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Lin HP, Singla B, Ahn W, Ghoshal P, Blahove M, Cherian-Shaw M, Chen A, Haller A, Hui DY, Dong K, Zhou J, White J, Stranahan AM, Jasztal A, Lucas R, Stansfield BK, Fulton D, Chlopicki S, Csányi G. Receptor-independent fluid-phase macropinocytosis promotes arterial foam cell formation and atherosclerosis. Sci Transl Med 2022; 14:eadd2376. [PMID: 36130017 PMCID: PMC9645012 DOI: 10.1126/scitranslmed.add2376] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Accumulation of lipid-laden foam cells in the arterial wall plays a central role in atherosclerotic lesion development, plaque progression, and late-stage complications of atherosclerosis. However, there are still fundamental gaps in our knowledge of the underlying mechanisms leading to foam cell formation in atherosclerotic arteries. Here, we investigated the role of receptor-independent macropinocytosis in arterial lipid accumulation and pathogenesis of atherosclerosis. Genetic inhibition of fluid-phase macropinocytosis in myeloid cells (LysMCre+ Nhe1fl/fl) and repurposing of a Food and Drug Administration (FDA)-approved drug that inhibits macrophage macropinocytosis substantially decreased atherosclerotic lesion development in low-density lipoprotein (LDL) receptor-deficient and Apoe-/- mice. Stimulation of macropinocytosis using genetic (H-RASG12V) and physiologically relevant approaches promoted internalization of unmodified native (nLDL) and modified [e.g., acetylated (ac) and oxidized (ox) LDL] lipoproteins in both wild-type and scavenger receptor (SR) knockout (Cd36-/-/Sra-/-) macrophages. Pharmacological inhibition of macropinocytosis in hypercholesterolemic wild-type and Cd36-/-/Sra-/- mice identified an important role of macropinocytosis in LDL uptake by lesional macrophages and development of atherosclerosis. Furthermore, serial section high-resolution imaging, LDL immunolabeling, and three-dimensional (3D) reconstruction of subendothelial foam cells provide visual evidence of lipid macropinocytosis in both human and murine atherosclerotic arteries. Our findings complement the SR paradigm of atherosclerosis and identify a therapeutic strategy to counter the development of atherosclerosis and cardiovascular disease.
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Affiliation(s)
- Hui-Ping Lin
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
| | - Bhupesh Singla
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
| | - WonMo Ahn
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
| | - Pushpankur Ghoshal
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
| | - Maria Blahove
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
| | - Mary Cherian-Shaw
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
| | - Alex Chen
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
| | - April Haller
- Department of Pathology, University of Cincinnati College of Medicine, USA
| | - David Y. Hui
- Department of Pathology, University of Cincinnati College of Medicine, USA
| | - Kunzhe Dong
- Department of Pharmacology & Toxicology, Medical College of Georgia, Augusta University, USA
| | - Jiliang Zhou
- Department of Pharmacology & Toxicology, Medical College of Georgia, Augusta University, USA
| | - Joseph White
- Department of Pathology, Medical College of Georgia, Augusta University, USA
| | - Alexis M. Stranahan
- Department of Neuroscience & Regenerative Medicine, Medical College of Georgia, Augusta University, USA
| | - Agnieszka Jasztal
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Krakow, Poland
| | - Rudolf Lucas
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
- Department of Pharmacology & Toxicology, Medical College of Georgia, Augusta University, USA
| | - Brian K. Stansfield
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
- Department of Pediatrics, Medical College of Georgia, Augusta University, USA
| | - David Fulton
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
- Department of Pharmacology & Toxicology, Medical College of Georgia, Augusta University, USA
| | - Stefan Chlopicki
- Jagiellonian Centre for Experimental Therapeutics, Jagiellonian University, Krakow, Poland
| | - Gábor Csányi
- Vascular Biology Center, Medical College of Georgia, Augusta University, USA
- Department of Pharmacology & Toxicology, Medical College of Georgia, Augusta University, USA
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2
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Parton A, McGilligan V, Chemaly M, O’Kane M, Watterson S. New models of atherosclerosis and multi-drug therapeutic interventions. Bioinformatics 2018; 35:2449-2457. [DOI: 10.1093/bioinformatics/bty980] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 11/05/2018] [Accepted: 12/05/2018] [Indexed: 12/16/2022] Open
Abstract
Abstract
Motivation
Atherosclerosis is amongst the leading causes of death globally. However, it is challenging to study in vivo or in vitro and no detailed, openly-available computational models exist. Clinical studies hint that pharmaceutical therapy may be possible. Here, we develop the first detailed, computational model of atherosclerosis and use it to develop multi-drug therapeutic hypotheses.
Results
We assembled a network describing atheroma development from the literature. Maps and mathematical models were produced using the Systems Biology Graphical Notation and Systems Biology Markup Language, respectively. The model was constrained against clinical and laboratory data. We identified five drugs that together potentially reverse advanced atheroma formation.
Availability and implementation
The map is available in the Supplementary Material in SBGN-ML format. The model is available in the Supplementary Material and from BioModels, a repository of SBML models, containing CellDesigner markup.
Supplementary information
Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Andrew Parton
- Northern Ireland Centre for Stratified Medicine, School of Biomedical Sciences, Ulster University, Altnagelvin Hospital Campus, Derry, Co Londonderry, UK
| | - Victoria McGilligan
- Northern Ireland Centre for Stratified Medicine, School of Biomedical Sciences, Ulster University, Altnagelvin Hospital Campus, Derry, Co Londonderry, UK
| | - Melody Chemaly
- Northern Ireland Centre for Stratified Medicine, School of Biomedical Sciences, Ulster University, Altnagelvin Hospital Campus, Derry, Co Londonderry, UK
| | - Maurice O’Kane
- Western Health and Social Care Trust, Altnagelvin Hospital, Derry, Co Londonderry, UK
| | - Steven Watterson
- Northern Ireland Centre for Stratified Medicine, School of Biomedical Sciences, Ulster University, Altnagelvin Hospital Campus, Derry, Co Londonderry, UK
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3
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Abstract
PURPOSE OF REVIEW Lipoprotein-induced intracellular lipid accumulation (foam cell formation) is a trigger of atherogenesis at the subendothelial arterial cell level. The purpose of this review is to describe the recent data related to the possible mechanisms of LDL-induced formation of lipid-laden foam cells and their role in the onset and development of atherosclerotic lesion. RECENT FINDINGS The most interesting current studies are related to the factors affecting foam cell formation. SUMMARY The phenomenon of lipid accumulation in cultured cells became the basis for creating a cellular test system that has already been successfully applied for development of drugs possessing direct antiatherosclerotic activity, and then the efficacy of these drugs was demonstrated in clinical studies. Moreover, this test system could be used for diagnostic assessing lipoproteins atherogenicity.
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Affiliation(s)
- Alexander N Orekhov
- Laboratory of Angiopatology, Institute of General Pathology and Pathophysiology
- Institute for Atherosclerosis Research, Skolkovo Innovative Center, Moscow, Russia
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4
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Barthwal MK, Anzinger JJ, Xu Q, Bohnacker T, Wymann MP, Kruth HS. Fluid-phase pinocytosis of native low density lipoprotein promotes murine M-CSF differentiated macrophage foam cell formation. PLoS One 2013; 8:e58054. [PMID: 23536783 PMCID: PMC3594233 DOI: 10.1371/journal.pone.0058054] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Accepted: 01/31/2013] [Indexed: 12/21/2022] Open
Abstract
During atherosclerosis, low-density lipoprotein (LDL)-derived cholesterol accumulates in macrophages to form foam cells. Macrophage uptake of LDL promotes foam cell formation but the mechanism mediating this process is not clear. The present study investigates the mechanism of LDL uptake for macrophage colony-stimulating factor (M-CSF)-differentiated murine bone marrow-derived macrophages. LDL receptor-null (LDLR−/−) macrophages incubated with LDL showed non-saturable accumulation of cholesterol that did not down-regulate for the 24 h examined. Incubation of LDLR−/− macrophages with increasing concentrations of 125I-LDL showed non-saturable macrophage LDL uptake. A 20-fold excess of unlabeled LDL had no effect on 125I-LDL uptake by wild-type macrophages and genetic deletion of the macrophage scavenger receptors CD36 and SRA did not affect 125I-LDL uptake, showing that LDL uptake occurred by fluid-phase pinocytosis independently of receptors. Cholesterol accumulation was inhibited approximately 50% in wild-type and LDLR−/− mice treated with LY294002 or wortmannin, inhibitors of all classes of phosphoinositide 3-kinases (PI3K). Time-lapse, phase-contrast microscopy showed that macropinocytosis, an important fluid-phase uptake pathway in macrophages, was blocked almost completely by PI3K inhibition with wortmannin. Pharmacological inhibition of the class I PI3K isoforms alpha, beta, gamma or delta did not affect macrophage LDL-derived cholesterol accumulation or macropinocytosis. Furthermore, macrophages from mice expressing kinase-dead class I PI3K beta, gamma or delta isoforms showed no decrease in cholesterol accumulation or macropinocytosis when compared with wild-type macrophages. Thus, non-class I PI3K isoforms mediated macropinocytosis in these macrophages. Further characterization of the components necessary for LDL uptake, cholesterol accumulation, and macropinocytosis identified dynamin, microtubules, actin, and vacuolar type H(+)-ATPase as contributing to uptake. However, Pak1, Rac1, and Src-family kinases, which mediate fluid-phase pinocytosis in certain other cell types, were unnecessary. In conclusion, our findings provide evidence that targeting those components mediating macrophage macropinocytosis with inhibitors may be an effective strategy to limit macrophage accumulation of LDL-derived cholesterol in arteries.
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Affiliation(s)
- Manoj K. Barthwal
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Joshua J. Anzinger
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Qing Xu
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Thomas Bohnacker
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | | | - Howard S. Kruth
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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Meyer JM, Ji A, Cai L, van der Westhuyzen DR. High-capacity selective uptake of cholesteryl ester from native LDL during macrophage foam cell formation. J Lipid Res 2012; 53:2081-2091. [PMID: 22833685 PMCID: PMC3435541 DOI: 10.1194/jlr.m026534] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Macrophage foam cells are a defining pathologic feature of atherosclerotic lesions. Recent studies have demonstrated that at high concentrations associated with hypercholesterolemia, native LDL induces macrophage lipid accumulation. LDL particles are taken up by macrophages as part of bulk fluid pinocytosis. However, the uptake and metabolism of cholesterol from native LDL during foam cell formation has not been clearly defined. Previous reports have suggested that selective cholesteryl ester (CE) uptake might contribute to cholesterol uptake from LDL independently of particle endocytosis. In this study we demonstrate that the majority of macrophage LDL-derived cholesterol is acquired by selective CE uptake in excess of LDL pinocytosis and degradation. Macrophage selective CE uptake does not saturate at high LDL concentrations and is not down-regulated during cholesterol accumulation. In contrast to CE uptake, macrophages exhibit little selective uptake of free cholesterol (FC) from LDL. Following selective uptake from LDL, CE is rapidly hydrolyzed by a novel chloroquine-sensitive pathway. FC released from LDL-derived CE hydrolysis is largely effluxed from cells but also is subject to ACAT-mediated reesterification. These results indicate that selective CE uptake plays a major role in macrophage metabolism of LDL.
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Affiliation(s)
- Jason M Meyer
- Departments of Internal Medicine and Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536
| | - Ailing Ji
- Department of Veterans Affairs Medical Center, Lexington, KY 40502; Departments of Internal Medicine and Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536; Barnstable Brown Kentucky Diabetes and Obesity Center, University of Kentucky, Lexington, KY 40536
| | - Lei Cai
- Department of Veterans Affairs Medical Center, Lexington, KY 40502; Departments of Internal Medicine and Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536; Barnstable Brown Kentucky Diabetes and Obesity Center, University of Kentucky, Lexington, KY 40536
| | - Deneys R van der Westhuyzen
- Department of Veterans Affairs Medical Center, Lexington, KY 40502; Departments of Internal Medicine and Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536; Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY 40536; Barnstable Brown Kentucky Diabetes and Obesity Center, University of Kentucky, Lexington, KY 40536.
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6
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Estronca LMBB, Silva JCP, Sampaio JL, Shevchenko A, Verkade P, Vaz ADN, Vaz WLC, Vieira OV. Molecular etiology of atherogenesis--in vitro induction of lipidosis in macrophages with a new LDL model. PLoS One 2012; 7:e34822. [PMID: 22514671 PMCID: PMC3325953 DOI: 10.1371/journal.pone.0034822] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Accepted: 03/06/2012] [Indexed: 02/02/2023] Open
Abstract
Background Atherosclerosis starts by lipid accumulation in the arterial intima and progresses into a chronic vascular inflammatory disease. A major atherogenic process is the formation of lipid-loaded macrophages in which a breakdown of the endolysomal pathway results in irreversible accumulation of cargo in the late endocytic compartments with a phenotype similar to several forms of lipidosis. Macrophages exposed to oxidized LDL exihibit this phenomenon in vitro and manifest an impaired degradation of internalized lipids and enhanced inflammatory stimulation. Identification of the specific chemical component(s) causing this phenotype has been elusive because of the chemical complexity of oxidized LDL. Methodology/Principal Findings Lipid “core aldehydes" are formed in oxidized LDL and exist in atherosclerotic plaques. These aldehydes are slowly oxidized in situ and (much faster) by intracellular aldehyde oxidizing systems to cholesteryl hemiesters. We show that a single cholesteryl hemiester incorporated into native, non-oxidized LDL induces a lipidosis phenotype with subsequent cell death in macrophages. Internalization of the cholesteryl hemiester via the native LDL vehicle induced lipid accumulation in a time- and concentration-dependent manner in “frozen" endolysosomes. Quantitative shotgun lipidomics analysis showed that internalized lipid in cholesteryl hemiester-intoxicated cells remained largely unprocessed in those lipid-rich organelles. Conclusions/Significance The principle elucidated with the present cholesteryl hemiester-containing native-LDL model, extended to other molecular components of oxidized LDL, will help in defining the molecular etiology and etiological hierarchy of atherogenic agents.
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Affiliation(s)
- Luis M. B. B. Estronca
- Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, Coimbra, Portugal
| | - Joao C. P. Silva
- Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, Coimbra, Portugal
| | - Julio L. Sampaio
- Max-Planck Institute for Molecular Cell Biology and Genetics. Pfotenhauerstrasse, Dresden, Germany
| | - Andrej Shevchenko
- Max-Planck Institute for Molecular Cell Biology and Genetics. Pfotenhauerstrasse, Dresden, Germany
| | - Paul Verkade
- Schools of Biochemistry, and Physiology and Pharmacology, Medical Sciences, University of Bristol, Bristol, United Kingdom
| | - Alfin D. N. Vaz
- Pharmacokinetics, Dynamics & Metabolism, Pfizer Global Research and Development, Groton, Connecticut, United States of America
| | | | - Otilia V. Vieira
- Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, Coimbra, Portugal
- * E-mail:
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7
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Anzinger JJ, Chang J, Xu Q, Barthwal MK, Bohnacker T, Wymann MP, Kruth HS. Murine bone marrow-derived macrophages differentiated with GM-CSF become foam cells by PI3Kγ-dependent fluid-phase pinocytosis of native LDL. J Lipid Res 2011; 53:34-42. [PMID: 22058424 DOI: 10.1194/jlr.m018887] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Accumulation of cholesterol by macrophage uptake of LDL is a key event in the formation of atherosclerotic plaques. Previous research has shown that granulocyte-macrophage colony-stimulating factor (GM-CSF) is present in atherosclerotic plaques and promotes aortic lipid accumulation. However, it has not been determined whether murine GM-CSF-differentiated macrophages take up LDL to become foam cells. GM-CSF-differentiated macrophages from LDL receptor-null mice were incubated with LDL, resulting in massive macrophage cholesterol accumulation. Incubation of LDL receptor-null or wild-type macrophages with increasing concentrations of ¹²⁵I-LDL showed nonsaturable macrophage LDL uptake that was linearly related to the amount of LDL added, indicating that LDL uptake was mediated by fluid-phase pinocytosis. Previous studies suggest that phosphoinositide 3-kinases (PI3K) mediate macrophage fluid-phase pinocytosis, although the isoform mediating this process has not been determined. Because PI3Kγ is known to promote aortic lipid accumulation, we investigated its role in mediating macrophage fluid-phase pinocytosis of LDL. Wild-type macrophages incubated with LDL and the PI3Kγ inhibitor AS605240 or PI3Kγ-null macrophages incubated with LDL showed an ∼50% reduction in LDL uptake and cholesterol accumulation compared with wild-type macrophages incubated with LDL only. These results show that GM-CSF-differentiated murine macrophages become foam cells by fluid-phase pinocytosis of LDL and identify PI3Kγ as contributing to this process.
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Affiliation(s)
- Joshua J Anzinger
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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8
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Kruth HS. Receptor-independent fluid-phase pinocytosis mechanisms for induction of foam cell formation with native low-density lipoprotein particles. Curr Opin Lipidol 2011; 22:386-93. [PMID: 21881499 PMCID: PMC4174540 DOI: 10.1097/mol.0b013e32834adadb] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
PURPOSE OF REVIEW Because early findings indicated that native low-density lipoprotein (LDL) did not substantially increase macrophage cholesterol content during in-vitro incubations, investigators presumed that LDL must be modified in some way to trigger its uptake by the macrophage. The purpose of this review is to discuss recent findings showing that native unmodified LDL can induce massive macrophage cholesterol accumulation mimicking macrophage foam cell formation that occurs within atherosclerotic plaques. RECENT FINDINGS Macrophages that show high rates of fluid-phase pinocytosis also show similar high rates of uptake of native unmodified LDL through nonreceptor mediated uptake within both macropinosomes and micropinosomes. Nonsaturable fluid-phase uptake of LDL by macrophages converts the macrophages into foam cells. Different macrophage phenotypes demonstrate either constitutive fluid-phase pinocytosis or inducible fluid-phase pinocytosis. Fluid-phase pinocytosis has been demonstrated by macrophages within mouse atherosclerotic plaques indicating that this pathway contributes to plaque macrophage cholesterol accumulation. SUMMARY Contrary to what has been believed previously, macrophages can take up large amounts of native unmodified LDL by receptor-independent, fluid-phase pinocytosis converting these macrophages into foam cells. Thus, targeting macrophage fluid-phase pinocytosis should be considered when investigating strategies to limit macrophage cholesterol accumulation in atherosclerotic plaques.
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Affiliation(s)
- Howard S Kruth
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland 20892-1422, USA.
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9
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Anzinger JJ, Chang J, Xu Q, Buono C, Li Y, Leyva FJ, Park BC, Greene LE, Kruth HS. Native low-density lipoprotein uptake by macrophage colony-stimulating factor-differentiated human macrophages is mediated by macropinocytosis and micropinocytosis. Arterioscler Thromb Vasc Biol 2010; 30:2022-31. [PMID: 20634472 DOI: 10.1161/atvbaha.110.210849] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE To examine the pinocytotic pathways mediating native low-density lipoprotein (LDL) uptake by human macrophage colony-stimulating factor-differentiated macrophages (the predominant macrophage phenotype in human atherosclerotic plaques). METHODS AND RESULTS We identified the kinase inhibitor SU6656 and the Rho GTPase inhibitor toxin B as inhibitors of macrophage fluid-phase pinocytosis of LDL. Assessment of macropinocytosis by time-lapse microscopy revealed that both drugs almost completely inhibited macropinocytosis, although LDL uptake and cholesterol accumulation by macrophages were only partially inhibited (approximately 40%) by these agents. Therefore, we investigated the role of micropinocytosis in mediating LDL uptake in macrophages and identified bafilomycin A1 as an additional partial inhibitor (approximately 40%) of macrophage LDL uptake that targeted micropinocytosis. When macrophages were incubated with both bafilomycin A1 and SU6656, inhibition of LDL uptake was additive (reaching 80%), showing that these inhibitors target different pathways. Microscopic analysis of fluid-phase uptake pathways in these macrophages confirmed that LDL uptake occurs through both macropinocytosis and micropinocytosis. CONCLUSIONS Our findings show that human macrophage colony-stimulating factor-differentiated macrophages take up native LDL by macropinocytosis and micropinocytosis, underscoring the importance of both pathways in mediating LDL uptake by these cells.
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Affiliation(s)
- Joshua J Anzinger
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Md 20892-1422, USA
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10
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Yao W, Li K, Liao K. Macropinocytosis contributes to the macrophage foam cell formation in RAW264.7 cells. Acta Biochim Biophys Sin (Shanghai) 2009; 41:773-80. [PMID: 19727526 DOI: 10.1093/abbs/gmp066] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The key event in the atherosclerosis development is the lipids uptake by macrophage and the formation of foam cell in subendothelial arterial space. Besides the uptake of modified low-density lipoprotein (LDL) by scavenger receptor-mediated endocytosis, macrophages possess constitutive macropinocytosis, which is capable of taking up a large quantity of solute. Macrophage foam cell formation could be induced in RAW264.7 cells by increasing the serum concentration in the culture medium. Foam cell formation induced by serum could be blocked by phosphoinositide 3-kinase inhibitor, LY294002 or wortmannin, which inhibited macropinocytosis but not receptor-mediated endocytosis. Further analysis indicated that macropinocytosis took place at the gangliosides-enriched membrane area. Cholesterol depletion by beta-methylcyclodextrin-blocked macropinocytosis without affecting scavenger receptor-mediated endocytosis of modified LDLs. These results suggested that macropinocytosis might be one of the important mechanisms for lipid uptake in macrophage. And it made significant contribution to the lipid accumulation and foam cell formation.
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Affiliation(s)
- Wenqi Yao
- Department of Hematology, Xiangya Hospital, Central South University, Changsha 410008, China
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11
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Buono C, Anzinger JJ, Amar M, Kruth HS. Fluorescent pegylated nanoparticles demonstrate fluid-phase pinocytosis by macrophages in mouse atherosclerotic lesions. J Clin Invest 2009; 119:1373-81. [PMID: 19363293 DOI: 10.1172/jci35548] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Accepted: 02/18/2009] [Indexed: 11/17/2022] Open
Abstract
The uptake of lipoproteins by macrophages is a critical step in the development of atherosclerotic lesions. Cultured monocyte-derived macrophages take up large amounts of native LDL by receptor-independent fluid-phase pinocytosis, either constitutively or in response to specific activating stimuli, depending on the macrophage phenotype. We therefore sought to determine whether fluid-phase pinocytosis occurs in vivo in macrophages in atherosclerotic lesions. We demonstrated that fluorescent pegylated nanoparticles similar in size to LDL (specifically nontargeted Qtracker quantum dot and AngioSPARK nanoparticles) can serve as models of LDL uptake by fluid-phase pinocytosis in cultured human monocyte-derived macrophages and mouse bone marrow-derived macrophages. Using fluorescence microscopy, we showed that atherosclerosis-prone Apoe-knockout mice injected with these nanoparticles displayed massive accumulation of the nanoparticles within CD68+ macrophages, including lipid-containing foam cells, in atherosclerotic lesions in the aortic arch. Similar results were obtained when atherosclerotic mouse aortas were cultured with nanoparticles in vitro. These results show that macrophages within atherosclerotic lesions can take up LDL-sized nanoparticles by fluid-phase pinocytosis and indicate that fluid-phase pinocytosis of LDL is a mechanism for macrophage foam cell formation in vivo.
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Affiliation(s)
- Chiara Buono
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute (NHLBI), NIH, Bethesda, Maryland 20892-1422, USA
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12
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Zhao B, Li Y, Buono C, Waldo SW, Jones NL, Mori M, Kruth HS. Constitutive receptor-independent low density lipoprotein uptake and cholesterol accumulation by macrophages differentiated from human monocytes with macrophage-colony-stimulating factor (M-CSF). J Biol Chem 2006; 281:15757-62. [PMID: 16606620 DOI: 10.1074/jbc.m510714200] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recently, we have shown that macrophage uptake of low density lipoprotein (LDL) and cholesterol accumulation can occur by nonreceptor mediated fluid-phase macropinocytosis when macrophages are differentiated from human monocytes in human serum and the macrophages are activated by stimulation of protein kinase C (Kruth, H. S., Jones, N. L., Huang, W., Zhao, B., Ishii, I., Chang, J., Combs, C. A., Malide, D., and Zhang, W. Y. (2005) J. Biol. Chem. 280, 2352-2360). Differentiation of human monocytes in human serum produces a distinct macrophage phenotype. In this study, we examined the effect on LDL uptake of an alternative macrophage differentiation phenotype. Differentiation of macrophages from human monocytes in fetal bovine serum with macrophage-colony-stimulating factor (M-CSF) produced a macrophage phenotype demonstrating constitutive fluid-phase uptake of native LDL leading to macrophage cholesterol accumulation. Fluid-phase endocytosis of LDL by M-CSF human macrophages showed non-saturable uptake of LDL that did not down-regulate over 48 h. LDL uptake was mediated by continuous actin-dependent macropinocytosis of LDL by these M-CSF-differentiated macrophages. M-CSF is a cytokine present within atherosclerotic lesions. Thus, macropinocytosis of LDL by macrophages differentiated from monocytes under the influence of M-CSF is a plausible mechanism to account for macrophage foam cell formation in atherosclerotic lesions. This mechanism of macrophage foam cell formation does not depend on LDL modification or macrophage receptors.
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Affiliation(s)
- Bin Zhao
- Section of Experimental Atherosclerosis, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1422, USA
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13
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Kruth HS, Jones NL, Huang W, Zhao B, Ishii I, Chang J, Combs CA, Malide D, Zhang WY. Macropinocytosis Is the Endocytic Pathway That Mediates Macrophage Foam Cell Formation with Native Low Density Lipoprotein. J Biol Chem 2005; 280:2352-60. [PMID: 15533943 DOI: 10.1074/jbc.m407167200] [Citation(s) in RCA: 190] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Previously, we reported that fluid-phase endocytosis of native LDL by PMA-activated human monocytederived macrophages converted these macrophages into cholesterol-enriched foam cells (Kruth, H. S., Huang, W., Ishii, I., and Zhang, W. Y. (2002) J. Biol. Chem. 277, 34573-34580). Uptake of fluid by cells can occur either by micropinocytosis within vesicles (<0.1 microm diameter) or by macropinocytosis within vacuoles ( approximately 0.5-5.0 microm) named macropinosomes. The current investigation has identified macropinocytosis as the pathway for fluid-phase LDL endocytosis and determined signaling and cytoskeletal components involved in this LDL endocytosis. The phosphatidylinositol 3-kinase inhibitor, LY294002, which inhibits macropinocytosis but does not inhibit micropinocytosis, completely blocked PMA-activated macrophage uptake of fluid and LDL. Also, nystatin and filipin, inhibitors of micropinocytosis from lipid-raft plasma membrane domains, both failed to inhibit PMA-stimulated macrophage cholesterol accumulation. Time-lapse video phase-contrast microscopy and time-lapse digital confocal-fluorescence microscopy with fluorescent DiI-LDL showed that PMA-activated macrophages took up LDL in the fluid phase by macropinocytosis. Macropinocytosis of LDL depended on Rho GTPase signaling, actin, and microtubules. Bafilomycin A1, the vacuolar H+-ATPase inhibitor, inhibited degradation of LDL and caused accumulation of undegraded LDL within macropinosomes and multivesicular body endosomes. LDL in multivesicular body endosomes was concentrated >40-fold over its concentration in the culture medium consistent with macropinosome shrinkage by maturation into multivesicular body endosomes. Macropinocytosis of LDL taken up in the fluid phase without receptor-mediated binding of LDL is a novel endocytic pathway that generates macrophage foam cells. Macropinocytosis in macrophages and possibly other vascular cells is a new pathway to target for modulating foam cell formation in atherosclerosis.
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Affiliation(s)
- Howard S Kruth
- Section of Experimental Atherosclerosis, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1422, USA.
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14
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Kruth HS, Huang W, Ishii I, Zhang WY. Macrophage foam cell formation with native low density lipoprotein. J Biol Chem 2002; 277:34573-80. [PMID: 12118008 DOI: 10.1074/jbc.m205059200] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
This investigation has elucidated a mechanism for development of macrophage foam cells when macrophages are incubated with native low density lipoprotein (LDL). LDL is believed to be the main source of cholesterol that accumulates in monocyte-derived macrophages within atherosclerotic plaques, but native LDL has not previously been shown to cause substantial cholesterol accumulation when incubated with macrophages. We have found that activation of human monocyte-derived macrophages with phorbol 12-myristate 13-acetate (PMA) stimulates LDL uptake and degradation and acyl-CoA:cholesterol acyltransferase-mediated esterification of LDL-derived cholesterol, resulting in massive macrophage cholesterol accumulation that could exceed 400 nmol/mg of cell protein. Cholesterol accumulation showed a biphasic linear LDL concentration dependence with LDL levels as high as 4 mg/ml, similar to LDL levels in artery intima. Protein kinase C mediated the PMA-stimulated macrophage uptake of LDL because the protein kinase C inhibitors, Gö6983 and GF109203X, inhibited cholesterol accumulation. LDL receptors did not mediate macrophage cholesterol accumulation because accumulation occurred with reductively methylated LDL and in the presence of an anti-LDL receptor-blocking monoclonal antibody. LDL-induced cholesterol accumulation was not inhibited by antioxidants, was not accompanied by increased LDL binding to macrophages, did not depend on the apoB component of LDL, and was not down-regulated by prior cholesterol enrichment of macrophages. We have shown that the mechanism of LDL uptake by macrophages was PMA-stimulated endocytosis of LDL taken up as part of the bulk phase fluid (i.e. fluid phase endocytosis). The amount of LDL taken up with the bulk phase fluid was measured with [(3)H]sucrose and accounted for a minimum of 83% of the LDL cholesterol delivery and accumulation in PMA-activated macrophages. This novel mechanism of macrophage cholesterol accumulation shows that modification of LDL is not necessary for foam cell formation to occur. In addition, the findings direct attention to macrophage fluid phase endocytosis as a relevant pathway to target for modulating macrophage cholesterol accumulation in atherosclerosis.
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Affiliation(s)
- Howard S Kruth
- Section of Experimental Atherosclerosis, NHLBI/National Institutes of Health, Bldg. 10 Rm. 5N-113, 10 Center Drive, MSC 1422, Bethesda, MD 20892, USA.
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15
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Hazell LJ, Baernthaler G, Stocker R. Correlation between intima-to-media ratio, apolipoprotein B-100, myeloperoxidase, and hypochlorite-oxidized proteins in human atherosclerosis. Free Radic Biol Med 2001; 31:1254-62. [PMID: 11705704 DOI: 10.1016/s0891-5849(01)00717-1] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The oxidative modification of low-density lipoprotein (LDL) is thought to contribute to atherogenesis, and there is evidence that oxidants derived from myeloperoxidase (MPO) contribute to such oxidative damage. Using human iliac arteries we investigated the relationship between lesion stage indicated by the intima-to-media (I/M) ratio and the presence of apolipoprotein B-100 (apoB, a marker for LDL), MPO, and hypochlorite (HOCl)-oxidized proteins identified by immunohistochemistry in the intima, media, and adventitia. More staining for apoB, MPO, and HOCl-oxidized proteins was observed in diseased than healthy vessels. Diseased segments also stained more for the three parameters than healthy segments in the same diseased vessel, highlighting the variability that can occur within a single cross-section of a vessel. However, significant positive correlation between I/M ratio and positive staining for apoB, MPO, and HOCl-oxidized proteins in different segments of individual arteries were apparent in segments with an I/M ratio of > 1.8. Also, the overall extent of intimal staining for apoB, MPO, and HOCl-oxidized proteins increased with increasing I/M ratio. In addition, the extent of apoB staining was greater and appeared at comparatively lower I/M ratios than that of MPO and HOCl-oxidized proteins. Our results support a contribution to atherogenesis of all three parameters assessed, although MPO and HOCl-oxidized proteins appear to participate in the disease process at a later stage than apoB.
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Affiliation(s)
- L J Hazell
- Biochemistry Group, The Heart Research Institute, Sydney, NSW, Australia
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16
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Dehouck B, Fenart L, Dehouck MP, Pierce A, Torpier G, Cecchelli R. A new function for the LDL receptor: transcytosis of LDL across the blood-brain barrier. J Biophys Biochem Cytol 1997; 138:877-89. [PMID: 9265653 PMCID: PMC2138047 DOI: 10.1083/jcb.138.4.877] [Citation(s) in RCA: 400] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Lipoprotein transport across the blood-brain barrier (BBB) is of critical importance for the delivery of essential lipids to the brain cells. The occurrence of a low density lipoprotein (LDL) receptor on the BBB has recently been demonstrated. To examine further the function of this receptor, we have shown using an in vitro model of the BBB, that in contrast to acetylated LDL, which does not cross the BBB, LDL is specifically transcytosed across the monolayer. The C7 monoclonal antibody, known to interact with the LDL receptor-binding domain, totally blocked the transcytosis of LDL, suggesting that the transcytosis is mediated by the receptor. Furthermore, we have shown that cholesterol-depleted astrocytes upregulate the expression of the LDL receptor at the BBB. Under these conditions, we observed that the LDL transcytosis parallels the increase in the LDL receptor, indicating once more that the LDL is transcytosed by a receptor-mediated mechanism. The nondegradation of the LDL during the transcytosis indicates that the transcytotic pathway in brain capillary endothelial cells is different from the LDL receptor classical pathway. The switch between a recycling receptor to a transcytotic receptor cannot be explained by a modification of the internalization signals of the cytoplasmic domain of the receptor, since we have shown that LDL receptor messengers in growing brain capillary ECs (recycling LDL receptor) or differentiated cells (transcytotic receptor) are 100% identical, but we cannot exclude posttranslational modifications of the cytoplasmic domain, as demonstrated for the polymeric immunoglobulin receptor. Preliminary studies suggest that caveolae are likely to be involved in the potential transport of LDL from the blood to the brain.
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Affiliation(s)
- B Dehouck
- Institut National de la Santé et de la Recherche Médicale U325, Department of Atherosclerosis Institut Pasteur, Lille, France
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17
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Rangaswamy S, Penn MS, Saidel GM, Chisolm GM. Exogenous oxidized low-density lipoprotein injures and alters the barrier function of endothelium in rats in vivo. Circ Res 1997; 80:37-44. [PMID: 8978320 DOI: 10.1161/01.res.80.1.37] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Oxidation converts low-density lipoprotein (LDL) into a cytotoxin in vitro. Oxidized LDL exists in vivo in atherosclerotic lesions and possibly in plasma. Many cell functions are altered in vitro by oxidized LDL, but few have been examined in vivo. To test whether oxidized LDL could injure endothelial cells and alter endothelial permeability to macromolecules in vivo, we infused oxidized LDL, native LDL, or their solvent intravenously into rats. Subsequently, endothelial cell injury and proliferation were measured, and the transport into the aorta wall of the macromolecule horseradish peroxidase (HRP) was quantified. Transport data were analyzed using mathematical models of macromolecular transport; parameters were estimated by optimally fitting model-predicted HRP concentrations to experimental data. Compared with native LDL or solvent control infusion, oxidized LDL infusion increased (1) the number of injured aortic endothelial cells fivefold to sixfold at 36 hours, (2) proliferation of endothelial cells at 48 hours, (3) intimal and medial accumulations of HRP twofold to threefold at 48 hours, and (4) the permeability coefficient of the endothelium to HRP fourfold to fivefold at 48 hours. Hence, oxidized LDL administered in vivo can injure the endothelium, despite the presence of endogenous antioxidants, compromising the function of the endothelium as a permeability barrier.
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Affiliation(s)
- S Rangaswamy
- Department of Cell Biology, Cleveland Clinic Foundation, OH 44195, USA
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18
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Dabbagh AJ, Frei B. Human suction blister interstitial fluid prevents metal ion-dependent oxidation of low density lipoprotein by macrophages and in cell-free systems. J Clin Invest 1995; 96:1958-66. [PMID: 7560088 PMCID: PMC185833 DOI: 10.1172/jci118242] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
LDL in the circulation is well protected against oxidation by the highly efficient antioxidant defense mechanisms of human plasma. LDL oxidation contributing to atherosclerosis, therefore, has been hypothesized to take place in the interstitial fluid of the arterial wall. We investigated the antioxidant composition and the capacity to inhibit LDL oxidation of human suction blister interstitial fluid (SBIF), a suitable representative of interstitial fluid. We found that the concentrations in SBIF of the aqueous small-molecule antioxidants ascorbate and urate were, respectively, significantly higher (P < 0.05) and identical to plasma concentrations. In contrast, lipoprotein-associated lipids and lipid-soluble antioxidants (alpha-tocopherol, ubiquinol-10, lycopene, and beta-carotene) were present at only 8-23% of the concentrations in plasma. No lipid hydroperoxides could be detected ( < 5 nM) in either fluid. The capacity of serum and SBIF to protect LDL from oxidation was investigated in three metal ion-dependent systems: copper, iron, and murine macrophages in Ham's F-10 medium. In all three systems, addition of > or = 6% (vol/vol) of either serum or SBIF inhibited LDL oxidation by > 90%. The concentration that inhibited macrophage-mediated LDL oxidation by 50% was as low as 0.3% serum and 0.7% SBIF. The enzymatic or physical removal of ascorbate or urate and other low molecular weight components did not affect the ability of either fluid to prevent LDL oxidation, and the high molecular weight fraction was as protective as whole serum or SBIF. These data demonstrate that both serum and SBIF very effectively protect LDL from metal ion-dependent oxidation, most probably because of a cumulative metal-binding effect of several proteins. Our data suggest that LDL in the interstitial fluid of the arterial wall is very unlikely to get modified by metal ion-mediated oxidation.
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Affiliation(s)
- A J Dabbagh
- Whitaker Cardiovascular Institute, Boston University School of Medicine, Massachusetts 02118, USA
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19
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Structural and functional changes in LDL after modification with both 4-hydroxynonenal and malondialdehyde. J Lipid Res 1993. [DOI: 10.1016/s0022-2275(20)37708-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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20
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Steinbrecher UP, Lougheed M. Scavenger receptor-independent stimulation of cholesterol esterification in macrophages by low density lipoprotein extracted from human aortic intima. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1992; 12:608-25. [PMID: 1576122 DOI: 10.1161/01.atv.12.5.608] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There is a growing body of evidence that suggests that modification of low density lipoprotein (LDL) in the artery wall may contribute to atherogenesis. A number of physiologically plausible modifications have been studied in vitro, including oxidation, aggregation, formation of complexes with glycosaminoglycans, and generation of LDL-immune complexes. Several studies of the properties of LDL extracted from the aortic intima have been published, but these indicate disagreement about both the nature and the extent of modification of LDL in the artery wall. The objectives of the present study were to determine the nature and extent of modification of LDL extracted from both normal and diseased human aortic intimas and to correlate this with the rate of LDL uptake in cultured cells. Analyses were performed on LDLs isolated from aortic intimas obtained at autopsy or at the time of organ harvest from 33 subjects. LDL from normal intima showed no clear evidence of oxidation but had slightly increased electrophoretic mobility compared with native plasma LDL, whereas LDL from plaques or fatty streaks exhibited variable but usually modest signs of oxidative change. Aortic LDL was more rapidly degraded by cultured macrophages than was plasma LDL and resulted in a greater stimulation of cholesterol esterification. The degree of stimulation of cholesterol esterification was correlated with the extent of modification of LDL as reflected by the degree of apolipoprotein B fragmentation. However, in all aortic LDLs the extent of oxidative change, as assessed by electrophoretic mobility or other physical parameters, was less than that required for scavenger receptor-mediated uptake. In all cases where sufficient amounts of LDL were recovered to permit degradation experiments, the uptake of aortic LDL was nonsaturable and could not be inhibited by polyinosinic acid or acetylated LDL. Chromatography on Sepharose CL-4B showed that most LDLs isolated from plaque contained a fraction that eluted in the void volume, and the size of this void peak correlated well with the stimulation of cholesterol esterification. Electron microscopy showed that the high-molecular-weight fraction contained several different types of aggregates. Some appeared to be clusters of LDL-size particles, but large vesicular structures with numerous adherent LDL particles as well as lipid droplets were also identified. These results indicate that the accelerated uptake by macrophages of LDL isolated from the arterial intima can largely be attributed to phagocytosis of LDL-containing aggregates.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- U P Steinbrecher
- Department of Medicine, University of British Columbia, Vancouver, Canada
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21
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Abstract
Oxidation of LDL is proposed to accelerate atherogenesis by the following sequence of events. LDL accumulates in atherosclerotic plaques, presumably due to interaction with intimal proteoglycans. The LDL then undergoes oxidation, and aldehydic products of lipid peroxidation such as HNE or other aldehyde products derived from lipid peroxidation, induce blocking of lysine residues on apo B. This results in its recognition by the scavenger receptor on tissue macrophages at sites in which LDL concentrations are low. At sites in which the LDL concentration is high, modification with such products induces intermolecular cross-linking and particle aggregation. The aggregated, oxidized LDL particles are then phagocytosed by tissue macrophages to induce lipid loading of these cells and the formation of foam cells, a characteristic of the earliest atherosclerotic lesion. By these mechanisms oxidation of LDL accelerates atherogenesis.
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Affiliation(s)
- H F Hoff
- Department of Vascular Cell Biology and Atherosclerosis, Cleveland Clinic Foundation
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22
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Hoff HF, O'Neil J. Lesion-derived low density lipoprotein and oxidized low density lipoprotein share a lability for aggregation, leading to enhanced macrophage degradation. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1991; 11:1209-22. [PMID: 1911707 DOI: 10.1161/01.atv.11.5.1209] [Citation(s) in RCA: 118] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In this study we assessed whether low density lipoproteins (LDL) isolated from minced aortic atherosclerotic plaques obtained at autopsy (A-LDL) shared structural and functional properties with LDL oxidized by incubation with Cu2+ for 8-18 hours at 20 degrees C (Ox-LDL). Although both A-LDL and Ox-LDL represented monomeric particles about the size of LDL, both differed from LDL in that they showed an increase in electrophoretic mobility relative to LDL, an increase in cholesterol to protein ratio, and an increase in reactivity with a monoclonal antibody that recognizes epitopes on malondialdehyde (MDA)-modified proteins. In addition, both showed an increase in fluorescence at 360 nm excitation, 430 nm emission, an increase in fragmentation of apolipoprotein B with patterns that were quite similar, and an increase in recognition by the scavenger receptor on mouse peritoneal macrophages (MPMs) based on competition of 125I-A-LDL and 125I-Ox-LDL degradation by excess acetylated LDL. In addition, inhibition of degradation by MPMs of 125I-A-LDL and 125I-Ox-LDL by excess unlabeled Ox-LDL and A-LDL were similar. When MDA was added in increasing amounts to labeled LDL and A-LDL, less MDA was required to modify A-LDL than LDl to obtain ligands that were degraded by MPMs to the same degree. Finally, both A-LDL and Ox-LDL but not LDL underwent aggregation (increased metastability) when concentrated to levels exceeding 1 mg protein/ml and showed enhanced macrophage uptake via phagocytosis (inhibition by cytochalasin D). These results demonstrate that A-LDL and Ox-LDL share properties additional to those previously reported, suggesting that oxidation may be a major mode of modification of LDL accumulating in atherosclerotic lesions. This could lead to lipid loading of macrophages induced by phagocytosis of aggregated particles, in addition to unregulated uptake via the scavenger receptor of monomeric particles.
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Affiliation(s)
- H F Hoff
- Department of Vascular Cell Biology and Atherosclerosis, Cleveland Clinic Foundation, OH 44195
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23
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Hoff HF, O'Neil J, Cole TB. Macrophage degradation of LDL extracted from human aortic plaques: effect of isolation conditions. Exp Mol Pathol 1991; 54:72-86. [PMID: 1995320 DOI: 10.1016/0014-4800(91)90045-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Several laboratories have recently reported on the structural and functional characteristics of an LDL fraction isolated from atherosclerotic lesions, designated A-LDL. Given the wide variety of tissue sources and isolation conditions that have been employed, we have addressed whether several procedures currently used affect the interaction of A-LDL with macrophages, and, if so, by what mechanisms. We isolated A-LDL from human aortic plaques by ultracentrifugation and gel filtration chromatography. Although some differences in the chromatographic elution profiles on gel filtration were apparent between homogenized and nonhomogenized extracts, A-LDL isolated from the same pool of plaque minces with or without homogenization showed no differences in macrophage degradation or inhibition of this degradation by excess acetyl-LDL. A-LDL isolated from plaques obtained at surgery or at autopsy less than 12 hr after death also showed no major differences in macrophage recognition, suggesting that post-mortem changes were probably not affecting cell recognition. However, A-LDL particles underwent aggregation when subjected to concentration, when stored for periods of 2 weeks or more, or when subjected to vortexing. The aggregated A-LDL was degraded more readily by macrophages than unaggregated A-LDL, and inhibition of degradation of aggregated A-LDL by excess acetyl-LDL was less than for unaggregated A-LDL. Collectively, these studies show that although post-mortem changes and tissue homogenization do not appreciably affect the interaction of A-LDL with macrophages in culture, other isolation and preparation conditions have dramatic effects which could explain some of the diversity of A-LDL metabolism reported in the literature.
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Affiliation(s)
- H F Hoff
- Department of Vascular Cell Biology and Atherosclerosis, Cleveland Clinic Foundation, Ohio 44195
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24
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Kovanen PT. Mast cell granule-mediated uptake of low density lipoproteins by macrophages: a novel carrier mechanism leading to the formation of foam cells. Ann Med 1991; 23:551-9. [PMID: 1756025 DOI: 10.3109/07853899109150517] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Mast cells are present in the arterial intima, the site of atherogenesis. To gain insight into the possible role of mast cells in the formation of the cholesterol-loaded macrophage foam cells typical of both early and late atherosclerotic lesions, a model system was developed in which isolated rat serosal mast cells were incubated with mouse peritoneal macrophages in medium to which low-density lipoproteins (LDL) had been added. Stimulation of the mast cells was found to induce a 50-fold enhancement of LDL uptake by the macrophages, which concomitantly accumulated LDL-derived cholesterol. This process, called the "granule-mediated uptake of LDL", involves the following steps: (i) exocytosis of the cytoplasmic granules of the mast cells, (ii) escape of soluble granule components, such as histamine and a fraction of the granule heparin proteoglycans into the medium, leaving granule remnants consisting of neutral proteases embedded in a heparin proteoglycan matrix, (ii) binding of LDL to binding sites on the glycosaminoglycan side chains of the heparin proteoglycan component of the granule remnants, (iv) proteolytic degradation of the bound LDL by the neutral proteases of the granule remnants, (v) fusion of degraded LDL particles on the surfaces of the granule remnants, and (vi) phagocytosis of the LDL-laden granule remnants by the macrophages. Simultaneously, the soluble heparin proteoglycans, to which no proteolytic enzymes are bound, interact with LDL with formation of insoluble complexes which are also phagocytosed by the macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P T Kovanen
- Wihuri Research Institute, Helsinki, Finland
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25
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Nordestgaard BG, Hjelms E, Stender S, Kjeldsen K. Different efflux pathways for high and low density lipoproteins from porcine aortic intima. ARTERIOSCLEROSIS (DALLAS, TEX.) 1990; 10:477-85. [PMID: 2344303 DOI: 10.1161/01.atv.10.3.477] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
To study the efflux of high (HDL) and low (LDL) density lipoproteins from the arterial wall in vivo, a surgical model in pigs was used. An isolated segment of the lesion-free thoracic aorta was pulse labeled from the lumen of the artery with 3H-cholesteryl ester labeled HDL and 14C-cholesteryl ester labeled LDL. Subsequently, the labeled aortic segment was exposed to cold chase in vivo. The transfer of HDL cholesteryl ester from plasma into intima expressed as intimal clearance was three to seven times greater than that of LDL cholesteryl ester. At least 50%, but possibly as much as 95%, of the HDL cholesteryl ester that entered the arterial intima during a period of 4 hours penetrated the arterial wall beyond the internal elastic lamina. In contrast, less than 15% of the LDL cholesteryl ester that entered the arterial intima in the same period penetrated beyond the luminal layer. After 24 hours of cold chase in vivo, more than 80% of both labeled HDL esterified cholesterol and labeled LDL esterified cholesterol had disappeared from the arterial wall. Transmural profiles after 9 hours of cold chase showed that labeled HDL was present throughout the entire arterial wall, whereas labeled LDL in quantitative amounts was present only in the luminal layer. The results suggest that the most important efflux route for HDL esterified cholesterol is through the vasa vasorum and lymphatics in the outer media and adventitia, whereas LDL esterified cholesterol predominantly leaves intima via the lumen of the artery.
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Affiliation(s)
- B G Nordestgaard
- Department of Clinical Chemistry, University of Copenhagen, Denmark
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26
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Spring PM, Hoff HF. LDL accumulation in the grossly normal human iliac bifurcation and common iliac arteries. Exp Mol Pathol 1989; 51:179-85. [PMID: 2806471 DOI: 10.1016/0014-4800(89)90018-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We had previously used an electrophoretic transfer procedure to determine the topographic distribution of low density lipoprotein (LDL) accumulation in the aortic intima of normolipemic swine. In this present study we have employed a similar procedure to assess whether LDL-rich sites consistently demonstrate increased intimal thickening at the iliac bifurcation and common iliac arteries. The topographic distribution of LDL-rich sites was determined in the aortas of six subjects ranging in age from 16 to 36 years, by transferring LDL by electrophoresis from the tissue into an agarose gel containing anti-LDL, and then staining the immunofixed LDL in the gel for lipid. LDL-rich sites were found in all but two of these cases. On the basis of control studies establishing the level of nonspecific staining, we determined that the cutoff between LDL-rich and LDL-poor zones was 37 mg apoB protein/mm2 intimal surface area. Intimal thickening was found to be threefold greater in LDL-rich than in LDL-poor regions. These results confirm and extend earlier immunohistochemical studies suggesting a preferential accumulation of LDL at sites of intimal thickening in human arteries.
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Affiliation(s)
- P M Spring
- Department of Atherosclerosis Research, Cleveland Clinic Foundation, Ohio 44195
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27
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Affiliation(s)
- W D Thompson
- Department of Pathology, University of Aberdeen, Scotland, U.K
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Hoff HF, Beck GJ, Skibinski CI, Jürgens G, O'Neil J, Kramer J, Lytle B. Serum Lp(a) level as a predictor of vein graft stenosis after coronary artery bypass surgery in patients. Circulation 1988; 77:1238-44. [PMID: 2967127 DOI: 10.1161/01.cir.77.6.1238] [Citation(s) in RCA: 180] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Although the serum lipoprotein fraction Lp(a) has been associated with coronary artery atherosclerosis, its relationship to narrowing of saphenous vein grafts has not previously been elucidated. We therefore measured serum Lp(a) levels in 167 symptomatic patients undergoing cardiac catheterization who had had coronary artery bypass surgery 0.7 to 14.3 years earlier. Lp(a), total cholesterol, and total triglyceride levels were compared with the degree of saphenous vein graft stenosis to test for any association. Serum Lp(a) levels were significantly associated with the degree of stenosis of saphenous vein grafts (r = .24, p = .002). Mean Lp(a) levels (mg/dl) in the 135 patients with stenosis were almost double (32.0 +/- 32.7, mean +/- SD) those in the 32 patients with no graft stenosis (16.7 +/- 22.6; p = .002). Graft stenosis was not associated with previous myocardial infarction, hypertension, obesity, diabetes, or smoking. Serum cholesterol levels (mg/dl) were slightly higher in the stenosis group (251.3 +/- 69) than in the no-stenosis group (231.8 +/- 48.8), but the difference was of borderline significance (p = .06). A stepwise increase in mean Lp(a) was found in groups of patients with increasing vein graft stenosis. At a serum Lp(a) level of 31.6 mg/dl or above, 92% of the patients demonstrated vein graft stenosis. Thus, patients with elevated Lp(a) levels have an increased risk of developing saphenous vein graft stenosis after coronary bypass surgery.
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Affiliation(s)
- H F Hoff
- Department of Brain, Research, Cleveland Clinic Foundation, OH 44106
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Abstract
We have isolated, by anti-LDL affinity chromatography, apo B-containing lipoproteins from homogenates of atherosclerotic plaques excised from the human aorta. This fraction, called A-LP, has similarities with plasma LDL, such as having similar size and relative lipid composition, along with containing apo B. However, the fraction also contains some particles larger than LDL, it is more electronegative than LDL, the relative protein content is less than in LDL, and its apo B is highly degraded. A-LP is recognized by a high affinity binding site on mouse peritoneal macrophages (MPM), as suggested by dose-response curves of stimulation of cholesterol esterification. The interaction is inhibited by negatively-charged carbohydrates such as fucoidin, but excess A-LP did not inhibit the degradation of labeled acetyl-LDL by MPM, suggesting that the binding site recognizing A-LP may not be the scavenger receptor. Finally, stimulation of cholesterol esterification by A-LP in MPM is unregulated over a 48 hr time interval, leading to massive accumulations of cholesteryl esters and a transition of these MPM to a morphology characteristic of foam cells. It is possible that when monocytes enter the arterial intima at specific sites and become tissue macrophages, they internalize A-LP in an unregulated fashion. This, in turn, would make the monocyte-macrophage lipid-laden, and could explain the etiology of foam cells in fatty streak lesions. The modification in A-LP relative to P-LDL responsible for the enhanced recognition still needs to be elucidated.
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Daugherty A, Lange LG, Sobel BE, Schonfeld G. Aortic accumulation and plasma clearance of beta-VLDL and HDL: effects of diet-induced hypercholesterolemia in rabbits. J Lipid Res 1985. [DOI: 10.1016/s0022-2275(20)34298-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Krause BR. The roles of apolipoproteins B and E in lipid transport and atherosclerosis. Drug Dev Res 1985. [DOI: 10.1002/ddr.430060207] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Newton RS. Modulation of hepatic and extrahepatic LDL receptors: Involvement in the progression of atherosclerosis. Drug Dev Res 1985. [DOI: 10.1002/ddr.430060206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Smith EB, Ashall C. Low-density lipoprotein concentration in interstitial fluid from human atherosclerotic lesions. Relation to theories of endothelial damage and lipoprotein binding. BIOCHIMICA ET BIOPHYSICA ACTA 1983; 754:249-57. [PMID: 6197091 DOI: 10.1016/0005-2760(83)90139-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Increased endothelial permeability to low-density lipoprotein (LDL) is believed to be an initiating factor for atherosclerotic lesions. Concentrations of LDL, alpha 2-macroglobulin and albumin were measured by immunoassay in interstitial fluid collected from normal intima and atherosclerotic lesions of human aortas. The concentration of LDL in interstitial fluid from normal intima was twice the concentration in the patient's serum. In early proliferative (gelatinous) lesions the amount of interstitial fluid was consistently increased but its LDL concentration varied between 80 and 200% of adjacent normal intima. Highest concentrations of LDL were found in interstitial fluid from more advanced proliferative lesions, but the amount was reduced, suggesting a shift in tissue water. LDL was consistently low in interstitial fluid from fatty streaks comprised of lipid-filled cells, and in four of 12 lesions it was absent although alpha 2-macroglobulin and albumin concentrations were normal. Electrophoretic mobility of LDL, reflecting surface charge, was unchanged or increased in interstitial fluid from normal intima and fatty streaks, but decreased in gelatinous lesions. The ratio of LDL to alpha 2-macroglobulin and albumin in interstitial fluid was higher than in adjacent intact tissue. The results do not support the idea that increased endothelial permeability to LDL initiates atherogenesis.
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Smith EB, Ashall C. Variability of the electrophoretic mobility of low density lipoprotein. Comparison of interstitial fluid from human aortic intima and serum. Atherosclerosis 1983; 49:89-98. [PMID: 6197077 DOI: 10.1016/0021-9150(83)90010-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Interstitial fluid was collected from human aortic intima and the low density lipoprotein (LDL) was compared with serum LDL by two-dimensional immunoelectrophoresis. In half the samples derived from normal intima the migration rate was within +/- 10% of migration of LDL in serum, but in the remaining samples it was higher, indicating an increase in net negative charge on the molecule. By contrast, in most samples of interstitial fluid from gelatinous thickenings the migration rate of LDL was lower than in serum, indicating reduction in net negative charge. To test for the effect of different electrolyte concentrations in interstitial fluid and serum, migration of alpha 2-macroglobulin (alpha 2-M) was measured simultaneously in both. This showed no significant difference between interstitial fluid and serum, and varied by less than 2% between different serum samples. However, the mobility of LDL relative to alpha 2-M showed a remarkable variation, ranging from 80.9 to 127.1% of alpha 2-M mobility in interstitial fluid and from 58.6 to 115.9% in 23 serum samples. In serum, LDL relative mobility showed no correlation with general acid-base status, as indicated by serum bicarbonate levels, with fatty meals or diabetic keto-acidosis, or with extent of glycosylation of haemoglobin. This suggested that the variation in surface charge is intrinsic to the molecule and not a transient reflection of the plasma environment. Experimental alterations in the surface charge of LDL change its interaction with smooth muscle cells and macrophages in vitro, and its mitogenic properties. This raises the possibility that physiological variation in the surface charge of LDL in different subjects could alter its atherogenic potential.
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Heideman CL, Hoff HF. Lipoproteins containing apolipoprotein A-I extracted from human aortas. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 711:431-44. [PMID: 6809057 DOI: 10.1016/0005-2760(82)90057-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Apolipoprotein A-I was quantitated by electroimmunoassay in buffer-soluble fractions of both grossly normal intima and raised atherosclerosis lesions of the human aorta. The mean value for apolipoprotein A-I content in microgram/mg tissue dry weight of normal intima (12 cases) was 0.71 +/- 0.10 S.E. and of aortic plaques (19 cases) was 0.64 +/- 0.40 S.E. When compared to the buffer-extractable apolipoprotein B content measured in these same cases from both regions, the ratio of apolipoprotein B to apolipoprotein A-I was approximately 6. No apolipoprotein A-I was measurable in tunica media. Following differential ultracentrifugation into d less than 1.063, d 1.063-1.21 and d greater than 1.21 fractions, the distributions of recovered apolipoprotein A-I were, respectively: 1, 94 and 5% for normal intima, 19, 31 and 50% for plaques and 1, 89 and 10% for plasma. Characterization of a chromatographically purified d 1.063-1.21 or HDL density fraction from fatty-fibrous plaques demonstrated particles of between 60 and 120 A diameter, a characteristic apolipoprotein A-I band by SDS-polyacrylamide gel electrophoresis, and a precipitin peak closely migrating with that for plasma HDL by two-dimensional immunoelectrophoresis. The d greater than 1.21 density fraction from plaques isolated by affinity chromatography on a Sepharose-anti-apolipoprotein A-I column contained small amounts of phospholipid but no measurable cholesterol. The d 1.063-1.21 density fraction from plaques showed a significant increase in percent free cholesterol and phospholipid contents and decrease in cholesteryl ester content relative to plasma HDL. This increase in free cholesterol could represent evidence for an anti-atherogenic mechanism wherein infiltrated HDL removes cholesterol together with phospholipid from the arterial wall.
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Hoff HF, Gaubatz JW. Isolation, purification, and characterization of a lipoprotein containing Apo B from the human aorta. Atherosclerosis 1982; 42:273-97. [PMID: 7073805 DOI: 10.1016/0021-9150(82)90157-5] [Citation(s) in RCA: 117] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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