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Objective: In a previous study we have shown that, in the presence of interleukin (IL)-33, repeated, per-nasal challenge of murine airways with Streptococcus pneumoniae ( S. pneumoniae ) organisms induces human asthma-like airways inflammation. It is not clear, however, whether this effect is unique or manifest in response to other common respiratory pathogens. Methods: To explore this, airways of BALB/c mice were repeatedly challenged per-nasally with formaldehyde-inactivated bacterial bodies in the presence or absence of murine recombinant IL-33. Serum concentrations of S.pneumoniae , Moraxella catarrhalis ( M.catarrhalis ) and Haemophilus influenzae ( H.influenzae ) lysates-specific IgE were measured in patients with asthma and control subjects. Results: We showed that in the presence of IL-33, repeated, per-nasal airways exposure to the bodies of these bacteria induced airways hyperresponsiveness (AHR) in the experimental mice. This was accompanied by cellular infiltration into bronchoalveolar lavage fluid (BALF), eosinophilic infiltration and mucous hypertrophy of the lung tissue, with elevated local expression of some type 2 cytokines and elevated, specific IgG and IgE in the serum. The precise characteristics of the inflammation evoked by exposure to each bacterial species were distinguishable. Conclusions: These results suggest that in the certain circumstances, inhaled or commensal bacterial body antigens of both Gram-positive ( S. pneumoniae ) and Gram-negative ( M. catarrhalis and H. influenzae ) respiratory tract bacteria may initiate type 2 inflammation typical of asthma in the airways. In addition, we demonstrated that human asthmatic patients manifest elevated serum concentrations of M.catarrhalis- and H.influenzae- specific IgE.

Background: Asthma is a common chronic respiratory disease characterized by airways inflammation, hyperresponsiveness and remodeling. IL-37, an anti-inflammatory cytokine, consists of five splice isoforms, that is, a-e. Although it has been previously shown that recombinant human IL-37b is able to inhibit airway inflammation and hyperresponsiveness in animal models of asthma, the effects and difference of other IL-37 isoforms, such as IL-37a on features of asthma are unknown., Methods: Animal models of chronic asthma were established using IL-37a and IL-37b transgenic mice with C57BL/6J background and wild-type (WT) mice sensitized and nasally challenged with ovalbumin (OVA). Airway hyperresponsiveness was measured using FlexiVent apparatus, while histological and immunohistological stainings were employed to measure airways inflammation and remodeling indexes, including goblet cell metaplasia, mucus production, deposition of collagen, hypertrophy of airway smooth muscles and pulmonary angiogenesis., Results: Compared to WT mice, both IL-37a and IL-37b transgenic mice had significant reduced airway hyperresponsiveness and the declined total numbers of inflammatory cells, predominant eosinophils into airways and lung tissues. Furthermore, all features of airways remodeling, including degrees of mucus expression, collagen deposition, hypertrophy of smooth muscles, thickness of airways and neovascularization markedly decreased in IL-37 transgenic mice compared with OVA-treated WT mice., Conclusion: Our data suggest that both IL-37a and IL-37b isoforms are able to not only ameliorate airways inflammation and airways hyperresponsiveness, but also greatly reduce airways structural changes of animal models of chronic asthma., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Respiratory tract infection early in life plays a significant role in the pathogenesis of asthma. In the present study we examine, using a murine surrogate, the effects of early life respiratory infection with Streptococcus pneumoniae (SP) on adult asthma induced by sensitisation and exposure to house dust mite (HDM) allergen. Mice (one week old) were infected with SP, then 3 weeks later sensitised to HDM emulsified with Al (OH)3 intraperitoneally and challenged intranasally with same allergen for up to a further 5 weeks to establish the asthma surrogate. Outcome measures were quantified using the FlexiVent apparatus, histology and immunohistology, ELISA and flow cytometry. The murine surrogates of asthma infected with SP early in life exhibited significantly more severe disease compared with the controls of mice without SP infection, as shown by airways responsiveness, inflammatory cellular infiltration of the airways, expression of markers of airways remodelling, serum concentrations of HDM-specific IgE and the concentrations of Th2-type cytokines and the numbers of activated Th2 and ILC2 cells in the lung tissues. These data are compatible with the hypothesis that early-life infection of the airways with SP exacerbates, at least in some individuals, subsequent HDM-induced allergic airways inflammation and associated asthma in adulthood in this murine surrogate., (Copyright © 2022. Published by Elsevier Inc.)

Allergic asthma is an allergic inflammatory disease of the airways, in which numerous cell types and cytokines have been shown to contribute to pathogenesis of the disease. Although increased expression of IL-9 has been shown to influence the activity of structural as well as eosinophils and mast cells in asthma, the influence of IL-9 on function of ILC2 and Th2 cells remains unclear. This study therefore aimed to elucidate the role of IL-9 on ILC2 and Th2 cells using a murine model of asthma. A murine model of asthma was established using wild type (WT) and IL-9-deficient (Il9 -/- ) transgenic mice sensitized to house dust mite (HDM). Bronchoalveolar lavage fluid (BALF) and lung tissues were collected, and analysed for inflammatory cells (eosinophils, mast cells, Th2 cells and ILC2 cells), histopathological changes, and several cytokines. HDM challenge significantly increased accumulation of ILC2 cells, Th2 cells and mast cells, as well as goblet cell hyperplasia, and the expression of cytokines IL-4, IL-5 and IL-13, but not IFN-γ, in WT mice compared to saline-challenged control group. In contrast, all pathological changes, including infiltration of ILC2 cells, Th2 cells and mast cells, were significantly attenuated in HDM-challenged Il9 -/- mice. Furthermore, the number of Ki67 + ILC2 cells, Ki67 + Th2 cells and Ki67 + mast cells were significantly reduced in the absence of IL-9 signalling. These data suggest that IL-9 promotes the proliferation and type 2 cytokine production of type 2 cells in the murine models of asthma, and therefore might be a potential therapeutic target for asthma treatment., (© 2022. The Author(s).)

While environmental aeroallergens and epithelial alarmins such as IL-33 are firmly implicated in asthma, the possible role of Streptococcus pneumoniae (S. pneumoniae) antigens is less clear. To explore this, wild-type BALB/c mice were repeatedly challenged per-nasally with IL-33 and inactivated S. pneumoniae, either agent alone or diluent control. Some animals were rested then later re-challenged with inactivated S. pneumoniae alone. Serum concentrations of S. pneumoniae lysates-specific IgE were measured in patients with asthma and control subjects. Interestingly, in the presence of IL-33, repeated exposure to inactivated S. pneumoniae induced asthma-like pathological changes accompanied by a systemic adaptive immune response. Subsequent re-exposure of the sensitized animals to inactivated S. pneumoniae alone was able to induce such changes. The concentration of S. pneumoniae lysates-specific IgE was significantly elevated in the asthma patients. These data suggest that antigens derived from infectious microorganisms may participate in generating the mucosal inflammation which characterizes asthma., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Although contributions of IL-33 to pulmonary diseases, including asthma, have been well documented, the complexity of such regulation warrants additional exploration. To better understand the involvement of IL-33, we used a murine asthma surrogate based on sensitisation and challenge with dust mite extract in the presence/absence of IL-33. Murine models were established with Dermatophagoides farinae (Der f) to establish (1) the effect of co-administered rmIL-33; (2) the effect of prior glucocorticoid intervention; (3) the effect of IL-33 on challenge with sub-threshold dosage Der f. The effects of rmIL-33 on bone marrow-derived dendritic cells were explored in vitro. Mice challenged with Der f combined with IL-33 compared with diluent control evinced significantly more airways inflammation and local cytokine production which was less sensitive to inhibition by dexamethasone. IL-33 also induced airways hyperresponsiveness, eosinophilic inflammation and cytokine production in lung tissues of animals exposed to sub-threshold dosage of Der f. In vitro, IL-33-stimulated DCs showed a significantly elevated capacity to stimulate CD4 + T cell proliferation and cytokine production and were also significantly more resistant to dexamethasone-induced apoptosis. Our data suggest that IL-33 reduces the threshold for allergen-induced inflammation of the airways in acorticosteroid-resistant fashion possibly in part through acting on DCs, a phenomenon which may be relevant to the development of severe, corticosteroid-resistant airways obstruction in human asthmatic patients., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Asthma is an inflammatory disease of the airways and numerous cytokines contribute to this pathogenesis. It is shown that challenge of airways with IL-33 induces asthma-like pathological changes in mice, but the possible downstream cytokines in this process remain to be characterised. To explore this, we compared changes in the airways of wildtype (WT) and IL-9 deficient mice challenged with IL-33. In line with previous report, per-nasal challenge of WT mice with IL-33 significantly increased the responsiveness of the airways along with infiltration of inflammatory cells, goblet cell hyperplasia, collagen deposition and smooth muscle hypertrophy, and the expression of cytokines compared with control group. Surprisingly, all of these pathological changes were significantly attenuated in IL-9 deficient mice following identical IL-33 challenge. These data suggest that IL-9 is one downstream cytokine relevant to the effects of IL-33 in asthmatic airways and consequently a potential therapeutic target for the treatment of asthma., (Copyright © 2020 Elsevier Inc. All rights reserved.)

ILC2s are implicated in asthma pathogenesis, but little is known about the mechanisms underlying their accumulation in airways. We investigated the time course of ILC2 accumulation in different tissues in murine models of asthma induced by a serial per-nasal challenge with ovalbumin (OVA), house dust mice (HDM), IL-25 and IL-33 and explored the potential roles of ILC2-attracting chemokines in this phenomenon. Flow cytometry was used to enumerate ILC2s at various time points. The effects of cytokines and chemokines on ILC2 migration were measured in vitro using a chemotaxis assay and in vivo using small animal imaging. Compared with saline and OVA challenge, both IL-25 and IL-33 challenge alone induced significant accumulation of ILC2s in the mediastinal lymph nodes, lung tissue and bronchoalveolar lavage fluid of challenged animals, but with a distinct potency and kinetics. In vitro, IL-33 and CXCL16, but not IL-25 or CCL25, directly induced ILC2 migration. Small animal in vivo imaging further confirmed that a single intranasal provocation with IL-33 or CXCL16 was sufficient to induce the accumulation of ILC2s in the lungs following injection via the tail vein. Moreover, IL-33-induced ILC2 migration involved the activation of ERK1/2, p38, Akt, JNK and NF-κB, while CXCL16-induced ILC2 migration involved the activation of ERK1/2, p38 and Akt. These data support the hypothesis that epithelium-derived IL-25 and IL-33 induce lung accumulation of ILC2s, while IL-33 exerts a direct chemotactic effect in this process. Although ILC2s express the chemokine receptors CXCR6 and CCR9, only CXCL16, the ligand of CXCR6, exhibits a direct chemoattractant effect.

The alarmin cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) play a critical role in asthma pathogenesis by inducing mucosal Th2-type cytokine production. Although environmental exposure to aeroallergens has been proposed as an alarmin trigger in asthma, there has been no systematic parallel study of the effects of allergen exposure on the expression of these cytokines in the airways of human asthmatics. Using single and sequential double immunohistochemistry, we evaluated the numbers and phenotypes of IL-25-, IL-33-, and TSLP-immunoreactive cells in sections of bronchial biopsies from mild atopic asthmatics ( n = 16) before and 24 h after allergen inhalational challenge. Allergen challenge highly increased expression of baseline immunoreactivity for IL-25, IL-33, and TSLP, both in the bronchial epithelium and submucosa ( p < 0.001), to a degree that correlated with the extent of the late phase of airway obstruction. Aside from epithelial cells, the principal source of immunoreactivity for all three alarmins, TSLP, and IL-33 immunoreactivity colocalized principally with endothelial cells and mast cells, neutrophils, and fibroblasts, whereas IL-25 immunoreactivity colocalized principally with eosinophils as well as endothelial cells, mast cells, and fibroblasts. The data implicate that allergen challenge directly increases airway alarmin expression in atopic asthmatics to a degree correlating with increase late-phase airway obstruction, affirming these molecules as potential molecular targets for the inhibition of allergen-induced airway inflammation and obstruction., (Copyright © 2018 by The American Association of Immunologists, Inc.)

The epithelial cytokines IL-33, thymic stromal lymphopoietin (TSLP), and IL-25 have been implicated in asthma pathogenesis because they promote Th2-type cytokine synthesis, but their expression is relatively poorly documented in "real-life" human asthma. Using bronchoalveolar lavage fluid (BALF), we measured airway concentrations of these mediators and compared them with those of Th1- and Th2-type cytokines, airway infiltration of neutrophils and eosinophils, and lung function in a large group of asthmatic patients with a range of disease severity ( n = 70) and control subjects ( n = 30). The median BALF concentrations of IL-33, TSLP, IL-4, IL-5, IL-13, and IL-12p70, but not IL-25, IL-2, or IFN-γ, were significantly elevated in asthmatics compared with controls ( p < 0.05). The concentrations of IL-33 and TSLP, but not IL-25, correlated inversely with the lung function (forced expiratory volume in the first second) of asthmatics (IL-33: r = -0.488, p < 0.0001; TSLP: r = -0.565, p < 0.0001) independently of corticosteroid therapy. When divided according to disease severity and corticosteroid therapy, all subgroups of asthmatics had elevated median numbers of eosinophils in BALF, whereas the patients with more severe disease who were treated with corticosteroids had higher numbers of neutrophils compared with milder asthmatics not so treated and control subjects ( p < 0.05). The data implicate TSLP and IL-33 in the pathogenesis of asthma that is characterized by persistent airway inflammation and impaired lung function despite intensive corticosteroid therapy, highlighting them as potential molecular targets., (Copyright © 2018 by The American Association of Immunologists, Inc.)

Objective: This study aimed to explore the value of elevated serum levels of tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), and eosinophil cationic protein (ECP) in the diagnosis of bronchial asthma (BA)., Methods: A total of 170 patients with BA (case group, 85 patients in acute attack and 85 patients in clinical remission) and 150 healthy individuals (control group) were enrolled in this study. Enzyme-linked immunosorbent assay and receiver operating characteristic (ROC) curves were calculated for the contents and diagnostic values of serum TNF-α, IL-8, and ECP in BA., Results: Compared with the control group, patients in acute attack and clinical remission had higher TNF-α, IL-8, and ECP levels (p < 0.05). The serum level of TNF-α was positively correlated with IL-8 and ECP (p < 0.05). ROC curves showed that the diagnostic threshold value of IL-8 was 13.53 ng/ml, its area under the curve (AUC) was 0.87, its specificity was 99.3%, and its sensitivity was 57.6%. The diagnostic threshold value of TNF-α was 1.29 ng/ml with AUC being 0.94, specificity was 89.3%, and sensitivity was 83.5%. ECP showed 7.22 ng/ml diagnostic threshold value (AUC = 0.88, specificity = 74.0%, sensitivity = 86.5%). The FEV 1 /pre(%) and FEV 1 /FVC were negatively correlated and the Z5/pre(%) and resonance frequency (Fres) were positively correlated with the serum levels of TNF-α, IL-8, and ECP in patients in acute attack and in clinical remission (all p < 0.05)., Conclusion: Our findings reveal that elevated serum levels of TNF-α, IL-8, and ECP can be involved in the development and progression of BA.

The T-helper cell type 2-promoting cytokine interleukin-33 (IL-33) has been implicated in asthma pathogenesis. Angiogenesis is a feature of airways remodelling in asthma. We hypothesized that IL-33 induces airways angiogenesis and expression of angiogenic factors in an established murine surrogate of asthma. In the present study, BALB/c mice were subjected to serial intranasal challenge with IL-33 alone for up to 70 days. In parallel, ovalbumin (OVA) -sensitized mice were subjected to serial intranasal challenge with OVA or normal saline to serve as positive and negative controls, respectively. Immunohistochemical analysis of expression of von Willebrand factor and erythroblast transformation-specific-related gene, both blood vessel markers, and angiogenic factors angiogenin, insulin-like growth factor-1, endothelin-1, epidermal growth factor and amphiregulin was performed in lung sections ex vivo. An established in-house assay was used to test whether IL-33 was able to induce microvessel formation by human vascular endothelial cells. Results showed that serial intranasal challenge of mice with IL-33 or OVA resulted in proliferation of peribronchial von Willebrand factor-positive blood vessels to a degree closely related to the total expression of the angiogenic factors amphiregulin, angiogenin, endothelin-1, epidermal growth factor and insulin-like growth factor-1. IL-33 also induced microvessel formation by human endothelial cells in a concentration-dependent fashion in vitro. Our data are consistent with the hypothesis that IL-33 has the capacity to induce angiogenesis at least partly by increasing local expression of multiple angiogenic factors in an allergen-independent murine asthma surrogate, and consequently that IL-33 or its receptor is a potential novel molecular target for asthma therapy., (© 2016 John Wiley & Sons Ltd.)

Interleukin-25 (IL-25) and IL-33, which belong to distinct cytokine families, induce and promote T helper type 2 airway inflammation. Both cytokines probably play a role in asthma, but there is a lack of direct evidence to clarify distinctions between their functions and how they might contribute to distinct 'endotypes' of disease. To address this, we made a direct comparison of the effects of IL-25 and IL-33 on airway inflammation and physiology in our established murine asthma surrogate, which involves per-nasal, direct airway challenge. Intranasal challenge with IL-33 or IL-25 induced inflammatory cellular infiltration, collagen deposition, airway smooth muscle hypertrophy, angiogenesis and airway hyper-responsiveness, but neither increased systemic production of IgE or IgG1. Compared with that of IL-25, the IL-33-induced response was characterized by more sustained laying down of extracellular matrix protein, neoangiogenesis, T helper type 2 cytokine expression and elevation of tissue damping. Hence, both IL-25 and IL-33 may contribute significantly and independently to asthma 'endotypes' when considering molecular targets for the treatment of human disease., (© 2015 John Wiley & Sons Ltd.)

Background and Objective: Interleukin (IL)-25 has been implicated in the pathogenesis of human asthma by inducing a Th2 cytokine response, but its possible role in the development of airway remodelling is less clear., Methods: We developed a murine surrogate of chronic airway inflammation induced by intranasal application of IL-25 alone. Comparison was with the 'classical' surrogate of ovalbumin (OVA) intranasal instillation into previously sensitized animals. Airway fibrotic biomarkers were analysed by immunohistochemistry and enzyme-linked immunosorbent assay. Additionally, proliferation assay and real-time polymerase chain reaction analysis were performed to assess IL-25's effects on primary human bronchial fibroblasts in vitro., Results: In Balb/c mice, intranasal instillation of IL-25 alone induced florid airway fibrosis, including increased lay down of extracellular matrix proteins such as collagen I, III, V and fibronectin, increased numbers of fibroblasts/myofibroblasts, a profibrotic imbalance in matrix metalloproteinase/tissue inhibitor of metalloproteinase production and increased expression of profibrotic mediators including connective tissue growth factor and transforming growth factor-β1. These changes broadly reproduced those seen with classical intranasal OVA challenge in OVA-sensitized animals. Furthermore, IL-25 induced proliferation and expression of collagen I and III and smooth muscle α-actin in primary human lung fibroblasts., Conclusions: We conclude that chronic exposure of the airways to IL-25 alone is sufficient to cause functionally relevant airway remodelling, with the corollary that targeting of IL-25 may attenuate bronchial remodelling and fibrosis in human asthmatics., (© 2015 Asian Pacific Society of Respirology.)

Background: Th2-promoting cytokine IL-25 might contribute to bronchial mucosal vascular remodelling in asthma through its receptor expressed by vascular endothelial and vascular smooth muscle cells., Methods: By utilising a newly established chronic asthma murine model induced by direct exposure of the airways to IL-25 alone, we examined effects of IL-25 on angiogenesis, vascular remodelling and expression of angiogenic factors, compared changes with those in a "classical" ovalbumin (OVA)-induced murine asthma model. IL-25 and OVA were intranasally instilled into the airways of BALB/c mice for up to 55 days. Airways vessels and angiogenic factors, including Von Willebrand Factor (vWF), amphiregulin, angiogenin, endothelin-1, transcription factor ERG, basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin-like growth factor (IGF-1) and vascular endothelial growth factor (VEGF) in lung sections, homogenates and BAL fluid were detected and quantified by immunostaining or enzyme linked immunosorbent assay (ELISA). An in house assay was also utilised to compare the effects of IL-25 and other Th2-cytokines on angiogenesis by human vascular endothelial cells., Results: Repetitive intranasal challenge with IL-25 alone or OVA alone in OVA-presensitised animals significantly increased peribronchial vWF (+) vessels in the murine airways, which was associated with remarkably elevated expression of amphiregulin, angiogenin, endothelin-1, bFGF, EGF, IGF-1, VEGF and ERG. IL-25, but not Th-2-cytokines induced human angiogenesis in vitro., Conclusions: The data suggest that chronic exposure of murine airways to IL-25 alone is able to reproduce a local angiogenic milieu. Thus, blocking IL-25 may attenuate vascular remodelling and improve outcomes in asthma patients.