Endocrine abnormalities in human temporal lobe epilepsy

Patients with temporal lobe epilepsy secrete ACTH at higher rates and in greater amounts than normal subjects. Temporal lobectomy restores ACTH secretion to normal amounts and rates. The ACTH secretion in temporal lobe epilepsy is independent of anticonvulsant drug effect and seizure frequency. Electrical stimulation of medial temporal lobe structures in patients with temporal lobe epilepsy affected ACTH secretion in a manner consistent with the hypothesis that ACTH secretion is regulated by tonic inhibition. A defect in the excitatory and/or inhibitory components of this regulatory process appears to exist in temporal lobe epilepsy.     

MST3在颞叶癫痫模型小鼠海马的表达变化

目的观察海人酸(kainic acid,KA)所致癫痫(epilepsy,EP)小鼠海马Ste20蛋白激酵素(MST3)表达水平的变化,探讨MST3在癫痫发病过程中的可能作用。方法选用成年雄性小鼠,并随机分成模型组和对照组。模型组小鼠侧脑室注射2μL(100 ng/μL)KA,分别于术后3、8、24 h收集动物标本以进行检测。使用RT-PCR和Western Blot测定MST3 mRNA含量和MST3蛋白动态表达变化,应用免疫组化观察MST3在海马的表达分布与特点。结果与正常对照组相比,模型组海马组织内MST3mRNA的表达随时间持续升高,24 h达到高峰;MST3的蛋白表达也表现出同样的动态升高趋势;术后3～24 h的模型组海马免疫组化检测显示,模型组MST3主要以海马齿状回、门回区、CA3区域表达增加为主,并且这些区域表达逐渐递增。结论随着时间的推移,MST3表达水平呈现逐渐增加趋势,可能与神经元损伤造成的凋亡之间有密切的关系,提示MST3可能在癫痫发病过程中起重要作用。     

Kallikrein 1 is overexpressed by astrocytes in the hippocampus of patients with refractory temporal lobe epilepsy, associated with hippocampal sclerosis

Kallikrein 1 (hK1) is a tissue enzyme responsible for kinin release in inflammatory cascade. This study was delineated to study the distribution and the co-localization of hK1 and kinin B1 and B2 receptors with glial and/or neuronal proteins markers, in the hippocampus of patients with refractory temporal lobe epilepsy, associated with hippocampal sclerosis (TLE-HS), comparing with control tissues. Hippocampal levels of KLK1 mRNA were also measured. hK1, kinin B1 and B2 receptors, NeuN and GFAP were analyzed using immunohistochemistry and confocal microscopy and KLK1 mRNA was quantified with real time PCR. Increased expression of hK1 by astrocytes co-localized with GFAP was found, contrasting with kinin B1 and B2 receptors, which were co-localized with NeuN in the sclerotic hippocampus. In addition, KLK1 mRNA was also up-regulated in same tissues. These data suggest an overexpression of kallikrein-kinin system and a neuron-glia interaction in the inflammatory process present in refractory TLE-HS.     

Aberrant cytosolic acyl-CoA thioester hydrolase in hippocampus of patients with mesial temporal lobe epilepsy

Summary. A series of enzyme alterations has been shown to be associated with several forms of epilepsy, in mesial temporal lobe epilepsy (MTLE), however, information is limited. It was therefore the aim of the study to determine brain enzyme protein expression using a proteomic screening approach. Hippocampi of controls and patients with drug-resistant MTLE were used for evaluation of protein expression. We applied two-dimensional electrophoresis (2-DE) with mass spectrometrical identification and immunoblotting. 2-DE revealed a remarkably decreased spot identified as cytosolic acyl-CoA thioester hydrolase (BACH; EC 3.1.2.2) in patients with MTLE. Western blotting showed absence of bands at 37kDa in MTLEs using an antibody against mouse BACH and at 140kDa in MTLEs using anti-rat BACH. This study demonstrates that BACHs were deranged in hippocampus of MTLE patients. This finding may well contribute to the understanding of the still elusive pathomechanisms involved in MTLE.J. W. Yang and T. Czech have equally contributed to the paper.     

Aberrant expression of cytoskeleton proteins in hippocampus from patients with mesial temporal lobe epilepsy

Summary. Mesial temporal lobe epilepsy (MTLE), the most common form of epilepsy, is characterised by cytoarchitectural abnormalities including neuronal cell loss and reactive gliosis in hippocampus. Determination of aberrant cytoskeleton protein expression by proteomics techniques may help to understand pathomechanism that is still elusive. We searched for differential expression of hippocampal proteins by an analytical method based on two-dimensional gel electrophoresis (2-DE) coupled with mass spectrometry unambiguously identifying 77 proteins analysed in eight control and eight MTLE hippocampi. Proteins were quantified and we observed 18 proteins that were altered in MTLE. Cytoskeleton proteins tubulin α-1 chain, β-tubulin, profilin II, neuronal tropomodulin were significantly reduced and one actin spot was missing, whereas ezrin and vinculin were significantly increased in MTLE. Proteins of several classes as e.g. antioxidant proteins (peroxiredoxins 3 and 6), chaperons (T-complex protein 1-α, stress-induced-phosphoprotein 1), signaling protein MAP kinase kinase 1, synaptosomal proteins (synaptotagmin I, α-synuclein), NAD-dependent deacetylase sirtuin-2 and 26S protease regulatory subunit 7 protein, neuronal-specific septin 3 were altered in MTLE. Taken together, the findings may represent or lead to cytoskeletal impairment; aberrant antioxidant proteins, chaperons, MAP kinase kinase 1 and NAD-dependent deacetylase sirtuin-2 may have been involved in pathogenetic mechanisms and altered synaptosomal protein expression possibly reflects synaptic impairment in MTLE. J. W. Yang and T. Czech have equally contributed to the paper.     

Expression of the group I metabotropic glutamate receptor in the hippocampus of patients with mesial temporal lobe epilepsy

Immunocytochemical studies at light and electron microscopic levels in hippocampi of patients with mesial temporal lobe epilepsy showed mGluR1 and mGluR5 immunoreactivity in the molecular layer of the dentate gyrus and CA1 area, especially at the border between stratum oriens and alveus. By electron microscopy, degenerating neuronal elements were found in all areas studied. There were glial filamentous tangles which appeared similar to intranuclear inclusions in astrocytes in all areas studied. Reactive product for mGluR1 was localised only in post-synaptic elements. However, mGluR5 immunoreactivity was demonstrated in both post- and pre-synaptic elements in the molecular layer of the dentate gyrus and CA1 area. Reactive product for mGluR5 was also demonstrated in astrocytes and in the periphery of fibrillary tangles. We postulate that in patients with mesial temporal lobe epilepsy, mGluR1 may increase hippocampal excitability through postsynaptic activation, and mGluR5 may do so through both pre- and post-synaptic mechanisms.     

Functional changes in the septal GABAergic system of animals with a model of temporal lobe epilepsy

The septal GABAergic system plays a central role in the regulation of activity and excitability of the hippocampus (the main locus of temporal lobe epilepsy, TLE), but the character of changes the septum undergoes in this pathology remains unknown. To address this issue we studied the influences on GABAergic receptors in septal slices from the brain of epileptic guinea pigs compared to a control. In the epileptic brain, the overall increase in the mean frequency of neuronal discharges and the rise in the number of bursting neurons were revealed. The inhibitory action of exogenously applied GABA on neuronal activity is sharply enhanced, whereas the efficacy of action of GABA(A) and GABA(B) receptor blockers decreases, indicating the alteration of intraseptal inhibitory processes in epilepsy. In epilepsy, GABA sharply increases the oscillatory activity of the part of pacemakers, and the opposite effect was observed in the control. In epileptic animals, the GABA receptor blockers did not affect burst neurons, indicating the disturbance of the tonic GABAergic control of the oscillatory activity. Thus, we demonstrated for the first time that the activity of septal neurons and their reactions to GABAergic substances in animals with TLE model changed sharply compared to healthy ones.     

The role of stereotactic amygdalotomy in the treatment of temporal lobe epilepsy associated with behavioral disorders

The efficacy of bilateral stereotactic amygdalotomy for the treatment of aggressive behavioral disorders has been evaluated in a retrospective study of 67 cases. In addition 4 cases with complex partial seizures accompanied by aggressive outbursts revealing a unilateral epileptogenic focus in the amygdala or periamygdala region during preoperative stereoelectroencephalographic (SEEG) evaluation received a unilateral stereotactic amygdalotomy. Long-term follow-up of these 4 cases shows that 3 patients had considerable improvement in seizure frequency and severity as well as behavioral disturbances. The results in the remaining patients evaluated by surface EEG were inconclusive.     

Expression of the group II and III metabotropic glutamate receptors in the hippocampus of patients with mesial temporal lobe epilepsy

By immunocytochemical study by both light and electron microscopy of the hippocampus of patients with mesial temporal lobe epilepsy, we have shown that mGluR2/3 and mGluR4α immunoreaction product was mainly localised in the molecular layer of the dentate gyrus and CA2 area. Electron microscopy showed that most of the immunoreaction product due to mGluR2/3, 4a and 8 was deposited in the postsynaptic elements of the CA2 pyramidal layer and the inner molecular layer of the dentate gyrus. Only mGluR8 immunoreaction product in the CA2 area and mGluR2/3 in the inner molecular layer of the dentate gyrus were demonstrated in presynaptic elements, suggesting that mGluR2/3 and 8 may be involved in presynaptic inhibition of glutamate release in these areas. The demonstration of some degenerating axon terminals in the inner molecular layer of the dentate gyrus suggests that degeneration of interneurons caused by repeated seizures was still in progress. The finding of mGluR2/3, 4 and 8 immunoreactive astrocytes in patient hippocampus suggests that mGluR2/3, 4 and 8 receptors may be involved in gliosis.     

Variations of ATP and its metabolites in the hippocampus of rats subjected to pilocarpine-induced temporal lobe epilepsy

Although purinergic receptor activity has lately been associated with epilepsy, little is known about the exact role of purines in epileptogenesis. We have used a rat model of temporal lobe epilepsy induced by pilocarpine to study the dynamics of purine metabolism in the hippocampus during different times of status epilepticus (SE) and the chronic phase. Concentrations of adenosine 5′-triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine in normal and epileptic rat hippocampus were determined by microdialysis in combination with high-performance liquid chromatography (HPLC). Extracellular ATP concentrations did not vary along 4 h of SE onset. However, AMP concentration was elevated during the second hour, whereas ADP and adenosine concentrations augmented during the third and fourth hour following SE. During chronic phase, extracellular ATP, ADP, AMP, and adenosine concentrations decreased, although these levels again increased significantly during spontaneous seizures. These results suggest that the increased turnover of ATP during the acute period is a compensatory mechanism able to reduce the excitatory role of ATP. Increased adenosine levels following 4 h of SE may contribute to block seizures. On the other hand, the reduction of purine levels in the hippocampus of chronic epileptic rats may result from metabolic changes and be part of the mechanisms involved in the onset of spontaneous seizures. This work provides further insights into purinergic signaling during establishment and chronic phase of epilepsy.     

Laboratory animal models of temporal lobe epilepsy

Temporal lobe epilepsy is a common human disease that is difficult to treat. The pathogenesis of temporal lobe epilepsy, which holds many unresolved questions, and opportunities for creating more effective treatments and preventative strategies are reviewed herein. Laboratory animal models are essential to meet these challenges. How models are created, how they compare with each other and with the disease in human patients, and how they advance our understanding of temporal lobe epilepsy are described.     

Immunoproteasome expression is induced in mesial temporal lobe epilepsy

Immunoproteasome has been associated to neurodegenerative and autoimmune diseases as a marker and regulator of inflammatory mechanisms. Its expression in the brain may occur upon neuroinflammation in different cell types and affect a variety of homeostatic and inflammatory pathways including the oxidized protein clearance and the self-antigen presentation. In the present study we investigated the immunoproteasome expression in hippocampi and cortex of patients affected by different histopathological forms of pharmaco-resistent mesial temporal lobe epilepsy. We identified a pathology-specific pattern of immunoproteasome expression, which could provide insight into the complex neuroinflammatory pathogenic components of this disease.     

海马中的内源性爆发式放电神经元与颞叶癫痫

颞叶癫痫(temporal lobe epilepsy,TLE)是常见的难治性癫痫,主要累及到海马及海马旁结构等边缘网络。爆发式放电神经元(bursting—firing neurons,BFNs)的活动是促使海马结构产生癫痫电活动及相关病理性改变的重要因素之一。BFNs是一类能够由刺激引起、甚至自发产生成串高频爆发式放电(bursting)的神经元。爆发式放电增加了突触传递的效率,促使突触活动产生短时程和长时程可塑性变化,募集邻近神经元产生同步化放电。BFNs的电活动在癫痫相关性电活动中可能具有起搏点的作用。同时,癫痫电活动也促使内源性BFNs的改变,以及调制非爆发式放电神经元向BFNs的转变,导致海马结构内癫痫电活动的进展和扩散,最终促使癫痫相关性病理性改变和脑的高级功能的损害。