In Vivo Oxidative Damage in Rats Is Associated with Barbiturate Response but Not Other Cytochrome P450 Inducers

Abstract

Previously published studies have shown that cytochrome P450 (P450) enzyme systems can produce reactive oxygen species and suggest roles of P450s in oxidative stress. However, most of the studies have been done in vitro, and the potential link between P450 induction and in vivo oxidative damage has not been rigorously explored with validated biomarkers. Male Sprague-Dawley rats were pretreated with typical P450 inducers (␤-naphthoflavone, phenobarbital (PB), Aroclor 1254, isoniazid, pregnenolone 16␣-carbonitrile, and clofibrate) or the general P450 inhibitor 1-aminobenztriazole; induction of P4501A, -2B, -2E, -3A, and -4A subfamily enzymes was confirmed by immunoblotting and the suppression of P450 by 1-aminobenztriazole using spectral analysis. PB and Aroclor 1254 significantly enhanced malondialdehyde and H 2 O 2 generation and NADPH oxidation in vitro and significantly enhanced formation in vivo, in both liver and plasma. Some of the other treatments changed in vitro parameters but none did in vivo. The PB-mediated increases in liver and plasma F 2 -isoprostanes could be ablated by 1-aminobenztriazole, implicating the PB-induced P450(s) in the F 2 -isoprostane elevation. The markers of in vivo oxidative stress were influenced mainly by PB and Aroclor 1254, indicative of an oxidative damage response only to barbiturate-type induction and probably related to 2B subfamily enzymes. These studies define the contribution of P450s to oxidative stress in vivo, in that the phenomenon is relatively restricted and most P450s do not contribute substantially.

Mode of action and human relevance analysis for nuclear receptor-mediated liver toxicity: A case study with phenobarbital as a model constitutive androstane receptor (CAR) activator

“…Some studies have reported that prolonged administration of PB may be associated with effects on oxidative stress. For example, CYP2B enzyme induction in rodent liver by PB can result in the enhanced production of reactive oxygen species (Dostalek et al, 2007; Imaoka et al, 2004) and the over expression of rat CYP2B1 in mouse liver was associated with enhanced spontaneous tumor formation (Lehman-McKeeman et al, 1999). However, an evaluation of the available literature did not reveal any clear role for oxidative stress in the MOA for PB-induced rodent liver tumor formation.…”

Induction of a detoxification gene in Drosophila melanogaster requires an interaction between tissue specific enhancers and a novel cis-regulatory element

“…However, insects are exposed to a variety of xenobiotics and require the presence of a number of different detoxification enzymes to combat these challenges. To constitutively express many different detoxification genes at levels high enough to detoxify compounds that the organism seldom encounters would incur an unnecessarily high metabolic cost and fitness costs for the organism (Zeng et al, 2009), including increased levels of oxidative stress (Dostalek et al, 2007(Dostalek et al, , 2008.…”

Human Cytochrome P450 2E1 Mutations That Alter Mitochondrial Targeting Efficiency and Susceptibility to Ethanol-induced Toxicity in Cellular Models

“…Further, Mito-CP and DAS both restored the GSH level to the untreated control cell level, showing a marked protection against alcohol-induced oxidative stress. Lipid peroxidation is an immediate consequence of oxidative stress (76,77), and the levels of F2-isoprostanes are probably the most reliable measure of oxidative stress (76 -78). Consistent with this result, the cellular isoprostane levels were found to be markedly increased in W23/30R cells following treatment with ethanol (Fig.…”