嘌呤霉素肾病大鼠肾小球中nephrin、Podocin和α-actinin与蛋白尿的关系

目的动态观察肾小球足细胞及裂孔隔膜分子nephrin,podocin和α-actinin在嘌呤霉素(puromycinaminonucleoside,PAN)大鼠肾病模型肾组织中表达的时相变化,探讨这些分子间及这些分子与蛋白尿发生的关系。方法用间接免疫荧光染色及实时定量PCR方法,检测PAN注射后12h、1d、36h、2d、5d、10d、15d及20d大鼠肾小球中nephrin,podocin和α-actinin分子分布和表达。结果(1)PAN注射后1d、2d及5d时,尿蛋白量无明显改变;10d时尿蛋白量明显增加(P=0.02);20d时恢复至对照组水平。(2)对照组大鼠肾小球中nephrin和podocin沿肾小球毛细血管袢呈连续线状分布,α-actinin沿肾小球毛细血管袢呈点线状分布。PAN注射1d后,nephrin和podocin的分布即发生改变,表现为断续、非线性分布。nephrin和podocin的分布改变随着尿蛋白的增多而加重,尿蛋白恢复时也逐渐恢复。20d时,α-actinin沿肾小球毛细血管袢呈连续线性分布。(3)免疫荧光定量分析结果表明,在PAN注射后36h(P=0.04)、2d(P=0.03)及5d(P=0.04)时,肾小球中podocin的免疫荧光染色强度明显下降,于第10d降至最低(P=0.006);自15d时逐渐恢复(P=0.007),20d后podocin的免疫荧光强度恢复至对照组水平。nephrin的免疫荧光染色强度在PAN注射第5天后出现下降(P=0.002),持续下降至第10天(P=     

罗格列酮对糖尿病肾病大鼠足细胞nephrin和podocin表达的影响

本研究采用糖尿病肾病（DN）大鼠模型，通过观察肾组织足细胞超微结构及其相关分子表达的变化，以及罗格列酮对其的影响，进一步揭示足细胞相关分子在实验性DN发病中的作用及脂质过氧化物增殖物激活受体γ（PPARγ）激动剂治疗DN的分子机制．为DN的预防和治疗提供理论依据。     

厄贝沙坦对早期糖尿病肾脏疾病大鼠足细胞nephrin和podocin表达的影响

目的：观察厄贝沙坦（irbesartan）对糖尿病肾脏疾病（diabetic kidney disease,DKD）大鼠足细胞裂孔隔膜蛋白分子（nephrin和 podocin）表达的影响,探讨厄贝沙坦对DKD的防治作用。方法以高脂高糖喂养8周联合小剂量链脲佐菌素（30 mg/kg）建立DKD大鼠模型,将 DKD大鼠模型随机分为2组：厄贝沙坦组及模型对照组;另设正常对照组。厄贝沙坦组给予厄旦沙坦（50 mg·kg-1·d-1）,另外2组每日给予等量0.9%生理盐水灌胃。各组于治疗前及药物干预后第4、8、12周周末检测大鼠血糖浓度和尿微量白蛋白量;观察大鼠体质量、肾重、肾肥大指数、血清尿素氮、肌酐、总胆固醇、三酰甘油变化;光镜观察肾脏病理改变;应用免疫组化技术观察足细胞相关蛋白 nephrin、podocin肾组织分布与表达;采用 Western blot技术测定肾皮质 nephrin、podocin 蛋白的表达。结果应用厄贝沙坦干预后与DKD对照组相比,大鼠的尿微量白蛋白总量、肾肥大指数、血糖、尿素氮、血肌酐较模型对照组明显降低（P〈0.05）,体质量增加（P〈0.05）,病理改变减轻,nephrin和 podocin蛋白表达增加（P〈0.05）。结论厄贝沙坦能上调 nephrin和 podocin的表达水平,降低尿微量白蛋白排泄,延缓DKD的进展。     

podocin基因敲低对小鼠足细胞nephrin和α-actinin表达与分布的影响

目的 研究足细胞分子podocin、nephrin和α-actinin之间的相互作用和联系。方法 将针对podocin分子设计的特异RNA干扰(RNAi)质粒导人体外培养的小鼠足细胞系(MPC5)；应用免疫荧光染色及双标记在共聚焦显微镜下观察nephrin、podocin和α-actinin的分布方式；半定量RT-PCR和免疫蛋白印迹检测podocin、nephrin，α-actinin-4及内参照GAPDH／β-actin在mRNA水平和蛋白水平的表达量。结果 (1)干扰组podocin的荧光强度显著低于对照组，其mRNA和蛋白的表达量分别下降了65％和89％。免疫双标记显示podocin的分布发生了明显变化：对照组podocin不但分布在胞核的周围，而且在胞浆呈放射性沿着细胞骨架分布，以及主要在胞膜上呈连续性的线状分布；干扰组podocin呈点状分布在胞核周围。(2)干扰组nephrin的荧光强度亦明显减低，其mRNA及蛋白的表达量分别减少了70％和78％。免疫双标记显示nephrin的分布也发生了显著变化：干扰组nephfin亦呈点状分布在胞核周围；在对照组，nephrin和podocin的分布方式相同。(3)干扰组和对照组α-actinin的分布及在mRNA和蛋白水平上的表达量无明显差异，呈细丝状均匀分布于胞质内，亦呈放射性分布于足细胞伸出的突起中。结论 通过RNAi成功地使MPC5的podocin表达下调。Podocin和nephrin分子关系紧密，可能存在着直接的分子间反应；podocin与α-actinin无直接的作用和联系。     

Glomerular expression of nephrin and synaptopodin, but not podocin, is decreased in kidney sections from women with preeclampsia.

BACKGROUND: Preeclampsia is a pregnancy-specific disorder characterized by hypertension and proteinuria. In other disease states, proteinuria has been linked to altered expressions of podocyte foot-process proteins, but this has not been studied in women with preeclampsia. We sought to test the hypothesis that proteinuria in preeclampsia is associated with dysregulated expression of the podocyte cytoskeleton and/or tight junction proteins. METHODS: Renal tissue was obtained from autopsy material from seven women who had severe preeclampsia during the second half of their pregnancies up to 48 h after delivery, and who subsequently died. As controls, we used autopsy material from two women who died accidentally during the second half of their otherwise normal pregnancies. Immunohistochemical stains for nephrin, synaptopodin and podocin were performed on representative sections prepared from paraffin-embedded material. RESULTS: Expression of both nephrin and synaptopodin was markedly decreased in preeclamptic compared with control kidney sections. By contrast, both cases and controls demonstrated strong staining for podocin. CONCLUSIONS: We conclude that down-regulation of nephrin and synaptopodin is associated with proteinuria in women with preeclampsia. Recent studies have demonstrated that soluble vascular endothelial growth factor receptor 1 (sFlt-1) levels are elevated in preeclampsia compared with normal pregnancy. Studies in mice have shown that sFlt-1 may play a role in inducing proteinuria by neutralizing vascular endothelial growth factor (VEGF) and suppressing nephrin. Proteinuria and elevations of sFlt-1 in preeclampsia are temporally related, further supporting a possible role of sFlt-1 in the dysregulation of podocyte foot-process proteins.     

nephrin、血管内皮生长因子及其受体表达与先兆子痫大鼠蛋白尿的关系

Objective To investigate the association of the expressions of glomerular nephrin, vascular endothelial growth factor (VEGF) and its receptor (VEGFR) with proteinuria in preeclampsia rats. Methods A rat model of preeclampsia was developed by inhibitor of nitric oxide synthase (L-NAME). The systolic blood pressure (SBP) and 24 h urine protein were compared among the normal female group (n=6), the normal pregnant group (n=8), nonpregnant control group (n=6) and preeclampsia group(n=8). The kidney biopsies of each group were observed by light and electron microscopy. The glomerular nephrin was detected by Western blotting and real-time PCR. Immunofluorescence was used to detect the expression of WT1. The level of glomerular VEGF and VEGFR (Flt-1 and Flk-1) were evaluated by Western blotting. Results The level of glomerular nephrin protein in the rats with preeclampsia (0.0726±0.0074) was significantly lower compared with normal female group (0.3795±0.0509), normal pregnant group (0.2361±0.0437) and nonpregnant control group (0.7265±0.0503) (P＜0.01, respectively), while the levels of nephrin mRNA were not significantly different among 4 groups. The expression of WT1 was not significantly different among 4 groups as well. The level of glomerular VEGF in preeclampsia group (1.5429±0.0898) was significantly higher compared with normal female group (1.1870±0.1160), normal pregnant group (1.3741 ±0.1165) and nonpregnant control group (1.0155±0.0742)(P＜0.01,respectively). VEGFR (Flt-1 and Flk-1) was also significantly higher in preeclampsia rats compared with other control groups (P＜0.05, respectively). Conclusions In preeclampsia rats, nephrin is decreased significantly and the glomerular VEGF-VEGFR is increased significantly compared with the other control groups. The abnormal expression of nephrin and VEGF-VEGFR may be involved in the preeclampsia proteinuria. The underlying mechanism of this phenomenon needs further research.     

nephrin、血管内皮生长因子及其受体表达与先兆子痫大鼠蛋白尿的关系

目的 研究nephrin、血管内皮生长因子（VEGF）及其受体（VEGFR）在先兆子痫大鼠肾组织的表达与蛋白尿的关系。 方法 采用一氧化氮合酶抑制剂（L-NAME）制备大鼠先兆子痫模型（n=8）,分别与正常雌性组（n=6）、正常妊娠组（n=8）、未孕L-NAME对照组（n=6）大鼠比较动脉收缩压（SBP）、尿蛋白量（24 h）。各组大鼠肾组织分别行光镜和电镜检查。Western印迹法、实时定量PCR检测nephrin在各组大鼠肾脏局部的表达;免疫荧光法检测各组大鼠肾小球内wilms肿瘤蛋白WT1的表达。Western印迹法检测VEGF及VEGFR（Flt-1、Flk-1）在各组大鼠肾脏局部的表达。 结果 先兆子痫模型组大鼠nephrin蛋白的表达（0.0726±0.0074）显著低于正常雌性组（0.3795±0.0509）、正常妊娠组（0.2361±0.0437）及未孕L-NAME对照组大鼠（0.7265±0.0503）（均P < 0.01）;而nephrin mRNA在各组大鼠间差异无统计学意义。各组大鼠足细胞数目差异无统计学意义。先兆子痫大鼠组VEGF的表达（1.5429±0.0898）显著高于正常雌性组（1.1870±0.1160）、正常妊娠组（1.3741±0.1165）、未孕L-NAME对照组大鼠（1.0155±0.0742）（均P < 0.01）;先兆子痫组大鼠VEGFR（Flt-1、Flk-1）的表达均显著高于其他各对照组大鼠（均P < 0.05）。 结论 先兆子痫大鼠中,nephrin蛋白水平表达明显降低,肾脏局部VEGF-VEGFR表达显著增强,可能参与了先兆子痫蛋白尿的生成,其具体机制有待进一步研究。     

nephrin、血管内皮生长因子及其受体表达与先兆子痫大鼠蛋白尿的关系

Objective To investigate the association of the expressions of glomerular nephrin, vascular endothelial growth factor (VEGF) and its receptor (VEGFR) with proteinuria in preeclampsia rats. Methods A rat model of preeclampsia was developed by inhibitor of nitric oxide synthase (L-NAME). The systolic blood pressure (SBP) and 24 h urine protein were compared among the normal female group (n=6), the normal pregnant group (n=8), nonpregnant control group (n=6) and preeclampsia group(n=8). The kidney biopsies of each group were observed by light and electron microscopy. The glomerular nephrin was detected by Western blotting and real-time PCR. Immunofluorescence was used to detect the expression of WT1. The level of glomerular VEGF and VEGFR (Flt-1 and Flk-1) were evaluated by Western blotting. Results The level of glomerular nephrin protein in the rats with preeclampsia (0.0726±0.0074) was significantly lower compared with normal female group (0.3795±0.0509), normal pregnant group (0.2361±0.0437) and nonpregnant control group (0.7265±0.0503) (P＜0.01, respectively), while the levels of nephrin mRNA were not significantly different among 4 groups. The expression of WT1 was not significantly different among 4 groups as well. The level of glomerular VEGF in preeclampsia group (1.5429±0.0898) was significantly higher compared with normal female group (1.1870±0.1160), normal pregnant group (1.3741 ±0.1165) and nonpregnant control group (1.0155±0.0742)(P＜0.01,respectively). VEGFR (Flt-1 and Flk-1) was also significantly higher in preeclampsia rats compared with other control groups (P＜0.05, respectively). Conclusions In preeclampsia rats, nephrin is decreased significantly and the glomerular VEGF-VEGFR is increased significantly compared with the other control groups. The abnormal expression of nephrin and VEGF-VEGFR may be involved in the preeclampsia proteinuria. The underlying mechanism of this phenomenon needs further research.     

Characterization of ANKRA, a novel ankyrin repeat protein that interacts with the cytoplasmic domain of megalin

Ankyrin-repeat family A protein (ANKRA) is a novel protein that interacts directly and specifically with the cytoplasmic tail of megalin in the yeast two-hybrid system and glutathione-S-transferase pull-down assays. ANKRA has three ankyrin repeats and shows 61% overall homology to regulatory factor X, ankyrin repeat-containing protein. Mapping studies show that the three ankyrin repeats and C-terminus of ANKRA are required for binding to a unique juxtamembrane, 19-amino acid sequence on the megalin tail. Point mutational analysis reveals that a proline-rich motif (PXXPXXP) within this region is the site of ANKRA binding. ANKRA interacts with megalin but not with low-density lipoprotein receptor related protein, in keeping with the fact that the sequence of the megalin tail is unique. By cell fractionation, ANKRA is found both in the cytosol and associated with membranes enriched in megalin in L2 cells and proximal tubule cells. By immunofluorescence, ANKRA is concentrated near megalin along the plasma membrane of L2 cells and in the kidney cortex is expressed in glomerular and proximal tubule epithelia which also express megalin. These observations suggest that ANKRA may play a unique role in megalin's function as a clearance receptor in the kidney and L2 cells. In addition, ANKRA may have other partners because northern blot analysis reveals that ANKRA is more broadly expressed than megalin, and by immunofluorescence ANKRA is also expressed in connecting tubule cells and principal cells of collecting ducts.     

Nitric oxide/platelet activating factor cross-talk in mesangial cells modulates the interaction with leukocytes

BACKGROUND: The secondary hyperparathyroidism of chronic kidney disease (CKD) produces a high turnover osteodystrophy that is associated with peritrabecular fibrosis. The nature of the cells involved in the development of peritrabecular fibrosis may represent osteoprogenitors expressing a fibroblastic phenotype that are retarded from progressing through osteoblast differentiation. METHODS: To test the hypothesis that osteoblast differentiation is retarded in secondary hyperparathyroidism due to CKD producing bone marrow fibrosis, we administered bone morphogenetic protein 7 (BMP-7), a physiologic regulator of osteoblast regulation, to C57BL6 mice that had CKD produced by electrocautery of one kidney followed by contralateral nephrectomy two weeks later. Following the second surgical procedure, a subgroup of mice received daily intraperitoneal injections of BMP-7 (10 microg/kg). Three to six weeks later, the animals were sacrificed, blood was obtained for measurements of blood urea nitrogen (BUN) and parathyroid hormone (PTH) levels, and the femora and tibiae were processed for histomorphometric analysis. RESULTS: The animals had significant renal insufficiency with BUN values of 77.79 +/- 22.68 mg/dL, and the level of renal impairment between the CKD untreated mice and the CKD mice treated with BMP-7 was the same in the two groups. PTH levels averaged 81.13 +/- 51.36 and 75.4 +/- 43.61 pg/mL in the CKD and BMP-7 treated groups, respectively. The animals with CKD developed significant peritrabecular fibrosis. In addition, there was an increase in osteoblast surface and osteoid accumulation as well as increased activation frequency and increased osteoclast surface consistent with high turnover renal osteodystrophy. Treatment with BMP-7 eliminated peritrabecular fibrosis, increased osteoblast number, osteoblast surface, mineralizing surface and single labeled surface. There was also a significant decrease in the eroded surface induced by treatment with BMP-7. CONCLUSIONS: These findings indicate that BMP-7 treatment in the setting of high turnover renal osteodystrophy prevents the development of peritrabecular fibrosis, affects the osteoblast phenotype and mineralizing surfaces, and decreases bone resorption. This is compatible with a role of osteoblast differentiation in the pathophysiology of osteitis fibrosa.     

Protein kinase C alpha modulates microvascular reactivity in the human coronary and skeletal microcirculation

BACKGROUND: Cardioplegic arrest (CP) and cardiopulmonary bypass (CPB) can lead to dysfunction in the coronary and skeletal microcirculation leading to impaired tissue perfusion. alpha-Adrenergic signaling pathways acting on these microcirculatory beds are thought to involve protein kinase C (PKC). We investigate here the role of the conventional PKCs in microvascular function in the setting of CP/CPB. METHODS: Atrial and skeletal muscle was harvested from 30 patients undergoing cardiac surgery before and after CP/CPB. Microvessels were used for Western blotting and immunofluorescent staining against conventional PKCs. Microvascular constriction was assessed in pre- and post-CP/CPB samples in response to alpha-adrenergic stimulation with phenylephrine, with and without a PKC-alpha inhibitor or PKC-alpha activator. PKC activity was assessed in isolated microvessels. RESULTS: Western blotting and immunostaining demonstrated only PKC-alpha in coronary and skeletal microvessels. CP/CPB diminished contractile responses to phenylephrine in coronary and skeletal samples. Inhibition of PKC-alpha reduced phenylephrine induced vasoconstriction in coronary and skeletal microvessels, whereas activation of PKC-alpha-augmented phenylephrine induced responses. PKC activity was decreased in coronary microvessels and to an even greater degree in skeletal microvessels after CP/CPB. CONCLUSIONS: PKC-alpha is the predominant conventional PKC present in the human coronary and skeletal microcirculation. It likely plays a key role in alpha-adrenergic signaling in microvessels and in the vasomotor dysfunction after CP/CPB.     

NIDDM associated with mutation in tyrosine kinase domain of insulin receptor gene.

A population of 103 patients with non-insulin-dependent diabetes mellitus (NIDDM) was screened for mutations in the tyrosine kinase domain of the insulin receptor gene. Patient genomic DNAs corresponding to exons 17-21 of the insulin receptor gene have been amplified by polymerase chain reaction and analyzed by denaturing gradient gel electrophoresis (DGGE). One patient was identified with an altered pattern of mobility of exon 20 in the DGGE assay. Direct sequence of amplified DNA showed a single nucleotide substitution in the codon 1152 (CGG-- greater than CAG), resulting in the replacement of Arg with Gln. Two bands appeared in the sequence of exon 20 of the insulin receptor (nucleotide position 3584), indicating that this patient was heterozygous for the mutation. Insulin binding to intact erythrocytes from the patient was in the normal range. Although autophosphorylation of the purified insulin receptor also seemed normal, its kinase activity toward the exogenous substrate poly Glu:Tyr (4:1) was undetectable. This mutation may impair insulin receptor kinase and contribute to insulin resistance in this patient.     

氧化应激与糖尿病大鼠nephrin表达及足细胞凋亡的关系

本研究观察,氧化应激对糖尿病大鼠nephrin表达改变及足细胞凋亡的影响,以探讨糖尿病大鼠蛋白尿发生发展的分子机制. 一、材料与方法 1.材料:雄性SD大鼠,体质量170～220 g,由武汉大学动物试验中心提供.褪黑素溶液和链脲佐菌素STZ溶液购自美国Sigma公司.     

Nephrin and podocin dissociate at the onset of proteinuria in experimental membranous nephropathy

BACKGROUND: The slit diaphragm plays a critical role in maintaining the barrier function of the glomerular capillary wall. The pathogenic mechanism of proteinuria in membranous nephropathy remains uncertain. This study was undertaken to analyze the pathogenic role of slit diaphragm in proteinuria in experimental membranous nephropathy. METHODS: The expression and the localization of slit diaphragm-associated molecules (nephrin, podocin, and CD2AP) and other podocyte-associated molecules (podocalyxin and alpha(3) integrin) in passive and active Heymann nephritis were analyzed by immunofluorescence and Western blot analysis. The interaction of slit diaphragm-associated molecules was investigated by the dual-labeling immunofluorescence method. The mRNA expression of these molecules was also analyzed. RESULTS: Shifts in nephrin and podocin staining patterns, from linear to granular, were detected in the early stages of passive Heymann nephritis. These shifts were not parallel, and the dissociation of these molecules was detected by the dual-labeling immunofluorescence method in passive and active Heymann nephritis. Western blot analyses with sequentially solubilized materials indicated that the nephrin-rich fraction changed from being partly detergent-resistant to being predominantly detergent-soluble. This change did not occur with podocin. Nephrin excreted into urine was already detected in the early stages of passive Heymann nephritis. Decreased mRNA expression of nephrin and podocin was observed before the onset of proteinuria. By contrast, no extensive change in the expression of alpha(3) integrin was observed in this study. CONCLUSION: Nephrin is dissociated from podocin and excreted into urine in the early stages of Heymann nephritis. The reduced expression of nephrin and podocin, along with their dissociation, may contribute to the development of proteinuria in Heymann nephritis.     

Deletion of the kinase domain in death-associated protein kinase attenuates tubular cell apoptosis in renal ischemia-reperfusion injury

Death-associated protein kinase (DAPK) is a calcium/calmodulin-dependent serine/threonine kinase localized to renal tubular epithelial cells. To elucidate the contribution of DAPK activity to apoptosis in renal ischemia-reperfusion (IR) injury, wild-type (WT) mice and DAPK-mutant mice, which express a DAPK deletion mutant that lacks a portion of the kinase domain, were subjected to renal pedicle clamping and reperfusion. After IR, DAPK activity was elevated in WT kidneys but not in mutant kidneys (1785.7 +/- 54.1 pmol/min/mg versus 160.7 +/- 60.6 pmol/min/mg). Furthermore, there were more TUNEL-positive nuclei and activated caspase 3-positive cells in WT kidneys than in mutant kidneys after IR (24.0 +/- 5.9 nuclei or 9.4 +/- 0.6 cells per high-power field [HPF] versus 6.3 +/- 2.2 nuclei or 4.4 +/- 0.7 cells/HPF at 40 h after ischemia). In addition, the increase in p53-positive tubule cells after IR was greater in WT kidney than in mutant kidneys (9.9 +/- 1.4 cells/HPF versus 0.8 +/- 0.4 cells/HPF), which is consistent with the theory that DAPK activity stabilizes p53 protein. Finally, serum creatinine levels after IR were higher in WT mice than in mutant mice (2.54 +/- 0.34 mg/dl versus 0.87 +/- 0.24 mg/dl at 40 h after ischemia). Thus, these results indicate that deletion of the kinase domain from DAPK molecule can attenuate tubular cell apoptosis and renal dysfunction after IR injury.     

Homodimerization and heterodimerization of the glomerular podocyte proteins nephrin and NEPH1

Nephrin and NEPH1, the gene products of NPHS1 and NEPH1, are podocyte membrane proteins of the Ig superfamily. Similar to the nephrin knockout, mice lacking NEPH1 show severe proteinuria leading to perinatal death. To identify the ligand of NEPH1, the extracellular domain of NEPH1 was fused to human IgG. This NEPH1-Ig fusion protein labeled the glomerular capillary wall of mouse kidneys in a staining pattern identical to NEPH1 and nephrin, prompting speculation that that NEPH1 might form homodimers and/or heterodimers with nephrin. In coimmunoprecipitation and pull-down assays, the NEPH1-Ig fusion protein precipitated wild-type NEPH1 from overexpressing HEK 293T cells. Truncational analysis revealed that the adhesive properties were not confined to a single Ig domain of NEPH1. Fusion proteins containing two Ig domains of NEPH1 were sufficient to immobilize NEPH1, but they failed to interact with control protein containing the phylogenetically related PKD repeats of polycystin-1. NEPH1 also precipitated nephrin, a protein with eight Ig domains and a fibronectin-like domain. Truncational analysis of nephrin revealed a very similar mode of interaction, i.e., two nephrin Ig domains fused to human IgG precipitated either nephrin or NEPH1, but not the control protein. Both NEPH1 and nephrin interactions were strictly dependent upon posttranslational glycosylation, and bacterially expressed protein failed to bind NEPH1. These findings demonstrate that the Ig domains of NEPH1 and nephrin form promiscuous homodimeric and heterodimeric interactions that may facilitate cis- and trans- homodimerizations and heterodimerizations of these molecules at the glomerular slit diaphragm.