Peroxiredoxin 6 as an antioxidant enzyme:: Protection of lung alveolar epithelial type II cells from H2O2-induced oxidative stress

We evaluated the antioxidant role of peroxiredoxin 6 (Prdx6) in primary lung alveolar epithelial type II cells (AEC II) that were isolated from wildtype (WT), Prdx6-/-, or Prdx6 transgenic (Tg)overexpressing mice and exposed to H2O2 at 50-500 mu M for 1-24 h. Expression of Prdx6 in Tg AEC II was sevenfold greater than WT. Prdx6 null AEC II exposed to H2O2 showed concentration-dependent cytotoxicity indicated by decreased "live/dead" cell ratio, increased propidium iodide (PI) staining, increased annexin V binding, increased DNA fragmentation by TUNEL assay, and increased lipid peroxidation by diphenylpyrenylphosphine (DPPP) fluorescence. Compared to Prdx6 null cells, oxidant-mediated damage was significantly less in WT AEC II and was least in Prdx6 Tg cells. Thus, Prdx6 functions as an antioxidant enzyme in mouse AEC II. Prdx6 has been shown previously to reduce phospholipid hydroperoxides and we postulate that this activity is a major mechanism for the effectiveness of Prdx6 as an antioxidant enzyme.