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Modifications of the Rat Airway Explant Transcriptome by Cigarette Smoke

ABSTRACT: Although a number of animal model studies have addressed changes in gene expression in the parenchyma and their relationship to emphysema, much less is known about the pathogenesis of cigarette smoke-induced small airway remodeling. In this study, we exposed rat tracheal explants to whole smoke for 15 minutes, and then cultured the explants in air. The airway transcriptome was evaluated using RAE 230_2 GeneChips. By 2 hours after starting smoke exposure, expression levels of 502 genes were changed up or down by more than 1.5 times (p values <0.01 or less), and by 24 hours, 1870 genes were significantly changed up or down. These included genes involved in anti-oxidant protection, epithelial defense and remodeling, inflammatory mediators and transcription factors, and a number of unexpected genes including the MMP-12 inducer, tachykinin-1 (substance P). Pre-treatment of the explants with 1 x 10-7 M dexamethasone reduced the number of significantly changed genes by approximately 47% at 2 hr and 68% at 24 hours, and in almost all instances, reduced the magnitude of the smoke-induced changes. We conclude that even a very brief exposure to cigarette smoke can lead to rapid changes in the expression of a large number of genes in rat tracheal explants, and that these effects are directly mediated by smoke, without a need for exogenous inflammatory cells. Steroids, contrary to the usual belief, are able to ameliorate many of these changes, at least in this very acute model.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE15563 | GEO | 2009/06/01

SECONDARY ACCESSION(S): PRJNA115657

REPOSITORIES: GEO

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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.

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Modifications of the Rat Airway Explant Transcriptome by Cigarette Smoke

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