Differences in airway remodeling between asthma and chronic obstructive pulmonary disease

Inhibition of acrolein-stimulated MUC5AC expression by Platycodon grandiflorum root-derived saponin in A549 cells

Mucin overproduction is a hallmark of chronic airway diseases such as chronic obstructive pulmonary disease. In this study, we investigated the inhibition of acrolein-induced expression of mucin 5, subtypes A and C (MUC5AC) by Changkil saponin (CKS) in A549 cells. Acrolein, a known toxin in tobacco smoke and an endogenous mediator of oxidative stress, increases the expression of airway MUC5AC, a major component of airway mucus. CKS, a Platycodon grandiflorum root-derived saponin, inhibited acrolein-induced MUC5AC expression and activity, through the suppression of NF-κB activation. CKS also repressed acrolein-induced phosphorylation of ERK1/2, JNK1/2, and p38MAPK, which are upstream signaling molecules that control MUC5AC expression. In addition, the MAPK inhibitors PD98059 (ERK1/2), SP600125 (JNK1/2), and SB203580 (p38 MAPK), and a PKC delta inhibitor (rottlerin; PKCδ) inhibited acrolein-induced MUC5AC expression and activity. CKS repressed acrolein-induced phosphorylation of PKCδ. Moreover, a reactive oxygen species (ROS) inhibitor, N-acetylcysteine, inhibited acrolein-induced MUC5AC expression and activity through the suppression of PKCδ and MAPK activation, and CKS repressed acrolein-induced ROS production. These results suggest that CKS suppresses acrolein-induced MUC5AC expression by inhibiting the activation of NF-κB via ROS-PKCδ-MAPK signaling.

Harnessing the clinical efficacy of phosphodiesterase 4 inhibitors in inflammatory lung diseases: dual-selective phosphodiesterase inhibitors and novel combination therapies

Phosphodiesterase (PDE) 4 inhibitors have been in development as a novel anti-inflammatory therapy for more than 20 years, with asthma and chronic obstructive pulmonary disease (COPD) being primary indications. Despite initial optimism, only one selective PDE4 inhibitor, roflumilast (Daxas (®)), has been approved for use in humans and available in Canada and the European Union in 2011 for the treatment of a specific population of patients with severe COPD. In many other cases, the development of PDE4 inhibitors of various structural classes has been discontinued due to lack of efficacy and/or dose-limiting adverse events. Indeed, for many of these compounds, it is likely that the maximum tolerated dose is either subtherapeutic or at the very bottom of the efficacy dose-response curve. Thus, a significant ongoing challenge that faces the pharmaceutical industry is to synthesize compounds with therapeutic ratios that are superior to roflumilast. Several strategies are being considered, but clinically effective compounds with an optimal pharmacophore have not, thus far, been reported. In this chapter, alternative means of harnessing the clinical efficacy of PDE4 inhibitors are described. These concepts are based on the assumption that additive or synergistic anti-inflammatory effects can be produced with inhibitors that target either two or more PDE families or with a PDE4 inhibitor in combination with other anti-inflammatory drugs such as a glucocorticoid.

Mouse models to unravel the role of inhaled pollutants on allergic sensitization and airway inflammation

Air pollutant exposure has been linked to a rise in wheezing illnesses. Clinical data highlight that exposure to mainstream tobacco smoke (MS) and environmental tobacco smoke (ETS) as well as exposure to diesel exhaust particles (DEP) could promote allergic sensitization or aggravate symptoms of asthma, suggesting a role for these inhaled pollutants in the pathogenesis of asthma. Mouse models are a valuable tool to study the potential effects of these pollutants in the pathogenesis of asthma, with the opportunity to investigate their impact during processes leading to sensitization, acute inflammation and chronic disease. Mice allow us to perform mechanistic studies and to evaluate the importance of specific cell types in asthma pathogenesis. In this review, the major clinical effects of tobacco smoke and diesel exhaust exposure regarding to asthma development and progression are described. Clinical data are compared with findings from murine models of asthma and inhalable pollutant exposure. Moreover, the potential mechanisms by which both pollutants could aggravate asthma are discussed.

Oxidative stress induced lung cancer and COPD: opportunities for epigenetic therapy

Reactive oxygen species (ROS) form as a natural by-product of the normal metabolism of oxygen and play important roles within the cell. Under normal circumstances the cell is able to maintain an adequate homeostasis between the formation of ROS and its removal through particular enzymatic pathways or via antioxidants. If however, this balance is disturbed a situation called oxidative stress occurs. Critically, oxidative stress plays important roles in the pathogenesis of many diseases, including cancer. Epigenetics is a process where gene expression is regulated by heritable mechanisms that do not cause any direct changes to the DNA sequence itself, and disruption of epigenetic mechanisms has important implications in disease. Evidence is emerging that histone deacetylases (HDACs) play decisive roles in regulating important cellular oxidative stress pathways including those involved with sensing oxidative stress and those involved with regulating the cellular response to oxidative stress. In particular aberrant regulation of these pathways by HDACs may play critical roles in cancer progression. In this review we discuss the current evidence linking epigenetics and oxidative stress and cancer, using chronic obstructive pulmonary disease and non-small cell lung cancer to illustrate the importance of epigenetics on these pathways within these disease settings.

Leukocyte elastase induces lung epithelial apoptosis via a PAR-1-, NF-kappaB-, and p53-dependent pathway

Leukocyte elastase induces apoptosis of lung epithelial cells via alterations in mitochondrial permeability, but the signaling pathways regulating this response remain uncertain. Here we investigated the involvement of proteinase-activated receptor-1 (PAR-1), the transcription factor NF-kappaB, and the protooncogene p53 in this pathway. Elastase-induced apoptosis of lung epithelial cells correlated temporally with activation of NF-kappaB, phosphorylation, and nuclear translocation of p53, increased p53 up-regulated modulator of apoptosis (PUMA) expression, and mitochondrial translocation of Bax resulting in enhanced permeability. Elastase-induced apoptosis was also prevented by pharmacologic inhibitors of NF-kappaB and p53 and by short interfering RNA knockdown of PAR-1, p53, or PUMA. These inhibitors prevented elastase-induced PUMA expression, mitochondrial translocation of Bax, increased mitochondrial permeability, and attenuated apoptosis. NF-kappaB inhibitors also reduced p53 phosphorylation. We conclude that elastase-induced apoptosis of lung epithelial cells is mediated by a PAR-1-triggered pathway involving activation of NF-kappaB and p53, and a PUMA- and Bax-dependent increase in mitochondrial permeability leading to activation of distal caspases. Further, p53 contributes to elastase-induced apoptosis by both transcriptional and post-transcriptional mechanisms.

A Holy Grail of asthma management: toward understanding how long-acting beta(2)-adrenoceptor agonists enhance the clinical efficacy of inhaled corticosteroids

There is unequivocal evidence that the combination of an inhaled corticosteroid (ICS) -- i.e. glucocorticoid -- and an inhaled long-acting beta(2)-adrenoceptor agonist (LABA) is superior to each component administered as a monotherapy alone in the clinical management of asthma. Moreover, Calverley and colleagues (Lancet 2003, 361: 449-456; N Engl J Med 2007, 356: 775-789) reporting for the 'TRial of Inhaled STeroids ANd long-acting beta(2)-agonists (TRISTAN)' and 'TOwards a Revolution in COPD Health (TORCH)' international study groups also demonstrated the superior efficacy of LABA/ICS combination therapies over ICS alone in the clinical management of chronic obstructive pulmonary disease. This finding has been independently confirmed indicating that the therapeutic benefit of LABA/ICS combination therapies is not restricted to asthma and may be extended to other chronic inflammatory diseases of the airways. Despite the unquestionable benefit of LABA/ICS combination therapies, there is a vast gap in our understanding of how these two drugs given together deliver superior clinical efficacy. In this article, we review the history of LABA/ICS combination therapies and critically evaluate how these two classes of drugs might interact at the biochemical level to suppress pro-inflammatory responses. Understanding the molecular basis of this fundamental clinical observation is a Holy Grail of current respiratory diseases research as it could permit the rational exploitation of this effect with the development of new 'optimized' LABA/ICS combination therapies.

Animal models of asthma

Animal models of asthma are a tool that allows studies to be conducted in the setting of an intact immune and respiratory system. These models have highlighted the importance of T-helper type 2 driven allergic responses in the progression of asthma and have been useful in the identification of potential drug targets for interventions involving allergic pathways. However, a number of drugs that have been shown to have some efficacy in animal models of asthma have shown little clinical benefit in human asthmatics. This may be due to a number of factors including the species of animal chosen and the methods used to induce an asthmatic phenotype in animals that do not normally develop a disease that could be characterized as asthma. The range of animal models available is vast, with the most popular models being rodents (inbred mice and rats) and guinea-pigs, which have the benefit of being easy to handle and being relatively cost effective compared with other models that are available. The recent advances in transgenic technology and the development of species-specific probes, particularly in mice, have allowed detailed mechanistic studies to be conducted. Despite these advances in technology, there are a number of issues with current animal models of asthma that must be recognized including the disparity in immunology and anatomy between these species and humans, the requirement for adjuvant during senitization in most models, the acute nature of the allergic response that is induced and the use of adult animals as the primary disease model. Some larger animal models using sheep and dogs have been developed that may address some of these issues but they also have different biology from humans in many ways and are extremely costly, with very few probes available for characterizing allergic responses in the airway in these species. As research in this area continues to expand, the relative merits and limitations of each model must be defined and understood in order to evaluate the information that is obtained from these models and to extrapolate these findings to humans so that effective drug therapies can be developed. Despite these issues, animal models have been, and will continue to be, vital in understanding the mechanisms that are involved in the development and progression of asthma.

Targeting the phosphatidylinositol 3-kinase pathway in airway smooth muscle: rationale and promise

The phosphatidylinositol 3-kinase (PI3K) signaling pathway plays a critical role in regulating cell growth, proliferation, survival, and motility. Structural alterations, e.g. airway remodeling, in asthma and chronic obstructive pulmonary disease (COPD) are associated with increased airway smooth muscle (ASM) cell growth and proliferation due to the frequent stimulation of ASM by inflammatory mediators, contractile agonists, and growth factors. The critical role of the PI3K signaling pathway in regulating ASM cell growth and proliferation is well established. However, recent discovery of the tumor suppressor proteins tuberous sclerosis complex 1 (TSC1) and TSC2, also known as hamartin and tuberin, as downstream effectors of PI3K and upstream regulators of the mammalian target of rapamycin (mTOR) and S6 kinase 1(S6K1) shed a new light on the PI3K signaling cascade in regulating cell growth and proliferation. The activity of TSC1/TSC2 is regulated by growth factors, nutrients, and energy; thus, TSC1/TSC2 serves as a signaling module for protein translational regulation, cell cycle progression, and cell size, which are key events controlling cell growth and proliferation. This article highlights the potential contribution of the PI3K-TSC1/TSC2-mTOR/S6K1 pathway in smooth muscle remodeling. Pharmacologic manipulation of this signaling pathway could have a major impact on treatment of asthma and COPD.

Cell death, remodeling, and repair in chronic obstructive pulmonary disease?

Apoptotic cells can be detected in the parenchyma and airways of patients with chronic obstructive pulmonary disease (COPD) in greater numbers than seen in normal lungs or those from smokers without COPD. Implications include more apoptosis and/or decreased clearance of apoptotic cells. Both epithelial and endothelial cells become apoptotic. What role does the apoptosis play in the emphysema or small airway alterations seen in COPD? In simple terms, loss of cells by apoptosis would be expected to accompany, or perhaps initiate, the overall tissue destruction normally believed responsible. Indeed, direct induction of apoptosis in pulmonary endothelial or epithelial cells in rodents is accompanied by emphysematous changes. On the other hand, apoptotic cells are normally removed from tissues rapidly with minimal tissue response, to be followed by cell replacement to maintain homeostasis. The presence of detectable apoptotic cells, therefore, may imply defects in these clearance mechanisms, and, in keeping with this hypothesis, there is increasing evidence for such defects in patients with COPD. Mice with abnormalities in apoptotic cell removal also tend to develop spontaneous "emphysema." A reconciling hypothesis is that recognition of apoptotic cells not only leads to removal but also, normally, to signals for cell replacement. If this latter response is lacking in COPD-susceptible smokers, defects in normal alveolar or small airway repair could significantly contribute to the structural disruption. The concept puts emphasis on defective repair as well as initial injury (i.e., persistent alteration of dynamic tissue homeostasis, as a key contributor to COPD), with, it is hoped, additional approaches for mitigation.

CD4/CD8 ratio and cytokine levels of the BAL fluid in patients with bronchiectasis caused by sulfur mustard gas inhalation

Objective

To analyze cytokine levels in BAL fluid of patients with bronchiectasis due to mustard gas inhalation.

Patients

29 victims with mustard gas-induced bronchiectasis and 25 normal veterans as control group.

Intervention

PFTs,, high-resolution CT scans of the chest, analyses of BAL fluids for five cytokines (IL-8, IL-1β, IL-6, TNF-α, IL-12) and analyses of BAL fluids for cellular and flow-cytometric analysis of the phenotype of bronchoalveolar cells were performed in all cases.

Results

CD4 lymphocytes expressed as percentage or absolute number were significantly higher in patients with bronchiectasis than in controls (32.17 ± 16.00 vs 23.40 ± 6.97%, respectively; p = 0.01; and 3.31 ± 2.03 vs 1.88 ± 0.83 × 10³ cells/ml, respectively; p = 0.001). The CD4/CD8 ratio was significantly higher in patients with bronchiectasis than in controls (3.08 ± 2.05 vs 1.68 ± 0.78; p = 0.002).

There were significant differences in cytokine (IL-8, IL-1β, IL-6, TNF-α, IL-12) levels of BAL fluid between patients with bronchiectasis and healthy controls.

A significant correlation was observed between the HRCT scores and both the percentage and the absolute number of CD4 lymphocytes in BAL fluid in patients with bronchiectasis (r = -0.49, p = 0.009; r = -0.50, p = 0.008; respectively). HRCT scores showed a significant correlation with CD4/CD8 ratios (r = 0.54, p = 0.004) too.

Of measured BAL cytokines, only IL-8 (r = -0.52, p = 0.005) and TNF-aα (r = 0.44, p = 0.01) showed significant correlations with the HRCT scores.

Conclusion

The increased levels of cytokines CD4 lymphocytes in the BAL fluid suggest the possible causative mechanism in the lung in sulfur mustard gas-induced bronchiectasis by the recruitment of neutrophils into the lung.

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.

Rapidly changing perspectives about mast cells at mucosal surfaces

Mast cells (MCs) are major effector cells of immunoglobulin E (IgE)-mediated allergic inflammation. However, it has become increasingly clear that they also play important roles in diverse physiological and pathological processes. Recent advances have focused on the importance of MCs in both innate and adaptive immune responses and have fostered studies of MCs beyond the myopic focus on allergic reactions. MCs possess a variety of surface receptors and may be activated by inflammatory mediators, IgE, IgG, light chains, complement fragments, proteases, hormones, neuropeptides, and microbial products. Following activation, they produce a plethora of pro-inflammatory mediators and participate in inflammatory reactions in many organs. This review focuses on the role of MCs in inflammatory reactions in mucosal surfaces with particular emphasis on their role in respiratory and gastrointestinal inflammatory conditions.

Tumor necrosis factor-alpha overexpression in lung disease: a single cause behind a complex phenotype

RATIONALE

Tumor necrosis factor alpha (TNF-alpha) has been implicated as a key cytokine in many inflammatory lung diseases. These effects are currently unclear, because a transgenic mouse overexpressing TNF-alpha in the lung has been shown in separate studies to produce elements of both emphysema and pulmonary fibrosis.

OBJECTIVES

We sought to elucidate the phenotypic effects of TNF-alpha overexpression in a mouse model.

MEASUREMENTS

We established the phenotype by measuring lung impedance and thoracic gas volume, and using micro-computed tomography and histology.

MAIN RESULTS

We found that airways resistance in this mouse was not different to control mice, but that lung tissue dampening, elastance, and hysteresivity were significantly elevated. Major heterogeneous abnormalities of the parenchyma were also apparent in histologic sections and in micro-computed tomography images of the lung. These changes included airspace enlargement, loss of small airspaces, increased collagen, and thickened pleural septa. We also found significant increases in lung and chest cavity volumes in the TNF-alpha-overexpressing mice.

CONCLUSIONS

We conclude that TNF-alpha overexpression causes pathologic changes consistent with both emphysema and pulmonary fibrosis combined with a general lung inflammation, and consequently does not model any single human disease. Our study thus confirms the pleiotropic effects of TNF-alpha, which has been implicated in multiple inflammatory disorders, and underscores the necessity of using a wide range of investigative techniques to link gene expression and phenotype in animal models of disease.