Decreased expression of synaptic vesicle protein 2A, the binding site for levetiracetam, during epileptogenesis and chronic epilepsy

Authors

  • Erwin A. Van Vliet,

    1. Epilepsy Institute in The Netherlands (SEIN), Heemstede, The Netherlands
    2. Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
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  • Eleonora Aronica,

    1. Academic Medical Center, Department of (Neuro) Pathology, University of Amsterdam, Amsterdam, The Netherlands
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  • Sandra Redeker,

    1. Academic Medical Center, Department of (Neuro) Pathology, University of Amsterdam, Amsterdam, The Netherlands
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  • Karin Boer,

    1. Academic Medical Center, Department of (Neuro) Pathology, University of Amsterdam, Amsterdam, The Netherlands
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  • Jan A. Gorter

    1. Epilepsy Institute in The Netherlands (SEIN), Heemstede, The Netherlands
    2. Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, The Netherlands
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Address correspondence to Jan A. Gorter, Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Kruislaan 320, Amsterdam, The Netherlands. E-mail: gorter@science.uva.nl

Summary

Purpose: We previously showed that gene expression of synaptic vesicle protein 2A (SV2A), the binding site for the antiepileptic drug levetiracetam, is reduced during epileptogenesis in the rat. Since absence of SV2A has been associated with increased epileptogenicity, changes in expression of SV2A could have consequences for the progression of epilepsy. Therefore we investigated hippocampal SV2A protein expression of temporal lobe epilepsy (TLE) patients and in rats during epileptogenesis and in the chronic epileptic phase.

Methods: SV2A immunocytochemistry and Western blot analysis were performed on the hippocampus of autopsy controls, patients that died from status epilepticus (SE), and pharmacoresistant TLE patients. In addition, in epileptic rats, SV2A expression was determined after SE during the acute, latent, and chronic epileptic phase.

Results: In control tissue, presynaptic SV2A was expressed in all hippocampal subfields, with strongest expression in mossy fiber terminals. SV2A positive puncta were distributed in a patchy pattern over the somata and dendrites of neurons. SV2A decreased throughout the hippocampus of TLE patients with hippocampal sclerosis (HS), compared to autopsy control, SE, and non-HS tissue. In most rats, SV2A was already decreased in the latent period especially in the inner molecular layer and stratum lucidum. Similarly as in humans, SV2A was also decreased throughout the hippocampus of chronic epileptic rats, specifically in rats with a progressive form of epilepsy.

Discussion: These data support previous findings that reduced expression of SV2A could contribute to the increased epileptogenicity. Whether this affects the effectiveness of levetiracetam needs to be further investigated.

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