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Clark JR, Gemin M, Youssef A, Marcovina SM, Prat A, Seidah NG, Hegele RA, Boffa MB, Koschinsky ML. Sortilin enhances secretion of apolipoprotein(a) through effects on apolipoprotein B secretion and promotes uptake of lipoprotein(a). J Lipid Res 2022; 63:100216. [PMID: 35469919 PMCID: PMC9131257 DOI: 10.1016/j.jlr.2022.100216] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 04/06/2022] [Accepted: 04/08/2022] [Indexed: 12/30/2022] Open
Abstract
Elevated plasma lipoprotein(a) (Lp(a)) is an independent, causal risk factor for atherosclerotic cardiovascular disease and calcific aortic valve stenosis. Lp(a) is formed in or on hepatocytes from successive noncovalent and covalent interactions between apo(a) and apoB, although the subcellular location of these interactions and the nature of the apoB-containing particle involved remain unclear. Sortilin, encoded by the SORT1 gene, modulates apoB secretion and LDL clearance. We used a HepG2 cell model to study the secretion kinetics of apo(a) and apoB. Overexpression of sortilin increased apo(a) secretion, while siRNA-mediated knockdown of sortilin expression correspondingly decreased apo(a) secretion. Sortilin binds LDL but not apo(a) or Lp(a), indicating that its effect on apo(a) secretion is likely indirect. Indeed, the effect was dependent on the ability of apo(a) to interact noncovalently with apoB. Overexpression of sortilin enhanced internalization of Lp(a), but not apo(a), by HepG2 cells, although neither sortilin knockdown in these cells or Sort1 deficiency in mice impacted Lp(a) uptake. We found several missense mutations in SORT1 in patients with extremely high Lp(a) levels; sortilin containing some of these mutations was more effective at promoting apo(a) secretion than WT sortilin, though no differences were found with respect to Lp(a) internalization. Our observations suggest that sortilin could play a role in determining plasma Lp(a) levels and corroborate in vivo human kinetic studies which imply that secretion of apo(a) and apoB are coupled, likely within the hepatocyte.
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Affiliation(s)
- Justin R Clark
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Matthew Gemin
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Amer Youssef
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | | | - Annik Prat
- Institut de Recherches Cliniques de Montreal, Montréal, QC, Canada
| | - Nabil G Seidah
- Institut de Recherches Cliniques de Montreal, Montréal, QC, Canada
| | - Robert A Hegele
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Medicine, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Michael B Boffa
- Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Department of Biochemistry, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Marlys L Koschinsky
- Department of Physiology & Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada; Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada.
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Nakajima K, Tokita Y, Tanaka A, Takahashi S. The VLDL receptor plays a key role in the metabolism of postprandial remnant lipoproteins. Clin Chim Acta 2019; 495:382-393. [PMID: 31078566 DOI: 10.1016/j.cca.2019.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 05/03/2019] [Accepted: 05/06/2019] [Indexed: 12/21/2022]
Abstract
A new concept to account for the process of postprandial remnant lipoprotein metabolism is proposed based on the characteristics of lipoprotein particles and their receptors. The characteristics of remnant lipoprotein (RLP) were investigated using an immuno-separation method. The majority of the postprandial lipoproteins increased after fat intake was shown to be VLDL remnants, not chylomicron (CM) remnants, based on the significantly high ratio of apoB100/apoB48 in the RLP and the high degree of similarity in the particle size of the apoB48 and apoB100 carrying lipoproteins, which fluctuate in parallel during a 6 h period after fat intake. The VLDL receptor was discovered as a receptor for TG-rich lipoprotein metabolism and is located in peripheral tissues such as skeletal muscle, adipose tissue, etc., but not in the liver. Postprandial VLDL particles are strongly bound and internalized into cells expressing the VLDL receptor. Ligands that bind to VLDL receptor, such as LPL and Lp(a), present in RLP. The presence of various specific ligands in VLDL remnants may enhance the capacity for binding to the VLDL receptor, which play the role primarily for energy delivery to the peripheral tissues, but is also a causal factor in atherogenic diseases when excessively and/or continuously remained in plasma.
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Affiliation(s)
- Katsuyuki Nakajima
- Laboratory of Clinical Nutrition and Medicine, Kagawa Nutrition University, Tokyo, Japan; Graduate School of Health Sciences, Gunma University, Maebashi, Gunma, Japan.
| | - Yoshiharu Tokita
- Laboratory of Clinical Nutrition and Medicine, Kagawa Nutrition University, Tokyo, Japan; Graduate School of Health Sciences, Gunma University, Maebashi, Gunma, Japan
| | - Akira Tanaka
- Laboratory of Clinical Nutrition and Medicine, Kagawa Nutrition University, Tokyo, Japan
| | - Sadao Takahashi
- Laboratory of Clinical Nutrition and Medicine, Kagawa Nutrition University, Tokyo, Japan; Division of Diabetes, Ageo Central General Hospital, Saitama, Japan
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Mogilenko DA, Kudriavtsev IV, Trulioff AS, Shavva VS, Dizhe EB, Missyul BV, Zhakhov AV, Ischenko AM, Perevozchikov AP, Orlov SV. Modified low density lipoprotein stimulates complement C3 expression and secretion via liver X receptor and Toll-like receptor 4 activation in human macrophages. J Biol Chem 2011; 287:5954-68. [PMID: 22194611 DOI: 10.1074/jbc.m111.289322] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Complement C3 is a pivotal component of three cascades of complement activation. C3 is expressed in human atherosclerotic lesions and is involved in atherogenesis. However, the mechanism of C3 accumulation in atherosclerotic lesions is not well elucidated. We show that acetylated low density lipoprotein and oxidized low density lipoprotein (oxLDL) increase C3 gene expression and protein secretion by human macrophages. Modified LDL (mLDL)-mediated activation of C3 expression mainly depends on liver X receptor (LXR) and partly on Toll-like receptor 4 (TLR4), whereas C3 secretion is increased due to TLR4 activation by mLDL. LXR agonist TO901317 stimulates C3 gene expression in human monocyte-macrophage cells but not in human hepatoma (HepG2) cells. We find LXR-responsive element inside of the promoter region of the human C3 gene, which binds to LXRβ in macrophages but not in HepG2 cells. We show that C3 expression and secretion is decreased in IL-4-treated (M2) and increased in IFNγ/LPS-stimulated (M1) human macrophages as compared with resting macrophages. LXR agonist TO901317 potentiates LPS-induced C3 gene expression and protein secretion in macrophages, whereas oxLDL differently modulates LPS-mediated regulation of C3 in M1 or M2 macrophages. Treatment of human macrophages with anaphylatoxin C3a results in stimulation of C3 transcription and secretion as well as increased oxLDL accumulation and augmented oxLDL-mediated up-regulation of the C3 gene. These data provide a novel mechanism of C3 gene regulation in macrophages and suggest new aspects of cross-talk between mLDL, C3, C3a, and TLR4 during development of atherosclerotic lesions.
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Affiliation(s)
- Denis A Mogilenko
- Department of Biochemistry, Institute of Experimental Medicine, Russian Academy of Medical Sciences, St. Petersburg 197376, Russia.
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Leucine-Aspartic Acid-Valine Sequence as Targeting Ligand and Drug Carrier for Doxorubicin Delivery to Melanoma Cells: In Vitro Cellular Uptake and Cytotoxicity Studies. Pharm Res 2009; 26:2578-87. [DOI: 10.1007/s11095-009-9971-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Accepted: 09/14/2009] [Indexed: 01/14/2023]
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Abstract
Lipoprotein(a) is a cholesterol-enriched lipoprotein, consisting of a covalent linkage joining the unique and highly polymorphic apolipoprotein(a) to apolipoprotein B100, the main protein moiety of low-density lipoproteins. Although the concentration of lipoprotein(a) in humans is mostly genetically determined, acquired disorders might influence synthesis and catabolism of the particle. Raised concentration of lipoprotein(a) has been acknowledged as a leading inherited risk factor for both premature and advanced atherosclerosis at different vascular sites. The strong structural homologies with plasminogen and low-density lipoproteins suggest that lipoprotein(a) might represent the ideal bridge between the fields of atherosclerosis and thrombosis in the pathogenesis of vascular occlusive disorders. Unfortunately, the exact mechanisms by which lipoprotein(a) promotes, accelerates, and complicates atherosclerosis are only partially understood. In some clinical settings, such as in patients at exceptionally low risk for cardiovascular disease, the potential regenerative and antineoplastic properties of lipoprotein(a) might paradoxically counterbalance its athero-thrombogenicity, as attested by the compatibility between raised plasma lipoprotein(a) levels and longevity.
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Affiliation(s)
- Giuseppe Lippi
- Istituto di Chimica e Microscopia Clinica, Dipartimento di Scienze Morfologiche e Biomediche, Università degli Studi di Verona, Verona, Italy
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Güvener M, Ucar I, Ozkan M, Dogan OF, Serter FT, Pasaoglu I. Effect of cardiopulmonary bypass on plasma levels of lipoprotein (a) in hypercholesterolemic patients. JAPANESE HEART JOURNAL 2001; 42:563-74. [PMID: 11804298 DOI: 10.1536/jhj.42.563] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Increments of lipoprotein (a) (Lp (a)) concentration during cardiopulmonary bypass (CPB) have not been justified in the literature yet. We have investigated whether Lp (a) levels remain constant or increase during CPB and if high plasma levels of low density lipoprotein (LDL; containing apolipoprotein (apo) B) in hypercholesterolemic patients affect the assembly of Lp (a) (containing apoB: Apo (a)). In this study, the change in plasma lipid and lipoprotein levels of 40 patients with hypercholesterolemia and 40 patients who have normal cholesterol values were determined and compared during CPB, and in the postoperative early stage. In our study, lipid and lipoproteins, except Lp (a), showed a falling trend and paradoxically, Lp (a) statistically showed a significant rising trend, like the acute phase reactant in two groups (p=0.011 for LDL, p=0.016 for high density lipoprotein (HDL) and p<0.001 for the others, in 80 patients). Concentrations of Lp (a) in plasma increased more sharply in the hypercholesterolemic group than the normocholesterolemic group during CPB. This difference was significant at the 60th minute of cardiopulmonary bypass with a nonparametric test (p<0.05 Mann-Whitney U test). High density lipoprotein values showed more decline in the hypercholesterolemic group patients than in the normocholesterolemic group patients (p<0.05). In conclusion, lipoprotein (a) levels increased more pronounced in patients with hypercholesterolemia during CPB. On the other hand, high LDL levels in hypercholesterolemic patients accelerated Lp(a)formation in the acute phase.
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Affiliation(s)
- M Güvener
- Department of Thoracic and Cardiovascular Surgery, Faculty of Medicine, Hacettepe University, Ankara, Turkey
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