Nicotine Formulation Influences the Autonomic and Arrhythmogenic Effects of Electronic Cigarettes.

INTRODUCTION: Evidence is mounting that electronic cigarette (e-cig) use induces cardiac sympathetic dominance and electrical dysfunction conducive to arrhythmias and dependent upon nicotine. A variety of nicotine types and concentrations are available in e-cigs, but their relative cardiovascular effects remain unclear. Here we examine how different nicotine forms (racemic, free-base, and salt) and concentrations influence e-cig-evoked cardiac dysfunction and arrhythmogenesis and provide a mechanism for nicotine-salt-induced autonomic imbalance. METHODS: ECG-telemetered C57BL/6J mice were exposed to filtered air (FA) or e-cig aerosols from propylene glycol and vegetable glycerin solvents either without nicotine (vehicle) or with increasing nicotine concentrations (1%, 2.5%, and 5%) for three 9-min puff sessions per concentration. Spontaneous ventricular premature beat (VPB) incidence rates, heart rate, and heart rate variability (HRV) were compared between treatments. Subsequently, to test the role of ß1-adrenergic activation in e-cig-induced cardiac effects, mice were pretreated with atenolol and exposed to either FA or 2.5% nicotine salt. RESULTS: During puffing and washout phases, ≥ 2.5% racemic nicotine reduced heart rate and increased HRV relative to FA and vehicle controls, indicating parasympathetic dominance. Relative to both controls, 5% nicotine salt elevated heart rate and decreased HRV during washout, suggesting sympathetic dominance, and also increased VPB frequency. Atenolol abolished e-cig-induced elevations in heart rate and declines in HRV during washout, indicating e-cig-evoked sympathetic dominance is mediated by ß1-adrenergic stimulation. CONCLUSIONS: Our findings suggest that inhalation of e-cig aerosols from nicotine salt-containing e-liquids could increase the cardiovascular risks of vaping by inducing sympathetic dominance and cardiac arrhythmias. IMPLICATIONS: Exposure to e-cig aerosols containing commercially relevant concentrations of nicotine salts may increase nicotine delivery and impair cardiac function by eliciting ß1-adrenoceptor-mediated sympathoexcitation and provoking ventricular arrhythmias. If confirmed in humans, our work suggests that regulatory targeting of nicotine salts through minimum pH standards or limits on acid additives in e-liquids may mitigate the public health risks of vaping.

The Antiarrhythmic Drug, Amiodarone, Decreases AKT Activity and Sensitizes Human Acute Myeloid Leukemia Cells to Apoptosis by ABT-263.

BACKGROUND: Successful treatment of leukemia requires new medications to combat drug resistance, but the development of novel therapies is an arduous and risky endeavor. Repurposing currently approved drugs or those already in clinical development to treat other indications is a more practical approach. Moreover, combinatorial therapeutics are often more efficacious than single agent therapeutics because the former can simultaneously target multiple pathways that mitigate tumor aggressiveness and induce cancer cell death. MATERIAL AND METHODS: In this study, we combined the class III antiarrhythmic agent amiodarone and the BH3 mimetic ABT-263 based on data from a prior drug screen to assess the degree of apoptotic induction in 2 human leukemia cell lines. RESULTS: The combination yielded statistically significant increases in apoptosis in both cell lines by downregulating AKT activity and increasing cleaved caspase-3. CONCLUSIONS: Overall, our findings suggest that combining K+ channel blockers with prosurvival Bcl-2 family inhibitors is a promising therapeutic approach in treating leukemia.