Ferroptosis in e-cigarette aerosol-associated respiratory injury.

E-cigarette use has increased substantially, particularly among adolescents and young adults, yet its long-term respiratory effects remain incompletely understood. E-cigarette aerosol contains biologically active constituents, including nicotine, propylene glycol, vegetable glycerin, flavoring chemicals, aldehydes, metals, particles, and reactive oxygen species, which may disrupt respiratory epithelial homeostasis. This review synthesizes experimental, preclinical, and human-relevant evidence linking e-cigarette aerosol exposure to respiratory epithelial injury, with emphasis on ferroptosis-related mechanisms. Available evidence indicates that e-cigarette aerosol can impair epithelial barrier integrity, alter mucociliary defense, increase MUC5AC expression, induce oxidative stress, and promote inflammatory signaling. Emerging preclinical data suggest that electronic nicotine delivery system exposure may induce ferroptosis-associated lung injury through increased CD71/TFR1 and ACSL4 expression, reduced GPX4, altered lipid profiles, BODIPY-C11-positive lipid peroxidation, epithelial cell death, inflammation, mucus accumulation, emphysema-like pathology, and fibrosis. Mechanistically, e-cigarette aerosol may create a ferroptosis-permissive epithelial environment by promoting redox imbalance, GPX4/GSH/SLC7A11 antioxidant defense impairment, altered iron handling, ACSL4-mediated PUFA-phospholipid remodeling, NRF2/ARE stress responses, mitochondrial dysfunction, and lipid peroxide accumulation. Ferroptotic epithelial injury may further amplify airway inflammation and remodeling through DAMP release, macrophage recruitment, cytokine production, barrier disruption, mucus dysregulation, and extracellular matrix deposition. However, direct human evidence remains limited, and many mechanistic links are extrapolated from cigarette smoke, particulate matter, and broader lung injury models. Future studies should use standardized exposure systems, human-relevant airway and alveolar models, comprehensive ferroptosis markers, and ferroptosis-specific rescue experiments to determine whether ferroptosis is a driver, amplifier, or downstream marker of e-cigarette-associated respiratory injury.