Showing papers on "Respiratory epithelium published in 2003"
TL;DR: Investigation of MUC5B expression demonstrated that IL-17's effect is at least partly mediated through IL-6 by a JAK2-dependent autocrine/paracrine loop, and evidence is presented to show that both IL-4, IL-9, and IL-13 mediate Muc5Bexpression through the ERK signaling pathway.
566 citations
TL;DR: Analysis of the ontogeny of the disease in children and use of gene array technology should provide some important answers to allow a better understanding of the critical role that the epithelium plays under normal conditions and in diseases such as asthma.
Abstract: The major function of the respiratory epithelium was once thought to be that of a physical barrier. However, it constitutes the interface between the internal milieu and the external environment as well as being a primary target for inhaled respiratory drugs. It also responds to changes in the external environment by secreting a large number of molecules and mediators that signal to cells of the immune system and underlying mesenchyme. Thus, the epithelium is in a unique position to translate gene-environment interactions. Normally, the epithelium has a tremendous capacity to repair itself following injury. However, evidence is rapidly accumulating to show that the airway epithelium of asthmatics is abnormal and has increased susceptibility to injury compared to normal epithelium. Areas of detachment and fragility are a characteristic feature not observed in other inflammatory diseases such as COPD. In addition to being more susceptible to damage, normal repair processes are also compromised. Failure of appropriate growth and differentiation of airway epithelial cells will cause persistent mucosal injury. The response to traditional therapy such as glucocorticoids may also be compromised. However, whether the differences observed in asthmatic epithelium are a cause of or secondary to the development of the disease remains unanswered. Strategies to address this question include careful examination of the ontogeny of the disease in children and use of gene array technology should provide some important answers, as well as allow a better understanding of the critical role that the epithelium plays under normal conditions and in diseases such as asthma.
556 citations
TL;DR: A new paradigm for asthma pathogenesis is presented in which exaggerated inflammation and remodeling in the airways are a consequence of abnormal injury and repair responses arising from a subject's susceptibility to components of the inhaled environment as discussed by the authors.
Abstract: A new paradigm for asthma pathogenesis is presented in which exaggerated inflammation and remodeling in the airways are a consequence of abnormal injury and repair responses arising from a subject's susceptibility to components of the inhaled environment. An epithelial-mesenchymal trophic unit becomes activated to drive pathologic remodeling and smooth muscle proliferation through complex cytokine interactions. Histamine, prostanoids, and cysteinyl leukotrienes (CysLTs) are potent contractile agonists of airway smooth muscle (ASM). The CysLTs appear to play a central role in regulating human ASM motor tone and phenotypic alterations, manifested as hypertrophy and hyperplasia in chronic severe asthma. The CysLTs augment growth factor–induced ASM mitogenesis through activation of CysLT receptors. Although they mediate their contractile effects by increasing phosphoinositide turnover and inducing increased cytosolic calcium, new data suggest that part of the contractile effect may be independent of calcium mobilization. Prostaglandin E 2 , the predominant eicosanoid product of the airway epithelium, is a potent inhibitor of mitogenesis, collagen synthesis, and mesenchymal cell chemotaxis and therefore can suppress inflammation and fibroblast activation. The capacity of the epithelium for CysLT synthesis is inversely related to its ability to make PGE 2 . The ASM is capable of expressing both leukotriene-synthesizing enzymes and CysLT receptors, and cytokines upregulate the receptor expression. This may be an explanation for the CysLTs promoting airway hyperresponsiveness in asthma. The CysLTs play an important role in the airway remodeling seen in persistent asthma that includes increases of airway goblet cells, mucus, blood vessels, smooth muscle, myofibroblasts, and airway fibrosis. Evidence from a mouse model of asthma demonstrated that CysLT 1 receptor antagonists inhibit the airway remodeling processes, including eosinophil trafficking to the lungs, eosinophil degranulation, T H 2 cytokine release, mucus gland hyperplasia, mucus hypersecretion, smooth muscle cell hyperplasia, collagen deposition, and lung fibrosis. (J Allergy Clin Immunol 2003;111:S18-36.)
306 citations
Journal Article•
TL;DR: Evidence from a mouse model of asthma demonstrated that CysLT(1) receptor antagonists inhibit the airway remodeling processes, including eos inophil trafficking to the lungs, eosinophil degranulation, T(H)2 cytokine release, mucus gland hyperplasia, smooth muscle, myofibroblasts, and airway fibrosis.
Abstract: A new paradigm for asthma pathogenesis is presented in which exaggerated inflammation and remodeling in the airways are a consequence of abnormal injury and repair responses arising from a subject's susceptibility to components of the inhaled environment. An epithelial-mesenchymal trophic unit becomes activated to drive pathologic remodeling and smooth muscle proliferation through complex cytokine interactions. Histamine, prostanoids, and cysteinyl leukotrienes (CysLTs) are potent contractile agonists of airway smooth muscle (ASM). The CysLTs appear to play a central role in regulating human ASM motor tone and phenotypic alterations, manifested as hypertrophy and hyperplasia in chronic severe asthma. The CysLTs augment growth factor-induced ASM mitogenesis through activation of CysLT receptors. Although they mediate their contractile effects by increasing phosphoinositide turnover and inducing increased cytosolic calcium, new data suggest that part of the contractile effect may be independent of calcium mobilization. Prostaglandin E 2 , the predominant eicosanoid product of the airway epithelium, is a potent inhibitor of mitogenesis, collagen synthesis, and mesenchymal cell chemotaxis and therefore can suppress inflammation and fibroblast activation. The capacity of the epithelium for CysLT synthesis is inversely related to its ability to make PGE 2 . The ASM is capable of expressing both leukotriene-synthesizing enzymes and CysLT receptors, and cytokines upregulate the receptor expression. This may be an explanation for the CysLTs promoting airway hyperresponsiveness in asthma. The CysLTs play an important role in the airway remodeling seen in persistent asthma that includes increases of airway goblet cells, mucus, blood vessels, smooth muscle, myofibroblasts, and airway fibrosis. Evidence from a mouse model of asthma demonstrated that CysLT 1 receptor antagonists inhibit the airway remodeling processes, including eosinophil trafficking to the lungs, eosinophil degranulation, T H 2 cytokine release, mucus gland hyperplasia, mucus hypersecretion, smooth muscle cell hyperplasia, collagen deposition, and lung fibrosis.
279 citations
TL;DR: It is suggested that RSV infection sensitizes airway epithelium to a subsequent environmental exposure (LPS) by altered expression and membrane localization of TLR4 and has the potential to profoundly alter airway inflammation.
274 citations
TL;DR: Data support the concept that IL-13 is in part able to induce a mucus hypersecretory phenotype through a direct interaction with the airway epithelium and that MAP kinase and PtdIns 3-kinase signaling pathways are involved.
Abstract: In addition to a direct proinflammatory role, IL-13 has been demonstrated to induce a goblet cell metaplastic phenotype in the airway epithelium in vivo. We have studied the direct effects of IL-13 (and IL-4) on well-differentiated, air-liquid interface cultures of human bronchial epithelial cells (HBEs) and provide a quantitative assessment of the development of a mucus hypersecretory phenotype induced by these cytokines. Using Alcian blue staining of goblet cells and immunohistochemical detection of MUC5AC, we found that IL-13 (and IL-4) induced increases in the goblet cell density (GCD) of the HBE cultures. The effects of these cytokines were critically dependent on concentration: 1 ng/ml routinely induced a 5- to 10-fold increase in GCD that was associated with a hypersecretory ion transport phenotype. Paradoxically, 10 ng/ml of either cytokine induced a profound reduction in GCD. Removal of EGF from the culture media or treatment of the cells with AG-1478 [a potent inhibitor of EGF receptor tyrosine kinase (EGFR-TK)] demonstrated that the EGFR-TK pathway was key to the regulation of the basal GCD but that it was not involved in the IL-13-driven increase. The IL-13-driven increase in GCD was, however, sensitive to inhibition of MEK (PD-98059, U-0126), p38 MAPK (SB-202190), and phosphatidylinositol (PtdIns) 3-kinase (LY-294002). These data support the concept that IL-13 is in part able to induce a mucus hypersecretory phenotype through a direct interaction with the airway epithelium and that MAP kinase and PtdIns 3-kinase signaling pathways are involved.
260 citations
TL;DR: The nature of aerosolized drugs, characteristics of delivery systems and the depositional and pulmonary clearance mechanisms display major targets to optimize pulmonary drug delivery, and the future characterization of pulmonary drug transport pathways can lead to new strategies in aerosol drug therapy.
229 citations
TL;DR: It is proposed that the antioxidant-related genes demonstrating the most variability in the level of expression in smokers may be useful genetic markers in epidemiologic studies assessing susceptibility to smoking-induced chronic bronchitis.
Abstract: Cigarette smoking is the major risk factor for developing chronic bronchitis, yet only 15-20% of smokers develop this disorder. Because oxidants are the major mechanism of smoking-induced airway damage, we hypothesized that smoking is associated with upregulation of various antioxidant-related genes in the airway epithelium, but the magnitude of the response shows high inter-individual variability. Microarray analysis was used to assess levels of expression of 44 antioxidant-related genes in four categories (catalase/superoxide dismutase family; glutathione metabolism; redox balance; and pentose phosphate cycle) in bronchoscopy-obtained airway epithelium of matched cohorts (13 current smokers, 9 nonsmokers), none of whom had lung disease. There was minimal variation in gene expression levels within the same individual (right versus left lung or over time), but significant upregulation of 16/44 antioxidant-related genes in smoker epithelium compared with nonsmokers. Subgroups of smokers were identified with clusters of expression levels of antioxidant-related genes. We propose that the antioxidant-related genes demonstrating the most variability in the level of expression in smokers may be useful genetic markers in epidemiologic studies assessing susceptibility to smoking-induced chronic bronchitis.
210 citations
TL;DR: It is demonstrated that airway epithelial cells play a prominent role in orchestrating the airway inflammatory response to LPS and suggest that NF-κB signaling in these cells is important for modulating innate immune responses to microbial products.
Abstract: To reveal the causal role of airway epithelial NF-kappaB activation in evoking airway inflammation, a transgenic mouse was created expressing a mutant version of the inhibitory protein I-kappaBalpha This I-kappaBalpha superrepressor (I-kappaBalpha(SR)) acts to repress NF-kappaB activation exclusively in airway epithelial cells, under the transcriptional control of the rat CC10 promoter (CC10-I-kappaBalpha(SR)) Compared with transgene-negative littermates, intranasal instillation of LPS did not induce nuclear translocation of NF-kappaB in airway epithelium of CC10-I-kappaBalpha(SR) transgenic mice Consequently, the influx of neutrophils into the airways and secretion of the NF-kappaB-regulated neutrophilic chemokine, macrophage-inflammatory protein-2, and the inflammatory cytokine, TNF-alpha, were markedly reduced in CC10-I-kappaBalpha(SR) mice relative to the transgene-negative mice exposed to LPS Despite an inability to activate NF-kappaB in airway epithelium, resident alveolar macrophages from transgene-positive mice were capable of activating NF-kappaB in a manner indistinguishable from transgene-negative mice These findings demonstrate that airway epithelial cells play a prominent role in orchestrating the airway inflammatory response to LPS and suggest that NF-kappaB signaling in these cells is important for modulating innate immune responses to microbial products
184 citations
TL;DR: Exposure to Zn2+ ions causes PTEN degradation and loss of function, which is mediated by an ubiquitin-associated proteolytic process in the airway epithelium.
149 citations
TL;DR: DEE-induced changes in inflammatory and lung epithelial responses to infection were associated with increased RSV gene expression in the lungs following DEE exposure, consistent with the concept thatDEE exposure modulates the lung host defense to respiratory viral infections and may alter the susceptibility to respiratory infections leading to increased lung disease.
Abstract: Although epidemiologic data strongly suggest a role for inhaled environmental pollutants in modulating the susceptibility to respiratory infection in humans, the underlying cellular and molecular mechanisms have not been well studied in experimental systems. The current study assessed the impact of inhaled diesel engine emissions (DEE) on the host response in vivo to a common pediatric respiratory pathogen, respiratory syncytial virus (RSV). Using a relatively resistant mouse model of RSV infection, prior exposure to either 30 microg/m3 particulate matter (PM) or 1,000 microg/m3 PM of inhaled DEE (6 h/d for seven consecutive days) increased lung inflammation to RSV infection as compared with air-exposed RSV-infected C57Bl/6 mice. Inflammatory cells in bronchoalveolar lavage fluid were increased in a dose-dependent manner with regard to the level of DEE exposure, concomitant with increased levels of inflammatory mediators. Lung histology analysis indicated pronounced peribronchial and peribronchiolar inflammation concordant with the level of DEE exposure during infection. Mucous cell metaplasia was markedly increased in the airway epithelium of DEE-exposed mice following RSV infection. Interestingly, both airway and alveolar host defense and immunomodulatory proteins were attenuated during RSV infection by prior DEE exposure. DEE-induced changes in inflammatory and lung epithelial responses to infection were associated with increased RSV gene expression in the lungs following DEE exposure. These findings are consistent with the concept that DEE exposure modulates the lung host defense to respiratory viral infections and may alter the susceptibility to respiratory infections leading to increased lung disease.
TL;DR: These data demonstrate that the differential response of endothelial cells in distal vascular beds and large central blood vessels is established early in lung development, and Precise temporal and spatial expression of VEGF-A is required for vascular patterning during lung morphogenesis.
TL;DR: L Laboratory studies now suggest that CFTR is involved in regulating some neutrophil functions and indicate that altered properties of CF neutrophils may depend on genetic factors.
TL;DR: The data suggest that RSV requires proper ARE-mediated protein sorting for efficient egress from the apical surface of polarized epithelial cells, which suggests thatRSV uses specific cellular trafficking pathways to accomplish viral replication.
Abstract: Respiratory syncytial virus (RSV) is the major viral cause of serious lower respiratory tract illness in infants and young children worldwide. RSV infection is limited to the superficial layers of the respiratory epithelium in immunocompetent individuals. Consistent with this in vivo observation, we and others have found that RSV buds preferentially from the apical surface of infected polarized epithelial cells. In contrast, directional budding is not observed in nonpolarized human epithelial cells. These findings suggest that RSV uses specific cellular trafficking pathways to accomplish viral replication. The host cell proteins that regulate directional budding of RSV are undefined. Apical sorting of cellular proteins in polarized epithelial cells involves the apical recycling endosome (ARE). To investigate whether ARE-mediated protein sorting plays a role during RSV replication, we expressed a fragment of the myosin Vb tail that functions as a dominant negative inhibitor of ARE-mediated protein sorting in polarized Madin-Darby canine kidney cells. When these cells were infected with RSV, a >9,000-fold reduction in viral yield was observed. A similar effect on virus replication was observed when a carboxyl-terminal fragment of another ARE-associated protein, the Rab11 family interacting protein 1, was expressed in Madin-Darby canine kidney cells. These data suggest that RSV requires proper ARE-mediated protein sorting for efficient egress from the apical surface of polarized epithelial cells.
TL;DR: Wide intercellular spaces and poorly developed desmosomes are closely correlated with a permeable nature, and there is still uncertainty over the phagocytotic activity of the epithelium.
Abstract: This review summarizes the biological properties of the junctional epithelium, focusing on its developmental aspects, wide intercellular spaces and desmosomes, dense granules, permeability barrier, phagocytotic activity, adhesive structures and nerve terminals. It also discusses the morphology and functions of long junctional epithelium and peri-implant epithelium. Junctional epithelium is derived from the reduced enamel epithelium during tooth development. Apoptosis occurs in the border between oral and reduced enamel epithelia during tooth eruption. Junctional epithelium expresses a cytokeratin-19 immunoreaction, suggesting that this protein is a consistent differentiation marker. Wide intercellular spaces, which contain neutrophils and nerve endings, are formed as there are fewer desmosomes than in the oral epithelium. Dense, membrane-bound granules in the epithelium might correspond with membrane-coating granules, as revealed by their shape, components and freeze-fracture images. Junctional epithelium with high permeability contains exogenously expressed alpha-defensins, while stratified epithelia contain endogenously expressed beta-defensins. The phagocytotic activity in this epithelium remains unclear. Integrin-alpha6beta4 and laminin-5 form a complex in the tooth surface internal basal lamina. Long junctional epithelium created experimentally attaches to the cementum surface by hemidesmosomes and basal lamina. The peri-implant epithelium differs in proliferation and in adhesive structure from the normal junctional epithelium. In conclusion, wide intercellular spaces and poorly developed desmosomes are closely correlated with a permeable nature. There is still uncertainty over the phagocytotic activity of the epithelium. Integrin-alpha6beta4 and laminin-5 form a significant complex in the internal basal lamina. Junctional epithelium receives a rich sensory nerve and has a high rate of cell turnover. Long junctional epithelium can be produced rapidly during wound healing, due to high proliferative activity. Peri-implant epithelium might be a poorly adhered and permeable epithelium.
TL;DR: The data suggest that GBC‐2(+) cells are ultimately responsible for regenerating olfactory neuroepithelium, and support the idea that a subpopulation of GBCs is the neural stem cell of the Olfactory epithelium.
Abstract: Despite a remarkable regenerative capacity, recovery of the mammalian olfactory epithelium can fail in severely injured areas, which subsequently reconstitute as aneuronal respiratory epithelium (metaplasia). We contrasted the cellular response of areas of the rat epithelium that recover as olfactory after methyl bromide lesion with those undergoing respiratory metaplasia in order to identify stem cells that restore lesioned epithelium as olfactory. Ventral olfactory epithelium is at particular risk for metaplasia after lesion and patches of it are rendered acellular by methyl bromide exposure. In contrast, globose basal cells (GBCs, marked by staining with GBC-2) are preserved in surrounding ventral areas and uniformly throughout dorsal epithelium, which consistently and completely recovers as olfactory after lesion. Over the next few days, neurons reappear, but only in those areas in which GBCs are preserved and multiply. In contrast, parts of the epithelium in which GBCs are destroyed are repopulated in part by Bowman's gland cells, which pile up above the basal lamina. Electron microscopy confirms the reciprocity between gland cells and globose basal cells. By 14 days after lesion, the areas that are undergoing metaplasia are repopulated by typical respiratory epithelial cells. As horizontal basal cells are eliminated from all parts of the ventral epithelium, the data suggest that GBC-2(+) cells are ultimately responsible for regenerating olfactory neuroepithelium. In contrast, GLA-13(+) cells may give rise to respiratory metaplastic epithelium where GBCs are eliminated. Thus, we support the idea that a subpopulation of GBCs is the neural stem cell of the olfactory epithelium.
TL;DR: It is demonstrated that ectopic expression of Notch3 in airway epithelium potentially contributes to the multistep evolution of lung cancer through the inhibition of terminal differentiation.
Abstract: Notch3 is a transmembrane receptor and a member of the Notch signaling pathway essential for cellular differentiation in a variety of developing tissues in both invertebrates and vertebrates. Emerging data support the role of the Notch signaling pathway in tumorigenesis. We have previously demonstrated the expression of Notch3 in a subset of lung adenocarcinomas. To further elucidate the role of Notch3 in development of lung cancer, we established a transgenic mouse model in which the intracellular domain of Notch3 is expressed using the surfactant protein C promoter/enhancer. Constitutive expression of Notch3 in the peripheral epithelium in the developing lung resulted in altered lung morphology and delayed development, leading to perinatal lethality in these transgenic mice. Cell-specific markers and electron microscopy examination showed that the majority of the epithelial cells are undifferentiated, with some maturation of type II pneumocytes. No type I alveolar cells were evident. Metaplasia of undifferentiated cells in the terminal airways was also observed. Although the mice did not live long enough to assess tumor development, these findings demonstrate that ectopic expression of Notch3 in airway epithelium potentially contributes to the multistep evolution of lung cancer through the inhibition of terminal differentiation.
TL;DR: The elderly are frequently classified as being particularly susceptible to air pollution, and the basis of this increased sensitivity is not known but it is likely that it is linked to age-related impaired function of the lung.
Abstract: The elderly are frequently classified as being particularly susceptible to air pollution. The basis of this increased sensitivity is not known but it is likely that it is linked to age-related impaired function of the lung. However, given this uncertainty and increased impact of air pollution of this section of the community there is a need to explore the mechanisms involved.
Gaseous air pollutants such as ozone and nitrogen dioxide, or many of the components adsorbed onto the surface of respirable particles, are either powerful oxidants or capable of generating free radicals. If unabated, oxidants can cause injury to the delicate cells that line the respiratory tract. Small molecular weight antioxidant defences present in respiratory tract lining fluid (RTLF) represent the first line of defence against a range of oxidants that enter the lung. The quantity and quality of the RTLF airways antioxidant network are, therefore, likely to be important determinants of the impact of the oxidant challenge on the underlying respiratory epithelium.
As yet, comprehensive information on the distribution and variability of respiratory tract lining fluid antioxidant defences is only available in young, mainly healthy volunteers. Studies undertaken in patients with a range of respiratory diseases suggest that marked changes in the distribution of respiratory tract lining fluid antioxidants can occur. Information is not currently available on the impact of ageing on the respiratory tract lining fluid antioxidant defence network. As several respiratory tract lining fluid antioxidants are of dietary origin, the elderly, who often have different dietary patterns to younger individuals, may have decreased availability of important antioxidants. Given these possibilities, a better understanding of respiratory tract lining fluid antioxidant defences in the aged lung is warranted.
TL;DR: It is hypothesized that zinc has a protective role for the airway epithelium against oxyradicals and other noxious agents, with important implications for asthma and other inflammatory diseases where the epithelial barrier is vulnerable and compromised.
TL;DR: Recent studies proved that the control occurs by different expressions of retinoid receptors as well as by time-dependent changes of the vitamin-A-metabolism respectively via cellular vitamin- A-binding proteins (CRBP: cytoplasmatic retinol binding protein; CRABP: Cytoplasmaatic retinoic acid binding protein).
TL;DR: In conclusion, epithelial cell death did not appear to be the stimulus driving epithelial proliferation and the increase in mucous cell numbers was primarily a result of Clara cell metaplasia.
Abstract: Increased mucus production in asthma is an important cause of airflow obstruction during severe exacerbations. To better understand the changes in airway epithelium that lead to increased mucus production, ovalbumin-sensitized and -challenged mice were used. The phenotype of the epithelium was dramatically altered, resulting in increased numbers of mucous cells, predominantly in the proximal airways. However, the total numbers of epithelial cells per unit area of basement membrane did not change. A 75% decrease in Clara cells and a 25% decrease in ciliated cells were completely compensated for by an increase in mucous cells. Consequently, by day 22, 70% of the total epithelial cell population in the proximal airways was mucous cells. Electron microscopy illustrated that Clara cells were undergoing metaplasia to mucous cells. Conversely, epithelial proliferation, detected with 5-chloro-2-deoxyuridine immunohistochemistry, was most marked in the distal airways. Using ethidium homodimer cell labeling to evaluate necrosis and terminal dUTP nick-end labeling immunohistochemistry to evaluate apoptosis, this proliferation was accompanied by negligible cell death. In conclusion, epithelial cell death did not appear to be the stimulus driving epithelial proliferation and the increase in mucous cell numbers was primarily a result of Clara cell metaplasia.
TL;DR: The novel finding of increased apoptosis of stimulated T cells in COPD is demonstrated and it is shown that the increased T-cell death may be associated with upregulation of apoptotic pathways, TGF-beta, TNF-alpha, and Fas in the peripheral blood in COPd.
Abstract: Chronic obstructive pulmonary disease (COPD) is associated with inflammation of airway epithelium, including an increase in the number of intraepithelial T cells. Increased apoptosis of these T cel...
TL;DR: Data show that selective expression of IκB kinases in airway epithelium results in NF-κB activation, inflammatory mediator production, and neutrophilic lung inflammation, and Therapies targeted to NF-σκB in lung epithelia may be beneficial in treating inflammatory lung diseases.
Abstract: To determine whether NF-kappaB activation is sufficient to generate lung inflammation in vivo, we selectively expressed a constitutively active form of IkappaB kinase 1 (cIKK1) or IkappaB kinase 2 (cIKK2) in airway epithelium. After intratracheal administration of adenoviral vectors expressing cIKK1 or cIKK2 to transgenic reporter mice that express Photinus luciferase under the control of an NF-kappaB-dependent promoter, we detected significantly increased luciferase activity over time (up to 96 h). Compared with control mice treated with adenoviral vectors expressing beta-galactosidase, lung bioluminescence and tissue luciferase activity were increased in NF-kappaB reporter mice treated with adenovirus (Ad)-cIKK1 or Ad-cIKK2. NF-kappaB activation in lungs of Ad-cIKK1- and Ad-cIKK2-treated mice was confirmed by immunoblots for RelA and EMSA from lung nuclear protein extracts. Mice treated with Ad-cIKK1 or Ad-cIKK2 showed induction of mRNA expression of several chemokines and cytokines in lung tissue. In lung lavage fluid, mice treated with Ad-cIKK1 or Ad-cIKK2 showed elevated concentrations of NF-kappaB-dependent chemokines macrophage-inflammatory protein 2 and KC and increased numbers of neutrophils. Coadministration of adenoviral vectors expressing a transdominant inhibitor of NF-kappaB with Ad-cIKK1 or Ad-cIKK2 resulted in abrogated NF-kappaB activation and other parameters of lung inflammation, demonstrating that the observed inflammatory effects of Ad-cIKK1 and Ad-cIKK2 were dependent on NF-kappaB activation by these kinases. These data show that selective expression of IkappaB kinases in airway epithelium results in NF-kappaB activation, inflammatory mediator production, and neutrophilic lung inflammation. Therapies targeted to NF-kappaB in lung epithelium may be beneficial in treating inflammatory lung diseases.
TL;DR: Bleomycin increases the number of airway secretory cells and their mucin production, and that oral N‐acetylcysteine improved pulmonary lesions and reduced the mucus hypersecretion in the bleomycin rat model.
Abstract: Oxidative stress is involved in the pathogenesis of pulmonary fibrosis, therefore antioxidants may be of therapeutic value. Clinical work indicates that N ‐acetylcysteine (NAC) may be beneficial in this disease. The activity of this antioxidant was examined on bleomycin-induced lung damage, mucus secretory cells hyperplasia and mucin Muc5ac gene expression in rats.
NAC (3 mmol·kg−1·day−1) or saline was given orally to Sprague-Dawley rats for 1 week prior to a single intratracheal instillation of bleomycin (2.5 U·kg−1) and for 14 days postinstillation.
NAC decreased collagen deposition in bleomycin-exposed rats (hydroxyproline content was 4,257±323 and 3,200±192 µg·lung−1 in vehicle- and NAC‐treated rats, respectively) and lessened the fibrotic area assessed by morphometric analysis. The bleomycin-induced increases in lung tumour necrosis factor‐α and myeloperoxidase activity were reduced by NAC treatment. The numbers of mucus secretory cells in airway epithelium, and the Muc5ac messenger ribonucleic acid and protein expression, were markedly augmented in rats exposed to bleomycin. These changes were significantly reduced in NAC‐treated rats.
These results indicate that bleomycin increases the number of airway secretory cells and their mucin production, and that oral N ‐acetylcysteine improved pulmonary lesions and reduced the mucus hypersecretion in the bleomycin rat model.
The present work was supported by research grants SAF2000‐0144 and SAF2002‐04667 from CICYT (Ministry of Science and Technology, Spain) and from Zambon Spa (Italy).
TL;DR: The amount of each cytokine released from bronchiolar cells is reduced during cell death, implying that the observed inflammatory response in influenza would be greater if cell death did not occur, and reduced cytokine release is also associated with fragmentation of the Golgi body.
Abstract: Infection of cells with influenza A virus results in cell death with apoptotic characteristics. Apoptosis is regarded as a non-inflammatory process. However, during influenza an inflammatory response occurs in the airway epithelium. An examination of this apparent paradox was made using influenza A virus infection of human nasal and bronchiolar epithelial cells. Some cytokine genes (IL-18, CCL2 and CCL5) were expressed constitutively in nasal cells but no cytokine was released. In bronchiolar cells, IL-1β, IL-6 and CXCL8 expression was constitutive, whilst CCL2 and CCL5 expression was upregulated following influenza virus infection. IL-6, CXCL8 and CCL5 were released but IL-1β and CCL2 were not. In bronchiolar cells, cell death was inhibited by the caspase-8 (Z-IETD-fmk) and pan-caspase (Z-VAD-fmk) inhibitors and these inhibitors enhanced expression of CCL5 and increased the levels of the three secreted cytokines significantly. Thus, the amount of each cytokine released from bronchiolar cells is reduced during cell death, implying that the observed inflammatory response in influenza would be greater if cell death did not occur. Reduced cytokine release is also associated with fragmentation of the Golgi body, as the caspase inhibitors also rescued influenza A virus-induced fragmentation of the Golgi ribbon.
TL;DR: Observations suggest LTB4 signaling to transepithelial migration is mediated via generation of reactive oxygen species, which leads to downstream activation of ERK, as well as the physiological relevance of this signaling pathway demonstrated in BALB/c mice.
Abstract: The epithelial cells that form a barrier lining the lung airway are key regulators of neutrophil trafficking into the airway lumen in a variety of lung inflammatory diseases. Although the lipid mediator leukotriene B(4) (LTB(4)) is known to be a principal chemoattractant for recruiting neutrophils to inflamed sites across the airway epithelium, the precise signaling mechanism involved remains largely unknown. In the present study, therefore, we investigated the signaling pathway through which LTB(4) induces transepithelial migration of neutrophils. We found that LTB(4) induces concentration-dependent transmigration of DMSO-differentiated HL-60 neutrophils and human polymorphonuclear neutrophils across A549 human lung epithelium. This effect was mediated via specific LTB(4) receptors and was inhibited by pretreating the cells with N-acetylcysteine (NAC), an oxygen free radical scavenger, with diphenylene iodonium (DPI), an inhibitor of NADPH oxidase-like flavoproteins, or with PD98059, an extracellular signal-regulated kinase (ERK) inhibitor. Consistent with those findings, LTB(4)-induced ERK phosphorylation was completely blocked by pretreating cells with NAC or DPI. Taken together, our observations suggest LTB(4) signaling to transepithelial migration is mediated via generation of reactive oxygen species, which leads to downstream activation of ERK. The physiological relevance of this signaling pathway was demonstrated in BALB/c mice, in which intratracheal instillation of LTB(4) led to acute recruitment of neutrophils into the airway across the lung epithelium. Notably, the response to LTB(4) was blocked by NAC, DPI, PD98059, or CP105696, a specific LTB(4) receptor antagonist.
TL;DR: Results demonstrate that PAR2 is the major PAR receptor that is capable of modulating eosinophil function, and not PAR1 and PAR2, as previously reported.
Abstract: Eosinophil recruitment to airway tissue is a key feature of asthma, and release of a wide variety of toxic mediators from eosinophils leads to the tissue damage that is a hallmark of asthma pathology. Factors that control the release of these toxic mediators are targets for potential therapeutic intervention. Protease-activated receptors (PARs) are a novel class of receptors that are activated by cleavage of the N terminus of the receptor by proteases such as thrombin or trypsin-like enzymes. To date, PAR1-4 have been identified, and there are several studies that have demonstrated the expression of PARs in airway tissue, particularly the respiratory epithelium. We have investigated whether eosinophils express PARs and if activation of these receptors will then trigger a functional response. Using a combination of reverse transcriptase-polymerase chain reaction, Western blotting, and flow cytometry analysis, we have demonstrated that eosinophils express PAR1 and PAR2. FACS analysis showed that PAR1 could be clearly detected on the surface of the cells, whereas PAR2 appeared to be primarily intracellular. Trypsin and the PAR2 agonist peptide were seen in trigger shape change, release of cysteinyl leukotrienes, and most obviously, generation of reactive oxygen species. In contrast, thrombin had no effect on eosinophil function. The PAR1 agonist peptide did have a minor effect on eosinophil function, but this was most likely down to its ability to activate PAR1 and PAR2. These results demonstrate that PAR2 is the major PAR receptor that is capable of modulating eosinophil function.
TL;DR: No production reduced P. aeruginosa adherence to human bronchial epithelial cells and enhanced killing of internalized bacteria, suggesting that a lack of epithelial iNOS in patients with CF may contribute to P.aeruginose infection and colonization.
Abstract: Cystic fibrosis (CF) is characterized by airway inflammation and chronic bacterial lung infection, most commonly with Pseudomonas aeruginosa, an opportunistic human pathogen. Despite the persistent airway inflammation observed in patients with CF, although phagocyte inducible nitric oxide synthase (iNOS) production is upregulated, expression of iNOS in the respiratory epithelium is markedly reduced. Given the antimicrobial action of NO, this may contribute to the chronic airway infection of this disease. To define the role of epithelium-derived NO in airway defense against P. aeruginosa, we infected differentiated human bronchial epithelial cells derived from a patient with CF (CFBE41o- cells) with different strains of this pathogen at low multiplicities of infection. Using cells transfected with human iNOS cDNA, we studied the effect of NO on P. aeruginosa replication, adherence, and internalization. P. aeruginosa adherence to iNOS-expressing cells was reduced by 44 to 72% (P = 0.02) compared with control values. Absolute P. aeruginosa uptake into these cells was reduced by 44%, but uptake expressed as a percentage of adherent bacteria did not differ from the control uptake. Survival of P. aeruginosa within iNOS-expressing cells was reduced at late times postinfection (P = 0.034). NO production did not alter host cell viability. NO production reduced P. aeruginosa adherence to human bronchial epithelial cells and enhanced killing of internalized bacteria, suggesting that a lack of epithelial iNOS in patients with CF may contribute to P. aeruginosa infection and colonization.
TL;DR: The results suggest that acute CS exposure imposes oxidative stress predominantly on bronchiolar epithelial and alveolar type II cells, confirming that cigarette smoking causes oxidative damage to the respiratory epithelium.
Abstract: Cigarette smoking generates an oxidative stress in the lung, which may contribute to the pathogenesis of chronic obstructive pulmonary disease. We performed an immunohistochemical study to evaluate oxidative stress in the lung after acute cigarette smoke (CS) exposure in mice. Paraffin-embedded lung tissue sections were prepared from mice exposed and unexposed to CS for 1 h. The sections were immunostained with antibodies against 8-hydroxy-2'-deoxyguanosine (8-OHdG), an oxidative DNA adduct, and 4-hydroxy-2-nonenal (4-HNE), a lipid peroxidation product. The bronchiolar and alveolar epithelium of mice unexposed to CS exhibited weak signals for 8-OHdG and 4-HNE, whereas by 1 h after CS exposure the signals in the bronchiolar epithelial cells and the alveolar epithelial cells, particularly type II cells, had increased dramatically. The increases in both were associated with increased 8-OHdG levels in bronchoalveolar lavage fluid as determined by enzyme-linked immunoassay. These results suggest that acute CS exposure imposes oxidative stress predominantly on bronchiolar epithelial and alveolar type II cells, confirming that cigarette smoking causes oxidative damage to the respiratory epithelium.
TL;DR: Investigation of whether neutrophil elastase may regulate expression of MUC4, a membrane-tethered mucin that has recently been identified as a ligand for ErbB2, the major heterodimerization partner of the epidermal growth factor receptor, found it to be a potential activator of epithelial repair mechanisms.
Abstract: In chronic obstructive pulmonary diseases, the airway epithelium is chronically exposed to neutrophil elastase, an inflammatory protease. The cellular response to neutrophil elastase dictates the balance between epithelial injury and repair. Key regulators of epithelial migration and proliferation are the ErbB receptor tyrosine kinases, including the epidermal growth factor receptor. In this context, we investigated whether neutrophil elastase may regulate expression of MUC4, a membrane-tethered mucin that has recently been identified as a ligand for ErbB2, the major heterodimerization partner of the epidermal growth factor receptor. In normal human bronchial epithelial cells, neutrophil elastase increased MUC4 mRNA levels in both a concentration- and time-dependent manner. RNA stability assays revealed that neutrophil elastase increased MUC4 mRNA levels by prolonging the mRNA half-life from 5 to 21 h. Neutrophil elastase also increased MUC4 glycoprotein levels as determined by Western analysis, using a monoclonal antibody specific for a nontandem repeat MUC4 sequence. Therefore, airway epithelial cells respond to neutrophil elastase exposure by increasing expression of MUC4, a potential activator of epithelial repair mechanisms.