Real-world traffic-polluted air and its impact on a 3D model of the human airway epithelium

Exposure to air pollution is linked to adverse health outcomes. To better reflect real-world conditions, we employed a mobile exposure system enabling direct field exposure of the human airway epithelial model MucilAir™ to ambient air in a traffic-burdened locality. This study represents a follow-up to our previous work, in which a 5-day exposure period under extreme traffic-related pollution conditions resulted in premature cell loss. Under different meteorological conditions characterized by increased precipitation and lower particle number concentrations, MucilAir™ cultures were exposed to traffic-polluted air for 2 days. The exposure resulted in a mild but significant increase in cytotoxicity markers, including lactate dehydrogenase release and elevated levels of 15-F2t-isoprostane, indicating induction of the cellular stress response rather than severe cytotoxicity. A transcriptomic analysis revealed extensive gene expression changes; the enrichment of the pathways related to polycyclic aromatic hydrocarbon detoxification and amino acid biosynthesis suggests adaptive metabolic responses to oxidative and genotoxic stress. In parallel, the pathways associated with epithelial proliferation and repair, extracellular matrix organization, focal adhesion, and immune signaling were suppressed, indicating potential disruption of the epithelial homeostasis. Overall, these findings demonstrate that 2 days of exposure to real-world traffic-polluted air elicits adaptive stress responses in airway epithelial cells while simultaneously impairing the processes essential for epithelial integrity, potentially leading to airway dysfunction.