Sputum proteomic signature of gastro-oesophageal reflux in patients with severe asthma

Gastro-oesophageal reflux disease (GORD) has long been associated with poor asthma control without an established cause-effect relationship. 610 asthmatics (421 severe/88 mild-moderate) and 101 healthy controls were assessed clinically and a subset of 154 severe asthmatics underwent proteomic analysis of induced sputum using untargeted mass spectrometry, LC-IMS-MS^E. Univariate and multiple logistic regression analyses (MLR) were conducted to identify proteins associated with GORD in this cohort. When compared to mild/moderate asthmatics and healthy individuals, respectively, GORD was three- and ten-fold more prevalent in severe asthmatics and was associated with increased asthma symptoms and oral corticosteroid use, poorer quality of life, depression/anxiety, obesity and symptoms of sino-nasal disease. Comparison of sputum proteomes in severe asthmatics with and without active GORD showed five differentially abundant proteins with described roles in anti-microbial defences, systemic inflammation and epithelial integrity. Three of these were associated with active GORD by multiple linear regression analysis: Ig lambda variable 1-47 (p = 0·017) and plasma protease C1 inhibitor (p = 0·043), both in lower concentrations, and lipocalin-1 (p = 0·034) in higher concentrations in active GORD. This study provides evidence which suggests that reflux can cause subtle perturbation of proteins detectable in the airways lining fluid and that severe asthmatics with GORD may represent a distinct phenotype of asthma.

Allergenic proteases cleave the chemokine CX3CL1 directly from the surface of airway epithelium and augment the effect of rhinovirus

CX3CL1 has been implicated in allergen-induced airway CD4⁺ T-lymphocyte recruitment in asthma. As epidemiological evidence supports a viral infection-allergen synergy in asthma exacerbations, we postulated that rhinovirus (RV) infection in the presence of allergen augments epithelial CX3CL1 release. Fully differentiated primary bronchial epithelial cultures were pretreated apically with house dust mite (HDM) extract and infected with rhinovirus-16 (RV16). CX3CL1 was measured by enzyme-linked immunosorbent assay and western blotting, and shedding mechanisms assessed using inhibitors, protease-activated receptor-2 (PAR-2) agonist, and recombinant CX3CL1-expressing HEK293T cells. Basolateral CX3CL1 release was unaffected by HDM but stimulated by RV16; inhibition by fluticasone or GM6001 implicated nuclear factor-κB and ADAM (A Disintegrin and Metalloproteinase) sheddases. Conversely, apical CX3CL1 shedding was stimulated by HDM and augmented by RV16. Although fluticasone or GM6001 reduced RV16+HDM-induced apical CX3CL1 release, heat inactivation or cysteine protease inhibition completely blocked CX3CL1 shedding. The HDM effect was via enzymatic cleavage of CX3CL1, not PAR-2 activation, yielding a product mitogenic for smooth muscle cells. Extracts of Alternaria fungus caused similar CX3CL1 shedding. We have identified a novel mechanism whereby allergenic proteases cleave CX3CL1 from the apical epithelial surface to yield a biologically active product. RV16 infection augmented HDM-induced CX3CL1 shedding-this may contribute to synergy between allergen exposure and RV infection in triggering asthma exacerbations and airway remodeling.

Structure-mechanics relationships of collagen fibrils in the osteogenesis imperfecta mouse model

The collagen molecule, which is the building block of collagen fibrils, is a triple helix of two α1(I) chains and one α2(I) chain. However, in the severe mouse model of osteogenesis imperfecta (OIM), deletion of the COL1A2 gene results in the substitution of the α2(I) chain by one α1(I) chain. As this substitution severely impairs the structure and mechanics of collagen-rich tissues at the tissue and organ level, the main aim of this study was to investigate how the structure and mechanics are altered in OIM collagen fibrils. Comparing results from atomic force microscopy imaging and cantilever-based nanoindentation on collagen fibrils from OIM and wild-type (WT) animals, we found a 33% lower indentation modulus in OIM when air-dried (bound water present) and an almost fivefold higher indentation modulus in OIM collagen fibrils when fully hydrated (bound and unbound water present) in phosphate-buffered saline solution (PBS) compared with WT collagen fibrils. These mechanical changes were accompanied by an impaired swelling upon hydration within PBS. Our experimental and atomistic simulation results show how the structure and mechanics are altered at the individual collagen fibril level as a result of collagen gene mutation in OIM. We envisage that the combination of experimental and modelling approaches could allow mechanical phenotyping at the collagen fibril level of virtually any alteration of collagen structure or chemistry.

Stability of phenotypes defined by physiological variables and biomarkers in adults with asthma

BACKGROUND

Although asthma is characterized by variable airways obstruction, most studies of asthma phenotypes are cross-sectional. The stability of phenotypes defined either by biomarkers or by physiological variables was assessed by repeated measures over 1 year in the Pan-European BIOAIR cohort of adult asthmatics.

METHODS

A total of 169 patients, 93 with severe asthma (SA) and 76 with mild-to-moderate asthma (MA), were examined at six or more visits during 1 year. Asthma phenotype clusters were defined by physiological variables (lung function, reversibility and age of onset of the disease) or by biomarkers (eosinophils and neutrophils in induced sputum).

RESULTS

After 1 year of follow-up, the allocation to clusters was changed in 23.6% of all asthma patients when defined by physiological phenotypes and, remarkably, in 42.3% of the patients when stratified according to sputum cellularity (P = 0.034). In the SA cohort, 30% and 48.6% of the patients changed allocation according to physiological and biomarker clustering, respectively. Variability of phenotypes was not influenced by change in oral or inhaled corticosteroid dose, nor by the number of exacerbations. Lower stability of single and repeated measure was found for all evaluated biomarkers (eosinophils, neutrophils and FeNO) in contrast to good stability of physiological variables (FEV1 ), quality of life and asthma control.

CONCLUSION

Phenotypes determined by biomarkers are less stable than those defined by physiological variables, especially in severe asthmatics. The data also imply that definition of asthma phenotypes is improved by repeated measures to account for fluctuations in lung function, biomarkers and asthma control.

Geographical variation in the prevalence of sensitization to common aeroallergens in adults: the GA(2) LEN survey

BACKGROUND

Geographical variation in the prevalence of sensitization to aeroallergens may reflect differences in exposure to risk factors such as having older siblings, being raised on a farm or other unidentified exposures.

OBJECTIVE

We wanted to measure geographical variation in skin prick test positivity and assess whether it was explained by differences in family size and/or farm exposure. We also compared prevalence in younger and older subjects.

METHODS

Within the Global Allergy and Asthma European Network (GA(2) LEN) survey, we measured the prevalence of skin prick positivity to a panel of allergens, and geometric mean serum total immunoglobulin E (IgE), in 3451 participants aged 18-75 years in 13 areas of Europe. Estimated prevalence was standardized to account for study design. We compared prevalence estimates in younger and older subjects and further adjusted for age, gender, smoking history, farm exposure, number of older siblings and body mass index (BMI).

RESULTS

Skin prick test positivity to any one of the measured allergens varied within Europe from 31.4% to 52.9%. Prevalence of sensitization to single allergens also varied. Variation in serum total IgE was less marked. Younger participants had higher skin prick sensitivity prevalence, but not total IgE, than older participants. Geographical variation remained even after adjustment for confounders.

CONCLUSION

Geographical variation in the prevalence of skin prick test positivity in Europe is unlikely to be explained by geographical variation in gender, age, smoking history, farm exposure, family size and BMI. Higher prevalence in younger, compared to older, adults may reflect cohort-associated increases in sensitization or the influence of ageing on immune or tissue responses.

Genome-wide association study to identify genetic determinants of severe asthma

BACKGROUND

The genetic basis for developing asthma has been extensively studied. However, association studies to date have mostly focused on mild to moderate disease and genetic risk factors for severe asthma remain unclear.

OBJECTIVE

To identify common genetic variants affecting susceptibility to severe asthma.

METHODS

A genome-wide association study was undertaken in 933 European ancestry individuals with severe asthma based on Global Initiative for Asthma (GINA) criteria 3 or above and 3346 clean controls. After standard quality control measures, the association of 480 889 genotyped single nucleotide polymorphisms (SNPs) was tested. To improve the resolution of the association signals identified, non-genotyped SNPs were imputed in these regions using a dense reference panel of SNP genotypes from the 1000 Genomes Project. Then replication of SNPs of interest was undertaken in a further 231 cases and 1345 controls and a meta-analysis was performed to combine the results across studies.

RESULTS

An association was confirmed in subjects with severe asthma of loci previously identified for association with mild to moderate asthma. The strongest evidence was seen for the ORMDL3/GSDMB locus on chromosome 17q12-21 (rs4794820, p=1.03×10((-8)) following meta-analysis) meeting genome-wide significance. Strong evidence was also found for the IL1RL1/IL18R1 locus on 2q12 (rs9807989, p=5.59×10((-8)) following meta-analysis) just below this threshold. No novel loci for susceptibility to severe asthma met strict criteria for genome-wide significance.

CONCLUSIONS

The largest genome-wide association study of severe asthma to date was carried out and strong evidence found for the association of two previously identified asthma susceptibility loci in patients with severe disease. A number of novel regions with suggestive evidence were also identified warranting further study.

Preliminary study of the cellular characteristics of primary bronchial fibroblasts in patients with asthma: expression of alpha-smooth muscle actin, fibronectin containing extra type III domain A, and smoothelin

BACKGROUND

The relationship between fibroblasts, myofibroblasts, and smooth muscle cells within the airway wall remains poorly understood.

OBJECTIVE

The cellular characteristics of primary bronchial fibroblasts from patients with asthma were investigated by evaluating the expression of 3 proteins: alpha-smooth muscle actin (SMA), fibronectin containing extra type III domain A (EDAcFN), and smoothelin.

METHODS

Expression of SMA, EDAcFN, and smoothelin was evaluated in primary fibroblasts from 3 patients with asthma of varying symptom severity, embryonic fibroblasts, and a healthy control. In addition, primary bronchial fibroblasts from patients with asthma were assessed for SMA at various incubation times (4 hours to 76 hours) and with different extracellular matrices (ECMs). Immunofluorescence was assessed by manually counting cells that stained positively as fine filamentous structures under a fluorescence microscope.

RESULTS

Expression of filamentous SMA tended to increase with the length of incubation. The positive to total cell ratio for filamentous cells did not differ significantly between the various kinds of ECMs onto which cells were plated (P > .05). Primary bronchial fibroblasts from asthma patients produced more prominent expression of EDAcFN than control fibroblasts. Smoothelin was not expressed in any fibroblasts.

CONCLUSIONS

More than 50% of primary bronchial fibroblasts were defined as myofibroblasts. Primary bronchial fibroblasts in patients with asthma had more potential for tissue fibrosis than control fibroblasts. No mature smooth muscle cells were observed in primary bronchial fibroblasts in patients with asthma.

The allergen specificity of the late asthmatic reaction

BACKGROUND

Allergen inhalation challenge in asthma may induce both early (EAR) and late (LAR) asthmatic reactions. The EAR is IgE and mast cell dependent. The mechanism of the LAR is less well defined and we have hypothesized may be allergen dependent. The aim of this study was to investigate the allergen specificity of the LAR to allergen inhalation in asthma.

METHODS

In a randomized, double-blind, crossover design six asthmatic volunteers with dual sensitization to house dust mite (HDM) allergen and grass pollen (GP) allergen underwent inhalation allergen challenge with these separate allergens on two occasions separated by 14 days. Lung function changes were followed for 8-h postchallenge. Bronchial reactivity (histamine PC(20)) and airway inflammation, assessed by induced sputum differential cell count, were measured 24-h pre and postallergen challenge. The allergen inhalation challenges were matched to achieve the same magnitude of EAR.

RESULTS

Despite comparable group mean EAR percent falls in FEV(1) (25.8% following GP and 28.0% following HDM (P = 0.917), the LAR was statistically greater on the HDM challenge day (13.0%vs 22.8% [P = 0.046]) and was associated with a significant airway eosinophil recruitment (mean (SD) of 5.4 (4.8)% to 22.1 (18.2)% (P = 0.028) that was not evident on the GP allergen challenge day.

CONCLUSIONS

These findings identify the allergen specificity of the LAR and indicate that factors independent of IgE contribute to the LAR. Such findings have relevance both to the understanding of the allergen-induced airway responses in asthma and the need for homogeneity in inhaled-allergen challenge studies in asthma.

Osteopontin is expressed and functional in human eosinophils

BACKGROUND

Eosinophils are critically involved in allergic inflammation and tissue remodeling. Osteopontin (OPN) is a glycoprotein molecule which exhibits pro-fibrogenic and pro-angiogenic properties and has recently also been implicated in allergic diseases. In this study, we investigated the expression and function of OPN in human eosinophils.

METHODS

Osteopontin mRNA (RT-PCR) and protein (immunofluorescence) expression in peripheral blood eosinophils from atopic human subjects were evaluated. Soluble OPN release was determined in resting and activated eosinophils. The contribution of OPN to eosinophil-induced angiogenesis was determined using the chick embryo chorio- allantoic membrane (CAM) assay and OPN-induced eosinophil chemotaxis was determined (ChemoTx System microplate wells). Finally, OPN expression in bronchoalveolar lavage (BAL) fluids from mild asthmatic and normal control subjects was determined.

RESULTS

Osteopontin is expressed in human eosinophils and is increased following GM-CSF and IL-5 activation. Eosinophil-derived OPN contributes to eosinophil-induced angiogenesis. Recombinant OPN promotes eosinophil chemotaxis in vitro and this effect is mediated by alpha(4)beta(1) integrin binding. Soluble OPN is increased in the bronchoalveolar lavage fluid from mild asthmatic subjects and correlates with eosinophil counts.

CONCLUSIONS

We therefore conclude that OPN is likely to contribute to the process of angiogenesis observed in the airways in asthma.

Transforming growth factor-beta in allergic inflammatory disease of the upper airways: friend or foe?

TGF-beta is a multi-functional cytokine with a huge array of effects on a variety of cell types. It is rapidly emerging as a key major player in the way the airway epithelium behaves and its ability to repair itself. This is not only of relevance to allergic airway diseases such as asthma and allergic rhinitis, which are increasing in prevalence worldwide, but in many other diseases. The full impact any disruption of TGF-beta signalling may have in the development and persistence of allergic inflammatory airway diseases is yet to be fully realized and remains the subject of ongoing research. There has been a recent revival of interest in the role of regulatory T cells in controlling allergic inflammation. Evidence is emerging of a significant contribution by TGF-beta to this regulatory process. This review aims to summarize current knowledge relating to TGF-beta in relation to allergic inflammatory upper airways disease, and attempts to clarify some of the discrepancies and inconsistencies in this area. It also considers the therapeutic implications of novel TGF-beta therapy, including potential future applications in the treatment of nasal polyposis and reduction of post-operative scar tissue formation following endoscopic sinus surgery.

Nasal mucosal expression of the leukotriene and prostanoid pathways in seasonal and perennial allergic rhinitis

BACKGROUND

Leukotrienes (LTs) and prostanoids are potent pro-inflammatory and vasoactive lipid mediators implicated in airway disease, but their cellular sources in the nasal airway in naturally occurring allergic rhinitis (AR) are unclear.

OBJECTIVE

To quantify cellular expression of enzymes of the 5-lipoxygenase (5-LO) and cyclooxygenase (COX) pathways by immunohistochemistry in nasal biopsies from patients with symptomatic perennial AR (PAR, n = 13) and seasonal AR (SAR, n = 14) and from normal subjects (n = 12).

METHODS

Enzymes of the 5-LO pathway (5-LO, FLAP, LT A4 hydrolase, LTC4 synthase) and the COX pathway (COX-1, COX-2, prostaglandin D2 synthase) were immunostained in glycol methacrylate resin-embedded inferior turbinate biopsy specimens, quantified in the lamina propria and epithelium, and co-localized to leucocyte markers by camera lucida.

RESULTS

In the lamina propria of PAR biopsies, median counts of cells expressing FLAP were fourfold higher than in normal biopsies (Mann-Whitney, P = 0.014), and also tended to be higher than in SAR biopsies (P = 0.06), which were not different from normal. PAR biopsies showed threefold more cells immunostaining for LTC4 synthase compared with SAR biopsies (P = 0.011) but this was not significant compared with normal biopsies (P = 0.2). These changes were associated with ninefold more eosinophils (P = 0.0005) with no differences in other leucocytes. There were no significant differences in the lamina propria in immunostaining for 5-LO, LTA4 hydrolase, COX-1, COX-2 or PGD2 synthase. Within the epithelium, increased expression of COX-1 was evident in PAR biopsies (P = 0.014) and SAR biopsies (P = 0.037), associated with more intra-epithelial mast cells in both rhinitic groups (P < 0.02).

CONCLUSIONS

In the nasal biopsies of PAR subjects, increased expression of regulatory enzymes of the cysteinyl-LT biosynthetic pathway was associated with lamina propria infiltration by eosinophils. Seasonal rhinitis biopsies shared only some of these changes, consistent with transient disease. Increased intra-epithelial mast cells and epithelial COX-1 expression in both rhinitic groups may generate modulatory prostanoids.

BSACI guidelines for the management of allergic and non-allergic rhinitis

This guidance for the management of patients with allergic and non‐allergic rhinitis has been prepared by the Standards of Care Committee (SOCC) of the British Society for Allergy and Clinical Immunology (BSACI). The guideline is based on evidence as well as on expert opinion and is for use by both adult physicians and paediatricians practicing in allergy. The recommendations are evidence graded. During the development of these guidelines, all BSACI members were included in the consultation process using a web‐based system. Their comments and suggestions were carefully considered by the SOCC. Where evidence was lacking, consensus was reached by the experts on the committee. Included in this guideline are clinical classification of rhinitis, aetiology, diagnosis, investigations and management including subcutaneous and sublingual immunotherapy. There are also special sections for children, co‐morbid associations and pregnancy. Finally, we have made recommendations for potential areas of future research.

Local genetic and environmental factors in asthma disease pathogenesis: chronicity and persistence mechanisms

While asthma is an inflammatory disorder of the airways usually associated with atopy, an important additional component is involvement of the epithelium and underlying mesenchyme acting as a trophic unit (EMTU). In addition to allergens, a wide range of environmental factors interact with the EMTU, such as virus infections, environmental tobacco smoke and pollutants, to initiate tissue damage and aberrant repair responses that are translated into remodelling of the airways. While candidate gene association studies have revealed polymorphic variants that influence asthmatic inflammation, positional cloning of previously unknown genes is identifying a high proportion of novel genes in the EMTU. Dipeptidyl peptidase (DPP) 10 and disintegrin and metalloproteinase (ADAM)33 are newly identified genes strongly associated with asthma that are preferentially expressed in the airway epithelium and underlying mesenchyme, respectively. Also of increasing importance is the recognition that genes associated with asthma and atopy have important interactions with the environment through epigenetic mechanisms that influence their expression. This type of research will not only identify biomarkers of different types of asthma across the full range of phenotypic expression, but will also identify novel therapeutic targets that could influence the natural history of the heterogenes lung disease.

The novel use of the human nasal epithelial cell line RPMI 2650 as an in vitro model to study the influence of allergens and cytokines on transforming growth factor-beta gene expression and protein release

BACKGROUND

The epithelial accumulation of mast cells is a feature of allergic rhinitis and this has been linked to the expression of the known mast cell chemoattractant transforming growth factor-beta (TGF-beta) at this site. Little is known concerning the regulation of TGF-beta gene expression or protein release by nasal epithelial cells. To address this we have utilized the RPMI 2650 human nasal epithelial cell line, which has some features that closely resemble normal nasal epithelium and has been reported to secrete a TGF-beta-like molecule.

OBJECTIVES

To investigate the regulation of TGF-beta gene expression and protein secretion in RPMI 2650 nasal epithelial cells following exposure to allergens (house dust mite (HDM) and grass pollen) and mast cell associated T-helper type 2 (Th2) cytokines (IL-4, IL-13, and TNF-alpha). Methods Light and scanning electron microscopy was used to evaluate the morphology of RPMI 2650 cells in culture, enzyme-linked immunosorbent assay was used to investigate their TGF-beta secretory capacity and the identification of the TGF-beta isotype(s) involved, flow cytometry was used to demonstrate the presence of TGF-beta receptors on the RPMI 2650 cells, and the quantitative real-time TaqMan PCR was used to measure TGF-beta gene expression.

RESULTS

TGF-beta(2) was identified as the main isotype secreted by the RPMI 2650 cells. HDM allergens and TNF-alpha increased both TGF-beta gene expression and protein release from these cells, whereas grass pollen, IL-4, and IL-13 were without effect.

CONCLUSIONS

The RPMI 2650 nasal epithelial cell line represents a valid in vitro model to evaluate the regulation of TGF-beta biology. In this system HDM allergens have stimulatory activity that is fundamentally different from that of grass pollen allergens, and the Th2 cytokines IL-4 and IL-13 are without effect. The ability of TNF-alpha to up-regulate both TGF-beta gene expression and protein release indicates that mast cell-epithelial interactions concerning TGF-beta are bi-directional and this may be fundamental to epithelial immunoregulation. The availability of a model system, such as the RPMI 2650 cells, will enable the early evaluation of future novel and targeted interventions directed toward the aberrant responses of upper airway structural cells.

Altered protein tyrosine phosphorylation in asthmatic bronchial epithelium

A disease-related, corticosteroid-insensitive increase in the expression of epidermal growth factor (EGF) receptor (EGFR) tyrosine kinase in asthmatic bronchial epithelium has been shown previously by the current authors. To determine whether this is associated with enhanced intracellular signalling, the aim of this study was to evaluate epithelial tyrosine phosphorylation. Bronchial biopsies were analysed for the presence of phosphotyrosine by immunohistochemistry. Bronchial epithelial cells were exposed to EGF, hydrogen peroxide or tumour necrosis factor-alpha in vitro for measurement of tyrosine phosphorylated signalling intermediates and interleukin (IL)-8 release. Phosphotyrosine was increased significantly in the epithelium of severe asthmatics when compared with controls or mild asthmatics; however, in mild asthma, phosphotyrosine levels were significantly decreased when compared with controls. There was no significant difference between phosphotyrosine levels before or after 8 weeks of treatment with budesonide. Stimulation of bronchial epithelial cells resulted in tyrosine phosphorylation of several proteins, including EGFR, Shc and p42/p44 mitogen-activated protein kinase. In the presence of salbutamol, a transient partial suppression of EGFR phosphorylation occurred, whereas dexamethasone was without effect. Neither salbutamol nor dexamethasone inhibited EGF-stimulated IL-8 release. These data indicate that regulation of protein tyrosine kinase activity is abnormal in severe asthma. The epidermal growth factor receptor and/or other tyrosine kinase pathways may contribute to persistent, corticosteroid-unresponsive inflammation in severe asthma.

Tumour necrosis factor (TNFalpha) as a novel therapeutic target in symptomatic corticosteroid dependent asthma

BACKGROUND

Tumour necrosis factor alpha (TNFalpha) is a major therapeutic target in a range of chronic inflammatory disorders characterised by a Th1 type immune response in which TNFalpha is generated in excess. By contrast, asthma is regarded as a Th2 type disorder, especially when associated with atopy. However, as asthma becomes more severe and chronic, it adopts additional characteristics including corticosteroid refractoriness and involvement of neutrophils suggestive of an altered inflammatory profile towards a Th1 type response, incriminating cytokines such as TNFalpha.

METHODS

TNFalpha levels in bronchoalveolar lavage (BAL) fluid of 26 healthy controls, 42 subjects with mild asthma and 20 with severe asthma were measured by immunoassay, and TNFalpha gene expression was determined in endobronchial biopsy specimens from 14 patients with mild asthma and 14 with severe asthma. The cellular localisation of TNFalpha was assessed by immunohistochemistry. An open label uncontrolled clinical study was then undertaken in 17 subjects with severe asthma to evaluate the effect of 12 weeks of treatment with the soluble TNFalpha receptor-IgG1Fc fusion protein, etanercept.

RESULTS

TNFalpha levels in BAL fluid, TNFalpha gene expression and TNFalpha immunoreative cells were increased in subjects with severe corticosteroid dependent asthma. Etanercept treatment was associated with improvement in asthma symptoms, lung function, and bronchial hyperresponsiveness.

CONCLUSIONS

These findings may be of clinical significance in identifying TNFalpha as a new therapeutic target in subjects with severe asthma. The effects of anti-TNF treatment now require confirmation in placebo controlled studies.

Nasal lavage fluid concentrations of eotaxin-1 (CCL11) in naturally occurring allergic rhinitis: relationship to disease activity, nasal luminal eosinophil influx, and plasma protein exudation

BACKGROUND

Eotaxin-1 (CCL11) is a CC chemokine whose nasal eosinophilic chemotactic activity in vivo and in vitro has been demonstrated primarily using nasal allergen challenge models. The extension of these challenge findings to the in vivo setting has been limited.

OBJECTIVE

To obtain nasal lavage fluid from volunteers with perennial and seasonal (in- and out-of-season) allergic rhinitis (AR) and non-atopic non-rhinitic controls for the measurement of eotaxin-1 concentrations and to relate these findings to the symptomatic disease severity, the percentage of lavage eosinophils, and to alpha(2)-macroglobulin (alpha(2)-MG) lavage concentrations, as a marker of vascular permeability and an index of airway inflammation.

METHODS

Thirty-seven volunteers with AR (16 seasonal and 21 perennial) and 20 non-atopic non-rhinitic volunteers were recruited and phenotyped. Nasal lavage fluid was obtained by standardized protocol. The nasal lavage fluid concentrations of eotaxin and alpha(2)-MG were measured by ELISA, and differential cell counts performed on cytospins.

RESULTS

Eotaxin-1 nasal lavage fluid concentrations were significantly higher in both the perennial and seasonal (in-season) AR groups compared with the controls, and significantly related to the severity of symptom expression and to the percentage of lavage eosinophils. The lavage eosinophil counts were significantly higher in both the symptomatic rhinitis groups compared with the control groups and correlated with the lavage concentrations of alpha(2)-MG. alpha(2)-MG levels were significantly increased in seasonal (in-season) rhinitics compared with both non-atopic controls and seasonal (out-of-season) rhinitics. A significant correlation was observed between the levels of alpha(2)-MG and levels of eotaxin in the symptomatic allergic rhinitic groups.

CONCLUSIONS

This study clearly demonstrates the relevance of eotaxin-1 to the pathogenesis of naturally occurring AR.

Endobronchial ultrasound to assess airway wall thickening: validation in vitro and in vivo

Endobronchial ultrasound (EBUS) allows identification of airway wall structures and could potentially be utilised for in vivo studies of airway thickening in asthma. The present study investigated whether inflation of the fluid-filled balloon sheath over the transducer (necessary to provide sonic coupling with the airway wall) influenced in vitro measurements. In vivo comparability of EBUS with high resolution computed tomography scanning (HRCT), an established method for measuring wall thickness, was determined in control subjects. The airway diameter and wall thickness were studied using EBUS in 24 cartilaginous airways obtained from four sheep, before and after balloon sheath inflation during immersion in saline. To assess EBUS versus HRCT comparability of airway measures in vivo, 12 control subjects underwent imaging of the posterior basal bronchus of the right lower lobe by both techniques. Intra- and interobserver agreement were also assessed. Results with and without the balloon sheath gave comparable measures of airway internal diameter and wall thickness in vitro. Statistical analysis showed agreement between EBUS and HRCT, and intra- and interobserver variability in vivo. The current study concludes that endobronchial ultrasound, which does not present a radiation risk, could be utilised in the in vivo study of cartilaginous airway wall remodelling in respiratory diseases, such as asthma.

Epithelial expression and release of FGF-2 from heparan sulphate binding sites in bronchial tissue in asthma

BACKGROUND

The most characteristic structural change evident in endobronchial biopsies in asthma, even in mild disease, is subepithelial collagen deposition within the lamina reticularis. This has been associated with progressive loss of lung function and the persistence of airway hyperresponsiveness, and has been linked to airway fibroblast proliferation. A potent fibroproliferative factor in bronchoalveolar lavage fluid in asthma is fibroblast growth factor-2 (FGF-2). FGF-2 is a member of a family of heparin binding growth factors that bind to heparan sulphate proteoglycans (HSPG), an important determinant of FGF-2 activity. This study compared the level of expression and distribution of FGF-2 in relation to HSPG in bronchial tissue from normal and asthmatic subjects.

METHODS

The distribution of FGF-2 and HSPG in intact and cleaved forms in endobronchial biopsies from normal and asthmatic subjects was examined using an immunohistochemical approach. A novel ELISA based method was developed to detect solubilisation of FGF-2 following addition of heparin and heparitinase to bronchial tissue slices.

RESULTS

Immunohistochemical analysis showed that FGF-2 was co-localised to HSPG in epithelial and endothelial basement membranes. Epithelial FGF-2, but not HSPG, was significantly more abundant in patients with mild asthma than in normal subjects. In vitro experiments indicated that FGF-2 was released from binding sites in the tissue by heparin and heparitinase I.

CONCLUSIONS

FGF-2 is bound by HSPG in bronchial tissue. The mast cell, through the release of heparin and endoglycosidase, may make a unique contribution to tissue remodelling in allergic asthma.

Remodelling of the upper airways in allergic rhinitis: is it a feature of the disease?

The traditional viewpoint that inflammation, owing to a genetic T-helper type 2 (Th2)-directed imbalance, is the cause of allergic rhinitis has meant that the potential coexistence of other genetic defects and the relevance of any airway remodelling changes to disease pathogenesis and persistence have received scant attention, and as such remain controversial areas. This is particularly so in view of the limited published work in this field, which has so far reported markedly conflicting findings. This review endeavours to outline what is known about the nature of the remodelling response within the upper airway in allergic rhinitis, in addition to highlighting specific areas where further research is warranted.

Allergic rhinitis: past, present and the future

Allergic rhinitis represents a global health issue affecting between 10% to 25% of the world population, with increasing prevalence over the last decade. Although often trivialized by patients and doctors, allergic rhinitis is a significant cause of morbidity, in addition to its substantial economic impact. While allergic rhinitis is an inflammatory disorder of the upper airways, inflammation alone is insufficient to explain the chronic nature of the disease. An exciting concept which has recently emerged in asthma concerns the role of the bronchial epithelium as a key regulator of airway inflammatory and remodelling responses in asthma. It has been shown by our group that the disruption and alteration in the function of the lower airway epithelium in asthma leads to the generation of a variety of stimuli that lead to the restructuring of the airway wall. This raises interesting questions regarding a similar role for the upper airway epithelium in allergic rhinitis. This review aims to interpret past and current research into allergic rhinitis, and to address specific areas where future research is warranted, particularly in relation to the possibility of an altered upper airway epithelial phenotype in allergic rhinitis.

Pharmacotherapy and airway remodelling in asthma?

Over the last few decades attention has largely focused on airway inflammation in asthma, but more recently it has been appreciated that there are important structural airway changes which have been grouped together under the term "airway remodelling". It is only now that questions have been asked about the impact of treatment on these structural changes. This review examines the nature of these structural airway changes, the mechanisms of their generation, their potential consequences, and what is known about the ability of anti-asthma treatments to modulate these changes.

Signal transducer and activator of transcription 6 (STAT-6) expression and function in asthmatic bronchial epithelium

BACKGROUND

Asthma is associated with increased production of IL-4 and IL-13.

OBJECTIVE

Because many of the effects of these cytokines are mediated by activation of signal transducer and activator of transcription 6 (STAT-6), we investigated expression and function of this transcription factor in the airways.

METHODS

STAT-6 expression was investigated through use of immunohistochemistry or RT-PCR applied to bronchial biopsy specimens or brushings from normal control or asthmatic subjects. STAT-6 function was investigated by means of Western blotting and ELISA applied to primary epithelial cell cultures.

RESULTS

Immunohistochemistry revealed that the bronchial epithelium was the major site of STAT-6 expression, both cytoplasmic and nuclear staining being observed. The level of STAT-6 expression in subjects with mild asthma (median [range] percent epithelial staining, 3.4% [0% to 16.0%]; n = 14) did not differ significantly from that in normal controls (4.7% [0.0% to 20.0%]; n = 11); however, in subjects with severe asthma, epithelial STAT-6 expression (13.7% [4.8% to 25.7%]; n = 9) was increased in comparison with subjects with mild asthma and normal controls (P < .05). RT-PCR analysis showed that epithelial STAT-6 expression was heterogeneous and comprised both full-length STAT-6 and the dominant-negative variant that lacks the SH2 domain. Treatment of primary cultures of bronchial epithelial cells with IL-4 resulted in STAT-6 phosphorylation and stimulation of IL-8 secretion; however, no difference in the responses of epithelial cells was observed between normal (n = 12) and asthmatic (n = 14) donors.

CONCLUSION

These data demonstrate expression and activation of STAT-6 in normal and asthmatic bronchial epithelium. The activity of this transcription factor is likely to play a key role in mediating the responses of the bronchial epithelium to T(H)2 cytokines that are characteristic of the asthmatic phenotype.

Why particle size should affect clinical response to inhaled therapy

Studies with beta2-adrenergic agonists have shown that particle size and total dose are important determinants of optimum bronchodilation. Drug deposition in the airways is probably the most important factor for bronchodilation, since beta2-adrenoceptors and muscarinic M3 receptors are present mainly in the peripheral and central airways, respectively. Furthermore, clinical efficacy can be maintained while minimizing systemic exposure by selecting an appropriate particle size. Changes in lung function provide a means of monitoring the relationship between delivery of the bronchodilator and its efficacy, whereas there is no such immediate means of assessing antiinflammatory preventative therapy such as inhaled corticosteroids. Asthma is primarily an inflammatory disease but there are no simple tests to detect the accumulation of inflammatory cells and mediators. Data are presented to demonstrate the reduction of certain inflammatory markers in bronchial biopsy tissue taken from asthmatic patients after corticosteroid therapy. Measurement of inflammatory markers in both bronchial biopsy tissue and bronchoalveolar lavage samples may provide a way of monitoring the site of action and efficacy of inhaled corticosteroids in the future. Furthermore, it is envisaged that the effect of corticosteroid particle size on efficacy and systemic bioavailability may be investigated by exploiting these methods.

Allergic rhinitis: not purely a histamine-related disease

Allergic rhinitis is an inflammatory disorder of the nasal mucosa typified by the symptoms of nasal itch, sneeze, anterior nasal secretions, and nasal blockage. These symptoms arise from the interaction between mediators and neural, vascular, and glandular structures within the nose. Nasal itch, sneezes, and rhinorrhoea are predominantly neural in origin, while nasal obstruction is predominantly vascular. Nasal biopsy studies show accumulation of eosinophils within the lamina propria and epithelium and an increase in tissue and cell surface basophils in both seasonal and perennial allergic rhinitis. These cells are in an activated state. Within the epithelium, increased numbers of mast cells, T cells and Langerhans' cells, which induce T-cell activation, are found. The accumulation of these cells can be linked to chemokine and cytokine generation by the epithelial cells themselves. Thus, the tissue cell recruitment is orchestrated by activated mast cells, T cells, and epithelial cells, with the recruited tissue eosinophils also contributing to their persistence at this site through autocrine mechanisms. Mast cells generate an array of mediators including histamine, tryptase, leukotrienes, and prostaglandins. Histamine is also generated by basophils. Eosinophils and basophils contribute to the leukotriene synthesis within the tissue. Histamine nasal insufflation induces nasal itch, sneeze, and rhinorrhoea as well as nasal blockage, thereby reproducing all the symptoms of allergic rhinitis. These effects are primarily mediated by H1-receptors, and H1-receptor antagonists are a prominent treatment. Antagonism of histamine at these receptors reduces symptoms by about 40-50%, with the greatest effect on the neurally mediated responses. Thus, histamine is a major mediator of allergic rhinitis, but not the sole contributor. Nasal insufflation with leukotrienes, prostaglandins, or kinins is associated with the development of nasal blockage. These mediators act primarily on the nasal vasculature and, in this respect, leukotrienes are potent mediators. Leukotrienes also induce plasma protein exudation, which contributes to the anterior nasal secretions. Studies with combination products have suggested that modifying the effects of both leukotrienes and histamine has complementary effects in relieving nasal symptoms, indicating that both these mediators are relevant to disease expression.

Increased expression of inducible nitric oxide synthase and cyclo-oxygenase-2 in the airway epithelium of asthmatic subjects and regulation by corticosteroid treatment

BACKGROUND

Nitric oxide (NO) and prostanoids are mediators of vascular and bronchial tone that are postulated to be involved in asthma. Increased levels of both are found in asthmatic subjects and are synthesised by enzymes that have cytokine inducible forms: inducible NO synthase (iNOS) and cyclo-oxygenase-2 (COX-2), respectively. We hypothesised that the in vivo expression of iNOS and COX-2 in the airways would be increased in asthma, and that these cytokine inducible enzymes may represent targets for regulation by corticosteroid treatment.

METHODS

Bronchial biopsy specimens were obtained from three groups of subjects: atopic asthmatics treated with beta(2) agonists alone (n=7), atopic asthmatics additionally receiving regular treatment with corticosteroids (n=8), and non-asthmatic control subjects (n=10). Expression of iNOS and COX-2 mRNA and immunoreactive protein was studied using in situ hybridisation and quantitative immunohistochemistry.

RESULTS

Immunoreactivity and the hybridisation signal for iNOS and COX-2 were mainly localised in the airway epithelium. The proportion of epithelium immunostained was significantly greater in the non-steroid treated asthmatic subjects (iNOS 8.6 (1.8)%; COX-2 26.3 (4.6)%) than either the steroid treated asthmatics (iNOS 3.4 (1.0)%, p=0.009; COX-2 13.0 (0.6)%, p=0.0015) or the non-asthmatic controls (iNOS 4.2 (0.9)%, p=0.018; COX-2 11.6 (0.6)%, p=0.0003). Similarly, the hybridisation signal was stronger in the non-steroid treated group of asthmatic subjects than in the other two groups.

CONCLUSIONS

These findings highlight the potential role of the airway epithelium both as a contributor to the inflammatory process in asthma and as a target for inhaled corticosteroid treatment in this disease.

The relationship between atopic status and IL-10 nasal lavage levels in the acute and persistent inflammatory response to upper respiratory tract infection

We examined the influence of atopy on virus-induced airway inflammation by comparing the nasal response to naturally acquired upper respiratory tract infection in atopic and nonatopic subjects by measurement of cytokine, chemokine, and mediator levels in nasal lavage from 44 adults (23 atopic) taken during the acute and the convalescent phases of the common cold. Nasal aspirates were examined for the presence of upper respiratory viruses by RT-PCR. In atopic and nonatopic subjects there were increased levels of IL-1beta, IL-6, IL-8, TNF-alpha, RANTES, sICAM-1, MPO, ECP, IL-10, and IFN-gamma in nasal lavage during the acute compared with the convalescent phase (p < 0.001). During the acute phase histamine levels were significantly higher in the atopic than in the nonatopic subjects (p < 0.05), whereas IL-10 levels were significantly greater in the nonatopic than in the atopic subjects (p < 0.05). At convalescence levels of IL-1beta, IL-6, sICAM-1, ECP, RANTES and albumin were significantly higher in the atopic group (p < 0.05). An upper respiratory tract virus was found in 27 volunteers (61%) during the acute stage and in two volunteers (4%) at convalescence. We conclude that virus-induced inflammatory changes within the nose are more prolonged in atopic than in nonatopic subjects and that this is associated with reduced IL-10 levels in atopic compared with nonatopic subjects during the acute phase of upper respiratory tract infection.

Exhaled nitric oxide levels in exacerbations of asthma, chronic obstructive pulmonary disease and pneumonia

OBJECTIVE

Nitric oxide is known to be present in the exhaled air of normal subjects and at higher concentrations in asthmatics. The aim of this study was to measure exhaled nitric oxide levels in patients admitted to hospital with acute exacerbations of asthma, or chronic obstructive pulmonary disease, or with pneumonia.

METHODS

Within 24 hours of admission exhaled nitric oxide levels were measured by a chemiluminescent analyzer in 11 patients with acute sever asthma, 19 patients with acute exacerbation of chronic obstructive pulmonary disease, and in 12 patients with pneumonia. In asthmatics measurements were made on 3 occasions, at day 1, 4, and 28 and were related to changes in peak expiratory flow rate.

RESULTS

On admission median exhaled nitric oxide levels (range) were significantly higher in asthmatics 22 (9.3-74) parts per billion in comparison to patients with chronic obstructive pulmonary disease 10.3 (2.7-34) parts per billion; p < 0.01, pneumonia 7 (4-17) parts per billion; p<0.001, and normal subjects 8.7 (5-13.3) parts per billion; p < 0.001. Following treatment the asthmatics had a significant reduction in their exhaled nitric oxide levels from 22 (9.3-74) parts per billion on day 1 to 9.7 (5.7-18.3) parts per billion on day 28; p = 0.005. Peak expiratory flow rate measurements increased from 200 (120-280) l/min on day 1 to 280 (150-475) l/min on day 4; p < 0.05 and to 390 (150-530) l/min on day 28; p < 0.01. A strong negative correlation existed between peak expiratory flow rate measurements and exhaled nitric oxide levels in asthmatics on day 28 (r = -0.70; p = 0.017).

CONCLUSION

Acute exacerbations of asthma are associated with increased levels of exhaled nitric oxide in contrast to exacerbations of chronic obstructive pulmonary disease and acute pneumonia. Exhaled nitric oxide may be a useful indirect marker of asthmatic airway inflammation. The differing time course of response of nitric oxide to peak flow measures suggests that these two measures are reflecting differing airway events.

A comparison of the anti-inflammatory properties of intranasal corticosteroids and antihistamines in allergic rhinitis

Allergic rhinitis manifests itself clinically due to the local release of mediators from activated cells within the nasal mucosa. Treatment strategies aim either to reduce the effects of these mediators on the sensory neural and vascular end organs, or to reduce the tissue accumulation of the activated cells that generate them. Corticosteroids intervene at a number of steps in the inflammatory pathway, and, by reducing the release of cytokines and chemokines, inhibit cell recruitment and activation. These effects are evident both in vivo and in vitro. While antihistamines also have some anti-inflammatory effects in vitro, these require higher concentrations than with corticosteroids and are not consistently reproduced in vivo. In addition, although antihistamines and corticosteroids might appear to have complementary mechanisms of action, clinical trials suggest that their co-administration does not confer any additional long-term benefits compared with that achieved with corticosteroids alone. Topical corticosteroids are therefore the preferred anti-inflammatory therapy for persistent allergic rhinitis.

Basic fibroblast growth factor in asthma: measurement in bronchoalveolar lavage fluid basally and following allergen challenge

Airway remodeling in asthma refers to a collection of chronic structural changes including subepithelial fibrosis, airway smooth muscle hypertrophy/hyperplasia, and possibly angiogenesis. The mechanisms leading to remodeling are not well defined. One molecule of possible relevance is basic fibroblast growth factor (bFGF), which is a potent mitogen for fibro-blasts, airway smooth muscle cells, and endothelial cells. To test the hypothesis that bFGF expression is increased in asthma, we measured levels of the growth factor in bronchoalveolar lavage (BAL) fluid. Basally, BAL fluid bFGF concentrations were significantly higher in subjects with atopic asthma than in control subjects without asthma (median 0.22 vs 0.06 pg/mL, P = .003). The effect of acute allergen exposure was examined with a segmental bronchoprovocation model in a separate group of subjects with atopic asthma. Ten minutes after segmental bronchoprovocation there was a 5-fold increase in bFGF levels in BAL fluid recovered from allergen-challenged sites compared with control saline-challenged sites (1.52 vs 0.30 pg/mL, P < .002). We conclude that basal levels of BAL fluid bFGF are increased in atopic asthma and that a further increase occurs in response to acute allergen exposure. These findings lend support to the hypothesis that bFGF is implicated in airway remodeling in asthma.

Invited lecture: activation of the epithelial mesenchymal trophic unit in the pathogenesis of asthma

BACKGROUND

A recent NIH Workshop and an ERS Task Force concluded that more work was needed to understand mechanisms of severe and chronic asthma. This report describes a series of studies that identify aberrant epithelial mesenchymal signalling in the airways as an important event in maintaining inflammation and driving remodelling in response to environmental injury.

METHODS

Immunohistochemistry, genotyping and functional studies conducted on cultured asthmatic cells and mucosal biopsies were used to identify biochemical pathways involved in epithelial injury and repair in asthma and their relationship to disease severity.

RESULTS

Our findings suggest that the asthmatic state results from an interaction between a susceptible epithelium and Th-2-mediated inflammation to alter the communication between the epithelium and the underlying mesenchyme - the epithelial mesenchymal trophic unit - leading to disease persistence, airway remodelling and refractoriness to corticosteroid treatment.

CONCLUSIONS

Asthma is more than an inflammatory disorder, but requires engagement of important signalling pathways involved in epithelial repair and tissue remodelling. These pathways involving EGFRs and TGF-betaRs provide targets against which to develop novel therapies for chronic asthma.

Validation of endobronchial biopsy specimens for nerve quantitation by computer-assisted image analysis

The aim of this study was to assess the validity of endoscopic bronchial biopsy specimens for the quantitation of nerves. To this end, endobronchial biopsy was simulated ex vivo on surgically resected lung specimens and nerve densities were compared in airway smooth muscle of biopsy and surrounding tissue. Specimens were stained immunohistochemically for the general neural marker protein gene product 9.5 (PGP 9.5) and for vasoactive intestinal peptide (VIP), and nerve densities were quantitated using computer-assisted image analysis. Nerve density for total (PGP 9.5-immunoreactive) nerves was slightly higher in biopsies than in corresponding lung tissue, but this difference did not reach statistical significance (p=0.08). There was also no significant difference in the density of VIP-immunoreactive nerves (p=0.60). These findings support the use of endobronchial biopsy specimens to quantitate nerves in asthma and other airway diseases.

Persistent airway T-lymphocyte activation in chronic corticosteroid-treated symptomatic asthma

BACKGROUND

A small proportion of patients with asthma have persistent symptoms despite regular treatment with high-dose inhaled and/or oral corticosteroids. There is little information regarding immunopathology in such patients.

OBJECTIVE

To compare airway inflammatory changes in subjects with chronic corticosteroid-dependent symptomatic asthma (n = 5) and subjects with asthma that was clinically well controlled on inhaled corticosteroid therapy (n = 9). Subjects in the corticosteroid-dependent group were receiving long-term treatment with oral prednisolone and high-dose inhaled corticosteroids.

METHODS

Subjects underwent fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) and bronchial biopsy. T-lymphocytes subsets and activation markers in BAL fluid and peripheral blood were determined by FACS analysis. Bronchial biopsies were stained immunohistochemically, and numbers of inflammatory cells quantitated. Inflammatory mediators in BAL fluid were measured by immunoassay.

RESULTS

There was significantly greater expression of CD25 (P = .02) and HLA-DR (P = .04) by BAL fluid T-lymphocytes in corticosteroid-treated symptomatic asthmatics. In bronchial biopsies there were no significant differences between the two groups in the numbers of AA1+ cells (mast cells), EG2+ cells (eosinophils) or MT1+ T-lymphocytes. Levels of albumin, histamine, tryptase, and eosinophil cationic protein in BAL fluid did not differ significantly between groups.

CONCLUSIONS

Chronic corticosteroid-treated symptomatic asthma is associated with persistent airway T-lymphocyte activation. This, however, is not necessarily accompanied by the recruitment and activation of inflammatory cells within the airways.

Expression of c-erbB receptors and ligands in human nasal epithelium

BACKGROUND

The epidermal growth factor (EGF) family of growth factors plays an important role in maintenance and repair in a variety of epithelial tissues. However, very little is known about coexpression of these factors and their receptors, the c-erbB family of receptor tyrosine kinases, in human nasal epithelium.

OBJECTIVE

We sought to investigate the expression of these molecules in cultured nasal epithelial cells and nasal mucosa from healthy individuals.

METHODS

Identification of c-erbB receptors and their ligands was sought by using reverse transcription PCR, Western blotting, and immunohistochemistry.

RESULTS

Messenger RNA encoding the EGF receptors (EGFR) c-erbB2 and c-erbB3, but not c-erbB4, was detected in primary cultures of human nasal epithelial cells. Transcripts encoding EGF, heparin-binding EGF, transforming growth factor (TGF) alpha, and amphiregulin were also detected. Receptor and ligand expression was confirmed by using immunocytochemical staining of the cells and Western blotting of the cell lysates. Immunohistochemical analysis of tissue sections obtained from biopsy specimens of nasal mucosa revealed intense membrane staining for the EGFR within the respiratory nasal epithelium, which was predominantly localized at the level of the columnar epithelial layers. Similar staining patterns were observed for c-erbB2 and c-erbB3 in the respiratory nasal epithelium. Evidence for EGF, transforming growth factor alpha, heparin-binding EGF, amphiregulin, and betacellulin immunostaining in the nasal epithelium was also obtained; their staining patterns paralleled that of EGFR immunostaining.

CONCLUSION

Colocalization of c-erbB receptors and ligands establishes a basis on which to investigate c-erbB receptor- mediated effects in human nasal epithelium.

The effect of long-acting beta2-agonists on airway inflammation in asthmatic patients

Early observations suggested that the inhibition by long-acting beta2-agonists (LABAs) of non-specific bronchial hyperresponsiveness following allergen challenge was unrelated to bronchodilation or functional antagonism and might be a reflection of anti-inflammatory activity. Investigation of the effect of LABAs on airway inflammatory responses has demonstrated an inhibition of eosinophil recruitment in allergen challenge studies. Nevertheless, results from biopsy and other studies suggest that the chronic inflammatory process in asthma patients is unaffected by these drugs. There is no evidence from biopsy studies that LABAs are pro-inflammatory or that they mask existing inflammation. The beneficial effects of LABAs in allergen challenge are probably mediated through stabilization of mast cells. Recent evidence suggests that LABAs may reduce numbers of neutrophils and their associated markers; this observation needs to be confirmed in future studies and its relevance to the treatment of asthma determined.

Involvement of the epidermal growth factor receptor in epithelial repair in asthma

Epithelial damage and airway remodeling are consistent features of bronchial asthma and are correlated with disease chronicity, severity, and bronchial hyperreactivity. To examine the mechanisms that control bronchial epithelial repair, we investigated expression of the epidermal growth factor receptor (c-erbB1, EGFR) in asthmatic bronchial mucosa and studied repair responses in vitro. In biopsies from asthmatic subjects, areas of epithelial damage were frequently observed and exhibited strong EGFR immunostaining. EGFR expression was also high in morphologically intact asthmatic epithelium. Using image analysis, EGFR immunoreactivity (% of total epithelial area, median (range) was found to increase from 9.4 (4.1-20.4) in normal subjects (n=10) to 18.4 (9.3-28.9) in mild asthmatics (P<0.01, n=13) and 25.4 (15.4-31.8) in severe asthmatics (P<0.00, n=5). Epithelial EGFR immunoreactivity remained elevated in patients treated with corticosteroids and was positively correlated with subepithelial reticular membrane thickening. Using 16HBE 14o- bronchial epithelial cells, we found that EGF accelerated repair of scrape-wounded monolayers and that the EGFR-selective inhibitor, tyrphostin AG1478, inhibited both EGF-stimulated and basal wound closure whereas dexamethasone was without effect. Intrinsic activation of the EGFR was confirmed by analysis of tyrosine phosphorylated proteins, which revealed a rapid, damage-induced phosphorylation of the EGFR, irrespective of the presence of exogenous EGF. To assess the relationship between EGFR-mediated repair and tissue remodeling, release of the profibrogenic mediator TGF-beta2 was also measured. Scrape wounding increased release of TGF-beta2 from epithelial monolayers and EGF had no additional stimulatory effect. However, when repair was retarded with AG1478, the amount of TGF-beta2 increased significantly. These data indicate that the EGFR may play an important role in bronchial epithelial repair in asthma and that impairment of this function may augment airway remodeling.

Localization of interleukin (IL) -4 but not IL-5 to human mast cell secretory granules by immunoelectron microscopy

BACKGROUND

Human mast cells synthesize and secrete many cytokines of relevance to the pathogenesis of allergic diseases such as asthma and rhinitis. In particular, interleukin (IL) -4 and IL-5 are likely to play key roles in the development of the inflammatory response that characterizes these diseases. Immunohistochemical studies on human nasal and bronchial mucosal biopsies suggest that IL-4 and IL-5 may be stored preformed in mast cells.

OBJECTIVE

To identify whether IL-4 and IL-5 are stored within mast cell secretory granules.

METHODS

We used immunogold electron microscopic analysis on bronchial mucosa and lung parenchyma from resected lung specimens, and a nasal mucosal biopsy from a patient with active allergic rhinitis. Samples were fixed in 4% paraformaldehyde plus 0.5% glutaraldehyde and processed into Lowicryl K4M resin by the 'Progressive Lowering of Temperature' technique. Ultrathin sections were stained immunohistochemically by an indirect immunogold method.

RESULTS

Immunoreactivity for IL-4, but not IL-5, was localized to the granules of mast cells in all tissue samples. IL-5 was localized to the matrix of eosinophil granules in these samples, but neither cytokine was detected in T cells. IL-4 immunoreactivity increased in the granules of mast cells 24 h after immunoglobulin (Ig) E-dependent activation (mean 17.5 +/- 1.4 gold particles per granule) compared with nonactivated mast cells (mean 6.8 +/- 0.8 gold particles per granule, P < 0.001), suggesting replenishment of stores by newly generated protein. Immunoreactive IL-5 remained undetectable in mast cells 24 h after activation, a time point at which they are known to secrete large quantities of this cytokine.

CONCLUSION

Human mast cells store IL-4 within the matrix of their granules. Very few, if any, lung or nasal mast cells store IL-5. A store of preformed IL-4 within mast cell granules is likely to have an important influence during the initiation and maintenance of the allergic immunological response.

Effects of short-term exposure to 0.2 ppm ozone on biomarkers of inflammation in sputum, exhaled nitric oxide, and lung function in subjects with mild atopic asthma

To gain further insight into the kinetics of airway inflammatory response and explore the possibility of nitric oxide as a surrogate marker of the lower airway inflammatory response to ozone, nine subjects with mild atopic asthma were exposed to filtered air or 0.2 ppm ozone for 2 hours with intermittent exercise. Lung function was measured at baseline and immediately after exposures. Sputum induction was performed at 6 hours and at 24 hours after exposures, and exhaled nitric oxide levels were measured at baseline, immediately, 6, and 24 hours after both exposures. A significant decline in forced expiratory volume in one second and inspiratory capacity was detectable following exposure to ozone. In addition, a 2-fold increase was observed in the percentage of polymorphonuclear leukocytes 6 hours after exposure to ozone, with no changes in other biomarkers at this time point. By 24 hours after ozone exposure, the neutrophilia had subsided but there was an increase in albumin, total protein, myeloperoxidase, and eosinophil cationic protein. Exhaled nitric oxide levels, histamine, interleukin-8, and growth-related oncogene-alpha in sputum did not change significantly following ozone exposure. It was concluded that short-term ozone exposure induces an acute inflammatory response in asthmatic airways, characterized by early polymorphonuclear leukocyte influx followed by plasma extravasation and activation of eosinophils and neutrophils. Exhaled nitric oxide is not a useful marker for detecting inflammatory response to ozone in persons with mild asthma.