Role of arachidonic acid, lipoxygenase, and mitochondrial depolarization in reperfusion arrhythmias.
We have sought evidence that arachidonic acid (AA) induces mitochondrial depolarization in isolated myocytes by a lipoxygenase (LOX)-dependent mechanism and that such depolarization might contribute to arrhythmogenesis following ischemia-reperfusion injury. A method was developed for measuring mitochondrial depolarization in isolated adult rat myocytes in suspension, using tetramethylrhodamine ethyl ester. The addition of AA to myocytes resulted in mitochondrial depolarization that was inhibited by the LOX inhibitor baicalein, by the reactive oxygen species (ROS) scavenger mercaptoproprionylglycine, and by the anion channel inhibitor diisothiocyanatostilbene-disulfonic acid (DIDS). AA induced mitochondrial uncoupling and mitochondrial ATPase activity in myocytes, but both were insensitive to baicalein. We conclude that the metabolic effect of AA in myocytes puts mitochondria into an energetically compromised state where membrane potential is easily changed by the DIDS-sensitive LOX/ROS-mediated opening of an inner membrane anion channel. In an in vivo anesthetized rat model of coronary artery occlusion, baicalein was found to strongly inhibit arrhythmias induced by ischemia-reperfusion injury. Arrhythmias following ischemia-reperfusion injury have been previously associated with DIDS-sensitive ROS-mediated mitochondrial depolarization, and free fatty acids including AA were previously found to accumulate during such injury. We therefore conclude that arrhythmias following ischemia-reperfusion injury might originate from mitochondrial depolarization mediated by LOX and AA.
Haworth
Robert A
RA
Cardiology Section, Medical Service, Wm. S. Middleton Memorial Veterans Hospital, Madison WI 53792, USA. haworth@surgery.wisc.edu
Potter
Katherine T
KT
Russell
Douglas C
DC
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001145:Arrhythmias, Cardiac / Q000201:enzymology / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D004195:Disease Models, Animal; D004734:Energy Metabolism; D005260:Female; D044950:Flavanones / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006019:Glycolysis; D008084:Lipoxygenase / Q000378:metabolism*; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D008297:Male; D053078:Membrane Potential, Mitochondrial; D008929:Mitochondria, Heart / Q000187:drug effects / Q000201:enzymology*; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D015428:Myocardial Reperfusion Injury / Q000150:complications* / Q000188:drug therapy / Q000201:enzymology / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D008625:Tiopronin / Q000494:pharmacology
D044950:Flavanones; D016166:Free Radical Scavengers; D016859:Lipoxygenase Inhibitors; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017382:Reactive Oxygen Species; D016718:Arachidonic Acid; C006680:baicalein; D008625:Tiopronin; D008084:Lipoxygenase; D000251:Adenosine Triphosphatases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid