title: Antiinflammatory effect of lipocortin 1 in experimental arthritis.
abstract: The glucocorticoid-induced antiinflammatory protein lipocortin 1 is present in arthritic synovium but its ability to regulate joint inflammation has not previously been studied. We investigated the role of lipocortin 1 in the antiinflammatory activity of glucocorticoids in an acute arthritis model induced by intraarticular injection of carrageenan. Compared to control joints (0.09 +/- 0.08 x 10(6) synovial fluid cell count), carrageenan injected joints exhibited marked infiltration of PMN (10.2 +/- 0.7 x 10(6), p < 0.001). Both intraperitoneal (1.0 mg/kg) and intraarticular administration (5 micrograms) of dexamethasone (DEX) significantly suppressed arthritis severity (p < 0.001 and 0.005, respectively), and the effects of DEX were significantly prevented by intra-articular injection of antilipocortin 1 mAb (p < 0.05). Carrageenan arthritis was also significantly inhibited by intraarticular administration of the N-terminal lipocortin 1 peptide Ac2-26 at doses of 1 or 2 mg/kg (p < 0.01). Intraarticular injection antilipocortin 1 mAb in the absence of DEX also significantly exacerbated arthritis severity (p < 0.005). In vitro treatment of PMN with DEX was associated with significant inhibition of phagocytosis (p < 0.005) and reactive oxygen species (ROS) generation (p < 0.001). Antilipocortin 1 mAb significantly reduced the inhibitory effects of DEX (p < 0.01 and 0.005, respectively). These results demonstrate that lipocortin 1 mediates the effects of exogenous glucocorticoids on neutrophil migration in carrageenan-induced acute arthritis, exerts an endogenous antiinflammatory influence, and mediates glucocorticoid inhibition of neutrophil activation.
authors.affiliation: Centre for Inflammatory Diseases, Monash University Department of Medicine, Monash Medical Centre, Clayton, Melbourne, Australia.
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
authors.forename: M
authors.initials: M
authors.lastname: Leech
authors.forename: P
authors.initials: P
authors.lastname: Hutchinson
authors.forename: S R
authors.initials: SR
authors.lastname: Holdsworth
authors.forename: E F
authors.initials: EF
authors.lastname: Morand
mesh_terms: D000818:Animals; D017305:Annexin A1 / Q000627:therapeutic use*; D001168:Arthritis / Q000139:chemically induced / Q000188:drug therapy* / Q000503:physiopathology; D002351:Carrageenan / Q000008:administration & dosage; D004195:Disease Models, Animal; D005079:Excipients / Q000008:administration & dosage; D007249:Inflammation / Q000188:drug therapy; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D017305:Annexin A1; D005079:Excipients; D002351:Carrageenan