Endocannabinoid signaling via cannabinoid receptor 1 is involved in ethanol preference and its age-dependent decline in mice

Alcohol inhibits luteinizing hormone-releasing hormone release by activating the endocannabinoid system

We hypothesized that ethanol (EtOH) might act through the endocannabinoid system to inhibit luteinizing hormone-releasing hormone (LHRH) release. Therefore, we examined the mechanism by which EtOH and anandamide (AEA), an endogenous cannabinoid, inhibit LHRH release from incubated medial basal hypothalamic explants. In previous work, we demonstrated that EtOH inhibits the N-methyl-D-aspartic acid-stimulated release of LHRH by increasing the release of two neurotransmitters: beta-endorphin and gamma-aminobutyric acid (GABA). In the present work, bicuculline, a GABAergic antagonist, completely prevented the inhibition of AEA (10(-9)M) on N-methyl-D-aspartic acid-induced LHRH release, but naltrexone, a micro-opioid receptor antagonist, had no effect. AEA also significantly increased GABA release but had no effect on beta-endorphin release. Therefore, AEA could inhibit LHRH release by increasing GABA but not beta-endorphin release. Because EtOH and AEA acted similarly to inhibit LHRH release, we investigated whether both substances would affect the adenylate cyclase activity acting through the same GTP-coupled receptors, the cannabinoid receptors 1 (CB1-rs). AEA and EtOH (10(-1)M) reduced the forskolin-stimulated accumulation of cAMP, but AM251, a specific antagonist of CB1-r, significantly blocked that inhibition. Additionally we investigated whether CB1-r is involved in the inhibition of LHRH by EtOH and AEA. AEA and EtOH reduced forskolin-stimulated LHRH release, but AM251 significantly blocked that inhibition. Also, we demonstrated that EtOH did not act by increasing AEA synthase activity to inhibit LHRH release in our experimental conditions. Therefore, our results indicate that EtOH inhibits the release of LHRH acting through the endocannabinoid system.

Lipopolysaccharide induces anandamide synthesis in macrophages via CD14/MAPK/phosphoinositide 3-kinase/NF-kappaB independently of platelet-activating factor

Macrophage-derived endocannabinoids have been implicated in endotoxin (lipopolysaccharide (LPS))-induced hypotension, but the endocannabinoid involved and the mechanism of its regulation by LPS are unknown. In RAW264.7 mouse macrophages, LPS (10 ng/ml) increases anandamide (AEA) levels >10-fold via CD14-, NF-kappaB-, and p44/42-dependent, platelet-activating factor-independent activation of the AEA biosynthetic enzymes, N-acyltransferase and phospholipase D. LPS also induces the AEA-degrading enzyme fatty acid amidohydrolase (FAAH), and inhibition of FAAH activity potentiates, whereas actinomycin D or cycloheximide blocks the LPS-induced increase in AEA levels and N-acyltransferase and phospholipase D activities. In contrast, cellular levels of the endocannabinoid 2-arachidonoylglycerol (2-AG) are unaffected by LPS but increased by platelet-activating factor. LPS similarly induces AEA, but not 2-AG, in mouse peritoneal macrophages where basal AEA levels are higher, and the LPS-stimulated increase in AEA is potentiated in cells from FAAH-/- as compared with FAAH+/+ mice. Intravenous administration of 107 LPS-treated mouse macrophages to anesthetized rats elicits hypotension, which is much greater in response to FAAH-/- than FAAH+/+ cells and is susceptible to inhibition by SR141716, a cannabinoid CB1 receptor antagonist. We conclude that AEA and 2-AG synthesis are differentially regulated in macrophages, and AEA rather than 2-AG is a major contributor to LPS-induced hypotension.

Neuroprotective and brain edema-reducing efficacy of the novel cannabinoid receptor agonist BAY 38-7271

BAY 38-7271 is a new high-affinity cannabinoid receptor agonist with strong neuroprotective efficacy in a rat model of traumatic brain injury (acute subdural hematoma, SDH). In the present study we investigated CB1 receptor signal transduction by [35S]GTPgammaS binding in situ and in vitro to assess changes in receptor functionality after SDH. Further, we continued to investigate the neuroprotective properties of BAY 38-7271 in the rat SDH and transient middle cerebral artery occlusion (tMCA-O) model as well as the efficacy with respect to SDH-induced brain edema. [35S]GTPgammaS binding revealed minor attenuation of CB1 receptor functionality on brain membranes from injured hemispheres when compared to non-injured hemispheres or controls. In the rat SDH model, BAY 38-7271 displayed strong neuroprotective efficacy when administered immediately after SDH either as a 1 h (65% infarct volume reduction at 0.1 microg/kg) or short-duration (15 min) infusion (53% at 10 microg/kg). When administered as a 4 h infusion with a 5 h delay after injury, significant neuroprotection was observed (49% at 1.0 microg/kg/h). This was also observed when BAY 38-7271 was administered as a 5 h delayed 15 min short-duration infusion (64% at 3 microg/kg). In addition, the neuroprotective potential of BAY 38-7271 was demonstrated in the rat tMCA-O model, displaying pronounced neuroprotective efficacy in the cerebral cortex (91% at 1 ng/kg/h) and striatum (53% at 10 ng/kg/h). BAY 38-7271 also reduced intracranial pressure (28% at 250 ng/kg/h) and brain water content (20% at 250 ng/kg/h) when determined 24 h post-SDH. Based on these data it is concluded that the neuroprotective efficacy of BAY 38-7271 is mediated by multiple mechanisms triggered by cannabinoid receptors.

The cannabinoid system: a role in both the homeostatic and hedonic control of eating?

Knowledge of the cannabinoid system and its components has expanded greatly over the past decade. There is increasing evidence for its role in the regulation of food intake and appetite. Cannabinoid system activity in the hypothalamus is thought to contribute to the homeostatic regulation of energy balance, under the control of the hormone leptin. A second component of cannabinoid-mediated food intake appears to involve reward pathways and the hedonic aspect of eating. With the cannabinoid system contributing to both regulatory pathways, it presents an attractive therapeutic target for the treatment of both obesity and eating disorders.

Differential regulation of the endocannabinoids anandamide and 2-arachidonylglycerol within the limbic forebrain by dopamine receptor activity

Glutamatergic synaptic transmission within the striatum and prefrontal cortex regulates the neuronal synthesis of endocannabinoids. Because a primary role of dopamine is to modulate this excitatory transmission, we tested the hypothesis that dopaminergic transmission modulates endocannabinoid content in the limbic forebrain. Liquid chromatography/mass spectrometry was used to determine endogenous anandamide and 2-arachidonylglycerol (2-AG) contents within the limbic forebrain of mice after pharmacological manipulation of dopaminergic transmission. Increasing synaptic dopamine concentrations with methylphenidate significantly and dose dependently decreased both anandamide and 2-AG content. The selective dopamine reuptake inhibitor 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (GBR 12909) also significantly decreased anandamide and tended to decrease 2-AG content. The D1 receptor antagonist R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH 23390) increased and the D1 receptor agonist 2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine (SKF 33939) decreased anandamide content. 2-AG content was unaffected by SCH 23390 but was significantly increased by the D2 receptor antagonist eticlopride, which had no effect on anandamide content. The D2 agonist quinpirole had a biphasic effect on anandamide content with low, autoreceptor-preferring doses increasing anandamide and higher doses decreasing it back toward control. Quinpirole did not significantly affect 2-AG content. Together, these data indicate that endogenous dopamine exerts a differential, net suppressive effect upon anandamide and 2-AG content via activation of D1 and D2 receptors, respectively. These data are consistent with the hypothesis that modulation of endocannabinoid content by dopamine is secondary to changes in glutamatergic transmission, and they provide a pharmacological framework for the rational development of endocannabinoid-based therapeutic interventions for dopamine-related neuropsychiatric disorders.

Progesterone activates fatty acid amide hydrolase (FAAH) promoter in human T lymphocytes through the transcription factor Ikaros. Evidence for a synergistic effect of leptin

Physiological concentrations of progesterone stimulate the activity of the endocannabinoid-degrading enzyme fatty acid amide hydrolase (FAAH) in human T lymphocytes, up to a approximately 270% over the untreated controls. Stimulation of FAAH occurred through up-regulation of gene expression at transcriptional and translational level and was specific. Indeed, neither the activity of the anandamide-synthesizing N-acyltransferase and phospholipase D, nor the activity of the anandamide transporter, nor the binding to cannabinoid receptors were affected by progesterone under the same experimental conditions. The activation of FAAH by progesterone was paralleled by a decrease (down to 60%) of the cellular levels of anandamide and involved increased nuclear levels of the transcription factor Ikaros. Analysis of the FAAH promoter showed an Ikaros binding site, and mutation of this site prevented FAAH activation by progesterone in transient expression assays. Electrophoretic mobility shift and supershift assays further corroborated the promoter activity data. Furthermore, the effect of progesterone on FAAH promoter was additive to that of physiological amounts of leptin, which binds to a cAMP response element-like site in the promoter region. Taken together, these results suggest that progesterone and leptin, by up-regulating the FAAH promoter at different sites, enhance FAAH expression, thus tuning the immunomodulatory effects of anandamide. These findings might also have critical implications for human fertility.

Overeating, alcohol and sucrose consumption decrease in CB1 receptor deleted mice

Administration of the cannabinoid CB1 receptor antagonist SR141716 (3-10 mg/kg i.p.) abolished neuropeptide Y-induced overeating and significantly reduced ethanol and sucrose intake in CB1 wild-type (+/+) mice. In CB1 receptor knockout (-/-) mice, neuropeptide Y totally lost its capacity to increase food consumption. Similarly, sucrose and ethanol intakes were significantly lower in CB1-/- vs. CB1+/+ mice. In CB1 deficient mice, SR141716 had no effect in these models.

Cannabis and alcohol--a close friendship

Cannabinoids and alcohol activate the same reward pathways, and the cannabinoid CB(1) receptor system plays an important role in regulating the positive reinforcing properties of alcohol. Indeed, both cannabinoids and alcohol cause the release of dopamine in the nucleus accumbens. Recent research suggests that ethanol preference, which is dependent on CB(1) receptors, is higher in young mice than in old mice, and higher in female mice than in male mice.

Chronic ethanol inhibits the anandamide transport and increases extracellular anandamide levels in cerebellar granule neurons

Ethanol increases extracellular anandamide levels in neuronal cells. However, the molecular mechanisms by which this occurs are unknown. Chronic exposure of cerebellar granule neurons to ethanol increased the levels of anandamide accumulated in the cellular medium. Anandamide uptake was saturable and was inhibited (30% at 3 min) in response to chronic exposure to ethanol. Chronic ethanol treatment did not alter the K(m), but significantly decreased V(max) of anandamide transport (33%) (P<0.0001). Fatty acid amide hydrolase activity was not affected by chronic ethanol treatment. Anandamide transport processes are independent of cannabinoid CB1 receptor, as cannabinoid CB1 receptor knockout mice exhibited time-dependent anandamide transport and cannabinoid CB1 receptor antagonists did not alter the effects of chronic ethanol on anandamide transport. Furthermore, anandamide transport was inhibited by acute ethanol in a time- and dose-dependent manner. Interestingly, acute ethanol-induced inhibition of anandamide transport was abolished in neurons exposed to chronic ethanol, suggesting that the anandamide transport processes may play a role in the development of long-term cellular tolerance to ethanol.