Urinary leukotriene E4 after exercise challenge in children with asthma

Exercise-induced anaphylaxis unrelated to food ingestion and with hyperleukotrieneuria during challenge testing

BACKGROUND

Exercise-induced anaphylaxis (EIA) is a rare and potentially life-threatening disorder that can develop independently without food ingestion. Cold drinks can also trigger symptoms in some patients with cold-induced anaphylaxis. We present a case of a patient with EIA that was diagnosed on the basis of positive exercise loading test with hyperleukotrieneuria.

CASE PRESENTATION

A 12-year-old girl presented with acute flushing, cyanosis, swollen eyelids, and dyspnea after an endurance run in winter or swimming in a cold-water pool. She also developed dyspnea after having a cold drink. She had no history of food allergies, atopy, or asthma. No association was noted between anaphylaxis and food intake in her history. On the first day, she ingested 200 mL of 5 °C cold water in 30 s, which did not trigger symptomatic responses, but her urinary leukotriene E4 (LTE4) level increased (pre-challenge test: 295 pg/mg-creatinine (cr), post-challenge test: 400 pg/mg-cr). On the second day, she underwent the exercise loading test according to the Bruce protocol by using an ergometer to increase the power of exercise every 2 min. She had been fasting for > 15 h and did not have breakfast. Just after the exercise loading test, the plasma adrenaline and noradrenaline increased. At 15 min after the exercise loading test, her plasma adrenaline and histamine (pre-challenge test: 0.7 ng/mL, 15 min post-challenge test: 81 ng/mL) rose sharply with anaphylaxis symptoms accompanied by increasing urinary LTE4 (pre-challenge test: 579 pg/mg-cr, post-challenge test: 846 pg/mg-cr). After she was discharged, she was restricted from strenuous exercise especially in cold environments and prescribed an adrenaline autoinjector.

CONCLUSION

Cold stimulation can become a co-effector of EIA. Measurements of urinary LTE4 levels during challenge testing are useful for diagnosing EIA and capture the pre-anaphylaxis stage.

Phase 2 trial of montelukast for prevention of pain in sickle cell disease

Cysteinyl leukotrienes (CysLTs) are lipid mediators of inflammation. In patients with sickle cell disease (SCD), levels of CysLTs are increased compared with controls and associated with a higher rate of hospitalization for pain. We tested the hypothesis that administration of the CysLT receptor antagonist montelukast would improve SCD-related comorbidities, including pain, in adolescents and adults with SCD. In a phase 2 randomized trial, we administered montelukast or placebo for 8 weeks. The primary outcome measure was a >30% reduction in soluble vascular cell adhesion molecule 1 (sVCAM), a marker of vascular injury. Secondary outcome measures were reduction in daily pain, improvement in pulmonary function, and improvement in microvascular blood flow, as measured by laser Doppler velocimetry. Forty-two participants with SCD were randomized to receive montelukast or placebo for 8 weeks. We found no difference between the montelukast and placebo groups with regard to the levels of sVCAM, reported pain, pulmonary function, or microvascular blood flow. Although montelukast is an effective treatment for asthma, we did not find benefit for SCD-related outcomes. This clinical trial was registered at www.clinicaltrials.gov as #NCT01960413.

Pharmacologic Strategies for Exercise-Induced Bronchospasm with a Focus on Athletes

Exercise-induced bronchoconstriction (EIB) is the transient narrowing of the airways during and after exercise that occurs in response to increased ventilation in susceptible individuals. It occurs across the age spectrum in patients with underlying asthma and can occur in athletes without baseline asthma. The inflammatory mechanisms underlying EIB in patients without asthma may be distinct from those underlying EIB in patients with asthma. This review summarizes mechanistic and clinical data that can guide the choice of chronic and acute pharmacologic therapies targeting control of EIB. Relevant regulations from the World Anti-Doping Agency are also discussed.

Urinary excretion of 9α,11β-prostaglandin F2 and leukotriene E4 in patients with exercise-induced bronchoconstriction

BACKGROUND

Increased levels of mast cell-derived eicosanoids, such as prostaglandin (PG) D2 and cysteinyl leukotrienes (CysLTs), have been reported in patients with exercise-induced bronchoconstriction (EIB), suggesting that mast cell activation is involved in the mechanism of EIB. However, it is still controversial since these results have not been reproduced in other studies. The aim of this study was to evaluate the role of PGD2 and LTE4 in adult asthma with EIB, as measuring urinary levels of their metabolites-9α,11β-PGF2 and LTE4 before and after an exercise challenge test.

METHODS

Eight patients with asthma and EIB and five normal controls without EIB were enrolled. Exercise challenge tests comprised of 6 min of treadmill exercise or free running were performed in all study subjects, and urine samples before and 1 h after the challenge were collected. Urinary levels of 9α,11β-PGF2 and LTE4 were measured by enzyme immunoassay (EIA).

RESULTS

No significant differences were observed in 9α,11β-PGF2 and LTE4 levels before/after the exercise challenge between patients with EIB and normal controls. No significant increases in urinary levels of 9α,11β-PGF2 or LTE4 were detected during the exercise challenge in patients with EIB and normal controls. No significant correlations were observed between the percent decrease in forced expiratory volume in 1 s (FEV1) or percent changes in 9α,11β-PGF2 and LTE4 levels after the exercise challenge.

CONCLUSIONS

Urinary 9α,11β-PGF2 and LTE4 levels did not increase after an exercise challenge in patients with EIB, suggesting that urinary excretion of 9α,11β-PGF2 and LTE4 may not be a good marker of mast cell activation in patients with EIB.

Mass spectrometry-based proteomics in Chest Medicine, Gerontology, and Nephrology: subgroups omics for personalized medicine

Mass spectrometry (MS) is currently the most promising tool for studying proteomics to investigate largescale proteins in a specific proteome. Emerging MS-based proteomics is widely applied to decipher complex proteome for discovering potential biomarkers. Given its growing usage in clinical medicine for biomarker discovery to predict, diagnose and confer prognosis, MS-based proteomics can benefit study of personalized medicine. In this review we introduce some fundamental MS theory and MS-based quantitative proteomic approaches as well as several representative clinical MS-based proteomics issues in Chest Medicine, Gerontology, and Nephrology.

Liquid chromatography-mass spectrometry measurement of leukotrienes in asthma and other respiratory diseases

Leukotrienes (LTs), including cysteinyl-LTs (LTC4, LTD4 and LTE4) and LTB4, are potent inflammatory lipid mediators which have been involved in the pathophysiology of respiratory diseases. LC-MS/MS techniques for measuring LT concentrations in sputum supernatants, serum, urine and exhaled breath condensate (EBC) have been developed. In asthmatic adults, reported LTB4 and LTE4 concentrations in sputum range from 79 to 7,220 pg/ml and from 11.9 to 891 pg/ml, respectively. Data on sputum LT concentrations in healthy subjects are not available. In EBC, reported LTE4 concentrations range from 38 to 126 pg/ml (95% CI) in adult asthma patients and from 34 to 48 pg/ml in healthy subjects. LTB4 concentrations in EBC range from 175 to 315 pg/ml (interquartile range) in asthmatic children, and from 25 to 245 pg/ml in healthy children. Enabling an accurate quantitative assessment of LTs in biological fluids, LC-MS/MS techniques provide a valuable tool for exploring the pathophysiological role of LTs in respiratory disease and might be useful for assessing the effects of therapeutic intervention. This review presents the analytical aspects of the LC-MS/MS techniques for measuring LT concentrations in biological fluids and discusses their potential utility for the assessment of airway inflammation and monitoring of pharmacological treatment in patients with asthma phenotypes and other respiratory diseases.

Urinary leukotriene excretion profile in children with exercise-induced asthma compared with controls: a preliminary study

BACKGROUND

Leukotrienes are among the most important mediators associated with inflammatory responses in patients with exercise induced asthma (EIA). The aim of this study was to investigate the impact of exercise on the urinary leukotriene profile. Hence, we compared post exercise changes of urinary leukotriene E4 (LTE4) concentration between children with EIA and healthy controls.

METHODS

Ten children with EIA and 15 controls were enrolled. Both groups underwent a standardised exercise challenge test (ECT). LTE4 concentration was measured in urine samples obtained pre and post ECT, using enzyme immunoassay and adjusted by urinary creatinine concentrations.

RESULTS

Median (minimum-maximum) pre ECT concentration of LTE4 was 17.82 (7.58-90.23 pg/ml) in EIA and 17.24 (4.64-64.02 pg/ml) in controls, p=0.86. LTE4 concentration post ECT were 23.37 (4.02-93.00 pg/ml) in EIA and 11.74 (0.13-25.09 pg/ml) in controls, p=0.02. Changes of LTE4 concentration post ECT were 2.54 (-31.98 to 43.31 pg/ml) in cases and -13.53 (-46.00 to 11.02 pg/ml) in controls, p=0.03. There was no significant correlation between basal predicted FEV(1) [%] and changes in LTE4 concentration in cases (i.e., r(s)=0.14) nor controls (i.e., r(s)=0.12). There was a tendency towards more pronounced changes in LTE4 concentration post ECT in children with moderate/mild persistent asthma compared to those with mild but intermittent asthma.

CONCLUSIONS

Children with EIA had significantly higher changes of urinary LTE4 concentrations post ECT compared to healthy controls. Urinary measurement of LTE4 may be an interesting and non-invasive option to assess control of EIA in children.

Exercise-Induced Lung Disease: Too Much of a Good Thing?

Exercise in children has important health benefits. However, in elite endurance athletes, there is an increased prevalence of exercise-induced bronchoconstriction and airway inflammation. Particularly at risk are those who practice in cold weather, ice rinks, swimming pools, and air pollution. The inflammation is caused by repetitive episodes of hyperventilation of cold, dry air, allergens, or toxins such as chlorine or air pollution. Children may be particularly at risk for lung injury under these conditions because of the immaturity and ongoing development of their lung. However, studies in pediatric athletes and exercising young children are sparse. Epithelial injury associated with hyperventilation of cold, dry air has not been described in children. However, exercise in the presence of air pollution and chlorine is associated with airway injury and the development of asthma in children; the effect appears to be modulated by both atopy and genetic polymorphisms. While management of exercise-induced bronchoconstriction and asthma is well established, there is little data to guide treatment or prevention of remodeling in athletes or inhalational lung injury in children. Studies underscore the need to maintain high levels of air quality. More investigations should be undertaken to better define the natural history, pathophysiology, and treatment of exercise-induced pulmonary inflammation in both elite athletes and exercising children.

Leukotriene pathway in sickle cell disease: a potential target for directed therapy

Sickle cell disease (SCD) is characterized by recurrent episodes of vaso-occlusion, resulting in tissue ischemia and end-organ damage. Inflammation is critical to the pathogenesis of vaso-occlusion and has been associated with SCD-related morbidity and mortality. Despite the impact of inflammation, no directed anti-inflammatory therapies for the treatment or prevention of vaso-occlusive events currently exist. Among individuals with SCD, asthma is a comorbid inflammatory condition that increases the risk of pain episodes, acute chest syndrome and death. Inflammation associated with asthma could augment the proinflammatory state of SCD, increasing episodes of vaso-occlusion. Leukotrienes are inflammatory mediators that play a prominent role in the pathogenesis of asthma and have been associated with SCD-related morbidity. Targeting inflammatory mediators, such as leukotrienes, is a promising approach for the development of novel therapies for the treatment of SCD. This review will examine the relationship between inflammation and vaso-occlusion, with particular focus on the leukotriene pathway.

Leukotriene modifiers for asthma treatment

Leukotrienes (LTs), including cysteinyl LTs (CysLTs) and LTB(4) , are potent lipid mediators that have a role in the pathophysiology of asthma. At least two receptor subtypes for CysLTs, CysLT(1) and CysLT(2) , have been identified. The activation of the CysLT(1) receptor is responsible for most of the pathophysiological effects of CysLTs in asthma, including increased airway smooth muscle activity, microvascular permeability, and airway mucus secretion. LTB(4) might have a role in severe asthma, asthma exacerbations, and the development of airway hyperresponsiveness. CysLT(1) receptor antagonists can be given orally as monotherapy in patients with mild persistent asthma, but these drugs are generally less effective than inhaled glucocorticoids. Combination of CysLT(1) receptor antagonists and inhaled glucocorticoids in patients with more severe asthma may improve asthma control and enable the dose of inhaled glucocorticoids to be reduced while maintaining similar efficacy. The identification of subgroups of asthmatic patients who respond to CysLT(1) receptor antagonists is relevant for asthma management as the response to these drugs is variable. CysLT(1) receptor antagonists have a potential anti-remodelling effect that might be important for preventing or reversing airway structural changes in patients with asthma. This review discusses the role of LTs in asthma and the role of LT modifiers in asthma treatment.

Efficacy of leukotriene receptor antagonists and synthesis inhibitors in asthma

Cysteinyl leukotrienes are important mediators of asthmatic responses. They are the most potent bronchoconstrictors known; their release is triggered by exposure to inhaled allergens after exercise and after aspirin ingestion by subjects with aspirin-sensitive asthma. The cysteinyl leukotrienes promote inflammatory cell migration into the airways, as well as bone marrow eosinophilopoiesis after allergen inhalation. Leukotriene inhibitors are effective at attenuating asthmatic responses to all of these stimuli and are also effective at treating persistent asthma. These drugs are a viable alternative to low-dose inhaled corticosteroid (ICS) treatment but should be reserved for patients who cannot or will not use ICSs, often because of concerns about potential side effects of ICS treatment, which limits their use, particularly in children. Leukotriene receptor antagonists are also alternatives to long-acting inhaled beta(2)-agonists as add-on therapy to ICSs, but their efficacy together with ICSs is less than that of ICS/long-acting inhaled beta(2)-agonist combinations. Leukotriene receptor antagonists have an excellent safety profile.

Asthma and sickle cell disease: two distinct diseases or part of the same process?

A physician diagnosis of asthma in children and adults with sickle cell disease (SCD) has been associated with increased rates of pain and acute chest syndrome (ACS) episodes and premature death. Despite the clinical significance of a doctor’s diagnosis of asthma in individuals with SCD, the criteria for a physician diagnosis of asthma are not well defined. Many features of asthma are common in individuals with SCD, including symptoms of wheezing, obstructive lung disease and airway hyper-responsiveness. However, it is not clear if these signs and symptoms of asthma reflect a physician diagnosis of asthma, or if these asthma features are related to SCD. Further complicating the diagnosis of asthma in children with SCD is the significant overlap in clinical manifestations between an asthma exacerbation and an ACS episode. Evidence supporting the concept that asthma and SCD are separate co-morbid conditions includes a similar prevalence of asthma between children with SCD and those in the general population and the observation that asthma is inherited in a familial pattern in the families of children with SCD. In contrast, there is significant evidence that asthma-like features may be associated with SCD without a diagnosis of asthma, including a higher than expected prevalence of airway hyper-responsiveness and obstructive lung disease. Regardless of whether SCD and asthma are distinct or overlapping co-morbid conditions, we recommend a systematic and complete evaluation of asthma when the diagnosis is suspected or when patients have multiple episodes of pain or ACS.

Asthma and sickle cell disease: two distinct diseases or part of the same process?

A physician diagnosis of asthma in children and adults with sickle cell disease (SCD) has been associated with increased rates of pain and acute chest syndrome (ACS) episodes and premature death. Despite the clinical significance of a doctor's diagnosis of asthma in individuals with SCD, the criteria for a physician diagnosis of asthma are not well defined. Many features of asthma are common in individuals with SCD, including symptoms of wheezing, obstructive lung disease and airway hyper-responsiveness. However, it is not clear if these signs and symptoms of asthma reflect a physician diagnosis of asthma, or if these asthma features are related to SCD. Further complicating the diagnosis of asthma in children with SCD is the significant overlap in clinical manifestations between an asthma exacerbation and an ACS episode. Evidence supporting the concept that asthma and SCD are separate co-morbid conditions includes a similar prevalence of asthma between children with SCD and those in the general population and the observation that asthma is inherited in a familial pattern in the families of children with SCD. In contrast, there is significant evidence that asthma-like features may be associated with SCD without a diagnosis of asthma, including a higher than expected prevalence of airway hyper-responsiveness and obstructive lung disease. Regardless of whether SCD and asthma are distinct or overlapping co-morbid conditions, we recommend a systematic and complete evaluation of asthma when the diagnosis is suspected or when patients have multiple episodes of pain or ACS.

Eicosanoids in exhaled breath condensates in the assessment of childhood asthma

The value of measurements of eicosanoids in exhaled breath condensate (EBC) for the evaluation of childhood asthma is still inconclusive most likely because of the limited value of the methods used. In this case-control study in 48 asthmatic and 20 healthy children, we aimed to characterize the baseline profile of the inflammatory mediators cysteinyl leukotrienes (cysLTs), 9(alpha)11(beta)PGF(2), PGE(2), PGF(2alpha), 8-isoprostane (8-iso-PGF(2alpha)) within EBC in asthmatic compared with healthy children using new methods. In addition, we investigated their relation to other inflammatory markers. The assessment included collection of EBC, measurement of fractional exhaled nitric oxide (FE(NO)) and evaluation of urinary excretion of leukotriene E(4.) cysLTs were measured directly in EBC by radioimmunoassay and prostanoids were measured using gas chromatography negative-ion chemical ionization mass spectrometry. Only cysLT levels were significantly higher in asthmatic compared with healthy children (p = 0.002). No significant differences in cysLTs were found between steroid naïve and patients receiving inhaled corticosteroids. In contrast, FE(NO) was significantly higher in steroid naïve compared with steroid-treated asthmatic and healthy children (p = 0.04 and 0.024, respectively). The diagnostic accuracy of cysLTs in EBC for asthma was 73.6% for the whole group and 78.2% for steroid-naïve asthmatic children. The accuracy to classify asthmatic for FE(NO) was poor (62.9%) for the whole group, but improved to 79.9% when only steroid-naïve asthmatic children were taken into consideration. cysLTs in EBC is an inflammatory marker which distinguishes asthmatics, as a whole group, from healthy children.

The potential link between atherosclerosis and the 5-lipoxygenase pathway: investigational agents with new implications for the cardiovascular field

The 5-lipoxygenase pathway is responsible for the production of leukotrienes--inflammatory lipid mediators that have a role in innate immunity, but that can also have pathological effects in inflammatory diseases. Recently, a potential link between leukotriene production and atherosclerosis has been proposed. The expression of leukotriene biosynthetic enzymes and leukotriene receptors has been identified in coronary and carotid atherosclerotic plaques, and the levels of biosynthetic enzymes have been correlated with the clinical symptoms of unstable plaques. Genetic variants in 5-lipoxygenase pathway genes have also been associated with a relative risk of developing myocardial infarction and stroke. On the basis of these discoveries, antileukotriene compounds are now being evaluated for the treatment of cardiovascular disease. Several tool compounds have been shown to limit the progression of lesion development in preclinical models of atherosclerosis, and three compounds, including two drugs previously developed for asthma, are undergoing clinical trials in patients with acute coronary syndromes.

Asthma

Asthma has been recognized as a disease since the earliest times. In the Corpus Hippocraticum, Hippocrates used the term “ασθμα” to indicate any form of breathing difficulty manifesting itself by panting. Aretaeus of Cappadocia, a well-known Greek physician (second century A.D.), is credited with providing the first detailed description of an asthma attack [13], and to Celsus it was a disease with wheezing and noisy, violent breathing. In the history of Rome, we find many members of the Julio-Claudian family affected with probable atopic respiratory disorders: Caesar Augustus suffered from bronchoconstriction, seasonal rhinitis as well as a highly pruritic skin disease. Claudius suffered from rhinoconjunctivitis and Britannicus was allergic to horse dander [529]. Maimonides (1136–1204) warned that to neglect treatment of asthma could prove fatal, whereas until the 19th century, European scholars defined it as “nervous asthma,” a term that was given to mean a defect of conductivity of the ninth pair of cranial nerves.

G-protein-coupled receptors and asthma endophenotypes: the cysteinyl leukotriene system in perspective

Genetic variation in specific G-protein coupled receptors (GPCRs) is associated with a spectrum of respiratory disease predispositions and drug response phenotypes. Although certain GPCR gene variants can be disease-causing through the expression of inactive, overactive, or constitutively active receptor proteins, many more GPCR gene variants confer risk for potentially deleterious endophenotypes. Endophenotypes are traits, such as bronchiole hyperactivity, atopy, and aspirin intolerant asthma, which have a strong genetic component and are risk factors for a variety of more complex outcomes that may include disease states. GPCR genes implicated in asthma endophenotypes include variants of the cysteinyl leukotriene receptors (CYSLTR1 and CYSLTR2), and prostaglandin D2 receptors (PTGDR and CRTH2), thromboxane A2 receptor (TBXA2R), beta2-adrenergic receptor (ADRB2), chemokine receptor 5 (CCR5), and the G protein-coupled receptor associated with asthma (GPRA). This review of the contribution of variability in these genes places the contribution of the cysteinyl leukotriene system to respiratory endophenotypes in perspective. The genetic variant(s) of receptors that are associated with endophenotypes are discussed in the context of the extent to which they contribute to a disease phenotype or altered drug efficacy.

Onset and duration of protection against exercise-induced bronchoconstriction by a single oral dose of montelukast

BACKGROUND

Leukotriene modifiers have been shown to protect against exercise-induced bronchoconstriction (EIB) with repeated, chronic dosing.

OBJECTIVE

To study the onset and duration of protection against EIB after a single dose of montelukast, a leukotriene receptor antagonist.

METHODS

In this randomized, crossover, double-blind study, 51 adult asthma patients with EIB (> or = 20% postexercise decrease in forced expiratory volume in 1 second [FEV1]) received a single oral dose of montelukast (10 mg), or placebo followed by exercise challenge 2, 12, and 24 hours after dosing. The primary end point was maximum percentage decrease in FEV1 from preexercise baseline during 60 minutes after the 2-hour challenge.

RESULTS

At 2, 12, and 24 hours after dosing, the maximum decrease in FEV1 was 10.8% +/- 7.9%, 8.4% +/- 7.5%, and 8.3% +/- 7.3% for montelukast and 22.3% +/- 13.1%, 16.1% +/- 10.2%, and 16.9% +/- 11.7% for placebo, respectively (P < or = .001 at each time point). Postexercise recovery was quicker with montelukast than with placebo (P < or = .001); mean (95% confidence interval) differences were -26.8 minutes (-35.1 to -18.4 minutes), -16.0 minutes (-22.9 to -9.2 minutes), and -17.4 minutes (-24.9 to -9.9 minutes) at the 3 time points, respectively. At all time points, area under the curve for percentage decrease in FEV1 during 60 minutes after exercise was smaller after montelukast (P < or = .001); montelukast protected more patients against EIB (P < or = .001). Fewer patients required postexercise beta-agonist rescue at 2 hours after dosing with montelukast (P = .03).

CONCLUSION

Montelukast provided significant protection against EIB as soon as 2 hours after a single oral dose, with persistent benefit up to 24 hours.

Particulate levels are associated with early asthma worsening in children with persistent disease

RATIONALE

Ambient particulate concentrations have been associated with variable physiologic effects in children with persistent asthma taking controller medications.

OBJECTIVE

To determine whether exposure to particulate matter has immediate effects on asthma control in children with persistent disease.

METHODS AND MEASUREMENTS

In a school-based cohort, 73 children, primarily with moderate and severe asthma, were followed daily over one or two winters (2001-2002, 2002-2003) in Denver, Colorado. The association among ambient fine particulate, bronchodilator use, and urinary leukotriene E4 levels was assessed.

RESULTS

Daily concentrations of fine particulate peaked in the morning hours when children were commuting to school. In a multivariable analysis that controlled for meteorology, time trends, and upper respiratory infections, an increase of one interquartile range in morning maximum fine particulate levels was related to an average increase of 3.8% in bronchodilator usage at school (95% confidence interval [CI], 0.2-7.4; p = 0.04). Children with severe asthma demonstrated significantly stronger associations (8.1% increase; 95% CI, 2.9-13.4; p = 0.003) than those with mild/moderate disease (1.6% increase; 95% CI, -2.2-5.4; p = 0.41; p = 0.03 for difference between groups). Morning maximum fine particulate levels were also associated with urinary leukotriene E4 measured during school hours (average increase of 6.2% per interquartile range increase; 95% CI, 1.9-10.5; p = 0.006). These associations were not discernable when 24-h averaged concentrations were used.

CONCLUSIONS

Peak concentrations of ambient fine particulate are associated with early increases in bronchodilator use and urinary leukotriene E4 levels among children with persistent asthma, despite the use of controller medications.

The G protein-coupled receptors: pharmacogenetics and disease

Genetic variation in G-protein coupled receptors (GPCRs) is associated with a wide spectrum of disease phenotypes and predispositions that are of special significance because they are the targets of therapeutic agents. Each variant provides an opportunity to understand receptor function that complements a plethora of available in vitro data elucidating the pharmacology of the GPCRs. For example, discrete portions of the proximal tail of the dopamine D1 receptor have been discovered, in vitro, that may be involved in desensitization, recycling and trafficking. Similar in vitro strategies have been used to elucidate naturally occurring GPCR mutations. Inactive, over-active or constitutively active receptors have been identified by changes in ligand binding, G-protein coupling, receptor desensitization and receptor recycling. Selected examples reviewed include those disorders resulting from mutations in rhodopsin, thyrotropin, luteinizing hormone, vasopressin and angiotensin receptors. By comparison, the recurrent pharmacogenetic variants are more likely to result in an altered predisposition to complex disease in the population. These common variants may affect receptor sequence without intrinsic phenotype change or spontaneous induction of disease and yet result in significant alteration in drug efficacy. These pharmacogenetic phenomena will be reviewed with respect to a limited sampling of GPCR systems including the orexin/hypocretin system, the beta2 adrenergic receptors, the cysteinyl leukotriene receptors and the calcium-sensing receptor. These developments will be discussed with respect to strategies for drug discovery that take into account the potential for the development of drugs targeted at mutated and wild-type proteins.

An update of the leukotriene modulators for the treatment of asthma

Bronchial asthma is a chronic inflammatory airway disease involving many cells and mediators. Chronic inflammation constitutes an important predisposing condition for airway remodelling with secondary irreversible airflow obstruction. Current approaches for asthma treatment involve many classes of drugs, adequate patient education for their correct use, environmental exposure control and daily monitoring of pulmonary function. Unfortunately, the use of multiple therapies complicates treatment regimens, thus leading to a reduced compliance to therapy. Available evidence from randomised clinical trials and real-word experience derived from managing patients with asthma justifies a broader role for leukotriene receptor antagonist drugs in asthma management than that recommended in the National Asthma Education and Prevention Programme and National Health Lung and Blood Institute Treatment Guidelines. While a low dose of inhaled corticosteroids remains the reference drug as a controller in mild-to-moderate persistent asthma, oral therapy with an leukotriene-receptor antagonist drug represents a good option providing the clinical efficacy requested in common clinical practice. For this reason the recent Global Initiative for Asthma Guidelines allocate this drug to the second and third steps of asthma treatment.

Exhaled breath condensate cysteinyl leukotrienes are increased in children with exercise-induced bronchoconstriction

BACKGROUND

It is recognized that airway inflammation has a central role in the pathogenesis of asthma, but how it relates to exercise-induced bronchoconstriction (EIB) is not completely understood.

OBJECTIVE

The aim of our study was to investigate the relationship between EIB and baseline concentrations of cysteinyl leukotrienes (Cys-LTs) and other inflammatory markers in exhaled breath condensate (EBC).

METHODS

EBC was collected, and the fraction of exhaled nitric oxide (FE NO ) was measured in a group of 19 asthmatic children, after which they performed a treadmill exercise test. Fourteen healthy children were enrolled as control subjects.

RESULTS

The asthmatic children were divided into the EIB group (decrease in FEV 1 , > or =12%) and the non-EIB group. The EBC was analyzed for the presence of Cys-LTs, leukotriene B 4 , and ammonia. Asthmatic patients with EIB (mean FEV 1 decrease, 23% +/- 3%) had higher Cys-LT concentrations than either asthmatic patients without EIB or control subjects (42.2 pg/mL [median] vs 11.7 pg/mL and 5.8 pg/mL; P < .05 and P < .001, respectively). Ammonia concentrations were lower in both the EIB and non-EIB groups than in control subjects (253.2 microM and 334.6 microM vs 798.4 microM; P < .01 and P < .05, respectively). No difference in EBC leukotriene B 4 levels was found among the 3 groups. Both asthmatic groups had higher FE NO levels than control subjects ( P < .001). EBC Cys-LT ( P < .01; r = 0.7) and FE NO ( P < .05; r = 0.5) values both correlated significantly with the postexercise FEV 1 decrease.

CONCLUSION

this study shows that EBC Cys-LT values are higher in asthmatic children with EIB and correlate with the decrease in FEV 1 after exercise. These findings suggest that the pathways of both Cys-LT and nitric oxide are involved in the pathogenesis of EIB.

Prolonged effect of montelukast in asthmatic children with exercise-induced bronchoconstriction

Accumulating evidence shows that cysteinyl leukotrienes are the most important mediators in exercise-induced bronchoconstriction (EIB). In contrast to several studies in adults, there are few long-term studies of leukotriene receptor antagonists (LTRAs) in children with EIB. The aim of this study was to assess the prolonged clinical and bronchoprotective effects of montelukast in asthmatic children with EIB. We randomly assigned 64 asthmatic children with EIB. Forty subjects received montelukast (5 mg/day), and 24 subjects received placebo once daily for 8 weeks. Exercise challenge was performed before and after 8 weeks of treatment. Of the 40 patients in the montelukast group, 28 patients crossed over after 8 weeks. The response was measured as asthma symptom score, maximum percent fall in forced expiratory volume in 1 sec (FEV(1)) from pre-exercise baseline, and time to recovery of FEV(1) to within 10% of pre-exercise baseline (time to recovery). Following 8 weeks of treatment with montelukast, the montelukast group compared with placebo showed significant improvements in all endpoints, including asthma symptom score, maximum percent fall in FEV(1) after exercise, and time to recovery. In the cross-over group, even 8 weeks after stopping montelukast treatment, all endpoints were significantly and persistently improved. These results indicate that montelukast provides clinical protection from airway hyperresponsiveness in asthmatic children with EIB, and suggest that LTRAs may be useful for the long-term management of asthmatic children with EIB.

Management of exercise-induced bronchospasm in children: the role of leukotriene antagonists

This review assesses the evidence on the efficacy of leukotriene antagonists in the management of exercise-induced bronchospasm (EIB) in children. Only two randomized, double-blind, placebo-controlled, crossover studies have examined the effect of leukotriene antagonists in EIB in a pediatric setting. All other studies, including those comparing leukotriene antagonists with other agents such as beta(2)-adrenoceptor agonists (beta(2)-agonists) and inhaled corticosteroids, primarily involve adult patients. In children, not receiving other asthma medication, leukotriene antagonists can offer statistically significant protection from EIB compared with placebo. However, protection is not complete, as a significant proportion of children will continue to experience a >15% reduction in FEV(1). None of the studies involved children treated concurrently with other asthma medications; therefore, comments on additive therapy cannot be made. Despite evidence from only a few studies, leukotriene antagonists are seen to be well tolerated, efficacious, and of benefit to some children. In addition, current management for EIB with short-acting beta(2)-agonists is less than ideal. It is therefore concluded that in children with EIB, leukotriene antagonists are indicated on a trial basis with individualized therapy and follow-up to evaluate treatment response.

A cysteinyl leukotriene 2 receptor variant is associated with atopy in the population of Tristan da Cunha

The clinical heterogeneity of asthma suggests that the contribution of genetic variability in candidate gene loci to well-defined phenotypes, such as atopy, may be examined to identify appropriate genetic risk factors for asthma. The gene encoding the cysteinyl leukotriene 2 (CysLT2) receptor has been implicated in atopy since it is localized to a region of chromosome 13q14 that has been linked to atopy in several populations and the cysteinyl leukotrienes are known to activate eosinophils and mast cells in atopy. Accordingly, we analysed the contribution of CysLT2 receptor gene variation to atopy in the inhabitants of Tristan da Cunha, a population characterized by both a founder effect and a 47% prevalence of atopy. Single-stranded conformational polymorphism analysis revealed four variants. Among these, the M201V [corrected] variant was activated with four-fold less potency by leukotriene D4 (LTD4) in a calcium flux assay. The CysLT2 receptor partial agonist, BAY u9773, also showed four-fold lower potency on the M201V [corrected] variant. The M201V [corrected] mutation is located within the extracellular region of the fifth transmembrane spanning domain of CysLT2 receptor, a position that may alter ligand binding and effector signalling. The novel M201V [corrected] CysLT2 receptor variant was associated with atopy (21%) on Tristan da Cunha compared with those who were non-atopic (7%) (Fisher's exact test, P=0.0016) in a manner that was independent of asthma (two-way ANOVA, P=0.0015). This represents the first association of a coding mutation in the CysLT2 receptor gene, located on chromosome 13q14, with the atopic phenotype found in the Tristan da Cunha population.

Fish oil supplementation reduces severity of exercise-induced bronchoconstriction in elite athletes

In elite athletes, exercise-induced bronchoconstriction (EIB) may respond to dietary modification, thereby reducing the need for pharmacologic treatment. Ten elite athletes with EIB and 10 elite athletes without EIB (control subjects) participated in a randomized, double-blind crossover study. Subjects entered the study on their normal diet, and then received either fish oil capsules containing 3.2 g eicosapentaenoic acid and 2.2 g docohexaenoic acid (n-3 polyunsaturated fatty acid [PUFA] diet; n = 5) or placebo capsules containing olive oil (placebo diet; n = 5) taken daily for 3 weeks. Diet had no effect on preexercise pulmonary function in either group or on postexercise pulmonary function in control subjects. However, in subjects with EIB, the n-3 PUFA diet improved postexercise pulmonary function compared with the normal and placebo diets. FEV1 decreased by 3 +/- 2% on n-3 PUFA diet, 14.5 +/- 5% on placebo diet, and 17.3 +/- 6% on normal diet at 15 minutes postexercise. Leukotriene (LT)E4, 9alpha, 11beta-prostaglandin F2, LTB4, tumor necrosis factor-alpha, and interleukin-1beta, all significantly decreased on the n-3 PUFA diet compared with normal and placebo diets and after the exercise challenge. These data suggest that dietary fish oil supplementation has a markedly protective effect in suppressing EIB in elite athletes, and this may be attributed to their antiinflammatory properties.

Effects of cysteinyl leukotrienes in small human bronchus and antagonist activity of montelukast and its metabolites

BACKGROUND

Evidence suggests that small airways contribute to clinically significant processes in asthma. Cysteinyl leukotrienes (CysLTs) are considered to be pivotal mediators in the pathogenesis of asthma. Montelukast (MK), a specific CysLT1 receptor antagonist, is metabolized in two main hydroxylated metabolites (termed M5 and M6, respectively).

OBJECTIVES

The aims of this study were to compare the responsiveness of small and large human bronchi to the three CysLTs, to evaluate the antagonist activity of MK, M5 and M6 in these preparations of human bronchi, and to characterize the CysLT receptors involved in the contractile response.

METHODS AND RESULTS

In isolated small bronchus (i.d. 0.5-2 mm), the potencies (-log molar EC50) of LTC4, LTD4 and LTE4 were 9.3 (n=11), 9.1 (n=30) and 8.4 (n=14), respectively. The three CysLTs were about 30-fold more potent in small bronchi than in larger bronchi (i.d. 4-6 mm). In small bronchi, MK significantly shifted to the right the CysLT concentration-effect curves with pA2 values against LTC4, LTD4 and LTE4 of 9.1 (n=3), 9.0 (n=11) and 8.7 (n=5), respectively. The antagonist potencies of M6 and M5 were similar to MK and fivefold lower, respectively. A similar activity of MK against the three CysLTs suggested that CysLT1 receptors are involved in the contraction of human bronchus. Analysis by RT-PCR also indicated that human bronchus mainly expressed CysLT1 receptors.

CONCLUSION

MK exerts a potent antagonist activity against the particularly potent constricting effects of CysLTs in isolated human small bronchi, which only expressed the CysLT1 receptor subtype. The metabolites of MK are also potent in vitro antagonists, but may not participate in the therapeutic activity of MK due to their low plasma concentrations in patients treated with the recommended dose of MK.

Protection against exercise-induced bronchoconstriction by montelukast in aspirin-sensitive and aspirin-tolerant patients with asthma

BACKGROUND

Montelukast, a cysteinyl-leukotriene receptor antagonist, was reported to have a protective effect against exercise-induced bronchoconstriction (EIB). Aspirin-induced asthma (AIA) is characterized by overproduction of cysteinyl-leukotrienes.

OBJECTIVE

The aim of the study was to compare the response to exercise and the effect of montelukast on EIB in AIA as compared to aspirin-tolerant asthma (ATA).

METHODS

A placebo-controlled, double blind, cross-over randomized study was performed in 19 AIA and 21 ATA patients with stable asthma. A single dose of montelukast (10 mg) or placebo (PL), was given orally one hour prior to exercise challenge. FEV1 was measured before and 5, 10, 15 min after exercise and then at 15-minute intervals for 4 h. Urinary LTE4 excretion and blood eosinophil count were measured at baseline, 2 h and 4 h following exercise challenge.

RESULTS

Positive bronchial response to exercise was observed in 47.5% of all patients studied. Exercise led to almost identical maximal fall in FEV1 in AIA and ATA patients (23.5% +/- 6.8% vs. 21.8% +/- 12.0%, respectively; P = 0.7). Montelukast, as compared to PL, significantly attenuated EIB in 63.2% of 19 patients with positive exercise test preceded by PL. The mean of maximum fall in FEV1 from the pre-exercise value was 10.2% +/- 13.8 after montelukast as compared to 22.5% +/- 10.2 after placebo (P < 0.001). No significant differences between protective effect of montelukast was observed in AIA as compared to ATA patients (P = 0.63, anova). Urinary LTE4 excretion showed no change following exercise, irrespective of the result of the test in all subjects.

CONCLUSION

Patients with AIA and ATA react similarly to exercise challenge and obtain similar protection against EIB by montelukast.

Leukotriene modifiers

Leukotrienes (LTs) are 5-lipoxygenase products formed from arachidonic acid metabolism. There is compelling evidence that LTs play an important role in the pathogenesis of asthma. LTs affect vascular permeability, mucus production, and smooth muscle constriction, and may contribute to airway remodeling. In mild-to-moderate asthma, LT modifiers improve measures of airflow limitation and quality of life and reduce the frequency of asthma exacerbations and the need for short-acting bronchodilator therapy. In moderate-to-severe asthma, an LT modifier in combination with an inhaled corticosteroid results in improvements in lung function and asthma control over that achieved with an inhaled corticosteroid alone. LT modifiers are effective in the treatment of exercise-induced bronchoconstriction and aspirin-induced asthma. There are few adverse effects of LT modifiers.

The role of antileukotrienes in the treatment of asthma

Cysteinyl leukotrienes (Cys-LTs) are mediators released in asthma and are both direct bronchoconstrictors and proinflammatory substances that mediated several steps in the pathophysiology of chronic asthma, including inflammatory cells recruitment, vascular leakage, and possibly airway remodelling. Available evidence from clinical trials and real world experience derived from managing patients with asthma justifies a broader role for antiLTRAs in asthma management than that recommended in the National Asthma Education and Prevention Programm (NAEPP) and National Health Lung and Blood Institute (NHLBI) treatment guidelines. Leukotriene-receptor antagonist drugs (LTRAs) seem to be effective alternatives to inhaled corticosteroids (ICS) either as monotherapy or as adjunctive therapy that reduces the need for higher doses of ICS in patients with mild-to-moderate persistent asthma. LTRAs may be used as adjunctive therapy for al levels of disease severity because they are effective in combination with ICS during long-term maintenance therapy. The agents seem especially effective in preventing aspirin-induced asthma, exercise-induced asthma (EIA) and they may provide an additional advantage of reducing nasal congestion in patients with both asthma and rhinitis.

Antileukotrienes in clinical development for asthma

Asthma is a serious world health problem characterised by a chronic inflammatory disorder of the airways. Asthma attacks, or exacerbations, are episodic but airway inflammation is chronically present. Thus, this disorder requires long-term management. The goals of asthma management include prevention steps for long-term control, action steps to stop attacks, recognising deteriorating asthma, how to treat deteriorating asthma, how and when to seek medical attention and education. In order to achieve the best therapeutic choice, a stepwise approach should be adopted. In recent years, much progress regarding the characterisation of leukotrienes (LTs) has been achieved. These substances are important products of action of the 5-lipoxygenase (5-LO) enzyme on arachidonic acid (AA) and it has been established that the leukotrienes are key mediators of both allergy and inflammation. Consequently, the important role of the cysteinyl-leukotrienes (Cys-LTs) in the pathophysiology of bronchial asthma has been suggested. Pharmacological support for the role of Cys-LTs in asthma has been observed using inhibitors of 5-LO and specific LT receptor antagonists. In the clinical setting, the LT receptor, which plays the most important role, is the Cys-LT1 receptor. The antagonists of this receptor have proven an effective therapy in chronic asthmatics, agonist antigens and exercise-induced bronchoconstriction and in aspirin-intolerant asthmatics. These drugs provide a new approach in asthmatic therapy and therefore may facilitate the compliance of daily therapy.

Urinary leukotriene E(4), eosinophil protein X, and nasal eosinophil cationic protein are not associated with respiratory symptoms in 1-year-old children

BACKGROUND

Eosinophilic airways inflammation forms the pathophysiologic basis for a proportion of children at risk of developing recurrent wheezing. Early preventive measures and/or anti-inflammatory treatment may be guided by the identification of such children. We aimed to study the relationship between respiratory symptoms and indirect markers of airway inflammation.

METHODS

We measured eosinophil protein X (EPX) and leukotriene E(4) (LTE(4)) in urine, as well as eosinophil cationic protein (ECP) in nasal lavages, in a random sample of 1-year-old children with a family history of atopy who participated in an international multicenter study on the prevention of allergy in Europe. For urine analyses, 10 children with upper respiratory illness and 19 healthy children without a family history of atopy were also enrolled. Endogenous urinary LTE(4) was separated by HPLC and determined by enzyme immunoassay with a specific antibody. The concentrations of nasal ECP and urinary EPX were determined by RIA analysis.

RESULTS

One hundred and ten children (mean age: 1.05+/-0.1 years) were enrolled. Prolonged coughing during the first year of life was reported in 29 children, wheezy breathing in 17 children, and dry skin in 33 children. A doctor's diagnosis of wheezy bronchitis was given to 17 children. Sensitization to dust mites (specific IgE > or =1.43 ML/units) was detected in two children. Children with a doctor's diagnosis of atopic dermatitis within the first 12 months of life (n=6) had significantly higher urinary EPX than children without this (66.7 vs 30.1 microg/mmol creatinine, P=0.01). Urinary excretion of EPX and LTE4 showed a weak correlation (r=0.22, P=0.02). There were no significant differences in urinary excretion of EPX and LTE(4) or nasal ECP between children with and without respiratory symptoms (P>0.1).

CONCLUSIONS

At the age of 1 year, urinary EPX is increased in children with atopic dermatitis. With regard to respiratory symptoms, urinary and nasal inflammatory parameters are not helpful in characterizing the phenotype of a single patient.

Elevating dietary salt exacerbates hyperpnea-induced airway obstruction in guinea pigs

Previous studies have indicated that increased dietary salt consumption worsens postexercise pulmonary function in humans with exercise-induced asthma (EIA). It has been suggested that EIA and hyperpnea-induced airway obstruction (HIAO) in guinea pigs (an animal model of EIA) are mediated by similar mechanisms. Therefore, the purpose of this study was to determine whether altering dietary salt consumption also exacerbated HIAO in guinea pigs. Furthermore, the potential pathway of action of dietary salt was investigated by blocking leukotriene (LT) production during HIAO in guinea pigs. Thirty-two male Hartley strain guinea pigs were split into two groups. One group (n = 16) of animals ingested a normal-salt diet (NSD) for 2 wk; the other group (n = 16) ingested a high-salt diet (HSD) for 2 wk. Thereafter, animals were anesthetized, cannulated, tracheotomized, and mechanically ventilated during a baseline period and during two dry gas hyperpnea challenges. After the first challenge, the animals were administered either saline or nordihydroguaiaretic acid, a LT inhibitor. Bladder urine was analyzed for electrolyte concentrations and urinary LTE(4). The HSD elicited higher airway inspiratory pressures (Ptr) than the NSD (P < 0.001) postchallenge. However, after infusion of the LT inhibitor and a second hyperpnea challenge, HIAO was blocked in both diet groups (P < 0.001). Nonetheless, the HSD group continued to demonstrate slightly higher Ptr than the NSD group (P < 0.05). Urinary LTE(4) excretion significantly increased in the HSD group compared with the NSD group within treatment groups. This study has demonstrated that dietary salt loading exacerbated the development of HIAO in guinea pigs and that LT release was involved in HIAO and may be moderated by changes in dietary salt loading.

Choices of therapy for exercise-induced asthma in children

Cough and wheezing interferes with sport and other forms of physical activity in half of asthmatic children. Airway obstruction can be induced by a standard exercise test in over 70% of children with asthma. A beta-adrenergic agonist or cromone taken by inhalation beforehand will usually inhibit bronchoconstriction provoked by a free running exercise test. The duration of protective effect with salbutamol, terbutaline and cromones is less than 4 h. The long acting beta-adrenergic agonists formoterol and salmeterol give protection against exercise-induced airway obstruction for up to 12 h, which implies that treatment given in the morning will offer protection from the effects of physical activity throughout the day. However, the duration of protective effect after a morning dose declines if these compounds are given regularly. Leukotriene receptor antagonists (LRAs) also provide good protection against exercise-induced asthma. Regular administration of LRAs is not associated with tolerance and loss of protective effect. The oral route makes for unobtrusive administration and this may help adherence to prescribed regimens.

The anti-inflammatory effects of leukotriene-modifying drugs and their use in asthma

Asthma is a chronic inflammatory disease of the airways. Anti-inflammatory drug therapy, primarily using corticosteroids, is now considered the first-line treatment in the management of all grades of asthma severity. Although corticosteroids are believed to be the most potent anti-inflammatory agents available, they do not suppress all inflammatory mediators involved in the asthmatic response. Leukotrienes, which are lipid mediators generated from the metabolism of arachidonic acid, play an important role in the pathogenesis of asthma. They produce bronchospasm, increase bronchial hyperresponsiveness, mucus production, and mucosal edema, and enhance airway smooth muscle cell proliferation and eosinophil recruitment into the airways, and their synthesis or release is unaffected by corticosteroid administration. The use of leukotriene synthesis inhibitors or leukotriene receptor antagonists as anti-inflammatory therapies in asthma has therefore been investigated. Beneficial effects of leukotriene-modifying drugs have been demonstrated in the management of all grades of asthma severity, and there is evidence that certain patient groups (such as those with exercise-induced asthma or aspirin-induced asthma) may be particularly suitable for such therapy.

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.

Leukotriene modifiers in pediatric asthma management

Cysteinyl leukotrienes (Cys-LTs) are mediators released in asthma and virus-induced wheezing. Corticosteroids appear to have little or no effect on this release in vivo. Cys-LTs are both direct bronchoconstrictors and proinflammatory substances that mediate several steps in the pathophysiology of chronic asthma, including inflammatory cell recruitment, vascular leakage, and possibly airway remodeling. Blocking studies show that Cys-LTs are pivotal mediators in the pathophysiology of asthma. Cys-LTs are key components in the early and late allergic airway response and also contribute to bronchial obstruction after exercise and hyperventilation of cold, dry air in asthmatics. LT modifiers reduce airway eosinophil numbers and exhaled nitric oxide levels. Together these findings support an important role for the Cys-LTs in the asthma airway inflammation. Cys-LT receptor antagonists (Cys-LTRA) are generally well-tolerated. Phase III randomized, controlled clinical trials (RCT) show that LT modifiers are moderately effective, apparently with a particular between-patient variability in their clinical response. The clinical effects of LT modifiers are additive to those of beta-agonists and corticosteroids. The onset of action of LT modifiers is within 1 to several days, and not rapid enough to make them useful as rescue treatment. Although LT modifiers possess some antiinflammatory activity, they cannot substitute for corticosteroids for inflammation control. LT modifiers are alternatives to long-acting beta-agonists as complementary treatment to inhaled corticosteroids in pediatric asthma management because they provide bronchodilation and bronchoprotection without development of tolerance, and complement the antiinflammatory activity unchecked by steroids. In addition, the Cys-LTRA montelukast has been shown to ameliorate asthmatic symptoms and provide bronchoprotection in asthmatic preschool children from 2 years of age, which is of particular importance in this difficult-to-manage group of asthmatics. Given their efficacy, antiinflammatory activity, oral administration, and safety, LT modifiers will play an important role in the treatment of asthmatic children.

Exercise-induced bronchoconstriction does not cause eosinophilic airway inflammation or airway hyperresponsiveness in subjects with asthma

The cysteinyl leukotrienes (LT) C(4), D(4), and E(4) may partially mediate eosinophilic airway inflammation in patients with asthma. High- intensity exercise by patients with asthma can result in exercise- induced bronchoconstriction, partly due to leukotriene production, but it is still debated whether this causes airway inflammation. Ten subjects completed a randomized, controlled study to examine the effects of exercise-induced bronchoconstriction on airway inflammatory cells. Subjects completed exercise challenge and methacholine challenge in random order separated by 1 wk. Spirometry was measured for 2 h after challenges, and airway responsiveness was measured the day before and 24 h after each challenge. Blood and sputum samples were obtained before, and 2, 4, 7, and 24 h after each challenge for measurement of inflammatory cells. Nine of the subjects inhaled allergen at least 3 wk before or 1 wk after the study. Sputum samples were collected before, 7 h, and 24 h after challenge. The maximum percentage fall in FEV(1) was 21.3 +/- 1.5% after exercise, 29.9 +/- 1.5% after methacholine, and 28.9+/-2.7% after allergen. Exercise had no effect on airway responsiveness or inflammatory cells measured in blood or sputum, unlike allergen inhalation, which resulted in significant airway hyperresponsiveness and increases in sputum eosinophils (p < 0.05). This study demonstrates that exercise-induced bronchoconstriction does not cause eosinophilic airway inflammation in subjects with asthma who develop airway inflammation with the same degree of allergen-induced bronchoconstriction. We conclude that exercise-induced bronchoconstriction does not cause airway inflammation or airway hyperresponsiveness.

Exercise-induced asthma: is it the right diagnosis in elite athletes?

Exercise-induced asthma, as recognized in asthmatic subjects, is an exaggerated airway response to airway dehydration in the presence of inflammatory cells and their mediators. The airway narrowing is primarily caused by contraction of bronchial smooth muscle. The milder airway narrowing documented in response to exercise in elite athletes and otherwise healthy subjects may simply be the result of the physiologic responses and pathologic changes in airway cells arising from dehydration injury. These changes, which include excessive mucus production and airway edema, would serve both to cause cough and to amplify the narrowing effects of normal bronchial smooth muscle contraction, resulting in symptoms. These changes are more likely to occur in healthy subjects who exercise intensely for long periods of time breathing cold air, dry air, or both. Under these conditions, the ability to humidify inspired air may be overwhelmed, causing significant dehydration of the airway mucosa and an increase in osmolarity, even in small airways. In addition to dehydration injury, airway narrowing to pharmacologic and physical agents may occur as a result of injury caused by large volumes of air containing irritant gases, particulate matter, or allergens being inspired during exercise. As a result, the airways may become inflamed, and the airway smooth muscle may become more sensitive. These events could result in the same exaggerated airway response to dehydration, as documented in asthmatic subjects.

Inflammatory mediators in blood and urine

Inflammation plays a major role in the pathophysiology of asthma. Therefore, monitoring of the disease and its management preferably should include assessment of mediators of airways inflammation. Much interest has been focused on using eosinophil granule proteins in blood and urine as markers of asthma inflammation. The eosinophil granule proteins are important mediators in allergic inflammation. They often function well as inflammatory markers when used in controlled clinical studies, and are therefore useful research tools. With urinary eosinophil-derived protein X (EPX) venous blood sampling is avoided. Disadvantages which limit usefulness in clinical practice are overlap between values in patients and controls, a rather weak correlation to traditional lung function variables, elevation of levels by concurrent allergic disease, and the delay between sampling and test results. Urinary excretion of leukotriene E4 (LTE(4)) reflects the production of cysteinyl leukotrienes, which are major mediators in asthma. The excretion of LTE4 possibly reflects lung function better than serum ECP. In the future, monitoring of cytokines may be used in clinical asthma to monitor control and aid in the prognosis of the disease in the young child. Techniques for simple and rapid monitoring of key type 1 and type 2 cytokines are needed.

Leukotriene receptor antagonists: efficacy and safety in children with asthma

To date, only one study of chronic use of a leukotriene receptor antagonist in children has been published. The efficacy and safety of montelukast in children 6-14 years of age with asthma (n = 336) was studied during an 8-week, double-blind, placebo-controlled trial. There was significantly greater improvement in forced expired volume in 1 sec (FEV(1)) from baseline for the montelukast group (8. 23%) compared to the placebo group (3.58%). There was a significant decrease in use of beta agonists for symptom relief and a significant decrease in the percentage of days and percentage of patients with asthma exacerbations. An asthma-specific quality of life questionnaire revealed significant overall improvement in quality of life and significant improvement in the quality of life domains for symptoms, activity, and emotions. Adverse effects were not significantly different for montelukast than for placebo, with the exception of allergic rhinitis which was more prevalent in the placebo group. A 6-month open follow-up of patients from the above study was undertaken. Effects of montelukast on FEV(1) were consistent over the 6 months, with the increase in FEV(1) not significantly different from a small control group treated with beclomethasone. Quality of life remained significantly improved throughout the open treatment period. In conclusion, leukotriene receptor antagonists are of value for the treatment of children with asthma.

Clinical evidence with montelukast in the management of chronic childhood asthma

OBJECTIVE

The aim of this article is to review data on the efficacy and safety of montelukast in the treatment of children with asthma.

METHODOLOGY

Available published literature, including published abstracts, is reviewed.

RESULTS

In patients aged 6 to 14 years with asthma (n = 27), montelukast 5mg demonstrated a significant decrease in exercise-induced bronchoconstriction 20 to 24 hours postdose after 2 days of treatment. For children with chronic asthma, only one study of the regular use of a leukotriene receptor antagonist has been published. The efficacy and safety of montelukast in children aged 6 to 14 years with asthma (n = 336) were studied during an 8-week, double-blind, placebocontrolled trial. There was a significantly greater improvement in forced expiratory volume in 1 second (FEV1) from baseline for the montelukast group (8.23%) compared with the placebo group (3.58%). There was a significant decrease in the use of a 3-agonist for symptom relief, as well as in the percentage of days and percentage of patients with asthma exacerbations. An asthma specific quality-of-life (QOL) questionnaire revealed a significant overall improvement in QOL and a significant improvement in the QOL domains for symptoms, activity and emotions in montelukast recipients. There was no significant difference between montelukast and placebo recipients in the frequency of adverse events, with the exception of allergic rhinitis, which was more prevalent in the placebo group. An open label follow-up of patients from the above study was undertaken. The effect of montelukast on FEV1 was consistent for up to 1.4 years, with the increase in FEV1 being not significantly different from that in a small control group treated with inhaled beclomethasone dipropionate. QOL remained significantly improved during the open treatment period.

CONCLUSIONS

Montelukast appears effective and safe for the treatment of children with asthma.

Oral montelukast compared with inhaled salmeterol to prevent exercise-induced bronchoconstriction. A randomized, double-blind trial. Exercise Study Group

BACKGROUND

Montelukast, an oral, once-daily leukotriene receptor antagonist, provides protection against exercise-induced bronchoconstriction.

OBJECTIVE

To evaluate the effect of 8 weeks of therapy with salmeterol aerosol or montelukast on exercise-induced bronchoconstriction in adults with asthma.

DESIGN

8-week multicenter, randomized, double-blind study.

SETTING

17 asthma treatment centers in the United States.

PATIENTS

191 adults with asthma who had documented exercise-induced bronchoconstriction.

INTERVENTION

Qualified patients were randomly assigned to double-blind treatment with montelukast (10 mg once in the evening) or salmeterol (50 microg [2 puffs] twice daily).

MEASUREMENTS

Changes in pre-exercise and postexercise challenge values; percentage inhibition in the maximal percentage decrease in FEV1; the area above the FEV1-time curve; and time to recovery of FEV1 at days 1 to 3, week 4, and week 8 of treatment.

RESULTS

By day 3, similar and statistically significant reductions in maximal percentage decrease in FEV1 were seen with both therapies. Sustained improvement occurred in the montelukast group at weeks 4 and 8; at these time points, the bronchoprotective effect of salmeterol decreased significantly. At week 8, the percentage inhibition in the maximal percentage decrease in FEV1 was 57.2% in the montelukast group and 33.0% in the salmeterol group (P = 0.002). By week 8, 67% of patients receiving montelukast and 46% of patients receiving salmeterol had a maximal percentage decrease in FEV1 of less than 20%.

CONCLUSIONS

The bronchoprotective effect of montelukast was maintained throughout 8 weeks of study. In contrast, significant loss of bronchoprotection at weeks 4 and 8 was seen with salmeterol. Long-term administration of montelukast provided consistent inhibition of exercise-induced bronchoconstriction at the end of the 8-week dosing interval without tolerance.

Pharmacotherapy of asthma in children, with special reference to leukotriene receptor antagonists

Asthma in adults is generally recognized as a chronic inflammatory airway disease, although this association is less well established in childhood asthma. Thus, recent asthma guidelines have emphasized that asthma treatment should be directed toward the underlying inflammatory aspects of the disease. The prevalence of asthma and resultant hospitalizations and deaths have increased or remained stable over the past 10 years in the United States. In part, this appears to be caused by shortcomings of available antiasthma therapeutic agents. Because these trends are particularly troublesome in children and young adults, there is a need for effective anti-inflammatory therapies that are safe and tolerable. The leukotrienes are a family of lipid mediators that appear to play an important role in the symptomology and pathogenesis of asthma. The results of clinical trials in adults with asthma demonstrated that antileukotriene drugs such as zafirlukast, montelukast, and zileuton improve pulmonary function, decrease asthma symptoms, and decrease the concomitant use of other antiasthma drugs. Most antileukotriene agents are orally bioavailable and well tolerated, offering the potential for improved patient compliance. Montelukast and zafirlukast have received approval for use in pediatric asthma patients, and approval of zafirlukast in this patient population is pending.