Tumor necrosis factor-inducible gene 6 protein ameliorates chronic liver damage by promoting autophagy formation in mice

Exp Mol Med. 2017 Sep 22;49(9):e380. doi: 10.1038/emm.2017.140.

Abstract

Tumor necrosis factor-inducible gene 6 protein (TSG-6) has recently been shown to protect the liver from acute damage. However, the mechanism underlying the effect of TSG-6 on the liver remains unclear. Autophagy is a catabolic process that targets cell components to lysosomes for degradation, and its functions are reported to be dysregulated in liver diseases. Here we investigate whether TSG-6 promotes liver regeneration by inducing autophagic clearance in damaged livers. Mice fed a methionine choline-deficient diet supplemented with 0.1% ethionine (MCDE) for 2 weeks were injected with TSG-6 (the M+TSG-6 group) or saline (the M+V group) and fed with MCDE for 2 additional weeks. Histomorphological evidence of injury and increased levels of liver enzymes were evident in MCDE-treated mice, whereas these symptoms were ameliorated in the M+TSG-6 group. Livers from this group contained less active caspase-3 and more Ki67-positive hepatocytic cells than the M+V group. The autophagy markers ATG3, ATG7, LC3-II, LAMP2A and RAB7 were elevated in the M+TSG-6 group compared with those in the M+V group. Immunostaining for LC3 and RAB7 and electron microscopy analysis showed the accumulation of autophagy structures in the M+TSG-6 group. TSG-6 also blocked both tunicamycin- and palmitate-induced apoptosis of hepatocytes and increased their viability by inducing autophagy formation in these cells. An autophagy inhibitor suppressed TSG-6-mediated autophagy in the injured hepatocytes and livers of MCDE-treated mice. These results therefore demonstrate that TSG-6 protects hepatocytes from damage by enhancing autophagy influx and contributes to liver regeneration, suggesting that TSG-6 has therapeutic potential for the treatment of liver diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagy / genetics*
  • Cell Adhesion Molecules / genetics*
  • Cell Adhesion Molecules / metabolism*
  • Cell Line
  • Cell Survival / genetics
  • Chronic Disease
  • Disease Models, Animal
  • Hepatocytes / metabolism
  • Hepatocytes / pathology
  • Hepatocytes / ultrastructure
  • Liver Diseases / genetics*
  • Liver Diseases / metabolism*
  • Liver Diseases / mortality
  • Liver Diseases / pathology
  • Liver Regeneration / genetics
  • Male
  • Mice

Substances

  • Cell Adhesion Molecules
  • Tnfaip6 protein, mouse