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Autoxidation Kinetics of Tetrahydrobiopterin-Giving Quinonoid Dihydrobiopterin the Consideration It Deserves. Molecules 2023; 28:molecules28031267. [PMID: 36770933 PMCID: PMC9921404 DOI: 10.3390/molecules28031267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/20/2023] [Accepted: 01/22/2023] [Indexed: 01/31/2023] Open
Abstract
In humans, tetrahydrobiopterin (H4Bip) is the cofactor of several essential hydroxylation reactions which dysfunction cause very serious diseases at any age. Hence, the determination of pterins in biological media is of outmost importance in the diagnosis and monitoring of H4Bip deficiency. More than half a century after the discovery of the physiological role of H4Bip and the recent advent of gene therapy for dopamine and serotonin disorders linked to H4Bip deficiency, the quantification of quinonoid dihydrobiopterin (qH2Bip), the transient intermediate of H4Bip, has not been considered yet. This is mainly due to its short half-life, which goes from 0.9 to 5 min according to previous studies. Based on our recent disclosure of the specific MS/MS transition of qH2Bip, here, we developed an efficient HPLC-MS/MS method to achieve the separation of qH2Bip from H4Bip and other oxidation products in less than 3.5 min. The application of this method to the investigation of H4Bip autoxidation kinetics clearly shows that qH2Bip's half-life is much longer than previously reported, and mostly longer than that of H4Bip, irrespective of the considered experimental conditions. These findings definitely confirm that an accurate method of H4Bip analysis should include the quantification of qH2Bip.
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Boulghobra A, Bonose M. Quantification of Monoamine Neurotransmitter Metabolites and Cofactors in Cerebrospinal Fluid: State-of-the-Art. Crit Rev Anal Chem 2022:1-16. [PMID: 36476251 DOI: 10.1080/10408347.2022.2151833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Inborn errors of monoamine neurotransmitter metabolism are rare diseases characterized by nonspecific neurological symptoms. These symptoms appear in early childhood and correspond to movement disorders, epilepsy, sleep disorders and/or mental disability. Cerebrospinal fluid biomarkers have been identified and validated to allow specific diagnosis of these diseases. Biomarkers of inborn errors of monoamine neurotransmitter metabolites are divided in two groups: monoamine neurotransmitter metabolites and pterins. Biomarkers quantification in cerebrospinal fluid is based on high-performance liquid chromatography separation coupled to electrochemical detection, fluorescence detection, or mass spectrometry. The following article reviews the advances in the proposed routine methods for the measurement of these analytes in cerebrospinal fluid. The purpose of this review is to compare the various proposed methods in terms of sample preparation, chromatographic conditions and detection modes. Despite the broad range of proposed methods, quantification of inborn errors of monoamine neurotransmitter biomarkers remains a great challenge, given the complexity of biological fluids and the low amounts of analytes that are present in cerebrospinal fluid.
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Affiliation(s)
- Ayoub Boulghobra
- Institut de Chimie Physique, Université Paris-Saclay, CNRS, UMR8000, 91405 Orsay, France
| | - Myriam Bonose
- Institut de Chimie Physique, Université Paris-Saclay, CNRS, UMR8000, 91405 Orsay, France
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Alhajji E, Boulghobra A, Bonose M, Berthias F, Moussa F, Maître P. Multianalytical Approach for Deciphering the Specific MS/MS Transition and Overcoming the Challenge of the Separation of a Transient Intermediate, Quinonoid Dihydrobiopterin. Anal Chem 2022; 94:12578-12585. [PMID: 36074025 DOI: 10.1021/acs.analchem.2c00924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Despite recent technological developments in analytical chemistry, separation and direct characterization of transient intermediates remain an analytical challenge. Among these, separation and direct characterization of quinonoid dihydrobiopterin (qH2Bip), a transient intermediate of tetrahydrobiopterin (H4Bip)-dependent hydroxylation reactions, essential in living organisms, with important and varied human pathophysiological impacts, are a clear illustration. H4Bip regeneration may be impaired by competitive nonenzymatic autoxidation reactions, such as isomerization of qH2Bip into a more stable 7,8-H2Bip (H2Bip) isomer, and subsequent nonenzymatic oxidation reactions. The quinonoid qH2Bip intermediate thus plays a key role in H4Bip-dependent hydroxylation reactions. However, only a few experimental results have indirectly confirmed this finding while revealing the difficulty of isolating qH2Bip from H4Bip-containing solutions. As a result, no current H4Bip assay method allows this isomer to be quantified even by liquid chromatography-tandem mass spectrometry (MS/MS). Here, we report isolation, structural characterization, and abundance of qH2Bip formed upon H4Bip autoxidation using three methods integrated into MS/MS. First, we characterized the structure of the two observed H2B isomers using IR photodissociation spectroscopy in conjunction with quantum chemical calculations. Then, we used differential ion mobility spectrometry to fully separate all oxidized forms of H4Bip including qH2Bip. These data are consistent and show that qH2Bip can also be unambiguously identified thanks to its specific MS/MS transition. This finding paves the way for the quantification of qH2Bip with MS/MS methods. Most importantly, the half-life value of this intermediate is nearly equivalent to that of H4Bip (tens of minutes), suggesting that an accurate method of H4Bip analysis should include the quantification of qH2Bip.
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Affiliation(s)
- Eskander Alhajji
- Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Ayoub Boulghobra
- Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Myriam Bonose
- Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Francis Berthias
- Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Fathi Moussa
- Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Philippe Maître
- Institut de Chimie Physique, CNRS UMR 8000, Université Paris-Saclay, 91405 Orsay Cedex, France
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Rubach MP, Mukemba JP, Florence SM, Lopansri BK, Hyland K, Simmons RA, Langelier C, Nakielny S, DeRisi JL, Yeo TW, Anstey NM, Weinberg JB, Mwaikambo ED, Granger DL. Cerebrospinal Fluid Pterins, Pterin-Dependent Neurotransmitters, and Mortality in Pediatric Cerebral Malaria. J Infect Dis 2021; 224:1432-1441. [PMID: 33617646 PMCID: PMC8682765 DOI: 10.1093/infdis/jiab086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 02/10/2021] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Cerebral malaria (CM) pathogenesis remains incompletely understood. Having shown low systemic levels of tetrahydrobiopterin (BH4), an enzymatic cofactor for neurotransmitter synthesis, we hypothesized that BH4 and BH4-dependent neurotransmitters would likewise be low in cerebrospinal fluid (CSF) in CM. METHODS We prospectively enrolled Tanzanian children with CM and children with nonmalaria central nervous system conditions (NMCs). We measured CSF levels of BH4, neopterin, and BH4-dependent neurotransmitter metabolites, 3-O-methyldopa, homovanillic acid, and 5-hydroxyindoleacetate, and we derived age-adjusted z-scores using published reference ranges. RESULTS Cerebrospinal fluid BH4 was elevated in CM (n = 49) compared with NMC (n = 51) (z-score 0.75 vs -0.08; P < .001). Neopterin was increased in CM (z-score 4.05 vs 0.09; P < .001), and a cutoff at the upper limit of normal (60 nmol/L) was 100% sensitive for CM. Neurotransmitter metabolite levels were overall preserved. A higher CSF BH4/BH2 ratio was associated with increased odds of survival (odds ratio, 2.94; 95% confidence interval, 1.03-8.33; P = .043). CONCLUSION Despite low systemic BH4, CSF BH4 was elevated and associated with increased odds of survival in CM. Coma in malaria is not explained by deficiency of BH4-dependent neurotransmitters. Elevated CSF neopterin was 100% sensitive for CM diagnosis and warrants further assessment of its clinical utility for ruling out CM in malaria-endemic areas.
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Affiliation(s)
- Matthew P Rubach
- Department of Medicine, Division of Infectious Diseases, Duke University, Durham, North Carolina, USA
- Duke Global Health Institute, Duke University, Durham, North Carolina, USA
| | - Jackson P Mukemba
- Department of Pediatrics, Hubert Kairuki Memorial University, Dar es Salaam, United Republic of Tanzania
| | - Salvatore M Florence
- Department of Pediatrics, Hubert Kairuki Memorial University, Dar es Salaam, United Republic of Tanzania
| | - Bert K Lopansri
- Department of Medicine, Intermountain Healthcare, Salt Lake City, Utah, USA
- Department of Medicine, University of Utah School of Medicine and VA Medical Center, Salt Lake City, Utah, USA
| | - Keith Hyland
- Medical Neurogenetics Laboratories, Atlanta, Georgia, USA
| | - Ryan A Simmons
- Duke Global Health Institute, Duke University, Durham, North Carolina, USA
- Department of Biostatistics, Duke University, Durham, North Carolina, USA
| | - Charles Langelier
- Department of Medicine, Division of Infectious Diseases, University of California San Francisco, San Francisco, California, USA
- Chan Zuckerberg Biohub, San Francisco, California, USA
| | - Sara Nakielny
- Chan Zuckerberg Biohub, San Francisco, California, USA
| | - Joseph L DeRisi
- Chan Zuckerberg Biohub, San Francisco, California, USA
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Tsin W Yeo
- Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia
- Division of Medicine, Royal Darwin Hospital, Darwin, Northern Territory, Australia
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
| | - Nicholas M Anstey
- Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia
- Division of Medicine, Royal Darwin Hospital, Darwin, Northern Territory, Australia
| | - J Brice Weinberg
- Department of Medicine, Duke University and VA Medical Centers, Durham, North Carolina, USA
| | - Esther D Mwaikambo
- Department of Pediatrics, Hubert Kairuki Memorial University, Dar es Salaam, United Republic of Tanzania
| | - Donald L Granger
- Department of Medicine, University of Utah School of Medicine and VA Medical Center, Salt Lake City, Utah, USA
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Yuan TF, Huang HQ, Gao L, Wang ST, Li Y. A novel and reliable method for tetrahydrobiopterin quantification: Benzoyl chloride derivatization coupled with liquid chromatography-tandem mass spectrometry analysis. Free Radic Biol Med 2018; 118:119-125. [PMID: 29501564 DOI: 10.1016/j.freeradbiomed.2018.02.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 02/02/2018] [Accepted: 02/26/2018] [Indexed: 01/15/2023]
Abstract
Tetrahydrobiopterin (BH4) is a crucial cofactor for nitric oxide synthase, acylglycerol mono-oxygenase and aromatic amino acids hydroxylases. Its significant function for redox pathways in vivo attracted much attention for long. However, because of the oxidizable and substoichiometric nature, analysis of BH4 has never been truly achieved with adequate sensitivity and applicability. In the present work, we pioneeringly stabilized BH4 by derivatizing the active secondary amine on five-position with benzoyl chloride (BC). Benefiting from the favorable chemical stability and excellent mass spectrometric sensitivity of the product (BH4-BC), ultra-sensitive and reliable quantification of endogenous BH4 in plasma was achieved using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. In such methodology, BH4-BC-d5 was introduced as stable isotopic internal standard. And the limit of quantification (LOQ) could reach 0.02 ng mL-1. In the end, after investigation of plasma BH4 in healthy volunteers (n = 38), we found that the levels of BH4 were significantly and negatively correlated to age. Comparing with all the other existed strategies, the present method was obviously superior in sensitivity, specificity and practical applicability. It could be expected that this work could largely promote the future studies in BH4-related fields.
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Affiliation(s)
- Teng-Fei Yuan
- Department of Clinical Laboratory, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Han-Qi Huang
- Department of Clinical Laboratory, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Ling Gao
- Department of Clinical Laboratory, Renmin Hospital of Wuhan University, Wuhan 430060, China
| | - Shao-Ting Wang
- Department of Clinical Laboratory, Renmin Hospital of Wuhan University, Wuhan 430060, China.
| | - Yan Li
- Department of Clinical Laboratory, Renmin Hospital of Wuhan University, Wuhan 430060, China.
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Nitric oxide-polyamines cross-talk during dormancy release and germination of apple embryos. Nitric Oxide 2016; 68:38-50. [PMID: 27890695 DOI: 10.1016/j.niox.2016.11.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/15/2016] [Accepted: 11/16/2016] [Indexed: 12/20/2022]
Abstract
Nitric oxide (NO) and polyamines (PAs) belong to plant growth and development regulators. These compounds play a key role in numerous physiological processes e.g. seed germination. Based on the suggestion of overlapping of NO and PAs biosynthetic pathways, we demonstrated a cross-talk of NO and PAs in regulation of embryonic dormancy release. The aim of the work was to investigate an impact of PAs (Put, Spd and Spm) or NO short-term fumigation on nitrite, urea, Arg and ornithine (Orn) content, NO synthase-like (NOS-like) and arginase activity in axes of apple (Malus domestica Borkh.) embryos during dormancy alleviation and at the stage of termination of germination sensu stricto. NO, Put/Spd induced dormancy breakage and germination of apple embryos corresponded to stimulation of urea cycle and high free Arg pool in seedlings roots. After two days of the culture Put and Spd stimulated Arg dependent NO formation, inhibition of which was observed after Spm application. Put or Spd application as well as NO short-term pretreatment of apple embryos influenced level of ubiquitin-conjugated proteins. Higher abundance of such modified proteins correlated well to the declined content of nitrated proteins, suggesting their important role in regulation of embryo germination. NO led to stimulation of embryos germination by increasing level of free PAs (mostly Put). While transcriptomic approach showed down regulation of Spm synthesis and up-regulation of Spm degradation by NO, confirming negative role of Spm over-accumulation in embryo dormancy removal. Our data clearly indicate positive relationship of NO-Put/Spd acting as dormancy removing factors.
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Krasuska U, Ciacka K, Orzechowski S, Fettke J, Bogatek R, Gniazdowska A. Modification of the endogenous NO level influences apple embryos dormancy by alterations of nitrated and biotinylated protein patterns. PLANTA 2016; 244:877-91. [PMID: 27299743 DOI: 10.1007/s00425-016-2553-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 06/06/2016] [Indexed: 05/18/2023]
Abstract
NO donors and Arg remove dormancy of apple embryos and stimulate germination. Compounds lowering NO level (cPTIO, L -NAME, CAN) strengthen dormancy. Embryo transition from dormancy state to germination is linked to increased nitric oxide synthase (NOS)-like activity. Germination of embryos is associated with declined level of biotin containing proteins and nitrated proteins in soluble protein fraction of root axis. Pattern of nitrated proteins suggest that storage proteins are putative targets of nitration. Nitric oxide (NO) acts as a key regulatory factor in removal of seed dormancy and is a signal necessary for seed transition from dormant state into germination. Modulation of NO concentration in apple (Malus domestica Borkh.) embryos by NO fumigation, treatment with NO donor (S-nitroso-N-acetyl-D,L-penicillamine, SNAP), application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), N ω-nitro-L-arginine methyl ester (L-NAME), canavanine (CAN) or arginine (Arg) allowed us to investigate the NO impact on seed dormancy status. Arg analogs and NO scavenger strengthened embryo dormancy by lowering reactive nitrogen species level in embryonic axes. This effect was accompanied by strong inhibition of NOS-like activity, without significant influence on tissue NO2 (-) concentration. Germination sensu stricto of apple embryos initiated by dormancy breakage via short term NO treatment or Arg supplementation were linked to a reduced level of biotinylated proteins in root axis. Decrease of total soluble nitrated proteins was observed at the termination of germination sensu stricto. Also modulation of NO tissue status leads to modification in nitrated protein pattern. Among protein bands that correspond to molecular mass of approximately 95 kDa, storage proteins (legumin A-like and seed biotin-containing protein) were identified, and can be considered as good markers for seed dormancy status. Moreover, pattern of nitrated proteins suggest that biotin containing proteins are also targets of nitration.
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Affiliation(s)
- Urszula Krasuska
- Department of Plant Physiology, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Katarzyna Ciacka
- Department of Plant Physiology, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Sławomir Orzechowski
- Department of Biochemistry, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Joerg Fettke
- Biopolymer Analytics, University of Potsdam, Karl-Liebknecht 24-25, 14476, Potsdam-Golm, Germany
| | - Renata Bogatek
- Department of Plant Physiology, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, 02-776, Warsaw, Poland
| | - Agnieszka Gniazdowska
- Department of Plant Physiology, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, 02-776, Warsaw, Poland.
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Zvarik M, Martinicky D, Hunakova L, Sikurova L. Differences in pteridine urinary levels in patients with malignant and benign ovarian tumors in comparison with healthy individuals. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2015; 153:191-7. [PMID: 26414289 DOI: 10.1016/j.jphotobiol.2015.09.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 08/17/2015] [Accepted: 09/16/2015] [Indexed: 10/23/2022]
Abstract
Pteridines belong to a class of fluorescent metabolites that are excreted by humans in urine and their concentrations can reflect various pathophysiological states. We quantified the differences in urinary pteridine levels in patients with malignant and benign ovarian tumors and in healthy individuals. Urine samples were centrifuged and supernatants were oxidized by MnO2 before analysis. Levels of neopterin, biopterin, and pterin were assessed by fluorescence analysis of human urine after HPLC separation. We have revealed that the median neopterin levels were higher in urine samples from patients with malignant (0.226 μmol/mmol creatinine) and benign ovarian tumors (0.150 μmol/mmol creatinine) than in healthy subjects (0.056 μmol/mmol creatinine). The median neopterin levels of patients with malignant tumors were higher (1.5-times) than in patients with benign tumors. The median biopterin level in urine of patients with benign ovarian tumors (0.268 μmol/mmol creatinine) was found to be very close to the level in patients with malignant ovarian tumors (0.239 μmol/mmol creatinine), and both were higher than in healthy samples (0.096 μmol/mmol creatinine). The levels of urine pterin followed a pattern similar to neopterin levels for both ovarian tumors, but their concentrations were about three times lower than neopterin levels.
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Affiliation(s)
- M Zvarik
- Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Computer Science, Comenius University, Bratislava, Slovakia.
| | - D Martinicky
- Department of Gynecological Oncology, National Cancer Institute, Bratislava, Slovakia.
| | - L Hunakova
- Cancer Research Institute, Slovak Academy of Sciences, Bratislava, Slovakia.
| | - L Sikurova
- Department of Nuclear Physics and Biophysics, Faculty of Mathematics, Physics and Computer Science, Comenius University, Bratislava, Slovakia.
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Rubach MP, Mukemba J, Florence S, Lopansri BK, Hyland K, Volkheimer AD, Yeo TW, Anstey NM, Weinberg JB, Mwaikambo ED, Granger DL. Impaired systemic tetrahydrobiopterin bioavailability and increased oxidized biopterins in pediatric falciparum malaria: association with disease severity. PLoS Pathog 2015; 11:e1004655. [PMID: 25764173 PMCID: PMC4357384 DOI: 10.1371/journal.ppat.1004655] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 01/05/2015] [Indexed: 12/17/2022] Open
Abstract
Decreased bioavailability of nitric oxide (NO) is a major contributor to the pathophysiology of severe falciparum malaria. Tetrahydrobiopterin (BH4) is an enzyme cofactor required for NO synthesis from L-arginine. We hypothesized that systemic levels of BH₄ would be decreased in children with cerebral malaria, contributing to low NO bioavailability. In an observational study in Tanzania, we measured urine levels of biopterin in its various redox states (fully reduced [BH₄] and the oxidized metabolites, dihydrobiopterin [BH₂] and biopterin [B₀]) in children with uncomplicated malaria (UM, n = 55), cerebral malaria (CM, n = 45), non-malaria central nervous system conditions (NMC, n = 48), and in 111 healthy controls (HC). Median urine BH4 concentration in CM (1.10 [IQR:0.55-2.18] μmol/mmol creatinine) was significantly lower compared to each of the other three groups - UM (2.10 [IQR:1.32-3.14];p<0.001), NMC (1.52 [IQR:1.01-2.71];p = 0.002), and HC (1.60 [IQR:1.15-2.23];p = 0.005). Oxidized biopterins were increased, and the BH4:BH2 ratio markedly decreased in CM. In a multivariate logistic regression model, each Log10-unit decrease in urine BH4 was independently associated with a 3.85-fold (95% CI:1.89-7.61) increase in odds of CM (p<0.001). Low systemic BH4 levels and increased oxidized biopterins contribute to the low NO bioavailability observed in CM. Adjunctive therapy to regenerate BH4 may have a role in improving NO bioavailability and microvascular perfusion in severe falciparum malaria.
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Affiliation(s)
- Matthew P. Rubach
- Department of Medicine, Duke University and VA Medical Centers, Durham, North Carolina, United States of America
| | - Jackson Mukemba
- Department of Pediatrics, Hubert Kairuki Memorial University, Dar es Salaam, United Republic of Tanzania
| | - Salvatore Florence
- Department of Pediatrics, Hubert Kairuki Memorial University, Dar es Salaam, United Republic of Tanzania
| | - Bert K. Lopansri
- Department of Medicine, Intermountain Healthcare, Salt Lake City, Utah, United States of America
- Department of Medicine, University of Utah School of Medicine and VA Medical Center, Salt Lake City, Utah, United States of America
| | - Keith Hyland
- Neurochemistry Division, Medical Neurogenetics, Atlanta, Georgia, United States of America
| | - Alicia D. Volkheimer
- Department of Medicine, Duke University and VA Medical Centers, Durham, North Carolina, United States of America
| | - Tsin W. Yeo
- Global and Tropical Health Division, Menzies School for Health Research and Charles Darwin University, Darwin, Australia
- Division of Medicine, Royal Darwin Hospital, Darwin, Northern Territory, Australia
- Department of Medicine, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
| | - Nicholas M. Anstey
- Global and Tropical Health Division, Menzies School for Health Research and Charles Darwin University, Darwin, Australia
- Division of Medicine, Royal Darwin Hospital, Darwin, Northern Territory, Australia
| | - J. Brice Weinberg
- Department of Medicine, Duke University and VA Medical Centers, Durham, North Carolina, United States of America
| | - Esther D. Mwaikambo
- Department of Pediatrics, Hubert Kairuki Memorial University, Dar es Salaam, United Republic of Tanzania
| | - Donald L. Granger
- Department of Medicine, University of Utah School of Medicine and VA Medical Center, Salt Lake City, Utah, United States of America
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Mercimek-Mahmutoglu S, Sidky S, Hyland K, Patel J, Donner EJ, Logan W, Mendoza-Londono R, Moharir M, Raiman J, Schulze A, Siriwardena K, Yoon G, Kyriakopoulou L. Prevalence of inherited neurotransmitter disorders in patients with movement disorders and epilepsy: a retrospective cohort study. Orphanet J Rare Dis 2015; 10:12. [PMID: 25758715 PMCID: PMC4342151 DOI: 10.1186/s13023-015-0234-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 01/27/2015] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Inherited neurotransmitter disorders are primary defects of neurotransmitter metabolism. The main purpose of this retrospective cohort study was to identify prevalence of inherited neurotransmitter disorders. METHODS This retrospective cohort study does not have inclusion criteria; rather included all patients who underwent cerebrospinal fluid (CSF) homovanillic and 5-hydroxyindol acetic acid measurements. Patients with CSF neurotransmitter investigations suggestive of an inherited neurotransmitter disorder and patients with normal or non-diagnostic CSF neurotransmitter investigations underwent direct sequencing of single gene disorders. RESULTS There were 154 patients between October 2004 and July 2013. Four patients were excluded due to their diagnosis prior to this study dates. Two major clinical feature categories of patients who underwent lumbar puncture were movement disorders or epilepsy in our institution. Twenty out of the 150 patients (13.3%) were diagnosed with a genetic disorder including inherited neurotransmitter disorders (6 patients) (dihydropteridine reductase, 6-pyruvoyl-tetrahydropterin synthase, guanosine triphosphate cyclohydrolase I, tyrosine hydroxylase, pyridoxine dependent epilepsy due to mutations in the ALDH7A1 gene and pyridoxamine-5-phosphate oxidase deficiencies) and non-neurotransmitter disorders (14 patients). CONCLUSION Prevalence of inherited neurotransmitter disorders was 4% in our retrospective cohort study. Eight out of the 150 patients (5.3%) had one of the treatable inherited metabolic disorders with favorable short-term neurodevelopmental outcomes, highlighting the importance of an early and specific diagnosis. Whole exome or genome sequencing might shed light to unravel underlying genetic defects of new inherited neurotransmitter disorders in near future.
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Affiliation(s)
- Saadet Mercimek-Mahmutoglu
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada. .,Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Canada. .,Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, Genetic and Genome Biology, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
| | - Sarah Sidky
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | | | - Jaina Patel
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | - Elizabeth J Donner
- Division of Neurology, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | - William Logan
- Division of Neurology, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | - Roberto Mendoza-Londono
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | - Mahendranath Moharir
- Division of Neurology, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | - Julian Raiman
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | - Andreas Schulze
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada. .,Genetics and Genome Biology, Research Institute, The Hospital for Sick Children, Toronto, Canada.
| | - Komudi Siriwardena
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | - Grace Yoon
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada. .,Division of Neurology, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
| | - Lianna Kyriakopoulou
- Biochemical Genetics Laboratory, Department of Laboratory Medicine, University of Toronto, The Hospital for Sick Children, Toronto, Canada.
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Tomšíková H, Solich P, Nováková L. Sample preparation and UHPLC-FD analysis of pteridines in human urine. J Pharm Biomed Anal 2014; 95:265-72. [DOI: 10.1016/j.jpba.2014.03.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 03/05/2014] [Accepted: 03/09/2014] [Indexed: 11/30/2022]
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12
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Mortensen A, Lykkesfeldt J. Does vitamin C enhance nitric oxide bioavailability in a tetrahydrobiopterin-dependent manner? In vitro, in vivo and clinical studies. Nitric Oxide 2014; 36:51-7. [PMID: 24333161 DOI: 10.1016/j.niox.2013.12.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 10/09/2013] [Accepted: 12/03/2013] [Indexed: 12/31/2022]
Abstract
Ascorbate (Asc) has been shown to increase nitric oxide (NO) bioavailability and thereby improve endothelial function in patients showing signs of endothelial dysfunction. Tetrahydrobiopterin (BH₄) is a co-factor of endothelial nitric oxide synthase (eNOS) which may easily become oxidized to the inactive form dihydrobiopterin (BH₂). Asc may increase NO bioavailability by a number of mechanisms involving BH₄ and eNOS. Asc increases BH₄ bioavailability by either reducing oxidized BH₄ or preventing BH₄ from becoming oxidized in the first place. Asc could also increase NO bioavailability in a BH₄-independent manner by increasing eNOS activity by changing its phosphorylation and S-nitrosylation status or by upregulating eNOS expression. In this review, we discuss the putative mechanisms by which Asc may increase NO bioavailability through its interactions with BH₄ and eNOS.
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Affiliation(s)
- Alan Mortensen
- Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Jens Lykkesfeldt
- Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
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13
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Determination of pteridines in biological samples with an emphasis on their stability. Bioanalysis 2013; 5:2307-26. [DOI: 10.4155/bio.13.194] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Pteridines are a group of endogenous heterocyclic compounds whose concentrations in biological fluids may be increased in some disorders, such as infections, autoimmune disorders and cancer. In particular, pteridine concentrations in urine may represent promising noninvasive markers. However, their specificity requires further investigation. Pteridines can occur in three oxidation states with different stability. In order to enable the analysis of the unstable di- and tetra-hydroforms either an oxidation (mainly with iodine) or stabilization by reducing agents is applied. Due to the high polarity of pteridines, many analytical procedures employed ion-pair, ion-exchange or hydrophilic interaction liquid chromatography using mostly fluorescence detection. In the last decade, MS was found to be applicable. The objective of this Review is to show possibilities and different approaches in pteridine analysis in biological samples.
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14
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Frye RE, DeLatorre R, Taylor HB, Slattery J, Melnyk S, Chowdhury N, James SJ. Metabolic effects of sapropterin treatment in autism spectrum disorder: a preliminary study. Transl Psychiatry 2013; 3:e237. [PMID: 23462988 PMCID: PMC3625913 DOI: 10.1038/tp.2013.14] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/30/2012] [Accepted: 02/02/2013] [Indexed: 12/15/2022] Open
Abstract
Sapropterin, a synthetic form of tetrahydrobiopterin (BH4), has been reported to improve symptoms in children with autism spectrum disorder (ASD). However, as BH4 is involved in multiple metabolic pathway that have been found to be dysregulated in ASD, including redox, pterin, monoamine neurotransmitter, nitric oxide (NO) and immune metabolism, the metabolic pathway by which sapropterin exerts its therapeutic effect in ASD effect remains unclear. This study investigated which metabolic pathways were associated with symptomatic improvement during sapropterin treatment. Ten participants (ages 2-6 years old) with current social and/or language delays, ASD and a central BH4 concentration 30 nM l(-1) were treated with a daily morning 20 mg kg(-1) dose of sapropterin for 16 weeks in an open-label fashion. At baseline, 8 weeks and 16 weeks after starting the treatment, measures of language, social function and behavior and biomarkers of redox, pterin, monoamine neurotransmitter, NO and immune metabolism were obtained. Two participants discontinued the study, one from mild adverse effects and another due to noncompliance. Overall, improvements in subscales of the Preschool Language Scale (PLS), Vineland Adaptive Behavior Scale (VABS), Aberrant Behavior Checklist (ABC) and autism symptoms questionnaire (ASQ) were seen. Significant changes in biomarkers of pterin, redox and NO were found. Improvement on several subscales of the PLS, VABS, ABC and ASQ were moderated by baseline and changes in biomarkers of NO and pterin metabolism, particularly baseline NO metabolism. These data suggest that behavioral improvement associated with daily 20 mg kg(-1) sapropterin treatment may involve NO metabolism, particularly the status of pretreatment NO metabolism.
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Affiliation(s)
- R E Frye
- Department of Pediatrics, Arkansas Children's Hospital Research Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72202, USA.
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15
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Mortensen A, Lykkesfeldt J. Kinetics of acid-induced degradation of tetra- and dihydrobiopterin in relation to their relevance as biomarkers of endothelial function. Biomarkers 2013; 18:55-62. [PMID: 23066920 DOI: 10.3109/1354750x.2012.730552] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The ratio of the nitric oxide synthase (NOS) cofactor tetrahydrobiopterin (BH(4)) to its oxidized form dihydrobiopterin (BH(2)) has been suggested as an index of endothelial dysfunction. Consequently, much effort has been put into preserving the in vivo equilibrium between these labile analytes. In the present study, we conducted a series of stability experiments in aqueous solutions and blood to identify the most appropriate way of stabilizing BH(4) and BH(2). Based on our results, we are able to recommend that blood samples are immediately stabilized with dithioerythriol and protein precipitation conducted using trichloroacetic acid (TCA).
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Affiliation(s)
- Alan Mortensen
- Faculty of Health and Medical Sciences, Department of Veterinary Disease Biology, University of Copenhagen, Copenhagen, Denmark.
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16
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Fismen L, Eide T, Djurhuus R, Svardal AM. Simultaneous quantification of tetrahydrobiopterin, dihydrobiopterin, and biopterin by liquid chromatography coupled electrospray tandem mass spectrometry. Anal Biochem 2012; 430:163-70. [PMID: 22940649 DOI: 10.1016/j.ab.2012.08.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 07/05/2012] [Accepted: 08/20/2012] [Indexed: 11/27/2022]
Abstract
A simple and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method was developed for the quantification of tetrahydrobiopterin (BH4), dihydrobiopterin (BH2), and biopterin (B) in human umbilical vein endothelial cells (HUVECs). Freshly prepared cell samples were treated with a mixture consisting of 0.2M trichloroacetic acid (TCA) and a cocktail of various antioxidants in order to precipitate proteins and other cellular components and to stabilize red/ox conditions in the lysates. Chromatography of the cell lysates was performed on a Poroshell 120 SB-C18 column (2.7μm, 150×2.1mm) using a stepwise gradient elution made from two mobile phases. Quantification was performed on a triple quadrupole mass spectrometer employing electrospray ionization with the operating conditions as multiple reaction monitoring (MRM) at positive ion mode. Total chromatographic run time was 23min. The method was validated for analysis in HUVECs, and the limits of quantification were 1nM for BH4 and BH2 and 2.5nM for B. Standard curves were linear in the concentration ranges of 1 to 100nM for BH4 and BH2 and 2.5 to 100nM for B. The current study reports a novel method for the simultaneous and direct quantification of BH4, BH2, and B in a single injection.
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Affiliation(s)
- Lise Fismen
- Norwegian Underwater Intervention (NUI), 5848 Bergen, Norway.
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17
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Farook MF, DeCuypere M, Hyland K, Takumi T, LeDoux MS, Reiter LT. Altered serotonin, dopamine and norepinepherine levels in 15q duplication and Angelman syndrome mouse models. PLoS One 2012; 7:e43030. [PMID: 22916201 PMCID: PMC3420863 DOI: 10.1371/journal.pone.0043030] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 07/16/2012] [Indexed: 01/18/2023] Open
Abstract
Childhood neurodevelopmental disorders like Angelman syndrome and autism may be the result of underlying defects in neuronal plasticity and ongoing problems with synaptic signaling. Some of these defects may be due to abnormal monoamine levels in different regions of the brain. Ube3a, a gene that causes Angelman syndrome (AS) when maternally deleted and is associated with autism when maternally duplicated has recently been shown to regulate monoamine synthesis in the Drosophila brain. Therefore, we examined monoamine levels in striatum, ventral midbrain, frontal cerebral cortex, cerebellar cortex and hippocampus in Ube3a deficient and Ube3a duplication animals. We found that serotonin (5HT), a monoamine affected in autism, was elevated in the striatum and cortex of AS mice. Dopamine levels were almost uniformly elevated compared to control littermates in the striatum, midbrain and frontal cortex regardless of genotype in Ube3a deficient and Ube3a duplication animals. In the duplication 15q autism mouse model, paternal but not maternal duplication animals showed a decrease in 5HT levels when compared to their wild type littermates, in accordance with previously published data. However, maternal duplication animals show no significant changes in 5HT levels throughout the brain. These abnormal monoamine levels could be responsible for many of the behavioral abnormalities observed in both AS and autism, but further investigation is required to determine if any of these changes are purely dependent on Ube3a levels in the brain.
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Affiliation(s)
- M. Febin Farook
- Department of Neurology, UTHSC, Memphis, Tennessee, United States of America
| | - Michael DeCuypere
- Department of Neurosurgery, UTHSC, Memphis, Tennessee, United States of America
| | - Keith Hyland
- Medical Neurogenetics, LCC, Atlanta, Georgia, United States of America
| | - Toru Takumi
- Hiroshima University, School of Medicine, Hiroshima, Japan
| | - Mark S. LeDoux
- Department of Neurology, UTHSC, Memphis, Tennessee, United States of America
- Department of Anatomy and Neurobiology, UTHSC, Memphis, Tennessee, United States of America
| | - Lawrence T. Reiter
- Department of Neurology, UTHSC, Memphis, Tennessee, United States of America
- Department of Anatomy and Neurobiology, UTHSC, Memphis, Tennessee, United States of America
- Department of Pediatrics, UTHSC, Memphis, Tennessee, United States of America
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18
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Design of a single AAV vector for coexpression of TH and GCH1 to establish continuous DOPA synthesis in a rat model of Parkinson's disease. Mol Ther 2012; 20:1315-26. [PMID: 22294150 DOI: 10.1038/mt.2012.1] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Preclinical efficacy of continuous delivery of 3,4-dihydroxyphenylalanine (DOPA) with adeno-associated viral (AAV) vectors has recently been documented in animal models of Parkinson's disease (PD). So far, all studies have utilized a mix of two monocistronic vectors expressing either of the two genes, tyrosine hydroxylase (TH) and GTP cyclohydrolase-1 (GCH1), needed for DOPA production. Here, we present a novel vector design that enables efficient DOPA production from a single AAV vector in rats with complete unilateral dopamine (DA) lesions. Functional efficacy was assessed with drug-induced and spontaneous motor behavioral tests where vector-treated animals showed near complete and stable recovery within 1 month. Recovery of motor function was associated with restoration of extracellular DA levels as assessed by online microdialysis. Histological analysis showed robust transgene expression not only in the striatum but also in overlying cortical areas. In globus pallidus, we noted loss of NeuN staining, which might be due to different sensitivity in neuronal populations to transgene expression. Taken together, we present a single AAV vector design that result in efficient DOPA production and wide-spread transduction. This is a favorable starting point for continued translation toward a therapeutic application, although future studies need to carefully review target region, vector spread and dilution with this approach.
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19
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Higgins CE, Gross SS. The N-terminal peptide of mammalian GTP cyclohydrolase I is an autoinhibitory control element and contributes to binding the allosteric regulatory protein GFRP. J Biol Chem 2010; 286:11919-28. [PMID: 21163945 DOI: 10.1074/jbc.m110.196204] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GTP cyclohydrolase I (GTPCH) is the rate-limiting enzyme for biosynthesis of tetrahydrobiopterin (BH4), an obligate cofactor for NO synthases and aromatic amino acid hydroxylases. BH4 can limit its own synthesis by triggering decameric GTPCH to assemble in an inhibitory complex with two GTPCH feedback regulatory protein (GFRP) pentamers. Subsequent phenylalanine binding to the GTPCH·GFRP inhibitory complex converts it to a stimulatory complex. An N-terminal inhibitory peptide in GTPCH may also contribute to autoregulation of GTPCH activity, but mechanisms are undefined. To characterize potential regulatory actions of the N-terminal peptide in rat GTPCH, we expressed, purified, and characterized a truncation mutant, devoid of 45 N-terminal amino acids (Δ45-GTPCH) and contrasted its catalytic and GFRP binding properties to wild type GTPCH (wt-GTPCH). Contrary to prior reports, we show that GFRP binds wt-GTPCH in the absence of any small molecule effector, resulting in allosteric stimulation of GTPCH activity: a 20% increase in Vmax, 50% decrease in KmGTP, and increase in Hill coefficient to 1.6, from 1.0. These features of GFRP-stimulated wt-GTPCH activity were phenocopied by Δ45-GTPCH in the absence of bound GFRP. Addition of GFRP to Δ45-GTPCH failed to elicit complex formation or a substantial further increase in GTPCH catalytic activity. Expression of Δ45-GTPCH in HEK-293 cells elicited 3-fold greater BH4 accumulation than an equivalent of wt-GTPCH. Together, results indicate that the N-terminal peptide exerts autoinhibitory control over rat GTPCH and is required for GFRP binding on its own. Displacement of the autoinhibitory peptide provides a molecular mechanism for physiological up-regulation of GTPCH activity.
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Affiliation(s)
- Christina E Higgins
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021, USA
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20
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Frye RE. Central tetrahydrobiopterin concentration in neurodevelopmental disorders. Front Neurosci 2010; 4:52. [PMID: 20661295 PMCID: PMC2906199 DOI: 10.3389/fnins.2010.00052] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 06/22/2010] [Indexed: 02/02/2023] Open
Abstract
Tetrahydrobiopterin (BH4) is a naturally occurring cofactor essential for critical metabolic pathways. Studies suggest that BH4 supplementation may ameliorate autism symptoms; the biological mechanism for such an effect is unknown. To help understand the relation between central BH4 concentration and systemic metabolism and to develop a biomarker of central BH4 concentration, the relationship between cerebrospinal fluid BH4 concentration and serum amino acids was studied. BH4 concentration was found to be distributed in two groups, a lower and higher BH4 concentration group. Two serum amino acids, citrulline and methionine, differentiated these groups, and the ratio of serum citrulline-to-methionine was found to correlate with the cerebrospinal fluid BH4 concentration (r = −0.67, p < 0.05). Both citrulline and methionine are substrates in inflammation and oxidative stress pathways – two pathways that utilize BH4 and are abnormally activated in autism. These data suggests that central BH4 concentration may be related to systemic inflammation and oxidative stress pathways.
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Affiliation(s)
- Richard E Frye
- Department of Pediatrics, Division of Child and Adolescent Neurology and The Children's Learning Institute, University of Texas Health Science Center Houston, TX, USA
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21
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Björklund T, Carlsson T, Cederfjäll EA, Carta M, Kirik D. Optimized adeno-associated viral vector-mediated striatal DOPA delivery restores sensorimotor function and prevents dyskinesias in a model of advanced Parkinson's disease. ACTA ACUST UNITED AC 2010; 133:496-511. [PMID: 20129936 DOI: 10.1093/brain/awp314] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Viral vector-mediated gene transfer utilizing adeno-associated viral vectors has recently entered clinical testing as a novel tool for delivery of therapeutic agents to the brain. Clinical trials in Parkinson's disease using adeno-associated viral vector-based gene therapy have shown the safety of the approach. Further efforts in this area will show if gene-based approaches can rival the therapeutic efficacy achieved with the best pharmacological therapy or other, already established, surgical interventions. One of the strategies under development for clinical application is continuous 3,4-dihydroxyphenylalanine delivery. This approach has been shown to be efficient in restoring motor function and reducing established dyskinesias in rats with a partial lesion of the nigrostriatal dopamine projection. Here we utilized high purity recombinant adeno-associated viral vectors serotype 5 coding for tyrosine hydroxylase and its co-factor synthesizing enzyme guanosine-5'-triphosphate cyclohydrolase-1, delivered at an optimal ratio of 5 : 1, to show that the enhanced 3,4-dihydroxyphenylalanine production obtained with this optimized delivery system results in robust recovery of function in spontaneous motor tests after complete dopamine denervation. We found that the therapeutic efficacy was substantial and could be maintained for at least 6 months. The tyrosine hydroxylase plus guanosine-5'-triphosphate cyclohydrolase-1 treated animals were resistant to developing dyskinesias upon peripheral l-3,4-dihydroxyphenylalanine drug challenge, which is consistent with the interpretation that continuous dopamine stimulation resulted in a normalization of the post-synaptic response. Interestingly, recovery of forelimb use in the stepping test observed here was maintained even after a second lesion depleting the serotonin input to the forebrain, suggesting that the therapeutic efficacy was not solely dependent on dopamine synthesis and release from striatal serotonergic terminals. Taken together these results show that vector-mediated continuous 3,4-dihydroxyphenylalanine delivery has the potential to provide significant symptomatic relief even in advanced stages of Parkinson's disease.
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Affiliation(s)
- Tomas Björklund
- Brain Repair and Imaging in Neural Systems, 22184 Lund, Sweden.
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22
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Kim HL, Kim DH, Lee YK, Park SO, Lee YW, Kwon OS, Park YS. An enzymatic method to distinguish tetrahydrobiopterin from oxidized biopterins using UDP-glucose:tetrahydrobiopterin glucosyltransferase. Anal Biochem 2010; 397:79-83. [PMID: 19819217 DOI: 10.1016/j.ab.2009.10.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 09/28/2009] [Accepted: 10/06/2009] [Indexed: 11/15/2022]
Abstract
The quantitative determination of tetrahydrobiopterin (BH4) and its oxidized forms (dihydrobiopterin and biopterin) is important in searching for possible markers of neuropsychiatric and cardiovascular disorders as well as in diagnosing BH4 deficiencies. Currently, two high-performance liquid chromatography (HPLC) methods are available, although both have some limitations. We developed an enzymatic method to distinguish BH4 from the oxidized forms by employing BH4:UDP-glucose alpha-glucosyltransferase (BGluT), which catalyzes glucosyl transfer from UDP-glucose to BH4. The recombinant BGluT isolated from Escherichia coli converted essentially all of the BH4 in a mixture containing oxidized biopterins to the glucoside while leaving the oxidized forms intact. Therefore, acidic iodine oxidation of the reaction mixture followed by single fluorescence HPLC permitted the determination of biopterin and biopterin-glucoside, which represent oxidized biopterins and BH4, respectively. The validity of the method was evaluated using authentic biopterins and animal samples such as human urine, rat plasma, and rat liver. The BGluT-catalyzed reaction not only would reduce the burden of chromatographic separation but also would promise non-HPLC analysis of BH4.
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Affiliation(s)
- Hye-Lim Kim
- Frontier Inje Research for Science and Technology Research Group, School of Biological Sciences, Inje University, Kimhae 621-749, Republic of Korea
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23
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Hyland K. Clinical Utility of Monoamine Neurotransmitter Metabolite Analysis in Cerebrospinal Fluid. Clin Chem 2008; 54:633-41. [DOI: 10.1373/clinchem.2007.099986] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractBackground: Measurements of monoamine neurotransmitters and their metabolites in plasma and urine are commonly used to aid in the detection and monitoring of neuroblastoma and pheochromocytoma and the evaluation of hypotension or hypertension. Measurements of these neurotransmitters and metabolites can also be helpful in the investigation of disorders that primarily affect the central nervous system, but only when the measurements are made in cerebrospinal fluid (CSF).Content: I describe CSF profiles of monoamine metabolites in the primary and secondary defects affecting serotonin and catecholamine metabolism. I outline the methods required to analyze these metabolites together with details of specific sample handling requirements, sample stability, and interfering compounds, and I emphasize a need for age-related reference intervals.Summary: Measured values of monoamine metabolites in CSF provide only a single-time snapshot of the overall turnover of the monoamine neurotransmitters within the brain. Because these measurements reflect the average concentrations accumulated from all brain regions plus the regional changes that occur within the spinal cord, they may miss subtle abnormalities in particular brain regions or changes that occur on a minute-to-minute or diurnal basis. Clearly defined diagnosed disorders are currently limited to those affecting synthetic and catabolic pathways. In many cases, abnormal monoamine metabolite concentrations are found in CSF and an underlying etiology cannot be found. Molecular screening of candidate genes related to steps in the neurotransmission process, including storage in presynaptic nerve vesicles, release, interaction with receptors, and reuptake, might be a fruitful endeavor in these cases.
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24
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Nandi M, Kelly P, Vallance P, Leiper J. Over-expression of GTP-cyclohydrolase 1 feedback regulatory protein attenuates LPS and cytokine-stimulated nitric oxide production. Vasc Med 2008; 13:29-36. [PMID: 18372436 DOI: 10.1177/1358863x07085916] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
GTP-cyclohydrolase 1 (GTP-CH1) catalyses the first and rate-limiting step for the de novo production of tetrahydrobiopterin (BH(4)), an essential cofactor for nitric oxide synthase (NOS). The GTP-CH1-BH(4) pathway is emerging as an important regulator in a number of pathologies associated with over-production of nitric oxide (NO) and hence a more detailed understanding of this pathway may lead to novel therapeutic targets for the treatment of certain vascular diseases. GTP-CH1 activity can be inhibited by BH(4) through its protein-protein interactions with GTP-CH1 regulatory protein (GFRP), and transcriptional and post-translational modification of both GTP-CH1 and GFRP have been reported in response to proinflammatory stimuli. However, the functional significance of GFRP/GTP-CH1 interactions on NO pathways has not yet been demonstrated. We aimed to investigate whether over-expression of GFRP could affect NO production in living cells. Over-expression of N-terminally Myc-tagged recombinant human GFRP in the murine endothelial cell line sEnd 1 resulted in no significant effect on basal BH(4) nor NO levels but significantly attenuated the rise in BH(4) and NO observed following lipopolysaccharide and cytokine stimulation of cells. This study demonstrates that GFRP can play a direct regulatory role in iNOS-mediated NO synthesis and suggests that the allosteric regulation of GTP-CH1 activity by GFRP may be an important mechanism regulating BH(4) and NO levels in vivo.
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Affiliation(s)
- Manasi Nandi
- Centre for Clinical Pharmacology, Division of Medicine, University College London, London, UK.
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25
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Lam AAJ, Hyland K, Heales SJR. Tetrahydrobiopterin availability, nitric oxide metabolism and glutathione status in the hph-1 mouse; implications for the pathogenesis and treatment of tetrahydrobiopterin deficiency states. J Inherit Metab Dis 2007; 30:256-62. [PMID: 17242981 DOI: 10.1007/s10545-006-0502-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 12/13/2006] [Accepted: 12/18/2006] [Indexed: 01/23/2023]
Abstract
Tetrahydrobiopterin (BH4) is an essential cofactor for all isoforms of nitric oxide synthase. While it is well established that BH4 deficiency states are associated with impairment of dopamine, serotonin and phenylalanine metabolism, less is known with regard to the effects of deficiency of the cofactor upon nitric oxide (NO) metabolism. In this study, we have evaluated the effects of partial BH4 deficiency upon (a) tissue availability of the antioxidant glutathione, (b) basal NO production and (c) NO generation following exposure to lipopolysaccharide (LPS), which is known to increase expression of the inducible form of nitric oxide synthase. Using the hph-1 mouse, which displays a partial BH4 deficiency owing to impaired activity of GTP cyclohydrolase, we report decreased levels of glutathione in brain and kidney and evidence for decreased basal generation of nitric oxide in the periphery (as judged by the plasma nitrate plus nitrite concentration). Following LPS administration, peripheral NO generation increases. However, the concentration of plasma nitrate plus nitrite achieved was significantly decreased in the hph-1 mouse. Furthermore, LPS administration caused loss of glutathione in both wild-type and hph-1 liver and kidney. It is concluded that cofactor replacement, sufficient to fully correct a cellular BH4 deficiency, may be of benefit to patients with inborn errors of BH4 metabolism.
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Affiliation(s)
- A A J Lam
- Department of Molecular Neuroscience, Institute of Neurology, London, UK
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26
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Hyland K. Cerebrospinal fluid analysis in the diagnosis of treatable inherited disorders of neurotransmitter metabolism. FUTURE NEUROLOGY 2006. [DOI: 10.2217/14796708.1.5.593] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The inherited disorders affecting dopamine and serotonin (5-hydroxytryptamine) metabolism are being recognized as treatable causes of neurological problems that affect infants, children and adults. Diagnosis of these conditions in many cases requires that neurotransmitter metabolites, and the cofactors required for their synthesis, be measured in cerebrospinal fluid (CSF). This review will concentrate on the inherited disorders that affect dopamine and serotonin biosynthesis and an overview will be given of the metabolism of these two neurotransmitters. The metabolite pattern found in each known defect is also given. Emphasis is put on the need to collect and handle CSF in the appropriate manner if meaningful results from neurotransmitter metabolite measurements are to be obtained. The clinical phenotypes that might be associated with neurotransmitter deficiency are described, and finally, speculation will be provided as to the metabolite patterns that might occur in the CSF in disorders that are yet to be discovered.
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Affiliation(s)
- Keith Hyland
- Horizon Molecular Medicine, One Dunwoody Park, Suite 250, Atlanta, GA 30338, USA
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27
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Lopansri BK, Anstey NM, Stoddard GJ, Mwaikambo ED, Boutlis CS, Tjitra E, Maniboey H, Hobbs MR, Levesque MC, Weinberg JB, Granger DL. Elevated plasma phenylalanine in severe malaria and implications for pathophysiology of neurological complications. Infect Immun 2006; 74:3355-9. [PMID: 16714564 PMCID: PMC1479261 DOI: 10.1128/iai.02106-05] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cerebral malaria is associated with decreased production of nitric oxide and decreased levels of its precursor, l-arginine. Abnormal amino acid metabolism may thus be an important factor in malaria pathogenesis. We sought to determine if other amino acid abnormalities are associated with disease severity in falciparum malaria. Subjects were enrolled in Dar es Salaam, Tanzania (children) (n = 126), and Papua, Indonesia (adults) (n = 156), in two separate studies. Plasma samples were collected from subjects with WHO-defined cerebral malaria (children), all forms of severe malaria (adults), and uncomplicated malaria (children and adults). Healthy children and adults without fever or illness served as controls. Plasma amino acids were measured using reverse-phase high-performance liquid chromatography with fluorescence detection. Several plasma amino acids were significantly lower in the clinical malaria groups than in healthy controls. Despite the differences, phenylalanine was the only amino acid with mean levels outside the normal range (40 to 84 microM) and was markedly elevated in children with cerebral malaria (median [95% confidence interval], 163 [134 to 193] microM; P < 0.0001) and adults with all forms of severe malaria (median [95% confidence interval], 129 [111 to 155] microM; P < 0.0001). In adults who survived severe malaria, phenylalanine levels returned to normal, with clinical improvement (P = 0.0002). Maintenance of plasma phenylalanine homeostasis is disrupted in severe malaria, leading to significant hyperphenylalaninemia. This is likely a result of an acquired abnormality in the function of the liver enzyme phenylalanine hydroxylase. Determination of the mechanism of this abnormality may contribute to the understanding of neurological complications in malaria.
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Affiliation(s)
- Bert K Lopansri
- Division of Infectious Diseases, VA and University of Utah School of Medicine, Salt Lake City, Utah 84132, USA.
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Huang A, Zhang YY, Chen K, Hatakeyama K, Keaney JF. Cytokine-stimulated GTP cyclohydrolase I expression in endothelial cells requires coordinated activation of nuclear factor-kappaB and Stat1/Stat3. Circ Res 2005; 96:164-71. [PMID: 15604419 DOI: 10.1161/01.res.0000153669.24827.df] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Endothelial production of nitric oxide (NO) is dependent on adequate cellular levels of tetrahydrobiopterin (BH4), an important cofactor for the nitric oxide synthases. Vascular diseases are often characterized by vessel wall inflammation and cytokine treatment of endothelial cells increases BH4 levels, in part through the induction of GTP cyclohydrolase I (GTPCH I), the rate-limiting enzyme for BH4 biosynthesis. However, the molecular mechanisms of cytokine-mediated GTPCH I induction in the endothelium are not entirely clear. We sought to investigate the signaling pathways whereby cytokines induce GTPCH I expression in human umbilical vein endothelial cells (HUVECs). Interferon-gamma (IFN-gamma) induced endothelial cell GTPCH I protein and BH4 modestly, whereas high-level induction required combinations of IFN-gamma and tumor necrosis factor-alpha (TNF-alpha). In the presence of IFN-gamma, TNF-alpha increased GTPCH I mRNA in a manner dependent on nuclear factor-kappaB (NF-kappaB), as this effect was abrogated by overexpression of a dominant-negative IkappaB construct. HUVEC IFN-gamma treatment resulted in signal transducer and activator of transcription 1 (Stat1) activation and DNA binding in a Jak2-dependent manner, as this was inhibited by AG490. Conversely, overexpression of Jak2 effectively substituted for IFN-gamma in supporting TNF-alpha-mediated GTPCH I induction. The role of IFN-gamma was also Stat1-dependent as Stat1-null cells exhibited no GTPCH I induction in response to cytokines. However, Stat1 activation with oncostatin M failed to support TNF-alpha-mediated GTPCH I induction because of concomitant Stat3 activation. Consistent with this notion, siRNA-mediated Stat3 gene silencing allowed oncostatin M to substitute for IFN-gamma in this system. These data implicate both NF-kappaB and Stat1 in endothelial cell cytokine-stimulated GTPCH I induction and highlight the role of Stat3 in modulating Stat1-supported gene transcription. Thus, IFN-gamma and TNF-alpha exert distinct but cooperative roles for BH4 biosynthesis in endothelium that may have important implications for vascular function during vascular inflammation.
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Affiliation(s)
- Annong Huang
- Evans Memorial Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Mass 02118, USA
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Kweon GR, Marks JD, Krencik R, Leung EH, Schumacker PT, Hyland K, Kang UJ. Distinct mechanisms of neurodegeneration induced by chronic complex I inhibition in dopaminergic and non-dopaminergic cells. J Biol Chem 2004; 279:51783-92. [PMID: 15469939 DOI: 10.1074/jbc.m407336200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Chronic mitochondrial dysfunction, in particular of complex I, has been strongly implicated in the dopaminergic neurodegeneration in Parkinson's disease. To elucidate the mechanisms of chronic complex I disruption-induced neurodegeneration, we induced differentiation of immortalized midbrain dopaminergic (MN9D) and non-dopaminergic (MN9X) neuronal cells, to maintain them in culture without significant cell proliferation and compared their survivals following chronic exposure to nanomolar rotenone, an irreversible complex I inhibitor. Rotenone killed more dopaminergic MN9D cells than non-dopaminergic MN9X cells. Oxidative stress played an important role in rotenone-induced neurodegeneration of MN9X cells, but not MN9D cells: rotenone oxidatively modified proteins more in MN9X cells than in MN9D cells and antioxidants decreased rotenone toxicity only in MN9X cells. MN9X cells were also more sensitive to exogenous oxidants than MN9D cells. In contrast, disruption of bioenergetics played a more important role in MN9D cells: rotenone decreased mitochondrial membrane protential and ATP levels in MN9D cells more than in MN9X cells. Supplementation of cellular energy with a ketone body, D-beta-hydroxybutyrate, decreased rotenone toxicity in MN9D cells, but not in MN9X cells. MN9D cells were also more susceptible to disruption of oxidative phosphorylation or glycolysis than MN9X cells. These findings indicate that, during chronic rotenone exposure, MN9D cells die primarily through mitochondrial energy disruption, whereas MN9X cells die primarily via oxidative stress. Thus, intrinsic properties of individual cell types play important roles in determining the predominant mechanism of complex I inhibition-induced neurodegeneration.
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Affiliation(s)
- Gi-Ryang Kweon
- Department of Neurology, The University of Chicago, Chicago, Illinois 60637, USA
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Abstract
The investigation of infants and children with suspected pediatric neurotransmitter diseases affecting serotonin and catecholamine metabolism is complicated because the measurement of metabolites in peripheral fluids is generally uninformative. Disorders that affect catecholamine (dopamine and norepinephrine) and serotonin neurotransmission, and that do not present with hyperphenylalaninemia, require that a lumbar puncture be performed and that specific metabolites be assessed in the collected cerebrospinal fluid. This review will discuss the disorders affecting catecholamine and serotonin biosynthesis, sample collection and handling, diagnostic methods and expected profiles, problems with diagnosis, and as yet to be described conditions that might be detected using current diagnostic methodologies.
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Affiliation(s)
- Keith Hyland
- Institute of Metabolic Disease, Dallas, TX 75229, USA.
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Nakai K, Urushihara M, Kubota Y, Kosaka H. Ascorbate enhances iNOS activity by increasing tetrahydrobiopterin in RAW 264.7 cells. Free Radic Biol Med 2003; 35:929-37. [PMID: 14556857 DOI: 10.1016/s0891-5849(03)00463-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Studies on the effect of ascorbic acid on inducible nitric oxide synthase (iNOS) activity are few and diverse, likely to be dependent on the species of cells. We investigated a role of ascorbic acid in iNOS induction and nitric oxide (NO) generation in mouse macrophage cell line RAW 264.7. Although interferon- (IFN-) gamma alone produced NO end products, ascorbic acid enhanced NO production only when cells were synergistically stimulated with IFN-gamma plus Escherichia coli lipopolysaccharide (LPS). Ascorbate neither enhanced nor decreased the expression of iNOS protein in RAW 264.7 cells, in contrast to the reports that ascorbic acid augments iNOS induction in a mouse macrophage-like cell line J774.1 and that ascorbate suppresses iNOS induction in rat skeletal muscle endothelial cells. Intracellular levels of tetrahydrobiopterin (BH4), a cofactor for iNOS, were increased by ascorbate in RAW 264.7 cells. However, ascorbate did not increase GTP cyclohydrolase I mRNA, the main enzyme at the critical steps in the BH4 synthetic pathway, expression levels and activity. Sepiapterin, which supplies BH4 via salvage pathway, more efficiently enhanced NO production if ascorbate was added. These data suggest that enhanced activation of iNOS by ascorbic acid is mediated by increasing the stability of BH4 in RAW 264.7 cells.
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Affiliation(s)
- Kozo Nakai
- Department of Dermatology, Kagawa Medical University, Kagawa, Japan
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Li W, Knowlton D, Woodward WR, Habecker BA. Regulation of noradrenergic function by inflammatory cytokines and depolarization. J Neurochem 2003; 86:774-83. [PMID: 12859689 DOI: 10.1046/j.1471-4159.2003.01890.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although the sympathetic neurons innervating the heart are exposed to the inflammatory cytokines cardiotrophin-1 (CT-1), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFalpha) after myocardial infarction, the effects of these cytokines on noradrenergic function are not well understood. We used cultured sympathetic neurons to investigate the effects of these cytokines on catecholamine content, the tyrosine hydroxylase co-factor, tetrahydrobiopterin (BH4), and norepinephrine (NE) uptake. CT-1, but not IL-6 or TNFalpha, suppressed NE uptake and catecholamines in these neurons, whereas CT-1 and, to a lesser extent, IL-6 decreased BH4 content. CT-1 exerted these effects by decreasing tyrosine hydroxylase, GTP cyclohydrolase (GCH) and NE transporter mRNAs, while IL-6 lowered only GCH mRNA. The neurons innervating the heart are also activated by the central nervous system after myocardial infarction. We examined the combined effect of depolarization and cytokines on noradrenergic function. In CT-1-treated cells, depolarization caused a small increase in BH4 and NE uptake, and a large increase in catecholamines. These changes were accompanied by increased TH, GCH and NE transporter mRNAs. CT-1 and depolarization regulate expression of noradrenergic properties in an opposing manner, and the combined treatment results in elevated cellular catecholamines and decreased NE uptake relative to control cells.
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Affiliation(s)
- Wei Li
- Department of Physiology & Pharmacology, Oregon Health & Science University School of Medicine, Portland, Oregon 97239, USA
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Abstract
During development, sympathetic neurons innervating rodent sweat glands undergo a target-induced change in neurotransmitter phenotype from noradrenergic to cholinergic. Although the sweat gland innervation in the adult mouse is cholinergic and catecholamines are absent, these neurons continue to express tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis. The developmental suppression of noradrenergic function in these mouse sympathetic neurons is not well understood. We investigated whether the downregulation of the enzyme aromatic l-amino acid decarboxylase (AADC) or the TH cofactor tetrahydrobiopterin (BH4) could account for the loss of catecholamines in these neurons. AADC levels did not decrease during development, and adult cholinergic sympathetic neurons were strongly immunoreactive for AADC. In contrast, BH4 levels dropped significantly in murine sweat gland-containing footpads during the time period when the gland innervation was switching from making norepinephrine to acetylcholine. Immunoreactivity for the rate-limiting BH4 synthetic enzyme GTP cyclohydrolase (GCH) became undetectable in the sweat gland neurons during this phenotypic conversion, suggesting that sweat glands reduce BH4 levels by suppressing GCH expression during development. Furthermore, extracts from sweat gland-containing footpads suppressed BH4 in cultured mouse sympathetic neurons, and addition of the BH4 precursor sepiapterin rescued catecholamine production in neurons treated with footpad extracts. Together, these results suggest that the mouse sweat gland-derived cholinergic differentiation factor functionally suppresses the noradrenergic phenotype during development by inhibiting production of the TH cofactor, BH4. These data also indicate that GCH expression, which is often coordinately regulated with TH expression, can be controlled independently of TH during development.
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Hurshman AR, Marletta MA. Reactions catalyzed by the heme domain of inducible nitric oxide synthase: evidence for the involvement of tetrahydrobiopterin in electron transfer. Biochemistry 2002; 41:3439-56. [PMID: 11876653 DOI: 10.1021/bi012002h] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The heme domain (iNOS(heme)) of inducible nitric oxide synthase (iNOS) was expressed in Escherichia coli and purified to homogeneity. Characterization of the expressed iNOS(heme) shows it to behave in all respects like full-length iNOS. iNOS(heme) is isolated without bound pterin but can be readily reconstituted with (6R)-5,6,7,8-tetrahydro-L-biopterin (H(4)B) or other pterins. The reactivity of pterin-bound and pterin-free iNOS(heme) was examined, using sodium dithionite as the reductant. H(4)B-bound iNOS(heme) catalyzes both steps of the NOS reaction, hydroxylating arginine to N(G)-hydroxy-L-arginine (NHA) and oxidizing NHA to citrulline and *NO. Maximal product formation (0.93 plus minus 0.12 equiv of NHA from arginine and 0.83 plus minus 0.08 equiv of citrulline from NHA) requires the addition of 2 to 2.5 electron equiv. Full reduction of H(4)B-bound iNOS(heme) with dithionite also requires 2 to 2.5 electron equiv. These data together demonstrate that fully reduced H(4)B-bound iNOS(heme) is able to catalyze the formation of 1 equiv of product in the absence of electrons from dithionite. Arginine hydroxylation requires the presence of a bound, redox-active tetrahydropterin; pterin-free iNOS(heme) or iNOS(heme) reconstituted with a redox-inactive analogue, 6(R,S)-methyl-5-deaza-5,6,7,8-tetrahydropterin, did not form NHA under these conditions. H(4)B has an integral role in NHA oxidation as well. Pterin-free iNOS(heme) oxidizes NHA to citrulline, N(delta)-cyanoornithine, an unidentified amino acid, and NO(-). Maximal product formation (0.75 plus minus 0.01 equiv of amino acid products) requires the addition of 2 to 2.5 electron equiv, but reduction of pterin-free iNOS(heme) requires only 1 to 1.5 electron equiv, indicating that both electrons for the oxidation of NHA by pterin-free iNOS(heme) are derived from dithionite. These data provide strong evidence that H(4)B is involved in electron transfer in NOS catalysis.
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Affiliation(s)
- Amy R Hurshman
- Howard Hughes Medical Institute, Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109-0606, USA
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Laursen JB, Boesgaard S, Trautner S, Rubin I, Poulsen HE, Aldershvile J. Endothelium-dependent vasorelaxation in inhibited by in vivo depletion of vascular thiol levels: role of endothelial nitric oxide synthase. Free Radic Res 2001; 35:387-94. [PMID: 11697135 DOI: 10.1080/10715760100300901] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Thiols like glutathione may serve as reducing cofactors in the production of nitric oxide (NO) and protect NO from inactivation by radical oxygen species. Depletion of thiol compounds reduces NO-mediated vascular effects in vitro and in vivo. The mechanisms underlying these actions are not clear, but may involve decreased synthesis of NO and/or increased degradation of NO. This study investigates the effect of glutathione depletion on the response to NO-mediated vasodilation induced by acetylcholine (Ach, 10 micrograms/kg), endothelial NO synthase (eNOS) activity and potential markers of vascular superoxide anion (O2.-) production in conscious chronically catheterized rats. Thiol depletion induced by buthionine sulfoximine (BSO, 1 g i.p. within 24 h) decreased the hypotensive effect of Ach by 30% (MAP reduction before BSO 27 +/- 3 mmHg, 19 +/- 3 mmHg after BSO, (mean +/- SEM), p < .05, n = 8). The impaired effect of Ach was associated with a significant reduction in eNOS activity (control: 7.7 +/- 0.8, BSO: 3.9 +/- 0.4 pmol/min/mg protein (p < .05), n = 6). In contrast, neither NADH/NADPH driven membrane-associated oxidases nor lucigenin reductase activity were significantly (p < .05) affected by BSO (BSO: 4415 +/- 123, control: 4105 +/- 455 counts/mg; n = 6) in rat aorta. It is concluded that in vivo thiol depletion results in endothelial dysfunction and a reduced receptor-mediated vascular relaxation. This effect is caused by reduced endothelial NO formation.
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Affiliation(s)
- J B Laursen
- Medical Department B, Division of Cardiology, Institute of Biochemistry, Department of Clinical Pharmacology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
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Abstract
Inducible nitric-oxide synthase (NOS) was expressed and purified in the absence of 6(R)-tetrahydro-l-biopterin (H(4)B). Pterin-free NOS exhibits a Soret band (416-420 nm) characteristic of predominantly low spin heme and does not catalyze the formation of nitric oxide (. NO) (Rusche, K. M., Spiering, M. M., and Marletta, M. A. (1998) Biochemistry 37, 15503-15512). Reconstitution of pterin-free NOS with H(4)B was monitored by a shift in the Soret band to 396-400 nm, the recovery of.NO-forming activity, and the measurement of H(4)B bound to the enzyme. As assessed by these properties, H(4)B binding was not rapid and required the presence of a reduced thiol. Spectral changes and recovery of activity were incomplete in the absence of reduced thiol. Full reconstitution of holoenzyme activity and stoichiometric H(4)B binding was achieved in the presence of 5 mm glutathione (GSH). Preincubation with GSH before the addition of H(4)B decreased, whereas lower concentrations of GSH extended, the time required for reconstitution. Six protected cysteine residues in pterin-free NOS were identified by labeling of NOS with cysteine-directed reagents before and after reduction with GSH. Heme and metal content of pterin-free and H(4)B-reconstituted NOS were also measured and were found to be independent of H(4)B content. Additionally, pterin-free NOS was reconstituted with 6-methylpterin analogs, including redox-stable deazapterins. Reconstitution with the redox-stable pterin analogs was neither time- nor thiol-dependent. Apparent binding constants were determined for the 6-methyl- (50 microm) and 6-ethoxymethyl (200 microm) deazapterins. The redox-stable pterin analogs appear to bind to NOS in a different manner than H(4)B.
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Affiliation(s)
- K M Rusche
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, Michigan 48109-0606, USA
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Abstract
PURPOSE To evaluate the role of CNS dopaminergic systems in Restless Legs Syndrome (RLS), homovanillic acid (HVA), tetrahydrobiopterin (BH4), and neopterin (NEOP), were assayed in CSF from RLS patients. The serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA), was also measured. METHODS CSF was taken from 16 RLS patients after 2 weeks off medication and from 14 control subjects. The CSF metabolites were determined using HPLC techniques. RESULTS There was no significant difference in HVA or 5-HIAA, but NEOP and BH4 were higher in RLS patients. The RLS group was significantly older than the control group (64.2 +/- 9.2 years vs. 51.4 +/- 6.3 years; P < 0.001). A multiple regression analysis showed a strong correlation between age and 5-HIAA (r = 0.46, P = 0.04) and between age and NEOP (r = 0.61, P < 0.01). To eliminate the potential error created by the age difference between groups, an age-adjusted subgroup of RLS and control subjects were compared. There was still no difference found for HVA; however, 5-HIAA was now significantly lower (P < 0.01) in the RLS subgroup. Age-adjustment eliminated the differences previously found for NEOP, (P = 0.12), but BH4 continued to remain higher in the RLS group (P < 0.01). CONCLUSION Differences in CSF HVA concentrations were not found. The changes in 5-HIAA and BH4 are of unclear clinical significance and require further assessment with appropriate age-matched controls.
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Affiliation(s)
- C J Earley
- Department of Neurology, Johns Hopkins Bayview Medical Center, Baltimore, Maryland 21224, USA
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Huang A, Vita JA, Venema RC, Keaney JF. Ascorbic acid enhances endothelial nitric-oxide synthase activity by increasing intracellular tetrahydrobiopterin. J Biol Chem 2000; 275:17399-406. [PMID: 10749876 DOI: 10.1074/jbc.m002248200] [Citation(s) in RCA: 268] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Ascorbic acid enhances NO bioactivity in patients with vascular disease through unclear mechanism(s). We investigated the role of intracellular ascorbic acid in endothelium-derived NO bioactivity. Incubation of porcine aortic endothelial cells (PAECs) with ascorbic acid produced time- and dose-dependent intracellular ascorbic acid accumulation that enhanced NO bioactivity by 70% measured as A23187-induced cGMP accumulation. This effect was due to enhanced NO production because ascorbate stimulated both PAEC nitrogen oxide (NO(2)(-) + NO(3)(-)) production and l-arginine to l-citrulline conversion by 59 and 72%, respectively, without altering the cGMP response to authentic NO. Ascorbic acid also stimulated the catalytic activity of eNOS derived from either PAEC membrane fractions or baculovirus-infected Sf9 cells. Ascorbic acid enhanced bovine eNOS V(max) by approximately 50% without altering the K(m) for l-arginine. The effect of ascorbate was tetrahydrobiopterin (BH(4))-dependent, because ascorbate was ineffective with BH(4) concentrations >10 microm or in PAECs treated with sepiapterin to increase intracellular BH(4). The effect of ascorbic acid was also specific because A23187-stimulated cGMP accumulation in PAECs was insensitive to intracellular glutathione manipulation and only ascorbic acid, not glutathione, increased the intracellular concentration of BH(4). These data suggest that ascorbic acid enhances NO bioactivity in a BH(4)-dependent manner by increasing intracellular BH(4) content.
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Affiliation(s)
- A Huang
- Evans Memorial Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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Abstract
Diagnostic testing for genetically determined metabolic disease has for many years relied heavily on the use of generalized screening tests that analyze groups of related compounds in easily accessible peripheral fluids such as plasma and urine. Organic acid profiles in urine and amino acid analysis in plasma are two of the most commonly requested tests; these, together with other protocols that examine peripheral fluids, have been and continue to be invaluable tools. There is, however, an emerging realization that many metabolic encephalopathies do not arise secondary to peripheral metabolic changes but rather have their origins within the central nervous system. In these cases, testing of peripheral fluids might be uninformative. This review is designed to examine the role of cerebrospinal fluid analyses in the investigation of infants and children with undefined encephalopathies. The aims are to review the conditions in which measurement of metabolites in cerebrospinal fluid is critical if a diagnosis is to be made, and to emphasize that considerable forethought is often required to ensure correct collection and handling of cerebrospinal fluid. Thus, fidelity of the diagnostic analytic procedures is maintained. This review will help the pediatric neurologist establish practical diagnostic guidelines that in turn will help in the recognition of recently described conditions. Those conditions can, in general, be identified only after specialized cerebrospinal fluid testing.
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Affiliation(s)
- K Hyland
- Department of Neurochemistry, Institute of Metabolic Disease, Baylor University Medical Center, Dallas, TX 75226, USA.
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Oettl K, Reibnegger G. Pteridines as inhibitors of xanthine oxidase: structural requirements. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1430:387-95. [PMID: 10082966 DOI: 10.1016/s0167-4838(99)00023-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Different pteridine derivatives were investigated for their inhibitory action on xanthine oxidase. From 27 investigated compounds, 13 showed concentration-dependent inhibition of the enzyme. Concentrations necessary for 50% inhibition ranged from <0.1 up to >100 microM. Different types of inhibition were found concerning xanthine and pterin as substrates: competitive, noncompetitive and mixed type. Out of 18 aromatic compounds tested, 12 were inhibitors. Only one out of nine reduced derivatives served as inhibitor. A simple regression model was used to specify the structural requirements for a pteridine to be an inhibitor. The most characteristic features of an inhibitor are aromaticity and no substitution at position 7 of the pteridine ring.
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Affiliation(s)
- K Oettl
- Medical Chemical Institute and Pregl Laboratory, Karl-Franzens-University Graz, Harrachgasse 21/II, A-8010, Graz,
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Brashear A, Butler IJ, Hyland K, Farlow MR, Dobyns WB. Cerebrospinal fluid homovanillic acid levels in rapid-onset dystonia-parkinsonism. Ann Neurol 1998; 43:521-6. [PMID: 9546335 DOI: 10.1002/ana.410430417] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Rapid-onset dystonia-parkinsonism (RDP) is characterized by sudden onset over hours to days of dystonia, dysphagia, dysarthria, and parkinsonism. RDP has been reported by our group in two apparently unrelated families. We now report analysis of cerebrospinal fluid metabolites of dopamine, norepinephrine, and serotonin for mild and severely affected individuals, known asymptomatic gene carriers, and at-risk individuals from both families with RDP. Levels of the dopamine metabolite homovanillic acid (HVA) were decreased in severely affected patients and in some asymptomatic gene carriers. HVA levels increased with treatment in some affected individuals, but this increase did not predict clinical response to carbidopa/levodopa. We suggest that a low HVA level is a biological marker with modest association to the diagnosis of RDP.
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Affiliation(s)
- A Brashear
- Department of Neurology, Indiana University School of Medicine, Indianapolis, USA
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Vita JA, Frei B, Holbrook M, Gokce N, Leaf C, Keaney JF. L-2-Oxothiazolidine-4-carboxylic acid reverses endothelial dysfunction in patients with coronary artery disease. J Clin Invest 1998; 101:1408-14. [PMID: 9502783 PMCID: PMC508696 DOI: 10.1172/jci1155] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The effective action of endothelium-derived nitric oxide (EDNO) is impaired in patients with atherosclerosis. This impairment has been attributed in part to increased vascular oxidative stress. EDNO action is improved by administration of ascorbic acid, a water-soluble antioxidant. Ascorbic acid is a potent free-radical scavenger in plasma, and also regulates intracellular redox state in part by sparing cellular glutathione. We specifically investigated the role of intracellular redox state in EDNO action by examining the effect of L-2-oxo-4-thiazolidine carboxylate (OTC) on EDNO-dependent, flow-mediated dilation in a randomized double-blind placebo-controlled study of patients with angiographically proven coronary artery disease. OTC augments intracellular glutathione by providing substrate cysteine for glutathione synthesis. Brachial artery flow-mediated dilation was examined with high-resolution ultrasound before and after oral administration of 4.5 g of OTC or placebo in 48 subjects with angiographically documented coronary artery disease. Placebo treatment produced no change in flow-mediated dilation (7.0+/-3.9% vs. 7.2+/-3.7%), whereas OTC treatment was associated with a significant improvement in flow-mediated dilation (6.6+/-4.4% vs. 11.0+/-6.3%; P = 0.005). OTC had no effect on arterial dilation to nitroglycerin, systemic blood pressure, heart rate, or reactive hyperemia. These data suggest that augmenting cellular glutathione levels improves EDNO action in human atherosclerosis. Cellular redox state may be an important regulator of EDNO action, and is a potential target for therapy in patients with coronary artery disease.
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Affiliation(s)
- J A Vita
- Evans Memorial Department of Medicine, Cardiology Section and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
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Candito M, Nagatsu T, Chambon P, Chatel M. High-performance liquid chromatographic measurement of cerebrospinal fluid tetrahydrobiopterin, neopterin, homovanillic acid and 5-hydroxindoleacetic acid in neurological diseases. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL APPLICATIONS 1994; 657:61-6. [PMID: 7524948 DOI: 10.1016/0378-4347(94)80070-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Cerebrospinal fluid (CSF) samples from patients with a variety of neurological disorders were assayed to determine the concentrations of tetrahydrobiopterin (BH4), the active cofactor of hydroxylases. Dihydroneopterin (NH2) and neopterin (N), which are linked with BH4 synthesis and are inflammatory biochemical markers, were also measured simultaneously in a number of patients. 5-Hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA), the main products of serotonin and dopamine breakdown, were analyzed in parallel whenever possible. As BH4 and NH2 are difficult to analyze owing to their instability, CSF samples were collected under special conditions to preserve the reduced BH4 and NH2. Liquid chromatographic assays and detection of the various substances measured also required particular precautions. BH4 concentrations were elevated in patients with neurological disorders such as syphilis and lupus-like disease and especially in an AIDS patient with neurological complications with an increased N/BH4 ratio.
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Affiliation(s)
- M Candito
- Laboratoire de Biochimie, Hôpital Pasteur, Nice, France
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Hyland K, Heales SJ. Tetrahydrobiopterin and quinonoid dihydrobiopterin concentrations in CSF from patients with dihydropteridine reductase deficiency. J Inherit Metab Dis 1993; 16:608-10. [PMID: 7609464 DOI: 10.1007/bf00711695] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- K Hyland
- Institute of Child Health, London, UK
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Hoffmann GF, Meier-Augenstein W, Stöckler S, Surtees R, Rating D, Nyhan WL. Physiology and pathophysiology of organic acids in cerebrospinal fluid. J Inherit Metab Dis 1993; 16:648-69. [PMID: 8412012 DOI: 10.1007/bf00711898] [Citation(s) in RCA: 151] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Concentrations of organic acids in cerebrospinal fluid (CSF) appear to be directly dependent upon their rate of production in the brain. There is evidence that the net release of short-chain monocarboxylic acids from the brain is a major route for removing these products of cerebral metabolism. Concentrations of organic acids in blood and CSF are largely independent of each other. Quantitative reference values for the concentrations of organic acids in CSF and plasma as well as ratios of individual organic acids between CSF and plasma were determined in 35 pairs of samples from paediatric patients. Over 25 organic acids were quantifiable in all or in the majority of CSF and/or plasma specimens (limit of detection 1 mumol/L). There were substantial differences in the CSF/plasma ratios between subgroups of organic acids. Metabolites related to fatty-acid oxidation were present in CSF in substantially less amounts than in plasma. Organic acids related to carbohydrate and energy metabolism and to amino acid degradation were present in CSF in the same amounts as or slightly smaller amounts than in plasma. Finally, some organic acids were found in substantially higher amounts in CSF than in plasma, e.g. glycolate, glycerate, 2,4-dihydroxybutyrate, citrate and isocitrate. Studies of organic acids in CSF and plasma samples are presented from patients with 'cerebral' lactic acidosis, disorders of propionate and methylmalonate metabolism, glutaryl-CoA dehydrogenase deficiency and L-2-hydroxy-glutaric aciduria. It became apparent that derangements of organic acids in the CSF may occur independently of the systemic metabolism. Quantitative organic acid analysis in CSF will yield new information on the pathophysiology in the central nervous system (CNS) of these disorders and may prove necessary for successful monitoring of treatment of organoacidopathies, which present mainly with neurological disease. For example, in glutaryl-CoA dehydrogenase deficiency the urinary excretion of glutarate appears to be an inadequate parameter for monitoring the effect of dietary therapy, without plasma and CSF determinations. In L-2-hydroxyglutaric aciduria the elevation of L-2-hydroxyglutarate was found to be greater in CSF than in plasma. In addition, some other organic acids, glycolate, glycerate, 2,4-dihydroxybutyrate, citrate and isocitrate, were also elevated in the CSF of the patients out of proportion to normal levels in plasma and urine. High concentrations of an unknown compound, which was tentatively identified as 2,4-dihydroxyglutarate, were found in the CSF of patients with L-2-hydroxyglutaric aciduria.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- G F Hoffmann
- Department of Pediatrics, University of Heidelberg, Germany
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Abstract
The term biogenic amine is an umbrella term that encompasses all amines with an origin in biological processes. This review will be restricted to the biogenic amine abnormalities that affect the metabolism of serotonin and the catecholamines. The synthesis and catabolism of these neurotransmitters are outlined, and a summary is given of the neurological details, biochemical features, and treatment of the inborn errors that primarily affect their metabolism. An idea is also developed that proposes that abnormalities of biogenic amine metabolism are far more common than is currently considered, and that the search for these problems may be appropriate in any neonate or infant who presents with neurological problems of unknown origin.
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Affiliation(s)
- K Hyland
- Metabolic Disease Center, Baylor Research Institute, Dallas, TX 75226
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Affiliation(s)
- K Hyland
- Institute of Child Health, Department of Child Health, London, UK
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Heales S, Hyland K. Determination of quinonoid dihydrobiopterin by high-performance liquid chromatography and electrochemical detection. JOURNAL OF CHROMATOGRAPHY 1989; 494:77-85. [PMID: 2584347 DOI: 10.1016/s0378-4347(00)82658-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Sodium bisulphite is shown to react with quinonoid dihydrobiopterin to form a stable adduct. Sodium bisulphite does not react with tetrahydrobiopterin. Quinonoid dihydrobiopterin reacts with dithioerythritol to form tetrahydrobiopterin, whereas the quinonoid dihydrobiopterin bisulphite adduct does not. Using these properties we have developed an indirect method for the quantitative measurement of quinonoid dihydrobiopterin. The method requires division of a sample into two. Dithioerythritol is added to one half (a). This converts quinonoid dihydrobiopterin to tetrahydrobiopterin and prevents the oxidation of tetrahydrobiopterin. Measurement of the tetrahydrobiopterin content of this sample by electrochemistry following high-performance liquid chromatographic separation (with dithioerythritol present in the mobile phase to prevent autoxidation of the tetrahydrobiopterin on column), therefore provides a total value of the tetrahydrobiopterin plus quinonoid dihydrobiopterin present within the original sample. Sodium bisulphite is added to the other portion of the sample (b), followed immediately by dithioerythritol which prevents autoxidation of the remaining tetrahydrobiopterin. The bisulphite reacts with the quinonoid dihydrobiopterin present and the quinonoid dihydrobiopterin-bisulphite adduct is no longer detected by electrochemistry at the retention time of tetrahydrobiopterin. Using reversed-phase high-performance liquid chromatography and redox electrochemical detection, measurement of tetrahydrobiopterin in the absence (a) and presence (b) of bisulphite enables the concentration of quinonoid dihydrobiopterin to be calculated by subtraction (a - b). This method is shown to be quantitative and preliminary experiments demonstrate that it can be adapted for biological samples.
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Affiliation(s)
- S Heales
- Department of Child Health, Institute of Child Health, London, U.K
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Nissen HP, Kreysel HW. HPLC-methods in the clinical-chemical laboratory of the department of dermatology of the University of Bonn. Chromatographia 1989. [DOI: 10.1007/bf02290383] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Affiliation(s)
- T Nagatsu
- Department of Biochemistry, Nagoya University School of Medicine, Japan
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