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Airway hyperresponsiveness (AHR) is a key clinical feature of asthma. The presence of AHR in people with asthma provides the substrate for bronchoconstriction in response to numerous diverse stimuli, contributing to airflow limitation and symptoms including breathlessness, wheeze, and chest tightness. Dysfunctional airway smooth muscle significantly contributes to AHR and is displayed as increased sensitivity to direct pharmacologic bronchoconstrictor stimuli, such as inhaled histamine and methacholine (direct AHR), or to endogenous mediators released by activated airway cells such as mast cells (indirect AHR). Research in in vivo human models has shown that the disrupted airway epithelium plays an important role in driving inflammation that mediates indirect AHR in asthma through the release of cytokines such as thymic stromal lymphopoietin and IL-33. These cytokines upregulate type 2 cytokines promoting airway eosinophilia and induce the release of bronchoconstrictor mediators from mast cells such as histamine, prostaglandin D 2 , and cysteinyl leukotrienes. While bronchoconstriction is largely due to airway smooth muscle contraction, airway structural changes known as remodeling, likely mediated in part by epithelial-derived mediators, also lead to airflow obstruction and may enhance AHR. In this review, we outline the current knowledge of the role of the airway epithelium in AHR in asthma and its implications on the wider disease. Increased understanding of airway epithelial biology may contribute to better treatment options, particularly in precision medicine., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Patients with type-2 (T2) cytokine-low severe asthma often have persistent symptoms despite suppression of T2 inflammation with corticosteroids., Objectives: We sought to analyze whole blood transcriptome from 738 samples in T2-biomarker-high/-low patients with severe asthma to relate transcriptomic signatures to T2 biomarkers and asthma symptom scores., Methods: Bulk RNA-seq data were generated for blood samples (baseline, week 24, week 48) from 301 participants recruited to a randomized clinical trial of corticosteroid optimization in severe asthma. Unsupervised clustering, differential gene expression analysis, and pathway analysis were performed. Patients were grouped by T2-biomarker status and symptoms. Associations between clinical characteristics and differentially expressed genes (DEGs) associated with biomarker and symptom levels were investigated., Results: Unsupervised clustering identified 2 clusters; cluster 2 patients were blood eosinophil-low/symptom-high and more likely to be receiving oral corticosteroids (OCSs). Differential gene expression analysis of these clusters, with and without stratification for OCSs, identified 2960 and 4162 DEGs, respectively. Six hundred twenty-seven of 2960 genes remained after adjusting for OCSs by subtracting OCS signature genes. Pathway analysis identified dolichyl-diphosphooligosaccharide biosynthesis and assembly of RNA polymerase I complex as significantly enriched pathways. No stable DEGs were associated with high symptoms in T2-biomarker-low patients, but numerous associated with elevated T2 biomarkers, including 15 that were upregulated at all time points irrespective of symptom level., Conclusions: OCSs have a considerable effect on whole blood transcriptome. Differential gene expression analysis demonstrates a clear T2-biomarker transcriptomic signature, but no signature was found in association with T2-biomarker-low patients, including those with a high symptom burden., (Crown Copyright © 2023. Published by Elsevier Inc. All rights reserved.)

Background: Asthma is a complex chronic disease underpinned by pathological changes within the airway wall. How variations in structural airway pathology and cellular inflammation contribute to the expression and severity of asthma are poorly understood., Objectives: Therefore we evaluated pathological heterogeneity using topological data analysis (TDA) with the aim of visualizing disease clusters and microclusters., Methods: A discovery population of 202 adult patients (142 asthmatic patients and 60 healthy subjects) and an external replication population (59 patients with severe asthma) were evaluated. Pathology and gene expression were examined in bronchial biopsy samples. TDA was applied by using pathological variables alone to create pathology-driven visual networks., Results: In the discovery cohort TDA identified 4 groups/networks with multiple microclusters/regions of interest that were masked by group-level statistics. Specifically, TDA group 1 consisted of a high proportion of healthy subjects, with a microcluster representing a topological continuum connecting healthy subjects to patients with mild-to-moderate asthma. Three additional TDA groups with moderate-to-severe asthma (Airway Smooth Muscle High , Reticular Basement Membrane High , and Remodeling Low groups) were identified and contained numerous microclusters with varying pathological and clinical features. Mutually exclusive T H 2 and T H 17 tissue gene expression signatures were identified in all pathological groups. Discovery and external replication applied to the severe asthma subgroup identified only highly similar "pathological data shapes" through analyses of persistent homology., Conclusions: We have identified and replicated novel pathological phenotypes of asthma using TDA. Our methodology is applicable to other complex chronic diseases., (Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.)

Background: IgE sensitization to Aspergillus fumigatus and a positive sputum fungal culture result are common in patients with refractory asthma. It is not clear whether these patients would benefit from antifungal treatment., Objectives: We sought to determine whether a 3-month course of voriconazole improved asthma-related outcomes in patients with asthma who are IgE sensitized to A fumigatus., Methods: Asthmatic patients who were IgE sensitized to A fumigatus with a history of at least 2 severe exacerbations in the previous 12 months were treated for 3 months with 200 mg of voriconazole twice daily, followed by observation for 9 months, in a double-blind, placebo-controlled, randomized design. Primary outcomes were improvement in quality of life at the end of the treatment period and a reduction in the number of severe exacerbations over the 12 months of the study., Results: Sixty-five patients were randomized. Fifty-nine patients started treatment (32 receiving voriconazole and 27 receiving placebo) and were included in an intention-to-treat analysis. Fifty-six patients took the full 3 months of medication. Between the voriconazole and placebo groups, there were no significant differences in the number of severe exacerbations (1.16 vs 1.41 per patient per year, respectively; mean difference, 0.25; 95% CI, 0.19-0.31), quality of life (change in Asthma Quality of Life Questionnaire score, 0.68 vs 0.88; mean difference between groups, 0.2; 95% CI, -0.05 to -0.11), or any of our secondary outcome measures., Conclusion: We were unable to show a beneficial effect of 3 months of treatment with voriconazole in patients with moderate-to-severe asthma who were IgE sensitized to A fumigatus on either the rate of severe exacerbations, quality of life, or other markers of asthma control., (Copyright © 2013 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: The airway epithelium is exposed to a range of physical and chemical irritants in the environment that are known to trigger asthma. Transient receptor potential (TRP) cation channels play a central role in sensory responses to noxious physical and chemical stimuli. Recent genetic evidence suggests an involvement of transient receptor potential vanilloid 1 (TRPV1), one member of the vanilloid subfamily of TRP channels, in the pathophysiology of asthma. The functional expression of TRPV1 on airway epithelium has yet to be elucidated., Objective: In this study we examined the molecular, functional, and immunohistochemical expression of TRPV1 in asthmatic and healthy airways., Methods: Bronchial biopsy specimens and bronchial brushings were obtained from healthy volunteers (n = 18), patients with mild-to-moderate asthma (n = 24), and patients with refractory asthma (n = 22). Cultured primary bronchial epithelial cells from patients with mild asthma (n = 4), nonasthmatic coughers (n = 4), and healthy subjects (n = 4) were studied to investigate the functional role of TRPV1., Results: Quantitative immunohistochemistry revealed significantly more TRPV1 expression in asthmatic patients compared with healthy subjects, with the greatest expression in patients with refractory asthma (P = .001). PCR and Western blotting analysis confirmed gene and protein expression of TRPV1 in cultured primary bronchial epithelial cells. Patch-clamp electrophysiology directly confirmed functional TRPV1 expression in all 3 groups. In functional assays the TRPV1 agonist capsaicin induced dose-dependent IL-8 release, which could be blocked by the antagonist capsazepine. Reduction of external pH from 7.4 to 6.4 activated a capsazepine-sensitive outwardly rectifying membrane current., Conclusions: Functional TRPV1 channels are present in the human airway epithelium and overexpressed in the airways of patients with refractory asthma. These channels might represent a novel therapeutic target for the treatment of uncontrolled asthma., (Copyright © 2013 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: Eosinophilic airway inflammation is heterogeneous in asthmatic patients. We recently described a distinct subtype of asthma defined by the expression of genes inducible by T(H)2 cytokines in bronchial epithelium. This gene signature, which includes periostin, is present in approximately half of asthmatic patients and correlates with eosinophilic airway inflammation. However, identification of this subtype depends on invasive airway sampling, and hence noninvasive biomarkers of this phenotype are desirable., Objective: We sought to identify systemic biomarkers of eosinophilic airway inflammation in asthmatic patients., Methods: We measured fraction of exhaled nitric oxide (Feno), peripheral blood eosinophil, periostin, YKL-40, and IgE levels and compared these biomarkers with airway eosinophilia in asthmatic patients., Results: We collected sputum, performed bronchoscopy, and matched peripheral blood samples from 67 asthmatic patients who remained symptomatic despite maximal inhaled corticosteroid treatment (mean FEV(1), 60% of predicted value; mean Asthma Control Questionnaire [ACQ] score, 2.7). Serum periostin levels are significantly increased in asthmatic patients with evidence of eosinophilic airway inflammation relative to those with minimal eosinophilic airway inflammation. A logistic regression model, including sex, age, body mass index, IgE levels, blood eosinophil numbers, Feno levels, and serum periostin levels, in 59 patients with severe asthma showed that, of these indices, the serum periostin level was the single best predictor of airway eosinophilia (P = .007)., Conclusion: Periostin is a systemic biomarker of airway eosinophilia in asthmatic patients and has potential utility in patient selection for emerging asthma therapeutics targeting T(H)2 inflammation., (Copyright © 2012 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: Influx of extracellular Ca(2+) into human lung mast cells (HLMCs) is essential for the FcεRI-dependent release of preformed granule-derived mediators and newly synthesized autacoids and cytokines. However, the identity of the ion channels underlying this Ca(2+) influx is unknown. The recently discovered members of the CRACM/Orai ion channel family that carries the Ca(2+) release-activated Ca(2+) current are candidates., Objectives: To investigate the expression and function of CRACM channels in HLMCs., Methods: CRACM mRNA, protein, and functional expression were examined in purified HLMCs and isolated human bronchus., Results: CRACM1, -2, and -3 mRNA transcripts and CRACM1 and -2 proteins were detectable in HLMCs. A CRACM-like current was detected following FcεRI-dependent HLMC activation and also in HLMCs dialyzed with 30 μM inositol triphosphate. The Ca(2+)-selective current obtained under both conditions was blocked by 10 μM La(3+) and Gd(3+), known blockers of CRACM channels, and 2 distinct and specific CRACM-channel blockers-GSK-7975A and Synta-66. Both blockers reduced FcεRI-dependent Ca(2+) influx, and 3 μM GSK-7975A and Synta-66 reduced the release of histamine, leukotriene C(4), and cytokines (IL-5/-8/-13 and TNFα) by up to 50%. Synta-66 also inhibited allergen-dependent bronchial smooth muscle contraction in ex vivo tissue., Conclusions: The presence of CRACM channels, a CRACM-like current, and functional inhibition of HLMC Ca(2+) influx, mediator release, and allergen-induced bronchial smooth muscle contraction by CRACM-channel blockers supports a role for CRACM channels in FcεRI-dependent HLMC secretion. CRACM channels are therefore a potential therapeutic target in the treatment of asthma and related allergic diseases., (Copyright © 2012 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: Thymic stromal lymphopoietin (TSLP) is a cytokine implicated in the pathophysiology of asthma through 2 distinct pathways: a TSLP-OX40 ligand (OX40L)-T cell axis and a TSLP-mast cell axis. Whether these pathways are active in human asthma is unknown., Objective: We sought to investigate whether mucosal TSLP protein expression relates to asthma severity and distinct immunologic pathways., Methods: In healthy subjects and patients with mild-to-severe asthma, we immunostained bronchial biopsy specimens for TSLP, OX40, OX40L, T(H)2 cytokines, and inflammatory cell markers. We examined gene expression using RNA microarrays and quantitative RT-PCR., Results: There was considerable heterogeneity in the levels of TSLP, IL-13, and IL-4 immunostaining across the cohort of asthmatic patients examined. Overall, TSLP protein expression was significantly increased in airway epithelium and lamina propria of asthmatic patients, particularly in patients with severe asthma. TSLP immunostaining in both compartments correlated with the severity of airflow obstruction. The majority of leukocytes expressing IL-13 were possibly nuocytes. Accounting for intersubject variability, the 55% of asthmatic patients with increased IL-13 immunostaining in the lamina propria also had increased IL-4 and TSLP expression. This was further substantiated by significant correlations between TSLP gene expression, a T(H)2 gene expression signature, and eosinophilic inflammation in bronchial biopsy specimens. Immunostaining for OX40, OX40L, and CD83 was sparse, with no difference between asthmatic patients and healthy subjects., Conclusion: TSLP expression is increased in a subset of patients with severe asthma in spite of high-dose inhaled or oral corticosteroid therapy. Targeting TSLP might only be efficacious in the subset of asthma characterized by increased TSLP expression and T(H)2 inflammation., (Copyright © 2011 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: Fibrocytes are bone marrow-derived CD34(+) collagen I-positive cells present in peripheral blood that develop α-smooth muscle actin expression and contractile activity in tissue culture. They are implicated in the pathogenesis of tissue remodeling and fibrosis in both patients with asthma and those with idiopathic pulmonary fibrosis. Targeting fibrocyte migration might therefore offer a new approach for the treatment of these diseases. Ion channels play key roles in cell function, but the ion-channel repertoire of human fibrocytes is unknown., Objective: We sought to examine whether human fibrocytes express the K(Ca)3.1 K(+) channel and to determine its role in cell differentiation, survival, and migration., Methods: Fibrocytes were cultured from the peripheral blood of healthy subjects and patients with asthma. Whole-cell patch-clamp electrophysiology was used for the measurement of ion currents, whereas mRNA and protein were examined to confirm channel expression. Fibrocyte migration and proliferation assays were performed in the presence of K(Ca)3.1 ion-channel blockers., Results: Human fibrocytes cultured from the peripheral blood of both healthy control subjects and asthmatic patients expressed robust K(Ca)3.1 ion currents together with K(Ca)3.1 mRNA and protein. Two specific and distinct K(Ca)3.1 blockers (TRAM-34 and ICA-17043) markedly inhibited fibrocyte migration in transwell migration assays. Channel blockers had no effect on fibrocyte growth, apoptosis, or differentiation in cell culture., Conclusions: The K(+) channel K(Ca)3.1 plays a key role in human fibrocyte migration. Currently available K(Ca)3.1-channel blockers might therefore attenuate tissue fibrosis and remodeling in patients with diseases such as idiopathic pulmonary fibrosis and asthma through the inhibition of fibrocyte recruitment., (Copyright © 2011 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: In human subjects platelet-activating factor (PAF) concentrations are markedly increased in the plasma after anaphylactic reactions, and these correlate strongly with the severity of the response. The mechanism for the systemic spread of mast cell (MC) activation in anaphylaxis is often assumed to relate to the hematogenous spread of allergen, but this is implausible, and amplification mechanisms need to be considered., Objective: We have investigated the ability of PAF to induce human MC degranulation using skin, lung, and peripheral blood (PB)-derived cultured MCs and the signaling pathways activated in PB-derived MCs in response to PAF., Methods: The expression of PAF receptor was investigated by means of RT-PCR and Western blot analysis. Cell-signaling pathways in PB-derived MCs in response to PAF were investigated by analyzing the effect of various inhibitors and the silencing of phospholipase C (PLC) mRNA on PAF-mediated histamine release., Results: We show for the first time that PAF induces histamine release from human lung MCs and PB-derived MCs but not skin MCs. Activation of PAF receptor-coupled G(alphai) leads to degranulation through PLCgamma1 and PLCbeta2 activation in human MCs. PAF-induced degranulation was rapid, being maximal at 5 seconds, and was partially dependent on extracellular Ca(2+)., Conclusion: Our findings provide a mechanism whereby PAF mediates an amplification loop for MC activation in the generation of anaphylaxis., (Copyright 2010 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: Mast cells contribute to the pathophysiology of asthma with the sustained release of both preformed and newly generated mediators in response to allergens and other diverse stimuli. Stem cell factor (SCF) is the key human mast cell growth factor, but also primes mast cells for mediator release. SCF expression is markedly increased in asthmatic airways. Short-acting beta(2)-adrenoceptor drugs such as albuterol inhibit human lung mast cell (HLMC) degranulation in vitro in the absence of SCF, but their effect in the presence of SCF is not known., Objective: The aim of this study was to elucidate the effects of albuterol on HLMC function in the presence of SCF., Methods: Mediator release and K(Ca)3.1 ion channel activity were analyzed in purified HLMC. Intracellular signalling and beta(2)-adrenoceptor phosphorylation and internalization were analyzed in the HMC-1 human mast cell line., Results: beta(2)-Adrenoceptor agonist-dependent inhibition of K(Ca)3.1 ion channels and HLMC mediator release was markedly attenuated in the presence of SCF. Remarkably, albuterol actually potentiated IgE-induced histamine release in a dose-dependent manner when both SCF and IgE were present. These effects were related to the SCF-dependent phosphorylation of Tyr350 on the beta(2)-adrenoceptor with immediate uncoupling of the receptor followed by receptor internalization., Conclusion: The potentially beneficial effects of beta(2)-adrenoceptor agonists in asthmatic airways may be blunted as a result of the high concentrations of SCF present., (Copyright 2010 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.)

Background: Airway smooth muscle (ASM) hyperplasia is a hallmark of asthma that is associated with disease severity and persistent airflow obstruction., Objectives: We sought to investigate whether fibrocytes, a population of peripheral blood mesenchymal progenitors, are recruited to the ASM compartment in asthma., Methods: We assessed the number of fibrocytes in bronchial biopsy specimens and peripheral blood from subjects with mild-to-severe refractory asthma versus healthy control subjects. In vitro we investigated potential mechanisms controlling fibrocyte migration toward the ASM bundle., Results: Fifty-one subjects with asthma and 33 control subjects were studied. In bronchial biopsy specimens, the number of fibrocytes was increased in the lamina propria of subjects with severe refractory asthma (median [interquartile range] number, 1.9/mm(2) [1.7/mm(2)]) versus healthy control subjects (median [interquartile range] number, 0/mm(2) [0.3/mm(2)], P < .0001) and in the ASM bundle of subjects with asthma of all severities (subjects with severe asthma, median [interquartile range] number, 3.8/mm(2) [9.4/mm(2)]; subjects with mild-to-moderate asthma, median [interquartile range] number, 1.1/mm(2) [2.4/mm(2)]); healthy control subjects, (median [interquartile range] number, 0/mm(2) [0/mm(2)]); P = .0004). In the peripheral blood the fibrocyte number was also increased in subjects with severe refractory asthma (median [interquartile range] number, 1.4 x 10(4)/mL [2.6 x 10(4)/mL]) versus healthy control subjects (median [interquartile range] number, 0.4 x 10(4)/mL [1.0 x 10(4)/mL], P = .002). We identified that in vitro ASM promotes fibrocyte chemotaxis and chemokinesis (distance of migration after 4.5 hours, 31 microm [2.9 microm] vs 17 microm [2.4 microm], P = .0001), which was in part mediated by platelet-derived growth factor (mean inhibition by neutralizing antibody, 16% [95% CI, 2% to 32%], P = .03) but not by activation of chemokine receptors., Conclusion: This study provides the first evidence that fibrocytes are present in the ASM compartment in asthma and that ASM can augment fibrocyte migration. The importance of fibrocytes in the development of ASM hyperplasia and airway dysfunction in asthma remains to be determined.

Background: Nonasthmatic eosinophilic bronchitis (EB) has emerged as a useful tool to study the structural and inflammatory mechanisms of airway hyperresponsiveness (AHR) in asthma. We have previously shown that vascular remodeling and reticular basement membrane (RBM) thickening are present in EB. However, it is not known whether other features of structural remodeling including increased airway smooth muscle (ASM) mass, matrix deposition, and glandular hyperplasia are also present in EB., Objectives: We sought to determine whether structural remodeling occurs in EB and is associated with AHR and airflow limitation., Methods: Forty-two patients with asthma, 21 patients with EB, and 19 healthy volunteers were recruited. ASM area, RBM thickness, collagen 3 deposition, glandular area, mast cells, and granulocytes were assessed in bronchial biopsy samples., Results: Nonasthmatic eosinophilic bronchitis and asthma were associated with a significant increase in ASM mass and RBM thickness compared with healthy subjects. In contrast, we did not observe any significant differences in collagen 3 deposition in the lamina propria and ASM or the % area of glands in the lamina propria. Univariate analysis demonstrated that mast cell numbers in the ASM were the only feature of remodeling associated with AHR (beta = -0.51; P = .004). Stepwise linear regression revealed that a combination of mast cell numbers in the ASM (beta = -0.43) and disease duration (beta = -0.25; model-adjusted R(2) = 0.26; P = .027) best modeled AHR., Conclusion: Mast cell localization to the ASM bundle, but not structural remodeling of the airway wall, is associated with AHR in asthma.

Background: The importance of IL-13 in the asthma paradigm is supported by increased expression in human subjects, particularly in patients with mild-to-moderate asthma. However, the role of IL-13 in severe asthma needs to be further defined., Objective: We sought to assess IL-13 expression in sputum and bronchial biopsy specimens from subjects with mild-to-severe asthma., Methods: Sputum IL-13 concentrations were measured in 32 control subjects, 34 subjects with mild asthma, 21 subjects with moderate asthma, and 26 subjects with severe asthma. Enumeration of mast cells, eosinophils, and IL-13+ cells in the bronchial submucosa and airway smooth muscle (ASM) bundle was performed in 7 control subjects, 14 subjects with mild asthma, 7 subjects with moderate asthma, and 7 subjects with severe asthma., Results: The proportion of subjects with measurable IL-13 in the sputum was increased in the mild asthma group (15/34) and severe asthma group (10/26) compared with that seen in the control group (4/32; P = .004). IL-13+ cells were increased within the submucosa in all asthma severity groups compared with control subjects (P = .006). The number of IL-13+ cells were increased within the ASM bundle in the severe asthma group compared with that seen in the other groups (P < .05). Asthma control questionnaire scores positively correlated with sputum IL-13 concentrations (R(s) = 0.35, P = .04) and mast cells in the ASM bundle (R(s) = 0.7, P = .007). IL-13+ cells within the submucosa and ASM correlated with sputum eosinophilia (R(s) = 0.4, P < or = .05)., Conclusions: IL-13 overexpression in sputum and bronchial biopsy specimens is a feature of severe asthma.

Rationale: Increased vascularity and expression of vascular endothelial growth factor (VEGF) are recognized features of the asthmatic airway. The association of vascular remodeling with airway hyperresponsiveness (AHR) is unclear., Objective: To assess vascular remodeling and sputum VEGF concentration in subjects with asthma, subjects with nonasthmatic eosinophilic bronchitis (EB), and healthy controls., Methods: In cohort 1, 19 patients with asthma (Global Initiative for Asthma [GINA] 1-2, n = 9; GINA 3-5, n = 10), 10 patients with EB, and 11 healthy matched controls were recruited. Expression of the endothelial marker EN4 was assessed in bronchial biopsy samples. Vessels were counted using the validated mean Chalkley count by a blind observer. For cohort 2, a second independent cohort of 31 patients with asthma (GINA 1-2, n = 11; GINA 3-5, n = 20), 14 patients with EB, and 15 matched controls was recruited. Induced sputum supernatant VEGF was measured by ELISA., Results: The mean chalkley count was significantly greater in GINA 3-5 asthma (5.2 [0.4]) and EB (4.8 [0.3]) compared with controls (3.5 [0.5]) and demonstrated a significant inverse correlation with the postbronchodilator FEV(1)% predicted in patients with asthma (R(2) = 0.28; P = .02). Sputum VEGF concentration was also increased in GINA 3-5 asthma (2365 [1361-4110] pg/g) and EB (4699 [2818-7834] pg/g) compared with controls (1094 [676-1774] pg/g) and was inversely related to postbronchodilator FEV(1)% predicted in asthma (R(2) = 0.2; P = .01)., Conclusion: Vascular remodeling is a feature of asthma, and EB and is inversely associated with the postbronchodilator FEV(1) in asthma, suggesting that vascular remodeling is associated with airflow obstruction but not AHR., Clinical Implications: Vascular remodeling is dissociated from AHR in asthma and associated with airflow limitation.

There is compelling evidence that human mast cells contribute to the pathophysiology of asthma. Mast cells, but not T cells or eosinophils, localize within the bronchial smooth muscle bundles in patients with asthma but not in normal subjects or those with eosinophilic bronchitis, a factor likely to be important in determining the asthmatic phenotype. The mechanism of mast cell recruitment by asthmatic airway smooth muscle involves the CXCL10/CXCR3 axis, and several mast cell mediators have profound effects on airway smooth muscle function. The autacoids are established as potent bronchoconstrictors, whereas the proteases tryptase and chymase are being demonstrated to have a range of actions consistent with key roles in inflammation, tissue remodeling, and bronchial hyperresponsiveness. IL-4 and IL-13, known mast cell products, also induce bronchial hyperresponsiveness in the mouse independent of the inflammatory response and enhance the magnitude of agonist-induced intracellular Ca2+ responses in cultured human airway smooth muscle. There are therefore many pathways by which the close approximation of mast cells with airway smooth muscle cells might lead to disordered airway smooth muscle function. Mast cells also infiltrate the airway mucous glands in subjects with asthma, showing features of degranulation, and a positive correlation with the degree of mucus obstructing the airway lumen, suggesting that mast cells play an important role in regulating mucous gland secretion. The development of potent and specific inhibitors of mast cell secretion, which remain active when administered long-term to asthmatic airways, should offer a novel approach to the treatment of asthma.

Background: Nonasthmatic eosinophilic bronchitis is a condition characterized by the presence of eosinophilic airway inflammation in the absence of airflow obstruction or airway hyperresponsiveness. In asthma, the T H 2-type cytokine IL-13 has been implicated in the development of airway inflammation and hyperresponsiveness. Whether the expression of IL-13 is different between these 2 conditions is unknown., Objective: We sought to investigate whether IL-13 expression is increased in asthma compared with eosinophilic bronchitis., Methods: Sputum samples from subjects with mild asthma (n = 30) and eosinophilic bronchitis (n = 15) and normal controls (n = 16) were dialyzed, and IL-13 concentration was measured by ELISA. In a subgroup of these patients, IL-13 protein expression in bronchial biopsies was assessed by immunohistochemistry., Results: The concentration of sputum IL-13 was higher in patients with mild asthma than in normal controls ( P = .03) and in patients with eosinophilic bronchitis ( P = .03). The median (interquartile range) number of IL-13 + cells/mm 2 submucosa was significantly higher in asthma 4 (8) than eosinophilic bronchitis 1.7 (1.9) and normal controls 0.5 (1.1; P = .004). Eighty-three percent of the cells expressing IL-13 in the submucosa were eosinophils, and 8% were mast cells. The median (interquartile range) proportion of eosinophils that expressed IL-13 was higher in the subjects with asthma, 16 (10)%, than those with eosinophilic bronchitis, 7 (3)% ( P = .02)., Conclusion: The increased expression of IL-13 in asthma compared with eosinophilic bronchitis supports the concept that IL-13 may play a critical role in the pathophysiology of asthma.

Background: Human lung and blood-derived mast cells express a Ca2+-activated K+ channel (KCA) that has electrophysiological properties resembling the intermediate conductance KCA (iKCA1). This channel is predicted to enhance IgE-dependent mast cell responses., Objective: To confirm the identity of this channel as iKCA1 in human lung mast cells and to examine the effect of an iKCA1 opener, 1-ethyl-2-benzimidazolinone (1-EBIO), on Ca2+ influx and degranulation after IgE-dependent activation., Methods: iKCA1 expression was examined by using RT-PCR. Ion currents were measured by using the patch clamp technique in human peripheral blood-derived mast cells, freshly isolated human lung mast cells (HLMCs), and long-term cultured HLMCs (LTHLMCs). Currents were manipulated with the specific iKCA1 opener 1-EBIO and the iKCA1 blockers clotrimazole and TRAM-34. Ratiometric Ca2+ imaging was performed on single fura-2-loaded cells, and histamine release was measured by radioenzymatic assay., Results: Both fresh HLMCs and LTHLMCs expressed iKCA1 mRNA. The iKCA1 opener 1-EBIO induced iKCA1 currents in 89% of human peripheral blood-derived mast cells, 12% of fresh HLMCs, and 67% of LTHLMCs, which were blocked by the iKCA1 blockers clotrimazole and TRAM-34. After cell activation with a suboptimal concentration of anti-IgE, 1-EBIO enhanced the IgE-dependent rise in cytosolic-free Ca2+ and potentiated IgE-dependent histamine release., Conclusion: Opening of iKCA1 enhances IgE-dependent Ca2+ influx and histamine release in HLMCs. Inhibition of iKCA1 may provide a novel approach to the treatment of mast cell-mediated disease., (Copyright 2004 American Academy of Allergy, Asthma and Immunology)

Background: Human lung mast cells (HLMCs) and the human mast cell line HMC-1 express a strongly outwardly rectifying Cl- current characteristic of that carried by the voltage-dependent Cl- channel ClC-5. A similar but distinct current has been implicated in the control of cell proliferation in astrocytes., Objective: In this study, we have examined the effects of the Cl- channel blocker tamoxifen on ion channel activity and cell proliferation in both HMC-1 and HLMCs., Methods: We used the whole-cell patch-clamp technique to characterize macroscopic ion currents in mast cells before and after addition of tamoxifen. HMC-1 proliferation was assessed by incorporation of tritiated thymidine, HLMC proliferation was determined by counting cells in long-term culture, and cell viability was assessed by annexin V binding and propidium iodide uptake., Results: In HMC-1, tamoxifen reduced the outward Cl- current at +130 mV by 73% +/- 9% at a concentration of 3 micromol/L and simultaneously opened a novel inwardly rectifying nonselective cation current with a mean inward current of 153 +/- 18 pA at -130 mV. Tamoxifen produced a dose-dependent inhibition of HMC-1 proliferation (90.3% +/- 4.0% inhibition at 30 micromol/L) without altering cell viability. Tamoxifen inhibited the outward ClC-5-like current in HLMCs, did not open an inward current, and produced a dose-dependent inhibition of HLMC proliferation in long-term culture., Conclusion: Tamoxifen inhibits HMC proliferation, possibly through ion channel modulation. This suggests that tamoxifen might be useful in the treatment of mast-cell-mediated diseases, including mastocytosis, asthma, and pulmonary fibrosis.

Background: Asthma is characterized by variable airflow obstruction and airway hyperresponsiveness in association with airway inflammation under the influence of T(H)2 cytokines. Eosinophilic bronchitis has similar immunopathology to asthma but without disordered airway physiology. Whether eosinophilic bronchitis is associated with increased expression of T(H)2 cytokines is unknown., Objective: We sought to assess the expression of T(H)2 cytokines in eosinophilic bronchitis., Methods: Expression of activation markers and chemokine receptors from blood and bronchoalveolar lavage (BAL) fluid T cells and the T(H)2 cytokine expression from these T cells and bronchial mucosa biopsy specimens were assessed from subjects with eosinophilic bronchitis, subjects with asthma, and healthy control subjects., Results: The proportion of resting (stimulated) CD4 BAL fluid T cells expressing intracellular IL-4 was significantly higher in the subjects with eosinophilic bronchitis 7.2% (11.4%) and subjects with asthma 5.3% (5.5%) than in healthy control subjects 2.8% (3.9%) (P =.03). The number of IL-4(+) (P <.001) and IL-5(+) (P =.003) cells per square millimeter of bronchial submucosa was significantly higher in the disease groups than in the healthy control subjects. Expression of intracellular IFN-gamma was significantly higher in stimulated blood CD8 T cells from subjects with eosinophilic bronchitis (24%) and asthma (17%) than in the healthy control subjects (5%; P =.003). There were no between-group differences in expression of IFN-gamma in the BAL fluid T cells or in the bronchial submucosa and no differences in expression of activation markers or chemokine receptors., Conclusion: These findings support the concept of asthma as a disease associated with activation of T(H)2 lymphocytes in the airway and provide evidence that these cytokines play a role in the development of airway inflammation in eosinophilic bronchitis but suggest that the release of T(H)2 cytokines is not sufficient for the elaboration of disordered airway physiology in asthma.

This article briefly reviews the advances in our understanding of asthma with a particular focus on the role of inflammation, before providing a concise overview of current knowledge of leukotrienes in the pathophysiology of the disease. The development of leukotriene receptor antagonists and synthesis inhibitors in briefly described; and acute exercise, allergen, and aspirin challenge studies with these agents are reviewed. Clinical studies with leukotriene antagonists and inhibitors have confirmed the central role of leukotrienes in asthma pathophysiology. In conclusion, we suggest that the new generation of leukotriene receptor antagonists may be suitable as first-line therapy in patients with mild to moderate asthma. Further studies are required to determine whether the leukotriene synthesis inhibitors will be equally effective or provide any additional antiinflammatory benefit.