The Endocannabinoid System and Synthetic Cannabinoids in Preclinical Models of Seizure and Epilepsy

CBD in the Treatment of Epilepsy

It has been several years since highly purified cannabidiol (CBD) was registered as a medication that can be used in children of at least 2 years of age to treat different types of seizures related to Lennox-Gastaut syndrome (LGS), Dravet syndrome (DS), and more recently tuberous sclerosis complex (TSC). During this time, 39 randomized clinical trials (RCTs) and 13 meta-analyses on the efficacy and safety of CBD treatment have been published. Each of the meta-analyses had its own criteria for the RCTs' inclusion and, therefore, slightly different interpretations of the analyzed data. Each of them contributed in its own way to the understanding of CBD pharmacology, mechanisms of therapeutic action, development of adverse reactions, and drug-drug interactions. Hence, it seemed reasonable to gather the most relevant data in one article and present all the current knowledge on the use of CBD in epilepsy. The results of the 13 meta-analyses presented herein confirmed the effectiveness and safety of CBD in children and adolescents with DREs. In adults, reliable conclusions cannot be drawn due to insufficient data.

Behavioral and Molecular Responses to Exogenous Cannabinoids During Pentylenetetrazol-Induced Convulsions in Male and Female Rats

Epilepsy is a disabling, chronic brain disease,affecting ~1% of the World’s population, characterized by recurrent seizures (sudden, uncontrolled brain activity), which may manifest with motor symptoms (e.g., convulsions) or non-motor symptoms. Temporal lobe epilepsies (TLE) compromising the hippocampus are the most common form of focal epilepsies. Resistance in ~1/3 of epileptic patients to the first line of treatment, i.e., antiepileptic drugs (AEDs), has been an important motivation to seek alternative treatments. Among these, the plant Cannabis sativa (commonly known as marihuana) or compounds extracted from it (cannabinoids) have gained widespread popularity. Moreover, sex differences have been proposed in epilepsy syndromes and in cannabinoid action. In the hippocampus, cannabinoids interact with the CB1R receptor whose membrane levels are regulated by β-Arrestin2, a protein that promotes its endocytosis and causes its downregulation. In this article, we evaluate the modulatory role of WIN 55,212-2 (WIN), a synthetic exogenous cannabinoid on behavioral convulsions and on the levels of CB1R and β-Arrestin2 in female and male adolescent rats after a single injection of the proconvulsant pentylenetetrazol (PTZ). As epilepsies can have a considerable impact on synaptic proteins that regulate neuronal toxicity, plasticity, and cognition, we also measured the levels of key proteins markers of excitatory synapses, in order to examine whether exogenous cannabinoids may prevent such pathologic changes after acute seizures. We found that the exogenous administration of WIN prevented convulsions of medium severity in females and males and increased the levels of phosphorylated CaMKII in the hippocampus. Furthermore, we observed a higher degree of colocalization between CB1R and β-Arrestin2 in the granule cell layer.

Neuroplastic alterations in cannabinoid receptors type 1 (CB1) in animal models of epileptic seizures

Currently, there is an urgent need to better comprehend neuroplastic alterations in cannabinoid receptors type 1 (CB1) and to understand the biological meaning of these alterations in epileptic disorders. The present study reviewed neuroplastic changes in CB1 distribution, expression, and functionality in animal models of epileptic seizures. Neuroplastic alterations in CB1 were consistently observed in chemical, genetic, electrical, and febrile seizure models. Most studies assessed changes in hippocampal and cortical CB1, while thalamic, hypothalamic, and brainstem nuclei were rarely investigated. Additionally, the relationship between CB1 alteration and the control of brain excitability through modulation of specific neuronal networks, such as striatonigral, nigrotectal and thalamocortical pathways, and inhibitory projections to hippocampal pyramidal neurons, were all presented and discussed in the present review. Neuroplastic alterations in CB1 detected in animal models of epilepsy may reflect two different scenarios: (1) endogenous adaptations aimed to control neuronal hyperexcitability in epilepsy or (2) pathological alterations that facilitate neuronal hyperexcitability. Additionally, a better comprehension of neuroplastic and functional alterations in CB1 can improve pharmacological therapies for epilepsies and their comorbidities.

The endocannabinoid system in zebrafish and its potential to study the effects of Cannabis in humans

Zebrafish is considered an unprecedented animal model in drug discovery. A review of the literature presents highlights and elucidates the biological effects of chemical components found in Cannabis sativa. Particular attention is paid to endocannabinoid system (eCB) and its main receptors (CB1 and CB2). The zebrafish model is a promising one for the study of cannabinoids because of the many similarities to the human system. Despite the recent advances on the eCB system, there is still the need to elucidate some of the interactions and, thus, the zebrafish model can be used for that purpose as it respects the 3Rs concept and reduced time and costs. In view of the relevance of cannabinoids in the treatment and prevention of diseases, as well as the importance of the zebrafish animal model in elucidating the biological effects of new drugs, the aim of this study was to bring to light information on the use of the zebrafish animal model in testing C. sativa-based medicines.

Cannabidiol in the Treatment of Epilepsy

Anecdotal reports addressing the successful seizure treatment of severe epilepsies with cannabidiol (CBD) have increased both public interest and academic research. Placebo-controlled, randomized, controlled trials proved the efficacy of pharmaceutical-grade CBD in epilepsy treatment, thus leading to pharmaceutical-grade CBD approval by the US Food and Drug Administration and the European Medicines Agency for the treatment of seizures in Dravet syndrome and Lennox–Gastaut syndrome as well as for tuberous complex syndrome by the Food and Drug Administration only. However, the CBD market is confusing because an array of products of different origins, purity, and concentration is available. Additionally, the results from the pivotal studies with plant-derived, pharmaceutical-grade CBD cannot simply be transferred to other epilepsy types or CBD of any origin. Because of the high demands and expectations that patients with epilepsy and their caregivers have regarding CBD, information outlining the proven facts and potential risks is essential. The aim of this article is to thoroughly review available research data and practical recommendations to provide the treating physician with the necessary information for counseling patients with epilepsy.

Dissociable changes in spike and wave discharges following exposure to injected cannabinoids and smoked cannabis in Genetic Absence Epilepsy Rats from Strasbourg

There is significant interest in the use of cannabinoids for the treatment of many epilepsies including absence epilepsy (AE). Genetic Absence Epilepsy Rats from Strasbourg (GAERS) model many aspects of AE including the presence of spike-and-wave discharges (SWDs) on electroencephalogram (EEG) and behavioral comorbidities, such as elevated anxiety. However, the effects of cannabis plant-based phytocannabinoids have not been tested in GAERS. Therefore, we investigated how SWDs in GAERS are altered by the two most common phytocannabinoids, Δ⁹ -tetrahydrocannabinol (THC) and cannabidiol (CBD), and exposure to smoke from two different chemovars of cannabis. Animals were implanted with bipolar electrodes in the somatosensory cortex and EEGs were recorded for 2 hr. Injected THC (1-10 mg/kg, i.p.) dose-dependently increased SWDs to over 200% of baseline. In contrast, CBD (30-100 mg/kg, i.p.) produced a ~50% reduction in SWDs. Exposure to smoke from a commercially available chemovar of high-THC cannabis (Mohawk, Aphria Inc.) increased SWDs whereas a low-THC/high-CBD chemovar of cannabis (Treasure Island, Aphria Inc.) did not significantly affect SWDs in GAERS. Pre-treatment with a CB1R antagonist (SR141716A) did not prevent the high-THC cannabis smoke from increasing SWDs, suggesting that the THC-mediated increase may not be CB1R-dependent. Plasma concentrations of THC and CBD were similar to previously reported values following injection and smoke exposure. Compared to injected CBD, it appears Treasure Island did not increase plasma levels sufficiently to observe an anti-epileptic effect. Together these experiments provide initial evidence that acute phytocannabinoid administration exerts the biphasic modulation of SWDs and may differentially impact patients with AE.

Plant derived versus synthetic cannabidiol: Wishes and commitment of epilepsy patients

PURPOSE

A special component of cannabis, cannabidiol (CBD), is currently in the focus of epilepsy treatment and research. In this context, we investigated patients' expectations and preferences pertaining to plant-derived versus synthetic formulation of cannabidiol, as well as their willingness to get this treatment.

METHODS

One hundred and four of 153 patients with different forms of epilepsy (54 % female, mean age 40 ± 16 yrs.) responded to the survey. The survey consisted of 8 questions addressing expectations of and concerns towards CBD treatment, preferences of plant-derived versus synthetic CBD, estimated monthly costs, and willingness to buy CBD at one's own expense.

RESULTS

The majority (73 %) of the responding epilepsy patients wished to receive plant-derived CBD; 5 % preferred synthetic CBD. Reasons for this choice were botanic origin, lack of chemistry, and the assumption of fewer and less dangerous side effects. Eighty-two percent of the patients estimated the monthly costs of CBD treatment to be below €500. Using the willingness-to-pay approach to assess the commitment of patients, 68 % could imagine buying the drug themselves. Fifty-three percent of these would be willing to pay up to €100, 40 % €100 to €200, and another 7 % €200 to €500 per month.

CONCLUSION

There is an overwhelming preference towards plant-derived cannabidiol in epilepsy patients, driven by the idea of organic substances being safer and better tolerated than synthetic. The willingness-to-pay approach reflects the high burden and pressure of uncontrolled epilepsy and the expectation of relief. Non-realistic ideas of pricing as well as what patients would be willing and able to pay confirm this perception.

Phenotype-Based Screening of Synthetic Cannabinoids in a Dravet Syndrome Zebrafish Model

Dravet syndrome is a catastrophic epilepsy of childhood, characterized by cognitive impairment, severe seizures, and increased risk for sudden unexplained death in epilepsy (SUDEP). Although refractory to conventional antiepileptic drugs, emerging preclinical and clinical evidence suggests that modulation of the endocannabinoid system could be therapeutic in these patients. Preclinical research on this topic is limited as cannabis, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), are designated by United States Drug Enforcement Agency (DEA) as illegal substances. In this study, we used a validated zebrafish model of Dravet syndrome, scn1lab homozygous mutants, to screen for anti-seizure activity in a commercially available library containing 370 synthetic cannabinoid (SC) compounds. SCs are intended for experimental use and not restricted by DEA designations. Primary phenotype-based screening was performed using a locomotion-based assay in 96-well plates, and a secondary local field potential recording assay was then used to confirm suppression of electrographic epileptiform events. Identified SCs with anti-seizure activity, in both assays, included five SCs structurally classified as indole-based cannabinoids JWH 018 N-(5-chloropentyl) analog, JWH 018 N-(2-methylbutyl) isomer, 5-fluoro PB-22 5-hydroxyisoquinoline isomer, 5-fluoro ADBICA, and AB-FUBINACA 3-fluorobenzyl isomer. Our approach demonstrates that two-stage phenotype-based screening in a zebrafish model of Dravet syndrome successfully identifies SCs with anti-seizure activity.