The human genome has tens of thousands of genes, and the profile of genes that are switched on and off can be used to understand whether exposure to an aerosol has had a toxic effect
Scientists at British American Tobacco used nicotine as a reference point and exposed MucilAir™, a realistic in vitro 3D model of a human airway, to e-cigarette vapour and cigarette smoke to assess their comparative effect on gene expression.
The MucilAir™ human respiratory tissue was exposed to smoke from a reference cigarette (3R4F) or vapour from an e-cigarette (Vype ePen) continuously for an hour. Two doses of vapour were tested, matching or doubling the amount of nicotine reaching the cells compared to smoke. Then, to measure the cell response, the scientists mapped the genes that were switched on and off at 24 hours and 48 hours after the one-hour exposure.
In the tissue exposed to smoke, the scientists found 873 and 205 genes were affected after 24 and 48 hours of recovery, respectively. However, significantly fewer genes--only 3 and 1, respectively--were affected after exposure to e-cigarette vapour
Further analysis revealed that the exposure to cigarette smoke had caused changes in the expression of genes involved in the development of lung cancer, inflammation and fibrosis, while the test e-cigarette vapour only caused minor changes in genes known to be involved in cell metabolism and oxidative stress mechanisms.
'Our results clearly show that cigarette smoke has an adverse effect on cells, triggering a robust gene expression response,' says Dr James Murphy, Head of Reduced Risk Substantiation at British American Tobacco. 'However,' he said, 'even at equivalent or higher dose of nicotine, acute exposure to the test e-cigarette vapour has very limited impact on gene expression compared to cigarette smoke exposure--it's a striking difference.'
These results, which are published in Scientific Reports (DOI: 10.1038/s41598-017-00852-y) add to an increasing weight of evidence that e-cigarette vapour causes less damage to cells compared to cigarette smoke.
Previous research conducted by British American Tobacco has shown that Vype ePen vapour contains around 95% less toxicants (Chem. Res. Toxicol, DOI: 10.1021/acs.chemrestox.6b00188) compared to cigarette smoke from a reference cigarette (in terms of the priority list of nine toxicants which the World Health Organisation recommends to reduce).
Many in the public health community believe e-cigarettes offer great potential for reducing the projected public health impact of smoking. Public Health England, an executive body of the UK Department of Health, published a report saying that the current expert estimate is that using e-cigarettes is around 95% safer than smoking cigarettes. The Royal College of Physicians have said that the public can be reassured that e-cigarettes are much safer than smoking and that they should be widely promoted as an alternative to cigarettes.