Shiga toxin targets the podocyte causing hemolytic uremic syndrome through endothelial complement activation

Area of Science:

• Nephrology
• Immunology
• Pediatrics

Background:

• Shiga toxin–producing Escherichia coli hemolytic uremic syndrome (STEC-HUS) is a primary cause of acute kidney injury in children.
• STEC-HUS has a significant mortality rate (up to 5%) and its underlying mechanisms remain unclear.
• The susceptibility of glomerular microvasculature to Shiga toxin (Stx) injury is not well understood.

Purpose of the Study:

• To elucidate the mechanisms by which Stx targets the glomerular microvasculature in STEC-HUS.
• To investigate the role of podocyte expression of the Stx receptor (Gb3) in STEC-HUS pathogenesis.
• To evaluate the therapeutic potential of complement pathway inhibition in STEC-HUS.

Main Methods:

• Engineered transgenic mice (Pod-Gb3) to express the Stx receptor (Gb3) exclusively in kidney podocytes.
• Challenged Pod-Gb3 mice with systemic Stx and assessed for STEC-HUS development.
• Utilized human glomerular cell models and kidney biopsies from STEC-HUS patients for analysis.

Main Results:

• Pod-Gb3 mice challenged with Stx developed STEC-HUS, confirming podocyte targeting.
• Stx-induced HUS was mediated by reduced podocyte vascular endothelial growth factor A (VEGF-A).
• This led to glomerular endothelial cell (GEnC) glycocalyx loss, impaired complement factor H binding, and complement activation. Early C5 inhibitor treatment rescued the STEC-HUS phenotype.

Conclusions:

• Systemic Stx exposure specifically targets the glomerulus via podocyte-mediated mechanisms.
• Reduced VEGF-A and subsequent complement activation in GEnCs are key events in STEC-HUS.
• Early inhibition of the terminal complement pathway shows promise as a therapeutic strategy for STEC-HUS.