Cannabidiol Impairs Brain Mitochondrial Metabolism and Neuronal Integrity.

Background: The mechanisms underlying the clinical effects of CBD remain poorly understood. Given the increasing evidence for CBD's effects on mitochondria, we sought to examine in more detail whether CBD impacts mitochondrial function and neuronal integrity. Methods: We utilized BE(2)-M17 neuroblastoma cells or acutely isolated brain mitochondria from rodents using a Seahorse extracellular flux analyzer and a fluorescent spectrofluorophotometer assay. Mitochondrial ion channel activity and hippocampal long-term potentiation were measured using standard cellular electrophysiological methods. Spatial learning/memory function was evaluated using the Morris water maze task. Plasma concentrations of CBD were assessed with liquid chromatography-mass spectrometry, and cellular viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction neuronal injury assay. Results: At low micromolar concentrations, CBD reduced mitochondrial respiration, the threshold for mitochondrial permeability transition, and calcium uptake, blocked a novel mitochondrial chloride channel, and reduced the viability of hippocampal cells. These effects were paralleled by in vitro and in vivo learning/memory deficits. We further found that these effects were independent of cannabinoid receptor 1 and mitochondrial G-protein-coupled receptor 55. Conclusion: Our results provide evidence for concentration- and dose-dependent toxicological effects of CBD, findings that may bear potential relevance to clinical populations.

Electrophysiological characterization of a mitochondrial inner membrane chloride channel in rat brain.

Mitochondria are an essential component of cellular integrity and homeostasis, and their functions and pathological processes are highly dependent on mitochondrial ion channels. Anion channels of the inner mitochondrial membrane have been described by direct patch-clamp electrophysiological methods in mitoplasts prepared in cardiac, liver, and brown adipose tissue, but not in brain. Here, using acutely isolated rat brain mitoplasts, we describe the properties of a large conductance, voltage-gated, pH-sensitive, outwardly rectifying chloride channel with conductances of 98 pS and 129 pS at negative and positive membrane potentials, respectively. While the molecular identity of this chloride conductance is unknown, it is unlikely to be a CLIC channel due to differences in the observed electrophysiological properties.