title: Neutrophil elastase induces inflammation and pain in mouse knee joints via activation of proteinase-activated receptor-2.
abstract: OBJECTIVE
  Neutrophil elastase plays a crucial role in arthritis. Here, its potential in triggering joint inflammation and pain was assessed, and whether these effects were mediated by proteinase-activated receptor-2 (PAR2).
  
  
  METHODS
  Neutrophil elastase (5 μg) was injected into the knee joints of mice and changes in blood perfusion, leukocyte kinetics and paw withdrawal threshold were assessed. Similar experiments were performed in animals pretreated with the neutrophil elastase inhibitor sivelestat, the PAR2 antagonist GB83, the p44/42 MAPK inhibitor U0126 and in PAR2 receptor knockout (KO) mice. Neutrophil elastase activity was also evaluated in arthritic joints by fluorescent imaging and sivelestat was assessed for anti-inflammatory and analgesic properties.
  
  
  RESULTS
  Intra-articular injection of neutrophil elastase caused an increase in blood perfusion, leukocyte kinetics and a decrease in paw withdrawal threshold. Sivelestat treatment suppressed this effect. The PAR2 antagonist GB83 reversed neutrophil elastase-induced synovitis and pain and these responses were also attenuated in PAR2 KO mice. The MAPK inhibitor U0126 also blocked neutrophil elastase-induced inflammation and pain. Active neutrophil elastase was increased in acutely inflamed knees as shown by an activatable fluorescent probe. Sivelestat appeared to reduce neutrophil elastase activity, but had only a moderate anti-inflammatory effect in this model.
  
  
  CONCLUSIONS
  Neutrophil elastase induced acute inflammation and pain in knee joints of mice. These changes are PAR2-dependent and appear to involve activation of a p44/42 MAPK pathway. Blocking neutrophil elastase, PAR2 and p44/42 MAPK activity can reduce inflammation and pain, suggesting their utility as therapeutic targets.
authors.affiliation: Department of Pharmacology, Dalhousie University, Halifax, NS, Canada.
authors.forename: Milind M
authors.initials: MM
authors.lastname: Muley
authors.affiliation: Department of Pharmacology, Dalhousie University, Halifax, NS, Canada.
authors.forename: Allison R
authors.initials: AR
authors.lastname: Reid
authors.affiliation: Department of Pharmacology and Pharmacotherapy, University of Pécs, School of Medicine, Pécs, Hungary.|János Szentágothai Research Centre, University of Pécs, Molecular Pharmacology Research Team, Pécs, Hungary.
authors.forename: Bálint
authors.initials: B
authors.lastname: Botz
authors.affiliation: Department of Pharmacology and Pharmacotherapy, University of Pécs, School of Medicine, Pécs, Hungary.|János Szentágothai Research Centre, University of Pécs, Molecular Pharmacology Research Team, Pécs, Hungary.
authors.forename: Kata
authors.initials: K
authors.lastname: Bölcskei
authors.affiliation: Department of Pharmacology and Pharmacotherapy, University of Pécs, School of Medicine, Pécs, Hungary.|MTA NAP B Pain Research Group, University of Pécs, School of Medicine, Pécs, Hungary.|János Szentágothai Research Centre, University of Pécs, Molecular Pharmacology Research Team, Pécs, Hungary.
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Helyes
authors.affiliation: Department of Pharmacology, Dalhousie University, Halifax, NS, Canada.|Department of Anaesthesia, Pain Management & Perioperative Medicine, Dalhousie University, Halifax, NS, Canada.
authors.forename: Jason J
authors.initials: JJ
authors.lastname: McDougall
mesh_terms: D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D007249:Inflammation / Q000378:metabolism; D007719:Knee Joint / Q000378:metabolism*; D019272:Leukocyte Elastase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009570:Nitriles / Q000494:pharmacology; D010146:Pain / Q000378:metabolism*; D044464:Receptor, PAR-2 / Q000172:deficiency / Q000378:metabolism*
chemical_list: D002070:Butadienes; D009570:Nitriles; D044464:Receptor, PAR-2; C113580:U 0126; D019272:Leukocyte Elastase