Ingestion of aristolochic acid (AA) is associated with development of urothelial tumors linked with AA nephropathy and is implicated in the development of Balkan endemic nephropathy-associated urothelial tumors. We investigated the efficiency of human NAD(P)H:quinone oxidoreductase (NQO1) to activate aristolochic acid I (AAI) and used in silico docking, using soft-soft (flexible) docking procedure, to study the interactions of AAI with the active site of human NQO1. AAI binds to the active site of NQO1 indicating that the binding orientation allows for direct hydride transfer (i.e., two electron reductions) to the nitro group of AAI. NQO1 activated AAI, generating DNA adduct patterns reproducing those found in urothelial tissues from humans exposed to AA. Because reduced aromatic nitro-compounds are often further activated by sulfotransferases (SULTs) or N,O-acetlytransferases (NATs), their roles in AAI activation were investigated. Our results indicate that phase II reactions do not play a major role in AAI bioactivation; neither native enzymes present in human hepatic or renal cytosols nor human SULT1A1, -1A2, -1A3, -1E, or -2A nor NAT1 or NAT2 further enhanced DNA adduct formation by AAI. Instead under the in vitro conditions used, DNA adducts arise by enzymatic reduction of AAI through the formation of a cyclic hydroxamic acid (N-hydroxyaristolactam I) favored by the carboxy group in peri position to the nitro group without additional conjugation. These results emphasize the major importance of NQO1 in the metabolic activation of AAI and provide the first evidence that initial nitroreduction is the rate limiting step in AAI activation.

Department of Biochemistry Charles University Albertov Prague Czech Republic

Citace poskytuje Crossref.org

The impact of p53 on aristolochic acid I-induced nephrotoxicity and DNA damage in vivo and in vitro

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

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

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