Recovery of leukotriene E4 from the urine of patients with airway obstruction

Indeno[1,2,3-cd]pyrene enhances the sensitivity of airway epithelial cells to ferroptosis and aggravates asthma

Particulate matter of aerodynamic diameter ≤2.5 μm (PM2.5) exposure induces oxidative stress in lung tissues. Ferroptosis is a form of regulated cell death based on oxidative damage and lipid peroxidation. Whether PM2.5 exposure-induced oxidative stress can promote ferroptosis to aggravate asthma is not known. To investigate if PM2.5 exposure induces oxidative stress to promote ferroptosis and influence asthma development, a cockroach extract-induced asthma model in mice was used for in vivo studies. Airway epithelial cell (AEC) ferroptosis was detected by assays (CCK8, malonaldehyde, and 4-hydroxynonenal). Molecular mechanisms were investigated by real-time reverse transcription-quantitative polymerase chain reaction, western blotting, flow cytometry, liquid chromatography-tandem mass spectrometry, and chromatin immunoprecipitation. We found that exposure to PM2.5 and Indeno[1,2,3-cd] pyrene (IP; one of the prominent absorbed polycyclic aromatic hydrocarbons in PM2.5) enhanced the sensitivity of AECs to ferroptosis to aggravate asthma, whereas ferroptosis inhibitors and cytosolic phospholipase A2 (cPLA2) inhibitors reversed this augmented inflammatory response in mice suffering from asthma. IP treatment enhanced cPLA2 expression/activation through aryl hydrocarbon receptor (AhR) genomic and non-genomic pathways, resulting in arachidonic-acid release to promote the sensitivity of AECs to ferroptosis. IP exposure enhanced the release of leukotriene-B4 from lung macrophages, resulting in enhanced expression of acyl-coA synthetase long chain family member4 (ACSL4) and the sensitivity of AECs to ferroptosis. This finding suggests that exposure to PM2.5 and IP promote ferroptosis sensitivity in AECs to aggravate asthma, which may provide new targets for the prevention and treatment of asthma.

Tuft cells in the pathogenesis of chronic rhinosinusitis with nasal polyps and asthma

OBJECTIVE

To review the latest discoveries regarding the role of tuft cells in the pathogenesis of chronic rhinosinusitis (CRS) with nasal polyposis and asthma.

DATA SOURCES

Reviews and primary research manuscripts were identified from PubMed, Google, and bioRxiv using the search words airway epithelium, nasal polyposis, CRS or asthma and chemoreceptor cell, solitary chemosensory cell, brush cell, microvillus cell, and tuft cell.

STUDY SELECTIONS

Studies were selected on the basis of novelty and likely relevance to the functions of tuft cells in chronic inflammatory diseases in the upper and lower airways.

RESULTS

Tuft cells coordinate a variety of immune responses throughout the body. After the activation of bitter-taste receptors, tuft cells coordinate the secretion of antimicrobial products by adjacent epithelial cells and initiate the calcium-dependent release of acetylcholine resulting in neurogenic inflammation, including mast cell degranulation and plasma extravasation. Tuft cells are also the dominant source of interleukin-25 and a significant source of cysteinyl leukotrienes that play a role in initiating inflammatory processes in the airway. Tuft cells have also been found to seem de novo in the distal airway after a viral infection, implicating these cells in dysplastic remodeling in the distal lung in the pathogenesis of asthma.

CONCLUSION

Tuft cells bridge innate and adaptive immunes responses and play an upstream role in initiating type 2 inflammation in the upper and possibly the lower airway. The role of tuft cells in respiratory pathophysiology must be further investigated, because tuft cells are putative high-value therapeutic targets for novel therapeutics in CRS with nasal polyps and asthma.

Current perspective on eicosanoids in asthma and allergic diseases: EAACI Task Force consensus report, part I

Eicosanoids are biologically active lipid mediators, comprising prostaglandins, leukotrienes, thromboxanes, and lipoxins, involved in several pathophysiological processes relevant to asthma, allergies, and allied diseases. Prostaglandins and leukotrienes are the most studied eicosanoids and established inducers of airway pathophysiology including bronchoconstriction and airway inflammation. Drugs inhibiting the synthesis of lipid mediators or their effects, such as leukotriene synthesis inhibitors, leukotriene receptors antagonists, and more recently prostaglandin D₂ receptor antagonists, have been shown to modulate features of asthma and allergic diseases. This review, produced by an European Academy of Allergy and Clinical Immunology (EAACI) task force, highlights our current understanding of eicosanoid biology and its role in mediating human pathology, with a focus on new findings relevant for clinical practice, development of novel therapeutics, and future research opportunities.

Leukotriene D4 paradoxically limits LTC4-driven platelet activation and lung immunopathology

BACKGROUND

The 3 cysteinyl leukotrienes (cysLTs), leukotriene (LT) C₄ (LTC₄), LTD₄, and LTE₄, have different biologic half-lives, cellular targets, and receptor specificities. CysLT₂R binds LTC₄ and LTD₄in vitro with similar affinities, but it displays a marked selectivity for LTC₄in vivo. LTC₄, but not LTD₄, strongly potentiates allergen-induced pulmonary eosinophilia in mice through a CysLT₂R-mediated, platelet- and IL-33-dependent pathway.

OBJECTIVE

We sought to determine whether LTD₄ functionally antagonizes LTC₄ signaling at CysLT₂R.

METHODS

We used 2 different in vivo models of CysLT₂R-dependent immunopathology, as well as ex vivo activation of mouse and human platelets.

RESULTS

LTC₄-induced CD62P expression; HMGB1 release; and secretions of thromboxane A₂, CXCL7, and IL-33 by mouse platelets were all were blocked by a selective CysLT₂R antagonist and inhibited by LTD₄. These effects did not depend on CysLT₁R. Inhaled LTD₄ blocked LTC₄-mediated potentiation of ovalbumin-induced eosinophilic inflammation; recruitment of platelet-adherent eosinophils; and increases in IL-33, IL-4, IL-5, and IL-13 levels in lung tissue. In contrast, the effect of administration of LTE₄, the preferred ligand for CysLT₃R, was additive with LTC₄. The administration of LTD₄ to Ptges^-/- mice, which display enhanced LTC₄ synthesis similar to that in aspirin-exacerbated respiratory disease, completely blocked the physiologic response to subsequent lysine-aspirin inhalation challenges, as well as increases in levels of IL-33, type 2 cytokines, and biochemical markers of mast cell and platelet activation.

CONCLUSION

The conversion of LTC₄ to LTD₄ may limit the duration and extent of potentially deleterious signaling through CysLT₂R, and it may contribute to the therapeutic properties of desensitization to aspirin in aspirin-exacerbated respiratory disease.

Airway brush cells generate cysteinyl leukotrienes through the ATP sensor P2Y2

Chemosensory epithelial cells (EpCs) are specialized cells that promote innate type 2 immunity and protective neurally mediated reflexes in the airway. Their effector programs and modes of activation are not fully understood. Here, we define the transcriptional signature of two choline acetyltransferase-expressing nasal EpC populations. They are found in the respiratory and olfactory mucosa and express key chemosensory cell genes including the transcription factor Pou2f3, the cation channel Trpm5, and the cytokine Il25 Moreover, these cells share a core transcriptional signature with chemosensory cells from intestine, trachea and thymus, and cluster with tracheal brush cells (BrCs) independently from other respiratory EpCs, indicating that they are part of the brush/tuft cell family. Both nasal BrC subsets express high levels of transcripts encoding cysteinyl leukotriene (CysLT) biosynthetic enzymes. In response to ionophore, unfractionated nasal BrCs generate CysLTs at levels exceeding that of the adjacent hematopoietic cells isolated from naïve mucosa. Among activating receptors, BrCs express the purinergic receptor P2Y2. Accordingly, the epithelial stress signal ATP and aeroallergens that elicit ATP release trigger BrC CysLT generation, which is mediated by the P2Y2 receptor. ATP- and aeroallergen-elicited CysLT generation in the nasal lavage is reduced in mice lacking Pou2f3, a requisite transcription factor for BrC development. Last, aeroallergen-induced airway eosinophilia is reduced in BrC-deficient mice. These results identify a previously undescribed BrC sensor and effector pathway leading to generation of lipid mediators in response to luminal signals. Further, they suggest that BrC sensing of local damage may provide an important sentinel immune function.

The cysteinyl leukotriene 3 receptor regulates expansion of IL-25-producing airway brush cells leading to type 2 inflammation

Respiratory epithelial cells (EpCs) orchestrate airway mucosal inflammation in response to diverse environmental stimuli, but how distinct EpC programs are regulated remains poorly understood. Here, we report that inhalation of aeroallergens leads to expansion of airway brush cells (BrCs), specialized chemosensory EpCs and the dominant epithelial source of interleukin-25 (IL-25). BrC expansion was attenuated in mice lacking either LTC₄ synthase, the biosynthetic enzyme required for cysteinyl leukotriene (CysLT) generation, or the EpC receptor for leukotriene E₄ (LTE₄), CysLT₃R. LTE₄ inhalation was sufficient to elicit CysLT₃R-dependent BrC expansion in the murine airway through an IL-25-dependent but STAT6-independent signaling pathway. Last, blockade of IL-25 attenuated both aeroallergen and LTE₄-elicited CysLT₃R-dependent type 2 lung inflammation. These results demonstrate that CysLT₃R senses the endogenously generated lipid ligand LTE₄ and regulates airway BrC number and function.

Role of lipid mediators and control of lymphocyte responses in type 2 immunopathology

Type 2 immunopathology is a cardinal feature of allergic diseases and involves cooperation between adaptive immunity and innate effector responses. Virtually all cell types relevant to this pathology generate leukotriene and/or prostaglandin mediators that derive from arachidonic acid, express receptors for such mediators, or both. Recent studies highlight prominent functions for these mediators in communication between the innate and adaptive immune systems, as well as amplification or suppression of type 2 effector responses. This review focuses on recent advances and insights, and highlights existing and potential therapeutic applications of drugs that target these mediators or their receptors, with a special emphasis on their regulation of the innate and adaptive lymphocytes relevant to type 2 immunopathology.

Leukotriene Receptor Antagonists and Antiallergy Drugs

As one of the candidates of the therapeutic strategy for asthma in addition to inhaled corticosteroids (ICS), leukotriene receptor antagonists (LTRAs) are known to be useful for long-term management of asthma patients complicated by allergic rhinitis (AR) or exercise-induced asthma (EIA). Currently available LTRAs are pranlukast hydrate, zafirlukast, and montelukast. These LTRAs have a bronchodilator action and inhibit airway inflammation, resulting in a significant improvement of asthma symptoms, respiratory function, inhalation frequency of as-needed inhaled β2-agonist, airway inflammation, airway hyperresponsiveness, dosage of ICSs, asthma exacerbations, and patients' QOL. Although cys-LTs are deeply associated with the pathogenesis of asthma, LTRAs alone are less effective compared with ICS. However, the effects of LTRAs in combination with ICS are the same as those of LABAs in combination with ICS in steroid-naïve asthmatic patients. Concerning antiallergy drugs other than LTRAs, some mediator-release suppressants, H1 histamine receptor antagonists (H1RAs), thromboxane A2 (TXA2) inhibitors/antagonists, and Th2 cytokine inhibitor had been used mainly in Japan until the late 1990s. However, the use of these agents rapidly decreased after ICS/long acting beta agonist (LABA) combination was introduced and recommended for the management of asthma in the early 2000s. The effectiveness of other antiallergic agents on asthma management seems to be quite limited, and the safety of oral antiallergic agents has not been demonstrated in fetuses during pregnancy. Further effectiveness studies are needed to determine the true value of these orally administered agents in combination with ICS as an anti-asthma treatment.

Prenatal tobacco smoke exposure predisposes offspring mice to exacerbated allergic airway inflammation associated with altered innate effector function

Background

Epidemiological studies suggest that prenatal and early life environmental exposures have adverse effects on pulmonary function and are important contributors in the development of childhood asthma and allergic disease. The mechanism by which environmental tobacco smoke (ETS) exposure in utero promotes the development of allergic asthma remains unclear. In this study, we investigated the immunological consequences of prenatal exposure to ETS in order to understand events responsible for the development or exacerbation of allergic asthma.

Methods

Pregnant C57BL/6 mice were exposed to either ETS or filtered air throughout gestation and the effect on pulmonary inflammation in the offspring were examined and compared. Specifically, the effects on eosinophilic inflammation, airway hyperreactivity, goblet cell hyperplasia, properties of pulmonary natural killer (NK) cells and type 2 cytokines elicited in response to inhaled house dust mite (HDM) allergen were investigated in the progeny.

Results

Exposure to ETS prenatally significantly exacerbated HDM-induced airway eosinophilic inflammation, hyperreactivity, mucus secretion, cysteinyl leukotriene biosynthesis and type 2 cytokine production in the offspring. Consistently, lung mononuclear cells from ETS-exposed offspring secreted higher levels of IL-13 when stimulated in vitro with anti-αβ TCR antibody or HDM allergen. Moreover, offspring from ETS-exposed dams exhibited a higher frequency of CD11b⁺ dendritic cells and CD3⁺CD4⁺ T lymphocytes in the lungs following allergen inhalation compared to air-exposed mice. Unexpectedly, the exacerbated allergic inflammation in the ETS-exposed offspring was associated with a reduction in CD3⁻CD19⁻NK1.1⁺CD94⁺ NK cell numbers and their IFN-γ production, highlighting a role for altered innate immunity in the enhanced allergic response.

Conclusion

Our results reveal that prenatal exposure to ETS predisposes offspring to an exacerbated allergic airway inflammation that is associated with a reduction in pulmonary NK cell function, suggesting that NK cells play a key role in controlling asthma severity.

Lipid Mediators of Allergic Disease: Pathways, Treatments, and Emerging Therapeutic Targets

Bioactive lipids are critical regulators of inflammation. Over the last 75 years, these diverse compounds have emerged as clinically-relevant mediators of allergic disease pathophysiology. Animal and human studies have demonstrated the importance of lipid mediators in the development of asthma, allergic rhinitis, urticaria, anaphylaxis, atopic dermatitis, and food allergy. Lipids are critical participants in cell signaling events which influence key physiologic (bronchoconstriction) and immune phenomena (degranulation, chemotaxis, sensitization). Lipid-mediated cellular mechanisms including: (1) formation of structural support platforms (lipid rafts) for receptor signaling complexes, (2) activation of a diverse family of G-protein coupled receptors, and (3) mediating intracellular signaling cascades by acting as second messengers. Here, we review four classes of bioactive lipids (platelet activating factor, the leukotrienes, the prostanoids, and the sphingolipids) with special emphasis on lipid synthesis pathways and signaling, atopic disease pathology, and the ongoing development of atopy treatments targeting lipid mediator pathways.

Urinary Leukotriene E4 to Determine Aspirin Intolerance in Asthma: A Systematic Review and Meta-Analysis

BACKGROUND

Urinary leukotriene E4 (ULTE4) may be a biomarker that distinguishes aspirin-intolerant asthma from other asthma subtypes.

OBJECTIVE

To estimate the diagnostic testing accuracy of ULTE4 as a marker of aspirin intolerance in patients with asthma using previously published studies.

METHODS

We identified relevant clinical studies from a systematic review of English and non-English articles using MEDLINE, EMBASE, and CENTRAL (inception to February 10, 2015). Articles were screened at the abstract and full-text level by 2 independent reviewers. We included previously published studies that analyzed ULTE4 in human subjects with asthma characterized as having or not having aspirin intolerance on the basis of a specified definition: convincing history of aspirin intolerance, positive aspirin challenge, or both as the criterion standard. Individual-level data points from all included studies were obtained and analyzed.

RESULTS

The search strategy identified 867 potential articles, of which 86 were reviewed at the full-text level and 10 met criteria for inclusion. The sensitivity, specificity, positive predictive value, and negative predictive values of ULTE4 to determine aspirin intolerance in subjects with asthma were 0.55, 0.82, 0.75, and 0.66 (Amersham-enzyme immunoassay); 0.76, 0.77, 0.70, and 0.78 (Cayman-enzyme immunoassay); 0.70, 0.81, 0.86, and 0.79 (mass spectrometry); and 0.81,0.79, 0.65, and 0.88 (radioimmunoassay) at optimal thresholds of 192, 510, 167 to 173, and 66 to 69 pg/mg Cr, respectively. The diagnostic odds ratio for each methodology was 6.0, 11.9, 10.5, and 19.1, respectively.

CONCLUSIONS

ULTE4 is a marker for aspirin-intolerant asthma and could potentially be used as a clinical test to identify the risk of aspirin intolerance in subjects with asthma.

Cysteinyl leukotriene E4 activates human group 2 innate lymphoid cells and enhances the effect of prostaglandin D2 and epithelial cytokines

Background

Group 2 innate lymphoid cells (ILC2s) are a potential innate source of type 2 cytokines in the pathogenesis of allergic conditions. Epithelial cytokines (IL-33, IL-25, and thymic stromal lymphopoietin [TSLP]) and mast cell mediators (prostaglandin D₂ [PGD₂]) are critical activators of ILC2s. Cysteinyl leukotrienes (cysLTs), including leukotriene (LT) C₄, LTD₄, and LTE₄, are metabolites of arachidonic acid and mediate inflammatory responses. Their role in human ILC2s is still poorly understood.

Objectives

We sought to determine the role of cysLTs and their relationship with other ILC2 stimulators in the activation of human ILC2s.

Methods

For ex vivo studies, fresh blood from patients with atopic dermatitis and healthy control subjects was analyzed with flow cytometry. For in vitro studies, ILC2s were isolated and cultured. The effects of cysLTs, PGD₂, IL-33, IL-25, TSLP, and IL-2 alone or in combination on ILC2s were defined by using chemotaxis, apoptosis, ELISA, Luminex, quantitative RT-PCR, and flow cytometric assays. The effect of endogenous cysLTs was assessed by using human mast cell supernatants.

Results

Human ILC2s expressed the LT receptor CysLT₁, levels of which were increased in atopic subjects. CysLTs, particularly LTE₄, induced migration, reduced apoptosis, and promoted cytokine production in human ILC2s in vitro. LTE₄ enhanced the effect of PGD₂, IL-25, IL-33, and TSLP, resulting in increased production of type 2 and other proinflammatory cytokines. The effect of LTE₄ was inhibited by montelukast, a CysLT₁ antagonist. Interestingly, addition of IL-2 to LTE₄ and epithelial cytokines significantly amplified ILC2 activation and upregulated expression of the receptors for IL-33 and IL-25.

Conclusion

CysLTs, particularly LTE₄, are important contributors to the triggering of human ILC2s in inflammatory responses, particularly when combined with other ILC2 activators.

Cannabinoid receptor 2 augments eosinophil responsiveness and aggravates allergen-induced pulmonary inflammation in mice

Background

Accumulation of activated eosinophils in tissue is a hallmark of allergic inflammation. The endocannabinoid 2‐arachidonoylglycerol (2‐AG) has been proposed to elicit eosinophil migration in a CB₂ receptor/G_i/o‐dependent manner. However, it has been claimed recently that this process may also involve other mechanisms such as cytokine priming and the metabolism of 2‐AG into eicosanoids. Here, we explored the direct contribution of specific CB₂ receptor activation to human and mouse eosinophil effector function in vitro and in vivo.

Methods

In vitro studies including CB₂ expression, adhesion and migratory responsiveness, respiratory burst, degranulation, and calcium mobilization were conducted in human peripheral blood eosinophils and mouse bone marrow‐derived eosinophils. Allergic airway inflammation was assessed in mouse models of acute OVA‐induced asthma and directed eosinophil migration.

Results

CB₂ expression was significantly higher in eosinophils from symptomatic allergic donors. The selective CB₂ receptor agonist JWH‐133 induced a moderate migratory response in eosinophils. However, short‐term exposure to JWH‐133 potently enhanced chemoattractant‐induced eosinophil shape change, chemotaxis, CD11b surface expression, and adhesion as well as production of reactive oxygen species. Receptor specificity of the observed effects was confirmed in eosinophils from CB₂ knockout mice and by using the selective CB₂ antagonist SR144528. Of note, systemic application of JWH‐133 clearly primed eosinophil‐directed migration in vivo and aggravated both AHR and eosinophil influx into the airways in a CB₂‐specific manner. This effect was completely absent in eosinophil‐deficient ∆dblGATA mice.

Conclusion

Our data indicate that CB₂ may directly contribute to the pathogenesis of eosinophil‐driven diseases. Moreover, we provide new insights into the molecular mechanisms underlying the CB₂‐mediated priming of eosinophils. Hence, antagonism of CB₂ receptors may represent a novel pharmacological approach for the treatment of allergic inflammation and other eosinophilic disorders.

Leukotriene E4 elicits respiratory epithelial cell mucin release through the G-protein-coupled receptor, GPR99

Cysteinyl leukotrienes (cysLTs), leukotriene C4 (LTC4), LTD4, and LTE4 are proinflammatory lipid mediators with pathobiologic function in asthma. LTE4, the stable cysLT, is a weak agonist for the type 1 and type 2 cysLT receptors (CysLTRs), which constrict airway smooth muscle, but elicits airflow obstruction and pulmonary inflammation in patients with asthma. We recently identified GPR99 as a high-affinity receptor for LTE4 that mediates cutaneous vascular permeability. Here we demonstrate that a single intranasal exposure to extract from the respiratory pathogen Alternaria alternata elicits profound epithelial cell (EpC) mucin release and submucosal swelling in the nasal mucosa of mice that depends on cysLTs, as it is absent in mice deficient in the terminal enzyme for cysLT biosynthesis, LTC4 synthase (LTC4S). These mucosal changes are associated with mast cell (MC) activation and absent in MC-deficient mice, suggesting a role for MCs in control of EpC function. Of the three CysLTRs, only GPR99-deficient mice are fully protected from EpC mucin release and swelling elicited by Alternaria or by intranasal LTE4 GPR99 expression is detected on lung and nasal EpCs, which release mucin to doses of LTE4 one log lower than that required to elicit submucosal swelling. Finally, mice deficient in MCs, LTC4S, or GPR99 have reduced baseline numbers of goblet cells, indicating an additional function in regulating EpC homeostasis. These results demonstrate a novel role for GPR99 among CysLTRs in control of respiratory EpC function and suggest that inhibition of LTE4 and of GPR99 may have therapeutic benefits in asthma.

Pediatric acute asthma exacerbations: Evaluation and management from emergency department to intensive care unit

OBJECTIVE

The goal of this report is to review available modalities for assessing and managing acute asthma exacerbations in pediatric patients, including some that are not included in current expert panel guidelines. While it is not our purpose to provide a comprehensive review of the National Asthma Education and Prevention Program (NAEPP) guidelines, we review NAEPP-recommended treatments to provide the full range of treatments available for managing exacerbations with an emphasis on the continuum of care between the ER and ICU.

DATA SOURCES

We searched PubMed using the following search terms in different combinations: asthma, children, pediatric, exacerbation, epidemiology, pathophysiology, guidelines, treatment, management, oxygen, albuterol, β2-agonist, anticholinergic, theophylline, corticosteroid, magnesium, heliox, BiPAP, ventilation, mechanical ventilation, non-invasive mechanical ventilation and respiratory failure. We attempted to weigh the evidence using the hierarchy in which meta-analyses of randomized controlled trials (RCTs) provide the strongest evidence, followed by individual RCTs, followed by observational studies. We also reviewed the NAEPP and Global Initiative for Asthma expert panel guidelines.

RESULTS AND CONCLUSIONS

Asthma is the most common chronic disease of childhood, and acute exacerbations are a significant burden to patients and to public health. Optimal assessment and management of exacerbations, including appropriate escalation of interventions, are essential to minimize morbidity and prevent mortality. While inhaled albuterol and systemic corticosteroids are the mainstay of exacerbation management, escalation may include interventions discussed in this review.

Structure based virtual screening of ligands to identify cysteinyl leukotriene receptor 1 antagonist

Montelukast and Zafirlukast are known leukotriene receptor antagonists prescribed in asthma treatment. However, these fall short as mono therapy and are frequently used in combination with inhaled glucocorticosteroids with or without long acting beta 2 agonists. Therefore, it is of interest to apply ligand and structure based virtual screening strategies to identify compounds akin to lead compounds Montelukast and Zafirlukast. Hence, compounds with structures having 95% similarity to these compounds were retrieved from NCBI׳s PubChem database. Compounds similar to lead were grouped and docked at the antagonist binding site of cysteinyl leukotriene receptor 1. This exercise identified compounds UNII 70RV86E50Q (Pub Cid 71587778) and Sure CN 9587085 (Pub Cid 19793614) with higher predicted binding compared to Montelukast and Zafirlukast. It is shown that the compound Sure CN 9587085 showed appreciable ligand receptor interaction compared to UNII 70RV86E50Q. Thus, the compound Sure CN 9587085 is selected as a potent antagonist to cysteinyl leukotriene receptor 1 for further consideration in vitro and in vivo validation.

Cysteinyl leukotrienes and their receptors; emerging concepts

Cysteinyl leukotrienes (cys-LTs) are potent mediators of inflammation derived from arachidonic acid through the 5-lipoxygenase/leukotriene C4 synthase pathway. The derivation of their chemical structures and identification of their pharmacologic properties predated the cloning of their classical receptors and the development of drugs that modify their synthesis and actions. Recent studies have revealed unanticipated insights into the regulation of cys-LT synthesis, the function of the cys-LTs in innate and adaptive immunity and human disease, and the identification of a new receptor for the cys-LTs. This review highlights these studies and summarizes their potential pathobiologic and therapeutic implications.

Childhood asthma: a guide for pediatric emergency medicine providers

Pediatric asthma is a disease that is managed across outpatient physicians, hospitalists, critical care physicians, and emergency department (ED) physicians. Scoring systems may facilitate a rapid assessment of the child with asthma in the ED. Short-acting beta agonists are still the mainstay of therapy for acute exacerbations along with corticosteroids and ipratropium bromide. ED providers must also know the indications for noninvasive ventilation and intubation. Most patients can be treated and discharged from the ED after acute exacerbation, and should be given a plan for going home that provides educational material and emergency scenarios to help prevent future acute incidents.

Differential regulation of cysteinyl leukotriene receptor signaling by protein kinase C in human mast cells

Cysteinyl leukotrienes (cys-LTs) are a group of lipid mediators that are potent bronchoconstrictors, powerful inducers of vascular leakage and potentiators of airway hyperresponsiveness. Cys-LTs play an essential role in asthma and are synthesized as well as activated in mast cells (MCs). Cys-LTs relay their effects mainly through two known GPCRs, CysLT₁R and CysLT₂R. Although protein kinase C (PKC) isoforms are implicated in the regulation of CysLT₁R function, neither the role of PKCs in cys-LT-dependent MC inflammatory signaling nor the involvement of specific isoforms in MC function are known. Here, we show that PKC inhibition augmented LTD₄ and LTE₄-induced calcium influx through CysLT₁R in MCs. In contrast, inhibition of PKCs suppressed c-fos expression as well MIP1β generation by cys-LTs. Interestingly, cys-LTs activated both PKCα and PKCε isoforms in MC. However, knockdown of PKCα augmented cys-LT mediated calcium flux, while knockdown of PKCε attenuated cys-LT induced c-fos expression and MIP1β generation. Taken together, these results demonstrate for the first time that cys-LT signaling downstream of CysLT₁R in MCs is differentially regulated by two distinct PKCs which modulate inflammatory signals that have significant pathobiologic implications in allergic reactions and asthma pathology.

Identification of GPR99 protein as a potential third cysteinyl leukotriene receptor with a preference for leukotriene E4 ligand

The cysteinyl leukotrienes (cys-LTs), leukotriene C4 (LTC4), a conjugation product of glutathione and eicosatetraenoic acid, and its metabolites, LTD4 and LTE4, are lipid mediators of smooth muscle constriction and inflammation in asthma. LTD4 is the most potent ligand for the type 1 cys-LT receptor (CysLT1R), and LTC4 and LTD4 have similar lesser potency for CysLT2R, whereas LTE4 has little potency for either receptor. Cysltr1/Cysltr2(-/-) mice, lacking the two defined receptors, exhibited a comparable dose-dependent vascular leak to intradermal injection of LTC4 or LTD4 and an augmented response to LTE4 as compared with WT mice. As LTE4 retains a cysteine residue and might provide recognition via a dicarboxylic acid structure, we screened cDNAs within the P2Y nucleotide receptor family containing CysLTRs and dicarboxylic acid receptors with trans-activator reporter gene assays. GPR99, previously described as an oxoglutarate receptor (Oxgr1), showed both a functional and a binding response to LTE4 in these transfectants. We generated Gpr99(-/-) and Gpr99/Cysltr1/Cysltr2(-/-) mice for comparison with WT and Cysltr1/Cysltr2(-/-) mice. Strikingly, GPR99 deficiency in the Cysltr1/Cysltr2(-/-) mice virtually eliminated the vascular leak in response to the cys-LT ligands, indicating GPR99 as a potential CysLT3R active in the Cysltr1/Cysltr2(-/-) mice. Importantly, the Gpr99(-/-) mice showed a dose-dependent loss of LTE4-mediated vascular permeability, but not to LTC4 or LTD4, revealing a preference of GPR99 for LTE4 even when CysLT1R is present. As LTE4 is the predominant cys-LT species in inflamed tissues, GPR99 may provide a new therapeutic target.

Cysteinyl leukotriene receptors, old and new; implications for asthma

The cysteinyl leukotrienes (cys-LTs) are three structurally similar, but functionally distinct lipid mediators of inflammation. The parent cys-LT, LTC(4) , is synthesized by and released from mast cells, eosinophils, basophils, and macrophages, and is converted to the potent constrictor LTD(4) and the stable metabolite, LTE(4) . While only two cys-LT-selective receptors (CysLTRs) have been identified, cloned, and characterized, studies dating back three decades predicted the existence of at least three functional CysLTRs, each with a characteristic physiological function in airways and other tissues. The recent demonstration that mice lacking both known CysLTRs exhibit full (and in some instances, augmented) physiological responses to cys-LTs verifies the existence of unidentified CysLTRs. Moreover, the ability to manipulate receptor expression in both whole animal and cellular systems reveals that the functions of CysLTRs are controlled at multiple levels, including receptor-receptor interactions. Finally, studies in transgenic mice have uncovered a potentially major role for cys-LTs in controlling the induction of Th(2) responses to common allergens. This review focuses on these recent findings and their potential clinical implications.

Repeated allergen exposure reduce early phase airway response and leukotriene release despite upregulation of 5-lipoxygenase pathways

Background

Allergen induced early phase airway response and airway plasma exudation are predominantly mediated by inflammatory mast cell mediators including histamine, cysteinyl leukotrienes (cysLTs) and thromboxane A2 (TXA2). The aim of the present study was to evaluate whether repeated allergen exposure affects early phase airway response to allergen challenge.

Methods

A trimellitic anhydride (TMA) sensitized guinea pig model was used to investigate the effects of low dose repeated allergen exposure on cholinergic airway responsiveness, early phase airway response and plasma exudation, as well as local airway production of mast cell derived cysteinyl leukotrienes and thromboxane B2 (TXB2) after allergen challenge.

Results

Repeated low dose allergen exposure increased cholinergic airway responsiveness. In contrast, early phase airway response and plasma exudation in response to a high-dose allergen challenge were strongly attenuated after repeated low dose allergen exposure. Inhibition of the airway response was unspecific to exposed allergen and independent of histamine receptor blocking. Furthermore, a significant reduction of cysteinyl leukotrienes and TXB2 was found in the airways of animals repeatedly exposed to a low dose allergen. However, in vitro stimulation of airway tissue from animals repeatedly exposed to a low dose allergen with arachidonic acid and calcium ionophore (A23187) induced production of cysteinyl leukotrienes and TXB2, suggesting enhanced activity of 5-lipoxygenase and cyclooxygenase pathways.

Conclusions

The inhibition of the early phase airway response, cysteinyl leukotriene and TXB2 production after repeated allergen exposure may result from unresponsive effector cells.

Leukotriene E4 activates human Th2 cells for exaggerated proinflammatory cytokine production in response to prostaglandin D2

PGD(2) exerts a number of proinflammatory responses through a high-affinity interaction with chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) and has been detected at high concentrations at sites of allergic inflammation. Because cysteinyl leukotrienes (cysLTs) are also produced during the allergic response, we investigated the possibility that cysLTs may modulate the response of human Th2 cells to PGD(2). PGD(2) induced concentration-dependent Th2 cytokine production in the absence of TCR stimulation. Leukotrienes D(4) and E(4) (LTE(4)) also stimulated the cytokine production but were much less active than PGD(2). However, when combined with PGD(2), cysLTs caused a greater than additive enhancement of the response, with LTE(4) being most effective in activating Th2 cells. LTE(4) enhanced calcium mobilization in response to PGD(2) in Th2 cells without affecting endogenous PGD(2) production or CRTH2 receptor expression. The effect of LTE(4) was inhibited by montelukast but not by the P2Y(12) antagonist methylthioadenosine 5'-monophosphate. The enhancing effect was also evident with endogenous cysLTs produced from immunologically activated mast cells because inhibition of cysLT action by montelukast or cysLT synthesis by MK886, an inhibitor of 5-lipoxygenase-activating protein, reduced the response of Th2 cells to the levels produced by PGD(2) alone. These findings reveal that cysLTs, in particular LTE(4), have a significant proinflammatory impact on T cells and demonstrate their effects on Th2 cells are mediated by a montelukast-sensitive receptor.

Exhaled nitric oxide levels in childhood asthma: a more reliable indicator of asthma severity than lung function measurement?

The level of exhaled nitric oxide (NO) has been demonstrated to reflect the degree of airway inflammation in patients with asthma and to be related to the severity of asthma, as well as to the efficacy of treatment. In contrast, lung function tests provide information about airway volumes and flows reflecting the level of airway obstruction, but do not allow any direct information about the degree of airway inflammation. Several studies have evaluated the relationships between the level of airway inflammation assessed by exhaled NO and the levels of airway obstruction and/or bronchial hyperresponsiveness in asthmatic adults and children. These studies highlight the complex pathophysiology of asthma and suggest that exhaled NO may have a promising role in addition to lung function measurement in the evaluation of asthma severity in children.

Can montelukast shorten prednisolone therapy in children with mild to moderate acute asthma? A randomized controlled trial

OBJECTIVE

To examine whether outpatient post-stabilization therapy with montelukast produces more treatment failures than prednisolone.

STUDY DESIGN

In this randomized, double-blind, double-dummy non-inferiority trial, 130 children 2 to 17 years of age with mild to moderate acute asthma stabilized with prednisolone in the emergency department received 5 daily treatments with either prednisolone or montelukast after discharge. The primary outcome was treatment failure within 8 days (ie, an asthma-related unscheduled visit, hospitalization, or additional systemic corticosteroids).

RESULTS

The rates of treatment failure were 7.9% in the prednisolone group and 22.4% in the montelukast group (95% CI, 26.5%-2.4%). Treatment was more likely to fail in younger patients (odds ratio, 4.9). In the montelukast group, more patients received additional pharmacotherapy than in patients receiving prednisolone (23.9% versus 9.5%, P = .03). The differences in the daily salbutamol treatments, asymptomatic days, and changes in the Pediatric Respiratory Assessment Measure score were not significant (P = .85, .75, and .26, respectively).

CONCLUSION

Montelukast does not represent an adequate alternative to corticosteroids after outpatient stabilization in mild to moderate acute asthma. This population should receive oral corticosteroids after discharge.

Leukotriene E4-induced pulmonary inflammation is mediated by the P2Y12 receptor

Of the potent lipid inflammatory mediators comprising the cysteinyl leukotrienes (LTs; LTC₄, LTD₄, and LTE₄), only LTE₄ is stable and abundant in vivo. Although LTE₄ shows negligible activity at the type 1 and 2 receptors for cys-LTs (CysLT₁R and CysLT₂R), it is a powerful inducer of mucosal eosinophilia and airway hyperresponsiveness in humans with asthma. We show that the adenosine diphosphate (ADP)–reactive purinergic (P2Y₁₂) receptor is required for LTE₄-mediated pulmonary inflammation. P2Y₁₂ receptor expression permits LTE₄ -induced activation of extracellular signal-regulated kinase in Chinese hamster ovary cells and permits chemokine and prostaglandin D₂ production by LAD2 cells, a human mast cell line. P2Y₁₂ receptor expression by LAD2 cells is required for competition between radiolabeled ADP and unlabeled LTE₄ but not for direct binding of LTE₄, suggesting that P2Y₁₂ complexes with another receptor to recognize LTE₄. Administration of LTE₄ to the airways of sensitized mice potentiates eosinophilia, goblet cell metaplasia, and expression of interleukin-13 in response to low-dose aerosolized allergen. These responses persist in mice lacking both CysLT₁R and CysLT₂R but not in mice lacking P2Y₁₂ receptors. The effects of LTE₄ on P2Y₁₂ in the airway were abrogated by platelet depletion. Thus, the P2Y₁₂ receptor is required for proinflammatory actions of the stable abundant mediator LTE₄ and is a novel potential therapeutic target for asthma.

Molecular and cellular mechanisms in the viral exacerbation of asthma

The aetiology of asthma associated with viral infection is complex. The dynamics that contribute to disease pathogenesis are multifactorial and involve overlapping molecular and cellular mechanisms, particularly the immune response to respiratory virus infection or allergen sensitization. This review summarizes the evidence associated with factors that may contribute to the development or exacerbation of asthma including age, host factors, genetic polymorphisms, altered immune responses, and aspects of viral antigen expression. This review also provides an important perspective of key events linked to the development of asthmatic disease and related pulmonary inflammation from human and animal studies, and discusses their relationship as targets for disease intervention strategies.

Leukotriene E4 activates peroxisome proliferator-activated receptor gamma and induces prostaglandin D2 generation by human mast cells

Cysteinyl leukotrienes (cys-LTs) are potent inflammatory lipid mediators, of which leukotriene (LT) E(4) is the most stable and abundant in vivo. Although only a weak agonist of established G protein-coupled receptors (GPCRs) for cys-LTs, LTE(4) potentiates airway hyper-responsiveness (AHR) by a cyclooxygenase (COX)-dependent mechanism and induces bronchial eosinophilia. We now report that LTE(4) activates human mast cells (MCs) by a pathway involving cooperation between an MK571-sensitive GPCR and peroxisome proliferator-activated receptor (PPAR)gamma, a nuclear receptor for dietary lipids. Although LTD(4) is more potent than LTE(4) for inducing calcium flux by the human MC sarcoma line LAD2, LTE(4) is more potent for inducing proliferation and chemokine generation, and is at least as potent for upregulating COX-2 expression and causing prostaglandin D(2) (PGD(2)) generation. LTE(4) caused phosphorylation of extracellular signal-regulated kinase (ERK), p90RSK, and cyclic AMP-regulated-binding protein (CREB). ERK activation in response to LTE(4), but not to LTD(4), was resistant to inhibitors of phosphoinositol 3-kinase. LTE(4)-mediated COX-2 induction, PGD(2) generation, and ERK phosphorylation were all sensitive to interference by the PPARgamma antagonist GW9662 and to targeted knockdown of PPARgamma. Although LTE(4)-mediated PGD(2) production was also sensitive to MK571, an antagonist for the type 1 receptor for cys-LTs (CysLT(1)R), it was resistant to knockdown of this receptor. This LTE(4)-selective receptor-mediated pathway may explain the unique physiologic responses of human airways to LTE(4) in vivo.

Urinary leukotriene E4

Measurement of urinary leukotriene E4 (LTE4) is a sensitive and noninvasive method of assaying total body cysteinyl leukotriene production and changes in cysteinyl leukotriene levels in specific microenvironments, such as the airway. Urinary LTE4 measurements can be used as sensitive biomarkers of exposure to asthma triggers, such as air pollution and viral infections. Recent studies suggest the potential of using urinary LTE4 concentrations as predictors of asthma control and markers of susceptibility to treatment with leukotriene receptor antagonists.

Mast cells and eicosanoid mediators: a system of reciprocal paracrine and autocrine regulation

When activated by specific antigen, complement, or other transmembrane stimuli, mast cells (MCs) generate three eicosanoids: prostaglandin (PG)D(2), leukotriene (LT)B(4), and LTC(4), the parent molecule of the cysteinyl leukotrienes (cysLTs). These diverse lipid mediators, which are generated from a single cell membrane-associated precursor, arachidonic acid, can initiate, amplify, or dampen inflammatory responses and influence the magnitude, duration, and nature of subsequent immune responses. PGD(2) and cysLTs, which were originally recognized for their bronchoconstricting and vasoactive properties, also serve diverse and pivotal functions in effector cell trafficking, antigen presentation, leukocyte activation, matrix deposition, and fibrosis. LTB(4) is a powerful chemoattractant for neutrophils and certain lymphocyte subsets. Thus, MCs can contribute to each of these processes through eicosanoid generation. Additionally, MCs express G-protein-coupled receptors specific for cysLTs, LTB(4), and another eicosanoid, PGE(2). Each of these receptors can regulate MC functions in vivo by autocrine and paracrine mechanisms. This review focuses on the biologic functions for MC-associated eicosanoids, the regulation of their production, and the mechanisms by which eicosanoids may regulate MC function in host defense and disease.

Relationship between urinary cysteinyl leukotriene E4 levels and clinical response to antileukotriene treatment in patients with asthma

The aim of this study was to investigate and identify the relationship between urinary cysteinyl leukotriene E(4) levels and clinical response to antileukotriene treatment in patients with asthma. Forty-eight patients with stable mild to moderate asthma were treated with montelukast in a four-week trail. Asthmatic symptom score, beta(2)-agonist usage, percentage of eosinophil, total serum IgE concentration, forced expiratory volume in the first second (FEV(1)), peak expiratory flow rate (PEFR), and urinary leukotriene E(4) (uLTE(4)) were measured before and after treatment. Clinical response was assessed by the improvement of asthma symptom scores, beta(2)-agonist usage, and FEV(1). Responders were defined as patients who had to fit the following three criteria: a reduction of more than 20% in mean symptom score; a reduction of more than 20% in beta(2)-agonist usage, and a mean improvement of FEV(1) of more than 10% from baseline value. Others were classified as nonresponders. Logistic analysis was used to access the various clinical factors correlated with the clinical response. There were 25 responders and 23 nonresponders. The mean uLTE(4) level from the responders was higher than that from the nonresponders (224.5 +/- 34.4 vs. 175.3 +/- 37.1 pg/mg creatinine, p < 0.05). There was a significant correlation between the clinical response and the uLTE(4) level but not demographic features, percentage of eosinophils, serum IgE concentration, or spirometry (p > 0.05). Subjects with a uLTE(4) level of >/= 200 pg/mg creatinine were 3.5 times more likely to respond to montelukast than those with less than 200 pg/mg creatinine (95% confidence interval [CI] = 1.7-15.8). The uLTE(4) level is closely correlated with antileukotriene treatment. uLTE(4) is a good biomarker for selecting this drug to treat asthma.

Association between a leukotriene C4 synthase gene promoter polymorphism and coronary artery calcium in young women: the Muscatine Study

OBJECTIVE

A majority of the recognized risk factors for atherosclerosis and the development of cardiovascular disease have been derived from the study of older populations who have already manifested clinical symptoms. If risk factors can be identified earlier in life, such as genetic variation, preventive measures may be taken before overt symptoms of pathology have manifested, and when treatments may be most effective.

METHODS AND RESULTS

In an effort to identify individuals at increased risk for cardiovascular disease, we genotyped 732 members of the Muscatine Study Longitudinal Adult Cohort for candidate genetic markers associated with several pathogenetic processes. We identified age-adjusted increased risks for coronary artery calcium (OR 4.29; 95% CI 1.78, 10.31) and increased mean carotid artery intimal-medial thickness associated with the (-444)A>C promoter polymorphism of Leukotriene C4 Synthase (LTC4S) in women. There were no similar associations in men.

CONCLUSIONS

LTC4S plays a key role in the process of inflammation as the rate limiting enzyme in the conversion of arachidonic acid to cysteinyl-leukotrienes, important mediators of inflammatory responses. The (-444)C variant upregulates LTC4S mRNA expression, increasing the synthesis of proinflammatory leukotrienes. Our results support genetic variation modifying inflammatory pathways as an important mechanism in the development of atherosclerosis.

Regulating leukotriene synthesis: the role of nuclear 5-lipoxygenase

Leukotrienes are lipid messengers involved in autocrine and paracrine cellular signaling. They are synthesized from arachidonic acid by the 5-lipoxygenase pathway. Current models of this enzymatic pathway recognize that a key step in initiating leukotriene synthesis is the calcium-mediated movement of enzymes, including 5-lipoxygenase, to intracellular membranes. However, 5-lipoxygenase can be imported into or exported from the nucleus before calcium activation. As a result, its subcellular localization will affect its ability to be activated by calcium, as well as the membrane to which it binds and its interaction with other enzymes. This commentary focuses on the role of 5-lipoxygenase compartmentation in determining its regulation and, ultimately, leukotriene synthesis.

Effect of montelukast, a cysteinyl receptor antagonist, on myofibroblasts in interstitial lung disease

Montelukast, a potent cysteinyl receptor antagonist, may be an antifibrotic therapeutic agent for lung fibrosis. Seven sarcoidosis patients and 10 with unusual interstitial pneumonia underwent conventional bronchoalveolar lavage, from which myofibroblasts were recovered. Myofibroblast proliferation was assayed, alpha smooth muscle actin levels were measured, TGFbeta mRNA RT-PCR transcripts were semiquantitated, and secretion was evaluated in myofibroblast supernatants. Montelukast at 10(-8) M concentration had a suppressive effect on cell proliferation (31 +/- 18%), which was significantly enhanced by LTD4 10(-8) M. No differences were found between sarcoidosis (31.28 +/- 15.9%) and unusual interstitial pneumonia (30.56 +/- 24.3%) lines. Fetal calf serum (20%) produced an enhancing effect (29.8 +/- 21.6%) in all lines. Myofibroblasts recovered from sarcoidosis patients showed lower alpha-smooth muscle actin contents than unusual interstitial pneumonia lines (0.09 +/- 0.02 vs. 0.34 +/- 0.16, p =0.039, respectively). Montelukast suppressed alpha-actin in short-term cultures in sarcoidosis myofibroblasts and in long-term unusual interstitial pneumonia myofibroblasts. Montelukast at 10(-6) M concentratin decreased the TGFbeta-induced alpha-actin expression in all lines tested. Montelukast decreased mRNA expression of TGFbeta. Montelukast may be a therapeutic agent in pathological conditions involving fibrotic and remodeling processes.

Leukotriene E(4)-induced persistent eosinophilia and airway obstruction are reversed by zafirlukast in patients with asthma

BACKGROUND

We have shown that inhalation of leukotriene (LT) E 4 contributes to specific recruitment of eosinophils to the airway mucosa in patients with asthma at the time of maximal decrease in airway-specific conductance.

OBJECTIVE

We examined the ability of the cysteinyl LT 1 receptor antagonist, zafirlukast, to improve or prevent LT-mediated eosinophilia and airway obstruction in asthma.

METHODS

Bronchial biopsies were taken and pulmonary function was measured before and 4 to 6 hours after the dose of inhaled LTE 4 causing a > or =15% fall in FEV 1 at baseline both at week 0 and after 6-week randomly assigned treatment with a high dose of zafirlukast, 80 mg twice daily.

RESULTS

Leukotriene E 4 inhalation at week 0 doubled the number of eosinophils in the airway mucosa in 21 of 25 patients with mild asthma, increased the numbers of neutrophils and lymphocytes, and decreased FEV 1 (-17%). Zafirlukast reduced both airway eosinophilia and obstruction in FEV 1 , whereas with a double-blind placebo treatment, the effect of LTE 4 on both parameters persisted for 6 weeks. On repeat LTE 4 inhalation challenge after 6 weeks, zafirlukast treatment prevented further airway eosinophilia and decrease in FEV 1 seen in the placebo group.

CONCLUSION

Persistent LTE 4 -induced airway eosinophilia may form the basis of an amplification mechanism for further eosinophil recruitment. Zafirlukast prevents LTE 4 -induced eosinophilic airway inflammation in mild asthma.

Zafirlukast treatment for acute asthma: evaluation in a randomized, double-blind, multicenter trial

CONTEXT

Acute asthma causes nearly 2 million hospital emergency department (ED) visits in the United States annually, and hospitalization after an ED visit and relapse after ED discharge are common.

OBJECTIVE

To evaluate the adding of therapy with zafirlukast to standardized care for patients with acute asthma in the ED and a 28-day follow-up period.

DESIGN AND PATIENTS

A total of 641 patients presenting to the ED with acute asthma were randomized to receive either single-dose zafirlukast, 160 mg (Z160) [162 patients], zafirlukast, 20 mg (Z20) [158 patients]), or placebo (321 patients) as adjunct treatment to standard care in this double-blind, multicenter trial. Assessments, including spirometry and symptom scores, were obtained before each albuterol treatment and at 4 h. Patients who were discharged from the ED after 4 h continued outpatient therapy over a 28-day period and received either Z20 bid (276 patients) or placebo (270 patients) in addition to prednisone, albuterol, and their previous asthma medications. FEV(1) was measured at clinic visits on days 10 and 28. Patients recorded outpatient clinical data twice daily on a home diary card.

MAIN OUTCOME MEASURES

the effect of zafirlukast on relapse after ED discharge. Other assessments were the rate of extended care (ie, ED stay for > 4 h or hospitalization), FEV(1), and symptoms.

RESULTS

At the end of the outpatient period, 65 of 276 patients (23.6%) treated with zafirlukast and 78 of 270 patients (28.9%) treated with placebo relapsed (p = 0.047; absolute reduction, 5.3%; relative reduction, 18.3%). At the end of the ED period, 16 of 162 patients (9.9%) treated with Z160, 26 of 158 patients (16.5%) treated with Z20, and 48 of 321 patients (15.0%) treated with placebo required extended care (p = 0.052; absolute reduction with Z160 compared to placebo, 5.1%; relative reduction, 34%). These findings were supported by a significant improvement in FEV(1) and dyspnea in the ED with the use of Z160 therapy, and by greater improvement in FEV(1) and symptoms during the outpatient period for patients treated with Z20.

CONCLUSIONS

When added to standardized care, therapy with Z20 bid reduced the risk of relapse compared with placebo over a 28-day treatment period. One dose of Z160 in the ED also reduced the rate of extended care.

Pycnogenol as an adjunct in the management of childhood asthma

A randomized, placebo-controlled, double-blind study involving 60 subjects, aged 6-18 years old, was conducted over a period of 3 months to determine the effect of Pycnogenol (a proprietary mixture of water-soluble bioflavonoids extracted from French maritime pine) on mild-to-moderate asthma. After baseline evaluation, subjects were randomized into two groups to receive either Pycnogenol or placebo. Subjects were instructed to record their peak expiratory flow with an Assess Peak Flow Meter each evening. At the same time, symptoms, daily use of rescue inhalers (albuterol), and any changes in oral medications were also recorded. Urine samples were obtained from the subjects at the end of the run-in period, and at 1-, 2-, and 3-month visits. Urinary leukotriene C4/D4/E4 was measured by an enzyme immunoassay. Compared with subjects taking placebo, the group who took Pycnogenol had significantly more improvement in pulmonary functions and asthma symptoms. The Pycnogenol group was able to reduce or discontinue their use of rescue inhalers more often than the placebo group. There was also a significant reduction of urinary leukotrienes in the Pycnogenol group. The results of this study demonstrate the efficacy of Pycnogenol as an adjunct in the management of mild-to-moderate childhood asthma.

Cysteinyl leukotrienes and their receptors: cellular distribution and function in immune and inflammatory responses

The cysteinyl leukotrienes (cys-LTs) are a family of potent bioactive lipids that act through two structurally divergent G protein-coupled receptors, termed the CysLT(1) and CysLT(2) receptors. The cloning and characterization of these two receptors has not only reconciled findings of previous pharmacologic profiling studies of contractile tissues, but also has uncovered their expression on a wide array of circulating and tissue-dwelling leukocytes. With the development of receptor-selective reagents, as well as mice lacking critical biosynthetic enzymes, transporter proteins, and the CysLT(1) receptor, diverse functions of cys-LTs and their receptors in immune and inflammatory responses have been identified. We review cys-LT biosynthesis; the molecular biology and distribution of the CysLT(1) and CysLT(2) receptors; the functions of cys-LTs and their receptors in the recruitment and activation of effector leukocytes and induction of adaptive immunity; and the development of fibrosis and airway remodeling in animal models of lung injury and allergic inflammation.

Evaluation of montelukast in 8 to 14 year old children with mild persistent asthma and compared with inhaled corticosteroids

OBJECTIVES

To determine the clinical effectiveness, tolerability and reliability of montelukast and to compare this drug with inhaled corticosteroids.

METHODS

We performed a randomized, 14-week, 2-period, prospective parallel group study. After a 2-week run-in period, patients received treatment for 12 weeks. Sixty-three clinically stable outpatients aged 8 to 14 years with a history of mild persistent asthma for at least 1 year and a forced expiratory volume in one second (FEV1) greater than 80 % of the predicted value were evaluated.

RESULTS

Montelukast produced improvement in airway obstruction, daily symptom scores, total daily as-needed beta-agonist use, nocturnal awakenings, percentage of days and percentage of patients with asthma exacerbations, and urinary leukotriene E4 levels. These beneficial effects were similar to those produced by inhaled corticosteroids. There were no significant adverse effects requiring treatment discontinuation.

CONCLUSIONS

Montelukast may be a well-tolerated and effective therapeutic option in 8 to 14-year-old patients with mild persistent asthma.

Increase in urinary leukotriene LTE4 levels in acute asthma: correlation with airflow limitation

BACKGROUND

Leukotrienes play a key role in the pathophysiology of chronic asthma. Activation of leukotriene pathways is accompanied by rises in detectable urinary levels of leukotriene E4 (LTE4). The relationship between urinary LTE4 levels and factors associated with acute asthma has not been determined.

METHODS

Adults aged 15-54 years presenting with moderate to severe acute asthma were evaluated at emergency departments in 16 US sites. Forced expiratory volume in 1 second (FEV1) was measured during the first 60 minutes after arrival and at specified times until discharge or admission. Urine samples for measurement of LTE4 levels were obtained either on arrival at the study site and/or before discharge. Patients were seen 2 weeks later for follow up, at which time repeat FEV1 measurements and urine samples for LTE4 were obtained.

RESULTS

One hundred and eighty four patients were evaluated; LTE4 results from both the acute and follow up periods were available for analysis in 146. Urinary LTE4 levels were increased during asthma exacerbations compared with levels obtained 2 weeks later (geometric means 111.7 and 75.6 pg/mg creatinine, respectively, mean percentage change -32.3; 95% confidence interval (CI) for the mean percentage change -39.6 to -24.3, p<0.001). The correlation between improvement in FEV1 and decline in LTE4 over the 2 week interval was significant (p<0.001, r=0.43).

CONCLUSIONS

Activation of leukotriene pathways in acute asthma is correlated with the degree of airflow obstruction, and resolution of the asthma exacerbation is associated with a reduction in leukotriene levels.

High levels of urinary leukotriene E4 excretion in steroid treated patients with severe asthma

Urinary LTE4 reflects the whole body production of the cysteinyl-leukotrienes (LTC4, LTD4 and LTE4) that are established mediators in asthma. The influence of chronic inhaled and oral glucocorticoid treatment on urinary excretion of leukotriene (LT) E4 was investigated in subjects with asthma. Enzyme immunoassay analysis of LTE4 was performed in spot urine samples collected from 40 patients with severe asthma, 25 patients with mild-moderate asthma and 20 non-asthmatic control subjects. Urinary LTE4 was significantly higher in patients with severe asthma (69.7 +/- 5.5) as compared to mild-moderate asthma (45.7 +/- 3.3 with P < 0.0004) and control (42.5 +/- 2.5 with P < 0.0001). Despite chronic systemic treatment with glucocorticoids, chronically severe asthma had presented with higher levels of LTE4 compared to mild moderate asthma and healthy controls. The findings support previous indications that one important component in asthmatic airway inflammation, the cysteinyl-leukotriene pathway remains relatively unopposed by oral glucocorticoids.