Bronchial Smooth Muscle Remodeling in Nonsevere Asthma

Bronchial wall T2w MRI signal as a new imaging biomarker of severe asthma

OBJECTIVES

Severe asthma patients are prone to severe exacerbations with a need of hospital admission increasing the economic burden on healthcare systems. T2w lung MRI was found to be useful in the assessment of bronchial inflammation. The main goal of this study is to compare quantitative MRI T2 signal bronchial intensity between patients with severe and non-severe asthma.

METHODS

This is an ancillary study of a prospective single-center study (NCT03089346). We assessed the mean T2 intensity MRI signal of the bronchial wall area (BrWall_T2-MIS) in 15 severe and 15 age and sex-matched non-severe asthmatic patients. They also have had pulmonary function tests (PFTs), fractional exhaled nitric oxide (FeNO) and blood eosinophils count (Eos). Comparisons between the two groups were performed using Student's t-test. Correlations were assessed using Pearson coefficients. Reproducibility was assessed using intraclass correlation coefficient and Bland-Altman analysis.

RESULTS

BrWall_T2-MIS was higher in severe than in non-severe asthma patients (74 ± 12 vs 49 ± 14; respectively p < 0.001). BrWall_T2-MIS showed a moderate inverse correlation with PFTs in the whole cohort (r = -0.54, r = -0.44 for FEV1(%pred) and FEV1/FVC respectively, p ≤ 0.01) and in the severe asthma group (r = -0.53, r = -0.44 for FEV1(%pred) and FEV1/FVC respectively, p ≤ 0.01). Eos was moderately correlated with BrWall_T2-MIS in severe asthma group (r = 0.52, p = 0.047). Reproducibility was almost perfect with ICC = 0.99 and mean difference in Bland-Altman analysis of -0.15 [95% CI = -0.48-0.16].

CONCLUSION

Quantification of bronchial wall T2w signal intensity appears to be able to differentiate severe from non-severe asthma and correlates with obstructive PFTs' parameters and inflammatory markers in severe asthma.

CRITICAL RELEVANCE STATEMENT

The development of non-ionizing imaging biomarkers could play an essential role in the management of patients with severe asthma in the current era of biological therapies.

KEY POINTS

Severe asthma exhibits severe exacerbations with a high burden on healthcare systems. T2w bronchial wall signal intensity is related to inflammatory biomarker in severe asthma. T2w MRI may represent a non-invasive tool to follow up severe asthma patients.

Targeting mitochondrial function as a potential therapeutic approach for allergic asthma

Allergic asthma is a chronic complex airway disease characterized by airway hyperresponsiveness, eosinophilic inflammation, excessive mucus secretion, and airway remodeling, with increasing mortality and incidence globally. The pathogenesis of allergic asthma is influenced by various factors including genetics, environment, and immune responses, making it complex and diverse. Recent studies have found that various cellular functions of mitochondria such as calcium regulation, adenosine triphosphate production, changes in redox potential, and free radical scavenging, are involved in regulating the pathogenesis of asthma. This review explores the involvement of mitochondrial functional changes in the pathogenesis of asthma, and investigate the potential of targeting cellular mitochondria as a therapeutic approach for asthma. Those insights can provide a novel theoretical foundations and treatment strategies for understanding and preventing asthma.

Airway Remodeling in Asthma: Mechanisms, Diagnosis, Treatment, and Future Directions

Airway remodeling (AR) with chronic inflammation, are key features in asthma pathogenesis. AR characterized by structural changes in the bronchial wall is associated with a specific asthma phenotype with poor clinical outcomes, impaired lung function and reduced treatment response. Most studies focus on the role of inflammation, while understanding the mechanisms driving AR is crucial for developing disease-modifying therapeutic strategies. This review paper summarizes current knowledge on the mechanisms underlying AR, diagnostic tools, and therapeutic approaches. Mechanisms explored include the role of the resident cells and the inflammatory cascade in AR. Diagnostic methods such as bronchial biopsy, lung function testing, imaging, and possible biomarkers are described. The effectiveness on AR of different treatments of asthma including corticosteroids, leukotriene modifiers, bronchodilators, macrolides, biologics, and bronchial thermoplasty is discussed, as well as other possible therapeutic options. AR poses a significant challenge in asthma management, contributing to disease severity and treatment resistance. Current therapeutic approaches target mostly airway inflammation rather than smooth muscle cell dysfunction and showed limited benefits on AR. Future research should focus more on investigating the mechanisms involved in AR to identify novel therapeutic targets and to develop new effective treatments able to prevent irreversible structural changes and improve long-term asthma outcomes.

Pulmonary adaptation to repeated poly(I:C) exposure is impaired in asthmatic mice: an observational study

BACKGROUND

While asthma exacerbations remain a major challenge in patient management, few animal models exist to explore the underlying mechanisms. Here, we established an animal model of asthma that can be used to study pathophysiological mechanisms and therapeutic strategies on asthma exacerbation.

METHODS

Female BALB/c mice were sensitized and exposed to PBS or Dermatophagoides pteronyssinus (DerP) extract for 11 weeks. Asthmatic phenotype was assessed through lung inflammation, bronchial hyperresponsiveness and bronchial smooth muscle remodeling. Asthmatic and control mice were exposed once or three times to poly(I:C) to simulate virus-induced inflammation.

RESULTS

Fourteen days after exposure to DerP, asthmatic mice showed resolution of inflammation with sustained bronchial hyperresponsiveness and bronchial smooth muscle remodeling compared to control. At this stage, when mice were subjected to a single exposure to poly(I:C), control and asthmatic mice were characterized by a significant increase in neutrophilic inflammation and bronchial hyperresponsiveness. When mice were repeatedly exposed to poly(I:C), control mice showed a significant decrease in neutrophilic inflammation and bronchial hyperresponsiveness, while asthmatic mice experienced worsening of these outcomes.

CONCLUSIONS

This observational study report an asthmatic mouse model that can undergo exacerbation after repeated exposure to poly(I:C). Our findings on pulmonary adaptation in control mice may also pave the way for further research into the mechanism of adaptation that may be impaired in asthma and raise the question of whether asthma exacerbation may be a loss of adaptation.

Epithelial-Mesenchymal Transition Mechanisms in Chronic Airway Diseases: A Common Process to Target?

Epithelial-to-mesenchymal transition (EMT) is a reversible process, in which epithelial cells lose their epithelial traits and acquire a mesenchymal phenotype. This transformation has been described in different lung diseases, such as lung cancer, interstitial lung diseases, asthma, chronic obstructive pulmonary disease and other muco-obstructive lung diseases, such as cystic fibrosis and non-cystic fibrosis bronchiectasis. The exaggerated chronic inflammation typical of these pulmonary diseases can induce molecular reprogramming with subsequent self-sustaining aberrant and excessive profibrotic tissue repair. Over time this process leads to structural changes with progressive organ dysfunction and lung function impairment. Although having common signalling pathways, specific triggers and regulation mechanisms might be present in each disease. This review aims to describe the various mechanisms associated with fibrotic changes and airway remodelling involved in chronic airway diseases. Having better knowledge of the mechanisms underlying the EMT process may help us to identify specific targets and thus lead to the development of novel therapeutic strategies to prevent or limit the onset of irreversible structural changes.

Bronchial Remodeling-based Latent Class Analysis Predicts Exacerbations in Severe Preschool Wheezers

Rationale: Children with preschool wheezing represent a very heterogeneous population with wide variability regarding their clinical, inflammatory, obstructive, and/or remodeling patterns. We hypothesized that assessing bronchial remodeling would help clinicians to better characterize severe preschool wheezers. Objectives: The main objective was to identify bronchial remodeling-based latent classes of severe preschool wheezers. Secondary objectives were to compare cross-sectional and longitudinal clinical and biological data between classes and to assess the safety of bronchoscopy. Methods: This double-center prospective study (NCT02806466) included severe preschool wheezers (1-5 yr old) requiring fiberoptic bronchoscopy. Bronchial remodeling parameters (i.e., epithelial integrity, reticular basement membrane [RBM] thickness, mucus gland, fibrosis and bronchial smooth muscle [BSM] areas, the density of blood vessels, and RBM-BSM distance) were assessed and evaluated by latent class analysis. An independent cohort of severe preschool wheezers (NCT04558671) was used to validate our results. Measurements and Main Results: Fiberoptic bronchoscopy procedures were well tolerated. A two-class model was identified: Class BR1 was characterized by increased RBM thickness, normalized BSM area, the density of blood vessels, decreased mucus gland area, fibrosis, and RBM-BSM distance compared with Class BR2. No significant differences were found between classes in the year before fiberoptic bronchoscopy. By contrast, Class BR1 was associated with a shorter time to first exacerbation and an increased risk of both frequent (3 or more) and severe exacerbations during the year after bronchoscopy in the two cohorts. Conclusions: Assessing bronchial remodeling identified severe preschool wheezers at risk of frequent and severe subsequent exacerbations with a favorable benefit to risk ratio.

Visualization and Validation of The Microstructures in The Airway Wall in vivo Using Diffractive Optical Coherence Tomography

RATIONALE AND OBJECTIVES

At present, there is no available method to study the in vivo microstructures of the airway wall (epithelium, smooth muscle, adventitia, basement membrane, glands, cartilage). Currently, we rely on ex vivo histologic evaluation of airway biopsies. To overcome this obstacle, we have developed an endoscopic ultrahigh-resolution diffractive optical coherence tomography (OCT) system, operating at a wavelength of 800 nm, to non-invasively study the in vivo microstructures of the airway wall. Prior to human study, validation of diffractive OCT's ability to quantitate airway microstructural components is required.

MATERIALS AND METHODS

To validate and demonstrate the accuracy of this OCT system, we used an ovine model to image small airways (∼ 2 mm in diameter). Histologic samples and correlated OCT images were matched. The cross-sectional area of the airway wall, lumen, and other microstructures were measured and compared.

RESULTS

A total of 27 sheep were studied from which we identified 39 paired OCT-histology airway images. We found strong correlations between the OCT and the histology measurements of the airway wall area and the microstructural area measurements of the epithelium, basement membrane, airway smooth muscle, glands, cartilage, and adventitia. The correlations ranged from r=0.61 (p<0.001) for the epithelium to r=0.86 (p<0.001) for the adventitia with the correlation between the OCT and the histology measurements for the entire airway wall of r=0.76 (p<0.001).

CONCLUSION

Given the high degree of correlation, these data validate the ability to acquire and quantify in vivo microscopic level imaging with this newly developed 800nm ultra-high resolution diffractive OCT system.

The airway smooth muscle sodium/calcium exchanger NCLX is critical for airway remodeling and hyperresponsiveness in asthma

The structural changes of airway smooth muscle (ASM) that characterize airway remodeling (AR) are crucial to the pathogenesis of asthma. During AR, ASM cells dedifferentiate from a quiescent to a proliferative, migratory, and secretory phenotype. Calcium (Ca²⁺) is a ubiquitous second messenger that regulates many cellular processes, including proliferation, migration, contraction, and metabolism. Furthermore, mitochondria have emerged as major Ca²⁺ signaling organelles that buffer Ca²⁺ through uptake by the mitochondrial Ca²⁺ uniporter and extrude it through the Na⁺/Ca²⁺ exchanger (NCLX/Slc8b1). Here, we show using mitochondrial Ca²⁺-sensitive dyes that NCLX only partially contributes to mitochondrial Ca²⁺ extrusion in ASM cells. Yet, NCLX is necessary for ASM cell proliferation and migration. Through cellular imaging, RNA-Seq, and biochemical assays, we demonstrate that NCLX regulates these processes by preventing mitochondrial Ca²⁺ overload and supporting store-operated Ca²⁺ entry, activation of Ca²⁺/calmodulin-dependent kinase II, and transcriptional and metabolic reprogramming. Using small animal respiratory mechanic measurements and immunohistochemistry, we show that smooth muscle-specific NCLX KO mice are protected against AR, fibrosis, and hyperresponsiveness in an experimental model of asthma. Our findings support NCLX as a potential therapeutic target in the treatment of asthma.

Direct Visualization and Quantitative Imaging of Small Airway Anatomy In Vivo Using Deep Learning Assisted Diffractive OCT

OBJECTIVE/BACKGROUND

In vivo imaging and quantification of the microstructures of small airways in three dimensions (3D) allows a better understanding and management of airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD). At present, the resolution and contrast of the currently available conventional optical coherence tomography (OCT) imaging technologies operating at 1300 nm remain challenging to directly visualize the fine microstructures of small airways in vivo.

METHODS

We developed an ultrahigh-resolution diffractive endoscopic OCT at 800 nm to afford a resolving power of 1.7 µm (in tissue) with an improved contrast and a custom deep residual learning based image segmentation framework to perform accurate and automated 3D quantification of airway anatomy.

RESULTS

The 800-nm diffractive OCT enabled the direct delineation of the structural components in the small airway wall in vivo. We further first demonstrated the 3D anatomic quantification of critical tissue compartments of small airways in sheep using the automated segmentation method.

CONCLUSION

The deep learning assisted diffractive OCT provides a unique ability to access the small airways, directly visualize and quantify the important tissue compartments, such as airway smooth muscle, in the airway wall in vivo in 3D.

SIGNIFICANCE

These pilot results suggest a potential technology for calculating volumetric measurements of small airways in patients in vivo.

Asthmatic bronchial smooth muscle increases rhinovirus replication within the bronchial epithelium

Rhinovirus (RV) infection of the bronchial epithelium is implicated in the vast majority of severe asthma exacerbations. Interestingly, the susceptibility of bronchial epithelium to RV infection is increased in persons with asthma. Bronchial smooth muscle (BSM) remodeling is an important feature of severe asthma pathophysiology, and its reduction using bronchial thermoplasty has been associated with a significant decrease in the exacerbation rate. We hypothesized that asthmatic BSM can play a role in RV infection of the bronchial epithelium. Using an original co-culture model between bronchial epithelium and BSM cells, we show that asthmatic BSM cells increase RV replication in bronchial epithelium following RV infection. These findings are related to the increased production of CCL20 by asthmatic BSM cells. Moreover, we demonstrate an original downregulation of the activity of the epithelial protein kinase RNA-activated (PKR) antiviral pathway. Finally, we identify a direct bottom-up effect of asthmatic BSM cells on bronchial epithelium susceptibility to RV infection.

Rhinovirus infection of bronchial epithelium induces specific bronchial smooth muscle cell migration of severe asthmatic patients

BACKGROUND

Patients with severe asthma show an increase in both exacerbation frequency and bronchial smooth muscle (BSM) mass. Rhinovirus (RV) infection of the bronchial epithelium (BE) is the main trigger of asthma exacerbations. Histological analysis of biopsies shows that a close connection between BE and hypertrophic BSM is a criterion for severity of asthma.

OBJECTIVE

We hypothesized that RV infection of BE specifically increases asthmatic BSM cell migration.

METHODS

Serum samples, biopsies or BSM cells were obtained from 86 patients with severe asthma and 31 non-asthmatic subjects. BE cells from non-asthmatic subjects were cultured in an air-liquid interface and exposed to RV-16. Migration of BSM cells was assessed in response to BE supernatant using chemotaxis assays. Chemokine concentrations were analyzed by transcriptomics and ELISAs. Immunocytochemistry, western blotting and flow cytometry were used to quantify CXCR3 isoform distribution. CXCR3 downstream signaling pathways were assessed by calcium imaging and western blots.

RESULTS

BSM cells from severe asthmatic patients specifically migrated toward RV-infected BE, whereas those from non-asthmatic subjects did not. This specific migration is driven by BE CXCL10, which was increased in vitro in response to RV infection as well as in vivo in serum from exacerbating patients with severe asthma. The mechanism is related to both decreased expression and activation of the CXCR3-B-specific isoform in severe asthmatic BSM cells.

CONCLUSION

We have demonstrated a novel mechanism of BSM remodeling in severe asthmatic patients following RV exacerbation. This study highlights the CXCL10/CXCR3-A axis as a potential therapeutic target in severe asthma.

STIM1 is a core trigger of airway smooth muscle remodeling and hyperresponsiveness in asthma

Airway remodeling and airway hyperresponsiveness are central drivers of asthma severity. Airway remodeling is a structural change involving the dedifferentiation of airway smooth muscle (ASM) cells from a quiescent to a proliferative and secretory phenotype. Here, we show up-regulation of the endoplasmic reticulum Ca2+ sensor stromal-interacting molecule 1 (STIM1) in ASM of asthmatic mice. STIM1 is required for metabolic and transcriptional reprogramming that supports airway remodeling, including ASM proliferation, migration, secretion of cytokines and extracellular matrix, enhanced mitochondrial mass, and increased oxidative phosphorylation and glycolytic flux. Mechanistically, STIM1-mediated Ca2+ influx is critical for the activation of nuclear factor of activated T cells 4 and subsequent interleukin-6 secretion and transcription of pro-remodeling transcription factors, growth factors, surface receptors, and asthma-associated proteins. STIM1 drives airway hyperresponsiveness in asthmatic mice through enhanced frequency and amplitude of ASM cytosolic Ca2+ oscillations. Our data advocates for ASM STIM1 as a target for asthma therapy.

[Remodeling in equine asthma - Effects of antigen avoidance and pharmacological therapy]

The term remodeling describes the process resulting in a tissue that is structurally and architecturally altered compared to its healthy counterpart. At least in severe equine asthma, this occurs mainly, but not exclusively, as a consequence of neutrophilic airway inflammation and is characterized by hypertrophy of the smooth muscle layers in airway and arterial walls as well as fibrosis of the bronchial walls and pulmonary interstitial tissue. To date, much less is known for mild to moderate equine asthma. For a long time it was assumed that these processes are irreversible, and at least for the remodeling of airway smooth muscle this is valid until today. In contrast, remodeling of the extracellular matrix disappears almost completely following long-term remission in consequence to strict antigen avoidance and environmental improvement as well as after glucocorticoid therapy. The remodeling of the arterial vasculature is also reversible following at least 12 months of antigen avoidance and bronchodilatory therapy, but not by inhaled glucocorticoids alone. Although not proven to date, the mild to moderate forms with a good prognosis for complete recovery may be a progenitor for severe equine asthma, in which lung function is restricted even during disease remission despite the absence of obvious clinical signs. Early diagnosis and therapy are, therefore, essential for the management of equine asthma prior to the development of irreversible remodeling, in particular of the bronchial smooth muscle. Antigen avoidance is of highest importance, and should be supported by glucocorticoids and bronchodilators.

Mitochondrial Dysfunction in Chronic Respiratory Diseases: Implications for the Pathogenesis and Potential Therapeutics

Mitochondria are indispensable for energy metabolism and cell signaling. Mitochondrial homeostasis is sustained with stabilization of mitochondrial membrane potential, balance of mitochondrial calcium, integrity of mitochondrial DNA, and timely clearance of damaged mitochondria via mitophagy. Mitochondrial dysfunction is featured by increased generation of mitochondrial reactive oxygen species, reduced mitochondrial membrane potential, mitochondrial calcium imbalance, mitochondrial DNA damage, and abnormal mitophagy. Accumulating evidence indicates that mitochondrial dysregulation causes oxidative stress, inflammasome activation, apoptosis, senescence, and metabolic reprogramming. All these cellular processes participate in the pathogenesis and progression of chronic respiratory diseases, including chronic obstructive pulmonary disease, pulmonary fibrosis, and asthma. In this review, we provide a comprehensive and updated overview of the impact of mitochondrial dysfunction on cellular processes involved in the development of these respiratory diseases. This not only implicates mechanisms of mitochondrial dysfunction for the pathogenesis of chronic lung diseases but also provides potential therapeutic approaches for these diseases by targeting dysfunctional mitochondria.

Crucial role of fatty acid oxidation in asthmatic bronchial smooth muscle remodelling

BACKGROUND

Bronchial smooth muscle (BSM) remodelling in asthma is related to an increased mitochondrial biogenesis and enhanced BSM cell proliferation in asthma. Since (i) mitochondria produce the highest levels of cellular energy and (ii) fatty acid beta-oxidation is the most powerful way to produce ATP, we hypothesized that, in asthmatic BSM cells, energetic metabolism is shifted towards the beta-oxidation of fatty acids.

OBJECTIVES

We aimed to characterize BSM cell metabolism in asthma both in vitro and ex vivo to identify a novel target for reducing BSM cell proliferation.

METHODS

Twenty-one asthmatic and 31 non-asthmatic patients were enrolled. We used metabolomic and proteomic approaches to study BSM cells. Oxidative stress, ATP synthesis, fatty acid endocytosis, metabolite production, metabolic capabilities, mitochondrial networks, cell proliferation and apoptosis were assessed on BSM cells. Fatty acid content was assessed in vivo using MALDI-spectrometry imaging.

RESULTS

Asthmatic BSM cells were characterized by an increased rate of mitochondrial respiration with a stimulated ATP production and mitochondrial β-oxidation. Fatty acid consumption was increased in asthmatic BSM both in vitro and ex vivo. Proteome remodelling of asthmatic BSM occurred via 2 canonical mitochondrial pathways. The levels of CPT2 and LDL-receptor, which internalize fatty acids through mitochondrial and cell membranes, respectively, were both increased in asthmatic BSM cells. Blocking CPT2 or LDL-receptor drastically and specifically reduced asthmatic BSM cell proliferation.

CONCLUSION

This study demonstrates a metabolic switch towards mitochondrial beta-oxidation in asthmatic BSM and identifies fatty acid metabolism as a new key target to reduce BSM remodelling in asthma.

Cellular and mitochondrial calcium communication in obstructive lung disorders

Calcium (Ca²⁺) signalling is well known to dictate cellular functioning and fate. In recent years, the accumulation of Ca²⁺ in the mitochondria has emerged as an important factor in Chronic Respiratory Diseases (CRD) such as Asthma and Chronic Obstructive Pulmonary Disease (COPD). Various reports underline an aberrant increase in the intracellular Ca²⁺, leading to mitochondrial ROS generation, and further activation of the apoptotic pathway in these diseases. Mitochondria contribute to Ca²⁺ buffering which in turn regulates mitochondrial metabolism and ATP production. Disruption of this Ca²⁺ balance leads to impaired cellular processes like apoptosis or necrosis and thus contributes to the pathophysiology of airway diseases. This review highlights the key role of cytoplasmic and mitochondrial Ca²⁺ signalling in regulating CRD, such as asthma and COPD. A better understanding of the dysregulation of mitochondrial Ca²⁺ homeostasis in these diseases could provide cues for the development of advanced therapeutic interventions in these diseases.

Zinc salicylate reduces airway smooth muscle cells remodelling by blocking mTOR and activating p21(Waf1/Cip1)

Asthma is characterized by chronic inflammation and tissue remodeling of the airways. Remodeling is resistant to pharmaceutical therapies. This study investigated the effect of zinc salicylate-methylsulfonylmethane (Zn-Sal-MSM) compared to zinc salicylate (Zn-Sal), or sodium salicylate (Na-Sal), or zinc chloride (ZnCl₂) on remodeling parameters of human airway smooth muscle cells (ASMC). Human ASMC obtained from asthma patients (n=7) and non-asthma controls (n=7) were treated with one of the reagents. Cell proliferation and viability was determined by direct cell counts and MTT assay. The expression of and phosphorylation proteins was determined by Western-blotting, ELISA, immunofluorescence, and mass spectrometry. Extracellular matrix deposition by ELISA. Zn-Sal-MSM, Zn-Sal and Na-Sal (0.1-100 µg/mL) significantly reduced PDGF-BB-induced proliferation in a concentration dependent manner, while ZnCl₂ was toxic. The reduced proliferation correlated with increased expression of the cell cycle inhibitor p21^(Waf1/Cip1), and reduced activity of Akt, p70S6K, and Erk1/2. Zn-Sal-MSM, Zn-Sal, but not Na-Sal reduced the deposition of fibronectin and collagen type-I. Furthermore, Zn-Sal-MSM reduced the mitochondria specific COX4 expression. Mass spectrometry indicated that Zn-Sal-MSM modified the expression of several signaling proteins and zinc-dependent enzymes. In conclusion, Zn-Sal-MSM and Zn-Sal potentially prevent airway wall remodeling in asthma by inhibition of both the Erk1/2 and mTOR signaling pathways.

In utero Exposure to Nicotine Containing Electronic Cigarettes Increases the Risk of Allergic Asthma in Female Offspring

E-cigarettes (eCig) are being considered as an alternative to quit cigarette smoking while their long-term effect on lung pathophysiology are unknown. Maternal eCig-vaping may be promoted and considered as a safer cigarette smoking-replacement during pregnancy thus needing further assessment. Using murine models of in utero vaping and allergic asthma with complementary in vitro experiments we tested whether maternal eCig vaping enhances features of allergic asthma in offspring. Female BALB/c mice were exposed to either eCig vapor (± nicotine) or room air. Female offspring from these mothers were subjected to an ovalbumin (OVA)-induced allergic asthma model. Lung function and airway inflammation was assessed. Tissues were histologically assessed with H&E, Periodic Acid-Schiff and Masson's trichrome. Mitochondrial homeostasis protein expression was measured using immunohistochemistry while human airway smooth muscle (ASM) and Beas-2B cells were used to further measure cellular function and mitochondrial respiration. Allergen-challenge in mice lead to significant increase in airway inflammation, development of airway hyperresponsiveness (AHR) and increase in mucus and airway wall thickening (hallmark features of allergic asthma). Allergic asthma features were significantly enhanced in offspring from eCig (+Nicotine)-exposed mothers and were mainly reliant upon Th2-dependent inflammation with complementary changes in mitochondrial homeostasis. Further, in vitro data demonstrated that eCig (±Nicotine)-exposure impaired airway cell homeostasis and perturbed mitochondrial function. Collectively, maternal eCig vaping enhanced and worsened features of allergic asthma and this could partly be attributed to aberrant mitochondrial function.

[Bronchial smooth muscle mitochondria: A new target for asthma therapy?]

The main purpose of this review is to highlight mitochondria as a new therapeutic target to prevent bronchial smooth muscle (BSM) remodeling in asthma. Severe asthmatic patients, representing 5-10% of all asthmatics, are characterized by an increased BSM mass which is highly correlated with the severity of the disease and the rate of exacerbations. None of the current asthma therapies are effective in reducing BSM remodelling. This review, based on the current literature, reports the role of mitochondria in BSM, particularly in calcium signaling.

Immunologic and Non-Immunologic Mechanisms Leading to Airway Remodeling in Asthma

Asthma increases worldwide without any definite reason and patient numbers double every 10 years. Drugs used for asthma therapy relax the muscles and reduce inflammation, but none of them inhibited airway wall remodeling in clinical studies. Airway wall remodeling can either be induced through pro-inflammatory cytokines released by immune cells, or direct binding of IgE to smooth muscle cells, or non-immunological stimuli. Increasing evidence suggests that airway wall remodeling is initiated early in life by epigenetic events that lead to cell type specific pathologies, and modulate the interaction between epithelial and sub-epithelial cells. Animal models are only available for remodeling in allergic asthma, but none for non-allergic asthma. In human asthma, the mechanisms leading to airway wall remodeling are not well understood. In order to improve the understanding of this asthma pathology, the definition of “remodeling” needs to be better specified as it summarizes a wide range of tissue structural changes. Second, it needs to be assessed if specific remodeling patterns occur in specific asthma pheno- or endo-types. Third, the interaction of the immune cells with tissue forming cells needs to be assessed in both directions; e.g., do immune cells always stimulate tissue cells or are inflamed tissue cells calling immune cells to the rescue? This review aims to provide an overview on immunologic and non-immunologic mechanisms controlling airway wall remodeling in asthma.

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

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

Metabolic Adaptation of Airway Smooth Muscle Cells to an SPHK2 Substrate Precedes Cytostasis

Thickening of the airway smooth muscle is central to bronchial hyperreactivity. We have shown that the sphingosine analog (R)-2-amino-4-(4-heptyloxyphenyl)-2-methylbutanol (AAL-R) can reverse preestablished airway hyperreactivity in a chronic asthma model. Because sphingosine analogs can be metabolized by SPHK2 (sphingosine kinase 2), we investigated whether this enzyme was required for AAL-R to perturb mechanisms sustaining airway smooth muscle cell proliferation. We found that AAL-R pretreatment reduced the capacity of live airway smooth muscle cells to use oxygen for oxidative phosphorylation and increased lactate dehydrogenase activity. We also determined that SPHK2 was upregulated in airway smooth muscle cells bearing the proliferation marker Ki67 relative to their Ki67-negative counterpart. Comparing different stromal cell subsets of the lung, we found that high SPHK2 concentrations were associated with the ability of AAL-R to inhibit metabolic activity assessed by conversion of the tetrazolium dye MTT. Knockdown or pharmacological inhibition of SPHK2 reversed the effect of AAL-R on MTT conversion, indicating the essential role for this kinase in the metabolic perturbations induced by sphingosine analogs. Our results support the hypothesis that increased SPHK2 levels in proliferating airway smooth muscle cells could be exploited to counteract airway smooth muscle thickening with synthetic substrates.

Bronchial thermoplasty decreases airway remodelling by blocking epithelium-derived heat shock protein-60 secretion and protein arginine methyltransferase-1 in fibroblasts

Bronchial thermoplasty (BT) is to date the only therapy that provides a lasting reduction in airway wall remodelling. However, the mechanism of action of BT is not well understood. This study aimed to characterise the changes of remodelling regulating signalling pathways by BT in asthma.Bronchoalveolar lavage fluid (BALF) was obtained from eight patients with severe asthma before and after BT. Primary bronchial epithelial cells were isolated from 23 patients before (n=66) and after (n=62) BT. Epithelial cell culture supernatant (Epi.S) was collected and applied to primary fibroblasts.Epithelial cells obtained from asthma patients after BT proliferated significantly faster compared with epithelial cells obtained before BT. In airway fibroblasts, BALF or Epi.S obtained before BT increased CCAAT enhancer-binding protein-β (C/EBPβ) expression, thereby downregulating microRNA-19a. This upregulated extracellular signal-regulated kinase-1/2 (ERK1/2) expression, protein arginine methyltransferase-1 (PRMT1) expression, cell proliferation and mitochondrial mass. BALF or Epi.S obtained after BT reduced the expression of C/EBPβ, ERK1/2, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α), PRMT1 and mitochondrial mass in airway fibroblasts. Proteome and transcriptome analyses indicated that epithelial cell-derived heat shock protein-60 (HSP60) is the main mediator of BT effects on fibroblasts. Further analysis suggested that HSP60 regulated PRMT1 expression, which was responsible for the increased mitochondrial mass and α-smooth muscle actin expression by asthmatic fibroblasts. These effects were ablated after BT. These results imply that BT reduces fibroblast remodelling through modifying the function of epithelial cells, especially by reducing HSP60 secretion and subsequent signalling pathways that regulate PRMT1 expression.We therefore hypothesise that BT decreases airway remodelling by blocking epithelium-derived HSP60 secretion and PRMT1 in fibroblasts.

The equine asthma model of airway remodeling: from a veterinary to a human perspective

Human asthma is a complex and heterogeneous disorder characterized by chronic inflammation, bronchospasm and airway remodeling. The latter is a major determinant of the structure-function relationship of the respiratory system and likely contributes to the progressive and accelerated decline in lung function observed in patients over time. Corticosteroids are the cornerstone of asthma treatment. While their action on inflammation and lung function is well characterized, their effect on remodeling remains largely unknown. An important hindrance to the study of airway remodeling as a major focus in asthma research is the lack of reliable non-invasive biomarkers. In consequence, the physiologic and clinical consequences of airway wall thickening and altered composition are not well understood. In this perspective, equine asthma provides a unique and ethical (non-terminal) preclinical model for hypothesis testing and generation. Severe equine asthma is a spontaneous disease affecting adult horses characterized by recurrent and reversible episodes of disease exacerbations. It is associated with bronchoalveolar neutrophilic inflammation, bronchospasm, and excessive mucus secretion. Severe equine asthma is also characterized by bronchial remodeling, which is only partially improved by prolonged period of disease remission induced by therapy or antigen avoidance strategies. This review will focus on the similarities and differences of airway remodeling in equine and human asthma, on the strengths and limitations of the equine model, and on the challenges the model has to face to keep up with human asthma research.

Profiling of remote skeletal muscle gene changes resulting from stimulation of atopic dermatitis disease in NC/Nga mouse model

Although atopic dermatitis (AD) is known to be a representative skin disorder, it also affects the systemic immune response. In a recent study, myoblasts were shown to be involved in the immune regulation, but the roles of muscle cells in AD are poorly understood. We aimed to identify the relationship between mitochondria and atopy by genome-wide analysis of skeletal muscles in mice. We induced AD-like symptoms using house dust mite (HDM) extract in NC/Nga mice. The transcriptional profiles of the untreated group and HDM-induced AD-like group were analyzed and compared using microarray, differentially expressed gene and functional pathway analyses, and protein interaction network construction. Our microarray analysis demonstrated that immune response-, calcium handling-, and mitochondrial metabolism-related genes were differentially expressed. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology pathway analyses, immune response pathways involved in cytokine interaction, nuclear factor-kappa B, and T-cell receptor signaling, calcium handling pathways, and mitochondria metabolism pathways involved in the citrate cycle were significantly upregulated. In protein interaction network analysis, chemokine family-, muscle contraction process-, and immune response-related genes were identified as hub genes with many interactions. In addition, mitochondrial pathways involved in calcium signaling, cardiac muscle contraction, tricarboxylic acid cycle, oxidation-reduction process, and calcium-mediated signaling were significantly stimulated in KEGG and Gene Ontology analyses. Our results provide a comprehensive understanding of the genome-wide transcriptional changes of HDM-induced AD-like symptoms and the indicated genes that could be used as AD clinical biomarkers.

Proteomic Analysis Provides Insights Into the Therapeutic Effect of GU-BEN-FANG-XIAO Decoction on a Persistent Asthmatic Mouse Model

Gubenfangxiao decoction (GBFXD) is a traditional Chinese medicine based on a combination of Yu-Ping-Feng-San and Erchen decoctions. GBFXD has been widely used for decades in treating asthma at the Affiliated Hospital of Nanjing University of Chinese Medicine. Previously, GBFXD was found to reduce lung inflammation and airway remodeling; however, the underlying mechanism remains unknown. In this study, the effects of GBFXD on asthmatic mice were evaluated based on pathology and lung function; airway hyperresponsiveness (AHR) and pathology were compared among the two different mouse models utilized. Furthermore, the mechanism of action of GBFXD on asthmatic mice was analyzed using iTRAQ labeling technology combined with ingenuity pathway analysis (IPA). Modeling analysis of pre- and post-treatment proteins identified 75 differentially expressed proteins. These proteins were related to B-cell development, calcium-induced lymphocyte apoptosis, antigen presentation, and Th1 and Th2 activation pathways. Moreover, 68 differentially expressed proteins were identified in the GBFXD treatment group compared with the model group. Upstream regulatory factors predicted that interleukin (IL)-4 (necessary for inducing polarization of type 2 [M2] macrophages), cyclooxygenase, and prostaglandin E2 are significantly elevated in the model group. Based on IPA analysis, it was concluded that several pathways, including mitochondrial dysfunction and oxidative phosphorylation, are closely associated with the therapeutic effects of GBFXD in asthma. Moreover, the differential expression of several proteins, including the M2 markers, MRC1, ARG1, Retnla, Chil3, and CHIA, were validated by western blotting, confirming that GBFXD can reduce airway inflammation, which fits the pattern of an alternative M2 activation state, and attenuate AHR. Overall, our findings indicate that GBFXD significantly suppresses M2 macrophage polarization, providing further insights into the mechanism underlying the protective effects of GBFXD.

Long acting β2-agonist's activation of cyclic AMP cannot halt ongoing mitogenic stimulation in airway smooth muscle cells

Airway smooth muscle cell (ASMC) hyperplasia causes airway wall remodelling, which is resisting to therapy. Long acting β2-agonists (LABA) relax airway muscles, but their effect on remodelling is unclear. This study compared the anti-proliferative effect of LABA in human primary ASMC, in situations where LABA were applied before, together, or after platelet derived growth factor (PDGF-BB). Cells obtained from controls (n = 5), and asthma patients (n = 5) were stimulated by PDGF-BB (10 ng/ml) before or after the application of formoterol or salmeterol. Proliferation was determined by direct cell counts over three days, cell cycle control proteins p21^(Waf1/Cip1), p27^(Kip1), signalling proteins Erk1/2 and p38 mitogen activated protein kinase (MAPK) were detected by immuno-blotting. PDGF-BB induced proliferation was significantly stronger in asthmatic ASMC versus controls. Proliferation was prevented by 30 min pre-incubation with LABA. When LABA were applied together or after PDGF-BB, their anti-proliferative effect was no longer significant. In untreated ASMC, LABA increased the expression of p21^(Waf1/Cip1) and p27^(Kip1) through cAMP, and this mechanism was abolished by the presence of PDGF-BB. The data show that the anti-proliferative effect of cAMP signalling cannot overcome the mitogenic signalling cascade once it was activated. Therefore, remodelling in asthma cannot be reduced by LABA.

IgE Downregulates PTEN through MicroRNA-21-5p and Stimulates Airway Smooth Muscle Cell Remodeling

The patho-mechanism leading to airway wall remodeling in allergic asthma is not well understood and remodeling is resistant to therapies. This study assessed the effect of immunoglobulin E (IgE) in the absence of allergens on human primary airway smooth muscle cell (ASMC) remodeling in vitro. ASMCs were obtained from five allergic asthma patients and five controls. Proliferation was determined by direct cell counts, mitochondrial activity by expression of cytochrome c, protein expression by immunoblotting and immuno-fluorescence, cell migration by microscopy imaging, and collagen deposition by cell based ELISA and RNA expression by real time PCR. Non-immune IgE activated two signaling pathways: (i) signal transducer and activator of transcription 3 (STAT3)→miR-21-5p→downregulating phosphatase and tensin homolog (PTEN) expression, and (ii) phosphatidylinositol 3-kinases (PI3K)→protein kinase B (Akt)→mammalian target of rapamycin (mTOR)→ribosomal protein S6 kinase beta-1 (p70s6k)→peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC1-α)→peroxisome proliferator-activated receptor-γ (PPAR-γ)→cyclooxygenase-2 (COX-2)→mitochondrial activity, proliferation, migration, and extracellular matrix deposition. Reduced PTEN expression correlated with enhanced PI3K signaling, which upregulated ASMC remodeling. The inhibition of microRNA-21-5p increased PTEN and reduced mTOR signaling and remodeling. Mimics of microRNA-21-5p had opposing effects. IgE induced ASMC remodeling was significantly reduced by inhibition of mTOR or STAT3. In conclusion, non-immune IgE alone is sufficient for stimulated ASMC remodeling by upregulating microRNA-21-5p. Our findings suggest that the suppression of micoRNA-21-5p may present a therapeutic target to reduce airway wall remodeling.

P2X4R promotes airway remodeling by acting on the phenotype switching of bronchial smooth muscle cells in rats

The P2X4 receptor (P2X4R) contributes to airway inflammation and airway remodeling in mice with allergic asthma. However, the molecular mechanism by which P2X4R affects the airway remodeling in allergic asthma remains largely unknown. We established an allergic asthma model by ovalbumin (OVA) inhalation in BALB/c mice. Compared with the mice in the control group, the expression of proliferating cell nuclear antigen (PCNA) increased and that of alpha-smooth muscle actin (α-SMA) decreased in the OVA-challenged mice. 5-BDBD, a P2X4R antagonist, alleviated the OVA-induced changes. To clarify the role of P2X4R in the phenotype switching of the bronchial smooth muscle, bronchial smooth muscle contractility and p38MAPK expression were investigated. Platelet-derived growth factor-BB (PDGF-BB) was used to activate the proliferation of primary-cultured rat bronchial smooth muscle cells (BSMCs). P2X4R, p38MAPK, and phenotype markers were evaluated using Western blotting or immunofluorescence. PDGF-BB administration increased the P2X4R and phospho-p38MAPK expression in BSMCs, and the increased phospho-p38MAPK expression was downregulated by silencing of the P2X4R mRNA. PDGF-BB stimulated the proliferation and synthetic phenotype of BSMCs, which was aggravated by a P2X4R agonist and alleviated by a P2X4R antagonist or silencing the P2X4R mRNA. The decreased contractile phenotype induced by PDGF-BB was alleviated by a P2X4R antagonist or by silencing the P2X4R mRNA. SB203580, p38MAPK inhibitor, inhibited the PDGF-BB-induced increasing of synthetic phenotype and the proliferation of BSMCs. These findings indicate that P2X4R acts directly on the phenotype switching of BSMCs. Inhibiting P2X4R can promote the contractile differentiation of BSMCs via p38MAPK signaling. Thus, the effect of P2X4R on airway remodeling indicates that this receptor could be a target for future drug candidates.

Mitochondrial Dysfunction Linking Obesity and Asthma

The bidirectional epidemiological association between asthma and obesity is well known. Recent evidence suggests that there is an intersection of the pathophysiological molecular pathways leading to either obesity or asthma, at the level of mitochondria. This is not surprising, because mitochondria, beyond their roles as the metabolic powerhouses of the cell, serve as sensors of threats, regulators of stress signaling, and effectors of cytotoxicity. Reduced mitochondrial function and low metabolic activity are well-recognized features of obesity. Three distinct lines of experimental evidences connect mitochondrial dysfunction with asthma. First, asthma is associated with aberrant mitochondrial metabolism. Second, mitochondrial dysfunction may either induce asthma-like features or increase asthma severity. Third, mitochondria-targeted therapies appear effective in preventing or reversing asthma features. Importantly, mitochondrial dysfunction in airway epithelial cells appears to be a powerful trigger for airway remodeling that is independent of cellular inflammation. This is clinically relevant to the obese-asthma phenotype, with exaggerated symptoms despite apparently low levels of inflammation, and poor response to antiinflammatory treatment. In summary, mitochondrial dysfunction is a common thread tying together the twin epidemics of obesity and asthma. Environmental and lifestyle factors leading to primary mitochondrial dysfunction may be increasing the risk for either disease. Further, secondary mitochondrial dysfunction emerging from the pathogenesis of either obesity or asthma may increase the risk of the other. Mitochondrial health-centric strategies may be relevant to prevention and treatment of both obesity and asthma, and should be actively considered.

Horses With Pasture Asthma Have Airway Remodeling That Is Characteristic of Human Asthma

Severe equine asthma, formerly recurrent airway obstruction (RAO), is the horse counterpart of human asthma, affecting horses maintained indoors in continental climates. Equine pasture asthma, formerly summer pasture RAO, is clinically similar but affects grazing horses during hot, humid conditions in the southeastern United States and United Kingdom. To advance translational relevance of equine pasture asthma to human asthma, histologic features of airway remodeling in human asthma were scored in lung lobes from 15 pasture asthma-affected and 9 control horses of mixed breeds. All noncartilaginous airways were scored using a standardized grading rubric (0-3) in hematoxylin and eosin (HE) and Movat's pentachrome-stained sections; 15 airways were chosen randomly from each lobe for analysis. Logistic regression identified disease, age, and lobe effects on probability of histologic outcomes. Airway smooth muscle (odds ratio [OR] = 2.5, P < .001), goblet cell hyperplasia/metaplasia (OR = 37.6, P < .0001), peribronchiolar elastic system fibers (OR = 4.2, P < .001), peribronchiolar fibrosis (OR = 3.8, P = .01), airway occlusion by mucus/inflammation (OR = 4.2, P = .04), and airway adventitial inflammation (OR = 3.0, P = .01) were significantly greater in diseased airways. A novel complex tissue disorganization, designated terminal bronchiolar remodeling, was overrepresented in diseased airways (OR = 3.7, P < .0001). Distribution of terminal bronchiolar remodeling corresponded to putative sites of air trapping in human asthma, at secondary pulmonary lobules. Age (>15 years) was an independent risk factor for increased peribronchiolar fibrosis, elastic system fibers, and terminal bronchiolar remodeling. Remodeling differed significantly between lung lobes, congruent with nonhomogeneous remodeling in human asthma. Equine pasture asthma recapitulates airway remodeling in human asthma in a manner not achieved in induced animal asthma models, endorsing its translational relevance for human asthma investigation.

Montelukast reverses airway remodeling in actively sensitized young mice

Asthma is characterized by airway hyperresponsiveness (AHR) and inflammation leading to airway remodeling (AR). In children, AR may occur very early prior to the age of 6 years. Treatments to prevent or reverse AR are unknown.

AIM

We sought to determine (i) whether short allergenic sensitization at a young age in a mouse model may induce enhanced AR and inflammation compared to adults; (ii) the effect of Montelukast on such AR.

METHODS

Immature and adult Balb/c mice were sensitized and challenged with ovalbumin. AHR and AR were measured using cultured precision-cut lung slices and inflammation by bronchoalveolar lavage. Experiments were repeated after administration of Montelukast.

RESULTS

OVA-challenged mice developed AHR to methacholine regardless of age of first exposure to OVA. Young mice developed greater thickened basement membrane, increased smooth muscle mass, and increased area of bronchovascular fibrosis compared with adult mice. Cellular infiltrates in BAL differed depending upon animal age at first exposure with higher eosinophilia measured in younger animals. Montelukast decreased ASM mass, BAL cellularity.

CONCLUSION

We provide thus evidence for a greater degree of AR after allergenic sensitization and challenge in younger mice versus adults. This study provides proof of concept that airway remodeling can be prevented and reversed in this case by anti-asthmatic drug Montelukast in this model.

Remodelling and inflammation in preschoolers with severe recurrent wheeze and asthma outcome at school age

BACKGROUND

The influence of airway remodelling and inflammation in preschoolers with severe recurrent wheeze on asthma outcomes is poorly understood.

OBJECTIVE

To assess their association with asthma symptoms and lung function at school age.

METHODS

Preschoolers (38.4 months) initially investigated with bronchial biopsies were re-assessed for asthma symptoms and lung function at school age.

RESULTS

Thirty-six of 49 preschoolers (73.5%) were assessed at 10.9 years. Twenty-six (72.2%) had persistent asthma. Submucosal eosinophil counts were higher in children with severe exacerbations at school age than in those without (16/0.1 mm² [11.2-30.4] vs 8/0.1 mm² [2.4-17.6], P = .02), and correlated with the number of severe exacerbations (P = .04, r = .35). Submucosal neutrophil counts correlated with FEV1/FVC (P < .01, r = .47) and FEF_25-75% predicted (P = .02, r = .43). Airway smooth muscle (ASM) area correlated with FEV1/FVC (P < .01, r = .51). Vessel numbers negatively correlated with FEV1% predicted and FEV1/FVC (P = .03, r = -.42; P = .04, r = -.41; respectively) and FEF_25-75% predicted (P = .02, r = -.46).

CONCLUSION

Eosinophilic inflammation in preschoolers with severe recurrent wheeze might be predictive of future severe exacerbations, neutrophilia might be associated with better lung function. Changes in ASM and vascularity might affect lung function at school age.

Impulse oscillometry and nitrogen washout test in the assessment of small airway dysfunction in asthma: Correlation with quantitative computed tomography

OBJECTIVE

Small airway dysfunction (SAD) and airway remodeling influence the disease control and progression in asthma. We investigated whether impulse oscillometry (IOS) and single breath nitrogen washout (SBN₂W) could be reliable tests in evaluating SAD and airway remodeling by correlating their data with radiological parameters derived from quantitative chest multidetector computed tomography (MDCT) imaging.

METHODS

Lung function tests were performed before and after bronchodilator. The MDCT lung scans were acquired at full inspiration and expiration using a portable spirometer to control the respiratory manoeuvres. Symptom control was assessed using the Asthma Control Test (ACT) questionnaire.

RESULTS

Twenty six patients were enrolled. The bronchial lumen area (LA) measured with MDCT lung scan, correlated inversely with airway resistance (Raw, p < 0.001) and with total and large airway oscillometric resistance (R5, p = 0.002 and R20, p = 0.006, respectively). However these two last correlations became non-significant after Bonferroni correction for multiple comparisons. The radiological quantification of air trapping correlated with Raw (p < 0.001), residual volume (RV, p < 0.001), and the slope of phase III of SBN₂W (DeltaN₂, p < 0.001) whereas the correlation with small airway oscillometric resistance (R5-20) was non-significant after Bonferroni adjustment. Finally, air trapping was significantly higher in patients with a fixed bronchial obstruction in comparison to patients with reversible obstruction.

CONCLUSIONS

Plethysmographic method remains the main tool to investigate SAD and airway remodeling in asthmatic patients. The integration with the SBN₂W test proved useful to better evaluate the small airway involvement whereas IOS showed a weaker correlation with both radiological and clinical data.

Regulating effect of glycyrrhetinic acid on bronchial asthma smooth muscle proliferation and apoptosis as well as inflammatory factor expression through ERK1/2 signaling pathway

OBJECTIVE

To study the influence of glycyrrhetinic acid (GA) on bronchial asthma (BA) smooth muscle proliferation and apoptosis as well as inflammatory factor expression and its molecular mechanism.

METHODS

Male SD guinea pigs were selected and made into asthma models, bronchial asthma smooth muscle cells were cultured and divided into BA group, GA group and GA + LM group that were treated with serum-free RPMI1640 culture medium, serum-free RPMI1640 culture medium containing 50 ng/mL glycyrrhetinic acid, serum-free RPMI1640 culture medium containing 50 ng/mL glycyrrhetinic acid and 100 ng/mL LM22B-10 respectively; normal guinea pigs were collected and bronchial smooth muscle cells were cultured as control group. The cell proliferation activity as well as the expression of proliferation and apoptosis genes, inflammatory factors and p-ERK1/2 was determined.

RESULTS

Proliferation activity value and mRNA expression of Bcl-2, TNF-α, IL-4, IL-6, YKL-40, protein expression of p-ERK1/2 of airway smooth muscle cell in BA group were significantly higher than those of control group while mRNA expression levels of Bax, caspase-9 as well as caspase-3 were significantly lower than that of control group (P < 0.05); proliferation activity value and mRNA expression of Bcl-2, TNF-α, IL-4, IL-6, YKL-40, protein expression of p-ERK1/2 of airway smooth muscle cell in GA group were significantly lower than those of BA group (P < 0.05) while the mRNA expression levels of Bax, caspase-9 as well as caspase-3 were significantly higher than those of BA group (P < 0.05); proliferation activity value and mRNA expression of Bcl-2, TNF-α, IL-4, IL-6, YKL-40 of airway smooth muscle cell in GA + LM group were significantly higher than those of GA group (P < 0.05) while mRNA expression levels of Bax, caspase-9 as well as caspase-3 were significantly lower that of GA group (P < 0.05).

CONCLUSION

GA can inhibit the proliferation of bronchial smooth muscle cells and reduce the expression of inflammatory factors by inhibiting the phosphorylation of ERK1/2.

Birefringence microscopy platform for assessing airway smooth muscle structure and function in vivo

The inability to visualize airway smooth muscle (ASM) cells in vivo is a major obstacle in understanding their role in normal physiology and diseases. At present, there is no imaging modality available to assess ASM in vivo. Confocal endomicroscopy lacks the penetration depth and field of view, and conventional optical coherence tomography (OCT) does not have sufficient contrast to differentiate ASM from surrounding tissues. We have developed a birefringence microscopy platform that leverages the micro-organization of tissue to add further dimension to traditional OCT. We have used this technology to validate ASM measurements in ex vivo swine and canine studies, visualize and characterize volumetric representations of ASM in vivo, and quantify and predict ASM contractile force as a function of optical retardation. We provide in vivo images and volumetric assessments of ASM in living humans and document structural disease variations in subjects with mild asthma. The opportunity to link inflammatory responses to ASM responses and to link ASM responses to clinical responses and outcomes could lead to an increased understanding of diseases of the airway and, ultimately, to improved patient outcomes.

Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.

Analysis of mitochondrial DNA alteration in new phenotype ACOS

BACKGROUND

Mitochondria contain their own DNA (MtDNA) that is very sensitive to oxidative stress and as a consequence could be damaged in quantity. Oxidative stress is largely recognized to play a key role in the pathogenesis of asthma and COPD and might have a role in the new intermediate phenotype ACOS (asthma-COPD overlap syndrome). The aim of this study was to investigate MtDNA alterations, as an expression of mitochondrial dysfunction, in ACOS and to verify whether they might help in the identification of this new phenotype and in its differentiation from asthma and COPD.

METHODS

Ten (10) ACOS according to Spanish guidelines, 13 ACOS according to GINA guidelines, 13 COPD, 14 asthmatic patients and ten normal subjects were enrolled. They further underwent a blood, induced sputum and exhaled nitric oxide collection. Content of MtDNA and nuclear DNA (nDNA) were measured in the blood cells of patients by Real Time PCR.

RESULTS

ACOS patients showed an increase of MtDNA/nDNA ratio. Dividing ACOS according to guidelines, those from the Spanish showed a higher value of MtDNA/nDNA compared to those from GINA/GOLD (92.69 ± 7.31 vs 80.68 ± 4.16). Spanish ACOS presented MtDNA/nDNA ratio closer to COPD than asthma. MtDNA was higher in asthmatic, COPD, GINA and Spanish ACOS patients compared to healthy subjects (73.30 ± 4.47-137.0 ± 19.45-80.68 ± 4.16-92.69 ± 7.31 vs 65.97 ± 20.56).

CONCLUSION

We found an increase of MtDNA/nDNA ratio in ACOS subjects that led us to conclude that there is presence of mitochondrial dysfunction in this disease, that makes it closer to COPD than to asthma. Although the MtDNA/nDNA ratio results are a useful marker for differential diagnosis from asthma, COPD and ACOS, further studies are needed to confirm the potentiality of MtDNA/nDNA ratio and to a better characterization of ACOS.