Endotoxemia in Transgenic Mice Overexpressing Human Glutathione Peroxidases

Abstract

Abstract-In response to endotoxemia induced by administration of lipopolysaccharide, a complex series of reactions occurs in mammalian tissues. During this inflammation response, cells produce different mediators, such as reactive oxygen species, a number of arachidonic acid metabolites, and cytokines. The reactive oxygen species thus generated have been suggested to produce tissue injury as a result of macromolecular damage or by interfering with regulatory processes. They may also act as important signaling molecules to induce redox-sensitive genes. We report here that transgenic mice overexpressing 2 major forms of human glutathione peroxidases (GPs), intra-and extracellular GP, are able to modulate host response during endotoxemic conditions. We show that these animals have a decreased hypotension and increased survival rate after administration of a high dosage of lipopolysaccharide. Overexpression of GPs alters vascular permeability and production of cytokines (interleukin-1␤ and tumor necrosis factor-␣) and NO, affects arachidonic acid metabolism, and inhibits leukocyte migration. These results suggest an important role for peroxides in pathogenesis during endotoxemia, and GPs, by regulating their level, may prove to be good candidates for antioxidant therapy to protect against such injury. 2 There is experimental evidence that suggests oxidative damage in pathogenesis of endotoxemia. 3 To evaluate the role of glutathione peroxidase (GP) in protection against endotoxemia in vivo, we have used transgenic mice overexpressing human extracellular (GPxP) and intracellular (GPx1) GP. In the present study, we report that these animals show an increased rate of survival after administration of a large dosage of LPS. Mice with human GPs are able to modulate levels of lipid peroxidation and inflammatory mediators. These transgenic animals represent a new model system for investigation of the role of GPs and reactive oxygen species (ROS) in endotoxemia and other inflammatory disorders. Materials and Methods Animals and TreatmentsHeterozygous transgenic mice 5 to 6 months old in a C57BL/ 6ϫCBA/J background overexpressing human GPxP (strain 17) and human GPx1 (strain 23) and their normal littermates were bred in our facility. We described the generation of these mice previously. 4 For survival studies, the mice were injected with LPS at a dose of 25 mg/kg (Escherichia coli serotype 0111:B4; Sigma). Arterial blood pressure and heart rate were measured using the Kent tail blood pressure system. For characterization of cytokine production and leukocyte distribution, blood was collected from the retro-orbital cavity of a group of animals dosed with LPS (16 mg/kg of body weight). Plasma was analyzed for cytokine (tumor necrosis factor-␣ [TNF-␣] and interleukin-1␤ [IL-1␤]) production with ELISA kits from R&D Systems. Vascular permeability was determined by assessing tissue accrual of Evan's Blue, as described previously. 5 Sixteen hours after PBS or LPS injection, the animals were administered 25 mg/kg Evan's Blue by tail ...

Nrf2 is a critical regulator of the innate immune response and survival during experimental sepsis

“…A previous study showed that GPX2 is the only inducible form of GSH peroxidase in the lungs that is regulated by Nrf2 (7). A protective role of GSH peroxidase in LPS-induced inflammation has been previously reported (39). These results indicate that Nrf2-directed constitutive regulation of cellular redox status is fundamental in determining the outcome of the innate immune response.…”

Inflammatory Response and Glutathione Peroxidase in a Model of Stroke

“…Transgenic animals manifested less vascular permeability, possibly due to an increased constitutive ability of GPx1-overexpressing cells to withstand oxidative stress and toxic metabolites. A dramatic effect of GP overexpression on leukocyte behavior has been previously reported in two other inflammationrelated injury models, kidney I/R and LPS-induced septic shock (6,7). Significant resistance to injury in both models correlated with the level of key inflammatory mediators.…”

“…The generation of transgenic mice with human GPx1 genes in a C57BL/ 6 ϫ CBA/J background was previously reported (4,7). The mouse line GPE23 (containing 200 copies of the human GPx1 gene) was used for these studies.…”

Overexpression of Glutathione Peroxidase Prevents Left Ventricular Remodeling and Failure After Myocardial Infarction in Mice

“…Our results are also consistent with a study showing that circulatory failure induced by a large dose of lipopolysaccharides was inhibited in GSHPx TG mice. 23 The beneficial effects of GSHPx overexpression shown in the present study were not a result of its MI size-sparing effect, because the infarct size was comparable between WTϩMI and TGϩMI mice. Furthermore, its effects might not be attributable to the effects of GSHPx overexpression on hemodynamics, because blood pressure and heart rate were not altered (Table).…”