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Xu Y, Li Y, Jadhav K, Pan X, Zhu Y, Hu S, Chen S, Chen L, Tang Y, Wang HH, Yang L, Wang DQH, Yin L, Zhang Y. Hepatocyte ATF3 protects against atherosclerosis by regulating HDL and bile acid metabolism. Nat Metab 2021; 3:59-74. [PMID: 33462514 PMCID: PMC7856821 DOI: 10.1038/s42255-020-00331-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 12/09/2020] [Indexed: 12/13/2022]
Abstract
Activating transcription factor (ATF)3 is known to have an anti-inflammatory function, yet the role of hepatic ATF3 in lipoprotein metabolism or atherosclerosis remains unknown. Here we show that overexpression of human ATF3 in hepatocytes reduces the development of atherosclerosis in Western-diet-fed Ldlr-/- or Apoe-/- mice, whereas hepatocyte-specific ablation of Atf3 has the opposite effect. We further show that hepatic ATF3 expression is inhibited by hydrocortisone. Mechanistically, hepatocyte ATF3 enhances high-density lipoprotein (HDL) uptake, inhibits intestinal fat and cholesterol absorption and promotes macrophage reverse cholesterol transport by inducing scavenger receptor group B type 1 (SR-BI) and repressing cholesterol 12α-hydroxylase (CYP8B1) in the liver through its interaction with p53 and hepatocyte nuclear factor 4α, respectively. Our data demonstrate that hepatocyte ATF3 is a key regulator of HDL and bile acid metabolism and atherosclerosis.
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Affiliation(s)
- Yanyong Xu
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
| | - Yuanyuan Li
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
- Zhongshan Institute for Drug Discovery, the Institutes of Drug Discovery and Development, Chinese Academy of Sciences, Zhongshan, China
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Kavita Jadhav
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
| | - Xiaoli Pan
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
- Divison of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yingdong Zhu
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
| | - Shuwei Hu
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
| | - Shaoru Chen
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
| | - Liuying Chen
- Divison of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yong Tang
- Department of Hepatobiliary Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Helen H Wang
- Department of Medicine and Genetics, Marion Bessin Liver Research Center and Albert Einstein College of Medicine, Bronx, NY, USA
| | - Ling Yang
- Divison of Gastroenterology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - David Q-H Wang
- Department of Medicine and Genetics, Marion Bessin Liver Research Center and Albert Einstein College of Medicine, Bronx, NY, USA
| | - Liya Yin
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA
| | - Yanqiao Zhang
- Department of Integrative Medical Sciences, Northeast Ohio Medical University, Rootstown, OH, USA.
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Ceres K, Fitzgerald H, Quiznon KS, McDonough S, Behling-Kelly E. Immunohistochemical Labeling of Low-Density Lipoprotein Receptor and Scavenger Receptor Class B Type 1 Are Increased in Canine Lymphoma. Front Vet Sci 2019; 5:340. [PMID: 30687727 PMCID: PMC6336922 DOI: 10.3389/fvets.2018.00340] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 12/18/2018] [Indexed: 12/11/2022] Open
Abstract
Altered lipid metabolism is a well-documented hallmark of neoplastic transformation and impacts disease progression. Two major lipoprotein receptors, the low-density lipoprotein receptor (LDL-R) and scavenger receptor class B, type 1 (SR-BI) are overexpressed in a number of cancer types in people. These receptors serve to deliver cholesterol to the tumor cells and have been used to target drug therapies. In this study, we performed a retrospective analysis of LDL-R and SR-B1 expression in canine lymphoma using archived formalin-fixed tissue samples. Cases were immunophenotyped and classified according to World Health Organization (WHO) standards prior to immunostaining for the LDL_R and SR-B1. A total of 45 cases were evaluated; 21 high grade B (HGB), 11 low grade B (LGB), 7 high grade T (HGT), and 6 low grade T (LGT) lymphomas. One sided Wilcoxon rank sum tests were used to compare staining intensity between neoplastic and hyperplastic lymphoid tissue. The relationships between histological score and tumor grade and score and stage at presentation were assessed using non-parametric Kruskal-Wallis tests. Neoplastic lymphoid tissue expressed higher levels of both receptors compared to reactive lymph nodes. Median LDL-R score was 85.0 (interquartile range = 101.7), Median SR-B1 score was 209.0 (interquartile range 105.2). No relationship between LDL-R or SR-B1 staining score and tumor grade or phenotype was found. Serum cholesterol concentration was compared between dogs with high and low grade tumors using a two sample T-test, and correlations between cholesterol concentration and histological score, and between the score for the two receptors were determined using a Spearman correlation. The high expression level of these lipoprotein receptors on most of the tumors could underlie the lack of relationship between score and tumor grade. The overexpression of LDL-R and SR-B1 in canine lymphoma holds therapeutic potential particularly in dogs that overexpress one or both of these receptors, and this warrants further investigation.
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Affiliation(s)
- Kristina Ceres
- Department of Population Medicine and Diagnostic Services, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Halle Fitzgerald
- College of Agriculture and Life Sciences, Cornell University, Ithaca, NY, United States
| | | | - Sean McDonough
- Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
| | - Erica Behling-Kelly
- Department of Population Medicine and Diagnostic Services, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States
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Linton MF, Tao H, Linton EF, Yancey PG. SR-BI: A Multifunctional Receptor in Cholesterol Homeostasis and Atherosclerosis. Trends Endocrinol Metab 2017; 28:461-472. [PMID: 28259375 PMCID: PMC5438771 DOI: 10.1016/j.tem.2017.02.001] [Citation(s) in RCA: 130] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 01/31/2017] [Accepted: 02/01/2017] [Indexed: 02/07/2023]
Abstract
The HDL receptor scavenger receptor class B type I (SR-BI) plays crucial roles in cholesterol homeostasis, lipoprotein metabolism, and atherosclerosis. Hepatic SR-BI mediates reverse cholesterol transport (RCT) by the uptake of HDL cholesterol for routing to the bile. Through the selective uptake of HDL lipids, hepatic SR-BI modulates HDL composition and preserves HDL's atheroprotective functions of mediating cholesterol efflux and minimizing inflammation and oxidation. Macrophage and endothelial cell SR-BI inhibits the development of atherosclerosis by mediating cholesterol trafficking to minimize atherosclerotic lesion foam cell formation. SR-BI signaling also helps limit inflammation and cell death and mediates efferocytosis of apoptotic cells in atherosclerotic lesions thereby preventing vulnerable plaque formation. SR-BI is emerging as a multifunctional therapeutic target to reduce atherosclerosis development.
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Affiliation(s)
- MacRae F Linton
- Atherosclerosis Research Unit, Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232-6300, USA; Atherosclerosis Research Unit, Cardiovascular Medicine, Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6300, USA.
| | - Huan Tao
- Atherosclerosis Research Unit, Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232-6300, USA
| | - Edward F Linton
- Perelman School of Medicine, University of Pennsylvania, Jordan Medical Education Center, 6th Floor, 3400 Civic Center Blvd, Philadelphia, PA 19104-6055, USA
| | - Patricia G Yancey
- Atherosclerosis Research Unit, Cardiovascular Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232-6300, USA.
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Abstract
PURPOSE OF REVIEW Scavenger receptor BI (SR-BI) is classically known for its role in antiatherogenic reverse cholesterol transport as it selectively takes up cholesterol esters from HDL. Here, we have highlighted recent literature that describes novel functions for SR-BI in physiology and disease. RECENT FINDINGS A large population-based study has revealed that patients heterozygous for the P376L mutant form of SR-BI showed significantly increased levels of plasma HDL-cholesterol and had increased risk of cardiovascular disease, demonstrating that SR-BI in humans is a significant determinant of cardiovascular disease. Furthermore, SR-BI has been shown to modulate the susceptibility to LPS-induced tissue injury and the ability of sphingosine 1 phosphate to interact with its receptor, linking SR-BI to the regulation of inflammation. In addition, important domains within the molecule (Trp-415) as well as novel regulators (procollagen C-endopeptidase enhancer protein 2) of SR-BI's selective uptake function have recently been identified. Moreover, relatively high expression levels of the SR-BI protein have been observed in a variety of cancer tissues, which is associated with a reduced overall survival rate. SUMMARY The HDL receptor SR-BI is a potential therapeutic target not only in the cardiovascular disease setting, but also in inflammatory conditions as well as in cancer.
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Affiliation(s)
- Menno Hoekstra
- Division of Biopharmaceutics, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden, The Netherlands, , Tel: +31-71-5276582
| | - Mary Sorci-Thomas
- Division of Endocrinology, Associate in Pharmacology and Toxicology, Medical College of Wisconsin, Senior Adjunct Investigator at the Blood Research Institute, Blood Center of Wisconsin, , Tel: 414-955-5728
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Fruhwürth S, Kovacs WJ, Bittman R, Messner S, Röhrl C, Stangl H. Differential basolateral-apical distribution of scavenger receptor, class B, type I in cultured cells and the liver. Histochem Cell Biol 2014; 142:645-55. [PMID: 25059650 PMCID: PMC4241236 DOI: 10.1007/s00418-014-1251-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2014] [Indexed: 12/11/2022]
Abstract
The high-density lipoprotein (HDL) receptor, scavenger receptor class B, type I (SR-BI), mediates selective cholesteryl ester uptake into the liver, which finally results in cholesterol secretion into the bile. Despite several reports, the distribution of hepatic SR-BI between the sinusoidal and canalicular membranes is still under debate. We present immunohistological data using specific markers showing that the bulk of SR-BI is present in sinusoidal membranes and, to a lesser extent, in canalicular membranes in murine and human liver sections. In addition, SR-BI was detected in preparations of rat liver canalicular membranes. We also compared the in vivo findings to HepG2 cells, a widely used in vitro hepatocyte model. Interestingly, SR-BI was enriched in bile canalicular-like (BC-like) structures in polarized HepG2 cells, which were cultivated either conventionally to form a monolayer or in Matrigel to form three-dimensional structures. Fluorescently labeled HDL was transported into close proximity of BC-like structures, whereas HDL labeled with the fluorescent cholesterol analog BODIPY-cholesterol was clearly detected within these structures. Importantly, similarly to human and mouse liver, SR-BI was localized in basolateral membranes in three-dimensional liver microtissues from primary human liver cells. Our results demonstrate that SR-BI is highly enriched in sinusoidal membranes and is also found in canalicular membranes. There was no significant basolateral-apical redistribution of hepatic SR-BI in fasting and refeeding experiments in mice. Furthermore, in vitro studies in polarized HepG2 cells showed explicit differences as SR-BI was highly enriched in BC-like structures. These structures are, however, functional and accumulated HDL-derived cholesterol. Thus, biological relevant model systems should be employed when investigating SR-BI distribution in vitro.
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Affiliation(s)
- Stefanie Fruhwürth
- Center for Pathobiochemistry and Genetics, Department of Medical Chemistry, Medical University of Vienna, Währingerstraße 10, 1090 Vienna, Austria
| | - Werner J. Kovacs
- Institute of Molecular Health Sciences, Swiss Federal Institute of Technology Zurich (ETHZ), Zurich, Switzerland
| | - Robert Bittman
- Department of Chemistry and Biochemistry, Queens College of the City University of New York, Flushing, NY USA
| | | | - Clemens Röhrl
- Center for Pathobiochemistry and Genetics, Department of Medical Chemistry, Medical University of Vienna, Währingerstraße 10, 1090 Vienna, Austria
| | - Herbert Stangl
- Center for Pathobiochemistry and Genetics, Department of Medical Chemistry, Medical University of Vienna, Währingerstraße 10, 1090 Vienna, Austria
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6
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Abstract
PURPOSE OF REVIEW To summarize the recent findings about the roles of scavenger receptor class B type I (SR-BI) in immunity and discuss the underlying mechanisms by which SR-BI prevents immune dysfunctions. RECENT FINDINGS SR-BI is well known as a high-density lipoprotein (HDL) receptor playing key roles in HDL metabolism and in protection against atherosclerosis. Recent studies have indicated that SR-BI is also an essential modulator in immunity. SR-BI deficiency in mice causes immune dysfunctions, including increased atherosclerosis, elevated susceptibility to sepsis, impaired lymphocyte homeostasis, and autoimmune disorders. SR-BI exerts its protective roles through a variety of HDL-dependent and HDL-independent mechanisms. SR-BI is also involved in hepatitis C virus cell entry. A deficiency of SR-BI in humanized mice has been shown to decrease hepatitis C virus infectivity. SUMMARY SR-BI regulates immunity via multiple mechanisms and its deficiency causes numerous diseases. A comprehensive understanding of the roles of SR-BI in protection against immune dysfunctions may provide a therapeutic target for intervention against its associated diseases.
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Affiliation(s)
- Zhong Zheng
- Department of Pediatrics, University of Kentucky College of Medicine, Lexington, Kentucky, USA
- Graduate Center for Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Junting Ai
- Department of Pediatrics, University of Kentucky College of Medicine, Lexington, Kentucky, USA
- Graduate Center for Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Xiang-An Li
- Department of Pediatrics, University of Kentucky College of Medicine, Lexington, Kentucky, USA
- Graduate Center for Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, USA
- Saha Cardiovascular Research Center, University of Kentucky College of Medicine, Lexington, Kentucky, USA
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Kocher O, Birrane G, Yesilaltay A, Shechter S, Pal R, Daniels K, Krieger M. Identification of the PDZ3 domain of the adaptor protein PDZK1 as a second, physiologically functional binding site for the C terminus of the high density lipoprotein receptor scavenger receptor class B type I. J Biol Chem 2011; 286:25171-86. [PMID: 21602281 PMCID: PMC3137089 DOI: 10.1074/jbc.m111.242362] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 04/21/2011] [Indexed: 12/11/2022] Open
Abstract
The normal expression, cell surface localization, and function of the murine high density lipoprotein receptor scavenger receptor class B type I (SR-BI) in hepatocytes in vivo, and thus normal lipoprotein metabolism, depend on its four PDZ domain (PDZ1-PDZ4) containing cytoplasmic adaptor protein PDZK1. Previous studies showed that the C terminus of SR-BI ("target peptide") binds directly to PDZ1 and influences hepatic SR-BI protein expression. Unexpectedly an inactivating mutation in PDZ1 (Tyr(20) → Ala) only partially, rather than completely, suppresses the ability of PDZK1 to control hepatic SR-BI. We used isothermal titration calorimetry to show that PDZ3, but not PDZ2 or PDZ4, can also bind the target peptide (K(d) = 37.0 μm), albeit with ∼10-fold lower affinity than PDZ1. This binding is abrogated by a Tyr(253) → Ala substitution. Comparison of the 1.5-Å resolution crystal structure of PDZ3 with its bound target peptide ((505)QEAKL(509)) to that of peptide-bound PDZ1 indicated fewer target peptide stabilizing atomic interactions (hydrogen bonds and hydrophobic interactions) in PDZ3. A double (Tyr(20) → Ala (PDZ1) + Tyr(253) → Ala (PDZ3)) substitution abrogated all target peptide binding to PDZK1. In vivo hepatic expression of a singly substituted (Tyr(253) → Ala (PDZ3)) PDZK1 transgene (Tg) was able to correct all of the SR-BI-related defects in PDZK1 knock-out mice, whereas the doubly substituted [Tyr(20) → Ala (PDZ1) + Tyr(253) → Ala (PDZ3)]Tg was unable to correct these defects. Thus, we conclude that PDZK1-mediated control of hepatic SR-BI requires direct binding of the SR-BI C terminus to either the PDZ1 or PDZ3 domains, and that binding to both domains simultaneously is not required for PDZK1 control of hepatic SR-BI.
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Affiliation(s)
- Olivier Kocher
- Department of Pathology, Harvard Medical School, Boston, Massachusetts 02215, USA.
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Gaidukov L, Nager AR, Xu S, Penman M, Krieger M. Glycine dimerization motif in the N-terminal transmembrane domain of the high density lipoprotein receptor SR-BI required for normal receptor oligomerization and lipid transport. J Biol Chem 2011; 286:18452-64. [PMID: 21454587 PMCID: PMC3099662 DOI: 10.1074/jbc.m111.229872] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 03/23/2011] [Indexed: 12/15/2022] Open
Abstract
Scavenger receptor class B, type I (SR-BI), a CD36 superfamily member, is an oligomeric high density lipoprotein (HDL) receptor that mediates negatively cooperative HDL binding and selective lipid uptake. We identified in the N-terminal transmembrane (N-TM) domain of SR-BI a conserved glycine dimerization motif, G(15)X(2)G(18)X(3)AX(2)G(25), of which the submotif G(18)X(3)AX(2)G(25) significantly contributes to homodimerization and lipid uptake activity. SR-BI variants were generated by mutations (single or multiple Gly → Leu substitutions) or by replacing the N-TM domain with those from other CD36 superfamily members containing (croquemort) or lacking (lysosomal integral membrane protein (LIMP) II) this glycine motif (chimeras). None of the SR-BI variants exhibited altered surface expression (based on antibody binding) or HDL binding. However, the G15L/G18L/G25L triple mutant exhibited reductions in cell surface homo-oligomerization (>10-fold) and the rate of selective lipid uptake (∼ 2-fold). Gly(18) and Gly(25) were necessary for normal lipid uptake activity of SR-BI and the SR-BI/croquemort chimera. The lipid uptake activity of the glycine motif-deficient SR-BI/LIMP II chimera was low but could be increased by introducing glycines at positions 18 and 25. The rate of lipid uptake mediated by SR-BI/LIMP II chimeras was proportional to the extent of receptor oligomerization. Thus, the glycine dimerization motif G(18)X(3)AX(2)G(25) in the N-TM domain of SR-BI contributes substantially to the homo-oligomerization and lipid transport activity of SR-BI but does not influence the negative cooperativity of HDL binding. Oligomerization-independent binding cooperativity suggests that classic allostery is not involved and that the negative cooperativity is probably the consequence of a "lattice effect" (interligand steric interference accompanying binding to adjacent receptors).
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Affiliation(s)
- Leonid Gaidukov
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Andrew R. Nager
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Shangzhe Xu
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Marsha Penman
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Monty Krieger
- From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Li T, Matozel M, Boehme S, Kong B, Nilsson LM, Guo G, Ellis E, Chiang JYL. Overexpression of cholesterol 7α-hydroxylase promotes hepatic bile acid synthesis and secretion and maintains cholesterol homeostasis. Hepatology 2011; 53:996-1006. [PMID: 21319191 PMCID: PMC3079544 DOI: 10.1002/hep.24107] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 12/02/2010] [Indexed: 12/15/2022]
Abstract
UNLABELLED We reported previously that mice overexpressing cytochrome P450 7a1 (Cyp7a1; Cyp7a1-tg mice) are protected against high fat diet-induced hypercholesterolemia, obesity, and insulin resistance. Here, we investigated the underlying mechanism of bile acid signaling in maintaining cholesterol homeostasis in Cyp7a1-tg mice. Cyp7a1-tg mice had two-fold higher Cyp7a1 activity and bile acid pool than did wild-type mice. Gallbladder bile acid composition changed from predominantly cholic acid (57%) in wild-type to chenodeoxycholic acid (54%) in Cyp7a1-tg mice. Cyp7a1-tg mice had higher biliary and fecal cholesterol and bile acid secretion rates than did wild-type mice. Surprisingly, hepatic de novo cholesterol synthesis was markedly induced in Cyp7a1-tg mice but intestine fractional cholesterol absorption in Cyp7a1-tg mice remained the same as wild-type mice despite the presence of increased intestine bile acids. Interestingly, hepatic but not intestinal expression of several cholesterol (adenosine triphosphate-binding cassette G5/G8 [ABCG5/G8], scavenger receptor class B, member 1) and bile acid (ABCB11) transporters were significantly induced in Cyp7a1-tg mice. Treatment of mouse or human hepatocytes with a farnesoid X receptor (FXR) agonist GW4064 or bile acids induced hepatic Abcg5/g8 expression. A functional FXR binding site was identified in the Abcg5 gene promoter. Study of tissue-specific Fxr knockout mice demonstrated that loss of the Fxr gene in the liver attenuated bile acid induction of hepatic Abcg5/g8 and gallbladder cholesterol content, suggesting a role of FXR in the regulation of cholesterol transport. CONCLUSION This study revealed a new mechanism by which increased Cyp7a1 activity expands the hydrophobic bile acid pool, stimulating hepatic cholesterol synthesis and biliary cholesterol secretion without increasing intestinal cholesterol absorption. This study demonstrated that Cyp7a1 plays a critical role in maintaining cholesterol homeostasis and underscores the importance of bile acid signaling in regulating overall cholesterol homeostasis.
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Affiliation(s)
- Tiangang Li
- Department of Integrative Medical Sciences, Northeastern Ohio Univ’s Colleges of Medicine & Pharmacy, Rootstown, OH 44272
| | - Michelle Matozel
- Department of Integrative Medical Sciences, Northeastern Ohio Univ’s Colleges of Medicine & Pharmacy, Rootstown, OH 44272
| | - Shannon Boehme
- Department of Integrative Medical Sciences, Northeastern Ohio Univ’s Colleges of Medicine & Pharmacy, Rootstown, OH 44272
| | - Bo Kong
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160
| | - Lisa-Mari Nilsson
- Unit for Transplantation Surgery, Department of Clinical Science, Intervention and Technology, Karolinska Institute, Stockholm, Sweden
| | - Grace Guo
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160
| | - Ewa Ellis
- Unit for Transplantation Surgery, Department of Clinical Science, Intervention and Technology, Karolinska Institute, Stockholm, Sweden
| | - John Y. L. Chiang
- Department of Integrative Medical Sciences, Northeastern Ohio Univ’s Colleges of Medicine & Pharmacy, Rootstown, OH 44272
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Gillard BK, Rosales C, Pillai BK, Lin HY, Courtney HS, Pownall HJ. Streptococcal serum opacity factor increases the rate of hepatocyte uptake of human plasma high-density lipoprotein cholesterol. Biochemistry 2010; 49:9866-73. [PMID: 20879789 PMCID: PMC2982792 DOI: 10.1021/bi101412m] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Serum opacity factor (SOF), a virulence determinant of Streptococcus pyogenes, converts plasma high-density lipoproteins (HDL) to three distinct species: lipid-free apolipoprotein (apo) A-I, neo HDL, a small discoidal HDL-like particle, and a large cholesteryl ester-rich microemulsion (CERM) that contains the cholesterol esters (CE) of up to ∼400000 HDL particles and apo E as its major protein. Similar SOF reaction products are obtained with HDL, total plasma lipoproteins, and whole plasma. We hypothesized that hepatic uptake of CERM-CE via multiple apo E-dependent receptors would be faster than that of HDL-CE. We tested our hypothesis using human hepatoma cells and lipoprotein receptor-specific Chinese hamster ovary (CHO) cells. The uptake of [(3)H]CE by HepG2 and Huh7 cells from HDL after SOF treatment, which transfers >90% of HDL-CE to CERM, was 2.4 and 4.5 times faster, respectively, than from control HDL. CERM-[(3)H]CE uptake was inhibited by LDL and HDL, suggestive of uptake by both the LDL receptor (LDL-R) and scavenger receptor class B type I (SR-BI). Studies in CHO cells specifically expressing LDL-R and SR-BI confirmed CERM-[(3)H]CE uptake by both receptors. RAP and heparin inhibit CERM-[(3)H]CE but not HDL-[(3)H]CE uptake, thereby implicating LRP-1 and cell surface proteoglycans in this process. These data demonstrate that SOF treatment of HDL increases the rate of CE uptake via multiple hepatic apo E receptors. In so doing, SOF might increase the level of hepatic disposal of plasma cholesterol in a way that is therapeutically useful.
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Affiliation(s)
- Baiba K. Gillard
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
| | - Corina Rosales
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
| | - Biju K. Pillai
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
| | - Hu Yu Lin
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
| | - Harry S. Courtney
- Veterans Affairs Medical Center and Department of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38104
| | - Henry J. Pownall
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030
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11
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Bietrix F, Yan D, Nauze M, Rolland C, Bertrand-Michel J, Coméra C, Schaak S, Barbaras R, Groen AK, Perret B, Tercé F, Collet X. Accelerated lipid absorption in mice overexpressing intestinal SR-BI. J Biol Chem 2006; 281:7214-9. [PMID: 16421100 PMCID: PMC2034750 DOI: 10.1074/jbc.m508868200] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dietary cholesterol absorption contributes to a large part of the circulating cholesterol. However, the mechanism of sterol intestinal uptake is not clearly elucidated. Scavenger receptor class B type I (SR-BI), major component in the control of cholesterol homeostasis, is expressed in the intestine, but its role in this organ remains unclear. We have generated transgenic mice overexpressing SR-BI primarily in the intestine by using the mouse SR-BI gene under the control of intestinal specific "apoC-III enhancer coupled with apoA-IV promoter." We found SR-BI overexpression with respect to the natural protein along the intestine and at the top of the villosities. After a meal containing [(14)C]cholesterol and [(3)H]triolein, SR-BI transgenic mice presented a rise in intestinal absorption of both lipids that was not due to a defect in chylomicron clearance nor to a change in the bile flow or the bile acid content. Nevertheless, SR-BI transgenic mice showed a decrease of total cholesterol but an increase of triglyceride content in plasma without any change in the high density lipoprotein apoA-I level. Thus, we described for the first time a functional role in vivo for SR-BI in cholesterol but also in triglyceride intestinal absorption.
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Affiliation(s)
- Florence Bietrix
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - Daoguang Yan
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - Michel Nauze
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - Corinne Rolland
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - Justine Bertrand-Michel
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - Christine Coméra
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - Stephane Schaak
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - Ronald Barbaras
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | | | - Bertrand Perret
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - François Tercé
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
| | - Xavier Collet
- Centre de Physiopathologie Toulouse Purpan
INSERM : U563 IFR30Université Paul Sabatier - Toulouse IIIHôpital de Purpan Place du Docteur Baylac
31024 TOULOUSE CEDEX 3,FR
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Abstract
BACKGROUND AND AIMS Biliary lipid absorption by the gall bladder mucosa and the cholesterol content of the gall bladder wall appear to play a role in cholesterol gall stone formation. As the scavenger receptor class B type I (SR- BI) regulates cellular cholesterol uptake, we studied its expression in human and murine gall bladders, its regulation by increased biliary lipid content, and its role in gall stone formation. METHODS AND RESULTS Using immunohistochemistry, SR-BI was found in the apical domain of human gall bladder epithelial cells. Immunoblotting of isolated membranes from gall bladder epithelial cells showed a specific signal for the 82 kDa SR-BI protein. In C57BL/6 mice, SR-BI was also found in the gall bladder epithelium. Using western blot analysis, an inverse relationship was observed between biliary cholesterol concentration and SR-BI expression in murine gall bladder mucosa. By comparing lithogenic diet fed wild-type and SR-BI deficient mice, gall bladder wall cholesterol content and gall stone formation were not found to be dependent on SR-BI expression. CONCLUSIONS (i) SR-BI is expressed in both human and murine gall bladder epithelium; (ii) biliary cholesterol hypersecretion is associated with decreased gall bladder SR-BI expression in mice; and (iii) murine SR-BI is not essential in controlling gall bladder wall cholesterol content and gall stone formation during diet induced cholelithiasis.
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Affiliation(s)
- J F Miquel
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica, Marcoleta 367, Santiago, Chile.
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