Drug repurposing for Dravet syndrome in scn1Lab-/- mutant zebrafish

Abstract

Dravet syndrome (DS) is a severe genetic epileptic encephalopathy with onset during the first year of life. Zebrafish models recapitulating human diseases are often used as drug discovery platforms, but also for drug repurposing testing. It was recently shown that pharmacological modulation of three serotonergic (5-HT) receptors (5-HT_1D , 5-HT_2C , 5-HT_2A ) exerts antiseizure effects in a zebrafish scn1Lab^-/- mutant model of DS. Using the zebrafish DS model, our aim was to examine the possibility of repurposing efavirenz (EFA), lisuride (LIS), and rizatriptan (RIZA), marketed medicines with a 5-HT on- or off-target profile, as antiepileptic drugs for DS. To examine whether these compounds have a broader antiseizure profile, they were tested in pentylenetetrazol and ethyl ketopentenoate (EKP) zebrafish models. Pharmacological effects were assessed by locomotor behavior, local field potential brain recordings, and bioluminescence. EFA was active in all models, whereas LIS was selectively active in the zebrafish DS model. Mainly, a poor response was observed to RIZA. Taken together, our preclinical results show that LIS could be a potential candidate for DS treatment. EFA was also active in the EKP model, characterized by a high level of treatment resistance, and hence these data are potentially important for future treatment of drug-resistant epilepsy.

Keywords: drug-resistant; epilepsy; marketed medicines.

Figure 1

Activity profiles of efavirenz (EFA; green bars), lisuride (LIS; blue bars), and rizatriptan (RIZA; orange bars) at their maximum tolerated concentrations (ie, 3.12, 0.10, and 100 μmol·L^–1, respectively) as shown by scatter plots with bars. Data of vehicle‐treated (VHC) wild‐type (wt) larvae are represented by white bars. Data of vehicle‐treated homozygous (ho) scn1Lab ^−/− mutant larvae or larvae treated with proconvulsant (pentylenetetrazol [PTZ] or ketopentenoate [EKP] chemical models) are represented by dark green bars (control [CTR]). A‐C, Locomotor activity. Values show the mean ± SD from independent experiments (n = 3 in all conditions, except in the case of ho scn1Lab ^−/− and wt larvae, where n = 9) normalized to the data represented by the dark green bars. In each experiment, the individual activities of larvae (n = 10 per experiment) were pooled and processed (represented by dots). A, Homozygous scn1Lab ^−/− mutants. B, C, Chemical models (PTZ and EKP). D‐F, Brain activity. Values show the mean ± SD of frequency of epileptiform events (n per 10 minutes) recorded in individual larvae (represented by dots). scn1Lab genetic model: VHC (wt) and RIZA (ho), n = 9; LIS (ho), n = 13; EFA (ho), n = 14; VHC (ho, CTR), n = 15; PTZ model: VHC and RIZA+PTZ, n = 7; EFA+PTZ, n = 9; LIS+PTZ, n = 10; PTZ (CTR), n = 21; EKP model: for each condition, n = 10‐11. G, Representative examples of bioluminescence recordings (35 minutes) of Tg(elavl3:GA) zebrafish exposed to VHC, PTZ, or EKP. The total photon emission (y‐axis) is counted per 5‐second interval (x‐axis). H, I, Bioluminescence. Values show the mean ± SD of percentage change in bioluminescence relative to the one observed for Tg(elavl3:GA) zebrafish exposed to PTZ or EKP (black dots, CTR). In each experiment, three larvae were used simultaneously (n = 3). Number of experiments performed (results represented by dots), in the case of PTZ: VHC, n = 3; EFA+PTZ, n = 5; RIZA+PTZ, n = 6; PTZ (CTR), n = 8; LIS+PTZ, n = 9; in the case of EKP: RIZA+EKP, n = 3; VHC, n = 4; EFA+EKP/LIS+EKP, n = 6; EKP (CTR), n = 9. Statistically significant differences between the mean represented by the dark green bars (black dots) and the mean of the other conditions: *P < 0.05, **P < 0.01, and ***P < 0.001 vs controls. Lack of statistically significant difference is left blank [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 2

Heat map comparison of zebrafish larval responses after rizatriptan (RIZA), efavirenz (EFA), and lisuride (LIS) treatment, as examined by locomotor tracking (LOC), electrographic activity recording (LFP), and bioluminescence measurements (BIOL). Data were normalized to vehicle control (VHC)‐treated mutant larvae (scn1Lab genetic model) or larvae treated with a proconvulsant (pentylenetetrazol [PTZ] or ketopentenoate [EKP], two chemical models; second column, 100% control [CTR]). VHC refers to VHC‐treated wild‐type larvae. The statistical differences mentioned in Figure 1 for the different conditions are shown: *P < 0.05, **P < 0.01, and ***P < 0.001 vs controls [Color figure can be viewed at http://wileyonlinelibrary.com]