Shiga Toxin 2 Targets the Murine Renal Collecting Duct Epithelium

Abstract

Hemolytic-uremic syndrome (HUS) caused by Shiga toxin-producingEscherichia coli infection is a leading cause of pediatric acute renal failure. Bacterial toxins produced in the gut enter the circulation and cause a systemic toxemia and targeted cell damage. It had been previously shown that injection of Shiga toxin 2 (Stx2) and lipopolysaccharide (LPS) caused signs and symptoms of HUS in mice, but the mechanism leading to renal failure remained uncharacterized. The current study elucidated that murine cells of the glomerular filtration barrier were unresponsive to Stx2 because they lacked the receptor glycosphingolipid globotriaosylceramide (Gb 3 ) in vitro and in vivo. In contrast to the analogous human cells, Stx2 did not alter inflammatory kinase activity, cytokine release, or cell viability of the murine glomerular cells. However, murine renal cortical and medullary tubular cells expressed Gb 3 and responded to Stx2 by undergoing apoptosis. Stx2-induced loss of functioning collecting ducts in vivo caused production of increased dilute urine, resulted in dehydration, and contributed to renal failure. Stx2-mediated renal dysfunction was ameliorated by administration of the nonselective caspase inhibitor Q-VD-OPH in vivo. Stx2 therefore targets the murine collecting duct, and this Stx2-induced injury can be blocked by inhibitors of apoptosis in vivo.

Shiga Toxin Subtypes Display Dramatic Differences in Potency

“…The role of apoptosis in Stx-mediated disease is also unclear. Several studies utilizing mouse models have observed apoptosis in renal cells following treatment with Stx (23,42,47), while other studies have observed necrosis (10,29,37,46,58,60).…”

Ouabain Protects against Shiga Toxin–Triggered Apoptosis by Reversing the Imbalance between Bax and Bcl-xL

“…Mice injected with this dose of Stx2 usually develop symptoms after 3-4 days. 4,28 Mice were euthanized before symptoms developed in order to detect early apoptotic changes.…”

“…3 Apoptosis is a major manifestation of Stx2 toxicity, as shown in biopsy samples from patients with HUS and in kidneys from mice inoculated with Stx2-producing versus Stx-nonproducing E. coli O157:H7, those treated with Stx2, and Stx2-exposed cells. 1,4,5 The mechanism by which Stx2 activates apoptotic pathways is not fully understood, but several lines of evidence suggest that it involves activation of caspase-8 and the intrinsic, mitochondrial pathway. It is well documented that Stx2 increases caspase-8 expression.…”

A novel murine infection model for Shiga toxin–producing Escherichia coli

“…Injection of Stx into mice results in the induction of proinflammatory cytokines, vascular damage, hemolysis, and renal damage (47)(48)(49)(50), but in contrast to piglet and rabbit infection models (23, 51-53), STEC strain originally isolated from ground beef (66). In preliminary screening of these C. rodentium lysogens, only C. rodentium (Φ1720a-02) produced significant amounts of toxin in vitro or caused systemic disease in mice (data not shown; see Figure 1).…”