Background: Cigarette smoking is the leading preventable cause of mortality in the world and the main risk factor for lung and head and neck cancer. E-cigarettes (ECs) are battery-operated devices that deliver nicotine via inhaled aerosols. Although ECs are marketed as a less harmful alternative to tobacco cigarettes and a smoking cessation aid, the health risks posed by exposure to EC aerosols are unknown. Nonetheless, the use of ECs has increased exponentially since 2003, with EC users reporting inhaling on average 200 puffs a day. EC aerosols have been reported to contain variable levels of genotoxins, including carcinogenic substances and reactive oxygen species (ROS). Some toxins in EC aerosols have been reported to reach the levels of similar to those in tobacco smoke. However, the genotoxicity of EC aerosols has not been characterized.

Aims: (1) To determine the cytotoxicity and genotoxicity of short and long-term exposure to EC aerosols on human epithelial normal and cancer cell lines. (2) To evaluate whether exposure of EC aerosols modifies the cellular total antioxidant capacity (TAC).

Methods: EC extracts were prepared from NJOY (12 or 18 mg/ml of nicotine) and Oakley eGo-T (0, 12 or 18 mg/ml of nicotine). Standard tobacco extracts were used for comparison. To assess the effects of short-term exposure, human epithelial normal (NuLi-1) and cancer (UD-SCC1) cell lines were exposed for 1 hour to various EC extract concentrations. To assess the effects of long-term exposure, cells lines were exposed every other day for 2 weeks to EC extracts. Cytotoxicity, DNA damage and TAC were evaluated at 1 h and 2 weeks. Cell viability was determined by MTT assay. DNA damage was quantified using the primer anchored DNA damage detection assay (PADDA). TAC was determined by the Antioxidant Assay Kit (Cayman). Data were analyzed by Student's t-test.

Results: At the range of EC extract concentrations used in this study and expected to occur in EC users (1 to 100 puffs/5 L of blood), no cytotoxicity was observed for either normal or cancer cells. However, significant levels of DNA damage were observed in cancer cells exposed to 10 or more puffs/5 L of EC extracts and in normal cells exposed to100 puffs/5 L. Long-term exposure to EC extracts resulted in a significant decrease in TAC, a measure of free radical scavengers.

Conclusion: Even short-term exposure to low levels of EC aerosols can cause significant DNA damage. Our study emphasizes the need to further investigate the carcinogenic potential of EC aerosols and highlights the importance of regulating EC use.

Grant support: This work was supported by the Oklahoma Tobacco Research Center (LQ). Dr. Queimado holds a Presbyterian Health Foundation Endowed Chair in Otorhinolaryngology.

Citation Format: Vengatesh Ganapathy, Jimmy Manyanga, Lacy Brame, David Rubenstein, Theodore L. Wagener, Ilangovan Ramachandran, Lurdes Queimado. Electronic cigarettes induce significant DNA damage and reduce cellular antioxidant levels. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3593.