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Wright J, Campos C, Herzog T, Covasa M, Czaja K, Ritter RC. Reduction of food intake by cholecystokinin requires activation of hindbrain NMDA-type glutamate receptors. Am J Physiol Regul Integr Comp Physiol 2011; 301:R448-55. [PMID: 21562094 DOI: 10.1152/ajpregu.00026.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intraperitoneal injection of CCK reduces food intake and triggers a behavioral pattern similar to natural satiation. Reduction of food intake by CCK is mediated by vagal afferents that innervate the stomach and small intestine. These afferents synapse in the hindbrain nucleus of the solitary tract (NTS) where gastrointestinal satiation signals are processed. Previously, we demonstrated that intraperitoneal (IP) administration of either competitive or noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonists attenuates reduction of food intake by CCK. However, because vagal afferents themselves express NMDA receptors at both central and peripheral endings, our results did not speak to the question of whether NMDA receptors in the brain play an essential role in reduction of feeding by CCK. We hypothesized that activation of NMDA receptors in the NTS is necessary for reduction of food intake by CCK. To test this hypothesis, we measured food intake following IP CCK, subsequent to NMDA receptor antagonist injections into the fourth ventricle, directly into the NTS or subcutaneously. We found that either fourth-ventricle or NTS injection of the noncompetitive NMDA receptor antagonist MK-801 was sufficient to inhibit CCK-induced reduction of feeding, while the same antagonist doses injected subcutaneously did not. Similarly fourth ventricle injection of d-3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphoric acid (d-CPPene), a competitive NMDA receptor antagonist, also blocked reduction of food intake following IP CCK. Finally, d-CPPene injected into the fourth ventricle attenuated CCK-induced expression of nuclear c-Fos immunoreactivity in the dorsal vagal complex. We conclude that activation of NMDA receptors in the hindbrain is necessary for the reduction of food intake by CCK. Hindbrain NMDA receptors could comprise a critical avenue for control and modulation of satiation signals to influence food intake and energy balance.
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Affiliation(s)
- Jason Wright
- Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology and Programs in Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, Washington 99164-6520, USA
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52
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Wang Y, Hodgkinson V, Zhu S, Weisman GA, Petris MJ. Advances in the understanding of mammalian copper transporters. Adv Nutr 2011; 2:129-37. [PMID: 22332042 PMCID: PMC3065767 DOI: 10.3945/an.110.000273] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Copper (Cu) is an essential micronutrient. Its ability to exist in 2 oxidation states (Cu(1+) and Cu(2+)) allows it to function as an enzymatic cofactor in hydrolytic, electron transfer, and oxygen utilization reactions. Cu transporters CTR1, ATP7A, and ATP7B play key roles in ensuring that adequate Cu is available for Cu-requiring processes and the prevention of excess Cu accumulation within cells. Two diseases of Cu metabolism, Menkes disease and Wilson disease, which are caused by mutations in ATP7A and ATP7B, respectively, exemplify the critical importance of regulating Cu balance in humans. Herein, we review recent studies of the biochemical and cell biological characteristics of CTR1, ATP7A, and ATP7B, as well as emerging roles for Cu in new areas of physiology.
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Affiliation(s)
- Yanfang Wang
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211
| | - Victoria Hodgkinson
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211
| | - Sha Zhu
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211
| | - Gary A. Weisman
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211
| | - Michael J. Petris
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211,To whom correspondence should be addressed. E-mail:
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53
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Whittle N, Li L, Chen WQ, Yang JW, Sartori SB, Lubec G, Singewald N. Changes in brain protein expression are linked to magnesium restriction-induced depression-like behavior. Amino Acids 2011; 40:1231-48. [DOI: 10.1007/s00726-010-0758-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Accepted: 01/31/2011] [Indexed: 01/22/2023]
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54
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Liao Y, Kristiansen AM, Oksvold CP, Tuvnes FA, Gu N, Rundén-Pran E, Ruth P, Sausbier M, Storm JF. Neuronal Ca2+-activated K+ channels limit brain infarction and promote survival. PLoS One 2010; 5:e15601. [PMID: 21209897 PMCID: PMC3012709 DOI: 10.1371/journal.pone.0015601] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 11/16/2010] [Indexed: 11/18/2022] Open
Abstract
Neuronal calcium-activated potassium channels of the BK type are activated by membrane depolarization and intracellular Ca(2+) ions. It has been suggested that these channels may play a key neuroprotective role during and after brain ischemia, but this hypothesis has so far not been tested by selective BK-channel manipulations in vivo. To elucidate the in vivo contribution of neuronal BK channels in acute focal cerebral ischemia, we performed middle cerebral artery occlusion (MCAO) in mice lacking BK channels (homozygous mice lacking the BK channel alpha subunit, BK(-/-)). MCAO was performed in BK(-/-) and WT mice for 90 minutes followed by a 7-hour-reperfusion period. Coronal 1 mm thick sections were stained with 2,3,5-triphenyltetrazolium chloride to reveal the infarction area. We found that transient focal cerebral ischemia by MCAO produced larger infarct volume, more severe neurological deficits, and higher post-ischemic mortality in BK(-/-) mice compared to WT littermates. However, the regional cerebral blood flow was not significantly different between genotypes as measured by Laser Doppler (LD) flowmetry pre-ischemically, intra-ischemically, and post-ischemically, suggesting that the different impact of MCAO in BK(-/-) vs. WT was not due to vascular BK channels. Furthermore, when NMDA was injected intracerebrally in non-ischemic mice, NMDA-induced neurotoxicity was found to be larger in BK(-/-) mice compared to WT. Whole-cell patch clamp recordings from CA1 pyramidal cells in organotypic hippocampal slice cultures revealed that BK channels contribute to rapid action potential repolarization, as previously found in acute slices. When these cultures were exposed to ischemia-like conditions this induced significantly more neuronal death in BK(-/-) than in WT cultures. These results indicate that neuronal BK channels are important for protection against ischemic brain damage.
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Affiliation(s)
- Yiliu Liao
- Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Ase-Marit Kristiansen
- Centre of Molecular Biology and Neuroscience, and Institute of Basal Medical Sciences, University of Oslo, Oslo, Norway
| | - Cecilie P. Oksvold
- Centre of Molecular Biology and Neuroscience, and Institute of Basal Medical Sciences, University of Oslo, Oslo, Norway
| | - Frode A. Tuvnes
- Centre of Molecular Biology and Neuroscience, and Institute of Basal Medical Sciences, University of Oslo, Oslo, Norway
| | - Ning Gu
- Centre of Molecular Biology and Neuroscience, and Institute of Basal Medical Sciences, University of Oslo, Oslo, Norway
| | - Elise Rundén-Pran
- Centre of Molecular Biology and Neuroscience, and Institute of Basal Medical Sciences, University of Oslo, Oslo, Norway
| | - Peter Ruth
- Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Matthias Sausbier
- Pharmacology and Toxicology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
- * E-mail: (MS); (JS)
| | - Johan F. Storm
- Centre of Molecular Biology and Neuroscience, and Institute of Basal Medical Sciences, University of Oslo, Oslo, Norway
- * E-mail: (MS); (JS)
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55
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Parisi E, Bozic M, Ibarz M, Panizo S, Valcheva P, Coll B, Fernández E, Valdivielso JM. Sustained activation of renal N-methyl-D-aspartate receptors decreases vitamin D synthesis: a possible role for glutamate on the onset of secondary HPT. Am J Physiol Endocrinol Metab 2010; 299:E825-31. [PMID: 20823451 PMCID: PMC2980358 DOI: 10.1152/ajpendo.00428.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Accepted: 09/07/2010] [Indexed: 01/16/2023]
Abstract
N-methyl-D-aspartate (NMDA) receptors (NMDAR) are tetrameric amino acid receptors that act as membrane calcium channels. The presence of the receptor has been detected in the principal organs responsible for calcium homeostasis (kidney, bone, and parathyroid gland), pointing to a possible role in mineral metabolism. The aim of this study was to test the effect of NMDAR activation in the kidney and on 1,25(OH)₂D₃ synthesis. We determined the presence of NMDAR subunits in HK-2 (human kidney cells) cells and proved its functionality. NMDA treatment for 4 days induced a decrease in 1α-hydroxylase levels and 1,25(OH)₂D₃ synthesis through the activation of the MAPK/ERK pathway in HK-2 cells. In vivo administration of NMDA for 4 days also caused a decrease in blood 1,25(OH)₂D₃ levels in healthy animals and an increase in blood PTH levels. This increase in PTH induced a decrease in the urinary excretion of calcium and an increase in urinary excretion of phosphorous and sodium as well as in diuresis. Bone turnover markers also increased. Animals with 5/6 nephrectomy showed low levels of renal 1α-hydroxylase as well as high levels of renal glutamate compared with healthy animals. In conclusion, NMDAR activation in the kidney causes a decrease in 1,25(OH)₂D₃ synthesis, which induces an increase on PTH synthesis and release. In animals with chronic kidney disease, high renal levels of glutamate could be involved in the downregulation of 1α-hydroxylase expression.
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Affiliation(s)
- Eva Parisi
- Institut de Recerca Biomèdica de Lleida, Spain
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56
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Chaves C, Marque CR, Trzesniak C, Machado de Sousa JP, Zuardi AW, Crippa JAS, Dursun SM, Hallak JE. Glutamate-N-methyl-D-aspartate receptor modulation and minocycline for the treatment of patients with schizophrenia: an update. Braz J Med Biol Res 2010; 42:1002-14. [PMID: 19855900 DOI: 10.1590/s0100-879x2009001100002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2009] [Accepted: 09/15/2009] [Indexed: 01/31/2023] Open
Abstract
Growing consistent evidence indicates that hypofunction of N-methyl-D-aspartate (NMDA) transmission plays a pivotal role in the neuropathophysiology of schizophrenia. Hence, drugs which modulate NMDA neurotransmission are promising approaches to the treatment of schizophrenia. The aim of this article is to review clinical trials with novel compounds acting on the NMDA receptor (NMDA-R). This review also includes a discussion and translation of neuroscience into schizophrenia therapeutics. Although the precise mechanism of action of minocycline in the brain remains unclear, there is evidence that it blocks the neurotoxicity of NMDA antagonists and may exert a differential effect on NMDA signaling pathways. We, therefore, hypothesize that the effects of minocycline on the brain may be partially modulated by the NMDA-R or related mechanisms. Thus, we have included a review of minocycline neuroscience. The search was performed in the PubMed, Web of Science, SciELO, and Lilacs databases. The results of glycine and D-cycloserine trials were conflicting regarding effectiveness on the negative and cognitive symptoms of schizophrenia. D-serine and D-alanine showed a potential effect on negative symptoms and on cognitive deficits. Sarcosine data indicated a considerable improvement as adjunctive therapy. Finally, minocycline add-on treatment appears to be effective on a broad range of psychopathology in patients with schizophrenia. The differential modulation of NMDA-R neurosystems, in particular synaptic versus extrasynaptic NMDA-R activation and specific subtypes of NMDA-R, may be the key mediators of neurogenesis and neuroprotection. Thus, psychotropics modulating NMDA-R neurotransmission may represent future monotherapy or add-on treatment strategies in the treatment of schizophrenia.
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Affiliation(s)
- C Chaves
- Departamento de Neurociências e Ciências do Comportamento, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
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57
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Zhang JZ, Jing L, Ma Y, Guo FY, Chang Y, Li PA. Monosialotetrahexosy-1 ganglioside attenuates diabetes-enhanced brain damage after transient forebrain ischemia and suppresses phosphorylation of ERK1/2 in the rat brain. Brain Res 2010; 1344:200-8. [PMID: 20546707 DOI: 10.1016/j.brainres.2010.05.044] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 05/11/2010] [Accepted: 05/12/2010] [Indexed: 11/19/2022]
Abstract
Monosialotetrahexosy-1 ganglioside (GM1) has been shown to reduce brain damage induced by cerebral ischemia. The objective of this study is to determine whether GM1 is able to ameliorate hyperglycemia-exacerbated ischemic brain damage in hyperglycemia-recruited areas such as the hippocampal CA3 sub regions and the cingulated cortex. Histologic stainings of Haematoxylin and Eosin, Nissl body, the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and phospho-ERK1/2 were performed on brain sections that have been subjected to 15 min of forebrain ischemia with reperfusion of 0, 1, 3, and 6h in normoglycemic, hyperglycemic and GM1-pretreated hyperglycemic groups. The results showed that GM1 ameliorated ischemic neuronal injuries in the CA3 area and cingulated cortex of the hyperglycemic animals after ischemia and reperfusion. Immunohistochemistry of phospho-ERK1/2 revealed that the neuroprotective effects of GM1 were associated with suppression of phospho-ERK1/2. The results suggest that GM1 attenuates diabetic-augmented ischemic neuronal injuries probably through suppression of ERK1/2 phosphorylation.
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Affiliation(s)
- Jian-Zhong Zhang
- Department of Pathology, Ningxia Medical University, Yinchuan 750004, PR China.
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58
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Glass MJ. The role of functional postsynaptic NMDA receptors in the central nucleus of the amygdala in opioid dependence. VITAMINS AND HORMONES 2010; 82:145-66. [PMID: 20472137 DOI: 10.1016/s0083-6729(10)82008-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Activation of ionotropic N-methyl-D-aspartate (NMDA)-type glutamate receptors in limbic system nuclei, such as the central nucleus of the amygdala (CeA), plays an essential role in autonomic, behavioral, and affective processes that are profoundly impacted by exposure to opioids. However, the heterogeneous ultrastructural distribution of the NMDA receptor, its complex pharmacology, and the paucity of genetic models have hampered the development of linkages between functional amygdala NMDA receptors and opioid dependence. To overcome these shortcomings, high-resolution imaging and molecular pharmacology were used to (1) Identify the ultrastructural localization of the essential NMDA-NR1 receptor (NR1) subunit and its relationship to the mu-opioid receptor (microOR), the major cellular target of abused opioids like morphine, in the CeA and (2) Determine the effect of CeA NR1 deletion on the physical, and particularly, psychological aspects of opioid dependence. Combined immunogold and immuoperoxidase electron microscopic analysis showed that NR1 was prominently expressed in postsynaptic (i.e., somata, dendrites) locations of CeA neurons, where they were also frequently colocalized with the microOR. A spatial-temporal deletion of NR1 in postsynaptic sites of CeA neurons was produced by local microinjection of a neurotropic recombinant adeno-associated virus (rAAV), expressing the green fluorescent protein (GFP) reporter and Cre recombinase (rAAV-GFP-Cre), in adult "floxed" NR1 (fNR1) mice. Mice with deletion of NR1 in the CeA showed no obvious impairments in sensory, motor, or nociceptive function. In addition, when administered chronic morphine, these mice also displayed an acute physical withdrawal syndrome precipitated by naloxone. However, opioid-dependent CeA NR1 knockout mice failed to exhibit a conditioned place aversion induced by naloxone-precipitated withdrawal. These results indicate that postsynaptic NMDA receptor activity in central amygdala neurons is required for the expression of a learned affective behavior associated with opioid withdrawal. The neurogenetic dissociation of physical and psychological properties of opioid dependence demonstrates the value of combined ultrastructural analysis and molecular pharmacology in clarifying the neurobiological mechanisms subserving opioid-mediated plasticity.
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Affiliation(s)
- Michael J Glass
- Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, USA
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59
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de Rivero Vaccari JP, Marcillo A, Nonner D, Dietrich WD, Keane RW. Neuroprotective effects of bone morphogenetic protein 7 (BMP7) treatment after spinal cord injury. Neurosci Lett 2009; 465:226-9. [PMID: 19765637 DOI: 10.1016/j.neulet.2009.09.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 08/31/2009] [Accepted: 09/11/2009] [Indexed: 11/16/2022]
Abstract
Bone morphogenetic protein 7 (BMP7) has been shown to ameliorate reduced dendritic growth induced by glutamate excitotoxicity in neuronal tissue cultures and/or provide an enhancement of functional recovery in central nervous system (CNS) injury. BMP7 expression is modulated by spinal cord injury (SCI), but the molecular mechanisms involved in neuroprotection have not been clearly defined. Here, we show that BMP7 treatment of rats subjected to mild cervical SCI significantly increased the pro-survival mitogen-activated protein kinase-38 (MAPK-38) pathway and levels of N-methyl-D-aspartate receptor 1 (NMDAR-1) resulting in a significant increase in neuronal sparing in the ventral horn of the spinal cord. Moreover, BMP7 was neuroprotective against glutamate-mediated excitotoxicity in cultured cortical neurons. These studies show that BMP7 administration may be used as a therapeutic strategy to reduce the damaging excitotoxic effects following SCI.
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Affiliation(s)
- Juan Pablo de Rivero Vaccari
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL 33136, United States
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60
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Weiss HR, Liu X, Hunter C, Chi OZ. Effects of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor blockade on increased cerebral O(2) consumption in Eker rats. Brain Res 2009; 1294:138-43. [PMID: 19686708 DOI: 10.1016/j.brainres.2009.08.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Revised: 08/03/2009] [Accepted: 08/05/2009] [Indexed: 11/27/2022]
Abstract
Previous work had demonstrated that there was elevated regional cerebral O2 consumption in the brains of a tuberous sclerosis model (Eker rat). We tested the hypothesis that the increased cerebral O2 consumption was related to an increased contribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors to the control of cerebral metabolism. Young (4weeks) male control Long Evans (N=14) and Eker (N=14) rats (70-100g) were divided into control and NBQX (50mg/kg, AMPA antagonist) treated animals. Cerebral regional blood flow (14C-iodoantipyrine) and O2 consumption (cryomicrospectrophotometry) were determined in isoflurane anesthetized rats. We found significantly increased basal O2 consumption (+85%) in the cortex, hippocampus, cerebellum and pons of the Eker rats. Regional cerebral blood flow was also elevated in Eker rats at baseline (+53%) as was cerebral O2 extraction (+22%). NBQX significantly lowered O2 consumption in all regions of the Long Evans rats (-41%). Cerebral O2 consumption was lowered in the cortex to a lesser extent (-24%) and there were no changes in other regions of the Eker rats after NBQX. Cerebral blood flow was reduced in the Long Evans, but not the Eker rats, after NBQX. In conclusion, Eker rats had significantly elevated cerebral O2 consumption, O2 extraction and blood flow, but this was not related to AMPA receptor activation. In fact, the importance of AMPA receptors in the control of basal cerebral O2 consumption was reduced.
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Affiliation(s)
- Harvey R Weiss
- Department of Physiology and Biophysics, UMDNJ - Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854, USA.
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61
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Izumi Y, Yamamoto N, Matsuo T, Wakita S, Takeuchi H, Kume T, Katsuki H, Sawada H, Akaike A. Vulnerability to glutamate toxicity of dopaminergic neurons is dependent on endogenous dopamine and MAPK activation. J Neurochem 2009; 110:745-55. [DOI: 10.1111/j.1471-4159.2009.06178.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Delgado-Rubín A, Chowen JA, Argente J, Frago LM. Growth hormone-releasing peptide 6 protection of hypothalamic neurons from glutamate excitotoxicity is caspase independent and not mediated by insulin-like growth factor I. Eur J Neurosci 2009; 29:2115-24. [DOI: 10.1111/j.1460-9568.2009.06770.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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63
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Pejchal J, Osterreicher J, Kassa J, Tichy A, Micuda S, Sinkorova Z, Zarybnicka L. Soman poisoning alters p38 MAPK pathway in rat cerebellar Purkinje cells. J Appl Toxicol 2009; 29:338-45. [DOI: 10.1002/jat.1415] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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64
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MORIKAWA T, FURUHAMA K. Effects of the NMDA Receptor Antagonists on Deltamethrin-Induced Striatal Dopamine Release in Conscious Unrestrained Rats. J Vet Med Sci 2009; 71:1129-32. [DOI: 10.1292/jvms.71.1129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Takuya MORIKAWA
- Division of the Veterinary Basic Medicine, Veterinary Medicine Academic Group, Iwate University
| | - Kazuhisa FURUHAMA
- Division of the Veterinary Basic Medicine, Veterinary Medicine Academic Group, Iwate University
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65
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Ramage L, Martel MA, Hardingham GE, Salter DM. NMDA receptor expression and activity in osteoarthritic human articular chondrocytes. Osteoarthritis Cartilage 2008; 16:1576-84. [PMID: 18554934 DOI: 10.1016/j.joca.2008.04.023] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Accepted: 04/27/2008] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Classical neuronal signalling molecules such as substance P and glutamate have been identified in cartilage and have roles in regulation of chondrocyte function. This study looks at expression and activity of the ionotropic glutamate NMDA (N-methyl-D-aspartic acid) receptor (NMDAR) in human osteoarthritic (OA) chondrocytes. METHOD Chondrocytes were obtained from human knee joint arthroplasty specimens. NMDAR subunits and PSD-95 (postsynaptic density protein 95) expression were analysed by reverse transcription-polymerase chain reaction and Western blotting. Activity of NMDAR was assayed by radioactive calcium(45) uptake and changes in membrane potential in the presence and absence of NMDA and NMDAR antagonists and blockade of cell membrane ion channels. RESULTS NMDAR 1, 2A, 2B and PSD-95 were detected in human OA chondrocytes whereas NR2B was absent from normal chondrocytes. NMDA induced calcium flux into OA chondrocytes and cell membrane depolarisation. These responses were blocked by NMDAR antagonists, removal of extracellular calcium, inhibition of nNOS (neuronal nitric oxide synthase) activity and uncoupling of NMDAR from PSD-95. Blockade of sodium channels by tetrodotoxin resulted in NMDA-induced membrane hyperpolarisation which was, in turn inhibited by apamin, a blocker of SK channels. NMDA-induced changes in cell membrane potential were not affected by l-type and stretch activated calcium channel inhibitors. CONCLUSIONS Human OA and normal articular chondrocytes differ in the expression of NMDAR subunits. In OA chondrocytes NMDAR signalling requires extracellular calcium, association with PSD-95, and nNOS activity. Downstream signalling results in activation of tetrodotoxin sensitive sodium channels and SK channels, a response that differs from that of normal chondrocytes suggesting altered activity of NMDAR in OA.
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Affiliation(s)
- L Ramage
- Centre for Inflammation Research, The Queens Medical Research Institute, The University of Edinburgh, Edinburgh, UK.
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66
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Changes in hippocampal NMDA‐R subunit composition induced by exposure of neonatal rats tol‐glutamate. Int J Dev Neurosci 2008; 27:197-204. [DOI: 10.1016/j.ijdevneu.2008.09.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 09/08/2008] [Accepted: 09/23/2008] [Indexed: 11/20/2022] Open
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67
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Li JL, Cui B, Qi L, Li XY, Deng LF, Ning G, Liu JM. NMDA enhances stretching-induced differentiation of osteoblasts through the ERK1/2 signaling pathway. Bone 2008; 43:469-75. [PMID: 18573356 DOI: 10.1016/j.bone.2008.05.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 05/19/2008] [Accepted: 05/23/2008] [Indexed: 11/18/2022]
Abstract
Activation of the excitatory neurotransmitter N-methyl-d-aspartate (NMDA) and stretching both increase Ca(2+) influx in osteoblastic cells. We postulated that NMDA would enhance the osteoblastic cell's response to stretching. The goal of this study was to investigate, in the presence of the neurotransmitter NMDA, the effect of mechanical loading on osteoblast's stage of differentiation and the mitogen-activated protein kinase (MAPK) signaling pathway associated with it. Rat primary osteoblastic cells were subjected to cyclic, equibiaxial stretch for 48 h in the presence or absence of NMDA. Pretreatment with 0.5 mM NMDA significantly enhanced the stretching magnitude-dependent increase in osteogenesis markers. MK801, an antagonist of NMDA receptors, abolished those responses. To further study the mechanism of this response, osteoblastic cells were stretched for 5, 15, or 60 min in the absence of NMDA. Cyclic stretch induced a rapid increase in extracellular signal-regulated kinase ERK1/2 phosphorylation with the peak at 15 min, but no changes were noted in p38 and JNK pathway signaling. NMDA could enhance ERK1/2 phosphorylation stimulated by stretching. U0126, an inhibitor of ERK1/2, blocked the increase in osteogenesis markers. In conclusion, the current study demonstrates that there is a synergistic effect between mechanical stimulation and NMDA in osteoblasts. ERK1/2 signaling may be the common pathway in the increased response to stretching in the presence of NMDA in osteoblastic cells.
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Affiliation(s)
- Jie-Li Li
- Department of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, PR China.
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Cao JL, Ruan JP, Ling DY, Guan XH, Bao Q, Yuan Y, Zhang LC, Song XJ, Zeng YM. Activation of peripheral ephrinBs/EphBs signaling induces hyperalgesia through a MAPKs-mediated mechanism in mice. Pain 2008; 139:617-631. [PMID: 18706764 DOI: 10.1016/j.pain.2008.06.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Revised: 04/30/2008] [Accepted: 06/23/2008] [Indexed: 11/16/2022]
Abstract
EphBs receptors and ephrinBs ligands are present in the adult brain and peripheral tissue and play a critical role in modulating multiple aspects of physiology and pathophysiology. Ours and other studies have demonstrated that spinal ephrinBs/EphBs signaling was involved in the modulation of nociceptive information and central sensitization. However, the role of ephrinBs/EphBs signaling in peripheral sensitization is poorly understood. This study shows that intraplantar (i.pl.) injection of ephrinB1-Fc produces a dose- and time-dependent thermal and mechanical hyperalgesia and the increase of spinal Fos protein expression in mice, which can be partially prevented by pre-treatment with EphB1-Fc. EphrinB1-Fc-induced hyperalgesia is accompanied with the NMDA receptor-mediated increase of expression in peripheral and spinal phosphorylated mitogen-activated protein kinases (phospho-MAPKs) including p-p38, pERK and pJNK, and also is prevented or reversed by the inhibition of peripheral and spinal MAPKs. Furthermore, in formalin inflammation pain model, pre-inhibition of EphBs receptors by the injection of EphB1-Fc reduces pain behavior, which is accompanied by the decreased expression of peripheral p-p38, pERK and pJNK. These data provide evidence that ephrinBs may act as a prominent contributor to peripheral sensitization, and demonstrate that activation of peripheral ephrinBs/EphBs system induces hyperalgesia through a MAPKs-mediated mechanism.
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Affiliation(s)
- Jun-Li Cao
- Department of Anesthesiology, Affiliated Hospital of Xuzhou Medical College, 99 Huaihai West Road, Xuzhou Jiangsu 221002, PR China Jiangsu Institute of Anesthesiology, Jiangsu Key Laboratory of Anesthesiology, 99 Huaihai West Road, Xuzhou 221002, PR China
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69
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García S, López E, López-Colomé AM. Glutamate accelerates RPE cell proliferation through ERK1/2 activation via distinct receptor-specific mechanisms. J Cell Biochem 2008; 104:377-90. [PMID: 18022816 DOI: 10.1002/jcb.21633] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The proliferation and migration of Retinal Pigment Epithelium cells resulting from an epithelial-mesenchymal transition plays a key role in proliferative vitreoretinopathy, which leads to retinal detachment and the loss of vision. In neurons, glutamate has been shown to activate the Ras/Raf/MEK/ERK cascade, which participates in the regulation of proliferation, differentiation, and survival processes. Although glutamate-stimulation and the activation of ERK1/2 by different stimuli have been shown to promote RPE cell proliferation, the signaling pathway(s) linking these effects has not been established. We analyzed the molecular mechanisms leading to glutamate-induced proliferation by determining ERK1/2 and CREB phoshporylation in chick RPE cells in primary culture and the human-derived RPE cell line ARPE-19. This study shows for the first time, that glutamate promotes RPE cell proliferation by activating two distinct signaling pathways linked to selective glutamate receptor subtypes. Results demonstrate that glutamate stimulates RPE cell proliferation as well as ERK and CREB phosphorylation. These effects were mimicked by the mGluR agonist ACPD and by NMDA, and were prevented by the respective receptor inhibitors MCPG and MK-801, indicating a cause-effect relationship between these processes. Whereas mGluR promoted proliferation by activating the MEK/ERK/CREB cascade, NMDA stimulated proliferation through the MEK-independent activation of Ca(2+)/calmodulin-dependent kinases. The blockage of both signaling pathways to proliferation by KN-62 suggests the involvement of CaMKs in the control of glutamate-induced proliferation at a common step, downstream of CREB, possibly the regulation of cell cycle progression. Based on these findings, the participation of glutamate in the development of PVR can be considered.
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Affiliation(s)
- Sofía García
- Instituto de Fisiología Celular, Departamento de Neurociencias, Universidad Nacional Autónoma de México, Mexico, Mexico
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70
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Cheng HT, Suzuki M, Hegarty DM, Xu Q, Weyerbacher AR, South SM, Ohata M, Inturrisi CE. Inflammatory pain-induced signaling events following a conditional deletion of the N-methyl-D-aspartate receptor in spinal cord dorsal horn. Neuroscience 2008; 155:948-58. [PMID: 18621103 DOI: 10.1016/j.neuroscience.2008.06.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2008] [Revised: 05/23/2008] [Accepted: 06/10/2008] [Indexed: 12/24/2022]
Abstract
The N-methyl-d-aspartate (NMDA) receptor in the spinal cord dorsal horn (SCDH) is one of the mechanisms involved in central sensitization during chronic pain. Previously, this laboratory created a spatio-temporal knockout (KO) of the N-methyl-d-aspartate receptor I (NR1) subunit in the mouse SCDH. The NR1 KO completely blocks NR1 gene and subsequent NMDA receptor expression and function in SCDH neurons. In the NR1 KO mice, the mechanical and cold allodynia induced at 24 h after complete Freund's adjuvant (CFA) was reduced. However, the protective effects of KO were transient and were not seen at 48 h after CFA. These observations suggest the presence of NMDA-independent pathways that contribute to CFA-induced pain. CFA induces the activation of several signaling cascades in the SCDH, including protein kinase C (PKC)gamma and extracellular signal-regulated kinases (ERK1/2). The phosphorylation of PKCgamma and ERK1/2 was inhibited in the SCDH of NR1 KO mice up to 48 h after CFA treatment, suggesting that these pathways are NMDA receptor-dependent. Interestingly, neuronal cyclooxygenase (COX) -2 expression and microglial p38 phosphorylation were induced in the SCDH of the NR1 KO at 48 h after CFA. Our findings provide evidence that inflammatory reactions are responsible for the recurrence of pain after NR1 KO in the SCDH.
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Affiliation(s)
- H T Cheng
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10065, USA.
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71
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Peng L, Gu L, Hu X, Zhao L, Hertz L. Complexity of Depolarization-mediated ERK Phosphorylation in Cerebellar Granule Cells in Primary Cultures. Neurochem Res 2007; 33:328-35. [DOI: 10.1007/s11064-007-9510-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2007] [Accepted: 09/13/2007] [Indexed: 01/31/2023]
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72
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Pacheco-Domínguez RL, Palma-Nicolas JP, López E, López-Colomé AM. The activation of MEK-ERK1/2 by glutamate receptor-stimulation is involved in the regulation of RPE proliferation and morphologic transformation. Exp Eye Res 2007; 86:207-19. [PMID: 18061165 DOI: 10.1016/j.exer.2007.10.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2007] [Revised: 10/15/2007] [Accepted: 10/18/2007] [Indexed: 10/22/2022]
Abstract
Retinal pigment epithelial (RPE) cells are the main cell type involved in the pathogenesis of proliferative vitreoretinopathy (PVR). As a result from retinal detachment or surgical procedures, RPE comes in contact with glutamate from serum, glial release and the injured retina. The purpose of this study was to explore a possible role for glutamate in the development of PVR, mediated by the receptor-stimulated activation of the ERK1/2 MAPK pathway, the alteration of cell proliferation and the transdifferentiation of RPE cells, using rat RPE cells in culture as a model system. We demonstrated the expression in these cells of Group I metabotropic-and ionotropic AMPA/KA and NMDA glutamate receptors (GluRs), predominantly of the NMDA subtype, which are targeted to the membrane, and exhibit pharmacological and biochemical characteristics equivalent to those previously established in brain tissue. Proliferation was measured by MTS-reduction colorimetric assay, and actin cytoskeleton dynamics was visualized by immunoflurescence using alpha-sma specific antibodies. Activation of metabotropic, AMPA and NMDA receptors by glutamate induced the time-and dose-dependent phosphorylation of ERK1/2, assessed by Western blot analysis, in parallel to a significant increase in cell proliferation and a decrease in alpha-sma expression and its recruitment into stress fibers. These effects were all prevented by the inhibition of MEK. Hence, results suggest that glutamate could be involved in the generation of PVR, through a GluR-mediated increase in proliferation and phenotypic transformation, cause-effect related to the activation of ERK1/2.
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Affiliation(s)
- Reyna Lizette Pacheco-Domínguez
- Departamento de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México (UNAM), México, DF, Mexico
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73
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Sasabe J, Chiba T, Yamada M, Okamoto K, Nishimoto I, Matsuoka M, Aiso S. D-serine is a key determinant of glutamate toxicity in amyotrophic lateral sclerosis. EMBO J 2007; 26:4149-59. [PMID: 17762863 PMCID: PMC2230675 DOI: 10.1038/sj.emboj.7601840] [Citation(s) in RCA: 209] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2007] [Accepted: 07/30/2007] [Indexed: 11/09/2022] Open
Abstract
Excitotoxicity has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). More recently, glial involvement has been shown to be essential for ALS-related motoneuronal death. Here, we identified an N-methyl-D-aspartate (NMDA) receptor co-agonist, D-serine (D-Ser), as a glia-derived enhancer of glutamate (Glu) toxicity to ALS motoneurons. Cell death assay indicated that primary spinal cord neurons from ALS mice were more vulnerable to NMDA toxicity than those from control mice, in a D-Ser-dependent manner. Levels of D-Ser and its producing enzyme, serine racemase, in spinal cords of ALS mice were progressively elevated, dominantly in glia, with disease progression. In vitro, expression of serine racemase was induced not only by an extracellular pro-inflammatory factor, but also by transiently expressed G93A-superoxide dismutase1 in microglial cells. Furthermore, increases of D-Ser levels were also observed in spinal cords of both familial and sporadic ALS patients. Collectively, Glu toxicity enhanced by D-Ser overproduced in glia is proposed as a novel mechanism underlying ALS motoneuronal death, and this mechanism may be regarded as a potential therapeutic target for ALS.
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Affiliation(s)
- Jumpei Sasabe
- Department of Anatomy, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
- Department of Cell Biology and Neuroscience, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
| | - Tomohiro Chiba
- Department of Anatomy, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
- Department of Cell Biology and Neuroscience, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
| | - Marina Yamada
- Department of Anatomy, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
- Department of Cell Biology and Neuroscience, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
| | - Koichi Okamoto
- Department of Neurology, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | | | - Masaaki Matsuoka
- Department of Anatomy, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
- Department of Cell Biology and Neuroscience, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
- Department of Cell Biology and Neuroscience/Anatomy, KEIO University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. Tel.: +81 3 5363 8427; Fax: +81 3 5363 8428; E-mail:
| | - Sadakazu Aiso
- Department of Anatomy, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
- Department of Cell Biology and Neuroscience, KEIO University School of Medicine, Shinjuku-ku, Tokyo, Japan
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74
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Lambert PJ, Shahrier AZ, Whitman AG, Dyson OF, Reber AJ, McCubrey JA, Akula SM. Targeting the PI3K and MAPK pathways to treat Kaposi's-sarcoma-associated herpes virus infection and pathogenesis. Expert Opin Ther Targets 2007; 11:589-99. [PMID: 17465719 DOI: 10.1517/14728222.11.5.589] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Cells require the ability to appropriately respond to signals in their extracellular environment. To initiate, inhibit and control these processes, the cell has developed a complex network of signaling cascades. The phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways regulate several responses including mitosis, apoptosis, motility, proliferation, differentiation and many others. It is not surprising, therefore, that many viruses target the PI3K and MAPK pathways as a means to manipulate cellular function. Recently, Kaposi's sarcoma-associated herpes virus (KSHV) has been added to the list. KSHV manipulates the PI3K and MAPK pathways to control such divergent processes as cell survival, cellular migration, immune responses, and to control its own reactivation and lytic replication. Manipulation of the PI3K and MAPK pathways also plays a role in malignant transformation. Here, the authors review the potential to target the PI3K and MAPK signaling pathways to inhibit KSHV infection and pathogenesis.
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Affiliation(s)
- Phelps J Lambert
- Brody School of Medicine at East Carolina University, Department of Microbiology & Immunology, Greenville, NC 27834, USA
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75
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Weiss HR, Liu X, Zhang Q, Chi OZ. Increased cerebral oxygen consumption in Eker rats and effects of N-methyl-D-aspartate blockade: Implications for autism. J Neurosci Res 2007; 85:2512-7. [PMID: 17549750 DOI: 10.1002/jnr.21378] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Because there is a strong correlation between tuberous sclerosis and autism, we used a tuberous sclerosis model (Eker rat) to test the hypothesis that these animals would have an altered regional cerebral O2 consumption that might be associated with autism. We also examined whether the altered cerebral O2 consumption was related to changes in the importance of N-methyl-D-aspartate (NMDA) receptors. Young (4 weeks) male control Long Evans (N = 14) and Eker (N = 14) rats (70-100 g) were divided into control and CGS-19755 (10 mg/kg, competitive NMDA antagonist)-treated animals. Cerebral regional blood flow (14C-iodoantipyrine) and O2 consumption (cryomicrospectrophotometry) were determined in isoflurane-anesthetized rats. NMDA receptor protein levels were determined by Western immunoblotting. We found significantly increased basal O2 consumption in the cortex (6.2 +/- 0.6 ml O2/min/100 g Eker vs. 4.7 +/- 0.4 Long Evans), hippocampus, cerebellum, and pons. Regional cerebral blood flow was also elevated in Eker rats at baseline, but cerebral O2 extraction was similar. CGS-19755 significantly lowered O2 consumption in the cortex (2.8 +/- 0.3), hippocampus, and pons of the Long Evans rats but had no effect on cortex (5.8 +/- 0.8) or other regions of the Eker rats. Cerebral blood flow followed a similar pattern. NMDA receptor protein levels (NR1 subunit) were similar between groups. In conclusion, Eker rats had significantly elevated cerebral O2 consumption and blood flow, but this was not related to NMDA receptor activation. In fact, the importance of NMDA receptors in the control of basal cerebral O2 consumption was reduced. This might have important implications in the treatment of autism.
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Affiliation(s)
- Harvey R Weiss
- Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854-5635, USA.
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76
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Abstract
Glutamate receptors regulate gene expression in neurons by activating intracellular signaling cascades that phosphorylate transcription factors within the nucleus. The mitogen-activated protein kinase (MAPK) cascade is one of the best characterized cascades in this regulatory process. The Ca(2+)-permeable ionotropic glutamate receptor, mainly the NMDA receptor subtype, activates MAPKs through a biochemical route involving the Ca(2+)-sensitive Ras-guanine nucleotide releasing factor, Ca(2+)/calmodulin-dependent protein kinase II, and phosphoinositide 3-kinase. The metabotropic glutamate receptor (mGluR), however, activates MAPKs primarily through a Ca(2+)-insensitve pathway involving the transactivation of receptor tyrosine kinases. The adaptor protein Homer also plays a role in this process. As an information superhighway between surface glutamate receptors and transcription factors in the nucleus, active MAPKs phosphorylate specific transcription factors (Elk-1 and CREB), and thereby regulate distinct programs of gene expression. The regulated gene expression contributes to the development of multiple forms of synaptic plasticity related to long-lasting changes in memory function and addictive properties of drugs of abuse. This review, by focusing on new data from recent years, discusses the signaling mechanisms by which different types of glutamate receptors activate MAPKs, features of each MAPK cascade in regulating gene expression, and the importance of glutamate/MAPK-dependent synaptic plasticity in memory and addiction.
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Affiliation(s)
- John Q Wang
- Department of Basic Medical Science, University of Missouri-Kansas City, School of Medicine, Kansas City, Missouri, USA.
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77
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van der Heide LP, Ramakers GMJ, Smidt MP. Insulin signaling in the central nervous system: Learning to survive. Prog Neurobiol 2006; 79:205-21. [PMID: 16916571 DOI: 10.1016/j.pneurobio.2006.06.003] [Citation(s) in RCA: 299] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 06/19/2006] [Accepted: 06/23/2006] [Indexed: 12/23/2022]
Abstract
Insulin is best known for its role in peripheral glucose homeostasis. Less studied, but not less important, is its role in the central nervous system. Insulin and its receptor are located in the central nervous system and are both implicated in neuronal survival and synaptic plasticity. Interestingly, over the past few years it has become evident that the effects of insulin, on neuronal survival and synaptic plasticity, are mediated by a common signal transduction cascade, which has been identified as "the PI3K route". This route has turned out to be a major integrator of insulin signaling in the brain. A pronounced feature of this insulin-activated route is that it promotes survival by directly inactivating the pro-apoptotic machinery. Interestingly, it is this same route that is required for the induction of long-term potentiation and depression, basic processes underlying learning and memory. This leads to the hypothesis that the PI3K route forms a direct link between learning and memory and neuronal survival. The implications of this hypothesis are far reaching, since it provides an explanation why insulin has beneficial effects on learning and memory and how synaptic activity can prevent cellular degeneration. Applying this knowledge may provide novel therapeutic approaches in the treatment of neurodegenerative diseases such as Alzheimer's disease.
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Affiliation(s)
- Lars P van der Heide
- Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
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78
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Abstract
Oligodendrocytes are known to express (Ca2+)-permeable glutamate receptors and to have low resistance to oxidative stress, two factors that make them potentially susceptible to injury. Oligodendrocyte injury is intrinsic to the loss of function experienced in conditions ranging from cerebral palsy to spinal cord injury, focal ischaemia and multiple sclerosis. NMDA receptors, a subtype of glutamate receptors, are vital to the remodeling of synaptic connections during postnatal development and associative learning abilities in adults and possibly in improvements in oligodendrocyte function. Previous studies had failed to detect NMDA receptor mRNA or current in oligodendrocytes but three new papers demonstrate NMDA receptor expression in oligodendrocytes and discuss its implications for ischaemia therapy.
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Affiliation(s)
- Richard Wong
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021, USA.
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