ABSTRACT
Renal ischemia/reperfusion (I/R) injury is a major cause of kidney damage. There is accumulating evidence that inflammatory reactions are involved in the pathogenesis of this process. Our studies demonstrate that transgenic mice overexpressing human extracellular and intracellular glutathione peroxidases (GP) are protected against kidney I/R injury. Importantly, significant reduction in neutrophil migration was observed in GP mice compared with nontransgenic mice. Analysis of signaling molecules mediating neutrophil activation and recruitment indicates reduction in the level of KC and macrophage inflammatory protein-2 chemokine expression in transgenic animals. The molecular mechanism mediating this effect appears to involve repression of NF-kappaB activation at the level of IkappaBalpha and IkappaBbeta degradation. In the case of IkappaBalpha, no apparent phosphorylation was detected. These results suggest that IkappaBalpha proteolysis is triggered during the renal I/R pro-oxidant state by a still unknown mechanism, which might be different from other stimuli. A central role of NF-kappaB in CXC chemokine activation was demonstrated in cell culture anoxia/ATP repletion experiments as a model of I/R. The data presented indicate the important role of GP-sensitive signal transduction pathways in the development of inflammatory response and tissue injury during I/R.
Subject(s)
Chemokines/biosynthesis , Gene Expression Regulation , Glutathione Peroxidase/biosynthesis , I-kappa B Proteins , Kidney/blood supply , Reperfusion Injury/metabolism , Adenosine Triphosphate/metabolism , Animals , Apoptosis/genetics , Apoptosis/immunology , Cell Hypoxia , Cell Movement/genetics , Cell Movement/immunology , Cells, Cultured , DNA-Binding Proteins/metabolism , Glutathione Peroxidase/genetics , Glutathione Peroxidase/metabolism , Humans , Immunity, Innate , Kidney/enzymology , Kidney/metabolism , Kidney/pathology , Lipid Peroxidation/genetics , Lipid Peroxidation/immunology , Mice , Mice, Inbred C57BL , Mice, Inbred CBA , Mice, Transgenic , NF-KappaB Inhibitor alpha , NF-kappa B/antagonists & inhibitors , NF-kappa B/metabolism , Neutrophils/immunology , Phosphorylation , Protein Binding , Reperfusion Injury/enzymology , Reperfusion Injury/immunology , Reperfusion Injury/pathologyABSTRACT
Acetaminophen is one of the most extensively used analgesics/antipyretics worldwide, and overdose or idiopathic reaction causes major morbidity and mortality in its victims. Research into the mechanisms of toxicity and possible therapeutic intervention is therefore essential. In this study, the response of transgenic mice overexpressing human antioxidant enzymes to acute acetaminophen overdose was investigated. Animals overexpressing superoxide dismutase or plasma glutathione peroxidase demonstrated dramatic resistance to acetaminophen toxicity. Intravenous injection of glutathione peroxidase provided normal mice with nearly complete protection against a lethal dose of acetaminophen. Surprisingly, animals overexpressing intracellular glutathione peroxidase in the liver were significantly more sensitive to acetaminophen toxicity compared with nontransgenic littermates. This sensitivity appears to be due to the inability of these animals to efficiently recover glutathione depleted as a result of acetaminophen metabolism. Finally, the results suggest that glutathione peroxidase overexpression modulates the synthesis of several acetaminophen metabolites. Our results demonstrate the ability of glutathione peroxidase levels to influence the outcome of acetaminophen toxicity.
Subject(s)
Acetaminophen/toxicity , Glutathione Peroxidase/metabolism , Isoenzymes/metabolism , Animals , Benzoquinones/metabolism , Glutathione Disulfide/metabolism , Humans , Imines/metabolism , Lipid Peroxidation , Liver/drug effects , Mice , Mice, Inbred C57BL , Mice, Inbred CBA , Mice, Transgenic , Oxidation-Reduction , Superoxide Dismutase/metabolismABSTRACT
As stroke is a major cause of disability and death in the western world, there is great interest in the basic mechanisms by which ischemia/reperfusion (I/R) causes damage. To this end, extensive research has been carried out which identifies reactive oxygen species (ROS) as key participants in brain damage resultant from I/R. Brain tissue is protected from ROS damage by antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GP). Overexpression of SOD in transgenic mice has already been demonstrated to confer protection against I/R damage in murine stroke models. We are using transgenic mice overexpressing the intracellular form of glutathione peroxidase (GP1) to determine the protective capacity of overexpression of this enzyme on stroke damage. 1 h of focal cerebral ischemia followed by 24 h of reperfusion was induced using the intraliminal suture method. Volume of infarction was reduced by 48% in GP1 mice compared to nontransgenic littermates. Brain edema was reduced by 33%. Behavioral deficits agreed with histologic data. Overexpression of glutathione peroxidase confers significant protection against I/R damage in our stroke model possibly through direct scavenging of ROS or through the influencing of signalling mechanisms which lead to tissue damage.