E‐Cigarette Use Increases Susceptibility to Bacterial Infection by Impairment of Human Neutrophil Chemotaxis, Phagocytosis and NET Formation

Abstract

Although E‐cigarettes are frequently portrayed as a safer alternative to conventional cigarettes, a growing body of evidence suggests that the use of these devices may adversely affect host defense against infection. Neutrophils, critical effector cells of the innate immune system and early responders to sites of infection, may represent a particularly important cellular target of E‐cigarette vapor components. Using primary human neutrophils isolated from healthy donors, we evaluated the impact of electronic vapor extract (EVE) exposure on multiple aspects of neutrophil cellular physiology, including chemotaxis, reactive oxygen species (ROS) production, generation of Neutrophil Extracellular Traps (NETs) and phagocytosis. Using a transwell chamber approach, we found that exposure to E‐cigarette vapor‐infused media (EVE) reduced neutrophil chemotaxis in response to the chemoattractant f‐Met‐Leu‐Phe (fMLP) by up to 4.2 fold (p < 0.001). Staining with the fluorescent actin probe rhodamine phalloidin revealed aberrant actin cytoskeleton polarization in EVE‐treated, fMLP‐stimulated neutrophils. Neutrophil membrane fluidity was also altered by EVE exposure, with holotomographic microscopy revealing alterations in cellular morphology in EVE‐treated neutrophils. ROS production was reduced in EVE‐treated neutrophils, and ROS‐dependent production of bactericidal extracellular traps was reduced by up to 3.5 fold (p < 0.01). Interestingly, this reduction in NET production (NETosis) was observed in neutrophils treated with EVE produced using propylene glycol‐based E‐cigarette liquid formulations both with and without nicotine. The rate of neutrophil phagocytosis, quantified using fluorescent E. coli/S. aureus bioparticles, was also reduced by up to 47% in EVE‐treated neutrophils (p < 0.05). To determine how such alterations of immune cell function might affect host response to infection, a physiologic mouse model of chronic E‐cigarette exposure and sepsis was utilized. In this model, E‐cigarette vapor inhalation led to reduced neutrophil migration into infected spaces and a higher burden of Pseudomonas aeruginosa. Taken together, these findings provide evidence that E‐cigarette use adversely impacts the innate immune system, potentially placing E‐cigarette users at higher risk for dysregulated inflammatory responses and invasive bacterial infections.