E-cigarette Aerosol Containing Nicotine Increases Aortic Stiffness in Young Mice

E-cigarettes (E-cigs) are widely used especially among young people, but the effects on vascular stiffening and remodeling are poorly understood. This study evaluates the effects of short-term e-cig exposure on young vs. adult mice and the effects of e-cig derived chemicals present in plasma and urine of exposed animals on cultured endothelial cells (EC) and vascular smooth muscle cells (SMC). C57BL/6J mice of 6- and 14-weeks of age were exposed to unflavored e-cig aerosol with and without nicotine (50% propylene glycol, 50% vegetable glycerol +/- 24 mg/ml nicotine 3 weeks, puff duration of 9 s per minute, for 60 min/day) and aortic tissue subjected to in- and ex-vivo assessment of stiffness and histological evaluation. Major chemical constituents of e-cig aerosol were analyzed in plasma and urine samples, and cultured human aortic ECs and SMCs were treated with these chemicals, including acrolein, formaldehyde and nicotine. Changes in gene and protein expression were quantified, and functional ROS and MMP assays were performed. Pulse wave velocity revealed increased stiffness upon treatment with e-cig aerosol, and to a greater extent with the inclusion of nicotine (114% in 6-week-old and 112% in 14-week-old mice vs. baseline, p < 0.001), which was also observed in ex-vivo myography in aortic infrarenal and thoracic segments in 6-week-old mice after e-cig exposure. Aortic elastin content in these mice was decreased when compared to room-air controls (-24% in 6-week-old and - 36% in 14-week-old mice in thoracic aorta, p < 0.05). In vitro treatment with some of the different chemical compounds present in e-cig aerosol led to an increase in endothelial activation markers, and extracellular remodeling proteins. Wire myography showed an endothelium-independent decrease in relaxation in young murine aortas treated with nicotine. Our results indicate that short-term exposure over three weeks to e-cig aerosol leads to marked changes in murine aortic stiffness and vascular remodeling, potentially predisposing for cardiovascular disease conditions despite the superior remodeling capabilities of young animals.