In vitro micronucleus assay for cigarette smoke using a whole smoke exposure system: A comparison of smoking regimens

Previous studies on the biological assessment of cigarette smoke (CS) mainly focused on the total particulate matter (TPM) collected using a Cambridge filter or gas vapor phase (GVP) bubbled through phosphate-buffered saline (PBS). To study the effects of native CS in vitro, direct exposure methods have been developed. Meanwhile, in vitro micronucleus (MN) assays have been reported to evaluate the mutagenicity of CS.The objective of this research is to investigate the MN-inducing activity of whole smoke (WS) and GVP using a whole smoke exposure system, CULTEX®, which allows direct exposure of cultured cells to native CS at the air/liquid interface (ALI). CS was generated according to the International Organization for Standardization (ISO; 35 ml, 2 s, once per 60 s) or the Health Canada Intensive (HCI; 55 ml, 2 s, once per 30 s, with complete ventilation block) regimens and Chinese hamster lung (CHL/IU) cells were then exposed to this smoke. Dosages were adjusted according to the amount of smoke entering the actual exposure position. Under both smoking regimens, WS and GVP from 2R4F reference cigarettes induced MN responses. The concept of the dosage and similar dose–response relationships between theoretical and monitored dosage values under the two regimens enabled us to compare the MN-inducing activities of cigarettes in the direct exposure assay, even in the case of various experimental settings or different TPM amounts. MN-inducing activities of 2R4F under the ISO regimen seemed to be higher than those under HCI estimated by the TPM equivalent calculated values.