Increased levels of cysteinyl-leukotrienes in saliva, induced sputum, urine and blood from patients with aspirin-intolerant asthma.

BACKGROUND: A diagnosis of aspirin-intolerant asthma requires aspirin provocation in specialist clinics. Urinary leukotriene E(4) (LTE(4)) is increased in aspirin-intolerant asthma. A study was undertaken to investigate new biomarkers of aspirin intolerance by comparing basal levels of cysteinyl-leukotrienes (CysLTs) and leukotriene B(4) (LTB(4)) in saliva, sputum and ex vivo stimulated blood in subjects with aspirin-intolerant and aspirin-tolerant asthma. The effects of aspirin- and allergen-induced bronchoconstriction on leukotriene levels in saliva and ex vivo stimulated blood were also compared with the effects of the provocations on urinary mediators. METHODS: Induced sputum, saliva, urine and blood were obtained at baseline from 21 subjects with asthma. At a separate visit, 11 subjects showed a positive response to lysine-aspirin inhalation and 10 were aspirin tolerant. Saliva, blood and urine were also collected on the provocation day. Analyses of CysLTs and LTB(4) and the prostaglandin D(2) metabolite 9alpha,11beta-prostaglandin F(2) were performed and the fraction of exhaled nitric oxide was measured. RESULTS: Subjects with aspirin-intolerant asthma had higher exhaled nitric oxide levels and higher baseline levels of CysLTs in saliva, sputum, blood ex vivo and urine than subjects with aspirin-tolerant asthma. There were no differences in LTB(4) levels between the groups. Levels of urinary LTE(4) and 9alpha,11beta-prostaglandin F(2) increased after aspirin provocation whereas leukotriene levels in saliva and ex vivo stimulated blood did not increase. CONCLUSION: These findings support a global and specific increase in CysLT production in aspirin-intolerant asthma. Measurement of CysLTs in saliva has the potential to be a new and convenient non-invasive biomarker of aspirin-intolerant asthma.

Release of prostaglandin D2 and leukotriene C4 in response to hyperosmolar stimulation of mast cells.

BACKGROUND: Mannitol-induced bronchoconstriction in subjects with exercise-induced asthma is associated with increased urinary excretion of 9alpha, 11beta-PGF(2), a metabolite of prostaglandin D(2) (PGD(2)) serving as a mast cell marker. It has however been questioned whether or not human mast cells release PGD(2) and leukotriene C(4) (LTC(4)) after osmotic challenge with mannitol in vitro. METHODS: Cord blood-derived human mast cells were stimulated osmotically, immunologically or with a combination of both. Supernatants were analysed for PGD(2), LTC(4) and histamine contents with enzyme immunoassays. RESULTS: Significant release of de novo synthesized eicosanoids, predominantly PGD(2) [12 (8.8, 14) pmol/10(6)cells; median (25th, 75th percentile) but also LTC(4) (0.1 (0.08, 0.15) pmol/10(6) cells] were found in mast cells in vitro in response to 0.7 M mannitol stimulation. A massive release of histamine [70 (5.3)% of total; mean (SEM)] was also found. There were no correlations between the levels of released mediators after mannitol stimulation. In contrast, there was a correlation between release of PGD(2) and LTC(4), following immunological stimulation. CONCLUSION: The findings support that hyperosmolar challenge activates mast cells, but different than antigen stimulation.

Saliva is one likely source of leukotriene B4 in exhaled breath condensate.

Leukotriene (LT)B4 in exhaled breath condensate (EBC) has been reported to be elevated in airway inflammation. The origin of leukotrienes in EBC is, however, not established. The aims of this study are to measure LTB4 levels in EBC collected in two challenges characterised by a strong neutrophilic airway inflammation and to compare LTB4 levels in EBC with levels in sputum and saliva. LTB4 and alpha-amylase were measured in EBC from 34 healthy subjects exposed in a pig confinement building or to a lipopolysaccharide provocation. These markers were also measured in induced sputum in 11 of the subjects. For comparison, LTB4 and alpha-amylase were measured in saliva from healthy subjects. Only four out of 102 EBC samples had detectable LTB4 (28-100 pg x mL(-1)). alpha-amylase activity was detected in the LTB4-positive samples. In contrast, LTB4 was detected in all examined sputum supernatants in the same study (median 1,190 pg x mL(-1)). The median LTB4 level in saliva was 469 pg x mL(-1). High levels of leukotriene B4 in saliva and the presence of leukotriene B4 in exhaled breath condensate only when alpha-amylase was detected, indicate that leukotriene B4 found in exhaled breath condensate is the result of saliva contamination. As leukotriene B4 was consistently present in sputum supernatants, exhaled breath condensate may be inappropriate for monitoring airway leukotriene B4.

Inhibition of mast cell PGD2 release protects against mannitol-induced airway narrowing.

Mannitol inhalation increases urinary excretion of 9alpha,11beta-prostaglandin F2 (a metabolite of prostaglandin D2 and marker of mast cell activation) and leukotriene E4. The present study tested the hypothesis that beta2-adrenoreceptor agonists and disodium cromoglycate (SCG) protect against mannitol-induced bronchoconstriction by inhibition of mast cell mediator release. Fourteen asthmatic subjects inhaled mannitol (mean dose 252+/-213 mg) in order to induce a fall in forced expiratory volume in one second (FEV1) of > or = 25%. The same dose was given 15 min after inhalation of formoterol fumarate (24 microg), SCG (40 mg) or placebo. Pre- and post-challenge urine samples were analysed by enzyme immunoassay for 9alpha,11beta-prostaglandin F2 and leukotriene E4. The maximum fall in FEV1 of 32+/-10% on placebo was reduced by 95% following formoterol and 63% following SCG. Following placebo, there was an increase in median urinary 9alpha,11beta-prostaglandin F2 concentration from 61 to 92 ng.mmol creatinine(-1), but no significant increase in 9alpha,11beta-prostaglandin F2 concentration in the presence of either formoterol (69 versus 67 ng.mmol creatinine(-1)) or SCG (66 versus 60 ng.mmol creatinine(-1)). The increase in urinary leukotriene E4 following placebo (from 19 to 31 ng.mmol creatinine(-1)) was unaffected by the drugs. These results support the hypothesis that the drug effect on airway response to mannitol is due to inhibition of mast cell prostaglandin D2 release.

Early rise in exhaled nitric oxide and mast cell activation in repeated low-dose allergen challenge.

Repeated low-dose allergen inhalation challenge mimics natural allergen exposure, providing a model for early mechanisms in the triggering of asthma. The current authors performed a controlled study to evaluate the time course of changes in exhaled nitric oxide fraction (F(e,NO)) and urinary biomarkers of airway inflammation. Eight subjects with mild allergic asthma completed two 7-day repeated low-dose challenge periods, with diluent and allergen, respectively. Subjects were symptom free at inclusion and were investigated when not exposed to specific allergen. Pulmonary function and symptoms were followed, and F(e,NO) and urinary mediators were correlated to changes in airway responsiveness to histamine and adenosine. Despite no change in pulmonary function (forced expiratory volume in one second mean+/-sem fall 0.3+/-0.7 versus 0.6+/-1.0%, for diluent and allergen, respectively) and no asthma symptoms, repeated allergen exposure, in contrast to diluent, caused significant increases in histamine responsiveness (2.3 doubling doses), an early and gradual increase in F(e,NO) (up to a doubling from baseline) and a small increase in the mast cell marker 9alpha11beta-prostaglandin F(2) after adenosine challenge. In conclusion, serial measurements of exhaled nitric oxide fraction have the potential to provide a very sensitive strategy for early detection of emerging airway inflammation and subsequent changes in airway hyperresponsiveness to histamine.

Relation between bronchial responsiveness to inhaled leukotriene D4 and markers of leukotriene biosynthesis.

BACKGROUND: While clinical trials with antileukotrienes have shown overall beneficial effects in asthma, the factors that determine leukotriene dependent asthma are still unclear. A study was undertaken to determine whether or not leukotriene responsiveness in the airways correlates with endogenous leukotriene biosynthesis. METHODS: Bronchial responsiveness to leukotriene (LT) D4 was assessed as PD20FEV1 in 20 subjects with mild asthma and 10 healthy controls, and compared with bronchial responsiveness to methacholine and two global measures of leukotriene production-urinary LTE4 and ex vivo production of LTB4 in whole blood. RESULTS: In patients with asthma the bronchoconstrictor activity of LTD4 was about 1300 times greater than methacholine (geometric mean PD20 0.69 nmol v 887 nmol). Those who were most responsive to LTD4 were relatively less responsive to methacholine (p<0.01). There was, however, no correlation between bronchial responsiveness to LTD4 and urinary LTE4 or blood ex vivo LTB4 levels in asthmatic subjects or healthy controls. Subjects with asthma treated with inhaled corticosteroids produced higher levels of LTB4 (p<0.05). CONCLUSIONS: General measures of leukotriene production cannot predict bronchial responsiveness to LTD4. The unique bronchoconstrictive potency of LTD4 on human airways may relate to the locally regulated expression of the cysteinyl LT1 receptor.

Evidence of mast cell activation and leukotriene release after mannitol inhalation.

The aim of this study was to investigate if mannitol inhalation, as a model of exercise-induced bronchoconstriction (EIB), causes mast cell activation and release of mediators of bronchoconstriction. Urinary excretion of previously identified mediators of EIB was investigated in association with mannitol-induced bronchoconstriction. Twelve asthmatic and nine nonasthmatic subjects inhaled mannitol and urine was collected 60 min before and for 90 min after challenge. The urinary concentrations of leukotriene (LT)E4, the prostaglandin (PG)D2 metabolite and the mast cell marker 9alpha,11beta-PGF2 were measured by enzyme immunoassay. N(tau)-methylhistamine was measured by radioimmunoassay. In asthmatic subjects, inhalation of a mean+/-SEM dose of 272+/-56 mg mannitol induced a reduction in forced expiratory volume in one second (FEV1) of 34.5+/-2.1%. This was associated with increases in urinary 9alpha,11beta-PGF2 (91.9+/-8.2 versus 66.9+/-6.6 ng x mmol creatinine(-1), peak versus baseline) and LTE4 (51.3+/-7.5 versus 32.9+/-4.7). In nonasthmatic subjects, the reduction in FEV1 was 1.0+/-0.5% after inhaling 635 mg of mannitol. Although smaller than in the asthmatics, significant increases of urinary 9alpha,11beta-PGF2 (68.4+/-6.9 versus 56.0+/-5.8 ng x mmol creatinine(-1)) and LTE4 (58.5+/-5.3 versus 43.0+/-3.3 ng x mmol creatinine(-1)) were observed in the nonasthmatic subjects. There was also a small increase in urinary excretion of N(tau)-methylhistamine in the nonasthmatics, but not in the asthmatics. The increased urinary levels of 9alpha,11beta-prostaglandin F2 support mast cell activation with release of mediators following inhalation of mannitol. Increased bronchial responsiveness to the released mediators could explain the exclusive bronchoconstriction in asthmatic subjects.

Cysteinyl leukotrienes in porcine acute allergic airway reactions: bronchial and vascular effects.

OBJECTIVE AND DESIGN: The role of cysteinyl leukotrienes (cysLTs) in the acute allergic airway reaction in the pig was investigated, with focus on the effects on the bronchial circulation, and compared with histamine-induced effects. MATERIAL: 31 barrier-bred pigs were used, of which 24 pigs were actively-sensitised to Ascaris suum. METHODS: Leukotriene D(4) (LTD(4)) and histamine were injected intravenously (i.v.) and given as an aerosol to non-sensitised pigs. Seventeen animals, sensitised to Ascaris suum, were challenged with Ascaris antigen aerosol. The effect of MK-571, a CysLT(1)-receptor antagonist, on LTD(4)- and allergen-induced responses were investigated. RESULTS: LTD(4) (2 nmol/kg) i.v. injection increased the airways resistance (R(aw)) by 46 +/- 20% and reduced bronchial vascular conductance (BVC) by 38 +/- 2%. Both these effects were blocked by MK-571 (0.1 mg/kg i.v.). Histamine injections (i.v.) in equimolar doses caused similar dose-dependent increases in R(aw), (22 +/- 7%) but induced vasodilatation and an increase in BVC (22 +/- 8%). Aerosolised LTD(4) (4 nmol/kg) caused a decrease in BVC but did not affect R(aw). In sensitised pigs, challenge with Ascaris aerosol led to an acute increase in Raw (198 +/- 57%) and increase in BVC (62 +/- 35%). MK-571 (0.5 mg/kg i.v.) pre-treatment did not significantly affect these responses (n = 9). CONCLUSIONS: LTD(4) causes constriction of the pig bronchi and of the bronchial circulation via activation of the CysLT(1) receptor and may counteract histamine-induced vasodilatory effects. However, in the allergen-induced acute airway response in the pig, cysLTs do not seem to be important bronchoconstrictive mediators.

An alternative pathway for metabolism of leukotriene D(4): effects on contractions to cysteinyl-leukotrienes in the guinea-pig trachea.

Contractions of guinea-pig tracheal preparations to cysteinyl-leukotrienes (LTC(4), LTD(4) and LTE(4)) were characterized in organ baths, and cysteinyl-leukotriene metabolism was studied using radiolabelled agonists and RP-HPLC separation. In the presence of S-hexyl GSH (100 microM) the metabolism of [(3)H]-LTC(4) into [(3)H]-LTD(4) was inhibited and the LTC(4)-induced contractions were resistant to CysLT(1) receptor antagonism but inhibited by the dual CysLT(1)/CysLT(2) receptor antagonist BAY u9773 (0.3 - 3 microM) with a pA(2)-value of 6.8+/-0.2. In the presence of L-cysteine (5 mM), the metabolism of [(3)H]-LTD(4) into [(3)H]-LTE(4) was inhibited and the LTD(4)-induced contractions were inhibited by the CysLT(1) receptor antagonist ICI 198,615 (1 - 10 nM) with a pA(2)-value of 9.3+/-0.2. However, at higher concentrations of ICI 198,615 (30 - 300 nM) a residual contraction to LTD(4) was unmasked, and this response was inhibited by BAY u9773 (1 - 3 microM). In the presence of the combination of S-hexyl GSH with L-cysteine, the LTD(4)-induced contractions displayed the characteristics of the LTC(4) contractile responses, i.e. resistant to CysLT(1) receptor antagonism, increased maximal contractions and slower time-course. This qualitative change of the LTD(4)-induced contraction was also observed in the presence of S-decyl GSH (100 microM), GSH (10 mM) and GSSG (10 mM). S-hexyl GSH, S-decyl GSH, GSH and GSSG all stimulated a formation of [(3)H]-LTC(4) from [(3)H]-LTD(4). In conclusion, GSH and GSH-related compounds changed the pharmacology of the LTD(4)-induced contractions by stimulating the conversion of LTD(4) into LTC(4). Moreover, the results indicate that, in addition to the metabolism of LTC(4) into LTD(4) and LTE(4), also the formation of LTC(4) from LTD(4) may regulate cysteinyl-leukotriene function.

Benefits of high altitude allergen avoidance in atopic adolescents with moderate to severe asthma, over and above treatment with high dose inhaled steroids.

Some patients with severe asthma cannot be controlled with high doses of inhaled steroids (ICS), which may be related to ongoing environmental allergen exposure. We investigated whether 10 weeks of high altitude allergen avoidance leads to sustained benefits regarding clinical and inflammatory markers of disease control in adolescents with persistent asthma despite treatment with high dose ICS. Eighteen atopic asthmatic adolescents (12-18 yr, 500-2000 microg ICS daily) with established house dust mite allergy, participated in a parallel-group study. Quality of life (PAQL), lung function, bronchial hyperresponsiveness (BHR) to adenosine and histamine, induced sputum and urine samples were collected repeatedly from 10 patients during a 10-week admission period to the Swiss Alps (alt. 1560 m) and at 6 weeks after return to sea level. Results were compared with those in eight patients, studied in their home environment at sea level for a similar time period. Throughout the study, asthma medication remained unchanged in both groups. During admission to high altitude, PAQL, lung function, BHR to adenosine and histamine, and urinary levels of eosinophil protein X (U-EPX), leukotriene E4 (U-LTE4) and 9alpha11beta prostaglandin F2 (U-9alpha11beta PGF2) improved significantly (P < 0.05), with a similar tendency for sputum eosinophils (P < 0.07). Furthermore, the changes in PAQL and BHR to adenosine and histamine were greater in the altitude than in the control group (P < 0.05). At 6 weeks after renewed allergen exposure at sea level, the improvements in PAQL (P < 0.05), BHR to adenosine (P < 0.07) and histamine (P < 0.05), as well as U-EPX (P < 0.05) and U-LTE4 (P < 0.05) were maintained. A short period of high altitude allergen avoidance, on top of regular treatment with ICS and long-acting beta2-agonists, results in improvement of asthma, as assessed by clinical and inflammatory markers of disease severity. These findings indicate that short-term, rigorous allergen avoidance can improve the long-term control of severe asthma over and above what can be achieved even by high doses of inhaled steroids.

The challenge procedure influences the extent of allergen-induced urinary excretion of leukotriene E4.

BACKGROUND: Cysteinyl-leukotrienes are central mediators in asthma and urinary leukotriene E4 (LTE4) is a reliable marker of their endogenous formation. OBJECTIVE: This study tested the hypothesis that the procedure used for allergen bronchoprovocation influences the bronchoconstrictor response and the amount of LTE4 excreted following allergen challenge. METHODS: Seven atopic asthmatic men underwent two allergen bronchoprovocations 4 weeks apart. The same total dose of allergen was given at both sessions, cumulatively on one occasion and as a single dose at the other session. Urine was collected in hourly samples before and after challenge and LTE4 was measured with previously validated methodology. RESULTS: The mean (+/- SE) drop in FEV1 was not significantly different between the cumulative (29 +/- 2.4%) and the single dose challenge (25 +/- 2.8%). There was a significant increase in post-challenge levels of urinary LTE4 after both sessions. The peak excretion of LTE4 occurred 1 h following the maximal drop in FEV1 for both challenges. However, the post-challenge increase in urinary LTE4 was significantly larger at the cumulative session. In fact, the net increase (post-challenge minus prechallenge) of urinary LTE4 was more than twofold higher after the cumulative session (AUC 0-3 h post-challenge: 46.7 +/- 8.2 vs 22.1 +/- 9.8, P < 0.05). CONCLUSION: The peak excretion of urinary LTE4 occurred within 2 h after the termination of either challenge but the magnitude of urinary excretion of LTE4 was larger when cumulative challenge was performed. The findings are important to consider when designing studies where allergen-induced urinary excretion of LTE4 is an outcome variable.

Analyses of prostaglandin D2 metabolites in urine: comparison between enzyme immunoassay and negative ion chemical ionisation gas chromatography-mass spectrometry.

Measurements of the prostaglandin (PGD2) metabolite 9 alpha, 11 beta-PGF2 in unextracted urine performed by enzyme immunoassay (EIA) were compared with values obtained by negative chemical ionisation gas chromatography-mass spectrometry (NCI GC-MS). Values determined by NCI GC-MS were in the same range but consistently lower than those obtained by EIA, suggesting that other endogenous compounds could be contributing to the immunoreactivity. Isoprostanes were generated by autoxidation of arachidonic acid and the 9 alpha, 11 beta-PGF2 antibody demonstrated less than 0.7% crossreactivity to the mix, making it unlikely that isoprostanes in urine interfere with quantification of 9 alpha, 11 beta-PGF2 by EIA. This was further supported by the 70% reduction in immunoreactive material measured in urine after three days treatment in a healthy volunteer with the cyclooxygenase inhibitor ibuprofen. Purification of urine samples by reverse phase high-performance liquid chromatography (HPLC) revealed the presence of two immunoreactive compounds in addition to 9 alpha, 11 beta-PGF2. The compounds were identified as dinor compounds by NCI GC-MS. One of the compounds was identical to 9 alpha, 11 beta-2,3-dinor-PGF2 which was generated by beta-oxidation of 9 alpha, 11 beta-PGF2 and identified by electron impact (EI)-GC-MS. In conclusion, urinary 9 alpha, 11 beta-PGF2 concentrations measured by EIA represent the sum of 9 alpha, 11 beta-PGF2 and two isomers of its dinor metabolite. Thus, the direct EIA is fast, sensitive and sufficiently specific to monitor activation of the PGD2 pathway, thereby providing a valuable clinical tool to assess the status of mast cell activation in vivo.

Markers of inflammation and bronchial reactivity in children with asthma, exposed to animal dander in school dust.

Several studies have confirmed the presence of animal dander allergens in school dust but the effect of this indirect animal exposure on health has not been evaluated. In this study we investigated bronchial reactivity and markers of eosinophil activity and inflammation during two separate weeks of school in 10 children with mild asthma and a positive skin prick test to cat and dog. At the beginning and the end of the first week the children underwent bronchial challenges with methacholine, and at the beginning and the end of the second week they underwent nasal lavages (NAL) and induced sputum samplings. Blood and urine samples for analysis of inflammatory markers were obtained before and after both school weeks. Peak expiratory flow (PEF) and symptoms of asthma and allergy were recorded daily, and spirometry was performed on each visit. The exposure to animal dander allergens was estimated from dust samples obtained in the subjects' schools and homes. Bronchial sensitivity to methacholine increased in the week when this was measured. The proportion of eosinophils in peripheral blood, and urinary eosinophil protein X (EPX), decreased in both weeks. There was a trend towards an increase of eosinophil peroxidase (EPO) and myeloperoxidase (MPO) in sputum in the week when these proteins were measured. The concentrations of cat (Fel d1) and dog (Can f1) allergens were higher in dust collected in schools than in homes. Our results show that in children with mild asthma and animal dander allergy, there is a significantly increased bronchial sensitivity to methacholine after one school week. There is also a significant decrease in the number of circulating eosinophils and a trend towards an increase of sputum EPO, which could correlate with the early phase of eosinophil recruitment to the lungs. These effects may be related to the continuous exposure to animal allergens in school dust.

Urinary excretion of inflammatory mediators during allergen-induced early and late phase asthmatic reactions.

BACKGROUND: It is generally accepted that the early asthmatic response to inhaled allergen is a result of IgE-mediated mast cell activation. In contrast, the underlying mechanism of the late asthmatic response is much less clear. OBJECTIVE: In order to investigate the pattern of mediator release during the early and late asthmatic responses to allergen, measurements of the urinary excretion of the mast cell markers 9alpha,11beta-PGF2 and Ntau-methylhistamine were made. In addition, urinary levels of eosinophil protein X (EPX) and leukotriene E4 (LTE4) were measured. METHODS: Twelve mild atopic asthmatics participated in the study. On the study day, pulmonary function was recorded at baseline and for 12 h after inhalation of allergen. Urine was collected prior to challenge and thereafter at 1 h intervals. Measurements of 9alpha, 11beta-PGF2 and LTE4 were made with enzyme-immunoassay, and levels of Ntau-methylhistamine and EPX were analysed with radioimmunoassay. RESULTS: All subjects developed both an early and late phase airway response. Within 1 h of the early peak airway response, there was a significant increase in the urinary concentrations (AUC/h) of 9alpha, 11beta-PGF2 (49.3 +/- 9.2 to 142.5 +/- 49.2; P < 0.001) Ntau-methylhistamine (10.4 +/- 1.4 to 19.5 +/- 1.4; P < 0.001) and LTE4 (43.7 +/- 5.9 to 105.9 +/- 21.3; P < 0.001). Levels of all three mediators were also significantly increased above baseline during the LAR to 79.4 +/- 9.5 (P < 0.01), 19.8 +/- 1.9 (P < 0.001) and 85.6 +/- 10.4 (P < 0.001), respectively. Levels of EPX remained unchanged during the early and late responses (39.2 +/- 10.2 to 37.5 +/- 18.5, 33.9 +/- 6.8). CONCLUSIONS: These results indicate that mast cell activation is a feature not only of the early but also the late asthmatic response. Finally, increased LTE4 supports the contribution of the leukotrienes to airway obstruction during both phases of the asthmatic response to allergen.

Evidence for mast cell activation during exercise-induced bronchoconstriction.

Controversy remains about the causative mediators in the bronchoconstrictive response to exercise in asthma. This study examined whether mast cell activation is a feature of exercise-induced bronchoconstriction by measuring urinary metabolites of mast cell mediators. Twelve nonsmoking subjects with mild asthma and a history of exercise-induced bronchoconstriction exercised on a stationary bicycle ergometer for 5 min at 80% maximum work load. Pulmonary function was monitored and urine was collected before and 30 and 90 min after the provocation. The urinary concentrations of the mast cell markers 9alpha,11beta-prostaglandin (PG)F2 and Ntau-methylhistamine, as well as leukotriene E4 (LTE4) were determined by immunoassay. Seven of the 12 subjects (responders) experienced bronchoconstriction (>15% fall in the forced expiratory volume in one second) following exercise, whereas the pulmonary function of the remaining five subjects (nonresponders) remained stable. The urinary excretion (mean+/-SE) of 9alpha,11beta-PGF2 in the responders increased significantly compared with the nonresponders at 30 (77.1+/-14.4 versus 37.2+/-5.6; p<0.05) and 90 min (79.3+/-8.6 versus 40.4+/-8.5, p<0.05) after exercise challenge. The urinary excretion of Ntau-methylhistamine and LTE4 was not significantly different between the two groups at 30 or 90 min after exercise. The findings represent the first documentation of increased urinary levels of 9alpha,11beta-prostaglandin F2 in adults following exercise challenge and provides clear evidence for mast cell activation during exercise-induced bronchoconstriction in asthmatics.

Benefits from adding the 5-lipoxygenase inhibitor zileuton to conventional therapy in aspirin-intolerant asthmatics.

From bronchoprovocation studies and investigations of the acute effects of drugs that inhibit leukotrienes (LT), the hypothesis has emerged that leukotrienes are important mediators of airway obstruction and other symptoms in aspirin-intolerant asthma (AIA). However, it has yet not been shown if subjects with AIA respond favorably to clinical treatment with leukotriene inhibitors. Therefore, in a double-blind placebo-controlled crossover study, we examined the effects of 6 wk of treatment with the leukotriene-pathway inhibitor zileuton (600 mg, four times daily) in 40 patients with well-characterized AIA. The treatment was added to existing therapy, which included medium to high doses of inhaled (average daily dose 1,030 microg of beclomethasone or budesonide) or oral glucocorticosteroids (4 to 25 mg/d) for all but one of the patients. On top of this treated baseline, there were no significant effects of adding placebo, indicating that their asthma was kept relatively stable. However, there was an acute and chronic improvement in pulmonary function after treatment with zileuton, expressed both as increased FEV1 from baseline compared with placebo, and higher morning and evening peak expiratory flow rate (PEFR) values on zileuton treatment compared with placebo. The improvements occurred despite lower use of rescue bronchodilator with zileuton. Zileuton also diminished nasal dysfunction, which is one of the cardinal signs of AIA. There was a remarkable return of smell, less rhinorrhea, and a trend for less stuffiness and higher nasal inspiratory flow during treatment with zileuton. Zileuton caused a small but distinct reduction of bronchial hyperresponsiveness to histamine and inhibited aspirin-induced bronchoconstriction. Zileuton inhibited urinary excretion of LTE4 but did not change airway reactivity to inhaled LTD4, supporting that zileuton specifically inhibited leukotriene biosynthesis. The findings indicate that leukotrienes are important mediators of persistent airway obstruction and chronic nasal dysfunction in AIA. The study also suggests that addition of a leukotriene pathway inhibitor such as zileuton may bring about greater control of asthma than what is achieved by treatment with medium to high doses of glucocorticosteroids alone.