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1.  Increased Nicotinamide Adenine Dinucleotide Phosphate Oxidase 4 Expression Mediates Intrinsic Airway Smooth Muscle Hypercontractility in Asthma 
Rationale: Asthma is characterized by disordered airway physiology as a consequence of increased airway smooth muscle contractility. The underlying cause of this hypercontractility is poorly understood.
Objectives: We sought to investigate whether the burden of oxidative stress in airway smooth muscle in asthma is heightened and mediated by an intrinsic abnormality promoting hypercontractility.
Methods: We examined the oxidative stress burden of airway smooth muscle in bronchial biopsies and primary cells from subjects with asthma and healthy controls. We determined the expression of targets implicated in the control of oxidative stress in airway smooth muscle and their role in contractility.
Measurements and Main Results: We found that the oxidative stress burden in the airway smooth muscle in individuals with asthma is heightened and related to the degree of airflow obstruction and airway hyperresponsiveness. This was independent of the asthmatic environment as in vitro primary airway smooth muscle from individuals with asthma compared with healthy controls demonstrated increased oxidative stress–induced DNA damage together with an increased production of reactive oxygen species. Genome-wide microarray of primary airway smooth muscle identified increased messenger RNA expression in asthma of NADPH oxidase (NOX) subtype 4. This NOX4 overexpression in asthma was supported by quantitative polymerase chain reaction, confirmed at the protein level. Airway smooth muscle from individuals with asthma exhibited increased agonist-induced contraction. This was abrogated by NOX4 small interfering RNA knockdown and the pharmacological inhibitors diphenyleneiodonium and apocynin.
Conclusions: Our findings support a critical role for NOX4 overexpression in asthma in the promotion of oxidative stress and consequent airway smooth muscle hypercontractility. This implicates NOX4 as a potential novel target for asthma therapy.
doi:10.1164/rccm.201107-1281OC
PMCID: PMC3402550  PMID: 22108207
asthma; airway smooth muscle; airway hyperresponsiveness; NOX4; SOD2
2.  Clinical management and outcome of refractory asthma in the UK from the British Thoracic Society Difficult Asthma Registry 
Thorax  2012;67(8):754-756.
Refractory asthma represents a significant unmet clinical need. Data from a national online registry audited clinical outcome in 349 adults with refractory asthma from four UK specialist centres in the British Thoracic Society Difficult Asthma Network. At follow-up, lung function improved, with a reduction in important healthcare outcomes, specifically hospital admission, unscheduled healthcare visits and rescue courses of oral steroids. The most frequent therapeutic intervention was maintenance oral corticosteroids and most steroid sparing agents (apart from omalizumab) demonstrated minimal steroid sparing benefit. A significant unmet clinical need remains in this group, specifically a requirement for therapies which reduce systemic steroid exposure.
doi:10.1136/thoraxjnl-2012-201869
PMCID: PMC3402747  PMID: 22581823
Refractory asthma; national registry; clinical assessment and outcome; asthma phenotypes; asthma; asthma epidemiology; asthma guidelines; allergic lung disease; eosinophil biology; occupational lung disease; airway epithelium; asthma mechanisms; asthma pharmacology; COPD epidemiology; COPD exacerbations
3.  Functional KCa3.1 K+ channels are required for human fibrocyte migration 
Background
Fibrocytes are bone marrow–derived CD34+ collagen I–positive cells present in peripheral blood that develop α-smooth muscle actin expression and contractile activity in tissue culture. They are implicated in the pathogenesis of tissue remodeling and fibrosis in both patients with asthma and those with idiopathic pulmonary fibrosis. Targeting fibrocyte migration might therefore offer a new approach for the treatment of these diseases. Ion channels play key roles in cell function, but the ion-channel repertoire of human fibrocytes is unknown.
Objective
We sought to examine whether human fibrocytes express the KCa3.1 K+ channel and to determine its role in cell differentiation, survival, and migration.
Methods
Fibrocytes were cultured from the peripheral blood of healthy subjects and patients with asthma. Whole-cell patch-clamp electrophysiology was used for the measurement of ion currents, whereas mRNA and protein were examined to confirm channel expression. Fibrocyte migration and proliferation assays were performed in the presence of KCa3.1 ion-channel blockers.
Results
Human fibrocytes cultured from the peripheral blood of both healthy control subjects and asthmatic patients expressed robust KCa3.1 ion currents together with KCa3.1 mRNA and protein. Two specific and distinct KCa3.1 blockers (TRAM-34 and ICA-17043) markedly inhibited fibrocyte migration in transwell migration assays. Channel blockers had no effect on fibrocyte growth, apoptosis, or differentiation in cell culture.
Conclusions
The K+ channel KCa3.1 plays a key role in human fibrocyte migration. Currently available KCa3.1-channel blockers might therefore attenuate tissue fibrosis and remodeling in patients with diseases such as idiopathic pulmonary fibrosis and asthma through the inhibition of fibrocyte recruitment.
doi:10.1016/j.jaci.2011.07.047
PMCID: PMC3526791  PMID: 21872912
Pulmonary fibrosis; asthma; fibrocyte; cell migration; ion channel; KCa3.1; patch clamp electrophysiology; 1-EBIO, 1-Ethyl-2-benzimidazolinone; αSMA, α-Smooth muscle actin; ASM, Airway smooth muscle; IPF, Idiopathic pulmonary fibrosis; Kd, Concentration producing 50% block
4.  Chromosome 17q21 SNP and Severe Asthma 
Journal of human genetics  2010;56(1):97-98.
doi:10.1038/jhg.2010.134
PMCID: PMC3027598  PMID: 20981039
severe asthma; 17q21; ORMDL3
5.  Refractory asthma in the UK: cross-sectional findings from a UK multicentre registry 
Thorax  2010;65(9):787-794.
Introduction
Refractory asthma represents a significant unmet clinical need where the evidence base for the assessment and therapeutic management is limited. The British Thoracic Society (BTS) Difficult Asthma Network has established an online National Registry to standardise specialist UK difficult asthma services and to facilitate research into the assessment and clinical management of difficult asthma.
Methods
Data from 382 well characterised patients, who fulfilled the American Thoracic Society definition for refractory asthma attending four specialist UK centres—Royal Brompton Hospital, London, Glenfield Hospital, Leicester, University Hospital of South Manchester and Belfast City Hospital—were used to compare patient demographics, disease characteristics and healthcare utilisation.
Results
Many demographic variables including gender, ethnicity and smoking prevalence were similar in UK centres and consistent with other published cohorts of refractory asthma. However, multiple demographic factors such as employment, family history, atopy prevalence, lung function, rates of hospital admission/unscheduled healthcare visits and medication usage were different from published data and significantly different between UK centres. General linear modelling with unscheduled healthcare visits, rescue oral steroids and hospital admissions as dependent variables all identified a significant association with clinical centre; different associations were identified when centre was not included as a factor.
Conclusion
Whilst there are similarities in UK patients with refractory asthma consistent with other comparable published cohorts, there are also differences, which may reflect different patient populations. These differences in important population characteristics were also identified within different UK specialist centres. Pooling multicentre data on subjects with refractory asthma may miss important differences and potentially confound attempts to phenotype this population.
doi:10.1136/thx.2010.137414
PMCID: PMC2975949  PMID: 20805172
Refractory asthma; National registry; clinical assessment; asthma phenotypes; asthma epidemiology; asthma
6.  Engagement of the EP2 prostanoid receptor closes the K+ channel KCa3.1 in human lung mast cells and attenuates their migration 
European Journal of Immunology  2008;38(9):2548-2556.
Human lung mast cells (HLMC) express the Ca2+-activated K+ channel KCa3.1, which plays a crucial role in their migration to a variety of diverse chemotactic stimuli. KCa3.1 activation is attenuated by the β2-adrenoceptor and the adenosine A2A receptor through a Gs-coupled mechanism independent of cyclic AMP. Prostaglandin E2 promotes degranulation and migration of mouse bone marrow-derived mast cells through the Gi-coupled EP3 prostanoid receptor, and induces LTC4 and cytokine secretion from human cord blood-derived mast cells. However, PGE2 binding to the Gs-coupled EP2 receptor on HLMC inhibits their degranulation. We show that EP2 receptor engagement closes KCa3.1 in HLMC. The EP2 receptor-specific agonist butaprost was more potent than PGE2 in this respect, and the effects of both agonists were reversed by the EP2 receptor antagonist AH6809. Butaprost markedly inhibited HLMC migration induced by chemokine-rich airway smooth muscle-conditioned media. Interestingly, PGE2 alone was chemotactic for HLMC at high concentrations (1 µM), but was a more potent chemoattractant for HLMC following EP2 receptor blockade. Therefore, the Gs-coupled EP2 receptor closes KCa3.1 in HLMC and attenuates both chemokine- and PGE2-dependent HLMC migration. EP2 receptor agonists with KCa3.1 modulating function may be useful for the treatment of mast cell-mediated disease.
doi:10.1002/eji.200738106
PMCID: PMC2699428  PMID: 18792407
Chemotaxis; Ion channel; KCa3.1; Mast cell; Prostaglandin E2

Results 1-6 (6)