The Cannabinoid Receptor 2 Protects Against Alcoholic Liver Disease Via a Macrophage Autophagy-Dependent Pathway

Sci Rep. 2016 Jun 27:6:28806. doi: 10.1038/srep28806.

Abstract

Kupffer cells, the resident macrophages of the liver, play a major role in the pathogenesis of alcoholic liver disease. We have previously demonstrated that CB2 receptor protects against alcoholic liver disease by inhibiting alcohol-induced inflammation and steatosis via the regulation of Kupffer cell activation. Here, we explored the mechanism underlying these effects and hypothesized that the anti-inflammatory properties of CB2 receptor in Kupffer cells rely on activation of autophagy. For this purpose, mice invalidated for CB2 receptor (CB2(Mye-/-) mice) or for the autophagy gene ATG5 (ATG5(Mye-/-) mice) in the myeloid lineage, and their littermate wild-type mice were subjected to chronic-plus-binge ethanol feeding. CB2(Mye-/-) mice showed exacerbated alcohol-induced pro-inflammatory gene expression and steatosis. Studies in cultured macrophages demonstrated that CB2 receptor activation by JWH-133 stimulated autophagy via a heme oxygenase-1 dependent pathway. Moreover, JWH-133 reduced the induction of inflammatory genes by lipopolysaccharide in wild-type macrophages, but not in ATG5-deficient cells. The CB2 agonist also protected from alcohol-induced liver inflammation and steatosis in wild-type mice, but not in ATG5(Mye-/-) mice demonstrating that macrophage autophagy mediates the anti-inflammatory and anti-steatogenic effects of CB2 receptor. Altogether these results demonstrate that CB2 receptor activation in macrophages protects from alcohol-induced steatosis by inhibiting hepatic inflammation through an autophagy-dependent pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Animals
  • Anti-Inflammatory Agents / chemistry
  • Autophagy*
  • Autophagy-Related Protein 5 / genetics
  • Cell Lineage
  • Ethanol / chemistry
  • Fatty Liver / metabolism
  • Heme Oxygenase-1 / metabolism
  • Hepatitis, Alcoholic / metabolism
  • Inflammation
  • Lipopolysaccharides / chemistry
  • Liver / metabolism
  • Liver Diseases, Alcoholic / metabolism*
  • Liver Diseases, Alcoholic / pathology
  • Liver Diseases, Alcoholic / prevention & control
  • Macrophages / metabolism*
  • Male
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Phenotype
  • RAW 264.7 Cells
  • Receptor, Cannabinoid, CB2 / agonists
  • Receptor, Cannabinoid, CB2 / genetics*
  • Receptor, Cannabinoid, CB2 / metabolism*

Substances

  • Anti-Inflammatory Agents
  • Atg5 protein, mouse
  • Autophagy-Related Protein 5
  • Lipopolysaccharides
  • Membrane Proteins
  • Receptor, Cannabinoid, CB2
  • Ethanol
  • Heme Oxygenase-1
  • Hmox1 protein, mouse