Interleukin-13: central mediator of allergic asthma

Genes, environment, and developmental timing: New insights from translational approaches to understand early origins of respiratory diseases

Over the past decade, "omics" approaches have advanced our understanding of the molecular programming of the airways in humans. Several studies have identified potential molecular mechanisms that contribute to early life epigenetic reprogramming, including DNA methylation, histone modifications, microRNAs, and the homeostasis of the respiratory mucosa (epithelial function and microbiota). Current evidence supports the notion that early infancy is characterized by heightened susceptibility to airway genetic reprogramming in response to the first exposures in life, some of which can have life-long consequences. Here, we summarize and analyze the latest insights from studies that support a novel epigenetic paradigm centered on human maturational and developmental programs including three cardinal elements: genes, environment, and developmental timing. The combination of these factors is likely responsible for the functional trajectory of the respiratory system at the molecular, functional, and clinical levels.

IL13 Acts Directly on Gastric Epithelial Cells to Promote Metaplasia Development During Chronic Gastritis

BACKGROUND & AIMS

It is well established that chronic inflammation promotes gastric cancer-associated metaplasia, but little is known regarding the mechanisms by which immune cells and cytokines regulate metaplastic cellular changes. The goals of this study were to identify interleukin 13 (IL13)-producing immune cells, determine the gastric epithelial cell response(s) to IL13, and establish the role(s) of IL13 in metaplasia development.

METHODS

Experiments used an established mouse model of autoimmune gastritis (TxA23), TxA23×Il4ra-/- mice, which develop gastritis but do not express the IL4/IL13-receptor subunit IL4Rα, and TxA23×Il13-Yfp mice, which express yellow fluorescent protein in IL13-producing cells. Flow cytometry was used to measure IL13 secretion and identify IL13-producing immune cells. Mouse and human gastric organoids were cultured with IL13 to determine epithelial cell response(s) to IL13. Single-cell RNA sequencing was performed on gastric epithelial cells from healthy and inflamed mouse stomachs. Mice with gastritis were administered IL13-neutralizing antibodies and stomachs were analyzed by histopathology and immunofluorescence.

RESULTS

We identified 6 unique subsets of IL13-producing immune cells in the inflamed stomach. Organoid cultures showed that IL13 acts directly on gastric epithelium to induce a metaplastic phenotype. IL4Rα-deficient mice did not progress to metaplasia. Single-cell RNA sequencing determined that gastric epithelial cells from IL4Rα-deficient mice up-regulated inflammatory genes but failed to up-regulate metaplasia-associated transcripts. Neutralization of IL13 significantly reduced and reversed metaplasia development in mice with gastritis.

CONCLUSIONS

IL13 is made by a variety of immune cell subsets during chronic gastritis and promotes gastric cancer-associated metaplastic epithelial cell changes. Neutralization of IL13 reduces metaplasia severity during chronic gastritis.

Ding Chuan Tang Attenuates Airway Inflammation and Eosinophil Infiltration in Ovalbumin-Sensitized Asthmatic Mice

Asthma is a T helper 2 (Th2) cell-associated chronic inflammatory diseases characterized with airway obstruction, increased mucus production, and eosinophil infiltration. Conventional medications for asthma treatment cannot fully control the symptoms, and potential side effects are also the concerns. Thus, complement or alternative medicine (CAM) became a new option for asthma management. Ding Chuan Tang (DCT) is a traditional Chinese herbal decoction applied mainly for patients with coughing, wheezing, chest tightness, and asthma. Previously, DCT has been proved to improve children airway hyperresponsiveness (AHR) in a randomized and double-blind clinical trial. However, the mechanisms of how DCT alleviates AHR remain unclear. Since asthmatic features such as eosinophil infiltration, IgE production, and mucus accumulation are relative with Th2 responses, we hypothesized that DCT may attenuate asthma symptoms through regulating Th2 cells. Ovalbumin (OVA) was used as a stimulant to sensitize BALB/c mice to establish an asthmatic model. AHR was detected one day before sacrifice. BALF and serum were collected for immune cell counting and antibody analysis. Splenocytes were cultured with OVA in order to determine Th2 cytokine production. Lung tissues were collected for histological and gene expression analyses. Our data reveal that DCT can attenuate AHR and eosinophil accumulation in the 30-day sensitization asthmatic model. Histological results demonstrated that DCT can reduce cell infiltration and mucus production in peribronchial and perivascular site. In OVA-stimulated splenocyte cultures, a significant reduction of IL-5 and IL-13 in DCT-treated mice suggests that DCT may alleviate Th2 responses. In conclusion, the current study demonstrates that DCT has the potential to suppress allergic responses through the reduction of mucus production, eosinophil infiltration, and Th2 activity in asthma.

Inflammation in Asthma Pathogenesis: Role of T cells, Macrophages, Epithelial Cells and Type 2 Inflammation

Asthma is a chronic disease with abnormal inflammatory and immunological responses. The disease initiated by antigens in subjects with genetic susceptibility. However, environmental factors play a role in the initiation and exacerbation of asthma attack. Asthma is T helper 2 (Th2)-cell-mediated disease. Recent studies indicated that asthma is not a single disease entity, but it is with multiple phenotypes and endotypes. The pathophysiological changes in asthma included a series of subsequent continuous vicious circle of cellular activation contributed to induction of chemokines and cytokines that potentiate inflammation. The heterogeneity of asthma influenced the treatment response. The asthma pathogenesis driven by varied set of cells such as eosinophils, basophils, neutrophils, mast cells, macrophages, epithelial cells and T cells. In this review the role of T cells, macrophage, and epithelial cells are discussed.

The STE20 kinase TAOK3 controls the development house dust mite-induced asthma in mice

BACKGROUND

The most common endotype of asthma is type 2-high asthma, which is sometimes driven by adaptive allergen-specific T_H2 lymphocytes that react to allergens presented by dendritic cells (DCs), or sometimes by an innate immune response dominated by type 2 innate lymphocytes (ILC2s). Understanding the underlying pathophysiology of asthma is essential to improve patient-tailored therapy. The STE20 kinase thousand-and-one kinase 3 (TAOK3) controls key features in the biology of DCs and lymphocytes, but to our knowledge, its potential usefulness as a target for asthma therapy has not yet been addressed.

OBJECTIVE

We examined if and how loss of Taok3 affects the development of house dust mite (HDM)-driven allergic asthma in an in vivo mouse model.

METHODS

Wild-type Taok3^+/+ and gene-deficient Taok3^-/- mice were sensitized and challenged with HDM, and bronchoalveolar lavage fluid composition, mediastinal lymph node cytokine production, lung histology, and bronchial hyperreactivity measured. Conditional Taok3^fl/fl mice were crossed to tissue- and cell-specific specific deletor Cre mice to understand how Taok3 acted on asthma susceptibility. Kinase-dead (KD) Taok3^KD mice were generated to probe for the druggability of this pathway. Activation of HDM-specific T cells was measured in adoptively transferred HDM-specific T-cell receptor-transgenic CD4⁺ T cells. ILC2 biology was assessed by in vivo and in vitro IL-33 stimulation assays in Taok3^-/- and Taok3^+/+, Taok3^KD, and Red5-Cre Taok3^fl/fl mice.

RESULTS

Taok3^-/- mice failed to mount salient features of asthma, including airway eosinophilia, T_H2 cytokine production, IgE secretion, airway goblet cell metaplasia, and bronchial hyperreactivity compared to controls. This was due to intrinsic loss of Taok3 in hematopoietic and not epithelial cells. Loss of Taok3 resulted in hampered HDM-induced lung DC migration to the draining lymph nodes and defective priming of HDM-specific T_H2 cells. Strikingly, HDM and IL-33-induced ILC2 proliferation and function were also severely affected in Taok3-deficient and Taok3^KD mice.

CONCLUSIONS

Absence of Taok3 or loss of its kinase activity protects from HDM-driven allergic asthma as a result of defects in both adaptive DC-mediated T_H2 activation and innate ILC2 function. This identifies Taok3 as an interesting drug target, justifying further testing as a new treatment for type 2-high asthma.

The Functional DNA Methylation Signatures Relevant to Altered Immune Response of Neonatal T Cells with l-Arginine Supplementation

l-Arginine is an important nutrient in the infant diet that significantly regulates the maturation of the immune system in neonates, including the maturation of CD4⁺ T cells. The biological activities of CD4⁺ T cells differ substantially between neonates and adults, and these differences may be governed by epigenetic processes. Investigating these differences and the causative processes may help understand neonatal and developmental immunity. In this study, we compared the functional DNA methylation profiles in CD4⁺ T cells of neonates and adults, focusing on the role of l-arginine supplementation. Umbilical cord blood and adult CD4⁺ T cells were cultured with/without l-arginine treatment. By comparing DNA methylation in samples without l-arginine treatment, we found that CD4⁺ T cells of neonatal cord blood generally showed higher DNA methylation than those of adults (average CpG methylation percentage 0.6305 for neonate and 0.6254 for adult, t-test p-value < 0.0001), suggesting gene silencing in neonates. By examining DNA methylation patterns of CpG dinucleotides induced by l-arginine treatment, we found that more CpG dinucleotides were hypomethylated and more genes appeared to be activated in neonatal T-cells as compared with adult. Genes activated by l-arginine stimulation of cord blood samples were more enriched regarding immune-related pathways. CpG dinucleotides at IL-13 promoter regions were hypomethylated after l-arginine stimulation. Hypomethylated CpG dinucleotides corresponded to higher IL-13 gene expression and cytokine production. Thus, DNA methylation partially accounts for the mechanism underlying differential immune function in neonates. Modulatory effects of l-arginine on DNA methylation are gene-specific. Nutritional intervention is a potential strategy to modulate immune function of neonates.

Anti-Inflammatory and Anti-Allergic Effects of Saponarin and Its Impact on Signaling Pathways of RAW 264.7, RBL-2H3, and HaCaT Cells

Saponarin{5-hydroxy-2-(4-hydroxyphenyl)-6-[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]-7-[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxychromen-4-one}, a flavone found in young green barley leaves, is known to possess antioxidant, antidiabetic, and hepatoprotective effects. In the present study, the anti-inflammatory, anti-allergic, and skin-protective effects of saponarin were investigated to evaluate its usefulness as a functional ingredient in cosmetics. In lipopolysaccharide-induced RAW264.7 (murine macrophage) cells, saponarin (80 μM) significantly inhibited cytokine expression, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, inducible nitric oxide synthase, and cyclooxygenase (COX)-2. Saponarin (80 μM) also inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 involved in the mitogen-activated protein kinase signaling pathway in RAW264.7 cells. Saponarin (40 μM) significantly inhibited β-hexosaminidase degranulation as well as the phosphorylation of signaling effectors (Syk, phospholipase Cγ1, ERK, JNK, and p38) and the expression of inflammatory mediators (tumor necrosis factor [TNF]-α, IL-4, IL-5, IL-6, IL-13, COX-2, and FcεRIα/γ) in DNP-IgE- and DNP-BSA-stimulated RBL-2H3 (rat basophilic leukemia) cells. In addition, saponarin (100 μM) significantly inhibited the expression of macrophage-derived chemokine, thymus and activation-regulated chemokine, IL-33, thymic stromal lymphopoietin, and the phosphorylation of signaling molecules (ERK, p38 and signal transducer and activator of transcription 1 [STAT1]) in TNF-α- and interferon (IFN)-γ-stimulated HaCaT (human immortalized keratinocyte) cells. Saponarin (100 μM) also significantly induced the expression of hyaluronan synthase-3, aquaporin 3, and cathelicidin antimicrobial peptide (LL-37) in HaCaT cells, which play an important role as skin barriers. Saponarin remarkably inhibited the essential factors involved in the inflammatory and allergic responses of RAW264.7, RBL-2H3, and HaCaT cells, and induced the expression of factors that function as physical and chemical skin barriers in HaCaT cells. Therefore, saponarin could potentially be used to prevent and relieve immune-related skin diseases, including atopic dermatitis.

High Th2 cytokine levels and upper airway inflammation in human inherited T-bet deficiency

We have described a child suffering from Mendelian susceptibility to mycobacterial disease (MSMD) due to autosomal recessive, complete T-bet deficiency, which impairs IFN-γ production by innate and innate-like adaptive, but not mycobacterial-reactive purely adaptive, lymphocytes. Here, we explore the persistent upper airway inflammation (UAI) and blood eosinophilia of this patient. Unlike wild-type (WT) T-bet, the mutant form of T-bet from this patient did not inhibit the production of Th2 cytokines, including IL-4, IL-5, IL-9, and IL-13, when overexpressed in T helper 2 (Th2) cells. Moreover, Herpesvirus saimiri-immortalized T cells from the patient produced abnormally large amounts of Th2 cytokines, and the patient had markedly high plasma IL-5 and IL-13 concentrations. Finally, the patient's CD4+ αβ T cells produced most of the Th2 cytokines in response to chronic stimulation, regardless of their antigen specificities, a phenotype reversed by the expression of WT T-bet. T-bet deficiency thus underlies the excessive production of Th2 cytokines, particularly IL-5 and IL-13, by CD4+ αβ T cells, causing blood eosinophilia and UAI. The MSMD of this patient results from defective IFN-γ production by innate and innate-like adaptive lymphocytes, whereas the UAI and eosinophilia result from excessive Th2 cytokine production by adaptive CD4+ αβ T lymphocytes.

COL4A3 is degraded in allergic asthma and degradation predicts response to anti-IgE therapy

BACKGROUND

Asthma is a heterogeneous syndrome substantiating the urgent requirement for endotype-specific biomarkers. Dysbalance of fibrosis and fibrolysis in asthmatic lung tissue leads to reduced levels of the inflammation-protective collagen 4 (COL4A3).

OBJECTIVE

To delineate the degradation of COL4A3 in allergic airway inflammation and evaluate the resultant product as a biomarker for anti-IgE therapy response.

METHODS

The serological COL4A3 degradation marker C4Ma3 (Nordic Bioscience, Denmark) and serum cytokines were measured in the ALLIANCE cohort (pediatric cases/controls: 134/35; adult cases/controls: 149/31). Exacerbation of allergic airway disease in mice was induced by sensitising to OVA, challenge with OVA aerosol and instillation of poly(cytidylic-inosinic). Fulacimstat (chymase inhibitor, Bayer) was used to determine the role of mast cell chymase in COL4A3 degradation. Patients with cystic fibrosis (CF, n=14) and CF with allergic broncho-pulmonary aspergillosis (ABPA, n=9) as well as severe allergic, uncontrolled asthmatics (n=19) were tested for COL4A3 degradation. Omalizumab (anti-IgE) treatment was assessed by the Asthma Control Test.

RESULTS

Serum levels of C4Ma3 were increased in asthma in adults and children alike and linked to a more severe, exacerbating allergic asthma phenotype. In an experimental asthma mouse model, C4Ma3 was dependent on mast cell chymase. Serum C4Ma3 was significantly elevated in CF plus ABPA and at baseline predicted the success of the anti-IgE therapy in allergic, uncontrolled asthmatics (diagnostic odds ratio 31.5).

CONCLUSION

C4Ma3 level depend on lung mast cell chymase and are increased in a severe, exacerbating allergic asthma phenotype. C4Ma3 may serve as a novel biomarker to predict anti-IgE therapy response.

Pathological Roles and Clinical Usefulness of Periostin in Type 2 Inflammation and Pulmonary Fibrosis

Periostin is known to be a useful biomarker for various diseases. In this article, we focus on allergic diseases and pulmonary fibrosis, for which we and others are now developing detection systems for periostin as a biomarker. Biomarker-based precision medicine in the management of type 2 inflammation and fibrotic diseases since heterogeneity is of utmost importance. Periostin expression is induced by type 2 cytokines (interleukin-4/-13) or transforming growth factor-β, and plays a vital role in the pathogenesis of allergic inflammation or interstitial lung disease, respectively, andits serum levels are correlated disease severity, prognosis and responsiveness to the treatment. We first summarise the importance of type 2 biomarker and then describe the pathological role of periostin in the development and progression of type 2 allergic inflammation and pulmonary fibrosis. In addition, then, we summarise the recent development of assay methods for periostin detection, and analyse the diseases in which periostin concentration is elevated in serum and local biological fluids and its usefulness as a biomarker. Furthermore, we describe recent findings of periostin as a biomarker in the use of biologics or anti-fibrotic therapy. Finally, we describe the factors that influence the change in periostin concentration under the healthy conditions.

Psoralen inhibits the inflammatory response and mucus production in allergic rhinitis by inhibiting the activator protein 1 pathway and the downstream expression of cystatin‑SN

Psoralen (PSO) exerts anti-inflammatory pharmacological effects and plays an important role in a variety of inflammatory diseases. However, the effects of PSO with allergic rhinitis (AR) are yet to be reported. In the present study, an in vitro AR model was generated by inducing JME/CF15 human nasal epithelial cells with IL-13, after which MTT was used to assess the cytotoxicity of PSO. The expression levels of inflammatory cytokines (granulocyte-macrophage colony-stimulating factor and Eotaxin) were determined by ELISA. Furthermore, the expression of inflammatory IL-6 and −8, as well as mucin 5AC, was assessed by reverse transcription-quantitative PCR and western blotting, and cellular reactive oxygen species were detected using a 2′,7′-dichlorodihydrofluorescein diacetate fluorescent probe. Western blotting was also used to detect the expression and phosphorylation of c-Fos and c-Jun in the activator protein 1 (AP-1) pathway, as well as the expression of cystatin-SN (CST1). PSO inhibited the inflammatory response and mucus production in IL-13-induced JME/CF15 cells. Furthermore, the levels of c-Fos and c-Jun phosphorylation in the AP-1 pathway were decreased in IL-13-induced JME/CF15 cells following PSO treatment. The expression of pathway proteins was activated by the addition of PMA, an AP-1 pathway activator, which concurrently reversed the inhibitory effects of PSO on the inflammatory response and mucus formation. The addition of an AP-1 inhibitor (SP600125) further inhibited pathway activity, and IL-13-induced inflammation and mucus formation was restored. In conclusion, PSO regulates the expression of CST1 by inhibiting the AP-1 pathway, thus suppressing the IL-13-induced inflammatory response and mucus production in nasal mucosal epithelial cells.

Neutralization of IL-33 modifies the type 2 and type 3 inflammatory signature of viral induced asthma exacerbation

Background

Respiratory viral infections are one of the leading causes of need for emergency care and hospitalizations in asthmatic individuals, and airway-secreted cytokines are released within hours of viral infection to initiate these exacerbations. IL-33, specifically, contributes to these allergic exacerbations by amplifying type 2 inflammation. We hypothesized that blocking IL-33 in RSV-induced exacerbation would significantly reduce allergic inflammation.

Methods

Sensitized BALB/c mice were challenged with aerosolized ovalbumin (OVA) to establish allergic inflammation, followed by RSV-A2 infection to yield four treatment groups: saline only (Saline), RSV-infected alone (RSV), OVA alone (OVA), and OVA-treated with RSV infection (OVA-RSV). Lung outcomes included lung mRNA and protein markers of allergic inflammation, histology for mucus cell metaplasia and lung immune cell influx by cytospin and flow cytometry.

Results

While thymic stromal lymphopoietin (TSLP) and IL-33 were detected 6 h after RSV infection in the OVA-RSV mice, IL-23 protein was uniquely upregulated in RSV-infected mice alone. OVA-RSV animals varied from RSV- or OVA-treated mice as they had increased lung eosinophils, neutrophils, group 2 innate lymphoid cells (ILC2) and group 3 innate lymphoid cells (ILC3) detectable as early as 6 h after RSV infection. Neutralized IL-33 significantly reduced ILC2 and eosinophils, and the prototypical allergic proteins, IL-5, IL-13, CCL17 and CCL22 in OVA-RSV mice. Numbers of neutrophils and ILC3 were also reduced with anti-IL-33 treatment in both RSV and OVA-RSV treated animals as well.

Conclusions

Taken together, our findings indicate a broad reduction in allergic-proinflammatory events mediated by IL-33 neutralization in RSV-induced asthma exacerbation.

Yap/Taz inhibit goblet cell fate to maintain lung epithelial homeostasis

Proper lung function relies on the precise balance of specialized epithelial cells that coordinate to maintain homeostasis. Herein, we describe essential roles for the transcriptional regulators YAP/TAZ in maintaining lung epithelial homeostasis, reporting that conditional deletion of Yap and Wwtr1/Taz in the lung epithelium of adult mice results in severe defects, including alveolar disorganization and the development of airway mucin hypersecretion. Through in vivo lineage tracing and in vitro molecular experiments, we reveal that reduced YAP/TAZ activity promotes intrinsic goblet transdifferentiation of secretory airway epithelial cells. Global gene expression and chromatin immunoprecipitation sequencing (ChIP-seq) analyses suggest that YAP/TAZ act cooperatively with TEA domain (TEAD) transcription factors and the NuRD complex to suppress the goblet cell fate program, directly repressing the SPDEF gene. Collectively, our study identifies YAP/TAZ as critical factors in lung epithelial homeostasis and offers molecular insight into the mechanisms promoting goblet cell differentiation, which is a hallmark of many lung diseases.

Jia-Wei-Yu-Ping-Feng-San Attenuates Group 2 Innate Lymphoid Cell-Mediated Airway Inflammation in Allergic Asthma

The incidence of asthma has increased in recent decades. Although corticosteroids and bronchodilators are used in clinical practice, the control of asthma remains a challenge. Allergic asthma is characterized airway inflammation mediated by type 2 immune response. Group 2 innate lymphoid cells (ILC2s) are an important source of type 2 cytokines IL-5 and IL-13, which contribute to the progress of asthma. Jia-Wei-Yu-Ping-Feng-San (JWYPFS), a traditional Chinese medicine, has been widely used to treat asthma in China. In this study we investigated the mechanisms of JWYPFS in the treatment of asthma, especially the effect on ILC2s important in airway inflammation. Female C57BL/6 mice were sensitized and challenged with OVA to establish a model of allergic asthma. Airway hyperresponsiveness was examined by direct airway resistance analysis. Inflammatory cell counts were determined in bronchoalveolar lavage fluid (BALF). Inflammatory cell infiltration and mucus hypersecretion in lung tissue sections was observed by HE and PAS staining, respectively. The numbers and proportions of ILC2s as well as the ILC2s-related transcription factors GATA3, IRF4, and type 2 cytokines were measured in lung tissue samples. Additionally, ILC2s were collected from mouse lung; ILC2s-related cytokines and GATA3 and IRF4 were evaluated after IL-33-induced activation of ILC2s in vitro. Elevated inflammatory cells, mucus secretion, airway hyperresponsiveness and type 2 cytokines in the OVA-treated asthma group indicated that an allergic asthma model had been established. JWYPFS treatment attenuated airway resistance and reduced inflammatory cells including eosinophils, and inhibited mucus production and type 2 cytokines in these asthmatic mice. Moreover, JWYPFS treatment dramatically decreased the numbers and proportions of ILC2s and the mRNA levels of GATA3 and IRF4. In an in vitro experiment JWYPFS significantly suppressed GATA3, IRF4 and type 2 cytokine expression, including IL-5 and IL-13 in IL-33-stimulated ILC2s. JWYPFS alleviates ILC2s-mediated airway inflammation, suggesting that JWYPFS might be an effective agent to treat allergic asthma.

Targeting TL1A/DR3 Signaling Offers a Therapeutic Advantage to Neutralizing IL13/IL4Rα in Muco-Secretory Fibrotic Disorders

Mucus secretion is an important feature of asthma that highly correlates with morbidity. Current therapies, including administration of mucolytics and anti-inflammatory drugs, show limited effectiveness and durability, underscoring the need for novel effective and longer lasting therapeutic approaches. Here we show that mucus production in the lungs is regulated by the TNF superfamily member 15 (TL1A) acting through the mucus-inducing cytokine IL-13. TL1A induces IL13 expression by innate lymphoid cells leading to mucus production, in addition to promoting airway inflammation and fibrosis. Reciprocally, neutralization of IL13 signaling through its receptor (IL4Rα), completely reverses TL1A-induced mucus secretion, while maintaining airway inflammation and fibrosis. Importance of TL1A is further demonstrated using a preclinical asthma model induced by chronic house dust mite exposure where TL1A neutralization by genetic deletion or antagonistic blockade of its receptor DR3 protected against mucus production and fibrosis. Thus, TL1A presents a promising therapeutic target that out benefits IL13 in reversing mucus production, airway inflammation and fibrosis, cardinal features of severe asthma in humans.

Comparative analysis of the role of mast cells in murine asthma models using Kit-sufficient mast cell-deficient animals

BACKGROUND

Asthma is a frequent chronic disease that can potentially severely affect the respiratory capacity and well-being of patients. Mast cells (MCs) are regarded as major players in human asthma due to their capacity to release crucial inflammatory mediators following allergen exposure. However, unambiguous characterization of their role in animal models has long been hindered by the unavailability of specific MC-deficient models lacking confounding MC-unrelated effects. This study aims to examine the role of MCs in Kit-sufficient MC-deficient Cpa3^{Cre /+} mice.

METHODS

We used a variety of models of acute and chronic asthma employing distinct routes and regimes of sensitization. These sensitizations were done via the peritoneal cavity, the skin, or the lung. Additionally, different allergens, i.e. ovalbumin and house dust mite extract, were used.

RESULTS

Our results show that the absence of MCs had no impact on the severity of allergic airway inflammation in any of the tested mouse models, as measured by leukocyte infiltration in the airways, cytokine expression, antibody production, airway hyper-responsiveness and mucus production.

CONCLUSION

This indicates that MCs do not play a major role in murine allergic airway inflammation.

Comparative effects of capsaicin in chronic obstructive pulmonary disease and asthma (Review)

Chronic obstructive pulmonary disease (COPD) and asthma are chronic respiratory diseases with high prevalence and mortality that significantly alter the quality of life in affected patients. While the cellular and molecular mechanisms engaged in the development and evolution of these two conditions are different, COPD and asthma share a wide array of symptoms and clinical signs that may impede differential diagnosis. However, the distinct signaling pathways regulating cough and airway hyperresponsiveness employ the interaction of different cells, molecules, and receptors. Transient receptor potential cation channel subfamily V member 1 (TRPV1) plays a major role in cough and airway inflammation. Consequently, its agonist, capsaicin, is of substantial interest in exploring the cellular effects and regulatory pathways that mediate these respiratory conditions. Increasingly more studies emphasize the use of capsaicin for the inhalation cough challenge, yet the involvement of TRPV1 in cough, bronchoconstriction, and the initiation of inflammation has not been entirely revealed. This review outlines a comparative perspective on the effects of capsaicin and its receptor in the pathophysiology of COPD and asthma, underlying the complex entanglement of molecular signals that bridge the alteration of cellular function with the multitude of clinical effects.

Integrin α2β1 regulates collagen I tethering to modulate hyperresponsiveness in reactive airway disease models

Severe asthma remains challenging to manage and has limited treatment options. We have previously shown that targeting smooth muscle integrin α5β1 interaction with fibronectin can mitigate the effects of airway hyperresponsiveness by impairing force transmission. In this study, we show that another member of the integrin superfamily, integrin α2β1, is present in airway smooth muscle and capable of regulating force transmission via cellular tethering to the matrix protein collagen I and, to a lesser degree, laminin-111. The addition of an inhibitor of integrin α2β1 impaired IL-13-enhanced contraction in mouse tracheal rings and human bronchial rings and abrogated the exaggerated bronchoconstriction induced by allergen sensitization and challenge. We confirmed that this effect was not due to alterations in classic intracellular myosin light chain phosphorylation regulating muscle shortening. Although IL-13 did not affect surface expression of α2β1, it did increase α2β1-mediated adhesion and the level of expression of an activation-specific epitope on the β1 subunit. We developed a method to simultaneously quantify airway narrowing and muscle shortening using 2-photon microscopy and demonstrated that inhibition of α2β1 mitigated IL-13-enhanced airway narrowing without altering muscle shortening by impairing the tethering of muscle to the surrounding matrix. Our data identified cell matrix tethering as an attractive therapeutic target to mitigate the severity of airway contraction in asthma.

Mucus, Microbiomes and Pulmonary Disease

The respiratory tract harbors a stable and diverse microbial population within an extracellular mucus layer. Mucus provides a formidable defense against infection and maintaining healthy mucus is essential to normal pulmonary physiology, promoting immune tolerance and facilitating a healthy, commensal lung microbiome that can be altered in association with chronic respiratory disease. How one maintains a specialized (healthy) microbiome that resists significant fluctuation remains unknown, although smoking, diet, antimicrobial therapy, and infection have all been observed to influence microbial lung homeostasis. In this review, we outline the specific role of polymerizing mucin, a key functional component of the mucus layer that changes during pulmonary disease. We discuss strategies by which mucin feed and spatial orientation directly influence microbial behavior and highlight how a compromised mucus layer gives rise to inflammation and microbial dysbiosis. This emerging field of respiratory research provides fresh opportunities to examine mucus, and its function as predictors of infection risk or disease progression and severity across a range of chronic pulmonary disease states and consider new perspectives in the development of mucolytic treatments.

Intrauterine growth restriction predisposes to airway inflammation without disruption of epithelial integrity in postnatal male mice

Evidence from animal models demonstrate that intrauterine growth restriction (IUGR) alters airway structure and function which may affect susceptibility to disease. Airway inflammation and dysregulated epithelial barrier properties are features of asthma which have not been examined in the context of IUGR. This study used a maternal hypoxia-induced IUGR mouse model to assess lung-specific and systemic inflammation and airway epithelial tight junctions (TJs) protein expression. Pregnant BALB/c mice were housed under hypoxic conditions (10.5% O2) from gestational day (GD) 11 to 17.5 (IUGR group; term, GD 21). Following hypoxic exposure, mice were returned to a normoxic environment (21% O2). A Control group was housed under normoxic conditions throughout pregnancy. Offspring weights were recorded at 2 and 8 weeks of age and euthanized for bronchoalveolar lavage (BAL) and peritoneal cavity fluid collection for inflammatory cells counts. From a separate group of mice, right lungs were collected for Western blotting of TJs proteins. IUGR offspring had greater inflammatory cells in the BAL fluid but not in peritoneal fluid compared with Controls. At 8 weeks of age, interleukin (IL)-2, IL-13, and eotaxin concentrations were higher in male IUGR compared with male Control offspring but not in females. IUGR had no effect on TJs protein expression. Maternal hypoxia-induced IUGR increases inflammatory cells in the BAL fluid of IUGR offspring with no difference in TJs protein expression. Increased cytokine release, specific to the lungs of IUGR male offspring, indicates that both IUGR and sex can influence susceptibility to airway disease.

Investigation of Active Anti-Inflammatory Constituents of Essential Oil from Pinus koraiensis (Sieb. et Zucc.) Wood in LPS-Stimulated RBL-2H3 Cells

In a previous study, we demonstrated the anti-inflammatory activity of the essential oil extracted from Korean pine (Pinus koraiensis, Sieb. et Zucc.) wood. This study aims to investigate the active anti-inflammatory constituents of P. koraiensis oil. The essential oil was extracted from P. koraiensis wood by hydrodistillation and was divided into six fractions (A-F) through fractional distillation. Then, the anti-inflammatory activities of the fractions (A-F) were determined. Fractions A and F markedly downregulated the production of pro-inflammatory cytokines as well as the secretion of β-hexosaminidase in lipopolysaccharide (LPS)-stimulated RBL-2H3 cells. The main constituents of the active anti-inflammatory A and F fractions were (+)-α-pinene, (-)-β-pinene, (+)-α-terpineol, 3-carene, (+)-limonene, and longifolene. These six single compounds decreased the expression of inflammatory-related genes (i.e., IL-4 and IL-13) as well as the secretion of β-hexosaminidase in LPS-stimulated RBL-2H3 cells. (+)-α-Pinene, (-)-β-pinene, (+)-α-terpineol, and longifolene exhibited the strongest effects; these effects were comparable to those of the positive control (i.e., dexamethasone). The findings indicate that the interactions between these components exhibit potential for the management and/or treatment of inflammatory conditions as well as base structures for the development of novel anti-inflammatory drugs.

The proprotein convertase furin inhibits IL-13-induced inflammation in airway smooth muscle by regulating integrin-associated signaling complexes

Furin is a proprotein convertase that regulates the activation and the inactivation of multiple proteins including matrix metalloproteinases, integrins, and cytokines. It is a serine endoprotease that localizes to the plasma membrane and can be secreted into the extracellular space. The role of furin in regulating inflammation in isolated canine airway smooth muscle tissues was investigated. The treatment of airway tissues with recombinant furin (rFurin) inhibited the activation of Akt and eotaxin secretion induced by IL-13, and it prevented the IL-13-induced suppression of smooth muscle myosin heavy chain expression. rFurin promoted a differentiated phenotype by activating β₁-integrin proteins and stimulating the activation of the adhesome proteins vinculin and paxillin by talin. Activated paxillin induced the binding of Akt to β-parvin IPP [integrin-linked kinase (ILK), PINCH, parvin] complexes, which inhibits Akt activation. Treatment of tissues with a furin inhibitor or the depletion of endogenous furin using shRNA resulted in Akt activation and inflammatory responses similar to those induced by IL-13. Furin inactivation or IL-13 caused talin cleavage and integrin inactivation, resulting in the inactivation of vinculin and paxillin. Paxillin inactivation resulted in the coupling of Akt to α-parvin IPP complexes, which catalyze Akt activation and an inflammatory response. The results demonstrate that furin inhibits inflammation in airway smooth muscle induced by IL-13 and that the anti-inflammatory effects of furin are mediated by activating integrin proteins and integrin-associated signaling complexes that regulate Akt-mediated pathways to the nucleus. Furin may have therapeutic potential for the treatment of inflammatory conditions of the lungs and airways.

Novel Anti-Cytokine Strategies for Prevention and Treatment of Respiratory Allergic Diseases

Asthma is a heterogeneous inflammatory disease characterized by airflow obstruction, wheezing, eosinophilia and neutrophilia of the airways. Identification of distinct inflammatory patterns characterizing asthma endotypes led to the development of novel therapeutic approaches. Cytokine or cytokine receptor targeting by therapeutic antibodies, such as anti-IL-4 and anti-IL-5, is now approved for severe asthma treatment. However, the complexity of cytokine networks in asthma should not be underestimated. Inhibition of one pro-inflammatory cytokine may lead to perturbed expression of another pro-inflammatory cytokine. Without understanding of the underlying mechanisms and defining the molecular predictors it may be difficult to control cytokine release that accompanies certain disease manifestations. Accumulating evidence suggests that in some cases a combined pharmacological inhibition of pathogenic cytokines, such as simultaneous blockade of IL-4 and IL-13 signaling, or blockade of upstream cytokines, such as TSLP, are more effective than single cytokine targeting. IL-6 and TNF are the important inflammatory mediators in the pathogenesis of asthma. Preliminary data suggests that combined pharmacological inhibition of TNF and IL-6 during asthma may be more efficient as compared to individual neutralization of these cytokines. Here we summarize recent findings in the field of anti-cytokine therapy of asthma and discuss immunological mechanisms by which simultaneous targeting of multiple cytokines as opposed to targeting of a single cytokine may improve disease outcomes.

VEGF receptor 2 (KDR) protects airways from mucus metaplasia through a Sox9-dependent pathway

Mucus-secreting goblet cells are the dominant cell type in pulmonary diseases, e.g., asthma and cystic fibrosis (CF), leading to pathologic mucus metaplasia and airway obstruction. Cytokines including IL-13 are the major players in the transdifferentiation of club cells into goblet cells. Unexpectedly, we have uncovered a previously undescribed pathway promoting mucous metaplasia that involves VEGFa and its receptor KDR. Single-cell RNA sequencing analysis coupled with genetic mouse modeling demonstrates that loss of epithelial VEGFa, KDR, or MEK/ERK kinase promotes excessive club-to-goblet transdifferentiation during development and regeneration. Sox9 is required for goblet cell differentiation following Kdr inhibition in both mouse and human club cells. Significantly, airway mucous metaplasia in asthmatic and CF patients is also associated with reduced KDR signaling and increased SOX9 expression. Together, these findings reveal an unexpected role for VEGFa/KDR signaling in the defense against mucous metaplasia, offering a potential therapeutic target for this common airway pathology.

G Protein-Coupled Receptor Kinase 2 (GRK2) Regulates T Cell Response in a Murine Model of House Dust Mite-Induced Asthma

G protein-coupled receptor kinase 2 (GRK2) is an adapter protein that modulates G protein-coupled receptor (GPCR) signaling. It also regulates the functions and activity of other intracellular proteins in many cell types. Accordingly, GRK2 is thought to contribute to disease progression by a variety of mechanisms related to its multifunctional roles. Indeed, GRK2 levels are enhanced in patient samples as well as in preclinical models of several diseases. We have previously shown that GRK2 regulates mast cell functions, and thereby contributes to exacerbated inflammation during allergic reactions. In the current study, we observed that GRK2 levels are enhanced in the lungs of human asthma patients and in mice sensitized to house dust mite extract (HDME) allergen. Consistent with these findings, interleukin (IL)-4 and IL-13 levels were reduced in the lungs of GRK2+/- mice in a HMDE mouse model of asthma. Because Th2 cells are the major source of these cytokines during asthma, we determined the role of GRK2 in regulating T cell-specific responses in our HMDE mouse model. We observed a significant reduction of airway hyperresponsiveness (AHR), lung eosinophil and lymphocyte counts, serum IgE, Th2 cytokines (IL-4 and IL-13), goblet cell hyperplasia and mucus production in mice that had reduced GRK2 expression specifically in T cells. Collectively, our studies reveal an important role for GRK2 in regulating T cell response during asthma pathogenesis and further elucidation of the mechanisms through which GRK2 modulates airway inflammation will lead to the development of new therapeutic strategies for asthma.

Cytokines Involved in the Pathogenesis of SSc and Problems in the Development of Anti-Cytokine Therapy

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology. SSc causes damage to the skin and various organs including the lungs, heart, and digestive tract, but the extent of the damage varies from patient to patient. The pathology of SSc includes ischemia, inflammation, and fibrosis, but the degree of progression varies from case to case. Many cytokines have been reported to be involved in the pathogenesis of SSc: interleukin-6 is associated with inflammation and transforming growth factor-β and interleukin-13 are associated with fibrosis. Therapeutic methods to control these cytokines have been proposed; however, which cytokines have a dominant role in SSc might differ depending on the extent of visceral lesions and the stage of disease progression. Therefore, it is necessary to consider the disease state of the patient to be targeted and the type of evaluation method when an anti-cytokine therapy is conducted. Here, we review the pathology of SSc and potential cytokine targets, especially interleukin-6, as well as the use of anti-cytokine therapy for SSc.

The axis of the receptor for advanced glycation endproducts in asthma and allergic airway disease

Asthma is a generalized term that describes a scope of distinct pathologic phenotypes of variable severity, which share a common complication of reversible airflow obstruction. Asthma is estimated to affect almost 400 million people worldwide, and nearly ten percent of asthmatics have what is considered "severe" disease. The majority of moderate to severe asthmatics present with a "type 2-high" (T2-hi) phenotypic signature, which pathologically is driven by the type 2 cytokines Interleukin-(IL)-4, IL-5, and IL-13. However, "type 2-low" (T2-lo) phenotypic signatures are often associated with more severe, steroid-refractory neutrophilic asthma. A wide range of clinical and experimental studies have found that the receptor for advanced glycation endproducts (RAGE) plays a significant role in the pathogenesis of asthma and allergic airway disease (AAD). Current experimental data indicates that RAGE is a critical mediator of the type 2 inflammatory reactions which drive the development of T2-hi AAD. However, clinical studies demonstrate that increased RAGE ligands and signaling strongly correlate with asthma severity, especially in severe neutrophilic asthma. This review presents an overview of the current understandings of RAGE in asthma pathogenesis, its role as a biomarker of disease, and future implications for mechanistic studies, and potential therapeutic intervention strategies.

Repeated exposure of house dust mite induces progressive airway inflammation in mice: Differential roles of CCL17 and IL-13

We conducted a systematic evaluation of lung inflammation indued by repeated intranasal exposure (for 10 consecutive days) to a human aeroallergen, house dust mite (HDM) in BALB/c mice. Peak influx of neutrophils, monocytes/lymphocytes, and eosinophils was observed in bronchoalveolar lavage (BAL) on days 1, 7 and 11, respectively, and normalized to baseline by day 21. Peak elevations of Th2, myeloid-derived cytokines/chemokines and serum IgE were seen both in BAL and lung tissue homogenates between days 7 and 11, and declined thereafter; however, IL-33 levels remained elevated from day 7 to day 21. Airway hyperreactivity to inhaled methacholine was significantly increased by day 11 and decreased to baseline by day 21. The lung tissue showed perivascular and peribronchial cuffing, epithelial hypertrophy and hyperplasia and goblet cell formation in airways by day 11, and resolution by day 21. Levels of soluble collagen and tissue inhibitors of metalloproteinases (TIMP) also increased reflecting tissue remodeling in the lung. Microarray analysis demonstrated a significant time-dependent up-regulation of several genes including IL-33, CLCA3, CCL17, CD4, CD10, CD27, IL-13, Foxa3, IL-4, IL-10, and CD19, in BAL cells as well as the lung. Pre-treatment of HDM challenged mice with CCL17 and IL-13 antibodies reduced BAL cellularity, airway hyper-responsiveness (AHR), and histopathological changes. Notably, anti-IL-13, but not anti-CCL17 monoclonal antibodies (mAbs) reduced BAL neutrophilia while both mAbs attenuated eosinophilia. These results suggest that CCL17 has an overlapping, yet distinct profile versus IL-13 in the HDM model of pulmonary inflammation and potential for CCL17-based therapeutics in treating Th2 inflammation.

The development of an in vitro 3D model of goblet cell hyperplasia using MUC5AC expression and repeated whole aerosol exposures

Goblet cell hyperplasia and overproduction of airway mucin are characteristic features of the lung epithelium of smokers and COPD patients. Tobacco heating products (THPs) are a potentially less risky alternative to combustible cigarettes, and through continued use solus THPs may reduce smoking-related disease risk. Using the MucilAir™ in vitro lung model, a 6-week feasibility study was conducted investigating the effect of repeated cigarette smoke (1R6F), THP aerosol and air exposure. Tissues were exposed to nicotine-matched whole aerosol doses 3 times/week. Endpoints assessed were dosimetry, tight-junction integrity, cilia beat frequency (CBF) and active area (AA), cytokine secretion and airway mucin MUC5AC expression. Comparison of incubator and air exposed controls indicated exposures did not have a significant effect on the transepithelial electrical resistance (TEER), CBF and AA of the tissues. Cytokine secretion indicated clear differences in secretion patterns in response to 1R6F and THP exposure. 1R6F exposure resulted in a significant decrease in the TEER and AA (p=0.000 and p=0.000, respectively), and an increase in MUC5AC positive cells (p=0.002). Repeated THP exposure did not result in a significant change in MUC5AC positive cells. This study demonstrates repeated cigarette smoke whole aerosol exposure can induce these morphological changes in vitro.

Gentiopicroside ameliorates ovalbumin-induced airway inflammation in a mouse model of allergic asthma via regulating SIRT1/NF-κB signaling pathway

Allergic asthma is a common airway inflammatory disorder with increasing morbidity and mortality worldwide. Gentiopicroside (GPS) is a secoiridoid glycoside compound that exhibits anti-inflammatory property. However, the effect of GPS on allergic asthma has not been reported yet. In this study, we investigated the role of GPS in a mouse model of ovalbumin (OVA)-induced allergic asthma and explored its potential mechanism. Mice were sensitized with OVA and gavaged with 20, 40, or 80 mg/kg GPS. Administration of GPS decreased lung wet-to-dry weight ratio. Histological analysis of H&E and PAS staining showed that GPS treatment alleviated inflammatory cell infiltration and goblet cell hyperplasia in lung tissue of OVA-sensitized mice. Moreover, GPS inhibited the recruitment of inflammatory cells including total cells, macrophages, eosinophils, lymphocytes and neutrophils and the secretion of T helper type 2 (Th2) cytokines (interleukin (IL)-4, IL-5 and IL-13) in bronchoalveolar lavage fluid (BALF) of OVA-sensitized mice in a dose dependent manner. The levels of OVA-specific immunoglobulin E (IgE) and pro-inflammatory tumor necrosis factor (TNF)-α were also attenuated by GPS treatment. Interestingly, GPS upregulated the expression of silent information regulator 1 (SIRT1) while downregulated the expression of acetyl-nuclear factor kappa B (NF-κB) p65 in lung tissue of OVA-sensitized mice. Furthermore, treatment with an SIRT1 inhibitor (EX-527) partially abolished the inhibitory effect of GPS on OVA-induced airway inflammation, suggesting that the anti-inflammation of GPS might be achieved through regulating SIRT1/NF-κB p65 signaling pathway. These findings indicate that GPS might be a novel drug candidate in the treatment of allergic asthma.

T helper 2-driven immune dysfunction in chronic arsenic-exposed individuals and its link to the features of allergic asthma

Limited information is available regarding the effects of arsenic exposure on immune function. We have recently reported that chronic exposure to As was associated asthma, as determined by spirometry and respiratory symptoms. Because T helper 2 (Th2)-driven immune responses are implicated in the pathogenesis of allergic diseases, including asthma, we studied the associations of serum Th1 and Th2 mediators with the As exposure markers and the features of asthma among individuals exposed to As. A total of 553 blood samples were selected from the same study subjects recruited in our previous asthma study. Serum levels of Th1 and Th2 cytokines were analyzed by immunoassay. Subjects' arsenic exposure levels (drinking water, hair and nail arsenic concentrations) were determined by inductively coupled plasma mass spectroscopy. Arsenic exposure levels of the subjects showed significant positive associations with serum Th2-mediators- interleukin (IL)-4, IL-5, IL-13, and eotaxin without any significant changes in Th1 mediators- interferon-γ and tumor necrosis factor-α. The ratios of Th2 to Th1 mediators were significantly increased with increasing exposure to As. Notably, most of the Th2 mediators were positively associated with serum levels of total immunoglobulin E and eotaxin. The serum levels of Th2 mediators were significantly higher in the subjects with asthma than those without asthma. The results of our study suggest that the exacerbated Th2-driven immune responses are involved in the increased susceptibility to allergic asthma among individuals chronically exposed to As.

Regulation of Eosinophilia in Asthma-New Therapeutic Approaches for Asthma Treatment

Asthma is a complex and chronic inflammatory disease of the airways, characterized by variable and recurring symptoms, reversible airflow obstruction, bronchospasm, and airway eosinophilia. As the pathophysiology of asthma is becoming clearer, the identification of new valuable drug targets is emerging. IL-5 is one of these such targets because it is the major cytokine supporting eosinophilia and is responsible for terminal differentiation of human eosinophils, regulating eosinophil proliferation, differentiation, maturation, migration, and prevention of cellular apoptosis. Blockade of the IL-5 pathway has been shown to be efficacious for the treatment of eosinophilic asthma. However, several other inflammatory pathways have been shown to support eosinophilia, including IL-13, the alarmin cytokines TSLP and IL-33, and the IL-3/5/GM-CSF axis. These and other alternate pathways leading to airway eosinophilia will be described, and the efficacy of therapeutics that have been developed to block these pathways will be evaluated.

MicroRNA Targets for Asthma Therapy

Asthma is a chronic inflammatory obstructive lung disease that is stratified into endotypes. Th2 high asthma is due to an imbalance of Th1/Th2 signaling leading to abnormally high levels of Th2 cytokines, IL-4, IL-5, and IL-13 and in some cases a reduction in type I interferons. Some asthmatics express Th2 low, Th1/Th17 high phenotypes with or without eosinophilia. Most asthmatics with Th2 high phenotype respond to beta-adrenergic agonists, muscarinic antagonists, and inhaled corticosteroids. However, 5-10% of asthmatics are not well controlled by these therapies despite significant advances in lung immunology and the pathogenesis of severe asthma. This problem is being addressed by developing novel classes of anti-inflammatory agents. Numerous studies have established efficacy of targeting pro-inflammatory microRNAs in mouse models of mild/moderate and severe asthma. Current approaches employ microRNA mimics and antagonists designed for use in vivo. Chemically modified oligonucleotides have enhanced stability in blood, increased cell permeability, and optimized target specificity. Delivery to lung tissue limits clinical applications, but it is a tractable problem. Future studies need to define the most effective microRNA targets and effective delivery systems. Successful oligonucleotide drug candidates must have adequate lung cell uptake, high target specificity, and efficacy with tolerable off-target effects.

B cells and upper airway disease: allergic rhinitis and chronic rhinosinusitis with nasal polyps evaluated

Introduction: The first mucosal site to encounter inhaled allergen, antigen, and microbes is the upper airway. It must perforce have a rapid system of environmental threat recognition and self-defense. B cells play a critical role in such airway host-defense, tissue surveillance, and immune modulation. Several common upper airway diseases can be defined in the expression of either exaggerated or dysregulated B-cell function within T2-high mucosal inflammatory states.Areas covered: In this review, the authors discuss the immunology of allergic rhinitis (AR) and chronic rhinosinusitis with nasal polyps (CRSwNP) in the context of highlighting key aspects of B-cell biology and function. The review is based on the findings of a literature search using the terms B cells, rhinitis, nasal polyps, and rhinosinusitis.Expert opinion: Despite the emerging role of B-cell overdrive and dysfunction in upper airway disease, studies are lacking specifics to B cells, particularly in association with sinonasal infection and mucosal inflammation. There is a pressing need to focus on how respiratory inflammation, alongside impaired or exaggerated B-cell function, amplifies and further dysregulates immune signaling pathways in the disease setting of AR and CRSwNP.

Uridine diphosphate-glucose/P2Y14R axis is a nonchemokine pathway that selectively promotes eosinophil accumulation

Allergic asthma is a chronic inflammatory airway disease characterized by dysregulated type 2 immune responses, including degranulating airway eosinophils that induce tissue damage and airway hyperresponsiveness (AHR). The type 2 cytokines interleukin 5 (IL-5) and IL-13 and the eosinophil-specific chemokine CCL11/CCL24/CCL26 axis recruit, activate, and regulate eosinophils in the airways. In this issue of the JCI, Karcz et al. identified a mechanism involving the nucleotide sugar UDP-glucose (UDP-G) and the purinergic receptor P2Y14R in amplifying eosinophil accumulation in the lung. During type 2 inflammation, UDP-G activates P2Y14R on eosinophils, inducing the cells to move and migrate into the lung. Pharmacologically or genetically inhibiting P2Y14R on eosinophils attenuated eosinophil infiltration and AHR. Future experiments, including identifying additional type 2 factors regulating P2Y14R expression on lung eosinophils, are necessary to ascertain the impact of targeting P2Y14R as an alternative or adjunctive therapy to current type 2 biologics for the treatment of asthma.

Roles of phosphatidyl inositol 3 kinase gamma (PI3Kγ) in respiratory diseases

Phosphatidyl inositol 3 kinase gamma (PI3Kγ) is expressed in all the cell types that are involved in airway inflammation and disease, including not only leukocytes, but also structural cells, where it is expressed at very low levels under physiological conditions, while is significantly upregulated after stress. In the airways, PI3Kγ behaves as a trigger or a controller, depending on the pathological context. In this review, the contribution of PI3Kγ in a plethora of respiratory diseases, spanning from acute lung injury, pulmonary fibrosis, asthma, cystic fibrosis and response to both bacterial and viral pathogens, will be commented.

Targetable pathogenic mechanisms in nasal polyposis

Chronic rhinosinusitis with nasal polyps (CRSwNP) represents a challenging disease entity with significant rates of recurrence following appropriate medical and surgical therapy. Recent approval of targeted biologics in CRSwNP compels deeper understanding of underlying disease pathophysiology. Both of the approved biologics for CRSwNP modulate the type 2 inflammatory pathway, and the majority of drugs in the clinical trials pathway are similarly targeted. However, there remain multiple other pathogenic mechanisms relevant to CRSwNP for which targeted therapeutics already exist in other inflammatory diseases that have not been studied directly. In this article we summarize pathogenic mechanisms of interest in CRSwNP and discuss the results of ongoing clinical studies of targeted therapeutics in CRSwNP and other related human inflammatory diseases.

Double-Edged Sword: Interleukin-2 Promotes T Regulatory Cell Differentiation but Also Expands Interleukin-13- and Interferon-γ-Producing CD8+ T Cells via STAT6-GATA-3 Axis in Systemic Lupus Erythematosus

Interleukin-2 (IL-2) expands the depleted T regulatory (Treg) cell population, and it has emerged as a potential therapy in systemic lupus erythematosus (SLE). However, IL-2 administration may involve the risk of expanding unwanted pro-inflammatory cells. We herein studied the effects of IL-2 on pro-inflammatory cytokine production by CD4+ and CD8+ T cells in parallel with Treg development following CD3/CD28 co-stimulation. While Treg cells are depleted in SLE patients, their CD4+ T cells were poised to receive and activate IL-2 signaling as evidenced by upregulation of CD25 and enhanced IL-2-incued STAT5 phosphorylation during Treg differentiation. In patients with SLE, however, IL-2 also expanded CD8+ T cells capable of producing interleukin-5, interkeukin-13 (IL-13), and interferon-γ (IFN-γ) that occurred with enhanced expression of GATA-3 and phosphorylation of STAT6 but not STAT5. Our data pinpoint a safety signal for systemic administration of IL-2 and challenges a long-held conceptual platform of type 1 and 2 cytokine antagonism by newly documenting the IL-2-dependent development of IL-13 and IFN-γ double-positive (IL-13+IFNγ+) CD8+ T cells in SLE.

Chronic rhinosinusitis with nasal polyps is associated with impaired TMEM16A-mediated epithelial chloride secretion

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is one of the most common chronic disorders with limited therapeutic options. However, the pathogenesis of CRSwNP remains poorly understood.

OBJECTIVE

We sought to determine the role of abnormalities in nasal epithelial ion transport in primary epithelial cultures and patients with CRSwNP.

METHODS

We studied epithelial ion transport and transcript levels of the Cl^- channels cystic fibrosis transmembrane conductance regulator and transmembrane protein 16A (TMEM16A) in human primary nasal epithelial cultures of patients with CRSwNP and healthy controls. Furthermore, we determined expression levels of proinflammatory cytokines that have been implicated in the regulation of epithelial ion channels (IL-1β, INF-γ, TNF-α, IL-13) and studied effects of the key T_H2 signaling molecule IL-13 in CRSwNP and control nasal epithelial cultures. Finally, we measured in vivo nasal potential difference to compare epithelial ion transport in patients with CRSwNP and controls.

RESULTS

Bioelectric studies demonstrated that Ca²⁺-activated Cl^- secretion was reduced in CRSwNP versus control nasal epithelial cultures. Transcript levels of IL-13 and the Ca²⁺-activated Cl^- channel TMEM16A were increased in CRSwNP cultures. Stimulation with IL-13 increased TMEM16A expression further and restored Ca²⁺-activated Cl^- secretion in CRSwNP cultures. Nasal potential difference measurements demonstrated reduced Ca²⁺-activated Cl^- transport in patients with CRSwNP versus controls.

CONCLUSIONS

This study demonstrates that TMEM16A-mediated Ca²⁺-activated Cl^- secretion is reduced in primary nasal epithelial cultures and nasal epithelia of patients with CRSwNP. Our data suggest that the Ca²⁺-activated Cl^- channel TMEM16A may be implicated in the pathogenesis and serve as a novel therapeutic target in patients with CRSwNP.

Novel Strategies to Target Mast Cells in Disease

Mast cells (MCs) are versatile effector cells of the immune system, characterized by a large content of secretory granules containing a variety of inflammatory mediators. They are implicated in the host protection toward various external insults, but are mostly well known for their detrimental impact on a variety of pathological conditions, including allergic disorders such as asthma and a range of additional disease settings. Based on this, there is currently a large demand for therapeutic regimens that can dampen the detrimental impact of MCs in these respective pathological conditions. This can be accomplished by several strategies, including targeting of individual mediators released by MCs, blockade of receptors for MC-released compounds, inhibition of MC activation, limiting mast cell growth or by inducing mast cell apoptosis. Here, we review the currently available and emerging regimens to interfere with harmful mast cell activities in asthma and other pathological settings and discuss the advantages and limitations of such strategies.

Modulating Th2 Cell Immunity for the Treatment of Asthma

It is estimated that more than 339 million people worldwide suffer from asthma. The leading cause of asthma development is the breakdown of immune tolerance to inhaled allergens, prompting the immune system's aberrant activation. During the early phase, also known as the sensitization phase, allergen-specific T cells are activated and become central players in orchestrating the subsequent development of allergic asthma following secondary exposure to the same allergens. It is well-established that allergen-specific T helper 2 (Th2) cells play central roles in developing allergic asthma. As such, 80% of children and 60% of adult asthma cases are linked to an unwarranted Th2 cell response against respiratory allergens. Thus, targeting essential components of Th2-type inflammation using neutralizing antibodies against key Th2 modulators has recently become an attractive option for asthmatic patients with moderate to severe symptoms. In addition to directly targeting Th2 mediators, allergen immunotherapy, also known as desensitization, is focused on redirecting the allergen-specific T cells response from a Th2-type profile to a tolerogenic one. This review highlights the current understanding of the heterogeneity of the Th2 cell compartment, their contribution to allergen-induced airway inflammation, and the therapies targeting the Th2 cell pathway in asthma. Further, we discuss available new leads for successful targeting pulmonary Th2 cell responses for future therapeutics.

Immunosensation: Neuroimmune Cross Talk in the Skin

Classically, skin was considered a mere structural barrier protecting organisms from a diversity of environmental insults. In recent decades, the cutaneous immune system has become recognized as a complex immunologic barrier involved in both antimicrobial immunity and homeostatic processes like wound healing. To sense a variety of chemical, mechanical, and thermal stimuli, the skin harbors one of the most sophisticated sensory networks in the body. However, recent studies suggest that the cutaneous nervous system is highly integrated with the immune system to encode specific sensations into evolutionarily conserved protective behaviors. In addition to directly sensing pathogens, neurons employ novel neuroimmune mechanisms to provide host immunity. Therefore, given that sensation underlies various physiologies through increasingly complex reflex arcs, a much more dynamic picture is emerging of the skin as a truly systemic organ with highly coordinated physical, immunologic, and neural functions in barrier immunology.

Chronic inflammation involves CCL11 and IL-13 to facilitate the development of liver cirrhosis and fibrosis in chronic hepatitis B virus infection

The pathogenesis involving non-alcoholic fatty liver disease (NAFLD) in the context of chronic HBV (CHB) virus infection requires to be understood for developing improved modalities of diagnosis and treatment. We retrospectively investigated the association between NAFLD and CHB virus infection in the context of liver fibrosis. Among the 522 consecutive CHB patients who underwent transient elastography between years 2013 and 2016, we studied 455 subjects in the current investigation. Controlled attenuation parameter (CAP) and liver stiffness measurement (LSM) scores were generally higher in patients with steatosis and fibrosis or cirrhosis. Antiviral treatment had significantly reduced the hepatitis B virus (HBV) viral load. Other liver function markers showed a significant positive correlation with both CAP and LSM scores. Plasma IL-13 was independently associated with increased CAP score where every increase of 1 unit of IL-13 was associated with an increase in CAP score by 0.98 unit. CCL11 was independently associated with LSM with every increase of CCL11 by a unit that, in turn, was associated with an increase of LSM score. We found that there was a high concurrence of NAFLD among patients with CHB virus infection. The presence of metabolic syndrome and chronic inflammation in CHB virus-infected patients were two independent factors that led to the progression of liver cirrhosis, with IL-13 playing the key role in linking the metabolic with the inflammatory components.

A Selective α7 Nicotinic Acetylcholine Receptor Agonist, PNU-282987, Attenuates ILC2s Activation and Alternaria-Induced Airway Inflammation

Background

The anti-inflammatory effect of an α7nAChR agonist, PNU-282987, has previously been explored in the context of inflammatory disease. However, the effects of PNU-282987 on type 2 innate lymphoid cells (ILC2s)-mediated allergic airway inflammation has not yet been established.

Aims

To determine the effects of PNU-282987 on the function of ILC2s in the context of IL-33– or Alternaria Alternata (AA)– induced airway inflammation.

Methods

PNU-282987 was administered to mice that received recombinant IL-33 or AA intranasal challenges. Lung histological analysis and flow cytometry were performed to determine airway inflammation and the infiltration and activation of ILC2s. The previously published α7nAChR agonist GTS-21 was employed as a comparable reagent. ILC2s were isolated from murine lung tissue and cultured in vitro in the presence of IL-33, IL-2, and IL-7 with/without either PNU-282987 or GTS-21. The expression of the transcription factors GATA3, IKK, and NF-κB were also determined.

Results

PNU-282987 and GTS-21 significantly reduced goblet cell hyperplasia in the airway, eosinophil infiltration, and ILC2s numbers in BALF, following IL-33 or AA challenge. In vitro IL-33 stimulation of isolated lung ILC2s showed a reduction of GATA3 and Ki67 in response to PNU-282987 or GTS-21 treatments. There was a significant reduction in IKK and NF-κB phosphorylation in the PNU-282987–treated group when compared to the GTS-21–treated ILC2s.

Conclusion

PNU-282987 inhibits ILC2-associated airway inflammation, where its effects were comparable to that of GTS-21.

Single-cell transcriptomic analysis reveals the immune landscape of lung in steroid-resistant asthma exacerbation

Exaggerated airway hyperresponsiveness and inflammation are hallmarks of asthma, and lipopolysaccharide (LPS) exposure is linked to the severity of the disease and steroid resistance. To investigate the mechanisms underlying asthma exacerbation, we established a mouse model of LPS-induced steroid-resistant exacerbation on the background of house dust mite (HDM)-induced asthma to profile the immune cells in lung by using single-cell RNA deep sequencing. Twenty immune subsets were identified by their molecular and functional properties. Specific cell clusters of basophils, type 2 innate lymphoid cells (ILC2), and CD8+ memory T cells were the predominant sources of interleukin (IL)-4 and IL-13 transcripts whose expressions were dexamethasone resistant. Production of IL-13 by these cells was validated by IL-13-reporter mice. Neutralization of IL-13 abolished HDM/LPS-induced airway hyperresponsiveness, airway inflammation, and decreased mucus hypersecretion. Furthermore, using Ingenuity Pathway Analysis systems, we identified canonical pathways and upstream regulators that regulate the activation of basophils, ILC2, and CD8+ memory T cells. Our study provides mechanistic insights and an important reference resource for further understanding of the immune landscape during asthma exacerbation.

Immunopathobiology and therapeutic targets related to cytokines in liver diseases

Chronic liver injury with any etiology can progress to fibrosis and the end-stage diseases cirrhosis and hepatocellular carcinoma. The progression of liver disease is controlled by a variety of factors, including liver injury, inflammatory cells, inflammatory mediators, cytokines, and the gut microbiome. In the current review, we discuss recent data on a large number of cytokines that play important roles in regulating liver injury, inflammation, fibrosis, and regeneration, with a focus on interferons and T helper (Th) 1, Th2, Th9, Th17, interleukin (IL)-1 family, IL-6 family, and IL-20 family cytokines. Hepatocytes can also produce certain cytokines (such as IL-7, IL-11, and IL-33), and the functions of these cytokines in the liver are briefly summarized. Several cytokines have great therapeutic potential, and some are currently being tested as therapeutic targets in clinical trials for the treatment of liver diseases, which are also described.

Salt-inducible kinases are required for the IL-33-dependent secretion of cytokines and chemokines in mast cells

Cytokines and chemokines are important regulators of airway hyper-responsiveness, immune cell infiltration, and inflammation and are produced when mast cells are stimulated with interleukin-33 (IL-33). Here, we establish that the salt-inducible kinases (SIKs) are required for the IL-33-stimulated transcription of il13, gm-csf and tnf and hence the production of these cytokines. The IL-33-stimulated secretion of IL-13, granulocyte-macrophage colony stimulating factor, and tumor necrosis factor was strongly reduced in fetal liver-derived mast cells from mice expressing a kinase-inactive mutant of SIK3 and abolished in cells expressing kinase-inactive mutants of SIK2 and SIK3. The IL-33-dependent secretion of these cytokines and several chemokines was also abolished in SIK2/3 double knock-out bone marrow-derived mast cells (BMMC), reduced in SIK3 KO cells but little affected in BMMC expressing kinase-inactive mutants of SIK1 and SIK2 or lacking SIK2 expression. In SIK2 knock-out BMMC, the expression of SIK3 was greatly increased. Our studies identify essential roles for SIK2 and SIK3 in producing inflammatory mediators that trigger airway inflammation. The effects of SIKs were independent of IκB kinase β, IκB kinase β-mediated NF-κB-dependent gene transcription, and activation of the mitogen-activated protein kinase family members p38α and c-jun N-terminal kinases. Our results suggest that dual inhibitors of SIK2 and SIK3 may have therapeutic potential for the treatment of mast cell-driven diseases.

Deletion of IL-4Rα signaling on B cells limits hyperresponsiveness depending on antigen load

BACKGROUND

B cells play an important role in allergies through secretion of IgE. IL-4 receptor α (IL-4Rα) is key in allergic asthma and regulates type 2 cytokine production, IgE secretion, and airway hyperresponsiveness. IL-4 activation of B cells is essential for class switching and contributes to the induction of B effector 2 (Be2) cells. The role of Be2 cells and signaling via IL-4Rα in B cells is not clearly defined.

OBJECTIVE

We sought to find out whether IL-4Rα-responsive B cells or Be2 function was essential in experimental allergic asthma.

METHODS

Mice lacking IL-4Rα on B cells (mb1^creIL-4Rα^-/lox) or littermate controls (IL-4Rα^-/lox) and mice lacking IL-4 or IL-4/IL-13 on B cells were sensitized and challenged with high-dose house dust mite (>10 μg) or with low-dose house dust mite (<3 μg). We also adoptively transferred naive IL-4Rα^-/lox or IL-4Rα^-/- B cells into μMT^-/- mice a day before sensitization or a day before challenge. We analyzed lung inflammation, cellular infiltrate, and airway hyperresponsiveness.

RESULTS

We found that IL-4Rα signaling on B cells was important for optimal T_H2 allergic immune responses mainly when the load of antigen is limited. IL-4Rα signaling on B cells was essential for germinal centers and in the effector phase of allergic responses. Be2 cells were essential in airway hyperresponsiveness, but not in other parameters.

CONCLUSIONS

IL-4Rα signaling on B cells is deleterious in allergic asthma because it is required for optimal T_H2 responses, Be2 function, germinal center formation, and T follicular helper cells, especially when the load of the antigen is limiting.

Protective Effect of S-Allyl Cysteine Against Neonatal Asthmatic Rats

S-Allyl cysteine (SAC), an organic compound and a natural constituent of Allium sativum, commonly known as garlic have been consumed in routine foods are known to possess various biological activities. Nevertheless, scientific evidence on the protective effect of SAC against neonatal asthmatic rats is not available. Hence, the present study aimed at investigating the anti-asthmatic activity of SAC in neonatal asthmatic rats using Wistar rats. The study conducted in 4 groups consists of normal control rats, asthma-induced, asthma animals administered with SAC (25 mg/kg), and SAC control. At the end of the experimental period, inflammatory cells in bronchoalveolar lavage fluid (BALF), inflammatory markers, fibrinogen level, activated partial thromboplastin time, coagulation factor activity, and histopathology were elucidated. The current investigation exhibits that SAC significantly reduced the total leukocytes, with restored fibrinogen level, and activated partial thromboplastin time. In addition, the levels of inflammatory cytokines such as TNF-α (tumor necrosis factor- α), IL-6 (Interleukin 6), and IL-1β have also attenuated in SAC treated animals. Furthermore, the mRNA expression levels of COX2 (cyclooxygenase-2), MCP-1 (monocyte chemoattractant protein-1), RANTES (regulated upon activation, normal T cell expressed and secreted), and eotaxin were reduced in SAC treated animals. Treatment of rats with SAC significantly reduced inflammation and eosinophil infiltration in the lungs. These results suggest that SAC exert protection in neonatal asthmatic rats suffering from acute or chronic inflammation by inducing anti-inflammatory and cell-protective responses.

Non-genetic Heterogeneity of Macrophages in Diseases-A Medical Perspective

Macrophages are sessile immune cells with a high functional plasticity. Initially considered as a uniform population of phagocytic scavengers, it is now widely accepted that these cells also assume developmental and metabolic functions specific of their tissue of residence. Hence, the paradigm is shifting while our comprehension of macrophage heterogeneity improves. Accordingly, exploiting this intrinsic versatility appears more and more promising for the establishment of innovative therapeutic strategies. Nevertheless, identifying relevant therapeutic targets remains a considerable challenge. Herein, we discuss various features of macrophage heterogeneity in five main categories of human diseases: infectious, inflammatory, metabolic, age-related, and neoplastic disorders. We summarize the current understanding of how macrophage heterogeneity may impact the pathogenesis of these diseases and propose a comprehensive overview with the aim to help in establishing future macrophage-targeted therapies.