Aristolochic acid (AA), a naturally occurring nephrotoxin and carcinogen, has been associated with the development of urothelial cancer in humans. Understanding which human enzymes are involved in AA activation and/or detoxication is important in the assessment of an individual's susceptibility to this plant carcinogen. Using the (32)P postlabeling assay, we examined the ability of microsomal samples from 8 human livers and from 1 human kidney to activate AAI, the major component of the plant extract AA, to metabolites forming adducts in DNA. Microsomes of both organs generated DNA adduct patterns reproducing those found in renal tissues from humans exposed to AA. 7-(deoxyadenosin-N(6)-yl)aristolactam I, 7-(deoxyguanosin-N(2)-yl)aristolactam I and 7-(deoxyadenosin-N(6)-yl)aristolactam II were identified as AA-DNA adducts formed from AAI by all human hepatic and renal microsomes. To define the role of human microsomal enzymes in the activation of AAI, we investigated the modulation of AAI-DNA adduct formation by cofactors and selective inhibitors of microsomal reductases, cytochrome P450 (CYP) enzymes, NADPH:CYP reductase and NADH:cytochrome b(5) reductase. We also determined whether the activities of CYP and NADPH:CYP reductase in different human hepatic microsomal samples correlated with the levels of AAI-DNA adducts formed by the same microsomal samples. On the basis of these studies, we attribute most of the activation of AAI in human hepatic microsomes to CYP1A2. In contrast to human hepatic microsomes, in human renal microsomes NADPH:CYP reductase is more effective in AAI activation. In addition, prostaglandin H synthase is another enzyme activating AAI in renal microsomes. The results demonstrate for the first time the potential of microsomal enzymes in human liver and kidney to activate AAI by nitroreduction.

Department of Biochemistry Faculty of Science Charles University Albertov 2030 128 40 Prague 2 Czech Republic

Citace poskytuje Crossref.org

Co-Exposure to Aristolochic Acids I and II Increases DNA Adduct Formation Responsible for Aristolochic Acid I-Mediated Carcinogenicity in Rats

DNA Adducts Formed by Aristolochic Acid Are Unique Biomarkers of Exposure and Explain the Initiation Phase of Upper Urothelial Cancer

Comparison of the oxidation of carcinogenic aristolochic acid I and II by microsomal cytochromes P450 in vitro: experimental and theoretical approaches

Impact of genetic modulation of SULT1A enzymes on DNA adduct formation by aristolochic acids and 3-nitrobenzanthrone

Balkan endemic nephropathy: an update on its aetiology

Induction of cytochromes P450 1A1 and 1A2 suppresses formation of DNA adducts by carcinogenic aristolochic acid I in rats in vivo

Active Site Mutations as a Suitable Tool Contributing to Explain a Mechanism of Aristolochic Acid I Nitroreduction by Cytochromes P450 1A1, 1A2 and 1B1

A Mechanism of O-Demethylation of Aristolochic Acid I by Cytochromes P450 and Their Contributions to This Reaction in Human and Rat Livers: Experimental and Theoretical Approaches

The anticancer drug ellipticine activated with cytochrome P450 mediates DNA damage determining its pharmacological efficiencies: studies with rats, Hepatic Cytochrome P450 Reductase Null (HRN™) mice and pure enzymes

Mechanisms of enzyme-catalyzed reduction of two carcinogenic nitro-aromatics, 3-nitrobenzanthrone and aristolochic acid I: Experimental and theoretical approaches

Bioactivation versus detoxication of the urothelial carcinogen aristolochic acid I by human cytochrome P450 1A1 and 1A2

Contribution of biotransformation enzymes to the development of renal injury and urothelial cancer caused by aristolochic acid: urgent questions, difficult answers