Article

Identification of compounds with anti-convulsant properties in a zebrafish model of epileptic seizures

University of Sheffield, UK.
Disease Models and Mechanisms (Impact Factor: 5.54). 06/2012; 5(6). DOI: 10.1242/dmm.010090
Source: PubMed

ABSTRACT The availability of animal models of epileptic seizures provides opportunities to identify novel anticonvulsants for the treatment of people with epilepsy. We found that exposure of 2-day-old zebrafish embryos to the convulsant agent pentylenetetrazole (PTZ) rapidly induces the expression of synaptic-activity-regulated genes in the CNS, and elicited vigorous episodes of calcium (Ca(2+)) flux in muscle cells as well as intense locomotor activity. We then screened a library of ~2000 known bioactive small molecules and identified 46 compounds that suppressed PTZ-induced transcription of the synaptic-activity-regulated gene fos in 2-day-old (2 dpf) zebrafish embryos. Further analysis of a subset of these compounds, which included compounds with known and newly identified anticonvulsant properties, revealed that they exhibited concentration-dependent inhibition of both locomotor activity and PTZ-induced fos transcription, confirming their anticonvulsant characteristics. We conclude that this in situ hybridisation assay for fos transcription in the zebrafish embryonic CNS is a robust, high-throughput in vivo indicator of the neural response to convulsant treatment and lends itself well to chemical screening applications. Moreover, our results demonstrate that suppression of PTZ-induced fos expression provides a sensitive means of identifying compounds with anticonvulsant activities.

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    • "Within the past decade, the usefulness of zebrafish in epilepsy research has been validated through studies involving pharmacologically induced acute seizure models [13] [14] [15] as well as zebrafish models of genetic epileptic syndromes (Angelman's [16], Lowe's [17], BNFC [18], EAST [19], and Dravet [20] [21]). More recently, some of these zebrafish models have been applied in high-throughput epilepsy drug discovery (PTZ [22] and Dravet [20]). The GABAergic system, one of the main inhibitory neurotransmitter pathways, has proven to be a valuable target for AEDs. "
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    ABSTRACT: Treatment-resistant seizures affect about a third of patients suffering from epilepsy. To fulfill the need for new medications targeting treatment-resistant seizures, a number of rodent models offer the opportunity to assess a variety of potential treatment approaches. The use of such models, however, has proven to be time-consuming and labor-intensive. In this study, we performed pharmacological characterization of the allylglycine (AG) seizure model, a simple in vivo model for which we demonstrated a high level of treatment resistance. (d,l)-Allylglycine inhibits glutamic acid decarboxylase (GAD) - the key enzyme in γ-aminobutyric acid (GABA) biosynthesis - leading to GABA depletion, seizures, and neuronal damage. We performed a side-by-side comparison of mouse and zebrafish acute AG treatments including biochemical, electrographic, and behavioral assessments. Interestingly, seizure progression rate and GABA depletion kinetics were comparable in both species. Five mechanistically diverse antiepileptic drugs (AEDs) were used. Three out of the five AEDs (levetiracetam, phenytoin, and topiramate) showed only a limited protective effect (mainly mortality delay) at doses close to the TD50 (dose inducing motor impairment in 50% of animals) in mice. The two remaining AEDs (diazepam and sodium valproate) displayed protective activity against AG-induced seizures. Experiments performed in zebrafish larvae revealed behavioral AED activity profiles highly analogous to those obtained in mice. Having demonstrated cross-species similarities and limited efficacy of tested AEDs, we propose the use of AG in zebrafish as a convenient and high-throughput model of treatment-resistant seizures. Copyright © 2015 Elsevier Inc. All rights reserved.
    Epilepsy & Behavior 04/2015; 45. DOI:10.1016/j.yebeh.2015.03.019 · 2.06 Impact Factor
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    • "Within the past decade, the usefulness of zebrafish in epilepsy research has been validated through studies involving pharmacologically induced acute seizure models [13] [14] [15] as well as zebrafish models of genetic epileptic syndromes (Angelman's [16], Lowe's [17], BNFC [18], EAST [19], and Dravet [20] [21]). More recently, some of these zebrafish models have been applied in high-throughput epilepsy drug discovery (PTZ [22] and Dravet [20]). The GABAergic system, one of the main inhibitory neurotransmitter pathways, has proven to be a valuable target for AEDs. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Treatment-resistant seizures affect about a third of patients suffering from epilepsy. To fulfill the need for new medications targeting treatment-resistant seizures, a number of rodent models offer the opportunity to assess a variety of potential treatment approaches. The use of such models, however, has proven to be timeconsuming and labor-intensive. In this study, we performed pharmacological characterization of the allylglycine (AG) seizure model, a simple in vivo model for which we demonstrated a high level of treatment resistance. (D,L)-Allylglycine inhibits glutamic acid decarboxylase (GAD) – the key enzyme in γ-aminobutyric acid (GABA) biosynthesis – leading to GABA depletion, seizures, and neuronal damage. We performed a side-by-side comparison of mouse and zebrafish acute AG treatments including biochemical, electrographic, and behavioral assessments. Interestingly, seizure progression rate and GABA depletion kinetics were comparable in both species. Five mechanistically diverse antiepileptic drugs (AEDs) were used. Three out of the five AEDs (levetiracetam, phenytoin, and topiramate) showed only a limited protective effect (mainly mortality delay) at doses close to the TD50 (dose inducing motor impairment in 50% of animals) in mice. The two remaining AEDs (diazepam and sodium valproate) displayed protective activity against AG-induced seizures. Experiments performed in zebrafish larvae revealed behavioral AED activity profiles highly analogous to those obtained in mice. Having demonstrated crossspecies similarities and limited efficacy of tested AEDs, we propose the use of AG in zebrafish as a convenient and high-throughput model of treatment-resistant seizures.
    Epilepsy & Behavior 03/2015; 45:53-63. · 2.06 Impact Factor
    • "Many other high-throughput screens using zebrafish models of ototoxicity (Esterberg et al., 2013), epilepsy (Baxendale et al., 2012; Baraban et al., 2013; Orellana-Paucar et al., 2013; Rahn et al., 2013) and cancer (Wang et al., 2010; Nguyen et al., 2012; Le et al., 2013) have uncovered new therapeutic candidates, and collectively provide a robust proof-of-principle of the extent to which zebrafish research can directly impact drug discovery. "
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    ABSTRACT: Advances in genomics and next-generation sequencing have provided clinical researchers with unprecedented opportunities to understand the molecular basis of human genetic disorders. This abundance of information places new requirements on traditional disease models, which have the potential to be used to confirm newly identified pathogenic mutations and test the efficacy of emerging therapies. The unique attributes of zebrafish are being increasingly leveraged to create functional disease models, facilitate drug discovery, and provide critical scientific bases for the development of new clinical tools for the diagnosis and treatment of human disease. In this short review and the accompanying poster, we highlight a few illustrative examples of the applications of the zebrafish model to the study of human health and disease.
    Disease Models and Mechanisms 07/2014; 7(7):739-743. DOI:10.1242/dmm.015545 · 5.54 Impact Factor
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