Neutrophilic inflammation in severe persistent asthma

Inflammatory markers in chronic obstructive pulmonary disease patients with different α1 antitrypsin genotypes

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) has been recently defined as a systemic pulmonary inflammatory disease, and congenital α1 antitrypsin deficiency is one of the well-established genetic risk factors for chronic obstructive pulmonary disease. The aim of our study was to evaluate the possible associations of α1 antitrypsin with inflammatory markers - CRP, sCD14, TNF-α, sTNFR-1, and sTNFR-2 - in patients with COPD with different α1 antitrypsin genotypes.

MATERIAL AND METHODS

Serum biomarkers from patients (n = 355) with COPD, defined according to the GOLD criteria, were analyzed using commercial ELISA kits; α1 antitrypsin concentrations were determined by nephelometry, and α1 antitrypsin phenotyping was carried out by means of isoelectric focusing.

RESULTS

No significant differences in CRP, TNF-α, sTNFR-1, sTNFR-2, and sCD14 levels were found comparing COPD patients with different genotypes. In patients without α1 antitrypsin deficiency (PI*MM), a significant negative correlation between lung function (FEV(1)) and serum α1 antitrypsin (r = -0.522, p = 0.03) and CRP concentration (r = -0.590, p = 0.011) was detected. The level of α1 antitrypsin positively correlated with: a) CRP concentration (r = 0.671, p = 0.005), b) sCD14 (r = 0.510, p = 0.008) and c) sTNFR-1 (r = 0.567, p = 0.007).

CONCLUSIONS

In patients without α1 antitrypsin deficiency, the positive association of α1 antitrypsin concentration with CRP, sCD14, and sTNFR-1 and the negative association with FEV(1) show the importance of α1 antitrypsin as a marker of systemic inflammation.

Lipopolysaccharide inhibits Th2 lung inflammation induced by house dust mite allergens in mice

The complex biology of asthma compels the use of more relevant human allergens, such as house dust mite (HDM), to improve the translation of animal models into human asthma. LPS exposure is associated with aggravations of asthma, but the mechanisms remain unclear. Here, we studied the effects of increasing LPS doses on HDM-evoked allergic lung inflammation. To this end, mice were intranasally sensitized and challenged with HDM with or without increasing doses of LPS (0.001-10 μg). LPS dose-dependently inhibited HDM-induced eosinophil recruitment into the lungs and mucus production in the airways. LPS attenuated the production of Th2 cytokines (IL-4, IL-5, IL-10, and IL-13) in HDM-challenged lungs, while enhancing the HDM-induced release of IL-17, IL-33, IFN-γ, and TNF-α. The shift toward a Th1 inflammatory response was further illustrated by predominant neutrophilic lung inflammation after LPS administration at higher doses. LPS did not influence HDM-induced plasma IgE concentrations. Although LPS did not significantly affect the activation of coagulation or complement in HDM-challenged lungs, it reduced HDM-initiated endothelial cell activation. This study is the first to provide insights into the effects of LPS in an allergic lung inflammation model making use of a clinically relevant allergen without a systemic adjuvant, revealing that LPS dose-dependently inhibits HDM-induced pulmonary Th2 responses.

Inflammation in COPD: implications for management

Chronic obstructive pulmonary disease (COPD) is recognized by the Global Initiative for Chronic Obstructive Lung Disease guidelines as an inflammatory disease state, and treatment rationales are provided accordingly. However, not all physicians follow or are even aware of these guidelines. Research has shown that COPD inflammation involves multiple inflammatory cells and mediators and the underlying pathology differs from asthma inflammation. For these reasons, therapeutic agents that are effective in asthma patients may not be optimal in COPD patients. COPD exacerbations are intensified inflammatory events compared with stable COPD. The clinical and systemic consequences believed to result from the chronic inflammation observed in COPD suggest that inflammation intensity is a key factor in COPD and exacerbation severity and frequency. Although inhaled corticosteroids are commonly used and are essential in asthma management, their efficacy in COPD is limited, with only a modest effect at reducing exacerbations. The importance of inflammation in COPD needs to be better understood by clinicians, and the differences in inflammation in COPD versus asthma should be considered carefully to optimize the use of anti-inflammatory agents.

The β-glucan receptor dectin-1 promotes lung immunopathology during fungal allergy via IL-22

Sensitization to fungi, such as the mold Aspergillus fumigatus, is increasingly becoming linked with asthma severity. We have previously shown that lung responses generated via the β-glucan receptor Dectin-1 are required for lung defense during acute, invasive A. fumigatus infection. Unexpectedly, in an allergic model of chronic lung exposure to live A. fumigatus conidia, β-glucan recognition via Dectin-1 led to the induction of multiple proallergic (Muc5ac, Clca3, CCL17, CCL22, and IL-33) and proinflammatory (IL-1β and CXCL1) mediators that compromised lung function. Attenuated proallergic and proinflammatory responses in the absence of Dectin-1 were not associated with changes in Ido (IDO), Il12p35/Ebi3 (IL-35), IL-10, or TGF-β levels. Assessment of Th responses demonstrated that purified lung CD4(+) T cells produced IL-4, IL-13, IFN-γ, and IL-17A, but not IL-22, in a Dectin-1-dependent manner. In contrast, we observed robust, Dectin-1-dependent IL-22 production by unfractionated lung digest cells. Intriguingly, the absence of IL-22 alone mimicked the attenuated proallergic and proinflammatory responses observed in the absence of Dectin-1, suggesting that Dectin-1-mediated IL-22 production potentiated responses that led to decrements in lung function. To this end, neutralization of IL-22 improved lung function in normal mice. Collectively, these results indicate that the β-glucan receptor Dectin-1 contributes to lung inflammation and immunopathology associated with persistent fungal exposure via the production of IL-22.

ORMDL3 is an inducible lung epithelial gene regulating metalloproteases, chemokines, OAS, and ATF6

Orosomucoid like 3 (ORMDL3) has been strongly linked with asthma in genetic association studies, but its function in asthma is unknown. We demonstrate that in mice ORMDL3 is an allergen and cytokine (IL-4 or IL-13) inducible endoplasmic reticulum (ER) gene expressed predominantly in airway epithelial cells. Allergen challenge induces a 127-fold increase in ORMDL3 mRNA in bronchial epithelium in WT mice, with lesser 15-fold increases in ORMDL-2 and no changes in ORMDL-1. Studies of STAT-6-deficient mice demonstrated that ORMDL3 mRNA induction highly depends on STAT-6. Transfection of ORMDL3 in human bronchial epithelial cells in vitro induced expression of metalloproteases (MMP-9, ADAM-8), CC chemokines (CCL-20), CXC chemokines (IL-8, CXCL-10, CXCL-11), oligoadenylate synthetases (OAS) genes, and selectively activated activating transcription factor 6 (ATF6), an unfolded protein response (UPR) pathway transcription factor. siRNA knockdown of ATF-6α in lung epithelial cells inhibited expression of SERCA2b, which has been implicated in airway remodeling in asthma. In addition, transfection of ORMDL3 in lung epithelial cells activated ATF6α and induced SERCA2b. These studies provide evidence of the inducible nature of ORMDL3 ER expression in particular in bronchial epithelial cells and suggest an ER UPR pathway through which ORMDL3 may be linked to asthma.

The role of protease-activated receptor-2 on pulmonary neutrophils in the innate immune response to cockroach allergen

Background

Serine proteases in German cockroach (GC) have been shown to mediate allergic airway inflammation through the activation of protease activated receptor (PAR)-2. Neutrophils play an important role in regulating the innate immune response, and are recruited into the airways following GC frass exposure. As such, we investigated the role of PAR-2 in airway neutrophil recruitment, activation and cytokine production following allergen exposure.

Methods

Wild type and PAR-2-deficient mice were administered a single intratracheal instillation of PBS or GC frass and neutrophil recruitment, expression of PAR-2, CD80, CD86, and MHC class II were assessed by flow cytometry and levels of tumor necrosis factor (TNF)α was assessed by ELISA. Uptake of AlexaFluor 405-labeled GC frass by neutrophils was performed by flow cytometry.

Results

Neutrophil recruitment in the lung and airways following GC frass exposure was significantly decreased in PAR-2-deficient mice compared to wild type mice. GC frass exposure increased the level of PAR-2 on pulmonary neutrophils and increased numbers of PAR-2-positive neutrophils were found in the lungs; however PAR-2 did not play a role in meditating allergen uptake. Comparing wild type and PAR-2-deficient mice, we found that a single exposure to GC frass increased levels of CD80 and CD86 on pulmonary neutrophils, an effect which was independent of PAR-2 expression. Neutrophils isolated from the whole lungs of naïve PAR-2-deficient mice treated ex vivo with GC frass produced significantly less TNFα than in similarly treated wild type neutrophils. Lastly, neutrophils were isolated from the bronchoalveolar lavage fluid of wild type and PAR-2-deficient mice following a single intratracheal exposure to GC frass. Airway neutrophils from PAR-2-deficient mice released substantially decreased levels of TNFα, suggesting a role for PAR-2 in neutrophil-derived cytokine production.

Conclusions

Together these data suggest PAR-2 expression can be upregulated on lung neutrophils following allergen exposure and the consequence is altered release of TNFα which could drive the early innate immune response.

Neutrophilic inflammatory response and oxidative stress in premenopausal women chronically exposed to indoor air pollution from biomass burning

The possibility of inflammation and neutrophil activation in response to indoor air pollution (IAP) from biomass fuel use has been investigated. For this, 142 premenopausal, never-smoking women (median age, 34 years) who cook exclusively with biomass (wood, dung, crop wastes) and 126 age-matched control women who cook with cleaner fuel liquefied petroleum gas (LPG) were enrolled. The neutrophil count in blood and sputum was significantly higher (p < 0.05) in biomass users than the control group. Flow cytometric analysis revealed marked increase in the surface expression of CD35 (complement receptor-1), CD16 (F(C)γ receptor III), and β(2) Mac-1 integrin (CD11b/CD18) on circulating neutrophils of biomass users. Besides, enzyme-linked immunosorbent assay showed that they had 72%, 67%, and 54% higher plasma levels of the proinflammatory cytokines tumor necrosis factor-alpha, interleukin-6, and interleukin-12, respectively, and doubled neutrophil chemoattractant interleukin-8. Immunocytochemical study revealed significantly higher percentage of airway neutrophils expressing inducible nitric oxide synthase, while the serum level of nitric oxide was doubled in women who cooked with biomass. Spectrophotometric analysis documented higher myeloperoxidase activity in circulating neutrophils of biomass users, suggesting neutrophil activation. Flow cytometry showed excess generation of reactive oxygen species (ROS) by leukocytes of biomass-using women, whereas their erythrocytes contained a depleted level of antioxidant enzyme superoxide dismutase (SOD). Indoor air of biomass-using households had two to four times more particulate matter with diameters of <10 μm (PM(10)) and <2.5 μm (PM(2.5)) as measured by real-time laser photometer. After controlling potential confounders, rise in proinflammatory mediators among biomass users were positively associated with PM(10) and PM(2.5) in indoor air, suggesting a close relationship between IAP and neutrophil activation. Besides, the levels of neutrophil activation and inflammation markers were positively associated with generation of ROS and negatively with SOD, indicating a role of oxidative stress in mediating neutrophilic inflammatory response following chronic inhalation of biomass smoke.

IL-13 in asthma and allergic disease: asthma phenotypes and targeted therapies

Decades of research in animal models have provided abundant evidence to show that IL-13 is a key T(H)2 cytokine that directs many of the important features of airway inflammation and remodeling in patients with allergic asthma. Several promising focused therapies for asthma that target the IL-13/IL-4/signal transducer and activator of transcription 6 pathway are in development, including anti-IL-13 mAbs and IL-4 receptor antagonists. The efficacy of these new potential asthma therapies depends on the responsiveness of patients. However, an understanding of how IL-13-directed therapies might benefit asthmatic patients is confounded by the complex heterogeneity of the disease. Recent efforts to classify subphenotypes of asthma have focused on sputum cellular inflammation profiles, as well as cluster analyses of clinical variables and molecular and genetic signatures. Researchers and clinicians can now evaluate biomarkers of T(H)2-driven airway inflammation in asthmatic patients, such as serum IgE levels, sputum eosinophil counts, fraction of exhaled nitric oxide levels, and serum periostin levels, to aid decision making in clinical trials and drug development and to identify subsets of patients who might benefit from therapies. Although it is unlikely that these therapies will benefit all asthmatic patients with this heterogeneous disease, advances in understanding asthma subphenotypes in relation to clinical variables and T(H)2 cytokine responses offer the opportunity to improve the efficacy and safety of proposed therapies for asthma.

The investigation of severe asthma to define phenotypes

Severe asthmatics often exhibit poor control despite high doses of inhaled corticosteroids with or without systemic corticosteroids and suffer from persistent symptoms and/or recurrent exacerbations. Five to ten percentage of the asthmatic population falls within this category. Patients with severe asthma are a heterogeneous group and should be investigated to confirm the diagnosis, identify comorbidities, exclude alternative diagnoses, together with an evaluation of treatment adherence and side-effects from medications. Optimization of asthma medications and monitoring the control and pattern of asthma usually takes place over a period of 6 months. In patients with confirmed severe refractory asthma, further evaluation is needed in terms of detailed lung function, of airway and lung structure using high resolution computed tomographic scanning, and of airway inflammatory processes and biomarkers using induced sputum or bronchial biopsies. Patients with severe asthma are best investigated and managed with a multidisciplinary team. Severe asthma consists of different phenotypes that need defining. Investigation of severe asthma should bring into the open the various characteristics of the disease that could point to particular phenotype. Inclusion of investigations based on transcriptomics and proteomics should expand, improve classification and understanding of severe asthma, with the ultimate hope of finding more effective treatments and a step towards personalized medicine.

Interleukin-25 induces type 2 cytokine production in a steroid-resistant interleukin-17RB+ myeloid population that exacerbates asthmatic pathology

This study identifies the IL-25 receptor, IL-17RB, is an important mediator of both innate and adaptive pulmonary type 2 immune responses. Allergen exposure upregulated IL-25 and induced type 2 cytokine production in a novel granulocytic population, termed Type 2 Myeloid (T2M) cells. Il17rb^−/− mice exhibited reduced lung pathology following chronic allergen exposure and decreased cytokine production in T2M cells and CD4⁺ T-lymphocytes. Airway instillation of IL-25 induced IL-4 and IL-13 production exclusively in T2M cells demonstrating their importance in generating T cell-independent inflammation. The adoptive transfer of T2M cells reconstituted IL-25-mediated responses in Il17rb^−/− mice. High dose dexamethasone treatment did not reduce the IL-25-induced T2M pulmonary response. Finally, a similar IL-4/IL-13 producing granulocytic population was identified in peripheral blood of asthmatics. These data establish IL-25/IL-17RB as targets for innate and adaptive immune responses in chronic allergic airways disease, and identify T2M cells as a novel steroid-resistant cell population.

Breath biomarkers in diagnosis of pulmonary diseases

Breath analysis provides a convenient and simple alternative to traditional specimen testing in clinical laboratory diagnosis. As such, substantial research has been devoted to the analysis and identification of breath biomarkers. Development of new analytes enhances the desirability of breath analysis especially for patients who monitor daily biochemical parameters. Elucidating the physiologic significance of volatile substances in breath is essential for clinical use. This review describes the use of breath biomarkers in diagnosis of asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), lung cancer, as well as other pulmonary diseases. A number of breath biomarkers in lung pathophysiology will be described including nitric oxide (NO), carbon monoxide (CO), hydrogen peroxide (H₂O₂) and other hydrocarbons.

Corticosteroids: still at the frontline in asthma treatment?

Inhaled corticosteroids (ICS) have led to improved asthma control and reduced asthma mortality in the Western world. ICS are effective in combating T-helper type 2-driven inflammation featuring mast cell and eosinophilic airway infiltration. Their effect on innate immunity-driven neutrophilic inflammation is poor and their ability to prevent airway remodeling and accelerated lung decline is controversial. Although ICS remain pivotal drugs in asthma management, research is needed to find drugs complementary to the combination ICS/long-acting β2-agonist in refractory asthma and perhaps a new class of drugs as a first-line treatment in mild to moderate noneosinophilic asthma.

Tissue-based and bronchoalveolar lavage-based biomarkers in asthma

In this article, tissue and bronchoalveolar lavage biomarkers of asthma are evaluated for their use in asthma and evaluated in the context of the phenotype that they may best represent. It is hoped that studies that better link biomarkers to specific phenotypes will eventually improve the ability to evaluate genetic features, diagnose, measure progression, and tailor treatments. Although some biomarkers may only be associated with disease, it is also likely that some may be mechanistically involved. Some of these biomarkers may then also become targets for specific treatment.

How to diagnose and phenotype asthma

Asthma has been described as a chronic disease of the airways characterized by variable airflow obstruction, airway hyperresponsiveness, and airway inflammation. This review discusses the diagnosis and phenotyping of asthma, with a special emphasis on phenotyping based on the nature of cellular inflammation and radiological imaging and how this could be used to direct the treatment of asthma and, in the future, to apply specifically directed therapies to specific phenotypes.

Inflammatory marker sTREM-1 reflects the clinical stage and respiratory tract obstruction in allergic asthma bronchiale patients and correlates with number of neutrophils

The knowledge that asthma is an inflammatory disorder has prompted us to investigate the plasma levels of a new inflammatory marker sTREM-1 that is released from the surfaces of activated neutrophils and monocytes. The plasma levels of sTREM-1 were analysed by a sandwich ELISA test in the cohort of 76 patients with allergic asthma bronchiale and 39 healthy controls. Our results revealed more than 3.5 times higher levels of sTREM-1 in AB patients (92.3 pg/mL ± 125.6) compared with healthy subjects (25.7 pg/mL ± 9.2; P = 0.0001). Higher levels of sTREM-1 were found also in patients with exacerbated AB (170.5 pg/mL ± 78.2) compared with nonexacerbated AB patients (59.1 ± 78.2; P < 0.0001), patients with respiratory tract obstruction (176.4 pg/mL ± 177.8), than those without obstruction (51.99 pg/mL ± 64.0; P < 0.0001) and patients with anti-IgE therapy (P < 0.0001). Levels of sTREM-1 correlated with number of leucocytes (P = 0.002), and absolute number of neutrophils (P = 0.001). Elevated plasma levels of sTREM-1 reflect the severity, state of exacerbation, presence of respiratory tract obstruction in AB patients and together with increased number of neutrophils point to the role of neutrophils in inflammation accompanying AB.

Asthma phenotypes: the evolution from clinical to molecular approaches

Although asthma has been considered as a single disease for years, recent studies have increasingly focused on its heterogeneity. The characterization of this heterogeneity has promoted the concept that asthma consists of multiple phenotypes or consistent groupings of characteristics. Asthma phenotypes were initially focused on combinations of clinical characteristics, but they are now evolving to link biology to phenotype, often through a statistically based process. Ongoing studies of large-scale, molecularly and genetically focused and extensively clinically characterized cohorts of asthma should enhance our ability to molecularly understand these phenotypes and lead to more targeted and personalized approaches to asthma therapy.

Complement C3a-induced IL-17 plays a critical role in an IgE-mediated late-phase asthmatic response and airway hyperresponsiveness via neutrophilic inflammation in mice

Allergen-specific IgE plays an essential role in the pathogenesis of allergic asthma. Although there has been increasing evidence suggesting the involvement of IL-17 in the disease, the relationship between IL-17 and IgE-mediated asthmatic responses has not yet been defined. In this study, we attempted to elucidate the contribution of IL-17 to an IgE-mediated late-phase asthmatic response and airway hyperresponsiveness (AHR). BALB/c mice passively sensitized with an OVA-specific IgE mAb were challenged with OVA intratracheally four times. The fourth challenge caused a late-phase increase in airway resistance associated with elevated levels of IL-17(+)CD4(+) cells in the lungs. Multiple treatments with a C3a receptor antagonist or anti-C3a mAb during the challenges inhibited the increase in IL-17(+)CD4(+) cells. Meanwhile, a single treatment with the antagonist or the mAb at the fourth challenge suppressed the late-phase increase in airway resistance, AHR, and infiltration by neutrophils in bronchoalveolar lavage fluid. Because IL-17 production in the lungs was significantly repressed by both treatments, the effect of an anti-IL-17 mAb was examined. The late-phase increase in airway resistance, AHR, and infiltration by neutrophils in bronchoalveolar lavage fluid was inhibited. Furthermore, an anti-Gr-1 mAb had a similar effect. Collectively, we found that IgE mediated the increase of IL-17(+)CD4(+) cells in the lungs caused by repeated Ag challenges via C3a. The mechanisms leading to the IgE-mediated late-phase asthmatic response and AHR are closely associated with neutrophilic inflammation through the production of IL-17 induced by C3a.

Bacteria in sputum of stable severe asthma and increased airway wall thickness

BACKGROUND

Patients with chronic asthma have thicker intrapulmonary airways measured on high resolution computed tomography (HRCT). We determined whether the presence of lower airway bacteria was associated with increased airway wall thickness.

METHODS

In 56 patients with stable severe asthma, sputum specimens obtained either spontaneously or after induction with hypertonic saline were cultured for bacteria and thoracic HRCT scans obtained. Wall thickness (WT) and area (WA) expressed as a ratio of airway diameter (D) and total area, respectively, were measured at five levels.

RESULTS

Positive bacterial cultures were obtained in 29 patients, with H. influenzae, P. aeruginosa and S. aureus being the commonest strains. Logistic regression analysis showed that this was associated with the duration of asthma and the exacerbations during the past year. In airways > 2 mm, there was no significant difference in WA (67.5 ± 5.4 vs 66.4 ± 5.4) and WT/D (21.6 ± 2.7 vs 21.3 ± 2.4) between the culture negative versus positive groups. Similarly, in airways (≤ 2 mm), there were no significant differences in these parameters. The ratio of √wall area to Pi was negatively correlated with FEV1% predicted (p < 0.05).

CONCLUSIONS

Bacterial colonization of the lower airways is common in patients with chronic severe asthma and is linked to the duration of asthma and having had exacerbations in the past year, but not with an increase in airway wall thickness.

Air trapping is a major determinant of persistent airway obstruction in asthmatics

Chronic persistent airway obstruction has been observed in moderate-to-severe asthmatics despite treatment with inhaled corticosteroids. We investigated which airway changes were associated with this obstruction. High-resolution computed tomography (HRCT) was performed at study entry and reexamined at the time of follow-up when the FEV1 reached a maximally constant level after treatment for 1 year or more with inhaled corticosteroids. Bronchial wall area and air trapping extent were compared in the recovered group (n = 18) and the persistent airway obstruction group (n = 14). Bronchial wall area and air trapping of the initial HRCT were similar between the two groups. On follow-up HRCT, air trapping was markedly decreased in the recovered group compared with that on initial HRCT (P = 0.017), whereas bronchial wall area did not change. In the persistent-airway-obstruction group, these two parameters did not change during follow-up. When follow-up HRCT was compared, air trapping was significantly greater in the persistent-airway-obstruction group than in the recovered group (P = 0.003). Difference post-bronchodilator FEV1 value between at initial and 2nd HRCT exam was correlated with difference air trapping value between at initial and 2nd HRCT exam(%) on the follow-up HRCT (P = 0.017). The presence of persistent airflow obstruction were significantly associated with the air trapping % difference between initial and 2nd time (RR = 1.70, P = 0.018). Persistence of AT could be a main contributing factor to chronic persistent airflow obstruction in asthma.

Dexamethasone and RU24858 Induce Survival and Growth Factor Receptor Bound Protein 2, Leukotriene B4 Receptor 1 and Annexin-1 Expression in Primary Human Neutrophils

Glucocorticoids are widely used anti-inflammatory medication in diseases like asthma and chronic obstructive pulmonary disease. Glucocorticoids can either activate (transactivation) or inhibit (transrepression) transcription. RU24858 was introduced as a “dissociated” glucocorticoid and it has been reported to transrepress but not to transactivate. The aim of this study was to compare the effects of RU24858 and dexamethasone in human neutrophils. RU24858 delayed spontaneous neutrophil apoptosis and further enhanced GM-CSF- induced neutrophil survival to a similar extent as dexamethasone. Like dexamethasone RU24858 also reduced CXCL8 and MIP-1α. Unexpectedly however, RU24858 increased the expression of the glucocorticoid-inducible genes BLT-1, Annexin-1 and Grb-2 in neutrophils to a similar level as seen with dexamethasone. We have shown here that dexamethasone and RU24858 both increase Grb-2, BLT1 and Annexin-1 expression and inhibit CXCL8 and MIP-1α production. This suggests that RU24858 was not able to dissociate between transactivation and transrepression in human neutrophils but enhanced neutrophil survival.

Current treatment of severe asthma

Severe asthma is considered a heterogeneous disease in which a variety of clinical, physiological and inflammatory markers determine disease severity. Pivotal studies in the last 5 years have led to substantial progress in many areas, ranging from a more accurate definition of truly severe, refractory asthma, to classification of the disease into distinct clinical phenotypes, and introduction of new therapies. This review focuses on three common clinical phenotypes of severe asthma in adults (early onset severe allergic asthma, late onset non-atopic eosinophilic asthma, late onset non-eosinophilic asthma with obesity), and provides an overview of recent developments regarding treatment options that are best suited for each of these phenotypes.

IL-8, IL-10, TGF-β, and GCSF levels were increased in severe persistent allergic asthma patients with the anti-IgE treatment

BACKGROUND

Allergic asthma is showed an increase in Th2-cytokine and IgE levels and an accumulation activation of Th2 cells, eosinophils and mast cells. However, recent studies focused on cell-based mechanisms for the pathogenesis of allergic asthma. Objectives. In this study, we compare the anti-IgE treatment modality in the dynamics of immune system cytokine levels in severe persistent asthma (SPA) patients who had no other any allergic disease, newly diagnosed allergic asthma patients and healthy volunteers.

STUDY DESIGN

The study population consisted of 14 SPA patients, 14 newly diagnosed allergic asthma patients and 14 healthy volunteers included as controls. Cytokine levels were measured. Total and specific IgE levels of anti-IgE monoclonal antibody treated patients, serum high-sensitivity C-reactive protein (hsCRP) levels, FEV1/FVC rates and asthma control test (ACT) were measured for the clinical follow-up.

RESULTS

We observed that SPA patients presented increasing levels of IL-8, IL-10, TGF-β and GCSF during the anti-IgE treatment in period of sampling times at 4 months and 18 months. However this increase was not correlated neither with serum hsCRP levels nor FEV1/FVC rates.

CONCLUSIONS

Our study gives a different perspective for the SPA and anti-IgE immunotherapy efficacy at the cell cytokine-linked step.

The Temporal Evolution of Airways Hyperresponsiveness and Inflammation

Airways hyperresponsiveness (AHR) is usually produced within days of first antigen exposure in mouse models of asthma. Furthermore, continual antigen challenge eventually results in the resolution of the AHR phenotype. Human asthma also waxes and wanes with time, suggesting that studying the time course of AHR in the allergic mouse would offer insights into the variation in symptoms seen in asthmatics. Mice were sensitized with ovalbumin (OVA) on days 0 and 14. As assessed by airway resistance (R_n ), lung elastance (H) and tissue damping (G), AHR was measured post an OVA inhalation on day 21 (Short Challenge group), after three days of OVA inhalation on day 25 (Standard Challenge group) and following an OVA inhalation on day 55 in mice previously challenged on days 21-23 (Recall Challenge group). Bronchoalveolar lavage was analyzed for inflammatory cells, cytokines and protein. AHR in the Short Challenge group was characterized by an increase in R_n and neutrophil accumulation in the lavage. AHR in the Standard Challenge group was characterized by increases in H and G but by only a modest response in R_n , while inflammation was eosinophilic. In the Standard Challenge protocol, mice lacking fibrinogen were no different from control in their AHR response. AHR in the Recall Challenge group was characterized by increases only in G and H and elevated numbers of both neutrophils and eosinophils. Lavage cytokines were only elevated in the Recall Challenge group. Lavage protein was significantly elevated in all groups. The phenotype in allergically inflamed mice evolves distinctly over time, both in terms of the nature of the inflammation and the location of the AHR response. The study of mouse models of AHR might be better served by focusing on this variation rather than simply on a single time point at which AHR is maximal.

Immunological basis of reversible and fixed airways disease

Asthma is characterized by airflow obstruction that is usually completely reversible either spontaneously or in response to treatment. However, a small subset of patients with asthma display FAO (fixed airflow obstruction) despite optimal treatment, a feature more commonly associated with smoking-induced COPD (chronic obstructive pulmonary disease). Why some asthma patients develop FAO is not understood, and it is not clear whether (i) they represent a subset of patients with more severe disease, (ii) they share some characteristics of patients who develop COPD, or (iii) they represent a different disease entity altogether. The present review compares the pulmonary inflammatory profile of asthma patients with FAO with those without FAO, as well as COPD sufferers. The inflammation in asthma patients with FAO can vary from neutrophilic with CD8 T-cell involvement, similar to that of COPD, to eosinophilic with CD4 Th2 cell involvement, akin to that of asthma patients without FAO. Although studies of FAO in asthma sufferers would benefit hugely from consistent inclusion criteria, further research work is also required to shed more light on the immunological processes involved.

T(H)17 cells in asthma and inflammation

BACKGROUND

The chronic airway disease asthma causes significant burden to patients as well as the healthcare system with limited options for prevention or cure. Inadequate treatment strategies are most likely due to the complex heterogeneous nature of asthma. Furthermore, the severe asthma phenotype is characterized by the lack of a response to standard medication, namely, corticosteroids.

SCOPE OF REVIEW

In the last several years it has been shown that the eosinophilic/atopic phenotype of asthma driven by T(H)2 mechanisms is not the only immunologic pathway contributing to disease. In fact, there has been evidence revealing that severe asthmatics in particular have neutrophilic inflammation, and this is associated with corticosteroid resistance. T(H)17 cells, a recently discovered lineage of T helper cells, play an important role in lung host defense against multiple pathogens via production of the cytokine IL-17. IL-17 promotes neutrophil production and chemotaxis via multiple factors.

MAJOR CONCLUSIONS

Mouse and human studies provide robust evidence that T(H)17 cells and IL-17 play a role in severe asthma and may contribute to corticosteroid resistance.

GENERAL SIGNIFICANCE

As we learn more about T(H)17 cells in severe asthma, the goal is to potentially target this pathway for treatment in the hope of significantly improving the quality of life for those children and adults affected with this disease. This article is part of a Special Issue entitled: Biochemistry of Asthma.

Establishment and characterization of a murine model for allergic asthma using allergen-specific IgE monoclonal antibody to study pathological roles of IgE

Allergen-specific IgE has long been regarded as a major molecular component of allergic asthma. Although IgE plays a central role in the early asthmatic response, its roles in the chronic phase, such as the late asthmatic response, airway hyperresponsiveness (AHR), and airway remodeling (goblet cell hyperplasia and subepithelial fibrosis) have not yet been defined well. In this study, we investigated the hypothesis that chronic responses could be induced by IgE-dependent mechanisms. BALB/c mice passively sensitized with an ovalbumin (OVA)-specific IgE monoclonal antibody (mAb) were repeatedly challenged with intratracheal administration of OVA. The first challenge induced early phase airway narrowing without any late response, but the fourth challenge caused not only an early but also a late phase response, AHR, and goblet cell hyperplasia. Macrophages, lymphocytes and neutrophils, but not eosinophils, were significantly increased in the lung 24h after the fourth challenge. Interestingly, levels of OVA-specific IgG1 in serum increased by multiple antigen challenges. A C3a receptor antagonist inhibited the late asthmatic response, AHR, and infiltration by neutrophils. In contrast, no late response, goblet cell hyperplasia, inflammatory cells, or production of IgG1 was observed in severe combined immunodeficient mice. On the other hand, seven challenges in BALB/c mice induced subepithelial fibrosis associated with infiltration by eosinophils. In conclusion, the allergic asthmatic responses induced by passive sensitization with IgE mAb can provide a useful model system to study the pathological roles of IgE in acute and chronic phases of allergic asthma.

Oxidative stress in asthma

Asthma is a chronic inflammatory lung disease that results in airflow limitation, hyperreactivity, and airway remodeling. There is strong evidence that an imbalance between the reducing and oxidizing systems favoring a more oxidative state is present in asthma. Endogenous and exogenous reactive oxygen species, such as superoxide anion, hydroxyl radical, hypohalite radical, and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide, peroxynitrite, and nitrite, play a major role in the airway inflammation and are determinants of asthma severity. Asthma is also associated with decreased antioxidant defenses, such as superoxide dismutase, catalase, and glutathione. In this review, we will summarize the current knowledge and discuss the current and future strategies for the modulation of oxidative stress in asthma.

Pathophysiology of allergic inflammation

Allergic inflammation is due to a complex interplay between several inflammatory cells, including mast cells, basophils, lymphocytes, dendritic cells, eosinophils, and sometimes neutrophils. These cells produce multiple inflammatory mediators, including lipids, purines, cytokines, chemokines, and reactive oxygen species. Allergic inflammation affects target cells, such as epithelial cells, fibroblasts, vascular cells, and airway smooth muscle cells, which become an important source of inflammatory mediators. Sensory nerves are sensitized and activated during allergic inflammation and produce symptoms. Allergic inflammatory responses are orchestrated by several transcription factors, particularly NF-κB and GATA3. Inflammatory genes are also regulated by epigenetic mechanisms, including DNA methylation and histone modifications. There are several endogenous anti-inflammatory mechanisms, including anti-inflammatory lipids and cytokines, which may be defective in allergic disease, thus amplifying and perpetuating the inflammation. Better understanding of the pathophysiology of allergic inflammation has identified new therapeutic targets but developing effective novel therapies has been challenging. Corticosteroids are highly effective with a broad spectrum of anti-inflammatory effects, including epigenetic modulation of the inflammatory response and suppression of GATA3.

Identification of an IFN-γ/mast cell axis in a mouse model of chronic asthma

Asthma is considered a Th2 cell–associated disorder. Despite this, both the Th1 cell–associated cytokine IFN-γ and airway neutrophilia have been implicated in severe asthma. To investigate the relative contributions of different immune system components to the pathogenesis of asthma, we previously developed a model that exhibits several features of severe asthma in humans, including airway neutrophilia and increased lung IFN-γ. In the present studies, we tested the hypothesis that IFN-γ regulates mast cell function in our model of chronic asthma. Engraftment of mast cell–deficient KitW(-sh/W-sh) mice, which develop markedly attenuated features of disease, with wild-type mast cells restored disease pathology in this model of chronic asthma. However, disease pathology was not fully restored by engraftment with either IFN-γ receptor 1–null (Ifngr1–/–) or Fcε receptor 1γ–null (Fcer1g–/–) mast cells. Additional analysis, including gene array studies, showed that mast cell expression of IFN-γR contributed to the development of many FcεRIγ-dependent and some FcεRIγ-independent features of disease in our model, including airway hyperresponsiveness, neutrophilic and eosinophilic inflammation, airway remodeling, and lung expression of several cytokines, chemokines, and markers of an alternatively activated macrophage response. These findings identify a previously unsuspected IFN-γ/mast cell axis in the pathology of chronic allergic inflammation of the airways in mice.

Diesel exhaust particulates exacerbate asthma-like inflammation by increasing CXC chemokines

Particulate matter heavily pollutes the urban atmosphere, and several studies show a link between increased ambient particulate air pollution and exacerbation of pre-existing pulmonary diseases, including asthma. We investigated how diesel exhaust particulates (DEPs) aggravate asthma-like pulmonary inflammation in a mouse model of asthma induced by a house dust extract (HDE) containing cockroach allergens and endotoxin. BALB/c mice were exposed to three pulmonary challenges via hypopharyngeal administration of an HDE collected from the home of an asthmatic child. One hour before each pulmonary challenge, mice were exposed to DEP or PBS. Pulmonary inflammation was assessed by histological features, oxidative stress, respiratory physiological features, inflammatory cell recruitment, and local CXC chemokine production. To prove the role of CXC chemokines in the augmented inflammation, CXC chemokine-specific antibodies were delivered to the lungs before DEP exposure. DEP exacerbated HDE-induced airway inflammation, with increased airway mucus production, oxidative stress, inflammatory cell infiltration, bronchoalveolar lavage concentrations of CXC chemokines, and airway hyperreactivity. Neutralization of airway keratinocyte-derived chemokine and macrophage inflammatory protein-2 significantly improves the respiratory function in addition to decreasing the infiltration of neutrophils and eosinophils. Blocking the chemokines also decreased airway mucus production. These results demonstrate that DEP exacerbates airway inflammation induced by allergen through increased pulmonary expression of the CXC chemokines (keratinocyte-derived chemokine and macrophage inflammatory protein-2).

The efficacy and tolerability of MK-0633, a 5-lipoxygenase inhibitor, in chronic asthma

Leukotriene B4 (LTB(4)) is a potent inflammatory mediator in asthma, and is increased in more severe asthma. Targeting LTB(4), in addition to cysteinyl leukotrienes, could be beneficial in asthma. This was a randomized, double-blind trial of once-daily MK-0633, a potent 5-lypoxygenase inhibitor, 10 mg, 50 mg, and 100 mg, and placebo in patients 18-70 years with a history of chronic asthma, and FEV(1) ≥45 and ≤85% predicted. There was a 6-week main period and optional 18-week and 34-week periods (52 weeks total), the latter two comparing only MK-0633 100 mg and placebo. The primary endpoint was the change from baseline in FEV(1) over the last 4 weeks of the 6-week primary treatment period. Secondary endpoints included symptom scores, β-agonist use, peak expiratory flow (PEF), asthma quality of life questionnaire (AQLQ), asthma control questionnaire (ACQ), asthma attacks, exacerbations, days with asthma control, post-β-agonist FEV(1), and blood eosinophils. MK-0633 100 mg was significantly more effective than placebo for the change from baseline in FEV(1) (0.20 L vs. 0.13 L; p = 0.004). The other MK-0633 doses were not significantly more effective than placebo. MK-0633 (at various doses) was also more effective than placebo for β-agonist use, AQLQ, AM and PM PEFR, ACQ, and post-β-agonist FEV(1) (p < 0.05 for all). MK-0633 was associated with a dose-dependent increase in elevated aspartate aminotransferase and alanine aminotransferase. Because of the relative benefit-risk ratio, the optional study periods were terminated after unblinding for the main study period. Overall, the benefit-risk ratio did not support the clinical utility of MK-0633 in asthma.

Inhibitory effects of inhaled complex traditional Chinese medicine on early and late asthmatic responses induced by ovalbumin in sensitized guinea pigs

Background

Many formulae of traditional Chinese medicines (TCMs) have been used for antiasthma treatment dating back many centuries. There is evidence to suggest that TCMs are effective as a cure for this allergenic disease administered via gastric tubes in animal studies; however, their efficacy, safety and side effects as an asthmatic therapy are still unclear.

Methods

In this study, guinea pigs sensitized with ovalbumin (OVA) were used as an animal model for asthma challenge, and the sensitization of animals by bronchial reactivity to methacholine (Mch) and the IgE concentration in the serum after OVA challenge were estimated. Complex traditional Chinese herbs (CTCM) were administered to the animals by nebulization, and the leukocytes were evaluated from bronchoalveolar lavage fluid (BALF).

Results

The results showed that inhalation of CTCM could abolish the increased lung resistance (13-fold increase) induced by challenge with OVA in the early asthmatic response (EAR), reducing to as low as baseline (1-fold). Moreover, our results indicated higher IgE levels (range, 78-83 ng/ml) in the serum of sensitized guinea pigs than in the unsensitized controls (0.9 ± 0.256 ng/ml). In addition, increased total leukocytes and higher levels of eosinophils and neutrophils were seen 6 hours after challenge, and the increased inflammatory cells were reduced by treatment with CTCM inhalation. The interleukin-5 (IL-5) level in BALF was also reduced by CTCM.

Conclusion

Our findings indicate a novel method of administering traditional Chinese medicines for asthma treatment in an animal model that may be more effective than traditional methods.

p38 mitogen-activated protein kinase pathways in asthma and COPD

The mitogen-activated protein kinase (MAPK) family includes the p38 kinases, which consist of highly conserved proline-directed serine-threonine protein kinases that are activated in response to inflammatory signals. Of the four isoforms, p38α is the most abundant in inflammatory cells and has been the most studied through mainly the availability of small molecule inhibitors. The p38 substrates include transcription factors; other protein kinases, which in turn phosphorylate transcription factors; cytoskeletal proteins and translational components; and other enzymes. Both asthma and COPD are characterized by chronic airflow obstruction, airway and lung remodeling, and chronic inflammation. p38 is involved in the inflammatory responses induced by cigarette smoke exposure, endotoxin, and oxidative stress through activation and release of proinflammatory cytokines/chemokines, posttranslational regulation of these genes, and activation of inflammatory cell migration. Inhibition of p38 MAPK prevented allergen-induced pulmonary eosinophilia, mucus hypersecretion, and airway hyperresponsiveness, effects that may partly result from p38 activation on eosinophil apoptosis and on airway smooth muscle cell production of cytokines/chemokines. In addition, p38 regulates the augmented contractile response induced by oxidative stress. The activation of p38 observed in epithelial cells and macrophages also may underlie corticosteroid insensitivity of severe asthma and COPD. Therefore, p38 inhibitors present a potential attractive treatment of these conditions. Second-generation p38 inhibitors have been disappointing in the treatment of rheumatoid arthritis. In two 6-week studies in patients with COPD, the results were encouraging. Side effects such as liver toxicity remain a possibility, and whether the beneficial effects of p38 inhibitors are clinically significant and sustained need to be determined.

Analyzing airway inflammation with chemical biology: dissection of acidic mammalian chitinase function with a selective drug-like inhibitor

Acidic mammalian chitinase (AMCase) is produced in the lung during allergic inflammation and asthma, and inhibition of enzymatic activity has been considered as a therapeutic strategy. However, most chitinase inhibitors are nonselective, additionally inhibiting chitotriosidase activity. Here, we describe bisdionin F, a competitive AMCase inhibitor with 20-fold selectivity for AMCase over chitotriosidase, designed by utilizing the AMCase crystal structure and dicaffeine scaffold. In a murine model of allergic inflammation, bisdionin F-treatment attenuated chitinase activity and alleviated the primary features of allergic inflammation including eosinophilia. However, selective AMCase inhibition by bisdionin F also caused dramatic and unexpected neutrophilia in the lungs. This class of inhibitor will be a powerful tool to dissect the functions of mammalian chitinases in disease and represents a synthetically accessible scaffold to optimize inhibitory properties in terms of airway inflammation.

IgG immune complex induces the recruitment of inflammatory cells into the airway and TNF-mediated late airway hyperresponsiveness via NF-κB activation in mice

BACKGROUND

Many of the inflammatory proteins that are expressed in asthmatic airways are regulated, at least partially, by nuclear factor (NF)-κB. Blockade of NF-κB activity has resulted in attenuation of the cardinal features of asthma. Thus, delineating the mechanisms involved in NF-κB activation in asthma might provide an interesting approach to improving the management of asthma. However, despite its importance, the mechanism for NF-κB activation in asthma has not yet been determined.

OBJECTIVE

To examine the role of IgE and IgG antibodies (Abs) in the activation of NF-κB in mouse lungs.

METHODS

To examine the effect of IgE, mice underwent intratracheal (i.t.) instillation of an IgE immune complex (IgE-IC) (anti-2,4-dinitrophenyl hapten (DNP) IgE + DNP-BSA or DNP-OVA) and anaphylactogenic anti-IgE (LO-ME-2). For IgG, mice underwent i.t. instillation with a complex of anti-chicken gamma globulin (CGG) IgG1 mAb + CGG. NF-κB activation was determined by gel shift assay. Small interfering RNA was used for blockade of p50 expression. The effect of tumor necrosis factor (TNF) blockade was determined using anti-TNF Ab. A previously established murine model of asthma was used to assess airway hyperresponsiveness (AHR).

RESULTS

A single i.t. instillation of either IgE-IC or LO-ME-2 failed to induce activation of NF-κB in the lungs. In contrast, single i.t. instillation of IgG-IC was capable of inducing NF-κB activation, as well as NF-κB-dependent proinflammatory molecules, such as TNF and CXC chemokines. Pretreatment of p50 small interfering RNA decreased bronchoalveolar lavage fluid levels of TNF and macrophage inflammatory protein-2 induced by IgG-IC instillation. Single i.t. instillation of IgG-IC caused the recruitment of neutrophils and macrophages into the airway and TNF-mediated late AHR, but failed to induce Th2 cell-mediated asthmatic phenotypes.

CONCLUSION

IgG, but not IgE, is the major Ab that induces not only NF-κB activation and NF-κB-dependent proinflammatory molecules in the lungs but also subsequent recruitment of inflammatory cells into the airway and TNF-mediated late AHR.

Asthma phenotypes in adults and clinical implications

It is becoming increasingly recognized that asthma is a heterogeneous disease, whether based on clinical factors, including the patient's age at diagnosis, symptom spectrum and treatment response, triggering factors, or the level and type of inflammation. Attempts to analyze the importance of these characteristics to the clinical presentation of asthma have led to the appreciation of numerous separate and overlapping asthma phenotypes. However, these approaches are 'biased' and based on the clinician/scientist's own experience. Recently, unbiased approaches have also been attempted using both molecular and statistical tools. Early results from these approaches have supported and expanded on the clinician's concepts. However, until specific biologic markers are identified for any of these proposed phenotypes, the definitive nature of any phenotype will remain speculative.

Unusual asthma syndromes and their management

Asthma usually presents with symptoms of wheeze, dyspnoea and cough. However, clinicians should be aware of atypical presentation of this disorder when cough is the main or only symptom in conditions such as cough-variant asthma, nonasthmatic eosinophilic bronchitis and atopic cough. Early diagnosis and treatment of these conditions with inhaled corticosteroids improves symptoms in the majority of patients. Up to 10% of patients with asthma remain poorly controlled in spite of optimal standard therapy. These patients have been encompassed under the term 'treatment-refractory asthma' (TRA), have the greatest morbidity and are responsible for more than 50% of healthcare costs. In this review we discuss investigations, management and pathophysiology of the various phenotypes of atypical presentations of asthma as well as novel biological agents licensed and those that have been reported in clinical trials in terms of their efficacy and safety in TRA.

Allergic Responses Induced by a Fungal Biopesticide Metarhizium anisopliae and House Dust Mite Are Compared in a Mouse Model

Biopesticides can be effective in controlling their target pest. However, research regarding allergenicity and asthma development is limited. We compared the ability of fungal biopesticide Metarhizium anisopliae (MACA) and house dust mite (HDM) extracts to induce allergic responses in BALB/c mice. The extracts were administered by intratracheal aspiration at doubling doses (2.5-80 μg protein) 4X over a four-week period. Three days after the last exposure, serum and bronchoalveolar lavage fluid (BALF) were collected. The extracts' relative allergenicity was evaluated based on response robustness (lowest significant dose response compared to control (0 μg)). MACA induced a more robust serum total IgE response than HDM. However, in the antigen-specific IgE assay, a similar dose of both MACA and HDM was required to achieve the same response level. Our data suggest a threshold dose of MACA for allergy induction and that M. anisopliae may be similar to HDM in allergy induction potential.

Protease-mediated house dust mite allergen-induced reactive oxygen species production by neutrophils

A growing body of evidence indicates that neutrophils may play an important role in the pathogenesis of asthma. However, the involvement of the house dust mite (HDM) in neutrophil activation associated with the pathogenesis of asthma is not fully understood yet. To address this situation, we harvested neutrophils isolated from 15 HDM-sensitized asthmatic subjects and 18 HDM-sensitized nonasthmatic subjects and measured the amounts of neutrophil reactive oxygen species (ROS) production in response to the major HDM allergens Der-f and Der-f1. Der-f and Der-f1 significantly increased ROS production in neutrophils isolated from asthmatic subjects versus nonasthmatic subjects. To assess the involvement of Der-f-specific IgE antibodies binding to their receptors in HDM allergen-induced ROS production, we examined whether neutrophils produce ROS by cross-linking of cell-bound IgE antibodies with anti-IgE. Treatment with anti-IgE antibodies did not induce ROS production by neutrophils isolated from 6 asthmatic subjects. On the other hand, pretreatment of Der-f with E-64, a cysteine protease inhibitor, eliminated Der-f-induced ROS production. These results suggest that HDM-allergen exposure may result in greater production of ROS in asthmatic patients and may be involved in the pathogenesis of asthma.

Inflammatory stimuli inhibit glucocorticoid-dependent transactivation in human pulmonary epithelial cells: rescue by long-acting beta2-adrenoceptor agonists

By repressing inflammatory gene expression, glucocorticoids are the most effective treatment for chronic inflammatory diseases such as asthma. However, in some patients with severe disease, or who smoke or suffer from chronic obstructive pulmonary disease, glucocorticoids are poorly effective. Although many investigators focus on defects in the repression of inflammatory gene expression, glucocorticoids also induce (transactivate) the expression of numerous genes to elicit anti-inflammatory effects. Using human bronchial epithelial (BEAS-2B) and pulmonary (A549) cells, we show that cytokines [tumor necrosis factor α (TNFα) and interleukin 1β], mitogens [fetal calf serum (FCS) and phorbol ester], cigarette smoke, and a G(q)-linked G protein-coupled receptor agonist attenuate simple glucocorticoid response element (GRE)-dependent transcription. With TNFα and FCS, this effect was not overcome by increasing concentrations of dexamethasone, budesonide, or fluticasone propionate. Thus, the maximal ability of the glucocorticoid to promote GRE-dependent transcription was reduced, and this was shown additionally for the glucocorticoid-induced gene p57(KIP2). The long-acting β(2)-adrenoceptor agonists (LABAs) formoterol fumarate and salmeterol xinafoate enhanced simple GRE-dependent transcription to a level that could not be achieved by glucocorticoid alone. In the presence of TNFα or FCS, which repressed glucocorticoid responsiveness, these LABAs restored glucocorticoid-dependent transcription to levels that were achieved by glucocorticoid alone. Given the existence of genes, such as p57(KIP2), which may mediate anti-inflammatory actions of glucocorticoids, we propose that repression of transactivation represents a mechanism for glucocorticoid resistance and for understanding the clinical benefit of LABAs as an add-on therapy in asthma and chronic obstructive pulmonary disease.

Increased leptin/leptin receptor pathway affects systemic and airway inflammation in COPD former smokers

Background

Leptin, a hormone produced mainly by adipose tissue, regulates food intake and energy expenditure. It is involved in inflammatory diseases such as chronic obstructive pulmonary disease (COPD) and its deficiency is associated with increased susceptibility to the infection. The leptin receptor is expressed in the lung and in the neutrophils.

Methods

We measured the levels of leptin, tumor necrosis factor alpha (TNF-α) and soluble form of intercellular adhesion molecule-1 (sICAM-1) in sputum and plasma from 27 smoker and former smoker patients with stable COPD using ELISA methods. Further we analyzed leptin and its receptor expression in sputum cells from 16 COPD patients using immunocytochemistry.

Results

In plasma of COPD patients, leptin was inversely correlated with TNF-α and positively correlated with the patient weight, whereas the levels of sICAM-1 were positively correlated with TNF-α. In sputum of COPD patients leptin levels were correlated with forced expiratory volume in 1 second/forced vitality capacity. Additionally, increased levels of sputum leptin and TNF-α were observed in COPD former smokers rather than smokers. Further the expression of leptin receptor in sputum neutrophils was significantly higher in COPD former smokers than in smokers, and the expression of leptin and its receptor was positively correlated in neutrophils of COPD former smokers.

Conclusion

Our findings suggest a role of leptin in the local and systemic inflammation of COPD and, taking into account the involvement of neutrophils in this inflammatory disease, describe a novel aspect of the leptin/leptin receptor pathway in the regulation of host defense after smoking cessation.

Prostanoid DP receptor antagonists suppress symptomatic asthma-like manifestation by distinct actions from a glucocorticoid in rats

While inhaled glucocorticoids are the best treatment for the majority of chronic asthmatics, there is a small group who do not respond to these drugs or whose disease can only be controlled by high doses of oral glucocorticoids with risks of severe side effects. Therefore, a safe novel anti-asthmatic agent which has a different mechanism from that of glucocorticoids is needed for the management of asthma. We have previously shown that an orally active prostanoid DP receptor antagonist, S-5751, had potent anti-inflammatory effects in guinea pig and sheep asthma models. In this study, using a rat asthma like model, we found that lung neutrophilia and proinflammatory cytokine secretion as well as bronchial hyperresponsiveness and lung eosinophilia were induced by repeated antigen-inhalations after antigen-sensitization. These symptoms are similar to the pathogenesis of symptomatic asthma. Orally-administered prostanoid DP receptor antagonists S-5751 and pinagladin significantly suppressed not only bronchial hyperresponsiveness and lung eosinophilia but also neutrophilia and mucus secretion in the lung, while oral prednisolone inhibited only bronchial hyperresponsiveness and eosinophil infiltration. In addition, prostanoid DP receptor antagonists significantly suppressed interleukin (IL)-1β, IL-6 and CXCL1 mRNA in contrast to suppression of IL-4 and CCL11 mRNA by prednisolone. The majority of prostanoid DP receptor-expressing cells in both rat and human asthmatic lungs are infiltrative macrophages and/or monocytes. These results suggest that prostanoid DP receptor antagonists utilize different mechanisms from glucocorticoids, and that they would be a novel alternative and/or combination drug for asthma therapy.

Steroid-insensitive ERK1/2 activity drives CXCL8 synthesis and neutrophilia by airway smooth muscle

Severe or refractory asthma affects 5 to 15% of all patients with asthma, but is responsible for more than half of the health burden associated with the disease. Severe asthma is characterized by a dramatic increase in smooth muscle and airway inflammation. Although glucocorticoids are the mainstay of treatment in asthma, they are unable to fully control the disease in individuals with severe asthma. We found that airway smooth muscle cells (ASMCs) from individuals with severe asthma showed elevated activities of the ERK1/ERK2 and p38 MAPK pathways despite treatment with oral and inhaled glucocorticoids, which increased the expression of DUSP1, a phosphatase shown to limit p38 MAPK activity. In ex vivo ASMCs, TNF-α but not IL-17A induced expression of the neutrophil chemoattractant CXCL8. Moreover, TNF-α led to up-regulation of the ERK1/ERK2 and p38 MAPKs pathways, with only the latter being sensitive to pretreatment with the glucocorticoid dexamethasone. In contrast to epithelial and endothelial cells, TNF-α-stimulated CXCL8 synthesis was dependent on ERK1/ERK2 but not on p38 MAPK. Moreover, suppressing ERK1/ERK2 activation prevented neutrophil recruitment by ASMCs, whereas suppressing p38 MAPK activity had no impact. Taken together, these results highlight the ERK1/ERK2 MAPK cascade as a novel and attractive target in severe asthma because the activation of this pathway is insensitive to the action of glucocorticoids and is involved in neutrophil recruitment, contributing the to inflammation seen in the disease.

Preventing asthma exacerbations: what are the targets?

Exacerbations of asthma are the main cause of asthma morbidity. They induce acute respiratory failure, and sometimes death. Two immunological signals acting in synergy are necessary for inducing asthma exacerbations. The first, triggered by allergens and/or unknown agents leads to the chronic Th2 inflammation characteristic of asthma. The second, caused by either viral infection, allergens, pollutants or a combination of these, results in an acute Th1 and Th2 inflammation precipitating symptoms. In both, innate and adaptive immunities are involved, providing a series of potential targets for therapy. Molecules associated to the first, chronic inflammation constitute targets for preventing therapies, when these related to the second, acute signal provide the rationale for curative treatments. Toll like receptors and bronchial epithelial cell-derived cytokines, engaged upstream of inflammation constitute interesting candidates for future treatments. The great heterogeneity of asthma has to be taken into account when considering targets for therapy to identify clusters of responders and nonresponders, and an integrative system biology approach will be necessary to go further.

Delayed asthmatic response to bronchial challenge with allergen-mediators, eicosanoids, eosinophil and neutrophil constituents in the blood and urine

BACKGROUND

In patients with allergic bronchial asthma, different immunologic mechanisms may participate and lead to different types of asthmatic response to allergen challenge, such as immediate/early (IAR/EAR), late (LAR) or delayed asthmatic response (DYAR).

OBJECTIVES

In 55 of 397 asthmatics, DYAR has been recorded (p < 0.001) and confirmed by repeated bronchial challenge with the same allergen (p < 0.001). DYAR began between 26 and 32 h, reached a maximum between 32 and 48 h and resolved within 56 h after the challenge. DYAR was associated with various clinical symptoms and diagnostic parameters having diverged from those recorded during the IARs/EARs and LARs.

METHODS

In 25 of 55 patients, repeated DYAR has been supplemented with the recording of leukotriene B(4) (LTB(4)), LTC(4), LTE(4), prostaglandin D(2) (PGD(2)), PGE(2), PGF(2)(α), thromboxane B(2), lipoxin A(4), eosinophil cationic protein, eosinophil-derived neurotoxin/eosinophil protein X, eosinophilic peroxidase, myeloperoxidase, histamine and tryptase in peripheral blood, and of LTC(4), thromboxane B(2), eosinophil-derived neurotoxin and 9α,11β-PGF(2) in urine, before and up to 72 h after the bronchial allergen challenge, by means of enzyme-linked immunoassay (ELISA/EIA) or ImmunoCAP.

RESULTS

DYAR was accompanied by a significant increase in the plasma concentrations of LTB(4) (p < 0.05) and myeloperoxidase (p < 0.05) at 24, 36 and 48 h after the challenge, whereas the plasma/serum or urine concentrations of the other factors did not demonstrate any significant changes (p > 0.05).

CONCLUSIONS

These results would indicate an active and prominent involvement of neutrophils, in addition to the previously demonstrated role of the Th1 lymphocytes, in the clinical DYAR.

TRP channels: emerging targets for respiratory disease

The mammalian transient receptor potential (TRP) superfamily of cation channels is divided into six subfamilies based on sequence homology TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPA (ankyrin), TRPP (polycystin) and TRPML (mucolipin). The expression of these channels is especially abundant in sensory nerves, and there is increasing evidence demonstrating their existence in a broad range of cell types which are thought to play a key role in respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD). These ion channels can be activated by a diverse range of chemical and physical stimuli. Physical stimuli include temperature, membrane potential changes and osmotic stress, and some of the more well known chemical stimuli include capsaicin (TRPV1), menthol (TRPM8) and acrolein (TRPA1). There is increasing evidence in this rapidly moving field to suggest that selective blockers of these channels may represent attractive novel strategies to treat characteristic features of respiratory diseases such as asthma and COPD. This review focuses on summarising the evidence that modulation of selected TRP channels may have beneficial effects at targeting key features of these respiratory diseases including airways inflammation, airways hyper-reactivity, mucus secretion and cough.