Challenges and Conundrums in Cannabinoid-Based Treatments for Epilepsy Syndromes and Associated Neurobehavioral Comorbidities

$Sketch of the Research Topic's main issues. Advances in the knowledge of cannabinoid-based treatments for epilepsy syndromes and associated neurobehavioral comorbidities should be fostered by greater integration between basic and patient-centered research. This Special Research Topic brings together scientific studies in experimental models and patients with epilepsy using a broad range of cutting-edge techniques, including molecular, histological, electrophysiological, pharmacological, and behavioral approaches as well as in silico and in vitro methodologies. In addition, it also contains integrative literature reviews that generate new frameworks and perspectives on the topic. This Topic collectively provides a comprehensive insight into the anticonvulsant effects of cannabidiol (CBD), role of the endocannabinoid system, pharmacoresistance mechanisms, potential interactions with classic antiseizure medications, possible side effects, with a view to tackle the use of cannabinoids in refractory epilepsy as well as comorbid anxiety and depression in epilepsy. Articles shown in the figure were grouped by methods and experimental approaches. Figure created with Canvas Software and icons based on Biorender.com.$

Editorial

11 November 2021

Editorial: Challenges and Conundrums in Cannabinoid-Based Treatments for Epilepsy Syndromes and Associated Neurobehavioral Comorbidities

Ricardo Gómez-Nieto

Dolores E. López

and

Norberto Garcia-Cairasco

3,843 views

2 citations

Editors

Dolores E López García

University of Salamanca

Ricardo Gómez-Nieto

Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca.

Norberto Garcia-Cairasco

Faculty of Medicine of Ribeirao Preto, University of Sao Paulo

Impact

Original Research

24 March 2021

Distribution of the Cannabinoid Receptor Type 1 in the Brain of the Genetically Audiogenic Seizure-Prone Hamster GASH/Sal

Alejando Fuerte-Hortigón

, 4 more and

Dolores E. López

6,603 views

13 citations

Original Research

23 February 2021

Functional Connectivity Derived From Electroencephalogram in Pharmacoresistant Epileptic Encephalopathy Using Cannabidiol as Adjunctive Antiepileptic Therapy

Lilia Maria Morales Chacón

, 3 more and

Abel Sánchez Coroneaux

4,208 views

7 citations

Cannabinoid receptors type 1 (CB1R) in neuronal networks associated with acute and chronic audiogenic seizures. The inferior colliculus is the main brainstem structure related to sound perception and plays a key role in the genesis of audiogenic seizures. Inferior colliculus projects to different brainstem areas, like superior colliculus, periaqueductal gray matter, and brainstem reticular formation. This brainstem neuronal network is crucial to acute audiogenic seizures manifestation, that are behaviorally characterized by wild running followed by tonic-clonic seizures. The substantia nigra pars reticulata sends GABAergic projections to the mesencephalic tectum. This inhibitory projection is involved with the so-called endogenous anticonvulsant system. During the audiogenic kindling protocol, the chronic seizures, and the epileptogenic events lead to forebrain/limbic recruitment. The limbic recruitment during the chronic seizures involves projections from inferior colliculus to medial geniculate nucleus and then to the dorsal hippocampus and basolateral amygdala nucleus. This brainstem-limbic network is crucial to limbic motor seizures expression during the audiogenic kindling. Spinal cord neurons receive inputs from central neuronal networks and lead to audiogenic seizures' motor manifestation. The intensity of green color represents the amount of CB1R in each structure. Therefore, the endocannabinoid system is directly associated with brainstem and limbic neuronal networks responsible for tonic-clonic and limbic audiogenic seizures manifestation. IC, inferior colliculus; SC, superior colliculus; PAG, periaqueductal gray matter; BRF, brainstem reticular formation; SNr, substantia nigra pars reticulata; MGN, medial geniculate body; DH, dorsal hippocampus; AMG, amygdaloid complex (basolateral amygdala nucleus, BLA). Red arrows represent inhibitory projections, blue arrows represent excitatory projections.

Review

11 February 2021

Cannabinoids in Audiogenic Seizures: From Neuronal Networks to Future Perspectives for Epilepsy Treatment

Willian Lazarini-Lopes

, 3 more and

Norberto Garcia-Cairasco

6,124 views

11 citations

Effects on body weight and hematological and biochemical profiles of treated GASH/Sal animals. (A) Graphs show the time course of body weight variations monitored during the 14-day treatment in sham-, VPA–, CBD–, and CBD+VPA-treated groups. Notice that all experimental groups showed a steady and persistent body weight throughout the treatment, and no significant differences were found as compared to the pre-treatment conditions (time 0 in the horizontal axis of the graphs). Data are shown as means ± SEM. (B) Table shows hematological and biochemical profiles of GASH/Sal animals after 14 days of chronic drug treatments. The hematological assessment of blood included the following parameters: hemoglobin concentration, hematocrit (volume percentage of red blood cells in blood), and number of red blood cells, white blood cells, and platelets in a microliter (μL). The analysis of liver function included five biochemical parameters: aspartate aminotransferase (AST), alanine aminotransferase (ALT), bilirubin (BT), albumin, and total protein. Asterisks and bold values in the table denote statistical significance (**p < 0.01, ***p < 0.001) as compared to the pre-treatment conditions and the sham group.

Original Research

22 January 2021

Behavioral and Molecular Effects Induced by Cannabidiol and Valproate Administration in the GASH/Sal Model of Acute Audiogenic Seizures

Giselda Cabral-Pereira

, 7 more and

Ricardo Gómez-Nieto

Despite evidence that supports cannabidiol (CBD) as an anticonvulsant agent, there remains controversy over the antiseizure efficacy, possible adverse effects, and synergistic interactions with classic antiepileptics such as valproate (VPA). The genetic audiogenic seizure hamster from the University of Salamanca (GASH/Sal) is a reliable experimental model of generalized tonic–clonic seizures in response to intense sound stimulation. The present study examines the behavioral and molecular effects of acute and chronic intraperitoneal administrations of VPA (300 mg/kg) and CBD (100 mg/kg) on the GASH/Sal audiogenic seizures, as well as the coadministration of both drugs. The GASH/Sal animals were examined prior to and after the corresponding treatment at 45 min, 7 days, and 14 days for seizure severity and neuroethology, open-field behaviors, body weight variations, and various hematological and biochemical parameters. Furthermore, the brain tissue containing the inferior colliculus (so-called epileptogenic nucleus) was processed for reverse transcription–quantitative polymerase chain reaction analysis to determine the treatment effects on the gene expression of neuronal receptors associated with drug actions and ictogenesis. Our results indicated that single dose of VPA helps prevent the animals from getting convulsions, showing complete elimination of seizures, whereas 7 days of chronic VPA treatment had few effects in seizure behaviors. Acute CBD administration showed subtle attenuation of seizure behaviors, increasing seizure latency and decreasing the duration of the convulsion phase, but without entirely seizure abolition. Chronic CBD treatments had no significant effects on sound-induced seizures, although some animals slightly improved seizure severity. Acute and chronic CBD treatments have no significant adverse effects on body weight, hematological parameters, and liver function, although locomotor activity was reduced. The combination of VPA and CBD did not alter the therapeutic outcome of the VPA monotherapy, showing no apparent synergistic effects. As compared to sham animals, chronic treatments with CBD caused abnormal mRNA expression levels for Trpv1, Adora1, Slc29a1, and Cnr1 genes, whereas no differences in gene expression were found for Htr1a and Sigmar1. Our study shed light on the behavioral and molecular effects of CBD and VPA on the GASH/Sal model and constituted the basis to develop further studies on the pharmacological effects of CBD and its interactions with other anticonvulsants.

7,706 views

21 citations

Original Research

20 January 2021

Drug-Resistant Temporal Lobe Epilepsy Alters the Expression and Functional Coupling to Gαi/o Proteins of CB1 and CB2 Receptors in the Microvasculature of the Human Brain

María de los Ángeles Nuñez-Lumbreras

, 10 more and

Luisa Rocha

5,813 views

11 citations

Review

12 January 2021

Cannabinoids: A New Perspective on Epileptogenesis and Seizure Treatment in Early Life in Basic and Clinical Studies

Angélica Vega-García

, 6 more and

Sandra Orozco-Suárez

6,719 views

8 citations

Original Research

15 December 2020

Cannabidiol Acts at 5-HT1A Receptors in the Human Brain: Relevance for Treating Temporal Lobe Epilepsy

Christopher Martínez-Aguirre

, 5 more and

Luisa Rocha

Experimental evidence indicates that cannabidiol (CBD) induces anxiolytic and antiepileptic effects through the activation of 5-HT_1A receptors. These receptors are coupled to G_i/o proteins and induce inhibitory effects. At present, the interaction of CBD with 5-HT_1A receptors in the human brain is unknown. The aim of this study focused on evaluating the interaction between CBD and 5-HT_1A receptors in cell membranes obtained from the hippocampus and temporal neocortex of autopsies and patients with drug-resistant mesial temporal lobe epilepsy (DR-MTLE). Cell membranes were isolated from the hippocampus and temporal neocortex of a group of patients with DR-MTLE who were submitted to epilepsy surgery (n = 11) and from a group of autopsies (n = 11). The [³H]-8-OH-DPAT binding assay was used to determine the pharmacological interaction of CBD with 5-HT_1A receptors. The [³⁵S]-GTPγS assay was used to investigate the CBD-induced activation of G_i/o proteins through its action on 5-HT_1A receptors.The CBD affinity (pK_i) for 5-HT_1A receptors was similar for autopsies and patients with DR-MTLE (hippocampus: 4.29 and 4.47, respectively; temporal neocortex: 4.67 and 4.74, respectively). Concerning the [³⁵S]-GTPγS assay, no statistically significant changes were observed for both hippocampal and neocortical tissue (p > 0.05) at low CBD concentrations (1 pM to 10 μM). In contrast, at high concentrations (100 μM), CBD reduced the constitutive activity of G_i/o proteins of autopsies and DR-MTLE patients (hippocampus: 39.2% and 39.6%, respectively; temporal neocortex: 35.2% and 24.4%, respectively). These changes were partially reversed in the presence of WAY-100635, an antagonist of 5-HT_1A receptors, in the autopsy group (hippocampus, 59.8%, p < 0.0001; temporal neocortex, 71.5%, p < 0.0001) and the group of patients with DR-MTLE (hippocampus, 53.7%, p < 0.0001; temporal neocortex, 68.5%, p < 0.001). Our results show that CBD interacts with human 5-HT_1A receptors of the hippocampus and temporal neocortex. At low concentrations, the effect of CBD upon G_i/o protein activation is limited. However, at high concentrations, CBD acts as an inverse agonist of 5-HT_1A receptors. This effect could modify neuronal excitation and epileptic seizures in patients with DR-MTLE.

13,404 views

47 citations

CB1R immunostaining in the amygdala after chronic seizures. WARs with limbic recruitment (LR) and WARs with no limbic recruitment (NLR). (A) Representative images of CB1R immunostaining in the amygdala in different experimental groups (left column) and their correspondent heatmap (right column). (B) CB1R immunostaining in the total amygdala area of WARs (n = 5) compared with WARs after the AuK with limbic recruitment (LR, n = 6) and with no limbic recruitment (NLR, n = 4). (C) CB1R signal intensity in different amygdala nuclei: lateral amygdala nucleus (LA), basolateral amygdala nucleus (BLA), basomedial amygdala nucleus (BMA), central amygdala nucleus (CeA), and medial amygdala nucleus (MeA). (D) Correlation between CB1R immunostaining and maximum limbic seizure severity in different amygdala nuclei. Data are expressed by mean ± standard error mean (SEM). Equal letters represent significant differences (p < 0.05) between groups: “a” in comparison to WAR; “b” in comparison to WAR-NLR. Scale bar: 500 μm. Color code scale (8 bits image): 0–255 (min–max).

Original Research

21 December 2020

Cannabinoid Receptor Type 1 (CB1R) Expression in Limbic Brain Structures After Acute and Chronic Seizures in a Genetic Model of Epilepsy

Willian Lazarini-Lopes

, 3 more and

Norberto Garcia-Cairasco

6,716 views

14 citations

Intracollicular, but not systemic cannabinoid (CB) receptor activation suppresses seizures evoked from Area Tempestas (AT). (A) Seizures were evoked by injection of the GABA-A receptor antagonist, bicuculline methiodide (BMI) into the AT after systemic administration of VEH or WIN 55,212-2. (B) Behavioral seizure severity under the vehicle (VEH) and WIN treated conditions did not differ. (C) Representative electrographic seizures from the same subject under VEH and WIN treated conditions, showing multiple high amplitude events and isolated interictal spiking. (D) Seizures were evoked by injection of BMI into the AT following either VEH or CP infusion into the DLSC. (E) Seizure severity was significantly reduced by CP infusion into the DLSC. (F) Representative electrographic activity following treatment of the DLSC with VEH (top) and CP (bottom) from the same subject, showing that behavioral seizure suppression co-occurred with suppression of electrographic seizure activity. Bars show median and interquartile range, symbols show individual subjects. *p < 0.05.

Brief Research Report

17 November 2020

Divergent Effects of Systemic and Intracollicular CB Receptor Activation Against Forebrain and Hindbrain-Evoked Seizures in Rats

Victor R. Santos

, 3 more and

Patrick A. Forcelli

2,155 views

7 citations

A simplified view of the endocannabinoid system and its main components. Endocannabinoids: Arachidonoylethanolamide (AEA, anandamide) and 2-arachidonoylglicerol (2-AG). Synthesizing enzymes: Diacylglycerol lipase (DAGL) and phospholipase-D (PLD). Membrane transporter (T). Cannabidiol (CBD) as inhibitor of anandamide reuptake and hydrolysis. Hydrolyzing enzymes: Monoacylglycerol lipase (MAGL), alpha/beta-Hydrolase domain containing 6 (ABHD6), and fatty acid amide hydrolase (FAAH). Enzymes inhibitors: JZL184 irreversible inhibitor for MAGL, URB597 relatively selective inhibitor of FAAH, WWL123 inhibitor of ABHD6. Receptors: cannabinoid type-1 (CB1), cannabinoid type-2 (CB2), and transient receptor potential vanilloid-1 (TRPV1). AEA metabolites: arachidonic acid (AA) and ethanolamide (EtNH). 2-AG metabolites: arachidonic acid (AA) and glicerol.

Review

13 November 2020

The Endocannabinoid System Activation as a Neural Network Desynchronizing Mediator for Seizure Suppression

Daniel de Castro Medeiros

, 3 more and

Márcio Flávio Dutra Moraes

5,028 views

14 citations

Representation of the maximal stimulation (Emax) and potency (EC50) values induced by WIN 55212-2 in the hippocampus and the temporal neocortex of autopsies (A) and patients with mesial temporal lobe epilepsy without (B) and with comorbid anxiety and depression (C). Values are expressed as mean ± SE. *p < 0.05; **p < 0.01.

Original Research

06 May 2020

Endocannabinoid System and Cannabinoid 1 Receptors in Patients With Pharmacoresistant Temporal Lobe Epilepsy and Comorbid Mood Disorders

Luisa Rocha

, 6 more and

Francia Carmona-Cruz

4,789 views

25 citations

Original Research

17 March 2020

Cannabidiol (CBD) Inhibited Rhodamine-123 Efflux in Cultured Vascular Endothelial Cells and Astrocytes Under Hypoxic Conditions

Jerónimo Auzmendi

, 7 more and

Alberto Lazarowski

Despite the constant development of new antiepileptic drugs (AEDs), more than 30% of patients develop refractory epilepsy (RE) characterized by a multidrug-resistant (MDR) phenotype. The “transporters hypothesis” indicates that the mechanism of this MDR phenotype is the overexpression of ABC transporters such as P-glycoprotein (P-gp) in the neurovascular unit cells, limiting access of the AEDs to the brain. Recent clinical trials and basic studies have shown encouraging results for the use of cannabinoids in RE, although its mechanisms of action are still not fully understood. Here, we have employed astrocytes and vascular endothelial cell cultures subjected to hypoxia, to test the effect of cannabidiol (CBD) on the P-gp-dependent Rhodamine-123 (Rho-123) efflux. Results show that during hypoxia, intracellular Rho-123 accumulation after CBD treatment is similar to that induced by the P-gp inhibitor Tariquidar (Tq). Noteworthy, this inhibition is like that registered in non-hypoxia conditions. Additionally, docking studies predicted that CBD could behave as a P-gp substrate by the interaction with several residues in the α-helix of the P-gp transmembrane domain. Overall, these findings suggest a direct effect of CBD on the Rho-123 P-gp-dependent efflux activity, which might explain why the CBD add-on treatment regimen in RE patients results in a significant reduction in seizure frequency.