Early specific free radical-related cytotoxicity of gas phase cigarette smoke and its paradoxical temporary inhibition by tar.An electron paramagnetic resonance study with the spin trap DEPMPO.

International audienceElectron paramagnetic resonance (EPR) spin trapping studies demonstrated aqueous tar particulate matter (TPM) and gas phase cigarette smoke (GPCS) to behave as different sources of free radicals in cigarette smoke (CS) but their cytotoxic implications have been only assessed in CS due to its relevance to the natural smoking process. Using a sensitive spin trapping detection with 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), this study compared the respective roles of CS- and GPCS-derived free radicals on smoke-induced cytotoxicity and lipid peroxidation of filtered and unfiltered, machine-smoked experimental and reference cigarettes yielding a wide range of TPM yields. In buffer bubbled with CS the DEPMPO/superoxide spin adduct was the major detected nitroxide. Use of appropriate control experiments with nitric oxide radical (NO•) or carbonyl sulfide, and a computer analysis of spin adduct diastereoisomery showed that the hydroxyl radical (HO•) adduct of DEPMPO seen in GPCS-bubbled was rather related to metal-catalyzed nucleophilic synthesis than to direct HO• trapping. Unexpectedly a protective effect of TPM on murine 3T3 fibroblasts was observed in early (