Epigenetic regulation of miR-34a expression in alcoholic liver injury

Am J Pathol. 2012 Sep;181(3):804-17. doi: 10.1016/j.ajpath.2012.06.010. Epub 2012 Jul 25.

Abstract

Epigenetic changes are associated with the regulation of transcription of key cell regulatory genes [micro RNAs (miRNAs)] during different types of liver injury. This study evaluated the role of methylation-associated miRNA, miR-34a, in alcoholic liver diseases. We identified that ethanol feeding for 4 weeks significantly up-regulated 0.8% of known miRNA compared with controls, including miR-34a. Treatment of normal human hepatocytes (N-Heps) and cholangiocytes [human intrahepatic biliary epithelial cells (HiBECs)] with ethanol and lipopolysaccharide induced a significant increase of miR-34a expression. Overexpression of miR-34a decreased ethanol-induced apoptosis in both N-Heps and HiBECs. In support of the concept that the 5'-promoter region of miR-34a was noted to be embedded within a CpG island, the expression level of miR-34a was significantly increased after demethylation treatment in N-Heps and HiBECs. By methylation-specific PCR, we confirmed that miR-34a activation is associated with ethanol-linked hypomethylation of the miR-34a promoter. A combination of bioinformatics, dual-luciferase reporter assay, mass spectrometry, and Western blot analysis revealed that caspase-2 and sirtuin 1 are the direct targets of miR-34a. Furthermore, modulation of miR-34a also altered expression of matrix metalloproteases 1 and 2, the mediators involved in hepatic remodeling during alcoholic liver fibrosis. These findings provide the basis for an exciting field in which the epigenomic microRNAs of hepatic cells may be manipulated with potential therapeutic benefits in human alcoholic liver diseases.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Caspase 2 / metabolism
  • Cell Line
  • Cell Movement / genetics
  • Cell Survival / genetics
  • Cell Transformation, Neoplastic
  • DNA (Cytosine-5-)-Methyltransferases / metabolism
  • DNA Methylation / genetics
  • Disease Models, Animal
  • Epigenesis, Genetic*
  • Ethanol
  • Fatty Liver / genetics
  • Fatty Liver / pathology
  • Gene Silencing
  • Humans
  • Liver / metabolism
  • Liver / pathology
  • Liver Diseases, Alcoholic / enzymology
  • Liver Diseases, Alcoholic / genetics*
  • Liver Diseases, Alcoholic / pathology
  • Matrix Metalloproteinases / genetics
  • Matrix Metalloproteinases / metabolism
  • Mice
  • Mice, Inbred C57BL
  • MicroRNAs / genetics*
  • MicroRNAs / metabolism
  • Molecular Sequence Data
  • Polymerase Chain Reaction
  • Sirtuin 1 / genetics
  • Sirtuin 1 / metabolism

Substances

  • MIRN34 microRNA, human
  • MIRN34a microRNA, mouse
  • MicroRNAs
  • Ethanol
  • DNA (Cytosine-5-)-Methyltransferases
  • DNA methyltransferase 3B
  • Caspase 2
  • Matrix Metalloproteinases
  • Sirtuin 1