title: Decoy receptor 3 suppresses RANKL-induced osteoclastogenesis via down-regulating NFATc1 and enhancing cell apoptosis.
abstract: OBJECTIVE
  Decoy receptor 3 (DCR3) has been known to modulate immune functions of monocyte or macrophage. In the present study, we investigated the mechanism and the effect of DCR3 on RANK ligand (RANKL)-induced osteoclastogenesis.
  
  
  METHODS
  We treated cells with DCR3 in RANKL-induced osteoclastogenesis to monitor osteoclast formation by tartrate-resistant acid phosphatase (TRAP) staining. Osteoclast activity was assessed by pit formation assay. The mechanism of inhibition was studied by biochemical analysis such as RT-PCR and immunoblotting. In addition, cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis and apoptosis signalling were evaluated by immunoblotting and using flow cytometry.
  
  
  RESULTS
  DCR3 inhibited RANKL-induced TRAP(+) multinucleated cells and inhibited RANKL-induced nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation and nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1) nuclear translocation in RAW264.7 cells. Also, DCR3 significantly inhibited the bone-resorbing activity of mature osteoclasts. Moreover, DCR3 enhanced RANKL-induced cell apoptosis and enhanced RANKL-induced Fas ligand expression. The mechanisms were mediated via the intrinsic cytochrome c and activated caspase 9 apoptosis pathway.
  
  
  CONCLUSIONS
  We postulated that the inhibitory activity of DCR3 on osteoclastogenesis occurs via down-regulation of RANKL-induced NFATc1 expression and induction of cell apoptosis. Our results postulated DCR3 as a possible new remedy against inflammatory bone destruction.
authors.affiliation: Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China.
authors.forename: Chia-Pi
authors.initials: CP
authors.lastname: Cheng
authors.forename: Ming-Jen
authors.initials: MJ
authors.lastname: Sheu
authors.forename: Huey-Kang
authors.initials: HK
authors.lastname: Sytwu
authors.forename: Deh-Ming
authors.initials: DM
authors.lastname: Chang
mesh_terms: D000135:Acid Phosphatase; D000328:Adult; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D015536:Down-Regulation; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D015151:Immunoblotting; D007527:Isoenzymes; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D053245:RANK Ligand / Q000378:metabolism*; D053323:Receptors, Tumor Necrosis Factor, Member 6b / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071681:Tartrate-Resistant Acid Phosphatase
chemical_list: D007527:Isoenzymes; D016328:NF-kappa B; D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D053245:RANK Ligand; D053323:Receptors, Tumor Necrosis Factor, Member 6b; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase