Evaluation method for the cytotoxicity of cigarette smoke by in vitro whole smoke exposure

An in vitro whole smoke (WS) exposure method was established to evaluate the toxicological effects of fresh cigarette smoke using the VITROCELL® system associated with the neutral red uptake (NRU) cytotoxicity assay. The VITROCELL® system is a newly representative culture and exposure system for in vitro studies of gases or complex mixtures. The impacts of two factors on cytotoxicity measurements of cigarette smoke were investigated using this WS exposure system. The factors include synthetic air exposure and optimal time to perform the NRU assay after smoke exposure. Results showed that synthetic air exposure used in the system did not significantly alter cell survival; 24 h after smoke exposure appeared to be an optimal time-point to assess the cytotoxicity of cigarette smoke. A clear dose–response relationship between smoke exposure and cell viability was demonstrated using this system, and the evaluation method was sensitive to distinguish the differences in smoke-induced cytotoxic effects from different cigarettes. In addition, we tried converting the values of EC50 from WS exposure testing into the values in unit used in total particulate matter (TPM) testing for a purpose of comparison, and the data indicate that the cytotoxicity of smoke measured by WS exposure is greater than that measured by TPM exposure.