell 1 (NFATc1)Myeloperoxidase