title: Role of lipocortin-1 in the anti-hyperalgesic actions of dexamethasone.
abstract: 1. The effect of dexamethasone, lipocorton-1(2-26) and an antiserum to lipocortin-1(2-26) (LCPS1) upon the hyperalgesic activities in rats of carrageenin, bradykinin, tumour necrosis factor alpha (TNF alpha), interleukin-1(2), interleukin-6 (IL-6), interleukin-8 (IL-8), prostaglandin E beta (PGE2) and dopamine were investigated in a model of mechanical hyperalgesia. 2. Hyperalgesic responses to intraplantar (i.pl.) injections of carrageenin (100 micrograms), bradykinin (500 ng), TNF alpha (2.5 pg), IL-1 beta (0.5 pg), and IL-6 (1.0 ng), but not responses to IL-8 (0.1 ng), PGE2 (100 ng) and dopamine (10 micrograms), were inhibited by pretreatment with dexamethasone (0.5 mg kg-1, subcutaneously, s.c., or 0.04-5.0 micrograms/paw). 3. Inhibition of hyperalgesic responses to injections (i.pl.) of bradykinin (500 ng) and IL-1 beta (0.5 pg) by dexamethasone (0.5 mg kg-1, s.c.) was reversed by LCPS1 (0.5 ml kg-1, injected s.c., 24 h and 1 h before hyperalgesic substances) and hyperalgesic responses to injections (i.pl.) of bradykinin (500 ng), TNF alpha (2.5 pg) and IL-1 beta (0.5 pg), but not responses to PGE2 (100 ng), were inhibited by pretreatment with lipocortin-1(2-26) (100 micrograms/paw). Also, lipocortin-1(2-26) (30 and 100 micrograms ml-1 and dexamethasone (10 micrograms ml-1) inhibited TNF alpha release by cells of the J774 (murine macrophage-like) cell-line stimulated with LPS (3 micrograms ml-1), and LCPS1 partially reversed the inhibition by dexamethasone. These data are consistent with an important role for endogenous lipocortin-1(2-26) in mediating the anti-hyperalgesic effect of dexamethasone, with inhibiton of TNF alpha production by lipocortin-1(2-26) contributing, in part, to this role. 4. Although arachidonic acid by itself was not hyperalgesic, the hyperalgesic response to IL-1 beta (0.25 pg, i.pl.) was potentiated by arachidonic acid (50 micrograms) and the potentiated response was inhibited by dexamethasone (50 micrograms, i.pl.) and lipocortin-1(2-26) (100 micrograms, i.pl.). Also, lipocortin-1(2-26) (30 and 100 micrograms ml-1) inhibited/abolished PGE2 release by J774 cells stimulated with LPS (3 micrograms ml-1). These data suggest that, in inflammatory hyperalgesia, inhibition of the induction of cyclo-oxygenase 2 (COX-2), rather than phospholipase A2, by dexamethasone and lipocortin-1(2-26) accounts for the anti-hyperalgesic effects of these agents. 5. The above data support the notion that induction of lipocortin by dexamethasone plays a major role in the inhibition by dexamethasone of inflammatory hyperalgesia evoked by carrageenin, bradykinin and the cytokines TNF alpha, IL-1 beta and IL-6, and provides additional evidence that the biological activity of lipocortin resides within the peptide lipocortin-1(2-26). Further, the data suggest that inhibition of lipocortin-1(2-26) of eicosanoid production by COX-2 also contributes to the anti-hyperalgesic effect of lipocortin-1.
authors.affiliation: Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
authors.forename: S H
authors.initials: SH
authors.lastname: Ferreira
authors.forename: F Q
authors.initials: FQ
authors.lastname: Cunha
authors.forename: B B
authors.initials: BB
authors.lastname: Lorenzetti
authors.forename: M A
authors.initials: MA
authors.lastname: Michelin
authors.forename: M
authors.initials: M
authors.lastname: Perretti
authors.forename: R J
authors.initials: RJ
authors.lastname: Flower
authors.forename: S
authors.initials: S
authors.lastname: Poole
mesh_terms: D000818:Animals; D017305:Annexin A1 / Q000276:immunology / Q000502:physiology*; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use*; D000906:Antibodies / Q000276:immunology; D002460:Cell Line; D003907:Dexamethasone / Q000627:therapeutic use*; D015232:Dinoprostone / Q000096:biosynthesis; D006801:Humans; D006930:Hyperalgesia / Q000139:chemically induced / Q000188:drug therapy*; D008070:Lipopolysaccharides; D008264:Macrophages; D008297:Male; D051379:Mice; D009619:Nociceptors / Q000187:drug effects; D010147:Pain Measurement / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D017305:Annexin A1; D000893:Anti-Inflammatory Agents; D000906:Antibodies; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone; D015232:Dinoprostone