Comparison of the cardiac effects of electronic cigarette aerosol exposure with waterpipe and combustible cigarette smoke exposure in rats

Aims: Electronic cigarette (ECIG) has been used as an alternative to tobacco smoking as it lacks the majority of toxicants found in tobacco smoke. However, the effect of ECIG aerosol inhalation on cardiac health are not well studied. The present study aimed to compare the effects of ECIGs with that of combustible tobacco cigarette (T-Cigs) and waterpipe (WP) smoke on cardiac biomarkers of oxidative stress, inflammation, and fibrosis. Main methods: Rats were randomized into control (fresh air, n = 12), ECIG aerosol (n = 12), T-Cig smoke (n = 15), or WP (n = 13) smoke conditions in which they were exposed 1 h/daily, 6 day/week for 4 weeks. Cardiac biomarkers of oxidative stress, inflammation, and remodeling were assessed. Key findings: Relative to control, significant increase in heart to body weight ratio was observed in all exposed groups. Cardiac endothelin-1 and myeloperoxidase were increased for ECIG and T-Cig. Cardiac nitrite and TBARS were increased in all exposed groups, but activity of superoxide dismutase was increased for ECIG and T-Cig only while glutathione levels increased for ECIG only. No changes were observed for cardiac C-reactive protein and catalase activity. Cardiac fibrosis was observed in all exposed groups coupled with an increase in the transforming growth factor beta protein that was significant for ECIG only. Significance: ECIG aerosol may promote cardiac alterations in similar manner to tobacco smoke by promoting myocardial oxidative stress and inflammation leading to fibrosis. With regard to cardiac health, exposure to ECIG aerosol and combustible T-Cig smoke may lead to similar adverse outcomes.