Analysis of endocannabinoids by Ag+ coordination tandem mass spectrometry

Identification of bioactive natural products using yeast：Application to monoacylglycerol lipase inhibitor extraction from Corydalis Rhizoma

Identification of bioactive principles from natural products is considered a challenging task in drug discovery. Recently, ligand fishing has been growing in interest as a sustainable strategy. In this study, a yeast-based drug discovery strategy was investigated to screen and fish active ingredients from natural products. Human monoacylglycerol lipase (MAGL) was first displayed on the cell wall of Pichia pastoris. The expression of MAGL on the cell surface was confirmed by immunofluorescence analysis. The activity toward 7-HCA which was consistent with free enzymes in solution. Recombinant yeast strains were used to screen the potential inhibitors from traditional Chinese medicines. Preliminary screening showed that the extracts of 12 herbs showed inhibition on MAGL activity, among which Corydalis Rhizoma had the highest inhibition rate of 60.66 ± 2.44%. Recombinant yeast fishing combined with HPLC-Q-TOF-MS/MS analysis was further used to identify the potential MAGL inhibitors. Finally, dehydrocorydaline (DHC) in Corydalis Rhizoma was determined as a ligand to MAGL with the IC₅₀ value at 154.7 μΜ. Corydalis Rhizoma has been used as a pain reliever in TCM. Intraperitoneal injection of 7 mg kg^- 1 DHC in chronic constriction injury model rats significantly attenuated the mechanical allodynia and thermal hyperalgesia. Meanwhile, 2-arachidonoylglycerol, the major MAGL substrate in the brain, was significantly increased both in the hippocampus and striatum. In conclusion, yeast-based ligand fishing combined with HPLC-Q-TOF-MS/MS is a powerful strategy for drug discovery in complex mixtures and DHC from Corydalis Rhizoma was confirmed with high inhibitory activity to MAGL either in vitro or in vivo .

Cocaine-induced endocannabinoid signaling mediated by sigma-1 receptors and extracellular vesicle secretion

Cocaine is an addictive drug that acts in brain reward areas. Recent evidence suggests that cocaine stimulates synthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG) in midbrain, increasing dopamine neuron activity via disinhibition. Although a mechanism for cocaine-stimulated 2-AG synthesis is known, our understanding of 2-AG release is limited. In NG108 cells and mouse midbrain tissue, we find that 2-AG is localized in non-synaptic extracellular vesicles (EVs) that are secreted in the presence of cocaine via interaction with the chaperone protein sigma-1 receptor (Sig-1R). The release of EVs occurs when cocaine causes dissociation of the Sig-1R from ADP-ribosylation factor (ARF6), a G-protein regulating EV trafficking, leading to activation of myosin light chain kinase (MLCK). Blockade of Sig-1R function, or inhibition of ARF6 or MLCK also prevented cocaine-induced EV release and cocaine-stimulated 2-AG-modulation of inhibitory synapses in DA neurons. Our results implicate the Sig-1R-ARF6 complex in control of EV release and demonstrate that cocaine-mediated 2-AG release can occur via EVs.

Anti-inflammatory ω-3 endocannabinoid epoxides

Clinical studies suggest that diets rich in ω-3 polyunsaturated fatty acids (PUFAs) provide beneficial anti-inflammatory effects, in part through their conversion to bioactive metabolites. Here we report on the endogenous production of a previously unknown class of ω-3 PUFA-derived lipid metabolites that originate from the crosstalk between endocannabinoid and cytochrome P450 (CYP) epoxygenase metabolic pathways. The ω-3 endocannabinoid epoxides are derived from docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) to form epoxyeicosatetraenoic acid-ethanolamide (EEQ-EA) and epoxydocosapentaenoic acid-ethanolamide (EDP-EA), respectively. Both EEQ-EAs and EDP-EAs are endogenously present in rat brain and peripheral organs as determined via targeted lipidomics methods. These metabolites were directly produced by direct epoxygenation of the ω-3 endocannabinoids, docosahexanoyl ethanolamide (DHEA) and eicosapentaenoyl ethanolamide (EPEA) by activated BV-2 microglial cells, and by human CYP2J2. Neuroinflammation studies revealed that the terminal epoxides 17,18-EEQ-EA and 19,20-EDP-EA dose-dependently abated proinflammatory IL-6 cytokines while increasing anti-inflammatory IL-10 cytokines, in part through cannabinoid receptor-2 activation. Furthermore the ω-3 endocannabinoid epoxides 17,18-EEQ-EA and 19,20-EDP-EA exerted antiangiogenic effects in human microvascular endothelial cells (HMVEC) and vasodilatory actions on bovine coronary arteries and reciprocally regulated platelet aggregation in washed human platelets. Taken together, the ω-3 endocannabinoid epoxides' physiological effects are mediated through both endocannabinoid and epoxyeicosanoid signaling pathways. In summary, the ω-3 endocannabinoid epoxides are found at concentrations comparable to those of other endocannabinoids and are expected to play critical roles during inflammation in vivo; thus their identification may aid in the development of therapeutics for neuroinflammatory and cerebrovascular diseases.

Shotgun Lipidomics Approach to Stabilize the Regiospecificity of Monoglycerides Using a Facile Low-Temperature Derivatization Enabling Their Definitive Identification and Quantitation

Monoglycerides play a central role in lipid metabolism and are important signaling metabolites. Quantitative analysis of monoglyceride molecular species has remained challenging due to rapid isomerization via α-hydroxy acyl migration. Herein, we describe a shotgun lipidomics approach that utilizes a single-phase methyl tert-butyl ether extraction to minimize acyl migration, a facile low temperature diacetyl derivatization to stabilize regiospecificity, and tandem mass spectrometric analysis to identify and quantify regioisomers of monoglycerides in biological samples. The rapid and robust diacetyl derivatization at low temperatures (e.g., -20 °C, 30 min) prevents postextraction acyl migration and preserves regiospecificity of monoglyceride structural isomers. Furthermore, ionization of ammonium adducts of diacetyl monoglyceride derivatives in positive-ion mode markedly increases analytic sensitivity (low fmol/μL). Critically, diacetyl derivatization enables the differentiation of discrete monoglyceride regioisomers without chromatography through their distinct signature fragmentation patterns during collision induced dissociation. The application of this approach in the analysis of monoglycerides in multiple biologic tissues demonstrated diverse profiles of molecular species. Remarkably, the regiospecificity of individual monoglyceride molecular species is also diverse from tissue to tissue. Collectively, this developed approach enables the profiling, identification and quantitation of monoglyceride regioisomers directly from tissue extracts.

Brain 2-Arachidonoylglycerol Levels Are Dramatically and Rapidly Increased Under Acute Ischemia-Injury Which Is Prevented by Microwave Irradiation

The involvement of brain 2-arachidonoylglycerol (2-AG) in a number of critical physiological and pathophysiological regulatory mechanisms highlights the importance for an accurate brain 2-AG determination. In the present study, we validated head-focused microwave irradiation (MW) as a method to prevent postmortem brain 2-AG alterations before analysis. We compared MW to freezing to prevent 2-AG induction and estimated exogenous and endogenous 2-AG stability upon exposure to MW. Using MW, we measured, for the first time, true 2-AG brain levels under basal conditions, 30 s after brain removal from the cranium, and upon exposure to 5 min of brain global ischemia. Our data indicate that brain 2-AG levels are instantaneously and dramatically increased approximately 60-fold upon brain removal from the cranium. With 5 min of brain global ischemia 2-AG levels are also, but less dramatically, increased 3.5-fold. Our data indicate that brain tissue fixation with MW is a required technique to measure both true basal 2-AG levels and 2-AG alterations under different experimental conditions including global ischemia, and 2-AG is stable upon exposure to MW.

Assay of Endocannabinoid Oxidation by Cyclooxygenase-2

The endocannabinoids, 2-arachidonoylglycerol (2-AG) and arachidonylethanolamide (AEA), are endogenous ligands for the cannabinoid receptors (CB1 and CB2) and are implicated in a wide array of physiological processes. These neutral arachidonic acid (AA) derivatives have been identified as efficient substrates for the second isoform of the cyclooxygenase enzyme (COX-2). A diverse family of prostaglandin glycerol esters (PG-Gs) and prostaglandin ethanolamides (PG-EAs) is generated by the action of COX-2 (and downstream prostaglandin synthases) on 2-AG and AEA. As the biological importance of the endocannabinoid system becomes more apparent, there is a tremendous need for robust, sensitive, and efficient analytical methodology for the endocannabinoids and their metabolites. In this chapter, we describe methodology suitable for carrying out oxygenation of endocannabinoids by COX-2, and analysis of products of endocannabinoid oxygenation by COX-2 and of endocannabinoids themselves from in vitro and cell assays.

Lipidomic Analysis of Endocannabinoid Signaling: Targeted Metabolite Identification and Quantification

The endocannabinoids N-arachidonoylethanolamide (or anandamide, AEA) and 2-arachidonoylglycerol (2-AG) belong to the larger groups of N-acylethanolamines (NAEs) and monoacylglycerol (MAG) lipid classes, respectively. They are biologically active lipid molecules that activate G-protein-coupled cannabinoid receptors found in various organisms. After AEA and 2-AG were discovered in the 1990s, they have been extensively documented to have a broad range of physiological functions. Along with AEA, several NAEs, for example, N-palmitoylethanolamine (PEA), N-stearoylethanolamine (SEA), and N-oleoylethanolamine (OEA) are also present in tissues, usually at much larger concentrations than AEA. Any perturbation that involves the endocannabinoid pathway may subsequently alter basal level or metabolism of these lipid mediators. Further, the altered levels of these molecules often reflect pathological conditions associated with tissue damage. Robust and sensitive methodologies to analyze these lipid mediators are essential to understanding how they act as endocannabinoids. The recent advances in mass spectrometry allow researchers to develop lipidomics approaches and several methodologies have been proposed to quantify endocannabinoids in various biological systems.

A robust capillary liquid chromatography/tandem mass spectrometry method for quantitation of neuromodulatory endocannabinoids

RATIONALE

Methods for quantifying anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) are needed to support programs investigating molecular mechanisms of the central nervous system. Existing methods, while useful, are not well adapted to efficiently process large numbers of very small tissue samples. A unique challenge involves the disparity in endogenous levels of AEA (pmol/g tissue) and 2-AG (nmol/g tissue).

METHODS

A simplified one-step solvent extraction procedure was developed for recovering endocannabinoids from rat brain tissues, and combined with capillary liquid chromatography/tandem mass spectrometry (LC/MS/MS). Various multiple reaction monitoring (MRM)-based methods were evaluated for limit of detection (LOD) and robustness.

RESULTS

The optimized simultaneous quantitation method achieves an LOQ of 50 amol for AEA and 25 fmol for 2-AG, both with a linearity over 3 orders of magnitude, and elution times under 3 min. Accuracy, expressed as relative error (RE), is less than 12% for AEA and less than 6% for 2-AG. Precision, expressed as relative standard deviation (RSD), is less than 6% for AEA and less than 3% for 2-AG. Sample handling routines are sufficiently robust to support the automated analysis of thousands of samples from a range of tissue types.

CONCLUSIONS

The microscale method is a sensitive, economical and robust alternative to the larger scale LC/MS methods currently implemented for quantitation of AEA and 2-AG.

Competition and allostery govern substrate selectivity of cyclooxygenase-2

Cyclooxygenase-2 (COX-2) oxygenates arachidonic acid (AA) and its ester analog, 2-arachidonoylglycerol (2-AG), to prostaglandins (PGs) and prostaglandin glyceryl esters (PG-Gs), respectively. Although the efficiency of oxygenation of these substrates by COX-2 in vitro is similar, cellular biosynthesis of PGs far exceeds that of PG-Gs. Evidence that the COX enzymes are functional heterodimers suggests that competitive interaction of AA and 2-AG at the allosteric site of COX-2 might result in differential regulation of the oxygenation of the two substrates when both are present. Modulation of AA levels in RAW264.7 macrophages uncovered an inverse correlation between cellular AA levels and PG-G biosynthesis. In vitro kinetic analysis using purified protein demonstrated that the inhibition of 2-AG oxygenation by high concentrations of AA far exceeded the inhibition of AA oxygenation by high concentrations of 2-AG. An unbiased systems-based mechanistic model of the kinetic data revealed that binding of AA or 2-AG at the allosteric site of COX-2 results in a decreased catalytic efficiency of the enzyme toward 2-AG, whereas 2-AG binding at the allosteric site increases COX-2's efficiency toward AA. The results suggest that substrates interact with COX-2 via multiple potential complexes involving binding to both the catalytic and allosteric sites. Competition between AA and 2-AG for these sites, combined with differential allosteric modulation, gives rise to a complex interplay between the substrates, leading to preferential oxygenation of AA.

Quantification of anandamide, oleoylethanolamide and palmitoylethanolamide in rodent brain tissue using high performance liquid chromatography-electrospray mass spectroscopy

Reported concentrations for endocannabinoids and related lipids in biological tissues can vary greatly; therefore, methods used to quantify these compounds need to be validated. This report describes a method to quantify anandamide (AEA), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) from rodent brain tissue. Analytes were extracted using acetonitrile without further sample clean up, resolved on a C18 reverse-phase column using a gradient mobile phase and detected using electrospray ionization in positive selected ion monitoring mode on a single quadrupole mass spectrometer. The method produced high recovery rates for AEA, OEA and PEA, ranging from 98.1% to 106.2%, 98.5% to 102.2% and 85.4% to 89.5%, respectively. The method resulted in adequate sensitivity with a lower limit of quantification for AEA, OEA and PEA of 1.4 ng/mL, 0.6 ng/mL and 0.5 ng/mL, respectively. The method was reproducible as intraday and interday accuracies and precisions were under 15%. This method was suitable for quantifying AEA, OEA and PEA from rat brain following pharmacological inhibition of fatty acid amide hydrolase.

Central anandamide deficiency predicts stress-induced anxiety: behavioral reversal through endocannabinoid augmentation

Stress is a major risk factor for the development of mood and anxiety disorders; elucidation of novel approaches to mitigate the deleterious effects of stress could have broad clinical applications. Pharmacological augmentation of central endogenous cannabinoid (eCB) signaling may be an effective therapeutic strategy to mitigate the adverse behavioral and physiological consequences of stress. Here we show that acute foot-shock stress induces a transient anxiety state measured 24 h later using the light-dark box assay and novelty-induced hypophagia test. Acute pharmacological inhibition of the anandamide-degrading enzyme, fatty acid amide hydrolase (FAAH), reverses the stress-induced anxiety state in a cannabinoid receptor-dependent manner. FAAH inhibition does not significantly affect anxiety-like behaviors in non-stressed mice. Moreover, whole brain anandamide levels are reduced 24 h after acute foot-shock stress and are negatively correlated with anxiety-like behavioral measures in the light-dark box test. These data indicate that central anandamide levels predict acute stress-induced anxiety, and that reversal of stress-induced anandamide deficiency is a key mechanism subserving the therapeutic effects of FAAH inhibition. These studies provide further support that eCB-augmentation is a viable pharmacological strategy for the treatment of stress-related neuropsychiatric disorders.

Regulation of circulating endocannabinoids associated with cancer and metastases in mice and humans

BACKGROUND AND AIMS

Endocannabinoids may modify cancer development, progression and associated pain. We determined whether cancer-evoked dysregulations in this system become manifest in altered tissue and plasma endocannabinoids.

METHODS

Endocannabinoid changes due to cancer were explored in a local and metastatic syngeneic mouse melanoma model. Endocannabinoid stratification in human cancer was cross-sectionally assessed in the plasma of 304 patients (147 men, 157 women, aged 32 - 87 years) suffering from several types of cancer at Roman Numeral Staging between I and IVc, mostly IV (n = 220), and compared with endocannabinoids of healthy controls.

RESULTS

In mice with local tumor growth, ethanolamide endocannabinoids, i.e., anandamide (AEA), palmitoylethanolamide (PEA) and oleoylethanolamide (OEA) were downregulated, whereas 2-arachidonoylglycerol (2-AG) was increased. Upon spreading of the cancer cells particularly 2-AG steadily increased in parallel to disease progression while OEA modulated cell migration. Results translated into humans, in whom cancer was associated with a decreased AEA, increased 2-AG and increased OEA correlating with the number of metastases.

CONCLUSIONS

The endocannabinoid system was subject to cancer-associated regulations to an extent that led to measurable changes in circulating endocannabinoid levels, emphasizing the importance of the endocannabinoid system in the pathophysiology of cancer.

Development and validation of a sensitive UPLC-ESI-MS/MS method for the simultaneous quantification of 15 endocannabinoids and related compounds in milk and other biofluids

The endocannabinoid (eCB) system has gained an increasing interest over the past decades since the discovery of anandamide and 2-arachidonoyl glycerol (2-AG). These, and structurally related compounds, are associated with a wide variety of physiological processes. For instance, eCB levels in milk have been associated with infants' feeding and sleeping behavior. A method based on ultraperformance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) was developed and validated for the simultaneous quantification of 15 eCBs and related compounds, including both fatty acid amides and glycerols. Linearity (0.9845 < R(2) < 1), limit of detection and quantification (0.52-293 pg on column), inter- and intraday accuracy (>70%) and precision (CV < 15%), stability, and recovery (in milk and plasma) were established in accordance to the U.S. Food and Drug Administration guidelines. The method was successfully applied to bovine and elk milk revealing species-specific eCB profiles, with significant different levels of 2-AG, 2-linoleoyl glycerol, docosahexaenoyl ethanolamide, palmitoyl ethanolamide, and oleoyl ethanolamide. Furthermore, stearoyl ethanolamide and docosatetraenoyl ethanolamide were only detected in elk milk. In summary, our UPLC-ESI-MS/MS method may be used for quantification of eCBs and related compounds in different biofluids and applied to investigations of the role of these emerging compounds in various physiological processes.

Fatty acid ethanolamides modulate CD36-mRNA through dietary fatty acid manipulation in Syrian Golden hamsters

Fatty acids convert to fatty acid ethanolamides which associate with lipid signalling, fat oxidation, and energy balance; however, the extent to which dietary fatty acids manipulation can impact such control processes through fatty acid ethanolamides-related mechanisms remains understudied. The objective was to examine the impact of diets containing 6% corn oil, high oleic canola oil, docosahexaenoic acid + high oleic canola oil, and fish oil on plasma and organ levels of fatty acid ethanolamides, peroxisome proliferator-activated receptor-α regulatory targets, and lipid metabolism in Syrian Golden hamsters. After 29 days, in plasma, animals that were fed fish oil showed greater (p < 0.05) oleoylethanolamide and lower (p < 0.05) arachidonoylethanolamide and palmitoylethanolamide levels compared with other groups, while animals fed canola oil showed higher (p < 0.05) oleoylethanolamide levels in proximal intestine and liver than groups that were fed coin oil and fish oil. The canola oil group showed elevated (p < 0.01) fat oxidation (%) and over 3.0-fold higher (p < 0.05) hepatic-CD36 expression compared with the corn oil group. Hepatic-lipogenesis was lower (p < 0.05) in hamsters that were fed DHA-canola oil compared with the corn oil group. To conclude, dietary fatty acids produced shifts in plasma and organ levels of arachidonoylethanolamide, oleoylethanolamide, and palmitoylethanolamid, which were accompanied by changes in gene expression, lipogenesis, and energy expenditure, suggesting mechanisms through which dietary fatty acids influence disease risk.

Quantitative analysis of multiple fatty acid ethanolamides using ultra-performance liquid chromatography-tandem mass spectrometry

Fatty acid ethanolamides (FAE) represent a group of lipid signaling molecules associated with many physiological and pharmacological actions; however, low FAE tissue levels pose challenges in terms of analytical characterization. The objective was to develop a competent ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for analysis of multiple FAE in animal and human tissue samples. Analytes were extracted using lipid-phase and solid-phase extraction procedures. Chromatographic separation was achieved using a gradient elution in 8 min. FAE were quantified by MS/MS in positive electrospray ionization mode. Linearity was shown in lower and higher FAE concentration ranges, with a limit of quantification (LOQ) ≤0.2 ng/ml for FAE including alpha-linolenoylethanolamide (ALEA), arachidonoylethanolamide (AEA), docosahexaenoylethanolamide (DHEA), linoleoylethanolamide (LEA), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). Accuracy was shown to be between 92.4% and 108.8%, and precision was <10% for all FAE species. In sum, this sensitive and reproducible method can be used to simultaneously determine multiple FAE at low concentrations in order to facilitate further study of the role of FAE on physiological state.

Cannabinoid receptor 1 suppresses transient receptor potential vanilloid 1-induced inflammatory responses to corneal injury

Cannabinoid receptor type 1 (CB1)-induced suppression of transient receptor potential vanilloid type 1 (TRPV1) activation provides a therapeutic option to reduce inflammation and pain in different animal disease models through mechanisms involving dampening of TRPV1 activation and signaling events. As we found in both mouse corneal epithelium and human corneal epithelial cells (HCEC) that there is CB1 and TRPV1 expression colocalization based on overlap of coimmunostaining, we determined in mouse corneal wound healing models and in human corneal epithelial cells (HCEC) if they interact with one another to reduce TRPV1-induced inflammatory and scarring responses. Corneal epithelial debridement elicited in vivo a more rapid wound healing response in wildtype (WT) than in CB1(-/-) mice suggesting functional interaction between CB1 and TRPV1. CB1 activation by injury is tenable based on the identification in mouse corneas of 2-arachidonylglycerol (2-AG) with tandem LC-MS/MS, a selective endocannabinoid CB1 ligand. Suppression of corneal TRPV1 activation by CB1 is indicated since following alkali burning, CB1 activation with WIN55,212-2 (WIN) reduced immune cell stromal infiltration and scarring. Western blot analysis of coimmunoprecipitates identified protein-protein interaction between CB1 and TRPV1. Other immunocomplexes were also identified containing transforming growth factor kinase 1 (TAK1), TRPV1 and CB1. CB1 siRNA gene silencing prevented suppression by WIN of TRPV1-induced TAK1-JNK1 signaling. WIN reduced TRPV1-induced Ca(2+) transients in fura2-loaded HCEC whereas pertussis toxin (PTX) preincubation obviated suppression by WIN of such rises caused by capsaicin (CAP). Whole cell patch clamp analysis of HCEC showed that WIN blocked subsequent CAP-induced increases in nonselective outward currents. Taken together, CB1 activation by injury-induced release of endocannabinoids such as 2-AG downregulates TRPV1 mediated inflammation and corneal opacification. Such suppression occurs through protein-protein interaction between TRPV1 and CB1 leading to declines in TRPV1 phosphorylation status. CB1 activation of the GTP binding protein, G(i/o) contributes to CB1 mediated TRPV1 dephosphorylation leading to TRPV1 desensitization, declines in TRPV1-induced increases in currents and pro-inflammatory signaling events.

Quantitative LC-MS/MS analysis of arachidonoyl amino acids in mouse brain with treatment of FAAH inhibitor

An additional class of endogenous lipid amides, N-arachidonoyl amino acids (Ara-AAs), is growing in significance in the field of endocannabinoids. The development, validation, and application of a sensitive and selective method to simultaneously monitor and quantify the level of Ara-AAs along with anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) in mouse brain has been established. The linearity of the method over the concentration ranges of 0.2-120 pg/μl for the standards of N-arachidonoyl amino acids, N-arachidonoyl alanine (NAAla), serine (NASer), γ-aminobutyric acid (NAGABA), and glycine (NAGly); 0.7-90 pg/μl for AEA-d(0)/d(8); and 7.5-950 pg/μl for 2-AG was determined with R(2) values of 0.99. Also the effects of the FAAH inhibitor URB 597 on the endogenous levels of these analytes were investigated. AEA and NASer brain levels exhibit a dose-dependent increase after systemic administration of URB 597, whereas NAGly and NAGABA were significantly decreased after treatment. NAAla and 2-AG were not altered after URB 597 treatment. The potential benefit of establishing this assay extends beyond the quantification of the Ara-AAs along with AEA and 2-AG in mouse brain, to reveal a variety of pharmacological effects and physiological roles of these analytes.

Application of Chemoenzymatic Hydrolysis in the Synthesis of 2-Monoacylglycerols

The selective biocatalyzed synthesis of 2-monoacylglycerols (2-MAGs) through the use of commercially available immobilized Candida antarctica (Novozym435) and Rhizomucor miehei is explored. Reactions at room temperature result in the formation of a 2-MAG and a corresponding ethyl ester of the fatty acid with immobilized Candida antarctica within 2h with yields ranging from 36%-83%. Similar reaction conditions with immobilized Rhizomucor miehei yielded exclusively the 2-MAG after 24h with yields ranging from 37% to 88%. Yields vary on the acyl group at the sn-2 position and choice of enzyme involved.

Simultaneous UPLC-MS/MS quantification of the endocannabinoids 2-arachidonoyl glycerol (2AG), 1-arachidonoyl glycerol (1AG), and anandamide in human plasma: minimization of matrix-effects, 2AG/1AG isomerization and degradation by toluene solvent extraction

Analysis of the endocannabinoid (EC) system's key molecules 2-arachidonoyl glycerol (2AG) and arachidonoyl ethanolamide (anandamide, AEA) is challenging due to several peculiarities. 2AG isomerizes spontaneously to its biologically inactive analogue 1-arachidonoyl glycerol (1AG) by acyl migration and it is only chromatographically distinguishable from 1AG. Matrix-effects caused primarily by co-extracted phospholipids may further compromise analysis. In addition, 2AG and 1AG are unstable under certain conditions like solvent evaporation or reconstitution of dried extracts. We examined effects of different organic solvents and their mixtures, such as toluene, ethyl acetate, and chloroform-methanol, on 2AG/1AG isomerisation, 2AG/1AG stability, and matrix-effects in the UPLC-MS/MS analysis of 2AG and AEA in human plasma. Toluene prevented, both, 2AG isomerisation to 1AG and degradation of 2AG/1AG during evaporation. Toluene extracts contain only 2% of matrix-effect-causing plasma phospholipids compared to extracts from the traditionally used solvent mixture chloroform-methanol. Toluene and all other tested organic solvents provide comparable 2AG and AEA extraction yields (60-80%). Based on these favourable toluene properties, we developed and validated a UPLC-MS/MS method with positive electrospray ionization (ESI+) that allows for simultaneous accurate and precise measurement of 2AG and AEA in human plasma. The UPLC-MS/MS method was cross-validated with a previously described fully-validated GC-MS/MS method for AEA in human plasma. A close correlation (r(2)=0.821) was observed between the results obtained from UPLC-MS/MS (y) and GC-MS/MS (x) methods (y=0.01+0.85x). The UPLC-MS/MS method is suitable for routine measurement of 2AG and AEA in human plasma samples (1 mL) in clinical settings as shown by quality control plasma samples processed over a period of 100 days. The UPLC-MS/MS method was further extended to human urine. In urine, AEA was not detectable and 2AG was detected in only 3 out of 19 samples from healthy subjects at 160, 180 and 212 pM corresponding to 12.3, 14.5 and 9.9 pmol/mmol creatinine, respectively.

Biochanin A, a naturally occurring inhibitor of fatty acid amide hydrolase

BACKGROUND AND PURPOSE

Inhibitors of fatty acid amide hydrolase (FAAH), the enzyme responsible for the metabolism of the endogenous cannabinoid (CB) receptor ligand anandamide (AEA), are effective in a number of animal models of pain. Here, we investigated a series of isoflavones with respect to their abilities to inhibit FAAH.

EXPERIMENTAL APPROACH

In vitro assays of FAAH activity and affinity for CB receptors were used to characterize key compounds. In vivo assays used were biochemical responses to formalin in anaesthetized mice and the 'tetrad' test for central CB receptor activation.

KEY RESULTS

Of the compounds tested, biochanin A was adjudged to be the most promising. Biochanin A inhibited the hydrolysis of 0.5 microM AEA by mouse, rat and human FAAH with IC(50) values of 1.8, 1.4 and 2.4 microM respectively. The compound did not interact to any major extent with CB(1) or CB(2) receptors, nor with FAAH-2. In anaesthetized mice, URB597 (30 microg i.pl.) and biochanin A (100 microg i.pl.) both inhibited the spinal phosphorylation of extracellular signal-regulated kinase produced by the intraplantar injection of formalin. The effects of both compounds were significantly reduced by the CB(1) receptor antagonist/inverse agonist AM251 (30 microg i.pl.). Biochanin A (15 mg.kg(-1) i.v.) did not increase brain AEA concentrations, but produced a modest potentiation of the effects of 10 mg.kg(-1) i.v. AEA in the tetrad test.

CONCLUSIONS AND IMPLICATIONS

It is concluded that biochanin A, in addition to its other biochemical properties, inhibits FAAH both in vitro and peripherally in vivo.

Simultaneous measurement of three N-acylethanolamides in human bio-matrices using ultra performance liquid chromatography-tandem mass spectrometry

Endocannabinoids including N-acylethanolamides (NAEs) are a family of lipid-related signaling molecules implicated in many physiological and disease states which elicit their activities via the cannabinoid receptors. Anandamide (N-arachidonoylethanolamine, AEA) is the most characterized endocannabinoid and has been detected in many tissues and bio-fluids including human plasma and the central nervous system. The endocannabinoid-like NAEs, oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) are described as entourage compounds because they illicit similar physiological effects to AEA but have little or no affinity for cannabinoid receptors. As entourage compounds, levels of these NAEs can greatly influence the efficacy of AEA yet there are few studies which measure these compounds in bio-fluids. Here we describe a rapid, highly sensitive, specific and highly reproducible ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the analysis of AEA, OEA, and PEA in human bio-fluids including plasma, serum, breast milk, and amniotic fluids. This validated method using deuterated (AEA-d(8), OEA-d(2), and PEA-d(4)) internal standards, represents an improvement over previous analyses in terms of run time (4 min), limit of detection (0.9 fmol on column for AEA and PEA and 4.4 fmol on column for OEA), precision (relative standard deviations of peak areas: 3.1% (AEA), 2.9% (OEA), and 5.4% (PEA) for 133 fmol on column) and accuracy (95.1-104.9%). The sensitivity and precision of the validated method described here suggests that this method is suitable for the analysis of AEA, OEA, and PEA in clinical samples and may be utilized for the investigation of bio-matrices containing limited amounts of NAEs.

The endocannabinoid 2-arachidonoylglycerol (2-AG) and metabolizing enzymes during rat fetoplacental development: a role in uterine remodelling

The main endocannabinoids (EC) identified in mammalian tissues are N-arachidonoylethanolamide (AEA, anandamide), and 2-arachidonoylglycerol (2-AG). AEA levels are critical in pregnancy, especially during implantation, decidualization, and placental development. As 2-AG functions in pregnancy are still largely undefined, we hypothesized that it may also have a role during fetoplacental development. We showed that 2-AG is not only present in the rat mesometrial decidua and plasma during fetoplacental development, but that both 2-AG synthesizing (diacylglycerol lipase) and degradation (monoacylglycerol lipase) enzymes are expressed by decidual cells. While lower concentrations of 2-AG induced apoptosis of rat primary decidual cells, via the CB1 receptor, higher concentrations induced a dramatic effect on cell morphology, cell viability and lactate dehydrogenase release, triggered through a mechanism independent of CB1. This study provides evidences that 2-AG fluctuation in maternal tissues throughout normal pregnancy is primarily regulated by its metabolizing enzymes. Together, these data supports the hypothesis that a deregulation of the endocannabinoid system through aberrant cannabinoid signalling may impact normal uterine remodelling process and consequently normal pregnancy.

Pitfalls in the sample preparation and analysis of N-acylethanolamines

N-acylethanolamines (NAEs) are a group of lipid mediators synthesized in response to a number of physiological and pathological stimuli. Because of the low tissue concentrations of NAEs, analyses often include liquid extraction followed by solid-phase extraction and subsequent quantitation by LC/MS or GC/MS. Reported levels of NAEs vary considerably, however, and often no explanation is given for these discrepancies. Brought on by difficulties encountered during method development, the effects of using four different brands of silica-containing solid phase extraction (SPE) columns and five different brands of chloroform for sample preparation were investigated. Considerable variation in the retention and recoveries of seven NAEs and 2-arachidonoylglycerol existed between the SPE columns. Furthermore, it was found that some chloroforms contained quantifiable amounts of N-palmitoylethanolamine and N-stearoylethanolamine. Finally, it was found that use of one of the chloroforms resulted in a loss of N-oleoylethanolamine from solution due to addition of chlorine to the ω-9 bond. The identity of this reaction product was confirmed by LC-MS/MS and NMR. It is recommended that these aspects of sample preparation and analysis should be thoroughly validated during method development and the relevant information on specific brands used be reported in future communications in order to better estimate the validity of reported quantitative data.

Lipidomic metabolism analysis of the endogenous cannabinoid anandamide (N-arachidonylethanolamide)

Elucidation of pathways involved with lipid metabolism has been limited by analytical challenges associated with detection and structure identification. A discovery-based mass spectrometry lipidomic approach has been applied to identify metabolites of the endogenous cannabinoid anandamide (N-arachidonylethanolamide). Previously, a model system was established to show that anandamide can be recycled by cells to form new endocannabinoids suggesting recycling of the arachidonate carbon chain. We hypothesized that distinct cellular pathways exist to direct the anandamide-derived arachidonate chain into a specific set of metabolites, different from the metabolite pool that is comprised of non-anandamide-derived arachidonic acid. Using stable isotope encoding and liquid chromatography-mass spectrometry, we identified a distinct pool of lipid metabolites derived from exogenous anandamide or arachidonic acid in RBL-2H3 cells. We discovered that arachidonic acid-derived metabolites were primarily comprised of the eicosanoid lipid class, whereas anandamide-derived arachidonic acid, in addition to eicosanoids, was metabolized into diradylglycerols, fatty acid amides, sterols, and glycerophospholipids. From the list of anandamide metabolites of particular interest was 1-O-arachidonyl-sn-glycero-3-phosphocholine. Furthermore, we determined that while 1-O-arachidonyl-sn-glycero-3-phosphocholine may be a metabolite of anandamide, the sn-2 compound was more abundant in mouse brain tissue. Overall, our results provide a novel approach to study the metabolic fate of endocannabinoids and fatty acid-derived signaling molecules.

Simultaneous determination of 2-arachidonoylglycerol, 1-arachidonoylglycerol and arachidonic acid in mouse brain tissue using liquid chromatography/tandem mass spectrometry

Endocannabinoids (ECs), such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG), modulate a number of physiological processes, including pain, appetite and emotional state. Levels of ECs are tightly controlled by enzymatic biosynthesis and degradation in vivo. However, there is limited knowledge about the enzymes that terminate signaling of the major brain EC, 2-AG. Identification and quantification of 2-AG, 1-AG and arachidonic acid (AA) is important for studying the enzymatic hydrolysis of 2-AG. We have developed a sensitive and specific quantification method for simultaneous determination of 2-AG, 1-AG and AA from mouse brain and adipose tissues by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using a simple brain sample preparation method. The separations were carried out based on reversed phase chromatography. Optimization of electrospray ionization conditions established the limits of detection (S/N = 3) at 50, 25 and 65 fmol for 2-AG, 1-AG and AA, respectively. The methods were selective, precise (%R.S.D. < 10%) and sensitive over a range of 0.02-20, 0.01-10 and 0.05-50 ng/mg tissue for 2-AG, 1-AG and AA, respectively. The quantification method was validated with consideration of the matrix effects and the mass spectrometry (MS) responses of the analytes and the deuterium labeled internal standard (IS). The developed methods were applied to study the hydrolysis of 2-AG from mouse brain extracts containing membrane bound monoacylglycerol lipase (MAGL), and to measure the basal levels of 2-AG, 1-AG and AA in mouse brain and adipose tissues.

Analysis of endocannabinoids, their congeners and COX-2 metabolites

Since the discovery of the endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG) in the early 1990s, the endocannabinoid system has been implicated in a wide array of physiological processes, such as control of food intake and energy balance, fertility and obesity. As the importance of this system becomes apparent, there is a tremendous need for robust, sensitive and efficient analytical methodology for the examination of the endocannabinoids, their congeners and putative metabolites. This review will summarize quantitative analytical methodology as reported in the literature from 1992 to present for the analysis of endocannabinoids and related compounds.

Development and validation of a quantitative method for the determination of 12 endocannabinoids and related compounds in human plasma using liquid chromatography-tandem mass spectrometry

A sensitive and specific LC-MS/MS method for the quantification of the endocannabinoids and related structures anandamide, 2-arachidonoyl glycerol, 2-arachidonyl glycerol ether, O-arachidonoyl ethanolamide, dihomo-gamma-linolenoyl ethanolamide, docosatetraenoyl ethanolamide, N-arachidonoyl dopamine, N-arachidonyl glycine, N-oleoyl dopamine, oleoyl ethanolamide, palmitoyl ethanolamide, and stearoyl ethanolamide in human plasma was developed and validated. Compounds were extracted using acetonitrile followed by solid-phase extraction. Separation was performed on a Xterra C8 column using gradient elution coupled to a triple-quadrupole MS. LLOQ levels ranged from 0.02 to 1.75 microg/mL, LODs ranged from 0.0002 to 0.1266 ng/mL, and accuracies were >80% (except stearoyl ethanolamide at lowest spike level) at all spike levels.

Quantitative and qualitative profiling of endocannabinoids in human plasma using a triple quadrupole linear ion trap mass spectrometer with liquid chromatography

Owing to the large implication of endocannabinoids (ECs) in many physiological and pathophysiological processes, a rapid liquid chromatography/electrospray ionisation triple quadrupole linear ion trap mass spectrometric assay (LC/ESI-QqQ(LIT)) was developed for the detection and characterization of anandamide (AEA), 2-arachidonoyl glycerol (2-AG), virodhamine (VA), noladin ether (2-AGE), and N-arachidonoyl dopamine (NADA) in human plasma. The ECs were extracted from 500 microL of plasma by liquid-liquid extraction (LLE) and separated by using an XTerra C18 MS column (50 x 3.0 mm i.d., 3.5 microm) with gradient elution. The mobile phase was composed of a mixture of acetonitrile, water, and formic acid (0.1%). For confirmatory analysis, an information-dependent acquisition (IDA) experiment was performed with selected reaction monitoring (SRM) as survey scan and enhanced product ion (EPI) as dependent scan. The assay was found to be linear in the concentration range of 0.1-5 ng/mL for AEA, 0.3-5 ng/mL for VA, 2-AGE, and NADA and 1-20 ng/mL for 2-AG using a 0.5 mL aliquot of plasma. Repeatability and intermediate precision were found less than 15% over the tested concentration ranges. The developed method thus provided the rapid, highly sensitive and highly selective requirement for assess quantitation, and identification of ECs in plasma.

Dynamic changes of the endogenous cannabinoid and opioid mesocorticolimbic systems during adolescence: THC effects

Adolescence is a critical phase of active brain development often characterized by the initiation of marijuana (Cannabis sativa) use. Limited information is known regarding the endogenous cannabinoid system of the adolescent brain as well as related neurotransmitters that appear sensitive to cannabis exposure. We recently observed that adult rats pre-exposed to Delta-9-tetrahydrocannabinol (THC) during adolescence self-administered higher amounts of heroin and had selective impairments of the enkephalin opioid system within the nucleus accumbens (NAc) implicated in reward-related behavior. To explore the ontogeny of the cannabinoid and opioid neuronal systems in association with adolescence THC exposure, rats were examined at different adolescent stages during an intermittent THC paradigm (1.5 mg/kg i.p. every third day) from postnatal days (PNDs) 28-49. Rat brains were examined 24 h after injection at PND 29 (early adolescence), PND 38 (mid adolescence) and PND 50 (late adolescence) and analyzed for endocannabinoids (anandamide and 2-arachidonoylglycerol), Met-enkephalin, cannabinoid CB(1) receptors and micro opioid receptors (microOR) in the NAc, caudate-putamen and prefrontal cortex (PFC). Of the markers studied, the endocannabinoid levels had the most robust alterations throughout adolescence and were specific to the PFC and NAc. Normal correlations between anandamide and 2-arachidonoylglycerol concentrations in the NAc (positive) and PFC (negative) were reversed by THC. Other significant THC-induced effects were confined to the NAc - increased anandamide, decreased Met-enkephalin and decreased microORs. These findings emphasize the dynamic nature of the mesocorticolimbic endocannabinoid system during adolescence and the selective mesocorticolimbic disturbance as a consequence of adolescent cannabis exposure.

Simultaneous Quantification of Anandamide and Other Endocannabinoids in Dorsal Vagal Complex of Rat Brainstem by LC-MS

A quantitative method has been developed and validated for the simultaneous determination of anandamide (AEA), docosatetraenylethanolamide (DEA) and N-arachidonyldopamine (NADA) in dorsal vagal complex (DVC) of rat brainstem by liquid chromatographic-electrospray ionization mass spectrometry. The analytes were extracted from the tissue samples of rat brainstem by a single step liquid extraction technique using acetonitrile. The chromatographic separation was conducted on a C18 column using a gradient mobile phase consisting of methanol and water at a flow rate of 0.3 mL min(-1). The analytes were quantified by positive electrospray ionization mass spectrometry with selected ion monitoring (SIM) mode. The limits of detection (LOD) for AEA, DEA and NADA were 0.5, 1 and 0.5 ng mL(-1), respectively. This method required only simple processing of the samples and could be applied to monitor the change in the level of these compounds in DVC of the rat brain tissue. Time dependent (10-70 min) accumulation of the endocannabinoids (AEA, DEA, and NADA) in brain tissue was also studied, which included a novel examination of the accumulation of DEA as a function of time in rat brain tissue after decapitation.

A solid-phase method for the extraction and measurement of anandamide from multiple human biomatrices

N-Arachidonoylethanolamine (AEA, anandamide) was the first endocannabinoid to be identified and has since become associated with the mediation of several physiological functions and disease states. AEA has been isolated from numerous tissues and biofluids, in the low nanomolar range, using lipid extraction techniques with organic solvents. These techniques require the drying down of relatively large volumes of solvents, making them unsuitable for high-throughput analysis. Here we describe a solid-phase extraction (SPE) method for the investigation of AEA concentrations in human plasma, serum, milk, urine, amniotic fluid, peritoneal fluid, saliva, follicular fluid, and fluid from an ovarian cyst. AEA was detected in serum and plasma from blood isolated from 20 adult women (means+/-standard deviations: 0.68+/-0.29 and 0.64+/-0.28 nM, respectively), from pregnant women at term (1.37+/-0.42 nM), and from umbilical vein (1.26+/-0.33 nM) and umbilical artery (1.14+/-0.35nM), in milk (0.12+/-0.05 nM) and from amniotic (0.03+/-0.02 nM), peritoneal (0.93+/-0.27 nM), follicular (1.17+/-0.51 nM), and ovarian cyst (0.32+/-0.01 nM) fluids. AEA was undetectable in saliva and urine. The 60% AEA extraction efficiency achieved with SPE from plasma was superior to the 19% efficiency achieved using the existing organic solvent extraction method. Limits of quantification and detection for AEA were also improved dramatically using SPE (8 and 4 fmol/ml) compared with organic extraction (25 and 18.75 fmol/ml plasma). These improvements allow the use of smaller plasma samples with SPE. Intra- and interday variability were comparable, and the mean AEA concentration of pooled plasma samples (1.18 nM, n=15) was identical with the two techniques. Similarly, when 56 plasma samples from laboring and nonlaboring women were analyzed using both techniques, no extraction method-dependent differences were observed. Consequently, we provide evidence for a robust SPE technique for the extraction of AEA from biomatrices to replace the existing liquid extraction methods, with the SPE technique being superior in terms of speed, extraction efficiency, and sample size required.

Membrane microdomains and metabolic pathways that define anandamide and 2-arachidonyl glycerol biosynthesis and breakdown

Anandamide (AEA) and 2-arachidonyl glycerol (2-AG), endogenous ligands for the CB1 and CB2 cannabinoid receptors, are referred to as endocannabinoids because they mimic the actions of delta9-tetrahydrocannabinol (Delta9-THC), a plant-derived cannabinoid. The processes by which AEA and 2-AG are biosynthesized, released, taken up by cells and hydrolyzed have been of much interest as potential therapeutic targets. In this review we will discuss the progress that has been made to characterize the primary pathways for AEA and 2-AG formation and breakdown as well as the role that specialized membrane microdomains known as lipid rafts play in these processes. Furthermore we will review the recent advances made to track and detect AEA in biological matrices.

N-arachidonyl maleimide potentiates the pharmacological and biochemical effects of the endocannabinoid 2-arachidonylglycerol through inhibition of monoacylglycerol lipase

Inhibition of the metabolism of the endocannabinoids, anandamide (AEA) and 2-arachidonyl glycerol (2-AG), by their primary metabolic enzymes, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), respectively, has the potential to increase understanding of the physiological functions of the endocannabinoid system. To date, selective inhibitors of FAAH, but not MAGL, have been developed. The purpose of this study was to determine the selectivity and efficacy of N-arachidonyl maleimide (NAM), a putative MAGL inhibitor, for modulation of the effects of 2-AG. Our results showed that NAM unmasked 2-AG activity in a tetrad of in vivo tests sensitive to the effects of cannabinoids in mice. The efficacy of 2-AG (and AEA) to produce hypothermia was reduced compared with Delta(9)-tetrahydrocannabinol; however, 2-AG differed from AEA by its lower efficacy for catalepsy. All tetrad effects were partially CB(1) receptor-mediated because they were attenuated (but not eliminated) by SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-H-pyrazole-3-carboxamide HCl] and in CB(1)(-/-) mice. In vitro, NAM increased endogenous levels of 2-AG in the brain. Furthermore, NAM raised the potency of 2-AG, but not AEA, in agonist-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate binding assay, a measure of G-protein activation. These results suggest that NAM is an MAGL inhibitor with in vivo and in vitro efficacy. NAM and other MAGL inhibitors are valuable tools to elucidate the biological functions of 2-AG and to examine the consequences of dysregulation of this endocannabinoid. In addition, NAM's unmasking of 2-AG effects that are only partially reversed by SR141716A offers support for the existence of non-CB(1), non-CB(2) cannabinoid receptors.

Changes in brain levels of N-acylethanolamines and 2-arachidonoylglycerol in focal cerebral ischemia in mice

The N-acylethanolamines (NAEs) and 2-arachidonoylglycerol (2-AG) are bioactive lipids that can modulate inflammatory responses and protect neurons against glutamatergic excitotoxicity. We have used a model of focal cerebral ischemia in young adult mice to investigate the relationship between focal cerebral ischemia and endogenous NAEs. Over the first 24 h after induction of permanent middle cerebral artery occlusion, we observed a time-dependent increase in all the investigated NAEs, except for anandamide. Moreover, we found an accumulation of 2-AG at 4 h that returned to basal level 12 h after induction of ischemia. Accumulation of NAEs did not depend on regulation of N-acylphosphatidylethanolamine-hydrolyzing phospholipase D or fatty acid amide hydrolase. Treatment with the fatty acid amide hydrolase inhibitor URB597 (cyclohexyl carbamic acid 3'-carbamoyl-biphenyl-3-yl ester; 1 mg/kg; i.p.) 1.5 h before arterial occlusion decreased the infarct volume in our model system. Our results suggest that NAEs and 2-AG may be involved in regulation of neuroprotection during focal cerebral ischemia in mice.

Hydrolysis of Prostaglandin Glycerol Esters by the Endocannabinoid-Hydrolyzing Enzymes, Monoacylglycerol Lipase and Fatty Acid Amide Hydrolase

Cyclooxygenase-2 (COX-2) can oxygenate the endocannabinoids, arachidonyl ethanolamide (AEA) and 2-arachidonylglycerol (2-AG), to prostaglandin-H2-ethanolamide (PGH2-EA) and -glycerol ester (PGH2-G), respectively. Further metabolism of PGH2-EA and PGH2-G by prostaglandin synthases produces a variety of prostaglandin-EA's and prostaglandin-G's nearly as diverse as those derived from arachidonic acid. Thus, COX-2 may regulate endocannabinoid levels in neurons during retrograde signaling or produce novel endocannabinoid metabolites for receptor activation. Endocannabinoid-metabolizing enzymes are important regulators of their action, so we tested whether PG-G levels may be regulated by monoacylglycerol lipase (MGL) and fatty acid amide hydrolase (FAAH). We found that PG-Gs are poor substrates for purified MGL and FAAH compared to 2-AG and/or AEA. Determination of substrate specificity demonstrates a 30-100- and 150-200-fold preference of MGL and FAAH for 2-AG over PG-Gs, respectively. The substrate specificity of AEA compared to those of PG-Gs was approximately 200-300 fold higher for FAAH. Thus, PG-Gs are poor substrates for the major endocannabinoid-degrading enzymes, MGL and FAAH.

Lipid profiling reveals glycerophospholipid remodeling in zymosan-stimulated macrophages

Comprehensive lipid profiling by mass spectrometry provides comparative data on the relative distribution of individual glycerophospholipids within each of the major classes. Application of this method to the analysis of glycerophospholipid remodeling in murine primary resident peritoneal macrophages (RPMs) during zymosan phagocytosis reveals significant decreases in the levels of every major arachidonic acid (20:4)-containing species of phosphatidylcholine (GPCho) and in selected 20:4-containing phosphatidylinositol (GPIns) and phosphatidylglycerol (GPGro) species. No net changes in 20:4-containing phosphatidylethanolamine (GPEtn) species were detected. Pretreatment of RPMs with LPS resulted in subtle changes in the magnitude and kinetics of the response but had no effect on the overall pattern of zymosan-induced glycerophospholipid remodeling. Inhibition of prostaglandin (PG) synthesis with indomethacin reduced the magnitude of the changes in 20:4-containing diacyl but not alkyl acyl species. Blockade of 20:4 reacylation with thimerosal had no effect on the magnitude of the zymosan-induced changes in GPCho, GPIns, or GPGro species but revealed decreases in the level of alkyl acyl GEtn species. RAW264.7 cells contain much lower levels of phospholipid 20:4 than do RPMs and synthesize PGs poorly in response to zymosan. Pretreatment with granulocyte-macrophage colony stimulating factor, lipopolysaccharide, and interferon-gamma substantially increased the extent of 20:4 mobilization and PG synthesis in these cells. However, under conditions of maximal zymosan-dependent PG synthesis, the only glycerophospholipid that exhibited a significant change was a 20:4-containing plasmenyl GPEtn. These results suggest that GPCho is the major ultimate source of 20:4 that is mobilized in zymosan-stimulated RPMs but that 20:4 mobilization may involve the intermediate turnover of alkyl acyl GPEtn species.

Determination of anandamide and other fatty acyl ethanolamides in human serum by electrospray tandem mass spectrometry

We developed a new selective liquid chromatography-electrospray ionization-tandem mass spectrometry method for the identification and quantification of anandamide (AEA), an endogenous cannabinoid receptor ligand, and other bioactive fatty acid ethanolamides (FAEs) in biological samples. Detection limit (0.025 pmol for AEA and 0.1 pmol for palmitoylethanolamide (PEA) and oleoylethanolamide (OEA)) and quantification limit (0.2 pmol for AEA and 0.4 pmol for OEA and PEA) were in the high fmol to low pmol range for all analytes. Linear correlations (r(2)=0.99) were observed in the calibration curves for standard AEA over the range of 0.025-25 pmol and for standard PEA and OEA over the range of 0.1-500 pmol. This method provides a time-saving and sensitive alternative to existing methods for the analysis of FAEs in biological samples.

Differential regulation of endocannabinoid synthesis and degradation in the uterus during embryo implantation

Preimplantation embryo development to the blastocyst stage and uterine differentiation to the receptive state are prerequisites for embryo implantation. Burgeoning evidence suggests that endocannabinoid signaling is critical to early pregnancy events. Anandamide (N-arachidonoylethanolamine) and 2-AG (2-arachidonoylglycerol) are two major endocannabinoids that bind to and activate G-protein coupled cannabinoid receptors CB1 and CB2. We have previously shown that a physiological tone of anandamide is critical to preimplantation events in mice, since either silencing or amplification of anandamide signaling causes retarded development and oviductal retention of embryos via CB1, leading to deferred implantation and compromised pregnancy outcome. Whether 2-AG, which also influences many biological functions, has any effects on early pregnancy remains unknown. Furthermore, mechanisms by which differential uterine endocannabinoid gradients are established under changing pregnancy state is not clearly understood. We show here that 2-AG is present at levels one order of magnitude higher than those of anandamide in the mouse uterus, but with similar patterns as anandamide, i.e. lower levels at implantation sites and higher at interimplantation sites. We also provide evidence that region- and stage-specific uterine expression of N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD) and fatty acid amide hydrolase (FAAH), and sn-1-diacylglycerol (DAG) lipase alpha (DAGLalpha) and monoacylglycerol lipase (MAGL) for synthesis and hydrolysis of anandamide and 2-AG, respectively, creates endocannabinoid gradients conducive to implantation. Our genetic evidence suggests that FAAH is the major degrading enzyme for anandamide, whereas COX-2, MAGL and to some extent COX-1 participate in metabolizing 2-AG in the pregnant uterus. The results suggest that aberrant functioning of these pathways impacting uterine anandamide and/or 2-AG levels would compromise pregnancy outcome.