Human Airway Epithelial Cell Monolayers Research Articles

Discovery of a Fungal Metabolite as a Novel TMEM16a Inhibitor in Human Airway Epithelial Cells

Transmembrane protein 16a (TMEM16a) is a Ca2+‐activated Cl‐ channel (CaCC) that expresses in various epithelia. Inhibition of TMEM16a has been reported as a potential strategy for attenuating severity and progression of asthma. The main objective of this study is to discover a novel TMEM16a inhibitor and mechanisms of its action. By screening, we found that N9, a fungal metabolite, inhibited UTP‐activated TMEM16a Cl‐ current in basolaterally permeabilized Calu‐3 cell monolayers with an IC50 of ~ 0.8 µM and maximal inhibitory effect being observed at 10 µM. Indeed, N9 had no cytotoxic effect and did not disrupt airway epithelial barrier function, suggesting that inhibitory effect of N9 on TMEM16a was not due to the disturbance of normal airway epithelial function. Electrophysiological analyses indicated that N9 suppressed both ionomycin‐ and thapsigargin‐activated TMEM16a Cl‐ current. In addition, N9 had no effect on elevated intracellular Ca2+ level induced by UTP and thapsigargin, suggesting that N9 reduced TMEM16a Cl‐ current in human airway epithelial cell monolayers in a Ca2+‐independent mechanism. Of particular importance, N9 also significantly suppressed TMEM16a‐mediated Cl‐ current induced by Eact, a direct activator of TMEM16a, indicating that N9 exerts a novel class of TMEM16a inhibitor in human airway epithelial cell monolayers. Hence, this study may lead to identification of a novel class of anti‐asthmatic drug from fungal metabolites.

Neisseria Heparin Binding Antigen is targeted by the human alternative pathway C3-convertase.

Neisserial Heparin Binding Antigen (NHBA) is a surface-exposed lipoprotein specific for Neisseria and constitutes one of the three main protein antigens of the Bexsero vaccine. Meningococcal and human proteases, cleave NHBA protein upstream or downstream of a conserved Arg-rich region, respectively. The cleavage results in the release of the C-terminal portion of the protein. The C-terminal fragment originating from the processing of meningococcal proteases, referred to as C2 fragment, exerts a toxic effect on endothelial cells altering the endothelial permeability. In this work, we reported that recombinant C2 fragment has no influence on the integrity of human airway epithelial cell monolayers, consistent with previous findings showing that Neisseria meningitidis traverses the epithelial barrier without disrupting the junctional structures. We showed that epithelial cells constantly secrete proteases responsible for a rapid processing of C2 fragment, generating a new fragment that does not contain the Arg-rich region, a putative docking domain reported to be essential for C2-mediated toxic effect. Moreover, we found that the C3-convertase of the alternative complement pathway is one of the proteases responsible for this processing. Overall, our data provide new insights on the cleavage of NHBA protein during meningococcal infection. NHBA cleavage may occur at different stages of the infection, and it likely has a different role depending on the environment the bacterium is interacting with.

Roflumilast reverses CFTR-mediated ion transport dysfunction in cigarette smoke-exposed mice

BackgroundDysfunction in cystic fibrosis transmembrane conductance regulator (CFTR) can be elicited by cigarette smoke and is observed in patients with chronic bronchitis. We have previously demonstrated in human airway epithelial cell monolayers that roflumilast, a clinically approved phosphodiesterase 4 inhibitor that reduces the risk of exacerbations in chronic obstructive pulmonary disease patients with chronic bronchitis and a history of exacerbations, activates CFTR-dependent chloride secretion via a cAMP-mediated pathway, partially restores the detrimental effects of cigarette smoke on CFTR-mediated ion transport, and increases CFTR-dependent gastrointestinal fluid secretion in isolated murine intestine segments. Based on these findings, we hypothesized that roflumilast could improve CFTR-mediated chloride transport and induce secretory diarrhea in mice exhibiting cigarette smoke-induced CFTR dysfunction.MethodsA/J mice expressing wild type CFTR (+/+) were exposed to cigarette smoke or air with or without roflumilast and the effect of treatment on CFTR-dependent chloride transport was quantified using nasal potential difference (NPD) measurements in vivo and short-circuit current (Isc) analysis of trachea ex vivo. Stool specimen were collected and the wet/dry ratio measured to assess the effect of roflumilast on secretory diarrhea.ResultsAcute roflumilast treatment increased CFTR-dependent chloride transport in both smoke- and air-exposed mice (smoke, −2.0 ± 0.4 mV, 131.3 ± 29.3 μA/cm2, P < 0.01 and air, 3.9 ± 0.8 mV, 147.7 ± 38.0 μA/cm2, P < 0.01 vs. vehicle −0.3 ± 0.7 mV, 10.4 ± 7.0 μA/cm2). Oral administration of roflumilast over five weeks completely reversed the deleterious effects of cigarette smoke on CFTR function in smoke-exposed animals, in which CFTR-dependent chloride transport was 64% that of air controls (roflumilast, −15.22 ± 2.7 mV vs. air, −14.45 ± 1.4 mV, P < 0.05). Smoke exposure increased the wet/dry ratio of stool specimen to a level beyond which roflumilast had little additional effect.ConclusionsRoflumilast effectively rescues CFTR-mediated chloride transport in vivo, further implicating CFTR activation as a mechanism through which roflumilast benefits patients with bronchitis.

Pulmonary Administration of a Water-Soluble Curcumin Complex Reduces Severity of Acute Lung Injury

Local or systemic inflammation can result in acute lung injury (ALI), and is associated with capillary leakage, reduced lung compliance, and hypoxemia. Curcumin, a plant-derived polyphenolic compound, exhibits potent anti-inflammatory properties, but its poor solubility and limited oral bioavailability reduce its therapeutic potential. A novel curcumin formulation (CDC) was developed by complexing the compound with hydroxypropyl-γ-cyclodextrin (CD). This results in greatly enhanced water solubility and stability that facilitate direct pulmonary delivery. In vitro studies demonstrated that CDC increased curcumin's association with and transport across Calu-3 human airway epithelial cell monolayers, compared with uncomplexed curcumin solubilized using DMSO or ethanol. Importantly, Calu-3 cell monolayer integrity was preserved after CDC exposure, whereas it was disrupted by equivalent uncomplexed curcumin solutions. We then tested whether direct delivery of CDC to the lung would reduce severity of ALI in a murine model. Fluorescence microscopic examination revealed an association of curcumin with cells throughout the lung. The administration of CDC after LPS attenuated multiple markers of inflammation and injury, including pulmonary edema and neutrophils in bronchoalveolar lavage fluid and lung tissue. CDC also reduced oxidant stress in the lungs and activation of the proinflammatory transcription factor NF-κB. These results demonstrate the efficacy of CDC in a murine model of lung inflammation and injury, and support the feasibility of developing a lung-targeted, curcumin-based therapy for the treatment of patients with ALI.

Glucocorticoids enhance airway epithelial barrier integrity

Asthma is a chronic inflammatory disorder of the airways, but its pathogenesis is incompletely understood. While asthma is a complex disease caused by multiple factors, epithelial barrier damage is a cardinal feature. Glucocorticoids (GCs) are the most effective anti-inflammatory drugs in the treatment of asthma. However, the effects of GCs on the airway epithelial barrier have not been evaluated. Epithelial barrier functions were evaluated in cultured human airway epithelial cell monolayers, Calu-3 and 16HBE. Then, the cells were treated with dexamethasone (Dex), fulticasone propionate (FP), or budesonide (BD) for 5days. Permeability measured by transepithelial electrical resistance was increased by treatment with Dex, FP, and BD in a dose-dependent manner. Permeability to fluorescein isothiocyanate-labeled dextran was markedly reduced by these treatments. Immunocytostaining revealed that Dex treatment potentiated tight junction formation in these polarized epithelial cells. Knockdown of epidermal growth factor receptor (EGFR) by small interference RNA blunted the effects of Dex on barrier integrity. Although EGFR expression was not affected by Dex treatment, EGFR phosphorylation was enhanced in Dex-treated cells. This is suggesting that EGFR are important for this phenomenon. These findings suggest that GC inhalation therapy can improve epithelial barrier integrity and might contribute to the therapeutic effects of GCs for treating asthma.

CD23-Dependent Transcytosis of IgE and Immune Complex across the Polarized Human Respiratory Epithelial Cells

IgE-mediated allergic inflammation occurs when allergens cross-link IgE on the surface of immune cells, thereby triggering the release of inflammatory mediators as well as enhancing Ag presentations. IgE is frequently present in airway secretions, and its level can be enhanced in human patients with allergic rhinitis and bronchial asthma. However, it remains completely unknown how IgE appears in the airway secretions. In this study, we show that CD23 (FcεRII) is constitutively expressed in established or primary human airway epithelial cells, and its expression is significantly upregulated when airway epithelial cells were subjected to IL-4 stimulation. In a transcytosis assay, human IgE or IgE-derived immune complex (IC) was transported across a polarized Calu-3 monolayer. Exposure of the Calu-3 monolayer to IL-4 stimulation also enhanced the transcytosis of either human IgE or the IC. A CD23-specific Ab or soluble CD23 significantly reduced the efficiency of IgE or IC transcytosis, suggesting a specific receptor-mediated transport by CD23. Transcytosis of both IgE and the IC was further verified in primary human airway epithelial cell monolayers. Furthermore, the transcytosed Ag-IgE complexes were competent in inducing degranulation of the cultured human mast cells. Because airway epithelial cells are the first cell layer to come into contact with inhaled allergens, our study implies CD23-mediated IgE transcytosis in human airway epithelial cells may play a critical role in initiating and contributing to the perpetuation of airway allergic inflammation.

Cystic fibrosis transmembrane conductance regulator trafficking modulates the barrier function of airway epithelial cell monolayers

The cystic fibrosis transmembrane conductance regulator (CFTR) is an integral membrane glycoprotein which functions as an anion channel and influences diverse cellular processes. We studied its role in the development of epithelial tightness by expressing wild-type (WT-CFTR) or mutant (Delta F508-CFTR) CFTR in human airway epithelial cell monolayers cultured at the air-liquid interface. Green fluorescent protein (GFP)-tagged WT or Delta F508 constructs were expressed in the CF bronchial cell line CFBE41o(-) using adenoviruses, and the results were compared with those obtained using CFBE41o(-) lines stably complemented with wild-type or mutant CFTR. As predicted, GFP-Delta WT-CFTR reached the apical membrane whereas GFP-F508-CFTR was only detected intracellularly. Although CFTR expression would be expected to reduce transepithelial resistance (TER), expressing GFP-CFTR significantly increased the TER of CFBE41o(-) monolayers whilst GFP-Delta F508-CFTR had no effect. Similar results were obtained with cell lines stably overexpressing Delta F508-CFTR or WT-CFTR. Preincubating Delta F508-CFTR monolayers at 29 degrees C reduced mannitol permeability and restored TER, and the effect on TER was reversible during temperature oscillations. Expression of GFP-Delta F508-CFTR or GFP-WT-CFTR in a cell line already containing endogenous WT-CFTR (Calu-3) did not alter TER. The CFTR- and temperature-dependence of TER were not affected by the CFTR inhibitor CFTR(inh)172 or low-chloride medium; therefore the effect of CFTR on barrier function was unrelated to its ion channel activity. Modulation of TER was blunted but not eliminated by genistein, implying the involvement of tyrosine phosphorylation and other mechanisms. Modulation of CFTR trafficking was correlated with an increase in tight junction depth. The results suggest that CFTR trafficking is required for the normal organisation and function of tight junctions. A reduction in barrier function caused by endoplasmic reticulum retention of Delta F508-CFTR may contribute to fluid hyperabsorption in CF airways.

CD23 dependent transcytosis of IgE and immune complex across the polarized human respiratory epithelial cells (141.20)

Abstract IgE is frequently present in airway secretions and its level can be enhanced in human patients with allergic rhinitis and bronchial asthma. However, it remains completely unknown how IgE appears in the airway secretions. In this study, we showed that CD23 (FceRII) was expressed in the established or primary human airway epithelial cells; its expression was significantly up-regulated when airway epithelial cells were subjected to IL-4 stimulation. In a transcytosis assay, CD23 was capable of transporting IgE across the polarized human Calu-3 monolayer in a bidirectional manner. Furthermore, CD23 was able to transport IgE derived immune complexes. CD23 specific antibody or soluble CD23 significantly reduced the efficiency of IgE or immune complex transcytosis, suggesting a specific receptor-mediated transport by CD23. Exposure of Calu-3 monolayer to IL-4 also enhanced the transcytosis of either human IgE or the immune complex. Transcytosis of both IgE and the immune complex was further verified in primary human airway epithelial cell monolayers. Furthermore, the transcytosed immune complexes were competent in inducing degranulation of the cultured human mast cells. Since airway epithelial cells are the first cell layer to come into contact with inhaled allergens, our study implies CD23-mediated IgE transcytosis in human airway epithelial cells may play a critical role in initiating and contributing to the perpetuation of airway allergic inflammation.

Glucose homeostasis across human airway epithelial cell monolayers: role of diffusion, transport and metabolism

Glucose in airway surface liquid (ASL) is maintained at low concentrations compared to blood glucose. Using radiolabelled [(3)H]-D: -glucose and [(14)C]-L: -glucose, detection of D: - and L: -glucose by high-performance liquid chromatography and metabolites by nuclear magnetic resonance, we found that glucose applied to the basolateral side of H441 human airway epithelial cell monolayers at a physiological concentration (5 mM) crossed to the apical side by paracellular diffusion. Transepithelial resistance of the monolayer was inversely correlated with paracellular diffusion. Appearance of glucose in the apical compartment was reduced by uptake of glucose into the cell by basolateral and apical phloretin-sensitive GLUT transporters. Glucose taken up into the cell was metabolised to lactate which was then released, at least in part, across the apical membrane. We suggest that glucose transport through GLUT transporters and its subsequent metabolism in lung epithelial cells help to maintain low glucose concentrations in human ASL which is important for protecting the lung against infection.

Extracellular autocrine nucleotide signalling in a microenvironment: integrative physiology in a minute volume of airway surface liquid

Before the cystic fibrosis (CF) gene was cloned and the topology of the cystic fibrosis transmembrane conductance regulator (CFTR) protein was mapped, there were multiple schools of thought and possible answers for what functional protein the CF gene encoded: dysfunctional chloride (Cl−) channel?; hyperactive sodium (Na+) channel?; and/or signal transduction effector and regulator of both Cl− and Na+ channels? The answer was a member of the ATP-binding cassette (ABC) transporter family that acted as an anion channel and as a regulator of multiple ion, acid–base and water transport proteins and cellular processes, including functioning as an inhibitor of Na+ channels. Loss of CFTR not only leads to loss of Cl− permeability and transport across epithelial cell membranes but it also to up-regulation of ENaC Na+ channels via mechanisms that remain debated, poorly defined, and likely multifactorial. Some have suggested that CFTR may be a signal transduction effector molecule itself. Its latter regulatory and signalling effector capability may be at the root of the CF genotype and lung and airways CF disease phenotype discordance observed to date in the CF condition. In an article in this issue of The Journal of Physiology, Button et al. (2007) have set the bar in both longevity and innovation in their quest to define the ion transport processes and their regulation within a tiny volume of extracellular fluid that bathes beating respiratory cilia, the so-called airway surface liquid (ASL) layer. Including this article, the UNC CF research group has published at least 11 original articles and reviews focused on aspects of the ASL and its regulation in the past several years (Lazarowski et al. 2004; Okada et al. 2004, 2006; Douillet et al. 2005; Tarran et al. 2005, 2006a,b; Matsui et al. 2006; Winters et al. 2006; Boucher, 2007; Button et al. 2007). Their power derives from the well-differentiated non-CF (‘normal’) and CF human airway epithelial cell monolayers that they grow in primary cultures to maintain cilia and a pseudo-stratified architecture. With this in vivo-like culture model, they have brought innovative methods as well as emerging mathematical modelling to these questions. Such a system is elegantly presented in an initial model figure by Button et al. (2007). To be brief, their collective work in this paper and as a whole over the past 5 years is summed by the cartoon provided in Fig. 1. It is the over-arching hypothesis of this group that secreted nucleotides and nucleosides within the ASL are key to local control of anion and cation channels and to the control of the volume of the ASL. Up-regulation of ATP secretion may be critical to the normalization of ASL depth. The ASL may be one of the most tightly regulated microenvironments in the body. With these well-differentiated non-CF and CF cultures, this paper and past papers before it showed that ASL in normal physiology is maintained at a depth of 7 μm, the approximate length of the beating respiratory cilia. In CF, however, the ASL volume is depleted to more than 50% of that depth, causing a ciliary beat and mucociliary clearance problem. When different mechanical stimuli are applied to this system (phasic motion, cyclic stress, chest percussion therapy?, exercise?), one can deepen the ASL in the normal model (not shown in Fig. 1). However and importantly for future therapeutic angles for CF, CF ASL volume is restored with these mechanical stimuli, some of which simulate normal breathing and some of which are designed to perturb the system and loosen the dehydrated and tenacious mucus. They propose and show that the accumulation of secreted ATP and its metabolities (principally adenosine) reset the normal regulation of ASL volume by rescuing Cl− and water secretion, while dampening Na+ hyperabsorption. The rescue of Cl− and anion secretion is independent of CFTR, because it remains trapped within the cell. An assumption is that water channel function remains intact in CF and follows osmotic forces within the ASL and the airway surface epithelium. Indeed, secreted ATP is also critical for regulation of cell volume within the columnar airway epithelial cells as well. Aquaporin biology is difficult to study in vitro, because expression of epithelial aquaporins is often lost in cell culture for reasons unknown. Figure 1 Cartoon depicting control of airway surface liquid via the integrative function of anion, cation and water transport and the local release of nucleotides and nucleosides with cyclic stress, phasic motion and other appropriate mechanostimuli Boucher and coworkers should be congratulated on this work and lauded for their comprehensive and innovative approach in this arena. This collective work is another example of how local signalling by purinergic ligands can never be overlooked as a critical cog in the minute-to-minute regulation of membrane, cell and tissue biology.

Effects of corticosteroid-induced apoptosis on airway epithelial wound closure in vitro

Damage to the airway epithelium is common in asthma. Corticosteroids induce apoptosis in and suppress proliferation of airway epithelial cells in culture. Whether apoptosis contributes to impaired epithelial cell repair after injury is not known. We examined whether corticosteroids would impair epithelial cell migration in an in vitro model of wound closure. Wounds (approximately 0.5-1.3 mm2) were created in cultured 1HAEo- human airway epithelial cell monolayers, after which cells were treated with up to 10 microM dexamethasone or budesonide for 24 h. Cultured cells were pretreated for 24 or 48 h with dexamethasone to observe the effect of long-term exposure on wound closure. After 12 h, the remaining wound area in monolayers pretreated for 48 h with 10 microM dexamethasone was 43+/-18% vs. 10+/-8% for untreated control monolayers. The addition of either corticosteroid immediately after injury did not slow closure significantly. After 12 h the remaining wound area in monolayers treated with 10 microM budesonide was 39+/-4% vs. 43+/-3% for untreated control monolayers. The proportion of apoptotic epithelial cells as measured by terminal deoxynucleotidyltransferase-mediated dUTP biotin nick end labeling both at and away from the wound edge was higher in monolayers treated with budesonide compared with controls. However, wound closure in the apoptosis-resistant 1HAEo-.Bcl-2+ cell line was not different after dexamethasone treatment. We demonstrate that corticosteroid treatment before mechanical wounding impairs airway epithelial cell migration. The addition of corticosteroids after injury does not slow migration, despite their ability to induce apoptosis in these cells.

Extracellular zinc and ATP restore chloride secretion across cystic fibrosis airway epithelia by triggering calcium entry.

Cystic fibrosis (CF) is caused by defective cyclic AMP-dependent cystic fibrosis transmembrane conductance regulator Cl(-) channels. Thus, CF epithelia fail to transport Cl(-) and water. A postulated therapeutic avenue in CF is activation of alternative Ca(2+)-dependent Cl(-) channels. We hypothesized that stimulation of Ca(2+) entry from the extracellular space could trigger a sustained Ca(2+) signal to activate Ca(2+)-dependent Cl(-) channels. Cytosolic [Ca(2+)](i) was measured in non-polarized human CF (IB3-1) and non-CF (16HBE14o(-)) airway epithelial cells. Primary human CF and non-CF airway epithelial monolayers as well as Calu-3 monolayers were used to assess anion secretion. In vivo nasal potential difference measurements were performed in non-CF and two different CF mouse (DeltaF508 homozygous and bitransgenic gut-corrected but lung-null) models. Zinc and ATP induced a sustained, reversible, and reproducible increase in cytosolic Ca(2+) in CF and non-CF cells with chemistry and pharmacology most consistent with activation of P2X purinergic receptor channels. P2X purinergic receptor channel-mediated Ca(2+) entry stimulated sustained Cl(-) and HCO(3)(-) secretion in CF and non-CF epithelial monolayers. In non-CF mice, zinc and ATP induced a significant Cl(-) secretory response similar to the effects of agonists that increase intracellular cAMP levels. More importantly, in both CF mouse models, Cl(-) permeability of nasal epithelia was restored in a sustained manner by zinc and ATP. These effects were reversible and reacquirable upon removal and readdition of agonists. Our data suggest that activation of P2X calcium entry channels may have profound therapeutic benefit for CF that is independent of cystic fibrosis transmembrane conductance regulator genotype.

Role of cell surface glycosylation in mediating repair of human airway epithelial cell monolayers.

Our laboratory recently demonstrated the pattern of cell surface glycosylation of nonsecretory central airway epithelium (Dorscheid DR, Conforti AE, Hamann KJ, Rabe KF, and White SR. Histochem J 31: 145-151, 1999), but the role of glycosylation in airway epithelial cell migration and repair is unknown. We examined the functional role of cell surface carbohydrates in wound repair after mechanical injury of 1HAEo(-) human airway epithelial and primary bronchial epithelial monolayers. Wound repair stimulated by epidermal growth factor was substantially attenuated by 10(-7) M tunicamycin (TM), an N-glycosylation inhibitor, but not by the inhibitors deoxymannojirimycin or castanospermine. Wound repair of 1HAEo(-) and primary airway epithelial cells was blocked completely by removal of cell surface terminal fucose residues by alpha-fucosidase. Cell adhesion to collagen matrix was prevented by TM but was only reduced ~20% from control values with prior alpha-fucosidase treatment. Cell migration in Blind Well chambers stimulated by epidermal growth factor was blocked by pretreatment with TM but alpha-fucosidase pretreatment produced no difference from control values. These data suggest that cell surface N-glycosylation has a functional role in airway epithelial cell adhesion and migration and that N-glycosylation with terminal fucosylation plays a role in the complex process of repair by coordination of certain cell-cell functions.

Role of Very Late Adhesion Integrins in Mediating Repair of Human Airway Epithelial Cell Monolayers after Mechanical Injury

Repair of the airway epithelium after injury requires that processes such as adhesion and cell migration occur in a defined order. Both of these processes depend on interactions between extracellular matrix (ECM) proteins and appropriate integrins. To study these interactions, we examined monolayer wound repair in a cultured human airway epithelial cell line, 16HBE14o-. Wounds created in confluent monolayers grown on either collagen-IV, laminin-1, or laminin-2 matrix closed quickly in response to 15 ng/ml epidermal growth factor (EGF). Concurrent treatment of cells grown on each matrix protein with EGF and a monoclonal antibody (mAb) to beta1-integrin inhibited wound closure. Treatment with a mAb to alpha2-, alpha3-, and alpha6-integrin blocked wound repair in monolayers grown on collagen-IV but did not do so in monolayers grown either on laminin-1 or laminin-2. Inhibition was not due to cell detachment or apoptosis. These data demonstrate that integrins expressed by airway epithelial cells mediate wound closure on different constitutive ECM proteins. These data suggest that beta1-integrin subunit function is required to permit migration and spreading of epithelial cells, and that alpha-integrin subunits alone do not mediate migration of epithelial cells grown on either laminin-1 or laminin-2. These differences may become important if the matrix protein composition of airway basement membrane changes in disease states such as asthma.

Asbestos exposure increases paracellular transport of fibrin degradation products across human airway epithelium

The inflammatory response to asbestos fiber inhalation suggests that the distal respiratory epithelium is an important early target of asbestos-induced injury. We have previously found that asbestos exposure increases the fibrinolytic activity and mannitol permeability of human airway epithelial cell monolayers. Because fibrin degradation products (FDP) are potent inflammatory mediators, we asked whether asbestos fiber exposure would increase the transepithelial flux of FDP into the interstitial space. To stimulate the pericellular environment following fiber deposition, asbestos-exposed epithelial monolayers grown on permeable filters were covered with human plasma containing fluorescein isothiocyanate (FITC)-labeled human fibrinogen. After 24 h, nearly twice as much FITC-FDP appeared in the abluminal chamber of asbestos-exposed monolayers compared with unexposed controls. This did not result solely from increased degradation product production because asbestos-exposed epithelium was more permeable at all apical FDP concentrations. The proteins that crossed asbestos-exposed monolayers included biologically relevant high-molecular-weight FDP, as demonstrated by streptavidin blotting of biotin-labeled FDP. We also found that FDP flux was not vectorial, was not saturable, did not involve proteolytic processing of FDP, and did not require active transport. Thus asbestos exposure increases the paracellular flux of intact FDP across human airway epithelium. This represents a novel mechanism whereby fiber-induced epithelial dysfunction may initiate and sustain inflammation in the distal airspace.

Effect of hypoxia on incorporation of glucose carbons into lipids by isolated rat lung.

ARTICLESEffect of hypoxia on incorporation of glucose carbons into lipids by isolated rat lungDJ Bassett, AB Fisher, and JL RabinowitzDJ Bassett, AB Fisher, and JL RabinowitzPublished Online:01 Nov 1974https://doi.org/10.1152/ajplegacy.1974.227.5.1103MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByLung Lipid Composition and Surfactant BiologyMetabolic precursors of surfactant disaturated-phosphatidylcholine in preterms with respiratory distressJournal of Lipid Research, Vol. 50, No. 11Glucose homeostasis across human airway epithelial cell monolayers: role of diffusion, transport and metabolism10 September 2008 | Pflügers Archiv - European Journal of Physiology, Vol. 457, No. 5The Lung, Whole-Body Metabolism and Disease30 May 2008Effect of inflation on adenosine triphosphate catabolism and lactate production during normothermic lung ischemiaThe Annals of Thoracic Surgery, Vol. 55, No. 5A study on optimal temperature for isolated lung preservationThe Annals of Thoracic Surgery, Vol. 53, No. 1Allosteric control of 6-phosphofructo-1-kinase from rat lungComparative Biochemistry and Physiology Part B: Comparative Biochemistry, Vol. 101, No. 1-2Glutathione redox status of control and cadmium oxide‐exposed rat lungs during oxidant stressJournal of Toxicology and Environmental Health, Vol. 22, No. 3Lactate metabolism in fetal type II pneumocytesLung, Vol. 164, No. 1Oxygen Utilization and Toxicity in the Lungs1 January 2011Glucose and Intermediary Metabolism of the Lungs1 January 2011Isolated perfused lung preparation for studying altered gaseous environments.Environmental Health Perspectives, Vol. 56Pentose pathway of glucose metabolism in isolated granular pneumocytesBiochemical Pharmacology, Vol. 33, No. 8Intermediary metabolism of the lung.Environmental Health Perspectives, Vol. 55Effect of ischemia on fatty acid metabolism in fetal lungLife Sciences, Vol. 33, No. 6De novo fatty acid synthesis in developing rat lungBiochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol. 711, No. 1Glycerol kinase activity and glycerol metabolism of rat granular pneumocytes in primary cultureBiochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol. 711, No. 1Tissue Slices in the Study of Lung MetabolismThe Chemical Composition of the LungLung as a model for evaluation of critical intracellular PO2 and PCOA. B. Fisher, and C. Dodia1 July 1981 | American Journal of Physiology-Endocrinology and Metabolism, Vol. 241, No. 1Glucose metabolism accelerates the decline of hypoxic vasoconstriction in rat lungsRespiration Physiology, Vol. 44, No. 2Reutilization of fatty acid carbons for lung lipid synthesisJ. L. Rabinowitz, T. Cardwell, and D. J. Bassett1 April 1981 | American Journal of Physiology-Endocrinology and Metabolism, Vol. 240, No. 4Inhibitors of oxidative ATP production cause transient vasoconstriction and block subsequent pressor responses in rat lungs.Circulation Research, Vol. 48, No. 3Pathways of Palmitate Metabolism in the Isolated Rat Lung2 July 2009 | Experimental Lung Research, Vol. 2, No. 1Phospholipids of the lung in normal, toxic, and diseased states26 September 2008 | CRC Critical Reviews in Toxicology, Vol. 9, No. 3Fatty acid synthesis in the perfused rat lungBiochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol. 619, No. 2Pyridine nucleotides in lung and liver of hypoxic ratsLife Sciences, Vol. 26, No. 23Effect of perfusate glucose concentration on rat lung glycolysis.J S Kerr, N J Baker, D J Bassett, and A B Fisher1 March 1979 | American Journal of Physiology-Endocrinology and Metabolism, Vol. 236, No. 3Pulmonary lipid biosynthesis: Simultaneous double-label in lipids from plasma, lung tissue and surfactant using a dog heart-lung preparationInternational Journal of Biochemistry, Vol. 8, No. 7Primary Pulmonary Responses to Toxic Agents26 September 2008 | CRC Critical Reviews in Toxicology, Vol. 5, No. 1 More from this issue > Volume 227Issue 5November 1974Pages 1103-1108 Copyright & PermissionsCopyright © 1974 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1974.227.5.1103PubMed4440751History Published online 1 November 1974 Published in print 1 November 1974 Metrics