Airway smooth muscle growth from the perspective of animal models

Temporal changes of the respiratory microbiota as cats transition from health to experimental acute and chronic allergic asthma

In humans, deviation from a core airway microbiota may predispose to development, exacerbation, or progression of asthma. We proposed to describe microbiota changes using 16 rRNA sequencing in samples from the upper and lower airways, and rectal swabs of 8 cats after experimental induction of asthma using Bermuda grass allergen, in acute (6 weeks) and chronic (36 weeks) stages. We hypothesized that asthma induction would decrease richness and diversity and alter microbiota composition and structure in the lower airways, without significantly impacting other sites. After asthma induction, richness decreased in rectal (p = 0.014) and lower airway (p = 0.016) samples. B diversity was significantly different between health and chronic asthma in all sites, and between all time points for lower airways. In healthy lower airways Pseudomonadaceae comprised 80.4 ± 1.3% whereas Sphingobacteriaceae and Xanthobacteraceae predominated (52.4 ± 2.2% and 33.5 ± 2.1%, respectively), and Pseudomonadaceae was absent, in 6/8 cats with chronic asthma. This study provides evidence that experimental induction of asthma leads to dysbiosis in the airways and distant sites in both the acute and chronic stages of disease. This article has been published alongside "Respiratory dysbiosis in cats with spontaneous allergic asthma" (1).

Long non-coding RNA00882 contributes to platelet-derived growth factor-induced proliferation of human fetal airway smooth muscle cells by enhancing Wnt/β-catenin signaling via sponging miR-3619-5p

Long non-coding RNAs (lncRNAs) are emerging as novel and critical regulators in the pathogenesis of asthma. However, the precise role of lncRNAs in pediatric asthma remains largely unknown. In this study, we aimed to investigate the biological function of lncRNA00882 (LINC00882) in regulating the proliferation of fetal airway smooth muscle (ASM) cells, which play an important role in airway remodeling during asthma development. Herein, we found that LINC00882 expression was significantly up-regulated in ASM cells stimulated with platelet-derived growth factor (PDGF). Functional experiments showed that the knockdown of LINC00882 markedly reduced the proliferation of fetal ASM cells induced by PDGF, while the overexpression of LINC00882 exhibited the opposite effect. Bioinformatics analysis, the luciferase reporter assay and the RNA pull-down assay revealed that LINC00882 directly interacted with microRNA-3619-5p (miR-3619-5p). LINC00882 negatively regulated miR-3619-5p expression in fetal ASM cells. Notably, β-catenin was identified as a target gene of miR-3619-5p. miR-3619-5p overexpression restricted PDGF-induced cell proliferation through inhibiting Wnt/β-catenin signaling. Moreover, miR-3619-5p overexpression significantly attenuated the LINC00882-induced promotion effect on PDGF-induced cell proliferation and Wnt/β-catenin signaling in fetal ASM cells. In contrast, miR-3619-5p inhibition significantly reversed the LINC00882 knockdown-mediated inhibitory effect on PDGF-induced cell proliferation and Wnt/β-catenin signaling. Taken together, our results demonstrate that LINC00882 promotes PDGF-induced cell proliferation of ASM cells by enhancing Wnt/β-catenin signaling via sponging miR-3619-5p, suggesting a potential role for LINC00882 in airway remodeling in pediatric asthma.

Stem cell-based Lung-on-Chips: The best of both worlds?

Pathologies of the respiratory system such as lung infections, chronic inflammatory lung diseases, and lung cancer are among the leading causes of morbidity and mortality, killing one in six people worldwide. Development of more effective treatments is hindered by the lack of preclinical models of the human lung that can capture the disease complexity, highly heterogeneous disease phenotypes, and pharmacokinetics and pharmacodynamics observed in patients. The merger of two novel technologies, Organs-on-Chips and human stem cell engineering, has the potential to deliver such urgently needed models. Organs-on-Chips, which are microengineered bioinspired tissue systems, recapitulate the mechanochemical environment and physiological functions of human organs while concurrent advances in generating and differentiating human stem cells promise a renewable supply of patient-specific cells for personalized and precision medicine. Here, we discuss the challenges of modeling human lung pathophysiology in vitro, evaluate past and current models including Organs-on-Chips, review the current status of lung tissue modeling using human pluripotent stem cells, explore in depth how stem-cell based Lung-on-Chips may advance disease modeling and drug testing, and summarize practical consideration for the design of Lung-on-Chips for academic and industry applications.

Calcium sensing receptor in developing human airway smooth muscle

Airway smooth muscle (ASM) regulation of airway structure and contractility is critical in fetal/neonatal physiology in health and disease. Fetal lungs experience higher Ca²⁺ environment that may impact extracellular Ca²⁺ ([Ca²⁺ ]_o ) sensing receptor (CaSR). Well-known in the parathyroid gland, CaSR is also expressed in late embryonic lung mesenchyme. Using cells from 18-22 week human fetal lungs, we tested the hypothesis that CaSR regulates intracellular Ca²⁺ ([Ca²⁺ ]_i ) in fetal ASM (fASM). Compared with adult ASM, CaSR expression was higher in fASM, while fluorescence Ca²⁺ imaging showed that [Ca²⁺ ]_i was more sensitive to altered [Ca²⁺ ]_o . The fASM [Ca²⁺ ]_i responses to histamine were also more sensitive to [Ca²⁺ ]_o (0-2 mM) compared with an adult, enhanced by calcimimetic R568 but blunted by calcilytic NPS2143. [Ca²⁺ ]_i was enhanced by endogenous CaSR agonist spermine (again higher sensitivity compared with adult). Inhibition of phospholipase C (U73122; siRNA) or inositol 1,4,5-triphosphate receptor (Xestospongin C) blunted [Ca²⁺ ]_o sensitivity and R568 effects. NPS2143 potentiated U73122 effects. Store-operated Ca²⁺ entry was potentiated by R568. Traction force microscopy showed responsiveness of fASM cellular contractility to [Ca²⁺ ]_o and NPS2143. Separately, fASM proliferation showed sensitivity to [Ca²⁺ ]_o and NPS2143. These results demonstrate functional CaSR in developing ASM that modulates airway contractility and proliferation.

MicroRNA-590-5p represses proliferation of human fetal airway smooth muscle cells by targeting signal transducer and activator of transcription 3

INTRODUCTION

Pediatric asthma has remained a health threat to children in recent years. The abnormal proliferation of airway smooth muscle (ASM) cells contributes to airway remodeling during development of asthma. MicroRNAs (miRNAs) are critical regulators of ASM cell proliferation during airway remodeling. miR-590-5p has been reported to regulate cell proliferation in various cell types. However, it remains unclear whether miR-590-5p regulates ASM cell proliferation. In this study, we aimed to investigate the potential role of miR-590-5p in regulating fetal ASM cell proliferation in vitro stimulated by platelet-derived growth factor (PDGF).

MATERIAL AND METHODS

miRNA, mRNA, and protein expression was detected by real-time quantitative polymerase chain reaction and western blot. Cell proliferation was detected by CCK-8 and BrdU assays. The target of miR-590-5p was confirmed by dual-luciferase reporter assay.

RESULTS

MiR-590-5p expression was significantly down-regulated in fetal ASM cells stimulated with PDGF (p < 0.05). Overexpression of miR-590-5p inhibited cell proliferation (p < 0.05), whereas the suppression of miR-590-5p promoted cell proliferation of fetal ASM cells stimulated with PDGF (p < 0.05). Signal transducer and activator of transcription 3 (STAT3) was identified as a target gene of miR-590-5p. In addition, miR-590-5p negatively regulated STAT3 expression (p < 0.05). Moreover, miR-590-5p also modulated downstream genes of STAT3 including cyclin D3 and p27 (p < 0.05). The restoration of STAT3 significantly reversed the inhibitory effect of miR-590-5p on fetal ASM cell proliferation.

CONCLUSIONS

MiR-590-5p inhibits proliferation of fetal ASM cells by down-regulating STAT3, thereby suggesting a novel therapeutic target for the treatment of pediatric asthma.

Circulating microRNAs and association with methacholine PC20 in the Childhood Asthma Management Program (CAMP) cohort

Introduction

Circulating microRNAs (miRNA) are promising biomarkers for human diseases. Our study hypothesizes that circulating miRNA would reveal candidate biomarkers related to airway hyperresponsiveness (AHR) and provide biologic insights into asthma epigenetic influences.

Methods

Serum samples obtained at randomization for 160 children in the Childhood Asthma Management Program were profiled using a TaqMan miRNA array set. The association of the isolated miRNA with methacholine PC₂₀ was assessed. Network and pathway analyses were performed. Functional validation of two significant miRNAs was performed in human airway smooth muscle cells (HASMs).

Results

Of 155 well-detected circulating miRNAs, eight were significantly associated with PC₂₀ with the strongest association with miR-296-5p. Pathway analysis revealed miR-16-5p as a network hub, and involvement of multiple miRNAs interacting with genes in the FoxO and Hippo signaling pathways by KEGG analysis. Functional validation of two miRNA in HASM showed effects on cell growth and diameter.

Conclusion

Reduced circulatory miRNA expression at baseline is associated with an increase in PC₂₀. These miRNA provide biologic insights into, and may serve as biomarkers of, asthma severity. miR-16-5p and -30d-5p regulate airway smooth muscle phenotypes critically involved in asthma pathogenesis, supporting a mechanistic link to these findings. Functional ASM phenotypes may be directly relevant to AHR.

MicroRNA regulation of airway smooth muscle function

Airway smooth muscle (ASM) controls airway narrowing and plays a pivotal role in the pathogenesis of asthma. MicroRNAs are small yet powerful gene tuners that regulate diverse cellular processes. Recent studies have demonstrated the versatile role of microRNAs in regulating multiple ASM phenotypes that are critically involved in asthma pathogenesis. These ASM phenotypes include proliferation, cell size, chemokine secretion, and contractility. Here we review microRNA-mediated regulation of ASM functions and discuss the potential of microRNAs as a novel class of therapeutic targets to improve ASM function for asthma therapy.

MiR-23b controls TGF-β1 induced airway smooth muscle cell proliferation via direct targeting of Smad3

BACKGROUND

MicroRNAs are small yet versatile gene tuners that regulate a variety of cellular processes, including cell growth and proliferation. Here we report that miR-23b inhibited airway smooth muscle cells (ASMCs) proliferation through directly targeting of Smad3.

METHODS

We obtained ASMCs by laser capture microdissection of normal and asthmatic mice lung tissues. Mice ASMCs were cultured and induced by TGF-β1. The implication between TGF-β1 and miR-23b in ASMCs were detected by RT-PCR. The effects of miR-23b on ASMCs proliferation and apoptosis were assessed by transient transfection of miR-23b mimics and inhibitor. The expression of Smad3 in ASMCs were detected by RT-PCR and Western blotting analysis. Dual-Luciferase Reporter Assay System will be applied to identify whether Smad3 is a target gene of miR-23b.

RESULTS

TGF-β1 and miR-23b mRNA expression of in-situ bronchial ASMCs collected by laser capture microdissection were increased in asthmatic mice compared to non-asthma controls. This is accompanied by an increase in miR-23b mRNA expression in TGF-β1 induced ASMCs. miR-23b up-regulation significantly inhibited TGF-β1-induced ASMCs proliferation and promoted apoptosis. MiR-23b negatively regulates the expression of Smad3 in ASMCs. Dual-Luciferase Reporter Assay System demonstrated that Smad3 was a direct target of miR-23b.

CONCLUSIONS

MiR-23b may function as an inhibitor of asthma airway remodeling by suppressing ASMCs proliferation via direct targeting of Smad3.

Simvastatin alleviates airway inflammation and remodelling through up-regulation of autophagy in mouse models of asthma

BACKGROUND AND OBJECTIVE

Statins have been widely used in inflammatory diseases including asthma, because of their anti-inflammatory and immunomodulatory properties. It has been shown that simvastatin induces autophagy and cell death in some circumstances. However, the possible cross-talk between simvastatin and autophagic processes in lung disease is largely unknown. Thus, we investigated the impact of simvastatin on airway inflammation and airway remodelling and the possible relationship of these processes to a simvastatin-induced autophagic pathway in mouse models of asthma.

METHODS

Ovalbumin (OVA)-sensitized and challenged mice were treated with simvastatin and sacrificed. The autophagy-related proteins Atg5, LC3B and Beclin1 were quantified, as well as the autophagy flux in bronchial smooth muscle cells (BSMCs). The relationship between airway inflammation and the autophagic process was investigated.

RESULTS

We show that simvastatin treatment mediates activation of autophagy in BSMCs, which is correlated with airway inflammation and airway remodelling in mouse models of asthma. Simvastatin increases autophagy-related protein Atg5, LC3B and Beclin1 expression and autophagosome formation in lung tissue. Simvastatin-induced autophagy is associated with increased interferon-gamma (IFN-γ) and decreased IL-4, IL-5 and IL-13 cytokines production in BSMCs, as well as reversed extracellular matrix (ECM) deposition. In contrast, autophagy inhibitor 3-methyladenine (3-MA) eliminates the therapeutic effect of simvastatin.

CONCLUSION

These findings demonstrate that simvastatin inhibits airway inflammation and airway remodelling through an activated autophagic process in BSMCs. We propose a crucial function of autophagy in statin-based therapeutic approaches in asthma.

MiR-21 modulates human airway smooth muscle cell proliferation and migration in asthma through regulation of PTEN expression

BACKGROUND

Asthma is characterized by airway remodeling arising from an increase in airway smooth muscle (ASM) mass. This increase is regulated in part by ASM cell proliferation and migration. MicroRNA (miR)-21 also plays a role in asthma, but the molecular mechanisms underlying its effects are not completely understood. This study investigated the effects and mechanism of miR-21 on the human ASM (HASM) cell proliferation and migration.

MATERIALS AND METHODS

HASM cells were transduced with a miR-21 vector, and the expression of miR-21 was determined by quantitative real-time polymerase chain reaction (qRT-PCR). The effect of the miR-21 on HASM cell proliferation and migration was analyzed by CCK8 and transwell assay. The expression level of PTEN (phosphatase and tensin homolog deleted on chromosome 10) in HASM cells was assessed by qRT-PCR and Western blot analysis. Meanwhile, the activity of PTEN was measured by PTEN malachite green assay kit.

RESULTS

Lentivirus-mediated miR-21 overexpression markedly enhanced the proliferation and migration of HASM cells (P < .05), and ablation of miR-21 by anti-miR-21 inhibitor markedly reduced cell proliferation and migration. We demonstrated that miR-21 overexpression significantly reduced the expression of PTEN (P < .05), while PTEN knock-down markedly increased HASM cell proliferation and migration. Furthermore, we found that overexpression of PTEN led to a decrease of HASM cell proliferation and migration. MiR-21 mediated HASM cell proliferation and migration through activation of the phosphoinositide 3-kinase pathway.

CONCLUSIONS

This study provides the first in vitro evidence that overexpression of miR-21 in HASM cells can trigger cell proliferation and migration, and the effects of miR-21 depend on the level of PTEN.

MiR-143-3p controls TGF-β1-induced cell proliferation and extracellular matrix production in airway smooth muscle via negative regulation of the nuclear factor of activated T cells 1

MicroRNAs (miRNAs) are small noncoding RNAs that function in diverse biological processes. However, little is known about the precise role of microRNAs in the functioning of airway smooth muscle cells (ASMCs). Here, we investigated the potential role and mechanisms of the miR-143 -3p on proliferation and the extracellular matrix (ECM) protein production of ASMCs. We demonstrated that miR-143-3p was aberrantly lower in ASMCs isolated from individuals with asthma than in individuals without asthma. Meanwhile, TGF-β1 caused a marked decrease in a time-dependent manner in miR-143-3p expression in ASMCs from asthmatics. Additionally, the overexpression of miR- 143-3p robustly reduced TGF-β1-induced ASMCs proliferation and downregulated CDK and cyclin expression, whereas the inhibition of miR-143-3p significantly enhanced ASMCs proliferation and upregulated the level of CDKs and cyclins. Re-expression of miR-143-3p attenuated ECM protein deposition reflected as a marked decrease in the expression of type I collagen and fibronectin, whereas miR-143-3p downregulation caused an opposite effect on the expression of type I collagen and fibronectin. Moreover, qRT-PCR and western blot analysis indicated that miR-143-3p negatively regulated the expression of nuclear factor of activated T cells 1 (NFATc1). Subsequent analyses demonstrated that NFATc1 was a direct and functional target of miR-143-3p, which was validated by the dual luciferase reporter assay. Most importantly, the overexpression of NFATc1 effectively reversed the inhibition of miR-143-3p on TGF-β1-induced proliferation, and strikingly abrogated the effect of miR-143-3p on the expression of CDK4 and Cyclin D1. Together, miR-143-3p may function as an inhibitor of asthma airway remodeling by suppressing proliferation and ECM protein deposition in TGF-β1-mediated ASMCs via the negative regulation of NFATc1 signaling, suggesting miR-143-3p as a potential therapeutic target for asthma.

MiR-23b controls TGF-β1 induced airway smooth muscle cell proliferation via TGFβR2/p-Smad3 signals

BACKGROUND

Abnormal proliferation of ASM (airway smooth muscle) directly contributes to the airway remodeling during development of lung diseases such as asthma. Here we report that a specific microRNA (miR-23b) controls ASMCs proliferation through directly inhibiting TGFβR2/p-Smad3 pathway.

METHODS

The expression of miR-23b in ASMCs was detected by quantitative real-time polymerase chain reaction (RT-PCR). The effects of miR-23b on cell proliferation and apoptosis of ASMCs were assessed by transient transfection of miR-23b mimics and inhibitor. The target gene of miR-23b and the downstream pathway were further investigated.

RESULTS

Overexpression of miR-23b significantly inhibited TGF-β1-induced ASMCs proliferation and promoted apoptosis. RT-PCR and Western blotting analysis showed miR-23b negatively regulates the expression of TGFβR2 and p-Smad3 in ASMCs. Subsequent analyses demonstrated that TGFβR2 was a direct and functional target of miR-23b, which was validated by the dual luciferase reporter assay.

CONCLUSIONS

MiR-23b may function as an inhibitor of airway smooth muscle cells proliferation through inactivation of TGFβR2/p-Smad3 pathway.

Microbiome and Asthma: What Have Experimental Models Already Taught Us?

Asthma is a chronic inflammatory disease that imposes a substantial burden on patients, their families, and the community. Although many aspects of the pathogenesis of classical allergic asthma are well known by the scientific community, other points are not yet understood. Experimental asthma models, particularly murine models, have been used for over 100 years in order to better understand the immunopathology of asthma. It has been shown that human microbiome is an important component in the development of the immune system. Furthermore, the occurrence of many inflammatory diseases is influenced by the presence of microbes. Again, experimental models of asthma have helped researchers to understand the relationship between the microbiome and respiratory inflammation. In this review, we discuss the evolution of murine models of asthma and approach the major studies involving the microbiome and asthma.

MicroRNA-10a controls airway smooth muscle cell proliferation via direct targeting of the PI3 kinase pathway

Airway smooth muscle (ASM) cells play important physiological roles in the lung, and abnormal proliferation of ASM directly contributes to the airway remodeling during development of lung diseases such as asthma. MicroRNAs are small yet versatile gene tuners that regulate a variety of cellular processes, including cell growth and proliferation; however, little is known about the precise role of microRNAs in the proliferation of the ASM. Here we report that a specific microRNA (miR-10a) controls ASM proliferation through directly inhibiting the phosphoinositide 3-kinase (PI3K) pathway. Next-generation sequencing identified miR-10a as the most abundant microRNA expressed in primary human airway smooth muscle (HASM) cells, accounting for > 20% of all small RNA reads. Overexpression of miR-10a reduced mitogen-induced HASM proliferation by ∼50%, whereas inhibition of miR-10a increased HASM proliferation by ∼40%. Microarray profiling of HASM cells expressing miR-10a mimics identified 52 significantly down-regulated genes as potential targets of miR-10a, including the catalytic subunit α of PI3K (PIK3CA), the central component of the PI3K pathway. MiR-10a directly suppresses PIK3CA expression by targeting the 3'-untranslated region (3'-UTR) of the gene. Inhibition of PIK3CA by miR-10a reduced V-akt murine thymoma viral oncogene homolog 1 (AKT) phosphorylation and blunted the expression of cyclins and cyclin-dependent kinases that are required for HASM proliferation. Together, our study identifies a novel microRNA-mediated regulatory mechanism for PI3K signaling and ASM proliferation and further suggests miR-10a as a potential therapeutic target for lung diseases whose etiology resides in abnormal ASM proliferation.

Oxygen dose responsiveness of human fetal airway smooth muscle cells

Maintenance of blood oxygen saturation dictates supplemental oxygen administration to premature infants, but hyperoxia predisposes survivors to respiratory diseases such as asthma. Although much research has focused on oxygen effects on alveoli in the setting of bronchopulmonary dysplasia, the mechanisms by which oxygen affects airway structure or function relevant to asthma are still under investigation. We used isolated human fetal airway smooth muscle (fASM) cells from 18-20 postconceptual age lungs (canalicular stage) to examine oxygen effects on intracellular Ca(2+) ([Ca(2+)](i)) and cellular proliferation. fASM cells expressed substantial smooth muscle actin and myosin and several Ca(2+) regulatory proteins but not fibroblast or epithelial markers, profiles qualitatively comparable to adult human ASM. Fluorescence Ca(2+) imaging showed robust [Ca(2+)](i) responses to 1 μM acetylcholine (ACh) and 10 μM histamine (albeit smaller and slower than adult ASM), partly sensitive to zero extracellular Ca(2+). Compared with adult, fASM showed greater baseline proliferation. Based on this validation, we assessed fASM responses to 10% hypoxia through 90% hyperoxia and found enhanced proliferation at <60% oxygen but increased apoptosis at >60%, effects accompanied by appropriate changes in proliferative vs. apoptotic markers and enhanced mitochondrial fission at >60% oxygen. [Ca(2+)](i) responses to ACh were enhanced for <60% but blunted at >60% oxygen. These results suggest that hyperoxia has dose-dependent effects on structure and function of developing ASM, which could have consequences for airway diseases of childhood. Thus detrimental effects on ASM should be an additional consideration in assessing risks of supplemental oxygen in prematurity.

Nonylphenol induces bronchial epithelial apoptosis via Fas-mediated pathway and stimulates bronchial epithelium to secrete IL-6 and IL-8, causing bronchial smooth muscle proliferation and migration

Features of airway remodelling have been described using tissue obtained from fatal cases of asthma and bronchial biopsies from mildly, moderately and severely asthmatic patients. Epithelial detachment and smooth muscle mass enhancement are common features of asthmatic bronchial tissue. This study is the first to investigate the inhibitory effect of nonylphenol (NP) on human bronchial epithelial cell lines BEAS-2B and HBE135-E6E7 (HBE). The results show that NP inhibits bronchial epithelial proliferation via the Fas/Fas ligand apoptotic system. We also treated BEAS-2B and HBE with NP and harvested the condition medium (CM), which was then added to bronchial smooth muscle cells (BSMC). Cultures of BSMC with NP-BEAS-2B-CM and NP-HBE-CM increased BSMC proliferation and migration. Exposure of BEAS-2B and HBE to NP caused epithelial cells to produce inflammatory cytokines IL-6 and IL-8, which subsequently induced BSMC proliferation and migration. Depleting both IL-6 and IL-8 completely reversed the effect of NP-BEAS-2B-CM- and NP-HBE-CM-mediated BSMC proliferation and migration, suggesting that this effect is a synergistic influence of IL-6 and IL-8. This study is the first to demonstrate that NP not only induces bronchial epithelial apoptosis via the Fas-mediated pathway but also stimulates the bronchial epithelium to secrete IL-6 and IL-8, which cause bronchial smooth muscle proliferation and migration - major features in asthma remodelling.

[Inflammation and remodeling of the distal airways: studies in humans and experimental models]

Asthma is characterized by inflammation and remodeling of the airways, giving rise to airway obstruction and symptoms of wheezing, chest tightness, cough and dyspnea. Most of these observations arise from the study of samples obtained from the central airways by distinct methods. However, it is currently accepted that this inflammatory process occurs not only in the central airway but also in the small airway and even in the pulmonary parenchyma of all asthmatic patients, even those with mild asthma. CD4+ lymphocytes, activated eosinophils and IL-5 mRNA expression are present in a greater quantity in the small airways. Also present is remodeling, with an increase in submucosal thickness, the muscular layer and adventitia. This inflammatory process causes a disconnection between the pulmonary parenchyma and the airway, giving rise to obstruction of the small airway, which is currently considered to be predominant in asthmatic patients. Likewise, studies of experimental asthma in animals support the substantial role of the distal airway. Recognition that asthma affects the entire airway could be clinically important and lead to the distal lung being considered as a target in any effective therapeutic strategy. However, longitudinal studies are required to evaluate the impact of distal airway inflammation and its treatment in asthma.

Pterostilbene suppresses benzo[a]pyrene-induced airway remodeling

This study has two novel findings: it is not only the first to demonstrate inflammatory cytokines, which are produced by the bronchial epithelium after exposure to benzo[a]pyrene (BaP) and contribute to airway remodeling by increasing human bronchial smooth muscle cells (BSMC) proliferation and migration, but also the first to reveal that pterostilbene, a constituent of grapes and berries, reverses BaP-mediated airway remodeling. Human bronchial epithelial cell lines BEAS-2B and HBE135-E6E7 (HBE) were treated with BaP, and then the condition medium (CM) was harvested, which was then added to BSMC. Cultures of BSMC with BaP-BEAS-2B-CM and -HBE-CM increased BSMC proliferation and migration, which are major features in asthma remodeling. Exposure of BEAS-2B and HBE to BaP caused epithelial cells to produce inflammatory cytokines IL-8, which subsequently induced BSMC proliferation and migration. Moreover, pterostilbene is more potent than resveratrol in suppressing BaP-mediated airway remodeling. This study suggests that pterostilbene is capable of preventing BaP-associated asthma.

Animal models of asthma: value, limitations and opportunities for alternative approaches

Asthma remains an area of considerable unmet medical need. Few new drugs have made it to the clinic during the past 50 years, with many that perform well in preclinical animal models of asthma, failing in humans owing to lack of safety and efficacy. The failure to translate promising drug candidates from animal models to humans has led to questions about the utility of in vivo studies and to demand for more predictive models and tools based on the latest technologies. Following a workshop with experts from academia and the pharmaceutical industry, we suggest here a disease modelling framework designed to better understand human asthma, and accelerate the development of safe and efficacious new asthma drugs that go beyond symptomatic relief.

Ginger suppresses phthalate ester-induced airway remodeling

This study has two novel findings: it is not only the first to demonstrate inflammatory cytokines, which are produced by the bronchial epithelium after exposure to phthalate esters and contribute to airway remodeling by increasing human bronchial smooth muscle cells (BSMC) migration and proliferation, but it is also the first to reveal that ginger reverses phthalate ester-mediated airway remodeling. Human bronchial epithelial cell lines BEAS-2B and HBE135-E6E7 (HBE) were treated with butylbenzyl phthalate (BBP), bis(2-ethylhexyl) phthalate (BEHP), dibutyl phthalate (DBP), and diethyl phthalate (DEP), and the conditioned medium (CM) was harvested and then added to BSMC. Cultures of BSMC with BBP-, BEHP-, DBP-, and DEP-BEAS-2B-CM and DEP-HBE-CM increased BSMC proliferation and migration, which are major features in asthma remodeling. Exposure of BEAS-2B and HBE to DBP caused epithelial cells to produce inflammatory cytokines IL-8 and RANTES, which subsequently induced BSMC proliferation and migration. Depleting both IL-8 and RANTES completely reversed the effect of DBP-BEAS-2B-CM and DBP-HBE-CM-mediated BSMC proliferation and migration, suggesting this effect is a synergistic influence of IL-8 and RANTES. Moreover, [6]-shogaol, [6]-gingerol, [8]-gingerol, and [10]-gingerol, which are major bioactive compounds present in Zingiber officinale , suppress phthalate ester-mediated airway remodeling. This study suggests that ginger is capable of preventing phthalate ester-associated asthma.

Effect of antigenic exposure on airway smooth muscle remodeling in an equine model of chronic asthma

Recent studies suggest that airway smooth muscle remodeling is an early event in asthma, but whether it remains a dynamic process late in the course of the disease is unknown. Moreover, little is known about the effects of an antigenic exposure on chronically established smooth muscle remodeling. We measured the effects of antigenic exposure on airway smooth muscle in the central and peripheral airways of horses with heaves, a naturally occurring airway disease that shares similarities with chronic asthma. Heaves-affected horses (n = 6) and age-matched control horses (n = 5) were kept on pasture before being exposed to indoor antigens for 30 days to induce airway inflammation and bronchoconstriction. Peripheral lung and endobronchial biopsies were collected before and after antigenic exposure by thoracoscopy and bronchoscopy, respectively. Immunohistochemistry and enzymatic labeling were used for morphometric analyses of airway smooth muscle mass and proliferative and apoptotic myocytes. In the peripheral airways, heaves-affected horses had twice as much smooth muscle as control horses. Remodeling was associated with smooth muscle hyperplasia and in situ proliferation, without reduced apoptosis. Further antigenic exposure had no effect on the morphometric data. In central airways, proliferating myocytes were increased compared with control horses only after antigenic exposure. Peripheral airway smooth muscle mass is stable in chronically affected animals subjected to antigenic exposure. This increased mass is maintained in a dynamic equilibrium by an elevated cellular turnover, suggesting that targeting smooth muscle proliferation could be effective at decreasing chronic remodeling.

Genetic influences on asthma susceptibility in the developing lung

Asthma is the leading serious pediatric chronic illness in the United States, affecting 7.1 million children. The prevalence of asthma in children under 4 years of age has increased dramatically in the last 2 decades. Existing evidence suggests that this increase in prevalence derives from early environmental exposures acting on a pre-existing asthma-susceptible genotype. We studied the origins of asthma susceptibility in developing lung in rat strains that model the distinct phenotypes of airway hyperresponsiveness (Fisher rats) and atopy (brown Norway [BN] rats). Postnatal BN rat lungs showed increased epithelial proliferation and tracheal goblet cell hyperplasia. Fisher pups showed increased lung resistance at age 2 weeks, with elevated neutrophils throughout the postnatal period. Diverse transcriptomic signatures characterized the distinct respiratory phenotypes of developing lung in both rat models. Linear regression across age and strain identified developmental variation in expression of 1,376 genes, and confirmed both strain and temporal regulation of lung gene expression. Biological processes that were heavily represented included growth and development (including the T Box 1 transcription factor [Tbx5], the epidermal growth factor receptor [Egfr], the transforming growth factor beta-1-induced transcript 1 [Tgfbr1i1]), extracellular matrix and cell adhesion (including collagen and integrin genes), and immune function (including lymphocyte antigen 6 (Ly6) subunits, IL-17b, Toll-interacting protein, and Ficolin B). Genes validated by quantitative RT-PCR and protein analysis included collagen III alpha 1 Col3a1, Ly6b, glucocorticoid receptor and Importin-13 (specific to the BN rat lung), and Serpina1 and Ficolin B (specific to the Fisher lung). Innate differences in patterns of gene expression in developing lung that contribute to individual variation in respiratory phenotype are likely to contribute to the pathogenesis of asthma.

Modulation of the allergic asthma transcriptome following resiquimod treatment

Resiquimod is a compound belonging to the imidazoquinoline family of compounds known to signal through Toll-like receptor 7. Resiquimod treatment has been demonstrated to inhibit the development of allergen induced asthma in experimental models. The aim of the present study was to elucidate the molecular processes that were altered following resiquimod treatment and allergen challenge in a mouse model of allergic asthma. Employing microarray analysis, we have characterized the "asthmatic" transcriptome of the lungs of A/J and C57BL/6 mice and determined that it includes genes involved in the control of cell cycle progression, the complement and coagulation cascades, and chemokine signaling. Our results demonstrated that resiquimod treatment resulted in the normalization of the expression of genes involved with airway remodeling, and generally, chemokine signaling. Resiquimod treatment also altered the expression of cell adhesion molecules, and molecules involved in natural killer (NK) cell-mediated cytotoxicity. Furthermore, we have demonstrated that systemic resiquimod administration resulted in the recruitment of NK cells to the lungs and livers of the mice, although no causal relationship between NK cell recruitment and treatment efficacy was found. Overall, our findings identified several genes, important in the development of asthma pathology, that were normalized following resiquimod treatment, thus improving our understanding of the molecular consequences of resiquimod treatment in the lung milieu. The recruitment of NK cells to the lungs may also have application in the treatment of virally induced asthma exacerbations.

Bronchodilator response in patients with persistent allergic asthma could not predict airway hyperresponsiveness

: Anticholinergics, or specific antimuscarinic agents, by inhibition of muscarinic receptors cause bronchodilatation, which might correlate with activation of these receptors by the muscarinic agonist methacholine. The aim of this study was to determine whether a positive bronchodilator response to the anticholinergic ipratropium bromide could predict airway hyperresponsiveness in patients with persistent allergic asthma. The study comprised 40 patients with mild and moderate persistent allergic asthma. Diagnosis was established by clinical and functional follow-up (skin-prick test, spirometry, bronchodilator tests with salbutamol and ipratropium bromide, and methacholine challenge testing). The bronchodilator response was positive to both bronchodilator drugs in all patients. After salbutamol inhalation, forced expiratory volume in 1 second (FEV1) increased by 18.39 +/- 6.18%, p < .01, whereas after ipratropium bromide, FEV1 increased by 19.14 +/- 6.74%, p < .01. The mean value of FEV1 decreased by 25.75 +/- 5.16%, p < .01 after methacholine (PC20 FEV1 [provocative concentration of methacholine that results in a 20% fall in FEV1] from 0.026 to 1.914 mg/mL). Using linear regression, between methacholine challenge testing and bronchodilator response to salbutamol, a positive, weak, and stastistically significant correlation for FEV1 was found (p < .05). Correlations between methacholine challenge testing and the bronchodilator response to ipratropium bromide were positive and weak but not statistically significant. The positive bronchodilator response to ipratropium bromide could not predict airway hyperresponsiveness.

Airway remodeling in asthma

Airway remodeling can be defined as changes in the composition, content, and organization of the cellular and molecular constituents of the airway wall. Airway remodeling is a characteristic feature of asthma, and has important functional implications. These structural changes include epithelial detachment, subepithelial fibrosis, increased airway smooth muscle (ASM) mass, decreased distance between epithelium and ASM cells, goblet cell hyperplasia, mucus gland hyperplasia, proliferation of blood vessels and airway edema and changes in the cartilage. Each can contribute to airway hyperreactivity (AHR), and may eventually lead to irreversible airflow obstruction with disease progression. Structural changes can be observed from early onset of the disease and thus remodeling is thought to be characteristic of asthma. Some aspects of airway remodeling can be explained as a consequence of TH2 inflammation, although it has also been suggested that the exaggerated inflammation and remodeling seen in asthmatic airways is the consequence of abnormal injury and repair responses stemming from the susceptibility of bronchial epithelia to components of the inhaled environment. According to this view, remodeling occurs by way of a noninflammatory mechanism, where inflammation of airways and altered structure and function of the airways are parallel and interacting factors. Airway remodeling in established asthma is poorly responsive to current therapies, such as inhalation of corticosteroids and administration of beta(2)-agonists, antileukotrienes, and theophylline.

Endothelin-1 induces hypertrophy and inhibits apoptosis in human airway smooth muscle cells

Endothelin-1 (ET-1), a G protein-coupled receptor-activating peptide, is increased in airway epithelium, plasma, and bronchoalveolar lavage fluid of asthmatic patients. We hypothesized that ET-1 may contribute to the increased airway smooth muscle mass found in severe asthma by inducing hypertrophy and inhibiting apoptosis of smooth muscle cells. To investigate this hypothesis, we determined that treatment of primary human bronchial smooth muscle cells with ET-1 dose dependently [10(-11)-10(-7) M] inhibited the apoptosis induced by serum withdrawal. ET-1 treatment also resulted in a significant increase in total protein synthesis, mediated through both ET(A) and ET(B) receptors, cell size, as well as increased expression of myosin heavy chain, alpha-smooth muscle actin, and calponin. ET-1-induced hypertrophy was accompanied by activation of JAK1/STAT-3 and MAPK1/2 (ERK1/2) cell signaling pathways. Inhibition of JAK1/STAT-3 pathways by piceatannol or ERK1/2 by the MAPK/ERK kinase 1/2 inhibitor U0126 blunted the increase in total protein synthesis. The hypertrophic effect of ET-1 was equivalent to that of the gp130 cytokine oncostatin M and greater than that induced by cardiotrophin-1. ET-1 induced release of IL-6 but not IL-11, leukemia inhibitory factor, oncostatin M, or cardiotrophin-1, although treatment of cells with IL-6 alone did not induce hypertrophy. These results suggest that ET-1 is a candidate mediator for the induction of increased smooth muscle mass in asthma and identify signaling pathways activated by this mediator.

Airway remodelling in asthma: current understanding and implications for future therapies

Airway remodelling refers to the structural changes that occur in the airway wall in asthma. These include epithelial hyperplasia and metaplasia, subepithelial fibrosis, muscle cell hyperplasia and angiogenesis. These structural changes result in thickening of the airway wall, airway hyperresponsiveness (AHR), and a progressive irreversible loss of lung function. The precise sequence of events that take place during the remodelling process and the mechanisms regulating these changes remain poorly understood. It is thought that airway remodelling is initiated and promoted by repeated episodes of allergic inflammation that damage the surface epithelium of the airway. However, other mechanisms are also likely to contribute to this process. Moreover, the interrelationship between airway remodelling, inflammation and AHR has not been clearly defined. Currently, there are no effective treatments that halt or reverse the changes of airway remodelling and its effects on lung function. Glucocorticoids have been unable to eliminate the progression of remodelling changes and there is limited evidence of a beneficial effect from other available therapies. The search for novel therapies that can directly target individual components of the remodelling process should be made a priority. In this review, we describe the current understanding of the airway remodelling process and the mechanisms regulating its development. The impact of currently available asthma therapies on airway remodelling is also discussed.

Immunohistochemical determination of the expression of endothelin receptors in bronchial smooth muscle and epithelium of healthy horses and horses affected by summer pasture-associated obstructive pulmonary disease

OBJECTIVE

To immunohistochemically determine the expression of endothelin (ET) receptors in bronchial smooth muscle and epithelium of healthy horses and horses affected by summer pasture-associated obstructive pulmonary disease (SPAOPD).

SAMPLE POPULATION

Tissue specimens obtained from 8 healthy and 8 SPAOPD-affected horses.

PROCEDURE

Horses were examined and assigned to healthy and SPAOPD groups. Horses were then euthanatized, and tissue specimens containing bronchi of approximately 4 to 8 mm in diameter were immediately collected from all lung lobes, fixed in zinc-formalin solution for 12 hours, and embedded in paraffin. Polyclonal primary antibodies against ET-A or ET-B receptors at a dilution of 1:200 and biotinylated IgG secondary antibodies were applied to tissue sections, followed by the addition of an avidin-biotin immunoperoxidase complex. Photographs of the stained slides were digitally recorded and analyzed by use of image analysis software to determine the intensity of staining. Two-way ANOVA was used for statistical analysis.

RESULTS

The left diaphragmatic lung lobe of SPAOPD-affected horses had a significantly greater area of bronchial smooth muscle that immunostained for ET-A, compared with that for healthy horses. All lung lobes of SPAOPD-affected horses, except for the right diaphragmatic lobe, had significantly greater staining for ET-B receptors in bronchial smooth muscle, compared with results for healthy horses.

CONCLUSIONS AND CLINICAL RELEVANCE

This study revealed overexpression of ET-A and, in particular, ETB receptors in the bronchial smooth muscle of SPAOPD-affected horses, which suggested upregulation of these receptors. These findings improve our understanding of the role of ET-1 in the pathogenesis of SPAOPD.

Protective effects of tiotropium bromide in the progression of airway smooth muscle remodeling

RATIONALE

Recent findings have demonstrated that muscarinic M(3) receptor stimulation enhances airway smooth muscle proliferation to peptide growth factors in vitro. Because both peptide growth factor expression and acetylcholine release are known to be augmented in allergic airway inflammation, it is possible that anticholinergics protect against allergen-induced airway smooth muscle remodeling in vivo.

OBJECTIVE

We investigated the effects of treatment with the long-acting muscarinic receptor antagonist tiotropium on airway smooth muscle changes in a guinea pig model of ongoing allergic asthma.

RESULTS

Twelve weekly repeated allergen challenges induced an increase in airway smooth muscle mass in the noncartilaginous airways. This increase was not accompanied by alterations in cell size, indicating that the allergen-induced changes were entirely from increased airway smooth muscle cell number. Morphometric analysis showed no allergen-induced changes in airway smooth muscle area in the cartilaginous airways. However, repeated ovalbumin challenge enhanced maximal contraction of open tracheal ring preparations ex vivo. This was associated with an increase in smooth muscle-specific myosin expression in the lung. Treatment with inhaled tiotropium considerably inhibited the increase in airway smooth muscle mass, myosin expression, and contractility.

CONCLUSIONS

These results indicate a prominent role for acetylcholine in allergen-induced airway smooth muscle remodeling in vivo, a process that has been thus far considered to be primarily caused by growth factors and other mediators of inflammation. Therefore, muscarinic receptor antagonists, like the long-acting anticholinergic tiotropium bromide, could be beneficial in preventing chronic airway hyperresponsiveness and decline in lung function in allergic asthma.

Factors controlling airway smooth muscle proliferation in asthma

Airway smooth muscle proliferation has been the focus of considerable attention, as it is a quantitatively important component of the airway wall remodeling response in asthma and has been suggested as a suitable target for the development of novel anti-asthma agents. Such agents are considered likely to reduce airway hyperresponsiveness and, consequently, airway obstruction, resulting in fewer symptoms and exacerbations. Identifying suitable drug targets has proved an elusive goal, as no dominant molecular mechanism for remodeling has emerged. Moreover, recent findings raise some doubt as to whether smooth muscle proliferation per se is the explanation of the increase in smooth muscle cell number in asthma, with alternative explanations including the proposal that cells migrate either from the interstitial compartment or from a circulating precursor stem cell population. Therefore, drug targeting of migration responses should be considered as an alternative approach to regulating the smooth muscle component of airway wall remodeling.

Allergen exposure of mouse airways evokes remodeling of both bronchi and large pulmonary vessels

Remodeling of airway structures is a well-documented feature of allergic airway inflammation. To investigate whether bronchial remodeling is associated with remodeling of adjacent pulmonary vessels, sensitized mice were subjected to repeated ovalbumin inhalations, and bronchi and pulmonary vessels were subjected to histologic analysis. Allergen challenges induced peribronchial as well as perivascular eosinophilia. Remodeling of systemic airway microcirculation, as studied in tracheal whole-mount preparations, revealed an allergen-induced increase in both the diameter and length of the airway microvessels. Immunostaining for alpha-smooth muscle actin disclosed an increase in smooth muscle mass in both bronchi and large pulmonary vessels. Both bronchi and pulmonary vessels also displayed increased expression of procollagen I and procollagen III. Staining for proliferating cell nuclear antigen revealed increased proliferation of bronchial epithelial and smooth muscle cells as well as pulmonary vascular endothelial and smooth muscle cells. We conclude that central features of remodeling that take place in allergen-exposed airways are present also in the pulmonary vessels. The significance of this finding with respect to occurrence in disease, pathophysiologic importance, and involved mechanisms warrants further investigation.

Proliferative aspects of airway smooth muscle

Increased airway smooth muscle (ASM) mass is perhaps the most important component of the airway wall remodeling process in asthma. Known mediators of ASM proliferation in cell culture models fall into 2 categories: those that activate receptors with intrinsic receptor tyrosine kinase activity and those that have their effects through receptors linked to heterotrimeric guanosine triphosphate-binding proteins. The major candidate signaling pathways activated by ASM mitogens are those dependent on extracellular signal-regulated kinase and phosphoinositide 3'-kinase. Increases in ASM mass may also involve ASM migration, and in culture, the key signaling mechanisms have been identified as the p38 mitogen-activated protein kinase and the p21-activated kinase 1 pathways. New evidence from an in vivo rat model indicates that primed CD4(+) T cells are sufficient to trigger ASM and epithelial remodeling after allergen challenge. Hyperplasia has been observed in an equine model of asthma and may account for the increase in ASM mass. Reduction in the rate of apoptosis may also play a role. beta(2)-Adrenergic receptor agonists and glucocorticoids have antiproliferative activity against a broad spectrum of mitogens, although it has become apparent that mitogens are differentially sensitive. Culture of ASM on collagen type I has been shown to enhance proliferative activity and prevent the inhibitory effect of glucocorticoids, whereas beta(2)-agonists are minimally affected. There is no evidence that long-acting beta(2)-agonists are more effective than short-acting agonists, but persistent stimulation of the beta(2)-adrenergic receptor probably helps suppress growth responses. The maximum response of fluticasone propionate against thrombin-induced proliferation is increased when it is combined with salmeterol.