title: The bromodomain protein inhibitor I-BET151 suppresses expression of inflammatory genes and matrix degrading enzymes in rheumatoid arthritis synovial fibroblasts.
abstract: OBJECTIVE
  To investigate the effects of BET bromodomain protein inhibition on inflammatory activation and functional properties of rheumatoid arthritis synovial fibroblasts (RASF).
  
  
  METHODS
  The expression of the BET bromodomain proteins BRD2, BRD3 and BRD4 was analysed in synovial tissue by immunohistochemistry. RASF were stimulated with tumour necrosis factor (TNF)-α, interleukin (IL)-1β and toll-like receptor (TLR) ligands (Pam3, pIC and lipopolysaccharide (LPS)) in the presence or absence of the BET inhibitor I-BET151, or siRNA targeting BRD2, BRD3 and BRD4. RASF expression of inflammatory mediators, including MMP1, MMP3, IL-6 and IL-8, was measured by q-PCR, q-PCR array and ELISA. Cellular viability, apoptosis, proliferation and chemoattractive properties of RASF were investigated using MTT, cell apoptosis ELISA, BrdU-based proliferation and transwell migration assays.
  
  
  RESULTS
  BRD2, BRD3 and BRD4 proteins were detected in rheumatoid arthritis (RA) synovial tissue, expressed in both RASF and macrophages. I-BET151 suppressed cytokine and TLR ligand-induced secretion of MMP1, MMP3, IL-6 and IL-8, and mRNA expression of more than 70% of genes induced by TNF-α and IL-1β. Combined silencing of BRD2, BRD3 and BRD4 significantly reduced cytokine and TLR ligand-induced expression of a subset of gene products targeted by I-BET151, including MMP1, CXCL10 and CXCL11. I-BET151 treatment of RASF reduced RASF proliferation, and the chemotactic potential for peripheral blood leucocytes of RASF conditioned medium.
  
  
  CONCLUSIONS
  Inhibition of BET family proteins suppresses the inflammatory, matrix-degrading, proliferative and chemoattractive properties of RASF and suggests a therapeutic potential in the targeting of epigenetic reader proteins in RA.
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, Schlieren, Switzerland.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Klein
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Pawel A
authors.initials: PA
authors.lastname: Kabala
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Aleksander M
authors.identifier: http://orcid.org/0000-0001-9472-850X
authors.initials: AM
authors.lastname: Grabiec
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, Schlieren, Switzerland.
authors.forename: Renate E
authors.initials: RE
authors.lastname: Gay
authors.affiliation: Schulthess Clinic, Zurich, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Kolling
authors.affiliation: Inflammation and Remodeling Research Unit, Pfizer, Cambridge, Massachusetts, USA.
authors.forename: Lih-Ling
authors.initials: LL
authors.lastname: Lin
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, Schlieren, Switzerland.
authors.forename: Steffen
authors.initials: S
authors.lastname: Gay
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands GlaxoSmithKline, Stevenage, UK Cambridge University, Cambridge, UK.
authors.forename: Paul P
authors.initials: PP
authors.lastname: Tak
authors.affiliation: GlaxoSmithKline, Stevenage, UK.
authors.forename: Rab K
authors.initials: RK
authors.lastname: Prinjha
authors.affiliation: Center of Experimental Rheumatology, University Hospital Zurich, Schlieren, Switzerland.
authors.forename: Caroline
authors.initials: C
authors.lastname: Ospelt
authors.affiliation: Department of Experimental Immunology and Department of Clinical Immunology and Rheumatology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Kris A
authors.initials: KA
authors.lastname: Reedquist
mesh_terms: D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000235:genetics*; D018797:Cell Cycle Proteins; D005347:Fibroblasts / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology*; D006801:Humans; D007150:Immunohistochemistry; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D010003:Osteoarthritis / Q000201:enzymology / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D013583:Synovial Membrane / Q000378:metabolism*; D051193:Toll-Like Receptors / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D000092468:Bromodomain Containing Proteins
chemical_list: D018797:Cell Cycle Proteins; D006576:Heterocyclic Compounds, 4 or More Rings; D053583:Interleukin-1beta; D015850:Interleukin-6; D016209:Interleukin-8; D008070:Lipopolysaccharides; D020781:Matrix Metalloproteinase 1; D019278:Matrix Metalloproteinase 3; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D051193:Toll-Like Receptors; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C098415:BRD2 protein, human; D000092468:Bromodomain Containing Proteins; C109106:BRD3 protein, human; C441289:BRD4 protein, human; C568713:GSK1210151A; C508600:IL6 protein, human; C511768:MMP3 protein, human; C522360:MMP1 protein, human
keywords: Fibroblasts; Inflammation; Rheumatoid Arthritis