anandamide and Glioma

The poor prognosis of gliomas is to a large extent attributed to the markedly proliferative and invasive nature of the disease. Endocannabinoids have emerged as novel potential anti-tumor agents. The present study aimed to investigate the anti-carcinogenic activity of anandamide (AEA), an endocannabinoid, on glioma cells. To assess the functional role of AEA in glioma, the effects of AEA on cell proliferation, migration, invasion, apoptosis and the cell cycle in vitro, and tumor growth in vivo, were investigated. AEA markedly inhibited the proliferation of U251 cells in a dose- and time-dependent manner. Flow cytometric assays revealed that the apoptosis rate of U251 cells upon treatment with AEA was increased. AEA also suppressed the adhesion, migration and invasion capabilities of the U251 cells. Furthermore, AEA inhibited tumor growth in vivo. These results highlighted the potential role of AEA in the tumorigenesis and progression of glioma, and suggested that AEA exhibits therapeutic potential in the management of human glioma.

Topics: Animals; Apoptosis; Arachidonic Acids; Carcinogenesis; Cell Cycle; Cell Line, Tumor; Cell Movement; Cell Proliferation; Endocannabinoids; Glioma; Humans; Mice; Neoplasm Invasiveness; Polyunsaturated Alkamides; Xenograft Model Antitumor Assays

Anandamide (AEA), an endogenous ligand of cannabinoid CB1 and CB2 receptors, which also binds transient receptor potential vanilloid type 1 receptor (TRPV1), has been shown to display substantial selective cytotoxicity toward some cancer cell lines in vitro, although the relevant data are not consistent. In the present study, we employed the MTT test to assess short-term cytotoxicity of AEA on C6 rat glioma cell culture. When anandamide was administered to the culture medium with foetal bovine serum (FBS), no cytotoxic effect was observed following 24 h exposure of the glioma cells to micromolar concentrations of AEA. However, if no serum was present in the medium, micro-to-submicromolar concentrations of AEA induced dose-dependent cytotoxicity clearly detectable after 24 h. Control experiments made it possible to exclude significant interference of serum with the MTT test per se. Bovine serum albumin mimicked the effect of FBS. We conclude that the apparent inhibition of short-term cytotoxicity of AEA toward C6 rat glioma cells in vitro is caused by binding AEA to serum proteins such as albumin. Taking into account that blood serum or albumin is practically always present in cell culture media, we discuss implications of binding substances to serum proteins for methodology and interpretation of in vitro cytotoxicity testing.

Topics: Albumins; Animals; Arachidonic Acids; Cannabinoid Receptor Agonists; Cell Line, Tumor; Cell Survival; Coloring Agents; Culture Media; Drug Screening Assays, Antitumor; Endocannabinoids; Glioma; Polyunsaturated Alkamides; Rats; Serum; Tetrazolium Salts; Thiazoles

Endocannabinoids are neuromodulatory lipids that mediate the central and peripheral neural functions. Endocannabinoids have demonstrated their anti-proliferative, anti-angiogenic and pro-apoptotic properties in a series of studies. In the present study, we investigated the levels of two major endocannabinoids, anandamide and 2-arachidonylglycerol (2-AG), and their receptors, CB1 and CB2, in human low grade glioma (WHO grade I-II) tissues, high grade glioma (WHO grade III-IV) tissues, and non-tumor brain tissue controls. We also measured the expressions and activities of the enzymes responsible for anandamide and 2-AG biosynthesis and degradation, that is, N-acylphosphatidylethanolamine-hydrolysing phospholipase D (NAPE-PLD), fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MGL), and diacylglycerol lipase-alpha (DGL), in the same samples. Liquid chromatography-mass spectometry analysis showed that the levels of anandamide decreased, whereas the levels of 2-AG increased in glioma tissues, comparing to the non-tumor controls. The expression levels and activities of NAPE-PLD, FAAH and MGL also decreased in glioma tissues. Furthermore, quantitative-PCR analysis and western-blot analysis revealed that the expression levels of cananbinoid receptors, CB1 and CB2, were elevated in human glioma tissues. The changes of anandamide and 2-AG contents in different stages of gliomas may qualify them as the potential endogenous biomarkers for glial tumor malignancy.

Topics: Adolescent; Adult; Aged; Arachidonic Acids; Brain; Brain Neoplasms; Cannabinoid Receptor Modulators; Down-Regulation; Endocannabinoids; Female; Glioma; Glycerides; Humans; Male; Middle Aged; Polyunsaturated Alkamides; Receptors, Cannabinoid; RNA, Messenger; Tritium; Young Adult

We studied the effects of endocannabinoid anandamide and its cyclooxygenase derivative prostamide E2 on cultured cerebellar granular cells and C6 glioma cells from rats. Prostamide E2 prevented apoptosis in cerebellar neurons induced by potassium deprivation of cultures, while anandamide had no neuroprotective properties. Prostamide E2 did not modulate the survival rate of glioma cells, while anandamide produced a cytotoxic effect. Our results indicate that cyclooxygenase transformation of anandamide is followed by the loss of antitumor activity of this agent. By contrast, prostamide E2 exhibited strong neuroprotective properties.

Topics: Animals; Apoptosis; Arachidonic Acids; Biotransformation; Cell Survival; Cells, Cultured; Cerebellum; Dinoprostone; Dose-Response Relationship, Drug; Endocannabinoids; Glioma; Neurons; Neuroprotective Agents; Polyunsaturated Alkamides; Potassium; Potassium Deficiency; Primary Cell Culture; Prostaglandin-Endoperoxide Synthases; Rats

Compounds blocking the uptake of the endogenous cannabinoid anandamide (AEA) have been used to explore the functions of the endogenous cannabinoid system in the CNS both in vivo and in vitro. In this study, the effects of four commonly used acyl-based uptake inhibitors [N-(4-hydroxyphenyl)arachidonylamide (AM404), N-(4-hydroxy-2-methylphenyl) arachidonoyl amide (VDM11), (5Z,8Z,11Z,14Z)-N-(3-furanylmethyl)-5,8,11,14-eicosatetraenamide (UCM707) and (9Z)-N-[1-((R)-4-hydroxybenzyl)-2-hydroxyethyl]-9-octadecen-amide (OMDM2)] and the related compound arvanil on C6 glioma cell viability were investigated. All five compounds reduced the ability of the cells to accumulate calcein, reduced the total nucleic acid content and increased the activity of lactate dehydrogenase recovered in the cell medium. AM404 (10 microm) and VDM11 (10 microm) acted rapidly, reducing cell viability after 3 h of exposure when cell densities of 5,000 per well were used. In contrast, UCM707 (30 microm), OMDM2 (10 microm) and the related compound arvanil (10 microm) produced a more slowly developing effect on cell viability, although robust effects were seen after 6-9 h of exposure. At higher cell densities, the toxicities of AM404 and UCM707 were reduced. Comparison of the compounds with arachidonic acid, arachidonic acid methyl ester, AEA, arachidonoyl glycine and oleic acid suggested that the toxicity of the arachidonoyl-based compounds was related primarily to the acyl side-chain rather than the head group. A variety of pre-treatments blocking possible metabolic pathways and receptor targets were tested, but the only consistent protective treatment against the effects of these compounds was the antioxidant N-acetyl-L-cysteine. It is concluded that AM404, VDM11, UCM707 and OMDM2 produce a rapid loss of C6 glioma cell viability over the same concentration range as is required for the inhibition of AEA uptake in vitro, albeit with a longer latency. Such effects should be kept in mind when acyl-derived compounds are used to probe the function of the endocannabinoid system in the CNS, particularly in chronic administration protocols.

Topics: Acylation; Animals; Antineoplastic Agents; Arachidonic Acids; Benzyl Compounds; Brain; Brain Neoplasms; Cannabinoid Receptor Modulators; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cytotoxins; Drug Screening Assays, Antitumor; Endocannabinoids; Fluoresceins; Furans; Glioma; L-Lactate Dehydrogenase; Neurons; Nucleic Acids; Polyunsaturated Alkamides; Rats; Time Factors; TRPV Cation Channels

Several G protein-coupled receptors function within lipid rafts plasma membrane microdomains, which may be important in limiting signal transduction. Here we show that treatment of rat C6 glioma cells with the raft disruptor methyl-beta-cyclodextrin (MCD) doubles the binding efficiency (i.e. the ratio between maximum binding and dissociation constant) of type-1 cannabinoid receptors (CB1R), which belong to the rhodopsin family of G protein-coupled receptors. In parallel, activation of CB1R by the endogenous agonist anandamide (AEA) leads to approximately 3-fold higher [35S]GTPgammaS binding in MCD-treated cells than in controls, and CB1R-dependent signaling via adenylate cyclase, and p42/p44 MAPK is almost doubled by MCD. Unlike CB1R, the other AEA-binding receptor TRPV1, the AEA synthetase NAPE-PLD, and the AEA hydrolase FAAH are not modulated by MCD, whereas the activity of the AEA membrane transporter (AMT) is reduced to approximately 50% of the controls. We also show that MCD reduces dose-dependently AEA-induced apoptosis in C6 cells but not in human CHP100 neuroblastoma cells, which mirror the endocannabinoid system of C6 cells but are devoid of CB1R. MCD reduces also cytochrome c release from mitochondria of C6 cells, and this effect is CB1R-dependent and partly mediated by activation of p42/p44 MAPK. Altogether, the present data suggest that lipid rafts control CB1R binding and signaling, and that CB1R activation underlies the protective effect of MCD against apoptosis.

Topics: Animals; Apoptosis; Arachidonic Acids; beta-Cyclodextrins; Biological Transport; Cannabinoid Receptor Modulators; Cell Line, Tumor; Cell Membrane; Cell Separation; Cholesterol; Cyclic AMP; Dose-Response Relationship, Drug; Endocannabinoids; Flow Cytometry; Glioma; Guanosine 5'-O-(3-Thiotriphosphate); Humans; Hydrolysis; Kinetics; Lipid Metabolism; Lipids; Membrane Microdomains; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Neuroblastoma; Neurons; Polyunsaturated Alkamides; Protein Binding; Rats; Receptor, Cannabinoid, CB1; Receptors, Cannabinoid; Rhodopsin; Signal Transduction; Time Factors

The anti-tumor properties of cannabinoids have recently been evidenced, mainly with delta9-tetrahydrocannabinol (THC). However, the clinical application of this drug is limited by possible undesirable side effects due to a broad expression of cannabinoid receptors (CB1 and CB2). An attractive field of research therefore is to identify molecules with more selective tumor targeting. This is particularly important for malignant gliomas, considering their poor prognosis and their location in the brain. Here we investigated whether the most potent endogenous cannabinoid, arachidonylethanolamide (AEA), could be a candidate. We observed that AEA induced apoptosis in long-term and recently established glioma cell lines via aberrantly expressed vanilloid receptor-1 (VR1). In contrast with their role in THC-mediated death, both CB1 and CB2 partially protected glioma against AEA-induced apoptosis. These data show that the selective targeting of VR1 by AEA or more stable analogues is an attractive research area for the treatment of glioma.

Topics: Antineoplastic Agents; Apoptosis; Arachidonic Acids; Brain Neoplasms; Cannabinoid Receptor Modulators; Cell Line, Tumor; Cells, Cultured; Endocannabinoids; Gene Expression Regulation, Neoplastic; Glioma; Humans; Polyunsaturated Alkamides; Receptor, Cannabinoid, CB1; Receptor, Cannabinoid, CB2; Receptors, Drug; RNA, Messenger

The GLYT1 subtypes of glycine transporter are expressed in glia surrounding excitatory synapses in the mammalian CNS and may regulate synaptic glycine concentrations required for activation of the NMDA subtypes of glutamate receptor. In this report we demonstrate that the rate of glycine transport by GLYT1 is inhibited by arachidonic acid. The cyclo-oxygenase and lipoxygenase inhibitors indomethacin and nordihydroguaiaretic acid, and the protein kinase C inhibitor staurosporine, had no effect on the extent of arachidonic acid inhibition of transport, which suggests that the inhibitory effects of arachidonic acid result from a direct interaction with the transporter. In contrast to arachidonic acid, its amide derivative, anandamide, and the more stable analogue R1-methanandamide stimulate glycine transport. This stimulation is unlikely to be a secondary effect of cannabinoid receptor stimulation because the cannabinoid receptor agonist WIN 55 212-2 had no effect on transport. We suggest that the stimulatory effects of anandamide on GLYT1 are due to a direct interaction with the transporter.

Topics: Amino Acid Transport Systems, Neutral; Animals; Arachidonic Acid; Arachidonic Acids; Biological Transport; Endocannabinoids; Glioma; Glycine; Glycine Plasma Membrane Transport Proteins; Oocytes; Patch-Clamp Techniques; Polyunsaturated Alkamides; Protein Isoforms; Rats; Transfection; Xenopus laevis

The abilities of 19 analogues of palmitoylethanolamide and two analogues of oleoylethanolamide to affect the Ca(2+) influx into human embryonic kidney cells expressing the human vanilloid receptor (hVR1-HEK293 cells) in response to anandamide (AEA) have been investigated using a FLIPR assay and a bovine serum albumin-containing assay medium. Only palmitoylethanolamide produced any effect in the absence of AEA. The ability of palmitoylethanolamide to potentiate the response to AEA was retained when the N-CH(2)CH(2)OH group was replaced by N-CH(2)CH(2)Cl,whereas replacement with N-alkyl substituents [from -H up to -(CH(2))(12)CH(3)] resulted either in a reduction or in a complete loss of this activity. The tertiary amide N-(CH(2)CH(3))(2) (19) and N-morpholino (20) analogues of palmitoylethanolamide potentiated the response to 1 microM AEA to a greater degree than the parent compound, whereas the N-(CH(3))(2) analogue was inactive. 19 and 20 produced leftward shifts in the dose-response curve for AEA activation of Ca(2+) influx into hVR1-HEK293 cells. EC(50) values for AEA to produce Ca(2+) influx into hVR1-HEK293 cells were 1.1, 1.1, 0.54 and 0.36 microM in the presence of 0, 1, 3 and 10 microM 19, respectively. The corresponding values for 20 were 1.5, 1.3, 0.77 and 0.17 microM, respectively. The compounds did not affect the dose-response curves to capsaicin. The ability of oleoylethanolamide to potentiate AEA is retained by the N-CH(2)CH(3) and N-CH(CH(3))(2) analogues (22 and 23, respectively). 22 and 23 produced a small ( approximately 25%) inhibition of the binding of [(3)H]-CP55,940 and [(3)H]-WIN 55,212-2 to CB(1) and CB(2) receptors, respectively, expressed in CHO cells. The compounds inhibited the metabolism of 2 microM [(3)H]-AEA by rat brain fatty acid amidohydrolase with IC(50) values of 5.6 and 11 microM, respectively. In contrast, 19 and 20 were without effect on either binding to CB receptors or fatty acid amidohydrolase activity. Minor reductions in the accumulation of 10 microM [(3)H]-AEA into C6 glioma cells were seen at 10 microM concentrations of 19 and 20. It is concluded that 19 and 20 selectively enhance AEA effects upon VR1 receptors without potentially confounding effects upon CB receptors or fatty acid amidohydrolase activity.

Topics: Amides; Amidohydrolases; Animals; Arachidonic Acids; Brain Neoplasms; Calcium Channel Blockers; Capsaicin; Endocannabinoids; Ethanolamines; Glioma; Humans; In Vitro Techniques; Kidney; Morpholines; Palmitic Acids; Polyunsaturated Alkamides; Radioligand Assay; Rats; Receptor, Cannabinoid, CB1; Receptors, Drug; Transfection; Tumor Cells, Cultured

The metabolism of anandamide by fatty acid amidohydrolase (FAAH) at different intra- and extracellular pH values has been investigated in intact C6 rat glioma cells. The cellular uptake of anandamide at 37 degrees C was found to decrease by 28% when the extracellular pH (pH(e)) was reduced from pH 7.4 to pH 6.2. In contrast, a selective decrease in intracellular pH (pH(i)), accomplished by acidifying the cells followed by incubation in sodium-free buffer at pH 7.4, did not affect the uptake. Anandamide uptake was inhibited by (R)-ibuprofen, with pI(50) values of 3.05+/-0.57, 3.66+/-0.23 and 3.94+/-0.88 at pH(e) values of 7.4, 6.8 and 6.2, respectively. In the presence of phenylmethylsulfonyl fluoride, however, (R)-ibuprofen failed to inhibit the uptake of anandamide. A reduction in pH(e) from 7.4 to 6.2 produced a 17% reduction in the FAAH-catalyzed metabolism of anandamide in the intact C6 cells. However, an increased sensitivity of FAAH activity to inhibition by (R)-ibuprofen as well as (R,S)-flurbiprofen and (S)-flurbiprofen was seen at a lower pH(e). For (R)-ibuprofen, pI(50) values of 3.57+/-0.08, 4.04+/-0.05 and 4.59+/-0.04 were found at pH(e) values of 7.4, 6.8 and 6.2, respectively. For (R,S)- and (S)-flurbiprofen, the pI(50) values at pH(e) 7.4 were 4.02+/-0.05 and 4.13+/-0.18, respectively at a pH(e) of 7.4, and 4.81+/-0.11 and 4.84+/-0.10, respectively, at a pH(e) of 6.2. In contrast, intracellular acidification did not affect either the rate of anandamide metabolism or its inhibition by (R)-ibuprofen or (S)-flurbiprofen. It is concluded that a reduction of extracellular pH produces an enhanced accumulation of the acidic NSAIDs ibuprofen and flurbiprofen into C6 glioma cells and thereby an inhibition of anandamide metabolism.

Topics: Amidohydrolases; Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonic Acids; Endocannabinoids; Extracellular Space; Flurbiprofen; Glioma; Hydrogen-Ion Concentration; Hydrolysis; Ibuprofen; Intracellular Space; Polyunsaturated Alkamides; Rats; Stereoisomerism; Time Factors; Tumor Cells, Cultured

AM404 [ N-(4-hydroxyphenyl)arachidonylamide] and VDM 11 [(5 Z,8 Z,11 Z,14 Z)- N-(4-hydroxy-2-methylphenyl)-5,8,11,14-eicosatetraenamide] are commonly used to prevent the cellular accumulation of the endocannabinoid anandamide, and thereby to potentiate its actions. However, it has been reported that AM404 can produce an influx of calcium into cells, which might be expected to have deleterious effects on cell proliferation. In the present study, AM404 and VDM 11 were found to reduce C6 glioma cell proliferation with IC(50) values of 4.9 and 2.7 microM, respectively. The inhibition of cell proliferation following a 96-h exposure was not accompanied by dramatic caspase activation, and was not prevented by either a combination of cannabinoid and vanilloid receptor antagonists, or by the antioxidant alpha-tocopherol, suggestive of a non-specific mode of action. Similar results were seen with palmitoylisopropylamide, although this compound only produced significant inhibition of cell proliferation at 30 microM concentrations. AM404 (1 microM), VDM 11 (1 microM) and palmitoylisopropylamide (3-30 microM), i.e. concentrations producing relatively modest effects on cell proliferation per se, reduced the vanilloid receptor-mediated antiproliferative effects of anandamide, as would be expected for compounds preventing the cellular accumulation of anandamide (and thereby access to its binding site on the vanilloid receptor). It is concluded that concentrations of AM404 and VDM 11 that are generally used to reduce the cellular accumulation of anandamide have deleterious effects upon cell proliferation, and that lower concentrations of these compounds may be more appropriate to use in vitro.

Topics: Animals; Arachidonic Acids; Brain Neoplasms; Cannabinoids; Cell Count; Cell Division; Cell Line, Tumor; Dose-Response Relationship, Drug; Endocannabinoids; Glioma; Inhibitory Concentration 50; Polyunsaturated Alkamides; Rats; Receptors, Drug

It has previously been shown that the endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG) inhibit the proliferation of C6 glioma cells in a manner that can be prevented by a combination of capsazepine (Caps) and cannabinoid (CB) receptor antagonists. It is not clear whether the effect of 2-AG is due to the compound itself, due to the rearrangement to form 1-arachidonoylglycerol (1-AG) or due to a metabolite. Here, it was found that the effects of 2-AG can be mimicked with 1-AG, both in terms of its potency and sensitivity to antagonism by Caps and CB receptor antagonists. In order to determine whether the effect of Caps could be ascribed to actions upon vanilloid receptors, the effect of a more selective vanilloid receptor antagonist, SB366791 was investigated. This compound inhibited capsaicin-induced Ca(2+) influx into rVR1-HEK293 cells with a pK(B) value of 6.8+/-0.3. The combination of SB366791 and CB receptor antagonists reduced the antiproliferative effect of 1-AG, confirming a vanilloid receptor component in its action. 1-AG, however, showed no direct effect on Ca(2+) influx into rVR1-HEK293 cells indicative of an indirect effect upon vanilloid receptors. Identification of the mechanism involved was hampered by a large inter-experimental variation in the sensitivity of the cells to the antiproliferative effects of 1-AG. A variation was also seen with anandamide, which was not a solubility issue, since its water soluble phosphate ester showed the same variability. In contrast, the sensitivity to methanandamide, which was not sensitive to antagonism by the combination of Caps and CB receptor antagonists, but has similar physicochemical properties to anandamide, did not vary between experiments. This variation greatly reduces the utility of these cells as a model system for the study of the antiproliferative effects of anandamide. Nevertheless, it was possible to conclude that the antiproliferative effects of anandamide were not solely mediated by either its hydrolysis to produce arachidonic acid or its CB receptor-mediated activation of phospholipase A(2) since palmitoyltrifluoromethyl ketone did not prevent the response to anandamide. The same result was seen with the fatty acid amide hydrolase inhibitor palmitoylethylamide. Increasing intracellular arachidonic acid by administration of arachidonic acid methyl ester did not affect cell proliferation, and the modest antiproliferative effect of umbelliferyl arachidonate was not prevented by

Topics: Anilides; Animals; Arachidonic Acid; Arachidonic Acids; Calcium; Calcium Channel Blockers; Cannabinoid Receptor Modulators; Cell Division; Cells, Cultured; Cinnamates; Endocannabinoids; Esters; Glioma; Glycerides; Humans; Ketones; Polyunsaturated Alkamides; Rats; Receptors, Cannabinoid; Receptors, Drug; Solubility; Tumor Cells, Cultured

It is not yet clear if the endocannabinoid 2-arachidonoylglycerol (2-AG) is transported into cells through the same membrane transporter mediating the uptake of the other endogenous cannabinoid, anandamide (N-arachidonoylethanolamine, AEA), and whether this process (a) is regulated by cells and (b) limits 2-AG pharmacological actions. We have studied simultaneously the facilitated transport of [14C]AEA and [3H]2-AG into rat C6 glioma cells and found uptake mechanisms with different efficacies but similar affinities for the two compounds (Km 11.0 +/- 2.0 and 15.3 +/- 3.1 microM, Bmax 1.70 +/- 0.30 and 0.24 +/- 0.04 nmol.min-1.mg protein-1, respectively). Despite these similar Km values, 2-AG inhibits [14C]AEA uptake by cells at concentrations (Ki = 30.1 +/- 3.9 microM) significantly higher than those required to either 2-AG or AEA to inhibit [3H]2-AG uptake (Ki = 18.9 +/- 1.8 and 20.5 +/- 3.2 microM, respectively). Furthermore: (a) if C6 cells are incubated simultaneously with identical concentrations of [14C]AEA and [3H]2-AG, only the uptake of the latter compound is significantly decreased as compared to that observed with [3H]2-AG alone; (b) the uptake of [14C]AEA and [3H]2-AG by cells is inhibited with the same potency by AM404 (Ki = 7.5 +/- 0.7 and 10.2 +/- 1.7 microM, respectively) and linvanil (Ki = 9.5 +/- 0.7 and 6.4 +/- 1.2 microM, respectively), two inhibitors of the AEA membrane transporter; (c) nitric oxide (NO) donors enhance the uptake of both [14C]AEA and [3H]2-AG, thus suggesting that 2-AG action can be regulated through NO release; (d) AEA and 2-AG induce a weak release of NO that can be blocked by a CB1 cannabinoid receptor antagonist, and significantly enhanced in the presence of AM404 and linvanil, thus suggesting that transport into C6 cells limits the action of both endocannabinoids.

Topics: Animals; Arachidonic Acids; Biological Transport, Active; Cannabinoid Receptor Modulators; Cell Membrane; Endocannabinoids; Glioma; Glycerides; Kinetics; Models, Chemical; Neurotransmitter Agents; Nitric Oxide; Polyunsaturated Alkamides; Rats; Receptors, Cannabinoid; Receptors, Drug; Tumor Cells, Cultured

N-Arachidonoylethanolamine (AEA) is a proposed endogenous ligand of the central cannabinoid receptor (CB1). Previous studies indicate that AEA is translocated across membranes via a process that has the characteristics of carrier-mediated facilitated diffusion. To date, studies of this mechanism have relied on [(3)H]AEA as a substrate for the carrier. We have synthesized an analog of AEA, SKM 4-45-1, that is nonfluorescent in the extracellular environment. When SKM 4-45-1 is exposed to intracellular esterases, it is de-esterified and becomes fluorescent. We have carried out studies to demonstrate that SKM 4-45-1 accumulation in cells occurs via the AEA carrier. SKM 4-45-1 is accumulated by both cerebellar granule cells and C6 glioma cells. Uptake of SKM 4-45-1 into C6 glioma is inhibited by AEA (IC(50)=53.8 +/- 1.8 microM), arachidonoyl-3-aminopyridine amide (IC(50)=10.1 +/- 1.4 microM), and arachidonoyl-4-hydroxyanilineamide (IC(50)=6.1 +/- 1.3 microM), all of which also inhibit [(3)H]AEA accumulation. Conversely, [(3)H]AEA accumulation by cerebellar granule cells is inhibited by SKM 4-45-1 with an IC(50) of 7.8 +/- 1. 3 microM. SKM 4-45-1 is neither a substrate nor inhibitor of fatty acid amide hydrolase, an enzyme that catabolizes AEA. SKM 4-45-1 does not bind the CB1 cannabinoid receptor at concentrations <10 microM. In summary, the cellular accumulation of SKM 4-45-1 occurs via the same pathway as AEA uptake and provides an alternative substrate for the study of this important cellular process.

Topics: Amidohydrolases; Animals; Arachidonic Acids; Brain Neoplasms; Cannabinoids; Carrier Proteins; Cell Membrane; Cerebellum; Cyclohexanols; Endocannabinoids; Esterases; Fluorescent Dyes; Glioma; Humans; Lactones; Microscopy, Fluorescence; Polyunsaturated Alkamides; Rats; Rats, Sprague-Dawley; Tumor Cells, Cultured

The endogenous cannabimimetic anandamide is hydrolyzed by a fatty acid amide hydrolase to yield arachidonic acid and ethanolamine. In the present study, the regional distribution of the activity and its sensitivity to inhibition by the enantiomers of ibuprofen, ketorolac, and flurbiprofen has been investigated. The rate of [3H]anandamide hydrolysis was found in both 7-week-old and 90-week-old rats to be in the order hippocampus > cerebral cortex > cerebellum > striatum approximately midbrain, with higher rates of hydrolysis for the 7-week-old rats than for the 90-week-old rats. In whole brain (minus cerebellum), the R(-)-enantiomer of ibuprofen was a mixed-type inhibitor of anandamide hydrolysis and was approximately 2-3 times more potent than the S(+)-enantiomer, IC50 values of 230 and 750 microM, respectively, being found. A similar pattern of inhibition of anandamide hydrolysis was seen when intact C6 rat glioma cells were used. Ketorolac inhibited rat brain anandamide hydrolysis, with IC50 values of 50, 440, and 80 microM being found for the R-, S-, and R,S-forms, respectively. The IC50 value for R-flurbiprofen (60 microM) was similar to the IC50 value for the S-enantiomer (50 microM). These data demonstrate that there is no dramatic enantiomeric selectivity of NSAID compounds as inhibitors of fatty acid amide hydrolase enzyme(s) responsible for the hydrolysis of anandamide. The enantiomers of flurbiprofen and R-ketorolac are the most potent NSAID inhibitors of fatty acid amide hydrolase yet reported.

Topics: Aging; Animals; Arachidonic Acids; Brain; Cell Extracts; Cell Survival; Dose-Response Relationship, Drug; Endocannabinoids; Flurbiprofen; Glioma; Hydrolysis; Ibuprofen; Inhibitory Concentration 50; Ketorolac; Kinetics; Polyunsaturated Alkamides; Rats; Rats, Sprague-Dawley; Stereoisomerism; Time Factors; Tolmetin; Tumor Cells, Cultured

1. Aminoalkylindoles, typified by WIN 55212-2, bind to G protein-coupled cannabinoid receptors in brain. Although cannabinoids inhibit adenylyl cyclase in NG108-15 neuroblastoma x glioma hybrid cells, cannabinoid receptor binding in these cells has not been described previously. This study compares pharmacological characteristics of [3H]WIN 55212-2 binding sites in rat cerebellar membranes and in NG108-15 membranes. 2. Although the KD of specified [3H]WIN 55212-2 binding was similar in brain and NG108-15 membranes, the Bmax was 10 times lower in NG108-15 than in cerebellar membranes. In both brain and NG108-15 membranes, aminoalkylindole analogues were relatively potent in displacing [3H]WIN 55212-2 binding. However, IC50 values for more traditional cannabinoids were significantly higher in NG108-15 membranes than in brain, e.g., the Ki values for CP55,940 were 1.2 nM in brain and > 5000nM in NG108-15 membranes. Moreover, sodium and GTP-gamma-S decreased [3H]WIN 55212-2 binding in brain but not in NG108-15 membranes. 3. These data suggest that WIN 55212-2 does not label traditional cannabinoid receptors in NG108-15 cells and that these novel aminoalkylindole binding sites are not coupled to G proteins.

Topics: Analgesics; Animals; Arachidonic Acids; Benzoxazines; Binding, Competitive; Calcium Channel Blockers; Cannabinoids; Cerebellum; Cyclohexanols; Endocannabinoids; Glioma; Guanosine 5'-O-(3-Thiotriphosphate); Hybrid Cells; Male; Membrane Proteins; Morpholines; Naphthalenes; Neuroblastoma; Polyunsaturated Alkamides; Radioligand Assay; Rats; Rats, Sprague-Dawley; Receptors, Cannabinoid; Receptors, Drug; Sensitivity and Specificity; Tritium

Low concentrations of 2-arachidonoylglycerol were found to induce rapid, transient elevation of intracellular free Ca2+ in NG108-15 cells (EC50 was 150 nM). Free arachidonic acid, 2-palmitoylglycerol, 2-oleoylglycerol, 2-linoleoylglycerol and 2-docosahexaenoylglycerol were inactive. Anandamide acted as a partial agonist. Importantly, desensitization was observed upon sequential challenge with 2-arachidonoylglycerol. Furthermore, cross-desensitization was observed between 2-arachidonoylglycerol and WIN 55212-2, a cannabinoid receptor agonist. Pretreatment of the cells with SR141716A, a cannabinoid receptor antagonist, abolished the activities of both 2-arachidonoylglycerol and WIN 55212-2. These results strongly suggest that 2-arachidonoylglycerol and WIN 55212-2 bind to a common cannabinoid receptor to elicit cellular responses and that 2-arachidonoylglycerol has some physiological role in nervous tissues.

Topics: Arachidonic Acids; Benzoxazines; Calcium; Cannabinoids; Dose-Response Relationship, Drug; Drug Interactions; Endocannabinoids; Glioma; Glycerides; Hybrid Cells; Ligands; Morpholines; Naphthalenes; Neuroblastoma; Neurons; Piperidines; Platelet Activating Factor; Polyunsaturated Alkamides; Pyrazoles; Receptors, Cannabinoid; Receptors, Drug; Rimonabant

Enzymatic activities have been identified which catalyze both the hydrolysis and synthesis of arachidonylethanolamide (anandamide). Anandamide was taken up by neuroblastoma and glioma cells in culture, but it did not accumulate since it was rapidly degraded by an amidase activity that resided mainly in the membrane fractions. This amidase activity was expressed in brain and the majority of cells and tissues tested. Phenylmethylsulfonyl fluoride (PMSF) was found to be a potent inhibitor of this amidase. A catalytic activity for the biosynthesis of anandamide from ethanolamine and arachidonic acid was readily apparent in incubations of rat brain homogenates. The stability of anandamide in serum and its rapid breakdown in cells and tissues are consistent with the observation that it is active when administered systemically, and its duration of action will be regulated by its rate of degradation in cells.

Topics: Amides; Animals; Arachidonic Acid; Arachidonic Acids; Brain Chemistry; Cell Line; Endocannabinoids; Ethanolamines; Fatty Acids, Unsaturated; Glioma; Neuroblastoma; Phenylmethylsulfonyl Fluoride; Polyunsaturated Alkamides; Rats; Receptors, Cannabinoid; Receptors, Drug; Subcellular Fractions; Tumor Cells, Cultured