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Jacques-Silva MC, Rodnight R, Lenz G, Liao Z, Kong Q, Tran M, Kang Y, Gonzalez FA, Weisman GA, Neary JT. P2X7 receptors stimulate AKT phosphorylation in astrocytes. Br J Pharmacol 2004; 141:1106-17. [PMID: 15023862 PMCID: PMC1574879 DOI: 10.1038/sj.bjp.0705685] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2003] [Revised: 11/25/2003] [Accepted: 01/07/2004] [Indexed: 12/29/2022] Open
Abstract
1. Emerging evidence indicates that nucleotide receptors are widely expressed in the nervous system. Here, we present evidence that P2Y and P2X receptors, particularly the P2X(7) subtype, are coupled to the phosphoinositide 3-kinase (PI3K)/Akt pathway in astrocytes. 2. P2Y and P2X receptor agonists ATP, uridine 5'-triphosphate (UTP) and 2',3'-O-(4-benzoyl)-benzoyl ATP (BzATP) stimulated Akt phosphorylation in primary cultures of rat cortical astrocytes. BzATP induced Akt phosphorylation in a concentration- and time-dependent manner, similar to the effect of BzATP on Akt phosphorylation in 1321N1 astrocytoma cells stably transfected with the rat P2X(7) receptor. Activation was maximal at 5 - 10 min and was sustained for 60 min; the EC(50) for BzATP was approximately 50 microM. In rat cortical astrocytes, the positive effect of BzATP on Akt phosphorylation was independent of glutamate release. 3. The effect of BzATP on Akt phosphorylation in rat cortical astrocytes was significantly reduced by the P2X(7) receptor antagonist Brilliant Blue G and the P2X receptor antagonist iso-pyridoxal-5'-phosphate-6-azophenyl-2',4'-disulfonic acid, but was unaffected by trinitrophenyl-ATP, oxidized ATP, suramin and reactive blue 2. 4. Results with specific inhibitors of signal transduction pathways suggest that extracellular and intracellular calcium, PI3K and a Src family kinase are involved in the BzATP-induced Akt phosphorylation pathway. 5. In conclusion, our data indicate that stimulation of astrocytic P2X(7) receptors, as well as other P2 receptors, leads to Akt activation. Thus, signaling by nucleotide receptors in astrocytes may be important in several cellular downstream effects related to the Akt pathway, such as cell cycle and apoptosis regulation, protein synthesis, differentiation and glucose metabolism.
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Affiliation(s)
- Maria C Jacques-Silva
- Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Richard Rodnight
- Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Guido Lenz
- Departamento de Biofísica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Zhongji Liao
- Department of Biochemistry, University of Missouri-Columbia, Columbia, MO, U.S.A
| | - Qiongman Kong
- Department of Biochemistry, University of Missouri-Columbia, Columbia, MO, U.S.A
| | - Minh Tran
- Research Service, VA Medical Center, Departments of Pathology, Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, FL, U.S.A
- Neuroscience Program, University of Miami School of Medicine, Miami, FL, U.S.A
| | - Yuan Kang
- Research Service, VA Medical Center, Departments of Pathology, Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, FL, U.S.A
- Neuroscience Program, University of Miami School of Medicine, Miami, FL, U.S.A
| | - Fernando A Gonzalez
- Department of Chemistry, University of Puerto Rico, Rio Piedras, Puerto Rico
| | - Gary A Weisman
- Department of Biochemistry, University of Missouri-Columbia, Columbia, MO, U.S.A
| | - Joseph T Neary
- Research Service, VA Medical Center, Departments of Pathology, Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, FL, U.S.A
- Neuroscience Program, University of Miami School of Medicine, Miami, FL, U.S.A
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102
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Crossthwaite AJ, Valli H, Williams RJ. Inhibiting Src family tyrosine kinase activity blocks glutamate signalling to ERK1/2 and Akt/PKB but not JNK in cultured striatal neurones. J Neurochem 2004; 88:1127-39. [PMID: 15009668 DOI: 10.1046/j.1471-4159.2004.02257.x] [Citation(s) in RCA: 40] [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
Glutamate receptor activation of mitogen-activated protein (MAP) kinase signalling cascades has been implicated in diverse neuronal functions such as synaptic plasticity, development and excitotoxicity. We have previously shown that Ca2+-influx through NMDA receptors in cultured striatal neurones mediates the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt/protein kinase B (PKB) through a phosphatidylinositol 3-kinase (PI 3-kinase)-dependent pathway. Exposing neurones to the Src family tyrosine kinase inhibitor PP2, but not the inactive analogue PP3, inhibited NMDA receptor-induced phosphorylation of ERK1/2 and Akt/PKB in a concentration-dependent manner, and reduced cAMP response element-binding protein (CREB) phosphorylation. To establish a link between Src family tyrosine kinase-mediated phosphorylation and PI 3-kinase signalling, affinity precipitation experiments were performed with the SH2 domains of the PI 3-kinase regulatory subunit p85. This revealed a Src-dependent phosphorylation of a focal adhesion kinase (FAK)-p85 complex on glutamate stimulation. Demonstrating that PI3-kinase is not ubiquitously involved in NMDA receptor signal transduction, the PI 3-kinase inhibitors wortmannin and LY294002 did not prevent NMDA receptor Ca2+-dependent phosphorylation of c-Jun N-terminal kinase 1/2 (JNK1/2). Further, inhibiting Src family kinases increased NMDA receptor-dependent JNK1/2 phosphorylation, suggesting that Src family kinase-dependent cascades may physiologically limit signalling to JNK. These results demonstrate that Src family tyrosine kinases and PI3-kinase are pivotal regulators of NMDA receptor signalling to ERK/Akt and JNK in striatal neurones.
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Affiliation(s)
- Andrew J Crossthwaite
- Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London, London, UK
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103
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Levinthal DJ, DeFranco DB. Transient phosphatidylinositol 3-kinase inhibition protects immature primary cortical neurons from oxidative toxicity via suppression of extracellular signal-regulated kinase activation. J Biol Chem 2004; 279:11206-13. [PMID: 14715649 DOI: 10.1074/jbc.m314261200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Oxidative stress has been shown to underlie a diverse range of neuropathological conditions. Glutamate-induced oxidative toxicity is a well described model of oxidative stress-induced neurodegeneration that relies upon the ability of extracellular glutamate to inhibit a glutamate/cystine antiporter, which results in a depletion of intracellular cysteine and the blockade of continued glutathione synthesis. Glutathione depletion leads to a gradual toxic accumulation of reactive oxygen species. We have previously determined that glutamate-induced oxidative toxicity is accompanied by a robust increase in activation of the mitogen-activated protein kinase (MAPK) member extracellular-signal regulated kinase (ERK) and that this activation is essential for neuronal cell death. This study demonstrates that delayed ERK activation is dependent upon the activity of phosphoinositol-3 kinase (PI3K) and that transient but not sustained PI3K inhibition leads to significant protection of neurons from oxidative stress-induced neurodegeneration. Furthermore, we show that transient PI3K inhibition prevents the delayed activation of MEK-1, a direct activator of ERK, during oxidative stress. Thus, this study is the first to demonstrate a novel level of cross-talk between the PI3K and ERK pathways in cultured immature cortical neuronal cultures that contributes to the unfolding of a cell death program. The PI3K pathway, therefore, may serve opposing roles during the progression of oxidative stress in neurons, acting at distinct kinetic phases to either promote or limit a slowly developing program of cell death.
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Affiliation(s)
- David J Levinthal
- Center for Neuroscience and Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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104
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Abstract
The past decade has seen a steady accumulation of evidence supporting a role for the excitatory amino acid (EAA) neurotransmitter, glutamate, and its receptors in depression and antidepressant activity. To date, evidence has emerged indicating that N-methyl-d-aspartate (NMDA) receptor antagonists, group I metabotropic glutamate receptor (mGluR1 and mGluR5) antagonists, as well as positive modulators of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have antidepressant-like activity in a variety of preclinical models. Moreover, antidepressant-like activity can be produced not only by drugs modulating the glutamatergic synapse, but also by agents that affect subcellular signaling systems linked to EAA receptors (e.g., nitric oxide synthase). In view of the extensive colocalization of EAA and monoamine markers in nuclei such as the locus coeruleus and dorsal raphe, it is likely that an intimate relationship exists between regulation of monoaminergic and EAA neurotransmission and antidepressant effects. Further, there is also evidence implicating disturbances in glutamate metabolism, NMDA, and mGluR1,5 receptors in depression and suicidality. Finally, recent data indicate that a single intravenous dose of an NMDA receptor antagonist is sufficient to produce sustained relief from depressive symptoms. Taken together with the proposed role of neurotrophic factors in the neuroplastic responses to stressors and antidepressant treatments, these findings represent exciting and novel avenues to both understand depressive symptomatology and develop more effective antidepressants.
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Affiliation(s)
- Ian A Paul
- Laboratory of Neurobehavioral Pharmacology and Immunology, Division of Neurobiology and Behavior Research, Department of Psychiatry, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA.
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105
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Lee EHY, Hsu WL, Ma YL, Lee PJ, Chao CC. Enrichment enhances the expression of sgk, a glucocorticoid-induced gene, and facilitates spatial learning through glutamate AMPA receptor mediation. Eur J Neurosci 2003; 18:2842-52. [PMID: 14656333 DOI: 10.1111/j.1460-9568.2003.03032.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have previously demonstrated that the serum and glucocorticoid-inducible kinase (sgk) gene plays a causal role in facilitating memory performance in rats. Environment enrichment is known to facilitate spatial learning. We therefore examined the effect of enrichment on sgk expression. We also examined the role of sgk in spatial and nonspatial learning and the regulation of sgk expression by activation of different glutamate receptors. Both real-time polymerase chain reaction and Western blot analyses revealed that enrichment training preferentially increased sgk mRNA and protein levels in the hippocampus. Transfection of sgk mutant DNA to the hippocampal CA1 area markedly impaired spatial learning, fear-conditioning learning and novel object-recognition learning in rats, but enrichment training effectively reversed these learning deficits. Meanwhile, S422A mutant DNA transfection prevented enrichment-induced spatial learning facilitation. In studying glutamate receptor regulation of sgk expression, we found that blockade of N-methyl-d-aspartate (NMDA) receptors in general, and the NR2B subunit in particular both effectively blocked enrichment-induced spatial learning facilitation, but they did not block enrichment-induced sgk expression. Upon various glutamate agonist infusions, only alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) increased sgk mRNA levels significantly in the hippocampus. Furthermore, blockade of AMPA receptors effectively blocked both enrichment-induced spatial learning facilitation and sgk expression. These results indicate that there is a dissociation between NMDA receptor activation and sgk expression. Enrichment enhanced spatial learning through both NMDA and AMPA receptor activation, whereas enrichment-induced sgk expression is specifically mediated through AMPA receptors. These results suggest that sgk could serve as a novel molecular mechanism, in addition to the NMDA receptor NR2B, underlying enrichment-induced learning facilitation.
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Affiliation(s)
- Eminy H Y Lee
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
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106
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Spencer JPE, Rice-Evans C, Williams RJ. Modulation of pro-survival Akt/protein kinase B and ERK1/2 signaling cascades by quercetin and its in vivo metabolites underlie their action on neuronal viability. J Biol Chem 2003; 278:34783-93. [PMID: 12826665 DOI: 10.1074/jbc.m305063200] [Citation(s) in RCA: 238] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Much recent interest has focused on the potential of flavonoids to interact with intracellular signaling pathways such as with the mitogen-activated protein kinase cascade. We have investigated whether the observed strong neurotoxic potential of quercetin in primary cortical neurons may occur via specific and sensitive interactions within neuronal mitogen-activated protein kinase and Akt/protein kinase B (PKB) signaling cascades, both implicated in neuronal apoptosis. Quercetin induced potent inhibition of both Akt/PKB and ERK phosphorylation, resulting in reduced phosphorylation of BAD and a strong activation of caspase-3. High quercetin concentrations (30 microM) led to sustained loss of Akt phosphorylation and subsequent Akt cleavage by caspase-3, whereas at lower concentrations (<10 microM) the inhibition of Akt phosphorylation was transient and eventually returned to basal levels. Lower levels of quercetin also induced strong activation of the pro-survival transcription factor cAMP-responsive element-binding protein, although this did not prevent neuronal damage. O-Methylated quercetin metabolites inhibited Akt/PKB to lesser extent and did not induce such strong activation of caspase-3, which was reflected in the lower amount of damage they inflicted on neurons. In contrast, neither quercetin nor its O-methylated metabolites had any measurable effect on c-Jun N-terminal kinase phosphorylation. The glucuronide of quercetin was not toxic and did not evoke any alterations in neuronal signaling, probably reflecting its inability to enter neurons. Together these data suggest that quercetin and to a lesser extent its O-methylated metabolites may induce neuronal death via a mechanism involving an inhibition of neuronal survival signaling through the inhibition of both Akt/PKB and ERK rather than by an activation of the c-Jun N-terminal kinase-mediated death pathway.
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Affiliation(s)
- Jeremy P E Spencer
- Wolfson Centre for Age-related Diseases, Guy's, King's and St. Thomas' School of Biomedical Sciences, Hodgkin Building, King's College, Guy's Campus, London, SE1 9RT, United Kingdom
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107
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Williams JM, Guévremont D, Kennard JTT, Mason-Parker SE, Tate WP, Abraham WC. Long-term regulation of N-methyl-D-aspartate receptor subunits and associated synaptic proteins following hippocampal synaptic plasticity. Neuroscience 2003; 118:1003-13. [PMID: 12732245 DOI: 10.1016/s0306-4522(03)00028-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Synaptic plasticity in the dentate gyrus is dependent on activation of the N-methyl-D-aspartate (NMDA)-subtype of glutamate receptors. In this study, we show that synaptic plasticity in turn regulates NMDA receptors, since subunits of the NMDA receptor complex are bidirectionally and independently regulated in the dentate gyrus following activation of perforant synapses in awake animals. Low-frequency stimulation that produced a mild synaptic depression resulted in a decrease in the NMDA receptor subunits NR1 and NR2B 48 h following stimulation. High-frequency stimulation that produced long-term potentiation resulted in an increase in NR1 and NR2B at the same time point. Further investigations revealed that in contrast to NR2B, NR1 levels increased gradually after long-term potentiation induction, reaching a peak level at 48 h, and were insensitive to the competitive NMDA receptor antagonist 3-3(2-carboxypiperazin-4-yl) propyl-1-phosphate. The increased levels of NR1 and NR2B at 48 h were found associated with synaptic membranes and with increased NMDA receptor-associated proteins, postsynaptic density protein 95, neuronal nitric oxide synthase and Ca(2+)/calmodulin-dependent protein kinase II, alpha subunit. These data suggest that the persistence of long-term potentiation is associated with an increase in the number of NMDA receptor complexes, which may be indicative of an increase in synaptic contact area.
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Affiliation(s)
- J M Williams
- Department of Anatomy and Structural Biology, Otago School of Medical Sciences, University of Otago, P.O. Box 913, Dunedin, New Zealand.
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108
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Gasull T, DeGregorio-Rocasolano N, Trullas R. Overactivation of α-amino-3-hydroxy-5-methylisoxazole-4-propionate and N-methyl-d-aspartate but not kainate receptors inhibits phosphatidylcholine synthesis before excitotoxic neuronal death. J Neurochem 2003. [DOI: 10.1046/j.1471-4159.2001.00187.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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109
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Deng W, Rosenberg PA, Volpe JJ, Jensen FE. Calcium-permeable AMPA/kainate receptors mediate toxicity and preconditioning by oxygen-glucose deprivation in oligodendrocyte precursors. Proc Natl Acad Sci U S A 2003; 100:6801-6. [PMID: 12743362 PMCID: PMC164527 DOI: 10.1073/pnas.1136624100] [Citation(s) in RCA: 152] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hypoxic-ischemic brain injury in premature infants results in cerebral white matter lesions with prominent oligodendroglial injury and loss, a disorder termed periventricular leukomalacia (PVL). We have previously shown that glutamate receptors mediate hypoxic-ischemic injury to oligodendroglial precursor cells (OPCs) in a model of PVL in the developing rodent brain. We used primary OPC cultures to examine the mechanism of cellular toxicity induced by oxygen-glucose deprivation (OGD) to simulate brain ischemia. OPCs were more sensitive to OGD-induced toxicity than mature oligodendrocytes, and OPC toxicity was attenuated by nonselective [2,3-dihydroxy-6-nitro-7-sulfamoylbenzo[f]quinoxaline (NBQX), 6-cyano-7-nitroquinoxaline-2,3-dione], alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-preferring (GYKI 52466), kainate-preferring (gamma-d-glutamylaminomethanesulfonic acid), or Ca2+-permeable AMPA/kainate receptor antagonists (joro spider toxin, JSTx) administered either during or after OGD. Furthermore, NBQX or JSTx blocked OGD-induced Ca2+ influx. Relevant to recurrent hypoxic-ischemic insults in developing white matter, we examined the effects of sublethal OGD preconditioning. A prior exposure of OPCs to sublethal OGD resulted in enhanced vulnerability to subsequent excitotoxic or OGD-induced injury associated with an increased Ca2+ influx. AMPA/kainate receptor blockade with NBQX or JSTx either during or after sublethal OGD prevented its priming effect. Furthermore, OGD preconditioning resulted in a down-regulation of the AMPA receptor subunit GluR2 on cell surface that increased Ca2+ permeability of the receptors. Overall, these data suggest that aberrantly enhanced activation of Ca2+-permeable AMPA/kainate receptors may be a major mechanism in acute and repeated hypoxic-ischemic injury to OPCs in disorders of developing cerebral white matter, such as PVL.
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Affiliation(s)
- Wenbin Deng
- Department of Neurology and Program in Neuroscience, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
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110
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Ferrer I, Friguls B, Dalfó E, Planas AM. Early modifications in the expression of mitogen-activated protein kinase (MAPK/ERK), stress-activated kinases SAPK/JNK and p38, and their phosphorylated substrates following focal cerebral ischemia. Acta Neuropathol 2003; 105:425-37. [PMID: 12677442 DOI: 10.1007/s00401-002-0661-2] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2002] [Accepted: 11/04/2002] [Indexed: 01/03/2023]
Abstract
Focal ischemia induced by middle cerebral artery occlusion (MCAO) to adult rats results in necrosis at the infarct core and activation of complex signal pathways for cell death and cell survival in the penumbra. Upstream from the cell death promoters and executioners are several kinases that, once activated by phosphorylation, may activate several transcription factor substrates involved in cell death and cell survival. In the present study we examined, by immunohistochemistry, the expression of phosphorylated (active) mitogen-activated protein kinase, extracellular signal-regulated kinase (MAPK/ERK), stress-activated protein kinase (SAPK), c-Jun N-terminal kinase (JNK) and p-38 kinase at early stages (1-4 h) following 1 h of MCAO in the rat. The expression of phosphorylation-dependent, active transcription substrates of these kinases, including cyclic AMP-responsive element-binding protein (CREB) Alk-1, ATF-2, c-Myc and c-Jun was examined at early stages following reperfusion. Increased nuclear phosphorylated SAPK/JNK (SAPK/JNK-P) and c-Jun-PSer63, and reduced CREB-P, occurred in the infarct core at 1 h following reperfusion, suggesting increased phosphorylated SAPK/JNK and c-JunSer63, together with decreased phospho-CREB associated with cell death in the infarct core. However, increased cytoplasmic expression of MAPK/ERK-P, SAPK/JNK-P, p38-P, CREB-P, Elk-1-P, c-Myc-P, ATF-2-P and c-Jun-P occurred in the region bordering the infarct core (penumbra) at 4 h following reperfusion. This indicates that different signals converge in the cytoplasm of neurons located at the borders of the infarct at 4 h following reperfusion, revealing the struggle of death promoters and life facilitators at the penumbra. Whether phosphorylated kinases and specific substrates participate in promoting cell death or survival in the penumbra probably depends on additional factors and on the interaction with other proteins.
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Affiliation(s)
- I Ferrer
- Institut de Neuropatologia, Servei d'Anatomia Patològica, Hospital Princeps d'Espanya, Universitat de Barcelona, Campus de Bellvitge, carrer Feixa LLarga sn, 08907 Hospitalet de Llobregat, Spain.
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111
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Suchak SK, Baloyianni NV, Perkinton MS, Williams RJ, Meldrum BS, Rattray M. The 'glial' glutamate transporter, EAAT2 (Glt-1) accounts for high affinity glutamate uptake into adult rodent nerve endings. J Neurochem 2003; 84:522-32. [PMID: 12558972 DOI: 10.1046/j.1471-4159.2003.01553.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The excitatory amino acid transporters (EAAT) removes neurotransmitters glutamate and aspartate from the synaptic cleft. Most CNS glutamate uptake is mediated by EAAT2 into glia, though nerve terminals show evidence for uptake, through an unknown transporter. Reverse-transcriptase PCR identified the expression of EAAT1, EAAT2, EAAT3 and EAAT4 mRNAs in primary cultures of mouse cortical or striatal neurones. We have used synaptosomes and glial plasmalemmal vesicles (GPV) from adult mouse and rat CNS to identify the nerve terminal transporter. Western blotting showed detectable levels of the transporters EAAT1 (GLAST) and EAAT2 (Glt-1) in both synaptosomes and GPVs. Uptake of [3H]D-aspartate or [3H]L-glutamate into these preparations revealed sodium-dependent uptake in GPV and synaptosomes which was inhibited by a range of EAAT blockers: dihydrokainate, serine-o-sulfate, l-trans-2,4-pyrrolidine dicarboxylate (PDC) (+/-)-threo-3-methylglutamate and (2S,4R )-4-methylglutamate. The IC50 values found for these compounds suggested functional expression of the 'glial, transporter, EAAT2 in nerve terminals. Additionally blockade of the majority EAAT2 uptake sites with 100 micro m dihydrokainate, failed to unmask any functional non-EAAT2 uptake sites. The data presented in this study indicate that EAAT2 is the predominant nerve terminal glutamate transporter in the adult rodent CNS.
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Affiliation(s)
- Sachin K Suchak
- Biochemical Neuropharmacology Group, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College London, United Kingdom
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112
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Mao L, Wang JQ. Phosphorylation of cAMP response element-binding protein in cultured striatal neurons by metabotropic glutamate receptor subtype 5. J Neurochem 2003; 84:233-43. [PMID: 12558986 DOI: 10.1046/j.1471-4159.2003.01256.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The metabotropic glutamate receptor subtype 5 (mGluR5) is densely expressed in striatal projection neurons. As a G protein-coupled receptor, mGluR5 may initiate an intracellular cascade that conveys extracellular signals to gene expression. This study investigated the possible role of mGluR5 in the inducible phosphorylation of a nuclear transcription factor, cAMP response element-binding protein (CREB), in primary cultures of striatal neurons from rat E19 embryos or neonatal day-1 pups. We found that selective activation of mGluR5 with a selective agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG) induced a rapid and transient increase in phosphorylated CREB immunoreactivity in striatal neurons as analyzed by both immunocytochemistry and western blot. The increase in CREB phosphorylation was concentration-dependent, and seen in neurochemically identified GABAergic neurons. Pre-treatment with the mGluR5 antagonist 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP) blocked the CHPG phosphorylation of CREB. In contrast, the mGluR1 antagonist, 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOet) did not alter CHPG-stimulated CREB phosphorylation. The mGluR5 antisense oligonucleotides, but not their controls, selectively reduced basal mGluR5 levels as well as CREB phosphorylation in response to CHPG addition. Lastly, using an immediate early gene c-fos as a reporter of inducible gene expression downstream to phosphorylated CREB, we found that CHPG induced a rapid and transient increase in c-fos mRNA levels in cultured neurons as revealed by quantitative in situ hybridization. The increase in c-fos was kinetically correlated well with the CREB phosphorylation and blocked by MPEP and the CREB antisense oligonucleotides. These results demonstrate a positive linkage from surface mGluR5 to CREB phosphorylation, which is able to facilitate immediate gene expression in striatal neurons.
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Affiliation(s)
- Limin Mao
- Department of Pharmacology, School of Pharmacy, University of Missouri-Kansas City, 64108, USA
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113
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Lu C, Fu W, Zhao D, Mattson MP. The DNA damaging agent etoposide activates a cell survival pathway involving alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors and mitogen-activated protein kinases in hippocampal neurons. J Neurosci Res 2002; 70:671-9. [PMID: 12424735 DOI: 10.1002/jnr.10413] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Etoposide, an inhibitor of topoisomerase II that induces DNA damage and can trigger cell death, is used as a chemotherapeutic agent. Because chemotherapies can result in neurological complications and because DNA damage in neurons is implicated in the pathogenesis of several neurodegenerative disorders, we studied the effects of etoposide on cultured hippocampal neurons. We found that etoposide induces neuronal apoptosis and that, prior to the cell death commitment point, there is an increase in whole-cell alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-induced current but no change in N-methyl-D-aspartate (NMDA)-induced current. Associated with the increase in AMPA-induced current was an increase in the amounts of AMPA receptor subunits GluR1 and GluR4, whereas levels of the NMDA receptor subunit NR1 were unaffected by etoposide. AMPA receptor activation can result in excitotoxic cell death but can also activate signaling pathways that promote synaptic plasticity and cell survival. We found that etoposide increases the activation of p42 and p44 mitogen-activated protein (MAP) kinases, and that activation of the MAP kinases by etoposide requires AMPA receptor activation. Pharmacological blockade of AMPA receptors and p42/p44 MAP kinases, but not of NMDA receptors, exacerbated etoposide-induced cell death. These findings suggest that, although etoposide is neurotoxic, it also activates a cell survival pathway involving AMPA receptor-mediated activation of p42/p44 MAP kinases. Agents that selectively inhibit the cell life or death pathways triggered by DNA damage may prove useful in the settings of cancer and neurodegenerative disorders, respectively.
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Affiliation(s)
- Chengbiao Lu
- Laboratory of Neurosciences, National Institute on Aging/NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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114
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Brami-Cherrier K, Valjent E, Garcia M, Pagès C, Hipskind RA, Caboche J. Dopamine induces a PI3-kinase-independent activation of Akt in striatal neurons: a new route to cAMP response element-binding protein phosphorylation. J Neurosci 2002; 22:8911-21. [PMID: 12388598 PMCID: PMC6757682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023] Open
Abstract
Akt is classically described as a prosurvival serine/threonine kinase activated in response to trophic factors. After activation by phosphoinositide 3-kinase (PI3-kinase), it can translocate to the nucleus where it promotes specific genetic programs by catalyzing phosphorylation of transcription factors. We report here that both dopamine (DA) D1 (SKF38393) and D2 (quinpirole) agonist treatments rapidly increase, in primary striatal neurons in culture, phosphorylation levels of Akt on Thr(308), a residue that is critically involved in its kinase activity. These treatments also activate the extracellular signal-regulated kinase (ERK) pathway in the same population of striatal neurons. Induction of active, phospho-Thr(308) Akt by dopamine D1 and D2 agonists is insensitive to wortmannin and thus PI3-kinase independent, in contrast to growth factor-induced Akt activity. D1- and D2-induced phospho-Thr(308) Akt is decreased by the mitogen-activated protein kinase kinase (MEK) inhibitor, U0126, as well as by overexpression of a dominant-negative version of MEK, thus implicating the Ras/ERK signaling cascade in this process. Furthermore, overexpression of a mutant form of Akt that cannot be activated impaired cAMP response element-binding protein (CREB) phosphorylation induced by SKF38393 and quinpirole treatments. Activation of Akt on Thr(308) was also found in vivo in striatal neurons after acute administration of cocaine, a psychostimulant that strongly increases DA transmission. Thus, multiple intracellular pathways can transduce signals from dopamine receptors to CREB in striatal neurons, one of these being Akt. We propose that this signaling pathway plays a pivotal role in DA-induced regulation of gene expression and long-term neuronal adaptation in the striatum.
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Affiliation(s)
- Karen Brami-Cherrier
- Laboratoire de Neurobiologie des Processus Adaptatifs, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie, Unité Mixte de Recherche 7102, 75005 Paris, France
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115
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Aguirre A, López-Bayghen E, Ortega A. Glutamate-dependent transcriptional regulation of the chkbp gene: signaling mechanisms. J Neurosci Res 2002; 70:117-27. [PMID: 12237870 DOI: 10.1002/jnr.10394] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Glutamate, the major excitatory neurotransmitter, induces a signal from the membrane to the nucleus that regulates gene expression. The gene encoding the chick kainate binding protein undergoes a glutamate-dependent transcriptional regulation via an activator protein-1 site within its promoter region. To characterize this event, cultured chick Bergmann glia cells were exposed to glutamate, and a dose-dependent increase in promoter activity was established. The glutamate effect is mediated through Ca(2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate receptors. The signaling cascade includes phosphatidyl inositol 3-kinase, Ca(2+)/calmodulin-dependent protein kinase II, mitogen-activated protein kinase, and p90 ribosomal S6 kinase activation. The cAMP response-element binding protein becomes phosphorylated and activates fos transcription. Finally, the activator protein-1 complex binds to the glutamate response element in the chick kainate binding protein promoter region inducing its activity. We propose that the mitogen-activated protein kinase/p90 ribosomal S6 kinase pathway plays a critical role in glutamate-induced gene transcription.
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Affiliation(s)
- Adán Aguirre
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México DF, México
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116
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Sutton G, Chandler LJ. Activity-dependent NMDA receptor-mediated activation of protein kinase B/Akt in cortical neuronal cultures. J Neurochem 2002; 82:1097-105. [PMID: 12358757 DOI: 10.1046/j.1471-4159.2002.01031.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The serine/threonine protein kinase B (PKB)/Akt is a phosphoinositide 3-kinase (PI3K) effector that is thought to play an important roll in a wide variety of cellular events. The present study examined whether PKB activation in cortical neuronal cultures is coupled with synaptic activity. A 1-h incubation of neuronal cultures with tetrodotoxin (TTX), the PI3K inhibitor wortmannin, the NMDA receptor antagonist MK-801 or removal of extracellular calcium significantly reduced basal levels of phospho(Ser473)-PKB, indicating that activity-dependent glutamate release maintains PKB activation through an NMDA receptor-PI3K pathway. A 5-min exposure to NMDA (50 micro m) in the presence of TTX increased phospho-PKB back to levels observed in the absence of TTX. NMDA stimulation of phospho-PKB was blocked by wortmannin, the CaMKII inhibitor KN-93, MK-801, and removal of extracellular calcium. We have previously shown that NMDA receptors can bi-directionally regulate activation of extracellular-signal regulated kinase (ERK), and NMDA receptor stimulation of PKB in the present study appeared to mirror activation of ERK. These results suggest that in cultured cortical neurons, PKB activity is dynamically regulated by synaptic activity and is coupled to NMDA receptor activation. In addition, NMDA receptor activation of ERK and PKB may occur through overlapping signaling pathways that bifurcate at the level of Ras.
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Affiliation(s)
- Greg Sutton
- Department of Physiology and Neuroscience, Medical University of South Carolina, Charleston 29425, USA
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117
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Mao L, Wang JQ. Glutamate cascade to cAMP response element-binding protein phosphorylation in cultured striatal neurons through calcium-coupled group I metabotropic glutamate receptors. Mol Pharmacol 2002; 62:473-84. [PMID: 12181423 DOI: 10.1124/mol.62.3.473] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Emerging evidence indicates that group I metabotropic glutamate receptors (mGluRs) play a significant role in the addictive plasticity of striatal neurons. The plasticity is probably mediated by altered cellular gene expression in relation to stimulation of group I mGluRs and associative signaling proteins. In this study, we investigated the signaling linkage of surface group I mGluRs to the nuclear transcription factor cAMP response element-binding protein (CREB) in cultured primary striatal neurons. We found that selective activation of group I mGluRs (primarily the mGluR5 subtype) was able to up-regulate CREB phosphorylation in neurochemically identified gamma-aminobutyratergic neurons but not glia. The CREB phosphorylation was independent of kainate/AMPA receptors but partially dependent of concomitant NMDA receptor activation. Because L-type voltage-operated Ca(2+) channel inhibitors substantially blocked the CREB phosphorylation, group I receptors are believed to lead to activation of L-type Ca(2+) channels, resulting in the CREB phosphorylation. Indeed, further studies on signaling pathways showed that group I mGluRs, by activating phospholipase C, induced a rapid and transient Ca(2+) release from the 1,4,5-triphosphate-sensitive rather than ryanodine-sensitive Ca(2+) store. The transient Ca(2+) rise in turn triggered the opening of L-type Ca(2+) channels, resulting in a progressively larger increase in cytoplasmic Ca(2+) levels that is responsible for subsequent CREB phosphorylation. These results indicate that Ca(2+)-coupled group I mGluRs possess the ability to up-regulate CREB phosphorylation via the intracellular Ca(2+) release-induced activation of L-type Ca(2+) channels and, to a lesser extent, NMDA receptors in primary striatal neurons.
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Affiliation(s)
- Limin Mao
- Department of Pharmacology, School of Pharmacy, University of Missouri-Kansas City, Kansas City, Missouri 64108, USA
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118
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Lax P, Limatola C, Fucile S, Trettel F, Di Bartolomeo S, Renzi M, Ragozzino D, Eusebi F. Chemokine receptor CXCR2 regulates the functional properties of AMPA-type glutamate receptor GluR1 in HEK cells. J Neuroimmunol 2002; 129:66-73. [PMID: 12161022 DOI: 10.1016/s0165-5728(02)00178-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Experiments were conducted in both HEK cells and cerebellar neurons to investigate whether CXC chemokine receptor 2 (CXCR2) is functionally coupled to GluR1. The co-expression of CXCR2 with GluR1 in HEK cells increased (i) the GluR1 "apparent" affinity for the transmitter; (ii) the GluR1 channel open probability; and (iii) GluR1 binding site cooperativity upon CXCR2 stimulation with CXC chemokine ligand 2 (CXCL2). The affinity of C-terminal-deleted GluR1 for glutamate (Glu) remained stable instead. Furthermore, CXCL2 increased the binding site cooperativity of AMPA receptors in rat cerebellar granule cells; and the amplitude of spontaneous excitatory postsynaptic current (sEPSCs) in Purkinje neurons (PNs). Our findings indicate that the coupling of CXCR2 with GluR1 may modulate glutamatergic synaptic transmission.
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MESH Headings
- Animals
- Binding Sites/drug effects
- Binding Sites/immunology
- Cells, Cultured
- Central Nervous System/immunology
- Central Nervous System/metabolism
- Cerebellar Cortex/drug effects
- Cerebellar Cortex/immunology
- Cerebellar Cortex/metabolism
- Chemokines, CXC/immunology
- Chemokines, CXC/metabolism
- Chemokines, CXC/pharmacology
- DNA, Complementary/genetics
- Dose-Response Relationship, Drug
- Excitatory Amino Acid Antagonists/pharmacology
- Excitatory Postsynaptic Potentials/drug effects
- Excitatory Postsynaptic Potentials/immunology
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/immunology
- Glutamic Acid/metabolism
- Glutamic Acid/pharmacology
- Humans
- Ion Channels/genetics
- Ion Channels/immunology
- Neurons/drug effects
- Neurons/immunology
- Neurons/metabolism
- Rats
- Rats, Sprague-Dawley
- Rats, Wistar
- Receptors, AMPA/genetics
- Receptors, AMPA/immunology
- Receptors, AMPA/metabolism
- Receptors, Interleukin-8B/genetics
- Receptors, Interleukin-8B/immunology
- Receptors, Interleukin-8B/metabolism
- Synapses/immunology
- Synapses/metabolism
- Synaptic Transmission/immunology
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Affiliation(s)
- P Lax
- Dipartimento di Fisiologia Umana e Farmacologia, Università di Roma, Piazzale Aldo Moro 5, I00185, Rome, Italy
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119
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Abstract
The overactivation of glutamate receptors is a major cause of Ca(2+) overload in cells, potentially leading to cell damage and death. There is an abundance of agents and mechanisms by which glutamate receptor activation can be prevented or modulated in order to control these effects. They include the well-established, competitive and non-competitive antagonists at the N-methyl-D-aspartate (NMDA) receptors and modulators of desensitisation of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors. More recently, it has emerged that some compounds can act selectively at different subunits of glutamate receptors, allowing a differential blockade of subtypes. It is also becoming clear that a number of endogenous compounds, including purines, can modify glutamate receptor sensitivity. The kynurenine pathway is an alternative but distinct pathway to the generation of glutamate receptor ligands. The products of tryptophan metabolism via the kynurenine pathway include both quinolinic acid, a selective agonist at NMDA receptors, and kynurenic acid, an antagonist at several glutamate receptor subtypes. The levels of these metabolites change as a result of the activation of inflammatory processes and immune-competent cells, and may have a significant impact on Ca(2+) fluxes and neuronal damage. Drugs which target some of these various sites and processes, or which change the balance between the excitotoxin quinolinic acid and the neuroprotective kynurenic acid, could also have potential as neuroprotective drugs.
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Affiliation(s)
- Trevor W Stone
- Institute of Biomedical and Life Sciences Division of Neuroscience and Biomed. System, West Medical Building, University of Glasgow, Glasgow G12 8QQ, UK.
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120
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Greenwood JM, Dragunow M. Muscarinic receptor-mediated phosphorylation of cyclic AMP response element binding protein in human neuroblastoma cells. J Neurochem 2002; 82:389-97. [PMID: 12124440 DOI: 10.1046/j.1471-4159.2002.00992.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This study describes the effect of signalling through muscarinic acetylcholine receptors on two transcription factors implicated in long-term synaptic plasticity and memory formation, EGR1 and the cyclic AMP response element binding protein (CREB). In SK-N-SH neuroblastoma cells, treatment with the cholinergic agonist carbachol led to maximal induction of EGR1 1 h after stimulation. This was preceded by the phosphorylation of CREB, which peaked as early as 5 minutes after carbachol treatment. The levels of both EGR1 and phosphorylated CREB (pCREB) slowly decayed over 4-8 h. CREB phosphorylation and EGR1 induction showed similar sensitivity to carbachol concentration, with EC(50) values in the range of 1-10 microM, and the changes in both transcription factors were blocked by the muscarinic antagonist atropine. As has been described elsewhere, EGR1 induction was dependent on activation of p42/44 MAP kinase, as it was blocked by the MEK inhibitor U0126. However, CREB phosphorylation by carbachol was largely unaffected by MAP kinase blockade. As both CREB phosphorylation and EGR1 induction have been linked to long-term potentiation and some forms of memory consolidation, these results may implicate CREB and EGR1 in independent or partially independent cholinergic signalling pathways involved in memory processes.
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Affiliation(s)
- Jeffrey M Greenwood
- Department of Pharmacology, Faculty of Medicine and Health Science, University of Auckland, Auckland, New Zealand
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121
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Fischer W, Franke H, Scheibler P, Allgaier C, Illes P. AMPA-induced Ca(2+) influx in cultured rat cortical nonpyramidal neurones: pharmacological characterization using fura-2 microfluorimetry. Eur J Pharmacol 2002; 438:53-62. [PMID: 11906710 DOI: 10.1016/s0014-2999(02)01296-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
Abstract
Immunocytochemical and Co(2+) uptake studies revealed that in primary cultures of rat cortical neurones, the majority of neurones are gamma-aminobutyric acid (GABA) immunopositive and can express Ca(2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors. By fura-2 microfluorimetry, it was shown that the stimulation with the selective agonist (S)-AMPA (0.3-300 microM) induced a concentration-dependent but cell-variable increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) (EC(50) value 7.4 microM) in more than 80% of the medium-sized multipolar neurones studied. The AMPA-induced rise in [Ca(2+)](i) seems to be due to Ca(2+) entry through AMPA receptor channels, because the response was abolished in Ca(2+)-free solution and by AMPA receptor selective antagonists, but was not significantly influenced by cyclopiazonic acid, an inhibitor of the endoplasmatic Ca(2+)-ATPase, by selective N-methyl-D-aspartic acid (NMDA) receptor antagonists, as well as the Na(+) channel blocker tetrodotoxin and the majority of tested Ca(2+) channel blockers. In conclusion, the results indicate that the cerebral cortical neurones in culture represent mostly GABAergic interneurone-like cells and the majority of them possess Ca(2+)-permeable AMPA receptors, important for intracellular signal transduction and neuronal plasticity.
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Affiliation(s)
- Wolfgang Fischer
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Härtelstrasse 16-18, D-04107 Leipzig, Germany.
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122
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Bahr BA, Bendiske J, Brown QB, Munirathinam S, Caba E, Rudin M, Urwyler S, Sauter A, Rogers G. Survival signaling and selective neuroprotection through glutamatergic transmission. Exp Neurol 2002; 174:37-47. [PMID: 11869032 DOI: 10.1006/exnr.2001.7852] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the brain, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors mediate glutamatergic neurotransmission and, when intensely activated, can induce excitotoxic cell death. In addition to their ionotropic properties, however, AMPA receptors have been functionally coupled to a variety of signal transduction events involving Src-family kinases, G-proteins, and the mitogen-activated protein kinase (MAPK). In the present study, we tested whether AMPA receptors are linked to appropriate signaling events in order to prevent neuronal injury and/or enhance recovery. AMPA stimulation in hippocampal slice cultures caused the selective activation of MAPK through the upstream activator MAPK kinase (MEK). Inhibition of either component of the AMPA receptor--MAPK pathway potentiated cellular damage due to serum deprivation, suggesting that this pathway facilitates compensatory signals in response to injury. Correspondingly, positive modulation of AMPA receptors with the Ampakine 1-(quinoxalin-6-ylcarbonyl)piperidine (CX516) enhanced MAPK activation and reduced the extent of synaptic and neuronal degeneration resulting from excitotoxic episodes. CX516 was neuroprotective when infused into slices either before or after the insult. The Ampakine derivative also elicited neuroprotection in an in vivo model of excitotoxicity as evidenced by reduction in lesion size and preservation of two different types of neurons. Interestingly, the AMPA receptor--MAPK pathway selectively protects against excitotoxicity since enhancing the pathway did not protect against the nonexcitotoxic, slow pathology initiated by lysosomal dysfunction. The results indicate that glutamatergic communication is important for cellular maintenance and that AMPA receptors activate survival signals to counterpoise their own excitotoxic potential.
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Affiliation(s)
- Ben A Bahr
- Department of Pharmaceutical Sciences and the Neurosciences Program, Center for Drug Discovery, University of Connecticut, Storrs, Connecticut, USA
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123
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Limatola C, Ciotti MT, Mercanti D, Santoni A, Eusebi F. Signaling pathways activated by chemokine receptor CXCR2 and AMPA-type glutamate receptors and involvement in granule cells survival. J Neuroimmunol 2002; 123:9-17. [PMID: 11880144 DOI: 10.1016/s0165-5728(01)00472-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We show that treatment of cerebellar granules with interleukin-8 (IL-8), growth-related gene product beta (GRObeta) or AMPA induced activation of PI3-K/Akt and of ERK pathways, the latter being independent of PI3-K and dependent on PTX-sensitive G proteins. We also show that AMPA-mediated neuron survival was abolished both by ERK kinase inhibitor PD98059 and AMPA-Rs blocker CNQX, and that chemokine-mediated survival was blocked by the PI3-K inhibitors LY294002 and wortmannin. We conclude that the neurotrophic effects of AMPA need the contemporary activation of ERKs and stimulation of AMPA-Rs, and that PI3-K/Akt activation is a determinant pathway for the IL-8/GRObeta anti-apoptotic activity.
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Affiliation(s)
- C Limatola
- Dipartimento di Fisiologia Umana e Farmacologia, Università di Roma "La Sapienza", Piazzale Aldo Moro 5, I-00185, Rome, Italy.
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124
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Barros DM, Mello e Souza T, de Souza MM, Choi H, DeDavid e Silva T, Lenz G, Medina JH, Izquierdo I. LY294002, an inhibitor of phosphoinositide 3-kinase given into rat hippocampus impairs acquisition, consolidation and retrieval of memory for one-trial step-down inhibitory avoidance. Behav Pharmacol 2001; 12:629-34. [PMID: 11856900 DOI: 10.1097/00008877-200112000-00007] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Adult male Wistar rats were bilaterally implanted with indwelling cannulae in the CA1 region of the dorsal hippocampus. Once recovered from surgery, animals were submitted to one session of step-down inhibitory avoidance training (3.0 s, 0.4 mA footshock). Animals received a 0.5-microl infusion of saline, or of LY294002 (5, 50 or 500 microM), an inhibitor of the phosphoinositide 3-kinase (PI 3-K) family. Infusions were given 10 min before training, immediately post-training or 10 min prior to a 24-h retention test. In the pre- and post-training groups, the animals were tested twice: at 1.5 and 24 h after training, for short- (STM) and long-term memory (LTM), respectively. Pre- and post-training infusion of the drug inhibited both STM and LTM. Pre-test infusions impaired LTM retrieval. The effects can not be attributed to influences on locomotor, exploratory, pro- or anti-conflict behaviour, since LY294002 had no influence on elevated plus-maze behaviour. The results suggest that hippocampal PI 3-K is necessary for memory acquisition, consolidation and retrieval of the consolidation of step-down inhibitory avoidance in rats. This could be due to an interaction with the N-methyl-d-aspartate (NMDA) receptor complex or with activity of the extracellularly regulated protein kinase (ERK)-Ras signalling pathway.
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Affiliation(s)
- D M Barros
- Departamento de Ciências Fisiológicas, Setor de Farmacologia, Fundação Universidade Federal de Rio Grande, Rio Grande, Brazil.
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125
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Mabuchi T, Kitagawa K, Kuwabara K, Takasawa K, Ohtsuki T, Xia Z, Storm D, Yanagihara T, Hori M, Matsumoto M. Phosphorylation of cAMP response element-binding protein in hippocampal neurons as a protective response after exposure to glutamate in vitro and ischemia in vivo. J Neurosci 2001; 21:9204-13. [PMID: 11717354 PMCID: PMC6763920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023] Open
Abstract
Although accumulating evidence indicates that cAMP response element-binding protein (CREB) phosphorylation mediates not only synaptic plasticity but also survival of certain neurons, it remains uncertain whether CREB phosphorylation induced after metabolic insult leads to CRE-mediated gene transcription and is involved in cell survival or not. In the present study, we clarified that (1) CREB phosphorylation and ischemic tolerance induced after preconditioning ischemia in the hippocampal neurons was abolished by MK801 administration in gerbil global ischemia model, (2) CREB phosphorylation induced after exposure to glutamate in cultured neurons was inhibited by removal of extracellular calcium, by MK801 and by an inhibitor of calcium-calmodulin-dependent protein kinase (CaMK) II and IV, (3) inhibitor of CaMK II-IV or CRE-decoy oligonucleotide suppressed upregulation of BCL-2 expression and accelerated neuronal damage after exposure to glutamate, and (4) CREB phosphorylation induced in the hippocampal neurons after ischemia and in cultured neurons after exposure to glutamate was followed by CRE-mediated gene transcription in transgenic mice with a CRE-LacZ reporter. Our results suggest that CREB phosphorylation in neurons after ischemia and exposure to glutamate is induced by NMDA receptor-gated calcium influx and subsequent activation of CaMK II-IV and that CREB phosphorylation after metabolic stress might show a neuroprotective response through CRE-mediated gene induction.
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Affiliation(s)
- T Mabuchi
- Division of Strokology, Department of Internal Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
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126
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Santos AE, Carvalho AL, Lopes MC, Carvalho AP. Differential postreceptor signaling events triggered by excitotoxic stimulation of different ionotropic glutamate receptors in retinal neurons. J Neurosci Res 2001; 66:643-55. [PMID: 11746384 DOI: 10.1002/jnr.10036] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The aim of this work was to investigate whether excitotoxicity induced by overstimulation of different ionotropic glutamate receptors could trigger different intracellular signaling cascades. Cultured chick neuronal retina cells, essentially amacrine-like, were particularly sensitive to the toxicity induced by non-NMDA glutamate receptor agonists. One hour stimulation with 100 microM kainate induced a reduction of cell viability of about 44%, as assessed by the MTT test 24 hr after stimulation. Kainate-induced toxicity was mediated through AMPA receptors. Glutamate (100 microM, 1 hr) reduced cell viability by 26%, essentially acting through N-methyl-D-aspartate receptors. Five hours after stimulation, neuronal retina cells had an apoptotic-like nuclear morphology. In retinal neurons, the excitotoxic stimulation, with either glutamate or kainate, induced a calcium-dependent enhancement of the DNA-binding activity of the activating protein-1 (AP-1) transcription factor, which was maximal 2 hr after stimulation. Glutamate induced a greater increase in the AP-1 DNA-binding activity than did kainate. Supershift assays using antibodies directed against different members of the Fos and Jun protein families showed that the AP-1 complex in retinal neurons includes proteins of the Fos family, namely, Fra-2, c-Jun, and Jun D. The DNA-binding activity of the nuclear factor-kappaB transcription factor was not significantly changed upon excitotoxic stimulation with any agonist. Stimulation of glutamate receptors with 100 microM kainate or 100 microM glutamate for 2 min was sufficient to induce the activation of the extracellular signal-regulated kinase (ERK). Inhibition of the ERK activation with the MEK inhibitors U 0126 and PD 98059 increased the toxicity induced by kainate but was without effect on the toxicity induced by glutamate. These results indicate that, although stimulation with both glutamate receptor agonists increased ERK phosphorylation, only kainate-induced ERK activation correlates with the activation of a survival signaling pathway. Our results suggest that, in chick embryo retinal neurons, the signaling pathways that mediate excitotoxic cell death and neuroprotection are stimulus specific.
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MESH Headings
- Amacrine Cells/drug effects
- Amacrine Cells/embryology
- Amacrine Cells/metabolism
- Animals
- Apoptosis/drug effects
- Apoptosis/physiology
- Cell Survival/drug effects
- Cell Survival/physiology
- Cells, Cultured/drug effects
- Cells, Cultured/metabolism
- Chick Embryo
- Enzyme Inhibitors/pharmacology
- Excitatory Amino Acid Agonists/pharmacology
- Excitatory Amino Acid Antagonists/pharmacology
- Glutamic Acid/metabolism
- Glutamic Acid/pharmacology
- Kainic Acid/pharmacology
- MAP Kinase Signaling System/drug effects
- MAP Kinase Signaling System/physiology
- Mitogen-Activated Protein Kinases/antagonists & inhibitors
- Mitogen-Activated Protein Kinases/metabolism
- NF-kappa B/drug effects
- NF-kappa B/metabolism
- Neurotoxins/pharmacology
- Receptors, AMPA/agonists
- Receptors, AMPA/antagonists & inhibitors
- Receptors, AMPA/metabolism
- Receptors, Glutamate/drug effects
- Receptors, Glutamate/metabolism
- Receptors, N-Methyl-D-Aspartate/agonists
- Receptors, N-Methyl-D-Aspartate/antagonists & inhibitors
- Receptors, N-Methyl-D-Aspartate/metabolism
- Transcription Factor AP-1/drug effects
- Transcription Factor AP-1/metabolism
- Transcription Factors/drug effects
- Transcription Factors/metabolism
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Affiliation(s)
- A E Santos
- Center for Neuroscience of Coimbra, Department of Zoology, University of Coimbra, Coimbra, Portugal
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127
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Spencer JP, Schroeter H, Crossthwaithe AJ, Kuhnle G, Williams RJ, Rice-Evans C. Contrasting influences of glucuronidation and O-methylation of epicatechin on hydrogen peroxide-induced cell death in neurons and fibroblasts. Free Radic Biol Med 2001; 31:1139-46. [PMID: 11677047 DOI: 10.1016/s0891-5849(01)00704-3] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The purpose of this study was to examine the comparative mechanisms by which the dietary form of the flavonoid epicatechin and its predominant in vivo metabolite, epicatechin glucuronide, influence oxidative stress-induced cell death in fibroblasts and neurons. The results demonstrate the contrasting influences of in vivo glucuronidation and methylation on the bioactivity of epicatechin.
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Affiliation(s)
- J P Spencer
- Wolfson Centre for Age-Related Diseases, GKT School of Biomedical Sciences, King's College, London, UK
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128
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Lin CH, Yeh SH, Lin CH, Lu KT, Leu TH, Chang WC, Gean PW. A role for the PI-3 kinase signaling pathway in fear conditioning and synaptic plasticity in the amygdala. Neuron 2001; 31:841-51. [PMID: 11567621 DOI: 10.1016/s0896-6273(01)00433-0] [Citation(s) in RCA: 287] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Western blot analysis of neuronal tissues taken from fear-conditioned rats showed a selective activation of phosphatidylinositol 3-kinase (PI-3 kinase) in the amygdala. PI-3 kinase was also activated in response to long-term potentiation (LTP)-inducing tetanic stimulation. PI-3 kinase inhibitors blocked tetanus-induced LTP as well as PI-3 kinase activation. In parallel, these inhibitors interfered with long-term fear memory while leaving short-term memory intact. Tetanus and forskolin-induced activation of mitogen-activated protein kinase (MAPK) was blocked by PI-3 kinase inhibitors, which also inhibited cAMP response element binding protein (CREB) phosphorylation. These results provide novel evidence of a requirement of PI-3 kinase activation in the amygdala for synaptic plasticity and memory consolidation, and this activation may occur at a point upstream of MAPK activation.
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Affiliation(s)
- C H Lin
- Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan City, Taiwan
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129
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Abstract
Studies of the signal transduction mechanisms underlying learning and memory have provided many new insights into the molecular mechanisms underlying associative conditioning in mammals. In this issue of Neuron, Gean and colleagues report the discovery that the PI-3 kinase/AKT(PKB) pathway contributes to LTP and the consolidation of amygdala-dependent cued fear conditioning in rats.
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Affiliation(s)
- J D Sweatt
- Division of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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130
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Hertz L, Hansson E, Rönnbäck L. Signaling and gene expression in the neuron-glia unit during brain function and dysfunction: Holger Hydén in memoriam. Neurochem Int 2001; 39:227-52. [PMID: 11434981 DOI: 10.1016/s0197-0186(01)00017-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Holger Hydén demonstrated almost 40 years ago that learning changes the base composition of nuclear RNA, i.e. induces an alteration in gene expression. An equally revolutionary observation at that time was that a base change occurred in both neurons and glia. From these findings, Holger Hydén concluded that establishment of memory is correlated with protein synthesis, and he demonstrated de novo synthesis of several high-molecular protein species after learning. Moreover, the protein, S-100, which is mainly found in glial cells, was increased during learning, and antibodies towards this protein inhibited memory consolidation. S-100 belongs to a family of Ca(2+)-binding proteins, and Holger Hydén at an early point realized the huge importance of Ca(2+) in brain function. He established that glial cells show more marked and earlier changes in RNA composition in Parkinson's disease than neurons. Holger Hydén also had the vision and courage to suggest that "mental diseases could as well be thought to depend upon a disturbance of processes in glia cells as in the nerve cells", and he showed that antidepressant drugs cause profound changes in glial RNA. The importance of Holger Hydén's findings and visions can only now be fully appreciated. His visionary concepts of the involvement of glia in neurological and mental illness, of learning being associated with changes in gene expression, and of the functional importance of Ca(2+)-binding proteins and Ca(2+) are presently being confirmed and expanded by others. This review briefly summarizes highlights of Holger Hydén's work in these areas, followed by a discussion of recent research, confirming his findings and expanding his visions. This includes strong evidence that glial dysfunction is involved in the development of Parkinson's disease, that drugs effective in mood disorders alter gene expression and exert profound effects on astrocytes, and that neuronal-astrocytic interactions in glutamate signaling, NO synthesis, Ca(2+) signaling, beta-adrenergic activity, second messenger production, protein kinase activities, and transcription factor phosphorylation control the highly programmed events that carry the memory trace through the initial, signal-mediated short-term and intermediate memory stages to protein synthesis-dependent long-term memory.
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Affiliation(s)
- L Hertz
- Hong Kong DNA Chips Ltd., Kowloon, Hong Kong, People's Republic of China
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131
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Abstract
Despite decades of research, the mechanisms that underlie opiate tolerance, dependence and withdrawal remain elusive. Evidence accumulated over the past ten years suggests that the NMDA receptor plays a central role in mediating the neuroplasticity induced by chronic opiate administration in adult animals. Yet, during ontogeny, the NMDA receptor complex undergoes qualitative developmental changes, which renders some of the basic assumptions for a role of the NMDA receptor in opiate withdrawal invalid in infants. Recent data indicate that NMDA receptor antagonists are not effective in blocking morphine tolerance, dependence and withdrawal in the neonatal rat. Roles for other glutamate receptor types (e.g. metabotropic glutamate receptors) have also been proposed recently. In this article, the latest evidence that characterizes the dynamic roles of glutamate receptors in these phenomena during ontogeny will be discussed.
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Affiliation(s)
- H Zhu
- Biopsychology Doctoral Program, Hunter College, 695 Park Avenue, New York, NY 10021, USA
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132
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Yip PK, Meldrum BS, Rattray M. Elevated levels of group-III metabotropic glutamate receptors in the inferior colliculus of genetically epilepsy-prone rats following intracollicular administration of L-serine-O-phosphate. J Neurochem 2001; 78:13-23. [PMID: 11432969 DOI: 10.1046/j.1471-4159.2001.00418.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The selective group-III metabotropic glutamate receptor agonist, L-serine-O-phosphate (L-SOP), when injected bilaterally into the inferior colliculus of the sound sensitive genetically epilepsy-prone (GEP) rats produces a short proconvulsant excitation followed by a long phase of protection against sound-induced seizures lasting for 2-4 days. We have studied this prolonged suppression of audiogenic seizures using pharmacological and molecular biological approaches including semiquantitative RT-PCR and western blotting. The intracerebroventricular injection of the protein synthesis inhibitor cycloheximide (120 microg) 30 min beforehand significantly reduces the proconvulsant seizure activity and the prolonged anticonvulsant effect of intracollicular L-SOP (500 nmol/side). The sensitive semiquantitative RT-PCR revealed a significant up-regulation in mGlu(4) and mGlu(7) mRNA levels in the inferior colliculus at 2 days (maximum suppression of audiogenic seizures) after intracollicular L-SOP injection compared with the non-injected, 2-day post-vehicle treated and 7-day (return to expressing audiogenic seizures) post-drug or vehicle-treated groups. No significant changes were observed in mGlu(6) or mGlu(8) mRNA expression levels in drug-treated compared with control groups. Examination of mGlu(4a) and mGlu(7a) protein levels using western blotting showed a significant increase in mGlu(7a) but no significant change in mGlu(4a) protein levels 2 days after L-SOP treatment compared with the control groups (non-injected and 2-day vehicle-injected group). These results suggest that up-regulation of mGlu(7) receptors is involved in the prolonged anticonvulsant effect of L-SOP against sound-induced seizures in GEP rats. The potential use of mGlu(7) agonists as novel anti-epileptic agents merits investigation.
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Affiliation(s)
- P K Yip
- Department of Neurology, Institute of Psychiatry, King's College London, London, UK
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133
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Lerma J, Paternain AV, Rodríguez-Moreno A, López-García JC. Molecular physiology of kainate receptors. Physiol Rev 2001; 81:971-98. [PMID: 11427689 DOI: 10.1152/physrev.2001.81.3.971] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
A decade ago, our understanding of the molecular properties of kainate receptors and their involvement in synaptic physiology was essentially null. A plethora of recent studies has altered this situation profoundly such that kainate receptors are now regarded as key players in the modulation of transmitter release, as important mediators of the postsynaptic actions of glutamate, and as possible targets for the development of antiepileptic and analgesic drugs. In this review, we summarize our current knowledge of the properties of kainate receptors focusing on four key issues: 1) their structural and biophysical features, 2) the important progress in their pharmacological characterization, 3) their pre- and postsynaptic mechanisms of action, and 4) their involvement in a series of physiological and pathological processes. Finally, although significant progress has been made toward the elucidation of their importance for brain function, kainate receptors remain largely an enigma and, therefore, we propose some new roads that should be explored to obtain a deeper understanding of this young, but intriguing, class of proteins.
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Affiliation(s)
- J Lerma
- Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
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134
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Kihara T, Shimohama S, Sawada H, Honda K, Nakamizo T, Shibasaki H, Kume T, Akaike A. alpha 7 nicotinic receptor transduces signals to phosphatidylinositol 3-kinase to block A beta-amyloid-induced neurotoxicity. J Biol Chem 2001; 276:13541-6. [PMID: 11278378 DOI: 10.1074/jbc.m008035200] [Citation(s) in RCA: 326] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Multiple lines of evidence, from molecular and cellular to epidemiological, have implicated nicotinic transmission in the pathogenesis of Alzheimer's disease (AD). Here we show the signal transduction mechanism involved in nicotinic receptor-mediated protection against beta-amyloid-enhanced glutamate neurotoxicity. Nicotine-induced protection was suppressed by an alpha7 nicotinic receptor antagonist (alpha-bungarotoxin), a phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002 and wortmannin), and a Src inhibitor (PP2). Levels of phosphorylated Akt, an effector of PI3K, and Bcl-2 were increased by nicotine. The alpha7 nicotinic receptor was physically associated with the PI3K p85 subunit and Fyn. These findings indicate that the alpha7 nicotinic receptor transduces signals to PI3K in a cascade, which ultimately contributes to a neuroprotective effect. This might form the basis of a new treatment for AD.
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Affiliation(s)
- T Kihara
- Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
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135
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Reyes-Reyes M, Mora N, Zentella A, Rosales C. Phosphatidylinositol 3-kinase mediates integrin-dependent NF-(κ)B and MAPK activation through separate signaling pathways. J Cell Sci 2001; 114:1579-89. [PMID: 11282033 DOI: 10.1242/jcs.114.8.1579] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integrin-mediated signals play an important but poorly understood role in regulating many leukocyte functions. In monocytes and monocytic leukemia cells, (β)1 integrin-mediated adhesion results in a strong induction of immediate-early genes that are important in inflammation. To investigate the signaling pathways from integrins in monocytic cells, THP-1 cells were stimulated via (β)1 integrins by binding to fibronectin and by crosslinking the integrins with specific monoclonal antibodies. The involvement of MAPK and PI 3-K on nuclear factor (κ)B (NF-(κ)B) activation was then analyzed. We found that integrins activated both NF-(κ)B and MAPK in a PI 3-K-dependent manner, as wortmannin and LY294002 blocked these responses. However, the specific MEK inhibitor PD98059 did not prevent integrin-mediated NF-(κ)B activation. In contrast, a dominant negative mutant of Rac completely prevented NF-(κ)B activation, but it did not affect MAPK activation. These results indicate that integrin signaling to NF-(κ)B is not mediated by the MAPK pathway, but rather by the small GTPase Rac. In addition, a dominant negative form of Ρ augmented NF-(κ)B activation and blocked MAPK activation, implying that these two pathways are in competition with each other. These data suggest that integrins activate different signaling pathways in monocytic cells. One uses PI 3-K and Rac to activate NF-(κ)B, while the other uses PI 3-K, MEK, and MAPK to activate other nuclear factors, such as Elk-1.
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Affiliation(s)
- M Reyes-Reyes
- Immunology Department at Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
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136
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Zanassi P, Paolillo M, Feliciello A, Avvedimento EV, Gallo V, Schinelli S. cAMP-dependent protein kinase induces cAMP-response element-binding protein phosphorylation via an intracellular calcium release/ERK-dependent pathway in striatal neurons. J Biol Chem 2001; 276:11487-95. [PMID: 11139572 DOI: 10.1074/jbc.m007631200] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of the cAMP-dependent protein kinase A (PKA) pathway may induce cAMP-response element-binding protein (CREB) phosphorylation either directly or via cross-talk mechanisms with other signal transduction pathways. In this study, we have investigated in striatal primary cultures the mechanism by which activation of the cAMP/PKA-dependent pathway leads to CREB phosphorylation via the extracellular signal-regulated kinase (ERK)-dependent pathway. We have found that PKA-induced CREB phosphorylation and CREB-dependent transcription are mediated by calcium (Ca(2+)) release from intracellular stores and are blocked by inhibitors of the protein kinase C and ERK pathways. This mechanism appears to be mediated by the small G-protein Rap1, whose activation appears to be primed by PKA-induced Ca(2+) release but not further induced by direct or indirect PKA- or protein kinase C-dependent phosphorylation. These results suggest that, in striatal neurons, intracellular Ca(2+) release, Rap1, and ERK pathway play a crucial role in the PKA-induced CREB phosphorylation and CREB-dependent transcription.
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Affiliation(s)
- P Zanassi
- Dipartimento di Farmacologia Sperimentale ed Applicata, Facoltà di Farmacia, Università di Pavia, Pavia 27100, Italy
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137
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Pearse D, Mirza A, Leah J. Jun, Fos and Krox in the hippocampus after noxious stimulation: simultaneous-input-dependent expression and nuclear speckling. Brain Res 2001; 894:193-208. [PMID: 11251193 DOI: 10.1016/s0006-8993(01)01993-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Stimulation of sensory C-fibres produces extensive expression of the Fos, Jun and Krox families of inducible transcription factors (ITFs) in many nociceptive CNS areas [28]. In the hippocampus, however, c-Fos is only weakly induced by such stimulation, and expression of the other ITFs has not been studied. Here we examine the effects of single, repeated and simultaneous C-fibre inputs on ITF expressions in the rat hippocampus. A brief, strong electrical stimulation of sciatic nerve C-fibres induced little or no expression of c-Fos or Krox-20. In contrast, FosB was induced and continued to rise in all areas, whereas the basal expressions of c-Jun and Krox-24 were initially reduced but then returned during the subsequent 36 h. A weak noxious cutaneous stimulus applied to one hindpaw induced only weak expressions of the ITFs. However, if the sciatic stimulation was applied contralaterally and 6 h beforehand, this weak stimulus strongly induced Krox-24, but not other ITFs, i.e. there was a potentiation of Krox-24 expression. When these two stimuli were applied simultaneously a few c-Fos labelled cells did appear, and there was and an increased Krox-24 expression. There was also a strong potentiation of FosB and a strong reduction in c-Jun expression. This simultaneous stimulation was the only type of stimulation to induce expression of Krox-20. Also after simultaneous stimulation the majority of the nuclear labelling for FosB, but not of the other ITFs, had a speckled appearance. MK-801 blocked these changes in ITF expressions, but it could also cause the C-fibre stimulations to induce c-Fos and c-Jun in specific areas of the hippocampus. Thus C-fibre stimulation does affect transcription factor activity in the hippocampus; and the strong responses of some ITFs to simultaneous inputs points to their having a role as 'genetic coincidence detectors' in the hippocampus.
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Affiliation(s)
- D Pearse
- School of Biomedical and Biomolecular Sciences, Griffith University, Nathan, Australia
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138
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Tanaka K, Nogawa S, Ito D, Suzuki S, Dembo T, Kosakai A, Fukuuchi Y. Activated phosphorylation of cyclic AMP response element binding protein is associated with preservation of striatal neurons after focal cerebral ischemia in the rat. Neuroscience 2001; 100:345-54. [PMID: 11008172 DOI: 10.1016/s0306-4522(00)00289-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phosphorylation of the DNA-binding transcription factor, cyclic AMP response element binding protein, has recently been suggested to provide neuroprotective signals in times of cellular stress. Medium-sized striatal neurons are among the cells that are most vulnerable to ischemic stress in the brain. In the present study, phosphorylation of cyclic AMP response element binding protein was immunohistochemically evaluated in rat striatum in order to examine the ischemic vulnerability of each striatal region from the standpoint of cyclic AMP response element binding protein. Rats were subjected to 90-min focal cerebral ischemia followed by various periods of recirculation. Focal ischemia was induced by occlusion of the middle cerebral artery by the intraluminal suture method. Local cerebral blood flow measured by the 14C-iodoantipyrine method in the lateral and the medial striatal regions during occlusion was 5.0+/-7. 1 and 42.5+/-8.1ml/100g/min, respectively. Cerebral blood flow in each region was restored to the control level during the recirculation period. The lateral and the medial regions of the striatum in the sham animals showed hardly any immunoreactivity with the specific antibody against phosphorylated cyclic AMP response element binding protein. By contrast, at 3.5h of recirculation, a number of phosphorylated cyclic AMP response element binding protein-positive neurons were detected in the medial striatal region on the occluded side, and the increase in the number of immunopositive cells continued until two weeks of recirculation with gradual decline. The lateral striatal region on the ischemic side showed only a mild increase in phosphorylated cyclic AMP response element binding protein-positive cells at 3.5h of recirculation, and the immunoreactivity rapidly disappeared during the subsequent recirculation period. Appreciable increase in immunoreactive cells was also noted in the contralateral striatum during the early phase of recirculation, and this increase seemed to be associated with spontaneous circling movements of the animals. Cresyl Violet staining revealed that striatal neurons in the medial region remained intact until two weeks of recirculation, whereas neurons in the lateral striatal region soon showed ischemic damage, followed by complete neuronal loss, and evolution of a frank infarct. Immunoreactivity for bcl-2, apoptosis-suppressive protein, was clearly detected in many neurons in the medial striatal region, but no such immunoreactivity was detected in the lateral striatal region. These findings suggest that persistently activated phosphorylation of cyclic AMP response element binding protein in the striatum during post-ischemic recirculation may be closely associated with protection of striatal neurons on the ischemic side, while it may be associated with spontaneous circling movements on the contralateral side.
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Affiliation(s)
- K Tanaka
- Department of Neurology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, 160-8582, Tokyo, Japan.
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139
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Chandler LJ, Sutton G, Dorairaj NR, Norwood D. N-methyl D-aspartate receptor-mediated bidirectional control of extracellular signal-regulated kinase activity in cortical neuronal cultures. J Biol Chem 2001; 276:2627-36. [PMID: 11062237 DOI: 10.1074/jbc.m003390200] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
N-Methyl D-aspartate (NMDA) receptor activation of extracellular-signal regulated kinase (ERK) was examined in primary cortical cultures. Tetrodotoxin, NMDA receptor antagonists, or reduced extracellular calcium (0.1 mm) greatly decreased basal levels of phospho-ERK2, indicating that activity-dependent activation of NMDA receptors maintained a high level of basal ERK2 activation. This activity-dependent activation of phospho-ERK2 was blocked by pertussis toxin and inhibition of calcium/calmodulin-dependent kinase II and phosphatidylinositol 3-kinase but not by inhibition of protein kinase C or cAMP-dependent protein kinase. Addition of a calcium ionophore or 100 microm NMDA decreased phospho-ERK2 in the presence of 1 mm extracellular calcium but enhanced phospho-ERK2 in 0.1 mm extracellular calcium. The reduction in basal phospho-ERK2 by 100 microm NMDA was also reflected as a decrease in phospho-cAMP response element-binding protein. Inhibition of tyrosine phosphatases and serine/threonine phosphatases protein phosphatase 1 (PP1), PP2A, and PP2B did not prevent the inhibitory effect of NMDA. In the presence of tetrodotoxin, NMDA produced a bell-shaped dose-response curve with stimulation of phospho-ERK2 at 10, 25, and 50 microm NMDA and reduced stimulation at 100 microm NMDA. NMDA (50 microm) stimulation of phospho-ERK2 was completely blocked by pertussis toxin and inhibitors of phosphatidylinositol 3-kinase and was partially blocked by a calcium/calmodulin-dependent kinase II inhibitor. These results suggests that NMDA receptors can bidirectionally control ERK signaling.
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Affiliation(s)
- L J Chandler
- Departments of Physiology/Neuroscience and Psychiatry, Medical University of South Carolina, Charleston 29425, USA.
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140
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Sweatt JD. The neuronal MAP kinase cascade: a biochemical signal integration system subserving synaptic plasticity and memory. J Neurochem 2001; 76:1-10. [PMID: 11145972 DOI: 10.1046/j.1471-4159.2001.00054.x] [Citation(s) in RCA: 879] [Impact Index Per Article: 38.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The mitogen-activated protein kinase (MAP kinase, MAPK) cascade, as the name implies, was originally discovered as a critical regulator of cell division and differentiation. As further details of this signaling cascade were worked out, it became clear that the MAPK cascade is in fact a prototype for a family of signaling cascades that share the motif of three serially linked kinases regulating each other by sequential phosphorylation. Thus, a revised nomenclature arose that uses the term MAPK to refer to the entire superfamily of signaling cascades (comprising the erks, the JNKs and the p38 stress activated protein kinases), and specifies the prototype MAPK as the extracellular signal-regulated kinase (erk). The two erk MAPK isoforms, p44 MAPK and p42 MAPK, are referred to as erk1 and erk2, respectively. The erks are abundantly expressed in neurons in the mature central nervous system, raising the question of why the prototype molecular regulators of cell division and differentiation are present in these non-dividing, terminally differentiated neurons. This review will describe the beginnings of an answer to this question. Interestingly, the general model has begun to emerge that the erk signaling system has been co-opted in mature neurons to function in synaptic plasticity and memory. Moreover, recent insights have led to the intriguing prospect that these molecules serve as biochemical signal integrators and molecular coincidence detectors for coordinating responses to extracellular signals in neurons. In this review I will first outline the essential components of this signal transduction cascade, and briefly describe recent results implicating the erks in mammalian synaptic plasticity and learning. I will then proceed to outline recent results implicating the erks as molecular signal integrators and, potentially, coincidence detectors. Finally, I will speculate on what the critical downstream effectors of the erks are in neurons, and how they might provide a readout of the integrated signal.
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Affiliation(s)
- J D Sweatt
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030-3498, USA.
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141
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Schroeter H, Williams RJ, Matin R, Iversen L, Rice-Evans CA. Phenolic antioxidants attenuate neuronal cell death following uptake of oxidized low-density lipoprotein. Free Radic Biol Med 2000; 29:1222-33. [PMID: 11118812 DOI: 10.1016/s0891-5849(00)00415-9] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Oxidative stress is implicated in neuronal loss associated with neurodegeneration such as in Parkinson's disease, Alzheimer's disease and age-related cognitive decline. Recent reports indicate that the consumption of flavonoid-rich fruits partly reverses the age-related neuronal and cognitive decline. In this study, cultured striatal neurons were exposed to oxidized lipids in the form of low-density lipoprotein (oxLDL) as a model for the induction of oxidative injury, and the abilities of phenolic antioxidants, flavonoids and hydroxycinnamic acid derivatives, to attenuate this neuronal damage were examined. OxLDL was demonstrated to enter neuronal cells and to be capable of eliciting neurotoxicity in a dose- and time-dependent manner, inducing DNA fragmentation and cell lysis. Flavonoids exert protective effects, which appear to be related to specific structural characteristics, particularly relevant being those defining their reduction potentials and partition coefficients. In summary, these data suggest a possible role for flavonoids in reducing neurodegeneration associated with chronic disorders in which oxidative stress is implicated.
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Affiliation(s)
- H Schroeter
- Wolfson Centre for Age-Related Diseases, Guy's, King's, and St. Thomas's School of Biomedical Sciences, King's College, Guy's Campus, London, England
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142
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Junn E, Lee KN, Ju HR, Han SH, Im JY, Kang HS, Lee TH, Bae YS, Ha KS, Lee ZW, Rhee SG, Choi I. Requirement of hydrogen peroxide generation in TGF-beta 1 signal transduction in human lung fibroblast cells: involvement of hydrogen peroxide and Ca2+ in TGF-beta 1-induced IL-6 expression. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:2190-7. [PMID: 10925306 DOI: 10.4049/jimmunol.165.4.2190] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Stimulation of human lung fibroblast cells with TGF-beta1 resulted in a transient burst of reactive oxygen species with maximal increase at 5 min after treatment. This reactive oxygen species increase was inhibited by the antioxidant, N-acetyl-l -cysteine (NAC). TGF-beta1 treatment stimulated IL-6 gene expression and protein synthesis in human lung fibroblast cells. Antioxidants including NAC, glutathione, and catalase reduced TGF-beta1-induced IL-6 gene expression, and direct H2O2 treatment induced IL-6 expression in a dose-dependent manner. NAC also reduced TGF-beta1-induced AP-1 binding activity, which is involved in IL-6 gene expression. It has been reported that Ca2+ influx is stimulated by TGF-beta1 treatment. EGTA suppressed TGF-beta1- or H2O2-induced IL-6 expression, and ionomycin increased IL-6 expression, with simultaneously modulating AP-1 activity in the same pattern. PD98059, an inhibitor of mitogen-activated protein kinase (MAPK) kinase/extracellular signal-related kinase kinase 1, suppressed TGF-beta1- or H2O2-induced IL-6 and AP-1 activation. In addition, TGF-beta1 or H2O2 increased MAPK activity which was reduced by EGTA and NAC, suggesting that MAPK is involved in TGF-beta1-induced IL-6 expression. Taken together, these results indicate that TGF-beta1 induces a transient increase of intracellular H2O2 production, which regulates downstream events such as Ca2+ influx, MAPK, and AP-1 activation and IL-6 gene expression.
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Affiliation(s)
- E Junn
- Laboratory of Immunology, Korea Research Institute of Bioscience and Biotechnology, Taejon, Republic of Korea
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143
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Zirpel L, Janowiak MA, Veltri CA, Parks TN. AMPA receptor-mediated, calcium-dependent CREB phosphorylation in a subpopulation of auditory neurons surviving activity deprivation. J Neurosci 2000; 20:6267-75. [PMID: 10934277 PMCID: PMC6772589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
Although dependence on afferent synaptic activity has been shown for central neurons in every sensory system, the mechanisms of afferent maintenance of target sensory neurons are not understood. Neurons in the cochlear nucleus (CN) require afferent activity for maintenance and survival. One of the earliest changes seen after activity deprivation is an increase in intracellular calcium that leads to the death of 30% of the neuronal population. Sixty minutes after deafferentation, the surviving neurons show increased phosphorylation of the transcription factor calcium/cAMP response element-binding protein (CREB). CREB phosphorylation in activity-deprived CN neurons is dependent on increased intracellular calcium resulting from influx through AMPA receptors and is mediated by calcium/calmodulin-dependent kinases and protein kinase A. We conclude that in CN neurons, the deafferentation-induced increase in calcium activates at least two kinase pathways that phosphorylate CREB in surviving neurons. We hypothesize that this phosphorylation results in the transcription of genes containing the calcium/cAMP response element within their promoter regions, and these genes code for proteins that allow the neurons to compensate for their hypercalcemic, activity-deprived state.
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Affiliation(s)
- L Zirpel
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah 84132-0001, USA.
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144
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Swank MW. Phosphorylation of MAP kinase and CREB in mouse cortex and amygdala during taste aversion learning. Neuroreport 2000; 11:1625-30. [PMID: 10852213 DOI: 10.1097/00001756-200006050-00006] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Mice were subjected to a taste aversion conditioning procedure in which they drank water, familiar saccharin, or novel saccharin, followed by injection of either NaCl or the emetic agent LiCl. Immunohistochemistry was used to localize phosphorylated MAP kinase (ppERK) and phosphoCREB (pCREB) in the brain shortly after conditioning. An examination of insular cortex and amygdala revealed specific phosphorylation of MAP kinase by novel saccharin and LiCl, and CREB by LiCl. Pairing of novel saccharin with LiCl was the only stimulus sufficient to increase ppERK and pCREB immunoreactivity in the lateral amygdala, suggesting this as a site of CS-US convergence. ppERK immunoreactivity was localized to both nuclear and non-nuclear compartments, suggesting multiple functional roles of MAP kinase during learning.
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Affiliation(s)
- M W Swank
- Department of Psychiatry and New York Presbyterian Hospital, Joan and Sanford I. Weill Medical College of Cornell University, White Plains 10605, USA
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Cunha RA, Malva JO, Ribeiro JA. Pertussis toxin prevents presynaptic inhibition by kainate receptors of rat hippocampal [(3)H]GABA release. FEBS Lett 2000; 469:159-62. [PMID: 10713263 DOI: 10.1016/s0014-5793(00)01272-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Kainate receptors are ionotropic receptors, also reported to couple to G(i)/G(o) proteins, increasing neuronal excitability through disinhibition of neuronal circuits. We directly tested in hippocampal synaptosomes if kainate receptor-mediated inhibition of GABA release involved a metabotropic action. The kainate analogue, domoate (3 microM), inhibited by 24% [(3)H]GABA-evoked release, an effect reduced by 76% in synaptosomes pre-treated with pertussis toxin. Protein kinase C inhibition attenuated by 82% domoate-induced inhibition of GABA release whereas protein kinase C activation did not change kainate receptor binding. Thus, domoate inhibition of GABA release recruits G(i)/G(o) proteins and a protein kinase C pathway.
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Affiliation(s)
- R A Cunha
- Laboratory of Neurosciences, Faculty of Medicine, University of Lisbon, Av. Prof. Egas Moniz, 1649-028, Lisbon, Portugal.
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