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Siddiqui H, Deo N, Rutledge MT, Williams MJ, Redpath GM, McCormick SP. Plasminogen Receptors Promote Lipoprotein(a) Uptake by Enhancing Surface Binding and Facilitating Macropinocytosis. Arterioscler Thromb Vasc Biol 2023; 43:1851-1866. [PMID: 37589135 PMCID: PMC10521804 DOI: 10.1161/atvbaha.123.319344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 08/02/2023] [Indexed: 08/18/2023]
Abstract
BACKGROUND High levels of Lp(a) (lipoprotein(a)) are associated with multiple forms of cardiovascular disease. Lp(a) consists of an apoB100-containing particle attached to the plasminogen homologue apo(a). The pathways for Lp(a) clearance are not well understood. We previously discovered that the plasminogen receptor PlgRKT (plasminogen receptor with a C-terminal lysine) promoted Lp(a) uptake in liver cells. Here, we aimed to further define the role of PlgRKT and to investigate the role of 2 other plasminogen receptors, annexin A2 and S100A10 (S100 calcium-binding protein A10) in the endocytosis of Lp(a). METHODS Human hepatocellular carcinoma (HepG2) cells and haploid human fibroblast-like (HAP1) cells were used for overexpression and knockout of plasminogen receptors. The uptake of Lp(a), LDL (low-density lipoprotein), apo(a), and endocytic cargos was visualized and quantified by confocal microscopy and Western blotting. RESULTS The uptake of both Lp(a) and apo(a), but not LDL, was significantly increased in HepG2 and HAP1 cells overexpressing PlgRKT, annexin A2, or S100A10. Conversely, Lp(a) and apo(a), but not LDL, uptake was significantly reduced in HAP1 cells in which PlgRKT and S100A10 were knocked out. Surface binding studies in HepG2 cells showed that overexpression of PlgRKT, but not annexin A2 or S100A10, increased Lp(a) and apo(a) plasma membrane binding. Annexin A2 and S100A10, on the other hand, appeared to regulate macropinocytosis with both proteins significantly increasing the uptake of the macropinocytosis marker dextran when overexpressed in HepG2 and HAP1 cells and knockout of S100A10 significantly reducing dextran uptake. Bringing these observations together, we tested the effect of a PI3K (phosphoinositide-3-kinase) inhibitor, known to inhibit macropinocytosis, on Lp(a) uptake. Results showed a concentration-dependent reduction confirming that Lp(a) uptake was indeed mediated by macropinocytosis. CONCLUSIONS These findings uncover a novel pathway for Lp(a) endocytosis involving multiple plasminogen receptors that enhance surface binding and stimulate macropinocytosis of Lp(a). Although the findings were produced in cell culture models that have limitations, they could have clinical relevance since drugs that inhibit macropinocytosis are in clinical use, that is, the PI3K inhibitors for cancer therapy and some antidepressant compounds.
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Affiliation(s)
- Halima Siddiqui
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Nikita Deo
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Malcolm T. Rutledge
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Michael J.A. Williams
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- Department of Medicine (M.J.A.W.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Gregory M.I. Redpath
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
| | - Sally P.A. McCormick
- Department of Biochemistry (H.S., N.D., M.T.R., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
- School of Biomedical Sciences, HeartOtago (H.S., N.D., M.T.R., M.J.A.W., G.M.I.R., S.P.A.M.), Dunedin School of Medicine, University of Otago, New Zealand
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Sabbah N, Jaisson S, Garnotel R, Anglés-Cano E, Gillery P. Small size apolipoprotein(a) isoforms enhance inflammatory and proteolytic potential of collagen-primed monocytes. Lipids Health Dis 2019; 18:166. [PMID: 31470857 PMCID: PMC6717332 DOI: 10.1186/s12944-019-1106-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 08/14/2019] [Indexed: 01/03/2023] Open
Abstract
Background Atherosclerosis is an inflammatory process involving activation of monocytes recruited by various chemoattractant factors, among which lipoprotein(a) and its specific apolipoprotein apo(a). Lp(a) contains a specific apolipoprotein apo(a) which size is determined by a variable number of repeats of a specific structural domain, the kringle IV type 2 (IV-2). Lp(a) plasma concentration and apo(a) size is inversely correlated, and smaller apo(a) are major risk factors for coronary heart disease. Design and methods The aim of this study was to evaluate the effect of recombinant apo(a) isoforms (containing 10, 18 or 34 kringles) on monocytes interacting with type I collagen. Results Apo(a) isoforms stimulated reactive oxygen species (ROS) and matrix metalloproteinase-9 (MMP-9) production by monocytes, and not modified monocytes adhesion on type I collagen. This effect was specific of apo(a) since no effect was observed in the presence of plasminogen and was inversely related to apo(a) size. The lysine analogue 6-aminohexanoic acid which blocks the lysine binding sites (LBS), and carboxypeptidase B (CpB) which cleaves carboxy-terminal lysine residues, abolished apo(a)-induced ROS and MMP-9 production, highlighting an effect mediated by apo(a) lysing-binding sites. Conclusions These results indicate that activation of collagen-primed monocytes stimulated with apo(a) is a Kringle number-dependent effect and reinforce the hypothesis of a role for small size apo(a) isoforms in atherothrombosis.
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Affiliation(s)
- Nadia Sabbah
- University of Reims- Champagne-Ardenne, CNRS, MEDyC UMR 7369, Reims, France. .,Endocrinology and Metabolic Diseases Department, Cayenne hospital, Cayenne, French Guiana. .,Clinical Investigation Center Antilles French Guiana (INSERM CIC 1424), Cayenne, French Guiana.
| | - Stéphane Jaisson
- University of Reims- Champagne-Ardenne, CNRS, MEDyC UMR 7369, Reims, France.,Laboratory of Biochemisry-Pharmacology-Toxicology, University Hospital of Reims, Maison Blanche Hospital, Reims, France
| | - Roselyne Garnotel
- Laboratory of Biochemisry-Pharmacology-Toxicology, University Hospital of Reims, Maison Blanche Hospital, Reims, France
| | - Eduardo Anglés-Cano
- Inserm UMR_S1140 "Innovative Therapies in Haemostasis"Faculté de Pharmacie de Paris, Paris, France
| | - Philippe Gillery
- University of Reims- Champagne-Ardenne, CNRS, MEDyC UMR 7369, Reims, France.,Laboratory of Biochemisry-Pharmacology-Toxicology, University Hospital of Reims, Maison Blanche Hospital, Reims, France
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McCormick SPA, Schneider WJ. Lipoprotein(a) catabolism: a case of multiple receptors. Pathology 2018; 51:155-164. [PMID: 30595508 DOI: 10.1016/j.pathol.2018.11.003] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 10/31/2018] [Accepted: 11/01/2018] [Indexed: 01/09/2023]
Abstract
Lipoprotein(a) [Lp(a)] is an apolipoprotein B (apoB)-containing plasma lipoprotein similar in structure to low-density lipoprotein (LDL). Lp(a) is more complex than LDL due to the presence of apolipoprotein(a) [apo(a)], a large glycoprotein sharing extensive homology with plasminogen, which confers some unique properties onto Lp(a) particles. ApoB and apo(a) are essential for the assembly and catabolism of Lp(a); however, other proteins associated with the particle may modify its metabolism. Lp(a) specifically carries a cargo of oxidised phospholipids (OxPL) bound to apo(a) which stimulates many proinflammatory pathways in cells of the arterial wall, a key property underlying its pathogenicity and association with cardiovascular disease (CVD). While the liver and kidney are the major tissues implicated in Lp(a) clearance, the pathways for Lp(a) uptake appear to be complex and are still under investigation. Biochemical studies have revealed an exceptional array of receptors that associate with Lp(a) either via its apoB, apo(a), or OxPL components. These receptors fall into five main categories, namely 'classical' lipoprotein receptors, toll-like and scavenger receptors, lectins, and plasminogen receptors. The roles of these receptors have largely been dissected by genetic manipulation in cells or mice, although their relative physiological importance for removal of Lp(a) from the circulation remains unclear. The LPA gene encoding apo(a) has an overwhelming effect on Lp(a) levels which precludes any clear associations between potential Lp(a) receptor genes and Lp(a) levels in population studies. Targeted approaches and the selection of unique Lp(a) phenotypes within populations has nevertheless allowed for some associations to be made. Few of the proposed Lp(a) receptors can specifically be manipulated with current drugs and, as such, it is not currently clear whether any of these receptors could provide relevant targets for therapeutic manipulation of Lp(a) levels. This review summarises the current status of knowledge about receptor-mediated pathways for Lp(a) catabolism.
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Affiliation(s)
- Sally P A McCormick
- Department of Biochemistry, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.
| | - Wolfgang J Schneider
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
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Apolipoprotein(a) inhibits the conversion of Glu-plasminogen to Lys-plasminogen on the surface of vascular endothelial and smooth muscle cells. Thromb Res 2018; 169:1-7. [DOI: 10.1016/j.thromres.2018.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 05/31/2018] [Accepted: 07/03/2018] [Indexed: 11/24/2022]
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Romagnuolo R, Scipione CA, Bazzi ZA, Boffa MB, Koschinsky ML. Inhibition of pericellular plasminogen activation by apolipoprotein(a): Roles of urokinase plasminogen activator receptor and integrins α Mβ 2 and α Vβ 3. Atherosclerosis 2018; 275:11-21. [PMID: 29852400 DOI: 10.1016/j.atherosclerosis.2018.05.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 05/10/2018] [Accepted: 05/16/2018] [Indexed: 01/06/2023]
Abstract
BACKGROUND AND AIMS Lipoprotein(a) (Lp(a)) is a causal risk factor for cardiovascular disorders including coronary heart disease and calcific aortic valve stenosis. Apolipoprotein(a) (apo(a)), the unique glycoprotein component of Lp(a), contains sequences homologous to plasminogen. Plasminogen activation is markedly accelerated in the presence of cell surface receptors and can be inhibited in this context by apo(a). METHODS We evaluated the role of potential receptors in regulating plasminogen activation and the ability of apo(a) to mediate inhibition of plasminogen activation on vascular and monocytic/macrophage cells through knockdown (siRNA or blocking antibodies) or overexpression of various candidate receptors. Binding assays were conducted to determine apo(a) and plasminogen receptor interactions. RESULTS The urokinase-type plasminogen activator receptor (uPAR) modulates plasminogen activation as well as plasminogen and apo(a) binding on human umbilical vein endothelial cells (HUVECs), human acute monocytic leukemia (THP-1) cells, and THP-1 macrophages as determined through uPAR knockdown and overexpression. Apo(a) variants lacking either the kringle V or the strong lysine binding site in kringle IV type 10 are not able to bind to uPAR to the same extent as wild-type apo(a). Plasminogen activation is also modulated, albeit to a lower extent, through the Mac-1 (αMβ2) integrin on HUVECs and THP-1 monocytes. Integrin αVβ3 can regulate plasminogen activation on THP-1 monocytes and to a lesser extent on HUVECs. CONCLUSIONS These results indicate cell type-specific roles for uPAR, αMβ2, and αVβ3 in promoting plasminogen activation and mediate the inhibitory effects of apo(a) in this process.
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Affiliation(s)
- Rocco Romagnuolo
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4, Canada.
| | - Corey A Scipione
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
| | - Zainab A Bazzi
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
| | - Michael B Boffa
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
| | - Marlys L Koschinsky
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4, Canada
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Boffa MB, Koschinsky ML. Lipoprotein (a): truly a direct prothrombotic factor in cardiovascular disease? J Lipid Res 2015; 57:745-57. [PMID: 26647358 DOI: 10.1194/jlr.r060582] [Citation(s) in RCA: 162] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Indexed: 01/13/2023] Open
Abstract
Elevated plasma concentrations of lipoprotein (a) [Lp(a)] have been determined to be a causal risk factor for coronary heart disease, and may similarly play a role in other atherothrombotic disorders. Lp(a) consists of a lipoprotein moiety indistinguishable from LDL, as well as the plasminogen-related glycoprotein, apo(a). Therefore, the pathogenic role for Lp(a) has traditionally been considered to reflect a dual function of its similarity to LDL, causing atherosclerosis, and its similarity to plasminogen, causing thrombosis through inhibition of fibrinolysis. This postulate remains highly speculative, however, because it has been difficult to separate the prothrombotic/antifibrinolytic functions of Lp(a) from its proatherosclerotic functions. This review surveys the current landscape surrounding these issues: the biochemical basis for procoagulant and antifibrinolytic effects of Lp(a) is summarized and the evidence addressing the role of Lp(a) in both arterial and venous thrombosis is discussed. While elevated Lp(a) appears to be primarily predisposing to thrombotic events in the arterial tree, the fact that most of these are precipitated by underlying atherosclerosis continues to confound our understanding of the true pathogenic roles of Lp(a) and, therefore, the most appropriate therapeutic target through which to mitigate the harmful effects of this lipoprotein.
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Affiliation(s)
- Michael B Boffa
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
| | - Marlys L Koschinsky
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada Robarts Research Institute, Western University, London, ON, Canada
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Romagnuolo R, Marcovina SM, Boffa MB, Koschinsky ML. Inhibition of plasminogen activation by apo(a): role of carboxyl-terminal lysines and identification of inhibitory domains in apo(a). J Lipid Res 2014; 55:625-34. [PMID: 24478033 DOI: 10.1194/jlr.m036566] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apo(a), the distinguishing protein component of lipoprotein(a) [Lp(a)], exhibits sequence similarity to plasminogen and can inhibit binding of plasminogen to cell surfaces. Plasmin generated on the surface of vascular cells plays a role in cell migration and proliferation, two of the fibroproliferative inflammatory events that underlie atherosclerosis. The ability of apo(a) to inhibit pericellular plasminogen activation on vascular cells was therefore evaluated. Two isoforms of apo(a), 12K and 17K, were found to significantly decrease tissue-type plasminogen activator-mediated plasminogen activation on human umbilical vein endothelial cells (HUVECs) and THP-1 monocytes and macrophages. Lp(a) purified from human plasma decreased plasminogen activation on THP-1 monocytes and HUVECs but not on THP-1 macrophages. Removal of kringle V or the strong lysine binding site in kringle IV10 completely abolished the inhibitory effect of apo(a). Treatment with carboxypeptidase B to assess the roles of carboxyl-terminal lysines in cellular receptors leads in most cases to decreases in plasminogen activation as well as plasminogen and apo(a) binding; however, inhibition of plasminogen activation by apo(a) was unaffected. Our findings directly demonstrate that apo(a) inhibits pericellular plasminogen activation in all three cell types, although binding of apo(a) to cell-surface receptors containing carboxyl-terminal lysines does not appear to play a major role in the inhibition mechanism.
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Affiliation(s)
- Rocco Romagnuolo
- Department of Chemistry & Biochemistry, University of Windsor, Windsor, ON, Canada; and
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Pepe G, Chimienti G, Liuzzi GM, Lamanuzzi BL, Nardulli M, Lolli F, Anglés-Cano E, Matà S. Lipoprotein(a) in the cerebrospinal fluid of neurological patients with blood-cerebrospinal fluid barrier dysfunction. Clin Chem 2006; 52:2043-8. [PMID: 16990412 DOI: 10.1373/clinchem.2006.073544] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Lipoprotein(a) [Lp(a)] is a recognized pathogenic particle in human plasma, but its presence in the cerebrospinal fluid and its possible role in the central nervous system have not been documented. We tested the hypothesis that apolipoprotein(a) [apo(a)], free or as a component of the Lp(a) particle, can cross the blood-cerebrospinal fluid barrier and be found in the cerebrospinal fluid of patients affected by neurologic pathologies. METHODS We studied paired cerebrospinal fluid/serum samples from 77 patients with inflammatory (n=20) or noninflammatory (n=34) blood-cerebrospinal fluid barrier dysfunction and without blood-cerebrospinal fluid barrier dysfunction (n=23). We used ELISA to measure Lp(a) concentrations and Western blot and immunodetection to analyze apo(a) isoforms in native and reducing conditions. RESULTS Entire Lp(a) with either small or large apo(a) isoforms was present in the cerebrospinal fluid of patients with blood-cerebrospinal fluid barrier dysfunction, regardless of its pathogenesis. Multiple linear regression analysis showed that both serum Lp(a) concentration (P=0.003) and cerebrospinal fluid/serum albumin ratio (P<0.001) were predictors of the Lp(a) concentration in cerebrospinal fluid. CONCLUSIONS Our results demonstrate that Lp(a) can cross a dysfunctional blood-cerebrospinal fluid barrier. The unusual presence of Lp(a) in the cerebrospinal fluid could extend some of its known pathogenic effects to the central nervous system.
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Affiliation(s)
- Gabriella Pepe
- Department of Biochemistry and Molecular Biology, University of Bari, Italy.
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Discepolo W, Wun T, Berglund L. Lipoprotein(a) and Thrombocytes: Potential Mechanisms Underlying Cardiovascular Risk. PATHOPHYSIOLOGY OF HAEMOSTASIS AND THROMBOSIS 2006; 35:314-21. [PMID: 16877880 DOI: 10.1159/000093224] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Plasma levels of lipoprotein(a), Lp(a), is an independent risk factor for cardiovascular disease. Lp(a) has many properties in common with low-density lipoprotein (LDL), including a cholesteryl ester-rich lipid core and the presence of one copy of apolipoprotein B-100; both apoB-100 and the lipid core are pro-atherogenic. In addition, Lp(a) contains a unique hydrophilic, carbohydrate-rich protein, apo(a), linked to apoB through a single disulfide bond connecting the C-terminal regions of the two proteins. The similarities between apolipoprotein(a), apo(a), and plasminogen has initiated numerous studies on the possible role of Lp(a) as a prothrombotic agent. Studies to date suggest that Lp(a) has antifibrinolytic and procoagulant properties. In this review, we summarize recent studies focused on the interaction between Lp(a) and platelets. Collectively, results to date illustrate that thrombogenicity associated with Lp(a) could be due to risk associated with the LDL moiety, with the apo(a) moiety, or from the combination of those in Lp(a). Present findings suggest that the various components of Lp(a) may impact to a varying degree on different underlying pathways involved in platelet activation and aggregation. On balance, results indicate an effect by Lp(a) on platelet function and future studies focused on specific Lp(a) components, such as the role of apo(a) and of the LDL-like lipid moiety, are needed.
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Calmarza P, Cordero J, Santos V, Vella JC. Apolipoprotein(a) isoforms in infarcted men under 60 years old. Clin Biochem 2005; 37:911-8. [PMID: 15369723 DOI: 10.1016/j.clinbiochem.2003.06.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2003] [Accepted: 06/28/2003] [Indexed: 11/28/2022]
Abstract
OBJECTIVE The aim of this study was to compare the Lp(a) concentration and the frequency distribution of the apo(a) isoforms of a myocardial infarcted male group under 60 years old and a group of healthy subjects (controls). METHODS A total of 111 infarcted men and 99 men free from disease were enrolled in this study. Lp(a) concentrations were measured by a commercial available rate nephelometry method, and apolipoprotein(a) isoform analysis was performed by sodium dodecyl sulfate (SDS) polyacrilamide gel electrophoresis (PAGE) and immunoblotting. RESULTS Infarcted patients had higher Lp(a) concentrations (0.33 +/- 0.36 g/l) than noninfarcted subjects did (0.19 +/- 0.22 g/l), and these differences were significant (P = 0.001). Infarcted patients have also shown a greater proportion of elevated (> or = 0.30 g/l) Lp(a) concentrations 37.8% than controls 20.2% (P < 0.01). The distributions of apo(a) phenotypes for patients with myocardial infarction and controls were remarkably different (P < 0.001), and the proportions of smaller isoforms were significantly different by chi-square analysis (P < 0.01). CONCLUSIONS Infarcted patients under 60 years old display higher Lp(a) concentrations and a significantly higher proportion of low molecular weight apolipoprotein(a) isoforms than controls.
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Affiliation(s)
- Pilar Calmarza
- Hospital General Yagüe., Avda. del Cid no. 96, 09005 Burgos, Spain.
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Alaoui M, Merle C, Garnotel R, Jolly D, Durlach V, Gillery P. Study of apo(a) length polymorphism and lipoprotein(a) concentrations in subjects with single or double apo(a) isoforms. Clin Chem Lab Med 2003; 41:634-9. [PMID: 12812260 DOI: 10.1515/cclm.2003.096] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Cardiovascular risk is associated with high lipoprotein(a) (Lp(a)) concentrations and low molecular weight apolipoprotein(a) (apo(a)) isoforms. We studied the relationship between these two biological parameters, particularly in subjects expressing two apo(a) isoforms. Plasma Lp(a) was measured by immunonephelometry in 530 unrelated Caucasian patients at high cardiovascular risk, and apo(a) size determined by immunoblotting using a recombinant standard. Two, one, or no apo(a) isoforms were detected in 258, 270, and 2 subjects, respectively. Lp(a) concentrations showed a non-Gaussian distribution, being higher in the 'double band' than in the 'single band' group (median 0.42 vs. 0.11 g/l, p < 0.0005). Apo(a) size distribution was bimodal, with two frequency peaks at 18 kringles (K) and 27 K. Small size apo(a) isoforms were more frequently found in the 'double band' group, where major isoforms were of lower size than minor isoforms (median 20 vs. 27 K). Regression analysis showed that apo(a) gene length accounted for 33% of Lp(a) variation, with a threshold effect at 20 K, no correlation being found over this value. The minor apo(a) isoform did not significantly influence Lp(a) concentration. These data confirm the relationship between apo(a) size and Lp(a) concentration and suggest that the assessment of cardiovascular risk should take into account the threshold effect at 20 K and the absence of influence of the minor apo(a) isoform.
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Affiliation(s)
- Mariam Alaoui
- Laboratory of Biochemistry, Robert Debré Hospital, CHU of Reims, Reims, France
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Martin I, Humbert M, Marfaing-Koka A, Capron F, Wolf M, Meyer D, Simonneau G, Anglés-Cano E. Plasminogen activation by blood monocytes and alveolar macrophages in primary pulmonary hypertension. Blood Coagul Fibrinolysis 2002; 13:417-22. [PMID: 12138369 DOI: 10.1097/00001721-200207000-00006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The pathophysiology of primary pulmonary hypertension (PPH) remains poorly understood. Vascular wall remodeling and endothelial dysfunction reflected by modifications in plasma fibrinolytic proteins and von Willebrand factor have been well documented in PPH. We hypothesize that endothelial mediators, produced in excess in PPH patients, may stimulate migrating mononuclear cells and thereby modulate alveolar macrophage function; in particular, the plasminogen activation system. Components of the fibrinolytic system were therefore studied in plasma, blood monocytes and alveolar macrophages obtained from bronchoalveolar lavage in 10 patients with PPH and in four controls. Compared with controls, PPH patients had elevated plasma levels of tissue-type plasminogen activator (15.6 +/- 9.9 versus 5.5 +/- 3 ng/ml) and plasminogen activator inhibitor-1 (27.8 +/- 23 versus 16.4 +/- 12 ng/ml). In contrast, binding and activation of plasminogen by single-chain urokinase-type plasminogen activator (scu-PA) at the surface of blood monocytes and alveolar macrophages were not different from those of control values. Dissociation constants (K(d)) for binding of scu-PA and plasminogen to alveolar macrophages were similar in both PPH (4.7 +/- 1.5 and 0.88 +/- 0.3 micromol/l, respectively) and control (6.7 +/- 0.1 and 1.02 +/- 0.12 micromol/l, respectively) groups. These results indicate that in PPH patients the fibrinolytic activity of alveolar macrophages is normal, whereas endothelial fibrinolytic proteins are abnormally elevated in plasma.
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Affiliation(s)
- I Martin
- UPRES EA 2705 Centre de Maladies Vasculaires Pulmonaires, Hôpital Antoine-Béclère, Clamart, France
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Abstract
High plasma concentrations of lipoprotein (a) [Lp(a)] are now considered a major risk factor for atherosclerosis and cardiovascular disease. This effect of Lp(a) may be related to its composite structure, a plasminogen-like inactive serine-proteinase, apoprotein (a) [apo(a)], which is disulfide-linked to the apoprotein B100 of an atherogenic low-density lipoprotein (LDL) particle. Apo(a) contains, in addition to the protease region and a copy of kringle 5 of plasminogen, a variable number of copies of plasminogen-like kringle 4, giving rise to a series of isoforms. This structural homology endows Lp(a) with the capacity to bind to fibrin and to membrane proteins of endothelial cells and monocytes, and thereby inhibits binding of plasminogen and plasmin formation. This mechanism favors fibrin and cholesterol deposition at sites of vascular injury and impairs activation of transforming growth factor-beta (TGF-beta) that may result in migration and proliferation of smooth muscle cells into the vascular intima. It is currently accepted that this effect of Lp(a) is linked to its concentration in plasma, and an inverse relationship between apo(a) isoform size and Lp(a) concentrations that is under genetic control has been documented. Recently, it has been shown that inhibition of plasminogen binding to fibrin by apo(a) from homozygous subjects is also inversely associated with isoform size. These findings suggest that the structural polymorphism of apo(a) is not only inversely related to the plasma concentration of Lp(a), but also to a functional heterogeneity of apo(a) isoforms. Based on these pathophysiological findings, it can be proposed that the predictive value of Lp(a) as a risk factor for vascular occlusive disease in heterozygous subjects would depend on the relative concentration of the isoform with the highest affinity for fibrin.
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Affiliation(s)
- A de la Peña-Díaz
- Departamento de Hematología, Instituto Nacional de Cardiología Ignacio Chávez, México, D.F., Mexico
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Soulat T, Dominguez M, Martin I, Anglés-Cano E. Immobilisation of monocytes to a solid support: a model for the study of ligand-binding interactions and plasminogen activation at the cell surface. Thromb Res 2000; 96:473-80. [PMID: 10632471 DOI: 10.1016/s0049-3848(99)00141-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The functional and immunological identification of receptors expressed by cells of the monocyte/ macrophage lineage may be facilitated with the use of immobilised cells. A procedure is described here for attaching human blood monocytes, alveolar macrophages, and THP-1 cells to a solid support activated with polymerised glutaraldehyde. Homogeneous monolayers visualised by optical microscopy were obtained at predefined input cell densities and were quantitatively characterised with the use of 125I-plasminogen (35000+/-2772 cells/well at approximately 76000 cells/50 microL) and 125I-pro-urokinase (39000+/-3839 cells/well at approximately 86000 cells/50 microL). The cells remained stably attached during washing and incubation procedures in ligand-binding studies. The functionality of membrane receptors and acceptors of the immobilised cells for a number of ligands was verified. Parameters of the interaction of plasminogen, urokinase, and human immunoglobulin G with their corresponding receptors were similar to those previously reported using cells in suspension. The functionality of bound ligands, such as urokinase and plasminogen, was verified by measuring their ability to generate plasmin. We conclude that immobilised monocytes/macrophages are a useful tool for studying ligand interactions with membrane proteins and for the realisation of plasminogen activation studies at the surface of the cell membrane.
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Affiliation(s)
- T Soulat
- INSERM U.143 Hémostase-Biologie Vasculaire, Hôpital de Bicêtre, Paris, France
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Anglés-Cano E, Loyau S, Cardoso-Saldaña G, Couderc R, Gillery P. A novel kringle-4 number-based recombinant apo[a] standard for human apo[a] phenotyping. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)33376-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Gazzaruso C, Geroldi D, Garzaniti A, Falcone C, Fratino P, Finardi G, Buscaglia P. Apolipoprotein(a) phenotypes as genetic markers of coronary atherosclerosis severity. Int J Cardiol 1998; 64:277-84. [PMID: 9672409 DOI: 10.1016/s0167-5273(98)00050-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We investigated Lp(a) levels and apo(a) polymorphism in relation to the severity of coronary artery disease, expressed both by the number of coronary arteries stenosed and three different coronary scoring systems. In a sample of 267 patients with coronary artery disease, a Mono-, Bi- or Multi-vessel coronary stenosis was documented by angiography. Twenty-five apo(a) isoforms were detected by a high resolution phenotyping method. Lp(a) levels did not show any differences among subgroups of patients. Both the percentage of apo(a) isoforms of low molecular weight (<655 kDa) (P=0.00015) and the percentage of subjects with at least one apo(a) isoform of low molecular weight (P=0.00027) were significantly correlated with increasing number of coronary vessels stenosed. In multivariate analysis, only apo(a) isoforms of low molecular weight were predictors of coronary atherosclerosis severity, when we used as the dependent variable both the '1-2-multi-vessels' categorization (P=0.000067) and the Gensini (P=0.008767), or Green Lane (P= 0.000001) or Dahlen (P=0.000102) coronary scoring system. Our data show that apo(a) isoforms of low molecular weight are associated with a greater severity of coronary atherosclerosis. If these data are confirmed by prospective studies, apo(a) phenotypes might be used as genetic markers of a greater severity of coronary atherosclerotic lesions.
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Affiliation(s)
- C Gazzaruso
- Department of Internal Medicine and Medical Therapeutics, IRCCS Policlinico San Matteo, University of Pavia, Italy
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