IL-13 And IL-4 Receptors Expression Mediate The Injury Of Renal Tubular Epithelial Cells

Focal segmental glomerulosclerosis (FSGS) is a common glomerular disease, accounting for adult primary glomerulonephritis in 7.0% in China,which is clinically manifested as massive proteinuria. Podocyte injury is closely related to massive proteinuria.Cellular immune dysfunction plays an important role in the pathogenesis, such as IL-13 and IL-4 have been regarded as major pathogenic factors. In patients with relapsing nephrotic syndrome, IL-13 and IL-4 mRNA and protein expression in CD4 + and CD8 + T cells were increased. IL-13 and IL-4 mRNA expression are detected by in situ hybridization technique in renal tissue of FSGS patients were increased,which were positive correlate to renal function and 24h urinary protein excretion. It was confirmed that IL-13 and IL-4 receptors express in podocyte.By binding with IL-13 receptor and/or IL-4 receptor on podocyte, IL-13 and IL-4 influence podocyte intercellular junction protein and skeleton structure after with the combination of receptors to promote proteolysis at the basolateral surface of podocyte, which may play a pathogenic role in destruction of filtration membrane permeability.In FSGS,podocyte injury is often accompanied by renal tubular epithelial cell injury, and the possible mechanism is that some factors which lesioned podocyte at the same time attack the renal tubular epithelial cells,chang their function and structure and further trigger tubulointerstitial lesions and interstitial fibrosis. Renal tubular epithelial cell injury is another feature of FSGS. At the same time, the obvious decrease of proteinuria is accompanied by renal tubular epithelial cell injury indicators(eg. NAG and RBP) improvement; Furthermore, previous studies have shown that renal tubular epithelial cell and podocyte share many common molecules.It can be speculated that certain injury factors may attack tubular cells and podocyte simultaneously,leading to the common injury pf the both cells.This study detect the expression of IL-13 receptor and IL-4 receptor on the human proximal renal tubular epithelial cell lines(HK2) and to investigate the effect of IL-13 and IL-4 on HK2, then to explore the mechanism. Part OneIL-13 receptor and IL-4 receptor expressed on human renal tubular cellObjective:To observe the expression of IL-13 receptor and IL-4 receptor on the human renal proximal renal tubular cell.Methodology:RT-PCR and immunofluorescence were applied to detect the expression of IL-13 receptor and IL-4 receptor on HK2.Results:1. The mRNA of IL-13Rα1 and IL-4Rα,which compose to type II IL-13 receptor and type I IL-4 receptor were detected in HK2 by RT-PCR.2. The protein of IL-13Rα1 and IL-4Rα,which compose to type II IL-13 receptor and type I IL-4 receptor were in the cytoplasm of HK2 by immunofluorescence.Conclusion:The mRNA and proteins expression of IL-13 and IL-4 receptors were detected in HK2.Part twoIL-13 receptor and IL-4 receptor mediate the injury of human renal tubular cellObjective:To observe the effect of IL-13 and IL-4 on HK2 and to explore the mechanism.Methodology:1. The direct effect of IL-13 and IL-4 on HK2 injury Immunofluorescence staining was used to observe the changes of HK2 injury marker.RANTES by using different concentrations of IL-13 and IL-4 on the HK2 separately for various times (12h, 24h ,48h ).2. The mechanism of IL-13 and IL-4 effect on HK21) Western blot was used to detect the degree of JAK-STAT6 signaling pathway activation of HK2 treated by IL-13 and IL-4 separately for various times (12h, 24h ,48h ).2) Western blot was used to detect the change of JAK-STAT6 signaling pathway activation of HK2,pretreated by leflunomide for 30 min,and then treated by IL-13 and IL-4 separately.3) Immunofluorescence staining was used to observe RANTES change of HK2, pretreated by leflunomide for 30 min,and then treated by IL-13 and IL-4 separately.Results:1.IL-13 and IL-4 induced the increasing of RANTES expression in a dose and time-dependent manner.It is obvious damaged by treated separately with 50ng/ml IL-13 and 100ng/ml IL-4 for 48h.RANTES is negative in normal cultured HK2. Treated with 50ng/ml IL-13 and 100ng/ml IL-4 for 48h, positive grains in HK2 is significantly increase.2. The phosphorylation of JAK-STAT6 signal pathway was found afer HK2 treated by 50ng/ml IL-13 and IL-4 separately for 10min,and reached to the peak when 50ng/ml IL-13 and 100ng/ml IL-4 treated for 20min.3. Compared with negative control group, phosphorylation of HK2 JAK-STAT6 signal pathway was few change of which was pretreated by leflunomide for 30 min,and then treated by IL-13 and IL-4 separately(43.6%±0.4% vs 41.2%±2.4%,P>0.05,20.6%±0.8% vs 14.9%±6.7%,P>0.05); comparing to positive control group,it was significant lower(43.6%±0.4% vs 89.3%±8.3%,P<0.01,20.6%±1.4% vs 44.8%±7.5%,P<0.05).4.Compared with negative control group, RANTES of HK2 was few change of which was pretreated by leflunomide for 30 min,and then treated by IL-13 and IL-4 separately.compared with positive control group,it was significantly weaken.Conclusion: 1.IL-13 receptor and IL-4 receptor mediat the injury of the human renal proximal tubular epithelial cell.2.The effects of IL-13 and IL-4 above were related with JAK-STAT6 signal pathway closely.