title: Protease-activated receptor 2, rather than protease-activated receptor 1, contributes to the aggressive properties of synovial fibroblasts in rheumatoid arthritis.
abstract: OBJECTIVE
  To investigate whether protease-activated receptor 1 (PAR-1) and/or PAR-2 promotes the invasiveness/proliferation of synovial fibroblasts (SFs) and to determine the signaling mechanisms of these pathways.
  
  
  METHODS
  SFs were isolated from the synovial tissue of patients with rheumatoid arthritis (RA), patients with osteoarthritis (OA), and PAR-1- or PAR-2-knockout (KO) mice. Expression of PAR-1 and PAR-2 was detected by immunofluorescence and Western blotting. The invasion and proliferation of SFs were measured by invasion assay and MTT assay, respectively. Matrix metalloproteinase 2 (MMP-2) and MMP-9 were detected by zymography, and cytokines were measured by enzyme-linked immunosorbent assay.
  
  
  RESULTS
  PAR-1 and PAR-2 were colocalized with SFs in RA and OA synovium and, to a considerably lesser extent, in normal synovium. Inhibition of PAR-2 by small interfering RNA (siRNA) inhibited RASF invasion and proliferation, whereas blocking of PAR-1 by siRNA had the reverse effects. SFs from PAR-2-KO mice exhibited slower rates of proliferation and invasion. SFs from PAR-1-KO mice produced less MMP-2 and, in response to tumor necrosis factor α (TNFα) stimulation, had increased MMP-9 secretion when compared to SFs from wild-type and PAR-2-KO mice. Inhibition of PAR-1, but not PAR-2, stimulated the secretion of interleukin-17 (IL-17) and TNFα by RASFs. Furthermore, PAR-1 and PAR-2 had opposing effects on the activation of ERK, p38, and NF-κB.
  
  
  CONCLUSIONS
  Activation of PAR-1 stimulates MMP-2 secretion, inhibits RASF growth and invasion, and decreases production of IL-17 and TNFα by RASFs, whereas activation of PAR-2 stimulates RASF growth and invasion and increases production of TNFα. Thus, although PAR-1 and PAR-2 are coexpressed by RASFs, PAR-2 alone appears to be responsible for the aggressive properties of RASFs and is likely to contribute to the pathologic progression of RA.
authors: Kolling Institute of Medical Research and University of Sydney at Royal North Shore Hospital, St. Leonards, New South Wales, Australia. meilang.xue@sydney.edu.au
authors: Meilang
authors: M
authors: Xue
authors: Yee-Ka Agnes
authors: YK
authors: Chan
authors: Kaitlin
authors: K
authors: Shen
authors: Suat
authors: S
authors: Dervish
authors: Lyn
authors: L
authors: March
authors: Philip N
authors: PN
authors: Sambrook
authors: Christopher J
authors: CJ
authors: Jackson
mesh_terms: D000368:Aged; D000818:Animals; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002465:Cell Movement; D049109:Cell Proliferation; D002470:Cell Survival; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005562:Formazans / Q000378:metabolism; D006801:Humans; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010003:Osteoarthritis; D020370:Osteoarthritis, Knee / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D044463:Receptor, PAR-1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D013778:Tetrazolium Salts / Q000378:metabolism; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
chemical_list: D005562:Formazans; D034741:RNA, Small Interfering; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D013778:Tetrazolium Salts; D014409:Tumor Necrosis Factor-alpha; C079782:MTT formazan; D020780:Matrix Metalloproteinase 9