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To explore the sesquiterpenoids in Curcuma longa L. and their activity related to anti-atherosclerosis. The chemical compounds of the rhizomes of C. longa were separated and purified by multiple chromatography techniques. Their structures were established by a variety of spectroscopic experiments. The absolute configurations were determined by comparing experimental and calculated NMR chemical shifts and electronic circular dichroism (ECD) spectra. Their anti-inflammatory effects and inhibitory activity against macrophage-derived foam cell formation were evaluated by lipopolysaccharide (LPS) and oxidized low-density lipoprotein (ox-LDL)-injured RAW264.7 macrophages, respectively. This study resulted in the isolation of 10 bisabolane-type sesquiterpenoids (1–10) from C. longa, including two pairs of new epimers (curbisabolanones A–D, 1–4). Compound 4 significantly inhibited LPS-induced nitric oxide (NO), interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and prostaglandin E2 (PGE2) production in RAW264.7 cells. Furthermore, compound 4 showed inhibitory activity against macrophage-derived foam cell formation, which was represented by markedly reducing ox-LDL-induced intracellular lipid accumulation as well as total cholesterol (TC), free cholesterol (FC), and cholesterol ester (CE) contents in RAW264.7 cells. These findings suggest that bisabolane-type sesquiterpenoids, one of the main types of components in C. longa, have the potential to alleviate the atherosclerosis process by preventing inflammation and inhibiting macrophage foaming.

(1) Background: The cholinergic anti-inflammatory pathway (CAP) has been implicated in the regulation of various diseases, including chronic inflammatory cardiovascular disorders such as atherosclerosis (AS). This study aims to explore the underlying regulatory mechanisms of CAP activity in the progression of AS. (2) Methods: The Apoe-/- mice were subjected to sham, bilateral cervical vagotomy surgery (VGX), and VGX supplemented with Gainesville Tokushima scientists (GTS)-21 (4 mg/kg/d) and then fed with a high-fat diet for 10 weeks. Atherosclerotic lesion size and inflammation levels were investigated by histology and inflammatory cytokines analysis. The blood M1/M2 macrophages were analyzed by flow cytometry. Primary mouse bone marrow-derived macrophages (BMDM), peritoneal macrophages, and RAW264.7 cells were treated with CAP agonists acetylcholine (Ach) and GTS-21 to study their effects on macrophage functions. (3) Results: Compared with the sham group, inhibition of CAP by the VGX resulted in growing aortic lipid plaque area, deteriorated inflammatory levels, and aberrant quantity of M1/M2 macrophages in Apoe-/- mice. However, these detrimental effects of VGX were significantly ameliorated by the reactivation of CAP through GTS-21 treatment. The in vitro study using macrophages revealed that stimulation with CAP agonists suppressed M1, but promoted M2 macrophage polarization through the upregulation of TNFAIP3 and phosphorylation STAT3 levels, respectively. Moreover, the activation of CAP inhibited the formation of macrophage foam cells in the peritoneal cavity by regulating genes related to cholesterol metabolism. (4) Conclusions: This study provides novel evidence and mechanisms that the CAP plays an important role in the regulation of AS development by controlling macrophage functions, implying a potential use of CAP activation as a therapeutic strategy for AS treatment.

Vascular smooth muscle cells (SMCs) are important vascular components that are essential for the regulation of vascular functions during vascular atherosclerogenesis and vascular injury. Oxidized low-density lipoprotein (oxLDL) is known to induce SMC activation and foam cell transformation. This study characterized the role of hepatoma-derived growth factor (HDGF) in oxLDL-induced foam cell formation in cultured primary rat aortic SMCs. OxLDL exposure significantly increased HDGF expression and extracellular release. It also upregulated atherogenic regulators in SMCs, including TLR4, MyD88, LOX-1, and CD36. Exogenous HDGF stimulation not only increased the expression of cognate receptor nucleolin, but also the innate immunity regulators TLR4/MyD88 and lipid metabolism regulators, including LOX-1 and CD36. Oil red O staining showed that HDGF did not initiate, but enhanced oxLDL-driven foam cell formation in SMCs. Further signaling characterization demonstrated that oxLDL evoked activation of PI3K/Akt and p38 MAPK signaling pathways, both of which were involved in the upregulation of HDGF, LOX-1, and CD36 induced by oxLDL. Gene knockdown experiments using LOX-1 targeted siRNA demonstrated that LOX-1 expression was critical for oxLDL-induced HDGF upregulation, while HDGF gene depletion completely abolished oxLDL-triggered TLR4, LOX-1, and CD36 overexpression and foam cell formation in SMCs. These findings strongly suggest that oxLDL-induced HDGF upregulation participates in subsequent LOX-1 and CD36 expression in aortic SMCs and mechanistically contributes to the formation of SMC-derived foam cells. The oxLDL/LOX-1/HDGF axis may serve as a target for anti-atherogenesis therapy.

Atherosclerosis is a major cause of human cardiovascular disease, which is the leading cause of mortality around the world. Various physiological and pathological processes are involved, including chronic inflammation, dysregulation of lipid metabolism, development of an environment characterized by oxidative stress and improper immune responses. Accordingly, the expansion of novel targets for the treatment of atherosclerosis is necessary. In this study, we focus on the role of foam cells in the development of atherosclerosis. The specific therapeutic goals associated with each stage in the formation of foam cells and the development of atherosclerosis will be considered. Processing and metabolism of cholesterol in the macrophage is one of the main steps in foam cell formation. Cholesterol processing involves lipid uptake, cholesterol esterification and cholesterol efflux, which ultimately leads to cholesterol equilibrium in the macrophage. Recently, many preclinical studies have appeared concerning the role of non-encoding RNAs in the formation of atherosclerotic lesions. Non-encoding RNAs, especially microRNAs, are considered regulators of lipid metabolism by affecting the expression of genes involved in the uptake (e.g., CD36 and LOX1) esterification (ACAT1) and efflux (ABCA1, ABCG1) of cholesterol. They are also able to regulate inflammatory pathways, produce cytokines and mediate foam cell apoptosis. We have reviewed important preclinical evidence of their therapeutic targeting in atherosclerosis, with a special focus on foam cell formation.

The persistence of macrophage-derived foam cells in the artery wall fuels atherosclerosis development. However, the mechanism of foam cell formation regulation remains elusive. We are committed to determining the role that CD147 might play in macrophage foam cell formation during atherosclerosis. In this study, we found that CD147 expression was primarily increased in mouse and human atherosclerotic lesions that were rich in macrophages and could be upregulated by ox-LDL. High-throughput compound screening indicated that ox-LDL-induced CD147 upregulation in macrophages was achieved through PI3K/Akt/mTOR signaling. Genetic deletion of macrophage CD147 protected against foam cell formation by impeding cholesterol uptake, probably through the scavenger receptor CD36. The opposite effect was observed in primary macrophages isolated from macrophage-specific CD147-overexpressing mice. Moreover, bioinformatics results indicated that CD147 suppression might exert an atheroprotective effect via various processes, such as cholesterol biosynthetic and metabolic processes, LDL and plasma lipoprotein clearance, and decreased platelet aggregation and collagen degradation. Our findings identify CD147 as a potential target for prevention and treatment of atherosclerosis in the future.

Background Macrophages that accumulate in atherosclerotic plaques contribute to progression of the lesions to more advanced and complex plaques. Although iron deposition was found in human atherosclerotic plaques, clinical and pre-clinical studies showed controversial results. Several epidemiological studies did not show the positive correlation between a systemic iron status and an incidence of cardiovascular diseases, suggesting that the iron involvement occurs locally, rather than systemically. Results To determine the direct in vivo effect of iron accumulation in macrophages on the progression of atherosclerosis, we generated Apoe−/− mice with a macrophage-specific ferroportin (Fpn1) deficiency (Apoe−/−Fpn1LysM/LysM). Fpn1 deficiency in macrophages dramatically accelerated the progression of atherosclerosis in mice. Pathophysiological evidence showed elevated levels of reactive oxygen species, aggravated systemic inflammation, and altered plaque-lipid composition. Moreover, Fpn1 deficiency in macrophages significantly inhibited the expression of ABC transporters (ABCA1 and ABCG1) by decreasing the expression of the transcription factor LXRα, which reduced cholesterol efflux and therefore promoted foam cell formation and enhanced plaque formation. Iron chelation relieved the symptoms moderately in vivo, but drastically ex vivo. Conclusions Macrophage iron content in plaques is a critical factor in progression of atherosclerosis. The interaction of iron and lipid metabolism takes place in macrophage-rich atherosclerotic plaques. And we also suggest that altering intracellular iron levels in macrophages by systemic iron chelation or dietary iron restriction may be a potential supplementary strategy to limit or even regress the progression of atherosclerosis.

Deciphering the molecular and cellular processes involved in foam cell formation is critical to understanding the pathogenesis of atherosclerosis. Interferon regulatory factor 1 (IRF1) was first identified as a transcriptional regulator of type-I interferons (IFNs) and IFN inducible genes. Our study aims to explore the role of IRF1 in atherosclerotic foam cell formation and understand the functional diversity of IRF1 in various cell types contributing to atherosclerosis. Methods: We induced experimental atherosclerosis in ApoE-/-IRF1-/- mice and evaluated the effect of IRF1 on disease progression and foam cell formation. Results: IRF1 expression was increased in human and mouse atherosclerotic lesions. IRF1 deficiency inhibited modified lipoprotein uptake and promoted cholesterol efflux, along with altered expression of genes implicated in lipid metabolism. Gene expression analysis identified scavenger receptor (SR)-AI as a regulated target of IRF1, and SR-AI silencing completely abrogated the increased uptake of modified lipoprotein induced by IRF1. Our data also explain a mechanism underlying endotoxemia-complicated atherogenesis as follows: two likely pro-inflammatory agents, oxidized low-density lipoprotein (ox-LDL) and bacterial lipopolysaccharide (LPS), exert cooperative effects on foam cell formation, which is partly attributable to a shift of IRF1-Ubc9 complex to IRF1- myeloid differentiation primary response protein 88 (Myd88) complex and subsequent IRF1 nuclear translocation. Additionally, it seems that improved function of vascular smooth muscle cells (VSMCs) also accounts for the diminished and more stable atherosclerotic plaques observed in ApoE-/-IRF1-/- mice. Conclusions: Our findings demonstrate an unanticipated role of IRF1 in the regulation of gene expression implicated in foam cell formation and identify IRF1 activation as a new risk factor in the development, progression and instability of atherosclerotic lesions.

Gynostemma pentaphyllum was widely consumed in China because of its various pharmacological activities. Numerous studies have confirmed the beneficial effects of G. pentaphyllum. However, the ultimate compounds responsible for its inhibitory effects on foam cell formation were still unknown. Gypenoside LVI (GPLVI), a dammarane-type gynosaponin was isolated and identified from G. pentaphyllum. Treatment of GPLVI successfully attenuated foam cell formation, as evidenced by Oil Red O staining, TG and cholesterol contents, and Dil-ox-LDL uptake analyses. GPLVI displayed significant inhibitory effects on secretion of IL-6 and IL-1β. In contrast, production of TNF-α was not markedly reduced. GPLVI also markedly induced ABCG1, SRB1 and LXRα expression. Additionally, GPLVI significantly blocked phosphorylation of ERK and JNK. Taken together, our results suggested that GPLVI might be responsible for the inhibitory effect of G. pentaphyllum on ox-LDL-induced foam cell formation mainly by promoting cholesterol efflux and inhibiting inflammatory response.

(1) Background: The cholinergic anti-inflammatory pathway (CAP) has been implicated in the regulation of various diseases, including chronic inflammatory cardiovascular disorders such as atherosclerosis (AS). This study aims to explore the underlying regulatory mechanisms of CAP activity in the progression of AS. (2) Methods: The Apoe-/- mice were subjected to sham, bilateral cervical vagotomy surgery (VGX), and VGX supplemented with Gainesville Tokushima scientists (GTS)-21 (4 mg/kg/d) and then fed with a high-fat diet for 10 weeks. Atherosclerotic lesion size and inflammation levels were investigated by histology and inflammatory cytokines analysis. The blood M1/M2 macrophages were analyzed by flow cytometry. Primary mouse bone marrow-derived macrophages (BMDM), peritoneal macrophages, and RAW264.7 cells were treated with CAP agonists acetylcholine (Ach) and GTS-21 to study their effects on macrophage functions. (3) Results: Compared with the sham group, inhibition of CAP by the VGX resulted in growing aortic lipid plaque area, deteriorated inflammatory levels, and aberrant quantity of M1/M2 macrophages in Apoe-/- mice. However, these detrimental effects of VGX were significantly ameliorated by the reactivation of CAP through GTS-21 treatment. The in vitro study using macrophages revealed that stimulation with CAP agonists suppressed M1, but promoted M2 macrophage polarization through the upregulation of TNFAIP3 and phosphorylation STAT3 levels, respectively. Moreover, the activation of CAP inhibited the formation of macrophage foam cells in the peritoneal cavity by regulating genes related to cholesterol metabolism. (4) Conclusions: This study provides novel evidence and mechanisms that the CAP plays an important role in the regulation of AS development by controlling macrophage functions, implying a potential use of CAP activation as a therapeutic strategy for AS treatment.

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Histone modifications play an important role in the occurrence and development of atherosclerosis in human and atherosclerosis-prone mice. Histone methylation in macrophages, monocytes and endothelial cells markedly influence the progression of atherosclerosis. However, it remains unclear whether treatment with a histone methyltransferase enhancer of zeste homolog 2 (EZH2) inhibitor may suppress atherosclerosis. The present study aimed to determine the effects of the EZH2 inhibitor, GSK126, on the suppression and regression of atherosclerosis in apolipoprotein E-deficient mouse models. In vitro, it was found that pharmacological inhibition of EZH2 by GSK126 markedly reduced lipid transportation and monocyte adhesion during atherogenesis, predominantly through increasing the expression levels of ATP-binding cassette transporter A1 and suppressing vascular cell adhesion molecule 1 in human THP-1 cells. In vivo, it was found that atherosclerotic plaques in GSK126-treated mice were significantly decreased when comparing with the vehicle-treated animals. These results indicated that the GSK126 has the ability to attenuate the progression of atherosclerosis by reducing macrophage foam cell formation and monocyte adhesion in cell and mouse models. In conclusion, the present study provided new insights into the molecular mechanism behind the action of GSK126 and suggested its therapeutic potential for the treatment of atherosclerosis.

Oxidation of low-density lipoprotein (LDL) plays a crucial role in the pathogenesis of atherosclerosis. Hemin (iron (III)-protoporphyrin IX) is a degradation product of hemoglobin that can be found in thalassemia patients. Hemin is a strong oxidant that can cause LDL oxidation and contributes to atherosclerosis in thalassemia patients. Lusianthridin from Dendrobium venustrum is a phenolic compound that possesses antioxidant activity. Hence, lusianthridin could be a promising compound to be used against hemin-induced oxidative stress. The major goal of this study is to evaluate the protective effect of lusianthridin on hemin-induced low-density lipoprotein oxidation (he-oxLDL). Here, various concentrations of lusianthridin (0.25, 0.5, 1, and 2 µM) were preincubated with LDL for 30 min, then 5 µM of hemin was added to initiate the oxidation, and oxidative parameters were measured at various times of incubation (0, 1, 3, 6, 12, 24 h). Lipid peroxidation of LDL was measured by thiobarbituric reactive substance (TBARs) assay and relative electrophoretic mobility (REM). The lipid composition of LDL was analyzed by using reverse-phase HPLC. Foam cell formation with he-oxLDL in RAW 264.7 macrophage cells was detected by Oil Red O staining. The results indicated that lusianthridin could inhibit TBARs formation, decrease REM, decrease oxidized lipid products, as well as preserve the level of cholesteryl arachidonate and cholesteryl linoleate. Moreover, He-oxLDL incubated with lusianthridin for 24 h can reduce the foam cell formation in RAW 264.7 macrophage cells. Taken together, lusianthridin could be a potential agent to be used to prevent atherosclerosis in thalassemia patients.

Oleacein is a polyphenol and can be found in unfiltered extra virgin olive oil and leaves Ligustrum vulgare L. (Oleaceae). The aim of the present study was to investigate whether oleacein could increase efflux cholesterol from macrophages. Oleacein in dose-dependent manner (OLEA20, OLEA50) significantly reduced lipid deposits in macrophages. The increase of SRB1 expression was found for OLEA50 and OLEA20 compared to oxLDL-induced macrophages. Oleacein significantly up-regulated protein expression of ABCA1 and ABCG1 transporter. Moreover, oleacein increased of HO-1 intracellular secretion, as well as increased activation of Nrf2. Whereas, the level of NF-κB protein was almost completely inhibited by oleacein at the same concentrations. For OLEA10, no significant changes were observed for the parameters tested. Our study demonstrated that oleacein may reduce foam cell formation. Therefore, we propose a novel explanation for the oleacein, that can be used to develop new therapeutic strategies for the treatment of atherosclerosis.

The persistence of cholesterol-engorged macrophages (foam cells) in the artery wall fuels the development of atherosclerosis. However, the mechanism that regulates the formation of macrophage foam cells and impedes their emigration out of inflamed plaques is still elusive. Here, we report that adhesion receptor CD146 controls the formation of macrophage foam cells and their retention within the plaque during atherosclerosis exacerbation. CD146 is expressed on the macrophages in human and mouse atheroma and can be upregulated by oxidized low-density lipoprotein (oxLDL). CD146 triggers macrophage activation by driving the internalization of scavenger receptor CD36 during lipid uptake. In response to oxLDL, macrophages show reduced migratory capacity toward chemokines CCL19 and CCL21; this capacity can be restored by blocking CD146. Genetic deletion of macrophagic CD146 or targeting of CD146 with an antibody result in much less complex plaques in high-fat diet-fed ApoE−/− mice by causing lipid-loaded macrophages to leave plaques. Collectively, our findings identify CD146 as a novel retention signal that traps macrophages within the artery wall, and a promising therapeutic target in atherosclerosis treatment.

Atherosclerosis (AS) is a common pathological basis for the development of various cardiovascular and cerebrovascular diseases, however, currently, no effective treatment against AS has been established. It has previously been suggested that intravascular cytochrome P450 (CYP) oxidase is involved in the pathogenesis of AS. The present study investigated the role of cytochrome P450, family 2, subfamily J, polypeptide 2 (CYP2J2), the most common subtype of CYP oxidase in the human body, in the occurrence and development of AS. CYP2J2 was overexpressed in human umbilical vein endothelial cells (HUVECs), human arterial smooth muscle cells (HASMCs), and human peripheral monocyte-derived foam cells by lentiviral infection. The mRNA and protein levels were measured by reverse-transcription quantitative polymerase chain reaction and western blotting, respectively. Cell proliferation and migration were determined by MTS and Transwell assays, respectively. Furthermore, lipid accumulation was detected with Oil red O staining. The concentrations of total and free cholesterol were measured using a quantitation kit. Following lentiviral infection, CYP2J2 was successfully overexpressed in HUVEC, HASMC and foam cells. CYP2J2 overexpression promoted proliferation and migration in HUVECs and suppressed these actions in HASMCs. In addition, it suppressed oxidized low-density lipoprotein-induced foam cell formation. In conclusion, it was hypothesized that CYP2J2 may have a protective role in AS, as proliferation of HASMCs and the formation of foam cells are notable characteristics of AS.

Pine (Pinus morrisonicola Hay, PM) needles have been used as folk medicine for their antihypertension and lipid-lowering effects. As supercritical fluid extraction (SFE) is considered an ideal technique for the extraction of essential oil from plant materials, the present work investigated the optimal SFE conditions and the protective effects of different resulting fractions of PM needles on lipid peroxidation and foam cell production in macrophages. Nine PM needle extracts (PME1–9) were obtained in 1%–4% yields using different SFE conditions, of which PME1 had the lowest yield (1.1%) and PME3 the highest (3.9%). PME3 exhibited lower cytotoxic effects and stronger inhibition of lipid peroxidation and formation of foam cell in RAW 264.7 macrophages than those of other PME extracts. PME3-1 purified from PME3 by column and thin layer chromatography inhibited LDL oxidation more effectively than did PME3 in a cell-free system oxidized by Cu2+. PME3-1 dose-dependently (25–100 μg/mL) decreased conjugated diene levels and foam cell formation induced by ox-LDL. GC/MS analyses revealed that 1-docosene, neophytadiene, and methyl abietate were increased 5.2-, 1.7- and 4.3-fold in PME3-1 relative to PME3. A new hydrocarbon compound, cedrane-8,13-diol, was identified in PME3-1. Overall, the present study demonstrates the optimal extraction conditions of SFE of PM and identifies the most potent antioxidant fractions and possible active compounds in PM.

Atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality worldwide. Atherosclerosis develops over several decades and is mediated by a complex interplay of cellular mechanisms that drive a chronic inflammatory milieu and cell-to-cell interactions between endothelial cells, smooth muscle cells and macrophages that promote plaque development and progression. While there has been significant therapeutic advancement, there remains a gap where novel therapeutic approaches can complement current therapies to provide a holistic approach for treating atherosclerosis to orchestrate the regulation of complex signalling networks across multiple cell types and different stages of disease progression. MicroRNAs (miRNAs) are emerging as important post-transcriptional regulators of a suite of molecular signalling pathways and pathophysiological cellular effects. Furthermore, circulating miRNAs have emerged as a new class of disease biomarkers to better inform clinical diagnosis and provide new avenues for personalised therapies. This review focusses on recent insights into the potential role of miRNAs both as therapeutic targets in the regulation of the most influential processes that govern atherosclerosis and as clinical biomarkers that may be reflective of disease severity, highlighting the potential theranostic (therapeutic and diagnostic) properties of miRNAs in the management of cardiovascular disease.

Conjugated linoleic acid (CLA) has the unique property of inducing regression of pre-established murine atherosclerosis. Understanding the mechanism(s) involved may help identify endogenous pathways that reverse human atherosclerosis. Here, we provide evidence that CLA inhibits foam cell formation via regulation of the nuclear receptor coactivator, peroxisome proliferator-activated receptor (PPAR)-γ coactivator (PGC)-1α, and that macrophage PGC-1α plays a role in atheroprotection in vivo. PGC-1α was identified as a hub gene within a cluster in the aorta of the apoE(-/-) mouse in the CLA-induced regression model. PGC-1α was localized to macrophage/foam cells in the murine aorta where its expression was increased during CLA-induced regression. PGC-1α expression was also detected in macrophages in human atherosclerosis and was inversely linked to disease progression in patients with the disease. Deletion of PGC-1α in bone marrow derived macrophages promoted, whilst over expression of the gene inhibited foam cell formation. Importantly, macrophage specific deletion of PGC-1α accelerated atherosclerosis in the LDLR(-/-) mouse in vivo. These novel data support a functional role for PGC-1α in atheroprotection.

Background Vascular disease in diabetes is initiated by monocyte adhesion to vascular endothelium, transmigration and formation of foam cells. Increasing clinical evidence supports a role for the secretory protein, cyclophilin A in diabetic vascular disease. The means by which cyclophilin A contributes to vascular lesion development in diabetes is however largely unknown. Methods In this study we investigated using THP1 cells and human monocytes whether cyclophilin A under hyperglycemic conditions, functions in the inflammatory cascade as a chemoattractant and increases lipid uptake by formation of foam cells invitro. We developed an invitro model of monocytes cultured in 20 mm glucose (high glucose) equivalent to 360 mg/dL of plasma glucose levels. These monocytes were then differentiated into macrophages using PMA and subsequently transformed to lipid laden foam cells using oxidized low density lipoproteins in the presence and absence of cyclophilin A. This cellular model was used to study monocyte to macrophage differentiation, transmigration and foam cell formation. A similar cellular model using siRNA mediated transient elimination of the cyclophilin A gene as well as chemical inhibitors were used to further confirm the role of cyclophilin A in the differentiation and foam cell formation process. Results Cyclophilin A effectively increased migration of high glucose treated monocytes to the endothelial cell monolayer (p

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

Cellular and Molecular Life Sciences, 62 (21), ISSN:1420-682X, ISSN:1420-9071

Foam cell formation occurs in vitro at lipoprotein concentrations above 50 m g/ml in pigeon macrophages. Hypothetically, intracellular trafficking of lipoproteins at higher concentrations may differ from uptake of lipoproteins associated with low concentrations, revealing a separate atherogenic endocytic pathway. Macrophage intracellular traf- ficking of pigeon b -very low density lipoprotein ( b -VLDL) and low density lipoprotein (LDL) at low concentrations (12 m g/ml) near the saturation of high affinity binding sites and high lipoprotein concentrations (50-150 m g/ml) used to in- duce foam cell formation were examined. Pigeon b -VLDL and LDL, differentially labeled with colloidal gold, were added simultaneously to contrast trafficking of b -VLDL, which causes in vitro foam cell formation, with LDL, which does not. The binding of lipoproteins to cell surface struc- tures, distribution of lipoproteins in endocytic organelles, and the extent of colabeling in the endocytic organelles were determined by thin-section transmission electron mi- croscopy. At low concentrations, the intracellular traffick- ing of pigeon LDL and b -VLDL was identical. At high con- centrations, LDL was removed more rapidly from the plasma membrane and reached lysosomes more quickly than b -VLDL. No separate endocytic route was present at high concentrations of b -VLDL; rather, an increased resi- dence on the plasma membrane, association with nonmi- crovillar portions of the plasma membrane, and slower traf- ficking in organelles of coated-pit endocytosis reflected a more atherogenic trafficking pattern. — Jones, N. L., J. A. Saunders, and R. R. Mallory. Intracellular trafficking of pi- geon b -very low density lipoprotein and low density lipopro- tein at low and high concentrations in pigeon macrophages. J. Lipid Res. 2000. 41: 1823-1831.

The nuclear receptor superfamily is composed of transcription factors that positively and negatively regulate gene expression in response to the binding of a diverse array of lipid-derived hormones and metabolites. Intense efforts are currently being directed at defining the biological roles and mechanisms of action of liver X receptors (LXRs) and peroxisome proliferator-activated receptors (PPARs). LXRs have been found to play essential roles in the regulation of whole body cholesterol absorption and excretion, in the efflux of cholesterol from peripheral cells, and in the biosynthesis and metabolism of very low density lipoproteins. PPARs have been found to regulate diverse aspects of lipid metabolism, including fatty acid oxidation, fat cell development, lipoprotein metabolism, and glucose homeostasis. Intervention studies indicate that activation of PPARalpha, PPARgamma, and LXRs by specific synthetic ligands can inhibit the development of atherosclerosis in animal models. Here, we review recent studies that provide new insights into the mechanisms by which these subclasses of nuclear receptors act to systemically influence lipid and glucose metabolism and regulate gene expression within the artery wall.

Keywords: glomerular atherosclerosis, sterol regulatory element-binding protein, foam cell formation