BS-454195-4 MITOCHONDRIAL REMODELING MEDIATES CARDIAC ELECTROPHYSIOLOGICAL INJURY IN INHALATION EXPOSURE TO FLAVORED ELECTRONIC NICOTINE DELIVERY SYSTEMS.

Abstract

Electronic nicotine delivery systems (ENDS) utilize “e-liquids” in order to generate “e-vapor”, an inhalable aerosolized mixture containing nicotine and flavors. Flavored ENDS are very popular among teens who vape, however, the possible cardiac electrophysiological harm of inhalation exposure to flavored ENDS are not fully understood. To test if inhalation exposure to flavoring carbonyls in e-liquids compromises mitochondrial integrity, increases oxidative stress, and leads to cardiac electrophysiological toxicity. Gas chromatography mass spectrometry (GC/MS), and flow cytometry, in-vivo programmed electrical stimulation (PES), confocal microscopy, and transmission electron microscopy (TEM) were used in atrial like HL-1 myocytes and in mice overexpressing the antioxidant mitochondrial catalase (MCAT) exposed to flavored e-vapor. We compared the toxicity of e-vapor exposure from 30 differently flavored e-liquids (70% vegetable glycerin, 30% propylene glycol, with 6 mg/ml nicotine) in HL-1 cells using apoptotic annexinV flow cytometry. Toxicity of most e-liquids was significantly higher than air control. We subsequently determined the composition and quantified the concentrations of major flavoring carbonyls (cinnamaldehyde, vanillin, ethyl vanillin, maltol, and ethyl maltol) in the e-liquids using GC/MS. Linear regression analysis showed that toxicity correlated significantly with carbonyls concentration. We then assessed oxidative stress (OS) via CellROX flow cytometry in HL-1 cells exposed to vanilla flavored e-vapor. OS increased in exposed cells but this was prevented by N-acetylcycteine antioxidant pretreatment. Moreover, Mitotracker confocal microscopy quantification of the mitochondrial network indicated that exposure significantly decreased the mitochondrial footprint likely due to the network’s disintegration. In-vivo inhalation exposure to vanilla flavored e-vapor (four weeks, 1 hour/day) increased the duration of PES induced ventricular tachycardia in WT but not in MCAT mice, compared to air controls. Finally, we investigated with TEM the cardiac mitochondrial ultrastructure. While mitochondrial perimeter was unaffected, cristae thickness decreased in exposed WT, but not in exposed MCAT overexpressing hearts compared to controls. Inhalation exposure to flavored ENDS negatively affects ventricular electrophysiology, in part via adverse mitochondrial remodeling, and increased oxidative stress.