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OBJECTIVE Ethanol-inducible cytochrome P450 2E1 (CYP2E1) has been shown to be involved in the metabolism of ethanol in both brain and liver.The enhanced levels of CYP2E1 were found in alcoholicsbrain, and oxidative stress is implicated in ethanol-induced brain damage.The objective of the study was to determine the contribution of CYP2E1-mediated reactive oxygen species (ROS) generation to toxic effects of chronic ethanol treatment in rat brain regions.METHODS Adult male Wistar rats (about 250 g) were treated intragastrically with ethanol at 3.0 g· kg-1 in sucrose solution (1% , W/V) for 30 d or received sucrose solution alone.Brain damage was assayed by measurement of lactate dehydrogenase (LDH) and histopathological examination.The CYP2E1 protein and mRNA levels were assessed by immunoblotting, quantitative quantum dot immunohistochemistry, and real-time RT-PCR.CYP2E1 activities probed by chlorzoxazone hydroxylation (CZXH) were determined by LC-MS.ROS levels in brain regions were determined by laser confocal scanning microscope.RESULTS Chronic ethanol treatment induced the damage to neural cells in hippocampus, cerebellum and brain stem, indicated by both lactate dehydrogenase activity and histopathological analysis.Compared with control rats, CYP2E1 proteins were increased in hippocampus (1.56-fold, P < 0.05), cerebellum (1.23-fold, P < 0.01) and brain stem (1.43-fold, P < 0.05) in ethanol-treated rats.CYP2E1 mRNA levels were significandy increased by chronic ethanol treatment in hippocampus and in cerebellum.The increase in CYP2E1 proteins was found to be accompanying an increase in CYP2E1 catalytic activitiesin hippocampus, cerebellum and brain stem after chronic ethanol treatment.CYP2E1 activities were positively correlated with LDH levels in hippocampus (r =0.746, P =0.005), cerebellum (r =0.837, P =0.010) and brain stem (r =0.861, P =0.006).ROS levels induced by ethanol were associated with the increased CYP2E1 levels in specific regions assayed by immunohistochemical analysis.CONCLUSION Chronic ethanol treatment can induce CYP2E1 proteins at transcriptional and/or post-transcriptional levels in various brain regions.Ethanol-mediated induction of CYP2E1 involves in the damage to neuronal cells after chronic ethanol treatment via ROS generation.The different sensitivity of brain regions to toxic actions of ethanol may attribute to regional and cellular-specific induction of CYP2E1 by ethanol.The results further support that the alteration of brain CYP2E1 activity may result in the modification of the therapeutic efficacy and/or toxicity of centrally acting drugs and activated toxins.