Oxidized phosphatidylcholines (OxPCs) as mediators of myocardial ischemia/reperfusion injury
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Date
2020
Authors
Stamenkovic, Aleksandra
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Abstract
The membrane phospholipid phosphatidylcholine (PC) is highly susceptible to oxidation during myocardial ischemia/reperfusion (I/R) injury. The production of oxidized phosphatidylcholines (OxPCs) results in cardiomyocyte death. However, the mechanism of cell death is unknown. The aim of this thesis is to determine the mechanisms by which OxPC triggers cardiomyocyte cell death during I/R injury and to identify possible therapeutic agent(s) to prevent OxPC-mediated cell death. Isolated cardiomyocytes were treated with increasing concentrations of fragmented OxPCs. Cardiomyocyte viability, bioenergetic response and calcium transients were determined. Cleaved caspase 3 and TUNEL staining were used as apoptosis markers and High mobility group box 1 (HMGB1) protein as a marker for necrosis. The role of ferroptosis was investigated by addition of ferrostatin-1. Isolated cardiomyocytes were exposed to 1 h ischemia followed by 1 h of reperfusion. Ferrostatin-1 or the antibody to OxPCs, E06, was added at the time of reperfusion. In a porcine model of I/R, the coronary artery was occluded for 1 h by inflation of a balloon inserted in the coronary artery. At reperfusion, the E06 antibody was infused for 1 h. When isolated cardiomyocytes were incubated with five different fragmented OxPCs, 1-palmitoyl-2-(5’-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC) and 1-palmitoyl-2-(9'-oxo-nonanoyl)-sn-glycero-3-phosphocholine (PONPC) had the most potent cardiotoxic effect. POVPC and PONPC also caused a significant decrease in Ca2+ transients and net contraction in isolated cardiomyocytes compared to vehicle treated control cells. PONPC and POVPC also depressed indices of cardiomyocyte respiration. Caspase 3 activation, TUNEL staining and nuclear HMGB1 activity were unaffected in cells treated with either POVPC or PONPC. However, glutathione peroxidase 4 (GPx4) activity was markedly suppressed in cardiomyocytes treated with POVPC and PONPC. An inhibitor of ferroptosis, ferrostatin-1 also suppressed cell death induced by OxPCs. The E06 antibody directed against OxPCs also protected cardiomyocytes and infarct size was reduced in in vivo I/R porcine models. The data support the conclusion that OxPCs induce cardiomyocyte death via ferroptosis in I/R via a disruption of mitochondrial bioenergetics, calcium transients. Cell death was inhibited by ferrostatin-1 and by neutralization of OxPC with E06. These results hold significant promise to provide a new therapeutic approach for myocardial I/R injury.
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Keywords
Myocardial ischemia/reperfusion injury