O₂delivery and redox state are determinants of compartment-specific reactive O₂species in myocardial reperfusion

Abstract

Stoner JD, Clanton TL, Aune SE, Angelos MG. O2 delivery and redox state are determinants of compartment-specific reactive O2 species in myocardial reperfusion. Am J Physiol Heart Circ Physiol 292: H109 -H116, 2007. First published October 6, 2006; doi:10.1152/ajpheart.00925.2006.-Reperfusion of the ischemic myocardium leads to a burst of reactive O2 species (ROS), which is a primary determinant of postischemic myocardial dysfunction. We tested the hypothesis that early O2 delivery and the cellular redox state modulate the initial myocardial ROS production at reperfusion. Isolated buffer-perfused rat hearts were loaded with the fluorophores dihydrofluorescein or Amplex red to detect intracellular and extracellular ROS formation using surface fluorometry at the left ventricular wall. Hearts were made globally ischemic for 20 min and then reperfused with either 95% or 20% O2-saturated perfusate. The same protocol was repeated in hearts loaded with dihydrofluorescein and perfused with either 20 or 5 mM glucose-buffered solution to determine relative changes in NADH and FAD. Myocardial O2 delivery during the first 5 min of reperfusion was 84.7 Ϯ 4.2 ml O2/min with 20% O2-saturated buffer and 354.4 Ϯ 22.8 ml O2/min with 95% O2 (n ϭ 8/group, P Ͻ 0.001). The fluorescein signal (intracellular ROS) was significantly increased in hearts reperfused with 95% O2 compared with 20% O2. However, the resorufin signal (extracellular ROS) was significantly increased with 20% O2 compared with 95% O2 during reperfusion. Perfusion of hearts with 20 mM glucose reduced the ⅐ NADH during ischemia (P Ͻ 0.001) and the ⅐ ROS at reperfusion (P Ͻ 0.001) compared with 5.5 mM-perfused glucose hearts. In conclusion, initial O2 delivery to the ischemic myocardium modulates a compartment-specific ROS response at reperfusion such that high O2 delivery promotes intracellular ROS and low O2 delivery promotes extracellular ROS. The redox state that develops during ischemia appears to be an important precursor for reperfusion ROS production. ischemia; reoxygenation; oxygen radicals REINTRODUCTION OF O 2 to the globally ischemic heart triggers a cascade of reperfusion events, including an initial burst of reactive O 2 species (ROS). Studies of the isolated heart suggest that ROS production peaks within the first few minutes of reperfusion (37). Although ROS at low levels appear to have signaling capabilities that are cardioprotective, particularly during ischemia (13), it is thought that the much larger ROS burst at the onset of reperfusion impairs recovery of ventricular function (8). Cell injury from ROS may be wide ranging and include direct injury to membrane lipids, oxidative modification of protein and deoxyribonucleic acid, and cellular signaling for mitochondrial apoptotic transition (32). Known sources for ROS during reperfusion include endothelial xanthine oxidase (30), NAD(P)H oxidase (12), and the mitochondrial electron transport chain (complexes 1 and 3) (6), although other sources are also possible.The role of ROS, including the ROS burst...

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Ischemic preconditioning attenuates mitochondrial localization of PTEN induced by ischemia-reperfusion

“…ROS production in perfused hearts was measured using the fluorescent probes dihydroethidium (DHE) and dihydrofluorescein (DHF) diacetate (DHFDA) as previously described (22,42). DHFDA passes through cell membranes and is converted to DHF by intracellular esterase and then oxidized to green fluorescein.…”

The Risk of Oxygen during Cardiac Surgery (ROCS) trial: study protocol for a randomized clinical trial

“…Following cardiopulmonary bypass pulsatile flow is restored, and ischemic tissues may be reperfused. In experimental models markers of oxidative damage surge following reperfusion [7–9, 28]. Markers of oxidative stress also surge after cardiopulmonary bypass [29, 30].…”

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