Mechanisms of immune sensitization of human bronchus

Use of human airway smooth muscle in vitro and ex vivo to investigate drugs for the treatment of chronic obstructive respiratory disorders

Isolated airway smooth muscle has been extensively investigated since 1840 to understand the pharmacology of airway diseases. There has often been poor predictability from murine experiments to drugs evaluated in patients with asthma or chronic obstructive pulmonary disease (COPD). However, the use of isolated human airways represents a sensible strategy to optimise the development of innovative molecules for the treatment of respiratory diseases. This review aims to provide updated evidence on the current uses of isolated human airways in validated in vitro methods to investigate drugs in development for the treatment of chronic obstructive respiratory disorders. This review also provides historical notes on the pioneering pharmacological research on isolated human airway tissues, the key differences between human and animal airways, as well as the pivotal differences between human medium bronchi and small airways. Experiments carried out with isolated human bronchial tissues in vitro and ex vivo replicate many of the main anatomical, pathophysiological, mechanical and immunological characteristics of patients with asthma or COPD. In vitro models of asthma and COPD using isolated human airways can provide information that is directly translatable into humans with obstructive lung diseases. Regardless of the technique used to investigate drugs for the treatment of chronic obstructive respiratory disorders (i.e., isolated organ bath systems, videomicroscopy and wire myography), the most limiting factors to produce high-quality and repeatable data remain closely tied to the manual skills of the researcher conducting experiments and the availability of suitable tissue.

Revisiting asthma pharmacotherapy: where do we stand and where do we want to go?

Several current guidelines/strategies outline a treatment approach to asthma, which primarily consider the goals of improving lung function and quality of life and reducing symptoms and exacerbations. They suggest a strategy of stepping up or down treatment, depending on the patient's overall current asthma symptom control and future risk of exacerbation. While this stepwise approach is undeniably practical for daily practice, it does not always address the underlying mechanisms of this heterogeneous disease. In the last decade, there have been attempts to improve the treatment of severe asthma, such as the addition of a long-acting antimuscarinic agent to the traditional inhaled corticosteroid/long-acting β2-agonist treatment and the introduction of therapies targeting key cytokines. However, despite such strategies several unmet needs in this population remain, motivating research to identify novel targets and develop improved therapeutic and/or preventative asthma treatments. Pending the availability of such therapies, it is essential to re-evaluate the current conventional "one-size-fits-all" approach to a more precise asthma management. Although challenging, identifying "treatable traits" that contribute to respiratory symptoms in individual patients with asthma may allow a more pragmatic approach to establish more personalised therapeutic goals.

Muscarinic receptor antagonists and airway inflammation: A systematic review on pharmacological models

Airway inflammation is crucial in the pathogenesis of many respiratory diseases, including chronic obstructive pulmonary disease (COPD) and asthma. Current evidence supports the beneficial impact of muscarinic receptor antagonists against airway inflammation from bench-to-bedside. Considering the numerous sampling approaches and the ethical implications required to study inflammation in vivo in patients, the use of pre-clinical models is inevitable. Starting from our recently published systematic review concerning the impact of muscarinic antagonists, we have systematically assessed the current pharmacological models of airway inflammation and provided an overview on the advances in in vitro and ex vivo approaches. The purpose of in vitro models is to recapitulate selected pathophysiological parameters or processes that are crucial to the development of new drugs within a controlled environment. Nevertheless, immortalized cell lines or primary airway cells present major limitations, including the inability to fully replicate the conditions of the corresponding cell types within a whole organism.

Induced animal models are extensively used in research in the attempt to replicate a respiratory condition reflective of a human pathological state, although considering animal models with spontaneously occurring respiratory diseases may be more appropriate since most of the clinical features are accompanied by lung pathology resembling that of the human condition.

In recent years, three-dimensional organoids have become an alternative to animal experiments, also because animal models are unable to fully mimic the complexity of human pulmonary diseases. Ex vivo studies performed on human isolated airways have a superior translational value compared to in vitro and animal models, as they retain the morphology and the microenvironment of the lung in vivo.

In the foreseeable future, greater effort should be undertaken to rely on more physiologically relevant models, that provide translational value into clinic and have a direct impact on patient outcomes.

Synergy across the drugs approved for the treatment of asthma

INTRODUCTION

Inhaled corticosteroids are the cornerstone for the treatment of stable asthma, however, when disease severity increases, escalating therapy to combinations of drugs acting on distinct signalling pathways is required. It is advantageous to providing evidence of a synergistic interaction across drug combinations, as it allows optimizing bronchodilation while lowering the dose of single agents. In the respiratory pharmacology field, two statistical models are accepted as gold standard to characterize drug interactions, namely the Bliss Independence criterion and the Unified Theory. In this review, pharmacological interactions across drugs approved for the treatment of asthma have been systematically assessed.

EVIDENCE ACQUISITION

A comprehensive literature search was performed in MEDLINE for studies that used a validated pharmacological method for assessing drug interaction. The results were extracted and reported via qualitative synthesis.

EVIDENCE SYNTHESIS

Overall, 45 studies were identified from literature search and 5 met the inclusion criteria. Current evidence coming from ex vivo models of asthma indicates that drug combinations modulating bronchial contractility induce a synergistic bronchorelaxant effect. In murine models of lung inflammation, the combination between inhaled corticosteroids and β2- adrenoceptor agonists synergistically improve lung function and the inflammatory profile.

CONCLUSIONS

There is still limited knowledge regarding the mechanistic basis underlying pharmacological interactions across drugs approved for asthma. The synergism elicited by combined agents is an effect of class. Specifically designed clinical trials are needed to confirm the results coming from preclinical evidence, but also to establish the minimal dose for combined agents to induce a synergistic interaction and maximize bronchodilation.

Targeting IL-5 pathway against airway hyperresponsiveness: A comparison between benralizumab and mepolizumab

BACKGROUND AND PURPOSE

Airway hyperresponsiveness (AHR) is a central abnormality in asthma. IL-5 may modulate AHR in animal models of asthma, but the available data is inconsistent on the impact of targeting IL-5 pathway against AHR. The difference between targeting IL-5 or the IL-5 receptor, α subunit (IL-5Rα) in modulating AHR remains to be investigated in human airways. The aim of this study was to compare the role of the anti-IL-5Rα benralizumab and the anti-IL-5 mepolizumab against AHR and to assess whether these agents influence the levels of cAMP.

EXPERIMENTAL APPROACH

Passively sensitized human airways were treated with benralizumab and mepolizumab. The primary endpoint was the inhibition of AHR to histamine. The secondary endpoints were the protective effect against AHR to parasympathetic activation and mechanical stress, and the tissue modulation of cAMP.

KEY RESULTS

Benralizumab and mepolizumab significantly inhibited the AHR to histamine (maximal effect -134.14 ± 14.93% and -108.29 ± 32.16%, respectively), with benralizumab being 0.73 ± 0.10 logarithm significantly more potent than mepolizumab. Benralizumab and mepolizumab significantly inhibited the AHR to transmural stimulation and mechanical stress. Benralizumab was 0.45 ± 0.16 logarithm significantly more potent than mepolizumab against AHR to parasympathetic activation. The effect of these agents was significantly correlated with increased levels of cAMP.

CONCLUSION AND IMPLICATIONS

Targeting the IL-5/IL-5Rα axis is an effective strategy to prevent the AHR. Benralizumab was more potent than the mepolizumab and the concentration-dependent beneficial effects of both these monoclonal antibodies were related to improved levels of cAMP in hyperresponsive airways.

Beclomethasone dipropionate and formoterol fumarate synergistically interact in hyperresponsive medium bronchi and small airways

Background

Corticosteroids increase the expression of β₂-adrenoceptors (β₂-ARs) and protect them against down-regulation. Conversely, β₂-AR agonists improve the anti-inflammatory action of corticosteroids. Nevertheless, it is still uncertain whether adding a long-acting β₂-AR agonist (LABA) to an inhaled corticosteroid (ICS) results in an additive effect, or there is true synergy.

Therefore, the aim of this study was to pharmacologically characterize the interaction between the ICS beclomethasone diproprionate (BDP) and the LABA formoterol fumarate (FF) in a validated human ex vivo model of bronchial asthma.

Methods

Human medium and small airways were stimulated by histamine and treated with different concentrations of BDP and FF, administered alone and in combination at concentration-ratio reproducing ex vivo that of the currently available fixed-dose combination (FDC; BDP/FF 100:6 combination-ratio). Experiments were performed in non-sensitized (NS) and passively sensitized (PS) airways. The pharmacological interaction was assessed by using Bliss Independence and Unified Theory equations.

Results

BDP/FF synergistically increased the overall bronchorelaxation in NS and PS airways (+ 15.15% ± 4.02%; P < 0.05 vs. additive effect). At low-to-medium concentrations the synergistic interaction was greater in PS than in NS bronchioles (+ 16.68% ± 3.02% and + 7.27% ± 3.05%, respectively). In PS small airways a very strong synergistic interaction (Combination Index: 0.08; + 20.04% ± 2.18% vs. additive effect) was detected for the total concentrations of BDP/FF combination corresponding to 10.6 ng/ml.

Conclusion

BDP/FF combination synergistically relaxed human bronchi; the extent of such an interaction was very strong at low-to-medium concentrations in PS small airways.

Trial registration

Not applicable.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0770-7) contains supplementary material, which is available to authorized users.

Glucagon-Like Peptide 1 Receptor: A Novel Pharmacological Target for Treating Human Bronchial Hyperresponsiveness

Asthma is associated with several comorbidities, such as type 2 diabetes mellitus, which may lead to bronchial hyperresponsiveness (BHR). Because glucagon-like peptide (GLP) 1 regulates glucose homeostasis, we pharmacologically investigated the influence of the GLP1 receptor (GLP1-R) agonist, exendin-4, on BHR induced in human isolated airways. The effect of exendin-4 was assessed in human isolated airways undergoing overnight passive sensitization and high-glucose stimulation, two conditions mimicking ex vivo the BHR typical of patients with asthma and diabetes, respectively. GLP1-R activation modulated the bronchial contractile tone induced by transmural stimulation (maximum effect -56.7 ± 3.6%; onset of action, 28.2 ± 4.4 min). Exendin-4 prevented BHR induced by both high-glucose stimulation and passive sensitization (-37.8 ± 7.5% and -74.9 ± 3.9%, P < 0.05 versus control, respectively) through selective activation of GLP1-R and in an epithelium-independent manner. The cAMP-dependent protein kinase A inhibitor, KT5720, reduced the protective role of exendin-4 (P > 0.05 versus passively sensitized tissues). The GLP1-R stimulation by overnight incubation with exendin-4 induced the overexpression of adenylyl cyclase isoform V (+48.4 ± 1.3%, P < 0.05 versus passively sensitized tissues) and restored the cAMP levels depleted by this procedure (+330.8 ± 63.3%, P < 0.05 versus passively sensitized tissues). In conclusion, GLP1-R may represent a novel target for treating BHR by activating the cAMP-dependent protein kinase A pathway in human airways, and GLP1-R agonists could be used as a "new" class to treat patients with asthma and patients with type 2 diabetes mellitus with BHR.

Influence of Omalizumab on Allergen-Specific IgE in Patients with Adult Asthma

BACKGROUND

Omalizumab, an anti-immunoglobulin E (IgE) monoclonal antibody, inhibits the binding of circulating IgE to mast cells and basophils, resulting in fewer episodes of airway inflammation, asthma symptoms and exacerbations in patients with severe allergic asthma. Treatment of patients with asthma using omalizumab increases serum total IgE (tIgE) levels. However, little is known about the influence of omalizumab on allergen-specific IgE (sIgE).

METHODS

tIgE and sIgE in 47 adult patients with severe asthma were measured with a fluorescent enzyme immunoassay (ImmunoCAP-FEIA) before and after omalizumab treatment.

RESULTS

Treatment with omalizumab increased tIgE and sIgE levels. The increases in sIgE by class category after omalizumab treatment were positively correlated with baseline sIgE positivity before treatment. The mean changes in sIgE levels after omalizumab treatment were also correlated with baseline sIgE levels before treatment. The mean changes in tIgE levels were positively correlated with the mean changes in IgE levels against Dermatophagoides pteronyssinus, crude house dust, Japanese cedar and moth. Omalizumab markedly influenced the negative-to-positive seroconversion rate for IgE against Japanese cedar (30.8%), Candida (29.0%) and moth (28.0%). Finally, all patients with negative-to-positive seroconversion for Japanese cedar-specific IgE had cedar pollinosis before beginning omalizumab treatment.

CONCLUSIONS

The changes in sIgE levels after omalizumab treatment may be dependent on the baseline sIgE levels. Our data may indicate the presence of undetectable but functional sIgE.

Interaction between corticosteroids and muscarinic antagonists in human airways

BACKGROUND

To date there is emerging clinical evidence to add long-acting anti-muscarinic agents (LAMAs) with inhaled corticosteroid (ICSs) in asthma, but the pharmacological rationale that supports the use of such a combination has not yet been explained. The aim of this study was to pharmacologically investigate the interaction between the ICS beclomethasone and the LAMA glycopyrronium on the human airway smooth muscle (ASM) tone.

METHODS

We investigated the rapid non-genomic bronchorelaxant effect of beclomethasone and glycopyrronium, administered alone and in combination, in human isolated bronchi and bronchioles. Experiments were carried out also in passively sensitized airways and the pharmacological analysis of drug interaction was performed by Bliss Independence method.

RESULTS

The acute administration of beclomethasone and glycopyrronium induced a significant relaxation of passively sensitized ASM pre-contracted with histamine, by causing submaximal/maximal inhibition of the contractile tone in both medium bronchi and bronchioles. Beclomethasone was characterized by a rapid non-genomic and epithelium independent bronchorelaxant effect. In passively sensitized airways, this effect seemed to be dependent by the activation of a Gsα--cyclic adenosine monophosphate (cAMP)--protein kinase A cascade. While no synergistic interaction was detected in non-sensitized bronchi, the beclomethasone/glycopyrronium combination synergistically enhanced the relaxation of passively sensitized medium and small bronchi. The synergistic interaction between beclomethasone and glycopyrronium was associated with an increase of cAMP concentrations.

CONCLUSIONS

Our study provides for the first time the pharmacological rationale for combining low doses of an ICS plus a LAMA.

The high affinity IgE receptor (FcεRI) expression and function in airway smooth muscle

The airway smooth muscle (ASM) is no longer considered as merely a contractile apparatus and passive recipient of growth factors, neurotransmitters and inflammatory mediators signal but a critical player in the perpetuation and modulation of airway inflammation and remodeling. In recent years, a molecular link between ASM and IgE has been established through Fc epsilon receptors (FcεRs) in modulating the phenotype and function of these cells. Particularly, the expression of high affinity IgE receptor (FcεRI) has been noted in primary human ASM cells in vitro and in vivo within bronchial biopsies of allergic asthmatic subjects. The activation of FcεRI on ASM cells suggests a critical yet almost completely ignored network which may modulate ASM cell function in allergic asthma. This review is intended to provide a historical perspective of IgE effects on ASM and highlights the recent updates in the expression and function of FcεRI, and to present future perspectives of activation of this pathway in ASM cells.

Epithelium integrity is crucial for the relaxant activity of brain natriuretic peptide in human isolated bronchi

BACKGROUND AND PURPOSE Brain natriuretic peptide (BNP) plays an important role in several biological functions, including bronchial relaxation. Here, we have investigated the role of BNP and its cognate receptors in human bronchial tone. EXPERIMENTAL APPROACH Effects of BNP on responses to carbachol and histamine were evaluated in non-sensitized, passively sensitized, epithelium-intact or denuded isolated bronchi and in the presence of methoctramine, N(ω) -nitro-L-arginine methyl ester (L-NAME) and aminoguanidine. Natriuretic peptide receptors (NPRs) were investigated by immunohistochemistry, RT-PCR and real-time PCR. Release of NO and acetylcholine from bronchial tissues and cultured BEAS-2B bronchial epithelial cells was also investigated. KEY RESULTS BNP reduced contractions mediated by carbachol and histamine, with decreased E(max) (carbachol: 22.7 ± 4.7%; histamine: 59.3 ± 1.8%) and increased EC(50) (carbachol: control 3.33 ± 0.88 µM, BNP 100 ± 52.9 µM; histamine: control 16.7 ± 1.7 µM, BNP 90 ± 30.6 µM); BNP was ineffective in epithelium-denuded bronchi. Among NPRs, only atrial NPR (NPR1) transcripts were detected in bronchial tissue. Bronchial NPR1 immunoreactivity was detected in epithelium and inflammatory cells but faint or absent in airway smooth muscle cells. NPR1 transcripts in bronchi increased after incubation with BNP, but not after sensitization. Methoctramine and quinine abolished BNP-induced relaxant activity. The latter was associated with increased bronchial mRNA for NO synthase and NO release, inhibited by L-NAME and aminoguanidine. In vitro, BNP increased acetylcholine release from bronchial epithelial cells, whereas NO release was unchanged. CONCLUSIONS AND IMPLICATIONS Epithelial cells mediate the BNP-induced relaxant activity in human isolated bronchi.

Pharmacological characterization of adenosine receptors on isolated human bronchi

Adenosine induces airways obstruction in subjects with asthma, but the receptor subtype responsible remains unknown. The objectives of this study were to determine the pharmacological profile of adenosine receptor subtypes mediating contraction and to investigate the mechanism in normal and passively sensitized human airway tissues. Contraction of bronchial rings isolated from resected lung tissue of patients with lung carcinoma was measured in response to nonselective adenosine receptor agonists, 5-AMP and 5'-(N-Ethylcarboxamido)adenosine, and A(1) receptor agonist, N(6)-cyclopentyladenosine, in the absence and presence of selective adenosine receptor antagonists. Pharmacological antagonists, chemical ablation of airway sensory nerves using capsaicin, and passive sensitization of tissue with serum from subjects with atopy and asthma was used to investigate the mechanism of contraction. Human bronchial tissue contracted in a concentration-dependent manner to adenosine agonists that showed a rank order of activity of A(1) > A(2B) >> A2(A) = A3. The maximum contractile response to N(6)-cyclopentyladenosine (231.0 ± 23.8 mg) was significantly reduced in tissues chemically treated with capsaicin to desensitize sensory nerves (desensitized: 101.6 ± 15.2 mg; P < 0.05). Passive sensitization significantly augmented the contraction induced by adenosine A(1) receptor activation (sensitized: 389.7 ± 52.8 mg versus nonsensitized; P < 0.05), which was linked to the release of leukotrienes, and not histamine (MK571: 25.5 ± 1.7 mg; epinastine 260.0 ± 22.2 mg versus control; P < 0.05). This study provides evidence for a role for adenosine A(1) receptors in eliciting human airway smooth muscle constriction, which, in part, is mediated by the action of capsaicin sensitive sensory nerves.

Airway smooth muscle modulation and airway hyper-responsiveness in asthma: new cellular and molecular paradigms

There is growing evidence indicating the existence of a causal relationship between abnormal airway smooth muscle (ASM) function and airway hyper-responsiveness, a poorly understood feature of asthma that can be defined as an excessive bronchospastic response. In recent years, there has been a veritable explosion of articles suggesting that ASM exposed to proasthmatic cytokines can elicit a hyper-responsive state to contractile G-protein-coupled receptor (GPCR) agonists. Aberrant airway responsiveness could result from abnormal calcium signaling, with changes occurring at various levels of GPCR-associated signal transduction. This review presents the latest observations describing novel mechanistic models that could explain the involvement of ASM in airway hyper-responsiveness. This review will discuss the role of ASM in beta(2)-agonist-mediated bronchial hyper-responsiveness and the clinical significance of cell-cell contact between ASM and mast cells recently described to be intimately infiltrated within the ASM tissues in asthmatic patients. The possibility that allergens could trigger airway hyper-responsiveness by directly acting on ASM via activation of immunoglobulin E receptors, FcepsilonRI and FCepsilonRII will also be discussed. These important findings further support the notion that targeting ASM could offer new treatment for many features of asthma, including airway hyper-responsiveness. Future therapeutic intervention includes: the prevention of ASM-inflammatory cell physical and/or functional interaction, the inhibition of Immunoglobulin E receptor-dependent signal transduction, and the abrogation of cytokine-dependent pathways that modulate receptor-associated calcium metabolism.

Relaxant effect of brain natriuretic peptide in nonsensitized and passively sensitized isolated human bronchi

Brain natriuretic peptide (BNP) relaxes guinea pig tracheal smooth muscle in vitro and is effective in preventing ovalbumin-induced bronchoconstriction and microvascular leakage in guinea pigs in vivo. Nonetheless, published studies on BNP in human airways in vitro are still lacking in the literature. The aim of this study was to investigate the effect of BNP in isolated human bronchi. The relaxant effect of BNP (1 nM to 10 microM) was assessed in nonsensitized and in passively sensitized human bronchial airways pre-contracted with submaximal concentration (EC(70)) of carbachol or histamine. At the end of the experiment, papaverine (500 microM) was then added. BNP induced a weak relaxant activity on carbachol-contracted bronchi in nonsensitized (relaxation: 4.23+/-0.51%) and passively sensitized bronchi (relaxation: 11.31+/-2.22%). On the other hand, BNP induced a relaxant activity on His-contracted bronchi in nonsensitized (relaxation: 42.52+/-9.03%) and in passively sensitized (relaxation: 60.57+/-9.58%). All these findings are a clear documentation of the modest relaxant role of BNP in asthma and, likely, COPD.

Blood lead levels and increased bronchial responsiveness

The immune system is one of the targets most sensitive to lead toxicity, and the association between lead exposure and serum immunoglobulin E (IgE) has been published. Recent studies also reported that lead caused the development of IgE-mediated allergy. To investigate whether blood lead levels contribute to other allergic conditions, we examined the effect of blood lead on bronchial responsiveness (BR) in the general population. We performed a cross-sectional study with adults aged 19 to 58 years in a Korean community. Blood lead level and the methacholine provocation test were performed. The overall mean blood lead level was 2.9 microg/dl, and the mean BR index was 1.14. The percent of subjects with clinically diagnosed asthma was 21 (4%) and there was no difference in blood lead level with and without asthma. In the multiple regression model, the elevation of blood lead level was related to the increase of BR after adjusting for age, sex, height, smoking status, and the presence of asthma. Blood lead level was significantly associated with increased BR that came from the elevation of the IgE level with lead exposure. Lead may contribute to the increase of asthma and other allergic conditions.

Bronchial hyperresponsiveness and the development of asthma and COPD in asymptomatic individuals: SAPALDIA cohort study

BACKGROUND

Bronchial hyperresponsiveness (BHR) is a common feature of asthma. However, BHR is also present in asymptomatic individuals and its clinical and prognostic significance is unclear. We hypothesised that BHR might play a role in the development of chronic obstructive pulmonary disease (COPD) as well as asthma.

METHODS

In 1991 respiratory symptoms and BHR to methacholine were evaluated in 7126 of the 9651 participants in the SAPALDIA cohort study. Eleven years later 5825 of these participants were re-evaluated, of whom 4852 performed spirometric tests. COPD was defined as an FEV1/FVC ratio of <0.70.

RESULTS

In 1991 17% of participants had BHR, of whom 51% were asymptomatic. Eleven years later the prevalence of asthma, wheeze, and shortness of breath in formerly asymptomatic subjects with or without BHR was, respectively, 5.7% v 2.0%, 8.3% v 3.4%, and 19.1% v 11.9% (all p<0.001). Similar differences were observed for chronic cough (5.9% v 2.3%; p = 0.002) and COPD (37.9% v 14.3%; p<0.001). BHR conferred an adjusted odds ratio (OR) of 2.9 (95% CI 1.8 to 4.5) for wheezing at follow up among asymptomatic participants. The adjusted OR for COPD was 4.5 (95% CI 3.3 to 6.0). Silent BHR was associated with a significantly accelerated decline in FEV1 by 12 (5-18), 11 (5-16), and 4 (2-8) ml/year in current smokers, former smokers and never smokers, respectively, at SAPALDIA 2.

CONCLUSIONS

BHR is a risk factor for an accelerated decline in FEV1 and the development of asthma and COPD, irrespective of atopic status. Current smokers with BHR have a particularly high loss of FEV1.

Immune sensitization of equine bronchus: glutathione, IL-1beta expression and tissue responsiveness

BACKGROUND

Increasing clinical epidemiological and experimental evidence indicates that excess of production of reactive oxygen free radicals (ROS) induced by an oxidative stress is involved in the pathogenesis of a number of human airway disorders, as well as equine recurrent airway obstruction. Free-radicals modulate the activation of transcription factors, such as nuclear factor-(NF)-kappaB and activator protein (AP)-1, in several different cells. This activation leads to expression of many pro-inflammatory cytokines, including interleukin (IL)-1beta. We have hypothesized that equine airway sensitization might induce an oxidative stress and increase the ROS production, which in turn might enhance a production of IL-1beta and airway hyperresponsiveness.

METHODS

We have examined the effect of passive sensitization on IL-1beta mRNA expression and electrical field stimulation (EFS)-induced contraction in equine isolated bronchi, and the potential interference of reduced-glutathione (GSH), an antioxidant, with these responses. Bronchi passively sensitized with serum from animals suffering from heaves and having high total level of IgE, and control tissues, either pretreated or not with GSH (100 microM), were used to quantify IL-1beta mRNA. Other tissues were used to study the effect of EFS (3-10-25 Hz).

RESULTS

Mean IL-1beta mRNA expression was higher in passively sensitized than in control rings. GSH significantly (p < 0.05) reduced the IL-1beta mRNA expression only in passively sensitized bronchi. ELF induced a frequency-dependent contraction in both non-sensitized and passively sensitized tissues, with a significantly greater response always observed in sensitized tissues. GSH did not modify the EFS-induced contraction in non-sensitized bronchi, but significantly (p < 0.05) decreased it in passively sensitized tissues.

CONCLUSION

Our data indicate that the passive sensitization of equine bronchi induces inflammation and hyperresponsiveness. These effects might be due to an oxidative stress because a pretreatment with GSH decreased the increased IL-1beta mRNA expression and responsiveness to EFS of passively sensitized bronchi.

Effects of treatment with anti-immunoglobulin E antibody omalizumab on airway inflammation in allergic asthma

IgE plays an important role in allergic asthma. We hypothesized that reducing IgE in the airway mucosa would reduce airway inflammation. Forty-five patients with mild to moderate persistent asthma with sputum eosinophilia of 2% or more were treated with humanized monoclonal antibody against IgE (omalizumab) (n = 22) or placebo (n = 23) for 16 weeks. Outcomes included inflammatory cells in induced sputum and bronchial biopsies, and methacholine responsiveness. Treatment with omalizumab resulted in marked reduction of serum IgE and a reduction of IgE+ cells in the airway mucosa. The mean percentage sputum eosinophil count decreased significantly (p < 0.001) from 6.6 to 1.7% in the omalizumab group, a reduction significantly (p = 0.05) greater than with placebo (8.5 to 7.0%). This was associated with a significant reduction in tissue eosinophils; cells positive for the high-affinity Fc receptor for IgE; CD3+, CD4+, and CD8+ T lymphocytes; B lymphocytes; and cells staining for interleukin-4, but not with improvement in airway hyperresponsiveness to methacholine. This study shows antiinflammatory effects of omalizumab treatment and provides clues for mechanisms whereby omalizumab reduces asthma exacerbations and other asthma outcomes in more severe asthma. The lack of effect of omalizumab on methacholine responsiveness suggests that IgE or eosinophils may not be causally linked to airway hyperresponsiveness to methacholine in mild to moderate asthma.

Interleukin-10 gene promoter region polymorphism is associated with eosinophil count and circulating immunoglobulin E in adult asthma

BACKGROUND

IL-10 has several functional effects relevant to asthma. It can modulate IgE production and induce apoptosis in eosinophils. Polymorphisms of IL-10 gene have been shown to affect IL-10 production.

OBJECTIVE

To establish whether IL-10 polymorphisms are associated with asthma and phenotype-related characteristics.

METHODS

The frequency of three single base exchange polymorphisms (at positions - 1082, - 819 and - 592) and corresponding haplotypes of the IL-10 gene were analysed in 245 adult asthmatic subjects and 405 controls using PCR and restriction fragment length polymorphism (RFLP). The data were assessed for correlations with the eosinophil count, serum IgE and lung function.

RESULTS

The IL-10 haplotype frequencies were similar in asthmatics and controls. Eosinophil count median was 2.0- to 3.2-fold higher among asthmatics with rare ATA/ATA genotype than in asthmatics with other genotypes. No such difference was seen in the control group. When analysed by IL-10 haplotype carrier state and gender, male asthmatics with ATA haplotype had 2.8-fold higher serum IgE than those without ATA. A converse association was found in male controls with ATA haplotype, who had 1.9-fold lower serum IgE than their ATA-negative counterparts. The high IL-10-producing GCC haplotype was associated with impaired lung function in smoking male controls while in asthmatics no clear effect on lung function was found with any of the haplotypes studied.

CONCLUSION

These results suggest that the eosinophil counts and serum IgE are differently regulated by IL-10 genotype in asthmatic and in normal subjects. However, IL-10 polymorphism is not related to susceptibility in asthma.

Contractile responses to adenosine, R-PIA and ovalbumen in passively sensitized guinea-pig isolated airways

1. Responses to adenosine, R-PIA and ovalbumen were examined in guinea-pig isolated superfused tracheal spirals to determine the effects of passive sensitization by overnight incubation in serum from ovalbumen (OA)-sensitized or non-sensitized guinea-pigs. 2. Tissues incubated with serum from non-sensitized and OA-sensitized guinea-pigs contracted (0.07+/-0.02 and 0.04+/-0.01 g, respectively) to adenosine (300 micro M) whereas non-incubated or Krebs-incubated tissues produced no contractions to adenosine or ovalbumen (10 micro g). Ovalbumen caused substantial contractions (0.40+/-0.09 g) after OA-sensitized serum incubation and significantly (P<0.05) smaller contractions (0.08+/-0.03 g) after non-sensitized serum incubation. Tracheae from guinea-pigs actively sensitized to ovalbumen 14-21 days beforehand also contracted to adenosine, R-PIA (3 micro M) and ovalbumen. 3. The A(1)/A(2) adenosine receptor antagonist, 8-phenyltheophylline (8-PT, 3 micro M), failed to antagonize these contractions, suggesting that A(1)/A(2) adenosine receptors were not involved. 4. Unlike adenosine, R-PIA (3 micro M) produced contractions in non-incubated (0.23+/-0.04 g) or Krebs-incubated (0.15+/-0.04 g) tracheae, as well as after passive and active sensitization. None of these responses were blocked by 8-PT. 5. The A(3) receptor agonist, IB-MECA, in the presence of 8-PT produced small contractions in passively sensitized tracheae (10 micro M, 0.02+/-0.003 g) and, in larger doses (100 micro M and 1 mM), contracted actively sensitized tracheae. 6. In actively sensitized trachea, the A(3) receptor antagonist, MRS-1220 (100 nM), significantly (P<0.05) attenuated adenosine contractions in the presence of 8-PT from 0.23+/-0.07 g to 0.07+/-0.03 g. 7. These results show that passive, like active sensitization, reveals bronchoconstrictions to adenosine of isolated tracheae. The insensitivity to 8-PT blockade, the antagonism by MRS-1220, and the fact that the A(3) receptor agonist, IB-MECA, mimics this response, suggest involvement of A(3) receptors. R-PIA, however, has a different profile of adenosine receptor activity.