Temporary changes in macrophages and MHC class-II molecule-expressing cells in the tubulointerstitium in response to uranyl acetate-induced acute renal failure in rats

In Vivo Comparison of the Phenotypic Aspects and Molecular Mechanisms of Two Nephrotoxic Agents, Sodium Fluoride and Uranyl Nitrate

Because of their nephrotoxicity and presence in the environment, uranium (U) and fluoride (F) represent risks to the global population. There is a general lack of knowledge regarding the mechanisms of U and F nephrotoxicity and the underlying molecular pathways. The present study aims to compare the threshold of the appearance of renal impairment and to study apoptosis and inflammation as mechanisms of nephrotoxicity. C57BL/6J male mice were intraperitoneally treated with a single dose of U (0, 2, 4 and 5 mg/kg) or F (0, 2, 5, 7.5 and 10 mg/kg) and euthanized 72 h after. Renal phenotypic characteristics and biological mechanisms were evaluated by urine biochemistry, gene/protein expression, enzyme activity, and (immuno)histological analyses. U and F exposures induced nephrotoxicity in a dose-dependent manner, and the highest concentrations induced severe histopathological alterations as well as increased gene expression and urinary excretion of nephrotoxicity biomarkers. KIM-1 gene expression was induced starting at 2 mg/kg U and 7.5 mg/kg F, and this increase in expression was confirmed through in situ detection of this biomarker of nephrotoxicity. Both treatments induced inflammation as evidenced by cell adhesion molecule expression and in situ levels, whereas caspase 3/7-dependent apoptosis was increased only after U treatment. Overall, a single dose of F or U induced histopathologic evidence of nephrotoxicity renal impairment and inflammation in mice with thresholds under 7.5 mg/kg and 4 mg/kg, respectively.

Comprehensive analysis of the renal transcriptional response to acute uranyl nitrate exposure

Background

Chemical and radiological toxicities related to uranium acute exposure have been widely studied in nuclear fuel workers and military personnel. It is well known that uranyl nitrate induces acute renal failure (ARF). However, the mechanisms of this metal-induced injury are not well defined at the molecular level.

Results

Renal function and histology were assessed in mice receiving uranyl nitrate (UN(+)) and controls (UN(-)). To identify the genomic response to uranium exposure, serial analysis gene expression (SAGE) of the kidney was performed in both groups. Over 43,000 mRNA SAGE tags were sequenced. A selection of the differentially expressed transcripts was confirmed by real-time quantitative PCR and Western blotting. UN(+) animals developed renal failure and displayed the characteristic histological lesions of UN nephropathy. Of the >14,500 unique tags identified in both libraries, 224 had a modified expression level; they are known to participate in inflammation, ion transport, signal transduction, oxidative stress, apoptosis, metabolism, and catabolism. Several genes that were identified had not previously been evaluated within the context of toxic ARF such as translationally controlled tumor protein, insulin like growth factor binding protein 7 and ribosomal protein S29, all apoptosis related genes.

Conclusion

We report a comprehensive description of the UN induced modifications in gene expression levels, including the identification of genes previously unrelated to ARF. The study of these genes and the metabolisms they control should improve our understanding of toxic ARF and enlighten on the molecular targets for potential therapeutic interventions.

Upregulation of osteopontin in Schwann cells of the sciatic nerves of Lewis rats with experimental autoimmune neuritis

We examined the expression of osteopontin (OPN) in the sciatic nerves of rats with experimental autoimmune neuritis (EAN), using immunohistochemistry and immunoblotting, to study its involvement in the pathogenesis of autoimmune peripheral nervous system diseases. Constitutive OPN expression was detected in some Schwann cells; expression was increased after immunization with adjuvant alone. At day 14 after induction of EAN, many Schwann cells had a granular pattern of immunoreactivity, whereas very few inflammatory cells were OPN-positive. Even after recovery from hindlimb paralysis, at 24 days post-immunization, OPN expression remained elevated in the Schwann cells. The results suggest that OPN expression in Schwann cells is easily induced by immunostimulation, and further enhanced by the inflammatory reaction in EAN. Continued elevation of OPN after recovery may represent a functional recovery after a transient inflammatory insult.