Phospholipase A2 (PLA2) enzymes are considered the primary source of arachidonic acid for cyclooxygenase (COX)-mediated biosynthesis of prostaglandins. Here, we show that a distinct pathway exists in brain, where monoacylglycerol lipase (MAGL) hydrolyzes the endocannabinoid 2-arachidonoylglycerol to generate a major arachidonate precursor pool for neuroinflammatory prostaglandins. MAGL-disrupted animals show neuroprotection in a parkinsonian mouse model. These animals are spared the hemorrhaging caused by COX inhibitors in the gut, where prostaglandins are instead regulated by cytosolic-PLA2. These findings identify MAGL as a distinct metabolic node that couples endocannabinoid to prostaglandin signaling networks in the nervous system and suggest that inhibition of this enzyme may be a new and potentially safer way to suppress the proinflammatory cascades that underlie neurodegenerative disorders.

Summary Cancer cells couple heightened lipogenesis with lipolysis to produce fatty acid networks that support malignancy. Monoacylglycerol lipase (MAGL) plays a principal role in this process by converting monoglycerides, including the endocannabinoid 2-arachidonoylglycerol (2-AG), to free fatty acids. Here, we show that MAGL is elevated in androgen-independent versus androgen-dependent human prostate cancer cell lines, and that pharmacological or RNA-interference disruption of this enzyme impairs prostate cancer aggressiveness. These effects were partially reversed by treatment with fatty acids or a cannabinoid receptor-1 (CB1) antagonist, and fully reversed by co-treatment with both agents. We further show that MAGL is part of a gene signature correlated with epithelial-to-mesenchymal transition and the stem-like properties of cancer cells, supporting a role for this enzyme in pro-tumorigenic metabolism that, for prostate cancer, involves the dual control of endocannabinoid and fatty acid pathways.

Delta(9)-tetrahydrocannabinol (THC), the psychoactive ingredient of marijuana, has useful medicinal properties but also undesirable side effects. The brain receptor for THC, CB(1), is also activated by the endogenous cannabinoids anandamide and 2-arachidonylglycerol (2-AG). Augmentation of endocannabinoid signaling by blockade of their metabolism may offer a more selective pharmacological approach compared with CB(1) agonists. Consistent with this premise, inhibitors of the anandamide-degrading enzyme fatty acid amide hydrolase (FAAH) produce analgesic and anxiolytic effects without cognitive defects. In contrast, we show that dual blockade of the endocannabinoid-degrading enzymes monoacylglycerol lipase (MAGL) and FAAH by selected organophosphorus agents leads to greater than ten-fold elevations in brain levels of both 2-AG and anandamide and to robust CB(1)-dependent behavioral effects that mirror those observed with CB(1) agonists. Arachidonic acid levels are decreased by the organophosphorus agents in amounts equivalent to elevations in 2-AG, which indicates that endocannabinoid and eicosanoid signaling pathways may be coordinately regulated in the brain.

The structure-activity relationships of organophosphorus (OP) and organosulfur compounds were examined in vitro and in vivo as inhibitors of mouse brain monoacylglycerol lipase (MAGL) hydrolysis of 2-arachidonoylglycerol (2-AG) and agonist binding at the CB1 receptor. Several compounds showed exceptional potency towards MAGL activity with IC 50 values of 0.1-10 nM in vitro and high inihibition at 10 mg/kg intraperitoneally in mice. We find for the first time that MAGL activity is a major in vivo determinant of 2-AG and arachidonic acid levels not only in brain but also in spleen, lung and liver. Apparent direct OP inhibition of CB1 agonist binding may be due instead to metabolic stabilization of 2-AG in brain membranes as the actual inhibitor. Keywords Monoacylglycerol lipase inhibitors; 2-Arachidonoylglycerol; Arachidonic acidThe endocannabinoids (EC) 2-arachidonoylglycerol (2-AG) and anandamide (AEA) regulate a diverse array of neurological and metabolic functions and are altered by neuropathic pain, anxiety, neurodegeneration, obesity and cardiovascular disorders. 1 2-AG is a full agonist towards the cannabinoid receptor type 1 (CB1) and its signaling is terminated primarily by monoacylglycerol lipase (MAGL). AEA levels are regulated by fatty acid amide hydrolase (FAAH). 2-4 Augmentation of EC signaling by blockade of 2-AG or AEA degradation (Scheme 1) is proposed as a therapeutic strategy. However, characterization of MAGL or 2-AG in brain and peripheral tissues is hindered by the paucity of systemic MAGL inhibitors and lack of a MAGL knockout mouse. Discovery of potent MAGL inhibitors is therefore essential in understanding the biochemical, physiological and therapeutic roles of this enzyme.Structural manipulation of organophosphorus (OP) and organosulfur (OS) compounds (Scheme 2) can potentially confer potency and selectivity for MAGL and FAAH compared to * Corresponding author. Tel.: +1 510 642 5424; fax: +1 510 642 6497. E-mail address: ectl@nature.berkeley.edu (J.E. Casida). Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. This study reports structure-activity relationships of OPs and OSs with MAGL, FAAH and CB1 and uses these tools to consider three interrelationships of the EC system components. The first is the in vitro potency for inhibiting MAGL, FAAH and CB1 agonist binding as a predictor of in vivo behavioral effects and pharmacological profile. The second is the variation among tissues in their MAGL activity and differential regulation of 2-AG and AA levels. Finally we consider the possibility that OP displacement of CB1 agonist binding is due to 2...

Serine hydrolase KIAA1363 is an acetyl monoalkylglycerol ether (AcMAGE) hydrolase involved in tumor cell invasiveness. It is also an organophosphate (OP) insecticide-detoxifying enzyme. The key to understanding these dual properties was the use of KIAA1363 +/+ (wildtype) and -/- (gene deficient) mice to define the role of this enzyme in brain and other tissues and its effectiveness in vivo in reducing OP toxicity. KIAA1363 was the primary AcMAGE hydrolase in brain, lung, heart and kidney and was highly sensitive to inactivation by chlorpyrifos oxon (CPO) (IC50 2 nM) [the bioactivated metabolite of the major insecticide chlorpyrifos (CPF)]. Although there was no difference in hydrolysis product monoalkylglycerol ether (MAGE) levels in +/+ and -/- mouse brains in vivo, isopropyl dodecylfluorophosphonate (30 mg/kg) and CPF (100 mg/kg) resulted in 23-51% decrease in brain MAGE levels consistent with inhibition of AcMAGE hydrolase activity. On incubating +/+ and -/- brain membranes with AcMAGE and cytidine-5'-diphosphocholine, the absence of KIAA1363 activity dramatically increased de novo formation of platelet-activating factor (PAF) and lyso-PAF, signifying that metabolically-stabilized AcMAGE can be converted to this bioactive lipid in brain. On considering detoxification, KIAA1363 -/- mice were significantly more sensitive than +/+ mice to ip-administered CPF (100 mg/kg) and parathion (10 mg/kg) with increased tremoring and mortality that correlated for CPF with greater brain acetylcholinesterase inhibition. Docking AcMAGE and CPO in a KIAA1363 active site model showed similar positioning of their acetyl and trichloropyridinyl moieties, respectively. This study establishes the relevance of KIAA1363 in ether lipid metabolism and OP detoxification.