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van der Sluis RJ, Hoekstra M. Glucocorticoids are active players and therapeutic targets in atherosclerotic cardiovascular disease. Mol Cell Endocrinol 2020; 504:110728. [PMID: 31968221 DOI: 10.1016/j.mce.2020.110728] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/19/2019] [Accepted: 01/17/2020] [Indexed: 02/07/2023]
Abstract
Adrenal-derived glucocorticoids mediate the physiological response to stress. Chronic disturbances in glucocorticoid homeostasis, i.e. in Addison's and Cushing's disease patients, predispose to the development of atherosclerotic cardiovascular disease. Here we review preclinical and clinical findings regarding the relation between changes in plasma glucocorticoid levels and the atherosclerosis extent. It appears that, although the altered glucocorticoid function can in most cases be restored in the different patient groups, current therapies do not necessarily reverse the associated risk for atherosclerotic cardiovascular disease. In our opinion much attention should therefore be given to the development of a Cushing's disease mouse model that can (1) effectively replicate the effect of hypercortisolemia on atherosclerosis outcome observed in humans and (2) be used to investigate, in a preclinical setting, the relative impact on atherosclerosis susceptibility of already available (e.g. metyrapone) and potentially novel (i.e. SR-BI activity modulators) therapeutic agents that target the adrenal glucocorticoid output.
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Affiliation(s)
- Ronald J van der Sluis
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Gorlaeus Laboratories, Einsteinweg 55, 2333CC, Leiden, the Netherlands
| | - Menno Hoekstra
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Gorlaeus Laboratories, Einsteinweg 55, 2333CC, Leiden, the Netherlands.
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2
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Martins Cardoso R, Creemers E, Absalah S, Hoekstra M, Gooris GS, Bouwstra JA, Van Eck M. Hyperalphalipoproteinemic scavenger receptor BI knockout mice exhibit a disrupted epidermal lipid barrier. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158592. [PMID: 31863970 DOI: 10.1016/j.bbalip.2019.158592] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 11/05/2019] [Accepted: 12/16/2019] [Indexed: 01/28/2023]
Abstract
Scavenger receptor class B type I (SR-BI) mediates the selective uptake of cholesteryl esters (CE) from high-density lipoproteins (HDL). An impaired SR-BI function leads to hyperalphalipoproteinemia with elevated levels of cholesterol transported in the HDL fraction. Accumulation of cholesterol in apolipoprotein B (apoB)-containing lipoproteins has been shown to alter skin lipid composition and barrier function in mice. To investigate whether these hypercholesterolemic effects on the skin also occur in hyperalphalipoproteinemia, we compared skins of wild-type and SR-BI knockout (SR-BI-/-) mice. SR-BI deficiency did not affect the epidermal cholesterol content and induced only minor changes in the ceramide subclasses. The epidermal free fatty acid (FFA) pool was, however, enriched in short and unsaturated chains. Plasma CE levels strongly correlated with epidermal FFA C18:1 content. The increase in epidermal FFA coincided with downregulation of cholesterol and FFA synthesis genes, suggesting a compensatory response to increased flux of plasma cholesterol and FFAs into the skin. Importantly, the SR-BI-/- epidermal lipid barrier showed increased permeability to ethyl-paraminobenzoic acid, indicating an impairment of the barrier function. In conclusion, increased HDL-cholesterol levels in SR-BI-/- mice can alter the epidermal lipid composition and lipid barrier function similarly as observed in hypercholesterolemia due to elevated levels of apoB-containing lipoproteins.
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Affiliation(s)
- Renata Martins Cardoso
- Division BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Zuid-Holland, the Netherlands.
| | - Eline Creemers
- Division BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Zuid-Holland, the Netherlands
| | - Samira Absalah
- Division BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Zuid-Holland, the Netherlands.
| | - Menno Hoekstra
- Division BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Zuid-Holland, the Netherlands.
| | - Gert S Gooris
- Division BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Zuid-Holland, the Netherlands.
| | - Joke A Bouwstra
- Division BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Zuid-Holland, the Netherlands.
| | - Miranda Van Eck
- Division BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Zuid-Holland, the Netherlands.
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Dong B, Singh AB, Guo GL, Young M, Liu J. Activation of FXR by obeticholic acid induces hepatic gene expression of SR-BI through a novel mechanism of transcriptional synergy with the nuclear receptor LXR. Int J Mol Med 2019; 43:1927-1938. [PMID: 30896855 PMCID: PMC6443341 DOI: 10.3892/ijmm.2019.4136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 02/13/2019] [Indexed: 11/06/2022] Open
Abstract
The farnesoid X receptor (FXR) is known to regulate the gene expression of SR‑BI, which mediates plasma high‑density lipoprotein (HDL)‑cholesterol uptake. Our previous study demonstrated that the activation of FXR by obeticholic acid (OCA) lowered plasma HDL‑cholesterol levels and increased the hepatic mRNA and protein expression levels of SR‑BI in hypercholesterolemic hamsters, but not in normolipidemic hamsters, suggesting that dietary cholesterol may be involved in the OCA‑induced transcription of SR‑BI. In the present study, a functional 90‑base‑pair regulatory region was identified in the first intron of the SR‑BI gene of hamster and mouse that contains a FXR response element (IR‑1) and an adjacent liver X receptor (LXR) response element (LXRE). By in vitro DNA binding and luciferase reporter gene assays, it was demonstrated that FXR and LXR bind to their recognition sequences within this intronic region and transactivate the SR‑BI reporter gene in a synergistic manner. It was also shown that mutations at either the IR‑1 site or the LXRE site eliminated OCA‑mediated gene transcription. Utilizing chow‑fed hamsters as an in vivo model, it was demonstrated that treating normolipidemic hamsters with OCA or GW3965 alone did not effectively induce levels of SR‑BI, whereas their combined treatment significantly increased the mRNA and protein levels of SR‑BI in the liver. The study further investigated effects of FXR and LXR coactivation on the gene expression of SR‑BI in human liver cells. The intronic FXRE and LXRE regulatory region was not conserved in the human SR‑BI genomic sequence, however, higher mRNA expression levels of SR‑BI were observed in human primary hepatocytes and HepG2 cells exposed to combined treatments of FXR and LXR agonists, compared with those in cells exposed to individual ligand treatment. Therefore, these results suggest that human SR‑BI gene transcription may also be subject to concerted activation by FXR and LXR, mediated via currently unidentified regulatory sequences.
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Affiliation(s)
- Bin Dong
- Department of Veterans Affairs, Palo Alto Health Care System, Palo Alto, CA 94304, USA
| | - Amar B Singh
- Department of Veterans Affairs, Palo Alto Health Care System, Palo Alto, CA 94304, USA
| | - Grace L Guo
- Department of Pharmacology and Toxicology, School of Pharmacy, Rutgers University, Piscataway, NJ 08854, USA
| | - Mark Young
- Mistral Therapeutics, San Diego, CA 92121, USA
| | - Jingwen Liu
- Department of Veterans Affairs, Palo Alto Health Care System, Palo Alto, CA 94304, USA
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Dong B, Young M, Liu X, Singh AB, Liu J. Regulation of lipid metabolism by obeticholic acid in hyperlipidemic hamsters. J Lipid Res 2016; 58:350-363. [PMID: 27940481 DOI: 10.1194/jlr.m070888] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 11/28/2016] [Indexed: 12/21/2022] Open
Abstract
The farnesoid X receptor (FXR) plays critical roles in plasma cholesterol metabolism, in particular HDL-cholesterol (HDL-C) homeostasis. Obeticholic acid (OCA) is a FXR agonist being developed for treating various chronic liver diseases. Previous studies reported inconsistent effects of OCA on regulating plasma cholesterol levels in different animal models and in different patient populations. The mechanisms underlying its divergent effects have not yet been thoroughly investigated. The scavenger receptor class B type I (SR-BI) is a FXR-modulated gene and the major receptor for HDL-C. We investigated the effects of OCA on hepatic SR-BI expression and correlated such effects with plasma HDL-C levels and hepatic cholesterol efflux in hyperlipidemic hamsters. We demonstrated that OCA induced a time-dependent reduction in serum HDL-C levels after 14 days of treatment, which was accompanied by a significant reduction of liver cholesterol content and increases in fecal cholesterol in OCA-treated hamsters. Importantly, hepatic SR-BI mRNA and protein levels in hamsters were increased to 1.9- and 1.8-fold of control by OCA treatment. Further investigations in normolipidemic hamsters did not reveal OCA-induced changes in serum HDL-C levels or hepatic SR-BI expression. We conclude that OCA reduces plasma HDL-C levels and promotes transhepatic cholesterol efflux in hyperlipidemic hamsters via a mechanism involving upregulation of hepatic SR-BI.
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Affiliation(s)
- Bin Dong
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304
| | - Mark Young
- Intercept Pharmaceuticals, Inc., San Diego, CA 92121
| | - Xueqing Liu
- Intercept Pharmaceuticals, Inc., San Diego, CA 92121
| | | | - Jingwen Liu
- Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304
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Franconi F, Rosano G, Basili S, Montella A, Campesi I. Human cells involved in atherosclerosis have a sex. Int J Cardiol 2016; 228:983-1001. [PMID: 27915217 DOI: 10.1016/j.ijcard.2016.11.118] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 11/06/2016] [Indexed: 12/30/2022]
Abstract
The influence of sex has been largely described in cardiovascular diseases. Atherosclerosis is a complex process that involves many cell types such as vessel cells, immune cells and endothelial progenitor cells; however, many, if not all, studies do not report the sex of the cells. This review focuses on sex differences in human cells involved in the atherosclerotic process, emphasizing the role of sex hormones. Furthermore, we report sex differences and issues related to the processes that determine the fate of the cells such as apoptotic and autophagic mechanisms. The analysis of the data reveals that there are still many gaps in our knowledge regarding sex influences in atherosclerosis, largely for the cell types that have not been well studied, stressing the urgent need for a clear definition of experimental conditions and the inclusion of both sexes in preclinical studies.
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Affiliation(s)
- Flavia Franconi
- Assessorato alle Politiche per la Persona of Basilicata Region, Potenza, Italy; Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Giuseppe Rosano
- Cardiovascular and Cell Sciences Research Institute, St. George's University of London, United Kingdom
| | - Stefania Basili
- Department of Internal Medicine and Medical Specialties - Research Center on Gender and Evaluation and Promotion of Quality in Medicine (CEQUAM), Sapienza University of Rome, Italy
| | - Andrea Montella
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Ilaria Campesi
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy; Laboratory of Sex-Gender Medicine, National Institute of Biostructures and Biosystems, Osilo, Italy.
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Yang F, Du Y, Zhang J, Jiang Z, Wang L, Hong B. Low-density lipoprotein upregulate SR-BI through Sp1 Ser702 phosphorylation in hepatic cells. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1861:1066-1075. [PMID: 27320013 DOI: 10.1016/j.bbalip.2016.06.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 05/04/2016] [Accepted: 06/10/2016] [Indexed: 01/25/2023]
Abstract
Scavenger receptor class B type I (SR-BI) is one of the key proteins in the process of reverse cholesterol transport (RCT), and its major function is to uptake high density lipoprotein (HDL) cholesterol from plasma into liver cells. The regulation of SR-BI expression is important for controlling serum lipid content and reducing the risks of cardiovascular diseases. Here we found that SR-BI expression was significantly increased by LDL in vivo and in vitro, and the transcription factor specific protein 1 (Sp1) plays a critical role in this process. Results from co-immunoprecipitation experiments indicate that the activation of SR-BI was associated with Sp1-recruited protein complexes in the promoter region of SR-BI, where histone acetyltransferase p300 was recruited and histone deacetylase HDAC1 was dismissed. As a result, histone acetylation increased, leading to activation of SR-BI transcription. With further investigation, we found that LDL phosphorylated Sp1 through ERK1/2 pathway, which affected Sp1 protein complexes formation in SR-BI promoter. Using mass spectrometry and site directed mutagenesis, a new Sp1 phosphorylation site Ser702 was defined to be associated with Sp1-HDAC1 interaction and may be important in SR-BI activation, shedding light on the knowledge of delicate mechanism of hepatic HDL receptor SR-BI gene modulation by LDL.
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Affiliation(s)
- Fan Yang
- Key Laboratory of Biotechnology of Antibiotics of Ministry of Health, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 1 Tiantan Xili, Beijing 100050, China
| | - Yu Du
- Key Laboratory of Biotechnology of Antibiotics of Ministry of Health, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 1 Tiantan Xili, Beijing 100050, China
| | - Jin Zhang
- Key Laboratory of Biotechnology of Antibiotics of Ministry of Health, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 1 Tiantan Xili, Beijing 100050, China
| | - Zhibo Jiang
- Key Laboratory of Biotechnology of Antibiotics of Ministry of Health, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 1 Tiantan Xili, Beijing 100050, China
| | - Li Wang
- Key Laboratory of Biotechnology of Antibiotics of Ministry of Health, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 1 Tiantan Xili, Beijing 100050, China.
| | - Bin Hong
- Key Laboratory of Biotechnology of Antibiotics of Ministry of Health, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 1 Tiantan Xili, Beijing 100050, China.
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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: 9] [Impact Index Per Article: 1.1] [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.
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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
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Association of macular pigment optical density with serum concentration of oxidized low-density lipoprotein in healthy adults. Retina 2015; 35:820-6. [PMID: 25473786 DOI: 10.1097/iae.0000000000000382] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PURPOSE To analyze the association between macular pigment optical density (MPOD), which reflects lutein (L), zeaxanthin (Z), and meso-zeaxanthin (MZ) in the macula, and background characteristics. METHODS Fifty-five healthy adult volunteers were analyzed. Macular pigment optical density was measured using a heterochromatic flicker photometry technique, and serum concentrations of carotenoids and lipoproteins were by high-performance liquid chromatography and enzyme-linked immunosorbent assay, respectively. Dietary intake of nutrient was determined by a validated self-administered questionnaire on ingestion frequency. RESULTS Macular pigment optical density was positively correlated with serum concentrations of L and Z and dietary L intake and inversely correlated with serum oxidized low-density lipoprotein (LDL). Although MPOD decreased with age (95% confidence interval, -0.011 to -0.002; correlation coefficient, -0.269; P = 0.007), serum L/Z and dietary L intake did not. In contrast, serum oxidized LDL was positively correlated with age (95% confidence interval, 0.69-2.34; correlation coefficient, 0.333; P = 0.0004). After adjusting for age, sex, and oxidized LDL, serum L was positively correlated with MPOD (95% confidence interval, 0.88-1.69; P = 0.000001). After adjusting for age, sex, and serum L, serum oxidized LDL was inversely correlated with MPOD (95% confidence interval, -0.002 to -0.0004; P = 0.006). CONCLUSION Macular pigment optical density was inversely correlated with serum oxidized LDL. Further study to know the impact of oxidized LDL on MPOD may be warranted.
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Martineau C, Kevorkova O, Brissette L, Moreau R. Scavenger receptor class B, type I (Scarb1) deficiency promotes osteoblastogenesis but stunts terminal osteocyte differentiation. Physiol Rep 2014; 2:2/10/e12117. [PMID: 25281615 PMCID: PMC4254088 DOI: 10.14814/phy2.12117] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Scavenger receptor class B type I (SR-BI), the Scarb1 gene product, is a high-density lipoprotein (HDL) receptor which was shown to influence bone metabolism. Its absence in mice is associated with alterations of the glucocorticoid/adrenocorticotropic hormone axis, and translated in high bone mass and enhanced bone formation. Since the cellular alterations underlying the enhanced bone formation remain unknown, we investigated Scarb1-deficient marrow stromal cells (MSC) behavior in vitro. No difference in HDL3, cholesteryl ester (CE) or estradiol (E) association/binding was measured between Scarb1-null and wild-type (WT) cells. Scarb1 genic expression was down-regulated twofold following osteogenic treatment. Neither WT nor null cell proliferation was influenced by HDL3 exposure whereas this condition decreased genic expression of osteoblastic marker osterix (Sp7), and osteocyte markers sclerostin (Sost) and dentin matrix protein 1 (Dmp1) independently of genotype. Sost and Dmp1 basal expression in null cells was 40% and 50% that of WT cells; accordingly, osteocyte density was 20% lower in vertebrae from Scarb1-null mice. Genic expression of co-receptors for Wnt signaling, namely LDL-related protein (Lrp) 5 and Lrp8, was increased, respectively, by two- and threefold, and of transcription target-genes axis inhibition protein 2 (Axin2) and lymphoid enhancer-binding factor 1 (Lef1) over threefold. Gene expression of Wnt signaling agonist Wnt5a and of the antagonist dickkopfs-related protein 1 (Dkk1) were found to be increased 10- to 20-fold in null MSC. These data suggest alterations of Wnt pathways in Scarb1-deficient MSC potentially explaining their enhanced function, hence contributing to the high bone mass observed in these mice.
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Affiliation(s)
- Corine Martineau
- Laboratoire du Métabolisme Osseux, BioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, H3C 3P8, Quebec, Canada
| | - Olha Kevorkova
- Laboratoire du Métabolisme Osseux, BioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, H3C 3P8, Quebec, Canada
| | - Louise Brissette
- Laboratoire du Métabolisme des Lipoprotéines, Département des Sciences Biologiques, BioMed, Université du Québec à Montréal, Montréal, H3C 3P8, Quebec, Canada
| | - Robert Moreau
- Laboratoire du Métabolisme Osseux, BioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, H3C 3P8, Quebec, Canada
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Martineau C, Martin-Falstrault L, Brissette L, Moreau R. Gender- and region-specific alterations in bone metabolism in Scarb1-null female mice. J Endocrinol 2014; 222:277-88. [PMID: 24928939 DOI: 10.1530/joe-14-0147] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A positive correlation between plasma levels of HDL and bone mass has been reported by epidemiological studies. As scavenger receptor class B, type I (SR-BI), the gene product of Scarb1, is known to regulate HDL metabolism, we recently characterized bone metabolism in Scarb1-null mice. These mice display high femoral bone mass associated with enhanced bone formation. As gender differences have been reported in HDL metabolism and SR-BI function, we investigated gender-specific bone alterations in Scarb1-null mice by microtomography and histology. We found 16% greater relative bone volume and 39% higher bone formation rate in the vertebrae from 2-month-old Scarb1-null females. No such alteration was seen in males, indicating gender- and region-specific differences in skeletal phenotype. Total and HDL-associated cholesterol levels, as well as ACTH plasma levels, were increased in both Scarb1-null genders, the latter being concurrent to impaired corticosterone response to fasting. Plasma levels of estradiol did not differ between null and WT females, suggesting that the estrogen metabolism alteration is not relevant to the higher vertebral bone mass in female Scarb1-null mice. Constitutively, high plasma levels of leptin along with 2.5-fold increase in its expression in white adipose tissue were measured in female Scarb1-null mice only. In vitro exposure of bone marrow stromal cells to ACTH and leptin promoted osteoblast differentiation as evidenced by increased gene expression of osterix and collagen type I alpha. Our results suggest that hyperleptinemia may account for the gender-specific high bone mass seen in the vertebrae of female Scarb1-null mice.
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Affiliation(s)
- Corine Martineau
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Louise Martin-Falstrault
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Louise Brissette
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
| | - Robert Moreau
- Laboratoire du Métabolisme OsseuxBioMed, Département des Sciences Biologiques Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3P8Laboratoire du Métabolisme des LipoprotéinesBioMed, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada H3C 3P8
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Sips FLP, Tiemann CA, Oosterveer MH, Groen AK, Hilbers PAJ, van Riel NAW. A computational model for the analysis of lipoprotein distributions in the mouse: translating FPLC profiles to lipoprotein metabolism. PLoS Comput Biol 2014; 10:e1003579. [PMID: 24784354 PMCID: PMC4006703 DOI: 10.1371/journal.pcbi.1003579] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 03/11/2014] [Indexed: 12/27/2022] Open
Abstract
Disturbances of lipoprotein metabolism are recognized as indicators of cardiometabolic disease risk. Lipoprotein size and composition, measured in a lipoprotein profile, are considered to be disease risk markers. However, the measured profile is a collective result of complex metabolic interactions, which complicates the identification of changes in metabolism. In this study we aim to develop a method which quantitatively relates murine lipoprotein size, composition and concentration to the molecular mechanisms underlying lipoprotein metabolism. We introduce a computational framework which incorporates a novel kinetic model of murine lipoprotein metabolism. The model is applied to compute a distribution of plasma lipoproteins, which is then related to experimental lipoprotein profiles through the generation of an in silico lipoprotein profile. The model was first applied to profiles obtained from wild-type C57Bl/6J mice. The results provided insight into the interplay of lipoprotein production, remodelling and catabolism. Moreover, the concentration and metabolism of unmeasured lipoprotein components could be determined. The model was validated through the prediction of lipoprotein profiles of several transgenic mouse models commonly used in cardiovascular research. Finally, the framework was employed for longitudinal analysis of the profiles of C57Bl/6J mice following a pharmaceutical intervention with a liver X receptor (LXR) agonist. The multifaceted regulatory response to the administration of the compound is incompletely understood. The results explain the characteristic changes of the observed lipoprotein profile in terms of the underlying metabolic perturbation and resultant modifications of lipid fluxes in the body. The Murine Lipoprotein Profiler (MuLiP) presented here is thus a valuable tool to assess the metabolic origin of altered murine lipoprotein profiles and can be applied in preclinical research performed in mice for analysis of lipid fluxes and lipoprotein composition.
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Affiliation(s)
- Fianne L P Sips
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands; Netherlands Consortium for Systems Biology, University of Amsterdam, Amsterdam, The Netherlands
| | - Christian A Tiemann
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands; Netherlands Consortium for Systems Biology, University of Amsterdam, Amsterdam, The Netherlands
| | - Maaike H Oosterveer
- Department of Pediatrics, University Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Albert K Groen
- Netherlands Consortium for Systems Biology, University of Amsterdam, Amsterdam, The Netherlands; Department of Pediatrics, University Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Laboratory Medicine, University Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Peter A J Hilbers
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands; Netherlands Consortium for Systems Biology, University of Amsterdam, Amsterdam, The Netherlands
| | - Natal A W van Riel
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands; Netherlands Consortium for Systems Biology, University of Amsterdam, Amsterdam, The Netherlands
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12
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Faam B, Daneshpour MS, Hedayati M, Halalkhor S, Mansournia MA, Zarkesh M, Azizi F. The age effect on the association between the scavenger receptor class B type I (SR-BI) polymorphism and HDL-C level: Tehran Lipid and Glucose Study. Endocr Res 2014; 39:91-3. [PMID: 24738490 DOI: 10.3109/07435800.2013.808207] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
INTRODUCTION The scavenger receptor class B type I (SR-BI) is a key component in the reverse cholesterol transportation. The aim of this study was to assess the association between exon1 (G → A) polymorphism of SR-BI gene and lipid profiles among the Tehran Lipid and Glucose Study (TLGS) population. MATERIALS AND METHODS This cross-sectional study included 774 adults (322 males and 452 females) aged 20-70 years who were randomly selected from among TLGS population. Anthropometrical and biochemical variables for participants were measured. Selected SR-BI gene polymorphism was determined with restriction fragment length polymorphism, via Alu restriction enzyme. RESULTS Minor allele frequency for SR-BI polymorphism in the selected population was 0.159. Allele frequencies were in conformity with Hardy-Weinberg equilibrium. Association between (G → A) SR-BI polymorphism and high density lipoprotein cholesterol (HDL-C) and HDL3 was significant only after adjustment for age as a potential covariate (p = 0.046, 0.041, respectively); however, the results did not improve after adjustment for sex. DISCUSSION The result of this study confirms the role of age as a potential confounder which could modify the association between the SR-BI single nucleotide polymorphism and HDL-C level.
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Affiliation(s)
- Bita Faam
- Cellular and Molecular Endocrine Research Center, Research Institute for Endocrine Science, Shahid Beheshti University of Medical Science , Tehran , Iran
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Martineau C, Martin-Falstrault L, Brissette L, Moreau R. The atherogenic Scarb1 null mouse model shows a high bone mass phenotype. Am J Physiol Endocrinol Metab 2014; 306:E48-57. [PMID: 24253048 PMCID: PMC3920004 DOI: 10.1152/ajpendo.00421.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Scavenger receptor class B, type I (SR-BI), the Scarb1 gene product, is a receptor associated with cholesteryl ester uptake from high-density lipoproteins (HDL), which drives cholesterol movement from peripheral tissues toward the liver for excretion, and, consequently, Scarb1 null mice are prone to atherosclerosis. Because studies have linked atherosclerosis incidence with osteoporosis, we characterized the bone metabolism in these mice. Bone morphometry was assessed through microcomputed tomography and histology. Marrow stromal cells (MSCs) were used to characterize influence of endogenous SR-BI in cell functions. Total and HDL-associated cholesterol in null mice were increased by 32-60%, correlating with its role in lipoprotein metabolism. Distal metaphyses from 2- and 4-mo-old null mice showed correspondingly 46 and 37% higher bone volume fraction associated with a higher number of trabeculae. Histomorphometric analyses in 2-mo-old null male mice revealed 1.42-fold greater osteoblast surface, 1.37-fold higher percent mineralizing surface, and 1.69-fold enhanced bone formation rate. In vitro assays for MSCs from null mice revealed 37% higher proliferation rate, 48% more alkaline phosphatase activity, 70% greater mineralization potential and a 2-fold osterix (Sp7) expression, yet a 0.5-fold decrease in caveolin-1 (Cav1) expression. Selective uptake levels of HDL-associated cholesteryl oleate and estradiol were similar between MSC from wild-type and Scarb1 null mice, suggesting that its contribution to this process is not its main role in these cells. However, Scarb1 knockout stunted the HDL-dependent regulation of Cav1 genic expression. Scarb1 null mice are not prone to osteoporosis but show higher bone mass associated with enhanced bone formation.
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Affiliation(s)
- Corine Martineau
- Laboratoire du Métabolisme Osseux, BioMed, Université du Québec à Montréal, Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Quebec, Canada; and
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Guo L, Chen M, Song Z, Daugherty A, Li XA. C323 of SR-BI is required for SR-BI-mediated HDL binding and cholesteryl ester uptake. J Lipid Res 2011; 52:2272-2278. [PMID: 21917726 DOI: 10.1194/jlr.m019091] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Scavenger receptor BI (SR-BI) is an HDL receptor. It binds HDL and mediates the uptake of cholesteryl ester from HDL. Early studies have pointed out that the extracellular domain of SR-BI is critical for SR-BI-mediated cholesteryl ester uptake. However, the extracellular loop of SR-BI is large: it contains 403 amino acids. The HDL binding site and the modulation of SR-BI-mediated cholesteryl ester uptake remain to be identified. In this study, using C323G mutant SR-BI, we showed that C323G mutant SR-BI lost its HDL binding and cholesteryl ester uptake activity, indicating that the highly conserved C323 is required for SR-BI-mediated HDL binding and cholesteryl ester uptake. Using a blocking antibody against C323 region, we demonstrated that C323 is directly involved in HDL binding and likely an HDL binding site. Using C323G mutant transgenic mouse model, we further demonstrated that C323 of SR-BI is required for regulating plasma cholesterol levels in vivo. Using redox reagents, we showed that physiological relevant levels of H(2)O(2) upregulated the SR-BI-mediated cholesteryl ester uptake activity by 65%, whereas GSH or DTT significantly downregulated SR-BI-mediated cholesteryl ester uptake activity by 45%. C323 of SR-BI is critical for SR-BI-mediated HDL binding and cholesteryl ester uptake, and changes in redox status may be a regulatory factor modulating SR-BI-mediated cholesterol transport.
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Affiliation(s)
- Ling Guo
- Department of Pediatrics, University of Kentucky Medical School, Lexington, KY
| | - Min Chen
- Department of Pediatrics, University of Kentucky Medical School, Lexington, KY; Taian Central Hospital, Taian, Shandong, China
| | - Zhiqing Song
- Department of Pediatrics, University of Kentucky Medical School, Lexington, KY; Taian Central Hospital, Taian, Shandong, China
| | - Alan Daugherty
- Saha Cardiovascular Research Center, University of Kentucky Medical School, Lexington, KY and
| | - Xiang-An Li
- Department of Pediatrics, University of Kentucky Medical School, Lexington, KY; Saha Cardiovascular Research Center, University of Kentucky Medical School, Lexington, KY and; Graduate Center for Nutritional Sciences, University of Kentucky Medical School, Lexington, KY; and.
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Simultaneous intake of oat bran and atorvastatin reduces their efficacy to lower lipid levels and atherosclerosis in LDLr−/− mice. Pharmacol Res 2011; 64:36-43. [DOI: 10.1016/j.phrs.2011.02.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 02/21/2011] [Accepted: 02/21/2011] [Indexed: 11/24/2022]
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Chiba-Falek O, Nichols M, Suchindran S, Guyton J, Ginsburg GS, Barrett-Connor E, McCarthy JJ. Impact of gene variants on sex-specific regulation of human Scavenger receptor class B type 1 (SR-BI) expression in liver and association with lipid levels in a population-based study. BMC MEDICAL GENETICS 2010; 11:9. [PMID: 20085651 PMCID: PMC2822818 DOI: 10.1186/1471-2350-11-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 01/19/2010] [Indexed: 02/03/2023]
Abstract
BACKGROUND Several studies have noted that genetic variants of SCARB1, a lipoprotein receptor involved in reverse cholesterol transport, are associated with serum lipid levels in a sex-dependent fashion. However, the mechanism underlying this gene by sex interaction has not been explored. METHODS We utilized both epidemiological and molecular methods to study how estrogen and gene variants interact to influence SCARB1 expression and lipid levels. Interaction between 35 SCARB1 haplotype-tagged polymorphisms and endogenous estradiol levels was assessed in 498 postmenopausal Caucasian women from the population-based Rancho Bernardo Study. We further examined associated variants with overall and SCARB1 splice variant (SR-BI and SR-BII) expression in 91 human liver tissues using quantitative real-time PCR. RESULTS Several variants on a haplotype block spanning intron 11 to intron 12 of SCARB1 showed significant gene by estradiol interaction affecting serum lipid levels, the strongest for rs838895 with HDL-cholesterol (p=9.2x10(-4)) and triglycerides (p=1.3x10(-3)) and the triglyceride:HDL cholesterol ratio (p=2.7x10(-4)). These same variants were associated with expression of the SR-BI isoform in a sex-specific fashion, with the strongest association found among liver tissue from 52 young women<45 years old (p=0.002). CONCLUSIONS Estrogen and SCARB1 genotype may act synergistically to regulate expression of SCARB1 isoforms and impact serum levels of HDL cholesterol and triglycerides. This work highlights the importance of considering sex-dependent effects of gene variants on serum lipid levels.
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Affiliation(s)
- Ornit Chiba-Falek
- Institute for Genome Sciences and Policy, Duke University Medical Center, Durham, NC 27710, USA
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Luangrath V, Brodeur MR, Rhainds D, Brissette L. Mouse CD36 has opposite effects on LDL and oxidized LDL metabolism in vivo. Arterioscler Thromb Vasc Biol 2008; 28:1290-5. [PMID: 18436808 DOI: 10.1161/atvbaha.107.161653] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The cluster of differentiation-36 (CD36) is a multifunctional protein which is recognized for its in vitro ability to take up oxidized low-density lipoproteins (oxLDL) in macrophages and is therefore considered atherogenic. It also binds LDL. Our objective was to define the physiological role of CD36 in both native LDL and oxLDL metabolism in mice. METHODS AND RESULTS Clearance studies of labeled LDL and oxLDL were conducted in wild-type, CD36 knockout (KO), scavenger receptor class B, type I (SR-BI) KO, and SR-BI/CD36 double KO mice. We found that CD36 impedes the disappearance of native LDL and favors that of oxLDL. This was confirmed by association and degradation assays with primary cultures of hepatic cells from wild-type and CD36 KO mice. In addition, our in vivo work indicates that neither SR-BI nor CD36 plays a significant role in cholesteryl esters (CE) selective uptake (SU) from oxLDL, whereas CD36, in absence of SR-BI, can selectively take CE from LDL. CONCLUSIONS Our investigation showed for the first time that CD36 plays a significant role in oxLDL uptake in vivo in the mouse. As CD36 also retards LDL clearance, its atherogenic character may also relate to its negative effect on LDL catabolism.
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Affiliation(s)
- Vilayphone Luangrath
- Département des Sciences Biologiques, Université du Québec à Montréal, C.P. 8888, Succursale Centreville, Montréal, Québec, Canada
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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: 3.2] [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.
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Parathath S, Darlington YF, de la Llera Moya M, Drazul-Schrader D, Williams DL, Phillips MC, Rothblat GH, Connelly MA. Effects of amino acid substitutions at glycine 420 on SR-BI cholesterol transport function. J Lipid Res 2007; 48:1386-95. [PMID: 17372332 DOI: 10.1194/jlr.m700086-jlr200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Scavenger receptor class B type I (SR-BI) facilitates the uptake of HDL cholesteryl esters (CEs) in a two-step process involving binding of HDL to its extracellular domain and transfer of HDL core CEs to a metabolically active membrane pool, where they are subsequently hydrolyzed by a neutral CE hydrolase. Recently, we characterized a mutant, G420H, which replaced glycine 420 in the extracellular domain of SR-BI with a histidine residue and had a profound effect on SR-BI function. The G420H mutant receptor exhibited a reduced ability to mediate selective HDL CE uptake and was unable to deliver HDL CE for hydrolysis, despite the fact that it retained the ability to bind HDL. This did not hold true if glycine 420 was replaced with an alanine residue; G420A maintained wild-type HDL binding and cholesterol transport activity. To further understand the role that glycine 420 plays in SR-BI function and why there was a disparity between replacing glycine 420 with a histidine versus an alanine, we generated a battery of point mutants by substituting glycine 420 with amino acids possessing side chains that were charged, hydrophobic, polar, or bulky and tested the resulting mutants for their ability to support HDL binding, HDL cholesterol transport, and delivery for hydrolysis. The results indicated that substitution with a negatively charged residue or a proline impaired cell surface expression of SR-BI or its interaction with HDL, respectively. Furthermore, substitution of glycine 420 with a positively charged residue reduced HDL CE uptake as well as its subsequent hydrolysis.
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Affiliation(s)
- Saj Parathath
- Department of Pharmacological Sciences, University Medical Center, Stony Brook University, Stony Brook, NY 11794-8651, USA
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Lapointe J, Truong TQ, Falstrault L, Brissette L. Differential abilities of mouse liver parenchymal and nonparenchymal cells in HDL and LDL (native and oxidized) association and cholesterol efflux. Biochem Cell Biol 2006; 84:250-6. [PMID: 16609706 DOI: 10.1139/o05-172] [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: 11/22/2022] Open
Abstract
The aim of this study was to quantify the abilities of mouse liver parenchymal and nonparenchymal cells with respect to (i) cholesteryl ester (CE) selective uptake from low-density lipoproteins (LDL), oxidized LDL (OxLDL), and high-density lipoprotein (HDL); and (ii) their free cholesterol efflux to HDL. The preparations of cells were incubated with lipoproteins labelled either in protein with iodine-125 or in CE with 3H-cholesterol oleate, and lipoprotein-protein and lipoprotein-CE associations were measured. The associations of LDL-protein and LDL-CE with nonparenchymal cells were 5- and 2-fold greater, respectively, than with parenchymal cells. However, in terms of CE-selective uptake (CE association minus protein association) both types of cell were equivalent. Similar results were obtained with OxLDL, but both types of cell showed higher abilities in OxLDL-CE than in LDL-CE selective uptake (on average by 3.4-fold). The association of HDL-protein with nonparenchymal cells was 3x that with parenchymal cells; however, nonparenchymal cells associated 45% less HDL-CE. Contrary to parenchymal cells, nonparenchymal cells did not show HDL-CE selective uptake activity. Thus parenchymal cells selectively take CE from the 3 types of lipoproteins, whereas nonparenchymal cells exert this function only on LDL and OxLDL. Efflux was 3.5-fold more important in nonparenchymal than in parenchymal cells.
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Affiliation(s)
- Jany Lapointe
- Département des Sciences Biologiques, Université du Québec à Montréal, Canada
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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.
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Affiliation(s)
- Bernardo L Trigatti
- Department of Biochemistry and Biomedical Sciences, Faculty of Health Sciences, McMaster University, West Hamilton, ON L8N 3Z5, Canada.
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Bourret G, Brodeur MR, Luangrath V, Lapointe J, Falstrault L, Brissette L. In vivo cholesteryl ester selective uptake of mildly and standardly oxidized LDL occurs by both parenchymal and nonparenchymal mouse hepatic cells but SR-BI is only responsible for standardly oxidized LDL selective uptake by nonparenchymal cells. Int J Biochem Cell Biol 2006; 38:1160-70. [PMID: 16427800 DOI: 10.1016/j.biocel.2005.12.005] [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] [Received: 01/21/2005] [Revised: 11/15/2005] [Accepted: 12/11/2005] [Indexed: 11/29/2022]
Abstract
In blood circulation, low density lipoproteins (LDL) can undergo modification, such as oxidation, and become key factors in the development of atherosclerosis. Although the liver is the major organ involved in the elimination of oxidized LDL (oxLDL), the identity of the receptor(s) involved remains to be defined. Our work aims to clarify the role of the scavenger receptor class B type I (SR-BI) in the hepatic metabolism of mildly and standardly oxLDL as well as the relative contribution of parenchymal (hepatocytes) and nonparenchymal liver cells with a special emphasis on CE-selective uptake. The association of native LDL and mildly or standardly oxLDL labeled either in proteins or in cholesteryl esters (CE) was measured on primary cultures of mouse hepatocytes from normal and SR-BI knock-out (KO) mice. These in vitro assays demonstrated that hepatocytes are able to mediate CE-selective uptake from both LDL and oxLDL and that SR-BI KO hepatocytes have a 60% reduced ability to selectively take CE from LDL but not towards mildly or standardly oxLDL. When lipoproteins were injected in the mouse inferior vena cava, parenchymal and nonparenchymal liver cells accumulated more CE than proteins from native, mildly and standardly oxLDL, indicating that selective uptake of CE from these lipoproteins occurs in vivo in these two cell types. The parenchymal cells contribute near 90% of the LDL-CE selective uptake and SR-BI for 60% of this pathway. Nonparenchymal cells capture mainly standardly oxLDL while parenchymal and nonparenchymal cells equally take up mildly oxLDL. An 82% reduction of standardly oxLDL-CE selective uptake by the nonparenchymal cells of SR-BI KO mice allowed emphasizing the contribution of SR-BI in hepatic metabolism of standardly oxLDL. However, SR-BI is not responsible for mildly oxLDL metabolism. Thus, SR-BI is involved in LDL- and standardly oxLDL-CE selective uptake in parenchymal and nonparenchymal cells, respectively.
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Affiliation(s)
- Geneviève Bourret
- Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Qué., Canada H3C 3P8
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