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Liu J, Gillard BK, Yelamanchili D, Gotto AM, Rosales C, Pownall HJ. High Free Cholesterol Bioavailability Drives the Tissue Pathologies in Scarb1 -/- Mice. Arterioscler Thromb Vasc Biol 2021; 41:e453-e467. [PMID: 34380332 PMCID: PMC8458258 DOI: 10.1161/atvbaha.121.316535] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective: Overall and atherosclerosis-associated mortality is elevated in humans with very high HDL (high-density lipoprotein) cholesterol concentrations. Mice with a deficiency of the HDL receptor, Scarb1 (scavenger receptor class B type 1), are a robust model of this phenotype and exhibit several additional pathologies. We hypothesized that the previously reported high plasma concentration of free cholesterol (FC)-rich HDL in Scarb1-/- mice produces a state of high HDL-FC bioavailability that increases whole-body FC and dysfunction in multiple tissue sites. Approach and Results: The higher mol% FC in Scarb1-/- versus WT (wild type) HDL (41.1 versus 16.0 mol%) affords greater FC bioavailability for transfer to multiple sites. Plasma clearance of autologous HDL-FC mass was faster in WT versus Scarb1-/- mice. FC influx from Scarb1-/- HDL to LDL (low-density lipoprotein) and J774 macrophages was greater ([almost equal to]4x) than that from WT HDL, whereas FC efflux capacity was similar. The higher mol% FC of ovaries, erythrocytes, heart, and macrophages of Scarb1-/- versus WT mice is associated with previously reported female infertility, impaired cell maturation, cardiac dysfunction, and atherosclerosis. The FC contents of other tissues were similar in the two genotypes, and these tissues were not associated with any overt pathology. In addition to the differences between WT versus Scarb1-/- mice, there were many sex-dependent differences in tissue-lipid composition and plasma FC clearance rates. Conclusions: Higher HDL-FC bioavailability among Scarb1-/- versus WT mice drives increased FC content of multiple cell sites and is a potential biomarker that is mechanistically linked to multiple pathologies.
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Affiliation(s)
- Jing Liu
- Department of Cardiovascular Medicine, Xiangya Hospital, Central South University, Changsha 410008, China
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston TX 77030, USA
| | - Baiba K. Gillard
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston TX 77030, USA
- Department of Medicine, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10065, USA
| | - Dedipya Yelamanchili
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston TX 77030, USA
| | - Antonio M. Gotto
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston TX 77030, USA
- Department of Medicine, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10065, USA
| | - Corina Rosales
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston TX 77030, USA
- Department of Medicine, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10065, USA
| | - Henry J. Pownall
- Center for Bioenergetics, Houston Methodist Research Institute, 6670 Bertner Avenue, Houston TX 77030, USA
- Department of Medicine, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10065, USA
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Hung AM, Tsuchida Y, Nowak KL, Sarkar S, Chonchol M, Whitfield V, Salas N, Dikalova A, Yancey PG, Huang J, Linton MF, Ikizler TA, Kon V. IL-1 Inhibition and Function of the HDL-Containing Fraction of Plasma in Patients with Stages 3 to 5 CKD. Clin J Am Soc Nephrol 2019; 14:702-711. [PMID: 31015261 PMCID: PMC6500942 DOI: 10.2215/cjn.04360418] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 03/15/2019] [Indexed: 12/24/2022]
Abstract
BACKGROUND AND OBJECTIVES Systemic inflammation modulates cardiovascular disease risk and functionality of HDL in the setting of CKD. Whether interventions that modify systemic inflammation can improve HDL function in CKD is unknown. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We conducted a post hoc analysis of two randomized, clinical trials, IL-1 trap in participants with GFR 15-59 ml/min per 1.73 m2 (study A) and IL-1 receptor antagonist in participants on maintenance hemodialysis (study B), to evaluate if IL-1 blockade had improved the anti-inflammatory activity (IL-6, TNF-α, and Nod-like receptor protein 3), antioxidant function (superoxide production), and net cholesterol efflux capacity of HDL. HDL function was measured using LPS-stimulated THP-1 macrophages or peritoneal macrophages of apoE-deficient mice exposed to the apoB-depleted, HDL-containing fraction obtained from the plasma of the study participants, collected before and after the interventions to block IL-1 effects. Analysis of covariance was used for between group comparisons. RESULTS The mean age of the participants was 60±13 years, 72% (n=33) were men, and 39% (n=18) were black. There were 32 CKD (16 IL-1 trap and 16 placebo) and 14 maintenance hemodialysis (7 IL-1 receptor antagonist and 7 placebo) participants. Compared with placebo, IL-1 inhibition, in study A and B reduced cellular expression of TNF-α by 15% (P=0.05) and 64% (P=0.02), IL-6 by 38% (P=0.004) and 56% (P=0.08), and Nod-like receptor protein 3 by 16% (P=0.01) and 25% (P=0.02), respectively. The intervention blunted superoxide production in the treated arm compared with placebo, with the values being higher by 17% in the placebo arm in study A (P<0.001) and 12% in the placebo arm in study B (P=0.004). Net cholesterol efflux capacity was not affected by either intervention. CONCLUSIONS IL-1 blockade improves the anti-inflammatory and antioxidative properties of the HDL-containing fraction of plasma in patients with stages 3-5 CKD, including those on maintenance hemodialysis.
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Affiliation(s)
- Adriana M Hung
- Division of Nephrology, Tennessee Valley Healthcare System, Nashville, Tennessee; .,Department of Medicine and
| | - Yohei Tsuchida
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee; and
| | - Kristen L Nowak
- Department of Medicine, University of Colorado Denver, Aurora, Colorado
| | | | - Michel Chonchol
- Department of Medicine, University of Colorado Denver, Aurora, Colorado
| | | | | | | | | | | | | | - T Alp Ikizler
- Division of Nephrology, Tennessee Valley Healthcare System, Nashville, Tennessee.,Department of Medicine and
| | - Valentina Kon
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee; and
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Abstract
Measuring cholesterol efflux involves the tracking of cholesterol movement out of cells. Cholesterol efflux is an essential mechanism to maintain cellular cholesterol homeostasis, and this process is largely regulated via the LXR transcription factors and their regulated genes, the ATP-binding cassette (ABC) cholesterol transporters ABCA1 and ABCG1. Typically, efflux assays are performed utilizing radiolabeled cholesterol tracers to label intracellular cholesterol pools, and these assays may be tailored to quantify the efflux of exogenously delivered cholesterol or alternatively the efflux of newly synthesized (endogenous) cholesterol, in different cell types (macrophages, hepatocytes). Cholesterol efflux may also be customized to quantify cholesterol flux out of the cell to various exogenous cholesterol acceptors, such as apolipoprotein A-I, high-density lipoprotein, or methyl-beta-cyclodextrin, depending on the purpose of the experiment. Here, we provide comprehensive protocols to quantify the net flux of cholesterol out of cells and recommendations on how this assay may be tailored as a function of the experimental question at hand.
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Anastasius M, Luquain-Costaz C, Kockx M, Jessup W, Kritharides L. A critical appraisal of the measurement of serum 'cholesterol efflux capacity' and its use as surrogate marker of risk of cardiovascular disease. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:1257-1273. [PMID: 30305243 DOI: 10.1016/j.bbalip.2018.08.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 08/02/2018] [Accepted: 08/03/2018] [Indexed: 12/15/2022]
Abstract
The 'cholesterol efflux capacity (CEC)' assay is a simple in vitro measure of the capacities of individual sera to promote the first step of the reverse cholesterol transport pathway, the delivery of cellular cholesterol to plasma HDL. This review describes the cell biology of this model and critically assesses its application as a marker of cardiovascular risk. We describe the pathways for cell cholesterol export, current cell models used in the CEC assay with their limitations and consider the contribution that measurement of serum CEC provides to our understanding of HDL function in vivo.
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Affiliation(s)
- Malcolm Anastasius
- ANZAC Research Institute, Concord Repatriation General Hospital, University of Sydney, Sydney, NSW, Australia
| | | | - Maaike Kockx
- ANZAC Research Institute, Concord Repatriation General Hospital, University of Sydney, Sydney, NSW, Australia
| | - Wendy Jessup
- ANZAC Research Institute, Concord Repatriation General Hospital, University of Sydney, Sydney, NSW, Australia
| | - Leonard Kritharides
- ANZAC Research Institute, Concord Repatriation General Hospital, University of Sydney, Sydney, NSW, Australia; Cardiology Department, Concord Repatriation General Hospital, University of Sydney, Sydney, NSW, Australia.
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5
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Manna PR, Sennoune SR, Martinez-Zaguilan R, Slominski AT, Pruitt K. Regulation of retinoid mediated cholesterol efflux involves liver X receptor activation in mouse macrophages. Biochem Biophys Res Commun 2015; 464:312-7. [PMID: 26119689 DOI: 10.1016/j.bbrc.2015.06.150] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 06/23/2015] [Indexed: 12/31/2022]
Abstract
Removal of cholesterol from macrophage-derived foam cells is a critical step to the prevention of atherosclerotic lesions. We have recently demonstrated the functional importance of retinoids in the regulation of the steroidogenic acute regulatory (StAR) protein that predominantly mediates the intramitochondrial transport of cholesterol in target tissues. In the present study, treatment of mouse macrophages with retinoids, particularly all-trans retinoic acid (atRA) and 9-cis RA, resulted in increases in cholesterol efflux to apolipoprotein AI (Apo-A1). Activation of the PKA pathway by a cAMP analog, (Bu)2cAMP, markedly augmented retinoid mediated cholesterol efflux. Macrophages overexpressing hormone-sensitive lipase increased the hydrolysis of cholesteryl esters and concomitantly enhanced the efficacy of retinoic acid receptor and liver X receptor (LXR) ligands on StAR and ATP-binding cassette transporter A1 (ABCA1) protein levels. RAs elevated StAR promoter activity in macrophages, and an increase in StAR levels augmented cholesterol efflux to Apo-A1, suggesting retinoid-mediated efflux of cholesterol involves enhanced oxysterol production. Further studies revealed that retinoids activate the LXR regulated genes, sterol receptor-element binding protein-1c and ABCA1. These findings provide insights into the regulatory events in which retinoid signaling effectively enhances macrophage cholesterol efflux and indicate that retinoid therapy may have important implications in limiting and/or regressing atherosclerotic cardiovascular disease.
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Affiliation(s)
- Pulak R Manna
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
| | - Souad R Sennoune
- Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Raul Martinez-Zaguilan
- Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Andrzej T Slominski
- Department of Dermatology, University of Alabama Birmingham, VA Medical Center, AL 35294, USA
| | - Kevin Pruitt
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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Potential Signal Transduction Regulation by HDL of the β2-Adrenergic Receptor Pathway. Implications in Selected Pathological Situations. Arch Med Res 2015; 46:361-71. [PMID: 26009249 DOI: 10.1016/j.arcmed.2015.05.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 05/12/2015] [Indexed: 01/09/2023]
Abstract
The main atheroprotective mechanism of high-density lipoprotein (HDL) has been regarded as reverse cholesterol transport, whereby cholesterol from peripheral tissues is removed and transported to the liver for elimination. Although numerous additional atheroprotective mechanisms have been suggested, the role of HDL in modulating signal transduction of cell membrane-bound receptors has received little attention to date. This potential was recently highlighted following the identification of a polymorphism in the adenylyl cyclase 9 gene (ADCY9) that was shown to be a determining factor in the risk of cardiovascular (CV) events in patients treated with the HDL-raising compound dalcetrapib. Indeed, ADCY9 is part of the signaling pathway of the β2-adrenergic receptor (β2-AR) and both are membrane-bound proteins affected by changes in membrane-rich cholesterol plasma membrane domains (caveolae). Numerous G-protein-coupled receptors (GPCRs) and ion channels are affected by caveolae, with caveolae composition acting as a 'signalosome'. Polymorphisms in the genes encoding ADCY9 and β2-AR are associated with response to β2-agonist drugs in patients with asthma, malaria and with sickle cell disease. Crystallization of the β2-AR has found cholesterol tightly bound to transmembrane structures of the receptor. Cholesterol has also been shown to modulate the activity of this receptor. Apolipoprotein A1 (ApoA1), the major protein component of HDL, destabilizes and removes cholesterol from caveolae with high affinity through interaction with ATP-binding cassette transporter. Furthermore, β2-AR activity may be affected by ApoA1/HDL-targeted therapies. Taken together, these observations suggest a common pathway that potentially links a primary HDL function to the regulation of signal transduction.
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Escolà-Gil JC, Lee-Rueckert M, Santos D, Cedó L, Blanco-Vaca F, Julve J. Quantification of In Vitro Macrophage Cholesterol Efflux and In Vivo Macrophage-Specific Reverse Cholesterol Transport. Methods Mol Biol 2015; 1339:211-233. [PMID: 26445792 DOI: 10.1007/978-1-4939-2929-0_15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Promotion of reverse cholesterol transport (RCT) is thought to be a major HDL-mediated mechanism for protecting against atherosclerosis. Preclinical studies support the concept that increasing cholesterol efflux from macrophages may confer atheroprotective benefits independently of the plasma HDL-cholesterol concentration. The application of the macrophage-to-feces RCT method in genetically engineered mice has provided evidence that this major HDL property correlates closely with changes in atherosclerosis susceptibility. This chapter provides details on the methodologies currently used to measure in vitro cholesterol efflux from macrophages or in vivo macrophage-specific RCT. The general principles and techniques described herein may be applied to measure the in vitro cholesterol efflux capacity of human serum in macrophage cultures and to evaluate the effect of different experimental pathophysiological conditions or the efficacy of different therapeutic strategies on the modulation of in vivo macrophage-RCT in mice.
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Affiliation(s)
- Joan Carles Escolà-Gil
- Institut de Recerca de l'Hospital de la Santa Creu i Sant Pau, Institut d'Investigacions Biomèdiques (IIB) Sant Pau, C/Antoni M. Claret 167, 08025, Barcelona, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas. CIBERDEM, Madrid, Spain
- Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Barcelona, Spain
| | | | - David Santos
- Institut de Recerca de l'Hospital de la Santa Creu i Sant Pau, Institut d'Investigacions Biomèdiques (IIB) Sant Pau, C/Antoni M. Claret 167, 08025, Barcelona, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas. CIBERDEM, Madrid, Spain
| | - Lídia Cedó
- Institut de Recerca de l'Hospital de la Santa Creu i Sant Pau, Institut d'Investigacions Biomèdiques (IIB) Sant Pau, C/Antoni M. Claret 167, 08025, Barcelona, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas. CIBERDEM, Madrid, Spain
| | - Francisco Blanco-Vaca
- Institut de Recerca de l'Hospital de la Santa Creu i Sant Pau, Institut d'Investigacions Biomèdiques (IIB) Sant Pau, C/Antoni M. Claret 167, 08025, Barcelona, Spain.
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas. CIBERDEM, Madrid, Spain.
- Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Barcelona, Spain.
| | - Josep Julve
- Institut de Recerca de l'Hospital de la Santa Creu i Sant Pau, Institut d'Investigacions Biomèdiques (IIB) Sant Pau, C/Antoni M. Claret 167, 08025, Barcelona, Spain.
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas. CIBERDEM, Madrid, Spain.
- Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Barcelona, Spain.
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8
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Sontag TJ, Chellan B, Bhanvadia CV, Getz GS, Reardon CA. Alginic acid cell entrapment: a novel method for measuring in vivo macrophage cholesterol homeostasis. J Lipid Res 2014; 56:470-83. [PMID: 25465389 DOI: 10.1194/jlr.d052985] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Macrophage conversion to atherosclerotic foam cells is partly due to the balance of uptake and efflux of cholesterol. Cholesterol efflux from cells by HDL and its apoproteins for subsequent hepatic elimination is known as reverse cholesterol transport. Numerous methods have been developed to measure in vivo macrophage cholesterol efflux. Most methods do not allow for macrophage recovery for analysis of changes in cellular cholesterol status. We describe a novel method for measuring cellular cholesterol balance using the in vivo entrapment of macrophages in alginate, which retains incorporated cells while being permeable to lipoproteins. Recipient mice were injected subcutaneously with CaCl2 forming a bubble into which a macrophage/alginate suspension was injected, entrapping the macrophages. Cells were recovered after 24 h. Cellular free and esterified cholesterol mass were determined enzymatically and normalized to cellular protein. Both normal and cholesterol loaded macrophages undergo measureable changes in cell cholesterol when injected into WT and apoA-I-, LDL-receptor-, or apoE-deficient mice. Cellular cholesterol balance is dependent on initial cellular cholesterol status, macrophage cholesterol transporter expression, and apolipoprotein deficiency. Alginate entrapment allows for the in vivo measurement of macrophage cholesterol homeostasis and is a novel platform for investigating the role of genetics and therapeutic interventions in atherogenesis.
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Affiliation(s)
| | - Bijoy Chellan
- Department of Pathology, University of Chicago, Chicago, IL
| | | | - Godfrey S Getz
- Department of Pathology, University of Chicago, Chicago, IL
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Kingwell BA, Chapman MJ, Kontush A, Miller NE. HDL-targeted therapies: progress, failures and future. Nat Rev Drug Discov 2014; 13:445-64. [DOI: 10.1038/nrd4279] [Citation(s) in RCA: 256] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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10
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Ray KK, Ditmarsch M, Kallend D, Niesor EJ, Suchankova G, Upmanyu R, Anzures-Cabrera J, Lehnert V, Pauly-Evers M, Holme I, Štásek J, van Hessen MWJ, Jones P. The effect of cholesteryl ester transfer protein inhibition on lipids, lipoproteins, and markers of HDL function after an acute coronary syndrome: the dal-ACUTE randomized trial. Eur Heart J 2014; 35:1792-800. [PMID: 24639426 DOI: 10.1093/eurheartj/ehu105] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
AIMS The effects of cholesteryl ester transfer protein (CETP) inhibition on lipids, inflammation, and markers of high-density lipoprotein (HDL) function, following an acute coronary syndrome (ACS), are unknown. METHODS AND RESULTS The dal-ACUTE study randomized 300 patients (1 : 1) to dalcetrapib 600 mg/day or placebo within 1 week of an ACS. The primary endpoint was per cent change in HDL-cholesterol (HDL-C) after 4 weeks. Secondary endpoints included apolipoprotein levels, markers of HDL function, and inflammation. Dalcetrapib treatment increased HDL-C and apolipoprotein A1 by 33.7 and 11.8%, respectively (both P < 0.001) and total cholesterol efflux by 9.5% (P = 0.003) after 4 weeks, principally via an increase in non-ATP-binding cassette transporter (ABC) A1-mediated efflux, without statistically significant changes in pre-β1-HDL levels. The increase in total efflux with dalcetrapib correlated most strongly with increases in apolipoprotein A1 and HDL-C (r = 0.46 and 0.43, respectively) rather than the increase in pre-β1-HDL (r = 0.32). Baseline and on-treatment ABCA1-mediated efflux correlated most strongly with pre-β1-HDL levels; in contrast, non-ABCA1-mediated efflux correlated better with apolipoprotein A1 and HDL-C levels. CONCLUSIONS High-density lipoprotein raised through CETP inhibition with dalcetrapib improves cholesterol efflux, principally via a non-ABCA1-mediated pathway. While HDL-C was increased by one-third, apolipoprotein A1 and total efflux were increased only by one-tenth, supporting the concept of dissociation between improvements in HDL function and HDL-C levels, which may be of relevance to ongoing trials and the development of therapeutic interventions targeting HDL.
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Affiliation(s)
- Kausik K Ray
- Cardiovascular Sciences Research Centre, St George's University of London, Cranmer Terrace, London, SW17 ORE UK
| | | | | | | | | | | | | | | | | | - Ingar Holme
- Department of Endocrinology, Obesity and Preventive Medicine, Oslo University Hospital, Ulleval, Oslo, Norway
| | - Josef Štásek
- Charles University Faculty Hospital, Hradec Králové, Czech Republic
| | | | - Peter Jones
- Baylor College of Medicine, Houston, TX, USA
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Weibel GL, Drazul-Schrader D, Shivers DK, Wade AN, Rothblat GH, Reilly MP, de la Llera-Moya M. Importance of evaluating cell cholesterol influx with efflux in determining the impact of human serum on cholesterol metabolism and atherosclerosis. Arterioscler Thromb Vasc Biol 2013; 34:17-25. [PMID: 24202308 DOI: 10.1161/atvbaha.113.302437] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
OBJECTIVE Cholesterol efflux relates to cardiovascular disease but cannot predict cellular cholesterol mass changes. We asked whether influx and net flux assays provide additional insights. APPROACH AND RESULTS Adapt a bidirectional flux assay to cells where efflux has clinical correlates and examine the association of influx, efflux, and net flux to serum triglycerides (TGs). Apolipoprotein B-depleted (high-density lipoprotein-fraction) serum from individuals with unfavorable lipids (median [interquartile range]; high-density lipoprotein-cholesterol=39 [32-42], low-density lipoprotein-cholesterol=109 [97-137], TGs=258 [184-335] mg/dL; n=13) promoted greater ATP-binding cassette transporter A1-mediated [1,2-(3H)] cholesterol efflux (3.8±0.3%/4 hour versus 1.2±0.4%/4 hour; P<0.0001) from cyclic 3',5'-amp(CTP-amp)-treated J774 macrophages than from individuals with favorable lipids (high-density lipoprotein-cholesterol=72 [58-88], low-density lipoprotein-cholesterol=111 [97-131], TGs=65 [56-69] mg/dL; n=10). Thus, high TGs associated with more ATP-binding cassette transporter A1 acceptors. Efflux of cholesterol mass (μg free cholesterol/mg cell protein per 8 hour) to serum was also higher (7.06±0.33 versus 5.83±0.48; P=0.04). However, whole sera from individuals with unfavorable lipids promoted more influx (5.14±0.65 versus 2.48±0.85; P=0.02) and lower net release of cholesterol mass (1.93±0.46 versus 3.36±0.47; P=0.04). The pattern differed when mass flux was measured using apolipoprotein B-depleted serum rather than serum. Although individuals with favorable lipids tended to have greater influx than those with unfavorable lipids, efflux to apolipoprotein B-depleted serum was markedly higher (6.81±0.04 versus 2.62±0.14; P<0.0001), resulting in an efflux:influx ratio of ≈3-fold. Thus both serum and apolipoprotein B-depleted serum from individuals with favorable lipids promoted greater net cholesterol mass release despite increased ATP-binding cassette transporter A1-mediated efflux in samples of individuals with high TGs/unfavorable lipids. CONCLUSIONS When considering the efficiency of serum specimens to modulate cell cholesterol content, both influx and efflux need to be measured.
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Affiliation(s)
- Ginny L Weibel
- From the Department of Pediatrics, Division of Gastroenterology, Hepatology, and Nutrition, The Children's Hospital of Philadelphia, PA (G.L.W., D.D.-S., D.K.S., G.H.R., M.d.l.L.-M.); Cardiovascular Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia (M.P.R.); and School of Public Health and School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa (A.N.W.)
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12
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Vasudevan M, Tchoua U, Gillard BK, Jones PH, Ballantyne CM, Pownall HJ. Modest diet-induced weight loss reduces macrophage cholesterol efflux to plasma of patients with metabolic syndrome. J Clin Lipidol 2013; 7:661-70. [PMID: 24314365 PMCID: PMC4108339 DOI: 10.1016/j.jacl.2013.05.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 05/15/2013] [Accepted: 05/20/2013] [Indexed: 11/15/2022]
Abstract
BACKGROUND Obesity-linked metabolic syndrome (MetS) is associated with a dyslipidemic profile that includes hypertriglyceridemia and low plasma high-density lipoprotein (HDL) cholesterol. HDL initiates reverse cholesterol transport via macrophage cholesterol efflux (MCE). Some hypothesize that dyslipidemic patients have impaired reverse cholesterol transport. MCE to patient plasma, a metric of HDL function, inversely correlates with atherosclerotic burden. Paradoxically, MCE to plasma of hypertriglyceridemic subjects is higher than that to normolipidemic (NL) plasma. OBJECTIVE Although weight loss reduces dyslipidemia, its effect on MCE to the plasma of obese patients with MetS is unknown. Thus, we tested the hypothesis that reducing dyslipidemia with weight loss reduces the MCE capacity of MetS plasma to that of NL plasma. METHODS Cholesterol efflux (MCE) from THP-1 macrophages to plasma from NL controls and to obese patients with MetS before and after weight loss was measured. RESULTS MCE to plasma of obese patients with MetS was higher than that of control plasma (P = .006). Weight loss in patients with MetS (mean, -9.77 kg) reduced dyslipidemia, insulin resistance, and systolic blood pressure. HDL cholesterol was unchanged, and apolipoprotein A-I decreased with weight loss. Weight loss in patients with MetS normalized MCE (P < .001) to that of NL subjects. MCE correlated with apolipoprotein B levels (r² = 0.13-0.38). Chromatography showed that macrophage cholesterol initially associates with HDL but accumulates in apolipoprotein B-containing lipoproteins at later times. CONCLUSIONS Although the initial acceptor of MCE is HDL, the elevated apolipoprotein B lipoproteins are a cholesterol sink that increases MCE in patients with MetS. Weight loss results in decreased apolipoprotein B lipoproteins and decreased MCE to plasma of patients with MetS.
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Affiliation(s)
- Madhuri Vasudevan
- Section of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
| | - Urbain Tchoua
- Section of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
| | - Baiba K. Gillard
- Section of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
| | - Peter H. Jones
- Section of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
- The Methodist Hospital DeBakey Heart and Vascular Center, 6565 Fannin St., Houston TX 77030
| | - Christie M. Ballantyne
- Section of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
- The Methodist Hospital DeBakey Heart and Vascular Center, 6565 Fannin St., Houston TX 77030
| | - Henry J. Pownall
- Section of Atherosclerosis and Vascular Medicine, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030
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Ledford KJ, Murphy N, Zeigler F, Bartel RL. Potential beneficial effects of ixmyelocel-T in the treatment of atherosclerotic diseases. Stem Cell Res Ther 2013; 4:135. [PMID: 24405662 PMCID: PMC4029553 DOI: 10.1186/scrt346] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 10/23/2013] [Indexed: 11/11/2022] Open
Abstract
Introduction Advanced atherosclerotic lesions are characterized by lipid accumulation, inflammation, and defective efferocytosis. An ideal therapy should address all aspects of this multifactorial disease. Ixmyelocel-T therapy, an expanded autologous multicellular therapy showing clinical promise in the treatment of diseases associated with advanced atherosclerosis, includes a novel population of M2-like macrophages. Here, we examine the macrophages of ixmyelocel-T and determine their ability to influx modified cholesterol in an atheroprotective manner, maintaining cholesterol homeostasis and preventing cellular dysfunction and death, ultimately promoting reverse cholesterol efflux. Methods Approximately 50 ml of whole bone marrow was obtained from healthy donors and shipped overnight. Bone marrow mononuclear cells (BMMNCs) were produced by using density gradient separation and cultured for approximately 12 days to generate ixmyelocel-T. CD14+ cells were isolated from ixmyelocel-T via positive selection for analysis. Ixmyelocel-T and human leukemia monocyte (THP-1) cells were loaded with acetylated low-density lipoprotein (Ac-LDL) for analysis. Flow cytometry and immunofluorescence were used to examine Ac-LDL uptake, expression of cytokines was analyzed by enzyme-linked immunofluorescence assay (ELISA), and quantitative real-time PCR was used to analyze expression of cholesterol-transport genes. Both the in vitro cholesterol efflux assay and in vivo reverse cholesterol transport assay were used to examine cholesterol transport. Results Ixmyelocel-T macrophages take up acetylated low-density lipoprotein and express the scavenger receptors CD36 and scavenger receptor-B1 (SR-B1). Ixmyelocel-T did not become apoptotic or proinflammatory after lipid loading. The cholesterol transporter genes ABAC1 and ABCG1 were both statistically significantly upregulated when ixmyelocel-T macrophages were loaded with cholesterol. Ixmyelocel-T also exhibited enhanced apolipoprotein A-I (ApoAI)-mediated cholesterol efflux. In addition, in vivo reverse cholesterol-transport assay demonstrated that ixmyelocel-T was able to efflux cholesterol in this model. Conclusions Ixmyelocel-T macrophages influx modified cholesterol, remained anti-inflammatory in the face of lipid loading and inflammatory challenge, and displayed enhanced cholesterol efflux capabilities. These combined features suggest that this autologous multicellular therapy may exert beneficial effects in atherosclerotic diseases.
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Diditchenko S, Gille A, Pragst I, Stadler D, Waelchli M, Hamilton R, Leis A, Wright SD. Novel Formulation of a Reconstituted High-Density Lipoprotein (CSL112) Dramatically Enhances ABCA1-Dependent Cholesterol Efflux. Arterioscler Thromb Vasc Biol 2013; 33:2202-11. [DOI: 10.1161/atvbaha.113.301981] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Svetlana Diditchenko
- From the CSL Behring AG, Berne, Switzerland (S.D., D.S., M.W.); CSL Limited, Parkville, Australia (A.G., R.H.); CSL Behring GmbH, Marburg, Germany (I.P.); AAHL Biosecurity Microscopy Facility, Geelong, Australia (A.L.); and CSL Behring, King of Prussia, PA (S.D.W.)
| | - Andreas Gille
- From the CSL Behring AG, Berne, Switzerland (S.D., D.S., M.W.); CSL Limited, Parkville, Australia (A.G., R.H.); CSL Behring GmbH, Marburg, Germany (I.P.); AAHL Biosecurity Microscopy Facility, Geelong, Australia (A.L.); and CSL Behring, King of Prussia, PA (S.D.W.)
| | - Ingo Pragst
- From the CSL Behring AG, Berne, Switzerland (S.D., D.S., M.W.); CSL Limited, Parkville, Australia (A.G., R.H.); CSL Behring GmbH, Marburg, Germany (I.P.); AAHL Biosecurity Microscopy Facility, Geelong, Australia (A.L.); and CSL Behring, King of Prussia, PA (S.D.W.)
| | - Dominik Stadler
- From the CSL Behring AG, Berne, Switzerland (S.D., D.S., M.W.); CSL Limited, Parkville, Australia (A.G., R.H.); CSL Behring GmbH, Marburg, Germany (I.P.); AAHL Biosecurity Microscopy Facility, Geelong, Australia (A.L.); and CSL Behring, King of Prussia, PA (S.D.W.)
| | - Marcel Waelchli
- From the CSL Behring AG, Berne, Switzerland (S.D., D.S., M.W.); CSL Limited, Parkville, Australia (A.G., R.H.); CSL Behring GmbH, Marburg, Germany (I.P.); AAHL Biosecurity Microscopy Facility, Geelong, Australia (A.L.); and CSL Behring, King of Prussia, PA (S.D.W.)
| | - Ross Hamilton
- From the CSL Behring AG, Berne, Switzerland (S.D., D.S., M.W.); CSL Limited, Parkville, Australia (A.G., R.H.); CSL Behring GmbH, Marburg, Germany (I.P.); AAHL Biosecurity Microscopy Facility, Geelong, Australia (A.L.); and CSL Behring, King of Prussia, PA (S.D.W.)
| | - Andrew Leis
- From the CSL Behring AG, Berne, Switzerland (S.D., D.S., M.W.); CSL Limited, Parkville, Australia (A.G., R.H.); CSL Behring GmbH, Marburg, Germany (I.P.); AAHL Biosecurity Microscopy Facility, Geelong, Australia (A.L.); and CSL Behring, King of Prussia, PA (S.D.W.)
| | - Samuel D. Wright
- From the CSL Behring AG, Berne, Switzerland (S.D., D.S., M.W.); CSL Limited, Parkville, Australia (A.G., R.H.); CSL Behring GmbH, Marburg, Germany (I.P.); AAHL Biosecurity Microscopy Facility, Geelong, Australia (A.L.); and CSL Behring, King of Prussia, PA (S.D.W.)
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Sanson M, Distel E, Fisher EA. HDL induces the expression of the M2 macrophage markers arginase 1 and Fizz-1 in a STAT6-dependent process. PLoS One 2013; 8:e74676. [PMID: 23991225 PMCID: PMC3749183 DOI: 10.1371/journal.pone.0074676] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 08/03/2013] [Indexed: 12/22/2022] Open
Abstract
Our lab has previously shown in a mouse model that normalization of a low HDL level achieves atherosclerotic plaque regression. This included the shift from a pro ("M1") to an anti-inflammatory ("M2") phenotypic state of plaque macrophages. Whether HDL can directly cause this phenotypic change and, if so, what the signaling mechanism is, were explored in the present studies. Murine primary macrophages treated with HDL showed increased gene expression for the M2 markers Arginase-1 (Arg-1) and Fizz-1, which are classically induced by IL-4. HDL was able to potentiate the IL-4-induced changes in Arg-1, and tended to do the same for Fizz-1, while suppressing the expression of inflammatory genes in response to IFNγ. The effects of either IL-4 or HDL were suppressed when macrophages were from STAT6(-/-) mice, but inhibitor studies suggested differential utilization of JAK isoforms by IL-4 and HDL to activate STAT6 by phosphorylation. Overall, our results describe a new function of HDL, namely its ability to directly enrich macrophages in markers of the M2, anti-inflammatory, state in a process requiring STAT6.
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Affiliation(s)
- Marie Sanson
- The Leon H. Charney Division of Cardiology and Marc and Ruti Bell Program in Vascular Biology, Department of Medicine, New York University School of Medicine, New York, New York, United States of America
| | - Emilie Distel
- The Leon H. Charney Division of Cardiology and Marc and Ruti Bell Program in Vascular Biology, Department of Medicine, New York University School of Medicine, New York, New York, United States of America
| | - Edward A. Fisher
- The Leon H. Charney Division of Cardiology and Marc and Ruti Bell Program in Vascular Biology, Department of Medicine, New York University School of Medicine, New York, New York, United States of America
- * E-mail:
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Abstract
Multiple human population studies have established the concentration of high density lipoprotein (HDL) cholesterol as an independent, inverse predictor of the risk of having a cardiovascular event. Furthermore, HDLs have several well-documented functions with the potential to protect against cardiovascular disease. These include an ability to promote the efflux of cholesterol from macrophages in the artery wall, inhibit the oxidative modification of low density lipoproteins (LDLs), inhibit vascular inflammation, inhibit thrombosis, promote endothelial repair, promote angiogenesis, enhance endothelial function, improve diabetic control, and inhibit hematopoietic stem cell proliferation. There are undoubtedly other beneficial functions of HDLs yet to be identified. The HDL fraction in human plasma is heterogeneous, consisting of several subpopulations of particles of varying size, density, and composition. The functions of the different HDL subpopulations remain largely unknown. Given that therapies that increase the concentration of HDL cholesterol have varying effects on the levels of specific HDL subpopulations, it is of great importance to understand how distribution of different HDL subpopulations contribute to the potentially cardioprotective functions of this lipoprotein fraction. This review summarizes current understanding of the relationship of HDL subpopulations to their cardioprotective properties and highlights the gaps in current knowledge regarding this important aspect of HDL biology.
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Affiliation(s)
- Kerry-Anne Rye
- Lipid Research Group, Centre for Vascular Research, University of New South Wales, Sydney, New South Wales, Australia 2052
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Kones R. Reducing residual risk: modern pharmacochemistry meets old-fashioned lifestyle and adherence improvement. Ther Adv Cardiovasc Dis 2013; 7:169-82. [DOI: 10.1177/1753944712467828] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Despite remarkable advances in identifying and managing coronary heart disease, the global burden of cardiovascular (CV) risk and levels of undetected, subclinical heart disease remain enormous. Substantial numbers of patients do not reach their therapeutic goals, others are unable to tolerate the treatments, half may fail to adhere to their programs, and in those who do attain their targets, major cardiovascular events may continue. Well-known risk factors, such as obesity and diabetes, have now gained the upper hand, with no evidence-based remedy capable of reversing this trend. All told, less than 1% of American adults and adolescents qualify for ideal CV health; world-wide, the growing prevalence of CV risk factors in children is imposing. A number of novel emerging drug therapies are in development, some recently approved for use in patients with familial hypercholesterolemia. Hopefully, they will contribute significantly to the current therapeutic armamentarium. However, for meaningful improvement in total and residual CV risk, an optimal mix of all available modalities will likely be necessary, including earlier and more effective prevention, aggressive medical care, revascularization and device implantation, judicious use of novel agents, and reengineering of the environment.
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Affiliation(s)
- Richard Kones
- Cardiometabolic Research Institute Inc., 8181 Fannin Street, U314 Houston, TX 77055, USA
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Kellner-Weibel G, de la Llera-Moya M. Update on HDL receptors and cellular cholesterol transport. Curr Atheroscler Rep 2011; 13:233-41. [PMID: 21302003 DOI: 10.1007/s11883-011-0169-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Efflux is central to maintenance of tissue and whole body cholesterol homeostasis. The discovery of cell surface receptors that bind high-density lipoprotein (HDL) with high specificity and affinity to promote cholesterol release has significantly advanced our understanding of cholesterol efflux. We now know that 1) cells have several mechanisms to promote cholesterol release, including a passive mechanism that depends on the physico-chemical properties of cholesterol molecules and their interactions with phospholipids; 2) a variety of HDL particles can interact with receptors to promote cholesterol transport from tissues to the liver for excretion; and 3) interactions between HDL and receptors show functional synergy. Therefore, efflux efficiency depends both on the arrays of receptors on tissue cells and HDL particles in serum.
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Affiliation(s)
- Ginny Kellner-Weibel
- Division of Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia, 3615 Civic Center Blvd., ARC1102G, Philadelphia, PA 19104-4318, USA.
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Weibel GL, Hayes S, Wilson A, Phillips MC, Billheimer J, Rader DJ, Rothblat GH. Novel in vivo method for measuring cholesterol mass flux in peripheral macrophages. Arterioscler Thromb Vasc Biol 2011; 31:2865-71. [PMID: 21940945 DOI: 10.1161/atvbaha.111.236406] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Reverse cholesterol transport is the process by which excess cholesterol is removed from peripheral tissue by HDL and delivered to the liver for excretion. Presently, methods of measuring in vivo reverse cholesterol transport do so by monitoring the appearance in the feces of labeled cholesterol that originated from peripheral macrophage foam cells. These methods do not account for changes in macrophage cholesterol mass. We have developed an in vivo assay to measure cholesterol mass changes in atherosclerotic foam cells. METHODS AND RESULTS Macrophages are entrapped in semipermeable (pore size 0.2 μm) hollow fibers and surgically implanted into the peritoneum of recipient mice. The fibers are removed from the peritoneum 24 hours after implantation. This method allows the complete recovery of the macrophages for quantification of changes in cholesterol mass and cellular protein. In wild-type mice we measured a significant reduction in total cell cholesterol (TC) when hollow fibers containing cholesterol-enriched macrophage cells were implanted (TC before implantation=105±18 μg/mg cell protein, TC 24 hours after implantation=60±16 μg/mg protein). Additionally, there was an increase in cholesterol content when hollow fibers containing cholesterol-normal macrophages were implanted in an atherogenic mouse model (LDLr/apobec dko) compared to a wild-type mouse (initial TC content=57±24 μg/mg protein, TC 24 hours after implantation: wild-type mice=52±10 μg/mg protein; LDLr/apobec dko mice=118±27 μg/mg protein). CONCLUSIONS This assay can quantify in vivo both cholesterol mass accumulation, and reduction, in macrophages. This method permits quantitative analysis of the progression and regression of foam cells.
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Affiliation(s)
- Ginny L Weibel
- Division of Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.
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Ouimet M, Franklin V, Mak E, Liao X, Tabas I, Marcel YL. Autophagy regulates cholesterol efflux from macrophage foam cells via lysosomal acid lipase. Cell Metab 2011; 13:655-67. [PMID: 21641547 PMCID: PMC3257518 DOI: 10.1016/j.cmet.2011.03.023] [Citation(s) in RCA: 593] [Impact Index Per Article: 42.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 01/24/2011] [Accepted: 03/23/2011] [Indexed: 12/20/2022]
Abstract
The lipid droplet (LD) is the major site of cholesterol storage in macrophage foam cells and is a potential therapeutic target for the treatment of atherosclerosis. Cholesterol, stored as cholesteryl esters (CEs), is liberated from this organelle and delivered to cholesterol acceptors. The current paradigm attributes all cytoplasmic CE hydrolysis to the action of neutral CE hydrolases. Here, we demonstrate an important role for lysosomes in LD CE hydrolysis in cholesterol-loaded macrophages, in addition to that mediated by neutral hydrolases. Furthermore, we demonstrate that LDs are delivered to lysosomes via autophagy, where lysosomal acid lipase (LAL) acts to hydrolyze LD CE to generate free cholesterol mainly for ABCA1-dependent efflux; this process is specifically induced upon macrophage cholesterol loading. We conclude that, in macrophage foam cells, lysosomal hydrolysis contributes to the mobilization of LD-associated cholesterol for reverse cholesterol transport.
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Affiliation(s)
- Mireille Ouimet
- University of Ottawa Heart Institute, Ottawa, Ontario, Canada
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Wong BXW, Kyle RA, Croft KD, Quinn CM, Jessup W, Yeap BB. Modulation of macrophage fatty acid content and composition by exposure to dyslipidemic serum in vitro. Lipids 2011; 46:371-80. [PMID: 21286835 DOI: 10.1007/s11745-011-3528-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Accepted: 11/14/2010] [Indexed: 10/18/2022]
Abstract
Macrophages in arterial walls accumulate lipids leading to the development of atherosclerotic plaques. However, mechanisms underlying macrophage lipid accumulation and foam cell formation are often studied without accounting for risk factors such as dyslipidemia. We investigated the effect of varying concentrations of triglyceride (TG) within physiological range on macrophage fatty acid (FA) accumulation and expression of cholesterol efflux proteins. Human monocytes were cultured in media supplemented with 10% sera containing low (0.7 mmol/L) to high (1.4 mmol/L) TG. The resulting macrophages were harvested after 10 days for analysis of FA content and composition and expression of genes involved in lipid metabolism. Exposure to higher TG and lower HDL concentrations in media increased macrophage lipid content. Macrophages exposed to higher TG had increased total FA content compared with controls (876 μg/mg protein vs. 652 μg/mg protein) and greater proportions of C16:0, C18:1 and C18:2. Macrophage expression of both ABCA1 and ABCG1 cholesterol efflux proteins were reduced when higher TG concentrations were present in the media. Expression of scavenger receptor CD36, involved in lipoprotein uptake, was also downregulated in macrophages exposed to higher TG. Culturing macrophages in conditions of higher versus lower TG influenced macrophage FA content and composition, and levels of regulatory proteins. Replicating in vitro levels of dyslipidemia encountered in vivo may provide an informative model for investigation of atherogenesis.
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Affiliation(s)
- Bruce X W Wong
- School of Medicine and Pharmacology, Fremantle and Royal Perth Hospitals, University of Western Australia, Perth, WA, Australia
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