Palmitic acid induces autophagy in hepatocytes via JNK2 activation

Acta Pharmacol Sin. 2014 Apr;35(4):504-12. doi: 10.1038/aps.2013.170. Epub 2014 Mar 10.


Aim: Free fatty acid-induced lipotoxicity plays a crucial role in the progression of nonalcoholic fatty liver disease (NAFLD). In the present study we investigated the effects of a high-fat diet and free fatty acids on the autophagic process in hepatocytes in vivo and in vitro and the underlying mechanisms.

Methods: LC3-II expression, a hallmark of autophagic flux, was detected in liver specimens from patients with non-alcoholic steatohepatitis (NASH) as well as in the livers of C57BL/6 mice fed a high-fat diet (HFD) up to 16 weeks. LC3-II expression was also analyzed in human SMMC-7721 and HepG2 hepatoma cells exposed to palmitic acid (PA), a saturated fatty acid. PA-induced apoptosis was detected by Annexin V staining and specific cleavage of PARP in the presence and absence of different agents.

Results: LC3-II expression was markedly increased in human NASH and in liver tissues of HFD-fed mice. Treatment of SMMC-7721 cells with PA increased LC3-II expression in time- and dose-dependent manners, whereas the unsaturated fatty acid oleic acid had no effect. Inhibition of autophagy with 3MA sensitized SMMC-7721 cells to PA-induced apoptosis, whereas activation of autophagy by rapamycin attenuated PA-induced PARP cleavage. The autophagy-associated proteins Beclin1 and Atg5 were essential for PA-induced autophagy in SMMC-7721 cells. Moreover, pretreatment with SP600125, an inhibitor of JNK, effectively abrogated PA-mediated autophagy and apoptosis. Specific knockdown of JNK2, but not JNK1, in SMMC-7721 cells significantly suppressed PA-induced autophagy and enhanced its pro-apoptotic activity; whereas specific knockdown of JNK1 had the converse effect. Similar results were obtained when HepG2 cells were tested.

Conclusion: JNK1 promotes PA-induced lipoapoptosis, whereas JNK2 activates pro-survival autophagy and inhibits PA lipotoxicity. Our results suggest that modulation of autophagy may have therapeutic benefits in the treatment of lipid-related metabolic diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Autophagy / drug effects*
  • Autophagy-Related Protein 5
  • Beclin-1
  • Diet, High-Fat
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Enzyme Activation
  • Hep G2 Cells
  • Hepatocytes / drug effects*
  • Hepatocytes / enzymology
  • Hepatocytes / pathology
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Mice, Inbred C57BL
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Mitogen-Activated Protein Kinase 8 / genetics
  • Mitogen-Activated Protein Kinase 8 / metabolism
  • Mitogen-Activated Protein Kinase 9 / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase 9 / genetics
  • Mitogen-Activated Protein Kinase 9 / metabolism*
  • Non-alcoholic Fatty Liver Disease / enzymology*
  • Non-alcoholic Fatty Liver Disease / etiology
  • Non-alcoholic Fatty Liver Disease / genetics
  • Non-alcoholic Fatty Liver Disease / pathology
  • Palmitic Acid / toxicity*
  • Protein Kinase Inhibitors / pharmacology
  • RNA Interference
  • Signal Transduction / drug effects
  • Time Factors
  • Transfection


  • ATG5 protein, human
  • Apoptosis Regulatory Proteins
  • Autophagy-Related Protein 5
  • BECN1 protein, human
  • Beclin-1
  • MAP1LC3A protein, human
  • Map1lc3b protein, mouse
  • Membrane Proteins
  • Microtubule-Associated Proteins
  • Protein Kinase Inhibitors
  • Palmitic Acid
  • Mitogen-Activated Protein Kinase 9
  • Mitogen-Activated Protein Kinase 8