Use of ex vivo precision-cut lung slices as a screening tool for potential respiratory toxicity of e-liquids
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 10 µM phortress and 13 µM 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 adenylate 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.