1
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Wu H, Liu Y, Jia Z, Huang S, Ding G, Zhang A, Yu J. Inhibition of RAC attenuates Adriamycin-induced podocyte injury. Biochem Biophys Res Commun 2024; 709:149807. [PMID: 38552554 DOI: 10.1016/j.bbrc.2024.149807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 03/17/2024] [Accepted: 03/19/2024] [Indexed: 04/13/2024]
Abstract
Minimal Change Disease (MCD), which is associated with podocyte injury, is the leading cause of nephrotic syndrome in children. A considerable number of patients experience relapses and require prolonged use of prednisone and immunosuppressants. Multi-drug resistance and frequent relapses can lead to disease progression to focal and segmental glomerulosclerosis (FSGS). To identify potential targets for therapy of podocyte injury, we examined microarray data of mRNAs in glomerular samples from both MCD patients and healthy donors, obtained from the GEO database. Differentially expressed genes (DEGs) were used to construct the protein-protein interactions (PPI) network through the application of the search tool for the retrieval of interacting genes (STRING) tool. The most connected genes in the network were ranked using cytoHubba. 16 hub genes were selected and validated by qRT-PCR. RAC2 was identified as a potential therapeutic target for further investigation. By downregulating RAC2, Adriamycin (ADR)-induced human podocytes (HPCs) injury was attenuated. EHT-1864, a small molecule inhibitor that targets the RAC (RAC1, RAC2, RAC3) family, proved to be more effective than RAC2 silencing in reducing HPCs injury. In conclusion, our research suggests that EHT-1864 may be a promising new molecular drug candidate for patients with MCD and FSGS.
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Affiliation(s)
- Hao Wu
- Nanjing Key Laboratory of Pediatrics, China; Department of Nephrology, Children's Hospital of Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China
| | - Yujin Liu
- Nanjing Key Laboratory of Pediatrics, China; Department of Nephrology, Children's Hospital of Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China
| | - Zhanjun Jia
- Nanjing Key Laboratory of Pediatrics, China; Department of Nephrology, Children's Hospital of Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China
| | - Songming Huang
- Nanjing Key Laboratory of Pediatrics, China; Department of Nephrology, Children's Hospital of Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China
| | - Guixia Ding
- Nanjing Key Laboratory of Pediatrics, China; Department of Nephrology, Children's Hospital of Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China.
| | - Aihua Zhang
- Nanjing Key Laboratory of Pediatrics, China; Department of Nephrology, Children's Hospital of Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China.
| | - Jing Yu
- Nanjing Key Laboratory of Pediatrics, China; Department of Nephrology, Children's Hospital of Nanjing Medical University, Nanjing, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China.
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2
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Salfi G, Casiraghi F, Remuzzi G. Current understanding of the molecular mechanisms of circulating permeability factor in focal segmental glomerulosclerosis. Front Immunol 2023; 14:1247606. [PMID: 37795085 PMCID: PMC10546017 DOI: 10.3389/fimmu.2023.1247606] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 09/05/2023] [Indexed: 10/06/2023] Open
Abstract
The pathogenetic mechanisms underlying the onset and the post-transplant recurrence of primary focal segmental glomerulosclerosis (FSGS) are complex and remain yet to be fully elucidated. However, a growing body of evidence emphasizes the pivotal role of the immune system in both initiating and perpetuating the disease. Extensive investigations, encompassing both experimental models and patient studies, have implicated T cells, B cells, and complement as crucial actors in the pathogenesis of primary FSGS, with various molecules being proposed as potential "circulating factors" contributing to the disease and its recurrence post kidney-transplantation. In this review, we critically assessed the existing literature to identify essential pathways for a comprehensive characterization of the pathogenesis of FSGS. Recent discoveries have shed further light on the intricate interplay between these mechanisms. We present an overview of the current understanding of the engagement of distinct molecules and immune cells in FSGS pathogenesis while highlighting critical knowledge gaps that require attention. A thorough characterization of these intricate immune mechanisms holds the potential to identify noninvasive biomarkers that can accurately identify patients at high risk of post-transplant recurrence. Such knowledge can pave the way for the development of targeted and personalized therapeutic approaches in the management of FSGS.
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Affiliation(s)
| | - Federica Casiraghi
- Istituto di Ricerche Farmacologiche Mario Negri Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Bergamo, Italy
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3
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Jarockyte G, Stasys M, Poderys V, Buivydaite K, Pleckaitis M, Bulotiene D, Matulionyte M, Karabanovas V, Rotomskis R. Biodistribution of Multimodal Gold Nanoclusters Designed for Photoluminescence-SPECT/CT Imaging and Diagnostic. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12193259. [PMID: 36234387 PMCID: PMC9565908 DOI: 10.3390/nano12193259] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 09/15/2022] [Accepted: 09/16/2022] [Indexed: 05/30/2023]
Abstract
Highly biocompatible nanostructures for multimodality imaging are critical for clinical diagnostics improvements in the future. Combining optical imaging with other techniques may lead to important advances in diagnostics. The purpose of such a system would be to combine the individual advantages of each imaging method to provide reliable and accurate information at the site of the disease bypassing the limitations of each. The aim of the presented study was to evaluate biodistribution of the biocompatible technetium-99m labelled bovine serum albumin-gold nanoclusters (99mTc-BSA-Au NCs) as photoluminescence-SPECT/CT agent in experimental animals. It was verified spectroscopically that radiolabelling with 99mTc does not influence the optical properties of BSA-Au NCs within the synthesized 99mTc-BSA-Au NCs bioconjugates. Biodistribution imaging of the 99mTc-BSA-Au NCs in Wistar rats was performed using a clinical SPECT/CT system. In vivo imaging of Wistar rats demonstrated intense cardiac blood pool activity, as well as rapid blood clearance and accumulation in the kidneys, liver, and urinary bladder. Confocal images of kidney, liver and spleen tissues revealed no visible uptake indicating that the circulation lifetime of 99mTc-BSA-Au NCs in the bloodstream might be too short for accumulation in these tissues. The cellular uptake of 99mTc-BSA-Au NCs in kidney cells was also delayed and substantial accumulation was observed only after 24-h incubation. Based on our experiments, it was concluded that 99mTc-BSA-Au NCs could be used as a contrast agent and shows promise as potential diagnostic agents for bloodstream imaging of the excretory organs in vivo.
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Affiliation(s)
- Greta Jarockyte
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
- Life Sciences Center, Vilnius University, LT-10257 Vilnius, Lithuania
| | - Marius Stasys
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
| | - Vilius Poderys
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
| | - Kornelija Buivydaite
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
- Life Sciences Center, Vilnius University, LT-10257 Vilnius, Lithuania
| | - Marijus Pleckaitis
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
- Life Sciences Center, Vilnius University, LT-10257 Vilnius, Lithuania
| | - Danute Bulotiene
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
| | - Marija Matulionyte
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
| | - Vitalijus Karabanovas
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
- Department of Chemistry and Bioengineering, Vilnius Gediminas Technical University, LT-10223 Vilnius, Lithuania
| | - Ricardas Rotomskis
- Biomedical Physics Laboratory, National Cancer Institute, LT-08406 Vilnius, Lithuania
- Laser Research Center, Faculty of Physics, Vilnius University, LT-10223 Vilnius, Lithuania
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4
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Hatakeyama S, Tojo A, Satonaka H, Yamada NO, Senda T, Ishimitsu T. Decreased Podocyte Vesicle Transcytosis and Albuminuria in APC C-Terminal Deficiency Mice with Puromycin-Induced Nephrotic Syndrome. Int J Mol Sci 2021; 22:ijms222413412. [PMID: 34948207 PMCID: PMC8708520 DOI: 10.3390/ijms222413412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/09/2021] [Accepted: 12/10/2021] [Indexed: 11/16/2022] Open
Abstract
In minimal change nephrotic syndrome, podocyte vesicle transport is enhanced. Adenomatous polyposis coli (APC) anchors microtubules to cell membranes and plays an important role in vesicle transport. To clarify the role of APC in vesicle transport in podocytes, nephrotic syndrome was induced by puromycin amino nucleoside (PAN) injection in mice expressing APC1638T lacking the C-terminal of microtubule-binding site (APC1638T mouse); this was examined in renal tissue changes. The kidney size and glomerular area of APC1638T mice were reduced (p = 0.014); however, the number of podocytes was same between wild-type (WT) mice and APC1638T mice. The ultrastructure of podocyte foot process was normal by electron microscopy. When nephrotic syndrome was induced, the kidneys of WT+PAN mice became swollen with many hyaline casts, whereas these changes were inhibited in the kidneys of APC1638T+PAN mice. Electron microscopy showed foot process effacement in both groups; however, APC1638T+PAN mice had fewer vesicles in the basal area of podocytes than WT+PAN mice. Cytoplasmic dynein-1, a motor protein for vesicle transport, and α-tubulin were significantly reduced in APC1638T+PAN mice associated with suppressed urinary albumin excretion compared to WT+PAN mice. In conclusion, APC1638T mice showed reduced albuminuria associated with suppressed podocyte vesicle transport when minimal change nephrotic syndrome was induced.
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Affiliation(s)
- Saaya Hatakeyama
- Department of Nephrology & Hypertension, Dokkyo Medical University, Tochigi 321-0293, Japan; (S.H.); (H.S.); (T.I.)
| | - Akihiro Tojo
- Department of Nephrology & Hypertension, Dokkyo Medical University, Tochigi 321-0293, Japan; (S.H.); (H.S.); (T.I.)
- Correspondence: ; Tel.: +81-282-86-1111
| | - Hiroshi Satonaka
- Department of Nephrology & Hypertension, Dokkyo Medical University, Tochigi 321-0293, Japan; (S.H.); (H.S.); (T.I.)
| | - Nami O. Yamada
- Department of Anatomy, Gifu University, Gifu 501-1193, Japan; (N.O.Y.); (T.S.)
| | - Takao Senda
- Department of Anatomy, Gifu University, Gifu 501-1193, Japan; (N.O.Y.); (T.S.)
| | - Toshihiko Ishimitsu
- Department of Nephrology & Hypertension, Dokkyo Medical University, Tochigi 321-0293, Japan; (S.H.); (H.S.); (T.I.)
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5
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Moriyama T, Hasegawa F, Miyabe Y, Akiyama K, Karasawa K, Uchida K, Nitta K. Intracellular trafficking pathway of albumin in glomerular epithelial cells. Biochem Biophys Res Commun 2021; 574:97-103. [PMID: 34450430 DOI: 10.1016/j.bbrc.2021.08.043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 08/18/2021] [Indexed: 10/20/2022]
Abstract
The intracellular trafficking pathway of albumin in podocytes remains controversial. We therefore analysed albumin endocytosis through caveolae, subsequent transcytosis, and exocytosis. In Western blot and immunofluorescence analysis in vitro, methyl-beta-cyclodextrin (MBCD) treatment significantly decreased the expression of caveolin-1 and albumin in cultured human podocytes after incubation with albumin; additionally, MBCD interfered with albumin endocytosis through caveolae in the experiment using Transwell plates. In the immunofluorescence analysis, albumin was incubated with cultured human podocytes, and colocalisation analysis with organelles and cytoskeletons in the podocytes showed that albumin particles colocalised with caveolin-1 and Fc-receptor but not clathrin in endocytosis, colocalised with actin cytoskeleton but not microtubules in transcytosis, and colocalised with early endosomes and lysosomes but not proteasome, endoplasmic reticulum, or Golgi apparatus. In the electron microscopic analysis of podocytes in nephrotic syndrome model mice, gold-labelled albumin was shown as endocytosis, transcytosis, and exocytosis with caveolae. These results indicate the intracellular trafficking of albumin through podocytes. Albumin enters through caveolae with the Fc-receptor, moves along actin, and reaches the early endosome, where some of them are sorted for lysosomal degradation, and others are directly transported outside the cells through exocytosis. This intracellular pathway may be a new aetiological hypothesis for albuminuria.
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Affiliation(s)
- Takahito Moriyama
- Department of Nephrology, Tokyo Women's Medical University, Tokyo, Japan.
| | - Fumio Hasegawa
- Department of Nephrology, Tokyo Women's Medical University, Tokyo, Japan.
| | - Yoei Miyabe
- Department of Nephrology, Tokyo Women's Medical University, Tokyo, Japan.
| | - Kenichi Akiyama
- Department of Nephrology, Tokyo Women's Medical University, Tokyo, Japan.
| | - Kazunori Karasawa
- Department of Nephrology, Tokyo Women's Medical University, Tokyo, Japan.
| | - Keiko Uchida
- Department of Nephrology, Tokyo Women's Medical University, Tokyo, Japan.
| | - Kosaku Nitta
- Department of Nephrology, Tokyo Women's Medical University, Tokyo, Japan.
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6
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Molecular determinants of protein reabsorption in the amphibian kidneys. Acta Histochem 2021; 123:151760. [PMID: 34303296 DOI: 10.1016/j.acthis.2021.151760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 06/28/2021] [Accepted: 07/11/2021] [Indexed: 11/23/2022]
Abstract
Participation of molecular determinants of endocytosis in the processes of glomerular filtration and tubular reabsorption of albumin and lysozyme in the mesonephros of grass frogs (Rana temporaria L.), lake frogs (Rana ridibunda P.), and newts (Triturus vulgaris L.) is investigated. In all studied species, the constitutive expression of endocytic receptors in proximal tubule (PT) cells is established using immunofluorescence microscopy and immunoblotting. The certain stages of lysozyme and albumin endocytosis involving megalin/LRP2, cubilin, clathrin and protein Rab11 are detailed, and the central role of ligand-induced megalin/LRP2 activity in this process is shown. Increased ligand-induced expression for clathrin and Rab11was also found. In grass frogs, the different patterns of endocytic receptors and both absorbed proteins in the initial parts of proximal tubules suggest the proximo-distal specialization of absorptive processes along these tubule segments, similar to this in more complex mammalian nephrons. This data, as well as the revealed peculiarities of ligand-receptor interactions during intracellular trafficking of proteins prove that megalin is mainly involved in the absorption of lysozyme. At the same time, albumin absorption is mediated by both receptors, or cubilin contributes the most. The detection of endocytic receptor in glomerular structural elements in frogs and newts suggests the participation of filtration barrier components in endocytosis of filterable proteins. The results represent a new contribution to the study of the fundamental mechanisms of renal protein uptake in the amphibian mesonephros as a more primitive kidney compared to mammalian metanephros.
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7
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Prutskova NP, Seliverstova EV. The Effect of Protein Overload on
Reabsorption of Different Proteins in Frog Renal Tubules. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021010105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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8
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Candelier JJ, Lorenzo HK. Idiopathic nephrotic syndrome and serum permeability factors: a molecular jigsaw puzzle. Cell Tissue Res 2019; 379:231-243. [PMID: 31848752 DOI: 10.1007/s00441-019-03147-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 11/19/2019] [Indexed: 12/14/2022]
Abstract
Nephrotic syndrome is traditionally defined using the triad of edema, hypoalbuminemia, and proteinuria, but this syndrome is very heterogeneous and difficult to clarify. Its idiopathic form (INS) is probably the most harmful and essentially comprises two entities: minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). We will consider some hypotheses regarding the mechanisms underlying INS: (i) the presence of several glomerular permeability factors in the sera of patients that alter the morphology and function of podocytes leading to proteinuria, (ii) the putative role of immune cells. Thanks to recent data, our understanding of these disorders is evolving towards a more multifactorial origin. In this context, circulating factors may be associated according to sequential kinetic mechanisms or micro-environmental changes that need to be determined. In addition, the resulting proteinuria may trigger more proteinuria enhancing the glomerular destabilization.
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Affiliation(s)
- Jean-Jacques Candelier
- INSERM U1197, Hôpital Paul Brousse, 14 Avenue Paul Vaillant Couturier, 94800, Villejuif, France.,Université Paris-Saclay, Campus Universitaire d'Orsay, 91405, Orsay, France
| | - Hans-Kristian Lorenzo
- INSERM U1197, Hôpital Paul Brousse, 14 Avenue Paul Vaillant Couturier, 94800, Villejuif, France. .,Université Paris-Saclay, Campus Universitaire d'Orsay, 91405, Orsay, France. .,Service de Néphrologie, Hôpital Bicêtre, Faculté de Médecine Paris-Saclay, 94270, Le Kremlin-Bicêtre, France.
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9
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Mechanism Underlying Selective Albuminuria in Minimal Change Nephrotic Syndrome. Int J Nephrol 2019; 2019:5859102. [PMID: 31781392 PMCID: PMC6874928 DOI: 10.1155/2019/5859102] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 09/24/2019] [Indexed: 01/04/2023] Open
Abstract
As water and solutes are filtered through the slit membrane, it is an a priori concept that a slit membrane is an essential filtration barrier for proteins, including albumin. However, in cases of minimal change nephrotic syndrome, the number of slit membranes is reduced by the foot process effacement and tight junction-like cell adhesion. Furthermore, albumin endocytosis is enhanced in the podocytes under condition of minimal change disease, and albumin is selectively transported by the albumin receptor FcRn. Suppressing the endocytosis of albumin with anti-FcRn antibody decreases the urinary protein level. The expression of motor molecules, such as cytoplasmic dynein 1 and myosin IX, is increased in the podocytes under conditions of minimal change nephrotic syndrome, suggesting the enhanced transport of vesicles containing albumin. Podocyte vesicle transport may play an important role in the pathology of selective albuminuria in cases of nephrotic syndrome.
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Gianesello L, Anglani F, Del Prete D. Protein uptake at glomerular level: is it just the work of podocytes? Nephrol Dial Transplant 2019; 35:1675-1677. [DOI: 10.1093/ndt/gfz127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Indexed: 11/14/2022] Open
Affiliation(s)
- Lisa Gianesello
- Clinical Nephrology Unit, Department of Medicine DIMED, Kidney Histomorphology and Molecular Biology Laboratory, University of Padua, Padua, Italy
| | - Franca Anglani
- Clinical Nephrology Unit, Department of Medicine DIMED, Kidney Histomorphology and Molecular Biology Laboratory, University of Padua, Padua, Italy
| | - Dorella Del Prete
- Clinical Nephrology Unit, Department of Medicine DIMED, Kidney Histomorphology and Molecular Biology Laboratory, University of Padua, Padua, Italy
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11
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Differential trafficking of albumin and IgG facilitated by the neonatal Fc receptor in podocytes in vitro and in vivo. PLoS One 2019; 14:e0209732. [PMID: 30811433 PMCID: PMC6392300 DOI: 10.1371/journal.pone.0209732] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 02/12/2019] [Indexed: 12/26/2022] Open
Abstract
Proteinuria is strongly associated with kidney disease progression but the mechanisms underlying podocyte handling of serum proteins such as albumin and IgG remain to be elucidated. We have previously shown that albumin and IgG are transcytosed by podocytes in vitro. In other epithelial cells, the neonatal Fc receptor (FcRn) is required to salvage albumin and IgG from the degradative pathway thereby allowing these proteins to be transcytosed or recycled. Here we directly examine the role of FcRn in albumin and IgG trafficking in podocytes by studying handling of these proteins in FcRn knockout (KO) podocytes in vitro and in a podocyte-specific FcRn knockout mice in vivo. In vitro, we find that knockout of FcRn leads to IgG accumulation in podocytes but does not alter albumin trafficking. Similarly, in vivo, podocyte-specific knockout of FcRn does not result in albumin accumulation in podocytes in vivo as measured by mean albumin fluorescence intensity whereas these mice demonstrate significant intraglomerular accumulation of IgG over time. In addition we find that podocyte-specific FcRn KO mice demonstrate mesangial expansion as they age and activation of mesangial cells as demonstrated by increased expression of α-smooth muscle actin. Taken together, these results suggest that trafficking pathways for albumin and IgG differ in podocytes and that sustained disruption of trafficking of plasma proteins alters glomerular structure.
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12
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Liu D, Lv LL. New Understanding on the Role of Proteinuria in Progression of Chronic Kidney Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1165:487-500. [PMID: 31399981 DOI: 10.1007/978-981-13-8871-2_24] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Proteinuria is identified as an important marker and risk factor of progression in chronic kidney disease. However, the precise mechanism of action in the progress of chronic kidney disease is still unclear. Mesangial toxicity from specific filtered compounds such as albumin-bound fatty acids and transferrin/iron, tubular overload and hyperplasia, and induction of proinflammatory molecules such as MCP-1 and inflammatory cytokines are some of the proposed mechanisms. Reversing intraglomerular hypertension with protein restriction or antihypertensive therapy may be beneficial both by diminishing hemodynamic injury to the glomeruli and by reducing protein filtration. Therefore, understanding proteinuria and its role in renal tubular interstitial inflammation and fibrosis is of great significance for the study of renal protective therapy, such as antiproteinuric treatments, and delaying the progression of chronic renal disease.
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Affiliation(s)
- Dan Liu
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, China
| | - Lin-Li Lv
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, China.
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13
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Intracellular albumin overload elicits endoplasmic reticulum stress and PKC-delta/p38 MAPK pathway activation to induce podocyte apoptosis. Sci Rep 2018; 8:18012. [PMID: 30573754 PMCID: PMC6301950 DOI: 10.1038/s41598-018-36933-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 11/29/2018] [Indexed: 12/22/2022] Open
Abstract
Podocyte injury is closely related to proteinuria and the progression of chronic kidney disease (CKD). Currently, there is no conclusive understanding about the mechanisms involved in albumin overload and podocyte apoptosis response. In this study, we sought to explore the ways by which intracellular albumin can mediate podocyte apoptosis. Here, immortalized mouse podocytes were treated with bovine serum albumin (BSA) at different times and concentrations, in the presence or absence of SB203580 (0.1 µM, inhibitor of mitogen-activated-protein kinase – p38MAPK). Using immunofluorescence images, flow cytometry and immunoblotting, we observed a time-dependent intracellular accumulation of fluorescent albumin-FITC-BSA, followed by concentration-and time-dependent effect of intracellular albumin overload on podocyte apoptosis, which was mediated by increased expression of the chaperone glucose-regulated-protein 78 (GRP 78) and phosphorylated inositol-requiring enzyme 1 alpha (pIRE1-α), as well as protein kinase C delta (PKC-δ), p38MAPK and cleaved caspase 12 expression. SB203580 prevented the cleavage of caspase 12 and the albumin-mediated podocyte apoptosis. These results suggest that intracellular albumin overload is associated with endoplasmic reticulum (ER) stress and upregulation of PKC-δ/p38MAPK/caspase 12 pathway, which may be a target for future therapeutic of albumin-induced podocyte apoptosis.
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14
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Tojo A, Hatakeyama S, Kinugasa S, Fukuda S, Sakai T. Enhanced podocyte vesicle transport in the nephrotic rat. Med Mol Morphol 2017; 50:86-93. [DOI: 10.1007/s00795-016-0151-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 12/19/2016] [Indexed: 01/27/2023]
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15
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Sun J, Hultenby K, Axelsson J, Nordström J, He B, Wernerson A, Lindström K. Proximal Tubular Expression Patterns of Megalin and Cubilin in Proteinuric Nephropathies. Kidney Int Rep 2017; 2:721-732. [PMID: 29142988 PMCID: PMC5678615 DOI: 10.1016/j.ekir.2017.02.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 02/09/2017] [Accepted: 02/21/2017] [Indexed: 01/10/2023] Open
Abstract
Introduction Receptor-mediated endocytosis is responsible for protein reabsorption in the proximal tubules. For albumin this process involves at least 2 interacting receptors, megalin and cubilin. Albumin is not usually present in the urine, indicating a highly efficient tubular reuptake under physiological conditions. However, early appearance of albuminuria may mean that the tubular system is overwhelmed by large quantities of albumin or that the function is impaired. Methods To better understand the physiological role of megalin and cubilin in human renal disease, renal biopsies from 15 patients with a range of albuminuria and 3 healthy living donors were analyzed for proximal tubular expression of megalin and cubilin using immunohistochemistry (IHC) and semiquantitative immune-electron microscopy. Their expression in proteinuric zebrafish was also studied. Results Megalin and cubilin were expressed in brush border and cytoplasmic vesicles. Patients with microalbuminuric IgA nephropathy and thin membrane disease had significantly higher megalin in proximal tubules, whereas those with macro- or nephrotic-range albuminuria had unchanged levels. Cubilin expression was significantly higher in all patients. In a proteinuric zebrafish nphs2 knockdown model, we found a dose-dependent increase in the expression of tubular megalin and cubilin in response to tubular protein uptake. Discussion Megalin and cubilin show different expression patterns in different human diseases, which indicates that the 2 tubular proteins differently cooperate in cleaning up plasma proteins in kidney tubules.
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Affiliation(s)
- Jia Sun
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Kjell Hultenby
- Division of Clinical Research Center, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Jonas Axelsson
- Division of Matrix Biology, Department of Medical Biochemistry and Biophysics; Karolinska Institutet, Stockholm, Sweden.,Department Clinical Immunology, Karolinska University Hospital, Stockholm, Sweden
| | - Johan Nordström
- Division of Transplantation, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.,Department of Transplant Surgery, Karolinska University Hospital, Stockholm, Sweden
| | - Bing He
- Division of Matrix Biology, Department of Medical Biochemistry and Biophysics; Karolinska Institutet, Stockholm, Sweden
| | - Annika Wernerson
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.,Department of Pathology, Karolinska University Hospital, Stockholm, Sweden
| | - Karin Lindström
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.,Department of Nephrology, Karolinska University Hospital, Stockholm, Sweden
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16
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Tojo A, Kinugasa S, Fujita T, Wilcox CS. A local renal renin-angiotensin system activation via renal uptake of prorenin and angiotensinogen in diabetic rats. Diabetes Metab Syndr Obes 2016; 9:1-10. [PMID: 26848273 PMCID: PMC4723098 DOI: 10.2147/dmso.s91245] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The mechanism of activation of local renal renin-angiotensin system (RAS) has not been clarified in diabetes mellitus (DM). We hypothesized that the local renal RAS will be activated via increased glomerular filtration and tubular uptake of prorenin and angiotensinogen in diabetic kidney with microalbuminuria. Streptozotocin (STZ)-induced DM and control rats were injected with human prorenin and subsequently with human angiotensinogen. Human prorenin uptake was increased in podocytes, proximal tubules, macula densa, and cortical collecting ducts of DM rats where prorenin receptor (PRR) was expressed. Co-immunoprecipitation of kidney homogenates in DM rats revealed binding of human prorenin to the PRR and to megalin. The renal uptake of human angiotensinogen was increased in DM rats at the same nephron sites as prorenin. Angiotensin-converting enzyme was increased in podocytes, but decreased in the proximal tubules in DM rats, which may have contributed to unchanged renal levels of angiotensin despite increased angiotensinogen. The systolic blood pressure increased more after the injection of 20 μg of angiotensinogen in DM rats than in controls, accompanied by an increased uptake of human angiotensinogen in the vascular endothelium. In conclusion, endocytic uptake of prorenin and angiotensinogen in the kidney and vasculature in DM rats was contributed to increased tissue RAS and their pressor response to angiotensinogen.
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Affiliation(s)
- Akihiro Tojo
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
- Correspondence: Akihiro Tojo, Division of Nephrology and Endocrinology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan, Tel +81 3 3815 5411 ext 37219, Fax +81 3 3814 0021, Email
| | - Satoshi Kinugasa
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
| | - Toshiro Fujita
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan
| | - Christopher S Wilcox
- Division of Nephrology and Hypertension, Center for Hypertension, Kidney and Vascular Research, Georgetown University, Washington, DC, USA
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17
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Eriguchi M, Yotsueda R, Torisu K, Kawai Y, Hasegawa S, Tanaka S, Noguchi H, Masutani K, Kitazono T, Tsuruya K. Assessment of urinary angiotensinogen as a marker of podocyte injury in proteinuric nephropathies. Am J Physiol Renal Physiol 2015; 310:F322-33. [PMID: 26632605 DOI: 10.1152/ajprenal.00260.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 12/01/2015] [Indexed: 01/13/2023] Open
Abstract
Urinary protein (UP) is widely used as a clinical marker for podocyte injury; however, not all proteinuric nephropathies fit this model. We previously described the elevation of urinary angiotensinogen (AGT) accompanied by AGT expression by injured podocytes in a nitric oxide inhibition rat model (Eriguchi M, Tsuruya K, Haruyama N, Yamada S, Tanaka S, Suehiro T, Noguchi H, Masutani K, Torisu K, Kitazono T. Kidney Int 87: 116-127, 2015). In this report, we performed the human and animal studies to examine the significance and origin of urinary AGT. In the human study, focal segmental glomerulosclerosis (FSGS) patients presented with higher levels of urinary AGT, corrected by UP, than minimal-change disease (MCD) patients. Furthermore, AGT was evident in podocin-negative glomerular segmental lesions. We also tested two different nephrotic models induced by puromycin aminonucleoside in Wistar rats. The urinary AGT/UP ratio and AGT protein and mRNA expression in sieved glomeruli from FSGS rats were significantly higher than in MCD rats. The presence of AGT at injured podocytes in FSGS rats was detected by immunohistochemistry and immunoelectron microscopy. Finally, we observed the renal tissue and urinary metabolism of exogenous injected human recombinant AGT (which is not cleaved by rodent renin) in FSGS and control rats. Significant amounts of human AGT were detected in the urine of FSGS rats, but not of control rats. Immunostaining for rat and human AGT identified that only rat AGT was detected in injured podocytes, and filtered human AGT was seen in superficial proximal tubules, but not in injured podocytes, suggesting AGT generation by injured podocytes. In conclusion, the urinary AGT/UP ratio represents a novel specific marker of podocyte injury.
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Affiliation(s)
- Masahiro Eriguchi
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Ryusuke Yotsueda
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Kumiko Torisu
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Yasuhiro Kawai
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Shoko Hasegawa
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Shigeru Tanaka
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Hideko Noguchi
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Kosuke Masutani
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Takanari Kitazono
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
| | - Kazuhiko Tsuruya
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and Department of Integrated Therapy for Chronic Kidney Disease, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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18
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Dobrinskikh E, Lewis L, Brian Doctor R, Okamura K, Lee MG, Altmann C, Faubel S, Kopp JB, Blaine J. Shank2 Regulates Renal Albumin Endocytosis. Physiol Rep 2015; 3:e12510. [PMID: 26333830 PMCID: PMC4600376 DOI: 10.14814/phy2.12510] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 07/22/2015] [Accepted: 07/26/2015] [Indexed: 12/22/2022] Open
Abstract
Albuminuria is a strong and independent predictor of kidney disease progression but the mechanisms of albumin handling by the kidney remain to be fully defined. Previous studies have shown that podocytes endocytose albumin. Here we demonstrate that Shank2, a large scaffolding protein originally identified at the neuronal postsynaptic density, is expressed in podocytes in vivo and in vitro and plays an important role in albumin endocytosis in podocytes. Knockdown of Shank2 in cultured human podocytes decreased albumin uptake, but the decrease was not statistically significant likely due to residual Shank2 still present in the knockdown podocytes. Complete knockout of Shank2 in podocytes significantly diminished albumin uptake in vitro. Shank2 knockout mice develop proteinuria by 8 weeks of age. To examine albumin handling in vivo in wild-type and Shank2 knockout mice we used multiphoton intravital imaging. While FITC-labeled albumin was rapidly seen in the renal tubules of wild-type mice after injection, little albumin was seen in the tubules of Shank2 knockout mice indicating dysregulated renal albumin trafficking in the Shank2 knockouts. We have previously found that caveolin-1 is required for albumin endocytosis in cultured podocytes. Shank2 knockout mice had significantly decreased expression and altered localization of caveolin-1 in podocytes suggesting that disruption of albumin endocytosis in Shank2 knockouts is mediated via caveolin-1. In summary, we have identified Shank2 as another component of the albumin endocytic pathway in podocytes.
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Affiliation(s)
| | - Linda Lewis
- University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | | | - Kayo Okamura
- University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Min Goo Lee
- Department of Pharmacology, Severance Biomedical Science Institute Yonsei University College of Medicine, Seoul, Korea
| | | | - Sarah Faubel
- University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Jeffrey B Kopp
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland
| | - Judith Blaine
- University of Colorado Anschutz Medical Campus, Aurora, Colorado
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19
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Schießl IM, Hammer A, Kattler V, Gess B, Theilig F, Witzgall R, Castrop H. Intravital Imaging Reveals Angiotensin II-Induced Transcytosis of Albumin by Podocytes. J Am Soc Nephrol 2015; 27:731-44. [PMID: 26116357 DOI: 10.1681/asn.2014111125] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 05/11/2015] [Indexed: 11/03/2022] Open
Abstract
Albuminuria is a hallmark of kidney disease of various etiologies and usually caused by deterioration of glomerular filtration barrier integrity. We recently showed that angiotensin II (Ang II) acutely increases albumin filtration in the healthy kidney. Here, we used intravital microscopy to assess the effects of Ang II on podocyte function in rats. Acute infusion of 30, 60, or 80 ng/kg per minute Ang II enhanced the endocytosis of albumin by activation of the type 1 Ang II receptor and resulted in an average (±SEM) of 3.7±2.2, 72.3±18.6 (P<0.001), and 239.4±34.6 µm(3) (P<0.001) albumin-containing vesicles per glomerulus, respectively, compared with none at baseline or 10 ng/kg per minute Ang II. Immunostaining of Ang II-infused kidneys confirmed the presence of albumin-containing vesicles, which colocalized with megalin, in podocin-positive cells. Furthermore, podocyte endocytosis of albumin was markedly reduced in the presence of gentamicin, a competitive inhibitor of megalin-dependent endocytosis. Ang II infusion increased the concentration of albumin in the subpodocyte space, a potential source for endocytic protein uptake, and gentamicin further increased this concentration. Some endocytic vesicles were acidified and colocalized with LysoTracker. Most vesicles migrated from the capillary to the apical aspect of the podocyte and were eventually released into the urinary space. This transcytosis accounted for approximately 10% of total albumin filtration. In summary, the transcellular transport of proteins across the podocyte constitutes a new pathway of glomerular protein filtration. Ang II enhances the endocytosis and transcytosis of plasma albumin by podocytes, which may eventually impair podocyte function.
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Affiliation(s)
| | | | | | | | - Franziska Theilig
- Department of Medicine, University of Fribourg, Fribourg, Switzerland
| | - Ralph Witzgall
- Molecular and Cellular Anatomy, University of Regensburg, Regensburg, Germany; and
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20
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Thi-Kim Vu H, Rink JC, McKinney SA, McClain M, Lakshmanaperumal N, Alexander R, Sánchez Alvarado A. Stem cells and fluid flow drive cyst formation in an invertebrate excretory organ. eLife 2015; 4:e07405. [PMID: 26057828 PMCID: PMC4500094 DOI: 10.7554/elife.07405] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 06/09/2015] [Indexed: 12/29/2022] Open
Abstract
Cystic kidney diseases (CKDs) affect millions of people worldwide. The defining pathological features are fluid-filled cysts developing from nephric tubules due to defective flow sensing, cell proliferation and differentiation. The underlying molecular mechanisms, however, remain poorly understood, and the derived excretory systems of established invertebrate models (Caenorhabditis elegans and Drosophila melanogaster) are unsuitable to model CKDs. Systematic structure/function comparisons revealed that the combination of ultrafiltration and flow-associated filtrate modification that is central to CKD etiology is remarkably conserved between the planarian excretory system and the vertebrate nephron. Consistently, both RNA-mediated genetic interference (RNAi) of planarian orthologues of human CKD genes and inhibition of tubule flow led to tubular cystogenesis that share many features with vertebrate CKDs, suggesting deep mechanistic conservation. Our results demonstrate a common evolutionary origin of animal excretory systems and establish planarians as a novel and experimentally accessible invertebrate model for the study of human kidney pathologies.
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Affiliation(s)
- Hanh Thi-Kim Vu
- Stowers Institute for Medical Research, Kansas City, United States
- Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, United States
| | - Jochen C Rink
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Sean A McKinney
- Stowers Institute for Medical Research, Kansas City, United States
| | - Melainia McClain
- Stowers Institute for Medical Research, Kansas City, United States
| | | | | | - Alejandro Sánchez Alvarado
- Stowers Institute for Medical Research, Kansas City, United States
- Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, United States
- Howard Hughes Medical Institute, Stowers Institute for Medical Research, Kansas City, United States
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21
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Chung JJ, Huber TB, Gödel M, Jarad G, Hartleben B, Kwoh C, Keil A, Karpitskiy A, Hu J, Huh CJ, Cella M, Gross RW, Miner JH, Shaw AS. Albumin-associated free fatty acids induce macropinocytosis in podocytes. J Clin Invest 2015; 125:2307-16. [PMID: 25915582 DOI: 10.1172/jci79641] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 03/19/2015] [Indexed: 01/26/2023] Open
Abstract
Podocytes are specialized epithelial cells in the kidney glomerulus that play important structural and functional roles in maintaining the filtration barrier. Nephrotic syndrome results from a breakdown of the kidney filtration barrier and is associated with proteinuria, hyperlipidemia, and edema. Additionally, podocytes undergo changes in morphology and internalize plasma proteins in response to this disorder. Here, we used fluid-phase tracers in murine models and determined that podocytes actively internalize fluid from the plasma and that the rate of internalization is increased when the filtration barrier is disrupted. In cultured podocytes, the presence of free fatty acids (FFAs) associated with serum albumin stimulated macropinocytosis through a pathway that involves FFA receptors, the Gβ/Gγ complex, and RAC1. Moreover, mice with elevated levels of plasma FFAs as the result of a high-fat diet were more susceptible to Adriamycin-induced proteinuria than were animals on standard chow. Together, these results support a model in which podocytes sense the disruption of the filtration barrier via FFAs bound to albumin and respond by enhancing fluid-phase uptake. The response to FFAs may function in the development of nephrotic syndrome by amplifying the effects of proteinuria.
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22
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Tojo A, Hatakeyama S, Kinugasa S, Nangaku M. Angiotensin receptor blocker telmisartan suppresses renal gluconeogenesis during starvation. Diabetes Metab Syndr Obes 2015; 8:103-13. [PMID: 25709483 PMCID: PMC4335621 DOI: 10.2147/dmso.s78771] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The kidney plays an important role in gluconeogenesis during starvation. To clarify the anti-diabetic action of angiotensin receptor blockers, we examined the effects of telmisartan on the sodium-glucose co-transporters (SGLT) and the pathways of renal gluconeogenesis in streptozotocin-induced diabetes mellitus (DM) rats. At 4 weeks, the DM rats treated with/without telmisartan for 2 weeks and normal control rats were used for the study after a 24-hour fast. SGLT2 expressed on the brush border membrane of the proximal convoluted tubules increased in the DM rats, but decreased in the rats treated with telmisartan. The expression of restriction enzymes of gluconeogenesis, glucose-6-phosphatase, and phosphoenolpyruvate carboxykinase increased in the proximal tubules in the DM rats, whereas these enzymes decreased in the kidneys of the rats treated with telmisartan. The elevated cytoplasmic glucose-6-phosphate and glucose levels in the kidney of DM rats significantly decreased in those treated with telmisartan, whereas those levels in the liver did not show significant change. Meanwhile, the high plasma glucose levels in the DM rats during the intravenous insulin tolerance tests were ameliorated by telmisartan. The increased fasting plasma glucose levels after 24 hours of starvation in the DM rats thus returned to the control levels by telmisartan treatment. In conclusion, the increased renal SGLT2 expression, elevated renal gluconeogenesis enzymes and extent of insulin-resistance in the DM rats were ameliorated by telmisartan therapy, thus resulting in decreased plasma glucose levels after 24 hours of fasting.
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Affiliation(s)
- Akihiro Tojo
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
- Correspondence: Akihiro Tojo, Division of Nephrology and Endocrinology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan, Tel +81 3 3815 5411 ext 37219, Fax +81 3 3814 0021, Email
| | - Saaya Hatakeyama
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
| | - Satoshi Kinugasa
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
| | - Masaomi Nangaku
- Division of Nephrology and Endocrinology, The University of Tokyo, Tokyo, Japan
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23
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Pawluczyk IZA, Pervez A, Ghaderi Najafabadi M, Saleem MA, Topham PS. The effect of albumin on podocytes: the role of the fatty acid moiety and the potential role of CD36 scavenger receptor. Exp Cell Res 2014; 326:251-8. [PMID: 24815572 DOI: 10.1016/j.yexcr.2014.04.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 04/07/2014] [Accepted: 04/21/2014] [Indexed: 10/25/2022]
Abstract
Evidence is emerging that podocytes are able to endocytose proteins such as albumin using kinetics consistent with a receptor-mediated process. To date the role of the fatty acid moiety on albumin uptake kinetics has not been delineated and the receptor responsible for uptake is yet to be identified. Albumin uptake studies were carried out on cultured human podocytes exposed to FITC-labelled human serum albumin either carrying fatty acids (HSA+FA) or depleted of them (HSA-FA). Receptor-mediated endocytosis of FITC-HSA+FA over 60 min was 5 times greater than that of FITC-HSA-FA. 24h exposure of podocytes to albumin up-regulated nephrin expression and induced the activation of caspase-3. These effects were more pronounced in response to HSA-FA. Individually, anti-CD36 antibodies had no effect upon endocytosis of FITC-HSA. However, a cocktail of 2 antibodies reduced uptake by nearly 50%. Albumin endocytosis was enhanced in the presence of the CD36 specific inhibitor sulfo-N-succinimidyl oleate (SSO) while knock-down of CD36 using CD36siRNA had no effect on uptake. These data suggest that receptor-mediated endocytosis of albumin by podocytes is regulated by the fatty acid moiety, although, some of the detrimental effects are induced independently of it. CD36 does not play a direct role in the uptake of albumin.
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Affiliation(s)
- I Z A Pawluczyk
- Department of Infection, Immunity and inflammation, University of Leicester, Leicester, UK; John Walls Renal Unit, Leicester General Hospital Leicester, UK.
| | - A Pervez
- Department of Infection, Immunity and inflammation, University of Leicester, Leicester, UK
| | - M Ghaderi Najafabadi
- Department of Infection, Immunity and inflammation, University of Leicester, Leicester, UK
| | - M A Saleem
- Academic and Children׳s Renal Unit, University of Bristol, Southmead Hospital, Bristol, UK
| | - P S Topham
- Department of Infection, Immunity and inflammation, University of Leicester, Leicester, UK; John Walls Renal Unit, Leicester General Hospital Leicester, UK
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24
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Dobrinskikh E, Okamura K, Kopp JB, Doctor RB, Blaine J. Human podocytes perform polarized, caveolae-dependent albumin endocytosis. Am J Physiol Renal Physiol 2014; 306:F941-51. [PMID: 24573386 PMCID: PMC4010685 DOI: 10.1152/ajprenal.00532.2013] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 02/26/2014] [Indexed: 11/22/2022] Open
Abstract
The renal glomerulus forms a selective filtration barrier that allows the passage of water, ions, and small solutes into the urinary space while restricting the passage of cells and macromolecules. The three layers of the glomerular filtration barrier include the vascular endothelium, glomerular basement membrane (GBM), and podocyte epithelium. Podocytes are capable of internalizing albumin and are hypothesized to clear proteins that traverse the GBM. The present study followed the fate of FITC-labeled albumin to establish the mechanisms of albumin endocytosis and processing by podocytes. Confocal imaging and total internal reflection fluorescence microscopy of immortalized human podocytes showed FITC-albumin endocytosis occurred preferentially across the basal membrane. Inhibition of clathrin-mediated endocytosis and caveolae-mediated endocytosis demonstrated that the majority of FITC-albumin entered podocytes through caveolae. Once internalized, FITC-albumin colocalized with EEA1 and LAMP1, endocytic markers, and with the neonatal Fc receptor, a marker for transcytosis. After preloading podocytes with FITC-albumin, the majority of loaded FITC-albumin was lost over the subsequent 60 min of incubation. A portion of the loss of albumin occurred via lysosomal degradation as pretreatment with leupeptin, a lysosomal protease inhibitor, partially inhibited the loss of FITC-albumin. Consistent with transcytosis of albumin, preloaded podocytes also progressively released FITC-albumin into the extracellular media. These studies confirm the ability of podocytes to endocytose albumin and provide mechanistic insight into cellular mechanisms and fates of albumin handling in podocytes.
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Affiliation(s)
- Evgenia Dobrinskikh
- Div. of Renal Diseases and Hypertension, 12700 E. 19th Ave., C281, Aurora, CO 80045.
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25
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Ceol M, Tiralongo E, Baelde HJ, Vianello D, Betto G, Marangelli A, Bonfante L, Valente M, Della Barbera M, D’Angelo A, Anglani F, Del Prete D. Involvement of the tubular ClC-type exchanger ClC-5 in glomeruli of human proteinuric nephropathies. PLoS One 2012; 7:e45605. [PMID: 23029130 PMCID: PMC3454393 DOI: 10.1371/journal.pone.0045605] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 08/23/2012] [Indexed: 01/15/2023] Open
Abstract
UNLABELLED Glomerular protein handling mechanisms have received much attention in studies of nephrotic syndrome. Histopathological findings in renal biopsies from severely proteinuric patients support the likelihood of protein endocytosis by podocytes. ClC-5 is involved in the endocytosis of albumin in the proximal tubule. AIM To investigate whether ClC-5 is expressed in the glomerular compartment and whether it has a role in proteinuric nephropathies. ClC-5 expression was studied using Real-time PCR in manually- and laser-microdissected biopsies from patients with type 2 diabetes (n 37) and IgA nephropathy (n 10); in biopsies of membranous glomerulopathy (MG) (n 14) immunohistochemistry for ClC-5 (with morphometric analysis) and for WT1 was done. CONTROLS cortical tissue (n 23) obtained from unaffected parts of tumor-related nephrectomy specimens. RESULTS ClC-5 was expressed at glomerular level in all biopsies. Glomerular ClC-5 levels were significantly higher in diabetic nephropaty and MG at both mRNA and protein level (p<0.002; p<0.01). ClC-5 and WT1 double-staining analysis in MG showed that ClC-5 was localized in the podocytes. ClC-5 ultrastructural immunolocalization was demonstrated in podocytes foot processes. Our study is the first to demonstrate that ClC-5 is expressed in human podocytes. The ClC-5 overexpression found in biopsies of proteinuric patients suggests that proteinuria may play a part in its expression and that podocytes are likely to have a key role in albumin handling in proteinuric states.
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Affiliation(s)
- Monica Ceol
- Department of Medicine, Nephrology Unit and Kidney Histomorphology and Molecular Biology Laboratory, University of Padova, Padova, Italy
| | - Emilia Tiralongo
- Department of Medicine, Nephrology Unit and Kidney Histomorphology and Molecular Biology Laboratory, University of Padova, Padova, Italy
| | - Hans J. Baelde
- Department of Pathology, Leiden University Medical Center, Leiden, The Netherlands
| | - Daniela Vianello
- Department of Medicine, Nephrology Unit and Kidney Histomorphology and Molecular Biology Laboratory, University of Padova, Padova, Italy
| | | | - Annunziata Marangelli
- Department of Medicine, Nephrology Unit and Kidney Histomorphology and Molecular Biology Laboratory, University of Padova, Padova, Italy
| | - Luciana Bonfante
- Department of Medicine, Nephrology Unit and Kidney Histomorphology and Molecular Biology Laboratory, University of Padova, Padova, Italy
| | - Marialuisa Valente
- Department of Diagnostic Medical Science and Special Therapies, Institute of Pathological Anatomy, University of Padova, Padova, Italy
| | - Mila Della Barbera
- Department of Diagnostic Medical Science and Special Therapies, Institute of Pathological Anatomy, University of Padova, Padova, Italy
| | - Angela D’Angelo
- Department of Medicine, Nephrology Unit and Kidney Histomorphology and Molecular Biology Laboratory, University of Padova, Padova, Italy
| | - Franca Anglani
- Department of Medicine, Nephrology Unit and Kidney Histomorphology and Molecular Biology Laboratory, University of Padova, Padova, Italy
| | - Dorella Del Prete
- Department of Medicine, Nephrology Unit and Kidney Histomorphology and Molecular Biology Laboratory, University of Padova, Padova, Italy
- * E-mail:
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26
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Application of low-vacuum scanning electron microscopy for renal biopsy specimens. Pathol Res Pract 2012; 208:503-9. [PMID: 22795691 DOI: 10.1016/j.prp.2012.05.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 01/26/2012] [Accepted: 05/03/2012] [Indexed: 11/22/2022]
Abstract
Low-vacuum scanning electron microscopy (LV-SEM) has been developed which enables the observation of soft, moist, and electrically insulating materials without any pretreatment unlike conventional scanning electron microscopy, in which samples must be solid, dry and usually electrically conductive. The purpose of this study was to assess the usefulness of LV-SEM for renal biopsy specimens. We analyzed 20 renal biopsy samples obtained for diagnostic purposes. The sections were stained with periodic acid methenamine silver to enhance the contrast, and subsequently examined by LV-SEM. LV-SEM showed a precise and fine structure of the glomerulus in both formalin fixed paraffin and glutaraldehyde-osmium tetroxide-fixed epoxy resin sections up to 10,000-fold magnification. The spike formation on the basement membrane was clearly observed in the membranous nephropathy samples. Similarly to transmission electron microscopy, electron dense deposits were observed in the epoxy resin sections of the IgA nephropathy and membranous nephropathy samples. LV-SEM could accurately show various glomerular lesions at high magnification after a simple and rapid processing of the samples. We consider that this is a novel and useful diagnostic tool for renal pathologies.
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27
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Mechanisms of glomerular albumin filtration and tubular reabsorption. Int J Nephrol 2012; 2012:481520. [PMID: 22685655 PMCID: PMC3363986 DOI: 10.1155/2012/481520] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 03/21/2012] [Accepted: 03/21/2012] [Indexed: 12/20/2022] Open
Abstract
Albumin is filtered through the glomerulus with a sieving coefficient of 0.00062, which results in approximately 3.3 g of albumin filtered daily in human kidneys. The proximal convoluted tubule reabsorbs 71%, the loop of Henle and distal tubule 23%, and collecting duct 3% of the glomerular filtered albumin, thus indicating that the kidney plays an important role in protein metabolism. Dysfunction of albumin reabsorption in the proximal tubules, due to reduced megalin expression, may explain the microalbuminuria in early-stage diabetes. Meanwhile, massive nonselective proteinuria is ascribed to various disorders of the glomerular filtration barrier, including podocyte detachment, glomerular basement membrane rupture, and slit diaphragm dysfunction in focal segmental glomerulosclerosis, membranous nephropathy, and other glomerulonephritis. Selective albuminuria associated with foot process effacement and tight junction-like slit alteration is observed in the patients with minimal-change nephrotic syndrome, and the albumin uptake is enhanced in the podocyte cell body, possibly mediated by albumin receptors in the low-dose puromycin model. The role of enhanced podocyte albumin transport needs to be investigated to elucidate the mechanism of the selective albuminuria in minimal-change disease.
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Selective albuminuria via podocyte albumin transport in puromycin nephrotic rats is attenuated by an inhibitor of NADPH oxidase. Kidney Int 2011; 80:1328-38. [PMID: 21849973 DOI: 10.1038/ki.2011.282] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mechanism of selective albuminuria in minimal change nephrotic syndrome, in which glomerular capillaries are diffusely covered by effaced podocyte foot processes with reduced slit diaphragms, is unknown. Podocyte injury is due, in part, to NADPH-induced oxidative stress. Here we studied mechanism of selective albuminuria in puromycin aminonucleoside (PAN) nephrotic rats, a model of minimal change nephrotic syndrome. In these rats, Evans Blue-labeled human albumin was taken up by podocytes and its urinary excretion markedly increased, with retained selectivity for albumin. Immunogold scanning electron micrographic images found increased human albumin in podocyte vesicles and on the apical membrane in nephrotic compared with control rats. Apocynin, an inhibitor of NADPH oxidase, decreased superoxide production in podocytes, and inhibited endocytosis and urinary albumin excretion. Real-time confocal microscopy found an initial delay in the appearance of Evans Blue-labeled human albumin in the tubular lumen, reflecting the time needed for transcellular transport. Immunoprecipitation analysis indicated that FcRn, a receptor for albumin transport, mediated podocyte albumin transport, and treatment with anti-FcRn antibody reduced proteinuria in these nephrotic rats. Thus, podocyte albumin transport was enhanced in PAN nephrotic rats by means of FcRn, which may explain the mechanism of selective proteinuria. This was blocked by apocynin, suggesting a new therapeutic approach.
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Zuo Y, Yang HC, Potthoff SA, Najafian B, Kon V, Ma LJ, Fogo AB. Protective effects of PPARγ agonist in acute nephrotic syndrome. Nephrol Dial Transplant 2011; 27:174-81. [PMID: 21565943 DOI: 10.1093/ndt/gfr240] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Peroxisome proliferator-activated receptor gamma (PPARγ) agonists have beneficial effects on renal structure and function in models of diabetes and chronic kidney diseases. However, the increased incidence of weight gain and edema potentially limits their usefulness. We studied an acute minimal-change disease-like nephrotic syndrome model to assess effects of PPARγ agonist on acute podocyte injury and effects on fluid homeostasis. METHODS Acute podocyte injury and nephrotic syndrome were induced by puromycin aminonucleoside (PAN) injection in rats. RESULTS PPARγ agonist, given at the time or after, but not before PAN, reduced proteinuria, restored synaptopodin, decreased desmin and trended to improve foot process effacement. There was no significant difference in glomerular filtration, effective circulating volume, blood pressure or fractional sodium excretion. PAN-injured podocytes had decreased PPARγ, less nephrin and α-actinin-4, more apoptosis and reduced phosphorylated Akt. In PAN-injured cultured podocytes, PPARγ agonist also reversed abnormalities only when given simultaneously or after injury. CONCLUSIONS These results show that PPARγ agonist has protective effects on podocytes in acute nephrotic syndrome without deleterious effects on fluid homeostasis. PPARγ agonist-induced decrease in proteinuria in acute nephrotic syndrome is dependent at least partially on regulation of peroxisome proliferator-response element-sensitive gene expression such as α-actinin-4 and nephrin and the restoration of podocyte structure.
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Affiliation(s)
- Yiqin Zuo
- Department of Pathology, Vanderbilt University Medical Center, Nashville, TN, USA
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Hanamura K, Tojo A, Kinugasa S, Asaba K, Onozato ML, Uozaki H, Fukayama M, Fujita T. Detection of myeloperoxidase in membranous nephropathy-like deposits in patients with anti-neutrophil cytoplasmic antibody–associated glomerulonephritis. Hum Pathol 2011; 42:649-58. [DOI: 10.1016/j.humpath.2010.08.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 08/13/2010] [Accepted: 08/20/2010] [Indexed: 11/30/2022]
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Kinugasa S, Tojo A, Sakai T, Fujita T. Silver-enhanced immunogold scanning electron microscopy using vibratome sections of rat kidneys: detection of albumin filtration and reabsorption. Med Mol Morphol 2011; 43:218-25. [DOI: 10.1007/s00795-010-0500-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Accepted: 02/02/2010] [Indexed: 10/18/2022]
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Abstract
PURPOSE OF REVIEW The nephrology community lacks a unified view of protein sieving through the glomerular capillary wall. The glomerular capillary wall consists of three distinct but closely interacting layers: the fenestrated endothelium, with its glycocalyx; the podocytes, with their interdigitated foot processes and slit diaphragms; and the intervening glomerular basement membrane. Proteinuria is associated with abnormalities in any one layer, suggesting that each contributes to the glomerular filtration barrier (GFB). Proteinuria can also be induced in the context of a normal glomerular capillary wall. Here, we review some classic studies as well as some newer concepts and present competing hypotheses about the GFB. RECENT FINDINGS Two almost forgotten concepts have recently emerged. One group has challenged the exquisite selectivity of the GFB to albumin and suggested that proteinuria is the result of abnormal tubular uptake. There has also been a reemphasis on diffusion through the glomerular basement membrane as the driving force behind macromolecular filtration. New evidence suggests that the endothelial glycocalyx is an important charge-selective barrier. SUMMARY We suggest viewing the GFB as a dynamic rather than as a rigid barrier, requiring three healthy layers and a hemodynamic steady state. Multiple challenges to studying the endothelium, the tubular handling of albumin, and the role of hemodynamic forces will require new tools, new hypotheses, and open minds.
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