title: Brief report: citrullination within the atherosclerotic plaque: a potential target for the anti-citrullinated protein antibody response in rheumatoid arthritis.
abstract: OBJECTIVE
  To investigate whether citrullinated proteins within the atherosclerotic plaque can be targeted by anti-citrullinated protein antibodies (ACPAs), forming stimulatory immune complexes that propagate the progression of atherosclerosis.
  
  
  METHODS
  Protein lysates prepared from atherosclerotic segments of human aorta were assessed for the presence of citrulline-modified proteins, and specifically citrullinated fibrinogen (Cit-fibrinogen), by immunoprecipitation and/or immunoblotting followed by mass spectrometry. Immunohistochemical analysis of coronary artery plaque was performed to determine the presence of citrullinated proteins and peptidylarginine deiminase type 4 (PAD-4). Serum levels of anti-cyclic citrullinated peptide (anti-CCP), anti-citrullinated vimentin (anti-Cit-vimentin), and anti-Cit-fibrinogen antibodies were measured in 134 women with seropositive rheumatoid arthritis; these subjects had previously been characterized for the presence of subclinical atherosclerosis, by electron beam computed tomography scanning.
  
  
  RESULTS
  Western blot analysis of atherosclerotic plaque lysates demonstrated several citrullinated proteins, and the presence of Cit-fibrinogen was confirmed by immunoprecipitation and mass spectrometry. Immunohistochemical analysis showed colocalization of citrullinated proteins and PAD-4 within the coronary artery plaque. In age-adjusted regression models, antibodies targeting Cit-fibrinogen and Cit-vimentin, but not CCP-2, were associated with an increased aortic plaque burden.
  
  
  CONCLUSIONS
  Citrullinated proteins are prevalent within atherosclerotic plaques, and certain ACPAs are associated with the atherosclerotic burden. These observations suggest that targeting of citrullinated epitopes, specifically Cit-fibrinogen, within atherosclerotic plaques could provide a mechanism for the accelerated atherosclerosis observed in patients with RA.
authors.affiliation: Stanford University Medical Center, Stanford, CA, USA. sokolove@stanford.edu
authors.forename: Jeremy
authors.initials: J
authors.lastname: Sokolove
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Brennan
authors.forename: Orr
authors.initials: O
authors.lastname: Sharpe
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Lahey
authors.forename: Amy H
authors.initials: AH
authors.lastname: Kao
authors.forename: Eswar
authors.initials: E
authors.lastname: Krishnan
authors.forename: Daniel
authors.initials: D
authors.lastname: Edmundowicz
authors.forename: Christin M
authors.initials: CM
authors.lastname: Lepus
authors.forename: Mary Chester
authors.initials: MC
authors.lastname: Wasko
authors.forename: William H
authors.initials: WH
authors.lastname: Robinson
mesh_terms: D000368:Aged; D000936:Antigen-Antibody Complex / Q000276:immunology; D001027:Aortography; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000378:metabolism; D001323:Autoantibodies / Q000276:immunology*; D015153:Blotting, Western; D002114:Calcinosis / Q000000981:diagnostic imaging / Q000276:immunology; D002956:Citrulline / Q000276:immunology / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005340:Fibrinogen / Q000276:immunology / Q000378:metabolism; D006801:Humans; D006867:Hydrolases / Q000378:metabolism; D007118:Immunoassay; D008297:Male; D010456:Peptides, Cyclic / Q000276:immunology; D058226:Plaque, Atherosclerotic / Q000276:immunology* / Q000378:metabolism; D000080002:Protein-Arginine Deiminase Type 4; D000076342:Protein-Arginine Deiminases; D012044:Regression Analysis; D014746:Vimentin / Q000276:immunology / Q000378:metabolism
chemical_list: D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D010456:Peptides, Cyclic; D014746:Vimentin; C487763:cyclic citrullinated peptide; D002956:Citrulline; D005340:Fibrinogen; D006867:Hydrolases; C000629235:PADI4 protein, human; D000080002:Protein-Arginine Deiminase Type 4; D000076342:Protein-Arginine Deiminases
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