Background Gouty is an arthritis disease characterized by metabolic disorder of monosodium urate (MSU) crystals, resulting in bone destruction in affected joints. MSU crystals induce secretion of interleukin-1b (IL-1b) that can enhance osteoclast differentiation and bone resorption.
Objectives This study is to investigate action mechanisms by MSU crystals for the regulation of osteoclastogenic activity through tumor necrosis factor receptor-associated factor 6 (TRAF-6) signal pathways in RAW 264.7 macrophage cells.
Methods Cell viability in RAW 264.7 macrophage cells was determined using a MTT assay after MSU crystal treatment. We examined the effects of MSU crystals on mitogen activated protein kinases (MAPK), their signaling cascade genes, and osteoclast differentiation markers were measured using real-time polymerase chain reaction and western blotting. Effects of TRAF6 knockdown using siRNA for TRAF6 on osteoclastic transcription factors and IL-1 b expression were measured by western blotting. We performed tartrate-resistant acid phosphatase (TRAP) staining to identify formation of osteoclasts.
Results MSU crystals induced expressions of IL-1b and MAPK signaling molecules. MSU, in the presence of RNAKL, also resulted in significantly enhanced expressions of osteoclatogenesis related genes including cathepsin K, MMP9, and carbonic anhydrase II, and TRAP activity. Furthermore, inhibition of TRAF6 decreased expressions of IL-1b and its transcription factors such as c-Jun and NFATc1.
Conclusions These results suggest that MSU crystal enhances osteoclast differentiation through TRAF6 signaling pathway.
Disclosure of Interest None Declared