[Antioxidative role of peroxiredoxin 6 in acute lung injury]

To confirm the antioxidant protective effect of peroxiredoxin 6 (Prdx6) in acute lung injury in mice.

Lung injury or lung alveolar type II epithelial cell (AEC II) injury models were induced in mice by 100% O2 exposure or H2O2 treatments. Mice and AEC II cell survival rate or BALF analysis were applied for evaluating the degree of acute lung injury. Western Blot assay was used to determine Prdx6 or Gpx1 protein expression in lung. Annexin V staining method was applied to detect cell apoptosis on cultured AEC II cell, and thiobarbituric acid reactive substance (TBARS) measurement and diphenyl-1-pyrenyl phospholine (DPPP) assays were separately used to measure the level of lipid peroxidation in mice lung and AEC II cell membrane.

Under 100% O2 exposure, Prdx6-/- mice presented 24 h shorter survival time compared to wild type (WT) mice, on the contrary, Prdx6 gene over-expressed (Tg Prdx6) mice showed enhanced mice survival; meanwhile, the degree of AEC II cell injury had H2O2-dose dependent pattern with interactive relationship of Prdx6 protection. Under 100% O2 exposure for 72 h, it caused 7-fold decreased Gpx1 expression in Prdx6-/- mouse lung with no remarkable decrease of Prdx6 expression in Gpx1-/- mice. The percentage of apoptotic cells was significantly increased in AEC II cells from Prdx6-/- mice, and the percentage of AEC II apoptotic cells from Tg Prdx6 kept consistently around 10% under H2O treatments; also, the lipid peroxidation level of AEC II cell membrane was the highest in the group of Prdx6-/- mice, which was about 2 or 4-fold increased compared to the groups of WT or Tg Prdx6, separately; meanwhile, the lipid peroxidation level in Prdx6-/- mice, was also the highest compared to the other groups.

Prdx6 plays a critical role in defending acute oxidative lung injury and its function of defending cell apoptosis and cell membrane lipid peroxidation suggests its unique cell-based protective effect.