Urinary leukotriene E4 in patients with asthma. Effect of airways reactivity and sodium cromoglycate

Leukotriene receptor antagonists in virus-induced wheezing : evidence to date

Virus-induced wheezing is a relatively benign entity that is usually transient in early childhood but is responsible for much health care utilization. The condition, seen traditionally as a subset of those children diagnosed as having frequent episodic asthma, is often treated with inhaled corticosteroids, despite their lack of efficacy. However, there remains some confusion differentiating atopic asthma from virus-induced wheezing in young children and their respective treatment strategies.The demonstration of cysteinyl leukotrienes in the nasopharyngeal secretions of infants and young children who wheeze prompted investigation of the role of leukotriene receptor antagonists in the treatment of virus-induced wheezing for young children with bronchiolitis and virus-induced wheezing.Montelukast, the only leukotriene receptor antagonist studied in young children, has been proven useful in increasing the number of symptom-free days and delaying the recurrence of wheeze in the month following a diagnosis of respiratory syncytial virus-induced wheezing in children aged 3-36 months. Subsequently, in children aged 2-5 years with frequent episodic asthma, primarily involving viral induced attacks in this age group, regular therapy with daily montelukast for 12 months reduced the rate of asthma exacerbations by 31% over placebo, delayed the time to the first exacerbation by 2 months, and lowered the need to prescribe inhaled corticosteroids as preventative therapy. Additionally, montelukast has been demonstrated to be efficacious as an acute episode modifier in children aged 2-14 years (85% children <6 years) with virus-induced wheezing where it was prescribed at the onset of a viral infection in children with an established pattern of viral induced episodes of wheeze in the preceding year. In this study, emergency department visits were reduced by 45%, visits to all health care practitioners were reduced by 23%, and time of preschool/school and parental time off work was reduced by 33% for children who took montelukast for a median of 10 days.At present, there is good evidence to support the use of bronchodilators in the acute treatment of virus- induced wheezing, and increasing evidence to support the use of leukotriene receptor antagonists, in particular montelukast, in the management of children with virus-induced wheezing.

Biomarkers for Bronchopulmonary Dysplasia in the Preterm Infant

Bronchopulmonary dysplasia (BPD) is a chronic inflammatory lung disease of very-low-birth-weight (VLBW) preterm infants, associated with arrested lung development and a need for supplemental oxygen. Over the past few decades, the incidence of BPD has significantly raised as a result of improved survival of VLBW infants requiring mechanical ventilation. While early disease detection is critical to prevent chronic lung remodeling and complications later in life, BPD is often difficult to diagnose and prevent due to the lack of good biomarkers for identification of infants at risk, and overlapping symptoms with other diseases, such as pulmonary hypertension (PH). Due to the current lack of effective treatment available for BPD and PH, research is currently focused on primary prevention strategies, and identification of biomarkers for early diagnosis, that could also represent potential therapeutic targets. In addition, novel histopathological, biochemical, and molecular factors have been identified in the lung tissue and in biological fluids of BPD and PH patients that could associate with the disease phenotype. In this review, we provide an overview of biomarkers for pediatric BPD and PH that have been identified in clinical studies using various biological fluids. We also present a brief summary of the information available on current strategies and guidelines to prevent and diagnose BPD and PH, as well as their pathophysiology, risk factors, and experimental therapies currently available.

Correlation of urinary inflammatory and oxidative stress markers in very low birth weight infants with subsequent development of bronchopulmonary dysplasia

Currently, bronchopulmonary dysplasia (BPD) occurs almost exclusively in pre-term infants. In addition to prematurity, other factors like oxygen toxicity and inflammation can contribute to the pathogenesis. This study aimed to compare urinary inflammatory and oxidative stress markers between the no/mild BPD group and moderate/severe BPD group and between BPD cases with significant early lung disease like respiratory distress syndrome (RDS) ('classic' BPD) and with minimal early lung disease ('atypical' BPD). A total of 60 patients who were a gestational age < 30 weeks or a birth weight < 1250 g were included. Urine samples were obtained on the 1(st), 3(rd) and 7(th) day of life and measured the levels of leukotriene E(4) (LTE(4)) and 8-hydroxydeoxyguanosine (8-OHdG). The 8-OHdG values on the 3(rd) day showed significant correlation to duration of mechanical ventilation. The 8-OHdG levels on the 7(th) day were the independent risk factor for developing moderate/severe BPD. In 'classic' BPD, the 8-OHdG values on the 3(rd) day were higher than those of 'atypical' BPD. In 'atypical' BPD, the LTE(4) values on the 7(th) day were higher than the values in 'classic' BPD. These results suggest that oxidative DNA damage could be the crucial mechanism in the pathogenesis of current BPD and the ongoing inflammatory process could be an important mechanism in 'atypical' BPD.

Failure of tacrolimus to prevent aspirin-induced respiratory reactions in patients with aspirin-exacerbated respiratory disease

BACKGROUND

In patients with aspirin-exacerbated respiratory disease (AERD), pretreatment with asthma controller medications (leukotriene modifiers, inhaled or systemic corticosteroids, and salmeterol) partially modifies the severity of aspirin-induced asthmatic reactions.

OBJECTIVE

A recent study showed that pretreatment with tacrolimus completely prevented aspirin-induced respiratory reactions and might allow silent aspirin desensitization.

METHODS

Ten patients with rhinosinusitis, nasal polyps, and asthma had a history of asthma attacks after ingesting aspirin and nonsteroidal anti-inflammatory drugs. All underwent baseline oral aspirin challenges and had typical respiratory reactions. They were then randomized to receive tacrolimus (0.1 mg/kg weight; 8 patients) or placebo (2 patients) in a double-blind protocol before rechallenge with aspirin using the previous provoking dose of aspirin. In addition, respiratory reactions sustained by 50 consecutive patients with AERD during 2004 were recorded, analyzed, and compared with the tacrolimus/placebo-treated patients to determine whether there were any differences.

RESULTS

Tacrolimus pretreatment failed to block respiratory reactions to provoking doses of aspirin in 5 of 8 patients with AERD, and in the other 3 patients did not block higher doses of aspirin. The results of oral aspirin challenges in the control population of 50 patients were compared with either the baseline or postchallenge data from the tacrolimus-pretreated or placebo-pretreated patients with AERD, and there were no significant differences.

CONCLUSIONS

Use of tacrolimus as add-on pretreatment to prevent reactions to aspirin in patients with AERD or to achieve the goal of silent aspirin desensitization could not be accomplished.

Concentrations of cysteinyl leukotrienes in urine and bronchoalveolar lavage fluid of cats with experimentally induced asthma

OBJECTIVE

To evaluate changes in cysteinyl leukotriene (LT) concentrations in urine and bronchoalveolar lavage fluid (BALF) in cats with experimentally induced asthma.

ANIMALS

19 cats with experimentally induced asthma and 5 control cats.

PROCEDURE

Cats were sensitized to Bermuda grass or house dust mite allergen, and phenotypic features of asthma were confirmed with intradermal skin testing, evaluation of BALF eosinophil percentages, and pulmonary function testing. A competitive ELISA kit for LTC4, LTD4, and LTE4 was used for quantitative analysis of LTs. Urinary creatinine concentrations and BALF total protein (TP) concentrations were measured, and urinary LT-to-creatinine ratios and BALF LT-to-TP ratios were calculated.

RESULTS

Mean urinary LT-to-creatinine ratios did not differ significantly between control cats and allergen-sensitized cats before or after sensitization and challenge exposure with saline (0.9% NaCl) solution or allergen, respectively. In BALF the mean LT-to-TP ratio of control cats did not differ significantly before or after sensitization and challenge exposure with saline. Asthmatic cats had BALF LT-to-TP ratios that were significantly lower than control cats at all time points, whereas ratios for asthmatic cats did not differ significantly among the various time points.

CONCLUSIONS AND CLINICAL RELEVANCE

Although LTs were readily detectable in urine, no significant increases in urinary LT concentrations were detected after challenge in allergen-sensitized cats. Spot testing of urinary LT concentrations appears to have no clinical benefit for use in monitoring the inflammatory asthmatic state in cats. The possibility that cysteinyl LTs bind effectively to their target receptors in BALF and, thus, decrease free LT concentrations deserves further study.

Anti-inflammatory activities of LDP-392, a dual PAF receptor antagonist and 5-lipoxygenase inhibitor

Leukotrienes (LTs) and platelet-activating factor (PAF) are important mediators of inflammation and allergy. LDP-392, a novel dual PAF receptor antagonist and 5-lipoxygenase (5-LO) inhibitor, has been identified. LDP-392 is 17.9-fold more potent than zileuton (5-LO inhibitor) in the RBL cytosolic 5-LO assay, and equally potent as MK 287 (PAF receptor antagonist) in the human platelet PAF receptor binding assay. The in vivo dual activities of LDP-392 were confirmed by measuring the inhibition of ex vivo LTB(4)production in rats and PAF-induced hemoconcentration in mice. Intravenous administration of LDP-392 demonstrated greater inhibition than zileuton, BN 50739 or MK 287 on arachidonic acid-induced ear edema and protected mice from LPS-induced lethality. Topical administration of LDP-392, in a dose-dependent manner, inhibited TPA-induced ear edema in mice and UVB-induced erythema in guinea-pigs. These data suggest that LDP-392, as a dual PAF receptor antagonist and 5-LO inhibitor, may be of greater clinical effectiveness.

Urinary leukotriene E(4) excretion during the first month of life and subsequent bronchopulmonary dysplasia in premature infants

BACKGROUND

Inflammation plays an important role in the pathogenesis of bronchopulmonary dysplasia (BPD), but the exact nature of this inflammatory process is incompletely understood. Older infants with established BPD have higher levels of urinary leukotriene E(4) (LTE(4)) compared to healthy infants of the same age. This suggests that cysteinyl leukotrienes may play a role in the abnormalities seen in BPD.

OBJECTIVES

To measure urinary LTE(4) levels during the first month of life in premature infants, and to determine whether there are significant differences in premature infants who develop BPD, as compared to those who do not develop BPD.

DESIGN

Prospective, blinded, controlled study.

SETTING

Neonatal ICUs of a tertiary-care university hospital.

METHODS

Thirty-seven premature infants (< 33 weeks of gestational age) were enrolled prospectively at birth. Urinary LTE(4) levels were measured blinded, using a standard radioimmunoassay technique at 2 days, 7 days, and 28 days of life. At 1 month of age, infants were classified as with or without BPD, based on need for supplemental oxygen, and characteristic chest radiographs. Clinical features and urinary LTE(4) were compared between the two groups.

RESULTS

Mean +/- SD gestational age was 29 +/- 2.6 weeks. None of the infants had a family history of asthma. Thirteen of 37 infants were classified as having BPD at 28 days after birth. Mean gestational age in infants who developed BPD was 27 +/- 2.4 weeks, compared to 30 +/- 2 weeks in infants who did not develop BPD (p < 0.05). In infants with BPD, mean urinary LTE(4) levels of urinary creatinine were 1,762 +/- 2,003 pg/mg, 1,236 +/- 992 pg/mg, and 5,541 +/- 5,146 pg/mg at days 2, 7, and 28, respectively, compared to 1,304 +/- 1,195 pg/mg, 1,158 +/- 1,133 pg/mg, and 2,800 +/- 2,080 pg/mg in infants without BPD. LTE(4) levels at 2 days, 7 days, and 28 days did not correlate with the subsequent development of BPD. LTE(4) levels at day 28 were significantly higher than LTE(4) levels at day 2 and day 7 in both groups, even after correcting for gestational age or birth weight (p < 0.05). There was significant inverse correlation between LTE(4) levels at day 2 with gestational age and birth weight (p < 0.05). All 13 infants with BPD received steroid pulses, compared to 3 of 26 infants without BPD. Gestational age and use of postnatal steroid pulses, diuretics, and theophylline (for apnea of prematurity) were significantly associated with each other and with the subsequent development of BPD.

CONCLUSION

Urinary LTE(4) levels measured on the second day of life in very-low-birth-weight infants inversely correlate with gestational age and birth weight. Urinary LTE(4) levels may reflect lung injury and/or inflammation in premature infants, not necessarily related to BPD as it is presently defined.

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.

Early increase in urinary leukotriene E4 (LTE4) is dependent on allergen dose inhaled during bronchial challenge in asthmatic subjects

BACKGROUND

Urinary leukotriene E4 (LTE4) excretion is a good marker of the rate of total body production of sulfidopeptide leukotrienes released during allergen challenge.

METHODS

Twenty-three subjects with allergic asthma were challenged with inhaled allergen, and the urinary excretion of LTE4 was determined by immunoenzymatic assay (associated with HPLC separation) at various intervals after challenge.

RESULTS

Allergen challenge caused an early airway response (EAR) with a drop in FEV1 of 40.3+/-9.9%. This was associated with an increase in urine LTE4 excretion for 0-3 h after allergen inhalation (296+/-225.25 pg/mg creatinine) in comparison with baseline values obtained during the night before challenge (101.02+/-61.97 pg/mg creatinine). Urinary LTE4 excretion was significantly higher in subjects who inhaled a higher dose of allergen during challenge (LTE4 during EAR: 211+/-192 pg/mg creatinine in subjects with inhaled total dose of allergen <0.1 biologic units; 408+/-223 pg/mg creatinine in subjects with inhaled total dose >0.1 biologic units). All subjects showed a late airway response (LAR) to allergen of different severity, from mild (FEV1 fall: 15-20%) to severe (>30%); no correlation was found between the increase in urine LTE4 excreted during LAR (3-7 h after challenge) and the severity of LAR, but only subjects with severe LAR showed a significant increase in LTE4 during LAR in comparison with baseline value.

CONCLUSIONS

A release of sulfidopeptide leukotrienes, as evaluated by urinary LTE4 excretion, can be documented during EAR and LAR to allergen in relation to the dose of inhaled allergen, and it can represent a useful index of the events underlying the airway inflammatory responses during allergen challenge.

Asthma therapy with agents preventing leukotriene synthesis or action

Elucidation of the biochemistry of leukotriene production and the pharmacology of its actions has led to the development of a number of therapeutic agents shown to be of value in the treatment of asthma. These agents either prevent the synthesis of the leukotrienes, by preventing the action of the 5-lipoxygenase-activating protein or the catalytic action of the 5-lipoxygenase, or by inhibiting the action of leukotrienes at the CysLT1 receptor. Numerous clinical trials in exercise-induced asthma, allergen-induced asthma, aspirin-induced asthma, and spontaneously occurring asthmatic episodes have indicated that these agents are safe and effective asthma treatments.

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.

Leukotrienes as mediators of airway obstruction

The cysteinyl leukotrienes are potent mediators of airway narrowing derived from the lipoxygenation of arachidonic acid and the adduction of glutathione to this eicosanoid backbone. In lower animals and humans, the cysteinyl leukotrienes are among the most potent airway contractile substances ever identified. Furthermore, these moieties can be recovered from the urine during induced or spontaneous asthma attacks. Most important, inhibition of the synthesis of the leukotrienes or prevention of their action at the CysLT1 receptor is associated with an improvement in the airway dysfunction that occurs in both induced and spontaneous asthma. These data indicate that the cysteinyl leukotrienes have a clinically significant role in the airway obstruction that characterizes asthma.

Immunoaffinity resin for purification of urinary leukotriene E4

Urinary leukotriene E4 (LTE4) has been used as an index of total leukotriene synthesis. A wide variety of methods have been applied to measure LTE4 which has made direct comparison of urinary levels reported by different laboratories difficult. A new peptidoleukotriene immunoaffinity resin was utilized for urinary LTE4 purification in a method that is easy and inexpensive, utilizing commercially available reagents. This method is described and compared to other methods. LTE4 (50-250 pg/mL) added to a urine extract was quantitatively recovered using the immunoaffinity resin. Similarly, LTE4 (50-400 pg/mL) added to urine was recovered between 63 and 76%. The coefficient of variation of samples purified and quantified on the same or on different days ranged from 8-10%. There was a strong correlation (r2 = 0.95) between LTE4 concentrations determined after immunofiltration and immunoaffinity purification. Although there was a good correlation between urinary LTE4 levels measured without purification compared to after immunoaffinity purification, the high y-intercept of 179 indicates the presence of interfering substances in unpurified urine. Urinary LTE4 in normal healthy adults was 80 +/- 7 pg/mg creatinine, similar to that previously reported following HPLC or immunofiltration purification. Urinary LTE4 was also measured in healthy children (age 3-12) and found to be 103 +/- 9.

The effects of a novel sulphidopeptide leukotriene antagonist, BAY x7195, against elicited bronchoconstriction in the anaesthetized guinea-pig

1. The novel leukotriene antagonist Bay x7195, has been evaluated against bronchoconstriction induced by leukotriene D4 (LTD4), the thromboxane A2 (TXA2) mimetic U46619, histamine and antigen, in the guinea-pig in vivo by use of a modified Konzett-Rössler preparation. 2. LTD4, given intravenously (i.v.) at 1 or 3 microg kg(-1) in the presence of indomethacin and sotalol, caused a 50-70% maximal bronchoconstriction in most animals. 3. BAY x7195, given i.v., orally (p.o.), by aerosol or dry powder insufflation, in lactose, reduced LTD4-induced bronchoconstriction dose-dependently. The approximate ID50 values were 83 microg kg(-1), 3 mg kg(-1), 0.0003% w/v for 20 breaths and 20 microg respectively. 4. The action of BAY x7195 (10 mg kg(-1), p.o.) was long lasting, causing significant inhibition of the LTD4-induced response (88% reduction) 8 h after dosing. 5. When given intravenously, in the presence of selected antagonists, BAY x7195 caused a dose-related reduction in the antigen-induced response, with an approximate ID50 of 2 mg kg(-1). 6. At 3 mg kg(-1), i.v., a dose which abolished the response to LTD4, BAY x7195 had no effect on U46619- or histamine-induced bronchoconstriction. 7. BAY x7195 is a potent, selective and long acting antagonist of LTD4-induced bronchoconstriction, in an anaesthetized, ventilated guinea-pig model. It is therefore worthy of clinical evaluation in diseases believed to involve the sulphidopeptide leukotrienes, such as asthma.

Immunofiltration purification for urinary leukotriene E4 quantitation

Leukotriene E4 (LTE4) is a major leukotriene metabolite in urine. Urinary LTE4 concentration is often utilized as an index of total leukotriene synthesis. A novel method employing immunofiltration for the purification of urinary LTE4 was developed. This immunofiltration method is based upon the addition of excess anti-LTE4 antibody to urine which binds LTE4. Separation of bound LTE4 (high M(r)) from high levels of unbound contaminants (low M(r)) is then accomplished by filtration through a 10,000 M(r) cut-off filter. The LTE4-antibody complex is separated by precipitation of the antibody with methanol which is subsequently removed by centrifugation. Following evaporation of the methanol, enzyme immunoassay is utilized for quantitation. This methodology was validated by determining the recovery of tritiated and unlabeled LTE4 added to urine and buffer and by comparison of results obtained with urine samples measured after HPLC purification (correlation r2 = 0.72). Reproducibility of the assay was assessed by analyzing the same sample on two different days (standard deviation of 18%). The mean urinary LTE4 levels in healthy subjects and asthmatics measured utilizing this method were found to be identical to levels determined by HPLC/immunoassay. The ease and accuracy of this assay make it amenable for the analysis of large numbers of samples.

Efficient method for the quantitation of urinary leukotriene E4: extraction using an Empore C18 disk cartridge

We describe here an efficient procedure for the precise quantitation of leukotriene E4 (LTE4) in a small volume of urine, which was achieved mainly by the use of an Empore extraction disk cartridge. After addition of [3H]LTE4 to 2 ml of urine, an Empore C18 cartridge was used for initial extraction of the urine, which resulted in the extraction of LTE4 in a small volume of solvent. The eluate could then be injected onto a high-performance liquid chromatography column without further concentration. After separation by high-performance liquid chromatography, LTE4 was extracted from the effluent using an Empore C18 cartridge. The concentration of LTE4 was subsequently quantified by enzyme immunoassay. LTE4 can be recovered from urine with sufficient efficiency (69.9+/-4.7%, mean+/-S.D., n=101). The coefficient of variation of the assay procedure was less than 10%. When urine was spiked with different amounts of LTE4, the recovery of LTE4 added to the urine specimen was less than 120%. The concentration of LTE4 in urine from normal healthy subjects was 48.0+/-15.3 pg/mg creatinine (n=15).

Urinary leukotriene E4 levels in high-altitude pulmonary edema. A possible role for inflammation

STUDY OBJECTIVES

Inflammation may contribute to the pathogenesis of high-altitude pulmonary edema (HAPE). This study was designed to determine whether a marker of inflammation, urinary leukotriene E4 (LTE4), is elevated in patients with HAPE.

DESIGN

We conducted a case-control study to collect clinical data and urine samples from HAPE patients and healthy control subjects at moderate altitude (> or = 2727 m), and follow-up urine samples from HAPE patients following their return to low altitude (< or = 1,600 m).

SETTING

Five medical clinics in Summit County, Colorado.

PATIENTS

Questionnaire data were evaluated in 71 HAPE patients and 36 control subjects. Urinary LTE4 levels were determined from a random subset of 38 HAPE patients and 10 control subjects presenting at moderate altitude, and on 5 HAPE patients who had returned to low altitude.

MEASUREMENTS AND RESULTS

Using an enzyme immunoassay technique, urinary LTE4 levels were found to be significantly higher in HAPE patients (123 [16 to 468] pg/mg creatinine, geometric mean [range]) than in control subjects (69 [38 to 135]), p = 0.02. Following return to low altitude, urinary LTE4 levels fell significantly from 122 (41.8 to 309) to 53.6 (27.6 to 104) pg/mg creatinine (p = 0.05). Urinary LTE4 levels were not related to age, sex, time at altitude, physical condition or habitual exercise, recent use of alcohol or nonsteroidal anti-inflammatory drugs (NSAIDs), or oxygen saturation. Clinical factors associated with HAPE included male sex, regular exercise, and recent use of NSAIDs.

CONCLUSIONS

We conclude that urinary LTE4 levels are elevated in patients with HAPE, supporting the view that HAPE involves inflammatory mechanisms.

Urinary leukotriene E4 in the assessment of nocturnal asthma

BACKGROUND

Urinary leukotriene E4 (LTE4) is a marker of the body's production of cysteinyl LTs, important mediators of airway inflammation. The role of the latter in nocturnal asthma is a topic of increasing interest.

OBJECTIVE

This investigation was aimed at determining whether nighttime attacks are associated with increased release of LTs, expressed by urinary LTE4, and the relationship between the two phenomena.

METHODS

Three groups were studied: group A, seven control subjects; group B, nine asthmatic patients without nocturnal attacks; and group C, nine asthmatic patients with a comparable daytime FEV1 but who were experiencing nocturnal exacerbations (morning dips in peak expiratory flow greater than 20%). Urine was collected over 24 hours in three samples (9:00 AM to 3:00 PM; 3:00 PM to 9:00 PM; and 9:00 PM to 9:00 AM). LTE4 was measured by high-performance liquid chromatography and radioimmunoassay and expressed as nanograms per millimole of creatinine.

RESULTS

No significant differences between urinary LTE4 were noticed within groups A and B. Conversely, in group C urinary LTE4 at night (geometric mean with 95% confidence interval; 35.16 with 28.77-42.85) was significantly higher than that of the other samples (respectively 23.12 with 17.78-30.06, p less than 0.05; and 25.18 with 21.03-30.13, p less than 0.02); it was also significantly higher than in all the samples of other groups. A significant (p less than 0.02) linear correlation was observed between morning dip in peak expiratory flow and the log urinary LTE4 in the nocturnal sample.

CONCLUSION

These results indicate the role of LTs in nocturnal asthma and suggest that urinary LTE4 may be a useful marker of this condition.

Diurnal variation of urinary leukotriene E4 and histamine excretion rates in normal subjects and patients with mild-to-moderate asthma

BACKGROUND

Leukotriene E4 (LTE4) and histamine excreted into the urine reflect the in vivo synthesis and release of cysteinyl leukotrienes and histamine, respectively. We examined the diurnal variation of the excretion rate of these mediators over 4 consecutive days in normal subjects (n = 5) and patients with stable mild-to-moderate asthma (n = 8).

METHODS

Sixteen consecutive 6-hour urine samples were collected over 4 days. Urinary LTE4 concentrations were determined by reverse-phase high-pressure liquid chromatography, followed by ELISA. Urinary histamine concentrations were measured by ELISA. The excretion rates of these compounds were normalized relative to urinary creatinine content.

RESULTS

The mean urinary LTE4 excretion rate was 83.8 +/- 38.2 pg/mg creatinine (mean +/- SD) in normal subjects; in patients with asthma, the urinary LTE4 excretion rate (110.0 +/- 59.2 pg/mg creatinine) was significantly higher than that in normal subjects (p < 0.05). The urinary histamine excretion rate was not different between normal subjects (24.0 +/- 12.5 ng/mg creatinine) and patients with asthma (31.5 +/- 25.8 ng/mg creatinine). A robust and systematic within-day variation (p < 0.01), but no day-to-day variation, was observed in histamine excretion rate. Although the magnitude of variation in LTE4 excretion within a day was significantly greater in patients with asthma than in normal subjects (p < 0.05), we could not identify any specific diurnal variation pattern in either the normal or the asthma group. No significant correlation was observed between urinary LTE4 and histamine excretion rate within any subject.

CONCLUSIONS

Patients with asthma excrete LTE4 in the urine at a greater rate than normal subjects. Although no systematic variation in urinary LTE4 excretion rates over the course of a day was observed in either normal subjects or patients with stable asthma, the presence of a systematic diurnal variation of urinary histamine excretion exists in both groups.

Persistent increase in plasma and urinary leukotrienes after acute asthma

Leukotrienes may mediate bronchoconstriction in asthma. Cysteinyl leukotriene production rises in vivo after allergen challenge, but few reports describe leukotriene concentrations in clinical asthma or in children. Using high performance liquid chromatography/radioimmunoassay, plasma and urinary leukotrienes in asthmatic children (aged 5-10 years) were measured during an acute exacerbation (peak expiratory flow (PEF) < 65%, n = 10) and one month later (PEF 74-169%, n = 9), and in non-atopic normal children (aged 1.3-13.2 years). In the asthmatics, geometric mean (95% confidence interval) plasma leukotriene B4 (LTB4) was 746 pg/ml (398 to 1403) acutely and 1026 pg/ml (662 to 1593) in remission, compared with 369 pg/ml (167 to 728) in the normal children (n = 14). Plasma cysteinyl leukotrienes were low or undetectable, but urinary leukotriene E4 (LTE4) was higher in the asthmatics during an acute episode (210 pmol/mmol creatinine, 101 to 454) and at follow up (179 pmol/mmol, 110 to 293), compared with the normal children (98 pmol/mmol, 81 to 118, n = 41). This persistent increase in plasma LTB4 and urinary LTE4 concentrations one month after a severe asthmatic episode suggests leukotriene production is related to chronic inflammation rather than to acute bronchoconstriction.

Eicosanoids and asthma: an update

There have been significant advances in our understanding of the role of eicosanoids as mediators in inflammation since their discovery over 50 years ago. Our more recent understanding of asthma as an inflammatory disease has led to the appreciation of eicosanoids potentially being pivotal mediators in promoting some of the changes in asthma. Of particular importance are the cysteinyl LTs in producing bronchospasm and bronchial hyperresponsivenss, and PGE2 in modulating the bronchospastic and inflammatory response. Evidence from clinical studies suggests that other eicosanoids may also contribute, but their importance is secondary and their relative contributions vary between individuals. The development of new drugs based on our partial understanding of the role that eicosanoid mediators may play in asthma promises new approaches to the treatment of this common chronic inflammatory condition.

Validation and application of a new simple strategy for measurements of urinary leukotriene E4 in humans

To monitor endogenous production of cysteinyl-containing leukotrienes, the end-metabolite leukotriene E4 (LTE4) was analysed in urine. Results obtained with a sensitive enzyme immunoassay (EIA), performed on crude urine samples correlated well with data obtained from a previously reported radioimmunoassay. Enzyme immunoassay analysis of unextracted urine was justified by an excellent agreement between analyses in crude samples and measurements achieved after purification on solid phase extraction followed by separation on reversed-phase high performance liquid chromatography. Moreover, LTE4 was stable in urine samples stored at -20 degrees C, for months without the addition of preservatives. The stability of LTE4 in urine was not improved by addition of the antioxidant 4-hydroxy-TEMPO and pH adjustment to 9. As assessed by EIA analysis in crude urine samples, baseline values for urinary leukotriene E4 were not significantly different between atopic asthmatic subjects and non-asthmatic individuals, and there was no diurnal variation in urinary excretion of LTE4 in healthy subjects. However, we confirmed earlier data on significantly higher basal levels of urinary LTE4 in aspirin-intolerant asthmatics. In addition, a post-challenge increase in urinary LTE4 levels was detected in association with allergen-induced airway obstruction in atopic asthmatics. The per cent increase in urinary LTE4 was similar, irrespective of whether the samples were purified or not prior to EIA. Thus, combined with random validation by high performance liquid chromatography, the strategy of direct EIA of serially diluted urine samples was found to be a good index of in vivo production of leukotrienes. This was further reinforced by the demonstration that pretreatment with the leukotriene biosynthesis inhibitor Bay x 1005 inhibited the post allergen-challenge increase in urinary LTE4, as shown both with unpurified and purified samples.

Effect of BAY x 7195, an oral receptor antagonist of cysteinyl-leukotrienes, on leukotriene D4-induced bronchoconstriction in normal volunteers

Leukotrienes (LT) have been proposed to play an important role in the pathogenesis of asthma. This paper reports the results of two studies investigating the effect of BAY x 7195, a new oral receptor antagonist of cysteinyl-leukotrienes, on LTD4-induced bronchoconstriction in healthy male volunteers. Using a double-blind, placebo-controlled, crossover design, volunteers received 250 mg (n = 6; study 1) and 100 and 500 mg (n = 6; study 2) of BAY x 7195. Bronchoprovocation with nebulized LTD4 was performed 2 (250 mg) and 2 and 8 (100 and 500 mg) h p.a. The specific airway's conductance (SGaw) was used to assess the airway's response. Blood samples to determine plasma concentrations of BAY x 7195 were taken at the end of bronchoprovocation. BAY x 7195 showed no effect on baseline lung function. Compared to placebo, the different doses of BAY x 7195 increased the concentration of LTD4 needed to produce a 35% decrease in SGaw 2 h p.a. between 1- and 23-fold. Eight hours p.a., 100 and 500 mg caused shifts in the concentration-response curve of between 1- and 13-fold. There was no predictive relationship between plasma concentrations of BAY x 7195 and the response to LTD4 challenge. However, there was a relationship between dose and effect. No relevant adverse effects were reported. In conclusion, the present results suggest that BAY x 7195 is an effective LTD4-receptor antagonist in man.

The pivotal role of 5-lipoxygenase products in the reaction of aspirin-sensitive asthmatics to aspirin

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)

Inactivation of leukotriene C4 in the airways and subsequent urinary leukotriene E4 excretion in normal and asthmatic subjects

Leukotrienes (LT) are synthesized in the lung during asthmatic reactions and mediate certain inflammatory symptoms. Pulmonary metabolism and clearance of exogenously added peptidoleukotrienes were studied in nonasthmatics, asthmatics, and asthmatics challenged with allergen. [3H]LTC4 and [14C]dextran were instilled into the airways, and bronchoalveolar lavage fluid (BALF) was obtained 15 min later. After comparing the [3H]/[14C] ratio of the instilled solution with that in BALF, 77% of LT were found to have been removed from the airways of nonasthmatics, and 72% of unchallenged asthmatics. Allergen administration to asthmatics 1 min before LT instillation inhibited LT transfer out of the airways by 26%, compared with asthmatics not challenged with allergen. This decrease in the removal of LT from the airways during allergic reactions could potentiate the physiologic effects of LT produced in the airways. The predominant LT in BALF was LTE4, constituting 56% of the LT in asthmatics and 61% in nonasthmatics. The percentage of LTE4 in BALF increased to 87% in allergen-stimulated asthmatics (p < 0.05 compared with the two other groups), this again reflecting decreased transfer of LT out of the lung rather than an increase in metabolism. Urinary excretion of LT metabolites occurred rapidly, the majority being excreted excreted within 6 h after instillation. LTE4, the major urinary LT metabolite identified by high-performance liquid chromatography, was a similar percentage concentration in the three groups and, thus, can be accurately used as an index of LT synthesis.

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)

Leukotrienes in bile during the early and the late airway responses after allergen challenge of sensitized rats

The Brown Norway rat produces high levels of IgE in response to active immunization and develops both early and late airway constrictor responses after subsequent allergen challenge. We have used this model of allergic asthma to investigate the temporal relationship between the in vivo synthesis of peptidoleukotrienes (peptido-LTs) and the late response. Brown Norway rats that had been sensitized by injection of ovalbumin 2 to 3 wk prior to the commencement of the experiment were subjected to bile duct cannulation and tracheal intubation. The rats were challenged 2 h later by intratracheal instillation of ovalbumin. Lung resistance was measured before and at frequent intervals after antigen challenge. Biliary peptido-LTs (LTC4, LTD4, LTE4, and N-acetyl-LTE4) were measured by a combination of high pressure liquid chromatography and radioimmunoassay in bile samples collected for a period of 1 h before instillation of ovalbumin, and between zero and 1 h, 1 and 4 h, 4 and 6 h, and 6 and 8 h, subsequently. All of the 10 rats subjected to antigen challenge developed early responses. Of these, six also developed late responses, whereas two died about 1 h after challenge. The levels of peptido-LTs excreted in bile between 4 and 8 h after antigen challenge (corresponding in time to the late responses) were about four times higher in the ovalbumin-instilled rats that developed late responses (n = 6) than in the ovalbumin-sensitized control rats that had been subjected to instillation of saline (n = 6; p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Asthma

There is an active inflammatory process in the airways of patients with asthma, even when the patients are asymptomatic. Some of the types of cells involved in this process possess the necessary biologic activities to produce many of the pathophysiologic features of asthma, but the underlying mechanisms have not yet been elucidated. Reducing the severity of the inflammatory process appears to be a reasonable goal of therapy, with potential long-range implications for the morbidity of asthma. Whether this theoretical benefit will be realized awaits further observation.

Effects of catecholamines on eicosanoid synthesis with special reference to prostanoid/leukotriene ratio

Catecholamines (adrenaline, dopamine, and noradrenaline) stimulate prostanoid synthesis by acting as "cosubstrates." On the other hand, many inhibitors of leukotriene synthesis, such as nordihydroguaiaretic acid and caffeic acid, have a catecholic structure. Catecholamines have opposite effects on prostanoid and leukotriene synthesis in human polymorphonuclear leukocytes and whole blood. Basic phenols (catechol, hydroquinone, and phenol) also increase the prostanoid/leukotriene ratio in polymorphonuclear leukocytes. These actions correlate to their antioxidant capacities and oxidation potentials, and they are not mediated via adrenergic receptors. There is only limited knowledge about the effects of natural catecholamines on the prostanoid/leukotriene ratio in vitro and in vivo. Indirect data suggest that catecholamines could increase prostanoid production in physiological or pathological situations, such as heavy physical exercise, myocardial infarction, and surgical stress. This interaction may also be of clinical importance in asthma, gastric ulcer, and psoriasis, where decreased prostanoid/leukotriene ratios have been reported.