Inflammatory Gene Expression Changes and Immune System Depression in Rats Exposed to a Single 4-hr Exposure to Electronic Cigarette Vapor

Introduction: lectronic cigarette (eC) or Vaping induced Lung Injury (EVALI) was first described in the summer of 2019 in patients presenting with acute respiratory distress. Several factors contributing to EVALI are suspected, including use of oil carriers, and heating and power elements. This study examined whether a single acute exposure to eC smoke using two popular heating elements on high or low power levels would induce inflammatory gene expression and proteins, and changes in alveolar macrophage function. Hypothesis: We hypothesize that nichrome, but not stainless-steel atomizers and high power wattage used in the eC device contribute to the extent of changes in pulmonary inflammatory response and alveolar macrophage activity. Methods: Adult Sprague Dawley rats were exposed to clean air (n=8) or eC vapor (50% propylene glycol, 50% vegetable glycerin, tobacco flavoring, no nicotine, n=8) for a single four hour period using devices equipped with stainless steel (SS) or nichrome (NC) heating elements at 45 or 70 wattage power (5 exposure conditions per sex group). Rats were euthanized and bronchoalveolar lavage was performed to collect alveolar macrophages for ex-vivo cell studies. The remaining lung tissue was homogenized for inflammatory protein and gene expression analyses. Results: Significant changes were observed in animals assigned to 70 watts. Increases ranging from 1.5-fold to 2-fold change in expression of the inflammation related genes IL-6, TNF-α and CRP occurred in rats assigned to NC atomizers (p ≤ 0.05), predominantly in males. While the concentration of CRP protein was significantly increased in females, CRP gene expression was decreased at the time point examined. Other proteins were not significantly elevated. Significant (p ≤ 0.05) changes in phagocytic activity were only observed in males exposed to 70 watts NC vapor, which generated exaggerated superoxide production by 4-fold during ex-vivo incubation. Evidence of depressed phagocytic activity was observed in other exposure groups, although not statistically significant. Conclusions: These results demonstrate that a single 4-hr exposure to e-cigarettes can initiate increased gene expression of inflammatory markers IL-6, TNF-α and CRP and oxidative changes in the lung.