Impairment of Macrophage Cholesterol Efflux by Cholesterol Hydroperoxide Trafficking (original) (raw)
Related papers
FEBS Letters, 2013
StAR family proteins in vascular macrophages participate in reverse cholesterol transport (RCT). We hypothesize that under pathophysiological oxidative stress, StARs will transport not only cholesterol to macrophage mitochondria, but also pro-oxidant cholesterol hydroperoxides (7-OOHs), thereby impairing early-stage RCT. Upon stimulation with dibutyryl-cAMP, RAW264.7 macrophages exhibited a strong time-dependent induction of mitochondrial StarD1 and plasma membrane ABCA1, which exports cholesterol. 7a-OOH uptake by stimulated RAW cell mitochondria (like cholesterol uptake) was strongly reduced by StarD1 knockdown, consistent with StarD1 involvement. Upon uptake by mitochondria, 7a-OOH (but not redox-inactive 7a-OH) triggered lipid peroxidation and membrane depolarization while reducing ABCA1 upregulation. These findings provide strong initial support for our hypothesis.
Cardiovascular Research, 2006
Objectives: Understanding the mechanisms involved in oxidative stress-induced foam cell formation is of fundamental importance for atherosclerosis. Our aim was to characterize the effects of oxidative stress on key receptors of macrophage cholesterol homeostasis, on the nuclear transcription factors PPAR and LXR regulating their expression, and on macrophage cholesterol handling. Methods and results: The incubation of macrophages derived from the human monocyte cell line THP-1 with iron (100 μm)/ascorbate (1000 μm) for a period of 4 h induced a strong peroxidation, as demonstrated by the elevation of malondialdehyde (220%, P b 0.001). The production of lipid peroxidation affected cholesterol efflux, which was probably due to decreased ABCAI gene and protein expression. On the other hand, cholesterol influx remained unchanged as did the mRNA and protein levels of SR-BI and CD36, important protein receptors that participate in cholesterol import. Experiments using RT-PCR showed that the ABCAI modulation was orchestrated by the nuclear receptors LXRα, LXRβ, PPARα, and PPARγ. Treatment with powerful antioxidants (Trolox and BHT) prevented the adverse effects of ironascorbate on cholesterol movement, conceivably supporting the role of oxidative stress. Conclusion: Our results show that oxidative stress can directly be induced in macrophages and concomitantly impairs the expression of receptors involved in cholesterol flux, which could influence foam cell formation and atherosclerosis development.
Cardiovascular Research, 2007
Objective: Elevated levels of high-density lipoprotein (HDL) cholesterol are inversely related to the risk of cardiovascular disease. The antiatherosclerotic function of HDL is mainly ascribed to its role in reverse cholesterol transport, and requires the integrity of HDL structure. Experimental evidence suggests that the ability of HDL to promote removal of excess cholesterol from peripheral cells is impaired upon oxidation. On the other hand, tyrosylation of HDL enhances its protective function, suggesting that not all forms of modified lipoprotein may be atherogenic. In the present study we investigated the effect of a mild oxidation of HDL 3 on its function as cholesterol acceptor. Methods and results: A mild oxidative stress (induced by 15 min exposure of HDL 3 to 1 μM Cu ++ or to 15-lipoxygenase) caused the formation of pre-β-migrating particles. Compared to native lipoprotein, mildly modified HDL 3 induced a significant ATP-binding cassette transporter 1 (ABCA1)-mediated increase of cholesterol and phospholipids efflux from J774 macrophages. This effect was abolished by an inhibitor of ABCA1-mediated lipid efflux (glyburide) and was absent in Tangier fibroblasts. Conclusions: A mild oxidative modification of HDL 3 may improve its function as cholesterol acceptor, increasing ABCA1-mediated lipid efflux from macrophages, a process that may reduce foam cell formation.
Overexpression of STARD3 in human monocyte/macrophages induces an anti-atherogenic lipid phenotype
Clinical Science (London, …, 2010
Dysregulated macrophage cholesterol homoeostasis lies at the heart of early and developing atheroma, and removal of excess cholesterol from macrophage foam cells, by efficient transport mechanisms, is central to stabilization and regression of atherosclerotic lesions. The present study demonstrates that transient overexpression of STARD3 {START [StAR (steroidogenic acute regulatory protein)-related lipid transfer] domain 3; also known as MLN64 (metastatic lymph node 64)}, an endosomal cholesterol transporter and member of the ‘START’ family of lipid trafficking proteins, induces significant increases in macrophage ABCA1 (ATP-binding cassette transporter A1) mRNA and protein, enhances [3H]cholesterol efflux to apo (apolipoprotein) AI, and reduces biosynthesis of cholesterol, cholesteryl ester, fatty acids, triacylglycerol and phospholipids from [14C]acetate, compared with controls. Notably, overexpression of STARD3 prevents increases in cholesterol esterification in response to acetylated LDL (low-density lipoprotein), blocking cholesteryl ester deposition. Thus enhanced endosomal trafficking via STARD3 induces an anti-atherogenic macrophage lipid phenotype, positing a potentially therapeutic strategy.
Mitochondrial (dys) function and regulation of macrophage cholesterol efflux
2013
Cholesterol trafficking from the outer to the cholesterol-poor inner mitochondrial membrane requires energized, polarized and actively respiring mitochondria, mediated by a highly regulated multimeric (140-200 kDa) protein complex comprising StAR (steroidogenic acute regulatory protein), mitochondrial TSPO (translocator protein), VDAC (voltage-dependent anion channel), ANT (adenine nucleotide transporter) and associated regulatory proteins. Mitochondrial cholesterol transport is rate-limiting in the CYP27A1 (sterol 27-hydroxylase)-dependent generation of oxysterol ligands for LXR (liver X receptor) transcription factors that regulate the expression of genes encoding proteins in the cholesterol efflux pathway, such as ABC transporters (ATP-binding cassette transporters) ABCA1 and ABCG1. These transporters transfer cholesterol and/or phospholipids across the plasma membrane to (apo)lipoprotein acceptors, generating nascent HDLs (high-density lipoproteins), which can safely transport excess cholesterol through the bloodstream to the liver for excretion in bile. Utilizing information from steroidogenic tissues, we propose that perturbations in mitochondrial function may reduce the efficiency of the cholesterol efflux pathway, favouring accumulation of cholesteryl ester 'foam cells' and allowing the toxic accumulation of free cholesterol at the interface between the endoplasmic reticulum and the mitochondrial membrane. In turn, this will trigger opening of the permeability transition pore, allowing unregulated production of oxysterols via CYP27A1, allowing the accumulation of esterified forms of this oxysterol within human atherosclerotic lesions. Defective cholesterol efflux also induces endoplasmic reticulum stress, proteasomal degradation of ABCA1 and Fas-dependent apoptosis, replicating findings in macrophages in advanced atherosclerotic lesions. Small molecules targeted to mitochondria, capable of sustaining mitochondrial function or improving cholesterol trafficking may aid cholesterol efflux from macrophage 'foam' cells, regressing and stabilizing the atherosclerotic plaque.
Lipids in Health and Disease, 2012
Background: Mitochondrial DNA damage, increased production of reactive oxygen species and progressive respiratory chain dysfunction, together with increased deposition of cholesterol and cholesteryl esters, are hallmarks of atherosclerosis. This study investigated the role of mitochondrial function in regulation of macrophage cholesterol efflux to apolipoprotein A-I, by the addition of established pharmacological modulators of mitochondrial function. Methods: Murine RAW 264.7 macrophages were treated with a range of concentrations of resveratrol, antimycin, dinitrophenol, nigericin and oligomycin, and changes in viability, cytotoxicity, membrane potential and ATP, compared with efflux of [ 3 H]cholesterol to apolipoprotein (apo) A-I. The effect of oligomycin treatment on expression of genes implicated in macrophage cholesterol homeostasis were determined by quantitative polymerase chain reaction, and immunoblotting, relative to the housekeeping enzyme, Gapdh, and combined with studies of this molecule on cholesterol esterification, de novo lipid biosynthesis, and induction of apoptosis. Significant differences were determined using analysis of variance, and Dunnett's or Bonferroni post t-tests, as appropriate.
PLoS ONE, 2013
Oxidation of low-density lipoprotein (LDL) is one of the major causative mechanisms in the development of atherosclerosis. In previous studies, we showed that minimally oxidized LDL (mmLDL) induced inflammatory responses in macrophages, macropinocytosis and intracellular lipid accumulation and that oxidized cholesterol esters (OxCEs) were biologically active components of mmLDL. Here we identified a specific OxCE molecule responsible for the biological activity of mmLDL and characterized signaling pathways in macrophages in response to this OxCE. Using liquid chromatography -tandem mass spectrometry and biological assays, we identified an oxidized cholesteryl arachidonate with bicyclic endoperoxide and hydroperoxide groups (BEP-CE) as a specific OxCE that activates macrophages in a TLR4/MD-2-dependent manner. BEP-CE induced TLR4/MD-2 binding and TLR4 dimerization, phosphorylation of SYK, ERK1/2, JNK and c-Jun, cell spreading and uptake of dextran and native LDL by macrophages. The enhanced macropinocytosis resulted in intracellular lipid accumulation and macrophage foam cell formation. Bone marrow-derived macrophages isolated from TLR4 and SYK knockout mice did not respond to BEP-CE. The presence of BEP-CE was demonstrated in human plasma and in the human plaque material captured in distal protection devices during percutaneous intervention. Our results suggest that BEP-CE is an endogenous ligand that activates the TLR4/SYK signaling pathway. Because BEP-CE is present in human plasma and human atherosclerotic lesions, BEP-CE-induced and TLR4/SYK-mediated macrophage responses may contribute to chronic inflammation in human atherosclerosis. Citation: Choi S-H, Yin H, Ravandi A, Armando A, Dumlao D, et al. (2013) Polyoxygenated Cholesterol Ester Hydroperoxide Activates TLR4 and SYK Dependent Signaling in Macrophages. PLoS ONE 8(12): e83145.
Circulation Research, 2014
Rationale: The efflux capacity of high-density lipoprotein (HDL) with cultured macrophages associates strongly and negatively with coronary artery disease status, indicating that impaired sterol efflux capacity might be a marker—and perhaps mediator—of atherosclerotic burden. However, the mechanisms that contribute to impaired sterol efflux capacity remain poorly understood. Objective: Our aim was to determine the relationship between myeloperoxidase-mediated oxidative damage to apolipoprotein A-I, the major HDL protein, and the ability of HDL to remove cellular cholesterol by the ATP-binding cassette transporter A1 (ABCA1) pathway. Methods and Results: We quantified both site-specific oxidation of apolipoprotein A-I and HDL’s ABCA1 cholesterol efflux capacity in control subjects and subjects with stable coronary artery disease or acute coronary syndrome. Subjects with coronary artery disease and acute coronary syndrome had higher levels of chlorinated tyrosine 192 and oxidized meth...