Natural history of eosinophil‑derived neurotoxin levels and the onset of allergic airway disease in preschool children

'Atopic march' is the progression of allergic conditions through infancy and childhood. The present study investigated the association between blood eosinophil-derived neurotoxin (EDN) levels in preschool children with food allergy (FA) or atopic dermatitis (AD) and the onset of allergic airway disease [bronchial asthma (BA), allergic rhinitis (AR)]. A total of 123 children below the age of 1 year were enrolled in the present study, along with controls (n=37). Blood specimens were taken, serum EDN levels were measured and immunoglobulin E was quantified. Finally, a total of 86 subjects were analyzed. EDN values were measured at 3 time-points: before 1 year of age, before 2 years of age and before 3 years of age. The EDN levels were initially similar between those patients who did and those who did not develop allergic airway disease but then markedly diverged at the 2-year time-point (226.6 vs. 65.0 ng/ml; P<0.01) and remained divergent at the 3-year time-point (173.9 vs. 62.7 ng/ml; P<0.01). EDN levels prior to diagnosis were compared between the two groups and they were much higher in the Onset group (n=10) compared to the Non-onset group (n=67) (171.2±34.28 vs. 81.3±10.02 ng/ml; P=0.003), with 4 cases of BA and 6 cases of AR in the Onset group. After diagnosis, EDN levels were compared twice: i) At 1 and 2 years of age; and ii) 1 and 3 years of age. A significant difference was found only in the comparison at 2 years (P=0.001). In conclusion, young children with elevated EDN levels during the FA/AD disease period were more likely to develop allergic airway disease (BA, AR) in their first three years of life. A factor leading to this progression may be increased eosinophil activity.

Inflammatory and antiviral responses to influenza A virus infection are dysregulated in pregnant mice with allergic airway disease

Influenza A virus (IAV) infections are increased during pregnancy especially with asthma as a comorbidity, leading to asthma exacerbations, secondary bacterial infections, intensive care unit admissions, and mortality. We aimed to define the processes involved in increased susceptibility and severity of IAV infections during pregnancy, especially with asthma. We sensitized mice to house dust mite (HDM), induced pregnancy, and challenged with HDM to induce allergic airway disease (AAD). At midpregnancy, we induced IAV infection. We assessed viral titers, airway inflammation, lung antiviral responses, mucus hypersecretion, and airway hyperresponsiveness (AHR). During early IAV infection, pregnant mice with AAD had increased mRNA expression of the inflammatory markers Il13 and IL17 and reduced mRNA expression of the neutrophil chemoattractant marker Kc. These mice had increased mucous hyperplasia and increased AHR. miR155, miR574, miR223, and miR1187 were also reduced during early infection, as was mRNA expression of the antiviral β-defensins, Bd1, Bd2, and Spd and IFNs, Ifnα, Ifnβ, and Ifnλ. During late infection, Il17 was still increased as was eosinophil infiltration in the lungs. mRNA expression of Kc was reduced, as was neutrophil infiltration and mRNA expression of the antiviral markers Ifnβ, Ifnλ, and Ifnγ and Ip10, Tlr3, Tlr9, Pkr, and Mx1. Mucous hyperplasia was still significantly increased as was AHR. Early phase IAV infection in pregnancy with asthma heightens underlying inflammatory asthmatic phenotype and reduces antiviral responses.NEW & NOTEWORTHY Influenza A virus (IAV) infection during pregnancy with asthma is a major health concern leading to increased morbidity for both mother and baby. Using murine models, we show that IAV infection in pregnancy with allergic airway disease is associated with impaired global antiviral and antimicrobial responses, increased lung inflammation, mucus hypersecretion, and airway hyperresponsiveness (AHR). Targeting specific β-defensins or microRNAs (miRNAs) may prove useful in future treatments for IAV infection during pregnancy.

Interleukin-10-alveolar macrophage cell membrane-coated nanoparticles alleviate airway inflammation and regulate Th17/regulatory T cell balance in a mouse model

Background

Allergic airway disease (AAD) is a chronic disease characterized by airway inflammation, bronchoconstriction, and hyperresponsiveness. Although exogenous interleukin-10 (IL-10) alleviates allergic inflammation, it has a short half-life in vivo. Cell membrane-coated nanomaterials have been shown to protect therapeutic payloads and increase therapeutic efficacy.

Objective

This study was aimed at investigating the efficacy of a novel macrophage-based nanoparticle drug for the treatment of house dust mite (HDM)-induced allergic airway diseases.

Methods

IL-10-poly (lactic-co-glycolic acid (PLGA) nanoparticles were encapsulated in alveolar macrophage cell membranes. An allergic airway disease mouse model was established by repeated inhalation of HDM extracts. The mice were treated with free IL-10, IL-10-PLGA nanoparticles (IL10-NP), or IL-10-alveolar macrophage cell membrane-coated nanoparticles (IL10-AMNP). The therapeutic effects were evaluated by measuring airway hyperresponsiveness, lung inflammation, cytokine levels, and regulatory T cells (Treg)- T-helper 17 (Th17) cell balance.

Results

Compared to free IL-10, IL10-AMNP significantly reduced airway hyperresponsiveness and T-helper 2 (Th2)/Th17 cytokines and inhibited neutrophilia and eosinophilia recruitment into the airways of HDM-induced mouse models. Additionally, the balance between Tregs and Th17 cells was significantly improved in groups treated with IL10-AMNP.

Conclusion

This study demonstrated that PLGA nanoparticle cores coated with alveolar macrophage cell membranes can effectively deliver therapeutic cytokines to the lungs and improve the homeostatic balance between Tregs and Th17 cells. These findings suggest that macrophage-based nanoparticle drugs represent a promising approach for treating allergic airway diseases.

DRP1-Mediated Mitochondrial Fission Regulates Lung Epithelial Response to Allergen

Mitochondria regulate a myriad of cellular functions. Dysregulation of mitochondrial control within airway epithelial cells has been implicated in the pro-inflammatory response to allergens in asthma patients. Because of their multifaceted nature, mitochondrial structure must be tightly regulated through fission and fusion. Dynamin Related Protein 1 (DRP1) is a key driver of mitochondrial fission. During allergic asthma, airway epithelial mitochondria appear smaller and structurally altered. The role of DRP1-mediated mitochondrial fission, however, has not been fully elucidated in epithelial response to allergens. We used a Human Bronchial Epithelial Cell line (HBECs), primary Mouse Tracheal Epithelial Cells (MTECs), and conditional DRP1 ablation in lung epithelial cells to investigate the impact of mitochondrial fission on the pro-inflammatory response to house dust mite (HDM) in vitro and in vivo. Our data suggest that, following HDM challenge, mitochondrial fission is rapidly upregulated in airway epithelial cells and precedes production of pro-inflammatory cytokines and chemokines. Further, deletion of Drp1 in lung epithelial cells leads to decreased fission and enhanced pro-inflammatory signaling in response to HDM in vitro, as well as enhanced airway hyper-responsiveness (AHR), inflammation, differential mucin transcription, and epithelial cell death in vivo. Mitochondrial fission, therefore, regulates the lung epithelial pro-inflammatory response to HDM.

CD44v3-Positive Intermediate Progenitor Cells Contribute to Airway Goblet Cell Hyperplasia

In allergic airway diseases, intermediate progenitor cells (IPCs) increase in number in the surface epithelium. IPCs arise from basal cells, the origin of hallmark pathological changes, including goblet cell hyperplasia and mucus hypersecretion. Thus, targeting IPCs will benefit future treatment of allergic airway diseases. However, the lack of adequate cell surface markers for IPCs limits their identification and characterization. We now show that CD44 containing exon v3 (CD44v3) is a surface marker for IPCs that are capable of both proliferating and generating differentiated goblet cells in allergic human nasal epithelium. In primary human nasal epithelial cells that had differentiated at an air-liquid interface, IL-4 upregulated mRNA expression of three CD44v variants that include exon v3 (CD44v3-v6, CD44v3,v8-v10, and CD44v3-v10), and it induced expression of CD44v3 protein in the basal and suprabasal layers of the culture. FACS analysis revealed two subpopulations differing in CD44v3 concentrations, as follows: CD44v3^low cells expressed high amounts of proliferative and basal cell markers (Ki-67 and TP63), whereas CD44v3^high cells strongly expressed progenitor and immature and mature goblet cell markers (SOX2, CA2, and SPDEF). Importantly, a blocking anti-CD44 antibody suppressed IL-4-induced mucin production by human nasal epithelial cells. Furthermore, CD44v3 was coexpressed with TP63, KRT5, or SOX2 and was upregulated in the basal and suprabasal layers of the nasal surface epithelium of subjects with allergic rhinitis. Taken together, these data demonstrate that high CD44v3 expression contributes to goblet cell hyperplasia in inflammation of the allergic airway.

Maternal microbiome regulation prevents early allergic airway diseases in mouse offspring

BACKGROUND

Asthma is a serious global health problem, severely affecting the lives of sufferers and their families. An exceptionally hygienic home and reduced microbial exposure can aggravate the incidence of childhood asthma.

METHODS

Specific-pathogen-free BALB/c mice were pre-treated with bacterial lysate (BL; 1 mg/kg) as a high microbial load maternal mouse model, and then, the offspring mice were established as an allergic airway disease (AAD) model. The expression levels of TLR2, TLR4, and HDAC9 in the mother's intestine and the offspring's lungs were detected. Relevant indicators of regulatory T cells (Tregs) were identified in the mother and offspring mice. The changes in the expression of Th1-, Th2-, Th9-, and Th17-related cytokines in the offspring mice were evaluated among different pre-treated groups.

RESULTS

After augmenting the mothers' intestinal microbiota through oral BL gavage, the expression of TLR2 and TLR4 in the colon mucosa and colon lymphoid tissues was enhanced and that of HDAC9 in the colon mucosa was decreased, and the proportion of spleen Tregs was increased. The offspring showed similar changes in the AAD model compared with the offspring of the control-group mothers: TLR2 and TLR4 expression in the lungs and the proportion of spleen Tregs increased, HDAC9 expression in the lungs decreased, and AAD-induced airway pathologic characteristics were reversed; additionally, Th1/Th2 and Th9 imbalances were rectified.

CONCLUSIONS

This study presents a new framework for the prevention of childhood asthma, elucidating the mechanism of regulating the mother's intestinal microbiome to protect the offspring's early asthma via animal experiments.

Airborne particulate matter from goat farm increases acute allergic airway responses in mice

Background: Inhalation exposure to biological particulate matter (BioPM) from livestock farms may provoke exacerbations in subjects suffering from allergy and asthma. The aim of this study was to use a murine model of allergic asthma to determine the effect of BioPM derived from goat farm on airway allergic responses.Methods: Fine (<2.5 μm) BioPM was collected from an indoor goat stable. Female BALB/c mice were ovalbumin (OVA) sensitized and challenged with OVA or saline as control. The OVA and saline groups were divided in sub-groups and exposed intranasally to different concentrations (0, 0.9, 3, or 9 μg) of goat farm BioPM. Bronchoalveolar lavage fluid (BALF), blood and lung tissues were collected.Results: In saline-challenged mice, goat farm BioPM induced 1) a dose-dependent increase in neutrophils in BALF and 2) production of macrophage inflammatory protein-3a. In OVA-challenged mice, BioPM induced 1) inflammatory cells in BALF, 2) OVA-specific Immunoglobulin (Ig)G1, 3) airway mucus secretion-specific gene expression. RNAseq analysis of lungs indicates that neutrophil chemotaxis and oxidation-reduction processes were the representative genomic pathways in saline and OVA-challenged mice, respectively.Conclusions: A single exposure to goat farm BioPM enhanced airway inflammation in both saline and OVA-challenged allergic mice, with neutrophilic response as Th17 disorder and eosinophilic response as Th2 disorder indicative of the severity of allergic responses. Identification of the mode of action by which farm PM interacts with airway allergic pathways will be useful to design potential therapeutic approaches.

Maternal Obesity in Mice Exacerbates the Allergic Inflammatory Response in the Airways of Male Offspring

It was previously demonstrated that non-allergen-sensitized rodents born to mothers exposed to a high-fat diet (HFD) spontaneously develop lower respiratory compliance and higher respiratory resistance. In the present study, we sought to determine if mice born to mothers consuming HFD would exhibit changes in inflammatory response and lung remodeling when subjected to ovalbumin (OVA) sensitization/challenge in adult life. Mice born to dams consuming either HFD or standard chow had increased bronchoalveolar lavage (BAL) levels of IL-1β, IL-4, IL-5, IL-10, IL-13, TNF-α and TGF-β1 after challenge with OVA. IL-4, IL-13, TNF-α and TGF-β1 levels were further increased in the offspring of HFD-fed mothers. Mice born to obese dams also had exacerbated values of leukocyte infiltration in lung parenchyma, eosinophil and neutrophil counts in BAL, mucus overproduction and collagen deposition. The programming induced by maternal obesity was accompanied by increased expression of miR-155 in peripheral-blood mononuclear cells and reduced miR-133b in trachea and lung tissue in adult life. Altogether, the present data support the unprecedented notion that the progeny of obese mice display exacerbated responses to sensitization/challenge with OVA, leading to the intensification of the morphological changes of lung remodeling. Such changes are likely to result from long-lasting changes in miR-155 and miR-133b expression.

Dysregulation of the glutaredoxin/S-glutathionylation redox axis in lung diseases

Glutathione is a major redox buffer, reaching millimolar concentrations within cells and high micromolar concentrations in airways. While glutathione has been traditionally known as an antioxidant defense mechanism that protects the lung tissue from oxidative stress, glutathione more recently has become recognized for its ability to become covalently conjugated to reactive cysteines within proteins, a modification known as S-glutathionylation (or S-glutathiolation or protein mixed disulfide). S-glutathionylation has the potential to change the structure and function of the target protein, owing to its size (the addition of three amino acids) and charge (glutamic acid). S-glutathionylation also protects proteins from irreversible oxidation, allowing them to be enzymatically regenerated. Numerous enzymes have been identified to catalyze the glutathionylation/deglutathionylation reactions, including glutathione S-transferases and glutaredoxins. Although protein S-glutathionylation has been implicated in numerous biological processes, S-glutathionylated proteomes have largely remained unknown. In this paper, we focus on the pathways that regulate GSH homeostasis, S-glutathionylated proteins, and glutaredoxins, and we review methods required toward identification of glutathionylated proteomes. Finally, we present the latest findings on the role of glutathionylation/glutaredoxins in various lung diseases: idiopathic pulmonary fibrosis, asthma, and chronic obstructive pulmonary disease.

Novel therapeutic targets for allergic airway disease in children

The aim of precision medicine is setting up targeted therapies for selected patients that would ideally have high effectiveness and few side effects. This is made possible by targeted therapy drugs that selectively act on a specific pathway. Precision medicine is spreading to many medical specialties, and there is increasing interest in the context of allergic airway diseases, such as allergic rhinitis, chronic rhinosinusitis, and asthma. This review is an update of new targets in the treatment of childhood allergic upper airway diseases and asthma, including the most recent biologic drugs that have already been licensed or are in the pipeline to be tested with children.

Targeting the ICOS/ICOS-L pathway in a mouse model of established allergic asthma disrupts T follicular helper cell responses and ameliorates disease

Background

Allergic asthma is characterized by chronic inflammation and remodelling of the airways, associated with dysregulated type 2 immune responses and allergen‐specific IgE. T follicular helper cells (T_FH) are crucial in T‐dependent B‐cell responses and have been implicated in allergic airway disease (AAD). T_FH, unlike other CD4⁺ T cells, are uniquely reliant on continuous ICOS signalling to maintain their phenotype after T‐cell priming; therefore, disrupting this signal can impair T_FH responses. However, the contribution of T_FH to disease during chronic aero‐allergen exposure and the therapeutic potential of targeting these cells have not been evaluated.

Methods

To establish AAD, female BALB/c mice were repeatedly exposed to house dust mite or Alternaria alternata three times a week for up to 5 weeks. To examine the impact of T_FH on AAD, mice were allergen exposed for 5 weeks and co‐administered anti‐ICOS Ligand‐targeted antibodies, three times a week for the last 2 weeks.

Results

T_FH were first observed in the lung‐draining lymph nodes and with further exposure were also found locally within the lungs. T_FH accumulated with sustained allergen exposure, alongside germinal centre (GC) B cells. Blockade of ICOS signalling after AAD establishment successfully depleted T_FH but did not affect the differentiation of other CD4⁺ T‐cell subsets. This reduced GC responses, allergen‐specific IgE, inflammation, pulmonary IL‐13 and airway hyper‐responsiveness.

Conclusions

T_FH are crucial in the regulation of AAD and the ICOS/ICOS‐L pathway could represent a novel therapeutic target in allergic asthma.

Ascaris Larval Infection and Lung Invasion Directly Induce Severe Allergic Airway Disease in Mice

Ascaris lumbricoides (roundworm) is the most common helminth infection globally and a cause of lifelong morbidity that may include allergic airway disease, an asthma phenotype. We hypothesize that Ascaris larval migration through the lungs leads to persistent airway hyperresponsiveness (AHR) and type 2 inflammatory lung pathology despite resolution of infection that resembles allergic airway disease. Mice were infected with Ascaris by oral gavage. Lung AHR was measured by plethysmography and histopathology with hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) stains, and cytokine concentrations were measured by using Luminex Magpix. Ascaris-infected mice were compared to controls or mice with allergic airway disease induced by ovalbumin (OVA) sensitization and challenge (OVA/OVA). Ascaris-infected mice developed profound AHR starting at day 8 postinfection (p.i.), peaking at day 12 p.i. and persisting through day 21 p.i., despite resolution of infection, which was significantly increased compared to controls and OVA/OVA mice. Ascaris-infected mice had a robust type 2 cytokine response in both the bronchoalveolar lavage (BAL) fluid and lung tissue, similar to that of the OVA/OVA mice, including interleukin-4 (IL-4) (P < 0.01 and P < 0.01, respectively), IL-5 (P < 0.001 and P < 0.001), and IL-13 (P < 0.001 and P < 0.01), compared to controls. By histopathology, Ascaris-infected mice demonstrated early airway remodeling similar to, but more profound than, that in OVA/OVA mice. We found that Ascaris larval migration causes significant pulmonary damage, including AHR and type 2 inflammatory lung pathology that resembles an extreme form of allergic airway disease. Our findings indicate that ascariasis may be an important cause of allergic airway disease in regions of endemicity.

RelB-Deficient Dendritic Cells Promote the Development of Spontaneous Allergic Airway Inflammation

RelB is a member of the NF-κB family, which is essential for dendritic cell (DC) function and maturation. However, the contribution of RelB to the development of allergic airway inflammation (AAI) is unknown. Here, we identify a pivotal role for RelB in the development of spontaneous AAI that is independent of exogenous allergen exposure. We assessed AAI in two strains of RelB-deficient (RelB^-/-) mice: one with a targeted deletion and one expressing a major histocompatibility complex transgene. To determine the importance of RelB in DCs, RelB-sufficient DCs (RelB^+/+ or RelB^-/-) were adoptively transferred into RelB^-/- mice. Both strains had increased pulmonary inflammation compared with their respective wild-type (RelB^+/+) and heterozygous (RelB^+/-) controls. RelB^-/- mice also had increased inflammatory cell influx into the airways, levels of chemokines (CCL2/3/4/5/11/17 and CXCL9/10/13) and T-helper cell type 2-associated cytokines (IL-4/5) in lung tissues, serum IgE, and airway remodeling (mucus-secreting cell numbers, collagen deposition, and epithelial thickening). Transfer of RelB^+/- CD11c⁺ DCs into RelB^-/- mice decreased pulmonary inflammation, with reductions in lung chemokines, T-helper cell type 2-associated cytokines (IL-4/5/13/25/33 and thymic stromal lymphopoietin), serum IgE, type 2 innate lymphoid cells, myeloid DCs, γδ T cells, lung Vβ13⁺ T cells, mucus-secreting cells, airway collagen deposition, and epithelial thickening. These data indicate that RelB deficiency may be a key pathway underlying AAI, and that DC-encoded RelB is sufficient to restore control of this inflammation.

Long-term exposure to low-dose Haemophilus influenzae during allergic airway disease drives a steroid-resistant neutrophilic inflammation and promotes airway remodeling

Growing evidences indicate that bacteria are associated with pathogenesis of neutrophilic asthma. However, the long-term effect of airway bacterial colonization remains unclear. We sought to establish a murine model to simulate the airway inflammation of long-term bacterial colonization, and to assess the effects of bacteria on allergic airway disease (AAD). BALB/c mice were sensitized twice and subsequently challenged with ovalbumin (OVA) and exposed to low-dose Haemophilus influenzae for approximately 2 months. Mice in treatment groups inhaled budesonide for consecutively 6 days in the last week. Airway inflammatory phenotype, immune response, phagocytic capacity, mucus production, airway remodeling and steroid sensitivity were assessed. Long-term exposure to low-dose H. influenzae during AAD did not cause serious infection but only a slightly increased airway inflammation, which resembled the colonization. Inflammatory phenotype was converted from a steroid-sensitive T helper (Th) 2-associated eosinophilic inflammation to a steroid-resistant Th17-associated neutrophilic inflammation. The increased neutrophilic inflammation was accompanied by defects in regulatory T cell (Treg)-associated immunosuppression and macrophage phagocytosis, and finally promoted mucus hypersecretion and airway remodeling. These features resembled those of refractory neutrophilic asthma in humans. These findings indicate that in asthmatic patients, airway bacterial colonization may be a potential therapeutic target. Minimizing the pathogen burden in airway, such as Haemophilus influenzae, may be beneficial.

Distribution and Interaction of Murine Pulmonary Phagocytes in the Naive and Allergic Lung

The division of labor between pulmonary phagocytic subsets [macrophage/monocyte and dendritic cell (DC) subpopulations] has been described at the functional level. However, whether these lung phagocytes also display unique spatial distribution remains unclear. Here, to analyze cellular distribution in lung compartments and contacts between phagocyte subpopulations, we established an immunohistochemistry (IHC)-based method to clearly identify murine lung phagocyte subsets in situ based on differential expression of CD11c, CD11b, MHC-II, Langerin and mPDCA-1. Furthermore, we investigated subset-specific functional differences in antigen uptake and spatial changes upon allergic sensitization. Our staining allowed the distinction between alveolar macrophages (AMs), interstitial macrophage (IM) subpopulations, CD11b⁺ DC subpopulations, CD103⁺ DCs, and plasmacytoid DCs (pDCs). We identified interstitial regions between airways and around airways as regions of IM/CD11b⁺ DC/CD103⁺ DC clusters, where a subset of IMs (IM2) and CD103⁺ DCs formed intense contacts that decreased upon allergic sensitization. These data indicate functional interactions between both cell types either in steady state or after antigen encounter affecting the development of allergies or tolerance. Furthermore, we observed major antigen uptake in AMs and IMs rather than DC subpopulations that was not restricted to airways and adjacent areas. This will enable to focus future studies to immunologically relevant cellular interactions and to unravel which cells are tipping the balance between pro-inflammatory immune responses or tolerance.

Asthma and poly(ADP-ribose) polymerase inhibition: a new therapeutic approach

Asthma is a chronic lung disease affecting people of all ages worldwide, and it frequently begins in childhood. Because of its chronic nature, it is characterized by pathological manifestations, including airway inflammation, remodeling, and goblet cell hyperplasia. Current therapies for asthma, including corticosteroids and beta-2 adrenergic agonists, are directed toward relieving the symptoms of the asthmatic response, with poor effectiveness against the underlying causes of the disease. Asthma initiation and progression depends on the T helper (Th) 2 type immune response carried out by a complex interplay of cytokines, such as interleukin (IL) 4, IL5, and IL13, and the signal transducer and activator of transcription 6. Much of the data resulting from different laboratories support the role of poly(ADP-ribose) polymerase (PARP) 1 and PARP14 activation in asthma. Indeed, PARP enzymes play key roles in the regulation and progression of the inflammatory asthma process because they affect the expression of genes and chemokines involved in the immune response. Consistently, PARP inhibition achievable either upon genetic ablation or by using pharmacological agents has shown a range of therapeutic effects against the disease. Indeed, in the last two decades, several preclinical studies highlighted the protective effects of PARP inhibition in various animal models of asthma. PARP inhibitors showed the ability to reduce the overall lung inflammation acting with a specific effect on immune cell recruitment and through the modulation of asthma-associated cytokines production. PARP inhibition has been shown to affect the Th1–Th2 balance and, at least in some aspects, the airway remodeling. In this review, we summarize and discuss the steps that led PARP inhibition to become a possible future therapeutic strategy against allergic asthma.

Airway remodelling and inflammation in asthma are dependent on the extracellular matrix protein fibulin-1c

Asthma is a chronic inflammatory disease of the airways. It is characterized by allergic airway inflammation, airway remodelling, and airway hyperresponsiveness (AHR). Asthma patients, in particular those with chronic or severe asthma, have airway remodelling that is associated with the accumulation of extracellular matrix (ECM) proteins, such as collagens. Fibulin-1 (Fbln1) is an important ECM protein that stabilizes collagen and other ECM proteins. The level of Fbln1c, one of the four Fbln1 variants, which predominates in both humans and mice, is increased in the serum and airways fluids in asthma but its function is unclear. We show that the level of Fbln1c was increased in the lungs of mice with house dust mite (HDM)-induced chronic allergic airway disease (AAD). Genetic deletion of Fbln1c and therapeutic inhibition of Fbln1c in mice with chronic AAD reduced airway collagen deposition, and protected against AHR. Fbln1c-deficient (Fbln1c^-/- ) mice had reduced mucin (MUC) 5 AC levels, but not MUC5B levels, in the airways as compared with wild-type (WT) mice. Fbln1c interacted with fibronectin and periostin that was linked to collagen deposition around the small airways. Fbln1c^-/- mice with AAD also had reduced numbers of α-smooth muscle actin-positive cells around the airways and reduced airway contractility as compared with WT mice. After HDM challenge, these mice also had fewer airway inflammatory cells, reduced interleukin (IL)-5, IL-13, IL-33, tumour necrosis factor (TNF) and CXCL1 levels in the lungs, and reduced IL-5, IL-33 and TNF levels in lung-draining lymph nodes. Therapeutic targeting of Fbln1c reduced the numbers of GATA3-positive Th2 cells in the lymph nodes and lungs after chronic HDM challenge. Treatment also reduced the secretion of IL-5 and IL-13 from co-cultured dendritic cells and T cells restimulated with HDM extract. Human epithelial cells cultured with Fbln1c peptide produced more CXCL1 mRNA than medium-treated controls. Our data show that Fbln1c may be a therapeutic target in chronic asthma. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Targeting PP2A and proteasome activity ameliorates features of allergic airway disease in mice

BACKGROUND

Asthma is an allergic airway disease (AAD) caused by aberrant immune responses to allergens. Protein phosphatase-2A (PP2A) is an abundant serine/threonine phosphatase with anti-inflammatory activity. The ubiquitin proteasome system (UPS) controls many cellular processes, including the initiation of inflammatory responses by protein degradation. We assessed whether enhancing PP2A activity with fingolimod (FTY720) or 2-amino-4-(4-(heptyloxy) phenyl)-2-methylbutan-1-ol (AAL_(S) ), or inhibiting proteasome activity with bortezomib (BORT), could suppress experimental AAD.

METHODS

Acute AAD was induced in C57BL/6 mice by intraperitoneal sensitization with ovalbumin (OVA) in combination with intranasal (i.n) exposure to OVA. Chronic AAD was induced in mice with prolonged i.n exposure to crude house dust mite (HDM) extract. Mice were treated with vehicle, FTY720, AAL_(S) , BORT or AAL_(S) +BORT and hallmark features of AAD assessed.

RESULTS

AAL_(S) reduced the severity of acute AAD by suppressing tissue eosinophils and inflammation, mucus-secreting cell (MSC) numbers, type 2-associated cytokines (interleukin (IL)-33, thymic stromal lymphopoietin, IL-5 and IL-13), serum immunoglobulin (Ig)E and airway hyper-responsiveness (AHR). FTY720 only suppressed tissue inflammation and IgE. BORT reduced bronchoalveolar lavage fluid (BALF) and tissue eosinophils and inflammation, IL-5, IL-13 and AHR. Combined treatment with AAL_(S) +BORT had complementary effects and suppressed BALF and tissue eosinophils and inflammation, MSC numbers, reduced the production of type 2 cytokines and AHR. AAL_(S) , BORT and AAL_(S) +BORT also reduced airway remodelling in chronic AAD.

CONCLUSION

These findings highlight the potential of combination therapies that enhance PP2A and inhibit proteasome activity as novel therapeutic strategies for asthma.

Fetal Phagocytes Take up Allergens to Initiate T-Helper Cell Type 2 Immunity and Facilitate Allergic Airway Responses

RATIONALE

Actively acquired tolerance occurs when foreign antigens come into contact with the immature fetal immune system.

OBJECTIVES

Armed with the knowledge of actively acquired tolerance, we attempted to prenatally abolish or diminish allergic responses.

METHODS

In utero injection of adjuvant-free ovalbumin (OVA) was conducted in Gestational Day 14 FVB/N mouse fetuses. Postnatally, mice were evaluated for their resistance to intraperitoneal OVA sensitization and oral or aerosolized OVA challenge, and then they were examined for humoral and cellular immunological profiles, airway hyperresponsiveness to bronchospastic stimuli, and lung histology. Fluorescent conjugates of OVA were used for further studies of mechanisms.

MEASUREMENTS AND MAIN RESULTS

This presumed tolerogenic action turned out to be a sensitization process with the development of anaphylaxis or heightened recall, T-helper cell type 2-skewed responses to postnatal encounter with OVA. Further postnatal aerosolized OVA stress triggered allergic lungs with functional and structural alterations of airways. The unintended consequence resulted from macrophage-like fetal phagocytes that took up OVA and differentiated toward dendritic cells. These fetal dendritic cell progenitors attenuated proteolysis of endocytosed OVA for delayed presentation in postnatal life. This specialty of fetal phagocytes effectively retains the memory of antigens internalized early before full development of the immune system, leading to an event of in utero sensitization.

CONCLUSIONS

Our results have mechanical implications for prenatal imprinting of atopy and shed light on the importance of fetal phagocytes in shaping the developing immune system and initiating allergic airway diseases.

D-tryptophan from probiotic bacteria influences the gut microbiome and allergic airway disease

BACKGROUND

Chronic immune diseases, such as asthma, are highly prevalent. Currently available pharmaceuticals improve symptoms but cannot cure the disease. This prompted demands for alternatives to pharmaceuticals, such as probiotics, for the prevention of allergic disease. However, clinical trials have produced inconsistent results. This is at least partly explained by the highly complex crosstalk among probiotic bacteria, the host's microbiota, and immune cells. The identification of a bioactive substance from probiotic bacteria could circumvent this difficulty.

OBJECTIVE

We sought to identify and characterize a bioactive probiotic metabolite for potential prevention of allergic airway disease.

METHODS

Probiotic supernatants were screened for their ability to concordantly decrease the constitutive CCL17 secretion of a human Hodgkin lymphoma cell line and prevent upregulation of costimulatory molecules of LPS-stimulated human dendritic cells.

RESULTS

Supernatants from 13 of 37 tested probiotic strains showed immunoactivity. Bioassay-guided chromatographic fractionation of 2 supernatants according to polarity, followed by total ion chromatography and mass spectrometry, yielded C₁₁H₁₂N₂O₂ as the molecular formula of a bioactive substance. Proton nuclear magnetic resonance and enantiomeric separation identified D-tryptophan. In contrast, L-tryptophan and 11 other D-amino acids were inactive. Feeding D-tryptophan to mice before experimental asthma induction increased numbers of lung and gut regulatory T cells, decreased lung T_H2 responses, and ameliorated allergic airway inflammation and hyperresponsiveness. Allergic airway inflammation reduced gut microbial diversity, which was increased by D-tryptophan.

CONCLUSIONS

D-tryptophan is a newly identified product from probiotic bacteria. Our findings support the concept that defined bacterial products can be exploited in novel preventative strategies for chronic immune diseases.

Plethysmography Phenotype QTL in Mice Before and After Allergen Sensitization and Challenge

Allergic asthma is common airway disease that is characterized in part by enhanced airway constriction in response to nonspecific stimuli. Genome-wide association studies have identified multiple loci associated with asthma risk in humans, but these studies have not accounted for gene-environment interactions, which are thought to be important factors in asthma. To identify quantitative trait loci (QTL) that regulate responses to a common human allergen, we applied a house dust mite mouse (HDM) model of allergic airway disease (AAD) to 146 incipient lines of the Collaborative Cross (CC) and the CC founder strains. We employed a longitudinal study design in which mice were phenotyped for response to the bronchoconstrictor methacholine both before and after HDM sensitization and challenge using whole body plethysmography (WBP). There was significant variation in methacholine responsiveness due to both strain and HDM treatment, as reflected by changes in the WBP parameter enhanced pause. We also found that distinct QTL regulate baseline [chromosome (Chr) 18] and post-HDM (Chr 19) methacholine responsiveness and that post-HDM airway responsiveness was correlated with other features of AAD. Finally, using invasive measurements of airway mechanics, we tested whether the Chr 19 QTL affects lung resistance per se using C57BL/6J mice and a consomic strain but found that QTL haplotype did not affect lung resistance. We conclude that aspects of baseline and allergen-induced methacholine responsiveness are associated with genetic variation, and that robust detection of airway resistance QTL in genetically diverse mice will be facilitated by direct measurement of airway mechanics.

Differential Expression and Function of PDE8 and PDE4 in Effector T cells: Implications for PDE8 as a Drug Target in Inflammation

Abolishing the inhibitory signal of intracellular cAMP is a prerequisite for effector T (Teff) cell function. The regulation of cAMP within leukocytes critically depends on its degradation by cyclic nucleotide phosphodiesterases (PDEs). We have previously shown that PDE8A, a PDE isoform with 40–100-fold greater affinity for cAMP than PDE4, is selectively expressed in Teff vs. regulatory T (Treg) cells and controls CD4⁺ Teff cell adhesion and chemotaxis. Here, we determined PDE8A expression and function in CD4⁺ Teff cell populations in vivo. Using magnetic bead separation to purify leukocyte populations from the lung draining hilar lymph node (HLN) in a mouse model of ovalbumin-induced allergic airway disease (AAD), we found by Western immunoblot and quantitative (q)RT-PCR that PDE8A protein and gene expression are enhanced in the CD4⁺ T cell fraction over the course of the acute inflammatory disease and recede at the late tolerant non-inflammatory stage. To evaluate PDE8A as a potential drug target, we compared the selective and combined effects of the recently characterized highly potent PDE8-selective inhibitor PF-04957325 with the PDE4-selective inhibitor piclamilast (PICL). As previously shown, PF-04957325 suppresses T cell adhesion to endothelial cells. In contrast, we found that PICL alone increased firm T cell adhesion to endothelial cells by ~20% and significantly abrogated the inhibitory effect of PF-04957325 on T cell adhesion by over 50% when cells were co-exposed to PICL and PF-04957325. Despite its robust effect on T cell adhesion, PF-04957325 was over two orders of magnitude less efficient than PICL in suppressing polyclonal Teff cell proliferation, and showed no effect on cytokine gene expression in these cells. More importantly, PDE8 inhibition did not suppress proliferation and cytokine production of myelin-antigen reactive proinflammatory Teff cells in vivo and in vitro. Thus, targeting PDE8 through PF-04957325 selectively regulates Teff cell interactions with endothelial cells without marked immunosuppression of proliferation, while PDE4 inhibition has partially opposing effects. Collectively, our data identify PF-04957325 as a novel function-specific tool for the suppression of Teff cell adhesion and indicate that PDE4 and PDE8 play unique and non-redundant roles in the control of Teff cell functions.

Allergy protection by cowshed bacteria - recent findings and future prospects

Since the first publication in 1999, numerous epidemiologic studies provided strong evidence that frequent contact to a traditional farm environment in early life protects children from the development of allergic airway diseases. These consistent findings prompted enormous efforts to identify and characterize the potential causative factors and the underlying immunologic mechanisms in experimental studies. The cumulating evidence for the role of the cowshed-associated bacterial flora led to enhanced efforts not only to identify the relevant species but also to examine their specific immunomodulatory capacity, the bacterial components involved, and particularly the cellular and molecular mechanisms of their interaction with the immune system. We review here the methods applied to identify relevant bacterial species, the species which emerged thereof, and the similarities and differences in their mode of action as revealed so far. We further consider the impact of the current knowledge on worthwhile clinical application and reflect on the required next steps to foster the translation of the encouraging scientific progress which has been made in recent years.

Airway epithelial NF-κB activation promotes the ability to overcome inhalational antigen tolerance

BACKGROUND

Inhalational antigen tolerance typically protects against the development of allergic airway disease but may be overcome to induce allergic sensitization preceding the development of asthma.

OBJECTIVES

We examined in vivo whether pre-existing inhalational antigen tolerance could be overcome by activation of the transcription factor NF-κB in conducting airway epithelial cells, and used a combination of in vivo and in vitro approaches to examine the mechanisms involved.

METHODS

Wild-type and transgenic mice capable of expressing constitutively active IκB kinase β (CAIKKβ) in airway epithelium were tolerized to inhaled ovalbumin. Twenty-eight days later, the transgene was transiently expressed and mice were exposed to inhaled OVA on Day 30 in an attempt to overcome inhalational tolerance.

RESULTS

Following ovalbumin challenge on days 40-42, CAIKKβ mice in which the transgene had been activated exhibited characteristic features of allergic airway disease, including airway eosinophilia and methacholine hyper-responsiveness. Increases in the CD103(+) and CD11b(HI) lung dendritic cell populations were present in CAIKKβ mice on Day 31. Bronchoalveolar lavage from mice expressing CAIKKβ mice induced CD4(+) T cells to secrete T(H)2 and T(H)17 cytokines, an effect that required IL-4 and IL-1 signalling, respectively. CAIKKβ mice on Dox demonstrated increased numbers of innate lymphoid type 2 cells (ILC2) in the lung, which also exhibited elevated mRNA expression of the T(H)2-polarizing cytokine IL-4. Finally, airway epithelial NF-kB activation induced allergic sensitization in CAIKKβ mice on Dox that required IL-4 and IL-1 signalling in vivo.

CONCLUSIONS

Our studies demonstrate that soluble mediators generated in response to airway epithelial NF-κB activation orchestrate the breaking of inhalational tolerance and allergic antigen sensitization through the effects of soluble mediators, including IL-1 and IL-4, on pulmonary dendritic cells as well as innate lymphoid and CD4(+) T cells.

Cbl-b Deficiency in Mice Results in Exacerbation of Acute and Chronic Stages of Allergic Asthma

Mice sensitized to ovalbumin (OVA) develop allergic airway disease (AAD) with short-term daily OVA aerosol challenge; inflammation resolves with long-term OVA aerosol exposure, resulting in local inhalational tolerance (LIT). Cbl-b is an E3 ubiquitin ligase involved with CD28 signaling; Cbl-b^−/− effector T cells are resistant to regulatory T cell-mediated suppression in vitro and in vivo. The present study utilized Cbl-b^−/− mice to investigate the role of Cbl-b in the development of AAD and LIT. Cbl-b^−/− mice exhibited increased airway inflammation during AAD, which failed to resolve with long-term OVA aerosol exposure. Exacerbation of inflammation in Cbl-b^−/− mice correlated with increased proinflammatory cytokine levels and expansion of effector T cells in the BAL during AAD, but did not result in either a modulation of lymphocyte subsets in systemic tissues or in OVA-specific IgE in serum. These results implicate a role for Cbl-b in the resolution of allergic airway inflammation.

MicroRNA Regulation of Airway Inflammation and Airway Smooth Muscle Function: Relevance to Asthma

Genetic and environmental factors contribute to the onset and severity of asthma. Molecular pathogenesis of asthma involves changes in gene expression by a variety of inflammatory mediators acting in autocrine and paracrine fashion on effector cells of the airways. Transcriptional regulation of gene expression in resident airway cells has been studied extensively. However, protein function in a target cell can be regulated at multiple levels starting from transcription followed by post-transcription, translation, and post-translation steps. In this context, small noncoding RNAs known as microRNAs (miRNAs) have evolved as one of the key regulators of gene expression post-transcriptionally. Most importantly, miRNA expression is dynamic in nature and can be regulated by a variety of external stimuli. Altered expression of individual or a group of miRNAs is thought to contribute to human diseases. Recent studies have implicated differential expression of miRNAs in the lungs during inflammation. Most importantly, advanced biochemical and molecular tools could be used to manipulate miRNA expression thereby effecting functional changes in target cells and organ systems. This review summarizes the current understanding of miRNA in the regulation of airway function in health and disease, and highlights the potential clinical utility of mRNAs as biomarkers of airway diseases and as potential therapeutic targets.

Airway responsiveness in CD38-deficient mice in allergic airway disease: studies with bone marrow chimeras

CD38 is a cell-surface protein involved in calcium signaling and contractility of airway smooth muscle. It has a role in normal airway responsiveness and in airway hyperresponsiveness (AHR) developed following airway exposure to IL-13 and TNF-α but appears not to be critical to airway inflammation in response to the cytokines. CD38 is also involved in T cell-mediated immune response to protein antigens. In this study, we assessed the contribution of CD38 to AHR and inflammation to two distinct allergens, ovalbumin and the epidemiologically relevant environmental fungus Alternaria. We also generated bone marrow chimeras to assess whether Cd38(+/+) inflammatory cells would restore AHR in the CD38-deficient (Cd38(-/-)) hosts following ovalbumin challenge. Results show that wild-type (WT) mice develop greater AHR to inhaled methacholine than Cd38(-/-) mice following challenge with either allergen, with comparable airway inflammation. Reciprocal bone marrow transfers did not change the native airway phenotypic differences between WT and Cd38(-/-) mice, indicating that the lower airway reactivity of Cd38(-/-) mice stems from Cd38(-/-) lung parenchymal cells. Following bone marrow transfer from either source and ovalbumin challenge, the phenotype of Cd38(-/-) hosts was partially reversed, whereas the airway phenotype of the WT hosts was preserved. Airway inflammation was similar in Cd38(-/-) and WT chimeras. These results indicate that loss of CD38 on hematopoietic cells is not sufficient to prevent AHR and that the magnitude of airway inflammation is not the predominant underlying determinant of AHR in mice.

Pro-inflammatory role of natural killer cells in the development of allergic airway disease

BACKGROUND

Natural Killer (NK) cells have been implicated in the development of allergic airway inflammation. However, the in vivo role of NK cells has not been firmly established due to the lack of animal models with selective deficiencies in NK cells.

OBJECTIVE

To determine the specific contribution of NK cells in a murine model of allergic airway disease (AAD).

METHODS

The role of NK cells in AAD was studied using NK-deficient (NKD) mice, perforin(-/-) mice, and mice depleted of Ly49A/D/G(+) NK cell subsets in an ovalbumin-induced model of allergic airway disease (OVA-AAD).

RESULTS

Induction of OVA-AAD in C57BL/6 wild-type (WT) mice resulted in the expansion of airway NK cells and the development of pronounced airway eosinophilia. In the absence of NK cells or specific subsets of NK cells, either in NKD mice, or after the depletion of Ly49A/D/G(+) NK cells, the development of OVA-AAD was significantly impaired as seen by decreased airway inflammation and eosinophilia, decreased secretion of the Th2 cytokines IL-4, IL-5 and IL-13 and diminished OVA-specific antibody production. Furthermore, while OVA-exposure induced a dramatic expansion of dendritic cells (DCs) in WT mice, their induction was significantly attenuated in NKD mice. Development of OVA-AAD in perforin(-/-) mice suggested that the proinflammatory role of NK cells is not dependent on perforin-mediated cytotoxicity. Lastly, induction of allergic disease by OVA-specific CD4 T cells from WT but not NK-depleted or NKD mice in RAG(-/-) recipients, demonstrates that NK cells are essential for T cell priming.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data demonstrate that conventional NK cells play an important and distinct role in the development of AAD. The presence of activated NK cells has been noted in patients with asthma. Understanding the mechanisms by which NK cells regulate allergic disease is therefore an important component of treatment approaches.

Integrative genetic analysis of allergic inflammation in the murine lung

Airway allergen exposure induces inflammation among individuals with atopy that is characterized by altered airway gene expression, elevated levels of T helper type 2 cytokines, mucus hypersecretion, and airflow obstruction. To identify the genetic determinants of the airway allergen response, we employed a systems genetics approach. We applied a house dust mite mouse model of allergic airway disease to 151 incipient lines of the Collaborative Cross, a new mouse genetic reference population, and measured serum IgE, airway eosinophilia, and gene expression in the lung. Allergen-induced serum IgE and airway eosinophilia were not correlated. We detected quantitative trait loci (QTL) for airway eosinophilia on chromosome (Chr) 11 (71.802-87.098 megabases [Mb]) and allergen-induced IgE on Chr 4 (13.950-31.660 Mb). More than 4,500 genes expressed in the lung had gene expression QTL (eQTL), the majority of which were located near the gene itself. However, we also detected approximately 1,700 trans-eQTL, and many of these trans-eQTL clustered into two regions on Chr 2. We show that one of these loci (at 147.6 Mb) is associated with the expression of more than 100 genes, and, using bioinformatics resources, fine-map this locus to a 53 kb-long interval. We also use the gene expression and eQTL data to identify a candidate gene, Tlcd2, for the eosinophil QTL. Our results demonstrate that hallmark allergic airway disease phenotypes are associated with distinct genetic loci on Chrs 4 and 11, and that gene expression in the allergically inflamed lung is controlled by both cis and trans regulatory factors.

Alternaria-derived serine protease activity drives IL-33-mediated asthma exacerbations

Background

The fungal allergen Alternaria alternata is implicated in severe asthma and rapid onset life-threatening exacerbations of disease. However, the mechanisms that underlie this severe pathogenicity remain unclear.

Objective

We sought to investigate the mechanism whereby Alternaria was capable of initiating severe, rapid onset allergic inflammation.

Methods

IL-33 levels were quantified in wild-type and ST2^−/− mice that lacked the IL-33 receptor given inhaled house dust mite, cat dander, or Alternaria, and the effect of inhibiting allergen-specific protease activities on IL-33 levels was assessed. An exacerbation model of allergic airway disease was established whereby mice were sensitized with house dust mite before subsequently being challenged with Alternaria (with or without serine protease activity), and inflammation, remodeling, and lung function assessed 24 hours later.

Results

Alternaria, but not other common aeroallergens, possessed intrinsic serine protease activity that elicited the rapid release of IL-33 into the airways of mice through a mechanism that was dependent upon the activation of protease activated receptor-2 and adenosine triphosphate signaling. The unique capacity of Alternaria to drive this early IL-33 release resulted in a greater pulmonary inflammation by 24 hours after challenge relative to the common aeroallergen house dust mite. Furthermore, this Alternaria serine protease–IL-33 axis triggered a rapid, augmented inflammation, mucus release, and loss of lung function in our exacerbation model.

Conclusion

Alternaria-specific serine protease activity causes rapid IL-33 release, which underlies the development of a robust T_H2 inflammation and exacerbation of allergic airway disease.

Identification of an interleukin 13-induced epigenetic signature in allergic airway inflammation

Epigenetic changes have been implicated in the pathogenesis of asthma. We sought to determine if IL13, a key cytokine in airway inflammation and remodeling, induced epigenetic DNA methylation and miRNAs expression changes in the airways in conjunction with its transcriptional gene regulation. Inducible expression of an IL13 transgene in the airways resulted in significant changes in DNA methylation in 177 genes, most of which were associated with the IL13 transcriptional signature in the airways. A large number of genes whose expression was induced by IL13 were found to have decreased methylation, including those involved in tissue remodeling (Olr1), leukocyte influx (Cxcl3, Cxcl5, CSFr2b), and the Th2 response (C3ar1, Chi3l4). Reciprocally, some genes whose expression was suppressed were found to have increased methylation (e.g. Itga8). In addition, miRNAs were identified with targets for lung development and Wnt signaling, amongst others. These results indicate that IL13 confers an epigenetic methylation and miRNA signature that accompanies its transcriptional program in the airways, which may play a critical role in airway inflammation and remodeling.

Silver nanoparticles modify VEGF signaling pathway and mucus hypersecretion in allergic airway inflammation

The anti-inflammatory action of silver nanoparticles (NPs) has been reported in a murine model of asthma in a previous study. But more specific mechanisms of silver NPs in an attenuation of allergic airway inflammation have not yet been established. Vascular and mucous changes are believed to contribute largely in pathophysiology in asthma. Among various factors related to vascular changes, vascular endothelial growth factor (VEGF) plays a pivotal role in vascular changes in asthma. Mucin proteins MUC5AC and MUC5B have been implicated as markers of goblet cell metaplasia in lung pathologies. The aim of this study was to investigate the effects of silver NPs on VEGF signaling pathways and mucus hypersecretion. Ovalbumin (OVA)-inhaled female BALBc mice were used to evaluate the role of silver NPs and the related molecular mechanisms in allergic airway disease. In this study, with an OVA-induced murine model of allergic airway disease, it was found that the increased levels of hypoxia-inducible factor (HIF)-1α, VEGF, phosphatidylinositol-3 kinase (PI3K) and phosphorylated-Akt levels, and mucous glycoprotein expression (Muc5ac) in lung tissues were substantially decreased by the administration of silver NPs. In summary, silver NPs substantially suppressed mucus hypersecretion and PI3K/HIF-1α/VEGF signaling pathway in an allergic airway inflammation.

Attenuation of allergic airway inflammation and hyperresponsiveness in a murine model of asthma by silver nanoparticles

The use of silver in the past demonstrated the certain antimicrobial activity, though this has been replaced by other treatments. However, nanotechnology has provided a way of producing pure silver nanoparticles, and it shows cytoprotective activities and possible pro-healing properties. But, the mechanism of silver nanoparticles remains unknown. This study was aimed to investigate the effects of silver nanoparticles on bronchial inflammation and hyperresponsiveness. We used ovalbumin (OVA)-inhaled female C57BL/6 mice to evaluate the roles of silver nanoparticles and the related molecular mechanisms in allergic airway disease. In this study with an OVA-induced murine model of allergic airway disease, we found that the increased inflammatory cells, airway hyperresponsiveness, increased levels of IL-4, IL-5, and IL-13, and the increased NF-κB levels in lungs after OVA inhalation were significantly reduced by the administration of silver nanoparticles. In addition, we have also found that the increased intracellular reactive oxygen species (ROS) levels in bronchoalveolar lavage fluid after OVA inhalation were decreased by the administration of silver nanoparticles. These results indicate that silver nanoparticles may attenuate antigen-induced airway inflammation and hyperresponsiveness. And antioxidant effect of silver nanoparticles could be one of the molecular bases in the murine model of asthma. These findings may provide a potential molecular mechanism of silver nanoparticles in preventing or treating asthma.

CC chemokine receptor (CCR)3/eotaxin is followed by CCR4/monocyte-derived chemokine in mediating pulmonary T helper lymphocyte type 2 recruitment after serial antigen challenge in vivo

Isolated peripheral blood CD4 cells from allergic individuals express CC chemokine receptor (CCR)3 and CCR4 after expansion in vitro. In addition, human T helper type 2 (Th2) cells polarized in vitro selectively express CCR3 and CCR4 at certain stages of activation/differentiation and respond preferentially to the ligands eotaxin and monocyte-derived chemokine (MDC). However, controversy arises when the in vivo significance of this distinct expression is discussed. To address the functional role of CCR3/eotaxin and CCR4/MDC during the in vivo recruitment of Th2 cells, we have transferred effector Th cells into naive mice to induce allergic airway disease. Tracking of these cells after repeated antigen challenge has established that both CCR3/eotaxin and CCR4/MDC axes contribute to the recruitment of Th2 cells to the lung, demonstrating the in vivo relevance of the expression of these receptors on Th2 cells. We have shown that involvement of the CCR3/eotaxin pathway is confined to early stages of the response in vivo, whereas repeated antigen stimulation results in the predominant use of the CCR4/MDC pathway. We propose that effector Th2 cells respond to both CCR3/eotaxin and CCR4/MDC pathways initially, but that a progressive increase in CCR4-positive cells results in the predominance of the CCR4/MDC axis in the long-term recruitment of Th2 cells in vivo.