Lipid Deposition In Macrophages Research Articles

Synergistic dual cell therapy for atherosclerosis regression: ROS-responsive Bio-liposomes co-loaded with Geniposide and Emodin

The development of nanomaterials for delivering natural compounds has emerged as a promising approach for atherosclerosis therapy. However, premature drug release remains a challenge. Here, we present a ROS-responsive biomimetic nanocomplex co-loaded with Geniposide (GP) and Emodin (EM) in nanoliposome particles (LP NPs) for targeted atherosclerosis therapy. The nanocomplex, hybridized with the macrophage membrane (Møm), effectively evades immune system clearance and targets atherosclerotic plaques. A modified thioketal (TK) system responds to ROS-rich plaque regions, triggering controlled drug release. In vitro, the nanocomplex inhibits endothelial cell apoptosis and macrophage lipid accumulation, restores endothelial cell function, and promotes cholesterol effluxion. In vivo, it targets ROS-rich atherosclerotic plaques, reducing plaque area ROS levels and restoring endothelial cell function, consequently promoting cholesterol outflow. Our study demonstrates that ROS-responsive biomimetic nanocomplexes co-delivering GP and EM exert a synergistic effect against endothelial cell apoptosis and lipid deposition in macrophages, offering a promising dual-cell therapy modality for atherosclerosis regression.

Hawthorn leaf flavonoids alleviate the deterioration of atherosclerosis by inhibiting SCAP-SREBP2-LDLR pathway through sPLA2-ⅡA signaling in macrophages in mice

Ethnopharmacological relevanceHawthorn leaves are a combination of the dried leaves of the Rosaceae plants, i.e., Crataegus pinnatifida Bge. or Crataegus pinnatifida Bge. var. major N. E. Br., is primarily cultivated in East Asia, North America, and Europe. hawthorn leaf flavonoids (HLF) are the main part of extraction. The HLF have demonstrated potential in preventing hypertension, inflammation, hyperlipidemia, and atherosclerosis. However, the potential pharmacological mechanism behind its anti-atherosclerotic effect has yet to be explored. Aim of the studyThe in vivo and in vitro effects of HLF on lipid-mediated foam cell formation were investigated, with a specific focus on the levels of secreted phospholipase A2 type IIA (sPLA2-II A) in macrophage cells. Materials and methodsThe primary constituents of HLF were analyzed using ultra-high performance liquid chromatography and liquid chromatography-tandem mass spectrometry. In vivo, HLF, at concentrations of 5 mg/kg, 20 mg/kg, and 40 mg/kg, were administered to apolipoprotein E knockout mice (ApoE−/−) fed by high-fat diet (HFD) for 16 weeks. Aorta and serum samples were collected to identify lesion areas and lipids through mass spectrometry analysis to dissect the pathological process. RAW264.7 cells were incubated with oxidized low-density lipoprotein (ox-LDL) alone, or ox-LDL combined with different doses of HLF (100, 50, and 25 μg/ml), or ox-LDL plus 24-h sPLA2-IIA inhibitors, for cell biology analysis. Lipids and inflammatory cytokines were detected using biochemical analyzers and ELISA, while plaque size and collagen content of plaque were assessed by HE and the Masson staining of the aorta. The lipid deposition in macrophages was observed by Oil Red O staining. The expression of sPLA2-IIA and SCAP-SREBP2-LDLR was determined by RT-qPCR and Western blot analysis. ResultsThe chemical profile of HLF was studied using UPLC-Q-TOF-MS/MS, allowing the tentative identification of 20 compounds, comprising 1 phenolic acid, 9 flavonols and 10 flavones, including isovitexin, vitexin-4″-O-glucoside, quercetin-3-O-robibioside, rutin, vitexin-2″-O-rhamnoside, quercetin, etc. HLF decreased total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and non-high-density lipoprotein cholesterol (non-HDL-C) levels in ApoE−/− mice (P < 0.05), reduced ox-LDL uptake, inhibited level of inflammatory factors, such as IL-6, IL-8, TNF-α, and IL-1ꞵ (P < 0.001), and alleviated aortic plaques with a thicker fibrous cap. HLF effectively attenuated foam cell formation in ox-LDL-treated RAW264.7 macrophages, and reduced levels of intracellular TC, free cholesterol (FC), cholesteryl ester (CE), IL-6, TNF-α, and IL-1β (P < 0.001). In both in vivo and in vitro experiments, HLF significantly downregulated the expression of sPLA2-IIA, SCAP, SREBP2, LDLR, HMGCR, and LOX-1 (P < 0.05). Furthermore, sPLA2-IIA inhibitor effectively mitigated inflammatory release in RAW264.7 macrophages and regulated SCAP-SREBP2-LDLR signaling pathway by inhibiting sPLA2-IIA secretion (P < 0.05). ConclusionHLF exerted a protective effect against atherosclerosis through inhibiting sPLA2-IIA to diminish SCAP-SREBP2-LDLR signaling pathway, to reduce LDL uptake caused foam cell formation, and to slow down the progression of atherosclerosis in mice.

Gypenoside XVII inhibits ox-LDL-induced macrophage inflammatory responses and promotes cholesterol efflux through activating the miR-182-5p/HDAC9 signaling pathway

Ethnopharmacological relevanceThe deposition of lipids in macrophages and the subsequent formation of foam cells significantly increase the risk of developing atherosclerosis (As). Targeting ATP-binding cassette transporter A1/G1 (ABCA1/ABCG1)-mediated reverse cholesterol transport is crucial for regulating foam cell formation. Therefore, the search for natural chemical components with the ability to regulate ABCA1/G1 is a potential drug target to combat the development of atherosclerosis. Gypenoside XVII (GP-17), a gypenoside monomer extracted from gynostemma pentaphyllum, presents an efficient anti-atherosclerosis function. However, the suppressed formation mechanism of foam cells by GP-17 remains elusive. Aim of studyTo explore the protective activities of GP-17 in ox-LDL-induced THP-1 macrophage-derived foam cells through modulating the promotion of cholesterol efflux and alleviation of inflammation. Materials and methodsMTT was used to detect cell viability. Bodipy493/503 and oil red O staining were performed to measure cell lipid deposition. Enzymatic assay was used to measure intracellular cholesterol measurement. Cholesterol efflux/uptake were determined by cholesterol efflux assay and Dil-ox-LDL uptake assay. Inflammatory cytokines were measured by ELISA. Bioinformatics prediction and dual luciferase reporter assay were performed to validate miR-182–5p targeting HDAC9. Relative protein levels were evaluated by immunoblotting and relative gene levels were determined by quantitative real-time PCR. ResultsOur results showed that GP-17 upregulated the expression of ABCA1, ABCG1 and miR-182–5p, but reduced HDAC9 expression levels in lipid-loaded macrophages, which promoted cholesterol efflux and inhibited lipid deposition. Additionally, GP-17 promoted the M2 phenotype of the macrophage and suppressed the inflammatory response in THP-1 macrophage-derived foam cells. Overexpression of HDAC9 or suppression of miR-182–5p eliminated the effects of ABCA1/G1 expression, lipid deposition and pro-inflammatory response. ConclusionThese findings suggest that GP-17 exerts a beneficial effect on macrophage lipid deposition and inflammation responses through activating the miR-182–5p/HDAC9 signaling pathway.

Doxorubicin inhibits cholesterol efflux through the miR-33/ABCA1 pathway

Doxorubicin (DOX) is extensively used for the treatment of kinds of cancers, and cardiovascular toxicity is one of the side effects. However, it is unclear whether DOX causes impairment of cardiac function by promoting atherosclerosis. Thus, we investigated the role of DOX in regulating the lipid deposition of macrophages and its molecular mechanism. RAW 264.7 cell line was stimulated with DOX in the presence or absence of low-density lipoprotein (LDL). We found that DOX increased miR-33 and reduced ATP binding cassette transporter A1 (ABCA1) protein. Moreover, cholesterol efflux was suppressed by DOX, which was more efficient under a high-cholesterol condition. After transfecting mimics or inhibitors of miR-33 into cells, ABCA1 protein was respectively decreased and increased, and intracellular lipid accumulation was correspondingly regulated. Overall, DOX suppresses the expression of ABCA1 protein by upregulating miR-33, promoting an intracellular lipid deposition in macrophages, which is a sign of early atherosclerosis. This provides new insights for clinical observation and evaluation of the side effects of DOX.

Botanical Antcin K Alleviates High-Fat Damage in Palm Acid Oil-Treated Vascular Endothelial Cells and Macrophages.

Lipid metabolism disorder is the most critical risk factor for atherosclerosis, and the process involves lipid deposition in the arterial intima. In Taiwan, antcin K, an active triterpenoid from the fruiting bodies of Antrodia camphorata, has been considered a potential lipid-lowering agent. Despite this, the possible therapeutic mechanisms of antcin K remain unclear. To explore the crucial role of botanical antcin K in reducing atherosclerotic plaque, we used SVEC4-10 vascular endothelial cells and RAW264.7 macrophages with palm acid oil-induced high-fat damage as our cell models. Our results showed through using the DPPH assay that antcin K had excellent free radical scavenging ability. Antcin K treatment can significantly alleviate the high-fat damage and reduce the levels of inflammatory factors of TNF-α and IL-1β in vascular endothelial cells and macrophages, as shown through MTT assay and ELISA. Furthermore, antcin K treatment can effectively enhance migration ability and clear lipid deposition in macrophages, as shown by using cell migration assay and oil red O staining. When stained with immunofluorescence, antcin K was shown to significantly decrease the expression of adhesion molecules of vascular cell adhesion molecule 1 (VCAM-1) in vascular endothelial cells involved in monocyte migration and inflammation. Antcin K not only reduced the expression of the CD36 scavenger receptor but also augmented the expression of Kruppel-like factor 4 (KLF4) transcription factor in macrophages, which inhibits the transformation of macrophages into foam cells underlying the pathological process of atherosclerosis. Taking our findings into account, we suggested that botanical antcin K could have therapeutic potential for the treatment of atherosclerosis.

Enhanced Anti-Atherosclerotic Efficacy of pH-Responsively Releasable Ganglioside GM3 Delivered by Reconstituted High-Density Lipoprotein

Recently, the atheroprotective role of endogenous GM3 and an atherogenesis-inhibiting effect of exogenous GM3 suggested a possibility of exogenous GM3 being recruited as an anti-atherosclerotic drug. This study seeks to endow exogenous GM3 with atherosclerotic targetability via reconstituted high-density lipoprotein (rHDL), an atherosclerotic targeting drug nanocarrier. Unloaded rHDL, rHDL loaded with exogenous GM3 at a low concentration (GM3L-rHDL), and rHDL carrying GM3 at a relatively high concentration (GM3H-rHDL) were prepared and characterized. The inhibitory effect of GM3-rHDL on lipid deposition in macrophages was confirmed, and GM3-rHDL did not affect the survival of red blood cells. In vivo experiments using ApoE−/− mice fed a high fat diet further confirmed the anti-atherosclerotic efficacy of exogenous GM3 and demonstrated that GM3 packed in HDL nanoparticles (GM3-rHDL) has an enhanced anti-atherosclerotic efficacy and a reduced effective dose of GM3. Then, the macrophage- and atherosclerotic plaque-targeting abilities of GM3-rHD, most likely via the interaction of ApoA-I on GM3-rHDL with its receptors (e.g., SR-B1) on cells, were certified via a microsphere-based method and an aortic fragment-based method, respectively. Moreover, we found that solution acidification enhanced GM3 release from GM3-rHDL nanoparticles, implying the pH-responsive GM3 release when GM3-rHDL enters the acidic atherosclerotic plaques from the neutral blood. The rHDL-mediated atherosclerotic targetability and pH-responsive GM3 release of GM3-rHDL enhanced the anti-atherosclerotic efficacy of exogenous GM3. The development of the GM3-rHDL nanoparticle may help with the application of exogenous GM3 as a clinical drug. Moreover, the data imply that the GM3-rHDL nanoparticle has the potential of being recruited as a drug nanocarrier with atherosclerotic targetability and enhanced anti-atherosclerotic efficacy.

LKB1 Regulates Vascular Macrophage Functions in Atherosclerosis.

Liver kinase B1 (LKB1) is known to shape the regulation of macrophage function by participating in multiple processes including cell metabolism, growth, and polarization. However, whether LKB1 also affects the functional plasticity of macrophages in atherosclerosis has not attracted much attention. Abnormal macrophage function is a pathophysiological hallmark of atherosclerosis, characterized by the formation of foam cells and the maintenance of vascular inflammation. Mounting evidence supports that LKB1 plays a vital role in the regulation of macrophage function in atherosclerosis, including affecting lipid metabolism reprogramming, inflammation, endoplasmic reticulum stress, and autophagy in macrophages. Thus, decreased expression of LKB1 in atherosclerosis aggravates vascular injury by inducing excessive lipid deposition in macrophages and the formation of foam cells. To systematically understand the role and potential mechanism of LKB1 in regulating macrophage functions in atherosclerosis, this review summarizes the relevant data in this regard, hoping to provide new ideas for the prevention and treatment of atherosclerosis.

CISD1 protects against atherosclerosis by suppressing lipid accumulation and inflammation via mediating Drp1

Atherosclerosis still remains the leading cause of morbidity and mortality worldwide, and deeper understanding of target signaling that protect from the atherosclerosis progression may provide novel therapeutic strategies. CDGSH iron-sulfur domain-containing protein 1 (CISD1) is a protein localized on the outer membrane of mitochondria, and plays key roles in regulating cell death and oxidative stress. However, its potential on atherosclerosis development and the underlying mechanisms are largely unknown. Here, in our study, we found markedly decreased CISD1 expression in lipid-laden THP1 macrophages. Notably, lentivirus (LV)-mediated CISD1 over-expression remarkably ameliorated lipid deposition in macrophages stimulated by ox-LDL. Furthermore, cellular total ROS and mitochondrial ROS generation, and impairment of mitochondrial membrane potential (MMP) were highly induced by ox-LDL in THP1 cells, while being considerably reversed upon CISD1 over-expression. Inflammatory response caused by ox-LDL was also significantly restrained in macrophages with CISD1 over-expression. Mechanistically, we found that CISD1 could interact with dynamin-related protein 1 (Drp1). Intriguingly, CISD1-improved mitochondrial dysfunction and inflammation in ox-LDL-treated macrophages were strongly abolished by Drp1 over-expression, indicating that Drp1 suppression might be necessary for CISD1 to perform its protective effects in vitro. In high fat diet (HFD)-fed apolipoprotein E-deficient (ApoE−/−) mice, tail vein injection of lentiviral vector expressing CISD1 remarkably decreased atherosclerotic lesion area, serum LDL cholesterol levels and triglyceride contents. Inflammatory response, cellular total and mitochondrial ROS production, and Drp1 expression levels in aorta tissues were also dramatically ameliorated in HFD-fed ApoE−/− mice, contributing to the inhibition of atherosclerosis in vivo. Therefore, improving CISD1 expression may be a novel therapeutic strategy for atherosclerosis treatment.

WISP1 alleviates lipid deposition in macrophages via the PPARγ/CD36 pathway in the plaque formation of atherosclerosis.

Lipid deposition in macrophages plays an important role in atherosclerosis. The WNT1‐inducible signalling pathway protein 1(WISP1) can promote proliferation and migration of smooth muscle cells. Its expression is up‐regulated in obesity, which is associated with atherosclerosis, but the effect of WISP1 on atherosclerosis remains unclear. Thus, the objective of our study was to elucidate the role of WISP and its mechanism of action in atherosclerosis via in vivo and in vitro experiments. In our experiment, ApoE‐/‐ mice were divided into 5 groups: control, high‐fat diet (HFD), null lentivirus (HFD + NC), lentivirus WISP1 (HFD + IvWISP1) and WISP1‐shRNA (HFD + shWISP1). Oil Red O staining, immunofluorescence and immunohistochemistry of the aortic sinuses were conducted. Macrophages (RAW264.7 cell lines and peritoneal macrophages) were stimulated with 50 μg/mL oxidized low‐density lipoprotein (ox‐LDL); then, the reactive oxygen species (ROS) level was measured. Oil Red O staining and Dil‐ox‐LDL (ox‐LDL with Dil dye) uptake measurements were used to test lipid deposition of peritoneal macrophages. WISP1, CD36, SR‐A and PPARγ expression levels were measured via Western blotting and ELISA. The results showed that HFD mice had increased WISP1, CD36 and SR‐A levels. The plaque lesion area increased when WISP1 was down‐regulated, and lipid uptake and foam cell formation were inhibited when WISP1 was up‐regulated. Treatment of RAW264.7 cell lines with ox‐LDL increased WISP1 expression via activation of the Wnt5a/β‐catenin pathway, whereas ROS inhibition reduced WISP1 expression. Moreover, WISP1 down‐regulated CD36 and SR‐A expression, and Oil Red O staining and Dil‐ox‐LDL uptake measurement showed that WISP1 down‐regulated lipid deposition in macrophages. These results clearly demonstrate that WISP1 is activated by ox‐LDL at high ROS levels and can alleviate lipid deposition in atherosclerosis through the PPARγ/CD36 pathway.

MiR-210-3p attenuates lipid accumulation and inflammation in atherosclerosis by repressing IGF2.

Previous studies have shown that miR-210-3p is involved in the development and progression of atherosclerosis, but its specific mechanisms are still unclear. This study aims to reveal the mechanism of miR-210-3p and its target genes in macrophage lipid deposition and inflammatory response, and provide new ideas for the treatment of atherosclerosis. We found miR-210-3p increased sharply in the first 12 h induced by higher doses of ox-LDL in THP-1 macrophages and then gradually decreased. MiR-210-3p mimic transfection inhibited lipid uptake and inflammatory cytokine production in ox-LDL-induced macrophages. By inhibiting IGF2/IGF2R, miR-210-3p suppressed the expression of fatty acid transcriptase CD36 and transcription factor NF-κB in ox-LDL-induced macrophages. In conclusion, miR-210-3p inhibits the expression of CD36 and NF-κB by inhibiting IGF2 / IGF2R, thereby reducing lipid accumulation and inflammatory response in ox-LDL-induced macrophages. Enhancing miR-210-3p expression may be a new strategy for the treatment of atherosclerosis.

Exogenous GM3 ganglioside inhibits atherosclerosis via multiple steps: A potential atheroprotective drug

Atherosclerosis is one of the leading causes of morbidity and mortality worldwide. A significant increase in ganglioside GM3 content generally happens in atherosclerotic plaques causing a GM3-enriched microenvironment. It remains unclear whether the GM3-enriched microenvironment influences atherogenesis. This study sought to answer the question by investigating exogenous GM3 effects on multiple steps involved in atherogenesis. First, the physicochemical properties of native low-density lipoprotein (LDL) and LDL enriched with exogenous GM3 (GM3-LDL) were characterized by dynamic laser scattering, atomic force microscopy, and agarose gel electrophoresis. Then, electrophoretic mobility, conjugated diene and malondialdehyde production, and amino group blockage of GM3-LDL/LDL were measured to determine LDL oxidation degrees and cellular recognition/internalization of GM3-LDL/GM3-oxLDL were detected via confocal microscopy and flow cytometry. Subsequently, influences of exogenous GM3 addition on the monocyte-adhering ability of endothelial cells and on lipid deposition in macrophages were investigated. Finally, exogenous GM3 effect on atherogenesis was evaluated using apoE−/− mice fed a high-fat diet. We found that exogenous GM3 addition increased the size, charge, and stability of LDL particles, reduced LDL susceptibility to oxidation and its cellular recognition/internalization, impaired the monocyte-adhering ability of endothelial cells and lipid deposition in macrophages. Moreover, exogenous GM3 treatment also significantly decreased blood lipid levels and atherosclerotic lesion areas in atherosclerotic mice. The data imply that exogenous GM3 had an inhibitory effect on atherogenesis, suggesting a protective role of a GM3-enriched microenvironment in atherosclerotic plaques and implying a possibility of exogenous GM3 as an anti-atherosclerotic drug.

Ethanol extracts of Danlou tablet attenuate atherosclerosis via inhibiting inflammation and promoting lipid effluent

As a chronic inflammatory disease, atherosclerosis is characterized by accumulation of lipid-rich macrophages on the inner walls of arteries. Deposited macrophages promote atherosclerotic lesion progression; therefore they are viewed as the main targets in order to alleviate atherosclerosis. Danlou tablet, a patented Chinese Medicine, has long been used to treat cardiovascular diseases. In the present study, we used Apolipoprotein E-deficient (ApoE−/−) mice model and in vitro cell line of RAW264.7 to explore the mechanisms of ethanol extracts of Danlou tablet (EEDT) in treating atherosclerosis. The potential targets that EEDT works to treat atherosclerosis were predicted by “Network pharmacology analysis”, based on which we designed mRNA array of 93 genes. Then mRNA array and oil red O staining were performed in aortic extracted from the cohorts of Control (C57BL/6 mice, chow fed), Model (ApoE-/- C57BL/6 mice, 20 weeks of high-fat diet) and EEDT intervening (ApoE-/- mice, 20 weeks of high-fat diet with 12 weeks of EEDT treatment) group. Furthermore, mRNA array, inflammation cytokines and lipid content were examined in RAW264.7 cell line. It was showed that EEDT decreased the expressions of inflammation cytokines by down regulating NF-κB singling pathway and accelerated cholesterol effluent through activating PPARα/ABCA1 signaling pathway. On the other hand, activation of NF-κB pathway or suppression of PPARα/ABCA1 signaling pathway both abolished the therapeutic effect of EEDT. In conclusion, EEDT played a key role in anti-inflammation and preventing lipid deposition in macrophages of atherosclerosis via suppressing NF-κB signaling and triggering PPARα/ABCA1 signaling pathway.

MiR-497 accelerates oxidized low-density lipoprotein-induced lipid accumulation in macrophages by repressing the expression of apelin.

microRNAs (miRNAs) play important roles in the pathogenesis of atherosclerosis. A previous study has reported that miR-497 is elevated in advanced atherosclerotic lesions in an apoE-deficient (apoE-/-) mouse model. The purpose of this study is to test whether miR-497 can modulate macrophage foam cell formation, an initiating event in atherosclerosis. We found that miR-497 was upregulated in THP-1 macrophages after treatment with oxidized low-density lipoprotein (oxLDL). Enforced expression of miR-497 promoted lipid accumulation and decreased cholesterol efflux in oxLDL-exposed THP-1 macrophages. In contrast, downregulation of miR-497 suppressed oxLDL-induced lipid accumulation in THP-1 macrophages. Apelin was identified to be a downstream target of miR-497. Overexpression of miR-497 significantly reduced the expression of apelin in THP-1 macrophages. Interestingly, delivery of a miR-497-resistant variant of apelin significantly inhibited lipid accumulation and enhanced cholesterol efflux in miR-497-overexpressing THP-1 macrophages in response to oxLDL. In addition, miR-497 expression was increased and negatively correlated with apelin protein expression in human atherosclerotic lesions. In conclusion, miR-497 contributes to oxLDL-induced lipid deposition in macrophages largely via targeting of apelin and thus represents a potential therapeutic target for atherosclerosis.

Triterpenoid-enriched extract of Ilex kudingcha inhibits aggregated LDL-induced lipid deposition in macrophages by downregulating low density lipoprotein receptor-related protein 1 (LRP1)

Macrophage-derived foam cell formation is considered to be a critical step in the development of atherosclerosis. In the present study, we evaluated the inhibitory effect of Ilex kudingcha triterpenoid-enriched extract (TS) on foam cell formation in THP-1 macrophage cells induced by aggregated low density lipoproteins (agLDL). The inhibition of low density lipoprotein receptor-related protein 1 (LRP1) expression after TS treatment is based on mRNA and protein levels in the macrophages. These inductions were sterol regulatory element-binding protein-2 (SREBP2) dependent. On the basis of the in vitro results, the anti-atherosclerotic activity of TS was investigated in ApoE−/− mice fed a high-fat diet, ApoE−/− mice treated with TS for 6 weeks appeared to have decreased aortic sinus lesions compared with the untreated mice. These findings indicate that TS may act as an anti-atherosclerotic agent.

Abstract 144: Zebrafish Larvae: A Model System for Early Stage Atherosclerosis?

Objectives: Published results show that overfeeding zebrafish larvae on a high-cholesterol diet (HCD) can result in hypercholesterolemia and sub-endothelial lipid deposition in macrophages and other cell types. However, results are so far based on small samples, and the atherogenic response has been heterogeneous. We aim to use zebrafish larvae for large-scale, CRISPR-Cas9-based genetic screens, using results from genome wide association studies for coronary heart disease as a starting point. Firstly however, we need to ensure the model system is appropriate and robust. Therefore, we examined the effect of a high-energy diet (HED) and HCD on vascular lipid deposition in a larger number of larvae (n=241). Methods: Starting at 5 days post fertilization (dpf), ~30 larvae/tank were fed 2x/day on: 1) 5 mg control diet (CD; n=33); 2) 15 mg control diet (HED; n=90); or 3) 15 mg control diet enriched with 4% cholesterol (HCD; n=94). At 14-17 dpf, larvae were soaked in monodansylpentane cadaverase - a lipid staining dye - for 45 min, before imaging the dorsal aorta and caudal vein with a Leica SP5 confocal microscope. We used a custom written script in Cell Profiler to quantify the surface area of lipid deposits in the vasculature. Results: Manual annotation of vascular lipid deposition in 30 images (10 randomly selected images per dietary condition) allowed us to calculate the sensitivity (36%) and specificity (71%) of the Cell Profiler script. Subsequent analyses showed that HED (p=0.004) and HCD (p=0.001) fed larvae have significantly more vascular lipid deposition than CD fed larvae after adjusting for age, batch and vessel length. There was no difference in vascular lipid deposition between HED and HCD fed larvae (p=0.11). Discussion and conclusion: Our results confirm that zebrafish larvae represent a promising model system for early-stage atherosclerosis. In addition, they show that enriching the diet with cholesterol is not required to prompt atherogenesis. Future directions: In the next few months, we will examine if overfeeding also triggers vascular infiltration by macrophages, neutrophils and oxidized LDL cholesterol, and if atherogenesis can be prevented or reduced by treating larvae with statins and/or ezetimibe, using our new, automated imaging setup.

Nifedipine inhibits ox-LDL-induced lipid accumulation in human blood-derived macrophages

Studies have shown that nifedipine, an anti-hypertensive drug, protects against atherosclerotic progression, but the underlying mechanisms remain elusive. Oxidized low-density lipoprotein (ox-LDL) is critically implicated in macrophage lipid deposition seen in atherosclerosis. In this study, we examined the effects of nifedipine on some ox-LDL-associated changes in human blood-derived macrophages. We isolated monocytes from normal human blood and differentiated them into macrophages. We then treated these human macrophages with ox-LDL and/or nifedipine, and examined lipid accumulation and expression levels of two scavenge receptors CD36 and SR-A as well as a protein kinase PKC-θ. Nifedipine treatment substantially reduced lipid accumulation and the expression of CD36, SR-A, and protein kinase C (PKC)-θ in human macrophages treated with ox-LDL. Silencing of PKC-θ using siRNA also reduced the expression of CD36 and SR-A in these cells. Our results thus suggest that nifedipine may inhibit atherosclerosis by reducing ox-LDL-induced lipid deposition through suppression of the CD36/SR-A-mediated uptake of ox-LDL by macrophages via a PKC-θ-dependent mechanism.

Amelioration of the foam cell formation by simvastatin due to increased expression of Niemann‐Pick disease type C1 protein and enhanced lysosomal lipids transport (606.4)

It is well accepted that statins, hypercholesterol‐lowing agents, have direct therapeutic effects on the atherosclerotic lesions. However, the underlying mechanism remains unknown. Given the pivotal role of macrophages in atherosclerosis, the present study was designed to investigate the effects of simvastatin, a prototype of the most statins used clinically, on the foam cell formation by examining lysosomal lipids in macrophages. Using fluorescent microplate reader and confocal microscopy, we found that simvastatin dose‐dependently (in nM: 0, 10, 50, 100, 150 and 200) decreased lysosomal lipid deposition in macrophages treated with oxLDL ( 40 µg/ml ) as stained by lysosomal lipid specific dye of Bodipy 493/503. Oil red O staining and electron microscopy showed that the foam cell formation was substantially attenuated. In simvastatin‐ treated macrophages, the cholesterol level in the purified lysosome fractions was markedly decreased. RT‐PCR analysis revealed that the expression of NPC1, a lysosomal cholesterol transporter, was significantly enhanced. Silencing of NPC1 markedly decreased simvastatin‐induced lysosomal lipids transport. These results indicate that simvastatin‐induced cholesterol transport out of lysosome in macrophages leads to foam cell formation attenuation via enhancing NPC1 expression, which may be a therapeutic mechanism of statins to ameliorate atherosclerotic lesions.Grant Funding Source: NIH R01HL115068

Nicotine potentiates proatherogenic effects of oxLDL by stimulating and upregulating macrophage CD36 signaling

Cigarette smoking is a major risk factor for atherosclerosis and cardiovascular disease. CD36 mediates oxidized LDL (oxLDL) uptake and contributes to macrophage foam cell formation. We investigated a role for the CD36 pathway in nicotine-induced activation of macrophages and foam cell formation in vitro and in vivo. Nicotine in the same plasma concentration range found in smokers increased the CD36(+)/CD14(+) cell population in human peripheral blood mononuclear cells, increased CD36 expression of human THP1 macrophages, and increased macrophage production of reactive oxygen species, PKCδ phosphorylation, and peroxisome proliferator-activated receptor-γ (PPARγ) expression. Nicotine-induced CD36 expression was suppressed by antioxidants and by specific PKCδ and PPARγ inhibitors, implicating mechanistic roles for these intermediates. Nicotine synergized with oxLDL to increase macrophage expression of CD36 and cytokines TNF-α, monocyte chemoattractant protein-1, IL-6, and CXCL9, all of which were prevented by CD36 small interfering (si)RNA. Incubation with oxLDL (50 μg/ml) for 72 h resulted in lipid deposition in macrophages and foam cell formation. Preincubation with nicotine further increased oxLDL-induced lipid accumulation and foam cell formation, which was also prevented by CD36 siRNA. Treatment of apoE-/- mice with nicotine markedly exacerbated inflammatory monocyte levels and atherosclerotic plaque accumulation, effects that were not seen in CD36-/- apoE-/- mice. Our results show that physiological levels of nicotine increase CD36 expression in macrophages, a pathway that may account at least in part for the known proinflammatory and proatherogenic properties of nicotine. These results identify such enhanced CD36 expression as a novel nicotine-mediated pathway that may constitute an independent risk factor for atherosclerosis in smokers. The results also suggest that exacerbated atherogenesis by this pathway may be an adverse side effect of extended use of high concentrations of nicotine independent of their mode of administration.

Erratum for: Inhibitory Effect of Triterpenoid Saponins from the Leaves ofIlex kudingchaon Aggregated LDL-Induced Lipid Deposition in Macrophages

Erratum for: Inhibitory Effect of Triterpenoid Saponins from the Leaves of<i>Ilex kudingcha</i>on Aggregated LDL-Induced Lipid Deposition in Macrophages

Inhibitory Effect of Triterpenoid Saponins from the Leaves ofIlex kudingchaon Aggregated LDL-Induced Lipid Deposition in Macrophages

We have investigated the inhibitory effect of triterpenoid saponins from the leaves of Ilex kudingcha C. J. Tseng on aggregated low-density lipoprotein (LDL)-induced lipid deposition in macrophages. A cell-based screening model was initially applied on aggregated LDL (aggLDL)-induced lipid deposition on macrophages to test the inhibitory effects of the 12 triterpenoid saponins from this plant. Eight of these compounds inhibited the formation of foam cells and reduced intracellular total cholesterol and triglyceride contents. Structure-activity relationship analysis showed the essential role of the delta-lactone ring for the biological activity. The promoter action of the OH group at the C-12 position, the number of monosaccharides in the sugar chain and the rhamnose at the terminal of the sugar chain is also discussed.