title: Reduction of arthritis severity in protease-activated receptor-deficient mice.
abstract: OBJECTIVE
  Protease-activated receptor 1 (PAR-1) is the cell surface receptor for thrombin. It is unclear whether thrombin contributes to inflammation other than by effects on coagulation. We investigated the proinflammatory participation of PAR-1 in antigen-induced arthritis (AIA).
  
  
  METHODS
  Arthritis was induced by intraarticular injection of methylated bovine serum albumin (mBSA) in preimmunized PAR-1-deficient (PAR-1(-/-)) and wild-type (WT) mice. The disease was assessed after 7 days by histologic examination of knee joints after decalcification and Safranin O/toluidine blue staining. Serum levels of anti-mBSA IgG, interferon-gamma, and interleukin-4 (IL-4) were determined by enzyme-linked immunosorbent assay. T cell proliferation response was determined by measuring the incorporation of (3)H-thymidine. Cytokine messenger RNA (mRNA) expression was detected in synovial tissues and peritoneal cells by real-time polymerase chain reaction.
  
  
  RESULTS
  Arthritis severity was significantly reduced in PAR-1(-/-) mice compared with WT mice (P = 0.017). Analysis of individual aspects of joint histology revealed significant reductions in synovial exudates (P < 0.001), cartilage degradation (P < 0.01), and bone damage (P = 0.05) in PAR-1(-/-) mice. Synovial IL-1, IL-6, and matrix metalloproteinase 13 (MMP-13) mRNA was significantly reduced in PAR-1(-/-) mice. The titers of antigen-specific serum anti-mBSA total IgG, IgG1, and IgG2a were significantly reduced, and serum IL-4 was significantly increased in arthritic PAR-1(-/-) mice. In contrast, no difference was observed in antigen-induced T cell proliferation between PAR-1(-/-) and WT mice. In vitro, thrombin-induced (but not lipopolysaccharide-induced) IL-1, IL-6, and MMP-13 mRNA expression was significantly impaired in PAR-1(-/-) mice compared with WT controls.
  
  
  CONCLUSIONS
  These data demonstrate the requirement of PAR-1 for the expression of AIA, the development of an antigen-specific Ig response, thrombin-induced macrophage cytokine and MMP expression, and the inhibitory effect of PAR-1 on serum IL-4. We conclude that PAR-1 plays a significant role in this model of arthritis.
authors.affiliation: Monash Medical Centre, Clayton, Victoria, Australia.
authors.forename: Yuan H
authors.initials: YH
authors.lastname: Yang
authors.forename: Pam
authors.initials: P
authors.lastname: Hall
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Little
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Fosang
authors.forename: Georgia
authors.initials: G
authors.lastname: Milenkovski
authors.forename: Leilani
authors.initials: L
authors.lastname: Santos
authors.forename: Jin
authors.initials: J
authors.lastname: Xue
authors.forename: Peter
authors.initials: P
authors.lastname: Tipping
authors.forename: Eric F
authors.initials: EF
authors.lastname: Morand
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000235:genetics* / Q000276:immunology / Q000473:pathology*; D049109:Cell Proliferation; D004195:Disease Models, Animal; D006614:Hindlimb; D007074:Immunoglobulin G / Q000097:blood; D007371:Interferon-gamma / Q000097:blood; D015847:Interleukin-4 / Q000097:blood; D007596:Joints / Q000276:immunology / Q000473:pathology*; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000276:immunology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000378:metabolism; D044463:Receptor, PAR-1 / Q000172:deficiency* / Q000235:genetics* / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012710:Serum Albumin, Bovine / Q000276:immunology; D013583:Synovial Membrane / Q000378:metabolism / Q000473:pathology; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology
chemical_list: D007074:Immunoglobulin G; D012333:RNA, Messenger; D044463:Receptor, PAR-1; D015847:Interleukin-4; D012710:Serum Albumin, Bovine; D007371:Interferon-gamma