Opening mitoKATP increases superoxide generation from complex I of the electron transport chain.
Opening the mitochondrial ATP-sensitive K(+) channel (mitoK(ATP)) increases levels of reactive oxygen species (ROS) in cardiomyocytes. This increase in ROS is necessary for cardioprotection against ischemia-reperfusion injury; however, the mechanism of mitoK(ATP)-dependent stimulation of ROS production is unknown. We examined ROS production in suspensions of isolated rat heart and liver mitochondria, using fluorescent probes that are sensitive to hydrogen peroxide. When mitochondria were treated with the K(ATP) channel openers diazoxide or cromakalim, their ROS production increased by 40-50%, and this effect was blocked by 5-hydroxydecanoate. ROS production exhibited a biphasic dependence on valinomycin concentration, with peak production occurring at valinomycin concentrations that catalyze about the same K(+) influx as K(ATP) channel openers. ROS production decreased with higher concentrations of valinomycin and with all concentrations of a classical protonophoretic uncoupler. Our studies show that the increase in ROS is due specifically to K(+) influx into the matrix and is mediated by the attendant matrix alkalinization. Myxothiazol stimulated mitoK(ATP)-dependent ROS production, whereas rotenone had no effect. This indicates that the superoxide originates in complex I (NADH:ubiquinone oxidoreductase) of the electron transport chain.
Andrukhiv
Anastasia
A
Dept. of Biology, Portland State Univ., PO Box 751, Portland, OR 97207, USA.
Costa
Alexandre D
AD
West
Ian C
IC
Garlid
Keith D
KD
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology; D019806:Cromakalim / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D003652:Decanoic Acids / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D042967:Electron Transport Complex I / Q000502:physiology*; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D006880:Hydroxy Acids / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008689:Methacrylates / Q000494:pharmacology; D008929:Mitochondria, Heart / Q000187:drug effects / Q000502:physiology*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000502:physiology*; D008954:Models, Biological; D015221:Potassium Channels / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013481:Superoxides / Q000378:metabolism*; D013844:Thiazoles / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D000889:Anti-Arrhythmia Agents; D000935:Antifungal Agents; D003652:Decanoic Acids; D005456:Fluorescent Dyes; D006880:Hydroxy Acids; D007476:Ionophores; D008689:Methacrylates; D015221:Potassium Channels; D013844:Thiazoles; D014665:Vasodilator Agents; C117780:mitochondrial K(ATP) channel; D019806:Cromakalim; D013481:Superoxides; D014634:Valinomycin; C052853:5-hydroxydecanoic acid; C030517:myxothiazol; D000255:Adenosine Triphosphate; D017869:Cyclic GMP-Dependent Protein Kinases; D011493:Protein Kinase C; D042967:Electron Transport Complex I; D003981:Diazoxide