Zhiqin Xi

Proteomic analysis of cerebrospinal fluid from patients with idiopathic temporal lobe epilepsy.

Proteomic analysis of cerebrospinal fluid (CSF) from patients with temporal lobe epilepsy (TLE) and controls was carried out using two-dimensional gel electrophoresis followed by liquid chromatography electrospray ionization tandem mass spectrometry. Five protein spots showed significant differential expression (p<0.05): vitamin D-binding protein (DBP) was elevated in the CSF of TLE patients whereas cathepsin D, apolipoprotein J, Fam3c, and superoxide dismutase 1 (SOD1) were decreased in the CSF of TLE patients. Additional six protein spots presented only in the CSF of epilepsy patients were identified as tetranectin (TN), talin-2, apolipoprotein E, immunoglobulin lambda light chain (IGL@), immunoglobulin kappa variable light chain 1-5 (IGKV1-5), and procollagen C-endopeptidase enhancer 1 (PCOLCE). Expression of DBP, SOD1 and talin-2 was validated by western blot. Our results may provide better understanding of the pathophysiologic mechanisms underlying epileptogenesis and possible epilepsy biomarkers.

Altered Expression of CX3CL1 in Patients with Epilepsy and in a Rat Model

Chemokine C-X3-C motif ligand 1 (CX3CL1, alias fractalkine), is highly expressed in the central nervous system and participates in inflammatory responses. Recent studies indicated that inflammatory processes within the brain constitute a common and crucial mechanism in the pathophysiological characteristics of epilepsy. This study investigated the expression pattern of CX3CL1 in epilepsy and its relationship with neuronal loss. Double immunolabeling, IHC, and immunoblotting results showed that CX3CL1 expression was up-regulated in the temporal neocortex of patients with temporal lobe epilepsy. In a rat model of epilepsy, CX3CL1 up-regulation began 6 hours after epilepsy, with relatively high expression for 60 days. In addition, ELISA revealed that the concentrations of CX3CL1 in cerebrospinal fluid and serum were higher in epileptic patients than in patients with neurosis but lower than in patients with inflammatory neurological diseases. Moreover, H&E staining demonstrated significant neuronal loss in the brains of epileptic patients and in the rat model. Finally, the expression of tumor necrosis factor-related apoptosis-inducing ligand was significantly increased in both patients and the animal model, suggesting that tumor necrosis factor-related apoptosis-inducing ligand may play a role in CX3CL1-induced cell death. Thus, our results indicate that CX3CL1 may serve as a possible biomarker of brain inflammation in epileptic patients.

Gene expression analysis on anterior temporal neocortex of patients with intractable epilepsy.

To elucidate the molecular basis of intractable epilepsy (IE), we used a whole‐genome transcriptomic approach to identify genes involved in the pathogenesis of this disease. Using a complementary DNAs microarray representing 4096 human genes, we analyzed differential gene expression in the anterior temporal neocortex (ATN) of IE patients relative to control patients who had an operation to relieve head trauma‐related intracranial pressure. The results were validated by real‐time fluorescence‐quantitative polymerase chain reaction (FQ‐PCR) and reverse transcription‐PCR (RT‐PCR). The expression of 143 genes (3.5%) was significantly altered in IE patients. Thirty‐seven genes (26%) were reduced relative to controls, and 106 (74%) were elevated (more than twofold change vs. controls), including genes involved in immunity, signal transduction, apoptosis, stress, synaptic plasticity, structural, and cellular reorganization, among other processes. Results for 13 of the 14 differentially expressed genes tested by FQ‐PCR were consistent with the microarray. Twelve abnormally expressed cytoskeletal genes were confirmed by RT‐PCR. Expression of 11 was significantly higher in the ATN of IE patients than in controls. Gene products altered in IE, namely HSPBAP1, TRAP220, glycogen synthase kinase‐3β (GSK‐3β), and cyclin‐dependent kinase 5 (CDK5), were tested by immunohistochemistry and immunoblotting. GSK‐3β and CDK5 levels were significantly higher in the ATN of IE patients. Our gene chip data are generally in agreement with the published findings on epilepsy. Thus, gene chips may serve as a screening tool to elucidate the pathophysiology of IE. Investigation of some of these newly identified genes should enhance our understanding of the molecular mechanisms of epileptogenesis. Synapse 63:1017–1028, 2009.

Down-regulation Synaptic Vesicle Protein 2A in the Anterior Temporal Neocortex of Patients with Intractable Epilepsy

Synaptic vesicle protein 2A (SV2A) involvement has been reported in the animal models of epilepsy. The aim of this study was to investigate the expression of SV2A in human intractable epilepsy (IE) brain tissue. Using immunohistochemistry, immunofluorescence, and Western blot, we detected SV2A expression in tissue samples from the anterior temporal neocortex of 33 patients who had been surgically treated for IE. We compared these tissues with nine histologically normal anterior temporal lobe samples from controls. SV2A immunoreactive staining was 0.1651 ± 0.0564 in patient group and 0.2347 ± 0.0187 in the control group (p < 0.05) using immunohistochemistry, and this finding was consistently observed with Western blot analysis (0.1727 ± 0.0471 versus 0.3976 ± 0.0983, p < 0.05). Immunofluorescence staining showed that SV2A was mainly accumulated in neurons. Our findings demonstrate that down-regulation of SV2A is present in patients with temporal lobe epilepsy.

Efficacy and Safety of Levetiracetam (3,000 mg/Day) as an Adjunctive Therapy in Chinese Patients with Refractory Partial Seizures

Aim: To evaluate the efficacy and safety of 3,000 mg daily levetiracetam (LEV; Keppra) as an adjunctive therapy for Chinese patients with refractory partial seizures. Methods: This randomized, placebo-controlled trial consisted of an 8-week baseline period followed by a 4-week titration interval and a 12-week maintenance period, and concluded with a 4-week medication withdrawal period or entered an open-label study. LEV was compared with placebo. Results: The 50% responder rate (the proportion of patients with a minimum of 50% reduction in partial seizure frequency) occurred in 46.4% of the LEV group, compared with 39.3% of the placebo group (p = 0.590). The median of the absolute weekly frequency reduction from baseline of partial seizures was 0.66 per week for LEV versus 0.48 per week for placebo (p = 0.187). The most common treatment-emergent adverse events, mostly mild to moderate in severity, were somnolence, dizziness and agitation. Conclusion: In this study, adjunctive therapy with LEV 3,000 mg daily was well tolerated but not as effective as expected in controlling partial seizures in this study population. Considering the lower mean weight of this study population, we suggest the dosage of LEV 3,000 mg daily may contribute to the results.

Abnormal expression and spatiotemporal change of Slit2 in neurons and astrocytes in temporal lobe epileptic foci: A study of epileptic patients and experimental animals.

Repellent guidance molecules provide targeting information to outgrowing axons along predetermined pathways during development. These molecules may also play a role in synaptic reorganization in the adult brain and thereby promote epileptogenesis. Our aim was to investigate the expression of Slit2, one of repellent guidance molecules, in temporal lobe epileptic foci from epileptic patients and experimental animals. Thirty-five temporal neocortex tissue samples from patients with intractable temporal lobe epilepsy (TLE) and fifteen histological normal temporal lobes from controls were selected. Fifty-four Sprague-Dawley rats were divided randomly into six groups, including five groups with epilepsy induced by lithium-pilocarpine administration and one control group. Temporal lobe tissue samples were taken from rats at 1, 7, 14, 30, and 60 days post-seizure and from controls. Expression of Slit2 was assessed by immunohistochemistry, immunofluorescence, and Western blot analysis. Slit2 was mainly expressed in neurons in human controls and in both neurons and astrocytes in TLE patients. Slit2 expression was significantly higher in TLE patients as compared with the controls. Slit2-positive cells were mainly neurons in the rat temporal lobe tissues of the control group, the acute period group, and the latent period group, while the Slit2-positive cells were mainly astrocytes in chronic phase. Compared with controls, Slit2 expression in animals in the TLE group gradually decreased from days 1 to 14 post-seizure, but then increased over the levels seen in controls, to peak levels at days 30 and 60. These results suggest that Slit2 may play an important role in the pathogenesis of TLE.

Extracellular signal-regulated protein kinase in human intractable epilepsy

Extracellular signal‐regulated kinases (ERK) such as ERK1 [p44 mitogen‐activated protein kinase (MAPK)] and ERK2 (p42 MAPK) are activated in the central nervous system under physiological and pathological conditions such as ischemia and epilepsy. Our aim is to investigate ERK1, ERK2, and phosphorylated ERK (p‐ERK) (Thr202/Tyr 204) expression in the temporal lobe of patients with intractable epilepsy (IE) and to explore its possible role of ERK in it. Tissue samples from temporal neocortices of 40 patients who had surgery for IE were used to detect ERK1, ERK2, and p‐ERK (Thr 202/Tyr 204) expression through immunohistochemistry and western blot. We compared these tissues against 17 histological normal temporal lobes from head‐traumat patients. ERK1, ERK2, and p‐ERK in IE were significantly higher than those in the controls. They were mainly expressed in the cytoplasm of neurons and glial cells. There was also increased detection of p‐ERK in the gliotic cortex of IE compared with the non‐gliotic cortex. These findings were consistently observed in western blot and immunohistochemistry techniques. ERK expression in patients with IE was significantly increased compared with the controls. This suggested a probable role of ERK in the pathogenesis of IE.

A new hypothesis of drug refractory epilepsy: Neural network hypothesis

Drug refractory is an important clinical problem in epilepsy, affecting a substantial number of patients globally. Mechanisms underlying drug refractory need to be understood to develop rational therapies. Current two prevailing theories on drug refractory epilepsy (DRE) include the target hypothesis and the transporter hypothesis. However, those hypotheses could not be adequate to explain the mechanisms of all the DRE. Thus, we propose another possible mechanism of DRE, which is neural network hypothesis. It is hypothesized that seizure-induced alterations of brain plasticity including axonal sprouting, synaptic reorganization, neurogenesis and gliosis could contribute to the formation of abnormal neural network, which has not only avoided the inhibitory effect of endogenous antiepileptic system but also prevented the traditional antiepileptic drugs from entering their targets, eventually leading to DRE. We will illustrate this hypothesis at molecular and structural level based on our recent studies and other related researches.

Downregulation of Gephyrin in Temporal Lobe Epilepsy Neurons in Humans and a Rat Model

Gephyrin, which is a postsynaptic scaffolding protein participated in clustering GABAA receptors at inhibitory synapses, has been reported to be involved in temporal lobe epilepsy (TLE) recently. Here, we investigate gephyrin protein expression in the temporal lobe epileptic foci in epileptic patients and experimental animals in order to explore the probable relationship between gephyrin expression and TLE. Using immunohistochemistry, immunofluorescence, and western blot analysis, gephyrin expression was examined in 30 human temporal neocortex samples from patients who underwent surgery to treat drug‐refractory TLE and 10 histological normal temporal neocortex from the controls. Meanwhile, we investigated the gephyrin expression in the hippocampus and adjacent neocortex from experimental rats on 24 h, 48 h, 1 week, 2 weeks, 1 month, and 2 months postseizure and from control rats. Gephyrin protein was mainly expressed in the membrane and cytoplasm of neurons in temporal lobe epileptic foci in humans and experimental rats. Gephyrin expression was significantly lower in the temporal neocortex of TLE patients compared to the controls. In experimental rats, the expression of gephyrin in temporal lobe was downregulated in epileptic groups compared to the control group. Gephyrin expression gradually decreased during the acute period and the latent period, but then began to increase below the levels seen in controls during the chronic phase. Our findings suggest that gephyrin may be involved in the development of TLE. Synapse, 2011.

Overexpression of N-WASP in the brain of human epilepsy.

Neuronal circuit remodeling is the most critical pathological characteristic closely associated with the initiation and maintenance of epilepsy; however, the exact mechanisms of neuronal remodeling need further elucidation. Neuronal Wiskott-Aldrich syndrome protein (N-WASP) is a key regulator of the actin cytoskeleton that causes actin polymerization and thus neurite extension. Our previous research demonstrated that the upstream regulator of N-WASP, cell division cycle 42 GTP-binding protein (Cdc42), is significantly upregulated in the brains of patients with intractable epilepsy (IE). In addition, cDNA microarray analysis has shown that gene expression of N-WASP is notably enhanced in the epileptic brain, suggesting a possible role for N-WASP in epileptogenesis. Here, we investigated the expression of N-WASP and its downstream effector, actin-related protein 2/3 (Arp2/3), at the protein level in the temporal lobe of IE patient brains to explore its possible role in the genesis of IE. Forty surgical samples from brains of patients with IE and 20 control brain tissues were obtained for this study. The expression of N-WASP in the anterior temporal neocortex was detected using immunohistochemistry, immunofluorescence and western blotting; Arp2/3 expression was detected by western blotting. Compared with controls, N-WASP expression in brains of IE patients was significantly higher; similarly, Arp2/3 level was markedly increased in the IE patient group. These results suggest that increased expression of N-WASP in the human brain may be associated with human IE.