The endocannabinoid 2-arachidonoylglycerol and dual ABHD6/MAGL enzyme inhibitors display neuroprotective and anti-inflammatory actions in the in vivo retinal model of AMPA excitotoxicity

• Published in: Neuropharmacology Vol. 185; p. 108450
• Main Authors: Kokona, Despina, Spyridakos, Dimitris, Tzatzarakis, Manolis, Papadogkonaki, Sofia, Filidou, Eirini, Arvanitidis, Konstantinos I., Kolios, George, Lamani, Manjunath, Makriyannis, Alexandros, Malamas, Michael S., Thermos, Kyriaki
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-03-2021
• Subjects: 2-Arachidonoylglycerol; ABHD6; CB1/CB2 cannabinoid receptors; MAGL; Microglia; Neuroinflammation; Neuroprotection; PI3K/Akt; Retina; Neuroprotection; 2-Arachidonoylglycerol; CB1/CB2 cannabinoid receptors; Retina; Neuroinflammation; ABHD6; MAGL; PI3K/Akt; Microglia
• ISSN: 0028-3908; 1873-7064
• DOI: 10.1016/j.neuropharm.2021.108450

The endocannabinoid system has been shown to be a putative therapeutic target for retinal disease. Here, we aimed to investigate the ability of the endocannabinoid 2-arachidonoylglycerol (2-AG) and novel inhibitors of its metabolic enzymes, α/β-hydrolase domain-containing 6 (ABHD6) and monoacylglycerol lipase (MAGL), a) to protect the retina against excitotoxicity and b) the mechanisms involved in the neuroprotection. Sprague-Dawley rats, wild type and Akt2−/− C57BL/6 mice were intravitreally administered with phosphate-buffered saline or (RS)-α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid hydrobromide (AMPA). 2-AG was intravitreally co-administered with AMPA in the absence and presence of AM251 or AM630 (cannabinoid 1 and 2 receptor antagonists, respectively) or Wortmannin [Phosphoinositide 3-Kinase (PI3K)/Akt inhibitor]. Inhibitors of ABHD6 and dual ABHD6/MAGL (AM12100 and AM11920, respectively) were co-administered with AMPA intravitreally in rats. Immunohistochemistry was performed using antibodies raised against retinal neuronal markers (bNOS), microglia (Iba1) and macroglia (GFAP). TUNEL assay and real-time PCR were also employed. The CB2 receptor was expressed in rat retina (approx. 62% of CB1 expression). 2-AG attenuated the AMPA-induced increase in TUNEL+ cells. 2-AG activation of both CB1 and CB2 receptors and the PI3K/Akt downstream signaling pathway, as substantiated by the use of Akt2−/− mice, afforded neuroprotection against AMPA excitotoxicity. AM12100 and AM11920 attenuated the AMPA-induced glia activation and produced a dose-dependent partial neuroprotection, with the dual inhibitor AM11920 being more efficacious. These results show that 2-AG has the pharmacological profile of a putative therapeutic for retinal diseases characterized by neurodegeneration and neuroinflammation, when administered exogenously or by the inhibition of its metabolic enzymes.
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•Acute 2-arachidonoylglycerol treatment protects the retina against excitotoxicity.•CB1/CB2 receptors/PI3/Akt downstream signaling pathway mediate 2-AG neuroprotection.•ABHD6/MAGL inhibitors protect amacrine cells and reduce micro/macroglia activation.