leukotriene-b4 and nimesulide

Inflammatory bowel disease (IBD) is a relapsing inflammation of intestine, which is mediated by release of inflammatory mediators. Both cyclo-oxygenase product prostaglandin (PGE2) and lipo-oxygenase product leukotriene (LTB4), may contribute to the pathogenesis of the inflammatory response. Nimesulide, a preferential COX-2 inhibitor was evaluated for its efficacy against experimental colitis in two different models (acetic acid- and LTB4-induced IBD) in rats. Inflammatory response was induced by intrarectal single administration of acetic acid or LTB4. Nimesulide (9 and 18 mg/kg, p.o.) significantly prevented development of inflammatory changes, decreased myeloperoxidase (MPO) activity, and also restored the altered contractility response of the isolated colon segment to KCl. The results suggested the involvement of both cyclo-oxygenase (COX) and lipo-oxygenase-mediated proinflammatory agents in colonic inflammatory process associated with IBD. Further, this study suggests that such therapeutic interventions may be of value in the treatment of IBD.

Topics: Acetic Acid; Animals; Anti-Inflammatory Agents, Non-Steroidal; Colon; Cyclooxygenase Inhibitors; Inflammatory Bowel Diseases; Leukotriene B4; Peroxidase; Rats; Rats, Wistar; Sulfasalazine; Sulfonamides

Clinical and experimental findings had indicated that cigarette smoke exposure, and cyclooxygenase-2, are strongly associated with inflammatory bowel disease. The present study aimed to evaluate the role of cyclooxygenase-2 in the pathogenesis of experimental inflammatory bowel disease as well as in the adverse action of cigarette-smoke exposure. Rats were pretreated with different cyclooxygenase-2 inhibitors (indomethacin, nimesulide, or SC-236 (4-[5-(4-chlorophenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide)) along with cigarette-smoke exposure before 2,4,6-trinitrobenzenesulfonic acid-enema. Results indicated that pretreatment with cyclooxygenase-2 inhibitors not only protected against 2,4,6-trinitrobenzenesulfonic acid-induced inflammatory bowel disease, but also attenuated the potentiating effect of cigarette-smoke exposure on colonic damage. Furthermore, the colonic cyclooxygenase-2 protein and mRNA expression was markedly induced by 2,4,6-trinitrobenzenesulfonic acid-enema, and it was potentiated further by cigarette-smoke exposure, while the cyclooxygenase-1 expression was not changed. The present study suggests that the highly induced cyclooxygenase-2 expression not only plays a pathogenic role in 2,4,6-trinitrobenzenesulfonic acid-induced inflammatory bowel disease, but also contributes to the adverse action of cigarette-smoke exposure on this disorder.

Topics: Animals; Blotting, Western; Colitis; Colon; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Gene Expression Regulation, Enzymologic; Indomethacin; Inflammation; Inflammatory Bowel Diseases; Isoenzymes; Leukotriene B4; Male; Membrane Proteins; Peroxidase; Prostaglandin-Endoperoxide Synthases; Prostaglandins; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sulfonamides; Tobacco Smoke Pollution; Trinitrobenzenesulfonic Acid

Nimesulide (CAS 51803-78-2) has been shown to exert a marked anti-inflammatory effect in several in vivo models of inflammation. Recent studies indicate that nimesulide not only inhibits prostaglandin synthesis in certain cell types, but also has pleiotropic effects on neutrophil functions, including the respiratory burst, integrin-mediated adherence and synthesis of platelet-activating factor (PAF). In the present study, the effect of nimesulide on PAF synthesis was compared with its effect on the production of leukotriene B4 (LTB4). Nimesulide dose-dependently inhibited both processes in neutrophils stimulated by serum-treated zymosan (STZ) with a comparable efficacy (IC50 values between 10 and 20 mumol/l). In formyl-methionyl-leucyl-phenylalanine-stimulated neutrophils (treated with cytochalasin B), these IC50 values were 30 and 50 mumol/l for PAF and LTB4 synthesis, respectively. These results indicate an inhibition by nimesulide of a common step in the release of these lipid mediators, i.e. the activation of phospholipase A2, possibly by elevating intracellular cAMP. In support of this latter hypothesis, it was observed that nimesulide increased the level of cAMP almost 3-fold after STZ stimulation, whereas in fMLP-stimulated neutrophils these changes in cAMP levels were more dramatic. Furthermore, the inhibitory effects of nimesulide on PAF and LTB4 production could largely be prevented by addition of H89, an inhibitor of cAMP-dependent protein kinase (PK-A). It is concluded that an increase in intracellular cAMP is instrumental in the observed effects of nimesulide on the release of PAF and LTB4 by activated neutrophils and that limited availability of arachidonic acid, also the substrate for the cyclooxygenase pathway, may very well contribute to the effects of nimesulide on prostaglandin synthesis observed in other cell types.

Topics: 1-Methyl-3-isobutylxanthine; Anti-Inflammatory Agents, Non-Steroidal; Arachidonic Acid; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cytochalasin B; Enzyme Inhibitors; Humans; In Vitro Techniques; Isoquinolines; Leukotriene B4; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Phosphodiesterase Inhibitors; Platelet Activating Factor; Protein Kinase Inhibitors; Sulfonamides; Zymosan