The Effect of Isoniazid on Cyp2e1- And Cyp4a-Mediated Hydroxylation of Arachidonic Acid in the Rat Liver and Kidney

Abstract

ABSTRACT:Cytochrome P450 (P450) bioactivation of arachidonic acid to hydroxyeicosatetraenoic acids (HETEs) has been reported to be isoform-and tissue-specific. To determine whether altered P450 expression affects the production of these metabolites, the formation of HETEs after isoniazid-mediated CYP2E1 induction was evaluated in the rat liver and kidney. Male Sprague-Dawley rats received isoniazid (200 mg/kg) or saline intraperitoneally once daily for 5 days. Chlorzoxazone, lauric acid, and arachidonic acid hydroxylation was measured in liver and kidney microsomes with and without preincubation with the specific CYP2E1 inhibitor, trans-1,2-dichloroethylene (DCE). P450 isoform content and tissue HETE metabolite concentrations were also determined. Isoniazid increased CYP2E1 protein, and the 6-hydroxychlorzoxazone formation rate was increased by 2.7 ؎ 0.3-and 2.2 ؎ 0.5-fold in liver and kidney, respectively. Formation of 19-HETE and 11-hydroxylauric acid was induced 2.3 ؎ 0.6-fold and 2.2 ؎ 0.4-fold in the liver, respectively, with no difference in the kidney. All of the induced activities were attenuated by DCE. An unanticipated decrease in liver CYP4A expression and in vitro 20-HETE formation rate was observed after isoniazid administration. Isoniazid decreased liver and kidney 20-HETE content to 34 ؎ 10% and 15.6 ؎ 5.3% of control, respectively, without significantly altering tissue 19-HETE concentration. Based on these findings, we conclude that under induced conditions, CYP2E1 is a primary enzyme involved in liver, but not kidney, formation of 19-HETE. In addition, formation of both CYP4A and 20-HETE is reduced in the liver by isoniazid. It was also demonstrated that tissue concentrations parallel in vitro inhibited formation rates for 20-HETE, but not the induced 19-HETE formation in the liver.

Chronic Doxorubicin Cardiotoxicity Modulates Cardiac Cytochrome P450-Mediated Arachidonic Acid Metabolism in Rats

“…Similar to our finding, several studies have reported that the increase in CYP2E1 expression did not correlate with the rate of 19-HETE formation (Amet et al, 1997;Poloyac et al, 2004). Of importance, overproduction of 20-HETE has been extensively implicated in development and/or progression of several cardiovascular diseases (Certíková Chábová et al, 2010;Bao et al, 2011).…”

Characterization of Arachidonic Acid Metabolism by Rat Cytochrome P450 Enzymes: The Involvement of CYP1As

“…Being an important P450-metabolizing enzyme in mammals (Martignoni et al, 2006), CYP2E1 has been considered a major v-1→4 AA hydroxylase. However, experimentally, CYP2E1 contribution to the constitutive formation of v-1→4 HETEs has been reported to be minor (Laethem et al, 1993;Capdevila et al, 2000;Poloyac et al, 2004). This contradiction is explainable by our results that CYP2E1 has one of the lowest AA-metabolizing activities among the tested P450 enzymes.…”

Determination of the Dominant Arachidonic Acid Cytochrome P450 Monooxygenases in Rat Heart, Lung, Kidney, and Liver: Protein Expression and Metabolite Kinetics

“…CYP2A isoforms were also observed to have a very low epoxygenase activity (19). CYP2E1 has a substantial contribution to ω-1-hydroxylation activity in the liver but not in the kidney of rats and rabbits; however, this was reported only after its induction and not in the constitutive state (32,34,35). Despite the documented physiological and pathophysiological role of P450-derived AA metabolites, the kinetic properties of the P450 epoxygenases and hydroxylases activities have not been investigated at the organ level.…”