Blockade of monoacylglycerol lipase inhibits oligodendrocyte excitotoxicity and prevents demyelinationin vivo

Abstract

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.

Lesion Expansion in Experimental Demyelination Animal Models and Multiple Sclerosis Lesions

“…We assume that the increased activation of microglia/monocytes and/or astrocytes in the white compared to the gray matter results in a higher lesion expansion. In support of this assumption is the observation that in the cuprizone model, explicit microgliosis is evident in regions of profound demyelination [62], that prevention of demyelination is paralleled by a reduced activation of microglia cells [63][64][65], and that the application of the microglia inhibitor minocycline [66] ameliorates demyelination in the cuprizone model [67]. Similar observations have been reported in the LPC model [68].…”

A Basal Tone of 2-Arachidonoylglycerol Contributes to Early Oligodendrocyte Progenitor Proliferation by Activating Phosphatidylinositol 3-Kinase (PI3K)/AKT and the Mammalian Target of Rapamycin (MTOR) Pathways

“…In fact, the increase of 2-AG availability by inhibiting the activity of monoacylglycerol lipase with JZL-184 restored cell proliferation in the absence of mitogens present in the culture media, an effect mimicked by exogenously added 2-AG. Interestingly, a recent report showed that JZL-184 protects oligodendrocytes in vitro from excitotoxic injury mediated by activation of AMPA receptors, an effect involving the activation of CB1 receptors (Bernal-Chico et al 2015).…”

Promoting in vivo remyelination with small molecules: a neuroreparative pharmacological treatment for Multiple Sclerosis

“…The protocol used was modified from previously described80. Demyelination was induced by feeding 8 weeks old male C57/BL6 mice ad libitum with 0.2% cuprizone (bis-cyclo-hexanone-oxaldihydrazone; Sigma) mixed with milled chow (Altromin) for 5 weeks.…”

“…The corpus callosum of three animals per condition was studied. For histological examination, forebrain coronal sections (20 μm) were taken of the rostral part of the corpus callosum as previously described8081 and stained with eriochrome cyanine using a standard protocol in order to study the myelin. Briefly, cryosections on glass slides were immersed in acetone for 5 minutes, dried and submerged in eriochrome cyanine solution (Sigma) for 1 hour and then differentiated in 5% (w/v) iron alum for 5–10 minutes, followed by a second differentiation with borax-ferricyanide solution for 5 minutes.…”