With as many flavors as there are epigenetic modifications, vaping has arrived on the scene as a safer alternative to the smoking of cigarettes and a means to give up a rather unhealthy habit. However, the rise in vaping-related lung injuries and the “unforeseen” massive uptake of vaping by teenagers have prompted scientists to undertake detailed analyses regarding the relative safety of this alternative to traditional smoking. Is the promise of safety for vapers just smoke and mirrors?
Intriguingly, a previous study from the laboratory of Ahmad Besaratinia (University of Southern California, Los Angeles, CA, USA) revealed that vapers exhibited similarly deregulated gene expression in the oral epithelium (a major target organ for smoking-associated cancer) as smokers. Given that carcinogens associated with vaping and cigarette smoking can induce epigenetic alterations, the team sought to extend their comparison to the epigenetic realm.
To compare and contrast the epigenetic consequences of smoking and vaping, Caliri and colleagues studied DNA methylation levels in leukocytes derived from peripheral blood samples of age-, gender-, and ethnicity- matched vapers, smokers, and control patients (non-vapers/non-smokers). Specifically, the team assessed 5-methylcytosine (5-mC) levels at Long Interspersed Nucleotide Element 1 (LINE-1) by employing a Global DNA Methylation LINE 1 Assay as a measure of global DNA methylation, and also global DNA hydroxymethylation (5-hmC) levels, the oxidation product of 5-mC.
What the authors discovered suggests that the idea that vaping represents a safe alternative to smoking may be running on fumes:
- Exclusive vapers and smokers display significant reductions in both DNA methylation levels at LINE-1 repeat elements and global 5-hmC levels when compared to samples derived from non-smokers/vapers
- However, vapers and smokers exhibit similar levels of these epigenetic modifications, suggesting that smoking and vaping affect peripheral blood in the same manner
- A positive and statistically significant correlation exists between DNA methylation levels at LINE-1 repeat elements and global 5-hmC levels
- Analyses of relevant enzyme levels reveal only modest changes in the transcription of factors that catalyze the addition (DNA methyltransferases 1, 3A, and 3B) or removal (ten-eleven translocation 1-3) of DNA methylation in both vapers and smokers
- The discovered alterations do not reach statistical significance when compared to controls
- Finally, the authors combined the vaping/smoking history of each participant with the verification of vaping/smoking status via measurements of plasma cotinine concentration (a prime metabolite of nicotine), exhaled carbon monoxide, and carboxyhemoglobin levels
- This analysis revealed an inverse statistically significant correlation between both LINE-1 methylation and global 5-hmC levels and both the duration and intensity of vaping/smoking and levels of plasma cotinine
While the authors note certain limitations to their study, which include small size and the use of peripheral blood leukocytes as a surrogate for target organs where tumorigenesis can occur, these data do provide evidence that both vaping and smoking alike can foster tumorigenesis-associated epigenetic alterations. It seems like the safety of vaping may be quickly going up in smoke.
“Our new study adds an important piece to that puzzle by demonstrating that epigenetic mechanisms, specifically changes in chemical tags attached to the DNA, may contribute to the abnormal expression of genes in vapers and smokers alike,” Besaratinia said. “The epidemic of teen vaping and the recent outbreak of vaping-related severe lung injury and deaths in the U.S. underscore the importance of generating scientific evidence on which future regulations for electronic cigarette manufacturing, marketing, and distribution can be based.”
To find out if the safety profile of vaping is genuinely running on fumes, head over to Epigenetics, February 2020.