Inhibition of histone methyltransferase G9a aggravates phenotypic severity of hepatic lipotoxicity in non-alcoholic steatohepatitis (NASH)

Biochem Biophys Res Commun. 2025 Jan:743:151171. doi: 10.1016/j.bbrc.2024.151171. Epub 2024 Dec 11.

Abstract

Lipotoxicity is a key pathological feature in the development of non-alcoholic steatohepatitis (NASH), which is characterized by liver injury, inflammation, and fibrosis. Although lipotoxicity has been shown to induce transcriptomic alterations in liver cells, the specific role of epigenetic regulators in NASH remains elusive. In this study, we demonstrate that pharmacological inhibition of histone methyltransferase G9a significantly worsens NASH progression in mice, as evidenced by increased hepatic cell death, inflammation, and fibrosis. Additionally, at a cellular level both genetic and pharmacological inhibition of G9a in HepG2 cells increased their susceptibility to palmitic acid-induced apoptosis and sub-cellular stress. Furthermore, treatment with G9a inhibitor enhanced TGF-β induced activation of primary human hepatic stellate cells (hHSCs), implicating the role of G9a in NASH pathobiology.

Keywords: Fibrosis; Histone methyltransferase G9a; Human hepatic stellate cells (hHSCs); Non-alcoholic steatohepatitis (NASH).

MeSH terms

  • Animals
  • Apoptosis
  • Hep G2 Cells
  • Hepatic Stellate Cells / drug effects
  • Hepatic Stellate Cells / metabolism
  • Hepatic Stellate Cells / pathology
  • Histocompatibility Antigens / genetics
  • Histocompatibility Antigens / metabolism
  • Histone-Lysine N-Methyltransferase* / antagonists & inhibitors
  • Histone-Lysine N-Methyltransferase* / genetics
  • Histone-Lysine N-Methyltransferase* / metabolism
  • Humans
  • Liver* / metabolism
  • Liver* / pathology
  • Male
  • Mice
  • Mice, Inbred C57BL*
  • Non-alcoholic Fatty Liver Disease* / metabolism
  • Non-alcoholic Fatty Liver Disease* / pathology
  • Palmitic Acid / pharmacology
  • Palmitic Acid / toxicity
  • Phenotype
  • Transforming Growth Factor beta / metabolism

Substances

  • Histone-Lysine N-Methyltransferase
  • G9a protein, mouse
  • Histocompatibility Antigens
  • EHMT2 protein, human
  • Palmitic Acid
  • Transforming Growth Factor beta