Abstract 545: Generation of Oxidized Phosphatidylcholines During Hypoxia-Reoxygenation Triggers Cell Death of Postnatal Cardiac Myocytes

Abstract

Reperfusion of ischemic heart tissue leads to a rapid burst of reactive oxygen species which initiates a cascade of events that cumulate in cell death. The most susceptible biomolecules to oxidative injury are membrane associated phospholipids. Oxidized phospholipids including oxidized phosphatidylcholines (OxPC), have shown to be potent activators of the intrinsic apoptotic signaling cascade. We hypothesize that the production of OxPC within hypoxic myocytes mediates damage from hypoxia-reoxygenation (H-R) by triggering inappropriate cardiac myocytes death. Hence, we determined whether, bioactive OxPC are produced in cardiomyocytes during H-R, and whether OxPC species induces apoptotic response resulting in cell death of cardiomyocytes. Post-natal rat cardiomyocytes were isolated from 2 d old rat pups and submitted to primary culture in serum-free medium. Cardiac myocytes were subjected to hypoxia (H) for 1 hour in a specialized gas-tight chamber under continuous nitrogen atmosphere followed by 1 hour reoxygenation (R). Lipidomic analysis of cardiac myocytes following H-R was determined by high performance liquid chromatography linked to tandem mass spectrometry was used to quantitate 82 distinct OxPC species from cell lipid extracts. Cell viability of cardiomyocytes was assessed in the absence and presence of known OxPC molecules (POVPC, PONPC, PGPC, PAzPC) and control non-oxidized PSPC. Lipidomic analysis of OxPC species showed increased generation of fragmented OxPC after H-R (10.20±0.67μg/mL vs1.95±0.24μg/mL, p<0.005) when compared to control cells. Cells exposed to POVPC and PONPC showed marked dose dependent increase in cell death compared to equal molar concentration of PSPC. There was also marked increase in mitochondrial permeability upon exposure to fragmented OxPC molecules. To our knowledge this is the first demonstration that OxPC are generated within post-natal cardiomyocytes during H-R and potent inducers of cell death of cardiac myocyte during H-R. Interventions designed to modulate the synthesis of cytotoxic OxPC during H-R may prove beneficial in suppressing aberrant cardiac myocyte cell death and loss of ventricular function in patients with ischemic heart disease or following myocardial infarction.