Cannabinoid CB1 and CB2 Receptor Signaling and Bias

Novel approaches and current challenges with targeting the endocannabinoid system

INTRODUCTION

The pathophysiological relevance of the endocannabinoid system has been widely demonstrated in a variety of diseases including cancer, neurological disorders, and metabolic issues. Therefore, targeting the receptors and the endogenous machinery involved in this system can provide a successful therapeutic outcome. Ligands targeting the canonical cannabinoid receptors, CB1 and CB2, along with inhibitors of the endocannabinoid enzymes have been thoroughly studied in diverse disease models. In fact, phytocannabinoids such as cannabidiol or Δ9-tetrahydrocannabinol are currently on the market for the management of neuropathic pain due to spasticity in multiple sclerosis or seizures in children epilepsy amongst others.

AREAS COVERED

Challenges in the pharmacology of cannabinoids arise from its pharmacokinetics, off-target effects, and psychoactive effects. In this context, the current review outlines the novel molecular approaches emerging in the field discussing their clinical potential.

EXPERT OPINION

Even if orthosteric CB1 and CB2 ligands are on the forefront in cannabinoid clinical research, emerging strategies such as allosteric or biased modulation of these receptors along with controlled off-targets effects may increase the therapeutic potential of cannabinoids.

The fundamental role of the endocannabinoid system in endometrium and placenta: implications in pathophysiological aspects of uterine and pregnancy disorders

BACKGROUND

The endocannabinoid system (ECS) consists of the cannabinoid receptors CB1 and CB2, the main endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) and their metabolic enzymes N-acylphosphatidylethanolamine-specific phospholipase D, fatty acid amide hydrolase, diacylglycerol lipase and monoacylglycerol lipase. This system is involved in the modulation of essential physiological processes. Its role in the reproductive system has become significantly important in recent years, given its major role in events such as gametogenesis, decidualisation, implantation and placentation.

OBJECTIVE AND RATIONALE

In this paper, we review the literature and summarize the role of the ECS elements in reproduction and their potential as early markers for diagnosis of reproductive disorders or as pharmacological targets for treatment.

SEARCH METHODS

Original research and review papers published from 1964 to June 2019 were selected in terms of relevance, reliability and quality by searching PubMed, MEDLINE and Web of Science, using the following search terms: endocannabinoid system and endometriosis; endocannabinoid system and ectopic pregnancy; endocannabinoid system and miscarriage; endocannabinoid system and pre-eclampsia; endocannabinoid system and endometrial cancer; endocannabinoid system and reproduction; endocannabinoid, endometrium; placenta; N-acylethanolamines; anandamide; 2-arachidonoylglycerol; and cannabinoids.

OUTCOMES

This review demonstrates relevant information concerning ECS alterations in endometriosis, ectopic pregnancy, miscarriage, pre-eclampsia and endometrial cancer. We highlight the importance of the endocannabinoids in endometrial and placental physiology and pathophysiology, from studies in vitro and in vivo and in clinical observations. The most studied of the endogenous cannabinoids is AEA. The levels of AEA were increased in plasma of patients with endometriosis and miscarriage, as well as in the fallopian tube of women with ectopic pregnancy and in endometrial biopsies of endometrial cancer. Changes in the pattern of expression of the cannabinoid receptor CB1 were also observed in endometrial biopsies of endometriosis, fallopian tube and decidua of patients with ectopic pregnancy and pre-eclamptic placenta. Moreover, alterations in CB2 expression have been reported in association with endometrial cancer. In general, studies on the cannabinoid signalling through CB2 and on the biological activities of the other major endocannabinoid, namely 2-AG, as well as its metabolic enzymes are scarce and avidly required.

WIDER IMPLICATIONS

The pathophysiological mechanisms involved in the described endometrial and placental pathologies are still unclear and lack the means for an early diagnosis. Based on current evidence, though alterations in ECS are demonstrated at tissue level, it is difficult to associate plasmatic changes in AEA with specific endometrial and placental diseases. Thus, pairing alterations in AEA levels with 2-AG and/or other endocannabinoid-like molecules may provide more accurate and early diagnoses. In addition, patients may benefit from new therapies that target the ECS and endocannabinoid signalling.

The Role of the Cannabinoid System in Pain Control: Basic and Clinical Implications

PURPOSE OF REVIEW

The purpose of this review is to provide a comprehensive update of the different known components of the endogenous cannabinoid system and the mechanisms of action, as it applies to analgesia.

RECENT FINDINGS

Following the discovery of the endogenous cannabinoid system in the early 1990s and the subsequent characterization of the cannabinoid receptor, there has been a renewed interest in cannabinoid research. Recent work has demonstrated its efficacy as a pharmacologic agent. There is limited evidence in the literature about the understanding of the endocannabinoid system and its role in the treatment and management of acute and chronic pain. Further work may elucidate additional roles for the endocannabinoid system within our nervous system and, moreover, additional subtypes of cannabinoid receptors have yet to be discovered. Cannabinoid compounds mediate their biological effects via binding and subsequent activation of cannabinoid receptors. These receptors are located throughout the body and make up the endocannabinoid system. These receptors are best understood and have been cloned, type 1 (CB₁) and type 2 (CB₂) [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)] [ (1, 2)]. The CB₂ receptor is located primarily in the immune system. CB₁ receptors are primarily located in the nervous system with the highest concentrations in the brain and lower concentrations in the spine and peripheral nervous tissues. Cannabinoids may be promising treatments for neuropathic pain with limited evidence, whereas, the evidence for other uses is insufficient.

Crosstalk between the M1 muscarinic acetylcholine receptor and the endocannabinoid system: A relevance for Alzheimer's disease?

Alzheimer's disease (AD) is a neurodegenerative disorder which accounts for 60-70% of the 50 million worldwide cases of dementia and is characterised by cognitive impairments, many of which have long been associated with dysfunction of the cholinergic system. Although the M1 muscarinic acetylcholine receptor (mAChR) is considered a promising drug target for AD, ligands targeting this receptor have so far been unsuccessful in clinical trials. As modulatory receptors to cholinergic transmission, the endocannabinoid system may be a promising drug target to allow fine tuning of the cholinergic system. Furthermore, disease-related changes have been found in the endocannabinoid system during AD progression and indeed targeting the endocannabinoid system at specific disease stages alleviates cognitive symptoms in numerous mouse models of AD. Here we review the role of the endocannabinoid system in AD, and its crosstalk with mAChRs as a potential drug target for cholinergic dysfunction.

A Guide to Targeting the Endocannabinoid System in Drug Design

The endocannabinoid system (ECS) is one of the most crucial systems in the human organism, exhibiting multi-purpose regulatory character. It is engaged in a vast array of physiological processes, including nociception, mood regulation, cognitive functions, neurogenesis and neuroprotection, appetite, lipid metabolism, as well as cell growth and proliferation. Thus, ECS proteins, including cannabinoid receptors and their endogenous ligands’ synthesizing and degrading enzymes, are promising therapeutic targets. Their modulation has been employed in or extensively studied as a treatment of multiple diseases. However, due to a complex nature of ECS and its crosstalk with other biological systems, the development of novel drugs turned out to be a challenging task. In this review, we summarize potential therapeutic applications for ECS-targeting drugs, especially focusing on promising synthetic compounds and preclinical studies. We put emphasis on modulation of specific proteins of ECS in different pathophysiological areas. In addition, we stress possible difficulties and risks and highlight proposed solutions. By presenting this review, we point out information pivotal in the spotlight of ECS-targeting drug design, as well as provide an overview of the current state of knowledge on ECS-related pharmacodynamics and show possible directions for needed research.

Effects of orthotopic implantation of rat prostate tumour cells upon components of the N-acylethanolamine and monoacylglycerol signalling systems: an mRNA study

There is good evidence that the N-acylethanolamine (NAE)/monoacylglycerol (MAG) signalling systems are involved in the pathogenesis of cancer. However, it is not known how prostate tumours affect these systems in the surrounding non-malignant tissue and vice versa. In the present study we have investigated at the mRNA level 11 components of these systems (three coding for anabolic enzymes, two for NAE/MAG targets and six coding for catabolic enzymes) in rat prostate tissue following orthotopic injection of low metastatic AT1 cells and high metastatic MLL cells. The MLL tumours expressed higher levels of Napepld, coding for a key enzyme in NAE synthesis, and lower levels of Naaa, coding for the NAE hydrolytic enzyme N-acylethanolamine acid amide hydrolase than the AT1 tumours. mRNA levels of the components of the NAE/MAG signalling systems studied in the tissue surrounding the tumours were not overtly affected by the tumours. AT1 cells in culture expressed Faah, coding for the NAE hydrolytic enzyme fatty acid amide hydrolase, at much lower levels than Naaa. However, the ability of the intact cells to hydrolyse the NAE arachidonoylethanolamide (anandamide) was inhibited by an inhibitor of FAAH, but not of NAAA. Treatment of the AT1 cells with interleukin-6, a cytokine known to be involved in the pathogenesis of prostate cancer, did not affect the expression of the components of the NAE/MAG system studied. It is thus concluded that in the model system studied, the tumours show different expressions of mRNA coding for key the components of the NAE/MAG system compared to the host tissue, but that these changes are not accompanied by alterations in the non-malignant tissue.

Terpenoids, Cannabimimetic Ligands, beyond the Cannabis Plant

Medicinal use of Cannabis sativa L. has an extensive history and it was essential in the discovery of phytocannabinoids, including the Cannabis major psychoactive compound-Δ9-tetrahydrocannabinol (Δ9-THC)-as well as the G-protein-coupled cannabinoid receptors (CBR), named cannabinoid receptor type-1 (CB1R) and cannabinoid receptor type-2 (CB2R), both part of the now known endocannabinoid system (ECS). Cannabinoids is a vast term that defines several compounds that have been characterized in three categories: (i) endogenous, (ii) synthetic, and (iii) phytocannabinoids, and are able to modulate the CBR and ECS. Particularly, phytocannabinoids are natural terpenoids or phenolic compounds derived from Cannabis sativa. However, these terpenoids and phenolic compounds can also be derived from other plants (non-cannabinoids) and still induce cannabinoid-like properties. Cannabimimetic ligands, beyond the Cannabis plant, can act as CBR agonists or antagonists, or ECS enzyme inhibitors, besides being able of playing a role in immune-mediated inflammatory and infectious diseases, neuroinflammatory, neurological, and neurodegenerative diseases, as well as in cancer, and autoimmunity by itself. In this review, we summarize and critically highlight past, present, and future progress on the understanding of the role of cannabinoid-like molecules, mainly terpenes, as prospective therapeutics for different pathological conditions.

Involvement of Metabolic Lipid Mediators in the Regulation of Apoptosis

Apoptosis is the physiological mechanism of cell death and can be modulated by endogenous and exogenous factors, including stress and metabolic alterations. Reactive oxygen species (ROS), as well as ROS-dependent lipid peroxidation products (including isoprostanes and reactive aldehydes including 4-hydroxynonenal) are proapoptotic factors. These mediators can activate apoptosis via mitochondrial-, receptor-, or ER stress-dependent pathways. Phospholipid metabolism is also an essential regulator of apoptosis, producing the proapoptotic prostaglandins of the PGD and PGJ series, as well as the antiapoptotic prostaglandins of the PGE series, but also 12-HETE and 20-HETE. The effect of endocannabinoids and phytocannabinoids on apoptosis depends on cell type-specific differences. Cells where cannabinoid receptor type 1 (CB1) is the dominant cannabinoid receptor, as well as cells with high cyclooxygenase (COX) activity, undergo apoptosis after the administration of cannabinoids. In contrast, in cells where CB2 receptors dominate, and cells with low COX activity, cannabinoids act in a cytoprotective manner. Therefore, cell type-specific differences in the pro- and antiapoptotic effects of lipids and their (oxidative) products might reveal new options for differential bioanalysis between normal, functional, and degenerating or malignant cells, and better integrative biomedical treatments of major stress-associated diseases.

Cryo-EM Structure of the Human Cannabinoid Receptor CB2-Gi Signaling Complex

Drugs selectively targeting CB2 hold promise for treating neurodegenerative disorders, inflammation, and pain while avoiding psychotropic side effects mediated by CB1. The mechanisms underlying CB2 activation and signaling are poorly understood but critical for drug design. Here we report the cryo-EM structure of the human CB2-G_i signaling complex bound to the agonist WIN 55,212-2. The 3D structure reveals the binding mode of WIN 55,212-2 and structural determinants for distinguishing CB2 agonists from antagonists, which are supported by a pair of rationally designed agonist and antagonist. Further structural analyses with computational docking results uncover the differences between CB2 and CB1 in receptor activation, ligand recognition, and G_i coupling. These findings are expected to facilitate rational structure-based discovery of drugs targeting the cannabinoid system.

Circulating Endocannabinoids and Mortality in Hemodialysis Patients

BACKGROUND

Mortality in patients with end-stage renal disease (ESRD) on maintenance hemodialysis (MHD) remains exceptionally high. While traditional risk factors such as obesity are paradoxically associated with better survival, nontraditional risk factors including cachexia increase the likelihood of poor outcomes. There is accumulating evidence that the endocannabinoid (ECB) system plays a major role in energy preservation and storage, factors which can prevent the deleterious effects of cachexia. Hence, in this study, we evaluated the association of circulating ECB levels with mortality in MHD patients.

METHODS

Serum concentrations of anandamide (AEA) and 2-arachidonoyl-sn-glycerol (2-AG), major ECB ligands, were measured in MHD patients. Their correlation with various clinical/laboratory indices and association with 12-month all-cause mortality were examined.

RESULTS

Serum 2-AG levels positively correlated with body mass index, serum triglycerides and body anthropometric measures. Meanwhile, serum AEA levels correlated positively with serum interleukin-6, and negatively with serum very low-density lipoprotein levels. While increased serum 2-AG levels were associated with reduced risk of all-cause mortality (hazard ratio [HR] 0.52, 95% CI 0.28-0.98), there was no clear association between serum AEA levels and mortality (HR 0.91, 95% CI 0.48-1.72).

CONCLUSIONS

In MHD patients, the circulating levels of ECB ligand, 2-AG, may play an important role in determining body mass and risk of mortality. These observations were unique to 2-AG as similar findings were not obtained with serum AEA. Future studies need to investigate the mechanisms responsible for these associations and examine the modulation of the ECB system as a potential target for therapy in ESRD.

Probing thermostability of detergent-solubilized CB2 receptor by parallel G protein-activation and ligand-binding assays

G protein-coupled receptors (GPCRs) comprise a large class of integral membrane proteins involved in the regulation of a broad spectrum of physiological processes and are a major target for pharmaceutical drug development. Structural studies can help advance the rational design of novel specific pharmaceuticals that target GPCRs, but such studies require expression of significant quantities of these proteins in pure, homogenous, and sufficiently stable form. An essential precursor for these structural studies is an assessment of protein stability under experimental conditions. Here we report that solubilization of a GPCR, type II cannabinoid receptor CB2, in a Façade detergent enables radioligand thermostability assessments of this receptor with low background from nonspecific interactions with lipophilic cannabinoid ligand. Furthermore, this detergent is compatible with a [35S]GTPγS radionucleotide exchange assay measuring guanine exchange factor activity that can be applied after heat treatment to further assess receptor thermostability. We demonstrate that both assays can be utilized to determine differences in CB2 thermostability caused by mutations, detergent composition, and the presence of stabilizing ligands. We report that a constitutively active CB2 variant has higher thermostability than the WT receptor, a result that differs from a previous thermostability assessment of the analogous CB1 mutation. We conclude that both ligand-binding and activity-based assays under optimized detergent conditions can support selection of thermostable variants of experimentally demanding GPCRs.

In vitro determination of the efficacy of illicit synthetic cannabinoids at CB1 receptors

BACKGROUND AND PURPOSE

The morbidity and mortality associated with recreational use of synthetic cannabinoid receptor agonists (SCRAs) may reflect strong activation of CB₁ receptors and is a major health concern. The properties of SCRA at CB₁ receptors are not well defined. Here we have developed an assay to determine acute CB₁ receptor efficacy using receptor depletion with the irreversible CB₁ receptor antagonist AM6544, with application of the Black and Leff operational model to calculate efficacy.

EXPERIMENTAL APPROACH

Receptor depletion in mouse AtT-20 pituitary adenoma cells stably expressing human CB₁ receptors was achieved by pretreatment of cells with AM6544 (10 μM, 60 min). The CB₁ receptor-mediated hyperpolarisation of AtT-20 cells was measured using fluorescence-based membrane potential dye. From data fit to the operational model, the efficacy (τ) and affinity (K_A ) parameters were obtained for each drug.

KEY RESULTS

AM6544 did not affect the potency or maximal effect of native somatostatin receptor-induced hyperpolarization. The τ value of ∆⁹ -THC was 80-fold less than the reference CB receptor agonist CP55940 and 260-fold less than the highest efficacy SCRA, 5F-MDMB-PICA. The operational efficacy of SCRAs ranged from 233 (5F-MDMB-PICA) to 28 (AB-PINACA), with CP55940 in the middle of the efficacy rank order. There was no correlation between the τ and K_A values.

CONCLUSIONS AND IMPLICATIONS

All SCRAs tested showed substantially higher efficacy at CB₁ receptors than ∆⁹ -THC, which may contribute to the adverse effects seen with these drugs but not ∆⁹ -THC.

Comparative studies of endocannabinoid modulation of pain

Cannabinoid-based therapies have long been used to treat pain, but there remain questions about their actual mechanisms and efficacy. From an evolutionary perspective, the cannabinoid system would appear to be highly conserved given that the most prevalent endogenous cannabinoid (endocannabinoid) transmitters, 2-arachidonyl glycerol and anandamide, have been found throughout the animal kingdom, at least in the species that have been analysed to date. This review will first examine recent findings regarding the potential conservation across invertebrates and chordates of the enzymes responsible for endocannabinoid synthesis and degradation and the receptors that these transmitters act on. Next, comparisons of how endocannabinoids modulate nociception will be examined for commonalities between vertebrates and invertebrates, with a focus on the medicinal leech Hirudo verbana. Evidence is presented that there are distinct, evolutionarily conserved anti-nociceptive and pro-nociceptive effects. The combined studies across various animal phyla demonstrate the utility of using comparative approaches to understand conserved mechanisms for modulating nociception. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.

Roles of the Hepatic Endocannabinoid and Apelin Systems in the Pathogenesis of Liver Fibrosis

Hepatic fibrosis is the consequence of an unresolved wound healing process in response to chronic liver injury and involves multiple cell types and molecular mechanisms. The hepatic endocannabinoid and apelin systems are two signalling pathways with a substantial role in the liver fibrosis pathophysiology-both are upregulated in patients with advanced liver disease. Endogenous cannabinoids are lipid-signalling molecules derived from arachidonic acid involved in the pathogenesis of cardiovascular dysfunction, portal hypertension, liver fibrosis, and other processes associated with hepatic disease through their interactions with the CB₁ and CB₂ receptors. Apelin is a peptide that participates in cardiovascular and renal functions, inflammation, angiogenesis, and hepatic fibrosis through its interaction with the APJ receptor. The endocannabinoid and apelin systems are two of the multiple cell-signalling pathways involved in the transformation of quiescent hepatic stellate cells into myofibroblast like cells, the main matrix-producing cells in liver fibrosis. The mechanisms underlying the control of hepatic stellate cell activity are coincident despite the marked dissimilarities between the endocannabinoid and apelin signalling pathways. This review discusses the current understanding of the molecular and cellular mechanisms by which the hepatic endocannabinoid and apelin systems play a significant role in the pathophysiology of liver fibrosis.

Do Toxic Synthetic Cannabinoid Receptor Agonists Have Signature in Vitro Activity Profiles? A Case Study of AMB-FUBINACA

Recreational consumption of synthetic cannabinoid receptor agonists (SCRAs) is a growing crisis in public health in many parts of the world. AMB-FUBINACA is a member of this class of drugs and is responsible for a large proportion of SCRA-related toxicity both in New Zealand and internationally. Strikingly, little is currently known about the mechanisms by which SCRAs exert toxic effects or whether their activity through the CB1 cannabinoid receptor (the mediator of cannabinoid-related psychoactivity) is sufficient to explain clinical observations. The current study therefore set out to perform a basic molecular pharmacology characterization of AMB-FUBINACA (in comparison to traditional research cannabinoids CP55,940, WIN55,212-2, and Δ9-THC) in fundamental pathways of receptor activity, including cAMP inhibition, pERK activation, ability to drive CB1 internalization, and ability to induce translocation of β-arrestins-1 and -2. Activity pathways were then compared by operational analysis to indicate whether AMB-FUBINACA may be a biased ligand. Results revealed that AMB-FUBINACA is highly efficacious and potent in all pathways assayed. However, surprisingly, bias analysis suggested that Δ9-THC, not AMB-FUBINACA, may be a biased ligand, with it being less active in both arrestin pathways than predicted by the activity of the other ligands tested. These data may help predict molecular characteristics of SCRAs. However, more research is required to determine whether these molecular effects manifest in toxicity at tissue/system level.

Beyond THC and Endocannabinoids

Research in the cannabinoid field, namely on phytocannabinoids, the endogenous cannabinoids anandamide and 2-arachidonoyl glycerol and their metabolizing and synthetic enzymes, the cannabinoid receptors, and anandamide-like cannabinoid compounds, has expanded tremendously over the last few years. Numerous endocannabinoid-like compounds have been discovered. The Cannabis plant constituent cannabidiol (CBD) was found to exert beneficial effects in many preclinical disease models ranging from epilepsy, cardiovascular disease, inflammation, and autoimmunity to neurodegenerative and kidney diseases and cancer. CBD was recently approved in the United States for the treatment of rare forms of childhood epilepsy. This has triggered the development of many CBD-based products for human use, often with overstated claims regarding their therapeutic effects. In this article, the recently published research on the chemistry and biological effects of plant cannabinoids (specifically CBD), endocannabinoids, certain long-chain fatty acid amides, and the variety of relevant receptors is critically reviewed.

Brodifacoum does not modulate human cannabinoid receptor-mediated hyperpolarization of AtT20 cells or inhibition of adenylyl cyclase in HEK 293 cells

Background

Synthetic cannabinoids are a commonly used class of recreational drugs that can have significant adverse effects. There have been sporadic reports of co-consumption of illicit drugs with rodenticides such as warfarin and brodifacoum (BFC) over the past 20 years but recently, hundreds of people have been reported to have been poisoned with a mixture of synthetic cannabinoids and BFC. We have sought to establish whether BFC directly affects cannabinoid receptors, or their activation by the synthetic cannabinoid CP55940 or the phytocannabinoid Δ⁹-tetrahydrocannabinol (Δ⁹-THC).

Methods

The effects of BFC on the hyperpolarization of wild type AtT20 cells, or AtT20 cells stably expressing human CB₁- or CB₂- receptors, were studied using a fluorescent assay of membrane potential. The effect of BFC on CB₁- and CB₂-mediated inhibition of forskolin-stimulated adenylyl cyclase (AC) activation was measured using a BRET assay of cAMP levels in HEK 293 cells stably expressing human CB₁ or CB₂.

Results

BFC did not activate CB₁ or CB₂ receptors, or affect the hyperpolarization of wild type AtT20 cells produced by somatostatin. BFC (1 µM) did not affect the hyperpolarization of AtT20-CB₁ or AtT20-CB₂ cells produced by CP55940 or Δ⁹-THC. BFC (1 µM) did not affect the inhibition of forskolin-stimulated AC activity by CP55940 in HEK 293 cells expressing CB₁ or CB₂. BFC (1 µM) also failed to affect the desensitization of CB₁ and CB₂ signaling produced by prolonged (30 min) application of CP55940 or Δ⁹-THC to AtT20 cells.

Discussion

BFC is not a cannabinoid receptor agonist, and appeared not to affect cannabinoid receptor activation. Our data suggests there is no pharmacodynamic rationale for mixing BFC with synthetic cannabinoids; however, it does not speak to whether BFC may affect synthetic cannabinoid metabolism or biodistribution. The reasons underlying the mixing of BFC with synthetic cannabinoids are unknown, and it remains to be established whether the “contamination” was deliberate or accidental. However, the consequences for people who ingested the mixture were often serious, and sometimes fatal, but this seems unlikely to be due to BFC action at cannabinoid receptors.

Absence of Entourage: Terpenoids Commonly Found in Cannabis sativa Do Not Modulate the Functional Activity of Δ9-THC at Human CB1 and CB2 Receptors

Introduction: Compounds present in Cannabis sativa such as phytocannabinoids and terpenoids may act in concert to elicit therapeutic effects. Cannabinoids such as Δ9-tetrahydrocannabinol (Δ9-THC) directly activate cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2); however, it is not known if terpenoids present in Cannabis also affect cannabinoid receptor signaling. Therefore, we examined six common terpenoids alone, and in combination with cannabinoid receptor agonists, on CB1 and CB2 signaling in vitro. Materials and Methods: Potassium channel activity in AtT20 FlpIn cells transfected with human CB1 or CB2 receptors was measured in real time using FLIPR® membrane potential dye in a FlexStation 3 plate reader. Terpenoids were tested individually and in combination for periods up to 30 min. Endogenous somatostatin receptors served as a control for direct effects of drugs on potassium channels. Results: α-Pinene, β-pinene, β-caryophyllene, linalool, limonene, and β-myrcene (up to 30-100 μM) did not change membrane potential in AtT20 cells expressing CB1 or CB2, or affect the response to a maximally effective concentration of the synthetic cannabinoid CP55,940. The presence of individual or a combination of terpenoids did not affect the hyperpolarization produced by Δ9-THC (10 μM): (CB1: control, 59%±7%; with terpenoids (10 μM each) 55%±4%; CB2: Δ9-THC 16%±5%, with terpenoids (10 μM each) 17%±4%). To investigate possible effect on desensitization of CB1 responses, all six terpenoids were added together with Δ9-THC and signaling measured continuously over 30 min. Terpenoids did not affect desensitization, after 30 min the control hyperpolarization recovered by 63%±6% in the presence of the terpenoids recovery was 61%±5%. Discussion: None of the six of the most common terpenoids in Cannabis directly activated CB1 or CB2, or modulated the signaling of the phytocannabinoid agonist Δ9-THC. These results suggest that if a phytocannabinoid-terpenoid entourage effect exists, it is not at the CB1 or CB2 receptor level. It remains possible that terpenoids activate CB1 and CB2 signaling pathways that do not involve potassium channels; however, it seems more likely that they may act at different molecular target(s) in the neuronal circuits important for the behavioral effect of Cannabis.

Discovery of Orexant and Anorexant Agents with Indazole Scaffold Endowed with Peripheral Antiedema Activity

The endocannabinoid system represents an integrated neuronal network involved in the control of several organisms' functions, such as feeding behavior. A series of hybrids of 5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide (mimonabant), a well-known inverse agonist of the type-1 cannabinoid receptor (CB1), once used as an antiobesity drug, and the N-(2S)-substitutes of 1-[(4-fluorophenyl)methyl]indazole-3-carboxamide with 1-amino-3-methyl-1-oxobutane (AB-Fubinaca), 1-amino-3,3-dimethyl-1-oxobutane (ADB-Fubinaca), and 3-methylbutanoate (AMB-Fubinaca), endowed with potent agonistic activity towards cannabinoid receptors CB1 and CB2 were in solution as C-terminal amides, acids, methyl esters and N-methyl amides. These compounds have been studied by binding assays to cannabinoid receptors and by functional receptor assays, using rat brain membranes in vitro. The most active among them as an agonist, (S)-1-(2,4-dichlorobenzyl)-N-(3,3-dimethyl-1-(methylamino)-1-oxobutan-2-yl)-1H-indazole-3-carboxamide (LONI11), and an antagonist, (S)-2-(1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxamido)-3-methylbutanoic acid (LONI4), were tested in vivo in mic, to evaluate their ability to stimulate or suppress feeding behavior after intraperitoneal (i.p.) administration. For a LONI11 formalin test and a tail flick test after an administration by the subcutaneous (s.c.) and intracerebroventricular (i.c.v.) routes, respectively, were also carried out in vivo in mice to investigate the antinociceptive property at the central and peripheral levesl. We observed a significant orexant effect for LONI11 and an intense anorexant effect for (S)-methyl 2-(1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxamido)-3,3-dimethylbutanoate (LONI2) and LONI4. In zymosan-induced edema and hyperalgesia, LONI11 reduced the percent of paw volume increase and paw latency after s.c. administration, also suggesting a possible peripheral anti-inflammatory activity.

Innovative Therapeutic Potential of Cannabinoid Receptors as Targets in Alzheimer’s Disease and Less Well-Known Diseases

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The discovery of cannabinoid receptors at the beginning of the 1990s, CB1 cloned in 1990 and CB2 cloned in 1993, and the availability of selective and potent cannabimimetics could only be justified by the existence of endogenous ligands that are capable of binding to them. Thus, the characterisation and cloning of the first cannabinoid receptor (CB1) led to the isolation and characterisation of the first endocannabinoid, arachidonoylethanolamide (AEA), two years later and the subsequent identification of a family of lipid transmitters known as the fatty acid ester 2-arachidonoylglycerol (2-AG).

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The endogenous cannabinoid system is a complex signalling system that comprises transmembrane endocannabinoid receptors, their endogenous ligands (the endocannabinoids), the specific uptake mechanisms and the enzymatic systems related to their biosynthesis and degradation.

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The endocannabinoid system has been implicated in a wide diversity of biological processes, in both the central and peripheral nervous systems, including memory, learning, neuronal development, stress and emotions, food intake, energy regulation, peripheral metabolism, and the regulation of hormonal balance through the endocrine system.

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In this context, this article will review the current knowledge of the therapeutic potential of cannabinoid receptor as a target in Alzheimer’s disease and other less well-known diseases that include, among others, multiple sclerosis, bone metabolism, and Fragile X syndrome.

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The therapeutic applications will be addressed through the study of cannabinoid agonists acting as single drugs and multi-target drugs highlighting the CB2 receptor agonist.

Comprehensive investigation on synthetic cannabinoids: Metabolic behavior and potency testing, using 5F-APP-PICA and AMB-FUBINACA as model compounds

Synthetic cannabinoids (SCs) represented 45% of new psychoactive substances seizures in Europe (data from 2016). The consumption of SCs is an issue of concern due to their still unknown toxicity and effects on human health, the great variety of compounds synthetized, and the continuous modifications being made to their chemical structure to avoid regulatory issues. These compounds are extensively metabolized in the organism and often cannot be detected as the intact molecule in human urine. The monitoring of SCs in forensic samples must be performed by the analysis of their metabolites. In this work, a workflow for the comprehensive study of SC consumption is proposed and applied to 5F-APP-PICA (also known as PX 1 or SRF-30) and AMB-FUBINACA (also known as FUB-AMB or MMB-FUBINACA), based not only on the elucidation of their metabolites but also including functional data using the NanoLuc approach, previously published. Both cannabinoids were completely metabolized by human hepatocytes (12 and 8 metabolites were elucidated by high resolution mass spectrometry for 5F-APP-PICA and AMB-FUBINACA, respectively) and therefore suitable consumption markers are proposed. The bioassays revealed that 5F-APP-PICA presented lower activity than AMB-FUBINACA at CB1 and CB2 receptors, based on the half maximal effective concentration (EC₅₀ ) and the maximum response (E_max ). These results are in agreement with the different intoxication cases found in the literature for AMB-FUBINACA.

Advances in the Understanding of the Cannabinoid Receptor 1 – Focusing on the Inverse Agonists Interactions

Background:

Cannabinoid Receptor 1 (CB1) is a membrane protein prevalent in the central nervous system, whose crystallographic structure has recently been solved. Studies will be needed to investigate CB1 complexes with its ligands and its role in the development of new drugs.

Objective:

Our goal here is to review the studies on CB1, starting with general aspects and focusing on the recent structural studies, with emphasis on the inverse agonists bound structures.

Methods:

We start with a literature review, and then we describe recent studies on CB 1 crystallographic structure and docking simulations. We use this structural information to depict protein-ligand interactions. We also describe the molecular docking method to obtain complex structures of CB 1 with inverse agonists.

Results:

Analysis of the crystallographic structure and docking results revealed the residues responsible for the specificity of the inverse agonists for CB 1. Most of the intermolecular interactions involve hydrophobic residues, with the participation of the residues Phe 170 and Leu 359 in all complex structures investigated in the present study. For the complexes with otenabant and taranabant, we observed intermolecular hydrogen bonds involving residues His 178 (otenabant) and Thr 197 and Ser 383 (taranabant).

Conclusion:

Analysis of the structures involving inverse agonists and CB 1 revealed the pivotal role played by residues Phe 170 and Leu 359 in their interactions and the strong intermolecular hydrogen bonds highlighting the importance of the exploration of intermolecular interactions in the development of novel inverse agonists.

Structural bioinformatics analysis of variants on GPCR function

G protein-coupled receptors (GPCRs) are key membrane-embedded receptor proteins, with critical roles in cellular signal transduction. In the era of precision medicine, understanding the role of natural variants on GPCR function is critical, especially from a pharmacogenomics viewpoint. Studies involved in mapping variants to GPCR structures are briefly reviewed here. The endocannabinoid system involving the central nervous system (CNS), the human cannabinoid receptor 1 (CB1), is an important drug target and its variability has implications for disease susceptibility and altered drug and pain response. We have carried out a computational study to map deleterious non-synonymous single nucleotide polymorphisms (nsSNPs) to CB1. CB1 mutations were computationally evaluated from neutral to deleterious, and the top twelve deleterious mutations, with structural information, were found to be either close to the ligand binding region or the G-protein binding site. We have mapped these to the active and inactive CB1 X-ray crystallographic structures to correlate variants with available phenotypic information. We have also carried out molecular dynamics simulations to functionally characterize four selected mutants.

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).

Enantiospecific Synthesis, Chiral Separation, and Biological Activity of Four Indazole-3-Carboxamide-Type Synthetic Cannabinoid Receptor Agonists and Their Detection in Seized Drug Samples

Synthetic cannabinoid receptor agonists (SCRAs) have been the largest group of illicit psychoactive substances reported to international monitoring and early warning systems for many years. Carboxamide-type SCRAs are amongst the most prevalent and potent. Enantiospecific synthesis and characterization of four indazole-3-carboxamides, AMB-FUBINACA, AB-FUBINACA, 5F-MDMB-PINACA (5F-ADB), and AB-CHMINACA is reported. The interactions of the compounds with CB1 and CB2 receptors were investigated using a G-protein coupled receptor (GPCR) activation assay based on functional complementation of a split NanoLuc luciferase and EC50 (a measure of potency) and Emax (a measure of efficacy) values determined. All compounds demonstrated higher potency at the CB2 receptor than at the CB1 receptor and (S)-enantiomers had an enhanced potency to both receptors over the (R)-enantiomers. The relative potency of the enantiomers to the CB2 receptor is affected by structural features. The difference was more pronounced for compounds with an amine moiety (AB-FUBINACA and AB-CHMINACA) than those with an ester moiety (AMB-FUBINACA and 5F-MDMB-PINACA). An HPLC method was developed to determine the prevalence of (R)-enantiomers in seized samples. Lux® Amylose-1 [Amylose tris(3,5-dimethylphenylcarbamate)] has the greatest selectivity for the SCRAs with a terminal methyl ester moiety and a Lux® i-Cellulose-5 column for SCRAs with a terminal amide moiety. Optimized isocratic separation methods yielded enantiomer resolution values (Rs) ≥ 1.99. Achiral GC-MS analysis of seized herbal materials (n = 16), found 5F-MDMB-PINACA (<1.0-91.5 mg/g herbal material) and AMB-FUBINACA (15.5-58.5 mg/g herbal material), respectively. EMB-FUBINACA, AMB-CHMICA, 5F-ADB-PINACA isomer 2, and ADB-CHMINACA were also tentatively identified. Analysis using chiral chromatography coupled to photodiode array and quadrupole time of flight mass spectrometry (chiral HPLC-PDA-QToF-MS/MS) confirmed that the (S)-enantiomer predominated in all samples (93.6-99.3% (S)-enantiomer). Small but significant differences in synthesis precursor enantiopurity may provide significant differences between synthesis batches or suppliers and warrants further study. A method to compare potency between samples containing different SCRAs at varying concentrations was developed and applied in this small preliminary study. A 10-fold difference in the "intrinsic" potency of samples in the study was noted. With the known heterogeneity of SCRA infused materials, the approach provides a simplified method for assessing and communicating the risk of their use.

Dark Classics in Chemical Neuroscience: Δ9-Tetrahydrocannabinol

Cannabis ( Cannabis sativa) is the most widely used illicit drug in the world, with an estimated 192 million users globally. The main psychoactive component of cannabis is (-)- trans-Δ⁹-tetrahydrocannabinol (Δ⁹-THC), a compound with a diverse range of pharmacological actions. The unique and distinctive intoxication caused by Δ⁹-THC primarily reflects partial agonist action at central cannabinoid type 1 (CB₁) receptors. Δ⁹-THC is an approved therapeutic treatment for a range of conditions, including chronic pain, chemotherapy-induced nausea and vomiting, and multiple sclerosis, and is being investigated in indications such as anorexia nervosa, agitation in dementia, and Tourette's syndrome. It is available as a regulated pharmaceutical in products such as Marinol, Sativex, and Namisol as well as in an ever-increasing range of unregistered medicinal and recreational cannabis products. While cannabis is an ancient medicament, contemporary use is embroiled in legal, scientific, and social controversy, much of which relates to the potential hazards and benefits of Δ⁹-THC itself. Robust contemporary debate surrounds the therapeutic value of Δ⁹-THC in different diseases, its capacity to produce psychosis and cognitive impairment, and the addictive and "gateway" potential of the drug. This review will provide a profile of the chemistry, pharmacology, and therapeutic uses of Δ⁹-THC as well as the historical and societal import of this unique, distinctive, and ubiquitous psychoactive substance.

Cannabinoid CB1 and CB2 Receptor-Mediated Arrestin Translocation: Species, Subtype, and Agonist-Dependence

Arrestin translocation and signaling have come to the fore of the G protein-coupled receptor molecular pharmacology field. Some receptor–arrestin interactions are relatively well understood and considered responsible for specific therapeutic or adverse outcomes. Coupling of arrestins with cannabinoid receptors 1 (CB₁) and 2 (CB₂) has been reported, though the majority of studies have not systematically characterized the differential ligand dependence of this activity. In addition, many prior studies have utilized bovine (rather than human) arrestins, and the most widely applied assays require reporter-tagged receptors, which prevent meaningful comparison between receptor types. We have employed a bioluminescence resonance energy transfer (BRET) method that does not require the use of tagged receptors and thereby allows comparisons of arrestin translocation between receptor types, as well as with cells lacking the receptor of interest – an important control. The ability of a selection of CB₁ and CB₂ agonists to stimulate cell surface translocation of human and bovine β-arrestin-1 and -2 was assessed. We find that some CB₁ ligands induce moderate β-arrestin-2 translocation in comparison with vasopressin V₂ receptor (a robust arrestin recruiter); however, CB₁ coupling with β-arrestin-1 and CB₂ with either arrestin elicited low relative efficacies. A range of efficacies between ligands was evident for both receptors and arrestins. Endocannabinoid 2-arachidonoylglycerol stood out as a high efficacy ligand for translocation of β-arrestin-2 via CB₁. Δ⁹-tetrahydrocannabinol was generally unable to elicit translocation of either arrestin subtype via CB₁ or CB₂; however, control experiments revealed translocation in cells not expressing CB₁/CB₂, which may assist in explaining some discrepancy with the literature. Overexpression of GRK2 had modest influence on CB₁/CB₂-induced arrestin translocation. Results with bovine and human arrestins were largely analogous, but a few instances of inconsistent rank order potencies/efficacies between bovine and human arrestins raise the possibility that subtle differences in receptor conformation stabilized by these ligands manifest in disparate affinities for the two arrestin species, with important potential consequences for interpretation in ligand bias studies. As well as contributing important information regarding CB₁/CB₂ ligand-dependent arrestin coupling, our study raises a number of points for consideration in the design and interpretation of arrestin recruitment assays.

Hepatic microcirculation and mechanisms of portal hypertension

The liver microcirculatory milieu, mainly composed of liver sinusoidal endothelial cells (LSECs), hepatic stellate cells (HSCs) and hepatic macrophages, has an essential role in liver homeostasis, including in preserving hepatocyte function, regulating the vascular tone and controlling inflammation. Liver microcirculatory dysfunction is one of the key mechanisms that promotes the progression of chronic liver disease (also termed cirrhosis) and the development of its major clinical complication, portal hypertension. In the present Review, we describe the current knowledge of liver microcirculatory dysfunction in cirrhotic portal hypertension and appraise the preclinical models used to study the liver circulation. We also provide a comprehensive summary of the promising therapeutic options to target the liver microvasculature in cirrhosis.

Cannabinoid Signaling in the Skin: Therapeutic Potential of the "C(ut)annabinoid" System

The endocannabinoid system (ECS) has lately been proven to be an important, multifaceted homeostatic regulator, which influences a wide-variety of physiological processes all over the body. Its members, the endocannabinoids (eCBs; e.g., anandamide), the eCB-responsive receptors (e.g., CB₁, CB₂), as well as the complex enzyme and transporter apparatus involved in the metabolism of the ligands were shown to be expressed in several tissues, including the skin. Although the best studied functions over the ECS are related to the central nervous system and to immune processes, experimental efforts over the last two decades have unambiguously confirmed that cutaneous cannabinoid ("c[ut]annabinoid") signaling is deeply involved in the maintenance of skin homeostasis, barrier formation and regeneration, and its dysregulation was implicated to contribute to several highly prevalent diseases and disorders, e.g., atopic dermatitis, psoriasis, scleroderma, acne, hair growth and pigmentation disorders, keratin diseases, various tumors, and itch. The current review aims to give an overview of the available skin-relevant endo- and phytocannabinoid literature with a special emphasis on the putative translational potential, and to highlight promising future research directions as well as existing challenges.

Translational potential of allosteric modulators targeting the cannabinoid CB1 receptor

The cannabinoid type-1 (CB1) receptor, a G-protein-coupled receptor, is an attractive target for drug discovery due to its involvement in many physiological processes. Historically, drug discovery efforts targeting the CB1 receptor have focused on the development of orthosteric ligands that interact with the active site to which endogenous cannabinoids bind. Research performed over the last several decades has revealed substantial difficulties in translating CB1 orthosteric ligands into druggable candidates. The difficulty is mainly due to the adverse effects associated with orthosteric CB1 ligands. Recent discoveries of allosteric CB1 modulators provide tremendous opportunities to develop CB1 ligands with novel mechanisms of action; these ligands may potentially improve the pharmacological effects and enhance drug safety in treating the disorders by regulating the functions of the CB1 receptor. In this paper, we review and summarize the complex pharmacological profiles of each class of CB1 allosteric modulators, the development of new classes of CB1 allosteric modulators and the results from in vivo assessments of their therapeutic value.

Progress in brain cannabinoid CB2 receptor research: From genes to behavior

The type 2 cannabinoid receptor (CB2R) was initially regarded as a peripheral cannabinoid receptor. However, recent technological advances in gene detection, alongside the availability of transgenic mouse lines, indicate that CB2Rs are expressed in both neurons and glial cells in the brain under physiological and pathological conditions, and are involved in multiple functions at cellular and behavioral levels. Brain CB2Rs are inducible and neuroprotective via up-regulation in response to various insults, but display species differences in gene and receptor structures, CB2R expression, and receptor responses to various CB2R ligands. CB2R transcripts also differ between the brain and spleen. In the brain, CB2A is the major transcript isoform, while CB2A and CB2B transcripts are present at higher levels in the spleen. These new findings regarding brain versus spleen CB2R isoforms may in part explain why early studies failed to detect brain CB2R gene expression. Here, we review evidence supporting the expression and function of brain CB2R from gene and receptor levels to cellular functioning, neural circuitry, and animal behavior.

Functional characterization of the cannabinoid receptors 1 and 2 in zebrafish larvae using behavioral analysis

RATIONALE

The endocannabinoid system (ECS) comprises the cannabinoids anandamide and 2-arachidonoylglycerol and the cannabinoid receptors 1 and 2 (Cnr1 and Cnr2). The function of these receptors in relation to zebrafish larval behavior is poorly understood, even though the zebrafish larva has become a versatile animal model in biomedical research.

OBJECTIVES

The objective of the present study is to characterize the function of Cnr1 and Cnr2 in relation to behavior in zebrafish.

METHODS

Behavioral analysis of zebrafish larvae was performed using a visual motor response (VMR) test, which allows locomotor activity to be determined under basal conditions and upon a dark challenge.

RESULTS

Treatment with the non-specific Cnr agonists WIN55,212-2 and CP55,940 resulted in a decrease in locomotion. This was observed for both basal and challenge-induced locomotion, although the potency for these two effects was different, which suggests different mechanisms of action. In addition, WIN55,212-2 increased the reaction time of the startle response after the dark challenge. Using the Cnr1 antagonist AM251 and a cnr1^-/- mutant line, it was shown that the effects were mediated by Cnr1 and not Cnr2. Interestingly, administration of the antagonist AM251 alone does not have an effect on locomotion, which indicates that endogenous cannabinoid activity does not affect locomotor activity of zebrafish larvae. Upon repeated dark challenges, the WIN55,212-2 effect on the locomotor activity decreased, probably due to desensitization of Cnr1.

CONCLUSIONS

Taken together, these results show that Cnr1 activation by exogenous endocannabinoids modulates both basal and challenge-induced locomotor activity in zebrafish larvae and that these behavioral effects can be used as a readout to monitor the Cnr1 responsiveness in the zebrafish larva model system.

A pharmacoinformatic approach on Cannabinoid receptor 2 (CB2) and different small molecules: Homology modelling, molecular docking, MD simulations, drug designing and ADME analysis

CB2 receptor belongs to the family of G-protein coupled receptors (GPCRs), which extensively controls a range of pointer transduction. CB2 plays an essential role in the immune system. It also associates in the pathology of different ailment conditions. In this scenario, the synthetic drugs are inducing side effects to the human beings after the drug use. Therefore, this study is seeking novel alternate drug molecules with least side effects than conventional drugs. The alternative drug molecules were chosen from the natural sources. These molecules were selected from cyanobacteria with the help of earlier research findings. The target and ligand molecules were obtained from recognized databases. The bioactive molecules are selected from various cyanobacterial species, which are selected by their biological and pharmacological properties, after, which we incorporated to the crucial findings such as homology modelling, molecular docking, MD simulations along with absorption, distribution, metabolism, and excretion (ADME) analysis. Initially, the homology modelling was performed to frame the target from unknown sequences of CB2, which revealed 44% of similarities and 66% of identities with the A2A receptor. Subsequently, the CB2 protein molecule has docked with already known and prepared bioactive molecules, agonists and antagonist complex. In the present study, the agonists (5) and antagonist (1) were also taken for comparing the results with natural molecules. At the end of the docking analysis, the cyanobacterial molecules and an antagonist TNC-201 are revealed better docking scores with well binding contacts than the agonists. Especially, the usneoidone shows better results than other cyanobacterial molecules, and it is very close docking scores with that of TCN-201. Therefore, the usneoidone has incorporated to MD simulation with Cannabinoid receptors 2 (CB2). In MD simulations, the complex (CB2 and usneoidone) reveals better stability in 30 ns. Based on the computational outcome, we concluded that usneoidone is an effectual and appropriate drug candidate for activating CB2 receptors and it will be serving as a better component for the complications of CB2. Moreover, these computational approaches can be motivated to discover novel drug candidates in the pharmacological and healthcare sectors.

Cannabinoids and Pain: New Insights From Old Molecules

Cannabis has been used for medicinal purposes for thousands of years. The prohibition of cannabis in the middle of the 20th century has arrested cannabis research. In recent years there is a growing debate about the use of cannabis for medical purposes. The term ‘medical cannabis’ refers to physician-recommended use of the cannabis plant and its components, called cannabinoids, to treat disease or improve symptoms. Chronic pain is the most commonly cited reason for using medical cannabis. Cannabinoids act via cannabinoid receptors, but they also affect the activities of many other receptors, ion channels and enzymes. Preclinical studies in animals using both pharmacological and genetic approaches have increased our understanding of the mechanisms of cannabinoid-induced analgesia and provided therapeutical strategies for treating pain in humans. The mechanisms of the analgesic effect of cannabinoids include inhibition of the release of neurotransmitters and neuropeptides from presynaptic nerve endings, modulation of postsynaptic neuron excitability, activation of descending inhibitory pain pathways, and reduction of neural inflammation. Recent meta-analyses of clinical trials that have examined the use of medical cannabis in chronic pain present a moderate amount of evidence that cannabis/cannabinoids exhibit analgesic activity, especially in neuropathic pain. The main limitations of these studies are short treatment duration, small numbers of patients, heterogeneous patient populations, examination of different cannabinoids, different doses, the use of different efficacy endpoints, as well as modest observable effects. Adverse effects in the short-term medical use of cannabis are generally mild to moderate, well tolerated and transient. However, there are scant data regarding the long-term safety of medical cannabis use. Larger well-designed studies of longer duration are mandatory to determine the long-term efficacy and long-term safety of cannabis/cannabinoids and to provide definitive answers to physicians and patients regarding the risk and benefits of its use in the treatment of pain. In conclusion, the evidence from current research supports the use of medical cannabis in the treatment of chronic pain in adults. Careful follow-up and monitoring of patients using cannabis/cannabinoids are mandatory.

Emerging strategies targeting CB2 cannabinoid receptor: Biased agonism and allosterism

During these last years, the CB₂ cannabinoid receptor has emerged as a potential anti-inflammatory target in diseases such as multiple sclerosis, amyotrophic lateral sclerosis, Huntington's disease, ischemic stroke, autoimmune diseases, osteoporosis, and cancer. However, the development of clinically useful CB₂ agonists reveals to be very challenging. Allosterism and biased-signaling mechanisms at CB₂ receptor may offer new avenues for the development of improved CB₂ receptor-targeted therapies. Although there has been some exploration of CB₁ receptor activation by new CB₁ allosteric or biased-signaling ligands, the CB₂ receptor is still at initial stages in this domain. In an effort to understand the molecular basis behind these pharmacological approaches, we have analyzed and summarized the structural data reported so far at CB₂ receptor.

Medical Cannabis and Cannabinoids: An Option for the Treatment of Inflammatory Bowel Disease and Cancer of the Colon?

In the past few years, we have witnessed a surge of new reports dealing with the role of cannabinoids, synthetic as well as herbal, in the mechanisms of inflammation and carcinogenesis. However, despite the wealth of in vitro data and anecdotal reports, evidence that cannabinoids could act as beneficial drugs in inflammatory bowel disease (IBD) or in neoplastic development of the human gastrointestinal tract is lacking. Some insight into the effects of medical Cannabis (usually meaning dried flowers) and cannabinoids in IBD has been gained through questionnaires and small pilot studies. As to colorectal cancer, only preclinical data are available. Currently, Δ⁹-tetrahydrocannabinol (THC) and its synthetic forms, dronabinol and nabilone, are used as an add-on treatment to alleviate chronic pain and spasticity in multiple sclerosis patients as well as chemotherapy-induced nausea. The use of medical Cannabis is authorized only in a limited number of countries. None of the mentioned substances are currently indicated for IBD. This review is an update of our knowledge on the role of cannabinoids in intestinal inflammation and carcinogenesis and a discussion on their potential therapeutic use.

Peripheral modulation of the endocannabinoid system in metabolic disease

Dysfunction of the endocannabinoid system (ECS) has been identified in metabolic disease. Cannabinoid receptor 1 (CB₁) is abundantly expressed in the brain but also expressed in the periphery. Cannabinoid receptor 2 (CB₂) is more abundant in the periphery, including the immune cells. In obesity, global antagonism of overexpressed CB₁ reduces bodyweight but leads to centrally mediated adverse psychological outcomes. Emerging research in isolated cultured cells or tissues has demonstrated that targeting the endocannabinoid system in the periphery alleviates the pathologies associated with metabolic disease. Further, peripheral specific cannabinoid ligands can reverse aspects of the metabolic phenotype. This Keynote review will focus on current research on the functionality of peripheral modulation of the ECS for the treatment of obesity.

Involvement of TRPV1 Channels in Energy Homeostasis

The ion channel TRPV1 is involved in a wide range of processes including nociception, thermosensation and, more recently discovered, energy homeostasis. Tightly controlling energy homeostasis is important to maintain a healthy body weight, or to aid in weight loss by expending more energy than energy intake. TRPV1 may be involved in energy homeostasis, both in the control of food intake and energy expenditure. In the periphery, it is possible that TRPV1 can impact on appetite through control of appetite hormone levels or via modulation of gastrointestinal vagal afferent signaling. Further, TRPV1 may increase energy expenditure via heat production. Dietary supplementation with TRPV1 agonists, such as capsaicin, has yielded conflicting results with some studies indicating a reduction in food intake and increase in energy expenditure, and other studies indicating the converse. Nonetheless, it is increasingly apparent that TRPV1 may be dysregulated in obesity and contributing to the development of this disease. The mechanisms behind this dysregulation are currently unknown but interactions with other systems, such as the endocannabinoid systems, could be altered and therefore play a role in this dysregulation. Further, TRPV1 channels appear to be involved in pancreatic insulin secretion. Therefore, given its plausible involvement in regulation of energy and glucose homeostasis and its dysregulation in obesity, TRPV1 may be a target for weight loss therapy and diabetes. However, further research is required too fully elucidate TRPV1s role in these processes. The review provides an overview of current knowledge in this field and potential areas for development.

The Chemistry and Pharmacology of Synthetic Cannabinoid Receptor Agonists as New Psychoactive Substances: Origins

Synthetic cannabinoid receptor agonists (SCRAs) have proliferated as new psychoactive substances (NPS) over the past decade. Relative to other classes of NPS, SCRAs are structurally heterogeneous; however, most SCRAs act as potent, high-efficacy agonists of cannabinoid type 1 and type 2 receptors (CB₁ and CB₂, respectively). Characterization of the pharmacology and toxicology of these substances is hindered by the dynamic nature of the SCRA marketplace. Beyond basic pharmacological profiling at CB₁ and CB₂ receptors, very little is known about the acute or chronic effects of SCRAs. Many of the effects of SCRAs are qualitatively similar to those of the Δ⁹-tetrahydrocannabinol (Δ⁹-THC) found in cannabis. However, unlike Δ⁹-THC, SCRAs are frequently associated with serious adverse effects, including cardiotoxicity, nephrotoxicity, and death. This chapter will provide an overview of the structure and function of the primary target for SCRAs, the CB₁ receptor, and survey the structure-activity relationships of the historical SCRAs that served as templates for the earliest generations of NPS.

Rare genetic variants in the endocannabinoid system genes CNR1 and DAGLA are associated with neurological phenotypes in humans

Rare genetic variants in the core endocannabinoid system genes CNR1, CNR2, DAGLA, MGLL and FAAH were identified in molecular testing data from 6,032 patients with a broad spectrum of neurological disorders. The variants were evaluated for association with phenotypes similar to those observed in the orthologous gene knockouts in mice. Heterozygous rare coding variants in CNR1, which encodes the type 1 cannabinoid receptor (CB1), were found to be significantly associated with pain sensitivity (especially migraine), sleep and memory disorders—alone or in combination with anxiety—compared to a set of controls without such CNR1 variants. Similarly, heterozygous rare variants in DAGLA, which encodes diacylglycerol lipase alpha, were found to be significantly associated with seizures and neurodevelopmental disorders, including autism and abnormalities of brain morphology, compared to controls. Rare variants in MGLL, FAAH and CNR2 were not associated with any neurological phenotypes in the patients tested. Diacylglycerol lipase alpha synthesizes the endocannabinoid 2-AG in the brain, which interacts with CB1 receptors. The phenotypes associated with rare CNR1 variants are reminiscent of those implicated in the theory of clinical endocannabinoid deficiency syndrome. The severe phenotypes associated with rare DAGLA variants underscore the critical role of rapid 2-AG synthesis and the endocannabinoid system in regulating neurological function and development. Mapping of the variants to the 3D structure of the type 1 cannabinoid receptor, or primary structure of diacylglycerol lipase alpha, reveals clustering of variants in certain structural regions and is consistent with impacts to function.

Targeting Cannabinoid Signaling in the Immune System: "High"-ly Exciting Questions, Possibilities, and Challenges

It is well known that certain active ingredients of the plants of Cannabis genus, i.e., the "phytocannabinoids" [pCBs; e.g., (-)-trans-Δ⁹-tetrahydrocannabinol (THC), (-)-cannabidiol, etc.] can influence a wide array of biological processes, and the human body is able to produce endogenous analogs of these substances ["endocannabinoids" (eCB), e.g., arachidonoylethanolamine (anandamide, AEA), 2-arachidonoylglycerol (2-AG), etc.]. These ligands, together with multiple receptors (e.g., CB₁ and CB₂ cannabinoid receptors, etc.), and a complex enzyme and transporter apparatus involved in the synthesis and degradation of the ligands constitute the endocannabinoid system (ECS), a recently emerging regulator of several physiological processes. The ECS is widely expressed in the human body, including several members of the innate and adaptive immune system, where eCBs, as well as several pCBs were shown to deeply influence immune functions thereby regulating inflammation, autoimmunity, antitumor, as well as antipathogen immune responses, etc. Based on this knowledge, many in vitro and in vivo studies aimed at exploiting the putative therapeutic potential of cannabinoid signaling in inflammation-accompanied diseases (e.g., multiple sclerosis) or in organ transplantation, and to dissect the complex immunological effects of medical and "recreational" marijuana consumption. Thus, the objective of the current article is (i) to summarize the most recent findings of the field; (ii) to highlight the putative therapeutic potential of targeting cannabinoid signaling; (iii) to identify open questions and key challenges; and (iv) to suggest promising future directions for cannabinoid-based drug development.

Betacaryophyllene - A phytocannabinoid as potential therapeutic modality for human sepsis?

Sepsis is a clinical condition resulting from a dysregulated immune response to an infection that leads to organ dysfunction. Despite numerous efforts to optimize treatment, sepsis remains to be the main cause of death in most intensive care units. The endogenous cannabinoid system (ECS) plays an important role in inflammation. Cannabinoid receptor 2 (CB2R) activation is immunosuppressive, which might be beneficial during the hyper-inflammatory phase of sepsis. Beta-caryophyllene (BCP) is a non-psychoactive natural cannabinoid (phytocannabinoid) found in Cannabis sativa and in essential oils of spices and food plants, that acts as a selective agonist of CB2R. We propose BCP administration as novel treatment to reduce hyper-inflammation in human sepsis.

Pepcan-12 (RVD-hemopressin) is a CB2 receptor positive allosteric modulator constitutively secreted by adrenals and in liver upon tissue damage

Pepcan-12 (RVD-hemopressin; RVDPVNFKLLSH) is the major peptide of a family of endogenous peptide endocannabinoids (pepcans) shown to act as negative allosteric modulators (NAM) of cannabinoid CB1 receptors. Noradrenergic neurons have been identified to be a specific site of pepcan production. However, it remains unknown whether pepcans occur in the periphery and interact with peripheral CB2 cannabinoid receptors. Here, it is shown that pepcan-12 acts as a potent (K_i value ~50 nM) hCB2 receptor positive allosteric modulator (PAM). It significantly potentiated the effects of CB2 receptor agonists, including the endocannabinoid 2-arachidonoyl glycerol (2-AG), for [35S]GTPγS binding and cAMP inhibition (5–10 fold). In mice, the putative precursor pepcan-23 (SALSDLHAHKLRVDPVNFKLLSH) was identified with pepcan-12 in brain, liver and kidney. Pepcan-12 was increased upon endotoxemia and ischemia reperfusion damage where CB2 receptors play a protective role. The adrenals are a major endocrine site of production/secretion of constitutive pepcan-12, as shown by its marked loss after adrenalectomy. However, upon I/R damage pepcan-12 was strongly increased in the liver (from ~100 pmol/g to ~500 pmol/g) independent of adrenals. The wide occurrence of this endogenous hormone-like CB2 receptor PAM, with unforeseen opposite allosteric effects on cannabinoid receptors, suggests its potential role in peripheral pathophysiological processes.

Synthesis and Pharmacological Profiling of the Metabolites of Synthetic Cannabinoid Drugs APICA, STS-135, ADB-PINACA, and 5F-ADB-PINACA

Synthetic cannabinoids (SCs) containing a 1-pentyl-1-H substituted indole or indazole are abused around the world and are associated with an array of serious side effects. These compounds undergo extensive phase 1 metabolism after ingestion with little understanding whether these metabolites are contributing to the cannabimimetic activity of the drugs. This work presents the synthesis and pharmacological characterization of the major metabolites of two high concern SCs; APICA and ADB-PINACA. In a fluorometric assay of membrane potential, all metabolites that did not contain a carboxylic acid functionality retained potent activity at both the CB₁ (EC₅₀ = 14-787 nM) and CB₂ (EC₅₀ = 5.5-291 nM) receptors regardless of heterocyclic core or 3-carboxamide substituent. Of note were the 5-hydroxypentyl and 4-pentanone metabolites which showed significant increases in CB₂ functional selectivity. These results suggest that the metabolites of SCs potentially contribute to the overall pharmacological profile of these drugs.