Inhibition of rat hepatic CYP2E1 by quinacrine: molecular modeling investigation and effects on 4-(methyl nitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced mutagenicity.

Increased activity of CYP2E1 has been associated with increased risk of chemically-mediated cancers, through enhanced activation of a variety of procarcinogens. In this context, inhibition of CYP2E1 is potentially of significance in xenobiotic toxicity. The aim of the present study was to test the hypothesis that quinacrine inhibits hepatic CYP2E1. For this purpose, disulfiram (75 mg/kg i.p) as an inhibitor and isoniazid (100 mg/kg i.p) as an inducer of CYP2E1, as well as quinacrine (50 mg/kg i.p) were administered to Wistar rats and the hepatic activity of CYP2E1 was measured. The expression of CYP2E1 was further assessed by Western blot analysis. As expected, disulfiram inhibited, while isoniazid induced the activity and expression of the enzyme. Interestingly, treatment with quinacrine resulted in a significant decrease of CYP2E1 activity and expression. To investigate any similarities in the inhibition of CYP2E1 by quinacrine and disulfiram, molecular modeling techniques were adopted and revealed that quinacrine molecule anchors inside the same binding pocket of the protein where disulfiram is also attached. Finally, as assessed by the sister chromatid exchanges (SCE) assay, quinacrine was demonstrated to reduce the mutagenic effects of the tobacco-specific N-nitrosamine 4-(methyl nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which is known to be converted to active mutagen in the liver principally through CYP2E1. We suggest that these antimutagenic effects of quinacrine could be possibly attributed, at least in part, to its ability to block the bioactivation of NNK, mainly by the inhibition of CYP2E1. Our results, even preliminary, indicate that quinacrine as an inhibitor of CYP2E1 might be protective against chemically-induced toxicities such as NNK-induced mutagenicity.