Nicotine inhalation via electronic cigarettes (e-cigs) is an emerging concern. However, little is known about the acute toxicity in the lungs following inhalation of nicotine-containing e-cig aerosols. We hypothesized that acute exposure to aerosolized nicotine causes lung toxicity by eliciting inflammatory and dysregulated repair responses. Adult C57BL/6J mice were exposed 2 h daily for 3 days to e-cig aerosols containing propylene glycol (PG) with or without nicotine. Acute exposure to nicotine-containing e-cig aerosols induced inflammatory cell influx (neutrophils and CD8a+ T-lymphocytes), and release of pro-inflammatory cytokines in bronchoalveolar lavage fluid in a sex-dependent manner. Inhalation of e-cig aerosol containing PG alone significantly augmented the lung levels of various homeostasis/repair mediators (PPARγ, ADRP, ACTA2, CTNNB1, LEF1, β-catenin, E-cadherin, and MMP2) in a sex-dependent manner when compared to air controls. These findings were accompanied by an increase in protein abundance and altered gene expression of lipogenic markers (PPARγ, ADRP) and myogenic markers (fibronectin, α-smooth muscle actin and β-catenin), suggesting a dysregulated repair response in mouse lungs. Furthermore, exposure to nicotine containing e-cig aerosols or PG alone differentially affected the release of pro-inflammatory cytokines in healthy and COPD human 3D EpiAirway tissues. Overall, acute exposure to nicotine containing e-cig aerosols was sufficient to elicit a pro-inflammatory response and altered mRNA and protein levels of myogenic, lipogenic, and extracellular matrix markers in mouse lung in a sex-dependent manner. Thus, acute exposure to inhaled nicotine via e-cig leads to dysregulated repair and inflammatory responses, which may lead to airway remodeling in the lungs.
Keywords: Nicotine; dysregulated repair; extracellular matrix remodeling; inflammation; propylene glycol.