Peter K. Jeffery

A study was undertaken to test the hypothesis that severe exacerbations of asthma are characterised by increased bronchial mucosal neutrophilia associated with upregulation of neutrophil chemoattractant ligands and their specific cell surface receptors. Immunohistology and in situ hybridisation were applied to endobronchial biopsy specimens from three groups: (1) 15 patients admitted to hospital with a severe exacerbation of asthma (E-asthma), (2) 15 with stable asthma (S-asthma) and (3) 15 non-atopic and non-smoker surgical controls (NSC). There were significantly more neutrophils and eosinophils in the epithelium and subepithelium of patients in the E-asthma group (median (range) neutrophils 7 (0-380) and 78 (10-898)/mm2, eosinophils 31 (0-167) and 60 (6-351)/mm2, p<or=0.01 compared with NSC: 0 (0-10, 0-7, 0-18 and 0-3)/mm2, respectively), resulting in similar final densities of eosinophils and neutrophils. With respect to neutrophil chemoattractants and receptors, counts of CXCL5, CXCL8, CXCR1 and CXCR2 mRNA-positive cells in the subepithelium of the E-asthma group were, respectively, 5, 4, 4 and 18 times greater (p<or=0.01) than those of the NSC group. In the E-asthma group, cells expressing CXCL5 or CXCR2 were eightfold and threefold more frequent than those expressing CXCL8 or CXCR1 mRNA, respectively (p<0.01). CXCL5 and CXCR2 in E-asthma were associated with the number of eosinophils (r=0.59 and 0.66, p<0.02 for both) rather than the number of neutrophils. In severe exacerbations of asthma there is a bronchial mucosal neutrophilia, eosinophilia and upregulation of CXC chemoattractants and their receptors. CXCL5 and CXCR2 have an association with eosinophila only, and these represent potentially new targets for treatment in exacerbations of asthma.

There is variability in the distribution of inflammatory cells in bronchial tissue in chronic obstructive pulmonary disease (COPD). Better strategies for biopsy sampling of the airway mucosa may improve the capacity to show a difference between study populations where variability in distribution exists.The current authors have examined sources of biological variability in the quantification of inflammatory cells in endobronchial biopsies using immunostained samples taken from 51 subjects with COPD, with a mean forced expiratory volume in one second of 1.71 L, 55% predicted.The distribution of variance contributed by different sources was similar for different inflammatory cell types. For CD8+ cells, a key inflammatory cell in COPD, the largest contribution to intra-subject variability (39%) was time (i.e.10 weeks between biopsies of placebo-treated subjects), followed by airway generation (23%), biopsy (2.5%), zone (within section; 1.4%) and section (0.4%).Power calculations demonstrated that examining one section from one biopsy, from each of two airway generations, would require a sample size of 32 subjects per group to show a difference of one doubling or halving in CD8+ cells, compared with 47 subjects per group if only one airway generation was sampled.Therefore, biopsies from more than one airway generation should be examined in order to maximise statistical power to detect a difference between study groups.

Although the anti-inflammatory effects of inhaled corticosteroids in the treatment of asthma are established, the effects of long-acting β₂-adrenergic receptor agonists on inflammation are the subject of debate. The aim of the present study was to determine the effect of salmeterol on the numbers of inflammatory cells in biopsy samples of distinct immunophenotype and those expressing the genes for interleukin-4 and -5, regulatory cytokines particularly relevant to asthma.Twenty patients (aged 18–55 yrs) with mild stable asthma were randomised in a three-way crossover study to 6 weeks of treatment with: 1) salmeterol (50 µgb.d.; SM₅₀); 2) fluticasone propionate (250 µgb.d.; FP₂₅₀), or 3) placebo.Compared with placebo, SM₅₀significantly reduced the numbers of neutrophils in bronchial biopsy samples and the concentrations of myeloperoxidase and soluble E-selectin in serum, each of which reflect neutrophil involvement. Compared with FP₂₅₀, SM₅₀reduced neutrophil number and human neutrophil lipocalin level in bronchial lavage fluid and intercellular adhesion molecule-1 level in bronchoalveolar lavage fluid. Compared with placebo, FP₂₅₀significantly reduced the numbers of (CD3+) T-lymphocytes, (CD4+) T-helper cells, (CD45RO+) activated T-helper cells and eosinophils in the biopsy samples; it also reduced the percentage of eosinophils and soluble intercellular adhesion molecule-1 in serum. The percentage of symptom-free days and nights and airways hyperresponsiveness improved significantly after SM₅₀compared to both placebo and FP₂₅₀.In conclusion, a novel antineutrophilic effect of the inhaled long-acting β₂-adrenergic receptor agonist, salmeterol, in mild asthma is reported.

We wished to determine if the inflammatory cells surrounding the airway mucus-secreting glands in chronic bronchitis (CB) were associated with interleukin (IL)-4 and IL-5 mRNA expression and whether the CD8 T cell population expressed these cytokines. Digoxigenin-labeled IL-4 and IL-5 antisense RNA probes were used to detect gene expression in 11 asymptomic smokers (AS), 11 smokers with CB alone with normal lung function, and 10 smokers with chronic bronchitis and coexisting chronic obstructive pulmonary disease (CB + COPD; FEV₁% of predicted of 43–77% and FEV₁/ FVC of 51–68%). There were approximately three times as many IL-4 than IL-5 mRNA⁺ cells. The highest number of IL-4 mRNA⁺ cells were in the submucosal glands of the CB group with normal lung function (216/mm²), significantly higher than the values in either the AS (63/mm²) or the CB + COPD (87/mm²) groups, respectively (p < 0.01). There were similar group differences when the total numbers of inflammatory cells were compared. Accordingly, there was a positive correlation between the number of IL-4 mRNA⁺ cells and the total number of inflammatory cells in both the subepithelium and glandular compartments (r = 0.60; p = 0.01 and r = 0.70; p = 0.02, respectively). There were no significant associations between the numbers of CD8⁺ and IL-4 or IL-5 mRNA⁺ cells. Of 1328 IL-4⁺ and 1404 CD8⁺ cells counted none was double labeled. Of 727 IL-5⁺ and 1569 CD8⁺ cells, none was double labeled. In contrast, as a positive control, 34% of tumor necrosis factor (TNF)- α⁺ cells were also CD8⁺ and 15% of CD8⁺ cells were TNF- α positive. Thus, cells other than the CD8⁺ phenotype produce IL-4 and IL-5 in CB. We conclude that there is increased inflammation and IL-4 gene expression in the mucus-secreting glands and the airway mucosa of smokers with bronchitis: both are lower in those with CB and coexisting COPD suggesting that airway inflammation in CB is reduced when airway obstruction develops.

Asthma and chronic obstructive lung disease (COPD) are both inflammatory conditions of the lung associated with structural “remodeling” inappropriate to the maintenance of normal lung function. The clinically observed distinctions between asthma and COPD are reflected by differences in the remodeling process, the patterns of inflammatory cells and cytokines, and also the predominant anatomic site at which these alterations occur. In asthma the epithelium appears to be more fragile than that of COPD, the epithelial reticular basement membrane (RBM) is significantly thicker, there is marked enlargement of the mass of bronchial smooth muscle, and emphysema does not occur in the asthmatic nonsmoker. In COPD, there is epithelial mucous metaplasia, airway wall fibrosis, and inflammation associated with loss of surrounding alveolar attachments to the outer wall of small airways: bronchiolar smooth muscle is increased also. Emphysema is a feature of severe COPD: in spite of the destructive process, alveolar wall thickening and focal fibrosis may be detected. The hypertrophy of submucosal mucus-secreting glands is similar in extent in asthma and COPD. The number of bronchial vessels and the area of the wall occupied by them increase in severe corticosteroid-dependent asthma: it is likely that these increases also occur in severe COPD as they do in bronchiectasis. Pulmonary vasculature is remodeled in COPD. In asthma several of these structural alterations begin early in the disease process, even in the child. In COPD the changes begin later in life and the associated inflammatory response differs from that in asthma. The following synopsis defines and compares the key remodeling processes and proposes several hypotheses.

Inflammation and remodeling are characteristic features of the conducting airways in asthma, but the relationships between inflammation, inappropriate remodeling, bronchial hyperresponsiveness, and reduced pulmonary function are still unclear. In both adults and children with asthma, there are structural changes of the conducting airways that include injury and loss of the surface epithelium, thickening of the reticular basement membrane, increases of underlying collagen, blood vessels, and airway smooth muscle, and plugging of the airways by exudate. Bronchial biopsies obtained from persons with mild stable asthma already demonstrate the presence of inflammation. Many of the inflammatory and structural changes begin early in childhood. Whereas corticosteroids markedly reduce many aspects of inflammation, it is not known whether and how they affect the changes associated with airway wall remodeling. Leukotriene receptor antagonists appear to be antiinflammatory and able to reduce the proliferation of bronchial smooth muscle.