The endocannabinoid system remains an attractive molecular target for pharmacological intervention due to its roles in the central nervous system in learning, thinking, emotional function, regulation of food intake or pain sensation, as well as in the peripheral nervous system, where it modulates the action of cardiovascular, immune, metabolic or reproductive function. alpha/beta hydrolase domain containing 6 (ABHD6)-an enzyme forming part of the endocannabinoid system-is a newly discovered post-genomic protein acting as a 2-AG (2-arachidonoylglycerol) serine hydrolase. We have recently reported a series of 1,2,5-thiadiazole carbamates as potent and selective ABHD6 inhibitors. Here, we present comparative molecular field analysis (CoMFA) and molecular dynamics studies of these compounds. First, we performed a homology modeling study of ABHD6 based on the assumption that the catalytic triad of ABHD6 comprises Ser148-His306-Asp 278 and the oxyanion hole is formed by Met149 and Phe80. A total of 42 compounds was docked to the homology model using the Glide module from the Schrodinger suite of software and the selected docking poses were used for CoMFA alignment. A model with the following statistics was obtained: R (2) = 0.98, Q (2) = 0.55. In order to study the molecular interactions of the inhibitors with ABHD6 in detail, molecular dynamics was performed with the Desmond program. It was found that, during the simulations, the hydrogen bond between the inhibitor carbonyl group and the main chain of Phe80 is weakened, whereas a new hydrogen bond with the side chain of Ser148 is formed, facilitating the possible formation of a covalent bond. Graphical Abstract Left-right: Docking pose of 1 in the binding pocket of alpha/beta hydrolase domain containing 6 (ABHD6) selected for molecular alignment; CoMFA steric and electrostatic contour fields; changes in potential energy of the complex during simulations for the complex of 6 and ABHD6.
The endocannabinoid 2-arachidonoylglycerol (2-AG) is biosynthesized by diacylglycerol lipases DAGLalpha and DAGLbeta. Chemical probes to perturb DAGLs are needed to characterize endocannabinoid function in biological processes. Here we report a series of 1,2,3-triazole urea inhibitors, along with paired negative-control and activity-based probes, for the functional analysis of DAGLbeta in living systems. Optimized inhibitors showed high selectivity for DAGLbeta over other serine hydrolases, including DAGLalpha ( approximately 60-fold selectivity), and the limited off-targets, such as ABHD6, were also inhibited by the negative-control probe. Using these agents and Daglb(-/-) mice, we show that DAGLbeta inactivation lowers 2-AG, as well as arachidonic acid and eicosanoids, in mouse peritoneal macrophages in a manner that is distinct and complementary to disruption of cytosolic phospholipase-A2. We observed a corresponding reduction in lipopolysaccharide-induced tumor necrosis factor-alpha release. These findings indicate that DAGLbeta is a key metabolic hub within a lipid network that regulates proinflammatory responses in macrophages.
