Abstract Background Flavored electronic nicotine delivery systems (ENDS) are increasingly consumed as a safer alternative to combustible cigarettes. While ENDS are maybe less harmful than cigarettes, long-term exposure to tobacco-flavored nicotine is not known. Our acute exposure studies with flavored ENDS have shown immunosuppression in mice, whereas tobacco-flavored subchronic ENDS have altered extracellular matrix (ECM) homeostasis. ENDS exposure-induced early transition from immune suppression to ECM remodeling prior to overt disease phenotype is not well understood. Rationale Chronic lung diseases such as chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis arise when immune resolution fails and ECM homeostasis becomes dysregulated. Identifying early remodeling signatures is necessary to determine how ENDS exposures may predispose lungs to chronic disease. Hypothesis Sub-chronic ENDS exposure suppresses immune resolution pathways and initiates early ECM remodeling, with nicotine augmenting remodeling through cholinergic signaling effects. Methods Male and female C57BL/6J mice were exposed to tobacco-flavored ENDS aerosols ±6 mg/mL nicotine (51 mL/puff, 2 puffs/min, 2 hr/day) for a month on consecutive days. Lung mechanics (FlexiVent), flow cytometry and cytokine profiling, gene expression and lung tissue proteome profiling were conducted to assess the elicited immune response in bronchoalveolar lavage (BALF) and lung tissue, along with lung function assessment. Results Both 0 mg and 6 mg nicotine-containing tobacco flavored-ENDS exposures downregulated immune-recruitment and resolution markers (IL-1β, CCL3, CCR1/CCR2, PIR-A/B, LYN) and reduced fibroblast-activation signals (OSM, TNFRSF1β). BALF from both groups showed increased epithelial stress and ECM-remodeling proteins (complement D, CRP, CD26, acidic FGF, Gas6, pro-MMP9, PAI-1). Lung tissue MMP-9, MPO, CCL6, and eotaxin were attenuated, indicating protease-antiprotease imbalance and impaired clearance. Nicotine-containing ENDS aerosols amplified pro-MMP9 and PAI-1 elevations and demonstrated greater increases in static compliance and reductions in elastance, suggesting nicotine enhances remodeling susceptibility, consistent with cholinergic suppression of immune resolution. Conclusion Sub-chronic ENDS exposure induces a pre-pathologic lung remodeling state characterized by immune resolution failure, protease-antiprotease imbalance, and early mechanical vulnerability. Nicotine further augments these remodeling trajectories, suggesting that repeated ENDS use may lower the threshold for COPD- and fibrosis-like disease progression, even in the absence of overt inflammation. The study was supported by the National Institutes of Health, NIH R00ES033835 This abstract is funded by: NIH R00ES033835
Muthumalage et al. (Fri,) studied this question.