The plant extract aristolochic acid (AA), containing aristolochic acids I (AAI) and II (AAII) as major components, causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), unique renal diseases associated with upper urothelial cancer. Recently (Chemical Research in Toxicology 33(11), 2804-2818, 2020), we showed that the in vivo metabolism of AAI and AAII in Wistar rats is influenced by their co-exposure (i.e., AAI/AAII mixture). Using the same rat model, we investigated how exposure to the AAI/AAII mixture can influence AAI and AAII DNA adduct formation (i.e., AA-mediated genotoxicity). Using 32P-postlabelling, we found that AA-DNA adduct formation was increased in the livers and kidneys of rats treated with AAI/AAII mixture compared to rats treated with AAI or AAII alone. Measuring the activity of enzymes involved in AA metabolism, we showed that enhanced AA-DNA adduct formation might be caused partially by both decreased AAI detoxification as a result of hepatic CYP2C11 inhibition during treatment with AAI/AAII mixture and by hepatic or renal NQO1 induction, the key enzyme predominantly activating AA to DNA adducts. Moreover, our results indicate that AAII might act as an inhibitor of AAI detoxification in vivo. Consequently, higher amounts of AAI might remain in liver and kidney tissues, which can be reductively activated, resulting in enhanced AAI DNA adduct formation. Collectively, these results indicate that AAII present in the plant extract AA enhances the genotoxic properties of AAI (i.e., AAI DNA adduct formation). As patients suffering from AAN and BEN are always exposed to the plant extract (i.e., AAI/AAII mixture), our findings are crucial to better understanding host factors critical for AAN- and BEN-associated urothelial malignancy.

• Klíčová slova
• Balkan endemic nephropathy, DNA adducts, NAD(P)H:quinone oxidoreductase 1, aristolochic acid I, aristolochic acid II, aristolochic acid nephropathy, aristolochic acid-mediated carcinogenesis, cytochrome P450, genotoxicity,
• MeSH
• adukty DNA metabolismus   MeSH
• DNA nádorová metabolismus   MeSH
• karcinogeneze * chemicky indukované   metabolismus   MeSH
• karcinogeny toxicita   MeSH
• krysa rodu Rattus MeSH
• kyseliny aristolochové toxicita   MeSH
• potkani Wistar MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• adukty DNA MeSH
• aristolochic acid B MeSH Prohlížeč
• aristolochic acid I MeSH Prohlížeč
• DNA nádorová MeSH
• karcinogeny MeSH
• kyseliny aristolochové MeSH

Exposure to aristolochic acid (AA) is associated with human nephropathy and urothelial cancer. The tumour suppressor TP53 is a critical gene in carcinogenesis and frequently mutated in AA-induced urothelial tumours. We investigated the impact of p53 on AAI-induced nephrotoxicity and DNA damage in vivo by treating Trp53(+/+), Trp53(+/-) and Trp53(-/-) mice with 3.5 mg/kg body weight (bw) AAI daily for 2 or 6 days. Renal histopathology showed a gradient of intensity in proximal tubular injury from Trp53(+/+) to Trp53(-/-) mice, especially after 6 days. The observed renal injury was supported by nuclear magnetic resonance (NMR)-based metabonomic measurements, where a consistent Trp53 genotype-dependent trend was observed for urinary metabolites that indicate aminoaciduria (i.e. alanine), lactic aciduria (i.e. lactate) and glycosuria (i.e. glucose). However, Trp53 genotype had no impact on AAI-DNA adduct levels, as measured by 32P-postlabelling, in either target (kidney and bladder) or non-target (liver) tissues, indicating that the underlying mechanisms of p53-related AAI-induced nephrotoxicity cannot be explained by differences in AAI genotoxicity. Performing gas chromatography-mass spectrometry (GC-MS) on kidney tissues showed metabolic pathways affected by AAI treatment, but again Trp53 status did not clearly impact on such metabolic profiles. We also cultured primary mouse embryonic fibroblasts (MEFs) derived from Trp53(+/+), Trp53(+/-) and Trp53(-/-) mice and exposed them to AAI in vitro (50 µM for up to 48 h). We found that Trp53 genotype impacted on the expression of NAD(P)H:quinone oxidoreductase (Nqo1), a key enzyme involved in AAI bioactivation. Nqo1 induction was highest in Trp53(+/+) MEFs and lowest in Trp53(-/-) MEFs; and it correlated with AAI-DNA adduct formation, with lowest adduct levels being observed in AAI-exposed Trp53(-/-) MEFs. Overall, our results clearly demonstrate that p53 status impacts on AAI-induced renal injury, but the underlying mechanism(s) involved remain to be further explored. Despite the impact of p53 on AAI bioactivation and DNA damage in vitro, such effects were not observed in vivo.

• Klíčová slova
• Aristolochic acid I, Carcinogen metabolism, DNA adducts, Mouse embryonic fibroblasts, Mouse models, Tumour suppressor p53,
• MeSH
• cytochrom P-450 CYP1A1 genetika   MeSH
• exprese genu účinky léků   MeSH
• fibroblasty účinky léků   metabolismus   patologie   MeSH
• kultivované buňky MeSH
• kyseliny aristolochové metabolismus   toxicita   MeSH
• mutageny metabolismus   toxicita   MeSH
• myši inbrední C57BL MeSH
• myši knockoutované MeSH
• NAD(P)H dehydrogenasa (chinon) genetika   MeSH
• nádorový supresorový protein p53 genetika   MeSH
• poškození DNA * MeSH
• proximální tubuly ledvin účinky léků   metabolismus   patologie   MeSH
• vyšetření funkce ledvin MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• aristolochic acid I MeSH Prohlížeč
• Cyp1a1 protein, mouse MeSH Prohlížeč
• cytochrom P-450 CYP1A1 MeSH
• kyseliny aristolochové MeSH
• mutageny MeSH
• NAD(P)H dehydrogenasa (chinon) MeSH
• nádorový supresorový protein p53 MeSH
• Nqo1 protein, mouse MeSH Prohlížeč
• Trp53 protein, mouse MeSH Prohlížeč

Aristolochic acid (AA) is a plant alkaloid that causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), unique renal diseases frequently associated with upper urothelial cancer (UUC). This review summarizes the significance of AA-derived DNA adducts in the aetiology of UUC leading to specific A:T to T:A transversion mutations (mutational signature) in AAN/BEN-associated tumours, which are otherwise rare in individuals with UCC not exposed to AA. Therefore, such DNA damage produced by AA-DNA adducts is one rare example of the direct association of exposure and cancer development (UUC) in humans, confirming that the covalent binding of carcinogens to DNA is causally related to tumourigenesis. Although aristolochic acid I (AAI), the major component of the natural plant extract AA, might directly cause interstitial nephropathy, enzymatic activation of AAI to reactive intermediates capable of binding to DNA is a necessary step leading to the formation of AA-DNA adducts and subsequently AA-induced malignant transformation. Therefore, AA-DNA adducts can not only be utilized as biomarkers for the assessment of AA exposure and markers of AA-induced UUC, but also be used for the mechanistic evaluation of its enzymatic activation and detoxification. Differences in AA metabolism might be one of the reasons for an individual's susceptibility in the multi-step process of AA carcinogenesis and studying associations between activities and/or polymorphisms of the enzymes metabolising AA is an important determinant to identify individuals having a high risk of developing AA-mediated UUC.

• Klíčová slova
• DNA adduct formation, aristolochic acid, carcinogenicity, mutagenesis, nephrotoxicity,
• MeSH
• adukty DNA metabolismus   MeSH
• balkánská nefropatie etiologie   metabolismus   MeSH
• biologické markery * MeSH
• karcinogeny chemie   metabolismus   MeSH
• kyseliny aristolochové chemie   metabolismus   MeSH
• lidé MeSH
• náchylnost k nemoci MeSH
• nádorová transformace buněk genetika   metabolismus   MeSH
• urologické nádory etiologie   metabolismus   patologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• adukty DNA MeSH
• biologické markery * MeSH
• karcinogeny MeSH
• kyseliny aristolochové MeSH

Balkan endemic nephropathy (BEN) is a unique, chronic renal disease frequently associated with upper urothelial cancer (UUC). It only affects residents of specific farming villages located along tributaries of the Danube River in Bosnia-Herzegovina, Croatia, Macedonia, Serbia, Bulgaria, and Romania where it is estimated that ~100,000 individuals are at risk of BEN, while ~25,000 have the disease. This review summarises current findings on the aetiology of BEN. Over the last 50 years, several hypotheses on the cause of BEN have been formulated, including mycotoxins, heavy metals, viruses, and trace-element insufficiencies. However, recent molecular epidemiological studies provide a strong case that chronic dietary exposure to aristolochic acid (AA) a principal component of Aristolochia clematitis which grows as a weed in the wheat fields of the endemic regions is the cause of BEN and associated UUC. One of the still enigmatic features of BEN that need to be resolved is why the prevalence of BEN is only 3-7 %. This suggests that individual genetic susceptibilities to AA exist in humans. In fact dietary ingestion of AA along with individual genetic susceptibility provides a scenario that plausibly can explain all the peculiarities of BEN such as geographical distribution and high risk of urothelial cancer. For the countries harbouring BEN implementing public health measures to avoid AA exposure is of the utmost importance because this seems to be the best way to eradicate this once mysterious disease to which the residents of BEN villages have been completely and utterly at mercy for so long.

• Klíčová slova
• Aristolochic acid, Aristolochic acid nephropathy, Balkan endemic nephropathy, Disease aetiology, Environmental and genetic factors, Upper urothelial cancer,
• MeSH
• Aristolochia chemie   růst a vývoj   toxicita   MeSH
• balkánská nefropatie chemicky indukované   epidemiologie   patofyziologie   prevence a kontrola   MeSH
• dieta škodlivé účinky   MeSH
• endemické nemoci * MeSH
• faktory vyvracející (epidemiologie) MeSH
• karcinogeny životního prostředí analýza   toxicita   MeSH
• kontaminace potravin * prevence a kontrola   MeSH
• kyseliny aristolochové analýza   toxicita   MeSH
• ledviny účinky léků   patofyziologie   MeSH
• léková rezistence MeSH
• lidé MeSH
• medicína založená na důkazech * MeSH
• mouka škodlivé účinky   analýza   MeSH
• plevel chemie   růst a vývoj   toxicita   MeSH
• prevalence MeSH
• pšenice růst a vývoj   MeSH
• riziko MeSH
• semena rostlinná růst a vývoj   MeSH
• urologické nádory chemicky indukované   epidemiologie   patofyziologie   prevence a kontrola   MeSH
• zemědělské plodiny růst a vývoj   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Geografické názvy
• východní Evropa epidemiologie   MeSH
• Názvy látek
• aristolochic acid I MeSH Prohlížeč
• karcinogeny životního prostředí MeSH
• kyseliny aristolochové MeSH

Aristolochic acid I (AAI) is a plant alkaloid causing aristolochic acid nephropathy, Balkan endemic nephropathy and their associated urothelial malignancies. AAI is detoxified by cytochrome P450 (CYP)-mediated O-demethylation to 8-hydroxyaristolochic acid I (aristolochic acid Ia, AAIa). We previously investigated the efficiencies of human and rat CYPs in the presence of two other components of the mixed-functions-oxidase system, NADPH:CYP oxidoreductase and cytochrome b₅, to oxidize AAI. Human and rat CYP1A are the major enzymes oxidizing AAI. Other CYPs such as CYP2C, 3A4, 2D6, 2E1, and 1B1, also form AAIa, but with much lower efficiency than CYP1A. Based on velocities of AAIa formation by examined CYPs and their expression levels in human and rat livers, here we determined the contributions of individual CYPs to AAI oxidation in these organs. Human CYP1A2 followed by CYP2C9, 3A4 and 1A1 were the major enzymes contributing to AAI oxidation in human liver, while CYP2C and 1A were most important in rat liver. We employed flexible in silico docking methods to explain the differences in AAI oxidation in the liver by human CYP1A1, 1A2, 2C9, and 3A4, the enzymes that all O-demethylate AAI, but with different effectiveness. We found that the binding orientations of the methoxy group of AAI in binding centers of the CYP enzymes and the energies of AAI binding to the CYP active sites dictate the efficiency of AAI oxidation. Our results indicate that utilization of experimental and theoretical methods is an appropriate study design to examine the CYP-catalyzed reaction mechanisms of AAI oxidation and contributions of human hepatic CYPs to this metabolism.

• Klíčová slova
• contribution of cytochromes P450 in detoxification of aristolochic acid I in human and rat livers, cytochrome P450-mediated detoxification of aristolochic acid I, molecular modeling, plant nephrotoxin and carcinogen aristolochic acid I,
• MeSH
• inhibitory cytochromu P450 farmakologie   MeSH
• jaterní mikrozomy účinky léků   metabolismus   MeSH
• játra účinky léků   metabolismus   MeSH
• katalytická doména MeSH
• katalýza MeSH
• krysa rodu Rattus MeSH
• kyseliny aristolochové škodlivé účinky   chemie   metabolismus   MeSH
• lidé MeSH
• metabolická aktivace MeSH
• metabolická inaktivace MeSH
• metylace účinky léků   MeSH
• molekulární konformace MeSH
• molekulární modely MeSH
• nemoci ledvin etiologie   metabolismus   MeSH
• oxidace-redukce účinky léků   MeSH
• systém (enzymů) cytochromů P-450 chemie   metabolismus   MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aristolochic acid I MeSH Prohlížeč
• inhibitory cytochromu P450 MeSH
• kyseliny aristolochové MeSH
• systém (enzymů) cytochromů P-450 MeSH

UNLABELLED: This review summarizes the results found in studies investigating the enzymatic activation of two genotoxic nitro-aromatics, an environmental pollutant and carcinogen 3-nitrobenzanthrone (3-NBA) and a natural plant nephrotoxin and carcinogen aristolochic acid I (AAI), to reactive species forming covalent DNA adducts. Experimental and theoretical approaches determined the reasons why human NAD(P)H: quinone oxidoreductase (NQO1) and cytochromes P450 (CYP) 1A1 and 1A2 have the potential to reductively activate both nitro-aromatics. The results also contributed to the elucidation of the molecular mechanisms of these reactions. The contribution of conjugation enzymes such as N,O-acetyltransferases (NATs) and sulfotransferases (SULTs) to the activation of 3-NBA and AAI was also examined. The results indicated differences in the abilities of 3-NBA and AAI metabolites to be further activated by these conjugation enzymes. The formation of DNA adducts generated by both carcinogens during their reductive activation by the NOQ1 and CYP1A1/2 enzymes was investigated with pure enzymes, enzymes present in subcellular cytosolic and microsomal fractions, selective inhibitors, and animal models (including knock-out and humanized animals). For the theoretical approaches, flexible in silico docking methods as well as ab initio calculations were employed. The results summarized in this review demonstrate that a combination of experimental and theoretical approaches is a useful tool to study the enzyme-mediated reaction mechanisms of 3-NBA and AAI reduction.

• MeSH
• acetyltransferasy metabolismus   MeSH
• adukty DNA chemie   metabolismus   MeSH
• aromatické hydroxylasy metabolismus   MeSH
• benz(a)anthraceny chemie   metabolismus   MeSH
• biokatalýza MeSH
• enzymy metabolismus   MeSH
• kyseliny aristolochové chemie   metabolismus   MeSH
• lidé MeSH
• molekulární modely * MeSH
• NAD(P)H dehydrogenasa (chinon) metabolismus   MeSH
• sulfotransferasy metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• 3-nitrobenzanthrone MeSH Prohlížeč
• acetyltransferasy MeSH
• adukty DNA MeSH
• aristolochic acid I MeSH Prohlížeč
• aromatické hydroxylasy MeSH
• benz(a)anthraceny MeSH
• enzymy MeSH
• kyseliny aristolochové MeSH
• NAD(P)H dehydrogenasa (chinon) MeSH
• sulfotransferasy MeSH