title: Activation of p38 mitogen-activated protein kinase abolishes insulin-mediated myocardial protection against ischemia-reperfusion injury.
abstract: Myocardial ischemia-reperfusion injury contributes significantly to morbidity and mortality in patients with diabetes. Insulin decreases myocardial infarct size in animals and the rate of apoptosis in cultured cells. Ischemia-reperfusion activates p38 mitogen-activated protein kinase (MAPK), which regulates cellular apoptosis. To examine whether p38 MAPK affects insulin's cardioprotection against ischemia-reperfusion injury, we studied overnight-fasted adult male rats by use of an in vivo rat model of myocardial ischemia-reperfusion. A euglycemic clamp (3 mU.min(-1).kg(-1)) was begun either 10 min before ischemia (InsulinBI), 5 min before reperfusion (InsulinBR), or 30 min after the onset of reperfusion (InsulinAR), and continued until the end of the study. Compared with saline control, insulin decreased the infarct size in both InsulinBI (P < 0.001) and InsulinBR (P < 0.02) rats but not in InsulinAR rats. The ischemic area showed markedly increased phosphorylation of p38 MAPK compared with the nonischemic area in saline animals. Acute activation of p38 MAPK with anisomycin (2 mg/kg iv 10 min before ischemia) had no effect on infarct size in saline rats. However, it completely abolished insulin's protective effect in InsulinBI and InsulinBR rats. Activation of p38 MAPK by anisomycin was associated with marked and persistent elevation in IRS-1 serine phosphorylation. Treatment of animals with SB-239063, a potent and specific inhibitor of p38 MAPK, 10 min before reperfusion enabled insulin-mediated myocardial protection in InsulinAR rats. We conclude that insulin protects myocardium against ischemia-reperfusion injury when given prior to ischemia or reperfusion, and activation of p38 MAPK abolishes insulin's cardioprotective effect.
authors.affiliation: Div. of Endocrinology and Metabolism, Dept. of Medicine, Univ. of Virginia Health System, PO Box 801410, Charlottesville, VA 22908, USA.
authors.forename: Weidong
authors.initials: W
authors.lastname: Chai
authors.forename: Yangsong
authors.initials: Y
authors.lastname: Wu
authors.forename: Guolian
authors.initials: G
authors.lastname: Li
authors.forename: Wenhong
authors.initials: W
authors.lastname: Cao
authors.forename: Zequan
authors.initials: Z
authors.lastname: Yang
authors.forename: Zhenqi
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004347:Drug Interactions; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy* / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D002316:Cardiotonic Agents; D004791:Enzyme Inhibitors; D007004:Hypoglycemic Agents; D007093:Imidazoles; D007328:Insulin; D011500:Protein Synthesis Inhibitors; D011743:Pyrimidines; D000841:Anisomycin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; C406525:SB 239063