Airway Hyperresponsiveness Responses Research Articles

Desert particulate matter from Afghanistan increases airway obstruction in human distal lungs exposed to type 2 cytokine IL-13.

Deployment related asthma-like symptoms including distal airway obstruction have been described in U.S. military personnel who served in Iraq and Afghanistan. The mechanisms responsible for the development of distal airway obstruction in deployers exposed to desert particulate matter (PM) is not well understood. We sought to determine if respiratory exposure to PM from Afghanistan (PMa) increases human distal airway hyperresponsiveness (AHR) with or without exposures to IL-13, a type 2 cytokine. We further tested whether mitochondrial dysfunction, such as ATP signaling and oxidative stress, may contribute to PMa- mediated AHR. Precision-cut lung slices from donors without a history of lung disease, tobacco smoking, or vaping were pre-treated with IL-13 for 24 h. This was followed by exposure to PMa or PM from California (PMc, control for PMa) for up to 72 h. The role of hydrogen peroxide and ATP in AHR was assessed using the antioxidant enzyme catalase or an ATP receptor P2Y13 antagonist MRS2211. AHR in response to methacholine challenges as well as cytokine IL-8 production were measured. PMa alone, but not PMc alone, trended to increase AHR. Importantly, the combination of PMa and IL-13 significantly amplified AHR compared to control or PMc+IL-13. PMa alone and in combination with IL-13 increased IL-8 as compared to the control. PMa increased H2O2 and ATP. MRS211 and catalase reduced AHR in PCLS exposed to both PMa and IL-13. Our data suggests that PMa in a type 2 inflammation-high lung increased AHR in part through oxidative stress and ATP signaling.

416 Smooth muscle–specific cystic fibrosis transmembrane conductance regulator loss induces airway hyperreactivity in response to transforming growth factor beta

416 Smooth muscle–specific cystic fibrosis transmembrane conductance regulator loss induces airway hyperreactivity in response to transforming growth factor beta

Lack of Ecto-5'-Nucleotidase Protects Sensitized Mice against Allergen Challenge.

Ecto-5′-nucleotidase (CD73), the ectoenzyme that together with CD39 is responsible for extracellular ATP hydrolysis and adenosine accumulation, regulates immune/inflammatory processes by controlling innate and acquired immunity cell functions. We previously demonstrated that CD73 is required for the assessment of a controlled allergic sensitization, in mice. Here, we evaluated the response to aerosolized allergen of female-sensitized mice lacking CD73 in comparison with their wild type counterpart. Results obtained show, in mice lacking CD73, the absence of airway hyperreactivity in response to an allergen challenge, paralleled by reduced airway CD23+B cells and IL4+T cells pulmonary accumulation together with reduced mast cells accumulation and degranulation. Our findings indicate CD73 as a potential therapeutic target for allergic asthma.

Linggan Wuwei Jiangxin formula ameliorates airway hyperresponsiveness through suppression of IL-1β and IL-17A expression in allergic asthmatic mice especially with diet-induced obesity.

BackgroundObese asthma represents a disease phenotype, which is associated with worse disease control and unresponsiveness to standard anti-inflammatory regimens, including inhaled corticosteroids. Obesity-related innate airway hyperresponsiveness (AHR) plays a role in this asthma phenotype via activation of the IL-1β/innate lymphoid cell 3 (ILC3)/IL-17A pathway. Linggan Wuwei Jiangxin (LGWWJX) formula may be a promising therapeutic option for obese asthma according to traditional Chinese medicine theory, clinical experience and related research.MethodsThe murine model of allergic asthma with obesity was induced by ovalbumin (OVA) sensitization and challenge in combination with a high fat diet (HFD). LGWWJX formula intervention was oral administrated. AHR and bronchoalveolar lavage fluid (BALF) cellularity were measured. Lung and liver histopathology assessment was performed by haematoxylin and eosin (H&E) staining. IL-1β and IL-17A in BALF and serum were evaluated by ELISA. Additionally, the influence of different concentrations of LGWWJX formula on IL-1β stimulated IL-17A mRNA expression in ILC3 cells was evaluated in vitro.ResultsLGWWJX treatment significantly reduced AHR and allergic airway inflammatory responses in asthmatic mice, as measured by pulmonary histopathology and BALF cellularity, and these effects were more pronounced in obese asthmatic mice. While eosinophil infiltration in BALF was suppressed with LGWWJX treatment in non-obese asthmatic mice, neutrophils and basophils were significantly decreased in obese asthmatic mice. Notably, LGWWJX also demonstrated remarkable efficacy for weight loss and improvements in hepatic steatosis in mice fed with a HFD. Furthermore, the protein levels of IL-1β in both serum and BALF, as well as those of BALF IL-17A, declined with LGWWJX intervention in both obese and non-obese asthmatic mice, and results from ex-vivo experiments found that LGWWJX significantly attenuated the expression of IL-17A in ILC3 cells with or without stimulation by IL-1β.ConclusionsLGWWJX may exert a protective effect on asthmatic individuals, especially those with concurrent obesity, most likely through mechanisms including the inhibition of the IL-1β/ILC3/IL-17A/AHR axis, anti-inflammatory effects, weight loss, and the regulation of lipid metabolism. This suggests a promising role of LGWWJX, alone or in combination with anti-inflammatory agents, for the treatment of obese asthma.

Analysis of TRPV gene expression in the respiratory epithelium of asthma patients with osmotic airway hyperresponsiveness

Introduction . The phenomenon of airway hyperresponsiveness in response to changes in air humidity is widespread among patients with asthma. Transient receptor potential channels of the vanilloid subfamily (TRPV) are of interest in terms of study of specific mechanisms of bronchial osmotic hyperresponsiveness. Aim . The aim of the study was to evaluate the expression TRPV1, TRPV2 and TRPV4 genes at mRNA level in the epithelium of the upper and lower respiratory tract in asthma patients with osmotic airway hyperresponsiveness. Materials and methods . We examined 35 patients with mild and moderate asthma. All patients underwent bronchoprovocation tests with hypo- and hyperosmotic solutions. Expression of TRPV receptors was studied in brush biopsies of the nasal and bronchial epithelium by quantitative PCR with reverse transcription. Results . Airway hyperrresponsiveness to hypoosmotic and hyperosmotic stimuli was observed in 25% and 50% of cases, respectively. It was found that patients with lower baseline FEV 1 had overexpression of TRPV1 (3.2 times, p=0.05) and TRPV2 (6.2 times, p=0.013) in the bronchial epithelium. Hypoosmotic airway hyperresponsiveness was associated with increased expression of the TRPV1 (7.4 times, p=0.004) and TRPV2 (18.5 times, p=0.014) genes in the bronchial epithelium. Airway hyperresponsiveness to hypertonic stimulus was also characterized by higher expression of TRPV1 (4.7 times, p=0.013) and TRPV2 (7.6 times, p=0.024). No difference in TRPV4 expression levels was found. Conclusion . The obtained data indicate the up-regulation of TRPV1 and TRPV2 in the bronchial epithelium of asthma patients with osmotic airway hyperresponsiveness, what, in turn, may indicate the role of these receptors in the development of airway osmotic-induced responses and in the pathogenesis of asthma.

Distinct Roles of LFA-1 and ICAM-1 on ILC2s Control Lung Infiltration, Effector Functions, and Development of Airway Hyperreactivity.

Asthma is a heterogeneous airway inflammatory disease characterized by increased airway hyperreactivity (AHR) to specific and unspecific stimuli. Group 2 innate lymphoid cells (ILC2)s are type-2 cytokine secreting cells capable of inducing eosinophilic lung inflammation and AHR independent of adaptive immunity. Remarkably, reports show that ILC2s are increased in the blood of human asthmatics as compared to healthy donors. Nevertheless, whether ILC2 expression of adhesion molecules regulates ILC2 trafficking remains unknown. Our results show that IL-33-activated ILC2s not only express LFA-1 but also strikingly LFA-1 ligand ICAM-1. Both LFA-1−/− and ICAM-1−/− mice developed attenuated AHR in response to IL-33 intranasal challenge, associated with a lower airway inflammation and less lung ILC2 accumulation compared to controls. Our mixed bone marrow chimera studies however revealed that ILC2 expression of LFA-1 — but not ICAM-1 — was required for their accumulation in the inflamed lungs. Importantly, we found that LFA-1 remarkably controlled ILC2 homing to the lungs, suggesting that LFA-1 is involved in ILC2 trafficking to the lungs. Our exploratory transcriptomic analysis further revealed that ICAM-1 deficiency on ILC2s significantly affects their effector functions. While it downregulated pro-inflammatory cytokines such as Il5, Il9, Il13, and Csf2, it however notably also upregulated cytokines including Il10 both at the transcriptomic and protein levels. These findings provide novel avenues for future investigations, as modulation of LFA-1 and/or ICAM-1 represents an unappreciated regulatory mechanism for ILC2 trafficking and cytokine production respectively, potentially serving as therapeutic target for ILC2-dependent diseases such as allergic asthma.

Exploration of plasma interleukin-27 levels in asthma patients and the correlation with lung function

BackgroundIL-27 attenuates allergic inflammation and improves lung function in mouse models of allergic asthma. However, plasma IL-27 levels of asthma patients and the association with clinical features remain poorly understood. MethodsThis study examined plasma IL-27 protein expression in untreated asthma patients and controls, analyzed its correlation with Th2 inflammation and lung function, and evaluated the effect of corticosteroids on IL-27 expression. ResultsPlasma IL-27 levels were lower in untreated asthma patients compared to controls. Plasma IL-27 levels were inversely correlated with sputum IL-5 mRNA expression in Th2Hi group. The Th2HiIL-27Low subgroup suffered from the highest airway hyperresponsiveness (AHR) and the worst pulmonary function. The patients in Th2LowIL-27Low subgroup were less likely to be atopic and had the worst improvement of symptoms after four weeks of standard treatment. In vitro, dexamethasone could decrease the expression of IL-27 in THP-1 cell line. The majority of asthma patients had further decreased IL-27 levels after standard treatment, whereas patients with sustained high levels of IL-27 post-treatment had more blood neutrophils at baseline compared with those without. ConclusionsThe results indicate that low levels of IL-27 in peripheral blood are closely related to Th2 inflammation and lung function of asthma patients. Low IL-27 levels in combination with high Th2 inflammation identify an asthma phenotype with high AHR and substantial response to corticosteroids. Understanding of this interaction could help to elucidate the inherent inflammation heterogeneity of asthma.

A phospholipid-based formulation for the treatment of airway inflammation in chronic respiratory diseases

Inflammation, the major hallmark of all chronic respiratory diseases is generally managed by inhaled corticosteroids. However, long term high dose treatment can result in significant side effects. Hence, there is a medical need for non-steroidal anti-inflammatory therapies to address airway inflammation. Phospholipids have been shown to reduce inflammation in several inflammatory conditions; however, their clinical translation has been limited to liposomal formulations traditionally used as drug carriers and their biological activity has not been investigated. Here we report the first application of empty liposomes as an anti-inflammatory treatment in airway inflammation. In the current study, liposomes (UTS-001) were prepared from cholesterol and a synthetic phospholipid (DOPC). The formulation was characterised in terms of size, charge, polydispersity index, morphology and stability as colloidal suspension and freeze-dried nanoparticles. Time-dependant uptake of UTS-001 in airway epithelial cells was observed which was inhibited by nystatin demonstrating that the uptake is via the caveolae pathway. In-vitro, in primary nasal epithelial cells, UTS-001 treatment successfully attenuated IL-6 levels following TNF-α stimulation. Consistent with the in-vitro findings, in-vivo, in the ovalbumin model of allergic airway inflammation, UTS-001 significantly reduced total immune cell counts in bronchoalveolar lavage fluid and reduced airway hyperresponsiveness in response to increasing doses of methacholine challenge. Therefore, our results establish UTS-001 as a potential anti-inflammatory treatment that may be useful as a therapeutic for lung inflammatory diseases.

Crude Turmeric Extract Improves the Suppressive Effects of Lactobacillus rhamnosus GG on Allergic Inflammation in a Murine Model of House Dust Mite-Induced Asthma.

There is a strong correlation between dysregulation of the gastrointestinal microbiota and development of allergic diseases. The most prevalent therapies for relieving asthma symptoms are associated with serious side effects, and therefore novel approaches are needed. Our objective was to elucidate whether oral administration of Lactobacillus rhamnosus GG (LGG) as a probiotic or turmeric powder (TP) as a prebiotic or both as a synbiotic mitigate allergic inflammation including lung function, airway inflammatory cell infiltration, Th2 cytokines/chemokine in a murine model of house dust mite (HDM)-induced asthma. BALB/c mice were intranasally sensitized and challenged with HDM received TP (20 mg/Kg mouse), or/and LGG (105 or 107 cfu/ml), or both orally. Interestingly, the synbiotic intervention (HDM-TP-LGG E7) specifically suppress the developement of airway hyperresponsiveness in response to methacholine. Besides, our synbiotic, TP, and LGG strongly down-regulated eosinophilia, IL-5, CCL17, IL-13. In terms of T cell response, CD4+ Th2 cells and CD4+ Th17 population were reduced in the splenocytes of the treatment groups compared to control. The synbiotic group not only elevated CD25+Foxp3+Treg frequency compared to asthmatic group, but also increased T reg cells compared to the probiotic group. The synbiotic also indicated the superior effect in suppressing Th2 cells compared to probiotic. Although, TP and LGG alone displayed suppressive effects, this study showed that the combination therapy consisting of TP and LGG (synbiotic) is more effective in some of the parameters than either of the treatments alone. This novel synbiotic, might be considered as a potential food-based drug for translational medicine and can possibly be used along with corticosteroid treatment.

Subacute TGFβ Exposure Drives Airway Hyperresponsiveness in Cystic Fibrosis Mice through the PI3K Pathway.

Cystic fibrosis (CF) is a lethal genetic disease characterized by progressive lung damage and airway obstruction. The majority of patients demonstrate airway hyperresponsiveness (AHR), which is associated with more rapid lung function decline. Recent studies in the neonatal CF pig demonstrated airway smooth muscle (ASM) dysfunction. These findings, combined with observed CF transmembrane conductance regulator (CFTR) expression in ASM, suggest that a fundamental defect in ASM function contributes to lung function decline in CF. One established driver of AHR and ASM dysfunction is transforming growth factor (TGF) β1, a genetic modifier of CF lung disease. Prior studies demonstrated that TGFβ exposure in CF mice drives features of CF lung disease, including goblet cell hyperplasia and abnormal lung mechanics. CF mice displayed aberrant responses to pulmonary TGFβ, with elevated PI3K signaling and greater increases in lung resistance compared with controls. Here, we show that TGFβ drives abnormalities in CF ASM structure and function through PI3K signaling that is enhanced in CFTR-deficient lungs. CF and non-CF mice were exposed intratracheally to an adenoviral vector containing the TGFβ1 cDNA, empty vector, or PBS only. We assessed methacholine-induced AHR, bronchodilator response, and ASM area in control and CF mice. Notably, CF mice demonstrated enhanced AHR and bronchodilator response with greater ASM area increases compared with non-CF mice. Furthermore, therapeutic inhibition of PI3K signaling mitigated the TGFβ-induced AHR and goblet cell hyperplasia in CF mice. These results highlight a latent AHR phenotype in CFTR deficiency that is enhanced through TGFβ-induced PI3K signaling.

Modulation of ILC2 trafficking and effector functions in ILC2-driven airway hyperreactivity

Abstract Background Asthma is a heterogeneous disease of the airways characterized by increased airway hyperreactivity (AHR) to specific and unspecific stimuli. Group 2 innate lymphoid cells (ILC2s) are type 2 secreting cells that are sufficient to induce eosinophilic lung inflammation and AHR independent of adaptive immunity in murine models. Identifying pathways that modulate ILC2 homeostasis and function are therefore an important step towards treating ILC2-dependent asthma. Objective We examined the expression of adhesion molecule lymphocyte-associated antigen 1 (LFA-1) and ligand intercellular adhesion molecule (ICAM)-1 on ILC2s and their effect on the development of lung inflammation and AHR in murine models. Methods Genetically modified mice constitutively lacking LFA-1 or ICAM-1 were assessed for the development of lung inflammation and AHR. We further generated mixed bone marrow chimeras and performed transcriptomic analysis to characterize their role on ILC2 homeostasis and function. Results LFA-1 is expressed on murine naïve and IL-33-activated ILC2s, while ICAM-1 is surprisingly expressed – and upregulated – upon activation. Compared to WT mice, both LFA-1−/− and ICAM-1−/− mice develop less lung inflammation and AHR in response to intranasal IL-33 challenge. Furthermore, experiments with chimeric mice revealed that LFA-1−/− ILC2s significantly traffic less to the lungs, unlike ICAM-1−/− ILC2s. Strikingly, ICAM-1−/− ILC2s however show a defect in proliferation and cytokine production, ultimately affecting lung inflammation. Conclusions The LFA-1-ICAM-1 interaction is involved in lung ILC2 trafficking, homeostasis and function. Such findings could lead to the development of new therapeutic targets.

Yan-Hou-Qing formula attenuates allergic airway inflammation via up-regulation of Treg and suppressing Th2 responses in Ovalbumin-induced asthmatic mice

Ethnopharmacological relevanceYan-Hou-Qing (YHQ), a Chinese medicine formula containing fourteen kinds of materials, has been designed for pharyngitis and cough treatment in Oriental medicine. In the present study, the anti-allergic effects and underlying mechanisms of YHQ in inhibition of airway hyper responsiveness (AHR) was explored in an ovalbumin (OVA)-induced allergic asthma mouse model. Materials and methodsBALB/c mice were sensitized by OVA and cholera toxin (CT) and challenged with OVA intranasally to induce allergic asthma mouse model. YHQ (200 mg/kg) was orally administered for 3 weeks from week-2 after OVA sensitization. The AHR and histological changes of lung tissues were evaluated by whole-body barometric plethysmography analysis and hematoxylin and eosin (H&E) staining, respectively. The serum concentration of OVA-specific IgE and T helper 2 (Th2) cytokines (IL-4 and IL-13) were determined by enzyme-linked immune sorbent assay (ELISA). Flow cytometry was performed to evaluate the percentage of CD4+CD25+Foxp3+ regulatory T cells (Treg) in the spleen. ResultsThe elevated AHR responses, heavier inflammatory cell infiltration and Th2 cytokines in allergic asthma group indicated Ovalbumin-induced asthmatic mouse models were built successfully. Compared to allergic asthma group, OVA-induced AHR responses and eosinophil infiltration in lung were improved significantly, and the productions of OVA-specific IgE and Th2 cytokines, IL-4 and IL-13, in the serum were also reduced dramatically after the treatment of YHQ. Moreover, YHQ treatment significantly increased the percentage of CD4+CD25+Foxp3+ Treg in OVA-induced allergic asthma mouse model. ConclusionsYHQ improves the allergic asthma related symptoms via promotion of CD4+CD25+Foxp3+ Treg and suppression of Th2 responses in mouse model, suggesting YHQ can be used as a potent agent to alleviate allergic asthma related symptoms.

IL33 signaling contributes to diesel exhaust particles-induced asthma exacerbations by promoting innate and adaptive type 2 and type 17 responses

Abstract Rationale Exposure to traffic pollution, notably diesel exhaust particles (DEP), promote asthma exacerbations and a mixed Th2/Th17 response. The contribution of TSLP and IL33, generated by sressed lung epithelial cells, to DEP-induced asthma exacerbations remains poorly understood. Method We used TSLP receptor deficient mice, mice lacking the IL33 receptor (ST2) and Balb/c control mice and exposed them 9 times over a 3-week period to saline, house dust mite extract (HDM; 10ug) and/or DEP (100ug). Seven weeks later some mice received a single HDM challenge to assess memory responses. Airway hyper-responsiveness (AHR), BALF inflammation and lung T-cells and ILC subsets were assessed after primary and recall responses. Results DEP co-exposure with HDM exacerbates HDM-induced AHR and Th2 responses. AHR was similar between TSLPR deficient mice and control mice exposed to HDM+DEP. In contrast, AHR was significantly decreased in ST2-deficient mice compared to wild type mice. The impact of ST2 deficiency on lung accumulation of ILC2 and Th2 cells was modest. Following HDM+DEP co-exposures, decreases in ILC3, γδ T-cells and Th17 cells were observed in the lungs of ST2 deficient mice compared to control mice. The in vivo HDM recall response recapitulated the impaired AHR associated with decreases in IL17A secreting cells observed after the primary response in HDM+DEP exposed ST2 deficient mice. Finally, a decrease in lung levels of pathogenic IL5/IL13/IL17A producing CD4+ T-cells was observed after the primary and recall responses. Conclusions IL33 but not TSLP contributes to DEP-induced asthma exacerbations by affecting the accumulation of innate and adaptive type 2 and type 17 cells, notably pathogenic Th2/Th17 cells.

CD34 Differentially Regulates Contractile and Noncontractile Elements of Airway Reactivity.

Airway hyperresponsiveness (AHR), a major hallmark of asthma, results from alterations of contractile and noncontractile elements of airway reactivity. CD34 is a sialomucin that is expressed on various cells involved in asthma, such as eosinophils and airway smooth muscle precursors, highlighting its potential influence in AHR. To study the role of CD34 in regulating the contractile and noncontractile elements of AHR, AHR was induced by chronic exposure to house dust mite (HDM) antigen. To assess the role of CD34 on the contractile elements of AHR, airway reactivity and airway smooth muscle contractility in response to methacholine were measured. To assess CD34's role in regulating the noncontractile elements of AHR, a chimeric mouse model was used to determine the impact of CD34 expression on inflammatory versus microenvironmental cells in AHR development. Extracellular matrix production, mucus production, and mast cell degranulation were also measured. Whereas wild-type mice developed AHR in response to HDM, a loss of airway reactivity was observed in Cd34-/- mice 24 hours after the last exposure to HDM compared with naive controls. This was reversed when airway reactivity was measured 1 week after the last HDM exposure. Additionally, mast cell degranulation and mucus production were altered in the absence of CD34 expression. Importantly, simultaneous expression of CD34 on cells originating from the hematopoietic compartment and the microenvironment was needed for expression of this phenotype. These results provide evidence that CD34 is required for AHR and airway reactivity maintenance in the early days after an inflammatory episode in asthma.

Levosalbutamol as alternative to drugs on the basis of racemic salbutamol: Review of the results of pre-clinical research

The aim of the work is to conduct an analytical review of the results of preclinical studies of levosalbutamol. The review discusses the pharmacodynamic features of the R-stereoisomer of salbutamol in vitro. The chemical bases of interaction of levosalbutamol with β2-adrenoreceptors, intracellular signaling cascades associated with β2-adrenoreceptors, and structural features of clinically significant ligands of β2-adrenoreceptors are presented. Broncholytic activity, influence on the contractility of the diaphragmatic muscles, mucociliary clearance of R-salbutamol in comparison with racemic salbutamol are described. The data presented indicate that all known β2-adrenergic receptor-dependent effects of racemic salbutamol, including bronchodilation, are realized by its R-enantiomer. There is evidence that the regular inhalation administration of racemic salbutamol is accompanied by a partial decrease in the bronchoprotective effect and an increase in airway hyperreactivity in response to the action of provocative factors. It was found that the development of hyperreactivity of the respiratory tract is excluded in the case of regular inhalation of levosalbutamol. Possible mechanisms of the paradoxical bronchoconstrictor effect of the salbutamol dystomer are described. This article shows the beneficial effect of levosalbutamol on mucociliary clearance, its anti-inflammatory activity and antiallergic effect. The image data are compared between the enantiomers and the racemate of salbutamol. Special attention is paid to the pharmacokinetics of enantiomers of salbutamol. The data presented from the preclinical studies provide evidence of chiral inversion of stereoisomers of salbutamol.

Mast cell-dependent IL-33/ST2 signaling is protective against the development of airway hyperresponsiveness in a house dust mite mouse model of asthma.

Interleukin-33 (IL-33) and its receptor ST2 have been influentially associated with the pathophysiology of asthma. Due to the divergent roles of IL-33 in regulating mast cell functions, there is a need to further characterize IL-33/ST2-dependent mast cell responses and their significance in the context of asthma. This study aimed to investigate how IL-33/ST2-dependent mast cell responses contribute to the development of airway hyperresponsiveness (AHR) and airway inflammation in a mouse model of house dust mite (HDM)-induced asthma. Mast cell-deficient C57BL/6-KitW-sh (Wsh) mice engrafted with either wild-type (Wsh + MC-WT) or ST2-deficient bone marrow-derived mast cells (Wsh + MC-ST2KO) were exposed to HDM delivered intranasally. An exacerbated development of AHR in response to HDM was seen in Wsh + MC-ST2KO compared with Wsh + MC-WT mice. The contribution of this IL-33/ST2-dependent mast cell response to AHR seems to reside within the smaller airways in the peripheral parts of the lung, as suggested by the isolated yet marked effect on tissue resistance. Considering the absence of a parallel increase in cellular inflammation in bronchoalveolar lavage fluid (BALF) and lung, the aggravated AHR in Wsh + MC-ST2KO mice seems to be independent of cellular inflammation. We observed an association between the elevated AHR and reduced PGE2 levels in BALF. Due to the protective properties of PGE2 in airway responses, it is conceivable that IL-33/ST2-dependent mast cell induction of PGE2 could be responsible for the dampening effect on AHR. In conclusion, we reveal that IL-33/ST2-dependent mast cell responses can have a protective, rather than causative role, in the development of AHR.

Virus-induced asthma attack: The importance of allergic inflammation in response to viral antigen in an animal model of asthma

Asthma exacerbation can be a life-threatening condition, and is most often triggered by common respiratory viruses. Poor asthma control and worsening of respiratory function is associated with increased airway inflammation, including eosinophilia. Prevention of asthma exacerbation relies on treatment with corticosteroids, which preferentially inhibit allergic inflammation like eosinophils. Human studies demonstrate that inactivated virus can trigger eosinophil activation in vitro through antigen presentation and memory CD4+ lymphocytes. We hypothesized that animals with immunologic memory to a respiratory virus would also develop airway hyperresponsiveness in response to a UV-inactivated form of the virus if they have pre-existing allergic airway inflammation. Guinea pigs were ovalbumin-sensitized, infected with live parainfluenza virus (PIV), aerosol-challenged with ovalbumin, and then re-inoculated 60 days later with live or UV-inactivated PIV. Some animals were either treated with dexamethasone prior to the second viral exposure. Lymphocytes were isolated from parabronchial lymph nodes to confirm immunologic memory to the virus. Airway reactivity was measured and inflammation was assessed using bronchoalveolar lavage and lung histology. The induction of viral immunologic memory was confirmed in infected animals. Allergen sensitized and challenged animals developed airway hyperreactivity with eosinophilic airway inflammation when re-exposed to UV-inactivated PIV, while non-sensitized animals did not. Airway hyperreactivity in the sensitized animals was inhibited by pre-treatment with dexamethasone. We suggest that the response of allergic inflammation to virus antigen is a significant factor causing asthma exacerbation. We propose that this is one mechanism explaining how corticosteroids prevent virus-induced asthma attack.

Sphingolipids, ORMDL3 and asthma: what is the evidence?

Genome-wide association studies identified ORMDL3, a protein of the endoplasmic reticulum, as a significant asthma risk factor. ORMDL3 is one of three ORMDL proteins that integrate multiple signals to maintain sphingolipid homeostasis. Studies that investigated potential mechanisms for how increased ORMDL3 might affect asthma are summarized. Investigations focused on decreased sphingolipid synthesis and on the unfolded protein response because ORMDL3 had been implicated in both.Airway reactivity is increased in a genetic model with decreased de-novo sphingolipid synthesis and in wild-type mice treated with myriocin, a sphingolipid synthesis inhibitor. Inflammation, mucus production and airway smooth muscle hypertrophy are absent. ORMDL3 was not evaluated directly but results suggest that decreased sphingolipid synthesis is sufficient to induce airway hyperreactivity (AHR).Direct effects of ORMDL3 were investigated in allergic asthma models. Sensitization with ovalbumin, house dust mites and Alternaria alternata increase ORMDL3 mRNA. Universal overexpression of ORMDL3 decreases serum sphingolipids, increases inflammatory markers, airway remodeling and AHR in response to allergic stimuli. Addition of myriocin during sensitization drastically exacerbates house dust mites-induced AHR.ORMDL3 knockout mice are protected from developing A. alternata-induced AHR. The effect is specific to Alternaria and limited to smooth muscle contraction, as inflammation persists. ORMDL3 might have a critical role for smooth muscle contraction.Little is known about how the different ORMDL3 single nucleotide polymorphisms affect human blood and tissue sphingolipid profiles. One group measured total sphingoid levels and found no association with ORMDL3 single nucleotide polymorphisms in a general population. Others evaluated sphingolipid profiles in 7-8-year old children with mild asthma and found significantly higher C18 and C20 ceramides in those with persistence of asthma symptoms 3 years later, suggesting that sphingolipid profiles might predict asthma persistence. Possible mechanisms how ORMDL3 affects asthma include inhibition of sphingolipid synthesis, synergistic effects with known allergens and a combination of both.

Pplase of Dermatophagoides farinae promotes ovalbumin-induced airway allergy by modulating the functions of dendritic cells in a mouse model

Our previous studies revealed that many proteins in addition to the known allergens of D. farinae have not been fully characterized. We observed that Pplase did not respond to serum collected from patients sensitized to D. farinae. In a mouse model, Pplase significantly enhanced airway hyperresponsiveness (AHR) and Th2 responses induced by ovalbumin (OVA) compared with mice treated with OVA alone. Moreover, exposure to Pplase significantly increased the expression of IRF4, CD80, CD83, MHCII and TNF-α in DC2.4 cells, which was abolished in the presence of a TLR4 inhibitor. In vitro T cell polarization experiments revealed that Pplase alone could not induce T cell polarization but enhanced T cell polarization together with OVA. In addition, transfer of Pplase-primed bone marrow-derived DCs (BMDCs) to naïve mice enhanced AHR and Th2 immune responses in mice sensitized to OVA. In conclusion, Pplase is not an allergen of D. farinae but can activate DC cells to facilitate OVA-induced allergic responses.

Phloretin Attenuates Allergic Airway Inflammation and Oxidative Stress in Asthmatic Mice.

Phloretin (PT), isolated from the apple tree, was previously demonstrated to have antioxidative and anti-inflammatory effects in macrophages and anti-adiposity effects in adipocytes. Inflammatory immune cells generate high levels of reactive oxygen species (ROS) for stimulated severe airway hyperresponsiveness (AHR) and airway inflammation. In this study, we investigated whether PT could reduce oxidative stress, airway inflammation, and eosinophil infiltration in asthmatic mice, and ameliorate oxidative and inflammatory responses in tracheal epithelial cells. BALB/c mice were sensitized with ovalbumin (OVA) to induce asthma symptoms. Mice were randomly assigned to the five experimental groups: normal controls; OVA-induced asthmatic mice; and OVA-induced mice injected intraperitoneally with one of the three PT doses (5, 10, or 20 mg/kg). In addition, we treated inflammatory human tracheal epithelial cells (BEAS-2B cells) with PT to assess oxidative responses and the levels of proinflammatory cytokines and chemokines. We found that PT significantly reduced goblet cell hyperplasia and eosinophil infiltration, which decreased AHR, inflammation, and oxidative responses in the lungs of OVA-sensitized mice. PT also decreased malondialdehyde levels in the lung and reduced Th2 cytokine production in bronchoalveolar lavage fluids. Furthermore, PT reduced ROS, proinflammatory cytokines, and eotaxin production in BEAS-2B cells. PT also suppressed monocyte cell adherence to inflammatory BEAS-2B cells. These findings suggested that PT alleviated pathological changes, inflammation, and oxidative stress by inhibiting Th2 cytokine production in asthmatic mice. PT showed therapeutic potential for ameliorating asthma symptoms in the future.