Diesel Exhaust Particles Remodel Lipid Raft-Associated Molecular Features Potentially Relevant to SARS-CoV-2 Susceptibility in A549 Cells

The overlap between the geographic distribution of COVID-19 outbreaks and pollution levels suggested a strong correlation between exposure to atmospheric particulate matter and an increased risk of developing severe forms of disease. This correlation has been highlighted by several epidemiological studies, indicating the existence of shared molecular mechanisms. Emerging evidence has highlighted the important role of lipid rafts in facilitating viral entry into cells. Specifically, the receptor binding domain of the SARS-CoV-2 spike protein interacts with sialylated glycans of the monosialic ganglioside GM1 and GM2 that are particularly enriched in lipid rafts. This interaction has been proposed to facilitate ACE2 recognition by the spike protein and may contribute to early events involved in viral attachment and entry. Here, we reveal that A549 alveolar lung cells, after DEP exposure, exhibit a significant shift in ACE2 into lipid rafts, accompanied by an increase in the immature form of ADAM17, the sheddase responsible for ACE2 cleavage. Additionally, DEP exposure results in a significant increase in IL-6 release, while no changes were observed in IL-8 and sACE2 release. This treatment does not cause significant alterations in protein levels or membrane redistribution of COX-2 and HO-1, proteins involved in the inflammatory response and oxidative stress following exposure to air pollution, and linked to COVID-19 pathogenesis. Finally, lipidomic analysis by UHPLC-MS revealed that DEP exposure induces a significant increase in GM2 levels, and a concomitant decrease in GM1 and GM3 levels. Together, these results indicate that DEP exposure remodels lipid raft-associated molecular features in A549 cells, including ACE2 membrane redistribution, altered ganglioside composition, and increased IL-6 release. Although these changes may be relevant to cellular mechanisms associated with SARS-CoV-2 susceptibility, the present study does not directly assess viral binding, viral entry, or infection, and further functional studies are required.