Mechanism of ischemic preconditioning in the mouse liver through the Akt kinase pathway

• Project/Area Number: 14571202
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Digestive surgery
• Research Institution: KAGAWA UNIVERSITY(FACULTY OF MEDICINE)
• Principal Investigator: IZUISHI Kunihiko Kagawa University, Faculty of Medicine, Research Associate, 医学部附属病院, 助手 (50325346)
• Project Period (FY): 2002 – 2003
• Project Status: Completed (Fiscal Year 2003)
• Budget Amount: ¥3,300,000 (Direct Cost: ¥3,300,000); Fiscal Year 2003: ¥1,600,000 (Direct Cost: ¥1,600,000); Fiscal Year 2002: ¥1,700,000 (Direct Cost: ¥1,700,000)
• Keywords: preconditioning / PI3 kinase / Akt / Wortmannin / liver / Ischemia reperfusion injury / PI13-kinase / apoptosis / 肝温虚血再潅流障害 / PI3-kinase

Research Abstract

Ischemic preconditioning (IPC) protects various organs from subsequent ischemia-reperfusion (I/R), but the mechanism underlying this phenomenon remains undefined. To investigate the molecular mechanism of this protective effect, we examined Akt activation in the phosphatidylinositol 3-kinase (PI3 kinase)/Akt-sigualing survival pathway by IPC. At first, 70 min of total hepatic ischemia was conducted following subcutaneous transposition of the spleen 2 week before to prevent mesenteric venous hypertension. We find IPC caused strong Akt phosphorylation after reperfusion and we presented the data in transplantation proceeding. However, in this ischemic model, we could not get stable data. Therefore, we changed the method of the total hepatic ischemia to 70% liver ischemia. And then, we obtained following results. After an IPC period of 10 min of ischemia and 10 min of reperfusion, the mice were subjected to prolonged hepatic ischemia in Balb/c mice. Akt protein and its phosphorylation were then assessed by Western blot analysis using liver tissues harvested at different time points. Within 30 min after reperfusion, mice that received IPC treatment showed a significantly greater activation of Akt than those that did not, and this strong activation persisted for 3 h. Pretreatment with wortmannin before reperfusion completely attenuated Akt phosphorylation. 90 min of ischemia caused significant serum alanine aminotransferase (ALT) elevation and histological damage. IPC improved these effects, and increased the survival rate from 33% to 73% on day7. Wortmannin abolished the organ protection of IPC ; mice in the wortmannin group had a mean survival rate of 40%, as well as ALT and histological damage. To confirm the significance of Akt activation in vitro, Hep G2 cells that had been transfected with dominant active or negative Akt1 expression vectors were exposed to ischemic conditions for 4 h, then reoxygenated in normal medium. Dominant active Akt1-transfected Hep G2 cells acquired strong resistance to I/R injury. These results indicate that the PI3 kinase/Akt pathway plays an essential role in the development of the protective effect of IPC against I/R injury in the mouse liver. The Akt pathway might become an important target for the therapeutic strategies for protection against I/R injury using chemical inducers or gene therapy.

Research Products

• [Publications] Izuishi K, Fujiwara M, Hossain MA, Usuki H, Maeta H.: "Significance of phosphoinositide 3-kinase pathway on ischemic preconditioning followed by ischemia reperfusion in mice liver."Transplant Proc.. 35. 132-133 (2003)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Izuishi K, Fujiwara M, Hossam MA, Usuki H, Maeta H.: "Significance of phosphoinositide 3-kinase pathway on ischemic preconditioning followed by ischemia reperfusion in mice liver."Transplant Proc.. 35(1). 132-133 (2003)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Izuishi K, Fujiwara M, Hossain MA, Usuki H, Maeta H.: "Significance of phosphoinositide 3-kinase pathway on ischemic preconditioning followed by ischemia reperfusion in mice liver"Transplant Proc.. 35(1). 132-133 (2003)