1
|
Sokolova TV, Rychkova MP, Avrova NF, Yefimova MG. Oxidative Stress Modulates Apoptotic
Substrate Phagocytosis by Primary Rat Astrocytes. J EVOL BIOCHEM PHYS+ 2020. [DOI: 10.1134/s0022093020060022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
2
|
Hydrogen Peroxide Gates a Voltage-Dependent Cation Current in Aplysia Neuroendocrine Cells. J Neurosci 2019; 39:9900-9913. [PMID: 31676600 DOI: 10.1523/jneurosci.1460-19.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 10/07/2019] [Accepted: 10/27/2019] [Indexed: 11/21/2022] Open
Abstract
Nonselective cation channels promote persistent spiking in many neurons from a diversity of animals. In the hermaphroditic marine-snail, Aplysia californica, synaptic input to the neuroendocrine bag cell neurons triggers various cation channels, causing an ∼30 min afterdischarge of action potentials and the secretion of egg-laying hormone. During the afterdischarge, protein kinase C is also activated, which in turn elevates hydrogen peroxide (H2O2), likely by stimulating nicotinamide adenine dinucleotide phosphate oxidase. The present study investigated whether H2O2 regulates cation channels to drive the afterdischarge. In single, cultured bag cell neurons, H2O2 elicited a prolonged, concentration- and voltage-dependent inward current, associated with an increase in membrane conductance and a reversal potential of ∼+30 mV. Compared with normal saline, the presence of Ca2+-free, Na+-free, or Na+/Ca2+-free extracellular saline, lowered the current amplitude and left-shifted the reversal potential, consistent with a nonselective cationic conductance. Preventing H2O2 reduction with the glutathione peroxidase inhibitor, mercaptosuccinate, enhanced the H2O2-induced current, while boosting glutathione production with its precursor, N-acetylcysteine, or adding the reducing agent, dithiothreitol, lessened the response. Moreover, the current generated by the alkylating agent, N-ethylmaleimide, occluded the effect of H2O2 The H2O2-induced current was inhibited by tetrodotoxin as well as the cation channel blockers, 9-phenanthrol and clotrimazole. In current-clamp, H2O2 stimulated burst firing, but this was attenuated or prevented altogether by the channel blockers. Finally, H2O2 evoked an afterdischarge from whole bag cell neuron clusters recorded ex vivo by sharp-electrode. H2O2 may regulate a cation channel to influence long-term changes in activity and ultimately reproduction.SIGNIFICANCE STATEMENT Hydrogen peroxide (H2O2) is often studied in a pathological context, such as ischemia or inflammation. However, H2O2 also physiologically modulates synaptic transmission and gates certain transient receptor potential channels. That stated, the effect of H2O2 on neuronal excitability remains less well defined. Here, we examine how H2O2 influences Aplysia bag cell neurons, which elicit ovulation by releasing hormones during an afterdischarge. These neuroendocrine cells are uniquely identifiable and amenable to recording as individual cultured neurons or a cluster from the nervous system. In both culture and the cluster, H2O2 evokes prolonged, afterdischarge-like bursting by gating a nonselective voltage-dependent cationic current. Thus, H2O2, which is generated in response to afterdischarge-associated second messengers, may prompt the firing necessary for hormone secretion and procreation.
Collapse
|
3
|
Beyrent E, Gomez G. Oxidative stress differentially induces tau dissociation from neuronal microtubules in neurites of neurons cultured from different regions of the embryonic Gallus domesticus brain. J Neurosci Res 2019; 98:734-747. [PMID: 31621106 DOI: 10.1002/jnr.24541] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 10/01/2019] [Accepted: 10/01/2019] [Indexed: 12/27/2022]
Abstract
Abnormal phosphorylation of microtubule-associated proteins such as tau has been shown to play a role in neurodegenerative disorders. It is hypothesized that oxidative stress-induced aggregates of hyperphosphorylated tau could lead to the microtubule network degradation commonly associated with neurodegeneration. We investigated whether oxidative stress induced tau hyperphosphorylation and focused on neurite degradation using cultured neurons isolated from the embryonic chick brain as a model system. Cells were isolated from the cerebrum, cerebellum, and tectum of 14-day-old chicks, grown separately in culture, and treated with tert-Butyl hydroperoxide (to simulate oxidative stress) for 48 hr. Relative expression and localization of tau or phospho-tau and β-tubulin III in neurites were determined using quantitative immunocytochemistry and confocal microscopy. In untreated cells, tau was tightly colocalized with β-tubulin III. Increasing levels of oxidative stress induced an increase in overall tau expression in neurites of cerebral and tectal but not the cerebellar neurons, coupled with a decrease in phospho-tau expression in tectal but not the cerebral or cerebellar neurons. In addition, oxidative stress induced the degeneration of the distal ends of the neurites and redistribution of phospho-tau toward the neuronal soma in the cerebral but not the tectal and cerebellar neurons. These results suggest that oxidative stress induces changes in tau protein that precede cytoskeletal degradation and neurite retraction. Additionally, there is a differential susceptibility of neuronal subpopulations to oxidative stress, which may offer potential avenues for investigation of the cellular mechanisms underlying the differential manifestations of neurodegenerative disorders in different regions of the brain.
Collapse
Affiliation(s)
- Erika Beyrent
- Biology Department, University of Scranton, Scranton, PA, USA
| | - George Gomez
- Biology Department, University of Scranton, Scranton, PA, USA
| |
Collapse
|
4
|
Interleukin-1β Protects Neurons against Oxidant-Induced Injury via the Promotion of Astrocyte Glutathione Production. Antioxidants (Basel) 2018; 7:antiox7080100. [PMID: 30044427 PMCID: PMC6115796 DOI: 10.3390/antiox7080100] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/04/2018] [Accepted: 07/21/2018] [Indexed: 01/13/2023] Open
Abstract
Interleukin-1β (IL-1β), a key cytokine that drives neuroinflammation in the Central Nervous System (CNS), is enhanced in many neurological diseases/disorders. Although IL-1β contributes to and/or sustains pathophysiological processes in the CNS, we recently demonstrated that IL-1β can protect cortical astrocytes from oxidant injury in a glutathione (GSH)-dependent manner. To test whether IL-1β could similarly protect neurons against oxidant stress, near pure neuronal cultures or mixed cortical cell cultures containing neurons and astrocytes were exposed to the organic peroxide, tert-butyl hydroperoxide (t-BOOH), following treatment with IL-1β or its vehicle. Neurons and astrocytes in mixed cultures, but not pure neurons, were significantly protected from the toxicity of t-BOOH following treatment with IL-1β in association with enhanced GSH production/release. IL-1β failed to increase the GSH levels or to provide protection against t-BOOH toxicity in chimeric mixed cultures consisting of IL-1R1+/+ neurons plated on top of IL-1R1−/− astrocytes. The attenuation of GSH release via block of multidrug resistance-associated protein 1 (MRP1) transport also abrogated the protective effect of IL-1β. These protective effects were not strictly an in vitro phenomenon as we found an increased striatal vulnerability to 3-nitropropionic acid-mediated oxidative stress in IL-1R1 null mice. Overall, our data indicate that IL-1β protects neurons against oxidant injury and that this likely occurs in a non-cell-autonomous manner that relies on an increase in astrocyte GSH production and release.
Collapse
|
5
|
Almeida AS, Soares NL, Sequeira CO, Pereira SA, Sonnewald U, Vieira HLA. Improvement of neuronal differentiation by carbon monoxide: Role of pentose phosphate pathway. Redox Biol 2018; 17:338-347. [PMID: 29793167 PMCID: PMC6007049 DOI: 10.1016/j.redox.2018.05.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 04/24/2018] [Accepted: 05/10/2018] [Indexed: 12/13/2022] Open
Abstract
Over the last decades, the silent-killer carbon monoxide (CO) has been shown to also be an endogenous cytoprotective molecule able to inhibit cell death and modulate mitochondrial metabolism. Neuronal metabolism is mostly oxidative and neurons also use glucose for maintaining their anti-oxidant status by generation of reduced glutathione (GSH) via the pentose-phosphate pathway (PPP). It is established that neuronal differentiation depends on reactive oxygen species (ROS) generation and signalling, however there is a lack of information about modulation of the PPP during adult neurogenesis. Thus, the main goal of this study was to unravel the role of CO on cell metabolism during neuronal differentiation, particularly by targeting PPP flux and GSH levels as anti-oxidant system. A human neuroblastoma SH-S5Y5 cell line was used, which differentiates into post-mitotic neurons by treatment with retinoic acid (RA), supplemented or not with CO-releasing molecule-A1 (CORM-A1). SH-SY5Y cell differentiation supplemented with CORM-A1 prompted an increase in neuronal yield production. It did, however, not alter glycolytic metabolism, but increased the PPP. In fact, CORM-A1 treatment stimulated (i) mRNA expression of 6-phosphogluconate dehydrogenase (PGDH) and transketolase (TKT), which are enzymes for oxidative and non-oxidative phases of the PPP, respectively and (ii) protein expression and activity of glucose 6-phosphate dehydrogenase (G6PD) the rate-limiting enzyme of the PPP. Likewise, whenever G6PD was knocked-down CO-induced improvement on neuronal differentiation was reverted, while pharmacological inhibition of GSH synthesis did not change CO's effect on the improvement of neuronal differentiation. Both results indicate the key role of PPP in CO-modulation of neuronal differentiation. Furthermore, at the end of SH-SY5Y neuronal differentiation process, CORM-A1 supplementation increased the ratio of reduced and oxidized glutathione (GSH/GSSG) without alteration of GSH metabolism. These data corroborate with PPP stimulation. In conclusion, CO improves neuronal differentiation of SH-S5Y5 cells by stimulating the PPP and modulating the GSH system.
Collapse
Affiliation(s)
- Ana S Almeida
- CEDOC, Faculdade de Ciência Médicas/NOVA Medical School, Universidade Nova de Lisboa, 1169-056 Lisboa, Portugal; Instituto de Tecnologia Química e Biológica (ITQB), Universidade Nova de Lisboa, Apartado 127, 2781-901 Oeiras, Portugal; Instituto de Biologia Experimental e Tecnológica (iBET), Apartado 12, 2781-901 Oeiras, Portugal
| | - Nuno L Soares
- CEDOC, Faculdade de Ciência Médicas/NOVA Medical School, Universidade Nova de Lisboa, 1169-056 Lisboa, Portugal
| | - Catarina O Sequeira
- CEDOC, Faculdade de Ciência Médicas/NOVA Medical School, Universidade Nova de Lisboa, 1169-056 Lisboa, Portugal
| | - Sofia A Pereira
- CEDOC, Faculdade de Ciência Médicas/NOVA Medical School, Universidade Nova de Lisboa, 1169-056 Lisboa, Portugal
| | | | - Helena L A Vieira
- CEDOC, Faculdade de Ciência Médicas/NOVA Medical School, Universidade Nova de Lisboa, 1169-056 Lisboa, Portugal; Instituto de Biologia Experimental e Tecnológica (iBET), Apartado 12, 2781-901 Oeiras, Portugal.
| |
Collapse
|
6
|
Rizvi F, Mathur A, Krishna S, Siddiqi MI, Kakkar P. Suppression in PHLPP2 induction by morin promotes Nrf2-regulated cellular defenses against oxidative injury to primary rat hepatocytes. Redox Biol 2015; 6:587-598. [PMID: 26513344 PMCID: PMC4633887 DOI: 10.1016/j.redox.2015.10.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 10/12/2015] [Accepted: 10/12/2015] [Indexed: 11/15/2022] Open
Abstract
Recent advances indicate a possible role of phytochemicals as modulatory factors in signaling pathways. We have previously demonstrated PHLPP2-mediated suppression of Nrf2 responses during oxidant attack. The present study was designed to explore Nrf2-potentiating mechanism of morin, a flavonol, via its possible role in intervening PHLPP2-regulated Akt/GSK3β/Fyn kinase axis. Efficacy of morin was evaluated against oxidative stress-mediated damage to primary hepatocytes by tert-butyl hydroperoxide (tBHP) and acetaminophen. The anti-cytotoxic effects of morin were found to be a consequence of fortification of Nrf2-regulated antioxidant defenses since morin failed to sustain activities of redox enzyme in Nrf2 silenced hepatocytes. Morin promoted Nrf2 stability and its nuclear retention by possibly modulating PHLPP2 activity which subdues cellular Nrf2 responses by activating Fyn kinase. Pull-down assay using morin-conjugated beads indicated the binding affinity of morin towards PHLPP2. Molecular docking also revealed the propensity of morin to occupy the active site of PHLPP2 enzyme. Thus, dietary phytochemical morin was observed to counteract oxidant-induced hepatocellular damage by promoting Nrf2-regulated transcriptional induction. The findings support the novel role of morin in potentiating Nrf2 responses by limiting PHLPP2 and hence Fyn kinase activation. Therefore, morin may be exploited in developing novel therapeutic strategy aimed at enhancing Nrf2 responses. Cytoprotection against tBHP-evoked oxidative stress by morin is Nrf2-regulated. Morin prevents Nrf2-destabilization via PHLPP2-Akt-GSK3β-Fyn kinase pathway. In silico docking studies confirmed PHLPP2 activity inhibition by morin. Morin mitigates APAP induced cytotoxicity by suppressing PHLPP2 pathway.
Collapse
Affiliation(s)
- Fatima Rizvi
- Herbal Research Laboratory, Food Drug and Chemical Toxicology Group, Council of Scientific and Industrial Research-Indian Institute of Toxicology Research (CSIR-IITR), Post Box No. 80, M.G. Marg, Lucknow 226001, Uttar Pradesh, India; Academy of Scientific and Innovative Research, CSIR-IITR campus, Lucknow, India
| | - Alpana Mathur
- Herbal Research Laboratory, Food Drug and Chemical Toxicology Group, Council of Scientific and Industrial Research-Indian Institute of Toxicology Research (CSIR-IITR), Post Box No. 80, M.G. Marg, Lucknow 226001, Uttar Pradesh, India
| | - Shagun Krishna
- Molecular and Structural Biology Division, Council of Scientific and Industrial Research-Central Drug Research Institute (CSIR-CDRI), Lucknow 226031, Uttar Pradesh, India
| | - Mohammad Imran Siddiqi
- Molecular and Structural Biology Division, Council of Scientific and Industrial Research-Central Drug Research Institute (CSIR-CDRI), Lucknow 226031, Uttar Pradesh, India
| | - Poonam Kakkar
- Herbal Research Laboratory, Food Drug and Chemical Toxicology Group, Council of Scientific and Industrial Research-Indian Institute of Toxicology Research (CSIR-IITR), Post Box No. 80, M.G. Marg, Lucknow 226001, Uttar Pradesh, India; Academy of Scientific and Innovative Research, CSIR-IITR campus, Lucknow, India.
| |
Collapse
|
7
|
Chiu SC, Lin YJ, Huang SY, Lien CF, Chen SP, Pang CY, Lin JH, Yang KT. The Role of Intermittent Hypoxia on the Proliferative Inhibition of Rat Cerebellar Astrocytes. PLoS One 2015; 10:e0132263. [PMID: 26172116 PMCID: PMC4501806 DOI: 10.1371/journal.pone.0132263] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2015] [Accepted: 06/11/2015] [Indexed: 01/28/2023] Open
Abstract
Sleep apnea syndrome, characterized by intermittent hypoxia (IH), is linked with increased oxidative stress. This study investigates the mechanisms underlying IH and the effects of IH-induced oxidative stress on cerebellar astrocytes. Rat primary cerebellar astrocytes were kept in an incubator with an oscillating O2 concentration between 20% and 5% every 30 min for 1–4 days. Although the cell loss increased with the duration, the IH incubation didn’t induce apoptosis or necrosis, but rather a G0/G1 cell cycle arrest of cerebellar astrocytes was noted. ROS accumulation was associated with cell loss during IH. PARP activation, resulting in p21 activation and cyclin D1 degradation was associated with cell cycle G0/G1 arrest of IH-treated cerebellar astrocytes. Our results suggest that IH induces cell loss by enhancing oxidative stress, PARP activation and cell cycle G0/G1 arrest in rat primary cerebellar astrocytes.
Collapse
Affiliation(s)
- Sheng-Chun Chiu
- Department of Research, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan
| | - Yu-Jou Lin
- Physiological and Anatomical Medicine, School of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Sung-Ying Huang
- Department of Ophthalmology, Mackay Memorial Hospital, Hsinchu, Taiwan
| | - Chih-Feng Lien
- Institute of Medical Sciences, School of Medicine, Tzu Chi University, Hualien, Taiwan
| | - Shee-Ping Chen
- Tzu Chi Stem Cells Center, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - Cheng-Yoong Pang
- Institute of Medical Sciences, School of Medicine, Tzu Chi University, Hualien, Taiwan
- Department of Medical Research, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien, Taiwan
| | - Jian-Hong Lin
- PhD program in Pharmacology and Toxicology, Tzu Chi University, Hualien, Taiwan
| | - Kun-Ta Yang
- Physiological and Anatomical Medicine, School of Medicine, Tzu Chi University, Hualien, Taiwan
- Department of Physiology, School of Medicine, Tzu Chi University, Hualien, Taiwan
- * E-mail:
| |
Collapse
|
8
|
He Y, Jackman NA, Thorn TL, Vought VE, Hewett SJ. Interleukin-1β protects astrocytes against oxidant-induced injury via an NF-κB-dependent upregulation of glutathione synthesis. Glia 2015; 63:1568-80. [PMID: 25880604 DOI: 10.1002/glia.22828] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 03/12/2015] [Indexed: 01/17/2023]
Abstract
Astrocytes produce and export the antioxidant glutathione (GSH). Previously, we found that interleukin-1β (IL-1β) enhanced the expression of astrocyte system xc (-) , the transporter that delivers the rate-limiting substrate for GSH synthesis-cyst(e)ine. Herein, we demonstrate directly that IL-1β mediates a time-dependent increase in extracellular GSH levels in cortical astrocyte cultures, suggesting both enhanced synthesis and export. This increased GSH production was blocked by inhibition of nuclear factor-κB (NF-κB) activity but not by inhibition of p38 MAPK. To determine whether this increase could provide protection against oxidative stress, the oxidants tert-butyl hydroperoxide (tBOOH) and ferrous sulfate (FeSO4 ) were employed. IL-1β treatment prevented the increase in reactive oxygen species produced in astrocytes following tBOOH exposure. Additionally, the toxicity induced by tBOOH or FeSO4 exposure was significantly attenuated following treatment with IL-1β, an effect reversed by concomitant exposure to l-buthionine-S,R-sulfoximine (BSO), which prevented the IL-1β-mediated rise in GSH production. IL-1β failed to increase GSH or to provide protection against t-BOOH toxicity in astrocyte cultures derived from IL-1R1 null mutant mice. Overall, our data indicate that under certain conditions IL-1β may be an important stimulus for increasing astrocyte GSH production, and potentially, total antioxidant capacity in brain, via an NF-κB-dependent process.
Collapse
Affiliation(s)
- Yan He
- Department of Biology and Program in Neuroscience, Syracuse University, Syracuse, New York
| | - Nicole A Jackman
- Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut
| | - Trista L Thorn
- Department of Biology and Program in Neuroscience, Syracuse University, Syracuse, New York
| | - Valarie E Vought
- Department of Biology and Program in Neuroscience, Syracuse University, Syracuse, New York
| | - Sandra J Hewett
- Department of Biology and Program in Neuroscience, Syracuse University, Syracuse, New York
| |
Collapse
|
9
|
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.
Collapse
|
10
|
Singh B, Das RS, Banerjee R, Mukhopadhyay S. Uncatalyzed and copper(II) catalyzed oxidation of glutathione by Co(III)2 bound superoxide complex. Inorganica Chim Acta 2014. [DOI: 10.1016/j.ica.2014.03.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
11
|
Generation of hydrogen peroxide-resistant murine neuroblastoma cells: a target discovery platform for novel neuroprotective genes. J Neural Transm (Vienna) 2013; 120:1171-8. [DOI: 10.1007/s00702-013-0995-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 02/09/2013] [Indexed: 10/27/2022]
|
12
|
|
13
|
Positive allosteric modulation of metabotropic glutamate receptor 5 down-regulates fibrinogen-activated microglia providing neuronal protection. Neurosci Lett 2011; 505:140-5. [PMID: 22015768 DOI: 10.1016/j.neulet.2011.10.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 09/30/2011] [Accepted: 10/03/2011] [Indexed: 12/19/2022]
Abstract
Microglial activation and blood brain barrier dysfunction are significant hallmarks in an array of neurodegenerative disorders. A leaky blood brain barrier potentially allows infiltration of blood-borne proteins into the CNS parenchyma, and previous studies have shown that the blood borne protein fibrinogen (FG) can activate microglia to produce a neurotoxic phenotype. Here we show that FG-mediated neurotoxicity and ERK1/2 phosphorylation in neuronal cultures is significantly attenuated by activation of metabotropic glutamate receptor 5 (mGluR5) but not mGluR2. Furthermore, FG-mediated microglial activation was down-regulated by direct mGluR5 activation on these cells but not by mGluR2, suggesting that targeting microglial mGluR5 provides neuronal protection against blood protein-triggered innate inflammatory responses.
Collapse
|
14
|
Macrophage replication screen identifies a novel Francisella hydroperoxide resistance protein involved in virulence. PLoS One 2011; 6:e24201. [PMID: 21915295 PMCID: PMC3167825 DOI: 10.1371/journal.pone.0024201] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 08/02/2011] [Indexed: 11/25/2022] Open
Abstract
Francisella tularensis is a Gram-negative facultative intracellular pathogen and the causative agent of tularemia. Recently, genome-wide screens have identified Francisella genes required for virulence in mice. However, the mechanisms by which most of the corresponding proteins contribute to pathogenesis are still largely unknown. To further elucidate the roles of these virulence determinants in Francisella pathogenesis, we tested whether each gene was required for replication of the model pathogen F. novicida within macrophages, an important virulence trait. Fifty-three of the 224 genes tested were involved in intracellular replication, including many of those within the Francisella pathogenicity island (FPI), validating our results. Interestingly, over one third of the genes identified are annotated as hypothetical, indicating that F. novicida likely utilizes novel virulence factors for intracellular replication. To further characterize these virulence determinants, we selected two hypothetical genes to study in more detail. As predicted by our screen, deletion mutants of FTN_0096 and FTN_1133 were attenuated for replication in macrophages. The mutants displayed differing levels of attenuation in vivo, with the FTN_1133 mutant being the most attenuated. FTN_1133 has sequence similarity to the organic hydroperoxide resistance protein Ohr, an enzyme involved in the bacterial response to oxidative stress. We show that FTN_1133 is required for F. novicida resistance to, and degradation of, organic hydroperoxides as well as resistance to the action of the NADPH oxidase both in macrophages and mice. Furthermore, we demonstrate that F. holarctica LVS, a strain derived from a highly virulent human pathogenic species of Francisella, also requires this protein for organic hydroperoxide resistance as well as replication in macrophages and mice. This study expands our knowledge of Francisella's largely uncharacterized intracellular lifecycle and demonstrates that FTN_1133 is an important novel mediator of oxidative stress resistance.
Collapse
|
15
|
Lavoie S, Allaman I, Petit JM, Do KQ, Magistretti PJ. Altered glycogen metabolism in cultured astrocytes from mice with chronic glutathione deficit; relevance for neuroenergetics in schizophrenia. PLoS One 2011; 6:e22875. [PMID: 21829542 PMCID: PMC3145770 DOI: 10.1371/journal.pone.0022875] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 07/03/2011] [Indexed: 01/12/2023] Open
Abstract
Neurodegenerative and psychiatric disorders including Alzheimer's, Parkinson's or Huntington's diseases and schizophrenia have been associated with a deficit in glutathione (GSH). In particular, a polymorphism in the gene of glutamate cysteine ligase modulatory subunit (GCLM) is associated with schizophrenia. GSH is the most important intracellular antioxidant and is necessary for the removal of reactive by-products generated by the utilization of glucose for energy supply. Furthermore, glucose metabolism through the pentose phosphate pathway is a major source of NADPH, the cofactor necessary for the regeneration of reduced glutathione. This study aims at investigating glucose metabolism in cultured astrocytes from GCLM knockout mice, which show decreased GSH levels. No difference in the basal metabolism of glucose was observed between wild-type and knockout cells. In contrast, glycogen levels were lower and its turnover was higher in knockout astrocytes. These changes were accompanied by a decrease in the expression of the genes involved in its synthesis and degradation, including the protein targeting to glycogen. During an oxidative challenge induced by tert-Butylhydroperoxide, wild-type cells increased their glycogen mobilization and glucose uptake. However, knockout astrocytes were unable to mobilize glycogen following the same stress and they could increase their glucose utilization only following a major oxidative insult. Altogether, these results show that glucose metabolism and glycogen utilization are dysregulated in astrocytes showing a chronic deficit in GSH, suggesting that alterations of a fundamental aspect of brain energy metabolism is caused by GSH deficit and may therefore be relevant to metabolic dysfunctions observed in schizophrenia.
Collapse
Affiliation(s)
- Suzie Lavoie
- Department of Psychiatry, University Hospital Centre and University of Lausanne, Lausanne, Switzerland.
| | | | | | | | | |
Collapse
|
16
|
Liddell JR, Zwingmann C, Schmidt MM, Thiessen A, Leibfritz D, Robinson SR, Dringen R. Sustained hydrogen peroxide stress decreases lactate production by cultured astrocytes. J Neurosci Res 2010; 87:2696-708. [PMID: 19382228 DOI: 10.1002/jnr.22093] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Oxidative stress and disrupted energy metabolism are common to many pathological conditions of the brain. Because astrocytes play an important role in the glucose metabolism of the brain, we have investigated whether sustained oxidative stress affects astroglial glucose metabolism with cultured primary rat astrocytes as a model system. Cultured astrocytes were exposed to a sustained concentration of approximately 50 muM H(2)O(2) in the presence of [U-(13)C]glucose, and cellular and extracellular contents of lactate and glucose were analysed by enzymatic assays and NMR spectroscopy. Exposure of the cells to sustained H(2)O(2) stress for up to 120 min significantly lowered the rate of lactate accumulation in the media to 61% +/- 14% of that in cultures incubated without peroxide. In addition, the ratio of lactate release to glucose consumption was lowered in peroxide-treated astrocytes to 77% +/- 13% of that in control cells, and the specific activity of glyceraldehyde-3-phosphate dehydrogenase had declined to about 10% of control cells within 90 min. In addition, the (13)C enrichment of intracellular and extracellular [(13)C]lactate was about 30% and 95%, respectively, and was not affected by the presence of peroxide, demonstrating that two metabolic pools of lactate are present in cultured astrocytes. The decreased rate of lactate production by astrocytes that have been exposed to peroxide stress is a new example of an alteration by oxidative stress of an important metabolic pathway in astrocytes. Such alterations could contribute to the pathological conditions that have been connected with oxidative stress and disrupted energy metabolism in the brain.
Collapse
Affiliation(s)
- Jeff R Liddell
- School of Psychology, Psychiatry, and Psychological Medicine, Monash University, Clayton, Victoria, Australia
| | | | | | | | | | | | | |
Collapse
|
17
|
The cytosolic redox state of astrocytes: Maintenance, regulation and functional implications for metabolite trafficking. ACTA ACUST UNITED AC 2009; 63:177-88. [PMID: 19883686 DOI: 10.1016/j.brainresrev.2009.10.003] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 10/24/2009] [Accepted: 10/27/2009] [Indexed: 12/31/2022]
Abstract
Astrocytes have important functions in the metabolism of the brain. These cells provide neurons with metabolic substrates for energy production as well as with precursors for neurotransmitter and glutathione synthesis. Both the metabolism of astrocytes and the subsequent supply of metabolites from astrocytes to neurons are strongly affected by alterations in the cellular redox state. The cytosolic redox state of astrocytes depends predominantly on the ratios of the oxidised and reduced partners of the redox pairs NADH/NAD(+), NADPH/NADP(+) and GSH/GSSG. The NADH/NAD(+) pair is predominately in the oxidised state to accept electrons that are produced during glycolysis. In contrast, the redox pairs NADPH/NADP(+) and GSH/GSSG are biased towards the reduced state under unstressed conditions to provide electrons for reductive biosyntheses and antioxidative processes, respectively. In this review article we describe the metabolic processes that maintain the redox pairs in their desired redox states in the cytosol of astrocytes and discuss the consequences of alterations of the normal redox state for the regulation of cellular processes and for metabolite trafficking from astrocytes to neurons.
Collapse
|
18
|
Walther UI, Mückter H. GLUTATHIONE SYNTHESIS AGAINST OXIDANT INJURY BY PEROXIDES IN TWO ALVEOLAR EPITHELIAL CELL LINES. Exp Lung Res 2009; 35:89-103. [DOI: 10.1080/01902140802441569] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
19
|
Walther UI, Stets R. Glucocorticoid pretreatment increases toxicity due to peroxides in alveolar epithelial-like cell lines. Toxicology 2008; 256:48-52. [PMID: 19056457 DOI: 10.1016/j.tox.2008.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Revised: 10/13/2008] [Accepted: 11/03/2008] [Indexed: 10/21/2022]
Abstract
In previous experiments an increase in zinc-mediated toxicity was found after pretreatment of alveolar epithelial type II-like cells with glucocorticoids. In this work toxicity of two peroxides (tertiary butyl hydroperoxide [tBHP], hydrogene peroxide [HP]) was assessed in L2 and A549 cells compared to dexamethasone (DEX) pretreated cells. Pretreatment of cells with 7.5micromol/l DEX for 72h decreased cellular glutathione content in both cell lines. Furthermore compared to not pretreated cells toxicity of both peroxides was increased in A549 cells, while in L2 cells only toxicity of tBHP was significantly increased by the glucocorticoid pretreatment. HP toxicity only showed a tendency to be increased in L2 cells after DEX pretreatment. The results point to a glucocorticoid-dependent increased oxidative stress of alveolar epithelial type II cells as antagonised by antioxidative enzymes such as catalase and/or preferentially by the glutathione system. This furthermore should be considered for all glucocorticoid applications in vivo as well.
Collapse
Affiliation(s)
- Udo I Walther
- Walther-Straub-Institut für Pharmakologie und Toxikologie der Ludwig-Maximilians-Universität München, Nussbaumstr. 26, 80336 München, Germany.
| | | |
Collapse
|
20
|
Kalia S, Bansal M. p53 is involved in inducing testicular apoptosis in mice by the altered redox status following tertiary butyl hydroperoxide treatment. Chem Biol Interact 2008; 174:193-200. [DOI: 10.1016/j.cbi.2008.06.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 06/04/2008] [Accepted: 06/10/2008] [Indexed: 11/27/2022]
|
21
|
Makino N, Mise T, Sagara JI. Kinetics of hydrogen peroxide elimination by astrocytes and C6 glioma cells analysis based on a mathematical model. Biochim Biophys Acta Gen Subj 2008; 1780:927-36. [PMID: 18402782 DOI: 10.1016/j.bbagen.2008.03.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Revised: 02/19/2008] [Accepted: 03/13/2008] [Indexed: 10/22/2022]
Abstract
Oxidative stress is implicated in a variety of disorders including neurodegenerative diseases, and H(2)O(2) is important in the generation of reactive oxygen and oxidative stress. In this study, we have examined the rate of extracellular H(2)O(2) elimination and relevant enzyme activities in cultured astrocytes and C6 glioma cells and have analyzed the results based on a mathematical model. As compared with other types of cultured cells, astrocytes showed higher activity of glutathione peroxidase (GPx) but lower activities for GSH recycling. C6 cells showed relatively low GPx activity, and treatment of C6 cells with dibutyryl-cAMP, which induces astrocytic differentiation, increased catalase activity and H(2)O(2) permeation rate but exerted little effect on other enzyme activities. A mathematical model [N. Makino, K. Sasaki, N. Hashida, Y. Sakakura, A metabolic model describing the H(2)O(2) elimination by mammalian cells including H(2)O(2) permeation through cytoplasmic and peroxisomal membranes: comparison with experimental data, Biochim. Biophys. Acta 1673 (2004) 149-159.], which includes relevant enzymes and H(2)O(2) permeation through membranes, was found to be fitted well to the H(2)O(2) concentration dependences of removal reaction with the permeation rate constants as variable parameters. As compared with PC12 cells as a culture model for neuron, H(2)O(2) removal activity of astrocytes was considerably higher at physiological H(2)O(2) concentrations. The details of the mathematical model are presented in Appendix.
Collapse
Affiliation(s)
- Nobuo Makino
- Center for Humanity and Sciences, Ibaraki Prefectural University of Health Sciences, Ami 4669-2, Ami, Ibaraki 300-0394, Japan.
| | | | | |
Collapse
|
22
|
Zhang P, Hatter A, Liu B. Manganese chloride stimulates rat microglia to release hydrogen peroxide. Toxicol Lett 2007; 173:88-100. [PMID: 17669604 PMCID: PMC2100035 DOI: 10.1016/j.toxlet.2007.06.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2007] [Revised: 06/21/2007] [Accepted: 06/21/2007] [Indexed: 12/21/2022]
Abstract
Elevated exposure to manganese is known to cause neurodegeneration in the basal ganglia and to induce movement abnormalities called manganism. However, the underlying mechanism of action is not fully understood. Activation of the resident immune cells in the brain, microglia that release a variety of neurotoxic factors, has been implicated to contribute to neurodegeneration. Of the various neurotoxic factors released by activated microglia, reactive oxygen species such as superoxide and hydrogen peroxide are particularly detrimental to the survival of the oxidative damage-prone neurons. In this study, we report that exposure of rat microglia to manganese chloride (MnCl(2)) resulted in a time- and concentration-dependent release of hydrogen peroxide (H(2)O(2)). The MnCl(2)-stimulated microglial H(2)O(2) release was sensitive to inhibitors of mitogen-activated protein kinases (MAPK) but not that of NADPH oxidase. MnCl(2)-induced a rapid activation of the extracellular signal-regulated kinase (ERK) and p38-MAPK in microglia that appeared to precede the MnCl(2)-induced H(2)O(2) release, suggesting that ERK and p38-MAPK influenced the MnCl(2)-induced H(2)O(2) release in microglia. In summary, these results demonstrate that manganese chloride is capable of activating microglia to release ROS and MAPK may, in part, be key regulators of the process. These findings may shed significant light on the potential role of microglia in the manganese-induced neurotoxicity.
Collapse
Affiliation(s)
- Ping Zhang
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA
| | - Angela Hatter
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA
| | - Bin Liu
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
- Corresponding author: Tel.: +1 352 392 3972; Fax: +1 352 392 9187. E-mail address:
| |
Collapse
|
23
|
Liddell JR, Dringen R, Crack PJ, Robinson SR. Glutathione peroxidase 1 and a high cellular glutathione concentration are essential for effective organic hydroperoxide detoxification in astrocytes. Glia 2007; 54:873-9. [PMID: 16998864 DOI: 10.1002/glia.20433] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Organic hydroperoxides are produced in the eicosanoid metabolism and by lipid peroxidation. To examine the contribution of glutathione peroxidase-1 (GPx1) and glutathione (GSH) in the disposal of organic hydroperoxides in brain astrocytes, primary astrocyte cultures from wild type or GPx1-deficient (GPx1(-/-)) mice were exposed to cumene hydroperoxide (CHP). After application of 100 microM CHP, the peroxide disappeared quickly from the incubation medium of wild type cells with a half-life of 9 min, whereas CHP clearance was strongly retarded in GPx1(-/-) astrocytes. Depletion of GSH by pre-incubation with buthionine sulfoximine (BSO) significantly slowed CHP clearance by wild type astrocytes, while almost completely preventing peroxide disposal by GPx1(-/-) cells. In contrast, the catalase inhibitor 3-aminotriazole (3AT) had no effect on CHP clearance. Application of CHP to wild type astrocytes was followed by a rapid and transient accumulation of GSSG, whereas in GPx1(-/-) cells no increase in the GSSG content was detected. Astrocytes from both mouse lines remained viable for up to 24 h following CHP exposure, however depletion of cellular GSH by pre-treatment with BSO compromised the viability of astrocytes, an effect that was stronger in GPx1(-/-) than in wild type cells. This cell death was almost completely prevented by iron chelators, whereas pre-incubation with iron increased CHP toxicity. These novel data demonstrate that the toxicity of organic hydroperoxides in astrocytes is iron-mediated, and that an intact GSH system is required for the effective removal of organic hydroperoxides and for protection from these peroxides.
Collapse
Affiliation(s)
- Jeff R Liddell
- School of Psychology, Psychiatry, and Psychological Medicine, Monash University, Clayton, Victoria, Australia.
| | | | | | | |
Collapse
|
24
|
Bond CE, Patel P, Crouch L, Tetlow N, Day T, Abu-Hayyeh S, Williamson C, Greenfield SA. Astroglia up-regulate transcription and secretion of 'readthrough' acetylcholinesterase following oxidative stress. Eur J Neurosci 2006; 24:381-6. [PMID: 16903848 DOI: 10.1111/j.1460-9568.2006.04898.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Novel and diverse functions of glial cells are currently the focus of much attention [A. Volterra and J. Meldolesi (2005) Nature Rev. 6, 626-640]. Here we present evidence that rat astroglia release acetylcholinesterase (AChE) as part of their response to hypoxic damage. Exposure of astroglia to tert-butyl hydroperoxide, and hence oxidative stress, subsequently leads to a switching in mRNA from the classical membrane-bound T-AChE to a preferential increase in the splice variant for a soluble form, R-AChE, This change in expression is reflected in increased perinuclear and reduced cytoplasmic AChE staining of the insulted glial cells, with a concomitant and marked increase in extracellular secretion that peaks at 1 h post-treatment. An analogous increase in R-AChE, over a similar time scale, occurs in response to psychological stress [D. Kaufer et al. (1998) Nature 93, 373-377], as well as to head injury and stroke [E. Shohami et al. (1999) J. Neurotrauma 6, 365-76]. The data presented here suggest that glial cells may be key chemical intermediaries in such situations and, perhaps more generally in pathological conditions involving oxidative stress, such as neurodegeneration.
Collapse
Affiliation(s)
- C E Bond
- University Department of Pharmacology, Mansfield Road, Oxford OX1 3QT, UK.
| | | | | | | | | | | | | | | |
Collapse
|
25
|
Kulahava TA, Semenkova GN, Kvacheva ZB, Cherenkevich SN, Timoshenko AV. Effects of peroxynitrite and lipopolysaccharide on mitotic activity of C6 glioma cells. Neurosci Lett 2006; 398:286-90. [PMID: 16480818 DOI: 10.1016/j.neulet.2006.01.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2005] [Revised: 12/28/2005] [Accepted: 01/05/2006] [Indexed: 11/23/2022]
Abstract
Peroxynitrite is one of the most potent neurotoxic agents with multiple targets in neurons and glial cells. This study addressed a question of whether peroxynitrite-mediated cytotoxicity can be prevented by Escherichia coli lypopolisaccharide (LPS) due to its mitogenic activity towards C6 glioma cells. A number of characteristic morphological changes (processes impairments, nuclei modifications, cytoplasm vacuolization) and apoptotic cells were observed in the cell culture after 24-h treatment with 3-morpholinosyndnonimine (SIN-1), a well-known donor of peroxynitrite. These morphological changes were clearly associated with a SIN-1 dose-dependent increase in the number of pathological mitoses as well as with SIN-1 inhibition of the menadione-induced, lucigenin-enhanced chemiluminescence of C6 glioma cells, an independent indicator of mitotic activity of these cells. The mitotic index of C6 glioma cells increased in response to LPS and underwent non-uniform changes depending on SIN-1 concentrations. At a mitogenic concentration of 100 ng/ml, LPS reduced significantly the toxicity of SIN-1 determined as the accumulation of pathological mitoses, thus acting as a protective agent. Taken together, our findings indicate that SIN-1 specifically impairs the mitotic process in C6 glioma cells, and provide the first evidence that antimitotic effects of peroxynitrite can be restored by LPS.
Collapse
Affiliation(s)
- Tatsiana A Kulahava
- Department of Biophysics, Physical Faculty, Belarusian State University, Skaryny ave.4, 220050 Minsk, Belarus.
| | | | | | | | | |
Collapse
|
26
|
Steinbrenner H, Alili L, Bilgic E, Sies H, Brenneisen P. Involvement of selenoprotein P in protection of human astrocytes from oxidative damage. Free Radic Biol Med 2006; 40:1513-23. [PMID: 16632112 DOI: 10.1016/j.freeradbiomed.2005.12.022] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2005] [Revised: 11/24/2005] [Accepted: 12/20/2005] [Indexed: 01/15/2023]
Abstract
Selenoprotein P (SeP) is a highly glycosylated, selenium-rich plasma protein. Aside from its role as selenium carrier protein, an antioxidative function of SeP has been suggested. Astrocytes, which detoxify reactive oxygen species in the brain, were described as potential target cells of SeP. We investigated the expression of SeP in human astrocytes and its involvement in the protection of these cells against tert-butyl hydroperoxide (t-BHP)-induced oxidative damage. We show that primary human astrocytes and the human astrocytoma cell line MOG-G-CCM express SeP as an unglycosylated protein, which is not secreted. SeP expression in astrocytes is constitutive. Preincubation of astrocytes with hepatocyte-derived SeP mimicks the protective effect of low-molecular-weight selenocompounds such as sodium selenite or selenomethionine against oxidative damage, shielding astrocytes from t-BHP-induced cytotoxicity. Selenium supplementation of astrocytes counteracts oxidative stress via an increase in expression and activity of the selenoenzyme cytosolic glutathione peroxidase (cGPx). Furthermore, specific downregulation of SeP expression by small interfering RNA decreases cell viability of human astrocytes and makes them more susceptible to t-BHP-induced cytotoxicity. Our results implicate an antioxidant activity of constitutively expressed SeP in selenium-deficient astrocytes, while during adequate selenium supply the enhanced protection against oxidative stress is exerted by cGPx.
Collapse
Affiliation(s)
- Holger Steinbrenner
- Institute for Biochemistry and Molecular Biology I, Heinrich-Heine-University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
| | | | | | | | | |
Collapse
|
27
|
Avshalumov MV, Chen BT, Koós T, Tepper JM, Rice ME. Endogenous hydrogen peroxide regulates the excitability of midbrain dopamine neurons via ATP-sensitive potassium channels. J Neurosci 2006; 25:4222-31. [PMID: 15858048 PMCID: PMC6725114 DOI: 10.1523/jneurosci.4701-04.2005] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
ATP-sensitive K+ (K(ATP)) channels link metabolic state to cell excitability. Here, we examined regulation of K(ATP) channels in substantia nigra dopamine neurons by hydrogen peroxide (H2O2), which is produced in all cells during aerobic metabolism. Blockade of K(ATP) channels by glibenclamide (100 nM) or depletion of intracellular H2O2 by including catalase, a peroxidase enzyme, in the patch pipette increased the spontaneous firing rate of all dopamine neurons tested in guinea pig midbrain slices. Using fluorescence imaging with dichlorofluorescein to visualize intracellular H2O2, we found that moderate increases in H2O2 during partial inhibition of glutathione (GSH) peroxidase by mercaptosuccinate (0.1-0.3 mM) had no effect on dopamine neuron firing rate. However, with greater GSH inhibition (1 mM mercaptosuccinate) or application of exogenous H2O2, 50% of recorded cells showed K(ATP) channel-dependent hyperpolarization. Responsive cells also hyperpolarized with diazoxide, a selective opener for K(ATP) channels containing sulfonylurea receptor SUR1 subunits, but not with cromakalim, a selective opener for SUR2-based channels, indicating that SUR1-based K(ATP) channels conveyed enhanced sensitivity to elevated H2O2. In contrast, when endogenous H2O2 levels were increased after inhibition of catalase, the predominant peroxidase in the substantia nigra, with 3-amino-1,2,4-triazole (1 mM), all dopamine neurons responded with glibenclamide-reversible hyperpolarization. Fluorescence imaging of H2O2 indicated that catalase inhibition rapidly amplified intracellular H2O2, whereas inhibition of GSH peroxidase, a predominantly glial enzyme, caused a slower, smaller increase, especially in nonresponsive cells. Thus, endogenous H2O2 modulates neuronal activity via K(ATP) channel opening, thereby enhancing the reciprocal relationship between metabolism and excitability.
Collapse
Affiliation(s)
- Marat V Avshalumov
- Department of Neurosurgery, New York University School of Medicine, New York, New York 10016, USA
| | | | | | | | | |
Collapse
|
28
|
Abstract
Peroxides are generated continuously in cells that consume oxygen. Among the different peroxides, hydrogen peroxide is the molecule that is formed in highest quantities. In addition, organic hydroperoxides are synthesized as products of cellular metabolism. Generation and disposal of peroxides is a very important process in the human brain, because cells of this organ consume 20% of the oxygen used by the body. To prevent cellular accumulation of peroxides and damage generated by peroxide-derived radicals, brain cells contain efficient antioxidative defense mechanisms that dispose of peroxides and protect against oxidative damage. Cultured brain cells have been used frequently to investigate peroxide metabolism of neural cells. Efficient disposal of exogenous hydrogen peroxide was found for cultured astrocytes, oligodendrocytes, microglial cells, and neurons. Comparison of specific peroxide clearance rates revealed that cultured oligodendrocytes dispose of the peroxide quicker than the other neural cell cultures. Both catalase and the glutathione system contribute to the clearance of hydrogen peroxide by brain cells. For efficient glutathione-dependent reduction of peroxides, neural cells contain glutathione in high concentration and have substantial activity of glutathione peroxidase, glutathione reductase, and enzymes that supply the NADPH required for the glutathione reductase reaction. This article gives an overview on the mechanisms involved in peroxide detoxification in brain cells and on the capacity of the different types of neural cells to dispose of peroxides.
Collapse
Affiliation(s)
- Ralf Dringen
- Interfakultäres Institut für Biochemie der Universität Tübingen, Hoppe-Seyler-Strasse 4, D-72076 Tübingen, Germany.
| | | | | |
Collapse
|
29
|
Ikeda M, Ikeda-Sagara M, Okada T, Clement P, Urade Y, Nagai T, Sugiyama T, Yoshioka T, Honda K, Inoué S. Brain oxidation is an initial process in sleep induction. Neuroscience 2005; 130:1029-40. [PMID: 15652998 DOI: 10.1016/j.neuroscience.2004.09.057] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2004] [Indexed: 11/23/2022]
Abstract
CNS activity is generally coupled to the vigilance state, being primarily active during wakefulness and primarily inactive during deep sleep. During periods of high neuronal activity, a significant volume of oxygen is used to maintain neuronal membrane potentials, which subsequently produces cytotoxic reactive oxygen species (ROS). Glutathione, a major endogenous antioxidant, is an important factor protecting against ROS-mediated neuronal degeneration. Glutathione has also been proposed to be a sleep-promoting substance, yet the relationship between sleep and cerebral oxidation remains unclear. Here we report that i.c.v. infusion of the organic peroxide t-butyl-hydroperoxide at a concentration below that triggering neurodegeneration (0.1 micromol/100 microl/10 h) promotes sleep in rats. Also, microinjection (2 nmol, 2 microl) or microdialysis (100 microM, 20 min) of t-butyl-hydroperoxide into the preoptic/anterior hypothalamus (POAH) induces the release of the sleep-inducing neuromodulators, nitric oxide and adenosine, without causing neurodegeneration. Nitric oxide and adenosine release was inhibited by co-dialysis of the N-methyl-D-aspartate receptor antagonist, d(-)-2-amino-5-phosphonopentanoic acid (D-AP5; 1 mM), suggesting that glutamate-induced neuronal excitation mediates the peroxide-induced release of nitric oxide and adenosine. Indeed, Ca2+ release from mitochondria and delayed-onset Ca2+ influx via N-methyl-D-aspartate receptors was visualized during peroxide exposure using Ca2+ indicator proteins (YC-2.1 and mitochondrial-targeted Pericam) expressed in organotypic cultures of the POAH. In the in vitro models, t-butyl-hydroperoxide (50 microM) causes dendritic swelling followed by the intracellular Ca2+ mobilization, and D-AP5 (100 microM) or glutathione (500 microM) inhibited t-butyl-hydroperoxide-induced intracellular Ca2+ mobilization and protected POAH neurons from oxidative stress. These data suggest that low-level subcortical oxidation under the control of an antioxidant system may trigger sleep via the Ca(2+)-dependent release of sleep-inducing neuromodulators in the POAH, and thus we propose that a moderate increase of ROS during wakefulness in the neuronal circuits regulating sleep may be an initial trigger in sleep induction.
Collapse
Affiliation(s)
- M Ikeda
- Department of Molecular Behavioral Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka 565-0874, Japan.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Choi JW, Shin CY, Yoo BK, Choi MS, Lee WJ, Han BH, Kim WK, Kim HC, Ko KH. Glucose deprivation increases hydrogen peroxide level in immunostimulated rat primary astrocytes. J Neurosci Res 2004; 75:722-31. [PMID: 14991848 DOI: 10.1002/jnr.20009] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Activated astrocytes produce a large amount of bioactive molecules, including reactive oxygen and nitrogen species. Astrocytes are in general resistant to those reactive species. However, we previously reported that immunostimulated astrocytes became highly vulnerable to metabolic insults, such as glucose deprivation. In this study, we investigated whether H(2)O(2) production was associated with the increased vulnerability. Glucose deprivation for up to 8 hr did not change the intracellular level of H(2)O(2) in astrocytes. Treatment with lipopolysaccharide plus interferon-gamma for 48 hr evoked astroglial H(2)O(2) production; however, no apparent death or injury was observed in immunostimulated astrocytes. Glucose deprivation after 48 hr of immunostimulation markedly increased H(2)O(2) level, depleted adenosine triphosphate (ATP), and enhanced lactate dehydrogenase (LDH) release. The ATP depletion and LDH release were in part prevented by catalase, mannitol, and N-acetyl-L-cysteine. The enhanced level of H(2)O(2) in glucose-deprived immunostimulated astrocytes appeared to be secondary to the depletion of reduced glutathione. 4-(2-Aminoethyl)bebzenesulfonyl fluoride (AEBSF), an inhibitor of NADPH oxidase, reduced H(2)O(2) level and LDH release in glucose-deprived immunostimulated astrocytes. H(2)O(2), either endogenously produced or exogenously added, depolarized mitochondrial transmembrane potential in glucose-deprived astrocytes, leading to their ATP depletion and death. The present results strongly indicate that glucose deprivation causes deterioration of immunostimulated astrocytes by increasing the intracellular concentration of H(2)O(2).
Collapse
Affiliation(s)
- Ji Woong Choi
- Department of Pharmacology, College of Pharmacy, Seoul National University, Seoul, Republic of Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Abstract
The antioxidant glutathione (GSH) is essential for the cellular detoxification of reactive oxygen species in brain cells. A compromised GSH system in the brain has been connected with the oxidative stress occuring in neurological diseases. Recent data demonstrate that besides intracellular functions GSH has also important extracellular functions in brain. In this respect astrocytes appear to play a key role in the GSH metabolism of the brain, since astroglial GSH export is essential for providing GSH precursors to neurons. Of the different brain cell types studied in vitro only astrocytes release substantial amounts of GSH. In addition, during oxidative stress astrocytes efficiently export glutathione disulfide (GSSG). The multidrug resistance protein 1 participates in both the export of GSH and GSSG from astrocytes. This review focuses on recent results on the export of GSH and GSSG from brain cells as well as on the functions of extracellular GSH in the brain. In addition, implications of disturbed GSH pathways in brain for neurodegenerative diseases will be discussed.
Collapse
Affiliation(s)
- Ralf Dringen
- Physiologisch-Chemisches Institut der Universität Tübingen, Hoppe-Seyler-Str. 4, D-72076 Tübingen, Germany
| | | |
Collapse
|
32
|
Kent KD, Harper WJ, Bomser JA. Effect of whey protein isolate on intracellular glutathione and oxidant-induced cell death in human prostate epithelial cells. Toxicol In Vitro 2003; 17:27-33. [PMID: 12537959 DOI: 10.1016/s0887-2333(02)00119-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cysteine is the rate-limiting amino acid for synthesis of the ubiquitous antioxidant glutathione (GSH). Bovine whey proteins are rich in cystine, the disulfide form of the amino acid cysteine. The objective of this study was to determine whether enzymatically hydrolyzed whey protein isolate (WPI) could increase intracellular GSH concentrations and protect against oxidant-induced cell death in a human prostate epithelial cell line (designated RWPE-1). Treatment of RWPE-1 cells with hydrolyzed WPI (500 microg/ml) significantly increased intracellular GSH by 64%, compared with control cells receiving no hydrolyzed WPI (P<0.05). A similar increase in GSH was observed with N-acetylcysteine (500 microM), a cysteine-donating compound known to elevate intracellular GSH. In contrast, treatment with hydrolyzed sodium caseinate (500 microg/ml), a cystine-poor protein source, did not significantly elevate intracellular GSH. Hydrolyzed WPI (500 microg/ml) significantly protected RWPE-1 cells from oxidant-induced cell death, compared with controls receiving no WPI (P<0.05). The results of this study indicate that WPI can increase GSH synthesis and protect against oxidant-induced cell death in human prostate cells.
Collapse
Affiliation(s)
- K D Kent
- Department of Food Science and Technology, The Ohio State University, 2015 Fyffe Road, Columbus, OH 43210, USA
| | | | | |
Collapse
|
33
|
Hirrlinger J, Resch A, Gutterer JM, Dringen R. Oligodendroglial cells in culture effectively dispose of exogenous hydrogen peroxide: comparison with cultured neurones, astroglial and microglial cells. J Neurochem 2002; 82:635-44. [PMID: 12153487 DOI: 10.1046/j.1471-4159.2002.00999.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To investigate the antioxidative capacities of oligodendrocytes, rat brain cultures enriched for oligodendroglial cells were prepared and characterized. These cultures contained predominantly oligodendroglial cells as determined by immunocytochemical staining for the markers galactocerebroside and myelin basic protein. If oligodendroglial cultures were exposed to exogenous hydrogen peroxide (100 micro m), the peroxide disappeared from the incubation medium following first order kinetics with a half-time of approximately 18 min. Normalization of the disposal rate to the protein content of the cultures by calculation of the specific hydrogen peroxide detoxification rate constant revealed that the cells in oligodendroglial cultures have a 60% to 120% higher specific capacity to dispose of hydrogen peroxide than cultures enriched for astroglial cells, microglial cells or neurones. Oligodendroglial cultures contained specific activities of 133.5 +/- 30.4 nmol x min(-1) x mg protein(-1) and 27.5 +/- 5.4 nmol x min(-1) x mg protein(-1) of glutathione peroxidase and glutathione reductase, respectively. The specific rate constant of catalase in these cultures was 1.61 +/- 0.54 min(-1) x mg protein(-1). Comparison with data obtained by identical methods for cultures of astroglial cells, microglial cells and neurones revealed that all three of the enzymes which are involved in hydrogen peroxide disposal were present in oligodendroglial cultures in the highest specific activities. These results demonstrate that oligodendroglial cells in culture have a prominent machinery for the disposal of hydrogen peroxide, which is likely to support the protection of these cells in brain against peroxides when produced by these or by surrounding brain cells.
Collapse
|
34
|
Sokolova T, Gutterer JM, Hirrlinger J, Hamprecht B, Dringen R. Catalase in astroglia-rich primary cultures from rat brain: immunocytochemical localization and inactivation during the disposal of hydrogen peroxide. Neurosci Lett 2001; 297:129-32. [PMID: 11121887 DOI: 10.1016/s0304-3940(00)01689-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The expression of catalase in cells of astroglia-rich primary cultures derived from the brains of newborn rats was investigated by double-labelling immunocytochemical staining. Strong catalase immunoreactivity was found in cells positive for glial fibrillary acidic protein and galactocerebroside, cellular markers for astroglial and oligodendroglial cells, respectively. The cells of these cultures dispose of exogenously applied hydrogen peroxide (initial concentration 200 microM) quickly with first order kinetics. In contrast, after inhibition of glutathione peroxidases by mercaptosuccinate the rate of the catalase-dependent disposal of H(2)O(2) declined with time and after about 10 min the extracellular concentration of H(2)O(2) remained almost constant at a concentration of about 100 microM. Catalase activity after 10 min of incubation under these conditions was no longer detectable. In contrast, in the absence of mercaptosuccinate catalase activity was maintained during H(2)O(2) disposal. These results demonstrate that in astroglia-rich cultures catalase is strongly expressed in the predominant astroglial cells and in the minor population of oligodendroglial cells and that the enzyme is rapidly inactivated during the disposal of H(2)O(2), if the glutathione system of the cells is compromised.
Collapse
Affiliation(s)
- T Sokolova
- Physiologisch-chemisches Institut der Universität, Hoppe-Seyler-Strasse 4, D-72076, Tübingen, Germany
| | | | | | | | | |
Collapse
|
35
|
Hirrlinger J, König J, Keppler D, Lindenau J, Schulz JB, Dringen R. The multidrug resistance protein MRP1 mediates the release of glutathione disulfide from rat astrocytes during oxidative stress. J Neurochem 2001; 76:627-36. [PMID: 11208926 DOI: 10.1046/j.1471-4159.2001.00101.x] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The release of glutathione disulfide has been considered an important process for the maintenance of a reduced thiol redox potential in cells during oxidative stress. In cultured rat astrocytes, permanent hydrogen peroxide-induced oxidative stress caused a rapid increase in intracellular glutathione disulfide, which was followed by the appearance of glutathione disulfide in the medium. Under these conditions, the viability of the cells was not compromised. In the presence of cyclosporin A and the quinoline-derivative MK571, inhibitors of multidrug resistance proteins (MRP1 and MRP2), glutathione disulfide accumulated in cells and the release of glutathione disulfide from astrocytes during H2O2 stress was potently inhibited, suggesting a contribution of MRP1 or MRP2 in the release of glutathione disulfide from astrocytes. Using RT-PCR we amplified a cDNA from astroglial RNA with a high degree of homology to MRP1 from humans and mouse. In contrast, no fragment was amplified by using primers specific for rat MRP2. In addition, the presence of MRP1 protein in astrocytes was demonstrated by its immunolocalization in cells expressing the astroglial marker protein glial fibrillary acidic protein. Our data identify rat astrocytes as a MRP1-expressin, brain cell type and demonstrate that this transporter participates in the release of glutathione disulfide from astrocytes during oxidative stress.
Collapse
MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- ATP-Binding Cassette Transporters
- Allopurinol/pharmacology
- Animals
- Antioxidants/pharmacology
- Astrocytes/cytology
- Astrocytes/drug effects
- Astrocytes/metabolism
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Catalase/pharmacology
- Cells, Cultured
- Cyclosporine/pharmacology
- Enzyme Inhibitors/pharmacology
- Glutathione Disulfide/metabolism
- Hydrogen Peroxide/pharmacology
- Leukotriene Antagonists
- Membrane Proteins
- Molecular Sequence Data
- Oxidants/pharmacology
- Oxidative Stress/drug effects
- Oxidative Stress/physiology
- Propionates/pharmacology
- Quinolines/pharmacology
- RNA, Messenger/analysis
- RNA, Messenger/biosynthesis
- Rats
- Rats, Wistar
- Receptors, Leukotriene
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
Collapse
Affiliation(s)
- J Hirrlinger
- Physiologisch-chemisches Institut der Universität, Tübingen, Germany
| | | | | | | | | | | |
Collapse
|
36
|
Abstract
The tripeptide glutathione is the thiol compound present in the highest concentration in cells of all organs. Glutathione has many physiological functions including its involvement in the defense against reactive oxygen species. The cells of the human brain consume about 20% of the oxygen utilized by the body but constitute only 2% of the body weight. Consequently, reactive oxygen species which are continuously generated during oxidative metabolism will be generated in high rates within the brain. Therefore, the detoxification of reactive oxygen species is an essential task within the brain and the involvement of the antioxidant glutathione in such processes is very important. The main focus of this review article will be recent results on glutathione metabolism of different brain cell types in culture. The glutathione content of brain cells depends strongly on the availability of precursors for glutathione. Different types of brain cells prefer different extracellular glutathione precursors. Glutathione is involved in the disposal of peroxides by brain cells and in the protection against reactive oxygen species. In coculture astroglial cells protect other neural cell types against the toxicity of various compounds. One mechanism for this interaction is the supply by astroglial cells of glutathione precursors to neighboring cells. Recent results confirm the prominent role of astrocytes in glutathione metabolism and the defense against reactive oxygen species in brain. These results also suggest an involvement of a compromised astroglial glutathione system in the oxidative stress reported for neurological disorders.
Collapse
Affiliation(s)
- R Dringen
- Physiologisch-chemisches Institut der Universität, Hoppe-Seyler-Str. 4, D-72076 Tübingen, Germany.
| |
Collapse
|
37
|
Lavoie JC, Laborie S, Rouleau T, Spalinger M, Chessex P. Peroxide-like oxidant response in lungs of newborn guinea pigs following the parenteral infusion of a multivitamin preparation. Biochem Pharmacol 2000; 60:1297-303. [PMID: 11008123 DOI: 10.1016/s0006-2952(00)00440-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The multivitamin solution is a major component responsible for the photo-induced generation of peroxides in parenteral nutrition. The lung is a target of oxidant injury; however, the specific role of infused peroxides is unknown. The aim of this study was to determine if parenteral multivitamins induce in the lung an oxidant challenge similar to that of peroxides. Newborn guinea pigs were infused with dextrose plus relevant concentrations of H(2)O(2) (0,250,500 microM) or multivitamins (0,1%), as well as parenteral nutrition supplemented with multivitamins (0,1%). After 4 days, total glutathione, glutathione-related enzymes, and oxidant-sensitive eicosanoids were measured in the lungs. Peroxides as well as multivitamins led to a significant decrease in glutathione and the activity of glutathione synthase, indicating that infused peroxides were not entirely transformed into free radicals, which would have stimulated glutathione synthesis. The multivitamin solution induced a response in oxidant-sensitive eicosanoids similar to the response to peroxides, suggesting an oxidant stress that was not alleviated by the antiradical properties of its components. The effects on prostaglandins occurred independently from the stimulation in glutathione levels induced by parenteral nutrition. The multivitamin solution carries an oxidant load and causes effects similar to those of peroxides in the lungs of newborn guinea pigs.
Collapse
Affiliation(s)
- J C Lavoie
- Perinatal Service and Research Center, Hôpital Ste-Justine, Montreal, Quebec, Canada
| | | | | | | | | |
Collapse
|
38
|
Chen Y, Ying W, Simma V, Copin JC, Chan PH, Swanson RA. Overexpression of Cu,Zn superoxide dismutase attenuates oxidative inhibition of astrocyte glutamate uptake. J Neurochem 2000; 75:939-45. [PMID: 10936174 DOI: 10.1046/j.1471-4159.2000.0750939.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glutamate neurotoxicity in brain is normally prevented by rapid uptake of glutamate by astrocytes. Increased expression of Cu,Zn superoxide dismutase (SOD1) can increase resistance to cerebral ischemia and other oxidative insults, but the cellular mechanisms by which this occurs are not well established. Here we examine whether increased SOD1 expression can attenuate inhibition of astrocyte glutamate uptake by reactive oxygen species. Primary cortical astrocyte cultures were prepared from transgenic mice that overexpress human SOD1 and from nontransgenic littermate controls. Glutamate uptake was assessed after exposure of these cultures to xanthine oxidase plus hypoxanthine, an extracellular superoxide generating system, or to menadione, which generates superoxide in the cytosol. These treatments produced dose-dependent reductions in astrocyte glutamate uptake, and the reductions were significantly attenuated in the SOD1 transgenic astrocytes. A specific effect of reactive oxygen species on glutamate transporters was suggested by the much smaller inhibitory effects of xanthine oxidase/hypoxanthine and menadione on GABA uptake than on glutamate uptake. These findings suggest that the cerebroprotective effects of increased SOD1 expression during cerebral ischemia-reperfusion could be mediated in part by astrocyte glutamate transport.
Collapse
Affiliation(s)
- Y Chen
- Department of Neurology, University of California and Veterans Affairs Medical Center, San Francisco, USA
| | | | | | | | | | | |
Collapse
|
39
|
Dringen R, Gutterer JM, Hirrlinger J. Glutathione metabolism in brain metabolic interaction between astrocytes and neurons in the defense against reactive oxygen species. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:4912-6. [PMID: 10931173 DOI: 10.1046/j.1432-1327.2000.01597.x] [Citation(s) in RCA: 539] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The cells of the adult human brain consume approximately 20% of the oxygen utilized by the body although the brain comprises only 2% of the body weight. Reactive oxygen species, which are produced continuously during oxidative metabolism, are generated at high rates within the brain. Therefore, the defense against the toxic effects of reactive oxygen species is an essential task within the brain. An important component of the cellular detoxification of reactive oxygen species is the antioxidant glutathione. The main focus of this short review is recent results on glutathione metabolism of brain astrocytes and neurons in culture. These two types of cell prefer different extracellular precursors for glutathione. Glutathione is involved in the disposal of exogenous peroxides by astrocytes and neurons. In coculture astrocytes protect neurons against the toxicity of reactive oxygen species. One mechanism of this interaction is the supply by astrocytes of glutathione precursors to neurons.
Collapse
Affiliation(s)
- R Dringen
- Physiologisch-chemisches Institut der Universität, Tübingen, Germany.
| | | | | |
Collapse
|
40
|
Nakamura K, Wright DA, Wiatr T, Kowlessur D, Milstien S, Lei XG, Kang UJ. Preferential resistance of dopaminergic neurons to the toxicity of glutathione depletion is independent of cellular glutathione peroxidase and is mediated by tetrahydrobiopterin. J Neurochem 2000; 74:2305-14. [PMID: 10820190 DOI: 10.1046/j.1471-4159.2000.0742305.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Depletion of glutathione in the substantia nigra is one of the earliest changes observed in Parkinson's disease (PD) and could initiate dopaminergic neuronal degeneration. Nevertheless, experimental glutathione depletion does not result in preferential toxicity to dopaminergic neurons either in vivo or in vitro. Moreover, dopaminergic neurons in culture are preferentially resistant to the toxicity of glutathione depletion, possibly owing to differences in cellular glutathione peroxidase (GPx1) function. However, mesencephalic cultures from GPx1-knockout and wild-type mice were equally susceptible to the toxicity of glutathione depletion, indicating that glutathione also has GPx1-independent functions in neuronal survival. In addition, dopaminergic neurons were more resistant to the toxicity of both glutathione depletion and treatment with peroxides than nondopaminergic neurons regardless of their GPx1 status. To explain this enhanced antioxidant capacity, we hypothesized that tetrahydrobiopterin (BH(4)) may function as an antioxidant in dopaminergic neurons. In agreement, inhibition of BH(4) synthesis increased the susceptibility of dopaminergic neurons to the toxicity of glutathione depletion, whereas increasing BH(4) levels completely protected nondopaminergic neurons against it. Our results suggest that BH(4) functions as a complementary antioxidant to the glutathione/glutathione peroxidase system and that changes in BH(4) levels may contribute to the pathogenesis of PD.
Collapse
Affiliation(s)
- K Nakamura
- Department of Neurology, University of Chicago, IL 60637, USA
| | | | | | | | | | | | | |
Collapse
|
41
|
Abstract
Reactive oxygen and nitrogen species (RO/NS) such as nitric oxide (NO), hydroxyl radical (OH.), and superoxide anion (O(2)(-)) are generated in a variety of neuropathological processes and damage neurons. In the present study, we investigated the neuroprotective effects of rat astrocytes against RO/NS-induced damage using neuron-glia cocultures, and the effects were compared to those of microglial cells. Sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1), and FeSO(4) were used to generate NO, O(2)(-) and NO, and OH., respectively. Solely cultured neurons, which were transiently exposed to these agents, degenerated, possibly through apoptotic mechanisms as revealed by in situ detection of DNA fragmentation, whereas neurons cocultured with either astrocytes or microglial cells were viable even after exposure to RO/NS. In contrast, most neurons cocultured with meningeal fibroblasts degenerated. Astrocyte-conditioned medium partially attenuated RO/NS-induced neuronal damage. When neurons were cultured on astrocyte-derived extracellular matrix (AsECM), neuronal death induced by SNP and FeSO(4) was almost completely inhibited. AsECM contained significant amounts of laminin and fibronectin, and pure fibronectin and laminin also protected neurons against RO/NS-induced damage in the same manner as AsECM. These results suggest that astrocytes can protect neurons against RO/NS-induced damage by secreting soluble and insoluble factors.
Collapse
Affiliation(s)
- J Tanaka
- Department of Physiology, School of Medicine, Ehime University, Shigenobu, Ehime, Japan.
| | | | | | | | | | | |
Collapse
|
42
|
Gutterer JM, Dringen R, Hirrlinger J, Hamprecht B. Purification of glutathione reductase from bovine brain, generation of an antiserum, and immunocytochemical localization of the enzyme in neural cells. J Neurochem 1999; 73:1422-30. [PMID: 10501185 DOI: 10.1046/j.1471-4159.1999.0731422.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glutathione reductase (GR) is an essential enzyme for the glutathione-mediated detoxification of peroxides because it catalyzes the reduction of glutathione disulfide. GR was purified from bovine brain 5,000-fold with a specific activity of 145 U/mg of protein. The homogeneity of the enzyme was proven by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining of the gel. The purified GR from bovine brain is a dimer of two subunits that have an apparent molecular mass of 55 kDa. The purified GR was used to generate a rabbit antiserum with the intention to localize GR in brain cells. The antiserum was useful for the detection of GR by double-labeling immunocytochemical staining in astroglia-rich and neuron-rich primary cultures from rat brain. In homogenates of these cultures, no significant difference in the specific activities of GR was determined. However, not all cell types present in these cultures showed identical staining intensity for GR. In astroglia-rich primary cultures, strong GR immunoreactivity was found in cells positive for the cellular markers galactocerebroside and C3b (antibody Ox42), indicating that oligodendroglial and microglial cells, respectively, contain GR. In contrast, only weak immunoreactivity for GR was found in cells positive for glial fibrillary acidic protein. In neuron-rich primary cultures, GAP43-positive cells stained with the antiserum against GR. These data demonstrate that, in cultures of neural cells, neurons, oligodendroglial cells, and microglial cells express high levels of GR.
Collapse
Affiliation(s)
- J M Gutterer
- Physiologisch-chemisches Institut der Universität, Tübingen, Germany
| | | | | | | |
Collapse
|
43
|
Kussmaul L, Hamprecht B, Dringen R. The detoxification of cumene hydroperoxide by the glutathione system of cultured astroglial cells hinges on hexose availability for the regeneration of NADPH. J Neurochem 1999; 73:1246-53. [PMID: 10461918 DOI: 10.1046/j.1471-4159.1999.0731246.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ability of astroglia-rich primary cultures derived from the brains of newborn rats to detoxify exogenously applied cumene hydroperoxide (CHP) was analyzed as a model to study glutathione-mediated peroxide detoxification by astrocytes. Under the conditions used, 200 microM CHP disappeared from the incubation buffer with a half-time of approximately 10 min. The half-time of CHP in the incubation buffer was found strongly elevated (a) in cultures depleted of glutathione by a preincubation with buthionine sulfoximine, an inhibitor of glutathione synthesis, (b) in the presence of mercaptosuccinate, an inhibitor of glutathione peroxidase, and (c) in the absence of glucose, a precursor for the regeneration of NADPH. The involvement of glutathione peroxidase in the clearance of CHP was confirmed by the rapid increase in the level of GSSG after application of CHP. The restoration of the initial high ratio of GSH to GSSG depended on the presence of glucose during the incubation. The high capacity of astroglial cells to clear CHP and to restore the initial ratio of GSH to GSSG was fully maintained when glucose was replaced by mannose. In addition, fructose and galactose at least partially substituted for glucose, whereas exogenous isocitrate and malate were at best marginally able to replace glucose during peroxide detoxification and regeneration of GSH. These results demonstrate that CHP is detoxified rapidly by astroglial cells via the glutathione system. This metabolic process strongly depends on the availability of glucose or mannose as hydride donors for the regeneration of the NADPH that is required for the reduction of GSSG by glutathione reductase.
Collapse
Affiliation(s)
- L Kussmaul
- Physiologisch-chemisches Institut der Universität, Tübingen, Germany
| | | | | |
Collapse
|
44
|
Hirrlinger J, Hamprecht B, Dringen R. Application and modulation of a permanent hydrogen peroxide-induced oxidative stress to cultured astroglial cells. BRAIN RESEARCH. BRAIN RESEARCH PROTOCOLS 1999; 4:223-9. [PMID: 10446418 DOI: 10.1016/s1385-299x(99)00023-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hydrogen peroxide is often applied to cultured brain cells to investigate functions of these cells under oxidative stress. However, this peroxide might be quickly detoxified by cultured neural cells. At least cultured astroglial cells dispose of exogenous H(2)O(2) with a half-time in the minute range [R. Dringen, B. Hamprecht, Involvement of glutathione peroxidase and catalase in the disposal of exogenous hydrogen peroxide by cultured astroglial cells, Brain. Res. 759 (1997) pp. 67-75]. Therefore, application of hydrogen peroxide to astroglial cells leads only to a period of transient oxidative stress which depends on the ability of the cells to detoxify the peroxide. In order to apply a permanent H(2)O(2)-induced oxidative stress to astroglial cells the generation of H(2)O(2) by the coupled reactions of xanthine oxidase (XO) and superoxide dismutase (SOD) was studied and this system was applied to cultured astroglial cells. In the presence of astroglial cells, an almost constant steady state concentration of H(2)O(2) in the range up to 100 microM was generated, which depended on the activity of the XO applied. These steady state levels of H(2)O(2) were: (i) elevated by application of additional XO, (ii) slowly reduced by application of the XO inhibitor allopurinol, and (iii) immediately reduced to zero by application of catalase or a combination of allopurinol plus catalase. In conclusion, the method presented allows the application of an almost constant exogenous H(2)O(2) stress to cultured cells.
Collapse
Affiliation(s)
- J Hirrlinger
- Physiologisch-chemisches Institut der Universität, Hoppe-Seyler-Str. 4, D-72076, Tübingen, Germany
| | | | | |
Collapse
|
45
|
Dringen R, Kussmaul L, Gutterer JM, Hirrlinger J, Hamprecht B. The glutathione system of peroxide detoxification is less efficient in neurons than in astroglial cells. J Neurochem 1999; 72:2523-30. [PMID: 10349863 DOI: 10.1046/j.1471-4159.1999.0722523.x] [Citation(s) in RCA: 184] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ability of neurons to detoxify exogenously applied peroxides was analyzed using neuron-rich primary cultures derived from embryonic rat brain. Incubation of neurons with H2O2 at an initial concentration of 100 microM (300 nmol/3 ml) led to a decrease in the concentration of the peroxide, which depended strongly on the seeding density of the neurons. When 3 x 10(6) viable cells were seeded per dish, the half-time for the clearance by neurons of H2O2 from the incubation buffer was 15.1 min. Immediately after application of 100 microM H2O2 to neurons, glutathione was quickly oxidized. After incubation for 2.5 min, GSSG accounted for 48% of the total glutathione. Subsequent removal of H2O2 caused an almost complete regeneration of the original ratio of GSH to GSSG within 2.5 min. Compared with confluent astroglial cultures, neuron-rich cultures cleared H2O2 more slowly from the incubation buffer. However, if the differences in protein content were taken into consideration, the ability of the cells to dispose of H2O2 was identical in the two culture types. The clearance rate by neurons for H2O2 was strongly reduced in the presence of the catalase inhibitor 3-aminotriazol, a situation contrasting with that in astroglial cultures. This indicates that for the rapid clearance of H2O2 by neurons, both glutathione peroxidase and catalase are essential and that the glutathione system cannot functionally compensate for the loss of the catalase reaction. In addition, the protein-normalized ability of neuronal cultures to detoxify exogenous cumene hydroperoxide, an alkyl hydroperoxide that is reduced exclusively via the glutathione system, was lower than that of astroglial cells by a factor of 3. These results demonstrate that the glutathione system of peroxide detoxification in neurons is less efficient than that of astroglial cells.
Collapse
Affiliation(s)
- R Dringen
- Physiologisch-chemisches Institut der Universität, Tübingen, Germany
| | | | | | | | | |
Collapse
|