Abou-Assali, O. J.; Reiser, M.; Chang, M.; Chidipi, B.; Asswaytte, R.; Zhang, Y.; Szekeres, C.; Calcul, L.; Noujaim, S. F.

Background: Electronic nicotine delivery systems (ENDS) heat \"E-liquids\" to generate \"E-vapor\", an aerosolized mixture containing nicotine and flavors. Flavored ENDS are popular among teens who vape, however, the possible cardiac electrophysiological harm of inhalation exposure to flavored ENDS are not fully understood. Objective: To test if inhalation exposure to flavoring carbonyls in E-liquids compromises mitochondrial integrity, increases oxidative stress, and leads to cardiac electrophysiological toxicity. Methods: Gas chromatography mass spectrometry (GC/MS), flow cytometry, oxygen consumption rate (OCR) measurement, in-vivo programmed electrical stimulation (PES), and multielectrode array (MEA) were used in atrial like HL-1 myocytes, hiPSC derived cardiomyocytes, and mice overexpressing mitochondrial catalase (mCAT). Results: We compared the toxicity of E-vapor exposure from 30 differently flavored E-liquids in HL-1 cells using apoptotic annexin V flow cytometry. Most E-liquids were toxic. We identified the major flavoring carbonyls in these E-liquids and quantified their concentrations using GC/MS. Linear regression analysis showed that toxicity correlated with carbonyls concentration. Using flow cytometry of CellROX and TMRE staining, HL-1 cells exposed to flavored E-vapor showed increased reactive oxygen species and depolarized mitochondrial membrane potential. Additionally, exposure decreased OCR in these cells. In-vivo inhalation exposure to flavored E-vapor increased the inducible ventricular tachycardia duration in WT but not in mCAT mice compared to controls. MEA recordings in hiPSC derived cardiomyocytes exposed to flavored E-vapor, with or without nicotine, resulted in changes in the spontaneous beating rate. Conclusions: Inhalation exposure to flavored ENDS negatively affects ventricular electrophysiology, in part via adverse mitochondrial remodeling, and increased oxidative stress.