1
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Makhammajanov Z, Gaipov A, Myngbay A, Bukasov R, Aljofan M, Kanbay M. Tubular toxicity of proteinuria and the progression of chronic kidney disease. Nephrol Dial Transplant 2024; 39:589-599. [PMID: 37791392 DOI: 10.1093/ndt/gfad215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Indexed: 10/05/2023] Open
Abstract
Proteinuria is a well-established biomarker of chronic kidney disease (CKD) and a risk predictor of associated disease outcomes. Proteinuria is also a driver of CKD progression toward end-stage kidney disease. Toxic effects of filtered proteins on proximal tubular epithelial cells enhance tubular atrophy and interstitial fibrosis. The extent of protein toxicity and the underlying molecular mechanisms responsible for tubular injury during proteinuria remain unclear. Nevertheless, albumin elicits its toxic effects when degraded and reabsorbed by proximal tubular epithelial cells. Overall, healthy kidneys excrete over 1000 individual proteins, which may be potentially harmful to proximal tubular epithelial cells when filtered and/or reabsorbed in excess. Proteinuria can cause kidney damage, inflammation and fibrosis by increasing reactive oxygen species, autophagy dysfunction, lysosomal membrane permeabilization, endoplasmic reticulum stress and complement activation. Here we summarize toxic proteins reported in proteinuria and the current understanding of molecular mechanisms of toxicity of proteins on proximal tubular epithelial cells leading to CKD progression.
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Affiliation(s)
| | - Abduzhappar Gaipov
- Department of Medicine, School of Medicine, Nazarbayev University, Astana, Kazakhstan
- Clinical Academic Department of Internal Medicine, CF "University Medical Center", Astana, Kazakhstan
| | - Askhat Myngbay
- Department of Biology, School of Sciences and Humanities, Nazarbayev University, Astana, Kazakhstan
| | - Rostislav Bukasov
- Department of Chemistry, School of Sciences and Humanities, Nazarbayev University, Astana, Kazakhstan
| | - Mohamad Aljofan
- Department of Biomedical Sciences, School of Medicine, Nazarbayev University, Astana, Kazakhstan
| | - Mehmet Kanbay
- Division of Nephrology, Department of Internal Medicine, Koc University, Istanbul, Turkey
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2
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Haeri H, Eisermann J, Schimm H, Büscher A, Hoyer P, Hinderberger D. Profound Changes in Functional Structure and Dynamics of Serum Albumin in Children with Nephrotic Syndrome: An Exploratory Research Study. J Med Chem 2023; 66:12115-12129. [PMID: 37648246 PMCID: PMC10510392 DOI: 10.1021/acs.jmedchem.3c00680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Indexed: 09/01/2023]
Abstract
Patients with nephrotic syndrome (NS) suffer from urinary loss of albumin. As a cause, previous studies focused on the glomerular filter rather than analyzing the molecular properties of albumin itself. Later one was initiated by clinical observations indicating unexplained molecular alterations of human serum albumin (HSA) in an NS pediatric patient. Therefore, we examined serum from eight pediatric patients with steroid-sensitive and -resistant NS and compared it with serum from healthy subjects as well as commercial HSA. We used dynamic and electrophoretic light scattering to characterize the protein size and effective surface charge and electron paramagnetic resonance spectroscopy to measure the local environment and binding dynamics of up to seven fatty acids associated with HSA. Our findings suggest that pronounced differences in binding behavior and surface charge of HSA could enhance their filtration through the GBM, leading to direct toxicity of HSA to podocytes.
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Affiliation(s)
- Haleh
H. Haeri
- Physical
Chemistry, Complex Self-Organizing Systems, Martin Luther University
Halle-Wittenberg, Institute of Chemistry, Von Danckelmann-Platz 4, 06120 Halle (Saale), Germany
| | - Jana Eisermann
- Department
of Chemistry, Molecular Sciences Research Hub, Imperial College London, 82 Wood Ln, W12 0BZ London, U.K.
| | - Heike Schimm
- Physical
Chemistry, Complex Self-Organizing Systems, Martin Luther University
Halle-Wittenberg, Institute of Chemistry, Von Danckelmann-Platz 4, 06120 Halle (Saale), Germany
| | - Anja Büscher
- Universitätsklinikum
Essen (AöR), Klinik für Kinderheilkunde II, Zentrum
für Kinder- und Jugendmedizin, Hufelandstraße 55, D-45147 Essen, Germany
| | - Peter Hoyer
- Universitätsklinikum
Essen (AöR), Klinik für Kinderheilkunde II, Zentrum
für Kinder- und Jugendmedizin, Hufelandstraße 55, D-45147 Essen, Germany
| | - Dariush Hinderberger
- Physical
Chemistry, Complex Self-Organizing Systems, Martin Luther University
Halle-Wittenberg, Institute of Chemistry, Von Danckelmann-Platz 4, 06120 Halle (Saale), Germany
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3
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Vincenti F, Angeletti A, Ghiggeri GM. State of the art in childhood nephrotic syndrome: concrete discoveries and unmet needs. Front Immunol 2023; 14:1167741. [PMID: 37503337 PMCID: PMC10368981 DOI: 10.3389/fimmu.2023.1167741] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 06/21/2023] [Indexed: 07/29/2023] Open
Abstract
Nephrotic syndrome (NS) is a clinical entity characterized by proteinuria, hypoalbuminemia, and peripheral edema. NS affects about 2-7 per 100,000 children aged below 18 years old yearly and is classified, based on the response to drugs, into steroid sensitive (SSNS), steroid dependent, (SDNS), multidrug dependent (MDNS), and multidrug resistant (MRNS). Forms of NS that are more difficult to treat are associated with a worse outcome with respect to renal function. In particular, MRNS commonly progresses to end stage renal failure requiring renal transplantation, with recurrence of the original disease in half of the cases. Histological presentations of NS may vary from minimal glomerular lesions (MCD) to focal segmental glomerulosclerosis (FSGS) and, of relevance, the histological patterns do not correlate with the response to treatments. Moreover, around half of MRNS cases are secondary to causative pathogenic variants in genes involved in maintaining the glomerular structure. The pathogenesis of NS is still poorly understood and therapeutic approaches are mostly based on clinical experience. Understanding of pathogenetic mechanisms of NS is one of the 'unmet needs' in nephrology and represents a significant challenge for the scientific community. The scope of the present review includes exploring relevant findings, identifying unmet needs, and reviewing therapeutic developments that characterize NS in the last decades. The main aim is to provide a basis for new perspectives and mechanistic studies in NS.
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Affiliation(s)
- Flavio Vincenti
- Division of Nephrology, Department of Medicine and Department of Surgery, University of California San Francisco, San Francisco, CA, United States
| | - Andrea Angeletti
- Nephrology Dialysis and Transplantation, Istituto di Ricerca e Cura a Carattere Scientifico (IRCCS) Istituto Giannina Gaslini, Genoa, Italy
| | - Gian Marco Ghiggeri
- Nephrology Dialysis and Transplantation, Istituto di Ricerca e Cura a Carattere Scientifico (IRCCS) Istituto Giannina Gaslini, Genoa, Italy
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4
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FATP2-targeted therapies - A role beyond fatty liver disease. Pharmacol Res 2020; 161:105228. [PMID: 33027714 DOI: 10.1016/j.phrs.2020.105228] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 09/26/2020] [Accepted: 09/27/2020] [Indexed: 12/31/2022]
Abstract
Fatty acid transport protein 2 (FATP2) is a multifunctional protein whose specific function is determined by the type of located cell, its intracellular location, or organelle-specific interactions. In the different diseases setting, a newfound appreciation for the biological function of FATP2 has come into view. Two main functions of FATP2 are to activate long-chain fatty acids (LCFAs) as a very long-chain acyl-coenzyme A (CoA) synthetase (ACSVL) and to transport LCFAs as a fatty acid transporter. FATP2 is not only involved in the occurrence of nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM), but also plays an important role in lithogenic diet-induced cholelithiasis, the formation of cancer tumor immunity, the progression of chronic kidney disease (CKD), and the regulation of zoledronate-induced nephrotoxicity. Herein, we review the updated information on the role of FATP2 in related diseases. In particular, we discuss the new functions of FATP2 and propose that FATP2 is a potential clinical biomarker and therapeutic target. In conclusion, regulatory strategies for FATP2 may bring new treatment options for cancer and lipid metabolism-related disorders.
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5
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Cosola C, Sabatino A, di Bari I, Fiaccadori E, Gesualdo L. Nutrients, Nutraceuticals, and Xenobiotics Affecting Renal Health. Nutrients 2018; 10:nu10070808. [PMID: 29937486 PMCID: PMC6073437 DOI: 10.3390/nu10070808] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 06/18/2018] [Accepted: 06/20/2018] [Indexed: 02/07/2023] Open
Abstract
Chronic kidney disease (CKD) affects 8–16% of the population worldwide. In developed countries, the most important risk factors for CKD are diabetes, hypertension, and obesity, calling into question the importance of educating and acting on lifestyles and nutrition. A balanced diet and supplementation can indeed support the maintenance of a general health status, including preservation of renal function, and can help to manage and curb the main risk factors for renal damage. While the concept of protein and salt restriction in nephrology is historically acknowledged, the role of some nutrients in renal health and the importance of nutrition as a preventative measure for renal care are less known. In this narrative review, we provide an overview of the demonstrated and potential actions of some selected nutrients, nutraceuticals, and xenobiotics on renal health and function. The direct and indirect effects of fiber, protein, fatty acids, curcumin, steviol glycosides, green tea, coffee, nitrates, nitrites, and alcohol on kidney health are reviewed here. In view of functional and personalized nutrition, understanding the renal and systemic effects of dietary components is essential since many chronic conditions, including CKD, are related to systemic dysfunctions such as chronic low-grade inflammation.
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Affiliation(s)
- Carmela Cosola
- Department of Emergency and Organ Transplantation-Nephrology, Dialysis and Transplantation Unit, University of Bari Aldo Moro, 70124 Bari, Italy.
| | - Alice Sabatino
- Department of Medicine and Surgery, Parma University Medical School, 43126 Parma, Italy.
| | - Ighli di Bari
- Department of Emergency and Organ Transplantation-Nephrology, Dialysis and Transplantation Unit, University of Bari Aldo Moro, 70124 Bari, Italy.
| | - Enrico Fiaccadori
- Department of Medicine and Surgery, Parma University Medical School, 43126 Parma, Italy.
| | - Loreto Gesualdo
- Department of Emergency and Organ Transplantation-Nephrology, Dialysis and Transplantation Unit, University of Bari Aldo Moro, 70124 Bari, Italy.
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6
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Bertelli R, Bonanni A, Caridi G, Canepa A, Ghiggeri GM. Molecular and Cellular Mechanisms for Proteinuria in Minimal Change Disease. Front Med (Lausanne) 2018; 5:170. [PMID: 29942802 PMCID: PMC6004767 DOI: 10.3389/fmed.2018.00170] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 05/15/2018] [Indexed: 12/15/2022] Open
Abstract
Minimal Change Disease (MCD) is a clinical condition characterized by acute nephrotic syndrome, no evident renal lesions at histology and good response to steroids. However, frequent recurrence of the disease requires additional therapies associated with steroids. Such multi-drug dependence and frequent relapses may cause disease evolution to focal and segmental glomerulosclerosis (FSGS) over time. The differences between the two conditions are not well defined, since molecular mechanisms may be shared by the two diseases. In some cases, genetic analysis can make it possible to distinguish MCD from FSGS; however, there are cases of overlap. Several hypotheses on mechanisms underlying MCD and potential molecular triggers have been proposed. Most studies were conducted on animal models of proteinuria that partially mimic MCD and may be useful to study glomerulosclerosis evolution; however, they do not demonstrate a clear-cut separation between MCD and FSGS. Puromycin Aminonucleoside and Adriamycin nephrosis are models of glomerular oxidative damage, characterized by loss of glomerular basement membrane polyanions resembling MCD at the onset and, at more advanced stages, by glomerulosclerosis resembling FSGS. Also Buffalo/Mna rats present initial lesions of MCD, subsequently evolving to FSGS; this mechanism of renal damage is clearer since this rat strain inherits the unique characteristic of overexpressing Th2 cytokines. In Lipopolysaccharide nephropathy, an immunological condition of renal toxicity linked to B7-1(CD80), mice develop transient proteinuria that lasts a few days. Overall, animal models are useful and necessary considering that they reproduce the evolution from MCD to FSGS that is, in part, due to persistence of proteinuria. The role of T/Treg/Bcells on human MCD has been discussed. Many cytokines, immunomodulatory mechanisms, and several molecules have been defined as a specific cause of proteinuria. However, the hypothesis of a single cell subset or molecule as cause of MCD is not supported by research and an interactive process seems more logical. The implication or interactive role of oxidants, Th2 cytokines, Th17, Tregs, B7-1(CD80), CD40/CD40L, c-Mip, TNF, uPA/suPAR, Angiopoietin-like 4 still awaits a definitive confirmation. Whole genome sequencing studies could help to define specific genetic features that justify a definition of MCD as a “clinical-pathology-genetic entity.”
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Affiliation(s)
| | | | | | - Alberto Canepa
- Nephrology, Dialysis, Transplantation Unit, Integrated Department of Pediatrics and Hemato-Oncology Sciences, Istituto Giannina Gaslini IRCCS, Genoa, Italy
| | - G M Ghiggeri
- Laboratory of Molecular Nephrology, Genoa, Italy.,Nephrology, Dialysis, Transplantation Unit, Integrated Department of Pediatrics and Hemato-Oncology Sciences, Istituto Giannina Gaslini IRCCS, Genoa, Italy
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7
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Turolo S, Edefonti A, Syren ML, Marangoni F, Morello W, Agostoni C, Montini G. Fatty Acids in Nephrotic Syndrome and Chronic Kidney Disease. J Ren Nutr 2017; 28:145-155. [PMID: 29153556 DOI: 10.1053/j.jrn.2017.08.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/04/2017] [Accepted: 08/07/2017] [Indexed: 12/14/2022] Open
Abstract
The role of fatty acids (FAs) in inflammation and in the related chronic diseases has been demonstrated. However, there is a lack of consistent and agreed knowledge about the role of FA profile and renal physiology and pathology, most articles focusing on the effect of polyunsaturated FAs supplementation, without considering the impact of basal FA metabolism on the efficacy of the supplementation. Here, we have summarized the specific literature concerning the assessment of circulating FA in 2 renal diseases, namely nephrotic syndrome and chronic kidney disease, also under hemodialytic treatment, and have received the most significant contributions in the last years. The effects of changes of FA profile and metabolism and the possible involvement of polyunsaturated FA metabolites in raising and modulating inflammation are discussed.
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Affiliation(s)
- Stefano Turolo
- Pediatric Department of Nephrology Dialysis and Transplantation, IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy.
| | - Alberto Edefonti
- Pediatric Department of Nephrology Dialysis and Transplantation, IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Marie Louise Syren
- Pediatric Clinic IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | | | - William Morello
- Pediatric Department of Nephrology Dialysis and Transplantation, IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Carlo Agostoni
- Pediatric Clinic IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Giovanni Montini
- Pediatric Department of Nephrology Dialysis and Transplantation, IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy; Pediatric Clinic IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
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8
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Khan S, Cabral PD, Schilling WP, Schmidt ZW, Uddin AN, Gingras A, Madhavan SM, Garvin JL, Schelling JR. Kidney Proximal Tubule Lipoapoptosis Is Regulated by Fatty Acid Transporter-2 (FATP2). J Am Soc Nephrol 2017; 29:81-91. [PMID: 28993506 DOI: 10.1681/asn.2017030314] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 08/08/2017] [Indexed: 11/03/2022] Open
Abstract
Albuminuria and tubular atrophy are among the highest risks for CKD progression to ESRD. A parsimonious mechanism involves leakage of albumin-bound nonesterified fatty acids (NEFAs) across the damaged glomerular filtration barrier and subsequent reabsorption by the downstream proximal tubule, causing lipoapoptosis. We sought to identify the apical proximal tubule transporter that mediates NEFA uptake and cytotoxicity. We observed transporter-mediated uptake of fluorescently labeled NEFA in cultured proximal tubule cells and microperfused rat proximal tubules, with greater uptake from the apical surface than from the basolateral surface. Protein and mRNA expression analyses revealed that kidney proximal tubules express transmembrane fatty acid transporter-2 (FATP2), encoded by Slc27a2, but not the other candidate transporters CD36 and free fatty acid receptor 1. Kidney FATP2 localized exclusively to proximal tubule epithelial cells along the apical but not the basolateral membrane. Treatment of mice with lipidated albumin to induce proteinuria caused a decrease in the proportion of tubular epithelial cells and an increase in the proportion of interstitial space in kidneys from wild-type but not Slc27a2-/- mice. Ex vivo microperfusion and in vitro experiments with NEFA-bound albumin at concentrations that mimic apical proximal tubule exposure during glomerular injury revealed significantly reduced NEFA uptake and palmitate-induced apoptosis in microperfused Slc27a2-/- proximal tubules and Slc27a2-/- or FATP2 shRNA-treated proximal tubule cell lines compared with wild-type or scrambled oligonucleotide-treated cells, respectively. We conclude that FATP2 is a major apical proximal tubule NEFA transporter that regulates lipoapoptosis and may be an amenable target for the prevention of CKD progression.
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Affiliation(s)
- Shenaz Khan
- Department of Medicine, The MetroHealth System and
| | - Pablo D Cabral
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
| | - William P Schilling
- Department of Medicine, The MetroHealth System and.,Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
| | | | - Asif N Uddin
- Department of Medicine, The MetroHealth System and
| | | | | | - Jeffrey L Garvin
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
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9
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Minami S, Yamamoto T, Takabatake Y, Takahashi A, Namba T, Matsuda J, Kimura T, Kaimori JY, Matsui I, Hamano T, Takeda H, Takahashi M, Izumi Y, Bamba T, Matsusaka T, Niimura F, Isaka Y. Lipophagy maintains energy homeostasis in the kidney proximal tubule during prolonged starvation. Autophagy 2017; 13:1629-1647. [PMID: 28813167 DOI: 10.1080/15548627.2017.1341464] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Macroautophagy/autophagy is a self-degradation process that combats starvation. Lipids are the main energy source in kidney proximal tubular cells (PTCs). During starvation, PTCs increase fatty acid (FA) uptake, form intracellular lipid droplets (LDs), and hydrolyze them for use. The involvement of autophagy in lipid metabolism in the kidney remains largely unknown. Here, we investigated the autophagy-mediated regulation of renal lipid metabolism during prolonged starvation using PTC-specific Atg5-deficient (atg5-TSKO) mice and an in vitro serum starvation model. Twenty-four h of starvation comparably induced LD formation in the PTCs of control and atg5-TSKO mice; however, additional 24 h of starvation reduced the number of LDs in control mice, whereas increases were observed in atg5-TSKO mice. Autophagic degradation of LDs (lipophagy) in PTCs was demonstrated by electron microscopic observation and biochemical analysis. In vitro pulse-chase assays demonstrated that lipophagy mobilizes FAs from LDs to mitochondria during starvation, whereas impaired LD degradation in autophagy-deficient PTCs led to decreased ATP production and subsequent cell death. In contrast to the in vitro assay, despite impaired LD degradation, kidney ATP content was preserved in 48-h starved atg5-TSKO mice, probably due to increased utilization of ketone bodies. This compensatory mechanism was accompanied by a higher plasma FGF21 (fibroblast growth factor 21) level and its expression in the PTCs; however, this was not essential for the production of ketone bodies in the liver during prolonged starvation. In conclusion, lipophagy combats prolonged starvation in PTCs to avoid cellular energy depletion.
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Affiliation(s)
- Satoshi Minami
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Takeshi Yamamoto
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Yoshitsugu Takabatake
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Atsushi Takahashi
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Tomoko Namba
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Jun Matsuda
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Tomonori Kimura
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Jun-Ya Kaimori
- b Department of Advanced Technology for Transplantation , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Isao Matsui
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Takayuki Hamano
- c Department of Comprehensive Kidney Disease Research (CKDR) , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
| | - Hiroaki Takeda
- d Division of Metabolomics, Medical Institute of Bioregulation , Kyushu University , Higashi-ku , Fukuoka , Japan
| | - Masatomo Takahashi
- d Division of Metabolomics, Medical Institute of Bioregulation , Kyushu University , Higashi-ku , Fukuoka , Japan
| | - Yoshihiro Izumi
- d Division of Metabolomics, Medical Institute of Bioregulation , Kyushu University , Higashi-ku , Fukuoka , Japan
| | - Takeshi Bamba
- d Division of Metabolomics, Medical Institute of Bioregulation , Kyushu University , Higashi-ku , Fukuoka , Japan
| | - Taiji Matsusaka
- e Institute of Medical Sciences and Department of Molecular Life Sciences , Tokai University School of Medicine , Isehara , Kanagawa , Japan
| | - Fumio Niimura
- f Department of Pediatrics , Tokai University School of Medicine , Isehara , Kanagawa , Japan
| | - Yoshitaka Isaka
- a Department of Nephrology , Osaka University Graduate School of Medicine , Suita , Osaka , Japan
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10
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Role of albumin and its modifications in glomerular injury. Pflugers Arch 2017; 469:975-982. [PMID: 28735420 DOI: 10.1007/s00424-017-2029-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 07/05/2017] [Indexed: 02/06/2023]
Abstract
Albuminuria is both a characteristic hallmark and a known risk factor for progressive glomerular disease. Although the molecular basis for a potential causative role for albuminuria in progressive chronic kidney disease remains poorly understood, there have been several recent advances in our understanding of the role of albumin, and its molecular modifications, in the development and progression of glomerular disease. This review discusses recent findings related to the ability of albumin and its associated factors to directly induce podocyte and glomerular injury. Additional recent studies confirming the ability and mechanisms by which podocytes endocytose albumin are also discussed. Lastly, we present several known molecular modifications in the albumin molecule itself, as well as substances bound to it, which may be important and potentially clinically relevant mediators of albumin-induced glomerular injury. These recent findings may create entirely new opportunities to develop novel future therapies directed at albumin that could potentially help reduce podocyte and renal tubular injury and slow the progression of chronic glomerular disease.
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11
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Yamamoto T, Takabatake Y, Takahashi A, Kimura T, Namba T, Matsuda J, Minami S, Kaimori JY, Matsui I, Matsusaka T, Niimura F, Yanagita M, Isaka Y. High-Fat Diet-Induced Lysosomal Dysfunction and Impaired Autophagic Flux Contribute to Lipotoxicity in the Kidney. J Am Soc Nephrol 2016; 28:1534-1551. [PMID: 27932476 DOI: 10.1681/asn.2016070731] [Citation(s) in RCA: 166] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 11/07/2016] [Indexed: 12/27/2022] Open
Abstract
Excessive fat intake contributes to the progression of metabolic diseases via cellular injury and inflammation, a process termed lipotoxicity. Here, we investigated the role of lysosomal dysfunction and impaired autophagic flux in the pathogenesis of lipotoxicity in the kidney. In mice, a high-fat diet (HFD) resulted in an accumulation of phospholipids in enlarged lysosomes within kidney proximal tubular cells (PTCs). In isolated PTCs treated with palmitic acid, autophagic degradation activity progressively stagnated in association with impaired lysosomal acidification and excessive lipid accumulation. Pulse-chase experiments revealed that the accumulated lipids originated from cellular membranes. In mice with induced PTC-specific ablation of autophagy, PTCs of HFD-mice exhibited greater accumulation of ubiquitin-positive protein aggregates normally removed by autophagy than did PTCs of mice fed a normal diet. Furthermore, HFD-mice had no capacity to augment autophagic activity upon another pathologic stress. Autophagy ablation also exaggerated HFD-induced mitochondrial dysfunction and inflammasome activation. Moreover, renal ischemia-reperfusion induced greater injury in HFD-mice than in mice fed a normal diet, and ablation of autophagy further exacerbated this effect. Finally, we detected similarly enhanced phospholipid accumulation in enlarged lysosomes and impaired autophagic flux in the kidneys of obese patients compared with nonobese patients. These findings provide key insights regarding the pathophysiology of lipotoxicity in the kidney and clues to a novel treatment for obesity-related kidney diseases.
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Affiliation(s)
| | | | | | | | | | | | | | - Jun-Ya Kaimori
- Advanced Technology for Transplantation, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | | | - Taiji Matsusaka
- Institute of Medical Sciences and Department of Molecular Life Sciences and
| | - Fumio Niimura
- Department of Pediatrics, Tokai University School of Medicine, Isehara, Kanagawa, Japan; and
| | - Motoko Yanagita
- Department of Nephrology, Kyoto University Graduate School of Medicine, Kyoto, Japan
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Abstract
The longstanding focus in chronic kidney disease (CKD) research has been on the glomerulus, which is sensible because this is where glomerular filtration occurs, and a large proportion of progressive CKD is associated with significant glomerular pathology. However, it has been known for decades that tubular atrophy is also a hallmark of CKD and that it is superior to glomerular pathology as a predictor of glomerular filtration rate decline in CKD. Nevertheless, there are vastly fewer studies that investigate the causes of tubular atrophy, and fewer still that identify potential therapeutic targets. The purpose of this review is to discuss plausible mechanisms of tubular atrophy, including tubular epithelial cell apoptosis, cell senescence, peritubular capillary rarefaction and downstream tubule ischemia, oxidative stress, atubular glomeruli, epithelial-to-mesenchymal transition, interstitial inflammation, lipotoxicity and Na(+)/H(+) exchanger-1 inactivation. Once a a better understanding of tubular atrophy (and interstitial fibrosis) pathophysiology has been obtained, it might then be possible to consider tandem glomerular and tubular therapeutic strategies, in a manner similar to cancer chemotherapy regimens, which employ multiple drugs to simultaneously target different mechanistic pathways.
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13
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Distinct urinary lipid profile in children with focal segmental glomerulosclerosis. Pediatr Nephrol 2016; 31:581-8. [PMID: 26537928 PMCID: PMC4962780 DOI: 10.1007/s00467-015-3239-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 10/04/2015] [Accepted: 10/05/2015] [Indexed: 10/22/2022]
Abstract
BACKGROUND Focal segmental glomerulosclerosis (FSGS) accounts for the majority of new-onset end-stage renal disease (ESRD) during adolescence. FSGS treatment is a great challenge for pediatric nephrologists due to intertwined molecular pathways underlining its complex pathophysiology. There is emerging evidence showing that perturbed lipid metabolism plays a role in the pathophysiology of FSGS. METHODS We postulate that the nephrotic milieu in FSGS differs from minimal change disease (MCD) and that urinary lipidomics can be used as a tool for early diagnosis of FSGS. We explored the urinary lipid profile of patients with FSGS and MCD using an unbiased metabolomics approach. RESULTS We discovered a unique lipid signature characterized by increased concentration of fatty acid (FA) and lysophosphatidylcholines (LPC) and a decrease in urinary concentration of phosphatidylcholine (PC) in patients with FSGS. These findings indicate increased metabolism of membrane phospholipid PC by phospholipase A2 (PLA2), resulting in higher urinary concentrations of LPC and FA. CONCLUSIONS We propose that increased PC by-products can be used as a biomarker to diagnose FSGS and shed light on the mechanism of tubular and podocyte damage. Validation of identified urinary lipids as a biomarker in predicting the diagnosis and progression of FSGS in a larger patient population is warranted.
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Santucci L, Bruschi M, Candiano G, Lugani F, Petretto A, Bonanni A, Ghiggeri GM. Urine Proteome Biomarkers in Kidney Diseases. I. Limits, Perspectives, and First Focus on Normal Urine. Biomark Insights 2016; 11:41-8. [PMID: 26997865 PMCID: PMC4795486 DOI: 10.4137/bmi.s26229] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Revised: 12/29/2015] [Accepted: 12/30/2015] [Indexed: 11/05/2022] Open
Abstract
Urine proteome is a potential source of information in renal diseases, and it is considered a natural area of investigation for biomarkers. Technology developments have markedly increased the power analysis on urinary proteins, and it is time to confront methodologies and results of major studies on the topics. This is a first part of a series of reviews that will focus on the urine proteome as a site for detecting biomarkers of renal diseases; the theme of the first review concerns methodological aspects applied to normal urine. Main issues are techniques for urine pretreatment, separation of exosomes, use of combinatorial peptide ligand libraries, mass spectrometry approaches, and analysis of data sets. Available studies show important differences, suggesting a major confounding effect of the technologies utilized for analysis. The objective is to obtain consensus about which approaches should be utilized for studying urine proteome in renal diseases.
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Affiliation(s)
- Laura Santucci
- Laboratory on Physiopathology of Uremia, Istituto Giannina Gaslini, Genova, Italy
| | - Maurizio Bruschi
- Laboratory on Physiopathology of Uremia, Istituto Giannina Gaslini, Genova, Italy
| | - Giovanni Candiano
- Laboratory on Physiopathology of Uremia, Istituto Giannina Gaslini, Genova, Italy
| | - Francesca Lugani
- Nephrology, Dialysis and Transplantation, Istituto Giannina Gaslini, Genova, Italy
| | - Andrea Petretto
- Laboratory of Mass Spectrometry - Core Facility, Istituto Giannina Gaslini, Genova, Italy
| | - Alice Bonanni
- Nephrology, Dialysis and Transplantation, Istituto Giannina Gaslini, Genova, Italy
| | - Gian Marco Ghiggeri
- Laboratory on Physiopathology of Uremia, Istituto Giannina Gaslini, Genova, Italy.; Nephrology, Dialysis and Transplantation, Istituto Giannina Gaslini, Genova, Italy
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Clement LC, Macé C, Del Nogal Avila M, Marshall CB, Chugh SS. The proteinuria-hypertriglyceridemia connection as a basis for novel therapeutics for nephrotic syndrome. Transl Res 2015; 165:499-504. [PMID: 25005737 PMCID: PMC4270958 DOI: 10.1016/j.trsl.2014.06.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 06/11/2014] [Accepted: 06/12/2014] [Indexed: 01/30/2023]
Abstract
The development of new and specific treatment options for kidney disease in general and glomerular diseases in specific has lagged behind other fields like heart disease and cancer. As a result, nephrologists have had to test and adapt therapeutics developed for other indications to treat glomerular diseases. One of the major factors contributing to this inertia has been the poor understanding of disease mechanisms. One way to elucidate these disease mechanisms is to study the association between the cardinal manifestations of glomerular diseases. Because many of these patients develop nephrotic syndrome, understanding the relationship of proteinuria, the primary driver in this syndrome, with hypoalbuminemia, hypercholesterolemia, hypertriglyceridemia, edema, and lipiduria could provide valuable insight. The recent unraveling of the relationship between proteinuria and hypertriglyceridemia mediated by free fatty acids, albumin, and the secreted glycoprotein angiopoietin-like 4 (Angptl4) offers a unique opportunity to develop novel therapeutics for glomerular diseases. In this review, the therapeutic potential of mutant forms of Angptl4 in reducing proteinuria and, as a consequence, alleviating the other manifestations of nephrotic syndrome is discussed.
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Affiliation(s)
- Lionel C Clement
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
| | - Camille Macé
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
| | - Maria Del Nogal Avila
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
| | - Caroline B Marshall
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
| | - Sumant S Chugh
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama.
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16
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Macé C, Chugh SS. Nephrotic syndrome: components, connections, and angiopoietin-like 4-related therapeutics. J Am Soc Nephrol 2014; 25:2393-8. [PMID: 24854282 DOI: 10.1681/asn.2014030267] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Nephrotic syndrome is recognized by the presence of proteinuria in excess of 3.5 g/24 h along with hypoalbuminemia, edema, hyperlipidemia (hypertriglyceridemia and hypercholesterolemia), and lipiduria. Each component has been investigated individually over the past four decades with some success. Studies published recently have started unraveling the molecular basis of proteinuria and its relationship with other components. We now have improved understanding of the threshold for nephrotic-range proteinuria and the pathogenesis of hypertriglyceridemia. These studies reveal that modifying sialylation of the soluble glycoprotein angiopoietin-like 4 or changing key amino acids in its sequence can be used successfully to treat proteinuria. Treatment strategies on the basis of fundamental relationships among different components of nephrotic syndrome use naturally occurring pathways and have great potential for future development into clinically relevant therapeutic agents.
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Affiliation(s)
- Camille Macé
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
| | - Sumant S Chugh
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
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17
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Macé C, Chugh SS. Nephrotic syndrome: components, connections, and angiopoietin-like 4-related therapeutics. J Am Soc Nephrol 2014. [PMID: 24854282 DOI: 10.1681/asn.20140303267] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Nephrotic syndrome is recognized by the presence of proteinuria in excess of 3.5 g/24 h along with hypoalbuminemia, edema, hyperlipidemia (hypertriglyceridemia and hypercholesterolemia), and lipiduria. Each component has been investigated individually over the past four decades with some success. Studies published recently have started unraveling the molecular basis of proteinuria and its relationship with other components. We now have improved understanding of the threshold for nephrotic-range proteinuria and the pathogenesis of hypertriglyceridemia. These studies reveal that modifying sialylation of the soluble glycoprotein angiopoietin-like 4 or changing key amino acids in its sequence can be used successfully to treat proteinuria. Treatment strategies on the basis of fundamental relationships among different components of nephrotic syndrome use naturally occurring pathways and have great potential for future development into clinically relevant therapeutic agents.
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Affiliation(s)
- Camille Macé
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
| | - Sumant S Chugh
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama
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18
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Chugh SS, Macé C, Clement LC, Del Nogal Avila M, Marshall CB. Angiopoietin-like 4 based therapeutics for proteinuria and kidney disease. Front Pharmacol 2014; 5:23. [PMID: 24611049 PMCID: PMC3933785 DOI: 10.3389/fphar.2014.00023] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 02/07/2014] [Indexed: 11/29/2022] Open
Abstract
Current drugs used to treat proteinuric disorders of the kidney have been borrowed from other branches of medicine, and are only partially effective. The discovery of a central, mechanistic role played by two different forms of the secreted glycoprotein angiopoietin-like 4 (Angptl4) in human and experimental glomerular disease has opened new treatment avenues. Localized upregulation of a hyposialylated form (lacks sialic acid residues) of Angptl4 secreted by podocytes induces the cardinal morphological and clinical manifestations of human minimal change disease, and is also being increasingly recognized as a significant contributor toward proteinuria in experimental diabetic nephropathy. Oral treatment with low doses of N-acetyl-D-mannosamine, a naturally occurring precursor of sialic acid, improves sialylation of Angptl4 in vivo, and reduces proteinuria by over 40%. By contrast, a sialylated circulating form of Angptl4, mostly secreted from skeletal muscle, heart and adipose tissue in all major primary glomerular diseases, reduces proteinuria while also causing hypertriglyceridemia. Intravenous administration of recombinant human Angptl4 mutated to avoid hypertriglyceridemia and cleavage has remarkable efficacy in reducing proteinuria by as much as 65% for 2 weeks after a single low dose. Both interventions are mechanistically relevant, utilize naturally occurring pathways, and represent new generation therapeutic agents for chronic kidney disease related to glomerular disorders.
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Affiliation(s)
- Sumant S Chugh
- Glomerular Disease Therapeutics Laboratory, Division of Nephrology, University of Alabama at Birmingham Birmingham, AL, USA
| | - Camille Macé
- Glomerular Disease Therapeutics Laboratory, Division of Nephrology, University of Alabama at Birmingham Birmingham, AL, USA
| | - Lionel C Clement
- Glomerular Disease Therapeutics Laboratory, Division of Nephrology, University of Alabama at Birmingham Birmingham, AL, USA
| | - Maria Del Nogal Avila
- Glomerular Disease Therapeutics Laboratory, Division of Nephrology, University of Alabama at Birmingham Birmingham, AL, USA
| | - Caroline B Marshall
- Glomerular Disease Therapeutics Laboratory, Division of Nephrology, University of Alabama at Birmingham Birmingham, AL, USA
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Khan S, Abu Jawdeh BG, Goel M, Schilling WP, Parker MD, Puchowicz MA, Yadav SP, Harris RC, El-Meanawy A, Hoshi M, Shinlapawittayatorn K, Deschênes I, Ficker E, Schelling JR. Lipotoxic disruption of NHE1 interaction with PI(4,5)P2 expedites proximal tubule apoptosis. J Clin Invest 2014; 124:1057-68. [PMID: 24531551 DOI: 10.1172/jci71863] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 12/11/2013] [Indexed: 12/12/2022] Open
Abstract
Chronic kidney disease progression can be predicted based on the degree of tubular atrophy, which is the result of proximal tubule apoptosis. The Na+/H+ exchanger NHE1 regulates proximal tubule cell survival through interaction with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], but pathophysiologic triggers for NHE1 inactivation are unknown. Because glomerular injury permits proximal tubule luminal exposure and reabsorption of fatty acid/albumin complexes, we hypothesized that accumulation of amphipathic, long-chain acyl-CoA (LC-CoA) metabolites stimulates lipoapoptosis by competing with the structurally similar PI(4,5)P2 for NHE1 binding. Kidneys from mouse models of progressive, albuminuric kidney disease exhibited increased fatty acids, LC-CoAs, and caspase-2-dependent proximal tubule lipoapoptosis. LC-CoAs and the cytosolic domain of NHE1 directly interacted, with an affinity comparable to that of the PI(4,5)P2-NHE1 interaction, and competing LC-CoAs disrupted binding of the NHE1 cytosolic tail to PI(4,5)P2. Inhibition of LC-CoA catabolism reduced NHE1 activity and enhanced apoptosis, whereas inhibition of proximal tubule LC-CoA generation preserved NHE1 activity and protected against apoptosis. Our data indicate that albuminuria/lipiduria enhances lipotoxin delivery to the proximal tubule and accumulation of LC-CoAs contributes to tubular atrophy by severing the NHE1-PI(4,5)P2 interaction, thereby lowering the apoptotic threshold. Furthermore, these data suggest that NHE1 functions as a metabolic sensor for lipotoxicity.
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20
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Clement LC, Macé C, Avila-Casado C, Joles JA, Kersten S, Chugh SS. Circulating angiopoietin-like 4 links proteinuria with hypertriglyceridemia in nephrotic syndrome. Nat Med 2013; 20:37-46. [PMID: 24317117 DOI: 10.1038/nm.3396] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Accepted: 10/08/2013] [Indexed: 01/01/2023]
Abstract
The molecular link between proteinuria and hyperlipidemia in nephrotic syndrome is not known. We show in the present study that plasma angiopoietin-like 4 (Angptl4) links proteinuria with hypertriglyceridemia through two negative feedback loops. In previous studies in a rat model that mimics human minimal change disease, we observed localized secretion by podocytes of hyposialylated Angptl4, a pro-proteinuric form of the protein. But in this study we noted high serum levels of Angptl4 (presumably normosialylated based on a neutral isoelectric point) in other glomerular diseases as well. Circulating Angptl4 was secreted by extrarenal organs in response to an elevated plasma ratio of free fatty acids (FFAs) to albumin when proteinuria reached nephrotic range. In a systemic feedback loop, these circulating pools of Angptl4 reduced proteinuria by interacting with glomerular endothelial αvβ5 integrin. Blocking the Angptl4-β5 integrin interaction or global knockout of Angptl4 or β5 integrin delayed recovery from peak proteinuria in animal models. But at the same time, in a local feedback loop, the elevated extrarenal pools of Angptl4 reduced tissue FFA uptake in skeletal muscle, heart and adipose tissue, subsequently resulting in hypertriglyceridemia, by inhibiting lipoprotein lipase (LPL)-mediated hydrolysis of plasma triglycerides to FFAs. Injecting recombinant human ANGPTL4 modified at a key LPL interacting site into nephrotic Buffalo Mna and Zucker Diabetic Fatty rats reduced proteinuria through the systemic loop but, by bypassing the local loop, without increasing plasma triglyceride levels. These data show that increases in circulating Angptl4 in response to nephrotic-range proteinuria reduces the degree of this pathology, but at the cost of inducing hypertriglyceridemia, while also suggesting a possible therapy to treat these linked pathologies.
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Affiliation(s)
- Lionel C Clement
- 1] Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, USA. [2]
| | - Camille Macé
- 1] Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, USA. [2]
| | - Carmen Avila-Casado
- 1] Department of Pathology, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada. [2] Department of Pathology, Instituto Nacional De Cardiologia, Mexico City, Mexico
| | - Jaap A Joles
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Sander Kersten
- Nutrition, Metabolism and Genomics Group, Wageningen University, Wageningen, The Netherlands
| | - Sumant S Chugh
- Glomerular Disease Therapeutics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama, USA
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21
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Inoki K. Proximal tubules forget "self-eating" when they meet Western meals. J Am Soc Nephrol 2013; 24:1711-3. [PMID: 24092931 DOI: 10.1681/asn.2013070794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Affiliation(s)
- Ken Inoki
- Life Sciences Institute, Department of Molecular and Integrative Physiology, Division of Nephrology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
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22
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Erkan E. Proteinuria and progression of glomerular diseases. Pediatr Nephrol 2013; 28:1049-58. [PMID: 23124512 DOI: 10.1007/s00467-012-2335-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 09/21/2012] [Accepted: 09/24/2012] [Indexed: 01/21/2023]
Abstract
One of the major challenges of nephrology is to develop therapeutic strategies to halt the progression of kidney diseases. In clinical settings, nephrotic-range proteinuria correlates with the rate of progression, particularly in glomerular diseases. Hence, the degree of proteinuria has been utilized to monitor the response to treatment as well as to predict outcome. However, the pathophysiology of proteinuria-induced progression remains unknown. Albumin accounts for the majority of the protein in nephrotic urine and as a result of this clinical observation studies have focused on understanding the adverse effects of albumin overload in the kidney. Albumin is internalized by receptor-mediated endocytosis in proximal tubule cells via low density lipoprotein (LDL) type receptor, megalin. Albumin at high concentrations mimicking nephrotic milieu has resulted in the upregulation of pro-inflammatory/fibrogenic genes and apoptosis in proximal tubule cells in in vivo and in vitro models of albumin overload. These properties of albumin on proximal tubule cells may explain extensive tubulointerstitial fibrosis and tubular atrophy observed in end-stage kidney disease. In addition to tubular toxicity, podocytes respond to proteinuric states by cytoskeletal alterations and loss of the differentiation marker synaptopodin. Identifying the molecular network of proteins involved in albumin handling will enable us to manipulate the specific signaling pathways and prevent damage caused by proteinuria.
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Affiliation(s)
- Elif Erkan
- Division of Pediatric Nephrology, Children's Hospital of Pittsburgh, 530 45th Street 5th Floor, Office # 5129, Pittsburgh, PA 15201, USA.
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23
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Bruschi M, Santucci L, Candiano G, Ghiggeri GM. Albumin heterogeneity in low-abundance fluids. The case of urine and cerebro-spinal fluid. Biochim Biophys Acta Gen Subj 2013; 1830:5503-8. [PMID: 23628703 DOI: 10.1016/j.bbagen.2013.04.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 04/16/2013] [Accepted: 04/19/2013] [Indexed: 11/18/2022]
Abstract
BACKGROUND Serum albumin is a micro-heterogeneous protein composed of at least 40 isoforms. Its heterogeneity is even more pronounced in biological fluids other than serum, the major being urine and cerebrospinal fluid. Modification 'in situ' and/or selectivity of biological barriers, such as in the kidney, determines the final composition of albumin and may help in definition of inflammatory states. SCOPE OF REVIEW This review focuses on various aspects of albumin heterogeneity in low 'abundance fluids' and highlights the potential source of information in diseases. MAJOR CONCLUSIONS The electrical charge of the protein in urine and CSF is modified but with an opposite change and depending on clinical conditions. In normal urine, the bulk of albumin is more anionic than in serum for the presence of ten times more fatty acids that introduce equivalent anionic charges and modify hydrophobicity of the protein. At the same time, urinary albumin is more glycosylated compared to the serum homolog. Finally, albumin fragments can be detected in urine in patients with proteinuria. For albumin in CSF, we lack information relative to normal conditions since ethical problems do not allow normal CSF to be studied. In multiple sclerosis, the albumin charge in CSF is more cationic than in serum, this change possibly involving structural anomalies or small molecules bindings. GENERAL SIGNIFICANCE Massively fatty albumin could be toxic for tubular cells and be eliminated on this basis. Renal handling of glycosylated albumin can alter the normal equilibrium of filtration/reabsorption and trigger mechanisms leading to glomerulosclerosis and tubulo-interstitial fibrosis. This article is part of a Special Issue entitled Serum Albumin.
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Affiliation(s)
- Maurizio Bruschi
- Division of Nephrology, Dialysis, and Transplantation, Istituto Giannina Gaslini, Genoa, Italy; Laboratory on Pathophysiology of Uremia, Istituto Giannina Gaslini, Genoa, Italy
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Bruschi M, Candiano G, Santucci L, Ghiggeri GM. Oxidized albumin. The long way of a protein of uncertain function. Biochim Biophys Acta Gen Subj 2013; 1830:5473-9. [PMID: 23618696 DOI: 10.1016/j.bbagen.2013.04.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 04/11/2013] [Accepted: 04/15/2013] [Indexed: 12/12/2022]
Abstract
BACKGROUND Proteins are extremely reactive to oxidants and should represent a potential target of instable reactive oxygen. This may represent a problem for plasma proteins since they may be directly modified in vivo in a compartment where antioxidant enzymatic systems are scarcely represented. On the other hand, it is possible that some plasma components have evolved over time to guarantee protection, in which case they can be considered as anti-oxidants. SCOPE OF REVIEW To present and discuss main studies which addressed the role of albumin in plasma antioxidant activity mainly utilizing in vitro models of oxidation. To present some advances on structural features of oxidized albumin deriving from studies carried out on in vitro models as well as albumin purified in vivo from patients affected by clinical conditions characterized by oxidative stress. MAJOR CONCLUSIONS There are different interaction with HOCl and chloramines. In the former case, HOCl produces an extensive alteration of (238)Trp and (162)Tyr, (425)Tyr, (47)Tyr, while thiol groups are only partially involved. Chloramines are extremely reactive with the unique free SH group of albumin ((34)Cys) with the formation of sulfenic and sulfinic acid as intermediates and sulfonic acid as end-product. Oxidized albumin has a modified electrical charge for the addition of an acidic residue and presents α-helix and random coil reorganization with subtle changes in domain orientation. GENERAL SIGNIFICANCE Albumin, is the major antioxidants in plasma with a concentration (0.8mM) higher than other antioxidants by an exponential factor. Functional and protective roles in the presence of oxidative stress must be defined. This article is part of a Special Issue entitled Serum Albumin.
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Affiliation(s)
- Maurizio Bruschi
- Laboratory on Pathophysiology of Uremia, Istituto Giannina Gaslini, Genoa, Italy
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Rosca MG, Vazquez EJ, Chen Q, Kerner J, Kern TS, Hoppel CL. Oxidation of fatty acids is the source of increased mitochondrial reactive oxygen species production in kidney cortical tubules in early diabetes. Diabetes 2012; 61:2074-83. [PMID: 22586586 PMCID: PMC3402323 DOI: 10.2337/db11-1437] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mitochondrial reactive oxygen species (ROS) cause kidney damage in diabetes. We investigated the source and site of ROS production by kidney cortical tubule mitochondria in streptozotocin-induced type 1 diabetes in rats. In diabetic mitochondria, the increased amounts and activities of selective fatty acid oxidation enzymes is associated with increased oxidative phosphorylation and net ROS production with fatty acid substrates (by 40% and 30%, respectively), whereas pyruvate oxidation is decreased and pyruvate-supported ROS production is unchanged. Oxidation of substrates that donate electrons at specific sites in the electron transport chain (ETC) is unchanged. The increased maximal production of ROS with fatty acid oxidation is not affected by limiting the electron flow from complex I into complex III. The maximal capacity of the ubiquinol oxidation site in complex III in generating ROS does not differ between the control and diabetic mitochondria. In conclusion, the mitochondrial ETC is neither the target nor the site of ROS production in kidney tubule mitochondria in short-term diabetes. Mitochondrial fatty acid oxidation is the source of the increased net ROS production, and the site of electron leakage is located proximal to coenzyme Q at the electron transfer flavoprotein that shuttles electrons from acyl-CoA dehydrogenases to coenzyme Q.
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Affiliation(s)
- Mariana G Rosca
- Center of Mitochondrial Diseases, Case Western Reserve University, Cleveland, Ohio, USA.
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26
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Santucci L, Candiano G, Bruschi M, D'Ambrosio C, Petretto A, Scaloni A, Urbani A, Righetti PG, Ghiggeri GM. Combinatorial peptide ligand libraries for the analysis of low-expression proteins: Validation for normal urine and definition of a first protein MAP. Proteomics 2012; 12:509-15. [DOI: 10.1002/pmic.201100404] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 09/19/2011] [Accepted: 10/25/2011] [Indexed: 11/10/2022]
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27
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Souma T, Abe M, Moriguchi T, Takai J, Yanagisawa-Miyazawa N, Shibata E, Akiyama Y, Toyohara T, Suzuki T, Tanemoto M, Abe T, Sato H, Yamamoto M, Ito S. Luminal alkalinization attenuates proteinuria-induced oxidative damage in proximal tubular cells. J Am Soc Nephrol 2011; 22:635-48. [PMID: 21372211 DOI: 10.1681/asn.2009111130] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
A highly acidic environment surrounds proximal tubular cells as a result of their reabsorption of HCO(3)(-). It is unclear whether this luminal acidity affects proteinuria-induced progression of tubular cell damage. Here, we investigated the contribution of luminal acidity to superoxide (O(2)(·-)) production induced by oleic acid-bound albumin (OA-Alb) in proximal tubular cells. Acidic media significantly enhanced OA-Alb-induced O(2)(·-) production in the HK-2 proximal tubular cell line. Simultaneous treatment with both OA-Alb and acidic media led to phosphorylation of the intracellular pH sensor Pyk2. Highly phosphorylated Pyk2 associated with activation of Rac1, an essential subcomponent of NAD(P)H oxidase. Furthermore, knockdown of Pyk2 with siRNA attenuated the O(2)(·-) production induced by cotreatment with OA-Alb and acid. To assess whether luminal alkalinization abrogates proteinuria-induced tubular damage, we studied a mouse model of protein-overload nephropathy. NaHCO(3) feeding selectively alkalinized the urine and dramatically attenuated the accumulation of O(2)(·-)-induced DNA damage and proximal tubular injury. Overall, these observations suggest that luminal acidity aggravates proteinuria-induced tubular damage and that modulation of this acidic environment may hold potential as a therapeutic target for proteinuric kidney disease.
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Affiliation(s)
- Tomokazu Souma
- Division of Nephrology, Endocrinology, and Vascular Medicine, Department of Medicine, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan.
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Hook AL, Thissen H, Voelcker NH. Surface plasmon resonance imaging of polymer microarrays to study protein-polymer interactions in high throughput. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:9173-81. [PMID: 19408906 DOI: 10.1021/la900735n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Polymer microarrays provide a high-throughput format in which to assess biointerfacial interactions. This endeavor greatly assists with the development of advanced biomaterials. In order to increase the scope of this platform technology, the development of analytical tools that are compatible with the microarray format and are capable of analyzing biomolecular interactions in high throughput is needed. Here, we show that surface plasmon resonance imaging (SPRi) is such a tool. SPRi enables spatially resolved, surface sensitive, label free, real-time analysis of multiple surface-biomolecular interactions in parallel. In order to demonstrate this, we first printed phenylazide-modified polymers onto a slide coated with a low fouling base polymer. UV irradiation of the slide resulted in the cross-linking of the printed polymer spots to the surface. SPRi was then employed to study the adsorption and desorption of bovine serum albumin, collagen, and fibronectin to these adhesive microarray spots. The spots were also incubated with an adherent cell line, enabling insight into the underlying mechanisms of cell attachment to the polymers studied. For the system analyzed here, electrostatic interactions were shown to dominate cell attachment.
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Affiliation(s)
- Andrew L Hook
- School of Chemistry, Physics and Earth Sciences, Flinders University, Adelaide, 5001, South Australia, Australia
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Mayrhofer C, Krieger S, Huttary N, Chang MWF, Grillari J, Allmaier G, Kerjaschki D. Alterations in fatty acid utilization and an impaired antioxidant defense mechanism are early events in podocyte injury: a proteomic analysis. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 174:1191-202. [PMID: 19264907 DOI: 10.2353/ajpath.2009.080654] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ultrastructural alterations of podocytes are closely associated with loss of glomerular filtration function. In the present study, we explored changes at the proteome level that paralleled the disturbances of podocyte architecture in the early stages of puromycin aminonucleoside (PA) nephrosis in vivo. Using two-dimensional fluorescence difference gel electrophoresis and vacuum matrix-assisted laser desorption/ionization mass spectrometry combined with postsource decay fragment ion analysis and high-energy collision-induced dissociation tandem mass spectrometry, 23 differentially expressed protein spots, corresponding to 16 glomerular proteins that are involved in various cellular functions, were unambiguously identified, and a subset was corroborated by Western blot analysis. The majority of these proteins were primarily related to fatty acid metabolism and redox regulation. Key enzymes of the mitochondrial beta-oxidation pathway and antioxidant enzymes were consistently down-regulated in PA nephrosis. These changes were paralleled by increased expression levels of CD36. PA treatment of murine podocytes in culture resembled these specific protein changes in vitro. In this cell system, the modulatory effects of albumin-bound fatty acids on the expression levels of Mn-superoxide dismutase in response to PA were demonstrated as well. Taken together, these results indicate that a disrupted fatty acid metabolism in concert with an impaired antioxidant defense mechanism in podocytes may play a role in the early stages of PA-induced lesions in podocytes.
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Affiliation(s)
- Corina Mayrhofer
- Clinical Institute of Pathology, Medical University of Vienna, Waehringer Gürtel 18-20, A-1090 Vienna, Austria.
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Miller WG, Bruns DE, Hortin GL, Sandberg S, Aakre KM, McQueen MJ, Itoh Y, Lieske JC, Seccombe DW, Jones G, Bunk DM, Curhan GC, Narva AS. Current issues in measurement and reporting of urinary albumin excretion. Clin Chem 2008; 55:24-38. [PMID: 19028824 DOI: 10.1373/clinchem.2008.106567] [Citation(s) in RCA: 233] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Urinary excretion of albumin indicates kidney damage and is recognized as a risk factor for progression of kidney disease and cardiovascular disease. The role of urinary albumin measurements has focused attention on the clinical need for accurate and clearly reported results. The National Kidney Disease Education Program and the IFCC convened a conference to assess the current state of preanalytical, analytical, and postanalytical issues affecting urine albumin measurements and to identify areas needing improvement. CONTENT The chemistry of albumin in urine is incompletely understood. Current guidelines recommend the use of the albumin/creatinine ratio (ACR) as a surrogate for the error-prone collection of timed urine samples. Although ACR results are affected by patient preparation and time of day of sample collection, neither is standardized. Considerable intermethod differences have been reported for both albumin and creatinine measurement, but trueness is unknown because there are no reference measurement procedures for albumin and no reference materials for either analyte in urine. The recommended reference intervals for the ACR do not take into account the large intergroup differences in creatinine excretion (e.g., related to differences in age, sex, and ethnicity) nor the continuous increase in risk related to albumin excretion. DISCUSSION Clinical needs have been identified for standardization of (a) urine collection methods, (b) urine albumin and creatinine measurements based on a complete reference system, (c) reporting of test results, and (d) reference intervals for the ACR.
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Affiliation(s)
- W Greg Miller
- Department of Pathology, Virginia Commonwealth University, Richmond, VA, USA.
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Urahama Y, Ohsaki Y, Fujita Y, Maruyama S, Yuzawa Y, Matsuo S, Fujimoto T. Lipid droplet-associated proteins protect renal tubular cells from fatty acid-induced apoptosis. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 173:1286-94. [PMID: 18832575 DOI: 10.2353/ajpath.2008.080137] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Proteinuria is a major cause of tubulointerstitial kidney damage, and free fatty acids bound to albumin are thought to play an important role in its pathogenesis. However, the mechanism whereby proteinuria causes tubulointerstitial damage to the kidney is unclear. Using primary human renal proximal tubular cells, we observed that albumin replete with fatty acids (rBSA) and defatted albumin (dBSA) complexed with linoleic acid (LA) induced significantly more apoptosis than did defatted albumin alone. Oxidative stress was partially involved in apoptotic induction by LA/dBSA but not by rBSA. Administration of fatty acid-bound BSA increased the number of lipid droplets (LDs) and the LD-associated proteins, adipocyte differentiation-related protein and TIP47. LDs are organelles that store esterified fatty acids, and the LD-associated proteins are presumed to facilitate LD formation. Knockdown of adipocyte differentiation-related protein or TIP47 by RNA interference enhanced induction of apoptosis by both rBSA and LA/dBSA. Apoptotic induction was observed similarly when either rBSA or LA/dBSA was applied to only the apical surfaces of polarized LLC-PK1 cells. The present results suggest that LDs and LD-associated proteins have protective effects against apoptosis induced by fatty acid-bound albumin by sequestering free fatty acids. Therapeutic manipulation of these LD-associated proteins could aid in the amelioration of nephritic diseases.
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Affiliation(s)
- Yoshimichi Urahama
- Division of Nephrology, Department of Internal Medicine, Nagoya University Graduate School of Medicine, Showa, Nagoya 466-8550, Japan.
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Aldámiz-Echevarría L, Vallo A, Aguirre M, Sanjurjo P, Gonzalez-Lamuño D, Elorz J, Prieto JA, Andrade F, Rodríguez-Soriano J. Essential fatty acid deficiency profile in patients with nephrotic-range proteinuria. Pediatr Nephrol 2007; 22:533-40. [PMID: 17123116 DOI: 10.1007/s00467-006-0366-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Revised: 10/18/2006] [Accepted: 10/18/2006] [Indexed: 10/23/2022]
Abstract
Plasma free fatty acids are bound to albumin, filtered through the glomeruli, and reabsorbed at the proximal nephron. The aim of the present investigation was to determine if urinary loss of fatty acids results in essential fatty acid (EFA) deficiency in patients with nephrotic-range proteinuria. We studied 12 patients aged 9 months to 23 years (eight male, four female) four suffering from congenital nephrotic syndrome (NS) and eight from different renal diseases. Six patients were studied postrenal transplantation. Proteinuria ranged between 41 and 829 mg/m2/h. Results were compared with data obtained in 83 healthy children. The patients had significantly lower values for plasma arachidonic acid content and EFA index (omega3 + omega6/omega7 + omega9). Deficiency in polyunsaturated fatty acids (PUFA) was especially manifest in infants with congenital NS. Plasma content of arachidonic and docosahexaenoic acids related negatively with the degree of proteinuria. In the lineal regression model, the degree of proteinuria explained 60% of the variability of plasma values of those fatty acids. We conclude that plasma fatty acid status should be regularly monitored in patients with nephrotic-range proteinuria, especially in young infants with congenital NS, who represent a population at special risk with regard to neurological development.
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Affiliation(s)
- Luis Aldámiz-Echevarría
- Division of Metabolism, Department of Pediatrics, Hospital de Cruces and Basque University School of Medicine, Bilbao, País Vasco, Spain.
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33
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Candiano G, Musante L, Bruschi M, Petretto A, Santucci L, Del Boccio P, Pavone B, Perfumo F, Urbani A, Scolari F, Ghiggeri GM. Repetitive fragmentation products of albumin and alpha1-antitrypsin in glomerular diseases associated with nephrotic syndrome. J Am Soc Nephrol 2006; 17:3139-48. [PMID: 17005933 DOI: 10.1681/asn.2006050486] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Even if nephrotic syndrome is characterized by massive urinary loss of major plasma proteins, a clear structural characterization based on proteomics has never been reported. Urine and plasma of 23 patients with different idiopathic nephrotic syndromes (10 steroid-sensitive minimal-change nephropathy, seven steroid-resistant FSGS, and six membranous glomerulonephritis) were analyzed with two-dimensional electrophoresis in soft gel, Western blot, and matrix-assisted laser desorption/ionization time of flight mass spectrometry; 72 urinary components corresponded to fragments of albumin and/or of alpha1-antitrypsin. Several repetitive fragmentation motives and a few differences among different pathologies were found. Several (21 of 72) urinary albumin fragments also were detected in plasma, although in lower concentration, suggesting a preferential excretion. The bulk of components with low molecular weight were detected only in urine, suggesting an in situ formation; zymograms with albumin as substrate showed the presence in urine of specific proteases. A final but not secondary point was the characterization of albumin adducts that harbor both the COOH and NH2 terminal parts of the protein, suggesting the formation of new covalent chemical groups. Altogether, these new findings reveal unexpected structural and functional aspects of proteinuria that may play a key role in pathogenesis. Characterization of urinary fragmentation patterns should be extended to other renal diseases.
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Affiliation(s)
- Giovanni Candiano
- Laboratory on Pathophysiology of Uremia, G. Gaslini Children Hospital, Genova, Italy
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Abstract
Excess fatty acids accompanied by triglyceride accumulation in parenchymal cells of multiple tissues including skeletal and cardiac myocytes, hepatocytes, and pancreatic beta cells results in chronic cellular dysfunction and injury. The process, now termed lipotoxicity, can account for many manifestations of the 'metabolic syndrome'. Most data suggest that the triglycerides serve primarily a storage function with toxicity deriving mainly from long-chain nonesterified fatty acids (NEFA) and their products such as ceramides and diacylglycerols. In the kidney, filtered NEFA carried on albumin can aggravate the chronic tubule damage and inflammatory phenotype that develop during proteinuric states and lipid loading of both glomerular and tubular cells is a common response to renal injury that contributes to progression of nephropathy. NEFA-induced mitochondrial dysfunction is the primary mechanism for energetic failure of proximal tubules during hypoxia/reoxygenation and persistent increases of tubule cell NEFA and triglycerides occur during acute renal failure in vivo in association with downregulation of mitochondrial and peroxisomal enzymes of beta oxidation. In acute renal failure models, peroxisome proliferator-activated receptor alpha ligand treatment can ameliorate the NEFA and triglyceride accumulation and limits tissue injury likely via both direct tubule actions and anti-inflammatory effects. Both acute and chronic kidney disease are associated with systemic manifestations of the metabolic syndrome.
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Affiliation(s)
- J M Weinberg
- Division of Nephrology, Department of Internal Medicine, Veterans Affairs Ann Arbor Healthcare System and University of Michigan, Ann Arbor, Michigan, USA.
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Ishola DA, Post JA, van Timmeren MM, Bakker SJL, Goldschmeding R, Koomans HA, Braam B, Joles JA. Albumin-bound fatty acids induce mitochondrial oxidant stress and impair antioxidant responses in proximal tubular cells. Kidney Int 2006; 70:724-31. [PMID: 16837928 DOI: 10.1038/sj.ki.5001629] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Albumin induces oxidative stress and cytokine production in proximal tubular cells (PTECs). Albumin-bound fatty acids (FAs) enhance tubulopathic effects of albumin in vivo. We proposed that FA aggravation of albumin-induced oxidative stress in PTECs might be involved. We hypothesized that mitochondria could be a source of such stress. Using a fluorescent probe, we compared reactive oxygen species (ROS) production after exposure of PTECs to bovine serum albumin (BSA) alone or loaded with oleic acid (OA-BSA) (3-30 g/l for 2 h). There was no difference in cellular albumin uptake, but OA-BSA dose-dependently induced more ROS than BSA alone (P<0.001). OA-BSA-induced ROS was significantly alleviated by mitochondrial inhibition, but not by inhibitors of nicotinamide adenine dinucleotide phosphate hydrogenase (NADPH) oxidase, xanthine oxidase, or nitric oxide synthase. Gene expression analysis showed that neither the NADPH oxidase component p22phox nor xanthine oxidase was induced by BSA or OA-BSA. OA-BSA, in contrast to BSA, failed to induce mitochondrial manganese superoxide dismutase 2 (SOD2) expression. OA-BSA showed a greater capacity than BSA to downregulate heme oxygenase-1 mRNA expression and accentuate inflammatory cytokine mRNA and protein. Supplementation of SOD activity with EUK-8 reduced ROS, and interleukin-6 protein expression was suppressed by both mitochondrial inhibition and SOD augmentation. Thus, in PTECs, FAs accentuate albumin-induced oxidative stress and inflammatory cytokine expression via increased mitochondrial ROS, while frustrating protective antioxidant responses.
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Affiliation(s)
- D A Ishola
- Department of Nephrology, University Medical Center, Utrecht, The Netherlands
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36
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Bruschi M, Musante L, Candiano G, Santucci L, Zennaro C, Carraro M, Del Boccio P, Gusmano R, Perfumo F, Urbani A, Ghiggeri GM. Transitions of serum albumin in patients with glomerulosclerosis ‘in vivo’ characterization by electrophoretic titration curves. Electrophoresis 2006; 27:2960-9. [PMID: 16764009 DOI: 10.1002/elps.200500641] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
HSA functions as a physiological transporter of solutes and small molecules that induce structural transitions 'in vitro'. Analysis of these transitions requires prior purification of HSA that could introduce bias due to conformational changes. We utilized electrophoretic titration curves to describe a neutral to acid (N-A) transition of HSA directly in sera of seven patients with active focal segmental glomerulosclerosis (FSGS). The divergent electrophoretic profile of HSA was characterized by a shift in the range of pHs between 4.5 and 7.5 with an average variation of free electrophoretic mobility corresponding to loss of 1 positive charge in the pKa protonation range of histidyl residues and should involve domain I of HSA. 'In-gel' determination by maleimide-PEO2-biotin of free SH 34 of domain I showed inaccessibility of the dye at this site in pathological HSA and alkylation with the same complex induced N-A transition in normal HSA. Potential binders of free imidazoles such as Ca++ and/or of SH 34 such as NO were excluded on the basis of direct titration and studies on binding stimulation. This is the first report describing a transition of HSA directly 'in vivo', and the utilization of electrophoretic titration curves was critical to this purpose. This transition appears to be specific to FSGS and is unrelated to the nephrotic syndrome, Ca++ and NO binding. Spectroscopic analysis will elucidate the structural implication.
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37
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Eardley KS, Zehnder D, Quinkler M, Lepenies J, Bates RL, Savage CO, Howie AJ, Adu D, Cockwell P. The relationship between albuminuria, MCP-1/CCL2, and interstitial macrophages in chronic kidney disease. Kidney Int 2006; 69:1189-97. [PMID: 16609683 DOI: 10.1038/sj.ki.5000212] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Glomerular-derived proteins may activate tubular cells to express the macrophage-directed chemokine monocyte chemoattractant protein-1 (MCP-1/CCL2). Macrophages at interstitial sites have a central role in directing renal scarring. We have prospectively assessed the relationship between albuminuria, urinary MCP-1/CCL2, interstitial macrophage infiltration, in situ damage, and clinical outcomes in a large group of patients with chronic kidney disease. We studied 215 patients and quantified albumin-creatinine ratio (ACR), urinary MCP-1/CCL2, interstitial macrophage numbers, and in situ damage. ACR correlated with urinary MCP-1/CCL2 (correlation 0.499; P<0.001), interstitial macrophage numbers (correlation 0.481; P<0.001), and index of chronic damage (correlation 0.363; P<0.001). Macrophage numbers closely correlated with in situ damage (correlation 0.755; P<0.001). By multivariate analysis ACR, urinary MCP-1/CCL2, and interstitial macrophage numbers were interdependent. By Kaplan-Meier survival analysis albuminuria, urinary MCP-1/CCL2, interstitial macrophages, and chronic damage predict the outcome. ACR, macrophage numbers, chronic damage, and creatinine independently predicted renal survival. The association of ACR with other variables was strongest in patients with less advanced disease states. There is a close association between albuminuria, urinary MCP-1/CCL2, and interstitial macrophage infiltration with in situ damage and clinical outcomes. These findings support the hypothesis that albuminuria triggers tubular MCP-1/CCL2 expression with subsequent macrophage infiltration. These processes may represent the dominant pathway for the progression of renal injury before the establishment of advanced renal scarring.
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Affiliation(s)
- K S Eardley
- Department of Nephrology, Queen Elizabeth Hospital, Birmingham, UK
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38
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Abstract
Macrophages and progressive tubulointerstitial disease. In chronic renal disease, tubulointerstitial inflammation and injury is associated with infiltrating macrophages. As a consequence of primary injury, proteinuria, chronic hypoxia, and glomerular-derived cytokines may all differentially modulate the expression of factors that promote macrophage recruitment. In addition to adhesion molecules and chemokines, products of complement system and renin-angiotensin system activation may direct this process. Once present at interstitial sites, macrophages interact with resident cells and extracellular matrix to generate a proinflammatory microenvironment that amplifies tissues injury and promotes scarring. There is now increasing evidence for the efficacy of interventions directed against factors that recruit, activate, or are produced by macrophages. A detailed understanding of the biology of this area may lead to the further development of therapies that will improve the outcome of renal disease.
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Affiliation(s)
- Kevin Sean Eardley
- Department of Nephrology, University Hospital Birmingham NHS Trust, Queen Elizabeth Hospital, Birmingham, United Kingdom
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van Timmeren MM, Bakker SJL, Stegeman CA, Gans ROB, van Goor H. Addition of oleic acid to delipidated bovine serum albumin aggravates renal damage in experimental protein-overload nephrosis. Nephrol Dial Transplant 2005; 20:2349-57. [PMID: 16144858 DOI: 10.1093/ndt/gfh964] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Non-esterified fatty acids (NEFA) carried on albumin may have a causal role in the development of chronic proteinuria-induced nephropathy. To investigate whether NEFA aggravate renal structural damage, we studied the effects of NEFA addition to delipidated bovine serum albumin (BSA) in protein-overload nephropathy. METHODS Three groups of Wistar rats received daily intraperitoneal injections (3 weeks) of either 1 g NEFA-free BSA (BSA-0), or NEFA-free BSA with three (BSA-3) or six (BSA-6) molecules oleic acid added per BSA molecule. An additional group received saline injections only (SAL). Renal damage was evaluated by immunohistochemistry and RT-PCR. RESULTS Interstitial and glomerular alpha-smooth muscle actin (alpha-SMA, marker of myofibroblast transformation) expression were higher in BSA-3/6 than in saline-injected controls (P < 0.001). Glomerular macrophage influx and desmin (marker of glomerular epithelial cell damage) expression were higher in all BSA-injected rats than SAL (P < 0.001). Interstitial macrophage influx was elevated in BSA-0/3 (P < 0.05) and BSA-6 (P < 0.001) compared to SAL. Addition of six molecules of oleic acid to BSA revealed higher interstitial and glomerular alpha-SMA expression (P < 0.001), increased interstitial macrophage numbers (P < 0.001) and enhanced glomerular desmin expression (P < 0.05) compared to BSA-0. RT-PCR revealed higher glomerular alpha-SMA mRNA expression in BSA-3/6 than SAL (P < 0.001 and 0.05, respectively), interstitial alpha-SMA mRNA was elevated in BSA-6 (P < 0.05). Interstitial TGF-beta1 mRNA expression was significantly higher in BSA-3 than SAL (P < 0.05). CONCLUSIONS These data show that addition of oleic acid to NEFA-free BSA aggravates renal damage, suggesting a role for NEFA in the pathogenesis of proteinuric nephropathies.
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Affiliation(s)
- Mirjan M van Timmeren
- Department of Pathology and Laboratory Medicine, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands.
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40
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Zandi-Nejad K, Eddy AA, Glassock RJ, Brenner BM. Why is proteinuria an ominous biomarker of progressive kidney disease? Kidney Int 2005:S76-89. [PMID: 15485426 DOI: 10.1111/j.1523-1755.2004.09220.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Progressive tubule injury and interstitial fibrosis frequently accompany glomerulopathies associated with proteinuria. Clinical experience indicates that higher levels of proteinuria prior to, as well as after initiation of treatment predict more rapid decline in renal function and more pronounced tubulointerstitial injury. It has been proposed that filtration of potentially tubulotoxic plasma proteins is responsible for the observed correlations between proteinuria and progression (i.e., proteinuria is a cause and not only a consequence of progressive renal injury). Numerous attempts have been made to identify the species of putative tubulotoxic proteins in this progressive injury process, but much uncertainty persists. These uncertainties stem from nonphysiologic exposure of apical cell surfaces to proteins in vitro, the extremely high concentrations of various proteins tested in vitro, and the nonuniformity of end points measured. Furthermore, there is often a lack of correlation between in vitro and in vivo findings, and a lack of uniformity of results even for seemingly similar in vitro experiments. Less controversy is evident in the potential pathways whereby injured tubules evoke a tubulointerstitial inflammatory and fibrotic response, with many in vivo models serving to incriminate excessive cytokine and chemokine production, infiltration of various inflammatory cells, and the balance between apoptosis and cell proliferation. Despite many years of concerted efforts, we believe it is still unclear whether proteinuria is a cause (and if so, which species of protein), or only a consequence of progressive renal injury. Nevertheless, pending the resolution of these uncertainties by more decisive and unambiguous experimentation, the strongly predictive inverse relationship between level of proteinuria and long-term renal survival currently justifies aggressive antiproteinuric treatment strategies, with a goal of reducing protein excretion rate to the lowest level possible without the induction of symptoms or undue risk.
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Affiliation(s)
- Kambiz Zandi-Nejad
- Renal Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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41
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Ghiggeri GM, Artero M, Carraro M, Candiano G, Musante L, Bruschi M, Zennaro C, Ginevri F, Caridi G, Faccini L, Perfumo F, Gusmano R. Glomerular albumin permeability as an in vitro model for characterizing the mechanism of focal glomerulosclerosis and predicting post-transplant recurrence. Pediatr Transplant 2004; 8:339-43. [PMID: 15265158 DOI: 10.1111/j.1399-3046.2004.00178.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The putative mechanisms of proteinuria in idiopathic focal glomerulosclerosis and of its post-transplant recurrence are discussed. It is proposed that a balance between circulating factors with permeability activity on glomeruli and putative inhibitors play a key role. The characterization of inductors is currently in progress; most inhibitors appear to be apolipoproteins (mainly apoJ and apo E) but we cannot exclude other substances. The goal is now to evaluate the concentration of both inducers and inhibitors of glomerular permeability in vivo. Permeability activity in plasma of patients with FSGS with and without recurrence of the disease may be evaluated by an in vitro functional essay with isolated glomeruli. Published data on permeability activity evaluated with this method in different proteinuric states gave, however, controversial results and this test cannot be readily considered of clear clinical utility. Only the definitive characterization and quantification in vivo of the different molecules that play a role in FSGS may furnish adequate answer.
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Affiliation(s)
- Bengt Rippe
- Department of Nephrology, University Hospital of Lund, S-211 85 Lund, Sweden.
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43
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Crook ED, Thallapureddy A, Migdal S, Flack JM, Greene EL, Salahudeen A, Tucker JK, Taylor HA. Lipid abnormalities and renal disease: is dyslipidemia a predictor of progression of renal disease? Am J Med Sci 2003; 325:340-8. [PMID: 12811230 DOI: 10.1097/00000441-200306000-00005] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Dyslipidemia is a cardiovascular disease (CVD) risk factor that is associated with enhanced atherosclerosis and plaque instability. Renal insufficiency is associated with abnormalities in lipoprotein metabolism in both the early and the advanced stages of chronic renal failure. These include alterations in apolipoprotein A (apo A)- and B- containing lipoproteins, high-density lipoproteins, and triglycerides. In animal models, these alterations in lipid metabolism and action lead to macrophage activation and infiltration in the kidney with resultant tubulointerstitial and endothelial cell injury. Limited data in humans suggest that, in addition to contributing to CVD, dyslipidemia may be a risk factor for the progression of renal disease. The effects of dyslipidemia on the kidney are mainly observed in those with other risk factors for renal disease progression such as hypertension, diabetes, and proteinuria. Renal disease is a strong risk factor for CVD and African Americans have high rates of renal disease. Therefore, examining the effects of dyslipidemia on the development or progression or renal disease will be an important question for the Jackson Heart Study and is the topic of this review.
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Affiliation(s)
- Errol D Crook
- Department of Medicine, Wayne State University School of Medicine and John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan 48302, USA.
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Arici M, Chana R, Lewington A, Brown J, Brunskill NJ. Stimulation of proximal tubular cell apoptosis by albumin-bound fatty acids mediated by peroxisome proliferator activated receptor-gamma. J Am Soc Nephrol 2003; 14:17-27. [PMID: 12506134 DOI: 10.1097/01.asn.0000042167.66685.ea] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
In nephrotic syndrome, large quantities of albumin enter the kidney tubule. This albumin carries with it a heavy load of fatty acids to which the proximal tubule cells are exposed at high concentration. It is postulated that exposure to fatty acids in this way is injurious to proximal tubule cells. This study has examined the ability of fatty acids to interact with peroxisome proliferator-activated receptors (PPAR) in primary cultures of human proximal tubule cells. Luciferase reporter assays in transiently transfected human proximal tubule cells were used to show that albumin bound fatty acids and other agonists activate PPARgamma in a dose-dependent manner. One of the consequences of this activation is apoptosis of the cells as determined by changes in cell morphology, evidence of PARP cleavage, and appearance of DNA laddering. Overexpression of PPARgamma in these cells also results in enhanced apoptosis. Both fatty acid-induced PPAR activation and apoptosis in these cells can be blocked by PPAR response element decoy oligonucleotides. Activation of PPARgamma by the specific agonist PGJ(2) is associated with inhibition of cell proliferation, whereas activation by albumin bound fatty acids is accompanied by increased proliferation. However, the net balance of apoptosis/proliferation favors deletion of cells. These results implicate albumin-bound fatty acids as important mediators of tubular injury in nephrosis and provide fresh impetus for pursuit of lipid-lowering strategies in proteinuric renal disease.
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Affiliation(s)
- Mustafa Arici
- Department of Cell Physiology, University of Leicester, Faculty of Medicine and Biological Sciences, Leicester, England
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45
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Kamijo A, Kimura K, Sugaya T, Yamanouchi M, Hase H, Kaneko T, Hirata Y, Goto A, Fujita T, Omata M. Urinary free fatty acids bound to albumin aggravate tubulointerstitial damage. Kidney Int 2002; 62:1628-37. [PMID: 12371963 DOI: 10.1046/j.1523-1755.2002.00618.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Evidence indicates that urinary protein is associated with tubulointerstitial damage and thus it is an aggravating factor for chronic renal disease. As free fatty acids (FFAs) are bound to serum albumin, we hypothesized that FFAs were overloaded to the proximal tubule in massive proteinuria and thus caused tubulointerstitial damage. To test this hypothesis, massive proteinuria was provoked in mice and the renal damage examined. METHODS Mice were intraperitoneally injected with bovine serum albumin (BSA) replete with FFAs (r-BSA group, N = 10), FFA-depleted BSA (d-BSA group, N = 10), or saline (saline group, N = 9) for 14 days. RESULTS The kidneys of the r-BSA group showed severe tubulointerstitial damage and those of the d-BSA group showed mild tubulointerstitial damage. Urinary excretion of both total protein and mouse albumin were significantly higher in the r-BSA group than in the d-BSA group. To examine the proximal tubular uptake of albumin, the BSA content in the cultured mouse proximal tubules was measured by ELISA after 90 minutes of incubation with each BSA. In terms of the BSA content in the proximal tubules, there was no significant difference between the r-BSA and the d-BSA groups. These results indicate that r-BSA and d-BSA were similarly reabsorbed into the proximal tubule and that r-BSA causes severe tubulointerstitial damage. CONCLUSIONS It is the FFAs bound to albumin, rather than albumin itself, which cause severe tubulointerstitial damage by being reabsorbed into the proximal tubule. To our knowledge, this is the first in vivo observation in which FFAs have caused severe tubulointerstitial injury.
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MESH Headings
- Albuminuria/metabolism
- Animals
- Antibodies/blood
- Blood Pressure
- Body Weight
- Cells, Cultured
- Endotoxins/analysis
- Fatty Acids, Nonesterified/urine
- Female
- Kidney Failure, Chronic/pathology
- Kidney Failure, Chronic/urine
- Kidney Tubules, Proximal/metabolism
- Kidney Tubules, Proximal/pathology
- Macrophages/pathology
- Mice
- Mice, Inbred BALB C
- Serum Albumin
- Serum Albumin, Bovine/immunology
- Serum Albumin, Bovine/pharmacokinetics
- Serum Albumin, Bovine/urine
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Affiliation(s)
- Atsuko Kamijo
- Internal Medicine, the University of Tokyo, Tokyo, Japan
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Thomas ME, Harris KPG, Walls J, Furness PN, Brunskill NJ. Fatty acids exacerbate tubulointerstitial injury in protein-overload proteinuria. Am J Physiol Renal Physiol 2002; 283:F640-7. [PMID: 12217854 DOI: 10.1152/ajprenal.00001.2002] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of the albumin-carried fatty acids in the induction of tubulointerstitial injury was studied in protein-overload proteinuria. Rats were injected with fatty acid-carrying BSA [FA(+)BSA], fatty acid-depleted BSA [FA(-)BSA], or saline. Macrophage infiltration was measured by immunohistochemical staining, apoptotic cells were detected by in situ end labeling, and proliferating cells were identified by in situ hybridization for histone mRNA. Macrophage infiltration was significantly greater in the FA(+)BSA group than in the FA(-)BSA and saline groups. The infiltrate was largely restricted to the outer cortex. Apoptosis was greater in the FA(+)BSA group than in the FA(-)BSA and saline groups. Compared with the saline group, apoptosis was significantly increased in the FA(+)BSA group but not in the FA(-)BSA group. Cortical cells proliferated significantly more in the FA(+)BSA and FA(-)BSA groups than in the saline group. FA(+)BSA is therefore a more potent inducer of macrophage infiltration and cell death than FA(-)BSA. The fatty acids carried on albumin may be the chief instigators of tubulointerstitial injury in protein-overload proteinuria.
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Affiliation(s)
- Mark E Thomas
- Department of Nephrology, Leicester General Hospital, United Kingdom
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Musante L, Candiano G, Bruschi M, Zennaro C, Carraro M, Artero M, Giuffrida MG, Conti A, Santucci A, Ghiggeri GM. Characterization of plasma factors that alter the permeability to albumin within isolated glomeruli. Proteomics 2002; 2:197-205. [PMID: 11840565 DOI: 10.1002/1615-9861(200202)2:2<197::aid-prot197>3.0.co;2-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Focal segmental glomerulosclerosis (FSGS) is responsible for intractable proteinuria and has become the leading cause of renal insufficiency in children. Protenuria in FSGS is probably due to the effect of one or more permeability plasma factors which increase the glomerular permeability to proteins. We fractioned serum from children with FSGS using two mixed chromatographic-electrophoretic approaches and have purified ten proteins among several hundreds which maintained the original permeability activity after renaturation, utilizing an isolated rat glomeruli assay. Six proteins were successfully characterized by mass spectometry as fibulin, apolipoprotein J, vitronectin, albumin isoforms, gamma chain fibrinogen and mannan-binding lectin-associated serine protease. Both procedures utilized for purification were based on affinity chromatography with Protein A-Sepharose and ended with two-dimensional electrophoresis, whereas the intermediate steps were different. Cross inhibition with zinc and aprotinin of purified factors and whole FSGS serum indicate strong homology. These are the first data demonstrating permeability activity for serum proteins, an observation with important implications in pathogenesis of proteinuria. Determination of the serum levels of each protein and a careful differentiation of FSGS from normal serum could provide the basis for clarifying the mechanism of proteinuria.
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Affiliation(s)
- Luca Musante
- Laboratorio di Fisiopatologia dell'uremia, Istituto G. Gaslini, Genova, Italy
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Cheung PK, Klok PA, Baller JF, Bakker WW. Induction of experimental proteinuria in vivo following infusion of human plasma hemopexin. Kidney Int 2000; 57:1512-20. [PMID: 10760087 DOI: 10.1046/j.1523-1755.2000.00996.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
BACKGROUND The human plasma constituent hemopexin (Hx), following incubation with renal tissue, is able to induce glomerular alterations in vitro that are similar to those seen in minimal change disease (MCD). Whether this acute phase reactant is also able to induce proteinuria and minimal change-like alterations in vivo is questioned. METHODS In the first set of experiments, Hx (4.0 mg in 5.0 mL saline) or equal amounts of control fraction, that is, heat-inactivated Hx (HI-Hx), were infused into conscious rats (N = 6) that had been surgically equipped with a cannula inserted into the suprarenal artery (SRA), enabling direct contact of the infusate and the renal microvasculature. Each animal received HI-Hx at day 1 for 15 minutes (flow rate 20.0 mL/h), subsequently followed by saline for seven hours (Flow rate 5.0 mL/h), after which the cannula was disconnected. At day 2, identical infusions in the same rat were carried out, using native Hx. Urine samples collected every 30 minutes during the experiments were monitored for protein content using standard methods. In the second set of experiments, unilateral perfusion was done ex vivo in anesthetized rats with Hx (N = 5) or HI-Hx (N = 3; 1.5 mg/mL; 4.0 mL during 6 min). After reconnection of the circulation, urine samples of both kidneys were collected every 30 minutes during five hours via ureter cannulation. Urinary protein (expressed as the difference in excretion between perfused and nonperfused kidney) was calculated in mg/24 h. In additional experiments, rats were sacrificed two hours after perfusion of Hx or heat-inactivated (control) Hx (first set of experiments) or after five hours (second set of experiments), and kidneys were processed for immunohistochemical and ultrastructural examination. RESULTS The results of experiment 1 show a significant increase of proteinuria after Hx infusion versus HI-Hx (means +/- SD, 41.91 +/- 16.01 mg/24 h vs. control, 21.22 +/- 5.69 mg/24 h; P </= 0.03). Histochemical and electron microscopical examination of kidney tissue fragments taken at the time of proteinuria showed diminished expression of glomerular ecto-ATPase and enhanced effacement of epithelial foot processes at the ultrastructural level. In the second set of experiments, the results show significant urinary protein excretion peaking one hour after perfusion (6.63 +/- 7.06 mg/24 h), exclusively in Hx-perfused animals (analysis of variance, P < or = 0.001). CONCLUSION It is concluded that Hx is able to induce proteinuria associated with MCD-like alterations in rat kidney in vivo.
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Affiliation(s)
- P K Cheung
- Department of Pathology and Laboratorium Medicine, University of Groningen, The Netherlands
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Lewis DM, Tooke JE, Beaman M, Gamble J, Shore AC. Peripheral microvascular parameters in the nephrotic syndrome. Kidney Int 1998; 54:1261-6. [PMID: 9767542 DOI: 10.1046/j.1523-1755.1998.00100.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Peripheral edema, in combination with severe proteinuria and low serum albumin levels, is pathognomonic of the nephrotic syndrome, yet the exact mechanism of its formation is unknown. Two of the most important of the factors in Starling's forces controlling fluid filtration across the capillary have hitherto not been studied in nephrotic subjects. METHODS The hydrostatic capillary pressure at the finger nail-fold in actively nephrotic subjects and age and sex matched controls was studied, using direct puncture of the apex of the capillary under video microscopy, and a servonulling apparatus to give a direct measurement of capillary pressure. Capillary filtration capacity (CFC) at the calf was measured noninvasively by a modern derivative of the technique of mercury strain gauge plethysmography. Fifteen nephrotic subjects with a variety of underlying pathological lesions, and age matched controls were studied. RESULTS Contrary to the assumption of the "overflow" hypothesis of edema formation, there was no evidence of capillary hypertension. The capillary pressure showed no difference between nephrotic subjects and controls: median (range) of 17.6 (12.0 to 24.2) compared with 17.3 (9.0 to 21.6) mm Hg, P = NS. CFC was significantly higher in nephrotic subjects than controls [5.23 (3.28 to 8.52) x 10(-3) versus 3.55 (2.43 to 5.28) x 10(-3) ml/min/100 g/mm Hg, P < 0.01]. CONCLUSIONS An increase in CFC provides a potentially novel mechanism contributing at least in part to the formation of peripheral edema in the nephrotic syndrome.
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Affiliation(s)
- D M Lewis
- Royal Devon and Exeter Hospital, and Department of Vascular Medicine, University of Exeter, England, United Kingdom.
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50
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Abstract
The cause of the relentless progression of chronic renal failure of diverse origins remains unknown and is likely to be multifactorial. Numerous studies have now demonstrated a correlation between the degree of proteinuria and the rate progression of renal failure, which has led to the hypothesis that proteinuria may be an independent mediator of progression rather than simply being a marker of glomerular dysfunction. This article reviews the evidence underlying this hypothesis and the mechanisms by which particular proteins may cause renal pathology. The abnormal filtration of proteins across the glomerular basement membrane will bring them into contact with the mesangium and with the tubular cells. There is evidence to support a role of lipoproteins on mesangial cell function, which ultimately could contribute to glomerular sclerosis. The proximal tubular cells reabsorb proteins from the tubular fluid, which leaves them particularly vulnerable to any adverse effects proteins may have. It has been postulated that the sheer amount of protein to be metabolized by these cells may overwhelm the lysosomes and result in leakage of cytotoxic enzymes into the cells. In addition, the increased metabolism of proteins may result in production of ammonia, which can mediate inflammation through activation of complement. Specific proteins that have been shown to be cytotoxic are transferrin/iron, low-density lipoprotein, and complement components, all of which appear in the urine in proteinuric states. Other specific proteins have been shown to stimulate production of cytokines, chemoattractants, and matrix proteins by tubular cells and thus may stimulate interstitial inflammation and scarring. The mechanisms by which the presence of proteins in the tubular fluid alters tubular cell biology is yet to be determined.
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Affiliation(s)
- C Burton
- Department of Nephrology, University of Leicester and Leicester General Hospital, Leicester, United Kingdom
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