Showing papers on "Endocannabinoid system published in 2015"
TL;DR: The evidence indicates that CBD and THCV are not rimonabant‐like in their action and thus appear very unlikely to produce unwanted CNS effects, illustrating how in vitro mechanistic studies do not always predict in vivo pharmacology and underlie the necessity of testing compounds in vivo before drawing any conclusion on their functional activity at a given target.
Abstract: Based upon evidence that the therapeutic properties of Cannabis preparations are not solely dependent upon the presence of Δ9-tetrahydrocannabinol (THC), pharmacological studies have been recently carried out with other plant cannabinoids (phytocannabinoids), particularly cannabidiol (CBD) and Δ9-tetrahydrocannabivarin (THCV). Results from some of these studies have fostered the view that CBD and THCV modulate the effects of THC via direct blockade of cannabinoid CB1 receptors, thus behaving like first-generation CB1 receptor inverse agonists, such as rimonabant. Here, we review in vitro and ex vivo mechanistic studies of CBD and THCV, and synthesize data from these studies in a meta-analysis. Synthesized data regarding mechanisms are then used to interpret results from recent pre-clinical animal studies and clinical trials. The evidence indicates that CBD and THCV are not rimonabant-like in their action and thus appear very unlikely to produce unwanted CNS effects. They exhibit markedly disparate pharmacological profiles particularly at CB1 receptors: CBD is a very low-affinity CB1 ligand that can nevertheless affect CB1 receptor activity in vivo in an indirect manner, while THCV is a high-affinity CB1 receptor ligand and potent antagonist in vitro and yet only occasionally produces effects in vivo resulting from CB1 receptor antagonism. THCV has also high affinity for CB2 receptors and signals as a partial agonist, differing from both CBD and rimonabant. These cannabinoids illustrate how in vitro mechanistic studies do not always predict in vivo pharmacology and underlie the necessity of testing compounds in vivo before drawing any conclusion on their functional activity at a given target.
412 citations
TL;DR: The whole world of ligands, receptors, and enzymes, a true “endocannabinoidome”, discovered after the cloning of CB1R and CB2R and the identification of anandamide and 2-AG are reviewed, and its interactions with phytocannabinoids are reviewed.
246 citations
TL;DR: Current in vitro data indicate the extent to which some established or putative orthosteric endocannabinoids seem to target non-cannabinoid receptors and ion channels, particularly at concentrations at which they have been found to interact with CB(1) or CB(2) receptors.
Abstract: The endocannabinoid system consists of G protein-coupled cannabinoid CB1 and CB2 receptors, of endogenous compounds known as endocannabinoids that can target these receptors, of enzymes that catalyse endocannabinoid biosynthesis and metabolism, and of processes responsible for the cellular uptake of some endocannabinoids. This review presents in vitro evidence that most or all of the following 13 compounds are probably orthosteric endocannabinoids since they have all been detected in mammalian tissues in one or more investigation, and all been found to bind to cannabinoid receptors, probably to an orthosteric site: anandamide, 2-arachidonoylglycerol, noladin ether, dihomo-γ-linolenoylethanolamide, virodhamine, oleamide, docosahexaenoylethanolamide, eicosapentaenoylethanolamide, sphingosine, docosatetraenoylethanolamide, N-arachidonoyldopamine, N-oleoyldopamine and haemopressin. In addition, this review describes in vitro findings that suggest that the first eight of these compounds can activate CB1 and sometimes also CB2 receptors and that another two of these compounds are CB1 receptor antagonists (sphingosine) or antagonists/inverse agonists (haemopressin). Evidence for the existence of at least three allosteric endocannabinoids is also presented. These endogenous compounds appear to target allosteric sites on cannabinoid receptors in vitro, either as negative allosteric modulators of the CB1 receptor (pepcan-12 and pregnenolone) or as positive allosteric modulators of this receptor (lipoxin A4) or of the CB2 receptor (pepcan-12). Also discussed are current in vitro data that indicate the extent to which some established or putative orthosteric endocannabinoids seem to target non-cannabinoid receptors and ion channels, particularly at concentrations at which they have been found to interact with CB1 or CB2 receptors.
217 citations
TL;DR: Using computational molecular docking and site-directed mutagenesis, this work identifies key residues within the active site of FAAH that confer the species-specific sensitivity to inhibition by CBD and sheds light on the mechanism of action of CBD in modulating the endocannabinoid tone in vivo.
213 citations
TL;DR: It is found that axon terminals of perisomatically projecting GABAergic interneurons possessed increased CB1 receptor number, active-zone complexity and receptor/effector ratio compared with dendritically projecting interneURons, consistent with higher efficiency of cannabinoid signaling at somatic versus dendritic synapses.
Abstract: A major challenge in neuroscience is to determine the nanoscale position and quantity of signaling molecules in a cell type- and subcellular compartment-specific manner. We developed a new approach to this problem by combining cell-specific physiological and anatomical characterization with super-resolution imaging and studied the molecular and structural parameters shaping the physiological properties of synaptic endocannabinoid signaling in the mouse hippocampus. We found that axon terminals of perisomatically projecting GABAergic interneurons possessed increased CB1 receptor number, active-zone complexity and receptor/effector ratio compared with dendritically projecting interneurons, consistent with higher efficiency of cannabinoid signaling at somatic versus dendritic synapses. Furthermore, chronic Δ(9)-tetrahydrocannabinol administration, which reduces cannabinoid efficacy on GABA release, evoked marked CB1 downregulation in a dose-dependent manner. Full receptor recovery required several weeks after the cessation of Δ(9)-tetrahydrocannabinol treatment. These findings indicate that cell type-specific nanoscale analysis of endogenous protein distribution is possible in brain circuits and identify previously unknown molecular properties controlling endocannabinoid signaling and cannabis-induced cognitive dysfunction.
206 citations
TL;DR: This work finds that CRH signaling in the amygdala promotes an anxious phenotype that is prevented by FAAH inhibition, and suggests that rapid reductions in amygdala AEA signaling following stress may prime the amygdala and facilitate the generation of downstream stress-linked behaviors.
Abstract: Corticotropin-releasing hormone (CRH) is a central integrator in the brain of endocrine and behavioral stress responses, whereas activation of the endocannabinoid CB1 receptor suppresses these responses. Although these systems regulate overlapping functions, few studies have investigated whether these systems interact. Here we demonstrate a novel mechanism of CRH-induced anxiety that relies on modulation of endocannabinoids. Specifically, we found that CRH, through activation of the CRH receptor type 1 (CRHR1), evokes a rapid induction of the enzyme fatty acid amide hydrolase (FAAH), which causes a reduction in the endocannabinoid anandamide (AEA), within the amygdala. Similarly, the ability of acute stress to modulate amygdala FAAH and AEA in both rats and mice is also mediated through CRHR1 activation. This interaction occurs specifically in amygdala pyramidal neurons and represents a novel mechanism of endocannabinoid–CRH interactions in regulating amygdala output. Functionally, we found that CRH signaling in the amygdala promotes an anxious phenotype that is prevented by FAAH inhibition. Together, this work suggests that rapid reductions in amygdala AEA signaling following stress may prime the amygdala and facilitate the generation of downstream stress-linked behaviors. Given that endocannabinoid signaling is thought to exert “tonic” regulation on stress and anxiety responses, these data suggest that CRH signaling coordinates a disruption of tonic AEA activity to promote a state of anxiety, which in turn may represent an endogenous mechanism by which stress enhances anxiety. These data suggest that FAAH inhibitors may represent a novel class of anxiolytics that specifically target stress-induced anxiety.
191 citations
TL;DR: Leukoc et al. as discussed by the authors summarized the metabolic pathways involved in the biosynthesis and metabolism of AEA and 2-AG, as well as the biologic effects of the 2AG and AEA lipidomes in the regulation of inflammation.
Abstract: Arachidonoyl-glycerol (2-AG) and arachidonyl- ethanolamide (AEA) are endocannabinoids that have been implicated in many physiologic disorders, including obesity, metabolic syndromes, hepatic diseases, pain, neurologic disorders, and inflammation. Their immuno- modulatory effects are numerous and are not always mediated by cannabinoid receptors, reflecting the pres- ence of an arachidonic acid (AA) molecule in their structure, the latter being the precursor of numerous bioactive lipids that are pro- or anti-inflammatory. 2-AG and AEA can thus serve as a source of AA but can also be metabolized by most eicosanoid biosynthetic enzymes, yielding additional lipids. In this regard, enhancing endo- cannabinoid levels by using endocannabinoid hydrolysis inhibitors is likely to augment the levels of these lipids that could regulate inflammatory cell functions. This review summarizes the metabolic pathways involved in the biosynthesis and metabolism of AEA and 2-AG, as well as the biologic effects of the 2-AG and AEA lipidomes in the regulation of inflammation. J. Leukoc. Biol. 97: 1049-1070; 2015.
168 citations
TL;DR: Three lines of evidence are presented that show the interest of eCBSS for the regulation of microglial activation in normal and pathological conditions and that M2 polarization occurs on exposure to the two main endocannabinoids 2-AG and AEA in microglia cultures.
Abstract: The ability of microglia to acquire diverse states of activation, or phenotypes, reflects different features that are determinant for their contribution to homeostasis in the adult CNS, and their activity in neuroinflammation, repair or immunomodulation. Despite the widely reported immunomodulatory effects of cannabinoids in both the peripheral immune system and the CNS, less is known about how the endocannabinoid signaling system (eCBSS) influence the microglial phenotype. The general aim of the present study was to investigate the role of endocannabinoids in microglia polarization by using microglia cell cultures. We show that alternative microglia (M2a) and acquired deactivated microglia (M2c) exhibit changes in the eCB machinery that favor the selective synthesis of 2-AG and AEA, respectively. Once released, these eCBs might be able to act through CB1 and/or CB2 receptors in order to influence the acquisition of an M2 phenotype. We present three lines of evidence that the eCBSS is critical for the acquisition of the M2 phenotype: (i) M2 polarization occurs on exposure to the two main endocannabinoids 2-AG and AEA in microglia cultures; (ii) cannabinoid receptor antagonists block M2 polarization; and (iii) M2 polarization is dampened in microglia from CB2 receptor knockout mice. Taken together, these results indicate the interest of eCBSS for the regulation of microglial activation in normal and pathological conditions.
164 citations
TL;DR: It is demonstrated that microglial extracellular vesicles carry on their surface N‐arachidonoylethanolamine (AEA), which is able to stimulate type‐1 cannabinoid receptors (CB1), and inhibit presynaptic transmission, in target GABAergic neurons.
Abstract: Endocannabinoids primarily influence neuronal synaptic communication within the nervous system. To exert their function, endocannabinoids need to travel across the intercellular space. However, how hydrophobic endocannabinoids cross cell membranes and move extracellularly remains an unresolved problem. Here, we show that endocannabinoids are secreted through extracellular membrane vesicles produced by microglial cells. We demonstrate that microglial extracellular vesicles carry on their surface N-arachidonoylethanolamine (AEA), which is able to stimulate type-1 cannabinoid receptors (CB1), and inhibit presynaptic transmission, in target GABAergic neurons. This is the first demonstration of a functional role of extracellular vesicular transport of endocannabinoids.
163 citations
TL;DR: It is reported that social contact increases, whereas isolation decreases, the mobilization of the endogenous marijuana-like neurotransmitter, anandamide, in the mouse nucleus accumbens (NAc), a brain structure that regulates motivated behavior.
Abstract: Marijuana exerts profound effects on human social behavior, but the neural substrates underlying such effects are unknown. Here we report that social contact increases, whereas isolation decreases, the mobilization of the endogenous marijuana-like neurotransmitter, anandamide, in the mouse nucleus accumbens (NAc), a brain structure that regulates motivated behavior. Pharmacological and genetic experiments show that anandamide mobilization and consequent activation of CB1 cannabinoid receptors are necessary and sufficient to express the rewarding properties of social interactions, assessed using a socially conditioned place preference test. We further show that oxytocin, a neuropeptide that reinforces parental and social bonding, drives anandamide mobilization in the NAc. Pharmacological blockade of oxytocin receptors stops this response, whereas chemogenetic, site-selective activation of oxytocin neurons in the paraventricular nucleus of the hypothalamus stimulates it. Genetic or pharmacological interruption of anandamide degradation offsets the effects of oxytocin receptor blockade on both social place preference and cFos expression in the NAc. The results indicate that anandamide-mediated signaling at CB1 receptors, driven by oxytocin, controls social reward. Deficits in this signaling mechanism may contribute to social impairment in autism spectrum disorders and might offer an avenue to treat these conditions.
161 citations
TL;DR: It is demonstrated that wheel running increases endocannabinoids and reduces both anxiety and sensation of pain in mice and shows for the first time to the authors' knowledge that cannabinoid receptors are crucial for main aspects of a runner’s high.
Abstract: Exercise is rewarding, and long-distance runners have described a runner’s high as a sudden pleasant feeling of euphoria, anxiolysis, sedation, and analgesia. A popular belief has been that endogenous endorphins mediate these beneficial effects. However, running exercise increases blood levels of both β-endorphin (an opioid) and anandamide (an endocannabinoid). Using a combination of pharmacologic, molecular genetic, and behavioral studies in mice, we demonstrate that cannabinoid receptors mediate acute anxiolysis and analgesia after running. We show that anxiolysis depends on intact cannabinoid receptor 1 (CB1) receptors on forebrain GABAergic neurons and pain reduction on activation of peripheral CB1 and CB2 receptors. We thus demonstrate that the endocannabinoid system is crucial for two main aspects of a runner9s high. Sedation, in contrast, was not influenced by cannabinoid or opioid receptor blockage, and euphoria cannot be studied in mouse models.
TL;DR: For instance, this paper found that 17β-estradiol (E2) acutely suppresses GABAergic inhibition in the hippocampus of female rats through a sex-specific estrogen receptor α (ERα), mGluR, and endocannabinoid-dependent mechanism.
Abstract: The possibility that mechanisms of synaptic modulation differ between males and females has far-reaching implications for understanding brain disorders that vary between the sexes. We found recently that 17β-estradiol (E2) acutely suppresses GABAergic inhibition in the hippocampus of female rats through a sex-specific estrogen receptor α (ERα), mGluR, and endocannabinoid-dependent mechanism. Here, we define the intracellular signaling that links ERα, mGluRs, and endocannabinoids in females and identify where in this pathway males and females differ. Using a combination of whole-cell patch-clamp recording and biochemical analyses in hippocampal slices from young adult rats, we show that E2 acutely suppresses inhibition in females through mGluR1 stimulation of phospholipase C, leading to inositol triphosphate (IP 3 ) generation, activation of the IP 3 receptor (IP 3 R), and postsynaptic endocannabinoid release, likely of anandamide. Analysis of sex differences in this pathway showed that E2 stimulates a much greater increase in IP 3 levels in females than males, whereas the group I mGluR agonist DHPG increases IP 3 levels equivalently in each sex. Coimmunoprecipitation showed that ERα–mGluR1 and mGluR1–IP 3 R complexes exist in both sexes but are regulated by E2 only in females. Independently of E2, a fatty acid amide hydrolase inhibitor, which blocks breakdown of anandamide, suppressed >50% of inhibitory synapses in females with no effect in males, indicating tonic endocannabinoid release in females that is absent in males. Together, these studies demonstrate sex differences in both E2-dependent and E2-independent regulation of the endocannabinoid system and suggest that manipulation of endocannabinoids in vivo could affect physiological and behavioral responses differently in each sex. SIGNIFICANCE STATEMENT Many brain disorders vary between the sexes, yet the degree to which this variation arises from differential experience versus intrinsic biological sex differences is unclear. In this study, we demonstrate intrinsic sex differences in molecular regulation of a key neuromodulatory system, the endocannabinoid system, in the hippocampus. Endocannabinoids are involved in diverse aspects of physiology and behavior that involve the hippocampus, including cognitive and motivational state, responses to stress, and neurological disorders such as epilepsy. Our finding that molecular regulation of the endocannabinoid system differs between the sexes suggests mechanisms through which experiences or therapeutics that engage endocannabinoids could affect males and females differently.
TL;DR: The effect of PEA is investigated in a murine model of colitis by studying its role in the regulation of intestinal inflammation through modulation of G protein‐coupled receptor 55.
Abstract: Background and Purpose
Palmitoylethanolamide (PEA) acts via several targets, including cannabinoid CB1 and CB2 receptors, transient receptor potential vanilloid type-1 (TRPV1) ion channels, peroxisome proliferator-activated receptor alpha (PPAR α) and orphan G protein-coupled receptor 55 (GRR55), all involved in the control of intestinal inflammation. Here, we investigated the effect of PEA in a murine model of colitis.
Experimental Approach
Colitis was induced in mice by intracolonic administration of dinitrobenzenesulfonic acid (DNBS). Inflammation was assessed by evaluating inflammatory markers/parameters and by histology; intestinal permeability by a fluorescent method; colonic cell proliferation by immunohistochemistry; PEA and endocannabinoid levels by liquid chromatography mass spectrometry; receptor and enzyme mRNA expression by quantitative RT-PCR.
Key Results
DNBS administration caused inflammatory damage, increased colonic levels of PEA and endocannabinoids, down-regulation of mRNA for TRPV1 and GPR55 but no changes in mRNA for CB1, CB2 and PPARα. Exogenous PEA (i.p. and/or p.o., 1 mg·kg−1) attenuated inflammation and intestinal permeability, stimulated colonic cell proliferation, and increased colonic TRPV1 and CB1 receptor expression. The anti-inflammatory effect of PEA was attenuated or abolished by CB2 receptor, GPR55 or PPARα antagonists and further increased by the TRPV1 antagonist capsazepine.
Conclusions and Implications
PEA improves murine experimental colitis, the effect being mediated by CB2 receptors, GPR55 and PPARα, and modulated by TRPV1 channels.
TL;DR: This review will focus on the localization of the best-known components of the endocannabinoid system for which the strongest anatomical evidence exists.
Abstract: The endocannabinoid system consists of endogenous cannabinoids (endocannabinoids), the enzymes that synthesize and degrade endocannabinoids, and the receptors that transduce the effects of endocannabinoids. Much of what we know about the function of endocannabinoids comes from studies that combine localization of endocannabinoid system components with physiological or behavioral approaches. This review will focus on the localization of the best-known components of the endocannabinoid system for which the strongest anatomical evidence exists.
TL;DR: The findings indicate that enhancement of anandamide signaling with URB597 is a promising pharmacological approach for the alleviation of chronic widespread nociception in stress-exposed mice, and thus, it could represent a potential treatment strategy for chronic pain associated with neuropsychiatric disorders in humans.
TL;DR: The general features of the EC system are described as related to pain and nociception and the wealth of preclinical and clinical data involving targeting theEC system is discussed, with focus on modulation of 2-AG signalling via specific enzyme inhibitors and the role of spinal CB2 in chronic pain states.
Abstract: Preparations of the Cannabis sativa plant have been used to analgesic effect for millenia, but only in recent decades has the endogenous system responsible for these effects been described The endocannabinoid (EC) system is now known to be one of the key endogenous systems regulating pain sensation, with modulatory actions at all stages of pain processing pathways The EC system is composed of two main cannabinoid receptors (CB1 and CB2) and two main classes of endogenous ligands or endocannabinoids (ECs) The receptors have distinct expression profiles, with CB1 receptors found at presynaptic sites throughout the peripheral and central nervous systems (PNS and CNS, respectively), whilst CB2 receptor is found principally (but not exclusively) on immune cells The endocannabinoid ligands are lipid neurotransmitters belonging to either the N-acyl ethanolamine (NAEs) class, eg anandamide (AEA), or the monoacylglycerol class, eg 2-arachidonoyl glycerol (2-AG) Both classes are short-acting transmitter substances, being synthesised on demand and with signalling rapidly terminated by specific enzymes ECs acting at CB1 negatively regulate neurotransmission throughout the nervous system, whilst those acting at CB2 regulate the activity of CNS immune cells Signalling through both of these receptor subtypes has a role in normal nociceptive processing and also in the development resolution of acute pain states In this chapter, we describe the general features of the EC system as related to pain and nociception and discuss the wealth of preclinical and clinical data involving targeting the EC system with focus on two areas of particular promise: modulation of 2-AG signalling via specific enzyme inhibitors and the role of spinal CB2 in chronic pain states
TL;DR: This study demonstrates an approach to validating and quantifying ligand-biased signaling and allosteric modulation at CB1Rs, revealing lig and-biased “fingerprints” that may ultimately allow the development of improved CB1R-targeted therapies.
Abstract: CB1 cannabinoid receptors (CB1Rs) are attractive therapeutic targets for numerous central nervous system disorders. However, clinical application of cannabinoid ligands has been hampered owing to their adverse on-target effects. Ligand-biased signaling from, and allosteric modulation of, CB1Rs offer pharmacological approaches that may enable the development of improved CB1R drugs, through modulation of only therapeutically desirable CB1R signaling pathways. There is growing evidence that CB1Rs are subject to ligand-biased signaling and allosterism. Therefore, in the present study, we quantified ligand-biased signaling and allosteric modulation at CB1Rs. Cannabinoid agonists displayed distinct biased signaling profiles at CB1Rs. For instance, whereas 2-arachidonylglycerol and WIN55,212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-napthalenylmethanone] showed little preference for inhibition of cAMP and phosphorylation of extracellular signal-regulated kinase 1/2 (pERK1/2), N-arachidonoylethanolamine (anandamide), methanandamide, CP55940 [2-[(1R,2R,5R)-5-hydroxy-2-(3-hydroxypropyl)cyclohexyl]-5-(2-methyloctan-2-yl)phenol], and HU-210 [11-hydroxy-Δ(8)-THC-dimethylheptyl] were biased toward cAMP inhibition. The small-molecule allosteric modulator Org27569 [5-chloro-3-ethyl-1H-indole-2-carboxylic acid [2-(4-piperidin-1-yl-phenyl)ethyl]amide] displayed biased allosteric effects by blocking cAMP inhibition mediated by all cannabinoid ligands tested, at the same time having little or no effect on ERK1/2 phosphorylation mediated by a subset of these ligands. Org27569 also displayed negative binding cooperativity with [(3)H]SR141716A [5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide]; however, it had minimal effects on binding of cannabinoid agonists. Furthermore, we highlight the need to validate the reported allosteric effects of the endogenous ligands lipoxin A4 and pregnenolone at CB1Rs. Pregnenolone but not lipoxin A4 displaced [(3)H]SR141716A, but there was no functional interaction between either of these ligands and cannabinoid agonists. This study demonstrates an approach to validating and quantifying ligand-biased signaling and allosteric modulation at CB1Rs, revealing ligand-biased "fingerprints" that may ultimately allow the development of improved CB1R-targeted therapies.
TL;DR: The findings indicate that constitutive CB1 activity has pivotal function in the tonic control of hippocampal GABA release and indicate that the synaptic effects of tonic 2-AG release are tightly controlled by presynaptic MGL activity and also by postsynaptic endovanilloid signaling and FAAH activity.
Abstract: Persistent CB1 cannabinoid receptor activity limits neurotransmitter release at various synapses throughout the brain. However, it is not fully understood how constitutively active CB1 receptors, tonic endocannabinoid signaling, and its regulation by multiple serine hydrolases contribute to the synapse-specific calibration of neurotransmitter release probability. To address this question at perisomatic and dendritic GABAergic synapses in the mouse hippocampus, we used a combination of paired whole-cell patch-clamp recording, liquid chromatography/tandem mass spectrometry, stochastic optical reconstruction microscopy super-resolution imaging, and immunogold electron microscopy. Unexpectedly, application of the CB1 antagonist and inverse agonist AM251 [N-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide], but not the neutral antagonist NESS0327 [8-chloro-1-(2,4-dichlorophenyl)-N-piperidin-1-yl-5,6-dihydro-4H-benzo[2,3]cyclohepta[2,4-b]pyrazole-3-carboxamine], significantly increased synaptic transmission between CB1-positive perisomatic interneurons and CA1 pyramidal neurons. JZL184 (4-nitrophenyl 4-[bis(1,3-benzodioxol-5-yl)(hydroxy)methyl]piperidine-1-carboxylate), a selective inhibitor of monoacylglycerol lipase (MGL), the presynaptic degrading enzyme of the endocannabinoid 2-arachidonoylglycerol (2-AG), elicited a robust increase in 2-AG levels and concomitantly decreased GABAergic transmission. In contrast, inhibition of fatty acid amide hydrolase (FAAH) by PF3845 (N-pyridin-3-yl-4-[[3-[5-(trifluoromethyl)pyridin-2-yl]oxyphenyl]methyl]piperidine-1-carboxamide) elevated endocannabinoid/endovanilloid anandamide levels but did not change GABAergic synaptic activity. However, FAAH inhibitors attenuated tonic 2-AG increase and also decreased its synaptic effects. This antagonistic interaction required the activation of the transient receptor potential vanilloid receptor TRPV1, which was concentrated on postsynaptic intracellular membrane cisternae at perisomatic GABAergic symmetrical synapses. Interestingly, neither AM251, JZL184, nor PF3845 affected CB1-positive dendritic interneuron synapses. Together, these findings are consistent with the possibility that constitutively active CB1 receptors substantially influence perisomatic GABA release probability and indicate that the synaptic effects of tonic 2-AG release are tightly controlled by presynaptic MGL activity and also by postsynaptic endovanilloid signaling and FAAH activity.
SIGNIFICANCE STATEMENT Tonic cannabinoid signaling plays a critical role in the regulation of synaptic transmission. However, the mechanistic details of how persistent CB1 cannabinoid receptor activity inhibits neurotransmitter release have remained elusive. Therefore, electrophysiological recordings, lipid measurements, and super-resolution imaging were combined to elucidate those signaling molecules and mechanisms that underlie tonic cannabinoid signaling. The findings indicate that constitutive CB1 activity has pivotal function in the tonic control of hippocampal GABA release. Moreover, the endocannabinoid 2-arachidonoylglycerol (2-AG) is continuously generated postsynaptically, but its synaptic effect is regulated strictly by presynaptic monoacylglycerol lipase activity. Finally, anandamide signaling antagonizes tonic 2-AG signaling via activation of postsynaptic transient receptor potential vanilloid TRPV1 receptors. This unexpected mechanistic diversity may be necessary to fine-tune GABA release probability under various physiological and pathophysiological conditions.
TL;DR: It is shown that CB1 receptor engagement protects striatal cells from excitotoxic death via the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin complex 1 pathway, which induces brain-derived neurotrophic factor (BDNF) expression through the selective activation of BDNF gene promoter IV, an effect that is mediated by multiple transcription factors.
Abstract: The CB1 cannabinoid receptor, the main molecular target of endocannabinoids and cannabis active components, is the most abundant G protein-coupled receptor in the mammalian brain. In particular, the CB1 receptor is highly expressed in the basal ganglia, mostly on terminals of medium-sized spiny neurons, where it plays a key neuromodulatory function. The CB1 receptor also confers neuroprotection in various experimental models of striatal damage. However, the assessment of the physiological relevance and therapeutic potential of the CB1 receptor in basal ganglia-related diseases is hampered, at least in part, by the lack of knowledge of the precise mechanism of CB1 receptor neuroprotective activity. Here, by using an array of pharmacological, genetic and pharmacogenetic (designer receptor exclusively activated by designer drug) approaches, we show that (1) CB1 receptor engagement protects striatal cells from excitotoxic death via the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin complex 1 pathway, which, in turn, (2) induces brain-derived neurotrophic factor (BDNF) expression through the selective activation of BDNF gene promoter IV, an effect that is mediated by multiple transcription factors. To assess the possible functional impact of the CB1/BDNF axis in a neurodegenerative-disease context in vivo, we conducted experiments in the R6/2 mouse, a well-established model of Huntington's disease, in which the CB1 receptor and BDNF are known to be severely downregulated in the dorsolateral striatum. Adeno-associated viral vector-enforced re-expression of the CB1 receptor in the dorsolateral striatum of R6/2 mice allowed the re-expression of BDNF and the concerted rescue of the neuropathological deficits in these animals. Collectively, these findings unravel a molecular link between CB1 receptor activation and BDNF expression, and support the relevance of the CB1/BDNF axis in promoting striatal neuron survival.
TL;DR: All experimental evidence, mainly obtained at the preclinical level, supporting that different cannabinoid compounds may be neuroprotective in adult and neonatal ischemia, brain trauma, Alzheimer's disease, Parkinson’s disease, Huntington's chorea, and amyotrophic lateral sclerosis are collected.
TL;DR: This timely review summarizes the evidence that the cannabinoid system is intricately associated with neuronal differentiation and maturation of NPCs and highlights intrinsic/extrinsic signalling mechanisms that are cannabinoid targets.
Abstract: The processes underpinning post-developmental neurogenesis in the mammalian brain continue to be defined. Such processes involve the proliferation of neural stem cells and neural progenitor cells (NPCs), neuronal migration, differentiation and integration into a network of functional synapses within the brain. Both intrinsic (cell signalling cascades) and extrinsic (neurotrophins, neurotransmitters, cytokines, hormones) signalling molecules are intimately associated with adult neurogenesis and largely dictate the proliferative activity and differentiation capacity of neural cells. Cannabinoids are a unique class of chemical compounds incorporating plant-derived cannabinoids (the active components of Cannabis sativa), the endogenous cannabinoids and synthetic cannabinoid ligands, and these compounds are becoming increasingly recognized for their roles in neural developmental processes. Indeed, cannabinoids have clear modulatory roles in adult neurogenesis, probably through activation of both CB1 and CB2 receptors. In recent years, a large body of literature has deciphered the signalling networks involved in cannabinoid-mediated regulation of neurogenesis. This timely review summarizes the evidence that the cannabinoid system is intricately associated with neuronal differentiation and maturation of NPCs and highlights intrinsic/extrinsic signalling mechanisms that are cannabinoid targets. Overall, these findings identify the central role of the cannabinoid system in adult neurogenesis in the hippocampus and the lateral ventricles and hence provide insight into the processes underlying post-developmental neurogenesis in the mammalian brain.
TL;DR: This review provides an overview of cannabinergic agents used in drug research and those being explored clinically, and the enzymes involved in their biosynthesis and biotransformation.
Abstract: The endocannabinoid system comprises the two well characterized Gi/o -protein coupled receptors (cannabinoid receptor 1 (CB1) and CB2), their endogenous lipid ligands, and the enzymes involved in their biosynthesis and biotransformation. Drug discovery efforts relating to the endocannabinoid system have been focused mainly on the two cannabinoid receptors and the two endocannabinoid deactivating enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL). This review provides an overview of cannabinergic agents used in drug research and those being explored clinically.
TL;DR: Chronic THC treatment reduced energy intake and prevented high fat diet-induced increases in body weight and adiposity; effects that were unlikely to be a result of sedation or altered gastrointestinal transit.
Abstract: Objective
Acute administration of cannabinoid CB1 receptor agonists, or the ingestion of cannabis, induces short-term hyperphagia. However, the incidence of obesity is lower in frequent cannabis users compared to non-users. Gut microbiota affects host metabolism and altered microbial profiles are observed in obese states. Gut microbiota modifies adipogenesis through actions on the endocannabinoid system. This study investigated the effect of chronic THC administration on body weight and gut microbiota in diet-induced obese (DIO) and lean mice.
TL;DR: Although inactive in acute seizure tests, repeated administration of SAR127303 delays the acquisition and decreases kindled seizures in mice, indicating that the drug slows down epileptogenesis, a finding deserving further investigation to evaluate the potential of MAGL inhibitors as antiepileptics.
Abstract: Monoacylglycerol lipase (MAGL) represents a primary degradation enzyme of the endogenous cannabinoid (eCB), 2-arachidonoyglycerol (2-AG). This study reports a potent covalent MAGL inhibitor, SAR127303. The compound behaves as a selective and competitive inhibitor of mouse and human MAGL, which potently elevates hippocampal levels of 2-AG in mice. In vivo, SAR127303 produces antinociceptive effects in assays of inflammatory and visceral pain. In addition, the drug alters learning performance in several assays related to episodic, working and spatial memory. Moreover, long term potentiation (LTP) of CA1 synaptic transmission and acetylcholine release in the hippocampus, two hallmarks of memory function, are both decreased by SAR127303. Although inactive in acute seizure tests, repeated administration of SAR127303 delays the acquisition and decreases kindled seizures in mice, indicating that the drug slows down epileptogenesis, a finding deserving further investigation to evaluate the potential of MAGL inhibitors as antiepileptics. However, the observation that 2-AG hydrolysis blockade alters learning and memory performance, suggests that such drugs may have limited value as therapeutic agents.
TL;DR: This review reassesses the existing evidence suggesting involvement of the endocannabinoid system in the cause, symptomatology, and treatment of PD and tries to identify future threads of research that will help in the understanding of the potential therapeutic benefits of the cannabinoid system for treating PD.
Abstract: Parkinson’s disease (PD) is a slow insidious neurological disorder characterized by a loss of dopaminergic neurons in the midbrain. Although several recent preclinical advances have proposed to treat PD, there is hardly any clinically proved new therapeutic for its cure. Increasing evidence suggests a prominent modulatory function of the cannabinoid signaling system in the basal ganglia. Hence, use of cannabinoids as a new therapeutic target has been recommended as a promising therapy for PD. The elements of the endocannabinoid system are highly expressed in the neural circuit of basal ganglia wherein they bidirectionally interact with dopaminergic, glutamatergic, and GABAergic signaling systems. As the cannabinoid signaling system undergoes a biphasic pattern of change during progression of PD, it explains the motor inhibition typically observed in patients with PD. Cannabinoid agonists such as WIN-55,212-2 have been demonstrated experimentally as neuroprotective agents in PD, with respect to their ability to suppress excitotoxicity, glial activation, and oxidative injury that causes degeneration of dopaminergic neurons. Additional benefits provided by cannabinoid related compounds including CE-178253, oleoylethanolamide, nabilone and HU-210 have been reported to possess efficacy against bradykinesia and levodopa-induced dyskinesia in PD. Despite promising preclinical studies for PD, use of cannabinoids has not been studied extensively at the clinical level. In this review, we reassess the existing evidence suggesting involvement of the endocannabinoid system in the cause, symptomatology, and treatment of PD. We will try to identify future threads of research that will help in the understanding of the potential therapeutic benefits of the cannabinoid system for treating PD.
TL;DR: This review will summarize available genetic tools and present knowledge on the consequences of gene knockout on reinforced behaviors in both opioid and cannabinoid systems, with a focus on their potential interactions.
Abstract: The opioid system consists of three receptors, mu, delta, and kappa, which are activated by endogenous opioid peptides (enkephalins, endorphins and dynorphins). The endogenous cannabinoid system comprises lipid neuromodulators (endocannabinoids), enzymes for their synthesis and their degradation and two well-characterized receptors, cannabinoid receptors CB1 and CB2. These systems play a major role in the control of pain as well as in mood regulation, reward processing and the development of addiction. Both opioid and cannabinoid receptors are coupled to G proteins and are expressed throughout the brain reinforcement circuitry. Extending classical pharmacology, research using genetically modified mice has provided important progress in the identification of the specific contribution of each component of these endogenous systems in vivo on reward process. This review will summarize available genetic tools and our present knowledge on the consequences of gene knockout on reinforced behaviors in both systems, with a focus on their potential interactions. A better understanding of opioid-cannabinoid interactions may provide novel strategies for therapies in addicted individuals.
TL;DR: It is shown that the endocannabinoid system is dysregulated in animal models of Parkinson's disease, and the level of dysregulation between the models themselves is revealed, indicating that targeting the CB2 receptor may represent a viable target for anti-inflammatory disease modification in Parkinson's Disease.
TL;DR: The results show that sustained exposure to GCs produces obesity and metabolic syndrome through a peripheral endocannabinoid mechanism, and indicate that glucocorticoids recruit peripheral endOCannabinoid signaling to promote metabolic dysregulation, with hepatic endoc cannabinoid signaling being especially important for changes in lipid metabolism.
Abstract: Glucocorticoids are known to promote the development of metabolic syndrome through the modulation of both feeding pathways and metabolic processes; however, the precise mechanisms of these effects are not well-understood. Recent evidence shows that glucocorticoids possess the ability to increase endocannabinoid signaling, which is known to regulate appetite, energy balance, and metabolic processes through both central and peripheral pathways. The aim of this study was to determine the role of endocannabinoid signaling in glucocorticoid-mediated obesity and metabolic syndrome. Using a mouse model of excess corticosterone exposure, we found that the ability of glucocorticoids to increase adiposity, weight gain, hormonal dysregulation, hepatic steatosis, and dyslipidemia was reduced or reversed in mice lacking the cannabinoid CB1 receptor as well as mice treated with the global CB1 receptor antagonist AM251. Similarly, a neutral, peripherally restricted CB1 receptor antagonist (AM6545) was able to attenuate the metabolic phenotype caused by chronic corticosterone, suggesting a peripheral mechanism for these effects. Biochemical analyses showed that chronic excess glucocorticoid exposure produced a significant increase in hepatic and circulating levels of the endocannabinoid anandamide, whereas no effect was observed in the hypothalamus. To test the role of the liver, specific and exclusive deletion of hepatic CB1 receptor resulted in a rescue of the dyslipidemic effects of glucocorticoid exposure, while not affecting the obesity phenotype or the elevations in insulin and leptin. Together, these data indicate that glucocorticoids recruit peripheral endocannabinoid signaling to promote metabolic dysregulation, with hepatic endocannabinoid signaling being especially important for changes in lipid metabolism.
TL;DR: It is shown that the endocannabinoid system plays a crucial role in the management of neuroinflammation by dampening the activation of an M1 phenotype by primarily controlled by the CB2 receptor, although functional cross talk with GPR18/GPR55 may occur.
Abstract: Microglial activation is a polarized process divided into potentially neuroprotective phenotype M2 and neurotoxic phenotype M1, predominant during chronic neuroinflammation Endocannabinoid system provides an attractive target to control the balance between microglial phenotypes Anandamide as an immune modulator in the central nervous system acts via not only cannabinoid receptors (CB1 and CB2) but also other targets (eg, GPR18/GPR55) We studied the effect of anandamide on lipopolysaccharide-induced changes in rat primary microglial cultures Microglial activation was assessed based on nitric oxide (NO) production Analysis of mRNA was conducted for M1 and M2 phenotype markers possibly affected by the treatment Our results showed that lipopolysaccharide-induced NO release in microglia was significantly attenuated, with concomitant downregulation of M1 phenotypic markers, after pretreatment with anandamide This effect was not sensitive to CB1 or GPR18/GPR55 antagonism Administration of CB2 antagonist partially abolished the effects of anandamide on microglia Interestingly, administration of a GPR18/GPR55 antagonist by itself suppressed NO release In summary, we showed that the endocannabinoid system plays a crucial role in the management of neuroinflammation by dampening the activation of an M1 phenotype This effect was primarily controlled by the CB2 receptor, although functional cross talk with GPR18/GPR55 may occur
TL;DR: Astrocytic-neuronal interplay provides distributed oversight of 2-AG metabolism and function and, through doing so, protects the nervous system from excessive CB1 receptor activation and promotes endocannabinoid crosstalk with other lipid transmitter systems.