H(2)O(2) opens mitochondrial K(ATP) channels and inhibits GABA receptors via protein kinase C-epsilon in cardiomyocytes.
Oxygen radicals and protein kinase C (PKC) mediate ischemic preconditioning. Using a cultured chick embryonic cardiomyocyte model of hypoxia and reoxygenation, we found that the oxygen radicals generated by ischemic preconditioning were H(2)O(2). Like preconditioning, H(2)O(2) selectively activated the epsilon-isoform of PKC in the particulate compartment and increased cell viability after 1 h of hypoxia and 3 h of reoxygenation. The glutathione peroxidase ebselen (converting H(2)O(2) to H(2)O) and the superoxide dismutase inhibitor diethyldithiocarbamic acid abolished the increased H(2)O(2) and the protection of preconditioning. PKC activation with phorbol 12-myristate 13-acetate increased cell survival; the protection of preconditioning was blocked by epsilonV(1-2), a selective PKC-epsilon antagonist. Similar to preconditioning, the protection of PKC activation was abolished by mitochondrial K(ATP) channel blockade with 5-hydroxydecanoate or by GABA receptor stimulation with midazolam or diazepam. In addition, PKC, mitochondrial ATP-sensitive K(+) (K(ATP)) channels, and GABA receptors had no effects on H(2)O(2) generated by ischemic preconditioning before prolonged hypoxia and reoxygenation. We conclude that H(2)O(2) opens mitochondrial K(ATP) channels and inhibits GABA receptors via activating PKC-epsilon. Through this signal transduction, preconditioning protects ischemic cardiomyocytes.
Zhang
Hong Yan
HY
Department of Anesthesiology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
McPherson
Bradley C
BC
Liu
Huiping
H
Baman
Timir S
TS
Rock
Peter
P
Yao
Zhenhai
Z
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002642:Chick Embryo; D003652:Decanoic Acids / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005452:Fluoresceins; D005456:Fluorescent Dyes; D018756:GABA Antagonists / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects / Q000196:embryology / Q000502:physiology*; D006352:Heart Ventricles / Q000196:embryology; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006880:Hydroxy Acids / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins / Q000187:drug effects / Q000502:physiology; D008874:Midazolam / Q000494:pharmacology; D017202:Myocardial Ischemia / Q000503:physiopathology; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D015221:Potassium Channels; D011493:Protein Kinase C / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D018079:Receptors, GABA / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D016276:Ventricular Function
D002121:Calcium Channel Blockers; D003652:Decanoic Acids; D004791:Enzyme Inhibitors; D005452:Fluoresceins; D005456:Fluorescent Dyes; D018756:GABA Antagonists; D006880:Hydroxy Acids; D007527:Isoenzymes; D008565:Membrane Proteins; D015221:Potassium Channels; D018079:Receptors, GABA; C117780:mitochondrial K(ATP) channel; C037631:2',7'-dichlorofluorescein; C052853:5-hydroxydecanoic acid; D006861:Hydrogen Peroxide; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D013755:Tetradecanoylphorbol Acetate; D008874:Midazolam