Glycogen synthase kinase-3 (GSK-3) inhibition attenuates hepatocyte lipoapoptosis

J Hepatol. 2011 Apr;54(4):765-72. doi: 10.1016/j.jhep.2010.09.039. Epub 2010 Nov 23.


Backgrounds & aims: Saturated free fatty acids induce hepatocyte lipoapoptosis, a key pathologic feature of non-alcoholic steatohepatitis. The saturated free fatty acid palmitate induces hepatocyte lipoapoptosis via an endoplasmic reticulum stress pathway resulting in c-Jun-N-terminal (JNK) activation. Glycogen synthase kinase (GSK)-3 is a serine/threonine kinase which may also promote JNK activation. Thus, our aim was to determine if GSK-3 inhibition suppresses palmitate induced JNK activation and lipoapoptosis.

Methods: For these studies, we employed mouse primary hepatocytes, Huh-7 and Hep3B cell lines.

Results: Palmitate-induced GSK-3 activation was identified by phosphorylation of its substrate glycogen synthase. GSK-3 pharmacologic inhibition, by GSK-3 inhibitor IX and enzastaurin, significantly reduced PA-mediated lipoapoptosis. More importantly, Huh-7 cells, in which either GSK-3α or GSK-3β isoforms were stably and selectively knocked down by shRNA, displayed resistance to palmitate-induced cytotoxicity. GSK-3 pharmacological inhibitors and shRNA-targeted knockdown of GSK-3α or GSK-3β also suppressed JNK activation by palmitate. JNK activation, in part, promotes lipoapotosis by inducing expression of the pro-apoptotic effector p53-upregulated modulator of apoptosis (PUMA). Consistent with this concept, GSK-3 pharmacologic inhibition also reduced PUMA cellular protein levels during exposure to palmitate. On the other hand, the GSK-3 inhibitors did not prevent PA induction of ER stress.

Conclusions: Our results suggest that GSK-3 activation promotes a JNK-dependent cytotoxic signaling cascade culminating in lipoapoptosis.

Publication types

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

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Base Sequence
  • Cell Line
  • Cells, Cultured
  • DNA Primers / genetics
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Fatty Liver / etiology
  • Fatty Liver / metabolism
  • Fatty Liver / pathology
  • Gene Knockdown Techniques
  • Glycogen Synthase Kinase 3 / antagonists & inhibitors*
  • Glycogen Synthase Kinase 3 / genetics
  • Glycogen Synthase Kinase 3 beta
  • Hepatocytes / cytology
  • Hepatocytes / drug effects*
  • Hepatocytes / metabolism*
  • Humans
  • Indoles / pharmacology
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Mice
  • Non-alcoholic Fatty Liver Disease
  • Palmitates / pharmacology
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism
  • RNA, Small Interfering / genetics
  • Signal Transduction / drug effects
  • Tumor Suppressor Proteins / metabolism


  • Apoptosis Regulatory Proteins
  • BBC3 protein, human
  • DNA Primers
  • Enzyme Inhibitors
  • Indoles
  • PUMA protein, mouse
  • Palmitates
  • Proto-Oncogene Proteins
  • RNA, Small Interfering
  • Tumor Suppressor Proteins
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Gsk3b protein, mouse
  • JNK Mitogen-Activated Protein Kinases
  • Glycogen Synthase Kinase 3
  • glycogen synthase kinase 3 alpha
  • enzastaurin