Role of phosphatidylinositol 3-kinase in the development of hepatocyte preconditioning

Gastroenterology. 2004 Sep;127(3):914-23. doi: 10.1053/j.gastro.2004.06.018.


Background & aims: Ischemic preconditioning has been proved effective in reducing ischemia/reperfusion injury during liver surgery. However, the mechanisms involved are still poorly understood. Here, we have investigated the role of phosphatidylinositol 3-kinase (PI3K) in the signal pathway leading to hepatic preconditioning.

Methods: PI3K activation was evaluated in isolated rat hepatocytes preconditioned by 10-minute hypoxia followed by 10-minute reoxygenation.

Results: Hypoxic preconditioning stimulated phosphatidylinositol-3,4,5-triphosphate production and the phosphorylation of PKB/Akt, a downstream target of PI3K. Conversely, PI3K inhibition by wortmannin or LY294002 abolished hepatocyte tolerance against hypoxic damage induced by preconditioning. PI3K activation in preconditioned hepatocytes required the stimulation of adenosine A 2A receptors and was mimicked by adenosine A 2A receptors agonist CGS21680. In the cells treated with CGS21680, PI3K activation was prevented either by inhibiting adenylate cyclase and PKA with, respectively, 2,5-dideoxyadenosine and H89 or by blocking Galphai-protein and Src tyrosine kinase with, respectively, pertussis toxin and PP2. H89 also abolished the phosphorylation of adenosine A 2A receptors. However, the direct PKA activation by forskolin failed to stimulate PI3K. This suggested that PKA-phosphorylated adenosine A 2A receptors may activate PI3K by coupling it with Galphai-protein through Src. We also observed that, by impairing PI3K-mediated activation of phospholypase Cgamma (PLCgamma), wortmannin and LY294002 blocked the downstream transduction of preconditioning signals via protein kinase C (PKC) delta/ isozymes.

Conclusions: PI3K is activated following hepatocyte hypoxic preconditioning by the combined stimulation of adenosine A 2A receptors, PKA, Galphai protein, and Src. By regulating PKC-/delta-dependent signals, PI3K can play a key role in the development of hepatic tolerance to hypoxia/reperfusion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • GTP-Binding Protein alpha Subunit, Gi2
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism
  • Hepatocytes / metabolism*
  • Ischemic Preconditioning / methods*
  • Male
  • Models, Animal
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Protein Kinase C / metabolism
  • Proto-Oncogene Proteins / metabolism
  • Rats
  • Rats, Wistar
  • Receptor, Adenosine A2A / metabolism
  • Reperfusion Injury / metabolism*
  • Signal Transduction
  • Type C Phospholipases / metabolism
  • src-Family Kinases / metabolism


  • Proto-Oncogene Proteins
  • Receptor, Adenosine A2A
  • Phosphatidylinositol 3-Kinases
  • src-Family Kinases
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C
  • Type C Phospholipases
  • GTP-Binding Protein alpha Subunit, Gi2
  • GTP-Binding Protein alpha Subunits, Gi-Go
  • Gnai2 protein, rat