title: Regulation of inflammatory responses in tumor necrosis factor-activated and rheumatoid arthritis synovial macrophages by JAK inhibitors.
abstract: OBJECTIVE
  JAK inhibitors have been developed as antiinflammatory and immunosuppressive agents and are currently undergoing testing in clinical trials. The JAK inhibitors CP-690,550 (tofacitinib) and INCB018424 (ruxolitinib) have demonstrated clinical efficacy in rheumatoid arthritis (RA). However, the mechanisms that mediate the beneficial actions of these compounds are not known. The purpose of this study was to examine the effects of both JAK inhibitors on inflammatory and tumor necrosis factor (TNF) responses in human macrophages.
  
  
  METHODS
  In vitro studies were performed using peripheral blood macrophages derived from healthy donors and treated with TNF and using synovial fluid macrophages derived from patients with RA. Levels of activated STAT proteins and other transcription factors were detected by Western blotting, and gene expression was measured by real-time polymerase chain reaction analysis. The in vivo effects of JAK inhibitors were evaluated in the K/BxN serum-transfer model of arthritis.
  
  
  RESULTS
  JAK inhibitors suppressed the activation and expression of STAT-1 and downstream inflammatory target genes in TNF-stimulated and RA synovial macrophages. In addition, JAK inhibitors decreased nuclear localization of NF-κB subunits in TNF-stimulated and RA synovial macrophages. CP-690,550 significantly decreased the expression of interleukin-6 in synovial macrophages. JAK inhibitors augmented nuclear levels of NF-ATc1 and cJun, followed by increased formation of osteoclast-like cells. CP-690,550 strongly suppressed K/BxN serum-transfer arthritis, which is dependent on macrophages, but not lymphocytes.
  
  
  CONCLUSIONS
  Our findings demonstrate that JAK inhibitors suppress macrophage activation and attenuate TNF responses and further suggest that suppression of cytokine/chemokine production and innate immunity contribute to the therapeutic efficacy of JAK inhibitors.
authors.affiliation: Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA. ivashkivl@hss.edu
authors.forename: Anna
authors.initials: A
authors.lastname: Yarilina
authors.forename: Kai
authors.initials: K
authors.lastname: Xu
authors.forename: Chunhin
authors.initials: C
authors.lastname: Chan
authors.forename: Lionel B
authors.initials: LB
authors.lastname: Ivashkiv
mesh_terms: D000818:Animals; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007249:Inflammation / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism; D053612:Janus Kinases / Q000037:antagonists & inhibitors*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000378:metabolism; D009570:Nitriles; D010880:Piperidines; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology / Q000627:therapeutic use; D011758:Pyrroles / Q000494:pharmacology / Q000627:therapeutic use; D050794:STAT1 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D015850:Interleukin-6; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D009570:Nitriles; D010880:Piperidines; D016755:Proto-Oncogene Proteins c-jun; D011720:Pyrazoles; D011743:Pyrimidines; D011758:Pyrroles; D050794:STAT1 Transcription Factor; D014409:Tumor Necrosis Factor-alpha; C540383:ruxolitinib; C479163:tofacitinib; D053612:Janus Kinases