We recently reported a mouse model of chronic electronic cigarette (e-cig) exposure-induced cardiovascular pathology, where long-term exposure to e-cig vape (ECV) induces cardiac abnormalities, impairment of endothelial function, and systemic hypertension. Here, we delineate the underlying mechanisms of ECV-induced vascular endothelial dysfunction (VED), a central trigger of cardiovascular disease. C57/BL6 male mice were exposed to ECV generated from e-cig liquid containing 0, 6, or 24 mg/ml nicotine for 16 and 60 weeks. Time-dependent elevation in blood pressure and systemic vascular resistance were observed, along with an impairment of acetylcholine-induced aortic relaxation in ECV-exposed mice, compared to air-exposed control. Decreased intravascular nitric oxide (NO) levels and increased superoxide generation with elevated 3-nitrotyrosine levels in the aorta of ECV-exposed mice were observed, indicating that ECV-induced superoxide reacts with NO to generate cytotoxic peroxynitrite. Exposure increased NADPH oxidase expression, supporting its role in ECV-induced superoxide generation. Downregulation of endothelial nitric oxide synthase (eNOS) expression and Akt-dependent eNOS phosphorylation occurred in the aorta of ECV-exposed mice, indicating that exposure inhibited de novo NO synthesis. Following ECV exposure, the critical NOS cofactor tetrahydrobiopterin was decreased, with a concomitant loss of its salvage enzyme, dihydrofolate reductase. NADPH oxidase and NOS inhibitors abrogated ECV-induced superoxide generation in the aorta of ECV exposed mice. Together, our data demonstrate that ECV exposure activates NADPH oxidase and uncouples eNOS, causing a vicious cycle of superoxide generation and vascular oxidant stress that triggers VED and hypertension with predisposition to other cardiovascular disease.

Electronic cigarette (e-cig) vaping (ECV) has been proposed as a safer alternative to tobacco cigarette smoking (TCS); however, this remains controversial due to a lack of long-term comparative studies. Therefore, we developed a chronic mouse exposure model, which mimics human vaping and allows comparison to TCS. Longitudinal studies were performed to evaluate alterations in cardiovascular function with TCS and ECV exposure durations of up to 60 weeks. For ECV, e-cig liquid with box-mod were used and for TCS, 3R4F-cigarettes. C57/BL6 male mice were exposed 2 hours/day, 5 days/week to TCS, ECV, or air-control. The role of vape nicotine levels was evaluated using e-cig-liquids with 0, 6 or 24 mg/ml nicotine. Following 16 weeks exposure, increased constriction to phenylephrine and impaired endothelium-dependent and endothelium-independent vasodilation were observed in aortic segments, paralleling the onset of systemic hypertension, with elevations in systemic vascular resistance. Following 32 weeks, TCS and ECV induced cardiac hypertrophy. All of these abnormalities further increased out to 60 weeks of exposure, with elevated heart weight and aortic thickness along with increased superoxide production in vessels and cardiac tissues of both ECV and TCS mice. While ECV-induced abnormalities were seen in the absence of nicotine, these occurred earlier and were more severe with higher nicotine exposure. Thus, long-term vaping of e-cig, can induce cardiovascular disease similar to TCS, and the severity of this toxicity increases with exposure duration and vape nicotine content.

In a chronic model of smoking-induced cardiovascular disease, we define underlying mechanisms of smoking-induced vascular endothelial dysfunction (VED). Smoking exposure triggered VED and hypertension and led to vascular macrophage infiltration with concomitant increase in superoxide and NADPH oxidase levels as early as 16 wk of exposure. This oxidative stress was accompanied by tetrahydrobiopterin depletion, resulting in endothelial nitric oxide synthase uncoupling with further superoxide generation triggering a vicious cycle of oxidative stress and VED.

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Background We recently reported a mouse model of chronic electronic cigarette (e‐cig) exposure‐induced cardiovascular pathology, where long‐term exposure to e‐cig vape (ECV) induces cardiac abnormalities, impairment of endothelial function, and systemic hypertension. Using this model, we performed studies to delineate the underlying mechanisms of ECV‐induced vascular endothelial dysfunction (VED), which is a central trigger of cardiovascular disease. Methods C57/BL6 male mice were exposed 2 hours/day, 5 days/week to ECV generated from e‐cig liquid containing 0, 6, or 24 mg/ml nicotine for 16 and 60 weeks. Blood pressure was measured by tail cuff and endothelial‐dependent and independent relaxation was measured on aortic segments using wire myography. Western blotting, immunofluorescence and ELISA were used to analyze the pathways involved in the mechanism of ECV‐induced VED. Results Time‐dependent elevation in blood pressure and systemic vascular resistance were observed, along with an impairment of acetylcholine‐induced aortic relaxation in ECV‐exposed mice, compared to air‐exposed control. Decreased intravascular nitric oxide (NO) levels and increased superoxide generation with elevated 3‐nitrotyrosine levels in the aorta of ECV‐exposed mice were observed, indicating that ECV‐induced superoxide reacts with NO to generate cytotoxic peroxynitrite. Exposure increased NADPH oxidase expression, supporting its role in ECV‐induced superoxide generation. Downregulation of endothelial nitric oxide synthase (eNOS) expression and Akt‐dependent eNOS phosphorylation occurred in the aorta of ECV‐exposed mice, indicating that exposure inhibited de novo NO synthesis. Following ECV exposure, the critical NOS cofactor tetrahydrobiopterin was decreased, with a concomitant loss of its salvage enzyme, dihydrofolate reductase. NADPH oxidase and NOS inhibitors abrogated ECV‐induced superoxide generation in the aorta of ECV exposed mice. Conclusion Our data demonstrate that ECV exposure activates NADPH oxidase and uncouples eNOS, causing a vicious cycle of superoxide generation and vascular oxidant stress that triggers VED and hypertension with predisposition to other cardiovascular disease.

Background Electronic cigarette (e‐cig) vaping (ECV) has been proposed as a safer alternative to tobacco cigarette smoking (TCS); however, this remains controversial due to a lack of long‐term comparative studies. Therefore, we developed and applied a chronic mouse exposure model, which mimics human vaping and allows comparison to TCS. This model was applied to determine the role of nicotine levels and exposure duration in the onset of cardiovascular changes and toxicity. Methods Longitudinal studies were performed to evaluate alterations in cardiovascular function with TCS and ECV exposure durations of up to 60 weeks. For ECV, e‐cig liquid formulations were used with box‐mod and for TCS, 3R4F‐cigarettes. C57/BL6 male mice were exposed 2 hours/day, 5 days/week to TCS, ECV, or air‐control. The role of vape nicotine levels was evaluated using e‐cig‐liquids with 0, 6 or 24 mg/ml nicotine. Results Following 16 weeks of exposure, increased constriction to phenylephrine and impaired endothelial‐dependent and endothelial‐independent vasodilation were observed in aortic segments of the TCS and ECV exposure groups. This paralleled the onset of systemic hypertension, with elevations in systemic vascular resistance. These changes were seen in all ECV and TCS exposed groups but were most severe with TCS and ECV with 24 mg/ml nicotine. Following 32 weeks, TCS and ECV induced cardiac hypertrophy with concentric left ventricular wall thickening. All of these abnormalities further increased out to 60 weeks of exposure, with elevated heart weight and aortic wall thickness along with increased superoxide production measured in vessels and cardiac tissues of both ECV and TCS mice. Conclusion While ECV‐induced abnormalities were seen in the absence of nicotine, these occurred earlier and were more severe with higher nicotine exposure. Thus, long‐term vaping of e‐cig, can induce cardiovascular disease similar to TCS, and the severity of this toxicity increases with exposure duration and vape nicotine content.

The addition of ezetimibe to peg-IFN/RBV combination significantly improves EVR rates in obese patients compared with nonobese patients, and remarkably improves the biochemical responses in both obese and nonobese patients with CHC-4. This may shed light on a new strategy for the treatment of CHC, particularly in obese Egyptian patients.