60 - The Phospholipase A2 (PLA2) and Phospholipid Hydroperoxide Glutathione Peroxidase Activities of Peroxiredoxin 6 (Prdx6) Are Required for Repair of Peroxidized Lung Cell Membranes

Abstract

Lipid peroxidation associated with peroxidative stress gradually resolves over several hours in wild type (WT) mouse lungs and isolated pulmonary endothelial cells (FRBM 87:356, 2015). However, resolution is greatly delayed in lungs or cells that are null for peroxiredoxin 6 (Prdx6). Prdx6 expresses 3 distinct enzymatic activities: phospholipase A 2 (PLA 2 ), GSH peroxidase (GPx), and lysophosphatidylcholine acyltransferase (LPCAT). All 3 activities contribute to the repair of peroxidized cell membranes. For the present study, we evaluated a mouse in which the H26 amino acid residue of Prdx6 was mutated (H26A). H26A-Prdx6 does not bind to phospholipids and, therefore, it lacks both PLA 2 activity and the ability to reduce phospholipid hydroperoxides (PLOOH GPx activity), but retains both LPCAT and peroxidase with H 2 O 2 substrate activities. Lungs were perfused with tert -butyl hydroperoxide (tBOOH, 15-25mM) for 1 h followed by 2 h perfusion with tBOOH–free solution. Lungs were assayed at intervals for lipid peroxidation by the ferrous xylenol orange and TBARS reactions. Lipid peroxidation in WT lungs increased approximately 3-fold after 2 h of lung perfusion with tBOOH but then returned to control values during during the subsequent 2 h of peroxide-free perfusion. However, lungs from H26A-Prdx6 mice showed no significant change in lipid peroxidation during the 2 h post-tBOOH period. These results indicate that the reduction (PLOOH GPx activity) or hydrolysis (PLA 2 activity) of phospholipid hydroperoxides by Prdx6 is required for reversal of lung lipid peroxidation. Further, the scavenging of low mol wt peroxides (eg, tBOOH) does not play a role in cell membrane repair.