nephrin and Kidney-Diseases

Podocyte dysfunction contributes to proteinuric chronic kidney disease. A number of key proteins are essential for podocyte function, including nephrin, podocin, CD2-associated protein (CD2AP), synaptopodin, and α-actinin-4 (ACTN4). Although most of these proteins were first identified through genetic studies associated with human kidney disease, subsequent studies have identified phosphorylation of these proteins as an important posttranslational event that regulates their function. In this review, a brief overview of the function of these key podocyte proteins is provided. Second, the role of phosphorylation in regulating the function of these proteins is described. Third, the association between these phosphorylation pathways and kidney disease is reviewed. Finally, challenges and future directions in studying phosphorylation are discussed. Better characterization of these phosphorylation pathways and others yet to be discovered holds promise for translating this knowledge into new therapies for patients with proteinuric chronic kidney disease.

Topics: Adaptor Proteins, Signal Transducing; Animals; Cytoskeletal Proteins; Humans; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Phosphorylation; Podocytes

Nephrin is a key molecule in podocytes to maintain normal slit diaphragm structure. Nephin interacts with many other podocyte and slit diaphragm protein and also mediates important cell signaling pathways in podocytes. Loss of nephrin during the development leads to the congenital nephrotic syndrome in children. Reduction of nephrin expression is often observed in adult kidney diseases including diabetic nephropathy and HIV-associated nephropathy. The critical role of nephrin has been confirmed by different animal models with nephrin knockout and knockdown. Recent studies demonstrate that knockdown of nephrin expression in adult mice aggravates the progression of unilateral nephrectomy and Adriamycin-induced kidney disease. In addition to its critical role in maintaining normal glomerular filtration unit in the kidney, nephrin is also expressed in other organs. However, the exact role of nephrin in kidney and extra-renal organs has not been well characterized. Future studies are required to determine whether nephrin could be developed as a drug target to treat patients with kidney disease.

Topics: Animals; Humans; Kidney; Kidney Diseases; Membrane Proteins

Podocytes are postmitotic renal glomerular cells with multiple ramifications that extend from the cell body. Processes departing from a podocyte interdigitate with corresponding projections from neighboring cells and form an intricate web that enwraps the glomerular capillary completely. Podocyte processes are interconnected by the slit diaphragm, an adhesion junction mostly formed by Ig-like molecules, cadherins/protocadherins, ephrin/eph, and neurexin molecules organized in an assembly that resembles synaptic junctions. Podocyte failure is primarily or secondarily implicated in all forms of proteinuric glomerular diseases, as confirmed by the morphological changes of their elaborate cell architecture detectable by electron microscopy. Importantly, mutations of podocyte proteins are responsible for the most severe forms of congenital nephrotic syndrome. In the last 15 years, progressive technological advances have aided the study of podocyte biology and pathology, confirming the relevance of podocyte molecules and signaling pathways for the function of the glomerular filter. This review will examine the most important and newest discoveries in the field, which is rapidly evolving, hopefully leading to a detailed knowledge of this fascinating cell and to the development of specific therapeutic options for proteinuric diseases.

Topics: Animals; Humans; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mice; Models, Biological; Podocytes; Proteinuria; Signal Transduction

Topics: Animals; Bone Morphogenetic Protein 2; Claudins; Diabetic Nephropathies; Diagnosis, Differential; Glomerulonephritis, IGA; Glomerulosclerosis, Focal Segmental; GTP-Binding Proteins; Humans; Kidney Diseases; Membrane Proteins; Nephrosis, Lipoid; Podocytes; Protein Glutamine gamma Glutamyltransferase 2; Transglutaminases

Topics: Animals; Cadherins; Cell Adhesion; Humans; Kidney; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mice; Models, Biological; Mutation; Podocytes; Proteinuria; Signal Transduction

Topics: Animals; Humans; Kidney Diseases; Membrane Proteins; Molecular Biology; Podocytes; Signal Transduction

Topics: Actinin; Adaptor Proteins, Signal Transducing; Animals; Collagen Type IV; Cytoskeletal Proteins; Glomerular Basement Membrane; Hepatocyte Nuclear Factor 1-beta; Humans; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Kidney Tubules; Membrane Proteins; Microfilament Proteins; Mutation; Podocytes; Proteins; TRPP Cation Channels; WT1 Proteins

Topics: Adult; Age Factors; Animals; Basement Membrane; Blotting, Western; Child; Diagnosis, Differential; Fluorescent Antibody Technique; Glomerular Filtration Rate; Humans; Immunohistochemistry; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mutation; Nephrotic Syndrome; Proteinuria; Rats; Reverse Transcriptase Polymerase Chain Reaction

The glomerular visceral epithelial cell plays a central role in ultrafiltration of the blood and in a wide variety of inherited and acquired diseases of the kidney. The discovery of nephrin and other slit diaphragm proteins has led to an explosion of knowledge in the biology of this cell type. The most significant recent discoveries are reviewed in this paper.. Together with the glomerular endothelial cells and intervening glomerular basement membrane, the podocyte constitutes a major portion of the glomerular filtration barrier that separates blood from the urinary space. A number of proteins have been identified that are localized to the slit diaphragms that separate podocyte foot processes. Although it has been suggested that the slit diaphragm represents the ultimate filtration barrier, additional roles for this structure as a signaling centre and in endocytosis have been identified. Mutations in genes that reside in the slit pore or interact with the actin cytoskeleton have been linked to a variety of inherited diseases of the podocyte. Additional mutations in these genes have been linked to sporadic forms of nephrotic syndrome and proposed as modifiers of renal risk. The generation of podocyte-specific transgenic models and genomic tools for the murine podocyte provide important resources for the glomerular biologist.. Over the past year, studies using human genetics, conditional gene targeting and cell biological approaches have led to a rapid increase in our understanding of podocyte and glomerular biology, which should lead to the development of novel therapies for individuals with glomerular disease.

Topics: Animals; Animals, Genetically Modified; Disease Models, Animal; Gene Targeting; Humans; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Proteins

Topics: Angiotensin II; Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Animals; Antihypertensive Agents; Benzimidazoles; Biphenyl Compounds; Cognition Disorders; Heart Failure; Humans; Hypertension; Kidney Diseases; Losartan; Membrane Proteins; Mineralocorticoid Receptor Antagonists; Proteins; Proteinuria; Randomized Controlled Trials as Topic; Stroke; Tetrazoles

The rapidly developing field of podocyte cell biology is reviewed, focusing on papers published in the last 12 months.. Four areas of particular progress can be discerned. First, podocytes proliferate during early metanephric development, are quiescent after the capillary loop stage, and re-enter the cell cycle only in the disease group termed collapsing glomerulopathy. We have learned that control of the podocyte cell cycle involves both expression of cell-cycle regulating proteins and the process of cytokinesis. Second, the podocyte slit diaphragm is the final component of the filtration barrier. The structure and maintenance of the slit diaphragm has been a major focus of research activity, and a multiplicity of relevant molecular interactions have been defined. Significant advances have been made in understanding the complex and interacting role of nephrin and podocin mutations in the genesis of clinical glomerular disease. Third, several proteins essential to controlling discrete podocyte transcriptional programs have been defined. Finally, conditionally-immortalized podocyte cell lines, derived from mouse and human tissue, have proven their worth as models to advance investigations of podocyte biology.. Podocyte injury occurs as a consequence of genetic mutation, immunological injury, viral infection, or abnormal hemodynamic forces within the glomerulus. As we understand more about the podocyte proteome and cell biology, we gain an increasingly detailed molecular understanding of podocyte structure and function. In this drama we have many molecular players and increasing stretches of molecular dialogue, but the script remains largely to be deciphered. Nevertheless, we do understand the consequences that arise when the podocyte cannot put its best foot (processes) forward.

Topics: Animals; Basement Membrane; Cell Adhesion; Cell Cycle; Cells, Cultured; Humans; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mutation; Proteins; Transcription, Genetic

Topics: Animals; Humans; Kidney Diseases; Membrane Proteins; Proteins; Proteinuria

Topics: Humans; Kidney Diseases; Membrane Proteins; Proteins; Signal Transduction

The past 5 years have witnessed an exponential increase in our understanding of the structure and function of the glomerular slit diaphragm. The identification of nephrin as the first transmembrane slit diaphragm protein was a watershed event in slit diaphragm biology. This article correlates some of the observations of the prenephrin era with more recent studies, and elaborates on the individual characteristics of each slit diaphragm protein. Recent studies on protein-protein interactions related to slit diaphragm permeability and cell signaling are elaborated, along with observations on their expression in human disease and experimental models of proteinuria. Developmental expression of components of the slit diaphragm in normal and knockout mice also is discussed. Finally, some areas of future investigation are proposed.

Topics: Animals; Biopsy, Needle; Cadherins; Disease Models, Animal; Forecasting; Humans; Immunohistochemistry; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Membrane Proteins; Mice; Mice, Knockout; Molecular Biology; Molecular Structure; Protein Binding; Proteins; Rodentia; Sensitivity and Specificity

Nephrin, a newly described protein, has been localized to the slit membrane between adjacent podocytes of the glomerulus. Its discovery followed the demonstration of the gene NPHS1 and its mutation, resulting in the absence of the protein product, nephrin, in the congenital nephrotic syndrome of the Finnish type. The link between permutations in nephrin expression and proteinuria has been shown in animal models by using neutralizing antibodies or studying mice with inactivation of the nephrin gene. Moreover, the expression of nephrin has been shown to be reduced in various animal models of proteinuric renal disease. The relationship between changes in nephrin expression and proteinuric renal disease in humans is not fully elucidated, with a reduction in expression of this protein reported in a range of renal diseases. Diabetic nephropathy, one of the major causes of end-stage renal disease, is associated with substantial proteinuria and in experimental models with a reduction in slit pore density. In experimental models of diabetes, nephrin expression has been described as being transiently increased in the first 8 weeks of diabetes, followed in longer-term studies with reduced nephrin expression in association with increasing proteinuria. An angiotensin II-receptor blocker has been shown to prevent depletion in glomerular nephrin expression in the diabetic kidney. Human studies in both type 1 and type 2 diabetes suggest down-regulation of nephrin expression in the diabetic kidney and it has been postulated that these changes may play a role in the pathogenesis of diabetic nephropathy, specifically the development of proteinuria in this condition. Although there are other proteins involved in the structure of the epithelial podocyte and specifically the slit pore, nephrin seems to play a pivotal role in preventing passage of protein through the glomerular barrier. Furthermore, it is suggested that the antiproteinuric effects of inhibition of the renin-angiotensin system may partly relate to the effects of these agents on nephrin expression.

Topics: Animals; Diabetic Nephropathies; Humans; Kidney Diseases; Membrane Proteins; Proteins; Proteinuria

Topics: Animals; Cell Count; Cytoskeleton; Glomerulosclerosis, Focal Segmental; Humans; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Kidney Glomerulus; Membrane Microdomains; Membrane Proteins; Proteins

Topics: Humans; Kidney; Kidney Diseases; Membrane Proteins; Proteins

Topics: Albuminuria; C-Reactive Protein; Creatinine; Diabetes Mellitus, Type 2; Fibrosis; Humans; Inflammation; Interleukin-6; Kidney Diseases; Membrane Proteins; Sodium-Glucose Transporter 2 Inhibitors; Transforming Growth Factor beta1; Tumor Necrosis Factor-alpha

Under healthy conditions, foot processes of neighbouring podocytes are interdigitating and connected by an electron-dense slit diaphragm. Besides slit diaphragm proteins, typical adherens junction proteins are also found to be expressed at this cell-cell junction. It is therefore considered as a highly specialized type of adherens junction. During podocyte injury, podocyte foot processes lose their characteristic 3D structure and the filtration slits typical meandering structure gets linearized. It is still under debate how this change of structure leads to the phenomenon of proteinuria. Using super-resolution 3D-structured illumination microscopy, we observed a spatially restricted up-regulation of the tight junction protein claudin-5 (CLDN5) in areas where podocyte processes of patients suffering from minimal change disease (MCD), focal and segmental glomerulosclerosis (FSGS) as well as in murine nephrotoxic serum (NTS) nephritis and uninephrectomy DOCA-salt hypertension models, were locally injured. CLDN5/nephrin ratios in human glomerulopathies and NTS-treated mice were significantly higher compared to controls. In patients, the CLDN5/nephrin ratio is significantly correlated with the filtration slit density as a foot process effacement marker, confirming a direct association of local CLDN5 up-regulation in injured foot processes. Moreover, CLDN5 up-regulation was observed in some areas of high filtration slit density, suggesting that CLND5 up-regulation preceded the changes of foot processes. Therefore, CLDN5 could serve as a biomarker predicting early foot process effacement.

Topics: Adult; Aged; Aged, 80 and over; Animals; Claudin-5; Disease Models, Animal; Female; Glomerulosclerosis, Focal Segmental; Humans; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Middle Aged; Podocytes

Hypertension associated with hyperhomocysteinemia (HHcy) is associated with a high risk of vascular diseases. However, the mechanisms of HHcy-associated hypertensive renal damage and the efficacy of folic acid (FA) as a treatment have not been fully elucidated. The aim of the present study was to evaluate whether lowering the plasma homocysteine (Hcy) level using different doses of FA can reduce HHcy-associated glomerular injury in spontaneously hypertensive rats (SHRs) and to clarify the potential mechanisms of such effects. SHRs were randomized into a control group, HHcy group, HHcy + low-dose FA (LFA) group, and HHcy + high-dose FA (HFA) group. Compared with the control group, the HHcy group had reduced serum superoxide dismutase and GFR levels and elevated serum malondialdehyde and urinary albumin creatinine ratio levels. Increased extracellular matrix of the glomerulus and an increased glomerular sclerosis index, podocyte foot process effacement and fusion, as well as increased podocyte apoptosis, were observed in the HHcy group compared with the control group; these effects were associated with increased expression of NOX2 and NOX4 and decreased nephrin expression in renal tissue from SHRs with HHcy. HHcy-induced changes were counteracted by LFA and HFA treatment. Apart from lower levels of NOX2 in the HHcy + HFA group, there were no significant differences in other indicators between the HHcy + LFA and HHcy + HFA groups. These results suggest that even at a low dose, FA can reduce plasma Hcy and attenuate HHcy-induced glomerular injury by inhibiting oxidative stress and apoptosis.

Topics: Animals; Blood Pressure; Drug Evaluation, Preclinical; Folic Acid; Homocysteine; Hyperhomocysteinemia; Hypertension; Kidney Cortex; Kidney Diseases; Male; Malondialdehyde; Membrane Proteins; NADPH Oxidase 2; NADPH Oxidase 4; Podocytes; Random Allocation; Rats, Inbred SHR; Superoxide Dismutase; Vitamin B Complex

While chronic kidney disease is prevalent in adults, obstructive nephropathy (ON) has been reported in both young and old patients. In ON, tubulointerstitial lesions (TILs) have been widely investigated, but glomerular lesions (GLs) have been largely neglected. Here, we show a novel mechanism underlying GL development in ON in young and old mice. TILs develop earlier than GLs owing to infiltration of inflammatory cells in the tubulointerstitium, but GLs develop following the activation of

Topics: Age Factors; Animals; Cells, Cultured; Cytokines; Disease Models, Animal; Endothelial Cells; Kidney Diseases; Kidney Glomerulus; Ligands; Membrane Proteins; Mice, Inbred C57BL; Microfilament Proteins; MicroRNAs; Podocytes; Signal Transduction; Toll-Like Receptor 8

ShenYanXiaoBai granules is a traditional Chinese herbal medicine, It is used widely for the treatment of proteinuria caused by various kidney diseases.. This study investigated the mechanism of Shenyan Xiaobai Granule in the treatment of nephritis proteinuria.. 100 male wistar rats were divided into a blank group (n = 20) and a nephropathy group (n = 80) using random number table after 1 week adaptive feeded. Rats were injected with adriamycin (6.5 mg/kg) via the tail vein to induce nephropathy except for blank group. Every rat's urine protein was checked with urine protein dipstick test after three days that showed all rats in nephropathy group were successful modelled. Nephropathy group was divided into model group, benazepril group, ShenYanXiaoBai low dose group, ShenYanXiaoBai high dose group equally. Blank and model group were given distilled water 2 ml as control, then benazepril group received benazepril 0.90 mg/kg, ShenYanXiaoBai low dose group received ShenYanXiaoBai granules 1.80 g/kg as high dose group was given 3.60 g/kg, gavage for 6 days a week last for seven weeks. Urinary albumin/urinary creatinine were measured in seventh day every week. Three rats were randomly selected from each group to be executed in 3th and 5th weekend to detect the mRNA and protein expression level in kidney. The rest rats were as well.. The therapeutic effect of ShenYanXiaoBai high dose group was better than the two other treated groups from the 5th week to the 7th week, the comparison had a significant difference. The therapeutic effect of benazepril group was better than the ShenYanXiaoBai low dose group in the 7 weeks and the comparison had a significant difference.

Topics: Animals; Creatinine; Doxorubicin; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Kidney Function Tests; Male; Medicine, Chinese Traditional; Membrane Proteins; Podocytes; Protective Agents; Proteinuria; Random Allocation; Rats, Wistar

Podocytes are specialized cells with a limited capacity for cell division that do not regenerate in response to injury and loss. Insults that compromise the integrity of podocytes promote proteinuria and progressive renal disease. The aim of this study was to evaluate the potential renoprotective and regenerative effects of mesenchymal stromal cells (mSC) in a severe form of the podocyte injury model induced by intraperitoneal administration of puromycin, aggravated by unilateral nephrectomy. Bone derived mSC were isolated and characterized according to flow cytometry analyses and to their capacity to differentiate into mesenchymal lineages. Wistar rats were divided into three groups: Control, PAN, and PAN+ mSC, consisting of PAN rats treated with 2 × 10

Topics: Animals; Cell Differentiation; Cell Division; Down-Regulation; Glomerulosclerosis, Focal Segmental; Hypertension; Inflammation; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Male; Membrane Proteins; Mesenchymal Stem Cells; Microfilament Proteins; Nephrectomy; Podocytes; Proteinuria; Puromycin Aminonucleoside; Rats; Rats, Wistar; Regeneration; Sialoglycoproteins; Vascular Endothelial Growth Factor A

We previously reported that humanized sickle cell (HbSS) mice develop spontaneous nephropathy, a major cause of morbidity and mortality in sickle cell disease (SCD). Because sex-dependent protective mechanisms in SCD have been reported, we examined the course of nephropathy in male and female HbSS mice to determine contributors and/or predictors of disease severity. In male HbSS mice, glomerular filtration rate was characterized by a rapid onset of hyperfiltration and subsequent progressive decline of renal function over 20 weeks. Early tubular injury presented with increased excretion of kidney injury marker 1 (KIM-1), progressive loss of tubular brush border, and interstitial fibrosis that preceded the onset of glomerular damage, suggesting a tubuloglomerular mechanism of kidney injury in these mice. Additionally, we observed a strong association between the magnitude of hyperfiltration and the degree of long-term kidney injury in male HbSS mice. Unlike males, female HbSS mice did not demonstrate a significant loss of renal function or severe kidney damage during the time course of the study. These results suggest that magnitude of hyperfiltration predicts the onset of chronic kidney damage in male HbSS mice, whereas protective mechanisms in female HbSS mice delay the onset of SCD nephropathy.

Topics: Anemia, Sickle Cell; Animals; Disease Models, Animal; Female; Glomerular Filtration Rate; Hemoglobin, Sickle; Hepatitis A Virus Cellular Receptor 1; Humans; Kidney; Kidney Diseases; Kidney Tubules, Proximal; Longitudinal Studies; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Transgenic

This study aimed to verify the toxic effects of prenatal caffeine exposure (PCE) on the podocyte development in male offspring, and to explore the underlying intrauterine programming mechanisms. The pregnant rats were administered with caffeine (30 to 120 mg/kg⋅d) during gestational day (GD) 9 to 20. The male fetus on GD20 and the offspring at postnatal week (PW) 6 and PW28 were sacrificed. The results indicated that PCE caused ultrastructural abnormalities on podocyte, and inhibited the expression of podocyte marker genes such as Nephrin, Wilms tumor 1 (WT1), the histone 3 lysine 9 acetylation (H3K9ac) level in the Kruppel-like factor 4 (KLF4) promoter and its expression in the male offspring from GD20 to PW28. Meanwhile, the expression of glucocorticoid receptor (GR) and histone deacetylase 7 (HDAC7) in the fetus were increased by PCE. In vitro, corticosterone increased GR and HDAC7 whereas reduced the H3K9ac level of KLF4 and KLF4/Nephrin expression. KLF4 over-expression reversed the reduction of Nephrin expression, knockdown of HDAC7 and GR antagonist RU486 partially reversed the inhibitory effects of corticosterone on H3K9ac level and KLF4 expression. In conclusion, PCE caused podocyte developmental toxicity in male offspring, which was associated with corticosterone-induced low-functional programming of KLF4 through GR/HDAC7/H3K9ac pathway.

Topics: Acetylation; Animals; Caffeine; Cells, Cultured; Central Nervous System Stimulants; Female; Gene Expression Regulation, Developmental; Gestational Age; Glucocorticoids; Histone Deacetylases; Histones; Kidney Diseases; Kruppel-Like Factor 4; Kruppel-Like Transcription Factors; Lysine; Male; Maternal Exposure; Membrane Proteins; Phenotype; Podocytes; Pregnancy; Prenatal Exposure Delayed Effects; Promoter Regions, Genetic; Rats, Wistar; Receptors, Glucocorticoid; Signal Transduction

Nephrin is a key structural component of the podocyte slit diaphragm, and proper expression of nephrin on the cell surface is critical to ensure integrity of the blood filtration barrier. Maintenance of nephrin within this unique cell junction has been proposed to require dynamic phosphorylation events and endocytic recycling, although the molecular mechanisms that control this interplay are poorly understood. Here, we investigated the possibility that the phosphotyrosine adaptor protein ShcA regulates nephrin turnover. Western blotting and immunostaining analysis confirmed that ShcA is expressed in podocytes. In immunoprecipitation and pulldown assays, ShcA,

Topics: Animals; Biotinylation; Cell Membrane; Cytosol; Endocytosis; HEK293 Cells; Humans; Kidney Diseases; Male; Membrane Proteins; Nephrosis; Phosphorylation; Podocytes; Proteinuria; Rats; Rats, Sprague-Dawley; Signal Transduction; Src Homology 2 Domain-Containing, Transforming Protein 1; Tyrosine; Up-Regulation

Genetic cell ablation using the human diphtheria toxin receptor (hDTR) is a new strategy used for analysing cellular function. Diphtheria toxin (DT) is a cytotoxic protein that leaves mouse cells relatively unaffected, but upon binding to hDTR it ultimately leads to cell death. We used a podocyte-specific hDTR expressing (Pod-DTR) mouse to assess the anti-permeability and cyto-protective effects of the splice isoform vascular endothelial growth factor (VEGF-A165b).. The Pod-DTR mouse was crossed with a mouse that over-expressed VEGF-A165b specifically in the podocytes (Neph-VEGF-A165b). Wild type (WT), Pod-DTR, Neph-VEGF-A165b and Pod-DTR X Neph-VEGF-A165b mice were treated with several doses of DT (1, 5, 100, and 1,000 ng/g bodyweight). Urine was collected and the glomerular water permeability (LpA/Vi) was measured ex vivo after 14 days. Structural analysis and podocyte marker expression were also assessed.. Pod-DTR mice developed an increased glomerular LpA/Vi 14 days after administration of DT (all doses), which was prevented when the mice over-expressed VEGF-A165b. No major structural abnormalities, podocyte ablation or albuminuria was observed in Pod-DTR mice, indicating this to be a mild model of podocyte disease. However, a change in expression and localisation of nephrin within the podocytes was observed, indicating disruption of the slit diaphragm in the Pod-DTR mice. This was prevented in the Pod-DTR X Neph-VEGF-A165b mice.. Although only a mild model of podocyte injury, over-expression of the anti-permeability VEGF-A165b isoform in the podocytes of Pod-DTR mice had a protective effect. Therefore, this study further highlights the therapeutic potential of VEGF-A165b in glomerular disease.

Topics: Albuminuria; Animals; Diphtheria Toxin; Glomerular Filtration Rate; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mice; Mice, Inbred C57BL; Permeability; Podocytes; Protein Isoforms; Vascular Endothelial Growth Factor A; Water

Glomerulopathy is an increasingly identified complication in young patients with sickle cell disease (SCD). Hyperfiltration and albuminuria followed by declining glomerular filtration rates and eventual end-stage renal disease (ESRD) is assumed to be the typical progression of glomerular disease. There are only a few reported biomarkers to identify early-stage renal disease in SCD.. We detail the renal profile of 101 children with SCD in Malawi and propose a novel urinary biomarker for the identification of early renal disease.. Among children with sickle cell anemia, 24.8% had a urine albumin-creatinine ratio of 30 mg/g or above. In univariate analysis, only patients with higher urinary nephrin, a urinary marker of glomerular injury, had significantly greater odds of having albuminuria. In multivariable analysis, nephrin remained significantly associated with albuminuria. A nephrin-creatinine ratio (NCR) cut-point of 622 ng/mg, the 50. These data suggest that a substantial number of children with SCD in Malawi have renal disease and could be at risk for worsening nephropathy and ESRD as they age. Our data suggest that urinary nephrin could be utilized as an early marker of glomerular disease in SCD.

Topics: Adolescent; Albuminuria; Anemia, Sickle Cell; Biomarkers; Child; Cross-Sectional Studies; Female; Follow-Up Studies; Glomerular Filtration Rate; Humans; Kidney Diseases; Kidney Function Tests; Malawi; Male; Membrane Proteins; Prognosis

Our previous study showed that angiotensin II (Ang II) exposure diminished the interaction between nephrin and c-Abl, then c-Abl mediated SHIP2-Akt pathway in the process of podocyte injury in vivo and vitro. However, the relationship between nephrin and c-Abl was unknown. Recently, various studies showed that nephrin was required for cytoskeletal remodeling in glomerular podocytes. But its specific mechanisms remain incompletely understood. As a nonreceptor tyrosine kinase involved in cytoskeletal regulation, c-Abl may be a candidate of signaling proteins interacting with Src homology 2/3 (SH2/SH3) domains of nephrin. Therefore, it is proposed that c-Abl contributes to nephrin-dependent cytoskeletal remodeling of podocytes. Herein, we observed that nephrin-c-Abl colocalization were suppressed in glomeruli of patients with proteinuria. Next, CD16/7-nephrin and c-Abl vectors were constructed to investigate the nephrin-c-Abl signaling pathway in podocyte actin-cytoskeletal remodeling. The disorganized cytoskeleton stimulated by cytochalasin D in COS7 cells was dramatically restored by co-transfection with phosphorylated CD16/7-nephrin and c-Abl full-length constructs. Further, co-immunoprecipitation showed that phosphorylated CD16/7-nephrin interacted with wild-type c-Abl, but not with SH2/SH3-defective c-Abl. These findings suggest that phosphorylated nephrin is able to recruit c-Abl in a SH2/SH3-dependent manner and detached c-Abl from dephosphorylated nephrin contributes to cytoskeletal remodeling in podocytes.

Topics: Adult; Angiotensin II; Animals; Binding Sites; Chlorocebus aethiops; COS Cells; Cytoskeleton; Female; Genes, abl; Humans; Kidney Diseases; Male; Membrane Proteins; Mice; Middle Aged; Phosphorylation; Podocytes; Proto-Oncogene Proteins c-abl; src Homology Domains; Young Adult

Neonatal nephron loss may follow hypoxic-ischemic events or nephrotoxic medications. Its long-term effects on the kidney are still unclear. Unlike term infants, preterm neonates less than 36 weeks gestational age show ongoing nephrogenesis. We hypothesized that nephron loss during nephrogenesis leads to more severe renal sequelae than nephron loss shortly after the completion of nephrogenesis. Rats show nephrogenesis until day 10 of life resembling the situation of preterm infants. Animals were uninephrectomized at day 1 (UNX d1) resulting in nephron reduction during nephrogenesis and at day 14 of life (UNX d14) inducing nephron loss after the completion of nephrogenesis. 28 days after uninephrectomy the compensatory renal growth was higher in UNX d1 compared to UNX d14. Nephrin was reduced and collagen deposition increased in UNX d1. At 1 year of age, glomerulosclerosis and markers of tubulointerstitial damage were most prevalent in UNX d1. Moreover, the number of desmin-positive podocytes was higher and nephrin was reduced in UNX d1 indicating podocyte damage. Infiltration of inflammatory cells was heightened after UNX d1. Uninephrectomized animals showed no arterial hypertension. We conclude that neonatal nephron loss during active nephrogenesis leads to more severe glomerular and tubulointerstitial damage, which is not a consequence of compensatory arterial hypertension.

Topics: Animals; Animals, Newborn; Collagen; Desmin; Disease Models, Animal; Kidney Diseases; Kidney Glomerulus; Kidney Tubules; Membrane Proteins; Nephrectomy; Nephrons; Organogenesis; Rats; Rats, Wistar

Hypertension-induced podocyte damage and the relationship with UAE is analyzed in diabetic and nondiabetic participants.. Sixty-four hypertensive patients, 30 diabetics, with glomerular filtration rate (eGFR) greater than 60 ml/min per 1.73 m were included. Urinary albumin excretion was measured in morning urine using a nephelometric immunoassay and expressed as albumin/creatinine ratio. Urinary pellets were obtained from fresh urine and mRNA was assessed by real-time quantitative PCR. Likewise, protein podocyte-specific molecules were measured by western blot using specific antibodies.. Fourteen nondiabetics and 20 diabetics had increased UAE greater than 30 mg/g. In individuals with increased EUA, the mRNA expression of nephrin and CD2AP was low in diabetics, whereas only nephrin mRNA in nondiabetics. No differences were observed in podocalyxin and aquaporin-1 mRNA levels. Concerning the protein values, in both nondiabetic and diabetic patients, nephrin, CD2AP and podocalyxin were increased in patients with increased UAE, with no differences in aquaporin-1. A significant positive relationship was observed between log UAE and nephrin protein values, and an inverse association observed with mRNA.. Hypertensive patients who had elevated UAE showed increased urinary excretion of podocyte-specific proteins coupled with a phenotype of decreased mRNA expression. The phenotype of podocyte-specific mRNA and the increment of nephrin can be used as a valuable marker of early glomerular injury.

Topics: Adaptor Proteins, Signal Transducing; Adult; Aged; Albuminuria; Aquaporin 1; Cytoskeletal Proteins; Diabetes Mellitus; Female; Humans; Hypertension; Kidney Diseases; Male; Membrane Proteins; Middle Aged; Podocytes; RNA, Messenger; Sialoglycoproteins

Hypertension is a major global public health issue. Uncontrolled hypertension leads to organ damage, especially renal damage. Calcitriol is used to treat osteoporosis, promote bone formation, and increase bone mass. Previous studies have demonstrated that 1,25(OH)2D3, in addition to its classic role, also has multiple immune regulation and renoprotective functions and inhibits the activity of the renin-angiotensin-aldosterone system (RASS). The aim of the current study was to investigate the renoprotective effects of calcitriol in a spontaneously hypertensive rat (SHR) model.. A total of 18 SHRs and 8 age-matched normal Wistar rats were enrolled. SHRs were randomly divided into a hypertensive nephropathy group (H), a hypertensive nephropathy treated with calcitriol group (D) and a control group (NS). The rats were sacrificed after 16 weeks of treatment. The blood pressure (BP) of rats were measured one time every 4 weeks. The levels of serum albumin, serum creatinine, blood calcium, serum Vitamin D and 24-h urinary protein were measured after 16 weeks treatment. The protein level of WT1, nephrin and vitamin D receptor (VDR) was examined by Western blotting and immunohistochemical staining.. There were no notable changes in blood pressure or serum creatinine in group H and D compared with group NS. The albumin, calcium and vitamin D serum levels in group H were significantly decreased compared with group NS and significantly increased in group D compared with group H. The level of 24-h urine protein significantly increased in group H compared with group NS and significantly decreased in group D compared with group H. The expression of VDR, WT1 and nephrin in the kidney were all significantly decreased in group H compared with group NS and significantly increased in group D compared with group H.. The present results indicated that there was injury of podocytes in hypertensive nephropathy, which can be ameliorated by calcitriol in SHR, but there was no significant anti-hypertensive effect. Vitamin D/VDR decreased proteinuria perhaps by increasing expression of nephrin and WT1 protein in podocyte of SHRs.

Topics: Animals; Blood Pressure; Calcitriol; Hypertension; Kidney Diseases; Male; Membrane Proteins; Podocytes; Rats; Rats, Inbred SHR; Rats, Wistar; Receptors, Calcitriol; Renin-Angiotensin System; WT1 Proteins

Astragali Radix (AR) has been used in the traditional Chinese medicine (TCM) in the treatment of various renal diseases for many years. In this study, a NMR based metabolomic approach coupled with biochemical assay and histopathological inspection had been employed to study the protective effect of total flavonoids (TFA) in AR against adriamycin-induced nephropathy using rats model. Multivariate analysis revealed that 11 of perturbed metabolites could be reversed by TFA, and the MetaboAnalyst analysis revealed that the anti-nephrotic syndrome effect of TFA was probably related with regulation of alanine, aspartate and glutamate metabolism, citrate cycle, pyruvate metabolism, cysteine and methionine metabolism and glyoxylate and dicarboxylate metabolism. The regulatory effects on the gene expression (ACE, nephrin, podocin) suggested that the anti-nephrotic syndrome effect of TFA was also related with the protection of renal filtration function and regulation of blood pressure. The system pharmacology analysis revealed 43 potential targets for TFA, and suggested that the protective effect of TFA on the nephrotic syndrome was probably related with the regulation of immune and renin-angiotensin system. These metabolic changes and the associated pathways, as well as the compound-target-disease network provide insights into the mechanisms of TFA for the treatment of nephrotic syndrome, and further studies are needed to validate the bioactive compounds responsible for the anti-nephrotic syndrome effect of TFA.

Topics: Animals; Astragalus propinquus; Disease Models, Animal; Doxorubicin; Drug Evaluation, Preclinical; Drugs, Chinese Herbal; Flavonoids; Humans; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Male; Medicine, Chinese Traditional; Membrane Proteins; Metabolomics; Rats; Rats, Sprague-Dawley; Renin-Angiotensin System

Preservation of glomerular structure and function is pivotal in the prevention of glomerulonephritis, a category of kidney disease characterized by proteinuria which can eventually lead to chronic and end-stage renal disease. The glomerulus is a complex apparatus responsible for the filtration of plasma from the body. In disease, structural integrity is lost and allows for the abnormal leakage of plasma contents into the urine. A method to isolate and examine glomeruli in culture is critical for the study of these diseases. In this protocol, an efficient method of retrieving intact glomeruli from adult rat kidneys while conserving structural and morphological characteristics is described. This process is capable of generating high yields of glomeruli per kidney with minimal contamination from other nephron segments. With these glomeruli, injury conditions can be mimicked by incubating them with a variety of chemical toxins, including protamine sulfate, which causes foot process effacement and proteinuria in animal models. Degree of injury can be assessed using transmission electron microscopy, immunofluorescence staining, and western blotting. Nephrin and Wilms Tumor 1 (WT1) levels can also be assessed from these cultures. Due to the ease and flexibility of this protocol, the isolated glomeruli can be utilized as described or in a way that best suits the needs of the researcher to help better study glomerular health and structure in diseased states.

Topics: Animals; Blotting, Western; Cell Separation; Kidney; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Rats; Rats, Sprague-Dawley

The glomerular podocytes control filtration barrier permeability in the kidney, and their disturbance underlies the pathogenesis of idiopathic nephrotic syndrome (INS), a kidney disease that predominantly occurs in children. In this study, we found that the interleukin-7 receptor (IL-7R) was induced in the glomeruli of adriamycin (ADR)-induced mouse nephropathy, a rodent model of nephrotic syndrome. In addition, IL-7R was also induced by ADR in mouse podocytes cultured in vitro. Functionally, we discovered that IL-7R activation through the stimulation of recombinant IL-7 induced apoptosis of podocytes, and moreover, IL-7 stimulation inhibited nephrin activation and caused actin cytoskeleton disorganization, indicating that IL-7 stimulation induces podocyte injury. Furthermore, IL-7 stimulation impaired the filtration barrier function of podocyte monolayer. Together, these results identify IL-7 and its receptor IL-7R as potential regulators of podocyte function, which might offer a novel therapeutic target in the treatment of INS.

Topics: Actin Cytoskeleton; Albumins; Animals; Apoptosis; Cell Line; Doxorubicin; Interleukin-7; Kidney Diseases; Male; Membrane Proteins; Mice, Inbred BALB C; Podocytes; Receptors, Interleukin-7; Up-Regulation

Topics: Biomarkers; Cross-Sectional Studies; Diabetes Mellitus, Type 2; Enzyme-Linked Immunosorbent Assay; Hepatitis A Virus Cellular Receptor 1; Humans; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Lipocalin-2; Membrane Proteins; Sialoglycoproteins; Tissue Inhibitor of Metalloproteinase-2

Topics: Acute Kidney Injury; Animals; Apoptosis; Disease Models, Animal; Doxorubicin; Humans; Inflammation; Kidney Diseases; Male; Membrane Proteins; Mice; Oxidative Stress; Piperidones; Pyrimidines; Repressor Proteins; WT1 Proteins

Injury of the glomerular filter causes proteinuria by disrupting the sensitive interplay of the glomerular protein network. To date, studies of the expression and trafficking of glomerular proteins have been mostly limited to in vitro or histologic studies. Here, we report a novel in vivo biotinylation assay that allows the quantification of surface expression of glomerular proteins in mice. Kidneys were perfused in situ with biotin before harvest. Afterwards glomeruli were isolated and lyzed. The protein of interest was separated by immunoprecipitation and the amount of surface-expressed protein was quantified by Western blot analysis with streptavidin staining. As proof-of-concept, we examined the presence of nephrin in the slit diaphragm in two well-established murine models of proteinuric kidney disease: nephrotoxic nephritis and adriamycin nephropathy. In proteinuric animals, significantly less nephrin was detected in the slit diaphragm. When proteinuria decreased once again during the course of disease, the amount of surface nephrin returned to the baseline. Our present results suggest that our assay is a valuable tool to study the glomerular filter in proteinuric kidney diseases. Note that the assay is not limited to proteins expressed in the slit diaphragm, and all surface proteins that are accessible to biotin perfusion and immunoprecipitation qualify for this analysis.

Topics: Albuminuria; Animals; Disease Models, Animal; Gene Expression; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Mice; Nephritis; Proteinuria; Time Factors

To investigate the effects of Huaiqihuang Granules (, HQH), a mixture of Chinese herbs including Trametes robiniophila Murr, Fructus Lycii and Polygonatum sibiricum, on adriamycininduced nephropathy (ADRN) in rats and its underlying mechanisms.. Rats with ADRN were divided into four groups: the sham group, the model group (distilled water), the low-dose HQH-treated (2 g/kg) group, and the high-dose HQH-treated (4 g/kg) group. Body weight and 24-h urinary protein (Upro) were checked every week. After 5-week intervention, at the end of the study, the rats were sacrificed and blood samples were collected for examination of biochemical parameters, including glomerular morphological makers, podocyte shape, cellular apoptosis, expressions of nephrin, inflammatory and apoptosis markers.. HQH ameliorated the rat's general status, proteinuria, renal morphological appearance and glomerulosclerosis. The decreased expression of nephrin in ADRN rats was increased by HQH, as well as the impaired podocyte foot process fusion. Cytosolic levels of p65 and inhibitor of nuclear factor κBα (IκBα) were decreased in ADRN rats, and recovered by the treatment of HQH. Consistently, the induced expression of tumor necrosis factor α (TNF-α), phosphorylated nuclear factor κB p65 (p-NFκB p65) and IκBα in ADRN were markedly suppressed by HQH. In addition, induction of Bax, cleaved caspase-3 and cytochrome C in ADRN rats were suppressed by HQH, indicating the amelioration of apoptosis.. HQH could ameliorate renal impairments in ADRN rats by increasing nephrin expression, inhibiting NF-κB signaling pathway via the down-regulation of p-NF-κB p65 and p-IκBα, and suppression of glomerular and tubular apoptosis.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Body Weight; Caspase 3; Chromatography, High Pressure Liquid; Cytochromes c; Doxorubicin; Drugs, Chinese Herbal; Kidney; Kidney Diseases; Kidney Glomerulus; Kidney Tubules; Male; Membrane Proteins; NF-kappa B; NF-KappaB Inhibitor alpha; Organ Size; Proteinuria; Rats, Sprague-Dawley; Signal Transduction; Transcription Factor RelA; Tumor Necrosis Factor-alpha

Podocytes play a central role in the formation of the glomerular filtration barrier in the kidney, and their dysfunction has been shown to result in proteinuria. In the present study, we sought to determine the cell-autonomous role of NF-κB, a proinflammatory signaling, within podocytes in proteinuric kidney disease.. Podocyte-specific IκBΔN transgenic (Pod-IκBΔN) mice, in which NF-κB was inhibited specifically in podocytes, were generated by the Cre-loxP technology, and their phenotype was compared with control mice in adriamycin-induced nephropathy.. Pod-IκBΔN mice were phenotypically normal and did not exhibit proteinuria at the physiological condition. By the intravenous administration of adriamycin, overt proteinuria appeared in Pod-IκBΔN mice, as well as in control mice. However, of interest, the amount of proteinuria was significantly lower in adriamycin-injected Pod-IκBΔN mice (373 ± 122 mg albumin/g creatinine), compared with adriamycin-injected control mice (992 ± 395 mg albumin/g creatinine). Expression of podocyte-selective slit diaphragm-associated proteins, such as nephrin and synaptopodin, was markedly decreased by adriamycin injection in control mice, whereas the reduction was attenuated in Pod-IκBΔN mice. Adriamycin-induced reduction in synaptopodin expression was also seen in cultured podocytes derived from control mice, but not in those from Pod-IκBΔN mice.. Because nephrin and synaptopodin are essential for the maintenance of the slit diaphragm in podocytes, these results suggest that proteinuria in adriamycin-induced nephropathy is caused by the reduction in expression of these proteins. The results also suggest that the NF-κB signalling in podocytes cell-autonomously contributes to proteinuria through the regulation of these proteins.

Topics: Albuminuria; Animals; Cells, Cultured; Disease Models, Animal; Doxorubicin; Gene Expression Regulation; Genotype; Humans; I-kappa B Proteins; Integrases; Kidney Diseases; Male; Membrane Proteins; Mice, Inbred C57BL; Mice, Transgenic; Microfilament Proteins; NF-kappa B; Phenotype; Podocytes; Signal Transduction

Renal fibrosis is characterized by glomerulosclerosis and tubulointerstitial fibrosis. Transforming growth factor-β (TGF-β) is postulated to play a central role in the development of both fibrotic processes. Extracellular matrix proteins, particularly type I collagen and fibronectin, accumulate in the tissue during renal fibrogenesis. CCN2, also known as connective tissue growth factor (CTGF), is increased in the setting of fibrosis and modulates a number of downstream signaling pathways involved in the fibrogenic properties of TGF-β. Unilateral ureteral obstruction is one of the most widely used models of renal tubulointerstitial fibrosis. Herein, we describe unilateral ureteral obstruction in mice as an animal model of renal fibrosis and methods for immunohistochemical analyses of extracellular matrix proteins and CCN2. In addition, we describe the construction of podocyte-specific CCN2-transgenic mice for analyzing mesangial matrix expansion and glomerulosclerosis.

Topics: Animals; CCN Intercellular Signaling Proteins; Disease Models, Animal; Extracellular Matrix Proteins; Fibrosis; Genetic Vectors; Humans; Immunohistochemistry; Kidney Diseases; Membrane Proteins; Mice; Mice, Transgenic; Promoter Regions, Genetic; Receptor, Platelet-Derived Growth Factor beta; Transforming Growth Factor beta

To investigate the function of nephrin in podocytes and its relation to proteinuria in kidney diseases, and to study more clearly theoretical basis for the molecular mechanism of losartan anti-proteinuria and the special beneficial effects of losartan on podocyte injury.. Experiment set up control, Ang II and losartan group. Cell morphology was observed perturbation, and using image processing software to analyze the cell body of cell morphology and size of the difference after 8 h, 24 h and 48 h. Detecting nephrin mRNA and protein expression changes by real time PCR (RT-PCR) and western blotting at different time points.. Podocyte cell bodies were significantly reduced after Ang II injury (p < 0.01), losartan directly reduces the rate of apoptotic podocytes induced by Ang. Apoptotic podocytes may related to the decrease of nephrin mRNA and protein expressions, losartan reduced the apoptosis and proteinuria by declining nephrin mRNA and protein expressions.. Ang II induced podocyte injury caused abnormal expression and distribution of nephrin in podocytes, losartan maybe maintain the stability of nephrin expression and the integrity of hole diaphragm (SD) structure and function by blocking the signal path, playing a important role in protection mechanisms of anti-proteinuria. Our findings provide some possible clues for further exploring the pharmacological targets to the proteinuria. These novel findings provide new insights into the beneficial effects of losartan on podocytes directly.

Topics: Angiotensin II; Anti-Arrhythmia Agents; Apoptosis; Blotting, Western; Cell Proliferation; Cells, Cultured; Humans; Kidney Diseases; Kidney Glomerulus; Losartan; Membrane Proteins; Podocytes; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Vasoconstrictor Agents

Activation of small GTPase Rac1 in podocytes is associated with rodent models of kidney injury and familial nephrotic syndrome. Induced Rac1 activation in podocytes in transgenic mice results in rapid transient proteinuria and foot process effacement, but not glomerular sclerosis. Thus it remains an open question whether abnormal activation of Rac1 in podocytes is sufficient to cause permanent podocyte damage. Using a number of transgenic zebrafish models, we showed that moderate elevation of Rac1 activity in podocytes did not impair the glomerular filtration barrier but aggravated metronidazole-induced podocyte injury, while inhibition of Rac1 activity ameliorated metronidazole-induced podocyte injury. Furthermore, a further increase in Rac1 activity in podocytes was sufficient to cause proteinuria and foot process effacement, which resulted in edema and lethality in juvenile zebrafish. We also found that activation of Rac1 in podocytes significantly downregulated the expression of

Topics: Animals; Animals, Genetically Modified; Disease Models, Animal; Down-Regulation; Glomerular Filtration Barrier; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Membrane Proteins; Metronidazole; Podocytes; rac1 GTP-Binding Protein; Zebrafish

Urinary nephrin is a potential non-invasive biomarker of disease. To date, however, most studies of urinary nephrin have been conducted in animal models of diabetic nephropathy, and correlations between urinary nephrin-to-creatinine ratio and other parameters have yet to be evaluated in animal models or patients of kidney disease with podocyte dysfunction. We hypothesized that urinary nephrin-to-creatinine ratio can be up-regulated and is negatively correlated with renal nephrin mRNA levels in animal models of kidney disease, and that increased urinary nephrin-to-creatinine ratio levels are attenuated following administration of glucocorticoids. In the present study, renal nephrin mRNA, urinary nephrin-to-creatinine ratio, urinary protein-to-creatinine ratio, and creatinine clearance ratio were measured in animal models of adriamycin nephropathy, puromycin aminonucleoside nephropathy, anti-glomerular basement membrane glomerulonephritis, and 5/6 nephrectomy. The effects of prednisolone on urinary nephrin-to-creatinine ratio and other parameters in puromycin aminonucleoside (single injection) nephropathy rats were also investigated. In all models tested, urinary nephrin-to-creatinine ratio and urinary protein-to-creatinine ratio increased, while renal nephrin mRNA and creatinine clearance ratio decreased. Urinary nephrin-to-creatinine ratio exhibited a significant negative correlation with renal nephrin mRNA in almost all models, as well as a significant positive correlation with urinary protein-to-creatinine ratio and a significant negative correlation with creatinine clearance ratio. Urinary protein-to-creatinine ratio exhibited a significant negative correlation with renal nephrin mRNA. Following the administration of prednisolone to puromycin aminonucleoside (single injection) nephropathy rats, urinary nephrin-to-creatinine ratio was significantly suppressed and exhibited a significant positive correlation with urinary protein-to-creatinine ratio. In addition, the decrease in number of glomerular Wilms tumor antigen-1-positive cells was attenuated, and urinary nephrin-to-creatinine ratio exhibited a significant negative correlation in these cells. In conclusion, these results suggest that urinary nephrin-to-creatinine ratio level is a useful and reliable biomarker for predicting the amelioration of podocyte dysfunction by candidate drugs in various kidney disease models with podocyte dysfunction. This suggestion will also be validated in a clinical set

Topics: Animals; Anti-Glomerular Basement Membrane Disease; Biomarkers; Creatinine; Diabetic Nephropathies; Doxorubicin; Kidney Diseases; Male; Membrane Proteins; Mice; Mice, Inbred BALB C; Podocytes; Puromycin Aminonucleoside; Rats; Rats, Wistar

The concentration of adenosine in the normal kidney increases markedly during renal hypoxia, ischemia, and inflammation. A recent study reported that an A3 adenosine receptor (A3AR) antagonist attenuated the progression of renal fibrosis. The adriamycin (ADX)-induced nephropathy model induces podocyte injury, which results in severe proteinuria and progressive glomerulosclerosis. In this study, we investigated the preventive effect of a highly selective A3AR antagonist (LJ1888) in ADX-induced nephropathy. Three groups of six-week-old Balb/c mice were treated with ADX (11 mg/kg) for four weeks and LJ1888 (10 mg/kg) for two weeks as following: 1) control; 2) ADX; and 3) ADX + LJ1888. ADX treatment decreased body weight without a change in water and food intake, but this was ameliorated by LJ1888 treatment. Interestingly, LJ1888 lowered plasma creatinine level, proteinuria, and albuminuria, which had increased during ADX treatment. Furthermore, LJ1888 inhibited urinary nephrin excretion as a podocyte injury marker, and urine 8-isoprostane and kidney lipid peroxide concentration, which are markers of oxidative stress, increased after injection of ADX. ADX also induced the activation of proinflammatory and profibrotic molecules such as TGF-β1, MCP-1, PAI-1, type IV collagen, NF-κB, NOX4, TLR4, TNFα, IL-1β, and IFN-γ, but they were remarkably suppressed after LJ1888 treatment. In conclusion, our results suggest that LJ1888 has a renoprotective effect in ADX-induced nephropathy, which might be associated with podocyte injury through oxidative stress. Therefore, LJ1888, a selective A3AR antagonist, could be considered as a potential therapeutic agent in renal glomerular diseases which include podocyte injury and proteinuria.

Topics: Actins; Adenosine; Adenosine A3 Receptor Antagonists; Albuminuria; Animals; Body Weight; Creatinine; Dinoprost; Disease Models, Animal; Doxorubicin; Immunohistochemistry; Kidney; Kidney Diseases; Lipid Peroxidation; Male; Membrane Proteins; Mice; Mice, Inbred BALB C; NF-kappa B; Oxidative Stress; Plasminogen Activator Inhibitor 1; Proteinuria; Transforming Growth Factor beta1

Proteinuria is not only a sign of kidney damage but is also involved in the progression of renal disease as an independent pathologic factor. Although patients with mutated type 1 cannabinoid receptors (CB1) polymorphism are associated with renal microvascular damage, the biologic role of CB1 signaling in proteinuria remains uncharacterized till now. Herein, we investigate whether CB1 participates in glomerular proteinuria in CB1 transgenic mice and treatment with CB1 agonist WIN55212-2 rat, neither of which are diabetic models. The CB1 transgenic mice and rats treated with CB1 agonist WIN55212-2 had higher kidney weight and urinary protein concentrations but not blood glucose levels compared with the wild-type group. A combination of laser-capture microsdissection, quantitative reverse transcription-polymerase chain reaction, immunoblotting and immunohistochemical validation revealed that CB1 transgenic mice and rats treated with CB1 agonist WIN55212-2 had higher vascular endothelial growth factor (VEGF) expression in renal glomeruli than that of the wild-type group. Geneticorpharmacological activation of CB1 by transgenic CB1 mice or treatment with WIN55212-2 reduced nephrin expression in the renal glomeruli compared with that of the wild-type group in the glomerular mesanglium. Taken together, CB1 transgenic mice and rats treated with CB1 agonist WIN55212-2 induced proteinuria with upregulation of CB1 resulting in impaired nephrin expression, by inducing excess VEGF reaction in the renal glomeruli. Genetic and pharmacological manipulation of CB1 signaling revealed VEGF-dependent nephrin depression of glomerulopathy. Controlling CB1 activity can be used an alternative strategy for sustaining renal function in the presence of CB1 activation.

Topics: Analgesics; Animals; Benzoxazines; Blood Glucose; Gene Expression Regulation; Glomerular Mesangium; Humans; Kidney Diseases; Male; Membrane Proteins; Mice; Mice, Transgenic; Morpholines; Naphthalenes; Organ Size; Proteinuria; Rats; Rats, Wistar; Receptor, Cannabinoid, CB1; Signal Transduction; Vascular Endothelial Growth Factor A

Blockade of the renin-angiotensin system plays a key role in suppressing the progression of renal diseases. It has not been well established whether this therapy provides additional effects when combined with vitamin D or its analog in a model of adriamycin (ADR)-induced nephropathy.. We evaluated the effect of an angiotensin II subtype 1 receptor blocker (telmisartan) combined with a vitamin D analog (oxacalcitriol) on mice ADR-induced nephropathy (9.5 mg/kg single intravenous injection). We also tested immortalized murine podocytes to examine the effects on podocyte apoptosis.. Mice with ADR-induced nephropathy developed progressive albuminuria and glomerulosclerosis within 30 days accompanied by decreased expression of slit diaphragm (SD)-associated proteins (nephrin and podocin), reduced numbers of podocytes, and increased systolic blood pressure. Treatment with telmisartan or oxacalcitriol alone moderately ameliorated kidney injury. The combined treatment most effectively reduced the albuminuria and glomerulosclerosis. These effects were accompanied by the restoration of SD-associated proteins, reduction of podocyte apoptosis, and prevention of podocyte depletion in the glomeruli. Treatment with telmisartan, oxacalcitriol, and the combination therapy resulted in similar reductions in systolic blood pressure. In cultured murine podocytes, ADR stimulated the expression of Bax/Bcl-2 and apoptosis as determined by Hoechst 33342 staining. These changes were effectively inhibited by telmisartan or oxacalcitriol, but the combination treatment most effectively reduced these effects.. These data demonstrated that application of a renin-angiotensin system blocker plus a vitamin D analog effectively prevented renal injury in ADR-induced nephropathy. The observed amelioration of renal injury may be partly attributable to antiapoptotic effects in podocytes.

Topics: Albuminuria; Angiotensin II Type 1 Receptor Blockers; Animals; Antibiotics, Antineoplastic; Apoptosis; Benzimidazoles; Benzoates; Calcitriol; Doxorubicin; Drug Therapy, Combination; Female; Glomerulosclerosis, Focal Segmental; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Membrane Proteins; Mice; Mice, Inbred BALB C; Podocytes; Telmisartan

Intrarenal angiotensin II is increased in kidney diseases independently of plasma angiotensin II and is thought to promote progressive deterioration of renal architecture. Here we investigated the mechanism of enhanced renal angiotensin II generation in kidney glomerular diseases. For this, kidney- or liver-specific angiotensinogen gene (Agt) knockout was superimposed on the mouse model of inducible podocyte injury (NEP25). Seven days after induction of podocyte injury, renal angiotensin II was increased ninefold in NEP25 mice with intact Agt, accompanied by increases in urinary albumin and angiotensinogen excretion, renal angiotensinogen protein, and its mRNA. Kidney Agt knockout attenuated renal Agt mRNA but not renal angiotensin II, renal, or urinary angiotensinogen protein. In contrast, liver Agt knockout markedly reduced renal angiotensin II to 18.7% of that of control NEP25 mice, renal and urinary angiotensinogen protein, but not renal Agt mRNA. Renal angiotensin II had no relationship with renal Agt mRNA, or with renal renin mRNA, which was elevated in liver Agt knockouts. Kidney and liver dual Agt knockout mice showed phenotypes comparable to those of liver Agt knockout mice. Thus, increased renal angiotensin II generation upon severe podocyte injury is attributed to increased filtered angiotensinogen of liver origin resulting from loss of macromolecular barrier function of the glomerular capillary wall that occurs upon severe podocyte injury.

Topics: Albuminuria; Angiotensin II; Angiotensinogen; Animals; Antibodies, Monoclonal; Disease Models, Animal; Exotoxins; Genotype; Kidney Diseases; Kidney Tubules, Proximal; Liver; Membrane Proteins; Mice, Knockout; Phenotype; Podocytes; RNA, Messenger; Sodium; Time Factors; Up-Regulation

The slit diaphragm (SD) is a highly specialized intercellular junction between podocyte foot processes and is crucial in the formation of the filtration barrier in the renal glomeruli. Zebrafish Nephrin and Podocin are important in the formation of the podocyte SD and mutations in NEPHRIN and PODOCIN genes cause human nephrotic syndrome. In the present study, the zebrafish Podocin protein was observed to be predominantly localized in the pronephric glomerular podocytes, as previously reported for Nephrin. To understand the function of Podocin and Nephrin in zebrafish, splice‑blocking morpholino antisense oligonucleotides were used. Knockdown of Podocin or Nephrin by this method induced pronephric glomerular hypoplasia with pericardial edema. Human Nephrin and Podocin mRNA rescued this glomerular phenotype, however, the efficacy of the rescues was greatly reduced when mRNA‑encoding human disease‑causing NEPHRIN‑R1109X and PODOCIN‑R138Q were used. Furthermore, an association between zebrafish Nephrin and Podocin proteins was observed. Notably, Podocin‑R150Q, corresponding to human PODOCIN‑R138Q, markedly interacted with Nephrin compared with wild‑type Podocin, suggesting that this strong binding capacity of mutated Podocin impairs the transport of Nephrin and Podocin out of the endoplasmic reticulum. The results suggest that the functions of Nephrin and Podocin are highly conserved between the zebrafish pronephros and mammalian metanephros. Accordingly, the zebrafish pronephros may provide a useful tool for analyzing disease‑causing gene mutations in human kidney disorders.

Topics: Animals; Humans; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Kidney Glomerulus; Mammals; Membrane Proteins; Mutation; Podocytes; Pronephros; Protein Binding; Zebrafish

Podocytes are kidney cells with specialized morphology that is required for glomerular filtration. Diseases, such as diabetes, or drug exposure that causes disruption of the podocyte foot process morphology results in kidney pathophysiology. Proteomic analysis of glomeruli isolated from rats with puromycin-induced kidney disease and control rats indicated that protein kinase A (PKA), which is activated by adenosine 3',5'-monophosphate (cAMP), is a key regulator of podocyte morphology and function. In podocytes, cAMP signaling activates cAMP response element-binding protein (CREB) to enhance expression of the gene encoding a differentiation marker, synaptopodin, a protein that associates with actin and promotes its bundling. We constructed and experimentally verified a β-adrenergic receptor-driven network with multiple feedback and feedforward motifs that controls CREB activity. To determine how the motifs interacted to regulate gene expression, we mapped multicompartment dynamical models, including information about protein subcellular localization, onto the network topology using Petri net formalisms. These computational analyses indicated that the juxtaposition of multiple feedback and feedforward motifs enabled the prolonged CREB activation necessary for synaptopodin expression and actin bundling. Drug-induced modulation of these motifs in diseased rats led to recovery of normal morphology and physiological function in vivo. Thus, analysis of regulatory motifs using network dynamics can provide insights into pathophysiology that enable predictions for drug intervention strategies to treat kidney disease.

Topics: Animals; Cells, Cultured; Cyclic AMP Response Element-Binding Protein; Cyclic AMP-Dependent Protein Kinases; Gene Expression; Gene Regulatory Networks; Immunoblotting; Kidney; Kidney Diseases; Male; Membrane Proteins; Mice; Microfilament Proteins; Microscopy, Electron; Podocytes; Proteomics; Puromycin; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction

To investigate the effects of artemisinin against proteinuria and glomerular filtration barrier damage in rats with adriamycin-induced nephropathy, and the potential mechanism underpinned the action.. Forty adriamycin rats were randomly divided into two groups with the ratio of 1 : 3; the small-number group served as control group (n = 10), and the rats in the large-number group were treated with adriamycin to induce nephropathy; then they were further randomly assigned into 3 subgroups: benazepril group (n = 10), artemisinin group (n = 10), and adriamycin group (n = 10). The benazepril group and artemisinin group were treated with benazepril suspl (5.0 mg/kg daily) and artemisinin suspl (150 mg/kg daily) respectively after being modeled; those in the control group and adriamycin group were intragastrically administered an equivalent volume of distilled water every day. The treatment after model establishment lasted for a total of 4 weeks. The 24 h uric protein, blood biochemicals, renal pathological changes, renal ultrastrutural changes, Nephrin and Podocin proteins and gene expressions were measured by Coomassie brilliant blue assay, completely automatic biochemical analyzer, light microscope, electron microscopy, Western blot and reverse transcription polymerase chain reaction, respectively.. The rats in adriamycin group showed a significant increase in 24 h uric protein excretion, serum total cholesterol (TC), triglyceride (TG), blood urea nitrogen (BUN), serum creatinine (Scr) and decrease in albumin (Alb) (P < 0.05 or P < 0.01). Compared with adriamycin group, artemisinin could reduce uric protein excretion, decrease the serum TC, TG elevation, increase the serum Alb level, up-regulate the expressions of Nephrin and Podocin (P < 0.05 or P < 0.01), but no statistical significance effects on the levels of BUN, Scr in artemisinin group (P > 0.05). The renal pathological and ultrastrutural observation indicate that artemisinin could attenuate the severity of foot process effacement and fusion in the nephropathic rats.. Artemisinin might have an effect on the nephropathy in rats caused by adriamycin, which may be at least partly correlated with attenu- ation of the severity of foot process effacement and fusion, up-regulation of the expressions of Nephrin and Podocin in the glomeruli in the rats.

Topics: Animals; Artemisinins; Doxorubicin; Humans; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Male; Membrane Proteins; Proteinuria; Rats

Experiments determined whether the combination of endothelin A (ETA) receptor antagonist [ABT-627, atrasentan; (2R,3R,4S)-4-(1,3-benzodioxol-5-yl)-1-[2-(dibutylamino)-2-oxoethyl]-2-(4-methoxyphenyl)pyrrolidine-3-carboxylic acid] and a thiazide diuretic (chlorthalidone) would be more effective at lowering blood pressure and reducing renal injury in a rodent model of metabolic syndrome compared with either treatment alone. Male Dahl salt-sensitive rats were fed a high-fat (36% fat), high-salt (4% NaCl) diet for 4 weeks. Separate groups of rats were then treated with vehicle (control), ABT-627 (ABT; 5 mg/kg per day, in drinking water), chlorthalidone (CLTD; 5 mg/kg per day, in drinking water), or both ABT plus CLTD. Mean arterial pressure (MAP) was recorded continuously by telemetry. After 4 weeks, both ABT and CLTD severely attenuated the development of hypertension, whereas the combination further reduced MAP compared with ABT alone. All treatments prevented proteinuria. CLTD and ABT plus CLTD significantly reduced nephrin (a podocyte injury marker) and kidney injury molecule-1 (a tubulointerstitial injury marker) excretion. ABT, with or without CLTD, significantly reduced plasma 8-oxo-2'-deoxyguanosine, a measure of DNA oxidation, whereas CLTD alone had no effect. All treatments suppressed the number of ED1(+) cells (macrophages) in the kidney. Plasma tumor necrosis factor receptors 1 and 2 were reduced only in the combined ABT and CLTD group. These results suggest that ABT and CLTD have antihypertensive and renal-protective effects in a model of metabolic syndrome that are maximally effective when both drugs are administered together. The findings support the hypothesis that combined ETA antagonist and diuretic treatment may provide therapeutic benefit for individuals with metabolic syndrome consuming a Western diet.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Antihypertensive Agents; Arterial Pressure; Atrasentan; Cell Adhesion Molecules; Chlorthalidone; Deoxyguanosine; Disease Models, Animal; Diuretics; Drug Combinations; Endothelin A Receptor Antagonists; Endothelins; Hypertension; Inflammation; Kidney Diseases; Male; Membrane Proteins; Metabolic Syndrome; Oxidative Stress; Proteinuria; Pyrrolidines; Rats; Rats, Inbred Dahl; Rats, Sprague-Dawley; Receptor, Endothelin A; Sodium Chloride, Dietary

Western blot is the gold standard method to determine individual protein expression levels. However, western blot is technically difficult to perform in large sample sizes because it is a time consuming and labor intensive process. Dot blot is often used instead when dealing with large sample sizes, but the main disadvantage of the existing dot blot techniques, is the absence of signal normalization to a housekeeping protein.. In this study we established a one dot two development signals (ODTDS) dot blot method employing two different signal development systems. The first signal from the protein of interest was detected by horseradish peroxidase (HRP). The second signal, detecting the housekeeping protein, was obtained by using alkaline phosphatase (AP).. Inter-assay results variations within ODTDS dot blot and western blot and intra-assay variations between both methods were low (1.04-5.71%) as assessed by coefficient of variation.. ODTDS dot blot technique can be used instead of western blot when dealing with large sample sizes without a reduction in results accuracy.

Topics: Alkaline Phosphatase; Animals; Biomarkers; Blotting, Western; Collagen Type I; Disease Models, Animal; Glyceraldehyde-3-Phosphate Dehydrogenases; Horseradish Peroxidase; Humans; Immunoblotting; Kidney; Kidney Diseases; Male; Membrane Proteins; Nephrectomy; Rats, Wistar; Reproducibility of Results; Smad2 Protein; Smad3 Protein; Specimen Handling

Alterations within the renal renin angiotensin system play a pivotal role in the development and progression of cardiovascular and renal disease. Angiotensin converting enzyme 2 (ACE2) is highly expressed in renal tubules and has been shown to be renoprotective in diabetes. The protease, a disintegrin and metalloprotease (ADAM) 17, is involved in the ectodomain shedding of several transmembrane proteins including ACE2. Renal ACE2 and ADAM17 were significantly increased in db/db mice compared to controls. We investigated the effect of the insulin sensitizer, rosiglitazone, on albuminuria, renal ADAM17 protein expression and ACE2 shedding in db/db diabetic mice. Rosiglitazone treatment of db/db mice normalized hyperglycemia, attenuated renal injury and decreased urinary ACE2 and renal ADAM17 protein expression. Urinary excreted ACE2 is enzymatically active. Western blot analysis of urinary ACE2 demonstrated two prominent immunoreactive bands at approximately 70 & 90 kDa. The predominant immunoreactive band is approximately 20 kDa shorter than the one demonstrated for kidney lysate, indicating possible ectodomain shedding of active renal ACE2 in the urine. Therefore, it is tempting to speculate that renoprotection of rosiglitazone could be partially mediated via downregulation of renal ADAM17 and ACE2 shedding. In addition, there was a positive correlation between blood glucose, urinary albumin, plasma glucagon, and triglyceride levels with urinary ACE2 excretion. In conclusion, urinary ACE2 could be used as a sensitive biomarker of diabetic nephropathy and for monitoring the effectiveness of renoprotective medication.

Topics: ADAM Proteins; ADAM17 Protein; Albuminuria; Angiotensin-Converting Enzyme 2; Animals; Blood Glucose; Diabetes Mellitus, Type 2; Disease Models, Animal; Glucagon; Glucose Tolerance Test; Glycosuria; Hyperglycemia; Hypoglycemic Agents; Kidney Diseases; Male; Membrane Proteins; Mice; Peptidyl-Dipeptidase A; Rosiglitazone; Thiazolidinediones; Tissue Inhibitor of Metalloproteinase-3; Triglycerides

Semaphorin-3A (Sema3a), a guidance protein secreted by podocytes, is essential for normal kidney patterning and glomerular filtration barrier development. Here, we report that podocyte-specific Sema3a gain-of-function in adult mice leads to proteinuric glomerular disease involving the three layers of the glomerular filtration barrier. Reversibility of the glomerular phenotype upon removal of the transgene induction provided proof-of-principle of the cause-and-effect relationship between podocyte Sema3a excess and glomerular disease. Mechanistically, excess Sema3a induces dysregulation of nephrin, matrix metalloproteinase 9, and αvβ3 integrin in vivo. Sema3a cell-autonomously disrupts podocyte shape. We identified a novel direct interaction between the Sema3a signaling receptor plexinA1 and nephrin, linking extracellular Sema3a signals to the slit-diaphragm signaling complex. We conclude that Sema3a functions as an extracellular negative regulator of the structure and function of the glomerular filtration barrier in the adult kidney. Our findings demonstrate a crosstalk between Sema3a and nephrin signaling pathways that is functionally relevant both in vivo and in vitro.

Topics: Animals; Cell Shape; Down-Regulation; Glomerular Basement Membrane; Integrin alphaVbeta3; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mice; Nerve Tissue Proteins; Podocytes; Protein Binding; Proteinuria; Receptors, Cell Surface; Semaphorin-3A; Signal Transduction

To discuss the mechanism of Yiqiyangyin recipe in rats with adriamycin (ADR)-induced nephropathy.. We randomly divided 30 Sprague-Dawley rats into 5 groups: control, model, glucocorticoid, Chinese herb, and Chinese herb plus glucocorticoid groups. The 24-h urine volume was collected on days 7, 14, 21, and 28 after ADR injection, and all rats were killed on day 28. We measured the 24-h levels of urinary protein, serum cholesterol, and serum triglycerides, and renal function of all rats by using routine biochemical methods. Pathological changes in the rat kidneys were observed under light and electron microscopes. Heparanase (HPA) mRNA expression levels were measured using real-time fluorescence-quantitative polymerase chain reaction. Urine levels of HPA in all groups were measured using enzyme-linked immunosorbent assay. The expression of nephrin was detected by immunohistochemical staining and quantitatively analyzed using Motic image analysis 3.2 software.. The levels of urinary protein and serum triglycerides and cholesterol in rats with ADR-induced nephropathy increased on day 14. The serum albumin levels simultaneously decreased. All the changes reached the peak on day 28. Examination under the light microscope showed inflammatory cells and slight fibroplasia in the renal interstitium in the model group, but fewer inflammatory cells were observed in the intervention groups than those in the model group. Examination under the electron microscope showed extensive fusion of foot processes in ADR rats. HPA mRNA expression was higher in the model group than that in the control group. The HPA mRNA levels in the intervention groups, especially in the Chinese herb group, and Chinese herb plus glucocorticoid group were significantly lower than the level in the model group. The HPA expression levels correlated significantly with the proteinuria level. No significant difference was found in the HPA level in urine between the intervention groups and the model group, whereas the model group had a higher urinary HPA level than the control group. Nephrin mRNA expression levels in the model group were higher than those in the control group. Nephrin mRNA expression levels were significantly lower in the intervention groups than that in the model group, especially the Chinese herb plus glucocorticoid group. Compared with the control group, the model group showed increased nephrin expression in the kidney. Nephrin levels in the other groups, especially in the Chinese herb plus glucocorticoid group, were significantly lower than that in the model group. The nephrin levels in the kidney were negatively correlated with the proteinuria level.. Yiqiyangyin recipe could attenuate foot process injury particularly in combination with a steroid reduce the development of proteinuria possibly by inhibition of HPA in the kidney, and regulate the expression of nephrin in rats with ADR-induced nephropathy. Our study showed that treatment with Yiqiyangyin recipe plus glucocorticoid was better than a singular intervention, and we explored the pharmacological mechanism of this combination by biochemical and molecular biological analysis to provide a basis for clinical application.

Topics: Animals; Doxorubicin; Drugs, Chinese Herbal; Glucuronidase; Humans; Kidney Diseases; Male; Membrane Proteins; Rats; Rats, Sprague-Dawley

The present study was conducted to investigate the effects of probucol on the progression of diabetic nephropathy and the underlying mechanism in type 2 diabetic db/db mice. Eight weeks db/db mice were treated with regular diet or probucol-containing diet (1%) for 12 weeks. Non-diabetic db/m mice were used as controls. We examined body weight, blood glucose, and urinary albumin. At 20 weeks, experimental mice were sacrificed and their blood and kidneys were extracted for the analysis of blood chemistry, kidney histology, oxidative stress marker, and podocyte marker. As a result, 24 h urinary albumin excretions were reduced after probucol treatment. There were improvements of extracellular matrix accumulation and fibronectin and collagen IV deposition in glomeruli in the probucol-treated db/db mice. The reduction of nephrin and the loss of podocytes were effectively prevented by probucol in db/db mice. Furthermore, probucol significantly decreased the production of thiobarbituric acid-reactive substances (TBARS), an index of reactive oxygen species (ROS) generation and down-regulated the expression of Nox2. Taken together, our findings support that probucol may have the potential to protect against type 2 diabetic nephropathy via amelioration of podocyte injury and reduction of oxidative stress.

Topics: Albuminuria; Animals; Antioxidants; Collagen Type IV; Diabetes Mellitus, Type 2; Disease Models, Animal; Fibronectins; Kidney Diseases; Male; Membrane Glycoproteins; Membrane Proteins; Mice; Mice, Mutant Strains; NADPH Oxidase 2; NADPH Oxidases; Podocytes; Probucol; WT1 Proteins

The present study employed a zinc-finger nuclease strategy to create heterozygous knockout (KO) rats for the transforming growth factor-β1 (Tgfb1) gene on the Dahl SS/Jr genetic background (TGF-β1(+/-) Dahl S). Intercrossing TGF-β1(+/-) rats did not produce any homozygous KO rats (66.4% +/-, 33.6% +/+), indicating that the mutation is embryonic lethal. Six-week-old wild-type (WT) littermates and TGF-β1(+/-) Dahl S rats were fed a 0.4% (low salt, LS) or 8% NaCl (high salt, HS) diet for 5 wk. Renal cortical expression of TGF-β1, urinary TGF-β1 excretion, proteinuria, glomerular injury and tubulointerstitial fibrosis, and systolic blood pressure were similar in WT and TGF-β1(+/-) Dahl S rats maintained on the LS diet. The expression and urinary excretion of TGF-β1 increased to a greater extent in WT than in TGF-β1(+/-)Dahl S rats fed an HS diet for 1 wk. Systolic blood pressure rose by the same extent to 235 ± 2 mmHg in WT and 239 ± 4 mmHg in TGF-β1(+/-) Dahl S rats fed a HS diet for 5 wk. However, urinary protein excretion was significantly lower in TGF-β1(+/-) Dahl S than in the WT animals. The degree of glomerular injury and renal cortical and outer medullary fibrosis was markedly less in TGF-β1(+/-) than in WT rats. These findings suggest that the loss of one copy of the TGF-β1 gene blunts the increase in renal TGF-β1 protein expression and slows the progression of proteinuria, glomerulosclerosis, and renal interstitial fibrosis in Dahl S rats fed an HS diet independently of changes in blood pressure.

Topics: Animals; Base Sequence; Fibrosis; Gene Expression Regulation; Gene Knockout Techniques; Hypertension; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Membrane Proteins; Molecular Sequence Data; Proteinuria; Rats; Rats, Inbred Dahl; Transforming Growth Factor beta1; Transforming Growth Factor beta2; Transforming Growth Factor beta3

Dogs of the soft-coated wheaten terrier breed (SCWT) are predisposed to adult-onset, genetically complex, protein-losing nephropathy (average onset age = 6.3 ± 2.0 years). A genome-wide association study using 62 dogs revealed a chromosomal region containing three statistically significant SNPs (p(raw) ≤ 4.13 × 10(-8); p(genome) ≤ 0.005) when comparing DNA samples from affected and geriatric (≥14 years) unaffected SCWTs. Sequencing of candidate genes in the region revealed single nucleotide changes in each of two closely linked genes, NPHS1 and KIRREL2, which encode the slit diaphragm proteins nephrin and Neph3/filtrin, respectively. In humans, mutations in nephrin and decreased expression of Neph3 are associated with podocytopathy and protein-losing nephropathy. The base substitutions change a glycine to arginine in the fibronectin type 3 domain of nephrin and a proline to arginine in a conserved proline-rich region in Neph3. These novel mutations are not described in other species, nor were they found in 550 dogs of 105 other breeds, except in 3 dogs, including an affected Airedale terrier, homozygous for both substitutions. Risk for nephropathy is highest in dogs homozygous for the mutations (OR = 9.06; 95 % CI = 4.24-19.35). This is the first molecular characterization of an inherited podocytopathy in dogs and may serve as a model for continued studies of complex genetic and environmental interactions in glomerular disease.

Topics: Amino Acid Sequence; Animals; Breeding; Chromosomes; Dog Diseases; Dogs; Genome-Wide Association Study; Genotype; Homozygote; Kidney Diseases; Membrane Proteins; Molecular Sequence Data; Mutation; Sequence Analysis, DNA

Previous studies have shown that renin-angiotensin (Ang) system vaccines may be effective for the treatment of hypertension, but their efficacy for the prevention of renal disease is unclear. The aim of this study was to compare the effects of an Ang II type 1 (AT1) receptor vaccine with an Ang II receptor blocker (ARB) and a vasodilator on blood pressure (BP) and renal injury in the L-NAME nephropathy model. Male spontaneously hypertensive rats (SHRs) were divided into six groups and treated transiently with three injections of vehicle or AT1 receptor vaccine (0.1 mg) at age 4, 6 and 8 weeks, or continuously with candesartan cilexetil (0.1 mg kg(-1) per day) or hydralazine hydrochloride (5 mg kg(-1) per day), then administered NG-nitro-L-arginine methyl ester (L-NAME) from age 18 to 21 weeks to induce renal injury. Vaccination against the AT1 receptor caused a significant increase in AT1 receptor titers, and a sustained decrease in BP. L-NAME treatment resulted in a marked increase in proteinuria in the control groups, which was completely suppressed in the AT1 vaccine-treated group, and glomerular injury scores were also significantly decreased. Real-time RT-PCR and immunofluorescence studies revealed increased renin mRNA, and increased glomerular expression of nephrin. Comparable results were seen in rats treated continuously with the ARB candesartan, but not with hydralazine. These results suggest that transient AT1 vaccination is as effective as continuous treatment with ARB, not only for the attenuation of hypertension, but also for the prevention of L-NAME-induced nephropathy in SHR.

Topics: Angiotensin II Type 1 Receptor Blockers; Animals; Benzimidazoles; Biphenyl Compounds; Enzyme Inhibitors; Hydralazine; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; NG-Nitroarginine Methyl Ester; Proteinuria; Rats; Rats, Inbred SHR; Receptor, Angiotensin, Type 1; Tetrazoles; Vaccines

Proteinuria is an important risk factor for the progression and prognosis of chronic kidney disease. Bufalin, a cardiotonic steroid, has been shown to posses a variety of biological activities including cardiotonic, anaesthetic and antineoplastic activities, and regulate the immune response. This study investigated the effects of bufalin against proteinuria and glomerular filtration barrier damage in rats with adriamycin (ADR)-induced nephropathy. We compared the blood and urine biochemical indices and the histologic and ultrastructure of the glomerulus in ADR rats with and without the intervention of bufalin or prednisone. The transcription, expression and distribution of the podocyte-associated molecules were compared utilising RT-PCR, western blotting and immunohistochemical staining. We found that bufalin reduced the urinary protein excretion and optimised the lipidaemia of the ADR rats. Bufalin alleviated the removal of podocyte foot processes and attenuated the changes in nephrin, podocin and integrin-linked kinase (ILK) stainings in the glomerulus of the ADR rats. Bufalin notably decreased the expression of nephrin and ILK but inhibited the down-regulation of podocin in protein levels on the renal cortex of the ADR rats. Additionally, bufalin inhibited the up-regulation of podocin and ILK in mRNA levels but did not affect nephrin mRNA levels. These results suggest that bufalin could alleviate ADR-induced proteinuria by protecting the glomerular filtration barrier and may be a novel potential therapeutic agent for proteinuria-associated kidney disease.

Topics: Animals; Bufanolides; Cardiotonic Agents; Doxorubicin; Gene Expression Regulation; Glomerular Filtration Barrier; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Male; Membrane Proteins; Podocytes; Prednisone; Protein Serine-Threonine Kinases; Proteinuria; Rats; Rats, Sprague-Dawley

The morphology of healthy podocyte foot processes is necessary for maintaining the characteristics of the kidney filtration barrier. In most forms of glomerular disease, abnormal filter barrier function results when podocytes undergo foot process spreading and retraction by remodeling their cytoskeletal architecture and intercellular junctions during a process known as effacement. The cell adhesion protein nephrin is necessary for establishing the morphology of the kidney podocyte in development by transducing from the specialized podocyte intercellular junction phosphorylation-mediated signals that regulate cytoskeletal dynamics. The present studies extend our understanding of nephrin function by showing that nephrin activation in cultured podocytes induced actin dynamics necessary for lamellipodial protrusion. This process required a PI3K-, Cas-, and Crk1/2-dependent signaling mechanism distinct from the previously described nephrin-Nck1/2 pathway necessary for assembly and polymerization of actin filaments. Our present findings also support the hypothesis that mechanisms governing lamellipodial protrusion in culture are similar to those used in vivo during foot process effacement in a subset of glomerular diseases. In mice, podocyte-specific deletion of Crk1/2 prevented foot process effacement in one model of podocyte injury and attenuated foot process effacement and associated proteinuria in a delayed fashion in a second model. In humans, focal adhesion kinase and Cas phosphorylation - markers of focal adhesion complex-mediated Crk-dependent signaling - was induced in minimal change disease and membranous nephropathy, but not focal segmental glomerulosclerosis. Together, these observations suggest that activation of a Cas-Crk1/2-dependent complex is necessary for foot process effacement observed in distinct subsets of human glomerular diseases.

Topics: Adolescent; Adult; Aged; Animals; Cell Line; Crk-Associated Substrate Protein; Female; Focal Adhesion Protein-Tyrosine Kinases; Humans; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mice; Mice, Knockout; Middle Aged; Phosphatidylinositol 3-Kinases; Podocytes; Proto-Oncogene Proteins c-crk; Pseudopodia; Rats; Rats, Sprague-Dawley; Recombinant Fusion Proteins; Signal Transduction; Young Adult

Pathological glomerular hyposialylation has been implicated in certain unexplained glomerulopathies, including minimal change nephrosis, membranous glomerulonephritis, and IgA nephropathy. We studied our previously established mouse model carrying a homozygous mutation in the key enzyme of sialic acid biosynthesis, N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase. Mutant mice died before postnatal day 3 (P3) from severe glomerulopathy with podocyte effacement and segmental glomerular basement membrane splitting due to hyposialylation. Administration of the sialic acid precursor N-acetylmannosamine (ManNAc) led to improved sialylation and survival of mutant pups beyond P3. We determined the onset of the glomerulopathy in the embryonic stage. A lectin panel, distinguishing normally sialylated from hyposialylated glycans, used WGA, SNA, PNA, Jacalin, HPA, and VVA, indicating glomerular hyposialylation of predominantly O-linked glycoproteins in mutant mice. The glomerular glycoproteins nephrin and podocalyxin were hyposialylated in this unique murine model. ManNAc treatment appeared to ameliorate the hyposialylation status of mutant mice, indicated by a lectin histochemistry pattern similar to that of wild-type mice, with improved sialylation of both nephrin and podocalyxin, as well as reduced albuminuria compared with untreated mutant mice. These findings suggest application of our lectin panel for categorizing human kidney specimens based on glomerular sialylation status. Moreover, the partial restoration of glomerular architecture in ManNAc-treated mice highlights ManNAc as a potential treatment for humans affected with disorders of glomerular hyposialylation.

Topics: Animals; Biomarkers; Carbohydrate Epimerases; Carrier Proteins; Dietary Supplements; Disease Models, Animal; Drug Evaluation, Preclinical; Hexosamines; Humans; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mice; Mice, Mutant Strains; Microscopy, Electron; Mutation; N-Acetylneuraminic Acid; Podocytes; Real-Time Polymerase Chain Reaction; Sialoglycoproteins

Rho family GTPases are molecular switches best known for their pivotal role in dynamic regulation of the actin cytoskeleton. The prototypic members of this family are Cdc42, Rac1, and RhoA; these GTPases contribute to the breakdown of glomerular filtration and the resultant proteinuria, but their functions in normal podocyte physiology remain poorly understood. Here, mice lacking Cdc42 in podocytes developed congenital nephropathy and died as a result of renal failure within 2 weeks after birth. In contrast, mice lacking Rac1 or RhoA in podocytes were overtly normal and lived to adulthood. Kidneys from Cdc42-mutant mice exhibited protein-filled microcysts with hallmarks of collapsing glomerulopathy, as well as extensive effacement of podocyte foot processes with abnormal junctional complexes. Furthermore, we observed aberrant expression of several podocyte markers and cell polarity proteins in the absence of Cdc42, indicating a disruption of the slit diaphragm. Kidneys from Rac1- and RhoA-mutant mice, however, had normal glomerular morphology and intact foot processes. A nephrin clustering assay suggested that Cdc42 deficiency, but not Rac1 or RhoA deficiency, impairs the polymerization of actin at sites of nephrin aggregates. Taken together, these data highlight the physiological importance of Cdc42, but not Rac1 or RhoA, in establishing podocyte architecture and glomerular function.

Topics: Animals; cdc42 GTP-Binding Protein; Disease Models, Animal; Female; Glomerular Filtration Barrier; Kidney Diseases; Membrane Proteins; Mice; Mice, Knockout; Mice, Transgenic; Podocytes; Pregnancy; rac1 GTP-Binding Protein; rho GTP-Binding Proteins; rhoA GTP-Binding Protein

The aim of this study is to investigate the expression of nephrin, vascular endothelial growth factor (VEGF), transforming growth factor-beta 1 (TGF-β1), and podocyte number in adriamycin (ADR)-induced nephropathy. A total of 60 male Sprague-Dawley rats were randomly divided into the control group and the ADR nephropathy group. The nephropathy was induced by tail-vein injection of ADR (4 mg/kg) twice at a 14-day interval. The expression levels of nephrin, VEGF, and TGF-β1 in glomeruli were assessed by immunohistochemistry and western blotting. The podocyte number was also evaluated after anti-Wilms' tumor-1 (WT1) immunohistochemical staining. In addition, the urinary protein content, biochemical parameters in serum samples and glomerular sclerosis index (SI) were compared between groups. In the ADR nephropathy group, the expression levels of nephrin was significantly decreased with the fusion of podocyte foot processes at 6 weeks after the first ADR injection, which was associated with a marked proteinuria. A decrease in podocyte number and an increase in SI with the overexpression of both VEGF and TGF-β1 were also observed in the glomeruli at 10 weeks after the first ADR injection. This was associated with focal segmental glomerulosclerosis (FSGS). The study data suggest that podocyte injury and decreased nephrin, as well as increased VEGF and TGF-β1, may contribute to the development of proteinuria and FSGS in ADR-induced nephropathy in rats.

Topics: Animals; Blotting, Western; Cell Count; Doxorubicin; Glomerular Basement Membrane; Glomerulosclerosis, Focal Segmental; Kidney Diseases; Male; Membrane Proteins; Podocytes; Proteinuria; Rats; Rats, Sprague-Dawley; Transforming Growth Factor beta1; Vascular Endothelial Growth Factor A

Proteinuria and/or albuminuria are widely used for noninvasive assessment of kidney diseases. However, proteinuria is a nonspecific marker of diverse forms of kidney injury, physiologic processes and filtration of small proteins of monoclonal and other pathologic processes. The opportunity to develop new glomerular disease biomarkers follows the realization that the degree of podocyte depletion determines the degree of glomerulosclerosis, and if persistent, determines the progression to end-stage kidney disease (ESKD). Podocyte cell lineage-specific mRNAs can be recovered in urine pellets of model systems and in humans. In model systems, progressive glomerular disease is associated with decreased nephrin mRNA steady-state levels compared with podocin mRNA. Thus, the urine podocin:nephrin mRNA ratio (PNR) could serve as a useful progression biomarker. The use of podocyte-specific transcript ratios also circumvents many problems inherent to urine assays.. To test this hypothesis, the human diphtheria toxin receptor (hDTR) rat model of progression was used to evaluate potentially useful urine mRNA biomarkers. We compared histologic progression parameters (glomerulosclerosis score, interstitial fibrosis score and percent of podocyte depletion) with clinical biomarkers [serum creatinine, systolic blood pressure (BP), 24-h urine volume, 24-h urine protein excretion and the urine protein:creatinine ratio(PCR)] and with the novel urine mRNA biomarkers.. The PNR correlated with histologic outcome as well or better than routine clinical biomarkers and other urine mRNA biomarkers in the model system with high specificity and sensitivity, and a low coefficient of assay variation.. We concluded that the PNR, used in combination with proteinuria, will be worth testing for its clinical diagnostic and decision-making utility.

Topics: Animals; Biomarkers; Humans; Intracellular Signaling Peptides and Proteins; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Podocytes; Proteinuria; Rats; Rats, Inbred F344; Real-Time Polymerase Chain Reaction; RNA, Messenger

We previously reported that in a model of spontaneously progressive glomerular injury with early podocyte loss, abnormal migration, and proliferation of glomerular parietal epithelial progenitor cells contributed to the formation of synechiae and crescentic lesions. Here we first investigated whether a similar sequence of events could be extended to rats with adriamycin (ADR)-induced nephropathy. As a second aim, the regenerative potential of therapy with bone marrow-derived mesenchymal stem cells (MSCs) on glomerular resident cells was evaluated. In ADR-treated rats, decrease of WT1(+) podocyte number due to apoptosis was associated with reduced glomerular expression of nephrin and CD2AP. As a consequence of podocyte injury, glomerular adhesions of the capillary tuft to the Bowman's capsule were observed, followed by crescent-like lesions and glomerulosclerosis. Cellular components of synechiae were either NCAM(+) parietal progenitor cells or nestin(+) podocytes. In ADR rats, repeated injections of MSCs limited podocyte loss and apoptosis and partially preserved nephrin and CD2AP. MSCs attenuated the formation of glomerular podocyte-parietal epithelial cell bridges and normalized the distribution of NCAM(+) progenitor cells along the Bowman's capsule, thereby reducing glomerulosclerosis. Finding that MSCs increased glomerular VEGF expression and limited microvascular rarefaction may explain the prosurvival effect by stem cell therapy. MSCs also displayed anti-inflammatory activity. Coculture of MSCs with ADR-damaged podocytes showed a functional role of stem cell-derived VEGF on prosurvival pathways. These data suggest that MSCs by virtue of their tropism for damaged kidney and ability to provide a local prosurvival environment may represent a useful strategy to preserve podocyte viability and reduce glomerular inflammation and sclerosis.

Topics: Adaptor Proteins, Signal Transducing; Animals; Apoptosis; Cell Count; Cell Movement; Coculture Techniques; Cytoskeletal Proteins; Disease Models, Animal; Doxorubicin; Kidney; Kidney Diseases; Male; Membrane Proteins; Mesenchymal Stem Cell Transplantation; Podocytes; Rats; Rats, Inbred Lew; Regeneration; Stem Cells; Treatment Outcome; Vascular Endothelial Growth Factor A

The involvement of nephrin in controlling renal function is unclear with the literature only emphasizing its role in albuminuria. We therefore investigated the potential association between nephrinuria as evidenced by the appearance of urinary immunopositive nephrin fragments, with multiple renal traits.. Western blot analysis of the urine samples from a cross-sectional study of 381 Chinese type 2 diabetic patients revealed four distinct protein fragments, indicative of nephrinuria. Albuminuria was measured in random spot urine samples using the albumin/creatinine ratio (ACR), while estimated glomerular filtration rate (eGFR) was calculated using the creatinine-based Modification of Diet in Renal Disease formula.. Each nephrin fragment was associated with a decline in eGFR (smallest P = 0.001). Even with the inclusion of logarithmic form of ACR (ln ACR) in the multivariate model, nephrinuria still remained significantly associated with lower eGFR (smallest P < 0.05). Nephrinuria was also strongly associated with lnACR and this finding was independent of eGFR (smallest P < 0.001). Thus, nephrinuria was independently associated with both renal traits in the form of lnACR and eGFR. Furthermore, nephrinuria was significantly associated with lower eGFR even among normoalbuminuric patients (ACR ≤ 30 mg/g) (smallest P = 0.002), potentially implicating nephrinuria in the development of normoalbuminuric renal insufficiency. Apart from the renal traits under investigation, the presence of nephrinuria did not associate with other patient clinical characteristics.. Nephrinuria was associated with multiple renal traits in type 2 diabetes even in normoalbuminuric patients who are traditionally perceived as having a low risk of chronic kidney disease.

Topics: Aged; Albuminuria; Blotting, Western; Creatinine; Cross-Sectional Studies; Diabetes Complications; Diabetes Mellitus, Type 2; Female; Glomerular Filtration Rate; Humans; Kidney Diseases; Kidney Function Tests; Male; Membrane Proteins; Prognosis; Risk Factors

Doxorubicin (DOX) is an anthracycline antibiotic utilized in antitumor therapy; however, its clinical use is frequently impeded by renal toxic effects. As peroxisome proliferator-activated receptor-α (PPAR-α) has renoprotective effects in drug-related kidney injuries, we tested its ability to inhibit DOX-induced renal injury. Although both male PPAR-α knockout mice and their wild-type littermates (pure 129/SvJ background) had significant proteinuria 4 weeks after DOX treatment, those with deletion of PPAR-α had more severe proteinuria. This was associated with more serious podocyte foot process effacement compared with wild-type mice. In contrast, the PPAR-α agonist fenofibrate effectively reduced proteinuria and attenuated DOX-induced podocyte foot process effacement. Consistently, glomerular nephrin expression was significantly lower in the knockout compared with wild-type mice following DOX treatment. Fenofibrate therapy significantly blunted the reduction in glomerular nephrin levels in DOX-treated wild-type mice. In cultured podocytes, DOX induced apoptosis, increased cleaved caspase-3 levels, and decreased Bcl-2 expression, all attenuated by pretreatment with fenofibrate. Thus, PPAR-α deficiency exacerbates DOX-related renal injury, in part, due to increased podocyte apoptosis.

Topics: Animals; Apoptosis; Caspase 3; Cell Line; Cytoprotection; Disease Models, Animal; Doxorubicin; Fenofibrate; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Mice; Mice, 129 Strain; Mice, Inbred BALB C; Mice, Knockout; Podocytes; PPAR alpha; Proteinuria; Proto-Oncogene Proteins c-bcl-2; Species Specificity; Time Factors; Transcription, Genetic

Aldosterone (Aldo) causes podocyte damage by an unknown mechanism. We examined the role of mitochondrial dysfunction (MtD) in Aldo-treated podocytes in vitro and in vivo. Exposure of podocytes to Aldo reduced nephrin expression dose dependently, accompanied by increased production of reactive oxygen species (ROS). The ROS generation and podocyte damage were abolished by the mitochondrial (mt) respiratory chain complex I inhibitor rotenone. Pronounced MtD, including reduced mt membrane potential, ATP levels, and mtDNA copy number were seen in Aldo-treated podocytes and in the glomeruli of Aldo-infused mice. The mineralocorticoid receptor antagonist eplerenone significantly inhibited Aldo-induced MtD. The MtD was associated with higher levels of ROS, reduction in the activity of complexes I, III, and IV, and expression of the peroxisome proliferator-activated receptor-γ (PPARγ) coactivator-1α and mt transcription factor A. Both the PPARγ agonist rosiglitazone and PPARγ overexpression protected against podocyte injury by preventing MtD and oxidative stress, as evidenced by reduced ROS production, by maintenance of mt morphology, by restoration of mtDNA copy number, by decrease in mt membrane potential loss, and by recovery of mt electron transport function. The protective effect of rosiglitazone was abrogated by the specific PPARγ small interference RNA, but not a control small interference RNA. We conclude that MtD is involved in Aldo-induced podocyte injury, and that the PPARγ agonist rosiglitazone may protect podocytes from this injury by improving mitochondrial function.

Topics: Aldosterone; Animals; Blotting, Western; DNA, Mitochondrial; Kidney Diseases; Male; Membrane Potential, Mitochondrial; Membrane Proteins; Mice; Mice, Inbred C57BL; Mitochondria; Podocytes; PPAR gamma; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; Transfection

Immunosuppressants and inhibitors of the renin angiotensin system are major reagents to treat nephrotic syndrome but their clinical effects are not necessarily satisfactory. Injection of doxorubicin in several strains of mice causes nephrotic syndrome-like disorder. Zhou et al. report that PPAR-α expression is downregulated in murine doxorubicin nephropathy and a PPAR-α agonist, fenofibrate, partially ameliorates the disorder induced likely through stabilization of nephrin expression and suppression of apoptosis in podocytes, providing a new preventive strategy.

Topics: Animals; Apoptosis; Caspase 3; Cytoprotection; Disease Models, Animal; Doxorubicin; Fenofibrate; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mice; Mice, Knockout; Podocytes; PPAR alpha; Proteinuria; Proto-Oncogene Proteins c-bcl-2; Time Factors; Transcription, Genetic

Topics: Blood Chemical Analysis; Child; Female; Fetal Diseases; Fetus; Genetic Testing; Humans; Infant, Newborn; Kidney Diseases; Male; Membrane Proteins; Pregnancy; Prenatal Diagnosis; Receptors, Cell Surface; Ultrasonography; Urinary Tract

Development of pharmacologic agents that protect podocytes from injury is a critical strategy for the treatment of kidney glomerular diseases. Retinoic acid reduces proteinuria and glomerulosclerosis in multiple animal models of kidney diseases. However, clinical studies are limited because of significant side effects of retinoic acid. Animal studies suggest that all trans retinoic acid (ATRA) attenuates proteinuria by protecting podocytes from injury. The physiological actions of ATRA are mediated by binding to all three isoforms of the nuclear retinoic acid receptors (RARs): RARα, RARβ, and RARγ. We have previously shown that ATRA exerts its renal protective effects mainly through the agonism of RARα. Here, we designed and synthesized a novel boron-containing derivative of the RARα-specific agonist Am580. This new derivative, BD4, binds to RARα receptor specifically and is predicted to have less toxicity based on its structure. We confirmed experimentally that BD4 binds to RARα with a higher affinity and exhibits less cellular toxicity than Am580 and ATRA. BD4 induces the expression of podocyte differentiation markers (synaptopodin, nephrin, and WT-1) in cultured podocytes. Finally, we confirmed that BD4 reduces proteinuria and improves kidney injury in HIV-1 transgenic mice, a model for HIV-associated nephropathy (HIVAN). Mice treated with BD4 did not develop any obvious toxicity or side effect. Our data suggest that BD4 is a novel RARα agonist, which could be used as a potential therapy for patients with kidney disease such as HIVAN.

Topics: AIDS-Associated Nephropathy; Animals; Benzoates; Benzopyrans; Binding, Competitive; Body Weight; Boron Compounds; Cell Differentiation; Cell Survival; Cells, Cultured; Female; Gene Expression Regulation; Kidney; Kidney Diseases; Male; Membrane Proteins; Mice; Mice, Transgenic; Microfilament Proteins; Molecular Structure; Podocytes; Proteinuria; Receptors, Retinoic Acid; Retinoic Acid Receptor alpha; Retinoids; Reverse Transcriptase Polymerase Chain Reaction; Tetrahydronaphthalenes; WT1 Proteins

We sought to examine the pathogenic role of excessive VEGF-A expression in podocytes, since it has been reported that diabetic nephropathy and other glomerular diseases are associated with increased VEGF-A expression. The induction of podocyte-specific VEGF164 overexpression in adult transgenic mice led to proteinuria, glomerulomegaly, glomerular basement membrane thickening, mesangial expansion, loss of slit diaphragms, and podocyte effacement. When doxycycline-mediated VEGF164 was stopped, these abnormalities reversed. These findings were associated with reversible downregulation of metalloproteinase 9 and nephrin expression. Using transmission electron microscopy, we established that VEGF-A receptor-2 (VEGFR2) was expressed in podocytes and glomerular endothelial cells. We also found that VEGF164 induced VEGFR2 phosphorylation in podocytes. Further, we were able to co-immunoprecipitate VEGFR2 and nephrin using whole kidney lysates, confirming interaction in vivo. This implies that autocrine and paracrine VEGF-A signaling through VEGFR2 occurs in podocytes and may mediate the glomerular phenotype caused by VEGF164 overexpression. Thus, we suggest that podocyte VEGF164 overexpression in adult mice is sufficient to induce glomerular filtration barrier structural and functional abnormalities similar to those present in murine diabetic nephropathy.

Topics: Age Factors; Animals; Autocrine Communication; Diabetic Nephropathies; Genotype; Glomerular Basement Membrane; Kidney Diseases; Matrix Metalloproteinase 9; Membrane Proteins; Mice; Mice, Transgenic; Paracrine Communication; Phenotype; Phosphorylation; Podocytes; Protein Binding; Proteinuria; Signal Transduction; Up-Regulation; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

Hepatocyte growth factor (HGF) is a potent antifibrotic protein that inhibits kidney fibrosis through several mechanisms. To study its role in podocyte homeostasis, injury, and repair in vivo, we generated conditional knockout mice in which the HGF receptor, c-met, was specifically deleted in podocytes using the Cre-LoxP system. Mice with podocyte-specific ablation of c-met (podo-met(-/-)) developed normally. No albuminuria or overt pathologic lesions were detected up to 6 months of age, suggesting that HGF signaling is dispensable for podocyte maturation, survival, and function under normal physiologic conditions. However, after adriamycin treatment, podo-met(-/-) mice developed more severe podocyte injury and albuminuria than their control littermates. Ablation of c-met also resulted in more profound suppression of Wilms tumor 1 (WT1) and nephrin expression, and podocyte apoptosis after injury. When HGF was expressed ectopically in vivo, it ameliorated adriamycin-induced albuminuria, preserved WT1 and nephrin expression, and inhibited podocyte apoptosis. However, exogenous HGF failed to significantly reduce albuminuria in podo-met(-/-) mice, suggesting that podocyte-specific c-met activation by HGF confers renal protection. In vitro, HGF was able to preserve WT1 and nephrin expression in cultured podocytes after adriamycin treatment. HGF also protected podocytes from apoptosis induced by a lethal dose of adriamycin primarily through a phosphoinositide 3-kinase (PI3K)/Akt-dependent pathway. Collectively, these results indicate that HGF/c-met signaling has an important role in protecting podocytes from injury, thereby reducing proteinuria.

Topics: Age Factors; Albuminuria; Animals; Apoptosis; Cells, Cultured; Cytoprotection; Disease Models, Animal; Doxorubicin; Hepatocyte Growth Factor; Kidney Diseases; Male; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Phosphatidylinositol 3-Kinases; Podocytes; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-met; Signal Transduction; Time Factors; WT1 Proteins

It is still unclear what happens in the glomerulus when proteinuria starts. Using puromycin aminonucleoside nephrosis (PAN) rats, we studied early ultrastructural and permeability changes in relation to the expression of the podocyte-associated molecules nephrin, α-actinin, dendrin, and plekhh2, the last two of which were only recently discovered in podocytes.. Using immune stainings, semiquantitative measurement was performed under the electron microscope. Permeability was assessed using isolated kidney perfusion with tracers. Possible effects of ACE inhibition were tested.. By day 2, some patchy foot process effacement, but no proteinuria, appeared. The amount of nephrin was reduced in both diseased and normal areas. The other proteins showed few changes, which were limited to diseased areas. By day 4, foot process effacement was complete and proteinuria appeared in parallel with signs of size barrier damage. Nephrin decreased further, while dendrin and plekhh2 also decreased but α-actinin remained unchanged. ACE inhibition had no significant protective effect.. PAN glomeruli already showed significant pathology by day 4, despite relatively mild proteinuria. This was preceded by altered nephrin expression, supporting its pivotal role in podocyte morphology. The novel proteins dendrin and plekhh2 were both reduced, suggesting roles in PAN, whereas α-actinin was unchanged.

Topics: Actinin; Animals; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Nephrosis; Nerve Tissue Proteins; Permeability; Proteins; Proteinuria; Puromycin Aminonucleoside; Rats; Rats, Sprague-Dawley

Glomerular epithelial cell (podocyte) injury is characterized by foot process retraction, slit diaphragm reorganization, and degradation of podocyte-specific proteins. However, the mechanisms underlying podocyte injury are largely unknown. The ubiquitin C-terminal hydrolase-L1 (UCH-L1) is a key modulator of ubiquitin modification in neurons. Like neurons, UCH-L1 expression was associated with an undifferentiated status in cultured human podocytes, whereas differentiation and arborization decreased UCH-L1 and monoUb expression. Inhibition of UCH-L1 induced time and concentration-dependent process formation with alpha-actinin-4 distribution to the cell membrane and processes. An immunohistochemical approach was used to evaluate whether UCH-L1 expression was associated with podocyte injury in 15 different human glomerular diseases. Whereas normal kidneys expressed no UCH-L1 and little ubiquitin, a subset of human glomerulopathies associated with podocyte foot process effacement (membranous nephropathy, SLE class V, FSGS) de novo expressed UCH-L1 in podocyte cell bodies, nuclei, and processes. Interestingly, UCH-L1 expression correlated with podocyte ubiquitin content and internalization of the podocyte-specific proteins nephrin and alpha-actinin-4. In contrast, minimal change glomerulonephritis, a reversible disease, demonstrated minimal UCH-L1 and ubiquitin expression with intact alpha-actinin-4 but internalized nephrin. Glomerular kidney diseases typically not associated with foot process effacement (SLE class IV, ANCA+ necrotizing GN, amyloidosis, IgA nephritis) expressed intermediate to no UCH-L1 and ubiquitin. These studies show a role for UCH-L1 and ubiquitin modification in podocyte differentiation and injury.

Topics: Actinin; Case-Control Studies; Cells, Cultured; Humans; Immunohistochemistry; Kidney Diseases; Membrane Proteins; Microscopy, Confocal; Podocytes; Reverse Transcriptase Polymerase Chain Reaction; Ubiquitin; Ubiquitin Thiolesterase

Activation of protein kinase C (PKC) has been implicated in the pathogenesis of diabetic nephropathy where therapy targeting the beta isoform of this enzyme is in advanced clinical development. However, PKC-beta is also increased in various forms of human glomerulonephritis with several potentially nephrotoxic factors, other than high glucose, resulting in PKC-beta activation. Accordingly, we sought to examine the effects of PKC-beta inhibition in a non-diabetic model of progressive kidney disease.. Subtotally nephrectomized (STNx) rats were randomly assigned to receive either the selective PKC-beta inhibitor, ruboxistaurin or vehicle. In addition to functional and structural parameters, gene expression of the podocyte slit-pore diaphragm protein, nephrin, was also assessed.. STNx animals developed hypertension, proteinuria and reduced glomerular filtration rate (GFR) in association with marked glomerulosclerosis and tubulointerstitial fibrosis. Glomerular nephrin expression was also reduced. Without affecting blood pressure, ruboxistaurin treatment attenuated the impairment in GFR and reduced the extent of both glomerulosclerosis and tubulointerstitial fibrosis in STNx rats. In contrast, neither proteinuria nor the reduction in nephrin expression was improved by ruboxistaurin.. These findings indicate firstly that PKC-beta inhibition may provide a new therapeutic strategy in non-diabetic kidney disease and secondly that improvement in GFR is not inextricably linked to reduction in proteinuria.

Topics: Animals; Disease Models, Animal; Enzyme Inhibitors; Glomerular Filtration Rate; Humans; Indoles; Kidney; Kidney Diseases; Male; Maleimides; Membrane Proteins; Mesangial Cells; Protein Kinase C; Protein Kinase C beta; Rats; Rats, Sprague-Dawley; RNA, Messenger; Transforming Growth Factor beta

The relationship between vascular endothelial growth factor (VEGF) and the phosphorylated critical podocyte slit diaphragm molecule nephrin is not fully clarified. This study investigated the dynamic changes in VEGF expression and nephrin phosphorylation, and the effects of the antiproteinuric drugs prednisone and lisinopril on them in Adriamycin nephropathy rats.. Renal tissues from Adriamycin rats were collected at days 3, 7, 14, and 28. Distribution and expression of VEGF was revealed by immunohistochemistry, real-time PCR and Western blot. Phosphorylated nephrin was evaluated by immunoprecipitation.. A discontinuous redistribution of VEGF was displayed at day 3, followed by significant protein reduction at day 7 with persistent downregulation to day 28. Phosphorylated nephrin decreased evidently at day 14 and persisted to day 28. The reduction in VEGF and phosphorylated nephrin was not a result of podocyte loss. The intervention of prednisone and lisinopril evidently reduced proteinuria, effectively attenuated the severe lesions of podocyte foot processes, and restored the reduction in VEGF and nephrin phosphorylation. At day 28, the reduction in VEGF and phosphorylated nephrin was negatively correlated with proteinuria, whereas the phosphorylated nephrin was positively correlated with VEGF protein from day 7 to day 28.. The reduction in VEGF protein and nephrin phosphorylation was possibly involved in the proteinuria in Adriamycin rats, and there might be some relationship between VEGF and nephrin phosphorylation. The antiproteinuric effects of lisinopril and prednisone were achieved at least partially by restoring VEGF protein and nephrin phosphorylation.

Topics: Animals; Doxorubicin; Kidney Diseases; Male; Membrane Proteins; Phosphorylation; Proteinuria; Rats; Rats, Sprague-Dawley; Vascular Endothelial Growth Factor A

Topics: Adaptor Proteins, Signal Transducing; Animals; Cell Cycle Proteins; Cell Movement; Cell Polarity; Humans; Intercellular Junctions; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Podocytes; Reference Values

Podocytes possess the complete machinery for glutamatergic signaling, raising the possibility that neuron-like signaling contributes to glomerular function. To test this, we studied mice and cells lacking Rab3A, a small GTPase that regulates glutamate exocytosis. In addition, we blocked the glutamate ionotropic N-methyl-d-aspartate receptor (NMDAR) with specific antagonists. In mice, the absence of Rab3A and blockade of NMDAR both associated with an increased urinary albumin/creatinine ratio. In humans, NMDAR blockade, obtained by addition of ketamine to general anesthesia, also had an albuminuric effect. In vitro, Rab3A-null podocytes displayed a dysregulated release of glutamate with higher rates of spontaneous exocytosis, explained by a reduction in Rab3A effectors resulting in freedom of vesicles from the actin cytoskeleton. In addition, NMDAR antagonism led to profound cytoskeletal remodeling and redistribution of nephrin in cultured podocytes; the addition of the agonist NMDA reversed these changes. In summary, these results suggest that glutamatergic signaling driven by podocytes contributes to the integrity of the glomerular filtration barrier and that derangements in this signaling may lead to proteinuric renal diseases.

Topics: Animals; Cells, Cultured; Cytoskeleton; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Exocytosis; Female; Glomerular Filtration Rate; Glutamic Acid; Ketamine; Kidney Diseases; Male; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Knockout; Podocytes; rab3A GTP-Binding Protein; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Signal Transduction

To investigate the expression of nephrin mRNA in adriamycin-induced nephropathy (AN) in rats, and to explore the effect of Qufengtongluo recipe on proteinuria in AN rats and on the expression of nephrin mRNA.. Adriamycin nephropathy was induced by a single tail intravenous injection of adriamycin. We randomly divided 140 rats into a normal control group (n=32) and a nephropathy model group (n=108). Three weeks later, 90 AN rats were randomly divided into 5 groups: a model group, a qufeng group, a qufeng and prednisone group, a prednisone group, and a benazepri group (18 rats in each group). They were treated respectively, and renal tissue samples were collected at week 0, 3, 5, and 7, respectively. The distribution and expression of nephrin mRNA were examined by indirect immunofluorescence and semi-quantity RT-PCR.. In the AN rats, the diffuse fusion and effacement of foot processes were observed at week 3. The fluorescence intensity of nephrin and the expression of nephrin mRNA significantly increased in the qufeng group and the prednisone group compared with the model group at the week 7 (P<0.01).. Abnormal expression of nephrin is the important molecular mechanism that leads to the occurrence and development of proteinuria in AN rats. Qufengtongluo recipe has effect on nephrotic syndrome through altering the expression and distribution of nephrin in glomerulus.

Topics: Animals; Doxorubicin; Drugs, Chinese Herbal; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Phytotherapy; Podocytes; Random Allocation; Rats; Rats, Sprague-Dawley; RNA, Messenger

The prevalence of chronic kidney disease (CKD) is increasing worldwide and proteinuria is a critical prognostic indicator of CKD. Nephrin is produced by podocytes and functions as a slit barrier for inhibition of proteinuria. Nephrin expression is frequently decreased in CKD patients. Nevertheless, the mechanism by which nephrin declines during CKD-related pathological states remains to be determined. Using tensin2-deficient mice (ICGN/Oa strain), we provide evidence that tensin2 is important for glomerular nephrin expression in vivo. In heterozygous mice with a single mutated tensin2 allele, nephrin expression was maintained, while albuminuria was not observed. In contrast, nephrin expression was impaired, especially in the central zones of glomeruli of homozygous mice (with double mutated tensin2 alleles), even at one week after birth. In homozygous mice, extension of synaptopodin, a key actin-associated protein, was also suppressed in the central zone of glomerular tufts. Consistent with the loss of nephrin and synaptopodin expression, severe albuminuria was detected in homozygous ICGN/Oa mice. Therefore, we suggested that tensin2 is involved in expression and extension of nephrin, while tensin2 deficiency may result in proteinuria, associated with the loss of slit integrity.

Topics: Albuminuria; Animals; Female; Humans; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Mice; Mice, Inbred Strains; Microfilament Proteins; Phosphoprotein Phosphatases; Podocytes; Tensins

There are several lines of evidence that the podocyte slit diaphragm (SD), which serves as a structural framework for the filtration barrier in kidney glomerulus, also plays an essential role as a signaling platform. Several SD components including nephrin and TRPC6 are known to be phosphorylated by a Src family tyrosine kinase (SFK), Fyn. Here we have characterized Neph1, another SD component, as a novel substrate of SFK. Fyn interacts with and phosphorylates the cytoplasmic domain of Neph1 in vitro and in intact cells. Peptide mass fingerprinting and site-directed mutagenesis identified several tyrosine phosphorylation sites. In pull-down assays using rat glomerular lysates, Neph1 but not nephrin specifically binds to adaptor protein Grb2 and tyrosine kinase Csk in a phosphorylation-dependent manner. Both tyrosine 637 and 638 of Neph1 are crucial for Neph1-Grb2 binding. Phosphorylation of tyrosine 637 is significantly up-regulated in in vivo models of podocyte injury. Furthermore, Neph1 attenuates ERK activation elicited by Fyn, and this inhibitory effect requires the intact binding motif for the Grb2 SH2 domain. Our results shown here demonstrate that Neph1 is a novel in vivo substrate of SFK and suggest that Neph1 modulates ERK signaling through phosphorylation-dependent interaction with Grb2. Thus, SFK orchestrates a wide spectrum of protein-protein interactions and intracellular signaling networks at SD through tyrosine phosphorylation.

Topics: Amino Acid Motifs; Animals; Cell Line; CSK Tyrosine-Protein Kinase; Disease Models, Animal; Extracellular Signal-Regulated MAP Kinases; GRB2 Adaptor Protein; Humans; Kidney Diseases; Male; MAP Kinase Signaling System; Membrane Proteins; Peptide Mapping; Peptides; Phosphorylation; Podocytes; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-fyn; Rats; Rats, Wistar; src Homology Domains; src-Family Kinases; TRPC Cation Channels; TRPC6 Cation Channel

Periodontitis was shown to have an impact on glucose levels in prediabetic and diabetic rats. The Zucker fatty rat (ZFR) is a well-characterized model of prediabetes presenting with impaired glucose tolerance, hyperinsulinemia, dyslipidemia, and moderate hypertension. The aim of the present study was to investigate whether periodontitis influences kidney changes in ZFRs.. Male adult ZFRs (N = 19) and their lean littermates (N = 18) were studied. Periodontitis was induced with ligatures in half of the ZFRs and lean rats, whereas the other half served as controls. After 4 weeks, the rats were sacrificed, and the kidneys, liver, and heart were removed and weighed. Kidneys were evaluated histologically for glomerular volume and renal mRNA levels of vascular endothelial growth factor (VEGF), VEGF receptor 2, transforming growth factor-beta, connective tissue growth factor, collagen IValpha1, fibronectin, and nephrin. Urinary albumin excretion and creatinine clearance were also evaluated.. In prediabetic ZFRs, periodontitis was associated with kidney hypertrophy (P = 0.03) and a tendency for increased glomerular volume (P = 0.06). In lean littermates, elevated fibronectin mRNA levels (P = 0.03) were noted in the presence of periodontitis.. Our findings suggest the participation of periodontitis in the development of early renal changes in ZFRs.

Topics: Albuminuria; Animals; Collagen Type IV; Connective Tissue Growth Factor; Creatinine; Fibronectins; Hypertrophy; Immediate-Early Proteins; Insulin-Like Growth Factor Binding Proteins; Intercellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Organ Size; Periodontitis; Prediabetic State; Random Allocation; Rats; Rats, Zucker; RNA, Messenger; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

Filtrin (NEPH3/KIRREL2) is a recently characterized member of the nephrin-like proteins of the immunoglobulin superfamily, and it has been suggested to participate in the maintenance of the glomerular filtration barrier in the kidney. In this study, the gene and protein expression of filtrin were examined in patients with acquired proteinuric diseases.. Filtrin mRNA levels in renal biopsies were measured with quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in two sets of patients with proteinuria. The mRNA levels were normalized to the housekeeping gene GAPDH and also related to the podocyte-specific genes nephrin and podocin. Immunofluorescence microscopy was employed to explore changes in the glomerular distribution of filtrin.. Reduced glomerular expression of filtrin mRNA was observed in all studied diagnostic groups. In focal segmental glomerulosclerosis, the filtrin mRNA level was only one-tenth of the control samples (P approximately 5.0x10(-6)), and this finding was confirmed in a second set of samples. The ratios of filtrin to nephrin and podocin demonstrated a marked decrease in the expression of filtrin relative to the podocyte marker genes. However, no correlation between the expression of filtrin and the levels of serum creatinine and proteinuria was observed. Immunostaining showed changes in the expression pattern of filtrin in renal biopsies. Immunoelectron microscopic studies localized filtrin at the slit diaphragm of the podocyte foot processes.. Down-regulation of the filtrin gene and protein expression in the renal biopsies together with the localization to the inter-podocyte filtration slit imply a potential role for this molecule in the pathogenesis of proteinuric diseases.

Topics: Biopsy; Fluorescent Antibody Technique; Humans; Immunoglobulins; Kidney; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Microscopy, Immunoelectron; Proteinuria; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tissue Distribution

Studies in experimental animals and younger women suggest a protective role for estrogen; however, clinical trials may not substantiate this effect in older females. Therefore, the present study assessed the outcome of ovariectomy in older mRen2. Lewis rats subjected to a high-salt diet for 4 wk. Intact or ovariectomized (OVX, 15 wk of age) mRen2. Lewis rats were aged to 60 wk and then placed on a high-salt (HS, 8% sodium chloride) diet for 4 wk. Systolic blood pressures were similar between groups [OVX 169 +/- 6 vs. Intact 182 +/- 7 mmHg; P = 0.22] after the 4-wk diet; however, proteinuria [OVX 0.8 +/- 0.2 vs. Intact 11.5 +/- 2.6 mg/mg creatinine; P < 0.002, n = 6], renal interstitial fibrosis, glomerular sclerosis, and tubular casts were lower in OVX vs. Intact rats. Kidney injury molecule-1 mRNA, a marker of tubular damage, was 53% lower in the OVX HS group. Independent from blood pressure, OVX HS rats exhibited significantly lower cardiac (24%) and renal (32%) hypertrophy as well as lower C-reactive protein (28%). Circulating insulin-like growth factor-I (IGF-I) levels were not different between the Intact and OVX groups; however, renal cortical IGF-I mRNA and protein were attenuated in OVX rats [P < 0.05, n = 6]. We conclude that ovariectomy in the older female mRen2. Lewis rat conveys protection against salt-dependent increase in renal injury.

Topics: Aging; Angiotensin I; Angiotensin II; Animals; Animals, Congenic; Blood Pressure; C-Reactive Protein; Cell Adhesion Molecules; Disease Models, Animal; Female; Fibrosis; Hypertension; Hypertrophy; Insulin-Like Growth Factor I; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Membrane Proteins; Ovariectomy; Peptide Fragments; Proteinuria; Rats; Rats, Inbred Lew; Renin; Renin-Angiotensin System; RNA, Messenger; Sodium Chloride, Dietary

Ephs and ephrins are a family of membrane-bound proteins that function as receptor-ligand pairs. Members of the Eph-ephrin-B family have recently been reported to regulate the paracellular permeability of epithelial cells. In this study, we analyzed the expression and the function of ephrin-B1 in glomeruli. Using immunofluorescence (IF), we found that ephrin-B1 was expressed along the glomerular capillary loop. Immunoelectron microscopy revealed that ephrin-B1 expression was restricted at the slit diaphragm. Dual labeled IF showed ephrin-B1 colocalized with the slit diaphragm proteins nephrin and CD2-associated protein. Ephrin-B1 colocalized with nephrin at the late capillary loop stage of kidney development. Additionally, injection of rats with a nephritogenic anti-nephrin antibody (ANA) reduced ephrin-B1 expression. When podocytes were cultured in vitro, they extruded processes that co-stained for ephrin-B1 and for CD2-associated protein. When these podocytes were treated in culture with small interfering RNA for ephrin-B1, CD2-associated protein was reduced in the processes, with a remaining faint perinuclear staining. We suggest that ephrin-B1 has a role in maintaining barrier function at the slit diaphragm.

Topics: Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Animals; Antibodies, Anti-Idiotypic; Cells, Cultured; Cytoskeletal Proteins; Ephrin-B1; Ephrin-B2; Female; Gene Expression Regulation; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Molecular Sequence Data; Podocytes; Rats; Rats, Wistar; RNA, Small Interfering

The mechanism by which glucocorticoids govern antiproteinuric effect in nephrotic syndrome remains unknown. Present study examined the protective role of dexamethasone (DEX) in the intracellular trafficking of nephrin under endoplasmic reticulum (ER) stress. Human embryonic kidney-293 cell line expressing a full-length human nephrin was cultured in mediums containing 5.5 or 25 mM glucose with or without DEX. The result revealed that glucose starvation evoked a rapid ER stress leading to formation of underglycosylated nephrin that was remained in the ER as a complex with calreticulin/calnexin. DEX rescued this interfered trafficking through binding to its receptor and stimulating the mitochondrial transcripts and adenosine 5' triphosphate (ATP) production, leading to synthesis of fully glycosylated nephrin. These results suggest that ER-stress in podocytes may cause alteration of nephrin N-glycosylation, which may be an underlying factor in the pathomechanism of the proteinuria in nephrotic syndrome. DEX may restore this imbalance by stimulating expression of mitochondrial genes, resulted in the production of ATP that is essential factor for proper folding machinery aided by the ER chaperones.

Topics: Adenosine Triphosphate; Biological Transport; Blotting, Northern; Blotting, Western; Cell Line; Culture Media; Dexamethasone; Endoplasmic Reticulum; Flow Cytometry; Fluorescent Antibody Technique, Indirect; Fluorescent Dyes; Glucocorticoids; Glucose; Humans; Hydrazines; Kidney Diseases; Membrane Proteins; Microscopy, Confocal; Precipitin Tests; Proteins; Stress, Physiological

The renoprotective potential of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist pioglitazone was explored in an immune model of progressive nephropathy, passive Heymann nephritis (PHN), compared with that of an angiotensin II receptor antagonist, taken as standard therapy for renoprotection. PHN rats received orally vehicle, pioglitazone (10 mg/kg twice daily), or candesartan (1 mg/kg twice daily) from months 2 to 8. Pioglitazone reduced proteinuria as effectively as candesartan and limited renal functional and structural changes. Kidneys from untreated PHN rats showed lower nephrin mRNA and protein than controls, both restored by pioglitazone. The effect was seen both early and late during the course of the disease. Whether the antiproteinuric effect of pioglitazone could be due to its effect on nephrin gene transcription also was investigated. HK-2 cells were transfected with plasmids that harbor the luciferase gene under portions (2-kb or 325-bp) of human nephrin gene promoter that contain putative peroxisome proliferator-responsive elements (PPRE) and incubated with pioglitazone (10 muM). Transcriptional activity of luciferase gene was highly increased by pioglitazone, with the strongest expression achieved with the 325-bp fragment. Increase in luciferase activity was prevented by bisphenol A diglycidyl ether, a PPAR-gamma synthetic antagonist. Electrophoretic mobility shift assay experiments showed a direct interaction of PPAR/retinoid X receptor heterodimers to PPRE present in the enhancer region of the nephrin promoter. In conclusion, pioglitazone exerts an antiproteinuric effect in immune-mediated glomerulonephritis as angiotensin II receptor antagonist does. Enhancement of nephrin gene transcription through specific PPRE in its promoter discloses a novel mechanism of renoprotection for PPAR-gamma agonists.

Topics: Angiotensin Receptor Antagonists; Animals; Benzimidazoles; Biphenyl Compounds; Gene Expression Regulation; Humans; Hypoglycemic Agents; Kidney Diseases; Male; Membrane Proteins; Pioglitazone; PPAR gamma; Proteinuria; Rats; Rats, Sprague-Dawley; Tetrazoles; Thiazolidinediones; Transcription, Genetic

Proteinuria is a poorly understood feature of many acquired renal diseases. Recent studies concerning congenital nephrotic syndromes and findings in genetically modified mice have demonstrated that podocyte molecules make a pivotal contribution to the maintenance of the selective filtration barrier of the normal glomerulus. However, it is unclear what role podocyte molecules play in proteinuria of acquired renal diseases. This study investigated the mRNA and protein expression of several podocyte-associated molecules in acquired renal diseases. Forty-eight patients with various renal diseases were studied, including minimal change nephropathy, focal segmental glomerulosclerosis, IgA nephropathy, lupus nephritis, and diabetic nephropathy, together with 13 kidneys with normal glomerular function. Protein levels of nephrin, podocin, CD2-associated protein, and podocalyxin were investigated using quantitative immunohistochemical assays. Real-time PCR was used to determine the mRNA levels of nephrin, podocin, and podoplanin in microdissected glomeruli. The obtained molecular data were related to electron microscopic ultrastructural changes, in particular foot process width, and to clinical parameters. In most acquired renal diseases, except in IgA nephropathy, a marked reduction was observed at the protein levels of nephrin, podocin, and podocalyxin, whereas an increase of the glomerular mRNA levels of nephrin, podocin, and podoplanin was found, compared with controls. The mean width of the podocyte foot processes was inversely correlated with the protein levels of nephrin (r = -0.443, P < 0.05), whereas it was positively correlated with podoplanin mRNA levels (r = 0.468, P < 0.05) and proteinuria (r = 0.585, P = 0.001). In the diseases studied, the decrease of slit diaphragm proteins was related to the effacement of foot processes and coincided with a rise of the levels of the corresponding mRNA transcripts. This suggests that the alterations in the expression of podocyte-associated molecules represent a compensatory reaction of the podocyte that results from damage associated with proteinuria.

Topics: Adaptor Proteins, Signal Transducing; Adult; Aged; Blotting, Western; CD2 Antigens; Cytoskeletal Proteins; DNA, Complementary; Female; Glomerulonephritis, IGA; Humans; Image Processing, Computer-Assisted; Immunohistochemistry; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Lupus Nephritis; Male; Membrane Proteins; Microscopy, Electron; Microscopy, Fluorescence; Middle Aged; Models, Statistical; Oligonucleotide Probes; Protein Biosynthesis; Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA; RNA, Messenger; Sialoglycoproteins

Recent progress in defining the genetic basis of inherited glomerular diseases has provided a completely new understanding of the glomerular filter of the kidney and has helped illuminate the pathogenesis of acquired and inherited renal proteinuric diseases. Based on the findings of molecular genetics in nephrology we will discuss the current understanding of the glomerular filter and provide an idea how genetic testing in the future may help to guide therapy in patients suffering from nephrotic syndrome and progressive renal failure.

Topics: Adult; Animals; Child; Finland; Genetic Predisposition to Disease; Glomerular Filtration Rate; Glomerulosclerosis, Focal Segmental; Humans; Infant, Newborn; Kidney Diseases; Kidney Failure, Chronic; Kidney Glomerulus; Membrane Proteins; Mice; Mutation; Nephrotic Syndrome; Proteins; Proteinuria

Molecular components of the glomerular filtration mechanism play critical roles in renal diseases. Many of these components are produced during the final stages of differentiation of glomerular visceral epithelial cells, also known as podocytes. While basic domain leucine zipper (bZip) transcription factors of the Maf subfamily have been implicated in cellular differentiation processes, Kreisler (Krml1/MafB), the gene affected in the mouse kreisler (kr) mutation, is known for its role in hindbrain patterning. Here we show that mice homozygous for the kr(enu) mutation develop renal disease and that Kreisler is essential for cellular differentiation of podocytes. Consistent with abnormal podocyte differentiation, kr(enu) homozygotes show proteinuria, and fusion and effacement of podocyte foot processes, which are also observed in the nephrotic syndrome. Kreisler acts during the final stages of glomerular development-the transition between the capillary loop and mature stages-and downstream of the Pod1 basic domain helix-loop-helix transcription factor. The levels of Podocin, the gene mutated in autosomal recessive steroid-resistant nephrotic syndrome (NPHS2), and Nephrin, the gene mutated in congenital nephrotic syndrome of the Finnish type (NPHS1), are slightly reduced in kr(enu)/kr(enu) podocytes. However, these observations alone are unlikely to account for the aberrant podocyte foot process formation. Thus, Kreisler must regulate other unknown genes required for podocyte function and with possible roles in kidney disease.

Topics: Animals; Animals, Newborn; Avian Proteins; Basic Helix-Loop-Helix Transcription Factors; Cell Differentiation; DNA-Binding Proteins; Epithelial Cells; Female; Homozygote; Humans; Intracellular Signaling Peptides and Proteins; Kidney; Kidney Diseases; Kidney Glomerulus; MafB Transcription Factor; Male; Membrane Proteins; Mice; Mice, Mutant Strains; Mutation; Oncogene Proteins; Proteins; Proteinuria; Survival Rate; Trans-Activators; Transcription Factors

The slit-diaphragm protein nephrin is an essential component of the glomerular filtration barrier. It is not clear whether renal injury in patients with acquired proteinuric diseases is associated with altered regulation of the nephrin gene or protein.. We examined expression patterns of nephrin protein and messenger RNA (mRNA) in renal biopsy specimens from patients with minimal lesion (n = 7), focal segmental glomerulosclerosis (FSGS; n = 14), or membranous nephropathy (MN; n = 7) and controls (n = 8) by immunohistochemistry, immunoelectron microscopy, in situ hybridization, and polymerase chain reaction (PCR) amplification of nephrin complementary DNA.. In normal kidney, nephrin staining showed a diffuse interrupted linear pattern along the glomerular basement membrane (GBM). Nephrin staining in minimal lesion specimens showed a finely granular pattern along the GBM and was positive in cell bodies of visceral glomerular epithelial cells. Nephrin staining was most disrupted in FSGS specimens. Immunoelectron microscopy showed that nephrin-specific gold particles were almost absent in effaced foot processes in proteinuric patients. An in situ hybridization study showed significantly decreased nephrin mRNA-expressing cells in cases of FSGS and MN compared with controls. Reverse-transcription PCR showed significantly lower levels of nephrin mRNA in cases of FSGS and MN than controls, but no significant difference between minimal lesion cases and controls. Relative levels of glomerular nephrin mRNA correlated inversely with percentage of glomeruli with sclerosis in proteinuric diseases.. These results suggest that nephrin-expression patterns in proteinuric diseases are different according to the specific glomerular disease or severity of glomerular damage.

Topics: Adolescent; Adult; Child; Child, Preschool; Female; Gene Expression Regulation; Humans; Immunohistochemistry; In Situ Hybridization; Kidney Diseases; Kidney Glomerulus; Male; Membrane Proteins; Microscopy, Immunoelectron; Middle Aged; Protein Biosynthesis; Proteins; Proteinuria; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

Many factors contribute to the pathogenesis of glomerular proteinuria, but no exact molecular mechanisms are known to date. The recently reported protein nephrin, encoded by the NPHS1 gene, appears to be crucial for the integrity of the glomerular filtration barrier.. Immunohistochemistry was used to detect possible changes in glomerular nephrin, and a new proteinuria-associated protein expression was developed in various diagnostic groups of human kidney biopsies.. In normal control kidney, antibodies to intracellular and extracellular nephrin domain showed a typical podocyte pattern of reactivity, while the 18C7 antibody to a normally inaccessible proteinuria-associated epitope was negative. Instead, strong glomerular positivity by 18C7 was seen in membranous glomerulonephropathy, membranoproliferative glomerulonephritis, systemic lupus erythematosus and cryoglobulinemic nephritis, while with antibodies to either intracellular or extracellular nephrin domains, a down-regulation in nephrin expression pattern was shown.. Unmasking or de novo expression of distinct glomerular proteins may be an important feature reflecting the pathophysiological events in these diseases with altered glomerular permeability, while only mild changes in the slit diaphragm protein nephrin appear to take place.

Topics: Amino Acid Sequence; Antibodies, Monoclonal; Biopsy; Epitopes; Gene Expression; Humans; Immunoenzyme Techniques; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Molecular Sequence Data; Proteins; Proteinuria

Glomerular disease is one of the most common causes of end-stage renal failure. Increasing evidence suggests that these glomerulopathies are frequently caused by primary lesions in the renal podocytes. One of the major consequences of podocyte lesions is the accumulation of mesangial matrix in the glomerular basement membrane, a process called glomerulosclerosis. Mesangial sclerosis is one of the most consistent findings in Denys-Drash patients and can be caused by dominant mutations in the Wilms' tumor 1 gene (WT1). The underlying mechanism, however, is poorly understood. WT1 is expressed in the podocytes throughout life, but its function in this cell type is unknown. Combining Wt1-knockout and inducible yeast artificial chromosome transgenic mouse models, we demonstrate that reduced expression levels of WT1 result in either crescentic glomerulonephritis or mesangial sclerosis depending on the gene dosage. Strikingly, the two podocyte-specific genes nphs1 and podocalyxin are dramatically downregulated in mice with decreased levels of Wt1, suggesting that these two genes act downstream of Wt1. Taken together, our data provide genetic evidence that reduced levels of Wt1 are responsible for the pathogenesis of two distinct renal diseases and offer a molecular explanation for the increased occurrence of glomerulosclerosis in patients with WAGR syndrome.

Topics: Animals; Down-Regulation; Glomerular Mesangium; Glomerulonephritis; Glomerulosclerosis, Focal Segmental; Humans; Kidney Diseases; Kidney Glomerulus; Membrane Proteins; Mice; Mice, Knockout; Proteins; Sclerosis; Sialoglycoproteins; WT1 Proteins

The role of the angiotensin type 2 (AT(2)) receptor in the pathogenesis of progressive renal injury has not been previously elucidated. The renal expression of the AT(1) and AT(2) receptors in subtotally nephrectomized rats (STNx) and the effects of AT(2) receptor blockade on renal injury were explored. Reduced renal expression of the AT(1) but not the AT(2) receptor was observed in STNx by reverse transcription-PCR, by in vitro autoradiography, and by immunohistochemical staining. The STNx rats were randomly assigned to AT(1) receptor antagonist valsartan, AT(2) receptor antagonist PD123319, or the combination of both for 4 wk. Increased proteinuria in STNx rats was reduced by PD123319 but to a lesser degree when compared with valsartan. Reduced gene and protein expression of the slit diaphragm protein nephrin was prevented by either valsartan or PD123319. Expression of osteopontin, proliferating cell nuclear antigen, and monocyte/macrophage infiltration was increased in STNx rats and was reduced by both AT(1) and AT(2) receptor antagonists. These effects of AT(2) receptor antagonism were observed in the presence of increased BP in STNx rats. These findings suggest that blockade of the AT(2) receptor alone confers a degree of renal protection; in particular, it seems that the combination of the AT(1) and AT(2) receptor antagonists may confer additive renal effects than either receptor antagonist as monotherapy.

Topics: Angiotensin Receptor Antagonists; Animals; Blood Pressure; Body Weight; Cytoprotection; Diuresis; Gene Expression; Imidazoles; Kidney; Kidney Diseases; Male; Membrane Proteins; Nephrectomy; Organ Size; Proteins; Pyridines; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Receptors, Angiotensin; Tetrazoles; Valine; Valsartan

Nephrin is a podocyte cell adhesion protein located at the slit diaphragm area of the kidney glomerulus. Mutations in the nephrin gene (NPHS1) lead to congenital nephrosis, suggesting that nephrin is essential for the glomerular filtration barrier. This prompted this study of the expression of nephrin in acquired pediatric kidney diseases using in situ hybridization and immunohistochemistry. In situ hybridization for nephrin mRNA was performed in biopsy samples from patients with proteinuria caused by minimal change nephrosis, focal segmental glomerulosclerosis, and membranous nephropathy. The expression of nephrin mRNA was evaluated by grading the signal intensity visually and by counting the number of grains in separate glomeruli. No significant difference was observed in these samples as compared with controls. Immunostaining for nephrin was performed using antibodies directed against extra- and intracellular parts of the molecule. Nephrin staining gave a linear pattern along the glomerular capillary loops. In minimal change nephrosis, focal segmental glomerulosclerosis, and membranous nephropathy, the distribution of nephrin was similar to that in controls. In proliferative forms of glomerulonephritides (Henoch-Schönlein nephritis, IgA nephropathy, postinfectious and membranoproliferative glomerulonephritis), crescents and sclerotic lesions were negative for nephrin, and mesangial proliferation led to a scattered and sparse staining pattern. The staining pattern of nephrin was compared to that of ZO-1, a component of the cytoplasmic face of the slit diaphragm. The distributions of these two proteins in capillary tufts were similar in all disease entities studied. In conclusion, immunohistochemistry and in situ hybridization did not reveal major alterations in the expression of nephrin in proteinuric kidney diseases in children. Further studies are needed for more precise evaluation of the role of nephrin in these diseases.

Topics: Animals; Child; Humans; Immunoenzyme Techniques; In Situ Hybridization; Kidney Diseases; Membrane Proteins; Phosphoproteins; Proteins; Rabbits; RNA, Messenger; Zonula Occludens-1 Protein

Topics: Humans; Kidney; Kidney Diseases; Membrane Proteins; Morphogenesis; Proteins