Oxygen radicals generated at reflow induce peroxidation of membrane lipids in reperfused hearts.

Abstract

To test whether generation of oxygen radicals during postischemic reperfusion might promote peroxidation of cardiac membrane lipids, four groups of Langendorff-perfused rabbit hearts were processed at the end of (a) control perfusion, (b) 30 min of total global ischemia at 370C without reperfusion, (c) 30 min of ischemia followed by reperfusion with standard perfusate, (d) 30 min of ischemia followed by reperfusion with the oxygen radical scavenger human recombinant superoxide dismutase (h-SOD). The left ventricle was homogenized and tissue content of malonyldialdehyde (MDA), an end product of lipid peroxidation, was measured on the whole homogenate as well as on various subcellular fractions. Reperfusion was accompanied by a significant increase in MDA content of the whole homogenate and of the fraction enriched in mitochondria and lysosomes. This phenomenon was not observed in hearts subjected to ischemia but not reperfused, and was similarly absent in those hearts which received h-SOD at reflow. Reperfused hearts also had significantly greater levels of conjugated dienes (another marker of lipid peroxidation) in the mitochondrial-lysosomal fraction. Again, this phenomenon did not occur in ischemic hearts or in reperfused hearts treated with h-SOD. Unlike the effect on tissue MDA and conjugated dienes, reperfusion did not significantly stimulate release of MDA in the cardiac effluent. Treatment with h-SOD was also associated with significant improvement in the recovery ofcardiac function. In conclusion, these data directly demonstrate that postischemic reperfusion results in enhanced lipid peroxidation of cardiac membranes, which can be blocked by h-SOD, and therefore is most likely secondary to oxygen radical generation at reflow. (J. Clin.

Cardioprotective Pathways During Reperfusion: Focus on Redox Signaling and Other Modalities of Cell Signaling

“…In fact, ONOO À reacts with sulfhydryl groups and iron-sulfur clusters in respiratory complexes, and induces nitration=oxidation of MnSOD, further augmenting mitochondrial oxidative stress in a vicious cycle (158).Yet, as said, when NO is sufficiently produced, ONOO À cytotoxicity can be reduced via a secondary reaction (164). NO deficiency can also cause vasoconstriction and formation of micro-thrombi into the lumen of the small vessels (1,162,169). These mechanisms, combined with the adhesion of the leucocytes to the endothelium, induced by ROS, can lead to the ''no-reflow phenomenon'' (1,162).…”

“…For instance, ROS indiscriminately react with lipids, proteins, and DNA. These are complex processes: in brief, ROS reaction with lipids gives rise to peroxyl and alkoxyl radicals leading to lipid peroxidation; reaction with amino acid residue side chains of proteins form protein carbonyls, and reaction with methionine forms methionine sulfide; reaction with DNA may oxidize DNA bases such as 8-OhdG, leading to mutation and DNA strand breaking (1,12,187,204,(208)(209)(210)(211)(212). Excessive ROS=RNS production is considered deleterious to cell function and mitochondria, where they act as inducers of mPTP opening (see below).…”

“…Oxidative stress related to the massive generation of ROS=RNS may play an important role in reperfusion injury (1,12,187,204,(208)(209)(210)(211)(212). At reperfusion, O 2 À and other ROS may strongly oxidize the cardiomyocytes already damaged by the ischemia, thus favoring cell death (1,2,53,116,183,184 in myocardial injury (10-12, 52, 135, 165).…”

“…At reperfusion, O 2 À and other ROS may strongly oxidize the cardiomyocytes already damaged by the ischemia, thus favoring cell death (1,2,53,116,183,184 in myocardial injury (10-12, 52, 135, 165). In particular, high ONOO À concentrations are considered to be highly cytotoxic (11,12,135,165).…”

The effect of oxygen free radicals on calcium current and dihydropyridine binding sites in guinea‐pig ventricular myocytes

“…Since it is known that production of OFRs promotes peroxidation of membrane lipids (Mak et al, 1983;Ambrosio et al, 1991;Sakomoto et al, 1991), the effect of BHT, a well characterized antioxidant agent (Mikuni et al, 1987), on OFRinduced reduction of DHP binding sites, was evaluated. A typical experiment is shown in Figure 4: [3H]-PN200-110 binding was evaluated in myocytes isolated from the same heart and incubated with or without DHF for 30 min in the absence or in the presence of BHT.…”