Macrophage/epithelial cell CCL2 contributes to rhinovirus-induced hyperresponsiveness and inflammation in a mouse model of allergic airways disease

Chemokine CCL2 and its receptor CCR2 in different age groups of patients with COVID-19

BACKGROUND

Despite the development of various antiviral drugs, most of them are not effective in the treatment of coronavirus disease 2019 (COVID-19) as a hyperinflammatory disorder. Chemokine (C-C motif) ligand 2 (CCL2) is one of the critical CC chemokines involved in the pathogenesis and severity of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. This study aimed to investigate the expression of CCL2 and CC chemokine receptor 2 (CCR2) in COVID-19 patients.

METHODS

Peripheral blood samples were collected from 60 confirmed COVID-19 patients and 60 age-matched healthy subjects. The ages of the subjects were categorized as follows: up to 20 years, 20 to 40 years, 40 to 60 years, and more than 60 years. CCL2 serum levels were measured using the enzyme-linked immunosorbent assay (ELISA). CCR2 gene expression in peripheral blood mononuclear cells (PBMCs) was measured employing real-time polymerase chain reaction (PCR).

RESULTS

In all age groups, CCL2 serum levels were significantly elevated in patients compared to healthy controls (P < 0.0001). CCL2 levels were higher in severe patients than in moderate patients. Moreover, CCR2 expression by PBMCs was higher in patients compared to control subjects. However, a significant difference between patients and controls over 60 years of age was identified (P = 0.0353). There was no significant difference in CCR2 expression between moderate and severe COVID-19 patients.

CONCLUSIONS

Taken together, the findings demonstrate that CCL2 and CCR2 are upregulated in COVID-19 patients at protein and mRNA levels, respectively. Therefore, the CCL2/CCR2 axis may be a potential therapeutic target in order to improve patient outcomes.

Adjuvant-independent airway sensitization and infection mouse models leading to allergic asthma

Asthma is a chronic respiratory disease of global importance. Mouse models of allergic asthma have been instrumental in advancing research and novel therapeutic strategies for patients. The application of relevant allergens and physiological routes of exposure in such models has led to valuable insights into the complexities of asthma onset and development as well as key disease mechanisms. Furthermore, environmental microbial exposures and infections have been shown to play a fundamental part in asthma pathogenesis and alter disease outcome. In this review, we delve into physiological mouse models of allergic asthma and explore literature reports on most significant interplays between microbial infections and asthma development with relevance to human disease.

High sucrose intake exacerbates airway inflammation through pathogenic Th2 and Th17 response in ovalbumin (OVA)-induced acute allergic asthma in C57BL/6 mice

Asthma is an inflammatory disease characterized by chronic inflammation in lung tissues and excessive mucus production. High-fat diets have long been assumed to be a potential risk factor for asthma. However, to date, very few direct evidence indicating the involvement of high sucrose intake (HSI) in asthma progression exists. In this study, we investigate the effect of HSI on ovalbumin (OVA)-sensitized allergic asthma mice. We observed that HSI increased the expression of inflammatory genes (IL-1β, IL-6, TNF-α) in adipose tissues and led to reactive oxygen species generation in the liver and lung. In addition, HSI accelerated the TLR4/NF-κB signaling pathway leading to MMP9 activation, which promotes the chemokines and TGF-β secretion in the lungs of OVA-sensitized allergic asthma mice. More importantly, HSI significantly promoted the pathogenic Th2 and Th17 responses. The increase of IL-17A secretion by HSI increased the expression of chemokines (MCP-1, CXCL1, CXCL5, CXCL8). It resulted in eosinophil and mast cell infiltration in the lung and trachea. We also demonstrated that HSI increased mucus hypersecretion, which was validated by increased main mucin protein (MUC5AC) secreted in the lungs. Our findings suggest that HSI exacerbates the development of Th2/Th17-predominant asthma by upregulating the TLR4-mediated NF-κB pathway, leading to excessive MMP9 production.

Macrophages Orchestrate Airway Inflammation, Remodeling, and Resolution in Asthma

Asthma is a heterogenous chronic inflammatory lung disease with endotypes that manifest different immune system profiles, severity, and responses to current therapies. Regardless of endotype, asthma features increased immune cell infiltration, inflammatory cytokine release, and airway remodeling. Lung macrophages are also heterogenous in that there are separate subsets and, depending on the environment, different effector functions. Lung macrophages are important in recruitment of immune cells such as eosinophils, neutrophils, and monocytes that enhance allergic inflammation and initiate T helper cell responses. Persistent lung remodeling including mucus hypersecretion, increased airway smooth muscle mass, and airway fibrosis contributes to progressive lung function decline that is insensitive to current asthma treatments. Macrophages secrete inflammatory mediators that induce airway inflammation and remodeling. Additionally, lung macrophages are instrumental in protecting against pathogens and play a critical role in resolution of inflammation and return to homeostasis. This review summarizes current literature detailing the roles and existing knowledge gaps for macrophages as key inflammatory orchestrators in asthma pathogenesis. We also raise the idea that modulating inflammatory responses in lung macrophages is important for alleviating asthma.

Prenatal exposure to ambient air pollution is associated with early life immune perturbations

BACKGROUND

Exposure to ambient air pollution has been linked to asthma, allergic rhinitis, and other inflammatory disorders, but little is known about the underlying mechanisms.

OBJECTIVE

We studied the potential mechanisms leading from prenatal ambient air pollution exposure to asthma and allergy in childhood.

METHODS

Long-term exposure to nitrogen dioxide (NO₂) as well as to particulate matter with a diameter of ≤2.5 and ≤10 μm (PM_2.5 and PM₁₀) were modeled at the residence level from conception to 6 years of age in 700 Danish children followed clinically for development of asthma and allergy. Nasal mucosal immune mediators were assessed at age 4 weeks and 6 years, inflammatory markers in blood at 6 months, and nasal epithelial DNA methylation and gene expression at age 6 years.

RESULTS

Higher prenatal air pollution exposure with NO₂, PM_2.5, and PM₁₀ was associated with an altered nasal mucosal immune profile at 4 weeks, conferring an increased odds ratio [95% confidence interval] of 2.68 [1.58, 4.62] for allergic sensitization and 2.63 [1.18, 5.81] for allergic rhinitis at age 6 years, and with an altered immune profile in blood at age 6 months conferring increased risk of asthma at age 6 years (1.80 [1.18, 2.76]). Prenatal exposure to ambient air pollution was not robustly associated with immune mediator, epithelial DNA methylation, or gene expression changes in nasal cells at age 6 years.

CONCLUSION

Prenatal exposure to ambient air pollution was associated with early life immune perturbations conferring risk of allergic rhinitis and asthma. These findings suggest potential mechanisms of prenatal exposure to ambient air pollution on the developing immune system.

Effect of Dermatophagoides pteronyssinus extract on the expression of genes involved in inflammation and tissue remodeling by peripheral blood mononuclear cells of allergic asthma patients

PURPOSE

House dust mite allergy constitutes a risk factor for asthma development and is associated with a faster decline of lung function in allergic asthmatics (AAs). To evaluate the effect of Dermatophagoides pteronyssinus (Dp) allergens on the expression of genes involved in inflammation and tissue remodeling by peripheral blood mononuclear cells (PBMCs) isolated from the blood of AAs.

MATERIALS AND METHODS

The cells from AAs, allergic rhinitis without asthma patients (ARs), and healthy controls (HCs) were cultured in the presence of Dp, lipopolysaccharide (LPS), or without any stimulation. The expression of 84 genes was evaluated using a low-density microarray whereas, the quantitative expression analysis of selected genes was performed using a real-time polymerase chain reaction. The concentration of selected proteins in the cell culture supernatants was assessed using ELISA.

RESULTS

Stimulation of PBMCs with Dp and LPS resulted in a significant upregulation of 8 and 15 among 84 studied genes, respectively. The greatest upregulation was observed for CCL2 and CCL3 using Dp and LPS, respectively. In comparison with HCs, in AAs, significantly increased upregulation of CCL2 in response to Dp was found. The secretion of CCL2 and CCL3 by PBMCs reflected the pattern of gene expression at the mRNA level. The mean Dp-stimulated secretion of CCL2 by PBMCs of ARs was less than in AAs (p ​< ​0.01), both being notably greater than in the HCs (p ​< ​0.01).

CONCLUSION

Rapid and potent upregulation of CCL2 expression by PBMCs in response to Dp may constitute an important contribution to the development of allergic asthma.

Immune Response Is Key to Genetic Mechanisms of SARS-CoV-2 Infection With Psychiatric Disorders Based on Differential Gene Expression Pattern Analysis

Existing evidence demonstrates that coronavirus disease 2019 (COVID-19) leads to psychiatric illness, despite its main clinical manifestations affecting the respiratory system. People with mental disorders are more susceptible to COVID-19 than individuals without coexisting mental health disorders, with significantly higher rates of severe illness and mortality in this population. The incidence of new psychiatric diagnoses after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is also remarkably high. SARS-CoV-2 has been reported to use angiotensin-converting enzyme-2 (ACE2) as a receptor for infecting susceptible cells and is expressed in various tissues, including brain tissue. Thus, there is an urgent need to investigate the mechanism linking psychiatric disorders to COVID-19. Using a data set of peripheral blood cells from patients with COVID-19, we compared this to data sets of whole blood collected from patients with psychiatric disorders and used bioinformatics and systems biology approaches to identify genetic links. We found a large number of overlapping immune-related genes between patients infected with SARS-CoV-2 and differentially expressed genes of bipolar disorder (BD), schizophrenia (SZ), and late-onset major depressive disorder (LOD). Many pathways closely related to inflammatory responses, such as MAPK, PPAR, and TGF-β signaling pathways, were observed by enrichment analysis of common differentially expressed genes (DEGs). We also performed a comprehensive analysis of protein-protein interaction network and gene regulation networks. Chemical-protein interaction networks and drug prediction were used to screen potential pharmacologic therapies. We hope that by elucidating the relationship between the pathogenetic processes and genetic mechanisms of infection with SARS-CoV-2 with psychiatric disorders, it will lead to innovative strategies for future research and treatment of psychiatric disorders linked to COVID-19.

Hijacking of the Host's Immune Surveillance Radars by Burkholderia pseudomallei

Burkholderia pseudomallei (B. pseudomallei) causes melioidosis, a potentially fatal disease for which no licensed vaccine is available thus far. The host-pathogen interactions in B. pseudomallei infection largely remain the tip of the iceberg. The pathological manifestations are protean ranging from acute to chronic involving one or more visceral organs leading to septic shock, especially in individuals with underlying conditions similar to COVID-19. Pathogenesis is attributed to the intracellular ability of the bacterium to ‘step into’ the host cell’s cytoplasm from the endocytotic vacuole, where it appears to polymerize actin filaments to spread across cells in the closer vicinity. B. pseudomallei effectively evades the host’s surveillance armory to remain latent for prolonged duration also causing relapses despite antimicrobial therapy. Therefore, eradication of intracellular B. pseudomallei is highly dependent on robust cellular immune responses. However, it remains ambiguous why certain individuals in endemic areas experience asymptomatic seroconversion, whereas others succumb to sepsis-associated sequelae. Here, we propose key insights on how the host’s surveillance radars get commandeered by B. pseudomallei.

Epithelial expression and role of secreted STC1 on asthma airway hyperresponsiveness through calcium channel modulation

BACKGROUND

Asthma is characterized by airway hyperresponsiveness (AHR), inflammation, and airway remodeling. Airway hyperresponsiveness results from enhanced airway smooth muscle (ASM) contraction potentially under the control of an epithelium-derived relaxing factor (EpDRF). However, relatively rare is known about EpDRF. We aimed to elucidate the role of epithelium-derived stanniocalcin-1 (STC1) on AHR and ASM contraction.

METHODS

Stanniocalcin-1 levels in the serum of asthmatic patients and healthy volunteers and in bronchoalveolar lavage fluid (BALF) from ovalbumin (OVA)-challenged mice were measured by ELISA. The effects of exogenous STC1 on AHR and on inflammation were examined in mice. IL-13 modulation of STC1 mRNA and protein levels was studied in human bronchial epithelial cell lines (16HBE). The function of STC1 on Ca²⁺ influx and ASM contraction was examined ex vivo.

RESULTS

Serum STC1 was decreased in asthma (n = 93) compared with healthy volunteers (1071 ± 30.4 vs 1414 ± 75.1 pg/ml, p < 0.0001, n = 23) and correlated with asthma control (p = 0.0270), lung function (FEV1, p = 0.0130), and serum IL-13 levels (p = 0.0009). Treatment of ten asthmatic subjects with inhaled corticosteroids/long-acting beta2-agonists (ICS/LABA) for 1 year enhanced STC1 expression which correlated with improved asthma control (p = 0.022). STC1 was mainly expressed in bronchial epithelium and intranasal administration of recombinant human STC1 (rhSTC1) reduced AHR and inflammation in mice. IL-13 suppressed STC1 release from 16HBE, whereas rhSTC1 blocked store-operated Ca²⁺ entry (SOCE) by suppressing stromal interaction molecule 1 (STIM1) and further inhibited ASM cell contractility by suppressing Ca²⁺ -dependent myosin light chain (MLC) phosphorylation.

CONCLUSION

Our data indicate that STC1 deficiency in asthmatic airways promotes STIM1 hyperactivity, enhanced ASM contraction, and AHR. STC1 may be a candidate EpDRF.

Role of ILC2 in Viral-Induced Lung Pathogenesis

Innate lymphoid type-2 cells (ILC2) are a population of innate cells of lymphoid origin that are known to drive strong Type 2 immunity. ILC2 play a key role in lung homeostasis, repair/remodeling of lung structures following injury, and initiation of inflammation as well as more complex roles during the immune response, including the transition from innate to adaptive immunity. Remarkably, dysregulation of this single population has been linked with chronic lung pathologies, including asthma, chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrotic diseases (IPF). Furthermore, ILC2 have been shown to increase following early-life respiratory viral infections, such as respiratory syncytial virus (RSV) and rhinovirus (RV), that may lead to long-term alterations of the lung environment. The detrimental roles of increased ILC2 following these infections may include pathogenic chronic inflammation and/or alterations of the structural, repair, and even developmental processes of the lung. Respiratory viral infections in older adults and patients with established chronic pulmonary diseases often lead to exacerbated responses, likely due to previous exposures that leave the lung in a dysregulated functional and structural state. This review will focus on the role of ILC2 during respiratory viral exposures and their effects on the induction and regulation of lung pathogenesis. We aim to provide insight into ILC2-driven mechanisms that may enhance lung-associated diseases throughout life. Understanding these mechanisms will help identify better treatment options to limit not only viral infection severity but also protect against the development and/or exacerbation of other lung pathologies linked to severe respiratory viral infections.

Mas receptor activation attenuates allergic airway inflammation via inhibiting JNK/CCL2-induced macrophage recruitment

BACKGROUND

Defective absorption of acute allergic airway inflammation is involved in the initiation and development of chronic asthma. After allergen exposure, there is a rapid recruitment of macrophages around the airways, which promote acute inflammatory responses. The Ang-(1-7)/Mas receptor axis reportedly plays protective roles in various tissue inflammation and remodeling processes in vivo. However, the exact role of Mas receptor and their underlying mechanisms during the pathology of acute allergic airway inflammation remains unclear.

OBJECTIVE

We investigated the role of Mas receptor in acute allergic asthma and explored its underlying mechanisms in vitro, aiming to find critical molecules and signal pathways.

METHODS

Mas receptor expression was assessed in ovalbumin (OVA)-induced acute asthmatic murine model. Then we estimated the anti-inflammatory role of Mas receptor in vivo and explored expressions of several known inflammatory cytokines as well as phosphorylation levels of MAPK pathways. Mas receptor functions and underlying mechanisms were studied further in the human bronchial epithelial cell line (16HBE).

RESULTS

Mas receptor expression decreased in acute allergic airway inflammation. Multiplex immunofluorescence co-localized Mas receptor and EpCAM, indicated that Mas receptor may function in the bronchial epithelium. Activating Mas receptor through AVE0991 significantly alleviated macrophage infiltration in airway inflammation, accompanied with down-regulation of CCL2 and phosphorylation levels of MAPK pathways. Further studies in 16HBE showed that AVE0991 pre-treatment inhibited LPS-induced or anisomycin-induced CCL2 increase and THP-1 macrophages migration via JNK pathways.

CONCLUSION

Our findings suggested that Mas receptor activation significantly attenuated CCL2 dependent macrophage recruitments in acute allergic airway inflammation through JNK pathways, which indicated that Mas receptor, CCL2 and phospho-JNK could be potential targets against allergic airway inflammation.

Blocking pannexin1 reduces airway inflammation in a murine model of asthma

Stressed or injured cells release ATP into the extracellular milieu via the pannexin1 (Panx1) channels, which is the basis of inflammation in a variety of conditions, including allergic lung inflammation. Although the role of Panx1 in mediating inflammation has been well established, the role of its mimetic peptide, ¹⁰Panx1, which inhibits ATP release from Panx1 channels, in allergic asthma remains understudied. The aim of this study was to evaluate the effects of using ¹⁰Panx1 to inhibit Panx1 channel in a murine model of ovalbumin (OVA)-induced asthma. We demonstrate that blockade of Panx1 significantly attenuated goblet cell hyperplasia and inflammatory cell infiltration into the lungs of OVA-sensitized mice. Inhibition of Panx1 also reduced the total and eosinophil cell numbers in the bronchoalveolar lavage fluid (BALF) and reduced expression of CCL11 and CCL2 in lung tissues from mice. Moreover, we detected lower levels of IL-5 and IL-13 in the culture supernatant of OVA-restimulated splenocytes from ¹⁰Panx1-treated mice. Collectively, our findings suggest that Panx1 inhibition of allergen-mediated lung inflammation has the potential to suppress allergic responses in asthma.

Asthmatic Bronchial Smooth Muscle Increases CCL5-Dependent Monocyte Migration in Response to Rhinovirus-Infected Epithelium

Asthma exacerbations, a major concern in therapeutic strategies, are most commonly triggered by viral respiratory infections, particularly with human rhinovirus (HRV). Infection of bronchial epithelial (BE) cells by HRV triggers inflammation, notably monocyte recruitment. The increase of bronchial smooth muscle (BSM) mass in asthma, a hallmark of bronchial remodeling, is associated with the annual rate of exacerbations. The aim of the present study was to assess whether or not BSM could increase monocyte migration induced by HRV-infected BE. We used an advanced in vitro model of co-culture of human BE cells in air-liquid interface with human BSM cells from control and asthmatic patients. Inflammation triggered by HRV infection (HRV-16, MOI 0.1, 1 h) was assessed at 24 h with transcriptomic analysis and multiplex ELISA. In vitro CD14⁺ monocyte migration was evaluated with modified Boyden chamber. Results showed that HRV-induced monocyte migration was substantially increased in the co-culture model with asthmatic BSM, compared with control BSM. Furthermore, the well-known monocyte migration chemokine, CCL2, was not involved in this increased migration. However, we demonstrated that CCL5 was further increased in the asthmatic BSM co-culture and that anti-CCL5 blocking antibody significantly decreased monocyte migration induced by HRV-infected BE. Taken together, our findings highlight a new role of BSM cells in HRV-induced inflammation and provide new insights in mucosal immunology which may open new opportunities for prevention and/or treatment of asthma exacerbation.

Pistacia weinmannifolia root exerts a protective role in ovalbumin‑induced lung inflammation in a mouse allergic asthma model

Pistacia weinmannifolia (Anacardiaceae) has been used in herbal medicine for the treatment of influenza, dysentery and enteritis in China. It was recently observed that P. weinmannifolia root extract (PWRE) exerts anti‑inflammatory effects both in in vitro and in vivo models. Based on the results from previous studies, the present study investigated the protective effect of PWRE on airway inflammation and mucus hypersecretion. Treatment with PWRE significantly decreased the number of eosinophils and the levels of Th2 cytokines, such as interleukin (IL)‑4, IL‑5 and IL‑13, in the bronchoalveolar lavage fluid (BALF) of OVA‑exposed mice. PWRE decreased the high serum levels of total and OVA‑specific immunoglobulin E. PWRE also effectively inhibited the influx of inflammatory cells into the lung, as well as airway mucus hypersecretion. In addition, the increased level of monocyte chemoattractant protein‑1 was significantly decreased with the PWRE treatment in the BALF of OVA‑exposed mice and in lipopolysaccharide‑stimulated RAW264.7 macrophages. These protective effects of PWRE on OVA‑induced pulmonary inflammation were accompanied by the downregulation of mitogen associated protein kinases and nuclear factor‑κB activation. Thus, the results from the present study indicate that PWRE could be valuable adjuvant for the treatment of asthma.

Impact of Rhinovirus Infections in Children

Rhinovirus (RV) is an RNA virus that causes more than 50% of upper respiratory tract infections in humans worldwide. Together with Respiratory Syncytial Virus, RV is one of the leading causes of viral bronchiolitis in infants and the most common virus associated with wheezing in children aged between one and two years. Because of its tremendous genetic diversity (>150 serotypes), the recurrence of RV infections each year is quite typical. Furthermore, because of its broad clinical spectrum, the clinical variability as well as the pathogenesis of RV infection are nowadays the subjects of an in-depth examination and have been the subject of several studies in the literature. In fact, the virus is responsible for direct cell cytotoxicity in only a small way, and it is now clearer than ever that it may act indirectly by triggering the release of active mediators by structural and inflammatory airway cells, causing the onset and/or the acute exacerbation of asthmatic events in predisposed children. In the present review, we aim to summarize the RV infection's epidemiology, pathogenetic hypotheses, and available treatment options as well as its correlation with respiratory morbidity and mortality in the pediatric population.

BpV(pic) confers neuroprotection by inhibiting M1 microglial polarization and MCP-1 expression in rat traumatic brain injury

Traumatic brain injury (TBI) is a major cause of motor and cognitive impairment in young adults. It is associated with high mortality rates and very few effective treatment options. Bisperoxovanadium (pyridine-2-carboxyl) [bpV(pic)] is an commercially available inhibitor of Phosphatase and tensin homolog (PTEN). Previous studies have shown that bpV(pic) has protective effects in central nervous system. However, the role of bpV(pic) in TBI is unclear. In this study we aimed to investigate the neuroprotective role of bpV(pic) in rat TBI model. We found that injection of bpV(pic) significantly reduces brain edema and neurological dysfunction after TBI and this is mediated by AKT pathway. TBI is known to promote the M1 pro-inflammatory phenotype of microglial polarization and this effect is inhibited by bpV(pic) treatment which, instead promotes M2 microglial polarization in vivo and in vitro. We also found evidence of bpV(pic)-regulated neuroinflammation mediated by AKT activation and NF-κB p65 inhibition. BpV(pic) treatment also suppressed microglia in the peri-TBI region. MCP-1 is known to recruit monocytes and macrophages to promote inflammation, we show that bpV(pic) can inhibit TBI-induced up-regulation of MCP-1 via the AKT/NF-κB p65 signaling pathway. Taken together, our findings demonstrate that bpV(pic) plays a neuroprotective role in rat TBI, which may be achieved by inhibiting M1 microglia polarization and MCP-1 expression by modulating AKT/NF-κB p65 signaling pathway.

Sonic hedgehog (Shh) and CC chemokine ligand 2 signaling pathways in asthma

Asthma is a chronic inflammatory disease of the airways in which many cells are involved, including mast cells, eosinophils, T lymphocytes, and so on. During the process, many chemokines and mediators are released to engage in recruiting and activating eosinophils and other inflammatory cells. Also, some signaling pathways are involved in the pathobiology of asthma. Sonic hedgehog (Shh) is one of the members of hedgehog gene families. Shh signaling plays a critical role in the embryonic development, including the lung. Previous findings from our team reveal that Shh is involved in the asthma pathogenesis. Recombinant Shh could induce the CC chemokine ligand 2 (CCL2) overexpressing and Smo inhibitor GDC-O449 could inhibit CCL2 expression in airway epithelial cells, monocytes, or macrophages. Hence, we reviewed the effects of Shh and CCL2 signaling pathways, and the interaction between signaling pathways in asthma.

Myristoylated rhinovirus VP4 protein activates TLR2-dependent proinflammatory gene expression

Asthma exacerbations are often caused by rhinovirus (RV). We and others have shown that Toll-like receptor 2 (TLR2), a membrane surface receptor that recognizes bacterial lipopeptides and lipoteichoic acid, is required and sufficient for RV-induced proinflammatory responses in vitro and in vivo. We hypothesized that viral protein-4 (VP4), an internal capsid protein that is myristoylated upon viral replication and externalized upon viral binding, is a ligand for TLR2. Recombinant VP4 and myristoylated VP4 (MyrVP4) were purified by Ni-affinity chromatography. MyrVP4 was also purified from RV-A1B-infected HeLa cells by urea solubilization and anti-VP4 affinity chromatography. Finally, synthetic MyrVP4 was produced by chemical peptide synthesis. MyrVP4-TLR2 interactions were assessed by confocal fluorescence microscopy, fluorescence resonance energy transfer (FRET), and monitoring VP4-induced cytokine mRNA expression in the presence of anti-TLR2 and anti-VP4. MyrVP4 and TLR2 colocalized in TLR2-expressing HEK-293 cells, mouse bone marrow-derived macrophages, human bronchoalveolar macrophages, and human airway epithelial cells. Colocalization was absent in TLR2-null HEK-293 cells and blocked by anti-TLR2 and anti-VP4. Cy3-labeled MyrVP4 and Cy5-labeled anti-TLR2 showed an average fractional FRET efficiency of 0.24 ± 0.05, and Cy5-labeled anti-TLR2 increased and unlabeled MyrVP4 decreased FRET efficiency. MyrVP4-induced chemokine mRNA expression was higher than that elicited by VP4 alone and was attenuated by anti-TLR2 and anti-VP4. Cytokine expression was similarly increased by MyrVP4 purified from RV-infected HeLa cells and synthetic MyrVP4. We conclude that, during RV infection, MyrVP4 and TLR2 interact to generate a proinflammatory response.

Physalis peruviana L. inhibits ovalbumin‑induced airway inflammation by attenuating the activation of NF‑κB and inflammatory molecules

Physalis peruviana L. (PP) is well known for its various properties, including its antioxidant property. In our previous study, the protective effects of PP against cigarette smoke‑induced airway inflammation were confirmed. The purpose of the present study was to evaluate the anti‑inflammatory effect of PP against ovalbumin (OVA)‑induced airway inflammation. Treatment with PP inhibited the numbers of eosinophils and the levels of inflammatory cytokines, including interleukin (IL)‑4, IL‑5 and IL‑13, in the bronchoalveolar lavage fluid (BALF) of animal models with OVA‑induced allergic asthma. PP also significantly decreased the production of total immunoglobulin E in the serum. Lung sections stained with hematoxylin and eosin revealed that the influx of inflammatory cells was decreased in the lungs of mice treated with PP compared with cells in the OVA group. The increased expression levels of monocyte chemoattractant protein‑1 (MCP‑1) and T cell marker KEN‑5 were also reduced following PP treatment in the lung tissues compared with those in the OVA group. The PAS staining results showed that PP attenuated the overproduction of mucus in the lung. Additionally, western blot analysis revealed that PP significantly downregulated the activation of nuclear factor‑κB/p38 mitogen‑activated protein kinase/c‑Jun N‑terminal kinase, and upregulated the expression of heme oxgenase‑1 in the lungs. In an in vitro experiment, PP effectively reduced the levels of LPS‑stimulated MCP‑1 in a concentration‑dependent manner. Taken together, these results indicate that PP has considerable potential in the treatment of allergic asthma.

Loss of the adhesion G-protein coupled receptor ADGRF5 in mice induces airway inflammation and the expression of CCL2 in lung endothelial cells

Background

Adhesion G-protein coupled receptor F5 (ADGRF5) was recently identified as an essential regulator of pulmonary surfactant homeostasis in alveolar type II cells. We previously showed that in addition to abnormal surfactant accumulation, Adgrf5-deficient (Adgrf5^−/−) mice exhibit emphysema-like signs, suggesting a possible role for ADGRF5 in immune regulation. Here, we extended the phenotypic analysis of Adgrf5^−/− mice to help understand its biological role in the lung, and especially in immune regulation.

Methods

Histological features of lungs were evaluated by Alcian blue and Masson’s trichrome staining. Quantitative real-time PCR (qPCR) and western blot analyses were performed to analyze the differential expression of genes/proteins related to airway inflammation in lungs between wildtype and Adgrf5^−/− mice. Acid–base status was assessed by performing blood gas tests and urine pH measurements. Inflammatory cell counting was performed using Giemsa-stained bronchoalveolar lavage cells. Serum IgE concentrations were determined by enzyme-linked immunosorbent assay. The expression of Ccl2, S100a8, S100a9, and Saa3 in primary lung endothelial cells (ECs) was determined by qPCR and/or western blotting. Finally, the effect of administrating RS504393 to 2-week-old Adgrf5^−/− mice on gene expression in the lungs was analyzed by qPCR.

Results

Adgrf5^−/− mice exhibited several features of chronic airway inflammation (mucous cell metaplasia, mucus hyperproduction, subepithelial fibrosis, respiratory acidosis, high serum IgE, mast cell accumulation, and neutrophilia) in parallel with elevated expression of genes involved in mucous cell metaplasia (Muc5ac, Muc5b, Slc26a4, and Clca1), fibrosis (Tgfb1, Col1a1, Fn1, and Tnc), and type 2 immune response (Il4, Il5, Il13, IL-25, and IL-33) at 12 and/or 30 weeks of age. In contrast, mRNA expression of Ccl2, S100a8, and S100a9 was upregulated in embryonic or neonatal Adgrf5^−/− lungs as well as in lung ECs of Adgrf5^−/− mice at 1 week of age. RS504393 treatment suppressed the upregulation of S100a8, S100a9, Slc26a4, and Il5 in Adgrf5^−/− lungs.

Conclusions

Targeted disruption of ADGRF5 results in the development of airway inflammation, which is likely mediated by the type 2 immune response and possibly CCL2-mediated inflammation. ADGRF5 also has a potential role in the regulation of genes encoding CCL2 in lung ECs, thereby maintaining immune homeostasis.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-0973-6) contains supplementary material, which is available to authorized users.

In vivo experimental models of infection and disease

Human and animal models continue to play a crucial role in research to understand host immunity to rhinovirus (RV) and identify disease mechanisms. Human models have provided direct evidence that RV infection is capable of exacerbating chronic respiratory diseases and identified immunological processes that correlate with clinical disease outcomes. Mice are the most commonly used nonhuman experimental RV infection model. Although semipermissive, under defined experimental conditions sufficient replication occurs to induce host immune responses that recapitulate immunity and disease during human infection. The capacity to use genetically modified mouse strains and drug interventions has shown the mouse model to be an invaluable research tool defining causal relationships between host immunity and disease and supporting development of new treatments. Used in combination the insights achieved from human and animal experimental infection models provide complementary insights into RV biology and yield novel therapeutic options to reduce the burden of RV-induced disease.

Oxidative stress and macrophages: driving forces behind exacerbations of asthma and chronic obstructive pulmonary disease?

Oxidative stress is a common feature of obstructive airway diseases like asthma and chronic obstructive pulmonary disease (COPD). Lung macrophages are key innate immune cells that can generate oxidants and are known to display aberrant polarization patterns and defective phagocytic responses in these diseases. Whether these characteristics are linked in one way or another and whether they contribute to the onset and severity of exacerbations in asthma and COPD remain poorly understood. Insight into oxidative stress, macrophages, and their interactions may be important in fully understanding acute worsening of lung disease. This review therefore highlights the current state of the art regarding the role of oxidative stress and macrophages in exacerbations of asthma and COPD. It shows that oxidative stress can attenuate macrophage function, which may result in impaired responses toward exacerbating triggers and may contribute to exaggerated inflammation in the airways.

Small Animal Models of Respiratory Viral Infection Related to Asthma

Respiratory viral infections are strongly associated with asthma exacerbations. Rhinovirus is most frequently-detected pathogen; followed by respiratory syncytial virus; metapneumovirus; parainfluenza virus; enterovirus and coronavirus. In addition; viral infection; in combination with genetics; allergen exposure; microbiome and other pathogens; may play a role in asthma development. In particular; asthma development has been linked to wheezing-associated respiratory viral infections in early life. To understand underlying mechanisms of viral-induced airways disease; investigators have studied respiratory viral infections in small animals. This report reviews animal models of human respiratory viral infection employing mice; rats; guinea pigs; hamsters and ferrets. Investigators have modeled asthma exacerbations by infecting mice with allergic airways disease. Asthma development has been modeled by administration of virus to immature animals. Small animal models of respiratory viral infection will identify cell and molecular targets for the treatment of asthma.

Role of epithelial chemokines in the pathogenesis of airway inflammation in asthma (Review)

As the first barrier to the outside environment, airway epithelial cells serve a central role in the initiation and development of airway inflammation. Chemokines are the most direct and immediate cell factors for the recruitment and migration of inflammatory cells. The present review focused on the role of epithelial chemokines in the pathogenesis of airway inflammation in asthma. In addition to traditional CC family chemokines and CXC family chemokines, airway epithelial cells also express other chemokines, including thymic stromal lymphopoietin and interleukin‑33. By expressing and secreting chemokines, airway epithelial cells serve a key role in orchestrating airway inflammation in asthma.

Human Airway Epithelial Cells Direct Significant Rhinovirus Replication in Monocytic Cells by Enhancing ICAM1 Expression

Human rhinovirus (RV) is the major cause of common cold, and it also plays a significant role in asthma and asthma exacerbation. The airway epithelium is the primary site of RV infection and production. In contrast, monocytic cells (e.g., monocytes and macrophages) are believed to be nonpermissive for RV replication. Instead, RV has been shown to modulate inflammatory gene expressions in these cells via a replication-independent mechanism. In the study presented here, replication of RV16 (a major-group RV) was found to be significantly enhanced in monocytes when it was cocultivated with airway epithelial cells. This effect appeared to be mediated by secretory components from epithelial cells, which stimulated RV16 replication and significantly elevated the expression of a number of proinflammatory cytokines. The lack of such an effect on RV1A, a minor-group RV that enters the cell by a different receptor, suggests that intercellular adhesion molecule 1 (ICAM1), the receptor for major-group RVs, may be involved. Indeed, conditioned media from epithelial cells significantly increased ICAM1 expression in monocytes. Consistently, ICAM1 overexpression and ICAM1 knockdown enhanced and blocked RV production, respectively, confirming the role of ICAM1 in this process. Thus, this is the first report demonstrating that airway epithelial cells direct significant RV16 replication in monocytic cells via an ICAM1-dependent mechanism. This finding will open a new avenue for the study of RV infection in airway disease and its exacerbation.

Gene expression patterns induced at different stages of rhinovirus infection in human alveolar epithelial cells

Human rhinovirus (HRV) is the common virus that causes acute respiratory infection (ARI) and is frequently associated with lower respiratory tract infections (LRTIs). We aimed to investigate whether HRV infection induces a specific gene expression pattern in airway epithelial cells. Alveolar epithelial cell monolayers were infected with HRV species B (HRV-B). RNA was extracted from both supernatants and infected monolayer cells at 6, 12, 24 and 48 hours post infection (hpi) and transcriptional profile was analyzed using Affymetrix GeneChip and the results were subsequently validated using quantitative Real-time PCR method. HRV-B infects alveolar epithelial cells which supports implication of the virus with LRTIs. In total 991 genes were found differentially expressed during the course of infection. Of these, 459 genes were up-regulated whereas 532 genes were down-regulated. Differential gene expression at 6 hpi (187 genes up-regulated vs. 156 down-regulated) were significantly represented by gene ontologies related to the chemokines and inflammatory molecules indicating characteristic of viral infection. The 75 up-regulated genes surpassed the down-regulated genes (35) at 12 hpi and their enriched ontologies fell into discrete functional entities such as regulation of apoptosis, anti-apoptosis, and wound healing. At later time points of 24 and 48 hpi, predominated down-regulated genes were enriched for extracellular matrix proteins and airway remodeling events. Our data provides a comprehensive image of host response to HRV infection. The study suggests the underlying molecular regulatory networks genes which might be involved in pathogenicity of the HRV-B and potential targets for further validations and development of effective treatment.

Airway Epithelial Cells Are Crucial Targets of Glucocorticoids in a Mouse Model of Allergic Asthma

Although glucocorticoids (GCs) are a mainstay in the clinical management of asthma, the target cells that mediate their therapeutic effects are unknown. Contrary to our expectation, we found that GC receptor (GR) expression in immune cells was dispensable for successful therapy of allergic airway inflammation (AAI) with dexamethasone. Instead, GC treatment was compromised in mice expressing a defective GR in the nonhematopoietic compartment or selectively lacking the GR in airway epithelial cells. Further, we found that an intact GR dimerization interface was a prerequisite for the suppression of AAI and airway hyperresponsiveness by GCs. Our observation that the ability of dexamethasone to modulate gene expression in airway epithelial cells coincided with its potency to resolve AAI supports a crucial role for transcriptional regulation by the GR in this cell type. Taken together, we identified an unknown mode of GC action in the treatment of allergic asthma that might help to develop more specific therapies in the future.

Bromodomain and Extra Terminal (BET) Inhibitor Suppresses Macrophage-Driven Steroid-Resistant Exacerbations of Airway Hyper-Responsiveness and Inflammation

BACKGROUND

Exacerbations of asthma are linked to significant decline in lung function and are often poorly controlled by corticosteroid treatment. Clinical investigations indicate that viral and bacterial infections play crucial roles in the onset of steroid-resistant inflammation and airways hyperresponsiveness (AHR) that are hallmark features of exacerbations. We have previously shown that interferon γ (IFNγ) and lipopolysaccharide (LPS) cooperatively activate pulmonary macrophages and induce steroid-resistant airway inflammation and AHR in mouse models. Furthermore, we have established a mouse model of respiratory syncytial virus (RSV)-induced exacerbation of asthma, which exhibits macrophage-dependent, steroid-resistant lung disease. Emerging evidence has demonstrated a key role for bromo- and extra-terminal (BET) proteins in the regulation of inflammatory gene expression in macrophages. We hypothesised that BET proteins may be involved in the regulation of AHR and airway inflammation in our steroid-resistant exacerbation models.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated the effects of a BET inhibitor (I-BET-762) on the development of steroid-resistant AHR and airway inflammation in two mouse models. I-BET-762 administration decreased macrophage and neutrophil infiltration into the airways, and suppressed key inflammatory cytokines in both models. I-BET treatment also suppressed key inflammatory cytokines linked to the development of steroid-resistant inflammation such as monocyte chemoattractant protein 1 (MCP-1), keratinocyte-derived protein chemokine (KC), IFNγ, and interleukin 27 (IL-27). Attenuation of inflammation was associated with suppression of AHR.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that BET proteins play an important role in the regulation of steroid-resistant exacerbations of airway inflammation and AHR. BET proteins may be potential targets for the development of future therapies to treat steroid-resistant inflammatory components of asthma.

Aquaporin-3 potentiates allergic airway inflammation in ovalbumin-induced murine asthma

Oxidative stress plays a pivotal role in the pathogenesis of asthma. Aquaporin-3 (AQP3) is a small transmembrane water/glycerol channel that may facilitate the membrane uptake of hydrogen peroxide (H2O2). Here we report that AQP3 potentiates ovalbumin (OVA)-induced murine asthma by mediating both chemokine production from alveolar macrophages and T cell trafficking. AQP3 deficient (AQP3(-/-)) mice exhibited significantly reduced airway inflammation compared to wild-type mice. Adoptive transfer experiments showed reduced airway eosinophilic inflammation in mice receiving OVA-sensitized splenocytes from AQP3(-/-) mice compared with wild-type mice after OVA challenge, consistently with fewer CD4(+) T cells from AQP3(-/-) mice migrating to the lung than from wild-type mice. Additionally, in vivo and vitro experiments indicated that AQP3 induced the production of some chemokines such as CCL24 and CCL22 through regulating the amount of cellular H2O2 in M2 polarized alveolar macrophages. These results imply a critical role of AQP3 in asthma, and AQP3 may be a novel therapeutic target.

TNF-α and Macrophages Are Critical for Respiratory Syncytial Virus-Induced Exacerbations in a Mouse Model of Allergic Airways Disease

Viral respiratory infections trigger severe exacerbations of asthma, worsen disease symptoms, and impair lung function. To investigate the mechanisms underlying viral exacerbation, we established a mouse model of respiratory syncytial virus (RSV)-induced exacerbation after allergen sensitization and challenge. RSV infection of OVA-sensitized/challenged BALB/c mice resulted in significantly increased airway hyperresponsiveness (AHR) and macrophage and neutrophil lung infiltration. Exacerbation was accompanied by increased levels of inflammatory cytokines (including TNF-α, MCP-1, and keratinocyte-derived protein chemokine [KC]) compared with uninfected OVA-treated mice or OVA-treated mice exposed to UV-inactivated RSV. Dexamethasone treatment completely inhibited all features of allergic disease, including AHR and eosinophil infiltration, in uninfected OVA-sensitized/challenged mice. Conversely, dexamethasone treatment following RSV-induced exacerbation only partially suppressed AHR and failed to dampen macrophage and neutrophil infiltration or inflammatory cytokine production (TNF-α, MCP-1, and KC). This mimics clinical observations in patients with exacerbations, which is associated with increased neutrophils and often poorly responds to corticosteroid therapy. Interestingly, we also observed increased TNF-α levels in sputum samples from patients with neutrophilic asthma. Although RSV-induced exacerbation was resistant to steroid treatment, inhibition of TNF-α and MCP-1 function or depletion of macrophages suppressed features of disease, including AHR and macrophage and neutrophil infiltration. Our findings highlight critical roles for macrophages and inflammatory cytokines (including TNF-α and MCP-1) in viral-induced exacerbation of asthma and suggest examination of these pathways as novel therapeutic approaches for disease management.

Double-stranded RNA evokes exacerbation in a mouse model of corticosteroid refractory asthma

RNA viruses are a major cause of respiratory infections and are known to exacerbate asthma and other respiratory diseases. Our aim was to test the ability of poly(I:C) (polyinosinic:polycytidylic acid), a viral surrogate, to elicit exacerbation in a model of severe asthma driven by HDM (house dust mite) in FCA (Freund's complete adjuvant). Poly(I:C) was administered intranasally around the HDM challenge in FCA-HDM-sensitized animals. Changes in AHR (airway hyperresponsiveness), BALF (bronchoalveolar lavage fluid) inflammatory infiltrate, HDM-specific immunoglobulins and cytokine/chemokine release were evaluated at different points after the challenge. The effect of oral dexamethasone was also assessed. Exacerbation was achieved when poly(I:C) was administered 24 h before the HDM challenge and was characterized by enhanced AHR and an increase in the numbers of neutrophils, macrophages and lymphocytes in the BALF. Th1, Th2 and Th17 cytokines were also elevated at different time points after the challenge. Peribronchial and alveolar inflammation in lung tissue were also augmented. AHR and inflammatory infiltration showed reduced sensitivity to dexamethasone treatment. We have set up a model that mimics key aspects of viral exacerbation in a corticosteroid-refractory asthmatic phenotype which could be used to evaluate new therapies for this condition.

CCL7 and IRF-7 Mediate Hallmark Inflammatory and IFN Responses following Rhinovirus 1B Infection

Rhinovirus (RV) infections are common and have the potential to exacerbate asthma. We have determined the lung transcriptome in RV strain 1B-infected naive BALB/c mice (nonallergic) and identified CCL7 and IFN regulatory factor (IRF)-7 among the most upregulated mRNA transcripts in the lung. To investigate their roles we employed anti-CCL7 Abs and an IRF-7-targeting small interfering RNA in vivo. Neutralizing CCL7 or inhibiting IRF-7 limited neutrophil and macrophage influx and IFN responses in nonallergic mice. Neutralizing CCL7 also reduced activation of NF-κB p65 and p50 subunits, as well as airway hyperreactivity (AHR) in nonallergic mice. However, neither NF-κB subunit activation nor AHR was abolished with infection of allergic mice after neutralizing CCL7, despite a reduction in the number of neutrophils, macrophages, and eosinophils. IRF-7 small interfering RNA primarily suppressed IFN-α and IFN-β levels during infection of allergic mice. Our data highlight a pivotal role of CCL7 and IRF-7 in RV-induced inflammation and IFN responses and link NF-κB signaling to the development of AHR.

CCL2/CCR2-dependent recruitment of Th17 cells but not Tc17 cells to the lung in a murine asthma model

BACKGROUND

Interleukin (IL)-17 has been implicated in the pathogenesis of asthma and the progression of airway inflammation. Here, we used a model of allergic asthma and found that the frequencies of IL-17-secreting T helper (Th)17 and CD8 (Tc)17 cells were both significantly increased, as was the expression of the CC chemokine receptor (CCR2) on the surface of these cells. CC chemokine ligand 2 (CCL2) has been shown to mediate the activation and recruitment of inflammatory cells in asthma, which are also skewed after ovalbumin (OVA) challenge. However, the role of CCL2 on Th17 cells and Tc17 cells in asthma has not been illuminated.

METHODS

Mice that were sensitized and challenged with OVA received anti-CCL2 antibody (Ab; 5 μg/day intratracheally) or CCR2 antagonist (RS504393, 2 mg/kg/day intraperitoneally) prior to the challenge. Some mice received an isotype control Ab or vehicle alone. We then assessed the effects of allergic asthma and anti-CCL2 Ab or CCR2 antagonist treatment on the levels of IL-17 and CCL2, the Th17 and Tc17 cell frequencies and lung tissue inflammation.

RESULTS

We demonstrated that CCL2 and IL-17 levels and the frequency of Th17 and Tc17 cells in lung tissues and bronchoalveolar lavage fluid increased in the asthma group compared with the normal control mice. Blocking the CCL2/CCR2 axis greatly reduced the Th17 but not the Tc17 cell frequency, and revealed a suppressive effect on airway inflammation.

CONCLUSION

These findings indicate a role for the CCL2/CCR2 axis in mediating Th17 but not Tc17 cell migration during acute allergic airway inflammation.

Virus Infection of Airway Epithelial Cells

The airway epithelial cell barrier serves as the main site of replication for most of the common respiratory viruses and is thereby the first line of defense against these viruses. Host epithelial cells are specially enriched for pattern recognition receptors that activate immune response genes to limit viral replication. A prominently expressed set of these genes encodes cytokines that orchestrate key aspects of host defense, such as recruitment of immune cells and repair of epithelial cell damage. Under some circumstances, airway epithelial cells may be programmed to release cytokines (notably IL-33) that activate a type 2 immune response, which in excess might contribute to the development of chronic obstructive lung disease. Moreover, long-term epithelial progenitor cells with this capability may explain an ongoing susceptibility to lung disease in response to acute respiratory infection or other types of inhaled danger signals. The mucosal airway epithelial cell can thereby mediate a beneficial response for host defense and a detrimental response leading to inflammatory disease.

Human rhinovirus induced cytokine/chemokine responses in human airway epithelial and immune cells

Infections with human rhinovirus (HRV) are commonly associated with acute upper and lower respiratory tract disease and asthma exacerbations. The role that HRVs play in these diseases suggests it is important to understand host-specific or virus-specific factors that contribute to pathogenesis. Since species A HRVs are often associated with more serious HRV disease than species B HRVs, differences in immune responses they induce should inform disease pathogenesis. To identify species differences in induced responses, we evaluated 3 species A viruses, HRV 25, 31 and 36 and 3 species B viruses, HRV 4, 35 and 48 by exposing human PBMCs to HRV infected Calu-3 cells. To evaluate the potential effect of memory induced by previous HRV infection on study responses, we tested cord blood mononuclear cells that should be HRV naïve. There were HRV-associated increases (significant increase compared to mock-infected cells) for one or more HRVs for IP-10 and IL-15 that was unaffected by addition of PBMCs, for MIP-1α, MIP-1β, IFN-α, and HGF only with addition of PBMCs, and for ENA-78 only without addition of PBMCs. All three species B HRVs induced higher levels, compared to A HRVs, of MIP-1α and MIP-1β with PBMCs and ENA-78 without PBMCs. In contrast, addition of CBMCs had less effect and did not induce MIP-1α, MIP-1β, or IFN-α nor block ENA-78 production. Addition of CBMCs did, however, increase IP-10 levels for HRV 35 and HRV 36 infection. The presence of an effect with PBMCs and no effect with CBMCs for some responses suggest differences between the two types of cells possibly because of the presence of HRV memory responses in PBMCs and not CBMCs or limited response capacity for the immature CBMCs relative to PBMCs. Thus, our results indicate that different HRV strains can induce different patterns of cytokines and chemokines; some of these differences may be due to differences in memory responses induced by past HRV infections, and other differences related to virus factors that can inform disease pathogenesis.

Phospholipase cε, an effector of ras and rap small GTPases, is required for airway inflammatory response in a mouse model of bronchial asthma

Background

Phospholipase Cε (PLCε) is an effector of Ras and Rap small GTPases and expressed in non-immune cells. It is well established that PLCε plays an important role in skin inflammation, such as that elicited by phorbol ester painting or ultraviolet irradiation and contact dermatitis that is mediated by T helper (Th) 1 cells, through upregulating inflammatory cytokine production by keratinocytes and dermal fibroblasts. However, little is known about whether PLCε is involved in regulation of inflammation in the respiratory system, such as Th2-cells-mediated allergic asthma.

Methods

We prepared a mouse model of allergic asthma using PLCε^+/+ mice and PLCε^ΔX/ΔX mutant mice in which PLCε was catalytically-inactive. Mice with different PLCε genotypes were immunized with ovalbumin (OVA) followed by the challenge with an OVA-containing aerosol to induce asthmatic response, which was assessed by analyzing airway hyper-responsiveness, bronchoalveolar lavage fluids, inflammatory cytokine levels, and OVA-specific immunoglobulin (Ig) levels. Effects of PLCε genotype on cytokine production were also examined with primary-cultured bronchial epithelial cells.

Results

After OVA challenge, the OVA-immunized PLCε^ΔX/ΔX mice exhibited substantially attenuated airway hyper-responsiveness and broncial inflammation, which were accompanied by reduced Th2 cytokine content in the bronchoalveolar lavage fluids. In contrast, the serum levels of OVA-specific IgGs and IgE were not affected by the PLCε genotype, suggesting that sensitization was PLCε-independent. In the challenged mice, PLCε deficiency reduced proinflammatory cytokine production in the bronchial epithelial cells. Primary-cultured bronchial epithelial cells prepared from PLCε^ΔX/ΔX mice showed attenuated pro-inflammatory cytokine production when stimulated with tumor necrosis factor-α, suggesting that reduced cytokine production in PLCε^ΔX/ΔX mice was due to cell-autonomous effect of PLCε deficiency.

Conclusions

PLCε plays an important role in the pathogenesis of bronchial asthma through upregulating inflammatory cytokine production by the bronchial epithelial cells.

Nasopharyngeal gene expression, a novel approach to study the course of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) causes mild infections in the vast majority of children. However, in some cases, it causes severe disease, such as bronchiolitis and pneumonia. Development of severe RSV infection is determined by the host response. Therefore, the main aim of this study was to identify biomarkers associated with severe RSV infection. To identify biomarkers, nasopharyngeal gene expression was profiled by microarray studies, resulting in the selection of five genes: ubiquitin D, tetraspanin 8, mucin 13, β-microseminoprotein and chemokine ligand 7. These genes were validated by real-time quantitative PCR in an independent validation cohort, which confirmed significant differences in gene expression between mildly and severely infected and between recovery and acute patients. Nasopharyngeal aspirate samples are regularly taken when a viral respiratory tract infection is suspected. In this article, we describe a method to discriminate between mild and severe RSV infection based on differential host gene expression. The combination of pathogen detection and host gene expression analysis in nasopharyngeal aspirates will significantly improve the diagnosis and prognosis of respiratory tract infections.

Transmigration and phagocytosis of macrophages in an airway infection model using four-dimensional techniques

During infection, recruited phagocytes transmigrate across the epithelium to remove the pathogens deposited on the airway surface. However, it is difficult to directly observe cellular behaviors (e.g., transmigration) in single-cell layer cultures or in live animals. Combining a three-dimensional (3D) cell coculture model mimicking airway infection with time-lapse confocal imaging as a four-dimensional technique allowed us to image the behaviors of macrophages in 3D over time. The airway infection model was moved to a glass-bottomed dish for live-cell imaging by confocal laser scanning microscopy. Using time-lapse confocal imaging, we recorded macrophages transmigrating across the polyethylene terephthalate (PET) membrane of the inserts through the 5-μm pores in the PET membrane. Macrophages on the apical side of the insert exhibited essentially three types of movements, one of which was transmigrating across the epithelial cell monolayer and arriving at the surface of monolayer. We found that adding Staphylococcus aureus to the model increased the transmigration index but not the transmigration time of the macrophages. Only in the presence of S. aureus were the macrophages able to transmigrate across the epithelial cell monolayer. Apical-to-basal transmigration of macrophages was visualized dynamically. We also imaged the macrophages phagocytizing S. aureus deposited on the surface of the monolayer in the airway infection model. This work provides a useful tool to study the cellular behaviors of immune cells spatially and temporally during infection.

M1 and M2 macrophages: the chicken and the egg of immunity

The purpose of this perspective is to describe a critical advance in understanding how immune responses work. Macrophages are required for all animal life: 'Inhibit' type macrophages in all animals (called M1) can rapidly kill pathogens, and are thus the primary host defense, and 'Heal' type macrophages (M2) routinely repair and maintain tissue integrity. Macrophages perform these activities in all animals without T cells, and also in T cell-deficient vertebrates. Although adaptive immunity can amplify macrophage polarization, the long-held notion that macrophages need to be 'activated' or 'alternatively activated' by T cells is incorrect; indeed, immunology has had it backward. M1/M2-type macrophages necessarily direct T cells toward Th1- or Th2-like activities, respectively. That such macrophage-innate activities are the central directing element in immune responses is a dramatic change in understanding how immune systems operate. Most important, this revelation is opening up whole new approaches to immunotherapy. For example, many modern diseases, such as cancer and atherosclerosis, may not display 'foreign' antigens. However, there are clear imbalances in M1/M2-type responses. Correcting such innate imbalances can result in better health. Macrophages are the chicken and the egg of immunity.

Periostin is required for maximal airways inflammation and hyperresponsiveness in mice

BACKGROUND

Periostin, a secreted extracellular matrix protein, has been localized to deposits of subepithelial fibrosis in asthmatic patients, and periostin levels have been linked to increases in IL-13.

OBJECTIVE

We hypothesized that periostin is required for airway inflammatory responses to a physiologic aeroallergen, house dust mite (HDM).

METHODS

We studied F4-F6 B6;129-Postn(tm1Jmol)/J wild-type (Postn(+/+)) and null (Postn(-/-)) mice, as well as C57BL/6 mice treated with either IgM or OC-20 periostin neutralizing antibody. Mice were exposed to 5 doses of HDM intranasally over a 16-day period.

RESULTS

HDM increased airways responsiveness in Postn(+/+) but not Postn(-/-) mice. In addition, HDM-treated C57BL/6 mice injected with OC-20 had lower airways responsiveness than HDM-treated mice injected with IgM. Compared with Postn(+/+) mice, Postn(-/-) mice showed decreases in HDM-induced inflammation and mucous metaplasia, as well as reduced IL-4, IL-25, CD68, Gob5, and periostin mRNA expression. OC-20 antibody produced similar results. HDM exposure increased periostin expression in the airway epithelium, subepithelium, smooth muscle and inflammatory cells. OC-20 blocked the HDM-induced IgE response, and T cells incubated with dendritic cells (DCs) from Postn(-/-) mice or treated with OC-20 showed deficient DNA synthesis and IL-13 responses compared with T cells incubated with wild-type DCs. Finally, adoptive transfer of bone marrow-derived DCs from Postn(+/+) mice was sufficient to promote allergic responses in F6 Postn(-/-) littermates.

CONCLUSIONS

In mice, periostin is required for maximal airways hyperresponsiveness and inflammation after HDM sensitization and challenge. Periostin is required for maximal HDM-induced T-cell responses.

Neonatal rhinovirus induces mucous metaplasia and airways hyperresponsiveness through IL-25 and type 2 innate lymphoid cells

BACKGROUND

Early-life human rhinovirus infection has been linked to asthma development in high-risk infants and children. Nevertheless, the role of rhinovirus infection in the initiation of asthma remains unclear.

OBJECTIVE

We hypothesized that, in contrast to infection of mature BALB/c mice, neonatal infection with rhinovirus promotes an IL-25-driven type 2 response, which causes persistent mucous metaplasia and airways hyperresponsiveness.

METHODS

Six-day-old and 8-week-old BALB/c mice were inoculated with sham HeLa cell lysate or rhinovirus. Airway responses from 1 to 28 days after infection were assessed by using quantitative PCR, ELISA, histology, immunofluorescence microscopy, flow cytometry, and methacholine responsiveness. Selected mice were treated with a neutralizing antibody to IL-25.

RESULTS

Compared with mature mice, rhinovirus infection in neonatal mice increased lung IL-13 and IL-25 production, whereas IFN-γ, IL-12p40, and TNF-α expression was suppressed. In addition, the population of IL-13-secreting type 2 innate lymphoid cells (ILC2s) was expanded with rhinovirus infection in neonatal but not mature mice. ILC2s were the major cell type secreting IL-13 in neonates. Finally, anti-IL-25 neutralizing antibody attenuated ILC2 expansion, mucous hypersecretion, and airways responsiveness.

CONCLUSIONS

These findings suggest that early-life viral infection could contribute to asthma development by provoking age-dependent, IL-25-driven type 2 immune responses.

Chemerin suppresses murine allergic asthma by inhibiting CCL2 production and subsequent airway recruitment of inflammatory dendritic cells

BACKGROUND

Chemerin has been implicated to play opposing roles, either pro-inflammatory or anti-inflammatory, in various tissue inflammation processes primarily through the regulation of tissue recruitment of immune cells. However, the effect of chemerin in allergic asthma has not yet been explored. We sought to investigate the role of chemerin in the murine model of allergic asthma and explore the underlying mechanism.

METHODS

We examined the effect of intranasal (i.n.) administration of chemerin during antigen challenge in murine models of asthma. Moreover, we examined whether administration of CCL2 or bone marrow-derived dendritic cells (BMDCs) transfer reversed the effects of chemerin on ovalbumin-induced asthma. We finally examined the effect of chemerin on CCL2 expression in activated lung epithelial cells in vitro.

RESULTS

The administration of chemerin attenuated allergic airway inflammation and airway hyperreactivity during antigen challenge. Chemerin treatment caused significant decreases in BALF CD4(+) T-cell accumulation and mRNA expression of Th2-attracting chemokines, CCL17 and CCL22, which was accompanied by significantly decreased BALF CD11c(+) CD11b(+) inflammatory DC accumulation and CCL2 production. Furthermore, airway administration of exogenous CCL2 or adoptive transfer of CD11c(+) CD11b(+) BMDCs abrogated the suppressive effects of chemerin on allergic asthma. Finally, in vitro study showed that chemerin inhibited CCL2 secretion by low-dose LPS-stimulated lung epithelial cells, which led to decreased chemotaxis of BMDCs.

CONCLUSIONS

Our study demonstrates that chemerin plays a protective role in allergic asthma by suppressing airway recruitment of inflammatory CD11c(+) CD11b(+) DCs through the inhibition of CCL2 secretion by active lung epithelial cells.

Development of a mouse model mimicking key aspects of a viral asthma exacerbation

Viral respiratory tract infections are known triggers of asthma exacerbations in both adults and children. The current standard of care, inhaled CS (corticosteroids) and LABAs (long-acting β2-adrenoceptor agonists), fails to prevent the loss of control that manifests as an exacerbation. In order to better understand the mechanisms underlying viral asthma exacerbations we established an in vivo model using the clinically relevant aeroallergen HDM (house dust mite) and the viral mimetic/TLR3 (Toll-like receptor 3) agonist poly(I:C). Poly(I:C) alone induced a similar neutrophilic inflammatory profile in the BAL (bronchoalveolar lavage) to that of HRV1b (human rhinovirus 1b) alone, accompanied by both elevated BAL KC (keratinocyte-derived chemokine) and IL-1β (interleukin-1β). When mice allergic to HDM were also challenged with poly(I:C) the neutrophilic inflammatory profile was exacerbated. Increased CD8(+) T-cell numbers, increased CD4(+) and CD8(+) cell activation and elevated KC and IL-1β were observed. No increases in Th2 cytokines or the eosinophil chemoattractant CCL11 [chemokine (C-C motif) ligand 11], above those induced by HDM alone, were observed. The poly(I:C)-exacerbated neutrophilia did not translate into changes in AHR (airways hyper-responsiveness), indicating that in this model inflammation and AHR are two mechanistically independent events. To test the clinical relevance of this model CS sensitivity was assessed using prednisone, a synthetic oral CS used to manage exacerbations in asthmatic patients already on maximal doses of inhaled CS. The increased neutrophils, and accompanying cytokines/chemokines KC and IL-1β induced by poly(I:C) challenge of HDM-sensitized and challenged mice were insensitive to oral prednisone therapy. In summary we have described a CS-resistant mouse model mimicking the key aspects of viral asthma exacerbation using the clinically relevant aeroallergen HDM and the viral mimic poly(I:C). This model may provide better understanding of disease mechanisms underlying viral exacerbations and could be used to build early confidence in novel therapeutic axes targeting viral asthma exacerbations in Th2 asthmatics.

Salmeterol attenuates chemotactic responses in rhinovirus-induced exacerbation of allergic airways disease by modulating protein phosphatase 2A

BACKGROUND

β-Agonists are used for relief and control of asthma symptoms by reversing bronchoconstriction. They might also have anti-inflammatory properties, but the underpinning mechanisms remain poorly understood. Recently, a direct interaction between formoterol and protein phosphatase 2A (PP2A) has been described in vitro.

OBJECTIVE

We sought to elucidate the molecular mechanisms by which β-agonists exert anti-inflammatory effects in allergen-driven and rhinovirus 1B-exacerbated allergic airways disease (AAD).

METHODS

Mice were sensitized and then challenged with house dust mite to induce AAD while receiving treatment with salmeterol, formoterol, or salbutamol. Mice were also infected with rhinovirus 1B to exacerbate lung inflammation and therapeutically administered salmeterol, dexamethasone, or the PP2A-activating drug (S)-2-amino-4-(4-[heptyloxy]phenyl)-2-methylbutan-1-ol (AAL[S]).

RESULTS

Systemic or intranasal administration of salmeterol protected against the development of allergen- and rhinovirus-induced airway hyperreactivity and decreased eosinophil recruitment to the lungs as effectively as dexamethasone. Formoterol and salbutamol also showed anti-inflammatory properties. Salmeterol, but not dexamethasone, increased PP2A activity, which reduced CCL11, CCL20, and CXCL2 expression and reduced levels of phosphorylated extracellular signal-regulated kinase 1 and active nuclear factor κB subunits in the lungs. The anti-inflammatory effect of salmeterol was blocked by targeting the catalytic subunit of PP2A with small RNA interference. Conversely, increasing PP2A activity with AAL(S) abolished rhinovirus-induced airway hyperreactivity, eosinophil influx, and CCL11, CCL20, and CXCL2 expression. Salmeterol also directly activated immunoprecipitated PP2A in vitro isolated from human airway epithelial cells.

CONCLUSIONS

Salmeterol exerts anti-inflammatory effects by increasing PP2A activity in AAD and rhinovirus-induced lung inflammation, which might potentially account for some of its clinical benefits.

Perilla frutescens leaf extract inhibits mite major allergen Der p 2-induced gene expression of pro-allergic and pro-inflammatory cytokines in human bronchial epithelial cell BEAS-2B

Perilla frutescens has been used in traditional medicine for respiratory diseases due to its anti-bacterial and anti-inflammatory activity. This study aimed to investigate effects of Perilla frutescens leaf extract (PFE) on expression of pro-allergic and pro-inflammatory cytokines in airway epithelial cells exposed to mite major allergen Der p 2 (DP2) and the underlying mechanisms. Our results showed that PFE up to 100 µg/mL had no cytotoxic effect on human bronchial epithelial cell BEAS-2B. Further investigations revealed that PFE dose-dependently diminished mRNA expression of pro-allergic cytokine IL-4, IL-5, IL-13 and GM-CSF, as well as pro-inflammatory cytokine IL-6, IL-8 and MCP-1 in BEAS-2B cells treated with DP2. In parallel to mRNA, the DP-2-elevated levels of the tested cytokines were decreased. Further investigation showed that DP2-indued phosphorylation of p38 MAPK (P38) and JNK, but not Erk1/2, was also suppressed by PFE. In addition, PFE elevated cytosolic IκBα level and decreased nuclear NF-κB level in DP2-stimulated BEAS-2B cells. Taken together, these findings revealed that PFE significantly diminished both mRNA expression and protein levels of pro-allergic and pro-inflammatory cytokines in response to DP2 through inhibition of P38/JNK and NK-κB activation. These findings suggest that PFE should be beneficial to alleviate both allergic and inflammatory responses on airway epithelium in response to aeroallergens.

ATF3 Protects against LPS-Induced Inflammation in Mice via Inhibiting HMGB1 Expression

Lipopolysaccharide (LPS) triggers innate immunity mainly via TLR4 signaling. ATF3 is a negative regulator of TLR4 signaling. HMGB1 plays a critical role in the final step of sepsis. However, the mechanisms of ATF3 and the role of HMGB1 in regulating innate immunity-induced sepsis are incompletely understood. In this study, we found that serum HMGB1 levels were 10-fold higher in patients with sepsis than normal controls. We further demonstrated that ATF3 gene knockout in mice subjected to LPS-induced endotoxemia correlates with an increase in the mortality rate and the elevated expression of IL-6, TNF-α, NO, MCP-1, and HMGB1 in the lung tissues or serum. The biochemical effects of ATF3 were observed in in vitro macrophages and blocked by ATF3 siRNA treatment. We have also shown that adeno-associated virus-mediated ATF3 gene transfer protected ATF3 knockout mice from LPS-induced mortality. In addition, ATF3 knockdown increased LPS-induced release of HMGB1. In conclusion, upregulation of ATF3 contributes to the reduced release of inflammatory molecules, especially HMGB1, which induced lung injury and increased the survival rate of mice after LPS challenge. Therefore, suppressing LPS-induced inflammation with ATF3 induction or ATF3 mimetics may be an important strategy for sepsis therapy.

Substance P-immunoreactive cells in the ovine pars tuberalis

The pars tuberalis (PT) is a distinct subdivision of the anterior pituitary gland that plays a central role in regulating seasonal prolactin release. In sheep, there is compelling evidence that seasonal changes in light, transformed into a melatonin signal, are interpreted by the PT to modulate the release of a factor which affects prolactin release. The identity of this factor(s) is unknown but has been preemptively called 'tuberalin'. In the present study, we report on an initial immunocytochemical investigation where we have identified that many ovine PT cells are immunoreactive for the tachykinin substance P (SP). Few cells in the pars distalis immunoreact for SP. The SP-immunoreactive cells did not colocalize with beta-luteinizing hormone. RT-PCR confirmed the presence of preprotachykinin A mRNA in the PT. We hypothesize that SP, and possibly other preprotachykinin A-derived tachykinins, may play a role in the seasonal regulation of prolactin secretion in sheep.