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Lu ZY, Jiang WD, Wu P, Liu Y, Ren HM, Jin XW, Kuang SY, Li SW, Tang L, Zhang L, Mi HF, Zhou XQ, Feng L. Cellular antioxidant mechanism of mannan-oligosaccharides involving in enhancing flesh quality in grass carp (Ctenopharyngodon idella). JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2023; 103:1172-1182. [PMID: 36085562 DOI: 10.1002/jsfa.12211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 09/05/2022] [Accepted: 09/09/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND Deterioration of flesh quality has bad effects on consumer satisfaction. Therefore, effects of safe mannan-oligosaccharides (MOS) on flesh quality of grass carp (Ctenopharyngodon idella) muscle were studied. A total of 540 healthy fish (215.85 ± 0.30 g) were randomly divided into six groups and fed six separate diets with graded levels of MOS (0, 200, 400, 600, 800 and 1000 mg kg-1 ) for 60 days. This study aimed at investigating the benefits of dietary MOS on flesh quality (fatty acids, amino acids and physicochemical properties) and the protection mechanism regarding antioxidant status. RESULTS Optimal MOS could improve tenderness (27.4%), pH (5.5%) while decreasing cooking loss (16.6%) to enhance flesh quality. Meanwhile, optimal MOS improved flavor inosine 5'-monophosphate (IMP) of 11.8%, sweetness and umami-associated amino acid, healthy unsaturated fatty acid (UFA) of 14.9% and n-3 polyunsaturated fatty acids (n-3 PUFAs) especially C20:5n-3 (15.8%) and C22:6n-3 (38.3%). Furthermore, the mechanism that MOS affected pH, tenderness and cooking loss could be partly explained by the reduced lactate, cathepsin and oxidation, respectively. The enhanced flesh quality was also associated with enhanced antioxidant ability concerning improving antioxidant enzymes activities and the corresponding transcriptional levels, which were regulated through NF-E2-related factor 2 (Nrf2) and target of rapamycin (TOR) signaling. Based on pH24h , cooking loss, shear force and DHA (docosahexaenoic acid, C22:6n-3), optimal MOS levels for grass carp were estimated to be 442.75, 539.53, 594.73 and 539.53 mg kg-1 , respectively. CONCLUSION Dietary MOS is a promising alternative strategy to improve flesh quality of fish muscle. © 2022 Society of Chemical Industry.
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Affiliation(s)
- Zhi-Yuan Lu
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, China
| | - Wei-Dan Jiang
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
- Key Laboratory of Animal Disease-Resistance Nutrition, Ministry of Education, Ministry of Agriculture and Rural Affairs, Key Laboratory of Sichuan Province, Sichuan, China
| | - Pei Wu
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
- Key Laboratory of Animal Disease-Resistance Nutrition, Ministry of Education, Ministry of Agriculture and Rural Affairs, Key Laboratory of Sichuan Province, Sichuan, China
| | - Yang Liu
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
- Key Laboratory of Animal Disease-Resistance Nutrition, Ministry of Education, Ministry of Agriculture and Rural Affairs, Key Laboratory of Sichuan Province, Sichuan, China
| | - Hong-Mei Ren
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
- Key Laboratory of Animal Disease-Resistance Nutrition, Ministry of Education, Ministry of Agriculture and Rural Affairs, Key Laboratory of Sichuan Province, Sichuan, China
| | - Xiao-Wan Jin
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
- Key Laboratory of Animal Disease-Resistance Nutrition, Ministry of Education, Ministry of Agriculture and Rural Affairs, Key Laboratory of Sichuan Province, Sichuan, China
| | - Sheng-Yao Kuang
- Animal Nutrition Institute, Sichuan Academy of Animal Science, Sichuan Animtech Feed Co. Ltd, Chengdu, China
| | - Shu-Wei Li
- Animal Nutrition Institute, Sichuan Academy of Animal Science, Sichuan Animtech Feed Co. Ltd, Chengdu, China
| | - Ling Tang
- Animal Nutrition Institute, Sichuan Academy of Animal Science, Sichuan Animtech Feed Co. Ltd, Chengdu, China
| | - Lu Zhang
- Tongwei Co., Ltd, Chengdu, China, Healthy Aquaculture Key Laboratory of Sichuan Province, Sichuan, China
| | - Hai-Feng Mi
- Tongwei Co., Ltd, Chengdu, China, Healthy Aquaculture Key Laboratory of Sichuan Province, Sichuan, China
| | - Xiao-Qiu Zhou
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
- Key Laboratory of Animal Disease-Resistance Nutrition, Ministry of Education, Ministry of Agriculture and Rural Affairs, Key Laboratory of Sichuan Province, Sichuan, China
| | - Lin Feng
- Animal Nutrition Institute, Sichuan Agricultural University, Chengdu, China
- Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu, China
- Key Laboratory of Animal Disease-Resistance Nutrition, Ministry of Education, Ministry of Agriculture and Rural Affairs, Key Laboratory of Sichuan Province, Sichuan, China
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Glutamine synthetase regulation by dexamethasone, RU486, and compound A in astrocytes derived from aged mouse cerebral hemispheres is mediated via glucocorticoid receptor. Mol Cell Biochem 2021; 476:4471-4485. [PMID: 34491525 DOI: 10.1007/s11010-021-04236-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Accepted: 07/27/2021] [Indexed: 01/01/2023]
Abstract
Glucocorticoids (GCs) regulate astrocyte function, while glutamine synthetase (GS), an enzyme highly expressed in astrocytes, is one of the most remarkable GCs-induced genes. GCs mediate their effects through their cognate glucocorticoid receptor (GRα and GRβ isoforms); however, the mechanism via which these isoforms regulate GS activity in astrocytes remains unknown. We used dexamethasone (DEX), a classical GRα/GRβ agonist, RU486, which is a specific GRβ ligand, and Compound A, a known "dissociated" ligand, to delineate the mechanism via which GR modulates GS activity. Aged Mouse Cerebral Hemisphere astrocytes were treated with DEX (1 μM), RU486 (1 nM-1 μM) or compound A (10 μM), alone or in combination with DEX. GS activity and expression, GR isoforms (mRNA and protein levels), and GRα subcellular trafficking were measured. DEX increased GS activity in parallel with GRα nuclear translocation. RU486 increased GS activity in absence of GRα nuclear translocation implicating thus a role of GRβ-mediated mechanism compound A had no effect on GS activity implicating a GRα-GRE-mediated mechanism. None of the compounds affected whole-cell GRα protein content. DEX reduced GRα and GRβ mRNA levels, while RU486 increased GRβ gene expression. We provide evidence that GS activity, in astrocytes, is regulated via GRα- and GRβ-mediated pathways with important implications in pathological conditions in which astrocytes are involved.
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Ryrfeldt Å, Hansson E, Brattsand R. Effects of Budesonide and Dexamethasone on Cell Morphology, Thymidine Incorporation and Glutamine Synthetase Activity in Rat Primary Astroglial Culture. Altern Lab Anim 2020. [DOI: 10.1177/026119298901600310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glucocorticoids are widely used in medical practice. Since astrocytes are target cells for glucocorticoids, the effects of two glucocorticoids, budesonide and dexamethasone, on cell morphology, thymidine incorporation into DNA and glutamine synthetase (GS) activity, were evaluated in primary astroglial cultures. Both budesonide and dexamethasone caused a threefold increase in GS activity over a dose range of 10-6–10-9M. There were no differences between the effects of the two glucocorticoids. No morphological changes were obtained with the glucocorticoids with the same concentration range as above and with incubation periods of up to 48 hours. Nor were any effects on [3H]-thymidine incorporation observed. It is concluded that glucocorticoids can regulate intracellular amino acid metabolism in astrocytes by an activation of GS, while cell morphology and cell replication appear not to be affected.
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Affiliation(s)
- Åke Ryrfeldt
- Safety Assessment, AB Astra, S-151 85 Södertälje, Sweden
| | - Elisabeth Hansson
- Institute of Neurobiology, University of Göteborg, P.O. Box 33031, S-400 33 Göteborg, Sweden
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Vizuete AFK, Hansen F, Negri E, Leite MC, de Oliveira DL, Gonçalves CA. Effects of dexamethasone on the Li-pilocarpine model of epilepsy: protection against hippocampal inflammation and astrogliosis. J Neuroinflammation 2018; 15:68. [PMID: 29506554 PMCID: PMC5839012 DOI: 10.1186/s12974-018-1109-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 02/28/2018] [Indexed: 11/25/2022] Open
Abstract
Background Temporal lobe epilepsy (TLE) is the most common form of partial epilepsy and is accompanied, in one third of cases, by resistance to antiepileptic drugs (AED). Most AED target neuronal activity modulated by ionic channels, and the steroid sensitivity of these channels has supported the use of corticosteroids as adjunctives to AED. Assuming the importance of astrocytes in neuronal activity, we investigated inflammatory and astroglial markers in the hippocampus, a key structure affected in TLE and in the Li-pilocarpine model of epilepsy. Methods Initially, hippocampal slices were obtained from sham rats and rats subjected to the Li-pilocarpine model of epilepsy, at 1, 14, and 56 days after status epilepticus (SE), which correspond to the acute, silent, and chronic phases. Dexamethasone was added to the incubation medium to evaluate the secretion of S100B, an astrocyte-derived protein widely used as a marker of brain injury. In the second set of experiments, we evaluated the in vivo effect of dexamethasone, administrated at 2 days after SE, on hippocampal inflammatory (COX-1/2, PGE2, and cytokines) and astroglial parameters: GFAP, S100B, glutamine synthetase (GS) and water (AQP-4), and K+ (Kir 4.1) channels. Results Basal S100B secretion and S100B secretion in high-K+ medium did not differ at 1, 14, and 56 days for the hippocampal slices from epileptic rats, in contrast to sham animal slices, where high-K+ medium decreased S100B secretion. Dexamethasone addition to the incubation medium per se induced a decrease in S100B secretion in sham and epileptic rats (1 and 56 days after SE induction). Following in vivo dexamethasone administration, inflammatory improvements were observed, astrogliosis was prevented (based on GFAP and S100B content), and astroglial dysfunction was partially abrogated (based on Kir 4.1 protein and GSH content). The GS decrease was not prevented by dexamethasone, and AQP-4 was not altered in this epileptic model. Conclusions Changes in astroglial parameters emphasize the importance of these cells for understanding alterations and mechanisms of epileptic disorders in this model. In vivo dexamethasone administration prevented most of the parameters analyzed, reinforcing the importance of anti-inflammatory steroid therapy in the Li-pilocarpine model and possibly in other epileptic conditions in which neuroinflammation is present. Electronic supplementary material The online version of this article (10.1186/s12974-018-1109-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Adriana Fernanda K Vizuete
- Department of Biochemistry, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcelos, 2600-Anexo, Porto Alegre, RS, 90035-003, Brazil.
| | - Fernanda Hansen
- Department of Biochemistry, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcelos, 2600-Anexo, Porto Alegre, RS, 90035-003, Brazil
| | - Elisa Negri
- Department of Biochemistry, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcelos, 2600-Anexo, Porto Alegre, RS, 90035-003, Brazil
| | - Marina Concli Leite
- Department of Biochemistry, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcelos, 2600-Anexo, Porto Alegre, RS, 90035-003, Brazil
| | - Diogo Losch de Oliveira
- Department of Biochemistry, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcelos, 2600-Anexo, Porto Alegre, RS, 90035-003, Brazil
| | - Carlos-Alberto Gonçalves
- Department of Biochemistry, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcelos, 2600-Anexo, Porto Alegre, RS, 90035-003, Brazil
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Minireview on Glutamine Synthetase Deficiency, an Ultra-Rare Inborn Error of Amino Acid Biosynthesis. BIOLOGY 2016; 5:biology5040040. [PMID: 27775558 PMCID: PMC5192420 DOI: 10.3390/biology5040040] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 10/03/2016] [Accepted: 10/12/2016] [Indexed: 12/25/2022]
Abstract
Glutamine synthetase (GS) is a cytosolic enzyme that produces glutamine, the most abundant free amino acid in the human body. Glutamine is a major substrate for various metabolic pathways, and is thus an important factor for the functioning of many organs; therefore, deficiency of glutamine due to a defect in GS is incompatible with normal life. Mutations in the human GLUL gene (encoding for GS) can cause an ultra-rare recessive inborn error of metabolism—congenital glutamine synthetase deficiency. This disease was reported until now in only three unrelated patients, all of whom suffered from neonatal onset severe epileptic encephalopathy. The hallmark of GS deficiency in these patients was decreased levels of glutamine in body fluids, associated with chronic hyperammonemia. This review aims at recapitulating the clinical history of the three known patients with congenital GS deficiency and summarizes the findings from studies done along with the work-up of these patients. It is the aim of this paper to convince the reader that (i) this disorder is possibly underdiagnosed, since decreased concentrations of metabolites do not receive the attention they deserve; and (ii) early detection of GS deficiency may help to improve the outcome of patients who could be treated early with metabolites that are lacking in this condition.
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Carter BS, Hamilton DE, Thompson RC. Acute and chronic glucocorticoid treatments regulate astrocyte-enriched mRNAs in multiple brain regions in vivo. Front Neurosci 2013; 7:139. [PMID: 23966905 PMCID: PMC3736049 DOI: 10.3389/fnins.2013.00139] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 07/19/2013] [Indexed: 12/03/2022] Open
Abstract
Previous studies have primarily interpreted gene expression regulation by glucocorticoids in the brain in terms of impact on neurons; however, less is known about the corresponding impact of glucocorticoids on glia and specifically astrocytes in vivo. Recent microarray experiments have identified glucocorticoid-sensitive mRNAs in primary astrocyte cell culture, including a number of mRNAs that have reported astrocyte-enriched expression patterns relative to other brain cell types. Here, we have tested whether elevations of glucocorticoids regulate a subset of these mRNAs in vivo following acute and chronic corticosterone exposure in adult mice. Acute corticosterone exposure was achieved by a single injection of 10 mg/kg corticosterone, and tissue samples were harvested 2 h post-injection. Chronic corticosterone exposure was achieved by administering 10 mg/mL corticosterone via drinking water for 2 weeks. Gene expression was then assessed in two brain regions associated with glucocorticoid action (prefrontal cortex and hippocampus) by qPCR and by in situ hybridization. The majority of measured mRNAs regulated by glucocorticoids in astrocytes in vitro were similarly regulated by acute and/or chronic glucocorticoid exposure in vivo. In addition, the expression levels for mRNAs regulated in at least one corticosterone exposure condition (acute/chronic) demonstrated moderate positive correlation between the two conditions by brain region. In situ hybridization analyses suggest that select mRNAs are regulated by chronic corticosterone exposure specifically in astroctyes based on (1) similar general expression patterns between corticosterone-treated and vehicle-treated animals and (2) similar expression patterns to the pan-astrocyte marker Aldh1l1. Our findings demonstrate that glucocorticoids regulate astrocyte-enriched mRNAs in vivo and suggest that glucocorticoids regulate gene expression in the brain in a cell type-dependent fashion.
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Affiliation(s)
- Bradley S Carter
- Neuroscience Graduate Program, University of Michigan Ann Arbor, MI, USA ; Molecular and Behavioral Neuroscience Institute, University of Michigan Ann Arbor, MI, USA
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Borisova T, Krisanova N, Sivko R, Borysov A. Cholesterol depletion attenuates tonic release but increases the ambient level of glutamate in rat brain synaptosomes. Neurochem Int 2010; 56:466-78. [DOI: 10.1016/j.neuint.2009.12.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 12/07/2009] [Accepted: 12/11/2009] [Indexed: 10/20/2022]
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Battú CE, Godinho GFRS, Thomazi AP, de Almeida LMV, Gonçalves CA, Kommers T, Wofchuk ST. Ontogenetic Changes in Glial Fibrillary Acid Protein Phosphorylation, Glutamate Uptake and Glutamine Synthetase Activity in Olfactory Bulb of Rats. Neurochem Res 2005; 30:1101-8. [PMID: 16292502 DOI: 10.1007/s11064-005-7587-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/21/2005] [Indexed: 10/25/2022]
Abstract
Phosphorylation of the glial fibrillary acidic protein (GFAP) in hippocampal and cerebellar slices from immature rats is stimulated by glutamate. This effect occurs via a group II metabotropic glutamate receptor in the hippocampus and an NMDA ionotropic receptor in the cerebellum. We investigated the glutamate modulation of GFAP phosphorylation in the olfactory bulb slices of Wistar rats of different ages (post-natal day 15 = P15, post-natal day 21 = P21 and post-natal day 60 = P60). Our results showed that glutamate stimulates GFAP phosphorylation in young animals and this is mediated by NMDA receptors. We also observed a decrease in glutamate uptake at P60 compared to P15, a finding similar to that found in the hippocampus. The activity of glutamine synthetase was elevated after birth, but was found to decrease with development from P21 to P60. Together, these data confirm the importance of glutamatergic transmission in the olfactory bulb, its developmental regulation in this brain structure and extends the concept of glial involvement in glutamatergic neuron-glial communication.
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Affiliation(s)
- Cíntia Eickhoff Battú
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, UFRGS, 90035-003, Porto Alegre, RS, Brasil
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Muscoli C, Visalli V, Colica C, Nisticò R, Palma E, Costa N, Rotiroti D, Nisticò G, Mollace V. The effect of inflammatory stimuli on NMDA-related activation of glutamine synthase in human cultured astroglial cells. Neurosci Lett 2005; 373:184-8. [PMID: 15619540 DOI: 10.1016/j.neulet.2004.09.079] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 09/28/2004] [Accepted: 09/29/2004] [Indexed: 11/28/2022]
Abstract
Removal of glutamate from the synaptic cleft by astroglial glutamine synthase (GS) is a crucial step in the regulation of glutamate turnover and metabolism, thus participating in endogenous neuroprotective processes occurring within brain tissues. Here we investigated on the effect of inflammatory cytokines on GS activity in astroglial cells undergoing NMDA receptors stimulation. Incubation of human cultured astroglial cells with NMDA (100 microM) enhanced GS expression, an effect driven by the generation of nitric oxide (NO) since l-NAME (500 microM), an inhibitor of NO synthase, reversed this effect. NMDA-related increase of GS activity and glutamine concentration was antagonised by previous incubation of astroglial cells with a mixture of LPS plus gammaIFN, an effect counteracted by dexamethasone, the latter effect being accompanied by inhibition of inducible NO synthase. These results show that LPS plus gammaIFN inhibit elevation of GS activity subsequent to NMDA receptor stimulation in astroglial cells via enhancement of inducible NO synthase, and this may represent the site of interaction between pro-inflammatory and excitotoxic stimuli in the brain.
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Affiliation(s)
- Carolina Muscoli
- Faculty of Pharmacy, Magna Graecia University of Catanzaro, Complesso Nini' Barbieri, Roccelletta di Borgia, 88100 Catanzaro, Italy
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Modulation of glutamatergic and GABAergic neurotransmission by corticosteroid hormones and stress. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s0921-0709(05)80029-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Sáenz DA, Goldin AP, Minces L, Chianelli M, Sarmiento MIK, Rosenstein RE. Effect of melatonin on the retinal glutamate/glutamine cycle in the golden hamster retina. FASEB J 2004; 18:1912-3. [PMID: 15448109 DOI: 10.1096/fj.04-2062fje] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Glutamate is the main excitatory neurotransmitter in the retina, but it is neurotoxic when present in excessive amounts. The metabolic dependence of glutamatergic neurons upon glia via the glutamate/glutamine cycle to provide the precursor for neurotransmitter glutamate is well established. Since melatonin has been shown to be neuroprotective in several systems, in the present report, its effect on the glutamate/glutamine cycle activity was examined in the golden hamster retina. Melatonin (0.1-10 nM) significantly increased retinal glutamine synthetase activity but it did not affect L-glutamine release. A characterization of the hamster retinal L-glutamine uptake mechanism was performed. This mechanism was partly Na+-dependent, and it was significantly inhibited by 2-aminobicyclo (2, 2, 1) heptane 2-carboxylic acid (BCH, a selective antagonists for the L-type system) and by alpha-(methylamino)-isobutyric acid (MeAIB, substrate characteristic for the A -type transporter) suggesting the coexistence of these transport systems in the hamster retina. Melatonin (0.1-10 nM) significantly increased total glutamine uptake as well as the BCH and the MeAIB-insensitive transporters activity. On the other hand, melatonin significantly decreased retinal glutaminase activity. On the basis of these results, it might be presumed that hamster retinal glutamate/glutamine cycle activity is regulated by physiological concentrations of melatonin. Furthermore, these findings suggest that a treatment with melatonin could be considered as a new approach to handling glutamate-mediated neuronal degeneration.
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Affiliation(s)
- Daniel A Sáenz
- Laboratorio de Neuroquímica Retiniana y Oftalmología Experimental, Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina
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Weibel M, Pettmann B, Labourdette G, Miehe M, Bock E, Sensenbrenner M. Morphological and biochemical maturation of rat astroglial cells grown in a chemically defined medium: Influence of an astroglial growth factor. Int J Dev Neurosci 2003; 3:617-30. [DOI: 10.1016/0736-5748(85)90052-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/1985] [Indexed: 10/27/2022] Open
Affiliation(s)
- M. Weibel
- Centre de Neurochimie du CNRS and INSERM U-44; 5, rue Blaise Pascal 67084 Strasbourg Cedex France
| | - B. Pettmann
- Centre de Neurochimie du CNRS and INSERM U-44; 5, rue Blaise Pascal 67084 Strasbourg Cedex France
| | - G. Labourdette
- Centre de Neurochimie du CNRS and INSERM U-44; 5, rue Blaise Pascal 67084 Strasbourg Cedex France
| | - M. Miehe
- Centre de Neurochimie du CNRS and INSERM U-44; 5, rue Blaise Pascal 67084 Strasbourg Cedex France
- The Protein Laboratory; University of Copenhagen; Sigurdsgade 34 2200 Copenhagen N Denmark
| | - E. Bock
- Centre de Neurochimie du CNRS and INSERM U-44; 5, rue Blaise Pascal 67084 Strasbourg Cedex France
- The Protein Laboratory; University of Copenhagen; Sigurdsgade 34 2200 Copenhagen N Denmark
| | - M. Sensenbrenner
- Centre de Neurochimie du CNRS and INSERM U-44; 5, rue Blaise Pascal 67084 Strasbourg Cedex France
- The Protein Laboratory; University of Copenhagen; Sigurdsgade 34 2200 Copenhagen N Denmark
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Abstract
Glutamine synthetase (GS) in brain is located mainly in astrocytes. One of the primary roles of astrocytes is to protect neurons against excitotoxicity by taking up excess ammonia and glutamate and converting it into glutamine via the enzyme GS. Changes in GS expression may reflect changes in astroglial function, which can affect neuronal functions. Hyperammonemia is an important factor responsible of hepatic encephalopathy (HE) and causes astroglial swelling. Hyperammonemia can be experimentally induced and an adaptive astroglial response to high levels of ammonia and glutamate seems to occur in long-term studies. In hyperammonemic states, astroglial cells can experience morphological changes that may alter different astrocyte functions, such as protein synthesis or neurotransmitters uptake. One of the observed changes is the increase in the GS expression in astrocytes located in glutamatergic areas. The induction of GS expression in these specific areas would balance the increased ammonia and glutamate uptake and protect against neuronal degeneration, whereas, decrease of GS expression in non-glutamatergic areas could disrupt the neuron-glial metabolic interactions as a consequence of hyperammonemia. Induction of GS has been described in astrocytes in response to the action of glutamate on active glutamate receptors. The over-stimulation of glutamate receptors may also favour nitric oxide (NO) formation by activation of NO synthase (NOS), and NO has been implicated in the pathogenesis of several CNS diseases. Hyperammonemia could induce the formation of inducible NOS in astroglial cells, with the consequent NO formation, deactivation of GS and dawn-regulation of glutamate uptake. However, in glutamatergic areas, the distribution of both glial glutamate receptors and glial glutamate transporters parallels the GS location, suggesting a functional coupling between glutamate uptake and degradation by glutamate transporters and GS to attenuate brain injury in these areas. In hyperammonemia, the astroglial cells located in proximity to blood-vessels in glutamatergic areas show increased GS protein content in their perivascular processes. Since ammonia freely crosses the blood-brain barrier (BBB) and astrocytes are responsible for maintaining the BBB, the presence of GS in the perivascular processes could produce a rapid glutamine synthesis to be released into blood. It could, therefore, prevent the entry of high amounts of ammonia from circulation to attenuate neurotoxicity. The changes in the distribution of this critical enzyme suggests that the glutamate-glutamine cycle may be differentially impaired in hyperammonemic states.
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Affiliation(s)
- I Suárez
- Departamento de Biología Celular y Genética, Facultad de Biología, Universidad de Alcalá, 28871, Madrid, Spain.
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Benton RL, Ross CD, Miller KE. Glutamine synthetase activities in spinal white and gray matter 7 days following spinal cord injury in rats. Neurosci Lett 2000; 291:1-4. [PMID: 10962139 DOI: 10.1016/s0304-3940(00)01362-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The glial enzyme glutamine synthetase (GS) is critical for central nervous system catabolism of glutamate and glutamine production. Upregulation of GS is a hallmark of reactive astrocytosis, although such induction following spinal cord injury (SCI) has not been reported. This study's purpose was to determine if GS activity is increased following SCI. Experimental rats received a complete spinal transection at the T5 segment and control rats received a laminectomy only. GS activities were determined using an enzymatic microassay. Glutamine levels were resolved in semi-adjacent sections. At 7 days following SCI, GS activity increased an average of 170-190% in white matter and 15-25% in gray matter immediately adjacent to the transection, and 70-90% in white matter and 40-45% in gray matter from cervical and lumbar enlargements. Correlative increases in glutamine were observed also. These findings further characterize the astrocytic response to SCI, which may contribute to altered glutamine metabolism in injured spinal tissue.
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Affiliation(s)
- R L Benton
- Department of Cell Biology, University of Oklahoma Health Sciences Center, PO Box 26901, Biomedical Sciences Building Room 553, OK 73190, Oklahoma City, USA.
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Maurel D, Sage D, Mekaouche M, Bosler O. Glucocorticoids up-regulate the expression of glial fibrillary acidic protein in the rat suprachiasmatic nucleus. Glia 2000; 29:212-21. [PMID: 10642748 DOI: 10.1002/(sici)1098-1136(20000201)29:3<212::aid-glia3>3.0.co;2-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Immunoreactivity against glial fibrillary acidic protein (GFAP) was used as a dynamic index in adrenalectomized rats subjected or not to corticosterone replacement to investigate whether glucocorticoids may interact with astrocytes in the suprachiasmatic nucleus (SCN), the master component of the central circadian clock. GFAP staining in the SCN was significantly higher in rats having received implants that restored physiological plasma levels of corticosterone within diurnal or nocturnal limits than in non-normalized rats. The effects of corticosterone were similar in the parvocellular portion of the paraventricular nucleus but were opposite in the hippocampus, another major site of negative feed-back regulation of the hypothalamic-pituitary-adrenal axis, where a decreased GFAP staining was observed in discrete regions of the dentate gyrus. This indicates that glucocorticoids may positively or negatively regulate GFAP, depending on the target brain structure. In the SCN, that contains only few if any glucocorticoid receptors, indirect mechanisms that may involve serotoninergic neurons are probably responsible for the effects of corticosterone level. It is proposed that the corticosterone-induced increase in GFAP staining in that nucleus accounts for dynamic changes in neurone-astrocyte interactions that might occur in relation with natural fluctuations of glucocorticoids over the 24 h period.
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Affiliation(s)
- D Maurel
- Interactions Fonctionnelles en Neuroendocrinologie, INSERM, Institut Fédératif Jean-Roche, Université de la Méditerranée, Marseille, France.
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16
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Abstract
The glucocorticoid signaling pathway is responsive to a considerable number of internal and external signals and can therefore establish diverse patterns of gene expression. A glial-specific pattern, for example, is shown by the glucocorticoid-inducible gene glutamine synthetase. The enzyme is expressed at a particularly high level in glial cells, where it catalyzes the recycling of the neurotransmitter glutamate, and at a low level in most other cells, for housekeeping duties. Glial specificity of glutamine synthetase induction is achieved by the use of positive and negative regulatory elements, a glucocorticoid response element and a neural restrictive silencer element. Though not glial specific by themselves, these elements may establish a glial-specific pattern of expression through their mutual activity and their combined effect. The inductive activity of glucocorticoids is markedly repressed by the c-Jun protein, which is expressed at relatively high levels in proliferating glial cells. The signaling pathway of c-Jun is activated by the disruption of glia-neuron cell contacts, by transformation with v-src, and in proliferating retinal cells of early embryonic ages. The c-Jun protein inhibits the transcriptional activity of the glucocorticoid receptor and thus represses glutamine synthetase expression. This repressive mechanism might also affect the ability of glial cells to cope with glutamate neurotoxicity in injured tissues.
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Affiliation(s)
- L Vardimon
- Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel
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17
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Lie-Venema H, Hakvoort TB, van Hemert FJ, Moorman AF, Lamers WH. Regulation of the spatiotemporal pattern of expression of the glutamine synthetase gene. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1998; 61:243-308. [PMID: 9752723 DOI: 10.1016/s0079-6603(08)60829-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Glutamine synthetase, the enzyme that catalyzes the ATP-dependent conversion of glutamate and ammonia into glutamine, is expressed in a tissue-specific and developmentally controlled manner. The first part of this review focuses on its spatiotemporal pattern of expression, the factors that regulate its levels under (patho)physiological conditions, and its role in glutamine, glutamate, and ammonia metabolism in mammals. Glutamine synthetase protein stability is more than 10-fold reduced by its product glutamine and by covalent modifications. During late fetal development, translational efficiency increases more than 10-fold. Glutamine synthetase mRNA stability is negatively affected by cAMP, whereas glucocorticoids, growth hormone, insulin (all positive), and cAMP (negative) regulate its rate of transcription. The signal transduction pathways by which these factors may regulate the expression of glutamine synthetase are briefly discussed. The second part of the review focuses on the evolution, structure, and transcriptional regulation of the glutamine synthetase gene in rat and chicken. Two enhancers (at -6.5 and -2.5 kb) were identified in the upstream region and two enhancers (between +156 and +857 bp) in the first intron of the rat glutamine synthetase gene. In addition, sequence analysis suggests a regulatory role for regions in the 3' untranslated region of the gene. The immediate-upstream region of the chicken glutamine synthetase gene is responsible for its cell-specific expression, whereas the glucocorticoid-induced developmental appearance in the neural retina is governed by its far-upstream region.
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Affiliation(s)
- H Lie-Venema
- Department of Anatomy and Embryology, University of Amsterdam, The Netherlands
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18
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Baas D, Fressinaud C, Vitkovic L, Sarlieve LL. Glutamine synthetase expression and activity are regulated by 3,5,3'-triodo-L-thyronine and hydrocortisone in rat oligodendrocyte cultures. Int J Dev Neurosci 1998; 16:333-40. [PMID: 9829169 DOI: 10.1016/s0736-5748(98)00040-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Glutamine synthetase plays a central role in the detoxification of brain ammonia. Previously, we demonstrated that in vitro glutamine synthetase is expressed by all macroglial cell types and is developmentally regulated in oligodendrocyte lineage. Furthermore, glutamine synthetase is increased in secondary cultures of oligodendrocytes following a 72 h treatment with 30 nM 3,5,3'-triodo-L-thyronine [Baas, D., Bourbeau, D., Sarliève, L. L., Ittel, M. E., Dussault, J. H. and Puymirat, J., Oligodendrocyte maturation and progenitor cell proliferation are independently regulated by thyroid hormone. Glia, 1997, 19, 324-332]. Hydrocortisone also increases glutamine synthetase activity after 72 h [Fressinaud, C., Weinrauder, H., Delaunoy, J. P., Tholey, G., Labourdette, G. and Sarliève, L. L., Glutamine synthetase expression in rat oligodendrocytes in culture: regulation by hormones and growth factors. J. Cell. Physiol., 1991, 149, 459-468]; however, it is still unknown whether these increases in glutamine synthetase expression in oligodendrocytes after 3,5,3'-triodo-L-thyronine and hydrocortisone application are dose- and time-dependent. To further investigate this issue, we measured glutamine synthetase levels by Northern analysis, immunostaining and determination of glutamine synthetase activity after 3,5,3'-triodo-L-thyronine or hydrocortisone stimulation. We find that in rat oligodendrocyte secondary cultures, 3,5,3'-triodo-L-thyronine and hydrocortisone cause a dose- and time-dependent increase in glutamine synthetase mRNA, protein and activity. However, these hormones do not exert an additive or synergistic effect. Because purines, pyrimidines, and certain amino acids necessary for the synthesis of myelin components, are, in part, provided by the glutamine synthetase pathway, 3,5,3'-triodo-L-thyronine effect on myelination development and maturation could be mediated in part, through the glutamine synthetase gene regulation.
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Affiliation(s)
- D Baas
- UPR 416 du CNRS, Strasbourg, France
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19
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Gardner DS, Jackson AA, Langley-Evans SC. Maintenance of maternal diet-induced hypertension in the rat is dependent on glucocorticoids. Hypertension 1997; 30:1525-30. [PMID: 9403577 DOI: 10.1161/01.hyp.30.6.1525] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Recent epidemiological evidence suggests that adult cardiovascular risk is determined by birth weight and factors that influence birth weight, such as maternal nutrition. Data from animal models suggest that an interaction between nutrition and glucocorticoid hormones "programs" increased risk of adult hypertension. Increased fetal exposure to maternal glucocorticoids that is proposed to occur from a reduction in the placental barrier to maternal glucocorticoid, 11beta-hydroxysteroid dehydrogenase, is suggested to program hypertension in the resultant offspring from both glucocorticoid-treated and maternally protein-restricted rats. The extent to which postnatal glucocorticoid stimulation may influence the progression of hypertension in the offspring from protein-restricted rat dams was assessed in 6-week-old male Wistar rats, prenatally exposed to either an 18% casein (control) or 9% casein (low protein) diet. Rats from each dietary group were sham operated, adrenalectomized or adrenalectomized, and treated with 20 mg corticosterone/kg body weight per day. Before surgery, systolic blood pressure was significantly higher in the low protein-exposed rats compared with controls (165+/-3.8 versus 142+/-3.3 mm Hg, P<.0001). Adrenalectomy of the low protein-exposed animals significantly reduced the blood pressure to control levels, while corticosterone replacement restored the hypertensive state. No effect of adrenalectomy on blood pressure was observed in 18% casein controls. In both dietary groups adrenalectomy decreased brain, but not hepatic, glucocorticoid-sensitive enzyme activities and corticosterone treatment elevated activities of all enzymes. The data suggest that maternal diet-induced hypertension is dependent on an intact adrenal gland postnatally and that glucocorticoids are key trophic agents in maintaining the high blood pressure.
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Affiliation(s)
- D S Gardner
- Institute of Human Nutrition, University of Southampton, Bassett Crescent East Southampton, UK
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20
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Sun SH, Ou HC, Jang TH, Lin LB, Huang HM. Altered phospholipid metabolism in sodium butyrate-induced differentiation of C6 glioma cells. Lipids 1997; 32:273-82. [PMID: 9076664 DOI: 10.1007/s11745-997-0034-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We examined the changes in phospholipid metabolisms in sodium butyrate-treated C6 glioma cells. Treatment of 2.5 mM sodium butyrate for 24 h induced an increase in the activity of glutamine synthetase, suggesting that these cells were under differentiation. Similar treatment was associated with (i) increased arachidonic acid incorporation into phosphatidylcholine, and (ii) decreased arachidonic acid incorporation into phosphatidylinositol and (iii) phosphatidylethanolamine. These effects were subsequently investigated by examining the acylation process, de novo biosynthesis, and the agonist-stimulated phosphoinositides hydrolysis in these cells. Our results indicated that sodium butyrate stimulated the acylation of arachidonic acid into lysophosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidylinositol. The glycerol incorporation into these lipids was not affected, but the inositol incorporation into total chloroform extracts and Pl and phosphatidylinositol 4-phosphate was decreased in the sodium butyrate-treated cells. Moreover, the accumulation of the rapid histamine-stimulated phosphoinositide metabolites, i.e., inositol monophosphate, inositol diphosphate, and inositol triphosphate (IP3) was decreased in these cells. To elucidate whether the decreased inositol phosphates were due to a decrease in the phosphoinositides hydrolysis, we measured the transient IP3 production directly by a receptor-binding assay. Our results indicated that histamine-stimulated transient IP3 formations were decreased. Taken together, these results indicated that multiple changes by multiple mechanisms of phospholipid metabolisms were found in sodium butyrate-treated C6 glioma cells. The decreased IP3 formation and its subsequent action, i.e., Ca2+ mobilization, may play an early but pivotal role by which sodium butyrate induces C6 glioma cell differentiation.
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Affiliation(s)
- S H Sun
- Institute of Neuroscience, National Yang Ming University, Taipei, Taiwan, Republic of China
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21
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Merle M, Martin M, Villégier A, Canioni P. Mathematical modelling of the citric acid cycle for the analysis of glutamine isotopomers from cerebellar astrocytes incubated with [1(-13)C]glucose. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 239:742-51. [PMID: 8774722 DOI: 10.1111/j.1432-1033.1996.0742u.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A mathematical model of the citric acid cycle devoted to the analysis of 13C-NMR data was developed for determining the relative flux of molecules through the anaplerotic versus oxidative pathways and the relative pyruvate carboxylase versus pyruvate dehydrogenase activities. Different variants of the model were considered depending on the reversibility of the conversion of fumarate into malate and oxaloacetate. The model also included the possibility of orientation-conserved transfer of the four-carbon citric acid cycle intermediates, leading to conversion of succinyl-CoA C1 into either malate C1 or C4. It was used to analyse NMR data from glutamine isotopomers produced by cerebellar astrocytes incubated with [1-13C]glucose. Partial cycling (39%) between oxaloacetate and fumarate was evident from the analysis. Application of the model to glutamate isotopomers from granule cells incubated with [1-13C]glucose [Martin, M.. Portais, J.C.. Labouesse. J., Canioni. P, & Merle, M. (1993) Eur. J. Biochem. 217, 617-625] indicated that total cycling of oxaloacetate into fumarate was, in this case, required to get the best fit. The results emphasized some important differences in carbon metabolism between cerebellar astrocytes and granule cells concerning the sources of carbon fuelling the citric acid cycle and the carbon fluxes on different pathways.
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Affiliation(s)
- M Merle
- Unité de Résonance Magnétique des Systemes Biologiques, CNRS-Université de Bordeaux II, France
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22
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Kawata M. Roles of steroid hormones and their receptors in structural organization in the nervous system. Neurosci Res 1995; 24:1-46. [PMID: 8848287 DOI: 10.1016/0168-0102(96)81278-8] [Citation(s) in RCA: 258] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Due to their chemical properties, steroid hormones cross the blood-brain barrier where they have profound effects on neuronal development and reorganization both in invertebrates and vertebrates, including humans mediated through their receptors. Steroids play a crucial role in the organizational actions of cellular differentiation representing sexual dimorphism and apoptosis, and in the activational effects of phenotypic changes in association with structural plasticity. Their sites of action are primarily the genes themselves but some are coupled with membrane-bound receptor/ion channels. The effects of steroid hormones on gene transcription are not direct, and other cellular components interfere with their receptors through cross-talk and convergence of the signaling pathways in neurons. These genomic and non-genomic actions account for the divergent effects of steroid hormones on brain function as well as on their structure. This review looks again at and updates the tremendous advances made in recent decades on the study of the role of steroid (gonadal and adrenal) hormones and their receptors on developmental processes and plastic changes in the nervous system.
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Affiliation(s)
- M Kawata
- Department of Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, Japan
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23
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Arcuri C, Tardy M, Rolland B, Armellini R, Menghini AR, Bocchini V. Glutamine synthetase gene expression in a glioblastoma cell-line of clonal origin: regulation by dexamethasone and dibutyryl cyclic AMP. Neurochem Res 1995; 20:1133-9. [PMID: 8746797 DOI: 10.1007/bf00995375] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We investigated the expression of glutamine synthetase (GS), an enzyme involved in astroglial metabolism and marker of astroglial functional maturity, in a glioblastoma cell-line (GL-15) of clonal origin. In spite of their phenotypic immaturity, evidenced in a mosaic fashion by a poor glial fibrillary acidic protein (GFAP) expression, the level of GS-mRNA is high in GL15 cells and the considerable amount of GS biological activity can be further induced and stabilized by glucocorticoids. A correlation between the induction by dexamethasone of the GS-mRNA level and the GS biological activity suggests a transcriptional regulation of GS expression by the aforesaid hormone. Under this hormonal action, changes in cell morphology occur and they are correlated with an overexpression of the GFAP, a marker of astroglial differentiation. On the contrary, dibutyryl cyclic AMP (dbc AMP) down-regulates the GS-mRNA expression and decreases GS activity. These results suggest that GL-15 cells have a common glucocorticoid dependent mechanism able to induce GS and GFAP as well as morphological changes. However in these cells AMPc responsive elements are involved in the negative modulation of the GS expression, contrary to what occurs in normal astroglial cells.
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Affiliation(s)
- C Arcuri
- INSERM U 421, Hôpital Henri Mondor, Creteil, France
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24
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Rich KA, Figueroa SL, Zhan Y, Blanks JC. Effects of Müller cell disruption on mouse photoreceptor cell development. Exp Eye Res 1995; 61:235-48. [PMID: 7556487 DOI: 10.1016/s0014-4835(05)80043-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Müller cells have been proposed to play an important role in photoreceptor cell development during the final stages of retinal maturation. The effect of disrupting Müller cells during mouse retinal development was investigated using the specific glial cell toxin, DL-alpha-aminoadipic acid (AAA). By giving multiple systemic injections over several days, impairment of Müller cell function was maintained during the period of photoreceptor migration and differentiation. Following three consecutive days of AAA treatment [commencing on post-natal (P) day 3, 5, 7 or 9, and examined at P8-P14], clumps of photoreceptor nuclei were displaced through the inner segments, lying immediately beneath the retinal pigment epithelium (RPE). Apart from the scalloped appearance of the outer retina, the overall lamination pattern of the retina was relatively well preserved. Even when AAA treatment commenced as early as P3, several days prior to the formation of the outer nuclear layer, the majority of photoreceptors migrated to their correct position and formed inner and outer segments. Therefore, the signals for photoreceptor migration are either provided by the Müller cells prior to P3, or, alternatively, are derived from different intrinsic or extrinsic cues. Disruption of Müller cell function was evidenced by decreased glutamine synthetase activity as well as by increased glial fibrillary acidic protein (GFAP) and decreased cellular retinaldehyde-binding protein (CRALBP) immunoreactivity. Immunocytochemistry with an antibody to CD44, which labels the microvilli of Müller cells at the outer limiting membrane, coupled with electron microscopic analysis, demonstrated that the zonulae adherentes between Müller cells and photoreceptors were either irregular or absent in areas adjacent to displaced clumps of photoreceptors. Thus AAA treatment of early post-natal mice results in localized disruption of the contacts between Müller cells and photoreceptors. These pathologic changes persist into adulthood since at P28, while short stretches of photoreceptors appeared relatively normal with fully developed outer segments, periodic clumps of displaced photoreceptor nuclei were still present adjacent to the RPE. In conclusion, Müller cell processes at the outer limiting membrane appear to play a critical role in providing a barrier to aberrant photoreceptor migration into the subretinal space.
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Affiliation(s)
- K A Rich
- Department of Pathology, University of Southern California School of Medicine, Los Angeles 90033, USA
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25
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Sallanon-Moulin M, Touret M, Didier-Bazes M, Roudier V, Fages C, Tardy M, Jouvet M. Glutamine synthetase modulation in the brain of rats subjected to deprivation of paradoxical sleep. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1994; 22:113-20. [PMID: 7912399 DOI: 10.1016/0169-328x(94)90038-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Changes in the level of glutamine synthetase (GS), an enzyme mainly located in astrocytes, were investigated in rat brain after deprivation of paradoxical sleep (PSD) and during recovery. An immunotitration method was used to evaluate the relative level of GS in brain tissue. At the end of a 24 h PSD, a significant increase in GS protein was observed both in the frontoparietal cortex (CX) and in the locus coeruleus area (LC). Four hours later during recovery, the level of GS protein returned to normal level in the CX but fell below control levels in the LC. In contrast, in the CX, the level of glial fibrillary acidic protein, an astroglial marker, did not change after PSD or during recovery. GS mRNA was quantified in the entire cortex by northern blot hybridization using of an oligonucleotidic GS-cDNA probe. We observed an increase in the GS mRNA level in the cortex of PSD rats of the same magnitude as the increase in GS protein. Both GS mRNA and GS protein tended to return to control values 4 h later during recovery. These results are discussed with particular attention to stress effects and possible physiological mechanisms regarding the regulation of amino acid levels by neurotransmitters during prolonged waking or neuronal excitation.
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Affiliation(s)
- M Sallanon-Moulin
- Department of experimental medicine, Claude Bernard University, Lyon, France
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26
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Vedder H, Weiss I, Holsboer F, Reul JM. Glucocorticoid and mineralocorticoid receptors in rat neocortical and hippocampal brain cells in culture: characterization and regulatory studies. Brain Res 1993; 605:18-24. [PMID: 8467386 DOI: 10.1016/0006-8993(93)91351-r] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Glucocorticoid and mineralocorticoid binding sites were characterized in cell cultures derived from neocortical and hippocampal brain tissue from fetal (E18) rats. Specific and saturable binding was detected in living cells with a sensitive whole cell binding method using [3H]dexamethasone ([3H]DEX) and [3H]aldosterone ([3H]ALDO) (in the presence of RU 28362, a selective glucocorticoid receptor (GR) agonist) as ligands for the measurement of glucocorticoid and mineralocorticoid receptors (MRs), respectively. Specific corticosteroid binding was demonstrated as early as day 4 in culture in neocortical cells, with a time-dependent increase in binding sites during further culturing time. At 7-9 days in vitro, Scatchard analysis of [3H]DEX binding revealed a maximum binding capacity (Bmax) of 83.4 +/- 5.0 fmol/mg protein and a binding affinity (Kd) of 3.6 +/- 0.4 nM in neocortical brain cells. Competition binding studies with [3H]DEX demonstrated a glucocorticoid specificity of receptor sites (relative binding affinity: RU 28362 = DEX > PROG > ALDO). Similar binding characteristics were demonstrated for GRs in cultures derived from fetal hippocampal tissue (Bmax 49.1 +/- 5.8 fmol/mg protein, Kd 3.5 +/- 0.2 nM). Analysis of MRs with [3H]ALDO (+RU 28362) revealed specific and saturable binding in hippocampal cultures, with a Bmax of 8.0 +/- 0.5 fmol/mg protein and a Kd of 0.2 +/- 0.1 nM. Competition studies with [3H]ALDO showed a mineralocorticoid-like pattern of receptor binding (relative binding affinity: CORT = ALDO > PROG > DEX). In addition, small numbers of MRs were detectable in cortex-derived cultures (Bmax: 3.7 +/- 0.8 fmol/mg protein, Kd: 0.3 +/- 0.2 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H Vedder
- Max Planck Institute of Psychiatry, Department of Neuroendocrinology, Munich, FRG
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27
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Kugler P. Enzymes involved in glutamatergic and GABAergic neurotransmission. INTERNATIONAL REVIEW OF CYTOLOGY 1993; 147:285-336. [PMID: 7901176 DOI: 10.1016/s0074-7696(08)60771-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- P Kugler
- Department of Anatomy, University of Würzburg, Germany
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28
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Zonta N, Ferrario P, Di Giulio AM, Zecca L, Gorio A, Mantegazza P. Neurochemical changes of long-term adrenalectomy in rat brain: effects on neurotransmitter amino acids. Int J Dev Neurosci 1992; 10:439-45. [PMID: 1362857 DOI: 10.1016/0736-5748(92)90034-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The levels of five amino acids together with glutamine synthetase activity, were measured in brain regions of rats with bilateral adrenalectomy, performed in newly weaning rats on postnatal day 22 and sacrificed 3 months later. Adrenalectomy caused a general decrease of glutamine concentration in three hippocampal regions (CA1-CA2, CA3, CA4-dentate gyrus), in hypothalamus, striatum and cerebellum. This reduction, which was particularly significant in hippocampus and cerebellum, was paralleled by a decrease of glutamine synthetase activity. Treatment with corticosterone reversed the effect of adrenalectomy. Little or no change was observed in the tissue levels of taurine, aspartic, glutamic or gamma-amino butyric acids.
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Affiliation(s)
- N Zonta
- Dipartimento di Farmacologia, Università di Milano, Italy
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29
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Stein-Behrens BA, Elliott EM, Miller CA, Schilling JW, Newcombe R, Sapolsky RM. Glucocorticoids exacerbate kainic acid-induced extracellular accumulation of excitatory amino acids in the rat hippocampus. J Neurochem 1992; 58:1730-5. [PMID: 1560229 DOI: 10.1111/j.1471-4159.1992.tb10047.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Glucocorticoids (GCs) compromise the ability of hippocampal neurons to survive various insults, and do so, at least in part, by exacerbating steps in the glutamate/N-methyl-D-aspartate (NMDA)/calcium cascade of damage. As evidence, GCs impair uptake of glutamate by hippocampal astrocytes, the GC endangerment of the hippocampus is NMDA receptor dependent, and GCs exacerbate kainic acid (KA)-induced calcium mobilization. These observations predict that GCs should also exacerbate KA-induced accumulation of extracellular glutamate and aspartate. To test this, adrenalectomized rats were given replacement GCs in either the low or high physiological range. Three days later, rats were anesthetized and 1 mM KA was infused through a dialysis probe placed in the dorsal hippocampus. Extracellular amino acid concentrations in the dialysate were then assessed by HPLC. After KA infusion, high-GC rats (30 +/- 3 micrograms/dl) had significantly elevated concentrations of glutamate and aspartate compared with low-GC rats (all less than 0.95 micrograms/dl). The glutamate accumulation was due to GCs raising pre-KA concentrations, whereas the aspartate accumulation was due to GCs exacerbating the KA-induced rise. Glutamine concentrations were unaffected by KA, whereas the high-GC regimen elevated glutamine concentrations both before and after KA. Taurine concentrations rose after infusion of KA, but were unaffected by GC regime, whereas alanine concentrations were unaffected by either manipulation. Serine concentrations were unaffected by KA, but were depressed both before and after KA in high-GC rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- B A Stein-Behrens
- Department of Biological Sciences, Stanford University, California 94305
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30
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Abstract
BACKGROUND Glutamate has been implicated in the pathophysiology of acute hypoxic-ischemic encephalopathy. Glutamine synthetase is an enzyme found in astrocytes that converts glutamate to its nontoxic analogue, glutamine. The present study tests the hypothesis that brain glutamine synthetase activity increases in response to acute hypoxic-ischemic insults and not in response to chronic hypoxia-ischemia or non-hypoxic-ischemic neurological disease. SUMMARY OF REPORT Frozen sections of cerebellum from children who died with acute or chronic hypoxic-ischemic insults or chronic non-hypoxic-ischemic neurological disease were spectrophotometrically assayed for glutamine synthetase activity by an observer who was blinded to the clinical group assignment of each specimen. Enzyme activity was elevated in specimens from children with acute hypoxic-ischemic insults (mean 6.5; range 5.4-7.2 units/g wet tissue wt) as compared with those from patients with chronic hypoxia-ischemia (mean 2.8; range 0.7-10.2 units/g wet tissue wt) or with non-hypoxic-ischemic neurological disease (mean 2.6; range 1.3-3.9 units/g wet tissue wt). This difference was not due to differences in the degree of histological astrocytosis or edema among the specimens. Statistical analysis by the Kruskal-Wallis one-way analysis of variance by ranks test indicates that the three data groups do not come from one population (p less than 0.05). CONCLUSIONS These results support the notion that glutamine synthetase activity increases in response to acute hypoxic-ischemic nervous system injury in children and that other compensatory mechanisms prevail in the case of chronic hypoxic-ischemic insults.
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Affiliation(s)
- D N Dao
- Department of Pediatrics, University of Pittsburgh, PA
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31
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Chou YC, Luttge WG, Sumners C. Expression of mineralocorticoid type I and glucocorticoid type II receptors in astrocyte glia as a function of time in culture. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1991; 61:55-61. [PMID: 1655310 DOI: 10.1016/0165-3806(91)90113-w] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In the present study we have examined the expression of mineralocorticoid Type I and glucocorticoid Type II receptors in astrocyte glia maintained in culture for different periods of time. Cytosolic mineralocorticoid Type I receptors were labeled with [3H]aldosterone (ALDO) in the presence of a 500-fold molar excess of the potent Type II receptor ligand RU 28362. [3H]Dexamethasone (DEX) was used to label cytosolic Type II receptors. Both Type I and Type II receptor binding was saturable in astrocyte glia that had been maintained in culture for 20 and 30 days following final plating (i.e. 20- and 30-day-old cultures). Scatchard analysis of [3H]ALDO binding revealed a single class of Type I receptors, with dissociation constants (Kd) of 0.45 +/- 0.13 nM and 0.53 +/- 0.07 nM, respectively, in 20- and 30-day-old cultures. The number of Type I receptors in 30-day-old cultures was nearly half that found in 20-day-old cultures (22.06 vs 42.64 fmol/mg protein). Linear Scatchard plots were also obtained for [3H]DEX binding to cytosol prepared from 20- and 30-day-old cultures. There were no significant differences in the Kd or Bmax values for [3H]DEX binding in 20- or 30-day-old cultures, i.e. 2.06 +/- 0.15 nM and 247.36 +/- 18.16 fmol/mg protein for 20-day-old cells and 2.3 +/- 0.74 nM and 261.02 +/- 3.08 fmol/mg protein for 30-day-old cells. These Bmax values are more than double the Bmax value for [3H]DEX binding observed in our previous studies in 10-day-old astrocyte glial cultures. Switching cultured astrocyte glial from serum-supplemented to serum-free medium had no significant effects on the Kd values of Type I or Type II receptors in all the cultures tested. However, treatment with serum-free medium increased the number of Type I receptors in 30-day-old cultures to a level similar to that found in 20-day-old cultures. Taken together, these binding data suggest that Type I and Type II receptors are expressed differently in astrocyte glia as a function of time in culture.
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Affiliation(s)
- Y C Chou
- Department of Neuroscience, University of Florida College of Medicine, Gainesville 32610
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32
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Jani MS, Telang SD, Katyare SS. Effect of corticosterone treatment on energy metabolism in rat liver mitochondria. J Steroid Biochem Mol Biol 1991; 38:587-91. [PMID: 1674880 DOI: 10.1016/0960-0760(91)90317-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. Effect of in vivo treatment (40 mg/kg body wt) with corticosterone on energy metabolism in rat liver mitochondria was examined under acute and chronic conditions in 20-, 35- and 60-day-old rats. 2. Acute treatment did not affect body or liver weight. However, chronic treatment caused increased liver weight in the former two age groups; in the 60-day-old animals the liver weight decreased. 3. Acute treatment resulted in a generalized decrease in state 3 respiration rates and state 4 respiration rates without having any significant effect on ADP/O ratios with glutamate, succinate and ascorbate + TMPD as substrates. However, rates of ATP synthesis decreased significantly. The effect was age-dependent, older animals showed increased resistance. 4. Chronic treatment resulted in uncoupling of oxidative phosphorylation without having significant effects on respiration rates. Once again, the effects were age-dependent. Consequently, the ATP synthesis rates were significantly lowered. However, it was apparent that the underlying mechanisms were entirely different. 5. With succinate as the substrate the state 3 respiration rates increased with age to reach adult values by day 60. The coupling efficiency was also exhibited via maturational changes.
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Affiliation(s)
- M S Jani
- Department of Biochemistry, Faculty of Science, M. S. University of Baroda, India
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33
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Tansey FA, Farooq M, Cammer W. Glutamine synthetase in oligodendrocytes and astrocytes: new biochemical and immunocytochemical evidence. J Neurochem 1991; 56:266-72. [PMID: 1670954 DOI: 10.1111/j.1471-4159.1991.tb02591.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The results of recent immunocytochemical experiments suggest that glutamine synthetase (GS) in the rat CNS may not be confined to astrocytes. In the present study, GS activity was assayed in oligodendrocytes isolated from bovine brain and in oligodendrocytes, astrocytes, and neurons isolated from rat forebrain, and the results were compared with new immunochemical data. Among the cells isolated from rat brain, astrocytes had the highest specific activities of GS, followed by oligodendrocytes. Oligodendrocytes isolated from white matter of bovine brain had GS specific activities almost fivefold higher than those in white matter homogenates. Immunocytochemical staining also showed the presence of GS in both oligodendrocytes and astrocytes in bovine forebrain, in three white-matter regions of rat brain, and in Vibratome sections as well as paraffin sections.
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Affiliation(s)
- F A Tansey
- Department of Neurology, Albert Einstein College of Medicine, Bronx, New York 10461
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34
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Langley SC, York DA. Increased type II glucocorticoid-receptor numbers and glucocorticoid-sensitive enzyme activities in the brain of the obese Zucker rat. Brain Res 1990; 533:268-74. [PMID: 2289143 DOI: 10.1016/0006-8993(90)91349-l] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The possibility that the glucocorticoid-dependence of obesity of the obese fa/fa rat reflects on overactivity of glucocorticoids on the brain has been investigated by studies of enzyme activities and glucocorticoid type II (GR) receptors. The activity of 2 glucocorticoid-sensitive enzymes, glycerol-3-phosphate dehydrogenase and glutamine synthetase, were increased in the hippocampus of obese rats. In contrast malate dehydrogenase and pyruvate kinase, glucocorticoid-insensitive enzymes, were normal. Adrenalectomy of obese rats reduced glycerol-3-phosphate dehydrogenase activity to the level of lean rats. Scatchard analysis of [3H]corticosterone binding showed that the number of type II (GR) receptors was increased in the hypothalamus and hippocampus of obese rats but the affinity of these receptors was reduced. The evidence supports the hypothesis of excessive central glucocorticoid activity in the obese rat.
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Affiliation(s)
- S C Langley
- Department of Human Nutrition, University of Southampton, School of Biochemical and Physiological Sciences, U.K
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35
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Armanini MP, Hutchins C, Stein BA, Sapolsky RM. Glucocorticoid endangerment of hippocampal neurons is NMDA-receptor dependent. Brain Res 1990; 532:7-12. [PMID: 2149301 DOI: 10.1016/0006-8993(90)91734-x] [Citation(s) in RCA: 173] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The adrenal stress hormones glucocorticoids (GCs) impair the ability of hippocampal neurons to survive neurological insults, including hypoxia-ischemia and seizure. These insults are thought to be toxic via a cascade of excessive synaptic concentrations of excitatory neurotransmitters (e.g. glutamate), activation of the NMDA receptor, and pathologic mobilization of cytosolic calcium post-synaptically. We tested whether GCs exacerbate these insults by exacerbating this 'NMDA cascade'. We sought a toxin which damaged independently of the NMDA cascade, and whose toxicity was enhanced by GCs. After testing a number of neurotoxins, we found that the antimetabolite 3-acetylpyridine (3AP) fit this requirement. We then tested if blockade of the NMDA receptor blocks the ability of GCs to enhance 3AP toxicity. Hippocampi were microinfused with 160 micrograms of 3AP. Elevating circulating GC concentrations to the range seen during major stressors for a week before and after microinfusion caused a significant increase in 3AP-induced damage (when compared to adrenalectomized rats kept GC-free for the same period). Infusing the NMDA receptor blocker APV with 3AP did not alter the toxicity in adrenalectomized rats. However, APV reduced 3AP-induced damage in GC-treated rats to levels seen in adrenalectomized rats. This suggests that GCs endanger hippocampal neurons by enhancing glutamatergic signals and/or enhancing vulnerability to such signals. As a possible explanation for this observation, GCs inhibit glucose uptake into hippocampal neurons, and numerous steps in the NMDA cascade are exacerbated when neuronal energy stores are diminished.
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Affiliation(s)
- M P Armanini
- Department of Biological Sciences, Stanford University, CA 94305
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36
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Vielkind U, Walencewicz A, Levine JM, Bohn MC. Type II glucocorticoid receptors are expressed in oligodendrocytes and astrocytes. J Neurosci Res 1990; 27:360-73. [PMID: 2097380 DOI: 10.1002/jnr.490270315] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Glucocorticoid hormones affect gene expression directly at the level of transcription via intracellular receptors that translocate to the nucleus in the presence of steroid. In the brain, two types of high-affinity receptors bind glucocorticoids, the type I, mineralocorticoid receptor and the type II, glucocorticoid receptor (GR). Both receptor types are expressed by many types of neurons. Although binding studies have suggested that glial cells may also express receptors, the expression of these receptors in specific classes of glia has not been studied previously. This immunocytochemical study was undertaken to determine which of the different classes of glial cells express type II GR. Primary cultures of mixed glial cells from rat cerebrum and cerebellum, purified oligodendrocytes and astrocytes, as well as two glial tumor cell lines were screened for the expression of glucocorticoid receptors using a mouse monoclonal antibody directed against rat liver GR (BuGR-2). Glial cell types were identified by morphology and immunoreactivity (IR) with antibodies directed against glial fibrillary acidic protein (GFAP), cyclic nucleotide phosphodiesterase (CNP), or myelin basic protein (MBP). Double immunofluorescence microscopy revealed that all GFAP-IR cells (type 1 and type 2 astrocytes), all CNP- or MBP-IR cells (oligodendrocytes), as well as immature and intermediate cell types expressed GR, although at different levels. C6 glioma and JScl1 Schwannoma cells were observed to express moderate to high levels of GR. Furthermore, cells grown in the absence of glucocorticoids had diffuse GR staining over the cytoplasm, whereas cells grown in the presence of the synthetic glucocorticoid dexamethasone had strong nuclear staining. These results demonstrate that, in vitro, all classes of glial cells express glucocorticoid receptors that can translocate to the nucleus in the presence of hormone. These observations suggest that glial cells are major targets for glucocorticoid-directed control of gene transcription in the nervous system.
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Affiliation(s)
- U Vielkind
- Department of Neurobiology, Rochester University School of Medicine, New York
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37
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Tombaugh GC, Sapolsky RM. Hippocampal glutamine synthetase: insensitivity to glucocorticoids and stress. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 258:E894-7. [PMID: 1970712 DOI: 10.1152/ajpendo.1990.258.5.e894] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Glucocorticoids enhance the neurotoxic potential of several insults to the rat hippocampus that involve overactivation of glutamatergic synapses. These hormones also stimulate the synthesis of glutamine synthetase (GS) in peripheral tissue. Because this enzyme helps regulate glutamate metabolism in the central nervous system, glucocorticoid induction of GS in the brain may underlie the observed synergy. We have measured GS activity in the hippocampus and skeletal muscle (plantaris) of adult rats after bilateral adrenalectomy (ADX), corticosterone (Cort) replacement, or stress. No significant changes in GS were observed in hippocampal tissue, whereas muscle GS was significantly elevated after Cort treatment or stress and was reduced after ADX. These results suggest that Cort-induced shifts in GS activity probably do not explain Cort neurotoxicity, although the stress-induced rise in muscle GS may be relevant to certain types of myopathy.
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Affiliation(s)
- G C Tombaugh
- Department of Biological Sciences, Stanford University, California 94305
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38
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Abstract
The method for the assay of glutamine synthetase (GlnS) relies on the gamma-glutamyl transferase reaction, i.e. the formation of glutamyl-gamma-hydroxamate from glutamine and hydroxylamine, and the chromatographic separation of the reaction product from the reactants. The method is not only simple and reliable, but also has a sensitivity comparable to those methods applying radioactively labelled substrates. This new procedure has been applied to the assay of GlnS in cultured rat cortical astroglial cells which have been treated with a homologous series of alpha, omega-bis-(dimethylamino)alkanes. Effects of these drugs on astroglial development are reported.
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39
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Khelil M, Rolland B, Fages C, Tardy M. Glutamine synthetase modulation in astrocyte cultures of different mouse brain areas. Glia 1990; 3:75-80. [PMID: 1968891 DOI: 10.1002/glia.440030110] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Astroglial cells from mouse cerebral hemispheres, cerebellum, olfactory bulbs, and medulla oblongata were grown in the presence of either hormones (hydrocortisone, insulin) or cell second messengers (dBcAMP, dBcGMP). Glutamine synthetase (GS) specific activity, GS protein level, and GS translation were investigated under the effect of these factors. Hydrocortisone produced a simultaneous increase in GS translation, GS level, and activity. This increase was observed in the astrocytes cultured from the four brain areas but at a variable magnitude depending on the area. The hydrocortisone effect appeared at the transcriptional level. Inversely, insulin decreased both the GS activity and the in vitro translated GS. This effect was seen only in the olfactory bulbs and the medulla. DBcAMP increased the GS biological activity only in the cerebral hemisphere cultures. It raised, however, the level of translated GS and GS protein in astrocytes from all the areas, suggesting a post-translational effect for intracellular cAMP. DBcGMP only affected GS in the astrocytes from cerebral hemispheres and the medulla modulating either the GS transcription or the messenger RNA stability. These results suggest specific regulation for GS expression, depending on the brain area from which the cells were dissociated or on the astroglial cell population present in these cultures affecting either the transcription, the mRNA stability, or the biological activity of the protein.
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Affiliation(s)
- M Khelil
- INSERM U 282, Hôpital Henri Mondor, Créteil, France
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40
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Monzon-Mayor M, Yanes C, Tholey G, De Barry J, Gombos G. Immunohistochemical localization of glutamine synthetase in mesencephalon and telencephalon of the lizard Gallotia galloti during ontogeny. Glia 1990; 3:81-97. [PMID: 1970551 DOI: 10.1002/glia.440030202] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The immunohistochemical localization of glutamine synthetase, an astrocyte marker in mammals, was determined in the telencephalon and mesencephalon of the lizard Gallotia galloti during development by using an antiserum raised against chicken brain glutamine synthetase. Ependymal glial cells and their radial processes were glutamine synthetase immunoreactive, and they were present also in the adult. Immunoreactivity was also detected in two populations of scattered cell bodies, each preferentially localized in different zones: star-shaped cells morphologically similar to mammalian astrocytes, and ovoid or pear-shaped cell bodies, the processes of which were aligned with radial fibers and formed perivascular end-feet. Both populations displayed ultrastructural characteristics of astrocytes even though a comparison with our previous results (Monzon-Mayor et al., 1989; Yanes et al., 1989) indicated that many of these cells did not react with antibodies directed against the astrocyte-specific glial fibrillary acidic protein. During ontogeny, glutamine synthetase immunoreactivity appeared in radial glial processes and in ependymal glial cells of midbrain at embryonic stage 35 (E35) and of telencephalon at E37; in both regions, immunoreactivity in the radial glia increased until hatching and then decreased until adulthood, but it did not disappear. Labelled scattered cells became progressively more numerous and more immunoreactive. A comparative analysis of the distribution of these cells at different ages tends to suggest that some of the "ovoid" astrocytes originate in, and migrate out from, the proliferative zone of the different sulci, whereas the star-shaped cells appear directly in situ, probably because they begin to express glutamine synthetase after they have reached their final location.
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Affiliation(s)
- M Monzon-Mayor
- Departamento de Histologia, Colegio Universitario de Las Palmas, Canary Islands, Spain
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41
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The Hippocampus: A Site for Modulatory Interactions Between Steroid Hormones, Neurotransmitters and Neuropeptides. ACTA ACUST UNITED AC 1990. [DOI: 10.1007/978-1-4612-3446-3_4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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42
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O'Callaghan JP, Brinton RE, McEwen BS. Glucocorticoids regulate the concentration of glial fibrillary acidic protein throughout the brain. Brain Res 1989; 494:159-61. [PMID: 2765916 DOI: 10.1016/0006-8993(89)90156-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The role of glucocorticoids in the in vivo regulation of glial fibrillary acidic protein (GFAP) was examined. Corticosterone administration to adult rats resulted in decreased levels of GFAP throughout the brain whereas adrenalectomy caused levels of GFAP to increase. Corticosterone administration to adrenalectomized rats lowered GFAP levels to values below those of sham controls. Thus, the expression of GFAP throughout the brain appears to be physiologically regulated by adrenal glucocorticoids.
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Affiliation(s)
- J P O'Callaghan
- Health Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
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43
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Hansson E. Regulation of glutamine synthetase synthesis and activity by glucocorticoids and adrenoceptor activation in astroglial cells. Neurochem Res 1989; 14:585-7. [PMID: 2569678 DOI: 10.1007/bf00964922] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Glucocorticoids are known to induce the synthesis and activity of glutamine synthetase (GS; EC 6.3.1.2.) in astroglial cells. In the present paper, noradrenaline (NA), in itself ineffective upon GS regulation, potentiated GS activity in astroglial primary cultures in the presence of the glucocorticoid dexamethasone, the GS activity being further stimulated in the presence of glutamate (glu). Thus, adrenoceptor activation might interact with the glucocorticoid induced GS activity in astroglial primary cultures.
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Affiliation(s)
- E Hansson
- Institute of Neurobiology, University of Göteborg, Sweden
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44
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Vitiello F, Clos J, Di Benedetta C, Gombos G. Developing rat cerebellum--III. Effects of abnormal thyroid states and undernutrition on gangliosides. Int J Dev Neurosci 1989; 7:335-41. [PMID: 2773669 DOI: 10.1016/0736-5748(89)90055-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Alteration of rat postnatal cerebellar development produced by undernutrition, thyroxine treatment and thyroid deficiency also involves ganglioside deposition. The distribution of the different ganglioside types is apparently unaffected but quantitative alterations are present that reflect the reduction of cell number and cell process surface in the adult, and either acceleration or slowing down or reduction of cell formation and maturation occurring during cerebellar development in the three experimental situations.
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Affiliation(s)
- F Vitiello
- Istituto di Fisiologia Umana, Facoltà di Medicina e Chirurgia, Bari, Italy
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45
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Warringa RA, van Berlo MF, Klein W, Lopes-Cardozo M. Cellular location of glutamine synthetase and lactate dehydrogenase in oligodendrocyte-enriched cultures from rat brain. J Neurochem 1988; 50:1461-8. [PMID: 2896229 DOI: 10.1111/j.1471-4159.1988.tb03031.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Glial cells were isolated from 1-week-old rat brain and cultured in a serum-free medium supplemented with the hormones insulin, hydrocortisone, and triiodothyronine. After 1 week in culture the cell population consisted mainly of galactocerebroside-positive cells (GC+; oligodendrocytes), the remainder of the cells being positive for glial fibrillary acidic protein (GFAP+; astrocytes). Oligodendrocytes were selectively removed from the cultures by complement-mediated cytolysis. The activities of glutamine synthetase and of various marker enzymes were measured in the nonlysed cells remaining after complement treatment of the cultures and in the culture medium containing proteins of the lysed cells. We found that the cellular activity of glutamine synthetase decreased in parallel with the lysis of GC+ cells and that the activity of glutamine synthetase in the supernatant increased. The activity of glycerol-3-phosphate dehydrogenase, a marker enzyme for oligodendrocytes, was no longer detectable in complement-treated cultures and the activity of glutamine synthetase was markedly lowered, whereas the activity of lactate dehydrogenase was as high as in untreated cultures. The location of glutamine synthetase both in oligodendrocytes and in astrocytes was confirmed by double-label immunocytochemistry with antisera against glutamine synthetase, GC, and GFAP. We conclude that in this culture system glutamine synthetase is expressed in both types of glial cells and that the activity of lactate dehydrogenase is at least one order of magnitude higher in astrocytes than in oligodendrocytes.
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Affiliation(s)
- R A Warringa
- Laboratory of Veterinary Biochemistry, State University of Utrecht, The Netherlands
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46
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Juurlink BH. Effects of medium glutamine, glutamate, and ammonia on glutamine synthetase activity in cultured mouse astroglial cells. Neurochem Res 1987; 12:1053-8. [PMID: 2894616 DOI: 10.1007/bf00971704] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Mouse astroglial cells were grown during the last week of culture in either glutamine-free or glutamine-containing medium. The addition of cortisol to the glutamine-containing medium resulted in a doubling of astroglial glutamine synthetase (GS) activity. Withdrawal of glutamine from the medium resulted in a 50% elevation of GS and addition of cortisol to such a medium resulted in a further increase in GS which was not additive to glutamine withdrawal. Both in glutamine-free and glutamine-containing medium, the addition of glutamate resulted in a depression of both basal and cortisol induced GS activity. The simultaneous addition of ammonia plus glutamate to the culture medium ameliorated the glutamate mediated depressive effects on cortisol induced but not basal GS activity. Glutamine withdrawal from the culture medium resulted in an astroglial protein deficit. The addition of ammonia to the medium considerably reduced this deficit and the addition of glutamate completely eliminated this protein deficit.
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Affiliation(s)
- B H Juurlink
- Department of Anatomy, University of Saskatchewan, Saskatoon, Canada
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47
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Hansson E. Co-cultivation of astroglial enriched cultures from striatum and neuronal containing cultures from substantia nigra. Life Sci 1986; 39:269-77. [PMID: 2874462 DOI: 10.1016/0024-3205(86)90541-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A co-cultivation system was developed with neuron-containing (neuron-specific enolase (NSE) positive) primary cultures from the substantia nigra of 15 to 17-day old embryonic rats which were grown 1 mm apart from astroglial-enriched (glial fibrillary acidic protein (GFAp) positive) primary cultures from the striatum of neonatal rats. The astroglial cells went through a morphological differentiation with extension of processes after co-cultivation with the immunohistochemically-identified neuronal cells. The astroglial-enriched striatum cultures showed a higher active uptake of 3H-L-glutamate after co-cultivation for one week, compared to control cultures from striatum. Vmax (nmol X mg protein-1 X min-1 X was 58.4 +/- 8.3 after co-cultivation and 37.2 +/- 6.3 for control cultures. The glutamine synthetase (GS) activity was slightly increased after co-cultivation. The validity and specificity of the results were ensured. The data suggest that astroglial cells in a primary culture are influenced by co-cultivation with fetal neuron containing cultures resulting in morphological differentiation, and increases in 3H-L-glutamate uptake and GS activity.
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48
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Patel AJ, Hunt A, Faraji-Shadan F. Effect of removal of glutamine and addition of dexamethasone on the activities of glutamine synthetase, ornithine decarboxylase and lactate dehydrogenase in primary cultures of forebrain and cerebellar astrocytes. Brain Res 1986; 391:229-38. [PMID: 2870781 DOI: 10.1016/0165-3806(86)90287-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The regulation of glutamine synthetase (GS) and ornithine decarboxylase (ODC) was studied in primary cultures of two types of astrocytes derived from either newborn forebrain or 8-day-old cerebellum of the rat. In the 14-day-old cultures the specific activities of both these enzymes were about twice as great in forebrain astrocytes as in cerebellar astrocytes. Treatment with dexamethasone or removal of glutamine from the culture medium caused a marked increase in the specific activity of GS. The glutamine-mediated relative increase in GS activity was similar in both types of astrocytes. Removal of glutamine caused a transient reduction in ODC activity in the forebrain astrocytes, while in cerebellar astrocytes the activity remained markedly decreased throughout the period of glutamine deprivation. The severe reduction in ODC activity had relatively little effect on the cell numbers of protein content of the astrocyte cultures. The increase in GS activities, involving protein synthesis de novo, caused by removal of glutamine and by addition of dexamethasone, were additive and therefore probably mediated by different mechanisms. The induction of GS after glutamine removal was blocked by cycloheximide but not by alpha-amanitin, suggesting regulation at the post-transcriptional level. In contrast, the dexamethasone-mediated induction of GS appeared to be regulated at the transcriptional level, as it was markedly reduced by alpha-amanitin. None of these conditions had any effect on lactate dehydrogenase activity. Treatment with alpha-amanitin resulted in a complete suppression of the activity of ODC (a protein with a very short half life), in both the control and dexamethasone treated cultures. However, this enzyme activity was reduced only partially in astrocytes cultured in glutamine deficient medium, suggesting that under these experimental conditions the mRNA may be markedly stabilized in astroglial cells.
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49
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Hansson E. Primary cultures from defined brain areas. III. Effects of seeding time on [3H]L-glutamate transport and glutamine synthetase activity. Brain Res 1986; 389:203-9. [PMID: 2868786 DOI: 10.1016/0165-3806(86)90188-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Primary astroglial-enriched cultures from various brain regions were studied with respect to age at seeding and time in culture and its effect on the [3H]L-glutamate transport capacity and glutamine synthetase (G.S.) activity. Three phylogenetically different rat brain areas were used: cerebral cortex, striatum and brainstem. There was a high-affinity and high-capacity [3H]glutamate uptake during development in all cultures studied with Km in the microM range and Vmax in the nmol range. Vmax was most prominent in cultures seeded from newborn rat cerebral cortex and striatum when grown for 2 weeks and in brainstem cultures seeded from 17-day-old rat embryos when grown for 4 weeks. There were no significant differences in Vmax comparing the cultures from the various brain regions, that is when seeded from 17-day-old embryos and grown for 2 or 3 weeks in culture. The G.S. activity was determined under similar culture conditions as above. The highest enzyme activities were found in cultures from cerebral cortex and striatum seeded from newborn and 7-day-old rats and grown for 2 or 3 weeks. G.S. activity increased during postnatal maturation in cerebral cortex, striatum and brainstem, the highest activity values being found in cerebral cortex and striatum. Vmax for glutamate uptake and G.S. activity showed many similarities in the respective cultures during cultivation. Both parameters were affected by age at seeding and time in culture. The differences between the cultures from the various brain regions, with lower values in cultures from brainstem, indicated a heterogeneity among astroglial cells in the brain regions studied.
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Patel AJ, Weir MD, Hunt A, Tahourdin CS, Thomas DG. Distribution of glutamine synthetase and glial fibrillary acidic protein and correlation of glutamine synthetase with glutamate decarboxylase in different regions of the rat central nervous system. Brain Res 1985; 331:1-9. [PMID: 2859090 DOI: 10.1016/0006-8993(85)90708-5] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The concentration of soluble glial fibrillary acidic (GFA) protein and the specific activity of glutamine synthetase (GS) were estimated in 11 central nervous system (CNS) regions of the 90-day-old rat. Marked differences were observed in the regional distribution of these astrocyte marker proteins. The striatum and spinal cord contained the lowest concentration (per g wet weight) of GFA protein and GS activity, respectively, while the olfactory bulbs had the highest level of both astrocytic proteins. Differences between the lowest and the highest values were 3-fold for GS and 4-fold for GFA protein. More significant was the marked variation in the ratio of GS to GFA protein in different CNS regions; the highest and lowest values were in the striatum and the spinal cord respectively, and the difference between the highest and the lowest value was about 5-fold. The spinal cord contained low GS and high GFA protein; on the other hand, the colliculi had high GS and relatively low GFA protein. Immunochemical detection of GS and GFA proteins in whole homogenates of different regions showed that the variation of the specific activities of GS and the concentration of soluble GFA protein were due to the differences in their absolute protein concentrations. In different regions of the brain the activity of GS was significantly correlated with that of glutamate decarboxylase, but not with that of choline acetyltransferase. These observations provide further evidence for differing biochemical properties of astrocytes from various CNS regions and for the involvement of GS in processes associated with amino acid neurotransmission.
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