Effect of the leukotriene receptor antagonist pranlukast on cellular infiltration in the bronchial mucosa of patients with asthma

Metabolite Dysregulation by Pranlukast in Mycobacterium tuberculosis

Mycobacterium tuberculosis has been infecting millions of people worldwide over the years, causing tuberculosis. Drugs targeting distinct cellular mechanisms including synthesis of the cell wall, lipids, proteins, and nucleic acids in Mtb are currently being used for the treatment of TB. Although extensive research is being carried out at the molecular level in the infected host and pathogen, the identification of suitable drug targets and drugs remains under explored. Pranlukast, an allosteric inhibitor of MtArgJ (Mtb ornithine acetyltransferase) has previously been shown to inhibit the survival and virulence of Mtb. The main objective of this study was to identify the altered metabolic pathways and biological processes associated with the differentially expressed metabolites by PRK in Mtb. Here in this study, metabolomics was carried out using an LC-MS/MS-based approach. Collectively, 50 metabolites were identified to be differentially expressed with a significant p-value through a global metabolomic approach using a high-resolution mass spectrometer. Metabolites downstream of argJ were downregulated in the arginine biosynthetic pathway following pranlukast treatment. Predicted human protein interactors of pranlukast-treated Mtb metabolome were identified in association with autophagy, inflammation, DNA repair, and other immune-related processes. Further metabolites including N-acetylglutamate, argininosuccinate, L-arginine, succinate, ergothioneine, and L-phenylalanine were validated by multiple reaction monitoring, a targeted mass spectrometry-based metabolomic approach. This study facilitates the understanding of pranlukast-mediated metabolic changes in Mtb and holds the potential to identify novel therapeutic approaches using metabolic pathways in Mtb.

Exhaled breath analysis in disease detection

Investigating the use of exhaled breath analysis to diagnose and monitor different diseases has attracted much interest in recent years. This review introduces conventionally used methods and some emerging technologies aimed at breath analysis and their relevance to lung disease, airway inflammation, gastrointestinal disorders, metabolic disorders and kidney diseases. One section correlates breath components and specific diseases, whereas the other discusses some unique ideas, strategies, and devices to analyze exhaled breath for the diagnosis of some common diseases. This review aims to briefly introduce the potential application of exhaled breath analysis for the diagnosis and screening of various diseases, thereby providing a new avenue for the detection of non-invasive diseases.

Leukotriene D4 role in allergic asthma pathogenesis from cellular and therapeutic perspectives

Asthma is a chronic inflammatory and allergic disease that is mainly characterized by reversible airway obstruction and bronchial hyperresponsiveness. The incidence of asthma is increasing with more than 350 million people worldwide are affected. Up to now, there is no therapeutic option for asthma and most of the prescribed drugs aim to ameliorate the symptoms of the disease especially during the acute exacerbations after trigger exposure. Asthma is a heterogonous disease that involves interactions between inflammatory mediators and cellular components within the disease microenvironment including inflammatory and structural cells. Cysteinyl leukotrienes (cys-LTs) are inflammatory lipid mediators that have potent roles in asthma pathogenesis. CysLTs consisting of LTC₄, LTD₄, and LTE₄ are mainly secreted by leukocytes and act through three main G-protein coupled receptors (CysLT₁R, CysLT₂R, and CysLT₃R). LTD₄ is the most potent bronchoconstrictor which gives it the priority to be discussed in detail in this review. LTD₄ binds with high affinity to CysLT₁R and many studies showed that using CysLT₁R antagonists such as montelukast has a beneficial effect for asthmatics especially in corticosteroid refractory cases. Since asthma is a heterogeneous inflammatory disease of many cell types involved in the disease pathogenies and LTD₄ has a special role in inflammation and bronchoconstriction, this review highlights the role of LTD₄ on each cellular component in asthma and the benefits of using CysLT₁R antagonists in ameliorating LTD₄-induced effects.

G Protein-Coupled Receptors in Asthma Therapy: Pharmacology and Drug Action

Asthma is a heterogeneous inflammatory disease of the airways that is associated with airway hyperresponsiveness and airflow limitation. Although asthma was once simply categorized as atopic or nonatopic, emerging analyses over the last few decades have revealed a variety of asthma endotypes that are attributed to numerous pathophysiological mechanisms. The classification of asthma by endotype is primarily routed in different profiles of airway inflammation that contribute to bronchoconstriction. Many asthma therapeutics target G protein-coupled receptors (GPCRs), which either enhance bronchodilation or prevent bronchoconstriction. Short-acting and long-acting β 2-agonists are widely used bronchodilators that signal through the activation of the β 2-adrenergic receptor. Short-acting and long-acting antagonists of muscarinic acetylcholine receptors are used to reduce bronchoconstriction by blocking the action of acetylcholine. Leukotriene antagonists that block the signaling of cysteinyl leukotriene receptor 1 are used as an add-on therapy to reduce bronchoconstriction and inflammation induced by cysteinyl leukotrienes. A number of GPCR-targeting asthma drug candidates are also in different stages of development. Among them, antagonists of prostaglandin D2 receptor 2 have advanced into phase III clinical trials. Others, including antagonists of the adenosine A2B receptor and the histamine H4 receptor, are in early stages of clinical investigation. In the past decade, significant research advancements in pharmacology, cell biology, structural biology, and molecular physiology have greatly deepened our understanding of the therapeutic roles of GPCRs in asthma and drug action on these GPCRs. This review summarizes our current understanding of GPCR signaling and pharmacology in the context of asthma treatment. SIGNIFICANCE STATEMENT: Although current treatment methods for asthma are effective for a majority of asthma patients, there are still a large number of patients with poorly controlled asthma who may experience asthma exacerbations. This review summarizes current asthma treatment methods and our understanding of signaling and pharmacology of G protein-coupled receptors (GPCRs) in asthma therapy, and discusses controversies regarding the use of GPCR drugs and new opportunities in developing GPCR-targeting therapeutics for the treatment of asthma.

Current state and future prospect of the therapeutic strategy targeting cysteinyl leukotriene metabolism in asthma

Asthma is an allergic disorder with dominant type 2 airway inflammation, and its prevalence is increasing worldwide. Inhalation of corticosteroids is the primary treatment for asthma along with add-on drugs, including long-acting β2 agonists and/or cysteinyl leukotriene (cys-LT) receptor antagonists, in patients with poorly controlled asthma. Cys-LTs are composed of leukotriene C4 (LTC₄), LTD₄, and LTE₄, which are enzymatically metabolized from arachidonic acid. These molecules act as inflammatory mediators through different types of high-affinity receptors, namely, CysLT₁, CysLT₂, and CysLT₃ (also named as GPR99). CysLT₁ antagonists possessing anti-inflammatory and bronchodilatory effects can be orally administered to patients with asthma. Recently, molecular biology-based studies have revealed the mechanism of inflammatory responses via other receptors, such as CysLT₂ and CysLT₃, as well as the importance of upstream inflammatory regulators, including type 2 cytokines (e.g., interleukins 4 and 5), in controlling cys-LT metabolism. These findings indicate the therapeutic potential of pharmacological agents targeting cys-LT metabolism-related receptors and enzymes, and antibody drugs neutralizing or antagonizing type 2 cytokines. This review focuses on the current state and future prospect of the therapeutic strategy targeting cys-LT metabolism.

Role of genetic variations of chitinase 3-like 1 in bronchial asthmatic patients

Background

Single nucleotide polymorphisms (SNPs) in chitinase 3-like 1 (CHI3L1) are associated with bronchial severity and pulmonary function. CHI3L1 proteins are involved in both innate and adaptive immune responses; however, to date, the correlation of these SNPs and their age of onset of bronchial asthma has not been demonstrated.

Methods

To address the role of these genetic variations, 390 patients with well-controlled bronchial asthma and living in Japan were recruited, genotyped, and had a pulmonary function test performed on them in this study. To analyze the concentration levels of CHI3L1 protein, bronchial lavage fluids were examined.

Results

Forced expiratory volume in one second, %predicted (%FEV1), was significantly decreased in homozygotes of rs1214194 compared to heterozygotes and wild type. The age of onset of adult bronchial asthma was significantly younger in GG homozygotes of rs4950928 and AA homozygotes of rs1214194 than in the other two genotypes. The concentration of CHI3L1 protein in bronchial lavage fluid increased in both homozygotes of rs4950928 and rs1214194.

Conclusions

Our study demonstrated that the homozygotes of rs4950928 and rs1214194 of CHI3L1 might predict an early onset of bronchial asthma and have the propensity to promote airway remodeling.

Trial registration JMA-IIA00045 remodeling-ICS

Leukotriene D4 induces chemotaxis in human eosinophilc cell line, EoL-1 cells via CysLT1 receptor activation

Numerous reports have shown that cysteinyl leukotrienes (CysLTs) contribute to tissue accumulation of eosinophils in allergic airway inflammation. To date, only a few studies have reported that CysLTs promote chemotactic activity of human eosinophils in vitro. The purpose of this study was to investigate whether CysLTs promote chemotaxis in the human eosinophilic cell line, EoL-1. EoL-1 cells were induced to differentiate into mature eosinophil-like cells via incubation with butyric acid and cytokines (IL-3, IL-5 and GM-CSF). The chemotactic activity of the differentiated EoL-1 cells was assessed using the commercial cell migration assay kit. LTD₄ elicited dose-related chemotactic activity in the differntiated EoL-1 cells in the range of 1–100 nM. A typical bell-shaped dose-response curve was observed with optimal activity at 10 nM. The chemotactic activity elicited by LTD₄ (10 nM) was significantly inhibited by montelukast (control, 345 ± 19.2 × 10³ RFU; LTD₄ 10 nM alone, 511 ± 39.2 × 10³ RFU; LTD₄ 10 nM plus montelukast 100 nM, 387 ± 28.2 × 10³ RFU). LTD₄ induces migration in eosinophilic cells via activation of CysLT1 receptor. The present in vitro model may be useful for elucidation of the mechanism underlying CysLT-induced tissue eosinophilia.

Regulation of Eosinophil and Group 2 Innate Lymphoid Cell Trafficking in Asthma

Asthma is an inflammatory disease usually characterized by increased Type 2 cytokines and by an infiltration of eosinophils to the airways. While the production of Type 2 cytokines has been associated with T_H2 lymphocytes, increasing evidence indicates that group 2 innate lymphoid cells (ILC2) play an important role in the production of the Type 2 cytokines interleukin (IL)-5 and IL-13, which likely amplifies the recruitment of eosinophils from the blood to the airways. In that regard, recent asthma treatments have been focusing on blocking Type 2 cytokines, notably IL-4, IL-5, and IL-13. These treatments mainly result in decreased blood or sputum eosinophil counts as well as decreased asthma symptoms. This supports that therapies blocking eosinophil recruitment and activation are valuable tools in the management of asthma and its severity. Herein, we review the mechanisms involved in eosinophil and ILC2 recruitment to the airways, with an emphasis on eotaxins, other chemokines as well as their receptors. We also discuss the involvement of other chemoattractants, notably the bioactive lipids 5-oxo-eicosatetraenoic acid, prostaglandin D₂, and 2-arachidonoyl-glycerol. Given that eosinophil biology differs between human and mice, we also highlight and discuss their responsiveness toward the different eosinophil chemoattractants.

Impact of the genetic variants of GLCCI1 on clinical features of asthmatic patients

BACKGROUND

Several gene variants are associated with a response to an inhaled corticosteroids (ICSs) treatment in patients with bronchial asthma. A variant of the glucocorticoid-induced transcript 1 (GLCCI1) genes has previously been associated with decreased lung function improvement upon treatment with ICSs in patients with bronchial asthma. Another report has also demonstrated that this genetic biomarker did not influence the change in flow volume in 1 second. However, no studies have considered the treatment content and the GLCCI1 variants. We were able to determine the relationship between the pulmonary function and clinical features and the variant of the GLCCI1 in Japanese asthmatic patients receiving long-term ICS treatment.

MATERIALS AND METHODS

In this study, 405 patients with bronchial asthma, who were receiving ICS and living in Japan, were recruited, genotyped and underwent pulmonary function tests. To identify the GLCCI1 protein expression cells, endobronchial biopsy specimens were examined.

RESULTS

We found that the pulmonary function was not significantly different in the homozygotes compared to the wild types. Also, the homozygotes increased the risk of a sustained step-up of the asthma treatment when compared to the wild type and heterozygotes. GLCCI1-positive cells were localized to the bronchial epithelial cells. The amount of GLCCI1 protein that cultured epithelial cells harboring GLCCI1 variants produced was less than the GLCCI1 wild type in the presence of a corticosteroid.

CONCLUSIONS

A worsening of pulmonary function caused by GLCCI1 variants could be prevented due to recently used medications based on new action mechanisms.

Patient stratification and the unmet need in asthma

Asthma is often described as an inflammatory disease of the lungs and in most patients symptomatic treatment with bronchodilators or inhaled corticosteroids is sufficient to control disease. Unfortunately there are a proportion of patients who fail to achieve control despite treatment with the best current treatment. These severe asthma patients have been considered a homogeneous group of patients that represent the unmet therapeutic need in asthma. Many novel therapies have been tested in unselected asthma patients and the effects have often been disappointing, particularly for the highly specific monoclonal antibody-based drugs such as anti-IL-13 and anti-IL-5. More recently, it has become clear that asthma is a syndrome with many different disease drivers. Clinical trials of anti-IL-13 and anti-IL-5 have focused on biomarker-defined patient groups and these trials have driven the clinical progression of these drugs. Work on asthma phenotyping indicates that there is a group of asthma patients where T helper cell type 2 (Th2) cytokines and inflammation predominate and these type 2 high (T2-high) patients can be defined by biomarkers and response to therapies targeting this type of immunity, including anti-IL-5 and anti-IL-13. However, there is still a subset of T2-low patients that do not respond to these new therapies. This T2-low group will represent the new unmet medical need now that the T2-high-targeting therapies have made it to the market. This review will examine the current thinking on patient stratification in asthma and the identification of the T2-high subset. It will also look at the T2-low patients and examine what may be the drivers of disease in these patients.

Therapeutic implication of genetic variants of IL13 and STAT4 in airway remodelling with bronchial asthma

BACKGROUND

Several gene variants identified in bronchial asthmatic patients are associated with a decrease in pulmonary function. The effects of this intervention on pulmonary function have not been fully researched.

OBJECTIVE

We determined the effects of high-dose inhaled corticosteroids (ICSs) on decreased pulmonary function in asthmatic Japanese patients with variants of IL13 and STAT4 during long-term treatments with low to mild doses of ICS.

METHODS

In this study, 411 patients with bronchial asthma who were receiving ICSs and living in Japan were recruited, were genotyped, and underwent pulmonary function tests and fibreoptic examinations. The effects of 2 years of high-dose ICSs administered to asthmatic patients who were homozygous for IL13 AA of rs20541 or STAT4 TT of rs925847 and who progressed to airway remodelling were investigated.

RESULTS

High-dose ICS treatment increased the pulmonary function of patients homozygous for IL13 AA of rs20541 but not of patients homozygous for STAT4 TT of rs925847. The increased concentrations of the mediators IL23, IL11, GMCSF, hyaluronic acid, IL24, and CCL8 in bronchial lavage fluid (BLF) were diminished after high-dose ICS treatment in patients homozygous for IL13 AA of rs20541.

CONCLUSION AND CLINICAL RELEVANCE

IL13 AA of rs20541 and STAT4 TT of rs925847 are potential genomic biomarkers for predicting lower pulmonary function. The administration of high-dose ICSs to asthmatic patients with genetic variants of IL13 AA may inhibit the advancement of airway remodelling. The genetic variants of STAT4 TT did not respond to high-dose ICSs. Therefore, using medications other than ICSs must be considered even during the initial treatment of bronchial asthma. These genetic variants may aid in the realization of personalized and phenotype-specific therapies for bronchial asthma.

Leukotriene-receptor antagonists versus placebo in the treatment of asthma in adults and adolescents: a systematic review and meta-analysis

BACKGROUND

Leukotriene-receptor antagonists (LTRAs) are recommended as an alternative treatment in patients with mild asthma, but their effect compared with placebo is unclear.

PURPOSE

To determine the benefits and harms of LTRAs as monotherapy or in combination with inhaled corticosteroids compared with placebo in adults and adolescents with asthma.

DATA SOURCES

MEDLINE and the Cochrane Central Register of Controlled Trials from inception through June 2015.

STUDY SELECTION

Peer-reviewed, English-language, randomized, controlled trials in patients with asthma that reported the effect of LTRAs versus placebo on measures of asthma control.

DATA EXTRACTION

Three researchers extracted data on study population, interventions, outcome measures, and adverse events. One researcher assessed risk of bias.

DATA SYNTHESIS

Of the 2008 abstracts that were screened, 50 trials met eligibility criteria. Random-effects meta-analyses of 6 trials of LTRA monotherapy showed that LTRAs reduced the risk for an exacerbation (summary risk ratio [RR], 0.60 [95% CI, 0.44 to 0.81]). In 4 trials of LTRAs as add-on therapy to inhaled corticosteroids, the summary RR for exacerbation was 0.80 (CI, 0.60 to 1.07). Leukotriene-receptor antagonists either as monotherapy or as add-on therapy to inhaled corticosteroids increased FEV1, whereas FEV1 percentage of predicted values was improved only in trials of LTRA monotherapy. Adverse event rates were similar in the intervention and comparator groups.

LIMITATION

Variation in definitions and reporting of outcomes, high risk of bias in some studies, heterogeneity of findings, possible selective outcome reporting bias, and inability to assess the effect of asthma severity on summary estimates.

CONCLUSION

Leukotriene-receptor antagonists as monotherapy improved asthma control compared with placebo, but which patients are most likely to respond to treatment with LTRAs remains unclear.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Assessment of various second-line medications in addition to inhaled corticosteroid in asthma patients: a randomized controlled trial

Many patients with persistent asthma cannot achieve the treatment goal for asthma with a single controller medication. The aim of the present study was to assess lung function and rescue medication use in asthma patients receiving four different categories of drugs in combination with an inhaled corticosteroid. Patients recruited to the study were randomized into four groups to receive budesonide with either formoterol, doxofylline, montelukast or tiotropium for a period of 3 months. Lung function (i.e. forced expiratory volume in 1 s (FEV1 )) and rescue medication use were determined at baseline and on Day 15, 30, 45, 60 and 90 of treatment. A total of 297 patients completed the study. At baseline, no significant differences (P > 0.05) were observed in any of the outcome measures. Significant within-group improvement in FEV1 was observed in all groups. On Day 90, between-group differences showed that the improvement in FEV1 was significantly (P < 0.05) higher for patients receiving budesonide + formoterol, followed by budesonide + montelukast and budesonide + doxofylline, and least for those receiving budesonide + tiotropium. Similarly, within- and between-group comparisons showed significant (P < 0.05) reductions in rescue medication use in all groups. However, the magnitude of the decrease was greater in the budesonide + formoterol group, followed by the budesonide + montelukast, budesonide + doxofylline and budesonide + tiotropium groups. Based on our findings, among the second-line treatment regimens, budesonide with either montelukast or doxofylline was found to be better than budesonide + tiotropium in patients with mild-to-moderate persistent asthma. Further studies with a longer duration are likely to be useful.

Physicochemical and crystal structure analysis of pranlukast pseudo-polymorphs II: Solvate and cocrystal

Pranlukast (PRS) is a leukotriene receptor antagonist for the treatment of bronchial asthma. In this study, six new solvates and one new cocrystal of PRS were characterized by PXRD, TG-DTA, DSC, vapor sorption analysis and the dissolution test. In addition, the crystal structures were determined by single crystal X-ray structure analysis. PRS was found to be a rare example of a promiscuous multicomponent crystal former. The crystal packing patterns of these crystals can be categorized into the sheet-like and channel-like patterns. The ethanol solvate (PRS/ethanol) and urea cocrystal (PRS/urea) were more stable than the others under humid conditions. PRS/ethanol showed an improved dissolution profile compared to PRS HH and PRS/urea.

Physicochemical and crystal structure analysis of pranlukast pseudo-polymorphs I: anhydrates and hydrate

Pranlukast (PRS) is a leukotriene receptor antagonist for the treatment of bronchial asthma. Pranlukast is formulated as a hemihydrate (HH) form in the drug product. Here, we report three new anhydrate forms of PRS (AH, form I-III). These polymorphs and PRS HH were characterized by PXRD, TG-DTA, simultaneous PXRD-DSC and vapor sorption analysis. In addition, the crystal structures of HH and AH-I were determined by single crystal X-ray structure analysis for the first time. HH transformed to AH-I, AH-II and AH-III as the temperature was increased from 25°C to 210°C. At 25°C, AH-I transformed to HH at above 5%RH. HH and AH-I possessed similar crystal packing patterns and molecular structures.

Effect of a cysteinyl leukotriene receptor antagonist on experimental emphysema and asthma combined with emphysema

The incidence of overlapping bronchial asthma and chronic obstructive pulmonary disease has increased in recent years. Cysteinyl leukotrienes (CysLTs) play an important role in asthma, and the type 1 CysLT receptor (CysLT1R) is expressed by many inflammatory cells. We evaluated the effect of montelukast, a CysLT1R antagonist, on mouse models of asthma, porcine pancreatic elastase (PPE)-induced emphysema, and asthma combined with emphysema. Mice were sensitized with ovalbumin (OVA) on Days 0 and 14 and subsequently challenged with OVA on Days 28, 29, and 30. Pulmonary emphysema was induced by intratracheal instillation of PPE on Day 25. Mice were treated subcutaneously with montelukast or vehicle from Day 25 to Day 31. Airway hyperresponsiveness (AHR), static compliance; the number of inflammatory cells, the levels of cytokines, chemokines, LTs, and perforin in the bronchoalveolar lavage fluid, and the quantitative morphometry of lung sections were analyzed on Day 32. Treatment with montelukast significantly attenuated the AHR and eosinophilic airway inflammation in OVA-sensitized and OVA-challenged mice. Administration of montelukast significantly reduced the AHR, static compliance, and neutrophilic airway inflammation, while attenuating emphysematous lung changes, in PPE-treated mice. In PPE-treated mice subjected to allergen sensitization and challenges, montelukast significantly suppressed the AHR, static compliance, and eosinophilic and neutrophilic airway inflammation in addition to the development of experimentally induced emphysema in the lungs. Our data suggest that CysLT1R antagonists may be effective in ameliorating the consequences of PPE-induced lung damage and the changes that follow allergen sensitization and challenges.

Cysteinyl leukotriene-receptor-1 antagonists interfere with PGE2 synthesis by inhibiting mPGES-1 activity

Because of their favourable safety profile and beneficial anti-inflammatory properties, the CysLT1 receptor antagonists (LTRA), montelukast, zafirlukast and pranlukast are approved for the treatment of asthma and are frequently prescribed as add-on therapeutics to reduce the amount of inhaled glucocorticoids and β2-agonists. There is evidence that some of these anti-inflammatory properties might be of a secondary nature and therefore, unrelated to the CysLT1 antagonism. Here, we show that LTRA inhibit PGE2 formation in cytokine-stimulated Hela and A549 carcinoma cells and in lipopolysaccharide (LPS)-stimulated human leukocyte preparations (IC50∼20μM). Neither expression of enzymes involved in PGE2 synthesis nor arachidonic acid release and COX activities were inhibited by the compounds. In contrast, mPGES-1 activity was suppressed at low micromolar levels (IC50 between 2 and 4μM). This suppression was specific for PGE2 synthesis, since PGD2 and PGI2 levels in LPS-stimulated leukocyte preparations were not negatively affected. PGF2α levels were concomitantly inhibited, probably due to its direct synthesis from PGE2. Several major conclusions can be drawn from this study: (A) clinical trials investigating elevated doses of the compounds are helpful to confirm suppression of PGE2 synthesis in vivo; (B) studies investigating the role of CysLTs in cell culture or animal models of inflammation and cancer have to be reassessed carefully, if higher doses of LTRA were applied or serum levels in cell culture assays were low; and (C) LTRA may serve as new scaffolds for the development of potent, selective and well tolerated mPGES-1 inhibitors.

Serine protease inhibitor attenuates ovalbumin induced inflammation in mouse model of allergic airway disease

Background

Serine proteases promote inflammation and tissue remodeling by activating proteinase-activated receptors, urokinase, metalloproteinases and angiotensin. In the present study, 4-(2-Aminoethyl) benzenesulfonyl fluoride (AEBSF) a serine protease inhibitor was evaluated for prophylactic and therapeutic treatment in mouse model of airway allergy.

Methods

BALB/c mice were sensitized by i.p route and challenged with ovalbumin. They were treated i.n. with 2, 10 and 50 µg of AEBSF, one hour before or after challenge and euthanized to collect BALF (bronchoalveolar lavage fluid), blood and lungs. Proteolytic activity, total cell/eosinophil/neutrophil count eosinophil peroxidase activity (EPO), IL-4, IL-5, IL-10, IL-13, cysteinyl leukotrienes and 8-isoprostane were determined in BALF and immunoglobulins were measured in serum. H&E and PAS stained lung sections were examined for cellular infiltration and airway inflammation.

Results

Mice exposed to ovalbumin and treated with PBS showed increased cellular infiltration in lungs and higher serum IgE, IgG1 and IgG2a levels as compared to sham mice. Treatment with AEBSF reduced total cells/eosinophil/neutrophil infiltration. Both prophylactic and therapeutic AEBSF treatment of 10 or 50 µg reduced serum IgE and IgG1 significantly (p<0.05) than control. AEBSF treatment reduced the proteolytic activity in BALF. IL-4 IL-5 and IL-13 levels decreased significantly (p<0.05) after AEBSF treatment while IL-10 levels increased significantly (p<0.05) in BALF. Airway inflammation and goblet cell hyperplasia reduced as demonstrated by lung histopathology, EPO activity and cysteinyl leukotrienes in BALF after treatment. AEBSF treatment also suppressed oxidative stress in terms of 8-isoprostane in BALF. Among the treatment doses, 10 or 50 µg of AEBSF were most effective in reducing the inflammatory parameters.

Conclusions

Prophylactic and therapeutic treatment with serine protease inhibitor attenuates the airway inflammation in mouse model of airway allergy and have potential for adjunct therapy.

Effect of genetic variation of IL-13 on airway remodeling in bronchial asthma

BACKGROUND

IL-13 is a major stimulator of inflammation and tissue remodeling at sites of Th2 inflammation, and common single-nucleotide polymorphisms in IL13 are associated with allergic phenotypes in several ethnically diverse populations. In particular, IL13Q110 is the non-conservative replacement of a positively charged arginine (R) with a neutral glutamine (Q) at position 110 of IL-13, and as we already know, individuals homozygous for glutamine (Q110/Q110) are strongly associated with asthma and IgE. IL13Q110 has been demonstrated to show that increased allergic inflammation depended on the enhanced IL-13-mediated Th2 effector function. Therefore, we investigated whether Q110/Q110 accelerated the decline in pulmonary function and development of airway remodeling of asthmatic patients in the general population.

METHODS

A total 336 asthmatic subjects living in Japan were recruited, genotyped, and had a pulmonary function test performed on them. To analyze airway inflammation and remodeling, bronchial lavage fluid (BLF) and endobronchial biopsy specimens were examined.

RESULTS

Forced expiratory volume in one second (FEV1), %predicted, forced expiratory volume/forced vital capacity ratio, and forced expiratory flow 25-75%, % predicted were significantly decreased in Q110/Q110 compared to R110/R110, and the decline in FEV1 was increased significantly in Q110/Q110 compared to R110/R110. The concentration of IL-13, IL-23, IL-11, GM-CSF, hyaluronic acid, and CCL8 in BLF were increased in Q110/Q110 compared to R110/R110 and the thickness of the subepithelial layer was thicker.

CONCLUSIONS

Our study demonstrates that Q110/Q110 increases, at least in part, allergic inflammation and the propensity for airway remodeling, thus resulting in low lung function.

Cysteinyl leukotriene antagonism inhibits bronchoconstriction in response to hypertonic saline inhalation in asthma

BACKGROUND

In asthma, cysteinyl leukotrienes (CysLTs) play varying roles in the bronchomotor response to multiple provocative stimuli. The contribution of CysLTs on the airway's response to hypertonic saline (HS) inhalation in asthma is unknown. Whether polymorphisms in the leukotriene biosynthetic pathway affect the contribution of CysLTs to this response is also unknown.

METHODS

In a prospective, randomized, double-blind, placebo-controlled cross-over study, mild and moderate asymptomatic asthmatics underwent inhaled 3% HS challenge by doubling the duration of nebulization (0.5, 1, 2, 4, and 8 min) 2 h after one dose of montelukast (a CysLT receptor 1 [CysLTR1] antagonist) or placebo, and after three-week courses. We examined the effect of the leukotriene C(4) synthase (LTC(4)S) polymorphism (A-444C) on the efficacy of montelukast against HS inhalation in an exploratory manner.

RESULTS

In 37 subjects, 2 h after administration of montelukast, the mean provocative dose of HS required to cause a 20% drop in FEV(1) (HS-PD(20)) increased by 59% (9.17 ml after placebo vs. 14.55 ml after montelukast, p=0.0154). Three weeks of cysLTR1 antagonism increased the HS-PD(20) by 84% (10.97 vs. 20.21 ml, p=0.0002). Three weeks of CysLTR1 antagonism appeared to produce greater effects on blocking bronchial hyper-responsiveness (2 h vs. three-week HS-PD(20) values 14.55 vs. 20.21 ml respectively, p=0.0898). We did not observe an effect of the LTC(4)S polymorphism on the response to CysLTR1 antagonism in this cohort.

CONCLUSIONS

A significant proportion of HS-induced bronchoconstriction is mediated by release of leukotrienes as evidenced by substantial acute inhibition with a CysLTR1 antagonist. There was a trend toward greater inhibition of bronchial responsiveness with three weeks of therapy as opposed to acute CysLTR1 antagonism. Clinicaltrials.gov registration number NCT00116324.

Hemopoietic progenitors: the role of eosinophil/basophil progenitors in allergic airway inflammation

Progenitor cells play important roles in the physiology and homeostasis of the overall hemopoietic system. The majority of hemopoietic activity takes place in the bone marrow, under the influence of resident marrow stromal cells, accessory cells, and/or their products. This constitutes the complex network of the hemopoietic inductive microenvironment, which is crucial for providing signals necessary for the maintenance of populations of progenitors at varying stages of lineage commitment. Accumulation of eosinophils and basophils in tissues is characteristic of allergic inflammation. A large body of evidence now exists which confirms that these tissue inflammatory events are coincident with relevant changes in progenitors; it has thus been hypothesized that the observed changes in mature cell numbers occur directly or indirectly as a result of differentiation of lineage-committed eosinophil/basophil, and perhaps other, progenitor cells. Differentiation and maturation of hemopoietic cells have traditionally been thought to be restricted to the bone marrow microenvironment. More recently, evidence has accumulated to suggest that some hemopoietic cells present in allergic tissue may be recruited from the bone marrow, traffic through the peripheral circulation and into tissues to participate in the ongoing inflammatory process at these distal sites. The clinical administration of monotherapy with topical corticosteroids, oral cysteinyl leukotriene antagonists and cytokine antagonists such as antibodies to interleukin-5, suggest that suppression of hemopoietic contributions to allergic inflammation may be necessary for full control of allergic inflammation and disease manifestations. In addition to progenitors being targets of therapy, they may well determine how and whether allergic inflammation is generated in early life, thus serving as biomarkers of disease.

Effects of KP-496, a novel dual antagonist for cysteinyl leukotriene receptor 1 and thromboxane A2 receptor, on Sephadex-induced airway inflammation in rats

Bronchial asthma is characterized by chronic airway inflammation. Eosinophils are involved in airway inflammation and play crucial roles in asthma. There is accumulating evidence to suggest contributions of cysteinyl leukotrienes (cysLTs) and thromboxane (TX) A(2) to the recruitment of eosinophils into lung in asthmatics. KP-496 is a novel dual antagonist for CysLT receptor type 1 and TXA(2) receptors. The aim of this study was to evaluate the anti-inflammatory effects of KP-496 on Sephadex-induced airway inflammation. Sephadex suspension was intratracheally injected into rats. Amounts of regulated on activation, normal T cell expressed and secreted (RANTES) and eotaxin, and numbers of infiltrating cells in bronchoalveolar lavage fluid were measured 24 and 48 h after Sephadex injection, respectively. KP-496 (30, 100 microg/head) was intratracheally administered to rats 1 h before and 7 h after Sephadex injection. KP-496 and prednisolone (10 mg/kg, per os) exhibited significant inhibitory effects on infiltration of total cells and eosinophils into lung. Production of RANTES was significantly inhibited by KP-496 and prednisolone. Production of eotaxin was significantly inhibited by prednisolone. KP-496 also inhibited the production of eotaxin, though this effect was not significant. These results demonstrate that KP-496 exhibited the anti-inflammatory effects by inhibiting infiltration of inflammatory cells and productions of RANTES and eotaxin.

Montelukast and bronchial inflammation in asthma: a randomised, double-blind placebo-controlled trial

BACKGROUND

Examination of bronchoalveolar lavage, induced sputum, and peripheral blood indicate that cysteinyl leukotriene receptor blockers decrease inflammatory cells in asthma but these do not examine airway tissue per se.

OBJECTIVES

Our objective was to determine the effect of montelukast, a leukotriene receptor antagonist, on airway tissue inflammatory cells by direct bronchoscopic examination of the bronchial mucosa.

METHODS

Adult subjects with mild asthma (pre-bronchodilator FEV(1)> or =70% predicted; PC(20) of < or =4 mg/mL) were given 10mg/day oral montelukast (N=38) or placebo (N=37) for 6 weeks. Bronchial mucosal eosinophils and mast cells were identified and counted.

RESULTS

Change from baseline in numbers of biopsy EG2+ ("activated") eosinophils was the primary endpoint; numbers of total (chromotrope 2R+) eosinophils and (tryptase+) mast cells were secondary. Unexpectedly, there were many patients with zero EG2+ eosinophils at baseline. There was a within-group decrease in EG2+ cells, from 13.54 cells/mm (at baseline) to 0.79 cells/mm at 6 weeks in the montelukast group (LS mean change; 95% confidence interval=-13.59 [-25.45, -1.74]cells/mm; P<0.05), a change not observed in the placebo group (-1.17 [-13.26, 10.91]cells/mm; NS). The zero-inflated Poisson statistical model demonstrated that montelukast significantly reduced post-treatment EG2+ cells by 80% compared with placebo (95% CI [70.6-86.8%]; P<0.0001). The data for total eosinophils showed similar changes. The reduction in mast cell numbers was 12% (95% CI [7.9, 16.0]; P<0.0001).

CONCLUSION

Direct examination of airway tissue confirms that montelukast decreases the number of eosinophils and mast cells in asthma.

The efficacy of montelukast and airway mast cell profiles in patients with cough variant asthma

BACKGROUND

Cough variant asthma (CVA) is characterized by chronic cough without apparent wheezing; its pathophysiology is considered to be similar to that of classic asthma.

OBJECTIVE

The clinical effects of montelukast, a cysteinyl-leukotriene receptor antagonist, on cough variant asthma were assessed, and the activation profile of airway mast cells was examined.

METHODS

Montelukast (10 mg/day) was given orally to 36 CVA patients (25 women and 11 men; median age, 37.5 years). Before treatment, the patients' bronchial mucosa underwent a biopsy with a fiberoptic bronchoscope. The biopsy specimens were double stained with anti-CD63 antibody and anti-human tryptase antibody.

RESULTS

After 2 weeks of montelukast treatment, cough symptoms improved in 22 patients (the effective group) but did not improve in 14 patients (the ineffective group); in the ineffective group, the symptoms disappeared 2 weeks after they were switched to fluticasone propionate (400 microg/day) inhalation therapy. In the effective group, the time interval from the onset of symptoms to the initiation of treatment was significantly shorter than in the ineffective group. The bronchial mucosa biopsy specimens showed that the proportion of CD63-positive cells in tryptase-positive mast cells was significantly higher in the effective group than in the ineffective group; although the total numbers of mast cells were not different between the two groups.

CONCLUSION

There is a subgroup of CVA patients in whom leukotrienes are closely involved in the pathogenesis of their chronic cough; activation of airway mast cells may be an essential feature in these patients.

Cysteinyl-leukotrienes and their receptors in asthma and other inflammatory diseases: critical update and emerging trends

Cysteinyl-leukotrienes (cysteinyl-LTs), that is, LTC4, LTD4, and LTE4, trigger contractile and inflammatory responses through the specific interaction with G protein-coupled receptors (GPCRs) belonging to the purine receptor cluster of the rhodopsin family, and identified as CysLT receptors (CysLTRs). Cysteinyl-LTs have a clear role in pathophysiological conditions such as asthma and allergic rhinitis (AR), and have been implicated in other inflammatory conditions including cardiovascular diseases, cancer, atopic dermatitis, and urticaria. Molecular cloning of human CysLT1R and CysLT2R subtypes has confirmed most of the previous pharmacological characterization and identified distinct expression patterns only partially overlapping. Interestingly, recent data provide evidence for the immunomodulation of CysLTR expression, the existence of additional receptor subtypes, and of an intracellular pool of CysLTRs that may have roles different from those of plasma membrane receptors. Furthermore, genetic variants have been identified for the CysLTRs that may interact to confer risk for atopy. Finally, a crosstalk between the cysteinyl-LT and the purine systems is being delineated. This review will summarize and attempt to integrate recent data derived from studies on the molecular pharmacology and pharmacogenetics of CysLTRs, and will consider the therapeutic opportunities arising from the new roles suggested for cysteinyl-LTs and their receptors.

Kimura Disease

We have encountered 11 cases of Kimura disease, comprising 10 males and 1 female. The ages at presentation ranged from 16 to 48 years, with a mean of 31.5 years. The sites of the subcutaneous masses were bilateral posterior auricular regions in two cases, frontal region in two cases, temporal region in two cases, head region in one case, parotid region in two cases, parotid and temporal regions in one case, and left earlobe in one case. The interval from onset to surgery ranged from 1 to 10 years, with a mean of 4.7 years. For diagnostic imaging, a combination of magnetic resonance imaging (MRI) and ultrasonography had a high diagnostic value. MRI depicted abnormalities at sites in contact with bone, such as posterior auricular regions, and sites with abundant soft tissue, such as parotid and cheek regions. Diffuse atrophy of subcutaneous fat was observed at the sites of the masses. On ultrasonography, the interior of lymph nodes was homogeneous and hyperechoic, whereas the periphery was hyperechoic, and blood vessels entering lymph nodes were clearly depicted. Surgery was performed in all cases. Postoperative adjuvant radiotherapy was conducted in one patient and radiotherapy and steroid therapy in one other patient. There were two relapses, and both were excised by repeated surgery. Surgical excision of the subcutaneous mass in Kimura disease has the advantages that the treatment period is short and precise histopathologic diagnosis can be obtained.

The effects of montelukast on tissue inflammatory and bone marrow responses in murine experimental allergic rhinitis: interaction with interleukin-5 deficiency

The cysteinyl leukotrienes (cysLTs) are potent lipid mediators in allergic disease, acting through the receptors, cysLT1R and cysLTR2, and are produced by eosinophils derived from eosinophil/basophil (Eo/B) bone marrow (BM) progenitors. We have demonstrated the suppressive effects of either interleukin-5 (IL-5) deficiency or montelukast on eosinophil recruitment in murine allergic rhinitis, but neither of them fully abrogated the symptoms caused by residual inflammation and cytokine redundancy in eliciting BM Eo/B responses. We hypothesized that IL-5 deficiency and montelukast act synergistically to suppress tissue inflammatory and BM responses. Our objective was to investigate the effects of the cysLT1R antagonist, montelukast, on in vivo tissue inflammatory and BM responses in murine experimental allergic rhinitis with or without IL-5 deficiency. Three groups of age-matched BALB/c mice with or without IL-5 deficiency were tested: controls (ovalbumin sensitization and challenge, placebo treatment) and two montelukast-treated groups (2.5 mg/kg or 5 mg/kg). Nasal symptoms, BM and nasal mucosal eosinophils, basophils, and BM Eo/B colony-forming units (CFU) were evaluated. Montelukast decreased nasal symptoms in a dose-dependent manner, and significantly decreased the number of eosinophils in both BM and nasal tissue in IL-5-replete mice compared to controls. In IL-5-deficient mice, in which eosinophilia was absent, montelukast significantly decreased both nasal symptoms and basophils in BM and nasal mucosal tissue, and lowered IL-5-responsive Eo/B-CFU ex vivo, compared to controls. The addition of cysLT1R blockade to IL-5 deficiency more fully attenuates symptoms and upper airway inflammation than either factor alone, providing evidence of systemic, BM mechanisms in allergic rhinitis.

The inhibitory effect of the leukotriene receptor antagonist on leukotriene D4-induced MUC2/5AC gene expression and mucin secretion in human airway epithelial cells

OBJECTIVES

Mucin gene expression and mucin production are markedly increased in inflammatory airway disorders such as asthma, chronic bronchitis and rhinosinusitis. Cytokines, lipopolysaccharides and other inflammatory mediators such as prostaglandin and leukotriene are related to the secretion and production of mucin. However, the relationship of leukotrienes with mucin genes expression is not clear. The aim of this study is to evaluate MUC2/5AC gene expression and mucin secretion by the leukotriene receptor in human airway epithelial cells.

METHODS

The effect of leukotriene D(4) and the leukotriene receptor antagonist, pranlukast hydrate (ONO-1078) on the regulation of MUC2/5AC gene expression and mucin secretion were observed in human airway NCI-H292 epithelial cells. The mRNA levels of MUC2/5AC and the amount of mucin were determined by reverse transcription-polymerase chain reaction (RT-PCR) and immunoassay.

RESULTS

Leukotriene D(4) upregulated MUC2/5AC gene expression and mucin secretion in a dose dependent pattern. Pranlukast hydrate (ONO-1078, 100 microM) downregulated the leukotriene D(4)-induced MUC2/5AC gene expression and mucin secretion.

CONCLUSION

These results suggest that the leukotriene receptor system is one of the mechanisms related to MUC2/5AC gene expression and mucin secretion in the human airway epithelium.

Allergic rhinitis and asthma: inflammation in a one-airway condition

Background

Allergic rhinitis and asthma are conditions of airway inflammation that often coexist.

Discussion

In susceptible individuals, exposure of the nose and lungs to allergen elicits early phase and late phase responses. Contact with antigen by mast cells results in their degranulation, the release of selected mediators, and the subsequent recruitment of other inflammatory cell phenotypes. Additional proinflammatory mediators are released, including histamine, prostaglandins, cysteinyl leukotrienes, proteases, and a variety of cytokines, chemokines, and growth factors. Nasal biopsies in allergic rhinitis demonstrate accumulations of mast cells, eosinophils, and basophils in the epithelium and accumulations of eosinophils in the deeper subepithelium (that is, lamina propria). Examination of bronchial tissue, even in mild asthma, shows lymphocytic inflammation enriched by eosinophils. In severe asthma, the predominant pattern of inflammation changes, with increases in the numbers of neutrophils and, in many, an extension of the changes to involve smaller airways (that is, bronchioli). Structural alterations (that is, remodeling) of bronchi in mild asthma include epithelial fragility and thickening of its reticular basement membrane. With increasing severity of asthma there may be increases in airway smooth muscle mass, vascularity, interstitial collagen, and mucus-secreting glands. Remodeling in the nose is less extensive than that of the lower airways, but the epithelial reticular basement membrane may be slightly but significantly thickened.

Conclusion

Inflammation is a key feature of both allergic rhinitis and asthma. There are therefore potential benefits for application of anti-inflammatory strategies that target both these anatomic sites.

Montelukast treatment attenuates the increase in myofibroblasts following low-dose allergen challenge

RATIONALE

Airway remodeling is believed to be important in the pathophysiology of asthma, and myofibroblasts are increased in the airways of asthmatic individuals 24 h after allergen challenge. Leukotriene receptor antagonists exert antiinflammatory activity in asthma, but it is unknown whether they influence indices of airway remodeling. In the present study, we evaluated the effect of montelukast on airway myofibroblasts following low-dose allergen challenge (LDAC).

METHODS

Stable subjects with mild asthma were included in a two-center, randomized, parallel-group study. A 2-week run-in period was followed by LDAC and endobronchial biopsy. Subjects were then randomized to receive either montelukast, 10 mg/d, or placebo (n = 10 in each group) for 8 weeks in a double-blind manner; at the end of the treatment period, subjects underwent a second LDAC and endobronchial biopsy. The effect of treatment on myofibroblasts, fibroblasts, and inflammatory cells was examined using electron microscopy techniques.

RESULTS

Treatment with montelukast showed no significant difference by comparison with placebo but did show a significant within-group treatment-related decrease in airway wall myofibroblasts not seen in the placebo group. In addition, the montelukast-treated group also showed a significant within-group reduction in lymphomononuclear cells and increased neutrophils.

CONCLUSIONS

The results suggest that montelukast has an inhibitory effect on airway structural cells that play a key role in airway remodeling in allergic airway inflammation, and that montelukast may be a useful therapy to attenuate airway remodeling in asthma.

Oral montelukast treatment of preschool-aged children with acute asthma

BACKGROUND

Increased amounts of cysteinyl leukotrienes have been demonstrated in urine samples from asthmatic patients, particularly during exacerbations of asthma. Although the use of leukotriene receptor antagonists has been recommended in the treatment of chronic asthma, no guidelines are available regarding their use in the treatment of acute asthma.

OBJECTIVE

To investigate the safety and effectiveness of a 4-mg tablet of oral montelukast in addition to short-acting beta2-agonist bronchodilator as the initial treatment in mild to moderate asthma exacerbations in children between 2 and 5 years old.

METHODS

Fifty-one patients who were experiencing mild to moderate asthma exacerbation were included in a randomized, double-blind, placebo-controlled, parallel-group study. Each patient received either a 4-mg tablet of montelukast or placebo in addition to inhaled salbutamol and were followed up for 4 hours. The pulmonary index score, respiratory rate, and pulse were determined at baseline and throughout 4 hours after administration.

RESULTS

Compared with placebo, the pulmonary index scores and respiratory rates were significantly lower in the montelukast group starting at 90 minutes (P = .01). This difference persisted at 120, 180, and 240 minutes of the study (P = .008, P = .02, and P = .048, respectively). At the end of the first hour of treatment, oral steroid need was 20.8% and 38.5% in patients randomized to the montelukast and placebo groups, respectively (P = .22). Hospitalization rates were not different between the 2 treatment groups.

CONCLUSION

A single 4-mg tablet of montelukast had the potential to provide additive clinical benefit in mild to moderate acute asthma in preschool-aged children when administered concomitantly with short-acting beta2-agonist bronchodilators as the initial treatment.

Differential effects of salbutamol and montelukast on eosinophil adhesion and superoxide anion generation

BACKGROUND

Beta2-agonists, a representative class of bronchodilators used for asthma, have been shown to modulate some functions of eosinophils, including cell adhesion. Similarly, a leukotriene receptor antagonist (LTRA) may be beneficial in controlling inflammation in asthma, as cysteinyl leukotrienes (cysLTs) can cause accumulation or activation of eosinophils. Recent evidence suggests that the addition of an LTRA, but not a long-acting beta2-agonist, to inhaled corticosteroid additionally reduces the number of eosinophils in sputum and blood from patients with asthma. The present study examined whether a beta2-agonist and an LTRA differentially modify eosinophil adhesion and activation induced by cysLTs and other activators.

METHODS

Eosinophils were isolated from blood of healthy donors and then incubated in the presence or absence of salbutamol (albuterol) or montelukast. Eosinophils were then exposed to leukotriene D4 (LTD4) or another activator, and the generation of superoxide anion (O2-) was evaluated by cytochrome C reduction assay. Eosinophil adhesion was examined by an eosinophil peroxidase assay.

RESULTS

Montelukast, but not salbutamol (both at 1 microM), inhibited LTD4-induced (100 nM) eosinophil adhesion to recombinant human intercellular adhesion molecule 1. Both drugs similarly and partially inhibited the 100 pM interleukin-5-induced adhesive response of eosinophils to recombinant human intercellular adhesion molecule 1. Montelukast, but not salbutamol, blocked LTD4-induced eosinophil O2- generation of eosinophils. Finally, neither salbutamol nor montelukast modified phorbol myristate acetate (1 ng/ml)-induced O2- generation from eosinophils.

CONCLUSION

These results confirm that LTD4 directly induces activation of eosinophils via the cysLT1 receptor. Furthermore, the results suggest that a beta2-agonist has no effect on eosinophil adhesion and activation induced by cysLTs. These results explain the differential effects of an LTRA and a beta2-agonist in the treatment of eosinophilic inflammation in asthma.

Therapeutic approach to vascular remodelling in asthma

Bronchial asthma can be characterized by some significant changes in airway blood vessels, which may contribute to airway remodelling. Despite the clinical and functional consequences of bronchial microvascular remodelling in asthma, up to now, little data have been published on the therapeutic approach to this phenomenon. Corticosteroids are the only anti-asthma drugs that act positively on the three aspects of bronchial vascular remodelling: angiogenesis, dilatation and permeability. Modest positive effects of treatments with beta2-agonists and leukotrienes receptor antagonists on bronchial microcirculatory changes have been reported. In the future, agents that specifically inhibit angiogenesis could represent a novel approach for positively acting on bronchial microvascular changes in chronic inflammatory airway diseases, such as chronic bronchitis and asthma.

Localization and upregulation of cysteinyl leukotriene-1 receptor in asthmatic bronchial mucosa

We have tested the hypothesis that the CysLT(1) receptor is expressed by a variety of bronchial mucosal immune cells and that the numbers of these cells increase in asthma, when stable and in exacerbations. We have applied in situ hybridization and immunohistochemistry to endobronchial biopsy tissue to identify and count inflammatory cells expressing CysLT(1) receptor mRNA and protein, respectively, and used double immunohistochemistry to identify the specific cell immunophenotypes expressing the receptor. Double-labeling demonstrated that bronchial mucosal eosinophils, neutrophils, mast cells, macrophages, B-lymphocytes, and plasma cells, but not T-lymphocytes, expressed the CysLT(1) receptor. The numbers of CysLT(1) receptor mRNA and protein positive inflammatory cells in nonsmoking, nonatopic control subjects without asthma were 13 and 16 mm(-2), respectively (median values; n = 15), and were significantly greater in stable asthma (50 and 43 mm(-2), respectively; n = 17; P < 0.001). Compared with stable asthma, there were further significant increases in subjects hospitalized for a severe exacerbation of their asthma (mRNA: median = 113 and protein: 156 mm(-2); n = 15; P < 0.002). For the combined data of both asthma subgroups, there were strong positive correlations between the increased numbers of CD45+ leukocytes and the greater numbers of cells expressing CysLT(1) receptor (mRNA: r = 0.60, P < 0.001; protein: r = 0.73, P < 0.0001). In conclusion, a variety of immunohistologically distinct inflammatory cells express the CysLT(1) receptor in the bronchial mucosa and both these and the total number of leukocytes increase in mild stable disease and increase further when there is a severe exacerbation of asthma.

An update of the leukotriene modulators for the treatment of asthma

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

Inflammatory basis of exercise-induced bronchoconstriction

RATIONALE

Exercise-induced bronchoconstriction (EIB) is a highly prevalent condition with unclear pathogenesis. Two competing theories of the pathogenesis of EIB differ regarding the inflammatory basis of this condition.

OBJECTIVES

Our goals were to establish whether epithelial cell and mast cell activation with release of inflammatory mediators occurs during EIB and how histamine and cysteinyl leukotriene antagonists alter the airway events occurring during EIB.

METHODS

Induced sputum was used to measure mast cell mediators and eicosanoids at baseline and 30 minutes after exercise challenge in 25 individuals with asthma with EIB. In a randomized, double-blind crossover study, the cysteinyl leukotriene antagonist montelukast and antihistamine loratadine or two matched placebos were administered for two doses before exercise challenge.

MAIN RESULTS

The percentage of columnar epithelial cells in induced sputum at baseline was associated with the severity of EIB. After exercise challenge, histamine, tryptase, and cysteinyl leukotrienes significantly increased and prostaglandin E(2) and thromboxane B(2) significantly decreased in the airways, and there was an increase in columnar epithelial cells in the airways. The concentration of columnar epithelial cells was associated with the levels of histamine and cysteinyl leukotrienes in the airways. Treatment with montelukast and loratadine inhibited the release of cysteinyl leukotrienes and histamine into the airways, but did not inhibit the release of columnar epithelial cells into the airways.

CONCLUSIONS

These data indicate that epithelial cells, mast cell mediators, and eicosanoids are released into the airways during EIB, supporting an inflammatory basis for EIB.

Effect of the cysteinyl leukotriene antagonist pranlukast on transendothelial migration of eosinophils

BACKGROUND

Evidence shows that leukotriene receptor antagonist (LTRA) can cause a partial reduction of eosinophils in the asthmatic airway. Although cysteinyl leukotrienes (CysLTs) can regulate the development of eosinophilic inflammation, LTRA might modulate the eosinophilic response to other inflammatory molecules involved in allergic inflammation. Montelukast is an LTRA that inhibits eosinophil transendothelial migration (TEM) in response to platelet-activating factor (PAF). The present study evaluates whether pranlukast (an LTRA) modifies eosinophil TEM in response to chemoattractants including PAF and C-C chemokines.

METHODS

Eosinophils isolated from the blood of healthy individuals were incubated with or without pranlukast. We then evaluated eosinophil transmigration across human umbilical vein endothelial cells in response to LTD(4), eotaxin, RANTES and PAF.

RESULTS

Pranlukast did not modify the spontaneous transmigration of eosinophils (n = 5). As reported, eosinophil TEM was significantly augmented by 0.1 microM LTD(4) and this enhancement was blocked by 1 microM pranlukast (p < 0.001; n = 6). On the other hand, pranlukast did not modify eosinophil transmigration in response to eotaxin, RANTES, or PAF (p > 0.1; n = 5).

CONCLUSION

The inhibitory effect of pranlukast on eosinophil transmigration is highly specific for the CysLT1-dependent pathway.

Impact of inhaled corticosteroids and leukotriene receptor antagonists on airway remodeling

Asthma is a chronic inflammatory disease of the airways that is characterized by the presence of inflammatory cells and remodeling, a term used to define complex morphological changes involving all the structures of the bronchial wall (e.g., goblet cell hyperplasia of the epithelium, thickening of reticular basement membrane, increases of airway smooth muscle[ASM], and blood vessels). An important factor in the pathophysiology of asthma is the recognition that airway inflammation and airway remodeling are linked, as they are in other chronic inflammatory diseases. First-line therapy of persistent asthma involves the use of inhaled corticosteroids to control the underlying inflammation of the airways. Because remodeling of the airway wall is thought to be a result of chronic inflammation within the bronchial wall, it follows that because steroids reduce or reverse inflammation, they may also prevent or modulate remodeling. It has been revealed that steroids improve the subepithelial fibrosis and also significantly reduce airway vascularity. The cysteinyl leukotrienes receptor antagonists may also be helpful regarding the targeting of the inflammation and remodeling in asthma. However,long-term studies were needed to appreciate the prevention and treatment of remodeling by drug therapies.

Effect of montelukast compared with inhaled fluticasone on airway inflammation

BACKGROUND

Inhaled corticosteroids are currently regarded as the gold standard in anti-inflammatory therapy, however, leukotriene receptor antagonists have been ascribed anti-inflammatory properties.

OBJECTIVE

We directly compared the anti-inflammatory effects of inhaled fluticasone propionate (FP, 100 microg Diskus, twice daily) and oral montelukast (MON 10 mg, nocte) in bronchial biopsies of patients with asthma in a double-blind, double-dummy, parallel-group design.

METHODS

Bronchial biopsies, serum and urine samples were collected from 36 atopic asthmatics before and after 8 weeks of treatment. Activated T cells (CD25+), eosinophils (MBP+) and mast cells (tryptase+) were analysed by immunohistochemistry. Serum eosinophil cationic protein (ECP) and IL-5 were analysed by radio and enzyme immunoassay (EIA), respectively. Urinary 9alpha-11beta-PGF2 and leukotriene E4 (LTE4) were measured by EIA.

RESULTS

A comparison of changes from baseline [FP/MON ratio (95% confidence interval)] of activated T cells was not different when subjects were treated with FP compared to treatment with MON [1.00 (0.18-4.86); P=0.924]. Following treatment, mast cells in the FP group were significantly lower than in the group treated with MON [0.39 (0.16-0.97); P=0.041]. There was no difference in the number of eosinophils in the lamina propria following either treatment [0.54 (0.05-2.57); P=0.263]. However, treatment with FP resulted in a significantly greater decrease in serum ECP, compared to treatment with MON [0.37 (0.25-0.71); P=0.002].

CONCLUSIONS

FP appears to be superior to MON as an anti-inflammatory therapy in mild asthmatics.

Leukotriene D4 and eosinophil transendothelial migration, superoxide generation, and degranulation via beta2 integrin

BACKGROUND

Evidence indicates that cysteinyl leukotriene (cysLT) 1 receptor antagonists possess anti-inflammatory properties in asthmatic patients in vivo. Although the exact mechanisms of these actions remain unknown, cysLTs regulate the locomotion and functions of eosinophils. We previously reported that leukotriene D4 augments the expression of eosinophil beta2 integrin and the adhesion of eosinophils to rh intercellular adhesion molecule 1 via beta2 integrin.

OBJECTIVE

To examine whether leukotriene D4 modifies the transendothelial migration (TEM) and effector functions of eosinophils.

METHODS

We evaluated the effects of leukotriene D4 on (1) eosinophil TEM across human umbilical vein endothelial cells, (2) superoxide anion (O2-) generation, and (3) eosinophil-derived neurotoxin release in eosinophils isolated from the blood of healthy individuals.

RESULTS

Leukotriene D4 (0.1-1 microM) significantly induced eosinophil TEM, O2- generation, and eosinophil-derived neurotoxin release. Pranlukast, a cysLT1 receptor antagonist, significantly inhibited all of these parameters, although the inhibitory effect on O2- generation was partial. All of these responses were significantly inhibited by anti-beta2 integrin but not by anti-alpha4 integrin antibodies.

CONCLUSIONS

Leukotriene D4 directly up-regulates the TEM and effector functions of eosinophils mainly via the cysLT1 receptor and beta2 integrin. These effects of leukotriene D4 probably contribute to the manifestation of eosinophil inflammation in asthmatic airways.

Pharmacological profile of CR3465, a new leukotriene CysLT1 receptor antagonist with broad anti-inflammatory activity

CR3465 (L-Tyrosine, N-[(2-quinolinyl)carbonyl]-O-(7-fluoro-2-quinolinylmethyl) sodium salt) is a potent antagonist of [3H]leukotriene D4 ([3H]LTD4) binding to guinea pig lung preparations, its Ki (4.7+/-0.7 nM) being comparable with that of montelukast (5.6+/-0.6 nM). In tracheal strips from standard or ovalbumin-sensitized guinea pigs, CR3465 caused parallel rightward shifts in the concentration-response curves obtained with either LTD4 or antigen (pA(2), 8.74 and 8.15). Intravenous (i.v.) administration of the agent both antagonized (ED50, 9.9+/-1.9 microg/kg) and reverted LTD4 -induced bronchoconstriction of anesthetized guinea pigs. CR3465 reduced inflammatory infiltrates in the bronchoalveolar lavage fluid after antigen challenge of sensitized animals, and proved also active in inhibiting phosphodiesterase 3 (PDE3) and phosphodiesterase 4 (PDE4) activities exhibited by human platelets and neutrophils (IC50, 2.01+/-0.07 and 4.7+/-0.5 microM). In line with properties shown by phosphodiesterase inhibitors, CR3465 reduced the contractile response of guinea pig airways to histamine and decreased N-formyl-Met-Leu-Phe (fMLP)-induced degranulation of human neutrophils (IC50, 13.8 microM). Oral administration (20 mg/kg) of the compound in rats produced a significant (37%) ex vivo inhibition of tumor necrosis factor-alpha (TNF-alpha) release from lipopolysaccharide-stimulated whole blood. Pharmacokinetic data in the rat demonstrated approximately 100% bioavailability of the agent. We conclude that CR3465 represents a potent leukotriene CysLT1 receptor antagonist with enhanced effects, being also useful for counteracting spasmogenic and inflammatory stimuli other than those elicited by cysteinyl-leukotrienes (Cys-LTs).

Current and emerging nonsteroidal anti-inflammatory therapies targeting specific mechanisms in asthma and allergy

Today inhaled corticosteroids (ICS) are regarded as the first-line controller anti-inflammatory treatment in the management of asthma. However, there is an increasing awareness of the risk of long-term adverse effects of ICS and that asthma is not only an organ-specific disease but also a systemic and small airway disease. This thinking has called for systemic treatment alternatives to treat asthma targeting more disease-specific mechanisms without influencing normal physiologic functions. Blocking of disease-specific mediators is a mechanism utilized by anti-leukotrienes and anti-immunoglobulin E treatment, each proven to be effective in both asthma and allergic rhinitis.Different cytokine-modifying strategies have been tested in clinical trials with variable results, some disappointing and some encouraging. Anti-interleukin (IL)-5 monoclonal antibody treatment effectively reduces the number of eosinophils locally in the airways and in peripheral blood in asthmatic patients. Unfortunately, this marked effect on eosinophils was not associated with an improvement in bronchial hyperresponsiveness and/or symptoms. Clinical trials with a recombinant soluble IL-4 receptor have been somewhat more successful at improving asthma control and allowing reduction of ICS therapy in asthma. Treatment with recombinant IL-12 had an effect on bronchial hyperresponsiveness and eosinophilic response, but was associated with unacceptable adverse effects. Other interesting cytokine-modulating treatments include those targeting IL-9, IL-10, IL-12 and IL-13.Immune-modulating treatment with bacterial antigens represents another strategy, originating from the hypothesis that some bacterial infections guide the immune system towards a T helper (Th) type 1 immune response. Mycobacterium vaccae, Bacille Calmette-Guerin (BCG) and immunostimulatory DNA sequences have all been tested in clinical trials, with encouraging results. Future asthma and allergy treatment will probably include not only one but also two or more disease-modifying agents administered to the same patient.

Comparison study between the mechanisms of allergic asthma amelioration by a cysteinyl-leukotriene type 1 receptor antagonist montelukast and methylprednisolone

We investigated the effects of cysteinyl-leukotriene (cysLT) type 1 receptor antagonist montelukast (MK) and compared them with those of methylprednisolone (MP) in an allergic asthma model. Rats sensitized to ovalbumin (OVA) received repeated intratracheal exposure to OVA for up to 3 consecutive days. Pretreatment with MK or MP before OVA exposure inhibited late airway response (LAR) and reduced cellular infiltration into the bronchial submucosa after the triple OVA. The amount of N-acetyl-leukotriene E(4) in the bile was significantly reduced by pretreatment with MK or MP, suggesting that both drugs reduced the production of cysLTs in the lungs. In the in vitro study, when the fragments of lungs that had been repeatedly pretreated with MK or MP and exposed to OVA were removed and incubated with OVA, the coaddition of either drug significantly reduced cysLT production. In contrast, the cysLT production following the addition of OVA to the lung fragments that had not received in vivo pretreatment with either drug was inhibited by MK but not by MP. These results indicate that MK and MP inhibit LAR by suppressing the infiltration of inflammatory cells into the bronchial submucosa, thereby inhibiting the production of cysLTs in the lungs, and that MK but not MP may inhibit cysLT production directly. The different effects on cysLT production between the two drugs may provide a rationale for the use of combination therapy with cysLT(1) receptor antagonists and steroids for the treatment of asthma.

Platelet-activating factor receptor develops airway hyperresponsiveness independently of airway inflammation in a murine asthma model

Lipid mediators play an important role in modulating inflammatory responses. Platelet-activating factor (PAF) is a potent proinflammatory phospholipid with eosinophil chemotactic activity in vitro and in vivo. We show in this study that mice deficient in PAF receptor exhibited significantly reduced airway hyperresponsiveness to muscarinic cholinergic stimulation in an asthma model. However, PAF receptor-deficient mice developed an eosinophilic inflammatory response at a comparable level to that of wild-type mice. These results indicate an important role for PAF receptor, downstream of the eosinophilic inflammatory cascade, in regulating airway responsiveness after sensitization and aeroallergen challenge.

Comparison of glucocorticoid and cysteinyl leukotriene receptor antagonist treatments in an experimental model of chronic airway inflammation in guinea-pigs

BACKGROUND

Leukotriene receptor antagonists have been demonstrated in several studies to possess bronchodilating and anti-inflammatory properties in asthma. However, there are few experimental studies performed to compare the effects of anti-leukotrienes and glucocorticoids, most used anti-inflammatory agents in asthma. In the present study, we evaluated the effects of treatment with dexamethasone or montelukast on eosinophil and mononuclear cell recruitment in an experimental model of allergen-induced chronic airway inflammation in guinea-pigs (GP).

METHODS

GP were submitted to increasing concentrations of aerosols of ovalbumin (OVA) twice a week for 4 weeks. After 2 weeks, animals were treated daily with dexamethasone, montelukast or saline solution. After this period, GP were anaesthetized, tracheostomized, mechanically ventilated and challenged with OVA aerosol.

RESULTS

Maximal changes of respiratory system resistance and elastance induced by OVA challenge were attenuated by dexamethasone (P<0.001), but not by montelukast treatment. Neither dexamethasone nor montelukast significantly influenced bronchial oedema formation. Dexamethasone but not montelukast induced a decrease in mononuclear cells in airways (P<0.001). Eosinophil infiltration in the bronchial wall was reduced by both dexamethasone and montelukast (P<0.005). Only dexamethasone treatment reduced the levels of exhaled nitric oxide (P<0.025).

CONCLUSION

Although leukotriene receptor antagonist treatment reduces eosinophil accumulation induced by multiple antigen challenges, glucocorticoid treatment attenuates both eosinophil and mononuclear cell infiltration.

Effects of inhaled corticosteroids, leukotriene receptor antagonists, or both, plus long-acting beta2-agonists on asthma pathophysiology: a review of the evidence

Chronic inflammation and smooth muscle dysfunction are consistent features of asthma, and are responsible for disease progression and airway remodelling. The development of chronic airway inflammation depends upon the recruitment and activation of inflammatory cells and the subsequent release of inflammatory mediators, including cytokines. Cellular and histological evaluation of drugs with anti-inflammatory activity, such as inhaled corticosteroids (ICSs), is achieved by analysing samples of lung tissue or biological fluids, obtained by techniques such as bronchial biopsy, bronchoalveolar lavage and sputum induction. These provide valuable information on the inflammatory processes occurring in the lung, although not all are equal in value. The beneficial effects of ICSs in asthma treatment are a consequence of their potent and broad anti-inflammatory properties. Furthermore, there have been promising results indicating that ICSs can reverse some of the structural changes that contribute to airway remodelling. Long-acting beta2-agonists (LABAs) added to ICSs provide greater clinical efficacy than ICSs alone, suggesting the possibility of complementary activity on the pathophysiological mechanisms of asthma: inflammation and smooth muscle dysfunction. Leukotrienes play a part in the pathogenesis of asthma. Leukotriene receptor antagonists (LTRAs) directly inhibit bronchoconstriction and may have some anti-inflammatory effects, although the extent to which inhibiting one set of inflammatory mediators attenuates the inflammatory response is questionable. In concert with their effect on a broad variety of inflammatory mediators and cells, treatment with ICSs (including ICSs and LABAs) results in superior control of the pathophysiology of asthma and superior clinical efficacy as assessed by the greater improvements in pulmonary function and overall control of asthma compared with LTRAs.

Recent advances in the management of asthma using leukotriene modifiers

Asthma is a chronic inflammatory disease of the airways that affects approximately 100 million people worldwide. In order to reduce symptoms, improve pulmonary function, and decrease morbidity, current treatment guidelines emphasize the importance of controlling the underlying inflammation in patients with asthma. Leukotrienes are leukocyte-generated lipid mediators that promote airway inflammation. Recognition of the importance of leukotrienes in the pathogenesis of asthma has led to the development of leukotriene modifiers, the first new class of drugs for the treatment of asthma to become available in 25 years. Controlled clinical trials with the four currently used leukotriene modifiers (montelukast, zafirlukast, and zileuton in the US and pranlukast in Japan) have established their efficacy in improving pulmonary function, reducing symptoms, decreasing night-time awakenings, and decreasing the need for rescue medications. They exert anti-inflammatory effects that attenuate cellular infiltration and bronchial hyperresponsiveness and complement the anti-inflammatory properties of inhaled corticosteroids. In patients with moderate and severe asthma, they permit tapering of the corticosteroid dose. In patients with exercise-induced asthma, leukotriene modifiers limit the decline in and quicken the recovery of pulmonary functions without the tolerance issues seen with chronic long-acting beta(2)-adrenoceptor agonist use. In patients with aspirin (acetylsalicylic acid)-induced asthma, they improve pulmonary function and shift the dose response curve to the right, reducing the patient's response to aspirin. In patients with seasonal allergic rhinitis, with or without concomitant asthma, they improve nasal, eye, and throat symptoms as well as quality of life. Leukotriene modifiers are generally safe and well tolerated with adverse effect profiles similar to that of placebo. The one safety issue raised with leukotriene modifiers, Churg-Strauss Syndrome, appears to be the unmasking of an already present syndrome that is manifested when the leukotriene modifiers permit corticosteroid doses to be reduced. Although current treatment guidelines recommend their use in patients with mild persistent asthma, these guidelines were developed just as leukotriene modifiers were coming to the market, before much of the clinical efficacy data were published. Because asthma is a heterogeneous disease, the different asthma phenotypes respond differently to therapies; consequently asthma therapy needs to be individualized. Leukotriene modifiers increase the therapeutic options for patients with asthma and, based on recent data, it is expected that future guidelines will describe expanded uses for these agents in clinical circumstances where these drugs are effective.