The endocannabinoids 2-araquidonoylglycerol (2-AG) and anandamide (AEA) are bioactive lipids crucially involved in the regulation of brain function in basal and pathological conditions. Blockade of endocannabinoid metabolism has emerged as a promising therapeutic strategy for inflammatory diseases of the central nervous system, including myelin disorders such as multiple sclerosis. Nevertheless, the biological actions of endocannabinoid degradation inhibitors in oligodendrocytes and white matter tracts are still ill defined. Here we show that the selective monoacylglycerol lipase (MAGL) inhibitor JZL184 suppressed cell death by mild activation of AMPA receptors in oligodendrocytes in vitro, an effect that was mimicked by MAGL substrate 2-AG and by the second major endocannabinoid AEA, in a concentration-dependent manner, whereas inhibition of the AEA metabolizing enzyme fatty acid amide hydrolase with URB597 was devoid of effect. Pharmacological experiments suggested that oligodendrocyte protection from excitotoxicity resulting from MAGL blockade involved the activation of cannabinoid CB1 receptors and the reduction of AMPA-induced cytosolic calcium overload, mitochondrial membrane depolarization, and production of reactive oxygen species. Administration of JZL184 under a therapeutic regimen decreased clinical severity, prevented demyelination, and reduced inflammation in chronic experimental autoimmune encephalomyelitis. Furthermore, MAGL inactivation robustly preserved myelin integrity and suppressed microglial activation in the cuprizone-induced model of T-cell-independent demyelination. These findings suggest that MAGL blockade may be a useful strategy for the treatment of immune-dependent and -independent damage to the white matter.

Multiple sclerosis (MS) is a chronic demyelinating disease of unknown etiology in which tissue pathology suggests both immune-dependent attacks to oligodendroglia and primary oligodendrocyte demise. The endocannabinoid system has been crucially involved in the control of autoimmune demyelination and cannabinoid-based therapies exhibit therapeutic potential, but also limitations, in MS patients. In this context, growing evidence suggests that targeting the hydrolysis of the main endocannabinoid 2-arachidonoylglycerol (2-AG) may offer a more favorable benefit-to-risk balance in MS than existing cannabinoid medicines. Here we evaluated the modulation of endocannabinoid signaling and the therapeutic potential of targeting the 2-AG hydrolytic enzyme alpha/beta-hydrolase domain-containing 6 (ABHD6) in the cuprizone model of non-immune dependent demyelination. The concentrations of N-arachidonoylethanolamine (anandamide, AEA) and its congener N-palmitoylethanolamine (PEA) were reduced following 6 weeks of cuprizone feeding. Deregulation of AEA and PEA levels was not due to differences in the expression of the hydrolytic and biosynthetic enzymes fatty acid amide hydrolase and N-acylphosphatidylethanolamine-phospholipase D, respectively. Conversely, we measured elevated transcript levels of 2-AG hydrolytic enzymes monoacylglycerol lipase, ABHD6 and ABHD12 without changes in bulk 2-AG concentration. Upregulated CB and CB receptors expression, ascribed in part to microglia, was also detected in the brain of cuprizone-treated mice. Administration of an ABHD6 inhibitor partially attenuated myelin damage, astrogliosis and microglia/macrophage reactivity associated to cuprizone feeding. However, ABHD6 blockade was ineffective at engaging protective or differentiation promoting effects in oligodendrocyte cultures. These results show specific alterations of the endocannabinoid system and modest beneficial effects resulting from ABHD6 inactivation in a relevant model of primary demyelination.

No abstract