Abstract. In minimal change nephrosis (MCN), proteinuria is associated with structural changes of the glomerular visceral epithelial cells (GVEC). The occurrence of MCN has been associated with T-helper2 lymphocyte-dependent conditions. To examine a direct role for type 2 cytokines in GVEC injury, the expression of interleukin (IL)-4/IL-13 receptors by GVEC and direct effects of IL-4 and IL-13 on GVEC were studied. Reverse transcription-PCR showed that isolated human and rat glomeruli and cultured human and rat GVEC expressed mRNA for IL-4Rα, IL-13Rα1, and IL-13Rα2. Protein expression of IL-4Rα and IL-13Rα2 by GVEC in human kidney biopsies and by cultured human GVEC was detected by immunohistochemistry. Western blotting demonstrated phosphorylation of STAT6 in cultured GVEC upon incubation with IL-4 or IL-13. This indicated signal transduction via the heterodimeric receptor complex IL-4R2, which is composed of the IL-4Rα and the IL-13Rα1. Direct effects on GVEC function were examined in monolayer experiments. IL-4 and IL-13 dose-dependently decreased transepithelial electrical resistance of monolayers of rat GVEC to approximately 30 and 40% of baseline values, respectively. The transepithelial electrical resistance decrease was associated with a significant increase in short-circuit current, whereas no changes were observed in the transmonolayer flux of the macromolecules horseradish peroxidase (molecular weight, 44 kD) and 14C-mannitol (molecular weight, 182 Da). No changes in cell structure were observed with electron microscopy. It is concluded that by binding to specific IL-4/IL-13 receptors, IL-4 and IL-13 can exert specific effects on GVEC function, which could be of pathogenetic relevance for glomerular injury in MCN.
A 24-Ch. Multi-Electrode Array Allowing Fast EIS to Determine Transepithelial Electrical Resistance