Epithelial to mesenchymal transition and renal protein handling in a rat model of Hemolytic Uremic Síndrome

OCHOA F, C, BRUNO A, IBARRA C, ZOTTA E.; LAGO NESTOR; OLTRA GISELA; GERHARDT ELIZABETH; TIRONI FARINATI CARLA; BRUNO ANTONELLA; IBARRA CRISTINA; ZOTTA ELSA

Buenos Aires

Simposio; VTEC2009: 7th International Symposium on Shiga Toxin (Verocytotoxin)-producing Escherichia coli infections.; 2009

Asociación Argentina d Microbiología

Escherichia coli strains producing Shiga toxins colonize the lower gastrointestinal tract and are associated with watery and bloody diarrhea and HUS. Acute renal failure (ARF) associated with acute tubular necrosis (ATN) and microangiophatic thrombosis (MAT) has been reported in children. Recovery from ARF generally occurs by regeneration of the damaged tubular epithelium. However, adaptive changes after the initial injury may cause scarring and nephron loss. The most frequent chronic renal lesion in HUS is characterized by the hyperfunction of the remaining nephron after the acute necrotizing lesion, which leads to progressive scarring. In our model, Sprague Dawley rats developed acute renal failure with oliguria, MAT and ATN, similar to that reported in humans. The aim of this work was to use a rat model of HUS to study the factors involved in the progression to chronicity through the development of epithelial to mesenchymal transition (EMT), the alterations in the glomerular filtration barrier and protein tubular reabsorption. To this end, Sprague Dawley rats were inoculated intraperitoneally, as follows: culture supernatant from recombinant E. coli containing Stx2 (20 ng/Kg) was used for the experimental group and supernatant without Stx2 was used for the control group. After 48 h of treatment the animals were sacrificed and functional, histological, molecular and immunohistochemical studies were performed. In the experimental group, we detected the expression of Bax and Stx2 in renal tubules. Epithelial tubular cells showed the presence of TGF-β1 and changes in their phenotypic characteristics showing de novo expression of α-SMA with loss of e-cadherin and β-catenin, thus developing EMT. In the experimental group, we also observed an alteration in the expression of glomerular nephrin and podocalyxin, as compared to the control rats, which could be associated with changes in protein filtration. In addition, we observed a focal reduction of megalin expression in the Stx2 group. In conclusion, alterations in protein excretion could be related to alterations in the filtration barrier, but can also be caused by a decrease in tubular reabsorption. Our results suggest that both mechanisms could be involved in the genesis of proteinuria as a result of the direct effect of Stx2 in tubules and glomeruli. EMT could be involved in the early steps of the evolution to fibrosis and the loss of the tubular function and the alteration in the proteinexpression of the slit diaphragm could indicate the development of glomerular proteinuria. Key words: Proteinuria, Nephrin, Megalin, EMT.