Abstract 646: Redox Control of Macropinocytosis; An Unexplored Target in Atherosclerosis

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Pushpankur Ghoshal ◽  
Bhupesh Singla ◽  
Douglas Feck ◽  
Nadiezhda Cantu-Medellin ◽  
Eric Kelley ◽  
...  
Keyword(s):  
Lipid Accumulation ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
Actin Binding ◽  
Lipid Uptake ◽  
Signaling Mechanism ◽  
Membrane Ruffling

Aims: Early studies established the paradigm that oxidation of low density lipoprotein (LDL) is necessary for scavenger receptor-mediated LDL uptake and lipid accumulation in macrophages. In addition to this “classical” mode of lipid internalization, scavenger receptor-independent uptake of native, non-oxidized LDL (nLDL) via macropinocytosis has been demonstrated to contribute to lipid uptake by macrophages. Despite this previous information the precise signaling mechanisms regulating macropinocytosis of nLDL and the relative contribution of lipid macropinocytosis to atherosclerosis remain unknown. This study was designed to examine the role of phagocyte NADPH oxidase (a.k.a. Nox2) in macropinocytosis and to investigate macropinocytotic uptake of lipids in hypercholesterolemic ApoE -/- mice in vivo . Results: Phorbol myristate acetate (4β-PMA) activation of human and murine macrophages stimulated membrane ruffling, macropinosome formation, and subsequent uptake of nLDL by macropinocytosis. FACS data indicated that 4β-PMA stimulates lipid accumulation following nLDL treatment in macrophages lacking scavenger receptor CD36. Mechanistically, we found that pharmacological blockade of protein kinase C (PKC), inhibition of flavoenzymes by diphenyleneiodonium, and scavenging intracellular superoxide anion abolished phorbol ester-induced macropinocytosis. Transcriptional knockdown of Nox2 using siRNA inhibited 4β-PMA-induced macropinocytosis in THP-1 macrophages. Delving further into the mechanism, we found that Nox2 via redox inactivation of PTEN and activation of the PI3K/Akt pathway dephosphorylates the actin-binding protein cofilin, stimulates membrane ruffling, and induces macropinocytosis. Finally, peritoneal chimera experiments indicate that macropinocytotic uptake of lipids in hypercholesterolemic ApoE -/- mice was attenuated in Nox2 y/- macrophages compared to wild type controls. Innovation and Conclusion: These findings suggest a previously undescribed redox-sensitive signaling pathway leading to internalization of nLDL by macropinocytosis. The signaling mechanism described herein may identify new targets in atherosclerosis and other disease conditions involving macropinocytosis.

scholarly journals Platelet CD36 signaling through ERK5 promotes caspase-dependent procoagulant activity and fibrin deposition in vivo

2018 ◽  
Vol 2 (21) ◽  
pp. 2848-2861 ◽  
Author(s):  
Moua Yang ◽  
Andaleb Kholmukhamedov ◽  
Marie L. Schulte ◽  
Brian C. Cooley ◽  
Na’il O. Scoggins ◽  
...  
Keyword(s):  
Platelet Reactivity ◽  
Low Density Lipoprotein ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
Signaling Molecules ◽  
Chow Diet ◽  
Glycoprotein Vi ◽  
Platelet Signaling ◽  
Clinically Significant

Abstract Dyslipidemia is a risk factor for clinically significant thrombotic events. In this condition, scavenger receptor CD36 potentiates platelet reactivity through recognition of circulating oxidized lipids. CD36 promotes thrombosis by activating redox-sensitive signaling molecules, such as the MAPK extracellular signal-regulated kinase 5 (ERK5). However, the events downstream of platelet ERK5 are not clear. In this study, we report that oxidized low-density lipoprotein (oxLDL) promotes exposure of procoagulant phosphatidylserine (PSer) on platelet surfaces. Studies using pharmacologic inhibitors indicate that oxLDL-CD36 interaction–induced PSer exposure requires apoptotic caspases in addition to the downstream CD36-signaling molecules Src kinases, hydrogen peroxide, and ERK5. Caspases promote PSer exposure and, subsequently, recruitment of the prothrombinase complex, resulting in the generation of fibrin from the activation of thrombin. Caspase activity was observed when platelets were stimulated with oxLDL. This was prevented by inhibiting CD36 and ERK5. Furthermore, oxLDL potentiates convulxin/glycoprotein VI–mediated fibrin formation by platelets, which was prevented when CD36, ERK5, and caspases were inhibited. Using 2 in vivo arterial thrombosis models in apoE-null hyperlipidemic mice demonstrated enhanced arterial fibrin accumulation upon vessel injury. Importantly, absence of ERK5 in platelets or mice lacking CD36 displayed decreased fibrin accumulation in high-fat diet–fed conditions comparable to that seen in chow diet–fed animals. These findings suggest that platelet signaling through CD36 and ERK5 induces a procoagulant phenotype in the hyperlipidemic environment by enhancing caspase-mediated PSer exposure.

scholarly journals Sagunja-Tang Improves Lipid Related Disease in a Postmenopausal Rat Model and HepG2 Cells

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Hiroe Go ◽  
Jin Ah Ryuk ◽  
Hye Won Lee ◽  
In Sil Park ◽  
Ki-Jung Kil ◽  
...  
Keyword(s):  
Lipid Accumulation ◽  
Hepg2 Cells ◽  
Cholesterol Synthesis ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Low Density ◽  
Protein Levels ◽  
Related Disease

The present study was conducted to investigate the effect of Sagunja-tang on the lipid related disease in a rat model of menopausal hyperlipidemia and lipid accumulation in methyl-β-cyclodextrin-induced HepG2 cells. Inin vivostudy using menopausal hyperlipidemia rats, Sagunja-tang reduced retroperitoneal and perirenal fat, serum lipids, atherogenic index, cardiac risk factor, media thickness, and nonalcoholic steatohepatitis score, when compared to menopausal hyperlipidemia control rats. In HepG2 cells, Sagunja-tang significantly decreased the lipid accumulation, total cholesterol levels, and low-density/very-low-density lipoprotein levels. Moreover, Sagunja-tang reversed the methyl-β-cyclodextrin-induced decrease in the protein levels of critical molecule involved in cholesterol synthesis, sterol regulatory element binding protein-2, and low-density lipoprotein receptor and inhibited protein levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase as well as activity. Phosphorylation level of AMP-activated protein kinase was stimulated by Sagunja-tang. These results suggest that Sagunja-tang has effect on inhibiting hepatic lipid accumulation through regulation of cholesterol synthesis and AMPK activityin vitro. These observations support the idea that Sagunja-tang is bioavailable bothin vivoandin vitroand could be developed as a preventive and therapeutic agent of hyperlipidemia in postmenopausal females.

scholarly journals Protection against Fatty Liver but Normal Adipogenesis in Mice Lacking Adipose Differentiation-Related Protein

2006 ◽  
Vol 26 (3) ◽  
pp. 1063-1076 ◽  
Author(s):  
Benny Hung-Junn Chang ◽  
Lan Li ◽  
Antoni Paul ◽  
Susumu Taniguchi ◽  
Vijayalakshmi Nannegari ◽  
...  
Keyword(s):  
Fatty Liver ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Lipid Uptake ◽  
Related Protein ◽  
Outer Leaflet ◽  
Adipose Differentiation ◽  
Deficient Mice

ABSTRACT Adipose differentiation-related protein (ADFP; also known as ADRP or adipophilin), is a lipid droplet (LD) protein found in most cells and tissues. ADFP expression is strongly induced in cells with increased lipid load. We have inactivated the Adfp gene in mice to better understand its role in lipid accumulation. The Adfp-deficient mice have unaltered adipose differentiation or lipolysis in vitro or in vivo. Importantly, they display a 60% reduction in hepatic triglyceride (TG) and are resistant to diet-induced fatty liver. To determine the mechanism for the reduced hepatic TG content, we measured hepatic lipogenesis, very-low-density lipoprotein (VLDL) secretion, and lipid uptake and utilization, all of which parameters were shown to be similar between mutant and wild-type mice. The finding of similar VLDL output in the presence of a reduction in total TG in the Adfp-deficient liver is explained by the retention of TG in the microsomes where VLDL is assembled. Given that lipid droplets are thought to form from the outer leaflet of the microsomal membrane, the reduction of TG in the cytosol with concomitant accumulation of TG in the microsome of Adfp −/− cells suggests that ADFP may facilitate the formation of new LDs. In the absence of ADFP, impairment of LD formation is associated with the accumulation of microsomal TG but a reduction in TG in other subcellular compartments.

scholarly journals Endogenously produced lipoprotein lipase enhances the binding and cell association of native, mildly oxidized and moderately oxidized low-density lipoprotein in mouse peritoneal macrophages

1999 ◽  
Vol 343 (2) ◽  
pp. 347-353 ◽  
Author(s):  
Xiaosong WANG ◽  
Joachim GREILBERGER ◽  
Sanja LEVAK-FRANK ◽  
Robert ZIMMERMANN ◽  
Rudolf ZECHNER ◽  
...  
Keyword(s):  
Lipoprotein Lipase ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Relative Proportion ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
Peritoneal Macrophages ◽  
Low Density ◽  
Cell Binding ◽  
Mouse Peritoneal Macrophages

It has been well established that purified lipoprotein lipase (LPL) can facilitate the cellular uptake of various native and modified lipoproteins when added exogenously to macrophages. Because activated macrophages express LPL endogenously, it was the aim of this study to investigate the effect of macrophage-produced LPL on the uptake of native low-density lipoprotein (LDL) and LDL that has been modified to various degrees by Cu2+-mediated oxidation. Cell binding and uptake of Eu3+-labelled native and oxidized LDL was determined in mouse peritoneal macrophages (MPM) from normal mice and induced mutant mice that lack LPL expression in MPM. We found that LPL expressed by MPM was able to increase cell binding and association of native LDL (by 121% and 101% respectively), mildly oxidized LDL (by 47% and 43%) and moderately oxidized LDL (by 30% and 22%). With increased levels of lipoprotein oxidation, the relative proportion of LPL-mediated LDL uptake decreased. This decrease was not due to weakened binding of LPL to oxidized LDL. The drastically increased uptake of highly oxidized LDL in MPM by scavenger-receptor-mediated pathways might dominate the simultaneous exogenous or endogenous LPL-mediated uptake of this lipoprotein. Competition experiments with positively charged poly(amino acids) furthermore suggested that histidine, arginine and lysine residues in LPL are important for the interaction between LDL and LPL. Our results imply that physiological levels of LPL produced by macrophages facilitate the uptake of native LDL as well as mildly and moderately oxidized LDL. This process might, in the micro-environment of arteries, contribute to the accumulation of macrophage lipids and the formation of foam cells.

Vascular responses and ion exchange in diabetes: Authors' reply

1992 ◽  
Vol 82 (3) ◽  
pp. 339-339
Author(s):  
J. M. Ritter ◽  
G. C. Viberti
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Large Body ◽  
Plasma Lipid ◽  
Density Lipoprotein ◽  
High Plasma ◽  
Diabetic Patients ◽  
Vascular Sensitivity

1. Na+/Li+ countertransport is not a gold standard, or indeed any other kind of standard. It is a measure of the activity of one particular cation exchanger. 2. There is a large body of literature regarding the effects of oxidized low-density lipoprotein (LDL) in experimental animals and in vitro. Whether abnormal oxidized LDL or one of many other possible mechanisms underlies the inverse relationship that we observed between vascular sensitivity in vivo to nitroprusside or carbachol with erythrocyte Na+/Li+ countertransport in diabetic patients remains to be seen. 3. We caution against post hoc subgroup analysis (smokers versus non-smokers, low versus high plasma lipid levels, etc.) in studies of this size.

scholarly journals Low-density lipoprotein oxidation, antioxidants, and atherosclerosis: a clinical biochemistry perspective

1996 ◽  
Vol 42 (4) ◽  
pp. 498-506 ◽  
Author(s):  
I Jialal ◽  
S Devaraj
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Atherosclerotic Lesion ◽  
Density Lipoprotein ◽  
Direct Methods ◽  
Ldl Oxidation ◽  
Low Density ◽  
Indirect Measures ◽  
Oxidatively Modified

Abstract Cardiovascular disease is the leading cause of mortality in westernized populations. An increased concentration of plasma low-density lipoprotein (LDL) cholesterol constitutes a major risk factor for atherosclerosis. Several lines of evidence support a role for oxidatively modified LDL in atherosclerosis and for its in vivo existence. Antioxidants have been shown to decrease atherosclerotic lesion formation in animal models and decrease LDL oxidation; the evaluation of LDL oxidation in vivo is therefore very important. However, there is a paucity of methods for direct measurement of LDL oxidation. Of the direct methods currently available, the preferred ones seem to be the measurement of F2-isoprostanes, autoantibodies to epitopes on oxidized LDL, and the assessment of antioxidant status. Of the indirect measures, the most uniformly accepted procedure is examining the oxidative susceptibility of isolated LDL by monitoring conjugated diene formation.

Abstract 570: Macrophage Catabolism of Aggregated Lipoproteins Using a Novel Extracellular Compartment Regulates Lipid Accumulation During Atherosclerosis

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Rajesh K Singh ◽  
Abigail S Haka ◽  
Valeria C Barbosa-Lorenzi ◽  
Arky Asmal ◽  
Frederik Lund ◽  
...  
Keyword(s):  
Lipid Accumulation ◽  
Actin Polymerization ◽  
Foam Cell ◽  
Low Density Lipoprotein ◽  
Cell Formation ◽  
Density Lipoprotein ◽  
Foam Cell Formation ◽  
Atherosclerotic Vascular Disease ◽  
Extracellular Compartment

Despite impressive advances in research, prevention, and treatment, atherosclerotic vascular disease remains the leading cause of death in the developed world. Mechanisms of cholesterol accumulation in the arteries have been studied intensively, but the in vivo contributions of different pathways leading to lipid accumulation and foam cell formation are not understood. In the arteries, low-density lipoprotein (LDL) is aggregated and bound to the extracellular matrix. When such aggregated LDL is presented to macrophages, they form a novel acidic, hydrolytic compartment that is topologically extracellular, to which lysosomal enzymes are secreted. Such compartments are observed in vivo in murine atherosclerotic plaque macrophages interacting with cholesterol rich deposits. Using state-of-the-art quantitative and high resolution microscopy techniques, characterization of compartment morphology reveals how macrophages use local actin polymerization to drive plasma membrane remodeling at the interface with aggregated LDL. This leads to sequestration of aggregated LDL into topologically convoluted structures that allow acidification, catabolism and internalization of LDL. We find that a TLR4/MyD88/Syk/PI3 kinase/Akt dependent signaling pathway in macrophages regulates the formation of such catabolic compartments. Consistent with this, deficiency of TLR4 in vivo can protect macrophages from lipid accumulation in murine atherosclerotic plaques. Herein, we provide compelling evidence for a novel form of catabolism that macrophages use to degrade aggregated LDL in vivo during atherosclerosis and this process leads to foam cell formation, cell death and promotes disease progression.

scholarly journals Scavenger Receptors Class A-I/II and CD36 Are the Principal Receptors Responsible for the Uptake of Modified Low Density Lipoprotein Leading to Lipid Loading in Macrophages

2002 ◽  
Vol 277 (51) ◽  
pp. 49982-49988 ◽  
Author(s):  
Vidya V. Kunjathoor ◽  
Maria Febbraio ◽  
Eugene A. Podrez ◽  
Kathryn J. Moore ◽  
Lorna Andersson ◽  
...  
Keyword(s):  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Gas Chromatography Mass Spectrometry ◽  
Scavenger Receptors ◽  
Low Density ◽  
Lipid Uptake ◽  
Modified Ldl ◽  
Ldl Uptake

Modification of low density lipoprotein (LDL) can result in the avid uptake of these lipoproteins via a family of macrophage transmembrane proteins referred to as scavenger receptors (SRs). The genetic inactivation of either of two SR family members, SR-A or CD36, has been shown previously to reduce oxidized LDL uptakein vitroand atherosclerotic lesions in mice. Several other SRs are reported to bind modified LDL, but their contribution to macrophage lipid accumulation is uncertain. We generated mice lacking both SR-A and CD36 to determine their combined impact on macrophage lipid uptake and to assess the contribution of other SRs to this process. We show that SR-A and CD36 account for 75–90% of degradation of LDL modified by acetylation or oxidation. Cholesteryl ester derived from modified lipoproteins fails to accumulate in macrophages taken from the double null mice, as assessed by histochemistry and gas chromatography-mass spectrometry. These results demonstrate that SR-A and CD36 are responsible for the preponderance of modified LDL uptake in macrophages and that other scavenger receptors do not compensate for their absence.

scholarly journals Scavenger Receptor CD36 Directs Nonclassical Monocyte Patrolling Along the Endothelium During Early Atherogenesis

2017 ◽  
Vol 37 (11) ◽  
pp. 2043-2052 ◽  
Author(s):  
Paola M. Marcovecchio ◽  
Graham D. Thomas ◽  
Zbigniew Mikulski ◽  
Erik Ehinger ◽  
Karin A.L. Mueller ◽  
...  
Keyword(s):  
Low Density Lipoprotein ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
Adaptor Protein ◽  
Fold Increase ◽  
Vascular Wall ◽  
Western Diet ◽  
Oxidized Lipoprotein

Objective— Nonclassical monocytes (NCM) function to maintain vascular homeostasis by crawling or patrolling along the vessel wall. This subset of monocytes responds to viruses, tumor cells, and other pathogens to aid in protection of the host. In this study, we wished to determine how early atherogenesis impacts NCM patrolling in the vasculature. Approach and Results— To study the role of NCM in early atherogenesis, we quantified the patrolling behaviors of NCM in ApoE −/− (apolipoprotein E) and C57BL/6J mice fed a Western diet. Using intravital imaging, we found that NCM from Western diet–fed mice display a 4-fold increase in patrolling activity within large peripheral blood vessels. Both human and mouse NCM preferentially engulfed OxLDL (oxidized low-density lipoprotein) in the vasculature, and we observed that OxLDL selectively induced NCM patrolling in vivo. Induction of patrolling during early atherogenesis required scavenger receptor CD36, as CD36 −/− mice revealed a significant reduction in patrolling activity along the femoral vasculature. Mechanistically, we found that CD36-regulated patrolling was mediated by a SFK (src family kinase) through DAP12 (DNAX activating protein of 12KDa) adaptor protein. Conclusions— Our studies show a novel pathway for induction of NCM patrolling along the vascular wall during early atherogenesis. Mice fed a Western diet showed increased NCM patrolling activity with a concurrent increase in SFK phosphorylation. This patrolling activity was lost in the absence of either CD36 or DAP12. These data suggest that NCM function in an atheroprotective manner through sensing and responding to oxidized lipoprotein moieties via scavenger receptor engagement during early atherogenesis.

scholarly journals The Dynamics of Oxidized LDL during Atherogenesis

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Hiroyuki Itabe ◽  
Takashi Obama ◽  
Rina Kato
Keyword(s):  
Time Course ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Oxidized Low Density Lipoprotein ◽  
Atherosclerotic Lesions ◽  
Long Duration ◽  
Course Changes ◽  
Classical Hypothesis

Accumulating evidence indicates that oxidized low-density lipoprotein (OxLDL) is a useful marker for cardiovascular disease. The uptake of OxLDL by scavenger receptors leads to the accumulation of cholesterol within the foam cells of atherosclerotic lesions. OxLDL has many stimulatory effects on vascular cells, and the presence of OxLDL in circulating blood has been established. According to the classical hypothesis, OxLDL accumulates in the atherosclerotic lesions over a long duration, leading to advanced lesions. However, recent studies on time-course changes of OxLDLin vivoraised a possibility that OxLDL can be transferred between the lesions and the circulation. In this paper, thein vivodynamics of OxLDL are discussed.

Sign in / Sign up

Export Citation Format

Share Document