The effects of flavored vaped e-liquids on cultured human macrophages derived from the central and peripheral nervous systems

Abstract

The use of the electronic cigarette (e-cig) to consume an aerosol is referred to as "vaping" and has become the most popular method for nicotine consumption amongst youth and many adults worldwide. This popularity is at least partially attributable to the availability of 1000s of distinctly flavored e-liquids. At present, a large number of studies have evaluated the potential negative effects of e-cig use in relation to pulmonary disease. These studies have demonstrated that vaping can lead to immune activation and cell death but typically include only epithelial cell line studies. At present, significantly less is known about the effects of vaped e-liquids on the central nervous system (CNS) and peripheral nervous system (PNS). To investigate this gap, we utilized human macrophage cell lines KG-1 (PNS-resident macrophages) and DBTRG-05MG (CNS-resident macrophages) and examined their exposure to vaped e-liquids. To carry out these investigations, measurements of: cell viability, expression of inflammatory cytokines, phagocytosis and reactive oxygen species (ROS) were employed. Our findings illustrate that when exposed to e-liquid, and especially flavored e-liquids, both peripheral and central macrophage cell lines decrease in cell viability, showcase an upregulated level of expression of pro-inflammatory cytokines, a diminished level of phagocytic activity and an overall increased level of reactive oxidative species. Thus, our study further indicates that the use of the e-cig can cause phenotype and immune disruptions within both the CNS and PNS.