A review on the monoacylglycerol lipase: at the interface between fat and endocannabinoid signalling.

Together with anandamide, 2-arachidonoylglycerol (2-AG) constitutes one of the main representatives of a family of endogenous lipids known as endocannabinoids. These act by binding to CB(1) and CB(2) cannabinoid receptors, the molecular target of the psychoactive compound Delta(9)-THC, both in the periphery and in the central nervous system, where they behave as retrograde messengers to modulate synaptic transmission. These last years, evidence has accumulated to demonstrate the lead role played by the monoacylglycerol lipase (MAGL) in the regulation of 2-arachidonoylglycerol (2-AG) levels. Considering the numerous physiological functions played by this endocannabinoid, MAGL is now considered a promising target for therapeutics, as inhibitors of this enzyme could reveal useful for the treatment of pain and inflammatory disorders, as well as in cancer research, among others. Here we review the milestones that punctuated MAGL history, from its discovery to recent advances in the field of inhibitors development. An emphasis is given on the recent elucidation of the tridimensional structure of the enzyme, which could offer new opportunities for rational drug design.

A MBP-FAAH fusion protein as a tool to produce human and rat fatty acid amide hydrolase: expression and pharmacological comparison.

Fatty acid amide hydrolase (FAAH), a membrane-anchored enzyme responsible for the termination of endocannabinoid signalling, is an attractive target for treating conditions such as pain and anxiety. Inhibitors of the enzyme, optimized using rodent FAAH, are known but their pharmacology and medicinal chemistry properties on the human FAAH are missing. Therefore recombinant human enzyme would represent a powerful tool to evaluate new drug candidates. However, the production of high amounts of enzyme is hampered by the known refractiveness of FAAH to overexpression. Here, we report the successful overexpression of rat and human FAAH as a fusion to the E. coli maltose-binding protein, retaining catalytic properties of native FAAH. Several known FAAH inhibitors were tested and differences in their potencies toward the human and rat FAAH were found, underscoring the importance of using a human FAAH in the development of inhibitors.

Lack of selectivity of URB602 for 2-oleoylglycerol compared to anandamide hydrolysis in vitro.

BACKGROUND AND PURPOSE: Two compounds, URB602 and URB754, have been reported in the literature to be selective inhibitors of monoacylglycerol lipase, although a recent study has questioned their ability to prevent 2-arachidonoyl hydrolysis by brain homogenates and cerebellar membranes. In the present study, the ability of these compounds to inhibit monoacylglycerol lipase and fatty acid amide hydrolase has been reinvestigated. EXPERIMENTAL APPROACH: Homogenates and cell lines were incubated with test compounds and, thereafter, with either [(3)H]-2-oleoylglycerol or [(3)H]-anandamide. Labelled reaction products were separated from substrate using chloroform: methanol extraction. KEY RESULTS: In cytosolic fractions from rat brain, URB602 and URB754 inhibited the hydrolysis of 2-oleoylglycerol with IC(50) values of 25 and 48 microM, respectively. Anandamide hydrolysis by brain membranes was not sensitive to URB754, but was inhibited by URB602 (IC(50) value 17 microM). Hydrolysis of 2-oleoylglycerol by human recombinant monoacylglycerol lipase was sensitive to URB602, but not URB754. The lack of selectivity of URB602 for 2-oleoylglycerol compared to anandamide hydrolysis was also observed for intact RBL2H3 basophilic leukaemia cells. C6 glioma expressed mRNA for monoacylglycerol lipase, and hydrolyzed 2-oleoylglycerol in a manner sensitive to inhibition by methyl arachidonoyl fluorophosphonate but not URB754 or URB597. MC3T3-E1 mouse osteoblastic cells, which did not express mRNA for monoacylglycerol lipase, hydrolyzed 2-oleoylglycerol in the presence of URB597, but the hydrolysis was less sensitive to methyl arachidonoyl fluorophosphonate than for C6 cells. CONCLUSIONS AND IMPLICATIONS: The data demonstrate that the compounds URB602 and URB754 do not behave as selective and/or potent inhibitors of monoacylglycerol lipase.