AIMS: Electronic(e)-cigarettes are proposed to be a safer alternative to tobacco-cigarettes. Hence, we evaluated if e-cigarette-vapors (eCV) impair cellular proteostasis similar to cigarette-smoke (CS)-exposure.

RESULTS: First, we evaluated the impact of eCV-exposure (2.5mg or 7.5mg) on Beas2b cells that showed significant increase in accumulation of total polyubiquitinated-proteins (ub, insoluble-fractions) with time-dependent decrease in proteasomal-activities from 1 r (p<0.05), 3hr (p<0.001) to 6hrs (p<0.001) of eCV-exposure as compared to room-air control. We verified that even minimal eCV-exposure (1hr) induces valosin containing protein (VCP; p<0.001), sequestosome-1/p62 (aberrant-autophagy marker; p<0.05) and aggresome-formation (total poly-ub-accumulation; p<0.001) using immunoblotting (IB), fluorescence microscopy and immunoprecipitation (IP). The inhibition of protein synthesis by 6 hr cyclohexamide (50µg/ml) treatment significantly (p<0.01) alleviates eCV-induced (1 hr) aggresome-bodies. We also observed that eCV (1hr) induced protein-aggregation can activate oxidative stress, apoptosis (caspase-3/7) and senescence (p<0.01) as compared to room-air controls. We verified by using an autophagy inducer carbamazepine (20 µM, 6 hrs) or cysteamine (250μM; 6 hrs, anti-oxidant), that eCV induced changes in oxidative stress, poly-ub-accumulation, proteasomal activity, autophagy, apoptosis and/or senescence could be controlled by autophagy induction. We further confirmed the role of acute eCV-exposure on autophagy impairment in murine lungs (C57BL/6 and CD1) by IB (Ub, p62, VCP) and IP (VCP, p62), similar to in-vitro experiments.

INNOVATION: In this study, we report for the first time that eCV-exposure induces proteostasis/autophagy impairment leading to oxidative stress, apoptosis and senescence that can be ameliorated by an autophagy inducer.

CONCLUSION: eCV-induced autophagy-impairment and aggresome-formation suggests its potential role in COPD-emphysema pathogenesis.