Effects of IQOS on macrophage viability and function

Heat not burn (HNB) devices are being sold as a less harmful alternative to traditional cigarettes. The newest HNB device from Philip Morris, IQOS, produces a smoke free tobacco vapour through which nicotine can be delivered. IQOS heats the glycerine impregnated tobacco stick to form a vapour instead of smoke. The device literature implies the sub-combustion temperature reduces of levels of harmful components. There is an urgent need to investigate potential adverse effects. Objective: To investigate the effects of IQOS vapour extract (IVE) and cigarette smoke extract (CSE) on THP-1 macrophage viability and function. Methods: Macrophages were differentiated from THP-1 monocytes by PMA challenge for 24 hours then rested for 3 days. CSE and IVE were produced by bubbling 3 Kentucky research cigarettes / 3 tobacco sticks through 10 ml media. Viability was assessed by Cell titre aqueous assay. Apoptosis and necrosis were assessed by flow cytometry using Annexin V / PI staining. Phagocytosis was assessed by Phrodo assay. Results: Both CSE and IVE produced a dose dependent reduction in viability after 24 hours, with significant loss of viability after 3% CSE and IVE challenge. Apoptosis was significantly increased after 6 hours with 3% and 5% CSE/IVE. There was a trend towards increased necrosis however this was not significant currently. There was no significant difference in apoptosis between CSE and IVE. Phagocytosis was significantly inhibited by CSE and IVE at 2% however CSE showed greater inhibition than IVE at all concentrations. Conclusion: Exposure to CSE and IVE produced similar toxic and inhibitory effects on THP-1 macrophages. As such these preliminary studies highlight potential toxicity concerns regarding use of IQOS devices.