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Yamamura-Miyazaki N, Sakakibara N, Nozu K, Shima Y, Satomura K, Yamamoto S, Baba M, Fujiwara K, Yamamoto K, Michigami T. Identification of CUBN variants in triplets with a 20-year history of proteinuria. CEN Case Rep 2024:10.1007/s13730-024-00919-6. [PMID: 39102129 DOI: 10.1007/s13730-024-00919-6] [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: 05/11/2024] [Accepted: 07/20/2024] [Indexed: 08/06/2024] Open
Abstract
CUBN encodes cubilin, which plays a role in the reabsorption of glomerular-filtered albumin in the proximal tubule. CUBN-related proteinuria was recently established as a new disease concept and may be present in proteinuric cases that were previously undiagnosed either genetically or histologically. We herein report a case of triplets diagnosed with chronic benign proteinuria due to CUBN variants 20 years after its onset. The proband, the first child of triplets, tested positive for urinary protein several times during the neonatal period. A urine screening test at 3 years old was positive. Proteinuria persisted for years within a non-nephrotic range. Kidney biopsy at 8 years old revealed minor glomerular abnormalities. Renin-angiotensin system inhibitors were started for albumin-based proteinuria but were ineffective. Since the two other triplets had similar courses, analyses of the NPHS1/2 and WT1 genes were performed but revealed no abnormalities. The triplets transitioned to adult care at 15 years old. CUBN-related proteinuria was reported in 2020; therefore, we re-analyzed their DNA samples and identified compound heterozygous variants in CUBN in all three triplets. The molecular diagnosis of CUBN-related proteinuria will save patients from unnecessary treatments and concerns about renal prognosis.
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Affiliation(s)
- Natsumi Yamamura-Miyazaki
- Department of Pediatric Nephrology and Metabolism, Osaka Women's and Children's Hospital, 840 Murodo-Cho, Izumi, Osaka, 594-1101, Japan.
| | - Nana Sakakibara
- Department of Pediatrics, Kobe University Graduate School of Medicine, Hyogo, Japan
| | - Kandai Nozu
- Department of Pediatrics, Kobe University Graduate School of Medicine, Hyogo, Japan
| | - Yuko Shima
- Department of Pediatrics, Wakayama Medical University, Wakayama, Japan
| | - Kenichi Satomura
- Department of Internal Medicine, Meisei Daini Hospital, Osaka, Japan
| | | | - Minato Baba
- Department of Pediatric Nephrology and Metabolism, Osaka Women's and Children's Hospital, 840 Murodo-Cho, Izumi, Osaka, 594-1101, Japan
| | - Kaori Fujiwara
- Department of Pediatric Nephrology and Metabolism, Osaka Women's and Children's Hospital, 840 Murodo-Cho, Izumi, Osaka, 594-1101, Japan
| | - Katsusuke Yamamoto
- Department of Pediatric Nephrology and Metabolism, Osaka Women's and Children's Hospital, 840 Murodo-Cho, Izumi, Osaka, 594-1101, Japan
| | - Toshimi Michigami
- Department of Pediatric Nephrology and Metabolism, Osaka Women's and Children's Hospital, 840 Murodo-Cho, Izumi, Osaka, 594-1101, Japan
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka, Japan
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2
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Ralph DL, Ha D, Lei H, Priver TS, Smith SD, McFarlin BE, Schwindt S, Pandya D, Koepsell H, Pastor-Soler NM, Edwards A, McDonough AA. Potassium-Alkali-Enriched Diet, Hypertension, and Proteinuria following Uninephrectomy. J Am Soc Nephrol 2024:00001751-990000000-00357. [PMID: 38913441 DOI: 10.1681/asn.0000000000000420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Accepted: 06/10/2024] [Indexed: 06/26/2024] Open
Abstract
Key Points
A K-alkali–enriched diet blunted post-uninephrectomy hypertension and facilitated acid clearance by suppressing Na+ reabsorption.Uninephrectomy-associated proteinuria could be attributed to elevated single-nephron GFR and downregulation of megalin, which reduced fractional protein endocytosis.
Background
Losing or donating a kidney is associated with risks of developing hypertension and albuminuria. Few studies address mechanisms or interventions. We investigate the potential benefits of a K+- alkali–enriched diet and the mechanisms underlying proteinuria.
Methods
Male Sprague Dawley rats were fed either a 2% NaCl+0.95% KCl diet (HNa-LK) or a 0.74% NaCl+3% K+-alkali diet (HK-alk) for 3 weeks before uninephrectomy and then maintained on respective diets for 12 weeks. BP (by tail-cuff), urine, blood, and kidney proteins were analyzed before and after uninephrectomy.
Results
Before uninephrectomy, HK-alk–fed versus HNa-LK–fed rats exhibited similar BPs and plasma [K+], [Na+], but lower proximal (NHE3, sodium bicarbonate cotransporter 1, NaPi2) and higher distal (NCC, ENaC, and pendrin) transporter abundance, a pattern facilitating K+ and HCO3
− secretion. After uninephrectomy, single-nephron GFR increased 50% and Li+ clearance doubled with both diets; in HK-alk versus HNa-LK, the increase in BP was less and ammoniagenesis was lower, abundance of proximal tubule transporters remained lower, ENaC-α fell, and NCCp increased, consistent with K+ conservation. After uninephrectomy, independent of diet, albuminuria increased eight-fold and abundance of endocytic receptors was reduced (megalin by 44%, disabled homolog 2 by 25%–35%) and kidney injury molecule-1 was increased.
Conclusions
The K-alkali–enriched diet blunted post-uninephrectomy hypertension and facilitated acid clearance by suppressing proximal Na+ transporters and increasing K+-alkali secretion. Furthermore, uninephrectomy-associated proteinuria could be attributed, at least in part, to elevated single-nephron GFR coupled with downregulation of megalin, which reduced fractional protein endocytosis and Vmax.
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Affiliation(s)
- Donna L Ralph
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Darren Ha
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Hillmin Lei
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Taylor S Priver
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Scotti D Smith
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Brandon E McFarlin
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Seth Schwindt
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Drishti Pandya
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Hermann Koepsell
- Institute for Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany
| | - Nuria M Pastor-Soler
- Division of Nephrology, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Aurelie Edwards
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts
| | - Alicia A McDonough
- Department of Physiology and Neuroscience, Keck School of Medicine, University of Southern California, Los Angeles, California
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3
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Carbayo J, Verdalles Ú, Díaz-Crespo F, Lázaro A, González-Nicolás M, Arroyo D, Blanco D, García-Gámiz M, Goicoechea M. Tubular biomarkers in proteinuric kidney disease: histology correlation and kidney prognosis of tubular biomarkers. Clin Kidney J 2024; 17:sfae146. [PMID: 38803396 PMCID: PMC11129590 DOI: 10.1093/ckj/sfae146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Indexed: 05/29/2024] Open
Abstract
Background Proteinuria is not only a biomarker of chronic kidney disease (CKD) but also a driver of CKD progression. The aim of this study was to evaluate serum and urinary tubular biomarkers in patients with biopsied proteinuric kidney disease and to correlate them with histology and kidney outcomes. Methods A single-center retrospective study was conducted on a cohort of 156 patients from January 2016 to December 2021. The following urinary and serum biomarkers were analyzed on the day of kidney biopsy: beta 2 microglobulin (β2-mcg), alpha 1 microglobulin (α1-mcg), neutrophil gelatinase-associated lipocalin (NGAL), urinary kidney injury molecule-1 (uKIM-1), monocyte chemoattractant protein-1 (MCP-1), urinary Dickkopf-3 (uDKK3), uromodulin (urinary uUMOD), serum kidney injury molecule-1 (sKIM-1) and serum uromodulin (sUMOD). A composite outcome of kidney progression or death was recorded during a median follow-up period of 26 months. Results Multivariate regression analysis identified sUMOD (β-0.357, P < .001) and uDKK3 (β 0.483, P < .001) as independent predictors of interstitial fibrosis, adjusted for age, estimated glomerular filtration rate (eGFR) and log proteinuria. Elevated levels of MCP-1 [odds ratio 15.61, 95% confidence interval (CI) 3.52-69.20] were associated with a higher risk of cortical interstitial inflammation >10% adjusted for eGFR, log proteinuria and microhematuria. Upper tertiles of uDKK3 were associated with greater eGFR decline during follow-up. Although not a predictor of the composite outcome, doubling of uDKK3 was a predictor of kidney events (hazard ratio 2.26, 95% CI 1.04-4.94) after adjustment for interstitial fibrosis, eGFR and proteinuria. Conclusions Tubular markers may have prognostic value in proteinuric kidney disease, correlating with specific histologic parameters and identifying cases at higher risk of CKD progression.
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Affiliation(s)
- Javier Carbayo
- Department of Nephrology, Hospital General Universitario Gregorio Marañón, Madrid, Spain
| | - Úrsula Verdalles
- Department of Nephrology, Hospital General Universitario Gregorio Marañón, Madrid, Spain
| | - Francisco Díaz-Crespo
- Department of Pathology, Hospital General Universitario Gregorio Marañón, Madrid, Spain
| | - Alberto Lázaro
- Renal Pathophysiology Laboratory, Instituto Investigación Sanitaria Gregorio Marañón, Madrid, Spain
| | - Marian González-Nicolás
- Renal Pathophysiology Laboratory, Instituto Investigación Sanitaria Gregorio Marañón, Madrid, Spain
| | - David Arroyo
- Department of Nephrology, Hospital General Universitario Gregorio Marañón, Madrid, Spain
| | - David Blanco
- Renal Pathophysiology Laboratory, Instituto Investigación Sanitaria Gregorio Marañón, Madrid, Spain
| | - Mercedes García-Gámiz
- Department of Biochemistry, Hospital General Universitario Gregorio Marañón, Madrid, Spain
| | - Marian Goicoechea
- Department of Nephrology, Hospital General Universitario Gregorio Marañón, Madrid, Spain
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Waller AP, Wolfgang KJ, Pruner I, Stevenson ZS, Abdelghani E, Muralidharan K, Wilkie TK, Blissett AR, Calomeni EP, Vetter TA, Brodsky SV, Smoyer WE, Nieman MT, Kerlin BA. Prothrombin Knockdown Protects Podocytes and Reduces Proteinuria in Glomerular Disease. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.20.544360. [PMID: 38464017 PMCID: PMC10925217 DOI: 10.1101/2023.06.20.544360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Chronic kidney disease (CKD) is a leading cause of death, and its progression is driven by glomerular podocyte injury and loss, manifesting as proteinuria. Proteinuria includes urinary loss of coagulation zymogens, cofactors, and inhibitors. Importantly, both CKD and proteinuria significantly increase the risk of thromboembolic disease. Prior studies demonstrated that anticoagulants reduced proteinuria in rats and that thrombin injured cultured podocytes. Herein we aimed to directly determine the influence of circulating prothrombin on glomerular pathobiology. We hypothesized that (pro)thrombin drives podocytopathy, podocytopenia, and proteinuria. Glomerular proteinuria was induced with puromycin aminonucleoside (PAN) in Wistar rats. Circulating prothrombin was either knocked down using a rat-specific antisense oligonucleotide or elevated by serial intravenous infusions of prothrombin protein, which are previously established methods to model hypo- (LoPT) and hyper-prothrombinemia (HiPT), respectively. After 10 days (peak proteinuria in this model) plasma prothrombin levels were determined, kidneys were examined for (pro)thrombin co-localization to podocytes, histology, and electron microscopy. Podocytopathy and podocytopenia were determined and proteinuria, and plasma albumin were measured. LoPT significantly reduced prothrombin colocalization to podocytes, podocytopathy, and proteinuria with improved plasma albumin. In contrast, HiPT significantly increased podocytopathy and proteinuria. Podocytopenia was significantly reduced in LoPT vs. HiPT rats. In summary, prothrombin knockdown ameliorated PAN-induced glomerular disease whereas hyper-prothrombinemia exacerbated disease. Thus, (pro)thrombin antagonism may be a viable strategy to simultaneously provide thromboprophylaxis and prevent podocytopathy-mediated CKD progression.
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5
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Molitoris BA, Dunn KW, Sandoval RM. Proximal tubule role in albumin homeostasis: controversy, species differences, and the contributions of intravital microscopy. Kidney Int 2023; 104:1065-1069. [PMID: 37981429 DOI: 10.1016/j.kint.2023.05.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 05/23/2023] [Accepted: 05/30/2023] [Indexed: 11/21/2023]
Affiliation(s)
- Bruce A Molitoris
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.
| | - Kenneth W Dunn
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Ruben M Sandoval
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
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6
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Wagner MC, Sandoval RM, Yadav SPS, Campos SB, Rhodes GJ, Phillips CL, Molitoris BA. Lrpap1 (RAP) Inhibits Proximal Tubule Clathrin Mediated and Clathrin Independent Endocytosis, Ameliorating Renal Aminoglycoside Nephrotoxicity. KIDNEY360 2023; 4:591-605. [PMID: 36848531 PMCID: PMC10278819 DOI: 10.34067/kid.0000000000000094] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 01/31/2023] [Indexed: 03/01/2023]
Abstract
Key Points Proximal tubule endocytosis of toxins often leads to nephrotoxicity. Inhibition of endocytosis with receptor-associated protein may serve as a clinical approach to reduce or eliminate kidney damage from a potential nephrotoxin. Background Proximal tubules (PTs) are exposed to many exogenous and endogenous nephrotoxins that pass through the glomerular filter. This includes many small molecules, such as aminoglycoside and myeloma light chains. These filtered molecules are rapidly endocytosed by the PTs and lead to nephrotoxicity. Methods To investigate whether inhibition of PT uptake of filtered toxins can reduce toxicity, we evaluated the ability of Lrpap1 or receptor-associated protein (RAP) to prevent PT endocytosis. Munich Wistar Frömter rats were used since both glomerular filtration and PT uptake can be visualized and quantified. The injury model chosen was the well-established gentamicin-induced toxicity, which leads to significant reductions in GFR and serum creatinine increases. CKD was induced with a right uninephrectomy and left 40-minute pedicle clamp. Rats had 8 weeks to recover and to stabilize GFR and proteinuria. Multiphoton microscopy was used to evaluate endocytosis in vivo and serum creatinine, and 24-hour creatinine clearances were used to evaluate kidney functional changes. Results Studies showed that preadministration of RAP significantly inhibited both albumin and dextran endocytosis in outer cortical PTs. Importantly, this inhibition was found to be rapidly reversible with time. RAP was also found to be an excellent inhibitor of PT gentamicin endocytosis. Finally, gentamicin administration for 6 days resulted in significant elevation of serum creatinine in vehicle-treated rats, but not in those receiving daily infusion of RAP before gentamicin. Conclusions This study provides a model for the potential use of RAP to prevent, in a reversible manner, PT endocytosis of potential nephrotoxins, thus protecting the kidney from damage.
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Affiliation(s)
- Mark C Wagner
- Indiana Center for Biological Microscopy, Indiana University School of Medicine, Indianapolis, Indiana
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7
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Yu A, Zhao J, Peng W, Yadav SPS, Molitoris BA, Wagner MC, Mechref Y. Proteomics profiling of kidney brush border membrane from rats using LC-MS/MS analysis. Proteomics Clin Appl 2023; 17:e2200063. [PMID: 36189891 DOI: 10.1002/prca.202200063] [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: 08/09/2022] [Revised: 12/12/1912] [Accepted: 09/30/2022] [Indexed: 03/15/2023]
Abstract
PURPOSE Chronic kidney disease (CKD) is defined by a reduced renal function, that is, glomerular filtration rate, and the extent of kidney damage is assessed by determining serum creatinine levels and proteins in urine, diagnosed as proteinuria/albuminuria. Albuminuria increases with age and can result from glomerular and/or proximal tubule (PT) alterations. Brush border membranes (BBMs) on PT cells are important in maintaining the stability of PT functions. EXPERIMENTAL DESIGN An LC-MS/MS bottom-up proteomics analysis of BBMs from four groups of rat models was applied to investigate protein abundance alterations associated with CKD progression. Moreover, systems biology analyses were used to identify key proteins that can provide insight into the different regulated molecular pathways and processes associated with CKD. RESULTS Our results indicated that 303 proteins showed significantly altered expressions from the severe CKD BBM group when compared to the control. Focusing on renal diseases, several proteins including Ctnnb1, Fah, and Icam1 were annotated to kidney damage and urination disorder. The up-regulation of Ctnnb1 (β-catenin) could contribute to CKD through the regulation of the WNT signaling pathway. CONCLUSION AND CLINICAL RELEVANCE Overall, the study of protein abundance changes in BBMs from rat models helps to reveal protein corrections with important pathways and regulator effects involved in CKD. Although this study is focused on rat models, the results provided more information for a deeper insight into possible CKD mechanisms in humans.
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Affiliation(s)
- Aiying Yu
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, USA
| | - Jingfu Zhao
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, USA
| | - Wenjing Peng
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, USA
| | - Shiv Pratap S Yadav
- Nephrology Division, Department of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Bruce A Molitoris
- Nephrology Division, Department of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Mark C Wagner
- Nephrology Division, Department of Medicine, Indiana University, Indianapolis, Indiana, USA
| | - Yehia Mechref
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, USA
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8
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Bryniarski MA, Sandoval RM, Ruszaj DM, Fraser-McArthur J, Yee BM, Yacoub R, Chaves LD, Campos-Bilderback SB, Molitoris BA, Morris ME. Defining the Intravital Renal Disposition of Fluorescence-Quenched Exenatide. Mol Pharm 2023; 20:987-996. [PMID: 36626167 PMCID: PMC9907348 DOI: 10.1021/acs.molpharmaceut.2c00671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 12/13/2022] [Accepted: 12/14/2022] [Indexed: 01/11/2023]
Abstract
Despite the understanding that renal clearance is pivotal for driving the pharmacokinetics of numerous therapeutic proteins and peptides, the specific processes that occur following glomerular filtration remain poorly defined. For instance, sites of catabolism within the proximal tubule can occur at the brush border, within lysosomes following endocytosis, or even within the tubule lumen itself. The objective of the current study was to address these limitations and develop methodology to study the kidney disposition of a model therapeutic protein. Exenatide is a peptide used to treat type 2 diabetes mellitus. Glomerular filtration and ensuing renal catabolism have been shown to be its principal clearance pathway. Here, we designed and validated a Förster resonance energy transfer-quenched exenatide derivative to provide critical information on the renal handling of exenatide. A combination of in vitro techniques was used to confirm substantial fluorescence quenching of intact peptide that was released upon proteolytic cleavage. This evaluation was then followed by an assessment of the in vivo disposition of quenched exenatide directly within kidneys of living rats via intravital two-photon microscopy. Live imaging demonstrated rapid glomerular filtration and identified exenatide metabolism occurred within the subapical regions of the proximal tubule epithelia, with subsequent intracellular trafficking of cleaved fragments. These results provide a novel examination into the real-time, intravital disposition of a protein therapeutic within the kidney and offer a platform to build upon for future work.
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Affiliation(s)
- Mark A. Bryniarski
- Department
of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical
Sciences, University at Buffalo, 304 Pharmacy Building, Buffalo, New York 14215, United States
| | - Ruben M. Sandoval
- Department
of Medicine, Indiana University, Indianapolis, Indiana 46202, United States
| | - Donna M. Ruszaj
- Department
of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical
Sciences, University at Buffalo, 304 Pharmacy Building, Buffalo, New York 14215, United States
| | - John Fraser-McArthur
- Department
of Pharmacy, University of Rochester Medical
Center, Rochester, New York 14642, United States
| | - Benjamin M. Yee
- Department
of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical
Sciences, University at Buffalo, 304 Pharmacy Building, Buffalo, New York 14215, United States
| | - Rabi Yacoub
- Department
of Internal Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203, United States
| | - Lee D. Chaves
- Department
of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical
Sciences, University at Buffalo, 304 Pharmacy Building, Buffalo, New York 14215, United States
- Department
of Neurosurgery, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203, United States
| | | | - Bruce A. Molitoris
- Department
of Medicine, Indiana University, Indianapolis, Indiana 46202, United States
| | - Marilyn E. Morris
- Department
of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical
Sciences, University at Buffalo, 304 Pharmacy Building, Buffalo, New York 14215, United States
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9
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Yadav SPS, Yu A, Zhao J, Singh J, Kakkar S, Chakraborty S, Mechref Y, Molitoris B, Wagner MC. Glycosylation of a key cubilin Asn residue results in reduced binding to albumin. J Biol Chem 2022; 298:102371. [PMID: 35970386 PMCID: PMC9485058 DOI: 10.1016/j.jbc.2022.102371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 08/09/2022] [Accepted: 08/10/2022] [Indexed: 10/28/2022] Open
Abstract
Kidney disease often manifests with an increase in proteinuria, which can result from both glomerular and/or proximal tubule injury. The proximal tubules are the major site of protein and peptide endocytosis of the glomerular filtrate, and cubilin is the proximal tubule brush border membrane glycoprotein receptor that binds filtered albumin and initiates its processing in proximal tubules. Albumin also undergoes multiple modifications depending upon the physiologic state. We previously documented that carbamylated albumin had reduced cubilin binding, but the effects of cubilin modifications on binding albumin remain unclear. Here, we investigate the cubilin-albumin binding interaction to define the impact of cubilin glycosylation and map the key glycosylation sites while also targeting specific changes in a rat model of proteinuria. We identified a key Asn residue, N1285, that when glycosylated reduced albumin binding. In addition, we found a pH-induced conformation change may contribute to ligand release. To further define the albumin-cubilin binding site, we determined the solution structure of cubilin's albumin-binding domain, CUB7,8, using small-angle X-ray scattering and molecular modeling. We combined this information with mass spectrometry crosslinking experiments of CUB7,8 and albumin that provides a model of the key amino acids required for cubilin-albumin binding. Together, our data supports an important role for glycosylation in regulating the cubilin interaction with albumin, which is altered in proteinuria and provides new insight into the binding interface necessary for the cubilin-albumin interaction.
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Affiliation(s)
- Shiv Pratap Singh Yadav
- Nephrology Division, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Aiying Yu
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, USA
| | - Jingfu Zhao
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, USA
| | - Jasdeep Singh
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, New Delhi, India
| | - Saloni Kakkar
- CSIR-Institute of Microbial Technology, Chandigarh, India
| | | | - Yehia Mechref
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas, USA
| | - Bruce Molitoris
- Nephrology Division, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA; Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Mark C Wagner
- Nephrology Division, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.
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10
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Comper WD, Vuchkova J, McCarthy KJ. New insights into proteinuria/albuminuria. Front Physiol 2022; 13:991756. [PMID: 36225307 PMCID: PMC9548894 DOI: 10.3389/fphys.2022.991756] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 08/29/2022] [Indexed: 11/13/2022] Open
Abstract
The fractional clearance of proteins as measured in healthy human subjects increases 10,000–100,000- fold when studied in nephrotic patients. This remarkable increase cannot be accounted for by extracellular biophysical mechanisms centered at the glomerular filtration barrier. Rather, it is the nephron and its combination of filtration and cellular uptake that can provide a plausible explanation of these fractional clearance changes. The nephron has two regions that critically determine the level proteinuria/albuminuria. Glomerular filtration of plasma proteins is primarily a size selective event that is basically unchanged in acquired and genetic kidney disease. The glomerular concepts of ‘charge selectivity’ and of ‘large pores’, previously used to explain proteinuria, are now recognized to be flawed and non-existent. Filtered proteins then encounter downstream two protein receptors of the Park and Maack type associated with the proximal tubular cell. The high capacity receptor is thought to retrieve the majority of filtered proteins and return them to the blood supply. Inhibition/saturation of this pathway in kidney disease may create the nephrotic condition and hypoproteinemia/hypoalbuminemia. Inhibitors of this pathway (possibly podocyte derived) are still to be identified. A relatively small proportion of the filtered protein is directed towards a high affinity, low capacity receptor that guides the protein to undergo lysosomal degradation. Proteinuria in normoproteinemic states is derived by inhibition of this pathway, such as in diabetes. The combination of glomerular sieving, and the degradation and retrieval pathways can quantitatively account for the changes in fractional clearance of proteins in the nephrotic condition. Finally, the general retrieval of filtered protein by the proximal tubular cell focuses on the teleological importance of this cell as this retrieval represents the third pillar of retrieval that this cell participates in (it also retrieves water and salt).
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Affiliation(s)
- Wayne D. Comper
- Salaqua Diagnostics Inc, New York, NY, United States
- *Correspondence: Wayne D. Comper,
| | | | - Kevin J. McCarthy
- Department of Cellular Biology and Anatomy, LSU Health Sciences Center, Shreveport, LA, United States
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11
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Silva-Aguiar RP, Peruchetti DB, Pinheiro AAS, Caruso-Neves C, Dias WB. O-GlcNAcylation in Renal (Patho)Physiology. Int J Mol Sci 2022; 23:ijms231911260. [PMID: 36232558 PMCID: PMC9569498 DOI: 10.3390/ijms231911260] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 09/19/2022] [Accepted: 09/20/2022] [Indexed: 12/29/2022] Open
Abstract
Kidneys maintain internal milieu homeostasis through a well-regulated manipulation of body fluid composition. This task is performed by the correlation between structure and function in the nephron. Kidney diseases are chronic conditions impacting healthcare programs globally, and despite efforts, therapeutic options for its treatment are limited. The development of chronic degenerative diseases is associated with changes in protein O-GlcNAcylation, a post-translation modification involved in the regulation of diverse cell function. O-GlcNAcylation is regulated by the enzymatic balance between O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) which add and remove GlcNAc residues on target proteins, respectively. Furthermore, the hexosamine biosynthetic pathway provides the substrate for protein O-GlcNAcylation. Beyond its physiological role, several reports indicate the participation of protein O-GlcNAcylation in cardiovascular, neurodegenerative, and metabolic diseases. In this review, we discuss the impact of protein O-GlcNAcylation on physiological renal function, disease conditions, and possible future directions in the field.
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Affiliation(s)
- Rodrigo P. Silva-Aguiar
- Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
| | - Diogo B. Peruchetti
- Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
| | - Ana Acacia S. Pinheiro
- Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Rio de Janeiro Innovation Network in Nanosystems for Health-NanoSAÚDE/FAPERJ, Rio de Janeiro 21045-900, Brazil
| | - Celso Caruso-Neves
- Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Rio de Janeiro Innovation Network in Nanosystems for Health-NanoSAÚDE/FAPERJ, Rio de Janeiro 21045-900, Brazil
- National Institute of Science and Technology for Regenerative Medicine, Rio de Janeiro 21941-902, Brazil
| | - Wagner B. Dias
- Carlos Chagas Filho Institute of Biophysics, Federal University of Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Correspondence:
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12
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Thompson LE, Joy MS. Endogenous markers of kidney function and renal drug clearance processes of filtration, secretion, and reabsorption. CURRENT OPINION IN TOXICOLOGY 2022; 31:100344. [PMID: 36777447 PMCID: PMC9910221 DOI: 10.1016/j.cotox.2022.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The kidneys are responsible for maintaining physiologic homeostasis. The kidneys clear a variety of drugs and other substances through passive (filtration) and active processes that utilize transport proteins. Renal clearance is comprised of the processes of glomerular filtration, tubular secretion, and tubular reabsorption. Endogenous biomarkers, such as creatinine and cystatin C, are routinely used to estimate renal clearance. Understanding the contributing components of renal function and clearance, through the use of biomarkers, is necessary in elucidating the renal pharmacology of drugs and other substances. While exogenous markers of kidney function have been known for decades, several complexities have limited their usage. Several endogenous markers are being evaluated and hold promise to elucidate the individual components of kidney function that represent filtration, secretion, and reabsorption.
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Affiliation(s)
- Lauren E. Thompson
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Melanie S. Joy
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA,Division of Renal Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
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13
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Park SJ, Kim Y, Li C, Suh J, Sivapackiam J, Goncalves TM, Jarad G, Zhao G, Urano F, Sharma V, Chen YM. Blocking CHOP-dependent TXNIP shuttling to mitochondria attenuates albuminuria and mitigates kidney injury in nephrotic syndrome. Proc Natl Acad Sci U S A 2022; 119:e2116505119. [PMID: 35994650 PMCID: PMC9436335 DOI: 10.1073/pnas.2116505119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 07/15/2022] [Indexed: 11/18/2022] Open
Abstract
Albuminuria is a hallmark of glomerular disease of various etiologies. It is not only a symptom of glomerular disease but also a cause leading to glomerulosclerosis, interstitial fibrosis, and eventually, a decline in kidney function. The molecular mechanism underlying albuminuria-induced kidney injury remains poorly defined. In our genetic model of nephrotic syndrome (NS), we have identified CHOP (C/EBP homologous protein)-TXNIP (thioredoxin-interacting protein) as critical molecular linkers between albuminuria-induced ER dysfunction and mitochondria dyshomeostasis. TXNIP is a ubiquitously expressed redox protein that binds to and inhibits antioxidant enzyme, cytosolic thioredoxin 1 (Trx1), and mitochondrial Trx2. However, very little is known about the regulation and function of TXNIP in NS. By utilizing Chop-/- and Txnip-/- mice as well as 68Ga-Galuminox, our molecular imaging probe for detection of mitochondrial reactive oxygen species (ROS) in vivo, we demonstrate that CHOP up-regulation induced by albuminuria drives TXNIP shuttling from nucleus to mitochondria, where it is required for the induction of mitochondrial ROS. The increased ROS accumulation in mitochondria oxidizes Trx2, thus liberating TXNIP to associate with mitochondrial nod-like receptor protein 3 (NLRP3) to activate inflammasome, as well as releasing mitochondrial apoptosis signal-regulating kinase 1 (ASK1) to induce mitochondria-dependent apoptosis. Importantly, inhibition of TXNIP translocation and mitochondrial ROS overproduction by CHOP deletion suppresses NLRP3 inflammasome activation and p-ASK1-dependent mitochondria apoptosis in NS. Thus, targeting TXNIP represents a promising therapeutic strategy for the treatment of NS.
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Affiliation(s)
- Sun-Ji Park
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Yeawon Kim
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Chuang Li
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Junwoo Suh
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
| | - Jothilingam Sivapackiam
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Tassia M. Goncalves
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110
| | - George Jarad
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Guoyan Zhao
- Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Fumihiko Urano
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Vijay Sharma
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110
- Department of Biomedical Engineering, School of Engineering & Applied Science, Washington University, St. Louis, MO 63105
| | - Ying Maggie Chen
- Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
- Department of Cell Biology & Physiology, Washington University School of Medicine, St. Louis, MO 63110
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14
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Molitoris BA, Sandoval RM, Yadav SPS, Wagner MC. Albumin Uptake and Processing by the Proximal Tubule: Physiologic, Pathologic and Therapeutic Implications. Physiol Rev 2022; 102:1625-1667. [PMID: 35378997 PMCID: PMC9255719 DOI: 10.1152/physrev.00014.2021] [Citation(s) in RCA: 46] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
For nearly 50 years the proximal tubule (PT) has been known to reabsorb, process, and either catabolize or transcytose albumin from the glomerular filtrate. Innovative techniques and approaches have provided insights into these processes. Several genetic diseases, nonselective PT cell defects, chronic kidney disease (CKD), and acute PT injury lead to significant albuminuria, reaching nephrotic range. Albumin is also known to stimulate PT injury cascades. Thus, the mechanisms of albumin reabsorption, catabolism, and transcytosis are being reexamined with the use of techniques that allow for novel molecular and cellular discoveries. Megalin, a scavenger receptor, cubilin, amnionless, and Dab2 form a nonselective multireceptor complex that mediates albumin binding and uptake and directs proteins for lysosomal degradation after endocytosis. Albumin transcytosis is mediated by a pH-dependent binding affinity to the neonatal Fc receptor (FcRn) in the endosomal compartments. This reclamation pathway rescues albumin from urinary losses and cellular catabolism, extending its serum half-life. Albumin that has been altered by oxidation, glycation, or carbamylation or because of other bound ligands that do not bind to FcRn traffics to the lysosome. This molecular sorting mechanism reclaims physiological albumin and eliminates potentially toxic albumin. The clinical importance of PT albumin metabolism has also increased as albumin is now being used to bind therapeutic agents to extend their half-life and minimize filtration and kidney injury. The purpose of this review is to update and integrate evolving information regarding the reabsorption and processing of albumin by proximal tubule cells including discussion of genetic disorders and therapeutic considerations.
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Affiliation(s)
- Bruce A. Molitoris
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States
- Dept.of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana, United States
| | - Ruben M. Sandoval
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States
| | - Shiv Pratap S. Yadav
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States
| | - Mark C. Wagner
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States
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15
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Molitoris BA, Sandoval RM, Wagner MC. Intravital Multiphoton Microscopy as a Tool for Studying Renal Physiology, Pathophysiology and Therapeutics. Front Physiol 2022; 13:827280. [PMID: 35399274 PMCID: PMC8988037 DOI: 10.3389/fphys.2022.827280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/09/2022] [Indexed: 11/13/2022] Open
Abstract
Intravital multiphoton microscopy has empowered investigators to study dynamic cell and subcellular processes in vivo within normal and disease organs. Advances in hardware, software, optics, transgenics and fluorescent probe design and development have enabled new quantitative approaches to create a disruptive technology pioneering advances in understanding of normal biology, disease pathophysiology and therapies. Offering superior spatial and temporal resolution with high sensitivity, investigators can follow multiple processes simultaneously and observe complex interactions between different cell types, intracellular organelles, proteins and track molecules for cellular uptake, intracellular trafficking, and metabolism in a cell specific fashion. The technique has been utilized in the kidney to quantify multiple dynamic processes including capillary flow, permeability, glomerular function, proximal tubule processes and determine the effects of diseases and therapeutic mechanisms. Limitations include the depth of tissue penetration with loss of sensitivity and resolution due to scattered emitted light. Tissue clearing technology has virtually eliminated penetration issues for fixed tissue studies. Use of multiphoton microscopy in preclinical animal models offers distinct advantages resulting in new insights into physiologic processes and the pathophysiology and treatment of diseases.
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16
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Silva-Aguiar RP, Peruchetti DB, Florentino LS, Takiya CM, Marzolo MP, Dias WB, Pinheiro AAS, Caruso-Neves C. Albumin Expands Albumin Reabsorption Capacity in Proximal Tubule Epithelial Cells through a Positive Feedback Loop between AKT and Megalin. Int J Mol Sci 2022; 23:ijms23020848. [PMID: 35055044 PMCID: PMC8776186 DOI: 10.3390/ijms23020848] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/05/2022] [Accepted: 01/11/2022] [Indexed: 12/20/2022] Open
Abstract
Renal proximal tubule cells (PTECs) act as urine gatekeepers, constantly and efficiently avoiding urinary protein waste through receptor-mediated endocytosis. Despite its importance, little is known about how this process is modulated in physiologic conditions. Data suggest that the phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) pathway regulates PTEC protein reabsorption. Here, we worked on the hypothesis that the physiologic albumin concentration and PI3K/AKT pathway form a positive feedback loop to expand endocytic capacity. Using LLC-PK1 cells, a model of PTECs, we showed that the PI3K/AKT pathway is required for megalin recycling and surface expression, affecting albumin uptake. Inhibition of this pathway stalls megalin at EEA1+ endosomes. Physiologic albumin concentration (0.01 mg/mL) activated AKT; this depends on megalin-mediated albumin endocytosis and requires previous activation of PI3K/mTORC2. This effect is correlated to the increase in albumin endocytosis, a phenomenon that we refer to as “albumin-induced albumin endocytosis”. Mice treated with L-lysine present decreased albumin endocytosis leading to proteinuria and albuminuria associated with inhibition of AKT activity. Renal cortex explants obtained from control mice treated with MK-2206 decreased albumin uptake and promoted megalin internalization. Our data highlight the mechanism behind the capacity of PTECs to adapt albumin reabsorption to physiologic fluctuations in its filtration, avoiding urinary excretion.
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Affiliation(s)
- Rodrigo P. Silva-Aguiar
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; (R.P.S.-A.); (D.B.P.); (L.S.F.); (C.M.T.); (W.B.D.); (A.A.S.P.)
| | - Diogo B. Peruchetti
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; (R.P.S.-A.); (D.B.P.); (L.S.F.); (C.M.T.); (W.B.D.); (A.A.S.P.)
| | - Lucas S. Florentino
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; (R.P.S.-A.); (D.B.P.); (L.S.F.); (C.M.T.); (W.B.D.); (A.A.S.P.)
| | - Christina M. Takiya
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; (R.P.S.-A.); (D.B.P.); (L.S.F.); (C.M.T.); (W.B.D.); (A.A.S.P.)
| | - María-Paz Marzolo
- Departamento de Biología Celular y Molecular, Pontificia Universidad Católica de Chile, Santiago 8330163, Chile;
| | - Wagner B. Dias
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; (R.P.S.-A.); (D.B.P.); (L.S.F.); (C.M.T.); (W.B.D.); (A.A.S.P.)
| | - Ana Acacia S. Pinheiro
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; (R.P.S.-A.); (D.B.P.); (L.S.F.); (C.M.T.); (W.B.D.); (A.A.S.P.)
- Redes de Pesquisa em Nanotecnologia para Saúde, NanoSaúde/FAPERJ, Rio de Janeiro 21040-900, Brazil
| | - Celso Caruso-Neves
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil; (R.P.S.-A.); (D.B.P.); (L.S.F.); (C.M.T.); (W.B.D.); (A.A.S.P.)
- Redes de Pesquisa em Nanotecnologia para Saúde, NanoSaúde/FAPERJ, Rio de Janeiro 21040-900, Brazil
- Instituto Nacional de Ciência e Tecnologia em Medicina Regenerativa, INCT-Regenera, Rio de Janeiro 21941-902, Brazil
- Correspondence: ; Tel.: +55-21-3938-6582
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17
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Wang H, Zhang S, Guo J. Lipotoxic Proximal Tubular Injury: A Primary Event in Diabetic Kidney Disease. Front Med (Lausanne) 2021; 8:751529. [PMID: 34760900 PMCID: PMC8573085 DOI: 10.3389/fmed.2021.751529] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 09/27/2021] [Indexed: 01/23/2023] Open
Abstract
The pathogenesis of diabetic nephropathy is a complex process that has a great relationship with lipotoxicity. Since the concept of “nephrotoxicity” was proposed, many studies have confirmed that lipotoxicity plays a significant role in the progression of diabetic nephropathy and causes various renal dysfunction. This review will make a brief summary of renal injury caused by lipotoxicity that occurs primarily and predominantly in renal tubules during diabetic progression, further leading to glomerular dysfunction. The latest research suggests that lipotoxicity-mediated tubular injury may be a major event in diabetic nephropathy.
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Affiliation(s)
- Hua Wang
- Department of Pharmacy, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Shu Zhang
- Department of Pharmacy, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Jia Guo
- Department of Nephrology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.,Department of Nephrology, Nephropathy Research Institutes of Zhengzhou University, Zhengzhou, China
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18
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Yu A, Zhao J, Yadav SPS, Molitoris BA, Wagner MC, Mechref Y. Changes in the Expression of Renal Brush Border Membrane N-Glycome in Model Rats with Chronic Kidney Diseases. Biomolecules 2021; 11:1677. [PMID: 34827675 PMCID: PMC8616023 DOI: 10.3390/biom11111677] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/08/2021] [Accepted: 11/09/2021] [Indexed: 12/15/2022] Open
Abstract
Chronic kidney disease (CKD) is defined by a reduced renal function i.e., glomerular filtration rate (GFR), and the presence of kidney damage is determined by measurement of proteinuria or albuminuria. Albuminuria increases with age and can result from glomerular and/or proximal tubule (PT) alterations. Brush-border membranes (BBMs) on PT cells play an important role in maintaining the stability of PT functions. The PT BBM, a highly dynamic, organized, specialized membrane, contains a variety of glycoproteins required for the functions of PT. Since protein glycosylation regulates many protein functions, the alteration of glycosylation due to the glycan changes has attracted more interests for a variety of disease studies recently. In this work, liquid chromatography-tandem mass spectrometry was utilized to analyze the abundances of permethylated glycans from rats under control to mild CKD, severe CKD, and diabetic conditions. The most significant differences were observed in sialylation level with the highest present in the severe CKD and diabetic groups. Moreover, high mannose N-glycans was enriched in the CKD BBMs. Characterization of all the BBM N-glycan changes supports that these changes are likely to impact the functional properties of the dynamic PT BBM. Further, these changes may lead to the potential discovery of glycan biomarkers for improved CKD diagnosis and new avenues for therapeutic treatments.
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Affiliation(s)
- Aiying Yu
- Department of Chemistry and Biochemistry, Texas Tech University, Texas City, TX 79409, USA; (A.Y.); (J.Z.)
| | - Jingfu Zhao
- Department of Chemistry and Biochemistry, Texas Tech University, Texas City, TX 79409, USA; (A.Y.); (J.Z.)
| | - Shiv Pratap S. Yadav
- Nephrology Division, Department of Medicine, Indiana University, Indianapolis, IN 46202, USA; (S.P.S.Y.); (B.A.M.); (M.C.W.)
| | - Bruce A. Molitoris
- Nephrology Division, Department of Medicine, Indiana University, Indianapolis, IN 46202, USA; (S.P.S.Y.); (B.A.M.); (M.C.W.)
| | - Mark C. Wagner
- Nephrology Division, Department of Medicine, Indiana University, Indianapolis, IN 46202, USA; (S.P.S.Y.); (B.A.M.); (M.C.W.)
| | - Yehia Mechref
- Department of Chemistry and Biochemistry, Texas Tech University, Texas City, TX 79409, USA; (A.Y.); (J.Z.)
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19
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Uchida Y, Torisu K, Ueki K, Tsuruya K, Nakano T, Kitazono T. Autophagy gene ATG7 regulates albumin transcytosis in renal tubule epithelial cells. Am J Physiol Renal Physiol 2021; 321:F572-F586. [PMID: 34541900 DOI: 10.1152/ajprenal.00172.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 09/13/2021] [Indexed: 01/03/2023] Open
Abstract
Receptor-mediated albumin transport in proximal tubule epithelial cells (PTECs) is important to control proteinuria. Autophagy is an evolutionarily conserved degradation pathway, and its role in intracellular trafficking through interactions with the endocytic pathway has recently been highlighted. Here, we determined whether autophagy regulates albumin transcytosis in PTECs and suppresses albumin-induced cytotoxicity using human proximal tubule (HK-2) cells. The neonatal Fc receptor (FcRn), a receptor for albumin transcytosis, is partially colocalized with autophagosomes. Recycling of FcRn was attenuated, and FcRn accumulated in autophagy-related 7 (ATG7) knockdown HK-2 cells. Colocalization of FcRn with RAB7-positive late endosomes and RAB11-positive recycling endosomes was reduced in ATG7 knockdown cells, which decreased recycling of FcRn to the plasma membrane. In ATG7 or autophagy-related 5 (ATG5) knockdown cells and Atg5 or Atg7 knockout mouse embryonic fibroblasts, albumin transcytosis was significantly reduced and intracellular albumin accumulation was increased. Finally, the release of kidney injury molecule-1, a marker of tubule injury, from ATG7 or ATG5 knockdown cells was increased in response to excess albumin. In conclusion, suppression of autophagy in tubules impairs FcRn transport, thereby inhibiting albumin transcytosis. The resulting accumulation of albumin induces cytotoxicity in tubules.NEW & NOTEWORTHY Albumin transport in proximal tubule epithelial cells (PTECs) is important to control proteinuria. The neonatal Fc receptor (FcRn), a receptor for albumin transcytosis, is partially colocalized with autophagosomes. Recycling of FcRn to the plasma membrane was decreased in autophagy-related 7 (ATG7) knockdown cells. In addition, albumin transcytosis was decreased in ATG7 or autophagy-related 5 (ATG5) knockdown PTECs. Finally, release of kidney injury molecule-1 from ATG7 or ATG5 knockdown cells was increased in response to excess albumin.
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Affiliation(s)
- Yushi Uchida
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Kumiko Torisu
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
- Department of Integrated Therapy for Chronic Kidney Disease, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Kenji Ueki
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | | | - Toshiaki Nakano
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Takanari Kitazono
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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20
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Fang H, Ghosh S, Sims LC, Stone KP, Hill CM, Spires D, Ilatovskaya DV, Morrison CD, Gettys TW, Stadler K. FGF21 prevents low-protein diet-induced renal inflammation in aged mice. Am J Physiol Renal Physiol 2021; 321:F356-F368. [PMID: 34151592 PMCID: PMC8530754 DOI: 10.1152/ajprenal.00107.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 06/14/2021] [Accepted: 06/14/2021] [Indexed: 02/07/2023] Open
Abstract
Low-protein (LP) diets extend lifespan through a comprehensive improvement in metabolic health across multiple tissues and organs. Many of these metabolic responses to protein restriction are secondary to transcriptional activation and release of FGF21 from the liver. However, the effects of an LP diet on the kidney in the context of aging has not been examined. Therefore, the goal of the current study was to investigate the impact of chronic consumption of an LP diet on the kidney in aging mice lacking FGF21. Wild-type (WT; C57BL/6J) and FGF21 knockout (KO) mice were fed a normal protein diet (20% casein) or an LP (5% casein) diet ad libitum from 3 to 22 mo of age. The LP diet led to a decrease in kidney weight and urinary albumin-to-creatinine ratio in both WT and FGF21 KO mice. Although the LP diet produced only mild fibrosis and infiltration of leukocytes in WT kidneys, the effects were significantly exacerbated by the absence of FGF21. Accordingly, transcriptomic analysis showed that inflammation-related pathways were significantly enriched and upregulated in response to LP diet in FGF21 KO mice but not WT mice. Collectively, these data demonstrate that the LP diet negatively affected the kidney during aging, but in the absence of FGF21, the LP diet-induced renal damage and inflammation were significantly worse, indicating a protective role of FGF21 in the kidney.NEW & NOTEWORTHY Long-term protein restriction is not advantageous for an otherwise healthy, aging kidney, as it facilitates the development of renal tubular injury and inflammatory cell infiltration. We provide evidence using FGF21 knockout animals that FGF21 is essential to counteract the renal injury and inflammation during aging on a low-protein diet.
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Affiliation(s)
- Han Fang
- Laboratory of Nutrient Sensing and Adipocyte Signaling, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Sujoy Ghosh
- Laboratory of Computational Biology, Pennington Biomedical Research Center, Baton Rouge, Louisiana
- Program in Cardiovascular and Metabolic Disorders and Centre for Computational Biology, Duke-NUS Graduate Medical School, Singapore
| | - Landon C Sims
- Laboratory of Nutrient Sensing and Adipocyte Signaling, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Kirsten P Stone
- Laboratory of Nutrient Sensing and Adipocyte Signaling, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Cristal M Hill
- Laboratory of Neurosignaling, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Denisha Spires
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Daria V Ilatovskaya
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Christopher D Morrison
- Laboratory of Neurosignaling, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Thomas W Gettys
- Laboratory of Nutrient Sensing and Adipocyte Signaling, Pennington Biomedical Research Center, Baton Rouge, Louisiana
| | - Krisztian Stadler
- Oxidative Stress and Disease Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana
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21
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Weisz OA. Endocytic adaptation to functional demand by the kidney proximal tubule. J Physiol 2021; 599:3437-3446. [PMID: 34036593 DOI: 10.1113/jp281599] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/06/2021] [Indexed: 12/28/2022] Open
Abstract
The kidney proximal tubule (PT) efficiently recovers the low level of albumin and other proteins that normally escape the glomerular filtration barrier. Two large receptors, megalin and cubilin/amnionless (CUBAM), bind to and efficiently retrieve these predominantly low molecular-weight proteins via clathrin-mediated endocytosis. Studies in cell culture models suggest that PT cells may sense changes in shear stress to modulate recovery of filtered proteins in response to normal variations in filtration rate. Impairments in PT endocytic function lead to the excretion of filtered proteins into the urine (tubular proteinuria). Remarkably, when the glomerular filtration barrier is breached, the PT is able to recover excess albumin with a capacity that is orders of magnitude higher than normal. What mediates this excess capacity for albumin uptake under nephrotic conditions, and why doesn't it compensate to prevent tubular proteinuria? Here we propose an integrated new working model to describe the PT recovery of filtered proteins under normal and nephrotic states. We hypothesize that uptake via the fluid phase provides excess capacity to recover high concentrations of filtered proteins under nephrotic conditions. Further, concentration of tubular fluid along the tubule axis will enhance the efficiency of uptake in more distal regions of the PT. By contrast to cells where fluid phase and receptor-mediated uptake are independent pathways, expression of megalin is required to maintain apical endocytic pathway integrity and is essential for both uptake mechanisms. This model accounts for both the high-affinity and the high-capacity responses to filtration load in physiological and pathological states.
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Affiliation(s)
- Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
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22
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Megalin-mediated albumin endocytosis in renal proximal tubules is involved in the antiproteinuric effect of angiotensin II type 1 receptor blocker in a subclinical acute kidney injury animal model. Biochim Biophys Acta Gen Subj 2021; 1865:129950. [PMID: 34144121 DOI: 10.1016/j.bbagen.2021.129950] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 06/07/2021] [Accepted: 06/10/2021] [Indexed: 12/11/2022]
Abstract
BACKGROUND Tubule-interstitial injury (TII) is one of the mechanisms involved in the progression of renal diseases with progressive proteinuria. Angiotensin II (Ang II) type 1 receptor blockers (ARBs) have been successfully used to treat renal diseases. However, the mechanism correlating treatment with ARBs and proteinuria is not completely understood. The hypothesis that the anti-proteinuric effect of losartan is associated with the modulation of albumin endocytosis in PT epithelial cells (PTECs) was assessed. METHODS We used a subclinical acute kidney injury animal model (subAKI) and LLC-PK1 cells, a model of PTECs. RESULTS In subAKI, PT albumin overload induced TII development, measured by: (1) increase in urinary lactate dehydrogenase and γ-glutamyltranspeptidase activity; (2) proteinuria associated with impairment in megalin-mediated albumin reabsorption; (3) increase in luminal and interstitial space in tubular cortical segments. These effects were avoided by treating the animals with losartan, an ARB. Using LLC-PK1 cells, we observed that: (1) 20 mg/mL albumin increased the secretion of Ang II and decreased megalin-mediated albumin endocytosis; (2) the effects of Ang II and albumin were abolished by 10-8 M losartan; (3) MEK/ERK pathway is the molecular mechanism underlying the Ang II-mediated inhibitory effect of albumin on PT albumin endocytosis. CONCLUSION Our results show that PT megalin-mediated albumin endocytosis is a possible target during the treatment of renal diseases patients with ARB. GENERAL SIGNIFICANCE The findings obtained in the present work represents a step forward to the current knowledge on about the role of ARBs in the treatment of renal disease.
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23
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Giani JF, Veiras LC, Shen JZY, Bernstein EA, Cao D, Okwan-Duodu D, Khan Z, Gonzalez-Villalobos RA, Bernstein KE. Novel roles of the renal angiotensin-converting enzyme. Mol Cell Endocrinol 2021; 529:111257. [PMID: 33781839 PMCID: PMC8127398 DOI: 10.1016/j.mce.2021.111257] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 02/03/2021] [Accepted: 03/20/2021] [Indexed: 12/14/2022]
Abstract
The observation that all components of the renin angiotensin system (RAS) are expressed in the kidney and the fact that intratubular angiotensin (Ang) II levels greatly exceed the plasma concentration suggest that the synthesis of renal Ang II occurs independently of the circulating RAS. One of the main components of this so-called intrarenal RAS is angiotensin-converting enzyme (ACE). Although the role of ACE in renal disease is demonstrated by the therapeutic effectiveness of ACE inhibitors in treating several conditions, the exact contribution of intrarenal versus systemic ACE in renal disease remains unknown. Using genetically modified mouse models, our group demonstrated that renal ACE plays a key role in the development of several forms of hypertension. Specifically, although ACE is expressed in different cell types within the kidney, its expression in renal proximal tubular cells is essential for the development of high blood pressure. Besides hypertension, ACE is involved in several other renal diseases such as diabetic kidney disease, or acute kidney injury even when blood pressure is normal. In addition, studies suggest that ACE might mediate at least part of its effect through mechanisms that are independent of the Ang I conversion into Ang II and involve other substrates such as N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), Ang-(1-7), and bradykinin, among others. In this review, we summarize the recent advances in understanding the contribution of intrarenal ACE to different pathological conditions and provide insight into the many roles of ACE besides the well-known synthesis of Ang II.
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Affiliation(s)
- Jorge F Giani
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA; Department of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA.
| | - Luciana C Veiras
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Justin Z Y Shen
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Ellen A Bernstein
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - DuoYao Cao
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Derick Okwan-Duodu
- Department of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Zakir Khan
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA; Department of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | | | - Kenneth E Bernstein
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, USA; Department of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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24
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Sałaga-Zaleska K, Pikul P, Kreft E, Herman S, Chyła G, Dąbkowski K, Kuchta A, Lenartowicz M, Jankowski M. Effect of suramin on urinary excretion of diabetes-induced glomerular and tubular injury parameters in rats. Biomed Pharmacother 2021; 139:111683. [PMID: 34243631 DOI: 10.1016/j.biopha.2021.111683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 04/27/2021] [Accepted: 04/28/2021] [Indexed: 11/18/2022] Open
Abstract
Diabetes mellitus causes changes in metabolism of extracellular nucleotides acting through P2 receptors (P2Rs). This affects renal function and may lead to glomerular and tubular disturbances. We measured urinary excretion of nucleotides (ATP, ADP, AMP, UTP, UDP, UMP) in streptozotocin-induced diabetic rats (65 mg/kg, i.p., day 0) and the effects of P2Rs' blockade by suramin (10 mg/kg, i.p., days +7, +14) on glomerular P2×7R expression and urinary excretion of glomerular (albumin, nephrin) and tubular (KIM-1, NGAL) injury markers, electrolytes, and oxidative stress markers (TBARS, 8-OHdG). Concentrations of nucleotides, specific proteins, electrolytes, and oxidative stress markers in 24-h urine samples collected in metabolic cages at days -1, +6 and +20 were measured using ion-paired reversed-phase HPLC, immunoenzymatic and fluorometric methods, and flame photometry, respectively. Expression of KIM-1 and P2×7R was examined by immunohistochemistry or immunoblotting. Diabetes was associated with increased urinary excretion of ATP, ADP, UTP, UDP and glomerular P2×7R expression. Suramin attenuated P2×7R expression but did not affect urinary excretion of nucleotides. Urinary excretion of albumin, nephrin, NGAL, and 8-OHdG were increased in diabetic rats and were not affected by suramin. TBARS was higher in diabetic rats and suramin attenuated the excretion dynamics in this group. KIM-1 excretion was higher in diabetic rats and suramin further increased excretion of KIM-1 in both diabetic and non-diabetic rats. Furthermore, suramin attenuated the diabetes-induced natriuresis and kaliuresis. It is possible that suramin affects both glomerular and tubular functions in diabetic rats.
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Affiliation(s)
- K Sałaga-Zaleska
- Department of Clinical Chemistry, Medical University of Gdansk, Dębinki 7, 80-210, Poland
| | - P Pikul
- Clinical Laboratory University Clinical Center in Gdansk, 80-211 Gdańsk, Poland
| | - E Kreft
- Department of Clinical Chemistry, Medical University of Gdansk, Dębinki 7, 80-210, Poland
| | - S Herman
- Laboratory of Genetics and Evolutionism, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
| | - G Chyła
- Department of Clinical Chemistry, Medical University of Gdansk, Dębinki 7, 80-210, Poland
| | - K Dąbkowski
- Department of Clinical Chemistry, Medical University of Gdansk, Dębinki 7, 80-210, Poland
| | - A Kuchta
- Department of Clinical Chemistry, Medical University of Gdansk, Dębinki 7, 80-210, Poland
| | - M Lenartowicz
- Laboratory of Genetics and Evolutionism, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387 Kraków, Poland
| | - M Jankowski
- Department of Clinical Chemistry, Medical University of Gdansk, Dębinki 7, 80-210, Poland.
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25
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Husain-Syed F, Gröne HJ, Assmus B, Bauer P, Gall H, Seeger W, Ghofrani A, Ronco C, Birk HW. Congestive nephropathy: a neglected entity? Proposal for diagnostic criteria and future perspectives. ESC Heart Fail 2020; 8:183-203. [PMID: 33258308 PMCID: PMC7835563 DOI: 10.1002/ehf2.13118] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 10/13/2020] [Accepted: 10/31/2020] [Indexed: 12/12/2022] Open
Abstract
Venous congestion has emerged as an important cause of renal dysfunction in patients with cardiorenal syndrome. However, only limited progress has been made in differentiating this haemodynamic phenotype of renal dysfunction, because of a significant overlap with pre-existing renal impairment due to long-term hypertension, diabetes, and renovascular disease. We propose congestive nephropathy (CN) as this neglected clinical entity. CN is a potentially reversible subtype of renal dysfunction associated with declining renal venous outflow and progressively increasing renal interstitial pressure. Venous congestion may lead to a vicious cycle of hormonal activation, increased intra-abdominal pressure, excessive renal tubular sodium reabsorption, and volume overload, leading to further right ventricular (RV) stress. Ultimately, renal replacement therapy may be required to relieve diuretic-resistant congestion. Effective decongestion could preserve or improve renal function. Congestive acute kidney injury may not be associated with cellular damage, and complete renal function restoration may be a confirmatory diagnostic criterion. In contrast, a persistently low renal perfusion pressure might induce renal dysfunction and histopathological lesions with time. Thus, urinary markers may differ. CN is mostly seen in biventricular heart failure but may also occur secondary to pulmonary arterial hypertension and elevated intra-abdominal pressure. An increase in central venous pressure to >6 mmHg is associated with a steep decrease in glomerular filtration rate. However, the central venous pressure range that can provide an optimal balance of RV and renal function remains to be determined. We propose criteria to identify cardiorenal syndrome subgroups likely to benefit from decongestive or pulmonary hypertension-specific therapies and suggest areas for future research.
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Affiliation(s)
- Faeq Husain-Syed
- Department of Internal Medicine II, Division of Nephrology, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany.,Department of Internal Medicine II, Division of Pulmonology and Critical Care Medicine, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany.,International Renal Research Institute of Vicenza, Via Rodolfi, 37-36100, Vicenza, Italy
| | - Hermann-Josef Gröne
- Department of Pharmacology, University of Marburg, Karl-von-Frisch-Strasse, 35043, Marburg, Germany
| | - Birgit Assmus
- Department of Internal Medicine I, Division of Cardiology and Angiology, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany
| | - Pascal Bauer
- Department of Internal Medicine I, Division of Cardiology and Angiology, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany
| | - Henning Gall
- Department of Internal Medicine II, Division of Pulmonology and Critical Care Medicine, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany.,Member of the German Centre for Lung Research (DZL), Universities of Giessen and Marburg Lung Centre (UGMLC), Giessen, Germany
| | - Werner Seeger
- Department of Internal Medicine II, Division of Nephrology, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany.,Department of Internal Medicine II, Division of Pulmonology and Critical Care Medicine, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany.,Member of the German Centre for Lung Research (DZL), Universities of Giessen and Marburg Lung Centre (UGMLC), Giessen, Germany.,Institute for Lung Health (ILH), Justus Liebig Medical University, Ludwigstrasse 23, 35390, Giessen, Germany.,The Cardio-Pulmonary Institute, Aulweg 130, 35392, Giessen, Germany.,Department of Lung Development and Remodeling, Max Planck Institute for Heart and Lung Research, Ludwigstrasse 43, 61231, Bad Nauheim, Germany
| | - Ardeschir Ghofrani
- Department of Internal Medicine II, Division of Pulmonology and Critical Care Medicine, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany.,Member of the German Centre for Lung Research (DZL), Universities of Giessen and Marburg Lung Centre (UGMLC), Giessen, Germany.,Department of Pulmonology, Kerckhoff Heart, Rheuma and Thoracic Centre, Benekestrasse 2-8, 61231, Bad Nauheim, Germany.,Department of Medicine, Imperial College London, London, UK
| | - Claudio Ronco
- International Renal Research Institute of Vicenza, Via Rodolfi, 37-36100, Vicenza, Italy.,Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital, Via Rodolfi, 37-36100, Vicenza, Italy.,Department of Medicine (DIMED), Università di Padova, Via Giustiniani, 2-35128, Padua, Italy
| | - Horst-Walter Birk
- Department of Internal Medicine II, Division of Nephrology, University Hospital Giessen and Marburg, Klinikstrasse 33, 35392, Giessen, Germany
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26
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Warady BA, Agarwal R, Bangalore S, Chapman A, Levin A, Stenvinkel P, Toto RD, Chertow GM. Alport Syndrome Classification and Management. Kidney Med 2020; 2:639-649. [PMID: 33094278 PMCID: PMC7568086 DOI: 10.1016/j.xkme.2020.05.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Alport syndrome affects up to 60,000 people in the United States. The proposed reclassification of thin basement membrane nephropathy and some cases of focal segmental glomerulosclerosis as Alport syndrome could substantially increase the affected population. The reclassification scheme categorizes Alport syndrome as 3 distinct diseases of type IV collagen α3/4/5 based on a genetic evaluation: X-linked, autosomal, and digenic. This approach has the advantage of identifying patients at risk for progressive loss of kidney function. Furthermore, the shared molecular cause of Alport syndrome and thin basement membrane nephropathy arises from mutations in the COL4A3, COL4A4, and COL4A5 genes, which contribute to downstream pathophysiologic consequences, including chronic kidney inflammation. Recent evidence indicates that chronic inflammation and its regulation through anti-inflammatory nuclear factor erythroid 2-related factor 2 (Nrf2) and proinflammatory nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) transcription factors plays a central role in renal tubular and glomerular cell responses to injury. Crosstalk between the Nrf2 and NF-κB pathways is important in the regulation of inflammation in patients with chronic kidney disease; moreover, there is evidence that an insufficient Nrf2 response to inflammation contributes to disease progression. Given the association between type IV collagen abnormalities and chronic inflammation, there is renewed interest in targeted anti-inflammatory therapies in Alport syndrome and other forms of progressive chronic kidney disease.
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Affiliation(s)
- Bradley A Warady
- Division of Pediatric Nephrology, Children's Mercy Kansas City, Kansas City, MO
| | - Rajiv Agarwal
- Division of Nephrology, Indiana University, Indianapolis, IN
| | | | - Arlene Chapman
- Division of Nephrology, University of Chicago, Chicago, IL
| | - Adeera Levin
- Division of Nephrology, University of British Columbia, Vancouver, BC, Canada
| | | | - Robert D Toto
- Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX
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27
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Battistone MA, Mendelsohn AC, Spallanzani RG, Allegretti AS, Liberman RN, Sesma J, Kalim S, Wall SM, Bonventre JV, Lazarowski ER, Brown D, Breton S. Proinflammatory P2Y14 receptor inhibition protects against ischemic acute kidney injury in mice. J Clin Invest 2020; 130:3734-3749. [PMID: 32287042 PMCID: PMC7324186 DOI: 10.1172/jci134791] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 04/08/2020] [Indexed: 12/24/2022] Open
Abstract
Ischemic acute kidney injury (AKI), a complication that frequently occurs in hospital settings, is often associated with hemodynamic compromise, sepsis, cardiac surgery, or exposure to nephrotoxins. Here, using a murine renal ischemia/reperfusion injury (IRI) model, we show that intercalated cells (ICs) rapidly adopted a proinflammatory phenotype after IRI. Wwe demonstrate that during the early phase of AKI either blockade of the proinflammatory P2Y14 receptor located on the apical membrane of ICs or ablation of the gene encoding the P2Y14 receptor in ICs (a) inhibited IRI-induced increase of chemokine expression in ICs, (b) reduced neutrophil and monocyte renal infiltration, (c) reduced the extent of kidney dysfunction, and (d) attenuated proximal tubule damage. These observations indicate that the P2Y14 receptor participates in the very first inflammatory steps associated with ischemic AKI. In addition, we show that the concentration of the P2Y14 receptor ligand UDP-glucose (UDP-Glc) was higher in urine samples from intensive care unit patients who developed AKI compared with patients without AKI. In particular, we observed a strong correlation between UDP-Glc concentration and the development of AKI in cardiac surgery patients. Our study identifies the UDP-Glc/P2Y14 receptor axis as a potential target for the prevention and/or attenuation of ischemic AKI.
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Affiliation(s)
- Maria Agustina Battistone
- Program in Membrane Biology, Division of Nephrology, Department of Medicine, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Alexandra C. Mendelsohn
- Program in Membrane Biology, Division of Nephrology, Department of Medicine, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Raul German Spallanzani
- Division of Immunology, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA
- Evergrande Center for Immunologic Diseases, Harvard Medical School and Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Andrew S. Allegretti
- Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Rachel N. Liberman
- Program in Membrane Biology, Division of Nephrology, Department of Medicine, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Juliana Sesma
- Marsico Lung Institute, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Sahir Kalim
- Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Susan M. Wall
- Renal Division, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA
| | | | - Eduardo R. Lazarowski
- Marsico Lung Institute, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Dennis Brown
- Program in Membrane Biology, Division of Nephrology, Department of Medicine, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Sylvie Breton
- Program in Membrane Biology, Division of Nephrology, Department of Medicine, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, USA
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28
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Ren Q, Weyer K, Rbaibi Y, Long KR, Tan RJ, Nielsen R, Christensen EI, Baty CJ, Kashlan OB, Weisz OA. Distinct functions of megalin and cubilin receptors in recovery of normal and nephrotic levels of filtered albumin. Am J Physiol Renal Physiol 2020; 318:F1284-F1294. [PMID: 32200668 DOI: 10.1152/ajprenal.00030.2020] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Proximal tubule (PT) cells express a single saturable albumin-binding site whose affinity matches the estimated tubular concentration of albumin; however, albumin uptake capacity is greatly increased under nephrotic conditions. Deciphering the individual contributions of megalin and cubilin to the uptake of normal and nephrotic levels of albumin is impossible in vivo, as knockout of megalin in mice globally disrupts PT endocytic uptake. We quantified concentration-dependent albumin uptake in an optimized opossum kidney cell culture model and fit the kinetic profiles to identify albumin-binding affinities and uptake capacities. Mathematical deconvolution fit best to a three-component model that included saturable high- and low-affinity uptake sites for albumin and underlying nonsaturable uptake consistent with passive uptake of albumin in the fluid phase. Knockdown of cubilin or its chaperone amnionless selectively reduced the binding capacity of the high-affinity site, whereas knockdown of megalin impacted the low-affinity site. Knockdown of disabled-2 decreased the capacities of both binding sites. Additionally, knockdown of megalin or disabled-2 profoundly inhibited the uptake of a fluid phase marker, with cubilin knockdown having a more modest effect. We propose a novel model for albumin retrieval along the PT in which cubilin and megalin receptors have different functions in recovering filtered albumin in proximal tubule cells. Cubilin binding to albumin is tuned to capture normally filtered levels of the protein. In contrast, megalin binding to albumin is of lower affinity, and its expression is also essential for enabling the recovery of high concentrations of albumin in the fluid phase.
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Affiliation(s)
- Qidong Ren
- School of Medicine, Tsinghua University, Beijing, China.,Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Kathrin Weyer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Youssef Rbaibi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Kimberly R Long
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Roderick J Tan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Rikke Nielsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | - Catherine J Baty
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Ossama B Kashlan
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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29
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Immunotoxin SS1P is rapidly removed by proximal tubule cells of kidney, whose damage contributes to albumin loss in urine. Proc Natl Acad Sci U S A 2020; 117:6086-6091. [PMID: 32123080 DOI: 10.1073/pnas.1919038117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Recombinant immunotoxins (RITs) are chimeric proteins composed of an Fv and a protein toxin being developed for cancer treatment. The Fv brings the toxin to the cancer cell, but most of the RITs do not reach the tumor and are removed by other organs. To identify cells responsible for RIT removal, and the pathway by which RITs reach these cells, we studied SS1P, a 63-kDa RIT that targets mesothelin-expressing tumors and has a short serum half-life. The major organs that remove RIT were identified by live mouse imaging of RIT labeled with FNIR-Z-759. Cells responsible for SS1P removal were identified by immunohistochemistry and intravital two-photon microscopy of kidneys of rats. The primary organ of SS1P removal is kidney followed by liver. In the kidney, SS1P passes through the glomerulus, is taken up by proximal tubular cells, and transferred to lysosomes. In the liver, macrophages are involved in removal. The short half-life of SS1P is due to its very rapid filtration by the kidney followed by degradation in proximal tubular cells of the kidney. In mice treated with SS1P, proximal tubular cells are damaged and albumin in the urine is increased. SS1P uptake by kidney is reduced by coadministration of l-lysine. Our data suggests that l-lysine administration to humans might prevent SS1P-mediated kidney damage, reduce albumin loss in urine, and alleviate capillary leak syndrome.
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30
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Long KR, Rbaibi Y, Gliozzi ML, Ren Q, Weisz OA. Differential kidney proximal tubule cell responses to protein overload by albumin and its ligands. Am J Physiol Renal Physiol 2020; 318:F851-F859. [PMID: 32068462 DOI: 10.1152/ajprenal.00490.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Albuminuria is frequently associated with proximal tubule (PT) cytotoxicity that can feed back to cause glomerular damage and exacerbate kidney disease. PT cells express megalin and cubilin receptors that bind to and internalize albumin over a broad concentration range. How the exposure to high concentrations of albumin leads to PT cytotoxicity remains unclear. Fatty acids and other ligands bound to albumin are known to trigger production of reactive oxygen species (ROS) that impair PT function. Alternatively or in addition, uptake of high concentrations of albumin may overload the endocytic pathway and elicit downstream responses. Here, we used a well-differentiated PT cell culture model with high endocytic capacity to dissect the effects of albumin versus its ligands on endocytic uptake and degradation of albumin, production of ROS, and cell viability. Cellular responses differed dramatically, depending on the preparation of albumin tested. Knockdown of megalin or cubilin failed to prevent ROS production mediated by albumin ligands, suggesting that receptor-mediated internalization of albumin was not necessary to trigger cellular responses to albumin ligands. Moreover, albumin induced cytotoxic responses when added to the basolateral surface of PT cells. Whereas overnight incubation with high concentrations of fatty acid-free albumin had no overt effects on cell function or viability, lysosomal degradation kinetics were slowed upon longer exposure, consistent with overload of the PT endocytic/degradative pathway. Together, the results of our study demonstrate that the PT responds independently to albumin and to its ligands and suggest that the consequences of albumin overload in vivo may be dependent on metabolic state.
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Affiliation(s)
- Kimberly R Long
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Youssef Rbaibi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Megan L Gliozzi
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Qidong Ren
- School of Medicine, Tsinghua University, Beijing, China
| | - Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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31
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Reverte V, Gogulamudi VR, Rosales CB, Musial DC, Gonsalez SR, Parra-Vitela AJ, Galeas-Pena M, Sure VN, Visniauskas B, Lindsey SH, Katakam PVG, Prieto MC. Urinary angiotensinogen increases in the absence of overt renal injury in high fat diet-induced type 2 diabetic mice. J Diabetes Complications 2020; 34:107448. [PMID: 31761419 PMCID: PMC6981045 DOI: 10.1016/j.jdiacomp.2019.107448] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 08/09/2019] [Accepted: 09/07/2019] [Indexed: 12/31/2022]
Abstract
AIM OF THE STUDY During type 2 diabetes (T2D) and hypertension there is stimulation of renal proximal tubule angiotensinogen (AGT), but whether urinary excretion of AGT (uAGT) is an indicator of glomerular damage or intrarenal RAS activation is unclear. We tested the hypothesis that elevations in uAGT can be detected in the absence of albuminuria in a mouse model of T2D. METHODS Male C57BL/6 mice (N = 10) were fed a high fat (HFD; 45% Kcal from fat) for 28 weeks, and the metabolic phenotype including body weight, blood pressures, glucose, insulin, ippGTT, HOMA-IR, and cholesterol was examined. In addition, kidney Ang II content and reactive oxygen species (ROS) was measured along with urinary albumin, creatinine, Ang II, and AGT. RESULTS All parameters consistent with T2D were present in mice after 12-14 weeks on the HFD. Systolic BP increased after 18 weeks in HFD but not NFD mice. Intrarenal ROS and Ang II concentrations were also increased in HFD mice. Remarkably, these changes paralleled the augmentation uAGT excretion (3.66 ± 0.50 vs. 0.92 ± 0.13 ng/mg by week 29; P < 0.01), which occurred in the absence of overt albuminuria. CONCLUSIONS In HFD-induced T2D mice, increases in uAGT occur in the absence of overt renal injury, indicating that this biomarker accurately detects early intrarenal RAS activation.
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Affiliation(s)
- Virginia Reverte
- Department of Physiology, Tulane University School of Medicine, New Orleans, USA
| | | | - Carla B Rosales
- Department of Physiology, Tulane University School of Medicine, New Orleans, USA
| | - Diego C Musial
- Department of Physiology, Tulane University School of Medicine, New Orleans, USA; Department of Pharmacology, Universidade Federal de Sao Paulo, Sao Paulo, Brazil
| | - Sabrina R Gonsalez
- Department of Physiology, Tulane University School of Medicine, New Orleans, USA; Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | | | - Michelle Galeas-Pena
- Department of Physiology, Tulane University School of Medicine, New Orleans, USA
| | - Venkata N Sure
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, USA
| | - Bruna Visniauskas
- Department of Physiology, Tulane University School of Medicine, New Orleans, USA
| | - Sarah H Lindsey
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, USA
| | - Prasad V G Katakam
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, USA
| | - Minolfa C Prieto
- Department of Physiology, Tulane University School of Medicine, New Orleans, USA; Hypertension and Renal Center of Excellence, New Orleans, USA.
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Ferrell N, Sandoval RM, Molitoris BA, Brakeman P, Roy S, Fissell WH. Application of physiological shear stress to renal tubular epithelial cells. Methods Cell Biol 2019; 153:43-67. [PMID: 31395384 DOI: 10.1016/bs.mcb.2019.04.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Renal tubular epithelial cells are consistently exposed to flow of glomerular filtrate that creates fluid shear stress at the apical cell surface. This biophysical stimulus regulates several critical renal epithelial cell functions, including transport, protein uptake, and barrier function. Defining the in vivo mechanical conditions in the kidney tubule is important for accurately recapitulating these conditions in vitro. Here we provide a summary of the fluid flow conditions in the kidney and how this translates into different levels of fluid shear stress down the length of the nephron. A detailed method is provided for measuring fluid flow in the proximal tubule by intravital microscopy. Devices to mimic in vivo fluid shear stress for in vitro studies are discussed, and we present two methods for culture and analysis of renal tubule epithelial cells exposed physiological levels of fluid shear stress. The first is a microfluidic device that permits application of controlled shear stress to cells cultured on porous membranes. The second is culture of renal tubule cells on an orbital shaker. Each method has advantages and disadvantages that should be considered in the context of the specific experimental objectives.
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Affiliation(s)
- Nicholas Ferrell
- Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, TN, United States; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States.
| | - Ruben M Sandoval
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Bruce A Molitoris
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Paul Brakeman
- Department of Pediatrics, University of California, San Francisco, CA, United States
| | - Shuvo Roy
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, United States
| | - William H Fissell
- Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, TN, United States
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Gyarmati G, Kadoya H, Moon JY, Burford JL, Ahmadi N, Gill IS, Hong YK, Dér B, Peti-Peterdi J. Advances in Renal Cell Imaging. Semin Nephrol 2019; 38:52-62. [PMID: 29291762 DOI: 10.1016/j.semnephrol.2017.09.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A great variety of cell imaging technologies are used routinely every day for the investigation of kidney cell types in applications ranging from basic science research to drug development and pharmacology, clinical nephrology, and pathology. Quantitative visualization of the identity, density, and fate of both resident and nonresident cells in the kidney, and imaging-based analysis of their altered function, (patho)biology, metabolism, and signaling in disease conditions, can help to better define pathomechanism-based disease subgroups, identify critical cells and structures that play a role in the pathogenesis, critically needed biomarkers of disease progression, and cell and molecular pathways as targets for novel therapies. Overall, renal cell imaging has great potential for improving the precision of diagnostic and treatment paradigms for individual acute kidney injury or chronic kidney disease patients or patient populations. This review highlights and provides examples for some of the recently developed renal cell optical imaging approaches, mainly intravital multiphoton fluorescence microscopy, and the new knowledge they provide for our better understanding of renal pathologies.
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Affiliation(s)
- Georgina Gyarmati
- Department of Physiology and Neuroscience, Department of Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - Hiroyuki Kadoya
- Department of Physiology and Neuroscience, Department of Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA; Department of Nephrology and Hypertension, Kawasaki Medical School, Kurashiki, Japan
| | - Ju-Young Moon
- Department of Physiology and Neuroscience, Department of Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA; Division of Nephrology, Department of Internal Medicine, Kyung Hee University, College of Medicine, Seoul, Korea
| | - James L Burford
- Department of Physiology and Neuroscience, Department of Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - Nariman Ahmadi
- Institute of Urology, Catherine & Joseph Aresty Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - Inderbir S Gill
- Institute of Urology, Catherine & Joseph Aresty Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - Young-Kwon Hong
- Department of Surgery and Biochemistry and Molecular Biology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - Bálint Dér
- Department of Physiology and Neuroscience, Department of Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - János Peti-Peterdi
- Department of Physiology and Neuroscience, Department of Medicine, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA.
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Kumari M, Sharma R, Pandey G, Ecelbarger CM, Mishra P, Tiwari S. Deletion of insulin receptor in the proximal tubule and fasting augment albumin excretion. J Cell Biochem 2019; 120:10688-10696. [PMID: 30644120 DOI: 10.1002/jcb.28359] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Accepted: 11/29/2018] [Indexed: 12/29/2022]
Abstract
The contribution of proximal tubules (PT) to albumin uptake is now well recognized, however, its regulation is understudied area. There are reports suggesting that insulin resistance is associated with the development of albuminuria in nondiabetic individuals. We have previously reported reduced insulin receptor (IR) expression in renal-tubular-epithelial cells, including PT in various models of insulin resistance. However, the effect of a physiological fall in insulin levels and the role for IR in PT in tubular albumin uptake is not clear. To address these gaps in our understanding, we estimated urine excretion and renal uptake of albumin in fasted and fed C57Bl/6 mice injected with fluorescein isothiocyanate (FITC)-albumin (5 µg/mL/kg body weight, intraperitoneal, n = 6 per group). In addition, we compared spot urine analysis from 33 clinically healthy humans after overnight fasting (when insulin levels are lower than in the fed state) and then at 2 hours after 75 g oral glucose challenge (postprandial). Fasted mice had attenuated renal uptake of FITC-albumin and higher excretion in urine, relative to fed mice ( P = 0.04). Moreover, a significant drop in urine albumin-to-creatinine ratio (ACR) and urine albumin concentration (UAC) was observed in the postprandial state in these subjects ( P = 0.001 and P = 0.017, for ACR and UAC, respectively). The drop was negatively associated with postprandial blood glucose levels (ρ = -0.36, P = 0.03 for ΔUAC and ρ = -0.34, P = 0.05 for ΔACR). To test the role of IR in PT, we analyzed 24-hour urine albumin excretion in male mice with targeted deletion of IR from PT (insulin receptor knockout [IRKO]) and their wild-type (WT) littermates ( n = 7 per group). IRKO mice had significantly higher 24-hour urine albumin excretion relative to WT. Moreover, kidneys from KO mice revealed reduced expression of megalin and cubulin proteins in the PT relative to the WT. We also demonstrated insulin (100 nM) induced albumin internalization in human proximal tubule cells (hPT) and this effect of insulin was attenuated in hydroxy-2-naphthalenylmethylphosphonic acid (100 µM), a tyrosine kinase inhibitor, pretreated hPT. Our findings revealed albumin excretion was attenuated by glucose administration to fasting individuals implying a regulatory role for insulin in PT albumin reabsorption. Thus albuminuria associated with insulin resistance/diabetes may relate not only to glomerular dysfunction but also to impairment in insulin-mediated reabsorption.
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Affiliation(s)
- Manju Kumari
- Department of Molecular Medicine and Biotechnology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Rajni Sharma
- Department of Molecular Medicine and Biotechnology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Gaurav Pandey
- Department of Molecular Medicine and Biotechnology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Carolyn M Ecelbarger
- Department of Medicine, Division of Endocrinology and Metabolism, Georgetown University, Washington, District of Columbia
| | - Prabhaker Mishra
- Department of Biostatistics and Health Informatics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
| | - Swasti Tiwari
- Department of Molecular Medicine and Biotechnology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India
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Sandoval RM, Molitoris BA, Palygin O. Fluorescent Imaging and Microscopy for Dynamic Processes in Rats. Methods Mol Biol 2019; 2018:151-175. [PMID: 31228156 PMCID: PMC6693343 DOI: 10.1007/978-1-4939-9581-3_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The rat is a favored model organism to study physiological function in vivo. This is largely due to the fact that it has been used for decades and is often more comparable to corresponding human conditions (both normal and pathologic) than mice. Although the development of genetic manipulations in rats has been slower than in mice, recent advances of new genomic editing tools allow for the generation of targeted global and specific cell type mutations in different rat strains. The rat is an ideal model for advancing imaging techniques like intravital multi-photon microscopy or IVMPM. Multi-photon excitation microscopy can be applied to visualize real-time physiologic events in multiple organs including the kidney. This imaging modality can generate four-dimensional high resolution images that are inherently confocal due to the fact that the photon density needed to excite fluorescence only occurs at the objective focal plane, not above or below. Additionally, longer excitation wavelengths allow for deeper penetration into tissue, improved excitation, and are inherently less phototoxic than shorter excitation wavelengths. Applying imaging tools to study physiology in rats has become a valuable scientific technique due to the relatively simple surgical procedures, improved quality of reagents, and reproducibility of established assays. In this chapter, the authors provide an example of the application of fluorescent techniques to study cardio-renal functions in rat models. Use of experimental procedures described here, together with multiple available genetically modified animal models, provide new prospective for the further application of multi-photon microscopy in basic and translational research.
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Affiliation(s)
- Ruben M Sandoval
- Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN, USA
- Indiana Center for Biological Microscopy, Indianapolis, IN, USA
| | - Bruce A Molitoris
- Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN, USA
- Indiana Center for Biological Microscopy, Indianapolis, IN, USA
| | - Oleg Palygin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.
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The Interaction of miR-378i-Skp2 Regulates Cell Senescence in Diabetic Nephropathy. J Clin Med 2018; 7:jcm7120468. [PMID: 30469549 PMCID: PMC6306775 DOI: 10.3390/jcm7120468] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 11/15/2018] [Accepted: 11/20/2018] [Indexed: 12/18/2022] Open
Abstract
Diabetic nephropathy (DN) is the major cause of end stage renal disease. Proximal tubular epithelial cell (PTEC) injury occurs early in diabetic kidney, and it is correlated with consequent renal failure. Cellular senescence participates in the pathophysiology of DN, but its role remains unclear. We conducted a cross-disciplinary study, including human, in vivo, and in vitro studies, to explore the novel molecular mechanisms of PTEC senescence in DN. We found that HG induced cell senescence in PTECs, supported by enhanced β-galactosidase staining, p53 and p27 expression, and reduced cyclin E levels. Transcriptome analysis of PTECs from a type 2 diabetic patient and a normal individual using next generation sequencing (NGS) and systematic bioinformatics analyses indicated that miR-378i and its downstream target S-phase kinase protein 2 (Skp2) contribute to HG-induced senescence in PTECs. High glucose (HG) elevated miR-378i expression in PTECs, and miR-378i transfection reduced Skp2 expression. Urinary miR-378i levels were elevated in both db/db mice and type 2 diabetic patients, whereas decreased Skp2 levels were shown in proximal tubule of db/db mice and human DN. Moreover, urinary miR-378i levels were positively correlated with urinary senescence-associated secretory phenotype cytokines and renal function in in vivo and human study. This study demonstrates that the interaction between miR-378i and Skp2 regulates PTEC senescence of DN. miR-378i has the potential to predict renal injury in DN. These findings suggest future applications in both therapy and in predicting renal dysfunction of DN.
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Schuh CD, Polesel M, Platonova E, Haenni D, Gassama A, Tokonami N, Ghazi S, Bugarski M, Devuyst O, Ziegler U, Hall AM. Combined Structural and Functional Imaging of the Kidney Reveals Major Axial Differences in Proximal Tubule Endocytosis. J Am Soc Nephrol 2018; 29:2696-2712. [PMID: 30301861 DOI: 10.1681/asn.2018050522] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 09/18/2018] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND The kidney proximal convoluted tubule (PCT) reabsorbs filtered macromolecules via receptor-mediated endocytosis (RME) or nonspecific fluid phase endocytosis (FPE); endocytosis is also an entry route for disease-causing toxins. PCT cells express the protein ligand receptor megalin and have a highly developed endolysosomal system (ELS). Two PCT segments (S1 and S2) display subtle differences in cellular ultrastructure; whether these translate into differences in endocytotic function has been unknown. METHODS To investigate potential differences in endocytic function in S1 and S2, we quantified ELS protein expression in mouse kidney PCTs using real-time quantitative polymerase chain reaction and immunostaining. We also used multiphoton microscopy to visualize uptake of fluorescently labeled ligands in both living animals and tissue cleared using a modified CLARITY approach. RESULTS Uptake of proteins by RME occurs almost exclusively in S1. In contrast, dextran uptake by FPE takes place in both S1 and S2, suggesting that RME and FPE are discrete processes. Expression of key ELS proteins, but not megalin, showed a bimodal distribution; levels were far higher in S1, where intracellular distribution was also more polarized. Tissue clearing permitted imaging of ligand uptake at single-organelle resolution in large sections of kidney cortex. Analysis of segmented tubules confirmed that, compared with protein uptake, dextran uptake occurred over a much greater length of the PCT, although individual PCTs show marked heterogeneity in solute uptake length and three-dimensional morphology. CONCLUSIONS Striking axial differences in ligand uptake and ELS function exist along the PCT, independent of megalin expression. These differences have important implications for understanding topographic patterns of kidney diseases and the origins of proteinuria.
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Affiliation(s)
| | | | | | - Dominik Haenni
- Institute of Anatomy.,Center for Microscopy and Image Analysis, and
| | - Alkaly Gassama
- Institute of Physiology, University of Zurich, Zurich, Switzerland; and
| | - Natsuko Tokonami
- Institute of Physiology, University of Zurich, Zurich, Switzerland; and
| | | | | | - Olivier Devuyst
- Institute of Physiology, University of Zurich, Zurich, Switzerland; and
| | - Urs Ziegler
- Center for Microscopy and Image Analysis, and
| | - Andrew M Hall
- Institute of Anatomy, .,Department of Nephrology, University Hospital Zurich, Zurich, Switzerland
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Megalin/cubilin has a minor role in the proximal tubular cell uptake of filtered albumin. Kidney Int 2018; 93:1014. [PMID: 29571435 DOI: 10.1016/j.kint.2017.12.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 12/21/2017] [Indexed: 11/22/2022]
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39
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Bryniarski MA, Yee BM, Jaffri I, Chaves LD, Yu JA, Guan X, Ghavam N, Yacoub R, Morris ME. Increased megalin expression in early type 2 diabetes: role of insulin-signaling pathways. Am J Physiol Renal Physiol 2018; 315:F1191-F1207. [PMID: 29949391 DOI: 10.1152/ajprenal.00210.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The megalin/cubilin complex is responsible for the majority of serum protein reclamation in the proximal tubules. The current study examined if decreases in their renal expression, along with the albumin recycling protein neonatal Fc receptor (FcRn) could account for proteinuria/albuminuria in the Zucker diabetic fatty rat model of type 2 diabetes. Immunoblots of renal cortex samples obtained at worsening disease stages demonstrated no loss in megalin, cubilin, or FcRn, even when proteinuria was measured. Additionally, early diabetic rats exhibited significantly increased renal megalin expression when compared with controls (adjusted P < 0.01). Based on these results, the ability of insulin to increase megalin was examined in a clonal subpopulation of the opossum kidney proximal tubule cell line. Insulin treatments (24 h, 100 nM) under high glucose conditions significantly increased megalin protein ( P < 0.0001), mRNA ( P < 0.0001), and albumin endocytosis. The effect on megalin expression was prevented with inhibitors against key effectors of insulin intracellular signaling, phosphatidylinositide 3-kinase and Akt. Studies using rapamycin to inhibit the mechanistic target of rapamycin complex 1 (mTORC1) resulted in a loss of insulin-induced megalin expression. However, subsequent evaluation demonstrated these effects were independent of initial mTORC1 suppression. The presented results provide insight into the expression of megalin, cubilin, and FcRn in type 2 diabetes, which may be impacted by elevated insulin and glucose. Furthermore, proximal tubule endocytic activity in early diabetics may be enhanced, a process that could have a significant role in proteinuria-induced renal damage.
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Affiliation(s)
- Mark A Bryniarski
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo , New York
| | - Benjamin M Yee
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo , New York
| | - Irum Jaffri
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo , New York
| | - Lee D Chaves
- Department of Internal Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo , New York
| | - Jin Ah Yu
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo , New York
| | - Xiaowen Guan
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo , New York
| | - Nazanin Ghavam
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo , New York
| | - Rabi Yacoub
- Department of Internal Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo , New York
| | - Marilyn E Morris
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo , New York
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Eriguchi M, Lin M, Yamashita M, Zhao TV, Khan Z, Bernstein EA, Gurley SB, Gonzalez-Villalobos RA, Bernstein KE, Giani JF. Renal tubular ACE-mediated tubular injury is the major contributor to microalbuminuria in early diabetic nephropathy. Am J Physiol Renal Physiol 2018; 314:F531-F542. [PMID: 29187372 PMCID: PMC5966765 DOI: 10.1152/ajprenal.00523.2017] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 11/13/2017] [Accepted: 11/28/2017] [Indexed: 12/30/2022] Open
Abstract
Diabetic nephropathy is a major cause of end-stage renal disease in developed countries. While angiotensin-converting enzyme (ACE) inhibitors are used to treat diabetic nephropathy, how intrarenal ACE contributes to diabetic renal injury is uncertain. Here, two mouse models with different patterns of renal ACE expression were studied to determine the specific contribution of tubular vs. glomerular ACE to early diabetic nephropathy: it-ACE mice, which make endothelial ACE but lack ACE expression by renal tubular epithelium, and ACE 3/9 mice, which lack endothelial ACE and only express renal ACE in tubular epithelial cells. The absence of endothelial ACE normalized the glomerular filtration rate and endothelial injury in diabetic ACE 3/9 mice. However, these mice developed tubular injury and albuminuria and displayed low renal levels of megalin that were similar to those observed in diabetic wild-type mice. In diabetic it-ACE mice, despite hyperfiltration, the absence of renal tubular ACE greatly reduced tubulointerstitial injury and albuminuria and increased renal megalin expression compared with diabetic wild-type and diabetic ACE 3/9 mice. These findings demonstrate that endothelial ACE is a central regulator of the glomerular filtration rate while tubular ACE is a key player in the development of tubular injury and albuminuria. These data suggest that tubular injury, rather than hyperfiltration, is the main cause of microalbuminuria in early diabetic nephropathy.
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Affiliation(s)
- Masahiro Eriguchi
- Department of Biomedical Sciences, Cedars-Sinai Medical Center , Los Angeles, California
| | - Mercury Lin
- Departments of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center , Los Angeles, California
| | - Michifumi Yamashita
- Departments of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center , Los Angeles, California
| | - Tuantuan V Zhao
- Department of Biomedical Sciences, Cedars-Sinai Medical Center , Los Angeles, California
| | - Zakir Khan
- Department of Biomedical Sciences, Cedars-Sinai Medical Center , Los Angeles, California
| | - Ellen A Bernstein
- Department of Biomedical Sciences, Cedars-Sinai Medical Center , Los Angeles, California
| | - Susan B Gurley
- Division of Nephrology, Department of Medicine, Duke University School of Medicine , Durham, North Carolina
| | | | - Kenneth E Bernstein
- Department of Biomedical Sciences, Cedars-Sinai Medical Center , Los Angeles, California
- Departments of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center , Los Angeles, California
| | - Jorge F Giani
- Department of Biomedical Sciences, Cedars-Sinai Medical Center , Los Angeles, California
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Lemmings into the sea or back across the bridge? The fate of albumin in nephrotic syndrome. Kidney Int 2018; 93:296-298. [DOI: 10.1016/j.kint.2017.08.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 08/10/2017] [Indexed: 11/18/2022]
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Dunn KW, Sutton TA, Sandoval RM. Live-Animal Imaging of Renal Function by Multiphoton Microscopy. ACTA ACUST UNITED AC 2018; 83:12.9.1-12.9.25. [PMID: 29345326 DOI: 10.1002/cpcy.32] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Intravital microscopy, microscopy of living animals, is a powerful research technique that combines the resolution and sensitivity found in microscopic studies of cultured cells with the relevance and systemic influences of cells in the context of the intact animal. The power of intravital microscopy has recently been extended with the development of multiphoton fluorescence microscopy systems capable of collecting optical sections from deep within the kidney at subcellular resolution, supporting high-resolution characterizations of the structure and function of glomeruli, tubules, and vasculature in the living kidney. Fluorescent probes are administered to an anesthetized, surgically prepared animal, followed by image acquisition for up to 3 hr. Images are transferred via a high-speed network to specialized computer systems for digital image analysis. This general approach can be used with different combinations of fluorescent probes to evaluate processes such as glomerular permeability, proximal tubule endocytosis, microvascular flow, vascular permeability, mitochondrial function, and cellular apoptosis/necrosis. © 2018 by John Wiley & Sons, Inc.
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Affiliation(s)
- Kenneth W Dunn
- Indiana University School of Medicine, Indianapolis, Indiana
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Zeni L, Norden AGW, Cancarini G, Unwin RJ. A more tubulocentric view of diabetic kidney disease. J Nephrol 2017; 30:701-717. [PMID: 28840540 PMCID: PMC5698396 DOI: 10.1007/s40620-017-0423-9] [Citation(s) in RCA: 154] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 07/22/2017] [Indexed: 12/14/2022]
Abstract
Diabetic nephropathy (DN) is a common complication of Diabetes Mellitus (DM) Types 1 and 2, and prevention of end stage renal disease (ESRD) remains a major challenge. Despite its high prevalence, the pathogenesis of DN is still controversial. Initial glomerular disease manifested by hyperfiltration and loss of glomerular size and charge permselectivity may initiate a cascade of injuries, including tubulo-interstitial disease. Clinically, 'microalbuminuria' is still accepted as an early biomarker of glomerular damage, despite mounting evidence that its predictive value for DN is questionable, and findings that suggest the proximal tubule is an important link in the development of DN. The concept of 'diabetic tubulopathy' has emerged from recent studies, and its causative role in DN is supported by clinical and experimental evidence, as well as plausible pathogenetic mechanisms. This review explores the 'tubulocentric' view of DN. The recent finding that inhibition of proximal tubule (PT) glucose transport (via SGLT2) is nephro-protective in diabetic patients is discussed in relation to the tubule's potential role in DN. Studies with a tubulocentric view of DN have stimulated alternative clinical approaches to the early detection of diabetic kidney disease. There are tubular biomarkers considered as direct indicators of injury of the proximal tubule (PT), such as N-acetyl-β-D-glucosaminidase, Neutrophil Gelatinase-Associated Lipocalin and Kidney Injury Molecule-1, and other functional PT biomarkers, such as Urine free Retinol-Binding Protein 4 and Cystatin C, which reflect impaired reabsorption of filtered proteins. The clinical application of these measurements to diabetic patients will be reviewed in the context of the need for better biomarkers for early DN.
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Affiliation(s)
- Letizia Zeni
- Department of Medical and Surgical Specialities, Radiological Sciences and Public Health, University of Brescia, Piazza del Mercato 15, 25121, Brescia, Italy.
- UCL Centre for Nephrology, UCL Medical School, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK.
- Operative Unit of Nephrology, ASST Spedali Civili, Piazzale Spedali Civili 1, Brescia, Italy.
| | - Anthony G W Norden
- UCL Centre for Nephrology, UCL Medical School, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK
| | - Giovanni Cancarini
- Department of Medical and Surgical Specialities, Radiological Sciences and Public Health, University of Brescia, Piazza del Mercato 15, 25121, Brescia, Italy
- Operative Unit of Nephrology, ASST Spedali Civili, Piazzale Spedali Civili 1, Brescia, Italy
| | - Robert J Unwin
- UCL Centre for Nephrology, UCL Medical School, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK
- Cardiovascular and Metabolic Diseases iMED ECD, AstraZeneca Gothenburg, Mölndal, Sweden
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44
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Han Y, Ly NDK, Tesch GH, Poronnik P, Nikolic-Paterson DJ. Reduced tubular degradation of glomerular filtered plasma albumin is a common feature in acute and chronic kidney disease. Clin Exp Pharmacol Physiol 2017; 45:241-249. [DOI: 10.1111/1440-1681.12878] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 10/16/2017] [Accepted: 10/19/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Yingjie Han
- Department of Nephrology; Monash Medical Centre; Clayton Victoria Australia
- Monash University Centre for Inflammatory Diseases; Monash Medical Centre; Clayton Victoria Australia
| | - Nguyen D K Ly
- Department of Nephrology; Monash Medical Centre; Clayton Victoria Australia
- School of Medical Sciences; RMIT University; Melbourne Victoria Australia
| | - Greg H Tesch
- Department of Nephrology; Monash Medical Centre; Clayton Victoria Australia
- Monash University Centre for Inflammatory Diseases; Monash Medical Centre; Clayton Victoria Australia
| | - Philip Poronnik
- School of Medical Sciences and Charles Perkins Centre; The University of Sydney; Camperdown NSW Australia
| | - David J Nikolic-Paterson
- Department of Nephrology; Monash Medical Centre; Clayton Victoria Australia
- Monash University Centre for Inflammatory Diseases; Monash Medical Centre; Clayton Victoria Australia
- School of Medical Sciences; RMIT University; Melbourne Victoria Australia
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45
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Fatah H, Benfaed N, Chana RS, Chunara MH, Barratt J, Baines RJ, Brunskill NJ. Reduced proximal tubular expression of protein endocytic receptors in proteinuria is associated with urinary receptor shedding. Nephrol Dial Transplant 2017; 33:934-943. [DOI: 10.1093/ndt/gfx321] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Accepted: 10/01/2017] [Indexed: 02/06/2023] Open
Affiliation(s)
- Hiwa Fatah
- Department of Infection Immunity and Inflammation, University of Leicester, Leicester, UK
| | - Nura Benfaed
- Department of Infection Immunity and Inflammation, University of Leicester, Leicester, UK
| | - Ravinder S Chana
- Department of Infection Immunity and Inflammation, University of Leicester, Leicester, UK
| | - Mohamed H Chunara
- Department of Infection Immunity and Inflammation, University of Leicester, Leicester, UK
| | - Jonathan Barratt
- Department of Infection Immunity and Inflammation, University of Leicester, Leicester, UK
- Department of Nephrology, Leicester General Hospital, Leicester, UK
| | - Richard J Baines
- Department of Infection Immunity and Inflammation, University of Leicester, Leicester, UK
- Department of Nephrology, Leicester General Hospital, Leicester, UK
| | - Nigel J Brunskill
- Department of Infection Immunity and Inflammation, University of Leicester, Leicester, UK
- Department of Nephrology, Leicester General Hospital, Leicester, UK
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46
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Abolishment of proximal tubule albumin endocytosis does not affect plasma albumin during nephrotic syndrome in mice. Kidney Int 2017; 93:335-342. [PMID: 29032953 DOI: 10.1016/j.kint.2017.07.024] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 07/11/2017] [Accepted: 07/27/2017] [Indexed: 11/22/2022]
Abstract
The megalin/cubilin receptor complex is required for proximal tubular endocytosis and degradation of filtered albumin. An additional high-capacity retrieval pathway of intact albumin for the recovery of large amounts of filtered albumin has been proposed, possibly involving cooperation between megalin/cubilin and the neonatal Fc receptor. To clarify the potential role of such a pathway, we examined the effects of megalin/cubilin gene inactivation on tubular albumin uptake and plasma albumin levels in nephrotic, podocin knockout mice. Immunofluorescence microscopy of megalin/cubilin/podocin knockout mouse kidneys demonstrated abolishment of proximal tubule albumin uptake, in contrast to the excessive albumin accumulation observed in podocin knockout mice compared to controls. Correspondingly, urinary albumin excretion was increased 1.4 fold in megalin/cubilin/podocin compared to podocin knockout mice (albumin/creatinine: 226 vs. 157 mg/mg). However, no difference in plasma albumin levels was observed between megalin/cubilin/podocin and podocin knockout mice, as both were reduced to approximately 40% of controls. There were no differences in liver albumin synthesis by mRNA levels and protein abundance. Thus, megalin/cubilin knockout efficiently blocks proximal tubular albumin uptake in nephrotic mice but plasma albumin levels did not differ as a result of megalin/cubilin-deficiency, suggesting no significance of the megalin/cubilin-pathway for albumin homeostasis by retrieval of intact albumin.
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47
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Acute kidney injury is a risk factor for subsequent proteinuria. Kidney Int 2017; 93:460-469. [PMID: 28927644 DOI: 10.1016/j.kint.2017.07.007] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 06/20/2017] [Accepted: 07/13/2017] [Indexed: 12/31/2022]
Abstract
Acute kidney injury (AKI) is associated with subsequent chronic kidney disease (CKD), but the mechanism is unclear. To clarify this, we examined the association of AKI and new-onset or worsening proteinuria during the 12 months following hospitalization in a national retrospective cohort of United States Veterans hospitalized between 2004-2012. Patients with and without AKI were matched using baseline demographics, comorbidities, proteinuria, estimated glomerular filtration rate, blood pressure, angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker (ACEI/ARB) use, and inpatient exposures linked to AKI. The distribution of proteinuria over one year post-discharge in the matched cohort was compared using inverse probability sampling weights. Subgroup analyses were based on diabetes, pre-admission ACEI/ARB use, and AKI severity. Among the 90,614 matched AKI and non-AKI pairs, the median estimated glomerular filtration rate was 62 mL/min/1.73m2. The prevalence of diabetes and hypertension were 48% and 78%, respectively. The odds of having one plus or greater dipstick proteinuria was significantly higher during each month of follow-up in patients with AKI than in patients without AKI (odds ratio range 1.20-1.39). Odds were higher in patients with Stage II or III AKI (odds ratios 1.32-1.81) than in Stage I AKI (odds ratios 1.18-1.32), using non-AKI as the reference group. Results were consistent regardless of diabetes status or baseline ACEI/ARB use. Thus, AKI is a risk factor for incident or worsening proteinuria, suggesting a possible mechanism linking AKI and future CKD. The type of proteinuria, physiology, and clinical significance warrant further study as a potentially modifiable risk factor in the pathway from AKI to CKD.
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48
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Multiple Targets for Novel Therapy of FSGS Associated with Circulating Permeability Factor. BIOMED RESEARCH INTERNATIONAL 2017; 2017:6232616. [PMID: 28951873 PMCID: PMC5603123 DOI: 10.1155/2017/6232616] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Revised: 05/10/2017] [Accepted: 06/15/2017] [Indexed: 01/13/2023]
Abstract
A plasma component is responsible for altered glomerular permeability in patients with focal segmental glomerulosclerosis. Evidence includes recurrence after renal transplantation, remission after plasmapheresis, proteinuria in infants of affected mothers, transfer of proteinuria to experimental animals, and impaired glomerular permeability after exposure to patient plasma. Therapy may include decreasing synthesis of the injurious agent, removing or blocking its interaction with cells, or blocking signaling or enhancing cell defenses to restore the permeability barrier and prevent progression. Agents that may prevent the synthesis of the permeability factor include cytotoxic agents or aggressive chemotherapy. Extracorporeal therapies include plasmapheresis, immunoadsorption with protein A or anti-immunoglobulin, or lipopheresis. Oral or intravenous galactose also decreases Palb activity. Studies of glomeruli have shown that several strategies prevent the action of FSGS sera. These include blocking receptor-ligand interactions, modulating cell reactions using indomethacin or eicosanoids 20-HETE or 8,9-EET, and enhancing cytoskeleton and protein interactions using calcineurin inhibitors, glucocorticoids, or rituximab. We have identified cardiotrophin-like cytokine factor 1 (CLCF-1) as a candidate for the permeability factor. Therapies specific to CLCF-1 include potential use of cytokine receptor-like factor (CRLF-1) and inhibition of Janus kinase 2. Combined therapy using multiple modalities offers therapy to reverse proteinuria and prevent scarring.
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49
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Sandoval RM, Molitoris BA. Intravital multiphoton microscopy as a tool for studying renal physiology and pathophysiology. Methods 2017; 128:20-32. [PMID: 28733090 DOI: 10.1016/j.ymeth.2017.07.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 06/12/2017] [Accepted: 07/17/2017] [Indexed: 01/10/2023] Open
Abstract
The kidney is a complex and dynamic organ with over 40 cell types, and tremendous structural and functional diversity. Intravital multi-photon microscopy, development of fluorescent probes and innovative software, have rapidly advanced the study of intracellular and intercellular processes within the kidney. Researchers can quantify the distribution, behavior, and dynamic interactions of up to four labeled chemical probes and proteins simultaneously and repeatedly in four dimensions (time), with subcellular resolution in near real time. Thus, multi-photon microscopy has greatly extended our ability to investigate cell biology intravitally, at cellular and subcellular resolutions. Therefore, the purpose of the chapter is to demonstrate how the use in intravital multi-photon microscopy has advanced the understanding of both the physiology and pathophysiology of the kidney.
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Affiliation(s)
- Ruben M Sandoval
- Indiana University School of Medicine, Roudebush VAMC, Indiana Center for Biological Microscopy, Indianapolis, IN 46202, USA
| | - Bruce A Molitoris
- Indiana University School of Medicine, Roudebush VAMC, Indiana Center for Biological Microscopy, Indianapolis, IN 46202, USA.
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50
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Surgical preparation of rats and mice for intravital microscopic imaging of abdominal organs. Methods 2017; 128:129-138. [PMID: 28698070 DOI: 10.1016/j.ymeth.2017.07.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 06/12/2017] [Accepted: 07/04/2017] [Indexed: 01/20/2023] Open
Abstract
Intravital microscopy is a powerful research tool that can provide insight into cellular and subcellular events that take place in organs in the body. However, meaningful results can only be obtained from animals whose physiology is preserved during the process of microscopy. Here I discuss the importance of preserving the overall state of health of the animal, methods of anesthesia, surgical techniques for intravital microscopy of various abdominal organs, methods to maintain and monitor the physiology of the animal during microscopy and associated peri- and post-operative recovery considerations.
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