Temporal variation in markers of immune signaling and wound repair in primary human airway epithelial cells following acute versus repeated woodsmoke condensate exposure

Wildfire smoke (WFS) exposures are becoming more common, and firefighters and community members are often exposed to WFS for days to weeks. Controlled studies assessing the effects of repeated exposure to WFS and woodsmoke (WS; as a surrogate for WFS) or compared acute versus repeated exposure have evaluated a limited number of timepoints and endpoints using rodent models. Here, we leveraged differentiated primary human bronchial epithelial cells (HBECs) to test the hypothesis that different molecular responses occur upon acute versus repeat exposures to WS. HBECs (n = 4 donors) were exposed to 22 µg/cm2 red oak WS condensate for an acute, 4-h exposure, or repeat exposures of 4 h/d, 3 d/wk, across 2 wk. Membrane permeability, cell viability, and transcriptional responses were measured at the end of each exposure paradigm, and secreted proteins were measured throughout the repeat exposure. Acute exposure significantly increased expression of genes involved in fibrosis and immune response, whereas repeated exposure significantly decreased expression of genes involved in tissue repair and remodeling. Secreted protein responses were similar to transcriptomic responses and demonstrated temporal variation in response to exposure. This study supports the feasibility of using HBECs to evaluate acute and repeat WS exposures and indicates differential responses from these exposures with direct relevance to pulmonary disease processes, including those involved in fibrosis, asthma, and chronic obstructive pulmonary disease. These findings highlight the need for future studies to better understand molecular responses to repeated smoke exposures.