Macrophage scavenger receptor class A: A multifunctional receptor in atherosclerosis

Gsα Regulates Macrophage Foam Cell Formation During Atherosclerosis

BACKGROUND

Many cardiovascular pathologies are induced by signaling through G-protein-coupled receptors via Gsα (G protein stimulatory α subunit) proteins. However, the specific cellular mechanisms that are driven by Gsα and contribute to the development of atherosclerosis remain unclear.

METHODS

High-throughput screening involving data from single-cell and bulk sequencing were used to explore the expression of Gsα in atherosclerosis. The differentially expression and activity of Gsα were analyzed by immunofluorescence and cAMP measurements. Macrophage-specific Gsα knockout (Mac-GsαKO) mice were generated to study the effect on atherosclerosis. The role of Gsα was determined by transplanting bone marrow and performing assays for foam cell formation, Dil-ox-LDL (oxidized low-density lipoprotein) uptake, chromatin immunoprecipitation, and luciferase reporter assays.

RESULTS

ScRNA-seq showed elevated Gnas in atherosclerotic mouse aorta's cholesterol metabolism macrophage cluster, while bulk sequencing confirmed increased GNAS expression in human plaque macrophage content. A significant upregulation of Gsα and active Gsα occurred in macrophages from human and mouse plaques. Ox-LDL could translocate Gsα from macrophage lipid rafts in short-term and promote Gnas transcription through ERK1/2 activation and C/EBPβ phosphorylation via oxidative stress in long-term. Atherosclerotic lesions from Mac-GsαKO mice displayed decreased lipid deposition compared with those from control mice. Additionally, Gsα deficiency alleviated lipid uptake and foam cell formation. Mechanistically, Gsα increased the levels of cAMP and transcriptional activity of the cAMP response element binding protein, which resulted in increased expression of CD36 and SR-A1. In the translational experiments, inhibiting Gsα activation with suramin or cpGN13 reduced lipid uptake, foam cell formation, and the progression of atherosclerotic plaques in mice in vivo.

CONCLUSIONS

Gsα activation is enhanced during atherosclerotic progression and increases lipid uptake and foam cell formation. The genetic or chemical inactivation of Gsα inhibit the development of atherosclerosis in mice, suggesting that drugs targeting Gsα may be useful in the treatment of atherosclerosis.

A multiscale modeling study of nanoparticle-based targeting therapy against atherosclerosis

Although researches on nanoparticle-based (NP-based) drug delivery system for atherosclerosis treatment have grown rapidly in recent years, there are limited studies in quantifying the effects of targeting drugs on plaque components and microenvironment. The purpose of the present study was to quantitatively assess the targeting therapeutic effects against atherosclerosis by establishing a multiscale mathematical model. The multiscale model involved subcellular, cellular and microenvironmental scales to simulate lipid catabolism, macrophage behaviors and dynamics of microenvironmental components, respectively. In vitro and in vivo experimental data were integrated into the mathematical model according to Bayesian statistics, in order to evaluate the therapeutic effects of a proposed NP-based platform for macrophage-specific delivery to simultaneously deliver SR-A siRNA (to reduce LDL uptake) and LXR-L (to stimulate cholesterol efflux). Dosage variation analysis was then performed to investigate the drug efficacy under varied dosage combinations of SR-A siRNA and LXR-L. The simulation results demonstrated that the dynamics of the microenvironmental components presented different developments in Untreated and Treated groups. We also found that the balance of lipid metabolism between uptake and efflux resulted in the improvement of lipid and inflammatory microenvironment, consequently in the plaque regression. In addition, the model predicted optimized dosage combinations according to the co-effect analysis of the two drugs on the lipid microenvironment. This study suggests that multiscale modeling can be a powerful quantitative tool for estimating the therapeutic effects of targeting drugs for plaque regression and designing the enhanced treatment strategies against atherosclerosis.

Macrophage-expressed SRA ameliorates alcohol-induced liver injury by suppressing S-glutathionylation of Notch1 via recruiting thioredoxin

Scavenger receptor A (SRA) is preferentially expressed in macrophages and implicated as a multifunctional pattern recognition receptor for innate immunity. Hepatic macrophages play a primary role in the pathogenesis of alcoholic liver disease. Herein, we observed that SRA expression was significantly increased in the liver tissues of mice with alcohol-related liver injury. SRA-deficient (SRA-/-) mice developed more severe alcohol-induced liver disease than wild-type mice. Enhanced liver inflammation existed in alcohol-challenged SRA-/- mice and was associated with increased Notch activation in hepatic macrophages compared with wild-type control animals. Mechanistically, SRA directly bound with Notch1 and suppressed its S-glutathionylation, thereby inhibiting Notch pathway activation. Further, we determined that the SRA interacted with thioredoxin-1 (Trx-1), a redox-active protein. SRA inhibited Trx-1 dimerization and facilitated the interaction of Trx-1 with Notch1. Application of a Trx-1-specific inhibitory agent during macrophage stimulation abolished SRA-mediated regulation of the Notch pathway and its downstream targets. In summary, our study revealed that SRA plays a critical role in macrophage inflammatory response by targeting Notch1 for its glutathionylation. SRA-mediated negative regulation of Notch activation might serve as a novel therapeutic strategy for alcohol-induced liver injury.

Sono-activated materials for enhancing focused ultrasound ablation: Design and application in biomedicine

The ablation effect of focused ultrasound (FUS) has played an increasingly important role in the biomedical field over the past decades, and its non-invasive features have great advantages, especially for clinical diseases where surgical treatment is not available or appropriate. Recently, rapid advances in the adjustable morphology, enzyme-mimetic activity, and biostability of sono-activated materials have significantly promoted the medical application of FUS ablation. However, a systematic review of sono-activated materials based on FUS ablation is not yet available. This progress review focuses on the recent design, fundamental principles, and applications of sono-activated materials in the FUS ablation biomedical field. First, the different ablation mechanisms and the key factors affecting ablation are carefully determined. Then, the design of sono-activated materials with high FUS ablation efficiencies is comprehensively discussed. Subsequently, the representative biological applications are summarized in detail. Finally, the primary challenges and future perspectives are also outlined. We believe this timely review will provide key information and insights for further exploration of focused ultrasound ablation and new inspiration for designing future sono-activated materials. STATEMENT OF SIGNIFICANCE: The ablation effect of focused ultrasound (FUS) has played an increasingly important role in the biomedical field over the past decades. However, there are also some challenges of FUS ablation, such as skin burns, tumour recurrence after thermal ablation, and difficulty in controlling cavitation ablation. The rapid advance in adjustable morphology, enzyme-mimetic activity, and biostability of sono-activated materials has significantly promoted the medical application of FUS ablation. However, the systematic review of sono-activated materials based on FUS ablation is not yet available. This progress review focuses on the recent design, fundamental principles, and applications in the FUS ablation biomedical field of sono-activated materials. We believe this timely review will provide key information and insights for further exploration of FUS ablation.

Recent Advances in Anti-Atherosclerosis and Potential Therapeutic Targets for Nanomaterial-Derived Drug Formulations

Atherosclerosis, the leading cause of death worldwide, is responsible for ≈17.6 million deaths globally each year. Most therapeutic drugs for atherosclerosis have low delivery efficiencies and significant side effects, and this has hampered the development of effective treatment strategies. Diversified nanomaterials can improve drug properties and are considered to be key for the development of improved treatment strategies for atherosclerosis. The pathological mechanisms underlying atherosclerosis is summarized, rationally designed nanoparticle-mediated therapeutic strategies, and potential future therapeutic targets for nanodelivery. The content of this study reveals the potential and challenges of nanoparticle use for the treatment of atherosclerosis and highlights new effective design ideas.

Micro- and Macrovascular Effects of Inflammation in Peripheral Artery Disease-Pathophysiology and Translational Therapeutic Approaches

Inflammation has a critical role in the development and progression of atherosclerosis. On the molecular level, inflammatory pathways negatively impact endothelial barrier properties and thus, tissue homeostasis. Conformational changes and destruction of the glycocalyx further promote pro-inflammatory pathways also contributing to pro-coagulability and a prothrombotic state. In addition, changes in the extracellular matrix composition lead to (peri-)vascular remodelling and alterations of the vessel wall, e.g., aneurysm formation. Moreover, progressive fibrosis leads to reduced tissue perfusion due to loss of functional capillaries. The present review aims at discussing the molecular and clinical effects of inflammatory processes on the micro- and macrovasculature with a focus on peripheral artery disease.

Atherosclerosis treatment with nanoagent: potential targets, stimulus signals and drug delivery mechanisms

Cardiovascular disease (CVDs) is the first killer of human health, and it caused up at least 31% of global deaths. Atherosclerosis is one of the main reasons caused CVDs. Oral drug therapy with statins and other lipid-regulating drugs is the conventional treatment strategies for atherosclerosis. However, conventional therapeutic strategies are constrained by low drug utilization and non-target organ injury problems. Micro-nano materials, including particles, liposomes, micelles and bubbles, have been developed as the revolutionized tools for CVDs detection and drug delivery, specifically atherosclerotic targeting treatment. Furthermore, the micro-nano materials also could be designed to intelligently and responsive targeting drug delivering, and then become a promising tool to achieve atherosclerosis precision treatment. This work reviewed the advances in atherosclerosis nanotherapy, including the materials carriers, target sites, responsive model and treatment results. These nanoagents precisely delivery the therapeutic agents to the target atherosclerosis sites, and intelligent and precise release of drugs, which could minimize the potential adverse effects and be more effective in atherosclerosis lesion.

Conversion of M1 Macrophages to Foam Cells: Transcriptome Differences Determined by Sex

BACKGROUND

M1 macrophages involved in pro-inflammatory processes can be induced by low-density lipoproteins (LDL), giving rise to foam cells. In the atheroma plaque, it has been identified that males present more advanced lesions associated with infiltration. Therefore, our study aims to investigate sex-related changes in the transcriptome of M1 macrophages during the internalization process of LDL particles.

METHODS

Peripheral blood mononuclear cells (PBMCs) from healthy male and female subjects were separated using Hystopaque, and monocytes were isolated from PBMCs using a positive selection of CD14+ cells. Cells were stimulated with LDL 10 µg/mL, and the transcriptional profile of M1 macrophages performed during LDL internalization was determined using a Clariom D platform array.

RESULTS

Chromosome Y influences the immune system and inflammatory responses in males expressing 43% of transcripts in response to LDL treatment. Males and females share 15 transcripts, where most correspond to non-coding elements involved in oxidative stress and endothelial damage.

CONCLUSIONS

During LDL internalization, male monocyte-derived M1 macrophages display more marked proinflammatory gene expression. In contrast, female M1 macrophages display a more significant number of markers associated with cell damage.

OxLDL-Induced Foam Cell Formation Inhibitory Activity of Pepsin Hydrolysate of Ark Shell (Scapharca subcrenata (Lischke, 1869)) in RAW264.7 Macrophages

Inhibitory effect of ark shell (Scapharca subcrenata (Lischke, 1869)) proteolytic hydrolysates (ASHs) on oxidized low-density lipoprotein (oxLDL)-induced macrophage foam cell formation was investigated. Two types of ASHs were prepared by Alcalase® and pepsin, ASAH (ark shell-Alcalase® hydrolysates), and ASPH (ark shell-pepsin hydrolysate). Oil Red O staining results showed that ASPH suppressed foam cell formation and lipid accumulation more than ASAH in oxLDL-induced foam cell formation of RAW264.7 macrophages. ASPH reduced the levels of total cholesterol, cholesterol ester, and free cholesterol in oxLDL-treated RAW264.7 macrophages. It was found that ASPH increased cholesterol efflux and decreased cholesterol influx rate. In this regard, protein expressions of CD36 and scavenger receptor class A1 (SR-A1) for cholesterol influx and ATP-binding cassette transporter A1 and G1 (ABCA1 and ABCG1) for cholesterol efflux were investigated. ASPH treatment resulted in an increase of ABCA1 and ABCG1 expression but downregulated CD36 and SR-A1 expression. Furthermore, ASPH suppressed production of proinflammatory cytokines, including tumor necrosis factor-α and interleukin-6 and -1β, through regulating nuclear factor-kappa B (NF-κB) in oxLDL-induced foam cell formation of RAW264.7 macrophages. Taken together, our data indicate that ASPH might be a useful ingredient in functional foods for ameliorating atherosclerosis by preventing foam cell formation.

Inflammation balance in skeletal muscle damage and repair

Responding to tissue injury, skeletal muscles undergo the tissue destruction and reconstruction accompanied with inflammation. The immune system recognizes the molecules released from or exposed on the damaged tissue. In the local minor tissue damage, tissue-resident macrophages sequester pro-inflammatory debris to prevent initiation of inflammation. In most cases of the skeletal muscle injury, however, a cascade of inflammation will be initiated through activation of local macrophages and mast cells and recruitment of immune cells from blood circulation to the injured site by recongnization of damage-associated molecular patterns (DAMPs) and activated complement system. During the inflammation, macrophages and neutrophils scavenge the tissue debris to release inflammatory cytokines and the latter stimulates myoblast fusion and vascularization to promote injured muscle repair. On the other hand, an abundance of released inflammatory cytokines and chemokines causes the profound hyper-inflammation and mobilization of immune cells to trigger a vicious cycle and lead to the cytokine storm. The cytokine storm results in the elevation of cytolytic and cytotoxic molecules and reactive oxygen species (ROS) in the damaged muscle to aggravates the tissue injury, including the healthy bystander tissue. Severe inflammation in the skeletal muscle can lead to rhabdomyolysis and cause sepsis-like systemic inflammation response syndrome (SIRS) and remote organ damage. Therefore, understanding more details on the involvement of inflammatory factors and immune cells in the skeletal muscle damage and repair can provide the new precise therapeutic strategies, including attenuation of the muscle damage and promotion of the muscle repair.

Scavenger Receptors in Myocardial Infarction and Ischemia/Reperfusion Injury: The Potential for Disease Evaluation and Therapy

Scavenger receptors (SRs) are a structurally heterogeneous superfamily of evolutionarily conserved receptors that are divided into classes A to J. SRs can recognize multiple ligands, such as modified lipoproteins, damage-associated molecular patterns, and pathogen-associated molecular patterns, and regulate lipid metabolism, immunity, and homeostasis. According to the literature, SRs may play a critical role in myocardial infarction and ischemia/reperfusion injury, and the soluble types of SRs may be a series of promising biomarkers for the diagnosis and prognosis of patients with acute coronary syndrome or acute myocardial infarction. In this review, we briefly summarize the structure and function of SRs and discuss the association between each SR and ischemic cardiac injury in patients and animal models in detail. A better understanding of the effect of SRs on ischemic cardiac injury will inspire novel ideas for therapeutic drug discovery and disease evaluation in patients with myocardial infarction.

Neuropeptide Y regulates cholesterol uptake and efflux in macrophages and promotes foam cell formation

The dysregulation of lipid metabolic pathways (cholesterol uptake and efflux) in macrophages results in the formation of lipid‐dense macrophages, named foam cells, that participate in plaque formation. NPY binding to NPY receptors in macrophages can modulate cell functions and affect the process of atherosclerotic plaques. The present study aimed to determine whether NPY affects the formation of macrophage‐derived foam cells and its underlying mechanisms in macrophages. THP‐1‐derived macrophages were incubated with oxidized low‐density lipoprotein (ox‐LDL) and treated with different concentrations of NPY. We analysed the relative levels of proteins related to cholesterol uptake and efflux. We found that NPY effectively increased cholesterol uptake and intracellular cholesterol content via the Y1 and Y5 receptors, and this effect was blocked by Y1 and Y5 antagonists. Mechanistically, NPY enhanced the expression of SRA and CD36 via the PKC/PPARγ pathways, promoting macrophage cholesterol uptake. Moreover, NPY significantly decreased cholesterol efflux to the extracellular cholesterol acceptors ApoA1 and HDL in macrophages. NPY mediated decreases in ABCA1, ABCG1 and SR‐BI expression through the inhibition of the JAK/STAT3 pathways. Our results suggest that NPY binding to the Y1 and Y5 receptors enhances foam cell formation by regulating cholesterol uptake and efflux in macrophages.

Scavenger receptor-targeted plaque delivery of microRNA-coated nanoparticles for alleviating atherosclerosis

Atherosclerosis treatments by gene regulation are garnering attention, yet delivery of gene cargoes to atherosclerotic plaques remains inefficient. Here, we demonstrate that assembly of therapeutic oligonucleotides into a three-dimensional spherical nucleic acid nanostructure improves their systemic delivery to the plaque and the treatment of atherosclerosis. This noncationic nanoparticle contains a shell of microRNA-146a oligonucleotides, which regulate the NF-κB pathway, for achieving transfection-free cellular entry. Upon an intravenous injection into apolipoprotein E knockout mice fed with a high-cholesterol diet, this nanoparticle naturally targets class A scavenger receptor on plaque macrophages and endothelial cells, contributing to elevated delivery to the plaques (∼1.2% of the injected dose). Repeated injections of the nanoparticle modulate genes related to immune response and vascular inflammation, leading to reduced and stabilized plaques but without inducing severe toxicity. Our nanoparticle offers a safe and effective treatment of atherosclerosis and reveals the promise of nucleic acid nanotechnology for cardiovascular disease.

Scavenger receptor A in immunity and autoimmune diseases: Compelling evidence for targeted therapy

INTRODUCTION

Scavenger receptor A (SR-A) is reported to be involved in innate and adaptive immunity and in recent years, the soluble form of SR-A has also been identified. Intriguingly, SR-A displays double-edged sword features in different diseases. Moreover, targeted therapy on SR-A, including genetic modulation, small molecule inhibitor, inhibitory peptides, fucoidan, and blocking antibodies, provides potential strategies for treatment. Currently, therapeutics targeting SR-A are in preclinical studies and clinical trials, revealing great perspectives in future immunotherapy.

AREAS COVERED

Through searching PubMed (January 1979-March 2022) and clinicaltrials.gov, we review most of the research and clinical trials involving SR-A. This review briefly summarizes recent study advances on SR-A, with particular concern on its role in immunity and autoimmune diseases.

EXPERT OPINION

Given the emerging evidence of SR-A in immunity, its targeted therapy has been studied in various diseases, especially autoimmune diseases. However, many challenges still remain to be overcome, such as the double-sworded effects and the specific isoform targeting. For further clinical success of SR-A targeted therapy, the crystal structure illustration and the dual function discrimination of SR-A should be further investigated. Nevertheless, although challenging, targeting SR-A would be a potential effective strategy in the treatment of autoimmune diseases and other immune-related diseases.

Disruption of USP9X in macrophages promotes foam cell formation and atherosclerosis

Subendothelial macrophage internalization of modified lipids and foam cell formation are hallmarks of atherosclerosis. Deubiquitinating enzymes (DUBs) are involved in various cellular activities; however, their role in foam cell formation is not fully understood. Here, using a loss-of-function lipid accumulation screening, we identified ubiquitin-specific peptidase 9 X-linked (USP9X) as a factor that suppressed lipid uptake in macrophages. We found that USP9X expression in lesional macrophages was reduced during atherosclerosis development in both humans and rodents. Atherosclerotic lesions from macrophage USP9X-deficient mice showed increased macrophage infiltration, lipid deposition, and necrotic core content than control apolipoprotein E–KO (Apoe^–/–) mice. Additionally, loss-of-function USP9X exacerbated lipid uptake, foam cell formation, and inflammatory responses in macrophages. Mechanistically, the class A1 scavenger receptor (SR-A1) was identified as a USP9X substrate that removed the K63 polyubiquitin chain at the K27 site. Genetic or pharmacological inhibition of USP9X increased SR-A1 cell surface internalization after binding of oxidized LDL (ox-LDL). The K27R mutation of SR-A1 dramatically attenuated basal and USP9X knockdown–induced ox-LDL uptake. Moreover, blocking binding of USP9X to SR-A1 with a cell-penetrating peptide exacerbated foam cell formation and atherosclerosis. In this study, we identified macrophage USP9X as a beneficial regulator of atherosclerosis and revealed the specific mechanisms for the development of potential therapeutic strategies for atherosclerosis.

The effects of high-intensity functional training on cardiometabolic risk factors and exercise enjoyment in men and women with metabolic syndrome: study protocol for a randomized, 12-week, dose-response trial

Background

Individuals with metabolic syndrome (MetS) are at a greater risk for developing atherosclerotic cardiovascular disease (ASCVD) than those without MetS, due to underlying endothelial dysfunction, dyslipidemia, and insulin resistance. Exercise is an effective primary and secondary prevention strategy for MetS; however, less than 25% of adults meet the minimum stated public recommendations. Barriers often identified are lack of enjoyment and lack of time. High-intensity functional training (HIFT), a time-efficient modality of exercise, has shown some potential to elicit positive affectivity and elicit increased fitness and improved glucose metabolism. However, the effects of HIFT on dyslipidemia and endothelial dysfunction have not been explored nor have the effects been explored in a population with MetS. Additionally, no studies have investigated the minimal dose of HIFT per week to see clinically meaningful changes in cardiometabolic health. The purpose of this study is to (1) determine the dose-response effect of HIFT on blood lipids, insulin resistance, and endothelial function and (2) determine the dose-response effect of HIFT on body composition, fitness, and perceived enjoyment and intention to continue the exercise.

Methods/design

In this randomized, dose-response trial, participants will undergo a 12-week HIFT intervention of either 1 day/week, 2 days/week, or 3 days/week of supervised, progressive exercise. Outcomes assessed at baseline and post-intervention will be multiple cardiometabolic markers, and fitness. Additionally, the participant’s affective response will be measured after the intervention.

Discussion

The findings of this research will provide evidence on the minimal dose of HIFT per week to see clinically meaningful improvements in the risk factors of MetS, as well as whether this modality is likely to mitigate the barriers to exercise. If an effective dose of HIFT per week is determined and if this modality is perceived positively, it may provide exercise specialists and health care providers a tool to prevent and treat MetS.

Trial registration

ClinicalTrials.gov NCT05001126. August 11, 2021.

Macrophage-Specific IGF-1 Overexpression Reduces CXCL12 Chemokine Levels and Suppresses Atherosclerotic Burden in Apoe-Deficient Mice

OBJECTIVE

IGF-1 (insulin-like growth factor 1) exerts pleiotropic effects including promotion of cellular growth, differentiation, survival, and anabolism. We have shown that systemic IGF-1 administration reduced atherosclerosis in Apoe^-/- (apolipoprotein E deficient) mice, and this effect was associated with a reduction in lesional macrophages and a decreased number of foam cells in the plaque. Almost all cell types secrete IGF-1, but the effect of macrophage-derived IGF-1 on the pathogenesis of atherosclerosis is poorly understood. We hypothesized that macrophage-derived IGF-1 will reduce atherosclerosis. Approach and Results: We created macrophage-specific IGF-1 overexpressing mice on an Apoe^-/- background. Macrophage-specific IGF-1 overexpression reduced plaque macrophages, foam cells, and atherosclerotic burden and promoted features of stable atherosclerotic plaque. Macrophage-specific IGF1 mice had a reduction in monocyte infiltration into plaque, decreased expression of CXCL12 (CXC chemokine ligand 12), and upregulation of ABCA1 (ATP-binding cassette transporter 1), a cholesterol efflux regulator, in atherosclerotic plaque and in peritoneal macrophages. IGF-1 prevented oxidized lipid-induced CXCL12 upregulation and foam cell formation in cultured THP-1 macrophages and increased lipid efflux. We also found an increase in cholesterol efflux in macrophage-specific IGF1-derived peritoneal macrophages.

CONCLUSIONS

Macrophage IGF-1 overexpression reduced atherosclerotic burden and increased features of plaque stability, likely via a reduction in CXCL12-mediated monocyte recruitment and an increase in ABCA1-dependent macrophage lipid efflux.

Tryptophanyl tRNA Synthetase from Human Macrophages Infected by Porphyromonas gingivalis Induces a Proinflammatory Response Associated with Atherosclerosis

Porphyromonas gingivalis is the most common microorganism associated with adult periodontal disease, causing inflammation around the subgingival lesion. In this study, we investigated tryptophanyl tRNA synthase (WRS) production by THP-1 cells infected with P. gingivalis. Cytokine production, leukocyte adhesion molecules, and low-density lipoprotein receptor (LDLR) expressions in cultured cells were examined. WRS was detected in THP-1 cell culture supernatants stimulated with P. gingivalis from 1 to 24 h, and apparent production was observed after 4 h. No change in WRS mRNA expression was observed from 1 to 6 h in THP-1 cells, whereas its expression was significantly increased 12 h after stimulation with P. gingivalis. Lactate dehydrogenase (LDH) activity was observed from 4 to 24 h. The TNF-α, IL-6, IL-8, and CXCL2 levels of THP-1 cells were upregulated after treatment with recombinant WRS (rWRS) and were significantly reduced when THP-1 cells were treated with C29. The MCP-1, ICAM-1, and VCAM-1 levels in human umbilical vein endothelial cells were upregulated following treatment with rWRS, and TAK242 suppressed these effects. Additionally, unmodified LDLR, macrophage scavenger receptor A, and lectin-like oxidized LDLRs were upregulated in THP-1 cells treated with rWRS. These results suggest that WRS from macrophages infected with P. gingivalis is associated with atherosclerosis.

Poly-β-cyclodextrin Supramolecular Nanoassembly with a pH-Sensitive Switch Removing Lysosomal Cholesterol Crystals for Antiatherosclerosis

Cholesterol crystals (CCs), originally accumulating in the lysosome of cholesterol-laden cells, can aggravate the progression of atherosclerosis. β-cyclodextrin (CD) is a potent cholesterol acceptor or CC solubilizer. However, the random extraction of cholesterol impedes the in vivo application of CD for removing lysosomal CCs. Here, we exploit poly-β-cyclodextrin (pCD) as a lysosomal CC solubilizer and dextran sulfate grafted with benzimidazole (BM) as a pH-sensitive switch (pBM) to self-assemble into a supramolecular nanoassembly (pCD/pBM-SNA). The CD cavity in pCD/pBM-SNA can be efficiently sealed by hydrophobic BM at pH 7.4 (OFF). After it enters the lysosome, pCD/pBM-SNA disassembles, recovers the CD cavity to dissolve CCs into free cholesterol due to the protonation of BM (ON), and reduces CCs, finally enhancing the cholesterol efflux and promoting atherosclerosis regression. Our findings provide an "OFF-ON" tactic to remove lysosomal CCs for antiatherosclerosis as well as other diseases such as Niemann-Pick type C diseases with excessive cholesterol accumulation in the lysosome.

Nanotechnology for Targeted Therapy of Atherosclerosis

Atherosclerosis is the major cause of heart attack and stroke that are the leading causes of death in the world. Nanomedicine is a powerful tool that can be engineered to target atherosclerotic plaques for therapeutic and diagnosis purposes. In this review, advances in designing nanoparticles with therapeutic effects on atherosclerotic plaques known as atheroprotective nanomedicine have been summarized to stimulate further development and future translation.

Recognition of lipoproteins by scavenger receptor class A members

Scavenger receptor class A (SR-A) proteins are type II transmembrane glycoproteins that form homotrimers on the cell surface. This family has five known members (SCARA1 to 5, or SR-A1 to A5) that recognize a variety of ligands and are involved in multiple biological pathways. Previous reports have shown that some SR-A family members can bind modified low-density lipoproteins (LDLs); however, the mechanisms of the interactions between the SR-A members and these lipoproteins are not fully understood. Here, we systematically characterize the recognition of SR-A receptors with lipoproteins and report that SCARA1 (SR-A1, CD204), MARCO (SCARA2), and SCARA5 recognize acetylated or oxidized LDL and very-low-density lipoprotein in a Ca²⁺-dependent manner through their C-terminal scavenger receptor cysteine-rich (SRCR) domains. These interactions occur specifically between the SRCR domains and the modified apolipoprotein B component of the lipoproteins, suggesting that they might share a similar mechanism for lipoprotein recognition. Meanwhile, SCARA4, a SR-A member with a carbohydrate recognition domain instead of the SRCR domain at the C terminus, shows low affinity for modified LDL and very-low-density lipoprotein but binds in a Ca²⁺-independent manner. SCARA3, which does not have a globular domain at the C terminus, was found to have no detectable binding with these lipoproteins. Taken together, these results provide mechanistic insights into the interactions between SR-A family members and lipoproteins that may help us understand the roles of SR-A receptors in lipid transport and related diseases such as atherosclerosis.

Broad-Spectrum Reactive Oxygen Species Scavenging and Activated Macrophage-Targeting Microparticles Ameliorate Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a refractory chronic inflammatory disease. An excessively high level of reactive oxygen species (ROS) in the colon is one of the characteristics and pathogenic factors of IBD. Therefore, scavenging excessive ROS is a feasible method to treat IBD. Because ROS include many types of species, scavenging a single kind of ROS is not enough to reduce the ROS level and cure IBD effectively. Herein, broad-spectrum ROS scavenging and activated macrophage-targeting microparticles (MPs) are successfully fabricated by coprecipitation of catalase (CAT) and bovine serum albumin into a MnCO₃ template followed by deposition of polydopamine (PDA), assembly of targeting molecules on the surface, and finally removal of MnCO₃. The CAT content of MPs is about 34.1%. The obtained MPs can effectively scavenge the broad spectrum of ROS and retain 88% of the radical scavenging activity even after the treatment of simulated gastric fluid. The surface-modified dextran sulfate endows MPs with the targeting ability toward activated macrophages, achieving a better therapeutic effect. The MPs with components mostly derived from natural substances exhibit good biocompatibility and can show excellent ROS scavenging ability in cell experiments. In animal experiments, oral administration of a proper dosage of MPs can substantially mitigate colonic inflammation, as evidenced by disease activity index scores reduced by ∼40%, reduced body weight loss, and the production of typical proinflammatory cytokines in the inflammatory colon. This kind of MP can also be utilized for the treatment of other inflammatory diseases.

L-theanine inhibits foam cell formation via promoting the scavenger receptor A degradation

Atherosclerosis is one of the most common cardiovascular diseases with highly mortality worldwide. The formation of foam cell plays an important role in the early stage of atherosclerosis pathogenesis. L-theanine is the most abundant free amino acid in tea, which possesses anti-inflammatory, anti-tumor and anti-atherosclerosis effects. However, little is known about the effects of L-theanine on the foam cell formation. In our study, RAW264.7 cells and primary mouse peritoneal macrophages were exposed to oxidized low density lipoprotein (ox-LDL) for inducing foam cell formation. We found that L-theanine significantly impeded cholesterol accumulation in macrophages, while inhibiting the formation of foam cell. Our further experiments showed that L-theanine attenuated the cholesterol uptake of RAW264.7 cells and primary mouse peritoneal macrophages by reducing the protein level of macrophage scavenger receptor A (SR-A), but not the level of mRNA suggesting that L-theanine regulates scavenger receptor A at the translational rather than transcriptional level. The present results demonstrated that L-theanine obviously promoted the degradation of scavenger receptor A protein and scavenger receptor A was degraded by ubiquitination dependent manner. Collectively, our research indicates that L-theanine suppresses the formation of macrophage foam cell by promoting the ubiquitination dependent degradation of scavenger receptor A.

Mitochondrial protein CMPK2 regulates IFN alpha-enhanced foam cell formation, potentially contributing to premature atherosclerosis in SLE

Background

Premature atherosclerosis occurs in patients with SLE; however, the mechanisms remain unclear. Both mitochondrial machinery and proinflammatory cytokine interferon alpha (IFN-α) potentially contribute to atherogenic processes in SLE. Here, we explore the roles of the mitochondrial protein cytidine/uridine monophosphate kinase 2 (CMPK2) in IFN-α-mediated pro-atherogenic events.

Methods

Foam cell measurements were performed by oil red O staining, Dil-oxLDL uptake and the BODIPY approach. The mRNA and protein levels were measured by qPCR and Western blotting, respectively. Isolation of CD4+ T cells and monocytes was performed with monoclonal antibodies conjugated with microbeads. Manipulation of protein expression was conducted by either small interference RNA (siRNA) knockdown or CRISPR/Cas9 knockout. The expression of mitochondrial reactive oxygen species (mtROS) was determined by flow cytometry and confocal microscopy.

Results

IFN-α enhanced oxLDL-induced foam cell formation and Dil-oxLDL uptake by macrophages. In addition to IFN-α, several triggers of atherosclerosis, including thrombin and IFN-γ, can induce CMPK2 expression, which was elevated in CD4+ T cells and CD14+ monocytes isolated from SLE patients compared to those isolated from controls. The analysis of cellular subfractions revealed that CMPK2 was present in both mitochondrial and cytosolic fractions. IFN-α-induced CMPK2 expression was inhibited by Janus kinase (JAK)1/2 and tyrosine kinase 2 (Tyk2) inhibitors. Both the knockdown and knockout of CMPK2 attenuated IFN-α-mediated foam cell formation, which involved the reduction of scavenger receptor class A (SR-A) expression. CMPK2 also regulated IFN-α-enhanced mtROS production and inflammasome activation.

Conclusions

The study suggests that CMPK2 plays contributing roles in the pro-atherogenic effects of IFN-α.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02470-6.

Neutrophils and IL-1α Regulate Surfactant Homeostasis during Cigarette Smoking

Cigarette smoke exposure induces inflammation marked by rapid and sustained neutrophil infiltration, IL-1α, release and altered surfactant homeostasis. However, the extent to which neutrophils and IL-1α contribute to the maintenance of pulmonary surfactant homeostasis is not well understood. We sought to investigate whether neutrophils play a role in surfactant clearance as well as the effect of neutrophil depletion and IL-1α blockade on the response to cigarette smoke exposure. In vitro and in vivo administration of fluorescently labeled surfactant phosphatidylcholine was used to assess internalization of surfactant by lung neutrophils and macrophages during or following cigarette smoke exposure in mice. We also depleted neutrophils using anti-Ly-6G or anti-Gr-1 Abs, or we neutralized IL-1α using a blocking Ab to determine their respective roles in regulating surfactant homeostasis during cigarette smoke exposure. We observed that neutrophils actively internalize labeled surfactant both in vitro and in vivo and that IL-1α is required for smoke-induced elevation of surfactant protein (SP)-A and SP-D levels. Neutrophil depletion during cigarette smoke exposure led to a further increase in SP-A levels in the bronchoalveolar lavage and increased IL-1α, CCL2, GM-CSF, and G-CSF release. Finally, macrophage expression of Mmp12, a protease linked to emphysema, was increased in neutrophil-depleted groups and decreased following IL-1α blockade. Taken together, our results indicate that neutrophils and IL-1α signaling are actively involved in surfactant homeostasis and that the absence of neutrophils in the lungs during cigarette smoke exposure leads to an IL-1α-dependent exacerbation of the inflammatory response.

High-Expressed Macrophage Scavenger Receptor 1 Predicts Severity Clinical Outcome in Transplant Patient in Idiopathic Pulmonary Fibrosis Disease

Background

Lung transplantation has been performed worldwide and admitted as an effective treatment for patients with various end-stage lung diseases. However, limit reliable clinical indicators exist to identify patients at high risk for allograft failure in lung transplant recipients. The recent advances in the knowledge of immunological aspects of the pulmonary diseases, for that innate macrophage activation, are induced by pathogen or pathogen-derived molecules and widely accepted as the critical evidence among the pathogenesis of lung inflammation and fibrosis. This study was aimed at evaluating the clinical significance of CD86- and macrophage scavenger receptor 1- (MSR1-) positive cells during the development of idiopathic pulmonary fibrosis (IPF) and pulmonary arterial hypertension (PAH), and their potential roles in the prediction of the outcomes after lung transplantation were examined.

Methods

Tissues from lung transplantation for 37 IPF and 15 PAH patients from the Department of Cardiothoracic Surgery in Wuxi People's Hospital from December 2015 to December 2016 were analyzed by immunohistochemistry (IHC) for detecting the expression and CD86 and MSR1 and correlated with clinical events after lung transplantation.

Results

IHC results showed that the expression of MSR1, IL-13, and arginase-1 (Arg1) but not CD86 in the lung section of IPF patients was dramatically enhanced when compared with that of PAH patients. The expression of MSR1, IL-13, and Arg1 but not CD86 in the lung from IPF patients with smoking was significantly increased when compared with that from nonsmoking subjects. In addition, the expression of MSR1-positive cells in IPF subjects with Klebsiella pneumoniae infection was dramatically enhanced than that in noninfection subjects. MSR1-positive macrophages were negatively associated with FEV1 and with FVC but not associated with TLC and with TL_CO. However, CD86-positive macrophages were not significantly associated with the above lung function-related factors. Furthermore, MSR1 had a higher area under the ROC curve (AUC) than CD86 for IPF diagnosis. Survival analysis indicated that high levels of MSR1-positive macrophages had a worse prognostic effect for IPF patients with lung transplantation.

Conclusion

Our study indicates the clinical significance of Klebsiella pneumoniae infection-related MSR1-positive cells in IPF progression, and it could be a prognostic marker in IPF after the lung transplant; development strategies to reduce the expression of MSR1-positive macrophages in IPF may be beneficial for the lung transplant.

Astragalus Flavone Ameliorates Atherosclerosis and Hepatic Steatosis Via Inhibiting Lipid-Disorder and Inflammation in apoE-/- Mice

Atherosclerosis is a major pathogenic driver of cardiovascular diseases. Foam cell formation plays a key role in atherogenesis, which is affected by lipid disorder and inflammation. Therefore, inhibition of foam cell formation is a therapeutic approach for atherosclerosis treatment. Total flavone of Astragalus membranaceus (TFA) is extracted from A. membranaceus that has protective effect on cardiovascular disease. However, the effect of TFA on atherosclerosis and the underlying mechanism remains unknown. In this study, we determined whether TFA could inhibit atherosclerosis and uncovered the underlying mechanism. In vivo, ApoE deficient mice were treated with TFA and high-fat diet for 16 weeks. Subsequently, atherosclerotic lesions, hepatic steatosis and associated genes expression in vitro and in vivo were determined. We found that TFA reduced atherosclerotic lesion size and enhanced plaque stability, which might be attributed to improved lipid disorder, reduced inflammation and decreased monocyte adhesion. Mechanistically, TFA inhibited hepatic steatosis via regulating the genes responsible for lipid metabolism, by which ameliorating the lipid disorder. Moreover, in macrophage, TFA reduced the expression of scavenger receptors such as CD36 and SRA; and promoted the expression of ATP-binding cassette transporter A1 and G1 (ABCA1/G1). More importantly, TFA reduced miR-33 expression and dampened NFκB activity, by which de-repressing ABCA1/G1 activity and inhibiting the inflammation. Collectively, TFA can attenuate atherosclerosis via dual suppression of miR-33 and NFκB pathway, and partially through inhibition of scavenger receptors in macrophage. In addition, TFA ameliorates the hepatic steatosis and lipid disorder, which in turn contributes to the amelioration of atherosclerosis, suggesting that TFA might be a novel therapeutic approach for inhibition of atherosclerosis and hepatic steatosis.

Unraveling the Role of Epicardial Adipose Tissue in Coronary Artery Disease: Partners in Crime?

The role of epicardial adipose tissue (EAT) in the pathophysiology of coronary artery disease (CAD) remains unclear. The present systematic review aimed at compiling dysregulated proteins/genes from different studies to dissect the potential role of EAT in CAD pathophysiology. Exhaustive literature research was performed using the keywords "epicardial adipose tissue and coronary artery disease", to highlight a group of proteins that were consistently regulated among all studies. Reactome, a pathway analysis database, was used to clarify the function of the selected proteins and their intertwined association. SignalP/SecretomeP was used to clarify the endocrine function of the selected proteins. Overall, 1886 proteins/genes were identified from 44 eligible studies. The proteins were separated according to the control used in each study (EAT non-CAD or subcutaneous adipose tissue (SAT) CAD) and by their regulation (up- or downregulated). Using a Venn diagram, we selected the proteins that were upregulated and downregulated (identified as 27 and 19, respectively) in EAT CAD for both comparisons. The analysis of these proteins revealed the main pathways altered in the EAT and how they could communicate with the heart, potentially contributing to CAD development. In summary, in this study, the identified dysregulated proteins highlight the importance of inflammatory processes to modulate the local environment and the progression of CAD, by cellular and metabolic adaptations of epicardial fat that facilitate the formation and progression of atherogenesis of coronaries.

Role of Microglia in Modulating Adult Neurogenesis in Health and Neurodegeneration

Microglia are the resident immune cells of the brain, constituting the powerhouse of brain innate immunity. They originate from hematopoietic precursors that infiltrate the developing brain during different stages of embryogenesis, acquiring a phenotype characterized by the presence of dense ramifications. Microglial cells play key roles in maintaining brain homeostasis and regulating brain immune responses. They continuously scan and sense the brain environment to detect any occurring changes. Upon detection of a signal related to physiological or pathological processes, the cells are activated and transform to an amoeboid-like phenotype, mounting adequate responses that range from phagocytosis to secretion of inflammatory and trophic factors. The overwhelming evidence suggests that microglia are crucially implicated in influencing neuronal proliferation and differentiation, as well as synaptic connections, and thereby cognitive and behavioral functions. Here, we review the role of microglia in adult neurogenesis under physiological conditions, and how this role is affected in neurodegenerative diseases.

Molecular Imaging of Inflammation in a Mouse Model of Atherosclerosis Using a Zirconium-89-Labeled Probe

Background

Beyond clinical atherosclerosis imaging of vessel stenosis and plaque morphology, early detection of inflamed atherosclerotic lesions by molecular imaging could improve risk assessment and clinical management in high-risk patients. To identify inflamed atherosclerotic lesions by molecular imaging in vivo, we studied the specificity of our radiotracer based on maleylated (Mal) human serum albumin (HSA), which targets key features of unstable atherosclerotic lesions.

Materials and Methods

Mal-HSA was radiolabeled with a positron-emitting metal ion, zirconium-89 (⁸⁹Zr⁴⁺). The targeting potential of this probe was compared with unspecific ⁸⁹Zr-HSA and ¹⁸F-FDG in an experimental model of atherosclerosis (Apoe^–/– mice, n=22), and compared with wild-type (WT) mice (C57BL/6J, n=21) as controls.

Results

PET/MRI, gamma counter measurements, and autoradiography showed the accumulation of ⁸⁹Zr-Mal-HSA in the atherosclerotic lesions of Apoe^–/– mice. The maximum standardized uptake values (SUV_max) for ⁸⁹Zr-Mal-HSA at 16 and 20 weeks were 26% and 20% higher (P<0.05) in Apoe^–/– mice than in control WT mice, whereas no difference in SUV_max was observed for ¹⁸F-FDG in the same animals. ⁸⁹Zr-Mal-HSA uptake in the aorta, as evaluated by a gamma counter 48 h postinjection, was 32% higher (P<0.01) for Apoe^–/– mice than in WT mice, and the aorta-to-blood ratio was 8-fold higher (P<0.001) for ⁸⁹Zr-Mal-HSA compared with unspecific ⁸⁹Zr-HSA. HSA-based probes were mainly distributed to the liver, spleen, kidneys, bone, and lymph nodes. The phosphor imaging autoradiography (PI-ARG) results corroborated the PET and gamma counter measurements, showing higher accumulation of ⁸⁹Zr-Mal-HSA in the aortas of Apoe^–/– mice than in WT mice (9.4±1.4 vs 0.8±0.3%; P<0.001).

Conclusion

⁸⁹Zr radiolabeling of Mal-HSA probes resulted in detectable activity in atherosclerotic lesions in aortas of Apoe^–/– mice, as demonstrated by quantitative in vivo PET/MRI. ⁸⁹Zr-Mal-HSA appears to be a promising diagnostic tool for the early identification of macrophage-rich areas of inflammation in atherosclerosis.

Deciphering Macrophage Phenotypes upon Lipid Uptake and Atherosclerosis

In the progression of atherosclerosis, macrophages are the key immune cells for foam cell formation. During hyperlipidemic condition, phagocytic cells such as monocytes and macrophages uptake oxidized low-density lipoproteins (oxLDLs) accumulated in subintimal space, and lipid droplets are accumulated in their cytosols. In this review, we discussed the characteristics and phenotypic changes of macrophages in atherosclerosis and the effect of cytosolic lipid accumulation on macrophage phenotype. Due to macrophage plasticity, the inflammatory phenotypes triggered by oxLDL can be re-programmed by cytosolic lipid accumulation, showing downregulation of NF-κB activation followed by activation of anti-inflammatory genes, leading to tissue repair and homeostasis. We also discuss about various in vivo and in vitro models for atherosclerosis research and next generation sequencing technologies for foam cell gene expression profiling. Analysis of the phenotypic changes of macrophages during the progression of atherosclerosis with adequate approach may lead to exact understandings of the cellular mechanisms and hint therapeutic targets for the treatment of atherosclerosis.

Lipoprotein(a): is it more, less or equal to LDL as a causal factor for cardiovascular disease and mortality?

PURPOSE OF REVIEW

To summarize the recent studies directly comparing LDL and lipoprotein(a) as causal factors for cardiovascular disease and mortality.

RECENT FINDINGS

In approximately 100,000 individuals from the Copenhagen General Population Study for risk of myocardial infarction, in observational analyses per 39 mg/dl (1 mmol/l) cholesterol increase, the hazard ratio was 1.3 (95% confidence interval: 1.2-1.3) for LDL cholesterol and 1.6 (1.4-1.9) for lipoprotein(a) cholesterol. In corresponding genetic analyses, the causal risk ratio was 2.1 (1.3-3.4) for LDL and 2.0 (1.6-2.6) for lipoprotein(a). Also, a 15 mg/dl (0.39 mmol/l) cholesterol increase was associated with a hazard ratio for cardiovascular mortality of 1.05 (1.04-1.07) for LDL cholesterol and 1.18 (1.12-1.25) for lipoprotein(a) cholesterol. Corresponding values for all-cause mortality were 1.01 (1.00-1.01) for LDL cholesterol and 1.07 (1.04-1.10) for lipoprotein(a) cholesterol. In genetic, causal analyses, the mortality increases for elevated lipoprotein(a) appeared to be through apolipoprotein(a) kringle IV-2 rather than through lipoprotein(a) levels per se.

SUMMARY

On cholesterol scales, lipoprotein(a) and LDL appeared equal as causal factors for myocardial infarction; however, lipoprotein(a) was most important for mortality. Lipoprotein(a) effects may not only be due to cholesterol content but could also be due to the structure of lipoprotein(a) resembling plasminogen.

Oleacein and Foam Cell Formation in Human Monocyte-Derived Macrophages: A Potential Strategy Against Early and Advanced Atherosclerotic Lesions

Background: Oleacein is a secoiridoid group polyphenol found mostly in Olea europea L. and Ligustrum vulgare L. (Oleaceae). The aim of the present study was to investigate a potential role of oleacein in prevention of the foam cell formation. Materials and Methods: Oleacein was isolated from Ligustrum vulgare leaves. Human monocyte-derived macrophages were obtained from monocytes cultured with Granulocyte-macrophage colony-stimulating factor (GM-CSF). Then, cells were incubated with 20 μM or 50 μM of oleacein and with oxidized low-density lipoprotein (oxLDL) (50 μg/mL). Visualization of lipid deposition within macrophages was carried out using Oil-Red-O. Expression of CD36, Scavenger receptor A1 (SRA1) and Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) was determined by Reverse transcription polymerase chain reaction (RT-PCR) and by flow cytometry. Apoptosis was determined by flow cytometry using Annexin V assay. STAT3 and Acyl-coenzyme A: cholesterol acyltransferase type 1 (ACAT1) levels were determined by ELISA. P-STAT3, P-JAK1, P-JAK2 expressions were determined by Western blot (WB). Results: Oleacein in dose-dependent manner significantly reduced lipid deposits in macrophages as well as their expression of selected scavenger receptors. The highest decrease of expression was found for CD36 and SRA1 receptors, from above 20% to more than 75% compared to oxLDL and the lowest for LOX-1 receptor, from approx. 8% to approx. 25% compared to oxLDL-stimulated macrophages. Oleacein significantly reduced (2.5-fold) early apoptosis of oxLDL-stimulated macrophages. Moreover, oleacein significantly increased the protein expression of JAK/STAT3 pathway and had no effect on ACAT1 level. Conclusions: Our study demonstrates, for the first time, that oleacein inhibits foam cell formation in human monocyte-derived macrophages and thus can be a valuable tool in the prevention of early and advanced atherosclerotic lesions.

Formononetin attenuates atherosclerosis via regulating interaction between KLF4 and SRA in apoE-/- mice

Background and Purpose: Atherosclerosis is an underlying cause of coronary heart disease. Foam cell, a hallmark of atherosclerosis, is prominently derived from monocyte-differentiated macrophage, and vascular smooth muscle cells (VSMCs) through unlimitedly phagocytizing oxidized low-density lipoprotein (oxLDL). Therefore, the inhibition of monocyte adhesion to endothelium and uptake of oxLDL might be a breakthrough point for retarding atherosclerosis. Formononetin, an isoflavone extracted from Astragalus membranaceus, has exhibited multiple inhibitory effects on proatherogenic factors, such as obesity, dyslipidemia, and inflammation in different animal models. However, its effect on atherosclerosis remains unknown. In this study, we determined if formononetin can inhibit atherosclerosis and elucidated the underlying molecular mechanisms.

Methods: ApoE deficient mice were treated with formononetin contained in high-fat diet for 16 weeks. After treatment, mouse aorta, macrophage and serum samples were collected to determine lesions, immune cell profile, lipid profile and expression of related molecules. Concurrently, we investigated the effect of formononetin on monocyte adhesion, foam cell formation, endothelial activation, and macrophage polarization in vitro and in vivo.

Results: Formononetin reduced en face and aortic root sinus lesions size. Formononetin enhanced lesion stability by changing the composition of plaque. VSMC- and macrophage-derived foam cell formation and its accumulation in arterial wall were attenuated by formononetin, which might be attributed to decreased SRA expression and reduced monocyte adhesion. Formononetin inhibited atherogenic monocyte adhesion and inflammation. KLF4 negatively regulated the expression of SRA at transcriptional and translational level.

Conclusions: Our study demonstrate that formononetin can substantially attenuate the development of atherosclerosis via regulation of interplay between KLF4 and SRA, which suggests the formononetin might be a novel therapeutic approach for inhibition of atherosclerosis.

Protein Kinase Cθ Via Activating Transcription Factor 2-Mediated CD36 Expression and Foam Cell Formation of Ly6Chi Cells Contributes to Atherosclerosis

BACKGROUND

Although the role of thrombin in atherothrombosis is well studied, its role in the pathogenesis of diet-induced atherosclerosis is not known.

METHODS

Using a mouse model of diet-induced atherosclerosis and molecular biological approaches, here we have explored the role of thrombin and its G protein-coupled receptor signaling in diet-induced atherosclerosis.

RESULTS

In exploring the role of G protein-coupled receptor signaling in atherogenesis, we found that thrombin triggers foam cell formation via inducing CD36 expression, and these events require Par1-mediated Gα12-Pyk2-Gab1-protein kinase C (PKC)θ-dependent ATF2 activation. Genetic deletion of PKCθ in apolipoprotein E (ApoE)^-/- mice reduced Western diet-induced plaque formation. Furthermore, thrombin induced Pyk2, Gab1, PKCθ, and ATF2 phosphorylation, CD36 expression, and foam cell formation in peritoneal macrophages of ApoE^-/- mice. In contrast, thrombin only stimulated Pyk2 and Gab1 but not ATF2 phosphorylation or its target gene CD36 expression in the peritoneal macrophages of ApoE^-/-:PKCθ^-/- mice, and it had no effect on foam cell formation. In addition, the aortic root cross-sections of Western diet-fed ApoE^-/- mice showed increased Pyk2, Gab1, PKCθ, and ATF2 phosphorylation and CD36 expression as compared with ApoE^-/-:PKCθ^-/- mice. Furthermore, although the monocytes from peripheral blood and the aorta of Western diet-fed ApoE^-/- mice were found to contain more of Ly6C^hi cells than Ly6C^lo cells, the monocytes from Western diet-fed ApoE^-/-:PKCθ^-/- mice were found to contain more Ly6C^lo cells than Ly6C^hi cells. It is interesting to note that the Ly6C^hi cells showed higher CD36 expression with enhanced capacity to form foam cells as compared with Ly6C^lo cells.

CONCLUSIONS

These findings reveal for the first time that thrombin-mediated Par1-Gα12 signaling via targeting Pyk2-Gab1-PKCθ-ATF2-dependent CD36 expression might be playing a crucial role in diet-induced atherogenesis.

Human serum albumin-based probes for molecular targeting of macrophage scavenger receptors

Background: Inflammation and accumulation of macrophages are key features of unstable atherosclerotic plaques. The ability of macrophages to take up molecular probes can be exploited in new clinical imaging methods for the detection of unstable atherosclerotic lesions. We investigated whether modifications of human serum albumin (HSA) could be used to target macrophages efficiently in vitro. Materials and methods: Maleylated and aconitylated HSA were compared with unmodified HSA. Fluorescent or radiolabeled (89Zr) modified HSA was used in in vitro experiments to study cellular uptake by differentiated THP-1 cells and primary human macrophages. The time course of uptake was evaluated by flow cytometry, confocal microscopy, real-time microscopy and radioactivity measurements. The involvement of scavenger receptors (SR-A1, SR-B2, LOX-1) was assessed by knockdown experiments using RNA interference, by blocking experiments and by assays of competition by modified low-density lipoprotein. Results: Modified HSA was readily taken up by different macrophages. Uptake was mediated nonexclusively via the scavenger receptor SR-A1 (encoded by the MSR1 gene). Knockdown of CD36 and ORL1 had no influence on the uptake. Modified HSA was preferentially taken up by human macrophages compared with other vascular cell types such as endothelial cells and smooth muscle cells. Conclusions: Modified 89Zr-labeled HSA probes were recognized by different subsets of polarized macrophages, and maleylated HSA may be a promising radiotracer for radionuclide imaging of macrophage-rich inflammatory vascular diseases.

SR-A-Targeted Phase-Transition Nanoparticles for the Detection and Treatment of Atherosclerotic Vulnerable Plaques

Atherosclerosis is a major cause of sudden death and myocardial infarction, instigated by unstable plaques. Thus, the early detection of unstable plaques and corresponding treatment can improve the prognosis and reduce mortality. In this study, we describe a protocol for the preparation of nanoparticles (NPs) combined with the phase transitional material perfluorohexane (PFH) and with dextran sulfate (DS) targeting class A scavenger receptors (SR-A) for the diagnosis and treatment of atherosclerotic vulnerable plaques. The results showed that the Fe-PFH-poly(lactic- co-glycolic acid) (PLGA)/chitosan (CS)-DS NPs were fabricated successfully, with the ability to undergo phase transition by low-intensity focused ultrasound (LIFU) irradiation to achieve ultrasound imaging; a high carrier rate of Fe₃O₄ had a good negative enhancement effect on magnetic resonance imaging (MRI). The NPs had a high binding affinity for activated macrophages and could be endocytosed by the macrophages and notably induced apoptosis under LIFU irradiation by an acoustic droplet vaporization effect in vitro. Furthermore, in an ex vivo atherosclerotic plaque model of apolipoprotein E knockout (KO) (apoE^-/-) mice induced by high cholesterol, the NPs selectively accumulated at the sites of SR-A expressed on the activated macrophages of the aortic region. This result was also confirmed by MRI in vivo, where the NPs could be targeted to the aortic plaque and reduced the T₂* signal. The LIFU-induced phase transition could lead to the apoptosis of macrophages on plaques in vivo. In summary, Fe-PFH-PLGA/CS-DS NPs may be applied as multimodal and multifunctional probes and are expected to enable the specific diagnosis and targeted therapy of vulnerable plaques.

Make It Simple: (SR-A1+TLR7) Macrophage Targeted NANOarchaeosomes

Hyperhalophilic archaebacteria exclusively produce sn2,3 diphytanylglycerol diether archaeolipids, unique structures absent in bacteria and eukaryotes. Nanovesicles made of archaeolipids known as nanoarchaeosomes (nanoARC), possess highly stable bilayers, some of them displaying specific targeting ability. Here we hypothesize that nanoARC made from Halorubrum tebenquichense archaebacteria, may constitute efficient carriers for the TLR7 agonist imiquimod (IMQ). NanoARC-IMQ takes advantage of the intense interaction between IMQ and the highly disordered, poorly fluid branched archaeolipid bilayers, rich in archaeol analog of methyl ester of phosphatidylglycerophosphate (PGP-Me), a natural ligand of scavenger receptor A1 (SR-A1). This approach lacks complex manufacture steps required for bilayers labeling, enabling future analytical characterization, batch reproducibility, and adaptation to higher scale production. SR-A1 mediated internalization of particulate material is mostly targeted to macrophages and is extensive because it is not submitted to a negative feedback. A massive and selective intracellular delivery of IMQ may concentrate its effect specifically into the endosomes, where the TLR7 is expressed, magnifying its immunogenicity, at the same time reducing its systemic bioavailability, and therefore it's in vivo adverse effects. NanoARC-IMQ (600-900 nm diameter oligolamellar vesicles of ~-43 mV Z potential) were heavily loaded with IMQ at ~44 μg IMQ/mg phospholipids [~20 folds higher than the non-SR-A1 ligand soyPC liposomes loaded with IMQ (LIPO-IMQ)]. In vitro, nanoARC-IMQ induced higher TNF-α and IL-6 secretion by J774A1 macrophages compared to same dose of IMQ and same lipid dose of LIPO-IMQ. In vivo, 3 subcutaneous doses of nanoARC-IMQ+ 10 μg total leishmania antigens (TLA) at 50 μg IMQ per Balb/C mice, induced more pronounced DTH response, accompanied by a nearly 2 orders higher antigen-specific systemic IgG titers than IMQ+TLA and LIPO-IMQ. The isotype ratio of nanoARC-IMQ+TLA remained ~0.5 indicating, the same as IMQ+TLA, a Th2 biased response distinguished by a pronounced increase in antibody titers, without negative effects on splenocytes lymphoproliferation, with a potential CD8+LT induction 10 days after the last dose. Overall, this first approach showed that highly SR-A1 mediated internalization of heavily loaded nanoARC-IMQ, magnified the effect of IMQ on TLR7 expressing macrophages, leading to a more intense in vivo immune response.

SIRT1 activator E1231 protects from experimental atherosclerosis and lowers plasma cholesterol and triglycerides by enhancing ABCA1 expression

BACKGROUND AND AIMS

Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide-dependent protein deacetylase. Recent studies have demonstrated that enhancing SIRT1 expression or activity may modulate cholesterol and lipid metabolism. However, pharmacological and molecular regulators for SIRT1 are scarce. Here, we aimed to find novel small molecule modulators of SIRT1 to regulate cholesterol and lipid metabolism.

METHODS

A high-throughput screening assay was established to identify SIRT1 activators. Surface plasmon resonance and immunoprecipitation were performed to confirm the interaction of E1231 with SIRT1. Cholesterol assay was performed to demonstrate the in vitro effect of E1231. The in vivo effect of E1231 was evaluated in experimental models.

RESULTS

E1231, a piperazine 1,4-diamide compound, was identified as a SIRT1 activator with EC₅₀ value of 0.83 μM. E1231 interacted with recombinant human SIRT1 protein and deacetylated liver X receptor-alpha (LXRα). E1231 increased ATP-binding cassette transporter A1 (ABCA1) expression in RAW 264.7 cells dependent on SIRT1 and LXRα. E1231 promoted cholesterol efflux and inhibited lipid accumulation in RAW 264.7 cells via SIRT1 and ABCA1. In the golden hamster hyperlipidemia model, E1231 treatment decreased total cholesterol and triglyceride levels in both serum and the liver, while increased cholesterol content in feces. Moreover, E1231 increased ABCA1 and SIRT1 protein expression in the liver. In ApoE^-/- mice, E1231 treatment reduced atherosclerotic plaque development compared with untreated ApoE^-/- mice.

CONCLUSIONS

We identified a novel SIRT1 activator E1231 and elucidated its beneficial effects on lipid and cholesterol metabolism. Our study suggests that E1231 might be developed as a novel drug for treating atherosclerosis.

Andrographolide Inhibits Oxidized LDL-Induced Cholesterol Accumulation and Foam Cell Formation in Macrophages

oxLDL is involved in the pathogenesis of atherosclerotic lesions through cholesterol accumulation in macrophage foam cells. Andrographolide, the bioactive component of Andrographis paniculata, possesses several biological activities such as anti-inflammatory, anti-oxidant, and anticancer functions. Scavenger receptors (SRs), including class A SR (SR-A) and CD36, are responsible for the internalization of oxLDL. In contrast, receptors for reverse cholesterol transport, including ABCA1 and ABCG1, mediate the efflux of cholesterol from macrophage foam cells. Transcription factor liver X receptor [Formula: see text] (LXR[Formula: see text] plays a key role in lipid metabolism and inflammation as well as in the regulation of ABCA1 and ABCG1 expression. Because of the contribution of inflammation to macrophage foam cell formation and the potent anti-inflammatory activity of andrographolide, we hypothesized that andrographolide might inhibit oxLDL-induced macrophage foam cell formation. The results showed that andrographolide reduced oxLDL-induced lipid accumulation in macrophage foam cells. Andrographolide decreased the mRNA and protein expression of CD36 by inducing the degradation of CD36 mRNA; however, andrographolide had no effect on SR-A expression. In contrast, andrographolide increased the mRNA and protein expression of ABCA1 and ABCG1, which were dependent on LXR[Formula: see text]. Andrographolide enhanced LXR[Formula: see text] nuclear translocation and DNA binding activity. Treatment with the LXR[Formula: see text] antagonist GGPP and transfection with LXR[Formula: see text] siRNA reversed the ability of andrographolide to stimulate ABCA1 and ABCG1 protein expression. In conclusion, inhibition of CD36-mediated oxLDL uptake and induction of ABCA1- and ABCG1-dependent cholesterol efflux are two working mechanisms by which andrographolide inhibits macrophage foam cell formation, which suggests that andrographolide could be a potential candidate to prevent atherosclerosis.

JNK1 Mediates Lipopolysaccharide-Induced CD14 and SR-AI Expression and Macrophage Foam Cell Formation

Foam cell formation is the key process in the development of atherosclerosis. The uptake of oxidized low-density lipoprotein (oxLDL) converts macrophages into foam cells. We recently reported that lipopolysaccharide (LPS)-induced foam cell formation is regulated by CD14 and scavenger receptor AI (SR-AI). In this study, we employed pharmaceutical and gene knockdown approaches to determine the upstream molecular mediators, which control LPS-induced foam cell formation. Our results demonstrated that the specific c-Jun N-terminal kinase (JNK) pathway inhibitor, SP600125, but neither the specific inhibitor of extracellular signaling-regulated kinase (ERK) kinase MEK1/2, U0126, nor the specific inhibitor of p38 MAPK, SB203580, significantly blocks LPS-induced oxLDL uptake, suggesting that the JNK pathway is the upstream mediator of LPS-induced oxLDL uptake/foam cell formation. To address whether JNK pathway mediates LPS-induced oxLDL uptake is due to JNK pathway-regulated CD14 and SR-AI expression, we assessed whether the pharmaceutical inhibitor of JNK influences LPS-induced expression of CD14 and SR-AI. Our results indicate that JNK pathway mediates LPS-induced CD14 and SR-AI expression. To conclusively address the isoform role of JNK family, we depleted JNK isoforms using the JNK isoform-specific siRNA. Our data showed that the depletion of JNK1, but not JNK2 blocked LPS-induced CD14/SR-AI expression and foam cell formation. Taken together, our results reveal for the first time that JNK1 is the key mediator of LPS-induced CD14 and SR-AI expression in macrophages, leading to LPS-induced oxLDL uptake/foam cell formation. We conclude that the novel JNK1/CD14/SR-AI pathway controls macrophage oxLDL uptake/foam cell formation.

Oral nicotine aggravates endothelial dysfunction and vascular inflammation in diet-induced obese rats: Role of macrophage TNFα

Obesity and cigarette smoke are major cardiovascular (CV) risk factors and, when coexisting in the same individuals, have additive/synergistic effects upon CVD. We studied the mechanisms involved in nicotine enhancement of CVD in Sprague Dawley rats with diet–induced obesity. The rats were fed either a high fat (HFD) or normal rat chow diet with or without nicotine (100 mg/L in drinking water) for 20 weeks. HFD rats developed central obesity, increased systolic blood pressure (SBP), aortic superoxide (O₂^-) production, and impaired endothelial nitric oxide synthase (eNOS) and endothelium-dependent relaxation to acetylcholine (EDR). Nicotine further increased SBP, O₂^- and impaired eNOS and EDR in obese rats. In the peritoneal macrophages from obese rats, tumor necrosis factor (TNF) α, interleukin 1β and CD36 were increased, and were further increased in nicotine-treated obese rats. Using PCR array we found that 3 of 84 target proinflammatory genes were increased by 2–4 fold in the aorta of obese rats, 11 of the target genes were further increased in nicotine-treated obese rats. HUVECs, incubated with conditioned medium from the peritoneal macrophages of nicotine treated-obese rats, exhibited reduced eNOS and increased NADPH oxidase subunits gp91phox and p22phox expression. Those effects were partially prevented by adding anti-TNFα antibody to the conditioned medium. Our results suggest that nicotine aggravates the CV effects of diet–induced obesity including the oxidative stress, vascular inflammation and endothelial dysfunction. The underlying mechanisms may involve in targeting endothelium by enhancement of macrophage-derived TNFα.

Pycnogenol Reduces Toll-Like Receptor 4 Signaling Pathway-Mediated Atherosclerosis Formation in Apolipoprotein E-Deficient Mice

Pycnogenol (PYC) is an extract from French maritime pine bark. Its antioxidative and anti-inflammatory effects have been shown to be beneficial for atherosclerosis. Here, we tested whether PYC could suppress high cholesterol and fat diet (HCD)-induced atherosclerosis formation in apolipoprotein E (apoE)-deficient mice. In our study, PYC suppressed oxidized low-density lipoprotein (ox-LDL)-induced lipid accumulation in peritoneal macrophages. Apolipoprotein E-deficient mice were orally administered PYC or a control solvent for ten weeks, and these mice were fed a standard diet or high cholesterol and fat diet during the latter eight weeks. Pycnogenol markedly decreased the size of atherosclerotic lesions induced by high cholesterol and fat diet compared with the nontreated controls. In addition, TLR4 expression in aortic sinus was stimulated by high cholesterol and fat diet feeding and was significantly reduced by PYC. A mechanistic analysis indicated that lipopolysaccharide (LPS) significantly increased expression of fatty acid binding protein (aP2) and macrophage scavenger receptor class A (SR-A), which were blocked by a JNK inhibitor. Furthermore, PYC inhibited the lipopolysaccharide-induced upregulation of aP2 and scavenger receptor class A via the JNK pathway. In conclusion, PYC administration effectively attenuates atherosclerosis through the TLR4-JNK pathway. Our results suggest that PYC could be a potential prophylaxis or treatment for atherosclerosis in humans.