Novel physiologic functions of endocannabinoids as revealed through the use of mutant mice

Multiple Cerebral Infarcts in a Young Patient Associated With Marijuana Use

: Cerebrovascular events associated with marijuana use have been reported previously. This association is plausible, but not well-established yet. A 14-year-old girl, long-term heavy cannabis user, presented with generalized tonic-clonic seizures and decreased level of consciousness a few hours after smoking cannabis. Brain magnetic resonance imaging showed multiple areas of acute, subacute and chronic ischemic lesions in the left frontal lobe, basal ganglia, and corpus callosum. History of other illicit drug use and other known causes of stroke were ruled out. Cannabis might cause stroke through direct effects on the cerebral blood circulation, orthostatic hypotension, vasculitis, vasospasm, and atrial fibrillation. Long-term daily use of marijuana in young people may cause serious damage to the cerebrovascular system.

Cannabinoid Regulation of Brain Reward Processing with an Emphasis on the Role of CB1 Receptors: A Step Back into the Future

Over the last decades, the endocannabinoid system has been implicated in a large variety of functions, including a crucial modulation of brain-reward circuits and the regulation of motivational processes. Importantly, behavioral studies have shown that cannabinoid compounds activate brain reward mechanisms and circuits in a similar manner to other drugs of abuse, such as nicotine, alcohol, cocaine, and heroin, although the conditions under which cannabinoids exert their rewarding effects may be more limited. Furthermore, there is evidence on the involvement of the endocannabinoid system in the regulation of cue- and drug-induced relapsing phenomena in animal models. The aim of this review is to briefly present the available data obtained using diverse behavioral experimental approaches in experimental animals, namely, the intracranial self-stimulation paradigm, the self-administration procedure, the conditioned place preference procedure, and the reinstatement of drug-seeking behavior procedure, to provide a comprehensive picture of the current status of what is known about the endocannabinoid system mechanisms that underlie modification of brain-reward processes. Emphasis is placed on the effects of cannabinoid 1 (CB1) receptor agonists, antagonists, and endocannabinoid modulators. Further, the role of CB1 receptors in reward processes is investigated through presentation of respective genetic ablation studies in mice. The vast majority of studies in the existing literature suggest that the endocannabinoid system plays a major role in modulating motivation and reward processes. However, much remains to be done before we fully understand these interactions. Further research in the future will shed more light on these processes and, thus, could lead to the development of potential pharmacotherapies designed to treat reward-dysfunction-related disorders.

DAGLβ inhibition perturbs a lipid network involved in macrophage inflammatory responses

The endocannabinoid 2-arachidonoylglycerol (2-AG) is biosynthesized by diacylglycerol lipases DAGLα and DAGLβ. Chemical probes to perturb DAGLs are needed to characterize endocannabinoid function in biological processes. Here we report a series of 1,2,3-triazole urea inhibitors, along with paired negative-control and activity-based probes, for the functional analysis of DAGLβ in living systems. Optimized inhibitors showed high selectivity for DAGLβ over other serine hydrolases, including DAGLα (∼60-fold selectivity), and the limited off-targets, such as ABHD6, were also inhibited by the negative-control probe. Using these agents and Daglb(-/-) mice, we show that DAGLβ inactivation lowers 2-AG, as well as arachidonic acid and eicosanoids, in mouse peritoneal macrophages in a manner that is distinct and complementary to disruption of cytosolic phospholipase-A2. We observed a corresponding reduction in lipopolysaccharide-induced tumor necrosis factor-α release. These findings indicate that DAGLβ is a key metabolic hub within a lipid network that regulates proinflammatory responses in macrophages.

Cannabinoid-dopamine interaction in the pathophysiology and treatment of CNS disorders

Endocannabinoids and their receptors, mainly the CB(1) receptor type, function as a retrograde signaling system in many synapses within the CNS, particularly in GABAergic and glutamatergic synapses. They also play a modulatory function on dopamine (DA) transmission, although CB(1) receptors do not appear to be located in dopaminergic terminals, at least in the major brain regions receiving dopaminergic innervation, e.g., the caudate-putamen and the nucleus accumbens/prefrontal cortex. Therefore, the effects of cannabinoids on DA transmission and DA-related behaviors are generally indirect and exerted through the modulation of GABA and glutamate inputs received by dopaminergic neurons. Recent evidence suggest, however, that certain eicosanoid-derived cannabinoids may directly activate TRPV(1) receptors, which have been found in some dopaminergic pathways, thus allowing a direct regulation of DA function. Through this direct mechanism or through indirect mechanisms involving GABA or glutamate neurons, cannabinoids may interact with DA transmission in the CNS and this has an important influence in various DA-related neurobiological processes (e.g., control of movement, motivation/reward) and, particularly, on different pathologies affecting these processes like basal ganglia disorders, schizophrenia, and drug addiction. The present review will address the current literature supporting these cannabinoid-DA interactions, with emphasis in aspects dealing with the neurochemical, physiological, and pharmacological/therapeutic bases of these interactions.

Plasma endocannabinoid levels in multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory disease of the CNS. Therapies that affect the endocannabinoid (EC) system may have immunomodulatory, symptomatic and neuroprotective effects.

AIM

The aim of this study was to determine how levels of EC and related compounds are altered in MS.

METHODS

Plasma and whole blood were collected from 24 MS patients (10 relapsing-remitting (RR); 8 secondary-progressive (SP); 6 primary-progressive (PP); 19 females; 25-66 years) and 17 controls (10 females; 22-62 years). Plasma EC and related compounds were quantified by liquid chromatography-tandem mass spectrometry. Fatty acid amide hydrolase (FAAH), cannabinoid receptors CB(1) and CB(2) mRNA were measured by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Anandamide (AEA) and palmitoylethanolamide (PEA) were higher in RRMS compared to controls (p=0.001 and p=0.027). AEA, PEA and oleoylethanolamide were also increased in SPMS plasma (p=0.001, p=0.004, and p=0.005). PPMS patients had higher AEA plasma levels compared to controls (p=0.009). FAAH mRNA was decreased in SPMS (p=0.04) but not in RRMS or PPMS blood. CB(1) (p=0.012) and CB(2) mRNA (p=0.003) were increased in the PPMS.

CONCLUSION

The EC system is altered in MS. It may be dynamically modulated depending on the subtype of the disease, but further studies with larger subgroups are needed to confirm this.

Participation of the endocannabinoid system in the effect of TNF-alpha on hypothalamic release of gonadotropin-releasing hormone

It is known that Delta(9)-tetrahydrocannabinol (THC), the major active ingredient of marijuana, can suppress reproductive function. Also, we reported previously that the endocannabinoid, anandamide (AEA), inhibited gonadotropin-releasing hormone (LHRH) release from medial basal hypothalamus (MBH) of male rats incubated in vitro as well as reduced plasma LH levels after i.c.v. AEA injections into the cerebral lateral ventricle. On the other hand, it is known that during endotoxemia the hypothalamic gonadotropin axis is inhibited. Therefore, the aim of the present study was to determine whether the effect of TNF-alpha, a proinflammatory cytokine induced by lipopolysaccharide (LPS) that inhibits LHRH release, is mediated by the activation of the endocannabinoid system. The intraperitoneal injection of LPS (5 mg/kg) as well as the i.c.v. injection of tumor necrosis factor-alpha (TNF-alpha) (100 ng/rat) increased significantly the AEA synthesis measured ex vivo in MBHs removed 3 h after the treatments. To examine the possibility that TNF-alpha also acted by increasing the synthesis of AEA that was released and activated the CB1-r followed by inhibition of LHRH release, we measured the effect of TNF-alpha on the AEA synthase activity in MBHs incubated in vitro. As expected, we found that TNF-alpha (2.9 x 10(-9) M) increased the AEA synthesis. Second, we showed that TNF-alpha reduced significantly the forskolin-stimulated LHRH release and that the CB1-r antagonist AM251 (10(-5) M) blocked that inhibition, supporting the hypothesis that TNF-alpha inhibits LHRH release, acting at least in part by activating the endocannabinoid system. Therefore, our data demonstrate a key role for the endocannabinoid system in the response of the reproductive system to inflammatory signals.

Ethanol self-administration and ethanol conditioned place preference are reduced in mice lacking cannabinoid CB1 receptors

Cannabinoids are postulated to play a role in modulating the reinforcing effects of abused drugs, including alcohol. Experiment 1 examined alcohol self-administration in cannabinoid CB1 receptor knockout (KO), heterozygous (HT) and wild type (WT) mice in a two-bottle choice paradigm. Mice were trained in a limited 8 h access/day to 10% (v/v) EtOH (EtOH) versus water. After baseline drinking levels (% EtOH preference and total EtOH intake (g/kg)), results indicated that the CB1 knockout mice displayed significantly lower baseline EtOH consumption compared to wild type mice. Subsequently, treatment with SR141716A (5mg/kg) significantly attenuated EtOH intake in the WT and HT mice but had little effect on the knockout mice. Experiment 2 examined the CB1 WT and CB1 KO strains in a conditioned place preference (CPP) procedure between saline and 2g/kg EtOH. The CB1 WT mice spent significantly more time in the EtOH-paired versus saline-paired chambers, whereas no significant preference was observed in the CB1 KO mice. Finally, we observed that CB1 KO mice were significantly lighter than WT and HT and that SR141716A did not significantly alter body weight. These results demonstrate that the cannabinoid CB1 receptor is an essential component of the molecular pathways underlying the reinforcing effects of alcohol. Thus, medications targeting the CB1 receptors may be beneficial for the treatment of alcoholism.

Keep off the grass: marijuana use and acute cardiovascular events

Marijuana is one of the most widely used recreational substances in the world, considered by many consumers as a relatively safe drug with few significant side-effects. We report the case of a 21-year-old man who suffered an acute myocardial infarction following the use of marijuana, despite having no other identifiable risk factors for an acute cardiovascular event. We review the published medical literature regarding acute cardiovascular events following marijuana use and postulate a possible mechanism for this unusual pathological consequence of marijuana use.

A role for cannabinoid CB1 receptors in mood and anxiety disorders

Mood and anxiety disorders, the most prevalent of the psychiatric disorders, cause immeasurable suffering worldwide. Despite impressive advances in pharmacological therapies, improvements in efficacy and side-effect profiles are needed. The present literature review examines the role that the endocannabinoid system may play in these disorders and the potential value of targeting this system in the search for novel and improved medications. Cannabis and its major psychoactive component (-)-trans-delta9-tetrahydrocannabinol, have profound effects on mood and can modulate anxiety and mood states. Cannabinoid receptors and other protein targets in the central nervous system (CNS) that modulate endocannabinoid function have been described. The discovery of selective modulators of some of these sites that increase or decrease endocannabinoid neurotransmission, primarily through the most prominent of the cannabinoid receptors in the CNS, the CB1 receptors, combined with transgenic mouse technology, has enabled detailed investigations into the role of these CNS sites in the regulation of mood and anxiety states. Although data point to the involvement of the endocannabinoid system in anxiety states, the pharmacological evidence seems contradictory: both anxiolytic- and anxiogenic-like effects have been reported with both endocannabinoid neurotransmission enhancers and blockers. Due to advances in the development of selective compounds directed at the CB1 receptors, significant progress has been made on this target. Recent biochemical and behavioural findings have demonstrated that blockade of CB1 receptors engenders antidepressant-like neurochemical changes (increases in extracellular levels of monoamines in cortical but not subcortical brain regions) and behavioural effects consistent with antidepressant/antistress activity in rodents.

Effects of the cannabinoid-1 receptor blocker rimonabant on weight reduction and cardiovascular risk factors in overweight patients: 1-year experience from the RIO-Europe study

BACKGROUND

In animal models, cannabinoid-1 receptor (CB1) blockade produces a lean phenotype, with resistance to diet-induced obesity and associated dyslipidaemia. We assessed the effect of rimonabant, a selective CB1 blocker, on bodyweight and cardiovascular risk factors in overweight or obese patients.

METHODS

patients with body-mass index 30 kg/m2 or greater, or body-mass index greater than 27 kg/m2 with treated or untreated dyslipidaemia, hypertension, or both, were randomised to receive double-blind treatment with placebo, 5 mg rimonabant, or 20 mg rimonabant once daily in addition to a mild hypocaloric diet (600 kcal/day deficit). The primary efficacy endpoint was weight change from baseline after 1 year of treatment in the intention-to-treat population.

FINDINGS

Weight loss at 1 year was significantly greater in patients treated with rimonabant 5 mg (mean -3.4 kg [SD 5.7]; p=0.002 vs placebo) and 20 mg (-6.6 kg [7.2]; p<0.001 vs placebo) compared with placebo (-1.8 kg [6.4]). Significantly more patients treated with rimonabant 20 mg than placebo achieved weight loss of 5% or greater (p<0.001) and 10% or greater (p<0.001). Rimonabant 20 mg produced significantly greater improvements than placebo in waist circumference, HDL-cholesterol, triglycerides, and insulin resistance, and prevalence of the metabolic syndrome. The effects of rimonabant 5 mg were of less clinical significance. Rimonabant was generally well tolerated with mild and transient side effects.

INTERPRETATION

CB1 blockade with rimonabant 20 mg, combined with a hypocaloric diet over 1 year, promoted significant decrease of bodyweight and waist circumference, and improvement in cardiovascular risk factors.

Cannabinoid modulation of peripheral autonomic and sensory neurotransmission

Cannabinoids are cell membrane-derived signalling molecules that are released from nerves, blood cells and endothelial cells, and have diverse biological effects. They act at two distinct types of G-protein-coupled receptors, cannabinoid CB(1) and CB(2) receptors. Cannabinoid CB(1) receptors are highly localised in the central nervous system and are also found in some peripheral tissues, and cannabinoid CB(2) receptors are found outside the central nervous system, in particular in association with immune tissues. Novel actions of cannabinoids at non-CB(1) non-CB(2) cannabinoid-like receptors and vanilloid VR1 receptors have also recently been described. There is growing evidence that, among other roles, cannabinoids can act at prejunctional sites to modulate peripheral autonomic and sensory neurotransmission, and the present article is aimed at providing an overview of this. Inhibitory cannabinoid CB(1) receptors are expressed on the peripheral terminals of autonomic and sensory nerves. The role of cannabinoid receptor ligands in modulation of sensory neurotransmission is complex, as certain of these (anandamide, an "endocannabinoid", and N-arachidonoyl-dopamine, an "endovanilloid") also activate vanilloid VR1 receptors (coexpressed with cannabinoid CB(1) receptors), which excites sensory nerves and causes a release of sensory neurotransmitter. The fact that the activities of anandamide and N-arachidonoyl-dopamine span two distinct receptor families raises important questions about cannabinoid/vanilloid nomenclature, and as both compounds are structurally related to the archetypal vanilloid capsaicin, all three are arguably members of the same family of signalling molecules. Anandamide is released from nerves, but unlike classical neurotransmitters, it is not stored in and released from nerve vesicles, but is released on demand from the nerve cell membrane. In the central nervous system, cannabinoids function as retrograde signalling molecules, inhibiting via presynaptic cannabinoid CB(1) receptors the release of classical transmitter following release from the postsynaptic cell. At the neuroeffector junction, it is more likely that cannabinoids are released from prejunctional sites, as the neuroeffector junction is wide in some peripheral tissues and cannabinoids are rapidly taken up and inactivated. Understanding the actions of cannabinoids as modulators of peripheral neurotransmission is relevant to a variety of biological systems and possibly their disorders.

Endogenous cannabinoid system as a modulator of food intake

The ability of Cannabis sativa (marijuana) to increase hunger has been noticed for centuries, although intensive research on its molecular mode of action started only after the characterization of its main psychoactive component Delta(9)-tetrahydrocannabinol in the late 1960s. Despite the public concern related to the abuse of marijuana and its derivatives, scientific studies have pointed to the therapeutic potentials of cannabinoid compounds and have highlighted their ability to stimulate appetite, especially for sweet and palatable food. Later, the discovery of specific receptors and their endogenous ligands (endocannabinoids) suggested the existence of an endogenous cannabinoid system, providing a physiological basis for biological effects induced by marijuana and other cannabinoids. Epidemiological reports describing the appetite-stimulating properties of cannabinoids and the recent insights into the molecular mechanisms underlying cannabinoid action have proposed a central role of the cannabinoid system in obesity. The aim of this review is to provide an extensive overview on the role of this neuromodulatory system in feeding behavior by summarizing the most relevant data obtained from human and animal studies and by elucidating the interactions of the cannabinoid system with the most important neuronal networks and metabolic pathways involved in the control of food intake. Finally, a critical evaluation of future potential therapeutical applications of cannabinoid antagonists in the therapy of obesity and eating disorders will be discussed.

N-Acylethanolamines in human reproductive fluids

N-Acylethanolamines (NAEs) are an important family of lipid-signaling molecules. Arachidonylethanolamide (anandamide) (AEA), palmitoylethanolamide (PEA), and oleoylethanolamide (OEA) are co-produced from similar phospholipid precursors when neurons are stimulated. AEA is an endogenous agonist (endocannabinoid) for cannabinoid receptors. It binds with higher affinity to type CB1 than to type CB2 cannabinoid receptors. PEA does not bind to CB1, while the hypothesis that it reacts with putative CB2-like receptors has been questioned. OEA does not activate currently known cannabinoid receptors, but it mimics the effects of AEA and cannabinoids in reducing the fertilizing capacity of sea urchin sperm. OEA and PEA also act as entourage compounds by inhibiting the hydrolysis of AEA by fatty acid amide hydrolase. Cannabinoid receptors and/or AEA are present in mammalian reproductive organs including the testis, epididymis, prostate, ovary, uterus, sperm, preimplantation embryo and placenta, as well as prostatic and mammary carcinomas. We now report that analysis by high-performance liquid chromatography/mass spectrometry (HPLC/MS) shows the presence of AEA, PEA, and OEA in human seminal plasma, mid-cycle oviductal fluid, follicular fluid, amniotic fluid, milk, and fluids from malignant ovarian cysts. Previous studies showed that AEA-signaling via cannabinoid receptors regulates capacitation and fertilizing potential of human sperm, early embryonic development and blastocyst implantation into the uterine mucosa of rodents, as well as proliferation of human mammary and prostatic carcinomas. Current results imply that NAEs also may modulate follicular maturation and ovulation, normal and pathological ovarian function, placental and fetal physiology, lactation, infant physiology, and behavior. Collectively, these findings suggest that NAEs in human reproductive fluids may help regulate multiple physiological and pathological processes in the reproductive system, and imply that exogenous cannabinoids delivered by marijuana smoke might impact these processes. This study has potential medical and public policy ramifications because of the incidence of marijuana abuse by adolescents and adults in our society, previously documented reproductive effects of marijuana, and the ongoing debate about medicinal use of marijuana and cannabinoids.

A peripheral mechanism for CB1 cannabinoid receptor-dependent modulation of feeding

Recent studies suggest that the endocannabinoid system modulates feeding. Despite the existence of central mechanisms for the regulation of food intake by endocannabinoids, evidence indicates that peripheral mechanisms may also exist. To test this hypothesis, we investigated (1) the effects of feeding on intestinal anandamide accumulation; (2) the effects of central (intracerebroventricular) and peripheral (intraperitoneal) administration of the endocannabinoid agonist anandamide, the synthetic cannabinoid agonist R-(+)-(2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrol[1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl) methanone monomethanesulfonate (WIN55,212-2), and the CB1-selective antagonist N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide (SR141716A) on food intake in rats; and (3) the effects of sensory deafferentation on the modulation of feeding by cannabinoids. Food deprivation produced a sevenfold increase in anandamide content in the small intestine but not in the brain or stomach. Refeeding normalized intestinal anandamide levels. Peripheral but not central administration of anandamide or WIN55,212-2 promoted hyperphagia in partially satiated rats. Similarly, peripheral but not central administration of SR141716A reduced food intake. Capsaicin deafferentation abolished the peripheral effects of both cannabinoid agonists and antagonists, suggesting that these agents modulate food intake by acting on CB1 receptors located on capsaicin-sensitive sensory terminals. Oleoylethanolamide, a noncannabinoid fatty ethanolamide that acts peripherally, prevented hyperphagia induced by the endogenous cannabinoid anandamide. Pretreatment with SR141716A enhanced the inhibition of feeding induced by intraperitoneal administration of oleoylethanolamide. The results reveal an unexpected role for peripheral CB1 receptors in the regulation of feeding.

Cardiovascular system effects of marijuana

Marijuana and delta9-tetrahydrocannabinol (THC) increase heart rate, slightly increase supine blood pressure, and on occasion produce marked orthostatic hypotension. Cardiovascular effects in animals are different, with bradycardia and hypotension the most typical response. Cardiac output increases, and peripheral vascular resistance and maximum exercise performance decrease. Tolerance to most of the initial cardiovascular effects appears rapidly. With repeated exposure, supine blood pressure decreases slightly, orthostatic hypotension disappears, blood volume increases, heart rate slows, and circulatory responses to exercise and Valsalva maneuver are diminished, consistent with centrally mediated, reduced sympathetic, and enhanced parasympathetic activity. Receptor-mediated and probably nonneuronal sites of action account for cannabinoid effects. The endocannabinoid system appears important in the modulation of many vascular functions. Marijuana's cardiovascular effects are not associated with serious health problems for most young, healthy users, although occasional myocardial infarction, stroke, and other adverse cardiovascular events are reported. Marijuana smoking by people with cardiovascular disease poses health risks because of the consequences of the resulting increased cardiac work, increased catecholamine levels, carboxyhemoglobin, and postural hypotension.

Cannabinoid modulation of sensory neurotransmission via cannabinoid and vanilloid receptors: roles in regulation of cardiovascular function

Capsaicin-sensitive sensory nerves are widely distributed in the cardiovascular system. They are activated by a variety of physical and chemical stimuli, characteristically by capsaicin acting via the vanilloid receptor VR1, and have a role in the regulation of peripheral vascular resistance and maintenance of homeostasis via their afferent and efferent functions. Cannabinoids, a recently discovered family of extracellular signalling molecules, can act at cannabinoid (CB) receptors expressed on sensory nerves, to cause inhibition of sensory neurotransmitter release. There is recent evidence, however, that anandamide, an endogenous cannabinoid, can activate VR1, coexpressed with CB receptors on the same sensory nerve terminals, causing a release of sensory neurotransmitter, vasorelaxation and hypotension. Hence, anandamide can elicit opposite actions, inhibition via CB receptors and excitation via VR1, on sensory neurotransmission. The possible biological significance of this is discussed.