Project description:Disparate Oxidant-related Gene Expression of Human Small Airway Epithelium Compared to Autologous Alveolar Macrophages in Response to the In Vivo Oxidant Stress of Cigarette Smoking The oxidant burden of cigarette smoking induces lung cell dysfunction, and play a significant role in the pathogenesis of lung disease. Two cell populations directly exposed to the oxidants in cigarette smoke are the small airway epithelium and alveolar macrophages. Of these, the epithelium appears to be more vulnerable to smoking, becoming disordered in differentiation, repair and function, while alveolar macrophages become activated, without becoming diseased. In this context, we asked: for the same individuals, what is the baseline trancriptome of oxidant-related genes in small airway epithelium compared to alveolar macrophages and do the responses of the transcriptome of these 2 cell populations differ substantially to inhaled cigarette smoke? To address these questions we used microarray gene expression and TaqMan analysis to assess the gene expression profile of known oxidant-related genes in paired samples recovered by bronchoscopy from small airway epithelium and alveolar macrophages from the same healthy nonsmokers and normal smokers. Of the 155 oxidant-related genes surveyed, 122 (77%) were expressed in both cell populations in nonsmokers. However, of the genes expressed by both cell populations, oxidant related gene expression levels were higher in alveolar macrophages (67 genes, 43%) than small airway epithelium (37 genes, 24%). There were more oxidant-related genes uniquely expressed in the small airway epithelium (17%), than in alveolar macrophages (5%). In healthy smokers, the majority of oxidant-related genes were expressed in both cell populations, but there were marked differences in the numbers of oxidant-related genes that smoking up- or down-regulated. While smoking up-regulated 15 genes (10%) and down-regulated 7 genes (5%) in the small airway epithelium, smoking had far less effect on alveolar macrophages [only 4 (3%) genes up-regulated, and only 1 (0.6%) down-regulated]. Only a small number of smoking responsive oxidant-related genes overlapped between the two cell types (2 up-regulated, and no down-regulated genes). Consistent with this observation, pathway analysis of smoking-responsive genes in the small airway epithelium showed oxidant-related pathways dominated, but in alveolar macrophages immune-response pathways dominated. Thus, the responses of the oxidant-related transcriptome of cells with an identical genome and exposed to the same oxidant stress of cigarette smoking are very different, with responses of oxidant-related genes of alveolar macrophages far more subdued than that of small airway epithelium, consistent with the clinical observation that, while the small airway epithelium is vulnerable, alveolar macrophages are not "diseased" in response to the oxidant stress of cigarette smoking. Gene expression profiles of known oxidant-related genes in paired samples recovered by bronchoscopy from small airway epithelium and alveolar macrophages from the same healthy nonsmokers and normal smokers.

Project description:Nuclear factor erythroid 2-related factor 2 (NFE2L2, Nrf2) is an oxidant responsive transcription factor known to induce phase 2 detoxifying and antioxidant genes to protect cells from oxidative stress. Cigarette smoke, with its large oxidant content, is a major stressor to the small airway epithelium, the cells of which are vulnerable to oxidant damage and consequent malignant transformation. In this study, we assessed the role of cigarette smoke in activation of Nrf2 in the human small airway epithelium in vivo. Fiberoptic bronchoscopy was used to sample a pure population of small airway epithelium in 38 healthy nonsmokers and 45 healthy smokers, and gene expression was assessed using Affymetrix HG-U133 Plus 2.0 microarrays. Compared to that of healthy nonsmokers, Nrf2 protein was significantly activated in the small airway epithelium of healthy normal smokers and localized in the nucleus (p<0.05). Of the human homologs of 201 known murine Nrf2-mediated genes, 13 highly smoking-responsive genes were identified (p<10-4, all comparisons smokers to nonsmokers). Using a “Nrf2-index” to quantify the extent of expression in the small airway epithelium of these 13 known Nrf2 genes, variability in the level of expression was observed among the 45 healthy smokers, but the variability was coordinately modulated among the 13 genes, an observation confirmed by TaqMan quantitative PCR. This variability in the coordinate level of expression of the 13 Nrf2-mediated genes was independent of the smoking history. Based on these observations, the “Nrf2 index” was used to evaluate whether other genes modulated by smoking in the small airway epithelium were also coordinately up- or down- modulated among the 45 healthy smokers. Two genes, pirin (PIR) and UDP glucuronosyltransferase 1 family polypeptide A4 (UGT1A4), not previously known to be modulated by Nrf2 were identified as being coordinately modulated among the 45 smokers. Both genes contain several functional antioxidant response elements in the promoter region. Using an electrophoretic mobility shift assay, these antioxidant response elements in the promoters of PIR and UGT1A4 responded in vitro to activated Nrf2. These observations are consistent with the concept that Nrf2 plays an important role in regulating cellular defenses against smoking in the highly vulnerable small airway epithelium cell population, and that there is variability among the population in the relative Nrf2 responsiveness to a similar oxidant burden. Affymetrix arrays were used to assess gene expression data in small airway epithelium obtained by fiberoptic bronchoscopy of 38 healthy non-smokers and 45 healthy smokers

Project description:The glutathione S-transferase (GST) gene family codes for enzymes that detoxify xenobiotics by catalyzing the conjugation of xenobiotics to glutathione. Based on reports that inherited copy number variations (CNV) in the genome modulate some GST expression levels and with the knowledge that cigarette smoke contains >3000 xenobiotics, and that the small airway epithelium and alveolar macrophages are involved early in the pathogensis of smoking-induced lung disease, we asked: do germline CNVs modulate GST expression level in the small airway epithelium and alveolar macrophages? Affymetrix HG U133 Plus 2.0 microarrays were used to survey GST gene expression in the small airway epithelium and alveolar macrophages obtained by bronchoscopic brushings from current smokers (n=35) and nonsmokers (n=35). The CNV genotypes of these 70 subjects were determined by Affymetrix Human SNP array 5.0 chips. Sixteen % of subjects had deletions of both GSTM1 alleles. These deletions were associated with reduced GSTM1 mRNA levels in both the small airway epithelium (p<10-7) and alveolar macrophages (p<0.05). Thirty % of subjects had homozygous deletions of GSTT1 with concomitant reduced mRNA levels in both small airway epithelium and alveolar macrophages (p<10-7). In contrast, genes flanking the CNV regions of both GST genes showed no difference in expression level among subjects with and without the GST deletions (p>0.3). Interestingly, GSTT2B, a duplicate gene of GSTT2, exhibited homozygous deletion in blood in 27% of subjects and was not expressed in small airway epithelium in the remainder of subjects but was expressed in alveolar macrophages of heterozygotes and wild type subjects, proportionate to genotype (p<10-3). These data demonstrate that highly prevalent CNV deletions of genes critical to ameliorating smoking-associated xenobiotic-induced damage in the lung can result in significant modulation of the gene expression levels, with the linear relationship of genotype to expression level suggesting minimal compensation of gene expression levels in heterozygotes consistent with GST polymorphisms playing a role in the risk for development of smoking-induced lung disease.

Project description:Nuclear factor erythroid 2-related factor 2 (NFE2L2, Nrf2) is an oxidant responsive transcription factor known to induce phase 2 detoxifying and antioxidant genes to protect cells from oxidative stress. Cigarette smoke, with its large oxidant content, is a major stressor to the small airway epithelium, the cells of which are vulnerable to oxidant damage and consequent malignant transformation. In this study, we assessed the role of cigarette smoke in activation of Nrf2 in the human small airway epithelium in vivo. Fiberoptic bronchoscopy was used to sample a pure population of small airway epithelium in 38 healthy nonsmokers and 45 healthy smokers, and gene expression was assessed using Affymetrix HG-U133 Plus 2.0 microarrays. Compared to that of healthy nonsmokers, Nrf2 protein was significantly activated in the small airway epithelium of healthy normal smokers and localized in the nucleus (p<0.05). Of the human homologs of 201 known murine Nrf2-mediated genes, 13 highly smoking-responsive genes were identified (p<10-4, all comparisons smokers to nonsmokers). Using a “Nrf2-index” to quantify the extent of expression in the small airway epithelium of these 13 known Nrf2 genes, variability in the level of expression was observed among the 45 healthy smokers, but the variability was coordinately modulated among the 13 genes, an observation confirmed by TaqMan quantitative PCR. This variability in the coordinate level of expression of the 13 Nrf2-mediated genes was independent of the smoking history. Based on these observations, the “Nrf2 index” was used to evaluate whether other genes modulated by smoking in the small airway epithelium were also coordinately up- or down- modulated among the 45 healthy smokers. Two genes, pirin (PIR) and UDP glucuronosyltransferase 1 family polypeptide A4 (UGT1A4), not previously known to be modulated by Nrf2 were identified as being coordinately modulated among the 45 smokers. Both genes contain several functional antioxidant response elements in the promoter region. Using an electrophoretic mobility shift assay, these antioxidant response elements in the promoters of PIR and UGT1A4 responded in vitro to activated Nrf2. These observations are consistent with the concept that Nrf2 plays an important role in regulating cellular defenses against smoking in the highly vulnerable small airway epithelium cell population, and that there is variability among the population in the relative Nrf2 responsiveness to a similar oxidant burden.

Project description:Although smoking-induced lung disease tends to be more common in the upper lobe, it is not known if this results from the skewed distribution of inhaled cigarette smoke or increased susceptibility of the upper lobes to these disorders. The distribution of inhaled cigarette smoke within the lung is complex, depending on lung pressure-volume relationships, gravity, individual smoking habits and the properties of the individual components of cigarette smoke. With the knowledge that the small airway epithelium is the earliest site of smoking-induced lung disease, and that the small airway epithelium is acutely sensitive to inhaled cigarette smoke with significant changes in the up- and down-regulation of hundreds of genes, we compared upper vs lower lobe gene expression in the small airway epithelium of the same cigarette smokers to determine if the gene expression patterns were similar or different. Active smokers (n=11) with early evidence of smoking-induced lung disease (normal spirometry but low diffusing capacity) underwent bronchoscopy and brushing of the small airway epithelium to compare upper vs lower lobe genome-wide gene expression assessed by microarray. Interestingly, cluster and principal component analysis demonstrated that, for each individual, the expression of the known small airway epithelium smoking-responsive genes were remarkably similar as upper vs lower lobe pairs, although, as expected, there were differences in the smoking-induced changes in gene expression from individual to individual. Thus, while there may be topographic differences in the distribution of cigarette smoke, sufficient smoke reaches the upper vs lower lobe small airway epithelium so that, within each smoker, the upper vs lower lobe gene expression are similar. These observations support the concept that the topographic differences in the occurrence of the smoking-induced lung diseases are likely secondary to topographic differences in the susceptibility of the upper vs lower lobes to cigarette smoke, not the topographic differences in distribution of inhaled cigarette smoke.

Project description:Despite overwhelming data that cigarette smoking causes chronic obstructive pulmonary disease (COPD), only a minority of chronic smokers are affected, strongly suggesting that genetic factors modify susceptibility to this disease. We hypothesized that there are individual variations in the response to cigarette smoking, with variability among smokers in expression levels of protective / susceptibility genes. Affymetrix arrays and TaqMan PCR were used to assess the variability of gene expression in the small airway epithelium obtained by fiberoptic bronchoscopy of 18 normal non-smokers, 18 normal smokers and 18 smokers with COPD. We identified 201 probesets representing 150 smoking-responsive genes that were significantly up- or down-regulated, and assessed the coefficient of variation in expression levels among the study population. Variation was a reproducible property of each gene as assessed by different microarray probesets and realtime PCR and was observed in both normal smokers and smokers with COPD. There was greater individual variability in smokers with COPD than in normal smokers. The majority of these highly variable smoking responsive genes were in the functional categories of signal transduction, xenobiotic degradation, metabolism, transport, oxidant-related and transcription. A similar pattern of the same highly variable genes was observed in an independent data set.We propose that there is likely genetic diversity within this subset of genes with highly variable individual to individual responses of the small airway epithelium to smoking, and this subset of genes represent putative candidates for assessment of susceptibility/protection from disease for future gene-based epidemiological studies for the risk of smokers for COPD. Experiment Overall Design: Affymetrix arrays and TaqMan PCR were used to assess the variability of gene expression in the small airway epithelium obtained by fiberoptic bronchoscopy of 18 normal non-smokers, 18 normal smokers and 18 smokers with COPD.

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.

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Disparate Oxidant-related Gene Expression of Human Small Airway Epithelium Compared to Autologous Alveolar Macrophages

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