title: Ischemic preconditioning protects by activating prosurvival kinases at reperfusion.
abstract: Pharmacological activation of the prosurvival kinases Akt and ERK-1/2 at reperfusion, after a period of lethal ischemia, protects the heart against ischemia-reperfusion injury. We hypothesized that ischemic preconditioning (IPC) protects the heart by phosphorylating the prosurvival kinases Akt and ERK-1/2 at reperfusion. In isolated perfused Sprague-Dawley rat hearts subjected to 35 min of lethal ischemia, the phosphorylation states of Akt, ERK-1/2, and p70 S6 kinase (p70S6K) were determined after 15 min of reperfusion, and infarct size was measured after 120 min of reperfusion. IPC induced a biphasic response in Akt and ERK-1/2 phosphorylation during the preconditioning and reperfusion phases after the period of lethal ischemia. IPC induced a fourfold increase in Akt, ERK-1/2, and p70S6K phosphorylation at reperfusion and reduced the infarct risk-to-volume ratio (56.9 +/- 5.7 and 20.9 +/- 3.6% for control and IPC, respectively, P < 0.01). Inhibiting the IPC-induced phosphorylation of Akt, ERK-1/2, and p70S6K at reperfusion with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY-294002 or the MEK-1/2 inhibitor PD-98059 abrogated IPC-induced protection (46.3 +/- 5.8, 49.2 +/- 4.0, and 20.9 +/- 3.6% for IPC + LY-294002, IPC + PD-98059, and IPC, respectively, P < 0.01), demonstrating that the phosphorylation of these kinases at reperfusion is required for IPC-induced protection. In conclusion, we demonstrate that the reperfusion phase following sustained ischemia plays an essential role in mediating IPC-induced protection. Specifically, we demonstrate that IPC protects the heart by phosphorylating the prosurvival kinases Akt and ERK-1/2 at reperfusion.
authors.affiliation: The Hatter Institute, University College London Hospital, London, United Kingdom.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Hausenloy
authors.forename: A
authors.initials: A
authors.lastname: Tsang
authors.forename: Mihaela M
authors.initials: MM
authors.lastname: Mocanu
authors.forename: Derek M
authors.initials: DM
authors.lastname: Yellon
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009203:Myocardial Infarction / Q000378:metabolism / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000473:pathology; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004791:Enzyme Inhibitors; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C494920:Akt1 protein, rat