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

Federico Ochoa¹, Gisela Oltra¹, Elizabeth Gerhardt¹, Ricardo Hermes², Lilian Cohen², Alicia E Damiano³, Cristina Ibarra¹, Nestor R Lago⁴, Elsa Zotta^1
1Departamento de Fisiologia, Facultad de Medicina UBA, ²Laboratorio Análisis Clínicos, Hospital Juan A Fernández, ³Departamento de Ciencias Biológicas, Facultad de Farmacia y Bioquímica, UBA, Buenos Aires, Argentina; ⁴Departamento de Patología, Facultad de Medicina UBA, Buenos Aires, Argentina

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 ß₁(TGF-ß₁). 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.

Keywords: microalbuminuria, nephrin, podocytes, podocalyxin, megalin, acute renal injury