P1193 NOD2 and Beyond: Unmasking Tobacco-Induced Epigenetic Changes in Crohn's Disease

Abstract Background Smoking has been shown to have a very negative impact on Crohn's disease (CD). Indeed, this harmful habit induces the early onset of the disease and doubles the risk of postoperative recurrence. This research project involves a thorough analysis of omics data, with a primary focus on DNA methylation, one of the most prevalent epigenetic modifications. Our hypothesis is that tobacco-induced alterations in gene methylation pattern of subcutaneous adipose tissue (SAT), particularly within key pathways, contribute to a more adverse disease profile in smokers. Methods A comprehensive epigenome-wide analysis was conducted using the Illumina EPIC/450k array to investigate subcutaneous adipose tissue in patients with CD, encompassing both smokers and non-smokers. Utilizing tools such as dmpfinder and Bumphunter (minfi), differentially methylated positions (DMPs) and regions (DMRs) were identified. Additionally, gene expression analysis for key genes was performed to establish correlations between methylation and subsequent gene expression, not only in SAT but also in other fat depots such as visceral adipose tissue (VAT) or peripheral blood mononuclear cells (PBMCs). Results A distinctive DNA methylation pattern in the SAT of smokers compared to non-smoker CD patients was identified (Fig. 1A). Over 27,270 DMPs associated with significant biological processes related to DNA damage, inflammation, or immunity were uncovered (Fig. 1B-C). Additionally, more than 13,000 DMRs located in the promoter region were identified (Fig. 1C). The relationship between methylation levels in the promoter regions and subsequent gene expression on SAT was validated for selected genes. Specifically, NOD2 exhibited higher DNA methylation in the promoter region among smokers compared to non-smokers CD patients (p value=0.04), resulting in reduced NOD2 gene expression on SAT (p value=0.04) (Fig.1D). Consistent results were observed in other tissues such as VAT and PBMCs (Fig. 1E). Finally, we observe the implication of NOD2 in pathways related to immune response, inflammation or apoptosis and a trend indicating that lower NOD2 expression is associated with higher levels of C-reactive protein (CRP)(Fig. 1F). Conclusion Our study reveals that smoking produces DNA methylation changes on SAT of CD patients and affects the expression of several key genes involved in the pathogeny of CD. Particularly, our results unveil a new link between tobacco-smoking and lower NOD2 expression and associate this to an elevated levels of PCR, paving the way for a fresh perspective in exploring disease prognosis.