Inhalation of Electrophilic and Redox Active Electronic Cigarette Aerosol Increases Oxidative Potential in the Lung in an Acute Manner.

Abstract

Electronic cigarettes (EC) are linked to pulmonary health effects involving oxidative stress, but underlying mechanisms are poorly understood. Induction of oxidative stress is thought to be mediated by imbalanced reactive oxygen species (ROS) production is implicated in the onset of inflammation in a multitude of pathogenic and diseases conditions. EC aerosol components deposited in the lungs can induce ROS generation and form electrophilic protein adducts, thereby promoting prooxidative redox environments in the airways. A variety of methods to assess oxidative stress exist but many are non-specific and have unclear molecular and/or biological interpretations confounding the understanding of mechanisms underlying EC toxicity. Here, we developed a method to detect prooxidant shifts in the redox environment of murine bronchoalveolar lavage fluid (BALF) following acute exposure to EC aerosol, using the terephthalate (TA) probe. Using acellular assays, we determined that the EC aerosol employed in this work has intrinsic electrophilic potential and capacity to generate •OH acellularly, suggesting that EC aerosols can promote prooxidative conditions by themselves. We then mathematically derived a parameter called the Iron (Fe)-Induced Oxidative Potential in BALF (FIBOP) that was calculated by measuring •OH generation rates in mixtures of 1-10 μM Fe(II) and 200 μM ascorbate in BALF. •OH generation rates normalized by total protein plotted as a function of [Fe(II)] allowed us to quantify FIBOP, 24 hours after acute exposure to EC. C57BL/6J mice exposed to EC aerosol for a total of 30 minutes in one day exhibited 60% enhancement of FIBOP compared to control mice exposed to filtered air (FA). This was accompanied by significantly increased levels of the free oxidized lipids, total HETEs (5-,12-,15-HETEs) (p<0.05) and total HODEs (9-,13-HODEs) (p<0.05) in BALF. Our results indicate that our method is sensitive to detecting prooxidant shifts in BALF induced by EC aerosol exposure in an acute manner.