Vapors produced by electronic cigarettes and e-juices with flavorings induce toxicity, oxidative stress, and inflammatory response in lung epithelial cells and in mouse lung

PLoS One. 2015 Feb 6;10(2):e0116732. doi: 10.1371/journal.pone.0116732. eCollection 2015.

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aerosols / adverse effects
  • Animals
  • Bronchoalveolar Lavage
  • Cell Line
  • Cotinine / blood
  • Electronic Nicotine Delivery Systems / adverse effects*
  • Flow Cytometry
  • Humans
  • Mice
  • Nicotine / administration & dosage
  • Nicotine / toxicity*
  • Oxidative Stress / drug effects*
  • Pneumonia / chemically induced*
  • Respiratory Mucosa / drug effects*
  • Solutions / administration & dosage
  • Solutions / toxicity
  • Volatilization

Substances

  • Aerosols
  • Solutions
  • Nicotine
  • Cotinine