Peter Bradding

Bidirectional Counterregulation of Human Lung Mast Cell and Airway Smooth Muscle β2 Adrenoceptors

Human lung mast cells (HLMCs) play a central role in asthma pathogenesis through their relocation to the airway smooth muscle (ASM) bundles. β2 adrenoceptor (β2-AR)-agonists are used to relieve bronchoconstriction in asthma, but may reduce asthma control, particularly when used as monotherapy. We hypothesized that HLMC and human ASM cell (HASMC) responsiveness to β2-AR agonists would be attenuated when HLMCs are in contact with HASMCs. Cells were cultured in the presence of the short-acting β2-agonist albuterol, and the long-acting β2-agonists formoterol and olodaterol. Constitutive and FcεRI-dependent HLMC histamine release, HASMC contraction, and β2-AR phosphorylation at Tyr350 were assessed. Constitutive HLMC histamine release was increased in HLMC–HASMC coculture and this was enhanced by β2-AR agonists. Inhibition of FcεRI-dependent HLMC mediator release by β2-agonists was greatly reduced in HLMC–HASMC coculture. These effects were reversed by neutralization of stem cell factor (SCF) or cell adhesion molecule 1 (CADM1). β2-AR agonists did not prevent HASMC contraction when HLMCs were present, but this was reversed by fluticasone. β2-AR phosphorylation at Tyr350 occurred within 5 min in both HLMCs and HASMCs when the cells were cocultured, and was inhibited by neutralizing SCF or CADM1. HLMC interactions with HASMCs via CADM1 and Kit inhibit the potentially beneficial effects of β2-AR agonists on these cells via phosphorylation of the β2-AR. These results may explain the potentially adverse effects of β2-ARs agonists when used for asthma therapy. Targeting SCF and CADM1 may enhance β2-AR efficacy, particularly in corticosteroid-resistant patients.

The relationship between biomarkers of fungal allergy and lung damage in asthma.

Immunological biomarkers are the key to the diagnosis of allergic bronchopulmonary aspergillosis (ABPA) and fungal sensitisation, but how these relate to clinically relevant outcomes is unclear.

Body Mass and Fat Mass in Refractory Asthma: An Observational 1 Year Follow-Up Study

Background. Asthma and obesity are common; however the impact of obesity upon asthma remains uncertain. Objectives. To assess relationships between obesity and fat mass with airway inflammation, lung function, and disease control in patients with refractory asthma. Methods. 151 refractory asthma patients were characterised for measures of airway inflammation, lung function, Juniper asthma control questionnaire (JACQ), body mass index (BMI), and fat mass index (FMI) derived from dual energy X-ray absorptiometry. Patients were reassessed over 12 months. Results. 74% of patients had an elevated BMI. BMI and FMI correlated (r = 0.9, P < .001). FMI and JACQ correlated in men (r = 0.3, P = .01). After 12 months 23% lost weight. Weight change over 12 months correlated with FEV1 change (r = −0.3, P = .03), but not with change in JACQ or exacerbations. Conclusion. Increased fat mass is common in refractory asthma and is associated with asthma symptom control in men. Loss of weight is associated with improvement in lung function in refractory asthma.

CD48 on blood leukocytes and in serum of asthma patients varies with severity

CD48 is a membrane receptor (mCD48) on eosinophils and mast cells and exists in a soluble form (sCD48). CD48 has a pivotal role in murine asthma and in the proinflammatory interactions of mast cells with eosinophils via its ligand CD244. Thus, CD48 might be important in human asthma.

A CEACAM6-High Airway Neutrophil Phenotype and CEACAM6-High Epithelial Cells Are Features of Severe Asthma

Severe asthma represents a major unmet clinical need; understanding the pathophysiology is essential for the development of new therapies. Using microarray analysis, we previously found three immunological clusters in asthma: Th2-high, Th17-high, and Th2/17-low. Although new therapies are emerging for Th2-high disease, identifying molecular pathways in Th2-low disease remains an important goal. Further interrogation of our previously described microarray dataset revealed upregulation of gene expression for carcinoembryonic Ag cell adhesion molecule (CEACAM) family members in the bronchi of patients with severe asthma. Our aim was therefore to explore the distribution and cellular localization of CEACAM6 using immunohistochemistry on bronchial biopsy tissue obtained from patients with mild-to-severe asthma and healthy control subjects. Human bronchial epithelial cells were used to investigate cytokine and corticosteroid in vitro regulation of CEACAM6 gene expression. CEACAM6 protein expression in bronchial biopsies was increased in airway epithelial cells and lamina propria inflammatory cells in severe asthma compared with healthy control subjects. CEACAM6 in the lamina propria was localized to neutrophils predominantly. Neutrophil density in the bronchial mucosa was similar across health and the spectrum of asthma severity, but the percentage of neutrophils expressing CEACAM6 was significantly increased in severe asthma, suggesting the presence of an altered neutrophil phenotype. CEACAM6 gene expression in cultured epithelial cells was upregulated by wounding and neutrophil elastase. In summary, CEACAM6 expression is increased in severe asthma and primarily associated with airway epithelial cells and tissue neutrophils. CEACAM6 may contribute to the pathology of treatment-resistant asthma via neutrophil and airway epithelial cell–dependent pathways.

Associations in asthma between quantitative computed tomography and bronchial biopsy-derived airway remodelling

Airway remodelling in asthma remains poorly understood. This study aimed to determine the association of airway remodelling measured on bronchial biopsies with 1) lung function impairment and 2) thoracic quantitative computed tomography (QCT)-derived morphometry and densitometry measures of proximal airway remodelling and air trapping. Subjects were recruited from a single centre. Bronchial biopsy remodelling features that were the strongest predictors of lung function impairment and QCT-derived proximal airway morphometry and air trapping markers were determined by stepwise multiple regression. The best predictor of air trapping was validated in an independent replication group. Airway smooth muscle % was the only predictor of post-bronchodilator forced expiratory volume in 1u2005s (FEV1) % pred, while both airway smooth muscle % and vascularity were predictors of FEV1/forced vital capacity. Epithelial thickness and airway smooth muscle % were predictors of mean segmental bronchial luminal area (R2=0.12; p=0.02 and R2=0.12; p=0.015), whereas epithelial thickness was the only predictor of wall area % (R2=0.13; p=0.018). Vascularity was the only significant predictor of air trapping (R2=0.24; p=0.001), which was validated in the replication group (R2=0.19; p=0.031). In asthma, airway smooth muscle content and vascularity were both associated with airflow obstruction. QCT-derived proximal airway morphometry was most strongly associated with epithelial thickness and airway smooth muscle content, whereas air trapping was related to vascularity. Airway remodelling in asthma biopsies is associated with proximal airway QCT-derived morphometry and air trapping http://ow.ly/ucoA308Jv9F

MUC5AC and a Glycosylated Variant of MUC5B Alter Mucin Composition in Children With Acute Asthma

BACKGROUND: Diffuse airway mucus obstruction is an important feature of severe and fatal asthma. MUC5AC and MUC5B are the principal gel‐forming mucins found in airway mucus. The mucin composition of airway mucus likely affects its functional properties. METHODS: We quantified the principal airway mucins MUC5AC and MUC5B in the sputum of age‐matched children with acute and stable asthma and healthy control subjects by using Western blotting. RESULTS: Sputum samples from 38 children (13 with acute asthma, 15 with stable asthma, 10 control subjects) were obtained. Sputum MUC5AC concentrations were 7.6 &mgr;g/mL in control subjects, 22.4 &mgr;g/mL in those with stable asthma (P = .17), and 44.7 &mgr;g/mL in those with acute asthma (P < .05). MUC5B concentrations showed less variation, with 238.5, 208.4 and 165.9 &mgr;g/mL in control subjects, those with stable asthma, and those with acute asthma, respectively. The greater MUC5AC concentration in those with acute asthma resulted in a significantly altered MUC5B:MUC5AC ratio between control subjects and those with acute asthma (P < .05). Significant differences in MUC5B glycoforms were present between the groups, with the low‐charge‐only glycoform being found uniquely in those with acute asthma. CONCLUSIONS: Increased MUC5AC and the presence of a low‐charge‐only MUC5B glycoform significantly altered mucin composition in children with acute asthma. These changes may be important contributory factors to the airway mucus obstruction observed during acute asthma.

A model of human lung fibrogenesis for the assessment of anti-fibrotic strategies in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease with limited therapeutic options. KCa3.1 ion channels play a critical role in TGFβ1-dependent pro-fibrotic responses in human lung myofibroblasts. We aimed to develop a human lung parenchymal model of fibrogenesis and test the efficacy of the selective KCa3.1 blocker senicapoc. 2u2009mm3 pieces of human lung parenchyma were cultured for 7u2009days in DMEMu2009±u2009TGFβ1 (10u2009ng/ml) and pro-fibrotic pathways examined by RT-PCR, immunohistochemistry and collagen secretion. Following 7 days of culture with TGFβ1, 41 IPF- and fibrosis-associated genes were significantly upregulated. Immunohistochemical staining demonstrated increased expression of ECM proteins and fibroblast-specific protein after TGFβ1-stimulation. Collagen secretion was significantly increased following TGFβ1-stimulation. These pro-fibrotic responses were attenuated by senicapoc, but not by dexamethasone. This 7 day ex vivo model of human lung fibrogenesis recapitulates pro-fibrotic events evident in IPF and is sensitive to KCa3.1 channel inhibition. By maintaining the complex cell-cell and cell-matrix interactions of human tissue, and removing cross-species heterogeneity, this model may better predict drug efficacy in clinical trials and accelerate drug development in IPF. KCa3.1 channels are a promising target for the treatment of IPF.

The relationship between the Leicester cough questionnaire, eosinophilic airway inflammation and asthma patient related outcomes in severe adult asthma

BackgroundSevere asthma is characterised by a variety of symptoms, which include chronic cough, however the mechanisms responsible for cough reflex hypersensitivity in asthma remain poorly elucidated. Current asthma patient-related outcome instruments such as the six-point Juniper Asthma Control Score (ACQ-6) and Asthma Quality of Life Questionnaire (AQLQ) were not primarily designed to capture cough and its related morbidity in asthma. The Leicester Cough Questionnaire (LCQ) is a patient-related outcome instrument designed to capture the health-related quality of life associated with cough. To date the LCQ has not been evaluated in a severe asthma population.MethodsWe evaluated 262 extensively characterised adult patients with severe asthma attending the Leicester Severe Asthma Service. All patients had a clinician diagnosis of asthma and objective physiological evidence and met the ATS/ERS criterion for servere asthma. In all patients we evaluated a) the LCQ distribution and b) the relationships between the LCQ and ACQ-6, AQLQ, airway inflammation in sputum.ResultsThe LCQ demonstrated the following properties; mean: 15.0, standard deviation: 4.54, median: 15.48, and range: 11.6–19.2. We found a moderate correlation between LCQ and ACQ-6 (ru2009=u2009− 0.605, pu2009<u20090.0001) and a LCQ and AQLQ (ru2009=u20090.710, pu2009<u20090.0001). There was no relationship between LCQ and log10 sputum percentage eosinophils (%).ConclusionA proportion of patients with severe asthma have a significant degree of cough-related morbidity that appears independent of eosinophilic airway inflammation and is not captured fully by existing asthma patient-reported outcome instruments. Our preliminary findings suggest that further research is now required to validate the LCQ and its responsiveness in severe asthma populations to capture cough-related morbidity and response to specific interventions.

The role of oral methotrexate as a steroid sparing agent in refractory eosinophilic asthma.

The use of oral methotrexate for refractory eosinophilic asthma in a tertiary asthma referral centre, Glenfield Hospital, Leicester, was evaluated between January 2006 and December 2014. The patients (n = 61) were carefully phenotyped at baseline with markers of airway inflammation. In addition, a structured oral methotrexate proforma was utilized to evaluate response to therapy and adverse events. Oral steroid withdrawal was attempted 3 months after commencing treatment. Several outcomes were evaluated at 12 months, including both efficacy and adverse effects; 15% (n = 9/61) responded by achieving a decrease in daily oral corticosteroid dose (mean 8.43 (±8.76) mg), although we were unable to identify factors that predicted a treatment response. There were no other significant changes in any other clinical outcome measures. There was a high rate of adverse events (19/61 (31%)), primarily gastrointestinal/hepatitis. Our findings support the use of biological agents in preference to using oral methotrexate as a steroid sparing agent at the first instance. In the event of failure of these agents, oral methotrexate remains a therapeutic option, which can be considered in highly specialist severe asthma centres.