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Azhar S, Shen WJ, Hu Z, Kraemer FB. MicroRNA regulation of adrenal glucocorticoid and androgen biosynthesis. VITAMINS AND HORMONES 2023; 124:1-37. [PMID: 38408797 DOI: 10.1016/bs.vh.2023.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Steroid hormones are derived from a common precursor molecule, cholesterol, and regulate a wide range of physiologic function including reproduction, salt balance, maintenance of secondary sexual characteristics, response to stress, neuronal function, and various metabolic processes. Among the steroids synthesized by the adrenal and gonadal tissues, adrenal mineralocorticoids, and glucocorticoids are essential for life. The process of steroidogenesis is regulated at multiple levels largely by transcriptional, posttranscriptional, translational, and posttranslational regulation of the steroidogenic enzymes (i.e., cytochrome P450s and hydroxysteroid dehydrogenases), cellular compartmentalization of the steroidogenic enzymes, and cholesterol processing and transport proteins. In recent years, small noncoding RNAs, termed microRNAs (miRNAs) have been recognized as major post-transcriptional regulators of gene expression with essential roles in numerous biological processes and disease pathologies. Although their role in the regulation of steroidogenesis is still emerging, several recent studies have contributed significantly to our understanding of the role miRNAs play in the regulation of the steroidogenic process. This chapter focuses on the recent developments in miRNA regulation of adrenal glucocorticoid and androgen production in humans and rodents.
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Affiliation(s)
- Salman Azhar
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, CA, United States; Division of Endocrinology, Gerontology and Metabolism, Stanford University School of Medicine, Stanford, CA, United States; Stanford Diabetes Research Center, Stanford, CA, United States.
| | - Wen-Jun Shen
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, CA, United States; Division of Endocrinology, Gerontology and Metabolism, Stanford University School of Medicine, Stanford, CA, United States
| | - Zhigang Hu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology and College of Life Sciences, Nanjing Normal University, Nanjing, P.R. China
| | - Fredric B Kraemer
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, CA, United States; Division of Endocrinology, Gerontology and Metabolism, Stanford University School of Medicine, Stanford, CA, United States; Stanford Diabetes Research Center, Stanford, CA, United States
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2
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Bitetto G, Lopez G, Ronchi D, Pittaro A, Melzi V, Peverelli E, Cribiù FM, Comi GP, Mantovani G, Di Fonzo A. SCARB1 downregulation in adrenal insufficiency with Allgrove syndrome. Orphanet J Rare Dis 2023; 18:152. [PMID: 37331934 DOI: 10.1186/s13023-023-02763-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 06/04/2023] [Indexed: 06/20/2023] Open
Abstract
BACKGROUND Allgrove disease is a rare genetic syndrome characterized by adrenal insufficiency, alacrimia, achalasia and complex neurological involvement. Allgrove disease is due to recessive mutations in the AAAS gene, which encodes for the nucleoporin Aladin, implicated in the nucleocytoplasmic transport. The adrenal insufficiency has been suggested to rely on adrenal gland-ACTH resistance. However, the link between the molecular pathology affecting the nucleoporin Aladin and the glucocorticoid deficiency is still unknown. RESULTS By analyzing postmortem patient's adrenal gland, we identified a downregulation of Aladin transcript and protein. We found a downregulation of Scavenger receptor class B-1 (SCARB1), a key component of the steroidogenic pathway, and SCARB1 regulatory miRNAs (mir125a, mir455) in patient's tissues. With the hypothesis of an impairment in the nucleocytoplasmic transport of the SCARB1 transcription enhancer cyclic AMP-dependent protein kinase (PKA), we detected a reduction of nuclear Phospho-PKA and a cytoplasmic mislocalization in patient's samples. CONCLUSIONS These results shed a light on the possible mechanisms linking ACTH resistance, SCARB1 impairment, and defective nucleocytoplasmic transport.
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Affiliation(s)
- Giacomo Bitetto
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Gianluca Lopez
- Division of Pathology, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Dario Ronchi
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Alessandra Pittaro
- Division of Pathology, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Valentina Melzi
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Erika Peverelli
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Fulvia Milena Cribiù
- Division of Pathology, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Giacomo P Comi
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Giovanna Mantovani
- Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
- Endocrinology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Alessio Di Fonzo
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy.
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3
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Guo L, Wang W, Wang Q, Hao D, Ito M, Huang B, Mineo C, Shaul PW, Choi J, Huang LF, Li XA. The adrenal stress response is an essential host response against therapy-induced lethal immune activation. Sci Signal 2023; 16:eadd4900. [PMID: 36943922 PMCID: PMC10091512 DOI: 10.1126/scisignal.add4900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
Cytokine release syndrome (CRS) is a systemic inflammatory syndrome associated with infection- or drug-induced T cell activation and can cause multiple organ failure and even death. Because current treatments are ineffective in some patients with severe CRS, we set out to identify risk factors and mechanisms behind severe CRS that might lead to preventive therapies and better clinical outcomes in patients. In mice, we found that deficiency in the adrenal stress response-with similarities to such in patients called relative adrenal insufficiency (RAI)-conferred a high risk for lethal CRS. Mice treated with CD3 antibodies were protected against lethal CRS by the production of glucocorticoids (GC) induced by the adrenal stress response in a manner dependent on the scavenger receptor B1 (SR-BI), a receptor for high-density lipoprotein (HDL). Mice with whole-body or adrenal gland-specific SR-BI deficiency exhibited impaired GC production, more severe CRS, and increased mortality in response to CD3 antibodies. Pretreatment with a low dose of GC effectively suppressed the development of CRS and rescued survival in SR-BI-deficient mice without compromising T cell function through apoptosis. Our findings suggest that RAI may be a risk factor for therapy-induced CRS and that pretreating RAI patients with GC may prevent lethal CRS.
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Affiliation(s)
- Ling Guo
- Saha Cardiovascular Research Center, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Weinan Wang
- Division of Experimental Hematology and Cancer Biology, Brain Tumor Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA
| | - Qian Wang
- Saha Cardiovascular Research Center, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Dan Hao
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Misa Ito
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Bin Huang
- Division of Cancer Biostatistics, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Chieko Mineo
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Philip W Shaul
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jaebok Choi
- Department of Medicine, Washington University School of Medicine at St. Louis, St. Louis, MO 63110, USA
| | - L Frank Huang
- Division of Experimental Hematology and Cancer Biology, Brain Tumor Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, 45229, USA
| | - Xiang-An Li
- Saha Cardiovascular Research Center, University of Kentucky College of Medicine, Lexington, KY 40536, USA
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY 40536, USA
- Lexington VA Healthcare System, 1101 Veterans Drive, Lexington, KY 40502, USA
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
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Abe RJ, Abe JI, Nguyen MTH, Olmsted-Davis EA, Mamun A, Banerjee P, Cooke JP, Fang L, Pownall H, Le NT. Free Cholesterol Bioavailability and Atherosclerosis. Curr Atheroscler Rep 2022; 24:323-336. [PMID: 35332444 PMCID: PMC9050774 DOI: 10.1007/s11883-022-01011-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2022] [Indexed: 11/30/2022]
Abstract
PURPOSE OF REVIEW As both a cholesterol acceptor and carrier in the reverse cholesterol transport (RCT) pathway, high-density lipoprotein (HDL) is putatively atheroprotective. However, current pharmacological therapies to increase plasma HDL cholesterol (HDL-c) concentration have paradoxically failed to prevent or reduce atherosclerosis and cardiovascular disease (CVD). Given that free cholesterol (FC) transfer between surfaces of lipoproteins and cells is reversible, excess plasma FC can be transferred to the cells of peripheral tissue sites resulting in atherosclerosis. Here, we summarize potential mechanisms contributing to this paradox and highlight the role of excess free cholesterol (FC) bioavailability in atherosclerosis vs. atheroprotection. RECENT FINDINGS Recent findings have established a complex relationship between HDL-c concentration and atherosclerosis. Systemic scavenger receptor class B type 1 (SR-B1) knock out (KO) mice exhibit with increased diet-induced atherosclerosis despite having an elevated plasma HDL-c concentration compared to wild type (WT) mice. The greater bioavailability of HDL-FC in SR-B1 vs. WT mice is associated with a higher FC content in multiple cell types and tissue sites. These results suggest that dysfunctional HDL with high FC bioavailability is atheroprone despite high HDL-c concentration. Past oversimplification of HDL-c involvement in cholesterol transport has led to the failures in HDL targeted therapy. Evidence suggests that FC-mediated functionality of HDL is of higher importance than its quantity; as a result, deciphering the regulatory mechanisms by which HDL-FC bioavailability can induce atherosclerosis can have far-reaching clinical implications.
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Affiliation(s)
- Rei J Abe
- Center for Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA
| | - Jun-Ichi Abe
- Department of Cardiology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Minh T H Nguyen
- Center for Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA
- University of Science and Technology of Hanoi, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | | | - Abrar Mamun
- Center for Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA
| | - Priyanka Banerjee
- Center for Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA
| | - John P Cooke
- Center for Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA
- Weill Cornell Medicine, New York, NY, USA
| | - Longhou Fang
- Center for Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA
- Weill Cornell Medicine, New York, NY, USA
| | - Henry Pownall
- Weill Cornell Medicine, New York, NY, USA
- Center for Bioenergetics, Department of Medicine, Houston Methodist Research Institute, Houston, TX, USA
| | - Nhat-Tu Le
- Center for Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX, USA.
- Weill Cornell Medicine, New York, NY, USA.
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Inhibition of Scavenger Receptor Class B Type 1 (SR-B1) Expression and Activity as a Potential Novel Target to Disrupt Cholesterol Availability in Castration-Resistant Prostate Cancer. Pharmaceutics 2021; 13:pharmaceutics13091509. [PMID: 34575583 PMCID: PMC8467449 DOI: 10.3390/pharmaceutics13091509] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 09/04/2021] [Accepted: 09/08/2021] [Indexed: 02/07/2023] Open
Abstract
There have been several studies that have linked elevated scavenger receptor class b type 1 (SR-B1) expression and activity to the development and progression of castration-resistant prostate cancer (CRPC). SR-B1 facilitates the influx of cholesterol to the cell from lipoproteins in systemic circulation. This influx of cholesterol may be important for many cellular functions, including the synthesis of androgens. Castration-resistant prostate cancer tumors can synthesize androgens de novo to supplement the loss of exogenous sources often induced by androgen deprivation therapy. Silencing of SR-B1 may impact the ability of prostate cancer cells, particularly those of the castration-resistant state, to maintain the intracellular supply of androgens by removing a supply of cholesterol. SR-B1 expression is elevated in CRPC models and has been linked to poor survival of patients. The overarching belief has been that cholesterol modulation, through either synthesis or uptake inhibition, will impact essential signaling processes, impeding the proliferation of prostate cancer. The reduction in cellular cholesterol availability can impede prostate cancer proliferation through both decreased steroid synthesis and steroid-independent mechanisms, providing a potential therapeutic target for the treatment of prostate cancer. In this article, we discuss and highlight the work on SR-B1 as a potential novel drug target for CRPC management.
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6
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Localisation and regulation of cholesterol transporters in the human hair follicle: mapping changes across the hair cycle. Histochem Cell Biol 2021; 155:529-545. [PMID: 33404706 PMCID: PMC8134313 DOI: 10.1007/s00418-020-01957-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/10/2020] [Indexed: 02/06/2023]
Abstract
Cholesterol has long been suspected of influencing hair biology, with dysregulated homeostasis implicated in several disorders of hair growth and cycling. Cholesterol transport proteins play a vital role in the control of cellular cholesterol levels and compartmentalisation. This research aimed to determine the cellular localisation, transport capability and regulatory control of cholesterol transport proteins across the hair cycle. Immunofluorescence microscopy in human hair follicle sections revealed differential expression of ATP-binding cassette (ABC) transporters across the hair cycle. Cholesterol transporter expression (ABCA1, ABCG1, ABCA5 and SCARB1) reduced as hair follicles transitioned from growth to regression. Staining for free cholesterol (filipin) revealed prominent cholesterol striations within the basement membrane of the hair bulb. Liver X receptor agonism demonstrated active regulation of ABCA1 and ABCG1, but not ABCA5 or SCARB1 in human hair follicles and primary keratinocytes. These results demonstrate the capacity of human hair follicles for cholesterol transport and trafficking. Future studies examining the role of cholesterol transport across the hair cycle may shed light on the role of lipid homeostasis in human hair disorders.
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Pedrini S, Chatterjee P, Hone E, Martins RN. High‐density lipoprotein‐related cholesterol metabolism in Alzheimer’s disease. J Neurochem 2020; 159:343-377. [DOI: 10.1111/jnc.15170] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 08/18/2020] [Accepted: 08/20/2020] [Indexed: 12/11/2022]
Affiliation(s)
- Steve Pedrini
- Sarich Neurosciences Research InstituteEdith Cowan University Nedlands WA Australia
| | - Pratishtha Chatterjee
- Sarich Neurosciences Research InstituteEdith Cowan University Nedlands WA Australia
- Department of Biomedical Sciences Faculty of Medicine, Health and Human Sciences Macquarie University Sydney NSW Australia
| | - Eugene Hone
- Sarich Neurosciences Research InstituteEdith Cowan University Nedlands WA Australia
| | - Ralph N. Martins
- Sarich Neurosciences Research InstituteEdith Cowan University Nedlands WA Australia
- Department of Biomedical Sciences Faculty of Medicine, Health and Human Sciences Macquarie University Sydney NSW Australia
- School of Psychiatry and Clinical Neurosciences University of Western Australia Nedlands WA Australia
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8
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Hoekstra M. Identification of scavenger receptor BI as a potential screening candidate for congenital primary adrenal insufficiency in humans. Am J Physiol Endocrinol Metab 2020; 319:E102-E104. [PMID: 32369415 DOI: 10.1152/ajpendo.00069.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucocorticoids belong to the superfamily of steroid hormones that are synthesized from the common precursor cholesterol. Adrenal gland-derived glucocorticoids, e.g., cortisol in humans and corticosterone in rodents, contribute to various processes essential for normal daily life. Glucocorticoid deficiency, also referred to as primary adrenal insufficiency, therefore, often becomes evident early in life and can be present with hypoglycemia, a failure to thrive, recurrent development of infections, and neurological problems, such as seizures and coma. The majority of congenital primary adrenal insufficiency cases are caused by deleterious mutations in genes involved in the intracellular mobilization of cholesterol and the subsequent conversion of cholesterol into glucocorticoids. A significant number of glucocorticoid deficiency cases, however, cannot be explained by known genetic variations. This perspective highlights existing literature regarding the importance of lipoprotein-derived cholesterol acquisition through scavenger receptor class B, type I (SR-BI/SCARB1) for the maintenance of an optimal adrenal glucocorticoid function in mice and humans. On the basis of the reviewed findings, it is suggested that the SCARB1 gene should be included in the standard glucocorticoid deficiency genetic screening panel to 1) facilitate knowledge development on the relative contribution of SR-BI-mediated cholesterol acquisition to steroid hormone synthesis in humans and 2) open up the possibility to reclassify glucocorticoid deficiency patients without a currently known genetic cause for concomitant treatment optimization.
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Affiliation(s)
- Menno Hoekstra
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Leiden University, Gorlaeus Laboratories, Leiden, The Netherlands
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Traughber CA, Opoku E, Brubaker G, Major J, Lu H, Lorkowski SW, Neumann C, Hardaway A, Chung YM, Gulshan K, Sharifi N, Brown JM, Smith JD. Uptake of high-density lipoprotein by scavenger receptor class B type 1 is associated with prostate cancer proliferation and tumor progression in mice. J Biol Chem 2020; 295:8252-8261. [PMID: 32358065 PMCID: PMC7294086 DOI: 10.1074/jbc.ra120.013694] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/28/2020] [Indexed: 12/30/2022] Open
Abstract
High-density lipoprotein (HDL) metabolism is facilitated in part by scavenger receptor class B, type 1 (SR-B1) that mediates HDL uptake into cells. Higher levels of HDL have been associated with protection in other diseases, however, its role in prostate cancer is not definitive. SR-B1 is up-regulated in prostate cancer tissue, suggesting a possible role of this receptor in tumor progression. Here, we report that knockout (KO) of SR-B1 in both human and mouse prostate cancer cell lines through CRISPR/Cas9-mediated genome editing reduces HDL uptake into the prostate cancer cells and reduces their proliferation in response to HDL. In vivo studies using syngeneic SR-B1 WT (SR-B1+/+) and SR-B1 KO (SR-B1-/-) prostate cancer cells in WT and apolipoprotein-AI KO (apoA1-KO) C57BL/6J mice revealed that WT hosts, containing higher levels of total and HDL-cholesterol, grew larger tumors than apoA1-KO hosts with lower levels of total and HDL-cholesterol. Furthermore, SR-B1-/- prostate cancer cells formed smaller tumors in WT hosts than SR-B1+/+ cells in the same host model. Increased tumor volume was overall associated with reduced survival. We conclude that knocking out SR-B1 in prostate cancer tumors reduces HDL-associated increases in prostate cancer cell proliferation and disease progression.
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Affiliation(s)
- C Alicia Traughber
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Emmanuel Opoku
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Gregory Brubaker
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Jennifer Major
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Hanxu Lu
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Shuhui Wang Lorkowski
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Chase Neumann
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Aimalie Hardaway
- Department of Cancer Biology, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Yoon-Mi Chung
- Department of Cancer Biology, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Kailash Gulshan
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - Nima Sharifi
- Department of Cancer Biology, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
| | - J Mark Brown
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
- Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio, USA
- Center for Microbiome and Human Health, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Jonathan D Smith
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
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10
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Wang D, Huang J, Gui T, Yang Y, Feng T, Tzvetkov NT, Xu T, Gai Z, Zhou Y, Zhang J, Atanasov AG. SR-BI as a target of natural products and its significance in cancer. Semin Cancer Biol 2020; 80:18-38. [PMID: 31935456 DOI: 10.1016/j.semcancer.2019.12.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/25/2019] [Accepted: 12/30/2019] [Indexed: 02/07/2023]
Abstract
Scavenger receptor class B type I (SR-BI) protein is an integral membrane glycoprotein. SR-BI is emerging as a multifunctional protein, which regulates autophagy, efferocytosis, cell survival and inflammation. It is well known that SR-BI plays a critical role in lipoprotein metabolism by mediating cholesteryl esters selective uptake and the bi-directional flux of free cholesterol. Recently, SR-BI has also been identified as a potential marker for cancer diagnosis, prognosis, or even a treatment target. Natural products are a promising source for the discovery of new drug leads. Multiple natural products were identified to regulate SR-BI protein expression. There are still a number of challenges in modulating SR-BI expression in cancer and in using natural products for modulation of such protein expression. In this review, our purpose is to discuss the relationship between SR-BI protein and cancer, and the molecular mechanisms regulating SR-BI expression, as well as to provide an overview of natural products that regulate SR-BI expression.
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Affiliation(s)
- Dongdong Wang
- The Second Affiliated Hospital of Guizhou University of Traditional Chinese Medicine, Fei Shan Jie 32, 550003, Guiyang, China
| | - Jiansheng Huang
- Department of Medicine, Vanderbilt University Medical Center, 318 Preston Research Building, 2200 Pierce Avenue, Nashville, Tennessee, 37232, USA
| | - Ting Gui
- Key Laboratory of Traditional Chinese Medicine for Classical Theory, Ministry of Education, Shandong University of Traditional Chinese Medicine, Jinan, 250355, China
| | - Yaxin Yang
- The Second Affiliated Hospital of Guizhou University of Traditional Chinese Medicine, Fei Shan Jie 32, 550003, Guiyang, China
| | - Tingting Feng
- College of Pharmacy, Guizhou University of Traditional Chinese Medicine, Huaxi university town, 550025, Guiyang, China
| | - Nikolay T Tzvetkov
- Department of Biochemical Pharmacology and Drug Design, Institute of Molecular Biology "Roumen Tsanev", Bulgarian Academy of Sciences, 21 Acad. G. Bonchev Str., 1113 Sofia, Bulgaria
| | - Tao Xu
- The Second Affiliated Hospital of Guizhou University of Traditional Chinese Medicine, Fei Shan Jie 32, 550003, Guiyang, China
| | - Zhibo Gai
- Department of Clinical Pharmacology and Toxicology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Ying Zhou
- College of Pharmacy, Guizhou University of Traditional Chinese Medicine, Huaxi university town, 550025, Guiyang, China.
| | - Jingjie Zhang
- The Second Affiliated Hospital of Guizhou University of Traditional Chinese Medicine, Fei Shan Jie 32, 550003, Guiyang, China.
| | - Atanas G Atanasov
- Department of Molecular Biology, Institute of Genetics and Animal Breeding of the Polish Academy of Sciences, 05-552, Jastrzębiec, Poland; Department of Pharmacognosy, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria; Institute of Neurobiology, Bulgarian Academy of Sciences, 23 Acad. G. Bonchev Str., 1113 Sofia, Bulgaria; Ludwig Boltzmann Institute for Digital Health and Patient Safety, Medical University of Vienna, Spitalgasse 23, 1090, Vienna, Austria.
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11
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Cedó L, Farràs M, Lee-Rueckert M, Escolà-Gil JC. Molecular Insights into the Mechanisms Underlying the Cholesterol- Lowering Effects of Phytosterols. Curr Med Chem 2019; 26:6704-6723. [DOI: 10.2174/0929867326666190822154701] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 01/18/2019] [Accepted: 02/22/2019] [Indexed: 12/11/2022]
Abstract
Dietary phytosterols, which comprise plant sterols and stanols, reduce plasma Low-Density Lipoprotein-Cholesterol (LDL-C) levels when given 2 g/day. Since this dose has not been reported to cause health-related side effects in long-term human studies, food products containing these plant compounds are used as potential therapeutic dietary options to reduce LDL-C and cardiovascular disease risk. Several mechanisms have been proposed to explain the cholesterol-lowering action of phytosterols. They may compete with dietary and biliary cholesterol for micellar solubilization in the intestinal lumen, impairing intestinal cholesterol absorption. Recent evidence indicates that phytosterols may also regulate other pathways. Impaired intestinal cholesterol absorption is usually associated with reduced cholesterol transport to the liver, which may reduce the incorporation of cholesterol into Very-Low- Density Lipoprotein (VLDL) particles, thereby lowering the rate of VLDL assembly and secretion. Impaired liver VLDL production may reduce the rate of LDL production. On the other hand, significant evidence supports a role for plant sterols in the Transintestinal Cholesterol Excretion (TICE) pathway, although the exact mechanisms by which they promote the flow of cholesterol from the blood to enterocytes and the intestinal lumen remains unknown. Dietary phytosterols may also alter the conversion of bile acids into secondary bile acids, and may lower the bile acid hydrophobic/hydrophilic ratio, thereby reducing intestinal cholesterol absorption. This article reviews the progress to date in research on the molecular mechanisms underlying the cholesterol-lowering effects of phytosterols.
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Affiliation(s)
- Lídia Cedó
- Institut d'Investigacions Biomediques (IIB) Sant Pau, Barcelona, Spain
| | - Marta Farràs
- Integrative Systems Medicine and Digestive Disease Division, Department of Surgery and Cancer, Imperial College London, London, United Kingdom
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Hoekstra M, Ouweneel AB, Nahon JE, van der Geest R, Kröner MJ, van der Sluis RJ, Van Eck M. ATP-binding cassette transporter G1 deficiency is associated with mild glucocorticoid insufficiency in mice. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:443-451. [PMID: 30633988 DOI: 10.1016/j.bbalip.2019.01.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 12/06/2018] [Accepted: 01/07/2019] [Indexed: 10/27/2022]
Abstract
OBJECTIVE Since cholesterol is the sole precursor for glucocorticoid synthesis, it is hypothesized that genetic defects in proteins that impact the cellular cholesterol pool may underlie glucocorticoid insufficiency in humans. In the current study, we specifically focused on the cholesterol efflux mediator ATP-binding cassette transporter G1 (ABCG1) as gene candidate. METHODS The adrenal transcriptional response to fasting stress was measured in wild-type mice to identify putative novel gene candidates. Subsequently, the adrenal glucocorticoid function was compared between ABCG1 knockout mice and wild-type controls. RESULTS Overnight food deprivation induced a change in relative mRNA expression levels of cholesterol metabolism-related proteins previously linked to steroidogenesis, i.e. scavenger receptor class B type I (+149%; P < 0.001), LDL receptor (-70%; P < 0.001) and apolipoprotein E (-41%; P < 0.01). Strikingly, ABCG1 transcript levels were also markedly decreased (-61%; P < 0.05). In contrast to our hypothesis that decreasing cholesterol efflux would increase the adrenal cholesterol pool and enhance glucocorticoid output, ABCG1 knockout mice as compared to wild-type mice exhibited a reduced ability to secrete corticosterone in response to an ACTH challenge (two-way ANOVA: P < 0.001 for genotype) or fasting stress. As a result, glucocorticoid target gene expression levels in liver and hypothalamus were reduced and blood lymphocyte concentrations and spleen weights increased in ABCG1 knockout mice under fasting stress conditions. This was paralleled by a 48% reduction in adrenal cholesteryl ester stores and stimulation of adrenal NPC intracellular cholesterol transporter 2 (+37%; P < 0.05) and apolipoprotein E (+59%; P < 0.01) mRNA expression. CONCLUSION ABCG1 deficiency is associated with mild glucocorticoid insufficiency in mice.
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Affiliation(s)
- Menno Hoekstra
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands.
| | - Amber B Ouweneel
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Joya E Nahon
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Rick van der Geest
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Mara J Kröner
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Ronald J van der Sluis
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Miranda Van Eck
- Division of BioTherapeutics, Leiden Academic Centre for Drug Research, Gorlaeus Laboratories, Einsteinweg 55, 2333CC Leiden, the Netherlands
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13
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Shen WJ, Asthana S, Kraemer FB, Azhar S. Scavenger receptor B type 1: expression, molecular regulation, and cholesterol transport function. J Lipid Res 2018; 59:1114-1131. [PMID: 29720388 DOI: 10.1194/jlr.r083121] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 04/26/2018] [Indexed: 12/16/2022] Open
Abstract
Cholesterol is required for maintenance of plasma membrane fluidity and integrity and for many cellular functions. Cellular cholesterol can be obtained from lipoproteins in a selective pathway of HDL-cholesteryl ester (CE) uptake without parallel apolipoprotein uptake. Scavenger receptor B type 1 (SR-B1) is a cell surface HDL receptor that mediates HDL-CE uptake. It is most abundantly expressed in liver, where it provides cholesterol for bile acid synthesis, and in steroidogenic tissues, where it delivers cholesterol needed for storage or steroidogenesis in rodents. SR-B1 transcription is regulated by trophic hormones in the adrenal gland, ovary, and testis; in the liver and elsewhere, SR-B1 is subject to posttranscriptional and posttranslational regulation. SR-B1 operates in several metabolic processes and contributes to pathogenesis of atherosclerosis, inflammation, hepatitis C virus infection, and other conditions. Here, we summarize characteristics of the selective uptake pathway and involvement of microvillar channels as facilitators of selective HDL-CE uptake. We also present the potential mechanisms of SR-B1-mediated selective cholesterol transport; the transcriptional, posttranscriptional, and posttranslational regulation of SR-B1; and the impact of gene variants on expression and function of human SR-B1. A better understanding of this unique pathway and SR-B1's role may yield improved therapies for a wide variety of conditions.
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Affiliation(s)
- Wen-Jun Shen
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| | - Shailendra Asthana
- Drug Discovery Research Center (DDRC), Translational Health Science and Technology Institute (THSTI), NCR Biotech Science Cluster, Faridabad 121001, Haryana, India
| | - Fredric B Kraemer
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
| | - Salman Azhar
- Geriatric Research, Education, and Clinical Research Center (GRECC), Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 and Division of Endocrinology, Gerontology, and Metabolism, Stanford University School of Medicine, Stanford, CA 94305
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14
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Shen WJ, Azhar S, Kraemer FB. SR-B1: A Unique Multifunctional Receptor for Cholesterol Influx and Efflux. Annu Rev Physiol 2017; 80:95-116. [PMID: 29125794 DOI: 10.1146/annurev-physiol-021317-121550] [Citation(s) in RCA: 219] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The scavenger receptor, class B type 1 (SR-B1), is a multiligand membrane receptor protein that functions as a physiologically relevant high-density lipoprotein (HDL) receptor whose primary role is to mediate selective uptake or influx of HDL-derived cholesteryl esters into cells and tissues. SR-B1 also facilitates the efflux of cholesterol from peripheral tissues, including macrophages, back to liver. As a regulator of plasma membrane cholesterol content, SR-B1 promotes the uptake of lipid soluble vitamins as well as viral entry into host cells. These collective functions of SR-B1 ultimately affect programmed cell death, female fertility, platelet function, vasculature inflammation, and diet-induced atherosclerosis and myocardial infarction. SR-B1 has also been identified as a potential marker for cancer diagnosis and prognosis. Finally, the SR-B1-linked selective HDL-cholesteryl ester uptake pathway is now being evaluated as a gateway for the delivery of therapeutic and diagnostic agents. In this review, we focus on the regulation and functional significance of SR-B1 in mediating cholesterol movement into and out of cells.
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Affiliation(s)
- Wen-Jun Shen
- Division of Endocrinology, Gerontology and Metabolism, Stanford University School of Medicine, Stanford, California 94305; .,VA Palo Alto Health Care System, Palo Alto, California 94304
| | - Salman Azhar
- Division of Endocrinology, Gerontology and Metabolism, Stanford University School of Medicine, Stanford, California 94305; .,VA Palo Alto Health Care System, Palo Alto, California 94304
| | - Fredric B Kraemer
- Division of Endocrinology, Gerontology and Metabolism, Stanford University School of Medicine, Stanford, California 94305; .,VA Palo Alto Health Care System, Palo Alto, California 94304
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15
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Menzies RI, Zhao X, Mullins LJ, Mullins JJ, Cairns C, Wrobel N, Dunbar DR, Bailey MA, Kenyon CJ. Transcription controls growth, cell kinetics and cholesterol supply to sustain ACTH responses. Endocr Connect 2017; 6:446-457. [PMID: 28720595 PMCID: PMC5574282 DOI: 10.1530/ec-17-0092] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 07/18/2017] [Indexed: 01/29/2023]
Abstract
Chronic ACTH exposure is associated with adrenal hypertrophy and steroidogenesis. The underlying molecular processes in mice have been analysed by microarray, histological and immunohistochemical techniques. Synacthen infused for 2 weeks markedly increased adrenal mass and plasma corticosterone levels. Microarray analysis found greater than 2-fold changes in expression of 928 genes (P < 0.001; 397 up, 531 down). These clustered in pathways involved in signalling, sterol/lipid metabolism, cell proliferation/hypertrophy and apoptosis. Signalling genes included some implicated in adrenal adenomas but also upregulated genes associated with cyclic AMP and downregulated genes associated with aldosterone synthesis. Sterol metabolism genes were those promoting cholesterol supply (Scarb1, Sqle, Apoa1) and disposal (Cyp27a1, Cyp7b1). Oil red O staining showed lipid depletion consistent with reduced expression of genes involved in lipid synthesis. Genes involved in steroidogenesis (Star, Cyp11a1, Cyp11b1) were modestly affected (P < 0.05; <1.3-fold). Increased Ki67, Ccna2, Ccnb2 and Tk1 expression complemented immunohistochemical evidence of a 3-fold change in cell proliferation. Growth arrest genes, Cdkn1a and Cdkn1c, which are known to be active in hypertrophied cells, were increased >4-fold and cross-sectional area of fasciculata cells was 2-fold greater. In contrast, genes associated with apoptosis (eg Casp12, Clu,) were downregulated and apoptotic cells (Tunel staining) were fewer (P < 0.001) and more widely distributed throughout the cortex. In summary, long-term steroidogenesis with ACTH excess is sustained by genes controlling cholesterol supply and adrenal mass. ACTH effects on adrenal morphology and genes controlling cell hypertrophy, proliferation and apoptosis suggest the involvement of different cell types and separate molecular pathways.
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Affiliation(s)
- Robert I Menzies
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
| | - Xin Zhao
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
| | - Linda J Mullins
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
| | - John J Mullins
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
| | - Carolynn Cairns
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
| | - Nicola Wrobel
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
| | - Donald R Dunbar
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
| | - Matthew A Bailey
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
| | - Christopher J Kenyon
- The University/BHF Centre for Cardiovascular ScienceUniversity of Edinburgh, The Queen's Medical Research Institute, Edinburgh, UK
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16
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Koch CE, Bartlang MS, Kiehn JT, Lucke L, Naujokat N, Helfrich-Förster C, Reber SO, Oster H. Time-of-day-dependent adaptation of the HPA axis to predictable social defeat stress. J Endocrinol 2016; 231:209-221. [PMID: 27660201 DOI: 10.1530/joe-16-0163] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 09/22/2016] [Indexed: 11/08/2022]
Abstract
In modern societies, the risk of developing a whole array of affective and somatic disorders is associated with the prevalence of frequent psychosocial stress. Therefore, a better understanding of adaptive stress responses and their underlying molecular mechanisms is of high clinical interest. In response to an acute stressor, each organism can either show passive freezing or active fight-or-flight behaviour, with activation of sympathetic nervous system and the hypothalamus-pituitary-adrenal (HPA) axis providing the necessary energy for the latter by releasing catecholamines and glucocorticoids (GC). Recent data suggest that stress responses are also regulated by the endogenous circadian clock. In consequence, the timing of stress may critically affect adaptive responses to and/or pathological effects of repetitive stressor exposure. In this article, we characterize the impact of predictable social defeat stress during daytime versus nighttime on bodyweight development and HPA axis activity in mice. While 19 days of social daytime stress led to a transient reduction in bodyweight without altering HPA axis activity at the predicted time of stressor exposure, more detrimental effects were seen in anticipation of nighttime stress. Repeated nighttime stressor exposure led to alterations in food metabolization and reduced HPA axis activity with lower circulating adrenocorticotropic hormone (ACTH) and GC concentrations at the time of predicted stressor exposure. Our data reveal a circadian gating of stress adaptation to predictable social defeat stress at the level of the HPA axis with impact on metabolic homeostasis underpinning the importance of timing for the body's adaptability to repetitive stress.
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Affiliation(s)
- C E Koch
- University of LübeckChronophysiology Group, Medical Department 1, Lübeck, Germany
| | - M S Bartlang
- University of WürzburgBiocenter, Theodor-Boveri-Institute, Neurobiology and Genetics, Würzburg, Germany
| | - J T Kiehn
- University of LübeckChronophysiology Group, Medical Department 1, Lübeck, Germany
| | - L Lucke
- Department of Behavioral and Molecular NeurobiologyUniversity of Regensburg, Regensburg, Germany
| | - N Naujokat
- University of LübeckChronophysiology Group, Medical Department 1, Lübeck, Germany
| | - C Helfrich-Förster
- University of WürzburgBiocenter, Theodor-Boveri-Institute, Neurobiology and Genetics, Würzburg, Germany
| | - S O Reber
- Department of Behavioral and Molecular NeurobiologyUniversity of Regensburg, Regensburg, Germany
| | - H Oster
- University of LübeckChronophysiology Group, Medical Department 1, Lübeck, Germany
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17
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Pal R, Ke Q, Pihan GA, Yesilaltay A, Penman ML, Wang L, Chitraju C, Kang PM, Krieger M, Kocher O. Carboxy-terminal deletion of the HDL receptor reduces receptor levels in liver and steroidogenic tissues, induces hypercholesterolemia, and causes fatal heart disease. Am J Physiol Heart Circ Physiol 2016; 311:H1392-H1408. [PMID: 27694217 DOI: 10.1152/ajpheart.00463.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 09/13/2016] [Indexed: 01/15/2023]
Abstract
The HDL receptor SR-BI mediates the transfer of cholesteryl esters from HDL to cells and controls HDL abundance and structure. Depending on the genetic background, loss of SR-BI causes hypercholesterolemia, anemia, reticulocytosis, splenomegaly, thrombocytopenia, female infertility, and fatal coronary heart disease (CHD). The carboxy terminus of SR-BI (505QEAKL509) must bind to the cytoplasmic adaptor PDZK1 for normal hepatic-but not steroidogenic cell-expression of SR-BI protein. To determine whether SR-BI's carboxy terminus is also required for normal protein levels in steroidogenic cells, we introduced into SR-BI's gene a 507Ala/STOP mutation that produces a truncated receptor (SR-BIΔCT). As expected, the dramatic reduction of hepatic receptor protein in SR-BIΔCT mice was similar to that in PDZK1 knockout (KO) mice. Unlike SR-BI KO females, SR-BIΔCT females were fertile. The severity of SR-BIΔCT mice's hypercholesterolemia was intermediate between those of SR-BI KO and PDZK1 KO mice. Substantially reduced levels of the receptor in adrenal cortical cells, ovarian cells, and testicular Leydig cells in SR-BIΔCT mice suggested that steroidogenic cells have an adaptor(s) functionally analogous to hepatic PDZK1. When SR-BIΔCT mice were crossed with apolipoprotein E KO mice (SR-BIΔCT/apoE KO), pathologies including hypercholesterolemia, macrocytic anemia, hepatic and splenic extramedullary hematopoiesis, massive splenomegaly, reticulocytosis, thrombocytopenia, and rapid-onset and fatal occlusive coronary arterial atherosclerosis and CHD (median age of death: 9 wk) were observed. These results provide new insights into the control of SR-BI in steroidogenic cells and establish SR-BIΔCT/apoE KO mice as a new animal model for the study of CHD.
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Affiliation(s)
- Rinku Pal
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Qingen Ke
- Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - German A Pihan
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Ayce Yesilaltay
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Marsha L Penman
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Li Wang
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Chandramohan Chitraju
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts
| | - Peter M Kang
- Division of Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Monty Krieger
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts; and
| | - Olivier Kocher
- Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts;
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18
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Li J, Wang J, Li M, Yin L, Li XA, Zhang TG. Up-regulated expression of scavenger receptor class B type 1 (SR-B1) is associated with malignant behaviors and poor prognosis of breast cancer. Pathol Res Pract 2016; 212:555-9. [PMID: 27067809 DOI: 10.1016/j.prp.2016.03.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 02/22/2016] [Accepted: 03/30/2016] [Indexed: 12/22/2022]
Abstract
Scavenger receptor class B type 1 (SR-B1) is an integral membrane protein that is expressed in numerous cells and tissue types. The primary role of SR-B1 is to facilitate uptake of cholesteryl esters from high-density lipoproteins (HDL) in the liver. Altered SR-B1 expression contributes to human diseases. This study assessed association of SR-B1 expression in breast tissue specimens with breast cancer development and prognosis. Tissue specimens from 30 cases of adjacent normal breast tissues, ductal carcinoma in situ (DCIS) and invasive ductal breast cancer (IDCA) were subjected to Western blot analysis, and 135 cases of DCIS and IDCA were used for quantitative immunohistochemical analysis of SR-B1 expression. The data showed that SR-B1 was significantly overexpressed in IDCA tissues compared to normal breast and DCIS tissues. SR-B1 expression was associated with pre-menopausal status, tumor size, and worse overall survival of patients. The data from this ex vivo study suggests that up-regulated SR-B1 protein expression is associated with malignant behaviors of breast cancer and that SR-B1 is an independent predictor for poor survival in breast cancer patients.
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Affiliation(s)
- Juan Li
- Department of Pathology, Shandong University School of Medicine, Jinan, Shandong 250012, China; Department of Pathology, The Fourth Hospital of Jinan, Jinan, Shandong 250031, China
| | - Jing Wang
- Department of Pathology, The Fourth Hospital of Jinan, Jinan, Shandong 250031, China
| | - Ming Li
- Department of Chest Surgery, The Chest Hospital of Shandong, Jinan, Shandong 250000, China
| | - Linlin Yin
- Department of Oncology, The Fourth Hospital of Jinan, Jinan, Shandong 250031, China
| | - Xiang-An Li
- Department of Pediatrics, Saha Cardiovascular Research Center, University of Kentucky College of Medicine, Lexington, KY 40536, USA.
| | - Ting-Guo Zhang
- Department of Pathology, Shandong University School of Medicine, Jinan, Shandong 250012, China.
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19
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Hu Z, Li J, Kuang Z, Wang M, Azhar S, Guo Z. Cell-Specific Polymorphism and Hormonal Regulation of DNA Methylation in Scavenger Receptor Class B, Type I. DNA Cell Biol 2016; 35:280-9. [PMID: 26981684 DOI: 10.1089/dna.2015.3185] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The scavenger receptor class B, type I (SR-BI), is a cell-surface glycoprotein that mediates selective uptake of high density lipoprotein (HDL)-derived cholesteryl ester. SR-BI plays an important role in cellular delivery of cholesterol. Both human and rodent SR-BI are expressed most abundantly in the liver parenchymal cells and steroidogenic cells of the adrenal gland and gonads, where the selective pathway exhibits its highest activity. In steroidogenic cells, the expression of SR-BI is regulated by trophic hormones (adrenocorticotropic hormone or gonadotropins luteinizing hormone or follicle-stimulating hormone) in concert with the regulation of steroid hormone production. DNA methylation has been implicated in a large number of biological processes mainly by regulating gene expression. The SR-BI promoter contains one CpG island (CGI) in its promoter and seven CGIs in its intronic regions. Here, we studied the DNA methylation status of SR-BI gene and provide evidence that the DNA methylation is cell specific in this gene promoter as well as in intronic regions. The DNA methylation in the SR-BI promoter is subject to N(6), 2'-O-dibutyryladenosine3':5'-cyclic monophosphate regulation in mouse adrenal Y1 cells and mouse Leydig tumor cells (MLTCs). The seven intron CGIs are methylated differentially in Y1 cells, MLTCs, ovarian granulosa cells, and mouse liver hepa 1-6 cells. Our experiments raised the possibility that DNA methylation participates in hormonal regulation of SR-BI expression in a tissue-specific manner. We further suggest that the cell-specific DNA methylation in SR-BI intronic regions may be associated with specific biological function(s) of these regions, including regulation of gene expression.
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Affiliation(s)
- Zhigang Hu
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing, China
| | - Jiaxin Li
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing, China
| | - Zhihui Kuang
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing, China
| | - Meina Wang
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing, China
| | - Salman Azhar
- 2 Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, and Stanford University School of Medicine , Palo Alto, California
| | - Zhigang Guo
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing, China
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20
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Abstract
The adrenal gland is one of the prominent sites for steroid hormone synthesis. Lipoprotein-derived cholesterol esters (CEs) delivered via SR-B1 constitute the dominant source of cholesterol for steroidogenesis, particularly in rodents. Adrenocorticotropic hormone (ACTH) stimulates steroidogenesis through downstream actions on multiple components involved in steroidogenesis. Both acute and chronic ACTH treatments can modulate SR-B1 function, including its transcription, posttranscriptional stability, phosphorylation and dimerization status, as well as the interaction with other protein partners, all of which result in changes in the ability of SR-B1 to mediate HDL-CE uptake and the supply of cholesterol for conversion to steroids. Here, we provide a review of the recent findings on the regulation of adrenal SR-B1 function by ACTH.
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Affiliation(s)
- Wen-Jun Shen
- The Division of Endocrinology, Stanford University, Stanford, CA, USA
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA
| | - Salman Azhar
- The Division of Endocrinology, Stanford University, Stanford, CA, USA
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA
| | - Fredric B. Kraemer
- The Division of Endocrinology, Stanford University, Stanford, CA, USA
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA
- *Correspondence: Fredric B. Kraemer,
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21
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Okpe GC, Ezeasor DN. Quantitative and cytological studies of interstitial (Leydig) cells in the scrotal and retained testes of unilateral cryptorchid West African Dwarf goats. Small Rumin Res 2016. [DOI: 10.1016/j.smallrumres.2015.11.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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22
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Chong EY, Huang Y, Wu H, Ghasemzadeh N, Uppal K, Quyyumi AA, Jones DP, Yu T. Local false discovery rate estimation using feature reliability in LC/MS metabolomics data. Sci Rep 2015; 5:17221. [PMID: 26596774 PMCID: PMC4657040 DOI: 10.1038/srep17221] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 10/27/2015] [Indexed: 11/20/2022] Open
Abstract
False discovery rate (FDR) control is an important tool of statistical inference in feature selection. In mass spectrometry-based metabolomics data, features can be measured at different levels of reliability and false features are often detected in untargeted metabolite profiling as chemical and/or bioinformatics noise. The traditional false discovery rate methods treat all features equally, which can cause substantial loss of statistical power to detect differentially expressed features. We propose a reliability index for mass spectrometry-based metabolomics data with repeated measurements, which is quantified using a composite measure. We then present a new method to estimate the local false discovery rate (lfdr) that incorporates feature reliability. In simulations, our proposed method achieved better balance between sensitivity and controlling false discovery, as compared to traditional lfdr estimation. We applied our method to a real metabolomics dataset and were able to detect more differentially expressed metabolites that were biologically meaningful.
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Affiliation(s)
- Elizabeth Y Chong
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA, 30322
| | - Yijian Huang
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA, 30322
| | - Hao Wu
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA, 30322
| | - Nima Ghasemzadeh
- Department of Medicine, School of Medicine, Emory University, Atlanta, GA, USA, 30322
| | - Karan Uppal
- Department of Medicine, School of Medicine, Emory University, Atlanta, GA, USA, 30322
| | - Arshed A Quyyumi
- Department of Medicine, School of Medicine, Emory University, Atlanta, GA, USA, 30322
| | - Dean P Jones
- Department of Medicine, School of Medicine, Emory University, Atlanta, GA, USA, 30322
| | - Tianwei Yu
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA, 30322
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23
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Hu Z, Hu J, Shen WJ, Kraemer FB, Azhar S. A Novel Role of Salt-Inducible Kinase 1 (SIK1) in the Post-Translational Regulation of Scavenger Receptor Class B Type 1 Activity. Biochemistry 2015; 54:6917-30. [PMID: 26567857 DOI: 10.1021/acs.biochem.5b00147] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Salt-inducible kinase 1 (SIK1) is a serine/threonine kinase that belongs to the stress- and energy-sensing AMPK family of kinases. SIK1 expression is rapidly induced in Y1 adrenal cells in response to ACTH via the cAMP-PKA signaling cascade, and it has been suggested that an increased level of SIK1 expression inhibits adrenal steroidogenesis by repressing the cAMP-dependent transcription of steroidogenic proteins, CYP11A1 and StAR, by attenuating CREB transcriptional activity. Here we show that SIK1 stimulates adrenal steroidogenesis by modulating the selective HDL-CE transport activity of SR-B1. Overexpression of SIK1 increases cAMP-stimulated and SR-B1-mediated selective HDL-BODIPY-CE uptake in cell lines without impacting SR-B1 protein levels, whereas knockdown of SIK1 attenuated cAMP-stimulated selective HDL-BODIPY-CE uptake. SIK1 forms a complex with SR-B1 by interacting with its cytoplasmic C-terminal domain, and in vitro kinase activity measurements indicate that SIK1 can phosphorylate the C-terminal domain of SR-B1. Among potential phosphorylation sites, SIK1-catalyzed phosphorylation of Ser496 is critical for SIK1 stimulation of the selective CE transport activity of SR-B1. Mutational studies further demonstrated that both the intact catalytic activity of SIK1 and its PKA-catalyzed phosphorylation are essential for SIK1 stimulation of SR-B1 activity. Finally, overexpression of SIK1 caused time-dependent increases in SR-B1-mediated and HDL-supported steroid production in Y1 cells; however, these effects were lost with knockdown of SR-B1. Taken together, these studies establish a role for SIK1 in the positive regulation of selective HDL-CE transport function of SR-B1 and steroidogenesis and suggest a potential mechanism for SIK1 signaling in modulating SR-B1-mediated selective CE uptake and associated steroidogenesis.
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Affiliation(s)
- Zhigang Hu
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System , Palo Alto, California 94304, United States
| | - Jie Hu
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System , Palo Alto, California 94304, United States
| | - Wen-Jun Shen
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System , Palo Alto, California 94304, United States
| | - Fredric B Kraemer
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System , Palo Alto, California 94304, United States
| | - Salman Azhar
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System , Palo Alto, California 94304, United States
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Corticosteroid Therapy Benefits Septic Mice With Adrenal Insufficiency But Harms Septic Mice Without Adrenal Insufficiency. Crit Care Med 2015; 43:e490-8. [PMID: 26308430 PMCID: PMC9798902 DOI: 10.1097/ccm.0000000000001264] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
OBJECTIVES Corticosteroid therapy is frequently used in septic patients given the rationale that there is an increased demand for corticosteroid in sepsis, and up to 60% of severe septic patients experience adrenal insufficiency. However, the efficacy of corticosteroid therapy and whether the therapy should be based on the results of adrenal function testing are highly controversial. The lack of an adrenal insufficiency animal model and our poor understanding of the pathogenesis caused by adrenal insufficiency present significant barriers to address this long-standing clinical issue. DESIGN Prospective experimental study. SETTING University laboratory. SUBJECTS Scavenger receptor BI null and adrenal-specific scavenger receptor BI null mice. INTERVENTIONS Sepsis was induced by cecal ligation and puncture. MEASUREMENTS AND MAIN RESULTS Using scavenger receptor BI mice as the first relative adrenal insufficiency animal model, we found that corticosteroid therapy significantly improved the survival in cecal ligation and puncture-treated scavenger receptor BI mice but causes more septic death in wild-type mice. We identified a corticosteroid cocktail that provides effective protection 18 hours post cecal ligation and puncture; using adrenal-specific scavenger receptor BI mice as an inducible corticosteroid-deficient animal model, we found that inducible corticosteroid specifically suppresses interleukin-6 production without affecting tumor necrosis factor-α, nitric oxide, and interleukin-10 production. We further found that inducible corticosteroid does not induce peripheral lymphocyte apoptosis but promotes phagocytic activity of macrophages and neutrophils. CONCLUSIONS This study demonstrates that corticosteroid treatment benefits mice with adrenal insufficiency but harms mice without adrenal insufficiency. This study also reveals that inducible corticosteroid has both immunosuppressive and immunopermissive properties, suppressing interleukin-6 production, promoting phagocytosis of immune effector cells, but not inducing peripheral lymphocyte apoptosis. These findings support our hypothesis that corticosteroid is an effective therapy for a subgroup of septic patients with adrenal insufficiency but harms septic patients without adrenal insufficiency and encourage further efforts to test this hypothesis in clinic.
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van der Sluis RJ, Van Eck M, Hoekstra M. Adrenocortical LDL receptor function negatively influences glucocorticoid output. J Endocrinol 2015; 226:145-54. [PMID: 26136384 DOI: 10.1530/joe-15-0023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/01/2015] [Indexed: 12/17/2022]
Abstract
Over 50% of the cholesterol needed by adrenocortical cells for the production of glucocorticoids is derived from lipoproteins. However, the overall contribution of the different lipoproteins and associated uptake pathways to steroidogenesis remains to be determined. Here we aimed to show the importance of LDL receptor (LDLR)-mediated cholesterol acquisition for adrenal steroidogenesis in vivo. Female total body LDLR knockout mice with a human-like lipoprotein profile were bilaterally adrenalectomized and subsequently provided with one adrenal either expressing or genetically lacking the LDLR under their renal capsule to solely modulate adrenocortical LDLR function. Plasma total cholesterol levels and basal plasma corticosterone levels were identical in the two types of adrenal transplanted mice. Strikingly, restoration of adrenal LDLR function significantly reduced the ACTH-mediated stimulation of adrenal steroidogenesis (P<0.001), with plasma corticosterone levels that were respectively 44-59% lower (P<0.01) as compared to adrenal LDLR negative controls. In addition, LDLR positive adrenal transplanted mice exhibited a significant decrease (-39%; P<0.001) in their plasma corticosterone level under fasting stress conditions. Biochemical analysis did not show changes in the expression of genes involved in cholesterol mobilization. However, LDLR expressing adrenal transplants displayed a marked 62% reduction (P<0.05) in the transcript level of the key steroidogenic enzyme HSD3B2. In conclusion, our studies in a mouse model with a human-like lipoprotein profile provide the first in vivo evidence for a novel inhibitory role of the LDLR in the control of adrenal glucocorticoid production.
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Affiliation(s)
- Ronald J van der Sluis
- Division of BiopharmaceuticsCluster BioTherapeutics, Gorlaeus Laboratories, Leiden Academic Centre for Drug Research, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Miranda Van Eck
- Division of BiopharmaceuticsCluster BioTherapeutics, Gorlaeus Laboratories, Leiden Academic Centre for Drug Research, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Menno Hoekstra
- Division of BiopharmaceuticsCluster BioTherapeutics, Gorlaeus Laboratories, Leiden Academic Centre for Drug Research, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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Wang Y, Meng C, Wei Q, Shi F, Mao D. Expression and regulation of scavenger receptor class B type 1 in the rat ovary and uterus during the estrous cycle. Acta Histochem 2015; 117:297-304. [PMID: 25817199 DOI: 10.1016/j.acthis.2015.03.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 03/11/2015] [Accepted: 03/11/2015] [Indexed: 01/19/2023]
Abstract
Scavenger receptor class B type 1 (SR-B1) preferentially mediates the selective uptake of high density lipoprotein-cholesterol ester and the delivery of cholesterol for steroidogenesis. Although multiple analyses have investigated the function of SR-B1 in the liver, adrenal and ovary, its expression in rat ovary and uterus during the estrous cycle is lacking. In the present study, real-time PCR, western blot and immunohistochemistry (IHC) were used to investigate SR-B1 expression in the rat ovary and uterus during the estrous cycle. The results demonstrated that ovarian SR-B1 expression was in a stage-dependent manner, continuously increased from proestrus and kept elevated during metoestrus, while uterine SR-B1 expression decreased from proestrus to diestrus. To determine whether ovarian and uterine SR-B1 expression were affected by sex steroid hormones, immature rats were treated with 17 β-estradiol (E2), progesterone (P4), or their antagonists from postnatal days 24-26. Results showed that the levels of SR-B1 mRNA and protein were significantly up-regulated by E2 in both the ovary and uterus. IHC results showed that SR-B1 was primarily localized in the oocytes, theca internal cells (T-I) of follicles, interstitial cells (IC) as well as corpus luteum (CL), but not granulosa cells (GC) in the ovary during the estrous cycle. Uterine SR-B1 was highly expressed in the endometrial luminal epithelial cells (LEC) and glandular epithelial cells (GEC) as well as in the circular muscle (CM) cells, and weak staining in stromal cells (SC) through estrous cycle. Taken together, SR-B1 expression in the ovary and uterus across the estrous cycle demonstrate that SR-B1 may be involved in uterine function, follicular development as well as luteal function.
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Abstract
The purpose of this article is to review fundamentals in adrenal gland histophysiology. Key findings regarding the important signaling pathways involved in the regulation of steroidogenesis and adrenal growth are summarized. We illustrate how adrenal gland morphology and function are deeply interconnected in which novel signaling pathways (Wnt, Sonic hedgehog, Notch, β-catenin) or ionic channels are required for their integrity. Emphasis is given to exploring the mechanisms and challenges underlying the regulation of proliferation, growth, and functionality. Also addressed is the fact that while it is now well-accepted that steroidogenesis results from an enzymatic shuttle between mitochondria and endoplasmic reticulum, key questions still remain on the various aspects related to cellular uptake and delivery of free cholesterol. The significant progress achieved over the past decade regarding the precise molecular mechanisms by which the two main regulators of adrenal cortex, adrenocorticotropin hormone (ACTH) and angiotensin II act on their receptors is reviewed, including structure-activity relationships and their potential applications. Particular attention has been given to crucial second messengers and how various kinases, phosphatases, and cytoskeleton-associated proteins interact to ensure homeostasis and/or meet physiological demands. References to animal studies are also made in an attempt to unravel associated clinical conditions. Many of the aspects addressed in this article still represent a challenge for future studies, their outcome aimed at providing evidence that the adrenal gland, through its steroid hormones, occupies a central position in many situations where homeostasis is disrupted, thus highlighting the relevance of exploring and understanding how this key organ is regulated. © 2014 American Physiological Society. Compr Physiol 4:889-964, 2014.
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Affiliation(s)
- Nicole Gallo-Payet
- Division of Endocrinology, Department of Medicine, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, and Centre de Recherche Clinique Étienne-Le Bel of the Centre Hospitalier Universitaire de Sherbrooke (CHUS), Sherbrooke, Quebec, Canada
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28
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Kwiterovich PO. Detection and Treatment of Children and Adolescents with Dyslipidemia. DYSLIPIDEMIAS 2015. [DOI: 10.1007/978-1-60761-424-1_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Song GJ, Kim SM, Park KH, Kim J, Choi I, Cho KH. SR-BI mediates high density lipoprotein (HDL)-induced anti-inflammatory effect in macrophages. Biochem Biophys Res Commun 2014; 457:112-8. [PMID: 25528585 DOI: 10.1016/j.bbrc.2014.12.028] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 12/06/2014] [Indexed: 11/24/2022]
Abstract
High density lipoprotein (HDL) receptor, scavenger receptor class B, type I (SR-BI), mediates selective cholesteryl ester uptake from lipoproteins into the liver as well as cholesterol efflux from macrophages to HDL. Recently, strong evidence has demonstrated the anti-inflammatory effect of HDL, although the mechanism of action is not fully understood. In this study, we showed that the anti-inflammatory effects of HDL are dependent on SR-BI expression in THP-1 macrophages. Consistent with earlier findings, pretreatment of macrophages with HDL abolished LPS-induced TNFα production. HDL also inhibited LPS-induced NF-κB activation. In addition, knockdown of SR-BI or inhibition of SR-BI ligand binding abolished the anti-inflammatory effect of HDL. SR-BI is a multi-ligand receptor that binds to modified lipoproteins as well as native HDL. Since modified lipoproteins have pro-inflammatory properties, it is unclear whether SR-BI activated by modified HDL has an anti- or pro-inflammatory effect. Glycated HDL induced NF-κB activation and cytokine production in macrophages in vitro, suggesting a pro-inflammatory effect for modified HDL. Moreover, inhibition of SR-BI function or expression potentiated glycated HDL-induced TNF-α production, suggesting an anti-inflammatory effect for SR-BI. In conclusion, SR-BI plays an important function in regulating HDL-mediated anti-inflammatory response in macrophages.
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Affiliation(s)
- Gyun Jee Song
- School of Biotechnology, Yeungnam University, Gyeongsan 712-749, Republic of Korea; Research Institute of Protein Sensor, Yeungnam University, Gyeongsan 712-749, Republic of Korea; BK21Plus Program Serum Biomedical Research and Education Team, Yeungnam University, Gyeongsan 712-749, Republic of Korea
| | - Seong-Min Kim
- School of Biotechnology, Yeungnam University, Gyeongsan 712-749, Republic of Korea; Research Institute of Protein Sensor, Yeungnam University, Gyeongsan 712-749, Republic of Korea; BK21Plus Program Serum Biomedical Research and Education Team, Yeungnam University, Gyeongsan 712-749, Republic of Korea
| | - Ki-Hoon Park
- School of Biotechnology, Yeungnam University, Gyeongsan 712-749, Republic of Korea; Research Institute of Protein Sensor, Yeungnam University, Gyeongsan 712-749, Republic of Korea; BK21Plus Program Serum Biomedical Research and Education Team, Yeungnam University, Gyeongsan 712-749, Republic of Korea
| | - Jihoe Kim
- School of Biotechnology, Yeungnam University, Gyeongsan 712-749, Republic of Korea; Research Institute of Protein Sensor, Yeungnam University, Gyeongsan 712-749, Republic of Korea; BK21Plus Program Serum Biomedical Research and Education Team, Yeungnam University, Gyeongsan 712-749, Republic of Korea
| | - Inho Choi
- School of Biotechnology, Yeungnam University, Gyeongsan 712-749, Republic of Korea; Research Institute of Protein Sensor, Yeungnam University, Gyeongsan 712-749, Republic of Korea; BK21Plus Program Serum Biomedical Research and Education Team, Yeungnam University, Gyeongsan 712-749, Republic of Korea
| | - Kyung-Hyun Cho
- School of Biotechnology, Yeungnam University, Gyeongsan 712-749, Republic of Korea; Research Institute of Protein Sensor, Yeungnam University, Gyeongsan 712-749, Republic of Korea; BK21Plus Program Serum Biomedical Research and Education Team, Yeungnam University, Gyeongsan 712-749, Republic of Korea.
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DeAngelis AM, Roy-O'Reilly M, Rodriguez A. Genetic alterations affecting cholesterol metabolism and human fertility. Biol Reprod 2014; 91:117. [PMID: 25122065 DOI: 10.1095/biolreprod.114.119883] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Single nucleotide polymorphisms (SNPs) represent genetic variations among individuals in a population. In medicine, these small variations in the DNA sequence may significantly impact an individual's response to certain drugs or influence the risk of developing certain diseases. In the field of reproductive medicine, a significant amount of research has been devoted to identifying polymorphisms which may impact steroidogenesis and fertility. This review discusses current understanding of the effects of genetic variations in cholesterol metabolic pathways on human fertility that bridge novel linkages between cholesterol metabolism and reproductive health. For example, the role of the low-density lipoprotein receptor (LDLR) in cellular metabolism and human reproduction has been well studied, whereas there is now an emerging body of research on the role of the high-density lipoprotein (HDL) receptor scavenger receptor class B type I (SR-BI) in human lipid metabolism and female reproduction. Identifying and understanding how polymorphisms in the SCARB1 gene or other genes related to lipid metabolism impact human physiology is essential and will play a major role in the development of personalized medicine for improved diagnosis and treatment of infertility.
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Affiliation(s)
| | | | - Annabelle Rodriguez
- Center for Vascular Biology, University of Connecticut Health Center, Farmington, Connecticut
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31
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Shen WJ, Hu J, Hu Z, Kraemer FB, Azhar S. Scavenger receptor class B type I (SR-BI): a versatile receptor with multiple functions and actions. Metabolism 2014; 63:875-86. [PMID: 24854385 PMCID: PMC8078058 DOI: 10.1016/j.metabol.2014.03.011] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 03/12/2014] [Accepted: 03/18/2014] [Indexed: 11/16/2022]
Abstract
Scavenger receptor class B type I (SR-BI), is a physiologically relevant HDL receptor that mediates selective uptake of lipoprotein (HDL)-derived cholesteryl ester (CE) in vitro and in vivo. Mammalian SR-BI is a 509-amino acid, ~82 kDa glycoprotein that contains N- and C-terminal cytoplasmic domains, two-transmembrane domains, as well as a large extracellular domain containing 5-6 cysteine residues and multiple sites for N-linked glycosylation. The size and structural characteristics of SR-BI, however, vary considerably among lower vertebrates and insects. Recently, significant progress has been made in understanding the molecular mechanisms involved in the posttranscriptional/posttranslational regulation of SR-BI in a tissue specific manner. The purpose of this review is to summarize the current body of knowledge about the events and molecules connected with the posttranscriptional/posttranslational regulation of SR-BI and to update the molecular and functional characteristics of the insect SR-BI orthologs.
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MESH Headings
- Animals
- Biological Transport
- Gene Expression Regulation
- Glycosylation
- Humans
- Insect Proteins/chemistry
- Insect Proteins/genetics
- Insect Proteins/metabolism
- Lipoproteins, HDL/chemistry
- Lipoproteins, HDL/genetics
- Lipoproteins, HDL/metabolism
- Liver/metabolism
- Organ Specificity
- Protein Conformation
- Protein Processing, Post-Translational
- Receptors, Lipoprotein/chemistry
- Receptors, Lipoprotein/genetics
- Receptors, Lipoprotein/metabolism
- Scavenger Receptors, Class B/chemistry
- Scavenger Receptors, Class B/genetics
- Scavenger Receptors, Class B/metabolism
- Species Specificity
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Affiliation(s)
- Wen-Jun Shen
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304; Division of Endocrinology, Stanford University, Stanford, California 94305
| | - Jie Hu
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304
| | - Zhigang Hu
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304; Division of Endocrinology, Stanford University, Stanford, California 94305
| | - Fredric B Kraemer
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304; Division of Endocrinology, Stanford University, Stanford, California 94305
| | - Salman Azhar
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304; Division of Gastroenterology and Hepatology, Stanford University, Stanford, California 94305.
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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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Hurt-Camejo E, Gautier T, Rosengren B, Dikkers A, Behrendt M, Grass DS, Rader DJ, Tietge UJF. Expression of type IIA secretory phospholipase A2 inhibits cholesteryl ester transfer protein activity in transgenic mice. Arterioscler Thromb Vasc Biol 2013; 33:2707-14. [PMID: 24115030 DOI: 10.1161/atvbaha.113.301410] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE High circulating levels of group IIA secretory phospholipase A2 (sPLA2-IIA) activity and mass are independent cardiovascular risk factors. Therefore, inhibition of sPLA2-IIA may be a target for the treatment of atherosclerotic cardiovascular disease. The present study evaluated the effects of sPLA2-IIA inhibition with varespladib acid in a novel mouse model, human apolipoprotein B (apoB)/human cholesteryl ester transfer protein (CETP)/human sPLA2-IIA triple transgenic mice (TTT) fed a Western-type diet. APPROACH AND RESULTS sPLA2-IIA expression increased atherosclerotic lesion formation in TTT compared with human apoB/human CETP double transgenic mice (P<0.01). Varespladib acid effectively inhibited plasma sPLA2-IIA activity. Surprisingly, however, administration of varespladib acid to TTT had no impact on atherosclerosis, which could be attributed to a proatherogenic plasma lipoprotein profile that appears in response to sPLA2-IIA inhibition because of increased plasma CETP activity. In the TTT model, sPLA2-IIA decreased CETP activity by reducing the acceptor properties of sPLA2-IIA-modified very low-density lipoproteins specifically because of a significantly lower apoE content. Increasing very low-density lipoprotein-apoE content by means of adenovirus-mediated gene transfer in sPLA2-IIA transgenic mice restored the acceptor properties for CETP. CONCLUSIONS These data show that in a humanized triple transgenic mouse model with hypercholesterolemia, sPLA2-IIA inhibition increases CETP activity via increasing the very low-density lipoprotein-apoE content, resulting in a proatherogenic lipoprotein profile.
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Affiliation(s)
- Eva Hurt-Camejo
- From the Department of Bioscience, CVMD iMED, AstraZeneca, R&D, Mölndal, Sweden (E.H.-C., B.R., M.B.); Department of Pediatrics, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands (T.G., A.D., U.J.F.T.); INSERM UMR866, Faculté de Médecine, Université de Bourgogne, Dijon, France (T.G.); Taconic, Hudson, NY (D.S.G.); and Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia (D.J.R.)
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Hu Z, Hu J, Zhang Z, Shen WJ, Yun CC, Berlot CH, Kraemer FB, Azhar S. Regulation of expression and function of scavenger receptor class B, type I (SR-BI) by Na+/H+ exchanger regulatory factors (NHERFs). J Biol Chem 2013; 288:11416-35. [PMID: 23482569 DOI: 10.1074/jbc.m112.437368] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Scavenger receptor class B, type I (SR-BI) binds HDL and mediates selective delivery of cholesteryl esters (CEs) to the liver, adrenals, and gonads for product formation (bile acids and steroids). Because relatively little is known about SR-BI posttranslational regulation in steroidogenic cells, we examined the roles of Na(+)/H(+) exchanger regulatory factors (NHERFs) in regulating SR-BI expression, SR-BI-mediated selective CE uptake, and steroidogenesis. NHERF1 and NHERF2 mRNA and protein are expressed at varying levels in model steroidogenic cell lines and the adrenal, with only low expression of PDZK1 (NHERF3) and NHERF4. Dibutyryl cyclic AMP decreased NHERF1 and NHERF2 and increased SR-BI mRNA expression in primary rat granulosa cells and MLTC-1 cells, whereas ACTH had no effect on NHERF1 and NHERF2 mRNA levels but decreased their protein levels in rat adrenals. Co-immunoprecipitation, colocalization, bimolecular fluorescence complementation, and mutational analysis indicated that SR-BI associates with NHERF1 and NHERF2. NHERF1 and NHERF2 down-regulated SR-BI protein expression through inhibition of its de novo synthesis. NHERF1 and NHERF2 also inhibited SR-BI-mediated selective CE transport and steroidogenesis, which were markedly attenuated by partial deletions of the PDZ1 or PDZ2 domain of NHERF1, the PDZ2 domain of NHERF2, or the MERM domains of NHERF1/2 or by gene silencing of NHERF1/2. Moreover, an intact COOH-terminal PDZ recognition motif (EAKL) in SR-BI is needed. Transient transfection of hepatic cell lines with NHERF1 or NHERF2 caused a significant reduction in endogenous protein levels of SR-BI. Collectively, these data establish NHERF1 and NHERF2 as SR-BI protein binding partners that play a negative role in the regulation of SR-BI expression, selective CE transport, and steroidogenesis.
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Affiliation(s)
- Zhigang Hu
- Geriatric Research, Education and Clinical Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304, USA
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Stanislovaitiene D, Lesauskaite V, Zaliuniene D, Smalinskiene A, Gustiene O, Zaliaduonyte-Peksiene D, Tamosiunas A, Luksiene D, Petkeviciene J, Zaliunas R. SCARB1 single nucleotide polymorphism (rs5888) is associated with serum lipid profile and myocardial infarction in an age- and gender-dependent manner. Lipids Health Dis 2013; 12:24. [PMID: 23510561 PMCID: PMC3599926 DOI: 10.1186/1476-511x-12-24] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 02/28/2013] [Indexed: 01/28/2023] Open
Abstract
Background Mutation in SCARB1 gene, exon 8 rs5888, has been associated with altered lipid levels and cardiovascular risk in humans though the results have been inconsistent. We analysed the impact of SCARB1 single nucleotide polymorphism (SNP) rs5888 with plasma lipid profile and association with coronary artery disease (CAD) in a Lithuanian population characterized by high morbidity and mortality from CAD and high prevalence of hypercholesterolemia. Methods The study included 1976 subjects from a random sample (reference group) and an myocardial infarction (MI) group of 463 patients. Genotyping of SCARB1 (rs5888) was carried out using the real-time polymerase chain reaction method. Results/principal findings Analysis of rs5888 C/T gene polymorphism in the reference group revealed that male TT genotype carriers (25–74 years) had significantly higher total cholesterol and triglyceride concentrations (5.70 mmol/l vs. 5.49 mmol/l; p = 0.036, and 1.70 mmol/l vs. 1.40 mmol/l, p = 0.023, respectively) than CT carriers and the oldest males (65–74 years) TT carriers had significantly higher high density lipoprotein cholesterol concentrations in comparison to heterozygous (1.52 mmol/l vs. 1.36 mmol/l, p = 0.033). The youngest female (25–44 years) TT genotype carriers had significantly lower low density lipoprotein cholesterol concentrations in comparison to C homozygous (2.59 mmol/l vs. 2.92 mmol/l, p = 0.023). The frequency of the SCARB1 TT genotype in the oldest male MI group (65–74 years) was significantly lower than in the corresponding reference group subjects (9.4% vs. 22.3%, p = 0.006). SCARB1 TT genotype was associated with decreased odds of MI in males aged 65–75 years (OR = 0.24, 95% CI 0.10-0.56, p = 0.001). Conclusions/significance SCARB1 polymorphism is associated with lipid metabolism and CAD in an age- and gender- dependent manner. Analysis of SCARB1 SNP rs5888 C/T genotypes revealed an atheroprotective phenotype of lipid profile in older men and in young women TT genotype carriers in the reference group. SCARB1 TT genotype was associated with decreased odds of MI in aged men.
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Affiliation(s)
- Daiva Stanislovaitiene
- Department of Ophthalmology, Medicine Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania.
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Hu Z, Shen WJ, Kraemer FB, Azhar S. MicroRNAs 125a and 455 repress lipoprotein-supported steroidogenesis by targeting scavenger receptor class B type I in steroidogenic cells. Mol Cell Biol 2012; 32:5035-45. [PMID: 23045399 PMCID: PMC3510537 DOI: 10.1128/mcb.01002-12] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 10/03/2012] [Indexed: 12/25/2022] Open
Abstract
We sought to identify and characterize microRNA (miRNAs) that posttranscriptionally regulate the expression of scavenger receptor class B type I (SR-BI) and SR-BI-linked selective high-density lipoprotein (HDL) cholesteryl ester (CE) transport and steroidogenesis. Four miRNAs (miRNA-125a, miRNA-125b, miRNA-145, and miRNA-455) with a potential to regulate SR-BI were identified in silico and validated by quantitative real-time PCR (qRT-PCR), Western blot analysis, and SR-BI 3' untranslated region (UTR) reporter assays. In vitro treatment of primary rat granulosa cells and MLTC-1 cells with cyclic AMP (cAMP) or in vivo treatment of rat adrenals with adrenocorticotropic hormone (ACTH) decreased the expression of miRNA-125a, miRNA-125b, and miRNA-455 and reciprocally increased SR-BI expression. Using luciferase constructs containing the 3' untranslated region of SR-BI combined with miRNA overexpression and mutagenesis, we have provided evidence that steroidogenic SR-BI is a direct target of miRNA-125a and miRNA-455. Moreover, the transfection of Leydig tumor cells with precursor miRNA 125a (pre-miRNA-125a) or pre-miRNA-455 resulted in the suppression of SR-BI at both the transcript and protein levels and reduced selective HDL CE uptake and HDL-stimulated progesterone production. Transfection of liver Hepa 1-6 cells with pre-miRNA-125a significantly reduced SR-BI expression and its selective transport function. In contrast, overexpression of miRNA-145 did not affect SR-BI expression or selective HDL CE uptake mediated by SR-BI in steroidogenic cell lines. These data suggest that a trophic hormone and cAMP inversely regulate the expression of SR-BI and miRNA-125a and miRNA-455 in steroidogenic tissues/cells and that both miRNA-125a and miRNA-455, by targeting steroidogenic SR-BI, negatively regulate selective HDL CE uptake and HDL CE-supported steroid hormone production.
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Affiliation(s)
- Zhigang Hu
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California, USA
- Division of Endocrinology
| | - Wen-Jun Shen
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California, USA
- Division of Endocrinology
| | - Fredric B. Kraemer
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California, USA
- Division of Endocrinology
| | - Salman Azhar
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California, USA
- Division of Gastroenterology and Hepatology, Stanford University, Stanford, California, USA
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Liu Z, Tian Y, Machida K, Lai MMC, Luo G, Foung SKH, Ou JHJ. Transient activation of the PI3K-AKT pathway by hepatitis C virus to enhance viral entry. J Biol Chem 2012; 287:41922-30. [PMID: 23095753 DOI: 10.1074/jbc.m112.414789] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The PI3K-AKT signaling pathway plays an important role in cell growth and metabolism. Here we report that hepatitis C virus (HCV) transiently activates the PI3K-AKT pathway. This activation was observed as early as 15 min postinfection, peaked by 30 min, and became undetectable at 24 h postinfection. The activation of AKT could also be mediated by UV-inactivated HCV, HCV pseudoparticle, and the ectodomain of the HCV E2 envelope protein. Because antibodies directed against CD81 and claudin-1, but not antibodies directed against scavenger receptor class B type I or occludin, could also activate AKT, the interaction between HCV E2 and its two co-receptors CD81 and claudin-1 probably triggered the activation of AKT. This activation of AKT by HCV was important for HCV infectivity, because the silencing of AKT by siRNA or the treatment of cells with its inhibitors or with the inhibitor of its upstream regulator PI3K significantly inhibited HCV infection, whereas the expression of constitutively active AKT enhanced HCV infection. The PI3K-AKT pathway is probably involved in HCV entry, because the inhibition of this pathway could inhibit the entry of HCV pseudoparticle but not the VSV pseudoparticle into cells. Furthermore, the treatment of cells with the AKT inhibitor AKT-V prior to HCV infection inhibited HCV infection, whereas the treatment after HCV infection had no obvious effect. Taken together, our studies indicated that HCV transiently activates the PI3K-AKT pathway to facilitate its entry. These results provide important information for understanding HCV replication and pathogenesis and raised the possibility of targeting this cellular pathway to treat HCV patients.
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Affiliation(s)
- Zhe Liu
- Department of Molecular Microbiology and Immunology, University of Southern California Keck School of Medicine, Los Angeles, California 90033, USA
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Guo L, Zheng Z, Ai J, Huang B, Li XA. Comment on "Class B scavenger receptor types I and II and CD36 targeting improves sepsis survival and acute outcomes in mice". THE JOURNAL OF IMMUNOLOGY 2012; 189:501; author reply 502. [PMID: 22773661 DOI: 10.4049/jimmunol.1290035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Casado ME, Huerta L, Ortiz AI, Pérez-Crespo M, Gutiérrez-Adán A, Kraemer FB, Lasunción MÁ, Busto R, Martín-Hidalgo A. HSL-knockout mouse testis exhibits class B scavenger receptor upregulation and disrupted lipid raft microdomains. J Lipid Res 2012; 53:2586-97. [PMID: 22988039 DOI: 10.1194/jlr.m028076] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
There is a tight relationship between fertility and changes in cholesterol metabolism during spermatogenesis. In the testis, class B scavenger receptors (SR-B) SR-BI, SR-BII, and LIMP II mediate the selective uptake of cholesterol esters from HDL, which are hydrolyzed to unesterified cholesterol by hormone-sensitive lipase (HSL). HSL is critical because HSL knockout (KO) male mice are sterile. The aim of the present work was to determine the effects of the lack of HSL in testis on the expression of SR-B, lipid raft composition, and related cell signaling pathways. HSL-KO mouse testis presented altered spermatogenesis associated with decreased sperm counts, sperm motility, and infertility. In wild-type (WT) testis, HSL is expressed in elongated spermatids; SR-BI, in Leydig cells and spermatids; SR-BII, in spermatocytes and spermatids but not in Leydig cells; and LIMP II, in Sertoli and Leydig cells. HSL knockout male mice have increased expression of class B scavenger receptors, disrupted caveolin-1 localization in lipid raft plasma membrane microdomains, and activated phospho-ERK, phospho-AKT, and phospho-SRC in the testis, suggesting that class B scavenger receptors are involved in cholesterol ester uptake for steroidogenesis and spermatogenesis in the testis.
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Affiliation(s)
- María Emilia Casado
- Servicio de Bioquímica-Investigación, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria, Madrid, Spain
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40
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Christianson MS, Yates M. Scavenger receptor class B type 1 gene polymorphisms and female fertility. Curr Opin Endocrinol Diabetes Obes 2012; 19:115-20. [PMID: 22261999 DOI: 10.1097/med.0b013e3283505771] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Multiple studies have demonstrated a role for scavenger receptor class B type 1 (SR-B1) in female fertility. Recent studies have implicated specific SR-B1 gene polymorphisms in decreased progesterone production and suboptimal fertility outcomes. RECENT FINDINGS The lipoprotein receptor SR-B1 has been known to mediate selective uptake of lipids into steroidogenic tissues such as the ovaries. SR-B1 plays a major role in the ability of the corpus luteum to produce progesterone, which is known to play a key role in sustaining early pregnancy. Animal studies have demonstrated that deficiency in SR-B1 results in subfertility that can be restored with addition of SR-B1 function. Single-nucleotide polymorphisms in SCARB1, the gene encoding SR-B1, have been associated with human lipid levels. Women undergoing infertility treatment with low SR-B1 expression in granulosa cells were noted to have plasma estradiol levels half the normal levels and a significantly lower number of retrieved oocytes. In vitro, deficiency of SR-B1 is associated with lower progesterone secretion in human granulosa cells. Certain SR-B1 polymorphisms have been associated with lower follicular progesterone levels and a significantly lower clinical pregnancy rate. SUMMARY Deficiency of SR-B1, particularly due to single-nucleotide polymorphisms, could explain some features of female human infertility.
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Affiliation(s)
- Mindy S Christianson
- Division of Reproductive Endocrinology and Infertility, Department of Gynecology and Obstetrics, Johns Hopkins University School of Medicine, Lutherville, Maryland 20193, USA
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Skelding KA, Rostas JAP. The role of molecular regulation and targeting in regulating calcium/calmodulin stimulated protein kinases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:703-30. [PMID: 22453966 DOI: 10.1007/978-94-007-2888-2_31] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Calcium/calmodulin-stimulated protein kinases can be classified as one of two types - restricted or multifunctional. This family of kinases contains several structural similarities: all possess a calmodulin binding motif and an autoinhibitory region. In addition, all of the calcium/calmodulin-stimulated protein kinases examined in this chapter are regulated by phosphorylation, which either activates or inhibits their kinase activity. However, as the multifunctional calcium/calmodulin-stimulated protein kinases are ubiquitously expressed, yet regulate a broad range of cellular functions, additional levels of regulation that control these cell-specific functions must exist. These additional layers of control include gene expression, signaling pathways, and expression of binding proteins and molecular targeting. All of the multifunctional calcium/calmodulin-stimulated protein kinases examined in this chapter appear to be regulated by these additional layers of control, however, this does not appear to be the case for the restricted kinases.
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Affiliation(s)
- Kathryn A Skelding
- School of Biomedical Sciences and Pharmacy and Hunter Medical Research Institute, Faculty of Health, The University of Newcastle, University Drive, Callaghan, NSW 2308, Australia
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Hu J, Zhang Z, Shen WJ, Nomoto A, Azhar S. Differential roles of cysteine residues in the cellular trafficking, dimerization, and function of the high-density lipoprotein receptor, SR-BI. Biochemistry 2011; 50:10860-75. [PMID: 22097902 DOI: 10.1021/bi201264y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The scavenger receptor, class B, type I (SR-BI) binds high-density lipoprotein (HDL) and mediates selective delivery of cholesteryl esters (CEs) to the liver and steroidogenic cells of the adrenal glands and gonads. Although it is clear that the large extracellular domain (ECD) of SR-BI binds HDL, the role of ECD in the selective HDL-CE transport remains poorly understood. In this study, we used a combination of mutational and chemical approaches to systematically evaluate the contribution of cysteine residues, especially six cysteine residues of ECD, in SR-BI-mediated selective HDL-CE uptake, intracellular trafficking, and SR-BI dimerization. Pretreatment of SR-BI-overexpressing COS-7 cells with a disulfide (S-S) bond reducing agent, β-mercaptoethanol (100 mM) or dithiothreitol (DTT) (10 mM), modestly but significantly impaired SR-BI-mediated selective HDL-CE uptake. Treatment of SR-BI-overexpressing COS-7 cells with the optimal doses of membrane permeant alkyl methanethiosulfonate (MTS) reagents, positively charged MTSEA or neutral MMTS, that specifically react with the free sulfhydryl group of cysteine reduced the rate of SR-BI-mediated selective HDL-CE uptake, indicating that certain intracellular free cysteine residues may also be critically involved in the selective cholesterol transport process. In contrast, use of membrane impermeant MTS reagent, positively charged MTSET and negatively charged MTSES, showed no such effect. Next, the importance of eight cysteine residues in SR-BI expression, cell surface expression, dimer formation, and selective HDL-derived CE transport was evaluated. These cysteine residues were replaced either singly or in pairs with serine, and the mutant SR-BIs were expressed in either COS-7 or CHO cells. Four mutations, C280S, C321S, C323S, and C334S, of the ECD, either singly or in various pair combinations, resulted in significant decreases in SR-BI (HDL) binding activity, selective CE uptake, and trafficking to the cell surface. Surprisingly, we found that mutation of the two remaining cysteine residues, C251 and C384 of the ECD, had no effect on either SR-BI expression or function. Other cysteine mutations and substitutions were also without effect. Western blot data indicated that single and double mutations at C280, C321, C323, and C334 residues strongly favor dimer formation. However, they are rendered nonfunctional presumably because of mutation-induced formation of aberrant disulfide linkages resulting in inhibition of optimal HDL binding and, thus, selective HDL-CE uptake. These results provide novel insights into the functional role of four cysteine residues, C280, C321, C323, and C334, of the SR-BI ECD in SR-BI expression and trafficking to the cell surface, its dimerization, and associated selective CE transport function.
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Affiliation(s)
- Jie Hu
- Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, California 94304, United States
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Induction of macrophage scavenger receptor type BI expression by tamoxifen and 4-hydroxytamoxifen. Atherosclerosis 2011; 218:435-42. [DOI: 10.1016/j.atherosclerosis.2011.06.048] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 06/28/2011] [Accepted: 06/28/2011] [Indexed: 12/30/2022]
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Mechanisms regulating hepatic SR-BI expression and their impact on HDL metabolism. Atherosclerosis 2011; 217:299-307. [DOI: 10.1016/j.atherosclerosis.2011.05.036] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 05/11/2011] [Accepted: 05/26/2011] [Indexed: 11/22/2022]
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Yasuda A, Natsume M, Osakabe N, Kawahata K, Koga J. Cacao polyphenols influence the regulation of apolipoprotein in HepG2 and Caco2 cells. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:1470-1476. [PMID: 21226458 DOI: 10.1021/jf103820b] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Cocoa powder is rich in polyphenols, such as catechins and procyanidins, and has been shown to inhibit low-density lipoprotein (LDL) oxidation and atherogenesis in a variety of models. Human studies have also shown daily intake of cocoa increases plasma high-density lipoprotein (HDL) and decreases LDL levels. However, the mechanisms responsible for these effects of cocoa on cholesterol metabolism have yet to be fully elucidated. The present study investigated the effects of cacao polyphenols on the production of apolipoproteins A1 and B in human hepatoma HepG2 and intestinal Caco2 cell lines. The cultured HepG2 cells or Caco2 cells were incubated for 24 h in the presence of cacao polyphenols such as (-)-epicatechin, (+)-catechin, procyanidin B2, procyanidin C1, and cinnamtannin A2. The concentration of apolipoproteins in the cell culture media was quantified using an enzyme-linked immunoassay, and the mRNA expression was quantified by RT-PCR. Cacao polyphenols increased apolipoprotein A1 protein levels and mRNA expression, even though apolipoprotein B protein and the mRNA expression were slightly decreased in both HepG2 cells and Caco2 cells. In addition, cacao polyphenols increased sterol regulatory element binding proteins (SREBPs) and activated LDL receptors in HepG2 cells. These results suggest that cacao polyphenols may increase the production of mature form SREBPs and LDL receptor activity, thereby increasing ApoA1 and decreasing ApoB levels. These results elucidate a novel mechanism by which HDL cholesterol levels become elevated with daily cocoa intake.
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Affiliation(s)
- Akiko Yasuda
- Food and Health R&D Laboratories, Meiji Seika Kaisha, Ltd., Saitama, Japan
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Brundert M, Heeren J, Merkel M, Carambia A, Herkel J, Groitl P, Dobner T, Ramakrishnan R, Moore KJ, Rinninger F. Scavenger receptor CD36 mediates uptake of high density lipoproteins in mice and by cultured cells. J Lipid Res 2011; 52:745-58. [PMID: 21217164 DOI: 10.1194/jlr.m011981] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mechanisms of HDL-mediated cholesterol transport from peripheral tissues to the liver are incompletely defined. Here the function of scavenger receptor cluster of differentiation 36 (CD36) for HDL uptake by the liver was investigated. CD36 knockout (KO) mice, which were the model, have a 37% increase (P = 0.008) of plasma HDL cholesterol compared with wild-type (WT) littermates. To explore the mechanism of this increase, HDL metabolism was investigated with HDL radiolabeled in the apolipoprotein (¹²⁵I) and cholesteryl ester (CE, [³H]) moiety. Liver uptake of [³H] and ¹²⁵I from HDL decreased in CD36 KO mice and the difference, i. e. hepatic selective CE uptake ([³H]¹²⁵I), declined (-33%, P = 0.0003) in CD36 KO compared with WT mice. Hepatic HDL holo-particle uptake (¹²⁵I) decreased (-29%, P = 0.0038) in CD36 KO mice. In vitro, uptake of ¹²⁵I-/[³H]HDL by primary liver cells from WT or CD36 KO mice revealed a diminished HDL uptake in CD36-deficient hepatocytes. Adenovirus-mediated expression of CD36 in cells induced an increase in selective CE uptake from HDL and a stimulation of holo-particle internalization. In conclusion, CD36 plays a role in HDL uptake in mice and by cultured cells. A physiologic function of CD36 in HDL metabolism in vivo is suggested.
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Affiliation(s)
- May Brundert
- University Hospital Hamburg Eppendorf Hamburg, Germany
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Hoekstra M, Berkel TJCV, Eck MV. Scavenger receptor BI: A multi-purpose player in cholesterol and steroid metabolism. World J Gastroenterol 2010; 16:5916-24. [PMID: 21157967 PMCID: PMC3007109 DOI: 10.3748/wjg.v16.i47.5916] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Scavenger receptor class B type I (SR-BI) is an important member of the scavenger receptor family of integral membrane glycoproteins. This review highlights studies in SR-BI knockout mice, which concern the role of SR-BI in cholesterol and steroid metabolism. SR-BI in hepatocytes is the sole molecule involved in selective uptake of cholesteryl esters from high-density lipoprotein (HDL). SR-BI plays a physiological role in binding and uptake of native apolipoprotein B (apoB)-containing lipoproteins by hepatocytes, which identifies SR-BI as a multi-purpose player in lipid uptake from the blood circulation into hepatocytes in mice. In adrenocortical cells, SR-BI mediates the selective uptake of HDL-cholesteryl esters, which is efficiently coupled to the synthesis of glucocorticoids (i.e. corticosterone). SR-BI knockout mice suffer from adrenal glucocorticoid insufficiency, which suggests that functional SR-BI protein is necessary for optimal adrenal steroidogenesis in mice. SR-BI in macrophages plays a dual role in cholesterol metabolism as it is able to take up cholesterol associated with HDL and apoB-containing lipoproteins and can possibly facilitate cholesterol efflux to HDL. Absence of SR-BI is associated with thrombocytopenia and altered thrombosis susceptibility, which suggests a novel role for SR-BI in regulating platelet number and function in mice. Transgenic expression of cholesteryl ester transfer protein in humanized SR-BI knockout mice normalizes hepatic delivery of HDL-cholesteryl esters. However, other pathologies associated with SR-BI deficiency, i.e. increased atherosclerosis susceptibility, adrenal glucocorticoid insufficiency, and impaired platelet function are not normalized, which suggests an important role for SR-BI in cholesterol and steroid metabolism in man. In conclusion, generation of SR-BI knockout mice has significantly contributed to our knowledge of the physiological role of SR-BI. Studies using these mice have identified SR-BI as a multi-purpose player in cholesterol and steroid metabolism because it has distinct roles in reverse cholesterol transport, adrenal steroidogenesis, and platelet function.
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Mavridou S, Venihaki M, Rassouli O, Tsatsanis C, Kardassis D. Feedback inhibition of human scavenger receptor class B type I gene expression by glucocorticoid in adrenal and ovarian cells. Endocrinology 2010; 151:3214-24. [PMID: 20463057 DOI: 10.1210/en.2009-1302] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Scavenger receptor class B type I (SR-BI) facilitates the reverse transport of excess cholesterol from peripheral tissues to the liver via high-density lipoproteins. In steroidogenic tissues, SR-BI supplies cholesterol for steroid hormone production. We show here that the transcription of the human SR-BI gene is subject to feedback inhibition by glucocorticoid in adrenal and ovarian cells. SR-BI mRNA levels were increased in adrenals from corticosterone-insufficient Crh(-/-) mice, whereas corticosterone replacement by oral administration inhibited SR-BI gene expression in these mice. SR-BI mRNA levels were increased in adrenals from wild-type mice treated with metyrapone, a drug that blocks corticosterone synthesis. Experiments in adrenocortical H295R and ovarian SKOV-3 cells using cycloheximide and siRNA-mediated gene silencing revealed that glucocorticoid-mediated inhibition of SR-BI gene transcription requires de novo protein synthesis and the glucocorticoid receptor (GR). No direct binding of GR to the SR-BI promoter could be demonstrated in vitro and in vivo, suggesting an indirect mechanism of repression of SR-BI gene transcription by GR in adrenal cells. Deletion analysis established that the region of the human SR-BI promoter between nucleotides -201 and -62 is sufficient to mediate repression by glucocorticoid. This region contains putative binding sites for transcriptional repressors that could play a role in SR-BI gene regulation in response to glucocorticoid. In summary, this is the first report showing that glucocorticoid suppress SR-BI expression suggesting that steroidogenic tissues maintain steroid hormone homeostasis by prohibiting SR-BI-mediated high-density lipoprotein cholesterol uptake when the endogenous levels of glucocorticoid are elevated.
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Affiliation(s)
- Sofia Mavridou
- Department of Basic Sciences, Foundation of Research and Technology-Hellas, Heraklion 71003, Greece
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Cellular cholesterol delivery, intracellular processing and utilization for biosynthesis of steroid hormones. Nutr Metab (Lond) 2010; 7:47. [PMID: 20515451 PMCID: PMC2890697 DOI: 10.1186/1743-7075-7-47] [Citation(s) in RCA: 286] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 06/01/2010] [Indexed: 11/28/2022] Open
Abstract
Steroid hormones regulate diverse physiological functions such as reproduction, blood salt balance, maintenance of secondary sexual characteristics, response to stress, neuronal function and various metabolic processes. They are synthesized from cholesterol mainly in the adrenal gland and gonads in response to tissue-specific tropic hormones. These steroidogenic tissues are unique in that they require cholesterol not only for membrane biogenesis, maintenance of membrane fluidity and cell signaling, but also as the starting material for the biosynthesis of steroid hormones. It is not surprising, then, that cells of steroidogenic tissues have evolved with multiple pathways to assure the constant supply of cholesterol needed to maintain optimum steroid synthesis. The cholesterol utilized for steroidogenesis is derived from a combination of sources: 1) de novo synthesis in the endoplasmic reticulum (ER); 2) the mobilization of cholesteryl esters (CEs) stored in lipid droplets through cholesteryl ester hydrolase; 3) plasma lipoprotein-derived CEs obtained by either LDL receptor-mediated endocytic and/or SR-BI-mediated selective uptake; and 4) in some cultured cell systems from plasma membrane-associated free cholesterol. Here, we focus on recent insights into the molecules and cellular processes that mediate the uptake of plasma lipoprotein-derived cholesterol, events connected with the intracellular cholesterol processing and the role of crucial proteins that mediate cholesterol transport to mitochondria for its utilization for steroid hormone production. In particular, we discuss the structure and function of SR-BI, the importance of the selective cholesterol transport pathway in providing cholesterol substrate for steroid biosynthesis and the role of two key proteins, StAR and PBR/TSO in facilitating cholesterol delivery to inner mitochondrial membrane sites, where P450scc (CYP11A) is localized and where the conversion of cholesterol to pregnenolone (the common steroid precursor) takes place.
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Shridas P, Bailey WM, Boyanovsky BB, Oslund RC, Gelb MH, Webb NR. Group X secretory phospholipase A2 regulates the expression of steroidogenic acute regulatory protein (StAR) in mouse adrenal glands. J Biol Chem 2010; 285:20031-9. [PMID: 20421306 DOI: 10.1074/jbc.m109.090423] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We developed C57BL/6 mice with targeted deletion of group X secretory phospholipase A(2) (GX KO). These mice have approximately 80% higher plasma corticosterone concentrations compared with wild-type (WT) mice under both basal and adrenocorticotropic hormone (ACTH)-induced stress conditions. This increased corticosterone level was not associated with increased circulating ACTH or a defect in the hypothalamic-pituitary axis as evidenced by a normal response to dexamethasone challenge. Primary cultures of adrenal cells from GX KO mice exhibited significantly increased corticosteroid secretion compared with WT cells. Conversely, overexpression of GX secretory phospholipase A(2) (sPLA(2)), but not a catalytically inactive mutant form of GX sPLA(2), significantly reduced steroid production 30-40% in Y1 mouse adrenal cell line. This effect was reversed by the sPLA(2) inhibitor, indoxam. Silencing of endogenous M-type receptor expression did not restore steroid production in GX sPLA(2)-overexpressing Y1 cells, ruling out a role for this sPLA(2) receptor in this regulatory process. Expression of steroidogenic acute regulatory protein (StAR), the rate-limiting protein in corticosteroid production, was approximately 2-fold higher in adrenal glands of GX KO mice compared with WT mice, whereas StAR expression was suppressed in Y1 cells overexpressing GX sPLA(2). Results from StAR-promoter luciferase reporter gene assays indicated that GX sPLA(2) antagonizes StAR promoter activity and liver X receptor-mediated StAR promoter activation. In summary, GX sPLA(2) is expressed in mouse adrenal glands and functions to negatively regulate corticosteroid synthesis, most likely by negatively regulating StAR expression.
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Affiliation(s)
- Preetha Shridas
- Graduate Center for Nutritional Sciences, the Cardiovascular Research Center, University of Kentucky Medical Center, Lexington, Kentucky 40536, USA
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