Neutrophilic inflammation in severe persistent asthma

Neutrophil-derived matrix metalloproteinase-9 is increased in severe asthma and poorly inhibited by glucocorticoids

BACKGROUND

Matrix metalloproteinase (MMP)-9 levels are increased in bronchoalveolar lavage (BAL) fluid from patients with severe asthma on high doses of glucocorticoids (GCs).

OBJECTIVE

We sought to identify neutrophils as the source of increased BAL fluid MMP-9 in severe asthma and to evaluate the effects of GCs on this MMP-9.

METHODS

MMP-9 protein, activity, and mRNA were measured in BAL fluid and cells at baseline, and after in vitro GCs in patients with severe asthma and controls using enzyme immunoassays, zymography, Western blotting, and real-time PCR.

RESULTS

The high molecular weight (HMW) form of MMP-9 was significantly increased in severe asthma (P =.02). Western blotting confirmed a heterodimer of MMP-9 and neutrophil gelatinase-associated lipocalin. The HMW MMP-9 correlated with BAL neutrophils (r =.65, P <.0001). BAL cell supernatant MMP-9 protein levels also tended to be higher in patients with severe asthma (overall, P =.09), whereas the HMW activity form was increased (P =.03). MMP-9 protein (and HMW activity) correlated with neutrophils in the cell pellet (r =.75, P <.0001). In contrast to protein and activity, BAL cell mRNA levels were marginally lower in patients with severe asthma than in control subjects (overall, P =.06). Although GCs decreased BAL cell MMP-9 protein and mRNA in vitro, the effect was significantly smaller in severe asthma (P <.01 for both). GCs decreased the pro-MMP-9 activity in patients with severe asthma and normal control subjects, while having no effects on the HMW form (P =.22). Peripheral blood neutrophil MMP-9 protein was not affected by GCs.

CONCLUSIONS

BAL neutrophils contribute to BAL fluid MMP-9 protein and activity and are poorly inhibited by GCs.

Inhibitors of p38 mitogen-activated protein kinase: potential as anti-inflammatory agents in asthma?

Asthma is an inflammatory disease of the airways, which in patients with mild to moderate symptoms is adequately controlled by either beta(2)-adrenoceptor agonists or corticosteroids, or a combination of both. Despite this, there are classes of patients that fail to respond to these treatments. In addition, there is a general trend towards increasing morbidity and mortality due to asthma, which suggests that there is a need for new and improved treatments. The p38 mitogen-activated protein kinases (MAPKs) represent a point of convergence for multiple signalling processes that are activated in inflammation and that impact on a diverse range of events that are important in inflammation. Small molecule pyridinyl imidazole inhibitors of p38 MAPK have proved to be highly effective in reducing various parameters of inflammation, in particular cytokine expression. Like corticosteroids, inhibitors of p38 MAPK appear to be able to repress gene expression at multiple levels, for example, by transcriptional, posttranscriptional and translational repression, and this raises the possibility of a similarly broad spectrum of anti-inflammatory activities. Indeed these molecules have proved to be effective in numerous in vitro and in vivo models of inflammation and septicaemia, which suggests that such compounds may be effective as therapeutic agents against inflammatory disorders. Despite these very promising indications of the possible therapeutic use of p38 MAPK inhibitors, a number of events that are p38-dependent are in fact also beneficial to the resolution or modulation of diseases such as asthma. We conclude that the overall effect of p38 MAPK inhibition would be beneficial in inflammatory diseases such as rheumatoid arthritis and asthma. However, these drugs may result in a complex phenotype that will require careful evaluation. Currently, a number of second or third generation inhibitors of p38 MAPK are being tested in phase I and phase II clinical trials.

Myocardial ischemia-reperfusion injury is enhanced in a model of systemic allergy and asthma

Despite epidemiological evidence of cardiovascular complications in asthmatics, the direct contribution of asthmatic pathophysiology to cardiovascular effects is unknown. Considering parallels in underlying pathophysiology, we tested the hypothesis that presence of systemic allergy and asthma worsens the outcome of myocardial ischemia-reperfusion injury. Systemic allergy and asthma were created in rabbits by repeated intraperitoneal injections of allergen with adjuvant, followed by an airway challenge in two groups. Nonsensitized animals served as controls. In situ myocardial ischemia-reperfusion was induced in anesthetized animals by a 30-min ligation of a coronary artery, followed by 3 h of reperfusion. Ischemia-reperfusion was done at 24 h after intraperitoneal boost (1 DB) and 7 days (7 DB) after the last intraperitoneal injection and at 24 h (1DAWCH) and 7 days (7DAWCH) after airway challenge. The infarct size (determined by 2,3,5-triphenyltetrazolium chloride staining, normalized to area at risk) was significantly higher in all sensitized groups compared with control (1DB, 31 +/- 4; 7DB, 28.9 +/- 2.6; 1DAWCH, 66.1 +/- 4.1; 7DAWCH, 28.9 +/- 9.2; control, 16.7 +/- 3.2; means +/- SE; P < 0.01 by ANOVA; n = 6). The 1DAWCH group showed significantly greater infarct than all other groups (P < 0.05). Myocardial neutrophil infiltration was significantly higher in the sensitized groups compared with control (P < 0.01). Tissue neutrophil counts showed a strong positive correlation to infarct sizes (r2 = 0.9). These observations indicate that the presence of systemic allergy and asthma is associated with increased myocardial neutrophil infiltration during acute ischemia-reperfusion and increased size of the resulting infarct.

High dose of inhaled fluticasone reduces high levels of urinary leukotriene E4 in the early morning in mild and moderate nocturnal asthma

BACKGROUND

The circadian variation in urinary leukotriene E(4) (LTE(4)) excretion with a morning acrophase has recently been reported in nocturnal asthma (NA); however, the effects of inhaled corticosteroids (ICS) on this circadian rhythmicity of leukotriene (LT) in patients with NA are controversial.

METHODS

We first measured peak expiratory flow (PEF), urinary LTE(4), 11-dehydro-thromboxane B(2) (TXB(2)), and creatinine levels six times every 4 h for 24 h in two groups: patients with mild-to-moderate, steroid-naive NA (n = 10, group A), and patients with severe NA treated with high-dose ICS (n = 10, group B). Next, group A patients received 2 weeks of treatment with 800 microg/d of inhaled fluticasone propionate (FP), and we compared the measured parameters before and after treatment.

RESULTS

In group A, a circadian rhythm in urinary LTE(4) with peak levels at approximately 4 AM associated with reduced PEF was observed. Group B had suppression of urinary LTE(4) excretion and had no circadian rhythmicity, as seen in group A, despite a dip in PEF at 4 AM. A high dose of FP in group A significantly (p < 0.05) reduced LTE(4) levels and abolished the circadian rhythm, as well as improving PEF. We found no significant difference in the circadian rhythm of urinary 11-dehydro-TXB(2) between groups A and B, and high-dose FP partially decreased urinary 11-dehydro-TXB(2) levels but not significantly.

CONCLUSIONS

A high-dose of ICS reduced urinary LTE(4) levels and abolished their circadian variation in patients with asthma, suggesting that LT might contribute to the mechanism of NA.

Cytokine-directed therapies for the treatment of chronic airway diseases

Multiple cytokines play a critical role in orchestrating and perpetuating inflammation in asthma and chronic obstructive pulmonary disease (COPD) and several specific cytokine and chemokine inhibitors now in development as future therapy for these diseases. Anti-IL-5 antibody markedly reduces peripheral blood and airway eosinophils, but does not appear to be effective in symptomatic asthma. Inhibition of IL-4 despite promising early results in asthma has been discontinued and blocking IL-13 might be more effective. Inhibitory cytokines, such as IL-10, interferons and IL-12 are less promising, as systemic delivery produces side effects. Inhibition of TNF-alpha may be useful in severe asthma and for treating severe COPD with systemic features. Many chemokines are involved in the inflammatory response of asthma and COPD and several small molecule inhibitors of chemokine receptors (CCR) are in development. CCR3 antagonists (which block eosinophil chemotaxis) and CXCR2 antagonists (which block neutrophil and monocyte chemotaxis) are in clinical development for asthma and COPD, respectively. Because so many cytokines are involved in asthma, drugs that inhibit the synthesis of multiple cytokines may prove to be more useful; several such classes of drug are now in clinical development and any risk of side effects with these non-specific inhibitors may be reduced by the inhaled route.

Persistent activation of nuclear factor-kappaB signaling pathway in severe uncontrolled asthma

The transcription factor nuclear factor-kappaB (NF-kappaB) is inactive when bound to its inhibitory protein IkappaBalpha. On cell stimulation with inflammatory signals, IkappaBalpha is phosphorylated by IkappaB kinases and subsequently degraded. Freed NF-kappaB then induces expression of cytokines such as granulocyte-macrophage colony-stimulating factor, interleukin-8, and regulated upon activation, normal T cell expressed and secreted. These mediators are overexpressed in asthma and are downregulated by glucocorticoids through NF-kappaB activity repression. However, high levels of granulocyte-macrophage colony-stimulating factor, interleukin-8, and regulated upon activation, normal T cell expressed and presumably secreted are released by peripheral blood mononuclear cells isolated from patients with severe asthma despite continuous systemic glucocorticoid treatment. We report that these mediators are markedly decreased by pyrrolidinedithiocarbamate, an inhibitor of NF-kappaB activation. To further characterize the persistent NF-kappaB activation in severe asthma, we analyzed the expression of various components of this activation pathway in healthy subjects and in asthmatics with mild controlled, and moderate and severe uncontrolled disease. We found high amounts of phosphorylated IkappaBalpha characterizing the three asthmatic groups. Western blot analyses indicated that in peripheral blood mononuclear cells the IkappaB kinase beta and p65 levels were greater in moderate and severe asthmatics than in normal subjects. Electrophoretic mobility shift assay and immunocytochemistry showed a greater activation status of p65 in severe asthmatics. Our data suggest that exaggerated NF-kappaB activation perpetuates inflammatory mediators production in severe asthma.

Interleukin-17 stimulates release of interleukin-8 by human airway smooth muscle cells in vitro: a potential role for interleukin-17 and airway smooth muscle cells in bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome is the major constraint on the long-term survival after lung transplantation. Both neutrophils and interleukin (IL)-8, a potent neutrophil attractant, have been shown to play an important role in the pathophysiology of obliterative bronchiolitis. We investigated the potential role of human airway smooth muscle cells in obliterative bronchiolitis by studying their release of IL-8 after stimulation with IL-17, a novel T-cell-derived chemokine capable of attracting and activating neutrophils. We demonstrated a significant increase in IL-8 release, reaching a concentration of 86.6 ng/ml (SEM 1.9 ng/ml) with 100 ng/ml IL-17 (p < 0.01, n = 4), as compared with non-stimulated cells. This IL-17-mediated IL-8 release could not be inhibited by dexamethasone. We conclude that human airway smooth muscle cells may play an important pro-inflammatory role in neutrophilic inflammatory diseases such as chronic rejection after lung transplantation; furthermore, IL-17 may be the link between lymphocytes and neutrophils.

Induction of C-X-C chemokines, growth-related oncogene alpha expression, and epithelial cell-derived neutrophil-activating protein-78 by ML-1 (interleukin-17F) involves activation of Raf1-mitogen-activated protein kinase kinase-extracellular signal-regulated kinase 1/2 pathway

Neutrophil recruitment into the airway typifies pulmonary inflammation and is regulated through chemokine network, in which two C-X-C chemokines play a critical role. Airway epithelial cells and vein endothelial cells are major cell sources of chemokines. ML-1 (interleukin-17F) is a recently discovered cytokine and its function still remains elusive. In this report, we investigated the functional effect of ML-1 in the expression of growth-related oncogene (GRO)alpha and epithelial cell-derived neutrophil activating protein (ENA)-78. The results showed first that ML-1 induces, in time- and dose-dependent manners, the gene and protein expressions for both chemokines in normal human bronchial epithelial cells and human umbilical vein endothelial cells. Furthermore, selective mitogen-activated protein kinase kinase (MEK) inhibitors 2'-amino-3'-methoxyflavone (PD98059), 1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto) butadiene (U0126), and Raf1 kinase inhibitor I partially inhibited Ml-1-induced GROalpha and ENA-78 production. In contrast, the combination of PD98059 and Raf1 kinase inhibitor I completely abrogated the chemokine production, whereas a protein kinase C inhibitor, 2-(1-(3-aminopropyl) indol-3-yl)-3-(1-methylindol-3-yl) maleimide, acetate (Ro-31-7549), and a phosphatidylinositol 3-kinase inhibitor, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), did not affect their production. Together, these data indicates a role for Raf1-MEK-extracellular signal-regulated kinase 1/2 pathway in ML-1 induced C-X-C chemokine expression, suggesting potential pharmacological targets for modulation.

A randomized controlled trial on the effect of montelukast on sputum eosinophil cationic protein in children with corticosteroid-dependent asthma

Previous adult studies demonstrated the clinical efficacy of an additional treatment with leukotriene receptor antagonists on steroid-dependent asthma, but there is little knowledge about anti-inflammatory add-on effects within the lung. In this study, we hypothesized that steroid-treated children exhibit a decrease in bronchial inflammation in induced sputum under additional treatment with montelukast. Twenty-five asthmatic children aged 6 to 14 y, who had been taking inhaled corticosteroids (400-800 microg/d budesonide) regularly for at least 12 wk, were randomized to receive additional treatment with either montelukast (5 mg orally, once daily) or placebo over a 4-wk period. As primary efficacy variable, eosinophil cationic protein (ECP) in induced sputum as direct measurement of bronchial inflammation was assessed before and after treatment. To assure a baseline level of inflammation, an ECP concentration above 100 microg/L was required. Sputum eosinophil count, concentration of exhaled nitric oxide, urinary excretion of eosinophil protein X, and quality-of-life items were considered as secondary outcome variables. After treatment with montelukast, ECP in sputum was significantly reduced (montelukast: median -975 microg/L [5 to 95% confidence interval: -4295 to 583 microg/L]; placebo: 561 microg/L [-1335 to 3320 microg/L]; p < 0.01) and the quality-of-life score had significantly improved (p < 0.05) compared with placebo. Partly explained by low baseline levels, no statistically significant change in concentration of exhaled nitric oxide (p > 0.05), urinary excretion of eosinophil protein X (p > 0.05), or eosinophil count (p > 0.05) was found. In conclusion, add-on treatment with montelukast can suppress sputum ECP in children with steroid-dependent asthma, while at the same time an improvement in quality of life items occurs.

Allergen-induced airway disease is mouse strain dependent

We investigated the development of airway hyperreactivity (AHR) and inflammation in the lungs of nine genetically diverse inbred strains of mice [129/SvIm, A/J, BALB/cJ, BTBR+(T)/tf/tf, CAST/Ei, C3H/HeJ, C57BL/6J, DBA/2J, and FVB/NJ] after sensitization and challenge with ovalbumin (OVA). At 24, 48, and 72 h post-OVA exposure, the severity of AHR and eosinophilic inflammation of the mouse strains ranged from relatively unresponsive to responsive. The severity of the airway eosinophilia of some strains did not clearly correlate with the development of AHR. The temporal presence of T helper type 2 cytokines in lung lavage fluid also varied markedly among the strains. The levels of IL-4 and IL-13 were generally increased in the strains with the highest airway eosinophilia at 24 and 72 h postexposure, respectively; the levels of IL-5 were significantly increased in most of the strains with airway inflammation over the 72-h time period. The differences of physiological and biological responses among the inbred mouse strains after OVA sensitization and challenge support the hypothesis that genetic factors contribute, in part, to the development of allergen-induced airway disease.

Relationships of allergic sensitization, total immunoglobulin E and blood eosinophils to asthma severity in children of the EGEA Study

BACKGROUND

Although allergy is highly associated with childhood asthma, it is not well known if there is a relationship between the intensity of allergic sensitization and asthma severity.

OBJECTIVE

The objectives of the study were to examine the relationships between several markers of allergy and asthma severity in asthmatic children included in the Epidemiological study on the Genetics and Environment of Asthma, bronchial hyper-responsiveness and atopy (EGEA).

METHODS

The population comprised 216 asthmatic children below 16 years of age. Total IgE and blood eosinophil counts were measured and skin prick tests to 11 aeroallergens were performed. The intensity of the allergic sensitization was assessed by the number of positive skin prick tests and by skin weal sizes. Asthma severity was measured with four criteria: a clinical severity score, history of hospitalization for asthma, FEV1% predicted and inhaled steroid use in the last 12 months.

RESULTS

Most of the children were sensitized to at least one aeroallergen (88.2%). Atopy was not related to the severity of asthma, except for a tendency for a more severe clinical score in non-atopic children. The type and intensity of the allergic sensitization were not associated with any criteria of asthma severity. Total IgE was significantly increased in children treated with inhaled corticosteroids and in children ever hospitalized for asthma (P-values 0.009 and 0.04, respectively). Eosinophil counts were not related to asthma severity.

CONCLUSION

Our results suggest that severe childhood asthma may be related to a high level of total IgE but not to blood eosinophil counts. The lack of positive relationships between both atopy and the intensity of allergic sensitization with asthma severity supports the hypothesis of different risk factors being associated with asthma and with the severity of asthma.

Regulation of airway epithelial cell NF-kappa B-dependent gene expression by protein kinase C delta

Airway epithelial cells synthesize proinflammatory molecules such as IL-8, GM-CSF, RANTES, and ICAM-1, the expression of which is increased in the airways of patients with asthma. We investigated the regulation of these NF-kappa B-dependent genes by the novel protein kinase C (PKC) isoform PKC delta in 16HBE14o- human airway epithelial cells, focusing on IL-8 expression. Transient transfection with the constitutively active catalytic subunit of PKC delta (PKC delta-CAT), and treatment with bryostatin 1, an activator of PKC delta, each increased transcription from the IL-8 promoter, whereas overexpression of PKC epsilon had minor effects. Expression of a dominant negative PKC delta mutant (PKC delta-KR) or pretreatment of cells with rottlerin, a chemical PKC delta inhibitor, attenuated TNF-alpha- and phorbol ester-induced transcription from the IL-8 promoter. Bryostatin 1 treatment increased IL-8 protein abundance in primary airway epithelial cells. Selective activation of PKC delta by bryostatin also activated NF-kappa B, as evidenced by p65 RelA and p50 NF-kappa B1 binding to DNA, NF-kappa B trans-activation, and I kappa B degradation. The sufficiency of PKC delta to induce NF-kappa B nuclear translocation and binding to DNA was confirmed in a 16HBE14o- cell line inducibly expressing PKC delta-CAT under the tet-off system. Deletion of the NF-kappa B response element severely attenuated PKC delta-induced IL-8 promoter activity. Finally, PKC delta-CAT induced transcription from the GM-CSF, RANTES, and ICAM-1 promoters. Together these data suggest that PKC delta plays a key role in the regulation of airway epithelial cell NF-kappa B-dependent gene expression.

Airway structural alterations selectively associated with severe asthma

To identify airway pathologic abnormalities selectively associated with severe asthma, we examined 10 control subjects, 10 patients with intermittent asthma, 15 patients with mild-to-moderate persistent asthma, 15 patients with severe persistent asthma, and 10 patients with chronic obstructive pulmonary disease. Bronchial biopsies were assessed for epithelial integrity; subepithelial basement membrane (SBM) thickness; collagen type III deposition; eosinophil, neutrophil, and fibroblast numbers; mucous gland and airway smooth muscle (ASM) areas; SBM-ASM distance; ASM hypertrophy (increased cell size); and the expression of the contractile proteins alpha-actin, smooth muscle myosin heavy-chain isoforms, myosin light-chain kinase, and the phosphorylated form of the regulatory light chain of myosin. Neither mucosal eosinophilia nor neutrophilia, epithelial damage, or SBM thickness reflected asthma severity. In contrast, higher numbers of fibroblasts (p < 0.001), an increase in collagen type III deposition (p < 0.020), larger mucous gland (p < 0.040) and ASM (p < 0.001) areas, augmented ASM cell size (p < 0.001), and myosin light-chain kinase expression (p < 0.005) distinguished patients with severe persistent asthma from patients with milder disease or with chronic obstructive pulmonary disease. Stepwise multivariate regression analysis established that fibroblast numbers and ASM cell size were negatively associated with prebronchodilator and postbronchodilator FEV1 values in patients with asthma. We conclude that fibroblast accumulation and ASM hypertrophy in proximal airways are selective determinants of severe persistent asthma.

Similar levels of nitric oxide in exhaled air in non-asthmatic rhinitis and asthma after bronchial allergen challenge

BACKGROUND

Nitric oxide in exhaled air (eNO) is elevated in allergic asthma compared with healthy subjects and has been proposed as a marker of bronchial inflammation. However, eNO is elevated to a lesser extent in allergic non-asthmatic rhinitis as well. Considering the distinctive clinical appearances of both allergic diseases, differences in eNO are expected to persist after allergen exposure. The aim of the study was to compare allergen-induced changes in eNO in house dust mite sensitized patients with asthma and patients with perennial rhinitis without asthma symptoms.

METHODS

Bronchial allergen challenge was performed in 52 patients sensitized to house dust mite (Dermatophagoides pteronyssinus), of whom 26 had non-asthmatic rhinitis and 26 had asthma. Levels of eNO were measured before and 1 h, 1 day and 1 week after challenge.

RESULTS

At baseline eNO was significantly lower in non-asthmatic rhinitis compared with asthma (geometric mean eNO (SEM): 121 (1.1) in non-asthmatic rhinitis vs 197 (1.1) nl/min in asthma, P < 0.006). However, the increase in eNO after bronchial allergen challenge in non-asthmatic rhinitis, in particular in those patients with a dual asthmatic response, significantly exceeded the increase in asthma resulting in similar levels of eNO after challenge (geometric mean eNO (SEM) at 24 h postchallenge 204 (1.1) in non-asthmatic rhinitis vs 244 (1.1)nl/min in asthma, P = 0.3).

CONCLUSION

The difference in eNO between non-asthmatic rhinitis and asthma at baseline is abolished after allergen exposure due to a significantly greater increase in eNO in non-asthmatic rhinitis.

Nitric oxide, nitrotyrosine, and nitric oxide modulators in asthma and chronic obstructive pulmonary disease

Nitric oxide (NO), a simple free-radical gas, elicits a diverse range of physiologic and pathophysiologic effects, and plays an important role in pulmonary diseases. Nitrosative stress and nitration of proteins in airway epithelium may be responsible for steroid resistance in asthma and their ineffectiveness in chronic obstructive pulmonary disease (COPD), supporting the potential role of future therapeutic strategies aimed at regulating NO synthesis in asthma and COPD. In this article, we review the potential role of NO modulators (NO synthase inhibitors and NO donors), which, if given on a regular basis, may have clinical benefit in asthma and COPD.

Airway hyperresponsiveness: a story of mice and men and cytokines

Bronchial hyperresponsiveness (BHR) is an essential part of the definition of asthma. Although our understanding of the allergic inflammatory and immunologic mechanisms of asthma have markedly increased, the mechanism of BHR remains to be elucidated. Increased BHR is associated temporally with exposure to allergens, certain respiratory viruses, pollutants such as ozone, and certain occupational chemicals. An important research use of determining the degree of BHR to direct and indirect challenge is to determine the efficacy of pharmacologic and immunodulatory agents. Beta-adrenergic agents inhibit BHR and certain genetic polymorphisms of the beta-adrenergic receptor are associated with increased BHR. When beta-adrenergic receptors are blocked, sensitivity to allergens is markedly increased in patients with asthma and animal models of asthma. Allergen challenge and clinical asthma are associated with synthesis and release of pro-inflammatory cytokines such as IL-1 and TNF-alpha which have been shown to decrease the response to beta-agonists and increased the reactivity to methacholine and the airways neutrophils and alveolar macrophages. The Th2 cytokine IL-13 is increased in the airways of asthmatics and increases BHR in normal unsensitized animals. The mechanisms of this effect of IL-13 are being intensively investigated. Our group has shown that IL-13 induced BHR persisted for at least 7 days and the soluble receptor IL-13R2alpha protected against their BHR. Other investigators have demonstrated that IL-13 is necessary and sufficient for the induction of BHR and that eosinophilic airway inflammation in the absence of IL-13 fails to induce BHR. These studies indicate that treatment of human asthma with antagonists of IL-13 may be very effective.

Differences in airway inflammation in patients with fixed airflow obstruction due to asthma or chronic obstructive pulmonary disease

To determine whether patients with fixed airflow obstruction have distinct pathologic and functional characteristics depending on a history of either asthma or chronic obstructive pulmonary disease (COPD), we characterized 46 consecutive outpatients presenting with fixed airflow obstruction by clinical history, pulmonary function tests, exhaled nitric oxide, sputum analysis, bronchoalveolar lavage, bronchial biopsy, and high-resolution computed tomography chest scans. Subjects with a history of COPD (n = 27) and subjects with a history of asthma (n = 19) had a similar degree of fixed airflow obstruction (FEV1: 56 +/- 2 versus 56 +/- 3% predicted) and airway hyperresponsiveness (PC20FEV1: 2.81 [3.1] versus 1.17 [3.3]). Subjects with a history of asthma had significantly more eosinophils in peripheral blood, sputum, bronchoalveolar lavage, and airway mucosa; fewer neutrophils in sputum and bronchoalveolar lavage fluid; a higher CD4+/CD8+ ratio of T cells infiltrating the airway mucosa; and a thicker reticular layer of the epithelial basement membrane. They also had significantly lower residual volume, higher diffusing capacity, higher exhaled nitric oxide, lower high-resolution computed tomography scan emphysema score, and greater reversibility to bronchodilator and steroids. In conclusion, despite similar fixed airflow obstruction, subjects with a history of asthma have distinct characteristics compared with subjects with a history of COPD and should be properly identified and treated.

The role of the epidermal growth factor receptor in sustaining neutrophil inflammation in severe asthma

BACKGROUND

The extent of epithelial injury in asthma is reflected by expression of the epidermal growth factor receptor (EGFR), which is increased in proportion to disease severity and is corticosteroid refractory. Although the EGFR is involved in epithelial growth and differentiation, it is unknown whether it also contributes to the inflammatory response in asthma.

OBJECTIVES

Because severe asthma is characterized by neutrophilic inflammation, we investigated the relationship between EGFR activation and production of IL-8 and macrophage inhibitory protein-1 alpha (MIP-1alpha) using in vitro culture models and examined the association between epithelial expression of IL-8 and EGFR in bronchial biopsies from asthmatic subjects.

METHODS

H292 or primary bronchial epithelial cells were exposed to EGF or H2O2 to achieve ligand-dependent and ligand-independent EGFR activation; IL-8 mRNA was measured by real-time PCR and IL-8 and MIP-1alpha protein measured by enzyme-linked immunosorbent assay (ELISA). Epithelial IL-8 and EGFR expression in bronchial biopsies from asthmatic subjects was examined by immunohistochemistry and quantified by image analysis.

RESULTS

Using H292 cells, EGF and H2O2 increased IL-8 gene expression and release and this was completely suppressed by the EGFR-selective tyrosine kinase inhibitor, AG1478, but only partially by dexamethasone. MIP-1alpha release was not stimulated by EGF, whereas H2O2 caused a 1.8-fold increase and this was insensitive to AG1478. EGF also significantly stimulated IL-8 release from asthmatic or normal primary epithelial cell cultures established from bronchial brushings. In bronchial biopsies, epithelial IL-8, MIP-1alpha, EGFR and submucosal neutrophils were all significantly increased in severe compared to mild disease and there was a strong correlation between EGFR and IL-8 expression (r = 0.70, P < 0.001).

CONCLUSIONS

These results suggest that in severe asthma, epithelial damage has the potential to contribute to neutrophilic inflammation through enhanced production of IL-8 via EGFR- dependent mechanisms.

The relationship between inflammation and dipalmitoyl phosphatidycholine in induced sputum of children with asthma

BACKGROUND

Animal studies have shown elevated surfactant production in response to lung injury. In human airways, the contribution of surfactant to the airway epithelial barrier and importance of eosinophilic inflammation is increasingly appreciated. The relationship between blood and sputum inflammatory indices of childhood asthma to surfactant levels is unknown. In this study we hypothesized that the degree of inflammation influences the level of dipalmitoyl phosphatidycholine (DPPC) in airways of children with asthma.

METHODS

Sixteen children with asthma (ages 5.5-16 years) underwent venipuncture, skin prick test, spirometry, hypertonic saline challenge, and induced sputum during a nonacute phase. Sputum (sp) and blood (se) markers of inflammation (eosinophils, neutrophils, eosinophilic cationic protein [ECP]), were related to sputum DPPC levels and several markers of asthma severity (airway hyperresponsiveness, quality of life, FEV1).

RESULTS

On multiple regression, sp-DPPC significantly correlated to sp-ECP (r=0.53, P=0.0048). Se-ECP, se-Eo, sp-eosinophils, sp-neutrophils, se-neutrophils, and inhaled steroids dose did not significantly influence sp-DPPC. Exposure to smoke did not influence inflammatory markers. FEV1 and quality of life data did not relate to any blood or sputum variable. A significant association between AHR and se-eosinophils, but not between AHR and se-ECP, sp-eosinophils, or sp-ECP was found.

CONCLUSION

Elevated DPPC levels occur in the presence of chronic eosinophilic inflammation in airways of children with stable asthma. Whether this represents an inherent lung mechanism for epithelial protection remains to be elucidated.

[Difficult asthma in children]

Difficult asthma in children is defined as the persistence of exacerbations or frequent symptoms requiring rescue bronchodilator, or persistent airway obstruction in spite of treatment with inhaled steroid >/= 800 microg/d beclomethasone or equivalent and beta-2 long acting agonist. Management of difficult asthma in children first requires to identify conditions that may mimic asthma, asthma with bad compliance to treatment, and difficult asthma in relation with avoidable factors that worsen symptoms. The pathological bases of genuine difficult asthma remain unknown. Different patterns have been described according to the cells that are involved (eosinophil, neutrophil), the degree of airway remodeling, or the distal localization of the lesions. Difficult asthma requires specialized management including airway inflammation evaluation. Studies on bronchoalveolar lavage and bronchial mucosa biopsies will perhaps help to better understand the pathophysiology and to improve the management.

Increased leukotrienes in exhaled breath condensate in childhood asthma

Cysteinyl leukotrienes (cys-LTs; LTC4, LTD4, and LTE4) are generated predominantly by mast cells and eosinophils and induce airway smooth muscle contraction, microvascular leakage, and mucous hypersecretion whereas leukotriene B4 (LTB4) is a potent chemoattractant of neutrophils. We measured cys-LTs and LTB4 in exhaled breath condensate from children aged 7-14 years including healthy nonatopic children (n = 11) and children with mild intermittent asthma (steroid naive, n = 11), mild persistent asthma (low-dose inhaled steroid treatment, n = 13), or moderate to severe persistent asthma (high-dose inhaled steroid treatment, n = 13). Exhaled LTB4 levels were increased in patients with mild and moderate to severe persistent asthma compared with patients with mild intermittent asthma (126.0 +/- 8.8 and 131.9 +/- 7.1 versus 52.7 +/- 3.8 pg/ml, p < 0.001 and p < 0.0001) and normal subjects (126.0 +/- 8.8 and 131.9 +/- 7.1 versus 47.9 +/- 4.1 pg/ml, p < 0.0001). Elevated exhaled cys-LT levels were found in patients with mild and moderate to severe persistent asthma compared with normal subjects (27.9 +/- 2.8 and 31.5 +/- 4.5 versus 18.5 +/- 0.5 pg/ml, p < 0.01 and p < 0.05). There was an inverse correlation between exhaled cys-LTs and LTB4 in patients with mild persistent asthma. We conclude that exhaled cys-LTs and LTB4 may be noninvasive markers of airway inflammation in pediatric asthma.

Nitric oxide and protein nitration in the cystic fibrosis airway

Cystic fibrosis (CF), characterized by chronic airway infection and inflammation, ultimately leads to respiratory failure. Exhaled nitric oxide (NO), elevated in most inflammatory airway diseases, is decreased in CF, suggesting either decreased production or accelerated metabolism of NO. The present studies performed on two groups of CF patients provide further support for a disordered NO airway metabolism in CF respiratory tract disease. Despite confirmation of subnormal NOS2 in the CF airway epithelium, alternative isoforms NOS1 and NOS3 were present, and inflammatory cells in the CF airway expressed abundant NOS2. Increased immunohistochemical staining for nitrotyrosine was demonstrated in lung tissues from patients with CF as compared to control. To our knowledge, this is the first report localizing nitrotyrosine in diseased CF lung tissue. While the relative NOS2 deficiency in CF respiratory tract epithelium may contribute to the lower expired NO levels, these results suggest that increased metabolism of NO is also present in advanced CF lung disease. The significance of altered NO metabolism and protein nitration in CF remains to be fully elucidated.

Sputum eosinophil count in a large population of patients with mild to moderate steroid-naive asthma: distribution and relationship with methacholine bronchial hyperresponsiveness

BACKGROUND

Although airway eosinophilia is seen as a cardinal feature of asthma, data eosinophilia are still lacking on the proportion of the asthma group exhibiting raised airway eosinophilia. This study aimed to assess the distribution of sputum eosinophil count and its relationship with methacholine bronchial hyperresponsiveness in mild to moderate steroid-naive asthmatic people.

METHODS

Sputum was induced by inhalation of hypertonic saline (NaCl 4.5%) in 118 mild to moderate steroid-naive asthmatic people consecutively recruited from our outpatient clinic, and in 44 healthy people. The asthma group was selected on the basis of an forced expiratory volume in 1 s (FEV(1)) of > or = 70% predicted, and a provocative methacholine concentration causing a fall of 20% in FEV(1) (PC20 methacholine; PC(20)M) < or = 16 mg/ml.

RESULTS

In the asthma group, the median (range) of the percentage and the absolute values of sputum eosinophils were 4.8% (0-75) and 38 10(3)/g (0-14,191), respectively, vs 0% (0-2.3) (P < 0.001) and 0 10(3)/g (0-53) (P < 0.001) in healthy participants. Based on the 95% percentile for normal values calculated from our healthy group, 69% of the asthma group had significantly raised sputum eosinophil count (that is > 2%). In the asthma group, multiple regression analysis followed by a stepwise procedure revealed that sputum eosinophil count was significantly and inversely associated with PC(20)M accounting for 16% of its total variance (P < 0.001) while neutrophil counts positively related to PC(20)M accounting for 4% of total variance (P < 0.05). By contrast, no significant relationship was found between either eosinophil or neutrophil counts and the slope of forced vital capacity (FVC) vs FEV(1) from the methacholine challenge.

CONCLUSIONS

We conclude that two-thirds of people in the mild to moderate asthma group had increased sputum eosinophilia, which plays a limited role in determining the degree of methacholine airway hyperresponsiveness.

Analysis of induced sputum in adults with asthma: identification of subgroup with isolated sputum neutrophilia and poor response to inhaled corticosteroids

BACKGROUND

The debate as to whether asthma is a single or heterogeneous disease remains unresolved although pathological studies, mostly using fibreoptic bronchoscopy on small numbers of subjects, have emphasised the similarities between different clinical phenotypes.

METHODS

Lower airway inflammation was assessed non-invasively using induced sputum in 34 normal controls and 259 adults with symptomatic asthma receiving treatment at steps 1-3 of the British Thoracic Society (BTS) guidelines. A subgroup of 49 patients treated with as required beta(2) agonists only who met BTS criteria for a step up in treatment were studied before and 2 months after treatment with inhaled budesonide 400 micro g twice daily.

RESULTS

There was considerable heterogeneity in induced sputum cell counts, particularly in non-atopic patients. A subgroup of 60 patients had a distinctive sputum cell profile with a neutrophil count higher than our normal range (>65.3%) and a normal sputum eosinophil count (<1.9%). These patients were older, predominantly female, and were more likely to be non-atopic but otherwise had similar clinical and physiological features to the group as a whole. Among the 49 subjects studied before and after inhaled budesonide, 11 patients had an isolated sputum neutrophilia. Following treatment, these patients showed significantly less improvement in visual analogue symptom scores (-5.5 v -19.4 mm; mean difference 13.9; 95% CI 0.7 to 27.0), forced expiratory volume in 1 second (FEV(1)) (-0.08 v 0.13 l; mean difference 0.21; 95% CI 0.03 to 0.39), and concentration of methacholine provoking a fall in FEV(1) of 20% or more (PC(20)) (0.15 v 1.29 doubling doses; mean difference 1.11; 95% CI 0.13 to 2.15) than the remaining 38 patients.

CONCLUSIONS

These results suggest the presence of a distinct subgroup of patients with mild to moderate asthma who have predominantly neutrophilic airway inflammation and who respond less well to treatment with inhaled corticosteroids.

Pathogenesis of asthma

There is now strong evidence that airway inflammation is a predominant underlying problem in patients with asthma, and it has been suggested that ongoing inflammation may lead to airway injury and remodeling. There is also recent evidence that longstanding asthma could be associated with loss of elastic recoil, which can enhance airway obstruction and worsen asthma control [82,83]. Therefore, the use of anti-inflammatory therapy has been advocated in all guidelines, including the National Asthma Education and Prevention Program (NAEPP) Expert Panel Report [84] and its recent update [85] that recommended inhaled steroids as a first mode of therapy for patients with mild, moderate, or severe, persistent asthma. There is preliminary evidence that early institution of anti-inflammatory therapy might lead to disease modification and limit the progression of subepithelial fibrosis and airway remodeling. The pathogenesis of asthma clearly involves many cells and mediators, although the contribution of each individual factor is probably different from patient to patient depending on the setting and stimulus. Although currently available therapies are highly effective in controlling asthma symptoms and limiting exacerbations in the majority of patients, there is still a subset of patients that proceed to develop severe asthma with decreased lung function, lack of responsiveness to therapy, or frequent exacerbations. It is hoped that rapid progress in the area of asthma genetics and pharmacogenetics will yield a more precise and patient-specific understanding of asthma pathogenesis and allow practitioners to prescribe therapies that are designed for a particular patient or exacerbation. That will undoubtedly help to improve the care of asthma, limit its morbidity, and reduce the side effect of medications.

Cooperative effects of Th2 cytokines and allergen on normal and asthmatic bronchial epithelial cells

In sensitized individuals, exposure to allergens such as Dermatophagoides pteronyssinus (Der p) causes Th2 polarization and release of cytokines, including IL-4 and IL-13. Because Der p extracts also have direct effects on epithelial cells, we hypothesized that allergen augments the effects of Th2 cytokines by promoting mediator release from the bronchial epithelium in allergic asthma. To test our hypothesis, primary bronchial epithelial cultures were grown from bronchial brushings of normal and atopic asthmatic subjects. RT-PCR showed that each culture expressed IL-4R(alpha), common gamma-chain, and IL-13R(alpha)(1), as well as IL-13R(alpha)(2), which negatively regulates IL-13 signaling; FACS analysis confirmed IL-13R(alpha)(2) protein expression. Exposure of epithelial cultures to either Der p extracts, TNF-alpha, IL-4, or IL-13 enhanced GM-CSF and IL-8 release, and this was partially suppressible by corticosteroids. Simultaneous exposure of the epithelial cultures to IL-4 or IL-13 together with Der p resulted in a further increase in cytokine release, which was at least additive. Release of TGF-alpha was also increased by TNF-alpha and combinations of IL-4, IL-13, and Der p; however, this stimulation was only significant in the asthma-derived cultures. These data suggest that, in an allergic environment, Th2 cytokines and allergen have the potential to sustain airway inflammation through a cooperative effect on cytokine release by the bronchial epithelium. Our novel finding that IL-4, IL-13, and allergen enhance release of TGF-alpha, a ligand for the epidermal growth factor receptor that stimulates fibroblast proliferation and goblet cell differentiation, provides a potential link between allergen exposure, Th2 cytokines, and airway remodelling in asthma.

Non-eosinophilic asthma: importance and possible mechanisms

There is increasing evidence that inflammatory mechanisms other than eosinophilic inflammation may be involved in producing the final common pathway of enhanced bronchial reactivity and reversible airflow obstruction that characterises asthma. A review of the literature has shown that, at most, only 50% of asthma cases are attributable to eosinophilic airway inflammation. It is hypothesised that a major proportion of asthma is based on neutrophilic airway inflammation, possibly triggered by environmental exposure to bacterial endotoxin, particulate air pollution, and ozone, as well as viral infections. If there are indeed two (or more) subtypes of asthma, and if non-eosinophilic (neutrophil mediated) asthma is relatively common, this would have major consequences for the treatment and prevention of asthma since most treatment and prevention strategies are now almost entirely focused on allergic/eosinophilic asthma and allergen avoidance measures, respectively. It is therefore important to study the aetiology of asthma further, including the underlying inflammatory profiles.

Clinical significance of bronchoalveolar eosinophils in childhood asthma

To evaluate the relationship between clinical parameters and differential cell counts, bronchoalveolar lavage was performed in 79 asthmatic infants and children with unusual asthma. Multivariate analysis showed significant associations between (1) allergic asthma and the presence of alveolar eosinophils and (2) persistent and longer asthma and an increased number of alveolar neutrophils. Our results provide the first evidence that in asthmatic infants and children eosinophilic inflammation is related to allergic sensitization.

Lipoxins are potential endogenous antiinflammatory mediators in asthma

Lipoxins, endogenous eicosanoids biosynthetized in vivo at inflammation sites, are potential antiinflammatory mediators. Subjects with severe asthma present chronic inflammation of the airways despite long-term treatment with oral glucocorticoids. Therefore it is of interest to investigate the potential antiinflammatory effects of lipoxin A4 (LXA4) and lipoxin B4 (LXB4) that could attenuate chronic inflammation. In a first time, we detected interleukin (IL)-8 and LXA4 in supernatants of induced sputum. IL-8 was heightened in severe asthma (p = 0.001), whereas high concentrations of lipoxin A4 were present in mild asthma (p = 0.001). We then studied the effects of LXA4 on IL-8 released in vitro. Nanomolar concentrations of LXA4 and LXB4 inhibited the IL-8 released by peripheral blood mononuclear cells from the two groups of patients with asthma: a maximal inhibition of 29.4% (p < 0.01) was observed for patients with mild asthma, and 41.5% inhibition (p < 0.001) for patients with severe asthma at 1 nM and 100 nM LXA4 concentrations, respectively. Polymerase chain reaction analysis indicated that peripheral blood mononuclear cells from patients with asthma expressed the LXA4 receptor mRNA. Moreover, pertussis toxin reversed LXA4- and LXB4-inhibited IL-8 release. These findings suggest that lipoxins have potential antiinflammatory action in asthma.

Airway neutrophil inflammation in nonasthmatic patients with food allergy

BACKGROUND

Patients with food allergy (FA) have been recently shown to develop bronchial hyperresponsiveness (BHR), despite the absence of any concomitant asthmatic manifestation. In order to explain this observation, we sought to examine the presence of a bronchial inflammation in induced sputum of nonasthmatic patients with FA.

METHODS

Twelve nonasthmatic patients with FA (urticaria, digestive symptoms, anaphylaxis) were included in the study. Results were compared to these obtained from eight asthmatic patients without food allergy and eight healthy controls. Diagnosis of FA was based on double-blind placebo-controlled challenge. Sputum cells and fluid-phase eosinophil cationic protein (ECP), myeloperoxidase (MPO) and interleukin-8 (IL-8) were measured in induced sputum. BHR was evaluated using methacholine inhalation.

RESULTS

Sputum from asthmatics, in comparison with the sputum of healthy subjects and patients with FA contained a higher proportion of eosinophils and higher levels of ECP (< 0.001). In marked contrast, patients with FA exhibited an increased proportion of neutrophils and IL-8 in comparison with asthmatics and controls (P < 0.05 for neutrophils and P < 0.001 for IL-8). There was a significant correlation between sputum neutrophils and IL-8 (r = 0.68, P < 0.001). MPO levels were not different between the groups. There was a trend toward higher levels of IL-8 and ECP in food allergic patients with BHR in comparison with patients with FA without BHR.

CONCLUSION

Our results demonstrate that a subclinical neutrophil airway inflammation is present in patients with food allergy free of clinical respiratory symptoms and that IL-8 may be an important mediator of this neutrophilia.

Association of forced expiratory volume with disease duration and sputum neutrophils in chronic asthma

Some patients with chronic asthma develop irreversible airflow obstruction. Our aim was to assess whether reported duration of asthma and induced sputum cell counts were associated with pulmonary function in patients with asthma who did not smoke. Maximal forced expiratory volume in the first second (FEV(1)) was determined following a steroid trial (oral prednisolone, 30 mg/d [n = 92 patients]; or inhaled fluticasone, 2000 microg/d [n = 5]; for 2 weeks) and 2.5 mg of nebulized albuterol. Asthma history was recorded with duration from first diagnosis. All subjects were nonsmokers, or were to have stopped smoking > or =5 years previously and smoked < or =5 pack-years (n = 12). Induced sputum was obtained from 59 subjects for analysis of airway cell counts. Maximal FEV(1) was inversely associated with asthma duration (r = -0.47, P <0.0001), age (r = -0.40, P <0.0001), and the proportion of sputum neutrophils (r(s) = -0.50, P = 0.00004). After adjusting for age, both duration of disease and sputum neutrophils were independently associated with maximal FEV(1). Neutrophil activation, as measured by sputum myeloperoxidase levels, was positively associated with the proportion of sputum neutrophils (r(s) = 0.45, P = 0.0004) and inversely associated with maximal FEV(1) (r(s) = -0.59, P <0.0001). Long disease duration may be a predisposing factor for the development of irreversible airflow obstruction in patients with chronic asthma. The negative associations of sputum neutrophil count and activation with maximal FEV(1) suggest that neutrophils may be involved in the pathophysiology of irreversible airflow obstruction in asthma.

Exhaled leukotrienes and prostaglandins in asthma

BACKGROUND

Most of the studies investigating the role of leukotrienes (LTs) and prostaglandins (PGs) in asthma have used invasive (eg, bronchoalveolar lavage fluid) or semi-invasive (eg, sputum induction) techniques. Others have measured eicosanoids in plasma or urine, probably reflecting systemic rather than lung inflammation. Collection of exhaled breath condensate (EBC) is a noninvasive method to collect airway secretions.

OBJECTIVE

We sought to investigate whether eicosanoids are measurable in EBC, to show possible differences in their concentrations in asthmatic patients and healthy subjects, and to investigate whether exhaled eicosanoids correlate with exhaled nitric oxide (NO), a marker of airway inflammation.

METHODS

Twelve healthy nonsmokers and 15 steroid-naive patients with mild asthma were studied. Subjects attended on one occasion for pulmonary function tests, collection of EBC, and exhaled NO measurements. Exhaled LTB(4)-like immunoreactivity, LTE(4)-like immunoreactivity, PGE(2)-like immunoreactivity, PGD(2)-methoxime, PGF(2)(alpha)-like immunoreactivity, and thromboxane B(2)-like immunoreactivity were measured by means of enzyme immunoassays.

RESULTS

LTE(4)-like immunoreactivity and LTB(4)-like immunoreactivity were detectable in EBC in healthy subjects, and their levels in asthmatic patients were increased about 3-fold (P <.0001) and 2-fold (P <.0005), respectively. Exhaled NO was increased in asthmatic patients compared with healthy subjects (P <.0001). There was a correlation between exhaled LTB(4) and exhaled NO (r = 0.56, P <.04) in patients with asthma. When measurable, prostanoid levels were similar in asthmatic patients and control subjects.

CONCLUSIONS

Exhaled LTE(4) and LTB(4) are increased in steroid-naive patients with mild asthma. EBC may be proved to be a novel method to monitor airway inflammation in asthma.

High resolution computed tomographic assessment of airway wall thickness in chronic asthma: reproducibility and relationship with lung function and severity

BACKGROUND

In some patients chronic asthma results in irreversible airflow obstruction. High resolution computed tomography (HRCT) has been advocated for assessing the structural changes in the asthmatic lung and permits investigation of the relationships between airway wall thickening and clinical parameters in this condition.

METHODS

High resolution CT scanning was performed in 49 optimally controlled asthmatic patients and measurements of total airway and lumen diameter were made by two independent radiologists using electronic callipers. Wall area as % total airway cross sectional area (WA%) and wall thickness to airway diameter ratio (T/D) were calculated for all airways clearly visualised with a transverse diameter of more than 1.5 mm, with a mean value derived for each patient. Intra- and inter-observer variability was assessed for scope of agreement in a subgroup of patients. Measurements were related to optimum forced expiratory volume in 1 second (FEV1), forced mid expiratory flow, carbon monoxide gas transfer, two scores of asthma severity, airway inflammation as assessed with induced sputum, and exhaled nitric oxide.

RESULTS

Neither observer produced a statistically significant difference between measurements performed on two occasions but there was a significant difference between observers (limits of agreement -2.6 to 6.8 for WA%, p<0.0001). However, mean WA% measured on two occasions differed by no more than 5.4% (limits of agreement -4.0 to 5.4; mean (SD) 0.7 (2.4)). Statistically significant positive associations were observed between both WA% and T/D ratio and asthma severity (r(S)=0.29 and 0.30, respectively, for ATS score), and an inverse association with gas transfer coefficient was observed (r(S)=-0.43 for WA% and r(S)=-0.41 for T/D). No association was identified with FEV1 or airway inflammation.

CONCLUSIONS

The airway wall is thickened in more severe asthma and is associated with gas transfer coefficient. This thickening does not relate directly to irreversible airflow obstruction as measured with FEV1.

Occupational asthma due to low molecular weight agents: eosinophilic and non-eosinophilic variants

BACKGROUND

Despite having a work related deterioration in peak expiratory flow (PEF), many workers with occupational asthma show a low degree of within day diurnal variability atypical of non-occupational asthma. It was hypothesised that these workers would have a neutrophilic rather than an eosinophilic airway inflammatory response.

METHODS

Thirty eight consecutive workers with occupational asthma induced by low molecular weight agents underwent sputum induction and assessment of airway physiology while still exposed at work.

RESULTS

Only 14 (36.8%) of the 38 workers had sputum eosinophilia (>2.2%). Both eosinophilic and non-eosinophilic groups had sputum neutrophilia (mean (SD) 59.5 (19.6)% and 55.1 (18.8)%, respectively). The diurnal variation and magnitude of fall in PEF during work periods was not significantly different between workers with and without sputum eosinophilia. Those with eosinophilia had a lower forced expiratory volume in 1 second (FEV1; 61.4% v 83% predicted, mean difference 21.6, 95% confidence interval (CI) 9.2 to 34.1, p=0.001) and greater methacholine reactivity (geometric mean PD20 253 microg v 1401 microg, p=0.007). They also had greater bronchodilator reversibility (397 ml v 161 ml, mean difference 236, 95% CI of difference 84 to 389, p=0.003) which was unrelated to differences in baseline FEV(1). The presence of sputum eosinophilia did not relate to the causative agent, duration of exposure, atopy, or lack of treatment.

CONCLUSIONS

Asthma caused by low molecular weight agents can be separated into eosinophilic and non-eosinophilic pathophysiological variants with the latter predominating. Both groups had evidence of sputum neutrophilia. Sputum eosinophilia was associated with more severe disease and greater bronchodilator reversibility but no difference in PEF response to work exposure.

CXCR2 is necessary for the development and persistence of chronic fungal asthma in mice

The role of CXCR during allergic airway and asthmatic diseases is yet to be fully characterized. Therefore, the present study addressed the role of CXCR2 during Aspergillus fumigatus-induced asthma. Mice deficient in CXCR2 (CXCR2-/-) and wild-type counterparts (CXCR2+/+) were sensitized to A. fumigatus Ags and challenged with A. fumigatus conidia, and the resulting allergic airway disease was monitored for up to 37 days. At days 3 and 7 after conidia, CXCR2-/- mice exhibited significantly greater methacholine-induced airway hyperreactivity than did CXCR2+/+ mice. In contrast, CXCR2-deficient mice exhibited significantly less airway hyperresponsiveness than the wild-type control groups at days 14 and 37 after conidia. At all times after conidia, whole lung levels of IL-4, IL-5, and eotaxin/CC chemokine ligand 11 were significantly lower in CXCR2-/- mice than in the wild-type controls. Eosinophil and T cell, but not neutrophil, recruitment into the airways of A. fumigatus-sensitized CXCR2-/- mice was significantly impaired compared with wild-type controls at all times after the conidia challenge. Whole lung levels of IFN-gamma, inflammatory protein-10/CXC ligand (CXCL) 10, and monokine induced by IFN-gamma (MIG)/CXCL9 were significantly increased in CXCR2-/- mice compared with CXCR2+/+ mice at various times after conidia. Interestingly, at day 3 after conidia, neutrophil recruitment and airway hyperresponsiveness in CXCR2-/- mice was mediated by inflammatory protein-10/CXCL10 and, to a lesser degree, MIG/CXCL9. Taken together, these data suggest that CXCR2 contributes to the persistence of asthmatic disease due to A. fumigatus.

CCL7 and CXCL10 orchestrate oxidative stress-induced neutrophilic lung inflammation

Oxidative stress from ozone (O(3)) exposure augments airway neutrophil recruitment and chemokine production. We and others have shown that severe and sudden asthma is associated with airway neutrophilia, and that O(3) oxidative stress is likely to augment neutrophilic airway inflammation in severe asthma. However, very little is known about chemokines that orchestrate oxidative stress-induced neutrophilic airway inflammation in vivo. To identify these chemokines, three groups of BALB/c mice were exposed to sham air, 0.2 ppm O(3), or 0.8 ppm O(3) for 6 h. Compared with sham air, 0.8 ppm O(3), but not 0.2 ppm O(3), induced pronounced neutrophilic airway inflammation that peaked at 18 h postexposure. The 0.8 ppm O(3) up-regulated lung mRNA of CXCL1,2,3 (mouse growth-related oncogene-alpha and macrophage-inflammatory protein-2), CXCL10 (IFN-gamma-inducible protein-10), CCL3 (macrophage-inflammatory protein-1alpha), CCL7 (monocyte chemoattractant protein-3), and CCL11 (eotaxin) at 0 h postexposure, and expression of CXCL10, CCL3, and CCL7 mRNA was sustained 18 h postexposure. O(3) increased lung protein levels of CXCL10, CCL7, and CCR3 (CCL7R). The airway epithelium was identified as a source of CCL7. The role of up-regulated chemokines was determined by administering control IgG or IgG Abs against six murine chemokines before O(3) exposure. As expected, anti-mouse growth-related oncogene-alpha inhibited neutrophil recruitment. Surprisingly, Abs to CCL7 and CXCL10 also decreased neutrophil recruitment by 63 and 72%, respectively. These findings indicate that CCL7 and CXCL10, two chemokines not previously reported to orchestrate neutrophilic inflammation, play a critical role in mediating oxidative stress-induced neutrophilic airway inflammation. These observations may have relevance in induction of neutrophilia in severe asthma.

Trimellitic anhydride-induced cellular infiltration into Guinea pig lung varies with age but not gender

BACKGROUND

In humans the incidence of asthma changes with age and gender. Immature guinea pigs have been used to model the allergic response to the occupational allergen trimellitic anhydride (TMA) where exposure to adults is paramount. We hypothesized that the TMA-induced allergic response in immature guinea pigs was similar to mature animals, regardless of gender.

METHODS

Sexually immature and mature female and male guinea pigs were sensitized intradermally with TMA. Three weeks after sensitization they were challenged intratracheally with TMA conjugated to guinea pig serum albumin (TMA-GPSA) or GPSA as a control. Twenty-four hours later cell infiltration into the lung was determined. TMA-specific IgG(1) and IgG(2) were measured in plasma and the complement activation product C3a was measured in the bronchoalveolar lavage fluid.

RESULTS

In control animals, numbers of eosinophils and neutrophils varied with age and gender. The TMA-GPSA- induced cellular infiltration was similar in all age/gender groups. However, neutrophils in the lung tissue increased only in immature animals. IgG antibodies differed between groups but did not account for differences in cell infiltration. C3a correlated with the extent of cell infiltration in all groups except mature females.

CONCLUSIONS

TMA-induced neutrophilia differs with age. TMA-induced changes in eosinophils and macrophages did not vary with age or gender. The relationship between complement activation and inflammation in mature females differs from that in the other groups, suggesting mediators of the response may change with age and gender. Effects of age and gender need to be considered in animal models of the allergic response.

A murine model of toluene diisocyanate-induced asthma can be treated with matrix metalloproteinase inhibitor

BACKGROUND

Toluene diisocyanate (TDI) is a leading cause of occupational asthma. TDI-induced asthma is an inflammatory disease of the airways that is associated with airway remodeling. However, there are little data available on the role of matrix metalloproteinases (MMPs) in TDI-induced asthma.

OBJECTIVE

We evaluated whether MMP-9 participates in the airway inflammation in TDI-induced asthma. An additional aim of the present study was to determine whether MMP inhibitors could be effective therapeutic agents for TDI-induced asthma.

METHODS

We developed a murine model of TDI-induced asthma to examine the involvement of MMPs by performing 2 sensitizations with 3% TDI and 1 challenge with 1% TDI using ultrasonic nebulization.

RESULTS

Murine TDI-induced asthma includes findings of (1) increased inflammatory cells, including neutrophils, lymphocytes, and eosinophils; (2) histologic changes, including infiltration of inflammatory cells around bronchioles, thickened airway epithelium, and accumulation of mucus and debris in the bronchioles; (3) increased MMP-9 activity in inflammatory cells in the airway lumen; and (4) airway hyperresponsiveness. Administration of an MMP inhibitor remarkably reduced all these pathophysiologic findings.

CONCLUSION

We conclude that TDI-induced occupational asthma is associated with the induction of MMP-9 in inflammatory cells, and the inhibition of MMP-9 may be a good therapeutic strategy.

Beclomethasone, budesonide and fluticasone propionate inhibit human neutrophil apoptosis

Inhaled glucocorticoids are widely used to treat chronic obstructive pulmonary disease without much evidence of efficiency in this disease where neutrophils may contribute to the pathophysiology. This prompted us to test the effects of several currently used inhaled and systemic glucocorticoids on human neutrophil apoptosis. Beclomethasone, budesonide, dexamethasone, fluticasone propionate, hydrocortisone and prednisolone inhibited apoptosis in a concentration-dependent manner as assessed by flow cytometric analysis, annexin-V binding and morphological analysis. The maximal inhibition of apoptosis was 50-60%. The order of potency was fluticasone propionate (EC(50) 0.6+/-0.2 nM) approximately equal to budesonide (EC(50) 0.8+/-0.2 nM)> dexamethasone approximately equal to prednisolone approximately equal to beclomethasone approximately equal to hydrocortisone. The inhibitory effects of glucocorticoids were reversed by mifepristone. Moreover, glucocorticoids slightly enhanced the inhibitory effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on neutrophil apoptosis. The present data suggests that budesonide and fluticasone propionate prolong human neutrophil survival by inhibiting apoptosis at clinically relevant drug concentrations via an effect on glucocorticoid receptor.

Relationship between airway inflammation, hyperresponsiveness, and obstruction in asthma

BACKGROUND

Although the role of eosinophils in airway inflammation in chronic asthma has been extensively studied, a role for neutrophils has not been well characterized. Furthermore, prior studies have not systematically sought or controlled for factors that might confound the relationship between cellular markers of inflammation and physiologic measures of airway function.

OBJECTIVE

The purpose of this study was to determine whether eosinophilic and neutrophilic inflammation independently contribute to abnormalities of airway function in asthma.

METHODS

Multivariate analysis of data collected during screening and enrollment of 205 asthmatic adults for clinical trials was conducted to examine the relationships between cellular inflammation in induced sputum and FEV(1) and methacholine responsiveness (PC(20)) while confounding factors were controlled for.

RESULTS

We found that age, sex, ethnicity, and use of inhaled corticosteroids were important confounding factors of the relationship between cellular inflammation and airway function. When these factors were controlled for, multivariate analysis showed that eosinophil percentage in induced sputum is independently associated with lower FEV(1) and lower PC(20) (P = .005 and P = .005, respectively). In the same models, increased sputum neutrophil percentage is independently associated with lower FEV(1) (P = .038) but not with PC(20) (P = .49).

CONCLUSIONS

These results suggest that both eosinophilic inflammation and neutrophilic inflammation independently contribute to abnormalities of FEV(1) in asthma. Therapies directed specifically at control of neutrophilic inflammation might be useful in improving airway caliber in patients with chronic asthma.

Cross-talk between pro-inflammatory transcription factors and glucocorticoids

Asthma is a chronic inflammatory disease of the airway that is characterized by cellular infiltration and activation. These processes are induced by overexpression of chemokines and cytokines, such as eotaxin, IL-1beta and GM-CSF. These mediators are downstream targets for the transcription factors activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB), which control the expression of most immunomodulatory genes and whose activity and expression are elevated in asthma. Glucocorticoids are the most effective anti-inflammatory drugs used in the treatment of chronic inflammatory diseases such as asthma. They act by binding to a specific glucocorticoid receptor (GR) that on activation translocates to the nucleus and either increases (transactivates) or decreases (transrepresses) the expression of responsive genes. Transrepression is the major mechanism of glucocorticoid action in inhibiting inflammatory gene expression. Thus, the ability of the transcription factors AP-1 and NF-kappaB to induce gene transcription is attenuated by GR. Although only 5-10% of asthmatic subjects are glucocorticoid-insensitive, these subjects account for over 50% of the health-care costs for asthma (> $6 billion per annum). Examining these patients also gives an insight into important aspects of glucocorticoid action in controlling inflammation and into the development of potential new drugs. Biochemical and genomic studies have indicated abnormal induction of the c-Jun N-terminal kinase (JNK) pathway in some of these patients. The ability of most patients to respond to dexamethasone with induction of histone acetylation correlated with nuclear translocation of GR. However, a subgroup of these patients had an inability to correctly interact with the basal transcription complex in spite of high levels of nuclear GR. This suggests that cross-talk between pro- and anti-inflammatory transcription factors may modulate activation of the transcriptional complex and thereby reduce steroid actions.

Inflammatory cell distribution in guinea pig airways and its relationship to airway reactivity

Although airway inflammation and airway hyperreactivity are observed after allergen inhalation both in allergic humans and animals, little is known about the mechanisms by which inflammatory cells can contribute to allergen-induced airway hyperreactivity. To understand how inflammatory cell infiltration can contribute to airway hyperreactivity, the location of these cells within the airways may be crucial Using a guinea pig model of acute allergic asthma, we investigated the inflammatory cell infiltration in different airway compartments at 6 and 24 h (i.e. after the early and the late asthmatic reaction, respectively) after allergen or saline challenge in relation to changes in airway reactivity (AR) to histamine. At 6 h after allergen challenge, a threefold (p < 0.01) increase in the AR to histamine was observed. At 24 h after challenge, the AR to histamine was lower, but still significantly enhanced (1.6-fold, p < 0.05). Adventitial eosinophil and neutrophil numbers in both bronchi and bronchioli were significantly increased at 6 h post-allergen provocation as compared with saline (p < 0.01 for all), while there was a strong tendency to enhanced eosinophils in the bronchial submucosa at this time point (p = 0.08). At 24h after allergen challenge, the eosinophilic and neutrophilic cell infiltration was reduced. CD3+ T lymphocytes were increased in the adventitial compartment of the large airways (p < 0.05) and in the parenchyma (p < 0.05) at 24h post-allergen, while numbers of CD8+ cells did not differ from saline treatment at any time point post-provocation. The results indicate that, after allergen provocation, inflammatory cell numbers in the airways are mainly elevated in the adventitial compartment. The adventitial inflammation could be important for the development of allergen-induced airway hyperreactivity.