Bioactivation mechanisms of N‐hydroxyaristolactams: Nitroreduction metabolites of aristolochic acids

Abstract

Aristolochic acids (AAs) are human nephrotoxins and carcinogens found in concoctions of Aristolochia plants used in traditional medicinal practices worldwide. Genotoxicity of AAs is associated with the formation of active species catalyzed by metabolic enzymes, the full repertoire of which is unknown. Recently, we provided evidence that sulfonation is important for bioactivation of AAs. Here, we employ Salmonella typhimurium umu tester strains expressing human N‐acetyltransferases (NATs) and sulfotransferases (SULTs), to study the role of conjugation reactions in the genotoxicities of N‐hydroxyaristolactams (AL‐I‐NOH and AL‐II‐NOH), metabolites of AA‐I and AA‐II. Both N‐hydroxyaristolactams show stronger genotoxic effects in umu strains expressing human NAT1 and NAT2, than in the parent strain. Additionally, AL‐I‐NOH displays increased genotoxicity in strains expressing human SULT1A1 and SULT1A2, whereas AL‐II‐NOH shows enhanced genotoxicity in SULT1A1/2 and SULT1A3 strains. 2,6‐Dichloro‐4‐nitrophenol, SULTs inhibitor, reduced umuC gene expression induced by N‐hydroxyaristolactams in SULT1A2 strain. N‐hydroxyaristolactams are also mutagenic in parent strains, suggesting that an additional mechanism(s) may contribute to their genotoxicities. Accordingly, using putative SULT substrates and inhibitors, we found that cytosols obtained from human kidney HK‐2 cells activate N‐hydroxyaristolactams in aristolactam‐DNA adducts with the limited involvement of SULTs. Removal of low‐molecular‐weight reactants in the 3.5–10 kDa range inhibits the formation of aristolactam‐DNA by 500‐fold, which could not be prevented by the addition of cofactors for SULTs and NATs. In conclusion, our results demonstrate that the genotoxicities of N‐hydroxyaristolactams depend on the cell type and involve not only sulfonation but also N,O‐acetyltransfer and an additional yet unknown mechanism(s). Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc.

The isolation-biological activities (2014–2022), bio, semi, total synthesis (1978–2022) and SAR studies of a potential naturally engineered scaffold aristolactam

“…7A. 27–29 In the beginning step, 4 electron reduction of the NO 2 of aristolactic acid (AA-1, AA-2) occurs to form N -hydroxy aristolactam. N -Hydroxy aristolactam (AL-I, AL-II) undergoes O -sulfonation or O -acetylation by the involvement of cytosolic sulfotransferases (SULTs) or N -acetyltransferases (NATs).…”

Aristolochic Acid-Induced Nephrotoxicity: Molecular Mechanisms and Potential Protective Approaches

“…In this context, Okuno and co-workers recently examined the role of conjugation reactions in the genotoxicity of N-hydroxyaristolactams in Salmonella typhimurium umu tester strains expressing human NATs and SULTs and reported that N-hydroxyaristolactams showed stronger genotoxic effects in umu strains expressing human NAT1 and NAT2 than in the parent. Strains expressing human SULT1A1 and SULT1A2 also showed increased genotoxicity of N-hydroxyaristolactams [38]. On the contrary, using native enzymes present in human cytosols and human recombinant enzymes including SULTs and NATs, Martinek and colleagues reported that these enzymes of phase II were not involved in AA bioactivation [39].…”

GPX3 rs8177412 Polymorphism Modifies Risk of Upper Urothelial Tumors in Patients with Balkan Endemic Nephropathy

“…AA exposure is associated with mitochondrial dysfunction, enhanced ROS production, impaired mitochondrial membrane potential and reduction in ATP production [ 9 , 10 ]. Furthermore, during the bioactivation of AA genotoxic metabolite N-hydroxyaristolactam I is formed [ 11 ]. Both disruption of redox homeostasis and N-hydroxyaristolactam lead to harmful effects on vital macromolecules, including DNA, which result in mutagenesis and carcinogenesis [ 12 ].…”