P-12 Alterations in standard DNA methylation patterns associated with exclusive e-cigarette use: a scoping review

Methods: A scoping review was conducted using a predefined research question and objectives. Inclusion criteria were established a priori and restricted to cross-sectional human studies assessing nuclear DNA methylation in exclusive e-cigarette users compared with tobacco smokers and/or non-smokers. A comprehensive literature search was performed in PubMed using Boolean combinations of the terms “DNA methylation,” “vaping,” and “e-cigarette use.” Retrieved records were de-duplicated and screened in two stages, including title and abstract screening followed by full-text review against predefined eligibility criteria. Relevant data were extracted systematically, and findings were collated and synthesized to identify common patterns in DNA methylation associated with e-cigarette use.

Results: Across studies, exclusive e-cigarette use was associated with detectable but variable DNA methylation changes. Global DNA methylation profiles in e-cigarette users were generally comparable to those of non-smokers and distinct from tobacco smokers. Smoking-associated loci, particularly AHRR cg05575921, consistently demonstrated hypomethylation in cigarette smokers but not in exclusive e-cigarette users. Analyses of repetitive elements revealed LINE-1 hypomethylation in e-cigarette users compared with non-smokers, although comparisons with smokers yielded inconsistent findings. Epigenome-wide studies identified limited overlap in differentially methylated regions between e-cigarette users and smokers, primarily within epithelial tissues, with changes that were context dependent.

Conclusion: Overall, current evidence suggests that e-cigarette-associated DNA methylation changes are modest and distinct from those induced by tobacco smoking. Longitudinal studies are required to clarify the persistence and clinical relevance of the noted epigenetic alterations