Interactions of Shiga-like toxin with human peripheral blood monocytes

The cytotoxic effect of Shiga-like toxin (Stx; produced by certain Escherichia coli strains) plays a central role in typical hemolytic uremic syndrome (HUS). It damages the renal endothelium by inhibiting the cellular protein synthesis. Also, the monocyte has a specific receptor for Stx but is not sensitive for the cytotoxic effect. In this work, monocytes were studied as a potential transporter for Stx to the renal endothelium. Coincubation of isolated human monocytes loaded with Stx and target cells (vero cells and human umbilical vascular endothelial cells) were performed. Transfer was determined by measuring the protein synthesis of target cells and by flow cytometry. Furthermore, the effect of a temperature shift on loaded monocytes was investigated. Stx-loaded monocytes reduced the protein synthesis of target cells. After adding an antibody against Stx, incomplete recovery occurred. Also, adding only the supernatant of coincubation was followed by protein synthesis inhibition. Stx detached from its receptor on the monocyte after a change in temperature, and no release was detected without this temperature shift. Although the monocyte plays an important role in the pathogenesis of HUS, it has no role in the transfer of Stx

Molecular genetic analysis of podocyte genes in focal segmental glomerulosclerosis—a review

This review deals with podocyte proteins that play a significant role in the structure and function of the glomerular filter. Genetic linkage studies has identified several genes involved in the development of nephrotic syndrome and contributed to the understanding of the pathophysiology of glomerular proteinuria and/or focal segmental glomerulosclerosis. Here, we describe already well-characterized genetic diseases due to mutations in nephrin, podocin, CD2AP, alpha-actinin-4, WT1, and laminin β2 chain, as well as more recently identified genetic abnormalities in TRPC6, phospholipase C epsilon, and the proteins encoded by the mitochondrial genome. In addition, the role of the proteins which have shown to be important for the structure and functions by gene knockout studies in mice, are also discussed. Furthermore, some rare syndromes with glomerular involvement, in which molecular defects have been recently identified, are briefly described. In summary, this review updates the current knowledge of genetic causes of congenital and childhood nephrotic syndrome and provides new insights into mechanisms of glomerular dysfunction

A novel mutation of the epithelial Na+ channel causes type 1 pseudohypoaldosteronism.

Type I pseudohypoaldosteronism (PHA-1) is a rare salt wasting syndrome occurring soon after birth, characterized by apathy and severe dehydration accompanied by hyponatremia, hyperkalemia, and metabolic acidosis despite high plasma aldosterone concentrations. The molecular defect involved in the systemic autosomal recessive form of the syndrome has been identified. Mutations in all three genes encoding the epithelial sodium channel (ENaC) lead to a decrease in the channel function, resulting in the disease. We report here two new cases of the autosomal recessive form of PHA-1 in the same family. We found a new homozygous mutation of the gene encoding the alpha ENaC subunit (alphaR492stop). The function of the mutated ENaC channel was assessed in the Xenopus laevis oocyte expression system. The mutant ENaC activity measured with the two-electrode voltage clamp method was drastically decreased compared with the wild type activity, in agreement with the salt-losing phenotype