title: Therapeutic promise of proteinase-activated receptor-2 antagonism in joint inflammation.
abstract: Biological therapies such as tumor necrosis factor-alpha inhibitors have advanced the treatment of rheumatoid arthritis, but one-third of patients do not respond to such therapy. Furthermore, these inhibitors are now usually administered in combination with conventional disease-modifying antirheumatic drugs, suggesting they have not achieved their early promise. This study investigates a novel therapeutic target, proteinase-activated receptor (PAR)-2, in joint inflammation. Intra-articular carrageenan/kaolin (C/K) injection in mice resulted in joint swelling that was associated with synovial PAR2 up-regulation. Inhibiting receptor up-regulation using small interfering RNA technology, as confirmed by immunoblotting, substantially reduced the inflammatory response in the joint. Serine proteinase-induced joint swelling was mediated primarily via PAR2 activation, since the response to exogenous application of trypsin and tryptase was absent in PAR2 knockout mice. Furthermore, serine proteinase inhibitors were effective anti-inflammatory agents in this model. Disrupting proteolytic activation of PAR2 using antiserum (B5) directed to the receptor cleavage/activation site also attenuated C/K-induced inflammation, as did the similarly targeted PAR2 monoclonal antibody SAM-11. Finally, we report the activity of a novel small molecule PAR2 antagonist, N1-3-methylbutyryl-N4-6-aminohexanoyl-piperazine (ENMD-1068), that dose dependently attenuated joint inflammation. Our findings represent a major advance in collectively identifying PAR2 as a novel target for the future treatment of arthritis.
authors.affiliation: Center for Rheumatic Diseases, Royal Infirmary, Glasgow, Scotland, United Kingdom.
authors.forename: Elizabeth B
authors.initials: EB
authors.lastname: Kelso
authors.forename: John C
authors.initials: JC
authors.lastname: Lockhart
authors.forename: Todd
authors.initials: T
authors.lastname: Hembrough
authors.forename: Lynette
authors.initials: L
authors.lastname: Dunning
authors.forename: Robin
authors.initials: R
authors.lastname: Plevin
authors.forename: Morley D
authors.initials: MD
authors.lastname: Hollenberg
authors.forename: Christian P
authors.initials: CP
authors.lastname: Sommerhoff
authors.forename: John S
authors.initials: JS
authors.lastname: McLean
authors.forename: William R
authors.initials: WR
authors.lastname: Ferrell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use*; D001168:Arthritis / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D010879:Piperazines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D044464:Receptor, PAR-2 / Q000037:antagonists & inhibitors*
chemical_list: C518710:1-3-methylbutyryl-N4-6-aminohexanoyl-piperazine; D000893:Anti-Inflammatory Agents; D010879:Piperazines; D034741:RNA, Small Interfering; D044464:Receptor, PAR-2