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Yardimoğlu M, Ilbay G, Dalcik C, Dalcik H, Sahin D, Ates N. Immunocytochemistry of neuron specific enolase (NSE) in the rat brain after single and repeated epileptic seizures. Int J Neurosci 2008; 118:981-93. [PMID: 18569155 DOI: 10.1080/00207450701769232] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The aim of this study was to investigate neuron-specific enolase (NSE) immunoreactivity of the different brain regions after pentylenetetrazol (PTZ)- induced epileptic seizures in rats. Light microscopic examinations provided evidences for changes of neuronal activity after single and repeated seizures. The number of NSE (+) cells was well correlated with Nissl staining. The results suggest that NSE immunoreactivity may be a valuable marker for determination of the number of metabolically active neurons in different brain regions after single and repeated experimental seizures.
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Affiliation(s)
- Melda Yardimoğlu
- Department of Histology & Embryology, Kocaeli University, School of Medicine, Kocaeli, Turkey.
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202
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Kolbaev S, Draguhn A. Glutamine-induced membrane currents in cultured rat hippocampal neurons. Eur J Neurosci 2008; 28:535-45. [DOI: 10.1111/j.1460-9568.2008.06365.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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203
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Eid T, Ghosh A, Wang Y, Beckström H, Zaveri HP, Lee TSW, Lai JCK, Malthankar-Phatak GH, de Lanerolle NC. Recurrent seizures and brain pathology after inhibition of glutamine synthetase in the hippocampus in rats. Brain 2008; 131:2061-70. [PMID: 18669513 PMCID: PMC2724901 DOI: 10.1093/brain/awn133] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Revised: 05/30/2008] [Accepted: 06/02/2008] [Indexed: 11/14/2022] Open
Abstract
An excess of extracellular glutamate in the hippocampus has been linked to the generation of recurrent seizures and brain pathology in patients with medically intractable mesial temporal lobe epilepsy (MTLE). However, the mechanism which results in glutamate excess in MTLE remains unknown. We recently reported that the glutamate-metabolizing enzyme glutamine synthetase is deficient in the hippocampus in patients with MTLE, and we postulated that this deficiency is critically involved in the pathophysiology of the disease. To further explore the role of glutamine synthetase in MTLE we created a novel animal model of hippocampal glutamine synthetase deficiency by continuous (approximately 28 days) microinfusion of methionine sulfoximine (MSO: 0.625 to 2.5 microg/h) unilaterally into the hippocampus in rats. This treatment led to a deficiency in hippocampal glutamine synthetase activity by 82-97% versus saline. The majority (>95%) of the MSO-treated animals exhibited recurrent seizures that continued for several weeks. Some of the MSO-treated animals exhibited neuropathological features that were similar to mesial temporal sclerosis, such as hippocampal atrophy and patterned loss of hippocampal neurons. However, many MSO-treated animals displayed only minimal injury to the hippocampus, with no clear evidence of mesial temporal sclerosis. These findings support the hypothesis that a deficiency in hippocampal glutamine synthetase causes recurrent seizures, even in the absence of classical mesial temporal sclerosis, and that restoration of glutamine synthetase may represent a novel approach to therapeutic intervention in this disease.
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Affiliation(s)
- Tore Eid
- Department of Laboratory Medicine, Yale University School of Medicine, 333 Cedar Street, P.O. Box 208035, New Haven, CT 06520-8035, USA.
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204
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Pan JW, Williamson A, Cavus I, Hetherington HP, Zaveri H, Petroff OAC, Spencer DD. Neurometabolism in human epilepsy. Epilepsia 2008; 49 Suppl 3:31-41. [PMID: 18304254 DOI: 10.1111/j.1528-1167.2008.01508.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Because of the large and continuous energetic requirements of brain function, neurometabolic dysfunction is a key pathophysiologic aspect of the epileptic brain. Additionally, neurometabolic dysfunction has many self-propagating features that are typical of epileptogenic processes, that is, where each occurrence makes the likelihood of further mitochondrial and energetic injury more probable. Thus abnormal neurometabolism may be not only a chronic accompaniment of the epileptic brain, but also a direct contributor to epileptogenesis. METHODS We examine the evidence for neurometabolic dysfunction in epilepsy, integrating human studies of metabolic imaging, electrophysiology, microdialysis, as well as intracranial EEG and neuropathology. RESULTS As an approach of noninvasive functional imaging, quantitative magnetic resonance spectroscopic imaging (MRSI) measured abnormalities of mitochondrial and energetic dysfunction (via 1H or 31P spectroscopy) are related to several pathophysiologic indices of epileptic dysfunction. With patients undergoing hippocampal resection, intraoperative 13C-glucose turnover studies show a profound decrease in neurotransmitter (glutamate-glutamine) cycling relative to oxidation in the sclerotic hippocampus. Increased extracellular glutamate (which has long been associated with increased seizure likelihood) is significantly linked with declining energetics as measured by 31P MR, as well as with increased EEG measures of Teager energy, further arguing for a direct role of glutamate with hyperexcitability. DISCUSSION Given the important contribution that metabolic performance makes toward excitability in brain, it is not surprising that numerous aspects of mitochondrial and energetic state link significantly with electrophysiologic and microdialysis measures in human epilepsy. This may be of particular relevance with the self-propagating nature of mitochondrial injury, but may also help define the conditions for which interventions may be developed.
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Affiliation(s)
- Jullie W Pan
- Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut, USA
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205
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Bidmon HJ, Görg B, Palomero-Gallagher N, Schleicher A, Häussinger D, Speckmann EJ, Zilles K. Glutamine synthetase becomes nitrated and its activity is reduced during repetitive seizure activity in the pentylentetrazole model of epilepsy. Epilepsia 2008; 49:1733-48. [PMID: 18479397 DOI: 10.1111/j.1528-1167.2008.01642.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
PURPOSE The astrocyte-specific glutamine synthetase (GS) plays a key role in glutamate recycling and Gamma-aminobutyric acid (GABA) metabolism. Changes in the expression or activity of GS have been proposed to contribute to epileptogenesis. The mechanisms or how and where GS may contribute to epilepsy is still a matter of discussion. Here we asked the question whether brain regions, which show an astrocytic stress response respond with alterations of GS. METHODS Biochemical and histological alterations of GS, HSP-27, and GFAP were studied after pentylenetetrazole-induced repetitive epileptic seizures (PIRS) in rats using a topographical quantification of the GS-immunoreactivity (GSIR) in relation to the focal heat shock response (HSR). Saline-treated rats served as controls and rats treated by the GS-inhibitor, L-methionine-sulfoximine (MSO) served as a positive control. RESULTS No changes in the amount of GSIR and GS-protein occurred during PIRS. A significant reduction of GSIR was observed by histochemistry (in situ) and in native (nonheated) protein extracts of MSO-treated rats. In rats affected by PIRS, GS-activity showed a significant, region-specific reduction in association with a nitration of the enzyme. DISCUSSION These results show that neither PIRS nor GS-inhibition reduced the amount of GS protein, but that MSO interferes with antibody binding to native GS. PIRS resulted in a focal increase of astrocytic stress response, whereas MSO caused a widespread, homogeneous astrocytic HSR independent from quantitative changes of GS content. In rats with PIRS the regions showing a strong glial HSR, respond with reduced GS-activity and GS-nitration, which all together are clear indicators of a nitrosative stress response.
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Affiliation(s)
- Hans-J Bidmon
- C & O Vogt Institute for Brain Research, Heinrich-Heine-University, Düsseldorf, Germany.
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206
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Cavus I, Pan JW, Hetherington HP, Abi-Saab W, Zaveri HP, Vives KP, Krystal JH, Spencer SS, Spencer DD. Decreased hippocampal volume on MRI is associated with increased extracellular glutamate in epilepsy patients. Epilepsia 2008; 49:1358-66. [PMID: 18410365 DOI: 10.1111/j.1528-1167.2008.01603.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE Temporal lobe epilepsy (TLE) is associated with smaller hippocampal volume and with elevated extracellular (EC) glutamate levels. We investigated the relationship between the hippocampal volume and glutamate in refractory TLE patients. METHODS We used quantitative MRI volumetrics to measure the hippocampal volume and zero-flow microdialysis to measure the interictal glutamate, glutamine, and GABA levels in the epileptogenic hippocampus of 17 patients with medication-resistant epilepsy undergoing intracranial EEG evaluation. The relationships between hippocampal volume, neurochemical levels, and relevant clinical factors were examined. RESULTS Increased EC glutamate in the epileptogenic hippocampus was significantly related to smaller ipsilateral (R(2)= 0.75, p < 0.0001), but not contralateral hippocampal volume when controlled for glutamine and GABA levels, and for clinical factors known to influence hippocampal volume. Glutamate in the atrophic hippocampus was significantly higher (p = 0.008, n = 9), with the threshold for hippocampal atrophy estimated as 5 microM. GABA and glutamine levels in the atrophic and nonatrophic hippocampus were comparable. Decreased hippocampal volume was related to higher seizure frequency (p = 0.008), but not to disease duration or febrile seizure history. None of these clinical factors were related to the neurochemical levels. CONCLUSIONS We provide evidence for a significant association between increased EC glutamate and decreased ipsilateral epileptogenic hippocampal volume in TLE. Future work will be needed to determine whether the increase in glutamate has a causal relationship with hippocampal atrophy, or whether another, yet unknown factor results in both. This work has implications for the understanding and treatment of epilepsy as well as other neurodegenerative disorders associated with hippocampal atrophy.
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Affiliation(s)
- Idil Cavus
- Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut 06511, USA.
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207
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Williamson A, Patrylo PR. Physiological studies of human dentate granule cells. PROGRESS IN BRAIN RESEARCH 2008; 163:183-98. [PMID: 17765719 DOI: 10.1016/s0079-6123(07)63011-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
The availability of human hippocampi obtained through surgery (usually for treatment of temporal lobe epilepsy) has allowed us to investigate the properties of the human dentate in a way that cannot be done with other brain regions. The dentate has been the primary focus of these studies because of its relative preservation in all patient specimens. Moreover, there is extensive synaptic reorganization of numerous neurotransmitter systems in this the fascia dentate (dentate gyrus and the hilus) in humans with specific forms of TLE. These changes are not evident in tissue from patients with seizure that begin outside the hippocampus, and, as a result, this tissue provides an invaluable resource for comparisons. Physiological data using both slices and acutely dissociated cells demonstrate that the granule cells have membrane properties similar to those of rodents although there are specific changes that appear to be associated with seizures. Similarly, in the non-sclerotic hippocampi, the synaptic properties are similar to those reported in rodents. There are also a number of parallels between the findings in humans and in status animal models of temporal lobe epilepsy. This review will cover analyses of membrane properties as well as of glutamatergic, GABAergic, and neuromodulatory systems. Thus, while there are a number of issues that invariably arise with studies of pathological human tissue, this tissue is ideally suited to verify and refine animal models of temporal lobe epilepsy. In addition, one can argue that human tissue provides the only resource to evaluate the ways that granule cells recorded from laboratory animals approximate human granule cell physiology.
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Affiliation(s)
- Anne Williamson
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT 06518, USA.
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208
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Eid T, Williamson A, Lee TSW, Petroff OA, De Lanerolle NC. Glutamate and astrocytes-Key players in human mesial temporal lobe epilepsy? Epilepsia 2008; 49 Suppl 2:42-52. [DOI: 10.1111/j.1528-1167.2008.01492.x] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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209
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Fotheringham J, Williams EL, Akhyani N, Jacobson S. Human Herpesvirus 6 (HHV-6) Induces Dysregulation of Glutamate Uptake and Transporter Expression in Astrocytes. J Neuroimmune Pharmacol 2007; 3:105-16. [DOI: 10.1007/s11481-007-9084-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Accepted: 07/30/2007] [Indexed: 10/22/2022]
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210
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Quintero JE, Day BK, Zhang Z, Grondin R, Stephens ML, Huettl P, Pomerleau F, Gash DM, Gerhardt GA. Amperometric measures of age-related changes in glutamate regulation in the cortex of rhesus monkeys. Exp Neurol 2007; 208:238-46. [PMID: 17927982 DOI: 10.1016/j.expneurol.2007.08.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 08/01/2007] [Accepted: 08/07/2007] [Indexed: 11/17/2022]
Abstract
l-glutamate (glutamate) is the principal excitatory neurotransmitter of the central nervous system and is involved in altered neural function during aging and in neurodegenerative diseases. Relatively little is known about the mechanisms of glutamate signaling in the primate brain, in part, because there is an absence of a method capable of rapidly measuring glutamate in either a non-clinical or a clinical setting. We have addressed this paucity of information by measuring extracellular glutamate at 1 Hz in the pre-motor and motor cortices of young, middle-aged, and aged monkeys using a minimally invasive amperometric recording method. In the motor cortex, mean resting glutamate levels were five times higher in the aged group compared to the young group while the pre-motor cortex showed an increasing trend in resting glutamate levels that was not statistically significant. In addition, we measured rapid, phasic glutamate release after local pressure-ejection of nanoliter volumes of either isotonic 70 mM potassium (to stimulate glutamate release) or 1 mM glutamate (to study glutamate uptake) into the pre-motor and motor cortex. In the pre-motor cortex, we measured reproducible glutamate uptake signals that had a significantly decreased (47%) rate of glutamate uptake in aged animals compared to young animals. However, following a 70 mM potassium delivery, we did not observe any consistent changes in evoked release between young versus aged animals. Using these non-clinical microelectrodes to measure glutamate signaling in the brain, our results support the hypothesis that the glutamatergic system undergoes reorganization with aging of the central nervous system.
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Affiliation(s)
- Jorge E Quintero
- Department of Anatomy and Neurobiology, University of Kentucky, Lexington, KY 40536-0098, USA
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211
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Samuelsson C, Hillered L, Zetterling M, Enblad P, Hesselager G, Ryttlefors M, Kumlien E, Lewén A, Marklund N, Nilsson P, Salci K, Ronne-Engström E. Cerebral glutamine and glutamate levels in relation to compromised energy metabolism: a microdialysis study in subarachnoid hemorrhage patients. J Cereb Blood Flow Metab 2007; 27:1309-17. [PMID: 17228333 DOI: 10.1038/sj.jcbfm.9600433] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Astrocytic glutamate (Glt) uptake keeps brain interstitial Glt levels low. Within the astrocytes Glt is converted to glutamine (Gln), which is released and reconverted to Glt in neurons. The Glt-Gln cycle is energy demanding and impaired energy metabolism has been suggested to cause low interstitial Gln/Glt ratios. Using microdialysis (MD) measurements from visually noninjured cortex in 33 neurointensive care patients with subarachnoid hemorrhage, we have determined how interstitial Glt and Gln, as a reflection of the Glt-Gln cycle turnover, relate to perturbed energy metabolism. A total of 3703 hourly samples were analyzed. The lactate/pyruvate (L/P) ratios correlated to the Gln/Glt ratios (r=-0.66), but this correlation was not stronger than the correlation between L/P and Glt (r=0.68) or the correlation between lactate and Glt (r=0.65). A novel observation was a linear relationship between interstitial pyruvate and Gln (r=0.52). There were 13 periods (404 h) of 'energy crisis', defined by L/P ratios above 40. All were associated with high interstitial Glt levels. Periods with L/P ratios above 40 and low pyruvate levels were associated with decreased interstitial Gln levels, suggesting ischemia and failing astrocytic Gln synthesis. Periods with L/P ratios above 40 and normal or high pyruvate levels were associated with increased interstitial Gln levels, which may represent an astrocytic hyperglycolytic response to high interstitial Glt levels. The results imply that moderately elevated L/P ratios cannot always be interpreted as failing energy metabolism and that interstitial pyruvate levels may discriminate whether or not there is sufficient astrocytic capacity for Glt-Gln cycling in the brain.
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Affiliation(s)
- Carolina Samuelsson
- Department of Neuroscience, Neurosurgery, Uppsala University Hospital, Uppsala, Sweden.
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212
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Abstract
UNLABELLED Seizures in neonates (NBs) remain the most frequent neurological problem in the nursery. Considerable debate about their consequences exists between data and deductions reached through animal experimentations and those obtained through clinical investigations. The main conflicting issues are whether seizures in NBs can plant the roots for epileptogenesis and cause long-term deficits. The purpose of this chapter is to evaluate both laboratory and clinical results. METHODS Clinical data will be presented, including a 20-year-long cohort of NBs. This will be followed by the main seminal discoveries obtained in neonatal models. The phenomenon of transient or persistent dysmaturity following NB seizures will be discussed in relation to etiological factors. RESULTS The findings and deductions from animal models support the notions that epileptogenesis and cognitive deficits result from NB seizures. These conclusions contrast with clinical investigations maintaining that NB seizures, per se, are symptomatic markers of preexisting or of ongoing morbidities. The reasons for contrasting views will be discussed. Suggestions will be advanced for more animal models whose seizures are consistent with the etiologies and the phenotypes of human NB seizures.
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Affiliation(s)
- Cesare T Lombroso
- Department of Neurology, Children's Hospital and Department of Neurology, Harvard Medical School, Boston, Massachusetts, USA.
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213
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Devall AJ, Blake R, Langman N, Smith CGS, Richards DA, Whitehead KJ. Monolithic column-based reversed-phase liquid chromatography separation for amino acid assay in microdialysates and cerebral spinal fluid. J Chromatogr B Analyt Technol Biomed Life Sci 2007; 848:323-8. [PMID: 17101306 DOI: 10.1016/j.jchromb.2006.10.049] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2006] [Revised: 10/27/2006] [Accepted: 10/27/2006] [Indexed: 11/22/2022]
Abstract
The development of a HPLC method using a monolithic C18 column is described using fluorescence detection for the assay of 21 amino acids and related substances with derivatisation using ortho-phthaldialdehyde (OPA) in the presence of 3-mercaptopropionic acid (3-MPA). The method employs a tertiary gradient and has a run time of 24 min. Linearity (r2) for each amino acid was found to be greater than 0.99 up to a 10 microM concentration; reproducibility across all analyses (relative standard deviation (R.S.D.)) was between 0.97 and 6.7% and limit of detection (LOD) between 30 and 300 fmol on column. This method has been applied to the analysis of amino acids in both spinal microdialysis and cerebral spinal fluid samples.
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Affiliation(s)
- A J Devall
- Pain Signalling Group, Department of Pharmacology, Division of Neuroscience, The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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214
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Eid T, Hammer J, Rundén-Pran E, Roberg B, Thomas MJ, Osen K, Davanger S, Laake P, Torgner IA, Lee TSW, Kim JH, Spencer DD, Ottersen OP, de Lanerolle NC. Increased expression of phosphate-activated glutaminase in hippocampal neurons in human mesial temporal lobe epilepsy. Acta Neuropathol 2007; 113:137-52. [PMID: 17115168 DOI: 10.1007/s00401-006-0158-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 10/06/2006] [Accepted: 10/07/2006] [Indexed: 11/25/2022]
Abstract
Patients with mesial temporal lobe epilepsy (MTLE) have increased basal concentrations of extracellular glutamate in the epileptogenic versus the non-epileptogenic hippocampus. Such elevated glutamate levels have been proposed to underlie the initiation and maintenance of recurrent seizures, and a key question is what causes the elevation of glutamate in MTLE. Here, we explore the possibility that neurons in the hippocampal formation contain higher levels of the glutamate synthesizing enzyme phosphate-activated glutaminase (PAG) in patients with MTLE versus patients with other forms of temporal lobe epilepsy (non-MTLE). Increased PAG immunoreactivity was recorded in subpopulations of surviving neurons in the MTLE hippocampal formation, particularly in CA1 and CA3 and in the polymorphic layer of the dentate gyrus. Immunogold analysis revealed that PAG was concentrated in mitochondria. Double-labeling experiments indicated a positive correlation between the mitochondrial contents of PAG protein and glutamate, as well as between PAG enzyme activity and PAG protein as determined by Western blots. These data suggest that the antibodies recognize an enzymatically active pool of PAG. Western blots and enzyme activity assays of hippocampal homogenates revealed no change in PAG between MTLE and non-MTLE, despite a greatly (>50%) reduced number of neurons in the MTLE hippocampal formation compared to non-MTLE. Thus, the MTLE hippocampal formation contains an increased concentration and activity of PAG per neuron compared to non-MTLE. This increase suggests an enhanced capacity for glutamate synthesis-a finding that might contribute to the disrupted glutamate homeostasis in MTLE.
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Affiliation(s)
- Tore Eid
- Department of Neurosurgery, Yale University School of Medicine, 333 Cedar Street, P.O. Box 208082, New Haven, CT 06520-8082, USA.
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215
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Bjørnsen LP, Eid T, Holmseth S, Danbolt NC, Spencer DD, de Lanerolle NC. Changes in glial glutamate transporters in human epileptogenic hippocampus: Inadequate explanation for high extracellular glutamate during seizures. Neurobiol Dis 2007; 25:319-30. [PMID: 17112731 DOI: 10.1016/j.nbd.2006.09.014] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2006] [Revised: 08/24/2006] [Accepted: 09/22/2006] [Indexed: 11/19/2022] Open
Abstract
Temporal lobe epilepsy (TLE) with hippocampal sclerosis is associated with high extracellular glutamate levels, which could trigger seizures. Down-regulation of glial glutamate transporters GLAST (EAAT1) and GLT-1 (EAAT2) in sclerotic hippocampi may account for such increases. Their distribution was compared immunohistochemically in non-sclerotic and sclerotic hippocampi and localized only in astrocytes, with weaker immunoreactivity for both transporters in areas associated with pronounced neuronal loss, especially in CA1, but no decrease or even an increase in areas with less neuronal loss, like CA2 and the subiculum in the sclerotic group. Such compensatory changes in immunoreactivity may account for the lack of differences between the groups in immunoblot studies as blots show the average concentrations in the samples. These data suggest that differences in glial glutamate transporter distribution between the two groups of hippocampi may be an insufficient explanation for the high levels of extracellular glutamate in sclerotic seizure foci observed through in vivo dialysis studies.
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Affiliation(s)
- L P Bjørnsen
- CMBN at Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Blindern, Norway
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216
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Malthankar-Phatak GH, de Lanerolle N, Eid T, Spencer DD, Behar KL, Spencer SS, Kim JH, Lai JCK. Differential glutamate dehydrogenase (GDH) activity profile in patients with temporal lobe epilepsy. Epilepsia 2006; 47:1292-9. [PMID: 16922873 DOI: 10.1111/j.1528-1167.2006.00543.x] [Citation(s) in RCA: 36] [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
PURPOSE Pathophysiologic mechanisms underlying temporal lobe epilepsy (TLE) are still poorly understood. One major hypothesis links alterations in energy metabolism to glutamate excitotoxicity associated with seizures in TLE. The purpose of this study was to determine whether changes in the activities of enzymes critical in energy and neurotransmitter metabolism contributed to the alterations in metabolic status leading to the excitotoxic effects of glutamate. METHODS Activities of four key enzymes involved in energy metabolism and glutamate cycling in the brain [aspartate aminotransferase (AAT), citrate synthase (CS), glutamate dehydrogenase (GDH), and lactate dehydrogenase (LDH)] were measured in anterolateral temporal neocortical and hippocampal tissues obtained from three different groups of medically intractable epilepsy patients having either mesial, paradoxical, or mass lesion-associated temporal lobe epilepsy (MTLE, PTLE, MaTLE), respectively. RESULTS We found that GDH activity was significantly decreased in the temporal cortex mainly in the MTLE group. A similar trend was recognized in the hippocampus of the MTLE. In all three patient groups, GDH activity was considerably lower, and AAT and LDH activities were higher in cortex of MTLE as compared with the corresponding activities in hippocampus (p<0.05). In the MTLE cortex and hippocampus, GDH activities were negatively correlated with the duration since the first intractable seizure. CONCLUSIONS Our results support the hypothesis suggesting major alteration in GDH activity mainly in the MTLE group. It is proposed that significant alterations in the enzyme activities may be contributing to decreased metabolism of glutamate, leading to its accumulation.
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Affiliation(s)
- Gauri H Malthankar-Phatak
- Department of Pharmaceutical Sciences, College of Pharmacy, Idaho State University, Pocatello, Idaho 83209, USA
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217
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Amin Z, Mason GF, Cavus I, Krystal JH, Rothman DL, Epperson CN. The interaction of neuroactive steroids and GABA in the development of neuropsychiatric disorders in women. Pharmacol Biochem Behav 2006; 84:635-43. [PMID: 16860856 DOI: 10.1016/j.pbb.2006.06.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Revised: 06/01/2006] [Accepted: 06/12/2006] [Indexed: 11/25/2022]
Abstract
A growing literature suggests that hormonal fluctuations occurring across the menstrual cycle, during and after pregnancy, and during the menopausal transition are associated with onset of affective disorders or exacerbation of existing disorders. This influence of the neuroendocrine system on psychiatric disorders is thought to be mediated by an abnormality in central nervous system response to neuroactive steroids such as estradiol, progesterone, and the progesterone derivative allopregnanolone (ALLO). This interplay is considerably complex as neuroactive steroids modulate the function of multiple neurotransmitter systems throughout various stages of development. While one could choose to study any number of steroid-neurotransmitter interactions, our group in addition to others has focused our investigative efforts on unraveling the contribution of neuroactive steroids to psychiatric syndromes and disorders via their modulation of gamma aminobutyric acid (GABA), the brain's major inhibitory neurotransmitter. The goal of this article is two-fold: to synthesize the clinical and preclinical research focusing on the interplay between neuroactive steroids and GABA as they relate to neuropsychiatric and substance use disorders in women and to integrate data from our laboratory using proton magnetic resonance spectroscopy into this context.
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218
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Abstract
Brain cells are highly energy dependent for maintaining ion homeostasis during high metabolic activity. During active periods, full mitochondrial function is essential to generate ATP from electrons that originate with the oxidation of NADH. Decreasing brain metabolism is a significant cause of cognitive abnormalities of Alzheimer disease (AD), but it remains uncertain whether this is the cause of further pathology or whether synaptic loss results in a lower energy demand. Synapses are the first to show pathological symptoms in AD before the onset of clinical symptoms. Because synaptic function has high energy demands, interruption in mitochondrial energy supply could be the major factor in synaptic failure in AD. A newly discovered age-related decline in neuronal NADH and redox ratio may jeopardize this function. Mitochondrial dehydrogenases and several mutations affecting energy transfer are frequently altered in aging and AD. Thus, with the accumulation of genetic defects in mitochondria at the level of energy transfer, the issue of neuronal susceptibility to damage as a function of age and age-related disease becomes important. In an aging rat neuron model, mitochondria are both chronically depolarized and produce more reactive oxygen species with age. These concepts suggest that multiple treatment targets may be needed to reverse this multifactorial disease. This review summarizes new insights based on the interaction of mitoenergetic failure, glutamate excitotoxicity, and amyloid toxicity in the exacerbation of AD.
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Affiliation(s)
- Mordhwaj S Parihar
- Department of Medical Microbiology, Immunology and Cell Biology, Southern Illinois University School of Medicine, Springfield, IL 62794-9626, USA
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Pittenger C, Krystal JH, Coric V. Glutamate-modulating drugs as novel pharmacotherapeutic agents in the treatment of obsessive-compulsive disorder. NeuroRx 2006; 3:69-81. [PMID: 16490414 PMCID: PMC3593363 DOI: 10.1016/j.nurx.2005.12.006] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
SUMMARY Obsessive-compulsive disorder (OCD) is a common psychiatric disorder that produces significant morbidity. The introduction of serotonin reuptake inhibitors in the 1980s represented an important advance in the treatment of OCD. However, few patients show complete remission of their symptoms, and some patients show minimal improvement with existing treatments. We review current treatment strategies and initial data supporting the efficacy of glutamate modulating agents as a novel class of pharmaceuticals for the treatment of OCD. Functional neuroimaging studies repeatedly reported metabolic hyperactivity in the cortico-striato-thalamo-cortical circuitry in patients with OCD. Recent magnetic resonance spectroscopy studies provide evidence of elevated glutamate levels in several brain regions in patients suffering from OCD. These findings raised the possibility that agents that reduce glutamate hyperactivity or its consequences in the CNS might be efficacious as novel therapeutic interventions. Indeed, initial evidence from our group suggests that the antiglutamatergic agent riluzole (Rilutek), which was developed for the treatment of amyotrophic lateral sclerosis, is effective in treatment-resistant OCD. Case reports suggest that other agents that modulate glutamatergic activity may likewise be effective. This new application of glutamate modulating agents holds promise for the treatment of this disabling and often inadequately treated disease.
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Brunner M, Langer O. Microdialysis versus other techniques for the clinical assessment of in vivo tissue drug distribution. AAPS JOURNAL 2006; 8:E263-71. [PMID: 16796376 PMCID: PMC3231569 DOI: 10.1007/bf02854896] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Quantification of target site pharmacokinetics (PK) is crucial for drug discovery and development. Clinical microdialysis (MD) has increasingly been employed for the description of drug distribution and receptor phase PK of the unbound fraction of various analytes. Costs for MD experiments are comparably low and given suitable analytics, target tissue PK of virtually any drug molecule can be quantified. The major limitation of MD stems from the fact that organs such as brain, lung or liver are not readily accessible without surgery. Recently, non-invasive imaging techniques, i.e. positron emission tomography (PET) or magnetic resonance spectroscopy (MRS), have become available for in vivo drug distribution assessment and allow for drug concentration measurements in practically every human organ. Spatial resolution of MRS imaging, however, is low and although PET enables monitoring of regional drug concentration differences with a spatial resolution of a few millimetres, discrimination between bound and unbound drug or parent compound and metabolite is difficult. Radiotracer development is furthermore time and labour intensive and requires special expertise and radiation exposure and costs originating from running a PET facility cannot be neglected. The recent complementary use of MD and imaging has permitted to exploit individual strengths of these diverse techniques. In conclusion, MD and imaging techniques have provided drug distribution data that have so far not been available. Used alone or in combination, these methods may potentially play an important role in future drug research and development with the potential to serve as translational tools for clinical decision making.
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Affiliation(s)
- Martin Brunner
- Department of Clinical Pharmacology, Division of Clinical Pharmacokinetics, Medical University of Vienna--Allgemeines Krankenhaus, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
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de Lanerolle NC, Lee TS. New facets of the neuropathology and molecular profile of human temporal lobe epilepsy. Epilepsy Behav 2005; 7:190-203. [PMID: 16098816 DOI: 10.1016/j.yebeh.2005.06.003] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Accepted: 06/01/2005] [Indexed: 11/27/2022]
Abstract
This review summarizes the salient features of the anatomical and molecular neuropathology of the hippocampus from patients with intractable temporal lobe epilepsy (TLE). It argues that sclerotic hippocampus is essential for seizure expression and that sclerosis is not a consequence of seizures, but is related to the epileptogenicity of the seizure focus. While neurons in sclerotic hippocampus may contribute to hippocampal hyperexcitability, this role is perhaps less important than that of the astrocytes. The astrocytes in sclerotic hippocampus may directly influence excitability through altered water homeostasis and K+ buffering by redistribution of AQP4 transporters on their plasma membrane. It is proposed that they contribute to a high extracellular glutamate level through reduced glutamine synthetase, and activation through pro-inflammatory factors that release chemokines and cytokines, which enhance calcium-dependent glutamate release. Such a focal pool of glutamate may diffuse to surrounding neuron-rich areas to generate seizure activity in TLE.
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Affiliation(s)
- Nihal C de Lanerolle
- Department of Neurosurgery, Yale University School of Medicine, New Haven, CT 06520, USA.
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