Equipotent Inhibition of Fatty Acid Amide Hydrolase and Monoacylglycerol Lipase – Dual Targets of the Endocannabinoid System to Protect against Seizure Pathology

Abstract

Advances in the understanding of the endogenous cannabinoid system have led to several therapeutic indications for new classes of compounds that enhance cannabinergic responses. Endocannabinoid levels are elevated during pathogenic conditions, and inhibitors of endocannabinoid inactivation promote such on-demand responses. The endocannabinoids anandamide and 2-arachidonoyl glycerol have been implicated in protective signaling against excitotoxic episodes, including seizures. To better understand modulatory pathways that can exploit such responses, we used the new generation compound AM6701 that blocks both the anandamide-deactivating enzyme fatty acid amide hydrolase (FAAH) and the 2-arachidonoyl glycerol-deactivating enzyme monoacylglycerol lipase (MAGL) with equal potency. Also studied was the structural isomer AM6702 which is 44-fold more potent for inhibiting FAAH versus MAGL. When applied before and during kainic acid (KA) exposure to cultured hippocampal slices, AM6701 protected against the resulting excitotoxic events of calpain-mediated cytoskeletal damage, loss of presynaptic and postsynaptic proteins, and pyknotic changes in neurons. The equipotent inhibitor was more effective than its close relative AM6702 at protecting against the neurodegenerative cascade assessed in the slice model. In vivo, AM6701 was also the more effective compound for reducing the severity of KA-induced seizures and protecting against behavioral deficits linked to seizure damage. Corresponding with the behavioral improvements, cytoskeletal and synaptic protection was elicited by AM6701, as found in the KA-treated hippocampal slice model. It is proposed that the influence of AM6701 on FAAH and MAGL exerts a synergistic action on the endocannabinoid system, thereby promoting the protective nature of cannabinergic signaling to offset excitotoxic brain injury.

Blast waves from detonated military explosive reduce GluR1 and synaptophysin levels in hippocampal slice cultures

“…In Fig. 6, the synaptic decline profile induced by RDX detonations was compared to 1) synaptic declines reported in excitotoxicity studies using hippocampal slice cultures (Bahr et al, 2002; Karanian et al, 2005; Naidoo et al, 2012) vs . 2) hippocampal slice synaptic declines from protein accumulation stress studies (Bendiske and Bahr, 2003; Butler et al, 2007; Wisniewski et al, 2011).…”

Cannabinoids and Epilepsy

“…Inhibition of both FAAH (with AM374) and the anandamide reuptake transporter (with AM404) in rat hippocampus prevented α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced excitotoxic insults (cytoskeletal damage and synaptic decline) in vitro and behavioral and memory impairment in vivo [149]. Blockage of FAAH and DAGLα (with AM6701, 5 mg/kg) raised levels of anandamide and 2-AG, protected against KA (10 mg/kg)-induced seizures, and reduced seizure-induced cytotoxicity [150]. The endocannabinoids, methanandamide, and 2-AG reduced neuronal firing in a low Mg 2+ in vitro model of status epilepticus, in a d o s e -d e p e n d e n t m a n n e r ( E C 5 0 1 4 5 ± 4 .…”

Elevating endocannabinoid levels: pharmacological strategies and potential therapeutic applications

“…Interestingly, however, another dual inhibitor of FAAH and MAG lipase, AM6701 (Fig. 1c), has been reported to reduce both severity of seizures and impairment of rotarod and balance beam performance induced in rats by kainic acid with significantly greater efficacy than AM6702, a compound that is significantly more potent at inhibiting FAAH than MAG lipase (78) . A dual inhibitor of FAAH and MAG lipase might of course have an acceptable benefit-to-risk ratio if, for example, its distribution is restricted to one or more particular regions of the body.…”