Antigen-induced mast cell expansion and bronchoconstriction in a mouse model of asthma

[Respiratory oscillometry: Theoretical foundations and clinical applications]

Oscillometry measures the mechanical properties of the respiratory system. As they are carried out during spontaneous breathing, oscillometry measurements do not require forced breathing maneuvers or the patient's active cooperation. The technique is complementary to conventional pulmonary function testing methods for the investigation of respiratory function, diagnosis and monitoring of respiratory diseases, and assessment of response to treatment. The present review aims to describe the theoretical foundations and practical methodology of oscillometry. It describes the gaps in scientific evidence regarding its clinical utility, and provides examples of current research and clinical applications.

The Impact of High-Fructose Diet and Co-Sensitization to House Dust Mites and Ragweed Pollen on the Modulation of Airway Reactivity and Serum Biomarkers in Rats

The topic of ragweed pollen (RW) versus house dust mites (HDMs) has often been deliberated, but the increasing incidence of co-sensitization between them has been scarcely addressed. Utilizing Sprague Dawley rats, we explored the effects of co-sensitization with the combination of HDMs and RW pollen extracts in correlation with high-fructose diet (HFrD) by in vitro tracheal reactivity analysis in isolated organ bath and biological explorations. Our findings unveiled interrelated connections between allergic asthma, dyslipidemia, and HFrD-induced obesity, shedding light on their compounding role through inflammation. The increased CRP values and airway hyperresponsiveness to the methacholine challenge suggest a synergistic effect of obesity on amplifying the existing inflammation induced by asthma. One of the major outcomes is that the co-sensitization to HDMs and RW pollen led to the development of a severe allergic asthma phenotype in rats, especially in those with HFrD. Therefore, the co-sensitization to these allergens as well as the HFrD may play a crucial role in the modulation of systemic inflammation, obesity, and airway reactivity.

Fluoxetine restrains allergic inflammation by targeting an FcɛRI-ATP positive feedback loop in mast cells

There is a clinical need for new treatment options addressing allergic disease. Selective serotonin reuptake inhibitors (SSRIs) are a class of antidepressants that have anti-inflammatory properties. We tested the effects of the SSRI fluoxetine on IgE-induced function of mast cells, which are critical effectors of allergic inflammation. We showed that fluoxetine treatment of murine or human mast cells reduced IgE-mediated degranulation, cytokine production, and inflammatory lipid secretion, as well as signaling mediated by the mast cell activator ATP. In a mouse model of systemic anaphylaxis, fluoxetine reduced hypothermia and cytokine production. Fluoxetine was also effective in a model of allergic airway inflammation, where it reduced bronchial responsiveness and inflammation. These data show that fluoxetine suppresses mast cell activation by impeding an FcɛRI-ATP positive feedback loop and support the potential repurposing of this SSRI for use in allergic disease.

Inhibiting Isoprenylation Suppresses FcεRI-Mediated Mast Cell Function and Allergic Inflammation

IgE-mediated mast cell activation is a driving force in allergic disease in need of novel interventions. Statins, long used to lower serum cholesterol, have been shown in multiple large-cohort studies to reduce asthma severity. We previously found that statins inhibit IgE-induced mast cell function, but these effects varied widely among mouse strains and human donors, likely due to the upregulation of the statin target, 3-hydroxy-3-methylgutaryl-CoA reductase. Statin inhibition of mast cell function appeared to be mediated not by cholesterol reduction but by suppressing protein isoprenylation events that use cholesterol pathway intermediates. Therefore, we sought to circumvent statin resistance by targeting isoprenylation. Using genetic depletion of the isoprenylation enzymes farnesyltransferase and geranylgeranyl transferase 1 or their substrate K-Ras, we show a significant reduction in FcεRI-mediated degranulation and cytokine production. Furthermore, similar effects were observed with pharmacological inhibition with the dual farnesyltransferase and geranylgeranyl transferase 1 inhibitor FGTI-2734. Our data indicate that both transferases must be inhibited to reduce mast cell function and that K-Ras is a critical isoprenylation target. Importantly, FGTI-2734 was effective in vivo, suppressing mast cell-dependent anaphylaxis, allergic pulmonary inflammation, and airway hyperresponsiveness. Collectively, these findings suggest that K-Ras is among the isoprenylation substrates critical for FcεRI-induced mast cell function and reveal isoprenylation as a new means of targeting allergic disease.

Four weeks of repetitive acute hypoxic preconditioning did not alleviate allergen-induced airway dysfunction in rats

Clinical case series suggest beneficial effects of low-dose intermittent hypoxia in asthma. We tested cardiopulmonary effects of repetitive acute hypoxic preconditioning (RAHP) during allergic inflammation. Brown Norway rats were sensitized to house dust mites (HDM) and exposed to 4-week RAHP or normoxia (SHAM), concurrent with weekly HDM or saline (SAL) challenges. We assessed methacholine responses and lung HIF-1α expression at endpoint, and weekly blood pressure (BP). RAHP relative to SHAM: 1) in HDM-challenged rats, showed no protection against HDM-induced airway dysfunction and did not significantly impact BP (week 4 mean BP difference = 10.51 mmHg, p = 0.09) or HIF-1α expression; 2) in SAL-challenged rats, attenuated airway responses to methacholine, reduced BP (week 4 mean BP average difference = -8.72 mmHg, p = 0.04) and amplified HIF-1α expression (p = 0.0086). Four weeks of RAHP did not mitigate the allergen-induced lower airway dysfunction and may detrimentally affect BP. However, it elicited beneficial cardiopulmonary responses in SAL-challenged rats, concurrent with increased HIF-1α expression.

Monensin inhibits mast cell mediated airway contractions in human and guinea pig asthma models

Asthma is a common respiratory disease associated with airway hyperresponsiveness (AHR), airway inflammation and mast cell (MC) accumulation in the lung. Monensin, an ionophoric antibiotic, has been shown to induce apoptosis of human MCs. The aim of this study was to define the effect of monensin on MC responses, e.g., antigen induced bronchoconstriction, and on asthmatic features in models of allergic asthma. Tracheal segments from house dust mite (HDM) extract sensitized guinea pigs were isolated and exposed to monensin, followed by histological staining to quantify MCs. Both guinea pig tracheal and human bronchi were used for pharmacological studies in tissue bath systems to investigate the monensin effect on tissue viability and antigen induced bronchoconstriction. Further, an HDM-induced guinea pig asthma model was utilized to investigate the effect of monensin on AHR and airway inflammation. Monensin decreased MC number, caused MC death, and blocked the HDM or anti-IgE induced bronchoconstriction in guinea pig and human airways. In the guinea pig asthma model, HDM-induced AHR, airway inflammation and MC hyperplasia could be inhibited by repeated administration of monensin. This study indicates that monensin is an effective tool to reduce MC number and MCs are crucial for the development of asthma-like features.

Immunoglobulin E-Dependent Activation of Immune Cells in Rhinovirus-Induced Asthma Exacerbation

Acute exacerbation is the major cause of asthma morbidity, mortality, and health-care costs. Respiratory viral infections, particularly rhinovirus (RV) infections, are associated with the majority of asthma exacerbations. The risk for bronchoconstriction with RV is associated with allergic sensitization and type 2 airway inflammation. The efficacy of the humanized anti-IgE monoclonal antibody omalizumab in treating asthma and reducing the frequency and severity of RV-induced asthma exacerbation is well-known. Despite these clinical data, mechanistic details of omalizumab's effects on RV-induced asthma exacerbation have not been well-defined for years due to the lack of appropriate animal models. In this Perspective, we discuss potential IgE-dependent roles of mast cells and dendritic cells in asthma exacerbations.

IL-6 family cytokines in respiratory health and disease

Chronic lung diseases including asthma, chronic obstructive pulmonary disease (COPD) and lung fibrosis represent a major burden on healthcare systems with limited effective therapeutic options. Developing effective treatments for these debilitating diseases requires an understanding of how alterations at the molecular level affect lung macroscopic architecture. A common theme among these lung disorders is the presence of an underlying dysregulated immune system which can lead to sustained chronic inflammation. In this respect, several inflammatory cytokines have been implicated in the pathogenesis of lung diseases, thus leading to the notion that cytokines are attractive therapeutic targets for these disorders. In this review, we discuss and highlight the recent breakthroughs that have enhanced our understanding of the role of the interleukin (IL)-6 family of cytokines in lung homeostasis and chronic diseases including asthma, COPD, lung fibrosis and lung cancer.

Therapeutic Potential of Antileukotriene Drug-Camellia sinensis Extract Co-Formulation on Histamine Induced Asthma in Guinea Pigs

BACKGROUND/OBJECTIVE

To study the therapeutic potential of Antileukotriene drug- Camellia sinensis extract co-formulation on histamine induced asthma in guinea pigs.

METHODS

SRSD of Montelukast sodium was prepared by the solvent evaporation method. Lyophilized aqueous extract of Camellia sinensis leaves and SRSD mixture was filled in capsule and the capsule shell was coated to achieve initial release lag time. In vitro and pharmacokinetic study of capsules was performed and compared with commercial tablets. A further role of green tea, as an antioxidant adjunct for asthma management, has been analyzed by lung histology, mast cell count and oxidative stress assay in the serum of control and experimental animals.

RESULTS

The drug release from the commercial tablet was immediate and rapid, but capsule has shown an initial 3.5 hr lag time followed by sustained action up to 8 hr. Pharmacokinetic results show that studied formulations are bioequivalent with respect to Cmax and AUC, while rest parameters showed asignificant difference. Mast cells count in lung tissue were increased (p<0.001) in the experimental group along with glycoprotein deposition in asthmatic bronchioles. Levels of SOD and GPX were decreased (p<0.05) while CAT was increased (p<0.04) in the asthma group in comparison to control.

CONCLUSION

In the experimental animal model, co-formulation was effective in modulating allergic inflammation and contributing to better control of the inflammatory response. Our findings suggest that Camellia sinensis leaves extract may be used as an adjunct for future improvements in asthma treatment and prevention.

Oscillometry of the respiratory system: a translational opportunity not to be missed

Airway oscillometry has become the de facto standard for quality assessment of lung physiology in laboratory animals and has demonstrated its usefulness in understanding diseases of small airways. Nowadays, it is seeing extensive use in daily clinical practice and research; however, a question that remains unanswered is how well physiological findings in animals and humans correlate? Methodological and device differences are obvious between animal and human studies. However, all devices deliver an oscillated airflow test signal and output respiratory impedance. In addition, despite analysis differences, there are ways to interpret animal and human oscillometry data to allow suitable comparisons. The potential with oscillometry is its ability to reveal universal features of the respiratory system across species, making translational extrapolation likely to be predictive. This means that oscillometry can thus help determine if an animal model displays the same physiological characteristics as the human disease. Perhaps more importantly, it can also be useful to determine whether an intervention is effective as well as to understand if it affects the desired region of the respiratory system, e.g., the periphery of the lung. Finally, findings in humans can also inform preclinical scientists and give indications as to what type of physiological changes should be observed in animal models to make them relevant as models of human disease. The present article will attempt to demonstrate the potential of oscillometry in respiratory research, an area where the development of novel therapies is plagued with a failure rate higher than in other disease areas.

Leukotriene B4 receptors contribute to house dust mite-induced eosinophilic airway inflammation via TH2 cytokine production

Leukotriene B₄ (LTB₄) is a lipid mediator of inflammation that is generated from arachidonic acid via the 5-lipoxygenase pathway. Previous studies have reported that the receptors of LTB₄, BLT1, and BLT2 play mediatory roles in the allergic airway inflammation induced by ovalbumin (OVA). However, considering that house dust mites (HDMs) are the most prevalent allergen and well-known risk factor for asthmatic allergies, we are interested in elucidating the contributory roles of BLT1/2 in HDM-induced allergic airway inflammation. Our aim in this study was to investigate whether BLT1/2 play any roles in HDM-induced allergic airway inflammation. In this study, we observed that the levels of ligands for BLT1/2 [LTB₄ and 12(S)-HETE (12(S)-hydroxyeicosatetraenoic acid)] were significantly increased in bronchoalveolar lavage fluid (BALF) after HDM challenge. Block-ade of BLT1 or BLT2 as well as of 5-lipoxygenase (5-LO) or 12-lipoxygenase (12-LO) markedly suppressed the production of T_H2 cytokines (IL-4, IL-5, and IL-13) and alleviated lung inflammation and mucus secretion in an HDM-induced eosinophilic airway-inflammation mouse model. Together, these results indicate that the 5-/12-LO-BLT1/2 cascade plays a role in HDM-induced airway inflammation by mediating the production of T_H2 cytokines. Our findings suggest that BLT1/2 may be a potential therapeutic target for patients with HDM-induced allergic asthma.

Back to the future: re-establishing guinea pig in vivo asthma models

Research using animal models of asthma is currently dominated by mouse models. This has been driven by the comprehensive knowledge on inflammatory and immune reactions in mice, as well as tools to produce genetically modified mice. Many of the identified therapeutic targets influencing airway hyper-responsiveness and inflammation in mouse models, have however been disappointing when tested clinically in asthma. It is therefore a great need for new animal models that more closely resemble human asthma. The guinea pig has for decades been used in asthma research and a comprehensive table of different protocols for asthma models is presented. The studies have primarily been focused on the pharmacological aspects of the disease, where the guinea pig undoubtedly is superior to mice. Further reasons are the anatomical and physiological similarities between human and guinea pig airways compared with that of the mouse, especially with respect to airway branching, neurophysiology, pulmonary circulation and smooth muscle distribution, as well as mast cell localization and mediator secretion. Lack of reagents and specific molecular tools to study inflammatory and immunological reactions in the guinea pig has however greatly diminished its use in asthma research. The aim in this position paper is to review and summarize what we know about different aspects of the use of guinea pig in vivo models for asthma research. The associated aim is to highlight the unmet needs that have to be addressed in the future.

Circulating mast cell progenitors correlate with reduced lung function in allergic asthma

BACKGROUND

Studies using mouse models have revealed that mast cell progenitors are recruited from the blood circulation to the lung during acute allergic airway inflammation. The discovery of a corresponding human mast cell progenitor population in the blood has enabled to study the relation of circulating mast cell progenitors in clinical settings.

OBJECTIVES

To explore the possible association between the frequency of mast cell progenitors in the blood circulation and allergic asthma, we assessed the relation of this recently identified cell population with asthma outcomes and inflammatory mediators in allergic asthmatic patients and controls.

METHODS

Blood samples were obtained, and spirometry was performed on 38 well-controlled allergic asthmatic patients and 29 controls. The frequency of blood mast cell progenitors, total serum IgE and 180 inflammation- and immune-related plasma proteins were quantified.

RESULTS

Allergic asthmatic patients and controls had a similar mean frequency of blood mast cell progenitors, but the frequency was higher in allergic asthmatic patients with reduced FEV₁ and PEF (% of predicted) as well as in women. The level of fibroblast growth factor 21 (FGF-21) correlated positively with the frequency of mast cell progenitors, independent of age and gender, and negatively with lung function. The expression of FcεRI on mast cell progenitors was higher in allergic asthmatic patients and correlated positively with the level of total IgE in the controls but not in the asthmatic patients.

CONCLUSION

Elevated levels of circulating mast cell progenitors are related to reduced lung function, female gender and high levels of FGF-21 in young adults with allergic asthma.

Airway epithelial specific deletion of Jun-N-terminal kinase 1 attenuates pulmonary fibrosis in two independent mouse models

The stress-induced kinase, c-Jun-N-terminal kinase 1 (JNK1) has previously been implicated in the pathogenesis of lung fibrosis. However, the exact cell type(s) wherein JNK1 exerts its pro-fibrotic role(s) remained enigmatic. Herein we demonstrate prominent activation of JNK in bronchial epithelia using the mouse models of bleomycin- or AdTGFβ1-induced fibrosis. Furthermore, in lung tissues of patients with idiopathic pulmonary fibrosis (IPF), active JNK was observed in various regions including type I and type II pneumocytes and fibroblasts. No JNK activity was observed in adjacent normal tissue or in normal control tissue. To address the role of epithelial JNK1, we ablated Jnk1 form bronchiolar and alveolar type II epithelial cells using CCSP-directed Cre recombinase-mediated ablation of LoxP-flanked Jnk1 alleles. Our results demonstrate that ablation of Jnk1 from airway epithelia resulted in a strong protection from bleomycin- or adenovirus expressing active transforming growth factor beta-1 (AdTGFβ1)-induced fibrosis. Ablation of the Jnk1 allele at a time when collagen increases were already present showed a reversal of existing increases in collagen content. Epithelial Jnk1 ablation resulted in attenuation of mesenchymal genes and proteins in lung tissue and preserved expression of epithelial genes. Collectively, these data suggest that epithelial JNK1 contributes to the pathogenesis of pulmonary fibrosis. Given the presence of active JNK in lungs from patients with IPF, targeting JNK1 in airway epithelia may represent a potential treatment strategy to combat this devastating disease.

Mast Cells and Their Progenitors in Allergic Asthma

Mast cells and their mediators have been implicated in the pathogenesis of asthma and allergy for decades. Allergic asthma is a complex chronic lung disease in which several different immune cells, genetic factors and environmental exposures influence the pathology. Mast cells are key players in the asthmatic response through secretion of a multitude of mediators with pro-inflammatory and airway-constrictive effects. Well-known mast cell mediators, such as histamine and bioactive lipids are responsible for many of the physiological effects observed in the acute phase of allergic reactions. The accumulation of mast cells at particular sites of the allergic lung is likely relevant to the asthma phenotype, severity and progression. Mast cells located in different compartments in the lung and airways have different characteristics and express different mediators. According to in vivo experiments in mice, lung mast cells develop from mast cell progenitors induced by inflammatory stimuli to migrate to the airways. Human mast cell progenitors have been identified in the blood circulation. A high frequency of circulating human mast cell progenitors may reflect ongoing pathological changes in the allergic lung. In allergic asthma, mast cells become activated mainly via IgE-mediated crosslinking of the high affinity receptor for IgE (FcεRI) with allergens. However, mast cells can also be activated by numerous other stimuli e.g. toll-like receptors and MAS-related G protein-coupled receptor X2. In this review, we summarize research with implications on the role and development of mast cells and their progenitors in allergic asthma and cover selected activation pathways and mast cell mediators that have been implicated in the pathogenesis. The review places an emphasis on describing mechanisms identified using in vivo mouse models and data obtained by analysis of clinical samples.

Anti-allergic activities of 5,7-dimethoxy-3,4'-dihydroxyflavone via inhalation in rat allergic models

Various studies have shown that flavones have several pharmacological activities including anti-allergy activities. However, the bioavailability of oral flavones is very low, and whether inhaled administration can improve efficacy in respiratory disease models is unclear. In the present study, the anti-allergic activities of inhaling 5,7-dimethoxy-3,4'-dihydroxyflavone (MHF), a synthetic flavonoid, was investigated by comparison with disodium cromoglycate (DSCG) and nedocromil sodium (NS) in rat allergic models. In an anti-DNP-IgE-induced asthmatic model, inhaled MHF dose-dependently inhibited the increase in airway resistance after antigen challenge. In an ovalbumin (OVA)-induced asthmatic model, inhaled MHF showed significant suppression of airway hyperresponsiveness; a decrease in eosinophil and neutrophil counts, IL-4, IL-5 and leukotriene D₄ in bronchoalveolar lavage fluid; a reduction in total IgE and OVA-specific IgE levels in serum; and suppression of eosinophil infiltration in lung tissue after antigen challenge. The efficacy of inhaled MHF was comparable to that of NS and DSCG. In conclusion, based on these findings, the report for the first time that that inhaled MHF may be a potential drug for the treatment of allergic asthma.

Towards the use of breath for detecting mycobacterial infection: a case study in a murine model

In the present research, the potential of breath analysis by comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC×GC-MS) was investigated for the discrimination between healthy and infected mice. A pilot study employing a total of 16 animals was used to develop a method for breath analysis in a murine model for studying Mycobacterium tuberculosis complex (MTBC) using the M. bovis bacillus Calmette-Guérin. Breath was collected in Tedlar bags and concentrated onto thermal desorption tubes for subsequent analysis by GC×GC-MS. Immunological test and bacterial cell count in bronchoalveolar lavage fluid and mice lung homogenate confirmed the presence of bacteria in the infected group. From the GC×GC-MS analysis, 23 molecules were found to mainly drive the separation between control and infected mice and their tentative identification is provided.This study shows that the overall used methodology is able to differentiate breath between healthy and infected animals, and the information herein can be used to further develop the mouse breath model to study MTBC pathogenesis, evaluate pre-clinical drug regimen efficacy, and to further develop the concept of breath-based diagnostics.

The independent effects of vitamin D deficiency and house dust mite exposure on lung function are sex-specific

Vitamin D deficiency is increasing around the world and has been associated with the development of asthma. This study aims to evaluate the effect of dietary vitamin D deficiency at different life stages on lung function using a murine model of allergic airways disease. BALB/c mice were challenged intranasally with HDM or saline alone for 10 days. Twenty four hours after the last challenge, mice were anesthetized and lung function was measured using the forced oscillation technique (FOT). Mice were euthanized for assessment of inflammation in the bronchoalveolar lavage (BAL) and total collagen content in lung homogenates by ELISA. Vitamin D deficiency impaired lung function in both male and female mice, increasing tissue damping and elastance, however had no effect on HDM induced inflammation. The impact of vitamin D deficiency was more evident in females. HDM also decreased airway distensibility, but only in females and this response was not altered by vitamin D deficiency. Our data suggest that vitamin D deficiency and HDM exposure have independent effects on lung mechanics and that females are more susceptible to these effects. Vitamin D deficiency may exacerbate lung function deficits by having a direct, but independent, effect on parenchymal mechanics.

Lung responses in murine models of experimental asthma: Value of house dust mite over ovalbumin sensitization

Ovalbumin (OVA) sensitization has limitations in modelling asthma. Thus, we examined the value of allergic sensitization using a purified natural allergen, house dust mite (HDM), over the sensitization performed with OVA. Mice were sham-treated, or sensitized with OVA- or HDM with identical chronology. Airway resistance, tissue damping and elastance were assessed under control conditions and after challenging the animals with methacholine (MCh) and the specific allergen. Inflammatory profile of the bronchoalveolar lavage fluid was characterized and lung histology was performed. While no difference in the lung responsiveness to the specific allergen was noted, hyperresponsiveness to MCh was observed only in the HDM-sensitized animals in the lung peripheral parameters. Lung inflammation differed between the models, but excessive bronchial smooth muscle remodelling occurred only with OVA. In conclusion, we demonstrate that a purified natural allergen offers a more relevant murine model of human allergic asthma by expressing the key features of this chronic inflammatory disease both in the lung function and structure.

Forced expiration measurements in mouse models of obstructive and restrictive lung diseases

Background

Pulmonary function measurements are important when studying respiratory disease models. Both resistance and compliance have been used to assess lung function in mice. Yet, it is not always clear how these parameters relate to forced expiration (FE)-related parameters, most commonly used in humans. We aimed to characterize FE measurements in four well-established mouse models of lung diseases.

Method

Detailed respiratory mechanics and FE measurements were assessed concurrently in Balb/c mice, using the forced oscillation and negative pressure-driven forced expiration techniques, respectively. Measurements were performed at baseline and following increasing methacholine challenges in control Balb/c mice as well as in four disease models: bleomycin-induced fibrosis, elastase-induced emphysema, LPS-induced acute lung injury and house dust mite-induced asthma.

Results

Respiratory mechanics parameters (airway resistance, tissue damping and tissue elastance) confirmed disease-specific phenotypes either at baseline or following methacholine challenge. Similarly, lung function defects could be detected in each disease model by at least one FE-related parameter (FEV_0.1, FEF_0.1, FVC, FEV_0.1/FVC ratio and PEF) at baseline or during the methacholine provocation assay.

Conclusions

FE-derived outcomes in four mouse disease models behaved similarly to changes found in human spirometry. Routine combined lung function assessments could increase the translational utility of mouse models.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0610-1) contains supplementary material, which is available to authorized users.

The role of iNKT cells on the phenotypes of allergic airways in a mouse model

iNKT cells and mast cells have both been implicated in the syndrome of allergic asthma through their activation-induced release of Th2 type cytokines and secretion of histamine and other mediators, respectively, which can promote airways hyperresponsiveness (AHR) to agents such as methacholine. However, a mechanistic link between iNKT cells and mast cell recruitment or activation has never been explored. Our objective was to determine whether iNKT cells are necessary for the recruitment of mast cells and if iNKT cells can influence the acute allergen induced bronchoconstriction (AIB) caused by mast cell mediator release. To do so, we pharmacologically eliminated iNKT cells using a specific antibody (NKT-14) and examined its impact on airway inflammation and physiological phenotype. In mice treated with NKT-14, the elimination of iNKT cells was sufficient to prevent AHR and pulmonary eosinophilic inflammation elicited by administration of the iNKT cell agonist αGalCer. In mice treated with NKT-14 and then sensitized and challenged with house dust mite extract (HDM), eliminating the iNKT cells significantly reduced both AHR and AIB but did not affect pulmonary inflammation, the mast cell population, nor the release of the mast cell mediators mast cell protease-1 and prostaglandin D2. We conclude that while iNKT cells contribute to the phenotype of allergic airways disease through the manifestation of AIB and AHR, their presence is not required for mast cell recruitment and activation, or to generate the characteristic inflammatory response subsequent to allergen challenge.

Oral administration of Clostridium butyricum CGMCC0313-1 reduces ovalbumin-induced allergic airway inflammation in mice

BACKGROUND AND OBJECTIVE

Probiotic bacteria can induce immune regulation or immune tolerance in patients with allergic diseases, but the underlying mechanisms are still unclear. There has been a growing interest in the use of beneficial bacteria for allergic diseases recently. This study aimed at exploring whether Clostridium butyricum CGMCC0313-1 (C. butyricum) can reduce ovalbumin (OVA)-induced allergic airway inflammation in a mouse model.

METHODS

Mouse model of allergic airway inflammation induced via OVA was used in this study. C. butyricum was administered daily by the oral route during or after the sensitization. Airway function, pulmonary airway inflammation, mast cell degranulation, T helper (Th)-specific and anti-inflammatory cytokines, OVA-specific Ig, matrix metalloproteinase 9 (MMP-9) and histopathological alterations were examined.

RESULTS

C. butyricum significantly reduced lung resistance in the asthmatic mice. Pulmonary airway inflammation, mast cell degranulation, airway remodelling and the expression of OVA-specific IgE/G1 were suppressed by oral C. butyricum. It also reversed the imbalance of Th1/Th2 and increased the anti-inflammatory cytokine IL-10.

CONCLUSION

C. butyricum reduces OVA-induced allergic airway inflammation in mice and might be an additional or supplementary therapy for allergic asthma.

The interleukin-33 receptor ST2 is important for the development of peripheral airway hyperresponsiveness and inflammation in a house dust mite mouse model of asthma

BACKGROUND

Several clinical and experimental studies have implicated IL-33 and its receptor ST2 in the development of asthma. However, the effect of IL-33/ST2 signalling on airway responses and inflammation in allergic asthma is not well established.

OBJECTIVE

To investigate the role of IL-33/ST2 signalling in promoting allergen-induced airway hyperresponsiveness (AHR), airway inflammation, antigen-specific IgE production and mast cell activity in a mouse model of asthma.

METHODS

ST2-deficient (ST2(-/-)) mice and control BALB/c mice were given house dust mite (HDM) extract over a 6-week period. Forty-eight hours after the final HDM administration, lung function and airway inflammation were evaluated. Airway responsiveness was determined in the central airways and peripheral lung. Cellular infiltration and mast cell protease mMCP-1 levels were quantified in bronchoalveolar lavage fluid (BALF). Recruitment of inflammatory cells and inflammatory cytokine profiles were assessed in pulmonary tissue, and HDM-specific IgE was measured in serum.

RESULTS

ST2 deficiency diminished HDM-induced AHR in the peripheral lung, while AHR in the central airways was unaffected. Inflammatory responses to HDM were also reduced in ST2(-/-) mice as reflected by the lower induction of HDM-specific serum IgE, inhibition of HDM-induced eosinophilia and reduced macrophage count in BALF, and a diminished influx of inflammatory cells and reduced goblet cell hyperplasia around the peripheral airways. Furthermore, the levels of the inflammatory cytokines IL-1β, IL-5, IL-13, IL-33, GM-CSF, thymic stromal lymphopoietin and mast cell protease mMCP-1 were reduced in HDM-treated ST2(-/-) mice compared with wild-type controls.

CONCLUSIONS

In addition to promoting Th2 inflammation, we now suggest a role for the IL-33/ST2 pathway for the induction of peripheral inflammation and mucus production that causes AHR in the peripheral lung. This mechanism for inducing AHR at distal parts of the lung may be of specific importance as asthma is considered as a small airway disease.

Mast cell-derived neurotrophin 4 mediates allergen-induced airway hyperinnervation in early life

Asthma often progresses from early episodes of insults. How early-life events connect to long-term airway dysfunction remains poorly understood. We demonstrated previously that increased neurotrophin 4 (NT4) levels following early-life allergen exposure cause persistent changes in airway smooth muscle (ASM) innervation and airway hyper-reactivity (AHR) in mice. Herein, we identify pulmonary mast cells as a key source of aberrant NT4 expression following early insults. NT4 is selectively expressed by ASM and mast cells in mice, nonhuman primates, and humans. We show in mice that mast cell-derived NT4 is dispensable for ASM innervation during development. However, upon insults, mast cells expand in number and degranulate to release NT4 and thus become the major source of NT4 under pathological condition. Adoptive transfer of wild-type mast cells, but not NT4^-/- mast cells restores ASM hyperinnervation and AHR in Kit^W-sh/W-sh mice following early-life insults. Notably, an infant nonhuman primate model of asthma also exhibits ASM hyperinnervation associated with the expansion and degranulation of mast cells. Together, these findings identify an essential role of mast cells in mediating ASM hyperinnervation following early-life insults by producing NT4. This role may be evolutionarily conserved in linking early insults to long-term airway dysfunction.

Interaction between allergic asthma and atherosclerosis

Prior studies have established an essential role of mast cells in allergic asthma and atherosclerosis. Mast cell deficiency or inactivation protects mice from allergen-induced airway hyper-responsiveness and diet-induced atherosclerosis, suggesting that mast cells share pathologic activities in both diseases. Allergic asthma and atherosclerosis are inflammatory diseases that contain similar sets of elevated numbers of inflammatory cells in addition to mast cells in the airway and arterial wall, such as macrophages, monocytes, T cells, eosinophils, and smooth muscle cells. Emerging evidence from experimental models and human studies points to a potential interaction between the 2 seemingly unrelated diseases. Patients or mice with allergic asthma have a high risk of developing atherosclerosis or vice versa, despite the fact that asthma is a T-helper (Th)2-oriented disease, whereas Th1 immunity promotes atherosclerosis. In addition to the preferred Th1/Th2 responses that may differentiate the 2 diseases, mast cells and many other inflammatory cells also contribute to their pathogenesis by more than just T cell immunity. Here, we summarize the different roles of airway and arterial wall inflammatory cells and vascular cells in asthma and atherosclerosis and propose an interaction between the 2 diseases, although limited investigations are available to delineate the molecular and cellular mechanisms by which 1 disease increases the risk of the other. Results from mouse allergic asthma and atherosclerosis models and from human population studies lead to the hypothesis that patients with atherosclerosis may benefit from antiasthmatic medications or that the therapeutic regimens targeting atherosclerosis may also alleviate allergic asthma.

Systems physiology of the airways in health and obstructive pulmonary disease

Fresh air entering the mouth and nose is brought to the blood-gas barrier in the lungs by a repetitively branching network of airways. Provided the individual airway branches remain patent, this airway tree achieves an enormous amplification in cross-sectional area from the trachea to the terminal bronchioles. Obstructive lung diseases such as asthma occur when airway patency becomes compromised. Understanding the pathophysiology of these obstructive diseases thus begins with a consideration of the factors that determine the caliber of an individual airway, which include the force balance between the inward elastic recoil of the airway wall, the outward tethering forces of its parenchymal attachments, and any additional forces due to contraction of airway smooth muscle. Other factors may also contribute significantly to airway narrowing, such as thickening of the airway wall and accumulation of secretions in the lumen. Airway obstruction becomes particularly severe when these various factors occur in concert. However, the effect of airway abnormalities on lung function cannot be fully understood only in terms of what happens to a single airway because narrowing throughout the airway tree is invariably heterogeneous and interdependent. Obstructive lung pathologies thus manifest as emergent phenomena arising from the way in which the airway tree behaves a system. These emergent phenomena are studied with clinical measurements of lung function made by spirometry and by mechanical impedance measured with the forced oscillation technique. Anatomically based computational models are linking these measurements to underlying anatomic structure in systems physiology terms. WIREs Syst Biol Med 2016, 8:423-437. doi: 10.1002/wsbm.1347 For further resources related to this article, please visit the WIREs website.

Identification and Characterization of Baicalin as a Phosphodiesterase 4 Inhibitor

Asthma is a chronic inflammatory disease of lung airways, and pharmacological inhibitors of cyclic adenosine monophosphate-specific phosphodiesterase 4 (PDE4) have been considered as therapeutics for the treatment of asthma. However, development of PDE4 inhibitors in clinical trials has been hampered because of the severe side effects of non-selective PDE4 inhibitors. Here, screening of a plant extract library in conjunction with dereplication technology led to identification of baicalin as a new type of PDE4-selective inhibitor. We demonstrated that while rolipram inhibited the enzyme activity of a range of PDE4 subtypes in in vitro enzyme assays, baicalin selectively inhibited the enzyme activity of PDE4A and 4B. In addition, baicalin suppressed lipopolysaccharide-induced TNF-α expression in macrophage where PDE4B plays a key role in lipopolysaccharide-induced signaling. Furthermore, baicalin treatment in an animal model of allergic asthma reduced inflammatory cell infiltration and TNF-α levels in bronchoalveolar lavage fluids, indicating that the antiinflammatory effects of baicalin in vivo are attributable, in part, to its ability to inhibit PDE4.

Mouse Invariant Monoclonal Antibody NKT14: A Novel Tool to Manipulate iNKT Cell Function In Vivo

Invariant Natural Killer T (iNKT) cells are a T cell subset expressing an invariant T Cell Receptor (TCR) that recognizes glycolipid antigens rather than peptides. The cells have both innate-like rapid cytokine release, and adaptive-like thymic positive selection. iNKT cell activation has been implicated in the pathogenesis of allergic asthma and inflammatory diseases, while reduced iNKT cell activation promotes infectious disease, cancer and certain autoimmune diseases such as Type 1 diabetes (T1D). Therapeutic means to reduce or deplete iNKT cells could treat inflammatory diseases, while approaches to promote their activation may have potential in certain infectious diseases, cancer or autoimmunity. Thus, we developed invariant TCR-specific monoclonal antibodies to better understand the role of iNKT cells in disease. We report here the first monoclonal antibodies specific for the mouse invariant TCR that by modifying the Fc construct can specifically deplete or activate iNKT cells in vivo in otherwise fully immuno-competent animals. We have used both the depleting and activating version of the antibody in the NOD model of T1D. As demonstrated previously using genetically iNKT cell deficient NOD mice, and in studies of glycolipid antigen activated iNKT cells in standard NOD mice, we found that antibody mediated depletion or activation of iNKT cells respectively accelerated and retarded T1D onset. In BALB/c mice, ovalbumin (OVA) mediated airway hyper-reactivity (AHR) was abrogated with iNKT cell depletion prior to OVA sensitization, confirming studies in knockout mice. Depletion of iNKT cells after sensitization had no effect on AHR in the conducting airways but did reduce AHR in the lung periphery. This result raises caution in the interpretation of studies that use animals that are genetically iNKT cell deficient from birth. These activating and depleting antibodies provide a novel tool to assess the therapeutic potential of iNKT cell manipulation.

Vitamin E Isoform γ-Tocotrienol Downregulates House Dust Mite-Induced Asthma

Inflammation and oxidative damage contribute to the pathogenesis of asthma. Although corticosteroid is the first-line treatment for asthma, a subset of patients is steroid resistant, and chronic steroid use causes side effects. Because vitamin E isoform γ-tocotrienol possesses both antioxidative and anti-inflammatory properties, we sought to determine protective effects of γ-tocotrienol in a house dust mite (HDM) experimental asthma model. BALB/c mice were sensitized and challenged with HDM. Bronchoalveolar lavage (BAL) fluid was assessed for total and differential cell counts, oxidative damage biomarkers, and cytokine levels. Lungs were examined for cell infiltration and mucus hypersecretion, as well as the expression of antioxidants and proinflammatory biomarkers. Sera were assayed for IgE and γ-tocotrienol levels. Airway hyperresponsiveness in response to methacholine was measured. γ-Tocotrienol displayed better free radical-neutralizing activity in vitro and inhibition of BAL fluid total, eosinophil, and neutrophil counts in HDM mouse asthma in vivo, as compared with other vitamin E isoforms, including α-tocopherol. Besides, γ-tocotrienol abated HDM-induced elevation of BAL fluid cytokine and chemokine levels, total reactive oxygen species and oxidative damage biomarker levels, and of serum IgE levels, but it promoted lung-endogenous antioxidant activities. Mechanistically, γ-tocotrienol was found to block nuclear NF-κB level and enhance nuclear Nrf2 levels in lung lysates to greater extents than did α-tocopherol and prednisolone. More importantly, γ-tocotrienol markedly suppressed methacholine-induced airway hyperresponsiveness in experimental asthma. To our knowledge, we have shown for the first time the protective actions of vitamin E isoform γ-tocotrienol in allergic asthma.

Effects of JNJ-40929837, a leukotriene A4 hydrolase inhibitor, in a bronchial allergen challenge model of asthma

Leukotriene B4 (LTB4) is a chemotactic mediator implicated in the pathogenesis of asthma. JNJ-40929837 is an oral inhibitor of LTA4 hydrolase, which catalyzes LTB4 production. We evaluated the effects of JNJ-40929837 in a human bronchial allergen challenge (BAC) model. In this double-blind, 3-period crossover study, 22 patients with mild, atopic asthma were randomized to one of three treatments per period: 100 mg/day JNJ-40929837 for 6 days followed by 50 mg/day on day 7; 10 mg/day montelukast for 6 days; and matched placebo. The BAC was performed on day 6 of each treatment period. Primary outcome was BAC-induced late asthmatic response (LAR) measured by maximal percent reduction in forced expiratory volume (FEV1) in one second. Secondary outcomes included early asthmatic response (EAR) by maximal percent reduction in FEV1, EAR and LAR evaluated by area under the FEV1/time curve (AUC0-2, AUC3-10, respectively), change in baseline FEV1 after 5-day treatment, safety, and correlation of JNJ-40929837 to the divalent cation ionophore A23187-stimulated whole blood LTB4 levels and sputum basal LTB4 levels. No significant differences were observed in the primary or secondary FEV1 endpoints with JNJ-40929837 versus placebo. Compared with placebo (n = 17, LS mean = 27.7), there was no significant attenuation of the maximal percent reduction in the LAR FEV1 with JNJ-40929837 (n = 16, LS mean = 28.6, P = 0.63) but montelukast (n = 17, LS mean = 22.6, P = 0.01) significantly attenuated the LAR. JNJ-40929837 substantially inhibited LTB4 production in whole blood, decreased sputum LTB4 levels and was well-tolerated. The number of adverse events leading to study withdrawal was the same in JNJ-40929837 and placebo groups. In conclusion, JNJ-40929837 demonstrated target engagement in blood and sputum. No significant impact in response to allergen inhalation was observed with JNJ-40929837 versus placebo.

REGISTRATION

This study is registered at ClinicalTrials.gov: NCT01241422.