Comparative Characterization of Shiga Toxin Type 2 and Subtilase Cytotoxin Effects on Human Renal Epithelial and Endothelial Cells Grown in Monolayer and Bilayer Conditions

PLoS One. 2016 Jun 23;11(6):e0158180. doi: 10.1371/journal.pone.0158180. eCollection 2016.

Abstract

Postdiarrheal hemolytic uremic syndrome (HUS) affects children under 5 years old and is responsible for the development of acute and chronic renal failure, particularly in Argentina. This pathology is a complication of Shiga toxin (Stx)-producing Escherichia coli infection and renal damage is attributed to Stx types 1 and 2 (Stx1, Stx2) produced by Escherichia coli O157:H7 and many other STEC serotypes. It has been reported the production of Subtilase cytotoxin (SubAB) by non-O157 STEC isolated from cases of childhood diarrhea. Therefore, it is proposed that SubAB may contribute to HUS pathogenesis. The human kidney is the most affected organ because very Stx-sensitive cells express high amounts of biologically active receptor. In this study, we investigated the effects of Stx2 and SubAB on primary cultures of human glomerular endothelial cells (HGEC) and on a human tubular epithelial cell line (HK-2) in monoculture and coculture conditions. We have established the coculture as a human renal proximal tubule model to study water absorption and cytotoxicity in the presence of Stx2 and SubAB. We obtained and characterized cocultures of HGEC and HK-2. Under basal conditions, HGEC monolayers exhibited the lowest electrical resistance (TEER) and the highest water permeability, while the HGEC/HK-2 bilayers showed the highest TEER and the lowest water permeability. In addition, at times as short as 20-30 minutes, Stx2 and SubAB caused the inhibition of water absorption across HK-2 and HGEC monolayers and this effect was not related to a decrease in cell viability. However, toxins did not have inhibitory effects on water movement across HGEC/HK-2 bilayers. After 72 h, Stx2 inhibited the cell viability of HGEC and HK-2 monolayers, but these effects were attenuated in HGEC/HK-2 bilayers. On the other hand, SubAB cytotoxicity shows a tendency to be attenuated by the bilayers. Our data provide evidence about the different effects of these toxins on the bilayers respect to the monolayers. This in vitro model of communication between human renal microvascular endothelial cells and human proximal tubular epithelial cells is a representative model of the human proximal tubule to study the effects of Stx2 and SubAB related to the development of HUS.

MeSH terms

  • Biological Transport / drug effects
  • Cell Culture Techniques
  • Cell Line
  • Cell Survival / drug effects
  • Cells, Cultured
  • Endothelial Cells / drug effects*
  • Endothelial Cells / metabolism
  • Epithelial Cells / drug effects*
  • Epithelial Cells / metabolism
  • Escherichia coli Proteins / toxicity*
  • Humans
  • Kidney Glomerulus / cytology
  • Kidney Glomerulus / drug effects
  • Kidney Tubules, Proximal / cytology
  • Kidney Tubules, Proximal / drug effects
  • Shiga Toxin 2 / toxicity*
  • Subtilisins / toxicity*

Substances

  • Escherichia coli Proteins
  • Shiga Toxin 2
  • Subtilisins
  • subtilase cytotoxin, E coli

Grants and funding

This study was supported by the National Agency for Promotion of Science and Technology (ANPCYT-PICT 12-0777), http://www.agencia.mincyt.gob.ar/frontend/agencia/fondo/foncyt, and the University of Buenos Aires (UBACYT-770), http://www.uba.ar (CI). It was also supported by the National Scientific and Technical Research Council (CONICET D4541, D3646) (MMA), http://www.conicet.gov.ar/.