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Raphael Mechoulam

Publications and source records attributed to Raphael Mechoulam.

At least 19 recordsLinked to original sources
PubMed2007

Cannabinoids induce glioma stem-like cell differentiation and inhibit gliomagenesis.

Glioma stem-like cells constitute one of the potential origins of gliomas, and therefore, their elimination is an essential factor for the development of efficient therapeutic strategies. Cannabinoids are known to exert an antitumoral action on gliomas that relies on at least two mechanisms: induction of apoptosis of transformed cells and inhibition of tumor angiogenesis. However, whether cannabinoids target human glioma stem cells and their potential impact in gliomagenesis are unknown. Here, we show that glioma stem-like cells derived from glioblastoma multiforme biopsies and the glioma cell lines U87MG and U373MG express cannabinoid type 1 (CB(1)) and type 2 (CB(2)) receptors and other elements of the endocannabinoid system. In gene array experiments, CB receptor activation altered the expression of genes involved in the regulation of stem cell proliferation and differentiation. The cannabinoid agonists HU-210 and JWH-133 promoted glial differentiation in a CB receptor-dependent manner as shown by the increased number of S-100beta- and glial fibrillary acidic protein-expressing cells. In parallel, cannabinoids decreased the cell population expressing the neuroepithelial progenitor marker nestin. Moreover, cannabinoid challenge decreased the efficiency of glioma stem-like cells to initiate glioma formation in vivo, a finding that correlated with decreased neurosphere formation and cell proliferation in secondary xenografts. Gliomas derived from cannabinoid-treated cancer stem-like cells were characterized with a panel of neural markers and evidenced a more differentiated phenotype and a concomitant decrease in nestin expression. Overall, our results demonstrate that cannabinoids target glioma stem-like cells, promote their differentiation, and inhibit gliomagenesis, thus giving further support to their potential use in the management of malignant gliomas.

Animals↗
PubMed2006

Evaluation of the neuroprotective effect of cannabinoids in a rat model of Parkinson's disease: importance of antioxidant and cannabinoid receptor-independent properties.

We have recently demonstrated that two plant-derived cannabinoids, Delta9-tetrahydrocannabinol and cannabidiol (CBD), are neuroprotective in an animal model of Parkinson's disease (PD), presumably because of their antioxidant properties. To further explore this issue, we examined the neuroprotective effects of a series of cannabinoid-based compounds, with more selectivity for different elements of the cannabinoid signalling system, in rats with unilateral lesions of nigrostriatal dopaminergic neurons caused by local application of 6-hydroxydopamine. We used the CB1 receptor agonist arachidonyl-2-chloroethylamide (ACEA), the CB2 receptor agonist HU-308, the non-selective agonist WIN55,212-2, and the inhibitors of the endocannabinoid inactivation AM404 and UCM707, all of them administered i.p. Daily administration of ACEA or WIN55,212-2 did not reverse 6-hydroxydopamine-induced dopamine (DA) depletion in the lesioned side, whereas HU-308 produced a small recovery that supports a possible involvement of CB2 but not CB1 receptors. AM404 produced a marked recovery of 6-hydroxydopamine-induced DA depletion and tyrosine hydroxylase deficit in the lesioned side. Possibly, this is caused by the antioxidant properties of AM404, which are derived from the presence of a phenolic group in its structure, rather than by the capability of AM404 to block the endocannabinoid transporter, because UCM707, another transporter inhibitor devoid of antioxidant properties, did not produce the same effect. None of these effects were observed in non-lesioned contralateral structures. We also examined the timing for the effect of CBD to provide neuroprotection in this rat model of PD. We found that CBD, as expected, was able to recover 6-hydroxydopamine-induced DA depletion when it was administered immediately after the lesion, but it failed to do that when the treatment started 1 week later. In addition, the effect of CBD implied an upregulation of mRNA levels for Cu,Zn-superoxide dismutase, a key enzyme in endogenous defenses against oxidative stress. In summary, our results indicate that those cannabinoids having antioxidant cannabinoid receptor-independent properties provide neuroprotection against the progressive degeneration of nigrostriatal dopaminergic neurons occurring in PD. In addition, the activation of CB2 (but not CB1) receptors, or other additional mechanisms, might also contribute to some extent to the potential of cannabinoids in this disease.

Animals↗
PubMed2006

Non-psychoactive CB2 cannabinoid agonists stimulate neural progenitor proliferation.

Cannabinoids, the active components of marijuana and their endogenous counterparts, act on the brain and many other organs through the widely expressed CB1 cannabinoid receptor. In contrast, the CB2 cannabinoid receptor is abundant in the immune system and shows a restricted expression pattern in brain cells. CB2-selective agonists are, therefore, very attractive therapeutic agents as they do not cause CB1-mediated psychoactive effects. CB2 receptor expression in brain has been partially examined in differentiated cells, while its presence and function in neural progenitor cells remain unknown. Here we show that the CB2 receptor is expressed, both in vitro and in vivo, in neural progenitors from late embryonic stages to adult brain. Selective pharmacological activation of the CB2 receptor in vitro promotes neural progenitor cell proliferation and neurosphere generation, an action that is impaired in CB2-deficient cells. Accordingly, in vivo experiments evidence that hippocampal progenitor proliferation is increased by administration of the CB2-selective agonist HU-308. Moreover, impaired progenitor proliferation was observed in CB2-deficient mice both in normal conditions and on kainate-induced excitotoxicity. These findings provide a novel physiological role for the CB2 cannabinoid receptor and open a novel therapeutic avenue for manipulating neural progenitor cell fate.

Animals↗
PubMed2006

Cannabidiol, a constituent of Cannabis sativa, modulates sleep in rats.

Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and cannabidiol (CBD) are two major constituents of Cannabis sativa. Delta(9)-THC modulates sleep, but no clear evidence on the role of CBD is available. In order to determine the effects of CBD on sleep, it was administered intracerebroventricular (icv) in a dose of 10 microg/5 microl at the beginning of either the lights-on or the lights-off period. We found that CBD administered during the lights-on period increased wakefulness (W) and decreased rapid eye movement sleep (REMS). No changes on sleep were observed during the dark phase. Icv injections of CBD (10 microg/5microl) induced an enhancement of c-Fos expression in waking-related brain areas such as hypothalamus and dorsal raphe nucleus (DRD). Microdialysis in unanesthetized rats was carried out to characterize the effects of icv administration of CBD (10 microg/5 microl) on extracellular levels of dopamine (DA) within the nucleus accumbens. CBD induced an increase in DA release. Finally, in order to test if the waking properties of CBD could be blocked by the sleep-inducing endocannabinoid anandamide (ANA), animals received ANA (10 microg/2.5 microl, icv) followed 15 min later by CBD (10 microg/2.5 microl). Results showed that the waking properties of CBD were not blocked by ANA. In conclusion, we found that CBD modulates waking via activation of neurons in the hypothalamus and DRD. Both regions are apparently involved in the generation of alertness. Also, CBD increases DA levels as measured by microdialysis and HPLC procedures. Since CBD induces alertness, it might be of therapeutic value in sleep disorders such as excessive somnolence.

Animals↗
PubMed2006

Involvement of neuronal cannabinoid receptor CB1 in regulation of bone mass and bone remodeling.

The CB1 cannabinoid receptor has been implicated in the regulation of bone remodeling and bone mass. A high bone mass (HBM) phenotype was reported in CB1-null mice generated on a CD1 background (CD1(CB1-/-) mice). By contrast, our preliminary studies in cb1-/- mice, backcrossed to C57BL/6J mice (C57(CB1-/-) mice), revealed low bone mass (LBM). We therefore analyzed CB1 expression in bone and compared the skeletons of sexually mature C57(CB1-/-) and CD1(CB1-/-) mice in the same experimental setting. CB1 mRNA is weakly expressed in osteoclasts and immunoreactive CB1 is present in sympathetic neurons, close to osteoblasts. In addition to their LBM, male and female C57(CB1-/-) mice exhibit decreased bone formation rate and increased osteoclast number. The skeletal phenotype of the CD1(CB1-/-) mice shows a gender disparity. Female mice have normal trabecular bone with a slight cortical expansion, whereas male CD1(CB1-/-) animals display an HBM phenotype. We were surprised to find that bone formation and resorption are within normal limits. These findings, at least the consistent set of data obtained in the C57(CB1-/-) line, suggest an important role for CB1 signaling in the regulation of bone remodeling and bone mass. Because sympathetic CB1 signaling inhibits norepinephrine (NE) release in peripheral tissues, part of the endocannabinoid activity in bone may be attributed to the regulation of NE release from sympathetic nerve fibers. Several phenotypic discrepancies have been reported between C57(CB1-/-) and CD1(CB1-/-) mice that could result from genetic differences between the background strains. Unraveling these differences can provide useful information on the physiologic functional milieu of CB1 in bone.

Adrenergic Fibers↗
PubMed2006

A cannabinoid quinone inhibits angiogenesis by targeting vascular endothelial cells.

Recent findings on the inhibition of angiogenesis and vascular endothelial cell proliferation by anthracycline antibiotics, which contain a quinone moiety, make this type of compound a very promising lead in cancer research/therapy. We have reported that a new cannabinoid anticancer quinone, cannabidiol hydroxyquinone (HU-331), is highly effective against tumor xenografts in nude mice. For evaluation of the antiangiogenic action of cannabinoid quinones, collagen-embedded rat aortic ring assay was used. The ability of cannabinoids to cause endothelial cell apoptosis was assayed by TUNEL staining and flow cytometry analysis. To examine the genes and pathways targeted by HU-331 in vascular endothelial cells, human cDNA microarrays and polymerase chain reaction were used. Immunostaining with anti-CD31 of tumors grown in nude mice served to indicate inhibition of tumor angiogenesis. HU-331 was found to be strongly antiangiogenic, significantly inhibiting angiogenesis at concentrations as low as 300 nM. HU-331 inhibited angiogenesis by directly inducing apoptosis of vascular endothelial cells without changing the expression of pro- and antiangiogenic cytokines and their receptors. A significant decrease in the total area occupied by vessels in HU-331-treated tumors was also observed. These data lead us to consider HU-331 to have high potential as a new antiangiogenic and anticancer drug.

Animals↗
PubMed2006

N-arachidonoyl L-serine, an endocannabinoid-like brain constituent with vasodilatory properties.

The endocannabinoid N-arachidonoyl ethanolamine (anandamide), found both in the CNS and in the periphery, plays a role in numerous physiological systems. One might expect that the chemically related N-arachidonoyl-L-serine (ARA-S) could also be formed alongside anandamide. We have now isolated ARA-S from bovine brain and elucidated its structure by comparison with synthetic ARA-S. Contrary to anandamide, ARA-S binds very weakly to cannabinoid CB1 and CB2 or vanilloid TRPV1 (transient receptor potential vanilloid 1) receptors. However, it produces endothelium-dependent vasodilation of rat isolated mesenteric arteries and abdominal aorta and stimulates phosphorylation of p44/42 mitogen-activated protein (MAP) kinase and protein kinase B/Akt in cultured endothelial cells. ARA-S also suppresses LPS-induced formation of TNF-alpha in a murine macrophage cell line and in wild-type mice, as well as in mice deficient in CB1 or CB2 receptors. Many of these effects parallel those reported for abnormal cannabidiol (Abn-CBD), a synthetic agonist of a putative novel cannabinoid-type receptor. Hence, ARA-S may represent an endogenous agonist for this receptor.

Animals↗
PubMed2006

Peripheral cannabinoid receptor, CB2, regulates bone mass.

The endogenous cannabinoids bind to and activate two G protein-coupled receptors, the predominantly central cannabinoid receptor type 1 (CB1) and peripheral cannabinoid receptor type 2 (CB2). Whereas CB1 mediates the cannabinoid psychotropic, analgesic, and orectic effects, CB2 has been implicated recently in the regulation of liver fibrosis and atherosclerosis. Here we show that CB2-deficient mice have a markedly accelerated age-related trabecular bone loss and cortical expansion, although cortical thickness remains unaltered. These changes are reminiscent of human osteoporosis and may result from differential regulation of trabecular and cortical bone remodeling. The CB2(-/-) phenotype is also characterized by increased activity of trabecular osteoblasts (bone-forming cells), increased osteoclast (the bone-resorbing cell) number, and a markedly decreased number of diaphyseal osteoblast precursors. CB2 is expressed in osteoblasts, osteocytes, and osteoclasts. A CB2-specific agonist that does not have any psychotropic effects enhances endocortical osteoblast number and activity and restrains trabecular osteoclastogenesis, apparently by inhibiting proliferation of osteoclast precursors and receptor activator of NF-kappaB ligand expression in bone marrow-derived osteoblasts/stromal cells. The same agonist attenuates ovariectomy-induced bone loss and markedly stimulates cortical thickness through the respective suppression of osteoclast number and stimulation of endocortical bone formation. These results demonstrate that the endocannabinoid system is essential for the maintenance of normal bone mass by osteoblastic and osteoclastic CB2 signaling. Hence, CB2 offers a molecular target for the diagnosis and treatment of osteoporosis, the most prevalent degenerative disease in developed countries.

Animals↗
PubMed2005

The endocannabinoid 2-AG protects the blood-brain barrier after closed head injury and inhibits mRNA expression of proinflammatory cytokines.

Endocannabinoids are involved in neuroprotection through numerous biochemical pathways. We have shown that the endocannabinoid 2-arachidonoyl glycerol (2-AG) is released in mouse brain after closed head injury (CHI), and treatment with exogenous 2-AG exerts neuroprotection via the central cannabinoid receptor CB1. This process involves inhibition of inflammatory signals that are mediated by activation of the transcription factor NF-kB. The present study was designed to examine the effect of 2-AG on the blood-brain barrier (BBB) and the possible inhibition of the early expression of proinflammatory cytokines, which are implicated in BBB disruption. We found that 2-AG decreased BBB permeability and inhibited the acute expression of the main proinflammatory cytokines: TNF-alpha, IL-1beta and IL-6. It also augmented the levels of endogenous antioxidants. We suggest that 2-AG exerts neuroprotection in part by inhibition of the early (1-4 h) inflammatory response and augmentation of the brain reducing power.

Animals↗
PubMed2005

Delta-9-tetrahydrocannabinol and cannabidiol, but not ondansetron, interfere with conditioned retching reactions elicited by a lithium-paired context in Suncus murinus: An animal model of anticipatory nausea and vomiting.

Chemotherapy patients report not only acute nausea and vomiting during the treatment itself, but also report anticipatory nausea and vomiting upon re-exposure to the cues associated with the treatment. We present a model of anticipatory nausea based on the emetic reactions of the Suncus murinus (musk shrew). Following three pairings of a novel distinctive contextual cue with the emetic effects of an injection of lithium chloride, the context acquired the potential to elicit conditioned retching in the absence of the toxin. The expression of this conditioned retching reaction was completely suppressed by pretreatment with each of the principal cannabinoids found in marijuana, Delta(9)-tetrahydrocannabinol or cannabidiol, at a dose that did not suppress general activity. On the other hand, pretreatment with a dose of ondansetron (a 5-HT(3) antagonist) that interferes with acute vomiting in this species, did not suppress the expression of conditioned retching during re-exposure to the lithium-paired context. These results support anecdotal claims that marijuana, but not ondansetron, may suppress the expression of anticipatory nausea.

Analysis of Variance↗
PubMed2005

Endocannabinoids affect neurological and cognitive function in thioacetamide-induced hepatic encephalopathy in mice.

Endocannabinoids function as neurotransmitters and neuromodulators in the central nervous system via specific receptors and apparently have a neuroprotective role. We assumed that the endocannabinoid system could be involved in the pathogenesis of hepatic encephalopathy (HE), a neuropsychiatric syndrome due to liver disease. We used a mouse model of a thioacetamide induced fulminant hepatic failure. We found that the levels of the endocannabinoid 2-arachidonoyl-glycerol (2-AG) were elevated in the brain. Treatment with either 2-AG or with the CB1 receptor antagonist, SR141716A, improved a neurological score, activity and cognitive function. Activation of the CB2 receptor by a selective agonist, HU308, also improved the neurological score. 2-AG activity could be blocked with the specific CB2 receptor antagonist SR144528A. The CB1 receptor agonist noladin ether was inactive. We conclude that the endocannabinoid system may play an important role in the pathogenesis of HE. Modulation of this system either by exogenous agonists specific for the CB2 receptors or possibly also by antagonists to the CB1 receptors may have therapeutic potential.

Animals↗
PubMed2005

Evidence that (-)-7-hydroxy-4'-dimethylheptyl-cannabidiol activates a non-CB(1), non-CB(2), non-TRPV1 target in the mouse vas deferens.

Previous experiments showed that R-(+)-WIN55212-induced inhibition of electrically-evoked contractions of mouse vasa deferentia could be antagonized by cannabidiol in a manner that appeared to be competitive but not to involve direct competition for established cannabinoid receptors. We have now discovered that (-)-7-hydroxy-4'-dimethylheptyl-cannabidiol (7-OH-DMH-CBD) inhibits electrically-evoked contractions of the vas deferens (EC(50)=13.3 nM). This it appeared to do by acting on prejunctional neurones as 100 nM 7-OH-DMH-CBD did not attenuate contractile responses to phenylephrine or beta,gamma-methylene-ATP. Although 7-OH-DMH-CBD was antagonized by SR141716A, it was less susceptible to antagonism by this CB(1) receptor antagonist than R-(+)-WIN55212. 7-OH-DMH-CBD was also antagonized by cannabidiol (1 microM; apparent K(B)=222.2 nM) but not by the CB(2) receptor antagonist, SR144528 (32 nM), or by naloxone (300 nM), ruthenium red (1 microM) or capsazepine (10 microM). Yohimbine (100 nM) enhanced the ability of 7-OH-DMH-CBD to inhibit electrically-evoked contractions. R-(+)-WIN55212 was also potentiated by 100 nM yohimbine, possibly reflecting ongoing sequestration of G(i/o) proteins from CB(1) receptors by alpha(2)-adrenoceptors. Our results suggest that 7-OH-DMH-CBD may activate a neuronal target in the vas deferens that is not a CB(1), CB(2), TRPV1, opioid or alpha(2)-adrenergic receptor but do not exclude the possibility that it also activates CB(1) receptors.

Adenosine Triphosphate↗
PubMed2005

Enantiomeric cannabidiol derivatives: synthesis and binding to cannabinoid receptors.

(-)-Cannabidiol (CBD) is a major, non psychotropic constituent of cannabis. It has been shown to cause numerous physiological effects of therapeutic importance. We have reported that CBD derivatives in both enantiomeric series are of pharmaceutical interest. Here we describe the syntheses of the major CBD metabolites, (-)-7-hydroxy-CBD and (-)-CBD-7-oic acid and their dimethylheptyl (DMH) homologs, as well as of the corresponding compounds in the enantiomeric (+)-CBD series. The starting materials were the respective CBD enantiomers and their DMH homologs. The binding of these compounds to the CB(1) and CB(2) cannabinoid receptors are compared. Surprisingly, contrary to the compounds in the (-) series, which do not bind to the receptors, most of the derivatives in the (+) series bind to the CB(1) receptor in the low nanomole range. Some of these compounds also bind weakly to the CB(2) receptor.

Animals↗
PubMed2005

Effects of the endocannabinoid noladin ether on body weight, food consumption, locomotor activity, and cognitive index in mice.

We have investigated the effect of 2-arachidonylglyceryl-ether (Noladin) on food consumption, weight, activity, and cognitive function in mice during diet restriction for 17 days and subsequent ad libitum feeding for 32 days. Female Sabra mice were given food for 2.5 h/day (equal to 60% diet restriction), received Noladin (0.001, 0.01, 0.1 mg/(kg day) intraperitonially (i.p.)) with or without the CB1 antagonist SR141716A (1 mg/kg i.p.) during days 3-17. Noladin (0.001 mg/kg) significantly increased food consumption without a change in body weight, probably due to increased activity and there was no change in cognitive function. A higher dose (0.1 mg/kg) did not affect food consumption, but increased activity and slightly decreased weight 32 days after termination of Noladin administration; however, cognitive deterioration was observed. At all doses tested, Noladin did not affect weight during the diet-restriction period, whereas the CB1 antagonist (with or without Noladin) caused a very significant decline in weight in this phase. Weight catch-up was observed 1 month after administration of Noladin was discontinued. Weight at day 32 after the termination of Noladin (0.1 mg/(kg day)) treatment was 5% less than control. Female C57BL/6 mice (same protocol, with 0.001 mg/(kg day) Noladin) gave similar results to 0.1 mg/kg in Sabra mice as regards weight. CB1 antagonist treatment caused very significant decline in both weight and food consumption; cognition and activity were unchanged. These results indicate that Noladin has a significant dose-dependent effect on food consumption, cognition and weight maintenance after weight loss. Low doses of Noladin may possibly allow an increase in food intake without a gain in weight after dieting. Thus, Noladin could be of potential clinical benefit in treating disorders of body weight. Noladin seems to signal food consumption and weight through CB1 receptors based on effects observed with the CB1 antagonist, while the cognition and activity are probably mediated by non-cannabinoid receptors.

Animals↗
PubMed2005

Hippocampal cannabinoid-1 receptor upregulation upon endothelin-B receptor deficiency: a neuroprotective substitution effect?

Endothelin (ETB)-receptors mediate anti-apoptotic actions. Lack of functional ETB-receptors leads to increased neuronal apoptosis in the hippocampus. The increased apoptosis must be compensated by other mechanisms, however, as ETB-deficient rats display normal overall brain morphology. To illuminate on brain plasticity in ETB-receptor deficiency, we studied the expression and function of another neuroprotective system, the cannabinoid CB1-receptors, in ETB-deficient hippocampus. We show that CB1 expression in hippocampus increases postnatally in all rats but that the increase in CB1-receptor expression is significantly higher in ETB-deficient compared to wildtype littermates. Neuronal apoptosis decreases during brain maturation but remains on a significantly higher level in the ETB-deficient compared to wildtype dentate. When investigating survival of hippocampal neurons in culture, we found significant protection against hypoxia-induced cell death with CB1-analogs (noladin, (9-tetrahydrocannabinol) only in ETB-deficient neurons. We suggest that CB1-receptor upregulation in the ETB-mutant hippocampus reflects an attempt to compensate for the lack of ETB-receptors.

Animals↗