Streptococcus pneumoniae aminopeptidase N regulates dendritic cells that attenuates type-2 airway inflammation in murine allergic asthma

Wogonoside Ameliorates Airway Inflammation and Mucus Hypersecretion via NF-κB/STAT6 Signaling in Ovalbumin-Induced Murine Acute Asthma

Asthma is recognized as a chronic respiratory illness characterized by airway inflammation and airway hyperresponsiveness. Wogonoside, a flavonoid glycoside, is reported to significantly alleviate the inflammation response and oxidative stress. Herein, this study aimed to investigate the therapeutic effect and underlying mechanism of wogonoside on airway inflammation and mucus hypersecretion in a murine asthma model and in human bronchial epithelial cells (16HBE). BALB/c mice were sensitized and challenged with ovalbumin (OVA). Pulmonary function and the number of cells in the bronchoalveolar lavage fluid (BALF) were examined. Pathological changes in lung tissue in each group were evaluated via hematoxylin and eosin and periodic acid-Schiff staining, and changes in levels of cytokines in BALF and of immunoglobulin E in serum were determined via an enzyme-linked immunosorbent assay. The expression of relevant genes in lung tissue was analyzed via real-time PCR. Western blotting and immunofluorescence were employed to detect the expression of relevant proteins in lung tissue and 16HBE cells. Treatment with 10 and 20 mg/kg wogonoside significantly attenuated the OVA-induced increase of inflammatory cell infiltration, mucus secretion, and goblet cell percentage and improved pulmonary function. Wogonoside treatment reduced the level of T-helper 2 cytokines including interleukin (IL)-4, IL-5, and IL-13 in BALF and of IgE in serum and decreased the mRNA levels of cytokines (IL-4, IL-5, IL-6, IL-13, and IL-1β and tumor necrosis factor-α), chemokines (CCL-2, CCL-11, and CCL-24), and mucoproteins (MUC5AC, MUC5B, and GOB5) in lung tissues. The expression of MUC5AC and the phosphorylation of STAT6 and NF-κB p65 in lung tissues and 16HBE cells were significantly downregulated after wogonoside treatment. Thus, wogonoside treatment may effectively decrease airway inflammation, airway remodeling, and mucus hypersecretion via blocking NF-κB/STAT6 activation.

Mediation of the JNC/ILC2 pathway in DBP-exacerbated allergic asthma: A molecular toxicological study on neuroimmune positive feedback mechanism

BACKGROUND

Dibutyl phthalate (DBP), a commonly used plasticizer, has been found to be strongly linked to a consistently high prevalence of allergic diseases, particularly allergic asthma. Previous animal experiments have demonstrated that exposure to DBP can worsen asthma by triggering the production of calcitonin gene-related peptide (CGRP), a neuropeptide in the lung tissue. However, the precise neuroimmune mechanism and pathophysiology of DBP-exacerbated allergic asthma with the assistance of CGRP remain unclear.

OBJECTIVE

The present study was to investigate the potential pathophysiological mechanism in DBP-exacerbated asthma from the perspective of neural-immune interactions.

METHODS AND RESULTS

C57BL/6 mice were orally exposed to different concentrations (0.4, 4, 40 mg/kg) of DBP for 28 days. They were then sensitized with OVA and nebulized with OVA for 7 consecutive excitations. To investigate whether DBP exacerbates allergic asthma in OVA induced mice, we analyzed airway hyperresponsiveness and lung histopathology. To investigate the activation of JNC and TRPV1 neurons and the release of CGRP by JNC cells, we measured the levels of TRPV1 channels, calcium inward flow, and downstream neuropeptide CGRP. Results showed that TRPV1 expression, inward calcium flux, and CGRP levels were significantly elevated in the lung tissues of the 40DBP + OVA group, suggesting the release of CGRP by JNC cells. To counteract the detrimental effects of DBP mediated by CGRP, we employed olcegepant (also known as BIBN-4096), a CGRP receptor specific antagonist. Results revealed that 40DBP + OVA + olcegepant led to notable decreases in TRPV1, calcium inward flow, and CGRP expression in lung tissues compare with 40DBP + OVA, further supporting the efficacy of olcegepant. Additionally, we also conducted ILC2 flow sorting and observed that neuropeptide CGRP-activated ILC2 cells have a crucial role as key effector cells in DBP-induced neuroimmune positive feedback regulation. Finally, we examined the protein expression of CGRP, GATA3 and P-GATA3, and found that significant upregulations of CGRP and P-GATA3 in the 40DBP + OVA group, suggest that GATA3 acted as a key regulator of CGRP-activated ILC2.

CONCLUSION

The aforementioned studies indicate that exposure to DBP can exacerbate allergic asthma, leading to airway inflammation. This exacerbation occurs through the activation of TRPV1 in JNC, resulting in the release of CGRP. The excessive release of CGRP further promotes the release of Th2 cytokines by inducing the activation of ILC2 through GATA phosphorylation. Consequently, this process contributes to the development of airway inflammation and allergic asthma. The increased production of Th2 cytokines also triggers the production of IgE, which interacts with FcεRI on JNC neurons, thereby mediating neuro-immune positive feedback regulation.

Single-cell analysis reveals alterations in cellular composition and cell-cell communication associated with airway inflammation and remodeling in asthma

BACKGROUND

Asthma is a heterogeneous disease characterized by airway inflammation and remodeling, whose pathogenetic complexity was associated with abnormal responses of various cell types in the lung. The specific interactions between immune and stromal cells, crucial for asthma pathogenesis, remain unclear. This study aims to determine the key cell types and their pathological mechanisms in asthma through single-cell RNA sequencing (scRNA-seq).

METHODS

A 16-week mouse model of house dust mite (HDM) induced asthma (n = 3) and controls (n = 3) were profiled with scRNA-seq. The cellular composition and gene expression profiles were assessed by bioinformatic analyses, including cell enrichment analysis, trajectory analysis, and Gene Set Enrichment Analysis. Cell-cell communication analysis was employed to investigate the ligand-receptor interactions.

RESULTS

The asthma model results in airway inflammation coupled with airway remodeling and hyperresponsiveness. Single-cell analysis revealed notable changes in cell compositions and heterogeneities associated with airway inflammation and remodeling. GdT17 cells were identified to be a primary cellular source of IL-17, related to inflammatory exacerbation, while a subpopulation of alveolar macrophages exhibited numerous significantly up-regulated genes involved in multiple pathways related to neutrophil activities in asthma. A distinct fibroblast subpopulation, marked by elevated expression levels of numerous contractile genes and their regulators, was observed in increased airway smooth muscle layer by immunofluorescence analysis. Asthmatic stromal-immune cell communication significantly strengthened, particularly involving GdT17 cells, and macrophages interacting with fibroblasts. CXCL12/CXCR4 signaling was remarkedly up-regulated in asthma, predominantly bridging the interaction between fibroblasts and immune cell populations. Fibroblasts and macrophages could jointly interact with various immune cell subpopulations via the CCL8/CCR2 signaling. In particular, fibroblast-macrophage cell circuits played a crucial role in the development of airway inflammation and remodeling through IL1B paracrine signaling.

CONCLUSIONS

Our study established a mouse model of asthma that recapitulated key pathological features of asthma. ScRNA-seq analysis revealed the cellular landscape, highlighting key pathological cell populations associated with asthma pathogenesis. Cell-cell communication analysis identified the crucial ligand-receptor interactions contributing to airway inflammation and remodeling. Our findings emphasized the significance of cell-cell communication in bridging the possible causality between airway inflammation and remodeling, providing valuable hints for therapeutic strategies for asthma.

The preprogrammed anti-inflammatory phenotypes of CD11chigh macrophages by Streptococcus pneumoniae aminopeptidase N safeguard from allergic asthma

BACKGROUND

Early microbial exposure is associate with protective allergic asthma. We have previously demonstrated that Streptococcus pneumoniae aminopeptidase N (PepN), one of the pneumococcal components, inhibits ovalbumin (OVA) -induced airway inflammation in murine models of allergic asthma, but the underlying mechanism was incompletely determined.

METHODS

BALB/c mice were pretreated with the PepN protein and exposed intranasally to HDM allergen. The anti-inflammatory mechanisms were investigated using depletion and adoptive transfer experiments as well as transcriptome analysis and isolated lung CD11chigh macrophages.

RESULTS

We found pretreatment of mice with PepN promoted the proliferation of lung-resident F4/80+CD11chigh macrophages in situ but also mobilized bone marrow monocytes to infiltrate lung tissue that were then transformed into CD11high macrophages. PepN pre-programmed the macrophages during maturation to an anti-inflammatory phenotype by shaping the metabolic preference for oxidative phosphorylation (OXPHOS) and also inhibited the inflammatory response of macrophages by activating AMP-activated protein kinase. Furthermore, PepN treated macrophages also exhibited high-level costimulatory signaling molecules which directed the differentiation into Treg.

CONCLUSION

Our results demonstrated that the expansion of CD11chigh macrophages in lungs and the OXPHOS metabolic bias of macrophages are associated with reduced allergic airway inflammation after PepN exposure, which paves the way for its application in preventing allergic asthma.

Relief of ovalbumin-induced airway remodeling by the glycyl-l-histidyl-l-lysine-Cu2+ tripeptide complex via activation of SIRT1 in airway epithelial cells

Fixed airflow limitation (FAO), prevalent in patients with severe or difficult-to-treat asthma, is mainly caused by airway remodeling. Airway remodeling is initiated by inflammation and involves subsequent pathological changes. Glycyl-l-histidyl-l-lysine (GHK) is a matrikine with anti-inflammatory and antioxidant effects, naturally existing in human tissue. At present, the GHK level in human plasma and whether it is related to airway remodeling of asthma remain unclear. This study was conducted to determine how GHK is involved in airway remodeling in asthma. Our result showed that the plasma GHK levels of patients with asthma were significantly lower than those of age-matched healthy controls. In asthma patients, plasma GHK levels display a moderate correlation with FEF_25-75%, and patients with FAO had significantly lower GHK levels. Ovalbumin-induced mice of asthma model treated with PBS or GHK-Cu (a form of GHK with higher bioavailability) were used to evaluate the effect of exogenous GHK supplement on airway remodeling. GHK-Cu administration alleviated airway remodeling, as reflected by decreased peribronchial collagen deposition and airway mucus secretion, and suppressed epithelial-mesenchymal transition. The therapeutical effect related to decreased TGF-β1 level. Successively, network pharmacology and the validation data of experiments in vivo and vitro demonstrated that GHK-Cu decreased TGF-β1 level by increasing SIRT1 expression and activating SIRT1 deacetylation in airway epithelial cells, thereby alleviating airway remodeling. Collectively, decreased plasma GHK levels were related to FAO in asthma patients. Through the direct binding and activation of SIRT1, exogenous GHK-Cu administration alleviated airway remodeling in asthmatic mice.

Progranulin deficiency suppresses allergic asthma and enhances efferocytosis via PPAR-γ/MFG-E8 regulation in macrophages

Efferocytosis can resolve airway inflammation and enhance airway tolerance in allergic asthma. While previous work has reported that progranulin (PGRN) regulated macrophage efferocytosis, but it is unclear whether PGRN-mediated efferocytosis is associated with asthma. Here, we found that in an ovalbumin (OVA)-induced allergic asthma model, the airway inflammation was suppressed and the apoptosis in lung tissues was ameliorated in PGRN-deficient mice. In contrast, PGRN knockdown in human bronchial epithelial cells increased apoptosis in vitro. Furthermore, PGRN-deficient macrophages had significantly stronger efferocytosis ability than wild type (WT) macrophages both in vitro and in vivo. PGRN-deficient peritoneal macrophages (PMs) exhibited increased expression of genes associated with efferocytosis including milk fat globule-epidermal growth factor 8 (MFG-E8), peroxisome proliferator-activated receptor gamma (PPAR-γ) and sirtuin1 (SIRT1) and increased capacity to produce the anti-inflammatory mediator interleukin (IL)-10 during efferocytosis. GW9662, the inhibitor of PPAR-γ, abolished increased efferocytosis and MFG-E8 expression in PGRN-deficient PMs suggesting that PGRN deficiency enhanced MFG-E8-mediated efferocytosis through PPAR-γ. Correspondingly, efferocytosis genes were increased in the lungs of OVA-induced PGRN-deficient mice. GW9662 treatment reduced MFG-E8 expression but did not significantly affect airway inflammation. Our results demonstrated that PGRN deficiency enhanced efferocytosis via the PPAR-γ/MFG-E8 pathway and this may be one of the reasons PGRN deficiency results in inhibition of airway inflammation in allergic asthma.

CD5L attenuates allergic airway inflammation by expanding CD11chigh alveolar macrophages and inhibiting NLRP3 inflammasome activation via HDAC2

Allergic asthma is an airway inflammatory disease dominated by type 2 immune responses and there is currently no curative therapy for asthma. CD5-like antigen (CD5L) has been known to be involved in a variety of inflammatory diseases. However, the role of CD5L in allergic asthma remains unclear. In the present study, mice were treated with recombinant CD5L (rCD5L) during house dust mite (HDM) and ovalbumin (OVA) challenge to determine the role of CD5L in allergic asthma, and the underlying mechanism was further explored. Compared with PBS group, serum CD5L levels of asthmatic mice were significantly decreased, and the levels of CD5L in lung tissues and bronchoalveolar lavage fluid (BALF) were significantly increased. CD5L reduced airway inflammation and Th2 immune responses in asthmatic mice. CD5L exerted its anti-inflammatory function by increasing CD11c^high alveolar macrophages (CD11c^high AMs), and the anti-inflammatory role of CD11c^high AMs in allergic asthma was confirmed by CD11c^high AMs depletion and transfer assays. In addition, CD5L increased the CD5L⁺ macrophages and inhibited NLRP3 inflammasome activation by increasing HDAC2 expression in lung tissues of asthmatic mice. Hence, our study implicates that CD5L has potential usefulness for asthma treatment.

Impact of Therapeutics on Unified Immunity During Allergic Asthma and Respiratory Infections

Asthma is a common chronic respiratory disease that affects millions of people worldwide. Patients with allergic asthma, the most prevalent asthma endotype, are widely considered to possess a defective immune response against some respiratory infectious agents, including viruses, bacteria and fungi. Furthermore, respiratory pathogens are associated with asthma development and exacerbations. However, growing data suggest that the immune milieu in allergic asthma may be beneficial during certain respiratory infections. Immunomodulatory asthma treatments, although beneficial, should then be carefully prescribed to avoid misuse and overuse as they can also alter the host microbiome. In this review, we summarize and discuss recent evidence of the correlations between allergic asthma and the most significant respiratory infectious agents that have a role in asthma pathogenesis. We also discuss the implications of current asthma therapeutics beyond symptom prevention.

The aggravation of allergic airway inflammation with dibutyl phthalate involved in Nrf2-mediated activation of the mast cells

Dibutyl phthalate (DBP)-an organic pollutant-is ubiquitous in the environment. DBP as an immune adjuvant is related to the development of multiple allergic diseases. However, the current research involving DBP-induced pulmonary toxicity remains poorly understood. Therefore, this research aimed to explore the adverse effect and potential mechanism of DBP exposure on the lungs in rats. In our study, ovalbumin was used to build a rat model of allergic airway inflammation to study any harmful effect of DBP exposure on lung tissues. Rats were treated by intragastric administration of DBP (500 mg kg^-1 or 750 mg kg^-1) and/or subcutaneous injection of SFN (4 mg kg^-1). The results of histopathological analysis, cell count, and myeloperoxidase showed that DBP promoted the inflammatory damage of lungs. In the lung tissues, the detection of terminal deoxynucleotidyl transferase dUNT nick end labeling and oxidative stress indices showed that DBP significantly increased the level of apoptosis and oxidative stress. Western blot analysis indicated that DBP raised the expression level of thymic stromal lymphopoietin and reduced the nuclear expression level of nuclear factor-erythroid-2-related factor 2 (Nrf2), which was further verified by quantitative real-time PCR. Meanwhile, DBP treatment markedly up-regulated the inflammatory cytokines such as IL-4 and IL-13, and rat mast cell protease-2, a marker secreted by mast cells (MCs). Conversely, sulforaphane, a Nrf2 inducer, ameliorated the pulmonary damage induced by DBP in the above. Altogether, our data provides a new insight into the impacts of the activation of MCs on the DBP-induced pulmonary toxicity as well as the safety evaluation of DBP.

Muc5ac Production Inhibited by Decreased lncRNA H19 via PI3K/Akt/NF-kB in Asthma

Introduction

LncRNAs play important roles in multiple diseases including asthma, while there are a few reports on the role of lncRNA H19 about asthma. This study aimed to investigate the roles and mechanisms of lncRNA H19 in asthma.

Methods

We detected lncRNA H19 and Muc5ac mRNA by establishing a murine asthma model and an in vitro inflammation model. Regulatory roles of lncRNA H19 in asthma were explored by lncRNA H19 overexpression or knockdown in vitro. To study its mechanisms, we detect p-NF-κB and p-Akt expression, and treated 16-HBE cells with inhibitors of PI3K. To study regulatory effects of miR-675-3p on Muc5ac, miR-675-3p mimics and inhibitors were respectively transfected into 16-HBE cells.

Results

Firstly, we established a murine asthma model and an in vitro inflammation model. We found that lncRNA H19 expression was decreased, while Muc5ac mRNA was increased in lung tissues of murine asthma model and in the in vitro inflammation model. lncRNA H19 overexpression increased Muc5ac mRNA expression and lncRNA H19 knockdown decreased Muc5ac mRNA expression in 16-HBE cells. Moreover, lncRNA H19 overexpression further increased Muc5ac expression in TNFα-induced in vitro inflammation model. lncRNA H19 knockdown decreased p-Akt and p-NF-κB expression. Inhibitors of PI3K abolished Muc5ac induced by lncRNA H19 overexpression. Although miR-675-3p was increased by lncRNA H19 overexpression, it had no regulatory effects on Muc5ac expression.

Discussion

These results demonstrated that lncRNA H19 positively regulates Muc5ac expression through PI3K/Akt /NF-κB pathway in the in vitro inflammation model. Therefore, this study indicated that decreased lncRNA H19 in asthma might play a protective role relieving mucus overproduction, and lncRNA H19 might be a potential target for asthma treatment.

Streptococcus pneumoniae aminopeptidase N regulates dendritic cells that attenuates type-2 airway inflammation in murine allergic asthma

BACKGROUND AND PURPOSE

Epidemiological and experimental studies suggest that microbial exposure in early childhood is linked with reduced risk to suffer asthma. Thus microbial components with immunoregulatory capabilities might serve as a preventive strategy for allergic asthma. Recently, it was identified that Streptococcus pneumoniae aminopeptidase N (PepN) could suppress T cell effector function. We sought to investigate the effect of PepN on murine allergic asthma and elucidate the underlying mechanism.

EXPERIMENTAL APPROACH

The effects of intranasal administration of PepN during or before sensitization were examined in ovalbumin (OVA)-induced murine allergic asthma. The roles of CD11b⁺ dendritic cells in PepN treated OVA-induced allergic asthma were evaluated by flow cytometry, cytokines detection and adoptive transfer. Moreover, the numbers of lung type 2 innate lymphoid cells (ILC2s) were also detected.

KEY RESULTS

Administration of PepN during or before sensitization attenuated type-2 airway inflammation (eosinophilia, mucus hypersecretion, Th2 cytokines production and IgE production) in allergic asthma mice. PepN reduced lung accumulation of CD11b⁺ dendritic cells, which was accompanied by diminished dendritic cell-attracting chemokine CCL20 production as well as CCL17 and CCL22, which are Th2-cell chemokines predominantly produced by CD11b⁺ dendritic cells. Adoptive transfer of BM-derived CD11b⁺ dendritic cells abolished the inhibitory effect of PepN on OVA-induced type-2 airway inflammation. The numbers of lung ILC2s were decreased in asthmatic mice receiving PepN.

CONCLUSION AND IMPLICATIONS

PepN alleviated type-2 inflammation in OVA-induced allergic asthma mice, which was mediated by regulation of lung CD11b⁺ dendritic cells. Our study provides a novel strategy for the prevention of allergic asthma.