Evaluation of the pharmacological activity of the pure cysteinyl-leukotriene receptor antagonists CGP 45715A (iralukast) and CGP 57698 in human airways.
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Benzopyrans↗
Biomedical subjects
G C Folco
Publications and source records attributed to G C Folco.
Inhibition of prostanoid synthesis protects against neuronal damage induced by focal ischemia in rat brain.
Changes in prostanoids concentration and effects of the non-specific COX inhibitor indomethacin on prostanoids levels and extension of tissue damage were studied following focal ischemia induction in the fronto-parietal region of rat brain. Ischemia was induced in animals bearing a transcerebral microdialysis probe by injection of Rose Bengal, a photosensitive dye, followed by light activation. Prostanoid levels were determined in the dialysate using immunoenzymatic techniques. PGD2 levels rose significantly up to 237+/-22 pg/ml compared to a basal level measured before ischemia induction which was below the detection limit. TXB2 changes were smaller and had a different time course. Treatment with indomethacin abolished the ischemia-induced PGD2 release and reduced the extent of injury to the area by 43+/-3.7%. These results suggest that prostanoid release may play an important role in neurodegenerative processes and that cyclooxygenase inhibitors may contribute to protect against cerebral tissue damage.
Animals↗
Pharmacological characterization of the cysteinyl-leukotriene antagonists CGP 45715A (iralukast) and CGP 57698 in human airways in vitro.
1. Cysteinyl-leukotrienes (cysteinyl-LTs) are important mediators in the pathogenesis of asthma. They cause bronchoconstriction, mucus hypersecretion, increase in microvascular permeability, plasma extravasation and eosinophil recruitment. 2. We investigated the pharmacological profile of the cysteinyl-LT antagonists CGP 45715A (iralukast), a structural analogue of LTD4 and CGP 57698, a quinoline type antagonist, in human airways in vitro, by performing binding studies on human lung parenchyma membranes and functional studies on human isolated bronchial strips. 3. Competition curves vs [3H]-LTD4 on human lung parenchyma membranes demonstrated that: (a) both antagonists were able to compete for the two sites labelled by [3H]-LTD4; (b) as in all the G-protein coupled receptors, iralukast and CGP 57698 did not discriminate between the high and the low affinity states of the CysLT receptor labelled by LTD4 (Ki1=Ki2= 16.6 nM+/-36% CV and Ki1= Ki2 = 5.7 nM+/-19% CV, respectively); (c) iralukast, but not CGP 57698, displayed a slow binding kinetic, because preincubation (15 min) increased its antagonist potency. 4. In functional studies: (a) iralukast and CGP 57698 antagonized LTD4-induced contraction of human bronchi, with pA2 values of 7.77+/-4.3% CV and 8.51+/-1.6% CV, respectively, and slopes not significantly different from unity; (b) the maximal LTD4 response in the presence of CGP 57698 was actually increased, thus clearly deviating from apparent simple competition. 5. Both antagonists significantly inhibited antigen-induced contraction of human isolated bronchial strips in a concentration-dependent manner, lowering the upper plateau of the anti-IgE curves. 6. In conclusion, the results of the present in vitro investigation indicate that iralukast and CGP 57698 are potent antagonists of LTD4 in human airways, with affinities in the nanomolar range, similar to those obtained for ICI 204,219 and ONO 1078, two of the most clinically advanced CysLT receptor antagonists. Thus, these compounds might be useful drugs for the therapy of asthma and other allergic diseases.
Antigens↗
The polymorphonuclear leukocyte: a cell tuned for transcellular biosynthesis of cys-leukotrienes.
Sulfidopeptide leukotrienes (cysLT) are potent vasoactive mediators that can constrict coronary vessels and alter caliber of the microcirculation. They can be formed "in situ" via a peculiar type of cell communication termed "transcellular biosynthesis" whereby donor cells (polymorphonuclear leukocytes, PMNL) feed acceptor cells (endothelial cells, EC) the unstable epoxide intermediate leukotriene A4 for further metabolism to cysLT. We have investigated the relative amount of leukotriene A4 that is synthesized by PMNL and made available for transcellular biosynthesis. This has been accomplished by measuring the relative amounts of enzymatic vs non-enzymatic leukotriene A4-derived metabolites after challenge with the Ca(2+)-ionophore A23187, using PMNL suspensions at different concentrations. Non-enzymatic leukotriene A4-derived metabolites were used as a quantitative index of the amount of leukotriene A4 released into the extracellular milieu. In human, as well as in bovine PMNL, the relative amounts of non-enzymatic vs enzymatic leukotriene A4-derived metabolites increased with decreasing cell concentrations. By diminishing possible cell-cell interactions via increased dilution, it is calculated that approx. 60% of leukotriene A4 synthesized is released from the PMNL. These data provide evidence that, in PMNL, transfer of leukotriene A4 to neighbouring acceptor cells is taking place as a predominant mechanisms of cell communication.
Animals↗
Vasoconstriction to polymorphonuclear leukocytes in the isolated, perfused rabbit heart: inhibition by prostacyclin mimetics.
Perfusion of the isolated rabbit heart with 5 x 10(6) human polymorphonuclear leukocytes (PMNL), under recirculating conditions (50 ml) and challenge with A-23187 (0.5 mu M) increased coronary perfusion pressure (CPP) sixfold, accompanied by increased levels of sulfidopeptide leukotrienes (CY-SLT), which had previously shown to correlate linearly with the increase in CPP. Pretreatment (20 min) of isolated rabbit hearts with the prostacyclin (PGI(2)) analogue iloprost (3 nM) resulted in significant protection against the increase in CPP and in almost complete inhibition of 5-lipoxygenase (5-LO) product synthesis. Similarly, pretreatment of isolated rabbit heart with defibrotide (200 mu g/ml), a polydeoxyribonucleotide derivative known to inhibit PMNL activation and enhance PGI(2) production by heart endothelial cells, produced significant protection against the increase in CPP and almost complete inhibition of 5-LO product synthesis. Neither iloprost nor defibrotide affected the A-23187-induced arachidonic acid (AA) metabolism in isolated PMNL alone. Inhibition of rabbit cyclooxygenase by intravenous (i.v.) administration of lysine-acetylsalicylate (60 mg/kg) 2 h before the animals were killed significantly reduced the protection provided by defibrotide, with a parallel fivefold increase in sulfidopeptide LT levels, returning to values in the range observed in control hearts. Control of endogenous modulators of leukocyte-vascular wall interactions such as PGI(2) results in significant changes in sulfidopeptide LT production in an organ model of transcellular metabolism of LT A(4), suggesting a novel mechanism of action for cardioprotective drugs in myocardial ischemia.
Animals↗
Myocardial protection by the leukotriene synthesis inhibitor BAY X1005: importance of transcellular biosynthesis of cysteinyl-leukotrienes.
Perfusion of the isolated rabbit heart with 5 x 10(6) human polymorphonuclear leukocytes, under recirculating conditions (50 ml), and challenge with A-23187 (0.5 microM) caused an increase in coronary perfusion pressure (from a prechallenge value of 46 +/- 1.1 to 176.2 +/- 29.7 mm Hg, 30 min after challenge, n = 6-4), which was linearly correlated (P < .006) with formation of cysteinyl leukotrienes (29.7 +/- 7.3 pmol/ml, 30 min after challenge). Pretreatment with the leukotriene synthesis inhibitor BAY X1005 (1 microM) (n = 6) resulted in significant protection against the increase in coronary perfusion pressure (76.7 +/- 12.8 mm Hg, 30 min after challenge) and in almost complete inhibition of sulfidopeptide leukotriene synthesis (3.2 +/- 1.7 pmol/ml, 30 min after challenge). In in vivo experiments, ligation of the left anterior descending coronary artery in the rabbit (n = 10) resulted in acute myocardial infarction marked by a mortality rate of 60% compared with sham-operated animals (n = 10). Intravenous treatment of the rabbits with BAY X1005 (10 mg/kg/h, for 2 h) (n = 10) markedly reduced the mortality rate (20%), protected the rabbits against the marked electrocardiogram derangement and abolished the significant increase in plasma creatine phosphokinase activity and cardiac tissue myeloperoxidase activity induced by coronary artery ligation. BAY X1005 exerts a significant cardioprotection and suggests that specific leukotriene synthesis inhibitors may lead to innovative therapy in myocardial ischemia.
Animals↗
Inhaled PGE2 prevents aspirin-induced bronchoconstriction and urinary LTE4 excretion in aspirin-sensitive asthma.
Bronchial overproduction of leukotrienes and inhibition of prostaglandin synthesis are involved in the pathogenesis of aspirin-induced asthma. We investigated whether inhaled prostaglandin E2 (PGE2) attenuates the response to bronchial challenge with lysine acetylsalicylate (LASA) and the associated increase in urinary leukotriene E4 (u-LTE4) in seven aspirin-sensitive subjects with asthma. Each subject performed two challenges with a single dose of LASA that caused a decrease in FEV1 of 20% or more in a preliminary test, immediately after inhaling 100 micrograms PGE2 in 4 ml saline or placebo, according to a randomized double-blind protocol. FEV1 was recorded at 30-min intervals for 4 h. u-LTE4 was measured by combined high-performance liquid chromatography enzyme immunoassay at 2-h intervals. After placebo, LASA caused an obstructive reaction in all patients, with a maximum decrease in FEV1 of 35 +/- 5% with respect to baseline. u-LTE4 rose from 911 +/- 261 picograms (pg)/mg creatinine at baseline to a maximum value of 2249 +/- 748 after challenge. Inhaled PGE2 provided almost complete protection in all patients. Baseline u-LTE4 was 883 +/- 243 pg/mg creatinine and did not change significantly during the test, reaching a maximum value of 864 +/- 290 (p < 0.05 versus placebo). These results confirm that PGE2 is highly effective in preventing aspirin-induced asthma and suggest that this effect is mediated by inhibition of sulfidopeptide leukotriene production.
Administration, Inhalation↗
New NSAIDs and gastroduodenal damage.
Two isoforms of cyclooxygenase (COX) are described: COX-1 is a constitutive enzyme and is widely expressed in most tissues, COX-2 is an inducible enzyme and is abundant throughout the gastrointestinal tract. Expression of COX-2 can be induced locally by inflammatory stimuli and appears coincident with local prostaglandin (PG) production. Currently available non-steroidal antiinflammatory drugs (NSAIDs) are widely used for the treatment of inflammatory diseases; however, significant side-effects due to inhibition of COX-1 limit their use. Inhibitors of COX-2 are as active as non-selective NSAIDs and inhibit PG synthesis in inflammatory cells. In contrast to other NSAIDs, selective COX-2 inhibitors do not cause ulcers in the stomach or intestine.
Animals↗
A new class of furoxan derivatives as NO donors: mechanism of action and biological activity.
1. The mechanism of action and biological activity of a series of R-substituted and di-R-substituted phenylfuroxans is reported. 2. Maximal potency as vasodilators on rabbit aortic rings, precontracted with noradrenaline (1 microM), was shown by phenyl-cyano isomers and by the 3,4-dicyanofuroxan, characterized by a potency ratio 3-10 fold higher than glyceryl trinitrate (GTN). This effect was reduced upon coincubation with methylene blue or oxyhaemoglobin (10 microM). 3. The furoxan derivatives showing maximal potency as vasodilators were also able to inhibit collagen-induced platelet aggregation, with IC50 values in the sub-micromolar range. 4. The furoxan derivatives were able to stimulate partially purified, rat lung soluble guanylate cyclase; among the most active compounds, the 3-R-substituted isomers displayed a higher level of stimulatory effect than the 4-R analogues. 5. Solutions (0.1 mM) of all the tested furoxans, prepared using 50 mM phosphate buffer, pH 7.4, (diluting 10 mM DMSO stock solutions) did not release nitric oxide (NO) spontaneously; however in presence of 5 mM L-cysteine, a significant NO-releasing capacity was observed, which correlated significantly with their stimulation of the guanylate cyclase activity.
Animals↗
Effect of SCH 37224 on anti-IgE-induced formation of sulfidopeptide leukotrienes in human lung parenchyma.
SCH 37224, 1-(1,2-dihydro-4-hydroxy-2-oxo-1-phenyl-1,8-naphthyridin-3-yl) pyrrolidinium, is a structurally novel compound that had been shown to inhibit leukotriene D4 formation in guinea pig lung in vitro. We tested whether SCH 37224 is able to inhibit both the formation of eicosanoids from human lung parenchyma in vitro and the binding of sulfidopeptide leukotrienes to membranes of lung parenchyma and bronchi. SCH 37224, at a concentration of 30 and 100 microM, was able to inhibit antigen-induced formation of sulfidopeptide leukotrienes, measured as leukotriene E4, while it did not significantly affect the formation of prostaglandin D2. At concentrations up to 100 microM, it did not affect either the binding of [3H]leukotriene C4 to membranes of human lung parenchyma or human bronchi, or the binding of [3H]leukotriene D4 to the parenchyma. In conclusion, SCH 37224 is a selective inhibitor of leukotriene formation in human lung in vitro, which might be of potential therapeutic interest in the treatment of asthma.
Eicosanoids↗
Eicosanoids in allergic reactions: quantitative determination by enzyme immunoassay.
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Chromatography, High Pressure Liquid↗
Modulation of arachidonic acid metabolism by orally administered morniflumate in man.
Unlike other classic NSAIDs, some fenamates given at therapeutic concentrations, have been shown to inhibit, both in vitro and in vivo, the 5-lipoxygenase pathway of arachidonic acid cascade as well as the synthesis of cyclooxygenase products. This dual inhibitory property might represent an improvement in anti-inflammatory therapy. The aim of this work was to characterize the effect of morniflumate, administered at therapeutic dosages to normal human volunteers, on leukotriene B4 (LTB4) and thromboxane (TXB2) synthesis, both in purified PMNs and in whole blood. PMNs, isolated two hours after a single oral administration of morniflumate and at steady-state condition, fully retain their capacity to release LTB4 and TXB2. Since intracellular concentrations of the drug were undetectable, in spite of its elevated concentrations in platelet poor plasma, the results obtained using PMNs suggest a drug loss during the cells purification procedure. In whole blood experiments, morniflumate reduced blood LTB4 synthesis induced by Ca-ionophore A23187 Bx approximately 50%, both after single dose and at steady state; the degree of inhibition showed a pattern similar to the plasma levels of the bioactive metabolite of morniflumate (M1). The inhibition of serum TXB2 levels was higher than 85%. Hence, morniflumate is capable of reducing arachidonic acid metabolism acting both on cyclooxygenase and 5-lipoxygenase. This characteristic might provide a better approach in anti-inflammatory therapy.
Administration, Oral↗
Metabolism of arachidonic acid in human alveolar macrophages from patients with sarcoidosis.
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Adult↗
Arachidonic acid and bradykinin share a common pathway to release neuropeptide from capsaicin-sensitive sensory nerve fibers of the guinea pig heart.
The ability of arachidonic acid (AA) and bradykinin to release calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) from capsaicin-sensitive primary afferents was studied in guinea pig isolated and perfused heart. Infusion of AA (50 microM to 5 mM, 0.5 ml/min over 2 min) produced a remarkable and dose-dependent CGRP-LI release that was abolished by in vitro capsaicin (10 microM) pretreatment or in the presence of indomethacin (10 microM). The capsaicin antagonist ruthenium red (10 microM) did not affect the CGRP-LI release produced by AA, whereas it blocked that produced by capsaicin (10 microM). In vitro capsaicin pretreatment reduced the increase in heart rate evoked by AA, whereas it did not affect the increase in coronary flow and decrease in contractility. Bradykinin (10 microM, 0.5 ml/min over 2 min) induced CGRP-LI release in a similar manner to that produced by AA, with the only difference being that in the presence of indomethacin, a residual increase in CGRP-LI outflow was still observed. AA increased the outflow of 6-keto-prostaglandin (PG) F1 alpha, PGE2 and leukotriene B4, whereas bradykinin enhanced only the release of 6-keto-PGF1 alpha. Infusion of either PGI2 or PGE2 (1-100 microM) released CGRP-LI in a dose-dependent manner and with a similar potency. PGI2 (100 microM)- or PGE2 (100 microM, 0.5 ml/min over 2 min)-evoked release was abolished by previous exposure to capsaicin and not affected by indomethacin.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Preparation of human and animal lung tissue for eicosanoid research.
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Anaphylaxis↗
Contractile and binding activities of structural analogues of LTC4 in the longitudinal muscle of guinea-pig ileum.
High affinity binding sites for LTC4 have been identified in various tissues, including guinea-pig ileal longitudinal muscle. More recently, it has been shown that LTC4 binds to non-receptor sites as well, particularly to glutathione transferases. In the present study, LTC4 and 9 chemically synthesized analogues, as well as the SRS-A antagonist FPL 55712 and S-decyl-glutathione, were tested for their ability to inhibit 3H-LTC4 binding in membranes from guinea-pig ileal longitudinal muscle and to affect the tone of the ileum in vitro. A significant correlation between binding and contractile activities was found for the LTC4 analogues and FPL 55712. However, S-decyl-glutathione, although possessing some affinity for LTC4 binding sites, was devoid of any effect on guinea-pig ileum tone at least up to 10(-5) M, thus indicating that these sites cannot be functional receptors, although they may represent other units involved in leukotriene action, e.g. uptake sites.
Animals↗
On the mechanism of aspirin asthma.
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Aspirin↗
The pharmacology of leukotrienes in human airways: in vitro and in vivo studies.
Immunological challenge of human lung parenchyma causes formation of arachidonate metabolites: prostaglandin D2 (PGD2) (70% of the formed mediators), leukotrienes E4 (LTE4) (15%) and D4 (LTD4) (10%). Leukotriene B4 (LTB4) was barely detectable (2%). Inhibition of PGD2 formation by indomethacin (15 microM) was approximately 90%, but was not accompanied by redistribution of arachidonate metabolism towards sulphidopeptide leukotrienes, as postulated for aspirin-sensitive asthma. Specific binding sites for leukotrienes C4 (LTC4) have been identified in membrane preparations of human bronchi. Binding of 3H-LTC4 is rapid (1 min) and quickly reversible following addition of excess. The sites are specific for LTC4 and competition curves fitted a two-site model. Moreover, clinical studies on specific endobronchial challenge of patients allergic to Dermatophagoides pteronyssinus, revealed narrowing of bronchial diameter and oedema of the bronchial mucosa; these symptoms were accompanied by an increase of immunoreactive-LTC4 and PGD2 present in the bronchial lavage fluids.
Asthma↗