The fruit fly Drosophila melanogaster as a screening model for antiseizure medications

Abstract

Objective: Resistance to antiseizure medications (ASMs) is a major challenge in the treatment of patients with epilepsy. Despite numerous newly marketed ASMs, the proportion of drug-resistant people with epilepsy has not significantly decreased over the years. Therefore, novel and innovative seizure models for preclinical drug screening are highly desirable. Here, we explore the efficacy of a broad spectrum of ASMs in suppressing seizure activity in two established Drosophila melanogaster bang-sensitive mutants. These mutants respond with seizures to mechanical stimulation, providing a promising platform for screening novel ASMs.

Methods: Seven frequently used ASMs (brivaracetam, cenobamate, lacosamide, lamotrigine, levetiracetam, phenytoin, and valproate) were administered to the bang-sensitive mutants easily shocked ^2F (eas ^2F ) and paralytic ^bss1 (para ^bss1 ). After 48 h of treatment, the flies were vortexed to induce mechanical stimulation. The seizure probability (i.e., ratio of seizing and non-seizing flies) as well as the seizure duration were analyzed.

Results: In case of eas ^2F mutants, treatment with the sodium channel blockers phenytoin and lamotrigine resulted in a robust reduction of seizure probability, whereas flies treated with lacosamide showed a decrease in seizure duration. Treatment with valproate resulted in both a reduction in seizure probability and in seizure duration. In contrast, levetiracetam, brivaracetam and cenobamate had no effect on the bang-sensitive phenotype of eas ^2F flies. In case of para ^bss1 flies, none of the tested medications significantly reduced seizure activity, supporting its role as a model of intractable epilepsy.

Significance: Our results show that particularly sodium channel blockers as well as valproate are effective in suppressing seizure activity in the bang-sensitive mutant eas ^2F . These findings demonstrate the usability of Drosophila for screening drugs with antiseizure properties. Due to fewer ethical concerns, the short life cycle, and low maintenance costs, Drosophila might provide an attractive and innovative high-throughput model for the discovery of novel antiseizure compounds.

Keywords: Drosophila melanogaster; animal model; antiseizure medications; drug screening; epilepsy; seizure model.

FIGURE 1

Seizure activity of eas ^2F flies treated with different solvents (A) Percentage of seizing eas ^2F flies after 10 s of vortex stimulation. Before testing, the flies were fed with 100 μL of water, ethanol or DMSO for 48 h. The data for flies treated with water or ethanol were derived from experiments shown in Figure 2. For statistical analysis, we performed a Fisher’s exact test (***p < 0.001, compared to water and ethanol). N indicates the total number of flies tested per condition. (B) Seizure duration in seconds of the same eas ^2F flies. The data was analyzed by a one-way ANOVA followed by Tukey’s post hoc t-tests (**p < 0.01, ***p < 0.001). Error bars indicate SD.

FIGURE 2

Seizure probability of eas ^2F flies treated with seven different ASMs. Percentage of seizing flies after 10 s of vortex stimulation. Before testing, the flies were treated with three different concentrations (0.03, 0.3, 3 mM) of seven different ASMs (phenytoin, lacosamide, lamotrigine, cenobamate, valproate, levetiracetam, brivaracetam) for 48 h. For statistical analysis, we performed a Fisher’s exact test (*p < 0.05, **p < 0.01, ***p < 0.001, compared to 0 mM). N indicates the total number of tested flies per condition.

FIGURE 3

Seizure duration of eas ^2F flies treated with seven different ASMs. Seizure duration in seconds of flies after 10 s of vortex stimulation. Before testing, the flies were treated with three different concentrations (0.03, 0.3, 3 mM) of seven different ASMs (phenytoin, lacosamide, lamotrigine, cenobamate, valproate, levetiracetam, brivaracetam) for 48 h. For statistical analysis, we performed a one-way ANOVA followed by Tukey’s post hoc t-tests (*p < 0.05, ***p < 0.001, compared to 0 mM). Error bars indicate SD.

FIGURE 4

Seizure activity of para ^bss1 flies treated with seven different ASMs. (A) Percentage of seizing flies after 10 s of vortex stimulation. Before testing, the flies were treated with 3 mM of seven different ASMs (phenytoin, lacosamide, lamotrigine, cenobamate, valproate, levetiracetam, brivaracetam) for 48 h. For statistical analysis, we performed a Fisher’s exact test (no significance, compared to control). N indicates the total number of tested flies per condition. (B) Seizure duration in seconds of the same flies described above. For statistical analysis, we performed a one-way ANOVA followed by Tukey’s post hoc t-tests (no significance, compared to control). Error bars indicate SD.