DNA Methylation of the Aryl Hydrocarbon Receptor Repressor Associations With Cigarette Smoking and Subclinical Atherosclerosis

Abstract

Background Tobacco smoke contains numerous agonists of the aryl-hydrocarbon receptor (AhR) pathway, and activation of the AhR pathway was shown to promote atherosclerosis in mice. Intriguingly, cigarette smoking is most strongly and robustly associated with DNA modifications to an AhR pathway gene, the aryl-hydrocarbon receptor repressor (AHRR). We hypothesized that altered AHRR methylation in monocytes, a cell type sensitive to cigarette smoking and involved in atherogenesis, may be a part of the biological link between cigarette smoking and atherosclerosis. Methods and Results DNA methylation profiles of AHRR in monocytes (542 CpG sites ± 150kb of AHRR, using Illumina 450K array) were integrated with smoking habits and ultrasound-measured carotid plaque scores from 1,256 participants of the Multi-Ethnic Study of Atherosclerosis (MESA). Methylation of cg05575921 significantly associated (p = 6.1×10−134) with smoking status (current vs. never). Novel associations between cg05575921 methylation and carotid plaque scores (p = 3.1×10−10) were identified, which remained significant in current and former smokers even after adjusting for self-reported smoking habits, urinary cotinine, and well-known CVD risk factors. This association replicated in an independent cohort using hepatic DNA (n = 141). Functionally, cg05575921 was located in a predicted gene expression regulatory element (enhancer), and had methylation correlated with AHRR mRNA profiles (p = 1.4×10−17) obtained from RNA sequencing conducted on a subset (n = 373) of the samples. Conclusions These findings suggest AHRR methylation may be functionally related to AHRR expression in monocytes, and represents a potential biomarker of subclinical atherosclerosis in smokers.

Distinct Epigenetic Effects of Tobacco Smoking in Whole Blood and among Leukocyte Subtypes

“…Smoking-related methylation changes in particular cell types could indicate different sensitivities to exposure and differing modes of action among cell lineages as well as potential functional effects that are important to cell-type specific disease etiology or to early detection of disease. With the exception of AHRR (cg05575921), in which methylation changes were observed to be significantly altered in smoker-derived lymphoblastoid cells and lung macrophages[7], or CD14+ monocytes and CD4+ T cells [31], most established smoking-associated CpG sites such as F2RL3 (cg03636183), ALPPL2 (cg21566642), IER3 (cg06126421) and GPR15 (cg19859270) have not been evaluated in multiple cell types. We expect that a more complete characterization of the relationship between differentially methylated regions (DMRs), chromatin context and transcription will help in elucidating the meaning of observed effects in whole blood and may reveal functional effects on immune cell subtypes.…”

Epidemiology of cardiovascular disease: recent novel outlooks on risk factors and clinical approaches

“…Recently developed techniques that couple next-generation sequencing with simultaneous analyses for DNA methylation have now enabled performing epigenome-wide association (EWA) studies based on peripheral blood samples of population cohorts. Although no EWA study of CVD per se has yet been performed, several studies have already identified specific DNA-methylation profiles associated with traditional CVD risk factors, such as smoking [113], diabetes [114], blood lipids [115], and BMI [116,117]. …”

Translating genomics into risk prediction

“…Associations between methylation at cg05575921 and subclinical carotid atherosclerosis11 and cardiovascular mortality12 have been reported in observational cohorts. Case-control studies have found that methylation levels at AHRR , both alone and in conjunction with data from other smoking-related methylation sites, was strongly associated with the future development of lung cancer13 and lung cancer-specific mortality 14.…”