== This project was approved by the University of Cincinnati Animal Care and Use Committee and was in compliance with the National Institutes of Health guidelines

== This project was approved by the University of Cincinnati Animal Care and Use Committee and was in compliance with the National Institutes of Health guidelines. mice occurred despite reduced inflammation and was associated with increased mitochondrial generation of H2O2and dysfunction. The mitochondrial dysfunction appeared to be related to complex I of the electron transport chain. These data suggest that hepatocyte Prdx6 traffics to the mitochondria during I/R to limit mitochondrial dysfunction as a protective mechanism against hepatocellular injury. Keywords:mitochondrial respiration, hepatocytes ischemia-reperfusion (i/r)injury is a major complication of transplantation, liver resection, and hemorrhagic shock (1,5,8,20,23). The injury resulting from warm hepatic I/R has a biphasic pattern. The early phase involves the production of reactive oxygen species (ROS) by Kupffer cells and hepatocytes and leads to an early oxidant-dependent injury (6,13,35). The late phase is characterized by a strong inflammatory cascade, culminating in the recruitment of neutrophils to the liver (11,32). The extent to which the initial cellular injury contributes to propagation of the inflammatory response and further tissue damage is usually poorly understood. There is considerable evidence suggesting that ROS generation is central to the injury response. ROS generated during early reperfusion often overwhelm endogenous antioxidant defenses, leading to induction of proinflammatory mediators (12), as well as direct damage to intracellular structures (25). Mitochondria are known to be a major source as well as a target for ROS. It was exhibited that treatment of hepatocytes withtert-butyl hydroperoxide, an analog of short-chain lipid hydroperoxides formed during oxidative stress, increased mitochondrial ROS production (29,30). The mitochondrial origin of the ROS burst during oxidant injury in hepatocytes supports the idea that mitochondria play a key role in hepatic I/R injury, since mitochondrial dysfunction is the main cause of hepatocellular death due to necrosis or apoptosis (19). Complexes I and III of the mitochondrial electron transport chain are major sources of ROS (3,4,39,42). The activities of these enzyme complexes are also considered rate-limiting actions for the mitochondrial respiratory chain. There are a number of endogenous antioxidants that protect the cell from ROS-induced damage. Superoxide dismutase, catalase, and glutathione peroxidase have been well studied. A relatively new group of antioxidants, the peroxiredoxins (Prdxs), belong to the rapidly growing family of the thiol-specific antioxidant proteins that are highly conserved from bacteria to mammals (7,34). The Prdxs are divided into two categories, the 1-Cys and 2-Cys Prdxs, based on the number of cysteine (Cys) residues directly involved in the reduction of peroxides. Mammalian cells express six Prdx isoforms (Prdxs1-6), which are divided into three categories. Four of the six mammalian Prdxs (Prdxs1-4) belong to the typical 2-Cys subgroup and have additional conserved Cys residues in the COOH-terminal region (34). Prdx5 is the single representative of the atypical 2-Cys Prdx class in mammalians (34). The Prdx6 isoform encloses only the NH2-terminal-conserved Cys and is, therefore, classified as a 1-Cys Prdx (16). Prdx6 uses glutathione and ascorbate as electron donors and is the only member of the Prdx family that has the ability to remove H2O2and phospholipid hydroperoxide and is, therefore, able to reduce the accumulation of phospholipid hydroperoxides in plasma membranes (24,28). Prdx6 expression has not previously been documented in mitochondria. However, Prdx6 has been described in other cell compartments, including the cytoplasm, maslinic acid secretory organelles, and lyosomes (10,44). In the present study, we examined changes to the hepatic mitochondrial maslinic acid proteasome during I/R maslinic acid injury. Our data show that this antioxidant Prdx6 shuttles from the cytoplasm to the mitochondria in hepatocytes during I/R injury. Furthermore, our data suggest that this translocation of Prdx6 helps to stabilize mitochondrial function during I/R injury. == MATERIALS AND METHODS == == Animals and hepatic I/R injury model. == This project was approved by the University of Cincinnati Animal Care and Use Committee and was in compliance with the National Institutes of Health guidelines. Male C57BL/6J mice (Jackson Laboratory, Bar Harbor, ME) and Prdx6 null mice (University of Pennsylvania, Philadelphia, PA), CTNND1 weighing 2125 g, were used in all experiments. The generation of Prdx6(/) mice is usually described elsewhere (27). The animals underwent either sham surgery or partial hepatic ischemia, as previously described (22). Briefly, mice were anesthetized with pentobarbital.