Dust Mite-induced Airway Inflammation Research Articles

Saturated Fatty Acid Increases Lung Macrophages and Augments House Dust Mite-Induced Airway Inflammation in Mice Fed with High-Fat Diet

Obesity is one of the phenotypes of severe asthma, which is considered to be a heterogeneous syndrome; however, its interaction with airway inflammation is not fully understood. The aim of this study was to clarify the role of saturated fatty acids in augmenting airway inflammation induced by house dust mite (HDM) in obesity. Subjects were Balb/c mice fed a high-fat diet (HFD) for 10 weeks, followed by sensitization and exposure to HDM. Subjects were also administered palmitic acid (PA) for 4 weeks with concurrent sensitization and exposure to HDM. Airway inflammation was assessed by quantifying the amount of inflammatory cells in bronchoalveolar lavage (BAL) and airway resistance was measured. In vitro, lipopolysaccharide (LPS)-primed macrophages were stimulated by PA. The amount of monocyte chemoattractant protein-1 (MCP-1), interleukin-1β (IL-1β), and tumor necrosis factor α (TNF-α) was examined in the supernatant. Compared to normal chow mice, HFD mice underwent significant increases in body weight; increases in number of lung macrophages, including circulating monocytes and alveolar macrophages; and increases in bronchoalveolar lavage fluid (BALF) total cell count, including neutrophils but not eosinophils, after HDM sensitization and exposure. In vitro, PA induced MCP-1 and augmented LPS-primed production of IL-1β and TNF-α in macrophages. Among HDM mice that were administered PA, there was an increase BALF total cell count, including neutrophils but not eosinophils, compared to vehicle mice. In conclusion, saturated fatty acid increased the number of lung macrophages and augmented HDM-induced neutrophilic airway inflammation in a HFD mouse model.

Female Mice Have Increased House Dust Mite Induced Airway Inflammation Compared to Male Mice

Female Mice Have Increased House Dust Mite Induced Airway Inflammation Compared to Male Mice

Protective Roles for RGS2 in a Mouse Model of House Dust Mite-Induced Airway Inflammation.

The GTPase-accelerating protein, regulator of G-protein signalling 2 (RGS2) reduces signalling from G-protein-coupled receptors (GPCRs) that signal via Gαq. In humans, RGS2 expression is up-regulated by inhaled corticosteroids (ICSs) and long-acting β2-adrenoceptor agonists (LABAs) such that synergy is produced in combination. This may contribute to the superior clinical efficacy of ICS/LABA therapy in asthma relative to ICS alone. In a murine model of house dust mite (HDM)-induced airways inflammation, three weeks of intranasal HDM (25 μg, 3×/week) reduced lung function and induced granulocytic airways inflammation. Compared to wild type animals, Rgs2-/- mice showed airways hyperresponsiveness (increased airways resistance and reduced compliance). While HDM increased pulmonary inflammation observed on hematoxylin and eosin-stained sections, there was no difference between wild type and Rgs2-/- animals. HDM-induced mucus hypersecretion was also unaffected by RGS2 deficiency. However, inflammatory cell counts in the bronchoalveolar lavage fluid of Rgs2-/- animals were significantly increased (57%) compared to wild type animals and this correlated with increased granulocyte (neutrophil and eosinophil) numbers. Likewise, cytokine and chemokine (IL4, IL17, IL5, LIF, IL6, CSF3, CXCLl, CXCL10 and CXCL11) release was increased by HDM exposure. Compared to wild type, Rgs2-/- animals showed a trend towards increased expression for many cytokines/chemokines, with CCL3, CCL11, CXCL9 and CXCL10 being significantly enhanced. As RGS2 expression was unaffected by HDM exposure, these data indicate that RGS2 exerts tonic bronchoprotection in HDM-induced airways inflammation. Modest anti-inflammatory and anti-remodelling roles for RGS2 are also suggested. If translatable to humans, therapies that maximize RGS2 expression may prove advantageous.

IκBNS induces Muc5ac expression in epithelial cells and causes airway hyper-responsiveness in murine asthma models.

In allergic asthma, environmental allergens including house dust mite (HDM) trigger pattern recognition receptors and activate downstream signaling pathways including NF-κB pathways not only in immune cells but also in airway epithelial cells. Recent studies have shown that NF-κB activation is regulated positively or negatively depending on the cellular context by IκBNS (encoded by the gene Nfkbid), one of atypical IκB proteins, in the nucleus. Therefore, we hypothesized that IκBNS expressed in immune cells or epithelial cells is involved in the regulation of asthmatic responses. To determine the roles of IκBNS in HDM-induced asthmatic responses. Roles of IκBNS in HDM-induced airway inflammation and airway hyper-responsiveness (AHR) were examined by using IκBNS-deficient (Nfkbid-/- ) mice. Roles of IκBNS expressed in hematopoietic cells and nonhematopoietic cells were separately evaluated by bone marrow chimeric mice. Roles of IκBNS expressed in murine tracheal epithelial cells (mTECs) were examined by air-liquid interface culture. House dust mite-induced airway inflammation and AHR were exacerbated in mice lacking IκBNS in hematopoietic cells. In contrast, HDM-induced airway inflammation was exacerbated, but AHR was attenuated in mice lacking IκBNS in nonhematopoietic cells. The induction of Muc5ac, a representative mucin in asthmatic airways, was reduced in Nfkbid-/- mTEC, whereas the induction of Spdef, a master regulator of goblet cell metaplasia, was not impaired in Nfkbid-/- mTEC. Moreover, IκBNS bound to and activated the MUC5AC distal promoter in epithelial cells. IκBNS is involved in inducing Muc5ac expression in lung epithelial cells and causing AHR in HDM-induced asthma models.

Interleukin-33 from Monocytes Recruited to the Lung Contributes to House Dust Mite-Induced Airway Inflammation in a Mouse Model.

BackgroundInterleukin-33 (IL-33) activates group 2 innate lymphoid cells (ILC2), resulting in T-helper-2 inflammation in bronchial asthma. Airway epithelial cells were reported as sources of IL-33 during apoptosis and necrosis. However, IL-33 is known to be from sources other than airway epithelial cells such as leukocytes, and the mechanisms of IL-33 production and release are not fully understood. The aim of this study was to clarify the role of IL-33 production by monocytes in airway inflammation.MethodsBALB/c mice were sensitized and challenged with a house dust mite (HDM) preparation. Airway inflammation was assessed by quantifying inflammatory cells in bronchoalveolar lavage (BAL) fluid, and IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) levels in lung. Immunohistochemistry for IL-33 in lung sections was also performed. Ly6c, CD11b, and CD11c expression was examined by flow cytometry. Clodronate liposomes were used in the HDM-airway inflammation model to deplete circulating monocytes.ResultsThe IL-33, but not IL-25 or TSLP, level in lung homogenates was markedly increased in HDM mice compared to control mice. IL-33-positive cells in the lungs were identified using immunohistochemistry and were increased in areas surrounding bronchi and vasculature. Furthermore, IL-33 levels were increased in mononuclear cells derived from lungs of HDM mice compared to controls. The expression of Ly6c in mononuclear cells was significantly higher in HDM mice than in controls. Treatment with clodronate liposomes led to inhibition of not only inflammatory cells in BAL fluid, airway hyper reactivity and Th2 cytokines in lung, but also IL-33 in lung.ConclusionIL-33 from monocytes recruited to the lung may contribute to the pathogenesis of HDM-induced airway inflammation.

Activation of the Prostaglandin E2 receptor EP2 prevents house dust mite-induced airway hyperresponsiveness and inflammation by restraining mast cells' activity.

Prostaglandin E2 (PGE2 ) has been proposed to exert antiasthmatic effects in patients, to prevent antigen-induced airway pathology in murine models, and to inhibit mast cells (MC) activity invitro. To assess in a murine model whether the protective effect of PGE2 may be a consequence of its ability to activate the E-prostanoid (EP)2 receptor on airway MC. Either BALB/c or C57BL/6 mice were exposed intranasally (i.n.) to house dust mite (HDM) aeroallergens. Both strains were given PGE2 locally (0.3mg/kg), but only BALB/c mice were administered butaprost (EP2 agonist: 0.3mg/kg), or AH6809 (EP2 antagonist; 2.5mg/kg) combined with the MC stabilizer sodium cromoglycate (SCG: 25mg/kg). Airway hyperresponsiveness (AHR) and inflammation, along with lung MC activity, were evaluated. In addition, butaprost's effect was assessed in MC-mediated passive cutaneous anaphylaxis (PCA) in mice challenged with 2,4-dinitrophenol (DNP). Selective EP2 agonism attenuated aeroallergen-caused AHR and inflammation in HDM-exposed BALB/c mice, and this correlated with a reduced lung MC activity. Accordingly, the blockade of endogenous PGE2 by means of AH6809 worsened airway responsiveness in sensitive BALB/c mice, and such worsening was reversed by SCG. The relevance of MC to PGE2 -EP2 driven protection was further highlighted in MC-dependent PCA, where butaprost fully prevented MC-induced ear swelling. Unlike in BALB/c mice, PGE2 did not protect the airways of HDM-sensitized C57BL/6 animals, a strain in which we showed MC to be irrelevant to aeroallergen-driven AHR and inflammation. The beneficial effect of both exogenous and endogenous PGE2 in aeroallergen-sensitized mice may be attributable to the activation of the EP2 receptor, which in turn acts as a restrainer of airway MC activity. This opens a path towards the identification of therapeutic targets against asthma along the 'EP2 -MC-airway' axis.

Immunomodulation of airway epithelium cell activation by mesenchymal stromal cells ameliorates house dust mite-induced airway inflammation in mice.

Allergic asthma is underpinned by T helper 2 (Th2) inflammation. Redundancy in Th2 cytokine function and production by innate and adaptive immune cells suggests that strategies aimed at immunomodulation may prove more beneficial. Hence, we sought to determine whether administration of mesenchymal stromal cells (MSCs) to house dust mite (HDM) (Dermatophagoides pteronyssinus)-sensitized mice would suppress the development of Th2 inflammation and airway hyperresponsiveness (AHR) after HDM challenge. We report that the intravenous administration of allogeneic donor MSCs 1 hour before allergen challenge significantly attenuated the features of allergic asthma, including tissue eosinophilia, Th2 cytokine (IL-5 and IL-13) levels in bronchoalveolar lavage fluid, and AHR. The number of infiltrating type 2 innate lymphoid cells was not affected by MSC transfer, suggesting that MSCs may modulate the adaptive arm of Th2 immunity. The effect of MSC administration was long lasting; all features of allergic airway disease were significantly suppressed in response to a second round of HDM challenge 4 weeks after MSC administration. Further, we observed that MSCs decreased the release of epithelial cell-derived alarmins IL-1α and high mobility group box-1 in an IL-1 receptor antagonist-dependent manner. This significantly decreased the expression of the pro-Th2 cytokine IL-25 and reduced the number of activated and antigen-acquiring CD11c(+)CD11b(+) dendritic cells in the lung and mediastinal lymph nodes. Our findings suggest that MSC administration can ameliorate allergic airway inflammation by blunting the amplification of epithelial-derived inflammatory cytokines induced by HDM exposure and may offer long-term protection against Th2-mediated allergic airway inflammation and AHR.

Treatment with a sphingosine analog after the inception of house dust mite-induced airway inflammation alleviates key features of experimental asthma

BackgroundIn vivo phosphorylation of sphingosine analogs with their ensuing binding and activation of their cell-surface sphingosine-1-phosphate receptors is regarded as the main immunomodulatory mechanism of this new class of drugs. Prophylactic treatment with sphingosine analogs interferes with experimental asthma by impeding the migration of dendritic cells to draining lymph nodes. However, whether these drugs can also alleviate allergic airway inflammation after its onset remains to be determined. Herein, we investigated to which extent and by which mechanisms the sphingosine analog AAL-R interferes with key features of asthma in a murine model during ongoing allergic inflammation induced by Dermatophagoides pteronyssinus.MethodsBALB/c mice were exposed to either D. pteronyssinus or saline, intranasally, once-daily for 10 consecutive days. Mice were treated intratracheally with either AAL-R, its pre-phosphorylated form AFD-R, or the vehicle before every allergen challenge over the last four days, i.e. after the onset of allergic airway inflammation. On day 11, airway responsiveness to methacholine was measured; inflammatory cells and cytokines were quantified in the airways; and the numbers and/or viability of T cells, B cells and dendritic cells were assessed in the lungs and draining lymph nodes.ResultsAAL-R decreased airway hyperresponsiveness induced by D. pteronyssinus by nearly 70%. This was associated with a strong reduction of IL-5 and IL-13 levels in the airways and with a decreased eosinophilic response. Notably, the lung CD4+ T cells were almost entirely eliminated by AAL-R, which concurred with enhanced apoptosis/necrosis in that cell population. This inhibition occurred in the absence of dendritic cell number modulation in draining lymph nodes. On the other hand, the pre-phosphorylated form AFD-R, which preferentially acts on cell-surface sphingosine-1-phosphate receptors, was relatively impotent at enhancing cell death, which led to a less efficient control of T cell and eosinophil responses in the lungs.ConclusionAirway delivery of the non-phosphorylated sphingosine analog, but not its pre-phosphorylated counterpart, is highly efficient at controlling the local T cell response after the onset of allergic airway inflammation. The mechanism appears to involve local induction of lymphocyte apoptosis/necrosis, while mildly affecting dendritic cell and T cell accumulation in draining lymph nodes.

Epithelial NF-κB Orchestrates House Dust Mite–Induced Airway Inflammation, Hyperresponsiveness, and Fibrotic Remodeling

NF-κB activation within the epithelium has been implicated in the pathogenesis of asthma, yet the exact role of epithelial NF-κB in allergen-induced inflammation and airway remodeling remains unclear. In the current study, we used an intranasal house dust mite (HDM) extract exposure regimen time course in BALB/c mice to evaluate inflammation, NF-κB activation, airway hyperresponsiveness (AHR), and airway remodeling. We used CC10-IκBαSR transgenic mice to evaluate the functional importance of epithelial NF-κB in response to HDM. After a single exposure of HDM, mRNA expression of proinflammatory mediators was significantly elevated in lung tissue of wild-type (WT) mice, in association with increases in nuclear RelA and RelB, components of the classical and alternative NF-κB pathway, respectively, in the bronchiolar epithelium. In contrast, CC10-IκBαSR mice displayed marked decreases in nuclear RelA and RelB and mRNA expression of proinflammatory mediators compared with WT mice. After 15 challenges with HDM, WT mice exhibited increases in inflammation, AHR, mucus metaplasia, and peribronchiolar fibrosis. CC10-IκBαSR transgenic mice displayed marked decreases in neutrophilic infiltration, tissue damping, and elastance parameters, in association will less peribronchiolar fibrosis and decreases in nuclear RelB in lung tissue. However, central airway resistance and mucus metaplasia remained elevated in CC10-IκBαSR transgenic mice, in association with the continued presence of lymphocytes, and partial decreases in eosinophils and IL-13. The current study demonstrates that following airway exposure with an asthma-relevant allergen, activation of classical and alternative NF-κB pathways occurs within the airway epithelium and may coordinately contribute to allergic inflammation, AHR, and fibrotic airway remodeling.

Peptidoglycan Recognition Protein 1 Promotes House Dust Mite–Induced Airway Inflammation in Mice

Peptidoglycan recognition protein (Pglyrp) 1 is a pattern-recognition protein that mediates antibacterial host defense. Because we had previously shown that Pglyrp1 expression is increased in the lungs of house dust mite (HDM)-challenged mice, we hypothesized that it might modulate the pathogenesis of asthma. Wild-type and Pglyrp1(-/-) mice on a BALB/c background received intranasal HDM or saline, 5 days/week for 3 weeks. HDM-challenged Pglyrp1(-/-) mice showed decreases in bronchoalveolar lavage fluid eosinophils and lymphocytes, serum IgE, and mucous cell metaplasia, whereas airway hyperresponsiveness was not changed when compared with wild-type mice. T helper type 2 (Th2) cytokines were reduced in the lungs of HDM-challenged Pglyrp1(-/-) mice, which reflected a decreased number of CD4(+) Th2 cells. There was also a reduction in C-C chemokines in bronchoalveolar lavage fluid and lung homogenates from HDM-challenged Pglyrp1(-/-) mice. Furthermore, secretion of CCL17, CCL22, and CCL24 by alveolar macrophages from HDM-challenged Pglyrp1(-/-) mice was markedly reduced. As both inflammatory cells and airway epithelial cells express Pglyrp1, bone marrow transplantation was performed to generate chimeric mice and assess which cell type promotes HDM-induced airway inflammation. Chimeric mice lacking Pglyrp1 on hematopoietic cells, not structural cells, showed a reduction in HDM-induced eosinophilic and lymphocytic airway inflammation. We conclude that Pglyrp1 expressed by hematopoietic cells, such as alveolar macrophages, mediates HDM-induced airway inflammation by up-regulating the production of C-C chemokines that recruit eosinophils and Th2 cells to the lung. This identifies a new family of innate immune response proteins that promotes HDM-induced airway inflammation in asthma.

Mast cell chymase modulates IL-33 levels and controls allergic sensitization in dust-mite induced airway inflammation.

Mast cells (MCs) are major effector cells contributing to allergic conditions. When activated, they can release large amounts of active proteases, including chymase from their secretory granules. Here we assessed the role of the chymase mouse mast cell protease 4 (mMCP-4) in allergic airway inflammation induced by house-dust mite (HDM) extract. mMCP-4-/-) mice demonstrated elevated airway reactivity and eosinophilia compared with wild-type (WT) animals, suggesting a protective role for mMCP-4 during the late inflammatory phase of the disease. However, mMCP-4 also contributed to the sensitization phase, as indicated by higher levels of serum immunoglobulin E in mMCP-4(-/-) vs. WT mice and higher levels of cytokines secreted by HDM-restimulated mMCP-4(-/-) vs. WT splenocytes. In line with a contribution of mMCP-4 in the early stages of disease, HDM extract directly induced chymase secretion from MCs. The elevated airway and inflammatory responses of mMCP-4(-/-) mice were associated with a profound increase in the levels of interleukin (IL)-33 in the lung tissue. Moreover, WT MCs degraded IL-33 more efficiently than did MCs lacking mMCP-4. Together, our findings identify a protective role of a MC chymase in a physiologically relevant model for airway inflammation and suggest that chymase-mediated regulation of IL-33 can account for this protective function.

P2Y12 Null Mice Are Protected Against Sepsis-Induced Lung Injury

AbstractAbstract 615The P2Y12 receptor is expressed on the platelet surface and mediates ADP-induced aggregation, but it has recently been shown to be expressed also in other cells of the immune system. Furthermore, the P2Y12 receptor gene variants correlate with pulmonary inflammation and asthma, and P2Y12 receptor deficiency or platelet depletion abrogated dust mite-induced airway inflammation, suggesting an important role for the P2Y12 receptor in pulmonary inflammation. Excessive neutrophil infiltration into the lungs is a hallmark of acute lung injury. The mechanisms that trigger this infiltration are poorly understood but may be the result of the development of a pro-inflammatory phenotype in the lung. Platelets are increasingly recognized for their ability to modulate immune responses through their interaction with neutrophils, dendritic cells, and T lymphocytes. These studies suggest an important regulatory role for the P2Y12 receptor and activated platelets in regulating neutrophil influx into the lung.Using a mouse model of intra-abdominal sepsis and acute lung injury (cecal ligation and double puncture (CLP)), we examined the role of the P2Y12 receptor in neutrophil migration and lung inflammation using P2Y12 null mice. In this study wild type (WT) and P2Y12 null (KO) mice underwent Sham surgery or CLP surgery (5 animals/group). At 24 hours post surgery, blood and lung tissue samples were collected.Our results show that the sepsis-induced increase in circulating white blood cells (WBC) was attenuated in CLP KO mice, compared with CLP WT mice (circulating WBC in CLP WT: 1.62 ± 0.41×103cell/ml* compared with CLP KO: 0.8 ± 0.4×103cell/ml, *p<0.05 WT CLP versus KO CLP mice). There were no significant differences in the WBC count in WT Sham surgery animals as compared to the KO sham surgery animals (Sham WT: 0.8 ± 0.2×103cell/ml vs. Sham KO: 0.8 ± 0.1×103cell/ml). Interestingly, no significant changes in the platelet count between the groups were observed. Next we investigated the role of P2Y12 in regulating sepsis-induced elevations in plasma levels of cytokines (TNF-a, IL-10, IL-6 and MIP-1b) (Figure 1). The concentration of each cytokine was elevated during sepsis in both WT and KO animals as compared to sham surgery animals, but, the sepsis-induced increase was significantly lower in P2Y12 null mice (**p < 0.01 KO CLP model versus WT- CLP). [Display omitted] Finally we studied neutrophil infiltration in lung tissues using hematoxylin and eosin (H & E) staining and myeloperoxidase (MPO) activity in lung tissue homogenates. Analysis of H & E staining demonstrated that the increase in inflammatory cell infiltration detected in WT was diminished in KO mice, suggesting a decrease in inflammation in the lungs of P2Y12 null mice. Furthermore, the MPO concentration was significantly decreased in KO CLP lung tissue as compared to WT CLP (Figure 2), (*p < 0.05; KO CLP model versus wild type). [Display omitted] In conclusion, our data shows a decrease in plasma cytokine levels and in circulating WBC, as well as a diminished neutrophil infiltration in the lungs indicating that P2Y12 null mice are protected against sepsis-induced lung injury. This suggests a regulatory role for P2Y12 receptor during inflammation. Disclosures:No relevant conflicts of interest to declare.

Interruption of CD28-mediated costimulation during allergen challenge protects mice from allergic airway disease

Allergic asthma is a T(H)2-promoted hyperreactivity with an immediate, IgE, and mast cell-dependent response followed by eosinophil-dominated inflammation and airway obstruction. Because costimulation by CD28 is essential for T(H)2 but not T(H)1 responses, we investigated the effect of selective interference with this pathway in mice using the models of ovalbumin and house dust mite-induced airway inflammation. To study the role of CD28 in the effector phase of allergic airway inflammation, we developed an inducibly CD28-deleting mouse strain or alternatively used a CD28 ligand-binding site-specific mouse anti-mouse mAb blocking CD28 engagement. We show that even after systemic sensitization to the allergen, interruption of CD28-mediated costimulation is highly effective in preventing airway inflammation during challenge. In addition to improving airway resistance and histopathologic presentation and reducing inflammatory infiltrates, antibody treatment during allergen challenge resulted in a marked relative increase in regulatory T-cell numbers among the CD4 T-cell subset of the challenged lung. Selective interference with CD28-mediated costimulation during allergen exposure might be an attractive therapeutic concept for allergic asthma.

Immunomodulatory Effects of CpG Oligodeoxynucleotides on House Dust Mite-Induced Airway Inflammation in Mice

Background: CpG oligodeoxynucleotides (CpG ODNs) are reported to protect against airway eosinophilia and hyperresponsiveness in animal models of asthma. However, little is known about the effects of CpG ODNs on house dust mites, one of the most common environmental allergens, causing allergic asthma. In the present study, we evaluated the immunomodulatory effects of CpG ODNs on the development of house dust mite-induced airway inflammation and remodeling in mice. Methods: Mice were instilled with Dermatophagoides farinae (Der f) into the trachea 8 times without any additional adjuvants. 48 h after the final allergen instillation, the airway responsiveness to acetylcholine (Ach) was measured, and bronchoalveolar lavage (BAL) and histopathological examination were carried out. CpG ODNs were instilled into the trachea mixed with Der f at the first allergen instillation. Results: Repeated instillation of Der f induced increases in airway responsiveness to Ach, the numbers of inflammatory cells, the levels of T-helper type 2 cytokines and transforming growth factor-β₁ in the BAL fluid. Furthermore, goblet cell hyperplasia, the thickness of the epithelium and subepithelial fibrosis were observed. The simultaneous instillation of CpG ODNs with Der f at the first allergen instillation showed significant inhibition of these parameters dose dependently. Conclusions: Our results demonstrate that CpG ODNs have inhibitory effects on Der f-induced airway hyperresponsiveness and eosinophilia, as well as airway remodeling, and that CpG ODNs can be a therapeutic approach for the treatment of house dust mite-induced asthma.

YS-4 House dust mite-induced airway inflammation, hyperresponsiveness and remodeling in mice(Young Seminar 4)

YS-4 House dust mite-induced airway inflammation, hyperresponsiveness and remodeling in mice(Young Seminar 4)