Deletion of peroxiredoxin 6 potentiates lipopolysaccharide-induced acute lung injury in mice*

To investigate the role and signaling pathway of peroxiredoxin 6, a newly identified peroxidase, in lipopolysaccharide-induced acute lung injury.Prospective, randomized, controlled study.Research laboratory.Peroxiredoxin 6 (-/-) and wild-type C57BL/6 mice.Wild-type or peroxiredoxin 6 (-/-) mice were challenged by intratracheal instillation of lipopolysaccharide (5 mg/kg) for 4 hrs or 24 hrs for lung injury measurement. In other studies, peritoneal macrophages, isolated from wild-type and peroxiredoxin 6 (-/-) mice, were preincubated in presence or absence of mitogen-activated protein kinases inhibitors for 30 mins before being stimulated with lipopolysaccharide (1 μg/mL) for 4 hrs.Bronchoalveolar lavage myeloperoxidase activity and the lung injury score were significantly increased in peroxiredoxin 6 (-/-) mice compared with wild-type mice after lipopolysaccharide instillation at both 4 hrs and 24 hrs. Hydrogen peroxide and malondialdehyde levels, as well as nuclear factor-κB activities, tumor necrosis factor-α, interleukin-1β, and matrix metalloproteinase-9 messenger RNA, protein concentration, and activities were significantly increased whereas total antioxidative capability was markedly decreased in lungs of peroxiredoxin 6 (-/-) mice compared with wild-type mice. In vitro studies showed intracellular reactive oxygen species levels and release of tumor necrosis factor-α, interleukin-1, and matrix metalloproteinase-9 were significantly increased in macrophages from peroxiredoxin 6 (-/-) mice compared with that from wild-type mice after lipopolysaccharide stimulation. Cytokines release was partially suppressed by extracellular signal-regulated kinase and c-Jun N-terminal kinase inhibitors, but not by the p38 mitogen-activated protein kinase inhibitor.Deletion of peroxiredoxin 6 exaggerates lipopolysaccharide-induced acute lung injury and inflammation with increased oxidative stress, inflammatory responses, and matrix degradation, all of which were partially dependent on nuclear factor-κB, extracellular signal-regulated kinase, and c-Jun N-terminal kinase pathways.