Characterization of the Baboon Responses to Shiga-Like Toxin

Abstract

The baboon response to intravenous infusion of Shiga toxin 1 (Stx-1) varied from acute renal failure, proteinuria, hyperkalemia, and melena with minimal perturbation of host inflammatory and hemostatic systems (high-dose group, 2.0 microg/kg; n = 5) to renal failure with hematuria, proteinuria, thrombocytopenia, schistocytosis, anemia, and melena (low-dose group, 0.05 to 0.2 microg/kg; n = 8). Both groups exhibited renal shutdown and died in 57 hours or less. Both groups produced urine that was positive for tumor necrosis factor and interleukin-6 although neither of these cytokines was detectable (</=5 ng/ml) in the general circulation. Light and electron microscopy showed organelle disintegration and necrosis of the renal proximal tubular epithelium and of the intestinal mucosal epithelium at the tips of the microvilli, both of which were previously shown to bear Gb3 receptors. The renal distal tubular epithelium was spared. The renal proximal tubular epithelial changes were accompanied by swelling of visceral epithelial cells (podocytes) and by swelling and detachment of endothelial cells of the glomerular capillaries. In addition, all of the animals receiving low-dose Stx-1 showed microvascular fibrin deposition and thrombosis in renal glomerular and peritubular capillaries in association with a fall in hematocrit and platelet count and a rise in schistocyte count. The gastrointestinal villous tip lesions were accompanied by varying degrees of mucosal and submucosal congestion, hemorrhage, or necrosis. Electron microscopic images of cerebral cortex and cerebellum showed diffuse unraveling of myelin sheaths with occasional disintegration of neuronal cell bodies. In contrast to the gastrointestinal mucosal and renal proximal tubular epithelium, the Gb3 receptor glycolipid of the renal glomerular and neuronal tissues as determined using toxin overlay thin-layer chromatography plates was below the limit of detection (<13 pM/g wet tissue). We conclude that, depending on the status of the host and amount of toxin infused, Stx-1 can produce a variety of responses ranging from damage to cells carrying the Gb3 receptor (renal proximal tubular epithelial cells and gastrointestinal mucosa) to damage to renal glomerular tissues with microvascular thrombosis as a result of the host's inflammatory response localized to the kidney. We conclude that this thrombotic coagulopathy arises from local changes in the kidney because the appearance of host inflammatory mediators was limited to the urine. This suggests that the initial host response is localized in the kidney, and that the systemic thrombocytopenia, anemia, and schistocytosis may arise secondarily.

Lipopolysaccharide Upregulates Renal Shiga Toxin Receptors in a Primate Model of Hemolytic Uremic Syndrome

“…Increased staining was also seen in most cortical tubules, as well as other cells in the glomeruli. Human proximal tubular epithelial cells in culture are exquisitely sensitive to Stx1 [17], as are renal tubular cells in culture [12]; tubular injury is a well-recognized component of HUS, both in humans [18] and in our primate model [4], and Stx has been demonstrated in renal tubules of children with D+ HUS [19]. …”

“…Rabbit and mouse animal models for the effects of Shiga toxin (Stx) do not develop the glomerular lesions characteristic of HUS [2, 3]. Therefore, we developed a baboon model of HUS in which small intravenous bolus injections of purified Stx1 result in microangiopathic hemolytic anemia, thrombocytopenia, and an acute nephropathy with glomerular thrombotic microangiopathy and tubular injury similar to that seen in humans with D+ HUS [4]. This model also bypasses the less predictable enteric phase of the disease, and permits us to study the host response in a controlled manner.…”

Neutral Glycosphingolipid-dependent Inactivation of Coagulation Factor Va by Activated Protein C and Protein S

“…In patients with hemolytic uremic syndrome, activation of the coagulation system and glomerular thrombotic microangiopathy are observed, and these effects are mediated by the binding of verotoxin B to Gb 3 Cer (43). Administration of verotoxin B causes fibrin deposition in an animal model (44). Therefore, we speculated that the blockade of Gb 3 Cer in the kidney by verotoxin B may locally stimulate the coagulation system, at least in part, by inhibiting Gb 3 Cer-dependent enhancement of APC/ protein S activities.…”

Sex steroids do not affect shigatoxin cytotoxicity on human renal tubular or glomerular cells

“…Such studies would, however, be problematic. Traditional animal models, such as mice, rats, rabbits or pigs do not develop typical renal disease when given either Stx or E. coli 0157:H7 [14]. Further, animal models that most closely reflect human HUS are only in the early stages of development [14].…”

“…Traditional animal models, such as mice, rats, rabbits or pigs do not develop typical renal disease when given either Stx or E. coli 0157:H7 [14]. Further, animal models that most closely reflect human HUS are only in the early stages of development [14]. Hence, the cell culture system remains the most reasonable means to assess an effect of sex steroids on renal cell Stx-1 responsiveness; such systems have clearly been demonstrated to be responsive to sex steroids (e.g.…”