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Stacpoole PW. Clinical physiology and pharmacology of GSTZ1/MAAI. Biochem Pharmacol 2023; 217:115818. [PMID: 37742772 DOI: 10.1016/j.bcp.2023.115818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/05/2023] [Accepted: 09/21/2023] [Indexed: 09/26/2023]
Abstract
Herein I summarize the physiological chemistry and pharmacology of the bifunctional enzyme glutathione transferase zeta 1 (GSTZ1)/ maleylacetoacetate isomerase (MAAI) relevant to human physiology, drug metabolism and disease. MAAI is integral to the catabolism of the amino acids phenylalanine and tyrosine. Genetic or pharmacological inhibition of MAAI can be pathological in animals. However, to date, no clinical disease consequences are unequivocally attributable to inborn errors of this enzyme. MAAI is identical to the zeta 1 family isoform of GST, which biotransforms the investigational drug dichloroacetate (DCA) to the endogenous compound glyoxylate. DCA is a mechanism-based inhibitor of GSTZ1 that significantly reduces its rate of metabolism and increases accumulation of potentially harmful tyrosine intermediates and of the heme precursor δ-aminolevulinic acid (δ-ALA). GSTZ1 is most abundant in rodent and human liver, with its concentration several fold higher in cytoplasm than in mitochondria. Its activity and protein expression are dependent on the age of the host and the intracellular level of chloride ions. Gene association studies have linked GSTZ1 or its protein product to various physiological traits and pathologies. Haplotype variations in GSTZ1 influence the rate of DCA metabolism, enabling a genotyping strategy to allow potentially safe, precision-based drug dosing in clinical trials.
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Affiliation(s)
- Peter W Stacpoole
- Departments of Medicine and Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL 32601, USA.
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2
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Schoenmann N, Tannenbaum N, Hodgeman RM, Raju RP. Regulating mitochondrial metabolism by targeting pyruvate dehydrogenase with dichloroacetate, a metabolic messenger. Biochim Biophys Acta Mol Basis Dis 2023; 1869:166769. [PMID: 37263447 PMCID: PMC10776176 DOI: 10.1016/j.bbadis.2023.166769] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 05/20/2023] [Accepted: 05/26/2023] [Indexed: 06/03/2023]
Abstract
Dichloroacetate (DCA) is a naturally occurring xenobiotic that has been used as an investigational drug for over 50 years. Originally found to lower blood glucose levels and alter fat metabolism in diabetic rats, this small molecule was found to serve primarily as a pyruvate dehydrogenase kinase inhibitor. Pyruvate dehydrogenase kinase inhibits pyruvate dehydrogenase complex, the catalyst for oxidative decarboxylation of pyruvate to produce acetyl coenzyme A. Several congenital and acquired disease states share a similar pathobiology with respect to glucose homeostasis under distress that leads to a preferential shift from the more efficient oxidative phosphorylation to glycolysis. By reversing this process, DCA can increase available energy and reduce lactic acidosis. The purpose of this review is to examine the literature surrounding this metabolic messenger as it presents exciting opportunities for future investigation and clinical application in therapy including cancer, metabolic disorders, cerebral ischemia, trauma, and sepsis.
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Affiliation(s)
- Nick Schoenmann
- Department of Emergency Medicine, Medical College of Georgia, Augusta University, Augusta, GA, United States of America
| | - Nicholas Tannenbaum
- Department of Emergency Medicine, Medical College of Georgia, Augusta University, Augusta, GA, United States of America
| | - Ryan M Hodgeman
- Department of Emergency Medicine, Medical College of Georgia, Augusta University, Augusta, GA, United States of America
| | - Raghavan Pillai Raju
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, Augusta, GA, United States of America.
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3
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Squirewell EJ, Mareus R, Horne LP, Stacpoole PW, James MO. Exposure of Rats to Multiple Oral Doses of Dichloroacetate Results in Upregulation of Hepatic Glutathione Transferases and NAD(P)H Dehydrogenase [Quinone] 1. Drug Metab Dispos 2020; 48:1224-1230. [PMID: 32873592 PMCID: PMC7589945 DOI: 10.1124/dmd.120.000143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 08/11/2020] [Indexed: 11/22/2022] Open
Abstract
Dichloroacetate (DCA) is an investigational drug that is used in the treatment of various congenital and acquired disorders of energy metabolism. Although DCA is generally well tolerated, some patients experience peripheral neuropathy, a side effect more common in adults than children. Repetitive DCA dosing causes downregulation of its metabolizing enzyme, glutathione transferase zeta 1 (GSTZ1), which is also critical in the detoxification of maleylacetoacetate and maleylacetone. GSTZ1 (-/-) knockout mice show upregulation of glutathione transferases (GSTs) and antioxidant enzymes as well as an increase in the ratio of oxidized glutathione (GSSG) to reduced glutathione (GSH), suggesting GSTZ1 deficiency causes oxidative stress. We hypothesized that DCA-mediated depletion of GSTZ1 causes oxidative stress and used the rat to examine induction of GSTs and antioxidant enzymes after repeated DCA exposure. We determined the expression of alpha, mu, pi, and omega class GSTs, NAD(P)H dehydrogenase [quinone] 1 (NQO1), gamma-glutamylcysteine ligase complex (GCLC), and glutathione synthetase (GSS). GSH and GSSG levels were measured by liquid chromatography-tandem mass spectrometry. Enzyme activity was measured in hepatic cytosol using 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene, and 2,6-dichloroindophenol as substrates. In comparison with acetate-treated controls, DCA dosing increased the relative expression of GSTA1/A2 irrespective of rodent age, whereas only adults displayed higher levels of GSTM1 and GSTO1. NQO1 expression and activity were higher in juveniles after DCA dosing. GSH concentrations were increased by DCA in adults, but the GSH:GSSG ratio was not changed. Levels of GCLC and GSS were higher and lower, respectively, in adults treated with DCA. We conclude that DCA-mediated depletion of GSTZ1 causes oxidative stress and promotes the induction of antioxidant enzymes that may vary between age groups. SIGNIFICANCE STATEMENT: Treatment with the investigational drug, dichloroacetate (DCA), results in loss of glutathione transferase zeta 1 (GSTZ1) and subsequent increases in body burden of the electrophilic tyrosine metabolites, maleylacetoacetate and maleylacetone. Loss of GSTZ1 in genetically modified mice is associated with induction of glutathione transferases and alteration of the ratio of oxidized to reduced glutathione. Therefore, we determined whether pharmacological depletion of GSTZ1 through repeat administration of DCA produced similar changes in the liver, which could affect responses to other drugs and toxicants.
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Affiliation(s)
- Edwin J Squirewell
- Departments of Medicinal Chemistry (E.J.S., R.M., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Ricky Mareus
- Departments of Medicinal Chemistry (E.J.S., R.M., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Lloyd P Horne
- Departments of Medicinal Chemistry (E.J.S., R.M., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Peter W Stacpoole
- Departments of Medicinal Chemistry (E.J.S., R.M., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Margaret O James
- Departments of Medicinal Chemistry (E.J.S., R.M., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
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Squirewell EJ, Smeltz MG, Rowland-Faux L, Horne LP, Stacpoole PW, James MO. Effects of Multiple Doses of Dichloroacetate on GSTZ1 Expression and Activity in Liver and Extrahepatic Tissues of Young and Adult Rats. Drug Metab Dispos 2020; 48:1217-1223. [PMID: 32873593 DOI: 10.1124/dmd.120.000142] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 08/04/2020] [Indexed: 12/19/2022] Open
Abstract
Glutathione transferase zeta 1 (GSTZ1), expressed in liver and several extrahepatic tissues, catalyzes dechlorination of dichloroacetate (DCA) to glyoxylate. DCA inactivates GSTZ1, leading to autoinhibition of its metabolism. DCA is an investigational drug for treating several congenital and acquired disorders of mitochondrial energy metabolism, including cancer. The main adverse effect of DCA, reversible peripheral neuropathy, is more common in adults treated long-term than in children, who metabolize DCA more quickly after multiple doses. One dose of DCA to Sprague Dawley rats reduced GSTZ1 expression and activity more in liver than in extrahepatic tissues; however, the effects of multiple doses of DCA that mimic its therapeutic use have not been studied. Here, we examined the expression and activity of GSTZ1 in cytosol and mitochondria of liver, kidney, heart, and brain 24 hours after completion of 8-day oral dosing of 100 mg/kg per day sodium DCA to juvenile and adult Sprague Dawley rats. Activity was measured with DCA and with 1,2-epoxy-3-(4-nitrophenoxy)propane (EPNPP), reported to be a GSTZ1-selective substrate. In DCA-treated rats, liver retained higher expression and activity of GSTZ1 with DCA than other tissues, irrespective of rodent age. DCA-treated juvenile rats retained more GSTZ1 activity with DCA than adults. Consistent with this finding, there was less measurable DCA in tissues of juvenile than adult rats. DCA-treated rats retained activity with EPNPP, despite losing over 98% of GSTZ1 protein. These data provide insight into the differences between children and adults in DCA elimination under a therapeutic regimen and confirm that the liver contributes more to DCA metabolism than other tissues. SIGNIFICANCE STATEMENT: Dichloroacetate (DCA) is one of few drugs exhibiting higher clearance from children than adults, after repeated doses, for reasons that are unclear. We hypothesized that juveniles retain more glutathione transferase zeta 1 (GSTZ1) than adults in tissues after multiple DCA doses and found this was the case for liver and kidney, with rat as a model to assess GSTZ1 protein expression and activity with DCA. Although 1,2-epoxy-3-(4-nitrophenoxy)propane was reported to be a selective GSTZ1 substrate, its activity was not reduced in concert with GSTZ1 protein.
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Affiliation(s)
- Edwin J Squirewell
- Departments of Medicinal Chemistry (E.J.S., M.G.S., L.R.-F., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Marci G Smeltz
- Departments of Medicinal Chemistry (E.J.S., M.G.S., L.R.-F., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Laura Rowland-Faux
- Departments of Medicinal Chemistry (E.J.S., M.G.S., L.R.-F., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Lloyd P Horne
- Departments of Medicinal Chemistry (E.J.S., M.G.S., L.R.-F., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Peter W Stacpoole
- Departments of Medicinal Chemistry (E.J.S., M.G.S., L.R.-F., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
| | - Margaret O James
- Departments of Medicinal Chemistry (E.J.S., M.G.S., L.R.-F., M.O.J.), Medicine (L.P.H., P.W.S.), and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida
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Joseph S, Sharma A, Horne LP, Wood CE, Langaee T, James MO, Stacpoole PW, Keller-Wood M. Pharmacokinetic and Biochemical Profiling of Sodium Dichloroacetate in Pregnant Ewes and Fetuses. Drug Metab Dispos 2020; 49:451-458. [PMID: 33811107 PMCID: PMC11019763 DOI: 10.1124/dmd.120.000330] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 03/16/2021] [Indexed: 11/22/2022] Open
Abstract
Sodium dichloroacetate (DCA) is an investigational drug that shows promise in the treatment of acquired and congenital mitochondrial diseases, including myocardial ischemia and failure. DCA increases glucose utilization and decreases lactate production, so it may also have clinical utility in reducing lactic acidosis during labor. In the current study, we tested the ability of DCA to cross the placenta and be measured in fetal blood after intravenous administration to pregnant ewes during late gestation and labor. Sustained administration of DCA to the mother over 72 hours achieved pharmacologically active levels of DCA in the fetus and decreased fetal plasma lactate concentrations. Multicompartmental pharmacokinetics modeling indicated that drug metabolism in the fetal and maternal compartments is best described by the DCA inhibiting lactate production in both compartments, consistent with our finding that the hepatic expression of the DCA-metabolizing enzyme glutathione transferase zeta1 was decreased in the ewes and their fetuses exposed to the drug. We provide the first evidence that DCA can cross the placental compartment to enter the fetal circulation and inhibit its own hepatic metabolism in the fetus, leading to increased DCA concentrations and decreased fetal plasma lactate concentrations during its parenteral administration to the mother. SIGNIFICANCE STATEMENT: This study was the first to administer sodium dichloroacetate (DCA) to pregnant animals (sheep). It showed that DCA administered to the mother can cross the placental barrier and achieve concentrations in fetus sufficient to decrease fetal lactate concentrations. Consistent with findings reported in other species, DCA-mediated inhibition of glutathione transferase zeta1 was also observed in ewes, resulting in reduced metabolism of DCA after prolonged administration.
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Affiliation(s)
- Serene Joseph
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Abhisheak Sharma
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Lloyd P Horne
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Charles E Wood
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Taimour Langaee
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Margaret O James
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Peter W Stacpoole
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
| | - Maureen Keller-Wood
- Departments of Pharmacodynamics (S.J., M.K.-W.), Pharmaceutics (A.S.), Medicinal Chemistry (M.O.J.), Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics and Precision Medicine (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (L.P.H., P.W.S.), Physiology and Functional Genomics (C.E.W.), University of Florida, Gainesville, Florida
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Abstract
The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.
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Affiliation(s)
- Patrick E Hanna
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN, USA
| | - M W Anders
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, USA
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Tian DD, Bennett SK, Coupland LA, Forwood K, Lwin Y, Pooryousef N, Tea I, Truong TT, Neeman T, Crispin P, D’Rozario J, Blackburn AC. GSTZ1 genotypes correlate with dichloroacetate pharmacokinetics and chronic side effects in multiple myeloma patients in a pilot phase 2 clinical trial. Pharmacol Res Perspect 2019; 7:e00526. [PMID: 31624634 PMCID: PMC6783648 DOI: 10.1002/prp2.526] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 08/08/2019] [Accepted: 08/29/2019] [Indexed: 12/16/2022] Open
Abstract
Dichloroacetate (DCA) is an investigational drug targeting the glycolytic hallmark of cancer by inhibiting pyruvate dehydrogenase kinases (PDK). It is metabolized by GSTZ1, which has common polymorphisms altering enzyme or promoter activity. GSTZ1 is also irreversibly inactivated by DCA. In the first clinical trial of DCA in a hematological malignancy, DiCAM (DiChloroAcetate in Myeloma), we have examined the relationship between DCA concentrations, GSTZ1 genotype, side effects, and patient response. DiCAM recruited seven myeloma patients in partial remission. DCA was administered orally for 3 months with a loading dose. Pharmacokinetics were performed on day 1 and 8. Trough and peak concentrations of DCA were measured monthly. GSTZ1 genotypes were correlated with drug concentrations, tolerability, and disease outcomes. One patient responded and two patients showed a partial response after one month of DCA treatment, which included the loading dose. The initial half-life of DCA was shorter in two patients, correlating with heterozygosity for GSTZ1*A genotype, a high enzyme activity variant. Over 3 months, one patient maintained DCA trough concentrations approximately threefold higher than other patients, which correlated with a low activity promoter genotype (-1002A, rs7160195) for GSTZ1. This patient displayed the strongest response, but also the strongest neuropathy. Overall, serum concentrations of DCA were sufficient to inhibit the constitutive target PDK2, but unlikely to inhibit targets induced in cancer. Promoter GSTZ1 polymorphisms may be important determinants of DCA concentrations and neuropathy during chronic treatment. Novel dosing regimens may be necessary to achieve effective DCA concentrations in most cancer patients while avoiding neuropathy.
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Affiliation(s)
- Dan Dan Tian
- ACRF Department of Cancer Biology and TherapeuticsThe John Curtin School of Medical ResearchThe Australian National UniversityCanberraACTAustralia
| | | | - Lucy A. Coupland
- ACRF Department of Cancer Biology and TherapeuticsThe John Curtin School of Medical ResearchThe Australian National UniversityCanberraACTAustralia
| | - Kathryn Forwood
- Department of HaematologyThe Canberra HospitalGarranACTAustralia
| | - Yadanar Lwin
- Department of HaematologyThe Canberra HospitalGarranACTAustralia
| | - Niloofar Pooryousef
- ACRF Department of Cancer Biology and TherapeuticsThe John Curtin School of Medical ResearchThe Australian National UniversityCanberraACTAustralia
| | - Illa Tea
- ACRF Department of Cancer Biology and TherapeuticsThe John Curtin School of Medical ResearchThe Australian National UniversityCanberraACTAustralia
| | - Thy T. Truong
- Joint Mass Spectrometry FacilityThe Australian National UniversityActonACTAustralia
| | - Teresa Neeman
- Statistical Consulting UnitThe Australian National UniversityActonACTAustralia
| | - Philip Crispin
- Department of HaematologyThe Canberra HospitalGarranACTAustralia
| | - James D’Rozario
- Department of HaematologyThe Canberra HospitalGarranACTAustralia
| | - Anneke C. Blackburn
- ACRF Department of Cancer Biology and TherapeuticsThe John Curtin School of Medical ResearchThe Australian National UniversityCanberraACTAustralia
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Smeltz MG, Hu Z, Zhong G, Jahn SC, Rowland-Faux L, Horne LP, Stacpoole PW, James MO. Mitochondrial Glutathione Transferase Zeta 1 Is Inactivated More Rapidly by Dichloroacetate than the Cytosolic Enzyme in Adult and Juvenile Rat Liver. Chem Res Toxicol 2019; 32:2042-2052. [PMID: 31524376 DOI: 10.1021/acs.chemrestox.9b00207] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Dichloroacetate (DCA) has potential for treating mitochondrial disorders and cancer by activating the mitochondrial pyruvate dehydrogenase complex. Repeated dosing of DCA results in reduced drug clearance due to inactivation of glutathione transferase ζ1 (GSTZ1), its metabolizing enzyme. We investigated the time-course of inactivation of GSTZ1 in hepatic cytosol and mitochondria after one oral dose of 100 mg/kg DCA to female Sprague-Dawley rats aged 4 weeks (young) and 52 weeks (adult) as models for children and adults, respectively. GSTZ1 activity with both DCA and an endogenous substrate, maleylacetone (MA), as well as GSTZ1 protein expression were rapidly reduced in cytosol from both ages following DCA treatment. In mitochondria, loss of GSTZ1 protein and activity with DCA were even more rapid. The cytosolic in vivo half-lives of the loss of GSTZ1 activity with DCA were 1.05 ± 0.03 and 0.82 ± 0.02 h (mean ± S.D., n = 6) for young and adult rats, respectively, with inactivation significantly more rapid in adult rats, p < 0.001. The mitochondrial inactivation half-lives were similar in young (0.57 ± 0.02 h) and adult rats (0.54 ± 0.02 h) and were significantly (p < 0.0001) shorter than cytosolic inactivation half-lives. By 24 h after DCA administration, activity and expression remained at 10% or less than control values. The in vitro GSTZ1 inactivation half-lives following incubation with 2 mM DCA in the presence of physiological chloride (Cl-) concentrations (cytosol = 44 mM, mitochondria = 1-2 mM) exhibited marked differences between subcellular fractions, being 3 times longer in the cytosol than in the mitochondria, regardless of age, suggesting that the lower Cl- concentration in mitochondria explained the faster degradation of GSTZ1. These results demonstrate for the first time that rat mitochondrial GSTZ1 is more readily inactivated by DCA than cytosolic GSTZ1, and cytosolic GSTZ1 is inactivated more rapidly in adult than young rats.
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Stakišaitis D, Juknevičienė M, Damanskienė E, Valančiūtė A, Balnytė I, Alonso MM. The Importance of Gender-Related Anticancer Research on Mitochondrial Regulator Sodium Dichloroacetate in Preclinical Studies In Vivo. Cancers (Basel) 2019; 11:cancers11081210. [PMID: 31434295 PMCID: PMC6721567 DOI: 10.3390/cancers11081210] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 08/16/2019] [Accepted: 08/16/2019] [Indexed: 12/28/2022] Open
Abstract
Sodium dichloroacetate (DCA) is an investigational medicinal product which has a potential anticancer preparation as a metabolic regulator in cancer cells’ mitochondria. Inhibition of pyruvate dehydrogenase kinases by DCA keeps the pyruvate dehydrogenase complex in the active form, resulting in decreased lactic acid in the tumor microenvironment. This literature review displays the preclinical research data on DCA’s effects on the cell pyruvate dehydrogenase deficiency, pyruvate mitochondrial oxidative phosphorylation, reactive oxygen species generation, and the Na+–K+–2Cl− cotransporter expression regulation in relation to gender. It presents DCA pharmacokinetics and the hepatocarcinogenic effect, and the safety data covers the DCA monotherapy efficacy for various human cancer xenografts in vivo in male and female animals. Preclinical cancer researchers report the synergistic effects of DCA combined with different drugs on cancer by reversing resistance to chemotherapy and promoting cell apoptosis. Researchers note that female and male animals differ in the mechanisms of cancerogenesis but often ignore studying DCA’s effects in relation to gender. Preclinical gender-related differences in DCA pharmacology, pharmacological mechanisms, and the elucidation of treatment efficacy in gonad hormone dependency could be relevant for individualized therapy approaches so that gender-related differences in treatment response and safety can be proposed.
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Affiliation(s)
- Donatas Stakišaitis
- Laboratory of Molecular Oncology, National Cancer Institute, 08660 Vilnius, Lithuania.
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, 44307 Kaunas, Lithuania.
| | - Milda Juknevičienė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, 44307 Kaunas, Lithuania
| | - Eligija Damanskienė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, 44307 Kaunas, Lithuania
| | - Angelija Valančiūtė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, 44307 Kaunas, Lithuania
| | - Ingrida Balnytė
- Department of Histology and Embryology, Medical Academy, Lithuanian University of Health Sciences, 44307 Kaunas, Lithuania
| | - Marta Maria Alonso
- Department of Pediatrics, Clínica Universidad de Navarra, University of Navarra, 55 Pamplona, Spain.
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Yang F, Li J, Deng H, Wang Y, Lei C, Wang Q, Xiang J, Liang L, Xia J, Pan X, Li X, Long Q, Chang L, Xu P, Huang A, Wang K, Tang N. GSTZ1-1 Deficiency Activates NRF2/IGF1R Axis in HCC via Accumulation of Oncometabolite Succinylacetone. EMBO J 2019; 38:e101964. [PMID: 31267557 PMCID: PMC6669923 DOI: 10.15252/embj.2019101964] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 05/24/2019] [Accepted: 06/02/2019] [Indexed: 12/19/2022] Open
Abstract
The IGF1R signaling is important in the malignant progression of cancer. However, overexpression of IGF1R has not been properly assessed in HCC. Here, we revealed that GSTZ1‐1, the enzyme in phenylalanine/tyrosine catabolism, is downregulated in HCC, and its expression was negatively correlated with IGF1R. Mechanistically, GSTZ1‐1 deficiency led to succinylacetone accumulation, alkylation modification of KEAP1, and NRF2 activation, thus promoting IGF1R transcription by recruiting SP1 to its promoter. Moreover, inhibition of IGF1R or NRF2 significantly inhibited tumor‐promoting effects of GSTZ1 knockout in vivo. These findings establish succinylacetone as an oncometabolite, and GSTZ1‐1 as an important tumor suppressor by inhibiting NRF2/IGF1R axis in HCC. Targeting NRF2 or IGF1R may be a promising treatment approach for this subset HCC.
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Affiliation(s)
- Fan Yang
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China.,Department of Infectious Diseases, The First Affiliated Hospital, Chongqing Medical University, Chongqing, China
| | - Jingjing Li
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Haijun Deng
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Yihao Wang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences (Beijing), Beijing Institute of Lifeomics, Beijing, China
| | - Chong Lei
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Qiujie Wang
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Jin Xiang
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Li Liang
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Jie Xia
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Xuanming Pan
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Xiaosong Li
- Department of Infectious Diseases, The First Affiliated Hospital, Chongqing Medical University, Chongqing, China
| | - Quanxin Long
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Lei Chang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences (Beijing), Beijing Institute of Lifeomics, Beijing, China
| | - Ping Xu
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences (Beijing), Beijing Institute of Lifeomics, Beijing, China
| | - Ailong Huang
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Kai Wang
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
| | - Ni Tang
- Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Department of Infectious Diseases, The Second Affiliated Hospital, Institute for Viral Hepatitis, Chongqing Medical University, Chongqing, China
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11
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Zhong G, James MO, Smeltz MG, Jahn SC, Langaee T, Simpson P, Stacpoole PW. Age-Related Changes in Expression and Activity of Human Hepatic Mitochondrial Glutathione Transferase Zeta1. Drug Metab Dispos 2018; 46:1118-1128. [PMID: 29853471 DOI: 10.1124/dmd.118.081810] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 05/29/2018] [Indexed: 12/12/2022] Open
Abstract
Glutathione transferase zeta1 (GSTZ1) catalyzes glutathione (GSH)-dependent dechlorination of dichloroacetate (DCA), an investigational drug with therapeutic potential in metabolic disorders and cancer. GSTZ1 is expressed in both hepatic cytosol and mitochondria. Here, we examined the ontogeny and characterized the properties of human mitochondrial GSTZ1. GSTZ1 expression and activity with DCA were determined in 103 human hepatic mitochondrial samples prepared from livers of donors aged 1 day to 84 years. DNA from each sample was genotyped for three common GSTZ1 functional single nucleotide polymorphisms. Expression of mitochondrial GSTZ1 protein increased in an age-dependent manner to a plateau after age 21 years. Activity with DCA correlated with expression, after taking into account the somewhat higher activity of samples that were homo- or heterozygous for GSTZ1A. In samples from livers with the GSTZ1C variant, apparent enzyme kinetic constants for DCA and GSH were similar for mitochondria and cytosol after correcting for the loss of GSH observed in mitochondrial incubations. In the presence of 38 mM chloride, mitochondrial GSTZ1 exhibited shorter half-lives of inactivation compared with the cytosolic enzyme (P = 0.017). GSTZ1 protein isolated from mitochondria was shown by mass spectrometry to be identical to cytosolic GSTZ1 protein in the covered primary protein sequence. In summary, we report age-related development in the expression and activity of human hepatic mitochondrial GSTZ1 does not have the same pattern as that reported for cytosolic GSTZ1. Some properties of cytosolic and mitochondrial GSTZ1 differed, but these were not related to differences in amino acid sequence or post-translationally modified residues.
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Affiliation(s)
- Guo Zhong
- Department of Medicinal Chemistry (G.Z., M.O.J., M.G.S., S.C.J.), Department of Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida; and Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin (P.S.)
| | - Margaret O James
- Department of Medicinal Chemistry (G.Z., M.O.J., M.G.S., S.C.J.), Department of Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida; and Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin (P.S.)
| | - Marci G Smeltz
- Department of Medicinal Chemistry (G.Z., M.O.J., M.G.S., S.C.J.), Department of Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida; and Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin (P.S.)
| | - Stephan C Jahn
- Department of Medicinal Chemistry (G.Z., M.O.J., M.G.S., S.C.J.), Department of Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida; and Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin (P.S.)
| | - Taimour Langaee
- Department of Medicinal Chemistry (G.Z., M.O.J., M.G.S., S.C.J.), Department of Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida; and Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin (P.S.)
| | - Pippa Simpson
- Department of Medicinal Chemistry (G.Z., M.O.J., M.G.S., S.C.J.), Department of Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida; and Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin (P.S.)
| | - Peter W Stacpoole
- Department of Medicinal Chemistry (G.Z., M.O.J., M.G.S., S.C.J.), Department of Pharmacotherapy and Translational Research (T.L.), Center for Pharmacogenomics (T.L.), and Departments of Medicine and Biochemistry and Molecular Biology (P.W.S.), University of Florida, Gainesville, Florida; and Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin (P.S.)
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12
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Wehmas LC, DeAngelo AB, Hester SD, Chorley BN, Carswell G, Olson GR, George MH, Carter JH, Eldridge SR, Fisher A, Vallanat B, Wood CE. Metabolic Disruption Early in Life is Associated With Latent Carcinogenic Activity of Dichloroacetic Acid in Mice. Toxicol Sci 2017; 159:354-365. [PMID: 28962523 PMCID: PMC6223632 DOI: 10.1093/toxsci/kfx146] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Early-life environmental factors can influence later-life susceptibility to cancer. Recent evidence suggests that metabolic pathways may mediate this type of latency effect. Previously, we reported that short-term exposure to dichloroacetic acid (DCA) increased liver cancer in mice 84 weeks after exposure was stopped. Here, we evaluated time course dynamics for key events related to this effect. This study followed a stop-exposure design in which 28-day-old male B6C3F1 mice were given the following treatments in drinking water for up to 93 weeks: deionized water (dH2O, control); 3.5 g/l DCA continuously; or 3.5 g/l DCA for 4-52 weeks followed by dH2O. Effects were evaluated at eight interim time points. A short-term biomarker study was used to evaluate DCA effects at 6, 15, and 30 days. Liver tumor incidence was higher in all DCA treatment groups, including carcinomas in 82% of mice previously treated with DCA for only 4 weeks. Direct effects of DCA in the short-term study included decreased liver cell proliferation and marked mRNA changes related to mitochondrial dysfunction and altered cell metabolism. However, all observed short-term effects of DCA were ultimately reversible, and prior DCA treatment did not affect liver cell proliferation, apoptosis, necrosis, or DNA sequence variants with age. Key intermediate events resulting from transient DCA exposure do not fit classical cytotoxic, mitogenic, or genotoxic modes of action for carcinogenesis, suggesting a distinct mechanism associated with early-life metabolic disruption.
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Affiliation(s)
- Leah C. Wehmas
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Anthony B. DeAngelo
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Susan D. Hester
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Brian N. Chorley
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Gleta Carswell
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Greg R. Olson
- Toxicologic Pathology Associates, Jefferson, AK,
USA
| | - Michael H. George
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | | | | | - Anna Fisher
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Beena Vallanat
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
| | - Charles E. Wood
- National Health and Environmental Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC,
USA
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13
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A Mechanism-Based Pharmacokinetic Enzyme Turnover Model for Dichloroacetic Acid Autoinhibition in Rats. J Pharm Sci 2017; 106:1396-1404. [PMID: 28163135 DOI: 10.1016/j.xphs.2017.01.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 01/18/2017] [Accepted: 01/27/2017] [Indexed: 12/15/2022]
Abstract
Dichloroacetic acid (DCA), a halogenated organic acid, is a pyruvate dehydrogenase kinase inhibitor that has been used to treat congenital or acquired lactic acidosis and is currently in early-phase clinical trials for cancer treatment. DCA was found to inhibit its own metabolism by irreversibly inactivating glutathione transferase zeta 1 (GSTZ1-1), resulting in nonlinear kinetics and abnormally high accumulation ratio after repeated dosing. In this analysis, a semi-mechanistic pharmacokinetic enzyme turnover model was developed for the first time to capture DCA autoinhibition, gastrointestinal region-dependent absorption, and time-dependent change in bioavailability in rats. The maximum rate constant for DCA-induced GSTZ1-1 inactivation is estimated to be 0.96/h, which is 110 times that of the rate constant for GSTZ1-1 natural degradation (0.00875/h). The model-predicted DCA concentration that corresponds to 50% of maximum enzyme inhibition (EC50) is 4.32 mg/L. The constructed pharmacokinetic enzyme turnover model, when applied to human data, could be used to predict the accumulation of DCA after repeated oral dosing, guide selection of dosing regimens in clinical studies, and facilitate clinical development of DCA.
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14
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Advances in drug metabolism and pharmacogenetics research in Australia. Pharmacol Res 2017; 116:7-19. [DOI: 10.1016/j.phrs.2016.12.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 12/07/2016] [Accepted: 12/08/2016] [Indexed: 01/04/2023]
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15
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James MO, Jahn SC, Zhong G, Smeltz MG, Hu Z, Stacpoole PW. Therapeutic applications of dichloroacetate and the role of glutathione transferase zeta-1. Pharmacol Ther 2016; 170:166-180. [PMID: 27771434 DOI: 10.1016/j.pharmthera.2016.10.018] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dichloroacetate (DCA) has several therapeutic applications based on its pharmacological property of inhibiting pyruvate dehydrogenase kinase. DCA has been used to treat inherited mitochondrial disorders that result in lactic acidosis, as well as pulmonary hypertension and several different solid tumors, the latter through its ability to reverse the Warburg effect in cancer cells and restore aerobic glycolysis. The main clinically limiting toxicity is reversible peripheral neuropathy. Although administration of high doses to rodents can result in liver cancer, there is no evidence that DCA is a human carcinogen. In all studied species, including humans, DCA has the interesting property of inhibiting its own metabolism upon repeat dosing, resulting in alteration of its pharmacokinetics. The first step in DCA metabolism is conversion to glyoxylate catalyzed by glutathione transferase zeta 1 (GSTZ1), for which DCA is a mechanism-based inactivator. The rate of GSTZ1 inactivation by DCA is influenced by age, GSTZ1 haplotype and cellular concentrations of chloride. The effect of DCA on its own metabolism complicates the selection of an effective dose with minimal side effects.
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Affiliation(s)
- Margaret O James
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States.
| | - Stephan C Jahn
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States
| | - Guo Zhong
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States
| | - Marci G Smeltz
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States
| | - Zhiwei Hu
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States
| | - Peter W Stacpoole
- Department of Medicine, University of Florida, Gainesville, FL 32610-0226, United States; Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, United States
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16
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Lu L, Pandey AK, Houseal MT, Mulligan MK. The Genetic Architecture of Murine Glutathione Transferases. PLoS One 2016; 11:e0148230. [PMID: 26829228 PMCID: PMC4734686 DOI: 10.1371/journal.pone.0148230] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 01/14/2016] [Indexed: 12/17/2022] Open
Abstract
Glutathione S-transferase (GST) genes play a protective role against oxidative stress and may influence disease risk and drug pharmacokinetics. In this study, massive multiscalar trait profiling across a large population of mice derived from a cross between C57BL/6J (B6) and DBA2/J (D2)—the BXD family—was combined with linkage and bioinformatic analyses to characterize mechanisms controlling GST expression and to identify downstream consequences of this variation. Similar to humans, mice show a wide range in expression of GST family members. Variation in the expression of Gsta4, Gstt2, Gstz1, Gsto1, and Mgst3 is modulated by local expression QTLs (eQTLs) in several tissues. Higher expression of Gsto1 in brain and liver of BXD strains is strongly associated (P < 0.01) with inheritance of the B6 parental allele whereas higher expression of Gsta4 and Mgst3 in brain and liver, and Gstt2 and Gstz1 in brain is strongly associated with inheritance of the D2 parental allele. Allele-specific assays confirmed that expression of Gsto1, Gsta4, and Mgst3 are modulated by sequence variants within or near each gene locus. We exploited this endogenous variation to identify coexpression networks and downstream targets in mouse and human. Through a combined systems genetics approach, we provide new insight into the biological role of naturally occurring variants in GST genes.
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Affiliation(s)
- Lu Lu
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38106, United States of America
- Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, 226001, China
| | - Ashutosh K. Pandey
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38106, United States of America
| | - M. Trevor Houseal
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38106, United States of America
| | - Megan K. Mulligan
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, 38106, United States of America
- * E-mail:
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17
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Moore JD, Staniszewska A, Shaw T, D'Alessandro J, Davis B, Surgenor A, Baker L, Matassova N, Murray J, Macias A, Brough P, Wood M, Mahon PC. VER-246608, a novel pan-isoform ATP competitive inhibitor of pyruvate dehydrogenase kinase, disrupts Warburg metabolism and induces context-dependent cytostasis in cancer cells. Oncotarget 2015; 5:12862-76. [PMID: 25404640 PMCID: PMC4350332 DOI: 10.18632/oncotarget.2656] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 11/02/2014] [Indexed: 11/25/2022] Open
Abstract
Pyruvate dehydrogenase kinase (PDK) is a pivotal enzyme in cellular energy metabolism that has previously been implicated in cancer through both RNAi based studies and clinical correlations with poor prognosis in several cancer types. Here, we report the discovery of a novel and selective ATP competitive pan-isoform inhibitor of PDK, VER-246608. Consistent with a PDK mediated MOA, VER-246608 increased pyruvate dehydrogenase complex (PDC) activity, oxygen consumption and attenuated glycolytic activity. However, these effects were only observed under D-glucose-depleted conditions and required almost complete ablation of PDC E1α subunit phosphorylation. VER-246608 was weakly anti-proliferative to cancer cells in standard culture media; however, depletion of either serum or combined D-glucose/L-glutamine resulted in enhanced cellular potency. Furthermore, this condition-selective cytostatic effect correlated with reduced intracellular pyruvate levels and an attenuated compensatory response involving deamination of L-alanine. In addition, VER-246608 was found to potentiate the activity of doxorubicin. In contrast, the lipoamide site inhibitor, Nov3r, demonstrated sub-maximal inhibition of PDK activity and no evidence of cellular activity. These studies suggest that PDK inhibition may be effective under the nutrient-depleted conditions found in the tumour microenvironment and that combination treatments should be explored to reveal the full potential of this therapeutic strategy.
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Affiliation(s)
- Jonathan D Moore
- Vernalis (R&D) Ltd, Granta Park, Cambridge, UK. Current address: Horizon discovery, Cambridge Research Park, Waterbeach, Cambridge, UK
| | | | | | | | - Ben Davis
- Vernalis (R&D) Ltd, Granta Park, Cambridge, UK
| | | | - Lisa Baker
- Vernalis (R&D) Ltd, Granta Park, Cambridge, UK
| | | | | | - Alba Macias
- Vernalis (R&D) Ltd, Granta Park, Cambridge, UK
| | - Paul Brough
- Vernalis (R&D) Ltd, Granta Park, Cambridge, UK
| | - Mike Wood
- Vernalis (R&D) Ltd, Granta Park, Cambridge, UK
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18
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Dourado DFAR, Fernandes PA, Mannervik B, Ramos MJ. Isomerization of Δ5-androstene-3,17-dione into Δ4-androstene-3,17-dione catalyzed by human glutathione transferase A3-3: a computational study identifies a dual role for glutathione. J Phys Chem A 2014; 118:5790-800. [PMID: 24739064 DOI: 10.1021/jp410810q] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Glutathione transferases (GSTs) are important enzymes in the metabolism of electrophilic xenobiotic and endobiotic toxic compounds. In addition, human GST A3-3 also catalyzes the double bond isomerization of Δ5-androstene-3,17-dione (Δ(5)-AD) and Δ(5)-pregnene-3,20-dione (Δ(5)-PD), which are the immediate precursors of testosterone and progesterone. In fact, GST A3-3 is the most efficient human enzyme known to exist in the catalysis of these reactions. In this work, we have used density functional theory (DFT) calculations to propose a refined mechanism for the isomerization of Δ(5)-AD catalyzed by GST A3-3. In this mechanism the glutathione (GSH) thiol and Tyr9 catalyze the proton transfer from the Δ(5)-AD C4 atom to the Δ(5)-AD C6 atom, with a rate limiting activation energy of 15.8 kcal · mol(-1). GSH has a dual function, because it is also responsible for stabilizing the negative charge that is formed in the O3 atom of the enolate intermediate. The catalytic role of Tyr9 depends on significant conformational rearrangements of its side chain. Neither of these contributions to catalysis has been observed before. Residues Phe10, Leu111, Ala 208, and Ala 216 complete the list of the important catalytic residues. The mechanism detailed here is based on the GST A3-3:GSH:Δ(4)-AD crystal structure and is consistent with all available experimental data.
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Affiliation(s)
- Daniel F A R Dourado
- REQUIMTE/Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto , Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal
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19
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Zhong G, Li W, Gu Y, Langaee T, Stacpoole PW, James MO. Chloride and other anions inhibit dichloroacetate-induced inactivation of human liver GSTZ1 in a haplotype-dependent manner. Chem Biol Interact 2014; 215:33-9. [PMID: 24632415 DOI: 10.1016/j.cbi.2014.02.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 02/15/2014] [Accepted: 02/28/2014] [Indexed: 11/16/2022]
Abstract
The in vivo elimination rate of dichloroacetate (DCA), an investigational drug; is determined by the rate of its biotransformation to glyoxylate, catalyzed by glutathione transferase ζ1 (GSTZ1). DCA is a mechanism-based inactivator of GSTZ1, thus elimination of DCA is slowed with repeated dosing. We observed that chloride, a physiologically important anion, attenuated DCA-induced GSTZ1 inactivation in human liver cytosol in a concentration and GSTZ1 haplotype-dependent way. In the absence of chloride, incubation with 0.5mM DCA resulted in inactivation of GSTZ1 with a half-life of 0.4h (samples with the KRT haplotype) to 0.5h (EGT haplotype). At the hepatic physiological chloride concentration, 38mM, samples with the EGT haplotype retained more activity (80%) following a 2-h incubation with 0.5mM DCA than those possessing the KRT haplotype (55%). The chloride concentration that protected 50% of the GSTZ1 activity following 2-h incubation with 0.5mM DCA (EC50) was 15.0±3.1mM (mean±S.D., n=3) for EGT samples and 36.2±2.2mM for KRT samples. Bromide, iodide and sulfite also protected GSTZ1 from inactivation by DCA, however fluoride, sulfate, carbonate, acetate, cyanide did not. Protection by bromide varied by GSTZ1 haplotype: EC50 was 1.3±0.3mM for the EGT haplotype and 5.0±0.60mM for the KRT haplotype. The EC50 values for iodide and sulfite in liver cytosol samples with EGT haplotype were respectively 0.14±0.06mM and 9.6±1.1mM (mean±S.D., n=3). Because the in vivo half-life of DCA is determined by the fraction of active GSTZ1 in the liver, identifying factors that regulate GSTZ1 activity is important in determining appropriate DCA dosing in humans.
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Affiliation(s)
- Guo Zhong
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States
| | - Wenjun Li
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States
| | - Yuan Gu
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States
| | - Taimour Langaee
- Center for Pharmacogenomics, College of Pharmacy, University of Florida, Gainesville, FL 32610-0486, United States
| | - Peter W Stacpoole
- Department of Medicine, University of Florida, Gainesville, FL 32610-0226, United States; Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610-0226, United States
| | - Margaret O James
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610-0485, United States.
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20
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Bocedi A, Fabrini R, Farrotti A, Stella L, Ketterman AJ, Pedersen JZ, Allocati N, Lau PCK, Grosse S, Eltis LD, Ruzzini A, Edwards TE, Morici L, Del Grosso E, Guidoni L, Bovi D, Lo Bello M, Federici G, Parker MW, Board PG, Ricci G. The impact of nitric oxide toxicity on the evolution of the glutathione transferase superfamily: a proposal for an evolutionary driving force. J Biol Chem 2013; 288:24936-47. [PMID: 23828197 DOI: 10.1074/jbc.m113.476135] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glutathione transferases (GSTs) are protection enzymes capable of conjugating glutathione (GSH) to toxic compounds. During evolution an important catalytic cysteine residue involved in GSH activation was replaced by serine or, more recently, by tyrosine. The utility of these replacements represents an enigma because they yield no improvements in the affinity toward GSH or in its reactivity. Here we show that these changes better protect the cell from nitric oxide (NO) insults. In fact the dinitrosyl·diglutathionyl·iron complex (DNDGIC), which is formed spontaneously when NO enters the cell, is highly toxic when free in solution but completely harmless when bound to GSTs. By examining 42 different GSTs we discovered that only the more recently evolved Tyr-based GSTs display enough affinity for DNDGIC (KD < 10(-9) M) to sequester the complex efficiently. Ser-based GSTs and Cys-based GSTs show affinities 10(2)-10(4) times lower, not sufficient for this purpose. The NO sensitivity of bacteria that express only Cys-based GSTs could be related to the low or null affinity of their GSTs for DNDGIC. GSTs with the highest affinity (Tyr-based GSTs) are also over-represented in the perinuclear region of mammalian cells, possibly for nucleus protection. On the basis of these results we propose that GST evolution in higher organisms could be linked to the defense against NO.
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Affiliation(s)
- Alessio Bocedi
- Department of Chemical Sciences and Technologies, University of Rome, Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
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21
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Board PG, Menon D. Glutathione transferases, regulators of cellular metabolism and physiology. Biochim Biophys Acta Gen Subj 2012. [PMID: 23201197 DOI: 10.1016/j.bbagen.2012.11.019] [Citation(s) in RCA: 259] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND The cytosolic glutathione transferases (GSTs) comprise a super family of proteins that can be categorized into multiple classes with a mixture of highly specific and overlapping functions. SCOPE OF REVIEW The review covers the genetics, structure and function of the human cytosolic GSTs with particular attention to their emerging roles in cellular metabolism. MAJOR CONCLUSIONS All the catalytically active GSTs contribute to the glutathione conjugation or glutathione dependant-biotransformation of xenobiotics and many catalyze glutathione peroxidase or thiol transferase reactions. GSTs also catalyze glutathione dependent isomerization reactions required for the synthesis of several prostaglandins and steroid hormones and the catabolism of tyrosine. An increasing body of work has implicated several GSTs in the regulation of cell signaling pathways mediated by stress-activated kinases like Jun N-terminal kinase. In addition, some members of the cytosolic GST family have been shown to form ion channels in intracellular membranes and to modulate ryanodine receptor Ca(2+) channels in skeletal and cardiac muscle. GENERAL SIGNIFICANCE In addition to their well established roles in the conjugation and biotransformation of xenobiotics, GSTs have emerged as significant regulators of pathways determining cell proliferation and survival and as regulators of ryanodine receptors that are essential for muscle function. This article is part of a Special Issue entitled Cellular functions of glutathione.
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Affiliation(s)
- Philip G Board
- John Curtin School of Medical Research, Australian National University, Canberra, Australia
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Dichloroacetic acid up-regulates hepatic glutathione synthesis via the induction of glutamate–cysteine ligase. Biochem Pharmacol 2012; 83:427-33. [DOI: 10.1016/j.bcp.2011.11.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 11/15/2011] [Accepted: 11/15/2011] [Indexed: 12/21/2022]
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Li W, Gu Y, James MO, Hines RN, Simpson P, Langaee T, Stacpoole PW. Prenatal and postnatal expression of glutathione transferase ζ 1 in human liver and the roles of haplotype and subject age in determining activity with dichloroacetate. Drug Metab Dispos 2011; 40:232-9. [PMID: 22028318 DOI: 10.1124/dmd.111.041533] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Glutathione transferase ζ 1 (GSTZ1), also known as maleylacetoacetate isomerase, catalyzes the penultimate step of tyrosine catabolism and metabolizes several α-halocarboxylic acids, including dichloroacetic acid (DCA), an investigational drug used for lactic acidosis and, recently, solid tumors. Age-related differences have been suggested in DCA pharmacotoxicology, but no information is available on GSTZ1 ontogeny in humans. Here, we investigated the cytosolic GSTZ1 developmental expression pattern and the influence of haplotype on GSTZ1 activity with DCA by using human livers from donors between 10 weeks gestation and 74 years. GSTZ1 expression was very low in fetal livers (<2 pmol of GSTZ1/mg cytosol). The expression began to increase after birth in an age-dependent manner until age 7 years. GSTZ1 was then sustained at stable, yet variable, levels (median, 20.0 pmol/mg cytosol; range, 4.8-47.3 pmol/mg cytosol) until age 74 years. GSTZ1 activity with DCA was strongly associated with haplotype and expression level. Samples homozygous or heterozygous for GSTZ1A exhibited ∼3-fold higher DCA dechlorinating activity than samples carrying other alleles at a given level of expression. The correlations (r²) between activity and expression were 0.90 and 0.68, respectively, for GSTZ1A carriers (n = 11) and noncarriers (n = 61). GSTZ1 is expressed in mitochondria in addition to cytosol. The GSTZ1A allele exhibited similar effects in the mitochondrial fraction by conferring a higher activity with DCA. In summary, we report a neonatal onset and an age-related increase in GSTZ1 protein expression during human liver development. Haplotype influenced GSTZ1 activity with DCA but not protein expression.
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Affiliation(s)
- Wenjun Li
- Department of Medicinal Chemistry, College of Pharmacy, University of Florida, Gainesville, FL 32610-0485, USA
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Board PG, Anders MW. Glutathione transferase zeta: discovery, polymorphic variants, catalysis, inactivation, and properties of Gstz1-/- mice. Drug Metab Rev 2011; 43:215-25. [PMID: 21303221 DOI: 10.3109/03602532.2010.549132] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Glutathione transferase zeta (GSTZ1) is a member of the GST superfamily of proteins that catalyze the reaction of glutathione with endo- and xenobiotics. GSTZ1-1 was discovered by a bioinformatics strategy that searched the human-expressed sequence-tag database with a sequence that matched a putative plant GST. A sequence that was found was expressed and termed GSTZ1-1. In common with other GSTs, GSTZ1-1 showed some peroxidase activity, but lacked activity with most known GST substrates. GSTZ1-1 was also found to be identical with maleylacetoacetate isomerase, which catalyzes the penultimate step in the tyrosine-degradation pathway. Further studies showed that dichloroacetate (DCA) and a range of α-haloalkanoates and α,α-dihaloalkanoates were substrates. A subsequent search of the human-expressed sequence-tag database showed the presence of four polymorphic alleles: 1a, 1b, 1c, and 1d; GSTZ1c was the most common and was designated as the wild-type gene. DCA was shown to be a k(cat) inactivator of human, rat, and mouse GSTZ1-1; human GSTZ1-1 was more resistant to inactivation than mouse or rat GSTZ1-1. Proteomic analysis showed that hGSTZ1-1 was inactivated when Cys-16 was modified by glutathione and the carbon skeleton of DCA. The polymorphic variants of hGSTZ1-1 differ in their susceptibility to inactivation, with 1a-1a being more resistant to inactivation than the other variants. The targeted deletion of GSTZ1 yielded mice that were not phenotypically distinctive. Phenylalanine proved, however, to be toxic to Gstz1(-/-) mice, and these mice showed evidence of organ damage and leucopenia.
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Affiliation(s)
- Philip G Board
- Molecular Genetics Group, John Curtin School of Medical Research, Australian National University, Canberra, Australia
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Hassoun EA, Cearfoss J. Dichloroacetate- and Trichloroacetate-Induced Modulation of Superoxide Dismutase, Catalase, and Glutathione Peroxidase Activities and Glutathione Level in the livers of Mice after Subacute and Subchronic exposure. TOXICOLOGICAL AND ENVIRONMENTAL CHEMISTRY 2011; 93:332-344. [PMID: 21170174 PMCID: PMC3002262 DOI: 10.1080/02772248.2010.509602] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Dichloroacetate (DCA) and trichloroacetate (TCA) were previously found to induce various levels of oxidative stress in the hepatic tissues of mice after subacute and subchronic exposure. The cells are known to have several protective mechansims against production of oxidative stress by different xenobiotics. To assess the roles of the antioxidant enzymes and glutathione (GSH) in DCA- and TCA-induced oxidative stress, groups of B6C3F1 mice were administered either DCA or TCA at doses of 7.7, 77, 154 and 410 mg/kg/day, by gavage for 4 weeks (4-W) and 13 weeks (13-W), and superoxide dismutase (SOD) catalase (CAT) and glutathione peroxidase (GSH-Px) activities, as well as GSH were determined in the hepatic tissues. DCA at doses ranging between 7.7-410, and 7.7-77 mg/kg/day, given for 4-W and 13-W, respectively, resulted in either suppression or no change in SOD, CAT and GSH-Px activities, but doses of 154-410 mg DCA/kg/day administered for 13-W were found to result in significant induction of the three enzyme activities. TCA administration on the other hand, resulted in increases in SOD and CAT activities, and suppression of GSH-Px activity in both periods. Except for the DCA doses of 77-154 mg/kg/day administered for 13-W that resulted in significant reduction in GSH levels, all other DCA, as well as TCA treatments produced no changes in GSH. Since these enzymes are involved in the detoxification of the reactive oxygen species (ROS), superoxide anion (SA) and H(2)O(2), it is concluded that SA is the main contributor to DCA-induced oxidative stress while both ROS contribute to that of TCA. The increases in the enzyme activities associated with 154-410 mg DCA/kg/day in the 13-W period suggest their role as protective mechanisms contributing to the survival of cells modified in response to those treatments.
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Stacpoole PW. The dichloroacetate dilemma: environmental hazard versus therapeutic goldmine--both or neither? ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:155-8. [PMID: 20920954 PMCID: PMC3040600 DOI: 10.1289/ehp.1002554] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 10/04/2010] [Indexed: 05/23/2023]
Abstract
BACKGROUND Dichloroacetate (DCA) is known to environmental scientists as a by-product of water chlorination and as a metabolite of industrial solvents, including Superfund chemicals. In contrast, DCA is studied by clinical investigators for its therapeutic potential in several life-threatening conditions, including genetic mitochondrial diseases, pulmonary arterial hypertension, and cancer. Thus, DCA holds an almost unique position at the interface between environmental science and allopathic medicine. OBJECTIVE I critically reviewed laboratory and clinical pharmacological research on DCA to address questions about the current and future status of DCA in relation to human health. DISCUSSION Recent information on the clinical toxicogenetics of DCA is interpreted particularly in light of its use as an investigational drug. Adverse effects from chronic DCA exposure have been identified in several target organs in animals. However, in humans, toxicity has so far been limited to reversible effects on the nervous system and liver. DCA is primarily biotransformed to glyoxylate by the bifunctional enzyme glutathione transferase zeta1 and maleylacetoacetate isomerase (GSTz1/MAAI), which also catalyzes the penultimate step in the phenylalanine and tyrosine catabolic pathway. DCA is a suicide inhibitor of GSTz1/MAAI, which can result in delayed plasma clearance of DCA and the accumulation of potentially toxic tyrosine intermediates. Age and GSTz1/MAAI haplotype can markedly affect the toxicokinetics of DCA in humans and rodents. CONCLUSIONS I have defined new potential avenues of research that focus on discrete human populations that may be at increased health risk or that may receive increased health benefit from chronic exposure to DCA at both environmentally and clinically relevant concentrations.
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Affiliation(s)
- Peter W Stacpoole
- Department of Medicine, Division of Endocrinology and Metabolism, College of Medicine, University of Florida, Gainesville, Florida 32610, USA.
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Schmidt MM, Rohwedder A, Dringen R. Effects of Chlorinated Acetates on the Glutathione Metabolism and on Glycolysis of Cultured Astrocytes. Neurotox Res 2010; 19:628-37. [DOI: 10.1007/s12640-010-9209-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 06/29/2010] [Accepted: 07/01/2010] [Indexed: 01/05/2023]
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Matthews JL, Schultz IR, Easterling MR, Melnick RL. Physiologically based pharmacokinetic modeling of dibromoacetic acid in F344 rats. Toxicol Appl Pharmacol 2010; 244:196-207. [PMID: 20045428 DOI: 10.1016/j.taap.2009.12.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 12/18/2009] [Accepted: 12/22/2009] [Indexed: 11/24/2022]
Abstract
A novel physiologically based pharmacokinetic (PBPK) model structure, which includes submodels for the common metabolites (glyoxylate (GXA) and oxalate (OXA)) that may be involved in the toxicity or carcinogenicity of dibromoacetic acid (DBA), has been developed. Particular attention is paid to the representation of hepatic metabolism, which is the primary elimination mechanism. DBA-induced suicide inhibition is modeled by irreversible covalent binding of the intermediate metabolite alpha-halocarboxymethylglutathione (alphaH1) to the glutathione-S-transferase zeta (GSTzeta) enzyme. We also present data illustrating the presence of a secondary non-GSTzeta metabolic pathway for DBA, but not dichloroacetic acid (DCA), that produces GXA. The model is calibrated with plasma and urine concentration data from DBA exposures in female F344 rats through intravenous (IV), oral gavage, and drinking water routes. Sensitivity analysis is performed to confirm identifiability of estimated parameters. Finally, model validation is performed with data sets not used during calibration. Given the structural similarity of dihaloacetates (DHAs), we hypothesize that the PBPK model presented here has the capacity to describe the kinetics of any member or mixture of members of this class in any species with the alteration of chemical-and species-specific parameters.
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Affiliation(s)
- Jessica L Matthews
- SRA International, Inc., 2605 Meridian Parkway, Suite 200, Durham, NC, 27713, USA.
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Phenylalanine-induced leucopenia in genetic and dichloroacetic acid generated deficiency of glutathione transferase Zeta. Biochem Pharmacol 2009; 77:1358-63. [DOI: 10.1016/j.bcp.2009.01.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Revised: 01/23/2009] [Accepted: 01/23/2009] [Indexed: 11/23/2022]
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Hassoun EA, Mehta J. Dichloroacetate-induced modulation of cellular antioxidant enzyme activities and glutathione level in the J774A.1 cells. J Appl Toxicol 2009; 28:931-7. [PMID: 18493934 DOI: 10.1002/jat.1356] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Dichloroacetate (DCA) is used for different medical and industrial purposes and has been found to be a toxic by-product produced during the process of water chlorination. The DCA effects on superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) activities and glutathione (GSH) level were assessed and correlated with each other and also with cellular viabilities in J774A.1 macrophage cells. A concentration of 24 mm of DCA resulted in time-dependent decreases in cellular viability and glutathione level, and time-dependent increases in SOD activity when incubated with the cells for 24-48 h. DCA also resulted in significant increases in CAT and GSH-Px activities of the viable cells when incubated with the cells for 36 and 48 h. The changes in antioxidant enzyme activities and GSH levels were found to be strongly correlated with each other, and with cellular viabilities at different time points. While GSH did not result in any significant effects when added to the cells at concentrations ranging between 15 and 60 nmol ml(-1), it resulted in concentration-dependent increases in cellular viability when added to the DCA-treated cells, with maximal effects achieved at 45-60 nmol GSH ml(-1). However, cellular viability of the GSH + DCA treated cells remained below that of the control. Since viable cells from the DCA-treated cultures displayed significantly higher antioxidant enzyme activities compared with the control, it is concluded that those increases may have contributed to the cellular protection against DCA-induced cell death. Also, glutathione depletion has a major contribution to the observed cellular death induced by DCA.
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Affiliation(s)
- Ezdihar A Hassoun
- The University of Toledo, College of Pharmacy, Toledo, OH 43606, USA.
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Clewell HJ, Andersen ME. Applying Mode-of-Action and Pharmacokinetic Considerations in Contemporary Cancer Risk Assessments: An Example with Trichloroethylene. Crit Rev Toxicol 2008; 34:385-445. [PMID: 15560567 DOI: 10.1080/10408440490500795] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The guidelines for carcinogen risk assessment recently proposed by the U.S. Environmental Protection Agency (U.S. EPA) provide an increased opportunity for the consideration of pharmacokinetic and mechanistic data in the risk assessment process. However, the greater flexibility of the new guidelines can also make their actual implementation for a particular chemical highly problematic. To illuminate the process of performing a cancer risk assessment under the new guidelines, the rationale for a state-of-the-science risk assessment for trichloroethylene (TCE) is presented. For TCE, there is evidence of increased cell proliferation due to receptor interaction or cytotoxicity in every instance in which tumors are observed, and most tumors represent an increase in the incidence of a commonly observed, species-specific lesion. A physiologically based pharmacokinetic (PBPK) model was applied to estimate target tissue doses for the three principal animal tumors associated with TCE exposure: liver, lung, and kidney. The lowest points of departure (lower bound estimates of the exposure associated with 10% tumor incidence) for lifetime human exposure to TCE were obtained for mouse liver tumors, assuming a mode of action primarily involving the mitogenicity of the metabolite trichloroacetic acid (TCA). The associated linear unit risk estimates for mouse liver tumors are 1.5 x 10(-6) for lifetime exposure to 1 microg TCE per cubic meter in air and 0.4 x 10(-6) for lifetime exposure to 1 microg TCE per liter in drinking water. However, these risk estimates ignore the evidence that the human is likely to be much less responsive than the mouse to the carcinogenic effects of TCA in the liver and that the carcinogenic effects of TCE are unlikely to occur at low environmental exposures. Based on consideration of the most plausible carcinogenic modes of action of TCE, a margin-of-exposure (MOE) approach would appear to be more appropriate. Applying an MOE of 1000, environmental exposures below 66 microg TCE per cubic meter in air and 265 microg TCE per liter in drinking water are considered unlikely to present a carcinogenic hazard to human health.
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Stacpoole PW, Kurtz TL, Han Z, Langaee T. Role of dichloroacetate in the treatment of genetic mitochondrial diseases. Adv Drug Deliv Rev 2008; 60:1478-87. [PMID: 18647626 DOI: 10.1016/j.addr.2008.02.014] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2008] [Accepted: 02/22/2008] [Indexed: 02/06/2023]
Abstract
Dichloroacetate (DCA) is an investigational drug for the treatment of genetic mitochondrial diseases. Its primary site of action is the pyruvate dehydrogenase (PDH) complex, which it stimulates by altering its phosphorylation state and stability. DCA is metabolized by and inhibits the bifunctional zeta-1 family isoform of glutathione transferase/maleylacetoacetate isomerase. Polymorphic variants of this enzyme differ in their kinetic properties toward DCA, thereby influencing its biotransformation and toxicity, both of which are also influenced by subject age. Results from open label studies and controlled clinical trials suggest chronic oral DCA is generally well-tolerated by young children and may be particularly effective in patients with PDH deficiency. Recent in vitro data indicate that a combined DCA and gene therapy approach may also hold promise for the treatment of this devastating condition.
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Marsh M, Shoemark DK, Jacob A, Robinson C, Cahill B, Zhou NY, Williams PA, Hadfield AT. Structure of bacterial glutathione-S-transferase maleyl pyruvate isomerase and implications for mechanism of isomerisation. J Mol Biol 2008; 384:165-77. [PMID: 18824004 DOI: 10.1016/j.jmb.2008.09.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 09/01/2008] [Accepted: 09/09/2008] [Indexed: 11/30/2022]
Abstract
Maleyl pyruvate isomerase (MPI) is a bacterial glutathione S-transferase (GST) from the pathway for degradation of naphthalene via gentisate that enables the bacterium Ralstonia to use polyaromatic hydrocarbons as a sole carbon source. Genome sequencing projects have revealed the presence of large numbers of GSTs in bacterial genomes, often located within gene clusters encoding the degradation of different aromatic compounds. This structure is therefore an example of this under-represented class of enzymes. Unlike many glutathione transferases, the reaction catalysed by MPI is an isomerisation of an aromatic ring breakdown product, and glutathione is a true cofactor rather than a substrate in the reaction. We have solved the structure of the enzyme in complex with dicarboxyethyl glutathione, an analogue of a proposed reaction intermediate, at a resolution of 1.3 A. The structure provides direct evidence that the glutathione thiolate attacks the substrate in the C2 position, with the terminal carboxylate buried at the base of the active site cleft. Our structures suggest that the C1-C2 bond remains fixed so when rotation occurs around the C2-C3 bond the atoms from C4 onwards actually move. We identified a conserved arginine that is likely to stabilize the enolate form of the substrate during the isomerisation. Arginines at either side of the active site cleft can interact with the end of the substrate/product and preferentially stabilise the product. MPI has significant sequence similarity to maleylacetoacetate isomerase (MAAI), which performs an analogous reaction in the catabolism of phenylalanine and tyrosine. The proposed mechanism therefore has relevance to the MAAIs. Significantly, whilst the overall sequence identity is 40% only one of the five residues from the Zeta motif in the active site is conserved. We re-examined the roles of the residues in the active site of both enzymes and the Zeta motif itself.
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Affiliation(s)
- May Marsh
- Department of Biochemistry and Centre for Molecular Recognition, University of Bristol, School of Medical Sciences, University Walk, Bristol BS81TD, UK
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McFate T, Mohyeldin A, Lu H, Thakar J, Henriques J, Halim ND, Wu H, Schell MJ, Tsang TM, Teahan O, Zhou S, Califano JA, Jeoung NH, Harris RA, Verma A. Pyruvate dehydrogenase complex activity controls metabolic and malignant phenotype in cancer cells. J Biol Chem 2008; 283:22700-8. [PMID: 18541534 DOI: 10.1074/jbc.m801765200] [Citation(s) in RCA: 293] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
High lactate generation and low glucose oxidation, despite normal oxygen conditions, are commonly seen in cancer cells and tumors. Historically known as the Warburg effect, this altered metabolic phenotype has long been correlated with malignant progression and poor clinical outcome. However, the mechanistic relationship between altered glucose metabolism and malignancy remains poorly understood. Here we show that inhibition of pyruvate dehydrogenase complex (PDC) activity contributes to the Warburg metabolic and malignant phenotype in human head and neck squamous cell carcinoma. PDC inhibition occurs via enhanced expression of pyruvate dehydrogenase kinase-1 (PDK-1), which results in inhibitory phosphorylation of the pyruvate dehydrogenase alpha (PDHalpha) subunit. We also demonstrate that PDC inhibition in cancer cells is associated with normoxic stabilization of the malignancy-promoting transcription factor hypoxia-inducible factor-1alpha (HIF-1alpha) by glycolytic metabolites. Knockdown of PDK-1 via short hairpin RNA lowers PDHalpha phosphorylation, restores PDC activity, reverts the Warburg metabolic phenotype, decreases normoxic HIF-1alpha expression, lowers hypoxic cell survival, decreases invasiveness, and inhibits tumor growth. PDK-1 is an HIF-1-regulated gene, and these data suggest that the buildup of glycolytic metabolites, resulting from high PDK-1 expression, may in turn promote HIF-1 activation, thus sustaining a feed-forward loop for malignant progression. In addition to providing anabolic support for cancer cells, altered fuel metabolism thus supports a malignant phenotype. Correction of metabolic abnormalities offers unique opportunities for cancer treatment and may potentially synergize with other cancer therapies.
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Affiliation(s)
- Thomas McFate
- Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA
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Hassoun EA, Dey S. Dichloroacetate- and trichloroacetate-induced phagocytic activation and production of oxidative stress in the hepatic tissues of mice after acute exposure. J Biochem Mol Toxicol 2008; 22:27-34. [DOI: 10.1002/jbt.20210] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Li T, Schultz I, Keys DA, Campbell JL, Fisher JW. Quantitative evaluation of dichloroacetic acid kinetics in human--a physiologically based pharmacokinetic modeling investigation. Toxicology 2007; 245:35-48. [PMID: 18242812 DOI: 10.1016/j.tox.2007.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Revised: 12/11/2007] [Accepted: 12/12/2007] [Indexed: 10/22/2022]
Abstract
Dichloroacetic acid is a common disinfection by-product in surface waters and is a probable minor metabolite of trichloroethylene. Dichloroacetic acid (DCA) liver carcinogenicity has been demonstrated in rodents but epidemiological evidence in humans is not available. High doses of DCA ( approximately 50mg/kg) are used clinically to treat metabolic acidosis. Biotransformation of DCA by glutathione transferase zeta (GSTzeta) in the liver is the major elimination pathway in humans. GSTzeta is also inactivated by DCA, leading to slower systemic clearance and nonlinear pharmacokinetics after multiple doses. A physiologically based pharmacokinetic (PBPK) model was developed to quantitatively describe DCA biotransformation and kinetics in humans administered DCA by intravenous infusion and oral ingestion. GSTzeta metabolism was described using a Michaelis-Menten equation coupled with rate constants to account for normal GSTzeta synthesis, degradation and irreversible covalent binding and inhibition by the glutathione-bound-DCA intermediate. With some departures between observation and model prediction, the human DCA PBPK model adequately predicted the DCA plasma kinetics over a 20,000-fold range in administered doses. Apparent inhibition of GSTzeta mediated metabolism of DCA was minimal for low doses of DCA (microg/kg day), but was significant for therapeutic doses of DCA. Plasma protein binding of DCA was assumed to be an important factor influencing the kinetics of low doses of DCA (microg/kg day). Polymorphisms of GSTzeta may help explain inter-individual variability in DCA plasma kinetics and warrants evaluation. In conclusion, using a previously published rodent DCA PBPK model (Keys, D.A., Schultz, I.R., Mahle, D.A., Fisher, J.W., 2004. A quantitative description of suicide inhibition of dichloroacetic acid in rats and mice. Toxicol. Sci. 82, 381-393) and this human DCA PBPK model, human equivalent doses (HEDs) were calculated for a 10% increase in mice hepatic liver cancer (2.1mg/kg day). The HEDs for the dosimetrics, area-under-the-concentration-curve (AUC) for total and free DCA in plasma, AUC of DCA in liver and amount of DCA metabolized per day were 0.02, 0.1, 0.1 and 1.0mg/kg day, respectively. Research on the mechanism of action of DCA and the relevance of mouse liver cancer is needed to better understand which dosimetric may be appropriate for extrapolation from animal studies to human.
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Affiliation(s)
- Ting Li
- University of Georgia, Department of Pharmaceutical and Biomedical Sciences, R.C. Wilson Pharmacy Building, Athens, GA 30602-2351, United States
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Board PG. The use of glutathione transferase-knockout mice as pharmacological and toxicological models. Expert Opin Drug Metab Toxicol 2007; 3:421-33. [PMID: 17539748 DOI: 10.1517/17425255.3.3.421] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
ADME/Tox studies are of increasing importance because of the necessity to eliminate poor drug candidates early in the development pipeline. The glutathione S-transferases (GSTs) are a family of phase II enzymes that have been shown to play a significant role in the disposition of a wide range of drugs and other xenobiotics. Several GST-knockout mice strains have been developed that can potentially be used in ADME/Tox studies. So far, mice have been generated with deficiencies of mGSTP1/2, mGSTA4-4, mGSTZ1-1, mGSTM1-1, mGSTO1-1 and mGSTS1-1, but studies of drug metabolism in these strains have been limited. As there are 21 recognised GST genes in mice there is potential for many more strains to be made. However, a review of the available data suggests that because of differences in the evolution of the GST gene family between rodents and humans, only some knockout strains can provide insights relevant to human drug metabolism. It is concluded that, of the strains generated so far, only those deficient in mGSTP1-1, mGSTA4-4, mGSTO1-1 and mGSTZ1-1 have direct human orthologues and can be considered as human models. In contrast, there may not be appropriate orthologues of some enzymes, such as hGSTM1-1, that are known to be of relevance in drug metabolism.
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Affiliation(s)
- Philip G Board
- Australian National University, Molecular Genetics Group, John Curtin School of Medical Research, PO Box 334, Canberra ACT 2601, Australia.
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Jia M, Coats B, Chadha M, Frentzen B, Perez-Rodriguez J, Chadik PA, Yost RA, Henderson GN, Stacpoole PW. Human kinetics of orally and intravenously administered low-dose 1,2-(13)C-dichloroacetate. J Clin Pharmacol 2007; 46:1449-59. [PMID: 17101744 DOI: 10.1177/0091270006292627] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Dichloroacetate (DCA) is a putative environmental hazard, owing to its ubiquitous presence in the biosphere and its association with animal and human toxicity. We sought to determine the kinetics of environmentally relevant concentrations of 1,2-(13)C-DCA administered to healthy adults. Subjects received an oral or intravenous dose of 2.5 microg/kg of 1,2-(13)C-DCA. Plasma and urine concentrations of 1,2-(13)C-DCA were measured by a modified gas chromatography-tandem mass spectrometry method. 1,2-(13)C-DCA kinetics was determined by modeling using WinNonlin 4.1 software. Plasma concentrations of 1,2-(13)C-DCA peaked 10 minutes and 30 minutes after intravenous or oral administration, respectively. Plasma kinetic parameters varied as a function of dose and duration. Very little unchanged 1,2-(13)C-DCA was excreted in urine. Trace amounts of DCA alter its own kinetics after short-term exposure. These findings have important implications for interpreting the impact of this xenobiotic on human health.
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Affiliation(s)
- Minghong Jia
- General Clinical Research Center, University of Florida, 1600 Archer Road, Gainesville, Florida 32610, USA
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Schultz IR, Reed S, Pratt A, Skillman AD. Quantitative oral dosing of water soluble and lipophilic contaminants in the Japanese medaka (Oryzias latipes). Comp Biochem Physiol C Toxicol Pharmacol 2007; 145:86-95. [PMID: 17188578 DOI: 10.1016/j.cbpc.2006.09.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 08/31/2006] [Accepted: 09/10/2006] [Indexed: 11/26/2022]
Abstract
Quantitative oral dosing in fish can be challenging, particularly with water soluble contaminants, which can leach into the aquarium water prior to ingestion. We applied a method of bioencapsulation using newly hatched brine shrimp (Artemia franciscana) nauplii to study the toxicokinetics of five chlorinated and brominated halogenated acetic acids (HAAs), which are drinking water disinfection by-products. These results are compared to those obtained in a previous study using a polybrominated diphenyl ether (PBDE-47), a highly lipophilic chemical. The HAAs and PBDE-47 were bioencapsulated using freshly hatched A. franciscana nauplii after incubation in concentrated solutions of the study chemicals for 18 h. Aliquots of the brine shrimp were quantitatively removed for chemical analysis and fed to individual fish that were able to consume 400-500 nauplii in less than 5 min. At select times after feeding, fish were euthanized and the HAA or PBDE-47 content determined. The absorption of HAAs was quantitatively similar to previous studies in rodents: rapid absorption with peak body levels occurring within 1-2 h, then rapidly declining with elimination half-life of 0.3-3 h depending on HAA. PBDE-47 was more slowly absorbed with peak levels occurring by 18 h and very slowly eliminated with an elimination half-life of 281 h.
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Affiliation(s)
- I R Schultz
- Battelle Pacific NW Division, Sequim, WA 98382, USA.
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Li S, Li X, Li YL, Shao CH, Bidasee KR, Rozanski GJ. Insulin regulation of glutathione and contractile phenotype in diabetic rat ventricular myocytes. Am J Physiol Heart Circ Physiol 2006; 292:H1619-29. [PMID: 17056675 DOI: 10.1152/ajpheart.00140.2006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Cardiovascular complications of diabetes mellitus involve oxidative stress and profound changes in reduced glutathione (GSH), an essential tripeptide that controls many redox-sensitive cell functions. This study examined regulation of GSH by insulin to identify mechanisms controlling cardiac redox state and to define the functional impact of GSH depletion. GSH was measured by fluorescence microscopy in ventricular myocytes isolated from Sprague-Dawley rats made diabetic by streptozotocin, and video and confocal microscopy were used to measure mechanical properties and Ca(2+) transients, respectively. Spectrophotometric assays of tissue extracts were also done to measure the activities of enzymes that control GSH levels. Four weeks after injection of streptozotocin, mean GSH concentration ([GSH]) in isolated diabetic rat myocytes was approximately 36% less than in control, correlating with decreased activities of two major enzymes regulating GSH levels: glutathione reductase and gamma-glutamylcysteine synthetase. Treatment of diabetic rat myocytes with insulin normalized [GSH] after a delay of 3-4 h. A more rapid but transient upregulation of [GSH] occurred in myocytes treated with dichloroacetate, an activator of pyruvate dehydrogenase. Inhibitor experiments indicated that insulin normalized [GSH] via the pentose pathway and gamma-glutamylcysteine synthetase, although the basal activity of glucose-6-phosphate dehydrogenase was not different between diabetic and control hearts. Diabetic rat myocytes were characterized by significant mechanical dysfunction that correlated with diminished and prolonged Ca(2+) transients. This phenotype was reversed by in vitro treatment with insulin and also by exogenous GSH or N-acetylcysteine, a precursor of GSH. Our data suggest that insulin regulates GSH through pathways involving de novo GSH synthesis and reduction of its oxidized form. It is proposed that a key function of glucose metabolism in heart is to supply reducing equivalents required to maintain adequate GSH levels for the redox control of Ca(2+) handling proteins and contraction.
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Affiliation(s)
- Shumin Li
- Dept of Cellular and Integrative Physiology, Univ of Nebraska College of Medicine, 985850 Nebraska Medical Center, Omaha, NE 68198-5850, USA
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Caldwell JC, Keshava N. Key issues in the modes of action and effects of trichloroethylene metabolites for liver and kidney tumorigenesis. ENVIRONMENTAL HEALTH PERSPECTIVES 2006; 114:1457-63. [PMID: 16966105 PMCID: PMC1570066 DOI: 10.1289/ehp.8692] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Trichloroethylene (TCE) exposure has been associated with increased risk of liver and kidney cancer in both laboratory animal and epidemiologic studies. The U.S. Environmental Protection Agency 2001 draft TCE risk assessment concluded that it is difficult to determine which TCE metabolites may be responsible for these effects, the key events involved in their modes of action (MOAs) , and the relevance of these MOAs to humans. In this article, which is part of a mini-monograph on key issues in the health risk assessment of TCE, we present a review of recently published scientific literature examining the effects of TCE metabolites in the context of the preceding questions. Studies of the TCE metabolites dichloroacetic acid (DCA) , trichloroacetic acid (TCA) , and chloral hydrate suggest that both DCA and TCA are involved in TCE-induced liver tumorigenesis and that many DCA effects are consistent with conditions that increase the risk of liver cancer in humans. Studies of S-(1,2-dichlorovinyl) -l-cysteine have revealed a number of different possible cell signaling effects that may be related to kidney tumorigenesis at lower concentrations than those leading to cytotoxicity. Recent studies of trichloroethanol exploring an alternative hypothesis for kidney tumorigenesis have failed to establish the formation of formate as a key event for TCE-induced kidney tumors. Overall, although MOAs and key events for TCE-induced liver and kidney tumors have yet to be definitively established, these results support the likelihood that toxicity is due to multiple metabolites through several MOAs, none of which appear to be irrelevant to humans.
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Affiliation(s)
- Jane C Caldwell
- National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA.
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Fang YY, Kashkarov U, Anders MW, Board PG. Polymorphisms in the human glutathione transferase zeta promoter. Pharmacogenet Genomics 2006; 16:307-13. [PMID: 16609361 DOI: 10.1097/01.fpc.0000205000.07054.b3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES The zeta-class glutathione transferase GSTZ1-1 catalyses the glutathione-dependent isomerization of maleylacetoacetate to fumarylacetoacetate in the tyrosine catabolic pathway and the biotransformation of alpha-halo acids, including dichloroacetic acid (DCA). Genetic polymorphisms in the coding sequence of GSTZ1 result in significant changes in enzyme function, and deficiency of GSTZ1-1 in mice causes induction of a range of Phase-II enzymes. In this study, the potential for polymorphisms in regulatory sequences to alter gene transcription was investigated. METHODS A total of 10 single-nucleotide polymorphisms (SNP) were identified in African and Australian European subjects in a region extending 1.5-kb upstream of the GSTZ1 start of transcription. These SNPs formed at least 10 haplotypes and only two were shared between the two population samples. The effect of these SNPs on gene expression was evaluated by the transient expression of specific alleles fused to a luciferase reporter gene. RESULTS Of the 10 SNPs identified, only -1002 G>A and -289 C>T caused significant changes in promoter activity. The -1002 G>A SNP converts a v-Myb site to a S8 homeodomain (Prx2) site, and the -289 C>T SNP abolishes an Egr1 binding site. CONCLUSION These SNPs may alter GSTZ1 expression, which may alter the pharmacokinetics of DCA, which is used therapeutically for the treatment of lactic acidosis.
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Affiliation(s)
- Yu-Yan Fang
- Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia
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Shield AJ, Murray TP, Board PG. Functional characterisation of ganglioside-induced differentiation-associated protein 1 as a glutathione transferase. Biochem Biophys Res Commun 2006; 347:859-66. [PMID: 16857173 DOI: 10.1016/j.bbrc.2006.06.189] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Accepted: 06/21/2006] [Indexed: 11/26/2022]
Abstract
Mutations in the ganglioside-induced differentiation-associated protein 1 (GDAP1) gene have been linked with Charcot-Marie-Tooth (CMT) disease. This protein, and its paralogue GDAP1L1, appear to be structurally related to the cytosolic glutathione S-transferases (GST) including an N-terminal thioredoxin fold domain with conserved active site residues. The specific function, of GDAP1 remains unknown. To further characterise their structure and function we purified recombinant human GDAP1 and GDAP1L1 proteins using bacterial expression and immobilised metal affinity chromatography. Like other cytosolic GSTs, GDAP1 protein has a dimeric structure. Although the full-length proteins were largely insoluble, the deletion of a proposed C-terminal transmembrane domain allowed the preparation of soluble protein. The purified proteins were assayed for glutathione-dependent activity against a library of 'prototypic' GST substrates. No evidence of glutathione-dependent activity or an ability to bind glutathione immobilised on agarose was found.
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Affiliation(s)
- Alison J Shield
- Molecular Genetics Group, Division of Molecular Biosciences, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
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Schultz IR, Shangraw RE. Effect of short-term drinking water exposure to dichloroacetate on its pharmacokinetics and oral bioavailability in human volunteers: a stable isotope study. Toxicol Sci 2006; 92:42-50. [PMID: 16611621 DOI: 10.1093/toxsci/kfj193] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Dichloroacetic acid (DCAA) is a by-product of drinking water disinfection, is a known rodent hepatocarcinogen, and is also used therapeutically to treat a variety of metabolic disorders in humans. We measured DCAA bioavailability in 16 human volunteers (eight men, eight women) after simultaneous administration of oral and iv DCAA doses. Volunteers consumed DCAA-free bottled water for 2 weeks to wash out background effects of DCAA. Subsequently, each subject consumed (12)C-DCAA (2 mg/kg) dissolved in 500 ml water over a period of 3 min. Five minutes after the start of the (12)C-DCAA consumption, (13)C-labeled DCAA (0.3 mg/kg) was administered iv over 20 s and plasma (12)C/(13)C-DCAA concentrations measured at predetermined time points over 4 h. Volunteers subsequently consumed for 14 consecutive days DCAA 0.02 microg/kg/day dissolved in 500 ml water to simulate a low-level chronic DCAA intake. Afterward, the (12)C/(13)C-DCAA administrations were repeated. Study end points were calculation of AUC(0-->infinity), apparent volume of distribution (V(ss)), total body clearance (Cl(b)), plasma elimination half-life (t((1/2),beta)), oral absorption rate (K(a)), and oral bioavailability. Oral bioavailability was estimated from dose-adjusted AUC ratios and by using a compartmental pharmacokinetic model after simultaneous fitting of oral and iv DCAA concentration-time profiles. DCAA bioavailability had large interindividual variation, ranging from 27 to 100%. In the absence of prior DCAA intake, there were no significant differences (p > 0.05) in any pharmacokinetic parameters between male and female volunteers, although there was a trend that women absorbed DCAA more rapidly (increased K(a)), and cleared DCAA more slowly (decreased Cl(b)), than men. Only women were affected by previous 14-day DCAA exposure, which increased the AUC(0-->infinity) for both oral and iv DCAA doses (p < 0.04 and p < 0.014, respectively) with a corresponding decrease in the Cl(b).
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Affiliation(s)
- Irvin R Schultz
- Battelle Pacific NW Division, 1259 West Sequim Bay Road, Sequim, WA 98382, USA.
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Langlois C, Jorquera R, Finegold M, Shroads AL, Stacpoole PW, Tanguay RM. Evaluation of dichloroacetate treatment in a murine model of hereditary tyrosinemia type 1. Biochem Pharmacol 2006; 71:1648-61. [PMID: 16581029 DOI: 10.1016/j.bcp.2006.02.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Revised: 02/22/2006] [Accepted: 02/22/2006] [Indexed: 11/16/2022]
Abstract
Hereditary tyrosinemia type 1 (HT1) is an autosomal recessive disease severely affecting liver and kidney and is caused by a deficiency in fumarylacetoacetate hydrolase (FAH). Administration of 2-(2-nitro-4-trifluoro-methylbenzyol)-1,3 cyclohexanedione (NTBC) improves the HT1 phenotype but some patients do not respond to NTBC therapy. The objective of the present study was to evaluate whether administration of dichloroacetate, an inhibitor of maleyl acetoacetate isomerase (MAAI) to FAH-knockout mice could prevent acute pathological injury caused by NTBC withdrawal. DCA (0.5 and 5g/L) was given in combination with a standard diet or with a tyrosine-restricted diet. With the low-tyrosine diet body weight loss and most of hepatic and renal injuries were prevented regardless the DCA dose. The administration of DCA with a standard diet did not prevent damage nor the oxidative stress response nor the AFP induction seen in FAH-knockout mice. DCA was shown to inhibit hepatic MAAI activity to 86% (0.5g/L) and 94% (5g/L) of untreated wild-type mice. Interestingly, FAH(-/-) mice deprived of NTBC (NTBC-OFF) and NTBC-treated FAH-knockout mice had similar low hepatic MAAI activity levels, corresponding to 10-20% of control. Thus the failure of DCA treatment in FAH(-/-) mice seems to be attributed to the residual MAAI activity, high enough to lead to FAA accumulation and HT1 phenotype.
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Affiliation(s)
- Chantale Langlois
- Laboratory of Cellular and Developmental Genetics, CREFSIP, Department of Medicine, University Laval, Que., Canada G1K 7P4
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Udomsinprasert R, Pongjaroenkit S, Wongsantichon J, Oakley A, Prapanthadara LA, Wilce M, Ketterman A. Identification, characterization and structure of a new Delta class glutathione transferase isoenzyme. Biochem J 2005; 388:763-71. [PMID: 15717864 PMCID: PMC1183455 DOI: 10.1042/bj20042015] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The insect GST (glutathione transferase) supergene family encodes a varied group of proteins belonging to at least six individual classes. Interest in insect GSTs has focused on their role in conferring insecticide resistance. Previously from the mosquito malaria vector Anopheles dirus, two genes encoding five Delta class GSTs have been characterized for structural as well as enzyme activities. We have obtained a new Delta class GST gene and isoenzyme from A. dirus, which we name adGSTD5-5. The adGSTD5-5 isoenzyme was identified and was only detectably expressed in A. dirus adult females. A putative promoter analysis suggests that this GST has an involvement in oogenesis. The enzyme displayed little activity for classical GST substrates, although it possessed the greatest activity for DDT [1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane] observed for Delta GSTs. However, GST activity was inhibited or enhanced in the presence of various fatty acids, suggesting that the enzyme may be modulated by fatty acids. We obtained a crystal structure for adGSTD5-5 and compared it with other Delta GSTs, which showed that adGSTD5-5 possesses an elongated and more polar active-site topology.
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Affiliation(s)
- Rungrutai Udomsinprasert
- *Institute of Molecular Biology and Genetics, Mahidol University, Salaya Campus, 25/25 Putthamonthol Road 4, Salaya, Nakon Pathom 73170, Thailand
| | | | - Jantana Wongsantichon
- *Institute of Molecular Biology and Genetics, Mahidol University, Salaya Campus, 25/25 Putthamonthol Road 4, Salaya, Nakon Pathom 73170, Thailand
| | - Aaron J. Oakley
- ‡Department of Pharmacology/Crystallography Centre, University of Western Australia, Crawley 6009, Australia
| | - La-aied Prapanthadara
- §Research Institute for Health Sciences, Chiangmai University, Chiangmai 50200, Thailand
| | - Matthew C. J. Wilce
- ‡Department of Pharmacology/Crystallography Centre, University of Western Australia, Crawley 6009, Australia
| | - Albert J. Ketterman
- *Institute of Molecular Biology and Genetics, Mahidol University, Salaya Campus, 25/25 Putthamonthol Road 4, Salaya, Nakon Pathom 73170, Thailand
- To whom correspondence should be addressed (email )
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Blackburn AC, Matthaei KI, Lim C, Taylor MC, Cappello JY, Hayes JD, Anders MW, Board PG. Deficiency of glutathione transferase zeta causes oxidative stress and activation of antioxidant response pathways. Mol Pharmacol 2005; 69:650-7. [PMID: 16278372 DOI: 10.1124/mol.105.018911] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glutathione S-transferase (GST) zeta (GSTZ1-1) plays a significant role in the catabolism of phenylalanine and tyrosine, and a deficiency of GSTZ1-1 results in the accumulation of maleylacetoacetate and its derivatives maleylacetone (MA) and succinylacetone. Induction of GST subunits was detected in the liver of Gstz1(-/-) mice by Western blotting with specific antisera and high-performance liquid chromatography analysis of glutathione affinity column-purified proteins. The greatest induction was observed in members of the mu class. Induction of NAD(P)H:quinone oxidoreductase 1 and the catalytic and modifier subunits of glutamate-cysteine ligase was also observed. Many of the enzymes that are induced in Gstz1(-/-) mice are regulated by antioxidant response elements that respond to oxidative stress via the Keap1/Nrf2 pathway. It is significant that diminished glutathione concentrations were also observed in the liver of Gstz1(-/-) mice, which supports the conclusion that under normal dietary conditions, the accumulation of electrophilic intermediates such as maleylacetoacetate and MA results in a high level of oxidative stress. Elevated GST activities in the livers of Gstz1(-/-) mice suggest that GSTZ1-1 deficiency may alter the metabolism of some drugs and xenobiotics. Gstz1(-/-) mice given acetaminophen demonstrated increased hepatotoxicity compared with wild-type mice. This toxicity may be attributed to the increased GST activity or the decreased hepatic concentrations of glutathione, or both. Patients with acquired deficiency of GSTZ1-1 caused by therapeutic exposure to dichloroacetic acid for the clinical treatment of lactic acidosis may be at increased risk of drug- and chemical-induced toxicity.
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Affiliation(s)
- Anneke C Blackburn
- Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, Canberra
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Guo X, Dixit V, Liu H, Shroads AL, Henderson GN, James MO, Stacpoole PW. Inhibition and recovery of rat hepatic glutathione S-transferase zeta and alteration of tyrosine metabolism following dichloroacetate exposure and withdrawal. Drug Metab Dispos 2005; 34:36-42. [PMID: 16199472 DOI: 10.1124/dmd.105.003996] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dichloroacetate (DCA) is an investigational drug for certain metabolic disorders, a by-product of water chlorination and a metabolite of certain industrial solvents and drugs. DCA is biotransformed to glyoxylate by glutathione S-transferase zeta (GSTz1-1), which is identical to maleylacetoacetate isomerase, an enzyme of tyrosine catabolism. Clinically relevant doses of DCA (mg/kg/day) decrease the activity and expression of GSTz1-1, which alters tyrosine metabolism and may cause hepatic and neurological toxicity. The effect of environmental DCA doses (microg/kg/day) on tyrosine metabolism and GSTz1-1 is unknown, as is the time course of recovery from perturbation following subchronic DCA administration. Male Sprague-Dawley rats (200 g) were exposed to 0 microg, 2.5 microg, 250 microg, or 50 mg DCA/kg/day in drinking water for up to 12 weeks. Recovery was followed after the 8-week exposure. GSTz specific activity and protein expression (Western immunoblotting) were decreased in a dose-dependent manner by 12 weeks of exposure. Enzyme activity and expression decreased 95% after a 1-week administration of high-dose DCA. Eight weeks after cessation of high-dose DCA, GSTz activity had returned to control levels. At the 2.5 or 250 microg/kg/day doses, enzyme activity also decreased after 8 weeks' exposure and returned to control levels 1 week after DCA was withdrawn. Urinary excretion of the tyrosine catabolite maleylacetone increased from undetectable amounts in control rats to 60 to 75 microg/kg/24 h in animals exposed to 50 mg/kg/day DCA. The liver/body weight ratio increased in the high-dose group after 8 weeks of DCA. These studies demonstrate that short-term administration of DCA inhibits rat liver GSTz across the wide concentration range to which humans are exposed.
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Affiliation(s)
- Xu Guo
- Division of Endocrinology and Metabolism, Department of Medicine, University of Florida, FL 32610, USA
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Abstract
Zeta-class glutathione transferases (GSTZs) were recently discovered by a bioinformatics approach and the availability of human expressed sequence tag databases. Although GSTZ showed little activity with conventional GST substrates (1-chloro-2,4-dinitrobenzene; organic hydroperoxides), GSTZ was found to catalyze the oxygenation of dichloroacetic acid (DCA) to glyoxylic acid and the cis-trans isomerization of maleylacetoacetate to fumarylacetoacetate. Hence, GSTZ plays a critical role in the tyrosine degradation pathway and in alpha-haloacid metabolism. The GSTZ-catalyzed biotransformation of DCA is of particular interest, because DCA is used in the human clinical management of congenital lactic acidosis and because DCA is a common drinking water contaminant. Substrate selectivity studies showed that GSTZ catalyzes the glutathione-dependent biotransformation of a range of dihaloacetic acids along with fluoroacetic acid, 2-halopropanoic acids, and 2,2-dichloropropanoic acid. Human clinical studies showed that the elimination half-life of DCA increases with repeated doses of DCA; also, rats given DCA show low GSTZ activity with DCA as the substrate. DCA was found to be a mechanism-based inactivator of GSTZ, and proteomic studies showed that Cys-16 of human GSTZ1-1 is covalently modified by a reactive intermediate that contains glutathione and the carbon skeleton of DCA. Bioinformatics studies also showed the presence of at least four polymorphic variants of human GSTZ; these variants differ considerably in the rates of catalysis and in their susceptibility to inactivation by DCA. Finally, Gstz1(-/-) mouse strains have been developed; these mice fail to biotransform DCA or maleylacetone. Although the mice have no obvious phenotype, a high incidence of lethality is observed in young mice given phenylalanine in their drinking water. Gstz1(-/-) mice should prove useful in expanding the role of GSTZ in alpha-haloacid metabolism and in the tyrosine degradation pathway.
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Affiliation(s)
- Philip G Board
- Molecular Genetics Group, John Curtin School of Medical Research, Australian National University, CAnaberra, Australia
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Saghir SA, Schultz IR. Toxicokinetics and oral bioavailability of halogenated acetic acids mixtures in naïve and GSTzeta-depleted rats. Toxicol Sci 2004; 84:214-24. [PMID: 15625187 DOI: 10.1093/toxsci/kfi070] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Disinfection of drinking water typically produces a mixture of mono-, di-, and tri-halogenated acetic acids (HAAs). In this study, we investigated the toxicokinetics of HAA mixtures in naive and glutathione transferase zeta 1 (GSTzeta)-depleted male F344 rats administered orally or iv to Mixture-1 (monobromo [MBAA]- dichloro- [DCAA], chlorodibromo- [CDBAA], tribromo- [TBAA] acetic acids) or Mixture-2 (bromochloro- [BCAA], dibromo- [DBAA], trichloro- [TCAA] bromodichloro- [BDCAA] acetic acids) at a dose of 25 micromol/kg HAA. Serial blood samples were collected at various times up to 36 h, and the plasma concentrations of each HAA quantified by GC-ECD. Rats were pretreated for 7 d with drinking water containing 0.2 g/l DCAA to deplete the GSTzeta (GSTZ1-1) activity in the liver. An additional group of GSTzeta-depleted rats were orally dosed with each mixture and euthanized at 0.25, 0.5, 1, 2, and 4 h to determine tissue distribution of mixture components. In both mixtures, GSTzeta depletion primarily affected the toxicokinetics of di-HAAs (DCAA, BCAA, and DBAA), with the total body clearance (Cl b) decreasing 3- to 10-fold. Interestingly, DCAA pretreatment appeared to increase the elimination of Mixture-2 tri-HAAs (TCAA and BDCAA). After oral administration, DCAA exhibited a complex time-course plasma profile with secondary peaks appearing long after completion of the initial absorption phase. This phenomenon coincided with elevated DCA levels in the lower portion of the GI tract compared to CDBAA and TBAA. Comparison of the results with previous studies employing similar or higher doses of individual HAAs indicated the primary difference in HAA toxicokinetics when administered as mixture was a reduction in Cl b. These results suggest competitive interactions between tri- and di-HAAs beyond what would be predicted from individual HAA studies. For di-HAAs, the total dose is important, as clearance is dose dependent due to competition for GSTzeta. When considering HAA dosimetry, importance should be placed on both the components of the mixture and prior exposure history to di-HAAs.
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Affiliation(s)
- Shakil A Saghir
- Battelle Pacific Northwest National Laboratory, Sequim, Washington 98352, USA
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