Uncovering the Dual Effect of Menthol and Nicotine Levels in Electronic Nicotine Delivery Systems on Pulmonary...

Electronic nicotine delivery systems (ENDS) are now increasingly used, with commercial electronic cigarettes frequently containing high levels of nicotine and menthol, which is a popular flavoring agent. This has raised multiple concerns about the health risks associated with menthol-flavored ENDS. Although menthol and nicotine are known for their individual effects on respiratory health, their combined impact on pulmonary surfactants remains poorly understood. Therefore, this study aimed at understanding the interactions between the primary components of all ENDS liquids (PG and VG), nicotine and menthol flavoring, and the pulmonary surfactant. This in vitro study used 1,2 dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and a stoichiometric mixture of DPPC/1-palmitoyl-2-Oleoyl-sn-glycero-3-phosphocholine (POPC)/2-Oleoyl-1-palmitoyl-sn-glycero-3- phospho-rac-(1-glycerol) sodium salt (POPG)/cholesterol at 48/32/10/10 to mimic the pulmonary surfactant. These systems were probed using a Langmuir-Blodgett Trough and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. The results indicate a concentration dependence of the impact of different nicotine concentrations combined with menthol on the surfactant mimics. Our findings also reveal the effect of menthol on the surface pressure. The combination of nicotine and menthol appears to alter the conformational state of the surfactant, proximately altering characteristic vibrational groups. Moreover, different behaviors are unveiled between the two model surfactants, particularly attributed to the complexities of the four surfactants mixture. Further research is suggested to address the mechanisms and implications involved with ENDS flavoring and additives on surfactant molecules in biological systems. Establishing well-informed regulations on ENDS consumption and distribution should be developed.