Spatial and phenotypic characterization of vascular remodeling in a mouse model of asthma

Korean Red Ginseng suppresses emphysematous lesions induced by cigarette smoke condensate through inhibition of macrophage-driven apoptosis pathways

Background

Cigarette smoke is generally accepted as a major contributor to chronic obstructive pulmonary disease (COPD), which is characterized by emphysematous lesions. In this study, we investigated the protective effects of Korean Red Ginseng (KRG) against cigarette smoke condensate (CSC)-induced emphysema.

Methods

Mice were instilled with 50 mg/kg of CSC intranasally once a week for 4 weeks, KRG was administered to the mice once daily for 4 weeks at doses of 100 or 300 mg/kg, and dexamethasone (DEX, positive control) was administered to the mice once daily for 2 weeks at 3 mg/kg.

Results

KRG markedly decreased the macrophage population in bronchoalveolar lavage fluid and reduced emphysematous lesions in the lung tissues. KRG suppressed CSC-induced apoptosis as revealed by terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling staining and Caspase 3 immunohistochemistry. Additionally, KRG effectively inhibited CSC-mediated activation of Bcl-2-associated X protein/Caspase 3 signaling, followed by the induction of cell survival signaling, including vascular endothelial growth factor/phosphoinositide 3-kinase/protein kinase B in vivo and in vitro. The DEX group also showed similar improved results in vivo and in vitro.

Conclusion

Taken together, KRG effectively inhibits macrophage-mediated emphysema induced by CSC exposure, possibly via the suppression of pro-apoptotic signaling, which results in cell survival pathway activation. These findings suggest that KRG has therapeutic potential for the prevention of emphysema in COPD patients.

Mild allergic airways responses to an environmental mixture increase cardiovascular risk in rats

Recent epidemiological findings link asthma to adverse cardiovascular responses. Yet, the precise cardiovascular impacts of asthma have been challenging to disentangle from the potential cardiovascular effects caused by asthma medication. The purpose of this study was to determine the impacts of allergic airways disease alone on cardiovascular function in an experimental model. Female Wistar rats were intranasally sensitized and then challenged once per week for 5 weeks with saline vehicle or a mixture of environmental allergens (ragweed, house dust mite, and Aspergillus fumigatus). Ventilatory and cardiovascular function, measured using double-chamber plethysmography and implantable blood pressure (BP) telemetry and cardiovascular ultrasound, respectively, were assessed before sensitization and after single and final allergen challenge. Responses to a single 0.5 ppm ozone exposure and to the cardiac arrhythmogenic agent aconitine were also assessed after final challenge. A single allergen challenge in sensitized rats increased tidal volume and specific airways resistance in response to provocation with methacholine and increased bronchoalveolar lavage fluid (BALF) eosinophils, neutrophils, lymphocytes, cytokines interleukin (IL)-4, IL-5, IL-10, IL-1β, tumor necrosis factor-α, and keratinocyte chemoattract-growth-related oncogene characteristic of allergic airways responses. Lung responses after final allergen challenge in sensitized rats were diminished, although ozone exposure increased BALF IL-6, IL-13, IL-1 β, and interferon-γ and modified ventilatory responses only in the allergen group. Final allergen challenge also increased systolic and mean arterial BP, stroke volume, cardiac output, end-diastolic volume, sensitivity to aconitine-induced cardiac arrhythmia, and cardiac gene expression with lesser effects after a single challenge. These findings demonstrate that allergic airways responses may increase cardiovascular risk in part by altering BP and myocardial function and by causing cardiac electrical instability.

Silencing of miR-10b-5p alleviates the mechanical stretch-induced proliferation of HASMCs

MicroRNAs (miRNAs) are important mediators to human airway smooth muscle cells (HASMCs) phenotype remodeling and airway diseases. MicroRNA-10b-5p (miR-10b-5p) has been extensively studied in different fields. This study set out to probe into the effect of miR-10b-5p in cyclic mechanical stretch-induced apoptosis in HASMCs. The results showed that after 15 % deformation, 0.5 s stretching and 0.5 s cyclic mechanical stretching relaxation (0.5 Hz) occurred to HASMCs, miR-10b-5p showed up-regulation without inducing significant apoptosis. Moreover, the mRNA and protein expressions of FLT1 were reduced. Then, dual-luciferase reporter assay verified that FLT1 was targeted by miR-10b-5p, and miR-10b-5p silencing increased FLT1 expression, leading to a prolonged arrest of stretch-treated HASMCs at the G1/S stage, and increased cell apoptosis compared with control group. Furthermore, the activity of Caspase-3 was reinforced, and the ratio of Bcl-2 to Bax was markedly reduced after miR-10b-5p silencing. The current study proved that expression levels of p-PI3K and p-Akt in stretch-treated HASMCs of the inhibition group were significantly inhibited in comparison to those of the controls. The effects of miR-10b-5p overexpression are opposite to that of inhibition of miR-10b-5p in stretched HASMCs. In conclusion, this study showed that miR-10b-5p silencing could weaken the hypertrophy of HASMCs. MiR-10b-5p negatively regulated FLT1 expression, but positively regulated the PI3K/Akt pathway in HASMCs. By referring to other previous studies, we concluded that miR-10b-5p might be a potent target in the treatment of airway diseases.

Mahuang decoction mitigates airway inflammation and regulates IL-21/STAT3 signaling pathway in rat asthma model

ETHNOPHARMACOLOGICAL RELEVANCE

Nowadays, bronchial asthma is still a severe disease threatening human health, and it is incumbent upon us to seek effective therapeutic drugs. Mahuang decoction (MHD), a classic famous Chinese prescription, has been used for thousands of years to prevent phlegm from forming, stop coughing and relieve asthma, but the relevant mechanism has not been thoroughly clarified. This study aims to investigate the anti-airway inflammation effect of MHD and the possible molecular mechanism underlying IL21/STAT3 signaling pathway, so as to provide guidance for the treatment of MHD on bronchial asthma.

MATERIALS AND METHODS

Specific pathogen free SD rats were randomly divided into 6 groups: normal control group, model group, positive group (Compound methoxyphenamine), MHD-treated groups at doses of 10 ml/kg, 5 ml/kg and 2.5 ml/kg, 10 rats in each group. Except for the normal control group, rats in other groups were sensitized with ovalbumin via introperitoneal injection and challenged with ovalbumin inhalation to trigger asthma model. At 24 h after the last excitation, bronchoalveolar lavage fluid (BALF) of every rat was drawn and the number of inflammatory cells was analyzed using cell counting method. ELISA method was performed to determine the concentrations of TXB₂, 6-keto-PGF_1α, MMP-9, TIMP-1, IL-2, IL-4, IL-5 and TNF-α in rat serum. The protein expressions of IL-21, IL-21R, STAT3 and p-STAT3 in murine pulmonary tissues were assessed with western blotting analysis.

RESULTS

Compared with the control group, the airway wall and airway smooth muscle of murine pulmonary tissues significantly thickened and massive inflammatory cells infiltration occurred around the bronchus in the model group, and the cell counts of WBC and EOS in BALF were also apparently increased, which indicated the rat asthma model was successfully established. MHD or Compound methoxyphenamine not only alleviated the pulmonary inflammatory pathological damages, but also down- regulated the numbers of WBC and EOS in BALF. What's more, the levels of TXB₂, MMP-9, TIMP-1, ILs-(2, 4, 5) and TNF-α in rat serum were lessened by the treatment of MHD. In western blotting analysis, treatment with 10 ml/kg or 5 ml/kg MHD markedly declined the increased protein expressions of IL-21, IL-21R, STAT3 and p-STAT3 in lung tissues of asthmatic rats to normal level.

CONCLUSION

MHD intervention demonstrated a strong inhibitory action on the secretion of inflammatory mediators as well as the inflammatory cell infiltration in pulmonary tissues of asthmatic rats, and also depressed the protein expressions of IL-21, IL-21R, STAT3 and p-STAT3 in pulmonary tissues. MHD effectively mitigates airway inflammation and regulates the IL-21/STAT3 signaling pathway in rat asthma model.

IgE mediates broncho-vascular remodeling after neonatal sensitization in mice

The temporal origins of childhood asthma are incompletely understood. We hypothesize that allergen sensitization which begins in early infancy causes IgE-mediated airway and vascular remodeling, and airway hyper-responsiveness. Mice were sensitized with ovalbumin (OVA) without or with anti-IgE antibody from postnatal day (P) 10 through P42. We studied airway resistance in response to Methacholine (MCh) challenge, bronchoalveolar lavage fluid (BAL) inflammatory cell content, immunohistochemistry for inflammation, alpha-smooth muscle actin (alpha-SMA) and platelet/endothelial cell adhesion molecule (PECAM) proteins, and Western blotting for vascular endothelial growth factor (VEGF) protein. Compared to controls, mice treated with OVA had increased airway resistance (baseline: 192% of control; MCH 12 mg/mL 170% of control; P less than 0.0.5). OVA treatment also increased lung alpha-SMA, VEGF and PECAM compared to controls. Inflammatory cells in the BAL and perivascular and peribronchiolar inflammatory cell infiltrates increased over controls with OVA exposure. These changes were counteracted by anti-IgE treatment. We conclude that mice sensitized in early infancy develop an IgE-mediated hyper-reactive airway disease with airway and vascular remodeling. Preventive approaches in early infancy of at-risk individuals may reduce childhood asthma.

Asthma is not only an airway disease, but also a vascular disease

Multiple studies have identified an expansion and morphological dysregulation of the bronchial vascular network in the airways of asthmatics. Increased number, size and density of blood vessels, as well as vascular leakage and plasma engorgement, have been reported in the airways of patients with all grades of asthma from mild to fatal. This neovascularisation is an increasingly commonly reported feature of airway remodelling; however, the pathophysiological impact of the increased vasculature in the bronchial wall and its significance to pulmonary function in asthma are unrecognised at this time. Multiple factors capable of influencing the development and persistence of the vascular network exist within asthmatic airway tissue. These include structural components of the altered extracellular matrix (ECM), imbalance of proteases and their endogenous inhibitors, release of active matrikines and the dysregulated levels of both soluble and matrix sequestered growth factors. This review will explore the features of the asthmatic airway which influence the development and persistence of the increased vascular network, as well as the effect of enhanced tissue perfusion on chronic inflammation and airway dynamics. The response of cells of the airways to the altered vascular profile and the subsequent influence on the features of airway remodelling will also be highlighted. We will explore the failure of current asthma therapeutics in "normalising" this vascular remodelling. Finally, we will summarize the outcomes of recent clinical trials which provide hope that anti-angiogenic therapies may be a potent asthma-resolving class of drugs and provide a new approach to asthma management in the future.

Neuronal chemorepellent Semaphorin 3E inhibits human airway smooth muscle cell proliferation and migration

BACKGROUND

Chronic airway diseases, including asthma, are characterized by increased airway smooth muscle (ASM) mass that is due in part to growth factor-mediated ASM cell proliferation and migration. However, the molecular mechanisms underlying these effects are not completely understood. Semaphorin 3E (Sema3E) has emerged as an essential mediator involved in cell migration, proliferation, and angiogenesis, although its role in ASM cell function is not investigated.

OBJECTIVES

We sought to determine the expression of Sema3E receptor, plexinD1, in human ASM cells (HASMCs); effect of Sema3E on basal and platelet-derived growth factor (PDGF)-induced proliferation and migration; and underlying signaling pathways.

METHODS

Expression of plexinD1 in HASMCs was studied with RT-PCR, immunostaining, and flow cytometry. The effect of Sema3E on HASMC proliferation and migration was evaluated by 5-ethynyl-2'-deoxyuridine (EdU) incorporation, cell count, and Boyden chamber assay. Sema3E-mediated intracellular signaling was investigated with fluorescent microscopy, flow cytometry, Rac1 activation, and Western blot analysis.

RESULTS

HASMCs from healthy persons expressed plexinD1 more than HASMCs from asthmatic patients. Sema3E increased plexinD1 expression in HASMCs from asthmatic patients. Recombinant Sema3E inhibited PDGF-mediated HASMC proliferation and migration, which was associated with F-actin depolymerization, suppression of PDGF-induced Rac1 guanosine triphosphatase activity, and Akt and extracellular signal-regulated kinase 1 and 2 phosphorylation. Bronchial biopsies from patients with mild asthma displayed immunoreactivity of plexinD1, suggesting the potential in vivo role of Sema3E-PlexinD1 axis in HASMC function.

CONCLUSION

This study provides the first evidence that Sema3E receptor is expressed and plays functional roles in HASMCs. Our data suggest a regulatory role of Sema3E in PDGF-mediated proliferation and migration, leading to downregulation of ASM remodeling.

Are mouse models of asthma appropriate for investigating the pathogenesis of airway hyper-responsiveness?

Whether mouse models of chronic asthma can be used to investigate the relationship between airway inflammation/remodeling and airway hyper-responsiveness (AHR) is a vexed question. It raises issues about the extent to which such models replicate key features of the human disease. Here, we review some of the characteristic pathological features of human asthma and their relationship to AHR and examine some limitations of mouse models that are commonly used to investigate these relationships. We compare these conventional models with our mouse model of chronic asthma involving long-term low-level inhalational challenge and review studies of the relationship between inflammation/remodeling and AHR in this model and its derivatives, including models of an acute exacerbation of chronic asthma and of the induction phase of childhood asthma. We conclude that while extrapolating from studies in mouse models to AHR in humans requires cautious interpretation, such experimental work can provide significant insights into the pathogenesis of airway responsiveness and its molecular and cellular regulation.

Endothelial cell-specific deletion of transcription factor FoxM1 increases urethane-induced lung carcinogenesis

Vascular endothelial cells provide essential support to the tumor microenvironment, but little is known about the transcriptional control of endothelial functions during tumorigenesis. Here we define a critical role for the Forkhead transcription factor FoxM1 in modulating the development of tumor-associated endothelial cells. Pulmonary tumorigenesis induced by urethane administration was compared in mice genetically deleted for FoxM1 in endothelial cells (enFoxm1(-/-) mice). Notably, lung tumor number and size were increased in enFoxm1(-/-) mice. Increased tumorigenesis was associated with increased proliferation of tumor cells and increased expression of c-Myc and cyclin D1. Furthermore, perivascular infiltration by inflammatory cells was elevated and inflammatory cells in BAL fluid were increased. Expression of Flk-1 (vascular endothelial growth factor receptor 2) and FoxF1, known regulators of pulmonary inflammation, was decreased in enFoxm1(-/-) mice. siRNA-mediated knockdown of FoxM1 in endothelial cells reduced Flk-1 and FoxF1 expression, which was driven by direct transcriptional induction by FoxM1 as target genes. Endothelial specific deletion of FoxM1 in vivo or in vitro also decreased expression of Sfrp1 (secreted frizzled-related protein 1), a known inhibitor of canonical Wnt signaling, in a manner that was associated with increased Wnt signaling. Taken together, our results suggest that endothelial-specific expression of FoxM1 limits lung inflammation and canonical Wnt signaling in lung epithelial cells, thereby restricting lung tumorigenesis.

CXCR2 mediates the recruitment of endothelial progenitor cells during allergic airways remodeling

Airway remodeling is a central feature of asthma and includes the formation of new peribronchial blood vessels, which is termed angiogenesis. In a number of disease models, bone marrow-derived endothelial progenitor cells (EPCs) have been shown to contribute to the angiogenic response. In this study we set out to determine whether EPCs were recruited into the lungs in a model of allergic airways disease and to identify the factors regulating EPC trafficking in this model. We observed a significant increase in the number of peribronchial blood vessels at day 24, during the acute inflammatory phase of the model. This angiogenic response was associated with an increase in the quantity of EPCs recoverable from the lung. These EPCs formed colonies after 21 days in culture and were shown to express CD31, von Willebrand factor, and vascular endothelial growth factor (VEGF) receptor 2, but were negative for CD45 and CD14. The influx in EPCs was associated with a significant increase in the proangiogenic factors VEGF-A and the CXCR2 ligands, CXCL1 and CXCL2. However, we show directly that, while the CXCL1 and CXCL2 chemokines can recruit EPCs into the lungs of allergen-sensitized mice, VEGF-A was ineffective in this respect. Further, the blockade of CXCR2 significantly reduced EPC numbers in the lungs after allergen exposure and led to a decrease in the numbers of peribronchial blood vessels after allergen challenge with no effect on inflammation. The data presented here provide in vivo evidence that CXCR2 is critical for both EPC recruitment and the angiogenic response in this model of allergic inflammation of the airways.

Capillary defects and exaggerated inflammatory response in the airways of EphA2-deficient mice

Both Eph receptors and ephrin ligands have been implicated in blood vessel and neuronal development. Recent studies suggested that EphA2 inhibition reduces tumor angiogenesis, but its role in blood vessel development and inflammation is unclear. We examined these issues using either airways of pathogen-free, EphA2-deficient mice at various ages or EphA2-deficient mice whose airways were inflamed by either Mycoplasma pulmonis infection or ovalbumin sensitization and challenge. EphA2-deficient mice had fewer capillaries, a greater number of endothelial sprouts, and greater capillary diameters than age-matched, wild-type control mice. Moreover, capillaries in EphA2-deficient mice had significantly less pericyte coverage, suggesting abnormal interactions between endothelial cells and pericytes. These differences were apparent in early postnatal life but decreased during progression into adulthood. In inflamed airways, significantly more angiogenesis and lymphangiogenesis, a greater number of infiltrating leukocytes, and higher expression levels of inflammatory cytokine mRNA were present in EphA2-deficient mice after M. pulmonis infection. Additionally, in allergic airway inflammation with ovalbumin sensitization and challenge, a greater number of lymphatic sprouts and infiltrating leukocytes, higher mRNA expression levels of TH2 cytokines and chemokines related to allergic airway inflammation, and enhanced airway hyper-responsiveness were present in EphA2-deficient mice. We conclude that defective pericyte coverage causes capillary defects, abundant endothelial sprouts, and thick capillary diameters in EphA2-deficient mice, indicating that these animals have exaggerated responses to airway inflammation.