Project description:The small airway epithelium (SAE) the pseudostratified epithelium that covers the majority of the human airway surface from the 6th generation to the alveoli, is the major site of lung disease caused by smoking, and the cell population that exhibits the earliest manifestations of smoking-induced disease. The focus of this study is to use RNA-Seq (massive parallel sequencing technology) to sequence all polyA+ mRNAs expressed by the SAE of healthy nonsmokers to gain new insights into the biology of the SAE, and how these cells respond to cigarette smoke. Taking advantage of RNA-Seq providing quantitative mRNA levels, that data demonstrates that while the SAE shares its transcriptome with many cell types, it has unique characteristics that are enriched in this cell population, with the mostly highly expressed genes (SCGB1A1) characteristics of Clara cells, an airway epithelial cell unique to the human small airways. Among other genes expressed by the SAE are those characteristic of ciliated and mucin-producing cells, basal cells and neuroendocrine cells. The RNA-Seq data includes identification of the highly expressed SAE transcription factors, transmembrane receptors, signaling ligands and growth factors. RNA-Seq permitted quantification of expression of highly homologous gene families, the absolute smoking-induced changes in SAE gene expression, including genes expressed at low levels, and assessment of the effect of smoking on SAE gene splicing. Together, these observations can serve as the baseline for assessment of the dysregulation of SAE gene expression in human airway disease. The small airway epithelium (SAE) is the major site of lung disease caused by smoking, and the cell population that exhibits the earliest manifestations of smoking-induced disease. This study used RNA-Seq to sequence all polyA+ mRNAs expressed by the SAE of 5 healthy nonsmokers to gain new insights into the biology of the SAE, and evaluate how these cells respond to cigarette smoke using 6 healthy smoker samples (SRA029282.1). Taking advantage of RNA-Seq providing quantitative mRNA levels, that data demonstrates that while the SAE shares its transcriptome with many cell types, it has unique characteristics that are enriched in this cell population. Coverage of RNA-Seq expression was also compared to the HG-U133 Plus 2.0 microarray expression of 27 previously published healthy nonsmoker samples presented here.

Project description:The apical junctional complex (AJC), composed of tight junctions and adherens junctions, is essential for maintaining epithelial barrier function. Since cigarette smoking and chronic obstructive pulmonary disease (COPD), the major smoking-induced disease, are both associated with increased lung epithelial permeability, we hypothesized that smoking alters the transcriptional program regulating AJC integrity in the small airway epithelium (SAE), the primary site of pathological changes in COPD. Transcriptome analysis revealed a global down-regulation of physiological AJC gene expression in the SAE of healthy smokers (n=53) compared to healthy nonsmokers (n=59), an observation associated with changes in molecular pathways regulating epithelial differentiation such as PTEN signaling and accompanied by induction of cancer-related AJC genes. Genome-wide co-expression analysis identified a smoking-sensitive AJC transcriptional network. The overall expression of AJC-associated genes was further decreased in COPD smokers (n=23). Exposure of human airway epithelial cells to cigarette smoke extract in vitro resulted in down-regulation of several AJC-related genes, accompanied by decreased transepithelial resistance. Thus, cigarette smoking alters the AJC gene expression architecture in the human airway epithelium, providing a molecular basis for the dysregulation of airway epithelial barrier function during the development of smoking-induced lung disease. The apical junctional complex (AJC), composed of tight junctions and adherens junctions, is essential for maintaining epithelial barrier function. Since cigarette smoking and chronic obstructive pulmonary disease (COPD), the major smoking-induced disease, are both associated with increased lung epithelial permeability, we hypothesized that smoking alters the transcriptional program regulating AJC integrity in the small airway epithelium (SAE), the primary site of pathological changes in COPD. In this study, microarray analysis of the SAE obtained from 53 healthy nonsmokers, 59 healthy smokers, and 23 smokers with COPD was performed to determine physiological AJC gene expression architecture in the SAE and its modification by cigarette smoking and during the development of COPD.

Project description:Waterpipe (also called hookah, shisha, or narghile) smoking is a common form of tobacco use in the Middle East. Its use is becoming more prevalent in Western societies, especially among young adults as an alternative form of tobacco use to traditional cigarettes. While the risk to cigarette smoking is well documented, the risk to waterpipe smoking is not well defined with limited information on its health impact at the epidemiologic, clinical and biologic levels with respect to lung disease. Based on the knowledge that airway epithelial cell DNA methylation is modified in response to cigarette smoke and in cigarette smoking-related lung diseases, we assessed the impact of light-use water-pipe smoking on DNA methylation of the small airway epithelium (SAE) and whether changes in methylation were linked to the transcriptional output of the cells. Small airway epithelium was obtained from 7 nonsmokers and 7 light-use (2.6 ± 1.7 sessions/wk) waterpipe-only smokers. Genome-wide comparison of SAE DNA methylation of waterpipe smokers to nonsmokers identified 727 probesets differentially methylated (fold-change >1.5, p<0.05) representing 673 unique genes. Dominant pathways associated with these epigenetic changes include those linked to G-protein coupled receptor signaling, aryl hydrocarbon receptor signaling and xenobiotic metabolism signaling, all of which have been associated with cigarette smoking and lung disease. Of the genes differentially methylated, 11.3% exhibited a corresponding significant (p<0.05) change in gene expression with enrichment in pathways related to regulation of mRNA translation and protein synthesis (eIF2 signaling and regulation of eIF4 and p70S6K signaling). Overall, these data demonstrate that light-use waterpipe smoking is associated with epigenetic changes and related transcriptional modifications in the SAE, the cell population demonstrating the earliest pathologic abnormalities associated with chronic cigarette smoking. This study demonstrates that light-use waterpipe smoking in young adults is associated with a broad range of genome-wide DNA methylation-related changes of the SAE impacting a number of genes linked to pathways previously associated with cigarette smoking. Further, many of these methylation-related changes correlate with waterpipe smoking-associated changes in the SAE transcriptome. Together, these data add to the accumulating evidence that waterpipe smoking is harmful, and may lead to lung disease.

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Genotype-Smoking Environment Interactions affecting eQTL in the Human Lung

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