E-cigarette flavours and device types linked to differences in gene expression

Adults who use e-cigarettes showed differences in gene expression compared with non-users, with many of these changes varying according to the flavour and type of vaping device used.

Researchers from the Keck School of Medicine of the University of Southern California (USC), Los Angeles, found that vaping was associated with altered activity across 3124 genes in cells collected from the lining of the mouth. The researchers reported that differences in flavour and device type accounted for a larger proportion of the observed variation in gene expression than measures of vaping frequency or intensity, suggesting that different e-cigarette products may be associated with distinct molecular patterns.

'These product differences explained more of the variation in gene regulation than how much or how often people vaped,' said Professor Ahmad Besaratinia, senior author of the study published in Frontiers in Oncology, and professor of research population and public health sciences at the Keck School of Medicine of USC, Los Angeles. 'The implication is that each flavour has unique attributes that produce different biological effects.'

The researchers collected samples from the oral lining of 35 adults who used e-cigarettes, 24 cigarette smokers and 24 non-users. They used RNA sequencing to examine gene expression and compare molecular patterns between the groups.

Compared with non-users, both vaping and smoking were associated with substantial differences in gene expression. However, 60.1 percent of the altered genes identified in people who vaped were not shared with cigarette smokers, suggesting that vaping was associated with a distinct pattern of gene activity in this study population.

The researchers estimated that flavour and device type accounted for 66.6 percent of the observed gene expression changes, while measures of vaping frequency and intensity accounted for 28.8 percent. Fruit-flavoured products were associated with 31 percent of the altered genes, menthol flavours with 0.9 percent, sweet flavours with 2.9 percent and combinations of flavours with 64.3 percent. The strongest gene expression differences were observed among users of third-generation and multiple-generation devices, although relatively few participants used older devices.

The authors noted that the study was observational and involved a relatively small number of participants. While the findings suggest that different vaping products may be associated with different patterns of gene expression, they do not show that vaping causes specific diseases or health outcomes.

The researchers are planning a follow-up study to investigate which chemicals in vaping liquids might be linked to the observed gene expression changes. 'Once we identify these chemicals, policymakers could instruct manufacturers to either eliminate these chemicals or reduce their level in e-cigarette products to minimise potential harm,' said Professor Besaratinia.