Inflammatory Monocyte Responses and Endothelial Stress in Young Adult E-Cigarette Users 2253631

Abstract Introduction E-cigarettes (ECs) are increasingly used by youth and young adults, but their long-term health risks remain unclear due to limited clinical data. Since bi-directional communication between monocytes and endothelial cells is key in cardiovascular disease (CVD) development, with endothelial cells guiding monocyte activation and monocytes influencing atherosclerosis progression, we investigated how EC use impacts circulating monocytes and primary human endothelial cell function in the context of CVD risk. Methods Adults underwent venipuncture; EC users had ≥6 months of use, while healthy controls (HC) had none. PBMCs were isolated, monocyte subsets quantified by flow cytometry, and classical monocytes (CM) stimulated with vehicle or LPS (100 ng/mL) for 24 hours. To assess vascular effects, HUVECs were exposed to 3% EC liquid (ECL), cigarette smoke extract (CSE), PG vehicle, or media twice daily for 4 days, followed by analysis of adhesion molecules and ROS in supernatants. Results Compared to healthy controls (HC), e-cigarette users (EC) had fewer CD14+CD16⁻ classical monocytes (CM) and more CD14⁻CD16+ non-classical monocytes (NCM). CM from EC produced higher levels of TNFα, IL-6, and IL-1β in response to LPS stimulation than those from HC. HUVECs exposed to EC liquid (ECL) showed increased ROS production, elevated expression of endothelial damage marker CD62P, and upregulation of monocyte adhesion molecules VCAM-1, ICAM-1, and LFA-1. ECL exposure also increased expression of DLL1, a Notch2 ligand critical for CM-to-NCM differentiation. Conclusion Our findings show that e-cigarette (EC) users have fewer classical monocytes (CM) and more non-classical monocytes (NCM), a pattern linked to higher cardiovascular disease (CVD) risk. EC-derived CM released more inflammatory cytokines, and ECL exposure triggered endothelial activation and ROS production similar to cigarette smoke. These results suggest EC use may promote systemic inflammation and endothelial dysfunction, contributing to CVD risk. Funding Source n/a Topic Categories Innate Immune Responses and Host Defense: Cellular Mechanisms (INC)