Low Density Lipoprotein In Macrophages Research Articles

Regulation of low-density lipoprotein on lipid metabolism in macrophages of large yellow croaker (Larimichthys crocea)

Low-density lipoprotein (LDL) is the main carrier of cholesterol transport in plasma, which participates in regulating lipid homeostasis. Studies in mammals have shown that high levels of LDL in plasma absorbed by macrophages trigger the formation of lipid-rich foam cells, leading to the development of atherosclerotic plaques. Although lipid-rich atherosclerosis-like lesions have been discovered in the aorta of several fish species, the physiological function of LDL in fish macrophages remains poorly understood. In the present study, LDL was isolated from the plasma of large yellow croaker (Larimichthys crocea), and mass spectrometry analysis identified two truncated forms of apolipoprotein B100 in the LDL protein profile. Transcriptomic analysis of LDL-stimulated macrophages revealed that differentially expressed genes (DEGs) were enriched in various pathways related to lipid metabolism, as confirmed by the fact that LDL increased total cholesterol and cholesteryl esters content. Meanwhile, the gene and protein expression levels of perilipin2 (PLIN2), a DEG enriched in the PPAR signaling pathway, were upregulated in response to LDL stimulation. Importantly, knocking down plin2 significantly attenuates LDL-induced cholesterol accumulation and promotes cholesterol efflux. Furthermore, the transcription factor PPARγ, which is upregulated in response to LDL stimulation, can enhance the promoter activity of plin2. In conclusion, this study suggests that LDL may upregulate plin2 expression through PPARγ, resulting in cholesterol accumulation in fish macrophages. This study will facilitate the investigation of the function of LDL in regulating lipid homeostasis in macrophages and shed light on the evolutionary origin of LDL metabolism in vertebrates.

Von Willebrand factor: from figurant to main character in the scene of inflammation

von Willebrand factor: from figurant to main character in the scene of inflammation

Statins Directly Influence the Polarization of Adipose Tissue Macrophages: A Role in Chronic Inflammation.

Statins represent one of the most widely used classes of drugs in current medicine. In addition to a substantial decrease in atherogenic low density lipoprotein (LDL) particle concentrations, several large trials have documented their potent anti-inflammatory activity. Based on our preliminary data, we showed that statins are able to decrease the proportion of pro-inflammatory macrophages (CD14+16+CD36high) in visceral adipose tissue in humans. In the present study including 118 healthy individuals (living kidney donors), a very close relationship between the pro-inflammatory macrophage proportion and LDL cholesterol levels was found. This was confirmed after adjustment for the most important risk factors. The effect of statins on the proportion of pro-inflammatory macrophages was also confirmed in an experimental model of the Prague hereditary hypercholesterolemia rat. A direct anti-inflammatory effect of fluvastatin on human macrophage polarization in vitro was documented. Based on modifying the LDL cholesterol concentrations, statins are suggested to decrease the cholesterol inflow through the lipid raft of macrophages in adipose tissue and hypercholesterolemia to enhance the pro-inflammatory macrophage phenotype polarization. On the contrary, due to their opposite effect, statins respond with anti-inflammatory activity, affecting the whole organism.

Binding of Macrophage Receptor MARCO, LDL, and LDLR to Disease-Associated Crystalline Structures.

Endogenous and exogenous crystalline structures are involved in various pathologies and diseases in humans by inducing sterile inflammation, mechanical stress, or obstruction of excretory organs. The best studied of these diseases is gout, in which crystallization of uric acid in the form of monosodium urate (MSU) mainly in synovial fluid of the joints leads to sterile inflammation. Though some of these diseases have been described for centuries, little is known about if and how the immune system recognizes the associated crystals. Thus, in this study we aimed at identifying possible recognition molecules of MSU using liquid chromatography-mass spectrometry (LC-MS) analysis of MSU-binding serum proteins. Among the strongest binding proteins, we unexpectedly found two transmembrane receptors, namely macrophage receptor with collagenous structure (MARCO) and low-density lipoprotein (LDL) receptor (LDLR). We show that recombinant versions of both human and mouse MARCO directly bind to unopsonized MSU and several other disease-associated crystals. Recombinant LDLR binds many types of crystals mainly when opsonized with serum proteins. We show that this interaction is predominantly mediated by LDL, which we found to bind to all crystalline structures tested except for cholesterol crystals. However, murine macrophages lacking LDLR expression do neither show altered phagocytosis nor interleukin-1β (IL-1β) production in response to opsonized crystals. Binding of LDL to MSU has previously been shown to inhibit the production of reactive oxygen species (ROS) by human neutrophils. We extend these findings and show that LDL inhibits neutrophil ROS production in response to most crystals tested, even cholesterol crystals. The inhibition of neutrophil ROS production only partly correlated with the inhibition of IL-1β production by peripheral blood mononuclear cells (PBMCs): LDL inhibited IL-1β production in response to large MSU crystals, but not small MSU or silica crystals. This may suggest distinct upstream signals for IL-1β production depending on the size or the shape of the crystals. Together, we identify MARCO and LDLR as potential crystal recognition receptors, and show that LDL binding to diverse disease-associated crystalline structures has variable effects on crystal-induced innate immune cell activation.

GAS5 knockdown suppresses inflammation and oxidative stress induced by oxidized low-density lipoprotein in macrophages by sponging miR-135a.

A large number of long non-coding RNAs have been confirmed to play vital roles in regulating various biological processes. Abnormal expression of growth arrest-specific transcript 5 (GAS5) is reported to be involved in the development of atherosclerosis (AS). This work is to explore the detailed mechanism underling how GAS5 regulates AS progression. We found that the abundance of GAS5 was markedly increased, and miR-135a was decreased in AS patient serums and ox-LDL-induced human THP-1 cells dose and time dependently. Interference of GAS5 suppressed inflammation and oxidative stress induced by ox-LDL in THP-1 cells. Mechanistically, GAS5 acted as a molecular sponge of microRNA-135a (miR-135a). Rescue assays indicated that knockdown of miR-135a partially rescued small interference RNA for GAS5-inhibited inflammatory cytokines release and oxidative stress in ox-LDL-triggered THP-1 cells. In conclusion, the absence of GAS5-inhibited inflammatory response and oxidative stress induced by ox-LDL in THP-1 cells via sponging miR-135a, providing a deep insight into the molecular target for AS treatment.

Binding of lactoferrin to the surface of low-density lipoproteins modified by myeloperoxidase prevents intracellular cholesterol accumulation by human blood monocytes.

Myeloperoxidase (MPO) is a unique heme-containing peroxidase that can catalyze the formation of hypochlorous acid (HOCl). The strong interaction of MPO with low-density lipoproteins (LDL) promotes proatherogenic modification of LDL by HOCl. The MPO-modified LDL (Mox-LDL) accumulate in macrophages, resulting in the formation of foam cells, which is the pathognomonic symptom of atherosclerosis. A promising approach to prophylaxis and atherosclerosis therapy is searching for remedies that prevent the modification or accumulation of LDL in macrophages. Lactoferrin (LF) has several application points in obesity pathogenesis. We aimed to study LF binding to Mox-LDL and their accumulation in monocytes transformed into macrophages. Using surface plasmon resonance and ELISA techniques, we observed no LF interaction with intact LDL, whereas Mox-LDL strongly interacted with LF. The affinity of Mox-LDL to LF increased with the degree of oxidative modification of LDL. Moreover, an excess of MPO did not prevent interaction of Mox-LDL with LF. LF inhibits accumulation of cholesterol in macrophages exposed to Mox-LDL. The results obtained reinforce the notion of LF potency as a remedy against atherosclerosis.

Hesperidin blocks varenicline-aggravated atherosclerotic plaque formation in apolipoprotein E knockout mice by downregulating net uptake of oxidized low-density lipoprotein in macrophages

Varenicline is a widely used and effective drug for smoking cessation. We have previously reported experimental evidence suggesting that varenicline increases the risk of cardiovascular events. Varenicline progresses atherosclerotic plaque formation in apolipoprotein E knockout (ApoE KO) mice. This adverse effect is likely due to enhanced net uptake of oxidized low-density lipoprotein (oxLDL) in macrophages as a result of increased scavenger receptors and decreased cholesterol efflux transporters. However, a regimen has not yet been presented for avoidance or amelioration of the risk for varenicline-induced cardiovascular events. The aim of this study was to examine the effect of hesperidin, a citrus flavonoid, on varenicline-aggravated atherosclerotic plaque formation in apolipoprotein E knockout (ApoE KO) mice. Hesperidin inhibited the aggravating effect of varenicline in the whole aorta, aortic arch, and aortic root of ApoE KO mice. In addition, hesperidin protected against varenicline-enhanced oxLDL net uptake by blocking the increased expression of CD36 and LOX-1 scavenger receptors and decreased expression of ABCA1 and ABCG1 cholesterol efflux transporters in RAW 264.7 cells. Our findings suggest that hesperidin can avoid or ameliorate the risk for cardiovascular events induced by varenicline treatment.

Deletion of Macrophage Low-Density Lipoprotein Receptor-Related Protein 1 (LRP1) Accelerates Atherosclerosis Regression and Increases C-C Chemokine Receptor Type 7 (CCR7) Expression in Plaque Macrophages.

We previously showed that mice lacking MΦLRP1-/- (low-density lipoprotein receptor-related protein 1 in macrophages) undergo accelerated atherosclerotic plaque formation due to changes in macrophages including increased apoptosis, decreased efferocytosis, and exaggerated transition to the inflammatory M1 phenotype. Here we sought to explore the role of macrophage low-density lipoprotein receptor-related protein 1 during regression of atherosclerosis since regressing plaques are characterized by transitioning of macrophages to M2 status as inflammation resolves. Apolipoprotein E-/- mice on a high-fat diet for 12 weeks were reconstituted with bone marrow from apolipoprotein E-producing wild-type or MΦLRP1-/- mice, and then placed on a chow diet for 10 weeks (n=9 to 11 mice/group). A cohort of apolipoprotein E-/- mice reconstituted with apolipoprotein E-/- bone marrow served as baseline controls (n=9). Plaques of both wild-type and MΦLRP1-/- bone marrow recipients regressed compared with controls (11% and 22%, respectively; P<0.05), and plaques of MΦLRP1-/- recipients were 13% smaller than those of wild-type recipients ( P<0.05). Recipients of MΦLRP1-/- marrow had 36% fewer M1 macrophages ( P<0.01) and 2.5-fold more CCR7 (C-C chemokine receptor type 7)-positive macrophages in the plaque relative to wild-type mice ( P<0.01). Additionally, in vivo studies of cellular egress showed a 4.6-fold increase in 5-ethynyl-2´-deoxyuridine-labeled CCR7+ macrophages in mediastinal lymph nodes. Finally, in vivo studies of reverse cholesterol transport showed a 1.4-fold higher reverse cholesterol transport in MΦLRP1-/- recipient mice ( P<0.01). Absence of macrophage low-density lipoprotein receptor-related protein 1 unexpectedly accelerates atherosclerosis regression, enhances reverse cholesterol transport, and increases expression of the motility receptor CCR7, which drives macrophage egress from lesions.

Abstract 4: Deletion of Macrophage Low-density Lipoprotein Receptor-related Protein 1 (LRP1) Accelerates Atherosclerosis Regression by Increasing CCR7-dependent Egress of Plaque Macrophages

We previously showed that mice lacking macrophage LDL receptor-related protein 1 (LRP1) undergo accelerated lesion formation due to increased apoptosis, decreased efferocytosis, and enhanced macrophage transformation into the inflammatory M1 phenotype. In vitro, LRP1-deficient macrophages (MΦLRP1 -/- ) show enhanced plasticity with exaggerated polarization towards either the inflammatory M1- or the anti-inflammatory M2-phenotype depending on the stimulant (LPS or IL-4, respectively). During atherosclerosis regression, the M2:M1 macrophage ratio increases as lesion M1 macrophages egress and inflammation resolves. Thus, we hypothesize that atherosclerosis regression is accelerated in MΦLRP1 -/- mice via enhanced macrophage M2 polarization and CCR7-dependent M1 macrophage egress. ApoE-/- mice on high fat diet for 12 weeks were reconstituted with bone marrow from wildtype (WT) or MΦLRP1 -/- mice and then placed on chow diet for 8 weeks. In this model, apoE is reintroduced into circulation to correct the hyperlipidemia and induce regression of atherosclerotic lesions. A cohort of apoE -/- mice reconstituted with apoE -/- bone marrow served as baseline controls. Lesions in both WT and MΦLRP1 -/- mice regressed relative to controls (11% and 22%, respectively; p&lt;0.05), but MΦLRP1 -/- lesions were 13% smaller than those of WT mice (p&lt;0.05). LRP1 deletion increased M2 transformation of macrophages and a higher M2:M1 macrophage ratio (p&lt;0.01) in the plaque. MΦLRP1 -/- lesions contained 36% fewer M1 macrophages compared to WT (p&lt;0.01). In vivo studies of reverse cholesterol transport (RCT) revealed that MΦLRP1 -/- have a 1.4-fold higher RCT compared to WT mice (p&lt;0.01). MΦLRP1 -/- lesions contained 2.5-fold more CCR7 + macrophages relative to WT lesions (p&lt;0.01), and in our in vivo egress assay 4.6-fold more CCR7 + macrophages were found in mediastinal lymph nodes. In vitro , M1-differentiated MΦLRP1 -/- macrophages expressed 1.6-fold higher Ccr7 mRNA compared to WT controls (p&lt;0.01). Thus, the absence of macrophage LRP1 accelerates atherosclerosis regression due to enhanced transformation of macrophages into an anti-inflammatory M2 phenotype, increased cholesterol efflux, and increased CCR7-driven egress of M1 macrophages from lesions.

Role of NLRP3 Inflammasomes in Atherosclerosis.

Inflammation with macrophage infiltration is a key feature of atherosclerosis. Although the mechanisms had been unclear, emerging evidence unveiled that NLRP3 inflammasomes, which regulate caspase-1 activation and subsequent processing of pro-IL-1β, trigger vascular wall inflammatory responses and lead to progression of atherosclerosis. NLRP3 inflammasomes are activated by various danger signals, such as cholesterol crystals, calcium phosphate crystals, and oxidized low-density lipoprotein in macrophages, to initiate inflammatory responses in the atherosclerotic lesion. Recent studies have further clarified the regulatory mechanisms and the potential therapeutic agents that target NLRP3 inflammasomes. In this study, we reviewed the present state of knowledge on the role of NLRP3 inflammasomes in the pathogenesis of atherosclerosis and discussed the therapeutic approaches that target NLRP3 inflammasomes.

Ikarugamycin: A Natural Product Inhibitor of Clathrin-Mediated Endocytosis.

Ikarugamycin (IKA) is a previously discovered antibiotic, which has been shown to inhibit the uptake of oxidized low-density lipoproteins in macrophages. Furthermore, several groups have previously used IKA to inhibit clathrin-mediated endocytosis (CME) in plant cell lines. However, detailed characterization of IKA has yet to be performed. Consequently, we performed biochemistry and microscopy experiments to further characterize the effects of IKA on CME. We show that IKA has an IC50 of 2.7 μm in H1299 cells and acutely inhibits CME, but not other endocytic pathways, in a panel of cell lines. Although long-term incubation with IKA has cytotoxic effects, the short-term inhibitory effects on CME are reversible. Thus, IKA can be a useful tool for probing routes of endocytic trafficking.

Loss of Macrophage Low-Density Lipoprotein Receptor-Related Protein 1 Confers Resistance to the Antiatherogenic Effects of Tumor Necrosis Factor-α Inhibition.

Antiatherosclerotic effects of tumor necrosis factor-α (TNF-α) blockade in patients with systemic inflammatory states are not conclusively demonstrated, which suggests that effects depend on the cause of inflammation. Macrophage LRP1 (low-density lipoprotein receptor-related protein 1) and apoE contribute to inflammation through different pathways. We studied the antiatherosclerosis effects of TNF-α blockade in hyperlipidemic mice lacking either LRP1 (MΦLRP1(-/-)) or apoE from macrophages. Lethally irradiated low-density lipoprotein receptor (LDLR)(-/-) mice were reconstituted with bone marrow from either wild-type, MΦLRP1(-/-), apoE(-/-) or apoE(-/-)/MΦLRP1(-/-)(DKO) mice, and then treated with the TNF-α inhibitor adalimumab while fed a Western-type diet. Adalimumab reduced plasma TNF-α concentration, suppressed blood ly6C(hi) monocyte levels and their migration into the lesion, and reduced lesion cellularity and inflammation in both wild-type→LDLR(-/-) and apoE(-/-)→LDLR(-/-) mice. Overall, adalimumab reduced lesion burden by 52% to 57% in these mice. Adalimumab reduced TNF-α and blood ly6C(hi) monocyte levels in MΦLRP1(-/-)→LDLR(-/-) and DKO→LDLR(-/-) mice, but it did not suppress ly6C(hi) monocyte migration into the lesion or atherosclerosis progression. Our results show that TNF-α blockade exerts antiatherosclerotic effects that are dependent on the presence of macrophage LRP1.

Circulation Research “In This Issue” Anthology

Circulation Research “In This Issue” Anthology

Macrophage lipid accumulation is regulated by substrate stiffness

Abstract Atherosclerosis is characterized by the accumulation of lipid-laden macrophage foam cells within the vessel wall, formation of a plaque, and changes in tissue stiffness from soft near the necrotic core to stiff near the fibrous cap. The mechanisms governing foam cell formation are not well understood, but recent studies demonstrate that cells probe and respond to the physical properties of their surroundings. Stiffness regulates differentiation and function of mesenchymal stem cells and endothelial cells, yet until recently, its role in immune cell function has been largely unexplored. Our lab, and others, has found that substrate stiffness regulates murine macrophage cytokine secretion and phagocytic activity. Because macrophages accumulate near the soft necrotic core where there is abundant lipid, we hypothesized that macrophages on softer surfaces would exhibit enhanced lipid accumulation. To investigate this, we cultured murine macrophages on functionalized tunable polyacrylamide gels that model physiologically relevant stiffnesses. We then used a combination of flow cytometry and immunofluorescence microscopy to show that softer substrate stiffness results in more accumulation of the model lipid, oleic acid, as well as acetylated low-density lipoprotein in macrophages. Transcriptomic analysis identified up- or down-regulated genes in macrophages in response to increased substrate stiffness, including genes implicated in atherosclerosis and lipid metabolism. Together, these data demonstrate that lipid accumulation by macrophages is regulated in part by substrate stiffness and mechanotransduction signaling and reveal a potential link between changes in tissue stiffness and macrophage lipid accumulation.

Silencing Triggering Receptors Expressed on Myeloid Cells-1 Impaired the Inflammatory Response to Oxidized Low-Density Lipoprotein in Macrophages.

Atherosclerosis is a chronic progressive inflammatory disease characterized by the accumulation of lipid contents in arterial walls. Previous studies suggest participation of Toll-like receptors (TLRs) in lipid deposition and inflammatory response in vascular wall. The triggering receptor expressed on myeloid cells 1 (TREM-1) is a cell surface receptor of the immunoglobulin superfamily, which amplifies signal transduction of TLR pathway and enhances immune response to microbial infections. The aim of the present study was to investigate the effect of the oxidized low-density lipoprotein (oxLDL) on the expression of the TREM-1, as well as its engagement in proinflammatory cytokine production and foam cell formation in RAW264.7 mice macrophages. oxLDL enhanced TREM-1 and TLR-4, but not TLR-2 gene expression in macrophages; furthermore, silencing TREM-1 expression by short hairpin interfering RNA inhibited lipid phagocytosis and proinflammatory tumor necrosis factor-α (TNF-α) as well as interleukin-6 (IL-6) production in macrophages; moreover, application of synthetic antagonist, LP-17 polypeptide, reduced IL-6 production upon oxLDL stimulation in vitro and in vivo. In conclusion, in macrophages, oxLDL enhanced expression of TREM-1, which amplifies the innate immune response of TLR pathway; activation of TREM-1 contributes to atherogenesis process by enhancing proinflammatory cytokine production and foam cell formation.

In This Issue

HomeCirculation ResearchVol. 116, No. 5In This Issue Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published27 Feb 2015https://doi.org/10.1161/RES.0000000000000050Circulation Research. 2015;116:763Macrophage sortilin promotes LDL uptake, foam cell formation, and atherosclerosis (p 789)Sortilin protein drives cholesterol uptake in macrophages and promotes atherosclerosis, report Patel et al.Download figureDownload PowerPointA characteristic feature of atherosclerosis is the formation of foam cells that arise from cholesterol-loaded macrophages. But exactly how macrophages take up cholesterol from transporter proteins such as low-density lipoprotein (LDL) is unclear, especially since the deletion of known macrophage lipoprotein receptors in mice does not prevent foam cell formation. Patel and colleagues thus turned their attention to a protein called sortilin. This protein mediates hepatic LDL uptake and, through genome-wide association studies, has been linked with coronary artery disease. The function of sortilin in macrophages, however, was unknown. The team found that atherosclerosis-prone mice lacking sortilin—either in all cells or just macrophages—showed a significant reduction in the number of atherolsclerotic lesions compared to mice with normal levels of the protein. They also discovered that sortilin-lacking macrophages exhibited a reduction in LDL uptake, while macrophages that over-expressed sortilin actually increased their LDL uptake. These results suggest that preventing the sortilin-driven uptake of LDL in macrophages might reduce foam cell formation and thus be a novel strategy for treating, and perhaps even preventing, atherosclerosis in the future.Transcriptional reversion of cardiomyocyte fate during mammalian cardiac regeneration (p 804)O’Meara et al describe the transcriptional signature of mammalian heart regeneration.Download figureDownload PowerPointThe adult mammalian heart has a limited capacity for regeneration. In contrast, neonatal mice, within the first week of life, can completely repair their hearts after injury. During this regeneration, neonatal heart cells lose their sarcomeric structures, adopt a less-differentiated state, and reenter the cell cycle. If this same regenerative process could be recapitulated in the adult hearts, full recovery from myocardial injury might be possible. Hence to understand the mechanism underlying the regenerative capacity of the neonatal heart, O’Meara and colleagues examined changes in the global gene expression profiles of the neonatal heart after injury and during regeneration. They also studied the expression profiles of normal neonatal and adult cardiomyocytes, mouse embryonic stem cells during differentiation into cardiomyocytes, and adult cardiomyocytes induced to de-differentiate. After cross-referencing these data, the team identified a reference panel of genes involved in the differentiation and regeneration of a normal heart. They found that injury to the neonatal heart essentially reversed the differentiation process such that seven days post-injury the genes encoding sarcomeric proteins were reduced, while the expression of cell cycle genes was elevated. The team highlighted IL-13, STAT3 and STAT6 as regulators of cell cycle re-entry, but their results provide a large number of additional candidates that could be examined in future regeneration studies.Effects of DNA damage in smooth muscle cells in atherosclerosis (p 816)DNA damage promotes atherosclerotic plaque instability report Gray et al.Download figureDownload PowerPointDNA damage occurs in the vascular smooth muscle cells (VSMCs) of atherosclerotic plaques and it becomes more pervasive with disease progression. But whether such damage is a cause or consequence of the condition is unclear. It is known that DNA damage reduces cell proliferation—because cells stop cycling to repair the DNA, and this could arguably slow down plaque growth. If, however, the damage is severe, senescence and apoptosis can occur, which induces proinflammatory cytokine production and immune cell recruitment, thus exacerbating plaque growth. To better define the relationship between plaque growth and DNA damage, Gray and colleagues studied the effects of accelerating or inhibiting DNA repair in human VSMC from normal aorta and atherosclerotic plaques. As expected, they found that VSMCs from plaques had significantly higher levels of DNA damage as well as increased activation of DNA repair pathways. By accelerating this repair in a mouse model of atherosclerosis, they found that while plaque size remained the same, there was an increase in the stability of the fibrous caps of the plaques. Inhibiting repair, on the other hand, promoted plaque instability. Because unstable plaques are associated with a greater risk of myocardial infarction and stroke, preventing DNA damage, or promoting DNA repair could be a novel therapeutic strategy for enhancing plaque stability in patients with atherosclerotic disease. Previous Back to top Next FiguresReferencesRelatedDetails February 27, 2015Vol 116, Issue 5 Advertisement Article InformationMetrics © 2015 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000050 Originally publishedFebruary 27, 2015 PDF download Advertisement

Phytochemical Profiling and Assessment of Low-Density Lipoprotein Oxidation, Foam Cell-Preventing Ability and Antioxidant Activity of Commercial Products ofEmblica officinalisFruit

Emblica officinalis, a medicinal fruit, despite its versatility in preventing diseases, lacks widespread consumption owing to its astringent taste. Hence, it is commercially modified into various products to increase its consumption. This study compares antioxidant activity and atherosclerotic foam cell-prevention ability of popular commercial products of E. officinalis with that of unmodified fruit juice. The antioxidant activity of the capsule product was similar to pure juice, followed by sweetened fruit product. The capsule product showed the highest lowdensity lipoprotein (LDL) oxidation prevention (87%) next only to natural juice (91.15%). Capsule had the highest ability to prevent uptake of oxidized LDL in macrophages, equaling pure juice. Capsule had the highest phenolic content similar to pure juice. Phenolic compounds contributed 93% of the total antioxidant activity. High-performance liquid chromatography analysis of capsule and natural juice showed similar phenolic and flavonoid profiles indicating that capsule product could reproduce the beneficial effects of natural fruit with none of its astringent taste. PRACTICAL APPLICATION Emblica officinalis fruit is known for its versatility in curing diseases, but it has an astringent taste which is altered in commercially modified products to ensure widespread consumption. The health benefits of these products, however, are not well known. The study was conducted to detect the antioxidant activity and phenolic and flavonoid compound content in these various processed foods. This could help generate consumer awareness on the nutritional benefits of these products as compared with the fruit in its natural form.

Effects of miR-33a-5P on ABCA1/G1-mediated cholesterol efflux under inflammatory stress in THP-1 macrophages.

The present study is to investigate whether inflammatory cytokines inhibit ABCA1/ABCG1-mediated cholesterol efflux by regulating miR-33a-5P in THP-1 macrophages. We used interleukin-6 and tumor necrosis factor-alpha in the presence or absence of native low density lipoprotein (LDL) to stimulate THP-1 macrophages. THP-1 macrophages were infected by either control lentivirus vectors or lentivirus encoding miR-33a-5P or antisense miR-33a-5P. The effects of inflammatory cytokines, miR-33a-5P and antisense miR-33a-5P on intracellular lipids accumulation and intracellular cholesterol contents were assessed by oil red O staining and quantitative intracellular cholesterol assay. ApoA-I-mediated cholesterol efflux was examined using the fluorescent sterol (BODIPY-cholesterol). The gene and protein expressions of the molecules involved in cholesterol trafficking were examined using quantitative real-time polymerase chain reaction and Western blotting. Inflammatory cytokines or miR-33a-5P increased intracellular lipid accumulation and decreased apoA-I-mediated cholesterol efflux via decreasing the expression of ABCA1 and ABCG1 in the absence or presence of LDL in THP-1 macrophages. However, antisense miR-33a-5P reversed the effects of inflammatory cytokines on intracellular lipid accumulation, cholesterol efflux, and the expression of miR-33a-5P, ABCA1 and ABCG1 in the absence or presence of LDL in THP-1 macrophages. This study indicated that inflammatory cytokines inhibited ABCA1/ABCG1-mediated cholesterol efflux by up-regulating miR-33a-5P in THP-1 macrophages.

Major Vault Protein Regulates Class A Scavenger Receptor-mediated Tumor Necrosis Factor-α Synthesis and Apoptosis in Macrophages

Atherosclerosis is considered a disease of chronic inflammation largely initiated and perpetuated by macrophage-dependent synthesis and release of pro-inflammatory mediators. Class A scavenger receptor (SR-A) expressed on macrophages plays a key role in this process. However, how SR-A-mediated pro-inflammatory response is modulated in macrophages remains ill defined. Here through immunoprecipitation coupled with mass spectrometry, we reported major vault protein (MVP) as a novel binding partner for SR-A. The interaction between SR-A and MVP was confirmed by immunofluorescence staining and chemical cross-linking assay. Treatment of macrophages with fucoidan, a SR-A ligand, led to a marked increase in TNF-α production, which was attenuated by MVP depletion. Further analysis revealed that SR-A stimulated TNF-α synthesis in macrophages via the caveolin- instead of clathrin-mediated endocytic pathway linked to p38 and JNK, but not ERK, signaling pathways. Importantly, fucoidan invoked an enrichment of MVP in lipid raft, a caveolin-reliant membrane structure, and enhanced the interaction among SR-A, caveolin, and MVP. Finally, we demonstrated that MVP elimination ameliorated SR-A-mediated apoptosis in macrophages. As such, MVP may fine-tune SR-A activity in macrophages which contributes to the development of atherosclerosis.

Fluid-Phase Pinocytosis of Native Low Density Lipoprotein Promotes Murine M-CSF Differentiated Macrophage Foam Cell Formation

During atherosclerosis, low-density lipoprotein (LDL)-derived cholesterol accumulates in macrophages to form foam cells. Macrophage uptake of LDL promotes foam cell formation but the mechanism mediating this process is not clear. The present study investigates the mechanism of LDL uptake for macrophage colony-stimulating factor (M-CSF)-differentiated murine bone marrow-derived macrophages. LDL receptor-null (LDLR−/−) macrophages incubated with LDL showed non-saturable accumulation of cholesterol that did not down-regulate for the 24 h examined. Incubation of LDLR−/− macrophages with increasing concentrations of 125I-LDL showed non-saturable macrophage LDL uptake. A 20-fold excess of unlabeled LDL had no effect on 125I-LDL uptake by wild-type macrophages and genetic deletion of the macrophage scavenger receptors CD36 and SRA did not affect 125I-LDL uptake, showing that LDL uptake occurred by fluid-phase pinocytosis independently of receptors. Cholesterol accumulation was inhibited approximately 50% in wild-type and LDLR−/− mice treated with LY294002 or wortmannin, inhibitors of all classes of phosphoinositide 3-kinases (PI3K). Time-lapse, phase-contrast microscopy showed that macropinocytosis, an important fluid-phase uptake pathway in macrophages, was blocked almost completely by PI3K inhibition with wortmannin. Pharmacological inhibition of the class I PI3K isoforms alpha, beta, gamma or delta did not affect macrophage LDL-derived cholesterol accumulation or macropinocytosis. Furthermore, macrophages from mice expressing kinase-dead class I PI3K beta, gamma or delta isoforms showed no decrease in cholesterol accumulation or macropinocytosis when compared with wild-type macrophages. Thus, non-class I PI3K isoforms mediated macropinocytosis in these macrophages. Further characterization of the components necessary for LDL uptake, cholesterol accumulation, and macropinocytosis identified dynamin, microtubules, actin, and vacuolar type H(+)-ATPase as contributing to uptake. However, Pak1, Rac1, and Src-family kinases, which mediate fluid-phase pinocytosis in certain other cell types, were unnecessary. In conclusion, our findings provide evidence that targeting those components mediating macrophage macropinocytosis with inhibitors may be an effective strategy to limit macrophage accumulation of LDL-derived cholesterol in arteries.