Abstract
BackgroundElectronic cigarette (EC) aerosols contain unique compounds in addition to toxicants and carcinogens traditionally found in tobacco smoke. Studies are warranted to understand the public health risks of ECs.ObjectiveThe aim of this study was to determine the genotoxicity and the mechanisms induced by EC aerosol extracts on human oral and lung epithelial cells.MethodsCells were exposed to EC aerosol or mainstream smoke extracts and DNA damage was measured using the primer anchored DNA damage detection assay (q-PADDA) and 8-oxo-dG ELISA assay. Cell viability, reactive oxygen species (ROS) and total antioxidant capacity (TAC) were measured using standard methods. mRNA and protein expression were evaluated by RT-PCR and western blot, respectively.ResultsEC aerosol extracts induced DNA damage in a dose-dependent manner, but independently of nicotine concentration. Overall, EC aerosol extracts induced significantly less DNA damage than mainstream smoke extracts, as measured by q-PADDA. However, the levels of oxidative DNA damage, as indicated by the presence of 8-oxo-dG, a highly mutagenic DNA lesion, were similar or slightly higher after exposure to EC aerosol compared to mainstream smoke extracts. Mechanistically, while exposure to EC extracts significantly increased ROS, it decreased TAC as well as the expression of 8-oxoguanine DNA glycosylase (OGG1), an enzyme essential for the removal of oxidative DNA damage.ConclusionsExposure to EC aerosol extracts suppressed the cellular antioxidant defenses and led to significant DNA damage. These findings emphasize the urgent need to investigate the potential long-term cancer risk of exposure to EC aerosol for vapers and the general public.
Highlights
Electronic cigarettes (ECs) are battery-powered devices that heat up a solution of chemicals with or without nicotine and turn it into an inhalable aerosol
Exposure to EC aerosol extracts suppressed the cellular antioxidant defenses and led to significant DNA damage. These findings emphasize the urgent need to investigate the potential long-term cancer risk of exposure to EC aerosol for vapers and the general public
EC aerosols induce a dose-dependent increase in DNA damage
Summary
Electronic cigarettes (ECs) are battery-powered devices that heat up a solution of chemicals (eliquid) with or without nicotine and turn it into an inhalable aerosol. Whether ECs are a safer alternative to combustible tobacco products and/or assist patients with smoking cessation are still major controversies [1,2,3,4,5,6]. The use of ECs has increased sharply since 2003 [7,8,9]. The use of ECs among middle and high school students has had a 4-fold increase between 2013 and 2014 reaching 3.9% and 13.4%, respectively [11]. The U.S Food and Drug Administration (FDA) has called for additional scientific research to inform the development of effective EC regulations [13] and has extended its regulatory authority to cover all tobacco products, including ECs [14]. Electronic cigarette (EC) aerosols contain unique compounds in addition to toxicants and carcinogens traditionally found in tobacco smoke. Studies are warranted to understand the public health risks of ECs
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