title: Proteinase-activated receptor (PAR)-2 activation impacts bone resorptive properties of human osteoarthritic subchondral bone osteoblasts.
abstract: BACKGROUND
  In osteoarthritis (OA), the subchondral bone undergoes a remodelling process involving several factors synthesized by osteoblasts. In this study, we investigated the expression, production, modulation, and role of PAR-2 in human OA subchondral bone osteoblasts.
  
  
  METHODS
  PAR-2 expression and production were determined by real-time PCR and flow cytometry, respectively. PAR-2 modulation was investigated in OA subchondral bone osteoblasts treated with IL-1 beta (100 pg/ml), TNF-alpha (5 ng/ml), TGF-beta1 (10 ng/ml), PGE(2) (500 nM), IL-6 (10 ng/ml) and IL-17 (10 ng/ml). Membranous RANKL protein was assessed by flow cytometry, and OPG, MMP-1, MMP-9, MMP-13, IL-6 and intracellular signalling pathways by specific ELISAs. Bone resorptive activity was measured by using a co-culture model of human PBMC and OA subchondral bone osteoblasts.
  
  
  RESULTS
  PAR-2 expression and production (p<0.05) were markedly increased when human OA subchondral bone osteoblasts were compared to normal. On OA osteoblasts, PAR-2 production was significantly increased by IL-1 beta, TNF-alpha and PGE(2). Activation of PAR-2 with a specific agonist, SLIGKV-NH(2), induced a significant up-regulation of MMP-1, MMP-9, IL-6, and membranous RANKL, but had no effect on MMP-13 or OPG production. Interestingly, bone resorptive activity was also significantly enhanced following PAR-2 activation. The PAR-2 effect was mediated by activation of the MAP kinases Erk1/2 and JNK.
  
  
  CONCLUSIONS
  This study is the first to demonstrate that PAR-2 activation plays a role in OA subchondral bone resorption via an up-regulation of major bone remodelling factors. These results shed new light on the potential of PAR-2 as a therapeutic target in OA.
authors.affiliation: Osteoarthritis Research Unit, University of Montreal Hospital Centre (CRCHUM), Notre-Dame Hospital, 1560 Sherbrooke Street East, Montreal, Quebec, Canada. amiablenathalie@hotmail.com
authors.forename: Nathalie
authors.initials: N
authors.lastname: Amiable
authors.forename: Steeve Kwan
authors.initials: SK
authors.lastname: Tat
authors.forename: Daniel
authors.initials: D
authors.lastname: Lajeunesse
authors.forename: Nicolas
authors.initials: N
authors.lastname: Duval
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Pelletier
authors.forename: Johanne
authors.initials: J
authors.lastname: Martel-Pelletier
authors.forename: Christelle
authors.initials: C
authors.lastname: Boileau
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001862:Bone Resorption / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D020381:Interleukin-17 / Q000494:pharmacology; D053583:Interleukin-1beta / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism* / Q000473:pathology; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D044464:Receptor, PAR-2 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D020381:Interleukin-17; D053583:Interleukin-1beta; D015850:Interleukin-6; D053245:RANK Ligand; D044464:Receptor, PAR-2; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D053509:Matrix Metalloproteinase 13; D020780:Matrix Metalloproteinase 9; D020781:Matrix Metalloproteinase 1; D015232:Dinoprostone