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Salsaa M, Pereira B, Liu J, Yu W, Jadhav S, Hüttemann M, Greenberg ML. Valproate inhibits mitochondrial bioenergetics and increases glycolysis in Saccharomyces cerevisiae. Sci Rep 2020; 10:11785. [PMID: 32678210 PMCID: PMC7367371 DOI: 10.1038/s41598-020-68725-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 06/17/2020] [Indexed: 12/25/2022] Open
Abstract
The widely used mood stabilizer valproate (VPA) causes perturbation of energy metabolism, which is implicated in both the therapeutic mechanism of action of the drug as well as drug toxicity. To gain insight into these mechanisms, we determined the effects of VPA on energy metabolism in yeast. VPA treatment increased levels of glycolytic intermediates, increased expression of glycolysis genes, and increased ethanol production. Increased glycolysis was likely a response to perturbation of mitochondrial function, as reflected in decreased membrane potential and oxygen consumption. Interestingly, yeast, mouse liver, and isolated bovine cytochrome c oxidase were directly inhibited by the drug, while activities of other oxidative phosphorylation complexes (III and V) were not affected. These findings have implications for mechanisms of therapeutic action and toxicity.
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Affiliation(s)
- Michael Salsaa
- Department of Biological Sciences, Wayne State University, Detroit, MI, 48202, USA
| | - Bianca Pereira
- Department of Biological Sciences, Wayne State University, Detroit, MI, 48202, USA
| | - Jenney Liu
- Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Wenxi Yu
- Department of Biological Sciences, Wayne State University, Detroit, MI, 48202, USA.,Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Shyamalagauri Jadhav
- Department of Biological Sciences, Wayne State University, Detroit, MI, 48202, USA.,Genetics and Metabolism Section, Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Maik Hüttemann
- Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI, USA
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI, 48202, USA.
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Mollerup CB, Rasmussen BS, Johansen SS, Mardal M, Linnet K, Dalsgaard PW. Retrospective analysis for valproate screening targets with liquid chromatography–high resolution mass spectrometry with positive electrospray ionization: An omics‐based approach. Drug Test Anal 2018; 11:730-738. [DOI: 10.1002/dta.2543] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 11/06/2018] [Accepted: 11/08/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Christian Brinch Mollerup
- Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical SciencesUniversity of Copenhagen Frederik V's vej 11 2100 Copenhagen Ø Denmark
| | - Brian Schou Rasmussen
- Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical SciencesUniversity of Copenhagen Frederik V's vej 11 2100 Copenhagen Ø Denmark
| | - Sys Stybe Johansen
- Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical SciencesUniversity of Copenhagen Frederik V's vej 11 2100 Copenhagen Ø Denmark
| | - Marie Mardal
- Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical SciencesUniversity of Copenhagen Frederik V's vej 11 2100 Copenhagen Ø Denmark
| | - Kristian Linnet
- Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical SciencesUniversity of Copenhagen Frederik V's vej 11 2100 Copenhagen Ø Denmark
| | - Petur Weihe Dalsgaard
- Section of Forensic Chemistry, Department of Forensic Medicine, Faculty of Health and Medical SciencesUniversity of Copenhagen Frederik V's vej 11 2100 Copenhagen Ø Denmark
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Waring WS, Nixon AC. Acute liver impairment after sodium valproate overdose. BMJ Case Rep 2009; 2009:bcr06.2008.0057. [PMID: 21686945 DOI: 10.1136/bcr.06.2008.0057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Liver impairment is a recognised adverse effect of long-term sodium valproate treatment, but there are few reports concerning its occurrence after acute overdose. This report describes a 36-year-old woman who deliberately ingested 32 g of sodium valproate (Epilim). Serum valproate concentration was 4370 μmol/l (630 mg/l) at 4.3 h post-ingestion (therapeutic reference range: 300-600 μmol/l), and the elimination half-life was 14.1 h. Liver biochemistry tests were initially normal but gradually became impaired, and highest alanine aminotransferase (761 U/l) occurred 2.3 days after ingestion. Supportive measures alone were sufficient to allow recovery of liver function. This case indicates that sodium valproate overdose may cause acute hepatocellular injury, even in the absence of pre-existing liver disease.
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Affiliation(s)
- William Stephen Waring
- The Royal Infirmary of Edinburgh, Scottish Poisons Information Bureau, 51 Little France Crescent, Edinburgh EH16 4SA, UK
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Knapp AC, Todesco L, Beier K, Terracciano L, Sägesser H, Reichen J, Krähenbühl S. Toxicity of Valproic Acid in Mice with Decreased Plasma and Tissue Carnitine Stores. J Pharmacol Exp Ther 2007; 324:568-75. [DOI: 10.1124/jpet.107.131185] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Natarajan SK, Eapen CE, Pullimood AB, Balasubramanian KA. Oxidative stress in experimental liver microvesicular steatosis: role of mitochondria and peroxisomes. J Gastroenterol Hepatol 2006; 21:1240-9. [PMID: 16872304 DOI: 10.1111/j.1440-1746.2006.04313.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND Hepatic microvesicular steatosis is a clinical manifestation seen in a number of liver diseases. Although the role of mitochondrial beta-oxidation in the development of the disease has been well studied, information on lipid peroxidative damage in liver subcellular organelles is scarce. The present study looked at oxidative stress in hepatic peroxisomes and microsomes in microvesicular steatosis, using an animal model of the disease. METHODS Rats were given i.p. injections of sodium valproate (700 mg/kg bodyweight) to induce microvesicular steatosis, which was confirmed by histology. RESULTS Oxidative stress was evident in liver in steatosis, accompanied by structural and functional alterations in hepatic mitochondria. Alterations in lipid composition, with decreased phosphatidyl choline and ethanolamine and increased lysophosphatidyl choline and ethanolamine, were seen. An increase in triglyceride content was also seen. In addition, increased lipid peroxidation was also evident in peroxisomes and microsomes from steatotic rats. Pretreatment with clofibrate results in partial reversal of changes produced by valproate. CONCLUSIONS These results suggest that in addition to impaired mitochondrial beta-oxidation, oxidative stress is also seen in the hepatic peroxisomes and microsomes during microvesicular steatosis.
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Affiliation(s)
- Sathish Kumar Natarajan
- Wellcome Trust Research Laboratory, Department of Gastrointestinal Sciences, Christian Medical College, Vellore, India
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6
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Giardina WJ, Dart MJ, Harris RR, Bitner RS, Radek RJ, Fox GB, Chemburkar SR, Marsh KC, Waring JF, Hui JY, Chen J, Curzon P, Grayson GK, Komater VA, Ku Y, Lockwood M, Miner HM, Nikkel AL, Pan JB, Pu YM, Wang L, Bennani Y, Durmuller N, Jolly R, Roux S, Sullivan JP, Decker MW. Preclinical Profiling and Safety Studies of ABT-769: A Compound with Potential for Broad-spectrum Antiepileptic Activity. Epilepsia 2005; 46:1349-61. [PMID: 16146429 DOI: 10.1111/j.1528-1167.2005.02905.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The objective of this study was to characterize the antiseizure and safety profiles of ABT-769 [(R)-N-(2 amino-2-oxoethyl)spiro[2,5]octane-1-carboxamide]. METHODS ABT-769 was tested for protection against maximal electroshock and pentylenetetrazol-induced seizures in the mouse and for suppression of electrically kindled amygdala seizures and spontaneous absence-like seizures in the rat. The central nervous system safety profile was evaluated by using tests of motor coordination and inhibitory avoidance. The potential for liver toxicity was assessed in vitro by using a mitochondrial fatty acid beta-oxidation assay. Teratogenic potential was assessed in the mouse. RESULTS ABT-769 blocked maximal electroshock, subcutaneous pentylenetetrazol and intravenous pentylenetetrazol-induced seizures with median effective dose (ED50) values of 0.25, 0.38, and 0.11 mmol/kg, p.o., respectively. No tolerance was evident in the intravenous pentylenetetrazol test after twice-daily dosing of ABT-769 (0.3 mmol/kg, p.o.) for 4 days. ABT-769 blocked absence-like spike-wave discharge (ED50, 0.15 mmol/kg, p.o.) and shortened the cortical and amygdala afterdischarge duration of kindled seizures (1 and 3 mmol/kg, p.o.). The protective indices (ED50 rotorod impairment/ED50 seizure protection) were 4.8, 3.2, and 10.9 in the maximal electroshock, subcutaneous pentylenetetrazol and intravenous pentylenetetrazol seizure tests, respectively. ABT-769 did not affect inhibitory avoidance performance (0.1-1 mmol/kg, p.o.). ABT-769 did not affect mitochondrial fatty acid beta-oxidation or induce neural tube defects. CONCLUSIONS ABT-769 is an efficacious antiseizure agent in animal models of convulsive and nonconvulsive epilepsy and has a favorable safety profile. ABT-769 has a broad-spectrum profile like that of valproic acid. Its profile is clearly different from those of carbamazepine, phenytoin, lamotrigine, topiramate, vigabatrin, and tiagabine.
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MESH Headings
- Abnormalities, Drug-Induced/epidemiology
- Amygdala/drug effects
- Amygdala/physiopathology
- Animals
- Anticonvulsants/pharmacology
- Anticonvulsants/toxicity
- Behavior, Animal/drug effects
- Disease Models, Animal
- Drug Evaluation, Preclinical
- Electroshock
- Epilepsy/chemically induced
- Epilepsy/metabolism
- Epilepsy/prevention & control
- Epilepsy, Absence/chemically induced
- Epilepsy, Absence/metabolism
- Epilepsy, Absence/prevention & control
- Humans
- Injections, Intravenous
- Injections, Subcutaneous
- Kindling, Neurologic/drug effects
- Kindling, Neurologic/metabolism
- Kindling, Neurologic/physiology
- Male
- Mice
- Mitochondria, Liver/drug effects
- Mitochondria, Liver/metabolism
- Pentylenetetrazole/administration & dosage
- Rats
- Rats, Wistar
- Species Specificity
- Spiro Compounds/pharmacology
- Spiro Compounds/toxicity
- Valproic Acid/analogs & derivatives
- Valproic Acid/pharmacology
- Valproic Acid/toxicity
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Affiliation(s)
- William J Giardina
- Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064-6125, USA
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7
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Daniels T, Gallagher M, Tremblay G, Rodgers RL. Effects of valproic acid on cardiac metabolism. Can J Physiol Pharmacol 2005; 82:927-33. [PMID: 15573154 DOI: 10.1139/y04-096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether the antiepileptic valproic acid (VPA) might interfere with oxidative metabolism in heart, as it does in liver. We administered VPA to working rat hearts perfused with radiolabeled carbohydrate and fatty acid fuels. Measurements included oxidation rates of (i) glucose, pyruvate, or lactate in the presence of palmitate and (ii) palmitate, octanoate, or butyrate in the presence of glucose. Oxidation rates were quantified as the rate of appearance of 14CO2 or 3H2O from 14C- or 3H-labeled substrates. In hearts perfused with palmitate, VPA (1 mmol/L) strongly inhibited the oxidation of pyruvate and lactate but slightly stimulated the oxidation of glucose. VPA also inhibited lactate or pyruvate uptake into erythrocytes in vitro. In hearts perfused with glucose, VPA strongly inhibited the oxidation of palmitate and octanoate but had no effect on butyrate oxidation. The absence of valproate CoA ligase activity in cell-free homogenates indicated that the inhibition of fatty acid oxidation by VPA did not require prior activation to valproyl-CoA. The results are consistent with the hypothesis that VPA selectively interferes with myocardial fuel oxidation by mechanisms that are independent of conversion to the CoA thioester.
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Affiliation(s)
- Thomas Daniels
- Department of Cell and Molecular Biology, University of Rhode Island, Kingston 02881, USA
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8
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Nelson SD, Trager WF. THE USE OF DEUTERIUM ISOTOPE EFFECTS TO PROBE THE ACTIVE SITE PROPERTIES, MECHANISM OF CYTOCHROME P450-CATALYZED REACTIONS, AND MECHANISMS OF METABOLICALLY DEPENDENT TOXICITY. Drug Metab Dispos 2003; 31:1481-98. [PMID: 14625345 DOI: 10.1124/dmd.31.12.1481] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Critical elements from studies that have led to our current understanding of the factors that cause the observed primary deuterium isotope effect, (kH/kD)obs, of most enzymatically mediated reactions to be much smaller than the "true" or intrinsic primary deuterium isotope effect, kH/kD, for the reaction are presented. This new understanding has provided a unique and powerful tool for probing the catalytic and active site properties of enzymes, particularly the cytochromes P450 (P450). Examples are presented that illustrate how the technique has been used to determine kH/kD, and properties such as the catalytic nature of the reactive oxenoid intermediate, prochiral selectivity, the chemical and enzymatic mechanisms of cytochrome P450-catalyzed reactions, and the relative active site size of different P450 isoforms. Examples are also presented of how deuterium isotope effects have been used to probe mechanisms of the formation of reactive metabolites that can cause toxic effects.
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Affiliation(s)
- Sidney D Nelson
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, WA 98195-7631, USA
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9
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Sztajnkrycer MD. Valproic acid toxicity: overview and management. JOURNAL OF TOXICOLOGY. CLINICAL TOXICOLOGY 2002; 40:789-801. [PMID: 12475192 DOI: 10.1081/clt-120014645] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Acute valproic acid intoxication is an increasing problem, accounting for more than 5000 calls to the American Association of Poison Control Centers in 2000. The purpose of this paper is to review the pharmacology and toxicology of valproic acid toxicity. Unlike earlier antiepileptic agents, valproic acid appears to function neither through sodium channel inhibition nor through direct gamma-aminobutyric acid agonism, but through an indirect increase in regional brain gamma-aminobutyric acid levels. Manifestations of acute valproic acid toxicity are myriad, and reflect both exaggerated therapeutic effect and impaired intermediary metabolism. Central nervous system depression is the most common finding noted in overdose, and may progress to coma and respiratory depression. Cerebral edema has also been observed. Although hepatotoxicity is rare in the acute overdose setting, pancreatitis and hyperammonemia have been reported. Metabolic and hematologic derangements have also been described. Management of acute valproic acid ingestion requires supportive care and close attention to the airway. The use of controversial adjunctive therapies, including extracorporeal drug elimination and L-carnitine supplementation, will be discussed.
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10
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Silva MF, Ruiter JP, IJlst L, Jakobs C, Duran M, de Almeida IT, Wanders RJ. Differential effect of valproate and its Delta2- and Delta4-unsaturated metabolites, on the beta-oxidation rate of long-chain and medium-chain fatty acids. Chem Biol Interact 2001; 137:203-12. [PMID: 11566289 DOI: 10.1016/s0009-2797(01)00234-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Overall fatty acid oxidation rates were investigated in rat hepatocytes using [9,10-3H]-palmitic, [9,10-3H]-oleic, [9,10-3H]-myristic and [2,3-3H]-phenylpropionic acids. The effect of both valproate (VPA) (0-10 mM) and two of its unsaturated metabolites, Delta2(E)-VPA and Delta4-VPA (0-10 mM), on the overall 3H2O production rate was studied. The results give evidence of a general inhibitory effect of VPA on the beta-oxidation rate of all the tested substrates. Similar effects were observed with both VPA metabolites but these effects appeared to be dependent on the chain length of the substrate. When the effect on the oxidation of the medium-chain fatty acid 3-phenylpropionate (PPA) was studied, Delta2(E)-VPA at 0.5 mM caused a 94% inhibition of the overall beta-oxidation rate. However, with long-chain substrates, 0.5 mM Delta(4)-VPA was a more potent inhibitor (20-30% of control activity) than 0.5 mM Delta(2E)-VPA (60-80% of control activity). Our results suggest that VPA and/or its metabolites inhibit fatty acyl-CoA metabolism within the mitochondrion by two different mechanisms. The first mechanism involves CoASH sequestration, which affects the oxidation rate of all fatty acids with different chain length. The second mechanism is more specific in nature and involves selective inhibition of particular enzymes implicated in fatty acid beta-oxidation.
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Affiliation(s)
- M F Silva
- Department of Clinical Chemistry and Paediatrics, University of Amsterdam, Academic Medical Centre, 1105 AZ, Amsterdam, Netherlands
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11
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Neuman MG, Shear NH, Jacobson-Brown PM, Katz GG, Neilson HK, Malkiewicz IM, Cameron RG, Abbott F. CYP2E1-mediated modulation of valproic acid-induced hepatocytotoxicity. Clin Biochem 2001; 34:211-8. [PMID: 11408019 DOI: 10.1016/s0009-9120(01)00217-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVES To determine the cytotoxicity of valproic acid (VPA) and its metabolite, 4-ene-valproic acid (4-ene-VPA) in human hepatoblastoma cells (Hep G2), and to study the modulatory effect of cytochrome P450 2E1 induction in this model. METHODS Cells were exposed to VPA or 4-ene-VPA in the presence of either ethanol (EtOH), or EtOH combined with disulphiram (DS). Some cells were exposed to alpha-fluoro-VPA or to alpha-fluoro-4-ene-VPA in the absence of CYP2E1 inducers. Apoptosis and necrosis were measured by analyzing 6000 cells per sample using transmission electron microscopy, while cytokine release and apoptosis were quantitated by ELISA. RESULTS VPA + EtOH increased VPA cytotoxicity. 4-ene-VPA + EtOH significantly increased toxicity, while DS + EtOH significantly reduced this toxicity. Alpha-fluorinated analogues reduced cytotoxicity compared to the corresponding VPA compounds. Neither VPA nor alpha-fluorinated VPA increased the release of IL-6 or TNF-alpha in media. A significant increase in the release of TNF-alpha was observed in cells exposed to 4-ene-VPA that further increased with EtOH exposure. CONCLUSIONS Cells exposed to 4-ene-VPA experience greater cytotoxicity than those treated with VPA. Cytochrome P450 2E1 inducers enhance toxicity in VPA-exposed cells, while alpha-fluorination of VPA diminishes cytotoxicity by directly interfering with the beta-oxidation of the 4-ene-VPA metabolite.
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Affiliation(s)
- M G Neuman
- Division of Clinical Pharmacology, Sunnybrook & Women's College Health Sciences Centre and Department of Pathology, Toronto Health Network, Canada.
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12
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Silva MF, Ruiter JP, IJlst L, Allers P, ten Brink HJ, Jakobs C, Duran M, Tavares de Almeida I, Wanders RJ. Synthesis and intramitochondrial levels of valproyl-coenzyme A metabolites. Anal Biochem 2001; 290:60-7. [PMID: 11180937 DOI: 10.1006/abio.2000.4947] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A number of valproate adverse reactions are due to its interference with several metabolic pathways, including that of fatty acid oxidation. In order to resolve which mitochondrial enzymes of fatty acid oxidation are inhibited by which VPA intermediates we have developed methods to synthesize their CoA ester forms. This paper describes the synthesis of VPA acyl-CoA ester metabolites as well as data on the fate of VPA in rat liver mitochondria. Valproyl-CoA, Delta2-valproyl-CoA, and 3-OH-valproyl-CoA were obtained through chemical synthesis. 3-Keto-valproyl-CoA was prepared by a novel enzymatic procedure followed by a combination of solid-phase extraction and preparative HPLC purification. This approach proved to be efficient in obtaining all the beta-oxidation intermediates of valproyl-CoA. The synthetic standards were used for the determination of intramitochondrial concentrations of valproyl-CoA, Delta2-valproyl-CoA, 3-OH-valproyl-CoA, and 3-keto-valproyl-CoA by HPLC. These levels were determined after incubation of intact rat liver mitochondria with VPA under conditions of state 3 and state 4 respiration. The results show that valproyl-CoA and to a much lesser extent 3-keto-valproyl-CoA are the main metabolites of VPA in mitochondria. This information will be of great use in resolving the mechanisms involved in the inhibition of mitochondrial processes like fatty acid oxidation by VPA.
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Affiliation(s)
- M F Silva
- Department of Clinical Chemistry and Paediatrics, University of Amsterdam, The Netherlands
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13
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Darius J, Meyer FP, Sabel BA, Schroeder U. Influence of nanoparticles on the brain-to-serum distribution and the metabolism of valproic acid in mice. J Pharm Pharmacol 2000; 52:1043-7. [PMID: 11045883 DOI: 10.1211/0022357001774958] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The suitability of nanoparticles as a drug-carrier system for the antiepileptic valproic acid has been studied in mice. The aim of the study was to increase the brain-to-serum ratio of the drug to reduce dose-related side effects in the periphery. The influence of nanoparticles on the metabolism of valproic acid was also investigated. The serum kinetics and the brain tissue levels of valproic acid were not altered by administration with nanoparticles. However, the nanoparticles did inhibit the metabolic degradation of valproic acid via mitochondrial beta-oxidation but did not influence any other metabolic pathway. It can be concluded that nanoparticles loaded with valproic acid may help to reduce the toxic side effects of valproate therapy, not by reducing the therapeutically necessary dosage but by inhibition of formation of toxic metabolites. Using their ability to selectively block a pathway nanoparticles may serve as a tool to investigate the metabolic origin of metabolites and their contribution to therapeutic efficacy and side effects.
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Affiliation(s)
- J Darius
- Institute of Clinical Pharmacology, Medical Faculty, Otto-von-Guericke-University Magdeburg, Germany
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14
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Glasgow JF, Middleton B, Moore R, Gray A, Hill J. The mechanism of inhibition of beta-oxidation by aspirin metabolites in skin fibroblasts from Reye's syndrome patients and controls. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1454:115-25. [PMID: 10354521 DOI: 10.1016/s0925-4439(99)00025-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The effects of aspirin metabolites on beta-oxidation were studied in skin fibroblasts from eight typical Reye's syndrome (RS) patients and controls. RS patients' cells did not differ from controls in rates of palmitate oxidation or in the three component activities of the mitochondrial trifunctional enzyme (MTE), indicating no inherited beta-oxidation defect. Aspirin metabolites salicylate, hydroxyhippurate and gentisate, but not aspirin, directly inhibited palmitate oxidation in control and RS cells. RS cells were significantly more sensitive to inhibition than controls at 0.5 to 5 mM salicylate. Inhibition was concentration-dependent and reversible. Inhibition did not occur in fibroblasts lacking activity of the long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) activity of MTE. Salicylate was therefore inhibiting beta-oxidation at this step. Hydroxyhippurate and salicylate reversibly inhibited HAD activities in extracts of control and RS cells. Studies with pure short-chain HAD and LCHAD (MTE) showed hydroxyhippurate and salicylate were competitive inhibitors of the former but mixed (not competitive) inhibitors of the latter. Both compounds inhibited the combined, three-step, MTE reaction measured in the physiological direction. We conclude that (1) salicylate and hydroxyhippurate decrease beta-oxidation in intact cells by reversible inhibition of LCHAD activity of the MTE, and (2) beta-oxidation in RS cells is inherently more sensitive to inhibition by low concentrations of salicylate than controls.
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Affiliation(s)
- J F Glasgow
- Nuffield Department of Child Health, The Queen's University of Belfast, Royal Belfast Hospital for Sick Children, Belfast BT12 6BA, UK
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15
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Abstract
Valproate is currently one of the major antiepileptic drugs with efficacy for the treatment of both generalized and partial seizures in adults and children. Furthermore, the drug is increasingly used for therapy of bipolar and schizoaffective disorders, neuropathic pain and for prophylactic treatment of migraine. These various therapeutic effects are reflected in preclinical models, including a variety of animal models of seizures or epilepsy. The incidence of toxicity associated with the clinical use of valproate is low, but two rare toxic effects, idiosyncratic fatal hepatotoxicity and teratogenicity, necessitate precautions in risk patient populations. Studies from animal models on structure-relationships indicate that the mechanisms leading to hepatotoxicity and teratogenicity are distinct and also differ from the mechanisms of anticonvulsant action of valproate. Because of its wide spectrum of anticonvulsant activity against different seizure types, it has repeatedly been suggested that valproate acts through a combination of several mechanisms. As shown in this review, there is substantial evidence that valproate increases GABA synthesis and release and thereby potentiates GABAergic functions in some specific brain regions, such as substantia nigra, thought to be involved in the control of seizure generation and propagation. Furthermore, valproate seems to reduce the release of the epileptogenic amino acid gamma-hydroxybutyric acid and to attenuate neuronal excitation induced by NMDA-type glutamate receptors. In addition to effects on amino acidergic neurotransmission, valproate exerts direct effects on excitable membranes, although the importance of this action is equivocal. Microdialysis data suggest that valproate alters dopaminergic and serotonergic functions. Valproate is metabolized to several pharmacologically active metabolites, but because of the low plasma and brain concentrations of these compounds it is not likely that they contribute significantly to the anticonvulsant and toxic effects of treatment with the parent drug. By the experimental observations summarized in this review, most clinical effects of valproate can be explained, although much remains to be learned at a number of different levels of valproate's mechanisms of action.
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Affiliation(s)
- W Löscher
- Department of Pharmacology, Toxicology and Pharmacy, School of Veterinary Medicine, Hannover, Germany.
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