TY - JOUR
T1 - Role of phosphatidylinositol 3-kinase in the development of hepatocyte preconditioning
AU - Carini, Rita
AU - De Cesaris, Maria Grazia
AU - Splendore, Roberta
AU - Baldanzi, Gianluca
AU - Nitti, Maria Paola
AU - Alchera, Elisa
AU - Filigheddu, Nicoletta
AU - Domenicotti, Cinzia
AU - Pronzato, Maria Adelaide
AU - Graziani, Andrea
AU - Albano, Emanuele
N1 - Funding Information:
Supported by grants from University “Amedeo Avogadro” of East Piedmont; the Regional Government of Piedmont; and the Italian Ministry for Instruction, University, and Scientific Research (Research Program: Molecular Mechanisms of Protection of Steatosic Liver Against Ischemia Reperfusion).
PY - 2004/9
Y1 - 2004/9
N2 - 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 A2A receptors and was mimicked by adenosine A2A 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 Gαi-protein and Src tyrosine kinase with, respectively, pertussis toxin and PP2. H89 also abolished the phosphorylation of adenosine A2A receptors. However, the direct PKA activation by forskolin failed to stimulate PI3K. This suggested that PKA-phosphorylated adenosine A2A receptors may activate PI3K by coupling it with Gαi-protein through Src. We also observed that, by impairing PI3K-mediated activation of phospholypase Cγ (PLCγ), wortmannin and LY294002 blocked the downstream transduction of preconditioning signals via protein kinase C (PKC) δ/ε isozymes. Conclusions:PI3K is activated following hepatocyte hypoxic preconditioning by the combined stimulation of adenosine A2A receptors, PKA, Gαi protein, and Src. By regulating PKC-ε/δ-dependent signals, PI3K can play a key role in the development of hepatic tolerance to hypoxia/reperfusion.
AB - 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 A2A receptors and was mimicked by adenosine A2A 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 Gαi-protein and Src tyrosine kinase with, respectively, pertussis toxin and PP2. H89 also abolished the phosphorylation of adenosine A2A receptors. However, the direct PKA activation by forskolin failed to stimulate PI3K. This suggested that PKA-phosphorylated adenosine A2A receptors may activate PI3K by coupling it with Gαi-protein through Src. We also observed that, by impairing PI3K-mediated activation of phospholypase Cγ (PLCγ), wortmannin and LY294002 blocked the downstream transduction of preconditioning signals via protein kinase C (PKC) δ/ε isozymes. Conclusions:PI3K is activated following hepatocyte hypoxic preconditioning by the combined stimulation of adenosine A2A receptors, PKA, Gαi protein, and Src. By regulating PKC-ε/δ-dependent signals, PI3K can play a key role in the development of hepatic tolerance to hypoxia/reperfusion.
UR - http://www.scopus.com/inward/record.url?scp=4444359798&partnerID=8YFLogxK
U2 - 10.1053/j.gastro.2004.06.018
DO - 10.1053/j.gastro.2004.06.018
M3 - Article
SN - 0016-5085
VL - 127
SP - 914
EP - 923
JO - Gastroenterology
JF - Gastroenterology
IS - 3
ER -