Expression Of Scavenger Receptor CD36 Research Articles

Simvastatin Promotes Hematoma Absorption and Reduces Hydrocephalus Following Intraventricular Hemorrhage in Part by Upregulating CD36.

We previously found that hematoma worsens hydrocephalus after intraventricular hemorrhage (IVH) via increasing iron deposition and aggravating ependymal cilia injury; therefore, promoting hematoma absorption may be a promising strategy for IVH. Recently, some investigations imply that simvastatin has the ability of accelerating hematoma absorption. Thus, this study was designed to examine the efficacy of simvastatin for IVH in rats. Intracerebral hemorrhage with ventricular extension was induced in adult male Sprague-Dawley rats after autologous blood injection. Simvastatin or vehicle was administered orally at 1day after IVH and then daily for 1week. MRI studies were performed to measure the volumes of intracranial hematoma and lateral ventricle at days 1, 3, 7, 14, and 28 after IVH. Motor and neurocognitive functions were assessed at days 1 to 7 and 23 to 28, respectively. Iron deposition, iron-related protein expression, ependymal damage, and histology were detected at day 28. Expression of CD36 scavenger receptor (facilitating phagocytosis) was examined at day 3 after IVH using western blotting and immunofluorescence. Simvastatin significantly increased hematoma absorption ratio, reduced ventricular volume, and attenuated neurological dysfunction post-IVH. In addition, less iron accumulation and more cilia survival was observed in the simvastatin group when compared with the control. What's more, higher expression of CD36 was detected around the hematoma after simvastatin administration. Simvastatin significantly enhanced brain hematoma absorption, alleviated hydrocephalus, and improved neurological recovery after experimental IVH, which may in part by upregulating CD36 expression. Our data suggest that early simvastatin use may be a novel therapy for IVH patients.

High-density lipoprotein from subjects with coronary artery disease promotes macrophage foam cell formation: role of scavenger receptor CD36 and ERK/MAPK signaling.

Although high-density lipoprotein is atheroprotective, it can become dysfunctional in chronic inflammatory conditions and increase cardiovascular risk. We previously demonstrated that HDL from subjects with documented coronary artery disease is dysfunctional and is pro-oxidant/proinflammatory in macrophages. Here we examined the influence of dysfunctional/proinflammatory HDL (piHDL) on lipid accumulation in human macrophages, in comparison to functional HDL (nHDL). Exposure of macrophages to piHDL, in contrast to nHDL, resulted in oxidative stress and marked uptake of lipids from piHDL, leading to the formation of foam cell phenotype as noted by oil red O staining with concomitant increase in total cellular cholesterol content. Using western blotting, we identified that piHDL profoundly upregulated the expression of scavenger receptor CD36 and suppressed the expression of ABCG1 and SRB1 in macrophages, thereby facilitating cholesterol influx capacity of macrophages. We then identified that CD36 did not act alone, indeed it was activated in macrophages along with ERK/MAPK, in response to piHDL, which in turn led to lipid accumulation as well as proinflammatory response via activation of NFkB and subsequent release of proinflammatory markers-TNF-ά and MMP-9. These effects were confirmed using pharmacological inhibitors for either CD36 or ERK/MAPK. Furthermore, piHDL treatment moderately activated PPAR-γ and Nrf2, the known regulators of CD36 in macrophages, suggesting that the two forms of HDL differentially regulate CD36 expression. Taken together, the results demonstrate that a novel CD36-ERK/MAPK-dependent mechanism is involved in macrophage lipid accumulation by piHDL, there by revealing the importance of functional deficiency in HDL and its potential link to atherogenesis.

ROS via BTK-p300-STAT1-PPARγ signaling activation mediates cholesterol crystals-induced CD36 expression and foam cell formation

In understanding the mechanisms of cholesterol in the pathogenesis of atherosclerosis, previous studies from other laboratories have demonstrated that cholesterol crystals (CC) induce scavenger receptor CD36 expression and NLRP3-mediated inflammasome formation. In elucidating the mechanisms by which CC could enhance CD36 expression and foam cell formation, here we report that CC via NADPH and xanthine oxidases-mediated ROS production activates BTK, a non-receptor tyrosine kinase. In addition, CC induce p300 tyrosine phosphorylation and activation in a BTK-dependent manner, which in turn, leads to STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation. Furthermore, p300, STAT1 and PPARγ bound to a STAT binding site at −107 nt in CD36 promoter and enhanced its activity in ROS and BTK-dependent manner. Disruption of this STAT binding site by site-directed mutagenesis abolished CC-induced CD36 promoter activity. Together these results reveal for the first time that CC via producing ROS and activating BTK causes p300-mediated STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation.

339 - Reactive Oxygen Species via Activation of Bruton Tyrosine Kinase Mediate Cholesterol Crystals-Induced CD36 Expression and Foam Cell Formation

In understanding the mechanisms of cholesterol in the pathogenesis of atherosclerosis, previous studies from other laboratories have demonstrated that cholesterol crystals (CCs) induce scavenger receptor CD36 expression and NLRP3-mediated inflammasome formation. In understanding the mechanisms by which CCs could enhance CD36 expression and foam cell formation, here we report that CCs via NADPH oxidase and xanthine oxidase-mediated ROS production activates BTK, a non-receptor tyrosine kinase. In addition, CCs induce p300 tyrosine phosphorylation and activation in a BTK-dependent manner, which in turn, leads to STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation. Furthermore, p300, STAT1 and PPARγ bound to a STAT binding site at 107 nt in CD36 promoter and enhanced its activity in ROS-mediated BTK activation-dependent manner. Disruption of this STAT binding site by site-directed mutagenesis abolished CCs-induced CD36 promoter activity. Together these results reveal that CCs via producing ROS and activating BTK causes p300-mediated STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation in macrophages.

Isoflavone supplementation in postmenopausal women does not affect leukocyte LDL receptor and scavenger receptor CD36 expression: A double-blind, randomized, placebo-controlled trial.

Isoflavones are discussed to improve serum lipoproteins and body composition and to reduce cardiovascular disease risk in postmenopausal women (PMW). LDL receptors (LDLR) and scavenger receptor CD36 (CD36) play a pivotal role in the regulation of plasma LDL-cholesterol concentrations (LDL-chol). We investigated the impact of isoflavones on the receptor expression of both receptors in leukocytes of PMW. A randomized, double-blind, placebo-controlled trial in parallel design was conducted to assess the effects of an isoflavone-enriched soy extract (117.4 mg/day isoflavone aglycone equivalents) for 12 weeks on serum LDL-chol, LDLR, and CD36 expression on leukocytes in 170 healthy PMW. Baseline and after 12 weeks, blood lipid concentrations, anthropometric data and body composition were determined. Receptor expression on leukocytes was measured by means of flow cytometry. After the intervention, no significant differences were found for LDLR and CD36 expression on leukocytes. A significant increase of serum LDL-chol was shown for the isoflavone group (p = 0.03) after 12 weeks. Body fat content and VAT were not affected. Isoflavone supplementation for 12 weeks did not change LDLR and CD36 expression on leukocytes of PMW and did not affect body fat content and visceral adipose tissue (VAT), but slightly increased serum LDL-chol.

Accelerated transformation of macrophage-derived foam cells in the presence of collagen-induced arthritis mice serum is associated with dyslipidemia

Objective: Atherosclerosis characterized by accumulation of foam cells in the arterial intimal layer is accelerated in rheumatoid arthritis (RA) patients. We and others have previously demonstrated that serum from RA patients and collagen-induced arthritis (CIA) mice had proatherogenic features that might lead to progression of atherosclerosis. Here we further examined the effects of serum from CIA mice on the transformation of macrophage-derived foam cells, and investigated potential mechanism. Methods: DBA/1j mice were used to establish CIA model. Murine peritoneal macrophages and macrophage cell line RAW264.7 were treated with different dilute concentrations of mice serum. Results: CIA mice serum increased cholesterol influx and accumulation in murine macrophages, and markedly up-regulated scavenger receptor CD36 expression in the cells, but had no effect on intracellular lipid efflux. Neutralizing monocyte chemotactic protein (MCP)-1, the most significant altered cytokine we observed between normal and CIA mice serum to CIA mice could not reverse these effects. However, administering simvastatin to CIA mice could lower high-density lipoprotein-cholesterol (HDL-C) level and elevate oxidized low-density lipoprotein (ox-LDL) level in CIA mice serum, with attendant decreased lipid accumulation as well as CD36 expression in murine macrophages. Conclusion: Accelerated transformation of macrophage-derived foam cells via up-regulated CD36 expression is related to dyslipidemia rather than elevated inflammatory factor MCP-1 level in CIA mice serum. Decreased HDL-C and higher ox-LDL levels in CIA mice serum may link RA to atherosclerosis.

PPARγ-induced upregulation of CD36 enhances hematoma resolution and attenuates long-term neurological deficits after germinal matrix hemorrhage in neonatal rats

Germinal matrix hemorrhage remains the leading cause of morbidity and mortality in preterm infants in the United States with little progress made in its clinical management. Survivors are often afflicted with long-term neurological sequelae, including cerebral palsy, mental retardation, hydrocephalus, and psychiatric disorders. Blood clots disrupting normal cerebrospinal fluid circulation and absorption after germinal matrix hemorrhage are thought to be important contributors towards post-hemorrhagic hydrocephalus development. We evaluated if upregulating CD36 scavenger receptor expression in microglia and macrophages through PPARγ stimulation, which was effective in experimental adult cerebral hemorrhage models and is being evaluated clinically, will enhance hematoma resolution and ameliorate long-term brain sequelae using a neonatal rat germinal matrix hemorrhage model. PPARγ stimulation (15d-PGJ2) increased short-term PPARγ and CD36 expression levels as well as enhanced hematoma resolution, which was reversed by a PPARγ antagonist (GW9662) and CD36 siRNA. PPARγ stimulation (15d-PGJ2) also reduced long-term white matter loss and post-hemorrhagic ventricular dilation as well as improved neurofunctional outcomes, which were reversed by a PPARγ antagonist (GW9662). PPARγ-induced upregulation of CD36 in macrophages and microglia is, therefore, critical for enhancing hematoma resolution and ameliorating long-term brain sequelae.

Neopterin and 7,8-dihydroneopterin are generated within atherosclerotic plaques

Abstract Plasma neopterin correlates with the level of cardiovascular disease. Neopterin is the oxidation product of 7,8-dihydroneopterin, which is released by γ-interferon-stimulated macrophages. 7,8-Dihydroneopterin is a potent antioxidant, which inhibits lipid oxidation, macrophage cell death and scavenger receptor CD36 expression. The concentration of neopterin within atherosclerotic plaques was measured in tissue removed from carotid and femoral arteries. The excised plaques were cut into 3-mm-thick sections, and each section was analysed for neopterin, total neopterin, cholesterol, lipid peroxides, α-tocopherol and protein-bound 3,4-dihydroxyphenylalanine. Selected plaques were placed in tissue culture, and the media was analysed for 7,8-dihydroneopterin and neopterin release. Total neopterin levels ranged from 14 to 18.8 nmol/g of tissue. Large ranges of values were seen both within the same plaque and between plaques. No correlation between neopterin and any of the other analytes was observed, nor was there any significant trend in levels along the length of the plaques. γ-Interferon stimulation of cultured plaque generated total neopterin concentrations from 1 to 4 nmol/(g 24 h). The level of 7,8-dihydroneopterin generated within the plaque was within the range that inhibits lipid oxidation. The data show that atherosclerotic plaques are extremely dynamic in biochemistry and are the likely source of the plasma 7,8-dihydroneopterin and neopterin.

Genistein suppresses smooth muscle cell-derived foam cell formation through tyrosine kinase pathway

PurposeGenistein, as a protein tyrosine kinase inhibitor, has been shown to possess anti-atherosclerotic effects. Since the smooth muscle cell-derived foam cells are key components of atherosclerotic plaques. The aim of this study is to investigate the influence of genistein on foam cell transformation from vascular smooth muscle cells and possible mechanisms contributing to these effects. Methods and ResultsVascular smooth muscle cells exposed to ox-LDL developed into foam cell, as demonstrated by Oil Red O staining and cholesterol content analysis. Ox-LDL induced phenotype transformation of smooth muscle cells, decreased expression of α-actin and increased expression of CD68 (a specific marker for monocytes, can also function as a subtype of scavenger receptors). The expression of scavenger receptors CD36 and LOX-1 was measured, and their role in foam cell formation in the presence of genistein, daidzein (a structurally similar analogue of genistein) and herbimycin A (a commonly tyrosine kinase inhibitor). The results showed that foam cell formation was markedly reduced by genistein and herbimycin A, as well as the expression of CD68, CD36 and LOX-1. However, daidzein had no such effect. In addition, genistein-induced down-regulation of CD68, CD36 and LOX-1 could be reversed by sodium orthovanadate (a membrane-permeable protein tyrosine phosphatase inhibitor). ConclusionThe results showed that ox-LDL induce smooth muscle cell-derived foam cell formation and transform the phenotype of smooth muscle cell. While tyrosine kinase inhibitor, genistein could suppress smooth muscle cell-derived foam cell formation through inhibiting the protein expressions of CD68, CD36 and LOX-1.

Abstract 15724: Intermittent Hypoxia Induces Early Pro-Atherogenic Changes in Aortic Wall Macrophages in a Murine Model of Obstructive Sleep Apnea

Background: OSA is a highly prevalent condition throughout the lifespan, and has emerged as an independent risk factor for atherosclerosis. Macrophages play a key role in the pathogenesis of atherosclerosis through shifts in the continuum between the pro-inflammatory M1 and the athero-protective M2. We hypothesized that Intermittent Hypoxia (IH) during the sleep period, a model for OSA, will induce shifts towards a pro-atherogenic state in the spectrum of macrophages within the aortic vascular wall. Methods: 8-week old male C57BL/6J mice were exposed to IH for 12-hr/day during the light period or to room air (RA) for 6 weeks and were kept on a regular low-fat chow. Following exposure, full-length aortas were dissected and enzymatically digested. Single cell suspensions were prepared and cells were incubated with antibodies for macrophage markers previously implicated in atherogenesis and metabolic dysregulation - CD11b, F4/80, Ly6c, CD36, and CD64, and analyzed by FACS. Results: Macrophages were defined as CD11b+/F4/80+ cells. Significant increases in the percentage of macrophages emerged in IH-exposed mice (6.4%±0.3 vs. 8%±0.3, p=0.003, n=19-20/group). Furthermore, IH induced shifts in the macrophage population toward an M1 pro-inflammatory phenotype. Specifically, IH group showed significantly higher expression of Ly6c, (MFI:522±23 vs. 699±43, p=0.004, n=12/group) and increased the percentage of Ly6c+(hi) cells (9.2% vs. 11.7%, p=0.03). Conversely, tissue-resident marker CD64 expression in the aortic macrophages was down-regulated following IH exposures (MFI:3207±453 vs. 2967±483, p=0.03, n=12/group), while scavenger receptor CD36 expression was increased in the IH-exposed group (MFI:1694±56 vs.2129±209, p=0.005). Conclusion: Intermittent hypoxia during the sleep period leads to early expansion of the macrophage population in the aortic wall in a relatively resistant animal model for development of atherosclerosis, i.e., in the absence of a high-fat diet or of high atherogenic risk predisposing gene knockout. Furthermore IH induces changes in macrophage phenotypes, including a shift towards a pro-inflammatory phenotype, and recruitment of bone-marrow derived macrophages expressing indicators of metabolic activation.

Antioxidant and Atherogenic Foam cell Prevention Ability of Methanol and Aqueous Extract ofEmblica OfficinalisFruits and Its Effect onCD36andABCA1Gene Expression in RAW 264.7 Macrophage Cell Line

Different solvent extracts of Emblica officinalis fruits were assessed for antioxidant activity, and it was seen that the methanol and water extracts showed the highest activity. Foam cell formation, the basis of atherosclerotic plaque formation, was prevented by only the methanol and water extracts of Emblica and not by acetone, ethyl acetate and hexane extracts in RAW 264.7 cell lines. Gene expression studies showed that CD36 scavenger receptor expression was downregulated and ABCA1 (cholesterol efflux receptor) expression was upregulated in a dose- and timedependent manner with the upregulation seen at 12 and 24 h time points. Highperformance liquid chromatography analysis for methanol and water extracts showed coumaric acid to be the next abundant compound followed by caffeic acid after myricetin and gallic acid, which were also present in other extracts in high amounts. A high correlation was seen between caffeic acid, gallic acid, coumaric acid and total antioxidant capacity. PRACTICAL APPLICATIONS Emblica officinalis fruits, commonly incorporated in various food products, has been known to be a “wonder fruit” since ancient times and has been known to dissolve atherosclerotic plaque in arteries. However, the precise molecular mechanism of its action has not been elucidated yet. Furthermore, a systematic study of the extraction system is yet to be done. The present work attempts to shed some light on these questions to form a basis for further research on this precious, but under exploited fruit, and also to promote its consumption on a large scale.

PKCδ is dispensible for oxLDL uptake and foam cell formation by human and murine macrophages.

Uptake of oxidized lipoprotein particles (oxLDL) and foam cell formation by macrophages is one of the first steps in the development of atherosclerosis. Recently, protein kinase C δ (PKCδ) has been implicated as a regulator of oxLDL uptake and foam cell formation via down-regulation of PKCβ and scavenger receptors CD36 and SR-A expression. Here, we describe studies in which we have re-evaluated the role of PKCδ in oxLDL uptake and foam cell formation. PKCδ expression was silenced in the human monocytic cell lines and also in primary human monocytes to analyse oxLDL uptake and CD36 expression. Additionally, bone marrow-derived macrophages of PKCδ knockout mice and macrophages cultured from patients with rare null mutations in the PRKCD gene were tested for uptake of oxLDL and foam cell formation. Expression of scavenger receptor CD36 was determined and levels of PKCβ isoforms were quantified. Neither a reduction in PKCδ levels nor its complete absence resulted in a detectable effect on the uptake of oxLDL and the formation of foam cells. PKCδ is dispensible for oxLDL uptake and foam cell formation by monocytes and macrophages.

DIABETES MELLITUS TIPO 2: QUAL O PAPEL DA INSULINA NA EXPRESSÃO DE NF-KappaB, PPARϒ E CD36?

No diabetes mellitus tipo 2 (DM2) e na síndrome de resistência à insulina, as complicações cardiovasculares resultam de um conjunto de processos aterogênicos envolvendo hiperglicemia crônica, excessiva glicação de proteínas (AGEs), ativação do fator nuclear kappa B (NKκB) associada com o aumento da expressão de citocinas inflamatórias e estresse oxidativo, observando-se ainda alteração de LDL e expressão do receptor de scavenger CD36. A contribuição da hiperinsulinemia nesta sequência não é completamente elucidada. Nesta revisão, relata-se como a insulina pode modular a expressão proteica de NFκB, PPAR gama (PPARγ) e CD36 em células da musculatura lisa vascular (CMLV) da aorta de ratos estimuladas pelos AGE.

Modulation of Phosphorylation of Tocopherol and Phosphatidylinositol by hTAP1/SEC14L2-Mediated Lipid Exchange

The vitamin E derivative, alpha-tocopheryl phosphate (αTP), is detectable in cultured cells, plasma and tissues in small amounts, suggesting the existence of enzyme(s) with α-tocopherol (αT) kinase activity. Here, we characterize the production of αTP from αT and [γ-32P]-ATP in primary human coronary artery smooth muscle cells (HCA-SMC) using separation by thin layer chromatography (TLC) and subsequent analysis by Ultra Performance Liquid Chromatography (UPLC). In addition to αT, although to a lower amount, also γT is phosphorylated. In THP-1 monocytes, γTP inhibits cell proliferation and reduces CD36 scavenger receptor expression more potently than αTP. Both αTP and γTP activate the promoter of the human vascular endothelial growth factor (VEGF) gene with similar potency, whereas αT and γT had no significant effect. The recombinant human tocopherol associated protein 1 (hTAP1, hSEC14L2) binds both αT and αTP and stimulates phosphorylation of αT possibly by facilitating its transport and presentation to a putative αT kinase. Recombinant hTAP1 reduces the in vitro activity of the phosphatidylinositol-3-kinase gamma (PI3Kγ) indicating the formation of a stalled/inactive hTAP1/PI3Kγ heterodimer. The addition of αT, βT, γT, δT or αTP differentially stimulates PI3Kγ, suggesting facilitated egress of sequestered PI from hTAP1 to the enzyme. It is suggested that the continuous competitive exchange of different lipophilic ligands in hTAPs with cell enzymes and membranes may be a way to make these lipophiles more accessible as substrates for enzymes and as components of specific membrane domains.

Modulation of CD36 scavenger receptor expression by curcumin and vitamin E affects cellular uptake of lipids and bacteria (639.1)

The CD36/FAT scavenger receptor/fatty acid translocase mediates uptake of fatty acids into various tissues. Other CD36 ligands include oxLDL, β‐amyloid, Plasmodium falciparum ‐infected erythrocytes, and bacteria. The ability of nutritional components to affect CD36 expression and to change the inflammatory and phagocytic response to lipids and bacteria in monocytes/macrophages could be important for modulating inflammation and atherosclerosis. Here we show that curcumin, a natural polyphenol from turmeric plant Curcuma longa, is rapidly taken up into cells and increases surface localization of CD36 leading to increased lipid uptake in THP‐1 monocytes/macrophages. The curcumin metabolite, tetrahydrocurcumin, has no effect, most likely since it is not efficiently taken up into cells. In contrast, CD36 surface localization and lipid uptake were decreased by α‐tocopherol and more so by α‐tocopheryl phosphate. Interestingly, phagocytosis of inactivated Staphylococcus aureus fluorescent bioparticles was affected by these compounds in a similar manner as observed for lipids, suggesting that binding and uptake of lipids and bacteria may share common molecular mechanisms. Thus, these dietary components may not only directly modulate the cellular anti‐microbial and inflammatory response but also indirectly by influencing host‐microbe interactions. Supported by USDA Contract #58‐1950‐0‐014.Grant Funding Source: Supported by USDA Contract #58‐1950‐0‐014.

Detailed characterization of the endocannabinoid system in human macrophages and foam cells, and anti-inflammatory role of type-2 cannabinoid receptor

ObjectiveCannabinoid receptors are activated in murine macrophages upon exposure to oxidized low-density lipoproteins (oxLDL), and type-1 cannabinoid receptor (CB1R) is considered as a risk factor in atherosclerosis, because it promotes cholesterol accumulation and release of inflammatory mediators. Conversely, accumulated evidence suggests a protective role for type-2 cannabinoid receptor (CB2R). Here, we sought to ascertain whether different elements of the endocannabinoid system (ECS) were activated in human lipid-laden macrophages, and whether CB2R played any role in atherogenesis and inflammation of these cells. Methods and resultsHuman macrophages were exposed to oxLDL in order to obtain lipid-laden foam cells. Liquid chromatography/mass spectrometry (LC/MS) was used to measure the production of the endocannabinoids in both macrophages and foam cells, and radiometric assays were performed to measure cannabinoid receptor binding and activity of endocannabinoid metabolizing enzymes. OxLDL accumulation was investigated by confocal imaging, and cytokine production and release were measured by means of flow cytometry and ELISA. The results showed that human macrophages possess a fully functional ECS, which was modulated by oxLDL. Selective CB2R activation reduced cellular oxLDL accumulation, which was associated with decreased expression of CD36 scavenger receptor, and decreased production of TNFα, IL-12 and IL-10. These anti-atherogenic and anti-inflammatory effects were reverted by the selective CB2R antagonist SR144528. ConclusionsA fully active ECS is present in human macrophages and macrophage-derived foam cells. Selective activation of CB2R reduces CD36-dependent oxLDL accumulation and modulates production of inflammatory cytokines, thus representing a potential therapeutic strategy to combat atherosclerosis.

Overexpression of NF-κB p65 in macrophages ameliorates atherosclerosis in apoE-knockout mice

The transcription factor NF-κB p65 is a key regulator in the regulation of an inflammatory response and in the pathology of atherosclerosis. However, there is no direct evidence for the role of NF-κB in macrophages in the development of atherosclerosis. We investigated whether macrophage overexpression of p65 in apoE-knockout mice could improve atherosclerosis. Transgenic (Tg) mice overexpressing p65 in macrophages were generated by crossing fatty acid-binding protein 4 (aP2) promoter-controlled p65 mice with apoE-knockout (KO) mice. Tg mice exhibited functional activation of NF-κB signaling in macrophages and fat tissues. We observed that the atherosclerotic lesion was 40% less in the Tg mice compared with the apoE-KO controls fed a standard atherogenic diet for 16 wk (n = 12). The Tg mice were leaner from reduced fat mass by increased energy expenditure. Moreover, the overexpression of p65 in macrophages suppressed foam cell formation. Our results show that there is 1) an increased fatty acid oxidation in macrophages, 2) a reduced scavenger receptor CD36 expression and lipid accumulation in microphages, 3) reduced-inflammation cytokines in serum, and 4) enhanced energy expenditure in Tg mice. Our data suggest that activation of NF-κB in macrophages has atheroprotective effects in mice by enhancing lipid metabolism and energy expenditure.

Abstract 381: IL-19 Inhibits Atherosclerosis in LDLR-/- Mice by Modulating Cholesterol Uptake in Macrophages and Vascular Smooth Muscle Cells

IL-19 is a recently described, putative anti-inflammatory cytokine which had previously been ascribed to be leukocyte specific. IL-19 is not detected in normal artery, but we detected IL-19 in multiple cell types in human atherosclerotic plaque suggesting a role for this interleukin in atherosclerosis. The purpose of this study was to determine whether administration of exogenous IL-19 could attenuate development of pre-formed atherosclerotic plaque, and to identify potential molecular mechanisms. LDLR-/- mice were fed high-fat diet for 12 weeks and then administered with 10ng/g/day IL-19 or PBS for an additional 8 weeks. En face analysis demonstrated that IL-19 could halt, but not reverse existing plaque (26.7+/-1.7%, 41.03+/-3.1%, 23.70+/-2.6% for baseline, PBS control, and IL-19-treated mice). Foam cell formation by macrophages and vascular smooth muscle cells (VSMC) is a hallmark event during atherosclerosis. Nothing has been reported regarding IL-19 effects on macrophage or VSMC lipid uptake; we therefore investigated whether IL-19 affects macrophage and VSMC cholesterol handling. Addition of IL-19 to wild-type bone marrow derived macrophages (BMDM) significantly promoted oxLDL uptake, conversely, BMDM from IL-19-/- mice had significantly less oxLDL uptake compared to wild-type BMDM. Addition of IL-19 to wild type BMDM significantly increased expression of scavenger receptor B1 (SR-B1), and decreased expression of inflammatory cytokines TNFα, IL-12b, MCP1. Interestingly, converse results were obtained with VSMC, as addition of IL-19 to wild-type VSMC decreased uptake of oxLDL ( p<0.05 ) and decreased expression of scavenger receptor CD36. VSMC isolated from IL-19-/- mice had increased uptake of oxLDL (p<0.0001). It is reported that M2 macrophages participate in plaque regression. IL-19 decreased IL-12b and significantly promoted the polarization of anti-inflammatory M2 phenotype in BMDM as evidenced by the increased expression of YM1 and IL-10 mRNA. These data demonstrate that IL-19 can inhibit progression of existing atherosclerotic plaque by modulating lipid metabolism in VSMC and macrophages and by promoting macrophage differentiation into an alternative, anti-inflammatory M2 phenotype.

PPARγ/RXRα-Induced and CD36-Mediated Microglial Amyloid-β Phagocytosis Results in Cognitive Improvement in Amyloid Precursor Protein/Presenilin 1 Mice

Alzheimer's disease (AD) is characterized by the extracellular deposition of amyloid-β (Aβ), neurofibrillary tangle formation, and a microglial-driven inflammatory response. Chronic inflammatory activation compromises microglial clearance functions. Because peroxisome proliferator-activated receptor γ (PPARγ) agonists suppress inflammatory gene expression, we tested whether activation of PPARγ would also result in improved microglial Aβ phagocytosis. The PPARγ agonist pioglitazone and a novel selective PPARα/γ modulator, DSP-8658, currently in clinical development for the treatment of type 2 diabetes, enhanced the microglial uptake of Aβ in a PPARγ-dependent manner. This PPARγ-stimulated increase of Aβ phagocytosis was mediated by the upregulation of scavenger receptor CD36 expression. In addition, combined treatment with agonists for the heterodimeric binding partners of PPARγ, the retinoid X receptors (RXRs), showed additive enhancement of the Aβ uptake that was mediated by RXRα activation. Evaluation of DSP-8658 in the amyloid precursor protein/presenilin 1 mouse model confirmed an increased microglial Aβ phagocytosis in vivo, which subsequently resulted in a reduction of cortical and hippocampal Aβ levels. Furthermore, DSP-8658-treated mice showed improved spatial memory performance. Therefore, stimulation of microglial clearance by simultaneous activation of the PPARγ/RXRα heterodimer may prove beneficial in prevention of AD.

Berberine-induced inhibition of adipocyte enhancer-binding protein 1 attenuates oxidized low-density lipoprotein accumulation and foam cell formation in phorbol 12-myristate 13-acetate-induced macrophages

The phagocytosis of oxidized low-density lipoprotein (oxLDL) by monocyte-derived macrophages and the subsequent differentiation of macrophages into foam cells are the key steps in atherogenesis. Scavenger receptors, such as CD36 and lectin-like low-density lipoprotein receptor 1 (LOX-1), are responsible for the uptake of oxLDL. Adipocyte enhancer-binding protein 1 (AEBP1) regulates many key genes associated with intracellular cholesterol efflux. The present study investigated the function of berberine, a compound isolated from Rhizoma coptidis, on foam cell formation, and explored the possible underlying mechanism. We found that berberine inhibited the oxLDL uptake of macrophages and reduced foam cell formation in a dose-dependent manner. Moreover, AEBP1 expression in macrophages increased and decreased after oxLDL and berberine treatments in a dose-dependent manner, respectively. Berberine reduced the expression of scavenger receptors CD36 and LOX-1, but did not affect the expression of CD68 in oxLDL-stimulated macrophages. Overall, berberine reduced foam cell formation by a dual mechanism, which decreased oxLDL internalization via the suppression of CD36 and LOX-1, and increased cholesterol efflux by inhibiting AEBP1 expression in macrophages.