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Query: UNIPROT:P21554 (cannabinoid receptor)
 3,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cannabinoid compounds, including the major psychoactive component of marihuana, delta 9-tetrahydrocannabinol (delta 9-THC), have been widely established as being inhibitory on a broad array of humoral and cell-mediated immune responses. The presence of cannabinoid receptors has been identified recently on mouse spleen cells, which possess structural and functional characteristics similar to those of the G-protein coupled cannabinoid receptor originally identified in rat brain. These findings, together with those demonstrating that delta 9-THC inhibits adenylate cyclase in splenocytes, strongly suggest that certain aspects of immune inhibition by cannabinoids may be mediated through a cannabinoid receptor-associated mechanism. The objective of the present studies was to determine whether inhibition of adenylate cyclase is relevant to mouse spleen cell immune function and, if so, whether this inhibition is mediated through a Gi-protein coupled mechanism as previously described in neuronal tissue. Spleen cell activation by the phorbol ester phorbol-12-myristate-13-acetate (PMA), plus the calcium ionophore ionomycin, produced a rapid but transient increase in cytosolic cAMP, which was inhibited completely by immunosuppressive concentrations of delta 9-THC (22 microM) and the synthetic bicyclic cannabinoid CP-55940 (5.2 microM), which produced no effect on cell viability. Inhibition by cannabinoids of lymphocyte proliferative responses to PMA plus ionomycin and sheep erythrocyte (sRBC) IgM antibody-forming cell (AFC) response, was abrogated completely by low concentrations of dibutyryl-cAMP (10-100 microM). Inhibition of the sRBC AFC response by both delta 9-THC (22 microM) and CP-55940 (5.2 microM) was also abrogated by preincubation of splenocytes for 24 hr with pertussis toxin (0.1-100 ng/mL). Pertussis toxin pretreatment of spleen cells was also found to directly abrogate cannabinoid inhibition of adenylate cyclase, as measured by forskolin-stimulated accumulation of intracellular cAMP. These results indicate that inhibition of the sRBC AFC response by cannabinoids is mediated, at least in part, by inhibition of adenylate cyclase through a pertussis toxin-sensitive Gi-protein coupled cannabinoid receptor. Additionally, these studies further support the premise that cAMP is an important mediator of lymphocyte activation.
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PMID:Suppression of the humoral immune response by cannabinoids is partially mediated through inhibition of adenylate cyclase by a pertussis toxin-sensitive G-protein coupled mechanism. 798 1

Characterization of the newly discovered G-protein-coupled cannabinoid receptor in brain requires determination of its functional significance. The effects are reported of several potent cannabinoid analogs (CP 55,244, CP 55,940, levonantradol and WIN 55,212-2) on cultured neurons from hippocampus, a brain region that exhibits high cannabinoid receptor density. The electrophysiological effects of cannabinoids were determined by whole-cell patch clamp recordings of voltage-dependent potassium currents. The voltage dependence of the rapidly inactivating potassium A current (IA), characteristic of hippocampal neurons, was significantly altered in a concentration-dependent manner by cannabinoid analogs. Decreased inactivation, which led to an increased activation of IA near resting levels in these cells, was observed after brief local extracellular applications of cannabinoids. These actions were blocked by pertussis toxin. Cellular dialysis of GTP-gamma-S mimicked the actions of cannabinoids on IA while blocking further effects due to added cannabinoids. The rank order of potency of the cannabinoid analogs was similar to that observed with respect to binding at cannabinoid receptors in brain membranes. The concentration-related effectiveness of cannabinoid analogs in modulating IA was similar to their potency in stimulating low Km GTPase in cell membranes isolated from the cannabinoid receptor-rich dentate gyrus. These data support the conclusion that cannabinoid effects on IA are mediated through G-protein-coupled receptors. This cannabinoid-induced shift in the voltage dependence of IA could serve to counteract fast, transient, depolarizing events such as action potentials and synaptic currents in hippocampal neurons.
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PMID:Cannabinoids modulate potassium current in cultured hippocampal neurons. 808 16

Anandamide (arachidonyl ethanolamide) has been identified as an endogenous ligand of cannabinoid receptors on the basis of its ability to displace 3H-labeled synthetic cannabinoid in a binding assay. One well characterized cellular action of cannabinoids is inhibition of hormonally stimulated adenylyl cyclase. Another action of synthetic cannabinoids is potent, stereospecific, and reversible inhibition of N-type calcium currents (ICa) in the NG108-15 neuroblastoma-glioma cell line via a pertussis toxin (PTX)-sensitive pathway, independently of cAMP metabolism. Here we used the N18 neuroblastoma cell line and the whole-cell voltage-clamp technique to show that anandamide also potently inhibits N-type ICa in a PTX-sensitive fashion. As with the cannabinomimetic aminoalkylindole WIN 55,212-2, inhibition by anandamide was voltage dependent and N-ethylmaleimide sensitive. However, anandamide was less efficacious than either WIN 55,212-2 or the nonclassical cannabinoid CP 55,940. Indeed, anandamide appears to act as a partial agonist at the cannabinoid receptor. Application of WIN 55,212-2 always caused further inhibition of ICa in cells exposed to a maximally effective concentration of anandamide, and application of anandamide always caused a partial recovery of ICa in cells exposed to a maximally effective concentration of WIN 55,212-2. This partial agonist property of anandamide suggests that, although anandamide inhibits N-type ICa via a PTX-sensitive G protein, its action as a neuromodulator in the intact animal may be more complex than would be inferred by extrapolating the results of in vivo studies with (-)-delta 9-tetra-hydrocannabinol or synthetic cannabinoids.
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PMID:Anandamide, an endogenous cannabinoid, inhibits calcium currents as a partial agonist in N18 neuroblastoma cells. 837 11

Arachidonylethanolamide (anandamide), a candidate endogenous cannabinoid ligand, has recently been isolated from porcine brain and displayed cannabinoid-like binding activity to synaptosomal membrane preparations and mimicked cannabinoid-induced inhibition of the twitch response in isolated murine vas deferens. In this study, anandamide and several congeners were evaluated as cannabinoid agonists by examining their ability to bind to the cloned cannabinoid receptor, inhibit forskolin-stimulated cAMP accumulation, inhibit N-type calcium channels, and stimulate one or more functional second messenger responses. Synthetic anandamide, and all but one congener, competed for [3H]CP55,940 binding to plasma membranes prepared from L cells expressing the rat cannabinoid receptor. The ability of anandamide to activate receptor-mediated signal transduction was evaluated in Chinese hamster ovary (CHO) cells expressing the human cannabinoid receptor (HCR, termed CHO-HCR cells) and compared to control CHO cells expressing the muscarinic m5 receptor (CHOm5 cells). Anandamide inhibited forskolin-stimulated cAMP accumulation in CHO-HCR cells, but not in CHOm5 cells, and this response was blocked with pertussis toxin. N-type calcium channels were inhibited by anandamide and several active congeners in N18 neuroblastoma cells. Anandamide stimulated arachidonic acid and intracellular calcium release in both CHOm5 and CHO-HCR cells and had no effect on the release of inositol phosphates or phosphatidylethanol, generated after activation of phospholipase C and D, respectively. Anandamide appears to exhibit the essential criteria required to be classified as a cannabinoid/anandamide receptor agonist and shares similar nonreceptor effects on arachidonic acid and intracellular calcium release as other cannabinoid agonists.
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PMID:Anandamide, an endogenous cannabimimetic eicosanoid, binds to the cloned human cannabinoid receptor and stimulates receptor-mediated signal transduction. 839 53

The present investigation was undertaken to characterize cannabinoid receptor binding in the absence of the membrane environment, inasmuch as cannabinoid drugs have been noted to influence the behavior of integral membrane proteins. The zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) was able to solubilize the cannabinoid receptor from rat brain membranes, with the greatest yield and specific activity being obtained at a detergent/protein ratio of 0.5:1. [3H]CP-55940 bound to a single class of binding sites in the CHAPS extract, which exhibited a Kd of 0.94 nM as determined by nonlinear regression analysis of equilibrium binding data. The order of potency for cannabinoid agonists in heterologous equilibrium binding studies was CP-55244 > or = desacetyllevonantradol > delta 9-tetrahydrocannabinol > cannabinol >> cannabidiol, consistent with the relative affinities for these agonists in brain membrane preparations. CP-55243, the biologically inactive enantiomer of CP-55244, competed for binding of [3H]CP-55940 by < 50% at 1 microM, similar to its poor affinity for the receptor in membranes. The CHAPS-solubilized cannabinoid receptor exhibited functional interactions with guanine nucleotide-binding proteins (G proteins). GTP and nonhydrolyzable analogs decreased [3H]CP-55940 binding by 75%. The concentration-effect curves for guanine nucleotides exhibited a potency order similar to that observed for other G protein-linked receptors. Kinetic analyses indicated that GTP analogs increased the rate of agonist dissociation, decreasing the t1/2 from 60 min at 0-4 degrees to a multiphasic dissociation that exhibited a component having a t1/2 of < 1 min. The cannabinoid agonist desacetyllevonantradol was able to reduce pertussis toxin-catalyzed ADP-ribosylation of G proteins by 50%, demonstrating a receptor effect on G protein functions. These studies demonstrate that the membrane environment is not necessary for agonist binding to the cannabinoid receptor. Furthermore, the cannabinoid receptor maintains its functional interactions with pertussis toxin-sensitive G proteins in detergent solution.
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PMID:Solubilization of the cannabinoid receptor from rat brain and its functional interaction with guanine nucleotide-binding proteins. 842 66

A putative endogenous cannabinoid ligand, arachidonylethanolamide (termed "anandamide"), was isolated recently from porcine brain. Here we demonstrate that this compound is a specific cannabinoid agonist and exerts its action directly via the cannabinoid receptors. Anandamide specifically binds to membranes from cells transiently (COS) or stably (Chinese hamster ovary) transfected with an expression plasmid carrying the cannabinoid receptor DNA but not to membranes from control nontransfected cells. Moreover, anandamide inhibited the forskolin-stimulated adenylate cyclase in the transfected cells and in cells that naturally express cannabinoid receptors (N18TG2 neuroblastoma) but not in control nontransfected cells. As with exogenous cannabinoids, the inhibition by anandamide of the forskolin-stimulated adenylate cyclase was blocked by treatment with pertussis toxin. These data indicate that anandamide is an endogenous agonist that may serve as a genuine neurotransmitter for the cannabinoid receptor.
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PMID:Anandamide, a brain endogenous compound, interacts specifically with cannabinoid receptors and inhibits adenylate cyclase. 851 84

Modulation of neuronal ion channels by the cloned rat brain CB1 cannabinoid receptor was investigated with the use of a heterologous neuronal expression system. Transient expression of the rat brain CB1 cannabinoid receptor was accomplished through microinjection of in vitro transcribed cRNA into the cytoplasm of enzymatically dissociated adult rat superior cervical ganglion neurons. The cannabimimetic aminoalkylindole WIN 55,212-2 inhibited whole-cell Ca2+ currents in neurons injected 16-25 hr previously with rat brain CB1 cannabinoid receptor cRNA. Inhibition of the Ca2+ current was voltage and concentration dependent, with a maximal inhibition of 73% and an IC50 value of 47 nM. The synthetic cannabinoid analogue CP55,940 also inhibited Ca2+ currents, with a maximal inhibition of 38% and an IC50 value of 7 nM. Ca2+ current inhibition was blocked by inclusion of guanosine-5'-O-(2-thiodiphosphate) in the intracellular patch pipette solution or by pretreatment with pertussis toxin. Pretreatment with the N-type Ca2+ channel antagonist omega-conotoxin GVIA reduced the inhibition by 100 nM WIN 55,212-2 from 44% to 6%, indicating that N-type Ca2+ channels are a target of cannabinoid action. On washout of WIN 55,212-2, the Ca2+ current amplitude "overrecovered" in 47% of the neurons tested. Anandamide, the endogenous cannabimimetic compound, had an inconsistent effect on the voltage-dependent Ca2+ currents in the majority of neurons microinjected with cannabinoid receptor cRNA. Ca2+ channels were a specific effector target of the cannabinoid receptor, as two different K+ currents, the M current and the A current, were not modulated by the cannabimimetic WIN 55,212-2.
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PMID:Rat brain cannabinoid receptor modulates N-type Ca2+ channels in a neuronal expression system. 860

The purpose of this study was to investigate whether anandamide induces cannabimimetic responses, mainly mobilization of arachidonic acid, in primary cultures of rat brain cortical astrocytes. Confluent monolayer cultures of astrocytes, prelabeled with [3H]arachidonic acid, were incubated with anandamide or delta9-tetrahydrocannabinol (delta9-THC) in the presence or absence of thimerosal, a fatty acid acyl CoA transferase inhibitor and phenylmethylsulfonyl fluoride, an amidohydrolase inhibitor. Anandamide and delta9-THC induced a time- and concentration-dependent release of arachidonic acid in the presence, but not in the absence, of thimerosal. Anandamide- and delta9-THC-stimulated arachidonic acid release was pertussis toxin-sensitive, indicating a receptor/G-protein involvement. A novel and selective cannabinoid receptor antagonist, SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4- methyl-1H-pyrazole-3-carboximide hydrochloride], blocked the arachidonic acid release, suggesting a cannabinoid receptor-mediated pathway. In astrocytes, the magnitude of anandamide-induced arachidonic acid release was equal to that released by equimolar concentrations of delta9-THC. Furthermore, direct assay of amidohydrolase activity indicated that degradation of anandamide into arachidonic acid and ethanolamine was negligible in cortical astrocytes. Our results suggest that anandamide stimulates receptor-mediated release of arachidonic acid, and the receptor may be the cannabinoid receptor. Astrocytes, containing a cannabinoid receptor and lower or negligible amidohydrolase activity, may be an important brain cell model in which to study the cannabimimetic effects of anandamide at a cellular and molecular level.
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PMID:Anandamide- and delta9-tetrahydrocannabinol-evoked arachidonic acid mobilization and blockade by SR141716A [N-(Piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4 -methyl-1H-pyrazole-3-carboximide hydrochloride]. 861 4

Cannabinoids, known for their psychoactive effects, also possess immunomodulatory properties. The recent isolation and cloning of the G-protein-coupled peripheral cannabinoid receptor (CB2), mainly expressed in immune tissues, have provided molecular tools to determine how cannabinoid compounds may mediate immunomodulation. We here investigated the CB2 signaling properties using stably transfected Chinese hamster ovary cells expressing human CB2. First, we showed that stimulation by a cannabinoid agonist activated mitogen-activated protein (MAP) kinase in time- and dose-dependent manners. The rank order of potency for MAP kinase activation of cannabinoid agonists correlated well with their binding capacities. Second, we demonstrated that, following MAP kinase activation, cannabinoids induced the expression of the growth-related gene Krox-24, also known as NGFI-A, zif/268, and egr-1. Pertussis toxin completely prevented both MAP kinase activation and Krox-24 induction, even more these responses appeared to be dependent of specific protein kinase C isoforms and independent of inhibition of adenylyl cyclase. A similar coupling of CB2 to a mitogenic pathway and to the regulation of Krox-24 expression was also observed in human promyelocytic cells HL60. Taken together, these findings provide evidence for a functional role of the CB2 receptor in gene induction mediated by the MAP kinase network.
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PMID:Signaling pathway associated with stimulation of CB2 peripheral cannabinoid receptor. Involvement of both mitogen-activated protein kinase and induction of Krox-24 expression. 864 16

Activation of cannabinoid receptors inhibits voltage-gated Ca2+ channels and activates K+ channels, reminiscent of other G-protein-coupled signaling pathways that produce presynaptic inhibition. We tested cannabinoid receptor agonists for effects on excitatory neurotransmission between cultured rat hippocampal neurons. Reducing the extracellular Mg2+ concentration to 0.1 mM elicited repetitive, transient increases in intracellular Ca2+ concentration ([Ca2+]i spikes) that resulted from bursts of action potentials, as measured by combined whole-cell current clamp and indo-1-based microfluorimetry. Pharmacological characterization indicated that the [Ca2+]i spikes required glutamatergic synaptic transmission. Cannabinoid receptor ligands inhibited stereoselectively the frequency of [Ca2+]i spiking in the rank order of potency: CP 54,939 > CP 55,940 > Win 55,212-2 > anandamide, with EC50 values of 0.36, 1.2, 2.7, and 71 nM, respectively. CP 55,940 was potent, but not efficacious, and reversed the inhibition produced by Win 55,212-2, indicating that it is a partial agonist. Inhibition of [Ca2+]i spiking by Win 55,212-2 was prevented by treatment of cultures with active, but not heat-treated, pertussis toxin. Win 55,212-2 (100 nM) inhibited stereoselectively CNQX-sensitive excitatory postsynaptic currents (EPSCs) elicited by presynaptic stimulation with an extracellular electrode, but did not affect the presynaptic action potential or currents elicited by direct application of kainate. Consistent with a presynaptic site of action, Win 55,212-2 increased both the number of response failures and the coefficient of variation of the evoked EPSCs. In contrast, cannabimimetics did not affect bicuculline-sensitive inhibitory postsynaptic currents. Thus, activation of cannabinoid receptors inhibits the presynaptic release of glutamate via an inhibitory G-protein.
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PMID:Cannabinoid receptor agonists inhibit glutamatergic synaptic transmission in rat hippocampal cultures. 869 43


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