Showing papers by "Donna E. Davies published in 2011"

Defective epithelial barrier function in asthma.

Abstract: Background Asthma is a complex disease involving gene and environment interactions. Although atopy is a strong predisposing risk factor for asthma, local tissue susceptibilities are required for disease expression. The bronchial epithelium forms the interface with the external environment and is pivotally involved in controlling tissue homeostasis through provision of a physical barrier controlled by tight junction (TJ) complexes. Objectives To explain the link between environment exposures and airway vulnerability, we hypothesized that epithelial TJs are abnormal in asthma, leading to increased susceptibility to environmental agents. Methods Localization of TJs in bronchial biopsies and differentiated epithelial cultures was assessed by electron microscopy or immunostaining. Baseline permeability and the effect of cigarette smoke and growth factor were assessed by measurement of transepithelial electrical resistance and passage of fluorescently labeled dextrans. Results By using immunostaining, we found that bronchial biopsies from asthmatic subjects displayed patchy disruption of TJs. In differentiated bronchial epithelial cultures, TJ formation and transepithelial electrical resistance were significantly lower ( P P P Conclusions Our results show that the bronchial epithelial barrier in asthma is compromised. This defect may facilitate the passage of allergens and other agents into the airway tissue, leading to immune activation and may thus contribute to the end organ expression of asthma.

Effect of Bronchoconstriction on Airway Remodeling in Asthma

Abstract: Background Asthma is characterized pathologically by structural changes in the airway, termed airway remodeling. These changes are associated with worse long-term clinical outcomes and have been attributed to eosinophilic inflammation. In vitro studies indicate, however, that the compressive mechanical forces that arise during bronchoconstriction may induce remodeling independently of inflammation. We evaluated the influence of repeated experimentally induced bronchoconstriction on airway structural changes in patients with asthma. Methods We randomly assigned 48 subjects with asthma to one of four inhalation challenge protocols involving a series of three challenges with one type of inhaled agent presented at 48-hour intervals. The two active challenges were with either a dust-mite allergen (which causes bronchoconstriction and eosinophilic inflammation) or methacholine (which causes bronchoconstriction without eosinophilic inflammation); the two control challenges (neither of which causes bronchoconstri...

Exogenous IFN-β has antiviral and anti-inflammatory properties in primary bronchial epithelial cells from asthmatic subjects exposed to rhinovirus

Abstract: Background Rhinoviruses are the major cause of asthma exacerbations. Previous studies suggest that primary bronchial epithelial cells (PBECs) from asthmatic subjects are more susceptible to rhinovirus infection because of deficient IFN-β production. Although augmenting the innate immune response might provide a novel approach for treatment of virus-induced asthma exacerbations, the potential of IFN-β to modulate antiviral and proinflammatory responses in asthmatic epithelium is poorly characterized. Objectives We sought to compare responses of PBECs from nonasthmatic and asthmatic subjects to exogenous IFN-β and test the inflammatory effects of IFN-β in response to rhinovirus infection. Methods PBECs were treated with IFN-β and infected with a low inoculum of human rhinovirus serotype 1B to simulate a natural viral infection. Expression of interferon-responsive genes and inflammatory responses were analyzed by using reverse transcription–quantitative real-time PCR, cytometric bead arrays, or both; viral titers were assessed by using the 50% tissue culture infection dose. Results Expression of IFN-β–stimulated antiviral genes was comparable in PBECs from nonasthmatic or asthmatic donors. Exogenous IFN-β significantly protected PBECs from asthmatic donors against rhinovirus infection by suppressing viral replication. Interferon-inducible protein 10 (IP-10), RANTES, and IL-6 release in response to rhinovirus infection was triggered only in PBECs from asthmatic donors. Although exogenous IFN-β alone stimulated some release of IP-10 (but not IL-6 or RANTES), it significantly reduced rhinovirus-induced IP-10, RANTES, and IL-6 expression when tested in combination with rhinovirus. Conclusions PBECs from asthmatic donors have a normal antiviral response to exogenous IFN-β. The ability of IFN-β to suppress viral replication suggests that it might limit virus-induced exacerbations by shortening the duration of the inflammatory response.

Airway Epithelial Transcription Factor NK2 Homeobox 1 Inhibits Mucous Cell Metaplasia and Th2 Inflammation

Abstract: Rationale: Airway mucous cell metaplasia and chronic inflammation are pathophysiological features that influence morbidity and mortality associated with asthma and other chronic pulmonary disorders. Elucidation of the molecular mechanisms regulating mucous metaplasia and hypersecretion provides the scientific basis for diagnostic and therapeutic opportunities to improve the care of chronic pulmonary diseases.Objectives: To determine the role of the airway epithelial–specific transcription factor NK2 homeobox 1 (NKX2-1, also known as thyroid transcription factor-1 [TTF-1]) in mucous cell metaplasia and lung inflammation.Methods: Expression of NKX2-1 in airway epithelial cells from patients with asthma was analyzed. NKX2-1+/− gene targeted or transgenic mice expressing NKX2-1 in conducting airway epithelial cells were sensitized to the aeroallergen ovalbumin. In vitro studies were used to identify mechanisms by which NKX2-1 regulates mucous cell metaplasia and inflammation.Measurements and Main Results: NKX...

Sputum IL-6 concentrations in severe asthma and its relationship with FEV1

Abstract: As asthma becomes more severe it adopts additional characteristics including corticosteroid refractoriness and a neutrophil-predominant inflammatory response implicating Th1 or Th17 responses involving cytokines such as tumour necrosis factor α, interleukin (IL)-6 and IL-8. We have examined the role of IL-6 and IL-8 in severe asthma. Subjects with severe asthma (GINA stage IV) who were exacerbation-free for ≥4 weeks with a forced expiratory volume in 1 s (FEV1) >30% but <80% predicted were studied from the baseline parameters of a clinical trial.1 Cell counts and cytokines were measured in induced sputum (see online supplement for Methods). Eighteen subjects (9M, 9F) with severe asthma (mean±SD age 43.4±11.4 years (1SD), FEV1 59±14% predicted) were studied (see table 1 in online appendix). The median (IQR) levels of sputum IL-8, IL-6, neutrophils (%), macrophages (%) and eosinophils (%) were 1853.8 pg/ml (1376.8–2537.7), 70.0 pg/ml (28.55–127.5), 32.5% (24.1–42.6), 46.8% (39.8–54.8) and 4.4% (3.2–9.4), respectively. We observed significant negative correlations between FEV1 …

Iconographies supplémentaires de l'article : Differential roles of IL-16 and CD28/B7 costimulation in the generation of T-lymphocyte chemotactic activity in the bronchial mucosa of mild and moderate asthmatic individuals

Abstract: BACKGROUND IL-16 is an important T-cell chemotactic cytokine in asthmatic airways; its release from allergen-stimulated bronchial mucosa in mild asthma has been shown to be dependent on CD28/B7 costimulation. OBJECTIVE We have extended our previous studies to investigate the role of IL-16 and CD28/B7 costimulation in T-lymphocyte chemotactic activity (TLCA) released from the bronchial mucosa in more severe asthma. METHODS TLCA was determined in the supernatants of induced sputum and allergen-stimulated bronchial mucosal explants from healthy volunteers and volunteers with mild and moderately severe asthma by means of a Boyden chamber technique. The contribution of IL-16 to the activity was evaluated through use of a neutralizing monoclonal antibody; the contribution of CD28/B7 costimulation to allergen-induced release of TLCA was determined through use of CTLA4-Ig fusion protein and neutralizing monoclonal antibodies to CD80 (B7.1) and CD86 (B7.2). RESULTS Induced sputum and unstimulated explants from asthmatic subjects generated significant spontaneous TLCA (P <.05). Both mild and moderate asthmatic explants showed significantly elevated Dermatophagoides pteronyssinus -induced release of TLCA, but only in mild asthma could sputum and allergen-stimulated explant TLCA be inhibited by anti-IL-16 (median inhibition, 39% and 59%; P <.05). In addition, allergen released significant quantities of IL-16 from mild asthmatic explants (P <.05) but not from moderate asthmatic explants. Antibodies to the CD28 counter-ligands CD80 and CD86 inhibited allergen-induced release of TLCA in mild asthmatic explants by 94% (P <.05) and 62%, but TLCA release from moderate asthmatic explants was unaffected by CTLA4-Ig. CONCLUSION These results show that TLCA release in moderate asthmatic airways, in contrast to mild asthmatic airways, is not dependent on CD28/B7 costimulation and does not involve IL-16.

Artificial airways for the study of respiratory disease

Abstract: This review will focus on human cell-based experimental models to study respiratory diseases, in particular models of the large airways relevant to asthma and chronic obstructive pulmonary disease. Such models have the advantage of incorporating cells that can be derived from disease-relevant tissue and so have retained important genetic and epigenetic features that contribute to the human disease. These models can be used for mechanistic studies, target identification and validation and toxicological testing. While many models have been developed to varying degrees of sophistication, the challenge remains to develop an integrated system that recapitulates the complex cell-cell and cell-matrix interactions that occur in vivo and to provide these with a 'circulation' to study the dynamics of immune and inflammatory cell influx and efflux.

A panel of antibodies for identifying squamous metaplasia in endobronchial biopsies from smokers

Abstract: Toxic injury can induce squamous metaplasia of respiratory epithelium, which normally is pseudostratified. Terminally differentiated squamous epithelial cells have a flattened, elongated appearance. During differentiation, they have an intermediate phenotype that is difficult to identify and distinguish from tangentially cut columnar cells in tissue sections from endobronchial biopsies, whose small size makes orientation difficult. The aim of our study was to develop a panel of antibodies that could be employed to distinguish normal epithelium from metaplastic epithelium and would be suitable for use on endobronchial biopsies. Nasal polyp tissue and tonsil tissue, which have pseudostratified and squamous epithelia, respectively, were collected from surgical cases and embedded in glycol methacrylate resin. Cut sections were stained immunohistochemically with a panel of antibodies to cytokeratins (CK), whose expression varies with epithelial type and stage of differentiation, and involucrin, a marker of terminal squamous differentiation. Squamous epithelium stained positively for CK5/6, CK13 and involucrin. In the pseudostratified epithelium, basal cells exhibited weak staining for CK13 and strong staining for CK5/6, and columnar cells exhibited strong immunoreactivity for CK7, CK8 and CK18. Application of this panel to endobronchial biopsies from smokers enabled areas of squamous metaplasia to be distinguished from tangentially sectioned epithelium.