Cigarette Smoking Induces Small Airway Epithelial Epigenetic Changes with Corresponding Modulation of Gene Expression. Homo sapiens

The small airway epithelium (SAE), the first site of smoking-induced lung pathology, exhibits genome-wide changes in gene expression in response to cigarette smoking. Based on the increasing evidence that the epigenome can respond to external stimuli in a rapid manner, we assessed the SAE of smokers for genome-wide DNA methylation changes compared to nonsmokers, and whether changes in SAE DNA methylation were linked to the transcriptional output of these cells. Using genome-wide methylation analysis of SAE DNA of nonsmokers and smokers, the data identified 204 unique genes differentially methylated in SAE DNA of smokers compared to nonsmokers, with 67% of the regions with differential methylation occurring within 2 kb of the transcriptional start site. Among the genes with differential methylation were those related to metabolism, transcription, signal transduction and transport. For the differentially methylated genes, 34 exhibited a correlation with gene expression, 53% with an inverse correlation of DNA methylation with gene expression and 47% a direct correlation. These observations provide evidence that cigarette smoking alters the DNA methylation patterning of the SAE and that, for some genes, these changes are associated with the smoking-related changes in gene expression. Overall design: Small airway epithelium DNA was assessed for genome-wide methylation using the microarray-based high resolution HpaII tiny fragment enriched by ligation-mediated PCR (HELP) assay. Small airway epithelium transcriptome was also assessed for healthy nonsmokers (n=16) and healthy smokers (n=20) with Affymetirx HG-U133 Plus 2.0 arrays