The role of RhoA-mediated Ca2+ sensitization of bronchial smooth muscle contraction in airway hyperresponsiveness

β-Tocotrienol Decreases PDGF-BB-Induced Proliferation and Migration of Human Airway Smooth Muscle Cells by Inhibiting RhoA and Reducing ROS Production

BACKGROUND

Tocotrienols exhibit antioxidant and anti-inflammatory activities. RhoA, a small GTPase protein, plays a crucial role in regulating contractility in airway smooth muscle (ASM). Previous studies have demonstrated that γ-tocotrienols reduce ASM proliferation and migration by inhibiting the activation of RhoA. In this present study, we investigate the effect of another vitamin E isoform, β-tocotrienols, on human ASM cell proliferation and migration stimulated by platelet-derived growth factor-BB (PDGF-BB).

METHODS

Human ASM cells were pre-treated with β-tocotrienol prior to being stimulated with PDGF-BB to induce ASM cell proliferation and migration. The proliferation and migration of PDGF-BB-induced human ASM cells were assessed using colorimetric and transwell migration assays. The intracellular ROS assay kit was employed to quantify reactive oxygen species (ROS) in human ASM cells. Additionally, we explored the effect of β-tocotrienols on the signaling pathways involved in PDGF-BB-induced ASM proliferation and migration.

RESULTS

β-tocotrienol inhibited PDGF-BB-induced ASM cell proliferation and migration by reducing RhoA activation and ROS production. However, in this present study, β-tocotrienol did not affect the signaling pathways associated with cyclin D1, phosphorylated Akt1, and ERK1/2.

CONCLUSIONS

In conclusion, the inhibition of RhoA activation and ROS production by β-tocotrienol, resulting in the reduction in human ASM proliferation and migration, suggests its potential as a treatment for asthma airway remodeling.

The role of rhoA/rho-kinase and PKC in the inhibitory effect of L-cysteine/H2S pathway on the carbachol-mediated contraction of mouse bladder smooth muscle

We investigated the role of RhoA/Rho-kinase (ROCK) and PKC in the inhibitory effect of L-cysteine/hydrogen sulfide (H2S) pathway on the carbachol-mediated contraction of mouse bladder smooth muscle. Carbachol (10-8-10-4 M) induced a concentration-dependent contraction in bladder tissues. L-cysteine (H2S precursor; 10-2 M) and exogenous H2S (NaHS; 10-3 M) reduced the contractions evoked by carbachol by ~ 49 and ~ 53%, respectively, relative to control. The inhibitory effect of L-cysteine on contractions to carbachol was reversed by 10-2 M PAG (~ 40%) and 10-3 M AOAA (~ 55%), cystathionine-gamma-lyase (CSE) and cystathionine-β-synthase (CBS) inhibitor, respectively. Y-27632 (10-6 M) and GF 109203X (10-6 M), a specific ROCK and PKC inhibitor, respectively, reduced contractions evoked by carbachol (~ 18 and ~ 24% respectively), and the inhibitory effect of Y-27632 and GF 109203X on contractions was reversed by PAG (~ 29 and ~ 19%, respectively) but not by AOAA. Also, Y-27632 and GF 109203X reduced the inhibitory responses of L-cysteine on the carbachol-induced contractions (~ 38 and ~ 52% respectively), and PAG abolished the inhibitory effect of L-cysteine on the contractions in the presence of Y-27632 (~ 38%). Also, the protein expressions of CSE, CBS, and 3-MST enzymes responsible for endogenous H2S synthesis were detected by Western blot method. H2S level was increased by L-cysteine, Y-27632, and GF 109203X (from 0.12 ± 0.02 to 0.47 ± 0.13, 0.26 ± 0.03, and 0.23 ± 0.06 nmol/mg respectively), and this augmentation in H2S level decreased with PAG (0.17 ± 0.02, 0.15 ± 0.03, and 0.07 ± 0.04 nmol/mg respectively). Furthermore, L-cysteine and NaHS reduced carbachol-induced ROCK-1, pMYPT1, and pMLC20 levels. Inhibitory effects of L-cysteine on ROCK-1, pMYPT1, and pMLC20 levels, but not of NaHS, were reversed by PAG. These results suggest that there is an interaction between L-cysteine/H2S and RhoA/ROCK pathway via inhibition of ROCK-1, pMYPT1, and pMLC20, and the inhibition of RhoA/ROCK and/or PKC signal pathway may be mediated by the CSE-generated H2S in mouse bladder.

A lncRNA MALAT1 is a positive regulator of RhoA protein expression in bronchial smooth muscle cells

AIMS

Augmented smooth muscle contractility of the airways associated with an increased expression of RhoA, a monomeric GTPase responsible for Ca²⁺ sensitization of contraction, is one of the causes of airway hyperresponsiveness. However, the mechanism of the altered properties of airway smooth muscle cells, including the RhoA upregulation, is not fully understood. This study aims to define functional role of a long non-coding RNA MALAT1 in the RhoA expression and development of bronchial smooth muscle (BSM) hyper-contractility.

MAIN METHODS

Cultured human BSM cells were transfected with MALAT1 antisense oligonucleotide (AS), miR-133a-3p mimic, and/or inhibitor, and then stimulated with interleukin-13 (IL-13). In animal experiments, the ovalbumin (OA)-sensitized mice were repeatedly challenged with aerosolized OA to induce asthmatic reaction.

KEY FINDINGS

Treatment of the cells with IL-13 induced an increase in RhoA protein. Either MALAT1 AS or miR-133a-3p mimic transfection inhibited the IL-13-induced upregulation of RhoA. The inhibitory effect of MALAT1 AS was abolished by co-transfection with miR-133a-3p inhibitor. In BSMs of the murine asthma model, upregulations of Malat1 and RhoA protein were observed concomitantly with downregulation of miR-133a-3p.

SIGNIFICANCE

These findings suggest that MALAT1 positively regulates RhoA protein expression by inhibiting miR-133a-3p in BSM cells, and that its upregulation causes the RhoA upregulation, resulting in an augmented BSM contractility.

Therapeutic Approaches for Chronic Obstructive Pulmonary Disease (COPD) Exacerbations

Chronic Obstructive Pulmonary Disease (COPD) is a progressive pulmonary disorder underpinned by poorly reversible airflow resulting from chronic bronchitis or emphysema. The prevalence and mortality of COPD continue to increase. Pharmacotherapy for patients with COPD has included antibiotics, bronchodilators, and anti-inflammatory corticosteroids (but with little success). Oral diseases have long been established as clinical risk factors for developing respiratory diseases. The establishment of a very similar microbiome in the mouth and the lung confirms the oral-lung connection. The aspiration of pathogenic microbes from the oral cavity has been implicated in several respiratory diseases, including pneumonia and chronic obstructive pulmonary disease (COPD). This review focuses on current and future pharmacotherapeutic approaches for COPD exacerbation including antimicrobials, mucoregulators, the use of bronchodilators and anti-inflammatory drugs, modifying epigenetic marks, and modulating dysbiosis of the microbiome.

Airway smooth muscle function in asthma

Known to have affected around 340 million people across the world in 2018, asthma is a prevalent chronic inflammatory disease of the airways. The symptoms such as wheezing, dyspnea, chest tightness, and cough reflect episodes of reversible airway obstruction. Asthma is a heterogeneous disease that varies in clinical presentation, severity, and pathobiology, but consistently features airway hyperresponsiveness (AHR)—excessive airway narrowing due to an exaggerated response of the airways to various stimuli. Airway smooth muscle (ASM) is the major effector of exaggerated airway narrowing and AHR and many factors may contribute to its altered function in asthma. These include genetic predispositions, early life exposure to viruses, pollutants and allergens that lead to chronic exposure to inflammatory cells and mediators, altered innervation, airway structural cell remodeling, and airway mechanical stress. Early studies aiming to address the dysfunctional nature of ASM in the etiology and pathogenesis of asthma have been inconclusive due to the methodological limitations in assessing the intrapulmonary airways, the site of asthma. The study of the trachealis, although convenient, has been misleading as it has shown no alterations in asthma and it is not as exposed to inflammatory cells as intrapulmonary ASM. Furthermore, the cartilage rings offer protection against stress and strain of repeated contractions. More recent strategies that allow for the isolation of viable intrapulmonary ASM tissue reveal significant mechanical differences between asthmatic and non-asthmatic tissues. This review will thus summarize the latest techniques used to study ASM mechanics within its environment and in isolation, identify the potential causes of the discrepancy between the ASM of the extra- and intrapulmonary airways, and address future directions that may lead to an improved understanding of ASM hypercontractility in asthma.

Hypoxia-induced miR-182-5p regulates vascular smooth muscle cell phenotypic switch by targeting RGS5

In response to vascular injury or alterations in the local environment, such as hypoxia and hypertension, contractile vascular smooth muscle cells (VSMCs) are able to switch to a synthetic phenotype characterized by increased extracellular matrix synthesis with decreased expression of contractile markers. miR-182-5p has recently been reported to play a regulatory role in VSMCs proliferation. However, little is known about its target genes and related pathways in VSMCs phenotypic switch. Here, we investigated the function of miR-182-5p in VSMCs phenotypic switch. The results showed that upregulation of miR-182-5p promoted the switching of VSMCs from a contractile to a synthetic phenotype under hypoxic conditions. Mechanistically, hypoxia elevated miR-182-5p, leading to a reduction in expression of contractile markers and weakened RhoA signaling. Using bioinformatics analysis, dual-luciferase reporter assays and rescue assays, we demonstrated that miR-182-5p suppressed RhoA signaling by targeting RGS5. Collectively, the results from the present study indicated that miR-182-5p/RGS5/RhoA axis regulated hypoxia-induced VSMCs phenotypic switch.

Hyperresponsiveness to Extracellular Acidification-Mediated Contraction in Isolated Bronchial Smooth Muscles of Murine Experimental Asthma

PURPOSE

Extracellular acidification is a major component of tissue inflammation, including airway inflammation. The extracellular proton-sensing mechanisms are inherent in various cells including airway structural cells, although their physiological and pathophysiological roles in bronchial smooth muscles (BSMs) are not fully understood. In the present study, to explore the functional role of extracellular acidification on the BSM contraction, the isolated mouse BSMs were exposed to acidic pH under contractile stimulation.

METHODS AND RESULTS

The RT-PCR analyses revealed that the proton-sensing G protein-coupled receptors were expressed both in mouse BSMs and cultured human BSM cells. In the mouse BSMs, change in the extracellular pH from 8.0 to 6.8 caused an augmentation of contraction induced by acetylcholine. Interestingly, the acidic pH-induced BSM hyper-contraction was further augmented in the mice that were sensitized and repeatedly challenged with ovalbumin antigen. In this animal model of asthma, upregulations of G protein-coupled receptor 68 (GPR68) and GPR65, that were believed to be coupled with Gq and Gs proteins respectively, were observed, indicating that the acidic pH could cause hyper-contraction probably via an activation of GPR68. However, psychosine, a putative antagonist for GPR68, failed to block the acidic pH-induced responses.

CONCLUSION

These findings suggest that extracellular acidification contributes to the airway hyperresponsiveness, a characteristic feature of bronchial asthma. Further studies are required to identify the receptor(s) responsible for sensing extracellular protons in BSM cells.

Roles for α1-adrenoceptors during contractions by electrical field stimulation in mouse vas deferens

We have investigated the relative roles of α₁-adrenoceptors and purinoceptors in contractions to low and high frequency stimulation of the mouse vas deferens, in terms of the time course of responses. In separate experiments, isometric contractile responses were obtained to 10 pulses at 1 Hz and 40 pulses at 10 Hz. Responses to 1 Hz stimulation consisted of a series of discrete peaks. The α_1A-adrenoceptor antagonist RS100329 (10^–9M–10^–7M) significantly reduced the response to the first pulse, the α_1D-adrenoceptor antagonist BMY7378 (10^–7M–10^–6M) significantly reduced the response to the first two pulses, and the non-selective α₁-adrenoceptor antagonist prazosin (10^–8M) reduced the response to the first 4 pulses at 1 Hz. Responses to 10 Hz stimulation consisted of an early peak response and a maintained plateau response. RS100329 significantly reduced the peak response but did not significantly affect the plateau response. Prazosin, significantly reduced both the peak and plateau responses. The α_1A-adrenoceptor antagonist RS17053 in high concentrations reduced mainly the plateau response leaving a clear early peak response. The plateau response of contraction was almost abolished by the purinoceptor antagonist suramin. These results suggest that there is a relatively minor early α_1D-adrenoceptor and a larger early α_1A-adrenoceptor component to stimulation-evoked contractions of mouse vas deferens, but the major α₁-adrenoceptor component is revealed by prazosin to be α_1B-adrenoceptor mediated. α_1B-Adrenoceptor activation probably facilitates contractions mediated by other α₁-adrenoceptors and by purinoceptors. These results suggest that combined non-selective α₁-adrenoceptor blockade, particularly α_1B-adrenoceptor blockade, in addition to P2X1-purinoceptor blockade is useful in reducing male fertility.

Role of miR-185-5p as modulator of periostin synthesis and smooth muscle contraction in asthma

Asthma is a chronic respiratory disease produced by an aberrant immune response that originates with breathing difficulties and cough, through airway remodeling. The above pathophysiological events of asthma emerge the regulators of effectors, like epigenetics, which include microRNAs (miRNAs) who perform post‐transcriptional regulation, controlling diverse pathways in respiratory diseases. The objective of the study was to determine how miR‐185‐5p regulates the secretion of periostin by airway structural cells, and smooth muscle cells contraction, both related to airway remodeling in asthma. We used miR‐185‐5p mimic and inhibitors in bronchial smooth muscle cells (BSMCs) and small airway epithelial cells (SAECs) from healthy subjects. Gene expression and protein levels of periostin (POSTN), CDC42, and RHOA were analyzed by RT‐PCR and ELISA/Western blot, respectively. BSMC contractility was analyzed using cell‐embedded collagen gels and measurement of intracellular calcium was performed using Fura‐2. Additionally, miR‐185‐5p and periostin expression were evaluated in sputum from healthy and asthmatics. From these experiments, we observed that miR‐185‐5p modulation regulates periostin mRNA and protein in BSMCs and SAECs. A tendency for diminished miR‐185‐5p expression and higher periostin levels was seen in sputum cells from asthmatics compared to healthy, with an inverse correlation observed between POSTN and miR‐185‐5p. Inhibition of miR‐185‐5p produced higher BSMCs contraction induced by histamine. Calcium mobilization was not modified by miR‐185‐5p, showing that miR‐185‐5p role in BSMC contractility is performed by regulating CDC42 and RhoA pro‐contractile factors instead. In conclusion, miR‐185‐5p is a modulator of periostin secretion by airway structural cells and of smooth muscle contraction, which can be related to asthma pathophysiology, and thus, might be a promising therapeutic target.

Type II alveolar epithelial cell-specific loss of RhoA exacerbates allergic airway inflammation through SLC26A4

The small GTPase RhoA and its downstream effectors are critical regulators in the pathophysiological processes of asthma. The underlying mechanism, however, remains undetermined. Here, we generated an asthma mouse model with RhoA–conditional KO mice (Sftpc-cre;RhoA^fl/fl) in type II alveolar epithelial cells (AT2) and demonstrated that AT2 cell–specific deletion of RhoA leads to exacerbation of allergen-induced airway hyperresponsiveness and airway inflammation with elevated Th2 cytokines in bronchoalveolar lavage fluid (BALF). Notably, Sftpc-cre;RhoA^fl/fl mice showed a significant reduction in Tgf-β1 levels in BALF and lung tissues, and administration of recombinant Tgf-β1 to the mice rescued Tgf-β1 and alleviated the increased allergic airway inflammation observed in Sftpc-cre;RhoA^fl/fl mice. Using RNA sequencing technology, we identified Slc26a4 (pendrin), a transmembrane anion exchange, as the most upregulated gene in RhoA-deficient AT2 cells. The upregulation of SLC26A4 was further confirmed in AT2 cells of asthmatic patients and mouse models and in human airway epithelial cells expressing dominant-negative RHOA (RHOA-N19). SLA26A4 was also elevated in serum from asthmatic patients and negatively associated with the percentage of forced expiratory volume in 1 second (FEV₁%). Furthermore, SLC26A4 inhibition promoted epithelial TGF-β1 release and attenuated allergic airway inflammation. Our study reveals a RhoA/SLC26A4 axis in AT2 cells that functions as a protective mechanism against allergic airway inflammation.

Involvement of G proteins and Rho kinase in α1-adrenoceptor mediated contractions of the rat portal vein

Contractions of the rat portal vein in response to the α1-adrenoceptor agonist phenylephrine consist of phasic contractions at low concentrations, with tonic contractions superimposed at higher concentrations. The α1D-adrenoceptor antagonist BMY7378 (7.0, -log M) did not affect phasic or tonic contractions to phenylephrine. The relatively nonselective α1-adrenoceptor antagonist prazosin (7.5) shifted equally the potencies of phenylephrine at producing phasic and tonic contractions, with pKB values of 8.85 and 8.83 (-log M), respectively. The α1A-adrenoceptor antagonist RS100329 (8.5) produced a significantly greater shift in phenylephrine potency for phasic (pKB of 10.51) than tonic contractions (pKB of 9.78). Prazosin was less effective than RS100329 at reducing the effects of phenylephrine on frequency of phasic contractions. The Rho kinase inhibitor fasudil (5.0) did not affect phasic contractions to phenylephrine, but significantly reduced tonic contractions. It is concluded that there is no evidence for involvement of α1D-adrenoceptors in responses of the rat portal vein to phenylephrine, but phasic responses involve predominantly α1A-adrenoceptors. Tonic responses may involve predominantly α1B-adrenoceptors and are at least partly mediated by mechanisms involving Rho kinase sensitive to fasudil.

Neurotrophin Regulation and Signaling in Airway Smooth Muscle

Structural and functional aspects of bronchial airways are key throughout life and play critical roles in diseases such as asthma. Asthma involves functional changes such as airway irritability and hyperreactivity, as well as structural changes such as enhanced cellular proliferation of airway smooth muscle (ASM), epithelium, and fibroblasts, and altered extracellular matrix (ECM) and fibrosis, all modulated by factors such as inflammation. There is now increasing recognition that disease maintenance following initial triggers involves a prominent role for resident nonimmune airway cells that secrete growth factors with pleiotropic autocrine and paracrine effects. The family of neurotrophins may be particularly relevant in this regard. Long recognized in the nervous system, classical neurotrophins such as brain-derived neurotrophic factor (BDNF) and nonclassical ligands such as glial-derived neurotrophic factor (GDNF) are now known to be expressed and functional in non-neuronal systems including lung. However, the sources, targets, regulation, and downstream effects are still under investigation. In this chapter, we discuss current state of knowledge and future directions regarding BDNF and GDNF in airway physiology and on pathophysiological contributions in asthma.

Pharmacology and Therapeutics of Bronchodilators Revisited

Bronchodilators remain the cornerstone of the treatment of airway disorders such as asthma and chronic obstructive pulmonary disease (COPD). There is therefore considerable interest in understanding how to optimize the use of our existing classes of bronchodilator and in identifying novel classes of bronchodilator drugs. However, new classes of bronchodilator have proved challenging to develop because many of these have no better efficacy than existing classes of bronchodilator and often have unacceptable safety profiles. Recent research has shown that optimization of bronchodilation occurs when both arms of the autonomic nervous system are affected through antagonism of muscarinic receptors to reduce the influence of parasympathetic innervation of the lung and through stimulation of β ₂-adrenoceptors (β ₂-ARs) on airway smooth muscle with β ₂-AR-selective agonists to mimic the sympathetic influence on the lung. This is currently achieved by use of fixed-dose combinations of inhaled long-acting β ₂-adrenoceptor agonists (LABAs) and long-acting muscarinic acetylcholine receptor antagonists (LAMAs). Due to the distinct mechanisms of action of LAMAs and LABAs, the additive/synergistic effects of using these drug classes together has been extensively investigated. More recently, so-called "triple inhalers" containing fixed-dose combinations of both classes of bronchodilator (dual bronchodilation) and an inhaled corticosteroid in the same inhaler have been developed. Furthermore, a number of so-called "bifunctional drugs" having two different primary pharmacological actions in the same molecule are under development. This review discusses recent advancements in knowledge on bronchodilators and bifunctional drugs for the treatment of asthma and COPD. SIGNIFICANCE STATEMENT: Since our last review in 2012, there has been considerable research to identify novel classes of bronchodilator drugs, to further understand how to optimize the use of the existing classes of bronchodilator, and to better understand the role of bifunctional drugs in the treatment of asthma and chronic obstructive pulmonary disease.

RhoA/Rho-kinases in asthma: from pathogenesis to therapeutic targets

Asthma is a chronic and heterogeneous disease characterised by airway inflammation and intermittent airway narrowing. The key obstacle in the prevention and treatment of asthma has been our incomplete understanding of its aetiology and biological mechanisms. The ras homolog family member A (RhoA) of the Rho family GTPases has been considered to be one of the most promising and novel therapeutic targets for asthma. It is well known that RhoA/Rho‐kinases play an important role in the pathophysiology of asthma, including airway smooth muscle contraction, airway hyper‐responsiveness, β‐adrenergic desensitisation and airway remodelling. However, recent advances have suggested novel roles for RhoA in regulating allergic airway inflammation. Specifically, RhoA has been shown to regulate allergic airway inflammation through controlling Th2 or Th17 cell differentiation and to regulate airway remodelling through regulating mesenchymal stem cell (MSC) differentiation. In this review, we evaluate the literature regarding the recent advances in the activation of RhoA/Rho‐kinase, cytokine and epigenetic regulation of RhoA/Rho‐kinase, and the role of RhoA/Rho‐kinase in regulating major features of asthma, such as airway hyper‐responsiveness, remodelling and inflammation. We also discuss the importance of the newly identified role of RhoA/Rho‐kinase signalling in MSC differentiation and bronchial epithelial barrier dysfunction. These findings indicate the functional significance of the RhoA/Rho‐kinase pathway in the pathophysiology of asthma and suggest that RhoA/Rho‐kinase signalling may be a promising therapeutic target for the treatment of asthma.

The future of bronchodilation: looking for new classes of bronchodilators

Available bronchodilators can satisfy many of the needs of patients suffering from airway disorders, but they often do not relieve symptoms and their long-term use raises safety concerns. Therefore, there is interest in developing new classes that could help to overcome the limits that characterise the existing classes.At least nine potential new classes of bronchodilators have been identified: 1) selective phosphodiesterase inhibitors; 2) bitter-taste receptor agonists; 3) E-prostanoid receptor 4 agonists; 4) Rho kinase inhibitors; 5) calcilytics; 6) agonists of peroxisome proliferator-activated receptor-γ; 7) agonists of relaxin receptor 1; 8) soluble guanylyl cyclase activators; and 9) pepducins. They are under consideration, but they are mostly in a preclinical phase and, consequently, we still do not know which classes will actually be developed for clinical use and whether it will be proven that a possible clinical benefit outweighs the impact of any adverse effect.It is likely that if developed, these new classes may be a useful addition to, rather than a substitution of, the bronchodilator therapy currently used, in order to achieve further optimisation of bronchodilation.

Regulation of IL-17A and implications for TGF-β1 comodulation of airway smooth muscle remodeling in severe asthma

Severe asthma develops as a result of heightened, persistent symptoms that generally coincide with pronounced neutrophilic airway inflammation. In individuals with severe asthma, symptoms are poorly controlled by high-dose inhaled glucocorticoids and often lead to elevated morbidity and mortality rates that underscore the necessity for novel drug target identification that overcomes limitations in disease management. Many incidences of severe asthma are mechanistically associated with T helper 17 (T_H17) cell-derived cytokines and immune factors that mediate neutrophilic influx to the airways. T_H17-secreted interleukin-17A (IL-17A) is an independent risk factor for severe asthma that impacts airway smooth muscle (ASM) remodeling. T_H17-derived cytokines and diverse immune mediators further interact with structural cells of the airway to induce pathophysiological processes that impact ASM functionality. Transforming growth factor-β1 (TGF-β1) is a pivotal mediator involved in airway remodeling that correlates with enhanced T_H17 activity in individuals with severe asthma and is essential to T_H17 differentiation and IL-17A production. IL-17A can also reciprocally enhance activation of TGF-β1 signaling pathways, whereas combined T_H1/T_H17 or T_H2/T_H17 immune responses may additively impact asthma severity. This review seeks to provide a comprehensive summary of cytokine-driven T cell fate determination and T_H17-mediated airway inflammation. It will further review the evidence demonstrating the extent to which IL-17A interacts with various immune factors, specifically TGF-β1, to contribute to ASM remodeling and altered function in T_H17-driven endotypes of severe asthma.

Augmented Pla2g4c/Ptgs2/Hpgds axis in bronchial smooth muscle tissues of experimental asthma

Rationale

Augmented smooth muscle contractility of the airways is one of the causes of airway hyperresponsiveness in asthmatics. However, the mechanism of the altered properties of airway smooth muscle cells is not well understood.

Objectives

To identify differentially expressed genes (DEGs) related to the bronchial smooth muscle (BSM) hyper-contractility in a murine asthma model.

Methods

The ovalbumin (OA)-sensitized mice were repeatedly challenged with aerosolized OA to induce asthmatic reaction. Transcriptomic profiles were generated by microarray analysis of BSM tissues from the OA-challenged and control animals, and KEGG (Kyoto Encyclopedia of Genes and Genomes) Pathway Analysis was applied.

Measurements and main results

Tension study showed a BSM hyperresponsiveness to acetylcholine (ACh) in the OA-challenged mice. A total of 770 genes were differentially expressed between the OA-challenged and control animals. Pathway analysis showed a significant change in arachidonic acid (AA) metabolism pathway in BSM tissues of the OA-challenged mice. Validation of DEGs by quantitative RT-PCR showed a significant increase in PLA₂ group 4c (Pla2g4c)/COX-2 (Ptgs2)/PGD₂ synthase 2 (Hpgds) axis. PGD₂ level in bronchoalveolar fluids of the OA-challenged mice was significantly increased. A 24-h incubation of BSM tissues with PGD₂ caused a hyperresponsiveness to ACh in naive control mice.

Conclusions

AA metabolism is shifted towards PGD₂ production in BSM tissues of asthma. Increased PGD₂ level in the airways might be a cause of the BSM hyperresponsiveness in asthma.

Effects of Hyperoxia on the Developing Airway and Pulmonary Vasculature

Although it is necessary and part of standard practice, supplemental oxygen (40-90% O₂) or hyperoxia is a significant contributing factor to development of bronchopulmonary dysplasia, persistent pulmonary hypertension, recurrent wheezing, and asthma in preterm infants. This chapter discusses hyperoxia and the role of redox signaling in the context of neonatal lung growth and disease. Here, we discuss how hyperoxia promotes dysfunction in the airway and the known redox-mediated mechanisms that are important for postnatal vascular and alveolar development. Whether in the airway or alveoli, redox pathways are important and greatly influence the neonatal lung.

Gα12 facilitates shortening in human airway smooth muscle by modulating phosphoinositide 3-kinase-mediated activation in a RhoA-dependent manner

BACKGROUND AND PURPOSE

PI3K-dependent activation of Rho kinase (ROCK) is necessary for agonist-induced human airway smooth muscle cell (HASMC) contraction, and inhibition of PI3K promotes bronchodilation of human small airways. The mechanisms driving agonist-mediated PI3K/ROCK axis activation, however, remain unclear. Given that G12 family proteins activate ROCK pathways in other cell types, their role in M3 muscarinic acetylcholine receptor-stimulated PI3K/ROCK activation and contraction was examined.

EXPERIMENTAL APPROACH

Gα12 coupling was evaluated using co-immunoprecipitation and serum response element (SRE)-luciferase reporter assays. siRNA and pharmacological approaches, as well as overexpression of a regulator of G-protein signaling (RGS) proteins were applied in HASMCs. Phosphorylation levels of Akt, myosin phosphatase targeting subunit-1 (MYPT1), and myosin light chain-20 (MLC) were measured. Contraction and shortening were evaluated using magnetic twisting cytometry (MTC) and micro-pattern deformation, respectively. Human precision-cut lung slices (hPCLS) were utilized to evaluate bronchoconstriction.

KEY RESULTS

Knockdown of M3 receptors or Gα12 attenuated activation of Akt, MYPT1, and MLC phosphorylation. Gα12 coimmunoprecipitated with M3 receptors, and p115RhoGEF-RGS overexpression inhibited carbachol-mediated induction of SRE-luciferase reporter. p115RhoGEF-RGS overexpression inhibited carbachol-induced activation of Akt, HASMC contraction, and shortening. Moreover, inhibition of RhoA blunted activation of PI3K. Lastly, RhoA inhibitors induced dilation of hPCLS.

CONCLUSIONS AND IMPLICATIONS

Gα12 plays a crucial role in HASMC contraction via RhoA-dependent activation of the PI3K/ROCK axis. Inhibition of RhoA activation induces bronchodilation in hPCLS, and targeting Gα12 signaling may elucidate novel therapeutic targets in asthma. These findings provide alternative approaches to the clinical management of airway obstruction in asthma.

Role of ROCK2 in CD4+ cells in allergic airways responses in mice

BACKGROUND

Rho kinases (ROCKs) contribute to allergic airways disease. ROCKs also play a role in lymphocyte proliferation and migration.

OBJECTIVE

To determine the role of ROCK2 acting within CD4+ cells in allergic airways responses.

METHODS

ROCK2-haploinsufficient (ROCK2+/- ) and wild-type mice were sensitized with ovalbumin (OVA). ROCK2+/- mice then received either CD4+ cells from ROCK2-sufficient OVA TCR transgenic (OT-II) mice or saline i.v. 48 h before challenge with aerosolized OVA. Wild-type mice received saline before challenge. Allergic airways responses were measured 48 h after the last challenge. Allergic airways responses were also assessed in mice lacking ROCK2 only in CD4+ cells (ROCK2CD4Cre mice) vs. control (CD4-Cre and ROCK2flox/flox ) mice.

RESULTS

OVA-induced increases in bronchoalveolar lavage lymphocytes, eosinophils, IL-13, IL-5, and eotaxin were reduced in ROCK2+/- vs. wild-type mice, as were airway hyperresponsiveness and mucous hypersecretion. In ROCK2+/- mice, adoptive transfer with CD4+ cells from OT-II mice restored effects of OVA on lymphocytes, eosinophils, IL-13, IL-5, and mucous hypersecretion to wild-type levels, whereas eotaxin and airway hyperresponsiveness were not affected. ROCK2 inhibitors reduced IL-13-induced release of eotaxin from airway smooth muscle (ASM), similar to effects of these inhibitors on ASM contractility. Despite the ability of adoptive transfer to restore allergic airways inflammation in ROCK2-insufficient mice, allergic inflammation was not different in ROCK2CD4Cre vs. control mice.

CONCLUSION

ROCK2 contributes to allergic airways responses likely via effects within ASM cells and within non-lymphocyte cells involved in lymphocyte activation and migration into the airways.

A Hospital Based Study to Establish the Correlation between Recurrent Wheeze and Vitamin D Deficiency Among Children of Age Group Less than 3 Years in Indian Scenario

INTRODUCTION

Early childhood wheezing is a heterogeneous condition, which has several phenotypic expressions and a complex relationship with the development of asthma later in life. New studies indicate the prevalence of recurrent wheeze to be associated with Vitamin D deficiency. This has not been explored in Indian settings widely, mandating this exploration.

AIM

To determine the severity of Vitamin D deficiency and its association with recurrent wheeze in children less than 3 years of age.

MATERIALS AND METHODS

Consecutive type of non-probability sampling was followed for selection of study subjects with a total sample size to be 122 children in the Hospital setting. A pre- formed, pre- tested, structured interview schedule was used to obtain information. Estimation of 25 (OH) Vitamin D was done using ELISA method. Kit used for estimation was DLD Diagnostika GMBH 25(OH) Vitamin D ELISA from Germany. Standard statistical tools were used including Logistic regression analysis, and ROC curve, p value <0.05 was considered to be statistically significant. SPSS software version 17.0 was used.

RESULTS

Each 10ng/ml decrease in Vitamin D level is associated with 7.25% greater odds of wheezing. Our study also suggests, exclusive breast feeding and delaying of complementary feeding beyond 6 months of age are significant predictors of Vitamin D deficiency and have indirect association with increased incidence of wheezing in children.

CONCLUSION

The study concluded that Vitamin D deficiency is associated with increased risk of recurrent wheezing.

Effects of ethanol on RhoA/Rho-kinase-mediated calcium sensitization in mouse lung parenchymal tissue

Calcium sensitization by the RhoA/Rho-kinase (ROCK) pathway contributes to the contraction in smooth muscle. Contractile stimuli can sensitize myosin to Ca(2+) by activating RhoA/Rho-kinase that inhibits myosin light chain phosphatase activity. The present study was aimed at investigating the possible involvement of RhoA/Rho-kinase pathway in contractile responses to agonist (phenylephrine) and depolarizing (KCl) of mouse lung parenchymal tissues. Also, we investigated the effect of ethanol on RhoA/Rho-kinase pathway. Phenylephrine (10(-8)-10(-4) M) and KCl (10-80 mM) induced sustained contractions in parenchymal strips. Ethanol significantly attenuated the contractions to phenylephrine and KCl. The Rho-kinase inhibitors fasudil (5×10(-5) M) and Y-27632 (5×10(-5) M) inhibited contractions to in both control and ethanol-treated parenchymal strips. In addition, the relaxations induced by fasudil (10(-4) M) and Y-27632 (5×10(-4) M) on parenchymal strips contracted by phenylephrine but not KCl was decreased in ethanol-treatment group. Also, RhoA, ROCK1 and ROCK2 expressions were detected in mouse lung parenchymal tissue. In ethanol-treated group, expression of RhoA and ROCK1 but not ROCK2 decreased compared to control. Furthermore, ethanol causes apoptotic changes in alveolar type I epithelial cells of parenchymal tissue. These results suggest that RhoA/Rho-kinase signaling pathway plays an important role in phenylephrine- and KCl-induced Ca(2)(+) sensitization in mouse lung parenchymal tissue. Also, ethanol may be decrease phenylephrine- and KCl-induced contraction due to lowering the RhoA/Rho-kinase-mediated Ca(2+)-sensitizing by inhibiting RhoA/Rho-kinase pathway in parenchymal tissue. These results may be lead to important insights into the mechanisms of lung diseases due to alcohol consumption.

cAMP-mediated secretion of brain-derived neurotrophic factor in developing airway smooth muscle

Moderate hyperoxic exposure in preterm infants contributes to subsequent airway dysfunction and to risk of developing recurrent wheeze and asthma. The regulatory mechanisms that can contribute to hyperoxia-induced airway dysfunction are still under investigation. Recent studies in mice show that hyperoxia increases brain-derived neurotrophic factor (BDNF), a growth factor that increases airway smooth muscle (ASM) proliferation and contractility. We assessed the mechanisms underlying effects of moderate hyperoxia (50% O2) on BDNF expression and secretion in developing human ASM. Hyperoxia increased BDNF secretion, but did not alter endogenous BDNF mRNA or intracellular protein levels. Exposure to hyperoxia significantly increased [Ca2+]i responses to histamine, an effect blunted by the BDNF chelator TrkB-Fc. Hyperoxia also increased ASM cAMP levels, associated with reduced PDE4 activity, but did not alter protein kinase A (PKA) activity or adenylyl cyclase mRNA levels. However, 50% O2 increased expression of Epac2, which is activated by cAMP and can regulate protein secretion. Silencing RNA studies indicated that Epac2, but not Epac1, is important for hyperoxia-induced BDNF secretion, while PKA inhibition did not influence BDNF secretion. In turn, BDNF had autocrine effects of enhancing ASM cAMP levels, an effect inhibited by TrkB and BDNF siRNAs. Together, these novel studies suggest that hyperoxia can modulate BDNF secretion, via cAMP-mediated Epac2 activation in ASM, resulting in a positive feedback effect of BDNF-mediated elevation in cAMP levels. The potential functional role of this pathway is to sustain BDNF secretion following hyperoxic stimulus, leading to enhanced ASM contractility and proliferation.

Blebbistatin, a myosin II inhibitor, suppresses Ca(2+)-induced and "sensitized"-contraction of skinned tracheal muscles from guinea pig

Blebbistatin, a potent inhibitor of myosin II, has inhibiting effects on Ca(2+)-induced contraction and contractile filament organization without affecting the Ca(2+)-sensitivity to the force and phosphorylation level of myosin regulatory light chain (MLC20) in skinned (cell membrane permeabilized) taenia cecum from the guinea pig (Watanabe et al., Am J Physiol Cell Physiol. 2010; 298: C1118-26). In the present study, we investigated blebbistatin effects on the contractile force of skinned tracheal muscle, in which myosin filaments organization is more labile than that in the taenia cecum. Blebbistatin at 10 μM or higher suppressed Ca(2+)-induced tension development at any given Ca(2+) concentration, but had little effects on the Ca(2+)- induced myosin light chain phosphorylation. Also blebbistatin at 10 μM and higher significantly suppressed GTP-γS-induced "sensitized" force development. Since the force inhibiting effects of blebbistatin on the skinned trachea were much stronger than those in skinned taenia cecum, blebbistatin might directly affect myosin filaments organization.

Brain-derived neurotrophic factor in the airways

In addition to their well-known roles in the nervous system, there is increasing recognition that neurotrophins such as brain derived neurotrophic factor (BDNF) as well as their receptors are expressed in peripheral tissues including the lung, and can thus potentially contribute to both normal physiology and pathophysiology of several diseases. The relevance of this family of growth factors lies in emerging clinical data indicating altered neurotrophin levels and function in a range of diseases including neonatal and adult asthma, sinusitis, influenza, and lung cancer. The current review focuses on 1) the importance of BDNF expression and signaling mechanisms in early airway and lung development, critical to both normal neonatal lung function and also its disruption in prematurity and insults such as inflammation and infection; 2) how BDNF, potentially derived from airway nerves modulate neurogenic control of airway tone, a key aspect of airway reflexes as well as dysfunctional responses to allergic inflammation; 3) the emerging idea that local BDNF production by resident airway cells such as epithelium and airway smooth muscle can contribute to normal airway structure and function, and to airway hyperreactivity and remodeling in diseases such as asthma. Furthermore, given its pleiotropic effects in the airway, BDNF may be a novel and appealing therapeutic target.

ROCK1 translocates from non-caveolar to caveolar regions upon KCl stimulation in airway smooth muscle

Airway smooth muscle (ASM) membrane depolarization through KCl opens L-type voltage dependent Ca2+ channels (Ca(v)1.2); its opening was considered the cause of KCl contraction. This substance is used to bypass intracellular second messenger pathways. It is now clear that KCl also activates RhoA/Rho kinase (ROCK) pathway. ROCK isoforms are characterized as ROCK1 and ROCK2. Because ROCK1 seems the most abundant isotype in lung, we studied its participation in KCl stimulated bovine ASM. With methyl-beta-cyclodextrin (MbetaCD) we disrupted caveolae, a membrane compartment considered as the RhoA/ROCK assembly site, and found that KCl contraction was reduced to the same extent (~26%) as Y-27632 (ROCK inhibitor) treated tissues. We confirmed that KCl induces ROCK activation and this effect was annulled by Y-27632 or MbetaCD. In isolated plasmalemma, ROCK1 was localized in non-caveolar membrane fractions in Western blots from control tissues, but it transferred to caveolae in samples from tissues stimulated with KCl. Ca(v)1.2 was found at the non-caveolar membrane fractions in control and MbetaCD treated tissues. In MbetaCD treated tissues stimulated with KCl, contraction was abolished by nifedipine; only the response to Ca(v)1.2 opening remained as the ROCK component disappeared. Our results show that, in ASM, the KCl contraction involves the translocation of ROCK1 from non-caveolar to caveolar regions and that the proper physiological response depends on this translocation.

Abnormal tracheal smooth muscle function in the CF mouse

Increased airway smooth muscle (ASM) contractility is thought to underlie symptoms of airway hyperresponsiveness (AHR). In the cystic fibrosis (CF) airway, ASM anomalies have been reported, but have not been fully characterized and the underlying mechanisms are largely unknown. We examined ASM in an adult CF mouse tracheal ring preparation, and determined whether changes in contractility were associated with altered ASM morphology. We looked for inherent changes in the cellular pathways involved in contractility, and characterized trachea morphology in the adult trachea and in an embryonic lung culture model during development. Results showed that that there was a reduction in tracheal caliber in CF mice as indicated by a reduction in the number of cartilage rings; proximal cross-sectional areas of cftr (-/-) tracheas and luminal areas were significantly smaller, but there was no difference in the area or distribution of smooth muscle. Morphological differences observed in adult trachea were not evident in the embryonic lung at 11.5 days gestation or after 72 h in culture. Functional data showed a significant reduction in the amplitude and duration of contraction in response to carbachol (CCh) in Ca-free conditions. The reduction in contraction was agonist specific, and occurred throughout the length of the trachea. These data show that there is a loss in the contractile capacity of the CF mouse trachea due to downregulation of the pathway specific to acetylcholine (ACh) activation. This reduction in contraction is not associated with changes in the area or distribution of ASM.

IL-17A produced by αβ T cells drives airway hyper-responsiveness in mice and enhances mouse and human airway smooth muscle contraction

Emerging evidence suggests that the T_H17 subset of αβ T cells contributes to the development of allergic asthma. In this study we found that mice lacking αvβ8 on dendritic cells failed to generate T_H17 cells in the lung and were protected from AHR in response to house dust mite and ovalbumin sensitization and challenge. Because loss of T_H17 cells inhibited airway narrowing without obvious effects on airway inflammation or epithelial morphology, we examined the direct effects of T_H17 cytokines on mouse and human airway smooth muscle function. IL-17A enhanced contractile force generation through a NF-κB/RhoA/ROCK2 signaling cascade. Mice lacking integrin αvβ8 on dendritic cells showed impaired activation of this pathway after OVA sensitization and challenge, and the diminished contraction of tracheal rings from these mice was reversed by IL-17A. These data indicate that IL-17A produced by T_H17 cells contributes to allergen-induced AHR through direct effects on airway smooth muscle.

Genetic interactions between chromosomes 11 and 18 contribute to airway hyperresponsiveness in mice

We used two-dimensional quantitative trait locus analysis to identify interacting genetic loci that contribute to the native airway constrictor hyperresponsiveness to methacholine that characterizes A/J mice, relative to C57BL/6J mice. We quantified airway responsiveness to intravenous methacholine boluses in eighty-eight (C57BL/6J X A/J) F₂ and twenty-seven (A/J X C57BL/6J) F₂ mice as well as ten A/J mice and six C57BL/6J mice; all studies were performed in male mice. Mice were genotyped at 384 SNP markers, and from these data two-QTL analyses disclosed one pair of interacting loci on chromosomes 11 and 18; the homozygous A/J genotype at each locus constituted the genetic interaction linked to the hyperresponsive A/J phenotype. Bioinformatic network analysis of potential interactions among proteins encoded by genes in the linked regions disclosed two high priority subnetworks - Myl7, Rock1, Limk2; and Npc1, Npc1l1. Evidence in the literature supports the possibility that either or both networks could contribute to the regulation of airway constrictor responsiveness. Together, these results should stimulate evaluation of the genetic contribution of these networks in the regulation of airway responsiveness in humans.

The pivotal role of airway smooth muscle in asthma pathophysiology

Asthma is characterized by the association of airway hyperresponsiveness (AHR), inflammation, and remodelling. The aim of the present article is to review the pivotal role of airway smooth muscle (ASM) in the pathophysiology of asthma. ASM is the main effector of AHR. The mechanisms of AHR in asthma may involve a larger release of contractile mediators and/or a lower release of relaxant mediators, an improved ASM cell excitation/contraction coupling, and/or an alteration in the contraction/load coupling. Beyond its contractile function, ASM is also involved in bronchial inflammation and remodelling. Whereas ASM is a target of the inflammatory process, it can also display proinflammatory and immunomodulatory functions, through its synthetic properties and the expression of a wide range of cell surface molecules. ASM remodelling represents a key feature of asthmatic bronchial remodelling. ASM also plays a role in promoting complementary airway structural alterations, in particular by its synthetic function.

Role of Rho kinase isoforms in murine allergic airway responses

Inhibition of Rho-associated coiled-coil forming kinases (ROCKs) reduces allergic airway responses in mice. The purpose of this study was to determine the roles of the two ROCK isoforms, ROCK1 and ROCK2, in these responses. Wildtype (WT) mice and heterozygous ROCK1 and ROCK2 knockout mice (ROCK1(+/-) and ROCK2(+/-), respectively) were sensitised and challenged with ovalbumin. ROCK expression and activation were assessed by western blotting. Airway responsiveness was measured by forced oscillation. Bronchoalveolar lavage was performed and the lungs were fixed for histological assessment. Compared with WT mice, ROCK1 and ROCK2 expression were 50% lower in lungs of ROCK1(+/-) and ROCK2(+/-) mice, respectively, without changes in the other isoform. In WT lungs, ROCK activation increased after ovalbumin challenge and was sustained for several hours. This activation was reduced in ROCK1(+/-) and ROCK2(+/-) lungs. Airway responsiveness was comparable in WT, ROCK1(+/-), and ROCK2(+/-) mice challenged with PBS. Ovalbumin challenge caused airway hyperresponsiveness in WT, but not ROCK1(+/-) or ROCK2(+/-) mice. Lavage eosinophils and goblet cell hyperplasia were significantly reduced in ovalbumin-challenged ROCK1(+/-) and ROCK2(+/-) versus WT mice. Ovalbumin-induced changes in lavage interleukin-13, interleukin-5 and lymphocytes were also reduced in ROCK1(+/-) mice. In conclusion, both ROCK1 and ROCK2 are important in regulating allergic airway responses.

Caveolin-1 and force regulation in porcine airway smooth muscle

Caveolae are specialized membrane microdomains expressing the scaffolding protein caveolin-1. We recently demonstrated the presence of caveolae in human airway smooth muscle (ASM) and the contribution of caveolin-1 to intracellular calcium ([Ca(2+)](i)) regulation. In the present study, we tested the hypothesis that caveolin-1 regulates ASM contractility. We examined the role of caveolins in force regulation of porcine ASM under control conditions as well as TNF-α-induced airway inflammation. In porcine ASM strips, exposure to 10 mM methyl-β-cyclodextrin (CD) or 5 μM of the caveolin-1 specific scaffolding domain inhibitor peptide (CSD) resulted in time-dependent decrease in force responses to 1 μM ACh. Overnight exposure to the cytokine TNF-α (50 ng/ml) accelerated and increased caveolin-1 expression and enhanced force responses to ACh. Suppression of caveolin-1 with small interfering RNA mimicked the effects of CD or CSD. Regarding mechanisms by which caveolae contribute to contractile changes, inhibition of MAP kinase with 10 μM PD98059 did not alter control or TNF-α-induced increases in force responses to ACh. However, inhibiting RhoA with 100 μM fasudil or 10 μM Y27632 resulted in significant decreases in force responses, with lesser effects in TNF-α exposed samples. Furthermore, Ca(2+) sensitivity for force generation was substantially reduced by fasudil or Y27632, an effect even more enhanced in the absence of caveolin-1 signaling. Overall, these results indicate that caveolin-1 is a critical player in enhanced ASM contractility with airway inflammation.

A functional interaction between CPI-17 and RACK1 proteins in bronchial smooth muscle cells

CPI-17 is a phosphorylation-dependent inhibitor of smooth muscle myosin light chain. Using yeast two-hybrid system, we have identified the receptor for activated C kinase 1 (RACK1) as a novel interaction partner of CPI-17. The direct interaction and co-localization of CPI-17 with RACK1 were confirmed by immunoprecipitation and confocal microscopy analysis, respectively. An in vitro assay system using recombinant/purified proteins revealed that the PKC-mediated phosphorylation of CPI-17 was augmented in the presence of RACK1. These results suggest that RACK1 may play a role in PKC/CPI-17 signaling pathway.

Induction of RhoA gene expression by interleukin-4 in cultured human bronchial smooth muscle cells

RhoA, a small GTPase, is one of the key proteins of smooth muscle contraction. In allergic asthma, an upregulation of RhoA in bronchial smooth muscle has been suggested. However, the mechanism of its upregulation has not yet been clarified. In the present study, the effects of interleukin-4 (IL-4), one of the T-helper 2 cytokines, on RhoA mRNA expression and promoter activity of RhoA gene were examined in cultured human bronchial smooth muscle cells (hBSMCs). The quantitative real-time RT-PCR analyses revealed that incubation of hBSMCs with IL-4 (10, 30 and 100 ng/mL, for 24 hr) caused an increase in RhoA mRNA in a concentration-dependent manner. In luciferase reporter gene assay using hBSMCs that were transfected with luciferase constructs and were then stimulated with IL-4 (100 ng/mL), an importance of the most proximal STAT6 binding region (78-70 bp upstream of the transcription initiation site) was suggested. It is thus possible that IL-4 is capable of upregulating RhoA by promoting its transcription in hBSMCs. The proximal STAT6 binding region is required for the IL-4-induced increase in promoter activity of the human RhoA gene.

Upregulation of interleukin-13 receptor chains in bronchial smooth muscle tissues of mouse experimental asthma

Interleukin-13 (IL-13) is believed to be a central mediator of the induction of airway hyperresponsiveness (AHR), one of the characteristic features of allergic bronchial asthma. The IL-13-mediated events are mainly generated by its binding to functional IL-13 receptor, IL13Ralpha1 chain. In the present study, the changes in the levels of IL-13 receptors in bronchial smooth muscles were determined in mice with AHR induced by antigen inhalation. Mice were sensitized and repeatedly challenged with ovalbumin antigen. Total RNAs of the left main bronchi were extracted, and real-time RT-PCR analyses for IL13Ralpha1 and IL13Ralpha2 chains were conducted. As a result, both the receptor chains were significantly increased in the diseased bronchial smooth muscle. The time-course analyses revealed that the peaks of IL13Ralpha1 and IL13Ralpha2 upregulations were at 6 hour and 3-12 hour after the last antigen inhalation, respectively. It is thus possible that the IL-13-mediated signaling in bronchial smooth muscle is considerably augmented by the upregulations of IL-13 itself and its functional IL13Ralpha1 receptor in allergic asthmatics.

The proximal STAT6 and NF-kappaB sites are responsible for IL-13- and TNF-alpha-induced RhoA transcriptions in human bronchial smooth muscle cells

RhoA protein is involved in the Ca(2+) sensitization of bronchial smooth muscle (BSM) contraction, and an upregulation of RhoA in BSMs has been suggested in allergic bronchial asthma. However, the mechanism of upregulation of RhoA remains poorly understood. In the present study, the transcriptional regulation of human RhoA gene was investigated in cultured human BSM cells stimulated with IL-13 and TNF-alpha, both of which have an ability to upregulate RhoA protein. Luciferase-based assay showed that the RhoA promoter activity was augmented by both IL-13 and TNF-alpha. The deletion studies revealed a significant level of promoter activity between the 112 bp upstream and the transcription start site, which contains the STAT6 (78-70 bp upstream) and NF-kappaB (84-74 bp upstream) binding regions. The promoter activity was also decreased significantly by the mutations of these regions. Thus, the current study for the first time characterized the transcriptional regulation of the human RhoA gene. The findings also suggest that STAT6 and NF-kappaB are important for the upregulation of RhoA in human BSM induced by IL-13 and TNF-alpha, both of which are major cytokines in the pathogenesis of allergic bronchial asthma.

Interleukin-4 upregulates RhoA protein via an activation of STAT6 in cultured human bronchial smooth muscle cells

Interleukin-4 (IL-4) is believed to play a role in allergic bronchial asthma, and has been suggested to cause hyperresponsiveness of airway smooth muscle. In the present study, the effects of IL-4 on the expression of RhoA protein, a monomeric GTP-binding protein that contributes to the contraction of smooth muscle, were determined in cultured human bronchial smooth muscle cells (hBSMCs). Incubation of hBSMCs with IL-4 (100ng/mL) caused a distinct phosphorylation of signal transducer and activator of transcription 6 (STAT6), a major signal transducer activated by IL-4, indicating that IL-4 is capable of activating signal transduction in the hBSMCs directly. IL-4 also caused a significant increase in the expression level of RhoA protein: the peak of the upregulation of RhoA protein was observed at 12-24h after the IL-4 treatment. Both the phosphorylation of STAT6 and the upregulation of RhoA protein induced by IL-4 were inhibited by the co-incubation with AS1517499, a selective inhibitor of STAT6, in a concentration-dependent fashion. These findings suggest that IL-4 is capable of inducing an upregulation of RhoA via an activation of STAT6 in cultured hBSMCs. The RhoA upregulation induced by IL-4, one of the Th2 cytokines upregulated in the airways of allergic bronchial asthmatics, might result in an augmentation of bronchial smooth muscle contractility, that is one of the causes of airway hyperresponsiveness.

Inhibition of geranylgeranyltransferase inhibits bronchial smooth muscle hyperresponsiveness in mice

Recent studies revealed an involvement of RhoA/Rho-kinase in the contraction of bronchial smooth muscle (BSM), and this pathway has now been proposed as a new target for asthma therapy. A posttranslational geranylgeranylation of RhoA is required for its activation. Thus selective inhibition of geranylgeranyltransferase may be a novel strategy for treatment of the BSM hyperresponsiveness in asthmatics. To test this hypothesis, we investigated the effect of a geranylgeranyltransferase inhibitor, GGTI-2133, on antigen-induced BSM hyperresponsiveness by using mice with experimental asthma. Mice were sensitized and repeatedly challenged with ovalbumin antigen. Animals also were treated with GGTI-2133 (5 mg/kg ip) once a day before and during the antigen inhalation period. Repeated antigen inhalation caused a BSM hyperresponsiveness to acetylcholine with the increased expressions of RhoA and the anti-farnesyl-positive 21-kDa proteins, probably geranylgeranylated RhoA. The in vivo GGTI-2133 treatments significantly inhibited BSM hyperresponsiveness induced by antigen exposure. In another series of experiments, BSM tissues isolated from the repeatedly antigen-challenged mice were cultured for 48 h in the absence or presence of GGTI-2133. Under these conditions, the putative geranylgeranylated RhoA was decreased in a GGTI-2133 concentration-dependent manner. The in vitro incubation with GGTI-2133 also inhibited BSM hyperresponsiveness induced by antigen exposure. These findings suggest that GGTI-2133 inhibits antigen-induced BSM hyperresponsiveness, probably by reducing downstream signal transduction of RhoA. Selective geranylgeranyltransferase inhibitors may be beneficial for the treatment of airway hyperresponsiveness, one of the characteristic features of allergic bronchial asthma.

Down-regulation of miR-133a contributes to up-regulation of Rhoa in bronchial smooth muscle cells

RATIONALE

Augmented bronchial smooth muscle (BSM) contraction is one of the causes of bronchial hyperresponsiveness. The protein RhoA and its downstream pathways have now been proposed as a new target for asthma therapy. MicroRNAs (miRNAs) play important roles in normal and diseased cell functions, and a contribution of miR-133 to RhoA expression has been suggested in cardiomyocytes.

OBJECTIVES

To make clear the mechanism(s) of up-regulation of RhoA observed in the BSMs of experimental asthma, the role of miR-133a in RhoA expression was tested.

METHODS

Total proteins and RNAs (containing miRNAs) were extracted from cultured human BSM cells (hBSMCs) that were treated with antagomirs and/or IL-13, and bronchial tissues of BALB/c mice that were sensitized and repeatedly challenged with ovalbumin. RhoA protein and miR-133a were detected by immunoblotting and quantified real-time reverse transcriptase-polymerase chain reaction, respectively.

MEASUREMENTS AND MAIN RESULTS

In hBSMCs, an up-regulation of RhoA was observed when the function of endogenous miR-133a was inhibited by its antagomir. Treatment of hBSMCs with IL-13 caused an up-regulation of RhoA and a down-regulation of miR-133a. In bronchial tissues of the repeatedly ovalbumin-challenged mice, a significant increase in RhoA was observed. Interestingly, the level of miR-133a was significantly decreased in BSMs of the challenged mice.

CONCLUSIONS

These findings suggest that RhoA expression is negatively regulated by miR-133a in BSMs. IL-13 might, at least in part, contribute to the reduction of miR-133a.

Extraction of membrane cholesterol disrupts caveolae and impairs serotonergic (5-HT2A) and histaminergic (H1) responses in bovine airway smooth muscle: role of Rho-kinase

Some receptors and signaling molecules, such as Rho-kinase (ROCK), localize in caveolae. We asked whether the function of histamine receptors (H1) and 5-hydroxytryptamine (serotonin) receptors (5-HT2A) in bovine tracheal smooth muscle are modified after caveolae disruption and if so, whether the altered ROCK activity plays a role in this modification. Methyl-β-cyclodextrin (MβCD), used to deplete membrane cholesterol, was shown to disrupt caveolae and diminish sustained contractions to histamine (∼80%), 5-HT (100%), α-methyl-5-HT (100%), and KCl (∼30%). Cholesterol-loaded MβCD (CL-MβCD) restored the responses to KCl and partially restored the responses to agonists. ROCK inhibition by Y-27632 diminished contractions to histamine (∼85%) and 5-HT (∼59%). 5-HT or histamine stimulation augmented ROCK activity. These increases were reduced by MβCD and partially reestablished by CL-MβCD. The increase in intracellular Ca2+ that was induced by both agonists was reduced by MβCD. The presence of caveolin-1 (Cav-1), H1, 5-HT2A, and ROCK1 was corroborated by immunoblotting of membrane fractions from sucrose gradients and by confocal microscopy. H1 receptors coimmunoprecipitated with Cav-1 in caveolar and noncaveolar membrane fractions, whereas 5-HT2A receptors appeared to be restricted to noncaveolar membrane fractions. We conclude that caveolar and cholesterol integrity are indispensable for the proper functionality of the H1 and 5-HT2A receptors through their Rho/ROCK signaling.

A novel STAT6 inhibitor AS1517499 ameliorates antigen-induced bronchial hypercontractility in mice

Interleukin-13 (IL-13) is one of the central mediators for development of airway hyperresponsiveness in asthma. The signal transducer and activation of transcription 6 (STAT6) is one of the major signal transducers activated by IL-13, and a possible involvement of IL-13/STAT6 pathway in the augmented bronchial smooth muscle (BSM) contraction has been suggested. In the present study, the effect of a novel STAT6 inhibitor, AS1517499, on the development of antigen-induced BSM hyperresponsiveness was investigated. In cultured human BSM cells, IL-13 (100 ng/ml) caused a phosphorylation of STAT6 and an up-regulation of RhoA, a monomeric GTPase responsible for Ca2+ sensitization of smooth muscle contraction: both events were inhibited by co-incubation with AS1517499 (100 nM). In BALB/c mice that were actively sensitized and repeatedly challenged with ovalbumin antigen, an increased IL-13 level in bronchoalveolar lavage fluids and a phosphorylation of STAT6 in bronchial tissues were observed after the last antigen challenge. These mice had an augmented BSM contractility to acetylcholine together with an up-regulation of RhoA in bronchial tissues. Intraperitoneal injections of AS1517499 (10 mg/kg) 1 hour before each ovalbumin exposure inhibited both the antigen-induced up-regulation of RhoA and BSM hyperresponsiveness, almost completely. A partial but significant inhibition of antigen-induced production of IL-13 was also found. These findings suggest that the inhibitory effects of STAT6 inhibitory agents, such as AS1517499, both on RhoA and IL-13 up-regulations might be useful for asthma treatment.

Mechanisms of adaptive supersensitivity in vas deferens

Adaptive supersensitivity is a phenomenon characteristic of excitable tissues and discloses as a compensatory adjustment of tissue's response to unrelated stimulatory endogenous and exogenous substances after chronic interruption of excitatory neurotransmission. The mechanisms underlying such higher postjunctional sensitivity have been postulated for a variety of cell types. In smooth muscles, especially the vas deferens with its rich sympathetic innervation, the mechanisms responsible for supersensitivity are partly understood and appear to be different from one species to another. The present review provides a general understanding of adaptive supersensitivity and emphasizes early and recent information about the putative mechanisms involved in this phenomenon in rodent vas deferens.

CPI-17 silencing-reduced responsiveness in control and TNF-alpha-treated human bronchi

Under pathophysiologic conditions, the modulation of Ca2+ sensitivity and reactivity of bronchial smooth muscle is controlled by protein kinase C-dependent phosphorylation of the newly described protein, CPI-17. The goal of the present study was to assess the key role of this regulatory protein in airway hyperresponsiveness (AHR) using control and TNF-alpha-treated human bronchi as well as a specific siRNA duplex against human CPI-17 transcripts. Validity of a mixed transfection strategy was assessed using the reversible permeabilization method to introduce X-TremeGene (X-TG)-siRNA complexes in an overreactive model of human bronchi treated with TNF. Data demonstrate that X-TG-siRNA complexes targeted against CPI-17 transcripts resulted in a reduction in mRNA and specific protein expression in human bronchial tissues. This approach revealed that overall reactivity of bronchial smooth muscle to methacholine was reduced, while their relaxing responses to beta2-agonist were increased, when compared with responses triggered in control TNF-alpha-treated bronchi. Quantification analysis showed that Ca2+ -sensitivity in both untreated and TNF-alpha-treated bronchi were largely reduced upon transfection with human CPI-17 siRNA-X-TremeGene complexes, while Western blot analysis corroborated the decrease in CPI-17 and MLC phosphorylation levels in pretreated human bronchi. Identical results were obtained upon treatment with an antiinflammatory eicosanoid, 14,15-EET, known to inhibit CPI-17 phosphorylation. Together these results are consistent with a key molecular role for CPI-17 in AHR, in the absence of bronchial wall remodeling.

Interleukin-13 augments bronchial smooth muscle contractility with an up-regulation of RhoA protein

Interleukin-13 (IL-13) is one of the central mediators for development of airway hyperresponsiveness in asthma. However, its effect on bronchial smooth muscle (BSM) is not well known. Recent studies revealed an involvement of RhoA/Rho-kinase in BSM contraction, and this pathway has now been proposed as a new target for asthma therapy. To elucidate the role of IL-13 on the induction of BSM hyperresponsiveness, effects of IL-13 on contractility and RhoA expression in BSMs were investigated. Male BALB/c mice were sensitized and repeatedly challenged with ovalbumin antigen. In the repeatedly antigen-challenged mice, marked airway inflammation and BSM hyperresponsiveness with an up-regulation of IL-13 in bronchoalveolar lavage fluids were observed. In cultured human BSM cells, IL-13 caused an up-regulation of RhoA. The IL-13-induced up-regulation of RhoA was inhibited by leflunomide, an inhibitor of signal transducer and activator of transcription 6 (STAT6). In isolated BSM tissues of naive mice, the contractility was significantly enhanced by organ culture in the presence of IL-13. Moreover, in vivo treatment of airways with IL-13 by intranasal instillation caused a BSM hyperresponsiveness with an up-regulation of RhoA in naive mice. These findings suggest that IL-13/STAT6 signaling is critical for development of antigen-induced BSM hyperresponsiveness and that agents that specifically inhibit this pathway in BSM may provide a novel strategy for the treatment of asthma.

Molecular mechanisms underlying airway smooth muscle contraction and proliferation: implications for asthma

Airway smooth muscle (ASM) plays a key role in bronchomotor tone, as well as in structural remodeling of the bronchial wall. Therefore, ASM contraction and proliferation significantly participate in the development and progression of asthma. Many contractile agonists also behave as mitogenic stimuli, thus contributing to frame a hyperresponsive and hyperplastic ASM phenotype. In this review, the molecular mechanisms and signaling pathways involved in excitation-contraction coupling and ASM cell growth will be outlined. Indeed, the recent advances in understanding the basic aspects of ASM biology are disclosing important cellular targets, currently explored for the implementation of new, more effective anti-asthma therapies.