Effects of E-Cigarette Flavoring on Chondrocyte Viability and Arachidonic Acid Metabolism

The rise of electronic-cigarettes or “vaping” in the United States has introduced uniquely interesting questions as to their effects on overall pulmonary health. Specifically, more research is currently needed to understand how the individual ingredients of electronic cigarettes affect individual components of the pulmonary system, such as lung cartilage (1,2). Electronic-cigarette liquid flavoring additives (ELFAs) provide distinct tastes to inhalants which are an increasingly popular component added to electronic-cigarette cartridges (ECCs); however, the ingredients of these additives are not well disclosed and their effect on chondrocytes needs to be further reported (2). The purpose of this study was to determine if commonly used ELFAs such as cinnamon (CFAs), menthol (MFAs), tobacco (TFAs), strawberry kiwi (SKFAs), and flavorless (FAs) mixtures induce inflammation via the arachidonic acid pathway, increase incidences of cell death, and impair chondrocyte function. In an effort to understand ELFAs effects on chondrocyte cell viability and inflammatory pathways, ATDC5 murine chondrocytes were grown and treated with increasing concentrations (0-16%) of 5 ECCs flavorings (CFAs, MFAs, SKFAs, TFAs , & FAs) for 24 hours. After 24 hours, cells were assayed via flow cytometry, bicinchoninic acid assays (BCA), enzyme-linked immunosorbent assays (ELISA), and immunoblotting using standard methods to quantify cell death, total protein concentrations, prostaglandin E2 (PGE2) activity, and cyclo-oxygenase-2 (COX-2) levels, respectively. Results indicate that ELFA concentrations of 4-16% can lead to significant decrease in cell viability as seen from decreased overall protein concentrations and increased average percent cell death. The arachidonic acid cycle is also modulated as PGE2 levels significantly increase in 4% FA treated cells, with the exception of SKFAs. Our research provides further evidence that ELFAs present in ECCs have detrimental effects on chondrocytes, a component of pulmonary cartilage & supports other research in the field studying ELFAs and human health consequences.