Role of leukotrienes in exercise-induced bronchoconstriction

An Algorithm for Strategic Continuation or Restriction of Asthma Medication Prior to Exercise Challenge Testing in Childhood Exercise Induced Bronchoconstriction

Exercise induced bronchial (EIB) constriction is a common and highly specific feature of pediatric asthma and should be diagnosed with an exercise challenge test (ECT). The impact of EIB in asthmatic children's daily lives is immense, considering the effects on both physical and psychosocial development. Monitoring childhood asthma by ECT's can provide insight into daily life disease burden and the control of asthma. Current guidelines for bronchoprovocation tests restrict both the use of reliever and maintenance asthma medication before an exercise challenge to prevent false-negative testing, as both have significant acute bronchoprotective properties. However, restricting maintenance medication before an ECT may be less appropiate to evaluate EIB symptoms in daily life when a diagnosis of asthma is well established. Rigorous of maintenance medication before an ECT according to guidelines may lead to overestimation of the real, daily life asthma burden and lead to an inappropiate step-up in therapy. The protection against EIB offered by the combined acute and chronic bronchoprotective effects of maintenance medication can be properly assessed whilst maintaining them. This may aid in achieving the goal of unrestricted participation of children in daily play and sports activities with their peers without escalation of therapy. When considering a step down in medication, a strategic wash-out of maintenance medication before an ECT aids in providing objective support of potential discontinuation of maintenance medication.

Management of Exercise-Induced Bronchoconstriction in Athletes

Exercise-induced bronchoconstriction (EIB) is a phenomenon observed in asthma but is also seen in healthy individuals and frequently in athletes. High prevalence rates are observed in athletes engaged in endurance sports, winter sports, and swimming. The pathophysiology of EIB is thought to be related to hyperventilation, cold air, and epithelial damage caused by chlorine and fine particles in inspired air. Several diagnostic procedures can be used; however, the diagnosis of EIB based on self-reported symptoms is not reliable and requires an objective examination. The hyperosmolar inhalation test and eucapnic voluntary hyperpnea test, which involve indirect stimulation of the airway, are useful for the diagnosis of EIB. A short-acting β-agonist is the first choice for prevention of EIB, and an inhaled corticosteroid is essential for patients with asthma. Furthermore, treatment should accommodate antidoping requirements in elite athletes. Tailoring of the therapeutic strategy to the individual case and the prognosis after cessation of athletic activity are issues that should be clarified in the future.

Exercise-induced alterations in phospholipid hydrolysis, airway surfactant, and eicosanoids and their role in airway hyperresponsiveness in asthma

The mechanisms responsible for driving endogenous airway hyperresponsiveness (AHR) in the form of exercise-induced bronchoconstriction (EIB) are not fully understood. We examined alterations in airway phospholipid hydrolysis, surfactant degradation, and lipid mediator release in relation to AHR severity and changes induced by exercise challenge. Paired induced sputum (n = 18) and bronchoalveolar lavage (BAL) fluid (n = 11) were obtained before and after exercise challenge in asthmatic subjects. Samples were analyzed for phospholipid structure, surfactant function, and levels of eicosanoids and secreted phospholipase A₂ group 10 (sPLA₂-X). A primary epithelial cell culture model was used to model effects of osmotic stress on sPLA₂-X. Exercise challenge resulted in increased surfactant degradation, phospholipase activity, and eicosanoid production in sputum samples of all patients. Subjects with EIB had higher levels of surfactant degradation and phospholipase activity in BAL fluid. Higher basal sputum levels of cysteinyl leukotrienes (CysLTs) and prostaglandin D₂ (PGD₂) were associated with direct AHR, and both the postexercise and absolute change in CysLTs and PGD₂ levels were associated with EIB severity. Surfactant function either was abnormal at baseline or became abnormal after exercise challenge. Baseline levels of sPLA₂-X in sputum and the absolute change in amount of sPLA₂-X with exercise were positively correlated with EIB severity. Osmotic stress ex vivo resulted in movement of water and release of sPLA₂-X to the apical surface. In summary, exercise challenge promotes changes in phospholipid structure and eicosanoid release in asthma, providing two mechanisms that promote bronchoconstriction, particularly in individuals with EIB who have higher basal levels of phospholipid turnover.

Exercise-induced bronchoconstriction and bronchodilation: investigating the effects of age, sex, airflow limitation and FEV1

Exercise-induced bronchoconstriction (EIBc) is a recognised response to exercise in asthmatic subjects and athletes but is less well understood in an unselected broad population. Exercise-induced bronchodilation (EIBd) has received even less attention. The objective of this study was to investigate the effects of age, sex, forced expiratory volume in 1 s (FEV₁) and airflow limitation (FEV₁/forced vital capacity (FVC) <0.7) on the prevalence of EIBc and EIBd.This was a retrospective study based on incremental cardiopulmonary exercise testing on cycle ergometry to symptom limitation performed between 1988 and 2012. FEV₁ was measured before and 10 min after exercise. EIBc was defined as a percentage fall in FEV₁ post-exercise below the 5th percentile, while EIBd was defined as a percentage increase in FEV₁ above the 95th percentile.35 258 subjects aged 6-95 years were included in the study (mean age 53 years, 60% male) and 10.3% had airflow limitation (FEV₁/FVC <0.7). The lowest 5% of subjects demonstrated a ≥7.6% fall in FEV₁ post-exercise (EIBc), while the highest 5% demonstrated a >11% increase in FEV₁ post-exercise (EIBd). The probability of both EIBc and EIBd increased with age and was highest in females across all ages (OR 1.76, 95% CI 1.60-1.94; p<0.0001). The probability of EIBc increased as FEV₁ % pred declined (<40%: OR 4.38, 95% CI 3.04-6.31; p<0.0001), with a >2-fold increased likelihood in females (OR 2.31, 95% CI 1.71-3.11; p<0.0001), with a trend with airflow limitation (p=0.06). The probability of EIBd increased as FEV₁ % pred declined, in the presence of airflow limitation (OR 1.55, 95% CI 1.24-1.95; p=0.0001), but sex had no effect.EIBc and EIBd can be demonstrated at the population level, and are influenced by age, sex, FEV₁ % pred and airflow limitation.

Novel airway smooth muscle-mast cell interactions and a role for the TRPV4-ATP axis in non-atopic asthma

Mast cell–airway smooth muscle (ASM) interactions play a major role in the immunoglobulin (Ig)E- dependent bronchoconstriction seen in asthma but less is known about IgE-independent mechanisms of mast cell activation. Transient receptor potential cation channel, subfamily V, member 4 (TRPV4) activation causes contraction of human ASM via the release of cysteinyl leukotrienes (cysLTs) but the mechanism is unknown. The objective of the present study was to investigate a role for IgE-independent, mast cell–ASM interaction in TRPV4-induced bronchospasm.

A technique not previously applied to respiratory research now uncovers important IgE-independent mechanisms involved in human mast cell–airway smooth muscle interactions that may be responsible for the bronchospasm associated with non-atopic asthmahttp://bit.ly/2U1n5nT

Exercise-induced bronchoconstriction in elite or endurance athletes:: Pathogenesis and diagnostic considerations

OBJECTIVE

To review the pathogenesis and evaluation of exercise-induced bronchoconstriction pertaining to the elite or endurance athlete, as well as propose a diagnostic algorithm based on the current literature.

DATA SOURCES

Studies were identified using Ovid MEDLINE and reference lists of key articles.

STUDY SELECTIONS

Randomized controlled trials were selected when available. Systematic reviews and meta-analyses of peer-reviewed literature were included, as were retrospective studies and observational studies of clinical interest.

RESULTS

Exercise-induced bronchoconstriction (EIB) is the physiologic entity in which exercise induces acute narrowing of the airways and occurs in patients both with and without asthma. It may present with or without respiratory symptoms, and the underlying cause is likely attributable to environment stressors to the airway encountered during exercise. These include the osmotic effects of inhaled dry air, temperature variations, autonomic nervous system dysregulation, sensory nerve reactivity, and airway epithelial injury. Deposition of allergens, particulate matter, and gaseous pollutants into the airway also contribute. Elite and endurance athletes are exposed to these stressors more frequently and in greater duration than the general population.

CONCLUSION

A greater awareness of EIB among elite and endurance athletes is needed, and a thorough evaluation should be performed if EIB is suspected in this population. We propose an algorithm to aid in this evaluation. Symptoms should not be solely relied on for diagnosis but should be taken into the context of bronchoprovocative challenges, which should replicate the competitive environment as closely as possible. Further research is needed to validate these tests' predictive values.

Mechanisms and Biomarkers of Exercise-Induced Bronchoconstriction

Exercise is a common trigger of bronchoconstriction. In recent years, there has been increased understanding of the pathophysiology of exercise-induced bronchoconstriction. Although evaporative water loss and thermal changes have been recognized stimuli for exercise-induced bronchoconstriction, accumulating evidence points toward a pivotal role for the airway epithelium in orchestrating the inflammatory response linked to exercise-induced bronchoconstriction. Overproduction of inflammatory mediators, underproduction of protective lipid mediators, and infiltration of the airways with eosinophils and mast cells are all established contributors to exercise-induced bronchoconstriction. Sensory nerve activation and release of neuropeptides maybe important in exercise-induced bronchoconstriction, but further research is warranted.

Infant rhinitis and watery eyes predict school-age exercise-induced wheeze, emergency department visits and respiratory-related hospitalizations

BACKGROUND

Rhinitis and conjunctivitis are often linked to asthma development through an allergic pathway. However, runny nose and watery eyes can result from nonallergic mechanisms. These mechanisms can also underlie exercise-induced wheeze (EIW), which has been associated with urgent medical visits for asthma, independent of other indicators of asthma severity or control.

OBJECTIVE

To test the hypothesis that rhinitis or watery eyes without cold symptoms (RWWC) in infancy predict development of EIW and urgent respiratory-related medical visits at school age, independent of seroatopy.

METHODS

Within a prospective birth cohort of low-income, urban children (n = 332), RWWC was queried during the first year of life. Relative risks (RRs) for EIW, emergency department (ED) visits, and hospitalizations for asthma and other breathing difficulties at 5 to 7 years of age were estimated with multivariable models. Seroatopy was determined at 7 years of age.

RESULTS

Infant RWWC was common (49% of children) and predicted school-age EIW (RR, 2.8; P < .001), ED visits (RR, 1.8; P = .001), and hospitalizations (RR, 9.8; P = .002). These associations were independent of infant wheeze. They were also independent of birth order, an indicator of increased risk of exposure to viruses in infancy, and infant ear infections, an indicator of sequelae of upper airway infections. The association between infant RWWC and ED visits at 5 to 7 years of age was attenuated (RR, 1.2; P = .23) when EIW at 5 to 7 years of age was included in the model, suggesting EIW mediates the association. Adjustment for seroatopy did not diminish the magnitudes of any of these associations.

CONCLUSION

These findings suggest a nonallergic connection between infant nonwheeze symptoms and important consequences of urban respiratory health by school age through EIW.

Function of secreted phospholipase A2 group-X in asthma and allergic disease

Elevated secreted phospholipase A₂ (sPLA₂) activity in the airways has been implicated in the pathogenesis of asthma and allergic disease for some time. The identity and function of these enzymes in asthma is becoming clear from work in our lab and others. We focused on sPLA₂ group X (sPLA₂-X) after identifying increased levels of this enzyme in asthma, and that it is responsible for a large portion of sPLA₂ activity in the airways and that the levels are strongly associated with features of airway hyperresponsiveness (AHR). In this review, we discuss studies that implicated sPLA₂-X in human asthma, and murine models that demonstrate a critical role of this enzyme as a regulator of type-2 inflammation, AHR and production of eicosanoids. We discuss the mechanism by which sPLA₂-X acts to regulate eicosanoids in leukocytes, as well as effects that are mediated through the generation of lysophospholipids and through receptor-mediated functions. This article is part of a Special Issue entitled Novel functions of phospholipase A2 Guest Editors: Makoto Murakami and Gerard Lambeau.

Aronia-citrus juice (polyphenol-rich juice) intake and elite triathlon training: a lipidomic approach using representative oxylipins in urine

In the present study, we examined whether particular urinary oxylipins (isoprostanes (IsoPs), leukotrienes (LTs), prostaglandins (PGs), and thromboxanes (TXs)) in 16 elite triathletes could alter during 145 days of training. Within this time span, 45 days were dedicated to examining the effects of the intake of a beverage rich in polyphenols (one serving: 200 mL per day) supplemented in their diet. The beverage was a mixture of citrus juice (95%) and Aronia melanocarpa juice (5%) (ACJ). Fifty-two oxylipins were analyzed in the urine. The quantification was carried out using solid-phase extraction, liquid chromatography coupled with triple quadrupole mass spectrometry. The physical activity decreased the excretion of some PG, IsoP, TX, and LT metabolites from arachidonic acid, γ-dihomo-linolenic acid, and eicosapentaenoic acid. The ACJ also reduced the excretion of 2,3-dinor-11β-PGF_2α and 11-dehydro-TXB₂, although the levels of other metabolites increased after juice supplementation (PGE₂, 15-keto-15-F_2t-IsoP, 20-OH-PGE₂, LTE₄, and 15-epi-15-E_2t-IsoP), compared to the placebo. The metabolites that increased in abundance have been related to vascular homeostasis and smooth muscle function, suggesting a positive effect on the cardiovascular system. In conclusion, exercise influences mainly the decrease in oxidative stress and the inflammation status in elite triathletes, while ACJ supplementation has a potential benefit regarding the cardiovascular system that is connected in a synergistic manner with elite physical activity.

Exercise-induced bronchoconstriction in children with asthma: An observational cohort study

BACKGROUND/PURPOSE

The diagnosis of exercise-induced bronchoconstriction (EIB) was established by changes in lung function after exercise challenge. The prevalence of EIB and factors related to EIB were not fully described in children with asthma. The aim of this study was to investigate the prevalence and predictors of EIB in children with asthma.

METHODS

A total of 149 children with physician-diagnosed asthma above 5 years of age underwent standardized treadmill exercise challenge for EIB and methacholine challenge for airway hyper-responsiveness from October 2015 to December 2016.

RESULTS

EIB presented in 52.5% of children with asthma. Compared with children without EIB, there were more patients with atopic dermatitis in children with EIB (p = 0.038). Allergic to Dermatohagoides pteronyssinus and Dermatophagoides farinae were also found more in children with EIB (p = 0.045 and 0.048 respectively). Maximal decrease in forced expiratory volume in 1 s (FEV₁) were highest in patients who were most sensitive to methacholine provocation (provocation concentration causing 20% fall in FEV1 [PC₂₀] ≤ 1 mg/mL). Patients, who were more sensitive to methacholine challenge (with lower PC₂₀ levels), develop EIB with more decline in FEV₁ after exercise challenge (p = 0.038). Among patients with EIB, airflow limitation development in patient with methacholine-induced airway hyper-responsiveness was more abrupt and severe compared with patients without airway hyper-responsiveness (p = 0.045 and 0.033 respectively).

CONCLUSION

EIB presented in 52.5% of children with asthma. The more severe methacholine-induced hyper-responsiveness, the higher prevalence of EIB as well as the severity.

Exercise-Induced Bronchospasm and Allergy

Sport is an essential part of childhood, with precious and acknowledged positive health effects but the impact of exercise-induced bronchoconstriction (EIB) significantly reduces participation in physical activity. It is important to recognize EIB, differentiating EIB with or without asthma if the transient narrowing of the airways after exercise is associated with asthmatic symptoms or not, in the way to select the most appropriate treatment among the many treatment options available today. Therapy is prescribed based on symptoms severity but diagnosis of EIB is established by changes in lung function provoked by exercise evaluating by direct and indirect tests. Sometimes, in younger children it is difficult to obtain the registration of difference between the preexercise forced expiratory volume in the first second (FEV1) value and the lowest FEV1 value recorded within 30 min after exercise, defined as the gold standard, but interrupter resistance, in association with spirometry, has been showed to be a valid alternative in preschool age. Atopy is the main risk factor, as demonstrated by epidemiologic data showing that among the estimated pediatric population with EIB up to 40% of them have allergic rhinitis and 30% of these patients may develop adult asthma, according with atopic march. Adopting the right treatment and prevention, selecting sports with no marked hyperventilation and excessive cooling of the airways, children with EIB can be able to take part in physical activity like all others.

Lack of desensitization of the cough reflex in ovalbumin-sensitized rabbits during exercise

Introduction

Cough is a major symptom of asthma frequently experienced during exercise but little is known about interactions between cough and exercise. The goal of our study was to clarify the potential modulation of the cough reflex (CR) by exercise in a spontaneously breathing anaesthetized animal model of airway eosinophilic inflammation.

Materials & methods

Ten ovalbumin (OVA) sensitized adult rabbits and 8 controls were studied. The ventilatory response to direct tracheal stimulation, performed both at rest and during exercise was determined to quantify the incidence and the sensitivity of the CR.

Broncho-alveolar lavages (BAL) and cell counts were performed to assess the level of the airway inflammation following OVA-induced sensitization. Exercise was mimicked by Electrically induced hindlimb Muscular Contractions (EMC).

Results

Among 494 tracheal stimulations, 261 were performed at rest and 233 at exercise. OVA challenges in sensitized rabbits caused a significant increase in the percentage of eosinophils (p = 0.008) in BAL. EMC increased minute ventilation by 36% and 35% in OVA and control rabbits respectively, compared to rest values. The sensitivity of the CR decreased during exercise compared to baseline in control rabbits (p = 0.0313) while it remained unchanged in OVA rabbits.

Conclusion

The desensitization of the CR during exercise in control rabbits was abolished in OVA rabbits. The precise role of airway inflammation in this lack of CR desensitization needs to be further investigated but it might contribute to the exercise-induced cough in asthmatics.

Respiratory, ocular and skin health in recreational and competitive swimmers: Beneficial effect of a new method to reduce chlorine oxidant derivatives

BACKGROUND

Chlorine by-products may irritate the eyes, nose, skin and airways of swimmers and may cause chronic airway inflammation.

OBJECTIVE

To assess the salutary effects on swimmers health of a new method of water disinfection.

METHODS

Recreational (n=320) and competitive swimmers (n=53) participated in the study. The first part of the study (Phase A) was carried out while using the current standard method. The second part (Phase B) began 8 weeks after the new method had been introduced. Total oxidants in air and chlorine species in water were assessed by standard methods. All swimmers completed a questionnaire on health complaints. Exhaled breath condensate (EBC) was used to monitor the levels of leukotriene B4 (LTB₄) and cysteinyl leukotrienes (CysLTs) in airway from competitive swimmers.

RESULTS

The new system resulted in a 75% and 39% reduction in the concentration of total oxidants and of nitrogen trichloride respectively in the air of the swimming pool. With the new system recreational swimmers experienced fewer symptoms of cough and irritation of the eyes, nose and skin. A decrease in eye irritation symptoms was also noted by competitive swimmers. The baseline concentration of CysLTs in EBC decreased significantly in Phase B with respect to Phase A.

CONCLUSIONS

The new method markedly reduced the levels of irritant oxidant substances in the pool atmosphere that resulted in a reduction of eye, nose, skin and cough complaints in recreational swimmers, and eye irritation in competitive swimmers. It was also associated with reduced CysLT levels in the airways of competitive swimmers.

Can a single dose response predict the effect of montelukast on exercise-induced bronchoconstriction?

RATIONALE

Exercise-induced bronchoconstriction (EIB) can be prevented by a single dose of montelukast (MLK). The effect is variable, similar to the variable responsiveness observed after daily treatment with MLK. We hypothesized that the effect of a single MLK-dose (5 or 10 mg) on EIB could predict the clinical effectiveness of longer term once daily treatment.

METHODS

This was a prospective, open-label study. Twenty-four asthmatic adolescents (12-17 years) suboptimally controlled by low-dose inhaled corticosteroids, with ≥10% post-exercise fall in FEV1 , were included. They performed an exercise test at baseline, 20 hr after a single MLK-dose and 40-44 hr after the last dose of 4 weeks once daily treatment. The correlations between the effect of a single dose and 4 weeks treatment on area under the curve (AUC) and maximum % fall in FEV1 were calculated.

RESULTS

AUC0-20 min decreased significantly after a single MLK-dose (P = 0.001, CI: 64.9-218.2), but not after 4 weeks of treatment (P = 0.080, CI: -12.2 to 200.4). There was a moderate correlation between the effect of a single MLK-dose and 4 weeks treatment on AUC0-20 min , r = 0.49 (P = 0.011), and maximum % fall in FEV1 , r = 0.40 (P = 0.035).

CONCLUSION

The protection provided by a single MLK-dose against EIB only modestly predicts the effect of regular treatment against EIB in adolescent asthmatics on low-dose inhaled corticosteroids. If used on a daily base, MLK offered clinically significant protection against EIB in two thirds of adolescents suboptimally controlled by low-dose ICS.

Exercise and asthma: an overview

The terms 'exercise-induced asthma' (EIA) and 'exercise-induced bronchoconstriction' (EIB) are often used interchangeably to describe symptoms of asthma such as cough, wheeze, or dyspnoea provoked by vigorous physical activity. In this review, we refer to EIB as the bronchoconstrictive response and to EIA when bronchoconstriction is associated with asthma symptoms. EIB is a common occurrence for most of the asthmatic patients, but it also affects more than 10% of otherwise healthy individuals as shown by epidemiological studies. EIA and EIB have a high prevalence also in elite athletes, especially within endurance type of sports, and an athlete's asthma phenotype has been described. However, the occurrence in elite athletes shows that EIA/EIB, if correctly managed, may not impair physical activity and top sports performance. The pathogenic mechanisms of EIA/EIB classically involve both osmolar and vascular changes in the airways in addition to cooling of the airways with parasympathetic stimulation. Airways inflammation plays a fundamental role in EIA/EIB. Diagnosis and pharmacological management must be carefully performed, with particular consideration of current anti-doping regulations, when caring for athletes. Based on the demonstration that the inhaled asthma drugs do not improve performance in healthy athletes, the doping regulations are presently much less strict than previously. Some sports are at a higher asthma risk than others, probably due to a high environmental exposure while performing the sport, with swimming and chlorine exposure during swimming as one example. It is considered very important for the asthmatic child and adolescent to master EIA/EIB to be able to participate in physical activity on an equal level with their peers, and a precise early diagnosis with optimal treatment follow-up is vital in this aspect. In addition, surprising recent preliminary evidences offer new perspectives for moderate exercise as a potential therapeutic tool for asthmatics.

Exercise and asthma: an overview

The terms 'exercise-induced asthma' (EIA) and 'exercise-induced bronchoconstriction' (EIB) are often used interchangeably to describe symptoms of asthma such as cough, wheeze, or dyspnoea provoked by vigorous physical activity. In this review, we refer to EIB as the bronchoconstrictive response and to EIA when bronchoconstriction is associated with asthma symptoms. EIB is a common occurrence for most of the asthmatic patients, but it also affects more than 10% of otherwise healthy individuals as shown by epidemiological studies. EIA and EIB have a high prevalence also in elite athletes, especially within endurance type of sports, and an athlete's asthma phenotype has been described. However, the occurrence in elite athletes shows that EIA/EIB, if correctly managed, may not impair physical activity and top sports performance. The pathogenic mechanisms of EIA/EIB classically involve both osmolar and vascular changes in the airways in addition to cooling of the airways with parasympathetic stimulation. Airways inflammation plays a fundamental role in EIA/EIB. Diagnosis and pharmacological management must be carefully performed, with particular consideration of current anti-doping regulations, when caring for athletes. Based on the demonstration that the inhaled asthma drugs do not improve performance in healthy athletes, the doping regulations are presently much less strict than previously. Some sports are at a higher asthma risk than others, probably due to a high environmental exposure while performing the sport, with swimming and chlorine exposure during swimming as one example. It is considered very important for the asthmatic child and adolescent to master EIA/EIB to be able to participate in physical activity on an equal level with their peers, and a precise early diagnosis with optimal treatment follow-up is vital in this aspect. In addition, surprising recent preliminary evidences offer new perspectives for moderate exercise as a potential therapeutic tool for asthmatics.

Impact-driven, pulmonary emboli of osseous fat in exercise-induced bronchospasm

Exercise induced bronchospasm (EIB) affects approximately 10% of normal individuals with higher prevalence rates among children, obese adults, and competitive athletes. Although hyperpnea with dry air is the best known cause, the problem is multifactorial with atopy, asthma and chlorine all playing established roles. To date, no clear mechanism has connected musculoskeletal loading with the ensuing pulmonary compromise. This paper reviews evidence that impact-driven pulses in subchondral bone pressure may push osseous fat cells into the local venous sinusoids. The resultant showers of microemboli must then travel to the lung where lysis of membrane phospholipids leads to leukotriene formation with resultant inflammation and bronchial hypersensitivity. Concurrently, the same emboli deliver triglyceride fuels for further physical activity. Thus, pulmonary microemboli derived from osseous fat may resolve the seeming paradox of athletic excellence in persons afflicted with exercise-induced bronchospasm.

Which biomarkers are effective for identifying Th2-driven inflammation in asthma?

Recognition of asthma as a heterogeneous disease revealed different potential molecular targets and urged the development of targeted, customized treatment modalities. Evidence was provided for different inflammatory subsets of asthma and more recently, further refined to T helper (Th)2-high and Th2-low subphenotypes with different responsiveness to standard and targeted pharmacotherapy. Given these differences in immunology and pathophysiology, proof of concept studies of novel treatment modalities for asthma should be performed in adequate, well-defined phenotypes. In this review, we describe both existing and novel biomarkers of Th2-inflammation in asthma that can be applied to classify asthma subphenotypes in clinical studies and for treatment monitoring.

Regulation and function of epithelial secreted phospholipase A2 group X in asthma

RATIONALE

Indirect airway hyperresponsiveness (AHR) is a fundamental feature of asthma that is manifest as exercise-induced bronchoconstriction (EIB). Secreted phospholipase A2 group X (sPLA2-X) plays a key role in regulating eicosanoid formation and the development of inflammation and AHR in murine models.

OBJECTIVES

We sought to examine sPLA2-X in the airway epithelium and airway wall of patients with asthma, the relationship to AHR in humans, and the regulation and function of sPLA2-X within the epithelium.

METHODS

We precisely phenotyped 34 patients with asthma (19 with and 15 without EIB) and 10 normal control subjects to examine in vivo differences in epithelial gene expression, quantitative morphometry of endobronchial biopsies, and levels of secreted protein. The regulation of sPLA2-X gene (PLA2G10) expression was examined in primary airway epithelial cell cultures. The function of epithelial sPLA2-X in eicosanoid formation was examined using PLA2 inhibitors and murine tracheal epithelial cells with Pla2g10 deletion.

MEASUREMENTS AND MAIN RESULTS

We found that sPLA2-X protein is increased in the airways of patients with asthma and that epithelial-derived sPLA2-X may be increased in association with indirect AHR. The expression of sPLA2-X increases during in vitro epithelial differentiation; is regulated by inflammatory signals including tumor necrosis factor, IL-13, and IL-17; and is both secreted from the epithelium and directly participates in the release of arachidonic acid by epithelial cells.

CONCLUSIONS

These data reveal a relationship between epithelial-derived sPLA2-X and indirect AHR in asthma and that sPLA2-X serves as an epithelial regulator of inflammatory eicosanoid formation. Therapies targeting epithelial sPLA2-X may be useful in asthma.

Leptin and urinary leukotriene E4 and 9α,11β-prostaglandin F2 release after exercise challenge

BACKGROUND

Leptin-related effects on inflammation and bronchial hyperresponsiveness (BHR) in the human airway have not been demonstrated.

OBJECTIVES

To investigate the relationship between the levels of serum leptin and BHR and urinary leukotriene E4 (LTE4) and 9α,11β-prostaglandin F2 (9α,11β-PGF(2)) release after exercise challenge in asthmatic children.

METHODS

Eighty-six prepubertal children between 6 and 10 years old were enrolled and divided into 4 groups: 19 obese asthmatic children, 25 normal-weight asthmatic children, 21 obese nonasthmatic children, and 21 healthy controls. We measured serum leptin levels and urinary LTE4 and 9α,11β-PGF2 levels in children before and 30 minutes after the exercise challenge.

RESULTS

Serum leptin levels were significantly higher in obese asthmatic children compared with normal-weight asthmatic children. Significant increases in urinary levels of LTE4 and 9α,11β-PGF2 were observed in obese asthmatic children after the exercise challenge. Although smaller than in obese asthmatic children, significant increases in the urinary levels of LTE4 and 9α,11β-PGF2 were also observed in the normal-weight. Asthmatic children Logarithmic serum leptin values were significantly associated with the logarithmic maximum percentage change in forced expiratory volume in 1 second, the logarithmic urinary LTE4 change, and the logarithmic urinary 9α,11β-PGF2 change from baseline to after exercise in both obese and normal-weight asthmatic children.

CONCLUSION

The serum levels of leptin were significantly associated with BHR and urinary LTE4 and 9α,11β-PGF2 release induced by exercise challenge in asthmatic children.

Fatty acids induce leukotriene C4 synthesis in macrophages in a fatty acid binding protein-dependent manner

Obesity results in increased macrophage recruitment to adipose tissue that promotes a chronic low-grade inflammatory state linked to increased fatty acid efflux from adipocytes. Activated macrophages produce a variety of pro-inflammatory lipids such as leukotriene C4 (LTC4) and 5-, 12-, and 15-hydroxyeicosatetraenoic acid (HETE) suggesting the hypothesis that fatty acids may stimulate eicosanoid synthesis. To assess if eicosanoid production increases with obesity, adipose tissue of leptin deficient ob/ob mice was analyzed. In ob/ob mice, LTC4 and 12-HETE levels increased in the visceral (but not subcutaneous) adipose depot while the 5-HETE levels decreased and 15-HETE abundance was unchanged. Since macrophages produce the majority of inflammatory molecules in adipose tissue, treatment of RAW264.7 or primary peritoneal macrophages with free fatty acids led to increased secretion of LTC4 and 5-HETE, but not 12- or 15-HETE. Fatty acid binding proteins (FABPs) facilitate the intracellular trafficking of fatty acids and other hydrophobic ligands and in vitro stabilize the LTC4 precursor leukotriene A4 (LTA4) from non-enzymatic hydrolysis. Consistent with a role for FABPs in LTC4 synthesis, treatment of macrophages with HTS01037, a specific FABP inhibitor, resulted in a marked decrease in both basal and fatty acid-stimulated LTC4 secretion but no change in 5-HETE production or 5-lipoxygenase expression. These results indicate that the products of adipocyte lipolysis may stimulate the 5-lipoxygenase pathway leading to FABP-dependent production of LTC4 and contribute to the insulin resistant state.

Where to from here for exercise-induced bronchoconstriction: the unanswered questions

The role of epithelial injury is an unanswered question in those with established asthma and in elite athletes who develop features of asthma and exercise-induced bronchorestriction (EIB) after years of training. The movement of water in response to changes in osmolarity is likely to be an important signal to the epithelium that may be central to the onset of EIB. It is generally accepted that the mast cell and its mediators play a major role in EIB and the presence of eosinophils is likely to enhance EIB severity.

Exercise-induced bronchoconstriction

OBJECTIVE

To review the literature regarding the pathophysiology of exercise-induced bronchoconstriction (EIB).

DATA SOURCES

The databases of PubMed, Ovid MEDLINE, and Scopus were searched for articles using the subject headings and/or keywords asthma, exercise-induced/etiology, exercise, mechanism, pathogenesis, and bronchoconstriction.

STUDY SELECTIONS

Articles were selected based on their relevance to the focus of this review, with emphasis on the specific pathophysiologic mechanisms of EIB.

RESULTS

EIB occurs in response to the loss of water from the lower airways that results from heating and humidifying large volumes of air in a short period. The resulting hyperosmolar environment activates various cellular mechanisms to release mediators from mast cells, eosinophils, epithelial cells, and sensory nerves. These mediators, in turn, lead to airway smooth muscle contraction and bronchoconstriction. Airway hyperresponsiveness in elite athletes may develop from a process of airway injury and changes in the contractile properties of airway smooth muscle.

CONCLUSION

EIB commonly affects individuals with and without clinically recognized asthma, especially those who participate in competitive athletics. Through years of research, the pathophysiology of EIB is now better understood and involves a complex interaction between several different cell types and mediators. Continued research to improve the knowledge regarding the mechanisms of EIB should aid the identification, diagnosis, and treatment of this common condition.

Exercise-induced wheeze, urgent medical visits, and neighborhood asthma prevalence

OBJECTIVE

Exercise-induced wheeze (EIW) may identify a distinct population among asthmatics and give insight into asthma morbidity etiology. The prevalence of pediatric asthma and associated urgent medical visits varies greatly by neighborhood in New York City and is highest in low-income neighborhoods. Although increased asthma severity might contribute to the disparities in urgent medical visits, when controlling for health insurance coverage, we previously observed no differences in clinical measures of severity between asthmatic children living in neighborhoods with lower (3%-9%) versus higher (11%-19%) asthma prevalence. Among these asthmatics, we hypothesized that EIW would be associated with urgent medical visits and a child's neighborhood asthma prevalence.

METHODS

Families of 7- to 8-year-old children were recruited into a case-control study of asthma through an employer-based health insurance provider. Among the asthmatics (n = 195), prevalence ratios (PRs) for EIW were estimated. Final models included children with valid measures of lung function, seroatopy, and waist circumference (n = 140).

RESULTS

EIW was associated with urgent medical visits for asthma (PR, 2.29; P = .021), independent of frequent wheeze symptoms. In contrast to frequent wheeze, EIW was not associated with seroatopy or exhaled NO, suggesting a distinct mechanism. EIW prevalence among asthmatics increased with increasing neighborhood asthma prevalence (PR, 1.09; P = .012), after adjustment for race, ethnicity, maternal asthma, environmental tobacco smoke, household income, and neighborhood income.

CONCLUSIONS

EIW may contribute to the disparities in urgent medical visits for asthma between high- and low-income neighborhoods. Physicians caring for asthmatics should consider EIW an indicator of risk for urgent medical visits.

Distinctive bronchial inflammation status in athletes: basophils, a new player

The aim of the study was to establish bronchial inflammation status and to measure eicosanoids in sputum obtained from active elite athletes. A total of 68 subjects were enrolled. Twelve were non-athletes and non-asthmatic (NAtNAs), 21 non-athlete asthmatics (NAtAs), 11 athlete non-asthmatics (AtNAs), and 24 athletes with asthma (AtAs) with positive indirect or direct bronchial challenges. Induced sputum was used to measure cells and eicosanoids. Sputum differential cell counts in all the subject groups revealed eosinophilia with the exception of NAtNAs control subjects. Athletes with and without diagnosed asthma showed a significant increase in bronchial epithelial cells and lymphocytes present in their sputum. Also, flow cytometry revealed that a significantly higher number of basophils were present in sputum from athletes (without and with asthma) when compared with non-athletes (without and with asthma). Asthmatic athletes and non-athletes showed a higher increase in LTC(4) levels and PGE(2) metabolites in sputum when compared with healthy controls. The present study identifies basophils as a new player present in athletes bronchial inflammation defining athlete status and not necessarily associated with exercise-induced bronchoconstriction.

New insights into pathogenesis of exercise-induced bronchoconstriction

PURPOSE OF REVIEW

Exercise-induced bronchoconstriction (EIB) refers to acute airflow obstruction that is triggered by a period of physical exertion. Here we review recent findings about the epidemiology of EIB, immunopathology leading to EIB, and the latest understanding of the pathogenesis of EIB.

RECENT FINDINGS

Longitudinal studies demonstrated that airway hyper-responsiveness to exercise or cold air at an early age are among the strongest predictors of persistent asthma. Patients that are susceptible to EIB have epithelial disruption and increased levels of inflammatory eicosanoids such as cysteinyl leukotrienes (CysLT)s. The leukocytes implicated in production of eicosanoids in the airways include both a unique mast cell population as well as eosinophils. A secreted phospholipase A(2) (sPLA(2)) enzyme that serves as a regulator of CysLT formation is present in increased quantities in asthma. Transglutaminase 2 (TGM2) is expressed at increased levels in asthma and serves as a regulator of secreted phospholipase A(2) group X (sPLA(2)-X). Further, sPLA(2)-X acts on target cells such as eosinophils to initiate cellular eicosanoid synthesis.

SUMMARY

Recent studies have advanced our understanding of EIB as a syndrome that is caused by the increased production of inflammatory eicosanoids. The airway epithelium may be an important regulator of the production of inflammatory eicosanoids by leukocytes.

Smooth muscle in tissue remodeling and hyper-reactivity: airways and arteries

Smooth muscle comprises a key functional component of both the airways and their supporting vasculature. Dysfunction of smooth muscle contributes to and exacerbates a host of breathing-associated pathologies such as asthma, chronic obstructive pulmonary disease and pulmonary hypertension. These diseases may be marked by airway and/or vascular smooth muscle hypertrophy, proliferation and hyper-reactivity, and related conditions such as fibrosis and extracellular matrix remodeling. This review will focus on the contribution of airway or vascular smooth dysfunction to common airway diseases.

Evidence for phenotype-driven treatment in asthmatic patients

PURPOSE OF REVIEW

Asthma is a complex inflammatory disease and current therapy remains inadequate in many sufferers. There is phenotypic heterogeneity in its clinical expression as a consequence of gene-environment interactions and heterogeneity in response to therapy. This review summarizes the current state of knowledge on phenotype-driven treatment of asthma.

RECENT FINDINGS

Evidence is accumulating that even standard therapies such as inhaled corticosteroids benefit some groups of asthmatic patients more than others. Macrolide antibiotics and antifungal agents are examples of drugs that have established indications outside the field of airways disease but which may benefit a subset of patients with asthma. Finally, new and expensive biological therapies for asthma are emerging that may be highly efficacious, but only for a selected group of patients.

SUMMARY

The emergence of novel therapies, in particular highly specific treatments, bring the promise of improving healthcare in asthma but present the challenge of choosing the right therapy for the right patient. Phenotype-driven treatment of asthma is emerging as a potential reality and will pave the way for personalized healthcare.

Exercise increases exhaled breath condensate cysteinyl leukotriene concentration in asthmatic patients

BACKGROUND

Although the importance of cysteinyl leukotrienes (Cys-LTs) in exercise-induced bronchoconstriction (EIB) is supported by various sources of evidence, how the concentration of these mediators change during the development of EIB has not been investigated.

OBJECTIVES

Our goal was to determine the effect of exercise on the concentration of airway Cys-LT in asthmatic patients by measuring Cys-LT in exhaled breath condensate (EBC).

METHODS

Seventeen atopic asthmatic patients with a previous history of EIB and six healthy volunteers were studied. Before and two times within 10 minutes after exercise challenge, FEV₁ was measured and EBC was collected for Cys-LT measurement. Exhaled nitric oxide level, a marker of airway inflammation, was also determined at baseline.

RESULTS

Baseline Cys-LT level was higher in the asthmatic group versus healthy subjects (168 pg/mL /112-223/ vs. 77 pg/mL /36-119/, p = .03). EBC Cys-LT concentration increased in all asthmatic patients post-exercise (n = 17, p = .03), with the increase significantly greater in patients developing exercise-induced bronchospasm (n = 7, p = .03), whereas no change was observed in healthy controls (p = .59). The exercise-induced fall in FEV(1) in asthmatics was related to the increase in EBC Cys-LT concentration (r = -0.40, p = .03).

CONCLUSIONS

Our study shows that Cys-LT concentration of EBC is elevated minutes after physical exercise in asthmatic patients and strongly supports the concept that the release of this mediator is involved in the development of EIB.

Randomized controlled trial of fish oil and montelukast and their combination on airway inflammation and hyperpnea-induced bronchoconstriction

Background

Both fish oil and montelukast have been shown to reduce the severity of exercise-induced bronchoconstriction (EIB). The purpose of this study was to compare the effects of fish oil and montelukast, alone and in combination, on airway inflammation and bronchoconstriction induced by eucapnic voluntary hyperpnea (EVH) in asthmatics.

Methods

In this model of EIB, twenty asthmatic subjects with documented hyperpnea-induced bronchoconstriction (HIB) entered a randomized double-blind trial. All subjects entered on their usual diet (pre-treatment, n = 20) and then were randomly assigned to receive either one active 10 mg montelukast tablet and 10 placebo fish oil capsules (n = 10) or one placebo montelukast tablet and 10 active fish oil capsules totaling 3.2 g EPA and 2.0 g DHA (n = 10) taken daily for 3-wk. Thereafter, all subjects (combination treatment; n = 20) underwent another 3-wk treatment period consisting of a 10 mg active montelukast tablet or 10 active fish oil capsules taken daily.

Results

While HIB was significantly inhibited (p<0.05) by montelukast, fish oil and combination treatment compared to pre-treatment, there was no significant difference (p>0.017) between treatment groups; percent fall in forced expiratory volume in 1-sec was −18.4±2.1%, −9.3±2.8%, −11.6±2.8% and −10.8±1.7% on usual diet (pre-treatment), fish oil, montelukast and combination treatment respectively. All three treatments were associated with a significant reduction (p<0.05) in F_ENO, exhaled breathe condensate pH and cysteinyl-leukotrienes, while the fish oil and combination treatment significantly reduced (p<0.05) urinary 9α, 11β-prostaglandin F₂ after EVH compared to the usual diet; however, there was no significant difference (p>0.017) in these biomarkers between treatments.

Conclusion

While fish oil and montelukast are both effective in attenuating airway inflammation and HIB, combining fish oil with montelukast did not confer a greater protective effect than either intervention alone. Fish oil supplementation should be considered as an alternative treatment for EIB.

Trial Registration

ClinicalTrials.gov NCT00676468

Exercise but not mannitol provocation increases urinary Clara cell protein (CC16) in elite swimmers

Elite swimmers have an increased risk of developing asthma, and exposure to chloramine is believed to be an important trigger factor. The aim of the present study was to explore pathophysiological mechanisms behind induced bronchoconstriction in swimmers exposed to chloramine, before and after swim exercise provocation as well as mannitol provocation. Urinary Clara cell protein (CC16) was used as a possible marker for epithelial stress. 101 elite aspiring swim athletes were investigated and urinary samples were collected before and 1 h after completed exercise and mannitol challenge. CC16, 11β-prostaglandin (PG)F(2α) and leukotriene E(4) (LTE(4)) were measured. Urinary levels of CC16 were clearly increased after exercise challenge, while no reaction was seen after mannitol challenge. Similar to CC16, the level of 11β-PGF(2α) was increased after exercise challenge, but not after mannitol challenge, while LTE(4) was reduced after exercise. There was no significant difference in urinary response between those with a negative compared to positive challenge, but a tendency of increased baseline levels of 11β-PGF(2α) and LTE(4) in individuals with a positive mannitol challenge. The uniform increase of CC16 after swim exercise indicates that CC16 is of importance in epithelial stress, and may as such be an important pathogenic factor behind asthma development in swimmers. The changes seen in urinary levels of 11β-PGF(2α) and LTE(4) indicate a pathophysiological role in both mannitol and exercise challenge.

An update on the role of leukotrienes in asthma

PURPOSE OF REVIEW

Leukotrienes are lipid mediators involved in the pathogenesis of asthma. There is significant new information about the actions of leukotrienes in asthma and the evolving role of antileukotriene therapies. We review recent findings on regulation of leukotriene synthesis, biological function of leukotrienes in disease models, and use of leukotriene modifiers in clinical practice.

RECENT FINDINGS

Our understanding of the regulation of leukotriene synthesis at a molecular level has greatly advanced. Recent evidence indicates that genetic variation in the leukotriene synthetic pathway affects the clinical response to leukotriene modifiers. The participation of leukotriene B4 in the allergic sensitization process in animal models suggests a larger role for leukotriene B4 in asthma. Preclinical and in-vitro models suggest that the cysteinyl leukotrienes are important in airway remodeling. Leukotrienes are key mediators of exercise-induced bronchoconstriction with recent studies demonstrating that leukotriene modifiers reduce the severity of exercise-induced bronchoconstriction during short-term and long-term use.

SUMMARY

Leukotrienes are clearly involved in airway inflammation and certain clinical features of asthma. Evolving evidence indicates that leukotriene B4 has an important role in the development of asthma and that cysteinyl leukotrienes are key mediators of the airway remodeling process.

An update on exercise-induced bronchoconstriction with and without asthma

Exercise-induced bronchoconstriction (EIB) is defined as transient, reversible bronchoconstriction that develops after strenuous exercise. It is a heterogeneous syndrome made up of a spectrum of phenotypes ranging from the asymptomatic military recruit whose condition is detected by diagnostic exercise challenge to the athlete with known asthma to the elite athlete for whom EIB represents an overuse or injury syndrome. If exercise is the only identified trigger for bronchoconstriction, it is called EIB. However, when it is associated with known asthma, then it is defined as EIB with asthma. This review discusses the pathogenesis, presentation, diagnosis, and management of EIB and EIB with asthma.

Exercise-induced asthma: critical analysis of the protective role of montelukast

Exercise-induced asthma/exercise-induced bronchospasm (EIA/EIB) is a prevalent and clinically important disease affecting young children through older adulthood. These terms are often used interchangeably and the differences are not clearly defined in the literature. The pathogenesis of EIA/EIB may be different in those with persistent asthma compared to those with exercise-induced symptoms only. The natural history of EIA is unclear and may be different for elite athletes. Leukotriene biology has helped the understanding of EIB. The type and intensity of exercise are important factors for EIB. Exercise participation is necessary for proper development and control of EIA is recommended. Symptoms of EIB should be confirmed by proper testing. Biologic markers may also be helpful in diagnosis. Not all exercise symptoms are from EIB. Many medication and nonpharmacologic treatments are available. Asthma education is an important component of managing EIA. Many medications have been tested and the comparisons are complicated. Montelukast is a US Food and Drug Administration-approved asthma and EIB controller and has a number of potential advantages to other asthma medications including short onset of action, ease of use, and lack of tolerance. Not all patients improve with montelukast and rescue medication should be available.