Anthony E. Redington

Exhaled breath condensate pH and exhaled nitric oxide in allergic asthma and in cystic fibrosis

Background: It has been proposed that the pH of airway lining fluid may regulate the fractional exhaled concentration of nitric oxide (FeNO) in respiratory disease. Methods: FeNO, exhaled breath condensate (EBC) pH, and EBC concentrations of nitrite plus nitrate (NO2/NO3) were compared in 12 subjects with stable asthma, 18 with stable cystic fibrosis (CF), and 15 healthy control subjects. Eight of the CF patients were studied on a separate occasion at the start of a pulmonary exacerbation. Results: FeNO was significantly greater in asthmatic subjects than in control subjects (mean 35 v 9 ppb, p<0.001). EBC pH, however, was similar in the asthmatic and control groups (median 5.82 v 6.08, p = 0.23). Levels of NO2/NO3 were on average higher in EBC samples from asthmatic subjects, but the difference was not significant. In patients with stable CF both the FeNO (mean 4 ppb, p<0.001) and EBC pH (median 5.77, p = 0.003) were lower than in the control group. Levels of EBC NO2/NO3 (median 29.9 μM; p = 0.002) in patients with stable CF, in contrast, were significantly higher than in control subjects. During CF exacerbations, EBC pH was further reduced (median 5.30, p = 0.017) but FeNO and NO2/NO3 were unchanged. Conclusions: These findings demonstrate a dissociation between EBC pH and FeNO in inflammatory airways disease.

Dendritic cells in normal and asthmatic airways: expression of the α subunit of the high affinity immunoglobulin E receptor (FcεRI‐α)

Background Immunoglobulin E (IgE) plays an important role in asthma, with total serum IgE levels closely related to both clinical expression of the disease and airway hyperresponsiveness. IgE binds to a high affinity cell‐surface receptor (FcεRI) which is present on mast cells and which has also recently been demonstrated on cutaneous dendritic cells. If pulmonary dendritic cells were also able to express this receptor, this would have important implications with regard to their potential role in asthma.

Cytokine profiles of BAL T cells and T‐cell clones obtained from human asthmatic airways after local allergen challenge

Background: This study assessed the heterogeneity of cytokine expression in asthma before and after local allergen challenge.

Dendritic cells in normal and asthmatic airways: Expression of the alpha subunit of the high affinity immunoglobulin E receptor (FC epsilon RI-alpha)

BACKGROUND Immunoglobulin E (IgE) plays an important role in asthma, with total serum IgE levels closely related to both clinical expression of the disease and airway hyperresponsiveness. IgE binds to a high affinity cell-surface receptor (Fc epsilon RI) which is present on mast cells and which has also recently been demonstrated on cutaneous dendritic cells. If pulmonary dendritic cells were also able to express this receptor, this would have important implications with regard to their potential role in asthma. OBJECTIVES The aims of the study were to investigate the expression of the alpha subunit of the high affinity IgE receptor (Fc epsilon RI-alpha) in normal and asthmatic airways, and to analyse its cellular provenance with particular emphasis on the dendritic cell. METHODS Bronchial biopsy specimens were obtained using fibreoptic bronchoscopy from 10 atopic asthmatics and nine non-atopic non-asthmatic control subjects. Specimens were processed into glycolmethacrylate resin and analysed by immunohistochemistry using specific monoclonal antibodies against Fc epsilon RI-alpha, and against tryptase and CD1a, markers for mast cells and dendritic cells, respectively. RESULTS The numbers of dendritic cells were significantly higher in the airways of asthmatics compared with those of control subjects (P < 0.02). Analysis of sequential sections revealed that the alpha subunit of Fc epsilon RI was localized to both mast cells and dendritic cells. The proportion of dendritic cells expressing Fc epsilon RI-alpha was significantly increased in the asthmatic group (P < 0.003). CONCLUSION These results support the hypothesis that dendritic cells play an important role in allergic asthma although the functional significance of Fc epsilon RI-alpha expression needs further investigation.

15-lipoxygenase immunoreactivity in normal and in asthmatic airways

Products of the 15-lipoxygenase (15-LO) pathway of arachidonic acid metabolism such as the mono- and di-hydroxyeicosatetraenoic acids (HETEs) may contribute to the pathophysiology of allergic airway inflammation through the recruitment and activation of inflammatory cells and stimulation of glandular secretion. In this study we have examined the expression of 15-LO and its cellular localization in the asthmatic and normal bronchial mucosa. Bronchial mucosal biopsies were obtained by fiberoptic bronchoscopy from 10 patients with symptomatic allergic asthma and six normal control subjects and processed into glycolmethacrylate resin. Sections 2 microns thick were immunostained using a specific rabbit polyclonal antihuman 15-LO antibody. Strong immunoreactivity for 15-LO was present throughout the epithelium in both the asthmatic and the normal subjects, with no difference between the two groups. Cells expressing 15-LO immunoreactivity were also present in the submucosa of both groups, with a significantly greater number present in the asthmatic group (median, 15.3 cells/mm2) than in the normal group (median, 6.9 cells/mm2) (p = 0.01). The majority (85%) of the submucosal 15-LO+ cells were eosinophils. Patchy 15-LO immunoreactivity was also seen in the vascular endothelium in both groups. These findings demonstrated increased 15-LO expression in the bronchial submucosa of asthmatic subjects, and they suggest that 15-LO products in asthma originate from both bronchial epithelium and infiltrating eosinophils.

Abnormal oesophageal motility in patients with chronic cough

Background: Although gastro-oesophageal reflux is a recognised cause of chronic cough, the role of oesophageal dysmotility is unknown. The aim of this study was to determine the prevalence of abnormal oesophageal motility in a selected group of patients with chronic cough. Methods: Oesophageal manometry and 24 hour pH monitoring were performed in 43 patients with chronic cough, 34 of whom had symptoms suggestive of gastro-oesophageal reflux. Comparative manometric measurements were made in 21 healthy subjects. Results: Nine patients with chronic cough had normal manometry and 24 hour pH. Of the remaining 34 patients, 11 (32%) had abnormal manometry alone, five (15%) had abnormal 24 hour pH monitoring alone, and in 18 (53%) both tests were abnormal. Only one patient in the control group had manometric abnormalities. Conclusions: These results point to a previously unrecognised high prevalence of abnormal oesophageal manometry in patients presenting with chronic cough. Oesophageal dysmotility may therefore be important in the pathogenesis of cough in these patients.

Immunoreactive endothelin in bronchial biopsy specimens: Increased expression in asthma and modulation by corticosteroid therapy

BACKGROUND The human endothelin (ET) family comprises three 21-amino-acid peptides, which are potent bronchoconstrictors and have a number of other biologic properties relevant to the pathophysiology of asthma. OBJECTIVE We sought to compare the expression of immunoreactive ET in bronchial biopsy specimens from subjects with asthma treated only with inhaled beta2-agonists, subjects with asthma treated with beta2-agonists and corticosteroids, and control subjects without asthma. METHODS Biopsy specimens were obtained by fiberoptic bronchoscopy and stained immunohistochemically with a specific ET antiserum. Epithelial ET expression was quantitated by using a computer-assisted system of image analysis. Numbers of inflammatory cells and depth of subepithelial collagen deposition were also determined. RESULTS Immunoreactive ET was principally localized in the airway epithelium. The proportion of epithelium immunostained was significantly increased in the subjects with asthma not treated with steroids (35.4% +/- 3.8%) compared with that of both the control subjects (16.2% +/- 1.9%, p < 0.0001) and the subjects with asthma treated with steroids (14.3% +/- 2.0%, p < 0.0001). The last two groups did not differ significantly from one another. There were no significant correlations between ET expression and either physiologic parameters or indexes of airway inflammation and remodeling. CONCLUSION Bronchial epithelial expression of immunoreactive ET is increased in subjects with asthma receiving treatment only with beta2-agonists but not in subjects with asthma also receiving corticosteroid therapy. These findings are consistent with the hypothesis that ET is implicated in the pathophysiology of 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.

Epithelially derived endothelin and nitric oxide in asthma.

Immunohistochemical staining of endobronchial biopsies has identified increased expression of the 21-amino-acid peptide endothelin (ET) and the inducible form of the enzyme nitric oxide synthase (iNOS) within the airway epithelium in asthma. Elevated concentrations of ET are also recovered in bronchoalveolar lavage fluid from asthma patients. iNOS generates the gas nitric oxide from L-arginine, and elevated levels of NO in exhaled air have been described in asthma. ET is a potent bronchoconstrictor and levels of ET in lavage and resting airflow obstruction are correlated. The effects of ET on bronchomotor tone may be modified by NO as this is a bronchodilator. The relative balance between ET and NOS may thus contribute to resting bronchomotor tone. ET also stimulates fibroblast proliferation, collagen gene expression and through its inhibitory actions on collagenase will promote airway wall collagen deposition and contributes to airway wall thickening which underlies bronchial hyperresponsiveness. The regulation of these epithelial events may thus be important to the control of asthma.

Cytokines and Airway Inflammation

Cytokines are low-molecular-weight glycoproteins released by one cell and active either on themselves (autocrine) or on another cell population (paracrine) to modify cell function. They thus mediate communication both between cells of the immune system and between these cells and noninflammatory structural cells. Cytokines were originally described on the basis of their functional activity, but are now classified into a variety of families. the numerical positioning in the families reflecting their order ofdiscovery. The increasing identification ofcytokine genes and gene clusters along with the realization that cytokines often have multiple biological actions has. however. questioned the rationale of these present classifications. The interleukins are numbered 1 to 13. with the recently identified interleukin-I3 (IL-13)’ genetically encoded for chromosome Sq clustered with the genes for IL-3, IL-4. IL-S, and granulocyte-macrophage colony stimulating factor.’ all cytokines relevant to allergic airways inflammation. The interferons (IFNs) and tumor necrosis factors (TNFs) are similar to the interleukins but are classified separately. as are the chernokines, an expanding family of recently discovered small molecular-weight cytokines. such as regulated and normal T-lymphocytes expressed and secreted (RANTES). which share many properties. Colony stimulating factors act on immature haemopoietic cells to enhance growth while also exerting proliferative actions on mature cell populations and possessing interleu kinli ke activity . While the discovery of cytokines that regulate cell function relevant to airway inflammation, and thus clinical disease expression. generated the hope that modification of a single cytokine might provide global control of the disease process, it is now appreciated that cytokines exhibit both pleotropy and multiplicity of actions and that differing cytokines interact both synergistically and antagonistically. There is thus redundancy in the system and the net effect at any one time will depend upon the local balance of cytokine expression. This is evident with the regulation of IgE production by B-cells. Although the initiation of B-cell IgE synthesis is dependent upon IL-4, it is also enhanced by 1L-5, IL-6, and 1L-13, whereas the actions of these cytokines are opposed by interferon (IFN)y, IL-8. and IL-I2.’.’-’The relative regulation of B-cells by these cytokines at any one time determines the net balance between activation or repression of gene expression for IgE mRNA.