Bronchial angiogenesis in severe glucocorticoid-dependent asthma

Location, Location, Location: Spatial Immune-Stroma Crosstalk Drives Pathogenesis in Asthma

Chronic lung diseases including asthma are characterized by an abnormal immune response and active tissue remodeling. These changes in the architecture of the tissue are a fundamental part of the pathology across the life course of patients suffering from asthma. Current treatments aim at dampening the immune system hyperactivation, but effective drugs targeting stromal or acellular structures are still lacking. This is mainly due to the lack of a detailed understanding of the composition of the large airways and the cellular interactions taking place in this niche. We and others have revealed multiple aspects of the spatial architecture of the airway wall in response to airborne insults. In this review, we discuss four elements that we believe should be the focus of future asthma research across the life course, to increase understanding and improve therapies: (i) specialized lung niches, (ii) the 3D architecture of the epithelium, (iii) the extracellular matrix, and (iv) the vasculature. These components comprise the main stromal structures at the airway wall, each playing a key role in the development of asthma and directing the immune response. We summarize promising future directions that will enhance lung research, ultimately benefiting patients with asthma.

Rhinovirus induces airway remodeling: what are the physiological consequences?

BACKGROUND

Rhinovirus infections commonly evoke asthma exacerbations in children and adults. Recurrent asthma exacerbations are associated with injury-repair responses in the airways that collectively contribute to airway remodeling. The physiological consequences of airway remodeling can manifest as irreversible airway obstruction and diminished responsiveness to bronchodilators. Structural cells of the airway, including epithelial cells, smooth muscle, fibroblasts, myofibroblasts, and adjacent lung vascular endothelial cells represent an understudied and emerging source of cellular and extracellular soluble mediators and matrix components that contribute to airway remodeling in a rhinovirus-evoked inflammatory environment.

MAIN BODY

While mechanistic pathways associated with rhinovirus-induced airway remodeling are still not fully characterized, infected airway epithelial cells robustly produce type 2 cytokines and chemokines, as well as pro-angiogenic and fibroblast activating factors that act in a paracrine manner on neighboring airway cells to stimulate remodeling responses. Morphological transformation of structural cells in response to rhinovirus promotes remodeling phenotypes including induction of mucus hypersecretion, epithelial-to-mesenchymal transition, and fibroblast-to-myofibroblast transdifferentiation. Rhinovirus exposure elicits airway hyperresponsiveness contributing to irreversible airway obstruction. This obstruction can occur as a consequence of sub-epithelial thickening mediated by smooth muscle migration and myofibroblast activity, or through independent mechanisms mediated by modulation of the β2 agonist receptor activation and its responsiveness to bronchodilators. Differential cellular responses emerge in response to rhinovirus infection that predispose asthmatic individuals to persistent signatures of airway remodeling, including exaggerated type 2 inflammation, enhanced extracellular matrix deposition, and robust production of pro-angiogenic mediators.

CONCLUSIONS

Few therapies address symptoms of rhinovirus-induced airway remodeling, though understanding the contribution of structural cells to these processes may elucidate future translational targets to alleviate symptoms of rhinovirus-induced exacerbations.

Distribution, composition, and activity of airway-associated adipose tissue in the porcine lung

Patients with comorbid asthma-obesity experience greater disease severity and are less responsive to therapy. We have previously reported adipose tissue within the airway wall that positively correlated with body mass index. Accumulation of biologically active adipose tissue may result in the local release of adipokines and disrupt large and small airway function depending on its anatomical distribution. This study therefore characterized airway-associated adipose tissue distribution, lipid composition, and adipokine activity in a porcine model. Airway segments were systematically dissected from different locations of the bronchial tree in inflation-fixed lungs. Cryosections were stained with hematoxylin and eosin (H&E) for airway morphology, oil red O to distinguish adipose tissue, and Nile blue A for lipid subtype delineation. Excised airway-associated adipose tissue was cultured for 72 h to quantify adipokine release using immunoassays. Results showed that airway-associated adipose tissue extended throughout the bronchial tree and occupied an area proportionally similar to airway smooth muscle within the wall area. Lipid composition consisted of pure neutral lipids (61.7 ± 3.5%), a mixture of neutral and acidic lipids (36.3 ± 3.4%), or pure acidic lipids (2.0 ± 0.8%). Following tissue culture, there was rapid release of IFN-γ, IL-1β, and TNF-α at 12 h. Maximum IL-4 and IL-10 release was at 24 and 48 h, and peak leptin release occurred between 48 and 72 h. These data extend previous findings and demonstrate that airway-associated adipose tissue is prevalent and biologically active within the bronchial tree, providing a local source of adipokines that may be a contributing factor in airway disease.

Airway remodeling heterogeneity in asthma and its relationship to disease outcomes

Asthma affects an estimated 262 million people worldwide and caused over 461,000 deaths in 2019. The disease is characterized by chronic airway inflammation, reversible bronchoconstriction, and airway remodeling. Longitudinal studies have shown that current treatments for asthma (inhaled bronchodilators and corticosteroids) can reduce the frequency of exacerbations, but do not modify disease outcomes over time. Further, longitudinal studies in children to adulthood have shown that these treatments do not improve asthma severity or fixed airflow obstruction over time. In asthma, fixed airflow obstruction is caused by remodeling of the airway wall, but such airway remodeling also significantly contributes to airway closure during bronchoconstriction in acute asthmatic episodes. The goal of the current review is to understand what is known about the heterogeneity of airway remodeling in asthma and how this contributes to the disease process. We provide an overview of the existing knowledge on airway remodeling features observed in asthma, including loss of epithelial integrity, mucous cell metaplasia, extracellular matrix remodeling in both the airways and vessels, angiogenesis, and increased smooth muscle mass. While such studies have provided extensive knowledge on different aspects of airway remodeling, they have relied on biopsy sampling or pathological assessment of lungs from fatal asthma patients, which have limitations for understanding airway heterogeneity and the entire asthma syndrome. To further understand the heterogeneity of airway remodeling in asthma, we highlight the potential of in vivo imaging tools such as computed tomography and magnetic resonance imaging. Such volumetric imaging tools provide the opportunity to assess the heterogeneity of airway remodeling within the whole lung and have led to the novel identification of heterogenous gas trapping and mucus plugging as important predictors of patient outcomes. Lastly, we summarize the current knowledge of modification of airway remodeling with available asthma therapeutics to highlight the need for future studies that use in vivo imaging tools to assess airway remodeling outcomes.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

Cell-specific drug targeting in the lung

Non-targeted drug delivery systems have several limitations including the decreased bioavailability of the drug, poor stability and rapid clearance in addition to off-target distribution. Cell-specific targeted delivery approaches promise to overcome some of these limitations and enhance therapeutic selectivity. In this review, we aim to discuss cell-specific targeted approachesin the lung at the biochemical and molecular levels. These approaches include;a) directly administered small molecule drugs with intracellular action; b) targeted biologics and synthetic hybrids with extracellular action; c) site activateddrugs; and d) delivery systems.We discuss the pharmaceutical and biochemical parameters that govern the fate of drug molecules at delivery sites while presenting an overview of relevant literature surrounding this area of research and current advancements.

Lost in transition: biomarkers of remodeling in patients with asthma

PURPOSE OF REVIEW

'Biomarkers of remodeling' represent a loose collection of features referring to several biological adaptations of the lung to cope with stressing factors. In addition, remodel-'ing' infers a dynamic process that would require a spatiotemporal resolution. This review focuses on different aspects of remodeling in pediatric and adult care.

RECENT FINDINGS

This review will cover aspects of pediatric remodeling, adult remodeling and techniques and procedures to adequately assess remodeling across different age spectra. In pediatrics, the onset and first features of remodeling are discussed and the continuation into adolescence is addressed. For adults, this review addresses predominant features of remodeling throughout the adult life span and whether there are currently interventions available to treat or reverse remodeling.

SUMMARY

The term 'remodeling' is often referred to via biomarkers that reflect the endstage of a process, although it rather reflects a continuous process starting in childhood and progressing to all age-levels in patients with asthma. Hence, only few biomarkers or surrogates are able to 'capture' its spatiotemporal component, and hardly any are ready for routine use in clinical practice. Given the clinical impact of the remodeling processes, new biomarkers are needed to adequately treat patients with asthma and objectively monitor treatment response beyond symptom control and lung function.

Citrullinated histone H3, a marker of extracellular trap formation, is increased in blood of stable asthma patients

BACKGROUND

Emerging data indicates that extracellular traps (ETs), structures formed by various immune cell types, may contribute to the pathology of noninfectious inflammatory diseases. Histone hypercitrullination is an important step in ETs formation and citrullinated histone H3 (H3cit) is considered a novel and specific biomarker of that process. In the present study we have evaluated circulating H3cit in stable asthmatics and investigated its relationship with asthma severity, pulmonary function and selected blood and bronchoalveolar lavage (BAL) biomarkers.

METHODS

In 60 white adult stable asthmatics and 50 well-matched controls we measured serum levels of H3cit. In asthmatics we also performed bronchoscopy with BAL. We analyzed blood and BAL biomarkers, including interleukin (IL)-4, IL-5, IL-6, IL-10, IL-12p70, IL-17A and interferon γ. For statistical analysis, Mann-Whitney U-test, χ2 test, one-way ANCOVA, ROC curve analysis and univariate linear regression were applied. Independent determinants of H3cit were established in a multiple linear regression model.

RESULTS

Asthma was characterized by elevated circulating H3cit (17.49 [11.25-22.58] vs. 13.66 [8.66-18.87] ng/ml, p = 0.03). In asthmatics positive associations were demonstrated between serum H3cit and lung function variables, including total lung capacity (TLC) (β = 0.37 [95% CI 0.24-0.50]) and residual volume (β = 0.38 [95% CI 0.25-0.51]). H3cit was increased in asthma patients receiving systemic steroids (p = 0.02), as well as in subjects with BAL eosinophilia above 144 cells/ml (p = 0.02). In asthmatics, but not in controls, circulating H3cit correlated well with number of neutrophils (β = 0.31 [95% CI 0.19-0.44]) and monocytes (β = 0.42 [95% CI 0.29-0.55]) in peripheral blood. Furthermore, BAL macrophages, BAL neutrophils, TLC, high-sensitivity C-reactive protein, Il-12p70 and bronchial obstruction degree were independent determinants of H3cit in a multivariate linear regression model.

CONCLUSIONS

Asthma is characterized by increased circulating H3cit likely related to the enhanced lung ETs formation. Inhibition of ETs might be a therapeutic option in selected asthma phenotypes, such as neutrophilic asthma.

An endothelial microRNA-1-regulated network controls eosinophil trafficking in asthma and chronic rhinosinusitis

BACKGROUND

Airway eosinophilia is a prominent feature of asthma and chronic rhinosinusitis (CRS), and the endothelium plays a key role in eosinophil trafficking. To date, microRNA-1 (miR-1) is the only microRNA known to be regulated in the lung endothelium in asthma models.

OBJECTIVE

We sought to determine the role of endothelial miR-1 in allergic airway inflammation.

METHODS

We measured microRNA and mRNA expression using quantitative RT-PCR. We used ovalbumin and house dust mite models of asthma. Endothelium-specific overexpression of miR-1 was achieved through lentiviral vector delivery or induction of a transgene. Tissue eosinophilia was quantified by using Congo red and anti-eosinophil peroxidase staining. We measured eosinophil binding with a Sykes-Moore adhesion chamber. Target recruitment to RNA-induced silencing complex was assessed by using anti-Argonaute2 RNA immunoprecipitation. Surface P-selectin levels were measured by using flow cytometry.

RESULTS

Serum miR-1 levels had inverse correlations with sputum eosinophilia, airway obstruction, and number of hospitalizations in asthmatic patients and sinonasal tissue eosinophilia in patients with CRS. IL-13 stimulation decreased miR-1 levels in human lung endothelium. Endothelium-specific overexpression of miR-1 reduced airway eosinophilia and asthma phenotypes in murine models and inhibited IL-13-induced eosinophil binding to endothelial cells. miR-1 recruited P-selectin, thymic stromal lymphopoietin, eotaxin-3, and thrombopoietin receptor to the RNA-induced silencing complex; downregulated these genes in the lung endothelium; and reduced surface P-selectin levels in IL-13-stimulated endothelial cells. In our asthma and CRS cohorts, miR-1 levels correlated inversely with its target genes.

CONCLUSION

Endothelial miR-1 regulates eosinophil trafficking in the setting of allergic airway inflammation. miR-1 has therapeutic potential in asthmatic patients and patients with CRS.

Arginine metabolic control of airway inflammation

Inducible nitric oxide synthase (iNOS) and arginase-2 (ARG2) share a common substrate, arginine. Higher expression of iNOS and exhaled NO are linked to airway inflammation in patients. iNOS deletion in animal models suggests that eosinophilic inflammation is regulated by arginine metabolism. Moreover, ARG2 is a regulator of Th2 response, as shown by the development of severe eosinophilic inflammation in ARG2-/- mice. However, potential synergistic roles of iNOS and ARG2 in asthma have not been explored. Here, we hypothesized that arginine metabolic fate via iNOS and ARG2 may govern airway inflammation. In an asthma cohort, ARG2 variant genotypes were associated with arginase activity. ARG2 variants with lower arginase activity, combined with levels of exhaled NO, identified a severe asthma phenotype. Airway inflammation was present in WT, ARG2-/-, iNOS-/-, and ARG2-/-/iNOS-/- mice but was greatest in ARG2-/-. Eosinophilic and neutrophilic infiltration in the ARG2-/- mice was abrogated in ARG2-/-/iNOS-/- animals. Similarly, angiogenic airway remodeling was greatest in ARG2-/- mice. Cytokines driving inflammation and remodeling were highest in lungs of asthmatic ARG2-/- mice and lowest in the iNOS-/-. ARG2 metabolism of arginine suppresses inflammation, while iNOS metabolism promotes airway inflammation, supporting a central role for arginine metabolic control of inflammation.

Multi-Faceted Notch in Allergic Airway Inflammation

Notch is an evolutionarily conserved signaling family which iteratively exerts pleiotropic functions in cell fate decisions and various physiological processes, not only during embryonic development but also throughout adult life. In the context of the respiratory system, Notch has been shown to regulate ciliated versus secretory lineage differentiation of epithelial progenitor cells and coordinate morphogenesis of the developing lung. Reminiscent of its role in development, the Notch signaling pathway also plays a role in repair of lung injuries by regulation of stem cell activity, cell differentiation, cell proliferation and apoptosis. In addition to functions in embryonic development, cell and tissue renewal and various physiological processes, including glucose and lipid metabolism, Notch signaling has been demonstrated to regulate differentiation of literally almost all T-cell subsets, and impact on elicitation of inflammatory response and its outcome. We have investigated the role of Notch in allergic airway inflammation in both acute and chronic settings. In this mini-review, we will summarize our own work and recent advances on the role of Notch signaling in allergic airway inflammation, and discuss potential applications of the Notch signaling family in therapy for allergic airway diseases.

Contribution of airway eosinophils in airway wall remodeling in asthma: Role of MMP-10 and MET

BACKGROUND

Eosinophils play an important role in the pathophysiology of asthma being implicated in airway epithelial damage and airway wall remodeling. We determined the genes associated with airway remodeling and eosinophilic inflammation in patients with asthma.

METHODS

We analyzed the transcriptomic data from bronchial biopsies of 81 patients with moderate-to-severe asthma of the U-BIOPRED cohort. Expression profiling was performed using Affymetrix arrays on total RNA. Transcription binding site analysis used the PRIMA algorithm. Localization of proteins was by immunohistochemistry.

RESULTS

Using stringent false discovery rate analysis, MMP-10 and MET were significantly overexpressed in biopsies with high mucosal eosinophils (HE) compared to low mucosal eosinophil (LE) numbers. Immunohistochemical analysis confirmed increased expression of MMP-10 and MET in bronchial epithelial cells and in subepithelial inflammatory and resident cells in asthmatic biopsies. Using less-stringent conditions (raw P-value < 0.05, log2 fold change > 0.5), we defined a 73-gene set characteristic of the HE compared to the LE group. Thirty-three of 73 genes drove the pathway annotation that included extracellular matrix (ECM) organization, mast cell activation, CC-chemokine receptor binding, circulating immunoglobulin complex, serine protease inhibitors, and microtubule bundle formation pathways. Genes including MET and MMP10 involved in ECM organization correlated positively with submucosal thickness. Transcription factor binding site analysis identified two transcription factors, ETS-1 and SOX family proteins, that showed positive correlation with MMP10 and MET expression.

CONCLUSION

Pathways of airway remodeling and cellular inflammation are associated with submucosal eosinophilia. MET and MMP-10 likely play an important role in these processes.

Omalizumab may decrease the thickness of the reticular basement membrane and fibronectin deposit in the bronchial mucosa of severe allergic asthmatics

Introduction: Immunoglobulin E is an important modulator of the inflammatory reaction in allergic asthma. It also contributes to airway remodeling in the course of the disease. The authors evaluated airway structural changes in severe allergic asthma during the omalizumab therapy. Patients and methods: The study included 13 patients with severe allergic asthma treated with omalizumab for at least one year. In each patient clinical, laboratory, and spirometry parameters were evaluated before and after the treatment. In addition, bronchoscopy with bronchial mucosa biopsy and bronchoalveolar lavage was performed. The basal lamina thickness, inflammatory cell infiltration, fibronectin, as well as type I and III collagen accumulation were assessed in bronchial mucosa specimens, together with the assessment of bronchoalveolar lavage cellularity. Results: The omalizumab therapy led to a decrease in the basal lamina thickness (p = 0.002), and to a reduction in fibronectin (p = 0.02), but not collagen deposits in the bronchial mucosa. The decrease in fibronectin accumulation was associated with an improvement in asthma control and quality of life (p = 0.01, both), and a diminished dose of systemic corticosteroids (p = 0.001). It was also associated with a tendency towards reduction of the eosinophil count in the peripheral blood, bronchoalveolar lavage fluid, and bronchial mucosa specimens. Conclusion: Our study has shown that omalizumab, effective in the treatment of severe allergic asthma, may also decrease unfavorable structural airway changes in allergic asthmatics, at least with respect to the fibronectin deposit and an increased thickness of the basal lamina. However, more extensive observational studies are needed to verify the above hypothesis.

Recent advances in understanding the roles of blood platelets in the pathogenesis of allergic inflammation and bronchial asthma

Platelets play an essential role in hemostasis to minimize blood loss due to traumatic injury. In addition, they contain various immune-associated molecules and contribute to immunological barrier formation at sites of vascular injury, thereby protecting against invading pathogens. Platelets are also crucially involved in development of allergic diseases, including bronchial asthma. Platelets in asthmatics are more activated than those in healthy individuals. By using a murine asthma model, platelets were shown to be actively involved in progression of the disease, including in airway eosinophilia and airway remodeling. In the asthmatic airway, pathological microvascular angiogenesis, a component of airway remodeling, is commonly observed, and the degree of abnormality is significantly associated with disease severity. Therefore, in order to repair the newly formed and structurally fragile blood vessels under inflammatory conditions, platelets may be continuously activated in asthmatics. Importantly, platelets constitutively express IL-33 protein, an alarmin cytokine that is essential for development of bronchial asthma. Meanwhile, the concept of development of allergic diseases has recently changed dramatically, and allergy researchers now share a belief in the centrality of epithelial barrier functions. In particular, IL-33 released from epithelial barrier tissue at sites of eczema can activate the antigen-non-specific innate immune system as an alarmin that is believed to be necessary for subsequent antigen-specific acquired immunological responses. From this perspective, we propose in this review a possible mechanism for how activated platelets act as an alarmin in development of bronchial asthma.

Endothelial cells in the innate response to allergens and initiation of atopic asthma

Protease-activated receptor 2 (PAR-2), an airway epithelial pattern recognition receptor (PRR), participates in the genesis of house dust mite-induced (HDM-induced) asthma. Here, we hypothesized that lung endothelial cells and proangiogenic hematopoietic progenitor cells (PACs) that express high levels of PAR-2 contribute to the initiation of atopic asthma. HDM extract (HDME) protease allergens were found deep in the airway mucosa and breaching the endothelial barrier. Lung endothelial cells and PACs released the Th2-promoting cytokines IL-1α and GM-CSF in response to HDME, and the endothelium had PAC-derived VEGF-C-dependent blood vessel sprouting. Blockade of the angiogenic response by inhibition of VEGF-C signaling lessened the development of inflammation and airway remodeling in the HDM model. Reconstitution of the bone marrow in WT mice with PAR-2-deficient bone marrow also reduced airway inflammation and remodeling. Adoptive transfer of PACs that had been exposed to HDME induced angiogenesis and Th2 inflammation with remodeling similar to that induced by allergen challenge. Our findings identify that lung endothelium and PACs in the airway sense allergen and elicit an angiogenic response that is central to the innate nonimmune origins of Th2 inflammation.

New targets for resolution of airway remodeling in obstructive lung diseases

Airway remodeling (AR) is a progressive pathological feature of the obstructive lung diseases, including asthma and chronic obstructive pulmonary disease (COPD). The pathology manifests itself in the form of significant, progressive, and (to date) seemingly irreversible changes to distinct respiratory structural compartments. Consequently, AR correlates with disease severity and the gradual decline in pulmonary function associated with asthma and COPD. Although current asthma/COPD drugs manage airway contraction and inflammation, none of these effectively prevent or reverse features of AR. In this review, we provide a brief overview of the features and putative mechanisms affecting AR. We further discuss recently proposed strategies with promise for deterring or treating AR.

Upper and lower airway remodelling mechanisms in asthma, allergic rhinitis and chronic rhinosinusitis: The one airway concept revisited

Allergic rhinitis (AR), chronic rhinosinusitis (CRS) and asthma often co-exist. The one airway model proposes that disease mechanisms occurring in the upper airway may mirror lower airway events. Airway remodelling is the term used to describe tissue structural changes that occur in a disease setting and reflect the dynamic process of tissue restructuring during wound repair. Remodelling has been long identified in the lower airways in asthma and is characterized by epithelial shedding, goblet cell hyperplasia, basement membrane thickening, subepithelial fibrosis, airway smooth muscle hyperplasia and increased angiogenesis. The concept of upper airway remodelling has only recently been introduced, and data so far are limited and often conflicting, an indication that more detailed studies are needed. Whilst remodelling changes in AR are limited, CRS phenotypes demonstrate epithelial hyperplasia, increased matrix deposition and degradation along with accumulation of plasma proteins. Despite extensive research over the past years, the precise cellular and molecular mechanisms involved in airway remodelling remain incompletely defined. This review describes our current rather limited understanding of airway remodelling processes in AR, CRS and asthma and presents mechanisms both shared and distinct between the upper and lower airways. Delineation of shared and disease-specific pathogenic mechanisms of remodelling between the sinonasal system and the lung may guide the rational design of more effective therapeutic strategies targeting upper and lower airways concomitantly and improving the health of individuals with inflammatory airway diseases.

The beclomethasone anti-inflammatory effect occurs in cell/mediator-dependent manner and is additively enhanced by formoterol: NFkB, p38, PKA analysis

AIMS

Beclomethasone/formoterol (BDP/FOR) has been reported to be more effective than its separate components in airway disease control and in airway inflammation improvement. However, BDP/FOR effects on cytokine-induced inflammation in structural cells have not been described and whether these effects occur in a cell- and mediator-dependent manner has not been fully elucidated. We sought to evaluate BDP and/or FOR effects on endothelial ICAM-1, E-selectin, IL-8 and on bronchial epithelial ICAM-1 and IL-8. Specific intracellular signaling pathways were also investigated.

MATERIALS AND METHODS

Surface adhesion molecule expression and IL-8 release induced by TNF-alpha were measured by ELISA. Intracellular signaling pathways were investigated by a) EMSA and Western blot analysis to evaluate NF-κB DNA-binding and MAPK-p38 phosphorylation; b) PDTC/SB203580 as NF-κB/p38 inhibitors; c) forskolin/H-89 as PKA activator/inhibitor.

KEY FINDINGS

BDP/FOR additively reduced endothelial E-selectin and IL-8 as well as bronchial epithelial ICAM-1 and IL-8. BDP/FOR and SB203580 showed the highest inhibitory effect on epithelial IL-8, whereas endothelial ICAM-1 was never affected by BDP/FOR and PDTC. TNF-alpha-induced NF-κB DNA-binding and MAPK-p38 phosphorylation were not influenced by BDP/FOR. Forskolin mimicked FOR effects; H-89 partially reversed the BDP/FOR inhibition in a mediator-dependent manner.

SIGNIFICANCE

The BDP/FOR inhibition degree was related to the inflammatory mediator- and cell-type considered. FOR additively enhanced BDP effects by partially involving both dependent- and independent-PKA mechanisms. Our results might contribute to highlight the strong relationship between specific molecular pathways and different sensitivity to the corticosteroid/β2-agonist effects and to clarify the molecular mechanisms underlying the BDP/FOR anti-inflammatory activity in vivo.

Airway pathology in severe asthma is related to airflow obstruction but not symptom control

BACKGROUND

Patients with asthma present structural and inflammatory alterations that are believed to play a role in disease severity. However, airway remodeling and inflammation have not been extensively investigated in relation to both symptom control and airflow obstruction in severe asthmatics. We aimed to investigate several inflammatory and structural pathological features in bronchial biopsies of severe asthmatics that could be related to symptom control and airflow obstruction after standardized treatment.

METHODS

Fifty severe asthmatics received prednisone 40 mg/d for 2 weeks and maintenance therapy with budesonide/formoterol 400/12 μg twice daily + budesonide/formoterol 200/6 μg as needed for 12 weeks. Endobronchial biopsies were performed at the end of 12 weeks. We performed extensive immunopathological analyses of airway tissue inflammation and remodeling features in patients stratified by asthma symptom control and by airflow obstruction.

RESULTS

Airway tissue inflammation and remodeling were not associated with symptom control. Asthmatics with persistent airflow obstruction had greater airway smooth muscle (Asm) area with decreased periostin and transforming growth factor beta-positive cells within Asm bundles, in addition to lower numbers of chymase-positive mast cells in the submucosa compared to patients with nonpersistent obstruction.

CONCLUSIONS

Symptom control in severe asthmatics was not associated with airway tissue inflammation and remodeling, although persistent airflow obstruction in these patients was associated with bronchial inflammation and airway structural changes.

Interleukin-17A and vascular remodelling in severe asthma; lack of evidence for a direct role

BACKGROUND

Bronchial vascular remodelling may contribute to the severity of airway narrowing through mucosal congestion. Interleukin (IL)-17A is associated with the most severe asthmatic phenotype but whether it might contribute to vascular remodelling is uncertain.

OBJECTIVE

To assess vascular remodelling in severe asthma and whether IL-17A directly or indirectly may cause endothelial cell activation and angiogenesis.

METHODS

Bronchial vascularization was quantified in asthmatic subjects, COPD and healthy subjects together with the number of IL-17A⁺ cells as well as the concentration of angiogenic factors in the sputum. The effect of IL-17A on in vitro angiogenesis, cell migration and endothelial permeability was assessed directly on primary human lung microvascular endothelial cells (HMVEC-L) or indirectly with conditioned medium derived from normal bronchial epithelial cells (NHBEC), fibroblasts (NHBF) and airway smooth muscle cells (ASMC) after IL-17A stimulation.

RESULTS

Severe asthmatics have increased vascularity compared to the other groups, which correlates positively with the concentrations of angiogenic factors in sputum. Interestingly, we demonstrated that increased bronchial vascularity correlates positively with the number of subepithelial IL-17A⁺ cells. However IL-17A had no direct effect on HMVEC-L function but it enhanced endothelial tube formation and cell migration through the production of angiogenic factors by NHBE and ASMC.

CONCLUSIONS & CLINICAL RELEVANCE

Our results shed light on the role of IL-17A in vascular remodelling, most likely through stimulating the synthesis of other angiogenic factors. Knowledge of these pathways may aid in the identification of new therapeutic targets.

Proteomic identification of moesin upon exposure to acrolein

Background

Acrolein (allyl Aldehyde) as one of smoke irritant exacerbates chronic airway diseases and increased in sputum of patients with asthma and chronic obstructive lung disease. But underlying mechanism remains unresolved. The aim of study was to identify protein expression in human lung microvascular endothelial cells (HMVEC-L) exposed to acrolein.

Methods

A proteomic approach was used to determine the different expression of proteins at 8 h and 24 h after treatment of acrolein 30 nM and 300 nM to HMVEC-L. Treatment of HMVEC-L with acrolein 30 nM and 300 nM altered 21 protein spots on the two-dimensional gel, and these were then analyzed by MALDI-TOF MS.

Results

These proteins included antioxidant, signal transduction, cytoskeleton, protein transduction, catalytic reduction. The proteins were classified into four groups according to the time course of their expression patterns such as continually increasing, transient increasing, transient decreasing, and continually decreasing. For validation immunohistochemical staining and Western blotting was performed on lung tissues from acrolein exposed mice. Moesin was expressed in endothelium, epithelium, and inflammatory cells and increased in lung tissues of acrolein exposed mice compared with sham treated mice.

Conclusions

These results indicate that some of proteins may be an important role for airway disease exacerbation caused by acrolein exposure.

Electronic supplementary material

The online version of this article (10.1186/s12953-017-0130-4) contains supplementary material, which is available to authorized users.

Severe Asthma: Have We Made Progress?

Tremendous efforts have been invested in research to (1) discover risk factors, biomarkers, and clinical characteristics; (2) understand the pathophysiology and treatment response variability in severe asthma; and (3) design new therapies. However, to combat severe asthma, many questions concerning the pathogenesis of severe asthma, including its natural history, genetic and environmental risk factors, and disease mechanisms, must be answered. In this article we highlight some of the major discoveries concerning the pathogenesis of severe asthma and its therapeutic development. We conclude that discoveries on numerous fronts of severe asthma, from disease heterogeneity, features of airway remodeling, cytokine mediators and signaling pathways underlying disease pathogenesis, disease mechanisms, potential biomarkers, to new therapeutic targets, demonstrate that progress has been made in understanding and developing more effective treatments for this difficult-to-treat disease.

Anti-angiogenic Nanotherapy Inhibits Airway Remodeling and Hyper-responsiveness of Dust Mite Triggered Asthma in the Brown Norway Rat

Although angiogenesis is a hallmark feature of asthmatic inflammatory responses, therapeutic anti-angiogenesis interventions have received little attention. Objective: Assess the effectiveness of anti-angiogenic Sn2 lipase-labile prodrugs delivered via α_vβ₃-micellar nanotherapy to suppress microvascular expansion, bronchial remodeling, and airway hyper-responsiveness in Brown Norway rats exposed to serial house dust mite (HDM) inhalation challenges. Results: Anti-neovascular effectiveness of α_vβ₃-mixed micelles incorporating docetaxel-prodrug (Dxtl-PD) or fumagillin-prodrug (Fum-PD) were shown to robustly suppress neovascular expansion (p<0.01) in the upper airways/bronchi of HDM rats using simultaneous ¹⁹F/¹H MR neovascular imaging, which was corroborated by adjunctive fluorescent microscopy. Micelles without a drug payload (α_vβ₃-No-Drug) served as a carrier-only control. Morphometric measurements of HDM rat airway size (perimeter) and vessel number at 21d revealed classic vascular expansion in control rats but less vascularity (p<0.001) after the anti-angiogenic nanotherapies. CD31 RNA expression independently corroborated the decrease in airway microvasculature. Methacholine (MCh) induced respiratory system resistance (Rrs) was high in the HDM rats receiving α_vβ₃-No-Drug micelles while α_vβ₃-Dxtl-PD or α_vβ₃-Fum-PD micelles markedly and equivalently attenuated airway hyper-responsiveness and improved airway compliance. Total inflammatory BAL cells among HDM challenged rats did not differ with treatment, but α_vβ₃⁺ macrophages/monocytes were significantly reduced by both nanotherapies (p<0.001), most notably by the α_vβ₃-Dxtl-PD micelles. Additionally, α_vβ₃-Dxtl-PD decreased BAL eosinophil and α_vβ₃⁺ CD45⁺ leukocytes relative to α_vβ₃-No-Drug micelles, whereas α_vβ₃-Fum-PD micelles did not. Conclusion: These results demonstrate the potential of targeted anti-angiogenesis nanotherapy to ameliorate the inflammatory hallmarks of asthma in a clinically relevant rodent model.

BMPR2 mutation status influences bronchial vascular changes in pulmonary arterial hypertension

The impact of bone morphogenetic protein receptor 2 (BMPR2) gene mutations on vascular remodelling in pulmonary arterial hypertension (PAH) is unknown. We sought to identify a histological profile of BMPR2 mutation carriers.Clinical data and lung histology from 44 PAH patients were subjected to systematic analysis and morphometry.Bronchial artery hypertrophy/dilatation and bronchial angiogenesis, as well as muscular remodelling of septal veins were significantly increased in PAH lungs carrying BMPR2 mutations. We found that patients displaying increased bronchial artery remodelling and bronchial microvessel density, irrespective of the mutation status, were more likely to suffer from severe haemoptysis. History of substantial haemoptysis (>50 mL) was significantly more frequent in BMPR2 mutation carriers. 43.5% of BMPR2 mutation carriers, as opposed to 9.5% of noncarriers, displayed singular large fibrovascular lesions, which appear to be closely related to the systemic lung vasculature.Our analysis provides evidence for the involvement of the pulmonary systemic circulation in BMPR2 mutation-related PAH. We show that BMPR2 mutation carriers are more prone to haemoptysis and that haemoptysis is closely correlated to bronchial arterial remodelling and angiogenesis; in turn, pronounced changes in the systemic vasculature correlate with increased pulmonary venous remodelling, creating a distinctive profile in PAH patients harbouring a BMPR2 mutation.

Effectiveness of bronchial thermoplasty in patients with severe refractory asthma: Clinical and histopathologic correlations

BACKGROUND

The effectiveness of bronchial thermoplasty (BT) has been reported in patients with severe asthma, yet its effect on different bronchial structures remains unknown.

OBJECTIVE

We sought to examine the effect of BT on bronchial structures and to explore the association with clinical outcome in patients with severe refractory asthma.

METHODS

Bronchial biopsy specimens (n = 300) were collected from 15 patients with severe uncontrolled asthma before and 3 months after BT. Immunostained sections were assessed for airway smooth muscle (ASM) area, subepithelial basement membrane thickness, nerve fibers, and epithelial neuroendocrine cells. Histopathologic findings were correlated with clinical parameters.

RESULTS

BT significantly improved asthma control and quality of life at both 3 and 12 months and decreased the numbers of severe exacerbations and the dose of oral corticosteroids. At 3 months, this clinical benefit was accompanied by a reduction in ASM area (median values before and after BT, respectively: 19.7% [25th-75th interquartile range (IQR), 15.9% to 22.4%] and 5.3% [25th-75th IQR], 3.5% to 10.1%, P < .001), subepithelial basement membrane thickening (4.4 μm [25th-75th IQR, 4.0-4.7 μm] and 3.9 μm [25th-75th IQR, 3.7-4.6 μm], P = 0.02), submucosal nerves (1.0 ‰ [25th-75th IQR, 0.7-1.3 ‰] immunoreactivity and 0.3 ‰ [25th-75th IQR, 0.1-0.5 ‰] immunoreactivity, P < .001), ASM-associated nerves (452.6 [25th-75th IQR, 196.0-811.2] immunoreactive pixels per mm² and 62.7 [25th-75th IQR, 0.0-230.3] immunoreactive pixels per mm², P = .02), and epithelial neuroendocrine cells (4.9/mm² [25th-75th IQR, 0-16.4/mm²] and 0.0/mm² [25th-75th IQR, 0-0/mm²], P = .02). Histopathologic parameters were associated based on Asthma Control Test scores, numbers of exacerbations, and visits to the emergency department (all P ≤ .02) 3 and 12 months after BT.

CONCLUSION

BT is a treatment option in patients with severe therapy-refractory asthma that downregulates selectively structural abnormalities involved in airway narrowing and bronchial reactivity, particularly ASM, neuroendocrine epithelial cells, and bronchial nerve endings.

Eotaxin-Rich Proangiogenic Hematopoietic Progenitor Cells and CCR3+ Endothelium in the Atopic Asthmatic Response

Angiogenesis is closely linked to and precedes eosinophilic infiltration in asthma. Eosinophils are recruited into the airway by chemoattractant eotaxins, which are expressed by endothelial cells, smooth muscles cells, epithelial cells, and hematopoietic cells. We hypothesized that bone marrow-derived proangiogenic progenitor cells that contain eotaxins contribute to the initiation of angiogenesis and inflammation in asthma. Whole-lung allergen challenge of atopic asthma patients revealed vascular activation occurs within hours of challenge and before airway inflammation. The eotaxin receptor CCR3 was expressed at high levels on submucosal endothelial cells in patients and a murine model of asthma. Ex vivo exposure of murine endothelial cells to eotaxins induced migration and angiogenesis. In mechanistic studies, wild-type mice transplanted with eotaxin-1/2-deficient bone marrow had markedly less angiogenesis and inflammation in an atopic asthma model, whereas adoptive transfer of proangiogenic progenitor cells from wild-type mice in an atopic asthma model into the eotaxin-1/2-deficient mice led to angiogenesis and airway inflammation. The findings indicate that Th2-promoting hematopoietic progenitor cells are rapidly recruited to the lung upon allergen exposure and release eotaxins that coordinately activate endothelial cells, angiogenesis, and airway inflammation.

Angiopoietin-2 concentration in serum is associated with severe asthma phenotype

Background

Several proangiogenic molecules have been implicated in the pathogenies of asthmatic inflammation and remodeling. The aim of the study was to compare the concentration of proangiogenic factors in the sera of asthmatic patients and in healthy subjects (HS), and to refer the concentrations to both clinical and inflammatory markers of the disease severity.

Methods

Serum was collected from 45 patients with severe/refractory asthma (SRA) and 51 patients with non-severe asthma (nSA). The control group included 30 HS. Serum concentrations of Angiopoietin-1, Angiopoietin-2, vascular endothelial growth factor (VEGF) and osteopontin were assessed by the enzyme-linked immunosorbent assay.

Results

The levels of Angiopoietin-1 (68.8 ± 2.7 vs 56.4 ± 9.3 ng/ml; p < 0.05), Angiopoietin-2 (4.9 ± 0.35 vs 1.38 ± 0.14 ng/ml; p < 0.0001) and VEGF were significantly higher in asthmatic patients (n = 94) as compared to HS (255 ± 45.4 vs 424.5 ± 27.8 pg/ml; p < 0.01). The mean serum level of Angiopoietin-2 was found to be significantly higher in patients with SRA as compared to nSA patients (6.04 ± 0.46 vs 3.84 ± 0.43; p < 0.001). Angiopoietin-2 serum level correlated with respiratory function and with parameters of asthma severity: the mean number of asthma exacerbations in the preceding 12 months (R = 0.21; p < 0.05), mean number of emergency visits due to severe asthma exacerbation (R = 0.24; p < 0.04) and mean number of hospitalizations (R = 0.21; p < 0.05) or dose of inhaled glucocorticosteroids taken by the patients (R = 0.36; p < 0.001).

Conclusion

Angiopoietin-2 seems to be a crucial proangiogenic cytokine overproduced in patients with SRA characterized by repeated exacerbations and Angiopoietin-2 serum levels can serve as a biomarker of severe asthma.

Recent advances in understanding the roles of vascular endothelial cells in allergic inflammation

Allergic disorders commonly involve both chronic tissue inflammation and remodeling caused by immunological reactions to various antigens on tissue surfaces. Due to their anatomical location, vascular endothelial cells are the final responders to interact with various exogenous factors that come into contact with the epithelial surface, such as pathogen-associated molecular patterns (PAMPs) and antigens. Recent studies have shed light on the important roles of endothelial cells in the development and exacerbation of allergic disorders. For instance, endothelial cells have the greatest potential to produce several key molecules that are deeply involved in allergic inflammation, such as periostin and thymus and activation-regulated chemokine (TARC/CCL17). Additionally, endothelial cells were recently shown to be important functional targets for IL-33--an essential regulator of allergic inflammation. Notably, almost all endothelial cell responses and functions involved in allergic inflammation are not suppressed by corticosteroids. These corticosteroid-refractory endothelial cell responses and functions include TNF-α-associated angiogenesis, leukocyte adhesion, IL-33-mediated responses and periostin and TARC production. Therefore, these unique responses and functions of endothelial cells may be critically involved in the pathogenesis of various allergic disorders, especially their refractory processes. Here, we review recent studies, including ours, which have elucidated previously unknown pathophysiological roles of vascular endothelial cells in allergic inflammation and discuss the possibility of endothelium-targeted therapy for allergic disorders.

The Three A's in Asthma - Airway Smooth Muscle, Airway Remodeling & Angiogenesis

Asthma affects more than 300 million people worldwide and its prevalence is still rising. Acute asthma attacks are characterized by severe symptoms such as breathlessness, wheezing, tightness of the chest, and coughing, which may lead to hospitalization or death. Besides the acute symptoms, asthma is characterized by persistent airway inflammation and airway wall remodeling. The term airway wall remodeling summarizes the structural changes in the airway wall: epithelial cell shedding, goblet cell hyperplasia, hyperplasia and hypertrophy of the airway smooth muscle (ASM) bundles, basement membrane thickening and increased vascular density. Airway wall remodeling starts early in the pathogenesis of asthma and today it is suggested that remodeling is a prerequisite for other asthma pathologies. The beneficial effect of bronchial thermoplasty in reducing asthma symptoms, together with the increased potential of ASM cells of asthmatics to produce inflammatory and angiogenic factors, indicate that the ASM cell is a major effector cell in the pathology of asthma. In the present review we discuss the ASM cell and its role in airway wall remodeling and angiogenesis.

Pathobiology of severe asthma

Severe asthma (SA) afflicts a heterogeneous group of asthma patients who exhibit poor responses to traditional asthma medications. SA patients likely represent 5-10% of all asthma patients; however, they have a higher economic burden when compared with milder asthmatics. Considerable research has been performed on pathological pathways and structural changes associated with SA. Although limitations of the pathological approaches, ranging from sampling, to quantitative assessments, to heterogeneity of disease, have prevented a more definitive understanding of the underlying pathobiology, studies linking pathology to molecular markers to targeted therapies are beginning to solidify the identification of select molecular phenotypes. This review addresses the pathobiology of SA and discusses the current limitations of studies, the inflammatory cells and pathways linked to emerging phenotypes, and the structural and remodeling changes associated with severe disease. In all cases, an effort is made to link pathological findings to specific clinical/molecular phenotypes.

Analysis of growth factors in serum and induced sputum from patients with asthma

Epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), the AA and BB isoforms of platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) are involved in the pathogenesis of airway inflammation in asthma. In the present study, the associations between asthmatic phenotypes and the expression levels of these mediators in induced sputum and serum were investigated. A total of 62 asthmatic patients were divided into eosinophilic or neutrophilic phenotypes by cytological classification of the induced sputum. In addition, patients were classified according to lung function (FEV1/FVC >70% or FEV1/FVC <70%) and asthma severity (mild, moderate or severe). The concentrations of EGF, bFGF, PDGF-AA, PDGF-BB and VEGF in the serum and induced sputum were measured using sandwich enzyme immunoassays. VEGF levels in the serum and induced sputum were higher in patients with an eosinophilic phenotype compared with those with a neutrophilic phenotype. In addition, VEGF expression was higher in patients with an FEV1/FVC value of <70% as compared with patients with an FEV1/FVC value of >70%. Furthermore, the levels of VEGF were higher in patients with severe asthma compared with the patients with mild and moderate asthma. There were no statistically significant differences observed with regard to EGF, bFGF, PDGF-AA and PDGF-BB levels among the various phenotypes. Therefore, the observations of the present study indicated that increased VEGF expression in the serum and induced sputum of patients may be associated with eosinophilic airway inflammation, severe airflow limitation and the severity of asthma.

Hypoxia exerts dualistic effects on inflammatory and proliferative responses of healthy and asthmatic primary human bronchial smooth muscle cells

Background

For oxygen supply, airway wall cells depend on diffusion though the basement membrane, as well as on delivery by micro-vessels. In the asthmatic lung, local hypoxic conditions may occur due to increased thickness and altered composition of the basement membrane, as well as due to edema of the inflamed airway wall.

Objective

In our study we investigated the effect of hypoxia on proliferation and pro-inflammatory and pro-angiogenic parameter production by human bronchial smooth muscle cells (BSMC). Furthermore, conditioned media of hypoxia-exposed BSMC was tested for its ability to induce sprout outgrowth from endothelial cells spheroids.

Methods

BSMC were cultured in RPMI1640 (5% FCS) under normoxic (21% O₂) and hypoxic (1% and 5% O₂) conditions. Proliferation was determined by cell count and Western blot analysis for cyclin E and Proliferating Cell Nuclear Antigen (PCNA). Secretion of IL-6, IL-8, ENA-78 and VEGF-A was analyzed by ELISA. BSMC conditioned medium was tested for its angiogenic capacity by endothelial cell (EC)-spheroid in vitro angiogenesis assay.

Results

Proliferation of BSMC obtained from asthmatic and non-asthmatic patients was significantly reduced in the presence of 1% O2, whereas 5% O2 reduced proliferation of asthmatic BSMC only. Hypoxia induced HIF-1α expression in asthmatic and non-asthmatic BSMC, which coincided with significantly increased release of IL-6, IL-8 and VEGF-A, but not ENA-78. Finally, endothelial sprout outgrowth from EC spheroids was increased when exposed to hypoxia conditioned BSMC medium.

Conclusion

Hypoxia had dualistic effects on proliferative and inflammatory responses of asthmatic and non-asthmatic BSMC. First, hypoxia reduced BSMC proliferation. Second, hypoxia induced a pro-inflammatory, pro-angiogenic response. BSMC and EC may thus be promising new targets to counteract and/or alleviate airway wall remodeling.

Aortopulmonary collateral flow in cystic fibrosis assessed with phase-contrast MRI

BACKGROUND

Cystic fibrosis (CF) is a common genetic disease in Caucasians. Chronic pulmonary disease with progressive destruction of the pulmonary parenchyma is two of the major morbidities, but the relationship between clinical severity of CF and aortopulmonary collateral blood flow has not been assessed.

OBJECTIVE

The purpose of this study is to measure changes in aortopulmonary collateral blood flow by phase-contrast magnetic resonance imaging (MRI) in children with CF across the spectrum of disease severity as measured by the forced expiratory volume in one second as percent predicted value (FEV1% predicted).

MATERIALS AND METHODS

Sixteen patients with CF were prospectively evaluated. Eight were classified as having mild CF lung disease (FEV1 ≥80% predicted) and eight were classified as having moderate to severe CF lung disease (FEV1 <80% predicted). Seventeen age- and gender-matched non-CF subjects without cardiac or lung disease served as controls. Phase-contrast flow was measured at the ascending aorta, main pulmonary artery and both pulmonary arteries. Aortopulmonary collateral blood flow was calculated for each subject. The relationship between collateral flow and FEV1% predicted was modeled using nonparametric regression. Group differences were assessed by analysis of variance.

RESULTS

Aortopulmonary collateral blood flow began to increase as FEV1% predicted in subjects with CF fell below 101.5% with significant further increase in the aortopulmonary collateral blood flow in the subjects with CF with moderate to severe lung disease compared to controls (0.89 vs. 0.20 L/min, P < 0.0001). Aortopulmonary collateral blood flow correlated negatively with FEV1% predicted (r=0.70, P = 0.0050) confirming its relationship to this established marker of disease severity. There was no statistically significant difference in results obtained from two independent observers.

CONCLUSION

These preliminary findings suggest that phase-contrast MRI can be performed reliably with consistent results and without interobserver variability. While the aortopulmonary collateral blood flow is within the normal range in subjects with mild CF disease, it begins to increase even when lung function is still in the normal range. A significant increase in the aortopulmonary collateral blood flow compared to controls is measured in patients with moderate to severe CF lung disease. The studies support the notion that aortopulmonary collateral blood flow may serve as a novel and sensitive biomarker of early pulmonary disease in cystic fibrosis.

Vascular endothelial growth factor as a key inducer of angiogenesis in the asthmatic airways

Asthma is a chronic inflammatory disease of the airways characterized by structural airway changes, which are known as airway remodeling, including smooth muscle hypertrophy, goblet cell hyperplasia, subepithelial fibrosis, and angiogenesis. Vascular remodeling in asthmatic lungs results from increased angiogenesis, which is mainly mediated by vascular endothelial growth factor (VEGF). VEGF is a key regulator of blood vessel growth in the airways of asthma patients by promoting proliferation and differentiation of endothelial cells and inducing vascular leakage and permeability. In addition, VEGF induces allergic inflammation, enhances allergic sensitization, and has a role in Th2 type inflammatory responses. Specific inhibitors of VEGF and blockers of its receptors might be useful to control chronic airway inflammation and vascular remodeling, and might be a new therapeutic approach for chronic inflammatory airway disease like asthma.

Cytokines in chronic respiratory diseases

Cytokines are small, secreted proteins that control immune responses. Within the lung, they can control host responses to injuries or infection, resulting in clearance of the insult, repair of lung tissue, and return to homeostasis. Problems can arise when this response is over exuberant and/or cytokine production becomes dysregulated. In such cases, chronic and repeated inflammatory reactions and cytokine production can be established, leading to airway remodeling and fibrosis with unintended, maladaptive consequences. In this report, we describe the cytokines and molecular mechanisms behind the pathology observed in three major chronic diseases of the lung: asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis. Overlapping mechanisms are presented as potential sites for therapeutic intervention.

The pharmacological modulation of allergen-induced asthma

Aeroallergens are the most common triggers for the development of asthma. Recent birth cohort studies have identified viral infections occurring against a background of aeroallergen sensitization as a potent risk factor for initiation of asthma. Viral infection enhances immunopathogenic potential of pre-existing inhalant allergy via modulating airway mucosal dendritic cells. By using an allergen inhalation challenge clinical model, studies have shown that the late asthma response (LAR) is associated with more pronounced allergen-induced airway inflammation and airway hyperresponsiveness. The degree of airway eosinophilia, regulated by bone marrow progenitor cells and interleukin-5 level, correlates with the magnitude of the LAR and the increase in hyperresponsiveness. Both myeloid and plasmacytoid dendritic cell subsets have been involved in the pathogenesis of allergen-induced LAR. Myeloid dendritic cells are responsible for the allergen presentation and induction of inflammation and plasmacytoid dendritic cells play a role in the resolution of allergen-induced inflammation. A variety of potential new classes of asthma medication has also been evaluated with the allergen inhalation challenge in mild asthmatic subjects. Examples are TPI ASM8, an inhaled anti-sense oligonucleotide drug product, which attenuated both early and LARs via inhibition of the target gene mRNA of chemokine receptor 3, and the common β chain of interleukin-3, interleukin-5 and granulocyte-macrophage colony-stimulating factor receptor. Anti-human antibody interleukin-13 (IM-638) significantly attenuated both early and late allergen-induced asthma response. Pitrakinra, which targets both interleukin-4 and interleukin-13, substantially diminishes allergen-induced airway responses. Allergen-induced airway responses are a valuable way to evaluate the activity of possible new therapies in asthmatic airways.

A friend to the airways: a review of the emerging clinical importance of the bronchial arterial circulation

Lungs receive the bulk of their blood supply through the pulmonary arteries. The bronchial arteries, on the other hand, vascularize the bronchi and their surroundings. These two arteries anastomose near the alveolar ducts. Contrary to the pulmonary circulation which is fairly well studied, the bronchial arteries have been appreciated more by their absence, and in some cases, by an interruption in the pulmonary arterial flow. Therefore, a more accurate anatomical and functional knowledge of these atherosclerosis-resistant vessels is needed to help surgeons and clinicians to avoid iatrogenic injuries during pulmonary interventions. In this review, we have revisited the anatomy and pathophysiology of the bronchial arteries in humans, considering the recent advances in imaging techniques. We have also elaborated on the known clinical applications of these arteries in both the pathogenesis and management of common pulmonary conditions.

Increased levels of angiopoietins 1 and 2 in sputum supernatant in severe refractory asthma

BACKGROUND

Airway and vascular remodeling may play a prominent role in the clinical severity of severe refractory asthma (SRA). Angiopoietin-1 (Ang-1) is an essential mediator of angiogenesis by establishing vascular integrity, whereas angiopoietin-2 (Ang-2) acts as its natural inhibitor.

OBJECTIVE

We aimed to determine the levels of angiopoietins in sputum supernatants of patients with SRA and to investigate the possible associations with mediators and cells involved in both the inflammatory and the vascular remodeling processes.

METHODS

Thirty-eight patients with SRA, 35 patients with moderate asthma, and 20 healthy subjects were studied. All participants underwent lung function tests, bronchial hyperresponsiveness assessment and sputum induction for cell count identification and Ang-1, Ang-2, VEGF, TGF-β1, Cys-LTs, MMP-2, IL-13, ECP, and IL-8 measurement in supernatants. Airway vascular permeability (AVP) index was also assessed.

RESULTS

Ang-1 (ng/ml) and Ang-2 (pg/ml) levels were significantly elevated in patients with SRA compared with patients with moderate asthma and control subjects [median, interquartile ranges: 30 (17-39) vs 7.5 (5-11) vs 4.7 (3.8-5.9) respectively, P < 0.001; and 506 (400-700) vs 190 (146-236) vs 96 (89-120) respectively, P < 0.001]. Regression analysis showed a significant positive association between Ang-2 and AVP index, MMP-2, Ang-1, and VEGF in SRA. A weak association was also observed between Ang-1 and sputum eosinophils% in SRA.

CONCLUSION

Our results indicate that both angiopoietins levels are higher in SRA compared with moderate asthma and healthy subjects. In SRA, Ang-2 is associated with mediators involved in both the inflammatory and the vascular remodeling processes.

Reticular Basement Membrane Vessels Are Increased in COPD Bronchial Mucosa by Both Factor VIII and Collagen IV Immunostaining and Are Hyperpermeable

Background and Objective. Using Collagen IV staining, we have previously reported that the reticular basement membrane (Rbm) is hypervascular and the lamina propria (LP) is hypovascular in COPD airways. This study compared Collagen IV staining with vessels marked with anti-Factor VIII and examined vessel permeability in bronchial biopsies from COPD and normal subjects using albumin staining. Results. Anti-Collagen IV antibody detected more vessels in the Rbm (P = 0.002) and larger vessels in both Rbm (P < 0.001) and LP (P = 0.003) compared to Factor VIII. COPD airways had more vessels (with greater permeability) in the Rbm (P = 0.01) and fewer vessels (with normal permeability) in the LP compared to controls with both Collagen IV and Factor VIII antibodies (P = 0.04 and P = 0.01). Conclusion. Rbm vessels were increased in number and were hyperpermeable in COPD airways. Anti-Collagen IV and anti-Factor VIII antibodies did not uniformly detect the same vessel populations; the first is likely to reflect larger and older vessels with the latter reflecting smaller, younger vessels.

Mechanisms of remodeling in asthmatic airways

Asthma is a chronic inflammatory airway disorder characterized by airway hyperresponsiveness and reversible airflow obstruction. Subgroups of asthma patients develop airflow obstruction that is irreversible or only partially reversible and experience an accelerated rate of lung function decline. The structural changes in the airways of these patients are referred to as airway remodeling. All elements of the airway wall are involved, and remodeled airway wall thickness is substantially increased compared to normal control airways. Airway remodeling is thought to contribute to the subphenotypes of irreversible airflow obstruction and airway hyperresponsiveness, and it has been associated with increased disease severity. Reversal of remodeling is therefore of paramount therapeutic importance, and mechanisms responsible for airway remodeling are feasible therapeutic targets for asthma treatment. This paper will focus on our current understanding of the mechanisms of airway remodeling in asthma and potential targets for future intervention.

Airway epithelial cells from asthmatic children differentially express proremodeling factors

BACKGROUND

The airway epithelium can express factors that drive subepithelial airway remodeling. TGF-β2, vascular epithelial growth factor (VEGF), a disintegrin and metalloprotease 33 (ADAM33), and periostin are hypothesized to be involved in subepithelial remodeling and are overexpressed in adult asthmatic airways. Epidemiologic data suggest that lung function deficits in asthmatic patients are acquired in childhood.

OBJECTIVES

We sought to determine whether airway epithelial cells (AECs) from asthmatic children differentially express TGF-β2, VEGF, ADAM33, or periostin compared with cells from atopic nonasthmatic and healthy children intrinsically or in response to IL-4/IL-13 stimulation.

METHODS

Bronchial and nasal epithelial cells were obtained from brushings from well-characterized asthmatic (n = 16), atopic nonasthmatic (n = 9), and healthy (n = 15) children after achievement of anesthesia for elective procedures. After differentiation at an air-liquid interface (ALI) for 3 weeks, conditioned media were sampled and RNA was extracted from unstimulated and IL-4/IL-13-stimulated cultures. TGF-β2 and VEGF levels were measured with ELISA. ADAM33 and periostin expression was assessed by using real-time PCR.

RESULTS

TGF-β2 and VEGF production was significantly greater in bronchial and nasal ALI cultures from asthmatic children than in cultures from atopic nonasthmatic and healthy children. TGF-β2 levels increased significantly in asthmatic cultures after IL-4/IL-13 stimulation. Within-subject correlation between nasal and bronchial ALI production of TGF-β2 (r = 0.64, P = .001) and VEGF (r = 0.73, P < .001) was good. Periostin expression was 3.7-fold higher in bronchial cells (P < .001) and 3.9-fold higher in nasal cells (P < .004) from asthmatic children than in cells from atopic nonasthmatic or healthy children. ADAM33 was not differentially expressed by AECs from asthmatic patients compared with that from cells from atopic nonasthmatic or healthy children.

CONCLUSION

AECs from asthmatic children differentially express TGF-β2, VEGF, and periostin compared with cells from atopic nonasthmatic and healthy children. Nasal epithelial cells might be a suitable surrogate for bronchial cells that could facilitate investigation of the airway epithelium in future longitudinal pediatric studies.

Role of Inhaled Steroids in Vascular Airway Remodelling in Asthma and COPD

In chronic obstructive airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD), changes in bronchial microvasculature are present in response to inflammatory stimuli. Vascular changes may significantly contribute to airway wall remodelling. Angiogenesis and vascular leakage are prevalent in asthma, while vasodilation and vascular leakage dominate in COPD. An endothelial dysfunction may be present both in asthma and in COPD. Vascular changes may occur simultaneously with the thickening of the airway wall and the narrowing of the bronchial lumen. Consequently, pharmacological control of bronchial vascular remodelling may be crucial for symptom control in asthma and COPD. In asthmatic airways, inhaled steroids can downregulate vascular remodelling by acting on proangiogenic factors. Additionally, studies on combination therapy with long-acting β2-agonists and inhaled steroids have provided evidence of a possible synergistic action on components of vascular remodelling in asthma. In COPD, there is less experimental evidence on the effect of inhaled steroids on airway microvascular changes. Importantly, vascular endothelial growth factor (VEGF), the most specific growth factor for vascular endothelium, is crucially involved in the pathophysiology of airway vascular remodelling, both in asthma and COPD. The inhibition of VEGF and its receptor may be useful in the treatment of the vascular changes in the airway wall.

Lung gene expression in a rhesus allergic asthma model correlates with physiologic parameters of disease and exhibits common and distinct pathways with human asthma and a mouse asthma model

Experimental nonhuman primate models of asthma exhibit multiple features that are characteristic of an eosinophilic/T helper 2 (Th2)-high asthma subtype, characterized by the increased expression of Th2 cytokines and responsive genes, in humans. Here, we determine the molecular pathways that are present in a house dust mite-induced rhesus asthma model by analyzing the genomewide lung gene expression profile of the rhesus model and comparing it with that of human Th2-high asthma. We find that a prespecified human Th2 inflammation gene set from human Th2-high asthma is also present in rhesus asthma and that the expression of the genes comprising this gene set is positively correlated in human and rhesus asthma. In addition, as in human Th2-high asthma, the Th2 gene set correlates with physiologic markers of allergic inflammation and disease in rhesus asthma. Comparison of lung gene expression profiles from human Th2-high asthma, the rhesus asthma model, and a common mouse asthma model indicates that genes associated with Th2 inflammation are shared by all three species. However, some pathophysiologic aspects of human asthma (ie, subepithelial fibrosis, angiogenesis, neural biology, and immune host defense biology) are better represented in the gene expression profile of the rhesus model than in the mouse model. Further study of the rhesus asthma model may yield novel insights into the pathogenesis of human Th2-high asthma.

Pro-angiogenic hematopoietic progenitor cells and endothelial colony-forming cells in pathological angiogenesis of bronchial and pulmonary circulation

Dysregulation of angiogenesis is a common feature of many disease processes. Vascular remodeling is believed to depend on the participation of endothelial progenitor cells, but the identification of endothelial progenitors in postnatal neovascularization remains elusive. Current understanding posits a role for circulating pro-angiogenic hematopoietic cells that interact with local endothelial cells to establish an environment that favors angiogenesis in physiologic and pathophysiologic responses. In the lung, increased and dysregulated angiogenesis is a hallmark of diseases of the bronchial and pulmonary circulations, manifested by asthma and pulmonary arterial hypertension (PAH), respectively. In asthma, T(Helper)-2 immune cells produce angiogenic factors that mobilize and recruit pro-inflammatory and pro-angiogenic precursors from the bone marrow into the airway wall where they induce angiogenesis and fuel inflammation. In contrast, in PAH, upregulation of hypoxia-inducible factor (HIF) in vascular cells leads to the production of bone marrow-mobilizing factors that recruit pro-angiogenic progenitor cells to the pulmonary circulation where they contribute to angiogenic remodeling of the vessel wall. This review focuses on current knowledge of pro-angiogenic progenitor cells in the pathogenesis of asthma and PAH.