A mouse model of E-cigarette or vaping product use-associated lung injury (EVALI) induced by nose-only exposure to aerosolized vitamin E acetate and associated macrophage dysfunction.

Background: E-cigarette or vaping product use-associated Lung Injury (EVALI) has become a public health concern since 2019, with vitamin E acetate (VEA) identified as a potential causative agent. While previous studies have used whole-body VEA aerosol exposure or intratracheal instillation models, these approaches may introduce confounding exposure routes or do not fully reflect real-world vaping conditions. To better understand VEA-induced EVALI, there remains a need for an animal model that isolates airway exposure and closely mimics human vaping behaviour.

Methods: We utilized a nose-only exposure system to develop a mouse model of EVALI, with VEA aerosol generated by a commercially available vaping device. Puffs were generated at a volume of 55 mL over 3 s, delivered every 30 s for 1 h per day, up to 6 consecutive days. Lung injury was assessed through histopathological analysis, and airway function was measured via invasive airway function test. Ultrastructural changes in mouse alveoli were analyzed with transmission electron microscopy. Alveolar macrophages were assessed for pro-inflammatory polarization and functional impairment. Potential pathogenic mechanisms were explored with RNA-seq analysis.

Results: Our findings revealed acute lung injuries, characterized by pulmonary edema and typical histopathological findings. Additionally, we observed changes in airway functions with altered respiratory patterns and decreased lung dynamic compliance. Transmission electron microscopy further revealed type II pneumocyte hypertrophy, type I pneumocyte swelling, and prolonged activation of alveolar macrophages with electron-dense phagocytic contents. We also demonstrated macrophage dysfunction with sustained pro-inflammatory polarization and impaired efferocytosis function. The persistent inflammation of the lung was also characterized by the increased level of pro-inflammatory cytokines in the bronchoalveolar lavage fluid, especially IL-6. RNA-seq analysis highlighted pathways related to T cell activation, cytokine signaling, and leukocyte migration.

Conclusion: This study established a mouse model using a nose-only VEA aerosol exposure system to examine the respiratory effects of VEA in EVALI. Our results revealed that VEA inhalation triggered acute lung injury, accompanied by early signs of airway dysfunction. The findings support the hypothesis that VEA drives EVALI pathogenesis through both direct cytotoxic effects and macrophage-mediated inflammation. Our findings offer new insights into the mechanisms of EVALI and present a valuable model for future research.