1
|
Hu S, Zhu Y, Zhao X, Li R, Shao G, Gong D, Hu C, Liu H, Xu K, Liu C, Xu M, Zhao Z, Li T, Hu Z, Shao M, Liu J, Li X, Wu H, Li J, Xu Y. Hepatocytic lipocalin-2 controls HDL metabolism and atherosclerosis via Nedd4-1-SR-BI axis in mice. Dev Cell 2023; 58:2326-2337.e5. [PMID: 37863040 DOI: 10.1016/j.devcel.2023.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 07/03/2023] [Accepted: 09/25/2023] [Indexed: 10/22/2023]
Abstract
High-density lipoprotein (HDL) metabolism is regulated by complex interplay between the scavenger receptor group B type 1 (SR-BI) and multiple signaling molecules in the liver. Here, we show that lipocalin-2 (Lcn2) is a key regulator of hepatic SR-BI, HDL metabolism, and atherosclerosis. Overexpression of human Lcn2 in hepatocytes attenuates the development of atherosclerosis via SR-BI in western-diet-fed Ldlr-/- mice, whereas hepatocyte-specific ablation of Lcn2 has the opposite effect. Mechanistically, hepatocyte Lcn2 improves HDL metabolism and alleviates atherogenesis by blocking Nedd4-1-mediated SR-BI ubiquitination at K500 and K508. The Lcn2-improved HDL metabolism is abolished in mice with hepatocyte-specific Nedd4-1 or SR-BI deletion and in SR-BI (K500A/K508A) mutation mice. This study identifies a regulatory axis from Lcn2 to HDL via blocking Nedd4-1-mediated SR-BI ubiquitination and demonstrates that hepatocyte Lcn2 may be a promising target to improve HDL metabolism to treat atherosclerotic cardiovascular diseases.
Collapse
Affiliation(s)
- Shuwei Hu
- School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China; Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH 44272, USA
| | - Yingdong Zhu
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH 44272, USA
| | - Xiaojie Zhao
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Rui Li
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Guangze Shao
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Dongxu Gong
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Chencheng Hu
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Hongjun Liu
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Kexin Xu
- Department of Nephrology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China
| | - Chenxi Liu
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Minghuan Xu
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Zhonghua Zhao
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Tao Li
- Department of Hepatobiliary Surgery, Peking University People's Hospital Xizhimen South Street, West District, Beijing 100044, China
| | - Zhigang Hu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Mengle Shao
- Center for Microbes, Development and Health, CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jun- Liu
- Department of Nephrology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China
| | - Xinwei Li
- State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Key Laboratory for Zoonosis Research of the Ministry of Education, Institute of Zoonosis, and College of Veterinary Medicine, Jilin University, Changchun 130062, China
| | - Huijuan Wu
- Department of Pathology, School of Basic Medical Sciences, Fudan University Shanghai, Shanghai 200032, China
| | - Jing Li
- Department of Endocrinology, Beijing Chao-yang Hospital, Capital Medical University, Beijing 100020, China.
| | - Yanyong Xu
- Key Laboratory of Metabolism and Molecular Medicine of the Ministry of Education, Department of Pathology of School of Basic Medical Sciences, Frontier Innovation Center, Fudan University Shanghai, Shanghai 200032, China; Diabetes, Obesity and Metabolism Research Center, Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH 44272, USA.
| |
Collapse
|
2
|
Vishnyakova TG, Bocharov AV, Baranova IN, Kurlander R, Drake SK, Chen Z, Amar M, Sviridov D, Vaisman B, Poliakov E, Remaley AT, Eggerman TL, Patterson AP. SR-BI mediates neutral lipid sorting from LDL to lipid droplets and facilitates their formation. PLoS One 2020; 15:e0240659. [PMID: 33057430 PMCID: PMC7561250 DOI: 10.1371/journal.pone.0240659] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 09/30/2020] [Indexed: 12/30/2022] Open
Abstract
SR-BI binds various lipoproteins, including HDL, LDL as well as VLDL, and mediates selective cholesteryl ester (CE) uptake. HDL derived CE accumulates in cellular lipid droplets (LDs), which also store triacylglycerol (TAG). We hypothesized that SR-BI could significantly facilitate LD formation, in part, by directly transporting LDL derived neutral lipids (NL) such as CE and TAG into LDs without lipolysis and de novo lipid synthesis. SR-BI overexpression greatly increased LDL uptake and LD formation in stably transfected HeLa cells (SR-BI-HeLa). LDs isolated from SR-BI-HeLa contained 4- and 7-times more CE and TAG, respectively, than mock-transfected HeLa (Mock-HeLa). In contrast, LDL receptor overexpression in HeLa (LDLr-HeLa) greatly increased LDL uptake, degradation with moderate 1.5- and 2-fold increases of CE and TAG, respectively. Utilizing CE and TAG analogs, BODIPY-TAG (BP-TAG) and BODIPY-CE (BP-CE), for tracking LDL NL, we found that after initial binding of LDL to SR-BI-HeLa, apoB remained at the cell surface, while BP-CE and BP-TAG were sorted and simultaneously transported together to LDs. Both lipids demonstrated limited internalization to lysosomes or endoplasmic reticulum in SR-BI-HeLa. In LDLr-HeLa, NLs demonstrated clear lysosomal sequestration without their sorting to LDs. An inhibition of TAG and CE de novo synthesis by 90-95% only reduced TAG and CE LD content by 45-50%, and had little effect on BP-CE and BP-TAG transport to LDs in SR-BI HeLa. Furthermore, intravenous infusion of 1-2 mg of LDL increased liver LDs in normal (WT) but not in SR-BI KO mice. Mice transgenic for human SR-BI demonstrated higher liver LD accumulation than WT mice. Finally, Electro Spray Infusion Mass Spectrometry (ESI-MS) using deuterated d-CE found that LDs accumulated up to 40% of unmodified d-CE LDL. We conclude that SR-BI mediates LDL-induced LD formation in vitro and in vivo. In addition to cytosolic NL hydrolysis and de novo lipid synthesis, this process includes selective sorting and transport of LDL NL to LDs with limited lysosomal NL sequestration and the transport of LDL CE, and TAG directly to LDs independently of de novo synthesis.
Collapse
Affiliation(s)
- Tatyana G. Vishnyakova
- Clinical Center, The National Institutes of Health, Bethesda, Maryland,
United States of America
| | - Alexander V. Bocharov
- Clinical Center, The National Institutes of Health, Bethesda, Maryland,
United States of America
- * E-mail:
| | - Irina N. Baranova
- Clinical Center, The National Institutes of Health, Bethesda, Maryland,
United States of America
| | - Roger Kurlander
- Clinical Center, The National Institutes of Health, Bethesda, Maryland,
United States of America
| | - Steven K. Drake
- Clinical Center, The National Institutes of Health, Bethesda, Maryland,
United States of America
| | - Zhigang Chen
- Clinical Center, The National Institutes of Health, Bethesda, Maryland,
United States of America
| | - Marcelo Amar
- National Heart, Lung and Blood Institute, Bethesda, Maryland, United
States of America
| | - Denis Sviridov
- National Heart, Lung and Blood Institute, Bethesda, Maryland, United
States of America
| | - Boris Vaisman
- National Heart, Lung and Blood Institute, Bethesda, Maryland, United
States of America
| | - Eugenia Poliakov
- National Eye Institute, Bethesda, Maryland, United States of
America
| | - Alan T. Remaley
- National Heart, Lung and Blood Institute, Bethesda, Maryland, United
States of America
| | - Thomas L. Eggerman
- Clinical Center, The National Institutes of Health, Bethesda, Maryland,
United States of America
- National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda,
Maryland, United States of America
| | - Amy P. Patterson
- Clinical Center, The National Institutes of Health, Bethesda, Maryland,
United States of America
- National Heart, Lung and Blood Institute, Bethesda, Maryland, United
States of America
| |
Collapse
|
3
|
Yu XH, Zhang DW, Zheng XL, Tang CK. Cholesterol transport system: An integrated cholesterol transport model involved in atherosclerosis. Prog Lipid Res 2018; 73:65-91. [PMID: 30528667 DOI: 10.1016/j.plipres.2018.12.002] [Citation(s) in RCA: 150] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 10/30/2018] [Accepted: 12/01/2018] [Indexed: 02/07/2023]
Abstract
Atherosclerosis, the pathological basis of most cardiovascular disease (CVD), is closely associated with cholesterol accumulation in the arterial intima. Excessive cholesterol is removed by the reverse cholesterol transport (RCT) pathway, representing a major antiatherogenic mechanism. In addition to the RCT, other pathways are required for maintaining the whole-body cholesterol homeostasis. Thus, we propose a working model of integrated cholesterol transport, termed the cholesterol transport system (CTS), to describe body cholesterol metabolism. The novel model not only involves the classical view of RCT but also contains other steps, such as cholesterol absorption in the small intestine, low-density lipoprotein uptake by the liver, and transintestinal cholesterol excretion. Extensive studies have shown that dysfunctional CTS is one of the major causes for hypercholesterolemia and atherosclerosis. Currently, several drugs are available to improve the CTS efficiently. There are also several therapeutic approaches that have entered into clinical trials and shown considerable promise for decreasing the risk of CVD. In recent years, a variety of novel findings reveal the molecular mechanisms for the CTS and its role in the development of atherosclerosis, thereby providing novel insights into the understanding of whole-body cholesterol transport and metabolism. In this review, we summarize the latest advances in this area with an emphasis on the therapeutic potential of targeting the CTS in CVD patients.
Collapse
Affiliation(s)
- Xiao-Hua Yu
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Medical Research Experiment Center, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, Hunan 421001, China
| | - Da-Wei Zhang
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, University of Alberta, Alberta, Canada
| | - Xi-Long Zheng
- Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Health Sciences Center, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Chao-Ke Tang
- Institute of Cardiovascular Disease, Key Laboratory for Arteriosclerology of Hunan Province, Medical Research Experiment Center, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, Hunan 421001, China.
| |
Collapse
|
4
|
Hoekstra M, Van Eck M. HDL is redundant for adrenal steroidogenesis in LDLR knockout mice with a human-like lipoprotein profile. J Lipid Res 2016; 57:631-7. [PMID: 26891738 DOI: 10.1194/jlr.m066019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Indexed: 11/20/2022] Open
Abstract
The contribution of HDL to adrenal steroidogenesis appears to be different between mice and humans. In the current study, we tested the hypothesis that a difference in lipoprotein profile may be the underlying cause. Hereto, we determined the impact of HDL deficiency on the adrenal glucocorticoid output in genetically modified mice with a human-like lipoprotein profile. Genetic deletion of APOA1 in LDL receptor (LDLR) knockout mice was associated with HDL deficiency and a parallel increase in the level of cholesterol associated with nonHDL fractions. Despite a compensatory increase in the adrenal relative mRNA expression levels of the cholesterol synthesis gene, HMG-CoA reductase, adrenals from APOA1/LDLR double knockout mice were severely depleted of neutral lipids, as compared with those of control LDLR knockout mice. However, basal corticosterone levels and the adrenal glucocorticoid response to stress were not different between the two types of mice. In conclusion, we have shown that HDL is not critical for proper adrenal glucocorticoid function when mice are provided with a human-like lipoprotein profile. Our findings provide the first experimental evidence that APOB-containing lipoproteins may facilitate adrenal steroidogenesis, in an LDLR-independent manner, in vivo in mice.
Collapse
Affiliation(s)
- Menno Hoekstra
- Division of Biopharmaceutics, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, 2333CC Leiden, The Netherlands
| | - Miranda Van Eck
- Division of Biopharmaceutics, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, 2333CC Leiden, The Netherlands
| |
Collapse
|
5
|
Niemsiri V, Wang X, Pirim D, Radwan ZH, Bunker CH, Barmada MM, Kamboh MI, Demirci FY. Genetic contribution of SCARB1 variants to lipid traits in African Blacks: a candidate gene association study. BMC MEDICAL GENETICS 2015; 16:106. [PMID: 26563154 PMCID: PMC4643515 DOI: 10.1186/s12881-015-0250-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 10/30/2015] [Indexed: 12/03/2022]
Abstract
Background High-density lipoprotein cholesterol (HDL-C) exerts many anti-atherogenic properties including its role in reverse cholesterol transport (RCT). Scavenger receptor class B member 1 (SCARB1) plays a key role in RCT by selective uptake of HDL cholesteryl esters. We aimed to explore the genetic contribution of SCARB1 to affecting lipid levels in African Blacks from Nigeria. Methods We resequenced 13 exons and exon-intron boundaries of SCARB1 in 95 individuals with extreme HDL-C levels using Sanger method. Then, we genotyped 147 selected variants (78 sequence variants, 69 HapMap tagSNPs, and 2 previously reported relevant variants) in the entire sample of 788 African Blacks using either the iPLEX Gold or TaqMan methods. A total of 137 successfully genotyped variants were further evaluated for association with major lipid traits. Results The initial gene-based analysis demonstrated evidence of association with HDL-C and apolipoprotein A-I (ApoA-I). The follow-up single-site analysis revealed nominal evidence of novel associations of nine common variants with HDL-C and/or ApoA-I (P < 0.05). The strongest association was between rs11057851 and HDL-C (P = 0.0043), which remained significant after controlling for multiple testing using false discovery rate. Rare variant association testing revealed a group of 23 rare variants (frequencies ≤1 %) associated with HDL-C (P = 0.0478). Haplotype analysis identified four SCARB1 regions associated with HDL-C (global P < 0.05). Conclusions To our knowledge, this is the first report of a comprehensive association study of SCARB1 variations with lipid traits in an African Black population. Our results showed the consistent association of SCARB1 variants with HDL-C across various association analyses, supporting the role of SCARB1 in lipoprotein-lipid regulatory mechanism. Electronic supplementary material The online version of this article (doi:10.1186/s12881-015-0250-6) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Vipavee Niemsiri
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA.
| | - Xingbin Wang
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA.
| | - Dilek Pirim
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA.
| | - Zaheda H Radwan
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA.
| | - Clareann H Bunker
- Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA.
| | - M Michael Barmada
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA.
| | - M Ilyas Kamboh
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA.
| | - F Yesim Demirci
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA, 15261, USA.
| |
Collapse
|
6
|
Lino M, Farr S, Baker C, Fuller M, Trigatti B, Adeli K. Intestinal scavenger receptor class B type I as a novel regulator of chylomicron production in healthy and diet-induced obese states. Am J Physiol Gastrointest Liver Physiol 2015; 309:G350-9. [PMID: 26138463 DOI: 10.1152/ajpgi.00086.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 06/25/2015] [Indexed: 01/31/2023]
Abstract
The small intestine contributes to diabetic dyslipidemia through the overproduction of apolipoprotein B48 (apoB48)-containing chylomicron particles. An important regulator of chylomicron generation is dietary lipid absorption, underlining the potential involvement of intestinal lipid transporters for developing dyslipidemia. Intestinal expression of scavenger receptor class B type I (SR-BI) has been found to be upregulated in animal models of insulin resistance. Here we characterized the potential importance of SR-BI in contributing to chylomicron production and postprandial hypertriglyceridemia in vivo. Postprandial triglyceride (TG)-rich lipoprotein (TRL) production was characterized in hamsters treated with the SR-BI inhibitor to block lipid transport-1 (BLT-1) under healthy conditions or conditions of diet-induced obesity and dyslipidemia. BLT-1 (1 mg/kg) or vehicle was administered acutely in chow-fed hamsters or gavaged twice daily over 10 days during high-fructose, high-fat, high-cholesterol (FFC) feeding. Effects of acute SR-BI inhibition by BLT-1 were confirmed in healthy fat-loaded rats. Finally, plasma lipid levels were compared between SR-BI(-/-) mice and their wild-type counterparts fed either chow or a 12-wk high-fat diet. Acute BLT-1 treatment reduced postprandial plasma and TRL TG levels in healthy hamsters and rats. Chronic BLT-1 treatment of FFC-fed hamsters blunted diet-induced weight gain and fasting hypertriglyceridemia, and lowered postprandial TRL-TG, -cholesterol, and -apoB48 levels. Finally, SR-BI(-/-) mice displayed lower plasma and TRL TG levels relative to wild type, and diet-induced weight gain and postprandial hypertriglyceridemia were hindered in SR-BI(-/-) mice. We conclude that intestinal SR-BI is a critical regulator of postprandial lipoprotein production, emphasizing its potential as a target for preventing diabetic dyslipidemia.
Collapse
Affiliation(s)
- Marsel Lino
- Department of Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and
| | - Sarah Farr
- Department of Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and
| | - Chris Baker
- Department of Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Mark Fuller
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Bernardo Trigatti
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Khosrow Adeli
- Department of Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and
| |
Collapse
|
7
|
Zannis VI, Fotakis P, Koukos G, Kardassis D, Ehnholm C, Jauhiainen M, Chroni A. HDL biogenesis, remodeling, and catabolism. Handb Exp Pharmacol 2015; 224:53-111. [PMID: 25522986 DOI: 10.1007/978-3-319-09665-0_2] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In this chapter, we review how HDL is generated, remodeled, and catabolized in plasma. We describe key features of the proteins that participate in these processes, emphasizing how mutations in apolipoprotein A-I (apoA-I) and the other proteins affect HDL metabolism. The biogenesis of HDL initially requires functional interaction of apoA-I with the ATP-binding cassette transporter A1 (ABCA1) and subsequently interactions of the lipidated apoA-I forms with lecithin/cholesterol acyltransferase (LCAT). Mutations in these proteins either prevent or impair the formation and possibly the functionality of HDL. Remodeling and catabolism of HDL is the result of interactions of HDL with cell receptors and other membrane and plasma proteins including hepatic lipase (HL), endothelial lipase (EL), phospholipid transfer protein (PLTP), cholesteryl ester transfer protein (CETP), apolipoprotein M (apoM), scavenger receptor class B type I (SR-BI), ATP-binding cassette transporter G1 (ABCG1), the F1 subunit of ATPase (Ecto F1-ATPase), and the cubulin/megalin receptor. Similarly to apoA-I, apolipoprotein E and apolipoprotein A-IV were shown to form discrete HDL particles containing these apolipoproteins which may have important but still unexplored functions. Furthermore, several plasma proteins were found associated with HDL and may modulate its biological functions. The effect of these proteins on the functionality of HDL is the topic of ongoing research.
Collapse
Affiliation(s)
- Vassilis I Zannis
- Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, 02118, USA,
| | | | | | | | | | | | | |
Collapse
|
8
|
Postprandial phase time influences the uptake of TAG from postprandial TAG-rich lipoproteins by THP-1 macrophages. Br J Nutr 2014; 112:1469-77. [DOI: 10.1017/s000711451400244x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Postprandial TAG-rich lipoproteins (TRL) can be taken up by macrophages, leading to the formation of foam cells, probably via receptor-mediated pathways. The present study was conducted to investigate whether the postprandial time point at which TRL are collected modulates this process. A meal containing refined olive oil was given to nine healthy young men and TRL were isolated from their serum at 2, 4 and 6 h postprandially. The lipid class and apoB compositions of TRL were determined by HPLC and SDS–PAGE, respectively. The accumulation of lipids in macrophages was determined after the incubation of THP-1 macrophages with TRL. The gene expression of candidate receptors was measured by real-time PCR. The highest concentrations of TAG, apoB48 and apoB100 in TRL were observed at 2 h after the consumption of the test meal. However, excessive intracellular TAG accumulation in THP-1 macrophages was observed in response to incubation with TRL isolated at 4 h, when their particle size (estimated as the TAG:apoB ratio) was intermediate. The abundance of mRNA transcripts in macrophages in response to incubation with TRL was down-regulated for LDL receptor (LDLR), slightly up-regulated for VLDL receptor and remained unaltered for LDLR-related protein, but no effect of the postprandial time point was observed. In contrast, the mRNA expression of scavenger receptors SRB1, SRA2 and CD36 was higher when cells were incubated with TRL isolated at 4 h after the consumption of the test meal. In conclusion, TRL led to excessive intracellular TAG accumulation in THP-1 macrophages, which was greater when cells were incubated with intermediate-sized postprandial TRL isolated at 4 h and was associated with a significant increase in the mRNA expression of scavenger receptors.
Collapse
|
9
|
Niemsiri V, Wang X, Pirim D, Radwan ZH, Hokanson JE, Hamman RF, Barmada MM, Demirci FY, Kamboh MI. Impact of genetic variants in human scavenger receptor class B type I (SCARB1) on plasma lipid traits. ACTA ACUST UNITED AC 2014; 7:838-47. [PMID: 25245032 DOI: 10.1161/circgenetics.114.000559] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Scavenger receptor class B type 1 (SCARB1) plays an important role in high-density lipoprotein cholesterol (HDL-C) metabolism in selective cholesteryl ester uptake and in free cholesterol cellular efflux. METHODS AND RESULTS This study aims to identify common (minor allele frequency ≥5%) and low-frequency/rare (minor allele frequency <5%) variants, using resequencing all 13 exons and exon-intron boundaries of SCARB1 in 95 individuals with extreme HDL-C levels selected from a population-based sample of 623 US non-Hispanic whites. The sequencing step identified 44 variants, of which 11 were novel with minor allele frequency <1%. Seventy-six variants (40 sequence variants, 32 common HapMap tag single nucleotide polymorphisms, and 4 relevant variants) were selected for genotyping in the total sample of 623 subjects followed by association analyses with lipid traits. Seven variants were nominally associated with apolipoprotein B (apoB; n=4) or HDL-C (n=3; P<0.05). Three variants associated with apoB remained significant after controlling false discovery rate. The most significant association was observed between rs4765615 and apoB (P=0.0059), while rs11057844 showed the strongest association with HDL-C (P=0.0035). A set of 17 rare variants (minor allele frequency ≤1%) showed significant association with apoB (P=0.0284). Haplotype analysis revealed 4 regions significantly associated with either apoB or HDL-C. CONCLUSIONS Our findings provide new information about the genetic role of SCARB1 in affecting plasma apoB levels in addition to its established role in HDL-C metabolism.
Collapse
Affiliation(s)
- Vipavee Niemsiri
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Sun TT, Tang JY, Du W, Zhao HJ, Zhao G, Yang SL, Chen HY, Hong J, Fang JY. Bidirectional regulation between TMEFF2 and STAT3 may contribute to Helicobacter pylori-associated gastric carcinogenesis. Int J Cancer 2014; 136:1053-64. [PMID: 24996057 DOI: 10.1002/ijc.29061] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 06/04/2014] [Indexed: 12/12/2022]
Abstract
The transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is a single-pass transmembrane protein, and it is downregulated in human gastric cancer and levels correlate with tumor progression and time of survival. However, the mechanism of its dysregulation in gastric cancer is little known. Here we investigate its regulatory mechanism and the bidirectional regulation between TMEFF2 and STAT3 in gastric carcinogenesis. TMEFF2 expression was decreased after Helicobacter pylori (H. pylori) infection in vivo and in vitro. STAT3 directly binds to the promoter of TMEFF2 and regulates H. pylori-induced TMEFF2 downregulation in normal gastric GES-1 cells and gastric cancer AGS cells. Conversely, TMEFF2 may suppress the phosphorylation of STAT3 and TMEFF2-induced downregulation of STAT3 phosphorylation may depend on SHP-1. A highly inverse correlation between the expression of TMEFF2 and pSTAT3 was also revealed in gastric tissues. We now show the deregulation mechanism of TMEFF2 in gastric carcinogenesis and identify TMEFF2 as a new target gene of STAT3. The phosphorylation of STAT3 may be negatively regulated by TMEFF2, and the bidirectional regulation between TMEFF2 and STAT3 may contribute to H. pylori-associated gastric carcinogenesis.
Collapse
Affiliation(s)
- Tian-Tian Sun
- State Key Laboratory for Oncogenes and Related Genes, Key Laboratory of Gastroenterology & Hepatology, Ministry of Health, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai Cancer Institute, Shanghai Institute of Digestive Disease, Shanghai, 200001, China
| | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Xiong H, Du W, Sun TT, Lin YW, Wang JL, Hong J, Fang JY. A positive feedback loop between STAT3 and cyclooxygenase-2 gene may contribute to Helicobacter pylori-associated human gastric tumorigenesis. Int J Cancer 2014; 134:2030-40. [PMID: 24127267 DOI: 10.1002/ijc.28539] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 09/12/2013] [Accepted: 09/26/2013] [Indexed: 12/27/2022]
Abstract
Persistent infection with Helicobacter pylori (H. pylori) contributes to gastric diseases including chronic gastritis and gastric cancer. However, the pathogenesis of this carcinogenic bacterium has not been completely elucidated. Here, we report that H. pylori rapidly triggers STAT3 signaling and induces STAT3-dependent COX-2 expression both in vitro and in vivo. STAT3 upregulates COX-2 by binding to and increasing the activity of COX-2 promoter. COX-2 in turn regulates IL-6/STAT3 signaling under basal conditions and during H. pylori infection. These findings suggest that a positive feedback loop between STAT3 and COX-2 exists in the basal condition and H. pylori infectious condition. Immunohistochemical staining revealed that H. pylori-positive gastritis tissues exhibited markedly higher levels of pSTAT3(Tyr705) than H. pylori-negative ones. High pSTAT3(Tyr705) levels are correlated with intestinal metaplasia and dysplasia, suggesting pSTAT3(Tyr705) may be useful in the early detection of gastric tumorigenesis. Additionally, a strong positive correlation between STAT3/pSTAT3(Tyr705) levels and COX-2 expression was identified in gastritis and gastric cancer tissues. Together, these findings provide new evidence for a positive feedback loop between STAT3 signaling and COX-2 in H. pylori pathogenesis and may lead to new approaches for early detection and effective therapy of gastric cancer
Collapse
|
12
|
Challenges in using cultured primary rodent hepatocytes or cell lines to study hepatic HDL receptor SR-BI regulation by its cytoplasmic adaptor PDZK1. PLoS One 2013; 8:e69725. [PMID: 23936087 PMCID: PMC3720616 DOI: 10.1371/journal.pone.0069725] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 06/12/2013] [Indexed: 12/15/2022] Open
Abstract
Background PDZK1 is a four PDZ-domain containing cytoplasmic protein that binds to a variety of membrane proteins via their C-termini and can influence the abundance, localization and/or function of its target proteins. One of these targets in hepatocytes in vivo is the HDL receptor SR-BI. Normal hepatic expression of SR-BI protein requires PDZK1 - <5% of normal hepatic SR-BI is seen in the livers of PDZK1 knockout mice. Progress has been made in identifying features of PDZK1 required to control hepatic SR-BI in vivo using hepatic expression of wild-type and mutant forms of PDZK1 in wild-type and PDZK1 KO transgenic mice. Such in vivo studies are time consuming and expensive, and cannot readily be used to explore many features of the underlying molecular and cellular mechanisms. Methodology/Principal Findings Here we have explored the potential to use either primary rodent hepatocytes in culture using 2D collagen gels with newly developed optimized conditions or PDZK1/SR-BI co-transfected cultured cell lines (COS, HEK293) for such studies. SR-BI and PDZK1 protein and mRNA expression levels fell rapidly in primary hepatocyte cultures, indicating this system does not adequately mimic hepatocytes in vivo for analysis of the PDZK1 dependence of SR-BI. Although PDZK1 did alter SR-BI protein expression in the cell lines, its influence was independent of SR-BI’s C-terminus, and thus is not likely to occur via the same mechanism as that which occurs in hepatocytes in vivo. Conclusions/Significance Caution must be exercised in using primary hepatocytes or cultured cell lines when studying the mechanism underlying the regulation of hepatic SR-BI by PDZK1. It may be possible to use SR-BI and PDZK1 expression as sensitive markers for the in vivo-like state of hepatocytes to further improve primary hepatocyte cell culture conditions.
Collapse
|
13
|
Hepatitis C virus, cholesterol and lipoproteins--impact for the viral life cycle and pathogenesis of liver disease. Viruses 2013; 5:1292-324. [PMID: 23698400 PMCID: PMC3712309 DOI: 10.3390/v5051292] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 04/10/2013] [Accepted: 04/27/2013] [Indexed: 02/07/2023] Open
Abstract
Hepatitis C virus (HCV) is a leading cause of chronic liver disease, including chronic hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Hepatitis C infection associates with lipid and lipoprotein metabolism disorders such as hepatic steatosis, hypobetalipoproteinemia, and hypocholesterolemia. Furthermore, virus production is dependent on hepatic very-low-density lipoprotein (VLDL) assembly, and circulating virions are physically associated with lipoproteins in complexes termed lipoviral particles. Evidence has indicated several functional roles for the formation of these complexes, including co-opting of lipoprotein receptors for attachment and entry, concealing epitopes to facilitate immune escape, and hijacking host factors for HCV maturation and secretion. Here, we review the evidence surrounding pathogenesis of the hepatitis C infection regarding lipoprotein engagement, cholesterol and triglyceride regulation, and the molecular mechanisms underlying these effects.
Collapse
|
14
|
Goldberg IJ, Huang LS, Huggins LA, Yu S, Nagareddy PR, Scanlan TS, Ehrenkranz JR. Thyroid hormone reduces cholesterol via a non-LDL receptor-mediated pathway. Endocrinology 2012; 153:5143-9. [PMID: 22948212 PMCID: PMC3473203 DOI: 10.1210/en.2012-1572] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 08/07/2012] [Indexed: 12/27/2022]
Abstract
Although studies in vitro and in hypothyroid animals show that thyroid hormone can, under some circumstances, modulate the actions of low-density lipoprotein (LDL) receptors, the mechanisms responsible for thyroid hormone's lipid-lowering effects are not completely understood. We tested whether LDL receptor (LDLR) expression was required for cholesterol reduction by treating control and LDLR-knockout mice with two forms of thyroid hormone T(3) and 3,5-diiodo-l-thyronine. High doses of both 3,5-diiodo-l-thyronine and T(3) dramatically reduced circulating total and very low-density lipoprotein/LDL cholesterol (∼70%) and were associated with reduced plasma T(4) level. The cholesterol reduction was especially evident in the LDLR-knockout mice. Circulating levels of both apolipoprotein B (apo)B48 and apoB100 were decreased. Surprisingly, this reduction was not associated with increased protein or mRNA expression of the hepatic lipoprotein receptors LDLR-related protein 1 or scavenger receptor-B1. Liver production of apoB was markedly reduced, whereas triglyceride production was increased. Thus, thyroid hormones reduce apoB lipoproteins via a non-LDLR pathway that leads to decreased liver apoB production. This suggests that drugs that operate in a similar manner could be a new therapy for patients with genetic defects in the LDLR.
Collapse
Affiliation(s)
- Ira J Goldberg
- Department of Medicine, Columbia University, New York, New York 10032, USA.
| | | | | | | | | | | | | |
Collapse
|
15
|
Abstract
PURPOSE OF REVIEW This review highlights the diverse roles of the high-affinity HDL receptor scavenger receptor class B, type I (SR-BI) in the modulation of global cholesterol homeostasis and vascular cell function, and the potential implications of these processes in atherosclerosis. RECENT FINDINGS SR-BI in the liver plays a critical role in reverse cholesterol transport and it dramatically impacts the characteristics of the HDL particle, and through reverse cholesterol transport it promotes an antiatherogenic lipid environment in the vascular wall. SR-BI in macrophages may influence their inflammatory phenotype. In endothelial cells, SR-BI mediates HDL-induced endothelial nitric oxide synthase activation and proliferation and migration, and in platelets SR-BI may be prothrombotic in the setting of dyslipidemia. Several polymorphisms of SR-BI have been reported in humans that influence receptor expression or function. SUMMARY In addition to regulating global lipid metabolism, SR-BI influences the functions of a variety of vascular cells relevant to atherosclerosis. Studies of SR-BI genetics in humans partially support the conclusions drawn from experimental models. However, because of the multiple functions of SR-BI, the diversity of cell types in which it is expressed, and the influence of the receptor on the characteristics of its own ligand, our understanding of the biology of the receptor is just emerging.
Collapse
Affiliation(s)
- Chieko Mineo
- Division of Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9063, USA.
| | | |
Collapse
|
16
|
Wang L, Shearer GC, Budamagunta MS, Voss JC, Molfino A, Kaysen GA. Proteinuria decreases tissue lipoprotein receptor levels resulting in altered lipoprotein structure and increasing lipid levels. Kidney Int 2012; 82:990-9. [PMID: 22785171 DOI: 10.1038/ki.2012.244] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Rats with nephrotic syndrome (NS) have a fivefold increase in lipids and a similar decrease in triglyceride-rich lipoprotein (TRL) clearance. Lipoprotein lipase (LPL) is reduced both in NS and in the Nagase analbuminemic rat. These rats have nearly normal triglyceride levels and TRL clearance, suggesting that reduction in LPL alone is insufficient to cause increased TRL levels. Apolipoprotein E (apoE) was decreased in lipoprotein fractions in NS, but not in analbuminemia. Here we tested whether decreased apoE binding to lipoproteins in NS contributes to hyperlipidemia by decreasing their affinity for lipoprotein receptors. Plasma apoE was increased 60% in both NS and analbuminemia compared with control (CTRL) as a result of a 60% decreased apoE clearance. Very-low-density lipoprotein and high-density lipoprotein in NS had significantly less apoE per mole of phospholipid compared with analbuminemia or CTRL and significantly greater lipid content; however, apoE binding did not differ by lipoprotein class or group. There was a significant reduction of receptors for lipoproteins in nearly all tissues in NS compared with CTRL and analbuminemia. Thus, apoE within lipoprotein fractions was reduced by dilution resulting from expansion of the lipid fraction due to decreased lipolysis and not to differing affinity for apoE. Decreased lipoprotein receptors result from proteinuria and contribute to hyperlipidemia in NS.
Collapse
Affiliation(s)
- Limin Wang
- Department of Veteran's Affairs, Northern California Health Care System, Mather, California, USA.
| | | | | | | | | | | |
Collapse
|
17
|
Kent AP, Stylianou IM. Scavenger receptor class B member 1 protein: hepatic regulation and its effects on lipids, reverse cholesterol transport, and atherosclerosis. Hepat Med 2011; 3:29-44. [PMID: 24367219 PMCID: PMC3846864 DOI: 10.2147/hmer.s7860] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Scavenger receptor class B member 1 (SR-BI, also known as SCARB1) is the primary receptor for the selective uptake of cholesterol from high-density lipoprotein (HDL). SR-BI is present in several key tissues; however, its presence and function in the liver is deemed the most relevant for protection against atherosclerosis. Cholesterol is transferred from HDL via SR-BI to the liver, which ultimately results in the excretion of cholesterol via bile and feces in what is known as the reverse cholesterol transport pathway. Much of our knowledge of SR-BI hepatic function and regulation is derived from mouse models and in vitro characterization. Multiple independent regulatory mechanisms of SR-BI have been discovered that operate at the transcriptional and post-transcriptional levels. In this review we summarize the critical discoveries relating to hepatic SR-BI cholesterol metabolism, atherosclerosis, and regulation of SR-BI, as well as alternative functions that may indirectly affect atherosclerosis.
Collapse
Affiliation(s)
- Anthony P Kent
- Department of Medicine and Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - Ioannis M Stylianou
- Department of Medicine and Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| |
Collapse
|
18
|
D'Ambrosio DN, Clugston RD, Blaner WS. Vitamin A metabolism: an update. Nutrients 2011; 3:63-103. [PMID: 21350678 PMCID: PMC3042718 DOI: 10.3390/nu3010063] [Citation(s) in RCA: 374] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 12/24/2010] [Accepted: 01/11/2011] [Indexed: 12/18/2022] Open
Abstract
Retinoids are required for maintaining many essential physiological processes in the body, including normal growth and development, normal vision, a healthy immune system, normal reproduction, and healthy skin and barrier functions. In excess of 500 genes are thought to be regulated by retinoic acid. 11-cis-retinal serves as the visual chromophore in vision. The body must acquire retinoid from the diet in order to maintain these essential physiological processes. Retinoid metabolism is complex and involves many different retinoid forms, including retinyl esters, retinol, retinal, retinoic acid and oxidized and conjugated metabolites of both retinol and retinoic acid. In addition, retinoid metabolism involves many carrier proteins and enzymes that are specific to retinoid metabolism, as well as other proteins which may be involved in mediating also triglyceride and/or cholesterol metabolism. This review will focus on recent advances for understanding retinoid metabolism that have taken place in the last ten to fifteen years.
Collapse
Affiliation(s)
- Diana N D'Ambrosio
- Department of Medicine and Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
| | | | | |
Collapse
|
19
|
Hoekstra M, Berkel TJCV, Eck MV. Scavenger receptor BI: A multi-purpose player in cholesterol and steroid metabolism. World J Gastroenterol 2010; 16:5916-24. [PMID: 21157967 PMCID: PMC3007109 DOI: 10.3748/wjg.v16.i47.5916] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Scavenger receptor class B type I (SR-BI) is an important member of the scavenger receptor family of integral membrane glycoproteins. This review highlights studies in SR-BI knockout mice, which concern the role of SR-BI in cholesterol and steroid metabolism. SR-BI in hepatocytes is the sole molecule involved in selective uptake of cholesteryl esters from high-density lipoprotein (HDL). SR-BI plays a physiological role in binding and uptake of native apolipoprotein B (apoB)-containing lipoproteins by hepatocytes, which identifies SR-BI as a multi-purpose player in lipid uptake from the blood circulation into hepatocytes in mice. In adrenocortical cells, SR-BI mediates the selective uptake of HDL-cholesteryl esters, which is efficiently coupled to the synthesis of glucocorticoids (i.e. corticosterone). SR-BI knockout mice suffer from adrenal glucocorticoid insufficiency, which suggests that functional SR-BI protein is necessary for optimal adrenal steroidogenesis in mice. SR-BI in macrophages plays a dual role in cholesterol metabolism as it is able to take up cholesterol associated with HDL and apoB-containing lipoproteins and can possibly facilitate cholesterol efflux to HDL. Absence of SR-BI is associated with thrombocytopenia and altered thrombosis susceptibility, which suggests a novel role for SR-BI in regulating platelet number and function in mice. Transgenic expression of cholesteryl ester transfer protein in humanized SR-BI knockout mice normalizes hepatic delivery of HDL-cholesteryl esters. However, other pathologies associated with SR-BI deficiency, i.e. increased atherosclerosis susceptibility, adrenal glucocorticoid insufficiency, and impaired platelet function are not normalized, which suggests an important role for SR-BI in cholesterol and steroid metabolism in man. In conclusion, generation of SR-BI knockout mice has significantly contributed to our knowledge of the physiological role of SR-BI. Studies using these mice have identified SR-BI as a multi-purpose player in cholesterol and steroid metabolism because it has distinct roles in reverse cholesterol transport, adrenal steroidogenesis, and platelet function.
Collapse
|
20
|
Abstract
PURPOSE OF REVIEW Remnant lipoproteins that persist in the bloodstream after each meal have become increasingly important contributors to atherosclerotic vascular disease, owing to the spread of overnutrition, underexertion, obesity, insulin resistance, and type 2 diabetes. Here, we review recent work that clarified long-standing controversies over the molecular mediators of remnant clearance by the liver, as well as their dysregulation - but possible correction - during alterations in caloric balance. RECENT FINDINGS Two endocytic receptors, the syndecan-1 heparan sulfate proteoglycan (HSPG) and the LDL receptor, plus one docking receptor, SR-BI, significantly contribute to normal hepatic remnant catabolism. Compelling evidence exists for dysfunction of the syndecan-1 HSPG in diabetic states. The major molecular defect identified so far in poorly controlled type 1 diabetes is impaired hepatic HSPG assembly. In contrast, the primary defect in hepatic HSPGs in type 2 diabetes appears to arise from accelerated de-sulfation, owing to the induction of a sulfatase. Moreover, short-term caloric restriction restores hepatic expression of this sulfatase towards normal. SUMMARY Correct identification of hepatic remnant receptors has finally allowed investigations of their molecular dysregulation in diabetes and related conditions. New work points to novel therapeutic targets to correct postprandial dyslipoproteinemia and its consequent arterial damage.
Collapse
Affiliation(s)
- Kevin Jon Williams
- Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
| | | |
Collapse
|
21
|
Foley EM, Esko JD. Hepatic heparan sulfate proteoglycans and endocytic clearance of triglyceride-rich lipoproteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2010; 93:213-33. [PMID: 20807647 DOI: 10.1016/s1877-1173(10)93010-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hypertriglyceridemia, characterized by the accumulation of triglyceride-rich lipoproteins in the blood, affects 10-20% of the population in western countries and increases the risk of atherosclerosis, coronary artery disease, and pancreatitis. The etiology of hypertriglyceridemia is complex, and much interest exists in identifying and characterizing the biological and environmental factors that affect the synthesis and turnover of plasma triglycerides. Genetic studies in mice have recently identified that heparan sulfate proteoglycans are a class of receptors that mediate the clearance of triglyceride-rich lipoproteins in the liver. Heparan sulfate proteoglycans are expressed by endothelial cells that line the hepatic sinusoids and the underlying hepatocytes, and are present in the perisinusoidal space (space of Disse). This chapter discusses the dependence of lipoprotein binding on heparan sulfate structure and the identification of hepatocyte syndecan-1 as the primary proteoglycan that mediates triglyceride-rich lipoprotein clearance.
Collapse
Affiliation(s)
- Erin M Foley
- Department of Cellular and Molecular Medicine, Glycobiology Research and Training Center, University of California, San Diego, La Jolla, CA, USA
| | | |
Collapse
|
22
|
Röhrl C, Fruhwürth S, Schreier SM, Lohninger A, Dolischka A, Hüttinger M, Zemann N, Hermann M, Strobl W, Stangl H. Scavenger receptor, Class B, Type I provides an alternative means for beta-VLDL uptake independent of the LDL receptor in tissue culture. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1801:198-204. [PMID: 19932762 DOI: 10.1016/j.bbalip.2009.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 10/20/2009] [Accepted: 11/13/2009] [Indexed: 11/19/2022]
Abstract
Recent evidence suggests that scavenger receptor, class B, type I (SR-BI) plays a physiological role in VLDL metabolism. SR-BI was reported to mediate beta-VLDL uptake; however, cellular details of this process are not well characterized. In the present study we show that SR-BI delivers cholesterol derived from beta-VLDL to LDL receptor negative SR-BI over-expressing Chinese Hamster Ovarian cells (ldlA7-SRBI). Cell association of beta-VLDL was approximately 3 times higher after SR-BI over-expression, which was competed by beta-VLDL, but only to a lesser extent by HDL and LDL. Almost all of the associated beta-VLDL was located intracellularly, and therefore could not be released by a 50-fold excess of unlabeled beta-VLDL. beta-VLDL was degraded at a rate of 6 ng beta-VLDL/mg cell protein and hour. In contrast to ldlA7 cells, beta-VLDL association was competed by LDL in cells with a functional LDL receptor like CHO and HepG2 cells, indicating a strong impact of the LDL receptor in beta-VLDL uptake. beta-VLDL degradation was similar to ldlA7-SRBI cells. When beta-VLDL uptake was followed using fluorescence microscopy, beta-VLDL showed a different uptake pattern in SR-BI over-expressing cells, ldlA7-SRBI, compared to LDL receptor containing cells, CHO and HepG2.
Collapse
Affiliation(s)
- Clemens Röhrl
- Center for Physiology and Pathophysiology, Department of Medical Chemistry, Medical University of Vienna, Währingerstrabetae 10, 1090 Vienna, Austria
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Wiersma H, Nijstad N, Gautier T, Iqbal J, Kuipers F, Hussain MM, Tietge UJF. Scavenger receptor BI facilitates hepatic very low density lipoprotein production in mice. J Lipid Res 2009; 51:544-53. [PMID: 19723664 DOI: 10.1194/jlr.m000844] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Scavenger receptor BI (SR-BI) is a selective uptake receptor for HDL cholesterol but is also involved in the catabolism of apolipoprotein (apo)B-containing lipoproteins. However, plasma levels of apoB-containing lipoproteins increase following hepatic SR-BI overexpression, suggesting that SR-BI not solely mediates their catabolism. We therefore tested the hypothesis that hepatic SR-BI impacts on VLDL production. On day 7 following adenovirus (Ad)-mediated overexpression of SR-BI, VLDL-triglyceride and VLDL-apoB production rates were significantly increased (P < 0.001), whereas VLDL production was significantly lower in SR-BI knockout mice compared with controls (P < 0.05). In mice injected with AdSR-BI, hepatic cholesterol content increased (P < 0.001), microsomal triglyceride transfer protein activity was higher (P < 0.01) and expression of sterol-regulatory element binding protein (SREBP)2 and its target genes was decreased (P < 0.01). Conversely, in SR-BI knockout mice, microsomal triglyceride transfer protein activity was lower and expression of SREBP2 target genes was increased (P < 0.01). Finally, we demonstrate in vitro in isolated primary hepatocytes as well as in vivo that cholesterol derived from HDL and taken up via SR-BI into the liver can be resecreted within VLDL. These data indicate that hepatic SR-BI expression is linked to VLDL production, and within liver, a metabolic shunt might exist that delivers HDL cholesterol, at least in part, to a pool from which cholesterol is mobilized for VLDL production. These results might have implications for HDL-based therapies against atherosclerotic cardiovascular disease, especially with SR-BI as target.
Collapse
Affiliation(s)
- Harmen Wiersma
- Department of Pediatrics, Center for Liver, Digestive and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
24
|
Narvekar P, Berriel Diaz M, Krones-Herzig A, Hardeland U, Strzoda D, Stöhr S, Frohme M, Herzig S. Liver-specific loss of lipolysis-stimulated lipoprotein receptor triggers systemic hyperlipidemia in mice. Diabetes 2009; 58:1040-9. [PMID: 19188430 PMCID: PMC2671043 DOI: 10.2337/db08-1184] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE In mammals, proper storage and distribution of lipids in and between tissues is essential for the maintenance of energy homeostasis. In contrast, aberrantly high levels of triglycerides in the blood ("hypertriglyceridemia") represent a hallmark of the metabolic syndrome and type 2 diabetes. As hypertriglyceridemia has been identified as an important risk factor for cardiovascular complications, in this study we aimed to identify molecular mechanisms in aberrant triglyceride elevation under these conditions. RESEARCH DESIGN AND METHODS To determine the importance of hepatic lipid handling for systemic dyslipidemia, we profiled the expression patterns of various hepatic lipid transporters and receptors under healthy and type 2 diabetic conditions. A differentially expressed lipoprotein receptor was functionally characterized by generating acute, liver-specific loss- and gain-of-function animal models. RESULTS We show that the hepatic expression of lipid transporter lipolysis-stimulated lipoprotein receptor (LSR) is specifically impaired in mouse models of obesity and type 2 diabetes and can be restored by leptin replacement. Experimental imitation of this pathophysiological situation by liver-specific knockdown of LSR promotes hypertriglyceridemia and elevated apolipoprotein (Apo)B and E serum levels in lean wild-type and ApoE knockout mice. In contrast, genetic restoration of LSR expression in obese animals to wild-type levels improves serum triglyceride levels and serum profiles in these mice. CONCLUSIONS The dysregulation of hepatic LSR under obese and diabetic conditions may provide a molecular rationale for systemic dyslipidemia in type 2 diabetes and the metabolic syndrome and represent a novel target for alternative treatment strategies in these patients.
Collapse
MESH Headings
- Animals
- Apolipoproteins E/deficiency
- Blood Glucose/metabolism
- Cholesterol/blood
- Diabetes Mellitus, Experimental/physiopathology
- Diabetes Mellitus, Type 2/physiopathology
- Disease Models, Animal
- Fatty Acids, Nonesterified/blood
- Hyperlipidemias/physiopathology
- Ketone Bodies/blood
- Lipolysis
- Lipoproteins, VLDL/metabolism
- Liver/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Obese
- RNA Interference
- Receptors, LDL/deficiency
- Receptors, LDL/genetics
- Receptors, LDL/physiology
- Receptors, Lipoprotein/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Triglycerides/blood
Collapse
Affiliation(s)
- Prachiti Narvekar
- Emmy Noether and Marie Curie Research Group “Molecular Metabolic Control,” DKFZ-ZMBH Alliance, German Cancer Research Center Heidelberg, Heidelberg, Germany
| | - Mauricio Berriel Diaz
- Emmy Noether and Marie Curie Research Group “Molecular Metabolic Control,” DKFZ-ZMBH Alliance, German Cancer Research Center Heidelberg, Heidelberg, Germany
| | - Anja Krones-Herzig
- Emmy Noether and Marie Curie Research Group “Molecular Metabolic Control,” DKFZ-ZMBH Alliance, German Cancer Research Center Heidelberg, Heidelberg, Germany
| | - Ulrike Hardeland
- Emmy Noether and Marie Curie Research Group “Molecular Metabolic Control,” DKFZ-ZMBH Alliance, German Cancer Research Center Heidelberg, Heidelberg, Germany
| | - Daniela Strzoda
- Emmy Noether and Marie Curie Research Group “Molecular Metabolic Control,” DKFZ-ZMBH Alliance, German Cancer Research Center Heidelberg, Heidelberg, Germany
| | - Sigrid Stöhr
- Department of Animal Physiology, Philipps University Marburg, Marburg, Germany; and
| | - Marcus Frohme
- Technische und forschende Hochschule Wildau, Wildau, Germany
| | - Stephan Herzig
- Emmy Noether and Marie Curie Research Group “Molecular Metabolic Control,” DKFZ-ZMBH Alliance, German Cancer Research Center Heidelberg, Heidelberg, Germany
- Corresponding author: Stephan Herzig,
| |
Collapse
|
25
|
Connelly MA. SR-BI-mediated HDL cholesteryl ester delivery in the adrenal gland. Mol Cell Endocrinol 2009; 300:83-8. [PMID: 18840501 DOI: 10.1016/j.mce.2008.09.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Accepted: 09/04/2008] [Indexed: 10/21/2022]
Abstract
In adrenocortical cells, scavenger receptor class B, type I (SR-BI) is localized in specialized plasma membrane compartments, called microvillar channels, that retain high density lipoprotein particles (HDL) and are sites for the selective uptake of cholesteryl esters (CE). Formation of microvillar channels is regulated by adrenocorticotropic hormone (ACTH) and requires SR-BI expression. Subsequent to SR-BI-mediated delivery to the plasma membrane, HDL-CE is metabolized to free cholesterol by hormone sensitive lipase and transported to the mitochondria for steroid synthesis via START domain proteins. The relevance of SR-BI to adrenal steroidogenesis is evident by the impairment of glucocorticoid-mediated stress response in the absence of SR-BI-mediated HDL-CE uptake in mice. On the molecular level, SR-BI mediates HDL-CE selective uptake by forming a hydrophobic channel. In addition, SR-BI facilitates bi-directional flux of cholesterol by modifying the phospholipid content of the plasma membrane. SR-BI most likely accomplishes these functions by forming homo-oligomers in the plasma membrane. Examination of SR-BI oligomerization using fluorescence resonance energy transfer spectroscopy revealed that SR-BI multimerizes via its C-terminal region. Overall, SR-BI is the cell surface receptor responsible for selective uptake of lipoprotein cholesterol and its ultimate delivery to sites of hormone synthesis in steroidogenic tissues.
Collapse
Affiliation(s)
- Margery A Connelly
- Metabolic Diseases, Johnson & Johnson Pharmaceutical Research and Development, LLC, Welsh & McKean Roads, Spring House, PA 19477-0776, United States.
| |
Collapse
|
26
|
Fenske SA, Yesilaltay A, Pal R, Daniels K, Barker C, Quiñones V, Rigotti A, Krieger M, Kocher O. Normal hepatic cell surface localization of the high density lipoprotein receptor, scavenger receptor class B, type I, depends on all four PDZ domains of PDZK1. J Biol Chem 2008; 284:5797-806. [PMID: 19116202 DOI: 10.1074/jbc.m808211200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PDZK1 is a four PDZ domain-containing scaffold protein that binds to scavenger receptor class B, type I (SR-BI), the high density lipoprotein receptor, by its first PDZ domain (PDZ1). PDZK1 knock-out mice exhibit a >95% decrease in hepatic SR-BI protein and consequently an approximately 70% increase in plasma cholesterol in abnormally large high density lipoprotein particles. These defects are corrected by hepatic overexpression of full-length PDZK1 but not the PDZ1 domain alone, which partially restores SR-BI protein abundance but not cell surface expression or function. We have generated PDZK1 knock-out mice with hepatic expression of four PDZK1 transgenes encoding proteins with nested C-terminal truncations: pTEM, which lacks the three C-terminal residues (putative PDZ-binding motif), and PDZ1.2, PDZ1.2.3, or PDZ1.2.3.4, which contain only the first two, three, or four N-terminal PDZ domains, respectively, but not the remaining C-terminal sequences. Hepatic overexpression of pTEM restored normal hepatic SR-BI abundance, localization, and function. Hepatic overexpression of PDZ1.2 or PDZ1.2.3 partially restored SR-BI abundance ( approximately 12 or approximately 30% of wild type, respectively) but did not (PDZ1.2) or only slightly (PDZ1.2.3) restored hepatic SR-BI cell surface localization and function. Hepatic overexpression of PDZ1.2.3.4 completely restored SR-BI protein abundance, cell surface expression, and function (normalization of plasma cholesterol levels). Thus, all four PDZ domains in PDZK1, but not PDZ1-3 alone, are sufficient for its normal control of the abundance, localization, and therefore function of hepatic SR-BI, whereas the residues C-terminal to the PDZ4 domain, including the C-terminal putative PDZ-binding domain, are not required.
Collapse
Affiliation(s)
- Sara A Fenske
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Fenske SA, Yesilaltay A, Pal R, Daniels K, Rigotti A, Krieger M, Kocher O. Overexpression of the PDZ1 domain of PDZK1 blocks the activity of hepatic scavenger receptor, class B, type I by altering its abundance and cellular localization. J Biol Chem 2008; 283:22097-104. [PMID: 18544532 DOI: 10.1074/jbc.m800029200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PDZK1 is a four-PDZ domain-containing scaffold protein that, via its first PDZ domain (PDZ1), binds to the C terminus of the high density lipoprotein (HDL) receptor scavenger receptor, class B, type I (SR-BI). Abolishing PDZK1 expression in PDZK1 knock-out (KO) mice leads to a post-transcriptional, tissue-specific decrease in SR-BI protein level and an increase in total plasma cholesterol carried in abnormally large HDL particles. Here we show that, although hepatic overexpression of PDZK1 restored normal SR-BI protein abundance and function in PDZK1 KO mice, hepatic overexpression of only the PDZ1 domain was not sufficient to restore normal SR-BI function. In wild-type mice, overexpression of the PDZ1 domain overcame the activity of the endogenous hepatic PDZK1, resulting in a 75% reduction in hepatic SR-BI protein levels and intracellular mislocalization of the remaining SR-BI. As a consequence, the plasma lipoproteins in PDZ1 transgenic mice resembled those in PDZK1 KO mice (hypercholesterolemia due to large HDL). These results indicate that the PDZ1 domain can control the abundance and localization, and therefore the function, of hepatic SR-BI and that structural features of PDZK1 in addition to its SR-BI-binding PDZ1 domain are required for normal hepatic SR-BI regulation.
Collapse
Affiliation(s)
- Sara A Fenske
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | | | | | | | | | | |
Collapse
|
28
|
Hu L, van der Hoogt CC, Espirito Santo SMS, Out R, Kypreos KE, van Vlijmen BJM, Van Berkel TJC, Romijn JA, Havekes LM, van Dijk KW, Rensen PCN. The hepatic uptake of VLDL in lrp-ldlr-/-vldlr-/- mice is regulated by LPL activity and involves proteoglycans and SR-BI. J Lipid Res 2008; 49:1553-61. [PMID: 18367731 DOI: 10.1194/jlr.m800130-jlr200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
LPL activity plays an important role in preceding the VLDL remnant clearance via the three major apolipoprotein E (apoE)-recognizing receptors: the LDL receptor (LDLr), LDL receptor-related protein (LRP), and VLDL receptor (VLDLr). The aim of this study was to determine whether LPL activity is also important for VLDL remnant clearance irrespective of these receptors and to determine the mechanisms involved in the hepatic remnant uptake. Administration of an adenovirus expressing LPL (AdLPL) into lrp(-)ldlr(-/-)vldlr(-/-) mice reduced both VLDL-triglyceride (TG) and VLDL-total cholesterol (TC) levels. Conversely, inhibition of LPL by AdAPOC1 increased plasma VLDL-TG and VLDL-TC levels. Metabolic studies with radiolabeled VLDL-like emulsion particles showed that the clearance and hepatic association of their remnants positively correlated with LPL activity. This hepatic association was independent of the bridging function of LPL and HL, since heparin did not reduce the liver association. In vitro studies demonstrated that VLDL-like emulsion particles avidly bound to the cell surface of primary hepatocytes from lrp(-)ldlr(-/-)vldlr(-/-) mice, followed by slow internalization, and involved heparin-releaseable cell surface proteins as well as scavenger receptor class B type I (SR-BI). Collectively, we conclude that hepatic VLDL remnant uptake in the absence of the three classical apoE-recognizing receptors is regulated by LPL activity and involves heparan sulfate proteoglycans and SR-BI.
Collapse
Affiliation(s)
- Lihui Hu
- Netherlands Organization for Applied Scientific Research-Quality of Life, Gaubius Laboratory, 2301 CE Leiden, The Netherlands
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Scavenger receptor of class B expressed by osteoblastic cells are implicated in the uptake of cholesteryl ester and estradiol from LDL and HDL3. J Bone Miner Res 2008; 23:326-37. [PMID: 17967141 DOI: 10.1359/jbmr.071022] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
UNLABELLED Lipoproteins transport many vitamins and hormones that have been shown to be necessary for bone formation. However, the metabolism of LDL and HDL3 by bone-forming osteoblastic cells remains unknown. Here we report that osteoblastic cells express scavenger receptors of class B that are implicated in the uptake of cholesterol and estradiol from LDL and HDL3. INTRODUCTION The bone tissue is continuously remodeled, and its integrity requires a balance between osteoclastic bone resorption and osteoblastic bone formation. Recent studies have reported the importance of triglyceride-rich lipoproteins for the delivery of lipophilic vitamins necessary for normal bone metabolism. However, the ability of osteoblastic cells to process low- and high-density lipoproteins (LDL and HDL3) and the receptors involved remain unknown. MATERIALS AND METHODS Binding, competition, degradation, and selective uptake assays with LDL and HDL3 radiolabeled in their protein and lipid moieties or with [3H]estradiol were conducted on human osteoblasts (MG-63 cell line and primary cultures of human osteoblasts [hOB cells]) and on mouse osteoblasts (MC3T3-E1 cell line and primary cultures of murine osteoblasts [mOB cells]). The expression of scavenger receptors (SRs) by osteoblastic cells was determined by RT-PCR and Western immunoblotting, and cellular localization was assessed by sucrose gradient fractionation. RESULTS Osteoblastic cells were able to bind, internalize, and degrade HDL3 and LDL and are capable of selectively taking up cholesteryl esters (CEs) from these lipoproteins. Also, we provide evidence that osteoblastic cells express SR-BI, SR-BII, and CD36 (SR-Bs receptors) and that these receptors are localized in membrane lipid rafts or caveolin-rich membranes. The selective uptake of CE from LDL and HDL3 by osteoblastic cells was strongly inhibited by the known SR-B ligand oxidized LDL, indicating that SR-B receptors are responsible for the selective uptake. Finally, estradiol carried by LDL and HDL3 was selectively transferred to the osteoblastic cells also through SR-B receptors. CONCLUSIONS Overall, our results suggest a novel mechanism for the routing of cholesterol and estradiol to osteoblasts involving the metabolism of LDL and HDL3 by SR-B receptors.
Collapse
|
30
|
Densupsoontorn N, Carpentier YA, Racine R, Murray FM, Seo T, Ramakrishnan R, Deckelbaum RJ. CD36 and proteoglycan-mediated pathways for (n-3) fatty acid enriched triglyceride-rich particle blood clearance in mouse models in vivo and in peritoneal macrophages in vitro. J Nutr 2008; 138:257-61. [PMID: 18203888 PMCID: PMC2440719 DOI: 10.1093/jn/138.2.257] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Because the mechanisms of (n-3) fatty acid-enriched triglyceride-rich particle [(n-3)-TGRP] uptake are not well characterized, we questioned whether (n-3)-TGRP are removed via "nonclassical" pathways, e.g., pathways other than an LDL receptor and/or involving apolipoprotein E (apoE). Chylomicron-sized model (n-3)-TGRP labeled with [3H]cholesteryl ether were injected into wild-type (WT) and CD36 knockout (CD36-/-) mice at low, nonsaturating and high, saturating doses. Blood clearance of (n-3)-TGRP was determined by calculating fractional catabolic rates. At saturating doses, blood clearance of (n-3)-TGRP was slower in CD36-/- mice relative to WT mice, suggesting that in part CD36 contributes to (n-3)-TGRP uptake. To further examine the potential nonclassical clearance pathways, peritoneal-elicited macrophages from WT and CD36-/- mice were incubated with (n-3)-TGRP in the presence of apoE, lactoferrin, and/or sodium chlorate. Cellular (n-3)-TGRP uptake was measured to test the roles of apoE-mediated pathways and/or proteoglycans. ApoE-mediated pathways compensated in part for defective (n-3)-TGRP uptake in CD36-/- cells. Lactoferrin decreased (n-3)-TGRP uptake in the presence of apoE. Inhibition of cell proteoglycan synthesis by chlorate reduced (n-3)-TGRP uptake in both groups of macrophages, and chlorate effects were independent of apoE. We conclude that although CD36 is involved, it is not the primary contributor to the blood clearance of (n-3)-TGRP. The removal of (n-3)-TGRP likely relies more on nonclassical pathways, such as proteoglycan-mediated pathways.
Collapse
Affiliation(s)
- Narumon Densupsoontorn
- Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand,Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032
| | - Yvon A. Carpentier
- Laboratory for Experimental Surgery, Universite Libre de Bruxelles, Brussels 1070, Belgium
| | - Radjini Racine
- Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032
| | - Faith M. Murray
- Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032
| | - Toru Seo
- Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032
| | - Rajasekhar Ramakrishnan
- Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032,Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, NY 10032
| | - Richard J. Deckelbaum
- Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, New York, NY 10032,Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, NY 10032
| |
Collapse
|
31
|
Out R, Jessup W, Le Goff W, Hoekstra M, Gelissen IC, Zhao Y, Kritharides L, Chimini G, Kuiper J, Chapman MJ, Huby T, Van Berkel TJC, Van Eck M. Coexistence of foam cells and hypocholesterolemia in mice lacking the ABC transporters A1 and G1. Circ Res 2007; 102:113-20. [PMID: 17967783 DOI: 10.1161/circresaha.107.161711] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The concept that macrophages can become foam cells as a result of a disturbed balance between the uptake of cholesterol from lipoproteins and cholesterol efflux is generally accepted. ABCA1 and ABCG1 are two cholesterol transporters that may act sequentially to remove cellular cholesterol, but currently their combined role in vivo is unknown. We report here that targeted disruption of both ABCA1 and ABCG1 in mice, despite severe plasma hypocholesterolemia, leads to massive lipid accumulation and foam cell formation of tissue macrophages. A complete ablation of cellular cholesterol efflux in vitro is observed, whereas in vivo macrophage-specific reverse cholesterol transport to the feces is markedly decreased. Despite the massive foam cell formation of tissue macrophages, no lipid accumulation was observed in the vascular wall, even in mice of 1 year old, indicating that the double knockout mice, possibly because of their hypocholesterolemia, lack the trigger to attract macrophages to the vessel wall. In conclusion, even under hypocholesterolemic conditions macrophages can be converted into foam cells, and ABCA1 and ABCG1 play an essential role in the prevention of foam cell formation.
Collapse
Affiliation(s)
- Ruud Out
- Division of Biopharmaceutics, Leiden/Amsterdam Center for Drug Research, Leiden University, The Netherlands.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Nieland TJF, Shaw JT, Jaipuri FA, Maliga Z, Duffner JL, Koehler AN, Krieger M. Influence of HDL-cholesterol-elevating drugs on the in vitro activity of the HDL receptor SR-BI. J Lipid Res 2007; 48:1832-45. [PMID: 17533223 DOI: 10.1194/jlr.m700209-jlr200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Treatment of atherosclerotic disease often focuses on reducing plasma LDL-cholesterol or increasing plasma HDL-cholesterol. We examined in vitro the effects on HDL receptor [scavenger receptor class B type I (SR-BI)] activity of three classes of clinical and experimental plasma HDL-cholesterol-elevating compounds: niacin, fibrates, and HDL376. Fenofibrate (FF) and HDL376 were potent (IC(50) approximately 1 microM), direct inhibitors of SR-BI-mediated lipid transport in cells and in liposomes reconstituted with purified SR-BI. FF, a prodrug, was a more potent inhibitor of SR-BI than an activator of peroxisome proliferator-activated receptor alpha, a target of its active fenofibric acid (FFA) derivative. Nevertheless, FFA, four other fibrates (clofibrate, gemfibrozil, ciprofibrate, and bezafibrate), and niacin had little, if any, effect on SR-BI, suggesting that they do not directly target SR-BI in vivo. However, similarities of HDL376 treatment and SR-BI gene knockout on HDL metabolism in vivo (increased HDL-cholesterol and HDL particle sizes) and structure-activity relationship analysis suggest that SR-BI may be a target of HDL376 in vivo. HDL376 and other inhibitors may help elucidate SR-BI function in diverse mammalian models and determine the therapeutic potential of SR-BI-directed pharmaceuticals.
Collapse
Affiliation(s)
- Thomas J F Nieland
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | | | | | | | | | | |
Collapse
|
33
|
van der Hoogt CC, de Haan W, Westerterp M, Hoekstra M, Dallinga-Thie GM, Romijn JA, Princen HMG, Jukema JW, Havekes LM, Rensen PCN. Fenofibrate increases HDL-cholesterol by reducing cholesteryl ester transfer protein expression. J Lipid Res 2007; 48:1763-71. [PMID: 17525476 DOI: 10.1194/jlr.m700108-jlr200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In addition to efficiently decreasing VLDL-triglycerides (TGs), fenofibrate increases HDL-cholesterol levels in humans. We investigated whether the fenofibrate-induced increase in HDL-cholesterol is dependent on the expression of the cholesteryl ester transfer protein (CETP). To this end, APOE*3-Leiden (E3L) transgenic mice without and with the human CETP transgene, under the control of its natural regulatory flanking regions, were fed a Western-type diet with or without fenofibrate. Fenofibrate (0.04% in the diet) decreased plasma TG in E3L and E3L.CETP mice (-59% and -60%; P < 0.001), caused by a strong reduction in VLDL. Whereas fenofibrate did not affect HDL-cholesterol in E3L mice, fenofibrate dose-dependently increased HDL-cholesterol in E3L.CETP mice (up to +91%). Fenofibrate did not affect the turnover of HDL-cholesteryl ester (CE), indicating that fenofibrate causes a higher steady-state HDL-cholesterol level without altering the HDL-cholesterol flux through plasma. Analysis of the hepatic gene expression profile showed that fenofibrate did not differentially affect the main players in HDL metabolism in E3L.CETP mice compared with E3L mice. However, in E3L.CETP mice, fenofibrate reduced hepatic CETP mRNA (-72%; P < 0.01) as well as the CE transfer activity in plasma (-73%; P < 0.01). We conclude that fenofibrate increases HDL-cholesterol by reducing the CETP-dependent transfer of cholesterol from HDL to (V)LDL, as related to lower hepatic CETP expression and a reduced plasma (V)LDL pool.
Collapse
Affiliation(s)
- Caroline C van der Hoogt
- Netherlands Organization for Applied Scientific Research-Quality of Life, Gaubius Laboratory, 2301 CE Leiden, The Netherlands
| | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Tanaka T, Delgado-Lista J, Lopez-Miranda J, Perez-Jimenez F, Marin C, Perez-Martinez P, Gomez P, Ordovas JM. Scavenger receptor class B type I (SCARB1) c.1119C>T polymorphism affects postprandial triglyceride metabolism in men. J Nutr 2007; 137:578-82. [PMID: 17311943 DOI: 10.1093/jn/137.3.578] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The scavenger receptor class B type I (SCARB1) is a cell surface glycoprotein that plays a key role in reverse cholesterol transport. A polymorphism in exon 8 (c.1119C>T) has been associated with fasting HDL- and LDL- cholesterol concentrations in Caucasian populations. This study evaluated whether this variant is associated with postprandial lipemia in 59 normolipidemic males. After an overnight fast, the subjects were given a single fat load comprising 60% of energy as fat, 15% as protein, and 25% as carbohydrate. Blood was drawn every hour from baseline to 6 h, then every 2.5 h until h 11. We measured plasma lipid concentrations including triglycerides (TG) in large and small triglyceride rich lipoprotein particles (TRL). Changes in postprandial small TRL TG differed among groups over time (Pgeno x time = 0.034) whereby TT and CT subjects maintained lower concentrations throughout most of the postprandial period compared with CC subjects. Significant differences occurred at h 1, 2, 4, and 5 (P < 0.05). Postprandial changes in large TRL TG (Pgeno x time = 0.923) or total TG (Pgeno x time = 0.529) did not differ by genotype. These results suggest that the c.1119C>T polymorphism is associated with a lower postprandial TG response in the smaller, partially catabolized lipoprotein fraction.
Collapse
Affiliation(s)
- Toshiko Tanaka
- Nutrition and Genomics Laboratory, JM-USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts 02111, USA.
| | | | | | | | | | | | | | | |
Collapse
|
35
|
Harada LM, Carrilho AJF, Oliveira HCF, Nakandakare ER, Quintão ECR. Regulation of hepatic cholesterol metabolism in CETP/LDLr mice by cholesterol feeding and by drugs (cholestyramine and lovastatin) that lower plasma cholesterol. Clin Exp Pharmacol Physiol 2007; 33:1209-15. [PMID: 17184503 DOI: 10.1111/j.1440-1681.2006.04512.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. The hepatic mechanisms involved in the simultaneous regulation of plasma cholesterol concentration and cholesteryl ester transfer protein (CETP) activity were investigated by sharply modifying the hepatic rates of cholesterol synthesis. This was accomplished by cholestyramine, lovastatin and cholesterol feeding in human CETP transgenic mice cross-bred with low-density lipoprotein receptor (LDLr)-knockout mice, generating CETP(+/-)/LDLr(+/-) mice, which present a plasma lipoprotein profile resembling that of humans. 2. Analyses of pooled data showed that the plasma CETP activity correlated positively with plasma total cholesterol concentration, hepatic CETP mRNA and the liver microsomal cholesterol content; a negative correlation was found between plasma CETP activity and the liver 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and LDLr mRNA levels. These coordinated events represent an efficient control system that stabilizes the cell cholesterol content. 3. Nonetheless, not all cholesterol metabolism regulatory systems seem to fit into a coherent pattern of responses, suggesting that other unknown cellular mechanisms play roles depending on the type of pharmacological intervention. 4. For example, microsomal cholesterol content was not affected by cholestyramine, but was increased on cholesterol feeding (as predicted), and, surprisingly, on lovastatin treatment. Furthermore, although both plasma cholesterol-lowering drugs increased CYP7A1 mRNA and had no effect on CYP27 mRNA, other metabolic components were differentially modified. Cholestyramine and lovastatin, respectively, did not modify and increased both HMG-CoA and sterol responsive element binding protein 1c mRNA, did not modify and lowered liver X receptor alpha mRNA, lowered and increased ATP binding cassette A1 mRNA and lowered and did not modify scavenger receptor B1 mRNA. 5. That is, different to unabsorbed cholestyramine, lovastatin, as an absorbed plasma cholesterol-lowering drug, may have modified the activity of other unknown genes that play roles in the interaction of CETP with the metabolism of hepatic cholesterol.
Collapse
Affiliation(s)
- Lila M Harada
- Lipid Laboratory, University of São Paulo Medical School, São Paulo, Brazil
| | | | | | | | | |
Collapse
|
36
|
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: 4.8] [Reference Citation Analysis] [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.
Collapse
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
Collapse
Affiliation(s)
- Thierry Huby
- INSERM U551, Université Pierre et Marie Curie-Paris 6, Dyslipoproteinemia and Atherosclerosis Research Unit, Hôpital de la Pitié, Paris, France.
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
López-Miranda J, Pérez-Martínez P, Marín C, Moreno JA, Gómez P, Pérez-Jiménez F. Postprandial lipoprotein metabolism, genes and risk of cardiovascular disease. Curr Opin Lipidol 2006; 17:132-8. [PMID: 16531749 DOI: 10.1097/01.mol.0000217894.85370.c2] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Several lines of evidence suggest that postprandial lipemia increases the risk of atherogenesis, and in each of the systems involved in postprandial metabolism the roles of many genes have been explored in order to establish the possible implications of their variability in coronary heart disease risk. RECENT FINDINGS This report focuses on recent results pertaining to postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and coronary heart disease. The postprandial lipid response was modified by polymorphisms within the genes for apolipoprotein AI, apolipoprotein E, apolipoprotein B, apolipoprotein CI, apolipoprotein CIII, apolipoprotein AIV, apolipoprotein AV, lipoprotein lipase, hepatic lipase, fatty acid-binding protein-2, the fatty acid transport proteins, microsomal triglyceride transfer protein and scavenger receptor class B type I. We also discuss recent advances in the effects of gene regulation using knockdown animal models on postprandial lipoprotein metabolism. SUMMARY The review discusses several of these factors as well as the potential impact of gene polymorphism on the variability of postprandial lipoprotein metabolism as intermediate phenotypes for coronary heart disease. The variability in postprandial lipid response is highly complex. Future studies will need to be large if they are to assess the effects of multiple polymorphisms.
Collapse
Affiliation(s)
- José López-Miranda
- Lipid and Arteriosclerosis Unit, Department of Internal Medicine, Reina Sofía University Hospital, University of Cordoba, Cordoba, Spain.
| | | | | | | | | | | |
Collapse
|
38
|
Zannis VI, Chroni A, Krieger M. Role of apoA-I, ABCA1, LCAT, and SR-BI in the biogenesis of HDL. J Mol Med (Berl) 2006; 84:276-94. [PMID: 16501936 DOI: 10.1007/s00109-005-0030-4] [Citation(s) in RCA: 285] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 11/21/2005] [Indexed: 12/12/2022]
Abstract
The concentration, composition, shape, and size of plasma high-density lipoprotein (HDL) are determined by numerous proteins that influence its biogenesis, remodeling, and catabolism. The discoveries of the HDL receptor (scavenger receptor class B type I, SR-BI) and the ABCA1 (ATP-binding cassette transporter A1) lipid transporter provided two missing links that were necessary to understand the biogenesis and some of the functions of HDL. Existing data indicate that functional interactions between apoA-I and ABCA1 are necessary for the initial lipidation of apoA-I. Through a series of intermediate steps, lipidated apoA-I proceeds to form discoidal HDL particles that can be converted to spherical particles by the action of lecithin:cholesterol acyltransferase (LCAT). Discoidal and spherical HDL can interact functionally with SR-BI and these interactions lead to selective lipid uptake and net efflux of cholesterol and thus remodel HDL. Defective apoA-I/ABCA1 interactions prevent lipidation of apoA-I that is necessary for the formation of HDL particles. In the same way, specific mutations in apoA-I or LCAT prevent the conversion of discoidal to spherical HDL particles. The interactions of lipid-bound apoA-I with SR-BI are affected in vitro by specific mutations in apoA-I or SR-BI. Furthermore, deficiency of SR-BI affects the lipid and apolipoprotein composition of HDL and is associated with increased susceptibility to atherosclerosis. Here we review the current status of the pathway of HDL biogenesis and mutations in apoA-I, ABCA1, and SR-BI that disrupt different steps of the pathway and may lead to dyslipidemia and atherosclerosis in mouse models. The phenotypes generated in experimental mouse models for apoA-I, ABCA1, LCAT, SR-BI, and other proteins of the HDL pathway may facilitate early diagnosis of similar phenotypes in the human population and provide guidance for proper treatment.
Collapse
Affiliation(s)
- Vassilis I Zannis
- Molecular Genetics, Whitaker Cardiovascular Institute and Department of Biochemistry, Boston University School of Medicine, MA 02118, USA.
| | | | | |
Collapse
|
39
|
Trigatti BL. Hepatic high-density lipoprotein receptors: roles in lipoprotein metabolism and potential for therapeutic modulation. Curr Atheroscler Rep 2006; 7:344-50. [PMID: 16105476 DOI: 10.1007/s11883-005-0045-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
High-density lipoprotein (HDL) plays an important role in protection against atherosclerosis. A major part of HDL's antiatherogenic role is through mediating reverse cholesterol transport from peripheral cells, such as macrophages and other cells in the artery wall, to the liver. Hepatic HDL receptors should, therefore, play an important role in either mediating or modulating HDL-dependent reverse cholesterol transport. The scavenger receptor class B type I (SR-BI) was first identified as a hepatic HDL receptor almost 10 years ago and is well characterized at the molecular level. This review highlights recent studies that provide insight into the cellular pathways involved in SR-BI-mediated lipid transfer between bound lipoproteins and cells, supports a role for this receptor in reverse cholesterol transport and protection against experimental atherosclerosis in mice, and explores the consequences of sequence variations in the gene encoding SR-BI in humans.
Collapse
Affiliation(s)
- Bernardo L Trigatti
- Department of Biochemistry and Biomedical Sciences, Faculty of Health Sciences, McMaster University, West Hamilton, ON L8N 3Z5, Canada.
| |
Collapse
|
40
|
Yu H, Zhang W, Yancey PG, Koury MJ, Zhang Y, Fazio S, Linton MF. Macrophage apolipoprotein E reduces atherosclerosis and prevents premature death in apolipoprotein E and scavenger receptor-class BI double-knockout mice. Arterioscler Thromb Vasc Biol 2005; 26:150-6. [PMID: 16269665 DOI: 10.1161/01.atv.0000194096.89476.73] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Mice null for both apolipoprotein (apo)E and scavenger receptor (SR)-BI (DKO) develop severe hypercholesterolemia, occlusive coronary atherosclerosis, myocardial infarction, and premature death. The current study examines the ability of macrophage apoE to improve the dyslipidemia, reduce atherosclerosis, and rescue the lethal phenotype of DKO mice. METHODS AND RESULTS Initially, bone marrow transplantation (BMT) was unsuccessful, because the DKO mice died from a rapidly fatal anemia 3 to 5 days after lethal irradiation. Therefore, probucol was used to rescue the DKO mice during BMT and was discontinued 2-weeks after BMT, allowing successful reconstitution with donor marrow. Twelve male apoE(-/-)SR-BI(-/-) mice fed 0.5% probucol in a chow diet were lethally irradiated and transplanted with either wild-type (WT) or DKO bone marrow. Two-weeks after BMT, apoE was detected in serum in WT-->DKO mice, and mean serum cholesterol levels were reduced by 70% versus DKO-->DKO mice. Lipoprotein profiles and HDL subpopulations in WT-->DKO mice were similar to apoE(+/+)SR-BI(-/-)-->DKO mice and resembled those of SR-BI(-/-) mice. In WT-->DKO mice, aortic atherosclerosis was reduced by 88% to 90% versus DKO-->DKO mice. Furthermore, the DKO-->DKO mice died &8 weeks after BMT, whereas WT-->DKO mice exhibited a life span >40 weeks after BMT. CONCLUSIONS Macrophage apoE is able to rescue the lethal phenotype of apoE(-/-)SR-BI(-/-) mice by improving the dyslipidemia and dramatically reducing atherosclerotic lesion development.
Collapse
Affiliation(s)
- Hong Yu
- Division of Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232-6300, USA
| | | | | | | | | | | | | |
Collapse
|