Characterization of the CYP isozyme profile induced by cyclohexanol.

Abstract

In a previous report we described the ability of cyclohexanol to induce CYP activity. In order to characterize this induction we tested the capacity of liver S9 from rats orally treated with cyclohexanol for 5 days, to activate several carcinogenic nitrosamines into mutagens in the Salmonella typhimurium TA100 test system. Additionally, Western blot analysis of hepatic microsomes from the same treated animals were analysed with specific antibodies against P450 protein families 1A1/A2, 2B1/B2 and 2E1. Cyclohexanol-S9 mixture was more efficient in activating the following nitrosamines: N-nitrosodimethylamine (NDMA), N-nitrosodipropylamine (NDPA), N-nitrosomethylpropylamine (NMPA), N-nitrosodibutylamine (NDBA), and N-nitrosopyrrolidine (NPYR) into bacterial mutagens than S9 from non-treated animals. The mutagenicity of N-nitrosodiethylamine (NDEA) was not modified in the presence of S9 from cyclohexanol-treated animals. Since the main metabolic pathway leading to the production of mutagenic intermediates of NDMA and NPYR is catalysed by isozyme CYP2E1 and that of NDPA, NMPA and NDBA by CYP2B1/B2, mutagenicity experiments predicted that cyclohexanol induces these two P450 isozyme families. Western blot analysis confirmed the results of the mutagenicity assay, showing an increase in the intensity of CYP2E1 and CYP2B1/B2 protein bands in hepatic microsomes from cyclohexanol treated rats in comparison with non-treated controls. Bacterial mutagenicity tests with specific pro-mutagens were good predictors of the P450 induction properties of cyclohexanol.