Hydrogen peroxide generation by mitochondria isolated from regionally ischemic and nonischemic dog myocardium

Abstract

We occluded the left anterior descending coronary artery of anesthetized, open-chest dogs, for 1 or 2 h. Some hearts were reperfused for 1 h after 1 h of ischemia. We isolated mitochondria from the central ischemic zone (CIZ) and a surrounding nonischemic zone (NIZ) of the left ventricle, and assayed H2O2 production using a horseradish peroxidase-dual wavelength spectrophotometric technique. Mitochondria, studied in the absence of exogenous respiratory chain inhibitors, generated H2O2 during State 4 respiration with succinate as the substrate. NIZ mitochondria in all groups produced ca. 1.5 nmols H2O2/min/mg protein (no significant differences between groups). The State 4 O2 consumption rates of NIZ mitochondria from hearts subjected to 1 h ischemia plus reperfusion, or 2 h of ischemia (ca. 30 nmols/min/mg) were significantly higher than that of NIZ mitochondria of hearts subjected to only 1 h of ischemia (23 nmols/min/mg). Thus, the ratio between H2O2 produced and State 4 O2 consumption fell from 6.5% to 5%. Mitochondria from all CIZ samples had State 4 O2 consumption rates that were not different from corresponding NIZ values. However CIZ mitochondria of hearts subjected to 1 h ischemia without reperfusion produced less H2O2 (1.1 +/- 0.1 nmols/min/mg), and had a slightly reduced H2O2/O2 ratio (4.4 +/- 0.7%), compared with their NIZ samples (1.5 +/- 0.1 nmols/min/mg; 5.3%). Reperfusion after 1 h of ischemia abolished these regional differences. The CIZ mitochondria from hearts subjected to 2 h ischemia produced only 0.75 +/- 0.22 nmols H2O2/min/mg (2.5% of State 4 O2 consumption). These values were 50% of corresponding NIZ values, and were significantly less than for any other group or tissue region. If similar phenomena occur in conscious animals subjected to incomplete regional ischemia, especially of relatively brief duration or if accompanied by reduced intracellular defenses against oxidants such as H2O2, they suggest that mitochondria persist as H2O2 sources and so may contribute to the oxidant load and myocardial dysfunction.

Cardiolipin Remodeling in the Heart

“…Mitochondria are substantial contributors to myocardial injury during ischemia and reperfusion. 83,[96][97][98] Ischemia leads to progressive damage to the ETC, [99][100][101][102][103][104] resulting in damage to complexes III and IV. 23,102,[105][106][107] The progression of ischemic damage is more rapid in subsarcolemmal mitochondria (SSM) located beneath the plasma membrane than in interfibrillar mitochondria (IFM) present between the myofibrils.…”

Blockade of Electron Transport during Ischemia Protects Cardiac Mitochondria

“…Mitochondria play a cardinal role in myocardial injury during ischemia and reperfusion (1)(2)(3)(4). Ischemia leads to progressive damage to the electron transport chain (5)(6)(7)(8)(9)(10).…”

The Dual Role of Reactive Oxygen Species-Generating Nicotinamide Adenine Dinucleotide Phosphate Oxidases in Gastrointestinal Inflammation and Therapeutic Perspectives

“…Electron leakage from the mitochondrial respiratory chain complex I and III could result in the reduction of molecular oxygen to O2°- (87). The mitochondria ability to generate ROS was initially described based on in vitro experiments with isolated organelles (147,160). More recent studies have however shown that spontaneous ROS release by mitochondria in living cells does not occur unless there are changes in the physical state of the membrane, such as fluidity (125).…”