Abstract
Smoking has been recognized as a risk factor of cancer, heart disease, stroke, diabetes, and lung diseases such as chronic obstructive pulmonary disease, and nicotine appears to be the responsible component of tobacco smoke that affects lung development. While nicotine-free electronic cigarettes (e-cigarettes) are often promoted as a safer alternative to traditional smoking, recent evidence suggests that they might pose significant health risks. This study investigates the effects of nicotine-free e-cigarette vapor (ECV) on lung tissue and endothelial function. A mouse model of ECV-induced lung injury and human pulmonary microvascular endothelial cells (HPMVECs) were utilized to evaluate the impact of ECV exposure on mitochondrial function, endothelial cell viability, and glycocalyx shedding. ECV exposure significantly damages lung tissue, characterized by alveolar enlargement, inflammation, and vascular remodeling, indicative of emphysematous changes. In vitro, HPMVECs exposed to nicotine-free e-cigarette extract (ECE) demonstrated dose-dependent increases in mitochondrial reactive oxygen species (ROS), mitochondrial membrane depolarization, mPTP opening, and reduced ATP production, leading to enhanced endothelial permeability and glycocalyx degradation. The inhibition of mPTP opening with Cyclosporin A (CsA) was found to mitigate the mitochondrial dysfunction and glycocalyx damage induced by ECE, indicating a protective role of mPTP inhibition in preserving endothelial integrity. The AKT/GSK3β signaling pathway was identified as a key regulator of these processes, with ECE exposure downregulating p-AKT and p-GSK3β, thereby promoting mPTP opening. Activation of AKT signaling partially reversed these effects, highlighting the potential of targeting the AKT/GSK3β-mPTP axis to mitigate the adverse effects of e-cigarette exposure on lung and endothelial function. These findings underscore the potential risks associated with nicotine-free e-cigarettes and suggest novel therapeutic targets for preventing lung injury progression.