Both L-α-lysophosphatidylinositol (LPI) and 2-arachidonoyl-sn-glycero-3-phosphoinositol (2-AGPI) have been reported to activate the putative cannabinoid receptor, GPR55. Recent microsecond time-scale molecular dynamics (MD) simulations and isothiocyanate covalent labeling studies have suggested that a transmembrane helix 6/7 (TMH6/7) lipid pathway for ligand entry may be necessary for interaction with cannabinoid receptors. Because LPI and 2-AGPI are lipid-derived ligands, conformations that each assumes in the lipid bilayer are therefore likely important for their interaction with GPR55. We report here the results of 70 ns NAMD molecular dynamics (MD) simulations of LPI and of 2-AGPI in a fully hydrated bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). These simulations are compared with a 70 ns simulation of the cannabinoid CB1 receptor endogenous ligand, N-arachidonoylethanolamine (anandamide, AEA) in a POPC bilayer. These simulations revealed that (1) LPI and 2-AGPI sit much higher in the bilayer than AEA, with inositol headgroups that can at times be solvated completely by water; (2) the behavior of the acyl chains of AEA and 2-AGPI are similar in their flexibilities in the bilayer, while the acyl chain of LPI has reduced flexibility; and (3) both 2-AGPI and LPI can adopt a tilted headgroup orientation by hydrogen bonding to the phospholipid phosphate/glycerol groups or via intramolecular hydrogen bonding. This tilted head group conformation (which represents over 40% of the conformer population of LPI (42.2 ± 3.3%) and 2-AGPI (43.7 ± 1.4%)) may provide a low enough profile in the lipid bilayer for LPI and 2-AGPI to enter GPR55 via the putative TMH6/7 entry port.

Autophagy is a catabolic process involved in homeostatic and regulated cellular protein recycling and degradation via the lysosomal degradation pathway. Emerging data associate impaired autophagy, increased activity in the endocannabinoid system, and upregulation of suppressor of cytokine signaling-3 (SOCS3) protein expression during intestinal inflammation. We have investigated whether these three processes are linked. By assessing the impact of the phytocannabinoid cannabidiol (CBD), the synthetic cannabinoid arachidonyl-2'-chloroethylamide (ACEA), and the endocannabinoid N-arachidonoylethanolamine (AEA) on autophagosome formation, we explored whether these actions were responsible for cyclic SOCS3 protein levels. Our findings show that all three cannabinoids induce autophagy in a dose-dependent manner in fully differentiated Caco-2 cells, a model of mature intestinal epithelium. ACEA and AEA induced canonical autophagy, which was cannabinoid type 1 receptor-mediated. In contrast, CBD was able to bypass the cannabinoid type 1 receptor and the canonical pathway to induce autophagy, albeit to a lesser extent. Functionally, all three cannabinoids reduced SOCS3 protein expression, which was reversed by blocking early and late autophagy. In conclusion, the regulatory protein SOCS3 is regulated by autophagy, and cannabinoids play a role in this process, which could be important when therapeutic applications for the cannabinoids in inflammatory conditions are considered.

Inhibition of fatty acid amide hydrolase (FAAH) or monoacylglycerol lipase (MAGL), the primary hydrolytic enzymes for the respective endocannabinoids N-arachidonoylethanolamine (AEA) and 2-arachidonylglycerol (2-AG), produces antinociception but with minimal cannabimimetic side effects. Although selective inhibitors of either enzyme often show partial efficacy in various nociceptive models, their combined blockade elicits augmented antinociceptive effects, but side effects emerge. Moreover, complete and prolonged MAGL blockade leads to cannabinoid receptor type 1 (CB1) receptor functional tolerance, which represents another challenge in this potential therapeutic strategy. Therefore, the present study tested whether full FAAH inhibition combined with partial MAGL inhibition would produce sustained antinociceptive effects with minimal cannabimimetic side effects. Accordingly, we tested a high dose of the FAAH inhibitor PF-3845 (N-​3-​pyridinyl-​4-​[[3-​[[5-​(trifluoromethyl)-​2-​pyridinyl]oxy]phenyl]methyl]-​1-​piperidinecarboxamide; 10 mg/kg) given in combination with a low dose of the MAGL inhibitor JZL184 [4-nitrophenyl 4-(dibenzo[d][1,3]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate] (4 mg/kg) in mouse models of inflammatory and neuropathic pain. This combination of inhibitors elicited profound increases in brain AEA levels (>10-fold) but only 2- to 3-fold increases in brain 2-AG levels. This combination produced significantly greater antinociceptive effects than single enzyme inhibition and did not elicit common cannabimimetic effects (e.g., catalepsy, hypomotility, hypothermia, and substitution for Δ(9)-tetrahydrocannabinol in the drug-discrimination assay), although these side effects emerged with high-dose JZL184 (i.e., 100 mg/kg). Finally, repeated administration of this combination did not lead to tolerance to its antiallodynic actions in the carrageenan assay or CB1 receptor functional tolerance. Thus, full FAAH inhibition combined with partial MAGL inhibition reduces neuropathic and inflammatory pain states with minimal cannabimimetic effects.

The endocannabinoid system (ECS) controls energy balance by regulating both energy intake and energy expenditure. Endocannabinoid levels are elevated in obesity suggesting a potential causal relationship. This study aimed to elucidate the rate of dysregulation of the ECS, and the metabolic organs involved, in diet-induced obesity. Eight groups of age-matched male C57Bl/6J mice were randomized to receive a chow diet (control) or receive a high fat diet (HFD, 45% of calories derived from fat) ranging from 1 day up to 18 weeks before euthanasia. Plasma levels of the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide (N-arachidonoylethanolamine, AEA), and related N-acylethanolamines, were quantified by UPLC-MS/MS and gene expression of components of the ECS was determined in liver, muscle, white adipose tissue (WAT) and brown adipose tissue (BAT) during the course of diet-induced obesity development. HFD feeding gradually increased 2-AG (+132% within 4 weeks, P < 0.05), accompanied by upregulated expression of its synthesizing enzymes Daglα and β in WAT and BAT. HFD also rapidly increased AEA (+81% within 1 week, P < 0.01), accompanied by increased expression of its synthesizing enzyme Nape-pld, specifically in BAT. Interestingly, Nape-pld expression in BAT correlated with plasma AEA levels (R² = 0.171, β = 0.276, P < 0.001). We conclude that a HFD rapidly activates adipose tissue depots to increase the synthesis pathways of endocannabinoids that may aggravate the development of HFD-induced obesity.

Endocannabinoid signaling regulates feeding and metabolic processes and has been linked to obesity development. Several hormonal signals, such as glucocorticoids and ghrelin, regulate feeding and metabolism by engaging the endocannabinoid system. Similarly, studies have suggested that leptin interacts with the endocannabinoid system, yet the mechanism and functional relevance of this interaction remain elusive. Therefore, we explored the interaction between leptin and endocannabinoid signaling with a focus on fatty acid amide hydrolase (FAAH), the primary degradative enzyme for the endocannabinoid N-arachidonoylethanolamine (anandamide; AEA). Mice deficient in leptin exhibited elevated hypothalamic AEA levels and reductions in FAAH activity while leptin administration to WT mice reduced AEA content and increased FAAH activity. Following high fat diet exposure, mice developed resistance to the effects of leptin administration on hypothalamic AEA content and FAAH activity. At a functional level, pharmacological inhibition of FAAH was sufficient to prevent leptin-mediated effects on body weight and food intake. Using a novel knock-in mouse model recapitulating a common human polymorphism (FAAH C385A; rs324420), which reduces FAAH activity, we investigated whether human genetic variance in FAAH affects leptin sensitivity. While WT (CC) mice were sensitive to leptin-induced reductions in food intake and body weight gain, low-expressing FAAH (AA) mice were unresponsive. These data demonstrate that FAAH activity is required for leptin's hypophagic effects and, at a translational level, suggest that a genetic variant in the FAAH gene contributes to differences in leptin sensitivity in human populations.

OBJECTIVE

Numerous studies have shown that N-arachidonoylethanolamine (AEA) can inhibit sperm motility and function but the ability of cannabinoids to inhibit sperm motility is not well understood. We investigated the effects of WIN 55,212-2, a CB(1) cannabinoid receptor agonist, and Δ(9) -tetrahydracannabinol (Δ(9) -THC) on the ATP levels and motility of murine sperm in vitro. In addition, the effects of acute administration of Δ(9) -THC on male fecundity were determined.

METHODS

Effects of Δ(9) -THC on basal sperm kinematics were determined using computer-assisted sperm analysis (CASA). Stop-motion imaging was performed to measure sperm beat frequency. The effect of Δ(9) -THC on sperm ATP was determined using a luciferase assay. Male fertility was determined by evaluating the size of litters sired by Δ(9) -THC-treated males. KEY RESULTS Pretreatment of sperm for 15 min with 1 µM Δ(9) -THC reduced their basal motility and attenuated the ability of bicarbonate to stimulate flagellar beat frequency. Treatment with 5 µM WIN 55,212-2 or 10 µM Δ(9) -THC for 30 min reduced sperm ATP levels. In sperm lacking CB(1) receptors this inhibitory effect of WIN 55,212-2 on ATP was attenuated whereas that of Δ(9) -THC persisted. Administration of 50 mg·kg(-1) Δ(9) -THC to male mice just before mating caused a 20% decrease in embryonic litter size.

CONCLUSIONS

Δ(9) -THC inhibits both basal and bicarbonate-stimulated sperm motility in vitro and reduces male fertility in vivo. High concentrations of WIN 55,212-2 or Δ(9) -THC inhibit ATP production in sperm; this effect of WIN 55,212-2 is CB(1) receptor-dependent whereas that of Δ(9) -THC is not. LINKED ARTICLES This article is part of a themed section on Cannabinoids in Biology and Medicine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-8. To view Part I of Cannabinoids in Biology and Medicine visit http://dx.doi.org/10.1111/bph.2011.163.issue-7.

Anandamide (N -arachidonoylethanolamine, AEA) is a major endocannabinoid, shown to impair mouse pregnancy and embryo development and to induce apoptosis in blastocysts. Here, we review the roles of AEA, of the AEA-binding cannabinoid (CB) receptors, of the selective AEA membrane transporter (AMT), and of the AEA-hydrolyzing enzyme fatty acid amide hydrolase (FAAH), in human gestation. In particular, we discuss the interplay between the endocannabinoid system and the hormone-cytokine array involved in the control of human pregnancy, showing that the endocannabinoids take part in the immunological adaptation occurring during early pregnancy. In this line, we discuss the critical role of FAAH in human peripheral lymphocytes, showing that the expression of this enzyme is regulated by progesterone, Th1 and Th2 cytokines, which also regulate fertility. Moreover, we show that AEA and the other endocannabinoid, 2-arachidonoylglycerol, inhibit the release of the fertility-promoting cytokine leukemia inhibitory factor from human lymphocytes. Taken together, low FAAH and consistently high blood levels of AEA, but not CB receptors or AMT, can be early (<8 weeks of gestation) markers of spontaneous abortion, potentially useful as diagnostic tools for large-scale, routine monitoring of gestation in humans.

The phospholipid bilayer plays a central role in the lifecycle of the endogenous cannabinoid, N-arachidonoylethanolamine (anandamide, AEA). Therefore, the orientation and location of AEA in the phospholipid bilayer with respect to key membrane associated proteins, is a central issue in understanding the mechanism of endocannabinoid signaling. In this paper, we report a test of the hypothesis that a betaXXbeta motif (formed by beta branching amino acids, V6.43 and I6.46) on the lipid face of the cannabinoid CB1 receptor in its inactive state may serve as an initial CB1 interaction site for AEA. Eight 6 ns NAMD2 molecular dynamics simulations of AEA were conducted in a model system composed of CB1 transmembrane helix 6 (TMH6) in a 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayer. In addition, eight 6 ns NAMD2 molecular dynamics simulations of a low CB1 affinity (20:2, n-6) analog of AEA were conducted in the same model system. AEA was found to exhibit a higher incidence of V6.43/I6.46 groove insertion than did the (20:2, n-6) analog. In certain cases, AEA established a high energy of interaction with TMH6 by first associating with the V6.43/I6.46 groove and then molding itself to the lipid face of TMH6 to establish a hydrogen bonding interaction with the exposed backbone carbonyl of P6.50. Based upon these results, we propose that the formation of this hydrogen bonded AEA/TMH6 complex may be the initial step in CB1 recognition of AEA in the lipid bilayer.

Anandamide (N-arachidonoylethanolamine) has been identified as an endogenous ligand of the G-protein coupled cannabinoid CB(1) receptor. Recent studies have postulated the existence of carrier-mediated anandamide transport which is involved in the termination of the biological effects of anandamide. A membrane bound amidohydrolase (fatty acid amide hydrolase, FAAH), located intracellulary, hydrolyzes and inactivates anandamide and other endogenous cannabinoids such as 2-arachidonoylglycerol (2-AG). Structure-activity relationships (SARs) for endocannabinoid interaction with the CB receptors, the anandamide transporter and FAAH are currently emerging in the literature. This review considers the divergences between these SARs and focuses upon the conformational implications for endocannabinoid recognition at each of these biological targets.

The quest for possible targets for the development of novel analgesics has identified the activation of the cannabinoid type 1 (CB1) receptor outside the CNS as a potential means of providing relief from persistent pain, which currently constitutes an unmet medical need. Increasing tissue levels of the CB1 receptor endogenous ligand N-arachidonoylethanolamine (anandamide), by inhibiting anandamide degradation through blocking the anandamide-hydrolysing enzyme fatty acid amide hydrolase, has been suggested to be used to activate the CB1 receptor. However, recent clinical trials revealed that this approach does not deliver the expected relief from pain. Here, we discuss one of the possible reasons, the activation of the transient receptor potential vanilloid type 1 ion channel (TRPV1) on nociceptive primary sensory neurons (PSNs) by anandamide, which may compromise the beneficial effects of increased tissue levels of anandamide. We conclude that better design such as concomitant blocking of anandamide hydrolysis and anandamide uptake into PSNs, to inhibit TRPV1 activation, could overcome these problems.

Anandamide (N -arachidonoylethanolamine) was the first ligand to be identified as an endogenous ligand of the G-protein coupled cannabinoid CB1 receptor. Subsequently, two other fatty acid ethanolamides, N -homo- gamma -linolenylethanolamine and N -7,10,13,16-docosatetraenylethanolamine were identified as endogenous cannabinoid ligands. A fatty acid ester, 2-arachidonoylglycerol (2-AG), and a fatty acid ether, 2-arachidonyl glyceryl ether also have been isolated and shown to be endogenous cannabinoid ligands. Recent studies have postulated the existence of carrier-mediated anandamide transport that is essential for termination of the biological effects of anandamide. A membrane bound amidohydrolase (fatty acid amide hydrolase, FAAH), located intracellularly, hydrolyzes and inactivates anandamide and other endogenous cannabinoids such as 2-AG. 2-AG has also been proposed to be an endogenous CB2 ligand. Structure-activity relationships (SARs) for endocannabinoid interaction with the CB receptors are currently emerging in the literature. This review considers cannabinoid receptor SAR developed to date for the endocannabinoids with emphasis upon the conformational implications for endocannabinoid recognition at the cannabinoid receptors.

The endocannabinoid system (ECS) is a group of neuromodulatory lipids, enzymes, and receptors involved in numerous behavioral and physiological processes such as mood, memory, and appetite. Recently, longitudinal and postmortem studies have shown that the ECS might be involved in neuropsychiatric disorders like schizophrenia. However, despite the large amount of research, our knowledge of the ECS and its implication in this debilitating disorder is still largely limited. This review aims at providing a comprehensive overview of the current state of knowledge of the ECS in schizophrenia and presenting some potential antipsychotic compounds that modulate this system. Findings from animal and human studies, and their implications for pharmacotherapy, will be integrated and discussed in this paper. A closer look will be given at the roles of the cannabinoid receptors type 1 (CB1) and type 2 (CB2), as well as the endogenous ligand N-arachidonoylethanolamine (AEA) and 2-arachidonylglycerol (2-AG), in the development of psychotic and schizophrenia-like symptoms.

The endocannabinoid system has been considered as a target for pharmacological intervention. Accordingly, inhibition of fatty acid amide hydrolase (FAAH), a degrading enzyme of the endocannabinoids N-arachidonoylethanolamine (anandamide; AEA) and 2-arachidonoylglycerol (2-AG) as well as of the endocannabinoid-like substances N-oleoylethanolamine (OEA) and N-palmitoylethanolamine (PEA), can cause augmented endogenous cannabinoid tone. Using liquid chromatography coupled with positive electrospray ionisation mass spectrometry, we herein describe a method to simultaneously quantify levels of AEA, OEA, PEA and 2-AG in cultured cells. The procedure was developed according to the FDA guidelines for bioanalytical methods validation. The limits of quantification (LOQs) were 0.05 pmol for AEA, 0.09 pmol for OEA, 0.10 pmol for PEA and 0.80 pmol for 2-AG when molecular ion monitoring was used. In H460 human lung carcinoma cells, basal levels of all four analytes ranged between 2 and 17 pmol mg(-1) protein with PEA showing the lowest and OEA the highest concentrations. Endocannabinoid levels observed in mesenchymal stem cells were of the same order of magnitude when compared to those in H460 human lung carcinoma cells.

The Cys-loop ligand-gated ion channel (LGIC) family comprises a group of membrane ion channel receptors that play a crucial role in fast synaptic neurotransmission in the central and peripheral nervous system. The members of this superfamily include gamma-aminobutyric acid type A (GABA(A)), neuronal nicotinic acetylcholine (nACh), 5-HT(3), and glycine receptors. These receptors serve as therapeutic sites for general anesthetic, antipsychoactive, antinociceptive, and anxiolytic drugs in the brain. These receptors are also thought to be primary targets of alcohol and other drugs of abuses. A number of studies reported that fatty acids affected the function of GABA(A) receptors in the early nineties. Accumulating evidence has suggested that the derivatives of arachidonic acid (AA), such as anandamide (N-arachidonoylethanolamine, AEA) and arachidonoylglycerol (2-AG), can critically regulate the other members of the Cys-loop LGIC superfamily through a cannabinoid receptor-independent mechanism. This chapter focuses on the results of recent studies showing that the Cys-loop LGICs could be additional molecular targets for fatty acid and endocannabinoid action in the central and peripheral nervous system. Some of these targets may mediate behavioral effects for cannabinoids to alter neuronal function.

Endocannabinoids are a new class of lipids, which include amides, esters and ethers of long chain polyunsaturated fatty acids. Anandamide (N-arachidonoylethanolamine; AEA) and 2-arachidonoylglycerol are the main endogenous agonists of cannabinoid receptors, able to mimic several pharmacological effects of Delta(9)-tetrahydrocannabinol, the active principle of Cannabis sativa preparations like hashish and marijuana. It is known that the activity of AEA is limited by cellular uptake through a specific membrane transporter, followed by intracellular degradation by a fatty acid amide hydrolase. Together with AEA and congeners these proteins form the "endocannabinoid system". The endogenous cannabinoids were identified in brain, and also in neuronal and endothelial cells, suggesting a potential role as modulators in the central nervous system and in the periphery. This review summarises the metabolic routes for the synthesis and degradation of AEA, and the latest advances in the involvement of this lipid in neurovascular biology. In addition, the therapeutic potential of the modulation of endocannabinoid metabolism for neuronal and vascular system will be also reviewed.

BACKGROUND

Anandamide (N-arachidonoylethanolamine [AEA]) is one of the main endocannabinoids. Endocannabinoids are implicated in various physiological and pathologic functions, inducing not only nociception but also regeneration and inflammation. The role of the endocannabinoid system in peripheral organs was recently described. The aim of this study was to investigate the effect of AEA on matrix metalloproteinase (MMP)-2 induction in human dental pulp cells (HPC).

METHODS

We examined AEA-induced MMP-2 production and the expression of AEA receptors (cannabinoid [CB] receptor-1, CB2, and transient receptor potential vanilloid-1 [TRPV1]) in HPC by Western blot. MMP-2 concentrations in supernatants were determined by enzyme-linked immunosorbent assay. We then investigated the role of the AEA receptors and mitogen-activated protein kinase in AEA-induced MMP-2 production in HPC.

RESULTS

AEA significantly induced MMP-2 production in HPC. HPC expressed all 3 types of AEA receptor (CB1, CB2, and TRPV1). AEA-induced MMP-2 production was blocked by CB1 or TRPV1 antagonists and by small interfering RNA for CB1 or TRPV1. Furthermore, c-Jun N-terminal kinase inhibitor also reduced MMP-2 production.

CONCLUSIONS

We demonstrated for the first time that AEA induced MMP-2 production via CB1 and TRPV1 in HPC.

Sweet taste perception is important for animals to detect carbohydrate source of calories and has a critical role in the nutritional status of animals. Recent studies demonstrated that sweet taste responses can be modulated by leptin and endocannabinoids [anandamide (N-arachidonoylethanolamine) and 2-arachidonoyl glycerol]. Leptin is an anorexigenic mediator that reduces food intake by acting on hypothalamic receptor, Ob-Rb. Leptin is shown to selectively suppress sweet taste responses in wild-type mice but not in leptin receptor-deficient db/db mice. In marked contrast, endocannabinoids are orexigenic mediators that act via CB(1) receptors in hypothalamus and limbic forebrain to induce appetite and stimulate food intake. In the peripheral taste system, endocannabinoids also oppose the action of leptin and enhance sweet taste sensitivities in wild-type mice but not in mice genetically lacking CB(1) receptors. These findings indicate that leptin and endocannabinoids not only regulate food intake via central nervous systems but also may modulate palatability of foods by altering peripheral sweet taste responses via their cognate receptors.

BACKGROUND

Corticotropin-releasing factor (CRF) mediates anxiogenic responses by activating CRF type 1 (CRF1) receptors in limbic brain regions. Anxiety is further modulated by the endogenous cannabinoid (eCB) system that attenuates the synaptic effects of stress. In the amygdala, acute stress activates the enzymatic clearance of the eCB N-arachidonoylethanolamine via fatty acid amide hydrolase (FAAH), although it is unclear whether chronic dysregulation of CRF systems induces maladaptive changes in amygdalar eCB signaling. Here, we used genetically selected Marchigian Sardinian P (msP) rats carrying an innate overexpression of CRF1 receptors to study the role of constitutive upregulation in CRF systems on amygdalar eCB function and persistent anxiety-like effects.

METHODS

We applied behavioral, pharmacological, and biochemical methods to broadly characterize anxiety-like behaviors and amygdalar eCB clearance enzymes in msP versus nonselected Wistar rats. Subsequent studies examined the influence of dysregulated CRF and FAAH systems in altering excitatory transmission in the central amygdala (CeA).

RESULTS

msPs display an anxious phenotype accompanied by elevations in amygdalar FAAH activity and reduced dialysate N-arachidonoylethanolamine levels in the CeA. Elevations in CRF-CRF1 signaling dysregulate FAAH activity, and this genotypic difference is normalized with pharmacological blockade of CRF1 receptors. msPs also exhibit elevated baseline glutamatergic transmission in the CeA, and dysregulated CRF-FAAH facilitates stress-induced increases in glutamatergic activity. Treatment with an FAAH inhibitor relieves sensitized glutamatergic responses in msPs and attenuates the anxiety-like phenotype.

CONCLUSIONS

Pathological anxiety and stress hypersensitivity are driven by constitutive increases in CRF1 signaling that dysregulate N-arachidonoylethanolamine signaling mechanisms and reduce neuronal inhibitory control of CeA glutamatergic synapses.

Currently, the involvement of the endocannabinoid system in cancer development and possible options for a cancer-regressive effect of cannabinoids are controversially discussed. In recent decades, a number of preclinical studies have shown that cannabinoids have an anticarcinogenic potential. Therefore, especially against the background of several legal simplifications with regard to the clinical application of cannabinoid-based drugs, an extended basic knowledge about the complex network of the individual components of the endocannabinoid system is required. The canonical endocannabinoid system consists of the endocannabinoids N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol as well as the G_i/o protein-coupled transmembrane cannabinoid receptors CB₁ and CB₂. As a result of extensive studies on the broader effect of these factors, other fatty acid derivatives, transmembrane and intracellular receptors, enzymes and lipid transporters have been identified that contribute to the effect of endocannabinoids when defined in the broad sense as "extended endocannabinoid system." Among these additional components, the endocannabinoid-degrading enzymes fatty acid amide hydrolase and monoacylglycerol lipase, lipid transport proteins of the fatty acid-binding protein family, additional cannabinoid-activated G protein-coupled receptors such as GPR55, members of the transient receptor family, and peroxisome proliferator-activated receptors were identified as targets for possible strategies to combat cancer progression. Other endocannabinoid-related fatty acids such as 2-arachidonoyl glyceryl ether, O-arachidonoylethanolamine, N-arachidonoyldopamine and oleic acid amide showed an effect via cannabinoid receptors, while other compounds such as endocannabinoid-like substances exert a permissive action on endocannabinoid effects and act via alternative intracellular target structures. This review gives an overview of the modulation of the extended endocannabinoid system using the example of anticancer cannabinoid effects, which have been described in detail in preclinical studies.

Animal studies point to an implication of the endocannabinoid system on executive functions. In humans, several studies have suggested an association between acute or chronic use of exogenous cannabinoids (Δ9-tetrahydrocannabinol) and executive impairments. However, to date, no published reports establish the relationship between endocannabinoids, as biomarkers of the cannabinoid neurotransmission system, and executive functioning in humans. The aim of the present study was to explore the association between circulating levels of plasma endocannabinoids N-arachidonoylethanolamine (AEA) and 2-Arachidonoylglycerol (2-AG) and executive functions (decision making, response inhibition and cognitive flexibility) in healthy subjects. One hundred and fifty seven subjects were included and assessed with the Wisconsin Card Sorting Test; Stroop Color and Word Test; and Iowa Gambling Task. All participants were female, aged between 18 and 60 years and spoke Spanish as their first language. Results showed a negative correlation between 2-AG and cognitive flexibility performance (r = -.37; p<.05). A positive correlation was found between AEA concentrations and both cognitive flexibility (r = .59; p<.05) and decision making performance (r = .23; P<.05). There was no significant correlation between either 2-AG (r = -.17) or AEA (r = -.08) concentrations and inhibition response. These results show, in humans, a relevant modulation of the endocannabinoid system on prefrontal-dependent cognitive functioning. The present study might have significant implications for the underlying executive alterations described in some psychiatric disorders currently associated with endocannabinoids deregulation (namely drug abuse/dependence, depression, obesity and eating disorders). Understanding the neurobiology of their dysexecutive profile might certainly contribute to the development of new treatments and pharmacological approaches.

In the central nervous system, the endocannabinoid anandamide [N-arachidonoylethanolamine (AEA)] is believed to increase food intake through on-demand activation of hypothalamic circuits. The present study examined the effects of hypothalamic paraventricular nucleus (PVN) injections of AEA (25-400 pmol) on food intake and energy substrate oxidation [respiratory quotient (RQ)]. PVN administration of AEA increased eating behavior and RQ, indicating enhanced carbohydrate oxidation. Further, PVN administration of the cannabinoid type 1 receptor inverse agonist AM251 (5-10 μg) attenuated both the eating and the RQ responses elicited by AEA (100 pmol). AM251 administered alone did not alter food intake or RQ. Overall, these findings are consistent with a role for PVN cannabinoid type 1 receptors in the regulation of eating and energy homeostasis.

N-acylethanolamines (NAEs) (e.g., N-palmitoylethanolamine, N-arachidonoylethanolamine, N-oleoylethanolamine) are bioactive lipids involved in many physiological processes including pain, inflammation, anxiety, cognition and food intake. Two enzymes are responsible for the hydrolysis of NAEs and therefore regulate their endogenous levels and effects: fatty acid amide hydrolase (FAAH) and N-acylethanolamine-hydrolyzing acid amidase (NAAA). As discussed here, extensive biochemical characterization of NAAA was carried out over the years that contributed to a better understanding of NAAA enzymology. An increasing number of studies describe the synthesis and pharmacological characterization of NAAA inhibitors. Recent medicinal chemistry efforts have led to the development of potent and stable inhibitors that enable studying the effects of NAAA inhibition in preclinical disease models, notably in the context of pain and inflammation.

The endogenous cannabinoid (eCB) system has been suggested to play a key role in ethanol preference and intake, the acute effects of ethanol, and in the development of withdrawal symptoms following ethanol dependence. Ethanol-dependent alterations in glutamatergic signaling within the lateral/basolateral nucleus of the amygdala (BLA) are critical for the development and expression of withdrawal-induced anxiety. Notably, the eCB system significantly regulates both glutamatergic and GABAergic synaptic activity within the BLA. Chronic ethanol exposure significantly alters eCB system expression within regions critical to the expression of emotionality and anxiety-related behavior, including the BLA. Here, we investigated specific interactions between the BLA eCB system and its functional regulation of synaptic activity during acute and chronic ethanol exposure. In tissue from ethanol naïve-rats, a prolonged acute ethanol exposure caused a dose dependent inhibition of glutamatergic synaptic activity via a presynaptic mechanism that was occluded by CB1 antagonist/inverse agonists SR141716a and AM251. Importantly, this acute ethanol inhibition was attenuated following 10 day chronic intermittent ethanol vapor exposure (CIE). CIE exposure also significantly down-regulated CB1-mediated presynaptic inhibition at glutamatergic afferent terminals but spared CB1-inhibition of GABAergic synapses arising from local inhibitory-interneurons. CIE also significantly elevated BLA N-arachidonoylethanolamine (AEA or anandamide) levels and decreased CB1 receptor protein levels. Collectively, these data suggest a dynamic regulation of the BLA eCB system by acute and chronic ethanol.

Anandamide (N-arachidonoylethanolamine) is the first discovered endocannabinoid (endogenous ligand of cannabinoid receptors). In animal tissues, anandamide is principally formed together with other bioactive long-chain N-acylethanolamines from membrane glycerophospholipid by two enzyme reactions. The first reaction is the transfer of a fatty acyl chain from the sn-1 position of glycerophospholipid to phosphatidylethanolamine by calcium-dependent N-acyltransferase, resulting in the generation of N-acylphosphatidylethanolamine (NAPE). The second reaction is catalyzed by a phosphodiesterase of the phospholipase D (PLD)-type, which releases N-acylethanolamines from their corresponding NAPEs. The produced N-acylethanolamines are hydrolyzed to fatty acids and ethanolamine by fatty acid amide hydrolase or an amidase acting exclusively at acidic pH. Our recent cDNA cloning of the NAPE-hydrolyzing PLD (NAPE-PLD) from mouse, rat and human revealed that NAPE-PLD is a novel enzyme which has no homology with any known PLD enzymes, but belongs to the zinc metallo-hydrolase family of the beta-lactamase fold. The recombinant enzyme hydrolyzed various NAPEs, including the anandamide precursor N-arachidonoylphosphatidylethanolamine at similar rates, but was inactive with phosphatidylcholine and phosphatidylethanolamine. Considering cannabimimetic activities of anandamide, the enzymes involved in the biosynthesis and degradation of anandamide, including NAPE-PLD, may be promising targets for therapeutic agents.