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Marahrens B, Schulze A, Wysocki J, Lin MH, Ye M, Kanwar YS, Bader M, Velez JCQ, Miner JH, Batlle D. Knockout of aminopeptidase A in mice causes functional alterations and morphological glomerular basement membrane changes in the kidneys. Kidney Int 2020; 99:900-913. [PMID: 33316280 DOI: 10.1016/j.kint.2020.11.012] [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: 06/23/2020] [Revised: 10/28/2020] [Accepted: 11/19/2020] [Indexed: 11/29/2022]
Abstract
Aminopeptidase A is one of the most potent enzymes within the renin-angiotensin system in terms of angiotensin II degradation. Here, we examined whether there is a kidney phenotype and any compensatory changes in other renin angiotensin system enzymes involved in the metabolism of angiotensin II associated with aminopeptidase A deficiency. Kidneys harvested from aminopeptidase A knockout mice were examined by light and electron microscopy, immunohistochemistry and immunofluorescence. Kidney angiotensin II levels and the ability of renin angiotensin system enzymes in the glomerulus to degrade angiotensin II ex vivo, their activities, protein and mRNA levels in kidney lysates were evaluated. Knockout mice had increased blood pressure and mild glomerular mesangial expansion without significant albuminuria. By electron microscopy, knockout mice exhibited a mild increase of the mesangial matrix, moderate thickening of the glomerular basement membrane but a striking appearance of knob-like structures. These knobs were seen in both male and female mice and persisted after the treatment of hypertension. In isolated glomeruli from knockout mice, the level of angiotensin II was more than three-fold higher as compared to wild type control mice. In kidney lysates from knockout mice angiotensin converting enzyme activity, protein and mRNA levels were markedly decreased possibly as a compensatory mechanism to reduce angiotensin II formation. Thus, our findings support a role for aminopeptidase A in the maintenance of glomerular structure and intra-kidney homeostasis of angiotensin peptides.
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Affiliation(s)
- Benedikt Marahrens
- Division of Nephrology and Hypertension, Department of Medicine, Northwestern University/Feinberg School of Medicine, Chicago, Illinois, USA; Charité University Medicine Berlin, Berlin, Germany
| | - Arndt Schulze
- Division of Nephrology and Hypertension, Department of Medicine, Northwestern University/Feinberg School of Medicine, Chicago, Illinois, USA; Charité University Medicine Berlin, Berlin, Germany
| | - Jan Wysocki
- Division of Nephrology and Hypertension, Department of Medicine, Northwestern University/Feinberg School of Medicine, Chicago, Illinois, USA
| | - Meei-Hua Lin
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Minghao Ye
- Division of Nephrology and Hypertension, Department of Medicine, Northwestern University/Feinberg School of Medicine, Chicago, Illinois, USA
| | - Yashpal S Kanwar
- Department of Pathology, Northwestern University/Feinberg School of Medicine, Chicago, Illinois, USA
| | - Michael Bader
- Charité University Medicine Berlin, Berlin, Germany; DZHK (German Center for Cardiovascular Research), Partner Site Berlin, Berlin, Germany; Max-Delbrück-Center for Molecular Medicine, Berlin, Germany; Institute for Biology, University of Lübeck, Lübeck, Germany
| | - Juan Carlos Q Velez
- Department of Nephrology, Ochsner Clinic Foundation, New Orleans, Louisiana, USA
| | - Jeffrey H Miner
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Daniel Batlle
- Division of Nephrology and Hypertension, Department of Medicine, Northwestern University/Feinberg School of Medicine, Chicago, Illinois, USA.
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Seifi M, Footz T, Taylor SAM, Elhady GM, Abdalla EM, Walter MA. Novel PITX2 gene mutations in patients with Axenfeld-Rieger syndrome. Acta Ophthalmol 2016; 94:e571-e579. [PMID: 27009473 DOI: 10.1111/aos.13030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 01/23/2016] [Indexed: 02/06/2023]
Abstract
PURPOSE Mutations in the bicoid-like transcription factor PITX2 gene often result in Axenfeld-Rieger syndrome (ARS), an autosomal-dominant inherited disorder. We report here the discovery and characterization of novel PITX2 deletions in a small kindred with ARS. METHODS Two familial patients (father and son) from a consanguineous family were examined in the present study. Patient DNA samples were screened for PITX2 mutations by DNA sequencing and for copy number variation by SYBR Green quantitative polymerase chain reaction (PCR) analysis. RESULTS We report a novel deletion involving the coding region of PITX2 in both patients. The minimum size of the deletion is 1 421 914 bp that spans one upstream regulatory element (CE4), PITX2 and a minimum of 13 neighbouring genes. The maximum size of the deletion is 3 789 983 bp. The proband (son) additionally possesses a novel 2-bp deletion in a non-coding exon of the remaining PITX2 allele predicted to alter correct splicing. CONCLUSION Our findings implicate a novel deletion of the PITX2 gene in the pathogenesis of ARS in the affected family. This ARS family presented with an atypical and extremely severe phenotype that resulted in four miscarriages and the death at 10 months of age of a sib of the proband. As the phenotypic manifestations in the proband are more severe than that of the father, we hypothesize that the deletion of the entire PITX2 allele plus a novel 2-bp deletion (observed in the proband) within the remaining PITX2 allele together contributed to the atypical ARS presentation in this family. This is the first study reporting on bi-allelic changes of PITX2 potentially contributing to a more severe ARS phenotype.
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Affiliation(s)
- Morteza Seifi
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Tim Footz
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Sherry A M Taylor
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Ghada M Elhady
- Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Ebtesam M Abdalla
- Department of Human Genetics, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Michael A Walter
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
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3
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Minimal change disease and idiopathic FSGS: manifestations of the same disease. Nat Rev Nephrol 2016; 12:768-776. [DOI: 10.1038/nrneph.2016.147] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Wennmann DO, Hsu HH, Pavenstädt H. The renin-angiotensin-aldosterone system in podocytes. Semin Nephrol 2013; 32:377-84. [PMID: 22958492 DOI: 10.1016/j.semnephrol.2012.06.009] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The renin-angiotensin-aldosterone system (RAAS) plays a critical role in kidney function and its inhibition reduces proteinuria and preserves kidney function in patients with chronic kidney disease. Recent studies have shown that podocytes generate many components of the RAAS and they express receptors of RAAS, including angiotensin II, mineralocorticoid, and prorenin receptors. Crucial functions of podocytes, such as contraction, apoptosis, autophagocytosis, and cytoskeletal organization, have been shown to be regulated by the angiotensin II type 1 receptors. An activation of the glomerular RAAS and protection from podocyte injury by RAAS inhibitors have been shown in many glomerular diseases. Exploring the interaction between the local RAAS and the signaling involved in RAAS activation in podocytes will lead to new therapeutic strategies of podocyte protection.
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Affiliation(s)
- Dirk Oliver Wennmann
- Department of Internal Medicine D, University Hospital Münster, Münster, Germany
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Ozawa MG, Zurita AJ, Dias-Neto E, Nunes DN, Sidman RL, Gelovani JG, Arap W, Pasqualini R. Beyond receptor expression levels: the relevance of target accessibility in ligand-directed pharmacodelivery systems. Trends Cardiovasc Med 2008; 18:126-32. [PMID: 18555185 DOI: 10.1016/j.tcm.2008.03.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Revised: 02/29/2008] [Accepted: 03/06/2008] [Indexed: 12/31/2022]
Abstract
For development of a new ligand-directed pharmacology, it is critical to measure delivery of targeted drug ligands via molecular imaging or diagnostic readouts (termed theranostics). Combinatorial peptide libraries serve as unbiased functional screens that can identify specific peptides targeting cell-surface receptors accessible to the circulation. As candidate drug leads, such peptides provide motifs likely to modify ligand-receptor interactions and downstream signal transduction pathways. This strategy is synergistic with genomic and proteomic approaches and has yielded insights into the specialized nature of the target tissue microenvironment. However, for this vision to be realized, one must look, as recent literature suggests, beyond receptor levels and critically analyze ligand accessibility as a key determinant in pharmacodelivery systems.
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Affiliation(s)
- Michael G Ozawa
- Department of Genitourinary Medical Oncology, The University of Texas M D Anderson Cancer Center, Houston, TX 77030, USA
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7
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Tonna S, Dandapani SV, Uscinski A, Appel GB, Schlöndorff JS, Zhang K, Denker BM, Pollak MR. Functional genetic variation in aminopeptidase A (ENPEP): lack of clear association with focal and segmental glomerulosclerosis (FSGS). Gene 2007; 410:44-52. [PMID: 18206321 DOI: 10.1016/j.gene.2007.11.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Revised: 11/16/2007] [Accepted: 11/19/2007] [Indexed: 01/07/2023]
Abstract
The aminopeptidase A (APA) ectopeptidase is an integral membrane-bound zinc metalloprotease that cleaves aspartic and glutamic acidic residues from the N-terminus of a number of protein substrates that includes angiotensin II. Angiotensin II, the most vasoactive component of the renin-angiotensin-aldosterone (RAAS) pathway, can contribute to renal disease by causing an increase in arterial blood pressure leading to glomerular injury and fibrosis. APA is expressed in many organs, including the kidney where it localizes mainly to the podocyte cell membrane and brush borders of the proximal tubule cells. Antibodies directed to the APA peptide can induce an acute massive albuminuria in wild-type BALB/c mice after intravenous injection. We examined whether variants in the APA encoding gene (ENPEP) are more frequent in individuals with the proteinuric disease focal and segmental glomerulosclerosis (FSGS) compared to control individuals. The ENPEP coding sequence was re-sequenced in 188 FSGS patients and 48 controls. Genetic variants were further genotyped in 181 individuals without any known kidney disease. We then examined the effect of the non-synonymous coding variants identified on their cell surface APA activity after transfection in COS-1 cells. Several of these ENPEP variants lead to reproducibly altered APA activity. However, we did not see a clear correlation between the presence of a functional ENPEP variant and FSGS. However, the existence of these variants with marked effect on APA activity suggests that both rare and common variation in ENPEP may contribute to the development of renal and hypertensive disorders and warrants further study.
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Affiliation(s)
- Stephen Tonna
- Renal Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
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Meyer TN, Schwesinger C, Wahlefeld J, Dehde S, Kerjaschki D, Becker JU, Stahl RAK, Thaiss F. A new mouse model of immune-mediated podocyte injury. Kidney Int 2007; 72:841-52. [PMID: 17653132 DOI: 10.1038/sj.ki.5002450] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Podocytes play a major role in the initiation and progression of glomerular diseases and are a target of both immune-mediated and non-immune-mediated injury. To establish a mouse model of such injury, we preimmunized mice with Freunds adjuvant 5 days before intravenous injection of a rabbit polyclonal antibody directed against a murine podocyte cell line. For the next 7 weeks, we collected urine, serum, and kidney samples. Nephritic animals developed severe albuminuria, which was maximal on day 10. Histochemistry revealed diffuse mesangial matrix expansion. Mouse immunoglobulin G and complement were detected in a linear pattern along the glomerular filtration barrier and in the mesangial hinge region. Complement depletion, however, did not prevent proteinuria. Glomerular T cells were increased, whereas podocytes were significantly reduced. Glomerular foot processes were flattened in regions with mesangial matrix deposition as viewed by electron microscopy. Immunohistochemistry detected the injected anti-podocyte antibody exclusively at the glomerular tuft on all days examined. Immunoelectron microscopy localized the antibody to podocyte foot processes and the glomerular basement membrane, which was morphologically intact. This suggests that the podocyte was the main target of the antiserum. Our study establishes a new mouse model of immune-mediated podocyte injury.
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Affiliation(s)
- T N Meyer
- Department of Internal Medicine, University Hospital Hamburg, Hamburg, Germany.
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Marchiò S, Lahdenranta J, Schlingemann RO, Valdembri D, Wesseling P, Arap MA, Hajitou A, Ozawa MG, Trepel M, Giordano RJ, Nanus DM, Dijkman HBPM, Oosterwijk E, Sidman RL, Cooper MD, Bussolino F, Pasqualini R, Arap W. Aminopeptidase A is a functional target in angiogenic blood vessels. Cancer Cell 2004; 5:151-62. [PMID: 14998491 DOI: 10.1016/s1535-6108(04)00025-x] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2003] [Revised: 11/17/2003] [Accepted: 01/07/2004] [Indexed: 11/17/2022]
Abstract
We show that a membrane-associated protease, aminopeptidase A (APA), is upregulated and enzymatically active in blood vessels of human tumors. To gain mechanistic insight, we evaluated angiogenesis in APA null mice. We found that, although these mice develop normally, they fail to mount the expected angiogenic response to hypoxia or growth factors. We then isolated peptide inhibitors of APA from a peptide library and show that they specifically bind to and inhibit APA, suppress migration and proliferation of endothelial cells, inhibit angiogenesis, and home to tumor blood vessels. Finally, we successfully treated tumor-bearing mice with APA binding peptides or anti-APA blocking monoclonal antibodies. These data show that APA is a regulator of blood vessel formation, and can serve as a functional vascular target.
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Affiliation(s)
- Serena Marchiò
- The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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Dijkman HBPM, Gerlofs-Nijland ME, van der Laak JAWM, Wetzels JFM, Groenen PJTA, Assmann KJM. Podocyte changes after induction of acute albuminuria in mice by anti-aminopeptidase A mAb. NEPHRON. EXPERIMENTAL NEPHROLOGY 2003; 94:e85-93. [PMID: 12902618 DOI: 10.1159/000072026] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2002] [Accepted: 05/13/2003] [Indexed: 11/19/2022]
Abstract
Administration of a specific combination of anti-aminopeptidase A (APA) mAb (ASD-37/41) in mice induces an acute albuminuria which is independent of angiotensin II, a well-known substrate of APA. In the present experiments, we examined whether binding of the mAb initiated changes in the podocytic expression of cytoskeleton (-associated), adhesion and slit-diaphragm proteins in relation to the time course of albuminuria. In addition, we measured ultrastructurally the extent of foot process retraction (the number of foot processes per microm GBM) and the width of the slit pore between the podocytes by morphometric methods. An injection of the mAb combination ASD-37/41 induced a massive but transient albuminuria that started at 6 h, and peaked at 8 h, after which it declined. However, even at day 7 after injection of the mAbs some albuminuria was present. Injection of the combination ASD-3/41 or saline did not induce an albuminuria. Notably, we observed changes in the staining of CD2AP and podocin, two slit-pore-associated proteins that coincided with the start of the albuminuria. Nephrin staining was reduced and podocytic actin staining became more granular only at a time albuminuria was declining (24 h). The number of foot processes per microm GBM was already decreased at 4 h with a further reduction thereafter. The width of the slit pore was unchanged at the time of peak albuminuria and gradually decreased thereafter. At day 7, podocytic foot process effacement was even more prominent although albuminuria was only slightly abnormal. Expression of CD2AP was still granular. We observed however a change toward normal in the expression of podocin. Injection of saline or ASD-3/41 had no effect on the expression of podocytic proteins, the number of foot processes or width of the slit pore. Our data show that the onset of albuminuria in the anti-APA model is related to alterations in CD2AP and podocin, proteins that are important for maintaining slit-diaphragm structure and podocytic function. Extended studies at day 7 demonstrated uncoupling of albuminuria, podocytic foot process effacement and CD2AP staining. Changes in podocin more closely paralleled changes in albuminuria.
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Affiliation(s)
- Henry B P M Dijkman
- Department of Pathology, Division of Nephrology, University Medical Center, Nijmegen, The Netherlands.
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Liu G, Kaw B, Kurfis J, Rahmanuddin S, Kanwar YS, Chugh SS. Neph1 and nephrin interaction in the slit diaphragm is an important determinant of glomerular permeability. J Clin Invest 2003; 112:209-21. [PMID: 12865409 PMCID: PMC164293 DOI: 10.1172/jci18242] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Neph1-deficient mice develop nephrotic syndrome at birth, indicating the importance of this protein in the development of a normal glomerular filtration barrier. While the precise subcellular localization of Neph1 remains unknown, its relationship with other components of the glomerular filtration barrier is of great interest in this field. In this paper, we localize the expression of Neph1 to the glomerular slit diaphragm by immunogold electron microscopy in rodents and describe its direct interaction with two other components of the slit diaphragm, nephrin and ZO-1. Both native and recombinant Neph1 associate with each other as dimers and multimers and interact with nephrin via their extracellular segments. Disruption of the Neph1-nephrin interaction in vivo by injecting combinations of individual subnephritogenic doses of anti-Neph1 and anti-nephrin results in complement- and leukocyte-independent proteinuria with preserved foot processes. This disruption modestly reduces Neph1 and nephrin protein expression in podocytes and dramatically reduces ZO-1 protein expression via the interaction of ZO-1 PDZ domains with the cytoplasmic tail of Neph1, independent of changes in mRNA expression of all three genes. The interaction between nephrin and Neph1 is specific and not shared by either protein with P-cadherin, another integral slit diaphragm protein. The interaction between nephrin and Neph1 therefore appears to be an important determinant of glomerular permeability.
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Affiliation(s)
- Gang Liu
- Department of Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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Liu G, Kaw B, Kurfis J, Rahmanuddin S, Kanwar YS, Chugh SS. Neph1 and nephrin interaction in the slit diaphragm is an important determinant of glomerular permeability. J Clin Invest 2003. [DOI: 10.1172/jci200318242] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Gerlofs-Nijland ME, Assmann KJM, van Son JPHF, Dijkman HBPM, te Loeke NAJM, van der Zee R, Wetzels JFM, Groenen PJTA. Epitope mapping of monoclonal antibodies directed to aminopeptidase A and their relevance for albuminuria in mice. NEPHRON. EXPERIMENTAL NEPHROLOGY 2003; 94:e25-34. [PMID: 12806185 DOI: 10.1159/000070816] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2002] [Accepted: 12/31/2002] [Indexed: 11/19/2022]
Abstract
We have shown previously that injection of specific combinations of anti-aminopeptidase A monoclonal antibodies induces an acute massive albuminuria in mice. This albuminuria is neither dependent on systemic mediators of inflammation nor angiotensin II. In this study, we examined the contribution of two individual antibodies, the enzyme-inhibiting antibody ASD-37 and the non-enzyme-inhibiting antibody ASD-41, in the induction of albuminuria as well as the interactions between these two monoclonals. In addition, we have mapped the epitopes of both antibodies using in vitro coupled transcription/translation of specifically designed cDNA fragments followed by immunoprecipitation, and using peptide enzyme-linked immunosorbent assay in case of a continuous epitope. A single intravenous injection of 4 mg of either ASD-37 or ASD-41 did not induce albuminuria. This dose of ASD-37 did not completely inhibit enzyme activity. The combination of 4 mg ASD-37/41 (1:1 weight ratio) induced albuminuria and almost completely inhibited enzyme activity. Similar results were obtained with a combination of ASD-37/41 in a 1:39 or 39:1 weight ratio. Administration of 2 mg ASD-41 24 h before injection of 2 mg ASD-37 significantly enhanced albuminuria. The epitope of ASD-37 is located at the C-terminal end of aminopeptidase A, whereas the ASD-41 epitope is mapped near the enzyme active site. Our data suggest that ASD-41 modulates the binding of ASD-37 to its epitope and/or vice versa. As a consequence, ASD-37 and ASD-41 act synergistically, not only in inhibiting enzyme activity but also in inducing albuminuria.
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Affiliation(s)
- Miriam E Gerlofs-Nijland
- Department of Pathology, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, The Netherlands
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14
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Assmann KJM, van Son JPHF, Dïjkman HBPM, Mentzel S, Wetzels JFM. Antibody-induced albuminuria and accelerated focal glomerulosclerosis in the Thy-1.1 transgenic mouse. Kidney Int 2002; 62:116-26. [PMID: 12081570 DOI: 10.1046/j.1523-1755.2002.00428.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Podocytes play an important role in the development of proteinuria and focal glomerulosclerosis. Previously we have demonstrated that a combination of two monoclonal antibodies (mAb) against aminopeptidase A (APA), an enzyme present on podocytes, induces a massive acute albuminuria in mice. The present study examined the relationship between the acute antibody-induced albuminuria and the development of focal glomerulosclerosis in the Thy-1.1 transgenic mouse. This mouse expresses a hybrid human-mouse Thy-1.1 antigen on the podocytes, and slowly but spontaneously develops albuminuria and focal glomerulosclerosis. METHODS Five-week-old non-albuminuric Thy-1.1 transgenic and non-transgenic control mice were injected with anti-APA and anti-Thy-1.1 mAb or saline. Albuminuria was measured at days 1, 7, 14 and 21. At day 21 kidneys were processed for light microscopy, immunofluorescence, and electron microscopy. RESULTS Injection of anti-APA and anti-Thy1.1 mAb in Thy-1.1 transgenic mice induced an albuminuria at day 1 that persisted at day 21. The acute albuminuria after injection of anti-APA mAb was more prominent but transient in non-transgenic mice. In non-trangenic mice no albuminuria could be induced with anti-Thy 1.1 mAb. Light microscopy revealed normal glomeruli at day 1 in all transgenic mice, however, at day 21 advanced glomerulosclerotic lesions were seen in mice injected with either anti-APA mAb (37+/-19% of glomeruli affected) or anti-Thy-1.1 mAb (71+/-5%). Non-transgenic mice did not reveal sclerotic lesions at any time investigated. In the transgenic mice the percentage of focal glomerulosclerosis at day 21 did not correlate with albuminuria at day 21. However, we found a highly significant correlation between percentage of focal glomerulosclerosis and the time-averaged albuminuria over the three-week study period (P < 0.001). CONCLUSION Injection of a combination of anti-APA or anti-Thy-1.1 mAb into one mo old, non-albuminuric Thy-1.1 transgenic mice induces an acute albuminuria at day 1 that is accompanied by an accelerated focal glomerulosclerosis at day 21. We suggest that the Thy-1.1 transgenic mouse is an excellent model to study specifically the relation between podocytic injury, albuminuria and the development of focal glomerulosclerosis.
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Affiliation(s)
- Karel J M Assmann
- Department of Pathology, Division of Nephrology, University Medical Center Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
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Gerlofs-Nijland ME, Assmann KJM, Dijkman HBPM, Dieker JWC, van Son JPHF, Mentzel S, van Kats JP, Danser AHJ, Smithies O, Groenen PJTA, Wetzels JFM. Albuminuria in mice after injection of antibodies against aminopeptidase A: role of angiotensin II. J Am Soc Nephrol 2001; 12:2711-2720. [PMID: 11729240 DOI: 10.1681/asn.v12122711] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
It has been shown that injection of combinations of anti-aminopeptidase A (APA) monoclonal antibodies (mAb) that inhibit the enzyme activity induces an acute albuminuria in mice. This albuminuria is not dependent on inflammatory cells, complement, or the coagulation system. APA is an important regulator of the renin-angiotensin system because it is involved in the degradation of angiotensin II (Ang II). This study examined the potential role of glomerular Ang II in the induction of albuminuria. The relation among renal Ang II, glomerular APAX enzyme activity, and albuminuria was examined first. Injection of the nephritogenic combinations ASD-3/37 and ASD-37/41 in BALB/c mice induced albuminuria, whereas the non-nephritogenic combination ASD-3/41 had no effect. There was no clear relation between the inhibition of glomerular APA activity and albuminuria, yet it was evident that intrarenal Ang II levels were significantly increased in albuminuric mice and not in nonalbuminuric mice. As a next step, anti-APA mAb were administered to angiotensinogen-deficient mice that do not produce Ang II, and kidney morphology and albuminuria were determined. Angiotensinogen-deficient mice also developed albuminuria upon ASD-37/41 administration. Altogether, these findings clearly demonstrate that Ang II is not required for the induction of albuminuria upon injection of enzyme-inhibiting anti-APA mAb.
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Affiliation(s)
- Miriam E Gerlofs-Nijland
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Karel J M Assmann
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Henry B P M Dijkman
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Jürgen W C Dieker
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Jacco P H F van Son
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Stef Mentzel
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Jorge P van Kats
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - A H Jan Danser
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Oliver Smithies
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Patricia J T A Groenen
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
| | - Jack F M Wetzels
- Departments of *Pathology and †Internal Medicine, Division of Nephrology, University Medical Centre Nijmegen, Nijmegen, and Departments of Internal Medicine and Pharmacology, Cardiovascular Research Institute Erasmus University Rotterdam (COEUR), Rotterdam, The Netherlands; and Department of Pathology, University of North Carolina, Chapel Hill, North Carolina
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Chugh S, Yuan H, Topham PS, Haydar SA, Mittal V, Taylor GA, Kalluri R, Salant DJ. Aminopeptidase A: a nephritogenic target antigen of nephrotoxic serum. Kidney Int 2001; 59:601-13. [PMID: 11168941 DOI: 10.1046/j.1523-1755.2001.059002601.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND We investigated potential targets of antibody-mediated glomerular injury induced with a noncomplement binding fraction of sheep anti-rat nephrotoxic serum (NTS). This model is characterized by severe complement- and leukocyte-independent proteinuria within 24 hours of NTS injection into rats. METHODS NTS-reactive glomerular cell and matrix proteins were identified by immunoprecipitation, Western blot analysis, protein sequencing, cDNA library screening, and enzyme-linked immunosorbent assay. Proteinuria was measured in rats injected with NTS from which reactivity against type IV collagen had been removed by immunoadsorption, and antibodies were eluted from the glomeruli of proteinuric rats that had been injected with unabsorbed NTS. Having identified aminopeptidase A (APA) as a major target of NTS, we studied the effect of NTS and anti-APA on mouse glomerular epithelial cells in culture. RESULTS NTS identified several podocyte and matrix proteins; however, APA was the only cell surface protein reactive with antibodies eluted from the glomeruli of rats injected with NTS. Although the eluate also contained reactivity to the noncollagenous domains of alpha1 and alpha3 chains of type IV collagen, immunodepletion of these antibodies did not diminish the ability of NTS to cause proteinuria. We also documented the surface expression of APA on mouse glomerular epithelial cells in culture, and found that NTS and specific anti-APA antibodies induce a time- and temperature-dependent redistribution of the antigen. CONCLUSIONS APA, a type II integral membrane metallopeptidase, is a major target of NTS in vivo and is known to be present on the surface of podocytes. NTS-induced proteinuria is independent of reactivity to known nephritogenic matrix proteins. These findings, in combination with previous studies showing that monoclonal anti-APA antibodies induce severe proteinuria in mice, suggest that anti-APA antibodies are responsible for complement-independent proteinuria in this model.
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Affiliation(s)
- S Chugh
- Department of Medicine, Evans Biomedical Research Center, Boston University Medical Center, Boston, Massachusetts 02118, USA
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17
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Wolf G, Wenzel U, Assmann KJ, Stahl RA. Renal expression of aminopeptidase A in rats with two-kidney, one-clip hypertension. Nephrol Dial Transplant 2000; 15:1935-42. [PMID: 11096137 DOI: 10.1093/ndt/15.12.1935] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Angiotensin II (ANG II) is a major factor involved in the progression of chronic renal disease. Although the generation of this vasoactive peptide has been investigated in great detail, only a few studies have hitherto addressed the metabolism of ANG II into fragments such as angiotensin III and IV (ANG III, IV) which may exert physiological effects independent of ANG II. Aminopeptidase A (APA) is the major enzyme degrading ANG II. The aim of the current study was to evaluate glomerular APA expression in rats with two-kidney, one-clip hypertension. METHODS The left renal artery was restricted with a 0.2-mm silver clip. Kidneys were harvested 1 and 4 weeks after surgery. APA enzyme and protein expression was evaluated in kidney sections. Total APA enzyme activity and mRNA expression was assessed in isolated glomeruli. Degradation of exogenous ANG II by isolated glomeruli was measured with reverse-phase high-performance liquid chromatography. RESULTS APA enzyme activity, protein, and mRNA expression were stimulated in the clipped kidney 1 week after surgery compared with the contralateral kidney or normal controls. In contrast, 4 weeks after clipping APA activity and expression was higher in the contralateral kidney. In parallel to these findings, degradation of ANG II was greatest in isolated glomeruli obtained from the clipped kidney after 1 week. However, preparations from the contralateral kidney 4 weeks after surgery were more active in the metabolism of exogenous ANG II. CONCLUSION The present study provides evidence that APA is complexly regulated in in vivo situations with an activated local renin-ANG II system. ANG II appears to play a direct role in this regulation. However, since conversion of ANG II to ANG III by APA is the initial step leading to the formation of ANG IV which may exert detrimental effects not mediated through classical ANG II receptors, a local increase in APA activity may contribute to the progression of chronic renal disease even during complete AT(1)-receptor blockade.
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Affiliation(s)
- G Wolf
- Department of Medicine, Division of Nephrology and Osteology, University of Hamburg, Hamburg, Germany
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18
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Mentzel S, Dijkman HB, van Son JP, Wetzels JF, Assmann KJ. In vivo antibody-mediated modulation of aminopeptidase A in mouse proximal tubular epithelial cells. J Histochem Cytochem 1999; 47:871-80. [PMID: 10375375 DOI: 10.1177/002215549904700704] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Aminopeptidase A (APA) is one of the many renal hydrolases. In mouse kidney, APA is predominantly expressed on the brush borders and sparsely on the basolateral membranes of proximal tubular epithelial cells. However, when large amounts of monoclonal antibodies (MAbs) against APA were injected into mice, we observed strong binding of the MAbs to the basolateral membranes, whereas the MAbs bound only transiently to the brush borders of the proximal tubular epithelial cells. In parallel, APA itself disappeared from the brush borders by both endocytosis and shedding, whereas it was increasingly expressed on the basolateral sides. Using ultrastructural immunohistology, we found no evidence for transcellular transport of endocytosed APA to the basolateral side of the proximal tubular epithelial cells. The absence of transcellular transport was confirmed by experiments in which we used a low dose of the MAbs. Such a low dose did not result in binding of the MAbs to the brush borders and had no effect on the presence of APA in the brush borders of the proximal tubular epithelial cells. In these experiments we still could observe binding of the MAbs to the basolateral membranes in parallel with the local appearance of APA. In addition, treatment of mice with chlorpromazine, a calmodulin antagonist that interferes with cytoskeletal function, largely inhibited the MAb-induced modulation of APA. Our studies suggest that injection of MAbs to APA specifically interrupts the normal intracellular traffic of this enzyme in proximal tubular epithelial cells. This intracellular transport is dependent on the action of cytoskeletal proteins.
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Affiliation(s)
- S Mentzel
- Departments of Pathology, Division of Nephrology, University Hospital Nijmegen, Nijmegen, The Netherlands
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