Abstract 13869: Inflammatory Changes in the Lungs of Rats Exposed to E-cigarettes Without Marijuana, Vitamin E Oil, or Nicotine

Abstract

Background: Recently, the clinical entity of EVALI (E-cigarette or vaping product use associated lung injury) was described and has similarities to COVID -19 pneumonia. We determined in a quantitative manner the inflammatory changes in the lungs associated with EVALI in a rodent model that does not include use of marijuana, vitamin E oil, or nicotine, which had been implicated as a cause. Methods: Adult Sprague Dawley rats were exposed to either pure air (n=5) or electronic cigarette (eC) vapor (propylene glycol/vegetable glycerin, tobacco flavoring) using a device with a nickel-chromium alloy (NC) heating element at 70 Watts (n=6) for 2 hours. The e-liquid did not contain nicotine, marijuana, or Vitamin E oil. Rats were euthanized within a few days of exposure and H&E-stained lung sections were assessed. Inflammatory cells were counted from 10 random areas per section at 20х magnification. Results: Alveolar structure appeared normal in the air group (Figure, panel C); the eC group using the NC heating element showed alveolar inflammation (D). The numbers of inflammatory cells per high power field in the lung parenchyma were significantly greater in the rats exposed to eC using NC heating element (67.5 ± 44.5) compared to the air group (6.7 ± 0.3; P < 0.001, Kruskal-Wallis test). The predominant cell type was mononuclear and secondary were neutrophils. Other features included accumulation of fibrin and inflammatory cells in the lumen of the trachea (A); thickened alveolar walls; and red blood cell congestion (D). Inflammation of the nasal passages was also observed (B). Exposure of rats to e cigarettes using a stainless steel heating element did not result in EVALI, and the amount of inflammatory cells was closer to air exposed rats (7.2± 0.4). Conclusion: Vaping using a nichrome heating element at high power leads to respiratory tract pathology and a significant increase in the number of inflammatory cells in the alveoli. EVALI occurred without marijuana, vitamin E oil or nicotine.