UNLABELLED: Aristolochic acid I (AAI) is the major toxic component of the plant extract AA, which leads to the development of nephropathy and urothelial cancer in human. Individual susceptibility to AAI-induced disease might reflect variability in enzymes that metabolise AAI. In vitro NAD(P)H: quinone oxidoreductase (NQO1) is the most potent enzyme that activates AAI by catalyzing formation of AAI-DNA adducts, which are found in kidneys of patients exposed to AAI. Inhibition of renal NQO1 activity by dicoumarol has been shown in mice. Here, we studied the influence of dicoumarol on metabolic activation of AAI in Wistar rats in vivo. In contrast to previous in vitro findings, dicoumarol did not inhibit AAI-DNA adduct formation in rats. Compared with rats treated with AAI alone, 11- and 5.4-fold higher AAI-DNA adduct levels were detected in liver and kidney, respectively, of rats pretreated with dicoumarol prior to exposure to AAI. Cytosols and microsomes isolated from liver and kidney of these rats were analysed for activity and protein levels of enzymes known to be involved in AAI metabolism. The combination of dicoumarol with AAI induced NQO1 protein level and activity in both organs. This was paralleled by an increase in AAI-DNA adduct levels found in ex vivo incubations with cytosols from rats pretreated with dicoumarol compared to cytosols from untreated rats. Microsomal ex vivo incubations showed a lower AAI detoxication to its oxidative metabolite, 8-hydroxyaristolochic acid (AAIa), although cytochrome P450 (CYP) 1A was practically unchanged. Because of these unexpected results, we examined CYP2C activity in microsomes and found that treatment of rats with dicoumarol alone and in combination with AAI inhibited CYP2C6/11 in liver. Therefore, these results indicate that CYP2C enzymes might contribute to AAI detoxication.

• MeSH
• adukty DNA účinky léků   metabolismus   MeSH
• cytochrom P-450 CYP1A1 metabolismus   MeSH
• cytochromy metabolismus   MeSH
• cytosol účinky léků   metabolismus   MeSH
• dikumarol farmakologie   MeSH
• jaterní mikrozomy účinky léků   metabolismus   MeSH
• játra účinky léků   metabolismus   MeSH
• karcinogeny farmakokinetika   toxicita   MeSH
• krysa rodu rattus MeSH
• kyseliny aristolochové farmakokinetika   toxicita   MeSH
• ledviny účinky léků   metabolismus   MeSH
• lidé MeSH
• metabolická aktivace účinky léků   MeSH
• mutageny farmakokinetika   toxicita   MeSH
• myši MeSH
• NAD(P)H dehydrogenasa (chinon) metabolismus   MeSH
• potkani Wistar MeSH
• testy genotoxicity MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

UNLABELLED: 1. Aristolochic acid I (AAI) is the predominant component in plant extract of Aristolochia genus that is involved in development of aristolochic acid nephropathy, Balkan endemic nephropathy and urothelial cancer. The diseases do not develop in all individuals exposed to AAI and patients exhibit different clinical outcomes. Differences in the activities of enzymes catalyzing the metabolism of AAI might be one of the reasons for this individual susceptibility. 2. Understanding which human enzymes are involved in reductive activation of AAI generating AAI-DNA adducts, and/or its detoxication to the O-demethylated metabolite, aristolochic acid Ia (AAIa), is necessary in the assessment of the susceptibility to this compound. 3. This review summarizes the results of the latest studies utilizing genetically engineered mouse models to identify which human and rodent enzymes catalyze the reductive activation of AAI to AAI-DNA adducts and its oxidative detoxication to AAIa in vivo. 4. The use of hepatic cytochrome P450 (Cyp) reductase null (HRN) mice, in which NADPH:Cyp oxidoreductase (Por) is deleted in hepatocytes, Cyp1a1((-/-)), Cyp1a2((-/-)) single-knockout, Cyp1a1/1a2((-/-)) double-knockout and CYP1A-humanized mice revealed that mouse and human CYP1A1 and 1A2, besides mouse NAD(P)H: quinone oxidoreductase, were involved in the activation of AAI but CYP1A1 and 1A2 also oxidatively detoxified AAI.

• MeSH
• adukty DNA metabolismus   MeSH
• cytochrom P-450 CYP1A1 genetika   metabolismus   MeSH
• cytochrom P-450 CYP1A2 genetika   metabolismus   MeSH
• enzymy genetika   metabolismus   MeSH
• inhibitory enzymů farmakologie   MeSH
• karcinogeny metabolismus   farmakokinetika   MeSH
• kyseliny aristolochové metabolismus   farmakokinetika   toxicita   MeSH
• lidé MeSH
• metabolická inaktivace * MeSH
• myši knockoutované * MeSH
• myši MeSH
• NAD(P)H dehydrogenasa (chinon) antagonisté a inhibitory   MeSH
• NADPH-cytochrom c-reduktasa genetika   metabolismus   MeSH
• nemoci ledvin chemicky indukované   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

Aristolochic acid (AA), a plant nephrotoxin and carcinogen, causes aristolochic acid nephropathy (AAN) and its associated urothelial malignancy, and is hypothesized to be responsible for Balkan endemic nephropathy (BEN). The major component of AA, aristolochic acid I (AAI), is the predominant compound responsible for these diseases. The reductive activation of AAI leads to the formation of covalent DNA adducts. The most abundant DNA adduct, 7-(deoxyadenosin-N6-yl)aristolactam I, causes characteristic AT→TA transversions found in the TP53 tumor suppressor gene in tumors from AAN and BEN patients. Understanding which human enzymes are involved in AAI activation to species forming DNA adducts and/or detoxication to the AAI O-demethylated metabolite, aristolochic acid Ia (AAIa), is important in the assessment of the susceptibility to this carcinogen. This review summarizes the latest data on identifying human and rodent enzymes participating in AAI metabolism. NAD(P)H:quinone oxidoreductase (NQO1) is the most efficient cytosolic nitroreductase activating AAI in vitro and in vivo. In human hepatic microsomes, AAI is activated by cytochrome P450 1A2 (CYP1A2) and, to a lesser extent, by CYP1A1; NADPH:CYP oxidoreductase also plays a minor role. Human and rodent CYP1A1 and 1A2 are also the principal enzymes involved in oxidative detoxication of AAI to AAIa in vitro and in vivo. The orientation of AAI in the active sites of human CYP1A1/2 and NQO1 was predicted from molecular modeling and is consistent with the efficient reduction of AAI by them observed experimentally. Molecular modeling also shows why CYP1A2 plays an important role in the oxidation of AAI to AAIa.

• MeSH
• kyseliny aristolochové farmakokinetika   toxicita   MeSH
• lidé MeSH
• nádory glandulární a epitelové chemicky indukované   metabolismus   MeSH
• nemoci ledvin chemicky indukované   metabolismus   MeSH
• oxidoreduktasy metabolismus   MeSH
• urotel metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

OBJECTIVES: The herbal drug aristolochic acid (AA) derived from Aristolochia species has been shown to be the cause of aristolochic acid nephropathy (AAN), Balkan endemic nephropathy (BEN) and their urothelial malignancies. One of the common features of AAN and BEN is that not all individuals exposed to AA suffer from nephropathy and tumor development. One cause for these different responses may be individual differences in the activities of the enzymes catalyzing the biotransformation of AA. Thus, the identification of enzymes principally involved in the metabolism of AAI, the major toxic component of AA, and detailed knowledge of their catalytic specificities is of major importance. Human cytochrome P450 (CYP) 1A1 and 1A2 enzymes were found to be responsible for the AAI reductive activation to form AAI-DNA adducts, while its structurally related analogue, CYP1B1 is almost without such activity. However, knowledge of the differences in mechanistic details of CYP1A1-, 1A2-, and 1B1- mediated reduction is still lacking. Therefore, this feature is the aim of the present study. METHODS: Molecular modeling capable of evaluating interactions of AAI with the active site of human CYP1A1, 1A2 and 1B1 under the reductive conditions was used. In silico docking, employing soft-soft (flexible) docking procedure was used to study the interactions of AAI with the active sites of these human enzymes. RESULTS: The predicted binding free energies and distances between an AAI ligand and a heme cofactor are similar for all CYPs evaluated. AAI also binds to the active sites of CYP1A1, 1A2 and 1B1 in similar orientations. The carboxylic group of AAI is in the binding position situated directly above heme iron. This ligand orientation is in CYP1A1/1A2 further stabilized by two hydrogen bonds; one between an oxygen atom of the AAI nitro-group and the hydroxyl group of Ser122/Thr124; and the second bond between an oxygen atom of dioxolane ring of AAI and the hydroxyl group of Thr497/Thr498. For the CYP1B1:AAI complex, however, any hydrogen bonding of the nitro-group of AAI is prevented as Ser122/Thr124 residues are in CYP1B1 protein replaced by hydrophobic residue Ala133. CONCLUSION: The experimental observations indicate that CYP1B1 is more than 10× less efficient in reductive activation of AAI than CYP1A2. The docking simulation however predicts the binding pose and binding energy of AAI in the CYP1B1 pocket to be analogous to that found in CYP1A1/2. We believe that the hydroxyl group of S122/T124 residue, with its polar hydrogen placed close to the nitro group of the substrate (AAI), is mechanistically important, for example it could provide a proton required for the stepwise reduction process. The absence of a suitable proton donor in the AAI-CYP1B1 binary complex could be the key difference, as the nitro group is in this complex surrounded only by the hydrophobic residues with potential hydrogen donors not closer than 5 Å.

• MeSH
• adukty DNA chemie   metabolismus   MeSH
• Aristolochia chemie   MeSH
• aromatické hydroxylasy chemie   genetika   metabolismus   MeSH
• chemické modely MeSH
• cytochrom P-450 CYP1A1 chemie   genetika   metabolismus   MeSH
• cytochrom P-450 CYP1A2 chemie   genetika   metabolismus   MeSH
• hydrofobní a hydrofilní interakce účinky léků   MeSH
• katalytická doména účinky léků   MeSH
• kyseliny aristolochové škodlivé účinky   chemie   farmakokinetika   MeSH
• léky rostlinné čínské škodlivé účinky   chemie   farmakokinetika   MeSH
• lidé MeSH
• molekulární sekvence - údaje MeSH
• nemoci ledvin chemicky indukované   MeSH
• nitroreduktasy škodlivé účinky   chemie   farmakokinetika   MeSH
• počítačová simulace MeSH
• sekvence aminokyselin MeSH
• terciární struktura proteinů účinky léků   MeSH
• vodíková vazba účinky léků   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Aristolochic acid causes a specific nephropathy (AAN), Balkan endemic nephropathy, and urothelial malignancies. Using Western blotting suitable to determine protein expression, we investigated in several transgenic mouse lines expression of NAD(P)H:quinone oxidoreductase (NQO1)-the most efficient cytosolic enzyme that reductively activates aristolochic acid I (AAI). The mouse tissues used were from previous studies [Arlt et al., Chem. Res. Toxicol. 24 (2011) 1710; Stiborova et al., Toxicol. Sci. 125 (2012) 345], in which the role of microsomal cytochrome P450 (CYP) enzymes in AAI metabolism in vivo had been determined. We found that NQO1 levels in liver, kidney and lung of Cyp1a1⁻/⁻, Cyp1a2⁻/⁻ and Cyp1a1/1a2⁻/⁻ knockout mouse lines, as well as in two CYP1A-humanized mouse lines harboring functional human CYP1A1 and CYP1A2 and lacking the mouse Cyp1a1/1a2 orthologs, differed from NQO1 levels in wild-type mice. NQO1 protein and enzymic activity were induced in hepatic and renal cytosolic fractions isolated from AAI-pretreated mice, compared with those in untreated mice. Furthermore, this increase in hepatic NQO1 enzyme activity was associated with bioactivation of AAI and elevated AAI-DNA adduct levels in ex vivo incubations of cytosolic fractions with DNA and AAI. In conclusion, AAI appears to increase its own metabolic activation by inducing NQO1, thereby enhancing its own genotoxic potential.

• MeSH
• adukty DNA metabolismus   MeSH
• balkánská nefropatie enzymologie   genetika   metabolismus   MeSH
• buněčné linie MeSH
• cytochrom P-450 CYP1A1 nedostatek   genetika   metabolismus   MeSH
• cytochrom P-450 CYP1A2 nedostatek   genetika   metabolismus   MeSH
• cytosol enzymologie   metabolismus   MeSH
• játra účinky léků   enzymologie   metabolismus   MeSH
• kyseliny aristolochové farmakokinetika   toxicita   MeSH
• lidé MeSH
• myši inbrední C57BL MeSH
• myši knockoutované MeSH
• myši transgenní MeSH
• myši MeSH
• NAD(P)H dehydrogenasa (chinon) biosyntéza   metabolismus   MeSH
• western blotting MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH

OBJECTIVES: Ingestion of aristolochic acid (AA) is associated with development of urothelial tumors linked with aristolochic acid nephropathy, and is implicated in the development of Balkan endemic nephropathy-associated urothelial tumors. Aristolochic acid I (AAI), the major toxic component of AA, is more toxic than its demethoxylated derivate AAII. A different enzymatic conversion of both carcinogens might be one of the reasons explaining this feature. Therefore, the present study has been designed to compare efficiency of human NAD(P)H:quinone oxidoreductase (NQO1) and phase II enzymes such as sulfotransferases (SULTs) and N,O-acetyltransferases (NATs) to activate AAI and AAII in vitro. In addition, to investigate the molecular mechanisms of AAI and AAII reduction by human NQO1, molecular modeling was used to compare interactions of AAI and AAII with the active site of this enzyme. METHODS: DNA adduct formation by AAI and AAII was investigated by the nuclease P1 version of the 32P-postlabeling method. In silico docking, employing soft-soft (flexible) docking procedure, was used to study the interactions of AAI and AAII with the active site of human NQO1. RESULTS: Human NQO1 activated AAI and AAII, generating DNA adduct patterns reproducing those found in several species including human exposed to these compounds. These results demonstrate that NQO1 is capable of reducing both AAs to reactive species binding to DNA. However, concentrations required for half-maximum DNA binding mediated by NQO1 were higher for AAII (158 µM) than for AAI (17 µM). One of the reasons causing this phenomenon is a lower efficiency of NQO1 to reduce AAII than AAI we found in this work; although both AAI and AAII are bound with similar binding affinities to the NQO1 active site, the binding orientation of AAII in the active site of NQO1 does not favor the effective reduction of its nitro group. Because reduced nitro-aromatics are often further activated by SULTs or NATs, their roles in AAI and AAII activation were investigated. Our results indicate that phase II reactions do not stimulate the bioactivation of AAs; neither enzymes present in human hepatic cytosols nor human SULT1A1, 1A2, 1A3, 1E, or 2A nor NAT1 or NAT2 further enhanced DNA adduct formation by AAs. In contrast, human SULT1A1, 1A2 and 1A3 as well as NAT1 and NAT2 enzymes even inhibited NQO1-mediated bioactivation of AAII. Therefore, under the in vitro conditions used, DNA adducts arise by enzymatic reduction of AAs through the formation of N-hydroxyaristolactams that are spontaneously decomposed to the reactive species forming DNA adducts. CONCLUSION: The results found in this study emphasize the importance of NQO1 in the metabolic activation of AAI and AAII and provide the evidence that initial nitroreduction is the rate limiting step in their activation. This enzyme is more effective in activation of AAI relative to AAII, which might contribute to its lower binding to DNA found both in vitro and in vivo, Moreover, inhibition effects of conjugation reactions on AAII activation might further contribute to its decreased capability of forming DNA adducts and its lower toxicity comparing with AAI.

• MeSH
• acetyltransferasy chemie   metabolismus   fyziologie   MeSH
• adukty DNA metabolismus   MeSH
• aktivace enzymů MeSH
• biotransformace fyziologie   MeSH
• katalytická doména MeSH
• kultivované buňky MeSH
• kyseliny aristolochové chemie   farmakokinetika   MeSH
• laktamy metabolismus   farmakokinetika   MeSH
• lidé MeSH
• molekulární konformace MeSH
• molekulární modely MeSH
• NAD(P)H dehydrogenasa (chinon) chemie   metabolismus   fyziologie   MeSH
• sulfotransferasy chemie   metabolismus   fyziologie   MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• hodnotící studie MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

OBJECTIVE: The herbal drug aristolochic acid (AA) derived from Aristolochia species has been shown to be the cause of aristolochic acid nephropathy (AAN), Balkan endemic nephropathy (BEN) and their urothelial malignancies. One of the common features of AAN and BEN is that not all individuals exposed to AA suffer from nephropathy and tumor development. One cause for these different responses may be individual differences in the activities of the enzymes catalyzing the biotransformation of AA. Thus, the identification of enzymes principally involved in the metabolism of AAI, the major toxic component of AA, and detailed knowledge of their catalytic specificities is of major importance. Therefore, the present study has been designed to evaluate the cytochrome P450 (CYP)-mediated oxidative detoxification and reductive activation of AAI in a rat model. METHODS: DNA adduct formation was investigated by the nuclease P1 version of the 32P-postlabeling method. The CYP-mediated formation of a detoxication metabolite of AAI, 8-hydroxyaristolochic acid I (AAIa), in vitro in rat hepatic microsomes was determined by HPLC. RESULTS: Rat hepatic CYPs both detoxicate AAI by its oxidation to AAIa and reductively activate this carcinogen to a cyclic N-acylnitrenium ion forming AAI-DNA adducts in vitro. To define the role of hepatic CYPs in AAI demethylation and activation, the modulation of AAIa and AAI-DNA adduct formation by CYP inducers and selective CYP inhibitors was investigated. Based on these studies, we attribute the major role of CYP1A1 and 1A2 in AAI detoxication by its demethylation to AAIa, and, under hypoxic conditions also to AAI activation to species forming DNA adducts. Using microsomes of Baculovirus transfected insect cells (Supersomes™) containing recombinantly expressed rat CYPs, NADPH:CYP reductase and/or cytochrome b5, a major role of CYP1A1 and 1A2 in both reactions in vitro was confirmed. CONCLUSION: Based on the results found in this and former studies we propose that AAI activation and detoxication in rats are dictated mainly by AAI binding affinity to CYP1A1/2 or NADPH(P)H:quinone oxidoreductase, by their turnover and by the balance between oxidation and reduction of AAI by CYP1A.

• MeSH
• adukty DNA metabolismus   MeSH
• biologické modely MeSH
• biotransformace MeSH
• cytochrom P-450 CYP1A1 genetika   metabolismus   MeSH
• cytochromy genetika   metabolismus   MeSH
• jaterní mikrozomy účinky léků   metabolismus   MeSH
• játra účinky léků   enzymologie   metabolismus   MeSH
• karcinogeny farmakokinetika   MeSH
• krysa rodu rattus MeSH
• kyseliny aristolochové farmakokinetika   MeSH
• metabolická inaktivace MeSH
• potkani Wistar MeSH
• preklinické hodnocení léčiv MeSH
• systém (enzymů) cytochromů P-450 genetika   metabolismus   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Aristolochic acid (AA) causes aristolochic acid nephropathy, Balkan endemic nephropathy, and their urothelial malignancies. To identify enzymes involved in the metabolism of aristolochic acid I (AAI), the major toxic component of AA we used HRN (hepatic cytochrome P450 [Cyp] reductase null) mice, in which NADPH:Cyp oxidoreductase (Por) is deleted in hepatocytes. AAI was demethylated by hepatic Cyps in vitro to 8-hydroxy-aristolochic acid I (AAIa), indicating that less AAI is distributed to extrahepatic organs in wild-type (WT) mice. Indeed, AAI-DNA-adduct levels were significantly higher in organs of HRN mice, having low hepatic AAI demethylation capacity, than in WT mice. Absence of AAI demethylation in HRN mouse liver was confirmed in vitro; hepatic microsomes from WT, but not from HRN mice, oxidized AAI to AAIa. To define the role of hepatic Cyps in AAI demethylation, modulation of AAIa formation by CYP inducers was investigated. We conclude that AAI demethylation is attributable mainly to Cyp1a1/2. The higher AAI-DNA adduct levels in HRN than WT mice were the result of the lack of hepatic AAI demethylation concomitant with a higher activity of cytosolic NAD(P)H:quinone oxidoreductase (Nqo1), which activates AAI. Mouse hepatic Cyp1a1/2 also activated AAI to DNA adducts under hypoxic conditions in vitro, but in renal microsomes, Por and Cyp3a are more important than Cyp1a for AAI-DNA adduct formation. We propose that AAI activation and detoxication in mice are dictated mainly by AAI binding affinity to Cyp1a1/2 or Nqo1, by their turnover, and by the balance between oxidation and reduction of AAI by Cyp1a.

• MeSH
• adukty DNA MeSH
• biotransformace MeSH
• cytochrom P-450 CYP1A1 metabolismus   MeSH
• cytochrom P-450 CYP1A2 metabolismus   MeSH
• játra enzymologie   metabolismus   MeSH
• karcinogeny farmakokinetika   MeSH
• krysa rodu rattus MeSH
• kyseliny aristolochové farmakokinetika   MeSH
• lidé MeSH
• metylace MeSH
• myši inbrední C57BL MeSH
• myši knockoutované MeSH
• myši MeSH
• NADPH-cytochrom c-reduktasa genetika   metabolismus   MeSH
• spektrometrie hmotnostní - ionizace laserem za účasti matrice MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: Ingestion of aristolochic acid (AA) is associated with the development of aristolochic acid nephropathy (AAN), which is characterized by chronic renal failure, tubulointerstitial fibrosis and urothelial cancer. AA may also cause another type of kidney fibrosis with malignant transformation of the urothelium, called Balkan Endemic Nephropathy (BEN). The compound predominantly responsible for the nephropathy and urothelial cancer of AA, is aristolochic acid I (AAI) which is a genotoxic mutagen after metabolic activation The activation pathway involves reduction of the nitro group to a cyclic N-acylnitrenium ion that can form covalent DNA adducts. These specific DNA adducts have been detected in experimental animals exposed to AAI, and in urothelial tissues from AAN patients. In rodent tumours induced by AAI, 7-(deoxyadenosin-N(6)-yl)aristolactam I was the most abundant DNA adduct formed and associated with activation of ras oncogenes through a characteristic transversion mutation. Such A:T-->T:A mutations have been identified in TP53 of urothelial tumour DNA of an AAN patient and in several patients suffering from BEN along with specific AA-DNA adducts. Understanding which enzymes are involved in AAI activation to species forming DNA adducts and/or detoxification to its O-demethylated metabolite aristolochic acid Ia (AAIa) is important in order to assess susceptibility to this carcinogen. METHODS AND RESULTS: A literature search. CONCLUSIONS: The most important human enzymes activating AAI by simple nitroreduction in vitro are hepatic and renal cytosolic NAD(P)H:quinone oxidoreductase, hepatic microsomal cytochrome P450 (CYP) 1A2 and renal microsomal NADPH:CYP reductase as well as cyclooxygenase which is highly expressed in urothelial tissue. However, the contribution of most of these enzymes to the development of AAN and BEN diseases is still unclear. Hepatic CYP enzymes were found to detoxify AAI to AAIa in mice, and thereby protect the kidney from injury. CYP enzymes of the 1A subfamily seem to play a major role in this process in mouse liver. Likewise, among human CYP enzymes, CYP1A1 and 1A2 were found to be the most efficient enzymes participating in AAI oxidation to AAIa in vitro. Nevertheless, which CYPs are the most important in this process in both animal models and in humans have not been entirely resolved as yet. In addition, the relative contribution of enzymes found to activate AAI to species responsible for induction of urothelial cancer in humans remains still to be resolved.

• MeSH
• adukty DNA metabolismus   MeSH
• aktivace enzymů MeSH
• biotransformace MeSH
• cytochrom P-450 CYP1A1 metabolismus   MeSH
• cytochrom P-450 CYP1A2 metabolismus   MeSH
• financování organizované MeSH
• kyseliny aristolochové farmakokinetika   toxicita   MeSH
• ledviny účinky léků   MeSH
• lidé MeSH
• myši MeSH
• NADPH-cytochrom c-reduktasa metabolismus   MeSH
• nemoci ledvin chemicky indukované   MeSH
• urologické nádory chemicky indukované   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• přehledy MeSH

OBJECTIVES: A carcinogenic and nephrotoxic plant alkaloid, aristolochic acid (AA), causes the development of aristolochic acid nephropathy, which is characterized by chronic renal failure, tubulointerstitial fibrosis and urothelial cancer. AA may also cause a similar type of kidney fibrosis with malignant transformation of the urothelium, the Balkan endemic nephropathy. The aim of the study was to resolve which cytochromes P450 (CYP) detoxicate the major component of AA, aristolochic acid I (AAI), to its O-demethylated metabolite, aristolochic acid Ia (AAIa). METHODS: High performance liquid chromatography (HPLC) was employed for separation and characterization of AAI metabolites generated by CYPs. RESULTS: Human, rat and mouse hepatic CYPs oxidize AAI into its detoxication metabolite AAIa. Most of the detoxication of AAI in human hepatic microsomes is mediated by CYP1A2 and 1A1, while other CYPs play a minor role. CONCLUSIONS: The data are the first report on identification of human CYP enzymes detoxicating AAI.

• MeSH
• cytochrom P-450 CYP1A1 izolace a purifikace   metabolismus   MeSH
• cytochrom P-450 CYP1A2 izolace a purifikace   metabolismus   MeSH
• jaterní mikrozomy enzymologie   MeSH
• karcinogeny farmakokinetika   MeSH
• krysa rodu rattus MeSH
• kyseliny aristolochové farmakokinetika   MeSH
• lidé MeSH
• metabolická inaktivace MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• vysokoúčinná kapalinová chromatografie MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH
• přehledy MeSH
• Research Support, N.I.H., Extramural MeSH