thromboxane-b2 and verlukast

In this study we investigate: 1) the role of multidrug resistance protein-4 (MRP4), an organic anion unidirectional transporter, in modulating aspirin action on human platelet cyclooxygenase (COX)-1; and 2) whether the impairment of aspirin-COX-1 interaction, found in coronary artery bypass grafting (CABG) patients, could be dependent on MRP4-mediated transport.. Platelets of CABG patients present a reduced sensitivity to aspirin despite in vivo and in vitro drug treatment. Aspirin is an organic anion and could be a substrate for MRP4.. Intracellular aspirin concentration and drug COX-1 activity, measured by thrombin-induced thromboxane B2 (TxB2) production, were evaluated in platelets obtained from healthy volunteers (HV) and hematopoietic-progenitor cell cultures reducing or not reducing MRP4-mediated transport. Platelet MRP4 expression was evaluated, in platelets from HV and CABG patients, by dot-blot or by immunogold-electromicrographs or immunofluorescence-microscopy analysis.. Inhibition of MRP4-mediated transport by dipyridamole or Mk-571 increases aspirin entrapment and its in vitro effect on COX-1 activity (142.7 ± 34.6 pg/10(8) cells vs. 343.7 ± 169.3 pg/10⁸ cells TxB2-production). Platelets derived from megakaryocytes transfected with MRP4 small interfering ribonucleic acid have a higher aspirin entrapment and drug COX-1 activity. Platelets from CABG patients showed a high expression of MRP4 whose in vitro inhibition enhanced aspirin effect on COX-1 (349 ± 141 pg/10⁸ cells vs. 1,670 ± 646 pg/10⁸ cells TxB2-production).. Aspirin is a substrate for MRP4 and can be extruded from platelet through its transportation. Aspirin effect on COX-1 is little-related to MRP4-mediated aspirin transport in HV, but in CABG patients with MRP4 over-expression, its pharmacological inhibition enhances aspirin action in an efficient way.

Topics: Adult; Aspirin; Biological Transport; Blood Platelets; Cells, Cultured; Coronary Artery Bypass; Cyclic AMP; Cyclooxygenase 1; Dinoprostone; Drug Interactions; Drug Resistance; Female; Fibrinolytic Agents; Humans; Male; Middle Aged; Multidrug Resistance-Associated Proteins; Platelet Aggregation; Platelet Aggregation Inhibitors; Propionates; Prostaglandin-Endoperoxide Synthases; Quinolines; RNA, Small Interfering; Salicylic Acid; Thromboxane B2

This study investigated, in isolated human internal mammary artery, the involvement of the cyclooxygenase and the lipoxygenase pathways of arachidonic acid metabolism in the contraction induced by angiotensin II.. Rings of human internal mammary arteries were suspended in organ baths for recording of isometric tension. In addition, the release of eicosanoids in response to angiotensin II (0.3 microM) was measured by enzyme immunoassay.. In human arterial rings without endothelial dependent relaxation in response to substance P or acetylcholine, the angiotensin II-induced contractions were significantly (P<0.05) reduced by 27% in the presence of GR32191 0.3 microM (thromboxane A(2) (TXA(2)) receptor antagonist) but remained unchanged in the presence of dazoxiben 100 microM (thromboxane synthase inhibitor). In addition, angiotensin II failed to modify TXB(2) and 6-keto-PGF(1alpha) production. These results suggest the contribution of a TXA(2)/PGH(2) agonist other than TXA(2) in angiotensin II-induced contractions. However, indomethacin increased (P<0.05) angiotensin II-mediated contractile response and cysteinyl leukotriene production, suggesting a redirection of arachidonic acid metabolism from the cyclooxygenase pathway to the lipoxygenase pathway. Indeed, the contractions induced by angiotensin II were inhibited (P<0.05) by phenidone 100 microM (cyclooxygenase and lipoxygenase inhibitor), baicalein 100 microM (5-, 12- and 15-lipoxygenases inhibitor), AA861 10 microM (5-lipoxygenase inhibitor) and MK571 1 microM (CysLT(1) receptor antagonist). Cysteinyl leukotrienes were released in response to angiotensin II (pg/mg dry weight tissue: 32+/-9 (basal, n=6) vs. 49+/-9 (angiotensin II 0.3 microM, n=6), P<0.05). LTD(4), and at a lesser degree LTC(4), induced contractions of internal mammary artery and MK571 1 microM abolished the contraction to LTD(4).. This study suggests that the in vitro vasoconstrictor effects of angiotensin II in human internal mammary artery are enhanced at least in part by eicosanoids produced by the cyclooxygenase pathway, probably PGH(2), acting on TXA(2)/PGH(2) receptors, and by lipoxygenase-derived products, particularly cysteinyl leukotrienes acting on CysLT(1) receptors.

Topics: 6-Ketoprostaglandin F1 alpha; Acetylcholine; Angiotensin II; Benzoquinones; Biphenyl Compounds; Cyclooxygenase Inhibitors; Depression, Chemical; Dose-Response Relationship, Drug; Enzyme Inhibitors; Flavanones; Flavonoids; Heptanoic Acids; Humans; Imidazoles; In Vitro Techniques; Indomethacin; Leukotrienes; Lipoxygenase Inhibitors; Mammary Arteries; Propionates; Pyrazoles; Quinolines; Receptors, Thromboxane; Substance P; Thromboxane B2; Thromboxane-A Synthase; Vasoconstriction

To determine the role of inflammatory products of phospholipid metabolism in acute otitis media (AOM), we infected 128 chinchillas with Streptococcus pneumoniae and randomly assigned them to one of four equal-sized treatment groups receiving intramuscular ampicillin sodium (control) or intramuscular ampicillin plus receptor blockers of platelet activating factor (WEB 2086, 5 mg/d orally), of leukotriene (MK 571, 0.5 mg/d orally), or of thromboxaneA2 (GR 32191B, 5 mg/d orally). All treatments were begun on day 2 postinoculation and continued for 10 days. On days 3, 6, 9, and 12, 8 animals from each group were sacrificed. Effusions were recovered for biochemical assay, and the right middle ears were prepared for histologic study. Differences among groups in the number of ears with effusion or in effusion volume were not statistically significant. In comparison to the control group, mucosal thickness and the number of ears with histopathologic signs of inflammation were significantly less in the GR and WEB treatment groups, but not the MK group. Also, effusion concentrations of free fatty acids, protease, and hydrolytic enzymes were significantly less in those groups. These results show that the addition of a receptor blocker for either platelet activating factor and/or thromboxane to ampicillin in the treatment of AOM reduces mucosal inflammation and decreases the production of other inflammatory chemicals. The failure of a receptor blocker of leukotrienes to moderate disease expression suggests either a less important role for these chemicals in AOM or an insufficient bioavailability of the specific MK 571 inhibitor. These results confirm that platelet activating factor and thromboxane are active mediators of inflammation in AOM.

Topics: 6-Ketoprostaglandin F1 alpha; Acute Disease; Animals; Azepines; Biphenyl Compounds; Chinchilla; Dinoprostone; Ear, Middle; Fatty Acids, Nonesterified; Heptanoic Acids; Hydrolases; Leukotriene Antagonists; Leukotriene C4; Mucous Membrane; Otitis Media; Phospholipids; Platelet Activating Factor; Platelet Membrane Glycoproteins; Pneumococcal Infections; Propionates; Quinolines; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Receptors, Thromboxane; Thromboxane B2; Triazoles

We studied the effects of two structurally unrelated sulfidopeptide leukotriene receptor antagonists on endotoxin-induced pulmonary dysfunction in chronically instrumented unanesthetized sheep. The agents employed were L-660,711 (MK-571) (Merck-Frosst, Canada) and SK&F 104,353 (Smith Kline and French, King of Prussia, PA). The efficacy and specificity of the agents were verified in sheep by administering boluses of exogenous leukotrienes (LTB4, LTC4, LTD4, and LTE4) in doses as great as 100 micrograms while monitoring lung mechanics and vascular pressures. The antagonists blocked the changes in lung mechanics and pulmonary hemodynamics induced by the sulfidopeptide leukotrienes (LTC4, LTD4, and LTE4) while having no effect on the animals' responses to LTB4. The endotoxin studies were performed by administering endotoxin alone (Escherichia coli endotoxin 0.75 microgram/kg) or endotoxin after pretreatment with one of the sulfidopeptide leukotriene receptor antagonists. In control studies, each animal received a continuous infusion of one of the receptor antagonists for a duration identical to that of the endotoxin studies. Neither L-660,711 nor SK&F 104,353 significantly altered the endotoxin-induced changes in pulmonary hemodynamics, lung mechanics, lung fluid and solute exchange, oxygenation, or leukopenia. Peak lung lymph thromboxane B2 levels were significantly lower in sheep pretreated with L-660,711. When the antagonists were given alone, no effects were seen. We conclude that (1) sulfidopeptide leukotrienes do not measurably contribute to endotoxin-induced pulmonary dysfunction in chronically instrumented sheep; (2) sulfidopeptide leukotrienes may contribute to thromboxane release after endotoxin.

Topics: Animals; Consciousness; Dicarboxylic Acids; Endotoxins; Escherichia coli; Female; Lymph; Male; Propionates; Pulmonary Circulation; Quinolines; Respiratory Distress Syndrome; Respiratory Mechanics; Sheep; SRS-A; Thromboxane B2