The antinociceptive triterpene β‐amyrin inhibits 2‐arachidonoylglycerol (2‐AG) hydrolysis without directly targeting cannabinoid receptors
Open Access
- 30 May 2012
- journal article
- research article
- Published by Wiley in British Journal of Pharmacology
- Vol. 167 (8), 1596-1608
- https://doi.org/10.1111/j.1476-5381.2012.02059.x
Abstract
BACKGROUND AND PURPOSE Pharmacological activation of cannabinoid CB1 and CB2 receptors is a therapeutic strategy to treat chronic and inflammatory pain. It was recently reported that a mixture of natural triterpenes α- and β-amyrin bound selectively to CB1 receptors with a subnanomolar Ki value (133 pM). Orally administered α/β-amyrin inhibited inflammatory and persistent neuropathic pain in mice through both CB1 and CB2 receptors. Here, we investigated effects of amyrins on the major components of the endocannabinoid system. EXPERIMENTAL APPROACH We measured CB receptor binding interactions of α- and β-amyrin in validated binding assays using hCB1 and hCB2 transfected CHO-K1 cells. Effects on endocannabinoid transport in U937 cells and breakdown using homogenates of BV2 cells and pig brain, as well as purified enzymes, were also studied. KEY RESULTS There was no binding of either α- or β-amyrin to hCB receptors in our assays (Ki > 10 µM). The triterpene β-amyrin potently inhibited 2-arachidonoyl glycerol (2-AG) hydrolysis in pig brain homogenates, but not that of anandamide. Although β-amyrin only weakly inhibited purified human monoacylglycerol lipase (MAGL), it also inhibited α,β-hydrolases and more potently inhibited 2-AG breakdown than α-amyrin and the MAGL inhibitor pristimerin in BV2 cell and pig brain homogenates. CONCLUSIONS AND IMPLICATIONS We propose that β-amyrin exerts its analgesic and anti-inflammatory pharmacological effects via indirect cannabimimetic mechanisms by inhibiting the degradation of the endocannabinoid 2-AG without interacting directly with CB receptors. Triterpenoids appear to offer a very broad and largely unexplored scaffold for inhibitors of the enzymic degradation of 2-AG. LINKED ARTICLES This article is part of a themed section on Cannabinoids. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.167.issue-8This publication has 52 references indexed in Scilit:
- The serine hydrolase ABHD6 controls the accumulation and efficacy of 2-AG at cannabinoid receptorsNature Neuroscience, 2010
- Discovery of Potent and Reversible Monoacylglycerol Lipase InhibitorsCell Chemical Biology, 2009
- Selective blockade of 2-arachidonoylglycerol hydrolysis produces cannabinoid behavioral effectsNature Chemical Biology, 2008
- Selectivity of inhibitors of endocannabinoid biosynthesis evaluated by activity-based protein profilingBioorganic & Medicinal Chemistry Letters, 2008
- Beta-caryophyllene is a dietary cannabinoidProceedings of the National Academy of Sciences of the United States of America, 2008
- Enzymatic Pathways That Regulate Endocannabinoid Signaling in the Nervous SystemChemical Reviews, 2008
- Cannabinoid CB2 receptors: a therapeutic target for the treatment of inflammatory and neuropathic painBritish Journal of Pharmacology, 2008
- A Comprehensive Profile of Brain Enzymes that Hydrolyze the Endocannabinoid 2-ArachidonoylglycerolCell Chemical Biology, 2007
- URB602 Inhibits Monoacylglycerol Lipase and Selectively Blocks 2-Arachidonoylglycerol Degradation in Intact Brain SlicesCell Chemical Biology, 2007
- Meta‐analysis of cannabinoid ligand binding affinity and receptor distribution: interspecies differencesBritish Journal of Pharmacology, 2007