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Propiconazole increases reactive oxygen species levels in mouse hepatic cells in culture and in mouse liver by a cytochrome P450 enzyme mediated process
Citation:
NESNOW, S., R. Grindstaff, G. Lambert, W. T. Padgett, M. Bruno, Y. GE, P. Chen, AND L. A. MURPHY. Propiconazole increases reactive oxygen species levels in mouse hepatic cells in culture and in mouse liver by a cytochrome P450 enzyme mediated process. CHEMICO-BIOLOGICAL INTERACTIONS. Elsevier Science Ltd, New York, NY, 194(1):79-89, (2011).
Impact/Purpose:
Here we sought to identify the source of the ROS induced by propiconazole using both AML 12 immortalized mouse hepatocytes in culture and liver tissues from mice. We also sought to further characterize the nature and effects of ROS formation induced by propiconazole treatment in mouse liver.
Description:
Propiconazole induces hepatocarcinomas and hepatoadenomas in mice and is a rat liver tumor promoter. Transcriptional, proteomic, metabolomic and biochemical studies of hepatic tissues from mice treated with propiconazole under the conditions of the chronic bioassay indicate that propiconazole induced oxidative stress. Here we sought to identify the source ofthe ROS induced by propiconazole using both AML 12 immortalized mouse hepatocytes in culture and liver tissues from mice. We also sought to further characterize the nature and effects of ROS formation induced by propiconazole treatment in mouse liver. AML 12 cells treated with propiconazole induced ROS whose levels were ameliorated by N-acetylcysteine. Propiconazole induced the levels of Cyp2b and Cyp3a proteins in both AML12 cells and in mouse liver and increased the levels of thiobarbituric acid reactive substances (TBARS) in AML12 cells. The TBARS levels were decreased by diphenylene iodonium chloride (DPIC), a cytochrome P450 reductase inhibitor. Salicylic acid hydroxylation was used as probe for reactive oxygen species (ROS) formation using microsomes from mice treated with propiconazole and this showed that levels of 2,3-dihydroxybenzoic acid (an ROS derived metabolite) were decreased by ketoconazole, melatonin and DPIC. In vivo, propiconazole increased malondialdehyde levels, GSTa protein levels and Akr1b7 message, and slightly decreased catalase and superoxide dismutase activities and Cat message. Previous studies have shown that Cyp2b and Cyp3a proteins undergo uncoupling of their CYP catalytic cycle releasing ROS. Based on these observations we conclude that propiconazole induces ROS in mouse liver by increasing CYP protein levels which results in increased ROS levels. Our data also suggest that propiconazole induces the hydroxyl radical as a major ROS form.
