Inducible targeting of IL-13 to the adult lung causes matrix metalloproteinase- and cathepsin-dependent emphysema

Association of TNF-α -308G/A, SP-B 1580 C/T, IL-13 -1055 C/T gene polymorphisms and latent adenoviral infection with chronic obstructive pulmonary disease in an Egyptian population

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a leading cause of disability and death. The most common cause of COPD is smoking. There is evidence suggesting that genetic factors influence COPD susceptibility and variants in several candidate genes have been significantly associated with COPD. In this study, we aimed to investigate the possible association of the TNF-α -308, SPB+1580, IL-13 -1055 gene polymorphisms and latent adenovirus C infection with COPD in an Egyptian population.

MATERIAL AND METHODS

Our study included 115 subjects (75 smokers with COPD, 25 resistant smokers and 15 non-smokers) who were subjected to spirometric measurements, identification of adenovirus C and genotyping of TNF-α -308G/A, SP-B+1580 C/T and IL-13 -1055 C/T polymorphisms by real-time PCR.

RESULTS

The adenovirus C gene was identified in all subjects. The distribution of TNF-α genotypes showed no significant differences between different groups. However, homozygous A genotype was associated with a significant decrease in FEV(1), FEV(1)/FVC and FEF25/75% of predicted in COPD (p < 0.05). As regards SP-B genotypes, resistant smokers had a significantly higher homozygous T genotype frequency compared to COPD and non smokers (p = 0.005). Interleukin 13 genotypes showed no significant difference between different groups. There was a significant decrease in FEF25/75% of predicted in T allele carriers in COPD patients (p = 0.001).

CONCLUSIONS

The COPD is a disease caused by the interaction of combined genes and environmental influences, in the presence of smoking and latent adenovirus C infection, TNF-α -308A, SPB +1580 T and IL-13 -1055 T polymorphisms predispose to the development of COPD.

Identification of an interleukin 13-induced epigenetic signature in allergic airway inflammation

Epigenetic changes have been implicated in the pathogenesis of asthma. We sought to determine if IL13, a key cytokine in airway inflammation and remodeling, induced epigenetic DNA methylation and miRNAs expression changes in the airways in conjunction with its transcriptional gene regulation. Inducible expression of an IL13 transgene in the airways resulted in significant changes in DNA methylation in 177 genes, most of which were associated with the IL13 transcriptional signature in the airways. A large number of genes whose expression was induced by IL13 were found to have decreased methylation, including those involved in tissue remodeling (Olr1), leukocyte influx (Cxcl3, Cxcl5, CSFr2b), and the Th2 response (C3ar1, Chi3l4). Reciprocally, some genes whose expression was suppressed were found to have increased methylation (e.g. Itga8). In addition, miRNAs were identified with targets for lung development and Wnt signaling, amongst others. These results indicate that IL13 confers an epigenetic methylation and miRNA signature that accompanies its transcriptional program in the airways, which may play a critical role in airway inflammation and remodeling.

Targeted deletion of Jun/AP-1 in alveolar epithelial cells causes progressive emphysema and worsens cigarette smoke-induced lung inflammation

Chronic obstructive pulmonary disease appears to occur slowly and progressively over many years, with both genetic factors and environmental modifiers contributing to its pathogenesis. Although the c-Jun/activator protein 1 transcriptional factor regulates cell proliferation, apoptosis, and inflammatory responses, its role in lung pathogenesis is largely unknown. In this study, we report decreased expression levels of c-Jun mRNA and protein in the lung tissues of patients with advanced chronic obstructive pulmonary disease, and the genetic deletion of c-Jun specifically in alveolar epithelial cells causes progressive emphysema with lung inflammation and alveolar air space enlargement, which are cardinal features of emphysema. Although mice lacking c-Jun specifically in lung alveolar epithelial cells appear normal at the age of 6 weeks, when exposed to long-term cigarette smoke, c-Jun-mutant mice display more lung inflammation with perivascular and peribronchiolar infiltrates compared with controls. These results demonstrate that the c-Jun/activator protein 1 pathway is critical for maintaining lung alveolar cell homeostasis and that loss of its expression can contribute to lung inflammation and progressive emphysema.

Studies of vascular endothelial growth factor in asthma and chronic obstructive pulmonary disease

Vascular endothelial growth factor (VEGF) is a potent stimulator of vascular angiogenesis, permeability, and remodeling that also plays important roles in wound healing and tissue cytoprotection. To begin to define the roles of VEGF in diseases like asthma and COPD, we characterized the effects of lung-targeted transgenic VEGF(165) and defined the innate immune pathways that regulate VEGF tissue responses. The former studies demonstrated that VEGF plays an important role in Th2 inflammation because, in addition to stimulating angiogenesis and edema, VEGF induced eosinophilic inflammation, mucus metaplasia, subepithelial fibrosis, myocyte hyperplasia, dendritic cell activation, and airways hyperresponsiveness via IL-13-dependent and -independent mechanisms. VEGF was also produced at sites of aeroallergen-induced Th2 inflammation, and VEGF receptor blockade ameliorated adaptive Th2 inflammation and Th2 cytokine elaboration. The latter studies demonstrated that activation of the RIG-like helicase (RLH) innate immune pathway using viral pathogen-associated molecular patterns such as Poly(I:C) or viruses ameliorated VEGF-induced tissue responses. In accord with these findings, Poly(I:C)-induced RLH activation also abrogated aeroallergen-induced Th2 inflammation. When viewed in combination, these studies suggest that VEGF excess can contribute to the pathogenesis of Th2 inflammatory disorders such as asthma and that abrogation of VEGF signaling via RLH activation can contribute to the pathogenesis of viral disorders such as virus-induced COPD exacerbations. They also suggest that RLH activation may be a useful therapeutic strategy in asthma and related disorders.

Regulating the adaptive immune response to respiratory virus infection

The respiratory tract is a major portal of entry for viruses into the body. Infection of the respiratory tract can, if severe, induce life-threatening damage to the lungs. Various strategies to control virus replication and to limit immune-mediated inflammation and tissue injury have evolved in the respiratory tract.

Multiple innate immune cell types, particularly dendritic cells (DCs), within the pulmonary interstitium and between airway epithelial cells are strategically poised to recognize and sample airway particulates, such as viruses.

In response to respiratory virus infection, several distinct DC subsets are stimulated to migrate from the site of infection in the lungs to the draining lymph nodes. Here, these migrant DCs have a crucial role in initiating the antivirus adaptive immune response to the invading viruses.

After entering the infected lungs, effector T cells that were generated in the lymph nodes undergo further modifications that are shaped by the inflammatory milieu.

Co-stimulatory receptor–ligand interactions between effector T cells and various cell types presenting viral antigens in the infected lungs modulate the host adaptive immune response in situ.

Effector T cells that produce pro-inflammatory mediators are also the major producers of regulatory (anti-inflammatory) cytokines, providing a fine-tuning mechanism of self-control by effector T cells responding to viruses in the inflamed tissue.

The immune mechanisms that control virus replication and/or excessive inflammation in the virus-infected lungs can also predispose the individual recovering from a virus infection to bacterial superinfection. Therapeutic strategies should consider balancing the need to inhibit virus replication and excessive inflammation with the need to optimize the antibacterial functions of innate immune phagocytes, which are crucial for clearing the bacteria from the lungs.

This article reviews the interplay between innate and adaptive immune cells in the response to viral infection of the lower respiratory tract and describes the fine-tuning mechanisms that control antiviral T cells in the lungs but that can also predispose an individual to subsequent pulmonary bacterial infections.

Recent years have seen several advances in our understanding of immunity to virus infection of the lower respiratory tract, including to influenza virus infection. Here, we review the cellular targets of viruses and the features of the host immune response that are unique to the lungs. We describe the interplay between innate and adaptive immune cells in the induction, expression and control of antiviral immunity, and discuss the impact of the infected lung milieu on moulding the response of antiviral effector T cells. Recent findings on the mechanisms that underlie the increased frequency of severe pulmonary bacterial infections following respiratory virus infection are also discussed.

T-cell biology in aging, with a focus on lung disease

T cells are essential for defending hosts against microorganisms and malignancy as well as for regulating the development of immune-mediated inflammatory diseases like autoimmunity. Alterations in T-cell immunity occur with aging, affecting the function and proportions of T-cell subsets. Probably, the most noticeable age-associated change in T-cell immunity is an alteration in the frequency of naive and memory CD4+ and CD8+ T cells. In fact, the frequency of naive CD4+ and CD8+ T cells decreases with aging, whereas the frequency of memory CD4+ and CD8+ T cells increases. Also, changes in T-cell proliferation, cytokine production, memory response, and cytotoxicity as well as in regulatory T-cell number and function have been reported with aging. Such alterations could contribute to the development of infections, malignancies, and inflammatory diseases that rise with aging. Of interest, T cells are closely involved in the development of inflammatory airway and lung diseases including asthma and chronic obstructive pulmonary disease, which are prevalent in the elderly people. In addition, T cells play a major role in defending host against influenza virus infection, a serious medical problem with high morbidity and mortality in the elderly people. Thus, it is conceivable that altered T-cell immunity may account in part for the development of such respiratory problems with aging. Here, we will review the recent advances in T-cell immunity and its alteration with aging and discuss the potential effects of such changes on the lung.

Active cathepsins B, H, K, L and S in human inflammatory bronchoalveolar lavage fluids

BACKGROUND INFORMATION

Chronic inflammation and tissue remodelling result from an imbalance between proteolytic enzymes and their inhibitors in the lungs in favour of proteolysis. While many studies have examined serine proteases (e.g. cathepsin G and neutrophil elastase) and matrix metalloproteases, little is known about the role of papain-like CPs (cysteine proteases). The present study focuses on the thiol-dependent cathepsins (CPs) and their specific cystatin-like inhibitors [CPIs (CP inhibitors)] in human inflammatory BALFs (BAL fluids, where BAL stands for broncho-alveolar lavage).

RESULTS

Cathepsins B, K and S found were mostly zymogens, whereas cathepsins H and L were predominantly in their mature forms. Little immunoreactive cystatin C was found and the high- and low-molecular-mass ('weight') kininogens were extensively degraded. The BALF procathepsins B and L could be activated autocatalytically, indicating that alveolar fluid pro-CPs are reservoirs of mature enzymes. Hydrolysis patterns of 7-amino-4-methylcoumarin-derived peptide substrates showed that extracellular alveolar CPs remain proteolytically active, and that cathepsins B and L are the most abundant thiol-dependent endoproteases. The CP/CPI balance was significantly tipped in favour of cathepsins (3- or 5-fold), as confirmed by the extensive CP-dependent degradation of exogenous kininogens by BALFs.

CONCLUSIONS

Although their importance for inflammation remains to be clarified, the presence of active cathepsins L, K and S suggests that they contribute to the extracellular breakdown of the extracellular matrix.

Assessment of intracellular mucin content in vivo

Airway mucus presents a first line of defense against inhaled materials. It also, however, is a significant pathological contributor to chronic lung diseases, such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease. Thus, gaining a better understanding of the mechanisms of mucus production and secretion is an important goal for improving respiratory health. Mucins, the chief glycoprotein components of airway mucus, are very large polymeric glycoproteins, and measuring their production and secretion in experimental animals presents significant technical challenges. Over the past several years, we have developed assays for accurately quantifying mucin production and secretion using histological and biochemical assays. These methods are described here.

Genetically manipulated mouse models of lung disease: potential and pitfalls

Gene targeting in mice (transgenic and knockout) has provided investigators with an unparalleled armamentarium in recent decades to dissect the cellular and molecular basis of critical pathophysiological states. Fruitful information has been derived from studies using these genetically engineered mice with significant impact on our understanding, not only of specific biological processes spanning cell proliferation to cell death, but also of critical molecular events involved in the pathogenesis of human disease. This review will focus on the use of gene-targeted mice to study various models of lung disease including airways diseases such as asthma and chronic obstructive pulmonary disease, and parenchymal lung diseases including idiopathic pulmonary fibrosis, pulmonary hypertension, pneumonia, and acute lung injury. We will attempt to review the current technological approaches of generating gene-targeted mice and the enormous dataset derived from these studies, providing a template for lung investigators.

Protective effects of basic fibroblast growth factor in the development of emphysema induced by interferon-γ

Recent clinical evidence indicates that the non-eosinophilic subtype of severe asthma is characterized by fixed airway obstruction, which may be related to emphysema. Transgenic studies have demonstrated that high levels of IFN-γ in the airways induce emphysema. Fibroblast growth factor 2 (FGF2), which is the downstream mediator of TGF-β, is important in wound healing. We investigated the role of FGF2 in IFN-γ-induced emphysema and the therapeutic effects of recombinant FGF2 in the prevention of emphysema in a severe non-eosinophilic asthma model. To evaluate the role of FGF2 in IFN-γ-induced emphysema, lung targeted IFN-γ transgenic mice were cross-bred with FGF2-deficient mice. A severe non-eosinophilic asthma model was generated by airway application of LPS-containing allergens twice a week for 4 weeks. To evaluate protective effects of FGF2, recombinant FGF2 (10 μg) was injected subcutaneously during allergen challenge in the severe asthma model. We found that non-eosinophilic inflammation and emphysema induced by transgenic overexpression of IFN-γ in the airways were aggravated by the absence of FGF2. Airway challenge with LPS-containing allergens induced more inflammation in mice sensitized with LPS-containing allergens compared to challenge with allergens alone. In addition, LPS-induced lung inflammation and emphysema depended on IFN-γ but not on IL-13. Interestingly, emphysema in the severe asthma model was significantly inhibited by treatment with recombinant FGF2 during allergen challenge, whereas lung inflammation was unaffected. Therefore, our present data suggest that FGF2 may help protect against IFN-γ-induced emphysema, and that recombinant FGF2 may help lessen the severity of emphysema.

Alterations of serum biomarkers associated with lung ventilation function impairment in coal workers: a cross-sectional study

BACKGROUND

Previous studies have demonstrated that alterations in certain circulating biomarkers may be correlated with Coal workers' pneumoconiosis (CWP). This study investigated the relationship between changes of serum biomarkers and pulmonary function during the development of CWP.

METHODS

Lung function parameters and specific serum indices were measured in 69 non-smoking coal workers, including 34 miners with CWP, 24 asymptomatic miners and 11 miners with minimal symptoms. The associations between changes in pulmonary function and serum indices were tested with Pearson's correlation coefficients. Multivariable analysis was used to estimate the predictive power of potential determinant variables for lung function.

RESULTS

Compared to healthy miners, lung function (FVC, FEV1, FEF50, FEF75, FEF25-75 % of predicted values) was decreased in miners with CWP (p < 0.05). Increased serum matrix metalloproteinase-9 (MMP-9) was associated with decreased FVC% of predicted values in the asymptomatic miners (r = -0.503, p = 0.014).

CONCLUSIONS

In coal mine workers, alterations of lung function parameters are associated with the development of CWP and with changes in circulating MMP-9, TIMP-9, IL-13 and IL-18R. These serum biomarkers may likely reflect the pathogenesis and progression of CWP in coal workers, and may provide for the importance of serum indicators in the early diagnosis of lung function injury in coal miners.

Sputum YKL-40 levels and pathophysiology of asthma and chronic obstructive pulmonary disease

BACKGROUND

Recent evidence suggests that YKL-40, also called chitinase-3-like-1 protein, is involved in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD). Details of sputum YKL-40 in asthma and COPD, however, remain unknown.

OBJECTIVES

To clarify associations of sputum YKL-40 levels with clinical indices in asthma and COPD.

METHODS

Thirty-nine patients with asthma, 14 age-matched never-smokers as controls, 45 patients with COPD, and 7 age-matched smokers as controls were recuited for this study. Sputum YKL-40 levels were measured and YKL-40 expression in sputum cells was evaluated by immunocytochemistry.

RESULTS

Sputum YKL-40 levels were higher in patients with COPD (346 ± 325 ng/ml) than in their smoker controls (125 ± 122 ng/ml; p < 0.05), but were not significantly different between patients with asthma (117 ± 170 ng/ml) and their controls (94 ± 44 ng/ml; p = 0.15). In patients with asthma only, sputum YKL-40 levels were positively correlated with disease severity (r = 0.34, p = 0.034) and negatively correlated with pre- and postbronchodilator %FEV(1) (r = -0.47 and -0.42, respectively; p < 0.01) and forced mid-expiratory flow (r = -0.48 and -0.46, respectively, p < 0.01). Sputum YKL-40 levels were positively correlated with sputum neutrophil counts in asthma (r = 0.55, p < 0.001) and with neutrophil and macrophage counts in COPD (r = 0.45 and 0.65, respectively, p < 0.01). YKL-40 was expressed in the cytoplasm of sputum neutrophils and macrophages in all groups.

CONCLUSIONS

Elevated sputum YKL-40 reflects airflow obstruction in asthma whereas the roles of YKL-40 in the proximal airways in COPD remain to be elucidated.

Studies of intestinal morphology and cathepsin B expression in a transgenic mouse aiming at intestine-specific expression of Cath B-EGFP

Cathepsin B has been shown to not only reside within endo-lysosomes of intestinal epithelial cells, but it was also secreted into the extracellular space of intestinal mucosa in physiological and pathological conditions. In an effort to further investigate the function of this protease in the intestine, we generated a transgenic mouse model that would enable us to visualize the localization of cathepsin B in vivo. Previously we showed that the A33-antigen promoter could be successfully used in vitro in order to express cathepsin B-green fluorescent protein chimeras in cells that co-expressed the intestine-specific transcription factor Cdx1. In this study an analog approach was used to express chimeric cathepsin B specifically in the intestine of transgenic animals. No overt phenotype was observed for the transgenic mice that reproduced normally. Biochemical and morphological studies confirmed that the overall intestinal phenotype including the structure and polarity of this tissue as well as cell numbers and differentiation states were not altered in the A33-CathB-EGFP mice when compared to wild type animals. However, transgenic expression of chimeric cathepsin B could not be visualized because it was not translated in situ although the transgene was maintained over several generations.

Modern concepts on the role of inflammation in pulmonary fibrosis

CONTEXT

Idiopathic pulmonary fibrosis is a uniformly lethal disease with limited biomarkers and no proven therapeutic intervention short of lung transplantation. Pulmonary fibrosis at one time was thought to be a result of inflammation in the lung. Although some forms of pulmonary fibrosis may result from inflammation, idiopathic pulmonary fibrosis is currently thought to result from cell death primarily and inflammation secondarily.

OBJECTIVE

To determine the role of inflammation in pulmonary fibrosis in light of our laboratory's published and unpublished research and published literature.

DATA SOURCES

Review based on our laboratory's published and unpublished experimental data with relevant background and clinical context provided.

CONCLUSIONS

Although cell death is central to pulmonary fibrosis, the proper cytokine environment leading to macrophage polarization is also critical. Evaluation of this environment is promising both for the development of disease biomarkers and for targets for therapeutic intervention.

Regulation of gene expression in human tendinopathy

Background

Chronic tendon injuries, also known as tendinopathies, are common among professional and recreational athletes. These injuries result in a significant amount of morbidity and health care expenditure, yet little is known about the molecular mechanisms leading to tendinopathy.

Methods

We have used histological evaluation and molecular profiling to determine gene expression changes in 23 human patients undergoing surgical procedures for the treatment of chronic tendinopathy.

Results

Diseased tendons exhibit altered extracellular matrix, fiber disorientation, increased cellular content and vasculature, and the absence of inflammatory cells. Global gene expression profiling identified 983 transcripts with significantly different expression patterns in the diseased tendons. Global pathway analysis further suggested altered expression of extracellular matrix proteins and the lack of an appreciable inflammatory response.

Conclusions

Identification of the pathways and genes that are differentially regulated in tendinopathy samples will contribute to our understanding of the disease and the development of novel therapeutics.

A model of chronic inflammation and pulmonary emphysema after multiple ozone exposures in mice

Oxidative stress plays a role in the pathophysiology of emphysema through the activation of tissue proteases and apoptosis. We examined the effects of ozone exposure by exposing BALB/c mice to either a single 3-h exposure or multiple exposures over 3 or 6 wk, with two 3-h exposures per week. Compared with air-exposed mice, the increase in neutrophils in bronchoalveolar lavage fluid and lung inflammation index was greatest in mice exposed for 3 and 6 wk. Lung volumes were increased in 3- and 6-wk-exposed mice but not in single-exposed. Alveolar space and mean linear intercept were increased in 6- but not 3-wk-exposed mice. Caspase-3 and apoptosis protease activating factor-1 immunoreactivity was increased in the airway and alveolar epithelium and macrophages of 3- and 6-wk-exposed mice. Interleukin-13, keratinocyte chemoattractant, caspase-3, and IFN-γ mRNA were increased in the 6-wk-exposed group, but heme oxygenase-1 (HO-1) mRNA decreased. matrix metalloproteinase-12 (MMP-12) and caspase-3 protein expression increased in lungs of 6-wk-exposed mice. Collagen area increased and epithelial area decreased in airway wall at 3- and 6-wk exposure. Exposure of mice to ozone for 6 wk induced a chronic inflammatory process, with alveolar enlargement and damage linked to epithelial apoptosis and increased protease expression.

Role of elastases in the pathogenesis of chronic obstructive pulmonary disease: implications for treatment

Neutrophil elastase, metalloproteinases, and their inhibitors play an important role in the development of chronic obstructive pulmonary disease (COPD), resulting in extensive tissue damage and malfunctioning of the airways. Nearly fifty years after the protease-antiprotease imbalance hypothesis has been suggested for the cause of emphysema, it is still appealing, but it does not explain the considerable variation in the clinical expressions of emphysema. However, there are many recent research findings to support the imbalance hypothesis as will be shown in this review. Although limited, there might be openings for the treatment of the disease.

Interleukin-13 (IL-13)/IL-13 receptor alpha1 (IL-13Ralpha1) signaling regulates intestinal epithelial cystic fibrosis transmembrane conductance regulator channel-dependent Cl- secretion

Interleukin-13 (IL-13) has been linked to the pathogenesis of inflammatory diseases of the gastrointestinal tract. It is postulated that IL-13 drives inflammatory lesions through the modulation of both hematopoietic and nonhematopoietic cell function in the intestine. To delineate the relevant contribution of elevated levels of intestinal IL-13 to intestinal structure and function, we generated an intestinal IL-13 transgenic mouse (iIL-13Tg). We show that constitutive overexpression of IL-13 in the small bowel induces modification of intestinal epithelial architecture (villus blunting, goblet cell hyperplasia, and increased epithelial proliferation) and epithelial function (altered basolateral → apical Cl(-) ion conductance). Pharmacological analyses in vitro and in vivo determined that elevated Cl(-) conductance is mediated by altered cystic fibrosis transmembrane conductance regulator expression and activity. Generation of iIL-13Tg/Il13rα1(-/-), iIL-13Tg/Il13rα2(-/-), and iIL-13Tg/Stat6(-/-) mice revealed that IL-13-mediated dysregulation of epithelial architecture and Cl(-) conductance is dependent on IL-13Rα1 and STAT-6. These observations demonstrate a central role for the IL-13/IL-13Rα1 pathway in the regulation of intestinal epithelial cell Cl(-) secretion via up-regulation of cystic fibrosis transmembrane conductance regulator, suggesting an important role for this pathway in secretory diarrhea.

Current concepts on oxidative/carbonyl stress, inflammation and epigenetics in pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a global health problem. The current therapies for COPD are poorly effective and the mainstays of pharmacotherapy are bronchodilators. A better understanding of the pathobiology of COPD is critical for the development of novel therapies. In the present review, we have discussed the roles of oxidative/aldehyde stress, inflammation/immunity, and chromatin remodeling in the pathogenesis of COPD. An imbalance of oxidants/antioxidants caused by cigarette smoke and other pollutants/biomass fuels plays an important role in the pathogenesis of COPD by regulating redox-sensitive transcription factors (e.g., NF-κB), autophagy and unfolded protein response leading to chronic lung inflammatory response. Cigarette smoke also activates canonical/alternative NF-κB pathways and their upstream kinases leading to sustained inflammatory response in lungs. Recently, epigenetic regulation has been shown to be critical for the development of COPD because the expression/activity of enzymes that regulate these epigenetic modifications have been reported to be abnormal in airways of COPD patients. Hence, the significant advances made in understanding the pathophysiology of COPD as described herein will identify novel therapeutic targets for intervention in COPD.

Computational and experimental analysis reveals a requirement for eosinophil-derived IL-13 for the development of allergic airway responses in C57BL/6 mice

Eosinophils are found in the lungs of humans with allergic asthma, as well as in the lungs of animals in models of this disease. Increasing evidence suggests that these cells are integral to the development of allergic asthma in C57BL/6 mice. However, the specific function of eosinophils that is required for this event is not known. In this study, we experimentally validate a dynamic computational model and perform follow-up experimental observations to determine the mechanism of eosinophil modulation of T cell recruitment to the lung during development of allergic asthma. We find that eosinophils deficient in IL-13 were unable to rescue airway hyperresponsiveness, T cell recruitment to the lungs, and Th2 cytokine/chemokine production in ΔdblGATA eosinophil-deficient mice, even if Th2 cells were present. However, eosinophil-derived IL-13 alone was unable to rescue allergic asthma responses in the absence of competence of other IL-13-producing cells. We further computationally investigate the role of other cell types in the production of IL-13, which led to the various predictions including early and late pulses of IL-13 during airway hyperresponsiveness. These experiments suggest that eosinophils and T cells have an interdependent relationship, centered on IL-13, which regulates T cell recruitment to the lung and development of allergic asthma.

Effects of IL-13 on mucociliary differentiation of pediatric asthmatic bronchial epithelial cells

Goblet cell hyperplasia (GCH) and decreased ciliated cells are characteristic of asthma. We examined the effects of IL-13 (2 and 20 ng/mL) on in vitro mucociliary differentiation in pediatric bronchial epithelial cells (PBECs) of normal PBEC [PBEC(N)] and asthmatic PBEC [PBEC(A)] children. Markers of differentiation, real-time PCR for MUC5AC, MUC5AC ELISA, and transepithelial electrical resistance (TEER) were assessed. Stimulation with 20 ng/mL IL-13 in PBEC(N) resulted in GCH [20 ng/mL IL-13: mean, 33.8% (SD, 7.2) versus unstimulated: mean, 18.9% (SD, 5.0); p < 0.0001] and decreased ciliated cell number [20 ng/mL IL-13: mean, 8% (SD, 5.6) versus unstimulated: mean, 22.7% (SD,7.6); p < 0.01]. PBEC(N) stimulated with 20 ng/mL IL-13 resulted in >5-fold (SD, 3.2) increase in MUC5AC mRNA expression, p < 0.001, compared with unstimulated PBEC(N). In PBEC(A), GCH was also seen [20 ng/mL IL-13: mean, 44.7% (SD, 16.4) versus unstimulated: mean, 30.4% (SD, 13.9); p < 0.05] with a decreased ciliated cell number [20 ng/mL IL-13: mean, 8.8% (SD, 7.5) versus unstimulated: mean, 16.3% (SD, 4.2); p < 0.001]. We also observed an increase in MUC5AC mRNA expression with 20 ng/mL IL-13 in PBEC(A), p < 0.05. IL-13 drives PBEC(N) toward an asthmatic phenotype and worsens the phenotype in PBEC(A) with reduced ciliated cell numbers and increased goblet cells.

Interleukin-13 induces mucin 5AC production involving STAT6/SPDEF in human airway epithelial cells

Mucus hypersecretion is commonly observed in many chronic airway inflammatory diseases. Mucin 5AC (MUC5AC) is a major airway mucin because of its high expression in goblet cells. Here, the authors identified a gene called SAM domain-containing prostate-derived Ets factor (SPDEF) that was induced by interleukin (IL)-13. Their results showed that specific knockdown of SPDEF reduced IL-13-induced MUC5AC expression in human airway epithelial cells. This finding was associated with decreased expression of anterior gradient 2 (AGR2) and Ca(2+)-activated Cl(-) channel (CLCA1), which regulate IL-13-mediated MUC5AC overproduction. Furthermore, transfection with SPDEF siRNA enhanced expression of forkhead box a2 (Foxa2), a key transcription factor that is known to prevent mucus production. The authors also demonstrated that the repression of STAT6 inhibited expression of SPDEF and MUC5AC induced by IL-13. These results show that SPDEF plays a critical role in regulating a transcriptional network mediating IL-13-induced MUC5AC synthesis dependent on STAT6.

The role of matrix metalloproteinases in cystic fibrosis lung disease

Significant airway remodelling is a major component of the increased morbidity and mortality observed in cystic fibrosis (CF) patients. These airways feature ongoing leukocytic inflammation and unrelenting bacterial infection. In contrast to acute bacterial pneumonia, CF infection is not cleared efficiently and the ensuing inflammatory response causes tissue damage. This structural damage is mainly a result of free proteolytic activity released by infiltrated neutrophils and macrophages. Major proteases in this disease are serine and matrix metalloproteases (MMPs). While the role of serine proteases, such as elastase, has been characterised in detail, there is emerging evidence that MMPs could play a key role in the pathogenesis of CF lung disease. This review summarises studies linking MMPs with CF lung disease and discusses the potential value of MMPs as future therapeutic targets in CF and other chronic lung diseases.

The effect of interleukin-13 (IL-13) and interferon-γ (IFN-γ) on expression of surfactant proteins in adult human alveolar type II cells in vitro

Background

Surfactant proteins are produced predominantly by alveolar type II (ATII) cells, and the expression of these proteins can be altered by cytokines and growth factors. Th1/Th2 cytokine imbalance is suggested to be important in the pathogenesis of several adult lung diseases. Recently, we developed a culture system for maintaining differentiated adult human ATII cells. Therefore, we sought to determine the effects of IL-13 and IFN-γ on the expression of surfactant proteins in adult human ATII cells in vitro. Additional studies were done with rat ATII cells.

Methods

Adult human ATII cells were isolated from deidentified organ donors whose lungs were not suitable for transplantation and donated for medical research. The cells were cultured on a mixture of Matrigel and rat-tail collagen for 8 d with differentiation factors and human recombinant IL-13 or IFN-γ.

Results

IL-13 reduced the mRNA and protein levels of surfactant protein (SP)-C, whereas IFN-γ increased the mRNA level of SP-C and proSP-C protein but not mature SP-C. Neither cytokine changed the mRNA level of SP-B but IFN-γ slightly decreased mature SP-B. IFN-γ reduced the level of the active form of cathepsin H. IL-13 also reduced the mRNA and protein levels of SP-D, whereas IFN-γ increased both mRNA and protein levels of SP-D. IL-13 did not alter SP-A, but IFN-γ slightly increased the mRNA levels of SP-A.

Conclusions

We demonstrated that IL-13 and IFN-γ altered the expression of surfactant proteins in human adult ATII cells in vitro. IL-13 decreased SP-C and SP-D in human ATII cells, whereas IFN-γ had the opposite effect. The protein levels of mature SP-B were decreased by IFN-γ treatment, likely due to the reduction in active form cathpesin H. Similarly, the active form of cathepsin H was relatively insufficient to fully process proSP-C as IFN-γ increased the mRNA levels for SP-C and proSP-C protein, but there was no increase in mature SP-C. These observations suggest that in disease states with an overexpression of IL-13, there would be some deficiency in mature SP-C and SP-D. In disease states with an excess of IFN-γ or therapy with IFN-γ, these data suggest that there might be incomplete processing of SP-B and SP-C.

Adjusting transgene expression levels in lymphocytes with a set of inducible promoters

BACKGROUND

Inducible gene expression systems are powerful research tools and could be of clinical value in the future, with lymphocytes being likely prime application targets. However, currently available regulatable promoters exhibit variation in their efficiency in a cell line-dependent-manner and are notorious for basal leakiness or poor inducibility. Data concerning the regulatory properties of different inducible promoters are scarce for lymphocytes. In the present study, we report a comprehensive analysis of how various inducible promoters perform and how their combination with a transsilencer and a reverse transactivator can result in optimally controlled gene expression in T-cells.

METHODS

The performance of the tetracycline-regulated (Tet)-inducible promoters Tet-responsive element (TRE), mouse mammary tumor virus (MMTV)/TRE, TREtight and second generation TRE (SG/TRE) was compared in several B-cell lines and in Jurkat T-cells using transient transfections in combination with Tet-On. To monitor transgene expression in a Jurkat cell line containing a transsilencer and a reverse transactivator, expression cassettes encoding enhanced green fluorescent protein, CD123 or a constitutively active, cytotoxic caspase-3 were flanked with insulators and stably integrated. The performance of TREtight and SG/TRE was furthermore analysed in transiently transfected primary CD4(+) human T-cells.

RESULTS

The promoters exhibit greatly diverging characteristics. MMTV/TRE permits moderate, TRE and TREtight permits intermediate and SG/TRE permits very high expression levels. TRE and SG/TRE are leaky, whereas MMTV/TRE and TREtight provide stringent expression control. Tetracycline derivatives add flexibility to transgene expression by introducing intermediate expression levels.

CONCLUSIONS

The different expression profiles of the promoters increase the flexibility to adjust transgene expression levels. The promoters provide an additional option to optimize system performance for many applications.

Quercetin prevents progression of disease in elastase/LPS-exposed mice by negatively regulating MMP expression

Background

Chronic obstructive pulmonary disease (COPD) is characterized by chronic bronchitis, emphysema and irreversible airflow limitation. These changes are thought to be due to oxidative stress and an imbalance of proteases and antiproteases. Quercetin, a plant flavonoid, is a potent antioxidant and anti-inflammatory agent. We hypothesized that quercetin reduces lung inflammation and improves lung function in elastase/lipopolysaccharide (LPS)-exposed mice which show typical features of COPD, including airways inflammation, goblet cell metaplasia, and emphysema.

Methods

Mice treated with elastase and LPS once a week for 4 weeks were subsequently administered 0.5 mg of quercetin dihydrate or 50% propylene glycol (vehicle) by gavage for 10 days. Lungs were examined for elastance, oxidative stress, inflammation, and matrix metalloproteinase (MMP) activity. Effects of quercetin on MMP transcription and activity were examined in LPS-exposed murine macrophages.

Results

Quercetin-treated, elastase/LPS-exposed mice showed improved elastic recoil and decreased alveolar chord length compared to vehicle-treated controls. Quercetin-treated mice showed decreased levels of thiobarbituric acid reactive substances, a measure of lipid peroxidation caused by oxidative stress. Quercetin also reduced lung inflammation, goblet cell metaplasia, and mRNA expression of pro-inflammatory cytokines and muc5AC. Quercetin treatment decreased the expression and activity of MMP9 and MMP12 in vivo and in vitro, while increasing expression of the histone deacetylase Sirt-1 and suppressing MMP promoter H4 acetylation. Finally, co-treatment with the Sirt-1 inhibitor sirtinol blocked the effects of quercetin on the lung phenotype.

Conclusions

Quercetin prevents progression of emphysema in elastase/LPS-treated mice by reducing oxidative stress, lung inflammation and expression of MMP9 and MMP12.

Genetic and pharmacological evaluation of cathepsin s in a mouse model of asthma

Cathepsin S (Cat S) is predominantly expressed in antigen-presenting cells and is up-regulated in several preclinical models of antigen-induced inflammation, suggesting a role in the allergic response. Prophylactic dosing of an irreversible Cat S inhibitor has been shown to attenuate pulmonary eosinophilia in mice, supporting the hypothesis that Cat S inhibition before the initiation of airway inflammation is beneficial in airway disease. In addition, Cat S has been shown to play a role in more distal events in the allergic response. To determine where Cat S inhibition may affect the allergic response, we used complementary genetic and pharmacological approaches to investigate the role of Cat S in the early and downstream allergic events in a murine model of antigen-induced lung inflammation. Cat S knockout mice did not develop ovalbumin-induced pulmonary inflammation, consistent with a role for Cat S in the development of the allergic response. Alternatively, wild-type mice were treated with a reversible, highly selective Cat S inhibitor in prophylactic and therapeutic dosing paradigms and assessed for changes in airway inflammation. Although both treatment paradigms resulted in potent Cat S inhibition, only prophylactic Cat S inhibitor dosing blocked lung inflammation, consistent with our findings in Cat S knockout mice. The findings indicate that although Cat S is up-regulated in allergic models, it does not appear to play a significant role in the downstream effector inflammatory phase in this model; however, our results demonstrate that Cat S inhibition in a prophylactic paradigm would ameliorate airway inflammation.

Overlap Between Asthma and COPD: Where the Two Diseases Converge

Asthma and chronic obstructive pulmonary disease (COPD) are traditionally recognized as distinct diseases, with some clearly separate characteristic. Asthma originates in childhood, is associated with allergies and eosinophils, and is best treated by targeting inflammation, whereas COPD occurs in adults who smoke, involves neutrophils, and is best treated with bronchodilators and the removal of risk factors. However, the distinction between the two is not always clear. Patients with severe asthma may present with fixed airway obstruction, and patients with COPD may have hyperresponsiveness and eosinophilia. Recognizing and understanding these overlapping features may offer new insight into the mechanisms and treatment of chronic airway inflammatory diseases.

Role of LTB₄ in the pathogenesis of elastase-induced murine pulmonary emphysema

Exaggerated levels of the leukotriene B₄ (LTB₄) frequently coexist at sites of inflammation and tissue remodeling. Therefore, we hypothesize that the LTB₄ pathway plays an important role in the pathogenesis of neutrophilic inflammation that contributes to pulmonary emphysema. In this study, significant levels of LTB₄ were detected in human lung tissues with emphysema compared with lungs without emphysema (9,497 ± 2,839 vs. 4,142 ± 1,173 pg/ml, n = 9 vs. 10, P = 0.04). To further determine the biological role of LTB₄ in the pathogenesis of emphysema, we compared the lungs of wild-type (WT) and LTA₄ hydrolase-/- mice (LTB₄ deficient, LTA₄H-/-) exposed to intranasal elastase or vehicle control. We found that intranasal elastase induced accumulation of LTB₄ in the lungs and caused progressively worsening emphysema between 14 and 28 days after elastase exposure in WT mice but not in LTA₄H-/- mice. Premortem physiology documented increased lung compliance in elastase-exposed WT mice compared with elastase-exposed LTA₄H-/- mice as measured by Flexivent (0.058 ± 0.005 vs. 0.041 ± 0.002 ml/cmH₂O pressure). Postmortem morphometry documented increased total lung volume and alveolar sizes in elastase-exposed WT mice compared with elastase-exposed LTA₄H-/- mice as measured by volume displacement and alveolar chord length assessment. Furthermore, elastase-exposed LTA₄H-/- mice were found to have significantly delayed influx of the CD45(high)CD11b(high)Ly6G(high) leukocytes compatible with neutrophils compared with elastase-exposed WT mice. Mechanistic insights to these phenotypes were provided by demonstrating protection from elastase-induced murine emphysema with neutrophil depletion in the elastase-exposed WT mice and by demonstrating time-dependent modulation of cysteinyl leukotriene biosynthesis in the elastase-exposed LTA₄H-/- mice compared with elastase-exposed WT mice. Together, these findings demonstrated that LTB₄ played an important role in promoting the pathogenesis of pulmonary emphysema associated with neutrophilic pulmonary inflammation.

Cbl-b regulates airway mucosal tolerance to aeroallergen

BACKGROUND

As an E3 ubiquitin ligase and a molecular adaptor, Cbl-b controls the activation threshold of the antigen receptor and negatively regulates CD28 costimulation, functioning as an intrinsic mediator of T cell anergy that maintains tolerance. However, the role of Cbl-b in the airway immune response to aeroallergens is unclear.

OBJECTIVE

To determine the contribution of Cbl-b in tolerance to aeroallergens, we examined ovalbumin (OVA)-induced lung inflammation in Cbl-b-deficient mice.

METHODS

Cbl-b(-/-) mice and wild-type (WT) C57BL/6 mice were sensitized and challenged with OVA intranasally, a procedure normally tolerated by WT mice. We analysed lung histology, bronchoalveolar lavage fluid total cell counts and differential, cytokines and chemokines in the airway, and cytokine response by lymphocytes after re-stimulation by OVA antigen.

RESULTS

Compared with WT mice, OVA-challenged Cbl-b(-/-) mice showed significantly increased neutrophilic and eosinophilic infiltration in the lung and mucus hyperplasia. The serum levels of IgG2a and IgG1, but not IgE, were increased. The levels of inflammatory mediators IFN-γ, IL-10, IL-12, IL-13, IP-10, MCP-1, MIP-1α, eotaxin, and RANTES, but not IL-17A or IL-6, were elevated in the airway of Cbl-b(-/-) mice. Lymphocytes from Cbl-b(-/-) mice released increased amount of IFN-γ, IL-10, IL-13, and IP-10 in response to OVA re-stimulation. However, no significant changes were noted in the CD4(+) CD25(+) T regulatory cell populations in the lung tissues after OVA stimulation and there was no difference between WT and Cbl-b(-/-) mice.

CONCLUSION

These results demonstrate that Cbl-b deficiency leads to a breakdown of tolerance to OVA allergen in the murine airways, probably through increased activation of T effector cells, indicating that Cbl-b is a critical factor in maintaining lung homeostasis upon environmental exposure to aeroallergens.

Involvement of IL-13 in tobacco smoke-induced changes in the structure and function of rat intrapulmonary airways

Chronic obstructive pulmonary disease (COPD) involves disease of small airways with an increase in airway smooth muscle sensitivity to spasmogens and with structural changes described as airway remodeling. We investigated the effect of tobacco smoke (TS) exposure on the structure and function of small airways in rats and the role of IL-13 in this response. Precision-cut lung slices (230-280 microm) were prepared from male Sprague-Dawley rats after acute (3 d) or chronic (8 or 16 wk) daily exposure to TS or air. Carbachol (CCh) and 5-hydroxytryptamine (5HT) concentration responses were performed on airways (50-400 microm diameter). The effect of IL-13 in vitro on small airway sensitivity to CCh and 5HT was also determined. Acute exposure to TS did not affect the sensitivity of the intrapulmonary airways to either spasmogen. After 8 weeks of TS exposure, airway hyperresponsiveness (AHR) to CCh was evident (log EC(50) CCh: air = 0.22 microM; TS = -0.12 microM; P = 0.019); AHR to 5HT was also observed after the 16-week exposure to TS (air = -0.85 microM; TS = -1.06 microM; P = 0.038). Chronic TS exposure increased airway wall SMA content, which correlated with increased expression of IL-13 and transforming growth factor (TGF)-beta(1) in the lung tissues. In vitro incubation with IL-13, but not TGF-beta(1), induced changes in small airway sensitivity to CCh and 5HT. Chronic TS exposure induces increased responsiveness in intrapulmonary airways of rats that may be mediated in part by an increase in IL-13.

Role of breast regression protein-39 in the pathogenesis of cigarette smoke-induced inflammation and emphysema

The exaggerated expression of chitinase-like protein YKL-40, the human homologue of breast regression protein-39 (BRP-39), was reported in a number of diseases, including chronic obstructive pulmonary disease (COPD). However, the in vivo roles of YKL-40 in normal physiology or in the pathogenesis of specific diseases such as COPD remain poorly understood. We hypothesized that BRP-39/YKL-40 plays an important role in the pathogenesis of cigarette smoke (CS)-induced emphysema. To test this hypothesis, 10-week-old wild-type and BRP-39 null mutant mice (BRP-39(-/-)) were exposed to room air (RA) and CS for up to 10 months. The expression of BRP-39 was significantly induced in macrophages, airway epithelial cells, and alveolar Type II cells in the lungs of CS-exposed mice compared with RA-exposed mice, at least in part via an IL-18 signaling-dependent pathway. The null mutation of BRP-39 significantly reduced CS-induced bronchoalveolar lavage and tissue inflammation. However, CS-induced epithelial cell apoptosis and alveolar destruction were further enhanced in the absence of BRP-39. Consistent with these findings in mice, the tissue expression of YKL-40 was significantly increased in the lungs of current smokers compared with the lungs of ex-smokers or nonsmokers. In addition, serum concentrations of YKL-40 were significantly higher in smokers with COPD than in nonsmokers or smokers without COPD. These studies demonstrate a novel regulatory role of BRP-39/YKL-40 in CS-induced inflammation and emphysematous destruction. These studies also underscore that maintaining physiologic concentrations of YKL-40 in the lung is therapeutically important in preventing excessive inflammatory responses or emphysematous alveolar destruction.

Persistent pneumocystis colonization leads to the development of chronic obstructive pulmonary disease in a nonhuman primate model of AIDS

Human immunodeficiency virus (HIV)-infected patients are at increased risk for development of pulmonary complications, including chronic obstructive pulmonary disease (COPD). Inflammation associated with subclinical infection has been postulated to promote COPD. Persistence of Pneumocystis is associated with HIV infection and COPD, although a causal relationship has not been established. We used a simian/human immunodeficiency virus model of HIV infection to study pulmonary effects of Pneumocystis colonization. Simian/human immunodeficiency virus-infected/Pneumocystis-colonized monkeys developed progressive obstructive pulmonary disease characterized by increased emphysematous tissue and bronchial-associated lymphoid tissue. Increased levels of T helper type 2 cytokines and proinflammatory mediators in bronchoalveolar lavage fluid coincided with Pneumocystis colonization and a decline in pulmonary function. These results support the concept that an infectious agent contributes to the development of HIV-associated lung disease and suggest that Pneumocystis colonization may be a risk factor for the development of HIV-associated COPD. Furthermore, this model allows examination of early host responses important to disease progression, thus identifying potential therapeutic targets for COPD.

Protease inhibitors in respiratory disease: focus on asthma and chronic obstructive pulmonary disease

Respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are a major health burden on society and current treatment modalities for these diseases have not significantly changed over the past 40 years. The only major pharmacological advancement for the treatment of these diseases has been to increase the duration of action of bronchodilators (asthma: salmeterol; COPD: tiotropium bromide) and glucocorticosteroids (asthma: fluticasone propionate) and, increasingly, to formulate these agents in the same delivery device. Despite our increasing understanding of the cell and molecular biology of these diseases, the development of novel treatments remains beyond the reach of the scientific community. Proteases are a family of proteins with diverse biological activity, which are found in abundance within the airways of asthma and COPD, and have been implicated in the pathogenesis of these diseases. The targeting of proteases, including mast cell tryptase, neutrophil elastase and matrix metalloprotease with low-molecular-weight inhibitors, has highlighted the potential role of these enzymes in mediating certain aspects of the disease process in preclinical studies. Several challenges remain regarding the development of protease inhibitors, including the synthesis of highly potent and specific inhibitors, and target validation in man.

Stromal regulation of vessel stability by MMP14 and TGFbeta

Innate regulatory networks within organs maintain tissue homeostasis and facilitate rapid responses to damage. We identified a novel pathway regulating vessel stability in tissues that involves matrix metalloproteinase 14 (MMP14) and transforming growth factor beta 1 (TGFbeta(1)). Whereas plasma proteins rapidly extravasate out of vasculature in wild-type mice following acute damage, short-term treatment of mice in vivo with a broad-spectrum metalloproteinase inhibitor, neutralizing antibodies to TGFbeta(1), or an activin-like kinase 5 (ALK5) inhibitor significantly enhanced vessel leakage. By contrast, in a mouse model of age-related dermal fibrosis, where MMP14 activity and TGFbeta bioavailability are chronically elevated, or in mice that ectopically express TGFbeta in the epidermis, cutaneous vessels are resistant to acute leakage. Characteristic responses to tissue damage are reinstated if the fibrotic mice are pretreated with metalloproteinase inhibitors or TGFbeta signaling antagonists. Neoplastic tissues, however, are in a constant state of tissue damage and exhibit altered hemodynamics owing to hyperleaky angiogenic vasculature. In two distinct transgenic mouse tumor models, inhibition of ALK5 further enhanced vascular leakage into the interstitium and facilitated increased delivery of high molecular weight compounds into premalignant tissue and tumors. Taken together, these data define a central pathway involving MMP14 and TGFbeta that mediates vessel stability and vascular response to tissue injury. Antagonists of this pathway could be therapeutically exploited to improve the delivery of therapeutics or molecular contrast agents into tissues where chronic damage or neoplastic disease limits their efficient delivery.

Oxidative stress targets in pulmonary emphysema: focus on the Nrf2 pathway

IMPORTANCE OF THE FIELD

Oxidative stress has been implicated in the pathogenesis of pulmonary emphysema. Nuclear factor erythroid-2-related factor 2 (Nrf2) a major antioxidant transcription factor could play a protective role in pulmonary emphysema.

AREAS COVERED IN THIS REVIEW

Nrf2 is ubiquitously expressed throughout the lung, but is predominantly found in epithelium and alveolar macrophages. Evidence suggests that Nrf2 and several Nrf2 downstream genes have an essential protective role in the lung against oxidative stress from environmental pollutants and toxicants such as cigarette smoke, a major causative factor for the development and progression of pulmonary emphysema. Application of Nrf2-deficient mice identified an extensive range of protective roles for Nrf2 against the pathogenesis of pulmonary emphysema. Therefore, Nrf2 promises to be an attractive therapeutic target for intervention and prevention strategies.

WHAT THE READER WILL GAIN

In this review, we discuss recent findings on the association of oxidative stress with pulmonary emphysema. We also address the mechanisms of Nrf2 lung protection against oxidative stress based on emerging evidence from experimental oxidative disease models and human studie.

TAKE HOME MESSAGE

The current literature suggests that among oxidative stress targets, Nrf2 is a valuable therapeutic target in pulmonary emphysema.

Use of a new-generation reverse tetracycline transactivator system for quantitative control of conditional gene expression in the murine lung

Conditional regulation of gene expression by the combined use of a lung-specific promoter and the tetracycline-regulated system provides a powerful tool for studying gene function in lung biology and disease pathogenesis in a development-independent fashion. However, the original version of the reverse tetracycline-dependent transactivator (rtTA) exhibited limited doxycycline sensitivity and residual affinity to its promoter (P(tet)), producing leaky transgene expression in the absence of doxycycline. These limitations impeded the use of this system in studying gene dosage effects in pulmonary pathogenesis and repair mechanisms in the diseased lung. Therefore, we used a new-generation rtTA, rtTA2(s)-M2, with no basal activity and increased doxycycline sensitivity, and the rat Clara cell secretory protein (CCSP) promoter to target its expression to pulmonary epithelia in mice. Novel CCSP-rtTA2(s)-M2 founder lines were crossed, with bi-transgenic reporter mice expressing luciferase and Cre recombinase. Background activity, doxycycline sensitivity, tissue and cell-type specificity, inducibility, and reversibility of doxycycline-dependent gene expression were determined by luciferase activity, immunohistochemistry, morphometry, and bioluminescence measurements in neonatal and adult lungs. We generated two distinct novel CCSP-rtTA2(s)-M2 activator mouse lines that confer tight and doxycycline dose-dependent regulation of transgene expression, with high inducibility, complete reversibility, and no background activity, in airway and alveolar epithelia. We conclude that rtTA2(s)-M2 enables quantitative control of conditional gene expression in respiratory epithelia of the murine lung, and that the new CCSP-rtTA2(s)-M2 activator mouse lines will be useful in the further elucidation of the pathogenesis of complex lung diseases and in studies of lung repair.

Polymorphisms in IL13 pathway genes in asthma and chronic obstructive pulmonary disease

BACKGROUND

Asthma and chronic obstructive pulmonary disease (COPD) are chronic respiratory diseases involving an interaction between genetic and environmental factors. Interleukin-13 (IL13) has been suggested to have a role in both asthma and COPD. We investigated whether single nucleotide polymorphisms (SNPs) in the IL13 pathway may contribute to the susceptibility and severity of asthma and COPD in adults.

METHODS

Twelve SNPs in IL13 pathway genes -IL4, IL13, IL4RA, IL13RA1, IL13RA2 and STAT6- were genotyped in subjects with asthma (n = 299) and in subjects with COPD or healthy smokers (n = 992). Genetic association was evaluated using genotype and allele models for asthma severity, atopy phenotypes and COPD susceptibility. Linear regression was used to determine the effects of polymorphism on baseline lung function (FEV(1), FEV(1)/FVC).

RESULTS

In asthmatics, three IL13 SNPs - rs1881457(-1512), rs1800925(-1111) and rs20541(R130Q) - were associated with atopy risk. One SNP in IL4RA1 [rs1805010(I75V)] was associated with asthma severity, and several IL13 SNPs showed borderline significance. IL13 SNPs rs1881457(-1512) and rs1800925(-1111) were associated with better FEV(1) and FEV(1)/FVC in asthmatics. IL13 SNPs rs2066960(intron 1), rs20541(R130Q) and rs1295685(exon 4) were associated with COPD risk and lower baseline lung function in the recessive model. In females, but not in males, rs2250747 of the IL13RA1 gene was associated with COPD and lower FEV(1).

CONCLUSION

These data suggest that IL13 SNPs (promoter and coding region) and, to a lesser extent, IL4RA SNPs may contribute to atopy and asthma. We also provide tentative evidence that IL13 SNPs in the coding region may be of significance in COPD susceptibility.

The aging immune system and its relationship to the development of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease of the lungs that usually manifests late in life. Physiologic and immunologic changes that occur in COPD often mimic changes seen in the aging lung. This has led some to characterize COPD as an "accelerated aging phenotype." At the molecular level, COPD and aging share common mechanisms and are associated with significant dysregulation of the immune systems. Aging and COPD are characterized by increases in proinflammatory cytokines such as interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha, which are implicated in aging-related inflammatory diseases and correlate with degree of obstruction in COPD. There is an age-dependent decline in naïve T cells with oligoclonal expansion of CD8(+) CD28(null) T cells from chronic antigenic stimulation. The increase in CD8(+) CD28 (null) T regulatory cells inhibits antigen-specific CD4(+) T cell responses, leading to a decline in adaptive immune response. To compensate for the decline in the adaptive immune function there is a paradoxical up-regulation of innate immune system resulting in a proinflammatory state. The dysregulated adaptive immune system with activated innate immune responses seen with aging results in recruitment and retention of neutrophils, macrophages, and CD4(+) and CD8(+) T cells in the lungs of smokers with COPD. Once the inflammation is triggered, there is a self-perpetuating cascade of inflammation and lung parenchymal damage. This review will focus on how the aging immune system may contribute to COPD development later in life in susceptible individuals.

Impact of female cigarette smoking on circulating B cells in vivo: the suppressed ICOSLG, TCF3, and VCAM1 gene functional network may inhibit normal cell function

As pivotal immune guardians, B cells were found to be directly associated with the onset and development of many smoking-induced diseases. However, the in vivo molecular response of B cells underlying the female cigarette smoking remains unknown. Using the genome-wide Affymetrix HG-133A GeneChip microarray, we firstly compared the gene expression profiles of peripheral circulating B cells between 39 smoking and 40 non-smoking healthy US white women. A total of 125 differential expressed genes were identified in our study, and 75.2% of them were down-regulated in smokers. We further obtained genotypes of 702 single nucleotide polymorphisms in those promising genes and assessed their associations with smoking status. Using a novel multicriteria evaluation model integrating information from microarray and the association studies, several genes were further revealed to play important roles in the response of smoking, including ICOSLG (CD275, inducible T-cell co-stimulator ligand), TCF3 (E2A immunoglobulin enhancer binding factors E12/E47), VCAM1 (CD106, vascular cell adhesion molecule 1), CCR1 (CD191, chemokine C-C motif receptor 1) and IL13 (interleukin 13). The differential expression of ICOSLG (p = 0.0130) and TCF3 (p = 0.0125) genes between the two groups were confirmed by real-time reverse transcription PCR experiment. Our findings support the functional importance of the identified genes in response to the smoking stimulus. This is the first in vivo genome-wide expression study on B cells at today's context of high prevalence rate of smoking for women. Our results highlight the potential usage of integrated analyses for unveiling the novel pathogenesis mechanism and emphasized the significance of B cells in the etiology of smoking-induced disease.

Il13 promoter (-1055) polymorphisms associated with chronic obstructive pulmonary disease in Taiwanese

Interleukin-13 (IL13) -1055 polymorphism has been implicated in the development of chronic obstructive pulmonary disease (COPD) in various studies with conflicting results. The aims of this study are to investigate whether IL13 -1055 polymorphism is associated with the development of COPD in Taiwanese smokers; and to determine if IL13 -1055 polymorphism is associated with the severity of COPD. A case-control study was conducted on COPD patients (n = 85) and healthy smoker (n = 72). Genomic DNA was extracted for genotyping of IL13 sequencing and serum IL-13 was measured using by enzyme-linked immunosorbent assay (ELISA). After adjusting smoking index and age confounding, the T-allelic frequencies of the IL13 -1055 gene polymorphisms in COPD group are significantly higher than those in control group (18.8% versus 1.4%; P < .001; odds ratio [OR] = 29.3; 95% confidence interval [CI]: 5.9-145.3); and the frequencies of CT/TT genotypes in COPD group are significantly higher than those in control group (27.1% versus 2.8%; P < .001; OR = 20.0; 95% CI: 3.9-100.8). In COPD patients, stepwise linear regression shows IL13 -1055 T allele is the independent factor associated with forced expiratory volume in 1 second (P = .007), but not associated with serum IL-13. In conclusion, IL13 -1055 T allele is associated with the development and severity of COPD in Taiwanese smokers.

Cell-based therapy improves cell viability and increases airway size in an explant model

Cell-based therapy is a promising treatment option for lung disease, but no studies have demonstrated its benefit in promoting perinatal lung growth. Embryonic day 18 (E18) fetal lungs treated with vascular inhibitors were grown as explant organ cultures to inhibit endothelial growth in the explant cultures. Disruption of pulmonary vasculature decreased explant mean cord length and viability, whereas coculture with fetal pulmonary or predifferentiated embryonic stem cells rescued both parameters. These results demonstrate in a model of perinatal lung growth, exogenous addition of fetal pulmonary cells or differentiated embryonic stem (ES) cells promotes survival and alveolar morphogenesis. These experiments represent the first evidence of the benefits of cell-based therapy for perinatal lung growth.

Role for cathepsin K in emphysema in smoke-exposed guinea pigs

The protease-antiprotease imbalance in the lung plays an important role in the pathogenesis of smoke-induced emphysema. The aim of this study was to characterize the proteolytic responses leading to emphysema formation in the guinea pig smoke exposure model. Guinea pigs were exposed to cigarette smoke for 1, 2, 4, 8, and 12 weeks. Age-matched guinea pigs exposed to room air served as controls. Cigarette smoke induced inflammation after 4 weeks and generated emphysematous changes in the guinea pigs after 12 weeks of smoke exposure. Increased phosphorylation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) mitogen-activated protein (MAP) kinases was demonstrated post cigarette smoke exposure. A decrease in elastin and collagen and the loss of type III collagen were observed in the alveolar wall of smoke-exposed guinea pigs. Interestingly, no change was seen in the expression of collagenolytic matrix metalloproteinases. Furthermore, the authors observed a 3-fold increase in cathepsin K activity in the lungs of smoke-exposed guinea pigs. The significance of this finding was supported by human studies that demonstrate increased expression of cathepsin K in the lungs of patients with emphysema. Elevation of cathepsin K in guinea pig lungs after smoke exposure likely constitutes a critical event leading to the disruption of lung extracellular matrix in this model.

Differential expression of tissue repair genes in the pathogenesis of chronic obstructive pulmonary disease

RATIONALE

The airflow limitation that defines severity of chronic obstructive pulmonary disease (COPD) is caused by a combination of small airway obstruction and emphysematous lung destruction.

OBJECTIVES

To examine the hypothesis that small airway obstructive and emphysematous destructive lesions are produced by differential expression of genes associated with tissue repair.

METHODS

The expression of 54 genes associated with repair of repetitively damaged tissue was measured in 136 paired samples of small bronchioles and surrounding lung tissue separated by laser capture microdissection. These samples were collected from 63 patients at different levels of disease severity who required surgery for either lung cancer or lung transplantation for very severe COPD. Gene expression was measured by quantitative polymerase chain reaction in these paired samples and compared with the FEV(1) by linear regression analysis.

MEASUREMENTS AND MAIN RESULTS

After corrections for false discovery rates, only 2 of 10 genes (serpin peptidase inhibitor/plasminogen activator inhibitor member 2 and matrix metalloproteinase [MMP] 10) increased, whereas 8 (MMP2, integrin-alpha1, vascular endothelial growth factor, a disintegrin and metallopeptidase domain 33, scatter factor/hepatocyte growth factor, tissue inhibitor of matrix metalloproteinase-2, fibronectin, and collagen 3alpha1) decreased in small airways in association with FEV(1). In contrast, 8/12 genes (early growth response factor 1, MMP1, MMP9, MMP10, plasminogen activator urokinase, plasminogen activator urokinase receptor, tumor necrosis factor, and IL13) increased and 4/12 (MMP2, tissue inhibitor of matrix metalloproteinase-1, collagen 1alpha1, and transforming growth factor-beta3) decreased in the surrounding lung tissue in association with progression of COPD.

CONCLUSIONS

The progression of COPD is associated with the differential expression of a cluster of genes that favor the degradation of the tissue surrounding the small conducting airways.