Airways Of Asthmatic Subjects Research Articles

Mucus plugs in the airways of asthmatic subjects and smoking status

BackgroundMucus plugs have been described in the airways of asthmatic subjects, particularly those with associated with type 2 inflammation and sputum eosinophilia. In the current study we addressed the question of whether smoking, neutrophilic inflammation and airway dimensions affected the prevalence of mucus plugs.MethodsIn a cohort of moderate to severe asthmatics (n = 50), including a group of ex-smokers and current smokers, the prevalence of mucus plugs was quantified using a semi-quantitative score based on thoracic computerized tomography. The relationships between mucus score, sputum inflammatory profile and airway architecture were tested according to patient’s smoking status.ResultsAmong the asthmatics (37% former or active smokers), 74% had at least one mucus plug. The median score was 3 and was unrelated to smoking status. A significant but weak correlation was found between mucus score, FEV1 and FEV1/FVC. Mucus score was significantly correlated with sputum eosinophils. Among former and active smokers, mucus score was correlated with sputum neutrophils. Mucus score was positively associated with FeNO in non-smoking subjects. The lumen dimensions of the main and lobar bronchi were significantly inversely correlated with mucus score.ConclusionAirway mucus plugs could define an asthma phenotype with altered airway architecture and can occur in asthmatic subjects with either neutrophilic or eosinophilic sputum according to their smoking status.

Dosimetry Sensitivity in a Lower Dimensional Model of Patient-Specific Asthma Subjects.

Experimental uncertainty will impact in silico model calculations of aerosol delivery and deposition. Patient-specific dosimetry models are often parameterized based on medical imaging data, which contain inherent experimental variability. Here, we created and parameterized 1D models of three subject-specific asthmatic subjects and randomly assigned perturbations of up to 15 % on airway diameter, segmental volume, and defected volume. Sensitivity of imaging data experimental variability on dosimetry metrics were quantified. Lobar particle delivery primarily depended on the distal segmental volumes; 15 % range of noise resulted in delivery to the upper right lobe to vary at most from 15.2 and 18.2 % for one of the severe subjects. Particle deposition was most sensitive to airway diameter; 95 % confidence intervals spanned from 8 to 10.6 % in the mild/moderate subject for 15 % variation on input metrics for 5 [Formula: see text] diameter particles. While these results provide possible ranges of dosimetry calculations for a specific subject, the perturbations were not sufficient to model the large observed inter-subject variability (8.9, 19, and 14.5 % deposition, subjects 1--3, respectively, 5 [Formula: see text] diameter particles). This study highlights that in silico model predictions are robust in the presence of experimental uncertainty and that it continues to be necessary to perform subject-specific simulations, especially within the presence of heterogeneous airway disease. Sensitivity analysis provides confidence in calculating deposition in the airways of asthmatic subjects within the presence of experimental uncertainty.

Effect of dyslipidemia, obesity, and atopic status on exhaled and alveolar nitric oxide in asthmatic children.

Dyslipidemia and obesity contribute to a pro-inflammatory state. Eosinophilic airway inflammation can be indirectly measured by fractional exhaled nitric oxide (FeNO) produced in the airways of asthmatic subjects. To compare exhaled nitric oxide (NO) and alveolar NO in asthmatic children with and without dyslipidemia. Asthmatic children (5-18 years old) had fasting serum low-density lipoprotein cholesterol, triglyceride, and high-density lipoprotein cholesterol (HDL-C) concentrations, and C-reactive protein (CRP) concentrations measured. FeNO was measured at constant flow rates of 20, 50, 100, and 300 ml/s by the chemiluminescence method. NO concentrations in tissue of the upper airways (CawNO) and the total flux of NO in the conducting airways (JawNO) were determined through FeNO at 20, 100, and 300 ml/s using a mathematical model. The atopic status was assessed using the skin prick test for aero-allergens. One hundred forty-one asthmatic children were enrolled with a mean (standard deviation) age of 11.82 (3.38) years. Sixty-four (45.4%) children had dyslipidemia and 20 (14.2%) were obese. Children with low HDL-C concentrations had significantly higher CawNO and JawNO than those with normal HDL-C concentrations (both p = 0.03). Asthmatic children with obesity had higher CRP concentrations than those with a normal weight (p < 0.001). Atopic children had a significantly higher FeNO, CawNO, and JawNO than non-atopic children (all p < 0.05). This study suggests an effect of HDL-C on CawNO and JawNO in asthmatic children. An intervention that normalizes HDL-C concentrations may be beneficial for airway inflammation in asthmatic children.

Thymic stromal lymphopoietin and IL-33 modulate migration of hematopoietic progenitor cells in patients with allergic asthma

Thymic stromal lymphopoietin (TSLP) and IL-33 are considered important initiators of type 2 immunity. In asthmatic patients allergic inflammatory responses are associated with increased lung homing of bone marrow-derived CD34(+) hematopoietic progenitor cells (HPCs), which include eosinophil lineage-committed progenitor cells. In this study we investigated the role of TSLP and IL-33 in the recruitment of progenitor cells to the airways in asthmatic subjects. We sought (i) to examine the effect of allergen inhalation challenge on expression levels of receptors for TSLP (thymic stromal lymphopoietin receptor [TSLPR] and CD127) and IL-33 (ST2) and (ii) investigate the functional effects of these cytokines on HPCs. Consenting patients with mild atopic asthma (n= 19) with an FEV1 of 70% or greater and methacholine PC20 of 16 mg/mL or less were recruited. Blood- and sputum-extracted progenitors were phenotyped by flow cytometry before and 24 hours after allergen challenge. Functional responses, including cytokine production and migration to TSLP and IL-33, were assessed invitro. Significant increases in mature eosinophil, HPC, and eosinophil lineage-committed progenitor cell counts in sputum were observed 24 hours after allergen and were associated with a significant allergen-induced increase in HPCs expressing TSLPR, CD127, and ST2. Pre-exposure to TSLP and IL-33 primed the migration of HPCs to a potent progenitor cell chemoattractant, stromal cell-derived factor 1α (CXCL12). Incubation with TSLP and IL-33 stimulated significant production of IL-5 and IL-13, but not IL-4, by HPCs. This priming effect was inhibited by blocking antibodies to TSLPR and ST2, respectively, and IL-13 receptor α1 in both scenarios. In allergic asthmatic responses increased lung homing of HPCs may be orchestrated by TSLP and IL-33 through an IL-13-dependent axis.

Current trends in upper airways and ocular allergic inflammation

Current trends in upper airways and ocular allergic inflammation

Epithelial cells and airway diseases

The airway epithelial cell is the initial cell type impacted both by inhaled environmental factors, such as pathogens, allergens, and pollutants, and inhaled medications for airway diseases. As such, epithelial cells are now recognized to play a central role in the regulation of airway inflammatory status, structure, and function in normal and diseased airways. This article reviews our current knowledge regarding the roles of the epithelial cell in airway inflammation and host defense. The interactions of inhaled environmental factors and pathogens with epithelial cells are also discussed, with an emphasis on epithelial innate immune responses and contributions of epithelial cells to immune regulation. Recent evidence suggesting that epithelial cells play an active role in inducing several of the structural changes, collectively referred to airway remodeling, seen in the airways of asthmatic subjects is reviewed. Finally, the concept that the epithelium is a major target for the actions of a number of classes of inhaled medications is discussed, as are the potential mechanisms by which selected drugs may alter epithelial function.

Ozone exposure enhances mast-cell inflammation in asthmatic airways despite inhaled corticosteroid therapy

Asthmatics are recognised to be more susceptible than healthy individuals to adverse health effects caused by exposure to the common air pollutant ozone. Ozone has been reported to induce airway neutrophilia in mild asthmatics, but little is known about how it affects the airways of asthmatic subjects on inhaled corticosteroids. We hypothesised that ozone exposure would exacerbate the pre-existent asthmatic airway inflammation despite regular inhaled corticosteroid treatment. Therefore, we exposed subjects with persistent asthma on inhaled corticosteroid therapy to 0.2 ppm ozone or filtered air for 2 h, on 2 separate occasions. Lung function was evaluated before and immediately after exposure, while bronchoscopy was performed 18 h post exposure. Compared to filtered air, ozone exposure increased airway resistance. Ozone significantly enhanced neutrophil numbers and myeloperoxidase levels in airway lavages, and induced a fourfold increase in bronchial mucosal mast cell numbers. The present findings indicate that ozone worsened asthmatic airway inflammation and offer a possible biological explanation for the epidemiological findings of increased need for rescue medication and hospitalisation in asthmatic people following exposure to ambient ozone.

Cytosolic phospholipase A2α activation induced by S1P is mediated by the S1P3 receptor in lung epithelial cells

Cytosolic phospholipase A(2)alpha (cPLA(2)alpha) activation is a regulatory step in the control of arachidonic acid (AA) liberation for eicosanoid formation. Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator involved in the regulation of many important proinflammatory processes and has been found in the airways of asthmatic subjects. We investigated the mechanism of S1P-induced AA release and determined the involvement of cPLA(2)alpha in these events in A549 human lung epithelial cells. S1P induced AA release rapidly within 5 min in a dose- and time-dependent manner. S1P-induced AA release was inhibited by the cPLA(2)alpha inhibitors methyl arachidonyl fluorophosphonate (MAFP) and pyrrolidine derivative, by small interfering RNA-mediated downregulation of cPLA(2)alpha, and by inhibition of S1P-induced calcium flux, suggesting a significant role of cPLA(2)alpha in S1P-mediated AA release. Knockdown of the S1P3 receptor, the major S1P receptor expressed on A549 cells, inhibited S1P-induced calcium flux and AA release. The S1P-induced calcium flux and AA release was associated with sphingosine kinase 1 (Sphk1) expression and activity. Furthermore, Rho-associated kinase, downstream of S1P3, was crucial for S1P-induced cPLA(2)alpha activation. Our data suggest that S1P acting through S1P3, calcium flux, and Rho kinase activates cPLA(2)alpha and releases AA in lung epithelial cells. An understanding of S1P-induced cPLA(2)alpha activation mechanisms in epithelial cells may provide potential targets to control inflammatory processes in the lung.

Extracellular ATP triggers and maintains airway inflammation in human and murine models of asthma by activating dendritic cells

Extracellular nucleotides have a key signaling role in cell-to-cell communication. In particular, extracellular ATP can act at plasma membrane P2 receptors (P2R) and thus serve as a danger signal to alert the immune system of tissue damage during the early phases of inflammation. Here we show that allergen challenge causes acute accumulation of ATP not only in the airways of asthmatic subjects but also in ovalbumin (OVA)-sensitized mice. In this mouse model, antigen challenge with OVA leads to airway eosinophilia, lymphocytosis, globet cell hyperplasia and Th2 cytokine secretion which were completely abrogated by intra tracheal (i.t.) instillation of the ATP hydrolyzing enzyme apyrase or by inhibition of P2R receptors. In addtition to these effects of ATP on ongoing Th2 responses, sensitization to inhaled antigen was also enhanced by endogenous or exogenous ATP or its analogues. The adjuvant effects of ATP appear to be due to a direct Th2-skewing activity on lung myeloid dendritic cells. Together these data show that purinergic signaling has a key role in allergen-driven lung inflammation, not only during established inflammation but also during Th2 priming in the lung. Anti-purinergic strategies might therefore have a therapeutical potential in the treatment of asthma.

Extracellular ATP triggers and maintains asthmatic airway inflammation by activating dendritic cells

Extracellular ATP serves as a danger signal to alert the immune system of tissue damage by acting on P2X or P2Y receptors. Here we show that allergen challenge causes acute accumulation of ATP in the airways of asthmatic subjects and mice with experimentally induced asthma. All the cardinal features of asthma, including eosinophilic airway inflammation, Th2 cytokine production and bronchial hyper-reactivity, were abrogated when lung ATP levels were locally neutralized using apyrase or when mice were treated with broad-spectrum P2-receptor antagonists. In addition to these effects of ATP in established inflammation, Th2 sensitization to inhaled antigen was enhanced by endogenous or exogenous ATP. The adjuvant effects of ATP were due to the recruitment and activation of lung myeloid dendritic cells that induced Th2 responses in the mediastinal nodes. Together these data show that purinergic signaling has a key role in allergen-driven lung inflammation that is likely to be amenable to therapeutic intervention.

Local blockade of IL-6R signaling induces lung CD4+ T cell apoptosis in a murine model of asthma via regulatory T cells

We previously reported high levels of the soluble form of the IL-6R (sIL-6R) in the airways of asthmatic subjects. Here, we analyzed the IL-6R effects on Th2 cell survival in the lung by locally antagonizing sIL-6R-mediated trans-signaling with a designer fusion protein (gp130-Fc) as well as IL-6R signaling with an antibody against the gp80 unit of the IL-6R (alphaIL-6R) in a murine model of asthma after ovalbumin peptide (OVA) sensitization and challenge. Blockade of the sIL-6R led to a significant decrease in inflammatory cells by an apoptosis-independent mechanism. In contrast, local treatment with alphaIL-6R antibodies that also block signaling via the membrane-bound IL-6R (mIL-6R) led to decreased signal transducers and activators of transcription (STAT)-3 but not STAT-1 phosphorylation in the lung of treated mice as compared with control-treated mice. Moreover, this treatment induced apoptosis of the cells present in the airways of OVA-treated mice as well as apoptosis of lung CD4+ effector T cells. Subsequent studies showed that this effect was mediated by lung CD4+CD25+Foxp3+ T regulatory cells by a cell-cell interaction, thereby contributing to the resolution of airway hyperresponsiveness in OVA-treated mice given anti-IL-6R antibodies. Taken together, these data suggest that blockade of mIL-6R signaling leads to cell death of lung effector T cells by activating regulatory T cells in experimental asthma. Local targeting of IL-6R signaling could be a novel approach for inducing Th2 T cell death in allergic airways via regulatory T cells.

Mast cell regulation of airway smooth muscle function in asthma

Asthma is a common disease affecting ≤10% of the adult Western population 1, 2. It is characterised by the presence of variable and potentially reversible airflow obstruction, which occurs as the result of bronchoconstriction, airway mucus plugging and airway oedema. Pathologically there is evidence of airway inflammation and remodelling 3–7. The mucosal inflammatory infiltrate commonly comprises activated T-cells, eosinophils and mast cells, while the accompanying structural changes include subepithelial collagen deposition, goblet cell- and mucous gland-hyperplasia, airway smooth muscle (ASM) hypertrophy and ASM hyperplasia. An important physiological feature of asthma is the presence of bronchial hyperresponsiveness (BHR) 8. This means there is an exaggerated bronchoconstrictor response of the ASM to direct and indirect stimuli such as histamine and exercise, respectively. While BHR is aggravated in the presence of classic allergic eosinophilic airway inflammation, it persists once this inflammation is controlled and is not present in patients with eosinophilic bronchitis 8, 9. This suggests that there is either a fundamental abnormality of ASM behaviour in asthmatic subjects or that there are interacting factors that have not been previously recognised. In support of the former, several phenotypic differences are evident in ASM cells cultured from the airways of asthmatic subjects. For example, when compared with normal ASM cells, cultured asthmatic ASM cells proliferate faster due to an altered pattern of matrix protein deposition 10, 11, secrete greater amounts of connective tissue-derived growth factor in response to transforming growth factor-β stimulation 12, and secrete markedly increased amounts of the chemokine CXCL10 in response to activation by cytokines 13. There is decreased expression of prostaglandin (PG)E2 by the asthmatic ASM 14, and proliferation of asthmatic ASM is not inhibited by corticosteroids due to impaired expression of the transcription factor CCAAT/enhancer …

Allergic Airway Inflammation and β-Adrenoceptor Dysfunction

A reduced response to beta-adrenoceptor agonists has been reported in airways of asthmatic subjects. Mechanisms for beta-adrenoceptor dysfunction are (1) inactivation or downregulation of beta-adrenoceptors by specific agonists (homologous desensitization) or by inflammatory mediations (heterologous desensitization), (2) inactivation or downregulation of second messengers of beta-adrenoceptor pathway. Studies from our laboratory have shown that allergen challenge of passively sensitized human bronchi causes a beta-adrenoceptor dysfunction as a result of reduced activity of the receptor-coupled Gs protein. The dysfunction was prevented by leukotriene-receptor antagonists or a cell membrane stabilizer, but not by an antihistimine or indomethacin, suggesting a central role of leukotrienes released from resident inflammatory cells in its genesis. Furthermore, the beta-adrenoceptor response and Gs protein function after allergen exposure were restored by short-term (3 h) incubation with beclomethasone dipropionate, suggesting an effect independent of gene transcription. Restoration of the intracellular beta-adrenoceptor effector pathway may contribute to the efficacy of corticosteroids in the acute treatment of asthma.

Association of asthma with a functional promoter polymorphism in the IL16 gene

IL-16, a multifunctional cytokine with increased expression in the airways of asthmatic subjects, inhibits allergic airway inflammation in animal models. A T-->C single nucleotide polymorphism (SNP) at the -295 position in the promoter region of the IL16 gene has been described. We sought to examine the functional significance of this promoter SNP and its relationship to asthma. We examined the effect of the -295 SNP on promoter activity in cell-line (HBE4-E6/E7) transfection experiments. We investigated the association of the IL16 -295 genotype with asthma among 341 affected sib-pair white families and 184 unrelated nonasthmatic control subjects. We analyzed the association between the IL16 genotype and asthma using family-based association test and case-control analyses. In in vitro transfection experiments the T allele in the -295 position was associated with substantially reduced promoter activity compared with the C allele. In the family study the more common T allele at the -295 position was significantly associated with all asthma phenotypes (P = .002 to P = .015). In the case-control analysis asthmatic subjects were more likely than unrelated nonasthmatic control subjects to have the -295 TT genotype, but this did not reach statistical significance (odds ratio, 1.36; 95% CI, 0.92-2.02). The T allele at the -295 position in the IL16 promoter region is associated with reduced promoter activity relative to the C allele and with asthma in this white population. Further investigation is needed to delineate the mechanisms underlying these findings and the relationship of the IL16 -295 genotype to asthma in other populations.

Antioxidants and oxidative stress in BAL fluid of atopic asthmatic children.

Earlier studies in adults have indicated that increased oxidative stress may occur in the blood and airways of asthmatic subjects. Therefore the aim of this study was to compare the concentrations of antioxidants and protein carbonyls in bronchoalveolar lavage fluid of clinically stable atopic asthmatic children (AA, n = 78) with our recently published reference intervals for nonasthmatic children (C, n = 124). Additionally, lipid peroxidation products (malondialdehyde) in bronchoalveolar lavage fluid and several antioxidants in plasma were determined. Bronchoalveolar lavage concentrations (median and interquartile range) of ascorbate [AA: 0.433 (0.294-0.678) versus C: 0.418 (0.253-0.646) micromol/L], urate [AA: 0.585 (0.412-0.996) versus C: 0.511 (0.372-0.687) micromol/L], alpha-tocopherol [AA: 0.025 (0.014-0.031) versus C: 0.017 (0.017-0.260) micromol/L], and oxidized proteins as reflected by protein carbonyls [AA: 1.222 (0.970-1.635) versus C: 1.243 (0.813-1.685) nmol/mg protein] were similar in both groups (p > 0.05 in all cases). The concentration of protein carbonyls correlated significantly with the number of eosinophils, mast cells, and macrophages in AA children only. Concentrations of oxidized proteins and lipid peroxidation products (malondialdehyde) correlated significantly in AA children (r = 0.614, n = 11, p = 0.044). Serum concentrations of ascorbate, urate, retinol, alpha-tocopherol, beta-carotene, and lycopene were similar in both groups whereas alpha-carotene was significantly reduced in asthmatics. Overall, increased bronchoalveolar lavage eosinophils indicate ongoing airway inflammation, which may increase oxidatively modified proteins as reflected by increased protein carbonyl concentrations.

The Functional Consequences of Structural Changes in the Airways: Implications for Airway Hyperresponsiveness in Asthma

Over the last decade, there has been increasing recognition that structural change (ie, remodeling) in the airways of asthmatic subjects is a characteristic feature of the disease and may have important functional implications. Remodeling can be defined as changes in the composition, content, and organization of the cellular and molecular constituents of the airway wall.

Activation of TGF-beta/Smad2 signaling is associated with airway remodeling in asthma.

Transforming growth factor beta (TGF-beta) has been suggested to play an important role in the development of airway remodeling in asthma; this suggestion is based on evidence that expression levels of TGF-beta are correlated with unique parameters of airway remodeling, such as thickness of basement membrane. However, the relevant studies were inconclusive because they were unable to demonstrate active signaling mediated by the cytokine in the airways of asthmatic individuals. We sought to determine whether TGF-beta signaling was active in the airways of asthmatic subjects and, if so, whether it was correlated with clinicopathologic features associated with the development of airway remodeling in asthma. We examined the phosphorylation status of Smad2 in bronchial biopsy samples obtained from 40 asthmatic subjects as a marker of active TGF-beta signaling, and we studied its correlation with basement membrane thickness. Expression levels of phosphorylated Smad2 in bronchial biopsy specimens from asthmatic subjects were higher than those in specimens from normal subjects, and they were correlated with basement membrane thickness in asthma. The findings provide evidence that TGF-beta signaling was active in asthmatic airways and that the activity was associated with the development of airway remodeling in asthma.

The effect of cysteinyl leukotrienes on growth of eosinophil progenitors from peripheral blood and bone marrow of atopic subjects.

The accumulation of eosinophils into the peripheral blood and airways of asthmatic subjects is, in part, dependent on cysteinyl leukotrienes (cysLTs). However, the effect of cysLTs on peripheral blood and bone marrow eosinophil pro-genitor cells in allergic subjects is not known. The purpose of this study was to evaluate the effects of leukotriene (LT) D(4) and LTE(4) and the cysLT(1) receptor antagonist montelukast on peripheral blood and bone marrow eosinophil-basophil progenitor growth and development in atopic subjects. Semisolid methylcellulose cultures for peripheral blood and bone marrow eosinophil-basophil colonies were counted after incubation with or without addition of LTD(4), LTE(4), and montelukast in the presence of suboptimal concentrations of GM-CSF, IL-3, and IL-5. Peripheral blood eosinophil-basophil colony-forming unit cultures grown in the presence of GM-CSF and bone marrow eosinophil-basophil colony-forming units grown in the presence of IL-5 were significantly increased by the addition of LTD(4) (0.1 micromol/L). This increase was suppressed by montelukast (1 micromol/L). This study has demonstrated that the cysLT LTD(4) can stimulate proliferation of eosinophil hematopoietic progenitor cells in the presence of eosinophilopoietic cytokines. The suppressive effect by montelukast demonstrates that this is a cysLT(1) receptor-mediated effect.

The Role of TARC in the Pathogenesis of Allergic Asthma.

TARC (thymus and activation-regulated chemokine), as a selective chemoattractant of Th2 cells, is a reasonable candidate as a key regulator of Th2-mediated inflammation in allergic asthma. Studies have determined that TARC is up-regulated in the airways of human subjects with asthma and that CCR4- and CCR8-bearing T cells are also present in the airways of asthmatic subjects after allergen challenge. Mouse models of allergic airway inflammation have shown that neutralization of TARC can not only inhibit T-cell and eosinophil infiltration into the lung but can also inhibit bronchial hyperresponsiveness. The exact mechanism by which TARC can participate in allergic inflammation and what triggers the expression of TARC following allergen exposure is still unknown. Studies suggest that it could be involved not only in allergic asthma, but in the pathogenesis of allergic Th2-mediated diseases in general. (c) 2002 Prous Science. All rights reserved.

Peroxidases inhibit nitric oxide (NO) dependent bronchodilation: development of a model describing NO-peroxidase interactions.

Recent studies demonstrate that nitric oxide (NO) serves as a physiological substrate for mammalian peroxidases [(2000) J. Biol. Chem. 275, 37524]. We now show that eosinophil peroxidase (EPO) and lactoperoxidase (LPO), peroxidases known to be enriched in airways of asthmatic subjects, function as a catalytic sink for NO, modulating its bioavailability and function. Using NO-selective electrodes and direct spectroscopic and rapid kinetic methods, we examined the interactions of NO with EPO and LPO compounds I and II and ferric forms and compared the results to those reported for myeloperoxidase. A unified kinetic model for NO interactions with intermediates of mammalian peroxidases during steady-state catalysis is presented that accommodates unique features observed with each member of the mammalian peroxidase superfamily. Potential functional consequences of peroxidase-NO interactions in asthma are investigated by utilizing organ chamber studies with tracheal rings. In the presence of pathophysiologically relevant levels of peroxidases and H(2)O(2), NO-dependent bronchodilation of preconstricted tracheal rings was reversibly inhibited. Thus, NO interaction with mammalian peroxidases may serve as a potential mechanism for modulating their catalytic activities, influencing the regulation of local inflammatory and infectious events in vivo.