The role of tyrosine phosphorylation in the mechanism of ischemic preconditioning

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13670752
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Circulatory organs internal medicine
• Research Institution: KANAZAWA MEDICAL UNIVERSITY
• Principal Investigator: OKUBO Shinji KANAZAWA MEDICAL UNIVERSITY, Medical department, Assistant Professor, 医学部, 助教授 (50213658)
• Co-Investigator(Kenkyū-buntansha): TAKEKOSHI Noboru KANAZAWA MEDICAL UNIVERSITY, Medical department, Professor, 医学部, 教授 (40064539)
• Project Period (FY): 2001 – 2002
• Keywords: Ischemic preconditioning / Myocardial infarction / Reperfusion injury / Alpha-adrenoceptor / Tyrosine kinase / Protein kinase C / rabbit

Research Abstract

We investigated whether ischemic preconditioning (IPC) attenuates irreversible ischemic reperfusion injury in part by decreasing apoptosis and whether tyrosine kinase (TK) can regulate the signaling pathway leading to apoptosis in delayed cardioprotection. Four groups of rabbits were studied in early phase and delayed phase. 1) controls c, 2) rabbit preconditioned with 4 cycles of 5 minutes' occlusion of LAD and 10 minutes' reperfusion (PC), 3)rabbits that received I.v genistein (a non-specific tyrosine kinase (TK) inhibitor) 5 mg/kg, 10 minutes before PC (Gen-PC), 4) rabbits that received I.v daidzein (an inactive structural analog of genistein) 5 mg/kg, 10 minutes before PC (Dzn-PC). All rabbits underwent 30 minutes' occlusion of LAD followed by 180 minutes' reperfusion. Infarct size was determined by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. Assessment of PKC isoforms from a left ventricular (LV) sample was conducted by western blotting. Apoptosis in situ was determined by the terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL) method. The percentage of TUNEL-positive cardiomyocytes was calculated and DNA ladder assay was performed. Infarct size was significantly (p<0.01) reduced in the early phase in the PC, Ge-PC and Dzn-PC group compared with controls. Delayed cardioprotection was blocked significantly (p<0.01) by genistein. In the early phase, apoptosis was significantly (p<0.01) decreased in PC, Gen-PC and Dzn-PC groups compared with controls. In the delayed phase, reduction of apoptosis was not shown in the Gen-PC group. This study suggests that ischemic preconditioning reduces lethal ischemic injury in part by decreasing apoptosis after ischemia/reperfusion and also that tyrosine kinase phosphorylation is involved in the signal transduction cascade leading to the decline of apoptosis in the delayed phase but not in the early phase.