Abstracts

Rationale: Cannabidiol (CBD) derived from cannabis plants has demonstrated seizure control activity in patients with Dravet syndrome and Lennox-Gastaut syndrome, and although it has been demonstrated to modulate TRPV1 and GPR55 activities, its mechanism of action remains to be fully elucidated. Here, we employ an unbiased approach to investigate this mechanism at a cellular level. Methods: To identify potential new mechanisms of CBD, we employed a tractable biomedical model organism, Dictyostelium, to identify proteins controlling the effect of CBD and characterize this mechanism. We then translate these results to a Dravet Syndrome mouse model and an acute in vitro epileptiform activity model using rat primary hippocampal neurons. Results: CBD caused a dose-dependent effect with an IC50 of 1.89µM in Dictyostelium, relating to therapeutically relevant concentrations. Using a genetic screen approach, we found CBD activity to be partially dependent upon the mitochondrial glycine cleavage system component, GcvH1, or the orthologous human GCSH protein, which are functionally linked to folate one-carbon metabolism (FOCM). Analysis of FOCM components identified a mechanism for CBD in directly inhibiting methionine synthesis. Consistent with a possible effect of CBD on one-carbon metabolism in epilepsy, brain tissue from a Dravet syndrome mouse model (Scn1a+/-) showed altered levels of glycine, methionine and cysteine, suggesting drastic changes in one-carbon metabolism in this model. Chronic treatment of this mutant with oral-dosed CBD further regulated methionine levels. Finally, an in vitro model of seizure-like activity in rat primary hippocampal neurons showed elevated methionine levels, implicating altered one-carbon metabolism in seizure activity, whilst acute CBD treatment reversed this increase. Conclusions: We therefore propose a novel role for one-carbon metabolism in Dravet syndrome and seizure activity, and a therapeutically-relevant mechanism for CBD in the regulation of methionine levels in one-carbon metabolism. Funding: Although funding has not been secured for this presentation, it would be sought from relevant commercial sponsors upon application approval.