Gene_locus Report for: human-MGLL

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage injury, hyperplasia of bone and inflammatory lesions of synovium. Monoacylglycerol lipase (MAGL), a member of the alpha/beta hydrolase superfamily, is involved in regulation of injury protection and immune-inflammation response. Autoinflammatory response of the synovium and the release of inflammatory mediators play critical roles in occurrence of early-stage OA. Fibroblast-like synoviocytes (FLSs) are resident mesenchymal cells of the synovial tissue. Considering that MAGL inhibition regulates the inflammatory signaling cascade, it is crucial to ascertain the biological effects and specific mechanisms of MAGL in alleviating inflammatory infiltration of OA FLSs. The aim of this study was to investigate the effect of MAGL on biological function in OA FLSs. Results from in vitro experiments showed that MAGL blockade not only effectively inhibited proliferation, invasion and migration of FLSs, but also downregulated expression of inflammatory-associated proteins. Sequencing results indicated that MAGL inhibition significantly suppressed NOX4-mediated oxidative stress, thus promoting Nrf2 nuclear accumulation and inhibiting generation of intracellular reactive oxygen species (ROS). Attenuation of NOX4 further alleviated redox dysplasia and ultimately improved tumor-like phenotypes, such as abnormal proliferation, migration and migration of FLSs. In vivo results corroborated this finding, with MAGL inhibition found to modulate pain and disease progression in an OA rat model. Collectively, these results indicate that MAGL administration is an ideal therapy treating OA.

INTRODUCTION: The high prevalence and severe symptoms of migraines in humans emphasizes the need to identify underlying mechanisms that can be targeted for therapeutic benefit. Clinical Endocannabinoid Deficiency (CED) posits that reduced endocannabinoid tone may contribute to migraine development and other neuropathic pain conditions. While strategies that increase levels of the endocannabinoid n-arachidonoylethanolamide have been tested, few studies have investigated targeting the levels of the more abundant endocannabinoid, 2-arachidonoylgycerol, as an effective migraine intervention. METHODS: Cortical spreading depression was induced in female Sprague Dawley rats via KCl (potassium chloride) administration, followed by measures of endocannabinoid levels, enzyme activity, and neuroinflammatory markers. Efficacy of inhibiting 2-arachidonoylglycerol hydrolysis to mitigate periorbital allodynia was then tested using reversal and prevention paradigms. RESULTS: We discovered reduced 2-arachidonoylglycerol levels in the periaqueductal grey associated with increased hydrolysis following headache induction. Pharmacological inhibition of the 2-arachidonoylglycerol hydrolyzing enzymes, alpha/beta-hydrolase domain-containing 6 and monoacylglycerol lipase reversed and prevented induced periorbital allodynia in a cannabinoid receptor-dependent manner. DISCUSSION: Our study unravels a mechanistic link between 2-arachidonoylglycerol hydrolysis activity in the periaqueductal grey in a preclinical, rat model of migraine. Thus, 2-arachidonoylglycerol hydrolysis inhibitors represent a potential new therapeutic avenue for the treatment of headache.

BACKGROUND: CXC-chemokine receptor 2 (CXCR2) expression was found to be down-regulated on circulating monocytes of cancer patients. Here, we analyze the percentage of CD14(+)CXCR2(+) monocyte subsets in hepatocellular carcinoma (HCC) patients, and investigate the mechanisms that regulate CXCR2 surface expression on monocytes and its biological function. METHODS: Flow cytometry was used to analyze the proportion of the CD14(+)CXCR2(+) subset from the total circulating monocytes of HCC patients. Interleukin 8 (IL-8) levels were measured from serum and ascites, and their correlation with the CD14(+)CXCR2(+) monocyte subset proportion was calculated. THP-1 cells were cultured in vitro and treated with recombinant human IL-8 and CXCR2 surface expression was analyzed. CXCR2 was knocked down to examine how it affects the antitumor activity of monocytes. Finally, a monoacylglycerol lipase (MAGL) inhibitor was added to analyze its effect on CXCR2 expression. RESULTS: A decrease in the proportion of the CD14(+)CXCR2(+) monocyte subset was observed in HCC patients compared with healthy controls. CXCR2(+) monocyte subset proportion was associated with the AFP value, TNM stage, and liver function. Overexpression of IL-8 was observed in the serum and ascites of HCC patients, and negatively correlated with CXCR2(+) monocyte proportion. IL-8 decreased CXCR2 expression in THP-1 cells, contributing to decreased antitumor activity toward HCC cells. MAGL expression in THP-1 cells was up-regulated after IL-8 treatment, and the MAGL inhibitor partially reversed the effects of IL-8 on CXCR2 expression. CONCLUSIONS: Overexpression of IL-8 drives CXCR2 down-regulation on circulating monocytes of HCC patients, which could be partially reversed by a MAGL inhibitor.

BACKGROUND: Engaging the endocannabinoid system through inhibition of monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), degrading endocannabinoids (endoCBs) 2-arachidonoylglycerol (2-AG) and anandamide (AEA), was proposed as a promising approach to ameliorate migraine pain. However, the activity of MAGL and FAAH and action of endoCB on spiking activity of meningeal afferents, from which migraine pain originates, has not been explored thus far. Therefore, we here explored the analgesic effects of endoCB enhancement in rat and human meningeal tissues. METHODS: Both MAGL and FAAH activity and local 2-AG and AEA levels were measured by activity-based protein profiling (ABPP) and LC-MS/MS, respectively, in rat meninges obtained from hemiskulls of P38-P40 Wistar rats and human meninges from elderly patients undergoing non-migraine related neurosurgery. The action on endoCBs upon administration of novel dual MAGL/FAAH inhibitor AKU-005 on meningeal afferents excitability was tested by investigating paired KCl-induced spiking and validation with local (co-)application of either AEA or 2-AG. Finally, the specific TRPV1 agonist capsaicin and blocker capsazepine were tested. RESULTS: The basal level of 2-AG exceeded that of AEA in rat and human meninges. KCl-induced depolarization doubled the level of AEA. AKU-005 slightly increased spontaneous spiking activity whereas the dual MAGL/FAAH inhibitor significantly decreased excitation of nerve fibres induced by KCl. Similar inhibitory effects on meningeal afferents were observed with local applications of 2-AG or AEA. The action of AKU-005 was reversed by CB1 antagonist AM-251, implying CB1 receptor involvement in the anti-nociceptive effect. The inhibitory action of AEA was also reversed by AM-251, but not with the TRPV1 antagonist capsazepine. Data cluster analysis revealed that both AKU-005 and AEA largely increased long-term depression-like meningeal spiking activity upon paired KCl-induced spiking. CONCLUSIONS: In the meninges, high anti-nociceptive 2-AG levels can tonically counteract meningeal signalling, whereas AEA can be engaged on demand by local depolarization. AEA-mediated anti-nociceptive effects through CB1 receptors have therapeutic potential. Together with previously detected MAGL activity in trigeminal ganglia, dual MAGL/FAAH inhibitor AKU-005 appears promising as migraine treatment.

Monoglyceride lipase (MGL) hydrolyzes monoacylglycerols (MG) to glycerol and one fatty acid. Among the various MG species, MGL also degrades 2-arachidonoylglycerol, the most abundant endocannabinoid and potent activator of the cannabinoid receptors 1 and 2. We investigated the consequences of MGL deficiency on platelet function using systemic (Mgl(-/-)) and platelet-specific Mgl-deficient (platMgl(-/-)) mice. Despite comparable platelet morphology, loss of MGL was associated with decreased platelet aggregation and reduced response to collagen activation. This was reflected by reduced thrombus formation in vitro, accompanied by a longer bleeding time and a higher blood volume loss. Occlusion time after FeCl(3)-induced injury was markedly reduced in Mgl(-/-) mice, which is consistent with contraction of large aggregates and fewer small aggregates in vitro. The absence of any functional changes in platelets from platMgl(-/-) mice is in accordance with lipid degradation products or other molecules in the circulation, rather than platelet-specific effects, being responsible for the observed alterations in Mgl(-/-) mice. We conclude that genetic deletion of MGL is associated with altered thrombogenesis.

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage injury, hyperplasia of bone and inflammatory lesions of synovium. Monoacylglycerol lipase (MAGL), a member of the alpha/beta hydrolase superfamily, is involved in regulation of injury protection and immune-inflammation response. Autoinflammatory response of the synovium and the release of inflammatory mediators play critical roles in occurrence of early-stage OA. Fibroblast-like synoviocytes (FLSs) are resident mesenchymal cells of the synovial tissue. Considering that MAGL inhibition regulates the inflammatory signaling cascade, it is crucial to ascertain the biological effects and specific mechanisms of MAGL in alleviating inflammatory infiltration of OA FLSs. The aim of this study was to investigate the effect of MAGL on biological function in OA FLSs. Results from in vitro experiments showed that MAGL blockade not only effectively inhibited proliferation, invasion and migration of FLSs, but also downregulated expression of inflammatory-associated proteins. Sequencing results indicated that MAGL inhibition significantly suppressed NOX4-mediated oxidative stress, thus promoting Nrf2 nuclear accumulation and inhibiting generation of intracellular reactive oxygen species (ROS). Attenuation of NOX4 further alleviated redox dysplasia and ultimately improved tumor-like phenotypes, such as abnormal proliferation, migration and migration of FLSs. In vivo results corroborated this finding, with MAGL inhibition found to modulate pain and disease progression in an OA rat model. Collectively, these results indicate that MAGL administration is an ideal therapy treating OA.

INTRODUCTION: The high prevalence and severe symptoms of migraines in humans emphasizes the need to identify underlying mechanisms that can be targeted for therapeutic benefit. Clinical Endocannabinoid Deficiency (CED) posits that reduced endocannabinoid tone may contribute to migraine development and other neuropathic pain conditions. While strategies that increase levels of the endocannabinoid n-arachidonoylethanolamide have been tested, few studies have investigated targeting the levels of the more abundant endocannabinoid, 2-arachidonoylgycerol, as an effective migraine intervention. METHODS: Cortical spreading depression was induced in female Sprague Dawley rats via KCl (potassium chloride) administration, followed by measures of endocannabinoid levels, enzyme activity, and neuroinflammatory markers. Efficacy of inhibiting 2-arachidonoylglycerol hydrolysis to mitigate periorbital allodynia was then tested using reversal and prevention paradigms. RESULTS: We discovered reduced 2-arachidonoylglycerol levels in the periaqueductal grey associated with increased hydrolysis following headache induction. Pharmacological inhibition of the 2-arachidonoylglycerol hydrolyzing enzymes, alpha/beta-hydrolase domain-containing 6 and monoacylglycerol lipase reversed and prevented induced periorbital allodynia in a cannabinoid receptor-dependent manner. DISCUSSION: Our study unravels a mechanistic link between 2-arachidonoylglycerol hydrolysis activity in the periaqueductal grey in a preclinical, rat model of migraine. Thus, 2-arachidonoylglycerol hydrolysis inhibitors represent a potential new therapeutic avenue for the treatment of headache.

BACKGROUND: CXC-chemokine receptor 2 (CXCR2) expression was found to be down-regulated on circulating monocytes of cancer patients. Here, we analyze the percentage of CD14(+)CXCR2(+) monocyte subsets in hepatocellular carcinoma (HCC) patients, and investigate the mechanisms that regulate CXCR2 surface expression on monocytes and its biological function. METHODS: Flow cytometry was used to analyze the proportion of the CD14(+)CXCR2(+) subset from the total circulating monocytes of HCC patients. Interleukin 8 (IL-8) levels were measured from serum and ascites, and their correlation with the CD14(+)CXCR2(+) monocyte subset proportion was calculated. THP-1 cells were cultured in vitro and treated with recombinant human IL-8 and CXCR2 surface expression was analyzed. CXCR2 was knocked down to examine how it affects the antitumor activity of monocytes. Finally, a monoacylglycerol lipase (MAGL) inhibitor was added to analyze its effect on CXCR2 expression. RESULTS: A decrease in the proportion of the CD14(+)CXCR2(+) monocyte subset was observed in HCC patients compared with healthy controls. CXCR2(+) monocyte subset proportion was associated with the AFP value, TNM stage, and liver function. Overexpression of IL-8 was observed in the serum and ascites of HCC patients, and negatively correlated with CXCR2(+) monocyte proportion. IL-8 decreased CXCR2 expression in THP-1 cells, contributing to decreased antitumor activity toward HCC cells. MAGL expression in THP-1 cells was up-regulated after IL-8 treatment, and the MAGL inhibitor partially reversed the effects of IL-8 on CXCR2 expression. CONCLUSIONS: Overexpression of IL-8 drives CXCR2 down-regulation on circulating monocytes of HCC patients, which could be partially reversed by a MAGL inhibitor.

Despite the well-described anticarcinogenic effects of endocannabinoids, the influence of the endocannabinoid system on tumor angiogenesis is still debated. In the present study, conditioned medium (CM) from A549 and H358 lung cancer cells treated with ascending concentrations of the monoacylglycerol lipase (MAGL) inhibitor JZL184 and 2-arachidonoylglycerol (2-AG), a prominent MAGL substrate, caused a concentration-dependent reduction in human umbilical vein endothelial cell (HUVEC) migration and tube formation compared with CM from vehicle-treated cancer cells. Comparative experiments with MAGL inhibitors JW651 and MJN110 showed the same results. On the other hand, the angiogenic properties of HUVECs were not significantly altered by direct stimulation with JZL184 or 2-AG or by exposure to CM of JZL184- or 2-AG-treated non-cancerous bronchial epithelial cells (BEAS-2B). Inhibition of HUVEC migration and tube formation by CM of JZL184- and 2-AG-treated A549 cells was abolished in the presence of the CB(1) antagonist AM-251. Increased release of tissue inhibitor of metalloproteinase-1 (TIMP-1) from JZL184- or 2-AG-stimulated A549 or H358 cells was shown to exert an antiangiogenic effect on HUVECs, as confirmed by siRNA experiments. In addition, JZL184 caused a dose-dependent regression of A549 tumor xenografts in athymic nude mice, which was associated with a decreased number of CD31-positive cells and upregulation of TIMP-1-positive cells in xenograft tissue. In conclusion, our data suggest that elevation of 2-AG by MAGL inhibition leads to increased release of TIMP-1 from lung cancer cells, which mediates an antiangiogenic effect on endothelial cells.

While the prevalence of breast cancer metastasis in the brain is significantly higher in triple negative breast cancers (TNBCs), there is a lack of novel and/or improved therapies for these patients. Monoacylglycerol lipase (MAGL) is a hydrolase involved in lipid metabolism that catalyzes the degradation of 2-arachidonoylglycerol (2-AG) linked to generation of pro- and anti-inflammatory molecules. Here, we targeted MAGL in TNBCs, using a potent carbamate-based inhibitor AM9928 (hMAGL IC(50) = 9 nM) with prolonged pharmacodynamic effects (46 h of target residence time). AM9928 blocked TNBC cell adhesion and transmigration across human brain microvascular endothelial cells (HBMECs) in 3D co-cultures. In addition, AM9928 inhibited the secretion of IL-6, IL-8, and VEGF-A from TNBC cells. TNBC-derived exosomes activated HBMECs resulting in secretion of elevated levels of IL-8 and VEGF, which were inhibited by AM9928. Using in vivo studies of syngeneic GFP-4T1-BrM5 mammary tumor cells, AM9928 inhibited tumor growth in the mammary fat pads and attenuated blood brain barrier (BBB) permeability changes, resulting in reduced TNBC colonization in brain. Together, these results support the potential clinical application of MAGL inhibitors as novel treatments for TNBC.

Monoacylglycerol lipase (MAGL) constitutes a serine hydrolase that orchestrates endocannabinoid homeostasis and exerts its function by catalyzing the degradation of 2-arachidonoylglycerol (2-AG) to arachidonic acid (AA). As such, selective inhibition of MAGL represents a potential therapeutic and diagnostic approach to various pathologies including neurodegenerative disorders, metabolic diseases and cancers. Based on a unique 4-piperidinyl azetidine diamide scaffold, we developed a reversible and peripheral-specific radiofluorinated MAGL PET ligand [(18)F]FEPAD. Pharmacokinetics and binding studies on [(18)F]FEPAD revealed its outstanding specificity and selectivity towards MAGL in brown adipose tissue (BAT) - a tissue that is known to be metabolically active. We employed [(18)F]FEPAD in PET studies to assess the abundancy of MAGL in BAT deposits of mice and found a remarkable degree of specific tracer binding in the BAT, which was confirmed by post-mortem tissue analysis. Given the negative regulation of endocannabinoids on the metabolic BAT activity, our study supports the concept that dysregulation of MAGL is likely linked to metabolic disorders. Further, we now provide a suitable imaging tool that allows non-invasive assessment of MAGL in BAT deposits, thereby paving the way for detailed mechanistic studies on the role of BAT in endocannabinoid system (ECS)-related pathologies.

The ocular endocannabinoid system (ECS) including enzymes and CB1/CB2 receptors determines various substantial effects, such as anti-inflammatory activity and reduction of the intraocular pressure (IOP). The modulation of 2-arachidonoylglycerol (2-AG) levels obtained via MAGL inhibition is considered as a promising pharmacological strategy to activate the ECS. Within the scope of this study, the effect of a selective monoacylglycerol lipase (MAGL) inhibitor (MAGL17b) was investigated by measuring the IOP reduction in normotensive rabbits after performing a solubilisation process of the molecule with non-ionic surfactants, to produce suitable eye drops containing the highest possible concentration of the drug. Furthermore, the study involved the evaluation of cytotoxicity and of in vitro/ex vivo corneal permeation of MAG17b of selected formulations based on polyoxyl(35)castor oil (C-EL) and polyethylene glycol (80) sorbitan monolaurate (TW80). The solubilisation of 0.5 mM MAGL17b with 3% w/w TW80 (TW80/3-17b), through the formation of NanoMicellar structures (diameter of 12.3 nm), determined a significant permeation of MAGL17b, both through excised rabbits corneas and reconstituted corneal epithelium, with a limited corneal epithelial cells death. The blockade of MAGL activity induced a IOP reduction up to 4 mmHg in albino and pigmented rabbits after topical instillation, thus confirming the potential efficacy of the MAGL inhibition approach in the treatment of ocular pathologies.

Migraine is a disabling neurovascular disorder characterized by severe pain with still limited efficient treatments. Endocannabinoids, the endogenous painkillers, emerged, alternative to plant cannabis, as promising analgesics against migraine pain. In this thematic review, we discuss how inhibition of the main endocannabinoid-degrading enzymes, monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), could raise the level of endocannabinoids (endoCBs) such as 2-AG and anandamide in order to alleviate migraine pain. We describe here: (i) migraine pain signaling pathways, which could serve as specific targets for antinociception; (ii) a divergent distribution of MAGL and FAAH activities in the key regions of the PNS and CNS implicated in migraine pain signaling; (iii) a complexity of anti-nociceptive effects of endoCBs mediated by cannabinoid receptors and through a direct modulation of ion channels in nociceptive neurons; and (iv) the spectrum of emerging potent MAGL and FAAH inhibitors which efficiently increase endoCBs levels. The specific distribution and homeostasis of endoCBs in the main regions of the nociceptive system and their generation 'on demand', along with recent availability of MAGL and FAAH inhibitors suggest new perspectives for endoCBs-mediated analgesia in migraine pain.

Inhibition of monoglyceride lipase (MGL), also known as monoacylglycerol lipase (MAGL), has emerged as a promising approach for treating neurological diseases. To gain useful insights in the design of agents with balanced potency and reactivity, we investigated the mechanism of MGL carbamoylation by the reference triazole urea SAR629 (IC(50) = 0.2 nM) and two recently described inhibitors featuring a pyrazole (IC(50) = 1800 nM) or a 4-cyanopyrazole (IC(50) = 8 nM) leaving group (LG), using a hybrid quantum mechanics/molecular mechanics (QM/MM) approach. Opposite to what was found for substrate 2-arachidonoyl-sn-glycerol (2-AG), covalent modification of MGL by azole ureas is controlled by LG expulsion. Simulations indicated that changes in the electronic structure of the LG greatly affect reaction energetics with triazole and 4-cyanopyrazole inhibitors following a more accessible carbamoylation path compared to the unsubstituted pyrazole derivative. The computational protocol provided reaction barriers able to discriminate between MGL inhibitors with different potencies. These results highlight how QM/MM simulations can contribute to elucidating structure-activity relationships and provide insights for the design of covalent inhibitors.

Monoacylglycerol lipase (MAGL) is one of the key enzymes in the endocannabinoid system. Inhibition of MAGL has been proposed as an attractive approach for the treatment of various diseases. In this study, we designed and successfully synthesized two series of piperazinyl pyrrolidin-2-one derivatives as novel reversible MAGL inhibitors. (R)-[(18)F]13 was identified through the preliminary evaluation of two carbon-11-labeled racemic structures [(11)C]11 and [(11)C]16. In dynamic positron-emission tomography (PET) scans, (R)-[(18)F]13 showed a heterogeneous distribution and matched the MAGL expression pattern in the mouse brain. High brain uptake and brain-to-blood ratio were achieved by (R)-[(18)F]13 in comparison with previously reported reversible MAGL PET radiotracers. Target occupancy studies with a therapeutic MAGL inhibitor revealed a dose-dependent reduction of (R)-[(18)F]13 accumulation in the mouse brain. These findings indicate that (R)-[(18)F]13 ([(18)F]YH149) is a highly promising PET probe for visualizing MAGL non-invasively in vivo and holds great potential to support drug development.

Monoacylglycerol lipase (MAGL) is a gatekeeper in regulating endocannabinoid signaling and has gained substantial attention as a therapeutic target for neurological disorders. We recently discovered a morpholin-3-one derivative as a novel scaffold for imaging MAGL via positron emission tomography (PET). However, its slow kinetics in vivo hampered the application. In this study, structural optimization was conducted and eleven novel MAGL inhibitors were designed and synthesized. Based on the results from MAGL inhibitory potency, in vitro metabolic stability and surface plasmon resonance assays, we identified compound 7 as a potential MAGL PET tracer candidate. [(11)C]7 was synthesized via direct (11)CO(2) fixation method and successfully mapped MAGL distribution patterns on rodent brains in in vitro autoradiography. PET studies in mice using [(11)C]7 demonstrated its improved kinetic profile compared to the lead structure. Its high specificity in vivo was proved by using MAGL KO mice. Although further studies confirmed that [(11)C]7 is a P-glycoprotein (P-gp) substrate in mice, its low P-gp efflux ratio on cells transfected with human protein suggests that it should not be an issue for the clinical translation of [(11)C]7 as a novel reversible MAGL PET tracer in human subjects. Overall, [(11)C]7 ([(11)C]RO7284390) showed promising results warranting further clinical evaluation.

Chronic inflammation and blood-brain barrier dysfunction are key pathological hallmarks of neurological disorders such as multiple sclerosis, Alzheimer's disease and Parkinson's disease. Major drivers of these pathologies include pro-inflammatory stimuli such as prostaglandins, which are produced in the central nervous system by the oxidation of arachidonic acid in a reaction catalyzed by the cyclooxygenases COX1 and COX2. Monoacylglycerol lipase hydrolyzes the endocannabinoid signaling lipid 2-arachidonyl glycerol, enhancing local pools of arachidonic acid in the brain and leading to cyclooxygenase-mediated prostaglandin production and neuroinflammation. Monoacylglycerol lipase inhibitors were recently shown to act as effective anti-inflammatory modulators, increasing 2-arachidonyl glycerol levels while reducing levels of arachidonic acid and prostaglandins, including PGE2 and PGD2. In this study, we characterized a novel, highly selective, potent and reversible monoacylglycerol lipase inhibitor (MAGLi 432) in a mouse model of lipopolysaccharide-induced blood-brain barrier permeability and in both human and mouse cells of the neurovascular unit: brain microvascular endothelial cells, pericytes and astrocytes. We confirmed the expression of monoacylglycerol lipase in specific neurovascular unit cells in vitro, with pericytes showing the highest expression level and activity. However, MAGLi 432 did not ameliorate lipopolysaccharide-induced blood-brain barrier permeability in vivo or reduce the production of pro-inflammatory cytokines in the brain. Our data confirm monoacylglycerol lipase expression in mouse and human cells of the neurovascular unit and provide the basis for further cell-specific analysis of MAGLi 432 in the context of blood-brain barrier dysfunction caused by inflammatory insults.

PURPOSE: Monoacylglycerol lipase (MAGL) regulates cannabinoid neurotransmission and the pro-inflammatory arachidonic acid pathway by degrading endocannabinoids. MAGL inhibitors may accordingly act as cannabinoid-potentiating and anti-inflammatory agents. Although MAGL dysfunction has been implicated in neuropsychiatric disorders, it has never been visualized in vivo in human brain. The primary objective of the current study was to visualize MAGL in the human brain using the novel PET ligand (18)F-T-401. METHODS: Seven healthy males underwent 120-min dynamic (18)F-T-401-PET scans with arterial blood sampling. Six subjects also underwent a second PET scan with (18)F-T-401 within 2 weeks of the first scan. For quantification of MAGL in the human brain, kinetic analyses using one- and two-tissue compartment models (1TCM and 2TCM, respectively), along with multilinear analysis (MA1) and Logan graphical analysis, were performed. Time-stability and test-retest reproducibility of (18)F-T-401-PET were also evaluated. RESULTS: (18)F-T-401 showed rapid uptake and gradual washout from the brain. Logan graphical analysis showed linearity in all subjects, indicating reversible radioligand kinetics. Using a metabolite-corrected arterial input function, MA1 estimated regional total distribution volume (V(T)) values by best identifiability. V(T) values were highest in the cerebral cortex, moderate in the thalamus and putamen, and lowest in white matter and the brainstem, which was in agreement with regional MAGL expression in the human brain. Time-stability analysis showed that MA1 estimated V(T) values with a minimal bias even using truncated 60-min scan data. Test-retest reliability was also excellent with the use of MA1. CONCLUSIONS: Here, we provide the first demonstration of in vivo visualization of MAGL in the human brain. (18)F-T-401 showed excellent test-retest reliability, reversible kinetics, and stable estimation of V(T) values consistent with known regional MAGL expressions. PET with (18)F-T-401-PET is promising tool for measurement of central MAGL.

As a serine hydrolase, monoacylglycerol lipase (MAGL) is principally responsible for the metabolism of 2-arachidonoylglycerol (2-AG) in the central nervous system (CNS), leading to the formation of arachidonic acid (AA). Dysfunction of MAGL has been associated with multiple CNS disorders and symptoms, including neuroinflammation, cognitive impairment, epileptogenesis, nociception and neurodegenerative diseases. Inhibition of MAGL provides a promising therapeutic direction for the treatment of these conditions, and a MAGL positron emission tomography (PET) probe would greatly facilitate preclinical and clinical development of MAGL inhibitors. Herein, we design and synthesize a small library of fluoropyridyl-containing MAGL inhibitor candidates. Pharmacological evaluation of these candidates by activity-based protein profiling identified 14 as a lead compound, which was then radiolabeled with fluorine-18 via a facile S(N)Ar reaction to form 2-[(18)F]fluoropyridine scaffold. Good blood-brain barrier permeability and high in vivo specific binding was demonstrated for radioligand [(18)F]14 (also named as [(18)F]MAGL-1902). This work may serve as a roadmap for clinical translation and further design of potent (18)F-labeled MAGL PET tracers.

The therapeutic potential of monoacylglycerol lipase (MAGL) inhibitors in central nervous system-related diseases has attracted attention worldwide. However, the availability of reversible-type inhibitor is still limited to clarify the pharmacological effect. Herein, we report the discovery of novel spiro chemical series as potent and reversible MAGL inhibitors with a different binding mode to MAGL using Arg57 and His121. Starting from hit compound 1 and its co-crystal structure with MAGL, structure-based drug discovery (SBDD) approach enabled us to generate various spiro scaffolds like 2a (azetidine-lactam), 2b (cyclobutane-lactam), and 2d (cyclobutane-carbamate) as novel bioisosteres of 3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl moiety in 1 with higher lipophilic ligand efficiency (LLE). Optimization of the left hand side afforded 4f as a promising reversible MAGL inhibitor, which showed potent in vitro MAGL inhibitory activity (IC(50) 6.2 nM), good oral absorption, blood-brain barrier penetration, and significant pharmacodynamic changes (2-arachidonoylglycerol increase and arachidonic acid decrease) at 0.3-10 mg/kg, po. in mice.

While current therapeutic strategies for people living with human immunodeficiency virus type 1 (HIV-1) suppress virus replication peripherally, viral proteins such as transactivator of transcription (Tat) enter the central nervous system early upon infection and contribute to chronic inflammatory conditions even alongside antiretroviral treatment. As demand grows for supplemental strategies to combat virus-associated pathology presenting frequently as HIV-associated neurocognitive disorders (HAND), the present study aimed to characterize the potential utility of inhibiting monoacylglycerol lipase (MAGL) activity to increase inhibitory activity at cannabinoid receptor-type 1 receptors through upregulation of 2-arachidonoylglycerol (2-AG) and downregulation of its degradation into proinflammatory metabolite arachidonic acid (AA). The MAGL inhibitor MJN110 significantly reduced intracellular calcium and increased dendritic branching complexity in Tat-treated primary frontal cortex neuron cultures. Chronic MJN110 administration in vivo increased 2-AG levels in the prefrontal cortex (PFC) and striatum across Tat(+) and Tat(-) groups and restored PFC N-arachidonoylethanolamine (AEA) levels in Tat(+) subjects. While Tat expression significantly increased rate of reward-related behavioral task acquisition in a novel discriminative stimulus learning and cognitive flexibility assay, MJN110 altered reversal acquisition specifically in Tat(+) mice to rates indistinguishable from Tat(-) controls. Collectively, our results suggest a neuroprotective role of MAGL inhibition in reducing neuronal hyperexcitability, restoring dendritic arborization complexity, and mitigating neurocognitive alterations driven by viral proteins associated with latent HIV-1 infection.

The endocannabinoid system is involved in the regulation of the stress response, but the relative contribution of N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) and their mechanisms have to be elucidated. In this study, we compared the effects of the pharmacological inhibition of the two major endocannabinoid-degrading enzymes [fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) for AEA and 2-AG, respectively] on stress-coping [forced swim test (FST) and tail suspension test (TST)] and anxiety-like [elevated-plus maze (EPM) and light-dark test (LDT)] behaviors in wild-type and FAAH knockout mice. In vivo microdialysis estimated the effects of FAAH and MAGL inhibition on dopamine (DA) and serotonin (5-HT) levels in the medial prefrontal cortex (mPFC) during an FST. Mice were treated with PF-3845 (FAAH inhibitor), JZL184 (MAGL inhibitor), JZL195 (dual FAAH/MAGL inhibitor) or vehicle. Our data showed that PF-3845 increased latency to immobility and decreased total immobility time in FST, but no effects were observed in TST compared with vehicle-treated wild-type mice. By contrast, JZL184 decreased latency and increased immobility in TST and FST. JZL195 in wild-type mice and JZL184 in FAAH knockout mice reproduced the same passive coping behaviors as JZL184 in wild-type mice in TST and FST. In the microdialysis experiment, FST was associated with increased DA and 5-HT levels in the mPFC. However, JZL184-treated wild-type mice displayed a significant attenuation of forced swim stress-induced DA release compared with vehicle-treated wild-type mice and PF-3845-treated wild-type mice. Finally, FAAH and/or MAGL inhibitors induced robust and consistent anxiolytic-like effects in EPM and LDT. These results suggested differences between FAAH and MAGL inhibition in stress-coping behaviors. Notably, MAGL inhibition induced a consistent avoidant coping behavior and attenuated the stress-induced mPFC DA response in FST. However, more investigation is needed to elucidate the functional association between DA and 2-AG signaling pathways, and the molecular mechanism in the regulation of passive coping strategies during inescapable stress.

A targeted modulation of the endocannabinoid system is currently discussed as a promising strategy for cancer treatment. An important enzyme for the endocannabinoid metabolism is the monoacylglycerol lipase (MAGL), which catalyzes the degradation of 2-arachidonoylglycerol (2-AG) to glycerol and free fatty acids. In this study, we investigated the influence of MAGL inhibition on lung cancer cell invasion and metastasis. Using LC-MS, significantly increased 2-AG levels were detected in A549 cells treated with the MAGL inhibitor JZL184. In athymic nude mice, JZL184 suppressed metastasis of A549 cells in a dose-dependent manner, whereby the antimetastatic effect was cancelled by the CB(1) receptor antagonist AM-251. In vitro, JZL184 induced a time- and concentration-dependent reduction of A549 cell invasion through Matrigel-coated membranes, which was likewise reversed by AM-251. An MAGL inhibition-associated reduction of free fatty acids as a cause of the anti-invasive effect could be excluded by add-back experiments with palmitic acid. Both JZL184 and the MAGL substrate 2-AG led to an increased formation of the tissue inhibitor of metalloproteinase-1 (TIMP-1), whereby a TIMP-1 knockdown using siRNA significantly attenuated the anti-invasive effects of both substances. Decreased invasion and TIMP-1 upregulation was also caused by the MAGL inhibitors JW651 and MJN110 or transfection with MAGL siRNA. A CB(1)- and TIMP-1-dependent anti-invasive effect was further confirmed for JZL184 in H358 lung cancer cells. In conclusion, MAGL inhibition led to a CB(1)-dependent decrease in human lung cancer cell invasion and metastasis via inhibition of 2-AG degradation, with TIMP-1 identified as a mediator of the anti-invasive effect.

Monoacylglycerol lipase (MAGL) is a 33 kDa serine protease primarily responsible for hydrolyzing 2-arachidonoylglycerol into the proinflammatory eicosanoid precursor arachidonic acid in the central nervous system. Inhibition of MAGL constitutes an attractive therapeutic concept for treating psychiatric disorders and neurodegenerative diseases. Herein, we present the design and synthesis of multiple reversible MAGL inhibitor candidates based on a piperazinyl azetidine scaffold. Compounds 10 and 15 were identified as the best-performing reversible MAGL inhibitors by pharmacological evaluations, thus channeling their radiolabeling with fluorine-18 in high radiochemical yields and favorable molar activity. Furthermore, evaluation of [(18)F]10 and [(18)F]15 ([(18)F]MAGL-2102) by autoradiography and positron emission tomography (PET) imaging in rodents and nonhuman primates demonstrated favorable brain uptakes, heterogeneous radioactivity distribution, good specific binding, and adequate brain kinetics, and [(18)F]15 demonstrated a better performance. In conclusion, [(18)F]15 was found to be a suitable PET radioligand for the visualization of MAGL, harboring potential for the successful translation into humans.

Monoacylglycerol lipase (MAGL) is the major enzyme that catalyzes the hydrolysis of monoacylglycerols (MAGs). MAGL is responsible for degrading 2-arachidonoylglycerol (2-AG) to arachidonic acid (AA) and glycerol in the brain and specific tissues. The inhibition of MAGL could attenuate the inflammatory response. Here, we report a series of reversible non-covalent MAGL inhibitors via virtual screening combined with biochemical analysis. The hit, DC630-8 showed low-micromolar activity against MAGL in vitro, and exhibited significant anti-inflammatory effects.

Tumorigenesis involves metabolic reprogramming and abnormal lipid metabolism, which is manifested by increased endogenous fat mobilization, hypertriglyceridemia, and increased fatty acid synthesis. Fatty acid synthase (FASN) is a key enzyme for the de novo synthesis of fatty acids, and monoacylglycerol esterase (MGLL) is an important metabolic enzyme that converts triglycerides into free fatty acids. Both enzymes play an important role in lipid metabolism and are associated with tumor-related signaling pathways, the most common of which is the PI3K-AKT signaling pathway. They can also regulate the immune microenvironment, participate in epithelial-mesenchymal transition, and then regulate tumor invasion and metastasis. Current literature have shown that these two genes are abnormally expressed in many types of tumors and are highly correlated with tumor migration and invasion. This article introduces the structures and functions of FASN and MGLL, their relationship with abnormal lipid metabolism, and the mechanism of the regulation of tumor invasion and metastasis and reviews the research progress of the relationship of FASN and MGLL with tumor invasion and metastasis.

CB1 receptor antagonists disrupt operant responding for food and drug reinforcers, and cue-induced reinstatement of cocaine and heroin seeking. Conversely, enhancing endocannabinoid signaling, particularly 2-arachidonyl glycerol (2-AG), by inhibition of monoacyl glycerol lipase (MAGL), may facilitate some aspects of reward seeking. To determine how endocannabinoid signaling affects responding to reward-predictive cues, we employed an operant task that allows us to parse the incentive motivational properties of cues. Rats were required to nosepoke during an intermittent audiovisual incentive cue (IC) to obtain a 10% sucrose reward. The CB1 receptor antagonist, rimonabant, dose-dependently decreased the response ratio (rewarded ICs/total presented) and active nosepokes per IC, while it increased the latency to respond to the cue and obtain the reward, indicating an overall decrease in both the choice and vigor of responding. Yet rats persisted in entering the reward cup. Using a modified version of the task, the novel MAGL inhibitor MJN110 increased the response ratio, decreased the latencies to respond to the IC and enhanced active nosepokes per IC, indicating a facilitation of cue-induced reward seeking. These effects were blocked by a subthreshold dose of rimonabant. Finally, MJN110 did not alter consumption of freely available sucrose within volumes obtained in the operant task. Together these data demonstrate blocking endocannabinoid tone at the CB1 receptor attenuates the ability of cues to induce reward seeking, while some aspects of motivation for the reward are retained. Conversely, enhancing 2-AG signaling at CB1 receptors facilitates IC responding and increases the motivational properties of the IC.

An interesting enzyme of the endocannabinoid system is monoacylglycerol lipase (MAGL). This enzyme, which metabolizes the endocannabinoid 2-arachidonoylglycerol (2-AG), has attracted great interest due to its involvement in several physiological and pathological processes, such as cancer progression. Experimental evidences highlighted some drawbacks associated with the use of irreversible MAGL inhibitors in vivo, therefore the research field concerning reversible inhibitors is rapidly growing. In the present manuscript, the class of benzoylpiperidine-based MAGL inhibitors was further expanded and optimized. Enzymatic assays identified some compounds in the low nanomolar range and steered molecular dynamics simulations predicted the dissociation itinerary of one of the best compounds from the enzyme, confirming the observed structure-activity relationship. Biological evaluation, including assays in intact U937 cells and competitive activity-based protein profiling experiments in mouse brain membranes, confirmed the selectivity of the selected compounds for MAGL versus other components of the endocannabinoid system. An antiproliferative ability in a panel of cancer cell lines highlighted their potential as potential anticancer agents. Future studies on the potential use of these compounds in the clinical setting are also supported by the inhibition of cell growth observed both in cancer organoids derived from high grade serous ovarian cancer patients and in pancreatic ductal adenocarcinoma primary cells, which showed genetic and histological features very similar to the primary tumors.

We have previously reported that Monoglyceride Lipase (MGL) expression is absent or reduced in various human malignancies and MGL-deficient mice develop tumors in multiple organs. Evidence also suggests MGL to be a tumor suppressor, however, the mechanisms underlying its tumor-suppressive actions remain to be investigated. Here, we report a novel function of MGL as a negative regulator of XIAP, an important inhibitor of apoptosis. We found that MGL directly interacted with XIAP and enhanced E3-ligase activity and proteasomal degradation of XIAP. MGL overexpression induced cell death that was coupled with caspase activation and reduced XIAP levels. N-terminus of MGL was found to mediate interactions with XIAP and induce cell death. MGL-deficient cells exhibited elevated XIAP levels and exhibited resistance to anticancer drugs. XIAP expression was significantly elevated in tissues of MGL-deficient animals as well as human lung cancers exhibiting reduced MGL expression. Thus, MGL appears to mediate its tumor-suppressive actions by inhibiting XIAP to induce cell death.

Acute environmental stress rarely implies long lasting neurophysiological and behavioral alterations. On the contrary, chronic stress exerts a potent toxic effect at the glutamatergic synapse whose altered physiology has been recognized as a core trait of neuropsychiatric disorders. The endocannabinoid system (ECS) plays an important role in the homeostatic response to acute stress. In particular, stress induces synthesis of endocannabinoid (eCB) 2-arachidonyl glycerol (2-AG). 2-AG stimulates presynaptic cannabinoid 1 (CB1) receptor contributing to stress response termination through inhibition of glutamate release, restraining thereafter anxiety arousal. We employ mouse models of stress response coupled to gene expression analyses, unravelling that in response to acute psychosocial stress in the mouse hippocampus, ECS-mediated synaptic modulation is enhanced via transcriptional repression of two enzymes involved in 2-AG degradation: alpha/beta-Hydrolase Domain containing 6 (ABHD6) and Monoacylglycerol Lipase (MAGL). Such a process is orchestrated by the epigenetic corepressor LSD1 who directly interacts with promoter regulatory regions of Abhd6 and Magl. Remarkably, negative transcriptional control of Abhd6 and Magl is lost in the hippocampus upon chronic psychosocial stress, possibly contributing to trauma-induced drift of synapse physiology toward uncontrolled glutamate transmission. We previously showed that in mice Lysine Specific Demethylase 1 (LSD1) increases its hippocampal expression in response to psychosocial stress preventing excessive consolidation of anxiety-related plasticity. With this work we unravel a nodal epigenetic modulation of eCB turn over, shedding new light on the molecular substrate of converging stress-terminating effects displayed by ECS and LSD1.

Nicotine, the primary psychoactive component in tobacco, plays a major role in the initiation and maintenance of tobacco dependence and addiction, a leading cause of preventable death worldwide. An essential need thus exists for more effective pharmacotherapies for nicotine-use cessation. Previous reports suggest that pharmacological and genetic blockade of CB1 receptors attenuate nicotine reinforcement and reward; while exogenous agonists enhanced these abuse-related behaviors. In this study, we utilized complementary genetic and pharmacologic approaches to test the hypothesis that increasing the levels of the endocannabinoid 2-arachindonoylglycerol (2-AG), will enhance nicotine reward by stimulating neuronal CB1 receptors. Contrary to our hypothesis, we found that inhibition of monoacylglycerol lipase (MAGL), the primary catabolic enzyme of 2-AG, attenuates nicotine conditioned place preference (CPP) in mice, through a non-CB1 receptor-mediated mechanism. MAGL inhibition did not alter palatable food reward or Lithium Chloride (LiCl) aversion. In support of our findings, repeated MAGL inhibition did not induce a reduction in CB1 brain receptor levels or hinder function. To explore the potential mechanism of action, we investigated if MAGL inhibition affected other fatty acid levels in our CPP paradigm. Indeed, MAGL inhibition caused a concomitant decrease in arachidonic acid (AA) levels in various brain regions of interest, suggesting an AA cascade-dependent mechanism. This idea is supported by dose-dependent attenuation of nicotine preference by the selective COX-2 inhibitors valdecoxib and LM-4131. Collectively, these findings, along with our reported studies on nicotine withdrawal, suggest that inhibition of MAGL represents a promising new target for the development of pharmacotherapies to treat nicotine dependence.

Metastatic breast cancer is prevalent worldwide, and one of the most common sites of metastasis is long bones. Of patients with disease, the major symptom is pain, yet current medications fail to adequately result in analgesic efficacy and present major undesirable adverse effects. In our study, we investigate the potential of a novel monoacylglycerol lipase (MAGL) inhibitor, MJN110, in a murine model of cancer-induced bone pain. Literature has previously demonstrated that MAGL inhibitors function to increase the endogenous concentrations of 2-arachydonylglycerol, which then activates CB1 and CB2 receptors to inhibit inflammation and pain. We demonstrate that administration of MJN110 significantly and dose dependently alleviates spontaneous pain behavior during acute administration compared with vehicle control. In addition, MJN110 maintains its efficacy in a chronic-dosing paradigm over the course of 7 days without signs of receptor sensitization. In vitro analysis of MJN110 demonstrated a dose-dependent and significant decrease in cell viability and proliferation of 66.1 breast adenocarcinoma cells to a greater extent than KML29, an alternate MAGL inhibitor, or the CB2 agonist JWH015. Chronic administration of the compound did not appear to affect tumor burden, as evidenced by radiograph or histologic analysis. Together, these data support the application for MJN110 as a novel therapeutic for cancer-induced bone pain. SIGNIFICANCE STATEMENT: Current standard of care for metastatic breast cancer pain is opioid-based therapies with adjunctive chemotherapy, which have highly addictive and other deleterious side effects. The need for effective, non-opioid-based therapies is essential, and harnessing the endogenous cannabinoid system is proving to be a new target to treat various types of pain conditions. We present a novel drug targeting the endogenous cannabinoid system that is effective at reducing pain in a mouse model of metastatic breast cancer to bone.

Inhibition of human Monoacylglycerol Lipase (hMGL) offers a novel approach for treating neurological diseases. The design of inhibitors, targeting active-inactive conformational transitions of the enzyme, can be aided by understanding the interplay between structure and dynamics. Here, we report the effects of mutations within the catalytic triad on structure, conformational gating and dynamics of hMGL by combining kinetics, NMR, and HDX-MS data with metadynamics simulations. We found that point mutations alter delicate conformational equilibria between active and inactive states. HDX-MS reveals regions of the hMGL that become substantially more dynamic upon substitution of catalytic acid Asp-239 by alanine. These regions, located far from the catalytic triad, include not only loops but also rigid alpha-helixes and beta-strands, suggesting their involvement in allosteric regulation as channels for long-range signal transmission. The results identify the existence of a preorganized global communication network comprising of tertiary (residue-residue contacts) and quaternary (rigid-body contacts) networks that mediate robust, rapid intraprotein signal transmission. Catalytic Asp-239 controls hMGL allosteric communications and may be considered as an essential residue for the integration and transmission of information to enzymes' remote regions, in addition to its well-known role to facilitate Ser-122 activation. Our findings may assist in the identification of new druggable sites in hMGL.

Monoacylglycerol lipase (MAGL) is the enzyme that is primarily responsible for hydrolyzing the endocannabinoid 2-arachidononylglycerol (2-AG) to arachidonic acid (AA). It has emerged in recent years as a potential drug target for a number of diseases. Herein, we report the discovery of compound 6g from a series of azetidine-piperazine di-amide compounds as a potent, selective, and reversible inhibitor of MAGL. Oral administration of compound 6g increased 2-AG levels in rat brain and produced full efficacy in the rat complete Freund's adjuvant (CFA) model of inflammatory pain.

Monoacylglycerol lipase (MAGL) is a serine hydrolase that degrades 2-arachidonoylglycerol (2-AG) in the endocannabinoid system (eCB). Selective inhibition of MAGL has emerged as a potential therapeutic approach for the treatment of diverse pathological conditions, including chronic pain, inflammation, cancer, and neurodegeneration. Herein, we disclose a novel array of reversible and irreversible MAGL inhibitors by means of "tail switching" on a piperazinyl azetidine scaffold. We developed a lead irreversible-binding MAGL inhibitor 8 and reversible-binding compounds 17 and 37, which are amenable for radiolabeling with (11)C or (18)F. [(11)C]8 ([(11)C]MAGL-2-11) exhibited high brain uptake and excellent binding specificity in the brain toward MAGL. Reversible radioligands [(11)C]17 ([(11)C]PAD) and [(18)F]37 ([(18)F]MAGL-4-11) also demonstrated excellent in vivo binding specificity toward MAGL in peripheral organs. This work may pave the way for the development of MAGL-targeted positron emission tomography tracers with tunability in reversible and irreversible binding mechanisms.

The serine hydrolase monoacylglycerol lipase (MAGL) is involved in a plethora of pathological conditions, in particular pain and inflammation, various types of cancer, metabolic, neurological and cardiovascular disorders, and is therefore a promising target for drug development. Although a large number of irreversible-acting MAGL inhibitors have been discovered over the past years, there are only few compounds known so far which inhibit the enzyme in a reversible manner. Therefore, much effort is put into the development of novel chemical entities showing reversible inhibitory behavior, which is thought to cause less undesired side effects. To explore a wide range of chemical structures as MAGL binders, we have applied a virtual screening approach by docking small molecules into the crystal structure of human MAGL (hMAGL) and envisaged a library of 45 selected compounds which were then synthesized. Biochemical investigations included the determination of the inhibitory potency on hMAGL and two related hydrolases, i.e. human fatty acid amide hydrolase (hFAAH) and murine cholesterol esterase (mCEase). The most promising candidates from theses analyses, i.e. three omega-quinazolinonylalkyl aryl ureas bearing alkyl spacers of three to five methylene groups, exhibited IC50 values of 20-41microM and reversible, detergent-insensitive behavior towards hMAGL. Among these compounds, the inhibitor 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-(4-oxo-3,4-dihydroquinazolin-2-yl)butyl)u rea (96) was selected for further kinetic characterization, yielding a dissociation constant Ki=15.4microM and a mixed-type inhibition with a pronounced competitive component (alpha=8.94). This mode of inhibition was further supported by a docking experiment, which suggested that the inhibitor occupies the substrate binding pocket of hMAGL.

Monoacylglycerol lipase (MAGL) is a cytosolic serine hydrolase involved in endocannabinoid and inflammatory signaling. Positron-emission tomography (PET) imaging of MAGL serves to validate target engagement of therapeutic MAGL inhibitors as well as to investigate MAGL levels under normal and disease conditions. However, PET radioligands with reversible binding kinetics for MAGL, which allow quantitative assessment of MAGL, are hitherto unavailable. In this study, we designed and synthesized fluoro-containing PET probes starting from a recently identified piperazinyl pyrrolidine-2-one derivative with reversible binding to MAGL. By tailoring the lipophilicity of the molecule to optimize nonspecific binding and blood-brain barrier permeability, we successfully identified two compounds that show high uptake to regions enriched with MAGL. PET imaging of wild-type and MAGL-deficient mice as well as a macaque monkey indicated that [(18)F]5 ((4 R)-1-{3-[2-((18)F)fluoro-4-methylpyridin-3-yl]phenyl}-4-[4-(1,3-thiazol-2-ylcarbo nyl)piperazin-1-yl]pyrrolidin-2-one, [(18)F]T-401) specifically binds to MAGL with adequate reversibility, yielding a high contrast for MAGL within an appropriate imaging time.

Heavy use of cannabis (marijuana) has been associated with decreased semen quality, which may reflect disruption of the endocannabinoid system (ECS) in the male reproductive tract by exogenous cannabinoids. Components of ECS have been previously described in human spermatozoa and in the rodent testis but there is little information on the ECS expression within the human testis. In this study we characterised the main components of the ECS by immunohistochemistry (IHC) on archived testis tissue samples from 15 patients, and by in silico analysis of existing transcriptome datasets from testicular cell populations. The presence of 2-arachidonoylglycerol (2-AG) in the human testis was confirmed by matrix-assisted laser desorption ionization imaging analysis. Endocannabinoid-synthesising enzymes; diacylglycerol lipase (DAGL) and N-acyl-phosphatidylethanolamine-specific phospholipase D (NAPE-PLD), were detected in germ cells and somatic cells, respectively. The cannabinoid receptors, CNR1 and CNR2 were detected at a low level in post-meiotic germ cells and Leydig- and peritubular cells. Different transcripts encoding distinct receptor isoforms (CB1, CB1A, CB1B and CB2A) were also differentially distributed, mainly in germ cells. The cannabinoid-metabolising enzymes were abundantly present; the alpha/beta-hydrolase domain-containing protein 2 (ABHD2) in all germ cell types, except early spermatocytes, the monoacylglycerol lipase (MGLL) in Sertoli cells, and the fatty acid amide hydrolase (FAAH) in late spermatocytes and post-meiotic germ cells. Our findings are consistent with a direct involvement of the ECS in regulation of human testicular physiology, including spermatogenesis and Leydig cell function. The study provides new evidence supporting observations that recreational cannabis can have possible deleterious effects on human testicular function.

Monoacylglycerol lipase (MAGL) is an attractive therapeutic target for many pathologies, including neurodegenerative diseases, cancer as well as chronic pain and inflammatory pathologies. The identification of reversible MAGL inhibitors, devoid of the side effects associated to prolonged MAGL inactivation, is a hot topic in medicinal chemistry. In this study, a novel phenyl(piperazin-1-yl)methanone inhibitor of MAGL was identified through a virtual screening protocol based on a fingerprint-driven consensus docking (CD) approach. Molecular modeling and preliminary structure-based hit optimization studies allowed the discovery of derivative 4, which showed an efficient reversible MAGL inhibition (IC50 = 6.1 microM) and a promising antiproliferative activity on breast and ovarian cancer cell lines (IC50 of 31-72 microM), thus representing a lead for the development of new and more potent reversible MAGL inhibitors. Moreover, the obtained results confirmed the reliability of the fingerprint-driven CD approach herein developed.

Monoacylglycerol lipase (MAGL) is a major serine hydrolase that hydrolyzes 2-arachidonoylglycerol (2-AG) to arachidonic acid (AA) and glycerol in the brain. Because 2-AG and AA are endogenous biologically active ligands in the brain, inhibition of MAGL is an attractive therapeutic target for CNS disorders, particularly neurodegenerative diseases. In this study, we report the structure-based drug design of novel piperazinyl pyrrolidin-2-ones starting from our hit compounds 2a and 2b. By enhancing the interaction of the piperazinyl pyrrolidin-2-one core and its substituents with the MAGL enzyme via design modifications, we identified a potent and reversible MAGL inhibitor, compound ( R)-3t. Oral administration of compound ( R)-3t to mice decreased AA levels and elevated 2-AG levels in the brain.

Monoacylglycerol lipase (MAGL) has been characterized as the main enzyme responsible for the inactivation of the most abundant brain endocannabinoid, 2-arachidonoylglycerol (2-AG). Besides this role, MAGL has progressively acquired a growing importance as an integrative metabolic hub that controls not only the in vivo levels of 2-AG but also of other monoacylglycerides and, indirectly, the levels of free fatty acids derived from their hydrolysis as well as other lipids with pro-inflammatory or pro-tumorigenic effects, coming from the further metabolism of fatty acids. All these functions have only started to be elucidated in the last years due to the progress made in the knowledge of the structure of MAGL and in the development of genetic and chemical tools. In this review we report the advances made in the field with a special focus on the last decade and how MAGL has become a promising therapeutic target for the treatment of several diseases that currently lack appropriate therapies.

Monoacylglycerol lipase (MAGL) inhibition provides a potential treatment approach to neuroinflammation through modulation of both the endocannabinoid pathway and arachidonoyl signaling in the central nervous system (CNS). Herein we report the discovery of compound 15 (PF-06795071), a potent and selective covalent MAGL inhibitor, featuring a novel trifluoromethyl glycol leaving group that confers significant physicochemical property improvements as compared with earlier inhibitor series with more lipophilic leaving groups. The design strategy focused on identifying an optimized leaving group that delivers MAGL potency, serine hydrolase selectivity, and CNS exposure while simultaneously reducing log D, improving solubility, and minimizing chemical lability. Compound 15 achieves excellent CNS exposure, extended 2-AG elevation effect in vivo, and decreased brain inflammatory markers in response to an inflammatory challenge.

Monoacylglycerol lipases (MGL) are a subclass of lipases that predominantly hydrolyze monoacylglycerol (MG) into glycerol and fatty acid. MGLs are ubiquitous enzymes across species and play a role in lipid metabolism, affecting energy homeostasis and signaling processes. Structurally, MGLs belong to the alpha/beta hydrolase fold family with a cap covering the substrate binding pocket. Analysis of the known 3D structures of human, yeast and bacterial MGLs revealed striking similarity of the cap architecture. Since MGLs from different organisms share very low sequence similarity, it is difficult to identify MGLs based on the amino acid sequence alone. Here, we investigated whether the cap architecture could be a characteristic feature of this subclass of lipases with activity towards MG and whether it is possible to identify MGLs based on the cap shape. Through database searches, we identified the structures of five different candidate alpha/beta hydrolase fold proteins with unknown or reported esterase activity. These proteins exhibit cap architecture similarities to known human, yeast and bacterial MGL structures. Out of these candidates we confirmed MGL activity for the protein LipS, which displayed the highest structural similarity to known MGLs. Two further enzymes, Avi_0199 and VC1974, displayed low level MGL activities. These findings corroborate our hypothesis that this conserved cap architecture can be used as criterion to identify lipases with activity towards MGs.

An understanding of how conformational dynamics modulates function and catalysis of human monoacylglycerol lipase (hMGL), an important pharmaceutical target, can facilitate the development of novel ligands with potential therapeutic value. Here, we report the discovery and characterization of an allosteric, regulatory hMGL site comprised of residues Trp-289 and Leu-232 that reside over 18 A away from the catalytic triad. These residues were identified as critical mediators of long-range communication and as important contributors to the integrity of the hMGL structure. Nonconservative replacements of Trp-289 or Leu-232 triggered concerted motions of structurally distinct regions with a significant conformational shift toward inactive states and dramatic loss in catalytic efficiency of the enzyme. Using a multimethod approach, we show that the dynamically relevant Trp-289 and Leu-232 residues serve as communication hubs within an allosteric protein network that controls signal propagation to the active site, and thus, regulates active-inactive interconversion of hMGL. Our findings provide new insights into the mechanism of allosteric regulation of lipase activity, in general, and may provide alternative drug design possibilities.

The biosynthetic and catabolic enzymes of the endocannabinoids tightly regulate endocannabinoid-mediated activation of the cannabinoid CB1 receptor. Monitoring the activities of these endocannabinoid hydrolases in different brain regions is, therefore, key to gaining insight into spatiotemporal control of CB1 receptor-mediated physiology. We have employed a comparative chemical proteomics approach to quantitatively map the activity profile of endocannabinoid hydrolases in various mouse brain regions at the same time. To this end, we used two different activity-based probes: fluorophosphonate-biotin (FP-biotin), which quantifies FAAH, ABHD6, and MAG-lipase activity, and MB108, which detects DAGL-alpha, ABHD4, ABHD6, and ABHD12. In total, 32 serine hydrolases were evaluated in the frontal cortex, hippocampus, striatum, and cerebellum. Comparison of endocannabinoid hydrolase activity in the four brain regions revealed that FAAH activity was highest in the hippocampus, and MAGL activity was most pronounced in the frontal cortex, whereas DAGL-alpha was most active in the cerebellum. Comparison of the activity profiles with a global proteomics data set revealed pronounced differences. This could indicate that post-translational modification of the endocannabinoid hydrolases is important to regulate their activity. Next, the effect of genetic deletion of the CB1 receptor was studied. No difference in the enzymatic activity was found in the cerebellum, striatum, frontal cortex, and hippocampus of CB1 receptor knockout animals compared to wild type mice. Our results are in line with previous reports and indicate that the CB1 receptor exerts no regulatory control over the basal production and degradation of endocannabinoids and that genetic deletion of the CB1 receptor does not induce compensatory mechanisms in endocannabinoid hydrolase activity.

Monoacylglycerol lipase (MAGL) is the main enzyme responsible for degradation of the endocannabinoid 2-arachidonoylglycerol (2-AG) in the CNS. MAGL catalyzes the conversion of 2-AG to arachidonic acid (AA), a precursor to the proinflammatory eicosannoids such as prostaglandins. Herein we describe highly efficient MAGL inhibitors, identified through a parallel medicinal chemistry approach that highlighted the improved efficiency of azetidine and piperidine-derived carbamates. The discovery and optimization of 3-substituted azetidine carbamate irreversible inhibitors of MAGL were aided by the generation of inhibitor-bound MAGL crystal structures. Compound 6, a highly efficient and selective MAGL inhibitor against recombinant enzyme and in a cellular context, was tested in vivo and shown to elevate central 2-AG levels at a 10 mg/kg dose.

Human monoacylglycerol lipase (hMAGL) plays a key role in homeostatic tuning of the endocannabinoid signaling system and supports aggressive tumorogenesis, making this enzyme a promising therapeutic target. hMAGL features a membrane-associated lid domain that regulates entry of endocannabinoid lipid substrates into the hydrophobic channel accessing the active site, likely from the membrane bilayer. The present work applied simultaneous surface plasmon resonance and electrochemical impedance spectroscopy measurements to show that, in absence of the substrate, hMAGL can remove phospholipid molecules from the membrane and, thereby, disintegrate pre-formed, intact, tethered phospholipid bilayer membrane mimetics (tBLMs) composed of unsaturated phosphatidylcholines. To probe the mechanism of hMAGL-induced on tBLMs compromise, we investigated the effect of wild type and mutant hMAGLs and hMAGL rendered catalytically inactive, as a function of concentration and in the presence of chemically distinct active-site inhibitors. Our data show that hMAGL's lid domain and hydrophobic substrate-binding pocket play important roles in hMAGL-induced bilayer lipid mobilization, whereas hydrolytic activity of the enzyme does not appear to be a factor.

BACKGROUND AND PURPOSE: Abrupt discontinuation of nicotine, the main psychoactive component in tobacco, induces a withdrawal syndrome in nicotine-dependent animals, consisting of somatic and affective signs, avoidance of which contributes to drug maintenance. While blockade of fatty acid amide hydrolase, the primary catabolic enzyme of the endocannabinoid arachidonoylethanolamine (anandamide), exacerbates withdrawal responses in nicotine-dependent mice, the role of monoacylglycerol lipase (MAGL), the main hydrolytic enzyme of a second endocannabinoid 2-arachidonylglycerol (2-AG), in nicotine withdrawal remains unexplored. EXPERIMENTAL APPROACH: To evaluate the role of MAGL enzyme inhibition in nicotine withdrawal, we initially performed a genetic correlation approach using the BXD recombinant inbred mouse panel. We then assessed nicotine withdrawal intensity in the mouse after treatment with the selective MAGL inhibitor, JZL184, and after genetic deletion of the enzyme. Lastly, we assessed the association between genotypes and smoking withdrawal phenotypes in two human data sets. KEY
RESULTS: BXD mice displayed significant positive correlations between basal MAGL mRNA expression and nicotine withdrawal responses, consistent with the idea that increased 2-AG brain levels may attenuate withdrawal responses. Strikingly, the MAGL inhibitor, JZL184, dose-dependently reduced somatic and aversive withdrawal signs, which was blocked by rimonabant, indicating a CB1 receptor-dependent mechanism. MAGL-knockout mice also showed attenuated nicotine withdrawal. Lastly, genetic analyses in humans revealed associations of the MAGL gene with smoking withdrawal in humans. CONCLUSIONS AND IMPLICATIONS: Overall, our findings suggest that MAGL inhibition maybe a promising target for treatment of nicotine dependence.

RATIONALE: To determine the role of the endocannabinoid, 2-arachodonyl glycerol (2-AG), in the regulation of nausea and vomiting. OBJECTIVE: We evaluated the effectiveness of the potent selective monoacylglycerol lipase (MAGL) inhibitor, MJN110, which selectively elevates the endocannabinoid 2-AG, to suppress acute nausea and vomiting, as well as anticipatory nausea in rat and shrew models.
METHODS: The rat gaping models were used to evaluate the potential of MJN110 (5, 10, and 20 mg/kg, intraperitoneally [IP]) to suppress acute nausea produced by LiCl and of MJN110 (10 and 20 mg/kg, IP) to suppress anticipatory nausea elicited by a LiCl-paired context. The potential as well of MJN110 (10 and 20 mg/kg, IP) to suppress vomiting and contextually elicited gaping in the Suncus murinus was evaluated.
RESULTS: MJN110 suppressed acute nausea in rats, LiCl-induced vomiting in shrews and contextually-elicited anticipatory nausea in both rats (accompanied by elevation of 2-AG in the visceral insular cortex) and shrews. These effects were reversed by the CB1 antagonist/inverse agonist, SR141716. The MAGL inhibitor did not modify locomotion at any dose. An activity-based protein profiling analysis of samples of tissue collected from the visceral insular cortex in rats and whole brain tissues in shrews revealed that MJN110 selectively inhibited MAGL and the alternative 2-AG hydrolase, ABHD6.
CONCLUSIONS: MAGL inhibition by MJN110 which selectively elevates endogenous 2-AG has therapeutic potential in the treatment of acute nausea and vomiting as well as anticipatory nausea, a distressful symptom that is resistant to currently available treatments.

The endocannabinoid ligand 2-arachidonoylglycerol (2-AG) is inactivated primarily by monoacylglycerol lipase (MAGL). We have shown recently that chronic treatments with MAGL inhibitor JZL184 produce antidepressant- and anxiolytic-like effects in a chronic unpredictable stress (CUS) model of depression in mice. However, the underlying mechanisms remain poorly understood. Adult hippocampal neurogenesis has been implicated in animal models of anxiety and depression and behavioral effects of antidepressants. We tested whether CUS and chronic JZL184 treatments affected adult neurogenesis and synaptic plasticity in the dentate gyrus (DG) of mouse hippocampus. We report that CUS induced depressive-like behaviors and decreased the number of bromodeoxyuridine-labeled neural progenitor cells and doublecortin-positive immature neurons in the DG, while chronic JZL184 treatments prevented these behavioral and cellular deficits. We also investigated the effects of CUS and chronic JZL184 on a form long-term potentiation (LTP) in the DG known to be neurogenesis-dependent. CUS impaired LTP induction, whereas chronic JZL184 treatments restored LTP in CUS-exposed mice. These results suggest that enhanced adult neurogenesis and long-term synaptic plasticity in the DG of the hippocampus might contribute to antidepressant- and anxiolytic-like behavioral effects of JZL184.

BACKGROUND AND PURPOSE: Since monoacylglycerol lipase (MAGL) has been firmly established as the predominant catabolic enzyme of the endocannabinoid 2-arachidonoylglycerol (2-AG), a great need has emerged for the development of highly selective MAGL inhibitors. Here, we tested the in vivo effects of one such compound, KML29 (1,1,1,3,3,3-hexafluoropropan-2-yl 4-(bis(benzo[d][1,3]dioxol-5-yl)(hydroxy)methyl)piperidine-1-carboxylate). EXPERIMENTAL APPROACH: In the present study, we tested KML29 in murine inflammatory (i.e. carrageenan) and sciatic nerve injury pain models, as well as the diclofenac-induced gastric haemorrhage model. KML29 was also evaluated for cannabimimetic effects, including measurements of locomotor activity, body temperature, catalepsy, and cannabinoid interoceptive effects in the drug discrimination paradigm. KEY
RESULTS: KML29 attenuated carrageenan-induced paw oedema and completely reversed carrageenan-induced mechanical allodynia. These effects underwent tolerance after repeated administration of high-dose KML29, which were accompanied by cannabinoid receptor 1 (CB1 ) receptor desensitization. Acute or repeated KML29 administration increased 2-AG levels and concomitantly reduced arachidonic acid levels, but without elevating anandamide (AEA) levels in the whole brain. Furthermore, KML29 partially reversed allodynia in the sciatic nerve injury model and completely prevented diclofenac-induced gastric haemorrhages. CB1 and CB2 receptors played differential roles in these pharmacological effects of KML29. In contrast, KML29 did not elicit cannabimimetic effects, including catalepsy, hypothermia and hypomotility. Although KML29 did not substitute for Delta(9) -tetrahydrocannabinol (THC) in C57BL/6J mice, it fully and dose-dependantly substituted for AEA in fatty acid amide hydrolase (FAAH) (-/-) mice, consistent with previous work showing that dual FAAH and MAGL inhibition produces THC-like subjective effects. CONCLUSIONS AND IMPLICATIONS: These results indicate that KML29, a highly selective MAGL inhibitor, reduces inflammatory and neuropathic nociceptive behaviour without occurrence of cannabimimetic side effects. LINKED ARTICLES: This article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6.

The primary route of inactivation of the endocannabinoid 2-arachidonoylglycerol in the central nervous system is through enzymatic hydrolysis, mainly carried out by monoacylglycerol lipase (MAGL), along with a small contribution by the alpha/beta-hydrolase domain (ABHD) proteins ABHD6 and ABHD12. Recent methodological progress allowing kinetic monitoring of glycerol liberation has facilitated substrate profiling of the human endocannabinoid hydrolases, and these studies have revealed that the three enzymes have distinct monoacylglycerol substrate and isomer preferences. Here, we have extended this substrate profiling to cover four prostaglandin glycerol esters, namely, 15-deoxy-Delta(12,14)-prostaglandin J2-2-glycerol (15d-PGJ2-G), PGD2-G, PGE2-G, and PGF2 alpha-G. We found that the three enzymes hydrolyzed the tested substrates, albeit with distinct rates and preferences. Although human ABHD12 (hABHD12) showed only marginal activity toward PGE2-G, hABHD6 preferentially hydrolyzed PGD2-G, and human MAGL (hMAGL) robustly hydrolyzed all four. This was particularly intriguing for MAGL activity toward 15d-PGJ2-G whose hydrolysis rate rivaled that of the best monoacylglycerol substrates. Molecular modeling studies combined with kinetic analysis supported favorable interaction with the hMAGL active site. Long and short MAGL isoforms shared a similar substrate profile, and hMAGL hydrolyzed 15d-PGJ2-G also in living cells. The ability of 15d-PGJ2-G to activate the canonical nuclear factor erythroid 2-related factor (Nrf2) signaling pathway used by 15d-PGJ2 was assessed, and these studies revealed for the first time that 15d-PGJ2 and 15d-PGJ2-G similarly activated Nrf2 signaling as well as transcription of target genes of this pathway. Our study challenges previous claims regarding the ability of MAGL to catalyze PG-G hydrolysis and extend the MAGL substrate profile beyond the classic monoacylglycerols.

Complementary genetic and pharmacological approaches to inhibit monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), the primary hydrolytic enzymes of the respective endogenous cannabinoids 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine, enable the exploration of potential therapeutic applications and physiologic roles of these enzymes. Complete and simultaneous inhibition of both FAAH and MAGL produces greatly enhanced cannabimimetic responses, including increased antinociception, and other cannabimimetic effects, far beyond those seen with inhibition of either enzyme alone. While cannabinoid receptor type 1 (CB1) function is maintained following chronic FAAH inactivation, prolonged excessive elevation of brain 2-AG levels, via MAGL inhibition, elicits both behavioral and molecular signs of cannabinoid tolerance and dependence. Here, we evaluated the consequences of a high dose of the MAGL inhibitor JZL184 [4-nitrophenyl 4-(dibenzo[d][1,3]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate; 40 mg/kg] given acutely or for 6 days in FAAH(-/-) and (+/+) mice. While acute administration of JZL184 to FAAH(-/-) mice enhanced the magnitude of a subset of cannabimimetic responses, repeated JZL184 treatment led to tolerance to its antinociceptive effects, cross-tolerance to the pharmacological effects of Delta(9)-tetrahydrocannabinol, decreases in CB1 receptor agonist-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate binding, and dependence as indicated by rimonabant-precipitated withdrawal behaviors, regardless of genotype. Together, these data suggest that simultaneous elevation of both endocannabinoids elicits enhanced cannabimimetic activity but MAGL inhibition drives CB1 receptor functional tolerance and cannabinoid dependence.

Monoacylglycerol lipase (MAGL) terminates the signaling function of the endocannabinoid, 2-arachidonoylglycerol (2-AG). During 2-AG hydrolysis, MAGL liberates arachidonic acid, feeding the principal substrate for the neuroinflammatory prostaglandins. In cancer cells, MAGL redirects lipid stores toward protumorigenic signaling lipids. Thus MAGL inhibitors may have great therapeutic potential. Although potent and increasingly selective MAGL inhibitors have been described, their number is still limited. Here, we have characterized piperazine and piperidine triazole ureas that combine the high potency attributable to the triazole leaving group together with the bulky aromatic benzodioxolyl moiety required for selectivity, culminating in compound JJKK-048 that potently (IC50 < 0.4 nM) inhibited human and rodent MAGL. JJKK-048 displayed low cross-reactivity with other endocannabinoid targets. Activity-based protein profiling of mouse brain and human melanoma cell proteomes suggested high specificity also among the metabolic serine hydrolases.

The endocannabinoid signaling system regulates diverse physiologic processes and has attracted considerable attention as a potential pharmaceutical target for treating diseases, such as pain, anxiety/depression, and metabolic disorders. The principal ligands of the endocannabinoid system are the lipid transmitters N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG), which activate the two major cannabinoid receptors, CB1 and CB2. Anandamide and 2-AG signaling pathways in the nervous system are terminated by enzymatic hydrolysis mediated primarily by the serine hydrolases fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), respectively. In this review, we will discuss the development of FAAH and MAGL inhibitors and their pharmacological application to investigate the function of anandamide and 2-AG signaling pathways in preclinical models of neurobehavioral processes, such as pain, anxiety, and addiction. We will place emphasis on how these studies are beginning to discern the different roles played by anandamide and 2-AG in the nervous system and the resulting implications for advancing endocannabinoid hydrolase inhibitors as next-generation therapeutics.

BACKGROUND & AIMS: The endocannabinoid and eicosanoid lipid signaling pathways have important roles in inflammatory syndromes. Monoacylglycerol lipase (MAGL) links these pathways, hydrolyzing the endocannabinoid 2-arachidonoylglycerol to generate the arachidonic acid precursor pool for prostaglandin production. We investigated whether blocking MAGL protects against inflammation and damage from hepatic ischemia/reperfusion (I/R) and other insults.
METHODS: We analyzed the effects of hepatic I/R in mice given the selective MAGL inhibitor JZL184, in Mgll(-/-) mice, fatty acid amide hydrolase(-/-) mice, and in cannabinoid receptor type 1(-/-) (CB1-/-) and cannabinoid receptor type 2(-/-) (CB2-/-). Liver tissues were collected and analyzed, along with cultured hepatocytes and Kupffer cells. We measured endocannabinoids, eicosanoids, and markers of inflammation, oxidative stress, and cell death using molecular biology, biochemistry, and mass spectrometry analyses.
RESULTS: Wild-type mice given JZL184 and Mgll(-/-) mice were protected from hepatic I/R injury by a mechanism that involved increased endocannabinoid signaling via CB2 and reduced production of eicosanoids in the liver. JZL184 suppressed the inflammation and oxidative stress that mediate hepatic I/R injury. Hepatocytes were the major source of hepatic MAGL activity and endocannabinoid and eicosanoid production. JZL184 also protected from induction of liver injury by D-(+)-galactosamine and lipopolysaccharides or CCl4.
CONCLUSIONS: MAGL modulates hepatic injury via endocannabinoid and eicosanoid signaling; blockade of this pathway protects mice from liver injury. MAGL inhibitors might be developed to treat conditions that expose the liver to oxidative stress and inflammatory damage.

AIM: The present study tested whether the selective monoacylglycerol lipase (MAGL) inhibitor JZL184 would reduce allodynia and paw edema in the carrageenan test. MAIN
METHODS: The anti-edematous and anti-allodynic effects of JZL184 were compared to those of PF-3845, an inhibitor of fatty acid amide hydrolase (FAAH), and diclofenac, a non-selective cyclooxygenase inhibitor. Cannabinoid receptor involvement in the anti-edematous and anti-allodynic effects of JZL184 was evaluated by administration of the respective CB1 and CB2 receptor antagonists rimonabant and SR144528 as well as with CB1(-/-) and CB2(-/-) mice. JZL184 (1.6, 4, 16, or 40mg/kg) was administered for six days to assess tolerance. KEY FINDINGS: JZL184 administered before or after carrageenan significantly attenuated carrageenan-induced paw edema and mechanical allodynia. Complementary genetic and pharmacological approaches revealed that the anti-allodynic effects of JZL184 required both CB1 and CB2 receptors, but only CB2 receptors mediated its anti-edematous actions. Importantly, both the anti-edematous and anti-allodynic effects underwent tolerance following repeated injections of high dose JZL184 (16 or 40mg/kg), but repeated administration of low dose JZL184 (4mg/kg) retained efficacy. SIGNIFICANCE: These results suggest that the MAGL inhibitor JZL184 reduces inflammatory nociception through the activation of both CB1 and CB2 receptors, with no evidence of tolerance following repeated administration of low doses.

Inhibition of the key hydrolytic enzymes of the endocannabinoid system, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), has been proposed as potential mode of action for various therapeutic applications. Continuing our previous work, we take the first steps of structure-activity relationship exploration and show that 1,3,4-oxadiazol-2-ones can serve as scaffold for both selective FAAH and MAGL inhibitors, and also function as a dual FAAH/MAGL inhibitor at sub-micromolar IC50 values. Moreover, 10-fold selectivity against MAGL over FAAH was achieved with compound 3d (FAAH and MAGL IC50; 2.0 and 0.22muM). Lastly, enzyme and ligand features contributing to the potency and selectivity differences are analysed by molecular docking.

The monoacylglycerol lipase (MAGL) inhibitor 4-nitrophenyl 4-(dibenzo[d][1,3]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate (JZL184) produces antinociceptive and anti-inflammatory effects. However, repeated administration of high-dose JZL184 (40 mg/kg) causes dependence, antinociceptive tolerance, cross-tolerance to the pharmacological effects of cannabinoid receptor agonists, and cannabinoid receptor type 1 (CB1) downregulation and desensitization. This functional CB1 receptor tolerance poses a hurdle in the development of MAGL inhibitors for therapeutic use. Consequently, the present study tested whether repeated administration of low-dose JZL184 maintains its antinociceptive actions in the chronic constriction injury of the sciatic nerve neuropathic pain model and protective effects in a model of nonsteroidal anti-inflammatory drug-induced gastric hemorrhages. Mice given daily injections of high-dose JZL184 (>/=16 mg/kg) for 6 days displayed decreased CB1 receptor density and function in the brain, as assessed in [(3)H]SR141716A binding and CP55,940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl) cyclohexanol]-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate binding assays, respectively. In contrast, normal CB1 receptor expression and function were maintained following repeated administration of low-dose JZL184 (</=8 mg/kg). Likewise, the antinociceptive and gastroprotective effects of high-dose JZL184 underwent tolerance following repeated administration, but these effects were maintained following repeated low-dose JZL184 treatment. Consistent with these observations, repeated high-dose JZL184, but not repeated low-dose JZL184, elicited cross-tolerance to the common pharmacological effects of Delta(9)-tetrahydrocannabinol. This same pattern of effects was found in a rimonabant [(5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyraz ole-3-carboxamide)]-precipitated withdrawal model of cannabinoid dependence. Taken together, these results indicate that prolonged, partial MAGL inhibition maintains potentially beneficial antinociceptive and anti-inflammatory effects, without producing functional CB1 receptor tachyphylaxis/tolerance or cannabinoid dependence.

Monoacylglycerol lipase (MAGL) is a principal metabolic enzyme responsible for hydrolyzing the endogenous cannabinoid (endocannabinoid) 2-arachidonoylglycerol (2-AG). Selective inhibitors of MAGL offer valuable probes to further understand the enzyme's function in biological systems and may lead to drugs for treating a variety of diseases, including psychiatric disorders, neuroinflammation, and pain. N-Hydroxysuccinimidyl (NHS) carbamates have recently been identified as a promising class of serine hydrolase inhibitors that shows minimal cross-reactivity with other proteins in the proteome. Here, we explore NHS carbamates more broadly and demonstrate their potential as inhibitors of endocannabinoid hydrolases and additional enzymes from the serine hydrolase class. We extensively characterize an NHS carbamate 1a (MJN110) as a potent, selective, and in-vivo-active MAGL inhibitor. Finally, we demonstrate that MJN110 alleviates mechanical allodynia in a rat model of diabetic neuropathy, marking NHS carbamates as a promising class of MAGL inhibitors.

Inhibition of the endocannabinoid catabolic enzymes, monoacylglycerol lipase (MAGL) or fatty acid amide hydrolase (FAAH) attenuates naloxone-precipitated opioid withdrawal signs in mice via activation of CB1 receptors. Complete FAAH inhibition blocks only a subset of withdrawal signs, whereas complete MAGL inhibition elicits enhanced antiwithdrawal efficacy, but is accompanied with some cannabimimetic side effects. Thus, the primary objective of the present study was to determine whether combined, full FAAH inhibition and partial MAGL represents an optimal strategy to reduce opioid withdrawal. To test this hypothesis, we examined whether combined administration of high-dose of the FAAH inhibitor PF-3845 and low-dose of the MAGL inhibitor JZL184, as well as the novel dual FAAH-MAGL inhibitor SA-57, which is 100-fold more potent in inhibiting FAAH than MAGL, would prevent spontaneous withdrawal in morphine-dependent mice, a model with greater face validity than precipitating withdrawal with mu-opioid receptor antagonists. Strikingly, a combination of low-dose JZL184 and high-dose PF-3845 as well as the dual inhibitor SA-57 reduced all abrupt withdrawal signs (ie, platform jumping, paw flutters, head shakes, diarrhea, and total body weight loss), but did not elicit any cannabimimetic side effects. In addition, JZL184 or PF-3845 blocked naloxone-precipitated hypersecretion in morphine-dependent small intestinal tissue. Collectively, these results are the first to show that endocannabinoid catabolic enzyme inhibitors reduce abrupt withdrawal in morpine-dependent mice and are effective in a novel in vitro model of opioid withdrawal. More generally, these findings support the idea that joint MAGL and FAAH inhibition represents a promising approach for the treatment of opioid dependence.

The endocannabinoids 2-arachidonoyl glycerol (2-AG) and N-arachidonoyl ethanolamine (anandamide) are principally degraded by monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), respectively. The recent discovery of O-aryl carbamates such as JZL184 as selective MAGL inhibitors has enabled functional investigation of 2-AG signaling pathways in vivo. Nonetheless, JZL184 and other reported MAGL inhibitors still display low-level cross-reactivity with FAAH and peripheral carboxylesterases, which can complicate their use in certain biological studies. Here, we report a distinct class of O-hexafluoroisopropyl (HFIP) carbamates that inhibits MAGL in vitro and in vivo with excellent potency and greatly improved selectivity, including showing no detectable cross-reactivity with FAAH. These findings designate HFIP carbamates as a versatile chemotype for inhibiting MAGL and should encourage the pursuit of other serine hydrolase inhibitors that bear reactive groups resembling the structures of natural substrates.

The endocannabinoid (eCB) system is involved in processes as diverse as control of appetite, perception of pain and the limitation of cancer cell growth and invasion. The enzymes responsible for eCB breakdown are attractive pharmacological targets, and fatty acid amide hydrolase inhibitors, which potentiate the levels of the eCB anandamide, are now undergoing pharmaceutical development. 'Drugable' selective inhibitors of monoacylglycerol lipase, a key enzyme regulating the levels of the other main eCB, 2-arachidonoylglycerol, were however not identified until very recently. Their availability has resulted in a large expansion of our knowledge concerning the pharmacological consequences of monoacylglycerol lipase inhibition and hence the role(s) played by the enzyme in the body. In this review, the pharmacology of monoacylglycerol lipase will be discussed, together with an analysis of the therapeutic potential of monoacylglycerol lipase inhibitors as analgesics and anticancer agents.

In the mammalian central nervous system, monoacylglycerol lipase (MGL) is principally responsible for inactivating the endocannabinoid signaling lipid 2-arachidonoylglycerol (2-AG) and modulates cannabinoid-1 receptor (CB1R) desensitization and signal intensity. MGL is also a drug target for diseases in which CB1R stimulation may be therapeutic. To inform the design of human MGL (hMGL) inhibitors, we have engineered a Leu(Leu(169);Leu(176))-to-Ser(Ser(169);Ser(176)) double hMGL mutant (sol-hMGL) which exhibited enhanced solubility properties, and we further mutated this variant by substituting its catalytic-triad Ser(122) with Cys (sol-S-hMGL). The hMGL variants hydrolyzed both 2-AG and a fluorogenic reporter substrate with comparable affinities. Our results suggest that the hMGL cysteine mutant maintains the same overall architecture as wild-type hMGL. The results also underscore the superior nucleophilic nature of the reactive catalytic Ser(122) residue as compared to that of Cys(122) in the sol-S-hMGL mutant and suggest that the nucleophilic character of the Cys(122) residue is not commensurately enhanced within the three dimensional architecture of hMGL. The interaction of the sol-hMGL variants with the irreversible inhibitors AM6580 and N-arachidonylmaleimide (NAM) and the reversible inhibitor AM10212 was profiled. LC/MS analysis of tryptic digests from sol-S-hMGL directly demonstrate covalent modification of this variant by NAM and AM6580, consistent with enzyme thiol alkylation and carbamoylation, respectively. These data provide insight into hMGL catalysis, the key role of the nucleophilic character of Ser(122), and the mechanisms underlying hMGL inhibition by different classes of small molecules.

The two major endocannabinoid transmitters, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are degraded by distinct enzymes in the nervous system, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), respectively. FAAH and MAGL inhibitors cause elevations in brain AEA and 2-AG levels, respectively, and reduce pain, anxiety, and depression in rodents without causing the full spectrum of psychotropic behavioral effects observed with direct cannabinoid receptor-1 (CB1) agonists. These findings have inspired the development of several classes of endocannabinoid hydrolase inhibitors, most of which have been optimized to show specificity for either FAAH or MAGL or, in certain cases, equipotent activity for both enzymes. Here, we investigate an unusual class of O-hydroxyacetamide carbamate inhibitors and find that individual compounds from this class can serve as selective FAAH or dual FAAH/MAGL inhibitors in vivo across a dose range (0.125-12.5 mg kg(-1)) suitable for behavioral studies. Competitive and click chemistry activity-based protein profiling confirmed that the O-hydroxyacetamide carbamate SA-57 is remarkably selective for FAAH and MAGL in vivo, targeting only one other enzyme in brain, the additional 2-AG hydrolase ABHD6. These data designate O-hydroxyacetamide carbamates as a versatile chemotype for creating endocannabinoid hydrolase inhibitors that display excellent in vivo activity and tunable selectivity for FAAH-anandamide versus MAGL (and ABHD6)-2-AG pathways.

Acute administration of Delta(9)-tetrahydrocannabinol (THC) or exposure to marijuana smoke impairs short-term spatial memory in water maze tasks through a CB(1) receptor mechanism of action. N-Arachidonoylethanolamine (anandamide; AEA) and 2-arachidonoylglycerol (2-AG) are endogenous cannabinoids that are predominantly metabolized by the respective enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). Although the MAGL inhibitor JZL184 enhances short-term synaptic plasticity, it has yet to be evaluated in the Morris water maze. Previous research demonstrated that simultaneous, complete blockade of FAAH and MAGL produces full blown THC-like effects. Thus, in the following studies we tested whether dual blockade of FAAH and MAGL would impair learning in a repeated acquisition Morris water maze task. Mice treated with the dual FAAH/MAGL inhibitor JZL195 (20 mg/kg) as well as JZL184-treated FAAH -/- mice displayed robust deficits in Morris water maze performance that were similar in magnitude to THC-treated mice. While 20 or 40 mg/kg impaired water maze performance in FAAH -/- mice, only the high dose of JZL184 disrupted performance in FAAH +/+ mice. The memory impairing effects of JZL184 were blocked by the CB(1) receptor antagonist rimonabant. Neither JZL184 nor JZL195 impaired performance in a cued version of the water maze task, arguing against the notion that sensorimotor or motivational deficits accounted for the impaired acquisition performance. JZL184 increased 2-AG levels in the hippocampus, prefrontal cortex, and cerebellum to a similar degree in FAAH -/- and +/+ mice. FAAH -/- mice, regardless of drug treatment, possessed elevated AEA levels in each brain region assessed. The results of this study reveal that concomitant increases in AEA and 2-AG disrupt short-term spatial memory performance in a manner similar to that of THC.

Endocannabinoid (eCB) signaling is tightly regulated by eCB biosynthetic and degradative enzymes. The eCB 2-arachidonoylglycerol (2-AG) is hydrolyzed primarily by monoacylglycerol lipase (MAGL). Here, we investigated whether eCB signaling, synaptic function, and learning behavior were altered in MAGL knock-out mice. We report that MAGL(-)/(-) mice exhibited prolonged depolarization-induced suppression of inhibition (DSI) in hippocampal CA1 pyramidal neurons, providing genetic evidence that the inactivation of 2-AG by MAGL determines the time course of the eCB-mediated retrograde synaptic depression. CB(1) receptor antagonists enhanced basal IPSCs in CA1 pyramidal neurons in MAGL(-)/(-) mice, while the magnitude of DSI or CB(1) receptor agonist-induced depression of IPSCs was decreased in MAGL(-)/(-) mice. These results suggest that 2-AG elevations in MAGL(-)/(-) mice cause tonic activation and partial desensitization of CB(1) receptors. Genetic deletion of MAGL selectively enhanced theta burst stimulation (TBS)-induced long-term potentiation (LTP) in the CA1 region of hippocampal slices but had no significant effect on LTP induced by high-frequency stimulation or long-term depression induced by low-frequency stimulation. The enhancement of TBS-LTP in MAGL(-)/(-) mice appears to be mediated by 2-AG-induced suppression of GABA(A) receptor-mediated inhibition. MAGL(-)/(-) mice exhibited enhanced learning as shown by improved performance in novel object recognition and Morris water maze. These results indicate that genetic deletion of MAGL causes profound changes in eCB signaling, long-term synaptic plasticity, and learning behavior.

A high-resolution structure of a ligand-bound, soluble form of human monoglyceride lipase (MGL) is presented. The structure highlights a novel conformation of the regulatory lid-domain present in the lipase family as well as the binding mode of a pharmaceutically relevant reversible inhibitor. Analysis of the structure lacking the inhibitor indicates that the closed conformation can accommodate the native substrate 2-arachidonoyl glycerol. A model is proposed in which MGL undergoes conformational and electrostatic changes during the catalytic cycle ultimately resulting in its dissociation from the membrane upon completion of the cycle. In addition, the study outlines a successful approach to transform membrane associated proteins, which tend to aggregate upon purification, into a monomeric and soluble form.

The endocannabinoid (eCB) 2-arachidonoylglycerol (2-AG) is hydrolysed primarily by monoacylglycerol lipase (MAGL). Here, we investigated whether eCB-mediated retrograde synaptic depression in cerebellar slices was altered in MAGL knockout (MAGL(-/-)) mice. Depolarization-induced suppression of excitation (DSE) and metabotropic glutamate receptor (mGluR1)-mediated synaptic depression are mediated by 2-AG-induced activation of CB(1) receptors. We show that genetic deletion of MAGL prolonged DSE at parallel fibre (PF) or climbing fibre (CF) to Purkinje cell (PC) synapses. Likewise, mGluR1-mediated synaptic depression, induced either by high-frequency stimulation of PF or mGluR1 agonist DHPG, was prolonged in MAGL(-/-) mice. About 15% of 2-AG in the brain is hydrolysed by serine hydrolase alpha-beta-hydrolase domain 6 and 12 (ABHD6 and ABHD12). However, the selective ABHD6 inhibitor WWL123 had no significant effect on cerebellar DSE in MAGL(+/+) and (-/-) mice. The CB(1) receptor antagonist SR141716 significantly increased the amplitude of basal excitatory postsynaptic currents (EPSCs) in MAGL(-/-) mice but not in MAGL(+/+) mice. Conversely, the CB(1) agonist WIN55212 induced less depression of basal EPSCs in MAGL(-/-) mice than in MAGL(+/+) mice. These results provide genetic evidence that inactivation of 2-AG by MAGL determines the time course of eCB-mediated retrograde synaptic depression and that genetic deletion of MAGL causes tonic activation and consequential desensitization of CB(1) receptors.

Monoglyceride lipase (MGL) is a serine hydrolase that hydrolyses 2-arachidonoylglycerol (2-AG) into arachidonic acid and glycerol. 2-AG is an endogenous ligand of cannabinoid receptors, involved in various physiological processes in the brain. We present here the first crystal structure of human MGL in its apo form and in complex with the covalent inhibitor SAR629. MGL shares the classic fold of the alpha/beta hydrolase family but depicts an unusually large hydrophobic occluded tunnel with a highly flexible lid at its entry and the catalytic triad buried at its end. Structures reveal the configuration of the catalytic triad and the shape and nature of the binding site of 2-AG. The bound structure of SAR629 highlights the key interactions for productive binding with MGL. The shape of the tunnel suggests a high druggability of the protein and provides an attractive template for drug discovery.

Monoacylglycerols (MAGs) are short-lived intermediates of glycerolipid metabolism. Specific molecular species, such as 2-arachidonoylglycerol, which is a potent activator of cannabinoid receptors, may also function as lipid signaling molecules. In mammals, enzymes hydrolyzing MAG to glycerol and fatty acids, resembling the final step in lipolysis, or esterifying MAG to diacylglycerol, are well known; however, despite the high level of conservation of lipolysis, the corresponding activities in yeast have not been characterized yet. Here we provide evidence that the protein Yju3p functions as a potent MAG hydrolase in yeast. Cellular MAG hydrolase activity was decreased by more than 90% in extracts of Yju3p-deficient cells, indicating that Yju3p accounts for the vast majority of this activity in yeast. Loss of this activity was restored by heterologous expression of murine monoglyceride lipase (MGL). Since yju3Delta mutants accumulated MAG in vivo only at very low concentrations, we considered the possibility that MAGs are re-esterified into DAG by acyltransferases. Indeed, cellular MAG levels were further increased in mutant cells lacking Yju3p and Dga1p or Lro1p acyltransferase activities. In conclusion, our studies suggest that catabolic and anabolic reactions affect cellular MAG levels. Yju3p is the functional orthologue of mammalian MGL and is required for efficient degradation of MAG in yeast.

2-Arachidonoylglycerol plays a major role in endocannabinoid signaling, and is tightly regulated by the monoacylglycerol lipase (MAGL). Here we report the crystal structure of human MAGL. The protein crystallizes as a dimer, and despite structural homologies to haloperoxidases and esterases, it distinguishes itself by a wide and hydrophobic access to the catalytic site. An apolar helix covering the active site also gives structural insight into the amphitropic character of MAGL, and likely explains how MAGL interacts with membranes to recruit its substrate. Docking of 2-arachidonoylglycerol highlights a hydrophobic and a hydrophilic cavity that accommodate the lipid into the catalytic site. Moreover, we identified Cys201 as the crucial residue in MAGL inhibition by N-arachidonylmaleimide, a sulfhydryl-reactive compound. Beside the advance in the knowledge of endocannabinoids degradation routes, the structure of MAGL paves the way for future medicinal chemistry works aimed at the design of new drugs exploiting 2-arachidonoylglycerol transmission.

Tumor cells display progressive changes in metabolism that correlate with malignancy, including development of a lipogenic phenotype. How stored fats are liberated and remodeled to support cancer pathogenesis, however, remains unknown. Here, we show that the enzyme monoacylglycerol lipase (MAGL) is highly expressed in aggressive human cancer cells and primary tumors, where it regulates a fatty acid network enriched in oncogenic signaling lipids that promotes migration, invasion, survival, and in vivo tumor growth. Overexpression of MAGL in nonaggressive cancer cells recapitulates this fatty acid network and increases their pathogenicity-phenotypes that are reversed by an MAGL inhibitor. Impairments in MAGL-dependent tumor growth are rescued by a high-fat diet, indicating that exogenous sources of fatty acids can contribute to malignancy in cancers lacking MAGL activity. Together, these findings reveal how cancer cells can co-opt a lipolytic enzyme to translate their lipogenic state into an array of protumorigenic signals. PAPERFLICK:

Monoglyceride lipase (MGL) is a serine hydrolase that terminates the signaling of the primary endocannabinoid, 2-arachidonoyl glycerol (2-AG). Versatile high-throughput screening methods allowing the testing of MGL inhibitors are rare, thereby limiting the development and analysis of novel inhibitors. Here we describe an improved fluorescence-based technique that is capable of determining time- and dose-dependent inhibition of MGL with one or multiple binding sites and, at the same time, is capable of revealing the reversibility of inhibitor binding in a simple kinetic assay format. Known reference compounds as well as novel inhibitors, such as JZL184 and CAY10499, were evaluated for their MGL-binding properties and potency.

Depolarization-induced suppression of excitation (DSE) is a major form of cannabinoid-mediated short-term retrograde neuronal plasticity and is found in numerous brain regions. Autaptically cultured murine hippocampal neurons are an architecturally simple model for the study of cannabinoid signaling, including DSE. The transient nature of DSE--tens of seconds--is probably determined by the regulated hydrolysis of the endocannabinoid 2-arachidonoyl glycerol (2-AG). No less than five candidate enzymes have been considered to serve this role: fatty acid amide hydrolase (FAAH), cyclooxygenase-2 (COX-2), monoacylglycerol lipase (MGL), and alpha/beta-hydrolase domain (ABHD) 6 and 12. We previously found that FAAH and COX-2 do not have a role in determining the duration of autaptic DSE. In the current study, we found that two structurally distinct inhibitors of MGL [N-arachidonoyl maleimide and 4-nitrophenyl 4-(dibenzo[d][1,3]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate (JZL184)] prolong DSE in autaptic hippocampal neurons, whereas inhibition of ABHD6 by N-methyl-N-[[3-(4-pyridinyl)phenyl]methyl]-4'-(aminocarbonyl)[1,1'-biphenyl]-4-yl ester, carbamic acid (WWL70) had no effect. In addition, we developed antibodies against MGL and ABHD6 and determined their expression in autaptic cultures. MGL is chiefly expressed at presynaptic terminals, optimally positioned to break down 2-AG that has engaged presynaptic CB(1) receptors. ABHD6 is expressed in two distinct locations on autaptic islands, including a prominent localization in some dendrites. In summary, we provide strong pharmacological and anatomical evidence that MGL regulates DSE in autaptic hippocampal neurons and, taken together with other studies, emphasizes that endocannabinoid signaling is terminated in temporally diverse ways.

Monoglyceride lipase (MGL) plays a major role in the metabolism of the lipid transmitter 2-arachidonoylglycerol (2-AG). This endocannabinoid is known to mediate a large number of physiological processes, and its regulation is thought to be of great therapeutic potential. However, the number of available monoglyceride lipase inhibitors is limited, mostly due to the lack of rapid and accurate pharmacological assays for the enzyme. We have developed a 96-well-format assay for MGL using a nonradiolabeled substrate, 4-nitrophenylacetate. The IC(50) values that were obtained for known inhibitors of MGL using 4-nitrophenylacetate were similar to those reported by using the radiolabeled form of an endogenous substrate, 2-oleoylglycerol. In a first small-scale screening, we identified CAY10499 as a novel monoglyceride lipase inhibitor. Thus, we report here the characterization of this submicromolar inhibitor, which acts on MGL through an unprecedented mechanism for inhibitors of this enzyme.

Endogenous ligands for cannabinoid receptors ("endocannabinoids") include the lipid transmitters anandamide and 2-arachidonoylglycerol (2-AG). Endocannabinoids modulate a diverse set of physiological processes and are tightly regulated by enzymatic biosynthesis and degradation. Termination of anandamide signaling by fatty acid amide hydrolase (FAAH) is well characterized, but less is known about the inactivation of 2-AG, which can be hydrolyzed by multiple enzymes in vitro, including FAAH and monoacylglycerol lipase (MAGL). Here, we have taken a functional proteomic approach to comprehensively map 2-AG hydrolases in the mouse brain. Our data reveal that approximately 85% of brain 2-AG hydrolase activity can be ascribed to MAGL, and that the remaining 15% is mostly catalyzed by two uncharacterized enzymes, ABHD6 and ABHD12. Interestingly, MAGL, ABHD6, and ABHD12 display distinct subcellular distributions, suggesting that they may control different pools of 2-AG in the nervous system.

Monoacylglycerol lipase (MAGL) is a key enzyme responsible for the termination of endocannabinoid signaling. Its crucial role in 2-arachidonoylglycerol (2-AG) metabolism, together with the numerous pharmacological properties mediated by this endocannabinoid, emphasize the interest in MAGL as therapeutic target, along with the need to design potent and selective inhibitors. Meanwhile, the complexity of 2-AG degradation pathways underscores the need to use a purified source of enzyme in evaluation studies of new inhibitors. We report here the first heterologous expression and purification of human MAGL. A highly pure protein was obtained and allowed us to measure the affinity of several MAGL inhibitors for the human enzyme. Importantly, disulfiram (tetraethylthiuram disulfide), a compound used to treat alcoholism, and other disulfide-containing compounds were shown to inhibit MAGL with good potency, likely through an interaction with cysteine residues.

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.

After the completion of a draft human genome sequence, the International Human Genome Sequencing Consortium has proceeded to finish and annotate each of the 24 chromosomes comprising the human genome. Here we describe the sequencing and analysis of human chromosome 3, one of the largest human chromosomes. Chromosome 3 comprises just four contigs, one of which currently represents the longest unbroken stretch of finished DNA sequence known so far. The chromosome is remarkable in having the lowest rate of segmental duplication in the genome. It also includes a chemokine receptor gene cluster as well as numerous loci involved in multiple human cancers such as the gene encoding FHIT, which contains the most common constitutive fragile site in the genome, FRA3B. Using genomic sequence from chimpanzee and rhesus macaque, we were able to characterize the breakpoints defining a large pericentric inversion that occurred some time after the split of Homininae from Ponginae, and propose an evolutionary history of the inversion.

Monoglyceride lipase (MGL) functions together with hormone-sensitive lipase to hydrolyze intracellular triglyceride stores of adipocytes and other cells to fatty acids and glycerol. In addition, MGL presumably complements lipoprotein lipase in completing the hydrolysis of monoglycerides resulting from degradation of lipoprotein triglycerides. Cosmid clones containing the mouse MGL gene were isolated from a genomic library using the coding region of the mouse MGL cDNA as probe. Characterization of the clones obtained revealed that the mouse gene contains the coding sequence for MGL on seven exons, including a large terminal exon of approximately 2.6 kb containing the stop codon and the complete 3' untranslated region. Two different 5' leader sequences, diverging 21 bp upstream of the predicted translation initiation codon, were isolated from a mouse adipocyte cDNA library. Western blot analysis of different mouse tissues revealed protein size heterogeneities. The amino acid sequence derived from human MGL cDNA clones showed 84% identity with mouse MGL. The mouse MGL gene was mapped to chromosome 6 in a region with known homology to human chromosome 3q21.

A novel poxvirus gene has been characterized within the genome of ectromelia virus. It has significant similarity to a family of lysophospholipases suggesting that it may function in the degradation of lysophospholipids. Since these molecules are active in the stimulation of inflammation, we hypothesize that this gene may play a role in virus virulence. This gene is expressed early in the ectromelia virus replication cycle, before DNA replication. We have also characterized a human cDNA that encodes a protein which is 49.5% identical to the ectromelia virus protein. By its presence in multiple cDNA libraries, this human gene is known to be expressed in a variety of body tissues and is likely to function in the normal regulation of lysophospholipid levels. This family of proteins have conserved blocks of amino acids that are indicative of a serine-aspartic acid-histidine catalytic triad, similar to those used by true lipases and a number of esterases.