151
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Kandil S, Brennan L, McBean GJ. Glutathione depletion causes a JNK and p38MAPK-mediated increase in expression of cystathionine-γ-lyase and upregulation of the transsulfuration pathway in C6 glioma cells. Neurochem Int 2010; 56:611-9. [DOI: 10.1016/j.neuint.2010.01.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Accepted: 01/05/2010] [Indexed: 11/27/2022]
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152
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Hydrogen sulfide: its production, release and functions. Amino Acids 2010; 41:113-21. [DOI: 10.1007/s00726-010-0510-x] [Citation(s) in RCA: 464] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Accepted: 01/29/2010] [Indexed: 11/25/2022]
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153
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One-carbon metabolism and schizophrenia: current challenges and future directions. Trends Mol Med 2009; 15:562-70. [PMID: 19896901 DOI: 10.1016/j.molmed.2009.10.001] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2009] [Revised: 10/05/2009] [Accepted: 10/05/2009] [Indexed: 01/08/2023]
Abstract
Schizophrenia is a heterogeneous disease generally considered to result from a combination of heritable and environmental factors. Although its pathophysiology has not been fully determined, biological studies support the involvement of several possible components including altered DNA methylation, abnormal glutamatergic transmission, altered mitochondrial function, folate deficiency and high maternal homocysteine levels. Although these factors have been explored separately, they all involve one-carbon (C1) metabolism. Furthermore, C1 metabolism is well positioned to integrate gene-environment interactions by influencing epigenetic regulation. Here, we discuss the potential roles of C1 metabolism in the pathophysiology of schizophrenia. Understanding the contribution of these mechanisms could yield new therapeutic approaches aiming to counteract disease onset or progression.
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154
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Martinov MV, Vitvitsky VM, Banerjee R, Ataullakhanov FI. The logic of the hepatic methionine metabolic cycle. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1804:89-96. [PMID: 19833238 DOI: 10.1016/j.bbapap.2009.10.004] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 10/02/2009] [Accepted: 10/06/2009] [Indexed: 12/18/2022]
Abstract
This review describes our current understanding of the "traffic lights" that regulate sulfur flow through the methionine bionetwork in liver, which supplies two major homeostatic systems governing cellular methylation and antioxidant potential. Theoretical concepts derived from mathematical modeling of this metabolic nexus provide insights into the properties of this system, some of which seem to be paradoxical at first glance. Cellular needs supported by this network are met by use of parallel metabolic tracks that are differentially controlled by intermediates in the pathway. A major task, i.e. providing cellular methylases with the methylating substrate, S-adenosylmethionine, is met by flux through the methionine adenosyltransferase I isoform. On the other hand, a second important function, i.e., stabilization of the blood methionine concentration in the face of high dietary intake of this amino acid, is achieved by switching to an alternative isoform, methionine adenosyltransferase III, and to glycine N-methyl transferase, which together bypass the first two reactions in the methionine cycle. This regulatory strategy leads to two metabolic modes that differ in metabolite concentrations and metabolic rates almost by an order of magnitude. Switching between these modes occurs in a narrow trigger zone of methionine concentration. Complementary experimental and theoretical analyses of hepatic methionine metabolism have been richly informative and have the potential to illuminate its response to oxidative challenge, to methionine restriction and lifespan extension studies and to diseases resulting from deficiencies at specific loci in this pathway.
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Affiliation(s)
- M V Martinov
- National Research Center for Hematology, RAMS, Moscow, Russia
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155
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Abstract
The unique biochemical profile of homocysteine is characterized by chemical reactivity supporting a wide range of molecular effects and by a tendency to promote oxidant stress-induced cellular toxicity. Numerous epidemiological reports have established hyperhomocysteinemia as an independent risk factor for cardiovascular disease, cerebrovascular disease, dementia-type disorders, and osteoporosis-associated fractures. Although combined folic acid and B-vitamin therapy substantially reduces homocysteine levels, results from randomized placebo-controlled clinical trials testing the effect of vitamin therapy on outcome in these diseases have generally fallen short of expectations. These results have led some to abandon homocysteine monitoring in the management of patients with cardiovascular or cognitive disorders. These trials, however, have generally included patients with only mildly elevated homocysteine levels and have not addressed several clinical scenarios in which homocysteine reduction may be effective, including the primary prevention of atherothrombotic disease in individuals at low or intermediate risk, or those with severe hyperhomocysteinemia.
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Affiliation(s)
- Bradley A Maron
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
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156
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Kraus JP, Hašek J, Kožich V, Collard R, Venezia S, Janošíková B, Wang J, Stabler SP, Allen RH, Jakobs C, Finn CT, Chien YH, Hwu WL, Hegele RA, Mudd SH. Cystathionine gamma-lyase: Clinical, metabolic, genetic, and structural studies. Mol Genet Metab 2009; 97:250-9. [PMID: 19428278 PMCID: PMC2752209 DOI: 10.1016/j.ymgme.2009.04.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 04/01/2009] [Accepted: 04/02/2009] [Indexed: 11/28/2022]
Abstract
We report studies of six individuals with marked elevations of cystathionine in plasma and/or urine. Studies of CTH, the gene that encodes cystathionine gamma-lyase, revealed the presence among these individuals of either homozygous or compound heterozygous forms of a novel large deletion, p.Gly57_Gln196del, two novel missense mutations, c.589C>T (p.Arg197Cys) and c.932C>T (p.Thr311Ile), and one previously reported alteration, c.200C>T (p.Thr67Ile). Another novel missense mutation, c.185G>T (p.Arg62His), was found in heterozygous form in three mildly hypercystathioninemic members of a Taiwanese family. In one severely hypercystathioninemic individual no CTH mutation was found. Brief clinical histories of the cystathioninemic/cystathioninuric patients are presented. Most of the novel mutations were expressed and the CTH activities of the mutant proteins determined. The crystal structure of the human enzyme, hCTH, and the evidence available as to the effects of the mutations in question, as well as those of the previously reported p.Gln240Glu, on protein structure, enzymatic activity, and responsiveness to vitamin B(6) administration are discussed. Among healthy Czech controls, 9.3% were homozygous for CTH c.1208G>T (p.Ser403Ile), previously found homozygously in 7.5% of Canadians for whom plasma total homocysteine (tHcy) had been measured. Compared to wild-type homozygotes, among the 55 Czech c.1208G>T (p.Ser403Ile) homozygotes a greater level of plasma cystathionine was found only after methionine loading. Three of the four individuals homozygous or compound heterozygous for inactivating CTH mutations had mild plasma tHcy elevations, perhaps indicating a cause-and-effect relationship. The experience with the present patients provides no evidence that severe loss of CTH activity is accompanied by adverse clinical effects.
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Affiliation(s)
- Jan P. Kraus
- Department of Pediatrics, University of Colorado School of Medicine
| | - Jindrich Hašek
- Department of Structure Analysis, Institute of Macromolecular Chemistry AS CR, Prague, Czech Republic
| | - Viktor Kožich
- Institute of Inherited Metabolic Diseases, Charles University in Prague-First Faculty of Medicine, Prague, Czech Republic
| | - Renata Collard
- Department of Pediatrics, University of Colorado School of Medicine
| | - Sarah Venezia
- Department of Pediatrics, University of Colorado School of Medicine
| | - Bohumila Janošíková
- Institute of Inherited Metabolic Diseases, Charles University in Prague-First Faculty of Medicine, Prague, Czech Republic
| | - Jian Wang
- Robarts Research Institute, London, Ontario, Canada
| | - Sally P. Stabler
- Division of Hematology, University of Colorado Health Sciences Center, Denver, CO
| | - Robert H. Allen
- Division of Hematology, University of Colorado Health Sciences Center, Denver, CO
| | - Cornelis Jakobs
- Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands
| | - Christine T. Finn
- Massachusetts General Hospital, Department of Psychiatry, Harvard-Partners Center for Genetics and Genomics, Boston, MA
| | - Yin-Hsiu Chien
- Departments of Medical Genetics and Pediatrics, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan
| | - Wuh-Liang Hwu
- Departments of Medical Genetics and Pediatrics, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan
| | | | - S. Harvey Mudd
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, MD
- Corresponding author: S.H. Mudd (Telephone: 301-496-0681; Fax: 301-402-0245, )
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157
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Singh S, Padovani D, Leslie RA, Chiku T, Banerjee R. Relative contributions of cystathionine beta-synthase and gamma-cystathionase to H2S biogenesis via alternative trans-sulfuration reactions. J Biol Chem 2009; 284:22457-22466. [PMID: 19531479 DOI: 10.1074/jbc.m109.010868] [Citation(s) in RCA: 466] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammals, the two enzymes in the trans-sulfuration pathway, cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CSE), are believed to be chiefly responsible for hydrogen sulfide (H2S) biogenesis. In this study, we report a detailed kinetic analysis of the human and yeast CBS-catalyzed reactions that result in H2S generation. CBS from both organisms shows a marked preference for H2S generation by beta-replacement of cysteine by homocysteine. The alternative H2S-generating reactions, i.e. beta-elimination of cysteine to generate serine or condensation of 2 mol of cysteine to generate lanthionine, are quantitatively less significant. The kinetic data were employed to simulate the turnover numbers of the various CBS-catalyzed reactions at physiologically relevant substrate concentrations. At equimolar concentrations of CBS and CSE, the simulations predict that H2S production by CBS would account for approximately 25-70% of the total H2S generated via the trans-sulfuration pathway depending on the extent of allosteric activation of CBS by S-adenosylmethionine. The relative contribution of CBS to H2S genesis is expected to decrease under hyperhomocysteinemic conditions. CBS is predicted to be virtually the sole source of lanthionine, and CSE, but not CBS, efficiently cleaves lanthionine. The insensitivity of the CBS-catalyzed H2S-generating reactions to the grade of hyperhomocysteinemia is in stark contrast to the responsiveness of CSE and suggests a previously unrecognized role for CSE in intracellular homocysteine management. Finally, our studies reveal that the profligacy of the trans-sulfuration pathway results not only in a multiplicity of H2S-yielding reactions but also yields novel thioether metabolites, thus increasing the complexity of the sulfur metabolome.
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Affiliation(s)
- Sangita Singh
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | - Dominique Padovani
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | - Rachel A Leslie
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | - Taurai Chiku
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | - Ruma Banerjee
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
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158
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Pinto JT, Khomenko T, Szabo S, McLaren GD, Denton TT, Krasnikov BF, Jeitner TM, Cooper AJL. Measurement of sulfur-containing compounds involved in the metabolism and transport of cysteamine and cystamine. Regional differences in cerebral metabolism. J Chromatogr B Analyt Technol Biomed Life Sci 2009; 877:3434-41. [PMID: 19523884 DOI: 10.1016/j.jchromb.2009.05.041] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 05/15/2009] [Accepted: 05/19/2009] [Indexed: 11/17/2022]
Abstract
An HPLC method with coulometric detection is presented for the quantitation of cysteamine, cystamine, thialysine, glutathione, glutathione disulfide and an oxidized metabolite of thialysine [S-(2-aminoethyl)-L-cysteine ketimine decarboxylated dimer (AECK-DD)]. The advantage of coulometric detection is that derivatization is unnecessary if the analyte is redox sensitive. The method was used to quantitate several sulfur-containing compounds in plasma and brain following gavage feeding of cysteamine to rats. Cysteamine, cystamine, thialysine and AECK-DD were detected in the brains of these animals. Interestingly, cysteamine treatment resulted in greatly elevated levels of cerebral methionine, despite the fact that cysteamine is not a precursor of methionine.
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Affiliation(s)
- John T Pinto
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA
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159
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Emerging hypotheses regarding the influences of butyrylcholinesterase-K variant, APOE epsilon 4, and hyperhomocysteinemia in neurodegenerative dementias. Med Hypotheses 2009; 73:230-50. [PMID: 19359103 DOI: 10.1016/j.mehy.2009.01.050] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 12/04/2008] [Accepted: 01/24/2009] [Indexed: 01/20/2023]
Abstract
Non-enzymatic functions of butyrylcholinesterase (BuChE) include prevention of the aggregation of amyloid-beta peptide (A beta) in a concentration-dependent manner. This is mediated by the C-terminus of the protein, distal from the enzymatic site. The BuChE-K variant polymorphism lowers expression of BuChE protein and/or alters C-terminal activity. In combination with factors that increase production or reduce elimination of A beta, and/or increase susceptibility to A beta toxicity - such as the apolipoprotein E (APOE) epsilon 4 allele and/or hyperhomocysteinemia - BuChE-K may accelerate cholinergic synaptic and neuronal damage and cognitive decline. A beta-mediated damage to ascending cholinergic pathways may be further accentuated by Lewy body and/or cerebrovascular disease. As the disease advances and functioning cholinergic synapses disappear, both the rapid cognitive decline and response to cholinesterase inhibitor therapy in individuals with these factors may diminish. Non-enzymatic functions of the BuChE protein, APOE epsilon 4 status and hyperhomocysteinemia influence the progression of pathology, symptom expression, and response to cholinesterase inhibition in a stage-specific manner in neurodegenerative disorders associated with Alzheimer, Lewy body and vascular pathology.
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160
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Chiku T, Padovani D, Zhu W, Singh S, Vitvitsky V, Banerjee R. H2S biogenesis by human cystathionine gamma-lyase leads to the novel sulfur metabolites lanthionine and homolanthionine and is responsive to the grade of hyperhomocysteinemia. J Biol Chem 2009; 284:11601-12. [PMID: 19261609 DOI: 10.1074/jbc.m808026200] [Citation(s) in RCA: 350] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although there is a growing recognition of the significance of hydrogen sulfide (H(2)S) as a biological signaling molecule involved in vascular and nervous system functions, its biogenesis and regulation are poorly understood. It is widely assumed that desulfhydration of cysteine is the major source of H(2)S in mammals and is catalyzed by the transsulfuration pathway enzymes, cystathionine beta-synthase and cystathionine gamma-lyase (CSE). In this study, we demonstrate that the profligacy of human CSE results in a variety of reactions that generate H(2)S from cysteine and homocysteine. The gamma-replacement reaction, which condenses two molecules of homocysteine, yields H(2)S and a novel biomarker, homolanthionine, which has been reported in urine of homocystinuric patients, whereas a beta-replacement reaction, which condenses two molecules of cysteine, generates lanthionine. Kinetic simulations at physiologically relevant concentrations of cysteine and homocysteine, reveal that the alpha,beta-elimination of cysteine accounts for approximately 70% of H(2)S generation. However, the relative importance of homocysteine-derived H(2)S increases progressively with the grade of hyperhomocysteinemia, and under conditions of severely elevated homocysteine (200 microm), the alpha,gamma-elimination and gamma-replacement reactions of homocysteine together are predicted to account for approximately 90% of H(2)S generation by CSE. Excessive H(2)S production in hyperhomocysteinemia may contribute to the associated cardiovascular pathology.
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Affiliation(s)
- Taurai Chiku
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0606, USA
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161
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Banerjee R, Vitvitsky V, Garg SK. The undertow of sulfur metabolism on glutamatergic neurotransmission. Trends Biochem Sci 2008; 33:413-9. [PMID: 18703339 DOI: 10.1016/j.tibs.2008.06.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 06/11/2008] [Accepted: 06/12/2008] [Indexed: 11/18/2022]
Abstract
Metabolic interdependence between specialized cells in an organ represents a strategy for energy economy by requiring expression of only a subset of pathway genes in a given cell type. In brain, sulfur metabolism exemplifies this principle of metabolic cooperation between glial and neuronal cells and furnishes three key reagents: S-adenosylmethionine, glutathione and taurine. The pathways for glutathione and taurine syntheses depend on metabolic integration between astrocytes and neurons and intersect with the glutamine-glutamate cycle, which underlies glutamatergic synaptic transmission and requires cooperation between these cell types. We propose that underlying waves of glutamate clearance by astrocytes are activation of cystine import and taurine efflux that result, respectively, from a shared transporter and an increase in solute concentration that triggers osmoregulatory responses.
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Affiliation(s)
- Ruma Banerjee
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-0606, USA.
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162
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Linden DR, Sha L, Mazzone A, Stoltz GJ, Bernard CE, Furne JK, Levitt MD, Farrugia G, Szurszewski JH. Production of the gaseous signal molecule hydrogen sulfide in mouse tissues. J Neurochem 2008. [PMID: 18513201 DOI: 10.1111/j.1471-4159.2008.05502.x/abstract] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The gaseous molecule hydrogen sulfide (H(2)S) has been proposed as an endogenous signal molecule and neuromodulator in mammals. Using a newly developed method, we report here for the first time the ability of intact and living brain and colonic tissue in the mouse to generate and release H(2)S. This production occurs through the activity of two enzymes, cystathionine-gamma-lyase and cystathionine-beta-synthase. The quantitative expression of messenger RNA and protein localization for both enzymes are described in the liver, brain, and colon. Expression levels of the enzymes vary between tissues and are differentially distributed. The observation that, tissues that respond to exogenously applied H(2)S can endogenously generate the gas, strongly supports its role as an endogenous signal molecule.
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Affiliation(s)
- David R Linden
- Enteric NeuroScience Program, and Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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163
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Linden DR, Sha L, Mazzone A, Stoltz GJ, Bernard CE, Furne JK, Levitt MD, Farrugia G, Szurszewski JH. Production of the gaseous signal molecule hydrogen sulfide in mouse tissues. J Neurochem 2008; 106:1577-85. [PMID: 18513201 DOI: 10.1111/j.1471-4159.2008.05502.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The gaseous molecule hydrogen sulfide (H(2)S) has been proposed as an endogenous signal molecule and neuromodulator in mammals. Using a newly developed method, we report here for the first time the ability of intact and living brain and colonic tissue in the mouse to generate and release H(2)S. This production occurs through the activity of two enzymes, cystathionine-gamma-lyase and cystathionine-beta-synthase. The quantitative expression of messenger RNA and protein localization for both enzymes are described in the liver, brain, and colon. Expression levels of the enzymes vary between tissues and are differentially distributed. The observation that, tissues that respond to exogenously applied H(2)S can endogenously generate the gas, strongly supports its role as an endogenous signal molecule.
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Affiliation(s)
- David R Linden
- Enteric NeuroScience Program, and Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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164
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Smerjac SM, Bizzozero OA. Cytoskeletal protein carbonylation and degradation in experimental autoimmune encephalomyelitis. J Neurochem 2008; 105:763-72. [PMID: 18088377 PMCID: PMC3599778 DOI: 10.1111/j.1471-4159.2007.05178.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Protein carbonylation, the non-enzymatic addition of aldehydes or ketones to specific amino acid residues, has been implicated in the pathophysiology of multiple sclerosis. In this study, we investigated whether protein carbonyls also accumulate in the spinal cord of Lewis rats with acute experimental autoimmune encephalomyelitis (EAE). Western blots analysis after derivatization with dinitrophenyl hydrazine (oxyblot) showed elevated protein carbonylation at the time of maximal clinical disability. During the same period glutathione levels were substantially reduced, suggesting a causal relationship between these two markers. In contrast, lipid peroxidation products accumulated in EAE spinal cord well before the appearance of neurological symptoms. Carbonyl staining was not restricted to inflammatory lesions but present throughout the spinal cord particularly in neuronal cell bodies and axons. By 2-dimensional-oxyblot, we identified several cytoskeletal proteins, including beta-actin, glial acidic fibrillary protein, and the neurofilament proteins as the major targets of carbonylation. These findings were confirmed by pull-down experiments, which also showed an increase in the number of carbonylated beta-actin molecules and a decrease in that of oxidized neurofilament proteins in EAE. These data suggest the possibility that oxidation targets neurofilament proteins for degradation, which may contribute to axonal pathology observed in multiple sclerosis and EAE.
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Affiliation(s)
- Suzanne M Smerjac
- Department of Cell Biology and Physiology, University of New Mexico - Health Sciences Center, Albuquerque, New Mexico 87131, USA
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165
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Obeid R, McCaddon A, Herrmann W. The role of hyperhomocysteinemia and B-vitamin deficiency in neurological and psychiatric diseases. Clin Chem Lab Med 2008; 45:1590-606. [PMID: 18067446 DOI: 10.1515/cclm.2007.356] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Hyperhomocysteinemia (HHcy) is related to central nervous system diseases. Epidemiological studies show a positive, dose-dependent relationship between plasma total homocysteine (tHcy) concentration and neurodegenerative disease risk. tHcy is a marker of B-vitamin (folate, B(12), B(6)) status. Hypomethylation, caused by low B-vitamin status and HHcy, is linked to key pathomechanisms of dementia; B-vitamin supplementation could potentially reduce neurological damage. In retrospective studies, the association between tHcy and cognition is impressive; there is also evidence that tHcy-lowering treatment could be effective in primary and secondary stroke prevention. Increased tHcy and low serum folate occur in patients with Parkinson's disease, especially those receiving L-dopa. There is also an association between HHcy and multiple sclerosis, and between B-vitamin status and depression. Studies also confirm a causal role for tHcy in epilepsy, and certain anti-epileptics enhance HHcy. B-vitamin status should be optimized by ensuring sufficient intake in patients with neuropsychiatric diseases. HHcy occurs commonly in the elderly and can contribute to age-related neurodegeneration. Treatment with folic acid, B(12) and B(6) lowers tHcy. For secondary and primary prevention from several neuropsychiatric disorders, it seems prudent to actively identify deficient subjects and ensure sufficient vitamin intake.
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Affiliation(s)
- Rima Obeid
- Department of Clinical Chemistry and Laboratory Medicine, Faculty of Medicine, University Hospital of Saarland, Homburg/Saar, Germany
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166
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Herrmann W, Obeid R. Biomarkers of folate and vitamin B(12) status in cerebrospinal fluid. Clin Chem Lab Med 2008; 45:1614-20. [PMID: 17892439 DOI: 10.1515/cclm.2007.310] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Folate and vitamin B(12) are essential cofactors for the methionine/homocysteine cycle in the brain. These vitamins mediate the remethylation of homocysteine (Hcy), which affects the production of the universal methyl donor, S-adenosylmethionine (SAM), in the brain among other organs. Additionally, increased plasma concentrations of total Hcy (tHcy) are associated with cerebrovascular disease and can compromise the blood-brain barrier. tHcy concentrations in the brain and cerebrospinal fluid become increased in several psychiatric and neurological disorders. Disturbances in the transmethylation pathway indicated by abnormal SAM, S-adenosylhomocysteine or their ratio have been reported in many neurodegenerative diseases, such as dementia, depression or Parkinson's disease. Cobalamin is essential for neuronal generation and its deficiency can cause degeneration of the nervous system. Available data emphasize that deficiency of folate and vitamin B(12) can lead to elevated concentrations of tHcy and disturbed methylation potential in the brain. Therefore, acquired or inherited disorders in these metabolic pathways are associated with brain abnormalities and severe neurological symptoms that are mostly irreversible, even after providing the missing cofactors. This review discusses the relationship between brain and blood levels of key vitamins and metabolites related to one carbon metabolism.
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Affiliation(s)
- Wolfgang Herrmann
- Department of Clinical Chemistry and Laboratory Medicine, Faculty of Medicine, University Hospital of Saarland, Homburg/Saar, Germany.
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167
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Finkelstein JD. Metabolic regulatory properties of S-adenosylmethionine and S-adenosylhomocysteine. Clin Chem Lab Med 2008; 45:1694-9. [PMID: 17963455 DOI: 10.1515/cclm.2007.341] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In mammalian liver, two intersecting pathways, remethylation and transsulfuration, compete for homocysteine that has been formed from methionine. Remethylation of homocysteine, employing either methyltetrahydrofolate or betaine as the methyl donor, forms a methionine cycle that functions to conserve methionine. In contrast, the transsulfuration sequence -- cystathionine synthase and cystathionase -- serves to irreversibly catabolize the homocysteine while synthesizing cysteine. The rate of homocysteine formation and its distribution between these two pathways are the sites for metabolic regulation and coordination. The mechanisms for regulation include both the tissue content and the kinetic properties of the component enzymes as well as the concentrations of their substrates and other metabolic effectors. Adenosylmethionine and adenosylhomocysteine are important regulatory metabolites and may use one or more mechanisms to affect the enzymes. Adenosylmethionine is a positive effector of its own synthesis, cystathionine synthase and glycine methyltransferase but impairs both homocysteine methylases. Thus, the concentration of adenosylmethionine may be self-regulatory in mammalian liver. By means of other enzymatic mechanisms, the hepatic concentration of adenosylhomocysteine, an index of homocysteine accumulation, is also self-regulated. These considerations pertain primarily to liver, which has the unique capacity to synthesize more adenosylmethionine in the presence of excess methionine. However, there are organ-specific patterns of methionine metabolism and its regulation. All tissues possess the methionine cycle with methyltetrahydrofolate as the methyl donor but only liver, kidney, pancreas, intestine and brain also contain the transsulfuration pathway. The limitation of adenosylmethionine concentrations may make adenosylhomocysteine a more significant metabolic regulator in extrahepatic tissues. However, estimates of regulatory changes based on determinations of the plasma concentrations of the two metabolites are of limited value and must be used with caution. In addition, the recent description of "cystathionine (CBS) domains" in proteins not involved with methionine metabolism raises the possibility that abnormal concentrations of the adenosyl metabolites may impact on other metabolic pathways.
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Affiliation(s)
- James D Finkelstein
- Veterans Affairs Medical Center and George Washington University, Washington, DC 20016, USA.
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168
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Akahoshi N, Kobayashi C, Ishizaki Y, Izumi T, Himi T, Suematsu M, Ishii I. Genetic background conversion ameliorates semi-lethality and permits behavioral analyses in cystathionine β-synthase-deficient mice, an animal model for hyperhomocysteinemia. Hum Mol Genet 2008; 17:1994-2005. [DOI: 10.1093/hmg/ddn097] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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169
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Jin Y, Brennan L. Effects of homocysteine on metabolic pathways in cultured astrocytes. Neurochem Int 2008; 52:1410-5. [PMID: 18417255 DOI: 10.1016/j.neuint.2008.03.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 03/02/2008] [Accepted: 03/06/2008] [Indexed: 11/30/2022]
Abstract
Homocysteine is an amino acid that is an important risk factor for several neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Increased homocysteine levels induce neuronal cell death in a variety of neuronal types. However, very few studies have probed the effects of homocysteine in astrocytes. The present study investigated the effects of homocysteine on primary cultures of astrocytes by exposing astrocytes to 400 microM homocysteine for 20 h. Metabolic extracts of cells were prepared following a 4-h incubation in minimum medium with 5.5 mM [U-(13)C]glucose in the presence or absence of homocysteine and analysed using (13)C NMR. The expression level of pyruvate dehydrogenase kinase isoform 2 (PDK-2), NAD(P)H levels and mitochondrial membrane potential responses were investigated following culture with homocysteine. Metabolomic analysis was performed using (1)H NMR spectroscopy and pattern recognition analysis. Following incubation with homocysteine there was a significant decrease (48%) in the ratio of flux through pyruvate carboxylase (PC) and pyruvate dehydrogenase (PDH) which was due to an increased flux through PDH. In addition, homocysteine culture resulted in a significant reduction in PDK-2 protein expression. Following stimulation with glucose there was a significant increase in NAD(P)H levels and an impaired hyperpolarisation of the mitochondrial membrane in homocysteine-treated cells. Metabolomic analysis showed that the most discriminating metabolites following homocysteine treatment were choline and hypotaurine. In summary, the results demonstrated that sub-lethal concentrations of homocysteine caused significant metabolic changes and altered mitochondrial function in primary cultures of astrocytes.
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Affiliation(s)
- Ying Jin
- UCD School of Agriculture, Food Science and Veterinary Medicine, UCD Conway Institute, UCD Dublin, Belfield, Dublin 4, Ireland
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170
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Blaise SA, Alberto JM, Audonnet-Blaise S, Guéant JL, Daval JL. Influence of preconditioning-like hypoxia on the liver of developing methyl-deficient rats. Am J Physiol Endocrinol Metab 2007; 293:E1492-502. [PMID: 17726145 DOI: 10.1152/ajpendo.00255.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Deficiency in nutritional determinants of homocysteine (HCY) metabolism, such as vitamin B(12) and folate, during pregnancy is known to influence HCY levels in the progeny, which in turn may exert adverse effects during development, including liver defects. Since short hypoxia has been shown to induce tolerance to subsequent stress in various cells including hepatocytes, and as vitamins B deficiency and hypoxic episodes may simultaneously occur in neonates, we aimed to investigate the influence of brief postnatal hypoxia (100% N(2) for 5 min) on the liver of rat pups born from dams fed a deficient regimen, i.e., depleted in vitamins B(12), B(2), folate, and choline. Four experimental groups were studied: control, hypoxia, deficiency, and hypoxia + deficiency. Although hypoxia transiently stimulated HCY catabolic pathways, it was associated with a progressive increase of hyperhomocysteinemia in deficient pups, with a fall of cystathionine beta-synthase activity at 21 days. At this stage, inducible NO synthase activity was dramatically increased and glutathione reductase decreased, specifically in the group combining hypoxia and deficiency. Also, hypoxia enhanced the deficiency-induced drop of the S-adenosylmethionine/S-adenosylhomocysteine ratio. In parallel, early exposure to the methyl-deficient regimen induced oxidative stress and led to hepatic steatosis, which was found to be more severe in pups additionally exposed to hypoxia. In conclusion, brief neonatal hypoxia may accentuate the long-term adverse effects of impaired HCY metabolism in the liver resulting from an inadequate nutritional regimen during pregnancy, and our data emphasize the importance of early factors on adult disease.
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Affiliation(s)
- Sébastien A Blaise
- INSERM U724, Faculté de Médecine, 9 Ave. de la Forêt de Haye, BP 184, F-54500 Vandoeuvre-lès-Nancy, France
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171
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Deth R, Muratore C, Benzecry J, Power-Charnitsky VA, Waly M. How environmental and genetic factors combine to cause autism: A redox/methylation hypothesis. Neurotoxicology 2007; 29:190-201. [PMID: 18031821 DOI: 10.1016/j.neuro.2007.09.010] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 07/27/2007] [Accepted: 09/27/2007] [Indexed: 01/17/2023]
Abstract
Recently higher rates of autism diagnosis suggest involvement of environmental factors in causing this developmental disorder, in concert with genetic risk factors. Autistic children exhibit evidence of oxidative stress and impaired methylation, which may reflect effects of toxic exposure on sulfur metabolism. We review the metabolic relationship between oxidative stress and methylation, with particular emphasis on adaptive responses that limit activity of cobalamin and folate-dependent methionine synthase. Methionine synthase activity is required for dopamine-stimulated phospholipid methylation, a unique membrane-delimited signaling process mediated by the D4 dopamine receptor that promotes neuronal synchronization and attention, and synchrony is impaired in autism. Genetic polymorphisms adversely affecting sulfur metabolism, methylation, detoxification, dopamine signaling and the formation of neuronal networks occur more frequently in autistic subjects. On the basis of these observations, a "redox/methylation hypothesis of autism" is described, in which oxidative stress, initiated by environment factors in genetically vulnerable individuals, leads to impaired methylation and neurological deficits secondary to reductions in the capacity for synchronizing neural networks.
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Affiliation(s)
- Richard Deth
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA 02468, United States.
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172
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Abstract
There is an association between cognitive function and vitamin B12 and folate status. Both vitamins participate in recycling the potentially toxic amino acid homocysteine to methionine and, ultimately, to the methyl donor S-adenosylmethionine (SAM). Consequently, B12 and folate indirectly influence glutathione synthesis – a major intracellular antioxidant. Neuroinflammation and oxidative stress are early features of Alzheimer’s disease (AD). Such stress impairs homocysteine recycling, degrades folate and decreases its cellular retention, resulting in limited SAM availability and increased homocysteine levels. Oxidized homocysteine derivatives, such as homocysteic acid, can initiate a vicious cycle by promoting free-radical formation. Decreased SAM also fosters development of characteristic AD neuropathologies – neurofibrillary tangles and amyloid plaques. The latter generate additional free radicals in a further feed-forward cascade. Future therapies should simultaneously halt neuroinflammation, restore redox homeostasis and replace depleted intracellular B vitamins. Developing early markers for these harmful processes will allow targeting of such therapy before irreversible cellular damage ensues.
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Affiliation(s)
- Andrew McCaddon
- Cardiff University, Cardiff School of Medicine, Gardden Road Surgery, Rhosllanerchrugog, Wrexham, North Wales, LL14 2EN, UK
| | - Peter R Hudson
- Maelor Hospital, Department of Medical Biochemistry, Croesnewydd Road, Wrexham, North Wales, LL13 7TD, UK
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173
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Qu K, Lee SW, Bian JS, Low CM, Wong PTH. Hydrogen sulfide: neurochemistry and neurobiology. Neurochem Int 2007; 52:155-65. [PMID: 17629356 DOI: 10.1016/j.neuint.2007.05.016] [Citation(s) in RCA: 194] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 05/16/2007] [Accepted: 05/24/2007] [Indexed: 11/19/2022]
Abstract
Current evidence suggests that hydrogen sulfide (H2S) plays an important role in brain functions, probably acting as a neuromodulator as well as an intracellular messenger. In the mammalian CNS, H2S is formed from the amino acid cysteine by the action of cystathionine beta-synthase (CBS) with serine (Ser) as the by-product. As CBS is a calcium and calmodulin dependent enzyme, the biosynthesis of H2S should be acutely controlled by the intracellular concentration of calcium. In addition, it is also regulated by S-adenosylmethionine which acts as an allosteric activator of CBS. H2S, as a sulfhydryl compound, has similar reducing properties as glutathione. In neurons, H2S stimulates the production of cAMP probably by direct activation of adenylyl cyclase and thus activate cAMP-dependent processes. In astrocytes, H2S increases intracellular calcium to an extent capable of inducing and propagating a "calcium wave", which is a form of calcium signaling among these cells. Possible physiological functions of H2S include potentiating long-term potentials through activation of the NMDA receptors, regulating the redox status, maintaining the excitatory/inhibitory balance in neurotransmission, and inhibiting oxidative damage through scavenging free radicals and reactive species. H2S is also involved in CNS pathologies such as stroke and Alzheimer's disease. In stroke, H2S appears to act as a mediator of ischemic injuries and thus inhibition of its production has been suggested to be a potential treatment approach in stroke therapy.
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Affiliation(s)
- K Qu
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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