Defective Recovery and Severe Renal Damage After Acute Hemolysis in Hemopexin-Deficient Mice

Knockout mouse models of iron homeostasis

Murine models have made valuable contributions to our understanding of iron metabolism. Investigation of mice with inherited forms of anemia has led to the discovery of novel proteins involved in iron homeostasis. A growing number of murine models are being developed to investigate mitochondrial iron metabolism. Mouse strains are available for the major forms of hereditary hemochromatosis. Findings in murine models support the concept that the pathogenesis of nearly all forms of hereditary hemochromatosis involves inappropriately low expression of hepcidin. The availability of mice with floxed iron-related genes allows the study of the in vivo consequences of cell-selective deletion of these genes.

Inhibition of neutrophil migration by hemopexin leads to increased mortality due to sepsis in mice

RATIONALE

The reduction of neutrophil migration to the bacterial focus is associated with poor outcome in sepsis.

OBJECTIVES

The objective of this study was to identify soluble substances in the blood of septic mice that inhibit neutrophil migration.

METHODS

A pool of serum obtained from mice 2 hours after the induction of severe sepsis by cecal ligation and puncture inhibited the neutrophil migration. The proteins with inhibitory activity on neutrophil migration were isolated by Blue-Sepharose chromatography, high-performance liquid chromatography, and electrophoresis, and identified by mass spectrometry.

MEASUREMENTS AND MAIN RESULTS

Hemopexin was identified as the serum component responsible for the inhibition of neutrophil migration. In sepsis, the pretreatment of wild-type mice with hemopexin inhibited neutrophil migration to the focus of infection and decreased the survival rate from 87.5 to 50.0%. Hemopexin-null mice subjected to severe sepsis presented normal neutrophil migration, low bacteremia, and an improvement of 40% in survival rate. Moreover, hemopexin inhibited the neutrophil chemotaxis response evoked by C5a or macrophage inflammatory protein-2 and induced a reduction of CXCR2 and L-selectin as well as the up-regulation of CD11b expression in neutrophil membranes. The inhibitory effect of hemopexin on neutrophil chemotaxis was prevented by serine protease inhibitors or ATP. In addition, serum levels of ATP were decreased 2 hours after severe sepsis.

CONCLUSIONS

These data demonstrate for the first time the inhibitory role of hemopexin in neutrophil migration during sepsis and suggest that the therapeutic inhibition of hemopexin or its protease activity could improve neutrophil migration to the focus of infection and survival in sepsis.

Proteomics of S-(1, 2-dichlorovinyl)-L-cysteine-induced acute renal failure and autoprotection in mice

Previous studies (Vaidya VS, Shankar K, Lock EA, Bucci TJ, Mehendale HM. Toxicol Sci 74: 215-227, 2003; Korrapati MC, Lock EA, Mehendale HM. Am J Physiol Renal Physiol 289: F175-F185, 2005; Korrapati MC, Chilakapati J, Lock EA, Latendresse JR, Warbritton A, Mehendale HM. Am J Physiol Renal Physiol 291: F439-F455, 2006) demonstrated that renal repair stimulated by a low dose of S-(1,2-dichlorovinyl)l-cysteine (DCVC; 15 mg/kg i.p.) 72 h before administration of a normally lethal dose (75 mg/kg i.p.) protects mice from acute renal failure (ARF) and death (autoprotection). The present study identified the proteins indicative of DCVC-induced ARF and autoprotection in male Swiss Webster mice. Renal dysfunction and injury were assessed by plasma creatinine and histopathology, respectively. Whole-kidney homogenates were run on two-dimensional gel electrophoresis gels, and the expression of 18 common proteins was maximally changed (> or =10-fold) in all the treatment groups and they were conclusively identified by liquid chromatography tandem mass spectrometry. These proteins were mildly downregulated after low dose alone and in autoprotected mice in contrast to severe downregulation with high dose alone. Glucose-regulated protein 75 and proteasome alpha-subunit type 1 were further investigated by immunohistochemistry for their localization in the kidneys of all the groups. These proteins were substantially higher in the proximal convoluted tubular epithelial cells in the low-dose and autoprotected groups compared with high-dose alone group. Proteins involved in energetics were downregulated in all the three groups of mice, leading to a compromise in cellular energy. However, energy is recovered completely in low-dose and autoprotected mice. This study provides the first report on proteomics of DCVC-induced ARF and autoprotection in mice and reflects the application of proteomics in mechanistic studies as well as biomarker development in a variety of toxicological paradigms.