And Hyperresponsiveness Research Articles

Novel aerosol treatment of airway hyper-reactivity and inflammation in a murine model of asthma with a soluble epoxide hydrolase inhibitor.

Asthma currently affects more than 339 million people worldwide. In the present preliminary study, we examined the efficacy of a new, inhalable soluble epoxide hydrolase inhibitor (sEHI), 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), to attenuate airway inflammation, mucin secretion, and hyper-responsiveness (AHR) in an ovalbumin (OVA)-sensitized murine model. Male BALB/c mice were divided into phosphate-buffered saline (PBS), OVA, and OVA+TPPU (2- or 6-h) exposure groups. On days 0 and 14, the mice were administered PBS or sensitized to OVA in PBS. From days 26-38, seven challenge exposures were performed with 30 min inhalation of filtered air or OVA alone. In the OVA+TPPU groups, a 2- or 6-h TPPU inhalation preceded each 30-min OVA exposure. On day 39, pulmonary function tests (PFTs) were performed, and biological samples were collected. Lung tissues were used to semi-quantitatively evaluate the severity of inflammation and airway constriction and the volume of stored intracellular mucosubstances. Bronchoalveolar lavage (BAL) and blood samples were used to analyze regulatory lipid mediator profiles. Significantly (p < 0.05) attenuated alveolar, bronchiolar, and pleural inflammation; airway resistance and constriction; mucosubstance volume; and inflammatory lipid mediator levels were observed with OVA+TPPU relative to OVA alone. Cumulative findings indicated TPPU inhalation effectively inhibited inflammation, suppressed AHR, and prevented mucosubstance accumulation in the murine asthmatic model. Future studies should determine the pharmacokinetics (i.e., absorption, distribution, metabolism, and excretion) and pharmacodynamics (i.e., concentration/dose responses) of inhaled TPPU to explore its potential as an asthma-preventative or -rescue treatment.

Isoimperatorin reduces the effective dose of dexamethasone in a murine model of asthma by inhibiting mast cell activation

Adverse effects that result from dexamethasone (DEX) use are common and serious in patients with asthma. Therefore, alternative anti-inflammatory treatments are being investigated. Isoimperatorin (ISO), an active natural furocoumarin, possesses multiple pharmacological properties, including an anti-inflammation effect. In this study, investigations were conducted on the effect of ISO on mast cell (MC) activation in vitro and whether ISO could reduce the effective dose of DEX in a mast cell-dependent murine model of asthma in vivo. Calcium imaging was used to assess intracellular Ca2+ mobilization. Enzyme-linked immunosorbent assay was used to measure the chemokines release. Western blot analysis was conducted to investigate the underlying pathway. Airway inflammation and hyperresponsiveness (AHR) were examined in an asthma model. ISO inhibited Ca2+ flux and MC degranulation via Lyn/PLCγ1/PKC, ERK, and P38 MAPK pathways. In the asthma model, ISO, in combination with DEX, showed an additive inhibitory effect on AHR, inflammation, and the number of activated MCs in the lungs and decreased the levels of interleukin (IL)-4, IL-5, IL-6, IL-13, tumor necrosis factor (TNF)-a, and C-C motif chemokine ligand (CCL)-2 in bronchoalveolar lavage fluid. A combination of DEX and ISO may be appropriate if a decrease in the steroid dose is desired owing to dose-dependent adverse effects.

ZDHXB-101 (3\u2032,5-Diallyl-2, 4\u2032-dihydroxy-[1,1\u2032-biphen-yl]-3,5\u2032-dicarbaldehyde) protects against airway remodeling and hyperresponsiveness via inhibiting both the activation of the mitogen-activated protein kinase and the signal transducer and activator of transcription-3 signaling pathways

Airway remodeling consists of the structural changes of airway walls, which is often considered the result of longstanding airway inflammation, but it may be present to an equivalent degree in the airways of children with asthma, raising the need for early and specific therapeutic interventions. The arachidonic acid cytochrome P-450 (CYP) pathway has thus far received relatively little attention in its relation to asthma. In this study, we studied the inhibition of soluble epoxide hydrolase (sEH) on airway remodeling and hyperresponsiveness (AHR) in a chronic asthmatic model which long-term exposure to antigen over a period of 12 weeks. The expression of sEH and CYP2J2, the level of 14, 15-epoxyeicosatrienoic acids (EETs), airway remodeling, hyperresponsiveness and inflammation were analyzed to determine the inhibition of sEH. The intragastric administration of 3 or 10 mg/kg ZDHXB-101, which is a structural derivative of natural product honokiol and a novel soluble epoxide hydrolase (sEH) inhibitor, daily for 9 weeks significantly increased the level of 14, 15-EETs by inhibiting the expression of sEH and increasing the expression of CYP2J2 in lung tissues. ZDHXB-101 reduced the expression of remodeling-related markers such as interleukin (IL)-13, IL-17, MMP-9 N-cadherin, α-smooth muscle actin, S100A4, Twist, goblet cell metaplasia, and collagen deposition in the lung tissue or in bronchoalveolar lavage fluid. Moreover, ZDHXB-101 alleviated AHR, which is an indicator that is used to evaluate the airway remodeling function. The inhibitory effects of ZDHXB-101 were demonstrated to be related to its direct inhibition of the extracellular signal-regulated kinase (Erk1/2) phosphorylation, as well as inhibition of c-Jun N-terminal kinases (JNK) and the signal transducer and activator of transcription-3 (STAT3) signal transduction. These findings first revealed the anti-remodeling potential of ZDHXB-101 lead in chronic airway disease.

Inhibition of soluble epoxide hydrolase attenuates airway remodeling in a chronic asthma model

Airway remodeling in asthma is difficult to treat because of its complex pathophysiology that involves proinflammatory cytokines, as well as the arachidonic acid cytochrome P-450 (CYP) pathway; however, it has received little attention. In this study, we assessed the efficacy of a soluble epoxide hydrolase (sEH) on airway remodeling in a mouse model of chronic asthma. The expression of sEH and CYP2J2 and the level of 14,15-epoxyeicosatrienoic acid (14,15-EET), airway remodeling and hyperresponsiveness (AHR) were analyzed to determine the level of sEH inhibition. AUDA, a sEH inhibitor, was given daily for 9 weeks orally, which significantly increased the level of 14,15-EET by inhibiting the expression of sEH and increasing the expression of CYP2J2 in lung tissues. The inhibition of sEH reduced the expression of remodeling-related molecular markers, such as interleukin (IL)-13, IL-17, matrix metalloproteinase 9, N-cadherin, α-smooth muscle actin (α-SMA), S100A4, Twist, epithelial goblet cell metaplasia, and collagen deposition in bronchoalveolar lavage fluid (BAL fluid) and lung tissues. Moreover, remodeling-related eosinophil accumulation in the BAL fluid and infiltration into the lung tissue were improved by AUDA. Finally, AUDA alleviated AHR, which is a functional indicator of airway remodeling. The effect of AUDA on airway remodeling was related to the downregulation of extracellular-regulated protein kinases (Erk1/2), c-Jun N-terminal kinases (JNK) and signal transducer and activator of transcription 3 (STAT3). To our knowledge, this is the first report to demonstrate that inhibition of sEH exerts significant protective effects on airway remodeling in asthma.

Novel Aspects of Insulin-like Growth Factor 1/insulin Network in Chronic Inflammatory Airway Disease.

At least a proportion of patients suffering from chronic inflammatory airway diseases respond poorly to the bronchodilator and corticosteroid therapies. There is a need for the development of improved anti-inflammatory treatment. Insulin Growth Factor 1 (IGF1) and insulin participate in not only metabolism and glucose homeostasis, but also many other physiological and pathophysiological processes, including growth and inflammation. Recently, it was shown that not only the classical IGF1 and IGF1 Receptor (IGF1R), but also the other molecules in the IGF1/insulin network, including insulin, insulin-like growth factor-binding protein (IGFBP), and IGFBP protease, have roles in chronic inflammatory airway diseases. This review aims to provide a comprehensive insight into recent endeavors devoted to the role of the IGF1/insulin network in chronic inflammatory airway diseases. Its participation in airway inflammation, remodeling, and hyper-responsiveness (AHR), as well as acute exacerbation, has been conclusively demonstrated. Its possible relation to glucocorticoid insensitivity has also been indicated. A better understanding of the IGF1/insulin network by further bench-to-bedside research may provide us with rational clinical therapeutic approaches against chronic inflammatory airway diseases.

Fra2 Overexpression in Mice Leads to Non-allergic Asthma Development in an IL-13 Dependent Manner.

Background: Asthma is a complex chronic inflammatory disease characterised by airway inflammation, remodelling and hyperresponsiveness (AHR). Members of the AP-1 transcription factor family play important roles in the activation of the immune system and the control of cellular responses; however, their role in the development of asthma has not been well studied. We aimed to investigate the role of the lesser known AP-1 family member, Fra2 in experimental asthma.Methods: Phenotypic characterisation and gene expression profiling was performed on Fra2 (TG) overexpressing and wild-type mice. The efficacy of therapeutic interventions in regulating the Fra2 phenotype was determined.Results: Transcriptional profiling of TG mice revealed a high abundance of regulated genes associated with airway remodelling, inflammation and mucus production. A concomitant increase in peribronchial collagen deposition, smooth muscle thickening and mucus production was observed. TG mice possessed increased inflammatory infiltration in the lung, predominantly consisting of eosinophils and T-cells and elevated expression of Th2 cytokines and eotaxin. Furthermore, TG mice possessed severe AHR in response to increasing doses of methacholine. Glucocorticoid treatment led to a partial improvement of the asthma phenotype, whereas blockade of IL-13 via neutralising antibodies ameliorated AHR and mucus production, but had no effect on collagen deposition.Conclusion: We here describe a novel model for non-allergic asthma that does not require the application of exogenous allergens, which mimics several key features of the disease, such as airway inflammation, remodelling and hyperresponsiveness. Fra2 may represent a key molecule coordinating multiple aspects of asthma pathogenesis.

A 4-Week Model of House Dust Mite (HDM) Induced Allergic Airways Inflammation with Airway Remodeling

Animal models of allergic airways inflammation are useful tools in studying the pathogenesis of asthma and potential therapeutic interventions. The different allergic airways inflammation models available to date employ varying doses, frequency, duration and types of allergen, which lead to the development of different features of asthma; showing varying degrees of airways inflammation and hyper-responsiveness (AHR) and airways remodeling. Models that also exhibit airway remodeling, a key feature of asthma, in addition to AHR and airway inflammation typically require 5–12 weeks to develop. In this report, we describe a 4-week mouse model of house dust mite (HDM)-induced allergic airways inflammation, and compare the phenotypic features of two different doses of HDM exposures (10 µg and 25 µg) for 5 days/week with a well-characterized 8-week chronic HDM model. We found that 4 weeks of intranasal HDM (25 µg in 35 µl saline; 5 days/week) resulted in AHR, airway inflammation and airway remodeling that were comparable to the 8-week model. We conclude that this new 4-week HDM model is another useful tool in studies of human asthma that offers advantages of shorter duration for development and decreased costs when compared to other models that require longer durations of exposure (5–12 weeks) to develop.

ATP/P2X7-NLRP3 axis of dendritic cells participates in the regulation of airway inflammation and hyper-responsiveness in asthma by mediating HMGB1 expression and secretion

The ATP/P2X7 axis of dendritic cells (DCs) mediates the activation of NLRP3 inflammasome and promotes secretion of interleukin (IL)−1β and IL-18 to induce T helper (Th) 2, Th17 differentiation in the pathogenesis of asthma. NLRP3 inflammasome also regulates high mobility protein 1 (HMGB1) release in DCs. Recent studies demonstrated the correlation between HMGB1 expression and airway inflammation and hyper-responsiveness (AHR) in asthma. However, the relationship between the ATP/P2X7-NLRP3 axis and HMGB1 in DCs in asthma is still unclear. ATP, apyrase, Brilliant Blue G, BzATP, glibenclamide, and Z-YVAD-FMK were administered to ovalbumin (OVA)-induced murine asthmatic model. For in vitro studies, bone marrow-derived mononuclear cells (BMDCs) were primed with LPS and stimulated with the same reagents. Activation of the ATP/P2X7 axis aggravated airway inflammation and AHR in the lung and induced Th2, Th17 polarization in asthmatic mice. Inhibition of NLRP3 inflammasome weakened cardinal features of asthma and blocked Th2, Th17 polarization. In vitro and vivo, ATP/P2X7 axis activated NLRP3 inflammasome and induced HMGB1 expression and release from DCs. Inhibition of NLRP3 inflammasome reduced HMGB1 expression and release. The ATP/P2X7-NLRP3 axis of DCs participates in mediating airway inflammation, AHR, and promoting Th2, Th17 inflammatory responses in asthmatic mice by inducing HMGB1 expression and secretion.

Salvianolic acid B improves airway hyperresponsiveness by inhibiting MUC5AC overproduction associated with Erk1/2/P38 signaling

Salvianolic acid B (SalB) is one of the main water-soluble composites from Chinese medicine Dansen (Radix miltiorrhiza). It is used for clinical treatment of various diseases including cardiovascular, lung, Liver, renal and cancers. However, the effects of SalB to allergy induced airway mucin hypersecretion, inflammation and hyperresponsiveness (AHR) remains not clear. Overproduction of airway MUC5AC is a central effector of inflammation that is strongly associated with AHR in asthmatic attack. In this study, we investigated the anti-asthmatic activity and mechanism of SalB in a murine model and human epithelial cells by monitoring changes in mucin expression and secretion, airway inflammation, AHR, and signaling pathways. SalB was administered by intragastric administration (i.g) daily for a week, starting at 21 days after sensitization of ovalbumin (OVA). All examinations were performed 24h after the last antigen challenge. We found that treatments with SalB significantly inhibited increase in the tracheobronchial secretion, glycosaminoglycan levels, interleukin (IL)−13, IL-4, and IL-5 cytokines mRNA and protein expression, and decrease in mucociliary clearance in lung tissues. Histological results demonstrated that SalB attenuated OVA-induced eosinophil infiltration, airway goblet cell hyperplasia, and MUC5AC and MUC5B mRNA and protein expression in lung tissues. SalB exhibited protective effects against AHR in OVA-challenged animals. In vitro, SalB significantly inhibited IL-13-induced MUC5AC and MUC5B mRNA and protein expression in human epithelial cells. These effects were blocked by SalB by downregulating the Erk1/2 and P38 signaling pathways. Taken together, these data indicate that treatment with SalB may improve AHR by inhibiting MUC5AC overproduction.

TNF-stimulated gene 6 promotes formation of hyaluronan–inter-α-inhibitor heavy chain complexes necessary for ozone-induced airway hyperresponsiveness

Exposure to pollutants, such as ozone, exacerbates airway inflammation and hyperresponsiveness (AHR). TNF-stimulated gene 6 (TSG-6) is required to transfer inter-α-inhibitor heavy chains (HC) to hyaluronan (HA), facilitating HA receptor binding. TSG-6 is necessary for AHR in allergic asthma, because it facilitates the development of a pathological HA-HC matrix. However, the role of TSG-6 in acute airway inflammation is not well understood. Here, we hypothesized that TSG-6 is essential for the development of HA- and ozone-induced AHR. TSG-6-/- and TSG-6+/+ mice were exposed to ozone or short-fragment HA (sHA), and AHR was assayed via flexiVent. The AHR response to sHA was evaluated in the isolated tracheal ring assay in tracheal rings from TSG-6-/- or TSG-6+/+, with or without the addition of exogenous TSG-6, and with or without inhibitors of Rho-associated, coiled-coil-containing protein kinase (ROCK), ERK, or PI3K. Smooth-muscle cells from mouse tracheas were assayed in vitro for signaling pathways. We found that TSG-6 deficiency protects against AHR after ozone (in vivo) or sHA (in vitro and in vivo) exposure. Moreover, TSG-6-/- tracheal ring non-responsiveness to sHA was reversed by exogenous TSG-6 addition. sHA rapidly activated RhoA, ERK, and Akt in airway smooth-muscle cells, but only in the presence of TSG-6. Inhibition of ROCK, ERK, or PI3K/Akt blocked sHA/TSG-6-mediated AHR. In conclusion, TSG-6 is necessary for AHR in response to ozone or sHA, in part because it facilitates rapid formation of HA-HC complexes. The sHA/TSG-6 effect is mediated by RhoA, ERK, and PI3K/Akt signaling.

Ovatodiolide suppresses allergic airway inflammation and hyperresponsiveness in a murine model of asthma

Asthma, a complex pulmonary allergic disease, major therapy is applied of drugs to control the disease, but quickly recur after the drugs are stopped. In patients with severe asthma may show steroid resistance and would benefit from the development of novel therapeutic drugs.Ovatodiolide, a unique macrocyclic diterpenoid isolated from Anisomeles indica, showed therapeutic potential for the treatment of allergic asthma. As a model of allergic inflammation, we used ovalbumin (OVA)-immunized mice, which displayed T helper cell type 2 (TH2) cytokine expression in bronchoalveolar lavage fluid (BALF), as well as airway inflammation and hyperresponsiveness (AHR). The results showed that ovatodiolide suppressed TH2 activation, including cell proliferation and production of the TH2 related cytokines, interleukin (IL)-4, IL-5, IL-13, IL-33, eosinophil chemotactic protein (eotaxin), and also reduced airway hyperresponsiveness. In this study, ovatodiolide inhibited allergic asthma through downregulation of TH2 responses in a murine model of asthma.

Bitter Taste Receptor Agonists Mitigate Features of Allergic Asthma in Mice

Asthma is characterized by airway inflammation, mucus secretion, remodeling and hyperresponsiveness (AHR). Recent research has established the bronchodilatory effect of bitter taste receptor (TAS2R) agonists in various models. Comprehensive pre-clinical studies aimed at establishing effectiveness of TAS2R agonists in disease models are lacking. Here we aimed to determine the effect of TAS2R agonists on features of asthma. Further, we elucidated a mechanism by which TAS2R agonists mitigate features of asthma. Asthma was induced in mice using intranasal house dust mite or aerosol ova-albumin challenge, and chloroquine or quinine were tested in both prophylactic and treatment models. Allergen challenge resulted in airway inflammation as evidenced by increased immune cells infiltration and release of cytokines and chemokines in the lungs, which were significantly attenuated in TAS2R agonists treated mice. TAS2R agonists attenuated features of airway remodeling including smooth muscle mass, extracellular matrix deposition and pro-fibrotic signaling, and also prevented mucus accumulation and development of AHR in mice. Mechanistic studies using human neutrophils demonstrated that inhibition of immune cell chemotaxis is a key mechanism by which TAS2R agonists blocked allergic airway inflammation and exerted anti-asthma effects. Our comprehensive studies establish the effectiveness of TAS2R agonists in mitigating multiple features of allergic asthma.

Inhibition of PI3K promotes dilation of human small airways in a rho kinase-dependent manner.

Background and PurposeAsthma manifests as a heterogeneous syndrome characterized by airway obstruction, inflammation and hyperresponsiveness (AHR). Although the molecular mechanisms remain unclear, activation of specific PI3K isoforms mediate inflammation and AHR. We aimed to determine whether inhibition of PI3Kδ evokes dilation of airways and to elucidate potential mechanisms.Experimental ApproachHuman precision cut lung slices from non‐asthma donors and primary human airway smooth muscle (HASM) cells from both non‐asthma and asthma donors were utilized. Phosphorylation of Akt, myosin phosphatase target subunit 1 (MYPT1) and myosin light chain (MLC) were assessed in HASM cells following either PI3K inhibitor or siRNA treatment. HASM relaxation was assessed by micro‐pattern deformation. Reversal of constriction of airways was assessed following stimulation with PI3K or ROCK inhibitors.Key ResultsSoluble inhibitors or PI3Kδ knockdown reversed carbachol‐induced constriction of human airways, relaxed agonist‐contracted HASM and inhibited pAkt, pMYPT1 and pMLC in HASM. Similarly, inhibition of Rho kinase also dilated human PCLS airways and suppressed pMYPT1 and pMLC. Baseline pMYPT1 was significantly elevated in HASM cells derived from asthma donors in comparison with non‐asthma donors. After desensitization of the β2‐adrenoceptors, a PI3Kδ inhibitor remained an effective dilator. In the presence of IL‐13, dilation by a β agonist, but not PI3K inhibitor, was attenuated.Conclusion and ImplicationsPI3Kδ inhibitors act as dilators of human small airways. Taken together, these findings provide alternative approaches to the clinical management of airway obstruction in asthma.

Enhanced allergic airway disease in old mice is associated with a Th17 response.

The prevalence of asthma in the elderly is increasing and associated with higher mortality than in children or young adults. However, the effects of age on the development and character of allergic asthma have been understudied. It has been suggested that mixed Th2/Th17 responses cause more severe forms of asthma, but the role of Th17 response in allergic airway disease and aging is not well understood. To investigate age-dependent characteristics and Th17 immune response in allergic airway disease in a murine house dust mite (HDM)-allergen model. Twelve-week-old and 15-month-old male BALB/c mice were sensitized and challenged with HDM. Bronchoalveolar lavage fluid (BALF), airway inflammation and hyperresponsiveness (AHR), serum immunoglobulin and splenic T cells were assessed. Age-related T cell activation was analyzed in a co-culture with bone marrow-derived dendritic cells (BMDC) and splenic CD4(+) T cells from young and old mice. Features of allergic airway disease such as mucous cell hyperplasia, infiltration of airway eosinophils and lymphocytes, Th2 cytokine expression and serum IgG1 levels were greater in old compared to young mice. In contrast to the more marked inflammatory/immune responses to HDM in old mice, AHR was greater in young HDM-treated mice. Only the old mice developed airway neutrophil infiltration and a Th17 immune response upon HDM exposure, with increases in BALF cytokines IL-17A and KC, and Th17 cytokine producing T cells in the spleen. Stimulation of CD4(+) T cells and BMDC co-cultures with HDM, resulted in an enhanced Th17 cytokine response in cells isolated from old mice. Our findings in mice suggest that the severity and character of allergic airway disease are age dependent, with a bias towards a Th17 immune response with aging. Elderly, asthmatics may be prone to develop severe allergic airway inflammation with a mixed Th2/Th17 immune response.

Adjuvant-dependent regulation of interleukin-17 expressing γδ T cells and inhibition of Th2 responses in allergic airways disease.

BackgroundTh2 immune responses are linked primarily to mild and moderate asthma, while Th17 cells, Interleukin-17A (IL-17) and neutrophilia have been implicated in more severe forms of disease. How Th2-dependent allergic reactions are influenced by Th17 and IL-17-γδ T cells is poorly understood. In murine models, under some conditions, IL-17 promotes Th2-biased airway inflammatory responses. However, IL-17-γδ T cells have been implicated in the inhibition and resolution of allergic airway inflammation and hyperresponsiveness (AHR).MethodsWe compared airway responses in Balb/c mice sensitized to OVA with (and without) a Th2-skewing aluminum-based adjuvant and the IL-17 skewing, complete Freund’s adjuvant (CFA). AHR was measured invasively by flexiVent, while serum OVA-IgE was quantified by an enzyme immunoassay. Airway inflammatory and cytokine profiles, and cellular sources of IL-17 were assessed from bronchoalveolar lavage and/or lungs. The role of γδ T cells in these responses was addressed in OVA/CFA sensitized mice using a γδ T cell antibody.ResultsFollowing OVA challenge, all mice exhibited mixed eosinophilic/neutrophilic airway inflammatory profiles and elevated serum OVA-IgE. Whereas OVA/alum sensitized mice had moderate inflammation and AHR, OVA/CFA sensitized mice had significantly greater inflammation but lacked AHR. This correlated with a shift in IL-17 production from CD4+ to γδ T cells. Additionally, OVA/CFA sensitized mice, given a γδ TCR stimulatory antibody, showed increased frequencies of IL-17-γδ T cells and diminished airway reactivity and eosinophilia.ConclusionsThus, the conditions of antigen sensitization influence the profile of cells that produce IL-17, the balance of which may then modulate the airway inflammatory responses, including AHR. The possibility for IL-17-γδ T cells to reduce AHR and robust eosinophilic inflammation provides evidence that therapeutic approaches focused on stimulating and increasing airway IL-17-γδ T cells may be an effective alternative in treating steroid resistant, severe asthma.Electronic supplementary materialThe online version of this article (doi:10.1186/s12931-014-0090-5) contains supplementary material, which is available to authorized users.

Group-2 Innate Lymphoid Cells Promote Air-Pollutant Induced Airway Inflammation and Hyperresponsiveness (AHR)

Group-2 Innate Lymphoid Cells Promote Air-Pollutant Induced Airway Inflammation and Hyperresponsiveness (AHR)

Critical Role of TLR4 in Human Metapneumovirus Mediated Innate Immune Responses and Disease Pathogenesis

Human metapneumovirus (hMPV) is one of the main causes of acute respiratory tract infections in children, elderly and immunocompromised patients. The mammalian Toll-like receptors (TLR) were identified as critical regulators of innate immunity to a variety of microbes, including viruses. We have recently shown that hMPV-induced cytokine, chemokine and type I interferon secretion in dendritic cells occurs via TLR4, however, its role in hMPV-induced disease is unknown. In this study, wild-type(WT) and TLR4-deficient mice (TLR4−/−) were infected with hMPV and examined for clinical disease parameters, such as body weight loss and airway obstruction, viral clearance, lung inflammation, dendritic cell maturation, T-cell proliferation and antibody production. Our results demonstrate that absence of TLR4 in hMPV-infected mice significantly reduced the inflammatory response as well as disease severity, shown by reduced body weight loss and airway obstruction and hyperresponsiveness (AHR), compared to WT mice. Levels of cytokines and chemokines were also significantly lower in the TLR4−/− mice. Accordingly, recruitment of inflammatory cells in the BAL, lungs, as well as in lymph nodes, was significantly reduced in the TLR4−/− mice, however, viral replication and clearance, as well as T-cell proliferation and neutralizing antibody production, were not affected. Our findings indicate that TLR4 is important for the activation of the innate immune response to hMPV, however it does play a role in disease pathogenesis, as lack of TLR4 expression is associated with reduced clinical manifestations of hMPV disease, without affecting viral protection.

Diesel exhaust particle induction of IL17A contributes to severe asthma (P6373)

Abstract The factors that promote IL17A production during the pathogenesis of severe asthma remain undefined. Diesel exhaust particles (DEP) are a major component of traffic related air pollution and are implicated in asthma exacerbation. We assessed the impact of DEP exposure on asthma severity in asthmatic children from the Greater Cincinnati Pediatric Clinic Repository. Among high DEP-exposed children with allergic asthma, 32.2% of the children had severe asthma, compared to only 14.2% in the low DEP-exposed group. Similarly, Balb/c mice co-exposed to DEP and house dust mite extract (HDM) markedly demonstrated enhanced airway inflammation and hyperresponsiveness (AHR) compared to HDM alone. Exposure to DEP alone did not induce classic features of asthma but generated a Th17 response. DEP and HDM co-exposures enhanced pulmonary Th2 and Th17 cell numbers compared to HDM alone. High DEP-exposed children with allergic asthma had elevated serum IL17A levels compared with low DEP-exposed children. Finally, IL17A neutralization alleviated DEP-induced exacerbation of AHR. In conclusion, Th17 cells contribute to DEP-mediated exacerbation of allergen-induced asthma. Neutralization of IL17A may be a useful therapeutic strategy to counteract the asthma promoting effects of traffic related air pollution especially in severe asthmatics.

Airway Hyperresponsiveness in Asthma: A Better Understanding Yet to Yield Clinical Benefit

Airway inflammation and hyperresponsiveness (AHR) are important features of asthma. Both inflammation and AHR are complex traits that can each originate from a plethora of factors, where every factor can be independent, interconnected and dispensable. This review examines the complexity of the indices that we use to assess airway responsiveness. These indices entail intricate information regarding the individual and the combined dynamic behavior of all the airways that constitute the tracheobronchial tree during the activation of airway smooth muscle (ASM). Because many factors other than ASM contractility can influence airway narrowing, the defects responsible for the manifestation of AHR are difficult to infer. New tests and technologies are being developed to decipher the meaning of the indices of airway responsiveness and have already leaped forward our understanding of AHR. This review also gives prominence to the concept of ASM plasticity.ASM mass and contractile capacity is not fixed over time. Several facets of inflammation can increase ASM force indirectly over a prolong period of time by causing tissue damage and repair, which ultimately leads of airway wall remodeling that embodies an enlargement of ASM mass. This could contribute to the fixed component of AHR. The gain of force due to inflammation can also be transient and conditional to the presence of inflammatory mediators that are capable of increasing the contractile capacity of ASM. This could contribute to the variable, and more readily modifiable, component of AHR. We are now aware that a multitude of muscle and non-muscle factors can contribute to AHR within an asthmatic individual, and that these factors are often times distinct between individuals. Consequently, the relative contribution of a single factor within a group of patients is usually very small. This is the reason why our ever-growing understanding of AHR in asthma does not quite yet avail patients.

Acute Exercise Decreases Airway Inflammation, but Not Responsiveness, in an Allergic Asthma Model

Previous studies have suggested that the asthmatic responses of airway inflammation, remodeling, and hyperresponsiveness (AHR) are interrelated; in this study, we used exercise to examine the nature of this interrelationship. Mice were sensitized and challenged with ovalbumin (OVA); mice were then exercised via running on a motorized treadmill at a moderate intensity. Data indicate that, within the lungs of OVA-treated mice, exercise attenuated the production of inflammatory mediators, including chemokines KC, RANTES, and MCP-1 and IL-12p40/p80. Coordinately, OVA-treated and exercised mice displayed decreases in leukocyte infiltration, including eosinophils, as compared with sedentary controls. Results also show that a single bout of exercise significantly decreased phosphorylation of the NFkappaB p65 subunit, which regulates the gene expression of a wide variety of inflammatory mediators. In addition, OVA-treated and exercised mice exhibited decreases in the levels of Th2-derived cytokines IL-5 and IL-13 and the prostaglandin PGE(2), as compared with sedentary controls. In contrast, results show that a single bout of exercise had no effect on AHR in OVA-treated mice challenged with increasing doses of aerosolized methacholine (0-50 mg/ml) as compared with sedentary mice. Exercise also had no effect on epithelial cell hypertrophy, mucus production, or airway wall thickening in OVA-treated mice as compared with sedentary controls. These findings suggest that a single bout of aerobic exercise at a moderate intensity attenuates airway inflammation but not AHR or airway remodeling in OVA-treated mice. The implication of these findings for the interrelationship between airway inflammation, airway remodeling, and AHR is discussed.