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Thies JL, Willicott K, Craig ML, Greene MR, DuGay CN, Caldwell GA, Caldwell KA. Xanthine Dehydrogenase Is a Modulator of Dopaminergic Neurodegeneration in Response to Bacterial Metabolite Exposure in C. elegans. Cells 2023; 12:cells12081170. [PMID: 37190079 DOI: 10.3390/cells12081170] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 04/03/2023] [Accepted: 04/11/2023] [Indexed: 05/17/2023] Open
Abstract
Oxidative stress is a contributing factor to Parkinson's disease (PD). Considering the prevalence of sporadic PD, environmental exposures are postulated to increase reactive oxygen species and either incite or exacerbate neurodegeneration. We previously determined that exposure to the common soil bacterium, Streptomyces venezuelae (S. ven), enhanced oxidative stress and mitochondrial dysfunction in Caenorhabditis elegans, leading to dopaminergic (DA) neurodegeneration. Here, S. ven metabolite exposure in C. elegans was followed by RNA-Seq analysis. Half of the differentially identified genes (DEGs) were associated with the transcription factor DAF-16 (FOXO), which is a key node in regulating stress response. Our DEGs were enriched for Phase I (CYP) and Phase II (UGT) detoxification genes and non-CYP Phase I enzymes associated with oxidative metabolism, including the downregulated xanthine dehydrogenase gene, xdh-1. The XDH-1 enzyme exhibits reversible interconversion to xanthine oxidase (XO) in response to calcium. S. ven metabolite exposure enhanced XO activity in C. elegans. The chelation of calcium diminishes the conversion of XDH-1 to XO and results in neuroprotection from S. ven exposure, whereas CaCl2 supplementation enhanced neurodegeneration. These results suggest a defense mechanism that delimits the pool of XDH-1 available for interconversion to XO, and associated ROS production, in response to metabolite exposure.
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Affiliation(s)
- Jennifer L Thies
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Karolina Willicott
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Maici L Craig
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Madeline R Greene
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Cassandra N DuGay
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Guy A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Kim A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Major benznidazole metabolites in patients treated for Chagas disease: Mass spectrometry-based identification, structural analysis and detoxification pathways. Toxicol Lett 2023; 377:71-82. [PMID: 36775077 DOI: 10.1016/j.toxlet.2023.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 01/22/2023] [Accepted: 02/08/2023] [Indexed: 02/12/2023]
Abstract
Benznidazole is the drug of choice for the treatment of Chagas disease, but its metabolism in humans is unclear. Here, we identified and characterized the major benznidazole metabolites and their biosynthetic mechanisms in humans by analyzing the ionic profiles of urine samples from patients and untreated donors through reversed-phase UHPLC-ESI-QTOF-MS and UHPLC-ESI-QqLIT-MS. A strategy for simultaneous detection and fragmentation of characteristic positive and negative ions was employed using information-dependent acquisitions (IDA). Selected precursor ions, neutral losses, and MS3 experiments complemented the study. A total of six phase-I and ten phase-II metabolites were identified and structurally characterized in urine of benznidazole-treated patients. Based on creatinine-corrected ion intensities, nitroreduction to amino-benznidazole (M1) and its subsequent N-glucuronidation to M5 were the main metabolic pathways, followed by imidazole-ring cleavage, oxidations, and cysteine conjugations. This extensive exploration of benznidazole metabolites revealed potentially toxic structures in the form of glucuronides and glutathione derivatives, which may be associated with recurrent treatment adverse events; this possibility warrants further exploration in future clinical trials. Incorporation of this knowledge of the benznidazole metabolic profile into clinical pharmacology trials could lead to improved treatments, facilitate the study of possible drug-drug interactions, and even mitigation of adverse drug reactions.
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Wang P, Wu R, Jia Y, Tang P, Wei B, Zhang Q, Wang VYF, Yan R. Inhibition and structure-activity relationship of dietary flavones against three Loop 1-type human gut microbial β-glucuronidases. Int J Biol Macromol 2022; 220:1532-1544. [PMID: 36096258 DOI: 10.1016/j.ijbiomac.2022.09.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 08/28/2022] [Accepted: 09/04/2022] [Indexed: 02/07/2023]
Abstract
Gut microbial β-glucuronidases (GUSs) inhibition is a new approach for managing some diseases and medication therapy. However, the structural and functional complexity of GUSs have posed tremendous challenges to discover specific or broad-spectrum GUSs inhibitors using Escherichia coli GUS (EcoGUS) alone. This study first assessed the effects of twenty-one dietary flavones employing three Loop 1-type GUSs of different taxonomic origins, which were considered to be the main GUSs involved in deglucuronidation of small molecules, on p-nitrophenyl-β-D-glucuronide hydrolysis and a structure-activity relationship is preliminarily proposed based on both in vitro assays and a docking study with representative compounds. EcoGUS and Staphylococcus pasteuri GUS showed largely similar inhibition propensities with potencies positively correlating with the total hydroxyl groups and those at ring B of flavones, while docking results revealed strong interactions developed via ring A and/or C. Streptococcus agalactiae GUS (SagaGUS) exhibited distinct inhibition propensities, displaying late-onset inhibition and steep dose-response profiles with most tested compounds. The α-helix in loop 1 region of SagaGUS which causes spatial hindrance but offers a hydrophobic surface for contacting with the carbonyl group on ring C of flavones is believed to be essential for the allosteric inhibition of SagaGUS. Taken together, the study with a series of flavones revealed varied preferences for GUSs belonging to the same Loop 1-type, highlighting the necessity of adopting multi-GUSs instead of EcoGUS alone for screening broad-spectrum GUSs inhibitors or tailoring the inhibition based on specific GUS structure.
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Affiliation(s)
- Panpan Wang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao.
| | - Rongrong Wu
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao.
| | - Yifei Jia
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao
| | - Puipui Tang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao
| | - Bin Wei
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao.
| | - Qingwen Zhang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao.
| | | | - Ru Yan
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao.
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Zhu B. Logic of the Temporal Compartmentalization of the Hepatic Metabolic Cycle. Physiology (Bethesda) 2022; 37:0. [PMID: 35658626 PMCID: PMC9394779 DOI: 10.1152/physiol.00003.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 05/05/2022] [Accepted: 05/28/2022] [Indexed: 12/25/2022] Open
Abstract
The mammalian liver must cope with various metabolic and physiological changes that normally recur every day and result primarily from rest-activity and fasting-feeding cycles. In this article, I present evidence supporting a temporal compartmentalization of rhythmic hepatic metabolic processes into four main clusters: regulation of energy homeostasis, maintenance of information integrity, immune response, and genetic information flow. I further review literatures and discuss how both the circadian and the newly discovered 12-h ultradian clock work together to regulate these four temporally separated processes in mouse liver, which, interestingly, is largely uncoupled from the liver zonation regulation.
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Affiliation(s)
- Bokai Zhu
- Aging Institute of UPMC, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Pittsburgh Liver Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania
- Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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Wang P, Jia Y, Wu R, Chen Z, Yan R. Human gut bacterial β-glucuronidase inhibition: An emerging approach to manage medication therapy. Biochem Pharmacol 2021; 190:114566. [PMID: 33865833 DOI: 10.1016/j.bcp.2021.114566] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/09/2021] [Accepted: 04/12/2021] [Indexed: 10/21/2022]
Abstract
Bacterial β-glucuronidase enzymes (BGUSs) are at the interface of host-microbial metabolic symbiosis, playing an important role in health and disease as well as medication outcomes (efficacy or toxicity) by deconjugating a large number of endogenous and exogenous glucuronides. In recent years, BGUSs inhibition has emerged as a new approach to manage diseases and medication therapy and attracted an increasing research interest. However, a growing body of evidence underlines great genetic diversity, functional promiscuity and varied inhibition propensity of BGUSs, which have posed big challenges to identifying BGUSs involved in a specific pathophysiological or pharmacological process and developing effective inhibition. In this article, we offered a general introduction of the function, in particular the physiological, pathological and pharmacological roles, of BGUSs and their taxonomic distribution in human gut microbiota, highlighting the structural features (active sites and adjacent loop structures) that affecting the protein-substrate (inhibitor) interactions. Recent advances in BGUSs-mediated deconjugation of drugs and carcinogens and the discovery and applications of BGUS inhibitors in management of medication therapy, typically, irinotecan-induced diarrhea and non-steroidal anti-inflammatory drugs (NSAIDs)-induced enteropathy, were also reviewed. At the end, we discussed the perspectives and the challenges of tailoring BGUS inhibition towards precision medicine.
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Affiliation(s)
- Panpan Wang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao, China
| | - Yifei Jia
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao, China
| | - Rongrong Wu
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao, China
| | - Zhiqiang Chen
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao, China
| | - Ru Yan
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Taipa, Macao, China.
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Little MS, Ervin SM, Walton WG, Tripathy A, Xu Y, Liu J, Redinbo MR. Active site flexibility revealed in crystal structures of Parabacteroides merdae β-glucuronidase from the human gut microbiome. Protein Sci 2018; 27:2010-2022. [PMID: 30230652 PMCID: PMC6237702 DOI: 10.1002/pro.3507] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 09/10/2018] [Accepted: 09/10/2018] [Indexed: 12/12/2022]
Abstract
β-Glucuronidase (GUS) enzymes in the gastrointestinal tract are involved in maintaining mammalian-microbial symbiosis and can play key roles in drug efficacy and toxicity. Parabacteroides merdae GUS was identified as an abundant mini-Loop 2 (mL2) type GUS enzyme in the Human Microbiome Project gut metagenomic database. Here, we report the crystal structure of P. merdae GUS and highlight the differences between this enzyme and extant structures of gut microbial GUS proteins. We find that P. merdae GUS exhibits a distinct tetrameric quaternary structure and that the mL2 motif traces a unique path within the active site, which also includes two arginines distinctive to this GUS. We observe two states of the P. merdae GUS active site; a loop repositions itself by more than 50 Å to place a functionally-relevant residue into the enzyme's catalytic site. Finally, we find that P. merdae GUS is able to bind to homo and heteropolymers of the polysaccharide alginic acid. Together, these data broaden our understanding of the structural and functional diversity in the GUS family of enzymes present in the human gut microbiome and point to specialization as an important feature of microbial GUS orthologs.
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Affiliation(s)
- Michael S. Little
- Department of ChemistryUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
| | - Samantha M. Ervin
- Department of ChemistryUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
| | - William G. Walton
- Department of ChemistryUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
| | - Ashutosh Tripathy
- Department of Biochemistry & BiophysicsUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
| | - Yongmei Xu
- Department of Chemical Biology and Medicinal ChemistryUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
| | - Jian Liu
- Department of Chemical Biology and Medicinal ChemistryUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
| | - Matthew R. Redinbo
- Department of ChemistryUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
- Department of Biochemistry & BiophysicsUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
- Department of Microbiology & ImmunologyUniversity of North CarolinaChapel HillNorth Carolina27599‐3290
- The Integrated Program for Biological and Genome Sciences, University of North CarolinaChapel HillNorth Carolina27599‐3290
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Rogers LJ, Basnakian AG, Orloff MS, Ning B, Yao-Borengasser A, Raj V, Kadlubar S. 2-amino-1-methyl-6-phenylimidazo(4,5-b) pyridine (PhIP) induces gene expression changes in JAK/STAT and MAPK pathways related to inflammation, diabetes and cancer. Nutr Metab (Lond) 2016; 13:54. [PMID: 27547236 PMCID: PMC4992261 DOI: 10.1186/s12986-016-0111-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 08/05/2016] [Indexed: 01/09/2023] Open
Abstract
Background 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), a heterocyclic aromatic amine (HCA) formed in meat that is cooked at high temperatures and then ingested, can potentially be retained in human adipose tissues. Methods To determine if PhIP is bioactive in the adipocyte, we exposed a human adipocyte cell line,HepG2 and Caco-2 cells to low dose PhIP. Uptake and retention of PhIP was determined and cytotoxicity was assessed by the TUNEL assay. Relative expression of PhIP-activating genes (CYP1A1, CYP1A2, SULT1A1 and UGT1A1) was determined by RT-PCR and global expression changes were also examined. Results The percent retention of 0.1 μCi [14C]-PhIP over a 24 h period was significantly higher in the adipocyte than the HepG2 (p = 0.0001) and Caco-2 (p = 0.0007) cell lines. Cytotoxicity rates were 14.4 and 2.6 % higher compared to controls in Caco-2 and HepG2 cells (p < 0.001 and 0.054, respectively); no significant differences were detected in adipocyte cells (p = 0.18). Caco-2 and HepG2 cells, respectively, had significantly higher basal expression of CYP1A1 (p = 0.001, p = 0.003), SULT1A1 (p = 0.04, p < 0.001) and UGT1A1 (p < 0.001, p = 0.01) compared to the adipocyte. Exposure to 5nM PhIP did not significantly induce expression of these genes in any of the cell lines. Global gene expression analysis of mature adipocytes exposed to 5nM PhIP for 72 h resulted in statistically significant changes in 8 genes (ANGPTL2, CD14, CIDEA, EGR1, FOS, IGFBP5, PALM and PSAT1). Gene-gene interaction and pathway analysis indicates that PhIP modulates genes controlled by the STAT3 transcriptional factor and initiates leptin signaling via the JAK/STAT and MAPK pathway cascades. Early growth response 1 (EGR1) and prostaglandin synthase 2 (COX-2) were down-regulated via c-Fos, while insulin binding protein 5 (IBP5) was up regulated. Expression of transcription factors (ANGPTL2, HP, LEP, SAA1, SAA2), genes related to inflammation (SAA1, LEP), diabetes (IGFBP5) and cancer risk (SAA2) were also elevated upon exposure to 5 nM PhIP.. Conclusions PhIP mediates gene expression changes within the adipocyte, and the pathways most affected are related to cancer and other chronic diseases. Further studies are needed on the relationship between dietary carcinogens such as PhIP with cancer, obesity and diabetes. Electronic supplementary material The online version of this article (doi:10.1186/s12986-016-0111-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lora J Rogers
- University of Arkansas for Medical Sciences, 4301 W Markham St, #580, Little Rock, AR 72205 USA
| | - Alexei G Basnakian
- University of Arkansas for Medical Sciences, 4301 W Markham St, #580, Little Rock, AR 72205 USA
| | - Mohammed S Orloff
- University of Arkansas for Medical Sciences, 4301 W Markham St, #580, Little Rock, AR 72205 USA
| | - Baitang Ning
- National Center for Toxicological Research, NCTR Rd, Redfield, AR 72132 USA
| | | | - Vinay Raj
- University of Arkansas for Medical Sciences, 4301 W Markham St, #580, Little Rock, AR 72205 USA
| | - Susan Kadlubar
- University of Arkansas for Medical Sciences, 4301 W Markham St, #580, Little Rock, AR 72205 USA
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Turesky RJ, White KK, Wilkens LR, Marchand LL. Caffeine Cytochrome P450 1A2 Metabolic Phenotype Does Not Predict the Metabolism of Heterocyclic Aromatic Amines in Humans. Chem Res Toxicol 2015; 28:1603-15. [PMID: 26203673 PMCID: PMC4571451 DOI: 10.1021/acs.chemrestox.5b00177] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
2-Amino-1-methylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) are carcinogenic heterocyclic aromatic amines (HAAs) formed in well-done cooked meats. Chemicals that induce cytochrome P450 (P450) 1A2, a major enzyme involved in the bioactivation of HAAs, also form in cooked meat. Therefore, well-done cooked meat may pose an increase in cancer risk because it contains both inducers of P450 1A2 and procarcinogenic HAAs. We examined the influence of components in meat to modulate P450 1A2 activity and the metabolism of PhIP and MeIQx in volunteers during a 4 week feeding study of well-done cooked beef. The mean P450 1A2 activity, assessed by caffeine metabolic phenotyping, ranged from 6.3 to 7.1 before the feeding study commenced and from 9.6 to 10.4 during the meat feeding period: the difference in means was significant (P < 0.001). Unaltered PhIP, MeIQx, and their P450 1A2 metabolites, N(2)-(β-1-glucosiduronyl)-2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (HON-PhIP-N(2)-Gl); N3-(β-1-glucosiduronyl)-2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (HON-PhIP-N3-Gl); 2-amino-3-methylimidazo-[4,5-f]quinoxaline-8-carboxylic acid (IQx-8-COOH); and 2-amino-8-(hydroxymethyl)-3-methylimidazo[4,5-f]quinoxaline (8-CH2OH-IQx) were measured in urine during days 2, 14, and 28 of the meat diet. Significant correlations were observed on these days between the levels of the unaltered HAAs and their oxidized metabolites, when expressed as percent of dose ingested or as metabolic ratios. However, there was no statistically significant correlation between the caffeine P450 1A2 phenotype and any urinary HAA biomarker. Although the P450 1A2 activity varied by greater than 20-fold among the subjects, there was a large intraindividual variation of the P450 1A2 phenotype and inconsistent responses to inducers of P450 1A2. The coefficient of variation of the P450 1A2 phenotype within-individual ranged between 1 to 112% (median = 40%) during the entire course of the study. The caffeine metabolic phenotype for P450 1A2 was a poor predictor of oxidative urinary metabolites of PhIP and MeIQx and may not be a reliable measure to assess the role of HAAs in cancer risk.
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Affiliation(s)
- Robert J. Turesky
- Masonic Masonic Cancer Center and Department of Medicinal Chemistry, College of Pharmacy, 2231 6th St SE, University of Minnesota, Minneapolis, MN 55455
| | - Kami K. White
- University of Hawaii Cancer Center, University of Hawaii, Honolulu, HI 9681
| | - Lynne R. Wilkens
- University of Hawaii Cancer Center, University of Hawaii, Honolulu, HI 9681
| | - Loïc Le Marchand
- University of Hawaii Cancer Center, University of Hawaii, Honolulu, HI 9681
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Kim JK, Gallaher DD, Chen C, Yao D, Trudo SP. Apiaceous vegetable consumption decreases PhIP-induced DNA adducts and increases methylated PhIP metabolites in the urine metabolome in rats. J Nutr 2015; 145:442-51. [PMID: 25733458 PMCID: PMC4336530 DOI: 10.3945/jn.114.202622] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Heterocyclic aromatic amines, such as 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), are carcinogenic compounds produced during heating of protein-containing foods. Apiaceous vegetables inhibit PhIP-activating enzymes, whereas cruciferous vegetables induce both PhIP-activating and -detoxifying enzymes. OBJECTIVE We investigated the effects of these vegetables, either alone or combined, on PhIP metabolism and colonic DNA adduct formation in rats. METHODS Male Wistar rats were fed cruciferous vegetables (21%, wt:wt), apiaceous vegetables (21%, wt:wt), or a combination of both vegetables (10.5% wt:wt of each). Negative and positive control groups were fed an AIN-93G diet. After 6 d, all groups received an intraperitoneal injection of PhIP (10 mg · kg body weight(-1)) except for the negative control group, which received only vehicle. Urine was collected for 24 h after the injection for LC-tandem mass spectrometry metabolomic analyses. On day 7, rats were killed and tissues processed. RESULTS Compared with the positive control, cruciferous vegetables increased the activity of hepatic PhIP-activating enzymes [39.5% and 45.1% for cytochrome P450 (CYP) 1A1 (P = 0.0006) and CYP1A2 (P < 0.0001), respectively] and of uridine 5'-diphospho-glucuronosyltransferase 1A (PhIP-detoxifying) by 24.5% (P = 0.0267). Apiaceous vegetables did not inhibit PhIP-activating enzymes, yet reduced colonic PhIP-DNA adducts by 20.4% (P = 0.0496). Metabolomic analyses indicated that apiaceous vegetables increased the relative abundance of urinary methylated PhIP metabolites. The sum of these methylated metabolites inversely correlated with colonic PhIP-DNA adducts (r = -0.43, P = 0.01). We detected a novel methylated urinary PhIP metabolite and demonstrated that methylated metabolites are produced in the human liver S9 fraction. CONCLUSIONS Apiaceous vegetables did not inhibit the activity of PhIP-activating enzymes in rats, suggesting that the reduction in PhIP-DNA adducts may involve other pathways. Further investigation of the importance of PhIP methylation in carcinogen metabolism is warranted, given the inverse correlation of methylated PhIP metabolites with a biomarker of carcinogenesis and the detection of a novel methylated PhIP metabolite.
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Affiliation(s)
| | | | | | | | - Sabrina P Trudo
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN
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Sridar C, Hanna I, Hollenberg PF. Quantitation of UGT1A1 in human liver microsomes using stable isotope-labelled peptides and mass spectrometry based proteomic approaches. Xenobiotica 2012; 43:336-45. [DOI: 10.3109/00498254.2012.719089] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Rodrigues C, Vieira E, Santos R, de Carvalho J, Santos-Silva A, Costa E, Bronze-da-Rocha E. Impact of UGT1A1 gene variants on total bilirubin levels in Gilbert syndrome patients and in healthy subjects. Blood Cells Mol Dis 2012; 48:166-72. [PMID: 22325916 DOI: 10.1016/j.bcmd.2012.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 01/09/2012] [Accepted: 01/11/2012] [Indexed: 10/14/2022]
Abstract
The Gilbert syndrome is a benign form of unconjugated hyperbilirubinemia, mainly associated with alterations in UGT1A1 gene. This work investigated the effect of UGT1A1 variants on total bilirubin levels in Gilbert patients (n=45) and healthy controls (n=161). Total bilirubin levels were determined using a colorimetric method; molecular analysis of exons 1-5 and two UGT1A1 promoter regions were performed by direct sequencing and automatic analysis of fragments. Five in silico methods predicted the effect of new identified variants. A significant different allelic distribution, in Gilbert patients and in controls, was found for two promoter polymorphisms. Among patients, 82.2% were homozygous and 17.8% heterozygous for the c.-41_-40dupTA allele; in control group, 9.9% were homozygous and 43.5% heterozygous for this promoter variant, while 46.6% (n=75) presented the [A(TA)6TAA]. For the T>G transition at c.-3279 promoter region, in patients, 86.7% were homozygous and 13.3% heterozygous; in control group, 33.5% were homozygous for the wild type allele, 44.1% were heterozygous and 22.4% homozygous for the mutated allele. The two polymorphisms were in Hardy-Weinberg equilibrium in both groups. Sequencing of UGT1A1 coding region identified nine novel variants, five in patients and four in controls. In silico analysis of these amino acids replacements predicted four of them as benign and three as damaging. In conclusion, we demonstrated that total bilirubin levels are mainly determined by the TA duplication in the TATA-box promoter and by the c.-3279T>G variant. Alterations in the UGT1A1 coding region seem to be associated with increased bilirubin levels, and, therefore, with Gilbert syndrome.
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Affiliation(s)
- Carina Rodrigues
- Departamento de Ciências Biológicas, Laboratório de Bioquímica, Faculdade de Farmácia da Universidade do Porto, Portugal
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Kim D, Lee YJ, Ryu HY, Lee JH, Kim HK, Kim E, Moon JD, Chang DD, Yoon HS. Genetic polymorphisms in metabolism of 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine. J Appl Toxicol 2011; 33:63-70. [PMID: 22131055 DOI: 10.1002/jat.1712] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 05/25/2011] [Indexed: 11/09/2022]
Abstract
Heterocyclic amines (HCAs) are naturally produced during common cooking processes for meats and fish. HCAs are metabolized by various enzymes, including cytochromes P450, N-acetyl transferases, and sulfotransferases, and their bioactivated metabolites are considered to bind to DNA or protein to show carcinogenic effects. More than 20 HCAs have been identified, of which 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is classified as 'reasonably anticipated to be a human carcinogen' to develop cancers in breast, colon and prostate. The purpose of this study was to evaluate human exposure levels of PhIP and to understand the role of genetic polymorphisms of enzymes on PhIP metabolism. Urine samples were collected from subjects (n = 100) before 3-day meat-restricted diets. Subjects consumed grilled chicken, and their blood and urine were collected before and after the administration of the chickens to investigate genetic polymorphisms and PhIP levels. The mean PhIP levels were 4.22 ± 0.12, 0.61 ± 0.19 and 22.64 ± 1.00 pg ml(-1) in urine under normal conditions and before and after chicken administration, respectively. Among 21 Single-nucleotide polymorphisms (SNP) of CYP1A1, CYP1A2, NATs and UGTs investigated in this study, genotypic groups of CYP1A1/T6235C (MSP I) and CYP1A2/-2467delT showed significant differences in PhIP excretion (P < 0.05). These results suggest that genetic polymorphisms might affect PhIP metabolism, which could improve understanding of populations subject to PhIP-derived health risk.
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Affiliation(s)
- Dojung Kim
- Korea Food and Drug Administration, 643 Yeonje-ri, Gangoe-myeon, Cheongwon-gun, Chungbuk, 363-951, Korea
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13
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Accelerator mass spectrometry-enabled studies: current status and future prospects. Bioanalysis 2011; 2:519-41. [PMID: 20440378 DOI: 10.4155/bio.09.188] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Accelerator mass spectrometry is a detection platform with exceptional sensitivity compared with other bioanalytical platforms. Accelerator mass spectrometry (AMS) is widely used in archeology for radiocarbon dating applications. Early exploration of the biological and pharmaceutical applications of AMS began in the early 1990s. AMS has since demonstrated unique problem-solving ability in nutrition science, toxicology and pharmacology. AMS has also enabled the development of new applications, such as Phase 0 microdosing. Recent development of AMS-enabled applications has transformed this novelty research instrument to a valuable tool within the pharmaceutical industry. Although there is now greater awareness of AMS technology, recognition and appreciation of the range of AMS-enabled applications is still lacking, including study-design strategies. This review aims to provide further insight into the wide range of AMS-enabled applications. Examples of studies conducted over the past two decades will be presented, as well as prospects for the future of AMS.
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Zhou SF, Wang B, Yang LP, Liu JP. Structure, function, regulation and polymorphism and the clinical significance of human cytochrome P450 1A2. Drug Metab Rev 2010; 42:268-354. [PMID: 19961320 DOI: 10.3109/03602530903286476] [Citation(s) in RCA: 179] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Human CYP1A2 is one of the major CYPs in human liver and metabolizes a number of clinical drugs (e.g., clozapine, tacrine, tizanidine, and theophylline; n > 110), a number of procarcinogens (e.g., benzo[a]pyrene and aromatic amines), and several important endogenous compounds (e.g., steroids). CYP1A2 is subject to reversible and/or irreversible inhibition by a number of drugs, natural substances, and other compounds. The CYP1A gene cluster has been mapped on to chromosome 15q24.1, with close link between CYP1A1 and 1A2 sharing a common 5'-flanking region. The human CYP1A2 gene spans almost 7.8 kb comprising seven exons and six introns and codes a 515-residue protein with a molecular mass of 58,294 Da. The recently resolved CYP1A2 structure has a relatively compact, planar active site cavity that is highly adapted for the size and shape of its substrates. The architecture of the active site of 1A2 is characterized by multiple residues on helices F and I that constitutes two parallel substrate binding platforms on either side of the cavity. A large interindividual variability in the expression and activity of CYP1A2 has been observed, which is largely caused by genetic, epigenetic and environmental factors (e.g., smoking). CYP1A2 is primarily regulated by the aromatic hydrocarbon receptor (AhR) and CYP1A2 is induced through AhR-mediated transactivation following ligand binding and nuclear translocation. Induction or inhibition of CYP1A2 may provide partial explanation for some clinical drug interactions. To date, more than 15 variant alleles and a series of subvariants of the CYP1A2 gene have been identified and some of them have been associated with altered drug clearance and response and disease susceptibility. Further studies are warranted to explore the clinical and toxicological significance of altered CYP1A2 expression and activity caused by genetic, epigenetic, and environmental factors.
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Affiliation(s)
- Shu-Feng Zhou
- Discpline of Chinese Medicine, School of Health Sciences, RMIT University, Bundoora, Victoria 3083, Australia.
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Girard H, Butler LM, Villeneuve L, Millikan RC, Sinha R, Sandler RS, Guillemette C. UGT1A1 and UGT1A9 functional variants, meat intake, and colon cancer, among Caucasians and African-Americans. Mutat Res 2008; 644:56-63. [PMID: 18675828 DOI: 10.1016/j.mrfmmm.2008.07.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Revised: 06/03/2008] [Accepted: 07/07/2008] [Indexed: 11/26/2022]
Abstract
Glucuronidation by the UDP-glucuronosyltransferase enzymes (UGTs) is one of the primary detoxification pathways of dietary heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). In a population-based case-control study of 537 cases and 866 controls, we investigated whether colon cancer was associated with genetic variations in UGT1A1 and UGT1A9 genes and we determined if those variations modify the association between colon cancer and dietary HCA and PAH exposure. We measured functional UGT1A1 polymorphisms at positions -53 (28; A(TA)6TAA to A(TA)7TAA), -3156 (G>A), -3279 (T>G) and the UGT1A9-275(T>A) polymorphism, and found no association with colon cancer overall. However, when stratified by race, the UGT1A1-3279 GG/TG intermediate/low activity genotypes were associated with an increased risk of colon cancer (odds ratio (OR)=1.5, 95% confidence interval (CI)=1.1-2.0) in Caucasians. This finding is also supported by haplotype analyses where the UGT1A1-3279G-allele-bearing haplotype is overrepresented in case group. Overall, UGT1A1-53 and -3156 genotypes modified the association between dietary benzo(a)pyrene (BaP) and colon cancer (P for interaction=0.02 and 0.03, respectively). The strongest association was observed for those with <7.7 ng/day BaP exposure and the low activity genotypes, for both UGT1A1 28/28 (OR=1.8, 95% CI=1.1-2.9) and -3156AA (OR=1.7, 95% CI=1.0-3.0), compared to >or=7.7 ng/day and combined high/intermediate genotypes. These data support a hypothesis that UGTs modify the association between meat-derived PAH exposure and colon cancer by their role in the elimination of dietary carcinogens.
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Affiliation(s)
- Hugo Girard
- Pharmacogenomics Laboratory, CHUQ Research Center and Faculty of Pharmacy, Laval University, G1V 4G2 Québec, Canada
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Bellocq D, Molina J, Rathahao E, Canlet C, Taché S, Martin PG, Pierre F, Paris A. High potency of bioactivation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in mouse colon epithelial cells with ApcMin mutation. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2008; 653:34-43. [DOI: 10.1016/j.mrgentox.2008.02.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Revised: 01/21/2008] [Accepted: 02/14/2008] [Indexed: 12/27/2022]
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Saracino MR, Lampe JW. Phytochemical regulation of UDP-glucuronosyltransferases: implications for cancer prevention. Nutr Cancer 2008; 59:121-41. [PMID: 18001207 DOI: 10.1080/01635580701458178] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Uridine 5'-diphospho-glucuronosyltransferases (UGTs) are Phase II biotransformation enzymes that metabolize endogenous and exogenous compounds, some of which have been associated with cancer risk. Many phytochemicals have been shown to induce UGTs in humans, rodents, and cell culture systems. Because UGTs maintain hormone balance and facilitate excretion of potentially carcinogenic compounds, regulation of their expression and activity may affect cancer risk. Phytochemicals regulate transcription factors such as the nuclear factor-erythroid 2-related factor 2 (Nrf2), aryl hydrocarbon, and pregnane X receptors as well as proteins in several signal transduction cascades that converge on Nrf2 to stimulate UGT expression. This induction can be modified by several factors, including phytochemical dose and bioavailability and interindividual variation in enzyme expression. In this review, we summarize the knowledge of dietary modulation of UGTs, particularly by phytochemicals, and discuss the potential mechanisms by which phytochemicals regulate UGT transcription.
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18
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Chapter 3 Glucuronidation-Dependent Toxicity and Bioactivation. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/s1872-0854(07)02003-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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19
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Trubetskoy OV, Finel M, Kurkela M, Fitzgerald M, Peters NR, Hoffman FM, Trubetskoy VS. High Throughput Screening Assay for UDP-Glucuronosyltransferase 1A1 Glucuronidation Profiling. Assay Drug Dev Technol 2007; 5:343-54. [PMID: 17638534 DOI: 10.1089/adt.2006.050] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Development of high throughput screening (HTS) assays for evaluation of a compound's toxicity and potential for drug-drug interactions is a critical step towards production of better drug candidates and cost reduction in the drug development process. HTS assays for drug metabolism mediated by cytochrome P450s are now routinely used in compound library characterization and for computer modeling studies. However, development and application of HTS assays involving UDP-glucuronosyltransferases (UGTs) are lagging behind. Here we describe the development of a fluorescence-based HTS assay for UGT1A1 using recombinant enzyme and fluorescent substrate in the presence of an aqueous solution of PreserveX-QML (QBI Life Sciences, Madison, WI) polymeric micelles, acting as a stabilizer and a blocker of nonspecific interactions. The data include assay characteristics in 384-well plate format obtained with robotic liquid handling equipment and structures of hits (assay modifiers) obtained from the screening of a small molecule library at the University of Wisconsin HTS screening facility. The application of the assay for predicting UGT-related drug-drug interactions and building pharmacophore models, as well as the effects of polymeric micelles on the assay performance and compound promiscuity, is discussed.
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Affiliation(s)
- O V Trubetskoy
- Quintessence Biosciences, University of Wisconsin, Madison, WI., School of Pharmacy, University of Wisconsin, Madison, WI 53719, USA.
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Hong AL, Huo D, Kim HJ, Niu Q, Fackenthal DL, Cummings SA, John EM, West DW, Whittemore AS, Das S, Olopade OI. UDP-Glucuronosyltransferase 1A1 Gene Polymorphisms and Total Bilirubin Levels in an Ethnically Diverse Cohort of Women. Drug Metab Dispos 2007; 35:1254-61. [PMID: 17478602 DOI: 10.1124/dmd.106.014183] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The objective of this study was to investigate variations in UGT1A1 polymorphisms and haplotypes among African-American and Caucasian women and to assess whether variants other than UGT1A1*28 are associated with total serum bilirubin levels. The (TA)(n) repeats and 14 single nucleotide polymorphisms (SNPs) in the UGT1A1 gene were genotyped in 335 African Americans and 181 Caucasians. Total serum bilirubin levels were available in a subset of 125 women. Allele frequencies of all SNPs and (TA)(n) repeats were significantly different between African Americans and Caucasians. In Caucasians, three common haplotypes accounted for 71.8% of chromosomes, whereas five common haplotypes accounted for only 46.6% of chromosomes in African Americans. Mean total serum bilirubin levels were significantly lower (p = 0.005) in African Americans (0.36 mg/dl) than in Caucasians (0.44 mg/dl). The (TA)(n) repeats explained a significant amount of variation in total bilirubin levels (R(2) = 0.27, p < 0.0001), whereas other SNPs were less correlative. Thus, significant variations in UGT1A1 haplotype structure exist between African Americans and Caucasians in this relatively large cohort of women. The correlation of UGT1A1 with total bilirubin levels was mainly due to (TA)(n) repeats in Caucasians but a clear correlation was not observed in African Americans because of the high diversity of haplotypes and the small sample size. These data have implications for the design of epidemiologic studies of cancer susceptibility and pharmacogenetic studies for adverse drug reactions in populations of African ancestry.
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Affiliation(s)
- Andrew L Hong
- Department of Medicine, Section of Hematology/Oncology, University of Chicago, 5841 S. Maryland Ave., MC 2115, Chicago, IL 60637, USA
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Wu X, Murphy P, Cunnick J, Hendrich S. Synthesis and characterization of deoxynivalenol glucuronide: its comparative immunotoxicity with deoxynivalenol. Food Chem Toxicol 2007; 45:1846-55. [PMID: 17507135 DOI: 10.1016/j.fct.2007.03.018] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 03/14/2007] [Accepted: 03/27/2007] [Indexed: 01/17/2023]
Abstract
Deoxynivalenol (DON) is a mycotoxin commonly contaminating wheat, barley and corn. DON glucuronide (DONGLU) is a major DON metabolite. We synthesized and purified DONGLU and tested its immunotoxicity, hypothesizing that DONGLU would be much less toxic to K562 cells compared with DON. DONGLU was synthesized using rat liver microsomes, uridine-5'-diphosphoglucuronic acid and DON, and purified with a Sephadex LH-20 column and reverse phase HPLC. beta-Glucuronidase hydrolysis formed a product with retention time and UV spectrum identical with DON. Using atmospheric pressure chemical ionization in negative mode, the molecular mass (M-1) of purified DONGLU was 471 g/mol; in agreement with an expected molecular weight of 472 g/mol. MS and NMR indicated that the glucuronide moiety was conjugated with the carbon-3-hydroxyl group of DON. The cytotoxicity of DON and DONGLU were compared in cell culture using human erythroleukemia cell line K562. Fifty percent inhibition of cell number was observed with a DON concentration of 1.31 microM using a methylthaizol tetrazolium (MTS) cell viability assay whereas no significant cytotoxicity was observed for DONGLU at up to 270 microM. DONGLU did not influence DON toxicity at 0.5 microM, 1.3 microM and 8.4 microM concentration combinations of each compound. These data verified that DONGLU is a detoxification product of DON.
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Affiliation(s)
- Xianai Wu
- Department of Food Science and Human Nutrition, Iowa State University, 224D Mackay Hall, Ames, IA 50011, USA
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Chang JL, Bigler J, Schwarz Y, Li SS, Li L, King IB, Potter JD, Lampe JW. UGT1A1 polymorphism is associated with serum bilirubin concentrations in a randomized, controlled, fruit and vegetable feeding trial. J Nutr 2007; 137:890-7. [PMID: 17374650 DOI: 10.1093/jn/137.4.890] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
UDP-glucuronosyltransferase (UGT) 1A1 glucuronidates bilirubin, estrogens, and exogenous compounds, including dietary carcinogens. The UGT1A1*28 polymorphism, characterized by variation in the number of thymine-adenine repeats in the promoter region, modulates UGT1A1 transcription. Observational and in vitro studies suggest that certain phytochemicals may increase UGT activity. We investigated, in a randomized, controlled, crossover feeding trial, whether approximately 10 servings/d (doses adjusted for body weight) of crucifers, soy, and citrus for 2 wk compared with a fruit- and vegetable-free basal diet affected UGT1A1 activity as measured by serum bilirubin concentrations and whether effects were modulated by the UGT1A1*28 polymorphism. Healthy men (n = 32) and women (n = 31), aged 20-40 y, enrolled based on UGT1A1 genotype, completed the study. We measured bilirubin in blood collected at d 8 and d 15 of each feeding period. Overall, fruit and vegetables (F&V) did not affect serum bilirubin; however, among 7/7 individuals, d 8 total (P = 0.057) and indirect (unconjugated) (P = 0.051) bilirubin tended to be lower when individuals consumed the F&V diet (28.97 +/- 2.36 micromol/L and 25.97 +/- 2.15 micromol/L) compared with the basal diet (32.46 +/- 2.63 micromol/L and 29.31 +/- 2.43 micromol/L). We no longer detected this difference at d 15, by which time bilirubin had also decreased when participants consumed the basal diet. Additionally, intervention effects on bilirubin were restricted to women with 7/7 genotype (P = 0.002). These results suggest that serum bilirubin glucuronidation is modulated by dietary intervention, but factors such as UGT1A1 genotype and sex may affect the response to diet.
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Affiliation(s)
- Jyh-Lurn Chang
- Interdisciplinary Graduate Program in Nutritional Sciences, Department of Epidemiology, University of Washington, Seattle, WA 98195, USA
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Chen C, Ma X, Malfatti MA, Krausz KW, Kimura S, Felton JS, Idle JR, Gonzalez FJ. A comprehensive investigation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) metabolism in the mouse using a multivariate data analysis approach. Chem Res Toxicol 2007; 20:531-42. [PMID: 17279779 PMCID: PMC1850849 DOI: 10.1021/tx600320w] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a potent rodent carcinogen and a potential human carcinogen because of its existence in the normal human diet. N2-OH-PhIP, a major PhIP metabolite, has been identified as a precursor of genotoxic species. In vitro data supported the view that CYP1A2 is the major enzyme responsible for the formation of N2-OH-PhIP. However, disruption of the CYP1A2 gene in mouse failed to inhibit PhIP-induced carcinogenesis. To investigate the mechanism underlying this observation, the metabolism of PhIP in wild-type, Cyp1a2-null, and CYP1A2-humanized mice was examined in detail using a metabolomic approach. Following data acquisition in a high-resolution LC-MS system, urinary metabolomes of the control and PhIP-treated mice were characterized in a principal component analysis (PCA) model. Comprehensive metabolite profiles of PhIP in high dose (10 mg/kg) and low dose (100 microg/kg) were established through analyzing urinary ions contributing to the separation of three mouse lines in the multivariate model and by measuring radiolabled PhIP metabolite in a radio-HPLC assay, respectively. The genotoxicity of PhIP to three mouse lines was evaluated by measuring DNA adduction levels in liver, lung, colon, and mammary gland. On the basis of the chemical identities of 17 urinary PhIP metabolites, including eight novel metabolites, multivariate data analysis revealed the role of CYP1A2 in PhIP metabolism and a human-mouse interspecies difference in the catalytic activity of CYP1A2. In addition, the results also showed that Cyp1a2-null mice still possess significant N2-hydroxylation and DNA adduction activities, which may be partially attributed to mouse CYP2C enzymes according to the results from in vitro microsome and Supersome incubations and antibody inhibition experiments.
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Affiliation(s)
- Chi Chen
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Dietrich CG, Geier A. It takes more than one--is a single UGT polymorphism enough to bother detoxification? Hepatology 2005; 42:1462; author reply 1463. [PMID: 16317666 DOI: 10.1002/hep.20963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
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