Elsevier

Experimental Neurology

Volume 201, Issue 2, October 2006, Pages 470-478
Experimental Neurology

Neuroprotective effect of topiramate on hypoxic ischemic brain injury in neonatal rats

https://doi.org/10.1016/j.expneurol.2006.04.038Get rights and content

Abstract

Perinatal hypoxia–ischemia is one of the most common risk factors for neonatal mortality and permanent neurodevelopmental disability. Topiramate [2,3:4,5-bis-o-(1-methylethylidene) β-d-fructo-pyranose sulfamate; TPM] is widely used as an antiepileptic agent with multiple targets. In the present study, we found that treatment with TPM reduced the neuronal damage induced by oxygen–glucose deprivation in vitro with strong inhibition of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor. Because perinatal hypoxia is mediated, at least in part, by aberrant glutamatergic excitation, we tested whether treatment with TPM was effective against perinatal brain hypoxia–ischemia. Intraperitoneal or oral pretreatment with TPM was found to reduce the brain damage and subsequent cognitive impairments induced by transient hypoxia–ischemia in perinatal rats. A potent neuroprotective effect of TPM was also observed in a post-treatment regime although post-treatment window appears to be relatively narrow (<2 h). These results suggest that TPM treatment may be beneficial for perinatal hypoxia–ischemia and related damage.

Introduction

Topiramate [2,3:4,5-bis-o-(1-methylethylidene) β-d-fructo-pyranose sulfamate; TPM] is widely used as an antiepileptic drug (Angehagen et al., 2003a, Shank et al., 1994). It is a chemically novel antiepileptic drug that has a broad spectrum of antiepileptic activities in both experimental and clinical studies (White, 1997). Its anticonvulsant activity is probably due to suppressing excitatory tone and/or enhancing inhibitory currents (Angehagen et al., 2003a, Poulsen et al., 2004, Skradski and White, 2000, White et al., 1997, White et al., 2000b). Among its many actions, TPM has an antiglutamatergic action, and it has been suggested that TPM may be effective against many brain pathologies mediated by glutamatergic excitotoxicity. For instance, ischemic brain injury rapidly stimulates synaptic glutamate release, and the aberrant activation of glutamate receptors leads to an increase in intracellular calcium concentration that triggers a chain of events resulting in neuronal death. Activation of glutamate receptors appears to play an essential role in this cascade since glutamate receptor antagonists are efficient at protecting neurons from ischemia-induce death (Calabresi et al., 2003, Johnston et al., 2001). Therefore, drug(s) which prevent the activation of glutamatergic receptors might be clinically useful in brain ischemia (Calabresi et al., 2003). Although several studies have challenged this idea (for review, White et al., 2000a), recent studies have shown that TPM reduces the spread of neuronal damage induced by transient global cerebral ischemia in the adult rodent model (Edmonds et al., 2001, Lee et al., 2000, Yang et al., 1998). Furthermore, TPM in combination with hypothermia is also neuroprotective in perinatal rats (Liu et al., 2004), although the mechanism involved is less clear.

There is substantial evidence that the immature brain differs in its susceptibility to ischemic injury and glutamatergic excitotoxicity (Herlenius and Lagercrantz, 2004, Johnston et al., 2001, Marini et al., 2001, Penning et al., 1991, Ikonomidou et al., 1989). This is due in part to differences in the expression of glutamate receptor subunits during brain development (Bahn et al., 1994, Jakowec et al., 1998, Monyer et al., 1994, Pagliusi et al., 1994) so that bursts of glutamate induced by hypoxia–ischemia (H–I) activate different types of receptor depending on age. In this study, we present evidence that TPM reduces neuronal damage caused by oxygen–glucose deprivation (OGD)-induced ischemia in vitro, mainly as a result of blockade of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor, and that it reduces perinatal hypoxic ischemic injury in vivo.

Section snippets

Primary cerebral cortical cell culture

Primary cerebral cortical neuron cultures were prepared from embryonic 17 days Sprague–Dawley rat (Sun et al., 2002). Briefly, the cerebral cortex was dissected and digested with 0.25% trypsin-EDTA (Gibco BRL). The dissociated cells were plated on poly-d-lysine (50 μg/ml)-coated coverslips at a density of 2 × 105 cells/24-well. The complete growth medium consisted of Neurobasal medium (Gibco BRL) containing B27 supplement (Gibco BRL), 200 mM l-gutamine (Gibco BRL), 5 mM glutamic acid

Protective effect of TPM against OGD-induced neuronal injury

Following exposure of cells to OGD for 60 min, there was progressive deterioration of cortical neurons during the reperfusion period. After 24 h of reperfusion, less than 5% of the neurons maintained their cellular integrity as defined by NeuN-immunoreactivity (Fig. 1). The morphology and viability of the neurons were similar to those previously reported (Choi, 1993). Viability of the OGD-treated cells was significantly enhanced by the treatment with TPM in a dose-dependent manner. By 30–300 μM

Discussion

We have shown that TPM has a potent neuroprotective effect on OGD-induced neuronal death in vitro and on damage due to H–I in the immature brain in vivo. Furthermore, neurobehavioral analyses revealed that TPM reduced the behavioral consequences of H–I-induced neurological complications. TPM therefore seems to have potential application in a wide range of clinical situations, because both pre- and post-treatments were highly effective by both routes (i.p. injection and oral administration).

Acknowledgments

We thank Drs. Sangduk Kim (Korea University) and Won Ki Kim (Ewha Womans University) for valuable comments on the manuscript. This work was supported by a grant from the Korean Health 21 R&D Project, Ministry of Health and Welfare, Republic of Korea (02-PJ1-PG1-CH06-0001). A part of this work was supported technically by a core facility service of the 21C Frontier Brain Research Center.

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    These two authors contributed equally to this work and are co-first authors.

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