Endocannabinoid Overload

The signaling capacity of endogenous cannabinoids (“endocannabinoids”) is tightly regulated by degradative enzymes. This Perspective highlights a research article in this issue (p. 996) in which the authors show that genetic disruption of monoacylglycerol lipase (MAGL), the principal degradative enzyme for the endocannabinoid 2-arachidonoylglycerol (2-AG), causes marked elevations in 2-AG levels that lead to desensitization of brain cannabinoid receptors. These findings highlight the central role that MAGL plays in endocannabinoid metabolism in vivo and reveal that excessive 2-AG signaling can lead to functional antagonism of the brain cannabinoid system

Preclinical characterization and first-in-human administration of a selective monoacylglycerol Lipase inhibitor, ABX-1431

Preclinical characterization and first-in-human administration of a selective monoacylglycerol lipase inhibitor, ABX-1431 Iain Fraser1*, Jacqueline Blankman1, Jason Clapper1, Cheryl Grice1, Gary O'Neill1, Alan Ezekowitz1, Archie Thurston2, Els Geenens3, Corinne Vandermeulen3 and Jan De Hoon3 1 Abide Therapeutics, N/A, United States 2 Seventh Wave Laboratories, N/A, United States 3 UZ Leuven, Center for Clinical Pharmacology, Belgium Background: Monoacylglycerol lipase (MGLL) is a serine hydrolase that breaks down 2-arachidonoylglycerol (2-AG), the major endocannabinoid. Inhibiting MGLL enhances 2-AG concentrations locally, which is expected to rectify neurotransmitter balance through activation of presynaptic CB1 receptors. ABX-1431 is a first-in-class, orally-available, selective, and potent covalent inhibitor of MGLL being developed for the treatment of diseases like multiple sclerosis, movement disorders and pain. Methods: ABX-1431 entered clinical studies supported by a comprehensive preclinical dossier. Selectivity for MGLL amongst other serine hydrolases was profiled using activity-based protein profiling, and MGLL enzyme-recovery kinetics were established. A translatable assay using peripheral blood mononuclear cells (PBMC) was developed to monitor clinical target engagement. ABX-1431 was evaluated in sequential single-, and multiple-ascending dose panels of healthy volunteers. Results: ABX-1431 doses administered orally were 2 to 200 mg as single doses, and 10 to 40 mg daily as multiple doses. Plasma concentrations of ABX-1431 increased in a dose-related fashion, with minimal accumulation. MGLL activity in PBMC was inhibited in a time- and dose-related fashion, with recovery of enzyme activity as drug concentrations declined. Central nervous system manifestations, consistent with activation of the endocannabinoid system were observed at higher doses of ABX-1431. Additional clinical assessments of mood, suicidality, cutaneous nociception and cognition revealed no clinically significant abnormalities. Conclusions: At oral doses that were generally safe and well-tolerated, ABX-1431 plasma concentrations and magnitude of inhibition of PBMC MGLL enzyme activity were similar to those associated with efficacy in preclinical models, supporting the continued clinical evaluation of this first-in-mechanism MGLL inhibitor.status: Published onlin

Activation of the endocannabinoid system by organophosphorus nerve agents

D 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 endogenous cannabinoid ('endocannabinoid') system consists of G protein-coupled cannabinoid receptors (CB 1 and CB 2 ) that bind two principal endogenous ligands: 2-AG (1) 1 and N-arachidonoylethanolamine (anandamide, 2) 2 (Scheme 1). Endocannabinoids regulate a diverse array of neurological (for example, memory and motility) and metabolic (for example, feeding and lipolysis) functions, and their levels are altered under pathophysiological conditions, including pain, anxiety, neurodegenerative disease, brain injury and metabolic disorders Cannabinoid receptors not only recognize endogenous lipid ligands but are also targets of exogenous agonists, the best known of which is THC (3), the principal psychoactive constituent of marijuana 14 . THC and other CB 1 agonists produce an array of intense behavioral effects, some of which, such as pain relief, have possible therapeutic utility. However, the beneficial properties of CB 1 agonists are accompanied by a number of untoward side effects, including hypomotility, hypothermia and cognitive dysfunction 14 . CB 1 agonists have also shown abuse potential in rodents, leading to dependence and withdrawal 14 . These findings raise legitimate concerns about the therapeutic potential of direct CB 1 agonists. Augmentation of endocannabinoid signaling by blockade of 2-AG and/or anandamide degradation has been proposed as an alternative therapeutic strategy that might produce a selective subset of the behavioral effects observed with direct CB 1 agonists 15 . Consistent with this premise, Faah -/-mice or rodents treated with FAAH inhibitors show elevated brain levels of anandamide (but not 2-AG) and exhibit analgesic, anxiolytic and antidepressant phenotypes without concomitant alterations in motility, cognition or body temperature Organophosphorus (OP) nerve agents produce their primary neurotoxicity through inactivation of acetylcholinesterase (AChE). However, many of the pharmacological effects of OP agents cannot be explained by disruption of cholinergic transmissio

Metabolic Interplay between Astrocytes and Neurons Regulates Endocannabinoid Action

The endocannabinoid 2-arachidonoylglycerol (2-AG) is a retrograde lipid messenger that modulates synaptic function, neurophysiology, and behavior. 2-AG signaling is terminated by enzymatic hydrolysis—a reaction that is principally performed by monoacylglycerol lipase (MAGL). MAGL is broadly expressed throughout the nervous system, and the contributions of different brain cell types to the regulation of 2-AG activity in vivo remain poorly understood. Here, we genetically dissect the cellular anatomy of MAGL-mediated 2-AG metabolism in the brain and show that neurons and astrocytes coordinately regulate 2-AG content and endocannabinoid-dependent forms of synaptic plasticity and behavior. We also find that astrocytic MAGL is mainly responsible for converting 2-AG to neuroinflammatory prostaglandins via a mechanism that may involve transcellular shuttling of lipid substrates. Astrocytic-neuronal interplay thus provides distributed oversight of 2-AG metabolism and function and, through doing so, protects the nervous system from excessive CB1 receptor activation and promotes endocannabinoid crosstalk with other lipid transmitter systems

Chronic monoacylglycerol lipase blockade causes functional antagonism of the endocannabinoid system

Prolonged exposure to drugs of abuse, such as cannabinoids and opioids, leads to pharmacological tolerance and receptor desensitization in the nervous system. We found that a similar form of functional antagonism was produced by sustained inactivation of monoacylglycerol lipase (MAGL), the principal degradative enzyme for the endocannabinoid 2-arachidonoylglycerol. After repeated administration, the MAGL inhibitor JZL184 lost its analgesic activity and produced cross-tolerance to cannabinoid receptor (CB1) agonists in mice, effects that were phenocopied by genetic disruption of Mgll (encoding MAGL). Chronic MAGL blockade also caused physical dependence, impaired endocannabinoid-dependent synaptic plasticity and desensitized brain CB1 receptors. These data contrast with blockade of fatty acid amide hydrolase, an enzyme that degrades the other major endocannabinoid anandamide, which produced sustained analgesia without impairing CB1 receptors. Thus, individual endocannabinoids generate distinct analgesic profiles that are either sustained or transitory and associated with agonism and functional antagonism of the brain cannabinoid system, respectively

The Serine Hydrolase ABHD6 Is a Critical Regulator of the Metabolic Syndrome

The serine hydrolase α/β hydrolase domain 6 (ABHD6) has recently been implicated as a key lipase for the endocannabinoid 2-arachidonylglycerol (2-AG) in the brain. However, the biochemical and physiological function for ABHD6 outside of the central nervous system has not been established. To address this, we utilized targeted antisense oligonucleotides (ASOs) to selectively knock down ABHD6 in peripheral tissues in order to identify in vivo substrates and understand ABHD6’s role in energy metabolism. Here, we show that selective knockdown of ABHD6 in metabolic tissues protects mice from high-fat-diet-induced obesity, hepatic steatosis, and systemic insulin resistance. Using combined in vivo lipidomic identification and in vitro enzymology approaches, we show that ABHD6 can hydrolyze several lipid substrates, positioning ABHD6 at the interface of glycerophospholipid metabolism and lipid signal transduction. Collectively, these data suggest that ABHD6 inhibitors may serve as therapeutics for obesity, nonalcoholic fatty liver disease, and type II diabetes