Abstract 885: The Role of Paraoxonase 2 (PON2) in Mitochondrial Membrane Phospholipid Composition and Lipid Peroxidation

Abstract

Introduction: We have recently reported that PON2 plays a protective role against myocardial ischemia-reperfusion injury (IRI) by reducing oxidative stress and mitochondrial dysfunction, in the form of improved calcium retention capacity and integrity of the mitochondrial membrane potential. It is known that mitochondrial phospholipids (PL) play critical roles in mitochondrial homeostasis via maintenance of normal bioenergetics and membrane function. These PLs undergo oxidative stress during IRI resulting in an increase in lipid peroxidation, damage of the respiratory complexes and loss of mitochondrial membrane potential. Hypothesis: PON2 protects cardiomyocytes against myocardial IRI by modulating the mitochondrial membrane phospholipid composition and lipid peroxidation. Methods: Two methods were developed to measure 1) various oxidized lipid species (i.e. 5, 12, and 15 HETE, 9, 13 HODE, and 5-oxoETE) and inflammatory markers (lipid panel) and 2) a panel of phospholipid species (i.e. PC, PE, PS) (PLP) via mass spectrometry (ESI LC-MS/MS). Mitochondria were isolated from male C57BL6/J (WT) and PON2 deficient (PON2-def) mice. PLs were then extracted using a modified Bligh and Dyer method with the respective internal standards, and run on a SCIEX 5500 QTrap run in negative ion mode and controlled by Analyst 1.6.2 software. Data is expressed as mean±SEM. Student’s T-test is used for statistical analysis, with p<0.05 considered statistically significant. Results: We determined that under baseline conditions, PON2-deficient mice have altered mitochondrial membrane PL composition and lipid peroxidation. We observe that PON2-def mitochondria have a significant decrease in various phosphatidylcholine species and an increase in phosphatidylethanolamine (42:9). In addition, there were variations in the composition of phosphatidylserine and phosphatidylinositol. The alteration of mitochondrial PL were accompanied by significant increases in various oxidized lipids including 9, 13-HODE, 14S, 17S-HDHA, 5, 15-HETE, and 5-oxoETE. Conclusion: Our preliminary studies point to the important role that PON2 plays in modulating mitochondrial PL composition and lipid peroxidation, and warrant further investigation under myocardial IRI.