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Large-Scale Phenotype-Based Antiepileptic Drug Screening in a Zebrafish Model of Dravet Syndrome(1,2,3).

Dinday MT, Baraban SC - eNeuro (2015)

Bottom Line: Mutations in a voltage-gated sodium channel (SCN1A) result in Dravet Syndrome (DS), a catastrophic childhood epilepsy.The effectiveness of compounds that block neuronal calcium current (dimethadione) or enhance serotonin signaling (fenfluramine) in our zebrafish model suggests that these may be important therapeutic targets in patients with DS.Over 150 compounds resulting in fatality were also identified.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurological Surgery, Epilepsy Research Laboratory, University of California San Francisco , San Francisco, California 94143.

ABSTRACT
Mutations in a voltage-gated sodium channel (SCN1A) result in Dravet Syndrome (DS), a catastrophic childhood epilepsy. Zebrafish with a mutation in scn1Lab recapitulate salient phenotypes associated with DS, including seizures, early fatality, and resistance to antiepileptic drugs. To discover new drug candidates for the treatment of DS, we screened a chemical library of ∼1000 compounds and identified 4 compounds that rescued the behavioral seizure component, including 1 compound (dimethadione) that suppressed associated electrographic seizure activity. Fenfluramine, but not huperzine A, also showed antiepileptic activity in our zebrafish assays. The effectiveness of compounds that block neuronal calcium current (dimethadione) or enhance serotonin signaling (fenfluramine) in our zebrafish model suggests that these may be important therapeutic targets in patients with DS. Over 150 compounds resulting in fatality were also identified. We conclude that the combination of behavioral and electrophysiological assays provide a convenient, sensitive, and rapid basis for phenotype-based drug screening in zebrafish mimicking a genetic form of epilepsy.

No MeSH data available.


Related in: MedlinePlus

Evaluation of putative antiepileptic drugs in scn1Lab mutants. a, Locomotion tracking plots for scn1Lab zebrafish at baseline and following huperzine A administration. Total movement is shown for a 10 min recording epoch. b, Plot showing the change in mean velocity for three different huperzine A concentrations (blue bars). Each bar is the mean change for six fish. The threshold for a positive hit is shown as a dashed line. WT fish exposed to PTZ and huperzine A are shown in red (N = 7). c, d, Same for fenfluramine. Note that 1 mm fenfluramine was toxic, as indicated. e, Representative field recordings from scn1Lab mutant larvae at 5 dpf. Electrographic activity is shown for a 5 min recording epoch (top traces); high-resolution traces are shown below, as indicated. Note that abnormal burst discharge activity persists in scn1Lab mutants exposed to 250 µm fenfluramine. The fish shown were tested in the locomotion assay first.
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Figure 4: Evaluation of putative antiepileptic drugs in scn1Lab mutants. a, Locomotion tracking plots for scn1Lab zebrafish at baseline and following huperzine A administration. Total movement is shown for a 10 min recording epoch. b, Plot showing the change in mean velocity for three different huperzine A concentrations (blue bars). Each bar is the mean change for six fish. The threshold for a positive hit is shown as a dashed line. WT fish exposed to PTZ and huperzine A are shown in red (N = 7). c, d, Same for fenfluramine. Note that 1 mm fenfluramine was toxic, as indicated. e, Representative field recordings from scn1Lab mutant larvae at 5 dpf. Electrographic activity is shown for a 5 min recording epoch (top traces); high-resolution traces are shown below, as indicated. Note that abnormal burst discharge activity persists in scn1Lab mutants exposed to 250 µm fenfluramine. The fish shown were tested in the locomotion assay first.

Mentions: Next, we tested two additional compounds that were not in our drug library, but have recently been described as potential antiepileptic treatments for DS. Huperzine A, a small-molecule alkaloid isolated from Chinese club moss with NMDA-type receptor blocking and anticholinesterase activity, has purported antiepileptic actions against NMDA- or soman-induced seizures (Tonduli et al., 2001; Coleman et al., 2008). In the locomotion assay, huperzine A failed to significantly alter scn1Lab seizure behavior at any concentration tested (Fig. 4a,b). In contrast, huperzine A was effective at 1 mm in the acute pentylenetetrazole (PTZ) assay (Fig. 4b). Fenfluramine is an amphetamine-like compound that has been reported to successfully reduce seizure occurrence in children with DS as a low-dose add-on therapy (Ceulemans et al., 2012). In the locomotion assay, fenfluramine significantly reduced mutant mean swim velocity at concentrations between 100 and 500 μm (Fig. 4c,d); 1 mm fenfluramine was toxic in the scn1Lab and PTZ assays (Fig. 4d). The fenfluramine-treated scn1Lab mutant exhibited a suppression of spontaneous electrographic seizure discharge to levels similar to controls at 500 μm, but only a partial reduction in electrographic activity at 250 μm (Fig. 4e).


Large-Scale Phenotype-Based Antiepileptic Drug Screening in a Zebrafish Model of Dravet Syndrome(1,2,3).

Dinday MT, Baraban SC - eNeuro (2015)

Evaluation of putative antiepileptic drugs in scn1Lab mutants. a, Locomotion tracking plots for scn1Lab zebrafish at baseline and following huperzine A administration. Total movement is shown for a 10 min recording epoch. b, Plot showing the change in mean velocity for three different huperzine A concentrations (blue bars). Each bar is the mean change for six fish. The threshold for a positive hit is shown as a dashed line. WT fish exposed to PTZ and huperzine A are shown in red (N = 7). c, d, Same for fenfluramine. Note that 1 mm fenfluramine was toxic, as indicated. e, Representative field recordings from scn1Lab mutant larvae at 5 dpf. Electrographic activity is shown for a 5 min recording epoch (top traces); high-resolution traces are shown below, as indicated. Note that abnormal burst discharge activity persists in scn1Lab mutants exposed to 250 µm fenfluramine. The fish shown were tested in the locomotion assay first.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4596025&req=5

Figure 4: Evaluation of putative antiepileptic drugs in scn1Lab mutants. a, Locomotion tracking plots for scn1Lab zebrafish at baseline and following huperzine A administration. Total movement is shown for a 10 min recording epoch. b, Plot showing the change in mean velocity for three different huperzine A concentrations (blue bars). Each bar is the mean change for six fish. The threshold for a positive hit is shown as a dashed line. WT fish exposed to PTZ and huperzine A are shown in red (N = 7). c, d, Same for fenfluramine. Note that 1 mm fenfluramine was toxic, as indicated. e, Representative field recordings from scn1Lab mutant larvae at 5 dpf. Electrographic activity is shown for a 5 min recording epoch (top traces); high-resolution traces are shown below, as indicated. Note that abnormal burst discharge activity persists in scn1Lab mutants exposed to 250 µm fenfluramine. The fish shown were tested in the locomotion assay first.
Mentions: Next, we tested two additional compounds that were not in our drug library, but have recently been described as potential antiepileptic treatments for DS. Huperzine A, a small-molecule alkaloid isolated from Chinese club moss with NMDA-type receptor blocking and anticholinesterase activity, has purported antiepileptic actions against NMDA- or soman-induced seizures (Tonduli et al., 2001; Coleman et al., 2008). In the locomotion assay, huperzine A failed to significantly alter scn1Lab seizure behavior at any concentration tested (Fig. 4a,b). In contrast, huperzine A was effective at 1 mm in the acute pentylenetetrazole (PTZ) assay (Fig. 4b). Fenfluramine is an amphetamine-like compound that has been reported to successfully reduce seizure occurrence in children with DS as a low-dose add-on therapy (Ceulemans et al., 2012). In the locomotion assay, fenfluramine significantly reduced mutant mean swim velocity at concentrations between 100 and 500 μm (Fig. 4c,d); 1 mm fenfluramine was toxic in the scn1Lab and PTZ assays (Fig. 4d). The fenfluramine-treated scn1Lab mutant exhibited a suppression of spontaneous electrographic seizure discharge to levels similar to controls at 500 μm, but only a partial reduction in electrographic activity at 250 μm (Fig. 4e).

Bottom Line: Mutations in a voltage-gated sodium channel (SCN1A) result in Dravet Syndrome (DS), a catastrophic childhood epilepsy.The effectiveness of compounds that block neuronal calcium current (dimethadione) or enhance serotonin signaling (fenfluramine) in our zebrafish model suggests that these may be important therapeutic targets in patients with DS.Over 150 compounds resulting in fatality were also identified.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurological Surgery, Epilepsy Research Laboratory, University of California San Francisco , San Francisco, California 94143.

ABSTRACT
Mutations in a voltage-gated sodium channel (SCN1A) result in Dravet Syndrome (DS), a catastrophic childhood epilepsy. Zebrafish with a mutation in scn1Lab recapitulate salient phenotypes associated with DS, including seizures, early fatality, and resistance to antiepileptic drugs. To discover new drug candidates for the treatment of DS, we screened a chemical library of ∼1000 compounds and identified 4 compounds that rescued the behavioral seizure component, including 1 compound (dimethadione) that suppressed associated electrographic seizure activity. Fenfluramine, but not huperzine A, also showed antiepileptic activity in our zebrafish assays. The effectiveness of compounds that block neuronal calcium current (dimethadione) or enhance serotonin signaling (fenfluramine) in our zebrafish model suggests that these may be important therapeutic targets in patients with DS. Over 150 compounds resulting in fatality were also identified. We conclude that the combination of behavioral and electrophysiological assays provide a convenient, sensitive, and rapid basis for phenotype-based drug screening in zebrafish mimicking a genetic form of epilepsy.

No MeSH data available.


Related in: MedlinePlus