Investigating Wildfire Smoke Effects on Patrolling Alveolar Macrophages

Under homeostatic conditions, patrolling alveolar macrophages migrate between alveoli to effectively clear inhaled noxious substances throughout the lung. However, certain pathogens and toxins can impair this migratory function, resulting in deleterious neutrophil recruitment and tissue injury. During wildfire events, animals and humans breathe in smoke containing large amounts of particulate matter and aerosolized microbes. Using intravital imaging, we aimed to characterize the impact of wildfire smoke particulate matter on alveolar macrophage migration to elucidate the mechanisms underlying wildfire smoke’s adverse respiratory effects. To this end, we administered sterilized biomass smoke particles or saline to 6-8 week old C57BL/6 mice (i.n.) for 3 days. On day 4, in vivo macrophage and neutrophil behaviour were assessed via spinning disk confocal microscopy. To further characterize the acute effects of sterile smoke particle inhalation, immunophenotyping of bronchoalveolar lavage fluid and whole lung homogenates was conducted using flow cytometry. Preliminary data indicate that exposure to sterile biomass smoke particulates does not significantly decrease alveolar macrophage displacement in the lung, suggesting that migratory capacity remained unchanged. Using unsterilized biomass smoke particulates, we will next determine whether alveolar macrophage migration is impaired following simultaneous particulate and microbial exposure, resulting in downstream neutrophilic inflammation. Given the increasing frequency of wildfires, investigating associated health impacts is increasingly warranted. Determining the impact of wildfire smoke on patrolling alveolar macrophages may ultimately uncover key mechanisms and therapies to alleviate adverse respiratory effects.