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Complement induces podocyte pyroptosis in membranous nephropathy by mediating mitochondrial dysfunction. Cell Death Dis 2022; 13:281. [PMID: 35351877 PMCID: PMC8964685 DOI: 10.1038/s41419-022-04737-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 02/25/2022] [Accepted: 03/15/2022] [Indexed: 12/23/2022]
Abstract
Podocyte damage mediated by in situ complement activation in the glomeruli is a key factor in the pathogenesis of membranous nephropathy (MN), but the molecular mechanism has not been fully elucidated. Pyroptosis is a special type of programmed cell death, mediate inflammatory response and induce tissue injury. However, it is not clear whether pyroptosis is involved in the development and progression of MN. Here, we report that pyroptosis plays an important role in promoting podocyte injury in MN. We first observed the occurrence of pyroptosis in the kidneys of MN patients and validated that complement stimulation triggered pyroptosis in podocytes and that inhibiting pyroptosis reversed complement-induced podocyte damage in vitro. In addition, stimulation of complement caused mitochondrial depolarization and reactive oxygen species (ROS) production in podocytes, and inhibition of ROS reversed complement-induced pyroptosis in podocytes. Interestingly, inhibition of pyroptosis in turn partially alleviated these effects. Furthermore, we also found the involvement of pyroptosis in the kidneys of passive Heymann nephritis (PHN) rats, and inhibitors of pyroptosis-related molecules relieved PHN-induced kidney damage in vivo. Our findings demonstrate that pyroptosis plays a critical role in complement-induced podocyte damage in MN and mitochondrial dysfunction is an important mechanism underlying this process. It provides new insight that pyroptosis may serve as a novel therapeutic target for MN treatment in future studies.
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Reinhard L, Stahl RAK, Hoxha E. Is primary membranous nephropathy a complement mediated disease? Mol Immunol 2020; 128:195-204. [PMID: 33142137 DOI: 10.1016/j.molimm.2020.10.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/04/2020] [Accepted: 10/20/2020] [Indexed: 12/25/2022]
Abstract
Membranous nephropathy (MN) is an immune complex mediated disease. Although limited to the kidney, in up to 20% of patients MN is associated with other autoimmune, infectious or malignant diseases. The initial pathogenetic event in what is still considered "primary" MN is the binding of circulating autoantibodies to proteins (autoantigens) expressed in glomerular podocytes. This antibody binding leads to the formation of immune complexes in the glomerular basement membrane. There is clinical and experimental evidence that these immune deposits lead to the activation of the complement system. Experimental studies in the MN model of Heymann's nephritis show that the terminal membrane attack complex (MAC) of the complement system induces a disturbance of the glomerular filtration barrier and leads to proteinuria, the clinical hallmark of MN. After the discovery of the phospholipase A2 receptor 1 and thrombospondin type 1 domain containing protein 7A as endogenous antigens, it is assumed that IgG4 antibodies directed against these proteins induce MN in over 85% of patients with primary MN. As a result, the role of complement in the pathogenesis of MN needs to be defined in light of these developments. In this review we describe the current knowledge on the function of the complement system in primary MN and discuss the open questions, which have to be solved for a better understanding of the potential role of complement in the pathophysiology of primary MN.
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Affiliation(s)
- Linda Reinhard
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany
| | - Rolf A K Stahl
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
| | - Elion Hoxha
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
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Matsuda J, Asano-Matsuda K, Kitzler TM, Takano T. Rho GTPase regulatory proteins in podocytes. Kidney Int 2020; 99:336-345. [PMID: 33122025 DOI: 10.1016/j.kint.2020.08.035] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 08/21/2020] [Accepted: 08/25/2020] [Indexed: 12/14/2022]
Abstract
The Rho family of small GTPases (Rho GTPases) are the master regulators of the actin cytoskeleton and consist of 22 members. Previous studies implicated dysregulation of Rho GTPases in podocytes in the pathogenesis of proteinuric glomerular diseases. Rho GTPases are primarily regulated by the three families of proteins; guanine nucleotide exchange factors (GEFs; 82 members), GTPase-activating proteins (GAPs; 69 members), and GDP dissociation inhibitors (GDIs; 3 members). Since the regulatory proteins far outnumber their substrate Rho GTPases and act in concert in a cell/context-dependent manner, the upstream regulatory mechanism directing Rho GTPases in podocytes is largely unknown. In this review, we summarize recent advances in the understanding of the role of Rho GTPase regulatory proteins in podocytes, including the known mutations of these proteins that cause proteinuria in humans. We also provide critical appraisal of the in vivo and in vitro studies and identify the knowledge gap in the field that will require further studies.
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Affiliation(s)
- Jun Matsuda
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada; Research Institute, McGill University Health Centre, Montreal, Quebec, Canada
| | - Kana Asano-Matsuda
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada; Research Institute, McGill University Health Centre, Montreal, Quebec, Canada
| | - Thomas M Kitzler
- Research Institute, McGill University Health Centre, Montreal, Quebec, Canada; Division of Medical Genetics, Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada; Department of Human Genetics, McGill University, Montreal, Quebec, Canada
| | - Tomoko Takano
- Division of Nephrology, McGill University Health Centre, Montreal, Quebec, Canada; Research Institute, McGill University Health Centre, Montreal, Quebec, Canada.
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Xie CB, Jane-Wit D, Pober JS. Complement Membrane Attack Complex: New Roles, Mechanisms of Action, and Therapeutic Targets. THE AMERICAN JOURNAL OF PATHOLOGY 2020; 190:1138-1150. [PMID: 32194049 DOI: 10.1016/j.ajpath.2020.02.006] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/24/2020] [Accepted: 02/03/2020] [Indexed: 12/11/2022]
Abstract
The complement membrane attack complex (MAC) is classically known as a cytolytic effector of innate and adaptive immunity that forms pores in the plasma membrane of pathogens or targeted cells, leading to osmolysis. Nucleated cells resist MAC-mediated cytolysis by expression of inhibitors that block MAC assembly or by rapid removal of MAC through endocytosis or shedding. In the absence of lysis, MAC may induce intracellular signaling and cell activation, responses implicated in a variety of autoimmune, inflammatory, and transplant disease settings. New discoveries into the structure and biophysical properties of MAC revealed heterogeneous MAC precursors and conformations that provide insights into MAC function. In addition, new mechanisms of MAC-mediated signaling and its contribution to disease pathogenesis have recently come to light. MAC-activated cells have been found to express proinflammatory proteins-often through NF-κB-dependent transcription, assemble inflammasomes, enabling processing, and facilitate secretion of IL-1β and IL-18, as well as other signaling pathways. These recent insights into the mechanisms of action of MAC provide an updated framework to therapeutic approaches that can target MAC assembly, signaling, and proinflammatory effects in various complement-mediated diseases.
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Affiliation(s)
- Catherine B Xie
- Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut
| | - Dan Jane-Wit
- Division of Cardiovascular Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Jordan S Pober
- Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut.
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Widmeier E, Tan W, Airik M, Hildebrandt F. A small molecule screening to detect potential therapeutic targets in human podocytes. Am J Physiol Renal Physiol 2016; 312:F157-F171. [PMID: 27760769 DOI: 10.1152/ajprenal.00386.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 09/30/2016] [Accepted: 10/06/2016] [Indexed: 01/01/2023] Open
Abstract
WIDMEIER E, TAN W, AIRIK M, HILDEBRANDT F A small molecule screening to detect potential therapeutic targets in human podocytes. Am J Physiol Renal Physiol 312: F157-F171, 2017. First published October 19, 2016; doi:10.1152/ajprenal.00386.2016. Steroid-resistant nephrotic syndrome (SRNS) inevitably progresses to end-stage kidney disease, requiring dialysis or transplantation for survival. However, treatment modalities and drug discovery remain limited. Mutations in over 30 genes have been discovered as monogenic causes of SRNS. Most of these genes are predominantly expressed in the glomerular epithelial cell, the podocyte, placing it at the center of the pathogenesis of SRNS. Podocyte migration rate (PMR) represents a relevant intermediate phenotype of disease in monogenic causes of SRNS. We therefore adapted PMR in a high-throughput manner to screen small molecules as potential therapeutic targets for SRNS. We performed a high-throughput drug screening of a National Institutes of Health Clinical Collection (NCC) library (n = 725 compounds) measuring PMR by videomicroscopy. We used the Woundmaker to perform individual 96-well scratch wounds and screened compounds using a quantitative kinetic live cell imaging migration assay using IncuCyte ZOOM technology. Using a normal distribution for the average PMR in wild-type podocytes with a vehicle control (DMSO), we applied a 90% confidence interval to define "distinct" compounds (5% faster/slower PMR) and found that 12 of 725 compounds (at 10 μM) reduced PMR. Clusters of drugs that alter PMR included actin/tubulin modulators such as the azole class of antifungals and antineoplastic vinca-alkaloids. We hereby identify compounds that alter PMR. The PMR assay provides a new avenue to test therapeutics for nephrotic syndrome. Positive results may reveal novel pathways in the study of glomerular diseases such as SRNS.
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Affiliation(s)
- Eugen Widmeier
- Division of Nephrology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts; and.,Department of Medicine, Renal Division, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Weizhen Tan
- Division of Nephrology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts; and
| | - Merlin Airik
- Division of Nephrology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts; and
| | - Friedhelm Hildebrandt
- Division of Nephrology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts; and
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Abstract
Genetic studies of hereditary forms of nephrotic syndrome have identified several proteins that are involved in regulating the permselective properties of the glomerular filtration system. Further extensive research has elucidated the complex molecular basis of the glomerular filtration barrier and clearly established the pivotal role of podocytes in the pathophysiology of glomerular diseases. Podocyte architecture is centred on focal adhesions and slit diaphragms - multiprotein signalling hubs that regulate cell morphology and function. A highly interconnected actin cytoskeleton enables podocytes to adapt in order to accommodate environmental changes and maintain an intact glomerular filtration barrier. Actin-based endocytosis has now emerged as a regulator of podocyte integrity, providing an impetus for understanding the precise mechanisms that underlie the steady-state control of focal adhesion and slit diaphragm components. This Review outlines the role of actin dynamics and endocytosis in podocyte biology, and discusses how molecular heterogeneity in glomerular disorders could be exploited to deliver more rational therapeutic interventions, paving the way for targeted medicine in nephrology.
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Georgiannakis A, Burgoyne T, Lueck K, Futter C, Greenwood J, Moss SE. Retinal Pigment Epithelial Cells Mitigate the Effects of Complement Attack by Endocytosis of C5b-9. THE JOURNAL OF IMMUNOLOGY 2015; 195:3382-9. [PMID: 26324770 PMCID: PMC4574521 DOI: 10.4049/jimmunol.1500937] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 07/29/2015] [Indexed: 01/01/2023]
Abstract
Retinal pigment epithelial (RPE) cell death is a hallmark of age-related macular degeneration. The alternative pathway of complement activation is strongly implicated in RPE cell dysfunction and loss in age-related macular degeneration; therefore, it is critical that RPE cells use molecular strategies to mitigate the potentially harmful effects of complement attack. We show that the terminal complement complex C5b-9 assembles rapidly on the basal surface of cultured primary porcine RPE cells but disappears over 48 h without any discernable adverse effects on the cells. However, in the presence of the dynamin inhibitor dynasore, C5b-9 was almost completely retained at the cell surface, suggesting that, under normal circumstances, it is eliminated via the endocytic pathway. In support of this idea, we observed that C5b-9 colocalizes with the early endosome marker EEA1 and that, in the presence of protease inhibitors, it can be detected in lysosomes. Preventing the endocytosis of C5b-9 by RPE cells led to structural defects in mitochondrial morphology consistent with cell stress. We conclude that RPE cells use the endocytic pathway to prevent the accumulation of C5b-9 on the cell surface and that processing and destruction of C5b-9 by this route are essential for RPE cell survival.
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Affiliation(s)
- Apostolos Georgiannakis
- Department of Cell Biology, University College London Institute of Ophthalmology, London EC1V9EL, United Kingdom
| | - Tom Burgoyne
- Department of Cell Biology, University College London Institute of Ophthalmology, London EC1V9EL, United Kingdom
| | - Katharina Lueck
- Department of Cell Biology, University College London Institute of Ophthalmology, London EC1V9EL, United Kingdom
| | - Clare Futter
- Department of Cell Biology, University College London Institute of Ophthalmology, London EC1V9EL, United Kingdom
| | - John Greenwood
- Department of Cell Biology, University College London Institute of Ophthalmology, London EC1V9EL, United Kingdom
| | - Stephen E Moss
- Department of Cell Biology, University College London Institute of Ophthalmology, London EC1V9EL, United Kingdom
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Abstract
Nephrotic syndrome (NS) is characterized by heavy proteinuria, hypoalbuminemia, and edema. The underlying causes of NS are diverse and are tied to inheritable and environmental factors. A common diagnostic marker for NS is effacement of podocyte foot processes. The formation and maintenance of foot processes are under the control of many signalling molecules including Rho-GTPases. Our knowledge of Rho-GTPases is based largely on the functions of three prototypic members: RhoA, Rac1, and Cdc42. In the event of podocyte injury, the rearrangement to the actin cytoskeleton is orchestrated largely by this family of proteins. The importance of maintaining proper actin dynamics in podocytes has led to much investigation as to how Rho-GTPases and their regulatory molecules form and maintain foot processes as a critical component of the kidney’s filtration barrier. Modern sequencing techniques have allowed for the identification of novel disease causing mutations in genes such as ARHGDIA, encoding Rho-GDIα. Continued use of whole exome sequencing has the potential to lead to the identification of new mutations in genes encoding Rho-GTPases or their regulatory proteins. Expanding our knowledge of the dynamic regulation of the actin network by Rho-GTPases in podocytes will pave the way for effective therapeutic options for NS patients.
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