Affinity For CB1 Receptor Research Articles

Cross-substitution of Δ9-tetrahydrocannabinol and JWH-018 in drug discrimination in rats

Synthetic indole-derived cannabinoids, originally developed to probe cannabinoid CB1 and CB2 receptors, have become widely abused for their marijuana-like intoxicating properties. The present study examined the effects of indole-derived cannabinoids in rats trained to discriminate Δ9-tetrahydrocannabinol (Δ9-THC) from vehicle. In addition, the effects of Δ9-THC in rats trained to discriminate JWH-018 from vehicle were assessed. Adult male Sprague–Dawley rats were trained to discriminate 3mg/kg Δ9-THC or 0.3mg/kg JWH-018 from vehicle. JWH-018, JWH-073, and JWH-210 fully substituted in Δ9-THC-trained rats and Δ9-THC substituted in JWH-018-trained rats. In contrast, JWH-320, an indole-derived cannabinoid without affinity for CB1 receptors, failed to substitute for Δ9-THC. Pre-treatment with 1mg/kg rimonabant significantly reduced responding on the JWH-018-associated lever in JWH-018-trained rats. These results support the conclusion that the interoceptive effects of Δ9-THC and synthetic indole-derived cannabinoids show a large degree of overlap, which is predictive of their use for their marijuana-like intoxicating properties. Characterization of the extent of pharmacological differences among structural classes of cannabinoids, and determination of their mechanisms remain important goals.

O-2050 facilitates noradrenaline release and increases the CB1 receptor inverse agonistic effect of rimonabant in the guinea pig hippocampus.

The cannabinoid CB1 receptors on the noradrenergic neurons in guinea pig hippocampal slices show an endogenous endocannabinoid tone. This conclusion is based on rimonabant, the facilitatory effect of which on noradrenaline release might be due to its inverse CB1 receptor agonism and/or the interruption of a tonic inhibition elicited by endocannabinoids. To examine the latter mechanism, a neutral antagonist would be suitable. Therefore, we studied whether O-2050 is a neutral CB1 receptor antagonist in the guinea pig hippocampus and whether it mimics the facilitatory effect of rimonabant. CB1 receptor affinity of O-2050 was quantified in cerebrocortical membranes, using (3)H-rimonabant binding. Its CB1 receptor potency and effect on (3)H-noradrenaline release were determined in superfused hippocampal slices. Its intrinsic activity at CB1 receptors was studied in hippocampal membranes, using (35)S-GTPγS binding. Endocannabinoid levels in hippocampus were determined by liquid chromatography-multiple reaction monitoring. O-2050 was about ten times less potent than rimonabant in its CB1 receptor affinity, potency and facilitatory effect on noradrenaline release. Although not affecting (35)S-GTPγS binding by itself, O-2050 shifted the concentration-response curve of a CB1 receptor agonist to the right but that of rimonabant to the left. Levels of anandamide and 2-arachidonoyl glycerol in guinea pig hippocampus closely resembled those in mouse hippocampus. In conclusion, our results with O-2050 confirm that the CB1 receptors on noradrenergic neurons of the guinea pig hippocampus show an endogenous tone. To differentiate between the two mechanisms leading to an endogenous tone, O-2050 is not superior to rimonabant since O-2050 may increase the inverse agonistic effect of endocannabinoids.

N-Alkyl dien- and trienamides from the roots of Otanthus maritimus with binding affinity for opioid and cannabinoid receptors

Two new thienylheptatrienamides (1, 5) and one new neo-lignan (12), together with thirteen known compounds (2, 3, 4, 6–11, 13–16) were isolated from the roots of Otanthus maritimus. The structures of the new compounds were elucidated on the basis of extensive 1D and 2D NMR experiments as well as high resolution mass spectrometry. All the isolated amides (1–10), the known pontica epoxide (11) and the new neo-lignan (12) were evaluated for their binding affinity to the CB1 and CB2 as well as to the μ and δ opioid receptors. Some alkylamides showed moderately high binding affinity for CB2 receptors and 1-[(2E,4E,8Z)-tetradecatrienoyl]piperidine (10) resulted the most active one with a Ki value of 160nM. As far as we know, this is the first example of a tertiary alkylamide that binds CB2 receptors with significant potency. Compounds that showed the highest affinity for cannabinoid receptors (6–8, 10) were much less potent against opioid receptors. Primary structure–activity relationship is discussed. Docking experiments were carried out with the aim to understand the key interactions of the most active compounds with CB2 receptor.

Novel Triaryl Sulfonamide Derivatives as Selective Cannabinoid Receptor 2 Inverse Agonists and Osteoclast Inhibitors: Discovery, Optimization, and Biological Evaluation

Cannabinoid receptors have gained increasing attention as drug targets for developing potential therapeutic ligands. Here, we report the discovery and optimization of triaryl sulfonamides as a novel series possessing significant CB2 receptor affinity and selectivity. Four sets of triaryl ligands were designed and synthesized for further structural modifications and led to the identification of eight compounds as potent and selective CB2 inverse agonists with high binding affinity (CB2K(i) < 10 nM). Especially, compound 57 exhibited the strongest binding affinity on the CB2 receptor (CB2K(i) of 0.5 nM) and the best selectivity over the CB1 receptor (selectivity index of 2594). Importantly, 57 also showed potent inhibitory activity on osteoclast formation, and it was confirmed by a cell viability assay that the inhibition effects were not derived from the cytotoxicity. Finally, 3D QSAR studies confirmed our SAR findings that three bulky groups play an important role for CB2 receptor binding affinity.

Evaluation of (Z)-2-((1-benzyl-1H-indol-3-yl)methylene)-quinuclidin-3-one analogues as novel, high affinity ligands for CB1 and CB2 cannabinoid receptors

A small library of N-benzyl indolequinuclidinone (IQD) analogs has been identified as a novel class of cannabinoid ligands. The affinity and selectivity of these IQDs for the two established cannabinoid receptor subtypes, CB1 and CB2, was evaluated. Compounds 8 (R=R2=H, R1=F) and 13 (R=COOCH3, R1=R2=H) exhibited high affinity for CB2 receptors with Ki values of 1.33 and 2.50nM, respectively, and had lower affinities for the CB1 receptor (Ki values of 9.23 and 85.7nM, respectively). Compound 13 had the highest selectivity of all the compounds examined, and represents a potent cannabinoid ligand with 34-times greater selectivity for CB2R over CB1R. These findings are significant for future drug development, given recent reports demonstrating beneficial use of cannabinoid ligands in a wide variety of human disease states including drug abuse, depression, schizophrenia, inflammation, chronic pain, obesity, osteoporosis and cancer.

2-Arylbenzofuran-based molecules as multipotent Alzheimer's disease modifying agents

The complex etiology of Alzheimer's disease prompts scientists to develop multi-target strategies to combat causes and symptoms. In line with this modern paradigm and as a follow-up to our previous studies, we designed and synthesized a focused collection of new 2-arylbenzofurans and evaluated their biological properties towards specific targets involved in AD, namely human AChE and human BuChE, and Aβ fibril formation. Selected compounds were also tested for their ability to inhibit Aβ neurotoxicity in terms of neuronal viability loss, and to prevent Aβ peptide-binding to cell membrane and intracellular reactive oxygen species (ROS) formation. The different modifications introduced in the structure of our lead compound led to an increase in activity towards one or more of the selected targets: the anticholinesterase activity of some compounds was found to be significantly higher than previously obtained related molecules, and the compounds also proved to possess Aβ anti-aggregating properties and neuroprotective effects. The most interesting multi-target compounds were 18, and 1. Interestingly, 1 also showed good selectivity and moderate affinity for CB1 receptor, opening new perspectives in the field of research on AD, since cannabinoid ligands have been widely reported to have neuroprotective properties.

Design, Synthesis, and Pharmacological Characterization of Indol-3-ylacetamides, Indol-3-yloxoacetamides, and Indol-3-ylcarboxamides: Potent and Selective CB2 Cannabinoid Receptor Inverse Agonists

In our search for new cannabinoid receptor modulators, we describe herein the design and synthesis of three sets of indole-based ligands characterized by an acetamide, oxalylamide, or carboxamide chain, respectively. Most of the compounds showed affinity for CB2 receptors in the nanomolar range, with K(i) values spanning 3 orders of magnitude (377-0.37 nM), and moderate to good selectivity over CB1 receptors. Their in vitro functional activity as inverse agonists was confirmed in vivo in the formalin test of acute peripheral and inflammatory pain in mice, in which compounds 10a and 11e proved to be able to reverse the effect of the CB2 selective agonist COR167.

Kavalactones and the endocannabinoid system: The plant-derived yangonin is a novel CB1 receptor ligand

To investigate the possible interactions between kavalactone-based molecules and proteins of the endocannabinoid system and provide novel and synthetically accessible structural scaffolds for the design of cannabinoid receptor ligands sharing pharmacological properties with kavapyrones, a preliminary SAR analysis was performed on five commercially available natural kavalactones and nine kavalactone-analogues properly synthesized. These compounds were investigated for assessing their cannabinoid receptor binding affinity and capability of inhibiting the activity of the two major metabolic enzymes of the endocannabinoid system, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). Among the molecules tested, only yangonin exhibited affinity for the human recombinant CB1 receptor with a Ki=0.72μM and selectivity vs. the CB2 receptor (Ki>10μM). None of the compounds exhibited strong inhibitory effects on the two enzymes analyzed. The CB1 receptor affinity of yangonin suggests that the endocannabinoid system might contribute to the complex human psychopharmacology of the traditional kava drink and the anxiolytic preparations obtained from the kava plant.

Regioselective synthesis and cannabinoid receptor binding affinity of N-alkylated 4,5-diaryl-1,2,3-triazoles

A series of N1- and N2-substituted 4-(2,4-dichlorophenyl)-5-(4-chlorophenyl)-1,2,3-triazoles were regioselectively synthesized to explore the binding motifs of the diaryl-1,2,3-triazole scaffold at CB1 receptors. The N1 analogs were regioselectively constructed via Click chemistry to furnish analogs with modest CB1 receptor affinity (Ki < 200 nM). The regioselective N2-alkylation of the 4-(2,4-dichlorophenyl)-5-(4-chlorophenyl)-1,2,3-triazole afforded analogs that exhibited good affinity for CB1 receptors (Ki < 100 nM).

ChemInform Abstract: 1‐Aryl‐5‐(1H‐pyrrol‐1‐yl)‐1H‐pyrazole‐3‐carboxamide: An Effective Scaffold for the Design of Either CB1 or CB2 Receptor Ligands.

AbstractThe compound (Ia) shows CB1 receptor affinity and selectivity (Ki = 2.3 nM, SI = 163.6) superior to Rimonabant and AM251.

1-Aryl-5-(1H-pyrrol-1-yl)-1H-pyrazole-3-carboxamide: An effective scaffold for the design of either CB1 or CB2 receptor ligands

New 1-aryl-5-(1H-pyrrol-1-yl)-1H-pyrazole-3-carboxamides were synthesized as cannabinoid (CB) receptor ligands. Compound 11 (CB1Ki=2.3nM, CB1 SI=163.6) showed CB1 receptor affinity and selectivity superior to Rimonabant and AM251. Acute administration of 2mg/kg 11 reduced sucrose, but not regular food, intake in rats. On the other hand, compound 23 (CB2Ki=0.51nM, CB2 SI=30.0) showed significant affinity and selectivity for the CB2 receptor. The results presented here show that the 1-aryl-5-(1H-pyrrol-1-yl)-1H-pyrazole-3-carboxamide may serve as an effective scaffold for the design of either CB1 or CB2 receptor ligands.

Three-dimensional quantitative structure–selectivity relationships analysis guided rational design of a highly selective ligand for the cannabinoid receptor 2

This paper describes a three-dimensional quantitative structure–selectivity relationships (3D-QSSR) study for selectivity of a series of ligands for cannabinoid CB1 and CB2 receptors. 3D-QSSR exploration was expected to provide design information for drugs with high selectivity toward the CB2 receptor. The proposed 3D computational model was performed by Phase and generated taking into account a number of structurally diverse compounds characterized by a wide range of selectivity index values. The model proved to be predictive, with r 2 of 0.95 and Q 2 of 0.63. In order to get prospective experimental validation, the selectivity of an external data set of 39 compounds reported in the literature was predicted. The correlation coefficient ( r 2 = 0.56) obtained on this unrelated test set provided evidence that the correlation shown by the model was not a chance result. Subsequently, we essayed the ability of our approach to help the design of new CB2-selective ligands. Accordingly, based on our interest in studying the cannabinergic properties of quinolones, the N-(adamantan-1-yl)-4-oxo-8-methyl-1-pentyl-1,4-dihydroquinoline-3-carboxamide ( 65) was considered as a potential synthetic target. The log(SI) value predicted by using our model was indicative of high CB2 selectivity for such a compound, thus spurring us to synthesize it and to evaluate its CB1 and CB2 receptor affinity. Compound 65 was found to be an extremely selective CB2 ligand as it displayed high CB2 affinity (Ki = 4.9 nM), while being devoid of CB1 affinity (Ki > 10,000 nM). The identification of a new selective CB2 receptor ligand lends support for the practicability of quantitative ligand-based selectivity models for cannabinoid receptors. These drug discovery tools might represent a valuable complementary approach to docking studies performed on homology models of the receptors.

Synthesis, binding studies and molecular modeling of novel cannabinoid receptor ligands

In the present work, we report upon the design, synthesis and biological evaluation of new anandamide derivatives obtained by modifications of the fatty acyl chain and/or of the ethanolamide ‘tail’. The compounds are of the general formula: 6-(substituted-phenyl)/naphthyl-4-oxohex-5-enoic acid N-substituted amide and 7-naphthyl-5-oxohept-6-enoicacid N-substituted amide. The novel compounds had been evaluated for their binding affinity to CB1/CB2 cannabinoid receptors, binding studies showed that some of the newly developed compounds have measurable affinity and selectivity for the CB2 receptor. Compounds XI and XVIII showed the highest binding affinity for CB2 receptor. None of the compounds exhibited inhibitory activity towards anandamide hydrolysis, thus arguing in favor of their enzymatic stability. The structure–activity relationship has been extensively studied through a tailor-made homological model using constrained docking in addition to pharmacophore analysis, both feature and field based.

POMD11 Cannabinoids are neuroprotective in a human cell culture model of Parkinson's disease

BackgroundWe have previously shown a protective effect of Δ9-tetrahydrocannabinol (THC) in Parkinson's disease (PD) cell culture models associated with increased CB1 cannabis receptor cDNA. Here we investigate whether this protective...

Isolation, structure determination and cannabinoid receptor activating effect of new metabolites of Echinacea purpurea root

Extracts of Echinacea purpurea are extensively used in the therapy of common cold and upper respiratory tract infections as immunomodulators and anti-inflammatory agents. The extracts of the root and herb of E. purpurea have a complex chemical composition, including alkamides, caffeic acid conjugates, and polysaccharides. Alkamides, the main lipophilic compounds, are the modulators of the endocannabinoid system in consequence of their structural similarity to the endogenous ligand anandamide. Recently, receptor binding assays demonstrated the CB2 receptor affinity of Echinacea alkamides, proving by this the CB2-receptor-dependent immunomodulatory effect [1,2]. The aim of the present study was to reinvestigate the chemical composition of the roots of E. purpurea and to gain new information about the affinity of the isolated compounds to the cannabinoid system. The nhexane-soluble extract of the root was subjected to multiple chromatographic separations affording 19 compounds. The structures were analysed by extensive NMR and MS studies resulting the identification of four new natural products (3 alkamides and nitidanin-diisovalerianate). In addition, five compounds were detected for the first time in this species, and ten known E. purpurea metabolites were identified. Cannabinoid receptor activation of thirteen isolated compounds has been studied by [35S]GTPγS binding assays in rat brain membranes. This test measures (i) receptor-mediated G-protein activation induced by agonists and (ii) inhibition by antagonist ligands. A number of E. purpurea compounds turned out to be weak-to-moderate partial agonists, while others displayed inverse-agonist actions. In the presence of a reference CB1 receptor agonist, both sort of compounds exhibited concentration-dependent competitive antagonist effects.

Synthesis and biological evaluation of carbon-11- and fluorine-18-labeled 2-oxoquinoline derivatives for type 2 cannabinoid receptor positron emission tomography imaging

The type 2 cannabinoid (CB(2)) receptor is part of the endocannabinoid system and has been suggested as a mediator of several central and peripheral inflammatory processes. Imaging of the CB(2) receptor has been unsuccessful so far. We synthesized and evaluated a carbon-11- and a fluorine-18-labeled 2-oxoquinoline derivative as new PET tracers with high specificity and affinity for the CB(2) receptor. Two 2-oxoquinoline derivatives were synthesized and radiolabeled with either carbon-11 or fluorine-18. Their affinity and selectivity for the human CB(2) receptor were determined. Biological evaluation was done by biodistribution, radiometabolite and autoradiography studies in mice. In vitro studies showed that both compounds are high affinity CB(2)-specific inverse agonists. Biodistribution study of the tracers in mice showed a high in vivo initial brain uptake and fast brain washout, in accordance with the low CB(2) receptor expression levels in normal brain. A persistently high in vivo binding to the spleen was observed, which was inhibited by pretreatment with two structurally unrelated CB(2) selective inverse agonists. In vitro autoradiography studies with the radioligands confirmed CB(2)-specific binding to the mouse spleen. We synthesized two novel CB(2) receptor PET tracers that show high affinity/selectivity for CB(2) receptors. Both tracers show favourable characteristics as radioligands for central and peripheral in vivo visualization of the CB(2) receptor and are promising candidates for primate and human CB(2) PET imaging.

Blood, adipose tissue and brain levels of the cannabinoid ligands WIN-55,212 and SR-141716A after their intraperitoneal injection in mice: Compound-specific and area-specific distribution within the brain

Cannabinoid ligands have wide ranging neural and behavioral effects; therefore, they are of substantial therapeutic interest. The levels of cannabinoids are tightly controlled in brain infusion and in vitro methodologies, although the studied dose-ranges are extremely wide (e.g. 0.4–470 nmol in brain infusion studies). The brain levels reached after systemic administration are virtually unknown. To investigate this issue, we injected intraperitoneally 3H-labeled WIN-55,212 and SR141716A (0.3, 1 and 3 mg/kg) and estimated their accumulation in the blood, adipose tissue and brain. Accumulation was dose-dependent. The largest amounts were found in the adipose tissue, while the levels seen in the blood and brain were approximately similar. The accumulation of SR141716A was markedly more pronounced than that of WIN-55,212 in all three tissues. The brain distribution of WIN-55,212 showed large regional differences. Such differences were significant but much smaller with SR141716A. The largest brain levels noticed after intraperitoneal injections did not exceed 2.5 nmol/g. This is larger than the brain level of the endocannabinoid anandamide but smaller than that of 2-arachidonoyl glycerol. Yet, the CB1 receptor affinity of WIN-55,212 and SR-141716A is two orders of magnitude larger than that of 2-arachidonoyl glycerol, suggesting that the exogenously administered compounds were functionally more active. Our findings also suggest that brain infusion and in vitro techniques employing considerably larger doses than 2.5 nmol should be dealt with caution. It appears that measuring brain levels after systemic injections increases our understanding of cannabinoid effects, and provides important clues for the comparison of results obtained with different methodologies.

CB1 Cannabinoid Receptor Inhibition: Promising Approach for Heart Failure?

Endocannabinoids are part of a novel signaling system, along with their cellular receptors and several proteins implicated in their synthesis, release, transport, and degradation. The endocannabinoids are endogenous lipid mediators generated by almost all cell types both in the brain and in the peripheral tissues, which have a wide range of biological effects similar to those of marijuana. 2-Arachidonoylglycerol and arachidonoyl ethanolamide (anandamide) are the 2 best characterized endocannabinoids. Their effects are mediated by 2 G protein–coupled receptors, CB1 and CB2, as well as additional, as-yet unidentified ones.1 2-Arachidonoylglycerol binds to both CB2 and CB1 receptors, whereas arachidonoyl ethanolamide has higher affinity for CB1 receptors and may also bind to vanilloid VR1 receptors. The tissue levels of endocannabinoids are determined by the balance between their biosynthesis (involving phospholipase D– and diacyl-glycerol lipase–dependent and other pathways), cellular uptake, and degradation by fatty acid amide hydrolase and/or monoacylglycerol lipases.1,2 Both CB2 and CB1 receptors are negatively coupled to adenylate cyclase through Gi/o proteins but can also signal via protein kinases A and C, mitogen-activated protein kinases, and cyclooxygenase 2 pathways, among others.1,3 The CB1 receptor is widely distributed in the central nervous system1 and at lower levels in various peripheral tissues (eg, myocardium,4–6 human coronary artery endothelial and smooth muscle cells,7,8 adipose tissue,9,10 and the liver10–12). Initially it was thought that CB2 receptors were expressed only in immune and hematopoietic cells, but recent studies have also established their presence in the myocardium,6 human coronary endothelial and smooth muscle cells,7,8 brain,13 and liver.12 Modulation of the endocannabinoid system (ECS) may be therapeutically exploited in various cardiovascular (CV) disorders ranging from circulatory shock, stroke, atherosclerosis and restenosis, and hypertension, to cirrhotic cardiomyopathy, myocardial infarction, and chronic heart failure.1,14,15

Investigations on the 4-Quinolone-3-carboxylic Acid Motif. 2. Synthesis and Structure−Activity Relationship of Potent and Selective Cannabinoid-2 Receptor Agonists Endowed with Analgesic Activity in Vivo

Quinolone-3-carboxamides 11 bearing at position 5, 6, 7, or 8 diverse substituents such as halides, alkyl, aryl, alkoxy, and aryloxy groups differing in their steric/electronic properties, were prepared. The new compounds were tested in vitro for CB1 and CB2 receptor affinity in comparison with the reference compounds rimonabant and SR144528. The tested compounds exhibited CB2 affinity in the range from 55.9 to 0.8 nM and CB1 affinity in the range from >10,000 to 5.3 nM, with selectivity indeces [Ki(CB1)/Ki(CB2)] varying from >2666.6 to 1.23. On the basis of the structure-selectivity relationship developed, the presence of a substituent at C6/C8 or C7 well accounts for the high or low CB2 selectivity, respectively. Compound 11c, characterized by high CB2 affinity and selectivity, showed analgesic activity in the formalin test of acute peripheral and inflammatory pain in mice as a result of selective CB2 agonistic activity.

Synthesis of potential theanine metabolites, related structures and their affinity for CB receptors

Synthesis of potential theanine metabolites, related structures and their affinity for CB receptors