ABSTRACT
Monoacylglycerol lipase (MAGL) is a pivotal enzyme in the endocannabinoid system, which metabolizes 2-arachidonoylglycerol (2-AG) into the proinflammatory eicosanoid precursor arachidonic acid (AA). MAGL and other endogenous cannabinoid (EC) degrading enzymes are involved in the fibrogenic signaling pathways that induce hepatic stellate cell (HSC) activation and ECM accumulation during chronic liver disease. Our group recently developed an 18F-labeled MAGL inhibitor ([18F]MAGL-4-11) for PET imaging and demonstrated highly specific binding in vitro and in vivo. In this study, we determined [18F]MAGL-4-11 PET enabled imaging MAGL levels in the bile duct ligation (BDL) and carbon tetrachloride (CCl4) models of liver cirrhosis; we also assessed the hepatic gene expression of the enzymes involved with EC system including MAGL, NAPE-PLD, FAAH and DAGL that as a function of disease severity in these models; [18F]MAGL-4-11 autoradiography was performed to assess tracer binding in frozen liver sections both in animal and human. [18F]MAGL-4-11 demonstrated reduced PET signals in early stages of fibrosis and further significantly decreased with disease progression compared with control mice. We confirmed MAGL and FAAH expression decreases with fibrosis severity, while its levels in normal liver tissue are high; in contrast, the EC synthetic enzymes NAPE-PLD and DAGL are enhanced in these different fibrosis models. In vitro autoradiography further supported that [18F]MAGL-4-11 bound specifically to MAGL in both animal and human fibrotic liver tissues. Our PET ligand [18F]MAGL-4-11 shows excellent sensitivity and specificity for MAGL visualization in vivo and accurately reflects the histological stages of liver fibrosis in preclinical models and human liver tissues.
ABSTRACT
As a serine hydrolase, monoacylglycerol lipase (MAGL) is principally responsible for the metabolism of 2-arachidonoylglycerol (2-AG) in the central nervous system (CNS), leading to the formation of arachidonic acid (AA). Dysfunction of MAGL has been associated with multiple CNS disorders and symptoms, including neuroinflammation, cognitive impairment, epileptogenesis, nociception and neurodegenerative diseases. Inhibition of MAGL provides a promising therapeutic direction for the treatment of these conditions, and a MAGL positron emission tomography (PET) probe would greatly facilitate preclinical and clinical development of MAGL inhibitors. Herein, we design and synthesize a small library of fluoropyridyl-containing MAGL inhibitor candidates. Pharmacological evaluation of these candidates by activity-based protein profiling identified
ABSTRACT
Due to ineffectiveness and side effects of existing analgesics, chronic pain has become one of the most complex and difficult problems in the clinic. Monoacylglycerol lipase (MAGL) is an essential hydrolase in the endocannabinoid system and has been identified as a potential target for the treatment of pain. In the present study, we designed and synthesized twelve tanshinone IIA analogs and screened their activity against MAGL. Selected compounds were tested for analgesic activity in vivo, with the acetic acid writhing test model. Among the test compounds, compound III-3 (IC 120 nmol·L) showed significant activity against MAGL and ameliorated the clinical progression in the mouse pain model. Additionally, compound III-3, substitution with N-methyl-2-morpholinoacetamide, demonstrated improved solubility relative to tanshinone IIA.
Subject(s)
Animals , Female , Humans , Male , Mice , Abietanes , Chemistry , Analgesics , Chemistry , Chronic Pain , Drug Therapy , Drug Evaluation, Preclinical , Enzyme Inhibitors , Chemistry , Mice, Inbred ICR , Monoacylglycerol Lipases , Metabolism , Structure-Activity RelationshipABSTRACT
Due to ineffectiveness and side effects of existing analgesics, chronic pain has become one of the most complex and difficult problems in the clinic. Monoacylglycerol lipase (MAGL) is an essential hydrolase in the endocannabinoid system and has been identified as a potential target for the treatment of pain. In the present study, we designed and synthesized twelve tanshinone IIA analogs and screened their activity against MAGL. Selected compounds were tested for analgesic activity in vivo, with the acetic acid writhing test model. Among the test compounds, compound III-3 (IC 120 nmol·L) showed significant activity against MAGL and ameliorated the clinical progression in the mouse pain model. Additionally, compound III-3, substitution with N-methyl-2-morpholinoacetamide, demonstrated improved solubility relative to tanshinone IIA.