Dw Reid

Airway inflammation, basement membrane thickening and bronchial hyperresponsiveness in asthma

Background: There are few data in asthma relating airway physiology, inflammation and remodelling and the relative effects of inhaled corticosteroid (ICS) treatment on these parameters. A study of the relationships between spirometric indices, airway inflammation, airway remodelling, and bronchial hyperreactivity (BHR) before and after treatment with high dose inhaled fluticasone propionate (FP 750 μg bd) was performed in a group of patients with relatively mild but symptomatic asthma. Methods: A double blind, randomised, placebo controlled, parallel group study of inhaled FP was performed in 35 asthmatic patients. Bronchoalveolar lavage (BAL) and airway biopsy studies were carried out at baseline and after 3 and 12 months of treatment. Twenty two normal healthy non-asthmatic subjects acted as controls. Results: BAL fluid eosinophils, mast cells, and epithelial cells were significantly higher in asthmatic patients than in controls at baseline (p<0.01). Subepithelial reticular basement membrane (rbm) thickness was variable, but overall was increased in asthmatic patients compared with controls (p<0.01). Multiple regression analysis explained 40% of the variability in BHR, 21% related to rbm thickness, 11% to BAL epithelial cells, and 8% to BAL eosinophils. The longitudinal data corroborated the cross sectional model. Forced expiratory volume in 1 second improved after 3 months of treatment with FP with no further improvement at 12 months. PD20 improved throughout the study. BAL inflammatory cells decreased following 3 months of treatment with no further improvement at 12 months (p<0.05 v placebo). Rbm thickness decreased in the FP group, but only after 12 months of treatment (mean change –1.9, 95% CI –3 to –0.7 μm; p<0.01 v baseline, p<0.05 v placebo). A third of the improvement in BHR with FP was associated with early changes in inflammation, but the more progressive and larger improvement was associated with the later improvement in airway remodelling. Conclusion: Physiology, airway inflammation and remodelling in asthma are interrelated and improve with ICS. Changes are not temporally concordant, with prolonged treatment necessary for maximal benefit in remodelling and PD20. Determining the appropriate dose of inhaled steroids only by reference to symptoms and lung function, as specified in current international guidelines, and even against indices of inflammation may be over simplistic. The results of this study support the need for early and long term intervention with ICS, even in patients with relatively mild asthma.

Reticular basement membrane fragmentation and potential epithelial mesenchymal transition is exaggerated in the airways of smokers with chronic obstructive pulmonary disease

Background and objective:  In COPD, the airways are chronically inflamed, and we have now observed fragmentation of the reticular basement membrane (Rbm). This appears to be a hallmark of the process known as epithelial mesenchymal transition (EMT), in which epithelial cells migrate through the Rbm and differentiate into fibroblasts. The aim of this study was to confirm the extent and relevance of Rbm fragmentation in smokers and patients with COPD, and to undertake a preliminary analysis of some classical markers of EMT.

Possible anti-inflammatory effect of salmeterol against interleukin-8 and neutrophil activation in asthma in vivo

In-vitro data suggest that long-acting β2-agonists may have a neutrophil-stabilising effect. A reduction in airway wall eosinophil number following introduction of salmeterol in persistent asthma has previously been described. There is currently interest in the “neutrophil system” in asthma, and thus the aim of the present study was to investigate the effect of salmeterol on interleukin (IL)-8, neutrophils and myeloperoxidase (MPO) in persistent asthma. In the same 12-week double-blind parallel-group placebo-controlled study as described previously, the effects on bronchoalveolar lavage fluid (BALF) IL-8, neutrophils and MPO of introducing salmeterol (50 µg b.i.d.) or giving additional inhaled corticosteroid (fluticasone 100 µg b.i.d.) in 45 subjects with persistent asthma already on low/moderate doses of inhaled corticosteroids were further investigated. At baseline, BALF IL-8 but not neutrophil or MPO levels were significantly raised in the asthmatic subjects compared to normal controls. MPO levels correlated strongly with IL-8 levels, and weakly with BALF neutrophil numbers in the asthmatics. Fluticasone treatment resulted in significantly elevated neutrophil numbers, but not MPO or IL-8 levels. In contrast, introducing salmeterol significantly reduced IL-8 and MPO levels, but did not affect BALF neutrophil numbers. Interestingly, salmeterol and fluticasone showed significantly contrasting effects on MPO and neutrophils, and there was a divergent effect on IL-8 levels that almost reached significance. Excessive interleukin-8 levels may be relevant to asthma pathogenesis, even in the setting of moderate-dose inhaled corticosteroid therapy. Reduction in interleukin-8 production and possibly stabilisation of airway neutrophil numbers may explain the greater clinical benefit of adding a long-acting β2-agonist rather than merely increasing inhaled corticosteroid doses. Indeed, high-dose inhaled corticosteroid therapy alone may promote airway neutrophilia.

Iron-binding compounds impair Pseudomonas aeruginosa biofilm formation, especially under anaerobic conditions.

The success of Pseudomonas aeruginosa in cystic fibrosis (CF) and other chronic infections is largely attributed to its ability to grow in antibiotic-resistant biofilm communities. This study investigated the effects of limiting iron levels as a strategy for preventing/disrupting P. aeruginosa biofilms. A range of synthetic and naturally occurring iron-chelating agents were examined. Biofilm development by P. aeruginosa strain PAO1 and CF sputum isolates from chronically infected individuals was significantly decreased by iron removal under aerobic atmospheres. CF strains formed poor biofilms under anaerobic conditions. Strain PAO1 was also tested under anaerobic conditions. Biofilm formation by this model strain was almost totally prevented by several of the chelators tested. The ability of synthetic chelators to impair biofilm formation could be reversed by iron addition to cultures, providing evidence that these effective chelating compounds functioned by directly reducing availability of iron to P. aeruginosa. In contrast, the biological chelator lactoferrin demonstrated enhanced anti-biofilm effects as iron supplementation increased. Hence biofilm inhibition by lactoferrin appeared to occur through more complex mechanisms to those of the synthetic chelators. Overall, our results demonstrate the importance of iron availability to biofilms and that iron chelators have potential as adjunct therapies for preventing biofilm development, especially under low oxygen conditions such as encountered in the chronically infected CF lung.

Increased airway iron as a potential factor in the persistence of Pseudomonas aeruginosa infection in cystic fibrosis

Iron availability is critical to many bacteria and increased iron has been described in airway secretions in cystic fibrosis (CF). The main aim of the present study was to assess the relationship between iron in CF sputum and the quantitative bacterial burden. Iron, ferritin and total cell counts (TCC) were assessed in sputum samples obtained from 15 clinically stable CF patients chronically infected with Pseudomonas aeruginosa. Sputum samples were also obtained at the commencement of episodes of acute exacerbation in 10 subjects and analyses were repeated in six of these exacerbation cases after i.v. antibiotic treatment. The relationship between iron indices and the presence of P. aeruginosa, as well as total anaerobic bacterial load, was determined. Sputum was also obtained from 10 CF patients with no evidence of infection with P. aeruginosa and 11 normal healthy controls. Sputum iron, ferritin and TCC were significantly elevated in all CF patients, even in those not infected with P. aeruginosa, compared with healthy controls. There was a strong positive relationship between sputum iron and P. aeruginosa in clinically stable patients, but not in samples obtained during an acute exacerbation. There was no relationship between sputum iron and anaerobic bacterial load. Antibiotic treatment significantly reduced sputum TCC and anaerobic bacterial load, but not iron, ferritin or the presence of P. aeruginosa during an exacerbation. In conclusion, the present study suggests that increased airway iron may be important to Pseudomonas aeruginosa persistence in cystic fibrosis.

Effects of inhaled fluticasone on angiogenesis and vascular endothelial growth factor in asthma

Background: Subepithelial hypervascularity and angiogenesis in the airways are part of structural remodelling of the airway wall in asthma, but the effects of inhaled corticosteroids (ICS) on these have not been explored. Increased vascularity in asthma may contribute to a number of functional abnormalities. A study was undertaken to explore angiogenic modulation by ICS and its likely regulation via vascular endothelial growth factor (VEGF), its receptors and the angiopoietins. Methods: A placebo-controlled intervention study with ICS in asthma was performed, examining vascularity, VEGF, its receptors (VEGFR1 and VEGFR2), and angiopoietin-1 (Ang1) to assess which of these factors were changed in the asthmatic airways after ICS treatment. Airway wall biopsy specimens, lavage fluid and cells were obtained from 35 patients with mild asthma randomised to receive ICS or placebo for 3 months, after which bronchoscopic examination and sample collection were repeated. Immunohistochemistry and image analysis were used to obtain quantitative measures of vessels, angiogenic sprouts, VEGF, VEGFR1, VEGFR2 and Ang1 staining in airway biopsy specimens. ELISA was used to assess VEGF concentrations in the lavage fluid. Results: Vessel, VEGF and sprout staining were decreased after 3 months of ICS treatment. VEGF levels remained unchanged. VEGF receptors and Ang1 staining were not reduced after treatment. Conclusions: The findings of this study support an effect of ICS in downregulating angiogenic remodelling in the airways in asthma, associated with decreasing VEGF activity within the airway wall. The environment of the airways after treatment with ICS, with changes in the balance between VEGF, its receptors, Ang1 and sprouts, appears to be less angiogenic than in untreated asthma.

Airway iron and iron-regulatory cytokines in cystic fibrosis

Iron availability is critical to Pseudomonas aeruginosa. The current authors determined sputum iron, ferritin, microalbumin levels and total cell counts (TCC) in 19 adult patients with cystic fibrosis (CF) during an acute exacerbation and repeated analyses following a median of 12 days antibiotic treatment. The current authors also determined sputum interleukin (IL)‐1β and tumour necrosis factor (TNF)‐α levels because of their putative role in intracellular iron homeostasis. Additional data were obtained from 17 stable CF patients, eight patients with stable chronic obstructive pulmonary disease (COPD) and six normal subjects. Overall, sputum iron, ferritin, microalbumin, IL‐1β and TNF‐α concentrations and TCCs were significantly elevated in the CF patients compared to those with COPD and normal controls. Sputum ferritin levels were significantly elevated in acute versus stable CF patients and there was a trend for sputum TCC to be higher, but all other inflammatory indices were similar. In the CF patients, sputum iron was positively and strongly related to IL‐1β, TNF‐α, ferritin and microalbumin levels, but negatively related to forced expiratory volume in one second % predicted. In those acute patients who clinically improved with antibiotics (n=14), there were significant decreases in sputum TCC, iron, ferritin and IL‐1β content, but not TNF‐α or albumin levels. However, changes in sputum TNF‐α in acute patients were still closely related to changes in iron, ferritin and albumin content, and changes in IL‐1β were related to changes in sputum ferritin content. Iron and iron-regulatory cytokines may play a role in cystic fibrosis lung disease and the increased iron content may even facilitate Pseudomonas aeruginosa infection.

Poor clinical outcomes associated with a multi-drug resistant clonal strain of Pseudomonas aeruginosa in the Tasmanian cystic fibrosis population

Background and objective:  Clonal strains of Pseudomonas aeruginosa have been identified in large cystic fibrosis (CF) centres. Whether such strains are more virulent or whether cross‐infection between patients explains their widespread prevalence is unknown. This study described the epidemiology of P. aeruginosa infection in CF patients in Tasmania, Australia, an area with a high CF birth incidence. Patients in Tasmania are geographically dispersed and when this study was conducted (2003) there was no central CF clinic, with patients receiving treatment in regional hospitals.

Inter-relationships between airway inflammation, reticular basement membrane thickening and bronchial hyper-reactivity to methacholine in asthma; a systematic bronchoalveolar lavage and airway biopsy analysis

Background Asthma is accepted as a disease characterized by airway inflammation, with evidence that airway structural changes, or ‘remodelling’ occurs. There are few studies relating airway physiology, inflammation and remodelling, however. We have carried out a study of inter‐relationships between airway inflammation, airway remodelling, reticular basement membrane (RBM) thickening, and bronchial hyper‐reactivity (BHR), before and after high‐dose inhaled corticosteroid (fluticasone propionate 750 μg b.d.), in a group of relatively mild but symptomatic, steroid naïve asthma patients.

Basement membrane and vascular remodelling in smokers and chronic obstructive pulmonary disease: a cross-sectional study

BackgroundLittle is known about airway remodelling in bronchial biopsies (BB) in smokers and chronic obstructive pulmonary disease (COPD). We conducted an initial pilot study comparing BB from COPD patients with nonsmoking controls. This pilot study suggested the presence of reticular basement membrane (Rbm) fragmentation and altered vessel distribution in COPD.MethodsTo determine whether Rbm fragmentation and altered vessel distribution in BB were specific for COPD we designed a cross-sectional study and stained BB from 19 current smokers and 14 ex-smokers with mild to moderate COPD and compared these to 15 current smokers with normal lung function and 17 healthy and nonsmoking subjects.ResultsThickness of the Rbm was not significantly different between groups; although in COPD this parameter was quite variable. The Rbm showed fragmentation and splitting in both current smoking groups and ex-smoker COPD compared with healthy nonsmokers (p < 0.02); smoking and COPD seemed to have additive effects. Rbm fragmentation correlated with smoking history in COPD but not with age. There were more vessels in the Rbm and fewer vessels in the lamina propria in current smokers compared to healthy nonsmokers (p < 0.05). The number of vessels staining for vascular endothelial growth factor (VEGF) in the Rbm was higher in both current smoker groups and ex-smoker COPD compared to healthy nonsmokers (p < 0.004). In current smoker COPD VEGF vessel staining correlated with FEV1% predicted (r = 0.61, p < 0.02).ConclusionsAirway remodelling in smokers and mild to moderate COPD is associated with fragmentation of the Rbm and altered distribution of vessels in the airway wall. Rbm fragmentation was also present to as great an extent in ex-smokers with COPD. These characteristics may have potential physiological consequences.