title: Preconditioning in cardiomyocytes protects by attenuating oxidant stress at reperfusion.
abstract: Cardiomyocyte death after ischemia/reperfusion correlates with oxidant stress, and antioxidants confer protection in that model. Preconditioning (PC) with hypoxia or adenosine also confers protection, leading us to hypothesize that PC protects by attenuating oxidant generation during subsequent ischemia/reperfusion. Chick cardiomyocytes were preconditioned with 10 minutes of hypoxia or adenosine (100 micromol/L), followed by 1 hour of simulated ischemia and 3 hours of reperfusion. Adenosine PC decreased cell death from 50+/-3% to 18+/-4% and enhanced the return of contractions during reperfusion, as observed previously with hypoxic PC. A transient burst of dichlorofluorescein (sensitive to H2O2 oxidation that was significantly attenuated by PC initiated by hypoxia or adenosine was seen at reperfusion. The protein kinase C (PKC) inhibitor Go-6976 and the mitochondrial ATP-sensitive K(+) (K(ATP)) channel inhibitor 5-hydroxydecanoate each abolished protection and abrogated the PC-induced attenuation of reperfusion oxidant stress. By contrast, when given only at reperfusion, the K(+) channel opener pinacidil or the antioxidants 2-mercaptopropionylglycine and 1,10-phenanthroline decreased oxidant stress at reperfusion and improved survival and return of contractions. Thus, PC protection is associated with an attenuation of the oxidant burst at reperfusion, regardless of the method by which PC is triggered. Loss of PC protection associated with PKC inhibition or K(ATP) channel inhibitors is associated with a restoration of that oxidant stress. These results suggest a mechanism for PC protection and reveal a functional link between PKC activation and K(ATP) channel activation in that pathway.
authors.affiliation: Section of Emergency Medicine, Department of Medicine, The University of Chicago, Chicago, Ill 60637, USA.
authors.forename: T
authors.initials: T
authors.lastname: Vanden Hoek
authors.forename: L B
authors.initials: LB
authors.lastname: Becker
authors.forename: Z H
authors.initials: ZH
authors.lastname: Shao
authors.forename: C Q
authors.initials: CQ
authors.lastname: Li
authors.forename: P T
authors.initials: PT
authors.lastname: Schumacker
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D003652:Decanoic Acids / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006880:Hydroxy Acids / Q000494:pharmacology; D019194:Ischemic Preconditioning; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000166:cytology / Q000201:enzymology; D009200:Myocardial Contraction / Q000502:physiology; D017202:Myocardial Ischemia / Q000378:metabolism*; D009206:Myocardium / Q000737:chemistry / Q000166:cytology / Q000201:enzymology*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D020110:Pinacidil / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015427:Reperfusion Injury / Q000378:metabolism*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000889:Anti-Arrhythmia Agents; D003652:Decanoic Acids; D006880:Hydroxy Acids; D016877:Oxidants; D015221:Potassium Channels; D017382:Reactive Oxygen Species; D014665:Vasodilator Agents; C052853:5-hydroxydecanoic acid; D020110:Pinacidil; D006861:Hydrogen Peroxide; D011493:Protein Kinase C