Binding and uptake of chylomicron remnants by primary and THP-1 human monocyte-derived macrophages: determination of binding proteins

2001 ◽  
Vol 101 (2) ◽  
pp. 111-119 ◽  
Author(s):  
Caryn L. ELSEGOOD ◽  
Sebely PAL ◽  
Paul D. ROACH ◽  
John C. L. MAMO
Keyword(s):  
Binding Site ◽  
Foam Cell ◽  
Ldl Receptor ◽  
Human Monocyte ◽  
Foam Cell Formation ◽  
Chylomicron Remnant ◽  
Surface Binding ◽  
Monocytic Cell ◽  
Monocytic Cell Line ◽  
Chylomicron Remnants

The binding and uptake of chylomicron remnants by human macrophages was studied in order to resolve paradoxical observations that have described the putative mechanisms by which postprandial lipoproteins induce foam cell formation. Chylomicron remnants bound to human monocyte-derived macrophages (HMMs) and to the transformed monocytic cell line THP-1 with high affinity (Kd of approx. 5.5 µg of chylomicron remnant protein/ml). Binding was found to be saturable for both cell types, and was strongly inhibited in the presence of unlabelled chylomicron remnants. Ligand blot studies with colloidal-gold-labelled chylomicron remnants identified two cell surface binding sites on both HMMs and THP-1 cells, with molecular masses of approx. 128 kDa and 43 kDa. The high-molecular-mass binding site was found to be the low-density lipoprotein (LDL) receptor, based on the strong inhibition of chylomicron remnant binding in the presence of unlabelled LDL, Fab2 antibody fragments to the LDL receptor or calcium chelators. Competition studies suggested that, in HMMs, the LDL receptor appeared to facilitate approximately half of the total chylomicron remnant uptake. In contrast, the LDL receptor was not significantly involved in macrophage uptake of chylomicron remnants by THP-1 cells. The identity of the 43 kDa binding site is presently unknown, but, importantly, expression was not inhibited as a consequence of sterol loading, which was induced by incubating HMMs and THP-1 cells with 25-hydroxycholesterol. In contrast, the expression of the LDL receptor was substantially attenuated following lipid loading. Collectively, our data suggest that, while the macrophage LDL receptor can bind chylomicron remnants and facilitate uptake in non-lipid-loaded HMMs, other sterol-insensitive sites are responsible for the unabated uptake of chylomicron remnants by macrophages. We propose that the 43 kDa macrophage chylomicron remnant binding protein may be a candidate for the sterol loading of macrophages.

scholarly journals High Uric Acid Activates the ROS-AMPK Pathway, Impairs CD68 Expression and Inhibits OxLDL-Induced Foam-Cell Formation in a Human Monocytic Cell Line, THP-1

2016 ◽  
Vol 40 (3-4) ◽  
pp. 538-548 ◽  
Author(s):  
Chaohuan Luo ◽  
Xueke Lian ◽  
Liangli Hong ◽  
Jingfang Zou ◽  
Zhi Li ◽  
...  
Keyword(s):  
Cell Line ◽  
Foam Cell ◽  
Cell Formation ◽  
Foam Cell Formation ◽  
Monocytic Cell ◽  
Monocytic Cell Line ◽  
Ampk Pathway ◽  
Human Monocytic Cell Line ◽  
Compound C ◽  
Human Monocytic Cell

Background/Aims: Hyperuricemia is part of the metabolic-syndrome cluster of abdominal obesity, impaired glucose tolerance, insulin resistance, dyslipidemia, and hypertension. Monocytes/macrophages are critical in the development of metabolic syndrome, including gout, obesity and atherosclerosis. However, how high uric acid (HUA) exposure affects monocyte/macrophage function remains unclear. In this study, we investigated the molecular mechanism of HUA exposure in monocytes/macrophages and its impact on oxidized low-density lipoprotein (oxLDL)-induced foam-cell formation in a human monocytic cell line, THP-1. Methods: We primed THP-1 cells with phorbol-12-myristate-13-acetate (PMA) for differentiation, then exposed cells to HUA and detected the production of reactive oxygen species (ROS) and analyzed the level of phospho-AMPKα. THP-1 cells were pre-incubated with Compound C, an AMPK inhibitor, or N-acetyl-L-cysteine (NAC), a ROS scavenger, or HUA before PMA, to assess CD68 expression and phospho-AMPKα level. PMA-primed THP-1 cells were pre-treated with oxLDL before Compound C and HUA treatment. Western blot analysis was used to examine the levels of phospho-AMPKα, CD68, ABCG1, ABCA1, cyclooxygenase-2 (COX-2) and NF-κB (p65). Flow cytometry was used to assess ROS production and CD68 expression in live cells. Oil-red O staining was used to observe oxLDL uptake in cells. Results: HUA treatment increased ROS production in PMA-primed THP-1 cells; NAC blocked HUA-induced oxidative stress. HUA treatment time-dependently increased phospho-AMPKα level in PMA-primed THP-1 cells. The HUA-induced oxidative stress increased phospho-AMPKα levels, which was blocked by NAC. HUA treatment impaired CD68 expression during cell differentiation by activating the AMPK pathway, which was reversed by Compound C treatment. Finally, HUA treatment inhibited oxLDL uptake in the formation of foam cells in THP-1 cells, which was blocked by Compound C treatment. HUA treatment significantly increased the expression of ABCG1 and reversed the oxLDL-reduced ABCG1 expression but did not affect the expression of ABCA1, NF-κB (p65) or COX-2. Conclusions: HUA exposure activated the ROS-AMPK pathway, impaired CD68 expression, and inhibited oxLDL-induced foam-cell formation in a human monocytic cell line, THP-1.

scholarly journals Study of the interaction of the C-reactive protein monomer with the U937 monocyte

2010 ◽  
Vol 15 (3) ◽  
Author(s):  
Jing Zhao ◽  
Xin-He Shi
Keyword(s):  
Foam Cell ◽  
Biological Effects ◽  
Cell Formation ◽  
Density Lipoprotein ◽  
Surface Proteins ◽  
Foam Cell Formation ◽  
C Reactive Protein ◽  
Monocytic Cell ◽  
Monocytic Cell Line ◽  
Reactive Protein

AbstractC-reactive protein (CRP) has two structurally distinct isoforms, the CRP pentamer and the CRP monomer. A role for the CRP monomer in atherosclerosis is emerging, but the underlying mechanisms are only beginning to be understood. Monocytes are an important contributor to atherosclerosis, and foam cell formation is the hallmark of atherogenesis. However, whether the CRP monomer can directly interact with the monocytes and modulate their responses remains unknown. Furthermore, although FcγRIII (CD16) has been identified as the receptor for the CRP monomer on neutrophils, its role in mediating the CRP monomer’s biological effects in other cell types has been questioned. In this study, we investigated the interaction of the CRP monomer with the monocytes using the U937 monocytic cell line. The CRP monomer specifically binds to U937 cells. This binding is unique in that it is independent of FcγRs and insensitive to protease digestion of the cell surface proteins. Further assays revealed that the CRP monomer directly incorporates into the plasma membrane. Interestingly, the presence of the CRP monomer efficiently retards oxidized low-density lipoprotein-induced foam cell formation of PMA-differentiated U937 macrophages and peripheral blood monocytic cell-derived macrophages. These findings provide additional evidence for the notion that the CRP monomer is an active CRP isoform that plays a role in atherogenesis via the direct modulation of the behavior of the monocytes.

Lipid synthesis in macrophages derived from the human cell line THP-1: modulation of the effects of native and oxidized chylomicron-remnant-like particles by oestrogen

2001 ◽  
Vol 101 (4) ◽  
pp. 403-413 ◽  
Author(s):  
Mariarosaria NAPOLITANO ◽  
Kelly V. BATT ◽  
Michael AVELLA ◽  
Elena BRAVO ◽  
Kathleen M. BOTHAM
Keyword(s):  
Cholesteryl Ester ◽  
Cell Line ◽  
Lipid Synthesis ◽  
Thiobarbituric Acid ◽  
Human Monocyte ◽  
Cholesterol Esterification ◽  
Chylomicron Remnant ◽  
Triacylglycerol Synthesis ◽  
Ester Formation ◽  
Chylomicron Remnants

The effects of native and oxidized chylomicron remnants on the synthesis of cholesteryl ester and triacylglycerol in macrophages, and the way that this is influenced by exposure of the cells to oestrogen, was investigated using the human monocyte cell line THP-1 and chylomicron-remnant-like particles containing human apolipoprotein E (CRLPs). Synthesis of the lipids was measured by the incorporation of [3H]oleate into cholesteryl ester and triacylglycerol. CRLPs (5-40μg of cholesterol/ml) containing either trilinolein or triolein as the triacylglycerol component caused a dose-dependent decrease in cholesteryl ester formation, while triacylglycerol production was unchanged. After oxidation of the CRLPs, the level of thiobarbituric acid-reactive substances was increased by 6.3-fold and 2.2-fold in particles containing trilinolein and triolein respectively. Furthermore, CRLPs containing oxidized trilinolein lost their ability to down-regulate cholesterol esterification, while CRLPs containing oxidized triolein did not. Both types of oxidized CRLPs decreased triacylglycerol synthesis. Treatment of the macrophages with 17β-oestradiol caused increases of approx. 94% and 34% in the synthesis of cholesteryl ester and triacylglycerol respectively in the absence of CRLPs. The differences between control and oestrogen-treated cells were abolished, however, when CRLPs (40μg of cholesterol/ml) were added to the incubations. In addition, in contrast with their lack of effect in control cells, CRLPs containing oxidized trilinolein decreased cholesterol esterification in oestrogen-treated cells by approx. 48%. These findings with CRLPs suggest that chylomicron remnants have significant effects on cholesteryl ester and triacylglycerol synthesis in macrophages, which may be modulated both by the oxidation state of the particles and by oestrogen.

GRO family chemokines are specialized for monocyte arrest from flow

2005 ◽  
Vol 289 (5) ◽  
pp. H1976-H1984 ◽  
Author(s):  
David F. Smith ◽  
Elena Galkina ◽  
Klaus Ley ◽  
Yuqing Huo
Keyword(s):  
Actin Polymerization ◽  
Human Monocyte ◽  
Flow Chamber ◽  
Monocytic Cell ◽  
Monocytic Cell Line ◽  
Downstream Signaling ◽  
Human Monocytic Cell Line ◽  
Monocyte Recruitment ◽  
Cell Arrest ◽  
And Migration

Chemokines participate in various processes of monocyte recruitment including monocyte arrest and migration. Our group and others have demonstrated that growth-related oncogene (GRO)-α (CXCL1) can support monocyte arrest in models of inflammation. Here we employed a parallel plate-flow chamber and Transwell reconstitution assay to test whether GRO family chemokines were sufficient for Mono Mac 6 (a human monocytic cell line) and isolated human monocyte recruitment. Our study shows that 1) GRO-α, -β (CXCL2), and -γ (CXCL3) all act as arrest chemokines for monocyte adhesion on vascular cell adhesion molecule (VCAM)-1 under flow in the presence of P-selectin; 2) CXCR2 is the functional receptor for GRO-family chemokines in monocyte arrest; however, CXCR2 is not an arrest chemokine receptor in general, since epithelial neutrophil-activating peptide ENA-78 failed to arrest monocytes; 3) GRO-α, -β, and -γ all fail to increase intracellular free Ca2+ or mediate monocyte chemotaxis; and 4) signaling through Gαi protein, phosphoinositide 3-kinase, and actin polymerization but not Ca2+ mobilization or the mitogen-activated kinases p38 and MAPK/extracellular signal-related kinase are necessary for GRO-α-mediated Mono Mac 6 cell arrest under flow. We conclude that the GRO-family chemokines are specialized monocyte-arrest chemokines. Their role in monocyte recruitment in inflammation can be inhibited by blocking CXCR2 function or downstream signaling events.

Protein convertase subtilisin/kexin type 9 biology in nephrotic syndrome: implications for use as therapy

2019 ◽  
Vol 35 (10) ◽  
pp. 1663-1674 ◽  
Author(s):  
Ruxandra Mihaela Busuioc ◽  
Adrian Covic ◽  
Mehmet Kanbay ◽  
Maciej Banach ◽  
Alexandru Burlacu ◽  
...  
Keyword(s):  
Nephrotic Syndrome ◽  
Foam Cell ◽  
Regulatory Element ◽  
Cell Formation ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Cumulative Effect ◽  
Lipid Lowering ◽  
Foam Cell Formation ◽  
Apoptosis Protein

Abstract Low-density lipoprotein cholesterol (LDL-C) levels almost constantly increased in patients with nephrotic syndrome (NS). Protein convertase subtilisin/kexin type 9 (PCSK9) [accelerates LDL-receptor (LDL-R) degradation] is overexpressed by liver cells in NS. Their levels, correlated inversely to LDL-R expression and directly to LDL-C, seem to play a central role in hypercholesterolaemia in NS. Hypersynthesis resulting from sterol regulatory element-binding protein dysfunction, hyperactivity induced by c-inhibitor of apoptosis protein expressed in response to stimulation by tumour necrosis factor-α produced by damaged podocytes and hypo-clearance are the main possible mechanisms. Increased LDL-C may damage all kidney cell populations (podocytes, mesangial and tubular cells) in a similar manner. Intracellular cholesterol accumulation produces oxidative stress, foam cell formation and apoptosis, all favoured by local inflammation. The cumulative effect of cellular lesions is worsened proteinuria and kidney function loss. Accordingly, NS patients should be considered high risk and treated by lowering LDL-C. However, there is still not enough evidence determining whether lipid-lowering agents are helpful in managing dyslipidaemia in NS. Based on good efficacy and safety proved in the general population, therapeutic modulation of PCSK9 via antibody therapy might be a reasonable solution. This article explores the established and forthcoming evidence implicating PCSK9 in LDL-C dysregulation in NS.

scholarly journals Oleacein and Foam Cell Formation in Human Monocyte-Derived Macrophages: A Potential Strategy against Early and Advanced Atherosclerotic Lesions

2020 ◽  
Vol 13 (4) ◽  
pp. 64
Author(s):  
Agnieszka Filipek ◽  
Tomasz P. Mikołajczyk ◽  
Tomasz J. Guzik ◽  
Marek Naruszewicz
Keyword(s):  
Flow Cytometry ◽  
Foam Cell ◽  
Low Density Lipoprotein ◽  
Cell Formation ◽  
Density Lipoprotein ◽  
Human Monocyte ◽  
Foam Cell Formation ◽  
Low Density ◽  
Oxidized Low Density Lipoprotein ◽  
Atherosclerotic Lesions

Background: Oleacein is a secoiridoid group polyphenol found mostly in Olea europea L. and Ligustrum vulgare L. (Oleaceae). The aim of the present study was to investigate a potential role of oleacein in prevention of the foam cell formation. Materials and Methods: Oleacein was isolated from Ligustrum vulgare leaves. Human monocyte-derived macrophages were obtained from monocytes cultured with Granulocyte-macrophage colony-stimulating factor (GM-CSF). Then, cells were incubated with 20 μM or 50 μM of oleacein and with oxidized low-density lipoprotein (oxLDL) (50 μg/mL). Visualization of lipid deposition within macrophages was carried out using Oil-Red-O. Expression of CD36, Scavenger receptor A1 (SRA1) and Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) was determined by Reverse transcription polymerase chain reaction (RT-PCR) and by flow cytometry. Apoptosis was determined by flow cytometry using Annexin V assay. STAT3 and Acyl-coenzyme A: cholesterol acyltransferase type 1 (ACAT1) levels were determined by ELISA. P-STAT3, P-JAK1, P-JAK2 expressions were determined by Western blot (WB). Results: Oleacein in dose-dependent manner significantly reduced lipid deposits in macrophages as well as their expression of selected scavenger receptors. The highest decrease of expression was found for CD36 and SRA1 receptors, from above 20% to more than 75% compared to oxLDL and the lowest for LOX-1 receptor, from approx. 8% to approx. 25% compared to oxLDL-stimulated macrophages. Oleacein significantly reduced (2.5-fold) early apoptosis of oxLDL-stimulated macrophages. Moreover, oleacein significantly increased the protein expression of JAK/STAT3 pathway and had no effect on ACAT1 level. Conclusions: Our study demonstrates, for the first time, that oleacein inhibits foam cell formation in human monocyte-derived macrophages and thus can be a valuable tool in the prevention of early and advanced atherosclerotic lesions.

WO14-OR-6 SCAP-MEDIATED DYSREGULATION OF LDL RECEPTOR UNDER INFLAMMATORY STRESS: A POTENTIAL NEW PATHWAY FOR FOAM CELL FORMATION

2007 ◽  
Vol 8 (1) ◽  
pp. 15
Author(s):  
X.Z. Ruan ◽  
D.C. Wheeler ◽  
J. Hunt ◽  
S.H. Powis ◽  
Z. Varghese ◽  
...  
Keyword(s):  
Foam Cell ◽  
Cell Formation ◽  
Ldl Receptor ◽  
Foam Cell Formation ◽  
Inflammatory Stress

scholarly journals Myriocin and d-PDMP ameliorate atherosclerosis in ApoE−/− mice via reducing lipid uptake and vascular inflammation

2020 ◽  
Vol 134 (5) ◽  
pp. 439-458 ◽  
Author(s):  
Zemou Yu ◽  
Qing Peng ◽  
Songyue Li ◽  
Hongjun Hao ◽  
Jianwen Deng ◽  
...  
Keyword(s):  
Inflammatory Responses ◽  
Therapeutic Potential ◽  
Foam Cell ◽  
Oxidized Ldl ◽  
Vascular Inflammation ◽  
Cell Formation ◽  
Ldl Receptor ◽  
Foam Cell Formation ◽  
Lipid Uptake ◽  
Atherosclerosis Progression

Abstract Sphingolipids have been implicated in the etiology of atherosclerosis. The commonly used sphingolipid inhibitors, myriocin (a ceramide inhibitor) and d-PDMP (d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol, a glycosphingolipid inhibitor), have shown therapeutic potential but their efficacy and their underlying mechanisms remain unclear. Here, apolipoprotein E-deficient (apoE−/−) mice were fed a high-fat diet (HFD) and treated with a control, myriocin, d-PDMP, or atorvastatin for 12 weeks. We analyzed the effects of these drugs on the size and detailed composition of atherosclerotic plaques. Molecular biological approaches were used to explore how the inhibitors affect lipid metabolism and foam-cell formation. Treatment with myriocin or d-PDMP led to smaller and less vulnerable atherosclerotic lesions and was almost as effective as atorvastatin. Sphingolipid inhibitors down-regulated the expression of monocyte chemotactic protein 1 (MCP-1) and its receptor chemoattractant cytokine receptor 2 (CCR2), which play a key role in monocyte recruitment. They also decreased pro-inflammatory Ly-6chigh monocytes and influenced the uptake of modified LDL by down-regulating the expression of cluster of differentiation 36 (CD36) and lectin-like oxidized LDL (ox-LDL) receptor-1 (LOX-1). The inhibitors exhibited the advantage of maintaining normal glucose homeostasis compared with atorvastatin. These findings reveal for the first time that the modulation of sphingolipid synthesis can effectively alleviate atherosclerosis progression by preventing lipid uptake and reducing inflammatory responses in the arterial walls.

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