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Zöllner HJ, Thiel TA, Füllenbach ND, Jördens MS, Ahn S, Wilms LM, Ljimani A, Häussinger D, Butz M, Wittsack HJ, Schnitzler A, Oeltzschner G. J-difference GABA-edited MRS reveals altered cerebello-thalamo-cortical metabolism in patients with hepatic encephalopathy. Metab Brain Dis 2023; 38:1221-1238. [PMID: 36729261 PMCID: PMC10897767 DOI: 10.1007/s11011-023-01174-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 01/17/2023] [Indexed: 02/03/2023]
Abstract
Hepatic encephalopathy (HE) is a common neurological manifestation of liver cirrhosis and is characterized by an increase of ammonia in the brain accompanied by a disrupted neurotransmitter balance, including the GABAergic and glutamatergic systems. The aim of this study is to investigate metabolic abnormalities in the cerebello-thalamo-cortical system of HE patients using GABA-edited MRS and links between metabolite levels, disease severity, critical flicker frequency (CFF), motor performance scores, and blood ammonia levels. GABA-edited MRS was performed in 35 participants (16 controls, 19 HE patients) on a clinical 3 T MRI system. MRS voxels were placed in the right cerebellum, left thalamus, and left motor cortex. Levels of GABA+ and of other metabolites of interest (glutamine, glutamate, myo-inositol, glutathione, total choline, total NAA, and total creatine) were assessed. Group differences in metabolite levels and associations with clinical metrics were tested. GABA+ levels were significantly increased in the cerebellum of patients with HE. GABA+ levels in the motor cortex were significantly decreased in HE patients, and correlated with the CFF (r = 0.73; p < .05) and motor performance scores (r = -0.65; p < .05). Well-established HE-typical metabolite patterns (increased glutamine, decreased myo-inositol and total choline) were confirmed in all three regions and were closely linked to clinical metrics. In summary, our findings provide further evidence for alterations in the GABAergic system in the cerebellum and motor cortex in HE. These changes were accompanied by characteristic patterns of osmolytes and oxidative stress markers in the cerebello-thalamo-cortical system. These metabolic disturbances are a likely contributor to HE motor symptoms in HE. In patients with hepatic encephalopathy, GABA+ levels in the cerebello-thalamo-cortical loop are significantly increased in the cerebellum and significantly decreased in the motor cortex. GABA+ levels in the motor cortex strongly correlate with critical flicker frequency (CFF) and motor performance score (pegboard test tPEG), but not blood ammonia levels (NH3).
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Affiliation(s)
- Helge Jörn Zöllner
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany.
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany.
| | - Thomas A Thiel
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Nur-Deniz Füllenbach
- Department of Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Markus S Jördens
- Department of Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | | | - Lena M Wilms
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Alexandra Ljimani
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Dieter Häussinger
- Department of Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Markus Butz
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Hans-Jörg Wittsack
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Alfons Schnitzler
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Georg Oeltzschner
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
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Simicic D, Cudalbu C, Pierzchala K. Overview of oxidative stress findings in hepatic encephalopathy: From cellular and ammonium-based animal models to human data. Anal Biochem 2022; 654:114795. [PMID: 35753389 DOI: 10.1016/j.ab.2022.114795] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 05/26/2022] [Accepted: 06/15/2022] [Indexed: 11/30/2022]
Abstract
Oxidative stress is a natural phenomenon in the body. Under physiological conditions intracellular reactive oxygen species (ROS) are normal components of signal transduction cascades, and their levels are maintained by a complex antioxidants systems participating in the in-vivo redox homeostasis. Increased oxidative stress is present in several chronic diseases and interferes with phagocytic and nervous cell functions, causing an up-regulation of cytokines and inflammation. Hepatic encephalopathy (HE) occurs in both acute liver failure (ALF) and chronic liver disease. Increased blood and brain ammonium has been considered as an important factor in pathogenesis of HE and has been associated with inflammation, neurotoxicity, and oxidative stress. The relationship between ROS and the pathophysiology of HE is still poorly understood. Therefore, sensing ROS production for a better understanding of the relationship between oxidative stress and functional outcome in HE pathophysiology is critical for determining the disease mechanisms, as well as to improve the management of patients. This review is emphasizing the important role of oxidative stress in HE development and documents the changes occurring as a consequence of oxidative stress augmentation based on cellular and ammonium-based animal models to human data.
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Affiliation(s)
- D Simicic
- CIBM Center for Biomedical Imaging, Switzerland; Animal Imaging and Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Laboratory of Functional and Metabolic Imaging, EPFL, Lausanne, Switzerland
| | - C Cudalbu
- CIBM Center for Biomedical Imaging, Switzerland; Animal Imaging and Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - K Pierzchala
- CIBM Center for Biomedical Imaging, Switzerland; Animal Imaging and Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Laboratory of Functional and Metabolic Imaging, EPFL, Lausanne, Switzerland.
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3
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Dąbrowska K, Skowrońska K, Popek M, Albrecht J, Zielińska M. The Role of Nrf2 Transcription Factor and Sp1-Nrf2 Protein Complex in Glutamine Transporter SN1 Regulation in Mouse Cortical Astrocytes Exposed to Ammonia. Int J Mol Sci 2021; 22:ijms222011233. [PMID: 34681893 PMCID: PMC8538223 DOI: 10.3390/ijms222011233] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/14/2021] [Accepted: 10/15/2021] [Indexed: 11/28/2022] Open
Abstract
Ammonia toxicity in the brain primarily affects astrocytes via a mechanism in which oxidative stress (OS), is coupled to the imbalance between glutamatergic and GABAergic transmission. Ammonia also downregulates the astrocytic N system transporter SN1 that controls glutamine supply from astrocytes to neurons for the replenishment of both neurotransmitters. Here, we tested the hypothesis that activation of Nrf2 is the process that links ammonia-induced OS formation in astrocytes to downregulation and inactivation of SN1 and that it may involve the formation of a complex between Nrf2 and Sp1. Treatment of cultured cortical mouse astrocytes with ammonia (5 mM NH4Cl for 24 h) evoked Nrf2 nuclear translocation, increased its activity in a p38 MAPK pathway-dependent manner, and enhanced Nrf2 binding to Slc38a3 promoter. Nrf2 silencing increased SN1 mRNA and protein level without influencing astrocytic [3H]glutamine transport. Ammonia decreased SN1 expression in Nrf2 siRNA treated astrocytes and reduced [3H]glutamine uptake. In addition, while Nrf2 formed a complex with Sp1 in ammonia-treated astrocytes less efficiently than in control cells, treatment of astrocytes with hybrid-mode inactivated Sp1-Nrf2 complex (Nrf2 silencing + pharmacological inhibition of Sp1) did not affect SN1 protein level in ammonia-treated astrocytes. In summary, the results document that SN1 transporter dysregulation by ammonia in astrocytes involves activation of Nrf2 but does not require the formation of the Sp1-Nrf2 complex.
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Koomen DC, Meads MB, Magaletti DM, Guingab-Cagmat JD, Oliveira PS, Fang B, Liu M, Welsh EA, Meke LE, Jiang Z, Hampton OA, Tungesvik A, De Avila G, Alugubelli RR, Nishihori T, Silva AS, Eschrich SA, Garrett TJ, Koomen JM, Shain KH. Metabolic Changes Are Associated with Melphalan Resistance in Multiple Myeloma. J Proteome Res 2021; 20:3134-3149. [PMID: 34014671 DOI: 10.1021/acs.jproteome.1c00022] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Multiple myeloma is an incurable hematological malignancy that impacts tens of thousands of people every year in the United States. Treatment for eligible patients involves induction, consolidation with stem cell rescue, and maintenance. High-dose therapy with a DNA alkylating agent, melphalan, remains the primary drug for consolidation therapy in conjunction with autologous stem-cell transplantation; as such, melphalan resistance remains a relevant clinical challenge. Here, we describe a proteometabolomic approach to examine mechanisms of acquired melphalan resistance in two cell line models. Drug metabolism, steady-state metabolomics, activity-based protein profiling (ABPP, data available at PRIDE: PXD019725), acute-treatment metabolomics, and western blot analyses have allowed us to further elucidate metabolic processes associated with melphalan resistance. Proteometabolomic data indicate that drug-resistant cells have higher levels of pentose phosphate pathway metabolites. Purine, pyrimidine, and glutathione metabolisms were commonly altered, and cell-line-specific changes in metabolite levels were observed, which could be linked to the differences in steady-state metabolism of naïve cells. Inhibition of selected enzymes in purine synthesis and pentose phosphate pathways was evaluated to determine their potential to improve melphalan's efficacy. The clinical relevance of these proteometabolomic leads was confirmed by comparison of tumor cell transcriptomes from newly diagnosed MM patients and patients with relapsed disease after treatment with high-dose melphalan and autologous stem-cell transplantation. The observation of common and cell-line-specific changes in metabolite levels suggests that omic approaches will be needed to fully examine melphalan resistance in patient specimens and define personalized strategies to optimize the use of high-dose melphalan.
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Affiliation(s)
- David C Koomen
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Mark B Meads
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Dario M Magaletti
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Joy D Guingab-Cagmat
- University of Florida College of Medicine, Gainesville, Florida 32610, United States
| | - Paula S Oliveira
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Bin Fang
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Min Liu
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Eric A Welsh
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Laurel E Meke
- University of Florida College of Medicine, Gainesville, Florida 32610, United States
| | | | | | - Alexandre Tungesvik
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Gabriel De Avila
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | | | - Taiga Nishihori
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Ariosto S Silva
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Steven A Eschrich
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Timothy J Garrett
- University of Florida College of Medicine, Gainesville, Florida 32610, United States
| | - John M Koomen
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
| | - Kenneth H Shain
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, United States
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Armada-Moreira A, Coelho JE, Lopes LV, Sebastião AM, Städler B, Vaz SH. Multicompartment Microreactors Prevent Excitotoxic Dysfunctions In Rat Primary Cortical Neurons. ACTA ACUST UNITED AC 2020; 4:e2000139. [PMID: 32869522 DOI: 10.1002/adbi.202000139] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 07/29/2020] [Indexed: 12/24/2022]
Abstract
Excitotoxicity is a cellular phenomenon that comprises the consequences of toxic actions of excitatory neurotransmitters, such as glutamate. This process is usually related to overproduction of reactive oxygen species (ROS) and ammonia (NH4 + ) toxicity. Platinum nanoparticle (Pt-NP)-based microreactors able to degrade hydrogen peroxide (H2 O2 ) and NH4 + , are previously described as a novel therapeutical approach against excitotoxicity, conferring protection to neuroblasts. Now, it is demonstrated that these microreactors are compatible with rat primary cortical neurons, show high levels of neuronal membrane interaction, and are able to improve cell survival and neuronal activity when neurons are exposed to H2 O2 or NH4 + . Additionally, more complex microreactors are assembled, including enzyme-loaded liposomes containing glutamate dehydrogenase and glutathione reductase, in addition to Pt-NP. The in vitro activity of these microreactors is characterized and they are compared to the Pt-NP-based microreactors in terms of biological activity, concluding that they enhance cell viability similarly or more extensively than the latter. Extracellular electrophysiological recordings demonstrate that these microreactors rescue neuronal functionality lost upon incubation with H2 O2 or NH4 + . This study provides more evidence for the potential application of these microreactors in a biomedical context with more complex cellular environments.
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Affiliation(s)
- Adam Armada-Moreira
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, Edifício Egas Moniz, Lisboa, 1649-028, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, 1649-028, Portugal
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, 8000, Denmark
| | - Joana E Coelho
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, 1649-028, Portugal
| | - Luísa V Lopes
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, 1649-028, Portugal
| | - Ana M Sebastião
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, Edifício Egas Moniz, Lisboa, 1649-028, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, 1649-028, Portugal
| | - Brigitte Städler
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, 8000, Denmark
| | - Sandra H Vaz
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, Edifício Egas Moniz, Lisboa, 1649-028, Portugal
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisboa, 1649-028, Portugal
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Compensatory Neuroprotective Response of Thioredoxin Reductase against Oxidative-Nitrosative Stress Induced by Experimental Autoimmune Encephalomyelitis in Rats: Modulation by Theta Burst Stimulation. Molecules 2020; 25:molecules25173922. [PMID: 32867364 PMCID: PMC7503723 DOI: 10.3390/molecules25173922] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 08/05/2020] [Accepted: 08/08/2020] [Indexed: 12/12/2022] Open
Abstract
Cortical theta burst stimulation (TBS) structured as intermittent (iTBS) and continuous (cTBS) could prevent the progression of the experimental autoimmune encephalomyelitis (EAE). The interplay of brain antioxidant defense systems against free radicals (FRs) overproduction induced by EAE, as well as during iTBS or cTBS, have not been entirely investigated. This study aimed to examine whether oxidative-nitrogen stress (ONS) is one of the underlying pathophysiological mechanisms of EAE, which may be changed in terms of health improvement by iTBS or cTBS. Dark Agouti strain female rats were tested for the effects of EAE and TBS. The rats were randomly divided into the control group, rats specifically immunized for EAE and nonspecifically immuno-stimulated with Complete Freund's adjuvant. TBS or sham TBS was applied to EAE rats from 14th-24th post-immunization day. Superoxide dismutase activity, levels of superoxide anion (O2•-), lipid peroxidation, glutathione (GSH), nicotinamide adenine dinucleotide phosphate (NADPH), and thioredoxin reductase (TrxR) activity were analyzed in rat spinal cords homogenates. The severity of EAE clinical coincided with the climax of ONS. The most critical result refers to TrxR, which immensely responded against the applied stressors of the central nervous system (CNS), including immunization and TBS. We found that the compensatory neuroprotective role of TrxR upregulation is a positive feedback mechanism that reduces the harmfulness of ONS. iTBS and cTBS both modulate the biochemical environment against ONS at a distance from the area of stimulation, alleviating symptoms of EAE. The results of our study increase the understanding of FRs' interplay and the role of Trx/TrxR in ONS-associated neuroinflammatory diseases, such as EAE. Also, our results might help the development of new ideas for designing more effective medical treatment, combining neuropsychological with noninvasive neurostimulation-neuromodulation techniques to patients living with MS.
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Sepehrinezhad A, Zarifkar A, Namvar G, Shahbazi A, Williams R. Astrocyte swelling in hepatic encephalopathy: molecular perspective of cytotoxic edema. Metab Brain Dis 2020; 35:559-578. [PMID: 32146658 DOI: 10.1007/s11011-020-00549-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 02/12/2020] [Indexed: 02/06/2023]
Abstract
Hepatic encephalopathy (HE) may occur in patients with liver failure. The most critical pathophysiologic mechanism of HE is cerebral edema following systemic hyperammonemia. The dysfunctional liver cannot eliminate circulatory ammonia, so its plasma and brain levels rise sharply. Astrocytes, the only cells that are responsible for ammonia detoxification in the brain, are dynamic cells with unique phenotypic properties that enable them to respond to small changes in their environment. Any pathological changes in astrocytes may cause neurological disturbances such as HE. Astrocyte swelling is the leading cause of cerebral edema, which may cause brain herniation and death by increasing intracranial pressure. Various factors may have a role in astrocyte swelling. However, the exact molecular mechanism of astrocyte swelling is not fully understood. This article discusses the possible mechanisms of astrocyte swelling which related to hyperammonia, including the possible roles of molecules like glutamine, lactate, aquaporin-4 water channel, 18 KDa translocator protein, glial fibrillary acidic protein, alanine, glutathione, toll-like receptor 4, epidermal growth factor receptor, glutamate, and manganese, as well as inflammation, oxidative stress, mitochondrial permeability transition, ATP depletion, and astrocyte senescence. All these agents and factors may be targeted in therapeutic approaches to HE.
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Affiliation(s)
- Ali Sepehrinezhad
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran
| | - Asadollah Zarifkar
- Shiraz Neuroscience Research Center and Department of Physiology, Shiraz University of Medical Sciences (SUMS), Shiraz, Iran
| | - Gholamreza Namvar
- Department of Neuroscience and Cognition, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Ali Shahbazi
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran.
- Cellular and Molecular Research Center, Iran University of Medical Sciences (IUMS), Tehran, Iran.
| | - Roger Williams
- The Institute of Hepatology London and Foundation for Liver Research, 111 Coldharbour Lane, London, SE5 9NT, UK.
- Faculty of Life Sciences & Medicine, King's College London, London, UK.
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Li LH, Qi HX. Effect of acute ammonia exposure on the glutathione redox system in FFRC strain common carp (Cyprinus carpio L.). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:27023-27031. [PMID: 31313232 DOI: 10.1007/s11356-019-05895-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 07/03/2019] [Indexed: 06/10/2023]
Abstract
Ammonia is one of the most common aquatic pollutants. To analyze the effect of ammonia exposure on the glutathione redox system, we investigated the levels of hydrogen peroxide (H2O2) and glutathione, and transcription and activities of glutathione-related enzymes in liver and gills of FFRC strain common carp (Cyprinus carpio L.) exposed to 0, 10, 20, and 30 mg/L of ammonia. The results showed that H2O2 content reached a maximum level at 48 h of exposure in the liver of fish. In gills, H2O2 increased rapidly at 6 h and reached to maximum levels at 24 h of exposure, indicating that gills experienced oxidative stress earlier than the liver of fish exposed to ammonia. Reduced glutathione (GSH) content and reduced glutathione/oxidized glutathione (GSH/GSSG) ratio increased significantly within 24 h of exposure. Meanwhile, the transcription and activities of glutathione S-transferase (GST) and glutathione reductase (GR) increased significantly in the liver, and glutathione peroxidase (GSH-Px) and GST increased in the gills of fish exposed to ammonia. Malondialdehyde (MDA) content kept at a low level after exposure to low concentration of ammonia, but increased significantly after exposure to 30 mg/L ammonia for 48 h along with a decrease in GSH content and GSH/GSSG ratio. These data showed that the glutathione redox system played an important role in protection against ammonia-induced oxidative stress in the liver and gills of FFRC strain common carp, though the defense capacity was not able to completely prevent oxidative damage occurring after exposure to higher concentration of ammonia. This research systematically studied the response of the glutathione redox system to ammonia stress and would provide novel information for a better understanding of the adaptive mechanisms of fish to environmental stress.
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Affiliation(s)
- Li-Hong Li
- College of Chemistry and Chemical Engineering, Jinzhong University, No.199 Wenhua Road, Yuci, Shanxi, 030619, China.
| | - Hong-Xue Qi
- College of Chemistry and Chemical Engineering, Jinzhong University, No.199 Wenhua Road, Yuci, Shanxi, 030619, China
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Galland F, Negri E, Da Ré C, Fróes F, Strapazzon L, Guerra MC, Tortorelli LS, Gonçalves CA, Leite MC. Hyperammonemia compromises glutamate metabolism and reduces BDNF in the rat hippocampus. Neurotoxicology 2017; 62:46-55. [PMID: 28506823 DOI: 10.1016/j.neuro.2017.05.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 03/31/2017] [Accepted: 05/11/2017] [Indexed: 12/31/2022]
Abstract
Ammonia is putatively the major toxin associated with hepatic encephalopathy (HE), a neuropsychiatric manifestation that results in cognitive impairment, poor concentration and psychomotor alterations. The hippocampus, a brain region involved in cognitive impairment and depressive behavior, has been studied less than neocortical regions. Herein, we investigated hippocampal astrocyte parameters in a hyperammonemic model without hepatic lesion and in acute hippocampal slices exposed to ammonia. We also measured hippocampal BDNF, a neurotrophin commonly related to synaptic plasticity and cognitive deficit, and peripheral S100B protein, used as a marker for brain damage. Hyperammonemia directly impaired astrocyte function, inducing a decrease in glutamate uptake and in the activity of glutamine synthetase, in turn altering the glutamine-glutamate cycle, glutamatergic neurotransmission and ammonia detoxification itself. Hippocampal BDNF was reduced in hyperammonemic rats via a mechanism that may involve astrocyte production, since the same effect was observed in astrocyte cultures exposed to ammonia. Ammonia induced a significant increase in S100B secretion in cultured astrocytes; however, no significant changes were observed in the serum or in cerebrospinal fluid. Data demonstrating hippocampal vulnerability to ammonia toxicity, particularly due to reduced glutamate uptake activity and BDNF content, contribute to our understanding of the neuropsychiatric alterations in HE.
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Affiliation(s)
- Fabiana Galland
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Elisa Negri
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Carollina Da Ré
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Fernanda Fróes
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Liliane Strapazzon
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Maria Cristina Guerra
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Lucas Silva Tortorelli
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Carlos-Alberto Gonçalves
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Marina Concli Leite
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
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10
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Neurotoxicity of Ammonia. Neurochem Res 2016; 42:713-720. [PMID: 27465396 DOI: 10.1007/s11064-016-2014-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 07/15/2016] [Accepted: 07/21/2016] [Indexed: 12/25/2022]
Abstract
Abnormal liver function has dramatic effects on brain functions. Hyperammonemia interferes profoundly with brain metabolism, astrocyte volume regulation, and in particular mitochondrial functions. Gene expression in the brain and excitatory and inhibitory neurotransmission circuits are also affected. Experiments with a number of pertinent animal models have revealed several potential mechanisms which could underlie the pathological phenomena occurring in hepatic encephalopathy.
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11
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Oeltzschner G, Butz M, Wickrath F, Wittsack HJ, Schnitzler A. Covert hepatic encephalopathy: elevated total glutathione and absence of brain water content changes. Metab Brain Dis 2016; 31:517-27. [PMID: 26563124 DOI: 10.1007/s11011-015-9760-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 11/06/2015] [Indexed: 01/20/2023]
Abstract
Recent pathophysiological models suggest that oxidative stress and hyperammonemia lead to a mild brain oedema in hepatic encephalopathy (HE). Glutathione (GSx) is a major cellular antioxidant and known to be involved in the interception of both. The aim of this work was to study total glutathione levels in covert HE (minimal HE and HE grade 1) and to investigate their relationship with local brain water content, levels of glutamine (Gln), myo-inositol (mI), neurotransmitter levels, critical flicker frequency (CFF), and blood ammonia. Proton magnetic resonance spectroscopy ((1)H MRS) data were analysed from visual and sensorimotor cortices of thirty patients with covert HE and 16 age-matched healthy controls. Total glutathione levels (GSx/Cr) were quantified with respect to creatine. Furthermore, quantitative MRI brain water content measures were evaluated. Data were tested for links with the CFF and blood ammonia. GSx/Cr was elevated in the visual (mHE) and sensorimotor (mHE, HE 1) MRS volumes and correlated with blood ammonia levels (both P < 0.001). It was further linked to Gln/Cr and mI/Cr (P < 0.01 in visual, P < 0.001 in sensorimotor) and to GABA/Cr (P < 0.01 in visual). Visual GSx/Cr correlated with brain water content in the thalamus, nucleus caudatus, and visual cortex (P < 0.01). Brain water measures did neither show group effects nor correlations with CFF or blood ammonia. Elevated total glutathione levels in covert HE (< HE 2) correlate with blood ammonia and may be a regional-specific reaction to hyperammonemia and oxidative stress. Brain water content is locally linked to visual glutathione levels, but appears not to be associated with changes of clinical parameters. This might suggest that cerebral oedema is only marginally responsible for the symptoms of covert HE.
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Affiliation(s)
- Georg Oeltzschner
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, D-40225, Düsseldorf, Germany.
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, D-40225, Düsseldorf, Germany.
| | - Markus Butz
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, D-40225, Düsseldorf, Germany
| | - Frithjof Wickrath
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, D-40225, Düsseldorf, Germany
| | - Hans-Jörg Wittsack
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, D-40225, Düsseldorf, Germany
| | - Alfons Schnitzler
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, D-40225, Düsseldorf, Germany
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12
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Jördens MS, Keitel V, Karababa A, Zemtsova I, Bronger H, Häussinger D, Görg B. Multidrug resistance-associated protein 4 expression in ammonia-treated cultured rat astrocytes and cerebral cortex of cirrhotic patients with hepatic encephalopathy. Glia 2015; 63:2092-2105. [PMID: 26102310 DOI: 10.1002/glia.22879] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 06/08/2015] [Indexed: 12/30/2022]
Abstract
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome frequently accompanying liver cirrhosis and reflects the clinical manifestation of a low grade cerebral edema associated with cerebral oxidative/nitrosative stress. The multidrug resistance-associated protein (Mrp) 4 is an export pump which transports metabolites that were recently suggested to play a major role in the pathogenesis of HE such as neurosteroids and cyclic nucleotides. We therefore studied Mrp4 expression changes in ammonia-exposed cultured astrocytes and postmortem human brain samples of cirrhotic patients with HE. NH4 Cl increased Mrp4 mRNA and protein levels in astrocytes in a dose- and time-dependent manner up to threefold after 72 h of exposure and concurrently inhibited N-glycosylation of Mrp4 protein. Upregulation of Mrp4 mRNA and protein as well as impaired N-glycosylation of Mrp4 protein by ammonia were sensitive towards the glutamine-synthetase inhibitor l-methionine-S-sulfoximine and were not induced by CH3 NH3 Cl (5 mmol/L). Upregulation of Mrp4 mRNA required ammonia-induced activation of nitric oxide synthases or NADPH oxidase and p38MAPK -dependent activation of PPARα. Inhibition of Mrp4 by ceefourin 1 synergistically enhanced both, inhibition of astrocyte proliferation as well as transcription of the oxidative stress surrogate marker heme oxygenase 1 by forskolin (10 µmol/L, 72 h) or NH4 Cl (5 mmol/L, 72 h) in cultured rat astrocytes. Increased Mrp4 mRNA and protein levels were also found in postmortem brain samples from patients with liver cirrhosis with HE but not in those without HE. The data show that Mrp4 is upregulated in HE, which may be relevant for the handling of neurosteroids and cyclic nucleotides in response to ammonia. GLIA 2015;63:2092-2105.
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Affiliation(s)
- Markus S Jördens
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine University, Düsseldorf, Germany
| | - Verena Keitel
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine University, Düsseldorf, Germany
| | - Ayse Karababa
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine University, Düsseldorf, Germany
| | - Irina Zemtsova
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine University, Düsseldorf, Germany
| | - Holger Bronger
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine University, Düsseldorf, Germany
| | - Dieter Häussinger
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine University, Düsseldorf, Germany
| | - Boris Görg
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich-Heine University, Düsseldorf, Germany
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13
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Glutathione-Dependent Detoxification Processes in Astrocytes. Neurochem Res 2014; 40:2570-82. [PMID: 25428182 DOI: 10.1007/s11064-014-1481-1] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 11/10/2014] [Accepted: 11/15/2014] [Indexed: 01/17/2023]
Abstract
Astrocytes have a pivotal role in brain as partners of neurons in homeostatic and metabolic processes. Astrocytes also protect other types of brain cells against the toxicity of reactive oxygen species and are considered as first line of defence against the toxic potential of xenobiotics. A key component in many of the astrocytic detoxification processes is the tripeptide glutathione (GSH) which serves as electron donor in the GSH peroxidase-catalyzed reduction of peroxides. In addition, GSH is substrate in the detoxification of xenobiotics and endogenous compounds by GSH-S-transferases which generate GSH conjugates that are efficiently exported from the cells by multidrug resistance proteins. Moreover, GSH reacts with the reactive endogenous carbonyls methylglyoxal and formaldehyde to intermediates which are substrates of detoxifying enzymes. In this article we will review the current knowledge on the GSH metabolism of astrocytes with a special emphasis on GSH-dependent detoxification processes.
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14
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Ruszkiewicz J, Albrecht J. Changes of the thioredoxin system, glutathione peroxidase activity and total antioxidant capacity in rat brain cortex during acute liver failure: modulation by L-histidine. Neurochem Res 2014; 40:293-300. [PMID: 25161077 PMCID: PMC4326661 DOI: 10.1007/s11064-014-1417-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 07/13/2014] [Accepted: 08/12/2014] [Indexed: 01/05/2023]
Abstract
Glutathione and thioredoxin are complementary antioxidants in the protection of mammalian tissues against oxidative–nitrosative stress (ONS), and ONS is a principal cause of symptoms of hepatic encephalopathy (HE) associated with acute liver failure (ALF). We compared the activities of the thioredoxin system components: thioredoxin (Trx), thioredoxin reductase (TrxR) and the expression of the thioredoxin-interacting protein, and of the key glutathione metabolizing enzyme, glutathione peroxidase (GPx) in the cerebral cortex of rats with ALF induced by thioacetamide (TAA). ALF increased the Trx and TrxR activity without affecting Trip protein expression, but decreased GPx activity in the brains of TAA-treated rats. The total antioxidant capacity (TAC) of the brain was increased by ALF suggesting that upregulation of the thioredoxin may act towards compensating impaired protection by the glutathione system. Intraperitoneal administration of l-histidine (His), an amino acid that was earlier reported to prevent acute liver failure-induced mitochondrial impairment and brain edema, abrogated most of the acute liver failure-induced changes of both antioxidant systems, and significantly increased TAC of both the control and ALF-affected brain. These observations provide further support for the concept of that His has a potential to serve as a therapeutic antioxidant in HE. Most of the enzyme activity changes evoked by His or ALF were not well correlated with alterations in their expression at the mRNA level, suggesting complex translational or posttranslational mechanisms of their modulation, which deserve further investigations.
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Affiliation(s)
- Joanna Ruszkiewicz
- Department of Neurotoxicology, Mossakowski Medical Research Centre, Polish Academy of Sciences, 02-106, Warsaw, Poland,
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Singh S, Mondal P, Trigun SK. Acute liver failure in rats activates glutamine-glutamate cycle but declines antioxidant enzymes to induce oxidative stress in cerebral cortex and cerebellum. PLoS One 2014; 9:e95855. [PMID: 24755687 PMCID: PMC3995888 DOI: 10.1371/journal.pone.0095855] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 04/01/2014] [Indexed: 01/28/2023] Open
Abstract
Background and Purpose Liver dysfunction led hyperammonemia (HA) causes a nervous system disorder; hepatic encephalopathy (HE). In the brain, ammonia induced glutamate-excitotoxicity and oxidative stress are considered to play important roles in the pathogenesis of HE. The brain ammonia metabolism and antioxidant enzymes constitute the main components of this mechanism; however, need to be defined in a suitable animal model. This study was aimed to examine this aspect in the rats with acute liver failure (ALF). Methods ALF in the rats was induced by intraperitoneal administration of 300 mg thioacetamide/Kg. b.w up to 2 days. Glutamine synthetase (GS) and glutaminase (GA), the two brain ammonia metabolizing enzymes vis a vis ammonia and glutamate levels and profiles of all the antioxidant enzymes vis a vis oxidative stress markers were measured in the cerebral cortex and cerebellum of the control and the ALF rats. Results The ALF rats showed significantly increased levels of ammonia in the blood (HA) but little changes in the cortex and cerebellum. This was consistent with the activation of the GS-GA cycle and static levels of glutamate in these brain regions. However, significantly increased levels of lipid peroxidation and protein carbonyl contents were consistent with the reduced levels of all the antioxidant enzymes in both the brain regions of these ALF rats. Conclusion ALF activates the GS-GA cycle to metabolize excess ammonia and thereby, maintains static levels of ammonia and glutamate in the cerebral cortex and cerebellum. Moreover, ALF induces oxidative stress by reducing the levels of all the antioxidant enzymes which is likely to play important role, independent of glutamate levels, in the pathogenesis of acute HE.
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Affiliation(s)
- Santosh Singh
- Department of Zoology, Guru Ghasidas Vishwavidyalaya, Bilaspur, Chhattisgarh, India
| | - Papia Mondal
- Biochemistry and Molecular Biology Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | - Surendra K. Trigun
- Biochemistry and Molecular Biology Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, Uttar Pradesh, India
- * E-mail:
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Sinha AK, AbdElgawad H, Giblen T, Zinta G, De Rop M, Asard H, Blust R, De Boeck G. Anti-oxidative defences are modulated differentially in three freshwater teleosts in response to ammonia-induced oxidative stress. PLoS One 2014; 9:e95319. [PMID: 24740135 PMCID: PMC3989309 DOI: 10.1371/journal.pone.0095319] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 03/25/2014] [Indexed: 12/19/2022] Open
Abstract
Oxidative stress and the antioxidant response induced by high environmental ammonia (HEA) were investigated in the liver and gills of three freshwater teleosts differing in their sensitivities to ammonia. The highly ammonia-sensitive salmonid Oncorhynchus mykiss (rainbow trout), the less ammonia sensitive cyprinid Cyprinus carpio (common carp) and the highly ammonia-resistant cyprinid Carassius auratus (goldfish) were exposed to 1 mM ammonia (as NH4HCO3) for 0 h (control), 3 h, 12 h, 24 h, 48 h, 84 h and 180 h. Results show that HEA exposure increased ammonia accumulation significantly in the liver of all the three fish species from 24 h–48 h onwards which was associated with an increment in oxidative stress, evidenced by elevation of xanthine oxidase activity and levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Unlike in trout, H2O2 and MDA accumulation in carp and goldfish liver was restored to control levels (84 h–180 h); which was accompanied by a concomitant increase in superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase activity and reduced ascorbate content. Many of these defence parameters remained unaffected in trout liver, while components of the glutathione redox cycle (reduced glutathione, glutathione peroxidase and glutathione reductase) enhanced to a greater extent. The present findings suggest that trout rely mainly on glutathione dependent defensive mechanism while carp utilize SOD, CAT and ascorbate as anti-oxidative sentinels. Hepatic cells of goldfish appear to utilize each of these protective systems, and showed more effective anti-oxidative compensatory responses towards HEA than carp, while trout were least effective. The present work also indicates that HEA exposure resulted in a relatively mild oxidative stress in the gills of all three species. This probably explains the almost complete lack of anti-oxidative responses in branchial tissue. This research suggests that oxidative stress, as well as the antioxidant potential clearly differ between salmonid and cyprinid species.
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Affiliation(s)
- Amit Kumar Sinha
- Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Antwerp, Belgium
- * E-mail:
| | - Hamada AbdElgawad
- Molecular Plant Physiology and Biotechnology group, Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Terri Giblen
- Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Gaurav Zinta
- Molecular Plant Physiology and Biotechnology group, Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Michelle De Rop
- Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Han Asard
- Molecular Plant Physiology and Biotechnology group, Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Ronny Blust
- Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Gudrun De Boeck
- Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Antwerp, Belgium
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Steinbrenner H, Sies H. Selenium homeostasis and antioxidant selenoproteins in brain: implications for disorders in the central nervous system. Arch Biochem Biophys 2013; 536:152-7. [PMID: 23500141 DOI: 10.1016/j.abb.2013.02.021] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 02/25/2013] [Accepted: 02/27/2013] [Indexed: 10/27/2022]
Abstract
The essential trace element selenium, as selenocysteine, is incorporated into antioxidant selenoproteins such as glutathione peroxidases (GPx), thioredoxin reductases (TrxR) and selenoprotein P (Sepp1). Although comparatively low in selenium content, the brain exhibits high priority for selenium supply and retention under conditions of dietary selenium deficiency. Liver-derived Sepp1 is the major transport protein in plasma to supply the brain with selenium, serving as a "survival factor" for neurons in culture. Sepp1 expression has also been detected within the brain. Presumably, astrocytes secrete Sepp1, which is subsequently taken up by neurons via the apolipoprotein E receptor 2 (ApoER2). Knock-out of Sepp1 or ApoER2 as well as neuron-specific ablation of selenoprotein biosynthesis results in neurological dysfunction in mice. Astrocytes, generally less vulnerable to oxidative stress than neurons, are capable of up-regulating the expression of antioxidant selenoproteins upon brain injury. Occurrence of neurological disorders has been reported occasionally in patients with inadequate nutritional selenium supply or a mutation in the gene encoding selenocysteine synthase, one of the enzymes involved in selenoprotein biosynthesis. In three large trials carried out among elderly persons, a low selenium status was associated with faster decline in cognitive functions and poor performance in tests assessing coordination and motor speed. Future research is required to better understand the role of selenium and selenoproteins in brain diseases including hepatic encephalopathy.
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Affiliation(s)
- Holger Steinbrenner
- Institute for Biochemistry and Molecular Biology I, Heinrich-Heine-University, Düsseldorf, Germany
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18
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Skowrońska M, Albrecht J. Oxidative and nitrosative stress in ammonia neurotoxicity. Neurochem Int 2012; 62:731-7. [PMID: 23142151 DOI: 10.1016/j.neuint.2012.10.013] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 10/18/2012] [Accepted: 10/28/2012] [Indexed: 12/16/2022]
Abstract
Increased ammonia accumulation in the brain due to liver dysfunction is a major contributor to the pathogenesis of hepatic encephalopathy (HE). Fatal outcome of rapidly progressing (acute) HE is mainly related to cytotoxic brain edema associated with astrocytic swelling. An increase of brain ammonia in experimental animals or treatment of cultured astrocytes with ammonia generates reactive oxygen and nitrogen species in the target tissues, leading to oxidative/nitrosative stress (ONS). In cultured astrocytes, ammonia-induced ONS is invariably associated with the increase of the astrocytic cell volume. Interrelated mechanisms underlying this response include increased nitric oxide (NO) synthesis which is partly coupled to the activation of NMDA receptors and increased generation of reactive oxygen species by NADPH oxidase. ONS and astrocytic swelling are further augmented by excessive synthesis of glutamine (Gln) which impairs mitochondrial function following its accumulation in there and degradation back to ammonia ("the Trojan horse" hypothesis). Ammonia also induces ONS in other cell types of the CNS: neurons, microglia and the brain capillary endothelial cells (BCEC). ONS in microglia contributes to the central inflammatory response, while its metabolic and pathophysiological consequences in the BCEC evolve to the vasogenic brain edema associated with HE. Ammonia-induced ONS results in the oxidation of mRNA and nitration/nitrosylation of proteins which impact intracellular metabolism and potentiate the neurotoxic effects. Simultaneously, ammonia facilitates the antioxidant response of the brain, by activating astrocytic transport and export of glutathione, in this way increasing the availability of precursors of neuronal glutathione synthesis.
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Affiliation(s)
- Marta Skowrońska
- Department of Neurotoxicology, Mossakowski Medical Research Center, Polish Academy of Sciences, Pawinskiego 5, 02-106 Warsaw, Poland.
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19
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Kruczek C, Görg B, Keitel V, Bidmon HJ, Schliess F, Häussinger D. Ammonia increases nitric oxide, free Zn(2+), and metallothionein mRNA expression in cultured rat astrocytes. Biol Chem 2012; 392:1155-65. [PMID: 22050230 DOI: 10.1515/bc.2011.199] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Ammonia is a major player in the pathogenesis of hepatic encephalopathy (HE) and affects astrocyte function by triggering a self-amplifying cycle between osmotic and oxidative stress. We recently demonstrated that hypoosmotic astrocyte swelling rapidly stimulates nitric oxide (NO) production and increases intracellular free Zn(2+) concentration ([Zn(2+)](i)). Here we report effects of ammonia on [Zn(2+)](i) homeostasis and NO synthesis. In cultured rat astrocytes, NH(4)Cl (5 mm) increased within 6 h both cytosolic and mitochondrial [Zn(2+)]. The [Zn(2+)](i) increase was transient and was mimicked by the nonmetabolizable CH(3)NH(3)Cl, and it was dependent on NO formation, as evidenced by the sensitivity toward the nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine. The NH(4)Cl-induced NO formation was sensitive to the Ca(2+) chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester and increases in both NO and [Zn(2+)](i) were blocked by the N-methyl-d-aspartate receptor antagonist MK-801. The NH(4)Cl-triggered increase in [Zn(2+)](i) was followed by a Zn(2+)-dependent nuclear appearance of the metal response element-binding transcription factor and metallothionein messenger RNA (mRNA) induction. Metallothionein mRNA was also increased in vivo in rat cerebral cortex 6 h after an NH(4)Ac challenge. NH(4)Cl increased peripheral-type benzodiazepine receptor (PBR) protein expression, whereas PBR mRNA levels were decreased in a Zn(2+)-independent manner. The Zn(2+)-dependent upregulation of metallothionein following ammonia intoxication may reflect a cytoprotective response, whereas the increase in PBR expression may augment HE development.
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Affiliation(s)
- Carolin Kruczek
- University Clinic of Düsseldorf, Clinic for Gastroenterology, Hepatology and Infectiology, Moorenstrasse 5, 40225 Düsseldorf, Germany
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20
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Kruczek C, Görg B, Keitel V, Bidmon HJ, Schliess F, Häussinger D. Ammonia increases nitric oxide, free Zn(2+), and metallothionein mRNA expression in cultured rat astrocytes. Biol Chem 2011. [PMID: 22050230 DOI: 10.1515/bc-2011-199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Ammonia is a major player in the pathogenesis of hepatic encephalopathy (HE) and affects astrocyte function by triggering a self-amplifying cycle between osmotic and oxidative stress. We recently demonstrated that hypoosmotic astrocyte swelling rapidly stimulates nitric oxide (NO) production and increases intracellular free Zn(2+) concentration ([Zn(2+)](i)). Here we report effects of ammonia on [Zn(2+)](i) homeostasis and NO synthesis. In cultured rat astrocytes, NH(4)Cl (5 mm) increased within 6 h both cytosolic and mitochondrial [Zn(2+)]. The [Zn(2+)](i) increase was transient and was mimicked by the nonmetabolizable CH(3)NH(3)Cl, and it was dependent on NO formation, as evidenced by the sensitivity toward the nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine. The NH(4)Cl-induced NO formation was sensitive to the Ca(2+) chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester and increases in both NO and [Zn(2+)](i) were blocked by the N-methyl-d-aspartate receptor antagonist MK-801. The NH(4)Cl-triggered increase in [Zn(2+)](i) was followed by a Zn(2+)-dependent nuclear appearance of the metal response element-binding transcription factor and metallothionein messenger RNA (mRNA) induction. Metallothionein mRNA was also increased in vivo in rat cerebral cortex 6 h after an NH(4)Ac challenge. NH(4)Cl increased peripheral-type benzodiazepine receptor (PBR) protein expression, whereas PBR mRNA levels were decreased in a Zn(2+)-independent manner. The Zn(2+)-dependent upregulation of metallothionein following ammonia intoxication may reflect a cytoprotective response, whereas the increase in PBR expression may augment HE development.
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Affiliation(s)
- Carolin Kruczek
- University Clinic of Düsseldorf, Clinic for Gastroenterology, Hepatology and Infectiology, Moorenstrasse 5, 40225 Düsseldorf, Germany
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21
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Hilgier W, Węgrzynowicz M, Ruszkiewicz J, Oja SS, Saransaari P, Albrecht J. Direct Exposure to Ammonia and Hyperammonemia Increase the Extracellular Accumulation and Degradation of Astroglia-Derived Glutathione in the Rat Prefrontal Cortex. Toxicol Sci 2010; 117:163-8. [DOI: 10.1093/toxsci/kfq171] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Ching B, Chew SF, Wong WP, Ip YK. Environmental ammonia exposure induces oxidative stress in gills and brain of Boleophthalmus boddarti (mudskipper). AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2009; 95:203-212. [PMID: 19819034 DOI: 10.1016/j.aquatox.2009.09.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Revised: 09/04/2009] [Accepted: 09/10/2009] [Indexed: 05/28/2023]
Abstract
This study aimed to elucidate whether exposure to a sublethal concentration (8mmoll(-1)) of NH(4)Cl (pH 7.0) for 12 or 48h would induce oxidative stress in gills and brain of the mudskipper Boleophthalmus boddarti which has high tolerance of environmental and brain ammonia. The gills of B. boddarti experienced a transient oxidative stress after 12h of ammonia exposure as evidenced by an increase in lipid hydroperoxide content, decreases in contents of reduced glutathione (GSH) and total GSH equivalent, and in activities of total glutathione peroxidase, glutathione reductase and catalase. There were also transient increases in protein abundance of p53 and p38 in gills of fish exposed to ammonia for 12h, although the protein abundance of phosphorylated p53 remained unchanged and there was a decrease in the protein abundance of phosphorylated p38, at hour 12. Since the majority of these oxidative parameters returned to control levels at hour 48, the ability of the gills of B. boddarti to recover from ammonia-induced oxidative stress might contribute to its high environmental ammonia tolerance. Ammonia also induced oxidative stress in the brain of B. boddarti at hours 12 and 48 as evidenced by the accumulation of carbonyl proteins, elevation in oxidized glutathione (GSSG) content and GSSG/GSH, decreases in activities of glutathione reductase and catalase, and an increase in the activity of superoxide dismutase. The capacity to increase glutathione synthesis and GSH content could alleviate severe ammonia-induced oxidative and nitrosative stress in the brain. Furthermore, the ability to decrease the protein abundance of p38 and phosphorylated p53 might prevent cell swelling, contributing in part to the high ammonia tolerance in the brain of B. boddarti. Overall, our results indicate that there could be multiple routes through which ammonia induced oxidative stress in and outside the brain.
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Affiliation(s)
- Biyun Ching
- Department of Biological Science, National University of Singapore, Republic of Singapore
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Lichter-Konecki U. Profiling of astrocyte properties in the hyperammonaemic brain: shedding new light on the pathophysiology of the brain damage in hyperammonaemia. J Inherit Metab Dis 2008; 31:492-502. [PMID: 18683079 DOI: 10.1007/s10545-008-0834-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2007] [Revised: 05/30/2008] [Accepted: 06/03/2008] [Indexed: 10/21/2022]
Abstract
Acute hyperammonaemia (HA) causes cerebral oedema and severe brain damage in patients with urea cycle disorders (UCDs) or acute liver failure (ALF). Chronic HA is associated with developmental delay and intellectual disability in patients with UCDs and with neuropsychiatric symptoms in patients with chronic liver failure. Treatment often cannot prevent severe brain injury and neurological sequelae. The causes of the brain oedema in hyperammonaemic encephalopathy (HAE) have been subject of intense controversy among physicians and scientists working in this field. Currently favoured hypotheses are astrocyte swelling due to increased intracellular glutamine content and neuronal cell death due to excitotoxicity caused by elevated extracellular glutamate levels. While many researchers focus on these mechanisms of cytotoxicity, others emphasize vascular causes of brain oedema. New data gleaned from expression profiling of astrocytes acutely isolated from hyperammonaemic mouse brains point to disturbed water and potassium homeostasis as regulated by astrocytes at the brain microvasculature and in the perisynaptic space as a potential mechanism of brain oedema development in hyperammonaemia.
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Affiliation(s)
- U Lichter-Konecki
- Center for Neuroscience Research, and Division of Genetics & Metabolism, Children's National Medical Center, Washington, DC 20010-2970, USA.
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Norenberg MD, Jayakumar AR, Rama Rao KV, Panickar KS. New concepts in the mechanism of ammonia-induced astrocyte swelling. Metab Brain Dis 2007; 22:219-34. [PMID: 17823859 DOI: 10.1007/s11011-007-9062-5] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
It is generally accepted that astrocyte swelling forms the major anatomic substrate of the edema associated with acute liver failure (ALF) and that ammonia represents a major etiological factor in its causation. The mechanisms leading to such swelling, however, remain elusive. Recent studies have invoked the role of oxidative stress in the mechanism of hepatic encephalopathy (HE), as well as in the brain edema related to ALF. This article summarizes the evidence for oxidative stress as a major pathogenetic factor in HE/ALF and discusses mechanisms that are triggered by oxidative stress, including the induction of the mitochondrial permeability transition (MPT) and activation of signaling kinases. We propose that a cascade of events initiated by ammonia-induced oxidative stress results in cell volume dysregulation leading to cell swelling/brain edema. Blockade of this cascade may provide novel therapies for the brain edema associated with ALF.
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Affiliation(s)
- M D Norenberg
- Veterans Affairs Medical Center, Miami, FL 33101, USA.
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Singh S, Koiri RK, Trigun SK. Acute and Chronic Hyperammonemia Modulate Antioxidant Enzymes Differently in Cerebral Cortex and Cerebellum. Neurochem Res 2007; 33:103-13. [PMID: 17676388 DOI: 10.1007/s11064-007-9422-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Accepted: 06/18/2007] [Indexed: 10/23/2022]
Abstract
Studies on acute hyperammonemic models suggest a role of oxidative stress in neuropathology of ammonia toxicity. Mostly, a low grade chronic type hyperammonemia (HA) prevails in patients with liver diseases and causes derangements mainly in cerebellum associated functions. To understand whether cerebellum responds differently than other brain regions to chronic type HA with respect to oxidative stress, this article compares active levels of all the antioxidant enzymes vis a vis extent of oxidative damage in cerebral cortex and cerebellum of rats with acute and chronic HA induced by intra-peritoneal injection of ammonium acetate (successive doses of 10 x 10(3) & 8 x 10(3) micromol/kg b.w. at 30 min interval for acute and 8 x 10(3) micromol/kg b.w. daily up to 3 days for chronic HA). As compared to the respective control sets, cerebral cortex of acute HA rats showed significant decline (P < 0.01-0.001) in the levels of superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) but with no change in glutathione reductase (GR). In cerebellum of acute HA rats, SOD, catalase and GR though declined significantly, GPx level was found to be stable. Contrary to this, during chronic HA, levels of SOD, catalase and GPx increased significantly in cerebral cortex, however, with a significant decline in the levels of SOD and GPx in cerebellum. The results suggest that most of the antioxidant enzymes decline during acute HA in both the brain regions. However, chronic HA induces adaptive changes, with respect to the critical antioxidant enzymes, in cerebral cortex and renders cerebellum susceptible to the oxidative stress. This is supported by approximately 2- and 3-times increases in the level of lipid peroxidation in cerebellum during chronic and acute HA respectively, however, with no change in the cortex due to chronic HA.
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Affiliation(s)
- Santosh Singh
- Biochemistry & Molecular Biology Laboratory, Department of Zoology, Banaras Hindu University, Varanasi 221005, India
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26
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Muyderman H, Wadey AL, Nilsson M, Sims NR. Mitochondrial glutathione protects against cell death induced by oxidative and nitrative stress in astrocytes. J Neurochem 2007; 102:1369-82. [PMID: 17484727 DOI: 10.1111/j.1471-4159.2007.04641.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The major cellular antioxidant, glutathione, is mostly localized in the cytosol but a small portion is found in mitochondria. We have recently shown that highly selective depletion of mitochondrial glutathione in astrocytes in culture markedly increased cell death induced by the peroxynitrite donor, 3-morpholino-syndnonimine. The present study was aimed at characterizing the increase in susceptibility arising from mitochondrial glutathione loss and testing the possibility that elevating this metabolite pool above normal values could be protective. The increased vulnerability of astrocytes with depleted mitochondrial glutathione to Sin-1 was confirmed. Furthermore, these cells showed marked increases in sensitivity to hydrogen peroxide and also to high concentrations of the nitric oxide donor, S-nitroso-N-acetyl-penicillamine. The increase in cell death was mostly due to necrosis as indicated by substantially increased release of lactate dehydrogenase and staining of nuclei with propidium iodide but little change in annexin V staining and caspase 3 activation. The enhanced cell loss was blocked by prior restoration of the mitochondrial glutathione content. It was also essentially fully inhibited by treatment with cyclosporin A, consistent with a role for the mitochondrial permeability transition in the development of cell death. Susceptibility to the classical apoptosis inducer, staurosporine, was only affected to a small extent in contrast to the response to the other substances tested. Incubation of normal astrocytes with glutathione monoethylester produced large and long-lasting increases in mitochondrial glutathione content with much smaller effects on the cytosolic glutathione pool. This treatment reduced cell death on exposure to 3-morpholino-syndnonimine or hydrogen peroxide but not S-nitroso-N-acetyl-pencillamine or staurosporine. These findings provide evidence for an important role for mitochondrial glutathione in preserving cell viability during periods of oxidative or nitrative stress and indicate that increases in this glutathione pool can confer protection against some of these stressors.
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Affiliation(s)
- Håkan Muyderman
- Centre for Neuroscience and Department of Medical Biochemistry, School of Medicine, Flinders University, Adelaide, Australia.
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27
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Sathyasaikumar KV, Swapna I, Reddy PVB, Murthy CRK, Dutta Gupta A, Senthilkumaran B, Reddanna P. Fulminant Hepatic Failure in Rats Induces Oxidative Stress Differentially in Cerebral Cortex, Cerebellum and Pons Medulla. Neurochem Res 2007; 32:517-24. [PMID: 17268843 DOI: 10.1007/s11064-006-9265-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2006] [Accepted: 11/07/2006] [Indexed: 10/23/2022]
Abstract
Hepatic Encephalopathy (HE) is one of the most common complications of acute liver diseases and is known to have profound influence on the brain. Most of the studies, available from the literature are pertaining to whole brain homogenates or mitochondria. Since brain is highly heterogeneous with functions localized in specific areas, the present study was aimed to assess the oxidative stress in different regions of brain-cerebral cortex, cerebellum and pons medulla during acute HE. Acute liver failure was induced in 3-month old adult male Wistar rats by intraperitoneal injection of thioacetamide (300 mg/kg body weight for two days), a well known hepatotoxin. Oxidative stress conditions were assessed by free radical production, lipid peroxidation, nitric oxide levels, GSH/GSSG ratio and antioxidant enzyme machinery in three distinct structures of rat braincerebral cortex, cerebellum and pons medulla. Results of the present study indicate a significant increase in malondialdehyde (MDA) levels, reactive oxygen species (ROS), total nitric oxide levels [(NO) estimated by measuring (nitrites + nitrates)] and a decrease in GSH/GSSG ratio in all the regions of brain. There was also a marked decrease in the activity of the antioxidant enzymes-glutathione peroxidase, glutathione reductase and catalase while the super oxide dismutase activity (SOD) increased. However, the present study also revealed that pons medulla and cerebral cortex were more susceptible to oxidative stress than cerebellum. The increased vulnerability to oxidative stress in pons medulla could be due to the increased NO levels and increased activity of SOD and decreased glutathione peroxidase and glutathione reductase activities. In summary, the present study revealed that oxidative stress prevails in different cerebral regions analyzed during thioacetamide-induced acute liver failure with more pronounced effects on pons medulla and cerebral cortex.
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Affiliation(s)
- K V Sathyasaikumar
- Department of Animal Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500 046, Andhra Pradesh, India
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28
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Albrecht J, Wegrzynowicz M. Endogenous neuro-protectants in ammonia toxicity in the central nervous system: facts and hypotheses. Metab Brain Dis 2005; 20:253-63. [PMID: 16382336 DOI: 10.1007/s11011-005-7904-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The paper overviews experimental evidence suggestive of the engagement of three endogenous metabolites: taurine, kynurenic acid, and glutathione (GSH) in the protection of central nervous system (CNS) cells against ammonia toxicity. Intrastriatal administration of taurine via microdialysis probe attenuates ammonia-induced accumulation of extracellular cyclic guanosine monophosphate (cGMP) resulting from over-activation of the N-methyl-D: -aspartate/nitric oxide (NMDA/NO) pathway, and this effect involves agonistic effect of taurine on the GABA-A and glycine receptors. Taurine also counteracts generation of free radicals, increased release of dopamine, and its metabolism to dihydroxyphenylacetic acid (DOPAC). Taurine reduces ammonia-induced increase of cell volume (edema) in cerebrocortical slices by a mechanism involving GABA-A receptors. Massive release of radiolabeled or endogenous taurine from CNS tissues by ammonia in vivo and in vitro is thought to promote its neuroprotective action, by making the amino acid available for interaction with cell membranes and/or by driving excess water out of the CNS cells (astrocytes) that underwent ammonia-induced swelling. Ammonia in vivo and in vitro affects in variable ways the synthesis of kynurenic acid (KYNA). Since KYNA is an endogenous NMDA receptor antagonist with a high affinity towards its glycine site, changes in its content may counter over-activation or depression of glutaminergic transmission observed at the different stages of hyperammonemia. GSH is a major antioxidant in the CNS whose synthesis is partly compartmented between neurons and astrocytes: astrocytic GSH is a source of precursors for the synthesis of neuronal GSH. Ammonia in vitro stimulates GSH synthesis in cultured astrocytes, which may compensate for increased GSH consumption (decreased GSH/GSSG ratio) in neurons.
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Affiliation(s)
- Jan Albrecht
- Department of Neurotoxicology, M. Mossakowski Medical Research Center, Polish Academy of Sciences, Warsaw, Poland.
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29
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Abstract
Astrocyte swelling represents the major factor responsible for the brain edema associated with fulminant hepatic failure (FHF). The edema may be of such magnitude as to increase intracranial pressure leading to brain herniation and death. Of the various agents implicated in the generation of astrocyte swelling, ammonia has had the greatest amount of experimental support. This article reviews mechanisms of ammonia neurotoxicity that contribute to astrocyte swelling. These include oxidative stress and the mitochondrial permeability transition (MPT). The involvement of glutamine in the production of cell swelling will be highlighted. Evidence will be provided that glutamine induces oxidative stress as well as the MPT, and that these events are critical in the development of astrocyte swelling in hyperammonemia.
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Affiliation(s)
- M D Norenberg
- Veterans Affairs Medical Center, Miami, Florida 33101, USA. mnorenbe@med,miami.edu
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Norenberg MD, Rama Rao KV, Jayakumar AR. Ammonia neurotoxicity and the mitochondrial permeability transition. J Bioenerg Biomembr 2005; 36:303-7. [PMID: 15377862 DOI: 10.1023/b:jobb.0000041758.20071.19] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Ammonia is a neurotoxin that predominantly affects astrocytes. Disturbed mitochondrial function and oxidative stress, factors implicated in the induction of the mitochondrial permeability transition (MPT), appear to be involved in the mechanism of ammonia neurotoxicity. We have recently shown that ammonia induces the MPT in cultured astrocytes. To elucidate the mechanisms of the MPT, we examined the role of oxidative stress and glutamine, a byproduct of ammonia metabolism. The ammonia-induced MPT was blocked by antioxidants, suggesting a causal role of oxidative stress. Direct application of glutamine (4.5-7.0 mM) to cultured astrocytes increased free radical production and induced the MPT. Treatment of astrocytes with the mitochondrial glutaminase inhibitor, 6-diazo-5-oxo-L-norleucine, completely blocked free radical formation and the MPT, suggesting that high ammonia concentrations in mitochondria resulting from glutamine hydrolysis may be responsible for the effects of glutamine. These studies suggest that oxidative stress and glutamine play major roles in the induction of the MPT associated with ammonia neurotoxicity.
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Affiliation(s)
- M D Norenberg
- Veterans Affairs Medical Center, Miami, Florida, USA.
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31
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Brennan L, Hewage C, Malthouse JPG, McBean GJ. Gliotoxins disrupt alanine metabolism and glutathione production in C6 glioma cells: a 13C NMR spectroscopic study. Neurochem Int 2004; 45:1155-65. [PMID: 15380625 DOI: 10.1016/j.neuint.2004.06.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2004] [Accepted: 06/23/2004] [Indexed: 11/20/2022]
Abstract
Gliotoxins are a group of amino acids that are toxic to astrocytes, and are substrates of high-affinity sodium-dependent glutamate transporters. In the present study, C6 glioma cells were preincubated for 20 h in the presence of 400 microM L-alpha-aminoadipate, L-serine-O-sulphate, D-aspartate or L-cysteate, as well as in the presence of the poorly transported L-glutamate uptake inhibitor, L-anti-endo-methanopyrrolidine dicarboxylate. In experiments following [3-13C]alanine metabolism, all toxins caused a decreased incorporation of label into glutamate. Production of labelled lactate changed only when cells were incubated in the presence of L-alpha-aminoadipate or L-serine-O-sulphate. Incubation with L-anti-endo-methanopyrrolidine dicarboxylate caused no change in the amount of label incorporated into either glutamate or lactate. When glutathione production was followed using 1 mM [2-13C]glycine, differential effects of the gliotoxins were revealed. Most notably, both L-serine-O-sulphate and L-alpha-aminoadipate caused significant increases in labelling of glutathione. Once again, L-anti-endo-methanopyrrolidine dicarboxylate was without effect. Overall, we have shown that the gliotoxins cause disruption to alanine metabolism and glutathione production in C6 glioma cells, but that there are notable differences in their mechanisms of action. In the absence of any disruption to metabolism by L-anti-endo-methanopyrrolidine dicarboxylate, it is concluded that their mode of action involves more than inhibition of glutamate transport.
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Affiliation(s)
- Lorraine Brennan
- Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
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Abstract
The pathogenesis of hepatic encephalopathy (HE) remains elusive. While it is clear that ammonia is the likely toxin and that astrocytes are the main target of its neurotoxicity, precisely how ammonia brings about cellular injury is poorly understood. Studies over the past decade have invoked the concept of oxidative stress as a pathogenetic mechanism for ammonia neurotoxicity. This review sets out the arguments in support of this concept based on evidence derived from human observations, animal studies, and cell culture investigations. The consequences and potential therapeutic implications of oxidative stress in HE are also discussed.
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Affiliation(s)
- M D Norenberg
- Department of Pathology, University of Miami School of Medicine, Miami, Florida 33101, USA.
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García MV, López-Mediavilla C, Juanes de la Peña MC, Medina JM. Antioxidant defence of the neonatal rat brain against acute hyperammonemia. Brain Res 2004; 1001:159-63. [PMID: 14972665 DOI: 10.1016/j.brainres.2003.12.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2003] [Indexed: 11/25/2022]
Abstract
Oxidative stress associated with the presence of elevated concentrations of ammonia in the brain has been proposed as one possible mechanism involved in ammonia toxicity. In a previous study [Brain Res.973 (2003) 31], we reported that neonatal rats are more resistant to acute ammonia toxicity than adult rats. In the present work, we studied the antioxidant status of the brain in hyperammonemic neonatal rats. Increased activities of the antioxidant enzymes and enhanced glutathione content were found in the brains of the hyperammonemic neonatal rats as compared to the controls. In addition, no changes in brain reactive oxygen species (ROS) levels and lipid peroxidation due to hyperammonemia were found. Therefore, acute ammonia intoxication does not induce oxidative stress in neonatal rats, a fact that may explain the resistance against hyperammonemia shown by neonatal rats.
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Affiliation(s)
- M Victoria García
- Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Salamanca, Edificio Departamental, Plaza de los Doctores de la Reina s/n, E-37007 Salamanca, Spain
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34
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Bachmann C, Braissant O, Villard AM, Boulat O, Henry H. Ammonia toxicity to the brain and creatine. Mol Genet Metab 2004; 81 Suppl 1:S52-7. [PMID: 15050974 DOI: 10.1016/j.ymgme.2003.10.014] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2003] [Revised: 09/28/2003] [Accepted: 10/07/2003] [Indexed: 11/16/2022]
Abstract
Symptoms of hyperammonemia are age-dependent and some are reversible. Multiple mechanisms are involved. Hyperammonemia increases the uptake of tryptophan into the brain by activation of the L-system carrier while brain glutamine plays a still undefined role. The uptake of tryptophan by the brain is enhanced when the plasma levels of branched-chain amino acids competing with the other large neutral amino acids are low. Hyperammonemia increases the utilization of branched-chain amino acids in muscle when ketoglutarate is low, and this is further enhanced by glutamine depletion (as a result of therapy with ammonia scavengers like phenylbutyrate). Anorexia, most likely a serotoninergic symptom, might further aggravate the deficiency of indispensable amino acids (e.g., branched-chain and arginine). The role of increased glutamine production in astrocytes and the excitotoxic and metabotropic effects of increased extracellular glutamate have been extensively investigated and found to differ between models of acute and chronic hyperammonemia. Using an in vitro model of cultured embryonic rat brain cell aggregates, we studied the role of creatine in ammonia toxicity. Cultures exposed to ammonia before maturation showed impaired cholinergic axonal growth accompanied by a decrease of creatine and phosphocreatine, a finding not observed in mature cultures. By using different antibodies, we have shown that the phosphorylated form of the intermediate neurofilament protein is affected. Adding creatine to the culture medium partially prevents impairment of axonal growth and the presence of glia in the culture is a precondition for this protective effect. Adequate arginine substitution is essential in the treatment of urea cycle defects as creatine is inefficiently transported into the brain.
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Affiliation(s)
- Claude Bachmann
- Laboratoire Central de Chimie Clinique, Centre Hospitalier Universitaire Vaudois, University of Lausanne, LCC, CHUV, Bugnon 46, 1011 Lausanne, Switzerland.
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35
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Rama Rao KV, Jayakumar AR, Norenberg DM. Ammonia neurotoxicity: role of the mitochondrial permeability transition. Metab Brain Dis 2003; 18:113-27. [PMID: 12822830 DOI: 10.1023/a:1023858902184] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hepatic encephalopathy (HE) is an important cause of morbidity and mortality in patients with severe liver disease. Although the mechanisms responsible for HE remain elusive, ammonia is generally considered to be involved in its pathogenesis, and astrocytes are thought to be the principal target of ammonia neurotoxicity. Altered bioenergetics and oxidative stress are also thought to play a major role in this disorder. In this paper, we present data invoking the mitochondrial permeability transition (MPT) as a factor in the pathogenesis of HE/hyperammonemia. The MPT is a Ca2+-dependent, cyclosporin A (CsA) sensitive process due to the opening of a pore in the inner mitochondrial membrane that leads to a collapse of ionic gradients and ultimately to mitochondrial dysfunction. Many of the factors that facilitate the induction of the MPT are also known to be implicated in the mechanism of HE, including free radicals, Ca2+, nitric oxide, alkaline pH, and glutamine. We have recently shown that treatment of cultured astrocytes with 5 mM NH4Cl resulted in a dissipation of the mitochondrial membrane potential (delta(psi)m), which was sensitive to CsA. Similarly treated cultured neurons failed to show a loss of the delta(psi)m. Further support for the ammonia induction of the MPT was obtained by observing an increase in mitochondrial permeability to 2-deoxyglucose-6-phosphate, and a decrease in calcein fluorescence in astrocytes after ammonia treatment, both of which were also blocked by CsA. CsA was likewise capable of exerting a protective effect against hyperammonemia in mice. Taken together, our data suggest that the MPT represents an important component of the pathogenesis of HE and other hyperammonemic states.
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Affiliation(s)
- K V Rama Rao
- Department of Pathology, University of Miami School of Medicine, Miami, Florida 33101, USA
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Warskulat U, Görg B, Bidmon HJ, Müller HW, Schliess F, Häussinger D. Ammonia-induced heme oxygenase-1 expression in cultured rat astrocytes and rat brain in vivo. Glia 2002; 40:324-36. [PMID: 12420312 DOI: 10.1002/glia.10128] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Ammonia is a key factor in the pathogenesis of hepatic encephalopathy (HE), which is a major complication in acute and chronic liver failure and other hyperammonemic states. The molecular mechanisms underlying ammonia neurotoxicity and the functional consequences of ammonia on gene expression in astrocytes are incompletely understood. Using cDNA array hybridization technique we identified ammonia as a trigger of heme oxygenase-1 (HO-1) mRNA levels in cultured rat astrocytes. As shown by Northern and Western blot analysis, HO-1 mRNA levels were upregulated by ammonia (0.1-5 mmol/L) after 24 h and protein expression after 72 h in astrocytes. These ammonia effects on HO-1 are probably triggered to a minor extent by ammonia-induced glutamine synthesis or by astrocyte swelling, because HO-1 expression was not inhibited by the glutamine synthetase inhibitor methionine sulfoximine (which abrogated ammonia-induced cell swelling in cultured astrocytes), and ammonia-induced HO-1 expression could only partly be mimicked by hypoosmotic astrocyte swelling. Hypoosmotic (205 mOsm/L) exposure of astrocytes led even to a decrease in HO-1 mRNA levels within 4 h, whereas hyperosmotic (405 mOsm/L) exposure increased HO-1 mRNA expression. After 24 h, hypoosmolarity slightly raised HO-1 mRNA expression. Taurine and melatonin diminished ammonia-induced HO-1 mRNA or protein expression, whereas other antioxidants (dimethylthiourea, butylated hydroxytoluene, N-acetylcysteine, and reduced glutathione) increased HO-1 mRNA levels under ammonia-free conditions. An in vivo relevance is suggested by the finding that increased HO-1 expression occurs in the brain cortex from acutely ammonia-intoxicated rats. It is concluded that ammonia-induced HO-1 expression may contribute to cerebral hyperemia in hyperammonic states.
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Affiliation(s)
- Ulrich Warskulat
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich Heine University, Düsseldorf, Germany.
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37
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Abstract
Hyperammonemia is mainly found in hepatic encephalopathy and in genetic defects of the urea cycle or other pathways of the intermediary metabolism. Clinically a difference has to be made between chronic moderate hyperammonemia and acutely increased concentrations. Pathogenetic mechanisms of ammonia toxicity to the brain are partly unraveled. In some animal models confounding variables, such as the reduced intake of food and amino acid imbalance due to liver insufficiency, do not allow to establish unequivocal causal relationships between the ammonia concentration and measured effects. In chronic moderate hyperammonemia an increased flux through the serotonin pathway is a key factor. It is caused by an increased transport of large neutral amino acids (including tryptophan) through the blood-brain barrier, accentuated by the imbalance of plasma amino acids in hepatic insufficiency. It is stimulated by D- or L-glutamine. Evidence is presented showing that a functioning gamma-glutamyl cycle (glutathione formation) is a prerequisite. In acute hyperammonemia involvement of NMDA receptors, glutamate, NO and cGMP plays an additional role. In hyperammonemic crises the increased cerebral blood flow leads to brain edema; factors discussed here are increased osmolytes in astrocytes and serotoninergic activity. Recent data indicate that axonal development is affected by ammonia and can be normalized in vitro by creatine supplementation in developing mixed brain cell aggregate cultures, thus reviving the old hypothesis of the impact of hyperammonemia on energy metabolism in the developing brain that could cause mental retardation.
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Affiliation(s)
- Claude Bachmann
- Laboratoire Central de Chimie Clinique, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Switzerland.
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38
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Britto DT, Kronzucker HJ. NH4+ toxicity in higher plants: a critical review. JOURNAL OF PLANT PHYSIOLOGY 2002. [PMID: 0 DOI: 10.1078/0176-1617-0774] [Citation(s) in RCA: 660] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
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Murthy CR, Rama Rao KV, Bai G, Norenberg MD. Ammonia-induced production of free radicals in primary cultures of rat astrocytes. J Neurosci Res 2001; 66:282-8. [PMID: 11592125 DOI: 10.1002/jnr.1222] [Citation(s) in RCA: 214] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Elevated levels of ammonia in blood and brain result in derangement of cerebral function. Recently, lipid peroxidation and oxidative stress have been implicated in ammonia neurotoxicity. Because ammonia is primarily detoxified in astrocytes, we postulated that pathophysiological concentrations of ammonia might induce free radical formation in these cells. To test this hypothesis, we examined the extent of free radical production in primary cultures of astrocytes that had been preloaded with the fluorescent dye 5- (and 6-)carboxy-2',7'-dichlorodihydrofluorescein diacetate (DCFDA). DCFDA fluorescence was found to be increased in a dose-dependent manner when astrocytes were exposed to 1, 5, and 10 mM NH(4)Cl. This phenomenon was transitory; it peaked at 2.5 min after exposure and declined subsequently. By 2 hr after treatment, DCFDA fluorescence was below control level. Addition of catalase or superoxide dismutase to 5 mM NH(4)Cl-treated astrocytes reduced free radical formation. Pretreatment with 3 mM methionine sulfoximine, an inhibitor of glutamine synthetase, also suppressed free radical formation by 5 mM NH(4)Cl. The results of this study suggest that elevated concentrations of ammonia induce the formation of free radicals in astrocytes and that this process is associated with the synthesis of glutamine. We propose that astrocyte-derived free radicals may be responsible for some of the pathophysiological changes associated with hyperammonemic conditions.
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Affiliation(s)
- C R Murthy
- Department of Animal Sciences, University of Hyderabad, Hyderabad, India
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