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Objective To investigate the effects of angiotensin Ⅱ (Ang Ⅱ) on the expression of C-terminal Src kinase (Csk) in Ang Ⅱ-infused rat model and cultured podocytes,and to explore the role of Csk in Ang Ⅱ-induced cytoskeletal rearrangement of podocytes.Methods Twenty-four Wista rats were randomly subjected to normal saline infusion,or Ang Ⅱ infusion at 400 ng · kg1 · min-1 (via subcutaneous osmotic minipumps) for 2 or 4 weeks.Renal histomorphology was evaluated through electron microscopy.The expression of glomerular Csk was analyzed by immunofluorescence and Western blotting.In vitro,conditionally immortalized mouse podocytes were cultured and treated with Ang Ⅱ doses ranging from 10-9 mol/L to 10-5 mol/L and for different hours.The expression of podocytes Csk was assessed by Western blotting.After transfection to podocytes with Csk siRNA,FITC-conjugated phalloidin was used to stain F-actin,to investigate the role of Csk in Ang Ⅱ-induced or cytochalasin D-induced cytoskeletal rearrangement.Results (1) Examination of Ang Ⅱ infusion rats glomerular and podocyte ultrastructure by electron microscopy revealed foot process effacement and fusion; (2) In Ang Ⅱ infusion rats,the expression of glomerular Csk was increased (P ＜ 0.05); (3) In vitro,Ang Ⅱ-stimuli up-regulated the expression of Csk (P ＜ 0.05),and the effects of Ang Ⅱ were on dose-dependent and time-dependent manner; (4) Ang Ⅱ-induced disruption of F-actin was alleviated by Csk siRNA transfection in cultured podocytes; furthermore,cytochalasin D depolymerized the F-actin cytoskeleton,while Csk siRNA stabilized the actin filaments.Conclusion The enhanced expression of Csk may be involved in Ang II-induced podocytes cytoskeletal rearrangement and foot process fusion.
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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.
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ObjectiveTo evaluate the effects of angiotensin Ⅱ (Ang Ⅱ )infusion on renal c-Abl expression in vivo,and on podocyte c-Abl expression change in cultured mouse podocytes.Methods Twenty four male Sprague-Dawley rats (Group C,D,E and F) were assigned to receive Ang Ⅱ(400 ng· kg-1 min-1) by osmotic minipump and of which 12 rats (Group D and F) were assigned to receive telmisartan (3 mg·kg-1·d-1),six rats received normal saline(Group B),and six rats were used as normal control(Group A).Animals were sacrificed at day 14 (Group C and D),day 28 (Group E and F) respectively.Conditionally immortalized mouse podocytes were used in vitro.Podocytes were studied 2 weeks after thermoswitching from 33℃ to 37℃.Cells were fetal bovine serum(FBS) starved for at least 12 hours prior to stimulation.The cultured podocytes were treated withAngⅡdosesranging from10 -9 mol/L to10 -6 mol/L andfor differenthours.Expression of renal and podocytes c-Abl was examined by immunofluorescence staining,real-time PCR and Western blotting.Results(1) Distribution of c-Abl expression was mainly in the cytoplasm and nuclear of the podocytes in vivo and in vitro. (2) Expressions of c-Abl mRNA and protein wereincreasedinAng Ⅱ-infusedratpodocytesandAng Ⅱ-inducedculturedmouse podocytes(P＜0.05),and the effects of Ang Ⅱ were dose-dependent and time-dependent in vitro.Conclusion There are c-Abl mRNA and protein expression in podocytes,and c-Abl may play a critical role in the pathogenesis of Ang Ⅱ -induced podocyte injury.
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Objective To evaluate the effect of aldosterone (Ald) on glomerular mesangial cells apoptosis and to explore the possible mechanisms.Methods Twenty-four Sprngue-Dawley rats were subcutaneously embedded with osmotic mini-pumps and randomly divided into 3 groups.Aldosterone (1.5 μg/h) was administrated subcutaneouly by osmotic mini-pumps in Ald group,eplerenone (Epl,100 mg·kg-1·d-1) and Ald (1.5 μg/h) was given to Epl group.And normal saline was used in control group (Con group).Systolic blood pressure and urinary albumin excretion rate (UAER) were detected on day 0,7,14,21,28.Blood and kidney samples were harvested on day 28.Plasma creatinine,potassium and aldosterone were measured.Renal paraffin sections were stained by PAS and the morphological changes were evaluated by light microscopy.Apoptosis index of mesangial cells were detected by TUNEL assay.The glomerular mesangial cells (MCs) were cultured in a DMEM-F12 media.MCs apoptosis was evaluated by staining cells with Annexin V and propidium iodide (PI) using flow cytometer.Expression of Bcl-2 and Bax mRNA was examined by RT-PCR.The protein level of Bad or phospho-Bad was measured by Western blotting.Results Ald-infused rats developed hyperaldosteronemia and hypokalemia.Rats in Ald group exhibited significant hypertension and marked albuminuria.Ald group rats showed increased number of TUNEL-positive mesangial cells when compared with control rats (P＜0.05).Aldosterone induced mesangial cells apoptosis in a time-dependent manner.Expression of Bcl-2 mRNA was decreased but Bax mRNA was increased in aldosterone treated MCs compared to that in Con group (P＜0.05).Aldosterone promoted dephosphorylation of cytosolic phospho-Bad compared with vehicle treated cells (P＜ 0.05).However,eplerenone attenuated these effects of aldosterone.Conclusion Aldosterone directly promotes mesangial cells apoptosis,and eplerenone can attenuate this effect of aldosterone.Dephosphorylation of cytosolic phospho-Bad may be the key role in the progression of mesangial cells apoptosis induced by aldosterone.
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ObjectiveTo evaluate the effects of Ang Ⅱ on apoptosis of podocytes and explore the signaling pathwayof nephrin in preventingAng Ⅱ-inducedpodocyte apoptosis.MethodsDifferentiated mouse podocytes were exposed to Ang Ⅱ at different concentrations for 18 h or at 10-8 mol/L for variable incubation times.Undifferentiated mouse pedocytes were transfected using lipofectamine 2000 with the pcDNA3.1-mNPHS1 plasmid and stably transfected cell lines were generated with G418 selection.In separated experiments,untransfected mouse podocytes (MPC) and stably transfected podocytes with pcDNA3.1-neo and PcDNA3.1-mNPHS1 were exposed toAng Ⅱ(10-8 mol/L) or LY294002(a selective Akt inhibitor,50 μmol/L) for indicated times.Apoptosis was evaluated by flow cytometry.The expression of nephrin was assessed by quantitative real-time PCR,immunofluorescence and Western blotting.The phosphorylation level of Akt was determined by Westem blotting.Results(1) AngⅡ promoted podocyte apoptosis in a dose-and time-dependentmanner. PretreatmentwithlosartansignificantlypreventedAngⅡ -induced apoptosis. (2) Nephfin mRNA and protein were obviously decreased in podocytes exposed to 10-8 mol/L Ang Ⅱ for at least 12 h than those in vehicle-treated cells (P＜0.05).(3) Ang Ⅱ exposure for more than 15 min inhibited the phosphorylation of AKT in MPC,which was dramatically reversed by pcDNA3.1-mNPHS1 transfection,but not by pcDNA3.1-neo transfection. (4) Podocyte apoptosis was promoted byLY294002. Conversely,Ang Ⅱ-induced podocyteapoptosis was significantly alleviated by pcDNA3.1-mNPHS1 transfection.ConclusionAng Ⅱinduces mouse podocyte apoptosis which is suppressed by overexpression of nephrin through PI3K-Akt signaling pathway.
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Objective To investigate the effect of angiotensin 1-7(Ang 1-7) on renal proximal tubular epithelial cell(HK-2) transdifferentiation induced by high glucose.Methods All the raised HK-2 cells were divided into 5 groups: normal control group,high glucose group,high glucose with Ang1-7 group,high glucose with Ang1-7 and A779 group,high glucose with pioglitazone group.Expression of peroxisome proliferator activated receptor-γ(PPAR-γ) and α-smooth muscle actin(α-SMA) was detected by Western blotting,real-time PCR and immunofluorescence.Results The levels of PPAR-γ protein and mRNA in HK-2 cells were significantly increased after treatment with high glucose and Ang 1-7.Expression of α-SMA protein and mRNA was inhibited remarkably after treatment with high glucose and Ang 1-7.These effects of Ang 1-7 on HK-2 cells could be reversed by Mas receptor antagonist A779.Conclusion Ang 1-7 inhibits high glucose-induced expression of o-SMA in HK-2 cells,which is in part through the Mas.
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Objective To investigate the effect of surfactant protein D(SP-D)overexpression on lipopolysaccharide(LPS)-induced monocyte chemoattractant protein-1(MCP-1)expression in human renal proximal tubular epithelial cells(HK-2)and its mechanism. Methods HK-2 cells were treated with LPS at various concentrations (0, 0.1, 1, 2, 5, 10 mg/L)for 8 h and at 5 mg/L for various time points(0, 2, 4, 8, 16, 24 h). Expression of SP-D was detected by Western blotting and real-time PCR. Expression of MCP-1 was determined by ELISA and real-time PCR. Human SP-D cDNA eukaryotic expression vector pEE14-hSP-D was transfected to HK-2 cells. The changes in transfected cells of SP-D protein were observed by Western blotting. Expression of MCP-1 was detected by ELJSA and real-time PCR. Results SP-D was expressed in HK-2 cells. The levels of SP-D protein and mRNA in HK-2 cells were significantly decreased after treatment with LPS(P<0.05). Expression of MCP-1 protein and mRNA was increased remarkably after treatment with LPS(P<0.05). HK-2 cells transfected with pEE14-hSP-D showed up-regulated expression of SP-D. The overexpression of SP-D inhibited the LPS-inducedexpression of MCP-1(P<0.01). Conclusions SP-D inhibits LPS-induced expression of MCP-1 in HK-2 cells. SP-D may play an important role in the modulation of renal inflammation.
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ObjectiveTo investigate whether aldosterone infusion induces glomerular or podocyte injury in rats and to evaluate the effects of eplerenoen (EPL), andodipine (CCB) and telmisartan (ARB) on aldosterone- induced injury. MethodsThirty male Sprague-Dawley rats were divided into 5 groups: control, subcutaneous infusion of aldosterone (1.5 μg/h, ALD group) and aldosterone infusion plus eplerenone (100 mg·kg-1·d-1, EPL group), amlodipine(10 nag·kg-1·d-1 CCB group), telmisartan (3 mg·kg-1·d-1, ARB group), respectively. Systolic blood pressure(SBP) and urinary albumin excretion ratio(UAER) were measured at day 0, 7, 14, 21, 28. Blood samples were harvested to detect plasma angiotensin Ⅱ, plasma aldosterone, serum sodium, serum potassium and serum creatinine at day 28. Glomerular damge was quantified by morphological glomerular injury score (GIS). Immunohistochemistry and RT-PCR were performed to evaluate podocyte lesion, and apoptosis ratio of pedocyte (ARP) in a glomerular cross section was analyzed by TUNEL. ResultsALD infusion progressively increased SBP and UAER compared with CTL (P＜0.01). SBP was significantly reduced in EPL, CCB or ARB-treated animals, meanwhile, UAER was decreased in EPL and ARB group, but not in CCB group. The ALD-infused rats exibited hypernatremia and hypopotassaemia, which were blocked by EPL adminstration but not by CCB or ARB treatment. ARB group had a significant increase in plasma angiotensin Ⅱ compared with ALD, CCB and EPL groups(P＜0.01). The ALD-infused animals developed hyperaldosteronemia compared with CTL, but with no difference of plasma aldosterone among ALD, EPL, CCB and ARB-treated rats. Treatment with EPL prevented an increase of GIS and ARP compared with CCB and ARB (P＜0.05, P＜0.01). Protein and mRNA expression of nephfin was up-regulated in ALD group (P＜ 0.01), but was significantly prevented by EPL treatment(P＜0.01), whereas CCB and ARB therapy had no such effect. Conclusion ALD infusion significantly induces glomerular and pedocyte injury which is blocked by EPL but not by CCB or ARB independently on systemic hemodynamics.