Use of Ex Vivo Precision-Cut Lung SLices as a Screening Tool for Potential Respiratory Toxicity of E-Liquids

October 17, 2019

The Family Smoking Prevention and Tobacco Control Act gave the FDA regulatory authority over next generation tobacco products (NGTP) such as E-vapor products. E-vapor product liquids contain a variety of ingredient combinations that should be assessed for human risk. One human lung-relevant testing platform with reasonable throughput, is human precision-cut lung slices (HuPCLS). HuPCLS are arguably the most complex non-animal model of the lung, retaining native architecture and immune-competent cells over multi-week culture periods. HuPCLS were exposed to three concentrations (0.1%, 0.5%, and 1.2%) of propylene glycol (PG ; an E-vapor product constituent) continuously for 16 days. Exposure-effects were evaluated biochemically (WST-8 assay) and histologically viability assessment of H&E stained slides). Positive control treatments consisted of 10μM Phortress and 13μM bleomycin. HuPCLS were fed every day with fresh medium ± treatment and harvested at days 4, 8, and 16. Untreated control UC) HuPCLS viability was confirmed using protein and a denylate kinase assays. Over 16 days in culture, UC lost 30% viability while WST-8 results indicated no loss over 16 days in culture. Phortress caused severe damage by day 4 and bleomycin by day 8 (histologically & WST-8 viability). Prolonged 1.2% PG exposure diminished WST-8 viability by ~30% at day 16 which agreed with histological results. High osmolality is the suspected mechanism of toxicity. There was no effect histologically or via WST-8 viability for prolonged exposure to 0.1% and 0.5% PG. In summary, PG, a common E-vapor product ingredient, at 1.2% had adverse effects in a human pulmonary model in an exaggerated exposure regimen(prolonged exposures with changes in osmolarity). The HuPCLS platform has huge potential to serve as a screening tool for e-liquid(and other materials of concern) by elucidating potentially relevant, long-term events following NGTP ingredient exposure.