Exploiting cannabinoid and vanilloid mechanisms for epilepsy treatment

Phytocannabinoids in neuromodulation: From omics to epigenetics

BACKGROUND

Recent developments in metabolomics, transcriptomic and epigenetics open up new horizons regarding the pharmacological understanding of phytocannabinoids as neuromodulators in treating anxiety, depression, epilepsy, Alzheimer's, Parkinson's disease and autism.

METHODS

The present review is an extensive search in public databases, such as Google Scholar, Scopus, the Web of Science, and PubMed, to collect all the literature about the neurobiological roles of cannabis extract, cannabidiol, 9-tetrahydrocannabinol specially focused on metabolomics, transcriptomic, epigenetic, mechanism of action, in different cell lines, induced animal models and clinical trials. We used bioinformatics, network pharmacology and enrichment analysis to understand the effect of phytocannabinoids in neuromodulation.

RESULTS

Cannabidomics studies show wide variability of metabolites across different strains and varieties, which determine their medicinal and abusive usage, which is very important for its quality control and regulation. CB receptors interact with other compounds besides cannabidiol and Δ9-tetrahydrocannabinol, like cannabinol and Δ8-tetrahydrocannabinol. Phytocannabinoids interact with cannabinoid and non-cannabinoid receptors (GPCR, ion channels, and PPAR) to improve various neurodegenerative diseases. However, its abuse because of THC is also a problem found across different epigenetic and transcriptomic studies. Network enrichment analysis shows CNR1 expression in the brain and its interacting genes involve different pathways such as Rap1 signalling, dopaminergic synapse, and relaxin signalling. CBD protects against diseases like epilepsy, depression, and Parkinson's by modifying DNA and mitochondrial DNA in the hippocampus. Network pharmacology analysis of 8 phytocannabinoids revealed an interaction with 10 (out of 60) targets related to neurodegenerative diseases, with enrichment of ErbB and PI3K-Akt signalling pathways which helps in ameliorating neuro-inflammation in various neurodegenerative diseases. The effects of phytocannabinoids vary across sex, disease state, and age which suggests the importance of a personalized medicine approach for better success.

CONCLUSIONS

Phytocannabinoids present a range of promising neuromodulatory effects. It holds promise if utilized in a strategic way towards personalized neuropsychiatric treatment. However, just like any drug irrational usage may lead to unforeseen negative effects. Exploring neuro-epigenetics and systems pharmacology of major and minor phytocannabinoid combinations can lead to success.

Cannabidiol Anticonvulsant Effects Against Lithium-Pilocarpine-Induced Status Epilepticus in Male Rats Are Mediated by Neuroinflammation Modulation and Cannabinoids 1 (CB1), But Not CB2 and GABAA Receptors

Background: Status epilepticus (SE) is a series of seizures that can lead to serious neurological damages. Cannabidiol (CBD) is extracted from the cannabis plant, which has been approved as an antiseizure medication. This study aimed to determine the efficacy of various doses of CBD on lithium-pilocarpine-induced SE in rats and possible involvement of multiple pharmacological pathways. We hypothesized that cannabinoid receptors type 1 (CB1) and CB2, as well as GABAA receptors, might have important roles in the anticonvulsant effects of CBD against SE by its anti-inflammatory effects. Methods: SE was induced by intraperitoneal (i.p.) injection of lithium (127 mg/kg, i.p.) and pilocarpine (60 mg/kg, i.p., 20 h after lithium). Forty-two male rats were divided into seven groups (including control and sham groups), and the treated groups received different doses of CBD (1, 3, 5, 10, and 25 mg/kg, i.p.). SE score was recorded over the next 2 h following pilocarpine injection. Then, we measured the levels of pro-inflammatory cytokines, including interleukin (IL)-lβ and tumor necrosis factor (TNF)-α, using ELISA kits. Also we analyzed the expression of CB1, CB2, and GABAA receptors using the Western blot technique. Results: CBD at 5 mg/kg significantly reduced Racine's scale and duration of seizures, and increased the onset time of seizure. Moreover, CBD 5 mg/kg caused significant reductions in the elevated levels of IL-lβ and TNF-α, as well as a significant increase in the decreased level of CB1 receptor expression compared to the control group. In other word, CBD reverted the effects of SE in terms of neuroinflammation and CB1 receptor. Based on the obtained results, CBD was not able to restore the declined levels of CB2 or GABAA receptors. Conclusion: Our study found anticonvulsant effects of CBD on the SE rat model induced by lithium-pilocarpine with probable involvement of CB1 receptors and anti-inflammatory effects by reducing IL-1β and TNF-α markers independent of CB2 and GABAA receptors.

Therapeutic applicability of cannabidiol and other phytocannabinoids in epilepsy, multiple sclerosis and Parkinson's disease and in comorbidity with psychiatric disorders

Studies have demonstrated the neuroprotective effect of cannabidiol (CBD) and other Cannabis sativa L. derivatives on diseases of the central nervous system caused by their direct or indirect interaction with endocannabinoid system-related receptors and other molecular targets, such as the 5-HT1A receptor, which is a potential pharmacological target of CBD. Interestingly, CBD binding with the 5-HT1A receptor may be suitable for the treatment of epilepsies, parkinsonian syndromes and amyotrophic lateral sclerosis, in which the 5-HT1A serotonergic receptor plays a key role. The aim of this review was to provide an overview of cannabinoid effects on neurological disorders, such as epilepsy, multiple sclerosis and Parkinson's diseases, and discuss their possible mechanism of action, highlighting interactions with molecular targets and the potential neuroprotective effects of phytocannabinoids. CBD has been shown to have significant therapeutic effects on epilepsy and Parkinson's disease, while nabiximols contribute to a reduction in spasticity and are a frequent option for the treatment of multiple sclerosis. Although there are multiple theories on the therapeutic potential of cannabinoids for neurological disorders, substantially greater progress in the search for strong scientific evidence of their pharmacological effectiveness is needed.

A Combined Ligand- and Structure-Based Virtual Screening To Identify Novel NaV1.2 Blockers: In Vitro Patch Clamp Validation and In Vivo Anticonvulsant Activity

Epilepsy is a neurological disorder characterized by recurrent seizures that arise from abnormal electrical activity in the brain. Voltage-gated sodium channels (NaVs), responsible for the initiation and propagation of action potentials in neurons, play a critical role in the pathogenesis of epilepsy. This study sought to discover potential anticonvulsant compounds that interact with NaVs, specifically, the brain subtype hNaV1.2. A ligand-based QSAR model and a docking model were constructed, validated, and applied in a parallel virtual screening over the DrugBank database. Montelukast, Novobiocin, and Cinnarizine were selected for in vitro testing, using the patch-clamp technique, and all of them proved to inhibit hNaV1.2 channels heterologously expressed in HEK293 cells. Two hits were evaluated in the GASH/Sal model of audiogenic seizures and demonstrated promising activity, reducing the severity of sound-induced seizures at the doses tested. The combination of ligand- and structure-based models presents a valuable approach for identifying potential NaV inhibitors. These findings may provide a basis for further research into the development of new antiseizure drugs for the treatment of epilepsy.

Parkinson's disease, epilepsy, and amyotrophic lateral sclerosis-emerging role of AMPA and kainate subtypes of ionotropic glutamate receptors

Ionotropic glutamate receptors (iGluRs) mediate the majority of excitatory neurotransmission and are implicated in various neurological disorders. In this review, we discuss the role of the two fastest iGluRs subtypes, namely, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors, in the pathogenesis and treatment of Parkinson's disease, epilepsy, and amyotrophic lateral sclerosis. Although both AMPA and kainate receptors represent promising therapeutic targets for the treatment of these diseases, many of their antagonists show adverse side effects. Further studies of factors affecting the selective subunit expression and trafficking of AMPA and kainate receptors, and a reasonable approach to their regulation by the recently identified novel compounds remain promising directions for pharmacological research.

Structure-Based Virtual Screening Identifies Novobiocin, Montelukast, and Cinnarizine as TRPV1 Modulators with Anticonvulsant Activity In Vivo

The transient receptor potential vanilloid 1 (TRPV1) receptor is a nonselective cation channel, known to be involved in the regulation of many important physiological and pathological processes. In the last few years, it has been proposed as a promising target to develop novel anticonvulsant compounds. However, thermoregulatory effects associated with the channel inhibition have hampered the path for TRPV1 antagonists to become marketed drugs. In this regard, we conducted a structure-based virtual screening campaign to find potential TRPV1 modulators among approved drugs, which are known to be safe and thermally neutral. To this end, different docking models were developed and validated by assessing their pose and score prediction powers. Novobiocin, montelukast, and cinnarizine were selected from the screening as promising candidates for experimental testing and all of them exhibited nanomolar inhibitory activity. Moreover, the in vivo profiles showed promising results in at least one of the three models of seizures tested.

Transient Receptor Potential Vanilloid 1 Function at Central Synapses in Health and Disease

The transient receptor potential vanilloid 1 (TRPV1), a ligand-gated nonselective cation channel, is well known for mediating heat and pain sensation in the periphery. Increasing evidence suggests that TRPV1 is also expressed at various central synapses, where it plays a role in different types of activity-dependent synaptic changes. Although its precise localizations remain a matter of debate, TRPV1 has been shown to modulate both neurotransmitter release at presynaptic terminals and synaptic efficacy in postsynaptic compartments. In addition to being required in these forms of synaptic plasticity, TRPV1 can also modify the inducibility of other types of plasticity. Here, we highlight current evidence of the potential roles for TRPV1 in regulating synaptic function in various brain regions, with an emphasis on principal mechanisms underlying TRPV1-mediated synaptic plasticity and metaplasticity. Finally, we discuss the putative contributions of TRPV1 in diverse brain disorders in order to expedite the development of next-generation therapeutic treatments.

The Endocannabinoid System in Glial Cells and Their Profitable Interactions to Treat Epilepsy: Evidence from Animal Models

Epilepsy is one of the most common neurological conditions. Yearly, five million people are diagnosed with epileptic-related disorders. The neuroprotective and therapeutic effect of (endo)cannabinoid compounds has been extensively investigated in several models of epilepsy. Therefore, the study of specific cell-type-dependent mechanisms underlying cannabinoid effects is crucial to understanding epileptic disorders. It is estimated that about 100 billion neurons and a roughly equal number of glial cells co-exist in the human brain. The glial population is in charge of neuronal viability, and therefore, their participation in brain pathophysiology is crucial. Furthermore, glial malfunctioning occurs in a wide range of neurological disorders. However, little is known about the impact of the endocannabinoid system (ECS) regulation over glial cells, even less in pathological conditions such as epilepsy. In this review, we aim to compile the existing knowledge on the role of the ECS in different cell types, with a particular emphasis on glial cells and their impact on epilepsy. Thus, we propose that glial cells could be a novel target for cannabinoid agents for treating the etiology of epilepsy and managing seizure-like disorders.

From an Alternative Medicine to a New Treatment for Refractory Epilepsies: Can Cannabidiol Follow the Same Path to Treat Neuropsychiatric Disorders?

Although cannabis has been known for ages as an "alternative medicine" to provide relief from seizures, pain, anxiety, and inflammation, there had always been a limited scientific review to prove and establish its use in clinics. Early studies carried out by Carlini's group in Brazil suggested that cannabidiol (CBD), a non-psychotropic phytocannabinoid present in Cannabis sativa, has anticonvulsant properties in animal models and reduced seizure frequency in limited human trials. Over the past few years, the potential use of cannabis extract in refractory epilepsy, including childhood epilepsies such as Dravet's syndrome and Lennox-Gastaut Syndrome, has opened a new era of treating epileptic patients. Thus, a considerable number of pre-clinical and clinical studies have provided strong evidence that phytocannabinoids has anticonvulsant properties, as well as being promising in the treatment of different neuropsychiatric disorders, such as depression, anxiety, post-traumatic stress disorder (PTSD), addiction, neurodegenerative disorders and autism spectrum disorder (ASD). Given the advances of cannabinoids, especially CBD, in the treatment of epilepsy, would the same expectation regarding the treatment of other neuropsychiatric disorders be possible? The present review highlights some contributions from Brazilian researchers and other studies reported elsewhere on the history, pre-clinical and clinical data underlying the use of cannabinoids for the already widespread treatment of refractory epilepsies and the possibility of use in the treatment of some neuropsychiatric disorders.

Neuropharmacological potentials of β-carboline alkaloids for neuropsychiatric disorders

Neuropsychiatric disorders are diseases of the central nervous system (CNS) which are characterised by complex pathomechanisms that including homeostatic failure, malfunction, atrophy, pathology remodelling and reactivity anomaly of the neuronal system where treatment options remain challenging. β-Carboline (βC) alkaloids are scaffolds of structurally diverse tricyclic pyrido[3,4-b]indole alkaloid with vast occurrence in nature. Their unique structural features which favour interactions with enzymes and protein receptor targets account for their potent neuropharmacological properties. However, our current understanding of their biological mechanisms for these beneficial effects, especially for neuropsychiatric disorders is sparse. Therefore, we present a comprehensive review of the scientific progress in the last two decades on the prospective pharmacology and physiology of the βC alkaloids in the treatment of some neuropsychiatric conditions such as depression, anxiety, Alzheimer's disease, Parkinson's disease, brain tumour, essential tremor, epilepsy and seizure, licking behaviour, dystonia, agnosia, spasm, positive ingestive response as demonstrated in non-clinical models. The current evidence supports that βC alkaloids offer potential therapeutic agents against most of these disorders and amenable for further drug design.

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

The understanding that hyper-excitability and hyper-synchronism in epilepsy are indissociably bound by a cause-consequence relation has only recently been challenged. Thus, therapeutic strategies for seizure suppression have often aimed at inhibiting excitatory circuits and/or activating inhibitory ones. However, new approaches that aim to desynchronize networks or compromise abnormal coupling between adjacent neural circuitry have been proven effective, even at the cost of enhancing local neuronal activation. Although most of these novel perspectives targeting circuitry desynchronization and network coupling have been implemented by non-pharmacological devices, we argue that there may be endogenous neurochemical systems that act primarily in the desynchronization component of network behavior rather than dampening excitability of individual neurons. This review explores the endocannabinoid system as one such possible pharmacological landmark for mimicking a form of "on-demand" desynchronization analogous to those proposed by deep brain stimulation in the treatment of epilepsy. This essay discusses the evidence supporting the role of the endocannabinoid system in modulating the synchronization and/or coupling of distinct local neural circuitry; which presents obvious implications on the physiological setting of proper sensory-motor integration. Accordingly, the process of ictogenesis involves pathological circuit coupling that could be avoided, or at least have its spread throughout the containment of other areas, if such endogenous mechanisms of control could be activated or potentiated by pharmacological intervention. In addition, we will discuss evidence that supports not only a weaker role played on neuronal excitability but the potential of the endocannabinoid system strengthening its modulatory effect, only when circuitry coupling surpasses a level of activation.

Cannabis sativa: Much more beyond Δ9-tetrahydrocannabinol

Cannabis is the most used illicit drug worldwide and its medicinal use is under discussion, being regulated in several countries. However, the psychotropic effects of Δ⁹-tetrahydrocannabinol (THC), the main psychoactive compound of Cannabis sativa, are of concern. Thus, the interest in the isolated constituents without psychotropic activity, such as cannabidiol (CBD) and cannabidivarin (CBDV) is growing. CBD and CBDV are lipophilic molecules with poor oral bioavailability and are mainly metabolized by cytochrome P450 (CYP450) enzymes. The pharmacodynamics of CBD is the best explored, being able to interact with diverse molecular targets, like cannabinoid receptors, G protein-coupled receptor-55, transient receptor potential vanilloid 1 channel and peroxisome proliferator-activated receptor-γ. Considering the therapeutic potential, several clinical trials are underway to study the efficacy of CBD and CBDV in different pathologies, such as neurodegenerative diseases, epilepsy, autism spectrum disorders and pain conditions. The anti-cancer properties of CBD have also been demonstrated by several pre-clinical studies in different types of tumour cells. Although less studied, CBDV, a structural analogue of CBD, is receiving attention in the last years. CBDV exhibits anticonvulsant properties and, currently, clinical trials are underway for the treatment of autism spectrum disorders. Despite the benefits of these phytocannabinoids, it is important to highlight their potential interference with relevant physiologic mechanisms. In fact, CBD interactions with CYP450 enzymes and with drug efflux transporters may have serious consequences when co-administered with other drugs. This review summarizes the therapeutic advances of CBD and CBDV and explores some aspects of their pharmacokinetics, pharmacodynamics and possible interactions. Moreover, it also highlights the therapeutic potential of CBD and CBDV in several medical conditions and clinical applications.