Comparative proteomics and correlated signaling network of rat hippocampus in the pilocarpine model of temporal lobe epilepsy

Abstract

In temporal lobe epilepsy (TLE), the seizure origin typically involves the hippocampal formation. The pilocarpine-induced TLE provides a model to investigate the molecular and functional characterization of epileptogenesis by mimicking the human epileptic condition. Here, we employed a 2-D gel-based proteomic technique to profile proteome changes in the rat hippocampus after pilocarpine treatment. Using MALDI MS and MS/MS, 57 differentially expressed proteins were identified, which were found either up-regulated and/or down-regulated at the two time points 12 h (acute period; Ap) and 72 h (silent period; Sp) compared with the control. These proteins can be related to underlying mechanism of pilocarpine-induced TLE, indicating cytoskeleton modification, altered synaptic function, mitochondrial dysfunction, changed ion channel, and chaperone. Five of the identified proteins, synaptosomal-associated protein 25 (SNAP25), synapsin-2 (SYN2), homer protein homolog 2 (HOMER2), alpha-internexin (INA), and voltage-dependent anion channel 2 (VDAC2) were investigated by semiquantitative RT-PCR, and SNAP25 and INA were further validated by Western blot and immunohistochemistry staining. Furthermore, association of these pilocarpine-induced proteins with biological functions using the Ingenuity Pathway Analysis (IPA) tool showed that nucleic acid metabolism, system development, tissue and cell morphology were significantly altered. IPA of the canonical networks indicated that six membrane proteins (e.g., SNAP25, SYN2, and HOMER2) participated in three biological networks as starting proteins. Our results offer a clue to identify biomarkers for the development of pharmacological therapies targeted at epilepsy.

Cooperative regulation of neurotransmitter release by Rab3a and synapsin II

“…Since synapsin levels are modified in animal models of epilepsy (Morimoto et al, 1998; Suemaru et al, 2000; Sato and Abe, 2001, Liu et al, 2008) and since synapsin mutation was identified in a human family with epilepsy (Garcia et al 2004), it is likely that some forms of epilepsy may result from impairments in presynaptic vesicle cycling, possibly in inhibitory GABAergic nerve terminals (Terada et al, 1999; Hirsch et al, 1999; Gitler et al, 2004) This suggestion is further strengthened by an observation that mice lacking a vesicle-associated protein SV2 demonstrated severe epileptic seizures (Crowder et al, 1999). Our finding that this type of epileptic seizure is rescued by Rab3a gene deletion warrants a systematic investigation of the effect of Rab3a regulation on synapsin deficient terminals in both glutamatergic and GABAergic synapses of the central nervous system.…”

Cortical hyperexcitability and epileptogenesis: Understanding the mechanisms of epilepsy - Part 2

“…[140][141][142][143][144][145][146] One study in patients with TLE reported an increase in BOLD signal at sites distant to the seizure focus in most patients. 146 Specifically, 83% of studies had BOLD responses that predominated in the spiking temporal lobe (activation or deactivation) and BOLD responses were often seen in the contralateral homologous temporal lobe and extratemporally.…”

Intermittent Hypercapnic Hypoxia Induced Protein Changes in the Piglet Hippocampus Identified by MALDI-TOF-MS

“…Via 2DE, we found piglets exposed to IHH had decreased a-internexin in the hippocampus. This protein has also been found to change in other proteomic studies using 2DE in the brain, including guinea-pig brain synaptosomes exposed to hypoxia [35] and rat hippocampus of temporal lobe epilepsy (increased expression) [36]. The result was supported by WB analysis which also showed decreased a-internexin, although IHC analysis did not show this change.…”