A multiorganism pipeline for antiseizure drug discovery: Identification of chlorothymol as a novel γ-aminobutyric acidergic anticonvulsant

Alistair Jones, Melissa Barker-Haliski, Andrei S. Ilie, Murray B. Herd, Sarah Baxendale, Celia J. Holdsworth, John Paul Ashton, Marysia Placzek, Bodiabaduge A. P. Jayasekera, Christopher J. A. Cowie, Jeremy J. Lambert, Andrew J. Trevelyan, H. Steve White, Anthony G. Marson, Vincent T. Cunliffe (Lead / Corresponding author), Graeme J. Sills (Lead / Corresponding author), Alan Morgan (Lead / Corresponding author)

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Abstract

Objective: Current medicines are ineffective in approximately one-third of people with epilepsy. Therefore, new antiseizure drugs are urgently needed to address this problem of pharmacoresistance. However, traditional rodent seizure and epilepsy models are poorly suited to high-throughput compound screening. Furthermore, testing in a single species increases the chance that therapeutic compounds act on molecular targets that may not be conserved in humans. To address these issues, we developed a pipeline approach using four different organisms.

Methods: We sequentially employed compound library screening in the zebrafish, Danio rerio, chemical genetics in the worm, Caenorhabditis elegans, electrophysiological analysis in mouse and human brain slices, and preclinical validation in mouse seizure models to identify novel antiseizure drugs and their molecular mechanism of action.

Results: Initially, a library of 1690 compounds was screened in an acute pentylenetetrazol seizure model using D rerio. From this screen, the compound chlorothymol was identified as an effective anticonvulsant not only in fish, but also in worms. A subsequent genetic screen in C elegans revealed the molecular target of chlorothymol to be LGC-37, a worm γ-aminobutyric acid type A (GABAA) receptor subunit. This GABAergic effect was confirmed using in vitro brain slice preparations from both mice and humans, as chlorothymol was shown to enhance tonic and phasic inhibition and this action was reversed by the GABAA receptor antagonist, bicuculline. Finally, chlorothymol exhibited in vivo anticonvulsant efficacy in several mouse seizure assays, including the 6-Hz 44-mA model of pharmacoresistant seizures.

Significance: These findings establish a multiorganism approach that can identify compounds with evolutionarily conserved molecular targets and translational potential, and so may be useful in drug discovery for epilepsy and possibly other conditions.

Original languageEnglish
Number of pages13
JournalEpilepsia
Early online date14 Aug 2020
DOIs
Publication statusE-pub ahead of print - 14 Aug 2020

Keywords

  • drug discovery
  • epilepsy
  • GABA
  • nematode
  • zebrafish

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    Jones, A., Barker-Haliski, M., Ilie, A. S., Herd, M. B., Baxendale, S., Holdsworth, C. J., Ashton, J. P., Placzek, M., Jayasekera, B. A. P., Cowie, C. J. A., Lambert, J. J., Trevelyan, A. J., White, H. S., Marson, A. G., Cunliffe, V. T., Sills, G. J., & Morgan, A. (2020). A multiorganism pipeline for antiseizure drug discovery: Identification of chlorothymol as a novel γ-aminobutyric acidergic anticonvulsant. Epilepsia. https://doi.org/10.1111/epi.16644