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Koga K, Iwahori Y, Ozaki S, Ohta H. Regulation of spontaneous Ca2+ spikes by metabotropic glutamate receptors in primary cultures of rat cortical neurons. J Neurosci Res 2010; 88:2252-62. [DOI: 10.1002/jnr.22382] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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52
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Cao Z, LePage KT, Frederick MO, Nicolaou KC, Murray TF. Involvement of caspase activation in azaspiracid-induced neurotoxicity in neocortical neurons. Toxicol Sci 2010; 114:323-34. [PMID: 20047973 DOI: 10.1093/toxsci/kfp312] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Azaspiracids (AZAs) are a novel group of marine phycotoxins that have been associated with severe human intoxication. We found that AZA-1 exposure increased lactate dehydrogense (LDH) efflux in murine neocortical neurons. AZA-1 also produced nuclear condensation and stimulated caspase-3 activity with an half maximal effective concentration (EC(50)) value of 25.8 nM. These data indicate that AZA-1 triggers neuronal death in neocortical neurons by both necrotic and apoptotic mechanisms. An evaluation of the structure-activity relationships of AZA analogs on LDH efflux and caspase-3 activation demonstrated that the full structure of AZAs was required to produce necrotic or apoptotic cell death. The similar potencies of AZA-1 to stimulate LDH efflux and caspase-3 activation and the parallel structure-activity relationships of azaspiracid analogs in the two assays are consistent with a common molecular target for both responses. To explore the molecular mechanism for AZA-1-induced neurotoxicity, we assessed the influence of AZA-1 on Ca(2+) homeostasis. AZA-1 suppressed spontaneous Ca(2+) oscillations (EC(50) = 445 nM) in neocortical neurons. A distinct structure-activity profile was found for inhibition of Ca(2+) oscillations where both the full structure as well as analogs containing only the FGHI domain attached to a phenyl glycine methyl ester moiety were potent inhibitors. The molecular targets for inhibition of spontaneous Ca(2+) oscillations and neurotoxicity may therefore differ. The caspase protease inhibitor Z-VAD-FMK produced a complete elimination of AZA-1-induced LDH efflux and nuclear condensation in neocortical neurons. Although the molecular target for AZA-induced neurotoxicity remains to be established, these results demonstrate that the observed neurotoxicity is dependent on a caspase signaling pathway.
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Affiliation(s)
- Zhengyu Cao
- Department of Pharmacology, School of Medicine, Creighton University, Omaha, Nebraska 68178, USA
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53
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Takayama Y, Moriguchi H, Kotani K, Jimbo Y. Spontaneous Calcium Transients in Cultured Cortical Networks During Development. IEEE Trans Biomed Eng 2009; 56:2949-56. [DOI: 10.1109/tbme.2009.2028419] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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54
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Santos SF, Pierrot N, Morel N, Gailly P, Sindic C, Octave JN. Expression of human amyloid precursor protein in rat cortical neurons inhibits calcium oscillations. J Neurosci 2009; 29:4708-18. [PMID: 19369541 PMCID: PMC6665322 DOI: 10.1523/jneurosci.4917-08.2009] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Revised: 02/12/2009] [Accepted: 02/27/2009] [Indexed: 12/19/2022] Open
Abstract
Synchronous calcium oscillations are observed in primary cultures of rat cortical neurons when mature networks are formed. This spontaneous neuronal activity needs an accurate control of calcium homeostasis. Alteration of intraneuronal calcium concentration is described in many neurodegenerative disorders, including Alzheimer disease (AD). Although processing of amyloid precursor protein (APP) that generates Abeta peptide has critical implications for AD pathogenesis, the neuronal function of APP remains unclear. Here, we report that expression of human APP (hAPP) in rat cortical neurons increases L-type calcium currents, which stimulate SK channels, calcium-dependent K(+) channels responsible for medium afterhyperpolarization (mAHP). In a neuronal network, increased mAHP in some neurons expressing hAPP leads to inhibition of calcium oscillations in all the cells of the network. This inhibition is independent of production and secretion of Abeta and other APP metabolites. In a neuronal network, reduction of endogenous APP expression using shRNA increases the frequency and reduces the amplitude of calcium oscillations. Altogether, these data support a key role for APP in the control of neuronal excitability.
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Affiliation(s)
| | | | - Nicole Morel
- Laboratory of Cell Physiology, Université catholique de Louvain, B-1200 Brussels, Belgium
| | - Philippe Gailly
- Laboratory of Cell Physiology, Université catholique de Louvain, B-1200 Brussels, Belgium
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55
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Hampson RE, España RA, Rogers GA, Porrino LJ, Deadwyler SA. Mechanisms underlying cognitive enhancement and reversal of cognitive deficits in nonhuman primates by the ampakine CX717. Psychopharmacology (Berl) 2009; 202:355-69. [PMID: 18985324 PMCID: PMC3107999 DOI: 10.1007/s00213-008-1360-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2008] [Accepted: 09/29/2008] [Indexed: 12/20/2022]
Abstract
RATIONALE Performance of cognitive tasks in nonhuman primates (NHPs) requires specific brain regions to make decisions under different degrees of difficulty or "cognitive load." OBJECTIVE Local cerebral metabolic activity ([18F]FDG PET imaging) in dorsolateral prefrontal cortex (DLPFC), medial temporal lobe (MTL), and dorsal striatum (DStr) is examined in NHPs performing a delayed-match-to-sample (DMS) task with variable degrees of cognitive load. MATERIALS AND METHODS Correlations between cognitive load and degree of brain metabolic activity were obtained with respect to the influence of the ampakine CX717 (Cortex Pharmaceuticals), using brain imaging and recordings of neuronal activity in NHPs and measures of intracellular calcium release in rat hippocampal slices. RESULTS Activation of DLPFC, MTL, and DStr reflected changes in performance related to cognitive load within the DMS task and were engaged primarily on high load trials. Similar increased activation patterns and improved performance were also observed following administration of CX717. Sleep deprivation in NHPs produced impaired performance and reductions in brain activation which was reversed by CX717. One potential basis for this facilitation of cognition by CX717 was increased firing of task-specific hippocampal cells. Synaptic mechanisms affected by CX717 were examined in rat hippocampal slices which showed that N-methyl-D-aspartic acid-mediated release of intracellular calcium was reduced in slices from sleep-deprived rats and reversed by application of CX717 to the bathing medium. CONCLUSIONS The findings provide insight into how cognition is enhanced by CX717 in terms of brain, and underlying neural, processes that are activated on high vs. low cognitive load trials.
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Affiliation(s)
- R. E. Hampson
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157-1083, USA
| | - R. A. España
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157-1083, USA
| | - G. A. Rogers
- Medical School of the Americas, Nevis, West Indies
| | - L. J. Porrino
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157-1083, USA
| | - S. A. Deadwyler
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157-1083, USA
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Mehta B, Begum G, Joshi NB, Joshi PG. Nitric oxide-mediated modulation of synaptic activity by astrocytic P2Y receptors. ACTA ACUST UNITED AC 2008; 132:339-49. [PMID: 18725529 PMCID: PMC2518726 DOI: 10.1085/jgp.200810043] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigated the mechanism of synaptic suppression by P2Y receptors in mixed hippocampal cultures wherein networked neurons exhibit synchronized Ca2+ oscillations (SCO) due to spontaneous glutamatergic synaptic transmission. Pharmacological studies suggested that SCO suppression was mediated by P2Y2/P2Y4 receptors. Immunostaining studies and characterization of ATP/UTP-stimulated Ca2+ responses in solitary neurons and astrocytes revealed that the SCO attenuation was effectuated by astrocytes. We demonstrate that nitric oxide released from activated astrocytes causes synaptic suppression by inhibiting neurotransmitter release. Physiological concentrations of ATP and UTP evoked NO production in astrocytes. SCO suppression was considerably diminished by removal of extracellular NO by membrane-impermeable scavenger c-PTIO or by pretreatment of cells with nitric oxide synthase inhibitor L-NAME. The nitric oxide donor DETA/NO effectively suppressed the SCO. ATP/UTP inhibited KCl-induced exocytosis at presynaptic terminals in an NO-dependent manner. In the absence of exogenously added ATP/UTP, both the NO scavenger and NOS inhibitor enhanced the frequency of SCO, implying that astrocytes release NO during spontaneous synaptic activity and exert a suppressive effect. We report for the first time that under physiological conditions astrocytes use NO as a messenger molecule to modulate the synaptic strength in the networked neurons.
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Affiliation(s)
- Bhupesh Mehta
- Department of Biophysics, National Institute of Mental Health and Neurosciences, Bangalore 560029, India
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Peterson B, Stovall K, Monian P, Franklin JL, Cummings BS. Alterations in phospholipid and fatty acid lipid profiles in primary neocortical cells during oxidant-induced cell injury. Chem Biol Interact 2008; 174:163-76. [PMID: 18602625 DOI: 10.1016/j.cbi.2008.05.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 05/19/2008] [Accepted: 05/22/2008] [Indexed: 10/22/2022]
Abstract
Specific phospholipids and fatty acids altered during oxidant-induced neuronal cell injury were determined using electrospray ionization mass spectrometry (ESI-MS) and ion trapping. The oxidants hydrogen peroxide (H(2)O(2), 0-1000 microM) and tert-butylhydroperoxide (TBHP, 0-400 microM) induced time- and concentration-dependent increases in reactive oxygen species in primary cultures of mouse neocortical cells as determined by 2',7'-dichlorofluorescein diacetate staining and thiobarbituric acid formation. ESI-MS analysis of 26 m/z values, representing 42 different phospholipids, demonstrated that H(2)O(2) and TBHP increased the abundance of phospholipids containing polyunsaturated fatty acids, but had minimal affect on those containing mono- or di-unsaturated fatty acids. These increases correlated to time-dependent increase in 16:1-20:4, 16:0-20:4, 18:1-20:4 and 18:0-20:4 phosphatidylcholine. Oxidant exposure also increased mystric (14:0), palmitic (16:0), and stearic (18:0) acid twofold, oleic acid (18:1) two- to threefold, and arachidonic acid (20:4) fourfold, compared to controls. Increases in arachidonic acid levels occurred prior to increases in the phospholipids, but after increases in ROS, and correlated to increases in oxidized arachidonic acid species, specifically [20:4-OOH]-H(2)O-, 20:4-OH-, and Tri-OH-20:4-arachidonic acid. Treatment of cells with methyl arachidonyl flourophosphonate an inhibitor of Group IV and VI PLA(2), decreased oxidant-induced arachidonic acid release, while bromoenol lactone, an inhibitor of Group VI PLA(2), did not. Collectively, these data identify phospholipids and fatty acids altered during oxidant treatment of neurons and suggest differential roles for Group IV and VI PLA(2) in oxidant-induced neural cell injury.
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Affiliation(s)
- Brianna Peterson
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia, Athens, GA 30602-2352, United States
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Dhingra V, Li Q, Allison AB, Stallknecht DE, Fu ZF. Proteomic profiling and neurodegeneration in West-Nile-virus-infected neurons. J Biomed Biotechnol 2008; 2005:271-9. [PMID: 16192685 PMCID: PMC1224697 DOI: 10.1155/jbb.2005.271] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
West Nile virus, a mosquito-borne flavivirus, is a
human, equine, and avian pathogen. High-resolution two-dimensional
differential-gel electrophoresis (2D-DIGE) was used to
characterize protein expression in primary rat neurons and to
examine the proteomic profiling to understand the pathogenesis of
West-Nile-associated meningoencephalitis. Three pH ranges, 3–10,
4–7, and 5–6, were used to analyze the protein spots. The
proteins are labeled with fluorescent dyes Cy3 and Cy5 before
being separated on the basis of charge and size respectively on a
two-dimensional platform. About 55 proteins showed altered
expression levels. These were then subsequently digested and
identified by matrix-assisted laser desorption/ionization
time-of-flight mass spectrometry (MALDI-TOF MS) analysis using
peptide mass fingerprinting and database searching. These cellular
proteins could represent distinct roles during infection related
to apoptosis. Our findings show that two-dimensional differential
gel electrophoresis combined with mass spectrometry is a powerful
approach that permits the identification of proteins whose
expression was altered due to West Nile virus infection.
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Affiliation(s)
- V. Dhingra
- Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - Q. Li
- Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - A. B. Allison
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - D. E. Stallknecht
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - Z. F. Fu
- Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
- *Z. F. Fu:
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Davis RC, Furukawa R, Fechheimer M. A cell culture model for investigation of Hirano bodies. Acta Neuropathol 2008; 115:205-17. [PMID: 17978823 DOI: 10.1007/s00401-007-0275-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Revised: 07/24/2007] [Accepted: 07/26/2007] [Indexed: 11/28/2022]
Abstract
Hirano bodies are paracrystalline F-actin-rich aggregations associated with a variety of conditions including aging, and neurodegenerative diseases. The composition and structure of these inclusions have been described by immunohistochemistry and ultrastructure, respectively. However, studies of the physiological function and dynamics of Hirano bodies have been hindered due to lack of a facile in vitro experimental system. We have developed a model for formation of Hirano bodies in mammalian cell cultures by expression of the carboxy-terminal fragment (CT) of a 34-kDa actin-bundling protein. Expression of the CT protein induces F-actin rearrangement in HEK 293, HeLa, Cos7 cells, neuroblastoma and astrocytic cells, and in primary neurons. We have termed these structures model Hirano bodies, since their composition and ultrastructure is quite similar to that reported in vivo. Model Hirano bodies in cell cultures sometimes appeared to be formed of a number of smaller domains, suggesting that small aggregates are intermediates in the formation of Hirano bodies. Stable lines expressing CT and bearing model Hirano bodies exhibit normal growth, morphology, and motility. This model provides a valuable system for the study of the dynamics of Hirano bodies, and their role in disease processes.
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Affiliation(s)
- Richard C Davis
- Department of Cellular Biology, University of Georgia, 724 Biological Sciences, Athens, GA 30602, USA
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Zhu SQ, Qi L, Rui YF, Li RX, He XP, Xie ZP. Astragaloside IV inhibits spontaneous synaptic transmission and synchronized Ca2+ oscillations on hippocampal neurons. Acta Pharmacol Sin 2008; 29:57-64. [PMID: 18158866 DOI: 10.1111/j.1745-7254.2008.00712.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
AIM To investigate the changes in the spontaneous neuronal excitability induced by astragaloside IV (AGS-IV) in the cultured hippocampal network. METHODS Hippocampal neurons in culture for 9-11 d were used for this study. The spontaneous synaptic activities of these hippocampal neurons were examined by Ca2+ imaging and whole-cell patch-clamp techniques. In total, 40 mg/L AGS-IV dissolved in DMSO and 2 mL/L DMSO were applied to the neurons under a microscope while the experiments were taking place. RESULTS AGS-IV inhibited the frequencies of synchronized spontaneous Ca2+ oscillations to 59.39%+/- 3.25%(mean+/-SEM), the spontaneous postsynaptic currents to 43.78%+/- 7.72%(mean+/-SEM), and the spontaneous excitatory postsynaptic currents to 49.25%+/- 7.06%(mean+/-SEM) of those of the control periods, respectively, at 16 min after the AGSIV applications. AGS-IV also decreased the peak values of the voltage-gated K+ and Na+ channel currents at that time point. CONCLUSION These results indicate that AGS-IV suppresses the spontaneous neuronal excitabilities effectively. Such a modulation of neuronal activity could represent new evidence for AGS-IV as a neuroprotector.
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Affiliation(s)
- Shao-qing Zhu
- Department of Biological Science and Biotechnology, State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University, Beijing, China
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Dravid SM, Baden DG, Murray TF. Brevetoxin augments NMDA receptor signaling in murine neocortical neurons. Brain Res 2005; 1031:30-8. [PMID: 15621010 DOI: 10.1016/j.brainres.2004.10.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/19/2004] [Indexed: 12/25/2022]
Abstract
Brevetoxins (PbTx) are potent allosteric enhancers of voltage-gated sodium channel (VGSC) function and are associated with periodic "red tide" blooms. These neurotoxins produce neuronal injury and death in cerebellar granule cells (CGC) following acute exposure. In murine neocortical neurons, brevetoxin induces Ca(2+) influx that is mediated through both glutamatergic and non-glutamatergic pathways. Inasmuch as Src kinase is capable of upregulating the NMDA subtype of glutamate receptors, we determined whether Src kinase participated in PbTx-2-induced Ca(2+) influx. Inhibition of Src kinase blocked PbTx-2-induced Ca(2+) influx. PbTx-2 treatment moreover increased tyrosine phosphorylation of the NR2B subunit. A rise in intracellular [Na(+)] and phosphorylation of NMDA receptors by Src kinase is known to increase NMDA receptor activity. We therefore explored the influence of brevetoxin on NMDA receptor function. We found that PbTx-2 augments NMDA receptor-mediated Ca(2+) influx in both spontaneously oscillating mature neurons and in non-oscillatory immature neurons. PbTx-2 also enhanced the effect of bath-applied NMDA on extracellular signal-regulated kinase 2 (ERK2) activation. These results suggest that brevetoxin augments NMDA receptor signaling in neocortical neurons, and this upregulation may be mediated by coincidence of an elevation in intracellular [Na(+)] and Src kinase activation.
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Affiliation(s)
- Shashank M Dravid
- College of Veterinary Medicine, Department of Physiology and Pharmacology, University of Georgia, Athens, GA 30602, USA
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