title: Identification of a novel chemokine-dependent molecular mechanism underlying rheumatoid arthritis-associated autoantibody-mediated bone loss.
abstract: OBJECTIVE
  Rheumatoid arthritis (RA)-specific anti-citrullinated protein/peptide antibodies (ACPAs) appear before disease onset and are associated with bone destruction. We aimed to dissect the role of ACPAs in osteoclast (OC) activation and to identify key cellular mediators in this process.
  
  
  METHODS
  Polyclonal ACPA were isolated from the synovial fluid (SF) and peripheral blood of patients with RA. Monoclonal ACPAs were isolated from single SF B-cells of patients with RA. OCs were developed from blood cell precursors with or without ACPAs. We analysed expression of citrullinated targets and peptidylarginine deiminases (PAD) enzymes by immunohistochemistry and cell supernatants by cytometric bead array. The effect of an anti-interleukin (IL)-8 neutralising antibody and a pan-PAD inhibitor was tested in the OC cultures. Monoclonal ACPAs were injected into mice and bone structure was analysed by micro-CT before and after CXCR1/2 blocking with reparixin.
  
  
  RESULTS
  Protein citrullination by PADs is essential for OC differentiation. Polyclonal ACPAs enhance OC differentiation through a PAD-dependent IL-8-mediated autocrine loop that is completely abolished by IL-8 neutralisation. Some, but not all, human monoclonal ACPAs derived from single SF B-cells of patients with RA and exhibiting distinct epitope specificities promote OC differentiation in cell cultures. Transfer of the monoclonal ACPAs into mice induced bone loss that was completely reversed by the IL-8 antagonist reparixin.
  
  
  CONCLUSIONS
  We provide novel insights into the key role of citrullination and PAD enzymes during OC differentiation and ACPA-induced OC activation. Our findings suggest that IL8-dependent OC activation may constitute an early event in the initiation of the joint specific inflammation in ACPA-positive RA.
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Akilan
authors.initials: A
authors.lastname: Krishnamurthy
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Vijay
authors.initials: V
authors.lastname: Joshua
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Aase
authors.initials: A
authors.lastname: Haj Hensvold
authors.affiliation: Department of Rheumatology and Inflammation Research, Institution of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Tao
authors.initials: T
authors.lastname: Jin
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Meng
authors.initials: M
authors.lastname: Sun
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Nancy
authors.initials: N
authors.lastname: Vivar
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: A Jimmy
authors.initials: AJ
authors.lastname: Ytterberg
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Marianne
authors.initials: M
authors.lastname: Engström
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Cátia
authors.initials: C
authors.lastname: Fernandes-Cerqueira
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Khaled
authors.initials: K
authors.lastname: Amara
authors.affiliation: Department of Rheumatology and Inflammation Research, Institution of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Magnusson
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Gustaf
authors.initials: G
authors.lastname: Wigerblad
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jungo
authors.initials: J
authors.lastname: Kato
authors.affiliation: UCB Unidad Académica Multidisciplinaria Reynosa Aztlán, Universidad Autónoma de Tamaulipas, Reynosa, Tamaulipas, México.
authors.forename: Juan Miguel
authors.initials: JM
authors.lastname: Jiménez-Andrade
authors.affiliation: UCB Pharma, Slough, UK.
authors.forename: Kerry
authors.initials: K
authors.lastname: Tyson
authors.affiliation: UCB Pharma, Slough, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Rapecki
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Lundberg
authors.affiliation: Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Sergiu-Bogdan
authors.initials: SB
authors.lastname: Catrina
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Per-Johan
authors.initials: PJ
authors.lastname: Jakobsson
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Camilla
authors.initials: C
authors.lastname: Svensson
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Vivianne
authors.initials: V
authors.lastname: Malmström
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Klareskog
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Heidi
authors.initials: H
authors.lastname: Wähämaa
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska University Hospital and Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anca I
authors.initials: AI
authors.lastname: Catrina
mesh_terms: D000818:Animals; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D001862:Bone Resorption / Q000000981:diagnostic imaging / Q000276:immunology*; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000187:drug effects / Q000276:immunology*; D018929:Cell Culture Techniques; D018925:Chemokines / Q000276:immunology; D002956:Citrulline / Q000276:immunology*; D005260:Female; D006801:Humans; D006867:Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007150:Immunohistochemistry; D016209:Interleukin-8 / Q000037:antagonists & inhibitors / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D010010:Osteoclasts / Q000187:drug effects / Q000276:immunology*; D000076342:Protein-Arginine Deiminases; D053700:Receptors, Interleukin-8 / Q000037:antagonists & inhibitors; D013449:Sulfonamides / Q000494:pharmacology; D013582:Synovial Fluid; D055114:X-Ray Microtomography
chemical_list: D001323:Autoantibodies; D018925:Chemokines; D016209:Interleukin-8; D053700:Receptors, Interleukin-8; D013449:Sulfonamides; D002956:Citrulline; D006867:Hydrolases; D000076342:Protein-Arginine Deiminases; C490707:reparixin
keywords: Ant-CCP; Autoantibodies; Early Rheumatoid Arthritis