Comparative cytotoxicity studies of smoke condensates from different types of cigarettes and tobaccos

The neutral red assay, a rapid and accurate method for estimating the cytotoxicity of chemicals, has been used to assess the cytotoxicity of cigarette smoke condensate (CSC), a complex chemical mixture containing over 3000 identified compounds. The first objective was to optimize the neutral red assay for evaluation of CSCs. This study also assessed and compared the cytotoxicity of smoke condensates from three reference cigarettes which differ in 'tar' content; cigarettes of different tobacco type composition; an ultra-low tar cigarette (R1); and an RJR test cigarette which heats but does not burn tobacco. Finally, this study investigated the cytotoxicity of a specific CSC component, nicotine, and its metabolite, cotinine. Exposure times of 24 hours or longer using CHO cells provided optimal conditions for evaluation of CSC cytotoxicity. The cytotoxicity of CSCs from reference cigarettes was similar. CSC from cigarettes comprised of flue-cured tobacco exhibited greater cytotoxicity than CSC from cigarettes comprised of burley tobacco. CSC from the R1 cigarette exhibited similar cytotoxicity compared with 1R4F CSC. The CSC from a cigarette that heated but did not burn tobacco (RJR test cigarette) demonstrated no cytotoxicity in CHO cells. Finally, nicotine and cotinine were not cytotoxic to CHO cells. The neutral red assay has been proved useful for quantifying differences in cytotoxicity of smoke condensates from cigarettes which vary in 'tar' yield and for assessing specific smoke constituents.