Oral Malodorous Compound Induces Osteoclast Differentiation Without Receptor Activator of Nuclear Factor κB Ligand

Background: Hydrogen sulfide (H2S), the main component of halitosis, is one of the etiologic factors for periodontitis. We recently reported that H2S may induce pathologic changes in rat alveolar bone. The objective of this study is to determine the effect of H2S on osteoclast differentiation. Methods: Murine macrophage cells RAW264 were cultured in medium lacking nuclear factor kappa B ligand (receptor activator of nuclear factor kappa B ligand) in 5% CO2 with air at 37 degrees C for 24 hours; then 0.05, 0.5, or 5 ng/ml H2S was added to the CO2-air mix for 4 days. The controls received the CO2-air mix with no H2S. Cell differentiation was evaluated by counting the tartrate-resistant acid-phosphatase (TRAP) positive cells. Extracellular signaling-regulated kinase1/2 (ERK1/2) and mitogen-activated protein kinase p38 phosphorylation were examined by Western blotting. The bone-resorption activity was determined with the resorption assay of calcium phosphate. Results: There were significantly more TRAP-positive cells at a concentration of 0.05 ng/ml H2S than at the other concentrations (P <0.001). Cathepsin K protein, a specific marker for osteoclasts, was expressed in the H2S-induced multinuclear cells. Resorption of calcium phosphate significantly increased in the H2S-induced TRAP-positive cells cultured on plates coated with calcium phosphate apatite (P <0.01). The phosphorylation of ERK1/2 and p38 were accelerated by H2S, and increased with time. PD98059 and SB203580, specific inhibitors of ERK1/2 and p38, suppressed the activation of these enzymes and osteoclast differentiation by H2S. Conclusion: Results demonstrate that H2S at physiologic concentrations in mouth air induces osteoclasts from RAW264 cells. J Periodontol 2010;81:1691-1697.