title: Histone deacetylase inhibitors suppress rheumatoid arthritis fibroblast-like synoviocyte and macrophage IL-6 production by accelerating mRNA decay.
abstract: BACKGROUND
  Histone deacetylase inhibitors (HDACi) display potent therapeutic efficacy in animal models of arthritis and suppress inflammatory cytokine production in rheumatoid arthritis (RA) synovial macrophages and tissue.
  
  
  OBJECTIVE
  To determine the molecular mechanisms contributing to the suppressive effects of HDACi on RA synovial cell activation, using interleukin 6 (IL-6) regulation as a model.
  
  
  METHODS
  RA fibroblast-like synoviocytes (FLS) and healthy donor macrophages were treated with IL-1β, tumour necrosis factor (TNF)α, lipopolysaccharide or polyinosinic:polycytidylic acid (poly(I:C)) in the absence or presence of the HDACi trichostatin A (TSA) or ITF2357 (givinostat). IL-6 production and mRNA expression was measured by ELISA and quantitative PCR (qPCR), respectively. Protein acetylation and the activation of intracellular signalling pathways were assessed by immunoblotting. The DNA-binding activity of nuclear factor κB (NFκB) and activator protein 1 (AP-1) components was measured by ELISA-based assays.
  
  
  RESULTS
  HDACi (0.25-1.0 μM) suppressed RA FLS IL-6 production induced by IL-1β, TNFα and Toll-like receptor ligands. Phosphorylation of mitogen-activated protein kinases and inhibitor of κBα (IκBα) following IL-1β stimulation were unaffected by HDACi, as were AP-1 composition and binding activity, and c-Jun induction. TSA induced a significant reduction in nuclear retention of NFκB in FLS 24 h after IL-1β stimulation, but this did not reduce NFκB transcriptional activity or correlate temporally with reductions in IL-6 mRNA accumulation. HDACi significantly reduced the stability of IL-6 mRNA in FLS and macrophages.
  
  
  CONCLUSIONS
  Our study identifies a novel, shared molecular mechanism by which HDACi can disrupt inflammatory cytokine production in RA synovial cells, namely the promotion of mRNA decay, and suggests that targeting HDAC activity may be clinically useful in suppressing inflammation in RA.
authors.affiliation: Division of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Aleksander M
authors.initials: AM
authors.lastname: Grabiec
authors.forename: Olexandr
authors.initials: O
authors.lastname: Korchynskyi
authors.forename: Paul P
authors.initials: PP
authors.lastname: Tak
authors.forename: Kris A
authors.initials: KA
authors.lastname: Reedquist
mesh_terms: D018501:Antirheumatic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001172:Arthritis, Rheumatoid / Q000378:metabolism / Q000473:pathology*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D006877:Hydroxamic Acids / Q000008:administration & dosage / Q000494:pharmacology; D018836:Inflammation Mediators / Q000378:metabolism; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D013583:Synovial Membrane / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018808:Transcription Factor AP-1 / Q000378:metabolism
chemical_list: D018501:Antirheumatic Agents; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D018836:Inflammation Mediators; D015850:Interleukin-6; D016328:NF-kappa B; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; C012589:trichostatin A; C502418:givinostat hydrochloride