Angiotensin Ⅱ induces nephrin dephosphorylation in podocytes both in vivo and in vitro / 中华肾脏病杂志

ABSTRACT

Objective To evaluate the effect of angiotensin Ⅱ (Ang Ⅱ ) on the change of nephrin phosphorylation both in Ang Ⅱ-infused rat model and cultured podocytes.Methods Thirty Wistar rats were subcutaneously embedded with osmotic minipumps and randomly divided into 3 groups according to receiving either Ang Ⅱ at a dose of 400 ng· kg-1· min-1 or Ang Ⅱ +telmisartan at a dose of 3 mg·kg-1 ·d-1,or normal saline as a control group.Blood pressure and 24-hour urinary albumin were measured at 0 d,7 d,14 d,21 d and 28 d of the experiment.Renal histomorphology was evaluated through electron microscopy.The concentrations of Ang Ⅱ both in blood plasma and kidney were detected by radioimmunoassay.In vitro,cultured murine podocytes were exposed to Ang Ⅱ (10-6 mol/L) pretreated with or without losartan (10-5 mol/L) for different time periods.Nephrin and its phosphorylation expression were analyzed by Western blotting.The distribution of F-actin was presented by FITC-phallodin labeling.The change in phenomenon of F-actin was evaluated by cortical F-actin score index (CFS).Results (1)Ang Ⅱ-infused rats exhibited increased Ang Ⅱ concentration,significant hypertension and marked albuminuria.(2)In Ang Ⅱ-infusion group,nephrin expression was decreased (P＜0.05).Ang Ⅱ-receiving rats displayed diminished phosphorylation of nephrin.(3)In vitro,the phosphorylation of nephrin was significantly reduced after Ang Ⅱ stimulation for 3-6 hours (P＜0.05).(4)Ang Ⅱ stimulatation resulted in irregularly arrangement of F-actin followed by the redistribution of F-actin to podocyte periphery and formation of F-actin ring,in which the CFS obviously increased compared to control (P＜0.05).Conclusions Phosphorylation of nephrin is important for the survival status of podocytes.Ang Ⅱ-induced nephrin dephosphorylation may be an important molecular mechanism for Ang Ⅱ-induced podocyte cytoskeleton rearrangement and foot process effacement.