Asthma: is it due to an abnormal airway smooth muscle cell?

Sphingosine-1-phosphate induces airway smooth muscle hyperresponsiveness and proliferation

BACKGROUND

The emerging role of sphingosine-1-phosphate (S1P) in regulating smooth muscle functions has led to the exploration of the possibility that this sphingolipid could represent a potential therapeutic target in asthma and other lung diseases. Several studies in animal surrogates have suggested a role for S1P-mediated signaling in the regulation of airway smooth muscle (ASM) contraction, airway hyperresponsiveness, and airway remodeling, but evidence from human studies is lacking.

OBJECTIVE

We sought to compare the responsiveness of the airways to S1P in healthy and asthmatic individuals in vivo, in isolated human airways ex vivo, and in murine airways dissected from healthy and house dust mite (HDM)-sensitized animals.

METHODS

Airway responsiveness was measured by spirometry during inhalation challenges and by wire myography in airways isolated from human and mouse lungs. Thymidine incorporation and calcium mobilization assays were used to study human ASM cell responses.

RESULTS

S1P did not induce contraction of airways isolated from healthy and HDM-exposed mice, nor in human airways. Similarly, there was no airway constriction observed in healthy and asthmatic subjects in response to increasing concentrations of inhaled S1P. However, a 30-minute exposure to S1P induced a significant concentration-dependent enhancement of airway reactivity to methacholine and to histamine in murine and human airways, respectively. HDM-sensitized mice demonstrated a significant increase in methacholine responsiveness, which was not further enhanced by S1P treatment. S1P also concentration-dependently enhanced proliferation of human ASM cells, an effect mediated through S1P receptor type 2, as shown by selective antagonism and S1P receptor type 2 small-interfering RNA knockdown.

CONCLUSIONS

Our data suggest that S1P released locally into the airways may be involved in the regulation of ASM hyperresponsiveness and hyperplasia, defining a novel target for future therapies.

The roles of microRNAs played in lung diseases via regulating cell apoptosis

MicroRNAs (miRNAs) are a type of endogenous non-coding short-chain RNA, which plays a crucial role in the regulation of many essential cellular functions, including cellular migration, proliferation, invasion, autophagy, oxidative stress, apoptosis, and differentiation. The lung can be damaged by pathogenic microorganisms, as well as physical or chemical factors. Research has confirmed that miRNAs and lung cell apoptosis can affect the development and progression of several lung diseases. This article reviews the role of miRNAs in the development of lung disease through regulating host cell apoptosis.

Network and co-expression analysis of airway smooth muscle cell transcriptome delineates potential gene signatures in asthma

Airway smooth muscle (ASM) is known for its role in asthma exacerbations characterized by acute bronchoconstriction and remodeling. The molecular mechanisms underlying multiple gene interactions regulating gene expression in asthma remain elusive. Herein, we explored the regulatory relationship between ASM genes to uncover the putative mechanism underlying asthma in humans. To this end, the gene expression from human ASM was measured with RNA-Seq in non-asthmatic and asthmatic groups. The gene network for the asthmatic and non-asthmatic group was constructed by prioritizing differentially expressed genes (DEGs) (121) and transcription factors (TFs) (116). Furthermore, we identified differentially connected or co-expressed genes in each group. The asthmatic group showed a loss of gene connectivity due to the rewiring of major regulators. Notably, TFs such as ZNF792, SMAD1, and SMAD7 were differentially correlated in the asthmatic ASM. Additionally, the DEGs, TFs, and differentially connected genes over-represented in the pathways involved with herpes simplex virus infection, Hippo and TGF-β signaling, adherens junctions, gap junctions, and ferroptosis. The rewiring of major regulators unveiled in this study likely modulates the expression of gene-targets as an adaptive response to asthma. These multiple gene interactions pointed out novel targets and pathways for asthma exacerbations.

Developing small activating RNA as a therapeutic: current challenges and promises

RNA activation (RNAa) allows specific gene upregulation mediated by a small activating RNA (saRNA). Harnessing this process would help in developing novel therapeutics for undruggable diseases. Since its discovery in mid 2000s, improvements of saRNA design, synthetic chemistry and understanding of the biology have matured the way to apply RNAa. Indeed, MiNA therapeutics Ltd has conducted the first RNAa clinical trial for advanced hepatocellular carcinoma patients with promising outcomes. However, to fully realize the RNAa potential better saRNA delivery strategies are needed to target other diseases. Currently, saRNA can be delivered in vivo by lipid nanoparticles, dendrimers, lipid and polymer hybrids and aptamers. Further developing these delivery technologies and novel application of RNAa will prove to be invaluable for new treatment development.

Testosterone Rescues the De-Differentiation of Smooth Muscle Cells Through Serum Response Factor/Myocardin

Prostatic smooth muscle cells (pSMCs) differentiation is a key factor for prostatic homeostasis, with androgens exerting multiple effects on these cells. Here, we demonstrated that the myodifferentiator complex Srf/Myocd is up-regulated by testosterone in a dose-dependent manner in primary cultures of rat pSMCs, which was associated to the increase in Acta2, Cnn1, and Lmod1 expressions. Blocking Srf or Myocd by siRNAs inhibited the myodifferentiator effect of testosterone. While LPS led to a dedifferentiated phenotype in pSMCs, characterized by down-regulation of Srf/Myocd and smooth muscle cell (SMC)-restricted genes, endotoxin treatment on Myocd-overexpressing cells did not result in phenotypic alterations. Testosterone at a physiological dose was able to restore the muscular phenotype by normalizing Srf/Myocd expression in inflammation-induced dedifferentiated pSMCs. Moreover, the androgen reestablished the proliferation rate and IL-6 secretion increased by LPS. These results provide novel evidence regarding the myodifferentiating role of testosterone on SMCs by modulating Srf/Myocd. Thus, androgens preserve prostatic SMC phenotype, which is essential to maintain the normal structure and function of the prostate. J. Cell. Physiol. 232: 2806-2817, 2017. © 2016 Wiley Periodicals, Inc.

Pharmacological investigation on the anti-oxidant and anti-inflammatory activity of N-acetylcysteine in an ex vivo model of COPD exacerbation

Background

Oxidative stress is recognized to be one of predisposing factor in the pathogenesis of COPD. The oxidant/antioxidant imbalance is significantly pronounced in patients with COPD exacerbation. N-acetylcysteine (NAC) seems to be able to reduce COPD exacerbations by modulating the oxidative stress in addition to its well-known mucolytic activity, but there are discordant findings on the actual anti-oxidant activity of NAC.

Methods

The anti-oxidant effect of NAC and its impact on the inflammatory response have been pharmacologically characterized on a human ex vivo model of COPD exacerbation induced by lipopolysaccharide (LPS).

Results

NAC prevented the desensitization induced by LPS incubation on the contractile tone in linear concentration-response manner. Concentrations of NAC ≥1 μM reduced the pro-oxidant response (peroxidase activity, hydrogen peroxide, malondialdehyde, nitric oxide), and improved the anti-oxidant response (total anti-oxidant capacity, glutathione, superoxide dismutase) induced by LPS. Lower concentrations of NAC (<1 μM) did not modulate the bronchial oxidative imbalance. Concentrations of NAC ≥300 μM inhibited the inflammatory response (release of IL-1β, IL-8, and TNF-α) of human airways induced by the overnight stimulation with LPS, whereas lower concentrations of NAC (≥1 μM) were sufficient to reduce the release of IL-6 elicited by LPS. Both the anti-oxidant effect and the anti-inflammatory effect of NAC were inversely correlated with the release of NKA.

Conclusions

The findings of this study suggest that NAC may have a role in modulating the detrimental effect induced by LPS in course of COPD exacerbation. It may elicit both anti-oxidant and anti-inflammatory effects when administered at high concentrations.

Molecular and cellular mechanisms underlying the therapeutic effects of budesonide in asthma

Inhaled glucocorticoids are the mainstay of asthma treatment. Indeed, such therapeutic agents effectively interfere with many pathogenic circuits underpinning asthma. Among these drugs, during the last decades budesonide has been probably the most used molecule in both experimental studies and clinical practice. Therefore, a large body of evidence clearly shows that budesonide, either alone or in combination with long-acting bronchodilators, provides a successful control of asthma in many patients ranging throughout the overall spectrum of disease severity. These excellent therapeutic properties of budesonide basically depend on its molecular mechanisms of action, capable of inhibiting within the airways the activity of multiple immune-inflammatory and structural cells involved in asthma pathobiology.

Brain natriuretic peptide protects against hyperresponsiveness of human asthmatic airway smooth muscle via an epithelial cell-dependent mechanism

Brain natriuretic peptide (BNP) relaxes airways by activating natriuretic peptide receptor-A and elevating cyclic guanosine monophosphate. BNP is more effective in passively sensitized human bronchi compared with control airways. The molecular and cellular patterns involved in this signaling are unknown. The aim of this study was to investigate the influence of BNP on airway smooth muscle (ASM) cells obtained from donors with asthma and healthy donors and to identify the mechanisms involved in BNP-mediated relaxation. The contractile response of ASM cells was microscopically assessed in vitro in the presence of 1 μM BNP or with supernatant from human bronchial epithelial (BEAS-2B) cells pretreated with 1 μM BNP. We investigated the role of muscarinic M2 receptors and inducible nitric oxide synthase (iNOS), quantified the release of acetylcholine and nitric oxide (NO), and assessed the gene/protein expression of iNOS and myosin phosphatase target subunit 1 (MYPT1). Supernatant from BEAS-2B cells treated with BNP reduced the hyperreactivity of asthmatic ASM cells by shifting the potency of histamine by 1.19-fold but had no effect in healthy ASM cells. BNP was not effective directly on ASM cells. Blocking muscarinic M2-receptors and iNOS abolished the protective role of supernatant from BEAS-2B treated with BNP. BNP stimulated the release of acetylcholine (210.7 ± 11.1%) from BEAS-2B cells that in turn increased MYPT1 and iNOS gene/protein expression and enhanced NO levels in asthmatic ASM supernatant (35.0 ± 13.0%). This study provides evidence that BNP protects against bronchial hyperresponsiveness via an interaction between respiratory epithelium and ASM in subjects with asthma.

Highly Protective Association of MMP-2-1306C/T Promoter Polymorphism With Asthma in a North Indian Population: A Pilot Study

Purpose

Asthma is the most prevalent disease in India according to the national survey conducted by NFHS 2 in 1998-1999. Matrix metalloproteinase-2 (MMP-2), a collagenase encoded by the MMP-2 gene, degrades the type IV collagen and is responsible for inflammatory responses. This is a pilot study evaluating the role of MMP-2 -1306C/T promoter single nucleotide polymorphism (SNP) in asthma pathogenesis.

Methods

A case-control study was performed with a total of 824 adult subjects, including 410 adult asthmatics and 414 healthy controls from regions of North India. The MMP-2 -1306C/T polymorphism was genotyped by the Tetra-Primer Amplification Refractory Mutation System Polymerase Chain Reaction (Tetra-Primer ARMS PCR).

Results

Statistical analysis of the results for the MMP-2 -1306C/T polymorphism revealed an extremely protective role of the mutant T allele in asthma pathogenesis with OR=0.45, 95% CI (0.35-0.58) and P=0.000. The heterozygous CT genotype also conferred protection from asthma with OR=0.37, 95% CI (0.27-0.51) and P=0.000. The homozygous TT genotype was also significantly associated with asthma with OR=0.35, 95% CI (0.16-0.72) and P=0.002. Moreover, the polymorphism was significantly associated with all the phenotypic traits of the disease.

Conclusion

The MMP-2 -1306C/T promoter polymorphism confers significant protection from asthma in the studied North Indian population

Exhaled matrix metalloproteinase-9 (MMP-9) in different biological phenotypes of asthma

BACKGROUND AND OBJECTIVES

Airway remodeling is a main feature of asthma. Different biological phenotypes of severe asthma have been recently recognized by the ENFUMOSA study group and among these one is characterized by neutrophilic airway inflammation. Concentrations of MMP-9 in airways have been suggested as a marker to monitor airway remodeling in asthma.

OBJECTIVE

The aim of the present study was to explore airway remodeling in different biological phenotypes of asthma by measuring MMP-9 in EBC and correlating these with other variables.

METHODS

Sixty consecutive subjects with asthma and 20 healthy controls were enrolled in the study. Exhaled MMP-9, pH and NO levels and inflammatory cells in sputum were measured in all subjects enrolled.

RESULTS

We observed an increase of exhaled MMP-9 in asthmatic subjects compared to controls. Higher exhaled MMP-9 concentrations were described in severe asthmatics compared to mild to moderate especially in those with neutrophilic airway inflammation. We further found a correlation between exhaled MMP-9 and percentage of neutrophils in sputum, FEV1, exhaled NO and pH.

CONCLUSION

Our results seem to substantiate the feasibility of measuring exhaled MMP-9 in the breath of asthmatic patients. MMP-9 may be considered a proxy of the amount of the ongoing airway remodeling in asthma. MMP-9 has been shown to be differentially released in different phenotypes of asthma. The measure of exhaled MMP-9 could help to monitor the ongoing airway remodeling, recognize severe stages of asthma, and possibly help determine the appropriate choice of therapy.

CCR3 induced-p42/44 MAPK activation protects against staurosporine induced-DNA fragmentation but not apoptosis in airway smooth muscle cells

BACKGROUND

Chemokine receptors (CCRs) are expressed on airway smooth muscle (ASM) cells. As their ligands are present in the airways in asthma, we hypothesized that ASM CCR activation could promote the increase in ASM mass seen in patients with chronic asthma.

OBJECTIVE

To determine which CCRs are expressed by ASM cells and their potential functional relevance to the chronic airway changes seen in asthma.

METHODS

CCR expression in primary ASM cell cultures and airway biopsies from patients with and without asthma was examined by RT-PCR, fluorescence-activated cell sorting and immunohistochemistry. ASM p42/44 MAPK activity, proliferation, migration and apoptosis were examined by western blotting, thymidine incorporation, transwell assay and TUNEL assay respectively.

RESULTS

CCR3 was the most frequently expressed CCR protein and was present on 79 ± 14% of cells. CX3CR1 and CXCR6 were present on 6% and 11% of cells respectively. CCR3 ligands CCL11 and CCL24 caused rapid activation of p42/44 MAPK but not Akt. CCR3 activation did not affect ASM proliferation, migration or VEGF secretion. DNA fragmentation detected by TUNEL staining could be induced by staurosporine and Fas activation although only Fas activation resulted in caspase 3 cleavage. CCL11 and CCL24 protected ASM cells against DNA fragmentation dependent upon p42/44 MAPK activity only via caspase 3 independent pathways. CCR3 was expressed in the smooth muscle and epithelium in the airways of patients with and without asthma. Smooth muscle cell DNA fragmentation in the airways of patients with stable asthma and controls was very uncommon.

CONCLUSIONS AND CLINICAL RELEVANCE

CCR3 is strongly expressed by ASM cells in vitro and in vivo. Protection against cell death by CCR3 activation is dependent on p42/44 MAPK but does not affect caspase 3 mediated apoptosis.

Neuroimmune semaphorin 4A downregulates the severity of allergic response

To define the role of semaphorin 4A (Sema4A) in allergic response, we employed Sema4A⁻/⁻ and wild-type (WT) mice in the experimental model of ovalbumin (OVA)-induced allergic airway inflammation. We observed a selective increase in eosinophilic airway infiltration accompanied by bronchial epithelial cell hyperplasia in allergen-treated Sema4A⁻/⁻ mice relative to WT mice. This enhanced inflammatory response was associated with a selective increase in bronchoalveolar lavage (BAL) interleukin 13 (IL-13) content, augmented airway hyperreactivity, and lower regulatory T cell (Treg) numbers. In vivo allergen-primed Sema4A⁻/⁻ CD4+ T cells were more effective in transferring T helper type 2 (Th2) response to naive mice as compared with WT CD4+ T cells. T-cell proliferation and IL-13 productions in OVA₃₂₃₋₃₃₉-restimulated Sema4A⁻/⁻ cell cultures were upregulated. Generated bone marrow chimeras showed an equal importance of both lung-resident cell and inflammatory cell Sema4A expression in optimal disease regulation. These data provide a new insight into Sema4A biology and define Sema4A as an important regulator of Th2-driven lung pathophysiology.

Asthma and COPD - The C/EBP Connection

Asthma and chronic obstructive pulmonary disease (COPD) are the two most prominent chronic inflammatory lung diseases with increasing prevalence. Both diseases are associated with mild or severe remodeling of the airways. In this review, we postulate that the pathologies of asthma and COPD may result from inadequate responses and/or a deregulated balance of a group of cell differentiation regulating factors, the CCAAT/Enhancer Binding Proteins (C/EBPs). In addition, we will argue that the exposure to environmental factors, such as house dust mite and cigarette smoke, changes the response of C/EBPs and are different in diseased cells. These novel insights may lead to a better understanding of the etiology of the diseases and may provide new aspects for therapies.

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.

Uridine adenosine tetraphosphate induces contraction of airway smooth muscle

Contraction of airway smooth muscle (ASM) plays an important role in the regulation of air flow and is potentially involved in the pathophysiology of certain respiratory diseases. Extracellular nucleotides regulate ASM contraction via purinergic receptors, but the signaling mechanisms involved are not fully understood. Uridine adenosine tetraphosphate (Up(4)A) contains both pyrimidine and purine moieties, which are known to potentially activate P2X and P2Y receptors. Both P2X and P2Y receptors have been identified in the lung, including airway epithelial cells and ASM. We report here a study of purinergic signaling in the respiratory system, with a focus on the effect of Up(4)A on ASM contraction. Up(4)A induced contraction of rat isolated trachea and extrapulmonary bronchi as well as human intrapulmonary bronchioles. Up(4)A-induced contraction was blocked by di-inosine pentaphosphate, a P2X antagonist, but not by suramin, a nonselective P2 antagonist. Up(4)A-induced contraction was also attenuated by α,β-methylene-ATP-mediated P2X receptor desensitization. Several P2X receptors were detected at the mRNA level: P2X1, P2X4, P2X6, and P2X7, and to a lesser extent P2X3. Furthermore, the Up(4)A response was inhibited by removal of extracellular Ca(2+) and by the presence of the L-type Ca(2+) channel blocker, nifedipine, or the Rho-associated kinase inhibitor, H1152. We conclude that Up(4)A stimulates ASM contraction, and the underlying signaling mechanism appears to involve P2X (most likely P2X1) receptors, extracellular Ca(2+) entry via L-type Ca(2+) channels, and Ca(2+) sensitization through the RhoA/Rho-associated kinase pathway. This study will add to our understanding of the pathophysiological roles of extracellular nucleotides in the lung.

Dedifferentiation of prostate smooth muscle cells in response to bacterial LPS

BACKGROUND

Prostate smooth muscle cells (SMCs) are strongly involved in the development and progression of benign prostatic hyperplasia and prostate cancer. However, their participation in prostatitis has not been completely elucidated. Thus, we aimed to characterize the response of normal SMC to bacterial lipopolysaccharide (LPS).

METHODS

Primary prostate SMCs from normal rats were stimulated with LPS (0.1, 1, or 10 µg/ml) for 24 or 48 hr. The phenotype was evaluated by electron microscopy, immunofluorescence, and Western blot of SMCα-actin (ACTA2), calponin, vimentin, and tenascin-C, while the innate immune response was assessed by immunodetection of TLR4, CD14, and nuclear NF-κB. The secretion of TNFα and IL6 was determined using ELISA.

RESULTS

Bacterial LPS induces SMCs to develop a secretory phenotype including dilated rough endoplasmic reticulum cisternae with well-developed Golgi complexes. Furthermore, SMCs displayed a decrease in ACTA2 and calponin, and an increase in vimentin levels after LPS challenge. The co-expression of ACTA2 and vimentin, together with the induction of tenascin-C expression indicate that a myofibroblastic-like phenotype was induced by the endotoxin. Moreover, LPS elicited a TLR4 increase, with a peak in NF-κB activation occurring after 10 min of treatment. Finally, LPS stimulated the secretion of IL6 and TNFα.

CONCLUSIONS

Prostate SMCs are capable of responding to LPS in vitro by dedifferentiating from a contractile to a miofibroblastic-like phenotype and secreting cytokines, with the TLR4 signaling pathway being involved in this response. In this way, prostate SMCs may contribute to the pathophysiology of inflammatory diseases by modifying the epithelial-stromal interactions.

Bronchial thermoplasty in asthma

Currently available treatments for asthma provide satisfactory control of the disease in most cases. However, a significant number of patients do not respond to such treatments (i.e., do not achieve effective symptom relief). One novel approach to treating asthma is bronchial thermoplasty, in which the airway smooth muscle is specifically and directly treated. This procedure delivers radiofrequency energy to the airways in order to reduce smooth muscle-mediated bronchoconstriction. In this article, we present the thermoplasty technique, summarizing the results of the major randomized clinical trials of the procedure, as well as discussing its mechanisms of action and potential adverse effects. We also propose strategies for the future clinical use of this new treatment.

Effects of specific prostanoid EP receptor agonists on cell proliferation and intracellular Ca(2+) concentrations in human airway smooth muscle cells

Increased airway smooth muscle mass due to cell proliferation contributes to airway hyper-responsiveness and remodeling in patients with asthma. Prostaglandin E2 (PGE2) inhibits proliferation of airway smooth muscle cells, but the role of prostanoid EP receptor subtypes in mechanisms involved has not been fully elucidated yet. We investigated the effects of specific prostanoid EP receptor agonists on cell proliferation and intracellular Ca(2+) concentrations ([Ca(2+)]i) in human airway smooth muscle cells. Cell numbers were assessed by mitochondria-dependent reduction of 4-[3-(4-lodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1, 3-benzene disulfonate to formazan (WST-1 assay). RT-PCR data showed that human airway smooth muscle cells express EP2, EP3, and EP4 but not EP1 receptor mRNA. PGE2 (1nM-1μM) inhibited cell proliferation induced by 5% fetal bovine serum (FBS) in a concentration-dependent manner. (16S)-9-deoxy-9β-chloro-15-deoxy-16-hydroxy-17, 17-trimethylene-19, 20-didehydro PGE2 sodium salt (ONO-AE1-259-01; EP2 receptor agonist) and 16-(3-methoxymethyl)phenyl-ω-tetranor-3,7-dithia PGE2 (ONO-AE1-329; EP4 receptor agonist) inhibited the 5% FBS-induced cell proliferation. ONO-AE1-259-01 and ONO-AE1-329 also significantly increased the cytosolic cAMP levels. In contrast, 11,15-O-dimethyl PGE2 (ONO-AE-248; EP3 receptor agonist) elicited an oscillatory increase in [Ca(2+)]i but did not affect the cell growth or cAMP levels. [(17S)-2,5-ethano-6-oxo-17,20-dimethyl PGE1] (ONO-DI-004; EP1 receptor agonist) did not affect cell growth, cAMP levels, or [Ca(2+)]i. In conclusion, PGE2 inhibits FBS-induced cell proliferation mostly via EP2 and EP4 receptor activation and subsequent cAMP elevation. The EP3 receptor agonist causes an increase in [Ca(2+)]i without affecting cell growth. There is no functional expression of the EP1 receptor. Research on prostanoid EP receptors may lead to novel therapeutic strategies for treatment of asthma.

Pharmacology and immunological actions of a herbal medicine ASHMI on allergic asthma

Allergic asthma is a chronic and progressive inflammatory disease for which there is no satisfactory treatment. Studies reported tolerability and efficacy of an anti-asthma herbal medicine intervention (ASHMI) for asthma patients, developed from traditional Chinese medicine. To investigate the pharmacological actions of ASHMI on early- and late-phase airway responses (EAR and LAR), Ovalbumin (OVA)-sensitized mice received 6 weeks of ASHMI treatment beginning 24 h following the first intratracheal OVA challenge. EAR were determined 30 min following the fourth challenge and LAR 48 h following the last challenge. ASHMI effects on cytokine secretion, murine tracheal ring contraction and human bronchial smooth muscle cell prostaglandin (PG) production were also determined.ASHMI abolished EAR, which was associated with significantly reduced histamine, leukotriene C4, and OVA-specific IgE levels, as well as LAR, which was associated with significantly reduced bronchoalveolar lavage fluid (BALF) eosinophils, decreased airway remodeling, and lower Th2 cytokine levels in BALF and splenocyte cultures. Furthermore, ASHMI inhibited contraction of murine tracheal rings and increased production of the potent smooth muscle relaxer PGI(2). ASHMI abrogation of allergic airway responses is associated with broad effects on asthma pathological mechanisms.

Airway epithelial NF-κB activation promotes allergic sensitization to an innocuous inhaled antigen

Activation of NF-κB in airway epithelium is observed in allergic asthma and is induced by inhalation of numerous infectious and reactive substances. Many of the substances that activate NF-κB in the airway epithelium are also capable of acting as adjuvants to elicit antigen-specific sensitization to concomitantly inhaled protein, thereby circumventing the inherent bias of the lung to promote tolerance to innocuous antigens. We have used a transgenic mouse inducibly expressing a constitutively active mutant of the inhibitor of nuclear factor κB (IκB) kinase β ((CA)IKKβ) that activates NF-κB only in nonciliated airway epithelial cells to test whether activation of this intracellular signaling pathway in this specific cell type is sufficient to establish a pulmonary environment permissive to the development of allergic sensitization to inhaled protein. When airway epithelial (CA)IKKβ was transiently expressed in antigen-naive mice only during initial inhalation of ovalbumin, the mice became allergically sensitized to the antigen. As a consequence, subsequent inhalation of ovalbumin alone led to an allergic asthma-like response that included airway hyperresponsiveness to methacholine, eosinophilia, mucus expression, elevated serum levels of antigen-specific IgE and IgG1, and splenic CD4(+) T cells that secreted T helper type 2 and type 17 cytokines in response to in vitro antigen restimulation. Furthermore, CD11c(+) cells in the mediastinal lymph nodes (MLN) of (CA)IKKβ-expressing mice displayed significantly elevated levels of activation markers. These data implicate airway epithelial NF-κB activation as a critical modulator of the adaptive immune response to inhaled antigens via the secretion of soluble mediators that affect the capacity of CD11c(+) cells to undergo maturation and promote antigen-specific allergic responses.

Animal models of airway inflammation and airway smooth muscle remodelling in asthma

Asthma is a complex disease that involves chronic inflammation and subsequent decline in airway function. The widespread use of animal models has greatly contributed to our understanding of the cellular and molecular pathways underlying human allergic asthma. Animal models of allergic asthma include smaller animal models which offer 'ease of use' and availability of reagents, and larger animal models that may be used to address aspects of allergic airways disease not possible in humans or smaller animal models. This review examines the application and suitability of various animal models for studying mechanisms of airway inflammation and tissue remodelling in allergic asthma, with a specific focus on airway smooth muscle.

Mechanistic systems biology of inflammatory gene expression in airway smooth muscle as tool for asthma drug development

There is compelling evidence that airway smooth muscle cells may function as inflammatory cells in the airway system by producing multiple inflammatory cytokines in response to a large array of external stimuli such as acetylcholine, bradykinin, inflammatory cytokines, and toll-like receptor activators. However, how multiple extracellular stimuli interact in the regulation of inflammatory gene expression in an airway smooth muscle cell remains poorly understood. This review addresses the mechanistic systems biology of inflammatory gene expression in airway smooth muscle by discussing: a) redundancy underlying multiple stimulus-product relations in receptor-mediated inflammatory gene expression, and their regulation by convergent activation of Erk1/2 mitogen-activated protein kinase (MAPK), b) Erk1/2 MAPK-dependent induction of phosphatase expression as a negative feedback mechanism in the robust maintenance of inflammatory gene expression, and c) cyclooxygenase 2-dependent regulation of the differential temporal dynamics of early and late inflammatory gene expression. It is becoming recognized that a single-target approach is unlikely to be effective for the treatment of inflammatory airway diseases because airway inflammation is a result of complex interactions among multiple inflammatory mediators and cells types in the airway system. Understanding the mechanistic systems biology of inflammatory gene expression in airway smooth muscle and other cell types in the airway system may lead to the development of multi-target drug regimens for the treatment of inflammatory airway diseases such as asthma.

Airway smooth muscle as a model for new investigative drugs in asthma

Bronchial asthma as such exists because airway smooth muscle (ASM) contracts excessively in response to various stimuli. After several decades during which research was mainly focused on airway inflammation, increasing attention is now being paid to a possible abnormal behaviour of ASM. Thus, ASM is regarded as a major target for anti-asthma treatments. This review first describes the mechanisms of ASM contraction and airway hyperresponsiveness, through cellular, animal and human models. The developments of new drugs targeting extra and/or intracellular pathway of ASM contraction are discussed.

Impaired translation of CCAAT/enhancer binding protein alpha mRNA in bronchial smooth muscle cells of asthmatic patients

BACKGROUND

Bronchial smooth muscle (BSM) cells of asthmatic patients have an impaired expression of CCAAT/enhancer binding protein (C/EBP) alpha, which is associated with increased proliferation.

OBJECTIVE

We sought to assess the translational regulation of CEBPA mRNA in cultured BSM cells of healthy control subjects (n = 11) and asthmatic patients (n = 12).

METHODS

Translation efficiency was studied by using a translation control reporter system driven by the control elements present in the CEBPA mRNA. Translation efficiency was determined by the ratio of 2 artificial hemagglutinin (HA.11) proteins: p23 and p12. We also analyzed levels of proteins that control translation of CEBPA mRNA, namely heterogeneous nuclear ribonucleoprotein E2, calreticulin, eukaryotic translation initiation factor (eIF4E), and 4E binding protein.

RESULTS

Compared with healthy control subjects, BSM cells of asthmatic patients proliferate faster (2.1-fold) and are primed for IL-6 secretion. Real-time RT-PCR showed that BSM cells of asthmatic patients express normal levels of CEBPA mRNA, whereas they express lower levels of C/EBPalpha (p42). Transient transfections with the translation control reporter system construct showed a disturbed p12/p23 ratio in BSM cells of asthmatic patients relative to healthy control subjects, which coincided with lower levels of eIF4E.

CONCLUSION

BSM cells of asthmatic patients have normal levels of CEBPA mRNA but inadequately reinitiate the translation into C/EBPalpha. Impaired translation control upstream of eIF4E might underlie the observed increased proliferation and priming of BSM cells of asthmatic patients.

Airway smooth muscle contraction - perspectives on past, present and future

Past and contemporary views of airway smooth muscle (ASM) have led to a high level of understanding of the control and intracellular regulation of force or shortening of ASM and of its possible role in airway disease. As well as the multitude of cellular mechanisms that regulate ASM contraction, a number of structural and mechanical factors, which are only present at the airway and lung level, provide overriding control over ASM. With new knowledge about the cellular physiology and biology of ASM, there is increasing need to understand how ASM contraction is regulated and expressed at these airway and system levels.

Airway smooth muscle in asthma: phenotype plasticity and function

Clinical asthma is characterized by reversible airway obstruction which is commonly due to an exaggerated airway narrowing referred to as airway hyperresponsiveness (AHR). Although debate exists on the complex etiology of AHR, it is clear that airway smooth muscle (ASM) mediated airway narrowing is a major contributor to airway dysfunction. More importantly, it is now appreciated that smooth muscle is far from being a simple cell with only contractile ability properties. Rather, it is more versatile with the capacity to exhibit numerous cellular functions as it adapts to the microenvironment to which it is exposed. The emerging ability of individual smooth muscle cells to undergo changes in their phenotype (phenotype plasticity) and function (functional plasticity) in response to physiological and pathological cues is an important and active area of research. This article provides a brief review of the current knowledge and emerging concepts in the field of ASM phenotype and function both under healthy and asthmatic conditions.

[Bronchial thermoplasty: report on the first endoscopic treatment for asthma in Latin America]

Bronchial thermoplasty is a new bronchoscopic procedure that delivers radiofrequency energy to the airway and potentially reduces the smooth muscle-mediated bronchoconstriction. We report the case of a 48-year-old man with persistent moderate asthma submitted to bronchial thermoplasty. The treatment increased the forced expiratory volume in one second, increased the number of symptom-free days, reduced the use of relief medications, and improved the Juniper Asthma Quality of Life Scale score. In this patient, bronchial thermoplasty was well tolerated and safe. This was the first bronchial thermoplasty performed in Latin America. At 12 months after the procedure, the results were encouraging in terms of its potential benefits in patients with difficult-to-control 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.

A contraction assay system using established human bronchial smooth muscle cells

BACKGROUND

To further understand the mechanisms of airway obstruction in asthma, it is crucial to investigate contractile responses of human airway smooth muscle. An in vitro assay system employing collagen gels embedded with well-established bronchial smooth muscle cells of human origin was explored in the present study.

METHODS

Commercially available cultured human bronchial smooth muscle cells were embedded into a collagen gel. Well-known constrictors, histamine and methacholine, were added to the gel. The gel images were captured by an image analyzer, and contractile responses were evaluated.

RESULTS

Histamine and methacholine induced contraction of the gels in a dose-dependent manner. Pyrilamine, an H1 receptor antagonist, inhibited gel contraction in an agonist-specific manner.

CONCLUSION

Our contraction assay system, employing widely distributed cultured cells, was highly reproducible and precise. It may go a long way toward understanding mechanisms of asthmatic responses and evaluation of antiasthma drugs.

Risk factors associated with irreversible airflow limitation in asthma

PURPOSE OF REVIEW

Irreversible airflow limitation develops in some patients with asthma and is related to poorer prognosis. This paper reviews recent literature on natural course, risk factors, and potential mechanisms of persistent airflow limitation in asthma.

RECENT FINDINGS

The natural course of persistent airflow limitation in asthma is poorly known, but reduced lung function at disease onset and an increased rate of decline during adult life contribute to its development. Risk factors for progressive irreversible airway obstruction in asthma include adult onset, frequent exacerbations, smoking, occupational exposure, ongoing eosinophilic airway inflammation and airway hyperresponsiveness. Polymorphisms of the ADAM33 gene predict excess decline in lung function, in asthma as well as at population level. It is still not clear how different components of airway remodeling affect lung function in asthma. Airway epithelium and airway smooth muscle seem to be highly important, but the interrelationship between persistent airflow limitation, airway inflammation, remodeling and airway hyperresponsiveness has not been clearly defined.

SUMMARY

Whereas several factors have been implicated as being important in the development of fixed airway obstruction in asthma, we are just beginning to explore the different components of airway remodeling and their relevance, deleterious or beneficial, to clinical outcome.

Gene expression in asthmatic airway smooth muscle

Airway smooth muscle abnormalities are central to the pathophysiology of asthma. These airway smooth muscle cell abnormalities may include changes in cell number, size, phenotype, or function. Gene expression studies performed using asthmatic airway smooth muscle cells represent one approach to identifying the abnormalities of airway smooth muscle that occur in asthma in vivo. However, due to the technical challenges involved, only two studies have been performed to date using freshly obtained tissue from subjects with asthma. The first of these studies suggested increased expression of myosin light-chain kinase in airway smooth muscle from patients with asthma, whereas the second study found no difference in myosin light-chain kinase expression, nor any difference in other markers of smooth muscle phenotype in asthma. Studies performed in cell culture through the application of gene expression microarrays to profile airway smooth muscle cells exposed to potential mediators of asthma yield more consistent results, including induction by IL-13 of tenascin, the H1 histamine receptor, and IL-13 receptor subunits. However, the significance of these microarray findings for smooth muscle function is uncertain. Furthermore, gene expression studies have a fundamental limitation in that many functional properties of airway smooth muscle are regulated at other levels (e.g., protein phosphorylation). Thus, gene expression studies ultimately must be integrated with other methodological approaches to adequately study airway smooth muscle in asthma in vivo.

Nuclear factor-kappaB activation in airway epithelium induces inflammation and hyperresponsiveness

RATIONALE

Nuclear factor (NF)-kappaB is a prominent proinflammatory transcription factor that plays a critical role in allergic airway disease. Previous studies demonstrated that inhibition of NF-kappaB in airway epithelium causes attenuation of allergic inflammation.

OBJECTIVES

We sought to determine if selective activation of NF-kappaB within the airway epithelium in the absence of other agonists is sufficient to cause allergic airway disease.

METHODS

A transgenic mouse expressing a doxycycline (Dox)-inducible, constitutively active (CA) version of inhibitor of kappaB (IkappaB) kinase-beta (IKKbeta) under transcriptional control of the rat CC10 promoter, was generated.

MEASUREMENTS AND MAIN RESULTS

After administration of Dox, expression of the CA-IKKbeta transgene induced the nuclear translocation of RelA in airway epithelium. IKKbeta-triggered activation of NF-kappaB led to an increased content of neutrophils and lymphocytes, and concomitant production of proinflammatory mediators, responses that were not observed in transgenic mice not receiving Dox, or in transgene-negative littermate control animals fed Dox. Unexpectedly, expression of the IKKbeta transgene in airway epithelium was sufficient to cause airway hyperresponsiveness and smooth muscle thickening in absence of an antigen sensitization and challenge regimen, the presence of eosinophils, or the induction of mucus metaplasia.

CONCLUSIONS

These findings demonstrate that selective activation NF-kappaB in airway epithelium is sufficient to induce airway hyperresponsiveness and smooth muscle thickening, which are both critical features of allergic airway disease.

Airway smooth muscle in bronchial tone, inflammation, and remodeling: basic knowledge to clinical relevance

Airway smooth muscle (ASM) plays a pivotal role in modulating bronchomotor tone but also orchestrates and perpetuates airway inflammation and remodeling. Despite substantial research, there remain important unanswered questions. In 2006, the National Heart, Lung, and Blood Institute sponsored a workshop to define new directions in ASM biology. Important questions concerning the key functions of ASM include the following: Does developmental dysregulation of ASM function promote airway disease, what key signaling pathways in ASM evoke airway hyperresponsiveness in vivo, do alterations in ASM mass affect excitation-contraction coupling, and can ASM modulate airway inflammation and remodeling in a physiologically relevant manner? This workshop identified critical issues in ASM biology to delineate areas for scientific investigation in the identification of new therapeutic and diagnostic approaches in asthma, chronic obstructive pulmonary disease, and cystic fibrosis.

The synergistic interactions of allergic lung inflammation and intratracheal cationic protein

RATIONALE

Airways hyperresponsiveness (AHR) is a hallmark feature of asthma, and can be caused by various disparate mechanisms. Mouse models of AHR have been useful for studying these mechanisms in isolation, but such models still typically do not exhibit the same degree of AHR as seen in severe human asthma. We hypothesized that more severe AHR in mice could be achieved by imbuing them with more than one mechanism of AHR.

OBJECTIVES

We sought to determine if the airway wall thickening accompanying allergic inflammation and the exaggerated smooth muscle shortening induced by intratracheal cationic protein could act together to produce a severe form of AHR.

METHODS

We used the forced oscillation technique to measure methacholine responsiveness in BALB/c mice that had been sensitized and challenged with ovalbumin followed by an intratracheal instillation of poly-l-lysine.

MEASUREMENTS AND MAIN RESULTS

We found that both ovalbumin and poly-l-lysine treatment alone caused moderate levels of AHR. When the two treatments were combined, however, they synergized in terms of their effect on lung stiffness to an extent that could even be fatal, reflecting a significantly enhanced level of airway closure.

CONCLUSIONS

Our results suggest that mechanistic synergy between airway wall thickening and exaggerated smooth muscle shortening produces a more germane mouse model of asthma that may have particular relevance to the pathophysiology of the acute severe asthma exacerbation.

Airway smooth muscle dynamics: a common pathway of airway obstruction in asthma

Excessive airway obstruction is the cause of symptoms and abnormal lung function in asthma. As airway smooth muscle (ASM) is the effecter controlling airway calibre, it is suspected that dysfunction of ASM contributes to the pathophysiology of asthma. However, the precise role of ASM in the series of events leading to asthmatic symptoms is not clear. It is not certain whether, in asthma, there is a change in the intrinsic properties of ASM, a change in the structure and mechanical properties of the noncontractile components of the airway wall, or a change in the interdependence of the airway wall with the surrounding lung parenchyma. All these potential changes could result from acute or chronic airway inflammation and associated tissue repair and remodelling. Anti-inflammatory therapy, however, does not "cure" asthma, and airway hyperresponsiveness can persist in asthmatics, even in the absence of airway inflammation. This is perhaps because the therapy does not directly address a fundamental abnormality of asthma, that of exaggerated airway narrowing due to excessive shortening of ASM. In the present study, a central role for airway smooth muscle in the pathogenesis of airway hyperresponsiveness in asthma is explored.

Asthma: new developments concerning immune mechanisms, diagnosis and treatment

PURPOSE OF REVIEW

This brief review discusses how recent research may modify our understanding of the immunology of asthma. Consideration is given to the possible impact that these observations may have upon diagnostic and therapeutic strategies.

RECENT FINDINGS

New studies indicate that current conceptions regarding the balance between Th1 and Th2 systems may need modification. The relationship between infection and the development of asthma in children has proven to be much more complex than originally suggested by the 'hygiene hypothesis'. In addition, important genetic differences have been found in the response of asthmatic patients to therapeutic agents.

SUMMARY

Greater insight into the mechanisms responsible for asthma and the introduction of new drugs will depend in part upon the development of reliable and simple methods for detecting airway inflammation. As the immunologic aspects of asthma are dissected, we can expect that many more potential targets for treatment will be discovered, but treatment may have to be individualized for genetic differences between different individuals.

Collagen I and thrombin activate MMP-2 by MMP-14-dependent and -independent pathways: implications for airway smooth muscle migration

Increased proinflammatory mediators and ECM deposition are key features of the airways in asthma. Matrix metalloproteinases (MMPs) are produced by airway smooth muscle (ASM) cells and have multiple roles in inflammation and tissue remodeling. We hypothesized that components of the asthmatic airway would stimulate MMP production and activation by ASM and contribute to airway remodeling. We measured human ASM-derived MMP mRNA, protein, and activity by real-time RT-PCR, zymography, Western blotting, and MMP activity assay. Collagen I and thrombin caused a synergistic increase in MMP-2 protein and total MMP activity but paradoxically decreased MMP-2 mRNA. Additionally, collagen I activated MMP-2 in culture supernatants independent of the cell surface. Together, collagen I and thrombin strongly enhanced MMP-14 mRNA and protein but had no effect individually, suggesting increased MMP-14, the activating protease for MMP-2, may be partially responsible for MMP-2 activation. Furthermore, collagen I reduced tissue inhibitor of metalloproteinase-2 protein (TIMP-2). We examined the role of MMPs in functions of ASM related to airway remodeling and found migration and proliferation were MMP dependent, whereas adhesion and apoptosis were not. Ilomastat inhibited migration by 25%, which was also inhibited by TIMPs 1-4 and increased by the MMP-2 activator thrombin. These in vitro findings suggest that the environment within the airways of patients with asthma enhances MMP-2 and -14 protein and activity by a complex interaction of transcriptional and posttranscriptional mechanisms, which may contribute to ASM migration.

Disease-specific expression and regulation of CCAAT/enhancer-binding proteins in asthma and chronic obstructive pulmonary disease

BACKGROUND

CCAAT/enhancer-binding proteins (C/EBPs) control cell proliferation; lack of C/EBPalpha correlates with increased proliferation of bronchial smooth muscle cells (BSMCs) of asthmatic patients.

OBJECTIVE

We sought to assess disease-specific expression of C/EBPalpha, beta, delta, and epsilon and the effects of budesonide (10(-8) mol/L) and formoterol (10(-8) mol/L).

METHODS

Expression and function of C/EBPalpha, beta, delta, and epsilon BSMCs of control subjects (n = 9), asthmatic patients (n = 12), and patients with chronic obstructive pulmonary disease (COPD; n = 10) were determined.

RESULTS

The control group expressed C/EBPalpha, beta, delta, and epsilon, which were upregulated by serum (5%). Budesonide completely inhibited C/EBPalpha and beta expression; formoterol increased C/EBPalpha expression (2-fold). C/EBPdelta and epsilon expression were not affected by the drugs. The asthmatic group did not appropriately express C/EBPalpha. Basal levels of C/EBPbeta, delta, and epsilon were upregulated by serum (5%). Budesonide and formoterol increased C/EBPbeta levels (3.4-fold and 2.5-fold, respectively), leaving C/EBPalpha, delta, and epsilon levels unaffected. The COPD group normally expressed C/EBPalpha, beta, and epsilon, which were upregulated by serum treatment (5%). Basal levels of C/EBPdelta were downregulated by serum in 7 of 10 BSMC lines. Budesonide inhibited C/EBPalpha and beta expression, upregulated C/EBPdelta (3.2-fold), and had no effect on C/EBPepsilon. Formoterol upregulated C/EBPalpha expression (3-fold) but not the other C/EBPs. Protein analysis and electrophoretic mobility shift assay confirmed the disease-specific expression pattern of C/EBPalpha in asthmatic patients and C/EBPdelta in patients with COPD.

CONCLUSIONS

The expression and regulation of C/EBPs in BSMCs of asthmatic patients and patients with COPD seems disease specific. Budesonide and formoterol modulate C/EBP expression in a drug- and disease-specific pattern.

CLINICAL IMPLICATIONS

The data could provide a method to discriminate between asthma and COPD at an early disease stage.