Cannabinoid Type 2 Receptors Mediate a Cell Type-Specific Plasticity in the Hippocampus

The anxiolytic effects of cannabinoids: A comprehensive review

Cannabinoids, notably cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC), have emerged as promising candidates for anxiety disorder treatment, supported by both preclinical and clinical evidence. CBD exhibits notable anxiolytic effects with a favourable safety profile, though concerns regarding mild side effects and drug interactions remain. Conversely, THC, the primary psychoactive compound, presents a range of side effects, underscoring the importance of careful dosage management and individualized treatment strategies. So far there are no FDA approved cannabinoid medications for anxiety. The review highlights challenges in cannabinoid research, including dosage variability, variable preclinical data, and limited long-term data. Despite these limitations, cannabinoids represent a promising avenue for anxiety management, with the potential for further optimization in formulation, dosing protocols, and consideration of interactions with conventional therapies. Addressing these challenges could pave the way for novel and personalized approaches to treating anxiety disorders using cannabinoid-based therapies.

CB2 expression in mouse brain: from mapping to regulation in microglia under inflammatory conditions

Since its detection in the brain, the cannabinoid receptor type 2 (CB2) has been considered a promising therapeutic target for various neurological and psychiatric disorders. However, precise brain mapping of its expression is still lacking. Using magnetic cell sorting, calibrated RT-qPCR and single-nucleus RNAseq, we show that CB2 is expressed at a low level in all brain regions studied, mainly by few microglial cells, and by neurons in an even lower proportion. Upon lipopolysaccharide stimulation, modeling neuroinflammation in non-sterile conditions, we demonstrate that the inflammatory response is associated with a transient reduction in CB2 mRNA levels in brain tissue, particularly in microglial cells. This result, confirmed in the BV2 microglial cell line, contrasts with the positive correlation observed between CB2 mRNA levels and the inflammatory response upon stimulation by interferon-gamma, modeling neuroinflammation in sterile condition. Discrete brain CB2 expression might thus be up- or down-regulated depending on the inflammatory context.

Daily Cannabidiol Administration for 10 Weeks Modulates Hippocampal and Amygdalar Resting-State Functional Connectivity in Cannabis Users: A Functional Magnetic Resonance Imaging Open-Label Clinical Trial

Introduction: Cannabis use is associated with brain functional changes in regions implicated in prominent neuroscientific theories of addiction. Emerging evidence suggests that cannabidiol (CBD) is neuroprotective and may reverse structural brain changes associated with prolonged heavy cannabis use. In this study, we examine how an ∼10-week exposure of CBD in cannabis users affected resting-state functional connectivity in brain regions functionally altered by cannabis use. Materials and Methods: Eighteen people who use cannabis took part in a ∼10 weeks open-label pragmatic trial of self-administered daily 200 mg CBD in capsules. They were not required to change their cannabis exposure patterns. Participants were assessed at baseline and post-CBD exposure with structural magnetic resonance imaging (MRI) and a functional MRI resting-state task (eyes closed). Seed-based connectivity analyses were run to examine changes in the functional connectivity of a priori regions-the hippocampus and the amygdala. We explored if connectivity changes were associated with cannabinoid exposure (i.e., cumulative cannabis dosage over trial, and plasma CBD concentrations and Δ9-tetrahydrocannabinol (THC) plasma metabolites postexposure), and mental health (i.e., severity of anxiety, depression, and positive psychotic symptom scores), accounting for cigarette exposure in the past month, alcohol standard drinks in the past month and cumulative CBD dose during the trial. Results: Functional connectivity significantly decreased pre-to-post the CBD trial between the anterior hippocampus and precentral gyrus, with a strong effect size (d=1.73). Functional connectivity increased between the amygdala and the lingual gyrus pre-to-post the CBD trial, with a strong effect size (d=1.19). There were no correlations with cannabinoids or mental health symptom scores. Discussion: Prolonged CBD exposure may restore/reduce functional connectivity differences reported in cannabis users. These new findings warrant replication in a larger sample, using robust methodologies-double-blind and placebo-controlled-and in the most vulnerable people who use cannabis, including those with more severe forms of Cannabis Use Disorder and experiencing worse mental health outcomes (e.g., psychosis, depression).

Dynamic endocannabinoid-mediated neuromodulation of retinal circadian circuitry

Circadian rhythms are biological rhythms that originate from the "master circadian clock," called the suprachiasmatic nucleus (SCN). SCN orchestrates the circadian rhythms using light as a chief zeitgeber, enabling humans to synchronize their daily physio-behavioral activities with the Earth's light-dark cycle. However, chronic/ irregular photic disturbances from the retina via the retinohypothalamic tract (RHT) can disrupt the amplitude and the expression of clock genes, such as the period circadian clock 2, causing circadian rhythm disruption (CRd) and associated neuropathologies. The present review discusses neuromodulation across the RHT originating from retinal photic inputs and modulation offered by endocannabinoids as a function of mitigation of the CRd and associated neuro-dysfunction. Literature indicates that cannabinoid agonists alleviate the SCN's ability to get entrained to light by modulating the activity of its chief neurotransmitter, i.e., γ-aminobutyric acid, thus preventing light-induced disruption of activity rhythms in laboratory animals. In the retina, endocannabinoid signaling modulates the overall gain of the retinal ganglion cells by regulating the membrane currents (Ca2+, K+, and Cl- channels) and glutamatergic neurotransmission of photoreceptors and bipolar cells. Additionally, endocannabinoids signalling also regulate the high-voltage-activated Ca2+ channels to mitigate the retinal ganglion cells and intrinsically photosensitive retinal ganglion cells-mediated glutamate release in the SCN, thus regulating the RHT-mediated light stimulation of SCN neurons to prevent excitotoxicity. As per the literature, cannabinoid receptors 1 and 2 are becoming newer targets in drug discovery paradigms, and the involvement of endocannabinoids in light-induced CRd through the RHT may possibly mitigate severe neuropathologies.

Physical Exercise Improves the Neuronal Function in Ischemic Stroke Via Microglial CB2R/P2Y12 Signaling

Physical exercise (PE) may be the single most important and accessible lifestyle habit throughout life, it inhibits the neuroinflammatory response and protects the brain against damage. As the innate cells in brain, microglia undergo morphological and functional changes to communicate with neurons protecting the neurons from injury. Herein, aiming at exploring the effects of PE on the communication between microglia-neuron during acute ischemic cerebral infarction, we carried out running wheel training before the conduction of transient middle cerebral artery occlusion (tMCAO) in C57BL/6 J and Cx3cr1-GFP mice. We found that microglial P2Y12 expression in the peri-infarct area was decreased, microglial dynamics and microglia-neuron communications were impaired, using in vivo two-photon imaging. PE up-regulated the microglial P2Y12 expression, increased the microglial dynamics, and promoted the contacts of microglia with neurons. As a result, PE inhibited neuronal Ca2+ overloads and protected against damage of the neuronal mitochondria in acute tMCAO. Mechanistically, PE increased the cannabinoid receptor 2 (CB2R) in microglia, promoted the phosphorylation of Nrf2 (NF-E2-related factor 2) at ser-344, increased the transcription factor level of Mafk, and up-regulated the level of P2Y12, whereby PE increased the levels of CB2R to promote microglia-neuron contacts to monitor and protect neuronal function.

Enantiomeric Agonists of the Type 2 Cannabinoid Receptor Reduce Retinal Damage during Proliferative Vitreoretinopathy and Inhibit Hyperactive Microglia In Vitro

Microglia are resident immune cells of the central nervous system (CNS) and propagate inflammation following damage to the CNS, including the retina. Proliferative vitreoretinopathy (PVR) is a condition that can emerge following retinal detachment and is characterized by severe inflammation and microglial proliferation. The type 2 cannabinoid receptor (CB2) is an emerging pharmacological target to suppress microglial-mediated inflammation when the eyes or brain are damaged. CB2-knockout mice have exacerbated inflammation and retinal pathology during experimental PVR. We aimed to assess the anti-inflammatory effects of CB2 stimulation in the context of retinal damage and also explore the mechanistic roles of CB2 in microglia function. To target CB2, we used a highly selective agonist, HU-308, as well as its enantiomer, HU-433, which is a putative selective agonist. First, β-arrestin2 and Gαi recruitment was measured to compare activation of human CB2 in an in vitro heterologous expression system. Both agonists were then utilized in a mouse model of PVR, and the effects on retinal damage, inflammation, and cell death were assessed. Finally, we used an in vitro model of microglia to determine the effects of HU-308 and HU-433 on phagocytosis, cytokine release, migration, and intracellular signaling. We observed that HU-308 more strongly recruited both β-arrestin2 and Gαi compared to HU-433. Stimulation of CB2 with either drug effectively blunted LPS- and IFNγ-mediated signaling as well as NO and TNF release from microglia. Furthermore, both drugs reduced IL-6 accumulation, total caspase-3 cleavage, and retinal pathology following the induction of PVR. Ultimately, this work supports that CB2 is a valuable target for drugs to suppress inflammation and cell death associated with infection or sterile retinopathy, although the magnitude of effector recruitment may not be predictive of anti-inflammatory capacity.

Potential Therapeutic Targets to Modulate the Endocannabinoid System in Alzheimer's Disease

Alzheimer's disease (AD), the most common neurodegenerative disease (NDD), is characterized by chronic neuronal cell death through progressive loss of cognitive function. Amyloid beta (Aβ) deposition, neuroinflammation, oxidative stress, and hyperphosphorylated tau proteins are considered the hallmarks of AD pathology. Different therapeutic approaches approved by the Food and Drug Administration can only target a single altered pathway instead of various mechanisms that are involved in AD pathology, resulting in limited symptomatic relief and almost no effect in slowing down the disease progression. Growing evidence on modulating the components of the endocannabinoid system (ECS) proclaimed their neuroprotective effects by reducing neurochemical alterations and preventing cellular dysfunction. Recent studies on AD mouse models have reported that the inhibitors of the fatty acid amide hydrolase (FAAH) and monoacylglycerol (MAGL), hydrolytic enzymes for N-arachidonoyl ethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), respectively, might be promising candidates as therapeutical intervention. The FAAH and MAGL inhibitors alone or in combination seem to produce neuroprotection by reversing cognitive deficits along with Aβ-induced neuroinflammation, oxidative responses, and neuronal death, delaying AD progression. Their exact signaling mechanisms need to be elucidated for understanding the brain intrinsic repair mechanism. The aim of this review was to shed light on physiology and pathophysiology of AD and to summarize the experimental data on neuroprotective roles of FAAH and MAGL inhibitors. In this review, we have also included CB1R and CB2R modulators with their diverse roles to modulate ECS mediated responses such as anti-nociceptive, anxiolytic, and anti-inflammatory actions in AD. Future research would provide the directions in understanding the molecular mechanisms and development of new therapeutic interventions for the treatment of AD.

Cannabinoid treatments in epilepsy and seizure disorders

Cannabis has been used to treat convulsions and other disorders since ancient times. In the last few decades, preclinical animal studies and clinical investigations have established the role of cannabidiol (CBD) in treating epilepsy and seizures and support potential therapeutic benefits for cannabinoids in other neurological and psychiatric disorders. Here, we comprehensively review the role of cannabinoids in epilepsy. We briefly review the diverse physiological processes mediating the central nervous system response to cannabinoids, including Δ9-tetrahydrocannabinol (Δ9-THC), cannabidiol, and terpenes. Next, we characterize the anti- and proconvulsive effects of cannabinoids from animal studies of acute seizures and chronic epileptogenesis. We then review the clinical literature on using cannabinoids to treat epilepsy, including anecdotal evidence and case studies as well as the more recent randomized controlled clinical trials that led to US Food and Drug Administration approval of CBD for some types of epilepsy. Overall, we seek to evaluate our current understanding of cannabinoids in epilepsy and focus future research on unanswered questions.

Cannabinoid type 2 receptor inhibition enhances the antidepressant and proneurogenic effects of physical exercise after chronic stress

Chronic stress is a major risk factor for neuropsychiatric conditions such as depression. Adult hippocampal neurogenesis (AHN) has emerged as a promising target to counteract stress-related disorders given the ability of newborn neurons to facilitate endogenous plasticity. Recent data sheds light on the interaction between cannabinoids and neurotrophic factors underlying the regulation of AHN, with important effects on cognitive plasticity and emotional flexibility. Since physical exercise (PE) is known to enhance neurotrophic factor levels, we hypothesised that PE could engage with cannabinoids to influence AHN and that this would result in beneficial effects under stressful conditions. We therefore investigated the actions of modulating cannabinoid type 2 receptors (CB2R), which are devoid of psychotropic effects, in combination with PE in chronically stressed animals. We found that CB2R inhibition, but not CB2R activation, in combination with PE significantly ameliorated stress-evoked emotional changes and cognitive deficits. Importantly, this combined strategy critically shaped stress-induced changes in AHN dynamics, leading to a significant increase in the rates of cell proliferation and differentiation of newborn neurons, overall reduction in neuroinflammation, and increased hippocampal levels of BDNF. Together, these results show that CB2Rs are crucial regulators of the beneficial effects of PE in countering the effects of chronic stress. Our work emphasises the importance of understanding the mechanisms behind the actions of cannabinoids and PE and provides a framework for future therapeutic strategies to treat stress-related disorders that capitalise on lifestyle interventions complemented with endocannabinoid pharmacomodulation.

The progress of small molecules against cannabinoid 2 receptor (CB2R)

The two subtypes of cannabinoid receptors (CBR), namely CB1R and CB2R, belong to the G protein-coupled receptor (GPCR) superfamily and are confirmed as potential therapeutic targets for a variety of diseases such as inflammation, neuropathic pain, and immune-related disorders. Since CB1R is mainly distributed in the central nervous system (CNS), it could produce severe psychiatric adverse reactions and addiction. In contrast, CB2R are predominantly distributed in the peripheral immune system with minimal CNS-related side effects. Therefore, more attention has been devoted to the discovery of CB2R ligands. In view of the favorable profile of CB2R, many high-binding affinity and selectivity CB2R ligands have been developed recently. This paper reviews recent research progress on CB2R ligands, including endogenous CB2R ligands, natural compounds, and novel small molecules, in order to provide a reference for subsequent CB2R ligand development.

Electrophysiological Phenotypes of Hippocampal Synaptic and Network Functions in Cannabinoid Receptor 2 Knockout Mice

Background: The cannabinoid receptor 2 (CB2R), a cannabinoid receptor primarily expressed in immune cells, has been found in the brain, particularly in the hippocampus, where it plays crucial roles in modulating various neural functions, including synaptic plasticity, neuroprotection, neurogenesis, anxiety and stress responses, and neuroinflammation. Despite this growing understanding, the intricate electrophysiological characteristics of hippocampal neurons in CB2R knockout (CB2R KO) mice remain elusive. Aim and Methods: This study aimed to comprehensively assess the electrophysiological traits of hippocampal synaptic and network functions in CB2R KO mice. The focus was on aspects such as synaptic transmission, short- and long-term synaptic plasticity, and neural network synchrony (theta oscillations). Results: Our findings unveiled multiple functional traits in these CB2R KO mice, notably elevated synaptic transmission in hippocampal CA1 neurons, decreased both synaptic short-term plasticity (paired-pulse facilitation) and long-term potentiation (LTP), and impaired neural network synchronization. Conclusion: In essence, this study yields insightful revelations about the influence of CB2Rs on hippocampal neural functions. By illuminating the electrophysiological modifications in CB2R KO mice, our research enriches the comprehension of CB2R involvement in hippocampal function. Such insights could hold implications for advancing our understanding of the neural mechanisms under the influence of CB2Rs within the brain.

Research progress on the cannabinoid type-2 receptor and Parkinson's disease

Parkinson's disease (PD) is featured by movement impairments, including tremors, bradykinesia, muscle stiffness, and imbalance. PD is also associated with many non-motor symptoms, such as cognitive impairments, dementia, and mental disorders. Previous studies identify the associations between PD progression and factors such as α-synuclein aggregation, mitochondrial dysfunction, inflammation, and cell death. The cannabinoid type-2 receptor (CB2 receptor) is a transmembrane G-protein-coupled receptor and has been extensively studied as part of the endocannabinoid system. CB2 receptor is recently emerged as a promising target for anti-inflammatory treatment for neurodegenerative diseases. It is reported to modulate mitochondrial function, oxidative stress, iron transport, and neuroinflammation that contribute to neuronal cell death. Additionally, CB2 receptor possesses the potential to provide feedback on electrophysiological processes, offering new possibilities for PD treatment. This review summarized the mechanisms underlying PD pathogenesis. We also discussed the potential regulatory role played by CB2 receptor in PD.

The Basic Science of Cannabinoids

The cannabis plant has been used for centuries to manage the symptoms of various ailments including pain. Hundreds of chemical compounds have been identified and isolated from the plant and elicit a variety of physiological responses by binding to specific receptors and interacting with numerous other proteins. In addition, the body makes its own cannabinoid-like compounds that are integrally involved in modulating normal and pathophysiological processes. As the legal cannabis landscape continues to evolve within the United States and throughout the world, it is important to understand the rich science behind the effects of the plant and the implications for providers and patients. This narrative review aims to provide an overview of the basic science of the cannabinoids by describing the discovery and function of the endocannabinoid system, pharmacology of cannabinoids, and areas for future research and therapeutic development as they relate to perioperative and chronic pain medicine.

Inhibition of fatty acid binding protein-5 in the basolateral amygdala induces anxiolytic effects and accelerates fear memory extinction

RATIONALE

The endocannabinoid (eCB) system critically controls anxiety and fear-related behaviours. Anandamide (AEA), a prominent eCB ligand, is a hydrophobic lipid that requires chaperone proteins such as Fatty Acid Binding Proteins (FABPs) for intracellular transport. Intracellular AEA transport is necessary for degradation, so blocking FABP activity increases AEA neurotransmission.

OBJECTIVE

To investigate the effects of a novel FABP5 inhibitor (SBFI-103) in the basolateral amygdala (BLA) on anxiety and fear memory.

METHODS

We infused SBFI-103 (0.5 μg-5 μg) to the BLA of adult male Sprague Dawley rats and ran various anxiety and fear memory behavioural assays, neurophysiological recordings, and localized molecular signaling analyses. We also co-infused SBFI-103 with the AEA inhibitor, LEI-401 (3 μg and 10 μg) to investigate the potential role of AEA in these phenomena.

RESULTS

Acute intra-BLA administration of SBFI-103 produced strong anxiolytic effects across multiple behavioural tests. Furthermore, animals exhibited acute and long-term accelerated associative fear memory extinction following intra-BLA FABP5 inhibition. In addition, BLA FABP5 inhibition induced strong modulatory effects on putative PFC pyramidal neurons along with significantly increased gamma oscillation power. Finally, we observed local BLA changes in the phosphorylation activity of various anxiety- and fear memory-related molecular biomarkers in the PI3K/Akt and MAPK/Erk signaling pathways. At all three levels of analyses, we found the functional effects of SBFI-103 depend on availability of the AEA ligand.

CONCLUSIONS

These findings demonstrate a novel intra-BLA FABP5 signaling mechanism regulating anxiety and fear memory behaviours, neuronal activity states, local anxiety-related molecular pathways, and functional AEA modulation.

Role of the CB2 Cannabinoid Receptor in the Regulation of Food Intake: A Systematic Review

The CB2 cannabinoid receptor has been found in brain areas that are part of the reward system and has been shown to play a role in food intake regulation. Herein, we conducted a systematic review of studies assessing the role of the CB2 receptor in food intake regulation. Records from the PubMed, Scopus, and EBSCO databases were screened, resulting in 13 studies that were used in the present systematic review, following the PRISMA guidelines. A risk of bias assessment was carried out using the tool of the Systematic Review Center for Laboratory Animal Experimentation (SYRCLE). The studies analyzed used two main strategies: (1) the intraperitoneal or intracerebroventricular administration of a CB2 agonist/antagonist; and (2) depletion of CB2 receptors via knockout in mice. Both strategies are useful in identifying the role of the CB2 receptor in food intake in standard and palatable diets. The conclusions derived from animal models showed that CB2 receptors are necessary for modulating food intake and mediating energy balance.

Exploring the 1,3-benzoxazine chemotype for cannabinoid receptor 2 as a promising anti-cancer therapeutic

The discovery of selective agonists of cannabinoid receptor 2 (CB2) is strongly pursued to successfully tuning endocannabinoid signaling for therapeutic purposes. However, the design of selective CB2 agonists is still challenging because of the high homology with the cannabinoid receptor 1 (CB1) and for the yet unclear molecular basis of the agonist/antagonist switch. Here, the 1,3-benzoxazine scaffold is presented as a versatile chemotype for the design of CB2 agonists from which 25 derivatives were synthesized. Among these, compound 7b5 (CB2 EC50 = 110 nM, CB1 EC50 > 10 μM) demonstrated to impair proliferation of triple negative breast cancer BT549 cells and to attenuate the release of pro-inflammatory cytokines in a CB2-dependent manner. Furthermore, 7b5 abrogated the activation of extracellular signal-regulated kinase (ERK) 1/2, a key pro-inflammatory and oncogenic enzyme. Finally, molecular dynamics studies suggested a new rationale for the in vitro measured selectivity and for the observed agonist behavior.

Neuroinflammation in the Central Nervous System: Exploring the Evolving Influence of Endocannabinoid System

Neuroinflammation is a complex biological process that typically originates as a protective response in the brain. This inflammatory process is triggered by the release of pro-inflammatory substances like cytokines, prostaglandins, and reactive oxygen and nitrogen species from stimulated endothelial and glial cells, including those with pro-inflammatory functions, in the outer regions. While neuronal inflammation is common in various central nervous system disorders, the specific inflammatory pathways linked with different immune-mediated cell types and the various factors influencing the blood-brain barrier significantly contribute to disease-specific characteristics. The endocannabinoid system consists of cannabinoid receptors, endogenous cannabinoids, and enzymes responsible for synthesizing and metabolizing endocannabinoids. The primary cannabinoid receptor is CB1, predominantly found in specific brain regions such as the brainstem, cerebellum, hippocampus, and cortex. The presence of CB2 receptors in certain brain components, like cultured cerebellar granular cells, Purkinje fibers, and microglia, as well as in the areas like the cerebral cortex, hippocampus, and cerebellum is also evidenced by immunoblotting assays, radioligand binding, and autoradiography studies. Both CB1 and CB2 cannabinoid receptors exhibit noteworthy physiological responses and possess diverse neuromodulatory capabilities. This review primarily aims to outline the distribution of CB1 and CB2 receptors across different brain regions and explore their potential roles in regulating neuroinflammatory processes.

Endocannabinoid signaling in adult hippocampal neurogenesis: A mechanistic and integrated perspective

Dentate gyrus of the hippocampus continuously gives rise to new neurons, namely, adult-born granule cells, which contribute to conferring plasticity to the mature brain throughout life. Within this neurogenic region, the fate and behavior of neural stem cells (NSCs) and their progeny result from a complex balance and integration of a variety of cell-autonomous and cell-to-cell-interaction signals and underlying pathways. Among these structurally and functionally diverse signals, there are endocannabinoids (eCBs), the main brain retrograde messengers. These pleiotropic bioactive lipids can directly and/or indirectly influence adult hippocampal neurogenesis (AHN) by modulating, both positively and negatively, multiple molecular and cellular processes in the hippocampal niche, depending on the cell type or stage of differentiation. Firstly, eCBs act directly as cell-intrinsic factors, cell-autonomously produced by NSCs following their stimulation. Secondly, in many, if not all, niche-associated cells, including some local neuronal and nonneuronal elements, the eCB system indirectly modulates the neurogenesis, linking neuronal and glial activity to regulating distinct stages of AHN. Herein, we discuss the crosstalk of the eCB system with other neurogenesis-relevant signal pathways and speculate how the hippocampus-dependent neurobehavioral effects elicited by (endo)cannabinergic medications are interpretable in light of the key regulatory role that eCBs play on AHN.

Mitochondria as central hubs in synaptic modulation

Mitochondria are present in the pre- and post-synaptic regions, providing the energy required for the activity of these very specialized neuronal compartments. Biogenesis of synaptic mitochondria takes place in the cell body, and these organelles are then transported to the synapse by motor proteins that carry their cargo along microtubule tracks. The transport of mitochondria along neurites is a highly regulated process, being modulated by the pattern of neuronal activity and by extracellular cues that interact with surface receptors. These signals act by controlling the distribution of mitochondria and by regulating their activity. Therefore, mitochondria activity at the synapse allows the integration of different signals and the organelles are important players in the response to synaptic stimulation. Herein we review the available evidence regarding the regulation of mitochondrial dynamics by neuronal activity and by neuromodulators, and how these changes in the activity of mitochondria affect synaptic communication.

The Role of the Endocannabinoid System in Binge Eating Disorder

Eating disorders are multifactorial disorders that involve maladaptive feeding behaviors. Binge eating disorder (BED), the most prevalent of these in both men and women, is characterized by recurrent episodes of eating large amounts of food in a short period of time, with a subjective loss of control over eating behavior. BED modulates the brain reward circuit in humans and animal models, which involves the dynamic regulation of the dopamine circuitry. The endocannabinoid system plays a major role in the regulation of food intake, both centrally and in the periphery. Pharmacological approaches together with research using genetically modified animals have strongly highlighted a predominant role of the endocannabinoid system in feeding behaviors, with the specific modulation of addictive-like eating behaviors. The purpose of the present review is to summarize our current knowledge on the neurobiology of BED in humans and animal models and to highlight the specific role of the endocannabinoid system in the development and maintenance of BED. A proposed model for a better understanding of the underlying mechanisms involving the endocannabinoid system is discussed. Future research will be necessary to develop more specific treatment strategies to reduce BED symptoms.

Endocannabinoid modulation of allergic responses: Focus on the control of FcεRI-mediated mast cell activation

Allergic reactions are highly prevalent pathologies initiated by the production of IgE antibodies against harmless antigens (allergens) and the activation of the high-affinity IgE receptor (FcεRI) expressed in the surface of basophils and mast cells (MCs). Research on the mechanisms of negative control of those exacerbated inflammatory reactions has been intense in recent years. Endocannabinoids (eCBs) show important regulatory effects on MC-mediated immune responses, mainly inhibiting the production of pro-inflammatory mediators. However, the description of the molecular mechanisms involved in eCB control of MC activation is far from complete. In this review, we aim to summarize the available information regarding the role of eCBs in the modulation of FcεRI-dependent activation of that cell type, emphasizing the description of the eCB system and the existence of some of its elements in MCs. Unique characteristics of the eCB system and cannabinoid receptors (CBRs) localization and signaling in MCs are mentioned. The described and putative points of cross-talk between CBRs and FcεRI signaling cascades are also presented. Finally, we discuss some important considerations in the study of the effects of eCBs in MCs and the perspectives in the field.

CB2 receptor in the CNS: from immune and neuronal modulation to behavior

Despite low levels of cannabinoid receptor type 2 (CB2R) expression in the central nervous system in human and rodents, a growing body of evidence shows CB2R involvement in many processes at the behavioral level, through both immune and neuronal modulations. Recent in vitro and in vivo evidence have highlighted the complex role of CB2R under physiological and inflammatory conditions. Under neuroinflammatory states, its activation seems to protect the brain and its functions, making it a promising target in a wide range of neurological disorders. Here, we provide a complete and updated overview of CB2R function in the central nervous system of rodents, spanning from modulation of immune function in microglia but also in other cell types, to behavior and neuronal activity, in both physiological and neuroinflammatory contexts.

17β-oestradiol inhibits ferroptosis in the hippocampus by upregulating DHODH and further improves memory decline after ovariectomy

Ovariectomy (OVX) conducted before the onset of natural menopause is considered to bringing forward and accelerate the process of ageing-associated neurodegeneration. However, the mechanisms underlying memory decline and other cognitive dysfunctions following OVX are unclear. Given that iron accumulates during ageing and after OVX, we hypothesized that excess iron accumulation in the hippocampus would cause ferroptosis-induced increased neuronal degeneration and death associated with memory decline. In the current study, female rats that underwent OVX showed decreased dihydroorotate dehydrogenase (DHODH) expression and reduced performance in the Morris water maze (MWM). We used primary cultured hippocampal cells to explore the ferroptosis resistance-inducing effect of 17β-oestradiol (E₂). The data supported a vital role of DHODH in neuronal ferroptosis. Specifically, E₂ alleviated ferroptosis induced by erastin and ferric ammonium citrate (FAC), which can be blocked by brequinar (BQR). Further in vitro studies showed that E₂ reduced lipid peroxidation levels and improved the behavioural performance of OVX rats. Our research interprets OVX-related neurodegeneration with respect to ferroptosis, and both our in vivo and in vitro data show that E₂ supplementation exerts beneficial antiferroptotic effects by upregulating DHODH. Our data demonstrate the utility of E₂ supplementation after OVX and provide a potential target, DHODH, for which hormone therapy has not been available.

N-adamantyl-anthranil amide derivatives: New selective ligands for the cannabinoid receptor subtype 2 (CB2R)

Cannabinoid type 2 receptor (CB2R) is a G-protein-coupled receptor that, together with Cannabinoid type 1 receptor (CB1R), endogenous cannabinoids and enzymes responsible for their synthesis and degradation, forms the EndoCannabinoid System (ECS). In the last decade, several studies have shown that CB2R is overexpressed in activated central nervous system (CNS) microglia cells, in disorders based on an inflammatory state, such as neurodegenerative diseases, neuropathic pain, and cancer. For this reason, the anti-inflammatory and immune-modulatory potentials of CB2R ligands are emerging as a novel therapeutic approach. The design of selective ligands is however hampered by the high sequence homology of transmembrane domains of CB1R and CB2R. Based on a recent three-arm pharmacophore hypothesis and latest CB2R crystal structures, we designed, synthesized, and evaluated a series of new N-adamantyl-anthranil amide derivatives as CB2R selective ligands. Interestingly, this new class of compounds displayed a high affinity for human CB2R along with an excellent selectivity respect to CB1R. In this respect, compounds exhibiting the best pharmacodynamic profile in terms of CB2R affinity were also evaluated for the functional behavior and molecular docking simulations provided a sound rationale by highlighting the relevance of the arm 1 substitution to prompt CB2R action. Moreover, the modulation of the pro- and anti-inflammatory cytokines production was also investigated to exert the ability of the best compounds to modulate the inflammatory cascade.

Update on the controversial identity of cells expressing cnr2 gene in the nervous system

The function of cannabinoid receptor type 2 (CB2R), mainly expressed by leukocytes, has long been limited to its peripheral immunomodulatory role. However, the use of CB2R-specific ligands and the availability of CB2R-Knock Out mice revealed that it could play a functional role in the CNS not only under physiological but also under pathological conditions. A direct effect on the nervous system emerged when CB2R mRNA was detected in neural tissues. However, accurate mapping of CB2R protein expression in the nervous system is still lacking, partly because of the lack of specificity of antibodies available. This review examines the regions and cells of the nervous system where CB2R protein is most likely present by cross-referencing mRNA and protein data published to date. Of the many antibodies developed to target CB2R, only a few have partially passed specificity tests and detected CB2R in the CNS. Efforts must be continued to support the development of more specific and better validated antibodies in each of the species in which CB2R protein is sought or needs to be quantified.

Therapeutic and clinical foundations of cannabidiol therapy for difficult-to-treat seizures in children and adults with refractory epilepsies

Novel and effective antiseizure medications are needed to treat refractory and rare forms of epilepsy. Cannabinoids, which are obtained from the cannabis plant, have a long history of medical use, including for neurologic conditions. In 2018, the US Food and Drug Administration approved the first phytocannabinoid, cannabidiol (CBD, Epidiolex), which is now indicated for severe seizures associated with three rare forms of developmental and epileptic encephalopathy: Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex. Compelling evidence supports the efficacy of CBD in experimental models and patients with epilepsy. In randomized clinical trials, highly-purified CBD has demonstrated efficacy with an acceptable safety profile in children and adults with difficult-to-treat seizures. Although the underlying antiseizure mechanisms of CBD in humans have not yet been elucidated, the identification of novel antiseizure targets of CBD preclinically indicates multimodal mechanisms that include non-cannabinoid pathways. In addition to antiseizure effects, CBD possesses strong anti-inflammatory and neuroprotective activities, which might contribute to protective effects in epilepsy and other conditions. This article provides a succinct overview of therapeutic approaches and clinical foundations of CBD, emphasizing the clinical utility of CBD for the treatment of seizures associated with refractory and rare epilepsies. CBD has shown to be a safe and effective antiseizure medicine, demonstrating a broad spectrum of efficacy across multiple seizure types, including those associated with severe epilepsies with childhood onset. Despite such promise, there are many perils with CBD that hampers its widespread use, including limited understanding of pharmacodynamics, limited exposure-response relationship, limited information for seizure freedom with continued use, complex pharmacokinetics with drug interactions, risk of adverse effects, and lack of expert therapeutic guidelines. These scientific issues need to be resolved by further investigations, which would decide the unique role of CBD in the management of refractory epilepsy.

Endocannabinoid signaling in brain diseases: Emerging relevance of glial cells

The discovery of cannabinoid receptors as the primary molecular targets of psychotropic cannabinoid Δ⁹ -tetrahydrocannabinol (Δ⁹ -THC) in late 1980s paved the way for investigations on the effects of cannabis-based therapeutics in brain pathology. Ever since, a wealth of results obtained from studies on human tissue samples and animal models have highlighted a promising therapeutic potential of cannabinoids and endocannabinoids in a variety of neurological disorders. However, clinical success has been limited and major questions concerning endocannabinoid signaling need to be satisfactorily addressed, particularly with regard to their role as modulators of glial cells in neurodegenerative diseases. Indeed, recent studies have brought into the limelight diverse, often unexpected functions of astrocytes, oligodendrocytes, and microglia in brain injury and disease, thus providing scientific basis for targeting glial cells to treat brain disorders. This Review summarizes the current knowledge on the molecular and cellular hallmarks of endocannabinoid signaling in glial cells and its clinical relevance in neurodegenerative and chronic inflammatory disorders.

Endocannabinoid signaling in the central nervous system

It is hard to overestimate the influence of the endocannabinoid signaling (ECS) system on central nervous system (CNS) function. In the 40 years since cannabinoids were found to trigger specific cell signaling cascades, studies of the ECS system continue to cause amazement, surprise, and confusion! CB1 cannabinoid receptors are expressed widely in the CNS and regulate cell-cell communication via effects on the release of both neurotransmitters and gliotransmitters. CB2 cannabinoid receptors are difficult to detect in the CNS but seem to "punch above their weight" as compounds targeting these receptors have significant effects on inflammatory state and behavior. Positive and negative allosteric modulators for both receptors have been identified and examined in preclinical studies. Concentrations of the endocannabinoid ligands, N-arachidonoylethanolamine and 2-arachidonoylglycerol (2-AG), are regulated by a combination of enzymatic synthesis and degradation and inhibitors of these processes are available and making their way into clinical trials. Importantly, ECS regulates many essential brain functions, including regulation of reward, anxiety, inflammation, motor control, and cellular development. While the field is on the cusp of preclinical discoveries providing impactful clinical and therapeutic insights into many CNS disorders, there is still much to be learned about this remarkable and versatile modulatory system.

Enhancing axonal myelination in seniors: A review exploring the potential impact cannabis has on myelination in the aged brain

Consumption of cannabis is on the rise as public opinion trends toward acceptance and its consequent legalization. Specifically, the senior population is one of the demographics increasing their use of cannabis the fastest, but research aimed at understanding cannabis' impact on the aged brain is still scarce. Aging is characterized by many brain changes that slowly alter cognitive ability. One process that is greatly impacted during aging is axonal myelination. The slow degradation and loss of myelin (i.e., demyelination) in the brain with age has been shown to associate with cognitive decline and, furthermore, is a common characteristic of numerous neurological diseases experienced in aging. It is currently not known what causes this age-dependent degradation, but it is likely due to numerous confounding factors (i.e., heightened inflammation, reduced blood flow, cellular senescence) that impact the many cells responsible for maintaining overall homeostasis and myelin integrity. Importantly, animal studies using non-human primates and rodents have also revealed demyelination with age, providing a reliable model for researchers to try and understand the cellular mechanisms at play. In rodents, cannabis was recently shown to modulate the myelination process. Furthermore, studies looking at the direct modulatory impact cannabis has on microglia, astrocytes and oligodendrocyte lineage cells hint at potential mechanisms to prevent some of the more damaging activities performed by these cells that contribute to demyelination in aging. However, research focusing on how cannabis impacts myelination in the aged brain is lacking. Therefore, this review will explore the evidence thus far accumulated to show how cannabis impacts myelination and will extrapolate what this knowledge may mean for the aged brain.

Mechanisms of acupuncture-electroacupuncture on inflammatory pain

Acupuncture, as a traditional treatment, has been extensively used in China for thousands of years. According to the World Health Organization (WHO), acupuncture is recommended for the treatment of 77 diseases. And 16 of these diseases are related to inflammatory pain. As a combination of traditional acupuncture and modern electrotherapy, electroacupuncture (EA) has satisfactory analgesic effects on various acute and chronic pain. Because of its good analgesic effects and no side effects, acupuncture has been widely accepted all over the world. Despite the increase in the number of studies, the mechanisms via which acupuncture exerts its analgesic effects have not been conclusively established. A literature review of related research is of great significance to elaborate on its mechanisms and to inform on further research directions. We elucidated on its mechanisms of action on inflammatory pain from two levels: peripheral and central. It includes the mechanisms of acupuncture in the periphery (immune cells and neurons, purinergic pathway, nociceptive ion channel, cannabinoid receptor and endogenous opioid peptide system) and central nervous system (TPRV1, glutamate and its receptors, glial cells, GABAergic interneurons and signaling molecules). In this review, we collected relevant recent studies to systematically explain the mechanisms of acupuncture in treating inflammatory pain, with a view to providing direction for future applications of acupuncture in inflammatory pain and promoting clinical development.

Role of integrating cannabinoids and the endocannabinoid system in neonatal hypoxic-ischaemic encephalopathy

Neonatal hypoxic-ischaemic events, which can result in long-term neurological impairments or even cell death, are among the most significant causes of brain injury during neurodevelopment. The complexity of neonatal hypoxic-ischaemic pathophysiology and cellular pathways make it difficult to treat brain damage; hence, the development of new neuroprotective medicines is of great interest. Recently, numerous neuroprotective medicines have been developed to treat brain injuries and improve long-term outcomes based on comprehensive knowledge of the mechanisms that underlie neuronal plasticity following hypoxic-ischaemic brain injury. In this context, understanding of the medicinal potential of cannabinoids and the endocannabinoid system has recently increased. The endocannabinoid system plays a vital neuromodulatory role in numerous brain regions, ensuring appropriate control of neuronal activity. Its natural neuroprotection against adult brain injury or acute brain injury also clearly demonstrate the role of endocannabinoid signalling in modulating neuronal activity in the adult brain. The goal of this review is to examine how cannabinoid-derived compounds can be used to treat neonatal hypoxic-ischaemic brain injury and to assess the critical function of the endocannabinoid system and its potential for use as a new neuroprotective treatment for neonatal hypoxic-ischaemic brain injury.

Peripheral sensory neuron CB2 cannabinoid receptors are necessary for both CB2-mediated antinociceptive efficacy and sparing of morphine tolerance in a mouse model of anti-retroviral toxic neuropathy

Painful peripheral neuropathy is a common neurological complication associated with human immunodeficiency virus (HIV) infection and anti-retroviral therapy. We characterized the impact of two CB2 cannabinoid agonists (AM1710 and LY2828360 - ligands differing in signaling bias and CNS penetration) on neuropathic nociception induced by the antiretroviral agent Zalcitabine (2',3'-dideoxycytidine; ddC). We also used a conditional knockout approach to identify cell types mediating CB2 agonist-induced antinociceptive efficacy and sparing of morphine tolerance. AM1710 and LY2828360 alleviated ddC-induced neuropathic nociception in mice of both sexes. These benefits were absent in global CB2 knockout mice, which exhibited robust morphine antinociception. Like morphine, AM1710 blunted ddC-induced increases in proinflammatory cytokine (IL-1β, TNF-α) and chemokine (CCL2) mRNA expression levels. We generated advillinCre/+;CB2f/f conditional knockout mice to ascertain the role of CB2 localized to primary sensory neurons in CB2-mediated therapeutic effects. Antinociceptive efficacy of both AM1710 and LY2828360, but not reference analgesics, were absent in advillinCre/+;CB2f/f mice, which exhibited robust ddC-induced neuropathy. In ddC-treated CB2f/f mice, LY2828360 suppressed development of morphine tolerance and reversed established morphine tolerance, albeit with greater efficacy in male compared to female mice. LY2828360 failed to block or reverse morphine tolerance in advillinCre/+;CB2f/f mice. The present studies indicate that CB2 activation may alleviate HIV-associated antiretroviral neuropathy and identify a previously unreported mechanism through which CB2 activation produces antinociceptive efficacy. Our results also provide the first evidence that a CB2 agonist can reverse established morphine tolerance and demonstrate that CB2 localized to peripheral sensory neurons mediates the opioid tolerance sparing efficacy of CB2 agonists.

Regulatory role of the endocannabinoid system on glial cells toward cognitive function in Alzheimer's disease: A systematic review and meta-analysis of animal studies

Objective: Over the last decade, researchers have sought to develop novel medications against dementia. One potential agent under investigation is cannabinoids. This review systematically appraised and meta-analyzed published pre-clinical research on the mechanism of endocannabinoid system modulation in glial cells and their effects on cognitive function in animal models of Alzheimer's disease (AD). Methods: A systematic review complying with PRISMA guidelines was conducted. Six databases were searched: EBSCOHost, Scopus, PubMed, CINAHL, Cochrane, and Web of Science, using the keywords AD, cannabinoid, glial cells, and cognition. The methodological quality of each selected pre-clinical study was evaluated using the SYRCLE risk of bias tool. A random-effects model was applied to analyze the data and calculate the effect size, while I² and p-values were used to assess heterogeneity. Results: The analysis included 26 original articles describing (1050 rodents) with AD-like symptoms. Rodents treated with cannabinoid agonists showed significant reductions in escape latency (standard mean difference [SMD] = -1.26; 95% confidence interval [CI]: -1.77 to -0.76, p < 0.00001) and ability to discriminate novel objects (SMD = 1.40; 95% CI: 1.04 to 1.76, p < 0.00001) compared to the control group. Furthermore, a significant decrease in Aβ plaques (SMD = -0.91; 95% CI: -1.55 to -0.27, p = 0.006) was observed in the endocannabinoid-treated group compared to the control group. Trends were observed toward neuroprotection, as represented by decreased levels of glial cell markers including glial fibrillary acid protein (SMD = -1.47; 95% CI: -2.56 to -0.38, p = 0.008) and Iba1 (SMD = -1.67; 95% CI: -2.56 to -0.79, p = 0.0002). Studies on the wild-type mice demonstrated significantly decreased levels of pro-inflammatory markers TNF-α, IL-1, and IL-6 (SMD = -2.28; 95% CI: -3.15 to -1.41, p = 0.00001). Despite the non-significant decrease in pro-inflammatory marker levels in transgenic mice (SMD = -0.47; 95% CI: -1.03 to 0.08, p = 0.09), the result favored the endocannabinoid-treated group over the control group. Conclusion: The revised data suggested that endocannabinoid stimulation promotes cognitive function via modulation of glial cells by decreasing pro-inflammatory markers in AD-like rodent models. Thus, cannabinoid agents may be required to modulate the downstream chain of effect to enhance cognitive stability against concurrent neuroinflammation in AD. Population-based studies and well-designed clinical trials are required to characterize the acceptability and real-world effectiveness of cannabinoid agents. Systematic Review Registration: [https://inplasy.com/inplasy-2022-8-0094/], identifier [Inplasy Protocol 3770].

Cannabinoid receptor 2 (Cb2r) mediates cannabinol (CBN) induced developmental defects in zebrafish

Of the three primary cannabinoids in cannabis: Δ⁹-Tetrahydrocannabinol (Δ⁹-THC), cannabidiol (CBD) and cannabinol (CBN), very little is known about the actions of CBN, the primary oxidative metabolite of THC. Our goal was to determine if CBN exposure during gastrulation alters embryonic development, and if so, does it act via the canonical cannabinoid receptors. Zebrafish embryos were exposed to CBN during gastrulation and exhibited dose-dependent malformations, increased mortality, decreased locomotion and a reduction in motor neuron branching. Moreover, larva showed a significant reduction in the response to sound stimuli. CBN exposure altered the development of hair cells associated with otic vesicles and the lateral line. Pharmacological block of Cb2rs with AM 630 or JTE 907 prevented many of the CBN-induced developmental defects, while block of Cb1rs with AM 251 or CP 945598 had little or no effect. Altogether we show that embryonic exposure to CBN results in alterations in embryonic growth, neuronal and hair cell development, physiology and behavior via Cb2r-mediated mechanisms.

Pharmacognosy and Effects of Cannabinoids in the Vascular System

Understanding the pharmacodynamics of cannabinoids is an essential subject due to the recent increasing global acceptance of cannabis and its derivation for recreational and therapeutic purposes. Elucidating the interaction between cannabinoids and the vascular system is critical to exploring cannabinoids as a prospective therapeutic agent for treating vascular-associated clinical conditions. This review aims to examine the effect of cannabinoids on the vascular system and further discuss the fundamental pharmacological properties and mechanisms of action of cannabinoids in the vascular system. Data from literature revealed a substantial interaction between endocannabinoids, phytocannabinoids, and synthetic cannabinoids within the vasculature of both humans and animal models. However, the mechanisms and the ensuing functional response is blood vessels and species-dependent. The current understanding of classical cannabinoid receptor subtypes and the recently discovered atypical cannabinoid receptors and the development of new synthetic analogs have further enhanced the pharmacological characterization of the vascular cannabinoid receptors. Compelling evidence also suggest that cannabinoids represent a formidable therapeutic candidate for vascular-associated conditions. Nonetheless, explanations of the mechanisms underlining these processes are complex and paradoxical based on the heterogeneity of receptors and signaling pathways. Further insight from studies that uncover the mechanisms underlining the therapeutic effect of cannabinoids in the treatment of vascular-associated conditions is required to determine whether the known benefits of cannabinoids thus currently outweigh the known/unknown risks.

Endocannabinoid signaling in microglia

Microglia, the innate immune cells of the central nervous system (CNS), execute their sentinel, housekeeping and defense functions through a panoply of genes, receptors and released cytokines, chemokines and neurotrophic factors. Moreover, microglia functions are closely linked to the constant communication with other cell types, among them neurons. Depending on the signaling pathway and type of stimuli involved, the outcome of microglia operation can be neuroprotective or neurodegenerative. Accordingly, microglia are increasingly becoming considered cellular targets for therapeutic intervention. Among signals controlling microglia activity, the endocannabinoid (EC) system has been shown to exert a neuroprotective role in many neurological diseases. Like neurons, microglia express functional EC receptors and can produce and degrade ECs. Interestingly, boosting EC signaling leads to an anti-inflammatory and neuroprotective microglia phenotype. Nonetheless, little evidence is available on the microglia-mediated therapeutic effects of EC compounds. This review focuses on the EC signals acting on the CNS microglia in physiological and pathological conditions, namely on the CB1R, CB2R and TRPV1-mediated regulation of microglia properties. It also provides new evidence, which strengthens the understanding of mechanisms underlying the control of microglia functions by ECs. Given the broad expression of the EC system in glial and neuronal cells, the resulting picture is the need for in vivo studies in transgenic mouse models to dissect the contribution of EC microglia signaling in the neuroprotective effects of EC-derived compounds.

In vivo Imaging of Cannabinoid Type 2 Receptors: Functional and Structural Alterations in Mouse Model of Cerebral Ischemia by PET and MRI

PURPOSE

Stroke is one of the most prevalent vascular diseases. Non-invasive molecular imaging methods have the potential to provide critical insights into the temporal dynamics and follow alterations of receptor expression and metabolism in ischemic stroke. The aim of this study was to assess the cannabinoid type 2 receptor (CB2R) levels in transient middle cerebral artery occlusion (tMCAO) mouse models at subacute stage using positron emission tomography (PET) with our novel tracer [18F]RoSMA-18-d6 and structural imaging by magnetic resonance imaging (MRI).

PROCEDURES

Our recently developed CB2R PET tracer [18F]RoSMA-18-d6 was used for imaging neuroinflammation at 24 h after reperfusion in tMCAO mice. The RNA expression levels of CB2R and other inflammatory markers were analyzed by quantitative real-time polymerase chain reaction using brain tissues from tMCAO (1 h occlusion) and sham-operated mice. [18F]fluorodeoxyglucose (FDG) was included for evaluation of the cerebral metabolic rate of glucose (CMRglc). In addition, diffusion-weighted imaging and T2-weighted imaging were performed for anatomical reference and delineating the lesion in tMCAO mice.

RESULTS

mRNA expressions of inflammatory markers TNF-α, Iba1, MMP9 and GFAP, CNR2 were increased to 1.3-2.5 fold at 24 h after reperfusion in the ipsilateral compared to contralateral hemisphere of tMCAO mice, while mRNA expression of the neuronal marker MAP-2 was markedly reduced to ca. 50 %. Reduced [18F]FDG uptake was observed in the ischemic striatum of tMCAO mouse brain at 24 h after reperfusion. Although higher activity of [18F]RoSMA-18-d6 in ex vivo biodistribution studies and higher standard uptake value ratio (SUVR) were detected in the ischemic ipsilateral compared to contralateral striatum in tMCAO mice, the in vivo specificity of [18F]RoSMA-18-d6 was confirmed only in the CB2R-rich spleen.

CONCLUSIONS

This study revealed an increased [18F]RoSMA-18-d6 measure of CB2R and a reduced [18F]FDG measure of CMRglc in the ischemic striatum of tMCAO mice at subacute stage. [18F]RoSMA-18-d6 might be a promising PET tracer for detecting CB2R alterations in animal models of neuroinflammation without neuronal loss.

Task-independent acute effects of delta-9-tetrahydrocannabinol on human brain function and its relationship with cannabinoid receptor gene expression: A neuroimaging meta-regression analysis

The neurobiological mechanisms underlying the effects of delta-9-tetrahydrocannabinol (THC) remain unclear. Here, we examined the spatial acute effect of THC on human regional brain activation or blood flow (hereafter called 'activation signal') in a 'core' network of brain regions from 372 participants, tested using a within-subject repeated measures design under experimental conditions. We also investigated whether the neuromodulatory effects of THC are related to the local expression of the cannabinoid-type-1 (CB1R) and type-2 (CB2R) receptors. Finally, we investigated the dose-response relationship between THC and key brain substrates. These meta-analytic findings shed new light on the localisation of the effects of THC in the human brain, suggesting that THC has neuromodulatory effects in regions central to many cognitive tasks and processes, related to dose, with greater effects in regions with higher levels of CB1R expression.

Hippocampal circuit dysfunction in psychosis

Despite strong evidence of the neurodevelopmental origins of psychosis, current pharmacological treatment is not usually initiated until after a clinical diagnosis is made, and is focussed on antagonising striatal dopamine receptors. These drugs are only partially effective, have serious side effects, fail to alleviate the negative and cognitive symptoms of the disorder, and are not useful as a preventive treatment. In recent years, attention has turned to upstream brain regions that regulate striatal dopamine function, such as the hippocampus. This review draws together these recent data to discuss why the hippocampus may be especially vulnerable in the pathophysiology of psychosis. First, we describe the neurodevelopmental trajectory of the hippocampus and its susceptibility to dysfunction, exploring this region's proneness to structural and functional imbalances, metabolic pressures, and oxidative stress. We then examine mechanisms of hippocampal dysfunction in psychosis and in individuals at high-risk for psychosis and discuss how and when hippocampal abnormalities may be targeted in these groups. We conclude with future directions for prospective studies to unlock the discovery of novel therapeutic strategies targeting hippocampal circuit imbalances to prevent or delay the onset of psychosis.

Cannabinoid type-2 receptors: An emerging target for regulating schizophrenia-relevant brain circuits

Although the cannabinoid type-2 receptor (CB2) is highly expressed in the immune system, emerging evidence points to CB2 playing a key role in regulating neuronal function in the central nervous system. Recent anatomical studies, combined with electrophysiological studies, indicate that CB2 receptors are expressed in specific dopaminergic and glutamatergic brain circuits that are hyperactive in schizophrenia patients. The ability of CB2 receptors to inhibit dopaminergic and hippocampal circuits, combined with the anti-inflammatory effects of CB2 receptor activation, make this receptor an intriguing target for treating schizophrenia, a disease where novel interventions that move beyond dopamine receptor antagonists are desperately needed. The development of new CB2-related pharmacological and genetic tools, including the first small molecule positive allosteric modulator of CB2 receptors, has greatly advanced our understanding of this receptor. While more work is needed to further elucidate the translational value of selectively targeting CB2 receptors with respect to schizophrenia, the studies discussed below could suggest that CB2 receptors are anatomically located in schizophrenia-relevant circuits, where the physiological consequence of CB2 receptor activation could correct circuit-based deficits commonly associated with positive and cognitive deficits.

A Review on the Bioactivity of Cannabinoids on Zebrafish Models: Emphasis on Neurodevelopment

For centuries, the cannabis plant has been used as a source of food, fiber, and medicine. Recently, scientific interest in cannabis has increased considerably, as its bioactive compounds have shown promising potential in the treatment of numerous musculoskeletal and neurological diseases in humans. However, the mechanisms that underlie its possible effects on neurodevelopment and nervous-system functioning remain poorly understood and need to be further investigated. Although the bulk of research on cannabis and cannabinoids is based on in vitro or rodent models, the zebrafish has now emerged as a powerful in vivo model for drug-screening studies and translational research. We here review the available literature on the use of cannabis/cannabinoids in zebrafish, and particularly in zebrafish models of neurological disorders. A critical analysis suggests that zebrafish could serve as an experimental tool for testing the bioactivity of cannabinoids, and they could thus provide important insights into the safety and efficacy of different cannabis-extract-based products. The review showed that zebrafish exhibit similar behaviors to rodents following cannabinoid exposure. The authors stress the importance of analyzing the full spectrum of naturally occurring cannabinoids, rather than just the main ones, THC and CBD, and they offer some pointers on performing behavioral analysis in zebrafish.

A GPCR-based yeast biosensor for biomedical, biotechnological, and point-of-use cannabinoid determination

Eukaryotic cells use G-protein coupled receptors to sense diverse signals, ranging from chemical compounds to light. Here, we exploit the remarkable sensing capacity of G-protein coupled receptors to construct yeast-based biosensors for real-life applications. To establish proof-of-concept, we focus on cannabinoids because of their neuromodulatory and immunomodulatory activities. We construct a CB₂ receptor-based biosensor, optimize it to achieve high sensitivity and dynamic range, and prove its effectiveness in three applications of increasing difficulty. First, we screen a compound library to discover agonists and antagonists. Second, we analyze 54 plants to discover a new phytocannabinoid, dugesialactone. Finally, we develop a robust portable device, analyze body-fluid samples, and confidently detect designer drugs like JWH-018. These examples demonstrate the potential of yeast-based biosensors to enable diverse applications that can be implemented by non-specialists. Taking advantage of the extensive sensing repertoire of G-protein coupled receptors, this technology can be extended to detect numerous compounds.

GPCRs are used for diverse sensing in eukaryotes. Here the authors use GPCRs to construct yeast-based biosensors, focussing on cannabinoids, and use these to screen agonists and antagonists, as well as generate a portable detection device.

Cannabinoids as Glial Cell Modulators in Ischemic Stroke: Implications for Neuroprotection

Stroke is the second leading cause of death worldwide following coronary heart disease. Despite significant efforts to find effective treatments to reduce neurological damage, many patients suffer from sequelae that impair their quality of life. For this reason, the search for new therapeutic options for the treatment of these patients is a priority. Glial cells, including microglia, astrocytes and oligodendrocytes, participate in crucial processes that allow the correct functioning of the neural tissue, being actively involved in the pathophysiological mechanisms of ischemic stroke. Although the exact mechanisms by which glial cells contribute in the pathophysiological context of stroke are not yet completely understood, they have emerged as potentially therapeutic targets to improve brain recovery. The endocannabinoid system has interesting immunomodulatory and protective effects in glial cells, and the pharmacological modulation of this signaling pathway has revealed potential neuroprotective effects in different neurological diseases. Therefore, here we recapitulate current findings on the potential promising contribution of the endocannabinoid system pharmacological manipulation in glial cells for the treatment of ischemic stroke.

Role of Cannabinoid CB2 Receptor in Alcohol Use Disorders: From Animal to Human Studies

Cumulative evidence has pointed out cannabinoid CB2 receptors (CB₂r) as a potential therapeutic key target for treating alcohol use disorder (AUD). This review provides the most relevant results obtained from rodent and human studies, including an integrative section focused on the involvement of CB₂r in the neurobiology of alcohol addiction. A literature search was conducted using the electronic databases Medline and Scopus for articles. The search strategy was as follows: “Receptor, Cannabinoid, CB2” AND “Alcohol-Related Disorders” AND “human/or patients”; “Receptor, Cannabinoid, CB2” AND “Alcohol” OR “Ethanol” AND “rodents/or mice/or rats”. Pharmacological approaches demonstrated that the activation or blockade of CB₂r modulated different alcohol-addictive behaviors. Rodent models of alcoholism revealed significant alterations of CB₂r in brain areas of the reward system. In addition, mice lacking CB₂r (CB₂KO) show increased alcohol consumption, motivation, and relapse alterations. It has been stressed that the potential neurobiological mechanisms underlying their behavioral effects involve critical elements of the alcohol reward system. Interestingly, recent postmortem studies showed CNR2 alterations in brain areas of alcoholic patients. Moreover, although the number of studies is limited, the results revealed an association between some genetic alterations of the CNR2 and an increased risk for developing AUD. This review provides evidence that CB₂r may play a role in alcohol addiction. Clinical studies are necessary to figure out whether CB₂r ligands may prove useful for the treatment of AUD in humans.

Evaluation of the terpenes β-caryophyllene, α-terpineol, and γ-terpinene in the mouse chronic constriction injury model of neuropathic pain: possible cannabinoid receptor involvement

Pain is one of the most common reasons to seek medical attention, and chronic pain is a worldwide epidemic. Anecdotal reports suggest cannabis may be an effective analgesic. As cannabis contains the terpenes α-terpineol, β-caryophyllene, and γ-terpinene, we hypothesized these terpenes would produce analgesia in a mouse model of neuropathic pain. We used the chronic constriction injury of the sciatic nerve mouse model, which produces mechanical allodynia, assessed via the von Frey assay, as well as thermal hyperalgesia assessed via the hotplate assay. Compounds were further assessed in tests of locomotor activity, hypothermia, and acute antinociception. Each terpene produced dose-related reversal of mechanical allodynia and thermal hyperalgesia. Thermal hyperalgesia displayed higher sensitivity to the effects of each terpene than mechanical allodynia, and the rank order potency of the terpenes was α-terpineol > β-caryophyllene > γ-terpinene. To examine the involvement of cannabinoid receptors, further tests were conducted in mice lacking either functional cannabinoid type 1 receptors (CB₁R (-/-)) or cannabinoid type 2 receptors (CB₂R (-/-)). Compared to wild type mice, CB₁R (-/-) mice treated with α-terpineol displayed a 2.91-fold decrease in potency to reverse mechanical allodynia; in CB₂R (-/-) mice, the potency of α-terpineol was decreased 11.73-fold. The potency of β-caryophyllene to reverse mechanical allodynia decreased 1.80-fold in CB₂R (-/-) mice. Each terpene produced a subset of effects in tests of locomotor activity, hypothermia, and acute antinociception. These findings suggest α-terpineol, β-caryophyllene, and γ-terpinene may have differential cannabinoid receptor activity and a pharmacological profile that may yield new efficacious analgesics.

Medicinal Cannabis and Central Nervous System Disorders

Cannabinoids, including those found in cannabis, have shown promise as potential therapeutics for numerous health issues, including pathological pain and diseases that produce an impact on neurological processing and function. Thus, cannabis use for medicinal purposes has become accepted by a growing majority. However, clinical trials yielding satisfactory endpoints and unequivocal proof that medicinal cannabis should be considered a frontline therapeutic for most examined central nervous system indications remains largely elusive. Although cannabis contains over 100 + compounds, most preclinical and clinical research with well-controlled dosing and delivery methods utilize the various formulations of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), the two most abundant compounds in cannabis. These controlled dosing and delivery methods are in stark contrast to most clinical studies using whole plant cannabis products, as few clinical studies using whole plant cannabis profile the exact composition, including percentages of all compounds present within the studied product. This review will examine both preclinical and clinical evidence that supports or refutes the therapeutic utility of medicinal cannabis for the treatment of pathological pain, neurodegeneration, substance use disorders, as well as anxiety-related disorders. We will predominately focus on purified THC and CBD, as well as other compounds isolated from cannabis for the aforementioned reasons but will also include discussion over those studies where whole plant cannabis has been used. In this review we also consider the current challenges associated with the advancement of medicinal cannabis and its derived potential therapeutics into clinical applications.

Medicinal Cannabis and Central Nervous System Disorders

Cannabinoids, including those found in cannabis, have shown promise as potential therapeutics for numerous health issues, including pathological pain and diseases that produce an impact on neurological processing and function. Thus, cannabis use for medicinal purposes has become accepted by a growing majority. However, clinical trials yielding satisfactory endpoints and unequivocal proof that medicinal cannabis should be considered a frontline therapeutic for most examined central nervous system indications remains largely elusive. Although cannabis contains over 100 + compounds, most preclinical and clinical research with well-controlled dosing and delivery methods utilize the various formulations of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), the two most abundant compounds in cannabis. These controlled dosing and delivery methods are in stark contrast to most clinical studies using whole plant cannabis products, as few clinical studies using whole plant cannabis profile the exact composition, including percentages of all compounds present within the studied product. This review will examine both preclinical and clinical evidence that supports or refutes the therapeutic utility of medicinal cannabis for the treatment of pathological pain, neurodegeneration, substance use disorders, as well as anxiety-related disorders. We will predominately focus on purified THC and CBD, as well as other compounds isolated from cannabis for the aforementioned reasons but will also include discussion over those studies where whole plant cannabis has been used. In this review we also consider the current challenges associated with the advancement of medicinal cannabis and its derived potential therapeutics into clinical applications.

Protective Effects of Cannabinoid Type 2 Receptor Against Microglia Overactivation and Neuronal Pyroptosis in Sepsis-Associated Encephalopathy

Sepsis-associated encephalopathy (SAE) has close association with long-term cognitive deficits, resulting in increased mortality. The mechanism of SAE is complicate, including excessive microglial activation and neuroinflammation. Pyroptosis is a type of proinflammatory cell death program. Cannabinoid type 2 receptor (CB2R) has been proved to be effective in neuronal protection and survival promotion. Microglia play a role in CB2R mediated neuronal protection when neurons are exposed to noxious stimuli. However, the underlying mechanisms involved in this process still remain to be explored. Previous studies have demonstrated that CB2R can reduce sepsis-induced lung injury by inhibiting pyroptosis. Here, SAE model was established by cecal ligation and puncture (CLP). Open field test (OFT), novel object recognition test (NORT), and Morris water maze (MWM) test were performed to assess cognitive function. Brain samples were obtained to detect cell injury, cytokine, CB2R and pyroptosis-associated protein expression by Hematoxylin-Eosin (HE) staining, Enzyme-linked immunosorbent assay (ELISA), Western blotting and Immunofluorescence staining. CLP could induce microglia hyperactivation and neuronal pyroptosis, aggravating brain tissue destruction and cognitive dysfunction. The activation of CB2R could have a protective effect against SAE by inhibiting microglia activity and neuronal pyroptosis. This will provide a new therapeutic option for the treatment of SAE.

Potential Neuroprotective Effect of Cannabinoids in Covid-19 Patients

The global pandemic caused by the SARS-CoV-2 virus began in early 2020 and is still present. The respiratory symptoms caused by COVID-19 are well established, however, neurological manifestations that may result from direct or indirect neurological damage after SARS-CoV-2 infection have been reported frequently. The main proposed pathophysiological processes leading to neurological damage in COVID-19 are cerebrovascular disease, and indirect mechanisms of inflammatory / autoimmune origin. A growing number of studies confirm that neuroprotective measures should be maintained in COVID-19 patients. On the other hand, cannabinoids have been the subject of various studies that propose them as potential promising drugs in chronic neurodegenerative diseases due to their powerful neuroprotective potential. In this review we address the possible mechanism of action of cannabinoids as a neuroprotective treatment in patients infected by SARS-CoV-2. The endocannabinoid system is found in multiple systems within the body, including the immune system. Its activation can lead to beneficial results, such as a decrease in viral entry, a decrease in viral replication, and a decrease in pro-inflammatory cytokines such as IL-2, IL-4, IL-6, IL-12, TNF-α or IFN-c through CB2R expression induced during inflammation by SARS-CoV-2 infection in the central nervous system.

Repeated cocaine administration upregulates CB2 receptor expression in striatal medium-spiny neurons that express dopamine D1 receptors in mice

Cannabinoid CB₂ receptors (CB₂R) are importantly involved in drug reward and addiction. However, the cellular mechanisms underlying CB₂R action remain unclear. We have previously reported that cocaine self-administration upregulates CB₂R expression in midbrain dopamine (DA) neurons. In the present study, we investigated whether cocaine or heroin also alters CB₂R expression in striatal medium-spiny neurons that express dopamine D₁ or D₂ receptors (D₁-MSNs, D₂-MSNs) and microglia. Due to the concern of CB₂R antibody specificity, we developed three mouse CB₂-specific probes to detect CB₂R mRNA using quantitative RT-PCR and RNAscope in situ hybridization (ISH) assays. We found that a single injection of cocaine failed to alter, while repeated cocaine injections or self-administration dose-dependently upregulated CB₂R gene expression in both brain (cortex and striatum) and periphery (spleen). In contrast, repeated administration of heroin produced a dose-dependent reduction in striatal CB₂ mRNA expression. RNAscope ISH assays detected CB₂R mRNA in striatal D₁- and D₂-MSNs, not in microglia. We then used transgenic CX3CR1^eGFP/+ microglia reporter mice and D₁- or D₂-Cre-RiboTag mice to purify striatal microglia or ribosome-associated mRNAs from CX3CR1^eGFP/+, D₁-MSNs, or D₂-MSNs, respectively. We found that CB₂R upregulation occurred mainly in D₁-MSNs, not in D₂-MSNs or microglia, in the nucleus accumbens rather than the dorsal striatum. These findings indicate that repeated cocaine exposure may upregulate CB₂R expression in both brain and spleen, with regional and cell type-specific profiles. In the striatum, CB₂R upregulation occurs mainly in D₁-MSNs in the nucleus accumbens. Given the important role of D₁-MSNs in brain reward function, the present findings provide new insight into mechanisms by which brain CB₂Rs modulate cocaine action.