Vaping has been touted as a safer alternative to smoking, but some recent studies are showing that the biological effects have similarities. Now, a team clears the air and reports that DNA methylation changes in vapers’ oral cells resemble those found in smokers, which suggests that vaping could have comparable long-term health effects.
Smoke gets in your eyes, but it also gets in your mouth, where oral cells are exposed to vape fumes and cigarette smoke. Because changes in methylation can lead to changes in gene expression, Ahmad Besaratinia and Stella Tommasi’s labs (University of Southern California) used whole-genome bisulfite sequencing (WGBS) to analyze the differentially methylated regions (DMRs) in oral cells. They analyzed data from vapers versus non-users, smokers versus non-users, and vapers versus smokers. Here’s what they found:
- Vapers have 831 DMRs and smokers have 2,863 DMRs relative to non-users
- Cells from vapers and smokers have 297 DMRs compared to each other
Next, the team looked at where these DMRs are and found a tie-in with transcription when they fanned away the fumes. Here’s what they found:
- DMRs are particularly enriched at CpG islands and shores, as well as at enhancers
- Vapers and smokers’ DMRs are enriched for bivalent states with activating and repressing histone marks
- Many DMRs are in transcription factor binding motifs and transcription factor genes
- Both vapers and smokers have a hypermethylated DMR in the promoter of the HIC1 (hypermethylated in cancer 1) gene, which is often silenced in smoking-related cancers
Knowing that where there’s smoke, there’s fire, the group performed a Gene Ontology (GO) analysis to determine how DMR-associated genes function. Here’s what they found:
- Common vapers and smoker GO terms include signaling functions
- Vape-specific genes are enriched for synapse and neuron terms, while smoke-specific genes are enriched for lipid metabolism terms
Overall, vapers and smokers have similar DMRs. In fact, almost half of the vaper unique gene IDs overlap with those from smokers. The results highlight a possible link between methylation changes and disease risk in vapers.
Feel your way through the smoke to the American Journal of Respiratory Cell and Molecular Biology, August 2024.