1
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Wang K, Gan C, Wang H, Ao M, Fan Y, Chen Y. AFM detects the effects of acidic condition on the size and biomechanical properties of native/oxidized low-density lipoprotein. Colloids Surf B Biointerfaces 2021; 208:112053. [PMID: 34438294 DOI: 10.1016/j.colsurfb.2021.112053] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 07/06/2021] [Accepted: 08/16/2021] [Indexed: 12/18/2022]
Abstract
Solution acidification exists under some physiological conditions (e.g. lysosomes in cells) and diseases (e.g. atherosclerosis, tumors, etc.). It is poorly understood whether and how acidification influences the size and biomechanical (stiffness and stickiness) properties of native Low-density lipoprotein (LDL) and its oxidized form (oxLDL) which plays a vital role in atherogenesis and tumorigenesis. Atomic force microscopy (AFM) evaluated that gradient acidification from pH 7.4 to pH 4.4 caused an expanding-first-and-then-shrinking decrease in size and a dramatic decrease in stiffness (but no statistically significant changes in stickiness) of LDL/oxLDL particles by influencing secondary/tertiary structures and lipid release detected by infrared spectral analysis and cholesterol detection, respectively. The smaller and softer characteristics of LDL/oxLDL at acidic conditions versus at the neutral pH partially explains the atherogenic role of acidification. The data may provide important information for a better understanding of LDL/oxLDL and some diseases (e.g. atherosclerosis and tumors).
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Affiliation(s)
- Kun Wang
- Jiangxi Key Laboratory for Microscale interdisciplinary Study, Institute for Advanced Study, Nanchang University, Nanchang, Jiangxi, 330031, PR China; School of Materials Science and Engineering, Nanchang University, Nanchang, Jiangxi, PR China
| | - Chaoye Gan
- Jiangxi Key Laboratory for Microscale interdisciplinary Study, Institute for Advanced Study, Nanchang University, Nanchang, Jiangxi, 330031, PR China
| | - Huaying Wang
- Jiangxi Key Laboratory for Microscale interdisciplinary Study, Institute for Advanced Study, Nanchang University, Nanchang, Jiangxi, 330031, PR China
| | - Meiying Ao
- School of Basic Medical Sciences, Jiangxi University of Traditional Chinese Medicine, Nanchang, Jiangxi, 330025, PR China
| | - Youlong Fan
- School of Basic Medical Sciences, Jiangxi University of Traditional Chinese Medicine, Nanchang, Jiangxi, 330025, PR China
| | - Yong Chen
- Jiangxi Key Laboratory for Microscale interdisciplinary Study, Institute for Advanced Study, Nanchang University, Nanchang, Jiangxi, 330031, PR China.
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2
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Öörni K, Kovanen PT. Aggregation Susceptibility of Low-Density Lipoproteins-A Novel Modifiable Biomarker of Cardiovascular Risk. J Clin Med 2021; 10:1769. [PMID: 33921661 PMCID: PMC8074066 DOI: 10.3390/jcm10081769] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 03/31/2021] [Accepted: 04/13/2021] [Indexed: 01/07/2023] Open
Abstract
Circulating low-density lipoprotein (LDL) particles enter the arterial intima where they bind to the extracellular matrix and become modified by lipases, proteases, and oxidizing enzymes and agents. The modified LDL particles aggregate and fuse into larger matrix-bound lipid droplets and, upon generation of unesterified cholesterol, cholesterol crystals are also formed. Uptake of the aggregated/fused particles and cholesterol crystals by macrophages and smooth muscle cells induces their inflammatory activation and conversion into foam cells. In this review, we summarize the causes and consequences of LDL aggregation and describe the development and applications of an assay capable of determining the susceptibility of isolated LDL particles to aggregate when exposed to human recombinant sphingomyelinase enzyme ex vivo. Significant person-to-person differences in the aggregation susceptibility of LDL particles were observed, and such individual differences largely depended on particle lipid composition. The presence of aggregation-prone LDL in the circulation predicted future cardiovascular events in patients with atherosclerotic cardiovascular disease. We also discuss means capable of reducing LDL particles' aggregation susceptibility that could potentially inhibit LDL aggregation in the arterial wall. Whether reductions in LDL aggregation susceptibility are associated with attenuated atherogenesis and a reduced risk of atherosclerotic cardiovascular diseases remains to be studied.
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Affiliation(s)
- Katariina Öörni
- Wihuri Research Institute, 00290 Helsinki, Finland;
- Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, 00014 Helsinki, Finland
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3
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Bång-Rudenstam A, Cerezo-Magaña M, Belting M. Pro-metastatic functions of lipoproteins and extracellular vesicles in the acidic tumor microenvironment. Cancer Metastasis Rev 2019; 38:79-92. [PMID: 30767150 PMCID: PMC6647379 DOI: 10.1007/s10555-019-09786-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Although the overall mortality in cancer is steadily decreasing, major groups of patients still respond poorly to available treatments. The key clinical challenge discussed here relates to the inherent capacity of cancer cells to metabolically adapt to hypoxic and acidic stress, resulting in treatment resistance and a pro-metastatic behavior. Hence, a detailed understanding of stress adaptive responses is critical for the design of more rational therapeutic strategies for cancer. We will focus on the emerging role of extracellular vesicles (EVs) and lipoprotein particles in cancer cell metabolic stress adaptation and how these pathways may constitute potential Achilles' heels of the cancer cell machinery and alternative treatment targets of metastasis. In this context, common extracellular lipid uptake mechanisms, involving specific cell-surface receptors and endocytic pathways, may operate during remodeling of acidic atherosclerotic plaques as well as the tumor microenvironment. The role of endocytosis in regulating the cellular response to hypoxic and acidic stress through spatial coordination of receptor proteins may be exploited for therapeutic purposes. As a consequence, molecular mechanisms of endocytosis have attracted increasing attention as potential targets for tumor specific delivery of therapeutic substances, such as antibody-drug conjugates. The identification of internalizing surface proteins specific to the acidic tumor niche remains an unmet need of high clinical relevance. Among the currently explored, acidosis-related, internalizing target proteins, we will focus on the cell-surface proteoglycan carbonic anhydrase 9.
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Affiliation(s)
- Anna Bång-Rudenstam
- Department of Clinical Sciences Lund, Section of Oncology and Pathology, Lund University, Barngatan 4, SE-221 85, Lund, Sweden
| | - Myriam Cerezo-Magaña
- Department of Clinical Sciences Lund, Section of Oncology and Pathology, Lund University, Barngatan 4, SE-221 85, Lund, Sweden
| | - Mattias Belting
- Department of Clinical Sciences Lund, Section of Oncology and Pathology, Lund University, Barngatan 4, SE-221 85, Lund, Sweden.
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4
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Öörni K, Lehti S, Sjövall P, Kovanen PT. Triglyceride-Rich Lipoproteins as a Source of Proinflammatory Lipids in the Arterial Wall. Curr Med Chem 2019; 26:1701-1710. [DOI: 10.2174/0929867325666180530094819] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 12/27/2017] [Accepted: 01/01/2018] [Indexed: 12/11/2022]
Abstract
Apolipoprotein B –containing lipoproteins include triglyceride-rich lipoproteins
(chylomicrons and their remnants, and very low-density lipoproteins and their remnants) and
cholesterol-rich low-density lipoprotein particles. Of these, lipoproteins having sizes below
70-80 nm may enter the arterial wall, where they accumulate and induce the formation of
atherosclerotic lesions. The processes that lead to accumulation of lipoprotein-derived lipids
in the arterial wall have been largely studied with a focus on the low-density lipoprotein particles.
However, recent observational and genetic studies have discovered that the triglyceriderich
lipoproteins and their remnants are linked with cardiovascular disease risk. In this review,
we describe the potential mechanisms by which the triglyceride-rich remnant lipoproteins can
contribute to the development of atherosclerotic lesions, and highlight the differences in the
atherogenicity between low-density lipoproteins and the remnant lipoproteins.
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Affiliation(s)
| | - Satu Lehti
- Wihuri Research Institute, Helsinki, Finland
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5
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Lu M, Gursky O. Aggregation and fusion of low-density lipoproteins in vivo and in vitro. Biomol Concepts 2015; 4:501-18. [PMID: 25197325 DOI: 10.1515/bmc-2013-0016] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Low-density lipoproteins (LDLs, also known as 'bad cholesterol') are the major carriers of circulating cholesterol and the main causative risk factor of atherosclerosis. Plasma LDLs are 20- to 25-nm nanoparticles containing a core of cholesterol esters surrounded by a phospholipid monolayer and a single copy of apolipoprotein B (550 kDa). An early sign of atherosclerosis is the accumulation of LDL-derived lipid droplets in the arterial wall. According to the widely accepted 'response-to-retention hypothesis', LDL binding to the extracellular matrix proteoglycans in the arterial intima induces hydrolytic and oxidative modifications that promote LDL aggregation and fusion. This enhances LDL uptake by the arterial macrophages and triggers a cascade of pathogenic responses that culminate in the development of atherosclerotic lesions. Hence, LDL aggregation, fusion, and lipid droplet formation are important early steps in atherogenesis. In vitro, a variety of enzymatic and nonenzymatic modifications of LDL can induce these reactions and thereby provide useful models for their detailed analysis. Here, we summarize current knowledge of the in vivo and in vitro modifications of LDLs leading to their aggregation, fusion, and lipid droplet formation; outline the techniques used to study these reactions; and propose a molecular mechanism that underlies these pro-atherogenic processes. Such knowledge is essential in identifying endogenous and exogenous factors that can promote or prevent LDL aggregation and fusion in vivo and to help establish new potential therapeutic targets to decelerate or even block these pathogenic reactions.
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Affiliation(s)
- Mengxiao Lu
- Department of Physiology and Biophysics, Boston University School of Medicine, W321, 700 Albany Street, Boston, MA 02118, USA.
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6
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Öörni K, Rajamäki K, Nguyen SD, Lähdesmäki K, Plihtari R, Lee-Rueckert M, Kovanen PT. Acidification of the intimal fluid: the perfect storm for atherogenesis. J Lipid Res 2014; 56:203-14. [PMID: 25424004 DOI: 10.1194/jlr.r050252] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Atherosclerotic lesions are often hypoxic and exhibit elevated lactate concentrations and local acidification of the extracellular fluids. The acidification may be a consequence of the abundant accumulation of lipid-scavenging macrophages in the lesions. Activated macrophages have a very high energy demand and they preferentially use glycolysis for ATP synthesis even under normoxic conditions, resulting in enhanced local generation and secretion of lactate and protons. In this review, we summarize our current understanding of the effects of acidic extracellular pH on three key players in atherogenesis: macrophages, apoB-containing lipoproteins, and HDL particles. Acidic extracellular pH enhances receptor-mediated phagocytosis and antigen presentation by macrophages and, importantly, triggers the secretion of proinflammatory cytokines from macrophages through activation of the inflammasome pathway. Acidity enhances the proteolytic, lipolytic, and oxidative modifications of LDL and other apoB-containing lipoproteins, and strongly increases their affinity for proteoglycans, and may thus have major effects on their retention and the ensuing cellular responses in the arterial intima. Finally, the decrease in the expression of ABCA1 at acidic pH may compromise cholesterol clearance from atherosclerotic lesions. Taken together, acidic extracellular pH amplifies the proatherogenic and proinflammatory processes involved in atherogenesis.
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7
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Partial-filling affinity capillary electrophoresis and quartz crystal microbalance with adsorption energy distribution calculations in the study of biomolecular interactions with apolipoprotein E as interaction partner. Anal Bioanal Chem 2014; 406:4137-46. [PMID: 24788890 DOI: 10.1007/s00216-014-7821-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 03/22/2014] [Accepted: 04/04/2014] [Indexed: 01/08/2023]
Abstract
Adsorption energy distribution (AED) calculations were successfully applied to partial-filling affinity capillary electrophoresis (PF-ACE) to facilitate more detailed studies of biomolecular interactions. PF-ACE with AED calculations was employed to study the interactions between two isoforms of apolipoprotein E (apoE) and dermatan sulfate (DS), and a quartz crystal microbalance (QCM) was used in combination with AED calculations to examine the interactions of the 15-amino-acid peptide fragment of apoE with DS. The heterogeneity of the interactions was elucidated. Microscale thermophoresis was used to validate the results. The interactions studied are of interest because, in vivo, apolipoprotein E localizes on DS-containing regions in the extracellular matrix of human vascular subendothelium. Two-site binding was demonstrated for the isoform apoE3 and DS, but only one-site binding for apoE2-DS. Comparable affinity constants were obtained for the apoE2-DS, apoE3-D3, and 15-amino-acid peptide of apoE-DS using the three techniques. The results show that combining AED calculations with modern biosensing techniques can open up another dimension in studies on the heterogeneity and affinity constants of biological molecules.
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8
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Abstract
PURPOSE OF REVIEW Hypoxia triggers various cellular processes, both in physiological and pathological conditions, and has recently also been implicated in atherosclerosis. This review summarizes the recent evidence for the presence and the role of hypoxia in atherosclerosis. Additionally, it will elucidate on hypoxic signaling, which is interlinked with inflammatory signaling, and discuss recent advances in imaging of hypoxia in atherosclerosis. RECENT FINDINGS Hypoxia is present in atherosclerotic plaques in humans and animal models, and systemic hypoxia promotes atherosclerosis. Hypoxia stimulates proatherosclerotic processes, like deficient lipid efflux, inflammation, interference with macrophage polarization and glucose metabolism. However, the molecular mechanism of hypoxia-mediated atherogenesis remains unclear. Noninvasive imaging directly targeting plaque hypoxia has been applied in animal models of atherosclerosis, but remains to be validated in humans. Meanwhile, the metabolic marker ¹⁸F-fluorodeoxyglucose, used to detect human atherosclerosis in vivo, may serve as an indirect marker of plaque hypoxia due to enhanced glucose uptake in anaerobic metabolism. SUMMARY Recent studies underscore the proatherogenic role of hypoxia in macrophage lipid and glucose metabolism, inflammation and polarization. These studies provide new insights into the pathogenesis of atherosclerosis and unravel novel therapeutic targets and new options for noninvasive imaging of human atherosclerotic plaques.
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Affiliation(s)
- Elke Marsch
- Department of Pathology, Cardiovascular Research Institute Maastricht-CARIM, Maastricht University Medical Center, Maastricht, the Netherlands
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9
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Li L, Liu B, Håversen L, Lu E, Magnusson LU, Ståhlman M, Borén J, Bergström G, Levin MC, Hultén LM. The importance of GLUT3 for de novo lipogenesis in hypoxia-induced lipid loading of human macrophages. PLoS One 2012; 7:e42360. [PMID: 22876317 PMCID: PMC3410913 DOI: 10.1371/journal.pone.0042360] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 07/04/2012] [Indexed: 12/15/2022] Open
Abstract
Atherosclerotic lesions are characterized by lipid-loaded macrophages (foam cells) and hypoxic regions. Although it is well established that foam cells are produced by uptake of cholesterol from oxidized LDL, we previously showed that hypoxia also promotes foam cell formation even in the absence of exogenous lipids. The hypoxia-induced lipid accumulation results from increased triglyceride biosynthesis but the exact mechanism is unknown. Our aim was to investigate the importance of glucose in promoting hypoxia-induced de novo lipid synthesis in human macrophages. In the absence of exogenous lipids, extracellular glucose promoted the accumulation of Oil Red O-stained lipid droplets in human monocyte-derived macrophages in a concentration-dependent manner. Lipid droplet accumulation was higher in macrophages exposed to hypoxia at all assessed concentrations of glucose. Importantly, triglyceride synthesis from glucose was increased in hypoxic macrophages. GLUT3 was highly expressed in macrophage-rich and hypoxic regions of human carotid atherosclerotic plaques and in macrophages isolated from these plaques. In human monocyte-derived macrophages, hypoxia increased expression of both GLUT3 mRNA and protein, and knockdown of GLUT3 with siRNA significantly reduced both glucose uptake and lipid droplet accumulation. In conclusion, we have shown that hypoxia-induced increases in glucose uptake through GLUT3 are important for lipid synthesis in macrophages, and may contribute to foam cell formation in hypoxic regions of atherosclerotic lesions.
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Affiliation(s)
- Lu Li
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Bo Liu
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Liliana Håversen
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Emma Lu
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lisa U. Magnusson
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Marcus Ståhlman
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Jan Borén
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Göran Bergström
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Malin C. Levin
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Lillemor Mattsson Hultén
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
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10
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Lu M, Gantz DL, Herscovitz H, Gursky O. Kinetic analysis of thermal stability of human low density lipoproteins: a model for LDL fusion in atherogenesis. J Lipid Res 2012; 53:2175-2185. [PMID: 22855737 DOI: 10.1194/jlr.m029629] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Fusion of modified LDL in the arterial wall promotes atherogenesis. Earlier we showed that thermal denaturation mimics LDL remodeling and fusion, and revealed kinetic origin of LDL stability. Here we report the first quantitative analysis of LDL thermal stability. Turbidity data show sigmoidal kinetics of LDL heat denaturation, which is unique among lipoproteins, suggesting that fusion is preceded by other structural changes. High activation energy of denaturation, E(a) = 100 ± 8 kcal/mol, indicates disruption of extensive packing interactions in LDL. Size-exclusion chromatography, nondenaturing gel electrophoresis, and negative-stain electron microscopy suggest that LDL dimerization is an early step in thermally induced fusion. Monoclonal antibody binding suggests possible involvement of apoB N-terminal domain in early stages of LDL fusion. LDL fusion accelerates at pH < 7, which may contribute to LDL retention in acidic atherosclerotic lesions. Fusion also accelerates upon increasing LDL concentration in near-physiologic range, which likely contributes to atherogenesis. Thermal stability of LDL decreases with increasing particle size, indicating that the pro-atherogenic properties of small dense LDL do not result from their enhanced fusion. Our work provides the first kinetic approach to measuring LDL stability and suggests that lipid-lowering therapies that reduce LDL concentration but increase the particle size may have opposite effects on LDL fusion.
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Affiliation(s)
- Mengxiao Lu
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118.
| | - Donald L Gantz
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
| | - Haya Herscovitz
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118
| | - Olga Gursky
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118.
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11
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Sneck M, Nguyen SD, Pihlajamaa T, Yohannes G, Riekkola ML, Milne R, Kovanen PT, Oörni K. Conformational changes of apoB-100 in SMase-modified LDL mediate formation of large aggregates at acidic pH. J Lipid Res 2012; 53:1832-9. [PMID: 22717515 DOI: 10.1194/jlr.m023218] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
During atherogenesis, the extracellular pH of atherosclerotic lesions decreases. Here, we examined the effect of low, but physiologically plausible pH on aggregation of modified LDL, one of the key processes in atherogenesis. LDL was treated with SMase, and aggregation of the SMase-treated LDL was followed at pH 5.5-7.5. The lower the pH, the more extensive was the aggregation of identically prelipolyzed LDL particles. At pH 5.5-6.0, the aggregates were much larger (size >1 µm) than those formed at neutral pH (100-200 nm). SMase treatment was found to lead to a dramatic decrease in α-helix and concomitant increase in β-sheet structures of apoB-100. Particle aggregation was caused by interactions between newly exposed segments of apoB-100. LDL-derived lipid microemulsions lacking apoB-100 failed to form large aggregates. SMase-induced LDL aggregation could be blocked by lowering the incubation temperature to 15°C, which also inhibited the changes in the conformation of apoB-100, by proteolytic degradation of apoB-100 after SMase-treatment, and by HDL particles. Taken together, sphingomyelin hydrolysis induces exposure of protease-sensitive sites of apoB-100, whose interactions govern subsequent particle aggregation. The supersized LDL aggregates may contribute to the retention of LDL lipids in acidic areas of atherosclerosis-susceptible sites in the arterial intima.
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Affiliation(s)
- Mia Sneck
- Wihuri Research Institute, Helsinki, Finland
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12
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Lipponen K, Liu Y, Stege PW, Öörni K, Kovanen PT, Riekkola ML. Capillary electrochromatography and quartz crystal microbalance, valuable techniques in the study of heparin–lipoprotein interactions. Anal Biochem 2012; 424:71-8. [DOI: 10.1016/j.ab.2012.02.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 02/09/2012] [Accepted: 02/10/2012] [Indexed: 11/16/2022]
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13
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Leppänen O, Ekstrand M, Bräsen JH, Levin M. Bioluminescence imaging of energy depletion in vascular pathology: patent ductus arteriosus and atherosclerosis. JOURNAL OF BIOPHOTONICS 2012; 5:336-344. [PMID: 22134948 DOI: 10.1002/jbio.201100096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 11/11/2011] [Accepted: 11/12/2011] [Indexed: 05/31/2023]
Abstract
The artery wall may develop energy depletion due to insufficient nutritional supply. However, until recently it has not been possible to validate this hypothesis because no available technology has allowed assessment of energy metabolism with sufficient spatial resolution. We use high resolution bioluminescence metabolic imaging to study energy metabolism in two mechanistically different vascular pathologies: patent ductus arteriosus and atherosclerosis. Physiological energy depletion in postnatally constricting ductus arteriosus promotes permanent closure. Insufficient ductus energy depletion, common in preterm infants, is associated with persistent patent ductus arteriosus, a condition with significantly increased morbidity and mortality. In contrast, in atherosclerosis, energy depletion in the macrophage-rich lesion core promotes cell death contributing to lesion instability and disease progression.
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Affiliation(s)
- Olli Leppänen
- Centre for R&D, Uppsala University/County Council of Gävleborg, Gävle, Sweden
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14
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Lähdesmäki K, Öörni K, Alanne-Kinnunen M, Jauhiainen M, Hurt-Camejo E, Kovanen PT. Acidity and lipolysis by group V secreted phospholipase A2 strongly increase the binding of apoB-100-containing lipoproteins to human aortic proteoglycans. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:257-67. [DOI: 10.1016/j.bbalip.2011.10.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 10/11/2011] [Accepted: 10/17/2011] [Indexed: 11/16/2022]
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15
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Singh SK, Thirumalai A, Hammond DJ, Pangburn MK, Mishra VK, Johnson DA, Rusiñol AE, Agrawal A. Exposing a hidden functional site of C-reactive protein by site-directed mutagenesis. J Biol Chem 2011; 287:3550-8. [PMID: 22158621 DOI: 10.1074/jbc.m111.310011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C-reactive protein (CRP) is a cyclic pentameric protein whose major binding specificity, at physiological pH, is for substances bearing exposed phosphocholine moieties. Another pentameric form of CRP, which exists at acidic pH, displays binding activity for oxidized LDL (ox-LDL). The ox-LDL-binding site in CRP, which is hidden at physiological pH, is exposed by acidic pH-induced structural changes in pentameric CRP. The aim of this study was to expose the hidden ox-LDL-binding site of CRP by site-directed mutagenesis and to generate a CRP mutant that can bind to ox-LDL without the requirement of acidic pH. Mutation of Glu(42), an amino acid that participates in intersubunit interactions in the CRP pentamer and is buried, to Gln resulted in a CRP mutant (E42Q) that showed significant binding activity for ox-LDL at physiological pH. For maximal binding to ox-LDL, E42Q CRP required a pH much less acidic than that required by wild-type CRP. At any given pH, E42Q CRP was more efficient than wild-type CRP in binding to ox-LDL. Like wild-type CRP, E42Q CRP remained pentameric at acidic pH. Also, E42Q CRP was more efficient than wild-type CRP in binding to several other deposited, conformationally altered proteins. The E42Q CRP mutant provides a tool to investigate the functions of CRP in defined animal models of inflammatory diseases including atherosclerosis because wild-type CRP requires acidic pH to bind to deposited, conformationally altered proteins, including ox-LDL, and available animal models may not have sufficient acidosis or other possible modifiers of the pentameric structure of CRP at the sites of inflammation.
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Affiliation(s)
- Sanjay K Singh
- Department of Pharmacology, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee 37614, USA
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16
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Plihtari R, Kovanen PT, Öörni K. Acidity increases the uptake of native LDL by human monocyte-derived macrophages. Atherosclerosis 2011; 217:401-6. [DOI: 10.1016/j.atherosclerosis.2011.04.013] [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: 06/17/2010] [Revised: 04/11/2011] [Accepted: 04/12/2011] [Indexed: 12/11/2022]
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17
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Hypoxia Stimulates Low-Density Lipoprotein Receptor–Related Protein-1 Expression Through Hypoxia-Inducible Factor-1α in Human Vascular Smooth Muscle Cells. Arterioscler Thromb Vasc Biol 2011; 31:1411-20. [DOI: 10.1161/atvbaha.111.225490] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Objective—
Hypoxia is considered a key factor in the progression of atherosclerotic lesions. Low-density lipoprotein receptor–related protein (LRP1) plays a pivotal role in the vasculature. The aim of this study was to investigate the effect of hypoxia on LRP1 expression and function in vascular smooth muscle cells (VSMC) and the role of hypoxia-inducible factor-α (HIF-1α).
Methods and Results—
Real-time polymerase chain reaction and Western blot analysis demonstrated that hypoxia (1% O
2
) time-dependently induced LRP1 mRNA (maximum levels at 1 to 2 hours) and protein expression (maximum levels at 12 to 24 hours). The delayed hypoxic upregulation of LRP1 protein versus mRNA may be explained by the long half-life of LRP1 protein. Luciferase assays demonstrated that hypoxia and HIF-1α overaccumulation induced LRP1 promoter activity and that 2 consensus hypoxia response element sites located at −1072/−1069 and −695/−692 participate in the induction. Chromatin immunoprecipitation showed the in vivo binding of HIF-1α to LRP1 promoter in hypoxic VSMC. Hypoxia effects on LRP1 protein expression were functionally translated into an increased cholesteryl ester (CE) accumulation from aggregated low-density lipoprotein (agLDL) uptake. The blockade of HIF-1α expression inhibited the upregulatory effect of hypoxia on LRP1 expression and agLDL-derived intracellular CE overaccumulation, suggesting that both LRP1 overexpression and CE overaccumulation in hypoxic vascular cells are dependent on HIF-1α. Immunohistochemical analysis showed the colocalization of LRP1 and HIF-1α in vascular cells of human advanced atherosclerotic plaques.
Conclusion—
Hypoxia upregulates LRP1 expression and agLDL-derived intracellular CE accumulation in human VSMC through HIF-1α induction.
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Chiba T, Chang MY, Wang S, Wight TN, McMillen TS, Oram JF, Vaisar T, Heinecke JW, De Beer FC, De Beer MC, Chait A. Serum amyloid A facilitates the binding of high-density lipoprotein from mice injected with lipopolysaccharide to vascular proteoglycans. Arterioscler Thromb Vasc Biol 2011; 31:1326-32. [PMID: 21474830 DOI: 10.1161/atvbaha.111.226159] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Levels of serum amyloid A (SAA), an acute-phase protein carried on high-density lipoprotein (HDL), increase in inflammatory states and are associated with increased risk of cardiovascular disease. HDL colocalizes with vascular proteoglycans in atherosclerotic lesions. However, its major apolipoprotein, apolipoprotein A-I, has no proteoglycan-binding domains. Therefore, we investigated whether SAA, which has proteoglycan-binding domains, plays a role in HDL retention by proteoglycans. METHODS AND RESULTS HDL from control mice and mice deficient in both SAA1.1 and SAA2.1 (SAA knockout mice) injected with bacterial lipopolysaccharide (LPS) was studied. SAA mRNA expression in the liver and plasma levels of SAA increased dramatically in C57BL/6 mice after LPS administration, although HDL cholesterol did not change. Fast protein liquid chromatography analysis showed most of the SAA to be in HDL. Mass spectrometric analysis indicated that HDL from LPS-injected control mice had high levels of SAA1.1/2.1 and reduced levels of apolipoprotein A-I. HDL from LPS-injected control mice demonstrated high-affinity binding to biglycan relative to normal mouse HDL. In contrast, HDL from LPS-injected SAA knockout mice showed very little binding to biglycan, consistent with SAA facilitating the binding of HDL to vascular proteoglycans. CONCLUSION SAA enrichment of HDL under inflammatory conditions plays an important role in the binding of HDL to vascular proteoglycans.
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Affiliation(s)
- Tsuyoshi Chiba
- Department of Medicine, University of Washington, Seattle, WA 98109, USA
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Asplund A, Fridén V, Stillemark-Billton P, Camejo G, Bondjers G. Macrophages exposed to hypoxia secrete proteoglycans for which LDL has higher affinity. Atherosclerosis 2011; 215:77-81. [DOI: 10.1016/j.atherosclerosis.2010.12.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Revised: 11/29/2010] [Accepted: 12/14/2010] [Indexed: 01/13/2023]
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Abstract
PURPOSE OF REVIEW It is important to address the factors involved in the progression of atherosclerosis because advanced atherosclerotic lesions are prone to rupture, leading to disability or death. Hypoxic areas are known to be present in human atherosclerotic lesions, and lesion progression is associated with the formation of lipid-loaded macrophages and increased local inflammation. Here we summarize the role of hypoxia in the development of advanced atherosclerotic lesions by promoting lipid accumulation, inflammation, ATP depletion, and angiogenesis. RECENT FINDINGS A recent study clearly demonstrated the presence of hypoxia in macrophage-rich regions of advanced human carotid atherosclerotic lesions. We showed that hypoxia increases the formation of lipid droplets in macrophages and promotes increased secretion of inflammatory mediators, and recent evidence indicates that lipid droplets may play a role in mediating the inflammatory response. Hypoxia also promotes lesion progression by exacerbating ATP depletion and lactate accumulation, and the presence of hypoxia in human carotid atherosclerotic lesions correlates with angiogenesis. SUMMARY Recent studies indicate that hypoxia may play a key role in the progression to advanced lesions by promoting lipid accumulation, increased inflammation, ATP depletion, and angiogenesis. Further understanding of the effects of hypoxia in atherosclerotic lesions could indicate potential therapeutic targets.
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Affiliation(s)
- Lillemor Mattsson Hultén
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, University of Gothenburg, Sweden.
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Choi JH, Do Y, Cheong C, Koh H, Boscardin SB, Oh YS, Bozzacco L, Trumpfheller C, Park CG, Steinman RM. Identification of antigen-presenting dendritic cells in mouse aorta and cardiac valves. ACTA ACUST UNITED AC 2009; 206:497-505. [PMID: 19221394 PMCID: PMC2699134 DOI: 10.1084/jem.20082129] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Presumptive dendritic cells (DCs) bearing the CD11c integrin and other markers have previously been identified in normal mouse and human aorta. We used CD11c promoter–enhanced yellow fluorescent protein (EYFP) transgenic mice to visualize aortic DCs and study their antigen-presenting capacity. Stellate EYFP+ cells were readily identified in the aorta and could be double labeled with antibodies to CD11c and antigen-presenting major histocompatability complex (MHC) II products. The DCs proved to be particularly abundant in the cardiac valves and aortic sinus. In all aortic locations, the CD11c+ cells localized to the subintimal space with occasional processes probing the vascular lumen. Aortic DCs expressed little CD40 but expressed low levels of CD1d, CD80, and CD86. In studies of antigen presentation, DCs selected on the basis of EYFP expression or binding of anti-CD11c antibody were as effective as DCs similarly selected from the spleen. In particular, the aortic DCs could cross-present two different protein antigens on MHC class I to CD8+ TCR transgenic T cells. In addition, after intravenous injection, aortic DCs could capture anti-CD11c antibody and cross-present ovalbumin to T cells. These results indicate that bona fide DCs are a constituent of the normal aorta and cardiac valves.
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Affiliation(s)
- Jae-Hoon Choi
- Laboratory of Cellular Physiology and Immunology, The Rockefeller University, New York, NY 10065, USA
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Devlin CM, Leventhal AR, Kuriakose G, Schuchman EH, Williams KJ, Tabas I. Acid sphingomyelinase promotes lipoprotein retention within early atheromata and accelerates lesion progression. Arterioscler Thromb Vasc Biol 2008; 28:1723-30. [PMID: 18669882 DOI: 10.1161/atvbaha.108.173344] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The key initial step in atherogenesis is the subendothelial retention of apolipoprotein B-containing lipoproteins. Acid sphingomyelinase (acid SMase), an enzyme present extracellularly within the arterial wall, strongly enhances lipoprotein retention in model systems in vitro, and retained lipoproteins in human plaques are enriched in ceramide, a product of SMase. We now sought to test a direct causative role for acid SMase in lipoprotein retention and atherogenesis in vivo. METHODS AND RESULTS We studied atherogenesis and lipoprotein retention in Asm(-/-) versus Asm(+/+) mice on the Apoe(-/-) and Ldlr(-/-) backgrounds. Asm(-/-);Apoe(-/-) mice had a approximately 40% to 50% decrease in early foam cell aortic root lesion area compared with Asm(+/+);Apoe(-/-) mice (P<0.05) despite no difference in plasma cholesterol or lipoproteins. To assay lipoprotein retention in vivo, the two groups of mice were injected with fluorescently labeled Apoe(-/-) lipoproteins. Early foam cell lesions of Asm(-/-);Apoe(-/-) mice showed a striking 87% reduction in lipoprotein trapping (P<0.0001) compared with Asm(+/+);Apoe(-/-) lesions. Similar results were obtained with Ldlr(-/-) mice, including an 81% reduction in lipoprotein retention within Asm(-/-);Ldlr(-/-) lesions compared with Asm(+/+);Ldlr(-/-) lesions (P<0.0005). CONCLUSIONS These findings support a causal role for acid SMase in lipoprotein retention and lesion progression and provides further support for the response-to-retention model of atherogenesis.
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Affiliation(s)
- Cecilia M Devlin
- Department of Medicine, Columbia University, New York, NY 10032, USA
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Oörni K, Kovanen PT. Proteolysis of low density lipoprotein particles by Porphyromonas gingivalis microorganisms: a novel biochemical link between periodontitis and cardiovascular diseases? J Intern Med 2008; 263:553-7. [PMID: 18410598 DOI: 10.1111/j.1365-2796.2008.01949.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Rodriguéz-Lee M, Bondjers G, Camejo G. Fatty acid-induced atherogenic changes in extracellular matrix proteoglycans. Curr Opin Lipidol 2007; 18:546-53. [PMID: 17885426 DOI: 10.1097/mol.0b013e3282ef534f] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [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 Nonesterified fatty acids change the expression and properties of the extracellular matrix proteoglycans of arterial and hepatic cells. We review how this may contribute to arterial disease in insulin resistance and type 2 diabetes. RECENT FINDINGS Elevated nonesterified fatty acids characterize the dyslipidemia of insulin resistance and type 2 diabetes. In hepatocytes high levels of fatty acids cause changes in proteoglycans leading to a matrix with decreased affinity for VLDL remnants. Furthermore, liver proteoglycans from insulin resistant hyperlipidemic Zucker rats showed alterations also associated with decreased remnant affinity. In arterial smooth muscle cells overexposure to fatty acids augmented expression of matrix proteoglycans for which LDL showed increased affinity. Fatty acids appeared to compromise insulin signaling by protein kinase C activation. The observed fatty acid-induced changes in matrix proteoglycans in liver and arteries can be an important component of the atherogenicity of the dyslipidemia of insulin resistance and type 2 diabetes. SUMMARY Overexposure to fatty acids can contribute to generate a remnant-rich dyslipidemia and to precondition the arterial intima for lipoprotein deposition via changes in expression of matrix proteoglycans. Normalizing fatty acid should be a key target in treatment of the atherogenic dyslipidemia of insulin resistance.
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Affiliation(s)
- Mariam Rodriguéz-Lee
- Wallenberg Laboratory for Cardiovascular Research, Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden
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Abstract
Our understanding of the relationship between the proatherogenic activities of arterial mast cells (MCs) and the development of atherosclerotic lesions is advancing. Atherosclerosis is a chronic inflammatory disease in which cholesterol and other lipids of circulating low-density lipoprotein (LDL) particles accumulate both extracellularly and intracellularly in the innermost layer of the arterial wall, the intima. One prerequisite for the proatherogenic activity of the LDL particles is their retention and proteolytic modification within the extracellular matrix of the intima. Experimental studies with activated chymase-secreting MCs have provided us fundamental insights into the molecular mechanisms of these processes. High-density lipoprotein (HDL) particles, again, remove cholesterol from the intracellular stores and carry it back to the circulation. MC chymase and tryptase actively degrade HDL and thus generate functionally defective particles that are unable to initiate cholesterol efflux from the arterial wall. In advanced atherosclerotic plaques, the accumulated lipids are separated from the circulation by a collagenous cap. By inducing apoptosis of endothelial cells (ECs), subendothelial MCs may induce detachment of ECs from the cap (plaque erosion). Moreover, MCs may weaken the cap if they disturb local collagen turnover by inducing apoptosis of the collagen-secreting smooth muscle cells or when they promote collagen degradation by activating matrix metalloproteinases. Plaques with a weak cap are vulnerable to rupture. The exposed subendothelial tissue at eroded and ruptured sites of plaques triggers local development of a platelet-rich thrombus. As regulators of the collagen-induced platelet activation and fibrin formation/fibrinolysis, the MCs may retard or accelerate the growth of the plaque-associated thrombus and ultimately participate in the wound-healing response of the injured plaque. We propose that by promoting cholesterol accumulation and plaque vulnerability and by locally regulating hemostasis, MCs in atherosclerotic lesions have the potential to contribute to the clinical outcomes of atherosclerosis, such as myocardial infarction and stroke.
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