1
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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: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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2
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Tao H, Yancey PG, Blakemore JL, Zhang Y, Ding L, Jerome WG, Brown JD, Vickers KC, Linton MF. Macrophage SR-BI modulates autophagy via VPS34 complex and PPARα transcription of Tfeb in atherosclerosis. J Clin Invest 2021; 131:94229. [PMID: 33661763 PMCID: PMC8011903 DOI: 10.1172/jci94229] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 02/17/2021] [Indexed: 12/11/2022] Open
Abstract
Autophagy modulates lipid turnover, cell survival, inflammation, and atherogenesis. Scavenger receptor class B type I (SR-BI) plays a crucial role in lysosome function. Here, we demonstrate that SR-BI regulates autophagy in atherosclerosis. SR-BI deletion attenuated lipid-induced expression of autophagy mediators in macrophages and atherosclerotic aortas. Consequently, SR-BI deletion resulted in 1.8- and 2.5-fold increases in foam cell formation and apoptosis, respectively, and increased oxidized LDL-induced inflammatory cytokine expression. Pharmacological activation of autophagy failed to reduce lipid content or apoptosis in Sr-b1-/- macrophages. SR-BI deletion reduced both basal and inducible levels of transcription factor EB (TFEB), a master regulator of autophagy, causing decreased expression of autophagy genes encoding VPS34 and Beclin-1. Notably, SR-BI regulated Tfeb expression by enhancing PPARα activation. Moreover, intracellular macrophage SR-BI localized to autophagosomes, where it formed cholesterol domains resulting in enhanced association of Barkor and recruitment of the VPS34-Beclin-1 complex. Thus, SR-BI deficiency led to lower VPS34 activity in macrophages and in atherosclerotic aortic tissues. Overexpression of Tfeb or Vps34 rescued the defective autophagy in Sr-b1-/- macrophages. Taken together, our results show that macrophage SR-BI regulates autophagy via Tfeb expression and recruitment of the VPS34-Beclin-1 complex, thus identifying previously unrecognized roles for SR-BI and potentially novel targets for the treatment of atherosclerosis.
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Affiliation(s)
- Huan Tao
- Department of Medicine, Atherosclerosis Research Unit, Division of Cardiovascular Medicine
| | - Patricia G. Yancey
- Department of Medicine, Atherosclerosis Research Unit, Division of Cardiovascular Medicine
| | - John L. Blakemore
- Department of Medicine, Atherosclerosis Research Unit, Division of Cardiovascular Medicine
| | - Youmin Zhang
- Department of Medicine, Atherosclerosis Research Unit, Division of Cardiovascular Medicine
| | - Lei Ding
- Department of Medicine, Atherosclerosis Research Unit, Division of Cardiovascular Medicine
| | - W. Gray Jerome
- Department of Pathology, Microbiology and Immunology, and
| | - Jonathan D. Brown
- Department of Medicine, Atherosclerosis Research Unit, Division of Cardiovascular Medicine
| | - Kasey C. Vickers
- Department of Medicine, Atherosclerosis Research Unit, Division of Cardiovascular Medicine
| | - MacRae F. Linton
- Department of Medicine, Atherosclerosis Research Unit, Division of Cardiovascular Medicine
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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3
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Zhou E, Li Z, Nakashima H, Liu C, Ying Z, Foks AC, Berbée JFP, van Dijk KW, Rensen PCN, Wang Y. Hepatic Scavenger Receptor Class B Type 1 Knockdown Reduces Atherosclerosis and Enhances the Antiatherosclerotic Effect of Brown Fat Activation in APOE*3-Leiden.CETP Mice. Arterioscler Thromb Vasc Biol 2021; 41:1474-1486. [PMID: 33567866 DOI: 10.1161/atvbaha.121.315882] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
[Figure: see text].
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MESH Headings
- Adipose Tissue, Brown/drug effects
- Adipose Tissue, Brown/metabolism
- Adrenergic beta-3 Receptor Agonists/pharmacology
- Animals
- Apolipoprotein E3/genetics
- Apolipoprotein E3/metabolism
- Atherosclerosis/genetics
- Atherosclerosis/metabolism
- Atherosclerosis/pathology
- Atherosclerosis/prevention & control
- Biomarkers/blood
- Cholesterol Ester Transfer Proteins/genetics
- Cholesterol Ester Transfer Proteins/metabolism
- Dioxoles/pharmacology
- Disease Models, Animal
- Gene Knockdown Techniques
- Humans
- Lipids/blood
- Lipolysis/drug effects
- Liver/metabolism
- Mice, Inbred C57BL
- Mice, Transgenic
- Plaque, Atherosclerotic
- RNA Interference
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Scavenger Receptors, Class B/deficiency
- Scavenger Receptors, Class B/genetics
- Mice
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Affiliation(s)
- Enchen Zhou
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
| | - Zhuang Li
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
| | - Hiroyuki Nakashima
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
| | - Cong Liu
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
| | - Zhixiong Ying
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
| | - Amanda C Foks
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, The Netherlands (A.C.F.)
| | - Jimmy F P Berbée
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
| | - Ko Willems van Dijk
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
- Department of Human Genetics (K.W.v.D.), Leiden University Medical Center, The Netherlands
| | - Patrick C N Rensen
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
- Department of Endocrinology, the First Affiliated Hospital of Xi'an Jiaotong University, China (P.C.N.R., Y.W.)
| | - Yanan Wang
- Division of Endocrinology, Department of Medicine, Einthoven Laboratory for Experimental Vascular Medicine (E.Z., Z.L., H.N., C.L., Z.Y., J.F.P.B., KW.v.D., P.C.N.R., Y.W.), Leiden University Medical Center, The Netherlands
- Department of Endocrinology, the First Affiliated Hospital of Xi'an Jiaotong University, China (P.C.N.R., Y.W.)
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4
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Abstract
Atherosclerotic plaques impair vascular function and can lead to arterial obstruction and tissue ischaemia. Rupture of an atherosclerotic plaque within a coronary artery can result in an acute myocardial infarction, which is responsible for significant morbidity and mortality worldwide. Prompt reperfusion can salvage some of the ischaemic territory, but ischaemia and reperfusion (IR) still causes substantial injury and is, therefore, a therapeutic target for further infarct limitation. Numerous cardioprotective strategies have been identified that can limit IR injury in animal models, but none have yet been translated effectively to patients. This disconnect prompts an urgent re-examination of the experimental models used to study IR. Since coronary atherosclerosis is the most prevalent morbidity in this patient population, and impairs coronary vessel function, it is potentially a major confounder in cardioprotective studies. Surprisingly, most studies suggest that atherosclerosis does not have a major impact on cardioprotection in mouse models. However, a major limitation of atherosclerotic animal models is that the plaques usually manifest in the aorta and proximal great vessels, and rarely in the coronary vessels. In this review, we examine the commonly used mouse models of atherosclerosis and their effect on coronary artery function and infarct size. We conclude that none of the commonly used strains of mice are ideal for this purpose; however, more recently developed mouse models of atherosclerosis fulfil the requirement for coronary artery lesions, plaque rupture and lipoprotein patterns resembling the human profile, and may enable the identification of therapeutic interventions more applicable in the clinical setting.
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MESH Headings
- Animals
- Aortic Diseases/complications
- Aortic Diseases/genetics
- Aortic Diseases/metabolism
- Aortic Diseases/pathology
- Atherosclerosis/complications
- Atherosclerosis/genetics
- Atherosclerosis/metabolism
- Atherosclerosis/pathology
- Coronary Artery Disease/complications
- Coronary Artery Disease/genetics
- Coronary Artery Disease/metabolism
- Coronary Artery Disease/pathology
- Diet, High-Fat
- Disease Models, Animal
- Genetic Predisposition to Disease
- Mice, Knockout, ApoE
- Myocardial Infarction/etiology
- Myocardial Infarction/genetics
- Myocardial Infarction/metabolism
- Myocardial Infarction/pathology
- Myocardium/pathology
- Phenotype
- Plaque, Atherosclerotic
- Receptors, LDL/deficiency
- Receptors, LDL/genetics
- Rupture, Spontaneous
- Scavenger Receptors, Class B/deficiency
- Scavenger Receptors, Class B/genetics
- Species Specificity
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Affiliation(s)
- Pelin Golforoush
- The Hatter Cardiovascular Institute, 67 Chenies Mews, London, WC1E 6HX, UK
| | - Derek M Yellon
- The Hatter Cardiovascular Institute, 67 Chenies Mews, London, WC1E 6HX, UK
| | - Sean M Davidson
- The Hatter Cardiovascular Institute, 67 Chenies Mews, London, WC1E 6HX, UK.
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5
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Abstract
Glucocorticoids belong to the superfamily of steroid hormones that are synthesized from the common precursor cholesterol. Adrenal gland-derived glucocorticoids, e.g., cortisol in humans and corticosterone in rodents, contribute to various processes essential for normal daily life. Glucocorticoid deficiency, also referred to as primary adrenal insufficiency, therefore, often becomes evident early in life and can be present with hypoglycemia, a failure to thrive, recurrent development of infections, and neurological problems, such as seizures and coma. The majority of congenital primary adrenal insufficiency cases are caused by deleterious mutations in genes involved in the intracellular mobilization of cholesterol and the subsequent conversion of cholesterol into glucocorticoids. A significant number of glucocorticoid deficiency cases, however, cannot be explained by known genetic variations. This perspective highlights existing literature regarding the importance of lipoprotein-derived cholesterol acquisition through scavenger receptor class B, type I (SR-BI/SCARB1) for the maintenance of an optimal adrenal glucocorticoid function in mice and humans. On the basis of the reviewed findings, it is suggested that the SCARB1 gene should be included in the standard glucocorticoid deficiency genetic screening panel to 1) facilitate knowledge development on the relative contribution of SR-BI-mediated cholesterol acquisition to steroid hormone synthesis in humans and 2) open up the possibility to reclassify glucocorticoid deficiency patients without a currently known genetic cause for concomitant treatment optimization.
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Affiliation(s)
- Menno Hoekstra
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Gorlaeus Laboratories, Leiden, The Netherlands
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6
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Leiva A, Contreras-Duarte S, Amigo L, Sepúlveda E, Boric M, Quiñones V, Busso D, Rigotti A. Gugulipid causes hypercholesterolemia leading to endothelial dysfunction, increased atherosclerosis, and premature death by ischemic heart disease in male mice. PLoS One 2017; 12:e0184280. [PMID: 28910310 PMCID: PMC5598962 DOI: 10.1371/journal.pone.0184280] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 08/21/2017] [Indexed: 12/29/2022] Open
Abstract
For proper cholesterol metabolism, normal expression and function of scavenger receptor class B type I (SR-BI), a high-density lipoprotein (HDL) receptor, is required. Among the factors that regulate overall cholesterol homeostasis and HDL metabolism, the nuclear farnesoid X receptor plays an important role. Guggulsterone, a bioactive compound present in the natural product gugulipid, is an antagonist of this receptor. This natural product is widely used globally as a natural lipid-lowering agent, although its anti-atherogenic cardiovascular benefit in animal models or humans is unknown. The aim of this study was to determine the effects of gugulipid on cholesterol homeostasis and development of mild and severe atherosclerosis in male mice. For this purpose, we evaluated the impact of gugulipid treatment on liver histology, plasma lipoprotein cholesterol, endothelial function, and development of atherosclerosis and/or ischemic heart disease in wild-type mice; apolipoprotein E knockout mice, a model of atherosclerosis without ischemic complications; and SR-B1 knockout and atherogenic–diet-fed apolipoprotein E hypomorphic (SR-BI KO/ApoER61h/h) mice, a model of lethal ischemic heart disease due to severe atherosclerosis. Gugulipid administration was associated with histological abnormalities in liver, increased alanine aminotransferase levels, lower hepatic SR-BI content, hypercholesterolemia due to increased HDL cholesterol levels, endothelial dysfunction, enhanced atherosclerosis, and accelerated death in animals with severe ischemic heart disease. In conclusion, our data show important adverse effects of gugulipid intake on HDL metabolism and atherosclerosis in male mice, suggesting potential and unknown deleterious effects on cardiovascular health in humans. In addition, these findings reemphasize the need for rigorous preclinical and clinical studies to provide guidance on the consumption of natural products and regulation of their use in the general population.
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Affiliation(s)
- Andrea Leiva
- Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail: (AL); (AR)
| | - Susana Contreras-Duarte
- Cellular and Molecular Physiology Laboratory (CMPL), Division of Obstetrics and Gynaecology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Ludwig Amigo
- Department of Gastroenterology, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Esteban Sepúlveda
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Mauricio Boric
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Verónica Quiñones
- Department of Nutrition, Diabetes and Metabolism, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Dolores Busso
- Department of Nutrition, Diabetes and Metabolism, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Attilio Rigotti
- Department of Nutrition, Diabetes and Metabolism, Pontificia Universidad Católica de Chile, Santiago, Chile
- Center of Molecular Nutrition and Chronic Diseases, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail: (AL); (AR)
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7
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Abstract
A positive correlation between plasma levels of HDL and bone mass has been reported by epidemiological studies. As scavenger receptor class B, type I (SR-BI), the gene product of Scarb1, is known to regulate HDL metabolism, we recently characterized bone metabolism in Scarb1-null mice. These mice display high femoral bone mass associated with enhanced bone formation. As gender differences have been reported in HDL metabolism and SR-BI function, we investigated gender-specific bone alterations in Scarb1-null mice by microtomography and histology. We found 16% greater relative bone volume and 39% higher bone formation rate in the vertebrae from 2-month-old Scarb1-null females. No such alteration was seen in males, indicating gender- and region-specific differences in skeletal phenotype. Total and HDL-associated cholesterol levels, as well as ACTH plasma levels, were increased in both Scarb1-null genders, the latter being concurrent to impaired corticosterone response to fasting. Plasma levels of estradiol did not differ between null and WT females, suggesting that the estrogen metabolism alteration is not relevant to the higher vertebral bone mass in female Scarb1-null mice. Constitutively, high plasma levels of leptin along with 2.5-fold increase in its expression in white adipose tissue were measured in female Scarb1-null mice only. In vitro exposure of bone marrow stromal cells to ACTH and leptin promoted osteoblast differentiation as evidenced by increased gene expression of osterix and collagen type I alpha. Our results suggest that hyperleptinemia may account for the gender-specific high bone mass seen in the vertebrae of female Scarb1-null mice.
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Affiliation(s)
- Corine Martineau
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Louise Martin-Falstrault
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Louise Brissette
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Robert Moreau
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
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8
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Abstract
PURPOSE OF REVIEW To summarize the recent findings about the roles of scavenger receptor class B type I (SR-BI) in immunity and discuss the underlying mechanisms by which SR-BI prevents immune dysfunctions. RECENT FINDINGS SR-BI is well known as a high-density lipoprotein (HDL) receptor playing key roles in HDL metabolism and in protection against atherosclerosis. Recent studies have indicated that SR-BI is also an essential modulator in immunity. SR-BI deficiency in mice causes immune dysfunctions, including increased atherosclerosis, elevated susceptibility to sepsis, impaired lymphocyte homeostasis, and autoimmune disorders. SR-BI exerts its protective roles through a variety of HDL-dependent and HDL-independent mechanisms. SR-BI is also involved in hepatitis C virus cell entry. A deficiency of SR-BI in humanized mice has been shown to decrease hepatitis C virus infectivity. SUMMARY SR-BI regulates immunity via multiple mechanisms and its deficiency causes numerous diseases. A comprehensive understanding of the roles of SR-BI in protection against immune dysfunctions may provide a therapeutic target for intervention against its associated diseases.
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Affiliation(s)
- Zhong Zheng
- Department of Pediatrics, University of Kentucky College of Medicine, Lexington, Kentucky, USA
- Graduate Center for Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Junting Ai
- Department of Pediatrics, University of Kentucky College of Medicine, Lexington, Kentucky, USA
- Graduate Center for Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Xiang-An Li
- Department of Pediatrics, University of Kentucky College of Medicine, Lexington, Kentucky, USA
- Graduate Center for Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, USA
- Saha Cardiovascular Research Center, University of Kentucky College of Medicine, Lexington, Kentucky, USA
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9
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Guo L, Zheng Z, Ai J, Howatt DA, Mittelstadt PR, Thacker S, Daugherty A, Ashwell JD, Remaley AT, Li XA. Scavenger receptor BI and high-density lipoprotein regulate thymocyte apoptosis in sepsis. Arterioscler Thromb Vasc Biol 2014; 34:966-75. [PMID: 24603680 DOI: 10.1161/atvbaha.113.302484] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVE Thymocyte apoptosis is a major event in sepsis; however, how this process is regulated remains poorly understood. APPROACH AND RESULTS Septic stress induces glucocorticoids production which triggers thymocyte apoptosis. Here, we used scavenger receptor BI (SR-BI)-null mice, which are completely deficient in inducible glucocorticoids in sepsis, to investigate the regulation of thymocyte apoptosis in sepsis. Cecal ligation and puncture induced profound thymocyte apoptosis in SR-BI(+/+) mice, but no thymocyte apoptosis in SR-BI(-/-) mice because of lack of inducible glucocorticoids. Unexpectedly, supplementation of glucocorticoids only partly restored thymocyte apoptosis in SR-BI(-/-) mice. We demonstrated that high-density lipoprotein (HDL) is a critical modulator for thymocyte apoptosis. SR-BI(+/+) HDL significantly enhanced glucocorticoid-induced thymocyte apoptosis, but SR-BI(-/-) HDL had no such activity. Further study revealed that SR-BI(+/+) HDL modulates glucocorticoid-induced thymocyte apoptosis via promoting glucocorticoid receptor translocation, but SR-BI(-/-) HDL loses such regulatory activity. To understand why SR-BI(-/-) HDL loses its regulatory activity, we analyzed HDL cholesterol contents. There was 3-fold enrichment of unesterified cholesterol in SR-BI(-/-) HDL compared with SR-BI(+/+) HDL. Normalization of unesterified cholesterol in SR-BI(-/-) HDL by probucol administration or lecithin cholesteryl acyltransferase expression restored glucocorticoid-induced thymocyte apoptosis, and incorporating unesterified cholesterol into SR-BI(+/+) HDL rendered SR-BI(+/+) HDL dysfunctional. Using lckCre-GR(fl/fl) mice in which thymocytes lack cecal ligation and puncture-induced thymocyte apoptosis, we showed that lckCre-GR(fl/fl) mice were significantly more susceptible to cecal ligation and puncture-induced septic death than GR(fl/fl) control mice, suggesting that glucocorticoid-induced thymocyte apoptosis is required for protection against sepsis. CONCLUSIONS The findings in this study reveal a novel regulatory mechanism of thymocyte apoptosis in sepsis by SR-BI and HDL.
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MESH Headings
- Animals
- Apoptosis/drug effects
- Cecum/microbiology
- Cecum/surgery
- Cells, Cultured
- Cholesterol, HDL/blood
- Corticosterone/metabolism
- Disease Models, Animal
- Female
- Humans
- Ligation
- Male
- Mice
- Mice, 129 Strain
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Phosphatidylcholine-Sterol O-Acyltransferase/genetics
- Phosphatidylcholine-Sterol O-Acyltransferase/metabolism
- Probucol/pharmacology
- Protein Transport
- Punctures
- Receptors, Glucocorticoid/metabolism
- Scavenger Receptors, Class B/deficiency
- Scavenger Receptors, Class B/genetics
- Scavenger Receptors, Class B/metabolism
- Sepsis/blood
- Sepsis/metabolism
- Sepsis/microbiology
- Sepsis/pathology
- Signal Transduction
- Thymocytes/drug effects
- Thymocytes/metabolism
- Thymocytes/pathology
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Affiliation(s)
- Ling Guo
- From the Department of Pediatrics (L.G., Z.Z., J.A., X.-A.L.), Graduate Center for Nutritional Sciences (Z.Z., J.A., X.-A.L.), and Saha Cardiovascular Research Center (D.A.H., A.D., X.-A.L.), University of Kentucky College of Medicine, Lexington; and Laboratory of Immune Cell Biology, National Cancer Institute (P.R.M., J.D.A.) and Lipoprotein Metabolism Section, National Heart, Lung, and Blood Institute (S.T., A.T.R.), National Institutes of Health, Bethesda, MD
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10
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Abstract
Scavenger receptor class B, type I (SR-BI), the Scarb1 gene product, is a receptor associated with cholesteryl ester uptake from high-density lipoproteins (HDL), which drives cholesterol movement from peripheral tissues toward the liver for excretion, and, consequently, Scarb1 null mice are prone to atherosclerosis. Because studies have linked atherosclerosis incidence with osteoporosis, we characterized the bone metabolism in these mice. Bone morphometry was assessed through microcomputed tomography and histology. Marrow stromal cells (MSCs) were used to characterize influence of endogenous SR-BI in cell functions. Total and HDL-associated cholesterol in null mice were increased by 32-60%, correlating with its role in lipoprotein metabolism. Distal metaphyses from 2- and 4-mo-old null mice showed correspondingly 46 and 37% higher bone volume fraction associated with a higher number of trabeculae. Histomorphometric analyses in 2-mo-old null male mice revealed 1.42-fold greater osteoblast surface, 1.37-fold higher percent mineralizing surface, and 1.69-fold enhanced bone formation rate. In vitro assays for MSCs from null mice revealed 37% higher proliferation rate, 48% more alkaline phosphatase activity, 70% greater mineralization potential and a 2-fold osterix (Sp7) expression, yet a 0.5-fold decrease in caveolin-1 (Cav1) expression. Selective uptake levels of HDL-associated cholesteryl oleate and estradiol were similar between MSC from wild-type and Scarb1 null mice, suggesting that its contribution to this process is not its main role in these cells. However, Scarb1 knockout stunted the HDL-dependent regulation of Cav1 genic expression. Scarb1 null mice are not prone to osteoporosis but show higher bone mass associated with enhanced bone formation.
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Affiliation(s)
- Corine Martineau
- Laboratoire du Métabolisme Osseux, BioMed, Université du Québec à Montréal, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada; and
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11
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Twiddy AL, Cox ME, Wasan KM. Knockdown of scavenger receptor class B type I reduces prostate specific antigen secretion and viability of prostate cancer cells. Prostate 2012; 72:955-65. [PMID: 22025344 DOI: 10.1002/pros.21499] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Accepted: 09/19/2011] [Indexed: 01/22/2023]
Abstract
BACKGROUND Scavenger Receptor Class B Type I (SR-BI) facilitates influx of cholesterol to the cell from lipoproteins in the circulation. This influx of cholesterol may be important for many cellular functions, including synthesis of androgens. Castration-resistant prostate cancer tumors are able to synthesize androgens de novo in order to supplement the loss of exogenous sources often induced by androgen deprivation therapy. Silencing of SR-BI may impact the ability of prostate cancer cells, particularly those of castration-resistant state, to maintain the intracellular supply of androgens by removing a supply of cholesterol. METHODS SR-BI expression was knocked down using small interfering RNA in LNCaP and C4-2 cells. The effect of down-regulation of SR-BI on PSA production, cell toxicity, and cell viability was measured in both cell types. In addition, compensatory cholesterol synthesis activity was measured using the radiolabeled precursor, (14) C-acetate. RESULTS SR-BI protein expression is higher basally in C4-2 cells than LNCaP cells. Silencing of SR-BI expression to greater than 85% reduced PSA production in LNCaP and C4-2 SRBI-KD cells by 55% and 58% compared to negative control cells, respectively. SR-BI-KD C4-2 cells demonstrated significantly reduced cell viability (>25%) compared the NC cells. CONCLUSIONS The down-regulation of SR-BI significantly impacts PSA production of prostate cancer cells, as well as the viability of C4-2 cells in the presence and absence of HDL. This may indicate a deficiency in cholesterol availability to the androgen synthesis pathway or may implicate a role for SR-BI in prostate cancer signal transduction pathways.
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Affiliation(s)
- Alexis L Twiddy
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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13
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Schäfer G, Guler R, Murray G, Brombacher F, Brown GD. The role of scavenger receptor B1 in infection with Mycobacterium tuberculosis in a murine model. PLoS One 2009; 4:e8448. [PMID: 20041149 PMCID: PMC2794535 DOI: 10.1371/journal.pone.0008448] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Accepted: 11/20/2009] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The interaction between Mycobacterium tuberculosis (Mtb) and host cells is complex and far from being understood. The role of the different receptor(s) implicated in the recognition of Mtb in particular remains poorly defined, and those that have been found to have activity in vitro were subsequently shown to be redundant in vivo. METHODS AND FINDINGS To identify novel receptors involved in the recognition of Mtb, we screened a macrophage cDNA library and identified scavenger receptor B class 1 (SR-B1) as a receptor for mycobacteria. SR-B1 has been well-described as a lipoprotein receptor which mediates both the selective uptake of cholesteryl esters and the efflux of cholesterol, and has also recently been implicated in the recognition of other pathogens. We show here that mycobacteria can bind directly to SR-B1 on transfected cells, and that this interaction could be inhibited in the presence of a specific antibody to SR-B1, serum or LDL. We define a variety of macrophage populations, including alveolar macrophages, that express this receptor, however, no differences in the recognition and response to mycobacteria were observed in macrophages isolated from SR-B1(-/-) or wild type mice in vitro. Moreover, when wild type and SR-B1(-/-) animals were infected with a low dose of Mtb (100 CFU/mouse) there were no alterations in survival, bacterial burdens, granuloma formation or cytokine production in the lung. However, significant reduction in the production of TNF, IFNgamma, and IL10 were observed in SR-B1(-/-) mice following infection with a high dose of Mtb (1000 CFU/mouse), which marginally affected the size of inflammatory foci but did not influence bacterial burdens. Deficiency of SR-B1 also had no effect on resistance to disease under conditions of varying dietary cholesterol. We did observe, however, that the presence of high levels of cholesterol in the diet significantly enhanced the bacterial burdens in the lung, but this was independent of SR-B1. CONCLUSION SR-B1 is involved in mycobacterial recognition, but this receptor plays only a minor role in anti-mycobacterial immunity in vivo. Like many other receptors for these pathogens, the loss of SR-B1 can be functionally compensated for under normal conditions.
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Affiliation(s)
- Georgia Schäfer
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), University of Cape Town, Cape Town, South Africa
| | - Reto Guler
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), University of Cape Town, Cape Town, South Africa
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town, South Africa
| | - Graeme Murray
- Section of Translational Medicine, Division of Applied Medicine, School of Medicine and Dentistry, University of Aberdeen, Foresterhill, United Kingdom
| | - Frank Brombacher
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), University of Cape Town, Cape Town, South Africa
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town, South Africa
| | - Gordon D. Brown
- Division of Immunology, Institute for Infectious Diseases and Molecular Medicine (IIDMM), University of Cape Town, Cape Town, South Africa
- Section of Immunology and Infection, Division of Applied Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, United Kingdom
- * E-mail:
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14
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West M, Greason E, Kolmakova A, Jahangiri A, Asztalos B, Pollin TI, Rodriguez A. Scavenger receptor class B type I protein as an independent predictor of high-density lipoprotein cholesterol levels in subjects with hyperalphalipoproteinemia. J Clin Endocrinol Metab 2009; 94:1451-7. [PMID: 19158204 PMCID: PMC2682469 DOI: 10.1210/jc.2008-1223] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT In mice, scavenger receptor class B, type I (SR-BI) receptor protein deficiency is associated with elevated high-density lipoprotein (HDL)-cholesterol (HDL-C) levels. OBJECTIVE Our objective was to determine the relationship between SR-BI protein and HDL-C levels in humans. DESIGN This was a prospective study of adults with hyperalphalipoproteinemia. Fasting blood was obtained for lipid and lipoprotein measurement, genomic DNA, and monocyte-derived macrophages. SR-BI protein levels were measured by Western blots, and SR-BI activity was measured by cholesteryl ester (CE) uptake of each donor's radiolabeled HDL with their monocyte-derived macrophages, or by degradation and specific cell association of dual-labeled HDL in vitro. SETTING The study was performed in a tertiary university teaching hospital. RESULTS The mean age was 57.2 +/- 10.9 yr (n = 65). SR-BI protein levels were inversely associated with HDL-C levels (P < 0.002), HDL particle size (P < 0.05), and positively associated with CE uptake (P < 0.004); there was no association with plasma apolipoprotein levels. SR-BI protein levels (P = 0.01) were independent predictors of HDL-C levels. Subjects who were carriers of the A allele for the rs4238001 (glycine to serine at position 2) polymorphism [single nucleotide polymorphism (SNP)] had lower SR-BI protein levels (P = 0.01), whereas carriers of the C allele for the rs2278986 SNP also had lower SR-BI protein levels (P = 0.02). Body mass index (P = 0.05), rs4238001 (P = 0.01), and rs2278986 (P = 0.01) SNPs were independent predictors of SR-BI protein levels. In vitro studies of murine macrophages stably expressing the glycine to serine at position 2 SNP showed less degradation (P < 0.0004) and specific cell association (P < 0.0004) of [(125)I, (3)H]-CE-labeled HDL. CONCLUSIONS SR-BI protein has an independent effect on HDL-C levels in women with hyperalphalipoproteinemia. Two SNPs were significantly associated with lower SR-BI protein levels.
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Affiliation(s)
- Michael West
- Department of Medicine, Division of Endocrinology and Metabolism, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA
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15
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Wang X, Collins HL, Ranalletta M, Fuki IV, Billheimer JT, Rothblat GH, Tall AR, Rader DJ. Macrophage ABCA1 and ABCG1, but not SR-BI, promote macrophage reverse cholesterol transport in vivo. J Clin Invest 2007; 117:2216-24. [PMID: 17657311 PMCID: PMC1924499 DOI: 10.1172/jci32057] [Citation(s) in RCA: 437] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2007] [Accepted: 05/10/2007] [Indexed: 01/21/2023] Open
Abstract
Macrophage ATP-binding cassette transporter A1 (ABCA1), scavenger receptor class B type I (SR-BI), and ABCG1 have been shown to promote cholesterol efflux to extracellular acceptors in vitro and influence atherosclerosis in mice, but their roles in mediating reverse cholesterol transport (RCT) from macrophages in vivo are unknown. Using an assay of macrophage RCT in mice, we found that primary macrophages lacking ABCA1 had a significant reduction in macrophage RCT in vivo, demonstrating the importance of ABCA1 in promoting macrophage RCT, however substantial residual RCT exists in the absence of macrophage ABCA1. Using primary macrophages deficient in SR-BI expression, we found that macrophage SR-BI, which was shown to promote cholesterol efflux in vitro, does not contribute to macrophage RCT in vivo. To investigate whether macrophage ABCG1 is involved in macrophage RCT in vivo, we used ABCG1-overexpressing, -knockdown, and -knockout macrophages. We show that increased macrophage ABCG1 expression significantly promoted while knockdown or knockout of macrophage ABCG1 expression significantly reduced macrophage RCT in vivo. Finally, we show that there was a greater decrease in macrophage RCT from cells where both ABCA1 and ABCG1 expression were knocked down than from ABCG1-knockdown cells. These results demonstrate that ABCA1 and ABCG1, but not SR-BI, promote macrophage RCT in vivo and are additive in their effects.
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Affiliation(s)
- Xun Wang
- Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Division of Molecular Medicine, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Heidi L. Collins
- Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Division of Molecular Medicine, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Mollie Ranalletta
- Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Division of Molecular Medicine, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Ilia V. Fuki
- Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Division of Molecular Medicine, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Jeffrey T. Billheimer
- Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Division of Molecular Medicine, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - George H. Rothblat
- Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Division of Molecular Medicine, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Alan R. Tall
- Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Division of Molecular Medicine, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
| | - Daniel J. Rader
- Institute for Translational Medicine and Therapeutics and Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Division of Molecular Medicine, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA
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Harder C, Lau P, Meng A, Whitman SC, McPherson R. Cholesteryl ester transfer protein (CETP) expression protects against diet induced atherosclerosis in SR-BI deficient mice. Arterioscler Thromb Vasc Biol 2007; 27:858-64. [PMID: 17272756 DOI: 10.1161/01.atv.0000259357.42089.dc] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To determine whether expression of the human CETP transgene protects against diet-induced atherosclerosis in SR-BI deficient mice. METHODS AND RESULTS SR-BI deficient (-/-) mice were crossed with CETP transgenic (CETPtg) mice to produce a colony of SR-BI(-/-) x CETPtg mice in a C57Bl/6 background. Age and sex matched groups of genetically modified and wild-type C57Bl/6 mice were fed a high fat, high cholesterol diet for 22 weeks. In both wild-type and SR-BI(-/-) mice, expression of the CETP transgene reduced the cholesterol content and increased the density of lipoprotein particles in the HDL density range. In SR-BI(-/-) x CETPtg mice, CETP activity inversely correlated with total plasma cholesterol levels and shifted the buoyant HDL typical of SR-BI deficiency toward a more normal density HDL particle. Atherosclerosis at the level of the aortic arch was evident in both male and female SR-BI deficient mice but occurred to a greater extent in the females. Expression of CETP markedly attenuated the development of atherosclerosis in SR-BI deficient mice fed an atherogenic diet (P<0.003). CONCLUSIONS Expression of the human CETP transgene protects SR-BI deficient mice from atherosclerosis, consistent with a role for CETP in remodeling HDL and providing an alternative pathway for the selective uptake of HDL-CE by the liver.
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Affiliation(s)
- Christopher Harder
- Lipoprotein and Atherosclerosis Research Group, University of Ottawa Heart Institute, Ottawa, Canada
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17
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Vishnyakova TG, Kurlander R, Bocharov AV, Baranova IN, Chen Z, Abu-Asab MS, Tsokos M, Malide D, Basso F, Remaley A, Csako G, Eggerman TL, Patterson AP. CLA-1 and its splicing variant CLA-2 mediate bacterial adhesion and cytosolic bacterial invasion in mammalian cells. Proc Natl Acad Sci U S A 2006; 103:16888-93. [PMID: 17071747 PMCID: PMC1636549 DOI: 10.1073/pnas.0602126103] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Indexed: 11/18/2022] Open
Abstract
CD36 and LIMPII analog 1, CLA-1, and its splicing variant, CLA-2 (SR-BI and SR-BII in rodents), are human high density lipoprotein receptors with an identical extracellular domain which binds a spectrum of ligands including bacterial cell wall components. In this study, CLA-1- and CLA-2-stably transfected HeLa and HEK293 cells demonstrated several-fold increases in the uptake of various bacteria over mock-transfected cells. All bacteria tested, including both Gram-negatives (Escherichia coli K12, K1 and Salmonella typhimurium) and Gram-positives (Staphylococcus aureus and Listeria monocytogenes), demonstrated various degrees of lower uptake in control cells. This result is consistent with the presence of high-density lipoprotein-receptor-independent bacterial uptake that is enhanced by CLA-1/CLA-2 overexpression. Bacterial lipopolysaccharides, lipoteichoic acid, and synthetic amphipathic helical peptides (L-37pA and D-37pA) competed with E. coli K12 for CLA-1 and CLA-2 binding. Transmission electron microscopy and confocal microscopy revealed cytosolic accumulation of bacteria in CLA-1/CLA-2-overexpressing HeLa cells. The antibiotic protection assay confirmed that E. coli K12 was able to survive and replicate intracellularly in CLA-1- and CLA-2-overexpressing HeLa, but both L-37pA and D-37pA prevented E. coli K12 invasion. Peritoneal macrophages isolated from SR-BI/BII-knockout mice demonstrated a 30% decrease in bacterial uptake when compared with macrophages from normal mice. Knockout macrophages were also characterized by decreased bacterial cytosolic invasion, ubiquitination, and proteasome mobilization while retaining bacterial lysosomal accumulation. These results indicate that, by facilitating bacterial adhesion and cytosolic invasion, CLA-1 and CLA-2 may play an important role in infection and sepsis.
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Affiliation(s)
| | | | | | | | | | | | | | - Daniela Malide
- Light Microscopy Core Facility, National Heart, Lung, and Blood Institute
| | | | | | - Gyorgy Csako
- Department of Laboratory Medicine, Clinical Center
| | - Thomas L. Eggerman
- Division of Diabetes, Endocrinology, and Metabolic Diseases, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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18
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Zhou H, Li Z, Silver DL, Jiang XC. Cholesteryl ester transfer protein (CETP) expression enhances HDL cholesteryl ester liver delivery, which is independent of scavenger receptor BI, LDL receptor related protein and possibly LDL receptor. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1482-8. [PMID: 17055779 PMCID: PMC1876826 DOI: 10.1016/j.bbalip.2006.09.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 07/17/2006] [Accepted: 09/06/2006] [Indexed: 11/25/2022]
Abstract
Cholesteryl ester transfer protein (CETP) is a hydrophobic plasma glycoprotein that mediates the transfer and exchange of cholesteryl ester (CE) and triglyceride (TG) between plasma lipoproteins, and also plays an important role in HDL metabolism. Previous studies have indicated that, compared to wild type mice, human CETP transgenic mice had significantly lower plasma HDL CE levels, which was associated with enhancement of HDL CE uptake by the liver. However, the mechanism of this process is still unknown. To evaluate the possibility that this might be directly mediated by CETP, we utilized CETP transgenic (CETPTg) mice with liver scavenger receptor BI (SR-BI) deficiency [i.e., PDZK1 gene knockout (PDZK1O)], and with receptor associated protein (RAP) overexpression, to block LDL receptor-related protein (LRP) and LDL receptor (LDLR). We found that (1) CETPTg/PDZK1O mice have significantly lower HDL-C than that of PDZK1 KO mice (36%, p<0.01); (2) CETPTg and CETPTg/PDZK1O mice have same HDL-C levels; (3) CETPTg/PDZK1O/RAP mice had significant lower plasma HDL-C levels than that of PDZK1O/RAP ones (50%, p<0.001); (4) there is no incremental transfer of HDL CE radioactivity to the apoB-containing lipoprotein fraction in mice expressing CETP; and (5) CETPTg/PDZK1O/RAP mice had significant higher plasma and liver [(3)H]CEt-HDL turnover rates than that of PDZK1O/RAP ones (50% and 53%, p<0.01, respectively). These results suggest that CETP expression in mouse increases direct removal of HDL CE in the liver and this process is independent of SR-BI, LRP, and possibly LDLR.
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Affiliation(s)
- Hongwen Zhou
- Department of Endocrinology, 1st Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China
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19
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Huby T, Doucet C, Dachet C, Ouzilleau B, Ueda Y, Afzal V, Rubin E, Chapman MJ, Lesnik P. Knockdown expression and hepatic deficiency reveal an atheroprotective role for SR-BI in liver and peripheral tissues. J Clin Invest 2006; 116:2767-76. [PMID: 16964311 PMCID: PMC1560348 DOI: 10.1172/jci26893] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Accepted: 07/18/2006] [Indexed: 11/17/2022] Open
Abstract
Scavenger receptor SR-BI has been implicated in HDL-dependent atheroprotective mechanisms. We report the generation of an SR-BI conditional knockout mouse model in which SR-BI gene targeting by loxP site insertion produced a hypomorphic allele (hypomSR-BI). Attenuated SR-BI expression in hypomSR-BI mice resulted in 2-fold elevation in plasma total cholesterol (TC) levels. Cre-mediated SR-BI gene inactivation of the hypomorphic SR-BI allele in hepatocytes (hypomSR-BI-KO(liver)) was associated with high plasma TC concentrations, increased plasma free cholesterol/TC (FC/TC) ratio, and a lipoprotein-cholesterol profile typical of SR-BI-/- mice. Plasma TC levels were increased 2-fold in hypomSR-BI and control mice fed an atherogenic diet, whereas hypomSR-BI-KO(liver) and SR-BI-/- mice developed severe hypercholesterolemia due to accumulation of FC-rich, VLDL-sized particles. Atherosclerosis in hypomSR-BI mice was enhanced (2.5-fold) compared with that in controls, but to a much lower degree than in hypomSR-BI-KO(liver) (32-fold) and SR-BI-/- (48-fold) mice. The latter models did not differ in either plasma lipid levels or in the capacity of VLDL-sized lipoproteins to induce macrophage cholesterol loading. However, reduced atherosclerosis in hypomSR-BI-KO(liver) mice was associated with decreased lesional macrophage content as compared with that in SR-BI-/- mice. These data imply that, in addition to its major atheroprotective role in liver, SR-BI may exert an antiatherogenic role in extrahepatic tissues.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily G, Member 1
- ATP-Binding Cassette Transporters/genetics
- Alleles
- Animals
- Antigens, CD/analysis
- Antigens, Differentiation, Myelomonocytic/analysis
- Apolipoproteins/blood
- Atherosclerosis/etiology
- Atherosclerosis/genetics
- Atherosclerosis/metabolism
- Cholesterol/blood
- Cholesterol, HDL/blood
- Cholesterol, LDL/blood
- Cholesterol, VLDL/blood
- Diet, Atherogenic
- Female
- Gene Expression/genetics
- Interleukin-6/blood
- Lipoproteins/blood
- Lipoproteins/chemistry
- Lipoproteins/genetics
- Liver/metabolism
- Liver/pathology
- Macrophages/chemistry
- Macrophages/pathology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Scavenger Receptors, Class B/deficiency
- Scavenger Receptors, Class B/genetics
- Scavenger Receptors, Class B/metabolism
- Sex Factors
- Triglycerides/blood
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Affiliation(s)
- Thierry Huby
- INSERM U551, Université Pierre et Marie Curie-Paris 6, Dyslipoproteinemia and Atherosclerosis Research Unit, Hôpital de la Pitié, Paris, France.
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21
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Meurs I, Hoekstra M, van Wanrooij EJA, Hildebrand RB, Kuiper J, Kuipers F, Hardeman MR, Van Berkel TJC, Van Eck M. HDL cholesterol levels are an important factor for determining the lifespan of erythrocytes. Exp Hematol 2006; 33:1309-19. [PMID: 16263415 DOI: 10.1016/j.exphem.2005.07.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Revised: 06/16/2005] [Accepted: 07/11/2005] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Scavenger receptor class B, type I (SR-BI) is a multifunctional receptor that promotes the selective uptake of cholesteryl esters from high-density lipoprotein (HDL). Disruption of SR-BI in mice results in a dramatic increase in HDL cholesterol. Interestingly, mice lacking SR-BI also develop anemia, as evidenced by accumulation of reticulocytes in the circulation. The objective of the current study was to delineate the mechanism underlying development of anemia in the absence of SR-BI. METHODS Expression of important mediators of erythropoiesis, as well as key enzymes in the degradation of erythrocytes, were analyzed using real-time polymerase chain reaction in SR-BI wild-type and SR-BI knockout mice. In addition, in vivo studies were performed using biotinylated erythrocytes to determine erythrocyte survival. RESULTS mRNA expression of TAL-1, GATA-1, FOG-1, erythropoietin receptor, and ferrochelatase, important mediators of erythropoiesis, was increased in spleens of SR-BI-deficient mice. In addition, the relative amount of early Ter119(high)CD71(high) -expressing erythroblasts was increased in SR-BI-deficient spleens. Interestingly, also expression of hemeoxygenase 1 and biliverdin reductase, enzymes involved in the degradation of erythrocytes, was increased. Furthermore, an elevated amount of conjugated bilirubin, the breakdown product of hemoglobin, was found in bile. Using biotinylated erythrocytes, we show that survival of erythrocytes was decreased in SR-BI-deficient mice. Thus, the observed increased erythropoiesis in the SR-BI-deficient mice is most likely a direct response to the reduced erythrocyte lifespan. Finally, we show that increased HDL cholesterol levels due to SR-BI deficiency induce erythrocyte cholesterol:phospholipid ratios, resulting in decreased deformability and increased osmotic fragility, thereby providing an explanation for the observed reduced lifespan. CONCLUSIONS SR-BI is not only essential for HDL cholesterol homeostasis and atherosclerosis susceptibility, but also for maintaining normal erythrocyte lifespan.
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Affiliation(s)
- Illiana Meurs
- Division of Biopharmaceutics, Leiden/Amsterdam Center for Drug Research, Gorlaeus Laboratories, Leiden, The Netherlands
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Zhang S, Picard MH, Vasile E, Zhu Y, Raffai RL, Weisgraber KH, Krieger M. Diet-Induced Occlusive Coronary Atherosclerosis, Myocardial Infarction, Cardiac Dysfunction, and Premature Death in Scavenger Receptor Class B Type I-Deficient, Hypomorphic Apolipoprotein ER61 Mice. Circulation 2005; 111:3457-64. [PMID: 15967843 DOI: 10.1161/circulationaha.104.523563] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
Normal chow (low fat)–fed mice deficient in both the HDL receptor SR-BI and apolipoprotein E (SR-BI/apoE dKO) provide a distinctive model of coronary heart disease (CHD). They exhibit early-onset hypercholesterolemia characterized by unesterified cholesterol-rich abnormal lipoproteins (lamellar/vesicular and stacked discoidal particles), occlusive coronary atherosclerosis, spontaneous myocardial infarction, cardiac dysfunction, and premature death (≈6 weeks of age). Mice in which similar features of CHD could be induced with a lipid-rich diet would represent a powerful tool to study CHD.
Methods and Results—
To generate a diet-inducible model of CHD, we bred SR-BI-deficient (SR-BI KO) mice with hypomorphic apolipoprotein E mice (
ApoeR61
h/h
) that express reduced levels of an apoE4-like murine apoE isoform and exhibit diet-induced hypercholesterolemia. When fed a normal chow diet, SR-BI KO/
ApoeR61
h/h
mice did not exhibit early-onset atherosclerosis or CHD; the low expression level of the apoE4-like murine apoE was atheroprotective and cardioprotective. However, when fed an atherogenic diet rich in fat, cholesterol, and cholate, they rapidly developed hypercholesterolemia, atherosclerosis, and CHD, a response strikingly similar to that of SR-BI/apoE dKO mice fed a chow diet, and they died 32±6 days (50% mortality) after initiation of the high-fat feeding.
Conclusions—
The SR-BI KO/
ApoeR61
h/h
mouse is a new model of diet-induced occlusive coronary atherosclerosis and CHD (myocardial infarction, cardiac dysfunction and premature death), allowing control of the age of onset, duration, severity, and possibly regression of disease. Thus, SR-BI KO/
ApoeR61
h/h
mice have the potential to contribute to our understanding of CHD and its prevention and treatment.
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Affiliation(s)
- Songwen Zhang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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