Abstract 2021: Differential expression of antioxidant and detoxifying enzymes induced by e-cigarette aerosol
Authors: Ganapathy Vengatesh , Manyanga Jimmy , Queimado Lurdes 
Published: July 2021

Abstract
Background: Last decade, there has been an increasing interest in the use of electronic cigarette (e-cig) among the youths. E-cigs are promoted as a safer alternative to tobacco cigarettes, but the long term health effects of e-cigs are unknown. E-cig aerosols contain harmful and potentially harmful substances, i.e., nicotine, ultrafine particles, flavoring agents, carbonyl compound, heavy metals, and carcinogens. In addition to containing reactive oxygen species (ROS), e-cig aerosols can also increase the cellular ROS production potentially leading to further alterations in the antioxidant system and its regulators. A recent in-vitro study from our laboratory showed that e-cigs aerosols can suppress the cellular antioxidant defenses and induced oxidative DNA damage in human epithelial cells. The effects of e-cig aerosols on antioxidant and detoxifying enzymes and its regulators are unknown.
Aims: To investigate whether exposure to EC aerosol extracts alters the expression of antioxidant and detoxifying enzymes in human epithelial cells.
Methods: Human oral epithelial cancer (UM-SCC-1) and non-cancer (POE9n) cell lines were exposed every other day for 2 weeks to e-cig aerosol. E-cig aerosols were prepared from two distinct e-cig brands (18 mg/ml of nicotine; tobacco flavor). Standard tobacco extracts (mainstream smoke, MS) were used as positive control. Gene and protein expression were quantified by RT-PCR and Western blotting respectively. Data were analyzed by Student's t-test and ANOVA.
Results: Exposure to e-cig aerosol, but not to MS smoke, led to a decrease in NRF2 and SOD2 mRNA expression in both cell lines. A significant decrease in protein expression was also observed for NRF2 protein after exposure to e-cig aerosol. A significant increase in CYP1B1 was observed after exposure to e-cig aerosol and MS smoke.
Conclusion: E-cig aerosol exposure decreases the expression of NRF2 a major regulator of the antioxidant response. This might put the cell under additional oxidative stress which can have major biological implications. E-cig aerosol exposure increases the expression of CYP1B1, a protein with a key role in the bioactivation of tobacco pro-carcinogens and the regulation of the redox homeostasis. Overall, our study suggests that e-cig aerosol not only carries high levels of ROS, but also alters the cellular detoxification and antioxidant system leading to a higher oxidative stress status that would be anticipated.
Grant support: This work was supported by the National Institutes of Health, National Cancer Institute (R01CA242168). Dr. Queimado holds a Presbyterian Health Foundation Endowed Chair in Otorhinolaryngology, Oklahoma Tobacco Research Center (LQ).
Citation Format: Vengatesh Ganapathy, Jimmy Manyanga, Lurdes Queimado. Differential expression of antioxidant and detoxifying enzymes induced by e-cigarette aerosol [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2021.