101
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Ku E, Lipkowitz MS, Appel LJ, Parsa A, Gassman J, Glidden DV, Smogorzewski M, Hsu CY. Strict blood pressure control associates with decreased mortality risk by APOL1 genotype. Kidney Int 2017; 91:443-450. [PMID: 27927600 PMCID: PMC5237400 DOI: 10.1016/j.kint.2016.09.033] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 09/14/2016] [Accepted: 09/15/2016] [Indexed: 02/06/2023]
Abstract
Although APOL1 high-risk genotype partially accounts for the increased susceptibility of blacks to chronic kidney disease (CKD), whether APOL1 associates differentially with mortality risk remains controversial. Here we evaluate the association between APOL1 genotype and risk of death and determine whether APOL1 status modifies the association between strict versus usual blood pressure control and mortality risk. We performed a retrospective analysis of the African American Study of Kidney Disease and Hypertension trial that randomized black participants with CKD to strict versus usual blood pressure control from 1995 to 2001. This included 682 participants with known APOL1 genotype (157 with high-risk genotype) previously assigned to either strict (mean arterial pressure [MAP] 92 mm Hg or less) versus usual blood pressure control (MAP 102-107 mm Hg) during the trial. During a median follow-up of 14.5 years, risk of death did not differ between individuals with high- versus low-risk APOL1 genotypes (unadjusted hazard ratio 1.00 [95% confidence interval 0.76-1.33]). However, a significant interaction was detected between the APOL1 risk group and blood pressure control strategy. In the APOL1 high-risk group, the risk of death was 42% lower comparing strict versus usual blood pressure control (0.58 [0.35-0.97]). In the APOL1 low-risk group, the risk of death comparing strict versus usual blood pressure control was not significantly different (1.09 [0.84-1.43]). Thus, strict blood pressure control during CKD associates with a lower risk of death in blacks with the high-risk CKD APOL1 genotype. Knowledge of APOL1 status could inform selection of blood pressure treatment targets in black CKD patients.
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Affiliation(s)
- Elaine Ku
- Division of Nephrology, Department of Medicine, University of California, San Francisco, San Francisco, California, USA; Division of Pediatric Nephrology, Department of Pediatrics, University of California, San Francisco, San Francisco, California, USA.
| | - Michael S Lipkowitz
- Division of Nephrology, Department of Medicine, Georgetown University, Washington, DC, USA
| | - Lawrence J Appel
- Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, Baltimore, Maryland, USA
| | - Afshin Parsa
- Division of Nephrology, Department of Medicine, University of Maryland, Baltimore, Maryland, USA; Department of Medicine, Baltimore VA Medical Center, Baltimore, Maryland, USA
| | - Jennifer Gassman
- Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio, USA
| | - David V Glidden
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California, USA
| | - Miroslaw Smogorzewski
- Division of Nephrology and Hypertension, Department of Medicine, University of Southern California, Los Angeles, California, USA
| | - Chi-Yuan Hsu
- Division of Nephrology, Department of Medicine, University of California, San Francisco, San Francisco, California, USA
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102
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Antagonism of scavenger receptor CD36 by 5A peptide prevents chronic kidney disease progression in mice independent of blood pressure regulation. Kidney Int 2017; 89:809-22. [PMID: 26994575 DOI: 10.1016/j.kint.2015.12.043] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 11/30/2015] [Accepted: 12/11/2015] [Indexed: 01/24/2023]
Abstract
Scavenger receptor CD36 participates in lipid metabolism and inflammatory pathways important for cardiovascular disease and chronic kidney disease (CKD). Few pharmacological agents are available to slow the progression of CKD. However, apolipoprotein A-I-mimetic peptide 5A antagonizes CD36 in vitro. To test the efficacy of 5A, and to test the role of CD36 during CKD, we compared wild-type to CD36 knockout mice and wild-type mice treated with 5A, in a progressive CKD model that resembles human disease. Knockout and 5A-treated wild-type mice were protected from CKD progression without changes in blood pressure and had reductions in cardiovascular risk surrogate markers that are associated with CKD. Treatment with 5A did not further protect CD36 knockout mice from CKD progression, implicating CD36 as its main site of action. In a separate model of kidney fibrosis, 5A-treated wild-type mice had less macrophage infiltration and interstitial fibrosis. Peptide 5A exerted anti-inflammatory effects in the kidney and decreased renal expression of inflammasome genes. Thus, CD36 is a new therapeutic target for CKD and its associated cardiovascular risk factors. Peptide 5A may be a promising new agent to slow CKD progression.
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103
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Bruggeman LA. HIV-1 Infection of Renal Cells in HIV-Associated Nephropathy. J Am Soc Nephrol 2017; 28:719-721. [PMID: 28069873 DOI: 10.1681/asn.2016111171] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Affiliation(s)
- Leslie A Bruggeman
- Department of Medicine, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio
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104
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Zwang NA, Shetty A, Sustento-Reodica N, Gordon EJ, Leventhal J, Gallon L, Friedewald JJ. APOL1-Associated End-Stage Renal Disease in a Living Kidney Transplant Donor. Am J Transplant 2016; 16:3568-3572. [PMID: 27588375 DOI: 10.1111/ajt.14035] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 08/09/2016] [Accepted: 08/27/2016] [Indexed: 01/25/2023]
Abstract
Homozygosity for apolipoprotein-L1 (APOL1) risk variants has emerged as an important predictor of renal disease in individuals of African descent over the past several years. Additionally, these risk variants may be important predictors of renal allograft failure when present in a living or deceased donor. Currently, there is no universal recommendation for screening of potential donors. We present a case of end-stage renal disease with focal segmental glomerulosclerosis in a living donor 7 years following donor nephrectomy. Genetic assessment revealed homozygosity for the G1 high-risk APOL1 variant.
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Affiliation(s)
- N A Zwang
- Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL.,McGaw Medical Center of Northwestern University, Chicago, IL
| | - A Shetty
- Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - N Sustento-Reodica
- Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - E J Gordon
- Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL.,Center for Healthcare Studies, and Center for Bioethics and Medical Humanities, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - J Leventhal
- Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - L Gallon
- Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - J J Friedewald
- Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, IL
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105
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Kruzel-Davila E, Shemer R, Ofir A, Bavli-Kertselli I, Darlyuk-Saadon I, Oren-Giladi P, Wasser WG, Magen D, Zaknoun E, Schuldiner M, Salzberg A, Kornitzer D, Marelja Z, Simons M, Skorecki K. APOL1-Mediated Cell Injury Involves Disruption of Conserved Trafficking Processes. J Am Soc Nephrol 2016; 28:1117-1130. [PMID: 27864431 DOI: 10.1681/asn.2016050546] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 10/05/2016] [Indexed: 01/08/2023] Open
Abstract
APOL1 harbors C-terminal sequence variants (G1 and G2), which account for much of the increased risk for kidney disease in sub-Saharan African ancestry populations. Expression of the risk variants has also been shown to cause injury to podocytes and other cell types, but the underlying mechanisms are not understood. We used Drosophila melanogaster and Saccharomyces cerevisiae to help clarify these mechanisms. Ubiquitous expression of the human APOL1 G1 and G2 disease risk alleles caused near-complete lethality in D. melanogaster, with no effect of the G0 nonrisk APOL1 allele, corresponding to the pattern of human disease risk. We also observed a congruent pattern of cellular damage with tissue-specific expression of APOL1. In particular, expression of APOL1 risk variants in D. melanogaster nephrocytes caused cell-autonomous accumulation of the endocytic tracer atrial natriuretic factor-red fluorescent protein at early stages and nephrocyte loss at later stages. We also observed differential toxicity of the APOL1 risk variants compared with the APOL1 nonrisk variants in S. cerevisiae, including impairment of vacuole acidification. Yeast strains defective in endosomal trafficking or organelle acidification but not those defective in autophagy displayed augmented APOL1 toxicity with all isoforms. This pattern of differential injury by the APOL1 risk alleles compared with the nonrisk alleles across evolutionarily divergent species is consistent with an impairment of conserved core intracellular endosomal trafficking processes. This finding should facilitate the identification of cell injury pathways and corresponding therapeutic targets of interest in these amenable experimental platforms.
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Affiliation(s)
- Etty Kruzel-Davila
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of
| | | | - Ayala Ofir
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of
| | - Ira Bavli-Kertselli
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of
| | | | - Pazit Oren-Giladi
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of
| | - Walter G Wasser
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of.,Department of Nephrology, Mayanei HaYeshua Medical Center, Bnei Brak, Israel
| | - Daniella Magen
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of.,Genetics and Developmental Biology and
| | | | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel; and
| | | | - Daniel Kornitzer
- Microbiology and Inflammation, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
| | - Zvonimir Marelja
- Imagine Institute, Paris Descartes University-Sorbonne Paris Cité, Paris, France
| | - Matias Simons
- Imagine Institute, Paris Descartes University-Sorbonne Paris Cité, Paris, France
| | - Karl Skorecki
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of .,Genetics and Developmental Biology and
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106
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Fu Y, Zhu JY, Richman A, Zhang Y, Xie X, Das JR, Li J, Ray PE, Han Z. APOL1-G1 in Nephrocytes Induces Hypertrophy and Accelerates Cell Death. J Am Soc Nephrol 2016; 28:1106-1116. [PMID: 27864430 DOI: 10.1681/asn.2016050550] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 10/09/2016] [Indexed: 01/17/2023] Open
Abstract
People of African ancestry carrying certain APOL1 mutant alleles are at elevated risk of developing renal diseases. However, the mechanisms underlying APOL1-associated renal diseases are unknown. Because the APOL1 gene is unique to humans and some primates, new animal models are needed to understand the function of APOL1 in vivo We generated transgenic Drosophila fly lines expressing the human APOL1 wild type allele (G0) or the predominant APOL1 risk allele (G1) in different tissues. Ubiquitous expression of APOL1 G0 or G1 in Drosophila induced lethal phenotypes, and G1 was more toxic than was G0. Selective expression of the APOL1 G0 or G1 transgene in nephrocytes, fly cells homologous to mammalian podocytes, induced increased endocytic activity and accumulation of hemolymph proteins, dextran particles, and silver nitrate. As transgenic flies with either allele aged, nephrocyte function declined, cell size increased, and nephrocytes died prematurely. Compared with G0-expressing cells, however, G1-expressing cells showed more dramatic phenotypes, resembling those observed in cultured mammalian podocytes overexpressing APOL1-G1. Expressing the G0 or G1 APOL1 transgene in nephrocytes also impaired the acidification of organelles. We conclude that expression of an APOL1 transgene initially enhances nephrocyte function, causing hypertrophy and subsequent cell death. This new Drosophila model uncovers a novel mechanism by which upregulated expression of APOL1-G1 could precipitate renal disease in humans. Furthermore, this model may facilitate the identification of APOL1-interacting molecules that could serve as new drug targets to treat APOL1-associated renal diseases.
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Affiliation(s)
- Yulong Fu
- Center for Cancer and Immunology Research, Washington, DC
| | - Jun-Yi Zhu
- Center for Cancer and Immunology Research, Washington, DC
| | - Adam Richman
- Center for Cancer and Immunology Research, Washington, DC
| | - Yi Zhang
- Center for Cancer and Immunology Research, Washington, DC.,Center for Genetic Medicine Research, Washington, DC
| | - Xuefang Xie
- Center for Genetic Medicine Research, Washington, DC
| | - Jharna R Das
- Center for Genetic Medicine Research, Washington, DC.,Division of Nephrology, Children's National Health Systems, Washington, DC; and.,Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC
| | - Jinliang Li
- Center for Genetic Medicine Research, Washington, DC.,Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC
| | - Patricio E Ray
- Center for Genetic Medicine Research, Washington, DC.,Division of Nephrology, Children's National Health Systems, Washington, DC; and.,Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC
| | - Zhe Han
- Center for Cancer and Immunology Research, Washington, DC; .,Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC
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107
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Ma L, Chou JW, Snipes JA, Bharadwaj MS, Craddock AL, Cheng D, Weckerle A, Petrovic S, Hicks PJ, Hemal AK, Hawkins GA, Miller LD, Molina AJA, Langefeld CD, Murea M, Parks JS, Freedman BI. APOL1 Renal-Risk Variants Induce Mitochondrial Dysfunction. J Am Soc Nephrol 2016; 28:1093-1105. [PMID: 27821631 DOI: 10.1681/asn.2016050567] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 08/12/2016] [Indexed: 11/03/2022] Open
Abstract
APOL1 G1 and G2 variants facilitate kidney disease in blacks. To elucidate the pathways whereby these variants contribute to disease pathogenesis, we established HEK293 cell lines stably expressing doxycycline-inducible (Tet-on) reference APOL1 G0 or the G1 and G2 renal-risk variants, and used Illumina human HT-12 v4 arrays and Affymetrix HTA 2.0 arrays to generate global gene expression data with doxycycline induction. Significantly altered pathways identified through bioinformatics analyses involved mitochondrial function; results from immunoblotting, immunofluorescence, and functional assays validated these findings. Overexpression of APOL1 by doxycycline induction in HEK293 Tet-on G1 and G2 cells led to impaired mitochondrial function, with markedly reduced maximum respiration rate, reserve respiration capacity, and mitochondrial membrane potential. Impaired mitochondrial function occurred before intracellular potassium depletion or reduced cell viability occurred. Analysis of global gene expression profiles in nondiseased primary proximal tubule cells from black patients revealed that the nicotinate phosphoribosyltransferase gene, responsible for NAD biosynthesis, was among the top downregulated transcripts in cells with two APOL1 renal-risk variants compared with those without renal-risk variants; nicotinate phosphoribosyltransferase also displayed gene expression patterns linked to mitochondrial dysfunction in HEK293 Tet-on APOL1 cell pathway analyses. These results suggest a pivotal role for mitochondrial dysfunction in APOL1-associated kidney disease.
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Affiliation(s)
- Lijun Ma
- Department of Internal Medicine, Section on Nephrology, .,Center for Public Health Genomics
| | - Jeff W Chou
- Center for Public Health Genomics.,Division of Public Health Sciences, Department of Biostatistical Sciences
| | | | - Manish S Bharadwaj
- Department of Internal Medicine, Section on Gerontology and Geriatric Medicine
| | | | - Dongmei Cheng
- Department of Internal Medicine, Section on Molecular Medicine
| | | | | | | | | | | | | | - Anthony J A Molina
- Department of Internal Medicine, Section on Gerontology and Geriatric Medicine
| | - Carl D Langefeld
- Center for Public Health Genomics.,Division of Public Health Sciences, Department of Biostatistical Sciences
| | - Mariana Murea
- Department of Internal Medicine, Section on Nephrology
| | - John S Parks
- Department of Internal Medicine, Section on Molecular Medicine
| | - Barry I Freedman
- Department of Internal Medicine, Section on Nephrology, .,Center for Public Health Genomics.,Center for Diabetes Research, Wake Forest School of Medicine, Winston-Salem, North Carolina
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108
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Mikulak J, Oriolo F, Portale F, Tentorio P, Lan X, Saleem MA, Skorecki K, Singhal PC, Mavilio D. Impact of APOL1 polymorphism and IL-1β priming in the entry and persistence of HIV-1 in human podocytes. Retrovirology 2016; 13:63. [PMID: 27599995 PMCID: PMC5011791 DOI: 10.1186/s12977-016-0296-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 08/16/2016] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Patients of African ancestry with untreated HIV-1 infection and carrying the G1 or G2 kidney disease risk variants (Vs) at the APOL1 gene have a tenfold higher risk of developing HIV-associated nephropathy (HIVAN) compared to those with the non-risk wild type (WT) G0 variant. However, the mechanistic contribution of the APOL1 allelic state to kidney injury in HIV-1 infection remains to be elucidated. RESULTS Non-risk WT APOL1 is associated with lower intracellular levels of HIV-1 in conditionally immortalized human podocytes, while the over expression of G1 or G2 risk Vs significantly increases viral accumulation. The priming of podocytes with exogenous IL-1β facilitates HIV-1 entry, via the up-regulation of DC-SIGN. The over expression of APOL1 G1 and G2 risk Vs in combination with an increase in IL-1β levels causes a greater increase in viral concentration than either condition alone. In turn, HIV-1 and exogenous IL-1β together induce a de novo secretion of endogenous IL-1β and an increase of APOL1 gene expression. CONCLUSIONS Our findings indicate that the presence of risk Vs of APOL1 is permissive of HIV-1 persistence in human podocytes in synergy with IL-1β, a cytokine that characterizes the inflammatory milieu of acute and chronic phases of HIV-1 infection. The elucidation of these molecular mechanisms explains, at least in part, the higher frequency of HIVAN in populations carrying the risk polymorphic genetic variant of APOL1 gene.
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Affiliation(s)
- Joanna Mikulak
- Unit of Clinical and Experimental Immunology, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. .,Istituto di Ricerca Genetica e Biomedica, UOS di Milano, Consiglio Nazionale delle Ricerche (UOS/IRGB/CNR), Rozzano, Milan, Italy.
| | - Ferdinando Oriolo
- Unit of Clinical and Experimental Immunology, Humanitas Clinical and Research Center, Rozzano, Milan, Italy
| | - Federica Portale
- Unit of Clinical and Experimental Immunology, Humanitas Clinical and Research Center, Rozzano, Milan, Italy
| | - Paolo Tentorio
- Unit of Clinical and Experimental Immunology, Humanitas Clinical and Research Center, Rozzano, Milan, Italy
| | - Xiqian Lan
- Center for Excellence for Immunology and Inflammation, Feinstein Institute for Medical Research, Hofstra North Shore Long Island Jewish Medical School, New Hyde Park, NY, USA
| | - Moin A Saleem
- Children's Renal Unit and Academic Renal Unit, University of Bristol, Bristol, UK
| | - Karl Skorecki
- Nephrology and Molecular Medicine, Technion Institute of Technology and Rambam Medical Center, Haifa, Israel
| | - Pravin C Singhal
- Center for Excellence for Immunology and Inflammation, Feinstein Institute for Medical Research, Hofstra North Shore Long Island Jewish Medical School, New Hyde Park, NY, USA
| | - Domenico Mavilio
- Unit of Clinical and Experimental Immunology, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. .,Department of Medical Biotechnologies and Translational Medicine (BioMeTra), University of Milan, Milan, Italy.
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109
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Besse W, Mansour S, Jatwani K, Nast CC, Brewster UC. Collapsing glomerulopathy in a young woman with APOL1 risk alleles following acute parvovirus B19 infection: a case report investigation. BMC Nephrol 2016; 17:125. [PMID: 27600725 PMCID: PMC5013576 DOI: 10.1186/s12882-016-0330-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 08/02/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Collapsing Glomerulopathy (CG), also known as the collapsing variant of Focal Segmental Glomerulosclerosis (FSGS), is distinct in both its clinical severity and its pathophysiologic characteristics from other forms of FSGS. This lesion occurs disproportionally in patients carrying two APOL1 risk alleles, and is the classic histologic lesion resulting from Human Immunodeficiency Virus (HIV) infection of podocytes. Other viral infections, including parvovirus B19, and drugs such as interferon that perturb the immune system, have also been associated with CG. Despite significant advances, explaining such genetic and immune/infectious associations with causative mechanisms and supporting evidence has proven challenging. CASE PRESENTATION We report the case of a healthy (HIV-negative) pregnant 36 year-old Caribbean-American woman who presented with nephrotic syndrome and fetal demise in the setting of acute parvovirus B19 infection. A series of three renal biopsies and rapid clinical course showed progression from significant podocyte injury with mild light microscopy findings to classic viral-associated CG to ESRD in less than 3 months. Genetic analysis revealed two APOL1 G1 risk alleles. CONCLUSIONS This is the first published case report of CG in the setting of acute parvovirus infection in a patient with two APOL1 risk allelles, and parvoviral proteins identified in renal epithelium on kidney biopsy. These findings support the causative role of parvovirus B19 infection in the development of CG on the background of APOL1 genetic risk.
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Affiliation(s)
- Whitney Besse
- Section of Nephrology, Yale University, 330 Cedar Street, BB 121, New Haven, CT 06520-8029, USA
| | - Sherry Mansour
- Section of Nephrology, Yale University, 330 Cedar Street, BB 121, New Haven, CT 06520-8029, USA
| | - Karan Jatwani
- Government Medical College & Hospital Chandigarh Sector, Chandigarh, India
| | - Cynthia C Nast
- Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Ursula C Brewster
- Section of Nephrology, Yale University, 330 Cedar Street, BB 121, New Haven, CT 06520-8029, USA.
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110
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Kotb AM, Simon O, Blumenthal A, Vogelgesang S, Dombrowski F, Amann K, Zimmermann U, Endlich K, Endlich N. Knockdown of ApoL1 in Zebrafish Larvae Affects the Glomerular Filtration Barrier and the Expression of Nephrin. PLoS One 2016; 11:e0153768. [PMID: 27138898 PMCID: PMC4854397 DOI: 10.1371/journal.pone.0153768] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 04/04/2016] [Indexed: 12/28/2022] Open
Abstract
APOL1, a secreted high-density lipoprotein, is expressed in different human tissues. Genetic variants of APOL1 are described to be associated with the development of end stage renal diseases in African Americans. In human kidney, APOL1 is mainly expressed in podocytes that are responsible for proper blood filtration. Since mice do not express ApoL1, the zebrafish is an ideal model to study the role of ApoL1. Injection of morpholinos against zApoL1 into zebrafish eggs and larvae, respectively, induces severe edema indicating a leakage of the filtration barrier. This was demonstrated in zApoL1 knockdown larvae by intravascular injection of fluorescently-labeled 10- and 500-kDa dextrans and by clearance of the vitamin D-binding protein from the circulation. Immunohistochemistry and RT-PCR revealed the reduction of nephrin, a podocyte-specific protein essential for blood filtration. Coinjection of human nephrin mRNA rescued the zApoL1 knockdown induced phenotype. Reduced APOL1 and nephrin levels were also found in biopsies of patients suffering from end stage renal diseases. Our results demonstrate that zApoL1 is essential for proper blood filtration in the zebrafish glomerulus and that zApoL1 affects the expression of nephrin.
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Affiliation(s)
- Ahmed M Kotb
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany.,Department of Anatomy and Histology, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt
| | - Ole Simon
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Antje Blumenthal
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Silke Vogelgesang
- Institute of Pathology, University Medicine Greifswald, Greifswald, Germany
| | - Frank Dombrowski
- Institute of Pathology, University Medicine Greifswald, Greifswald, Germany
| | - Kerstin Amann
- Department of Nephropathology, Institute of Pathology, University Hospital Erlangen, Erlangen, Germany
| | - Uwe Zimmermann
- Department of Urology, University Medicine Greifswald, Greifswald, Germany
| | - Karlhans Endlich
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Nicole Endlich
- Institute of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
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111
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Abstract
Collapsing glomerulopathy predominantly afflicts patients of African ancestry, often first presenting after the immune system is engaged by another disorder. Nichols et al. now show that collateral induction of pathogenic APOL1 allelic variants in podocytes by the ongoing immune response may be the long-sought-after explanation for the development of collapsing glomerulopathy in these patients.
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Affiliation(s)
- Bairbre A McNicholas
- Division of Nephrology and Kidney Research Institute, University of Washington, Seattle, Washington, USA
| | - Peter J Nelson
- Division of Nephrology and Kidney Research Institute, University of Washington, Seattle, Washington, USA
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112
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Friedman DJ, Pollak MR. Apolipoprotein L1 and Kidney Disease in African Americans. Trends Endocrinol Metab 2016; 27:204-215. [PMID: 26947522 PMCID: PMC4811340 DOI: 10.1016/j.tem.2016.02.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/05/2016] [Accepted: 02/08/2016] [Indexed: 02/06/2023]
Abstract
Genetic variants in the Apolipoprotein L1 (APOL1) gene cause high rates of kidney disease in African Americans. These variants, found only in individuals with recent African ancestry, confer enhanced innate immunity against African trypanosomes. Although they are among the most powerful disease-causing common variants discovered to date, we are just beginning to understand how they promote kidney injury. Since APOL1 is present in only a few primate species, much of our current knowledge has come from natural experiments in humans and in vitro studies while awaiting the development of transgenic animal models. Understanding more about the function of ApoL1 and how the high-risk variants behave differently from other ApoL1 molecules is a high priority in kidney disease research.
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Affiliation(s)
- David J. Friedman
- Beth Israel Deaconess Medical Center, Harvard Medical School, 99 Brookline Avenue, RN301, Boston, MA. 02215, 617 667 0253
| | - Martin R. Pollak
- Beth Israel Deaconess Medical Center, Harvard Medical School, 99 Brookline Avenue, RN325E, Boston, MA. 02215, 617 667 0461
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113
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Hu CAA, Ray PE. How complicated can it be? The link between APOL1 risk variants and lipoprotein heterogeneity in kidney and cardiovascular diseases. Nephrol Dial Transplant 2016; 31:509-11. [PMID: 26433015 PMCID: PMC4902870 DOI: 10.1093/ndt/gfv357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Accepted: 09/14/2015] [Indexed: 08/30/2023] Open
Abstract
….the findings of Gutierrez et al. (22) add more fuel to the ongoing controversy regarding the association of APOL1 G1/G2 risk status with cardiovascular outcome among African Americans. However, if we acknowledge that the APOL1 risk alleles may directly modify the circulating levels of small HDL and/or other factors and induce a proatherogenic state that precipitates CKD and cardiovascular complications, then we should begin to answer several questions ….
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Affiliation(s)
- Chien-An A. Hu
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, USA
| | - Patricio E. Ray
- Children's National Medical Center, Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, DC, USA
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114
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Bruggeman LA, Wu Z, Luo L, Madhavan SM, Konieczkowski M, Drawz PE, Thomas DB, Barisoni L, Sedor JR, O'Toole JF. APOL1-G0 or APOL1-G2 Transgenic Models Develop Preeclampsia but Not Kidney Disease. J Am Soc Nephrol 2016; 27:3600-3610. [PMID: 27026370 DOI: 10.1681/asn.2015111220] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/15/2016] [Indexed: 11/03/2022] Open
Abstract
APOL1 risk variants are associated with kidney disease in blacks, but the mechanisms of renal injury associated with APOL1 risk variants are unknown. Because APOL1 is unique to humans and some primates, we created transgenic (Tg) mice using the promoter of nephrin-encoding Nphs1 to express the APOL1 reference sequence (G0) or the G2 risk variant in podocytes, establishing Tg lines with a spectrum of APOL1 expression levels. Podocytes from Tg-G0 and Tg-G2 mice did not undergo necrosis, apoptosis, or autophagic cell death in vivo, even in lines with highly expressed transgenes. Further, Tg-G0 and Tg-G2 mice did not develop kidney pathology, proteinuria, or azotemia as of 300 days of age. However, by 200 days of age, Tg-G2 mice had significantly lower podocyte density than age-matched WT and Tg-G0 mice had, a difference that was not evident at weaning. Notably, a pregnancy-associated phenotype that encompassed eclampsia, preeclampsia, fetal/neonatal deaths, and small litter sizes occurred in some Tg-G0 mice and more severely in Tg-G2 mice. Similar to human placenta, placentas of Tg mice expressed APOL1. Overall, these results suggest podocyte depletion could predispose individuals with APOL1 risk genotypes to kidney disease in response to a second stressor, and add to other published evidence associating APOL1 expression with preeclampsia.
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Affiliation(s)
- Leslie A Bruggeman
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
| | - Zhenzhen Wu
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
| | - Liping Luo
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
| | - Sethu M Madhavan
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
| | | | - Paul E Drawz
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota; and
| | - David B Thomas
- Department of Pathology, University of Miami, Miami, Florida
| | - Laura Barisoni
- Department of Pathology, University of Miami, Miami, Florida
| | - John R Sedor
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and.,Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - John F O'Toole
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
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Kozlitina J, Zhou H, Brown PN, Rohm RJ, Pan Y, Ayanoglu G, Du X, Rimmer E, Reilly DF, Roddy TP, Cully DF, Vogt TF, Blom D, Hoek M. Plasma Levels of Risk-Variant APOL1 Do Not Associate with Renal Disease in a Population-Based Cohort. J Am Soc Nephrol 2016; 27:3204-3219. [PMID: 27005919 DOI: 10.1681/asn.2015101121] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 02/10/2016] [Indexed: 12/12/2022] Open
Abstract
Two common missense variants in APOL1 (G1 and G2) have been definitively linked to CKD in black Americans. However, not all individuals with the renal-risk genotype develop CKD, and little is known about how APOL1 variants drive disease. Given the association of APOL1 with HDL particles, which are cleared by the kidney, differences in the level or quality of mutant APOL1‑HDL particles could be causal for disease and might serve as a useful risk stratification marker. We measured plasma levels of G0 (low risk), G1, and G2 APOL1 in 3450 individuals in the Dallas Heart Study using a liquid chromatography-MS method that enabled quantitation of the different variants. Additionally, we characterized native APOL1‑HDL from donors with no or two APOL1 risk alleles by size-exclusion chromatography and analysis of immunopurified APOL1‑HDL particles. Finally, we identified genetic loci associated with plasma APOL1 levels and tested for APOL1-dependent association with renal function. Although we replicated the previous association between APOL1 variant status and renal function in nondiabetic individuals, levels of circulating APOL1 did not associate with microalbuminuria or GFR. Furthermore, the size or known components of APOL1‑HDL did not consistently differ in subjects with the renal-risk genotype. Genetic association studies implicated variants in loci harboring haptoglobin-related protein (HPR), APOL1, and ubiquitin D (UBD) in the regulation of plasma APOL1 levels, but these variants did not associate with renal function. Collectively, these data demonstrate that the risk of renal disease associated with APOL1 is probably not related to circulating levels of the mutant protein.
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Affiliation(s)
- Julia Kozlitina
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas; and
| | - Haihong Zhou
- Merck Research Laboratories, Kenilworth, New Jersey
| | | | - Rory J Rohm
- Merck Research Laboratories, Kenilworth, New Jersey
| | - Yi Pan
- Merck Research Laboratories, Kenilworth, New Jersey
| | | | - Xiaoyan Du
- Merck Research Laboratories, Kenilworth, New Jersey
| | - Eric Rimmer
- Merck Research Laboratories, Kenilworth, New Jersey
| | | | | | | | | | - Daniel Blom
- Merck Research Laboratories, Kenilworth, New Jersey
| | - Maarten Hoek
- Merck Research Laboratories, Kenilworth, New Jersey
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116
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Wahl P, Ducasa GM, Fornoni A. Systemic and renal lipids in kidney disease development and progression. Am J Physiol Renal Physiol 2016; 310:F433-45. [PMID: 26697982 PMCID: PMC4971889 DOI: 10.1152/ajprenal.00375.2015] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 12/22/2015] [Indexed: 12/14/2022] Open
Abstract
Altered lipid metabolism characterizes proteinuria and chronic kidney diseases. While it is thought that dyslipidemia is a consequence of kidney disease, a large body of clinical and experimental studies support that altered lipid metabolism may contribute to the pathogenesis and progression of kidney disease. In fact, accumulation of renal lipids has been observed in several conditions of genetic and nongenetic origins, linking local fat to the pathogenesis of kidney disease. Statins, which target cholesterol synthesis, have not been proven beneficial to slow the progression of chronic kidney disease. Therefore, other therapeutic strategies to reduce cholesterol accumulation in peripheral organs, such as the kidney, warrant further investigation. Recent advances in the understanding of the biology of high-density lipoprotein (HDL) have revealed that functional HDL, rather than total HDL per se, may protect from both cardiovascular and kidney diseases, strongly supporting a role for altered cholesterol efflux in the pathogenesis of kidney disease. Although the underlying pathophysiological mechanisms responsible for lipid-induced renal damage have yet to be uncovered, several studies suggest novel mechanisms by which cholesterol, free fatty acids, and sphingolipids may affect glomerular and tubular cell function. This review will focus on the clinical and experimental evidence supporting a causative role of lipids in the pathogenesis of proteinuria and kidney disease, with a primary focus on podocytes.
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Affiliation(s)
- Patricia Wahl
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida
| | - Gloria Michelle Ducasa
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida
| | - Alessia Fornoni
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida
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117
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Abstract
Apolipoprotein L1 (APOL1) is associated with increased incidence of chronic kidney disease (CKD) and end-stage renal disease, and with faster progression of CKD, in African Americans. APOL1 is expressed in intra- and extrarenal vascular tissue, making it a candidate to explain the increased incidence of cardiovascular disease in CKD. This Commentary discusses the disparate results from three studies showing that APOL1 renal risk genotypes are either harmful, neutral, or protective in the context of cardiovascular disease.
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118
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Peralta CA, Bibbins-Domingo K, Vittinghoff E, Lin F, Fornage M, Kopp JB, Winkler CA. APOL1 Genotype and Race Differences in Incident Albuminuria and Renal Function Decline. J Am Soc Nephrol 2016; 27:887-93. [PMID: 26180129 PMCID: PMC4769203 DOI: 10.1681/asn.2015020124] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 06/02/2015] [Indexed: 01/13/2023] Open
Abstract
Variants in the APOL1 gene are associated with kidney disease in blacks. We examined associations of APOL1 with incident albuminuria and kidney function decline among 3030 young adults with preserved GFR in the Coronary Artery Risk Development in Young Adults (CARDIA) study. eGFR by cystatin C (eGFRcys) and albumin-to-creatinine ratio were measured at scheduled examinations. Participants were white (n=1700), high-risk black (two APOL1 risk alleles, n=176), and low-risk black (zero/one risk allele, n=1154). Mean age was 35 years, mean eGFRcys was 107 ml/min per 1.73 m(2), and 13.2% of blacks had two APOL1 alleles. The incidence rate per 1000 person-years (95% confidence interval) for albuminuria over 15 years was 15.6 (10.6-22.1) for high-risk blacks, 7.8 (6.4-9.4) for low-risk blacks, and 3.9 (3.1-4.8) for whites. Compared with whites, the odds ratio (95% confidence interval) for incident albuminuria was 5.71 (3.64-8.94) for high-risk blacks and 2.32 (1.73-3.13) for low-risk blacks. Adjustment for risk factors attenuated the difference between low-risk blacks and whites (odds ratio 1.21, 95% confidence interval 0.86-1.71). After adjustment, high-risk blacks had a 0.45% faster yearly eGFRcys decline over 9.3 years compared with whites. Low-risk blacks also had a faster yearly eGFRcys decline compared with whites, but this difference was attenuated after adjustment for risk factors and socioeconomic position. In conclusion, blacks with two APOL1 risk alleles had the highest risk for albuminuria and eGFRcys decline in young adulthood, whereas disparities between low-risk blacks and whites were related to differences in traditional risk factors.
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Affiliation(s)
- Carmen A Peralta
- Department of Medicine, University of California, San Francisco, California; San Francisco VA Medical Center, San Francisco, California;
| | | | - Eric Vittinghoff
- Department of Biostatistics, University of California, San Francisco, California
| | - Feng Lin
- Department of Biostatistics, University of California, San Francisco, California
| | - Myriam Fornage
- The University of Texas Health Science Center at Houston, Houston, Texas
| | - Jeffrey B Kopp
- Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland; and
| | - Cheryl A Winkler
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Leidos Biomedical Inc., Frederick National Laboratory, Frederick, Maryland
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Olabisi OA, Zhang JY, VerPlank L, Zahler N, DiBartolo S, Heneghan JF, Schlöndorff JS, Suh JH, Yan P, Alper SL, Friedman DJ, Pollak MR. APOL1 kidney disease risk variants cause cytotoxicity by depleting cellular potassium and inducing stress-activated protein kinases. Proc Natl Acad Sci U S A 2016; 113:830-7. [PMID: 26699492 PMCID: PMC4743809 DOI: 10.1073/pnas.1522913113] [Citation(s) in RCA: 150] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Two specific genetic variants of the apolipoprotein L1 (APOL1) gene are responsible for the high rate of kidney disease in people of recent African ancestry. Expression in cultured cells of these APOL1 risk variants, commonly referred to as G1 and G2, results in significant cytotoxicity. The underlying mechanism of this cytotoxicity is poorly understood. We hypothesized that this cytotoxicity is mediated by APOL1 risk variant-induced dysregulation of intracellular signaling relevant for cell survival. To test this hypothesis, we conditionally expressed WT human APOL1 (G0), the APOL1 G1 variant, or the APOL1 G2 variant in human embryonic kidney cells (T-REx-293) using a tetracycline-mediated (Tet-On) system. We found that expression of either G1 or G2 APOL1 variants increased apparent cell swelling and cell death compared with G0-expressing cells. These manifestations of cytotoxicity were preceded by G1 or G2 APOL1-induced net efflux of intracellular potassium as measured by X-ray fluorescence, resulting in the activation of stress-activated protein kinases (SAPKs), p38 MAPK, and JNK. Prevention of net K(+) efflux inhibited activation of these SAPKs by APOL1 G1 or G2. Furthermore, inhibition of SAPK signaling and inhibition of net K(+) efflux abrogated cytotoxicity associated with expression of APOL1 risk variants. These findings in cell culture raise the possibility that nephrotoxicity of APOL1 risk variants may be mediated by APOL1 risk variant-induced net loss of intracellular K(+) and subsequent induction of stress-activated protein kinase pathways.
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Affiliation(s)
- Opeyemi A Olabisi
- Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114; Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | - Jia-Yue Zhang
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | | | | | - Salvatore DiBartolo
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - John F Heneghan
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - Johannes S Schlöndorff
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | - Jung Hee Suh
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | - Paul Yan
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | - Seth L Alper
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - David J Friedman
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - Martin R Pollak
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215;
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120
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Simmonds MJ. Using Genetic Variation to Predict and Extend Long-term Kidney Transplant Function. Transplantation 2016; 99:2038-48. [PMID: 26262502 DOI: 10.1097/tp.0000000000000836] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Renal transplantation has transformed the life of patients with end-stage renal disease and other chronic kidney disorders by returning endogenous kidney function and enabling patients to cease dialysis. Several clinical indicators of graft outcome and long-term function have been established. Although rising creatinine levels and graft biopsy can be used to determine graft loss, identifying early predictors of graft function will not only improve our ability to predict long-term graft outcome but importantly provide a window of opportunity to therapeutically intervene to preserve graft function before graft failure has occurred. Since understanding the importance of matching genetic variation at the HLA region between donors and recipients and translating this into clinical practise to improve transplant outcome, much focus has been placed on trying to identify additional genetic predictors of transplant outcome/function. This review will focus on how candidate gene studies have identified variants within immunosuppression, immune response, fibrotic pathways, and specific ethnic groups, which correlate with graft outcome. We will also discuss the challenges faced by candidate gene studies, such as differences in donor and recipient selection criteria and use of small data sets, which have led to many genes failing to be consistently associated with transplant outcome. This review will also look at how recent advances in our understanding of and ability to screen the genome are starting to provide new insights into the mechanisms behind long-term graft loss and with it the opportunity to target these pathways therapeutically to ultimately increase graft lifespan and the associated benefits to patients.
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Affiliation(s)
- Matthew J Simmonds
- 1 Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Churchill Hospital, Headington, Oxford, United Kingdom
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121
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Atta MG, Estrella MM, Skorecki KL, Kopp JB, Winkler CA, Wasser WG, Shemer R, Racusen LC, Kuperman M, Foy MC, Lucas GM, Fine DM. Association of APOL1 Genotype with Renal Histology among Black HIV-Positive Patients Undergoing Kidney Biopsy. Clin J Am Soc Nephrol 2015; 11:262-70. [PMID: 26668025 DOI: 10.2215/cjn.07490715] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 10/26/2015] [Indexed: 01/13/2023]
Abstract
BACKGROUND AND OBJECTIVES Prior studies have shown that the APOL1 risk alleles are associated with a greater risk of HIV-associated nephropathy and FSGS among blacks who are HIV positive. We sought to determine whether the APOL1 high-risk genotype incrementally improved the prediction of these underlying lesions beyond conventional clinical factors. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS In a cross-sectional study, we analyzed data from 203 blacks who are HIV positive, underwent kidney biopsies between 1996 and 2011, and were genotyped for the APOL1 G1 and G2 alleles. Predictive logistic regression models with conventional clinical factors were compared with those that also included APOL1 genotype using receiver-operating curves and bootstrapping analyses with crossvalidation. RESULTS The addition of APOL1 genotype to HIV-related risk factors for kidney disease in a predictive model improved the prediction of non-HIV-associated nephropathy FSGS, specifically, increasing the c statistic from 0.65 to 0.74 (P=0.04). Although two risk alleles were significantly associated with higher odds of HIV-associated nephropathy, APOL1 genotype did not add incrementally to the prediction of this specific histopathology. CONCLUSIONS APOL1 genotype may provide additional diagnostic information to traditional clinical variables in predicting underlying FSGS spectrum lesions in blacks who are HIV positive. In contrast, although APOL1 risk genotype predicts HIV-associated nephropathy, it lacked a high c statistic sufficient for discrimination to eliminate the role of kidney biopsy in the clinical care of blacks who are HIV positive with nephrotic proteinuria or unexplained kidney disease.
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Affiliation(s)
| | | | - Karl L Skorecki
- Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel; Department of Medicine, Rambam Health Care Campus, Haifa, Israel
| | - Jeffrey B Kopp
- Kidney Disease Section, Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Cheryl A Winkler
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute Frederick, Leidos Biomedical Research, Inc., Frederick National Laboratory, Frederick, Maryland
| | - Walter G Wasser
- Department of Medicine, Rambam Health Care Campus, Haifa, Israel
| | - Revital Shemer
- Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel; Department of Medicine, Rambam Health Care Campus, Haifa, Israel
| | - Lorraine C Racusen
- Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Michael Kuperman
- Department of Pathology, Baylor University Medical Center, Dallas, Texas; and
| | - Matthew C Foy
- Division of Internal Medicine, Louisiana State University Health Science Center, Baton Rouge, Louisiana
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122
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Weckerle A, Snipes JA, Cheng D, Gebre AK, Reisz JA, Murea M, Shelness GS, Hawkins GA, Furdui CM, Freedman BI, Parks JS, Ma L. Characterization of circulating APOL1 protein complexes in African Americans. J Lipid Res 2015; 57:120-30. [PMID: 26586272 DOI: 10.1194/jlr.m063453] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Indexed: 11/20/2022] Open
Abstract
APOL1 gene renal-risk variants are associated with nephropathy and CVD in African Americans; however, little is known about the circulating APOL1 variant proteins which reportedly bind to HDL. We examined whether APOL1 G1 and G2 renal-risk variant serum concentrations or lipoprotein distributions differed from nonrisk G0 APOL1 in African Americans without nephropathy. Serum APOL1 protein concentrations were similar regardless of APOL1 genotype. In addition, serum APOL1 protein was bound to protein complexes in two nonoverlapping peaks, herein referred to as APOL1 complex A (12.2 nm diameter) and complex B (20.0 nm diameter). Neither of these protein complexes associated with HDL or LDL. Proteomic analysis revealed that complex A was composed of APOA1, haptoglobin-related protein (HPR), and complement C3, whereas complex B contained APOA1, HPR, IgM, and fibronectin. Serum HPR was less abundant on complex B in individuals with G1 and G2 renal-risk variant genotypes, relative to G0 (P = 0.0002-0.037). These circulating complexes may play roles in HDL metabolism and susceptibility to CVD.
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Affiliation(s)
- Allison Weckerle
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - James A Snipes
- Nephrology, Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Dongmei Cheng
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Abraham K Gebre
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Julie A Reisz
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Mariana Murea
- Nephrology, Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Gregory S Shelness
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Gregory A Hawkins
- Center for Genomics and Personalized Medicine Research, Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Cristina M Furdui
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Barry I Freedman
- Nephrology, Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - John S Parks
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC 27157
| | - Lijun Ma
- Nephrology, Wake Forest School of Medicine, Winston-Salem, NC 27157
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Kasembeli AN, Duarte R, Ramsay M, Mosiane P, Dickens C, Dix-Peek T, Limou S, Sezgin E, Nelson GW, Fogo AB, Goetsch S, Kopp JB, Winkler CA, Naicker S. APOL1 Risk Variants Are Strongly Associated with HIV-Associated Nephropathy in Black South Africans. J Am Soc Nephrol 2015; 26:2882-90. [PMID: 25788523 PMCID: PMC4625661 DOI: 10.1681/asn.2014050469] [Citation(s) in RCA: 230] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 01/15/2015] [Indexed: 02/06/2023] Open
Abstract
APOL1 variants are associated with HIV-associated nephropathy and FSGS in African Americans. The prevalence of these variants in African populations with CKD in HIV-1 infection has not been investigated. We determined the role of APOL1 variants in 120 patients with HIV-associated nephropathy and CKD and 108 controls from a South-African black population. Patients with CKD were selected on the basis of histology. Genotypes were successfully determined for APOL1 G1 and G2 variants and 42 single nucleotide polymorphisms, including 18 ancestry informative markers, for 116 patients with CKD (96.7%; 38 patients with HIV-associated nephropathy, 39 patients with HIV-positive CKD, and 39 patients with HIV-negative CKD), and 108 controls (100%). Overall, 79% of patients with HIV-associated nephropathy and 2% of population controls carried two risk alleles. In a recessive model, individuals carrying any combination of two APOL1 risk alleles had 89-fold higher odds (95% confidence interval, 18 to 912; P<0.001) of developing HIV-associated nephropathy compared with HIV-positive controls. Population allele frequencies were 7.3% for G1 and 11.1% for G2. APOL1 risk alleles were not significantly associated with other forms of CKD. These results indicate HIV-positive, antiretroviral therapy-naïve South-African blacks with two APOL1 risk alleles are at very high risk for developing HIV-associated nephropathy. Further studies are required to determine the effect of APOL1 risk variants on kidney diseases in other regions of sub-Saharan Africa.
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Affiliation(s)
- Alex N Kasembeli
- Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Raquel Duarte
- Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Michèle Ramsay
- Division of Human Genetics, National Health Laboratory Service, School of Pathology, Faculty of Health Sciences, Sydney Brenner Institute for Molecular Bioscience, University of the Witwatersrand, Johannesburg, South Africa
| | - Pulane Mosiane
- Department of Anatomical Pathology, National Health Laboratory Service, University of the Witwatersrand, Johannesburg, South Africa
| | - Caroline Dickens
- Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Thérèse Dix-Peek
- Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Sophie Limou
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick National Laboratory, Leidos Biomedical Inc., Frederick, Maryland
| | - Efe Sezgin
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick National Laboratory, Leidos Biomedical Inc., Frederick, Maryland; Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - George W Nelson
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick National Laboratory, Leidos Biomedical Inc., Frederick, Maryland
| | - Agnes B Fogo
- Division of Renal Pathology/Electron Microscopy, Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee
| | | | - Jeffrey B Kopp
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Bethesda, Maryland; and
| | - Cheryl A Winkler
- Basic Research Laboratory, Center for Cancer Research, National Cancer Institute, Frederick National Laboratory, Leidos Biomedical Inc., Frederick, Maryland;
| | - Saraladevi Naicker
- Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; Division of Nephrology, University of the Witwatersrand, Johannesburg, South Africa
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125
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Freedman BI. APOL1 and kidney disease: new insights leading to novel therapies. Am J Kidney Dis 2015; 66:9-11. [PMID: 26111904 DOI: 10.1053/j.ajkd.2015.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 05/12/2015] [Indexed: 11/11/2022]
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Riella LV, Sheridan AM. Testing for High-Risk APOL1 Alleles in Potential Living Kidney Donors. Am J Kidney Dis 2015; 66:396-401. [DOI: 10.1053/j.ajkd.2015.04.046] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 04/21/2015] [Indexed: 11/11/2022]
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Lan X, Wen H, Lederman R, Malhotra A, Mikulak J, Popik W, Skorecki K, Singhal PC. Protein domains of APOL1 and its risk variants. Exp Mol Pathol 2015; 99:139-44. [PMID: 26091559 PMCID: PMC4509982 DOI: 10.1016/j.yexmp.2015.06.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 06/09/2015] [Indexed: 11/24/2022]
Abstract
Increasing lines of evidence have demonstrated that the development of higher rates of non-diabetic glomerulosclerosis (GS) in African Americans can be attributed to two coding sequence variants (G1 and G2) in the Apolipoprotein L1 (APOL) gene. Recent studies indicate that the gene products of these APOL1 risk variants have augmented toxicity to kidney cells. However, the biological characteristics of APOL1 and its risk variants are not well elucidated. The APOL1 protein can be divided into several functional domains, including signal peptide (SP), pore forming domain (PFD), membrane address domain (MAD), and SRA-interacting domain. To investigate the relative contribution of each domain to cell injury, we constructed a serial expression vectors to delete or express each domain. These vectors were transfected into the human embryonic kidney cell line 293T, and then compared the cytotoxicity. In addition, we conducted studies in which APOL1 wild type (G0) was co-transfected in combination with G1 or G2 to see whether G0 could counteract the toxicity of the risk variants. The results showed that deleting the SP did not abolish the toxicity of APOL1, though deletion of 26 amino acid residues of the mature peptide at the N-terminal partially decreased the toxicity. Deleting PFD or MAD or SRA-interacting domain abolished toxicity, while, overexpressing each domain alone could not cause toxicity to the host cells. Deletion of the G2 sites while retaining G1 sites in the risk state resulted in persistent toxicity. Either deletion or exchanging the BH3 domain in the PFD led to complete loss of the toxicity in this experimental platform. Adding G0 to either G1 or G2 did not attenuate the toxicity of the either moiety. These results indicate that the integrity of the mature APOL1 protein is indispensable for its toxicity. Our study not only reveals the contribution of each domain of the APOL1 protein to cell injury, but also highlights some potential suggested targets for drug design to prevent or treat APOL1-associated nephropathy.
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Affiliation(s)
- Xiqian Lan
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States.
| | - Hongxiu Wen
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States
| | - Rivka Lederman
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States
| | - Ashwani Malhotra
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States
| | | | | | - Karl Skorecki
- Nephrology and Molecular Medicine, Technion Institute of Technology and Rambam Medical Center, Haifa, Israel
| | - Pravin C Singhal
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States.
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Sampson MG, Robertson CC, Martini S, Mariani LH, Lemley KV, Gillies CE, Otto EA, Kopp JB, Randolph A, Vega-Warner V, Eichinger F, Nair V, Gipson DS, Cattran DC, Johnstone DB, O'Toole JF, Bagnasco SM, Song PX, Barisoni L, Troost JP, Kretzler M, Sedor JR. Integrative Genomics Identifies Novel Associations with APOL1 Risk Genotypes in Black NEPTUNE Subjects. J Am Soc Nephrol 2015; 27:814-23. [PMID: 26150607 DOI: 10.1681/asn.2014111131] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 05/31/2015] [Indexed: 01/13/2023] Open
Abstract
APOL1 variants have been associated with renal phenotypes in blacks. To refine clinical outcomes and discover mechanisms of APOL1-associated kidney injury, we analyzed clinical and genomic datasets derived from 90 black subjects in the Nephrotic Syndrome Study Network (NEPTUNE), stratified by APOL1 risk genotype. Ninety subjects with proteinuria ≥0.5 g/d were enrolled at first biopsy for primary nephrotic syndrome and followed. Clinical outcomes were determined, and renal histomorphometry and sequencing of Mendelian nephrotic syndrome genes were performed. APOL1 variants were genotyped, and glomerular and tubulointerstitial transcriptomes from protocol renal biopsy cores were analyzed for differential and correlative gene expression. Analyses were performed under the recessive model (high-risk genotype defined by two risk alleles). APOL1 high-risk genotype was significantly associated with a 17 ml/min per 1.73 m(2) lower eGFR and a 69% reduction in the probability of complete remission at any time, independent of histologic diagnosis. Neither APOL1 risk group was enriched for Mendelian mutations. On renal biopsy, high-risk genotype was associated with increased fractional interstitial area, interstitial fibrosis, and tubular atrophy. Risk genotype was not associated with intrarenal APOL1 mRNA expression levels. Differential expression analysis demonstrated an increased steady-state level of five genes associated with the high-risk genotype (CXCL9, CXCL11, and UBD in glomerulus; SNOR14B and MUC13 in tubulointerstitium). APOL1 tubulointerstitial coexpression analysis showed coexpression of APOL1 mRNA levels with a group of intrarenal transcripts that together were associated with increased interstitial fibrosis and tubular atrophy. These data indicate the high-risk APOL1 genotype confers renal risk across histopathologic diagnoses.
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Affiliation(s)
- Matthew G Sampson
- Division of Nephrology, Department of Pediatrics and Communicable Diseases,
| | | | - Sebastian Martini
- Division of Nephrology, Departments of Internal Medicine and Computational Medicine and Bioinformatics, and
| | - Laura H Mariani
- Division of Nephrology, Departments of Internal Medicine and Computational Medicine and Bioinformatics, and
| | - Kevin V Lemley
- Division of Nephrology, Department of Pediatrics, Children's Hospital of Los Angeles, University of Southern California School of Medicine, Los Angeles, California
| | | | - Edgar A Otto
- Division of Nephrology, Department of Pediatrics and Communicable Diseases
| | - Jeffrey B Kopp
- Kidney Diseases Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Anne Randolph
- Division of Nephrology, Departments of Internal Medicine and Computational Medicine and Bioinformatics, and
| | | | - Felix Eichinger
- Division of Nephrology, Departments of Internal Medicine and Computational Medicine and Bioinformatics, and
| | - Viji Nair
- Division of Nephrology, Departments of Internal Medicine and Computational Medicine and Bioinformatics, and
| | - Debbie S Gipson
- Division of Nephrology, Department of Pediatrics and Communicable Diseases
| | - Daniel C Cattran
- Department of Nephrology, University Health Network, University of Toronto, Toronto, Ontario, Canada
| | - Duncan B Johnstone
- Division of Nephrology, Department of Internal Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania
| | - John F O'Toole
- Division of Nephrology, Department of Internal Medicine and
| | - Serena M Bagnasco
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Peter X Song
- Department of Biostatistics, University of Michigan School of Public Health, Ann Arbor, Michigan; and
| | - Laura Barisoni
- Department of Pathology, University of Miami, Miller School of Medicine, Miami, Florida
| | - Jonathan P Troost
- Division of Nephrology, Department of Pediatrics and Communicable Diseases
| | - Matthias Kretzler
- Division of Nephrology, Departments of Internal Medicine and Computational Medicine and Bioinformatics, and Department of Computational Medicine and Bioinformatics, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - John R Sedor
- Division of Nephrology, Department of Internal Medicine and Department of Physiology and Biophysics, Case Western Reserve University and Rammelkamp Center for Education and Research, MetroHealth System, Cleveland, Ohio
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Anderson BR, Howell DN, Soldano K, Garrett ME, Katsanis N, Telen MJ, Davis EE, Ashley-Koch AE. In vivo Modeling Implicates APOL1 in Nephropathy: Evidence for Dominant Negative Effects and Epistasis under Anemic Stress. PLoS Genet 2015; 11:e1005349. [PMID: 26147622 PMCID: PMC4492502 DOI: 10.1371/journal.pgen.1005349] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 06/09/2015] [Indexed: 01/13/2023] Open
Abstract
African Americans have a disproportionate risk for developing nephropathy. This disparity has been attributed to coding variants (G1 and G2) in apolipoprotein L1 (APOL1); however, there is little functional evidence supporting the role of this protein in renal function. Here, we combined genetics and in vivo modeling to examine the role of apol1 in glomerular development and pronephric filtration and to test the pathogenic potential of APOL1 G1 and G2. Translational suppression or CRISPR/Cas9 genome editing of apol1 in zebrafish embryos results in podocyte loss and glomerular filtration defects. Complementation of apol1 morphants with wild-type human APOL1 mRNA rescues these defects. However, the APOL1 G1 risk allele does not ameliorate defects caused by apol1 suppression and the pathogenicity is conferred by the cis effect of both individual variants of the G1 risk haplotype (I384M/S342G). In vivo complementation studies of the G2 risk allele also indicate that the variant is deleterious to protein function. Moreover, APOL1 G2, but not G1, expression alone promotes developmental kidney defects, suggesting a possible dominant-negative effect of the altered protein. In sickle cell disease (SCD) patients, we reported previously a genetic interaction between APOL1 and MYH9. Testing this interaction in vivo by co-suppressing both transcripts yielded no additive effects. However, upon genetic or chemical induction of anemia, we observed a significantly exacerbated nephropathy phenotype. Furthermore, concordant with the genetic interaction observed in SCD patients, APOL1 G2 reduces myh9 expression in vivo, suggesting a possible interaction between the altered APOL1 and myh9. Our data indicate a critical role for APOL1 in renal function that is compromised by nephropathy-risk encoding variants. Moreover, our interaction studies indicate that the MYH9 locus is also relevant to the phenotype in a stressed microenvironment and suggest that consideration of the context-dependent functions of both proteins will be required to develop therapeutic paradigms. African Americans have a disproportionate risk for developing chronic kidney disease compared to European Americans. Previous studies have identified a region on chromosome 22 containing two genes, MYH9 and APOL1, which likely accounts for nearly all of this difference. Previous reports provided strong statistical evidence implicating APOL1 as the major contributor to nephropathy risk in African Americans, driven by two coding variants, termed G1 and G2. However, other groups still report statistical evidence for MYH9 association in kidney disease, and animal models have demonstrated biological relevance for MYH9 function in the kidney. Here, we show that suppressing apol1 in zebrafish embryos results in perturbed kidney function. Importantly, using this in vivo assay, we show that the G1 variant appears to cause a loss of APOL1 function, while the G2 variant results in an altered protein that may be acting antagonistically in the presence of normal APOL1. We also report a genetic interaction between apol1 and myh9 under anemic stress, which is consistent with our previous findings in sickle cell disease (SCD) nephropathy patients. Finally, we provide functional evidence in vivo that the G2-altered APOL1 may be interacting with MYH9 to confer nephropathy risk.
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Affiliation(s)
- Blair R. Anderson
- Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, United States of America
| | - David N. Howell
- Department of Pathology, Division of Pathology Clinical Services, Duke University, Durham, North Carolina, United States of America
| | - Karen Soldano
- Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Melanie E. Garrett
- Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Nicholas Katsanis
- Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Marilyn J. Telen
- Department of Medicine, Division of Hematology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Erica E. Davis
- Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Allison E. Ashley-Koch
- Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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130
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Matsha TE, Kengne AP, Masconi KL, Yako YY, Erasmus RT. APOL1 genetic variants, chronic kidney diseases and hypertension in mixed ancestry South Africans. BMC Genet 2015; 16:69. [PMID: 26112018 PMCID: PMC4482162 DOI: 10.1186/s12863-015-0228-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 06/10/2015] [Indexed: 01/07/2023] Open
Abstract
Background The frequencies of apolipoprotein L1 (APOL1) variants and their associations with chronic kidney disease (CKD) vary substantially in populations from Africa. Moreover, available studies have used very small sample sizes to provide reliable estimates of the frequencies of these variants in the general population. We determined the frequency of the two APOL1 risk alleles (G1 and G2) and investigated their association with renal traits in a relatively large sample of mixed-ancestry South Africans. APOL1 risk variants (G1: rs60910145 and rs73885319; G2: rs71785313) were genotyped in 859 African mixed ancestry individuals using allele-specific TaqMan technology. Glomerular filtration rate (eGFR) was estimated using the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. Results The frequencies of rs73885319, rs60910145 and rs71785313 risk alleles were respectively, 3.6 %, 3.4 %, and 5.8 %, resulting in a 1.01 % frequency of the APOL1 two-risk allele (G1:G1 or G1:G2 or G2:G2). The presence of the two-risk allele increased serum creatinine with a corresponding reduction in eGFR (either MDRD or CKD-EPI based). In dominant and log-additive genetic models, significant associations were found between rs71785313 and systolic blood pressure (both p ≤ 0.025), with a significant statistical interaction by diabetes status, p = 0.022, reflecting a negative non-significant effect in nondiabetics and a positive effect in diabetics. Conclusions Although the APOL1 variants are not common in the mixed ancestry population of South Africa, the study does provide an indication that APOL1 variants may play a role in conferring an increased risk for renal and cardiovascular risk in this population.
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Affiliation(s)
- Tandi E Matsha
- Department of Biomedical Sciences, Faculty of Health and Wellness Science, Cape Peninsula University of Technology, PO Box 1906, Bellville, Cape Town, 7530, South Africa.
| | - Andre P Kengne
- Non-Communicable Diseases Research Unit, South African Medical Research Council & University of Cape Town, Cape Town, South Africa.
| | - Katya L Masconi
- Department of Surgery, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
| | - Yandiswa Y Yako
- Department of Surgery, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
| | - Rajiv T Erasmus
- Division of Chemical Pathology, Faculty of Health Sciences, National Health Laboratory Service (NHLS) and University of Stellenbosch, Cape Town, South Africa.
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Cheng D, Weckerle A, Yu Y, Ma L, Zhu X, Murea M, Freedman BI, Parks JS, Shelness GS. Biogenesis and cytotoxicity of APOL1 renal risk variant proteins in hepatocytes and hepatoma cells. J Lipid Res 2015; 56:1583-93. [PMID: 26089538 DOI: 10.1194/jlr.m059733] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Indexed: 12/21/2022] Open
Abstract
Two APOL1 gene variants, which likely evolved to protect individuals from African sleeping sickness, are strongly associated with nondiabetic kidney disease in individuals with recent African ancestry. Consistent with its role in trypanosome killing, the pro-death APOL1 protein is toxic to most cells, but its mechanism of cell death is poorly understood and little is known regarding its intracellular trafficking and secretion. Because the liver appears to be the main source of circulating APOL1, we examined its secretory behavior and mechanism of toxicity in hepatoma cells and primary human hepatocytes. APOL1 is poorly secreted in vitro, even in the presence of chemical chaper-ones; however, it is efficiently secreted in wild-type transgenic mice, suggesting that APOL1 secretion has specialized requirements that cultured cells fail to support. In hepatoma cells, inducible expression of APOL1 and its risk variants promoted cell death, with the G1 variant displaying the highest degree of toxicity. To explore the basis for APOL1-mediated cell toxicity, endoplasmic reticulum stress, pyroptosis, autophagy, and apoptosis were examined. Our results suggest that autophagy represents the predominant mechanism of APOL1-mediated cell death. Overall, these results increase our understanding of the basic biology and trafficking behavior of circulating APOL1 from the liver.
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Affiliation(s)
- Dongmei Cheng
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC
| | - Allison Weckerle
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC
| | - Yi Yu
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC
| | - Lijun Ma
- Nephrology, Wake Forest School of Medicine, Winston-Salem, NC
| | - Xuewei Zhu
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC
| | - Mariana Murea
- Nephrology, Wake Forest School of Medicine, Winston-Salem, NC
| | | | - John S Parks
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC
| | - Gregory S Shelness
- Department of Internal Medicine, Sections on Molecular Medicine Wake Forest School of Medicine, Winston-Salem, NC
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132
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Lan X, Rao TKS, Chander PN, Skorecki K, Singhal PC. Apolipoprotein L1 (APOL1) Variants (Vs) a possible link between Heroin-associated Nephropathy (HAN) and HIV-associated Nephropathy (HIVAN). Front Microbiol 2015; 6:571. [PMID: 26106375 PMCID: PMC4460807 DOI: 10.3389/fmicb.2015.00571] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 05/24/2015] [Indexed: 11/26/2022] Open
Abstract
In 1970s, Heroin-associated Nephropathy (HAN), one form of focal and segmental glomerulosclerosis (FSGS), was a predominant cause of End-stage Kidney Disease (ESKD) in African-Americans (AAs). In 1980s, with the surge of Acquired Immune Deficiency Syndrome (AIDS) in AAs, HAN more or less disappeared, and the incidence of Human Immunodeficiency Virus associated Nephropathy (HIVAN) markedly increased. Recent studies in AAs have identified APOL1 variants (Vs) as a major risk factor for the development and progression of non-diabetic kidney diseases including idiopathic FSGS and hypertension-attributed nephrosclerosis. These observations have also offered partial insights into the mechanisms of development, and higher rate of occurrence of both HAN and HIVAN in AAs. AAs with APOL1Vs develop idiopathic FSGS at four-fold higher rate compared to European Americans (EAs). Similarly, HIV infected AAs with APOL1Vs (if not on antiviral therapy), risk a 50% (10-fold greater) chance of developing HIVAN. It has been suggested that APOL1Vs expression may render podocytes more vulnerable to various types of injury: bacterial, viral, and others. However, in addition to genetic variants, additional factors such as persistence of a second hit may determine the nature and severity of glomerular disease. In patients with HAN, heroin or contaminants may have been the offending second insult(s) which caused renal disease in susceptible AA patients. In the 80's, since heroin-induced second hit was neither consistent nor sustained (depending on drug availability in the street), the disease was masked or replaced HIV infected patients (especially in untreated subjects), by an overwhelming second hit by the virus which was both intense as well as persistent. It appears that APOL1Vs may be one of the links between the disappearance of HAN and emergence of HIVAN in AA patients.
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Affiliation(s)
- Xiqian Lan
- Hofstra North Shore-LIJ School of MedicineLong Island, NY, USA
| | - T. K. S. Rao
- Department of Medicine, State University of New York Downstate Medical CenterBrooklyn, NY, USA
| | | | - Karl Skorecki
- Technion Institute of Technology and Rambam Medical CenterHaifa, Israel
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Jotwani V, Shlipak MG, Scherzer R, Parekh RS, Kao WHL, Bennett M, Cohen MH, Nowicki M, Sharma A, Young M, Tien PC, Parikh CR, Estrella MM. APOL1 Genotype and Glomerular and Tubular Kidney Injury in Women With HIV. Am J Kidney Dis 2015; 65:889-98. [PMID: 25921719 PMCID: PMC4615696 DOI: 10.1053/j.ajkd.2015.02.329] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 02/15/2015] [Indexed: 12/17/2022]
Abstract
BACKGROUND APOL1 genotype is associated with advanced kidney disease in African Americans, but the pathogenic mechanisms are unclear. Here, associations of APOL1 genotype with urine biomarkers of glomerular and tubular injury and kidney function decline were evaluated. STUDY DESIGN Observational study. SETTING & PARTICIPANTS 431 human immunodeficiency virus (HIV)-infected African American women enrolled in Women's Interagency HIV Study (WIHS). PREDICTOR APOL1 genotype. OUTCOMES Albumin-creatinine ratio (ACR), 4 tubular injury biomarkers (interleukin 18 [IL-18], kidney injury molecule 1 [KIM-1], neutrophil gelatinase-associated lipocalin [NGAL], and α1-microglobulin [A1M]), and kidney function estimated using the CKD-EPI cystatin C equation. MEASUREMENTS Participants were genotyped for APOL1 single-nucleotide polymorphisms rs73885319 (G1 allele) and rs71785313 (G2 allele). Urine biomarkers were measured using stored samples from 1999-2000. Cystatin C was measured using serum collected at baseline and 4- and 8-year follow-ups. RESULTS At baseline, ACRs were higher among 47 women with 2 APOL1 risk alleles versus 384 women with 0/1 risk allele (median, 24 vs 11mg/g; P<0.001). Compared with women with 0/1 risk allele, women with 2 risk alleles had 104% higher ACRs (95% CI, 29-223mg/g) and 2-fold greater risk of ACR>30 (95% CI, 1.17-3.44) mg/g after multivariable adjustment. APOL1 genotype showed little association with urine IL-18:Cr ratio, KIM-1:Cr ratio, and NGAL:Cr ratio (estimates of -5% [95% CI, -24% to 18%], -20% [95% CI, -36% to -1%], and 10% [95% CI, -26% to 64%], respectively) or detectable urine A1M (prevalence ratio, 1.13; 95% CI, 0.65-1.97) in adjusted analyses. Compared with women with 0/1 allele, women with 2 risk alleles had faster eGFR decline, by 1.2 (95% CI, 0.2 to 2.2) mL/min/1.73m(2) per year, and 1.7- and 3.4-fold greater rates of incident chronic kidney disease (95% CI, 1.1 to 2.5) and 10% annual eGFR decline (95% CI, 1.7 to 6.7), respectively, with minimal attenuation after adjustment for glomerular and tubular injury biomarker levels. LIMITATIONS Results may not be generalizable to men. CONCLUSIONS Among HIV-infected African American women, APOL1-associated kidney injury appears to localize to the glomerulus, rather than the tubules.
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Affiliation(s)
- Vasantha Jotwani
- Department of Medicine, San Francisco VA Medical Center, San Francisco, CA; Department of Epidemiology and Biostatistics, University of California, San Francisco, CA.
| | - Michael G Shlipak
- Department of Medicine, San Francisco VA Medical Center, San Francisco, CA; Department of Epidemiology and Biostatistics, University of California, San Francisco, CA
| | - Rebecca Scherzer
- Department of Medicine, San Francisco VA Medical Center, San Francisco, CA; Department of Epidemiology and Biostatistics, University of California, San Francisco, CA
| | - Rulan S Parekh
- Hospital for Sick Children, University Healthy Network and University of Toronto, Toronto, Canada; Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD
| | - W H Linda Kao
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD
| | - Michael Bennett
- Division of Nephrology and Hypertension, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | - Mardge H Cohen
- Department of Medicine, Stroger Hospital, Rush University, Chicago, IL; Department of Medicine, Rush University, Chicago, IL
| | - Marek Nowicki
- Department of Medicine, University of Southern California, Los Angeles, CA
| | - Anjali Sharma
- Division of Infectious Diseases, Department of Medicine, SUNY Downstate Medical Center, Brooklyn, NY
| | - Mary Young
- Division of Infectious Diseases and Travel Medicine, Department of Medicine, Georgetown University Medical Center, Washington, DC
| | - Phyllis C Tien
- Department of Medicine, San Francisco VA Medical Center, San Francisco, CA
| | - Chirag R Parikh
- Section of Nephrology, Department of Medicine, Yale University, New Haven, CT; Program of Applied Translational Research, Yale University, New Haven, CT
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134
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Wasser WG, Kruzel-Davila E. Hemostatic Factors, APOL1, and ESRD Risk: Another Piece of the Puzzle? Clin J Am Soc Nephrol 2015; 10:723-5. [DOI: 10.2215/cjn.03220315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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135
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Tin A, Grams ME, Maruthur NM, Astor BC, Couper D, Mosley TH, Fornage M, Parekh RS, Coresh J, Kao WHL. Hemostatic Factors, APOL1 Risk Variants, and the Risk of ESRD in the Atherosclerosis Risk in Communities Study. Clin J Am Soc Nephrol 2015; 10:784-90. [PMID: 25887069 PMCID: PMC4422243 DOI: 10.2215/cjn.08340814] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 01/13/2015] [Indexed: 01/13/2023]
Abstract
BACKGROUND AND OBJECTIVES Hemostatic factors have been associated with kidney function decline, and evidence suggests stronger effects among African Americans. The presence of APOL1 renal risk variants, common in African Americans, might partly underlie this risk difference. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A total of 13,337 participants in the Atherosclerosis Risk in Communities study were followed from 1987-1989 until 2010. Participants were categorized into three groups by ancestry and APOL1 risk status: European Americans (n=10,206), African Americans with zero or one APOL1 risk allele (n=2,733), and African Americans with two APOL1 risk alleles (n=398). ESRD events were ascertained through linkage to the US Renal Data System. Cox regression was used to estimate the risk for ESRD associated with hemostatic factors (factor VIIc, factor VIIIc, fibrinogen, von Willebrand factor, protein C, and antithrombin III). RESULTS There were 232 cases of ESRD over 21.5 years (European Americans, 119; African Americans with zero or one APOL1 risk allele, 94; African Americans with two APOL1 risk alleles, 19). In unadjusted and adjusted analysis of the overall population, higher levels of all hemostatic factors, except antithrombin III, were significantly associated with ESRD (all P<0.05). Factor VIIc had the strongest association (per one interquartile range; adjusted hazard ratio, 1.46; 95% confidence interval, 1.21 to 1.76). With the exception of fibrinogen, the risk associated with each hemostatic factor was stronger in African Americans with two APOL1 risk alleles compared with the other two groups. Statistically significant interactions were seen for factor VIIIc and protein C (interaction between those with two APOL1 risk allele and the other two groups: P<0.02 for factor VIIIc and <0.04 for protein C). CONCLUSIONS Higher levels of factor VIIc, VIIIc, fibrinogen, von Willebrand factor, and protein C were associated with ESRD risk, with a significantly stronger association of factor VIIIc and protein C in African Americans with two APOL1 risk alleles.
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Affiliation(s)
- Adrienne Tin
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland;
| | | | - Nisa M Maruthur
- General Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Brad C Astor
- Department of Medicine and Department of Population Health Science, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - David Couper
- Collaborative Studies Coordinating Center, Department of Biostatistics, University of North Carolina, Chapel Hill, North Carolina
| | - Thomas H Mosley
- Division of Geriatrics, University of Mississippi Medical Center, Jackson, Mississippi
| | - Myriam Fornage
- Center for Human Genetics, University of Texas Health Science Center at Houston, Houston, Texas; and
| | - Rulan S Parekh
- Division of Nephrology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Josef Coresh
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Wen Hong Linda Kao
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
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136
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Kasembeli AN, Duarte R, Ramsay M, Naicker S. African origins and chronic kidney disease susceptibility in the human immunodeficiency virus era. World J Nephrol 2015; 4:295-306. [PMID: 25949944 PMCID: PMC4419140 DOI: 10.5527/wjn.v4.i2.295] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 01/06/2015] [Accepted: 01/18/2015] [Indexed: 02/06/2023] Open
Abstract
Chronic kidney disease (CKD) is a major public health problem worldwide with the estimated incidence growing by approximately 6% annually. There are striking ethnic differences in the prevalence of CKD such that, in the United States, African Americans have the highest prevalence of CKD, four times the incidence of end stage renal disease when compared to Americans of European ancestry suggestive of genetic predisposition. Diabetes mellitus, hypertension and human immunodeficiency virus (HIV) infection are the major causes of CKD. HIV-associated nephropathy (HIVAN) is an irreversible form of CKD with considerable morbidity and mortality and is present predominantly in people of African ancestry. The APOL1 G1 and G2 alleles were more strongly associated with the risk for CKD than the previously examined MYH9 E1 risk haplotype in individuals of African ancestry. A strong association was reported in HIVAN, suggesting that 50% of African Americans with two APOL1 risk alleles, if untreated, would develop HIVAN. However these two variants are not enough to cause disease. The prevailing belief is that modifying factors or second hits (including genetic hits) underlie the pathogenesis of kidney disease. This work reviews the history of genetic susceptibility of CKD and outlines current theories regarding the role for APOL1 in CKD in the HIV era.
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137
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Abstract
For a century, nephrosclerosis was ascribed to nonmalignant hypertension and aging. However, it was intuitively perceived that hypertension may follow rather than explain this nephrovasculopathy. Hypertensive nephrosclerosis was long considered a major cause of end-stage renal failure (ESRD). This is especially true in blacks of African descent but not in other ethnic populations. The term 'nephrosclerosis' is still an easy way out to classify a patient with renal insufficiency. This leads to neglect the possibility of an overlooked nephropathy complicated by hypertension and to believe that drastic blood pressure control may retard the progression to ESRD. Several clinical and experimental lines of evidence lead to the understanding that nephrosclerosis, especially in blacks, is a genetic renovasculopathy that precedes the rise in blood pressure. The identification of coding region variants in APOL1 encoding apolipoprotein L-1 in black but also white and Asians opens new lines of research on the genetics of nephroangiosclerosis and of FSGS. Metabolic derangements, such as obesity, oxidative stress, dyslipidemia and atherosclerosis may be considered confounding factors with regard to nephrosclerosis. Histomorphometric studies led to sorting out the lesions due to aging from those stemming from hypertension. They shed new light not only on glomerular lesions that comprise ischemic obsolescence but also on glomerulomegaly and focal-segmental sclerosis, the latter due to a loss of renal autoregulation. It appears that the control of hypertension is not credited with the expected benefit for slowing the decline of renal function. 'Nephrosclerosis' can be considered an umbrella term of poor significance that should be replaced by its pathologic description, that is, arterionephrosclerosis and incite to elucidate the various genetic and metabolic factors that lead to a lesion in quest of a specific disease.
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Affiliation(s)
- Alain Meyrier
- Service de Néphrologie, AP-HP, Hôpital Georges Pompidou, Université Paris-Descartes, Paris, France
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138
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Lan X, Wen H, Saleem MA, Mikulak J, Malhotra A, Skorecki K, Singhal PC. Vascular smooth muscle cells contribute to APOL1-induced podocyte injury in HIV milieu. Exp Mol Pathol 2015; 98:491-501. [PMID: 25796344 DOI: 10.1016/j.yexmp.2015.03.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 03/12/2015] [Indexed: 02/07/2023]
Abstract
Clinical reports have demonstrated that higher rates of non-diabetic glomerulosclerosis in African Americans can be attributed to two coding sequence variants (G1 and G2) in the APOL1 gene; however, the underlying mechanism is still unknown. Kidney biopsy data suggest enhanced expression of APOL1/APOL1 variants (Vs) in smooth muscle cells (SMCs) of renal vasculature. Since APOL1 is a secretory protein of relatively low molecular weight (41kDa), SMCs may be a contributory endocrine/paracrine source of APOL1 wild type (WT)/APOL1Vs in the glomerular capillary perfusate percolating podocytes. In the present study, we tested the hypothesis that an HIV milieu stimulated secretion of APOL1 and its risk variants by arterial SMCs contributes to podocyte injury. Human umbilical artery smooth muscle cells (HSMCs)-treated with conditioned media (CM) of HIV-infected peripheral mononuclear cells (PBMC/HIV-CM), CM of HIV-infected U939 cells, or recombinant IFN-γ displayed enhanced expression of APOL1. Podocytes co-cultured in trans-wells with HSMCs-over expressing APOL1WT showed induction of injury; however, podocytes co-cultured with HSMC-over expressing either APOL1G1 or APOL1G2 showed several folds greater injury when compared to HSMC-over expressing APOL1WT. Conditioned media collected from HSMC-over-expressing APOL1G1/APOL1G2 (HSMC/APOL1G1-CM or HSMC/APOL1G2-CM) also displayed higher percentages of injured podocytes in the form of swollen cells, leaky lysosomes, loss of viability, and enhanced sensitivity to adverse host factors when compared to HSMC/APOL1WT-CM. Notably, HSMC/APOL1WT-CM promoted podocyte injury only at a significantly higher concentrations compared to HSMC/APOL1G1/G2-CM. We conclude that HSMCs could serve as an endocrine/paracrine source of APOL1Vs, which mediate accelerated podocyte injury in HIV milieu.
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Affiliation(s)
- Xiqian Lan
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Department of Medicine, Hofstra North Shore LIJ Medical School, NY, USA
| | - Hongxiu Wen
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Department of Medicine, Hofstra North Shore LIJ Medical School, NY, USA
| | - Moin A Saleem
- Renal Academic Unit, Department of Pediatrics, University of Bristol, Bristol, UK
| | - Joanna Mikulak
- Unit of Clinical and Experimental Immunology, Humanitas Clinical and Research Center, Rozzano, Milan, Italy
| | - Ashwani Malhotra
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Department of Medicine, Hofstra North Shore LIJ Medical School, NY, USA
| | - Karl Skorecki
- Nephrology and Molecular Medicine, Technion Institute of Technology, Rambam Medical Center, Haifa, Israel
| | - Pravin C Singhal
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Department of Medicine, Hofstra North Shore LIJ Medical School, NY, USA.
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139
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Horowitz B, Miskulin D, Zager P. Epidemiology of hypertension in CKD. Adv Chronic Kidney Dis 2015; 22:88-95. [PMID: 25704344 DOI: 10.1053/j.ackd.2014.09.004] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/25/2014] [Accepted: 09/10/2014] [Indexed: 01/13/2023]
Abstract
Both hypertension (HTN) and CKD are serious interrelated global public health problems. Nearly 30% and 15% of US adults have HTN and CKD, respectively. Because HTN may cause or result from CKD, HTN prevalence is higher and control more difficult with worse kidney function. Etiology of CKD, presence and degree of albuminuria, and genetic factors all influence HTN severity and prevalence. In addition, socioeconomic and lifestyle factors influence HTN prevalence and control. There are racial and ethnic disparities in the prevalence, treatment, risks, and outcomes of HTN in patients with CKD. Control of blood pressure (BP) in Hispanic and African Americans with CKD is worse than it is whites. There are disparities in the patterns of treatment and rates of progression of CKD in patients with HTN. The presence and severity of CKD increase treatment resistance. HTN is also extremely prevalent in patients receiving hemodialysis, and optimal targets for BP control are being elucidated. Although the awareness, treatment, and control of HTN in CKD patients is improving, control of BP in patients at all stages of CKD remains suboptimal.
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140
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Genetic causes of proteinuria and nephrotic syndrome: impact on podocyte pathobiology. Pediatr Nephrol 2015; 30:221-33. [PMID: 24584664 PMCID: PMC4262721 DOI: 10.1007/s00467-014-2753-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 12/31/2013] [Accepted: 01/02/2014] [Indexed: 12/11/2022]
Abstract
In the past 20 years, multiple genetic mutations have been identified in patients with congenital nephrotic syndrome (CNS) and both familial and sporadic focal segmental glomerulosclerosis (FSGS). Characterization of the genetic basis of CNS and FSGS has led to the recognition of the importance of podocyte injury to the development of glomerulosclerosis. Genetic mutations induce injury due to effects on the podocyte's structure, actin cytoskeleton, calcium signaling, and lysosomal and mitochondrial function. Transgenic animal studies have contributed to our understanding of podocyte pathobiology. Podocyte endoplasmic reticulum stress response, cell polarity, and autophagy play a role in maintenance of podocyte health. Further investigations related to the effects of genetic mutations on podocytes may identify new pathways for targeting therapeutics for nephrotic syndrome.
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141
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Saab KR, Kendrick J, Yracheta JM, Lanaspa MA, Pollard M, Johnson RJ. New insights on the risk for cardiovascular disease in African Americans: the role of added sugars. J Am Soc Nephrol 2015; 26:247-57. [PMID: 25090991 PMCID: PMC4310665 DOI: 10.1681/asn.2014040393] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 06/30/2014] [Indexed: 12/26/2022] Open
Abstract
African Americans are at increased risk for cardiovascular and metabolic diseases, including obesity, high BP, diabetes, CKD, myocardial infarction, and stroke. Here we summarize the current risks and provide an overview of the underlying risk factors that may account for these associations. By reviewing the relationship between cardiovascular and renal diseases and the African-American population during the early 20th century, the historic and recent associations of African heritage with cardiovascular disease, and modern population genetics, it is possible to assemble strong hypotheses for the primary underlying mechanisms driving the increased frequency of disease in African Americans. Our studies suggest that underlying genetic mechanisms may be responsible for the increased frequency of high BP and kidney disease in African Americans, with particular emphasis on the role of APOL1 polymorphisms in causing kidney disease. In contrast, the Western diet, particularly the relatively high intake of fructose-containing sugars and sweetened beverages, appears to be the dominant force driving the increased risk of diabetes, obesity, and downstream complications. Given that intake of added sugars is a remediable risk factor, we recommend clinical trials to examine the reduction of sweetened beverages as a primary means for reducing cardiovascular risk in African Americans.
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Affiliation(s)
- Karim R Saab
- Renal Division, Department of Medicine, University of Colorado Anschutz Medical Center, Aurora, Colorado
| | - Jessica Kendrick
- Renal Division, Department of Medicine, University of Colorado Anschutz Medical Center, Aurora, Colorado
| | - Joseph M Yracheta
- Department of Pharmaceutics, University of Washington, School of Pharmacy, Seattle, Washington
| | - Miguel A Lanaspa
- Renal Division, Department of Medicine, University of Colorado Anschutz Medical Center, Aurora, Colorado; Colorado Research Partners LLC, Aurora, Colorado; and
| | | | - Richard J Johnson
- Renal Division, Department of Medicine, University of Colorado Anschutz Medical Center, Aurora, Colorado; Colorado Research Partners LLC, Aurora, Colorado; and
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142
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Kruzel-Davila E, Wasser WG, Aviram S, Skorecki K. APOL1 nephropathy: from gene to mechanisms of kidney injury. Nephrol Dial Transplant 2015; 31:349-58. [PMID: 25561578 DOI: 10.1093/ndt/gfu391] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 11/22/2014] [Indexed: 12/22/2022] Open
Abstract
The contribution of African ancestry to the risk of focal segmental glomerulosclerosis and chronic kidney disease has been partially explained by the recently described chromosome 22q variants in the gene apolipoprotein L1 (APOL1). The APOL1 variants appear at a high allele frequency in populations of West African ancestry as a result of apparent adaptive selection of the heterozygous state. Heterozygosity protects from infection with Trypanosoma brucei rhodesiense. This review will describe the role of the approaches in population genetics for the description of APOL1-associated nephropathies and draw inferences as to the biologic mechanisms from genetic epidemiology findings to date. Modifier loci can influence APOL1 risk for the development of kidney disease. 'Second hits', both viral and non-viral, may explain the discrepancy between the remarkably high odds ratios and the low lifetime risks of kidney disease in two allele carriers of APOL1 risk variants. Therapeutic strategies for APOL1-associated nephropathies will require the prevention and treatment of these 'second hits' and the development of drugs to protect the APOL1 downstream renal injury pathways.
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Affiliation(s)
- Etty Kruzel-Davila
- Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Rambam Health Care Campus, Haifa 3109601, Israel Rambam Health Care Campus, Haifa 3109601, Israel
| | - Walter G Wasser
- Rambam Health Care Campus, Haifa 3109601, Israel Mayanei HaYeshua Medical Center, Bnei Brak 51544, Israel
| | - Sharon Aviram
- Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Rambam Health Care Campus, Haifa 3109601, Israel
| | - Karl Skorecki
- Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Rambam Health Care Campus, Haifa 3109601, Israel Rambam Health Care Campus, Haifa 3109601, Israel
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143
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Sampson MG, Hodgin JB, Kretzler M. Defining nephrotic syndrome from an integrative genomics perspective. Pediatr Nephrol 2015; 30:51-63; quiz 59. [PMID: 24890338 PMCID: PMC4241380 DOI: 10.1007/s00467-014-2857-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 05/06/2014] [Accepted: 05/14/2014] [Indexed: 12/15/2022]
Abstract
Nephrotic syndrome (NS) is a clinical condition with a high degree of morbidity and mortality, caused by failure of the glomerular filtration barrier, resulting in massive proteinuria. Our current diagnostic, prognostic and therapeutic decisions in NS are largely based upon clinical or histological patterns such as "focal segmental glomerulosclerosis" or "steroid sensitive". Yet these descriptive classifications lack the precision to explain the physiologic origins and clinical heterogeneity observed in this syndrome. A more precise definition of NS is required to identify mechanisms of disease and capture various clinical trajectories. An integrative genomics approach to NS applies bioinformatics and computational methods to comprehensive experimental, molecular and clinical data for holistic disease definition. A unique aspect is analysis of data together to discover NS-associated molecules, pathways, and networks. Integrating multidimensional datasets from the outset highlights how molecular lesions impact the entire individual. Data sets integrated range from genetic variation to gene expression, to histologic changes, to progression of chronic kidney disease (CKD). This review will introduce the tenets of integrative genomics and suggest how it can increase our understanding of NS from molecular and pathophysiological perspectives. A diverse group of genome-scale experiments are presented that have sought to define molecular signatures of NS. Finally, the Nephrotic Syndrome Study Network (NEPTUNE) will be introduced as an international, prospective cohort study of patients with NS that utilizes an integrated systems genomics approach from the outset. A major NEPTUNE goal is to achieve comprehensive disease definition from a genomics perspective and identify shared molecular drivers of disease.
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Affiliation(s)
- Matthew G. Sampson
- Division of Nephrology, Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109, USA,to whom correspondence should be addressed: Matthew Sampson, Division of Nephrology, University of Michigan School of Medicine, 8220D MSRB III, West Medical Center Drive, Ann Arbor, MI 48109, kidneyomics.org, , Telephone and Fax: 734-647-9361. Matthias Kretzler, Medicine/Nephrology and Computational Medicine and Bioinformatics, University of Michigan, 1560 MSRB II, 1150 W. Medical Center Dr.-SPC5676, Ann Arbor, MI 48109-5676, 734-615-5757, fax: 734-763-0982,
| | - Jeffrey B. Hodgin
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Matthias Kretzler
- Division of Nephrology, Department of Internal Medicine and Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, MI 48109, USA,to whom correspondence should be addressed: Matthew Sampson, Division of Nephrology, University of Michigan School of Medicine, 8220D MSRB III, West Medical Center Drive, Ann Arbor, MI 48109, kidneyomics.org, , Telephone and Fax: 734-647-9361. Matthias Kretzler, Medicine/Nephrology and Computational Medicine and Bioinformatics, University of Michigan, 1560 MSRB II, 1150 W. Medical Center Dr.-SPC5676, Ann Arbor, MI 48109-5676, 734-615-5757, fax: 734-763-0982,
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144
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Langefeld CD, Divers J, Pajewski NM, Hawfield AT, Reboussin DM, Bild DE, Kaysen GA, Kimmel PL, Raj D, Ricardo AC, Wright JT, Sedor JR, Rocco MV, Freedman BI. Apolipoprotein L1 gene variants associate with prevalent kidney but not prevalent cardiovascular disease in the Systolic Blood Pressure Intervention Trial. Kidney Int 2015; 87:169-75. [PMID: 25029429 PMCID: PMC4281289 DOI: 10.1038/ki.2014.254] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 05/27/2014] [Accepted: 05/29/2014] [Indexed: 12/13/2022]
Abstract
Apolipoprotein L1 gene (APOL1) G1 and G2 coding variants are strongly associated with chronic kidney disease (CKD) in African Americans (AAs). Here APOL1 association was tested with baseline estimated glomerular filtration rate (eGFR), urine albumin:creatinine ratio (UACR), and prevalent cardiovascular disease (CVD) in 2571 AAs from the Systolic Blood Pressure Intervention Trial (SPRINT), a trial assessing effects of systolic blood pressure reduction on renal and CVD outcomes. Logistic regression models that adjusted for potentially important confounders tested for association between APOL1 risk variants and baseline clinical CVD (myocardial infarction, coronary, or carotid artery revascularization) and CKD (eGFR under 60 ml/min per 1.73 m(2) and/or UACR over 30 mg/g). AA SPRINT participants were 45.3% female with a mean (median) age of 64.3 (63) years, mean arterial pressure 100.7 (100) mm Hg, eGFR 76.3 (77.1) ml/min per 1.73 m(2), and UACR 49.9 (9.2) mg/g, and 8.2% had clinical CVD. APOL1 (recessive inheritance) was positively associated with CKD (odds ratio 1.37, 95% confidence interval 1.08-1.73) and log UACR estimated slope (β) 0.33) and negatively associated with eGFR (β -3.58), all significant. APOL1 risk variants were not significantly associated with prevalent CVD (1.02, 0.82-1.27). Thus, SPRINT data show that APOL1 risk variants are associated with mild CKD but not with prevalent CVD in AAs with a UACR under 1000 mg/g.
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Affiliation(s)
- Carl D. Langefeld
- Biostatistical Sciences, Wake Forest School of Medicine, Winston-Salem, NC
- Center for Public Health Genomics, Wake Forest School of Medicine, Winston-Salem, NC
| | - Jasmin Divers
- Biostatistical Sciences, Wake Forest School of Medicine, Winston-Salem, NC
- Center for Public Health Genomics, Wake Forest School of Medicine, Winston-Salem, NC
| | - Nicholas M. Pajewski
- Biostatistical Sciences, Wake Forest School of Medicine, Winston-Salem, NC
- Center for Public Health Genomics, Wake Forest School of Medicine, Winston-Salem, NC
| | - Amret T. Hawfield
- Internal Medicine–Nephrology, Wake Forest School of Medicine, Winston-Salem, NC
| | - David M. Reboussin
- Biostatistical Sciences, Wake Forest School of Medicine, Winston-Salem, NC
| | - Diane E. Bild
- Patient-Centered Outcomes Research Institute (PCORI), Washington, DC
| | - George A. Kaysen
- University of California Davis Healthcare System, Sacramento, CA
| | - Paul L. Kimmel
- National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD
| | - Dominic Raj
- Medicine-Nephrology, George Washington University School of Medicine, Washington, DC
| | - Ana C. Ricardo
- Medicine-Nephrology, University of Illinois College of Medicine at Chicago, Chicago, IL
| | - Jackson T. Wright
- Medicine-Hypertension, University Hospitals, Case Medical Center, Cleveland, OH
| | - John R. Sedor
- Medicine, Physiology & Biophysics, Case Western Reserve University, Cleveland, OH
| | - Michael V. Rocco
- Internal Medicine–Nephrology, Wake Forest School of Medicine, Winston-Salem, NC
| | - Barry I. Freedman
- Internal Medicine–Nephrology, Wake Forest School of Medicine, Winston-Salem, NC
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145
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Larsen CP, Beggs ML, Saeed M, Ambruzs JM, Cossey LN, Messias NC, Walker PD, Freedman BI. Histopathologic findings associated with APOL1 risk variants in chronic kidney disease. Mod Pathol 2015; 28:95-102. [PMID: 25081748 PMCID: PMC11163378 DOI: 10.1038/modpathol.2014.92] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 05/08/2014] [Indexed: 12/22/2022]
Abstract
The effects of nephropathy risk variants in the apolipoprotein L1 gene (APOL1) on renal histopathology in African Americans with arterionephrosclerosis or putative 'hypertension-associated' nephropathy are unknown. APOL1 genotype-phenotype correlations were performed in a blinded manner from renal biopsies in 196 self-reported African Americans with arterionephrosclerosis on kidney biopsy at a large national nephropathology practice. Subjects had chronic kidney disease without nephrotic syndrome. A discovery analysis compared histopathologic changes in the glomerular and tubulointerstitial compartments in 58 subjects with 2 versus 56 subjects with 0 APOL1 risk variants. Validation was performed in biopsies from 82 additional subjects with 0, 1, and 2 risk variants. Two risk variant versus zero risk variant group genotype associations and subphenotypes were assessed by χ(2) analyses. ANOVA compared means of continuous variables. In discovery analyses, significantly less obsolescent glomerulosclerosis, more (solidified and disappearing) glomerulosclerosis, more thyroidization-type tubular atrophy, and more microcystic tubular dilatation were seen in patients with two versus zero APOL1 risk alleles. Greater degrees of arteriosclerosis were present in those with zero risk alleles. Segmental glomerulosclerosis did not differ significantly between groups. Presence of two of the following discriminatory histopathologic findings from discovery, that is, <50% obsolescent glomerulosclerosis, thyroidization-type tubular atrophy, and microcystic tubular dilatation, was specific for the presence of two APOL1 risk alleles in the validation phase. African Americans with arterionephrosclerosis who possess two APOL1 risk variants more often lack obsolescent glomerulosclerosis and have greater degrees of (solidified and disappearing) glomerulosclerosis, thyroidization-type tubular atrophy, and microcystic tubular dilation than patients with fewer than two risk variants. These findings support involvement of multiple cell types in subnephrotic forms of APOL1-associated nephropathy, particularly renal tubule cells with resultant tubulointerstitial disease.
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Affiliation(s)
| | | | | | | | | | | | | | - Barry I Freedman
- Internal Medicine-Nephrology, Wake Forest School of Medicine, Winston-Salem, NC, USA
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146
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Madhavan SM, O'Toole JF. The biology of APOL1 with insights into the association between APOL1 variants and chronic kidney disease. Clin Exp Nephrol 2014; 18:238-42. [PMID: 24233469 DOI: 10.1007/s10157-013-0907-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 10/29/2013] [Indexed: 12/15/2022]
Abstract
Recent studies have identified genetic variants in APOL1 that may contribute to the increased incidence of kidney disease in populations with African ancestry. Here, we review the biology of APOL1 present in the circulation and localized to the kidney as it may contribute to the pathogenesis of APOL1-associated kidney disease.
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147
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Baldwin MD. The primary care physician/nephrologist partnership in treating chronic kidney disease. Prim Care 2014; 41:837-56. [PMID: 25439537 DOI: 10.1016/j.pop.2014.08.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Chronic kidney disease (CKD) continues to be an ever-increasing health problem in the United States and elsewhere. Diabetes mellitus and hypertension remain the primary causes, and much of this is related to increased rates of obesity. Studies have demonstrated that early referral to a nephrologist can be life-saving and can also markedly improve quality of life. Besides recommending treatments for CKD, early referral can assist in medication management and in minimizing exposure to potential nephrotoxins. In patients who progress to end-stage renal disease, having an established patient-PCP-nephrologist relationship can ease the transition to renal replacement therapy or transplantation.
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Affiliation(s)
- Mark D Baldwin
- Ohio University of Osteopathic Medicine, 3433 Alger Rd., Athens, OH, USA; Private Practice, Columbus Neighborhood Health Center, 3433 Agler Rd., Suite 2800, Columbus, OH 43219, USA.
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148
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Martín-Cleary C, Ortiz A. CKD hotspots around the world: where, why and what the lessons are. A CKJ review series. Clin Kidney J 2014; 7:519-23. [PMID: 25859368 PMCID: PMC4389150 DOI: 10.1093/ckj/sfu118] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 10/14/2014] [Indexed: 01/13/2023] Open
Abstract
Chronic kidney disease (CKD) is one of the three causes of death that has had the highest increase in the last 20 years. The increasing CKD burden occurs in the context of lack of access of most of the world population to adequate healthcare and an incomplete understanding of the pathogenesis of CKD. However, CKD is not homogeneously distributed. CKD hotspots are defined as countries, region, communities or ethnicities with higher than average incidence of CKD. Analysis of CKD hotspots has the potential to provide valuable insights into the pathogenesis of kidney disease and to improve the life expectancy of the affected communities. Examples include ethnicities such as African Americans in the USA or Aboriginals in Australia, regions such as certain Balkan valleys or Central America and even groups of people sharing common activities or interests such as young women trying to lose weight in Belgium. The study of these CKD hotspots has identified underlying genetic factors, such as ApoL1 gene variants, environmental toxins, such as aristolochic acid and socioeconomic factors leading to nutritional deprivation and inflammation/infection. The CKD hotspots series of CKJ reviews will explore the epidemiology and causes in CKD hotspots, beginning with Australian Aboriginals in this issue. An online map of CKD hotspots around the world will feature the reviewed hotspots, highlighting known or suspected causes as well as ongoing projects to unravel the cause and providing a directory of public health officials, physicians and basic scientists involved in these efforts. Since the high prevalence of CKD in a particular region or population may only be known to local physicians, we encourage readers to propose further CKD hotspots to be reviewed.
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Affiliation(s)
- Catalina Martín-Cleary
- IIS-Fundacion Jimenez Diaz, School of Medicine , Universidad Autonoma de Madrid, Fundacion Renal Iñigo Alvarez de Toledo-IRSIN and REDINREN , Madrid , Spain
| | - Alberto Ortiz
- IIS-Fundacion Jimenez Diaz, School of Medicine , Universidad Autonoma de Madrid, Fundacion Renal Iñigo Alvarez de Toledo-IRSIN and REDINREN , Madrid , Spain
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149
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Venkatachalam MA. Could Autophagic Exhaustion Be a Final Common Pathway for Podocytopathy in FSGS? J Am Soc Nephrol 2014; 26:999-1001. [PMID: 25406340 DOI: 10.1681/asn.2014090919] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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150
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Rethinking hypertensive kidney disease: arterionephrosclerosis as a genetic, metabolic, and inflammatory disorder. Curr Opin Nephrol Hypertens 2014; 22:266-72. [PMID: 23470819 DOI: 10.1097/mnh.0b013e3283600f8c] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
PURPOSE OF REVIEW Hypertension is the attributed cause of approximately 30% of end-stage kidney disease cases in the United States, but there has been controversy as to whether benign hypertension is a cause of chronic kidney disease. RECENT FINDINGS The histology of chronic kidney disease attributed to nonmalignant hypertension is arterionephrosclerosis, with pathology in the terminal branches of the interlobular arteries, together with global glomerulosclerosis. The identification of coding region variants in APOL1, encoding apolipoprotein L1, has opened a new perspective on this debate. These variants are restricted to populations of recent African descent and are strongly associated with clinically diagnosed arterionephrosclerosis, particularly when there is moderate-grade or high-grade proteinuria or progression to more advanced levels of kidney dysfunction. Nevertheless, not all African Americans with hypertension who progress to end-stage kidney disease have two APOL1 risk variants, and individuals of European and Asian descent also manifest arterionephrosclerosis. Further, we do not understand the mechanisms by which APOL1 initiates pathology in the renal microcirculation. SUMMARY APOL1 nephropathy comprises a disease spectrum (perhaps with distinct endophenotypes), including focal segmental glomerulosclerosis, collapsing glomerulopathy, and arterionephrosclerosis. The terms hypertensive kidney disease and hypertensive nephrosclerosis have outlived their usefulness. It may be time to use the established, etiologically neutral term, arterionephrosclerosis, to consider whether this is a disease rather than a pathologic description, and to determine the causal role of various clinical correlates including aging, obesity, hyperlipidemia, smoking, chronic inflammation, and oxidative stress.
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