Cannabinoid Receptors and the Endocannabinoid System: Signaling and Function in the Central Nervous System

A Perspective: Active Role of Lipids in Neurotransmitter Dynamics

Synaptic neurotransmission is generally considered as a function of membrane-embedded receptors and ion channels in response to the neurotransmitter (NT) release and binding. This perspective aims to widen the protein-centric view by including another vital component—the synaptic membrane—in the discussion. A vast set of atomistic molecular dynamics simulations and biophysical experiments indicate that NTs are divided into membrane-binding and membrane-nonbinding categories. The binary choice takes place at the water-membrane interface and follows closely the positioning of the receptors’ binding sites in relation to the membrane. Accordingly, when a lipophilic NT is on route to a membrane-buried binding site, it adheres on the membrane and, then, travels along its plane towards the receptor. In contrast, lipophobic NTs, which are destined to bind into receptors with extracellular binding sites, prefer the water phase. This membrane-based sorting splits the neurotransmission into membrane-independent and membrane-dependent mechanisms and should make the NT binding into the receptors more efficient than random diffusion would allow. The potential implications and notable exceptions to the mechanisms are discussed here. Importantly, maintaining specific membrane lipid compositions (MLCs) at the synapses, especially regarding anionic lipids, affect the level of NT-membrane association. These effects provide a plausible link between the MLC imbalances and neurological diseases such as depression or Parkinson’s disease. Moreover, the membrane plays a vital role in other phases of the NT life cycle, including storage and release from the synaptic vesicles, transport from the synaptic cleft, as well as their synthesis and degradation.

Placebo effects and the molecular biological components involved

Pharmacologically inactive substances have been used in medicine for more than 700 years and can trigger beneficial responses in the human body, which is referred to as the placebo effects or placebo responses. This effect is robust enough to influence psychosocial and physiological responses to the placebo and to active treatments in many settings, which has led to increased interest from researchers. In this article, we summarise the history of placebo, the characteristics of placebo effects and recent advancements reported from the studies on placebo effects and highlight placebome studies to identify various molecular biological components associated with placebo effects. Although placebos have a long history, the placebome concept is still in its infancy. Although behavioural, neurobiological and genetic studies have identified that molecules in the dopamine, opioid, serotonin and endocannabinoid systems might be targets of the placebo effect, placebome studies with a no-treatment control (NTC) are necessary to identify whole-genome genetic targets. Although bioinformatics analysis has identified the molecular placebome module, placebome studies with NTCs are also required to validate the related findings.

Cholinergic nervous system and glaucoma: From basic science to clinical applications

The cholinergic system has a crucial role to play in visual function. Although cholinergic drugs have been a focus of attention as glaucoma medications for reducing eye pressure, little is known about the potential modality for neuronal survival and/or enhancement in visual impairments. Citicoline, a naturally occurring compound and FDA approved dietary supplement, is a nootropic agent that is recently demonstrated to be effective in ameliorating ischemic stroke, traumatic brain injury, Parkinson's disease, Alzheimer's disease, cerebrovascular diseases, memory disorders and attention-deficit/hyperactivity disorder in both humans and animal models. The mechanisms of its action appear to be multifarious including (i) preservation of cardiolipin, sphingomyelin, and arachidonic acid contents of phosphatidylcholine and phosphatidylethanolamine, (ii) restoration of phosphatidylcholine, (iii) stimulation of glutathione synthesis, (iv) lowering glutamate concentrations and preventing glutamate excitotoxicity, (v) rescuing mitochondrial function thereby preventing oxidative damage and onset of neuronal apoptosis, (vi) synthesis of myelin leading to improvement in neuronal membrane integrity, (vii) improving acetylcholine synthesis and thereby reducing the effects of mental stress and (viii) preventing endothelial dysfunction. Such effects have vouched for citicoline as a neuroprotective, neurorestorative and neuroregenerative agent. Retinal ganglion cells are neurons with long myelinated axons which provide a strong rationale for citicoline use in visual pathway disorders. Since glaucoma is a form of neurodegeneration involving retinal ganglion cells, citicoline may help ameliorate glaucomatous damages in multiple facets. Additionally, trans-synaptic degeneration has been identified in humans and experimental models of glaucoma suggesting the cholinergic system as a new brain target for glaucoma management and therapy.

Clinicians' Guide to Cannabidiol and Hemp Oils

Cannabidiol (CBD) oils are low tetrahydrocannabinol products derived from Cannabis sativa that have become very popular over the past few years. Patients report relief for a variety of conditions, particularly pain, without the intoxicating adverse effects of medical marijuana. In June 2018, the first CBD-based drug, Epidiolex, was approved by the US Food and Drug Administration for treatment of rare, severe epilepsy, further putting the spotlight on CBD and hemp oils. There is a growing body of preclinical and clinical evidence to support use of CBD oils for many conditions, suggesting its potential role as another option for treating challenging chronic pain or opioid addiction. Care must be taken when directing patients toward CBD products because there is little regulation, and studies have found inaccurate labeling of CBD and tetrahydrocannabinol quantities. This article provides an overview of the scientific work on cannabinoids, CBD, and hemp oil and the distinction between marijuana, hemp, and the different components of CBD and hemp oil products. We summarize the current legal status of CBD and hemp oils in the United States and provide a guide to identifying higher-quality products so that clinicians can advise their patients on the safest and most evidence-based formulations. This review is based on a PubMed search using the terms CBD, cannabidiol, hemp oil, and medical marijuana. Articles were screened for relevance, and those with the most up-to-date information were selected for inclusion.

Comparative psychopharmacology of autism and psychotic-affective disorders suggests new targets for treatment

The first treatments showing effectiveness for some psychiatric disorders, such as lithium for bipolar disorder and chlorpromazine for schizophrenia, were discovered by accident. Currently, psychiatric drug design is seen as a scientific enterprise, limited though it remains by the complexity of brain development and function. Relatively few novel and effective drugs have, however, been developed for many years. The purpose of this article is to demonstrate how evolutionary biology can provide a useful framework for psychiatric drug development. The framework is based on a diametrical nature of autism, compared with psychotic-affective disorders (mainly schizophrenia, bipolar disorder and depression). This paradigm follows from two inferences: (i) risks and phenotypes of human psychiatric disorders derive from phenotypes that have evolved along the human lineage and (ii) biological variation is bidirectional (e.g. higher vs lower, faster vs slower, etc.), such that dysregulation of psychological traits varies in two opposite ways. In this context, the author review the evidence salient to the hypothesis that autism and psychotic-affective disorders represent diametrical disorders in terms of current, proposed and potential psychopharmacological treatments. Studies of brain-derived neurotrophic factor, the PI3K pathway, the NMDA receptor, kynurenic acid metabolism, agmatine metabolism, levels of the endocannabinoid anandamide, antidepressants, anticonvulsants, antipsychotics, and other treatments, demonstrate evidence of diametric effects in autism spectrum disorders and phenotypes compared with psychotic-affective disorders and phenotypes. These findings yield insights into treatment mechanisms and the development of new pharmacological therapies, as well as providing an explanation for the longstanding puzzle of antagonism between epilepsy and psychosis. Lay Summary: Consideration of autism and schizophrenia as caused by opposite alterations to brain development and function leads to novel suggestions for pharmacological treatments.

Monoacylglycerol lipase inhibition as potential treatment for interstitial cystitis

Interstitial cystitis is a chronic inflammatory condition of the urinary bladder with an unclear etiology. Currently, there are no widely accepted long-term treatment options available for patients with IC, with the European Association of Urology (EAU, 2017 guidelines), American Urology Association (AUA, 2014 guidelines), and the Royal College of Obstetricians and Gynaecologists (RCOG, 2016 guidelines) all suggesting various different conservative, pharmacological, intravesical, and surgical interventions. The endocannabinoid system represents a potential target for IC treatment and management. Activation of cannabinoid receptor 2 (CBR2) with various agonists has previously been shown to reduce leukocyte differentiation and migration, in addition to inhibiting the release of pro-inflammatory cytokines at the site of inflammation. These receptors have been identified in the detrusor and sensory nerves of the urothelium in various mammalian species, including humans. We hypothesize that by inhibiting the enzymes responsible for the catabolism of endogenous cannabinoids locally, bladder concentrations of CBR2 agonists will increase, particularly 2-arachidonyl glycerol, resulting in a diminished inflammatory response.

A Mechanistic and Pathophysiological Approach for Stroke Associated with Drugs of Abuse

Drugs of abuse are associated with stroke, especially in young individuals. The major classes of drugs linked to stroke are cocaine, amphetamines, heroin, morphine, cannabis, and new synthetic cannabinoids, along with androgenic anabolic steroids (AASs). Both ischemic and hemorrhagic stroke have been reported due to drug abuse. Several common mechanisms have been identified, such as arrhythmias and cardioembolism, hypoxia, vascular toxicity, vascular spasm and effects on the thrombotic mechanism, as causes for ischemic stroke. For hemorrhagic stroke, acute hypertension, aneurysm formation/rupture and angiitis-like changes have been implicated. In AAS abuse, the effect of blood pressure is rather substance specific, whereas increased erythropoiesis usually leads to thromboembolism. Transient vasospasm, caused by synthetic cannabinoids, could lead to ischemic stroke. Opiates often cause infective endocarditis, resulting in ischemic stroke and hypereosinophilia accompanied by pyogenic arthritis, provoking hemorrhagic stroke. Genetic variants are linked to increased risk for stroke in cocaine abuse. The fact that case reports on cannabis-induced stroke usually refer to the young population is very alarming.

Cannabinoid receptor-1 antagonism: a new perspective on treating a murine schistosomal liver fibrosis model

BACKGROUND

Formation of schistosomal granulomata surrounding the ova can result in schistosomiasis-associated liver fibrosis (SSLF). The current standard of treatment is praziquantel (PZQ), which cannot effectively reverse SSLF. The role of the cannabinoid (CB) receptor family in liver fibrosis has recently been highlighted.

OBJECTIVES

This study aimed to assess the therapeutic effect of CB1 receptor antagonism in reversing SSLF in a murine model of Schistosoma mansoni infection.

METHODS

One hundred male Swiss albino mice were divided equally into five groups: healthy uninfected control (group I), infected control (group II), PZQ treated (group III), rimonabant (RIM) (SR141716, a CB1 receptor antagonist)-treated (group IV) and group V was treated with combined PZQ and RIM. Liver sections were obtained for histopathological examination, alpha-1 smooth muscle actin (α-SMA) immunostaining and assessment of CB1 receptor expression using real-time polymerase chain reaction (RT-PCR).

FINDINGS

The most effective reduction in fibrotic marker levels and granuloma load was achieved by combined treatment with PZQ+RIM (group V): CB1 receptor expression (H = 26.612, p < 0.001), number of α-SMA-positive cells (F = 57.086, p < 0.001), % hepatic portal fibrosis (F = 42.849, p < 0.001) and number of granulomata (F = 69.088, p < 0.001).

MAIN CONCLUSIONS

Combining PZQ with CB1 receptor antagonists yielded the best results in reversing SSLF. To our knowledge, this is the first study to test this regimen in S. mansoni infection.

Cannabidiol Regulates the Expression of Keratinocyte Proteins Involved in the Inflammation Process through Transcriptional Regulation

Cannabidiol (CBD), a natural phytocannabinoid without psychoactive effect, is a well-known anti-inflammatory and antioxidant compound. The possibility of its use in cytoprotection of cells from harmful factors, including ultraviolet (UV) radiation, is an area of ongoing investigation. Therefore, the aim of this study was to evaluate the effect of CBD on the regulatory mechanisms associated with the redox balance and inflammation in keratinocytes irradiated with UVA [30 J/cm²] and UVB [60 mJ/cm²]. Spectrophotometric results show that CBD significantly enhances the activity of antioxidant enzymes such as superoxide dismutase and thioredoxin reductase in UV irradiated keratinocytes. Furthermore, despite decreased glutathione peroxidase and reductase activities, CBD prevents lipid peroxidation, which was observed as a decreased level of 4-HNE and 15d-PGJ₂ (measured using GC/MS and LC/MS). Moreover, Western blot analysis of protein levels shows that, under stress conditions, CBD influences interactions of transcription factors Nrf2- NFκB by inhibiting the NFκB pathway, increasing the expression of Nrf2 activators and stimulating the transcription activity of Nrf2. In conclusion, the antioxidant activity of CBD through Nrf2 activation as well as its anti-inflammatory properties as an inhibitor of NFκB should be considered during design of new protective treatments for the skin.

Regional changes in the type 1 cannabinoid receptor are associated with cognitive dysfunction in Parkinson's disease

PURPOSE

The endocannabinoid system plays a regulatory role in a number of physiological functions, including motor control but also mood, emotion, and cognition. A number of preclinical studies in Parkinson's disease (PD) models demonstrated that modulating the type 1 cannabinoid receptor (CB₁R) may improve motor symptoms and components of cognitive processing. However, the relation between CB₁R, cognitive decline and behavioral symptoms has not been investigated in PD patients so far. The aim of this study was to examine whether CB₁R availability is associated with measures of cognitive and behavioral function in PD patients.

METHODS

Thirty-eight PD patients and ten age- and gender-matched controls underwent a [¹⁸F]MK-9470 PET scan to assess CB₁R availability, as well as volumetric MR imaging. Neuropsychological symptoms were evaluated using an extensive cognitive and behavioral battery covering the five cognitive domains, depression, anxiety, apathy, and psychiatric complications, and were correlated to CB₁R availability using vowel-wise regression analysis (P < 0.05, corrected for familywise error).

RESULTS

PD patients with poorer performance in episodic memory, executive functioning, speed and mental flexibility (range P 0.003-0.03) showed lower CB₁R availability in predominantly the midcingulate cortex and middle to superior frontal gyrus (T_peak-level > 4.0). Also, PD patients with more severe visuospatial dysfunction showed decreased CB₁R availability in the precuneus, midcingulate, supplementary motor cortex, inferior orbitofrontal gyrus and thalamus (T_peak-level = 5.5). These correlations were not related to cortical gray matter atrophy. No relationship was found between CB₁R availability and mood or behavioral symptom scores.

CONCLUSIONS

Decreased CB₁R availability in the prefrontal and midcingulate cortex in PD patients is strongly correlated with disturbances in executive functioning, episodic memory, and visuospatial functioning. Further investigation of regional CB1R expression in groups of PD patients with mild cognitive impairment or dementia is warranted in order to further investigate the role of CB1R expression in different levels of cognitive impairment in PD.

Potential Adverse Drug Events and Drug-Drug Interactions with Medical and Consumer Cannabidiol (CBD) Use

Cannabidiol (CBD) is ubiquitous in state-based medical cannabis programs and consumer products for complementary health or recreational use. CBD has intrinsic pharmacologic effects and associated adverse drug events (ADEs) along with the potential for pharmacokinetic and pharmacodynamic drug–drug interactions (DDIs). Given CBD use among patients with complex conditions and treatment regimens, as well as its expanded consumer use, awareness of potential safety issues with CBD is needed. Prescribing information for federally approved products containing CBD were reviewed. Data on ADEs and DDIs were extracted and summarized. Nearly one-half of CBD users experienced ADEs, which displayed a general dose-response relationship. Common ADEs include transaminase elevations, sedation, sleep disturbances, infection, and anemia. Given CBD effects on common biological targets implicated in drug metabolism (e.g., CYP3A4/2C19) and excretion (e.g., P-glycoprotein), the potential for DDIs with commonly used medication is high. General clinical recommendations of reducing substrate doses, monitoring for ADEs, and finding alternative therapy should be considered, especially in medically complex patients. CBD is implicated as both a victim and perpetrator of DDIs and has its own ADE profile. These effects should be considered in the risk-benefit assessment of CBD therapy and patients and consumers made aware of potential safety issues with CBD use.

The effects of oleoylethanolamide, an endogenous PPAR-α agonist, on risk factors for NAFLD: A systematic review

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease. Recently, some novel compounds have been investigated for the prevention and treatment of NAFLD. Oleoylethanolamide (OEA), an endogenous PPAR-α agonist, has exhibited a plethora of pharmacological properties for the treatment of obesity and other obesity-associated metabolic complications. This systematic review was performed with a focus on the effects of OEA on the risk factors for NAFLD. PubMed, Scopus, Embase, ProQuest, and Google Scholar databases were searched up to December 2018 using relevant keywords. All articles written in English evaluating the effects of OEA on the risk factors for NAFLD were eligible for the review. The evidence reviewed in this article illustrates that OEA regulates multiple biological processes associated with NAFLD, including lipid metabolism, inflammation, oxidative stress, and energy homeostasis through different mechanisms. In summary, many beneficial effects of OEA have led to the understanding that OEA may be an effective therapeutic strategy for the management of NAFLD. Although a wide range of studies have demonstrated the most useful effects of OEA on NAFLD and the associated risk factors, further clinical trials, from both in vivo studies and in vitro experiments, are warranted to verify these outcomes.

Cannabinoid-induced relief of hypermotility in a rat model of the irritable bowel syndrome

Cannabinoid-2 receptor agonists may be useful in treating intestinal motility disorders.

Cannabinoid receptors as therapeutic targets for autoimmune diseases: where do we stand?

Described during the late 1980s and 1990s, cannabinoid receptors (CB1R and CB2R) are G-protein-coupled receptors (GPCRs) activated by endogenous ligands and cannabinoid drug compounds, such as Δ9-THC. Whereas CB1R has a role in the regulation of neurotransmission in different brain regions and mainly mediates the psychoactive effects of cannabinoids, CB2R is found predominantly in the cells and tissues of the immune system and mediates anti-inflammatory and immunomodulatory processes. Studies have demonstrated that CB1R and CB2R can affect the activation of T cells, B cells, monocytes, and microglial cells, inhibiting proinflammatory cytokine expression and upregulating proresolution mediators. Thus, in this review, we summarize the mechanisms by which CBRs interact with the autoimmune environment and the potential to suppress the development and activation of autoreactive cells. Finally, we highlight how the modulation of CB1R and CB2R is advantageous in the treatment of autoimmune diseases, including multiple sclerosis (MS), type 1 diabetes mellitus (T1DM) and rheumatoid arthritis (RA).

The Endocannabinoid System as a Potential Mechanism through which Exercise Influences Episodic Memory Function

Emerging research demonstrates that exercise, including both acute and chronic exercise, may influence episodic memory function. To date, mechanistic explanations of this effect are often attributed to alterations in long-term potentiation, neurotrophic production, angiogenesis, and neurogenesis. Herein, we discuss a complementary mechanistic model, suggesting that the endocannabinoid system may, in part, influence the effects of exercise on memory function. We discuss the role of the endocannabinoid system on memory function as well as the effects of exercise on endocannabinoid alterations. This is an exciting line of inquiry that should help delineate new insights into the mechanistic role of exercise on memory function.

Cannabis: From a Plant That Modulates Feeding Behaviors toward Developing Selective Inhibitors of the Peripheral Endocannabinoid System for the Treatment of Obesity and Metabolic Syndrome

In this review, we discuss the role of the endocannabinoid (eCB) system in regulating energy and metabolic homeostasis. Endocannabinoids, via activating the cannabinoid type-1 receptor (CB₁R), are commonly known as mediators of the thrifty phenotype hypothesis due to their activity in the central nervous system, which in turn regulates food intake and underlies the development of metabolic syndrome. Indeed, these findings led to the clinical testing of globally acting CB₁R blockers for obesity and various metabolic complications. However, their therapeutic potential was halted due to centrally mediated adverse effects. Recent observations that highlighted the key role of the peripheral eCB system in metabolic regulation led to the preclinical development of various novel compounds that block CB₁R only in peripheral organs with very limited brain penetration and without causing behavioral side effects. These unique molecules, which effectively ameliorate obesity, type II diabetes, fatty liver, insulin resistance, and chronic kidney disease in several animal models, are likely to be further developed in the clinic and may revive the therapeutic potential of blocking CB₁R once again.

Effect of endocannabinoid signalling on cell fate: life, death, differentiation and proliferation of brain cells

Cell fate events are regulated by different endogenous developmental factors such as the cell micro-environment, external or remote signals and epigenetic factors. Among the many regulatory factors, endocannabinoid-associated signalling pathways are known to conduct several of these events in the developing nervous system and in the adult brain. Interestingly, endocannabinoids exert modulatory actions in both physiological and pathological conditions. Endocannabinoid signalling can promote cell survival by acting on non-transformed brain cells (neurons, astrocytes or oligodendrocytes) and can have either a protumoural or antitumoural effect on transformed cells. Moreover, endocannabinoids are able to attenuate the detrimental effects on neurogenesis and neuroinflammation associated with ageing. Thus, the endocannabinoid system emerges as an important regulator of cell fate, controlling cell survival/cell death decisions depending on the cell type and its environment. LINKED ARTICLES: This article is part of a themed section on 8th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.

The Endocannabinoid/Endovanilloid System in Bone: From Osteoporosis to Osteosarcoma

Bone is a dynamic tissue, whose homeostasis is maintained by a fine balance between osteoclast (OC) and osteoblast (OB) activity. The endocannabinoid/endovanilloid (EC/EV) system’s receptors are the cannabinoid receptor type 1 (CB1), the cannabinoid receptor type 2 (CB2), and the transient receptor potential cation channel subfamily V member 1 (TRPV1). Their stimulation modulates bone formation and bone resorption. Bone diseases are very common worldwide. Osteoporosis is the principal cause of bone loss and it can be caused by several factors such as postmenopausal estrogen decrease, glucocorticoid (GC) treatments, iron overload, and chemotherapies. Studies have demonstrated that CB1 and TRPV1 stimulation exerts osteoclastogenic effects, whereas CB2 stimulation has an anti-osteoclastogenic role. Moreover, the EC/EV system has been demonstrated to have a role in cancer, favoring apoptosis and inhibiting cell proliferation. In particular, in bone cancer, the modulation of the EC/EV system not only reduces cell growth and enhances apoptosis but it also reduces cell invasion and bone pain in mouse models. Therefore, EC/EV receptors may be a useful pharmacological target in the prevention and treatment of bone diseases. More studies to better investigate the biochemical mechanisms underlining the EC/EV system effects in bone are needed, but the synthesis of hybrid molecules, targeting these receptors and capable of oppositely regulating bone homeostasis, seems to be a promising and encouraging prospective in bone disease management.

Future Aspects for Cannabinoids in Breast Cancer Therapy

Cannabinoids (CBs) from Cannabis sativa provide relief for tumor-associated symptoms (including nausea, anorexia, and neuropathic pain) in the palliative treatment of cancer patients. Additionally, they may decelerate tumor progression in breast cancer patients. Indeed, the psychoactive delta-9-tetrahydrocannabinol (THC), non-psychoactive cannabidiol (CBD) and other CBs inhibited disease progression in breast cancer models. The effects of CBs on signaling pathways in cancer cells are conferred via G-protein coupled CB-receptors (CB-Rs), CB1-R and CB2-R, but also via other receptors, and in a receptor-independent way. THC is a partial agonist for CB1-R and CB2-R; CBD is an inverse agonist for both. In breast cancer, CB1-R expression is moderate, but CB2-R expression is high, which is related to tumor aggressiveness. CBs block cell cycle progression and cell growth and induce cancer cell apoptosis by inhibiting constitutive active pro-oncogenic signaling pathways, such as the extracellular-signal-regulated kinase pathway. They reduce angiogenesis and tumor metastasis in animal breast cancer models. CBs are not only active against estrogen receptor-positive, but also against estrogen-resistant breast cancer cells. In human epidermal growth factor receptor 2-positive and triple-negative breast cancer cells, blocking protein kinase B- and cyclooxygenase-2 signaling via CB2-R prevents tumor progression and metastasis. Furthermore, selective estrogen receptor modulators (SERMs), including tamoxifen, bind to CB-Rs; this process may contribute to the growth inhibitory effect of SERMs in cancer cells lacking the estrogen receptor. In summary, CBs are already administered to breast cancer patients at advanced stages of the disease, but they might also be effective at earlier stages to decelerate tumor progression.

Cannabis for refractory epilepsy in children: A review focusing on CDKL5 Deficiency Disorder

Severe paediatric epilepsies such as CDKL5 Deficiency Disorder (CDD) are extremely debilitating, largely due to the early-onset and refractory nature of the seizures. Existing treatment options are often ineffective and associated with a host of adverse effects, causing those that are affected to seek alternative treatments. Cannabis based products have attracted significant attention over recent years, primarily driven by reports of miraculous cures and a renewed public preference for 'natural' therapies, thus placing intense pressure on health professionals and the government for regulatory change. This study provides a comprehensive overview of the potential role for cannabis in the treatment of CDD. Key areas discussed include the history, mechanism of action, efficacy and safety of cannabis based preparations as well as the burden related to CDD. The evidence supports the use of cannabinoids, especially cannabidiol, in similar forms of refractory epilepsy including Dravet and Lennox-Gastaut syndromes. Evidence for cannabinoids specifically in CDD is limited but growing, with multiple anecdotal reports and an open-label trial showing cannabidiol to be associated with a significant reduction in seizure activity. This review provides the first comprehensive overview of the potential role for cannabis based preparations in the treatment of CDD and provides justification for further clinical and observational research.

Cannabinoid Receptor Type 1 Agonist ACEA Improves Cognitive Deficit on STZ-Induced Neurotoxicity Through Apoptosis Pathway and NO Modulation

The cannabinoid system has the ability to modulate cellular and molecular mechanisms, including excitotoxicity, oxidative stress, apoptosis, and inflammation, acting as a neuroprotective agent, by its relationship with signaling pathways associated to the control of cell proliferation, differentiation, and survival. Recent reports have raised new perspectives on the possible role of cannabinoid system in neurodegenerative diseases like Alzheimer disease's (AD). AD is a neurodegenerative disorder characterized by the presence of amyloid plaques, neurofibrillary tangles, neuronal death, and progressive cognitive loss, which could be caused by energy metabolism impairment, changes in insulin signaling, chronic oxidative stress, neuroinflammation, Tau hyperphosphorylation, and Aβ deposition in the brain. Thus, we investigated the presumptive protective effect of the cannabinoid type 1 (CB1)-selective receptor agonist arachidonyl-2'-chloroethylamide (ACEA) against streptozotocin (STZ) exposure stimuli in an in vitro neuronal model (Neuro-2a neuroblastoma cells) and in vivo model (intracerebroventricular STZ injection), experimental models of sporadic AD. Our results demonstrated that ACEA treatment reversed cognitive impairment and increased activity of Akt and ERK triggered by STZ, and increased IR expression and increased the anti-apoptotic proteins levels, Bcl-2. In the in vitro model, ACEA was able to rescue cells from STZ-triggered death and modulated the NO release by STZ. Our study has demonstrated a participation of the cannabinoid system in cellular survival, involving the CB1 receptor, which occurs by positive regulation of the anti-apoptotic proteins, suggesting the participation of this system in neurodegenerative processes. Our data suggest that the cannabinoid system is an interesting therapeutic target for the treatment of neurodegenerative diseases.

Newly Emerging Drugs of Abuse

Drug use and the associated overdose deaths have been a serious public health threat in the United States and the world. While traditional drugs of abuse such as cocaine remain popular, recreational use of newer synthetic drugs has continued to increase, but the prevalence of use is likely underestimated. In this review, epidemiology, chemistry, pharmacophysiology, clinical effects, laboratory detection, and clinical treatment are discussed for newly emerging drugs of abuse in the following classes: (1) opioids (e.g., fentanyl, fentanyl analogues, and mitragynine), (2) cannabinoids [THC and its analogues, alkylindole (e.g., JWH-018, JWH-073), cyclohexylphenol (e.g., CP-47,497), and indazole carboxamide (e.g., FUB-AMB, ADB-FUBINACA)], (3) stimulants and hallucinogens [β-keto amphetamines (e.g., methcathinone, methylone), pyrrolidinophenones (e.g., α-PVP, MDPV), and dimethoxyphenethylamine ("2C" and "NBOMe")], (4) dissociative agents (e.g., 3-MeO-PCP, methoxetamine, 2-oxo-PCE), and (5) sedative-hypnotics (e.g., gabapentin, baclofen, clonazolam, etizolam). It is critically important to coordinate hospital, medical examiner, and law enforcement personnel with laboratory services to respond to these emerging threats.

Activating Cannabinoid Receptor 2 Protects Against Diabetic Cardiomyopathy Through Autophagy Induction

Cannabinoid receptor 2 (CB₂) has been reported to produce a cardio-protective effect in cardiovascular diseases such as myocardial infarction. Here in this study, we investigated the role of CB₂ in diabetic cardiomyopathy (DCM) and its underlying mechanisms. HU308 was used for the selective activation of CB₂. Bafilomycin A1 was used for the blockade of autophagy and compound C was used to inhibit AMPK signaling. An streptozotocin (STZ)-induced mice model and high glucose (HG)-challenged cardiomyocytes were applied for study. Cardiac function was detected by echocardiography and Western blot for the detection of autophagy-related and its signaling-related proteins. Transmission electron microscopy was used for the analysis of autophagosome number. Cell viability was detected by Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) release assays. We found that activating CB₂ by HU308 improved cardiac function in DCM as well as cell viability in cardiomyocytes under HG challenge, while the administration of bafilomycin A1 attenuated the protective effects. HU308 enhanced the level of autophagy in the heart tissues from DCM mice as well as cardiomyocytes under HG challenge. HU308 triggered the AMPK-mTOR-p70S6K signaling pathway, while the administration of compound C attenuated the cardio-protective effect of HU308 in cardiomyocytes under HG challenge. In conclusion, we initially demonstrated that activating CB₂ produced a cardio-protective effect in DCM as well as cardiomyocytes under HG challenge through inducing the AMPK-mTOR-p70S6K signaling-mediated autophagy.

Structure-Based Identification of Potent Natural Product Chemotypes as Cannabinoid Receptor 1 Inverse Agonists

Natural products are an abundant source of potential drugs, and their diversity makes them a rich and viable prospective source of bioactive cannabinoid ligands. Cannabinoid receptor 1 (CB1) antagonists are clinically established and well documented as potential therapeutics for treating obesity, obesity-related cardiometabolic disorders, pain, and drug/substance abuse, but their associated CNS-mediated adverse effects hinder the development of potential new drugs and no such drug is currently on the market. This limitation amplifies the need for new agents with reduced or no CNS-mediated side effects. We are interested in the discovery of new natural product chemotypes as CB1 antagonists, which may serve as good starting points for further optimization towards the development of CB1 therapeutics. In search of new chemotypes as CB1 antagonists, we screened the in silico purchasable natural products subset of the ZINC12 database against our reported CB1 receptor model using the structure-based virtual screening (SBVS) approach. A total of 18 out of 192 top-scoring virtual hits, selected based on structural diversity and key protein⁻ligand interactions, were purchased and subjected to in vitro screening in competitive radioligand binding assays. The in vitro screening yielded seven compounds exhibiting >50% displacement at 10 μM concentration, and further binding affinity (K_i and IC₅₀) and functional data revealed compound 16 as a potent and selective CB1 inverse agonist (K_i = 121 nM and EC₅₀ = 128 nM) while three other compounds-2, 12, and 18-were potent but nonselective CB1 ligands with low micromolar binding affinity (K_i). In order to explore the structure⁻activity relationship for compound 16, we further purchased compounds with >80% similarity to compound 16, screened them for CB1 and CB2 activities, and found two potent compounds with sub-micromolar activities. Most importantly, these bioactive compounds represent structurally new natural product chemotypes in the area of cannabinoid research and could be considered for further structural optimization as CB1 ligands.

G protein-coupled receptor heteromers are key players in substance use disorder

G protein-coupled receptors (GPCR) represent the largest family of membrane proteins in the human genome. Physical association between two different GPCRs is linked to functional interactions which generates a novel entity, called heteromer, with specific ligand binding and signaling properties. Heteromerization is increasingly recognized to take place in the mesocorticolimbic pathway and to contribute to various aspects related to substance use disorder. This review focuses on heteromers identified in brain areas relevant to drug addiction. We report changes at the molecular and cellular levels that establish specific functional impact and highlight behavioral outcome in preclinical models. Finally, we briefly discuss selective targeting of native heteromers as an innovative therapeutic option.

Role of the endocannabinoid system in drug addiction

Drug addiction is a chronic relapsing disorder that produces a dramaticglobal health burden worldwide. Not effective treatment of drug addiction is currently available probably due to the difficulties to find an appropriate target to manage this complex disease raising the needs for further identification of novel therapeutic approaches. The endocannabinoid system has been found to play a crucial role in the neurobiological substrate underlying drug addiction. Endocannabinoids and cannabinoid receptors are widely expressed in the main areas of the mesocorticolimbic system that participate in the initiation and maintenance of drug consumption and in the development of compulsion and loss of behavioral control occurring during drug addiction. The identification of the important role played by CB1 cannabinoid receptors in drug addiction encouraged the possible used of an early commercialized CB1 receptor antagonist for treating drug addiction. However, the incidence of serious psychiatric adverse events leaded to the sudden withdrawal from the market of this CB1 antagonist and all the research programs developed by pharmaceutical companies to obtain new CB1 antagonists were stopped. Currently, new research strategies are under development to target the endocannabinoid system for drug addiction avoiding these side effects, which include allosteric negative modulators of CB1 receptors and compounds targeting CB2 receptors. Recent studies showing the potential role of CB2 receptors in the addictive properties of different drugs of abuse have open a promising research opportunity to develop novel possible therapeutic approaches.

Highway to hell or magic smoke? The dose-dependence of Δ9-THC in place conditioning paradigms

The prerequisites for responsible cannabis use are at the heart of current inquiries into cannabis decriminalization by policy makers as well as academic and nonacademic stakeholders at a global scale. Δ⁹-tetrahydrocannabinol (Δ⁹-THC), the prime psychoactive compound of the cannabis sativa, as well as cannabimimetics that resemble the pharmacological properties and psychological effects of Δ⁹-THC, lend themselves handsomely to the preclinical scrutiny of reward-related behavior because they carry marked translational value. Although a functional dichotomy of the psychological effects of Δ⁹-THC (rewarding versus aversive) has been abundantly reported in place conditioning (PC) paradigms, and might be best attributed to a dose-dependence of Δ⁹-THC, most PC studies with Δ⁹-THC feature no significant effects at all. Therefore, after decades of rigorous research, it still remains undetermined whether Δ⁹-THC generally exerts rewarding or aversive effects in rodents. Here, we set out to extrapolate the commonly alleged dose-dependence of the rewarding and aversive effects of Δ⁹-THC from the existing literature, at the behavioral pharmacological level of analysis. Specifically, our meta-analysis investigated: (i) the alleged bidirectional effects and dose-dependence of Δ⁹-THC in the PC test; (ii) methodological inconsistencies between PC studies; and (iii) other pharmacological studies on cannabinoids (i.e., dopamine release, anxiety, stress, conditioned taste aversion, catalepsy) to substantiate the validity of PC findings. Our findings suggest that: (i) Δ⁹-THC dose-dependently generates rewarding (1 mg/kg) and aversive (5 mg/kg) effects in PC; (ii) an inconsistent use of priming injections hampers a clear establishment of the rewarding effects of Δ⁹-THC in PC tests and might explain the seemingly contradictory plethora of nonsignificant THC studies in the PC test; and (iii) other pharmacological studies on Δ⁹-THC substantiate the dose-dependent biphasic effects of Δ⁹-THC in PC. A standardized experimental design would advance evidence-based practice in future PC studies with Δ⁹-THC and facilitate the pointed establishment of rewarding and aversive effects of the substance.

Overlapping Distribution of Orexin and Endocannabinoid Receptors and Their Functional Interaction in the Brain of Adult Zebrafish

Hypocretins/Orexins neuropeptides are known to regulate numerous physiological functions, such as energy homeostasis, food intake, sleep/wake cycle, arousal and wakefulness, in vertebrates. Previous studies on mice have revealed an intriguing orexins/endocannabinoids (ECs) signaling interaction at both structural and functional levels, with OX-A behaving as a strong enhancer of 2-arachydonoyl-glycerol (2-AG) biosynthesis. In this study, we describe, for the first time in the brain of zebrafish, the anatomical distribution and co-expression of orexin (OX-2R) and endocannabinoid (CB1R) receptors, suggesting a functional interaction. The immunohistochemical colocalization of these receptors by confocal imaging in the dorsal and ventral telencephalon, suprachiasmatic nucleus (SC), thalamus, hypothalamus, preoptic area (PO) and cerebellum, is reported. Moreover, biochemical quantification of 2-AG levels by LC-MS supports the occurrence of OX-A-induced 2-AG biosynthesis in the zebrafish brain after 3 h of OX-A intraperitoneal (i.p.; 3 pmol/g) or intracerebroventricular (i.c.v.; 0.3 pmol/g) injection. This effect is likely mediated by OX-2R as it is counteracted by i.p./i.c.v administration of OX-2R antagonist (SB334867, 10 pmol/g). This study provides compelling morphological and functional evidence of an OX-2R/CB1R signaling interaction in the brain of adult zebrafish, suggesting the use of this well-established vertebrate animal model for the study of complex and phylogenetically conserved physiological functions.

The Trouble with CBD Oil

In just a few years, cannabidiol (CBD) has become immensely popular around the world. After initially being discovered as an effective self-medication for Dravet syndrome in children, CBD is now sold and used to treat a wide range of medical conditions and lifestyle diseases. The cannabinoid CBD, a non-psychoactive isomer of the more infamous tetrahydrocannabinol (THC), is available in a growing number of administration modes, but the most commonly known is CBD oil. There are currently dozens, if not hundreds, of producers and sellers of CBD oils active in the market, and their number is increasing rapidly. Those involved vary from individuals who prepare oils on a small scale for family and (Facebook) friends to compounding pharmacies, pharmaceutical companies, and licensed cannabis producers. Despite the growing availability of CBD, many uncertainties remain about the legality, quality, and safety of this new "miracle cure." As a result, CBD is under scrutiny on many levels, ranging from national health organizations and agricultural lobbyists to the WHO and FDA. The central question is whether CBD is simply a food supplement, an investigational new medicine, or even a narcotic. This overview paper looks into the known risks and issues related to the composition of CBD products, and makes recommendations for better regulatory control based on accurate labeling and more scientifically supported health claims. The intention of this paper is to create a better understanding of the benefits versus the risks of the current way CBD products are produced, used, and advertised.

Role of sphingolipids in the biogenesis and biological activity of extracellular vesicles

Extracellular vesicles (EVs) are membrane vesicles released by both eukaryotic and prokaryotic cells; they not only serve physiological functions, such as disposal of cellular components, but also play pathophysiologic roles in inflammatory and degenerative diseases. Common molecular mechanisms for EV biogenesis are evident in different cell biological contexts across eukaryotic phyla, and inhibition of this biogenesis may provide an avenue for therapeutic research. The involvement of sphingolipids (SLs) and their enzymes on EV biogenesis and release has not received much attention in current research. Here, we review how SLs participate in EV biogenesis by shaping membrane curvature and how they contribute to EV action in target cells. First, we describe how acid and neutral SMases, by generating the constitutive SL, ceramide, facilitate biogenesis of EVs at the plasma membrane and inside the endocytic compartment. We then discuss the involvement of other SLs, such as sphingosine-1-phosphate and galactosyl-sphingosine, in EV formation and cargo sorting. Last, we look ahead at some biological effects of EVs mediated by changes in SL levels in recipient cells.