Comparison of glutathione peroxidase 1 (GPx1) and peroxiredoxin 6 (Prdx6) in protection against lung oxidative stress in a perfused lung model

Abstract

Prdx6 plays an important role in lung anti‐oxidant defense, presumably due to its unique ability to reduce phospholipid hydroperoxides. Our previous studies with intact mice and isolated endothelial cells showed greater sensitivity to oxidant stress of Prdx6 null compared to wild type and GPx1 null. We now used isolated perfused mouse lungs to compare their response to 1 hr treatment with t‐butyl hydroperoxide (t‐BOOH, 5 mM) or paraquat (PQ, 1 mM) added to the perfusate. Lung injury as indicated by protein in the broncoalveolar lavage fluid (BALF), LDH in the lung perfusate, and protein carbonyls in the lung homogenate was increased significantly in Prdx6 null compared to GPx1 null lungs. Lipid peroxidation analyzed by TBARS and 8‐isoprostanes in the BALF and lung homogenate as well as by 235nm fluorescence (conjugated dienes), Fe2+‐xylenol orange, and DPPP assays was significantly greater in Prdx6 null compared to GPx1 null lungs. Analysis of expression levels of oxidant related genes using a PCR‐based Superarray (SA Biosciences) indicated no significant differences between the Prdx6 and the GPx1 null, except for the target genes. We conclude that Prdx6 null are significantly more sensitive to oxidant stress as compared to GPx1 null, suggesting that the ability of Prdx6 to scavenge phospholipid hydroperoxides and to repair membrane lipid oxidation can account for its major role in antioxidant defense.