title: Annexin I and dexamethasone effects on phospholipase and cyclooxygenase activity in human synoviocytes.
abstract: Annexin I is a glucocorticoid-induced mediator with anti-inflammatory activity in animal models of arthritis. We studied the effects of a bioactive annexin I peptide, ac 2-26, dexamethasone (DEX), and interleukin-1beta (IL-1beta) on phospholipase A2 (PLA2) and cyclooxygenase (COX) activities and prostaglandin E2 (PGE2) release in cultured human fibroblast-like synoviocytes (FLS). Annexin I binding sites on human osteoarthritic (OA) FLS were detected by ligand binding flow cytometry. PLA2 activity was measured using 3H-arachidonic acid release, PGE2 release and COX activity by ELISA, and COX2 content by flow cytometry. Annexin I binding sites were present on human OA FLS. Annexin I peptide ac 2-26 exerted a significant concentration-dependent inhibition of FLS constitutive PLA2 activity, which was reversed by IL-1beta. In contrast, DEX inhibited IL-1beta-induced PLA2 activity but not constitutive activity. DEX but not annexin I peptide inhibited IL-1beta-induced PGE2 release. COX activity and COX2 expression were significantly increased by IL-1beta. Annexin I peptide demonstrated no inhibition of constitutive or IL-1beta-induced COX activity. DEX exerted a concentration-dependent inhibition of IL-1beta-induced but not constitutive COX activity. Uncoupling of inhibition of PLA2 and COX by annexin I and DEX support the hypothesis that COX is rate-limiting for PGE2 synthesis in FLS. The effect of annexin I but not DEX on constitutive PLA2 activity suggests a glucocorticoid-independent role for annexin I in autoregulation of arachidonic acid production. The lack of effect of annexin I on cytokine-induced PGE2 production suggests PGE2-independent mechanisms for the anti-inflammatory effects of annexin I in vivo.
authors.affiliation: Monash Centre for Inflammatory Diseases, Monash University Department of Medicine, Monash Medical Centre, Clayton, Melbourne, Australia.
authors.forename: A V
authors.initials: AV
authors.lastname: Sampey
authors.forename: P
authors.initials: P
authors.lastname: Hutchinson
authors.forename: E F
authors.initials: EF
authors.lastname: Morand
mesh_terms: D000818:Animals; D017305:Annexin A1 / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D003907:Dexamethasone / Q000494:pharmacology*; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D007375:Interleukin-1 / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins; D010003:Osteoarthritis / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D013583:Synovial Membrane / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D017305:Annexin A1; D018836:Inflammation Mediators; D007375:Interleukin-1; D007527:Isoenzymes; D008565:Membrane Proteins; D003907:Dexamethasone; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054467:Phospholipases A2