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Wyse ATS, Bobermin LD, Dos Santos TM, Quincozes-Santos A. Homocysteine and Gliotoxicity. Neurotox Res 2021; 39:966-974. [PMID: 33786757 DOI: 10.1007/s12640-021-00359-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/21/2021] [Accepted: 03/23/2021] [Indexed: 12/15/2022]
Abstract
Homocysteine is a sulfur amino acid that does not occur in the diet, but it is an essential intermediate in normal mammalian metabolism of methionine. Hyperhomocysteinemia results from dietary intakes of Met, folate, and vitamin B12 and lifestyle or from the deficiency of specific enzymes, leading to tissue accumulation of this amino acid and/or its metabolites. Severe hyperhomocysteinemic patients can present neurological symptoms and structural brain abnormalities, of which the pathogenesis is poorly understood. Moreover, a possible link between homocysteine (mild hyperhomocysteinemia) and neurodegenerative/neuropsychiatric disorders has been suggested. In recent years, increasing evidence has emerged suggesting that astrocyte dysfunction is involved in the neurotoxicity of homocysteine and possibly associated with the physiopathology of hyperhomocysteinemia. This review addresses some of the findings obtained from in vivo and in vitro experimental models, indicating high homocysteine levels as an important neurotoxin determinant of the neuropathophysiology of brain damage. Recent data show that this amino acid impairs glutamate uptake, redox/mitochondrial homeostasis, inflammatory response, and cell signaling pathways. Therefore, the discussion of this review focuses on homocysteine-induced gliotoxicity, and its impacts in the brain functions. Through understanding the Hcy-induced gliotoxicity, novel preventive/therapeutic strategies might emerge for these diseases.
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Affiliation(s)
- Angela T S Wyse
- Programa de Pós-Graduação em Ciências Biológicas - Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. .,Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
| | - Larissa Daniele Bobermin
- Programa de Pós-Graduação em Ciências Biológicas - Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Tiago Marcon Dos Santos
- Programa de Pós-Graduação em Ciências Biológicas - Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - André Quincozes-Santos
- Programa de Pós-Graduação em Ciências Biológicas - Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.,Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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Huang G, Dragan M, Freeman D, Wilson JX. Activation of catechol-O-methyltransferase in astrocytes stimulates homocysteine synthesis and export to neurons. Glia 2005; 51:47-55. [PMID: 15779086 DOI: 10.1002/glia.20185] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Elevation of the total homocysteine (tHcy) concentration in plasma has been implicated in neurodegeneration in patients with stroke, dementia, Alzheimer disease, and Parkinson disease. Because the mechanisms controlling brain tHcy are unknown, the present study investigated its synthesis and transport in primary rat brain cell cultures. We found that the catechol-O-methyltransferase (COMT) substrate 3,4-dihydroxybenzoic acid (DHB) increased export of tHcy in astrocytes, but not in neurons. The export mechanism was selective for tHcy over cyst(e)ine, total glutathione (tGSH) or cysteinylglycine (Cys-Gly). tHcy export from astrocytes was also induced by the COMT substrates levodopa (L-DOPA), dopamine and quercetin, and it was blocked by the COMT inhibitors tropolone and entacapone. This export was associated with increased synthesis of tHcy because both intracellular and extracellular tHcy concentrations rose during COMT activation. Incubation in cyst(e)ine-deficient medium inhibited the tHcy export response to COMT activation. Exogenous tHcy (100 muM) was accumulated into neurons, but not into astrocytes. We conclude that activation of COMT causes sustained synthesis of Hcy in astrocytes and transport of this amino acid to neurons.
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Affiliation(s)
- Guowei Huang
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
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Benz B, Grima G, Do KQ. Glutamate-induced homocysteic acid release from astrocytes: possible implication in glia-neuron signaling. Neuroscience 2004; 124:377-86. [PMID: 14980387 DOI: 10.1016/j.neuroscience.2003.08.067] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2002] [Revised: 08/13/2003] [Accepted: 08/22/2003] [Indexed: 11/30/2022]
Abstract
Glial cells synthesise neuroactive substances and release them upon neurotransmitter receptor activation. Homocysteic acid (HCA), an endogenous agonist for glutamatergic N-methyl-D-aspartate (NMDA) receptors, is predominantly localised in glial cells. We have previously demonstrated the release of HCA from mouse astrocytes in culture following activation of beta-adrenergic receptors. Moreover, a release of HCA has also been observed in vivo upon physiological stimulation of sensory afferents in the thalamus. Here we report the glutamate-induced release of HCA from astrocytes. The effect of glutamate was mediated by the activation of ionotropic (NMDA and non-NMDA) as well as by metabotropic receptors. In addition, the release of HCA was Ca(2+)- and Na(+)-dependent, and its mechanism involved the activation of the Na+/Ca(2+)-exchanger. Furthermore, we provide evidence for the presence of functional NMDA receptors on astrocytes, which are coupled to an intracellular Ca2+ increase via stimulation of the Na+/Ca(2+)-exchanger. Our data thus favour a participation of glial cells in excitatory neurotransmission and corroborate the role of HCA as a "gliotransmitter."
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Affiliation(s)
- B Benz
- Centre for Research in Psychiatric Neuroscience, Department of Psychiatry, University of Lausanne, Route de Cery, CH-1008 Prilly-Lausanne, Switzerland
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Do KQ, Benz B, Binns KE, Eaton SA, Salt TE. Release of homocysteic acid from rat thalamus following stimulation of somatosensory afferents in vivo: feasibility of glial participation in synaptic transmission. Neuroscience 2004; 124:387-93. [PMID: 14980388 DOI: 10.1016/j.neuroscience.2003.08.068] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2002] [Revised: 08/13/2003] [Accepted: 08/22/2003] [Indexed: 11/29/2022]
Abstract
The sulphur-containing amino acid homocysteic acid (HCA) is present in and released in vitro from nervous tissue and is a potent neuronal excitant, predominantly activating N-methyl-d-aspartate (NMDA) receptors. However, HCA is localised not in neurones but in glial cells [Eur J Neurosci 3 (1991) 1370], and we have shown that it is released from astrocytes in culture upon glutamate receptor activation [Neuroscience 124 (2004) 377]. We now report the in vivo release of HCA from ventrobasal (VB) thalamus following natural stimulation of somatosensory afferents arising from the facial vibrissae of the rat. Simultaneously with multi-unit recording, [35S]-methionine, a HCA precursor, was perfused through a push-pull cannula in VB thalamus of anaesthetized rats. Perfusates were collected before, during and after 4 min stimulation of the vibrissal afferents with an air jet. A marked release of radiolabeled HCA was observed during and after the stimulation. Furthermore, the beta-adrenoreceptor agonist isoproterenol, which is known to evoke HCA release from glia in vitro, was found to increase the efflux of HCA in the perfusate in vivo. In separate experiments, the excitatory actions of iontophoretically applied HCA on VB neurones were inhibited by the NMDA receptor antagonist CPP, but not by the non-NMDA antagonist CNQX. These results suggest a possible "gliotransmitter" role for HCA in VB thalamus. The release of HCA from glia might exert a direct response or modulate responses to other neurotransmitters in postsynaptic neurons, thus enhancing excitatory processes.
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Affiliation(s)
- K Q Do
- Center for Research in Psychiatric Neuroscience, Department of Psychiatry, University of Lausanne, Route de Cery, CH-1008 Prilly-Lausanne, Switzerland.
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Jaffe EH, Garcia Y. Excitatory sulfur-containing amino acid-induced release of [3H]GABA from rat olfactory bulb. Neurochem Res 1997; 22:1477-84. [PMID: 9357013 DOI: 10.1023/a:1021954412216] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The effect of L-cysteine sulfinic acid (CSA) and L-homocysteic acid (HCA) on the release of tritiated gamma-amino butyric acid ([3H]GABA), from the external plexiform layer (EPL) of the rat olfactory bulb, was compared with that of glutamate. These amino acids induced release of GABA was strongly inhibited by the glutamate uptake blocker, pyrrolidine-2,4-dicarboxylate (2,4,PDC) (50 microM), while it was not inhibited by the specific GABA uptake blockers nipecotic acid (0.5 mM) or NO-711 (5 microM). Only the HCA induced GABA release was 60% inhibited by beta-alanine (0.5 mM), a glial GABA uptake blocker and 78% by the NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (AP-5) (100 microM). The non-NMDA receptor antagonists 6-cyano-2,3-dihydroxy-7-nitro-quinoxaline (CNQX) up to 500 microM had no effect on HCA or CSA stimulated GABA release. These results bring evidence for an excitatory role of HCA and CSA together with glutamate on GABAergic neuronal or glial elements, in the olfactory bulb. This role could be mediated through the reversal of the glutamate or/and the glial GABA transporter and through the activation of a NMDA type receptor.
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Affiliation(s)
- E H Jaffe
- Lab. Neuroquimica, Centro Biofisica y Bioquimica, IVIC, Caracas, Venezuela.
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Do KQ, Tappaz ML. Specificity of cysteine sulfinate decarboxylase (CSD) for sulfur-containing amino-acids. Neurochem Int 1996; 28:363-71. [PMID: 8740442 DOI: 10.1016/0197-0186(95)00109-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Cysteine sulfinate decarboxylase (CSD) which decarboxylates cysteine sulfinic acid (CSA) to form hypotaurine is thought to be involved in the biosynthesis of taurine. It was recently localized in astrocytes in the cerebellum and hippocampus by immunocytochemistry. Another sulfur-containing amino-acid (SCAA), homocysteic acid (HCA), was also found in astrocytes in these regions. We therefore investigated the specificity of CSD vs CSA and HCA as well as the related analogs homocysteine sulfinic acid (HCSA) and cysteic acid (CA). CSD was immunotrapped from brain and liver tissue supernatant using a specific CSD antiserum and Protein-A Sepharose. It was then incubated with the L-form of the various SCAA. Reaction products were identified and quantified by pre-column o-phthalaldehyde derivatization HPLC. CA and HCA from 2.5 to 25 mM inhibited the formation of hypotaurine from CSA (0.25 mM). Moreover, the inhibition curves were parallel for liver and brain CSD. CA or HCA (25 mM) elicited a near-total inhibition. HCSA did not produce a significant inhibition up to 25 mM. Incubation with 25 mM CSA or CA led to the formation of hypotaurine and taurine, respectively. The ratio of formation of taurine to that of hypotaurine was similar for CSD from liver and brain. In contrast no homotaurine, the decarboxylated reaction product of HCA, could be detected following incubation with 25 mM HCA. According to the sensitivity of the HPLC analysis this indicates that the decarboxylation of HCA, if any, was 130-fold and 50-fold less than that of CSA by CSD from liver and brain, respectively, in our experimental conditions. Similarly, following incubation with HCSA, no new peak appeared on the chromatogram when compared to a blank sample. These results show that CSD from either brain or liver has a high specificity for CSA and CA, which are the SCAA involved in the biosynthesis of taurine. HCA is an inhibitor of CSD but does not appear to be a substrate for CSD in vitro. HCSA is neither a substrate nor an inhibitor of CSD in vitro. Accordingly, CSD is unlikely to play a role in the metabolism of HCA or HCSA in vivo.
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Affiliation(s)
- K Q Do
- Brain Research Institute, University of Zürich, Switzerland
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8
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Thompson GA, Kilpatrick IC. The neurotransmitter candidature of sulphur-containing excitatory amino acids in the mammalian central nervous system. Pharmacol Ther 1996; 72:25-36. [PMID: 8981569 DOI: 10.1016/s0163-7258(96)00097-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
While L-glutamate (L-Glu) is considered to be the predominant excitatory amino acid transmitter in the mammalian CNS, other amino acids have come under scrutiny as possible rivals for such a role. These include four sulphur-containing analogues of L-Glu and L-aspartate known as the SAAs. The L-Glu analogues are L-homocysteic acid and L-homocysteine sulphinic acid, while the L-aspartate analogues are L-cysteic acid and L-cysteine sulphinic acid. They are mixed agonists of excitatory amino acid receptors on a variety of neurones and are reported to be present in and released from mammalian CNS tissue. This review serves to summarize the current state of research into the possibility that one or more of these compounds is indeed a transmitter within the mammalian CNS.
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Affiliation(s)
- G A Thompson
- Department of Cell Physiology and Pharmacology, University of Leicester, UK
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Ortega F, Hennequet L, Azkue J, Streit P, Grandes P. Neuronal and glial localization of homocysteate-like immunoreactivity in the rat retina. JOURNAL OF NEUROCYTOLOGY 1994; 23:783-91. [PMID: 7897442 DOI: 10.1007/bf01268090] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
To study the distribution of L-homocysteate in the rat retina, specific polyclonal and monoclonal anti-homocysteate antibodies have been used in combination with a highly sensitive postembedding method for light microscopic immunocytochemistry. In central and peripheral retina, the most strongly immunoreactive cell bodies lay in the inner nuclear layer. They represented about 17% of the total neuronal cell population of the layer and were identified as bipolar cells (19-20% of cells in the outer half of the inner nuclear layer) and amacrine cells (15% of cells in the inner half of the inner nuclear layer). A third cell type showing heavy homocysteate-like immunoreactivity was identified as Müller glial cells. Characteristically, their descending processes formed three immunoreactive bands in the inner plexiform layer. Furthermore, the outer and inner limiting membranes as well as glia around and between ganglion cell axons and in the vicinity of blood vessels were labelled intensely. Photoreceptors and their terminals, and ganglion cells, were not immunostained. These findings indicate the presence of homocysteate in some bipolar and amacrine cells of the inner nuclear layer and support a role for this sulphur-containing excitatory amino acid as a neurotransmitter candidate in the retina.
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Affiliation(s)
- F Ortega
- Department of Neurosciences, Faculty of Medicine and Dentistry, Basque Country University, Bilbao, Spain
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Ortega F, Pomposo I, Streit P, Grandes P. Homocysteate-like immunoreactivity in multiform glioblastoma of human brain. Neurosci Lett 1994; 168:41-4. [PMID: 8028791 DOI: 10.1016/0304-3940(94)90411-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Anti-homocysteate antibodies with postembedding immunohistochemistry for light microscopy were used to localize homocysteate-like immunoreactivity in human multiform glioblastoma. The most remarkable stained elements (6.8% of the total tumoral tissue) corresponded to distinct astrocytic cell bodies, intermingled fibrous processes and puncta of diverse size, some of them closely apposed to capillaries. In not affected peritumoral tissue, on the other hand, numerous labelled dots resembling portions of glial processes were observed in the neuropil and around blood vessels (2.7% of the total peritumoral tissue). However, glial and neuronal cell bodies could not be detected. These observations extend to a human brain tumor of glial nature the knowledge on the preferential localization of homocysteate in glia.
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Affiliation(s)
- F Ortega
- Department of Neurosciences, Faculty of Medicine and Dentistry, Basque Country University, Bilbao, Spain
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Orrego F, Villanueva S. The chemical nature of the main central excitatory transmitter: a critical appraisal based upon release studies and synaptic vesicle localization. Neuroscience 1993; 56:539-55. [PMID: 7902967 DOI: 10.1016/0306-4522(93)90355-j] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The chemical nature of the central transmitter responsible for fast excitatory events and other related phenomena is analysed against the historical background that has progressively clarified the structure and function of central synapses. One of the problems posed by research in this field has been whether one or more of the numerous excitatory substances endogenous to the brain is responsible for fast excitatory synaptic transmission, or if such a substance is, or was, a previously unknown one. The second question is related to the presence in the CNS of three main receptor types related to fast excitatory transmission, the so-called alpha-amino-3-hydroxy-5-methylisoxazole propionic acid, kainate and N-methyl-D-aspartate receptors. This implies the possibility that each receptor type might have its own endogenous agonist, as has sometimes been suggested. To answer such questions, an analysis was done of how different endogenous substances, including L-glutamate, L-aspartate, L-cysteate, L-homocysteate, L-cysteine sulfinate, L-homocysteine sulfinate, N-acetyl-L-aspartyl glutamate, quinolinate, L-sulfoserine, S-sulfo-L-cysteine, as well as possible unknown compounds, were able to fulfil the more important criteria for transmitter identification, namely identity of action, induced release, and presence in synaptic vesicles. The conclusion of this analysis is that glutamate is clearly the main central excitatory transmitter, because it acts on all three of the excitatory receptors, it is released by exocytosis and, above all, it is present in synaptic vesicles in a very high concentration, comparable to the estimated number of acetylcholine molecules in a quantum, i.e. 6000 molecules. Regarding a possible transmitter role for aspartate, for which a large body of evidence has been presented, it seems, when this evidence is carefully scrutinized, that it is either inconclusive, or else negative. This suggests that aspartate is not a classical central excitatory transmitter. From this analysis, it is suggested that the terms alpha-amino-3-hydroxy-5-methylisoxazole propionic acid, kainate and N-methyl-D-aspartate receptors, should be changed to that of glutamate receptors, and, more specifically, to GLUA, GLUK and GLUN receptors, respectively. When subtypes are described, a Roman numeral may be added, as in GLUNI, GLUNII, and so on.
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Affiliation(s)
- F Orrego
- Faculty of Medicine, Universidad de los Andes, Santiago, Chile
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Houssaini YS, Cazalets JR, Martini F, Clarac F. Induction of fictive locomotion by sulphur-containing amino acids in an in vitro newborn rat preparation. Eur J Neurosci 1993; 5:1226-32. [PMID: 8281325 DOI: 10.1111/j.1460-9568.1993.tb00977.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The role of the sulphur-containing amino acids (SAAs) in the initiation of fictive locomotion was tested in an isolated spinal cord preparation from newborn rats. These substances were bath-applied and the fictive locomotion was recorded in the lumbar ventral roots. It emerged from this study that all the compounds tested could trigger an organized pattern (alternating left and right bursts of activity) with a dose-dependent response. However, specific frequency and concentration ranges were observed with each of these SAAs. Moreover, a clear-cut difference between D and L isomers in the ability of the SAAs to induce this activity was observed; the SAAs of the D-forms were found to be generally more potent than those of the L-forms. The effects of the SAAs were found to be mediated by both NMDA and non-NMDA receptors, since they were blocked in a dose-dependent manner by the specific antagonists of these receptors. Moreover, it was observed that beta-p-chlorophenylglutamic acid, an uptake inhibitor of homocysteic acid (HCA), potentiated the effect of exogenously applied HCA, which supports the idea that HCA may act as a transmitter. The sulphuric and non-sulphuric amino acids were also classified in their order of potency. The most potent compound turned out to be D-homocysteine sulphinic acid, while D-cysteine sulphinic acid was the least potent. It also emerged that the maximal frequencies obtained with SAAs and excitatory amino acids were in the same range, which might correspond to the maximal limits of this system.
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Affiliation(s)
- Y S Houssaini
- Laboratoire de Neurobiologie et Mouvement, CNRS, Marseille, France
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