Abstract
Oxidative stress and inflammatory response are the key events in the pathogenesis of chronic airway diseases. The consumption of electronic cigarettes (e-cigs) with a variety of e-liquids/e-juices is alarmingly increasing without the unrealized potential harmful health effects. We hypothesized that electronic nicotine delivery systems (ENDS)/e-cigs pose health concerns due to oxidative toxicity and inflammatory response in lung cells exposed to their aerosols. The aerosols produced by vaporizing ENDS e-liquids exhibit oxidant reactivity suggesting oxidants or reactive oxygen species (OX/ROS) may be inhaled directly into the lung during a “vaping” session. These OX/ROS are generated through activation of the heating element which is affected by heating element status (new versus used), and occurs during the process of e-liquid vaporization. Unvaporized e-liquids were oxidative in a manner dependent on flavor additives, while flavors containing sweet or fruit flavors were stronger oxidizers than tobacco flavors. In light of OX/ROS generated in ENDS e-liquids and aerosols, the effects of ENDS aerosols on tissues and cells of the lung were measured. Exposure of human airway epithelial cells (H292) in an air-liquid interface to ENDS aerosols from a popular device resulted in increased secretion of inflammatory cytokines, such as IL-6 and IL-8. Furthermore, human lung fibroblasts exhibited stress and morphological change in response to treatment with ENDS/e-liquids. These cells also secrete increased IL-8 in response to a cinnamon flavored e-liquid and are susceptible to loss of cell viability by ENDS e-liquids. Finally, exposure of wild type C57BL/6J mice to aerosols produced from a popular e-cig increase pro-inflammatory cytokines and diminished lung glutathione levels which are critical in maintaining cellular redox balance. Thus, exposure to e-cig aerosols/juices incurs measurable oxidative and inflammatory responses in lung cells and tissues that could lead to unrealized health consequences.
Highlights
The consumption of electronic nicotine delivery systems (ENDS) and electronic cigarettes is rising and currently scientific information necessary to inform the FDA and clinicians of potential health risks is lacking
There is no clear indication that inhaling aerosols from ENDS/e-cigs will allow a healthy outcome for users and the manufactures that produce ENDS globally are not liable to disclose the materials and chemicals employed in their fabrication
oxidants/reactive oxygen species (OX/ROS) produced by ENDS/e-cigs were detected by drawing the aerosols through a fluorescein derived dye (DCFH solution) using an air flow pump
Summary
The consumption of electronic nicotine delivery systems (ENDS) and electronic cigarettes (ecigs) is rising and currently scientific information necessary to inform the FDA and clinicians of potential health risks is lacking. Other toxic chemicals including carcinogens which are not typically found in e-liquids may be released or generated from ENDS/ e-cigs and have been detected at low levels in various ENDS aerosols [4,5,6]. Some of these toxicants may emanate from heated structural materials while drawing air through an ENDS device, but are proposed to form during the vaporization process [7,8]. Heavy metals, and toxic carbonyls in ENDS/e-cig aerosols have recently been measured in ecigs aerosols as well [5,7,9,10]
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