Showing papers in "American Journal of Respiratory Cell and Molecular Biology in 2004"

Activation of Airway Epithelial Cells by Toll-Like Receptor Agonists

Abstract: Toll-like receptors (TLR) play an important role in pathogen recognition and innate immunity. We investigated the presence and function of TLRs in the BEAS-2B airway epithelial cell line and primary bronchial epithelial cells. Standard real-time reverse transcriptase–polymerase chain reaction (RT-PCR) analysis and Taqman RT-PCR revealed that BEAS-2B cells express mRNA for TLR1–10. Several TLR ligands were tested for their ability to activate gene expression in BEAS-2B cells using limited microarray analyses focusing on genes of the chemokine and chemokine receptor family, cytokines, and signaling pathways. While the TLR3 ligand double-stranded RNA was the most effective epithelial activator, clear responses to flagellin, lipopolysaccharide, CpG, peptidoglycan, and zymosan were also observed. RT-PCR and/or enzyme-linked immunosorbent assay were used to confirm results obtained with microarrays for five of the induced genes: interleukin-8, serum amyloid A, TLR3, macrophage inflammatory protein-3α, and granu...

Proteomic Analysis of Exosomes Isolated from Human Malignant Pleural Effusions

Abstract: Exosomes are membrane vesicles from endosomal origin secreted by various cells such as hematopoietic, epithelial, and tumor cells. Exosomes secreted by tumor cells contain specific antigens potentially useful for immunotherapeutic purposes. Our aim was to determine if exosomes are present in human cancerous pleural effusions and to identify their proteomic content. Exosomes were purified by sucrose gradient ultracentrifugation, and electron microscopy was used to check both concentration and purity of exosomes. Proteins were separated by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and protein bands were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry and Western blotting. Exosomes were present in pleural fluid obtained from patients suffering from mesothelioma (n = 4), lung cancer (n = 2), breast cancer (n = 2), and ovarian cancer (n = 1). As previously reported by others, antigen-presenting molecules, cytoskeletal proteins, and signal transduction-involved proteins were present. Proteins not previously reported were identified (SNX25, BTG1, PEDF, thrombospondin 2). Different types of immunoglobulins and complement factors were abundantly present in the sucrose fractions containing exosomes. Exosome-directed specificity of these immunoglobulins was not observed. In conclusion, sucrose gradient ultracentrifugation allows isolation of exosomes from malignant pleural effusions. However, pleural fluid proteins and especially immunoglobulins are coisolated and may hamper the use of exosomes isolated from malignant effusion for immunotherapy programs.

Cigarette smoke alters chromatin remodeling and induces proinflammatory genes in rat lungs

Abstract: Cigarette smoke–triggered inflammation is considered to play a central role in the development of chronic obstructive pulmonary disease by a mechanism that may involve enhanced proinflammatory gene transcription. Histone acetylation and deacetylation is a key regulator of the specificity and duration of gene transcription. Disruption in the nuclear histone acetylation:deacetylation balance (chromatin remodeling) may result in excessive transcription of specific proinflammatory genes in the lungs. In this study we show that cigarette smoke exposure results in an influx of inflammatory cells and chromatin modifications in rat lungs. This was associated with an increase in the active phosphorylated form of p38 mitogen-activated protein kinase concomitant with increased histone 3 phospho-acetylation, histone 4 acetylation, and increased DNA binding of the redox-sensitive transcription factor nuclear factor-κB, independent of inhibitory protein-κB degradation, and activator protein 1. We also observed decrease...

Mucin Is Produced by Clara Cells in the Proximal Airways of Antigen-Challenged Mice

Abstract: Airway mucus hypersecretion is a prominent feature of many obstructive lung diseases. We thus determined the ontogeny and exocytic phenotype of mouse airway mucous cells. In naive mice, ciliated (approximately 40%) and nonciliated (approximately 60%) epithelial cells line the airways, and > 95% of the nonciliated cells are Clara cells that contain Clara cell secretory protein (CCSP). Mucous cells comprise < 5% of the nonciliated cells. After sensitization and a single aerosol antigen challenge, alcian blue-periodic acid Schiff's positive mucous cell numbers increase dramatically, appearing 6 h after challenge (21% of nonciliated/nonbasal cells), peaking from Days 1-7 (99%), and persisting at Day 28 (65%). Throughout the induction and resolution of mucous metaplasia, ciliated and Clara cell numbers identified immunohistochemically change only slightly. Intracellular mucin content peaks at Day 7, and mucin expression is limited specifically to a Clara cell subset in airway generations 2-4 that continue to express CCSP. Functionally, Clara cells are secretory cells that express the regulated exocytic marker Rab3D and, in antigen-challenged mice, rapidly secrete mucin in response to inhaled ATP in a dose-dependent manner. Thus, Clara cells show great plasticity in structure and secretory products, yet have molecular and functional continuity in their identity as specialized apical secretory cells.

Toll-like receptors in normal and cystic fibrosis airway epithelial cells.

Abstract: Toll-like receptors (TLRs) mediate cellular responses to diverse microbial ligands. The distribution and function of TLRs in airway cells were studied to identify which are available to signal the presence of inhaled pathogens and to establish if differences in TLR expression are associated with the increased proinflammatory responses seen in cystic fibrosis (CF). Isogenic, polarized CF and control bronchial epithelial cell lines, human airway cells in primary culture, and cftr null and wild-type mice were compared. TLRs 1-10, MD2, and MyD88 were expressed in CF and normal cells. Only TLR2 transcription was modestly increased in CF as compared with normal epithelial cells following bacterial stimulation. TLR2 was predominantly at the apical surface of airway cells and was mobilized to cell surface in response to bacteria. TLR4 was present in a more basolateral distribution in airway cells, but appeared to have a limited role in epithelial responses. Lipopolysaccharide failed to activate nuclear factor-kappaB in these cells, and TLR2 dominant negative but not TLR4 dominant negative mutants inhibited activation by both Gram-negative and Gram-positive bacteria. Increased availability of TLR2 at the apical surfaces of CF epithelial cells is consistent with the increased proinflammatory responses seen in CF airways and suggests a selective participation of TLRs in the airway mucosa.

Pseudomonas aeruginosa Flagella Activate Airway Epithelial Cells through asialoGM1 and Toll-Like Receptor 2 as well as Toll-Like Receptor 5

Abstract: The distribution of specific toll-like receptors and components of the signaling pathways activated by Pseudomonas aeruginosa flagella were studied in airway epithelial cells. Initially flagella bound to the apical surface of polarized epithelial cells, where they prominently colocalized with asialoGM1. By 4 h of exposure to flagella, toll-like receptor (TLR)5 expression was induced, mobilized to the apical surface of the cells, and colocalized with superficial flagella. Interleukin-8 expression in airway cells was activated by flagella through induction of Ca(2+) fluxes, Src, Ras, and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase and nuclear factor-kappaB activation, a pathway previously associated with asialoGM1-mediated stimuli. There was evidence for participation of asialoGM1 and TLR2 as well as TLR5 in the response to flagella, and increased asialoGM1 correlated directly with increased signaling. TLR2 DN or TLR5 DN mutations inhibited interleukin-8 induction by 78% and 35%, respectively (P < 0.001 for each). The participation of TLR2 as well as TLR5 was confirmed in Chinese hamster ovary cells transfected with either human TLR2 or TLR5 in which flagella activated a nuclear factor-kappaB-luciferase reporter to the same extent. Flagella signaling in airway cells can be initiated by interactions with asialoGM1 and TLR2 as well as by activation of TLR5. The availability of exposed receptors on the apical surface of polarized airway epithelial cells is a major factor in the activation of signaling pathways by flagella.

Genome-wide search and identification of a novel gel-forming mucin MUC19/Muc19 in glandular tissues.

Abstract: Gel-forming mucins are major contributors to the viscoelastic properties of mucus secretion. Currently, four gel-forming mucin genes have been identified: MUC2, MUC5AC, MUC5B, and MUC6. All these genes have five major cysteine-rich domains (four von Willebrand factor [vWF] C or D domains and one Cystine-knot [CT] domain) as their distinctive features, in contrast to other non-gel-forming type of mucins. The CT domain is believed to be involved in the initial mucin dimer formation and have very succinct relationship between different gel-forming mucins across different species. Because of gene duplication and evolutional modification, it is very likely that other gel-forming mucin genes exist. To search for new gel-forming mucin candidate genes, a "Hidden Markov Model"(HMM) was built from the common features of the CT domains of those gel-forming mucins. By using this model to screen all protein databases as well as the six-frame translated expression sequence tag and translated human genomic databases, we identified a locus located at the peri-centromere region of human chromosome 12 and the corresponding homologous region of mouse chromosome 15. We cloned the 3' end of this gene and its mouse homolog. We found one vWF C domain, one CT domain, and various mucin-like threonine/serine-rich repeats. Phylogenetic analysis indicated the close relationship between this gene and the submaxillary mucin from porcine and bovine. A polydispersed signal was observed on the Northern blot, which indicates very large mRNA size. Further analysis of the upstream genomic sequences generated from human and mouse genome projects revealed three additional vWF D domains and many mucin-like threonine/serine-rich repeats. The expression of this gene is restricted to the mucous cells of various glandular tissues, including sublingual gland, submandibular gland, and submucosal gland of the trachea. Based on the chronological convention, we have given the name MUC19 to the human ortholog and Muc19 to the mouse.

The Use and Misuse of Penh in Animal Models of Lung Disease

Abstract: Models of the outer epithelia of the human body - namely the skin, the intestine and the lung - have found valid applications in both research and industrial settings as attractive alternatives to animal testing. A variety of approaches to model these barriers are currently employed in such fields, ranging from the utilization of ex vivo tissue to reconstructed in vitro models, and further to chip-based technologies, synthetic membrane systems and, of increasing current interest, in silico modeling approaches. An international group of experts in the field of epithelial barriers was convened from academia, industry and regulatory bodies to present both the current state of the art of non-animal models of the skin, intestinal and pulmonary barriers in their various fields of application, and to discuss research-based, industry-driven and regulatory-relevant future directions for both the development of new models and the refinement of existing test methods. Issues of model relevance and preference, validation and standardization, acceptance, and the need for simplicity versus complexity were focal themes of the discussions. The outcomes of workshop presentations and discussions, in relation to both current status and future directions in the utilization and development of epithelial barrier models, are presented by the attending experts in the current report.

Expression of Functional Toll-Like Receptor-2 and -4 on Alveolar Epithelial Cells

Abstract: The recognition of potentially harmful microorganisms involves the specific recognition of pathogen-associated molecular patterns (PAMPs) and the family of Toll-like receptors (TLRs) is known to play a central role in this process. TLR-4 is the major recognition receptor for lipopolysaccharide (LPS), a component of gram-negative bacterial cell walls, whereas TLR-2 responds to bacterial products from gram-positive organisms. Although resident alveolar macrophages are the first line of defense against microbial attack, it is now understood that the alveolar epithelium also plays a pivotal role in the innate immunity of the lung. The purpose of the current study was to determine whether human primary type II alveolar epithelial cells (ATII) express functional TLR-2 and TLR-4 and how they may be regulated by inflammatory mediators. We have used reverse transcriptase–polymerase chain reaction and flow cytometry to determine basal and inducible expression on ATII. We have used highly purified preparations of th...

Cigarette smoke induces senescence in alveolar epithelial cells.

Abstract: Cellular senescence is a state of irreversible growth arrest induced either by telomere shortening (replicative senescence) or by telomere-independent signals (stress-induced senescence). The alveolar epithelium is often injured by a variety of inhaled toxins, including cigarette smoke (CS). In the present study, we investigated whether exposure to CS induces senescence of alveolar epithelial cells. In vitro experiments showed that exposure of A549 cells or normal human alveolar epithelial cells to sublethal concentrations of aqueous CS extracts induced cellular senescence. The senescence was characterized by a dose- and time-dependent increase in senescence-associated β-galactosidase activity, senescence-associated changes in cell morphology, an increase in cell size and lysosomal mass, accumulation of lipofuscin, overexpression of p21CIP1/WAF1/Sdi1 protein, and irreversible growth arrest. In vivo experiments in Institute for Cancer Research mice showed that inhalation of CS for 2 wk induced increases in...

Gene Expression Profiling of Human Lung Tissue from Smokers with Severe Emphysema

Abstract: The mechanism by which inhaled smoke causes the anatomic lesions and physiologic impairment of chronic obstructive pulmonary disease remains unknown. We used high-density microarrays to measure gene expression in severely emphysematous lung tissue removed from smokers at lung volume reduction surgery (LVRS) and normal or mildly emphysematous lung tissue from smokers undergoing resection of pulmonary nodules. Class prediction algorithms identified 102 genes that accurately distinguished severe emphysema from non-/mildly emphysematous lung tissue. We also defined a number of genes whose expression levels correlated strongly with lung diffusion capacity for carbon monoxide and/or forced expiratory volume at 1 s. Genes related to oxidative stress, extracellular matrix synthesis, and inflammation were increased in severe emphysema, whereas expression of endothelium-related genes was decreased. To identify candidate genes that might be causally involved in the pathogenesis of emphysema, we linked gene expression profiles to chromosomal regions previously associated with chronic obstructive pulmonary disease in genome-wide linkage analyses. Unsupervised hierarchical clustering of the LVRS samples revealed distinct molecular subclasses of severe emphysema, with body mass index as the only clinical variable that differed between the groups. Class prediction models established a set of genes that predicted functional outcome at 6 mo after LVRS. Our findings suggest that the gene expression profiles from human emphysematous lung tissue may provide insight into pathogenesis, uncover novel molecular subclasses of disease, predict response to LVRS, and identify targets for therapeutic intervention.

Inhibition of Pulmonary Fibrosis by the Chemokine IP-10/CXCL10

Abstract: Pulmonary fibrosis is an enigmatic and devastating disease with few treatment options, now thought to result from abnormal wound healing in the lung in response to injury. We have previously noted a role for the chemokine interferon γ–inducible protein of 10 kD (IP-10)/CXC chemokine ligand 10 in the regulation of cutaneous wound healing, and consequently investigated whether IP-10 regulates pulmonary fibrosis. We found that IP-10 is highly expressed in a mouse model of pulmonary fibrosis induced by bleomycin. IP-10–deficient mice exhibited increased pulmonary fibrosis after administration of bleomycin, suggesting that IP-10 limits the development of fibrosis in this model. Substantial fibroblast chemoattractant and proliferative activities were generated in the lung after bleomycin exposure. IP-10 significantly inhibited fibroblast responses to the chemotactic, but not the proliferative activity generated, suggesting that IP-10 may attenuate fibroblast accumulation in bleomycin-induced pulmonary fibrosis ...

Cigarette smoke decreases pulmonary dendritic cells and impacts antiviral immune responsiveness.

Abstract: We investigated the impact of cigarette smoke exposure on respiratory immune defense mechanisms. Mice were exposed to two cigarettes daily, 5 d/wk, for 2-4 mo. Tobacco smoke decreased the number of dendritic cells (DCs) in the lung tissue. Furthermore, smoke exposure dramatically reduced the percentage of B7.1-expressing DCs. Because DCs are believed to be indispensable to the initiation of adaptive immune responses, we investigated the impact of cigarette smoke on immune responsiveness toward adenovirus. Mice were exposed to two cigarettes for 2-4 mo and inoculated with 2 x 10(8) pfu of a replication-deficient adenovirus on three occasions, 2 wk apart, during the last month of tobacco smoke exposure. Smoke exposure specifically prevented the expansion and maximal activation of CD4 T cells and reduced the number of both activated CD4 and CD8 T cells. Consequently, smoke exposure shifted the activated CD4:CD8 T cell ratio from 3 to 1.5 when compared with sham exposure. Significant decreases were also observed in serum adenovirus-specific pan IgG, IgG1, and IgG2a immunoglobulin levels, which was associated with diminished viral neutralization capacity. We demonstrate that chronic tobacco smoke exposure impairs the immune response against adenovirus. This may, in part, explain the increased prevalence of viral infections in chronic obstructive pulmonary disease.

Primary human alveolar type II epithelial cell chemokine release: effects of cigarette smoke and neutrophil elastase.

Abstract: An early response to cigarette smoke is an influx of leukocytes into the lung. Alveolar epithelial type II (ATII) cells may contribute by releasing chemokines in response to cigarette smoke and neutrophil elastase (NE). Human ATII cells were purified from normal regions of lungs resected for carcinoma (n = 14). In vitro, these cells exhibited ATII cell characteristics: lamellar bodies, apical microvilli, tight junctions, and expressed surfactant apoprotein C. Basal ATII cell release of five chemokines ranked as follows: monocyte chemotactic protein (MCP)-1 > interleukin (IL)-8 > growth-related oncogene (GRO)-alpha > macrophage inflammatory protein (MIP)-1alpha > regulated on activation, normal T cell expressed and secreted (RANTES). MIP-1alpha and RANTES were often not detectable. After stimulation with a mixture of lipopolysaccharide/endotoxin (LPS), tumor necrosis factor-alpha, IL-1beta, and IFN-gamma, MCP-1 and IL-8 secretion rose 4-6-fold, whereas GRO-alpha rose 25-fold. NE stimulated IL-8 mRNA expression, and 10nM NE stimulated IL-8 secretion; however, 100 nM NE caused a decrease in extracellular IL-8, MCP-1, and GRO-alpha, attributed to proteolysis. Cigarette smoke extract (CSE) inhibited IL-8 mRNA expression and release of all chemokines. Glutathione protected against the effects of CSE, suggesting oxidative mechanisms. GRO-alpha, important in growth and repair, was sensitive to both stimulation, by LPS:cytokines, and inhibition, by CSE. Thus, contrary to the original hypothesis, high concentrations of NE and CSE resulted in reduced extracellular chemokine levels. We hypothesize that reduced ATII cell-derived chemokine levels compromise alveolar repair, contributing to cigarette smoke-induced alveolar damage and emphysema.

Surfactant Protein-D Enhances Phagocytosis and Pulmonary Clearance of Respiratory Syncytial Virus

Abstract: Surfactant protein (SP)-D gene targeted (SP-D-/-) and wild-type mice were infected with respiratory syncytial virus (RSV) by intratracheal instillation. Decreased clearance of RSV was observed in SP-D-/- mice. Deficiency of SP-D was associated with increased inflammation and inflammatory cell recruitment in the lung after infection. In vitro, SP-D bound RSV-infected Vero cells. Binding was inhibited with ethylenediamine tetraacetic acid and maltose, suggesting that the carbohydrate recognition domain of SP-D recognizes RSV glycoproteins in a calcium-dependent manner. SP-D bound specifically to the RSV proteins G and F. Phagocytosis of RSV by alveolar macrophages was reduced in the absence of SP-D in vivo, and SP-D enhanced phagocytosis of RSV by alveolar macrophages and neutrophils but not peritoneal macrophages in vitro. Oxygen radical production by alveolar macrophages from SP-D+/+ and SP-D-/- mice was decreased after RSV infection, and SP-D ameliorated the inhibitory effects of RSV on oxygen radical production by macrophages and neutrophils in vitro. Because the airway is the usual portal of entry for RSV and other respiratory pathogens, the local production of SP-D is likely to play a role in innate defense responses to inhaled viruses.

Role of interleukin-5 and eosinophils in allergen-induced airway remodeling in mice.

Abstract: Asthma is a chronic inflammatory disease characterized by variable bronchial obstruction, hyperresponsiveness, and by tissue damage known as airway remodeling. In the present study we demonstrate that interleukin (IL)-5 plays an obligatory role in the airway remodeling observed in experimental asthma. BALB/c mice sensitized by intraperitoneal injections of ovalbumin and exposed daily to aerosol of ovalbumin for up to 3 wk, develop eosinophilic infiltration of the bronchi and subepithelial and peribronchial fibrosis. The lesions are associated with increased amounts of hydroxyproline in the lungs and elevated levels of eosinophils and transforming growth factor (TGF)-beta1 in the bronchoalveolar lavage fluid. After 1 wk of allergen challenge, TGF-beta is mainly produced by eosinophils accumulated in the peribronchial and perivascular lesions. At a later stage of the disease, the main source of TGF-beta is myofibroblasts, identified by alpha-smooth muscle actin mAb. We show that all these lesions, including fibrosis, are abolished in sensitized and allergen-exposed IL-5 receptor-null mice, whereas they are markedly accentuated in IL-5 transgenic animals. More importantly, treatment of wild-type mice with neutralizing anti-IL-5 antibody, administered before each allergen challenge, almost completely prevented subepithelial and peribronchial fibrosis. These findings demonstrated that eosinophils are involved in allergen-induced subepithelial and peribronchial fibrosis probably by producing a fibrogenic factor, TGF-beta1.

Conditional overexpression of bioactive transforming growth factor-β1 in neonatal mouse lung: A new model for bronchopulmonary dysplasia?

Abstract: Research interest in bronchopulmonary dysplasia (BPD) has steadily increased, and numerous potential mediators have been implicated in the development of the disease. Among such mediators is transforming growth factor (TGF)-β. Unfortunately, commonly utilized murine transgenic models are not optimal to investigate the effects of TGF-β specifically during the 2–3 wk period of alveolar formation, the developmental stage that corresponds histologically to early alveolar development in humans, and the time frame during which BPD develops. In the current study, we utilized a triple-transgenic construct to overexpress bioactive TGF-β1 in the neonatal mouse lung during the period of alveolar formation. Lungs were then examined by histologic, Western blot, and immunofluorescent methods. We found that overexpression of bioactive TGF-β1 in neonatal mouse lungs resulted in structural changes that have been described in BPD. Included in those characteristics are abnormal alveolar structure, cellular composition, and ...

Neutrophil defensins enhance lung epithelial wound closure and mucin gene expression in vitro.

Abstract: Human airways are frequently exposed to potentially harmful agents that cause tissue injury. Upon such injury, a repair process is initiated that comprises cell migration, proliferation, and differentiation. We have previously shown that human neutrophil defensins (human neutrophil peptides 1-3 [HNP1-3]) induce airway epithelial cell proliferation. Because of the role of cell proliferation in epithelial wound repair, we investigated the effect of HNP1-3 on airway epithelial wound closure and mucin gene expression in vitro. Using NCI-H292 airway epithelial cell cultures, we demonstrated that HNP1-3 cause a dose- and time-dependent increase of wound closure as well as increased cell migration. Furthermore, HNP1-3 caused a biphasic activation of the mitogen-activated protein kinase extracellular-regulated kinase 1 and 2 (ERK1/2). Both the effects of HNP1-3 on wound closure and ERK1/2 activation were blocked by specific inhibitors of the mitogen-activated protein kinase kinase MEK, whereas inhibitors of epidermal growth factor receptor tyrosine kinase, phosphatidylinositol 3-kinase, and Src did block defensin-enhanced wound closure but not ERK1/2 activation. Finally, HNP1-3 increased mRNA encoding the mucins MUC5B and MUC5AC, suggesting a role for defensins in mucous cell differentiation. These results indicate that neutrophil defensins increase epithelial wound repair in vitro, which involves migration and proliferation, and mucin production. Neutrophil defensin-enhanced wound repair appears to require epidermal growth factor receptor activation and downstream signaling pathways.

Cytoskeletal Activation and Altered Gene Expression in Endothelial Barrier Regulation by Simvastatin

Abstract: The statins, a class of HMG-CoA reductase inhibitors, directly affect multiple vascular processes via inhibition of geranylgeranylation, a covalent modification essential for Rho GTPase interaction with cell membrane-bound activators. We explored simvastatin effects on endothelial cell actomyosin contraction, gap formation, and barrier dysfunction produced by the edemagenic agent, thrombin. Human pulmonary artery endothelial cells exposed to prolonged simvastatin treatment (5 microM, 16 h) demonstrated significant reductions in thrombin-induced (1 U/ml) barrier dysfunction ( approximately 70% inhibition) with accelerated barrier recovery, as measured by transendothelial resistance. Furthermore, simvastatin attenuated basal and thrombin-stimulated (1 U/ml, 5 min) myosin light chain diphosphorylation and stress fiber formation while dramatically increasing peripheral immunostaining of actin and cortactin, an actin-binding protein, in conjunction with increased Rac GTPase activity. As both simvastatin-induced Rac activation and barrier protection were delayed (maximal after 16 h), we assessed the role of gene expression and protein translation in the simvastatin response. Simultaneous treatment with cycloheximide (10 microg/ml, 16 h) abolished simvastatin-mediated barrier protection. Robust alterations were noted in the expression of cytoskeletal proteins (caldesmon, integrin beta4), thrombin regulatory elements (PAR-1, thrombomodulin), and signaling genes (guanine nucleotide exchange factors) in response to simvastatin by microarray analysis. These novel observations have broad clinical implications in numerous vascular pathobiologies characterized by alterations in vascular integrity including inflammation, angiogenesis, and acute lung injury.

Connective tissue growth factor is crucial to inducing a profibrotic environment in "fibrosis-resistant" BALB/c mouse lungs.

Abstract: The individual susceptibility to pulmonary fibrosis (PF) remains a mystery, suggesting a role for genetic predisposition. The pathogenesis of PF involves a multitude of factors mediating crosstalk between various tissue components. Some factors, such as transforming growth factor , are recognized as key elements in the process, whereas the role of others, such as connective tissue growth factor (CTGF), is unclear. We investigated if Balb/c mice, known to be fibrosis resistant partly due to lack of CTGF induction upon stimulation with bleomycin, can be transformed into fibrosissensitive individuals by generation of a CTGF-rich environment using transient overexpression of CTGF by adenoviral gene transfer (AdCTGF). We show that AdCTGF is not sufficient to cause fibrosis, and that bleomycin challenge results in inflammation, but not fibrosis, in Balb/c mouse lungs. This inflammation is accompanied by lower levels of CTGF and tissue inhibitor of metalloproteinase–1 gene expression compared with fibrosis-prone C57BL/6 mice. However, concomitant administration of AdCTGF and bleomycin leads to a persistent upregulation of tissue inhibitor of metalloproteinase–1 gene and a significant fibrotic response in Balb/c similar to that in C57BL/6 mice. We propose that CTGF is an important mediator in the pathogenesis of PF in that it provides a local microenvironment in the lung that causes individual susceptibility. CTGF should be considered as a novel drug target and as a potential marker for identifying individuals at risk. Fibrosis is characterized by exaggerated extracellular matrix (ECM) accumulation due to excessive tissue repair and impaired matrix turnover (1). Although some agents capable of inducing this process are well described (e.g., drug-induced lung disease, irradiation damage), the causative agent frequently remains unknown, and the disorder seen in the lung is named idiopathic pulmonary fibrosis (PF) (2). The best-characterized drug-induced PF is caused by the antibiotic bleomycin, which is commonly integrated in chemotherapy protocols of leukemia and testicular cancer (3). In animal models, bleomycin is a helpful tool for studying the pathogenesis of lung fibrosis and for investigating the efficacy of new antifibrotic drugs (4). In humans, the individual susceptibility to PF remains a mystery, suggesting a role for genetic predisposition (5). In animal

Corticosteroid and cytokines synergistically enhance toll-like receptor 2 expression in respiratory epithelial cells

Abstract: Respiratory epithelial cells play important roles not only in host defense mechanisms, but also in inflammatory responses. Inhaled corticosteroids are widely used for the treatment of patients with inflammatory lung disorders, including asthma, chronic obstructive pulmonary disease, and sarcoidosis. Corticosteroids effectively reduce the production of inflammatory mediators, such as cytokines and chemokines. Although these molecules are also essential for host defense responses, there is no convincing evidence that inhaled corticosteroids increase susceptibility to lower respiratory tract infections. To test the involvement of Toll-like receptor (TLR) family molecules in this phenomenon, we examined the effects of various cytokines and corticosteroid on the expression of TLRs in human respiratory epithelial cells. Among the TLRs tested, TLR2 expression was significantly enhanced after stimulation with a combination of tumor necrosis factor-alpha and interferon-gamma. Dexamethasone synergistically enhanced TLR2 expression in combination with tumor necrosis factor-alpha and interferon-gamma in terms of both mRNA and protein levels. Furthermore, increased cell-surface TLR2 was functional, judging from the remarkable induction of interleukin-6, interleukin-8, and beta-defensin-2 after stimulation with peptidoglycan. These results provide evidence for a novel function of corticosteroids in airway inflammatory disorders, and indicate that the use of inhaled corticosteroids in such disorders may have a beneficial role in host defense mechanisms.

A2B Adenosine Receptors Increase Cytokine Release by Bronchial Smooth Muscle Cells

Abstract: Adenosine (Ado) has been suggested to play a role in inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease. The goal of this study was to determine the effect of Ado and its receptor subtypes on cytokine release by bronchial smooth muscle cells. The A2B Ado receptor (AdoR) was expressed at the highest level among the four AdoR subtypes. Activation of the A2B AdoR by an Ado analog, 5′-(N-ethylcarboxamido)-adenosine (NECA), increased cAMP accumulation with potency (EC50 value) of 21.2 ± 0.2 μM. The effect of NECA on the expression of the inflammatory cytokines was determined using a cDNA array consisting of 23 cytokine genes and confirmed using real-time reverse transcription–polymerase chain reaction and enzyme-linked immunosorbent assay. NECA increased the release of interleukin-6 and monocyte chemotactic protein-1 proteins with EC50 values of 1.26 ± 0.25 μM and 0.40 ± 0.08 μM, respectively, and the maximal folds of induction were 20.8 ± 1.7– and 6.4 ± 0.7–fold, respectivel...

MUC5AC and MUC5B mucins are decreased in cystic fibrosis airway secretions

Abstract: Cystic fibrosis (CF) is characterized by progressive airway obstruction. Although it has been postulated that this is due in part to mucus hypersecretion, there are no published data showing an increase in the gel-forming mucins MUC5AC or MUC5B in CF secretions. We used confocal microscopy to assess the amount of mucin-like glycoprotein and DNA in CF sputum and found more mucin in bronchitis sputum and a much greater amount of DNA in CF sputum. We then used antibodies to MUC5AC and MUC5B with Western gels and dot-blot to quantify mucin in sputum from 12 patients with CF and 11 subjects without lung disease. There was a 70% decrease in MUC5B and a 93% decrease in MUC5AC in CF sputum (P < 0.005 for both). We conclude that the vol/vol concentration of MUC5AC and MUC5B are decreased in the CF airways relative to normal mucus. This may be due to a relative increase in other components of sputum in the CF airway or to a primary defect in mucin secretion in CF.

Modulation of calcium signaling by interleukin-13 in human airway smooth muscle: role of CD38/cyclic adenosine diphosphate ribose pathway.

Abstract: CD38/cyclic adenosine diphosphate ribose (cADPR) signaling plays an important role in the regulation of intracellular calcium responses to agonists in a variety of cells, including airway smooth muscle (ASM) cells. The present study was aimed at determining the effect of interleukin (IL)-13, a cytokine implicated in the pathogenesis of asthma, on CD38/cADPR signaling and to ascertain the contribution of CD38/cADPR signaling to IL-13–induced airway hyperresponsiveness. Human ASM cells maintained in culture were exposed to 50 ng/ml IL-13 for 22 h and levels of CD38 expression and intracellular calcium responses to agonists were measured. Treatment of human ASM cells with IL-13 resulted in increased CD38 expression as determined by real-time polymerase chain reaction, Western blot analysis, and indirect immunofluorescence. Increased CD38 expression was reflected as increased ADP-ribosyl cyclase activity in the ASM cell membranes. The net intracellular calcium responses to bradykinin, thrombin, and histamine ...

Emphysema Lung Tissue Gene Expression Profiling

Abstract: Emphysema occurs in a subgroup of patients with chronic obstructive pulmonary disease and patients with the genetic defect of alpha(1)-antitrypsin deficiency who have a smoking history of many years' duration. Emphysema is generally the result of a chronic and progressive destruction of the alveolar structures, which is believed to be driven by chronic inflammation, infections, oxidative stress, and an imbalance of protease and antiprotease activity. Here, we use microarray technology to characterize the gene expression profile of lung tissue samples obtained from patients with advanced emphysema and that obtained from healthy subjects. We hypothesized that the gene expression profile of emphysema lung tissue is distinct when compared with the expression profile of normal lungs. We report that severely emphysematous tissue is characterized by a global decrease in gene expression and by an increased abundance of transcripts encoding proteins involved in inflammation, immune responses, and proteolysis. Whereas the gene expression profile is to some degree shared between "usual" emphysema and alpha(1)-antitrypsin deficiency-related emphysema, there are statistically significant differences in the modulation of groups of genes associated with protein and energy metabolism, and immune function, which allow distinction between these two emphysema types on the lung tissue level.

Neurotrophin and neurotrophin receptor protein expression in the human lung.

Abstract: Neurotrophins (NTs) promote survival and differentiation of central and peripheral neurons, and display several activities also in non-neuronal cells. Human lungs synthesize and release NTs, which are probably involved in the pathophysiology of pulmonary disturbances. In this article the expression and anatomic localization of nerve growth factor, brain-derived neurotrophic factor, and NT-3 and of corresponding high-affinity receptors TrkA, TrkB (full-length and truncated [TR-] isoforms), TrkC, and of the low-affinity p75 receptor, were assessed in surgical samples from adult human lung by reverse transcriptase–polymerase chain reaction, Western blot, and immunohistochemistry. NTs and their cognate receptor mRNA and protein transcripts were detected by reverse transcriptase–polymerase chain reaction and immunoblotting, respectively, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) mRNA and corresponding protein transcripts being the most expressed. High levels of TrkB-[TR-] mRNA and ...

Specific inhibition of type I interferon signal transduction by respiratory syncytial virus.

Abstract: Respiratory viruses often express mechanisms to resist host antiviral systems, but the biochemical basis for evasion of interferon effects by respiratory syncytial virus (RSV) is poorly defined. In this study, we identified RSV effects on interferon (IFN)-dependent signal transduction and gene expression in human airway epithelial cells. Initial experiments demonstrated inhibition of antiviral gene expression induced by IFN-alpha and IFN-beta, but not IFN-gamma, in epithelial cells infected with RSV. Selective viral effects on type I IFN-dependent signaling were confirmed when we observed impaired type I, but not type II, IFN-induced activation of the transcription factor Stat1 in RSV-infected cells. RSV infection of airway epithelial cells resulted in decreased Stat2 expression and function with preservation of upstream signaling events, providing a molecular mechanism for viral inhibition of the type I IFN JAK-STAT pathway. Furthermore, nonspecific pharmacologic inhibition of proteasome function in RSV-infected cells restored Stat2 levels and IFN-dependent activation of Stat1. The results indicate that RSV acts on epithelial cells in the airway to directly modulate the type I IFN JAK-STAT pathway, and this effect is likely mediated though proteasome-dependent degradation of Stat2. Decreased antiviral gene expression in RSV-infected airway epithelial cells may allow RSV replication and establishment of a productive viral infection through subversion of IFN-dependent immunity.

Interleukin-22: a potential immunomodulatory molecule in the lung.

Abstract: Interleukin (IL)-22 is a member of the human type I interferon family, which includes IL-10. IL-22 has the potential to interact with IL-10 because it binds to the IL-10R2c chain with IL-22R1 in its receptor complex. Binding can be blocked by the soluble receptor, IL-22 binding protein (IL-22BP). We hypothesize that IL-22 and IL-22BP are involved in inflammatory regulation and its subsequent role in the pathogenesis of inflammatory lung disease. We have demonstrated IL-22 mRNA expression in alveolar macrophages (AM), monocytes, and alveolar epithelial (AE) cells. IL-22BP mRNA is expressed in AM, AE cells, and neutrophils. In contrast, IL-22R1 is expressed in AE only. Immunohistochemistry on normal and interstitial lung disease lung sections has confirmed IL-22 protein expression. Western blotting for IL-22 in bronchoalveolar lavage fluid demonstrated that lower levels of IL-22 were present in patients with acute respiratory distress syndrome and sarcoidosis relative to control subjects (P = 0.0152 and P = 0.0213). Levels of IL-22 in idiopathic pulmonary fibrosis were not different than those of the control subjects (P = 0.5838). IL-22 did not affect IL-10 inhibition of tumor necrosis factor-alpha in monocytes, which do not express IL-22R1. By contrast, we demonstrated synergy between IL-10 and IL-22 in terms of IL-8 inhibition in IL-22R1-expressing A549 cells. These data suggest a role for IL-22 in the regulation of pulmonary inflammation.

Acute allergen-induced airway remodeling in atopic asthma.

Abstract: Studies in animals and in human atopic skin suggest that allergen challenge may activate acute tissue remodeling changes via transforming growth factor-beta pathways. We determined whether inhalational allergen challenge in subjects with mild asthma induces similar acute changes to the airway epithelial mesenchymal trophic unit (EMTU). Endobronchial mucosal biopsies obtained before and 24 h after challenge were examined by confocal microscopy for extracellular matrix deposition in the reticular basement membrane (RBM). Cells actively involved in extracellular matrix synthesis were identified as immunoreactive to heat shock protein 47, a chaperone of collagen synthesis. Interleukin-4/13 and transforming growth factor-beta-activated cells were identified by specific antibodies to phosphorylated (phospho-) signal transducer and activator of transcription 6 and phospho-Smad2, respectively. After allergen challenge, there was a significant increase in the number of heat shock protein 47-positive airway fibroblasts (P = 0.003) and in the thickness of tenascin in the RBM (P = 0.031). There were also increases in the number of phospho-Smad2+ epithelial cells (P = 0.04) and nuclear phospho-Smad2+ fibroblasts (P = 0.03), as well as phospho-signal transducer and activator of transcription 6+ epithelial cells (P = 0.03), after allergen challenge. Thus, allergen challenge in patients with mild asthma induces activation of epithelial cells and fibroblasts in the EMTU as well as increased tenascin deposition within the RBM. Airway remodeling in asthma may, in part, result from repeated acute activation of the EMTU by allergen exposure.