101
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Abstract
In recent years the role of the atherosclerotic core in promoting plaque rupture has become well recognized. A new insight into core development is its origination early in atherogenesis, before formation of the fibrous plaque. The early core is associated with accumulation of vesicular lipid rich in free cholesterol. Later in core development, lipid deposits become more diverse. The weight of evidence points toward a direct extracellular process, probably lipoprotein aggregation and fusion, as the chief pathway of cholesteryl ester accumulation, although foam cell death may also contribute cholesteryl ester. The mechanism or mechanisms of formation of vesicular, cholesterol-rich deposits are unknown. Since the increase in free cholesterol is likely to have deleterious effects on cells bordering the core, the further elucidation of cellular and biochemical pathways leading to and responding to free cholesterol accumulation is of great importance. Complement activation and cellular stress responses are prominent in the vicinity of core lipids, but their pathogenetic roles remain to be established. Since the core appears so early in atherogenesis, these as well as other, yet to be determined cellular responses to core lipids, oxidized and unoxidized, could have a considerable effect on overall lesion development. Much remains to be learned about macrophage and smooth muscle responses, calcification, capillarization, and matrix protein alterations in the evolution of the core and surrounding arterial intima.
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Affiliation(s)
- J R Guyton
- Department of Medicine, Sarah W. Stedman Center for Nutritional Studies, Duke University Medical Center, Durham, NC 27710, USA
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102
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Review. Clin Chem Lab Med 1996. [DOI: 10.1515/cclm.1996.34.8.599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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103
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Affiliation(s)
- B Frei
- Whitaker Cardiovascular Institute, Boston University School of Medicine, Massachusetts 02118, USA
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104
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Bhakdi S, Dorweiler B, Kirchmann R, Torzewski J, Weise E, Tranum-Jensen J, Walev I, Wieland E. On the pathogenesis of atherosclerosis: enzymatic transformation of human low density lipoprotein to an atherogenic moiety. J Exp Med 1995; 182:1959-71. [PMID: 7500042 PMCID: PMC2192243 DOI: 10.1084/jem.182.6.1959] [Citation(s) in RCA: 155] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Combined treatment with trypsin, cholesterol esterase, and neuraminidase transforms LDL, but not HDL or VLDL, to particles with properties akin to those of lipid extracted from atherosclerotic lesions. Single or double enzyme modifications, or treatment with phospholipase C, or simple vortexing are ineffective. Triple enzyme treatment disrupts the ordered and uniform structure of LDL particles, and gives rise to the formation of inhomogeneous lipid droplets 10-200 nm in diameter with a pronounced net negative charge, but lacking significant amounts of oxidized lipid. Enzymatically modified LDL (E-LDL), but not oxidatively modified LDL (ox-LDL), is endowed with potent complement-activating capacity. As previously found for lipid isolated from atherosclerotic lesions, complement activation occurs to completion via the alternative pathway and is independent of antibody. E-LDL is rapidly taken up by human macrophages to an extent exceeding the uptake of acetylated LDL (ac-LDL) or oxidatively modified LDL. After 16 h, cholesteryl oleate ester formation induced by E-LDL (50 micrograms/ml cholesterol) was in the range of 6-10 nmol/mg protein compared with 3-6 nmol/mg induced by an equivalent amount of acetylated LDL. At this concentration, E-LDL was essentially devoid of direct cytotoxic effects. Competition experiments indicated that uptake of E-LDL was mediated in part by ox-LDL receptor(s). Thus, approximately 90% of 125I-ox-LDL degradation was inhibited by a 2-fold excess of unlabeled E-LDL. Uptake of 125I-LDL was not inhibited by E-LDL. We hypothesize that extracellular enzymatic modification may represent an important step linking subendothelial deposition of LDL to the initiation of atherosclerosis.
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Affiliation(s)
- S Bhakdi
- Institute of Medical Microbiology and Hygiene, University of Mainz, Germany
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105
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Kruth HS, Skarlatos SI, Lilly K, Chang J, Ifrim I. Sequestration of acetylated LDL and cholesterol crystals by human monocyte-derived macrophages. J Biophys Biochem Cytol 1995; 129:133-45. [PMID: 7698980 PMCID: PMC2120365 DOI: 10.1083/jcb.129.1.133] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Monocyte-derived macrophages accumulate and process cholesterol in atherosclerotic lesions. Because of the importance of this process, we examined the interaction of cholesterol crystals and acetylated low density lipoprotein (AcLDL) with human monocyte-macrophages in a combined chemical and morphological study. These two forms of cholesterol induced extensive compartmentalization of the macrophage cytoplasm. Unexpectedly, the compartments maintained a physical connection to the extracellular space as demonstrated with ruthenium red staining. The compartments formed through invagination of the top surface of the macrophage plasma membrane. Some cholesterol crystals and AcLDL were sequestered within these surface-connected compartments for up to five days in the case of the crystals and for one day in the case of AcLDL. Pulse-chase studies of fractionated macrophages indicated that [3H]cholesterol redistributed from the surface-connected compartments into lysosomes (where the cholesterol remained unesterified) and into lipid droplets (where the cholesterol was stored as cholesteryl ester). Intracellular uptake and esterification of cholesterol was blocked by cytochalasin D. However, once cholesterol was sequestered in the surface-connected compartments, subsequent esterification of the cholesterol could not be inhibited by cytochalasin D. Apolipoprotein E was localized within the surface-connected compartments by immunogold labeling suggesting a possible function for this protein in the processing of lipid taken up through the sequestration pathway. Removal of microcrystalline cholesterol from the medium resulted in release of most of the accumulated cholesterol microcrystals from the macrophages, as well as disappearance of the surface-connected compartments. Thus, sequestration is a novel endocytic mechanism in which endocytic compartments remain connected to the extracellular space. This differs from phagocytosis where endocytic vacuoles rapidly pinch off from the plasma membrane. Sequestration provides a means for macrophages to remove substances from the extracellular space and later release them.
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Affiliation(s)
- H S Kruth
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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106
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Morganelli PM, Rogers RA, Kitzmiller TJ, Bergeron A. Enhanced metabolism of LDL aggregates mediated by specific human monocyte IgG Fc receptors. J Lipid Res 1995. [DOI: 10.1016/s0022-2275(20)40057-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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107
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Guyton JR. The role of lipoproteins in atherogenesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 369:29-38. [PMID: 7598014 DOI: 10.1007/978-1-4615-1957-7_4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Some of the concepts presented in this review can be recapped as follows: LDL is found in a much higher concentration in arterial intima than in any other connective tissue in the body. One response of the intimal to high LDL levels appears to be a toxic response resulting in atherosclerotic core formation, with eventual breakdown and rupture of the intima causing arterial thrombosis. The core does not develop simply from foam cell necrosis, but from a complex interaction of tissue lipoproteins, cells, and extracellular matrix. Core development is an early event in atherosclerosis progression, since the features of early cores can be found in lesions resembling fatty streaks. Lipoprotein aggregation and fusion may be key processes in extracellular lipid deposition. This is obviously an incomplete summary of the role of lipoproteins in atherosclerosis, but it does point toward new significant areas of research interest. There are several particularly intriguing research questions at the present time. How do the cholesterol-rich extracellular lipid deposits develop? Lipoprotein aggregation and fusion is a partial explanation, but how do deposits with 60% free cholesterol develop when the lipoproteins contributing to them have only 20-30% free cholesterol? Multiple hypotheses have been posed, but little evidence for any one pathway is available. Nevertheless, the extremely high levels of free cholesterol in the atherosclerotic core are likely to have effects on cellular membrane functions. Another intriguing question: How is core development related to the overall process of fatty streak to fibrous plaque conversion? The fibrous plaque has two hallmarks, one of which is a rather massive proliferation of cells and fibrous tissue, and the other is the development of the core. Our recent evidence suggests that core development may occur first (Guyton and Klemp, 1993).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J R Guyton
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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108
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Shibuya K, Tajima M, Saitoh T, Yamate J, Nunoya T. Suppressive effect of beta-carotene on the development of pulmonary foam cells in rats with hyper beta-lipoproteinemia. Toxicol Pathol 1995; 23:47-55. [PMID: 7770699 DOI: 10.1177/019262339502300106] [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: 01/27/2023]
Abstract
The effect of beta-carotene (BC) on the development of pulmonary foam cells (PFCs) was studied in rats with diet-induced hyper beta-lipoproteinemia. Rats were fed a standard diet; a hyper-beta-lipoproteinemia diet (HB) consisting of the standard diet, 4% cholesterol, and 1% cholic acid; or the standard diet plus 0.1% BC; or the HB diet plus 0.1% BC diet (HBC). Rats in the HB and HBC groups developed hyper-beta-lipoproteinemia, but no significant differences were observed in serum levels of total cholesterol, phospholipid, and beta- lipoprotein (B-LP) between both groups. The percentages of foamy, lipid-ingested monocytes (FMs) to the number of blood monocytes (BMs), the number and size of lipid droplets in FMs, the percentages of PFCs to the number of alveolar macrophages from bronchopulmonary lavage fluid, and the score of PFC development in the lungs of rats in the HBC group were reduced compared to those of rats in the HB group. There were no differences in latex-phagocytotic activity of BMs among rats in the control, HB, BC, and HBC groups. BC suppressed the foamy transformation of BMs and development of PFCs deriving from the influx of FMs into the alveoli of hyper-beta-lipoproteinemic rats. Based on the present results, it is presumed that the antioxidative property of BC may prevent an oxidative modification of B-LP under the hyper-beta-lipoproteinemic condition, leading to a decrease in the uptake of oxidatively modified B-LP by BMs.
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Affiliation(s)
- K Shibuya
- Nippon Institute for Biological Science, Tokyo, Japan
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109
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Narayanaswami V, Kay CM, Oikawa K, Ryan RO. Structural and binding characteristics of the carboxyl terminal fragment of apolipophorin III from Manduca sexta. Biochemistry 1994; 33:13312-20. [PMID: 7947739 DOI: 10.1021/bi00249a018] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The molecular basis of the interaction of apolipophorin III (apoLp-III), an exchangeable apolipoprotein from hemolymph of the sphinx moth. Manduca sexta, with lipoprotein surfaces and phospholipids was studied by investigating the structural and binding properties of the C-terminal fragment of the native protein. A 4K peptide, corresponding to the terminal helical segment of the native protein, was generated by cyanogen bromide treatment, purified by gel filtration and reverse-phase HPLC, and characterized by N-terminal sequencing and amino acid and mass spectrometric analysis. Circular dichroism (CD) spectroscopy of the peptide in buffer indicated a predominantly unstructured state while addition of trifluoroethanol (TFE), a helix-inducing agent, resulted in an alpha-helical structure. Sedimentation equilibrium studies revealed that the 4K peptide was monomeric in buffer. The 4K peptide assumed an alpha-helical conformation in the presence of sodium dodecyl sulfate (SDS) and lysolecithin, but was unstructured in the presence of dimyristoylphosphatidylcholine, either when added to preformed vesicles or upon cosonication, indicating an ability to bind to detergent micelles but not to phospholipid bilayers. Unlike native apoLp-III, the 4K peptide did not confer protection against turbidity development to human low density lipoprotein upon incubation with phospholipase C, indicating an inability to interact with the surface of lipoproteins. Upon interaction with SDS micelles, both the 4K peptide and apoLp-III were resistant to urea-induced denaturation when compared to free apoLp-III, as evaluated by CD spectroscopy. The structural stability conferred upon interaction with detergents was similar for both the peptide and the native protein.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- V Narayanaswami
- Lipid & Lipoprotein Research Group, University of Alberta, Edmonton, Canada
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110
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Hamblin MR, Newman EL. Photosensitizer targeting in photodynamic therapy. II. Conjugates of haematoporphyrin with serum lipoproteins. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1994; 26:147-57. [PMID: 7815189 DOI: 10.1016/1011-1344(94)07036-9] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Conjugates between haematoporphyrin (HP) and human low-density lipoprotein (LDL), human high-density lipoprotein (HDL) and bovine HDL have been prepared, purified and characterized. HP-LDL is aggregated possibly via interparticle apoB protein cross-linking. HP-HDL human and bovine conjugates show different degrees of intraparticle apoA polypeptide cross-linking. Receptor-mediated endocytosis of HP-LDL by NIH 3T3 cells is inferred from the increased uptake observed when LDL receptors are upregulated. HP-LDL uptake into HT29 cells faces competition from unlabelled LDL, albeit at rather high doses. HP-HDL uptake is also inhibited by LDL, suggesting that both lipoprotein conjugates may have cell-surface binding sites in addition to the specific LDL (apoB) receptor. J774.2 macrophages avidly accumulate HP-LDL, retaining most of the fluorescence and some of the protein while degrading the remainder. Oxidized LDL species compete in these processes, with the major effect on protein degradation. Chloroquine has little effect on the fluorescence uptake but inhibits protein degradation (and hence enhances protein accumulation). HP-HDL is also avidly taken up by J774.2 cells, but in the case of the bovine material with a sigmoidal concentration dependence. This is consistent with prior aggregation before the particles can be endocytosed. P388.D1 cells, which appear to be less activated than the J774.2 line, take up less fluorescence and retain and degrade less protein, but still to higher extents than observed for non-phagocytic cells. We conclude that photosensitizer-lipoprotein conjugates can be taken up in large amounts by cells possessing scavenger receptors and/or phagocytic activity, and that this may be a means of targeting photodynamic therapy.
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MESH Headings
- 3T3 Cells
- Animals
- Binding, Competitive
- Biological Transport
- Cattle
- Cell Line
- Cell Survival/drug effects
- Drug Carriers
- Endocytosis
- Hematoporphyrins/metabolism
- Hematoporphyrins/toxicity
- Humans
- Kinetics
- Lipoproteins, HDL/blood
- Lipoproteins, HDL/isolation & purification
- Lipoproteins, HDL/metabolism
- Lipoproteins, HDL/toxicity
- Lipoproteins, LDL/blood
- Lipoproteins, LDL/isolation & purification
- Lipoproteins, LDL/metabolism
- Lipoproteins, LDL/toxicity
- Mice
- Photochemotherapy
- Photosensitizing Agents/metabolism
- Photosensitizing Agents/toxicity
- Receptors, LDL/metabolism
- Spectrometry, Fluorescence
- Tumor Cells, Cultured
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Affiliation(s)
- M R Hamblin
- Department of Surgery, University of Dundee, Ninewells Hospital, UK
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111
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Singh T, Liu H, Bradley R, Scraba D, Ryan R. Effect of phospholipase C and apolipophorin III on the structure and stability of lipophorin subspecies. J Lipid Res 1994. [DOI: 10.1016/s0022-2275(20)41154-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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112
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Tabas I, Zha X, Beatini N, Myers J, Maxfield F. The actin cytoskeleton is important for the stimulation of cholesterol esterification by atherogenic lipoproteins in macrophages. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31681-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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113
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Daugherty A, Dunn JL, Rateri DL, Heinecke JW. Myeloperoxidase, a catalyst for lipoprotein oxidation, is expressed in human atherosclerotic lesions. J Clin Invest 1994; 94:437-44. [PMID: 8040285 PMCID: PMC296328 DOI: 10.1172/jci117342] [Citation(s) in RCA: 967] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Oxidatively modified lipoproteins have been implicated in atherogenesis, but the mechanisms that promote oxidation in vivo have not been identified. Myeloperoxidase, a heme protein secreted by activated macrophages, generates reactive intermediates that oxidize lipoproteins in vitro. To explore the potential role of myeloperoxidase in the development of atherosclerosis, we determined whether the enzyme was present in surgically excised human vascular tissue. In detergent extracts of atherosclerotic arteries subjected to Western blotting, a rabbit polyclonal antibody monospecific for myeloperoxidase detected a 56-kD protein, the predicted molecular mass of the heavy subunit. Both the immunoreactive protein and authentic myeloperoxidase bound to a lectin-affinity column; after elution with methyl mannoside their apparent molecular masses were indistinguishable by nondenaturing size-exclusion chromatography. Peroxidase activity in detergent extracts of atherosclerotic lesions likewise bound to a lectin column and eluted with methyl mannoside. Moreover, eluted peroxidase generated the cytotoxic oxidant hypochlorous acid (HOCl), indicating that enzymatically active myeloperoxidase was present in lesions. Patterns of immunostaining of arterial tissue with antihuman myeloperoxidase antibodies were similar to those produced by an antimacrophage antibody, and were especially prominent in the shoulder region of transitional lesions. Intense foci of myeloperoxidase immunostaining also appeared adjacent to cholesterol clefts in lipid-rich regions of advanced atherosclerotic lesions. These findings identify myeloperoxidase as a component of human vascular lesions. Because this heme protein can generate reactive species that damage lipids and proteins, myeloperoxidase may contribute to atherogenesis by catalyzing oxidative reactions in the vascular wall.
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Affiliation(s)
- A Daugherty
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
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114
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Maor I, Aviram M. Oxidized low density lipoprotein leads to macrophage accumulation of unesterified cholesterol as a result of lysosomal trapping of the lipoprotein hydrolyzed cholesteryl ester. J Lipid Res 1994. [DOI: 10.1016/s0022-2275(20)39175-6] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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115
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Hamblin MR, Newman EL. On the mechanism of the tumour-localising effect in photodynamic therapy. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1994; 23:3-8. [PMID: 8021748 DOI: 10.1016/s1011-1344(94)80018-9] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The proposed mechanisms by which tumours concentrate photosensitisers are reviewed. Tumour-associated macrophages have been shown by others to accumulate up to nine times the level of porphyrins as do tumour cells. Macrophages also take up and degrade oxidised or otherwise modified low-density lipoprotein (LDL). We propose that the interaction of photosensitisers with LDL is an important factor, leading to accumulation in macrophages. Uptake into these cells via liposomes and high-density lipoprotein is also possible. There may be three separate mechanisms for tumour destruction in photodynamic therapy: (i) direct damage to tumour cells; (ii) damage to the endothelial cells of the tumour microvasculature; and (iii) macrophage-mediated immune infiltration of the tumour. The association of photosensitisers with lipoproteins may accentuate the latter two (endothelial cells can also accumulate modified lipoproteins). Accumulation in macrophages may also largely explain the high porphyrin retention observed in atheromatous plaques.
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Affiliation(s)
- M R Hamblin
- Department of Surgery, University of Dundee, Ninewells Hospital and Medical School, UK
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116
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Macrophage-mediated oxidation of extracellular low density lipoprotein requires an initial binding of the lipoprotein to its receptor. J Lipid Res 1994. [DOI: 10.1016/s0022-2275(20)41191-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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117
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Abstract
Xanthelasma palpebrarum is the most common type of xanthoma. On average, only half the patients with xanthelasma palpebrarum are hyperlipidemic. This review is an attempt to elucidate the pathogenesis and clinical significance of xanthelasma palpebrarum, especially its suggested role as a marker for increased risk for atherosclerosis. In hyperlipidemic patients with xanthelasma, the risk for atherosclerosis may be inferred from the associated lipoprotein and apolipoprotein abnormalities. The possible risk for atherosclerosis in normolipidemic patients with xanthelasma is more obscure because of the relative paucity of epidemiologic data and the conflicting results in some of the lipid studies. Several studies, however, showed decreased high-density lipoprotein cholesterol levels and other lipoprotein and apolipoprotein abnormalities that are associated with atherosclerosis. Therefore, on the basis of the present data, determining the plasma lipoprotein and apolipoprotein levels (especially those associated with increased risk for atherosclerosis) in each normolipidemic patient with xanthelasma appears to be justified.
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Affiliation(s)
- R Bergman
- Guinter Kahn MD Department of Dermatology, Rambam Medical Center, Haifa, Israel
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118
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Tangirala R, Jerome W, Jones N, Small DM, Johnson WJ, Glick JM, Mahlberg FH, Rothblat GH. Formation of cholesterol monohydrate crystals in macrophage-derived foam cells. J Lipid Res 1994. [DOI: 10.1016/s0022-2275(20)40131-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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119
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Cynshi O, Takashima Y, Suzuki T, Kawabe Y, Ohba Y, Kodama T. Characterization of aggregated low density lipoproteins induced by copper-catalyzed oxidation. J Atheroscler Thromb 1994; 1:87-97. [PMID: 9222875 DOI: 10.5551/jat1994.1.87] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Oxidation of low density lipoproteins (LDL) has been shown to lead to enhanced uptake by macrophages mediated by the scavenger receptor. In the present study, changes in LDL induced by copper-catalyzed oxidation were investigated using gel permeation chromatography (GPC), and the results were compared with several parameters of oxidized LDL (ox-LDL). When LDL at 200 micrograms/ml was oxidized with 10 microM Cu2+ at 37 degrees C for up to 24 hours, increases in thiobarbituric acid-reactive substances and electrophoretic mobility were first observed within 3 hours. An increase in fluorescence and a decrease in intact apolipoprotein B (apoB) were than observed in parallel with an increase in 125I-LDL degradation by macrophages after 6 hours. Finally, LDL aggregation separated by liquid chromatography was observed after 24 hours. The aggregated and monomeric fractions of ox-LDL were analyzed and the results compared with the monomeric fraction of native LDL. Both fractions of ox-LDL contained hardly any intact apoB and showed an intense fluorescence. The electrophoretic mobility increment of aggregated ox-LDL was almost half that of monomeric ox-LDL, yet the lysine residues of aggregated ox-LDL were more extensively decreased than those of monomeric ox-LDL. Degradation of aggregated ox-LDL by macrophages showed a slightly greater increase than that of monomeric ox-LDL. GPC analysis is a useful method to estimate the LDL aggregation, and these results provide a basis to investigate the formation of aggregated LDL.
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Affiliation(s)
- O Cynshi
- Fujigotemba Research Laboratories Chugai Pharmaceutical Co., LTD., Shizuoka, Japan
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120
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Bergman R, Aviram M, Shemer A, Oiknine Y, Vardi DA, Friedman-Birnbaum R. Enhanced low-density lipoprotein degradation and cholesterol synthesis in monocyte-derived macrophages of patients with adult xanthogranulomatosis. J Invest Dermatol 1993; 101:880-2. [PMID: 8245517 DOI: 10.1111/1523-1747.ep12371711] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Adult xanthogranulomatosis is an uncommon disorder in which dermal macrophages accumulate cholesterol intracellularly despite normal plasma cholesterol levels. In an attempt to elucidate an underlying biochemical abnormality in this disorder, we studied the rates of 125I-labeled low-density lipoprotein degradation, and intracellular cholesterol synthesis, in human monocyte-derived macrophages of three patients with adult xanthogranulomatosis. In all three patients, the rates of cellular 125I-low-density lipoprotein degradation and of cholesterol synthesis were 22-37% and 14-84% higher than those of the respective normal controls (p < 0.01). These findings suggest that in MDM of adult xanthogranulomatosis patients, the uptake and degradation of low-density lipoprotein-derived cholesterol and intracellular cholesterol biosynthesis are enhanced. Because dermal macrophages are derived from blood monocytes, it is possible that such an enhancement might play a role in the accumulation of cholesteryl esters in the macrophages that form the xanthogranulomatosis lesions.
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Affiliation(s)
- R Bergman
- Guinter Kahn M.D. Department of Dermatology, Rambam Medical Center, Haifa, Israel
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121
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Graham A, Hogg N, Kalyanaraman B, O'Leary V, Darley-Usmar V, Moncada S. Peroxynitrite modification of low-density lipoprotein leads to recognition by the macrophage scavenger receptor. FEBS Lett 1993; 330:181-5. [PMID: 8365489 DOI: 10.1016/0014-5793(93)80269-z] [Citation(s) in RCA: 224] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Peroxynitrite is an oxidant which could be formed in the vasculature by the reaction of superoxide with nitric oxide. It is capable of modifying amino acid residues and of initiating lipid peroxidation. In the present study we have shown that peroxynitrite converts low density lipoprotein to a form recognized by the macrophage scavenger receptor and that this process is associated with modification of the protein and lipid, and with the oxidation of alpha-tocopherol to alpha-tocopherol quinone.
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Affiliation(s)
- A Graham
- Wellcome Research Laboratories, Beckenham, Kent, UK
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122
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Tabas I, Li Y, Brocia R, Xu S, Swenson T, Williams K. Lipoprotein lipase and sphingomyelinase synergistically enhance the association of atherogenic lipoproteins with smooth muscle cells and extracellular matrix. A possible mechanism for low density lipoprotein and lipoprotein(a) retention and macrophage foam cell formation. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(20)80745-5] [Citation(s) in RCA: 137] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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123
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Sparrow CP, Olszewski J. Cellular oxidation of low density lipoprotein is caused by thiol production in media containing transition metal ions. J Lipid Res 1993. [DOI: 10.1016/s0022-2275(20)37709-9] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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124
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Aviram M, Maor I. Phospholipase D-modified low density lipoprotein is taken up by macrophages at increased rate. A possible role for phosphatidic acid. J Clin Invest 1993; 91:1942-52. [PMID: 8486764 PMCID: PMC288189 DOI: 10.1172/jci116413] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Macrophage uptake of modified forms of LDL leads to cellular cholesterol accumulation. Upon incubation of LDL with phospholipase D (PLase D), a time- and enzyme dose-dependent production of phosphatidic acid (PA), paralleled by a rapid reduction in LDL phosphatidyl choline content (up to 65% within 15 min of incubation) was noted. No lipid peroxidation could be found in PLase D-modified LDL. Upon in vitro incubation of PLase D-LDL with copper ions, however, this modified LDL was substantially oxidized. The addition of 100 micrograms PA/ml to native LDL for the period of its in vitro oxidation resulted in a 63% elevation in the lipoprotein peroxides content. Incubation of PLase D-LDL with J-774A.1 macrophage-like cell line resulted in an increase in its cellular binding and degradation (up to 91 and 110%, respectively) in comparison with native LDL (via the LDL receptor). When PA was added to LDL before its incubation with the macrophages, a PA dose-dependent elevation in the cellular uptake of LDL (by up to twofold) was noted in comparison with LDL that was incubated without PA, suggesting that PA production in PLase D-LDL may be involved in the increased cellular uptake of PLase D-LDL. PLase D activity towards LDL was demonstrated in J-774A.1 macrophages. Human plasma was also shown to possess PLase D activity. Thus, PLase D modification of LDL may take place under certain pathological conditions and PLase D-LDL interaction with arterial wall macrophages can potentially lead to foam cell formation.
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Affiliation(s)
- M Aviram
- Lipid Research Laboratory, Rambam Medical Center, Haifa, Israel
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125
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Tangirala R, Mahlberg F, Glick J, Jerome W, Rothblat G. Lysosomal accumulation of unesterified cholesterol in model macrophage foam cells. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)98399-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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126
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Affiliation(s)
- D Steinberg
- Department of Medicine, University of California San Diego, La Jolla
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127
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Hazell LJ, Stocker R. Oxidation of low-density lipoprotein with hypochlorite causes transformation of the lipoprotein into a high-uptake form for macrophages. Biochem J 1993; 290 ( Pt 1):165-72. [PMID: 8439285 PMCID: PMC1132397 DOI: 10.1042/bj2900165] [Citation(s) in RCA: 239] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Oxidation of low-density lipoprotein (LDL) lipid is thought to represent the initial step in a series of oxidative modification reactions that ultimately transform this lipoprotein into an atherogenic high-uptake form that can cause lipid accumulation in cells. We have studied the effects of hypochlorite, a powerful oxidant released by activated monocytes and neutrophils, on isolated LDL. Exposure of LDL to reagent hypochlorite (NaOCl) at 4 degrees C resulted in immediate and preferential oxidation of amino acid residues of apoprotein B-100, the single protein associated with LDL. Neither lipoprotein lipid nor LDL-associated antioxidants, except ubiquinol-10, represented major targets for this oxidant. Even when high concentrations of NaOCl were used, only low levels of lipid hydroperoxides could be detected with the highly sensitive h.p.l.c. post-column chemiluminescence detection method. Lysine residues of apoprotein B-100 quantitatively represented the major target, scavenging some 68% of the NaOCl added, with tryptophan and cysteine together accounting for an additional 10% of the oxidant. Concomitant with the loss of LDL's amino groups, chloramines were formed and the anionic surface charge of the lipoprotein particle increased, indicated by a 3-4-fold increase in electrophoretic mobility above that of native LDL on agarose gels. While both these changes could be initially reversed by physiological reductants such as ascorbic acid and methionine, incubation of the NaOCl-modified LDL at 37 degrees C resulted in increasing resistance of the modified lysine residues against reductive reversal. Exposure of mouse peritoneal macrophages to NaOCl-oxidized LDL resulted in increased intracellular concentrations of cholesterol and cholesteryl esters. These findings suggest that lipid-soluble antioxidants associated with LDL do not efficiently protect the lipoprotein against oxidative damage mediated by hypochlorite, and that extensive lipid oxidation is not a necessary requirement for oxidative LDL modification that leads to a high-uptake form of the lipoprotein.
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Affiliation(s)
- L J Hazell
- Heart Research Institute, Biochemistry Group, Camperdown, N.S.W., Australia
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128
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Liu H, Scraba DG, Ryan RO. Prevention of phospholipase-C induced aggregation of low density lipoprotein by amphipathic apolipoproteins. FEBS Lett 1993; 316:27-33. [PMID: 8422936 DOI: 10.1016/0014-5793(93)81730-n] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Phospholipase C (PL-C) digestion of human low density lipoprotein (LDL) results in hydrolytic cleavage of the phosphocholine head group of phosphatidylcholine, thereby generating diacylglycerol. Loss of amphiphillic surface lipids and/or accumulation of diacylglycerol causes LDL samples to develop turbidity. Examination of PL-C treated LDL by electron microscopy revealed a progressive aggregation of LDL as a function of phosphatidylcholine hydrolysis: fused particles, clusters, and multiple stacked aggregates were observed. Lipid analysis of untreated and aggregated LDL confirmed that the phosphatidylcholine content of the latter had decreased with a corresponding increase in diacylglycerol. It is likely that phospholipolysis created hydrophobic gaps within the surface monolayer of LDL, thereby inducing LDL fusion and aggregation. When amphipathic alpha-helix-containing apolipoproteins, such as human apoA-I or Manduca sexta apolipophorin III (apoLp-III) were present, PL-C treated LDL did not aggregate. Compositional analysis of apolipoprotein-containing PL-C LDL showed that phospholipolysis was not affected by the presence of apolipoproteins. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of lipoproteins re-isolated following incubation with PL-C revealed an association of apoA-I or apoLp-III with PL-C digested LDL. Electron microscopy showed no major morphological differences between native LDL and apoprotein stabilized PL-C treated LDL and the average particle diameter of apoA-I stabilized PL-C LDL was 22.5 +/- 2.2 nm versus 22.8 +/- 1.6 nm for control LDL. Incubation of tritium-labeled apoLp-III with LDL and PL-C demonstrated that association of apoLp-III with PL-C LDL correlated with the extent of phospholipid hydrolysis, the apolipoproteins apparently being recruited to compensate for the increased hydrophobic surface created by conversion of phosphatidylcholine into diacylglycerol. The results suggest that transient association of amphipathic apolipoproteins with damaged or unstable LDL may provide a mechanism to obviate formation of atherogenic LDL aggregates in vivo.
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Affiliation(s)
- H Liu
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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129
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Simionescu N, Sima A, Dobrian A, Tirziu D, Simionescu M. Pathobiochemical changes of the arterial wall at the inception of atherosclerosis. CURRENT TOPICS IN PATHOLOGY. ERGEBNISSE DER PATHOLOGIE 1993; 87:1-45. [PMID: 8125021 DOI: 10.1007/978-3-642-76849-1_1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- N Simionescu
- Institute of Cellular Biology and Pathology, Bucharest, Romania
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130
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Khoo JC, Miller E, Pio F, Steinberg D, Witztum JL. Monoclonal antibodies against LDL further enhance macrophage uptake of LDL aggregates. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1992; 12:1258-66. [PMID: 1420085 DOI: 10.1161/01.atv.12.11.1258] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Self-aggregates of low density lipoprotein (LDL) are taken up and degraded more rapidly by macrophages than is native LDL. That enhanced uptake is attributable in part to phagocytosis via the LDL receptor pathway. However, arterial macrophages appear to express little LDL receptor activity. The present studies demonstrate an alternative mechanism by which LDL aggregates could contribute to foam cell formation. This could occur by the formation of large immune complexes that are taken up by macrophages via the Fc receptor. When immune complexes were formed with native, soluble LDL and MB47, a monoclonal antibody specific to the apoprotein B domain recognized by the LDL receptor, the subsequent uptake and degradation of the LDL by macrophages were inhibited 50-80% compared with native LDL alone. In contrast, when aggregated LDL was bound to MB47 at a similar molar ratio, the subsequent degradation of the insoluble immune complexes was two- to fivefold greater than that of aggregated LDL alone. The enhanced uptake was abolished when Fab or F(ab')2 fragments of MB47 were substituted for the intact antibody, indicating that the increased uptake was via the Fc receptor pathway. Furthermore, the uptake of the immune complexes of aggregated LDL was reduced by competition for the Fc receptor with heat-aggregated immunoglobulin. There was also an increase in the rate of cellular cholesterol esterification and an increase in macrophage cholesteryl ester mass. Since aggregates of LDL as well as autoantibodies against modified LDL have been demonstrated in atherosclerotic lesions, it is possible that immune complexes of aggregates of modified LDL may be generated in the intima.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J C Khoo
- Department of Medicine, University of California, San Diego, La Jolla 92093-0682
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131
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Rumsey SC, Obunike JC, Arad Y, Deckelbaum RJ, Goldberg IJ. Lipoprotein lipase-mediated uptake and degradation of low density lipoproteins by fibroblasts and macrophages. J Clin Invest 1992; 90:1504-12. [PMID: 1401083 PMCID: PMC443197 DOI: 10.1172/jci116018] [Citation(s) in RCA: 153] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Lipoprotein lipase (LPL), the rate limiting enzyme for hydrolysis of lipoprotein triglyceride, also mediates nonenzymatic interactions between lipoproteins and heparan sulfate proteoglycans. To determine whether cell surface LPL increases LDL binding to cells, bovine milk LPL was added to upregulated and nonupregulated human fibroblasts along with media containing LDL. LDL binding to cells was increased 2-10-fold, in a dose-dependent manner, by the addition of 0.5-10 micrograms/ml of LPL. The amount of LDL bound to the cells in the presence of LPL far exceeded the capacity for LDL binding via the LDL receptor. Treatment of fibroblasts with heparinase and heparitinase resulted in a 64% decrease in LPL-mediated LDL binding. Compared to studies performed without LPL, more LDL was internalized and degraded in the presence of LPL, but the time course was slower than that of classical lipoprotein receptor mediated pathways. In LDL receptor negative fibroblasts, LPL increased surface bound LDL > 140-fold, intracellular LDL > 40-fold, and LDL degradation > 6-fold. These effects were almost completely inhibited by heparin and anti-LPL monoclonal antibody. LPL also increased the binding and uptake by fibroblasts of apolipoprotein-free triglyceride emulsions; binding was increased > 8-fold and cellular uptake was increased > 40-fold with LPL. LPL increased LDL binding to THP-1 monocytes, and increased LDL uptake (4.5-fold) and LDL degradation (2.5-fold) by THP-1 macrophages. In the absence of added LPL, heparin and anti-LPL monoclonal antibodies decreased LDL degradation by > 40%, and triglyceride emulsion uptake by > 50%, suggesting that endogenously produced LPL mediated lipid particle uptake and degradation. We conclude that LPL increases lipid and lipoprotein uptake by cells via a pathway not involving the LDL receptor. This pathway may be important for lipid accumulation in LPL synthesizing cells.
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Affiliation(s)
- S C Rumsey
- Department of Pediatrics, Columbia University College of Physicians and Surgeons, New York 10032
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132
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Keidar S, Brook GJ, Rosenblat M, Fuhrman B, Dankner G, Aviram M. Involvement of the macrophage low density lipoprotein receptor-binding domains in the uptake of oxidized low density lipoprotein. ACTA ACUST UNITED AC 1992; 12:484-93. [PMID: 1373074 DOI: 10.1161/01.atv.12.4.484] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Macrophages, unlike most other cells, possess both low density lipoprotein (LDL) and scavenger receptors. The scavenger receptor has been shown to mediate the uptake of oxidized LDL (ox-LDL), which ultimately leads to cholesterol loading of the macrophages. The present study was undertaken to define epitopes on ox-LDL that are important for lipoprotein binding to macrophages and to ascertain whether ox-LDL can bind to the LDL receptor. Monoclonal antibodies (Mabs) directed against several epitopes along the apolipoprotein B-100 (apo B-100) molecule were used. LDL (300 micrograms/ml) was oxidized by incubation with 10 microM CuSO4 for 24 hours. Ox-LDL, as opposed to acetylated LDL (ac-LDL), reacted with Mabs directed against the LDL receptor-binding domains (Mabs B1B6 and B1B3). Similarly, uptake of ox-LDL but not ac-LDL by a murine J774 macrophage-like cell line was inhibited by as much as 40% after using Mab B1B6. The anti-LDL receptor antibody IgG-C7 also inhibited 125I-ox-LDL uptake by macrophages by 60%. Chromatography on heparin-Sepharose columns of LDL that was partially oxidized for only 3 hours resulted in two fractions: an unbound fraction with characteristics similar to those of ox-LDL and a bound fraction similar to native LDL. Macrophage degradation of the unbound fraction was inhibited by Mab IgG-C7 and Mab B1B6, which are directed toward the LDL receptor and the LDL receptor-binding domains on apo B-100, respectively. When incubated with three types of macrophages, J774 macrophage cells, mouse peritoneal macrophages, and human monocyte-derived macrophages, excess amounts of unlabeled ox-LDL, like native LDL but unlike ac-LDL, substantially suppressed the uptake and degradation of 125I-labeled LDL. Similar studies with fibroblasts, however, revealed that unlabeled LDL but not unlabeled ox-LDL or ac-LDL competed with 125I-LDL for cellular uptake and degradation. Mab directed against epitopes on the amino terminus domain of apo B-100 (C14) demonstrates a similar immunoreactivity with ox-LDL and native LDL but a much lower reactivity with ac-LDL. Mab C14 inhibited macrophage degradation of ox-LDL by 34% but had no inhibitory effect on the uptake of native LDL or ac-LDL. Thus, the ac-LDL and LDL receptor-binding domains as well as a unique epitope on the amino terminus of apo B-100 may be involved in macrophage binding of ox-LDL.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- S Keidar
- Lipid Research Laboratory, Rambam Medical Center, Haifa, Israel
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133
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Saxena U, Klein MG, Vanni TM, Goldberg IJ. Lipoprotein lipase increases low density lipoprotein retention by subendothelial cell matrix. J Clin Invest 1992; 89:373-80. [PMID: 1737833 PMCID: PMC442862 DOI: 10.1172/jci115595] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Lipoprotein lipase (LPL), the rate-limiting enzyme for hydrolysis of plasma lipoprotein triglycerides, is a normal constituent of the arterial wall. We explored whether LPL affects (a) lipoprotein transport across bovine aortic endothelial cells or (b) lipoprotein binding to subendothelial cell matrix (retention). When bovine milk LPL was added to endothelial cell monolayers before addition of 125I-labeled LDL, LDL transport across the monolayers was unchanged; but, at all concentrations of LDL tested (1-100 micrograms), LDL retention by the monolayers increased more than fourfold. 125I-labeled LDL binding to extracellular matrix increased when LPL was added directly to the matrix or was added to the basolateral side of the endothelial cell monolayers. Increased LDL binding required the presence of LPL and was not associated with LDL aggregation. LPL also increased VLDL, but not HDL, retention. Monoclonal anti-LPL IgG decreased both VLDL and LDL retention in the presence of LPL. Lipoprotein transport across the monolayers increased during hydrolysis of VLDL triglyceride (TG). In the presence of LPL and VLDL, VLDL transport across the monolayers increased 18% and LDL transport increased 37%. High molar concentrations of oleic acid to bovine serum albumin (3:1) in the medium increased VLDL transport approximately 30%. LDL transport increased 42% when oleic acid was added to the media. Therefore, LPL primarily increased retention of LDL and VLDL. A less remarkable increase in lipoprotein transport was found during hydrolysis of TG-containing lipoproteins. We hypothesize that LPL-mediated VLDL and LDL retention within the arterial wall potentiates conversion of these lipoproteins to more atherogenic forms.
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Affiliation(s)
- U Saxena
- Department of Medicine, Columbia University, College of Physicians and Surgeons, New York 10032
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134
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Lindstedt KA, Kokkonen JO, Kovanen PT. Soluble heparin proteoglycans released from stimulated mast cells induce uptake of low density lipoproteins by macrophages via scavenger receptor-mediated phagocytosis. J Lipid Res 1992. [DOI: 10.1016/s0022-2275(20)41884-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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135
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Aviram M. Low density lipoprotein modification by cholesterol oxidase induces enhanced uptake and cholesterol accumulation in cells. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)48482-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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136
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Xu X, Tabas I. Sphingomyelinase enhances low density lipoprotein uptake and ability to induce cholesteryl ester accumulation in macrophages. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54306-4] [Citation(s) in RCA: 131] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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137
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Nievelstein PF, Fogelman AM, Mottino G, Frank JS. Lipid accumulation in rabbit aortic intima 2 hours after bolus infusion of low density lipoprotein. A deep-etch and immunolocalization study of ultrarapidly frozen tissue. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1991; 11:1795-805. [PMID: 1931881 DOI: 10.1161/01.atv.11.6.1795] [Citation(s) in RCA: 129] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The intima from aortas of normal New Zealand White rabbits was studied 2 hours after infusion of 320 mg human low density lipoprotein (LDL), resulting in a plasma concentration of at least five times and maximally 20 times the values found in normal rabbit serum. The following techniques were used: 1) ultrarapid freezing without chemical fixation, followed by freeze-etching; 2) immunofluorescence microscopy; and 3) postembedding immunogold-labeling electron microscopy. In the latter two methods MB47, a murine monoclonal antibody against human apolipoprotein B, was used as the primary antibody. Control rabbits were infused with the same volume of buffer only. Rotary-shadowed replicas of samples from the LDL-injected rabbits showed the deposition of lipidlike particles in the subendothelial-intimal space that were the size of the injected LDL (23 nm). In focal areas of the intima, groups of 23-nm-sized lipidlike particles and larger lipidlike structures were found enmeshed in the extracellular matrix. Control replicas were essentially free of lipid deposition. Immunofluorescence microscopy of frozen aortic cross sections showed an overall increase in apolipoprotein B in the intima of the LDL-injected rabbits. The presence of apolipoprotein B in the intima was also confirmed by immunoelectron microscopy. These in vivo results show that clustering of LDL-sized particles occurs in the intima within 2 hours of excessive LDL uptake. It also demonstrates the interaction of these LDL-sized particles with the filaments of the extracellular matrix. The clustering of the LDL-sized particles supports the possibility that LDL self-aggregation may occur in vivo and that components of the extracellular matrix are involved in this process.
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138
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Heinecke JW, Suits AG, Aviram M, Chait A. Phagocytosis of lipase-aggregated low density lipoprotein promotes macrophage foam cell formation. Sequential morphological and biochemical events. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1991; 11:1643-51. [PMID: 1657129 DOI: 10.1161/01.atv.11.6.1643] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Macrophages internalize aggregated low density lipoprotein (LDL) by LDL receptor-dependent phagocytosis. To investigate this model of foam cell formation, we have used human and mouse macrophages to characterize biochemically and morphologically the fate of ingested phospholipase C-modified low density lipoprotein (PLC-LDL). When LDL was digested with phospholipase C, it lost phospholipid and aggregated. Human monocyte-derived macrophages rapidly ingested and degraded 125I-PLC-LDL. The degraded PLC-LDL released free cholesterol, measured either as free sterol mass or by the stimulation of [14C]oleate incorporation into cellular cholesteryl ester. Esterification was blocked by chloroquine, a weak base that inhibits lysosomal degradation. Macrophages exposed to PLC-LDL exhibited a 30-fold to a 50-fold increase in esterified sterol: by light microscopy, cytoplasmic inclusions were abundant. The inclusions were stained with oil red O, indicating that they were neutral lipid droplets. By electron microscopy, mouse peritoneal macrophages incubated with PLC-LDL contained numerous membrane-bounded vacuoles and cytoplasmic inclusions that were not surrounded by a limiting membrane. Pulse-chase experiments demonstrated that vacuoles filled with particulate material appeared first. Subsequently, the macrophages exhibited vacuoles containing multivesicular bodies. Last, inclusions that were homogeneously electron-dense and that lacked a tripartite membrane accumulated in the cytoplasm of the cells. These results are consonant with the following model of foam cell formation. Cultured macrophages rapidly ingest PLC-LDL that is initially localized in phagosomes. The aggregated lipoprotein subsequently is digested in secondary lysosomes, thus releasing free cholesterol that is reesterified, forming cytoplasmic cholesteryl ester droplets lacking a tripartite membrane.
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Affiliation(s)
- J W Heinecke
- Department of Medicine, University of Washington, Seattle
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139
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Daugherty A, Rateri D. Failure of the intracellular itinerary of beta very low density lipoproteins to augment cholesterol esterification in macrophages from Watanabe heritable hyperlipidemic rabbits. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)47369-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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140
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Inoue I, Ishibashi S, Harada K, Shimano H, Gotoda T, Shimada M, Takahashi K, Ishii J, Yazaki Y, Yamada N. Overexpression of low density lipoprotein receptor on Chinese hamster ovary cells generates foam cells. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1991; 11:1310-4. [PMID: 1911717 DOI: 10.1161/01.atv.11.5.1310] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The atherosclerotic lesion is characterized by the presence of cholesterol-loaded foam cells. Chinese hamster ovary (CHO) cells do not normally store cholesteryl esters because low density lipoprotein (LDL) receptors are suppressed by exposure of these cells to LDL cholesterol. We transfected LDL receptor cDNA linked to the simian virus 40 early promoter into CHO cells (CHO 29) and found that LDL receptor binding in these cells was not suppressed by an excess amount of LDL cholesterol, indicating no regulation of the LDL receptor in CHO 29 cells. Furthermore, CHO 29 cells showed a high activity of LDL uptake and intracellular accumulation of cholesteryl esters. Light-microscopic examination demonstrated the resulting formation of foam cells in CHO 29 cells in the presence of 5 micrograms LDL/ml. These results demonstrated that foam cell changes in atherosclerotic lesions can be reproduced in CHO cells, whose LDL receptor activity is overexpressed, through the mechanism of LDL receptor-mediated endocytosis of native LDL.
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Affiliation(s)
- I Inoue
- Third Department of Internal Medicine, University of Tokyo, Hongo, Japan
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141
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Parthasarathy S. Novel atherogenic, oxidative modification of low-density lipoprotein. DIABETES/METABOLISM REVIEWS 1991; 7:163-71. [PMID: 1817001 DOI: 10.1002/dmr.5610070305] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- S Parthasarathy
- Department of Medicine, University of California, San Diego, La Jolla 92093
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142
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Oxidized low density lipoprotein is resistant to cathepsins and accumulates within macrophages. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98717-x] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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143
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Aviram M, Keidar S, Rosenblat M, Brook G. Reduced uptake of cholesterol esterase-modified low density lipoprotein by macrophages. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98994-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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144
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Guyton JR, Klemp KF, Mims MP. Altered ultrastructural morphology of self-aggregated low density lipoproteins: coalescence of lipid domains forming droplets and vesicles. J Lipid Res 1991. [DOI: 10.1016/s0022-2275(20)41992-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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145
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Affiliation(s)
- S Ylă-Herttuala
- Department of Medicine, University of California, San Diego, La Jolla 92093-0613
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146
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Kovanen PT, Kokkonen JO. Modification of low density lipoproteins by secretory granules of rat serosal mast cells. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(20)64340-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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147
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Modified low density lipoprotein isolated from atherosclerotic lesions does not cause lipid accumulation in aortic smooth muscle cells. J Lipid Res 1991. [DOI: 10.1016/s0022-2275(20)42250-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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148
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Aviram M. Effect of Lipoproteins and Platelets on Macrophage Cholesterol Metabolism. BLOOD CELL BIOCHEMISTRY 1991. [DOI: 10.1007/978-1-4757-9531-8_7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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149
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Rosenfeld ME, Khoo JC, Miller E, Parthasarathy S, Palinski W, Witztum JL. Macrophage-derived foam cells freshly isolated from rabbit atherosclerotic lesions degrade modified lipoproteins, promote oxidation of low-density lipoproteins, and contain oxidation-specific lipid-protein adducts. J Clin Invest 1991; 87:90-9. [PMID: 1985115 PMCID: PMC294999 DOI: 10.1172/jci115006] [Citation(s) in RCA: 179] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Pure macrophage-derived foam cells (MFC) were isolated from the aortas of rabbits made atherosclerotic by balloon deendothelialization followed by diet-induced hypercholesterolemia. The MFC were isolated under sterile conditions using an enzymatic digestion procedure and discontinuous density gradient centrifugation. The purity of the MFC preparations was verified immunocytochemically with the macrophage specific monoclonal antibody RAM-11. MFC plated in medium containing 0.5% FCS for 24 h contained approximately 600 micrograms cholesterol per mg cell protein, 80% of which was esterified cholesterol. The MFC specifically degraded low density lipoprotein (LDL), acetyl-LDL, copper oxidized LDL, and beta-very low density lipoprotein (beta-VLDL) at rates comparable to mouse peritoneal macrophages (MPM) in 5-h assays. MFC within sections of the atherosclerotic lesions from the ballooned rabbits as well as the MFC isolated from the same lesions in the presence of antioxidants, exhibited positive immunoreactivity with polyclonal guinea pig antisera and mouse monoclonal antibodies directed against malondialdehyde-LDL, and 4-hydroxynonal-LDL. The MFC also exhibited the capacity to induce the oxidation of LDL at rates comparable to those exhibited by MPM and rabbit aortic endothelial cells. These data provide direct evidence that arterial wall macrophages express modified LDL receptors in vivo, contain epitopes found in oxidized-LDL and are capable of oxidizing LDL even when maximally loaded with cholesterol.
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Affiliation(s)
- M E Rosenfeld
- Department of Medicine, University of California San Diego, La Jolla 92093-0613
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Bergman R, Aviram M, Bitterman-Deutsch O, Oiknine Y, Shemer A, Srebnik A, Brook JG, Friedman-Birnbaum R. Neutral lipid storage disease with ichthyosis: serum apolipoprotein levels and cholesterol metabolism in monocyte-derived macrophages. J Inherit Metab Dis 1991; 14:241-6. [PMID: 1909403 DOI: 10.1007/bf01800597] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/26/2023]
Abstract
Neutral lipid storage disease with ichthyosis (NLSDI) is an inherited metabolic disorder characterized by accumulation of neutral lipids, in a wide variety of cells, by a still unknown mechanism. Previous studies have shown normal cholesterol content in NLSDI granulocytes, fibroblasts and skin cells. Monocyte-derived macrophages possess an additional pathway of cholesterol uptake, which is not shared by these cells and which is not regulated by intracellular cholesterol levels. This pathway is thought to play a rôle in the process of atherosclerosis. Three NLSDI patients were studied. The serum levels of triglycerides, cholesterol, high-density lipoprotein cholesterol, and apolipoproteins A-I and B were within normal limits in all three patients. The intracellular levels of free and esterified cholesterol were measured in the monocyte-derived macrophages of one patient and found to be normal, while the triglyceride concentrations were twice as high as normal. The cholesterol esterification rates, which serve as a sensitive indicator of intracellular changes in cholesteryl ester levels, were normal in the monocyte-derived macrophages of all three patients. These findings provide further evidence that cholesterol metabolism is not disturbed in NLSDI, and it may be inferred that in this respect these patients are not at increased risk for atherosclerosis.
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Affiliation(s)
- R Bergman
- Department of Dermatology, Rambam Medical Centre, Haifa, Israel
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