been recognized : contractile , synthetic and hyper- contractile phenotypes . Contractile cells , character- ized by a high density of contractile proteins includ- ing smoothmuscle α-actin and myosin heavy chains (MHC) and a few cytoskeletal proteins including non- muscle- MHC and vimentin, are mitotically quiescent and retain their ability to contract in response to spas- mogens. Synthetic cells , with a low density of con- tractile proteins and high fraction of cytoskeletal pro- teins, are mitotically active and may lose their ability to contract. 32 These cells may have additional func- tions such as production and release of pro- inflammatory mediators and extra-cellular matrix ele- ment described in later section . Hyper-contractile cells are obtained by prolonged withdrawal of serum from primary cultures of confluent canine tracheal smoothmuscle . 33 The content of smoothmuscle myosin light chain kinase in these cells are increased 30 fold, and they shorten faster and to a greater ex- tent. 33,34 Whether such phenotypic modulation hap- pens during remodeling of airwaysmoothmuscle in asthma has not been clarified yet. However, our pre- liminary data suggest possible existence of such phe- notypic modulation . Immuno-histochemical staining of airwaysmoothmuscle with antibodies for different MHC isoforms revealed that the expression of non- muscle (embryonic) type of MHC isoform is signifi- cantly enhanced in asthmatic airwaysmoothmuscle compared to control ( unpublished data ) . Woodruff and associates reported that there is a proliferation of smoothmuscle in asthmatic airways, but they could not observe the phenotypic modulation of smoothmuscle to hyper-contractile phenotype . 13 The exis- tence of such phenotypic modulation may make things more complicated, since the co-appearance of synthetic as well as hyper-contractile phenotypes may result the overall effect of increasing, decreasing, or causing no change in airwaysmoothmuscle contrac- tility despite an increase in airway wall smooth mus- cle content.
Acetylcholine is the primary parasympathetic neurotransmitter in the airways and is known to cause bronchoconstriction and mucus secretion. Recent findings suggest that acetylcholine also regulates aspects of remodeling and inflammation through its action on muscarinic receptors. In the present study, we aimed to determine effects of muscarinic receptor stimulation on cytokine production by human airwaysmoothmuscle cells (primary and immortalized cell lines). The muscarinic receptor agonists carbachol and methacholine both induced modest effects on basal IL-8 and IL-6 secretion, whereas the secretion of RANTES, eotaxin, VEGF-A and MCP-1 was not affected. Secretion of IL-8 and IL-6 was only observed in immortalized airwaysmoothmuscle cells that express muscarinic M 3 receptors. In these cells, methacholine also significantly augmented IL-8 secretion in combination with cigarette smoke extract in a synergistic manner, whereas synergistic effects on IL-6 secretion were not significant. Muscarinic M 3 receptors were the primary subtype involved in augmenting cigarette smoke extract-induced IL-8 secretion, as only tiotropium bromide and muscarinic M 3 receptor subtype selective antagonists abrogated the effects of methacholine. Collectively, these results indicate that muscarinic M 3 receptor
Exaggerated contraction of airwaysmoothmuscle is the major cause of symptoms in asthma, but the mecha- nisms that prevent exaggerated contraction are incompletely understood. Here, we showed that integrin α 9 β 1
on airwaysmoothmuscle localizes the polyamine catabolizing enzyme spermidine/spermine N 1 -acetyltrans- ferase (SSAT) in close proximity to the lipid kinase PIP5K1γ. As PIP5K1γ is the major source of PIP2 in airwaysmoothmuscle and its activity is regulated by higher-order polyamines, this interaction inhibited IP3-depen- dent airwaysmoothmuscle contraction. Mice lacking integrin α 9 β 1 in smoothmuscle had increased airway responsiveness in vivo, and loss or inhibition of integrin α 9 β 1 increased in vitro airway narrowing and airwaysmoothmuscle contraction in murine and human airways. Contraction was enhanced in control airways by the higher-order polyamine spermine or by cell-permeable PIP2, but these interventions had no effect on air- ways lacking integrin α 9 β 1 or treated with integrin α 9 β 1 –blocking antibodies. Enhancement of SSAT activity or knockdown of PIP5K1γ inhibited airway contraction, but only in the presence of functional integrin α 9 β 1 . Therefore, integrin α 9 β 1 appears to serve as a brake on airwaysmoothmuscle contraction by recruiting SSAT, which facilitates local catabolism of polyamines and thereby inhibits PIP5K1γ. Targeting key components of this pathway could thus lead to new treatment strategies for asthma.
The three A’s in asthma - airwaysmoothmuscle, airway remodeling angiogenesis
Keglowich, L F ; Borger, P
Abstract: Asthma affects more than 300 million people worldwide and its prevalence is still rising. Acute asthma attacks are characterized by severe symptoms such as breathlessness, wheezing, tightness of the chest, and coughing, which may lead to hospitalization or death. Besides the acute symptoms, asthma is characterized by persistent airway inflammation and airway wall remodeling. The term airway wall remodeling summarizes the structural changes in the airway wall: epithelial cell shedding, goblet cell hyperplasia, hyperplasia and hypertrophy of the airwaysmoothmuscle (ASM) bundles, basement mem- brane thickening and increased vascular density. Airway wall remodeling starts early in the pathogenesis of asthma and today it is suggested that remodeling is a prerequisite for other asthma pathologies. The beneficial effect of bronchial thermoplasty in reducing asthma symptoms, together with the increased potential of ASM cells of asthmatics to produce inflammatory and angiogenic factors, indicate that the ASM cell is a major effector cell in the pathology of asthma. In the present review we discuss the ASM cell and its role in airway wall remodeling and angiogenesis.
The straight-forward approach would be to use direct numerical simulation to describe these molecular interac- tions within an integrated cytoskeletal lattice and then go on to compute the macroscale integrative properties that result. Direct numerical simulation faces three daunting problems, however. The first is shear complexity; the number of cytoskeletal molecular species is counted in the scores. Moreover, integrated multi-molecular assemblies in airwaysmoothmuscle comprise a messy microstruc- tural geometry, one characterized by a degree of long range order that is far less than that observed in ordinary solids but far greater than that found in fluids. The second is that the list of species remains incomplete and the nature of most protein-protein interactions has yet to be characterized biophysically, with the acto-myosin interac- tion being the exception that proves the rule. And third, there is good evidence to suggest that in several regards these systems exist far away from local thermodynamic equilibrium (LTE); elemental components do not enjoy a fixed spatial address and, instead, are closely packed and continuously jostling one another in a never-ending search for a minimum energy configuration but never managing to find one. Accordingly, these configurations are adaptable, being in a continuous state of remodeling and, in the process, consuming energy on an ongoing basis via the hydrolysis of ATP. If the first two problems are not enough to saturate the most powerful present-day computers, the non-LTE nature of the problem is particu- larly thorny because it adds a crucial dimension to the biophysics at the same time that it invalidates a major class of computational approaches, namely, those based on principles of energy minimization.
as thermoplasty, are required. Thermoplasty is a newly licensed therapy for severe asthma that applies thermal energy to the airway wall via a bronchoscope. In early animal studies and in humans receiving thermoplasty prior to lung resection for cancer, ASM mass is re- duced, suggesting that the improved exacerbation fre- quency and health status following therapy in asthma may be in part due to a reduction in ASM mass . Importantly, to date this has not been confirmed in asthma. How the airway responds to this thermal injury might shed light not only upon the mechanism of ac- tion of this therapy, but also provide insights into air- way repair in response to injury. Such studies will help to determine the relationship between these structural changes and disordered airway function. As discussed, the role of mesenchymal stem and progenitor cells in airwaysmoothmuscle remodeling in asthma is ob- scure. There is a significant possibility that a degree of heterogeneity exists among these cells with some hav- ing immunomodulatory properties that ought to be promoted and others having pro-remodeling properties that ought to be suppressed, although this remains to be proven. In conclusion, the last few decades have ad- vanced greatly our understanding of the role of inflam- mation in asthma. The challenge for the next decade is to understand the mechanisms driving airway remodel- ing, particularly increased ASM mass and its clinical relevance, to inform the development of new therapies.
reveals a role for PYK2
Daniel P. Cook, … , Kin Fai Au, David A. Stoltz
JCI Insight. 2017;2(17):e95332. https://doi.org/10.1172/jci.insight.95332.
Abnormal airwaysmoothmuscle function can contribute to cystic fibrosis (CF) airway disease. We previously found that airwaysmoothmuscle from newborn CF pigs had increased basal tone, an increased bronchodilator response, and abnormal calcium handling. Since CF pigs lack airway infection and inflammation at birth, these findings suggest intrinsic airwaysmoothmuscle dysfunction in CF. In this study, we tested the hypothesis that CFTR loss in airwaysmoothmuscle would produce a distinct set of changes in the airwaysmoothmuscle transcriptome that we could use to develop novel therapeutic targets. Total RNA sequencing of newborn wild-type and CF airwaysmoothmuscle revealed changes in muscle contraction–related genes, ontologies, and pathways.
Pathways that control, or can be exploited to alter, the increase in airwaysmoothmuscle (ASM) mass and cellular remodeling that occur in asthma are not well defined. Here we report the expression of odorant receptors (ORs) belonging to the superfamily of G-protein coupled receptors (GPCRs), as well as the canonical olfaction machinery (G olf and AC3) in the smoothmuscle of human bronchi. In primary cultures of isolated human ASM, we identified mRNA expression for multiple ORs. Strikingly, OR51E2 was the most highly enriched OR transcript mapped to the human olfactome in lung-resident cells. In a heterologous expression system, OR51E2 trafficked readily to the cell surface and showed ligand selectivity and sensitivity to the short chain fatty acids (SCFAs) acetate and propionate. These endogenous metabolic byproducts of the gut microbiota slowed the rate of cytoskeletal remodeling, as well as the proliferation of human ASM cells. These cellular responses in vitro were found in ASM from non-asthmatics and asthmatics, and were absent in OR51E2-deleted primary human ASM. These results demonstrate a novel chemo-mechanical signaling network in the ASM and serve as a proof-of-concept that a specific receptor of the gut-lung axis can be targeted to treat airflow obstruction in asthma.
In summary, the current study provides the first evi- dence of the modulatory effects of human adipocytes on human airwaysmoothmuscle biology. We demonstrate that adipocytes per se do not have a plausible role to- wards modulating the ASM towards hyperplasia, hyper- trophy or hyperreactivity, but exhibits a potential to induce and maintain a low-grade inflammatory profile. It remains to be seen if this is likely to contribute to the tissue eosinophilic inflammation reported in obese pa- tients with asthma.
In the present study, there are several differences in the results from the cell-based cAMP assays and intact tissue organ bath studies with the dopamine D 1 receptor
agonist A68930. The first difference is that the relaxation evoked by isoproterenol and dopamine was rapid, while that evoked by A68930 was slow. These results suggest that the agonists’ interaction with the receptor can affect the speed of onset and duration of the induced relaxation. Vari- ations in the molecular structure of agonists can affect the onset and duration of bronchodilation. For example, iso- proterenol is a short-acting β agonist and has rapid onset, while the long-acting β 2 -adrenoceptor agonist salmeterol causes sustained relaxation in airwaysmoothmuscle of at least 12 hrs after a single administration , but the speed of onset is much slower than short-acting agonists such as isoproterenol . There are remarkable differences in mo- lecular structure between these agonists and these differ- ences affect the speed of onset and duration of their effects [45,46]. These findings suggest that, even though the ago- nists act on the same receptor, the molecular structure can affect the kinetics of the drug effect at the receptor. The second difference between cell-based and tissue-based re- sults with A68930 in the present study is the time required to reach significant relaxation in guinea pig airway rings was longer than the time required for significant stimula- tion of cAMP production in HASM cells. The dopamine D 1 agonists A68930 and A77636 contain an isochroman structure and are potent dopamine D 1 agonists which exert long-lasting effects compared with dopamine in vivo. For example, A68930 elicited prolonged contralateral turning behavior in 6-hydroxydopamine lesioned rats (>20 hrs) . In contrast, several reports showed that A68930 stim- ulated cAMP production within 15 - 20 min [37,48]. How- ever, it has not been determined whether the long-acting effects of A68930 rely exclusively on cAMP production.
This study addressed the hypothesis that rhinovirus (RV), the most common viral respiratory pathogen associated with acute asthma attacks, directly affects airwaysmoothmuscle (ASM) to produce proasthmatic changes in recep- tor-coupled ASM responsiveness. Isolated rabbit and hu- man ASM tissue and cultured ASM cells were inoculated with human RV (serotype 16) or adenovirus, each for 6 or 24 h. In contrast to adenovirus, which had no effect, inocula- tion of ASM tissue with RV induced heightened ASM tissue constrictor responsiveness to acetylcholine and attenuated the dose-dependent relaxation of ASM to b -adrenoceptor stimulation with isoproterenol. These RV-induced changes in ASM responsiveness were largely prevented by pretreating the tissues with pertussis toxin or with a monoclonal block- ing antibody to intercellular adhesion molecule-1 (ICAM-1), the principal endogenous receptor for most RVs. In ex- tended studies, we found that the RV-induced changes in ASM responsiveness were associated with diminished cAMP accumulation in response to dose-dependent administration of isoproterenol, and this effect was accompanied by autolo- gously upregulated expression of the G i protein subtype, G i a 3 , in the ASM. Finally, in separate experiments, we found that the RV-induced effects on ASM responsiveness were also accompanied by autologously induced upregu- lated mRNA and cell surface protein expression of ICAM-1.
In our study, we found a novel HuR/TGF-β1 feedback circuit that modulating airway remodeling in airwaysmoothmuscle cells and in asthmatic mouse firstly. In vitro, we detected that HuR and TGF-β1 demonstrated high expression in a time-dependent manner under the stimulation of PDGF, a strong stimulus for asthmatic re- sponse. Besides, α-SMA and Col-I simultaneously exhib- ited over-expression. Furthermore, knockdown of HuR led to an increase of ASM cells apoptosis and down-regulation of TGF-β1, α-SMA and Col-I. Moreover, the half-life of TGF-β1 was shorter compared with the control. However, interfering TGF-β1 with siRNA can obviously decrease HuR and Col-I expression. But exogenous TGF-β1 could recover HuR and Col-I expression. In vivo, OVA-induced mice showed widely infiltration of inflammatory cells sur- rounding the bronchioles in comparison with PBS-induced mice. Sirius red staining distinguished higher deposition of collagen type I and III around the bronchiole in OVA- induced mice then in PBS-induced mice. RT-PCR, western blotting and immunohistochemistry all showed higher levels of HuR, TGF-β1 and α-SMA in OVA -induced mice than PBS-induced mice. Thus we hypothesized that a HuR/TGF-β1 feedback is involved in airway remodeling and targeting them might have considerable potential for the control of asthma.
* Corresponding author
G protein-coupled receptorairway smooth muscleinflammationsynthetic functionairway remodeling
Signaling through G protein-coupled receptors (GPCRs) mediates numerous airwaysmoothmuscle (ASM) functions including contraction, growth, and "synthetic" functions that orchestrate airway inflammation and promote remodeling of airway architecture. In this review we provide a comprehensive overview of the GPCRs that have been identified in ASM cells, and discuss the extent to which signaling via these GPCRs has been characterized and linked to distinct ASM functions. In addition, we examine the role of GPCR signaling and its regulation in asthma and asthma treatment, and suggest an integrative model whereby an imbalance of GPCR-derived signals in ASM cells contributes to the asthmatic state.
Furong Yan 1 , Hongzhi Gao 1 , Hong Zhao 1 , Madhav Bhatia 2 and Yiming Zeng 3*
The airwaysmoothmuscle (ASM) plays an indispensable role in airway structure and function. Dysfunction in ASM plays a central role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and contributes to altera- tions of contractility, inflammatory response, immunoreaction, phenotype, quantity, and size of airways. ASM makes a key contribution in COPD by various mechanisms including altered contractility and relaxation induce by [Ca 2 + ] i , cell proliferation and hypertrophy, production and modulation of extracellular cytokines, and release of pro-and-anti- inflammatory mediators. Multiple dysfunctions of ASM contribute to modulating airway responses to stimuli, remod- eling, and fibrosis, as well as influence the compliance of lungs. The present review highlights regulatory roles of multiple factors in the development of ASM dysfunction in COPD, aims to understand the regulatory mechanism by which ASM dysfunctions are initiated, and explores the clinical significance of ASM on alterations of airway structure and function in COPD and development of novel therapeutic strategies for COPD.
Here we have discussed cell–matrix adhesion in the context of tidal breathing and airwaysmoothmuscle.
However, the models presented could be applicable to other contexts where dynamic environments occur.
Interesting examples include the adhesion dynamics that occur in response to large volume changes in the urinary bladder or in uterine smoothmuscle during pregnancy and childbirth. In both of these cases, it is thought that integrins play an important role in the adaptation of smoothmuscle to different lengths and functions (61, 62).
in relationship to other cellular functions such as chemo- taxis and proliferation. The mechanistic link between the CFTR channel and the contractile properties of airwaysmoothmuscle has not been established. However, Rob- ert et al have reported that CFTR channels are present in rat vascular smoothmuscle cells and that stimulation of the channels by specific CFTR agonists produces relaxa- tion of pre-contracted vascular tissue . Data from our laboratory show that CFTR channels are present and have functional effects on calcium signaling in ASM cells .
Conclusions: Together, these findings suggest that Plk1 is activated upon growth factor stimulation, which may control the activation of MEK1/2 and ERK1/2, and smoothmuscle cell proliferation.
Airwaysmoothmuscle cell proliferation contributes to the pathogenesis of airway remodeling, a key characteris- tic of chronic asthma . However, the mechanisms that regulate smoothmuscle cell proliferation are not fully understood.
Fay Hollins 1 † , Amanda Sutcliffe 1 † , Edith Gomez 1 , Rachid Berair 1 , Richard Russell 1 , Cédric Szyndralewiez 2 , Ruth Saunders 1 and Christopher Brightling 1*
The burden of oxidative stress is increased in chronic obstructive pulmonary disease (COPD). However, whether the intra-cellular mechanisms controlling the oxidant/anti-oxidant balance in structural airway cells such as airwaysmoothmuscle in COPD is altered is unclear. We sought to determine whether the expression of the NADPH oxidase (NOX)-4 is increased in airwaysmoothmuscle in COPD both in vivo and primary cells in vitro and its role in hydrogen peroxide-induced reactive oxygen species generation. We found that in vivo NOX4 expression was up-regulated in the airwaysmoothmuscle bundle in COPD ( n = 9) and healthy controls with >20 pack year history ( n = 4) compared to control subjects without a significant smoking history ( n = 6). In vitro NOX4 expression was increased in airwaysmoothmuscle cells from subjects with COPD ( n = 5) compared to asthma ( n = 7) and upregulated following TNF- α stimulation. Hydrogen peroxide-induced reactive oxygen species generation by airwaysmoothmuscle cells in COPD ( n = 5) was comparable to healthy controls ( n = 9) but lower than asthma ( n = 5); and was markedly attenuated by NOX4 inhibition. Our findings demonstrate that NOX4 expression is increased in vivo and in vitro in COPD and although we did not observe an intrinsic increase in oxidant-induced reactive oxygen species generation in COPD, it was reduced markedly by NOX4 inhibition supporting a potential therapeutic role for NOX4 in COPD.