Silberstein Claudia, Pistone Creydt Virginia, Gerhardt Elizabeth, Núñez Pablo, Ibarra Cristina
Laboratorio de Fisiopatogenia, Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
Pediatr Nephrol. 2008 Nov;23(11):1981-90. doi: 10.1007/s00467-008-0896-9. Epub 2008 Jul 8.
Postdiarrhea hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children in Argentina. It is well established that Shiga toxin type 2 (Stx2) causes direct damage to glomerular endothelial cells and tubular epithelial cells, leading to a reduction in the water handling capacity of the kidney. In this study, we demonstrate that Stx2 and its B subunit (Stx2B) were able to inhibit water absorption across human renal tubular epithelial cell (HRTEC) monolayers without altering the short circuit current and the (3)H-mannitol permeability. Quantitative evaluation of (14)C-inulin transport across HRTEC monolayers showed a similar transport rate both before and after HRTEC treatment with Stx2 that confirmed the integrity of the paracellular pathway. Furthermore, Stx2 produced significant protein synthesis inhibition of HRTEC at concentrations as low as 0.001 ng/ml and 1 h of incubation, whereas Stx2B did not modify it at concentrations as high as 10,000 ng/ml and 6 h of incubation. Our findings suggest that whereas the action of Stx2 appears to be caused mainly by the inhibition of protein synthesis mediated by the A subunit, the binding of Stx2B subunit to the Gb3 receptor may affect the membrane mechanisms related to water absorption. We speculate that inhibition of water absorption may occur in proximal tubular cells in vivo in response to Stx2 and may contribute to the early event of HUS pathogenesis.
腹泻后溶血尿毒综合征（HUS）是阿根廷儿童急性肾衰竭最常见的病因。众所周知，2型志贺毒素（Stx2）会对肾小球内皮细胞和肾小管上皮细胞造成直接损伤，导致肾脏的水处理能力下降。在本研究中，我们证明Stx2及其B亚基（Stx2B）能够抑制人肾小管上皮细胞（HRTEC）单层对水的吸收，而不改变短路电流和³H-甘露醇通透性。对¹⁴C-菊粉跨HRTEC单层转运的定量评估显示，在用Stx2处理HRTEC前后，转运速率相似，这证实了细胞旁途径的完整性。此外，Stx2在低至0.001 ng/ml的浓度和孵育1小时时，就能显著抑制HRTEC的蛋白质合成，而Stx2B在高达10,000 ng/ml的浓度和孵育6小时时，却不会对其产生影响。我们的研究结果表明，Stx2的作用似乎主要是由A亚基介导的蛋白质合成抑制引起的，而Stx2B亚基与Gb3受体的结合可能会影响与水吸收相关的膜机制。我们推测，体内近端肾小管细胞可能会因Stx2而发生水吸收抑制，这可能是HUS发病机制的早期事件。
