75 Effect of Atmospheric Aging on Soot Particle Toxicity in Airway Epithelial-Endothelial Co-Culture Models at the Air–Liquid Interface

Abstract Secondary organic aerosols (SOAs) formed from anthropogenic or biogenic volatile precursors in the atmosphere substantially contribute to the ambient fine particulate matter (PM2.5) burden, which has been associated with adverse human health effects. However, there is only limited evidence of their differential toxicological impact. To study those effects, we generated different aerosols by atmospheric aging of volatile biogenic (β-pinene) or anthropogenic (naphthalene) precursors of SOA that condensed on soot particles (SPs). In-depth, physicochemical aerosol characterization revealed very similar physical properties for SOAβPIN-SP and SOANAP-SP, but distinct differences in chemical composition. For example, SOANAP-SP was associated with the formation of more oxidized and more aromatic SOAs with a higher oxidative potential compared to β-pinene. By exposing a co-culture model system consisting of lung epithelial cells (A549) and endothelial cells (EA.hy926) at the air-liquid interface to different aerosol concentrations, we aimed to discriminate toxicological effects. Integrated transcriptomic and metabolomics analysis revealed induction of stress-related airways remodeling and an early type I immune response, for the A549 cells, especially after the exposure to SOANAP-SP. The underlying EA.hy926 cells showed similar transcriptomic changes in early response genes and genes related to cardiovascular pathologies after exposure to both SOA types, however to a greater extent after SOANAP-SP. While fresh SP without coating by SOA evinced only minor changes in both cell lines. Altogether, this supports the assumption of a pivotal role of atmospheric chemistry and the chemical PM composition on the toxicological outcomes and highlights the importance of organic compounds on cellular effects.