Inhibition of monoacylglycerol lipase, an anti-inflammatory and antifibrogenic strategy in the liver

Gut. 2019 Mar;68(3):522-532. doi: 10.1136/gutjnl-2018-316137. Epub 2018 Oct 9.

Abstract

Objective: Sustained inflammation originating from macrophages is a driving force of fibrosis progression and resolution. Monoacylglycerol lipase (MAGL) is the rate-limiting enzyme in the degradation of monoacylglycerols. It is a proinflammatory enzyme that metabolises 2-arachidonoylglycerol, an endocannabinoid receptor ligand, into arachidonic acid. Here, we investigated the impact of MAGL on inflammation and fibrosis during chronic liver injury.

Design: C57BL/6J mice and mice with global invalidation of MAGL (MAGL -/- ), or myeloid-specific deletion of either MAGL (MAGLMye-/-), ATG5 (ATGMye-/-) or CB2 (CB2Mye-/-), were used. Fibrosis was induced by repeated carbon tetrachloride (CCl4) injections or bile duct ligation (BDL). Studies were performed on peritoneal or bone marrow-derived macrophages and Kupffer cells.

Results: MAGL -/- or MAGLMye-/- mice exposed to CCl4 or subjected to BDL were more resistant to inflammation and fibrosis than wild-type counterparts. Therapeutic intervention with MJN110, an MAGL inhibitor, reduced hepatic macrophage number and inflammatory gene expression and slowed down fibrosis progression. MAGL inhibitors also accelerated fibrosis regression and increased Ly-6Clow macrophage number. Antifibrogenic effects exclusively relied on MAGL inhibition in macrophages, since MJN110 treatment of MAGLMye-/- BDL mice did not further decrease liver fibrosis. Cultured macrophages exposed to MJN110 or from MAGLMye-/- mice displayed reduced cytokine secretion. These effects were independent of the cannabinoid receptor 2, as they were preserved in CB2Mye-/- mice. They relied on macrophage autophagy, since anti-inflammatory and antifibrogenic effects of MJN110 were lost in ATG5Mye-/- BDL mice, and were associated with increased autophagic flux and autophagosome biosynthesis in macrophages when MAGL was pharmacologically or genetically inhibited.

Conclusion: MAGL is an immunometabolic target in the liver. MAGL inhibitors may show promising antifibrogenic effects during chronic liver injury.

Keywords: fibrosis; inflammation; lipid metabolism; liver; macrophages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Inflammatory Agents / pharmacology
  • Anti-Inflammatory Agents / therapeutic use*
  • Autophagy / drug effects
  • Carbamates / pharmacology
  • Carbamates / therapeutic use
  • Carbon Tetrachloride
  • Cell Count
  • Cells, Cultured
  • Cytokines / metabolism
  • Disease Progression
  • Drug Evaluation, Preclinical / methods
  • Hydrolases / metabolism
  • Inflammation Mediators / antagonists & inhibitors
  • Inflammation Mediators / metabolism
  • Liver / enzymology*
  • Liver Cirrhosis, Experimental / chemically induced
  • Liver Cirrhosis, Experimental / drug therapy*
  • Liver Cirrhosis, Experimental / enzymology
  • Liver Cirrhosis, Experimental / pathology
  • Macrophages / drug effects
  • Macrophages / metabolism
  • Macrophages / physiology
  • Male
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Molecular Targeted Therapy / methods
  • Monoacylglycerol Lipases / antagonists & inhibitors*
  • Monoacylglycerol Lipases / physiology
  • Receptor, Cannabinoid, CB2 / metabolism
  • Succinimides / pharmacology
  • Succinimides / therapeutic use

Substances

  • Anti-Inflammatory Agents
  • Carbamates
  • Cytokines
  • Inflammation Mediators
  • MJN110
  • Receptor, Cannabinoid, CB2
  • Succinimides
  • Carbon Tetrachloride
  • Hydrolases
  • Monoacylglycerol Lipases