Microalbuminuria and early renal response to lethal dose Shiga toxin type 2 in rats

Abstract

In Argentina, hemolytic uremic syndrome (HUS) constitutes the most frequent cause of acute renal failure in children. Approximately 2%–4% of patients die during the acute phase, and one-third of the 96% who survive are at risk of chronic renal sequelae. Little information is available about the direct effect of Shiga toxin type 2 (Stx2) on the onset of proteinuria and the evolution of toxin-mediated glomerular or tubular injury. In this work, rats were injected intraperitoneally with recombinant Escherichia coli culture supernatant containing Stx2 (sStx2; 20 μg/kg body weight) to induce HUS. Functional, immunoblotting, and immunohistochemistry studies were carried out to determine alterations in slit diaphragm proteins and the proximal tubule endocytic system at 48 hours post-inoculation. We detected a significant increase in microalbuminuria, without changes in the proteinuria values compared to the control rats. In immunoperoxidase studies, the renal tubules and glomerular mesangium showed an increased expression of transforming growth factor β1(TGF-β1). The expression of megalin was decreased by immunoperoxidase and the cytoplasm showed a granular pattern of megalin expression by immunofluorescence techniques. Western blot analysis performed in the renal cortex from sStx2-treated and control rats using anti-nephrin and anti-podocalyxin antibodies showed a decreased expression of these proteins. We suggest that the alterations in slit diaphragm proteins and megalin expression could be related to the development of microalbuminuria in response to lethal doses of Stx2.

Complement Activation Contributes to the Pathophysiology of Shiga Toxin-Associated Hemolytic Uremic Syndrome

“…These findings are supported by experimental evidence from a baboon model of HUS, in which glomerular endothelial injury was functionally linked to structural podocyte changes [111]. Furthermore, rats injected with Stx2 developed microalbuminuria, which can be considered an early sign of podocyte injury, as demonstrated by the concomitant altered glomerular pattern of nephrin and podocalyxin expression [112]. A recent study has shown that mice infected with STEC exhibited increased levels of platelet- and leukocyte-derived microvescicles coated with complement proteins in the renal microcirculation, from where they were transferred to glomerular endothelial cells and podocytes, possibly favoring cell injury [49,73].…”

Protection of Human Podocytes from Shiga Toxin 2-Induced Phosphorylation of Mitogen-Activated Protein Kinases and Apoptosis by Human Serum Amyloid P Component

“…Microalbuminuria is seen in rats soon after intraperitoneal injection of Stx2 (19), and it is also an early sign of renal involvement in patients with EHEC-HUS. Following recovery from the acute phase of the disease, proteinuria may persist; such persistence correlates with a poor long-term renal prognosis (20)(21)(22).…”