Abstract 225: Electronic Cigarettes Induced Exacerbation of Atherosclerosis: Contribution of MicroRNA-21

Abstract

Smoking is the foremost cause of preventable disease and pre-mature deaths. Although the rates of smoking have declined in the recent past, advent of electronic cigarettes (e-cig) pose new challenges. E-cig are extremely popular in youth and usage of e-cig has increased by 9-fold in the youth between 2011 and 2015. E-cig are battery-operated devices used for the delivery of aerosolized nicotine. Unlike conventional cigarettes, e-cig have lower levels of carcinogens. However, aerosolization of e-liquids generates reactive chemicals such as acrolein, which has adverse effects on cardiovascular health. To examine the effect of e-cig on atherosclerosis we exposed 8-week old apoE-KO mice (maintained on Western diet) to filtered air or e-cig (36 mg/ml nicotine aerosolized in glycerol/propylene glycol, 50/50, v/v) for 12 weeks (3 h/day; 7 days a week). Our data show that exposure to e-cig increased the aortic lesion area by 24% (P<0.05), without affecting plasma cholesterol (e-cig 1088±61 vs air 1102±61 mg/dL) and triglyceride (e-cig 95±9 vs air 77±5 mg/dL). Exposure to e-cig also increased the expression of micro RNA-21 (miR-21) in the aorta by 26% (P<0.05). In situ hybridization assay showed that miR-21 co-localizes with macrophages in atherosclerotic plaques. In vitro , e-cig constituents acrolein and nicotine induced the expression of miR-21 by 1.8-2.0 fold, in bone marrow derived macrophages. Similarly, 4,hydroxynonenal (HNE) generated by acrolein and nicotine induced reactive oxygen species (ROS) formation by 1.3-fold, and increased the expression of miR-21 in macrophages by 2-fold. Exposure to e-cig also activated matrix metalloproteinases (MMPs) in atherosclerotic plaques. Acrolein activated MMPs ex vivo in atherosclerotic plaques, and increased the secretion of MMP-9 from macrophages. Acrolein-induced ROS formation and MMP-9 secretion was prevented by free radical scavengers. Moreover, we also observed that HNE-induced macrophage apoptosis was significantly increased by miR-21 deficiency. This process was mediated by the activation of both, intrinsic and extrinsic pathways of apoptosis. Collectively, these data suggest miR-21 prevents e-cig-induced atherogenesis by inhibiting inflammatory and apoptotic pathways in macrophages.