Effect of mitoTEMPO on Redox Reactions in Different Body Compartments upon Endotoxemia in Rats

Mitochondrial ROS (mitoROS) control many reactions in cells. Biological effects of mitoROS in vivo can be investigated by modulation via mitochondria-targeted antioxidants (mtAOX, mitoTEMPO). The aim of this study was to determine how mitoROS influence redox reactions in different body compartments in a rat model of endotoxemia. We induced inflammatory response by lipopolysaccharide (LPS) injection and analyzed effects of mitoTEMPO in blood, abdominal cavity, bronchoalveolar space, and liver tissue. MitoTEMPO decreased the liver damage marker aspartate aminotransferase; however, it neither influenced the release of cytokines (e.g., tumor necrosis factor, IL-4) nor decreased ROS generation by immune cells in the compartments examined. In contrast, ex vivo mitoTEMPO treatment substantially reduced ROS generation. Examination of liver tissue revealed several redox paramagnetic centers sensitive to in vivo LPS and mitoTEMPO treatment and high levels of nitric oxide (NO) in response to LPS. NO levels in blood were lower than in liver, and were decreased by in vivo mitoTEMPO treatment. Our data suggest that (i) inflammatory mediators are not likely to directly contribute to ROS-mediated liver damage and (ii) mitoTEMPO is more likely to affect the redox status of liver cells reflected in a redox change of paramagnetic molecules. Further studies are necessary to understand these mechanisms.