leukotriene-e4 and zileuton

Patients with clonal mast cell activation syndromes (MCAS) including cutaneous and systemic mastocytosis (SM) may present with symptoms of mast cell activation, but in addition can have organ damage from the local effects of tissue infiltration by clonal mast cells. Patients with nonclonal MCAS may have chronic or episodic mast cell activation symptoms with an increase in serum tryptase and/or urinary metabolites of histamine, prostaglandin D2, and leukotrienes. Symptoms of MCAS and SM can be managed by blockade of mediator receptors (H1 and H2 antihistamines, leukotriene receptor blockade), inhibition of mediator synthesis (aspirin, zileuton), mediator release (sodium cromolyn), anti-IgE therapy, or a combination of these approaches. Acute episodes of mast cell activation require epinephrine, and prolonged episodes may be addressed with corticosteroids. Patients with clonal mast cell syndromes may need a reduction in the number of mast cells to prevent severe symptoms including anaphylaxis and/or progression to aggressive diseases.

Topics: Anti-Allergic Agents; Anti-Asthmatic Agents; Anti-Inflammatory Agents, Non-Steroidal; Aspirin; Cromolyn Sodium; Disease Management; Glucocorticoids; Histamine; Histamine Antagonists; Histamine H1 Antagonists; Histamine H2 Antagonists; Humans; Hydroxyurea; Interleukin-6; Leukotriene Antagonists; Leukotriene E4; Mastocytosis; Omalizumab; Prostaglandin D2; Tryptases

Cysteinyl-leukotrienes (cysteinyl-LTs), that is, LTC4, LTD4, and LTE4, trigger contractile and inflammatory responses through the specific interaction with G protein-coupled receptors (GPCRs) belonging to the purine receptor cluster of the rhodopsin family, and identified as CysLT receptors (CysLTRs). Cysteinyl-LTs have a clear role in pathophysiological conditions such as asthma and allergic rhinitis (AR), and have been implicated in other inflammatory conditions including cardiovascular diseases, cancer, atopic dermatitis, and urticaria. Molecular cloning of human CysLT1R and CysLT2R subtypes has confirmed most of the previous pharmacological characterization and identified distinct expression patterns only partially overlapping. Interestingly, recent data provide evidence for the immunomodulation of CysLTR expression, the existence of additional receptor subtypes, and of an intracellular pool of CysLTRs that may have roles different from those of plasma membrane receptors. Furthermore, genetic variants have been identified for the CysLTRs that may interact to confer risk for atopy. Finally, a crosstalk between the cysteinyl-LT and the purine systems is being delineated. This review will summarize and attempt to integrate recent data derived from studies on the molecular pharmacology and pharmacogenetics of CysLTRs, and will consider the therapeutic opportunities arising from the new roles suggested for cysteinyl-LTs and their receptors.

Topics: Adult; Animals; Asthma; Cardiovascular Diseases; Child; Child, Preschool; Dermatitis, Atopic; Female; Humans; Hydroxyurea; Leukotriene Antagonists; Leukotriene C4; Leukotriene D4; Leukotriene E4; Membrane Proteins; Pharmacogenetics; Receptors, Leukotriene; Receptors, Purinergic; Recombinant Proteins; Rhinitis, Allergic, Seasonal; SRS-A; Tissue Distribution

Twenty five years after the structure elucidation of slow reacting substance of anaphylaxis, antileukotrienes are established as a new therapeutic modality in asthma. The chapter reviews the biochemistry and pharmacology of leukotrienes and antileukotrienes with particular focus on the different usage of antileukotrienes for treatment of asthma and rhinitis in Europe and the US. Further research needs and new areas for leukotriene involvement in respiratory diseases are also discussed.

Topics: Acetates; Animals; Asthma; Clinical Trials as Topic; Cyclopropanes; Humans; Hydroxyurea; Leukotriene Antagonists; Leukotriene C4; Leukotriene D4; Leukotriene E4; Lipoxygenase Inhibitors; Membrane Proteins; Quinolines; Receptors, Leukotriene; Respiratory System; Rhinitis; Sulfides

COX-2 and 5-lipoxygenase (5-LO) use arachidonic acid for the synthesis of eicosanoids that have been implicated in carcinogenesis and cardiovascular disease. The ability of celecoxib, a selective COX-2 inhibitor, to redirect arachidonic acid into the 5-LO pathway can potentially reduce its efficacy as a chemopreventive agent and increase the risk of cardiovascular complications. Levels of urinary prostaglandin E metabolite (PGE-M) and leukotriene E4 (LTE4), biomarkers of the COX and 5-LO pathways, are elevated in smokers. Here, we investigated the effects of zileuton, a 5-LO inhibitor, versus zileuton and celecoxib for 6 ± 1 days on urinary PGE-M and LTE4 levels in smokers. Treatment with zileuton led to an 18% decrease in PGE-M levels (P = 0.03); the combination of zileuton and celecoxib led to a 62% reduction in PGE-M levels (P < 0.001). Levels of LTE4 decreased by 61% in subjects treated with zileuton alone (P < 0.001) and were unaffected by the addition of celecoxib. Although zileuton use was associated with a small overall decrease in PGE-M levels, increased PGE-M levels were found in a subset (19 of 52) of subjects. Notably, the addition of celecoxib to the 5-LO inhibitor protected against the increase in urinary PGE-M levels (P = 0.03). In conclusion, zileuton was an effective inhibitor of 5-LO activity resulting in marked suppression of urinary LTE4 levels and possible redirection of arachidonic acid into the COX-2 pathway in a subset of subjects. Combining celecoxib and zileuton was associated with inhibition of both the COX-2 and 5-LO pathways manifested as reduced levels of urinary PGE-M and LTE4.

Topics: Adult; Arachidonate 5-Lipoxygenase; Biomarkers; Celecoxib; Chromatography, Liquid; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Female; Humans; Hydroxyurea; Leukotriene E4; Lipoxygenase Inhibitors; Male; Maximum Tolerated Dose; Prognosis; Prostaglandins; Pyrazoles; Smoking; Sulfonamides; Tandem Mass Spectrometry

Leukotrienes have been implicated in the pathogenesis of acute exacerbations of COPD, but leukotriene modifiers have not been studied as a possible therapy for exacerbations.. We sought to test the safety and efficacy of adding oral zileuton (a 5-lipoxygenase inhibitor) to usual treatment for acute exacerbations of COPD requiring hospitalization.. Randomized double-blind, placebo-controlled, parallel group study of zileuton 600 mg orally, 4 times daily versus placebo for 14 days starting within 12 hours of hospital admission for COPD exacerbation. Primary outcome measure was hospital length of stay; secondary outcomes included treatment failure and biomarkers of leukotriene production.. Sixty subjects were randomized to zileuton and 59 to placebo (the study was stopped short of enrollment goals because of slow recruitment). There was no difference in hospital length of stay (3.75 +/- 2.19 vs. 3.86 +/- 3.06 days for zileuton vs. placebo, p = 0.39) or treatment failure (23% vs. 27% for zileuton vs. placebo, p = 0.63) despite a decline in urinary LTE(4) levels in the zileuton-treated group as compared to placebo at 24 hours (change in natural log-transformed ng/mg creatinine -1.38 +/- 1.19 vs. 0.14 +/- 1.51, p < 0.0001) and 72 hours (-1.32 +/- 2.08 vs. 0.26 +/- 1.93, p<0.006). Adverse events were similar in both groups.. While oral zileuton during COPD exacerbations that require hospital admission is safe and reduces urinary LTE(4) levels, we found no evidence suggesting that this intervention shortened hospital stay, with the limitation that our sample size may have been insufficient to detect a modest but potentially meaningful clinical improvement.

Topics: Aged; Biomarkers; Double-Blind Method; Drug Administration Schedule; Female; Hospitalization; Humans; Hydroxyurea; Length of Stay; Leukotriene B4; Leukotriene E4; Lipoxygenase Inhibitors; Male; Middle Aged; Pulmonary Disease, Chronic Obstructive; Treatment Failure; Treatment Outcome

Elevated urine and blood leukotriene levels have been reported after ascent to high altitude in association with acute mountain sickness (AMS) and high-altitude pulmonary edema. Zileuton is an inhibitor of the enzyme 5-lipoxygenase that catalyzes conversion of arachidonic acid to leukotrienes. Study objectives and design: The objectives of this randomized, double-blind, placebo-controlled clinical trial were to determine whether zileuton (600 mg po qid) is effective prophylaxis for AMS, and to measure the effect of ascent to high altitude and zileuton on urinary leukotriene E(4) levels.. The study group consisted of volunteers from among climbers on the West Buttress of Mt. McKinley (Denali), Alaska. After baseline urine samples at sea level, subjects flew by airplane to 2,300 m, and then ascended to the 4,200-m camp in 5 to 10 days.. Using an enzyme immunoassay, urinary leukotriene E(4) was found to decrease after ascent to high altitude in both the zileuton and placebo groups. Urinary leukotriene E(4) in the zileuton group (n = 9) decreased from 67 +/- 35 pg/mg creatinine at sea level to 33 +/- 22 pg/mg creatinine at high altitude (p = 0.003) [mean +/- SD]. Urinary leukotriene E(4) in the placebo group (n = 9) decreased from 97 +/- 82 pg/mg creatinine at sea level to 44 +/- 21 pg/mg creatinine at high altitude (p = 0.045). One subject in the zileuton group and three subjects in the placebo group met Lake Louise criteria for AMS after arriving at 4,200 m (p = 0.257).. Elevated leukotrienes are not associated with ascent to high altitude. In subjects with AMS, urinary leukotrienes were not elevated, suggesting that leukotrienes may not be a component of the pathophysiology of AMS. The low incidence of AMS and the small sample size in this study prevented determination of whether zileuton is effective prophylaxis for AMS.

Topics: Acclimatization; Administration, Oral; Adult; Alaska; Altitude Sickness; Arachidonate 5-Lipoxygenase; Double-Blind Method; Drug Administration Schedule; Female; Humans; Hydroxyurea; Inflammation Mediators; Leukotriene E4; Lipoxygenase Inhibitors; Male; Middle Aged; Mountaineering; Oximetry; Premedication; Statistics as Topic; Treatment Outcome

Segmental antigen challenge (SAC) and bronchoalveolar lavage (BAL) have been proven useful for investigating IgE-mediated lung inflammation in volunteers with allergies.. This model was used to evaluate the pulmonary antiinflammatory effects of an experimental 5-lipoxygenase inhibitor (zileuton) in subjects allergic to ragweed. We hypothesized that decreased generation of leukotrienes by inhibition of the 5-lipoxygenase pathway of arachidonic acid metabolism would diminish the subsequent inflammatory response resulting from antigen challenge.. Ten subjects with allergies received zileuton or placebo, 600 mg administered orally four times a day for 8 days, and then underwent bronchoscopy, BAL of a control segment, and SAC in the contralateral lung followed by BAL of the challenged segment 24 hours later in a double-blind, placebo-controlled, crossover protocol. Urinary excretion of leukotriene E4 induced by antigen challenge plus total and differential cell counts and the amount of total protein, albumin, urea, and eosinophil cationic protein in BAL fluid were determined.. A significant inhibition of leukotriene production (approximately 86%) was observed in subjects receiving zileuton. In addition, there was a statistically significant increase in eosinophils after antigen challenge (0.6 +/- 0.2 x 10(4) eosinophils/ml increasing to 49.0 +/- 25.0 x 10(4) in subjects receiving placebo, whereas the influx of eosinophils in subjects receiving zileuton was not statistically different from baseline (1.1 +/- 0.7 x 10(4) eosinophils/ml increasing to 16.5 +/- 4.1 x 10(4); analysis of variance for repeated measures with post hoc comparisons).. Treatment with zileuton altered the inflammatory response after antigen challenge. Products of the 5-lipoxygenase pathway appear to be important in recruiting eosinophils to the lung after SAC.

Topics: Adult; Antigens; Bronchoalveolar Lavage Fluid; Cell Count; Double-Blind Method; Eosinophils; Female; Humans; Hydroxyurea; Hypersensitivity; Leukotriene E4; Lipoxygenase Inhibitors; Male; Pneumonia; Pollen

To investigate the contribution of leukotrienes (LTs) to inflammation and bronchoconstriction in nocturnal asthma, we performed a randomized trial in 12 asthmatic patients and 6 normal control subjects. This study involved pulmonary function testing, methacholine challenge, bronchoscopy for cell counts, LT and thromboxane (TX) levels in bronchoalveolar lavage (BAL) fluid, and collection of urine for LTs at 4:00 P.M. and 4:00 A.M. At 4:00 P.M. BAL fluid LTB4 and sulfidopeptide LT levels in asthmatic and control subjects were not statistically different. At 4:00 A.M. alone, LTB4 and cysteinyl LT levels increased to become significantly greater in asthmatic than in control subjects, LTB4 levels correlating significantly (r = -0.66, p < 0.0001) with nocturnal fall in FEV1. Nocturnal asthmatic urinary LTE4 levels were also significantly higher than those of control subjects. The 4:00 A.M. testing was repeated during treatment with a 5-lipoxygenase inhibitor, zileuton. In asthmatic subjects, zileuton decreased BAL fluid LTB4 (p = 0.01) and urinary LTE4 (p = 0.01) while showing a trend for improving nocturnal FEV1 (p = 0.086). These decreases in LTB4 levels and improvement in FVE1 were associated with significant reductions in 4 A.M. BAL fluid and blood eosinophil percentages on zileuton compared with placebo administration. These findings demonstrate the importance of LTs in both the inflammation and the physiology of nocturnal asthma.

Topics: Adolescent; Adult; Asthma; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Bronchoconstriction; Cross-Over Studies; Double-Blind Method; Forced Expiratory Volume; Humans; Hydroxyurea; Inflammation; Leukotriene E4; Leukotrienes; Lipoxygenase Inhibitors; Middle Aged

This is a pilot study of zileuton, a selective 5-lipoxygenase inhibitor in systemic lupus erythematosus (SLE).. Forty patients with SLE received zileuton 600 mg qid or placebo in an 8 week, randomized prospective, double blind trial. Disease activity was manifested largely by constitutional, articular, and skin manifestations with no evidence of active renal, cardiac, or neurologic involvement. Concomitant administration of nonsteroidal antiinflammatories, corticosteroids, or antimalarials was not permitted. Disease activity was determined at baseline and at Days 15 and 57 by assessment of arthritis severity, the Systemic Lupus Activity Measure (SLAM), investigator and patient global ratings, hematologic indices, and serologic measures including autoantibody titers, complement levels, and interleukin 2 receptors (IL-2R). Total body sulfidopeptide leukotriene synthesis was measured by urinary leukotriene E4 (LTE4) concentrations.. Overall SLAM (the primary measure of efficacy in this study) was significantly improved with zileuton compared with placebo (-2.1 +/- 1.3, compared with an increase of 2.3 +/- 1.3 with placebo by Day 57, p = 0.048). Changes in individual SLAM subscores, arthritis severity, global ratings, and IL-2R levels compared with baseline did not achieve statistical significance, but were generally decreased from baseline with zileuton (indicating trends towards improvement) and increased from baseline with placebo (indicating trends towards clinical worsening). Urine LTE4 levels at Day 57 had increased from baseline in the placebo group (indicating worsening) and decreased in the zileuton group (indicating improvement).. Selective 5-lipoxygenase inhibition may be beneficial in mild SLE.

Topics: Adult; Aged; Double-Blind Method; Female; Humans; Hydroxyurea; Leukotriene Antagonists; Leukotriene E4; Lipoxygenase Inhibitors; Lupus Erythematosus, Systemic; Male; Middle Aged; Pilot Projects; Prospective Studies; Treatment Outcome

We have recently reported that the 5-lipoxygenase (5-LO) inhibitor, zileuton, alters lung inflammation produced by segmental antigen challenge in ragweed-allergic human subjects. Specifically, zileuton inhibited the urinary excretion of leukotriene E4 produced by antigen challenge, and the significant increase in bronchoalveolar lavage (BAL) eosinophils observed in subjects on placebo was not seen in subjects on zileuton. In this manuscript, we report additional data obtained during that study which provide information about mechanisms important during IgE-mediated inflammatory reactions in the lung. Three different areas are addressed: 1) the time to recovery of the lung from an IgE-mediated inflammatory response; 2) mechanisms related to the generation of cyclooxygenase products in the lung after antigen challenge and the effect of 5-LO inhibition on the production of cyclooxygenase metabolites; and 3) mechanisms responsible for the production of peptide leukotrienes in the lung and lung injury (as shown by albumin influx into the alveolar air space) 24 h after antigen challenge. We observed the following: 1) a significant BAL eosinophilia and basophilia remained 31 days (range 21-48) after segmental antigen challenge and bronchoalveolar lavage; 2) a decreased quantity of BAL cyclooxygenase products, as well as lipoxygenase products, in the presence of 5-LO inhibition; and 3) correlative analyses which suggest that while eosinophils appear most important for the production of peptide leukotrienes and lung injury 24 h after antigen challenge in subjects taking placebo, other effector mechanisms, perhaps those involving basophils and the initial mast cell triggering event, appear to gain in importance when the IgE-mediated inflammatory reaction is blunted by 5-LO inhibition.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Arachidonate 5-Lipoxygenase; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Bronchoscopy; Cross-Over Studies; Dinoprost; Dinoprostone; Double-Blind Method; Eosinophils; Humans; Hydroxyurea; Leukotriene B4; Leukotriene E4; Leukotrienes; Lipoxygenase Inhibitors; Lung; Lung Injury; Placebos; Prostaglandin D2; Prostaglandin-Endoperoxide Synthases; Proteins; Regression Analysis; Respiratory Hypersensitivity; Thromboxane B2

To evaluate the effectiveness of inhibiting the formation of the 5-lipoxygenase products of arachidonic acid by the 5-lipoxygenase inhibitor zileuton in the treatment of mild-to-moderate asthma.. Randomized, double-blind, placebo-controlled study.. University hospitals and private allergy and pulmonary practices.. A total of 139 persons with asthma who had a forced expiratory volume in 1 second (FEV1) of 40% to 75% of the predicted value and who were not being treated with inhaled or oral steroids.. Zileuton, 2.4 g/d or 1.6 g/d, or placebo for 4 weeks.. Airway function, beta-agonist use, and symptoms; inhibition of 5-lipoxygenase assessed by measurement of urinary leukotriene E4 (LTE4).. Zileuton produced a 0.35-L (95% CI, 0.25 to 0.45 L) increase in the FEV1 within 1 hour of administration (P < 0.001 compared with placebo), equivalent to a 14.6% increase from baseline. After 4 weeks of zileuton therapy, airway function and symptoms improved, with the greatest improvements occurring in the 2.4 g/d group: This group's FEV1 increased by 0.32 L (CI, 0.16 to 0.48 L), a 13.4% increase, compared with a 0.05-L (CI, -0.10 to 0.20 L) increase in patients taking placebo (P = 0.02). Symptoms and frequency of beta-agonist use also decreased with zileuton, 2.4 g/d. The mean urinary LTE4 level decreased by 39.2 pg/mg creatinine (CI, 18.1 to 60.4 pg/mg creatinine) and 26.5 pg/mg creatinine (CI, 6.6 to 46.5 pg/mg creatinine) in the 2.4 g/d and 1.6 g/d groups, respectively, compared with a slight increase in the placebo group (P = 0.007 and P = 0.05). No difference was noted in the number of adverse events among treatment groups.. Inhibition of 5-lipoxygenase can improve airway function and decrease symptoms and medication use in patients with asthma, suggesting that this inhibition can be useful therapy for asthma. Also, 5-lipoxygenase products may mediate part of the baseline airway obstruction in patients with mild-to-moderate asthma.

Topics: Adult; Albuterol; Asthma; Double-Blind Method; Drug Therapy, Combination; Female; Forced Expiratory Volume; Humans; Hydroxyurea; Leukotriene E4; Lipoxygenase Inhibitors; Male; Single-Blind Method

A subset of persons with asthma develop bronchospasm, naso-ocular, gastrointestinal, and/or dermal reactions after ingesting aspirin (ASA) or agents with the capacity to inhibit cyclooxygenase. The bronchopulmonary reactions have been associated with a rise in urinary LTE4. We examined the effects of an inhibitor of 5-lipoxygenase, zileuton, in a group of eight asthmatic patients with known sensitivity to ASA accompanied by LTE4 hyperexcretion. We first confirmed ASA sensitivity and an increase in urinary LTE4 after ASA ingestion in these patients using a placebo-controlled ASA challenge. Subjects were then randomized to a double-blind, crossover trial to examine the effects of zileuton versus placebo on the response to ASA. Zileuton treatment decreased baseline urinary LTE4 excretion from a mean of 469 +/- 141 pg/mg creatinine to 137 +/- 69 pg/mg creatinine (p < 0.02) and blunted the maximum increase in urinary LTE4 after ingestion of ASA (3,539 +/- 826 pg/mg creatinine versus 1,120 +/- 316 pg/mg creatinine [p < 0.01]). The pre-ASA challenge FEV1 was unchanged by zileuton (3.41 +/- 0.15 L versus 3.35 +/- 0.17 L, zileuton versus placebo). Zileuton prevented the fall in FEV1 in response to ingestion of ASA; post-ASA ingestion the mean of the minimal FEV1 fell to 2.72 +/- 0.18 L on the placebo day while there was no significant fall on the zileuton day (3.26 +/- 0.17 L; p < 0.014). Zileuton also prevented the development of the nasal, gastrointestinal (p < 0.006 and p < 0.025, respectively), and dermal symptoms which developed after ASA ingestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adult; Arachidonate 5-Lipoxygenase; Aspirin; Asthma; Bronchoconstriction; Double-Blind Method; Drug Hypersensitivity; Female; Forced Expiratory Volume; Humans; Hydroxyurea; Leukotriene E4; Lipoxygenase Inhibitors; Male; Middle Aged

The effect of a single oral dose (800 mg) of zileuton (A-64077), a specific 5-lipoxygenase inhibitor, on the early and late airway responses to inhaled allergen was studied in a randomised, double blind, placebo controlled, and crossover trial in nine subjects with atopic asthma. Leukotriene generation was also assessed in vivo by measuring urinary leukotriene (LT) E4 excretion, and ex vivo by measuring calcium ionophore stimulated whole blood LTB4 production. Zileuton almost completely inhibited ex vivo LTB4 production but reduced urinary excretion of LTE4 by only about half. There was a trend for the early asthmatic response to be less on the day of zileuton treatment, but this did not reach statistical significance (p = 0.08). The zileuton induced reduction in maximum fall in FEV1 in the early asthmatic response was, however, significantly related to the reduction in urinary LTE4 excretion (r = 0.8), but not to the reduction in LTB4 generation ex vivo. There was no significant change in the allergen induced late asthmatic response, or in the increase in airway responsiveness to methacholine following antigen. The results provide some support for the hypothesis that the cysteinyl leukotrienes have a role in the allergen induced early asthmatic response. More complete in vivo inhibition of 5-lipoxygenase may be needed to produce a significant reduction in airway response to allergen challenge.

Topics: Adult; Allergens; Asthma; Double-Blind Method; Forced Expiratory Volume; Humans; Hydroxyurea; Leukotriene B4; Leukotriene E4; Lipoxygenase Inhibitors; Male; SRS-A; Time Factors

We examined whether lung inflammatory mediators are increased during exercise and whether pharmacological blockade can prevent exercise-induced arterial hypoxemia (EIAH) in young athletes. Seventeen healthy athletes (9 men, 8 women; age 23 +/- 3 yr) with varying degrees of EIAH completed maximal incremental treadmill exercise tests after administration of fexofenadine, zileuton, and nedocromil sodium or placebo in a randomized double-blind crossover study. Lung function, arterial blood gases, and inflammatory metabolites in plasma, urine, and induced sputum were assessed. Drug administration did not improve EIAH or gas exchange during exercise. At maximal exercise, oxygen saturation fell to 91.4 +/- 2.6% (drug trial) and 91.9 +/- 2.1% (placebo trial) and alveolar-arterial oxygen difference widened to 28.1 +/- 6.3 Torr (drug trial) and 29.3 +/- 5.7 Torr (placebo trial). Oxygen consumption, ventilation, and other exercise variables were similarly unaffected by drug treatment. Although plasma histamine increased with exercise, values did not differ between trials, and urinary leukotriene E(4) and 11beta-prostaglandin F(2alpha) levels were unchanged after exercise. Postexercise sputum revealed no significant changes in markers of inflammation. These results demonstrate that EIAH in young athletes is not attenuated with acute administration of drugs targeting histamine and bioactive lipids. We conclude that airway inflammation is of insufficient magnitude to cause impairments in gas exchange and does not appear to be linked to EIAH in healthy young athletes.

Topics: Adult; Cell Count; Exercise; Female; Histamine H1 Antagonists; Humans; Hydroxyurea; Hypoxia; Inflammation Mediators; Leukotriene Antagonists; Leukotriene E4; Lung; Male; Oxygen Consumption; Pulmonary Gas Exchange; Respiratory Function Tests; Sports; Sputum; Terfenadine

1. The effect of troglitazone, an anti-diabetic drug with insulin-sensitizing action, on antigen-induced production of leukotriene (LT) B(4), C(4) and E(4) and prostaglandin D(2) (PGD(2)) was examined in dinitrophenol (DNP)-specific immunoglobulin E (IgE)-sensitized RBL-2H3 mast cells following stimulation by the antigen, DNP-conjugated human serum albumin. Levels of LTB(4), C(4) and E(4) and PGD(2) in the conditioned medium were enzyme-immunoassayed. 2. Troglitazone inhibited the antigen-induced production of LTB(4), C(4) and E(4) and the potency of the inhibition was comparable to that of zileuton, a specific inhibitor of 5-lipoxygenase (5-LOX) and a clinically used anti-asthmatic drug. Neither troglitazone nor zileuton affected antigen-induced production of PGD(2), arachidonic acid release from membrane phospholipids and degranulation. 3. Troglitazone inhibited LTB(4) production by the supernatant fraction of RBL-2H3 cell lysate with similar potency to zileuton, suggesting that troglitazone inhibits LT production by direct inhibition of 5-LOX activity. 4. Furthermore, it was shown that troglitazone as well as zileuton inhibited LTB(4) production in A23187-stimulated rat peritoneal neutrophils. 5. These findings suggest that troglitazone inhibits antigen-induced LT production in the IgE-sensitized RBL-2H3 cells and A23187-stimulated rat peritoneal neutrophils by direct inhibition of 5-LOX activity.

Topics: Animals; Antigens; Arachidonic Acid; Calcimycin; Cell Degranulation; Cell Line; Chromans; Culture Media, Conditioned; Hydroxyurea; Hypoglycemic Agents; Immunoglobulin E; Leukotriene B4; Leukotriene C4; Leukotriene E4; Leukotrienes; Lipoxygenase Inhibitors; Male; Mast Cells; Neutrophils; Prostaglandin D2; Rats; Rats, Sprague-Dawley; Thiazoles; Thiazolidinediones; Troglitazone

In man, the therapeutic effectiveness of specific inhibitors of leukotriene (LT) biosynthesis against allergen-induced bronchoconstriction appears to be related to the in vivo biochemical efficacy of these compounds, as measured by inhibition of whole blood LTB4 generation (upon A23187 stimulus) and, particularly, urinary LTE4 excretion. Accordingly, we have assessed the ability of two clinically documented LT biosynthesis inhibitors, zileuton and MK-886, and the structurally novel 5-lipoxygenase activating protein antagonist, MK-0591, to inhibit the production of these inflammatory arachidonic acid metabolites in laboratory dogs. Zileuton (2 mg/kg) was extremely bioavailable in dogs (> 10 microM plasma concentrations), and inhibited the A23187-induced ex vivo production of LTB4 by venous blood by > 90%, in concordance with its potency in canine blood in vitro (IC50 = 1.1 microM). Despite this degree of inhibition in whole blood, urinary LTE4 excretion was reduced by only 52%, a profile of activity similar to that seen in clinical studies. MK-886 was less well absorbed, with plasma concentrations of 3 microM being achieved only at 25 mg/kg. These levels resulted in < 45% inhibition of LTB4 production, but a significant (p < 0.05) 47% inhibition of urinary LTE4 excretion. MK-0591 was similarly bioavailable (compared with MK-886), but 10-fold more active in vivo as a 2 mg/kg dose resulted in 41-62% inhibition of urinary LTE4 excretion (p < 0.05 vs controls; n = 4, 28). Significant inhibition of ex vivo LTB4 synthesis was also observed at this dose (49%), in accord with peak plasma concentrations of 0.5 microM and an in vitro potency of 0.2-0.4 microM (IC50) in whole blood from these animals. At higher dose (10 mg/kg), MK-0591 inhibited LTE4 excretion by 69%, with 88% inhibition of the LT biosynthetic capacity of whole blood. These data demonstrate that the biochemical efficacy of structurally diverse leukotriene biosynthesis inhibitors can be assessed in vivo in normal laboratory dogs. Such measurements, combined with bioavailability data from other species, may be useful for predicting biochemical activity in man.

Topics: Animals; Calcimycin; Chromatography, High Pressure Liquid; Depression, Chemical; Dogs; Dose-Response Relationship, Drug; Hydroxyurea; Indoles; Leukotriene Antagonists; Leukotriene E4; Leukotrienes; Lipoxygenase Inhibitors; Male; Quinolines