Anesthetic preconditioning improves adenosine triphosphate synthesis and reduces reactive oxygen species formation in mitochondria after ischemia by a redox dependent mechanism.
BACKGROUND
Mitochondrial changes that characterize the heart after anesthetic preconditioning (APC) or the mechanisms by which mitochondrial triggering factors lead to protection are unknown. This study hypothesized that generation of reactive oxygen species (ROS) during APC is required to initiate the mitochondrial protective effects, and that APC leads to improved mitochondrial electron transport chain function and cardiac function during reperfusion.


METHODS
Isolated guinea pig hearts were subject to 30 min ischemia and 120 min reperfusion. Prior to ischemia hearts were either untreated (I/R), or treated with sevoflurane (APC), in the presence or absence of the ROS scavenger tiron (TIR), or the superoxide dismutase mimetic MnTBAP (TBAP). Intracellular ROS were measured by spectrofluorometry using the fluorescent probe dihydroethidium (DHE). In another series of experiments, using the same protocol, hearts were reperfused for only 5 min and removed for measurement of adenosine triphosphate (ATP) synthesis by luciferin-luciferase luminometry and ROS generation by dichlorohydro-fluorescein (DCF) fluorescence in isolated mitochondria.


RESULTS
The APC improved cardiac function and reduced infarction. Tiron or MnTBAP abrogated the protection afforded by APC. Mitochondrial ATP synthesis was decreased by 70 +/- 3% after IR alone, by only 7 +/- 3% after APC, by 69 +/- 2% after APC+TIR, and by 71 +/- 3% after APC + TBAP. Mitochondrial ROS formation (DCF) increased by 48 +/- 3% after IR alone, by 0 +/- 2% after APC, by 43 +/- 4% after APC + TIR, and by 46 +/- 3% after APC + TBAP. ROS generation (DHE) was increased in I/R group at 5 and 120 min reperfusion. This was attenuated by APC but this protective effect was abrogated in APC + TIR and APC + TBAP groups.


CONCLUSIONS
The results indicate that ROS are central both in triggering and mediating APC, and that the mitochondrion is the target for these changes.
Novalija
Enis
E
Medical College of Wisconsin, Department of Anesthesiology, M4280, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA. novalija@mcw.edu
Kevin
Leo G
LG
Eells
Janis T
JT
Henry
Michele M
MM
Stowe
David F
DF
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002458:Cell Fractionation; D003326:Coronary Circulation / Q000502:physiology; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008929:Mitochondria, Heart / Q000378:metabolism* / Q000648:ultrastructure; D023421:Models, Animal; D015425:Myocardial Reperfusion; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013997:Time Factors; D016277:Ventricular Function, Left / Q000502:physiology
D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate