Enhanced urinary excretion of leukotriene E4 in patients with mevalonate kinase deficiency

In patients with mevalonate kinase deficiency, urinary excretion of the leukotriene LTE4 was found to be elevated. A positive linear relationship between increased urinary excretion of mevalonate and LTE4 (n = 5) suggests that increased cysteinyl leukotriene synthesis is involved in the pathomechanisms of this disease.

Analysis of leukotrienes, prostaglandins, thromboxane B2 and their metabolites by capillary isotachophoresis

An analytical capillary isotachophoretic method for the analysis of the eicosanoids leukotriene E4, leukotriene B4, prostaglandins E1 and E2, 6-keto-prostaglandin F1 alpha, thromboxane B2, and their metabolites of omega- and/or beta-oxidation is described. The method is based on anionic separation and detection by UV absorbance (254 nm) and conductivity and allows simultaneous analysis of the primary compounds and their corresponding major urinary metabolites. The method was applicable to the qualitative and quantitative analysis of prostaglandin E1 in a drug preparation.

Differential effects of fluticasone propionate on allergen-evoked bronchoconstriction and increased urinary leukotriene E4 excretion

Allergen challenge is associated with an increased excretion of urinary leukotriene E4. The source of this increase is unknown, although the lack of effect of inhaled beta-agonists and sodium cromoglycate suggests that airway mast cells may not be involved. We investigated this further using a new and topically potent inhaled glucocorticoid, fluticasone propionate (FP). A group of 10 mild atopic asthmatic subjects (6 males; FEV1 > 60% of predicted; PC20 histamine < or = 8 mg/ml; and on inhaled beta 2-agonists only) were studied before and after a 2-wk period of FP (1,000 micrograms/day) or placebo administered by metered-dose inhalers as two puffs twice per day through a large-volume spacer. Treatments were assigned in a double-blind crossover fashion separated by a 3-wk washout period. The PC20 histamine was measured at the start and end of each treatment when subjects also received a bronchial allergen challenge. Urine was collected for 4 h after allergen challenge for determination of LTE4 using HPLC-RIA, and 2 h later the PC20 histamine measurement was repeated. The 2-wk treatment with FP significantly inhibited both early and late responses to allergen: the maximum % fall in FEV1 during the early (0 to 2 h) and late response (2 to 6 h) was 32.6 +/- 3.4 and 19.6 +/- 5.2, respectively, following placebo versus 19.5 +/- 4.5 and 3.6 +/- 2.6 following FP (both p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced synthesis of cysteinyl leukotrienes in atopic dermatitis

Synthesis of cysteinyl leukotrienes was assessed in patients with atopic dermatitis (AD; n = 8) and healthy volunteers (n = 8) by measuring urinary excretion of leukotriene E4 (LTE4), the main index metabolite of cysteinyl leukotrienes in man. Using this non-invasive method we demonstrated a significant (P < 0.05) 4.5-fold increase in excretion of LTE4 compared with healthy volunteers. The identity of LTE4 was unequivocally demonstrated by gas chromatography-mass spectrometry/mass spectrometry (GC-MS/MS). LTE4 was routinely measured by radioimmunoassay (RIA), and quantitative measurement of LTE4 by RIA was validated by GC-MS/MS. There was a linear correlation between LTE4 measured by RIA and by GC-MS/MS (r = 0.994). In representative samples, LTE4 was also quantitatively assessed by GC-MS/MS. In these samples, LTE4 values obtained by GC-MS/MS differed < 10% from those obtained by RIA. The present findings suggest that cysteinyl leukotrienes play a role in AD.

Potent leukotriene D4 receptor antagonist ICI 204,219 given by the inhaled route inhibits the early but not the late phase of allergen-induced bronchoconstriction

ICI 204,219 is a potent and specific leukotriene D4 receptor antagonist that blocks both the early and late responses to allergen challenge in humans when given orally at a dose of 40 mg. Here we report our findings with an inhaled formulation of ICI 204,219 against allergen-induced bronchoconstriction. A group of 10 atopic subjects (mean age 25.6 +/- 4.2; 6 females; FEV1 > 90% of predicted; on inhaled beta 2-agonists only) were studied on 2 separate days 2 to 3 wk apart. In a randomized placebo-controlled trial they inhaled eight puffs of a standard metered dose inhaler containing either ICI 204,219 (200 micrograms/puff, total dose 1,600 micrograms) or propellant alone. They underwent bronchial allergen challenge 30 min later using a single concentration of allergen previously shown to lower the FEV1 by > or = 15%. FEV1 was monitored hourly for 10 h, and urine was collected for LTE4 determination. Inhalation of ICI 204,219 was well tolerated, with no adverse clinical or biochemical effects. There was no significant effect of ICI 204,219 inhalation on basal airway caliber (change in FEV1 30 min after inhalation was -149 +/- 67 ml after placebo versus 3 +/- 38 ml after ICI 204,219; p = 0.08). The early response to allergen was significantly inhibited by ICI 204,219 (the maximum fall in FEV1 was -21.2 +/- 6.1% after ICI 204,219 compared with -38.8 +/- 6.5% on placebo; p = 0.007).(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of macrophage proteins bearing the functional leukotriene D4-binding site of an anti-cysteinylleukotriene monoclonal antibody

Protein conformations of the putative cysteinylleukotriene (LT) receptor of macrophages were characterized using anti-idiotypic IgG (AIAb) against an anti-LT monoclonal Ab (LTmAb). The AIAb nature of two rabbit antisera were demonstrated with titers of up to 1:1000 against F(ab')2 from the LTmAb (in an enzyme-linked immunoassay) which also inhibit LTD4 binding to the LTmAb (in a radioimmunoassay), whereas non-immunized rabbit serum was not reactive. The specific reactivity of Fc-purified AIAb towards LTmAb was measured by two fractions obtained after passage over columns of Sepharose either coupled with LTmAb (fraction A, representing immunoglobulins not absorbed to LTmAb) or coupled with homologous immunoglobins (fraction B, representing immunoglobulins not absorbed to homologous IgG). The difference in immunoreactivity between both fractions showed that fraction B contains AIAb against a LT-recognizing domain of the LTmAb (in enzyme-linked immunoassays coated with LTmAb and homologous IgG) and AIAb against the functional LT-binding site of LTmAb (in radioimmunoassay). Using the antisera, Western-blot analysis with peritoneal cell proteins detected signals at 236, 198, 118, 99, 75, 25 and 18 kDa. Dithiothreitol-reduced proteins were detected at 25 kDa and 18 kDa. In general, this suggested recognition of a 236-kDa oligomeric protein composed of subunits with molecular masses of 25 kDa and 18 kDa, including intramolecular disulfide bridges all bearing an epitope similar to the LTmAb. From these conformations, an overlay assay with [3H]LTD4 favoured a 75-kDa protein. Immunohistochemical analysis demonstrated that the recognized proteins may be located at cell membranes, because (a) in an ELISA, enriched plasma membrane preparations from peritoneal cells showed a threefold increase in reactivity to the AIAb, compared to the original cell homogenate; (b) after Western-blot analysis, the membrane-enriched protein fraction exhibited stronger protein signals than the microsomal fraction and the original cell homogenate; (c) regions of AIAb binding on the surface of cultured mouse peritoneal macrophages were detected by indirect immunofluorescence. Taken together, this study demonstrated AIAb binding to macrophage membrane-associated proteins bearing the LTD4-binding site of LTmAb, which may include identification of the putative LT receptor.

Leukotrienes D4 and E4 produced in myocardium impair coronary flow and ventricular function after two hours of global ischaemia in rat heart

OBJECTIVE

Leukotrienes D4 and E4 are potent coronary vasoconstrictors and myocardial depressants. The aim was to investigate the contribution of myocardial leukotrienes to impairment of coronary flow and recovery of contractile function in rat hearts subjected to 2 h of global ischaemia.

METHODS

Rat hearts were mounted on a working Langendorff apparatus and perfused with oxygenated Krebs-Henseleit solution at 37 degrees C for 30 min. Hearts were then arrested with either standard potassium crystalloid cardioplegic solution (n = 6), or with cardioplegic solution containing the leukotriene D4, E4 receptor antagonist Ly171883 (n = 6). Arrested hearts were maintained at 15 degrees C for 2 h, then rewarmed to 37 degrees C during 30 min working reperfusion. Coronary effluent was analysed by radioimmunoassay for leukotriene C4, D4, E4, and F4 levels. Immediately prior to cardiac arrest, and again after 30 min reperfusion, coronary flow, and aortic outflow and pressure were measured.

RESULTS

Postischaemic leukotriene levels were increased compared to preischaemic levels in both groups [pooled measurements: 133.3 (SD 136.4) v 20.7(17.8) pg.0.1 ml-1, p < 0.05]. Postischaemic coronary vascular resistance was increased by 80% in controls (p < 0.001) compared to 19% (p = NS) in treated hearts. In addition, functional recovery was significantly greater in treated hearts compared to controls [82(3)% v 53(3)% for coronary flow; 79(3)% v 50(2)% for cardiac output; 82(4)% v 54(3)% for stroke work].

CONCLUSIONS

Leukotrienes are endogenously produced by the heart, and this production is significantly increased after global ischaemia and reperfusion. Reversal of significantly increased coronary vascular resistance coupled with improved functional recovery in hearts treated with LY171883 demonstrates an important contribution of endogenously produced leukotrienes to coronary vascular impairment and functional stunning of the globally ischaemic, reperfused heart.

Sulphidopeptide leukotrienes in asthma

No single mediator is responsible for the clinical and pathological events in bronchial asthma. Nevertheless, there is now substantial evidence that the sulphidopeptide leukotrienes play an important role in the pathophysiology of the disease. They are potent in eliciting bronchoconstriction, mucus production and vasodilatation, and may enhance the airways hyperresponsiveness that is characteristic of the disease. The sulphidopeptide leukotrienes are present in the airways of asthmatic patients and their release has been demonstrated in acute severe asthma. They are released during asthmatic attacks provoked by a range of stimuli. The evidence from studies using sulphidopeptide leukotriene antagonists and 5-LO inhibitors suggests strongly that sulphidopeptide leukotrienes contribute to the resting asthmatic airways tone and to the asthmatic responses elicited by exercise, allergen, aspirin and cold, dry air challenges. These mediators may also contribute to the airways hyperresponsiveness induced by allergen challenge of sensitized subjects. Preliminary results indicate that the administration of leukotriene receptor antagonists and 5-LO inhibitors may benefit patients with chronic asthma. Further studies are now needed to define better the role of these novel drugs in the management of the disease.

Leukotriene E4 and granulocytic infiltration into asthmatic airways

Sulphidopeptide leukotrienes are potent bronchoconstrictors and increase bronchial hyperreactivity, one of the hallmarks of asthma. We have demonstrated that leukotriene LTE4, the most stable of the sulphidopeptide leukotrienes, elicited an increase in the numbers of eosinophils and neutrophils in the lamina propria of the airway mucosa 4 h after inhalation in 4 asthmatic subjects. The numbers of eosinophils were, on average, 10-fold greater than those of neutrophils. There was no significant change in numbers of lymphocytes, plasma cells, mast cells, or macrophages. Since LTE4 recruits granulocytes, the potential of antisulphidopeptide leukotriene drugs as anti-inflammatory and "steroid-sparing" agents should be tested.

Differential activation of the endogenous leukotriene biosynthesis by two different preparations of granulocyte-macrophage colony-stimulating factor in healthy volunteers

Results from in vitro investigations and recent data obtained in patients with drug-induced cytopenia or myelodysplasia suggest that leukotrienes may be involved in mediating some of the actions of granulocyte-macrophage colony-stimulating factor (GM-CSF). In the present study, the possible role of leukotrienes was further characterized in 21 healthy individuals to avoid modification of response to GM-CSF by disease-specific variables. The effects of two different preparations of human recombinant GM-CSF, ie, glycosylated GM-CSF as expressed in a Chinese hamster ovary carcinoma (CHO) cell line and nonglycosylated GM-CSF obtained from Escherichia coli, were compared. GM-CSF was administered subcutaneously at a single dose of 0.7 nmol/kg body weight. Pharmacokinetic parameters and hematopoietic and adverse effects were monitored by blood analyses or physical examination, respectively. Leukotriene generation in vivo was evaluated by determination of leukotriene E4 and N-acetyl-leukotriene E4 in urine. After the injection of GM-CSF from E coli, serum concentrations increased and decreased more rapidly and reached a 2.3-fold higher maximum compared with GM-CSF from CHO. GM-CSF induced a biphasic change in leukocyte counts that proceeded considerably faster after the E coli preparation than after GM-CSF from CHO. The urinary leukotriene concentration increased 1.3- to 14-fold or 2.1- to 44-fold after the administration of GM-CSF from CHO or E coli, respectively. Urinary leukotriene concentrations correlated significantly with the maximum of basophil counts and correlated with the occurrence of some adverse reactions, ie, flu-like symptoms, bone pain, or dyspnoea. Our data confirm the conception that leukotrienes may play a significant role in GM-CSF action in vivo. They especially direct attention to the possible relevance of leukotrienes to untoward effects of GM-CSF treatment.

Oral leukotriene inhibitor (MK-886) blocks allergen-induced airway responses

To elucidate the role of leukotrienes (LT) in allergic asthma in humans the effect of MK-886, an LT biosynthesis inhibitor, was evaluated on antigen-induced early (EAR) and late (LAR) asthmatic reactions and bronchial responsiveness to histamine. Eight atopic men participated in a two-part, double-blind, placebo-controlled, crossover trial. MK-886 was administered in two oral doses of 500 mg and 250 mg, 1 h before and 2 h after allergen inhalation, respectively. Biochemical effects of MK-886 were evaluated by the inhibition of urinary LTE4 excretion and calcium ionophore-stimulated LTB4 biosynthesis in whole blood ex vivo. MK-886 significantly inhibited the EAR by 58.4% (AUC0-3 h) and the LAR by 43.6% (AUC3-7 h) when compared with placebo (p < 0.01). There was no difference in PC20 histamine 30 h post allergen challenge between MK-886 and placebo (0.33 and 0.27 doubling doses, p > 0.1). MK-886 inhibited calcium ionophore-stimulated LTB4 production in whole blood (54.2 +/- 25.6%) for up to 6 h post allergen challenge. LTE4 excretion in urine was inhibited by 51.5% during the EAR by as much as 80% during the LAR. This indicates that LT play a role in allergen-induced asthmatic reactions in humans in vivo and that LT synthesis inhibitors such as MK-886 should be further explored for the treatment of asthma.

Effect of leukotrienes of renal water excretion

To investigate the renal actions of leukotrienes (LT), we infused arachidonic acid into the renal artery of anesthetized dogs during systemic cyclooxygenase inhibition (with ibuprofen) alone or in combination with lipoxygenase inhibition or LTD4/LTE4 receptor antagonism. Renal arachidonic acid infusion following ibuprofen alone decreased urine osmolality (945 +/- 143 to 698 +/- 144 mosm/kg; p < 0.01) and increased urine flow rate (0.34 +/- 0.11 to 0.56 +/- 0.16; p < 0.05) without altering renal blood flow, glomerular filtration rate or sodium excretion. In separate groups, prior inhibition of lipoxygenase (propylgallate) or blockade of LTD4/LTE4 receptors (LY171883) prevented the changes in urine osmolality and urine flow rate. Intrarenal oleic acid infusion following ibuprofen had no effect on renal function. Analysis of the renal papillae at the end of the experiment indicated that interstitial osmolality and sodium, potassium and urea contents were the same in all groups, ruling out a decrease in papillary interstitial osmolality as the cause of the decrease in urine osmolality in the arachidonic acid-infused group. Our experiments suggest that renal LT can decrease urine osmolality and increase urine flow rate and may play a role in renal water excretion.

Leukotriene generation and metabolism in dogs: inhibition of biosynthesis by MK-0591

Peptidoleukotriene metabolism in dogs was investigated to determine the suitability of this species for the development of in vivo biochemical models of asthma and inflammation. Circulatory metabolism of [3H]leukotriene (LT)C4 (0.5 microCi/kg, i.v.) to [3H]LTE4 and subsequent clearance was rapid (T1/2 = 100 sec). After 3 h, the major urinary metabolite was [3H]16-carboxydihydrotetranor LTE4 (identified by radiochromatography), with [3H]LTE4 accruing to a significant 1.7 +/- 0.9% (n = 3) of the original [3H]LTC4 dose. Immunoreactive LTE4 was excreted into canine urine at 1.85 +/- 0.35 to 2.35 +/- 0.57 ng/h (n = 4) over a 6-h period, suggesting that this metabolite may be an index of acute in vivo 5-lipoxygenase activity. MK-0591, a high-affinity ligand for the canine homolog of the human 5-lipoxygenase activating protein, dose-dependently inhibited the systemic generation of peptidoleukotrienes as measured by urinary LTE4 excretion (ED50 1 microgram/kg/min), the time course of disappearance of LTE4 from the urine being similar to that of the clearance of [3H]LTE4. Because the therapeutic improvements in human allergic asthmatics treated with LT synthesis inhibitors and challenged with antigen appear to be related to the degree of in vivo inhibition of LT biosynthesis (measured by urinary LTE4), the dog may be an appropriate species for preclinical assessment of LT inhibitors.

Photoaffinity labeling of the leukotriene D4 receptor in guinea pig lung

The leukotriene (LT)D4 receptor has been defined as a G-protein-coupled receptor. In order to characterize this receptor, an iodinated, photoactivatable azido derivative of LTD4 (125I-azido-LTD4) has been synthesized for use as a photoaffinity probe. The characteristics of 125I-azido-LTD4 specific binding to guinea pig lung membranes were directly comparable to those of [3H]LTD4 specific binding to this tissue. 125I-Azido-LTD4 specific binding was saturable and of high affinity, enhanced by divalent cations and inhibited by sodium ions, but not potassium ions. 125I-Azido-LTD4 specific binding was also strongly inhibited by the nonhydrolyzable GTP analog, GTP gamma S, with ATP gamma S being 100-fold less potent, suggesting this inhibition was due to selective interaction with a G-protein. The cysteinyl leukotrienes competed for 125I-azido-LTD4 specific binding to guinea pig lung membranes with the following rank order of potency: LTD4 > LTE4 > LTC4, while the non-cysteinyl LTB4 was virtually inactive. Two structurally different LTD4 receptor antagonists, MK-571 and ICI 204,219, also competed for 125I-azido-LTD4 specific binding with nanomolar potency, whereas the leukotriene synthesis inhibitor, MK-886, was 10,000-fold less active. These data are in agreement with 125I-azido-LTD4 binding specifically to a G-protein-coupled LTD4 receptor. Photolysis of 125I-azido-LTD4 under equilibrium binding conditions resulted in the selective radiolabeling of a 45-kDa guinea pig lung membrane protein. The photolabeling of this 45-kDa protein was saturable, modulated by cations and inhibited by nucleotide analogs in an analogous way to 125I-azido-LTD4 specific binding. In addition, the photolabeling of this protein was inhibited in a concentration-dependent manner by all competing ligands, with the same rank order of potency and IC50 values as determined in the 125I-azido-LTD4 binding assay. It is proposed, therefore, that this novel 45-kDa protein is the guinea pig lung LTD4 receptor.

Effect of nedocromil sodium on sulfidopeptide leukotrienes-stimulated human alveolar macrophages in asthma

Alveolar macrophages (AM) may take part in the amplification of the inflammatory mechanism involved in asthma. During an asthma attack, mast cells and eosinophils release arachidonic acid derivative mediators of inflammation such as sulfidopeptide leukotrienes. Among them, LTC4 has been shown to be present in bronchoalveolar fluid. In asthmatic patients, we showed that the ability of AM to transform LTC4 into its derivatives LTD4 and LTE4 was related to the intensity of the local inflammation observed during endoscopy. AM from asthmatics incubated in the presence of LTC4 or LTE4, generated LTB4 and 5-HETE, which are potent chemoattractants. Nedocromil sodium (10(-4) M) decreased LTB4 releasability and intracellular 5-HETE concentrations in zymosan-stimulated AM from asthmatic patients, and was shown to decrease the LTC4 or LTE4-promoted formation of LTB4 and 5-HETE.

Cysteinyl leukotrienes overproduction and mast cell activation in aspirin-provoked bronchospasm in asthma

In order to examine the hypothesis that in aspirin-induced asthma (AIA) cyclooxygenase inhibition is associated with enhanced release of leukotrienes (LTs), we measured urinary leukotriene E4 (LTE4) and 11-dehydro-thromboxane B2 (TXB2) (as a measure of cyclooxygenase production) following challenge with oral aspirin or inhaled methacholine, in 10 AIA patients. We also determined serum tryptase and eosinophilic catonic protein (ECP) levels, in order to evaluate mast cell and eosinophil activation. Urinary LTE4 excretion was increased sevenfold 4-6 h after aspirin challenge, while 11-dehydro-TXB2 decreased gradually reaching 50% baseline levels 24 h after challenge (p < 0.05). This was accompanied by a significant fall in blood eosinophil count at 6 h, and a tendency to a rise in ECP. The intensity of both LTE4 and 11-dehydro-TXB2 responses depended on the dose of aspirin used (p < 0.001, analysis of variance (ANOVA)). The accompanying maximum fall in forced expiratory volume in one second (FEV1) was not correlated with peak LTE4 levels. In contrast to aspirin, methacholine challenge producing comparable bronchial obstruction, did not alter eicosanoid excretion or serum tryptase or ECP levels. In a separate study, lysine-aspirin inhalation challenge was performed in seven AIA patients, four of whom had responded with a rise in serum tryptase to oral aspirin challenge. Challenge with inhaled aspirin led to similar bronchoconstriction as with oral challenge, but non-respiratory symptoms such as scarlet flush or rhinorrhea were absent, and serum tryptase levels remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Substituted 3-(phenylmethyl)-1H-indole-5-carboxamides and 1-(phenylmethyl)indole-6-carboxamides as potent, selective, orally active antagonists of the peptidoleukotrienes

Substituted indole-5-carboxamides and indole-6-carboxamides have been found to be potent and selective antagonists of the peptidoleukotrienes. Initial derivatives of these series (4-[[5-[(cyclopentylmethyl)carbamoyl]-1-methylindol-3-yl] methyl]-3-methoxy-N-[(2-methylphenyl)sulfonyl]benzamide (5a) and 4-[[6-[(cyclopentylmethyl)carbamoyl]-3-methylindol-1-yl] methyl]-3-methoxy-N-[(2-methylphenyl)sulfonyl]benzamide (6a), respectively), when compared to the corresponding indole amides (e.g. 28 and 29), were found to be approximately 10-fold less potent in vitro and substantially less active when administered orally to guinea pigs. Efforts to improve the potency of the title series by variation of the amide, indole, or sulfonamide substituents led to compounds of comparable in vitro potency to ICI 204,219, but of somewhat lower oral activity. A trend which suggested that more lipophilic transposed amides were needed to increase oral activity was exploited with some success and has led to the discovery of 5q (4-[[5-[(2-ethylbutyl)-carbamoyl]-1-ethylindol-3-yl]methyl]- 3- methoxy-N-[(2-methylphenyl)sulfonyl]benzamide), a transposed amide with subnanomolar affinity for the leukotriene receptor and an oral ED50 of 5 mg/kg in a model of asthma in guinea pigs. In this model, ICI 204,219 was active at 0.4 mg/kg. The absolute bioavailability of 5q has been found to be 28% in the rat, as compared to 68% for ICI 204,219, with significant levels of 5q observed in the blood of rats up to 24 h postdose.

n-3 fatty acids and cysteinyl-leukotriene formation in humans in vitro, ex vivo, and in vivo

In humans, dietary n-3 fatty acids ameliorate some chronic inflammatory diseases. In contrast, however, dietary n-3 fatty acids had no effect in patients with bronchial asthma. In bronchial asthma, the cysteinyl-leukotrienes C4, D4, and E4, formed from arachidonic acid, are considered important mediators. They are as vasoconstrictive and bronchoconstrictive as leukotrienes C5, D5, and E5, cysteinyl-leukotrienes derived from eicosapentaenoic acid. Whether and how n-3 fatty acids affect human cysteinyl-leukotriene metabolism is largely unknown. We therefore investigated human cysteinyl-leukotriene metabolism in vitro, ex vivo, and in vivo in the absence and presence of dietary n-3 fatty acids. We demonstrate formation of leukotrienes C5, D5, and E5 from eicosapentaenoic acid in vitro and ex vivo in stimulated human granulocytes. Proof of formation relies on cochromatography with authentic standards on reverse-phase high-performance liquid chromatography, ultraviolet-absorbance spectra, and radioactive tracer studies. In vitro, amounts of leukotrienes C5, D5, and E5 formed depended on the amount of exogenous eicosapentaenoic acid; leukotrienes C4, D4, and E4 formed from endogenous arachidonic acid, however, remained unaltered. A randomized, controlled, observer-blind study in 14 human volunteers, seven of whom supplemented their diet with 7 gm/day of an 85% n-3 fatty acid concentrate for 6 weeks was subsequently performed. Ex vivo, levels of leukotriene E5 almost equaled those of leukotriene E4. Moreover, urinary excretion of leukotriene E4 was assessed to estimate formation of cysteinyl leukotrienes from arachidonic acid in vivo. Urinary excretion of leukotriene E4 was reduced by 35% after dietary supplementation with n-3 fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of human myelopoiesis by leukotrienes B4 and C4: interactions with granulocyte-macrophage colony-stimulating factor

The regulatory role of leukotrienes (LT) on human myelopoiesis was investigated. Mononuclear bone marrow cells from 31 healthy donors were cultivated in the presence of suboptimal concentrations of recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) for 10 days in semisolid agar. The addition of LTC4 or LTB4 to the cultures dose-dependently stimulated myeloid stem cell proliferation. Maximal effects were observed at 10(-8) mol/L, at which LTC4 induced a 91% +/- 23% (mean +/- SEM; P = .004) and LTB4 a 73% +/- 22% (P = .008) increase in colony formation. In contrast, addition of the LTB4 isomer 5(S), 12(S)-diHETE did not affect the growth. LTD4 exerted a weak potentiating effect on progenitor proliferation (17% +/- 7% growth stimulation at 10(-10) mol/L; P = .034), whereas LTE4 was without consistent effect. Furthermore, LTC4-induced stimulation of colony formation was insensitive to the LTD4 antagonist ICI 198615. The dual lipoxygenase and prostaglandin endoperoxide synthase inhibitor CL42A potently suppressed the proliferation of myeloid colonies, a suppression that could be reversed by parallel addition of LTB4 or LTC4. The results suggest that both LTB4 and LTC4 possess strong and specific synergistic stimulatory effects on GM-CSF-induced human myeloid progenitor cell growth.

Inhibitory effect of DS-4574 on leukotriene- or antigen-induced bronchoconstriction in guinea pigs

We studied the leukotriene (LT) antagonistic activity of DS-4574 in vivo and the inhibitory effect of this compound on antigen-induced bronchoconstriction in actively sensitized guinea pigs. Bronchoconstriction induced by LTD4 was inhibited by intravenous and oral treatment with DS-4574 in a dose-dependent manner. Orally administered DS-4574 was also able to inhibit the bronchoconstriction mediated by intravenous administration of LTC4 and E4 and that by endogenous LTs. The inhibitory effect of DS-4574 showed similar potency to those of FPL-55712 and LY171883. In contrast, histamine-, acetylcholine- or 5-hydroxytryptamine-induced bronchoconstriction was not significantly affected by DS-4574. Moreover, DS-4574 given orally or intravenously inhibited antigen-induced bronchoconstriction in actively sensitized guinea pigs and this compound prevented antigen-induced mediator release from actively sensitized guinea-pig lung fragments. The anti-asthmatic effect of this compound appears to be associated with LT antagonism and inhibition of the release of chemical mediators. This study therefore shows DS-4574 to have orally effective LT antagonistic and anti-asthmatic activities. This compound may prove useful in the treatment of bronchial asthma.

Arachidonic acid metabolites in human nasal polyps

Arachidonic acid metabolites (AAMs) are known to be involved in inflammation. It is suggested that AAMs play an important role in the pathogenesis of nasal polyp. We have measured the levels of prostaglandin E2, 6-keto prostaglandin F1 alpha, thromboxane B2, leukotriene B4 and a mixture of leukotriene C4, D4 and E4 in both nasal polyp and maxillary sinus mucosa by radioimmunoassay. Our results showed that arachidonic acid metabolism in nasal polyps from allergic patients was more active than that from non-allergic patients. The arachidonic acid metabolism in nasal polyp was more active than in maxillary sinus mucosa among allergic patients. On the other hand, arachidonic acid metabolism in maxillary sinus mucosa was more active than that in nasal polyps among non-allergic patients. On the basis of these results, we hypothesized the causal mechanisms of nasal polyps as follows: The nasal polyp in allergic patients is caused by primary inflammation of the nasal mucosa, and sinusitis occurs secondarily. In non-allergic patients, the primary side of inflammation is located in the maxillary sinus mucosa, leading to the secondary formation of nasal polyp.

Eicosanoids in third ventricular cerebrospinal fluid of fetal and newborn sheep

A method to serially sample cerebrospinal fluid (CSF) from the third ventricle of chronically catheterized fetal and newborn sheep was developed. Either sampling cannulas of preset lengths ("fixed-probe" technique) or a single cannula that could be positioned at the desired depth ("roving-probe" technique) was used. The roving probe proved superior because free CSF flow was obtained in seven of ten animals after surgery compared with two of nine animals implanted with a fixed probe. CSF (5 animals) and plasma (7 animals) was collected serially from 2 wk before to 2 wk after birth, including the time around labor. Prostaglandin E2 (PGE2) levels (means +/- SE) were significantly higher in CSF (366 +/- 120 pg/ml; n = 5) and plasma (520 +/- 69 pg/ml; n = 7) before the day of delivery than in the same animals after birth. During labor, CSF and plasma PGE2 levels increased significantly to 1,428 +/- 643 pg/ml in CSF and to 2,015 +/- 414 pg/ml in plasma. However, by 1 h after birth, PGE2 had fallen to 366 +/- 165 pg/ml in CSF and to 338 +/- 106 pg/ml in plasma; levels similar to those observed in the fetus before labor. PGE2 continued to decrease precipitously and, at 24 h of age, levels were significantly less than those observed in the fetus. PGE2 levels were near the limit of detection of the assay in CSF (< 5 pg/ml) and were 49 +/- 10 pg/ml in plasma. In contrast, CSF thromboxane B2 (n = 2) and total peptidoleukotriene content (n = 4) showed little change during labor or after birth.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurally mediated actions of leukotrienes on ion transport in guinea pig distal colon

The effects of the sulfidopeptide leukotrienes (LT), LTC4, LTD4 and LTE4 on short-circuit current (Isc), a measure of active ion transport, were determined in muscle-stripped mucosa sheets from the guinea pig distal colon. LTC4 and D4, but not E4, evoked concentration-dependent increases in Isc. Auto- and cross-tachyphylaxis could be demonstrated in LT actions. LTD4 was more sensitive than LTC4 to inhibition by the LTD4 antagonist, 1-<2-hydroxy-3-propyl-4-<4-(1H-tetrazol-5-yl)butoxy>phenyl>etha none, and the intracellular Ca++ inhibitor, 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester. Mucosal LT effects were reduced in tissues pretreated with bumetanide or bathed in HCO3(-)-free media. Measurements of transepithelial Na+ and Cl- fluxes revealed that LTC4 increased unidirectional and net secretory fluxes of Cl- but had no effect on Na+ transport. Tetrodotoxin, atropine and indomethacin inhibited mucosal responses to LTC4 and D4; in addition prazosin inhibited LTD4 effects. The results suggest that LTC4 and D4 evoke anion secretion by acting through distinct LT receptor populations. These effects are mediated in part by cholinergic and adrenergic submucosal neurons as well as by colonic prostanoids.

Serum complement mediates endotoxin-induced cysteinyl leukotriene formation in rats in vivo

To investigate potential mediators responsible for cysteinyl leukotriene formation during endotoxemia, male Fischer rats received an intravenous bolus injection of 5 mg/kg Salmonella enteritidis endotoxin and cysteinyl leukotrienes were measured by gas chromatography-mass spectrometry. The biliary excretion of leukotriene (LT) C4 (0.20 +/- 0.02 pmol.min-1.g liver-1) and N-acetyl-LTE4 (0.37 +/- 0.07 pmol.min-1.g-1) was increased by 190 and 1,000%, respectively, during the first 30 min after endotoxin injection. Endotoxin also caused a temporary reduction of hepatic ATP levels by 84%. Depletion of serum complement almost completely abolished the endotoxin-induced increase of cysteinyl leukotrienes in bile without affecting the biliary excretion mechanism. Intravenous injection of activated complement factors caused cysteinyl leukotriene formation and reduced the hepatic ATP content similar to endotoxin. Depletion of glutathione in the liver prevented cysteinyl leukotriene formation and the complement-induced ATP depletion. It is concluded that endotoxin-induced cysteinyl leukotriene generation in vivo is mediated predominantly through activation of complement. The vasoconstrictive cysteinyl leukotrienes are then responsible for ATP depletion in the liver.