title: Regulatory effect of calcineurin inhibitor, tacrolimus, on IL-6/sIL-6R-mediated RANKL expression through JAK2-STAT3-SOCS3 signaling pathway in fibroblast-like synoviocytes.
abstract: BACKGROUND
  This study investigated whether the calcineurin inhibitor, tacrolimus, suppresses receptor activator of NF-κB ligand (RANKL) expression in fibroblast-like synoviocytes (FLS) through regulation of IL-6/Janus activated kinase (JAK2)/signal transducer and activator of transcription-3 (STAT3) and suppressor of cytokine signaling (SOCS3) signaling.
  
  
  METHODS
  The expression of RANKL, JAK2, STAT3, and SOCS3 proteins was assessed by western blot analysis, real-time PCR and ELISA in IL-6 combined with soluble IL-6 receptor (sIL-6R)-stimulated rheumatoid arthritis (RA)-FLS with or without tacrolimus treatment. The effects of tacrolimus on synovial inflammation and bone erosion were assessed using mice with arthritis induced by K/BxN serum. Immunofluorescent staining was performed to identify the effect of tacrolimus on RANKL and SOCS3. The tartrate-resistant acid phosphatase staining assay was performed to assess the effect of tacrolimus on osteoclast differentiation.
  
  
  RESULTS
  We found that RANKL expression in RA FLS is regulated by the IL-6/sIL-6R/JAK2/STAT3/SOCS3 pathway. Inhibitory effects of tacrolimus on RANKL expression in a serum-induced arthritis mice model were identified. Tacrolimus inhibits RANKL expression in IL-6/sIL-6R-stimulated FLS by suppressing STAT3. Among negative regulators of the JAK/STAT pathway, such as CIS1, SOCS1, and SOCS3, only SOCS3 is significantly induced by tacrolimus. As compared to dexamethasone and methotrexate, tacrolimus more potently suppresses RANKL expression in FLS. By up-regulating SOCS3, tacrolimus down-regulates activation of the JAK-STAT pathway by IL-6/sIL-6R trans-signaling, thus decreasing RANKL expression in FLS.
  
  
  CONCLUSIONS
  These data suggest that tacrolimus might affect the RANKL expression in IL-6 stimulated FLS through STAT3 suppression, together with up-regulation of SOCS3.
authors: Jung-Yoon
authors: JY
authors: Choe
authors: Ki-Yeun
authors: KY
authors: Park
authors: Sung-Hoon
authors: SH
authors: Park
authors: Sang-Il
authors: SI
authors: Lee
authors: Seong-Kyu
authors: SK
authors: Kim
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000188:drug therapy / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D015153:Blotting, Western; D065095:Calcineurin Inhibitors / Q000494:pharmacology*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000276:immunology / Q000378:metabolism; D053614:Janus Kinase 2 / Q000378:metabolism; D008297:Male; D059630:Mesenchymal Stem Cells / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D053245:RANK Ligand / Q000096:biosynthesis / Q000276:immunology; D060888:Real-Time Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000378:metabolism; D013583:Synovial Membrane / Q000166:cytology; D016559:Tacrolimus / Q000494:pharmacology*
chemical_list: D065095:Calcineurin Inhibitors; D015850:Interleukin-6; D053245:RANK Ligand; D050796:STAT3 Transcription Factor; C491411:Socs3 protein, mouse; C494087:Stat3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C505689:Tnfsf11 protein, mouse; D053614:Janus Kinase 2; D016559:Tacrolimus