Influence of dietary fatty acids on endocannabinoid and N-acylethanolamine levels in rat brain, liver and small intestine

Endocannabinoids and N-acylethanolamines are lipid mediators regulating a wide range of biological functions including food intake. We investigated short-term effects of feeding rats five different dietary fats (palm oil (PO), olive oil (OA), safflower oil (LA), fish oil (FO) and arachidonic acid (AA)) on tissue levels of 2-arachidonoylglycerol, anandamide, oleoylethanolamide, palmitoylethanolamide, stearoylethanolamide, linoleoylethanolamide, eicosapentaenoylethanolamide, docosahexaenoylethanolamide and tissue fatty acid composition. The LA-diet increased linoleoylethanolamide and linoleic acid in brain, jejunum and liver. The OA-diet increased brain levels of anandamide and oleoylethanolamide (not 2-arachidonoylglycerol) without changing tissue fatty acid composition. The same diet increased oleoylethanolamide in liver. All five dietary fats decreased oleoylethanolamide in jejunum without changing levels of anandamide, suggesting that dietary fat may have an orexigenic effect. The AA-diet increased anandamide and 2-arachidonoylglycerol in jejunum without effect on liver. The FO-diet decreased liver levels of all N-acylethanolamines (except eicosapentaenoylethanolamide and docosahexaenoylethanolamide) with similar changes in precursor lipids. The AA-diet and FO-diet had no effect on N-acylethanolamines, endocannabinoids or precursor lipids in brain. All N-acylethanolamines activated PPAR-alpha. In conclusion, short-term feeding of diets resembling human diets (Mediterranean diet high in monounsaturated fat, diet high in saturated fat, or diet high in polyunsaturated fat) can affect tissue levels of endocannabinoids and N-acylethanolamines.     

Depolarizing and calcium-mobilizing stimuli fail to enhance synthesis and release of endocannabinoids from rat brain cerebral cortex slices

The concentrations of the endocannabinoids 2-arachidonoylglycerol (2-AG) and N-arachidonylethanolamine (anandamide) were examined in rat brain cerebral cortex slices and surrounding medium. Basal concentrations of endocannabinoids were similar to those identified previously in rat brain, with anandamide content being much lower (19 pmol/g) than that of 2-AG (7300 pmol/g). In contrast, basal concentrations in the surrounding medium were proportionally much lower for 2-arachidonoylglycerol (16 pmol/mL) compared to anandamide (0.6 pmol/mL). Incubation of slices with glutamate receptor agonists, depolarizing concentrations of KCl, or ionomycin failed to alter tissue concentrations of endocannabinoids, while endocannabinoids in the medium were unaltered by elevated KCl. Cyclohexyl carbamic acid 3'-carbamoyl-biphenyl-3-yl ester, an inhibitor of fatty acid amide hydrolase, significantly enhanced tissue concentrations of anandamide (and related N-acylethanolamines), without altering 2-AG, while evoking proportional elevations of anandamide in the medium. Removal of extracellular calcium ions failed to alter tissue concentrations of anandamide, but significantly reduced 2-AG in the tissue by 90% and levels in the medium to below the detection limit. Supplementation of the medium with 50 μM N-oleoylethanolamine only raised tissue concentrations of N-oleoylethanolamine in the presence of cyclohexyl carbamic acid 3'-carbamoyl-biphenyl-3-yl ester and failed to alter either tissue or medium anandamide or 2-AG concentrations. These results highlight the ongoing turnover of endocannabinoids, and the importance of calcium ions in maintaining 2-AG concentrations in this tissue.     

Quantification of endocannabinoids in rat biological samples by GC/MS: technical and theoretical considerations

In the last several years, interest has increased significantly about the endocannabinoids anandamide and 2-arachidonylglycerol, two lipid messengers that activate cannabinoid receptors. Quantification of these compounds in biological samples presents numerous technical challenges. Because of their low abundance, endocannabinoids are usually quantified by isotope dilution assays using mass spectrometry coupled to either gas chromatography or high-performance liquid chromatography. Although endocannabinoid levels in biological fluids, such as plasma and cerebrospinal fluid, can be directly determined by these techniques, the complex lipid profile of brain tissue samples mandates purification of lipid extracts before GC/MS analysis; this step is not necessary when using HPLC/MS. We have found that when silica gel chromatography is used for endocannabinoid purification, poor recovery and loss of deuterium from the internal standards lead to inaccurate estimation of endocannabinoid levels. By contrast, purification strategies using C(18) solid-phase extraction permits precise and reproducible GC/MS quantification of endocannabinoids in tissue samples.     

Effect of polyunsaturated fatty acids on endocannabinoid and N-acyl-ethanolamine levels in mouse adipocytes

The tissue concentrations of the endocannabinoids, 2-arachidonoylglycerol (2-AG) and N-arachidonoyl-ethanolamine (anandamide), are altered in the adipose tissue of mice fed a high fat diet. We have investigated here the effect on endocannabinoid levels of incubation of mouse 3T3-F442A adipocytes with several free polyunstaurated fatty acids (PUFAs), including linolenic acid (LA), alpha-linolenic acid (ALA), arachidonic acid (AA) and docosahexaenoic acid (DHA), as well as oleic acid (OA) and palmitic acid (PA). By using mass spectrometric methods, we quantified the levels of endocannabinoids, of two anandamide congeners, N-palmitoyl-ethanolamine (PEA) and N-oleoyl-ethanolamine (OEA), and of fatty acids esterified in triacylglycerols or phospholipids, which act as 2-AG and/or N-acyl-ethanolamine precursors. Incubation with AA strongly elevated 2-AG levels and the amounts of AA esterified in triacylglycerols and on glycerol carbon atom 2 (sn-2), but not 1 (sn-1), in phospholipids. Incubation with DHA decreased 2-AG and anandamide levels and the amounts of AA esterified on both the sn-2 and sn-1 position of phospholipids, but not on triacylglycerols. PEA levels augmented following incubation of adipocytes with OA and PA, with no corresponding changes in phospholipids and triacylglycerols. We suggest that dietary PUFAs might modulate the levels of adipocyte phospholipids that act as endocannabinoid precursors.     

Endocannabinoids and related fatty acid amides,and their regulation,in the salivary glands of the lone star tick

The salivary glands and saliva from the lone star tick Amblyomma americanum (L.) were analyzed for the presence of the two endogenous agonists of cannabinoid receptors, N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG), as well as of the anandamide congener, N-palmitoylethanolamine (PEA), an anti-inflammatory and analgesic mediator that is inactive at cannabinoid receptors. Two very sensitive mass-spectrometric techniques were used for this purpose. Both 2-AG and PEA, as well as other N-acylethanolamines (NAEs), were identified in salivary glands, but anandamide was below detection. The levels of 2-AG were considerably higher in the salivary glands of partially fed than replete females. Ex vivo gland stimulation with arachidonic acid increased the levels of 2-AG, but not of PEA or other NAEs, and caused the formation of anandamide and of the potent analgesic compound N-arachidonoylglycine. Instead, the amounts of anandamide, 2-AG and PEA were not influenced by treatment of salivary glands with dopamine, which stimulates saliva secretion. The possible biosynthetic precursors of anandamide, PEA and other NAEs were also detected in salivary glands, whereas only PEA was detected in tick saliva. These data demonstrate for the first time that the salivary glands of an obligate ectoparasite species can make endocannabinoids and/or related congeners with analgesic and anti-inflammatory activity, which possibly participate in the inhibition of the host defense reactions.     

Gas chromatography-mass spectrometry analysis of endogenous cannabinoids in healthy and tumoral human brain and human cells in culture

Endocannabinoids are lipid mediators thought to modulate central and peripheral neural functions. We report here gas chromatography-electron impact mass spectrometry analysis of human brain, showing that lipid extracts contain anandamide and 2-arachidonoylglycerol (2-AG), the most active endocannabinoids known to date. Human brain also contained the endocannabinoid-like compounds N-oleoylethanolamine, N-palmitoylethanolamine and N-stearoylethanolamine. Anandamide and 2-AG (0.16 +/- 0.05 and 0.10 +/- 0.05 nmol/mg protein, respectively) represented 7.7% and 4.8% of total endocannabinoid-like compounds, respectively. N-Palmitoyethanolamine was the most abundant (50%), followed by N-oleoyl (23.6%) and N-stearoyl (13.9%) ethanolamines. A similar composition in endocannabinoid-like compounds was found in human neuroblastoma CHP100 and lymphoma U937 cells, and also in rat brain. Remarkably, human meningioma specimens showed an approximately six-fold smaller content of all N-acylethanolamines, but not of 2-AG, and a similar decrease was observed in a human glioblastoma. These ex vivo results fully support the purported roles of endocannabinoids in the nervous system.     

Anandamide, but not 2-arachidonoylglycerol, accumulates during in vivo neurodegeneration

Endogenous cannabinoid receptor ligands (endocannabinoids) may rescue neurons from glutamate excitotoxicity. As these substances also accumulate in cultured immature neurons following neuronal damage, elevated endocannabinoid concentrations may be interpreted as a putative neuroprotective response. However, it is not known how glutamatergic insults affect in vivo endocannabinoid homeostasis, i.e. N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG), as well as other constituents of their lipid families, N-acylethanolamines (NAEs) and 2-monoacylglycerols (2-MAGs), respectively. Here we employed three in vivo neonatal rat models characterized by widespread neurodegeneration as a consequence of altered glutamatergic neurotransmission and assessed changes in endocannabinoid homeostasis. A 46-fold increase of cortical NAE concentrations (anandamide, 13-fold) was noted 24 h after intracerebral NMDA injection, while less severe insults triggered by mild concussive head trauma or NMDA receptor blockade produced a less pronounced NAE accumulation. By contrast, levels of 2-AG and other 2-MAGs were virtually unaffected by the insults employed, rendering it likely that key enzymes in biosynthetic pathways of the two different endocannabinoid structures are not equally associated to intracellular events that cause neuronal damage in vivo. Analysis of cannabinoid CB(1) receptor mRNA expression and binding capacity revealed that cortical subfields exhibited an up-regulation of these parameters following mild concussive head trauma and exposure to NMDA receptor blockade. This may suggest that mild to moderate brain injury may trigger elevated endocannabinoid activity via concomitant increase of anandamide levels, but not 2-AG, and CB(1) receptor density.     

Cannabinoid receptor-inactive N-acylethanolamines and other fatty acid amides: metabolism and function

Although it is now generally accepted that long-chain N-acylethanolamines and their precursors, N-acylethanolamine phospholipids, exist as trace constituents in virtually all vertebrate cells and tissues, their possible biological functions are just emerging. While anandamide (N-arachidonoylethanolamine) has received much attention due to its ability to bind to and activate cannabinoid receptors, the saturated and monounsaturated N-acylethanolamines, which usually represent the vast majority, are cannabinoid receptor-inactive but appear to interact with endocannabinoids and to have other signaling functions as well. Also, primary fatty acid amides, including the amide of oleic acid, which acts as a sleep-inducing agent, do not interact with cannabinoid receptors but are catabolically related to endocannabinoids. Here we review published information on the occurrence, metabolism, and possible signaling functions of the cannabinoid receptor-inactive N-acylethanolamines and primary fatty acid amides.     

The endocannabinoid system in the brain of Carassius auratus and its possible role in the control of food intake

Cannabinoid receptors and the endocannabinoids anandamide and 2-arachidonoylglycerol have been suggested to regulate food intake in several animal phyla. Orthologs of the mammalian cannabinoid CB(1) and CB(2) receptors have been identified in fish. We investigated the presence of this endocannabinoid system in the brain of the goldfish Carassius auratus and its role in food consumption. CB(1)-like immunoreactivity was distributed throughout the goldfish brain. The prosencephalon showed strong CB(1)-like immunoreactivity in the telencephalon and the inferior lobes of the posterior hypothalamus. Endocannabinoids were detected in all brain regions of C. auratus and an anandamide-hydrolysing enzymatic activity with features similar to those of mammalian fatty acid amide hydrolase was found. Food deprivation for 24 h was accompanied by a significant increase of anandamide, but not 2-arachidonoylglycerol, levels only in the telencephalon. Anandamide caused a dose-dependent effect on food intake within 2 h of intraperitoneal administration to satiated fish and significantly enhanced or reduced food intake at low (1 pg/g body weight) or intermediate (10 pg/g) doses, respectively, the highest dose tested (100 pg/g) being inactive. We suggest that endocannabinoids might variously contribute to adaptive responses to food shortage in fish.     

Enzymatic formation of N-acylethanolamines from N-acylethanolamine plasmalogen through N-acylphosphatidylethanolamine-hydrolyzing phospholipase D-dependent and -independent pathways

Bioactive N-acylethanolamines include anandamide (an endocannabinoid), N-palmitoylethanolamine (an anti-inflammatory), and N-oleoylethanolamine (an anorexic). In the brain, these molecules are formed from N-acylphosphatidylethanolamines (NAPEs) by a specific phospholipase D, called NAPE-PLD, or through NAPE-PLD-independent multi-step pathways, as illustrated in the current study employing NAPE-PLD-deficient mice. Although N-acylethanolamine plasmalogen (1-alkenyl-2-acyl-glycero-3-phospho(N-acyl)ethanolamine, pNAPE) is presumably a major class of N-acylethanolamine phospholipids in the brain, its enzymatic conversion to N-acylethanolamines is poorly understood. In the present study, we focused on the formation of N-acylethanolamines from pNAPEs. While recombinant NAPE-PLD catalyzed direct release of N-palmitoylethanolamine from N-palmitoylethanolamine plasmalogen, the same reaction occurred in the brain homogenate of NAPE-PLD-deficient mice, suggesting that this reaction occurs through both the NAPE-PLD-dependent and -independent pathways. Liquid chromatography-mass spectrometry revealed a remarkable accumulation of 1-alkenyl-2-hydroxy-glycero-3-phospho(N-acyl)ethanolamines (lyso pNAPEs) in the brain of NAPE-PLD-deficient mice. We also found that brain homogenate formed N-palmitoylethanolamine, N-oleoylethanolamine, and anandamide from their corresponding lyso pNAPEs by a Mg(2+)-dependent "lysophospholipase D". Moreover, the brain levels of alkenyl-type lysophosphatidic acids, the other products from lyso pNAPEs by lysophospholipase D, also increased in NAPE-PLD-deficient mice. Glycerophosphodiesterase GDE1 can hydrolyze glycerophospho-N-acylethanolamines to N-acylethanolamines in the brain. In addition, we discovered that recombinant GDE1 has a weak activity to generate N-palmitoylethanolamine from its corresponding lyso pNAPE, suggesting that this enzyme is at least in part responsible for the lysophospholipase D activity. These results strongly suggest that brain tissue N-acylethanolamines, including anandamide, can be formed from N-acylated plasmalogen through an NAPE-PLD-independent pathway as well as by their direct release via NAPE-PLD.     

Biosynthesis and inactivation of endocannabinoids: relevance to their proposed role as neuromodulators.

The two putative endogenous ligands of cannabinoid receptors, anandamide and 2-arachidonoylglycerol, are synthesized by and released from neurons in a Ca2+-dependent fashion, and re-uptaken and catabolized by both neurons and astrocytes. These biochemical features of the endocannabinoids, as well as some of their pharmacological effects in both central and peripheral nervous systems, suggest a role as neuromodulators for these metabolites. This neuromodulatory role is supported by the brain regional distribution of anandamide, its biosynthetic precursor and its major inactivating enzyme, and by the existence of possible regulatory mechanisms for the biosynthesis and inactivation of endocannabinoids, which are reviewed in this article.     

Cell signaling by endocannabinoids and their congeners: questions of selectivity and other challenges

The major endocannabinoids, anandamide (N-arachidonoylethanolamide, 20:4n-6 N-acylethanolamine) and 2-arachidonoylglycerol (2-AG) are structurally and functionally similar, but they are produced by different metabolic pathways and their levels must therefore be regulated by different mechanisms. Both endocannabinoids are accompanied by cannabinoid receptor-inactive, saturated and mono- or di-unsaturated congeners which can influence their metabolism and function. Here we review published data on the presence and production of anandamide and 2-AG and their congeners in mammalian cells and discuss this information in terms of their proposed signaling functions.     

Endocannabinoid metabolism in human glioblastomas and meningiomas compared to human non-tumour brain tissue

The endogenous levels of the two cannabinoid receptor ligands 2-arachidonoyl glycerol and anandamide, and their respective congeners, monoacyl glycerols and N-acylethanolamines, as well as the phospholipid precursors of N-acylethanolamines, were measured by gas chromatography-mass spectrometry in glioblastoma (WHO grade IV) tissue and meningioma (WHO grade I) tissue and compared with human non-tumour brain tissue. Furthermore, the metabolic turnover of N-acylethanolamines was compared by measurements of the enzymatic activity of N-acyltransferase, N-acylphosphatidylethanolamine-hydrolysing phospholipase D and fatty acid amide hydrolase in the same three types of tissue. Glioblastomas were characterized by enhanced levels of N-acylethanolamines (eightfold, 128 +/- 59 pmol/micromol lipid phosphorus) including anandamide (17-fold, 4.6 +/- 3.1 pmol/micromol lipid phosphorus) and several species of N-acylphosphatidylethanolamines (three to eightfold). This was accompanied by a more than 60% reduction in the enzyme activities of N-acylphosphatidylethanolamine-hydrolysing phospholipase D and fatty acid amide hydrolase. By contrast, meningiomas were characterized by a massively enhanced level of 2-monoacyl glycerols (20-fold, 2293 +/- 361 pmol/micromol lipid phosphorus) including 2-arachidonoyl glycerol (20-fold, 1524 +/- 361 pmol/micromol lipid phosphorus). This was accompanied by an enhanced in vitro conversion of phosphatidylcholine to monoacyl glycerol (fivefold). The enhanced level of the 2-arachidonoyl glycerol, anandamide and other N-acylethanolamines detected in the two types of tumour tissue may possibly act as endogenous anti-tumour mediators by stimulation of both cannabinoid and non-cannabinoid receptor-mediated mechanisms.     

Enhanced levels of endogenous cannabinoids in the globus pallidus are associated with a reduction in movement in an animal model of Parkinson's disease.

In recent years, cannabinoid receptors and their endogenous ligands (endocannabinoids) have been identified within the brain. The high density of CB1 cannabinoid receptors within the basal ganglia suggests a potential role for endocannabinoids in the control of voluntary movement and in basal ganglia-related movement disorders such as Parkinson's disease. However, whether endocannabinoids play a role in regulating motor behavior in health and disease is unknown. Here we report the presence in two regions of the basal ganglia, the globus pallidus and substantia nigra, of the endocannabinoids 2-arachidonoylglycerol (2AG) and anandamide. The levels of the latter compound are approximately threefold higher than those previously reported in any other brain region. In the reserpine-treated rat, an animal model of Parkinson's disease, suppression of locomotion is accompanied by a sevenfold increase in the levels of the 2AG in the globus pallidus, but not in the other five brain regions analyzed. Stimulation of locomotion in the reserpine-treated rat by either of the two selective agonists of D2 and D1 dopamine receptors, quinpirole and R-(+/-)-3-allyl-6-chloro-7, 8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide (Cl-APB), respectively, results in the reduction of both anandamide and 2AG levels in the globus pallidus. Finally, full restoration of locomotion in the reserpine-treated rat is obtained by coadministration of quinpirole and the selective antagonist of the cannabinoid CB1 receptor subtype, SR141716A. These findings indicate a link between endocannabinoid signaling in the globus pallidus and symptoms of Parkinson's disease in the reserpine-treated rat, and suggest that modulation of the endocannabinoid signaling system might prove useful in treating this or other basal ganglia-related movement disorders.     

Differential modulation of white adipose tissue endocannabinoid levels by n-3 fatty acids in obese mice and type 2 diabetic patients

n-3 polyunsaturated fatty acids (n-3 PUFA) might regulate metabolism by lowering endocannabinoid levels. We examined time-dependent changes in adipose tissue levels of endocannabinoids as well as in parameters of glucose homeostasis induced by n-3 PUFA in dietary-obese mice, and compared these results with the effect of n-3 PUFA intervention in type 2 diabetic (T2DM) subjects. Male C57BL/6J mice were fed for 8, 16 or 24?weeks a high-fat diet alone (cHF) or supplemented with n-3 PUFA (cHF?+?F). Overweight/obese, T2DM patients on metformin therapy were given for 24?weeks corn oil (Placebo; 5?g/day) or n-3 PUFA concentrate as above (Omega-3; 5?g/day). Endocannabinoids were measured by liquid chromatography-tandem mass-spectrometry. Compared to cHF-fed controls, the cHF?+?F mice consistently reduced 2-arachidonoylglycerol (up to ~2-fold at week 24) and anandamide (~2-fold) in adipose tissue, while the levels of endocannabinoid-related anti-inflammatory molecules N-eicosapentaenoyl ethanolamine (EPEA) and N-docosahexaenoyl ethanolamine (DHEA) increased more than ~10-fold and ~8-fold, respectively. At week 24, the cHF?+?F mice improved glucose tolerance and fasting blood glucose, the latter being positively correlated with adipose 2-arachidonoylglycerol levels only in obese cHF-fed controls, like fasting insulin and HOMA-IR. In the patients, n-3 PUFA failed to reduce 2-arachidonoylglycerol and anandamide levels in adipose tissue and serum, but they increased both adipose tissue and serum levels of EPEA and DHEA. In conclusion, the inability of n-3 PUFA to reduce adipose tissue and serum levels of classical endocannabinoids might contribute to a lack of beneficial effects of these lipids on glucose homeostasis in T2DM patients.     

Involvement of N-acylethanolamine-hydrolyzing acid amidase in the degradation of anandamide and other N-acylethanolamines in macrophages

Bioactive N-acylethanolamines including the endocannabinoid anandamide are known to be hydrolyzed to fatty acids and ethanolamine by fatty acid amide hydrolase (FAAH). In addition, we recently cloned an isozyme termed "N-acylethanolamine-hydrolyzing acid amidase (NAAA)", which is active only at acidic pH [Tsuboi, Sun, Okamoto, Araki, Tonai, Ueda, J. Biol. Chem. 285 (2005) 11082-11092]. However, physiological roles of NAAA remained unclear. Here, we examined a possible contribution of NAAA to the degradation of various N-acylethanolamines in macrophage cells. NAAA mRNA as well as FAAH mRNA was detected in several macrophage-like cells, including RAW264.7, and mouse peritoneal macrophages. The homogenates of RAW264.7 cells showed both the NAAA and FAAH activities which were confirmed with the aid of their respective specific inhibitors, N-cyclohexanecarbonylpentadecylamine (CCP) and URB597. As analyzed with intact cells, RAW264.7 cells and peritoneal macrophages degraded anandamide, N-palmitoylethanolamine, N-oleoylethanolamine, and N-stearoylethanolamine. Pretreatment of the cells with CCP or URB597 partially inhibited the degradation, and a combination of the two compounds caused more profound inhibition. In contrast, the anandamide hydrolysis in mouse brain appeared to be principally attributable to FAAH despite the expression of NAAA in the brain. These results suggested that NAAA and FAAH cooperatively degraded various N-acylethanolamines in macrophages.     

Endocannabinoids acting at CB1 receptors mediate the cardiac contractile dysfunction in vivo in cirrhotic rats

Advanced liver cirrhosis is associated with hyperdynamic circulation consisting of systemic hypotension, decreased peripheral resistance, and cardiac dysfunction, termed cirrhotic cardiomyopathy. Previous studies have revealed the role of endocannabinoids and vascular CB(1) receptors in the development of generalized hypotension and mesenteric vasodilation in animal models of liver cirrhosis, and CB(1) receptors have also been implicated in the decreased beta-adrenergic responsiveness of isolated heart tissue from cirrhotic rats. Here we document the cardiac contractile dysfunction in vivo in liver cirrhosis and explore the role of the endocannabinoid system in its development. Rats with CCl(4)-induced cirrhosis developed decreased cardiac contractility, as documented through the use of the Millar pressure-volume microcatheter system, low blood pressure, and tachycardia. Bolus intravenous injection of the CB(1) antagonist AM251 (3 mg/kg) acutely increased mean blood pressure, as well as both load-dependent and -independent indexes of systolic function, whereas no such changes were elicited by AM251 in control rats. Furthermore, tissue levels of the endocannabinoid anandamide increased 2.7-fold in the heart of cirrhotic compared with control rats, without any change in 2-arachidonoylglycerol levels, whereas, in the cirrhotic liver, both 2-arachidonoylglycerol (6-fold) and anandamide (3.5-fold) were markedly increased. CB(1)-receptor expression in the heart was unaffected by cirrhosis, as verified by Western blotting. Activation of cardiac CB(1) receptors by endogenous anandamide contributes to the reduced cardiac contractility in liver cirrhosis, and CB(1)-receptor antagonists may be used to improve contractile function in cirrhotic cardiomyopathy and, possibly, in other forms of heart failure.     

Endocannabinoids and related fatty acid derivatives in pain modulation

The brain produces at least five compounds that possess sub-micromolar affinity for cannabinoid receptors: anandamide, 2-arachidonoylglycerol, noladin ether, virodhamine, and N-arachidonoyldopamine (NADA). One function of these and/or related compounds is to suppress pain sensitivity. Much evidence supports a role of endocannabinoids in pain modulation in general, and some evidence points to the role of particular endocannabinoids. Related endogenous fatty acid derivatives such as oleamide, palmitoylethanolamide, 2-lineoylglycerol, 2-palmitoylglycerol, and a family of arachidonoyl amino acids may interact with endocannabinoids in the modulation of pain sensitivity.     

Molecular characterization of a phospholipase D generating anandamide and its congeners

Anandamide (N-arachidonoylethanolamine) is known to be an endogenous ligand of cannabinoid and vanilloid receptors. Its congeners (collectively referred to as N-acylethanolamines) also show a variety of biological activities. These compounds are principally formed from their corresponding N-acyl-phosphatidylethanolamines by a phosphodiesterase of the phospholipase D-type in animal tissues. We purified the enzyme from rat heart, and by the use of the sequences of its internal peptides cloned its complementary DNAs from mouse, rat, and human. The deduced amino acid sequences were composed of 393-396 residues, and showed that the enzyme has no homology with the known phospholipase D enzymes but is classified as a member of the zinc metallohydrolase family of the beta-lactamase fold. As was overexpressed in COS-7 cells, the recombinant enzyme generated anandamide and other N-acylethanolamines from their corresponding N-acyl-phosphatidylethanolamines at comparable rates. In contrast, the enzyme was inactive with phosphatidylcholine and phosphatidylethanolamine. Assays of the enzyme activity and the messenger RNA and protein levels revealed its wide distribution in murine organs with higher contents in the brain, kidney, and testis. These results confirm that a specific phospholipase D is responsible for the generation of N-acylethanolamines including anandamide, strongly suggesting the physiological importance of lipid molecules of this class.     

Intestinal levels of anandamide and oleoylethanolamide in food-deprived rats are regulated through their precursors

The anorectic lipid oleoylethanolamide and the orexigenic lipid anandamide both belong to the group of N-acylethanolamines that are generated by the enzyme N-acylphosphatidylethanolamine-hydrolyzing phospholipase D. The levels of the two bioactive lipids were investigated in rat intestines after 24 h of starvation as well as after 1 and 4 h of re-feeding. Total levels of precursor phospholipids and N-acylethanolamines were decreased upon food-deprivation whereas the level of the anandamide precursor molecule was significantly increased. The level of 2-arachidonoyl-glycerol was unchanged as was the activity of N-acyltransferase, N-acylphosphatidylethanolamine-hydrolyzing phospholipase D, and fatty acid amide hydrolase upon starvation and re-feeding. It is concluded that remodeling of the amide-linked fatty acids of N-acylphosphatidylethanolamine is responsible for the opposite effects on levels of anandamide and oleoylethanolamide in intestines of food-deprived rats and not an alternative biochemical route for anandamide synthesis. Furthermore, linoleoylethanolamide, which accounted for more than 50 mol% of the endogenous pool of N-acylethanolamines, was found not to have the same inhibitory effect on food intake, as did oleoylethanolamide following oral administration.