Dataset Information

Differential gene expression in human conducting airway surface epithelia and submucosal glands.

ABSTRACT: Human conducting airways contain two anatomically distinct epithelial cell compartments: surface epithelium and submucosal glands (SMG). Surface epithelial cells interface directly with the environment and function in pathogen detection, fluid and electrolyte transport, and mucus elevation. SMG secrete antimicrobial molecules and most of the airway surface fluid. Despite the unique functional roles of surface epithelia and SMG, little is known about the differences in gene expression and cellular metabolism that orchestrate the specialized functions of these epithelial compartments. To approach this problem, we performed large-scale transcript profiling using epithelial cell samples obtained by laser capture microdissection (LCM) of human bronchus specimens. We found that SMG expressed high levels of many transcripts encoding known or putative innate immune factors, including lactoferrin, zinc alpha-2 glycoprotein, and proline-rich protein 4. By contrast, surface epithelial cells expressed high levels of genes involved in basic nutrient catabolism, xenobiotic clearance, and ciliated structure assembly. Selected confirmation of differentially expressed genes in surface and SMG epithelia demonstrated the predictive power of this approach in identifying genes with localized tissue expression. To characterize metabolic differences between surface epithelial cells and SMG, immunostaining for a mitochondrial marker (isocitrate dehydrogenase) was performed. Because greater staining was observed in the surface compartment, we predict that these cells use significantly more energy than SMG cells. This study illustrates the power of LCM in defining the roles of specific anatomic features in airway biology and may be useful in examining how disease states alter transcriptional programs in the conducting airways.

SUBMITTER: Fischer AJ

PROVIDER: S-EPMC2633141 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature

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Differential gene expression in human conducting airway surface epithelia and submucosal glands.

Fischer Anthony J AJ Goss Kelli L KL Scheetz Todd E TE Wohlford-Lenane Christine L CL Snyder Jeanne M JM McCray Paul B PB

American journal of respiratory cell and molecular biology 20080814 2

Human conducting airways contain two anatomically distinct epithelial cell compartments: surface epithelium and submucosal glands (SMG). Surface epithelial cells interface directly with the environment and function in pathogen detection, fluid and electrolyte transport, and mucus elevation. SMG secrete antimicrobial molecules and most of the airway surface fluid. Despite the unique functional roles of surface epithelia and SMG, little is known about the differences in gene expression and cellula ...[more]

PMID: 18703793

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Project description:Key pointsCl- and HCO3 - had similar paracellular permeabilities in human airway epithelia. PCl /PNa of airway epithelia was unaltered by pH 7.4 vs. pH 6.0 solutions. Under basal conditions, calculated paracellular HCO3 - flux was secretory. Cytokines that increased airway surface liquid pH decreased or reversed paracellular HCO3 - flux. HCO3 - flux through the paracellular pathway may counterbalance effects of cellular H+ and HCO3 - secretion.AbstractAirway epithelia control the pH of airway surface liquid (ASL), thereby optimizing respiratory defences. Active H+ and HCO3 - secretion by airway epithelial cells produce an ASL that is acidic compared with the interstitial space. The paracellular pathway could provide a route for passive HCO3 - flux that also modifies ASL pH. However, there is limited information about paracellular HCO3 - flux, and it remains uncertain whether an acidic pH produced by loss of cystic fibrosis transmembrane conductance regulator anion channels or proinflammatory cytokines might alter the paracellular pathway function. To investigate paracellular HCO3 - transport, we studied differentiated primary cultures of human cystic fibrosis (CF) and non-CF airway epithelia. The paracellular pathway was pH-insensitive at pH 6.0 vs. pH 7.4 and was equally permeable to Cl- and HCO3 - . Under basal conditions at pH ∼6.6, calculated paracellular HCO3 - flux was weakly secretory. Treating epithelia with IL-17 plus TNFα alkalinized ASL pH to ∼7.0, increased paracellular HCO3 - permeability, and paracellular HCO3 - flux was negligible. Applying IL-13 increased ASL pH to ∼7.4 without altering paracellular HCO3 - permeability, and calculated paracellular HCO3 - flux was absorptive. These results suggest that HCO3 - flux through the paracellular pathway counterbalances, in part, changes in the ASL pH produced via cellular mechanisms. As the pH of ASL increases towards that of basolateral liquid, paracellular HCO3 - flux becomes absorptive, tempering the alkaline pH generated by transcellular HCO3 - secretion.

Project description:Prolonged macrolide antibiotic therapy at low doses improves clinical outcome in patients affected with diffuse panbronchiolitis and cystic fibrosis. Consensus is building that the therapeutic effects are due to anti-inflammatory, rather than anti-microbial activities, but the mode of action is likely complex. To gain insights into how the macrolide azithromycin (AZT) modulates inflammatory responses in airways, well-differentiated primary cultures of human airway epithelia were exposed to AZT alone, an inflammatory stimulus consisting of soluble factors from cystic fibrosis airways, or AZT followed by the inflammatory stimulus. RNA microarrays were conducted to identify global and specific gene expression changes. Analysis of gene expression changes revealed that the AZT treatment alone altered the gene profile of the cells, primarily by significantly increasing the expression of lipid/cholesterol genes and decreasing the expression of cell cycle/mitosis genes. The increase in cholesterol biosynthetic genes was confirmed by increased filipin staining, an index of free cholesterol, after AZT treatment. AZT also affected genes with inflammatory annotations, but the effect was variable (both up- and down-regulation) and gene specific. AZT pretreatment prevented the up-regulation of some genes, such as MUC5AC and MMP9, triggered by the inflammatory stimulus, but the up-regulation of other inflammatory genes, e.g., cytokines and chemokines, such as interleukin-8, was not affected. On the other hand, HLA genes were increased by AZT. Notably, secreted IL-8 protein levels did not reflect mRNA levels, and were, in fact, higher after AZT pretreatment in cultures exposed to the inflammatory stimulus, suggesting that AZT can affect inflammatory pathways other than by altering gene expression. These findings suggest that the specific effects of AZT on inflamed and non-inflamed airway epithelia are likely relevant to its clinical activity, and their apparent complexity may help explain the diverse immunomodulatory roles of macrolides.

Dataset Information

Differential gene expression in human conducting airway surface epithelia and submucosal glands.

Publications

Differential gene expression in human conducting airway surface epithelia and submucosal glands.

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