Flavored and Nicotine-Containing E-Cigarettes Induce Impaired Angiogenesis and Diabetic Wound Healing via Increased Endothelial Oxidative Stress and Reduced NO Bioavailability

Abstract

The prevalent use of electronic cigarettes (e-cigarettes) has increased exponentially in recent years, especially in youth who are attracted to flavored e-cigarettes. Indeed, e-cigarette or vaping product use-associated lung injury (EVALI) cases started to emerge in the United States in August 2019, resulting in 2807 hospitalized cases and 68 deaths as of 18 February 2020. In the present study, we investigated, for the first time, whether flavored and nicotine containing e-cigarettes induce endothelial dysfunction to result in impaired angiogenesis and wound healing particularly under diabetic condition. Nicotine containing e-cigarettes with various contents of nicotine (0, 1.2%, 2.4%), and flavored e-cigarettes of classic tobacco, mint, menthol, and vanilla or fruit from BLU (nicotine 2.4%) or JUUL (nicotine 3%), were used to treat endothelial cells in vitro and streptozotocin-induced diabetic mice in vivo. Endothelial cell superoxide production, determined by dihydroethidium (DHE) fluorescent imaging and electron spin resonance (ESR), was markedly increased by exposure to e-cigarette extract (e-CSE) in a nicotine-content dependent manner, while nitric oxide (NO) bioavailability detected by DAF-FM fluorescent imaging was substantially decreased. All of the different flavored e-cigarettes examined also showed significant effects in increasing superoxide production while diminishing NO bioavailability. Endothelial cell apoptosis evaluated by caspase 3 activity was markedly increased by exposure to e-CSE prepared from flavored and nicotine containing e-cigarettes. Endothelial monolayer wound assays revealed that nicotine-containing and flavored e-cigarettes induced impaired angiogenic wound repair of endothelial cell monolayers. Furthermore, vascular endothelial growth factor (VEGF) stimulated wound healing in diabetic mice was impaired by exposure to e-CSEs prepared from nicotine-containing and flavored e-cigarettes. Taken together, our data demonstrate for the first time that flavored and nicotine-containing e-cigarettes induce endothelial dysfunction through excessive ROS production, resulting in decreased NO bioavailability, increased endothelial cell apoptosis, and impairment in angiogenesis and wound healing, especially under diabetic condition. These responses of endothelial dysfunction likely underlie harmful effects of e-cigarettes in endothelial-rich organs, such as heart and lungs. These data also indicate that rigorous regulation on e-cigarette use should be enforced in diabetic and/or surgical patients to avoid severe consequences from impaired angiogenesis/wound healing.

Varied effects of tobacco smoke and e-cigarette vapor suggest that nicotine does not affect endothelium-dependent relaxation and nitric oxide signaling

“…Besides its role in vasodilation, the endothelium inhibits platelet adhesion and aggregation, regulates inflammatory processes, is essential for capillary integrity, and promotes angiogenesis through cell migration. There is general agreement that the inhalation of tobacco smoke negatively affects these biological processes 3 , but the role of nicotine is controversial concerning angiogenesis/cell migration 61 – 63 , endothelial barrier function 64 , 65 , and platelet activation 66 – 68 . There is conclusive evidence that inhalation of e-cigarette vapor increases markers of oxidative stress and inflammation 19 , 20 , but e-cigarettes induce substantially less pronounced biological responses than tobacco smoke 69 , and a recent cross-sectional study found no differences in the levels of inflammatory markers between e-cigarette users and non-users 26 .…”

Vaping Versus Smoking: Are Electronic-Cigarettes the Savior?

“…8 Further in vitro studies revealed e-cigarette liquid–induced oxidative stress and DNA damage 7 and impaired angiogenesis. 9…”

“…8 Further in vitro studies revealed e-cigarette liquid-induced oxidative stress and DNA damage 7 and impaired angiogenesis. 9 Aside from in vitro cell culture studies, also in vivo animal studies were conducted. In an acute setting, Rao et al 10 exposed rats to aerosol of 3 different e-cigarette types (as well as different flavors and with or without nicotine), and the authors concluded that the range of tested e-cigarette aerosols impaired flow-mediated dilatation (FMD) comparable to conventional cigarettes after single use.…”

Tobacco and Menthol flavored electronic cigarettes induced inflammation and dysregulated repair in lung fibroblast and epithelium

“…We have shown that nicotine treatment could inhibit the TGFβ-induced broblast differentiation and wound recovery [18]. Another report described that mint, menthol, vanilla, and fruit-avored e-cig inhibited wound healing mediated by endothelium [27]. Exposure to e-cig aerosol also slowed the wound healing process on dermal cells, which showed even worse wound recovery than exposure to conventional cigarette smoke [28].…”