Cannabidiol and Vitamin E Compromise the Interfacial Stability of Model Lung Surfactant Lipid Monolayers by Altering Their Thermodynamic and Rheological Properties.

The increasing number of cases of E-cigarette or vaping product use-associated lung injury (EVALI) has raised concerns regarding their safe use, particularly because of the association of vaping additives with lung dysfunction. While the mechanisms by which vaping additives affect the LS film are unclear, labored breathing is a hallmark of EVALI, suggesting disruption of LS mechanics. We hypothesize that the accumulation of vape additives in the lungs alters their lipid packing and rheological properties. We investigate how two common vape additives, cannabidiol (CBD) and α-tocopherol (vitamin E), alter the interfacial mechanics of dipalmitoylphosphatidylcholine (DPPC) monolayers subjected to cyclic deformations mimicking breathing. Quasi-static surface properties were evaluated through compression/expansion isotherms using a Langmuir-Pockels trough with movable ribbon barriers, while epifluorescence microscopy was employed to visualize domain morphology. More importantly, since lung compliance depends on the dynamic restructuring of LS components at the alveolar surface, dilatational rheology was probed via oscillatory barrier deformations. Our results showed that both additives affected the surface activity and rheology of DPPC films in a concentration-dependent manner. However, the extent of impact also depended on the chemical composition of the additive, with vitamin E showing a larger impact than CBD at all concentrations studied. Further, when both additives were present, our results suggest that vitamin E plays a dominant role. This difference may be attributed to the bulkier molecular structure of vitamin E. Overall, our findings highlight that long-term exposure to vaping can disrupt film structure, altering its interfacial mechanics and thus reducing film stability.