Macrophages In Atherosclerosis Research Articles

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.

The multifaceted therapeutic value of targeting ATP-citrate lyase in atherosclerosis.

ATP-citrate lyase (Acly) is the target of the new class low-density lipoprotein-cholesterol (LDL-C)-lowering drug bempedoic acid (BA). Acly is a key metabolic enzyme synthesizing acetyl-CoA as the building block of cholesterol and fatty acids. Treatment with BA lowers circulating lipid levels and reduces systemic inflammation, suggesting a dual benefit of this drug for atherosclerosis therapy. Recent studies have shown that targeting Acly in macrophages can attenuate inflammatory responses and decrease atherosclerotic plaque vulnerability. Therefore, it could be beneficial to extend the application of Acly inhibition from solely lipid-lowering by liver-specific inhibition to also targeting macrophages in atherosclerosis. Here, we outline the possibilities of targeting Acly and describe the future needs to translate these findings to the clinic.

Trafficking of Mononuclear Phagocytes in Healthy Arteries and Atherosclerosis

Monocytes and macrophages play essential roles in all stages of atherosclerosis – from early precursor lesions to advanced stages of the disease. Intima-resident macrophages are among the first cells to be confronted with the influx and retention of apolipoprotein B-containing lipoproteins at the onset of hypercholesterolemia and atherosclerosis development. In this review, we outline the trafficking of monocytes and macrophages in and out of the healthy aorta, as well as the adaptation of their migratory behaviour during hypercholesterolemia. Furthermore, we discuss the functional and ontogenetic composition of the aortic pool of mononuclear phagocytes and its link to the atherosclerotic disease process. The development of mouse models of atherosclerosis regression in recent years, has enabled scientists to investigate the behaviour of monocytes and macrophages during the resolution of atherosclerosis. Herein, we describe the dynamics of these mononuclear phagocytes upon cessation of hypercholesterolemia and how they contribute to the restoration of tissue homeostasis. The aim of this review is to provide an insight into the trafficking, fate and disease-relevant dynamics of monocytes and macrophages during atherosclerosis, and to highlight remaining questions. We focus on the results of rodent studies, as analysis of cellular fates requires experimental manipulations that cannot be performed in humans but point out findings that could be replicated in human tissues. Understanding of the biology of macrophages in atherosclerosis provides an important basis for the development of therapeutic strategies to limit lesion formation and promote plaque regression.

Macrophages in Atherosclerosis, First or Second Row Players?

Macrophages represent a cell type that has been widely described in the context of atherosclerosis since the earliest studies in the 17th century. Their role has long been considered to be preponderant in the onset and aggravation of atherosclerosis, in particular by participating in the establishment of a chronic inflammatory state by the release of pro-inflammatory cytokines and by uncontrolled engorgement of lipids resulting in the formation of foam cells and later of the necrotic core. However, recent evidence from mouse models using an elegant technique of tracing vascular smooth muscle cells (VSMCs) during plaque development revealed that resident VSMCs display impressive plastic properties in response to an arterial injury, allowing them to switch into different cell types within the plaque, including mesenchymal-like cells, macrophage-like cells and osteochondrogenic-like cells. In this review, we oppose the arguments in favor or against the influence of macrophages versus VSMCs in all stages of atherosclerosis including pre-atherosclerosis, formation of lipid-rich foam cells, development of the necrotic core and the fibrous cap as well as calcification and rupture of the plaque. We also analyze the relevance of animal models for the investigation of the pathophysiological mechanisms of atherosclerosis in humans, and discuss potential therapeutic strategies targeting either VSMCs or macrophage to prevent the development of cardiovascular events. Overall, although major findings have been made from animal models, efforts are still needed to better understand and therefore prevent the development of atherosclerotic plaques in humans.

Single-cell RNA-seq reveals cellular heterogeneity of mouse carotid artery under disturbed flow

Disturbed blood flow (d-flow) has been known to induce changes of the cells in the arterial wall, increasing the risk of atherosclerosis. However, the heterogeneity of the vascular cell populations under d-flow remains less understood. To generate d-flow in vivo, partial carotid artery ligation (PCL) was performed. Seven days after ligation, single-cell RNA sequencing of nine left carotid arteries (LCA) from the PCL group (10,262 cells) or control group (14,580 cells) was applied and a single-cell atlas of gene expression was constructed. The integrated analysis identified 15 distinct carotid cell clusters, including 10 d-flow-relevant subpopulations. Among endothelial cells, at least four subpopulations were identified, including Klk8hi ECs, Lrp1hi ECs, Dkk2hi ECs, and Cd36hi ECs. Analysis of GSVA and single-cell trajectories indicated that the previously undescribed Dkk2hi ECs subpopulation was mechanosensitive and potentially transformed from Klk8hi ECs under d-flow. D-flow-induced Spp1hi VSMCs subpopulation that appeared to be endowed with osteoblast differentiation, suggesting a role in arterial stiffness. Among the infiltrating cell subpopulations, Trem2hi Mφ, Birc5hi Mφ, DCs, CD4+ T cells, CXCR6+ T cells, NK cells, and granulocytes were identified under d-flow. Of note, the novel Birc5hi Mφ was identified as a potential contributor to the accumulation of macrophages in atherosclerosis. Finally, Dkk2hi ECs, and Cd36hi ECs were also found in the proatherosclerotic area of the aorta where the d-flow occurs. In conclusion, we presented a comprehensive single-cell atlas of all cells in the carotid artery under d-flow, identified previously unrecognized cell subpopulations and their gene expression signatures, and suggested their specialized functions.

Metformin, Macrophage Dysfunction and Atherosclerosis.

Metformin is one of the most widely prescribed hypoglycemic drugs and has the potential to treat many diseases. More and more evidence shows that metformin can regulate the function of macrophages in atherosclerosis, including reducing the differentiation of monocytes and inhibiting the inflammation, oxidative stress, polarization, foam cell formation and apoptosis of macrophages. The mechanisms by which metformin regulates the function of macrophages include AMPK, AMPK independent targets, NF-κB, ABCG5/8, Sirt1, FOXO1/FABP4 and HMGB1. On the basis of summarizing these studies, we further discussed the future research directions of metformin: single-cell RNA sequencing, neutrophil extracellular traps (NETs), epigenetic modification, and metformin-based combination drugs. In short, macrophages play an important role in a variety of diseases, and improving macrophage dysfunction may be an important mechanism for metformin to expand its pleiotropic pharmacological profile. In addition, the combination of metformin with other drugs that improve the function of macrophages (such as SGLT2 inhibitors, statins and IL-1β inhibitors/monoclonal antibodies) may further enhance the pleiotropic therapeutic potential of metformin in conditions such as atherosclerosis, obesity, cancer, dementia and aging.

Molecular and Nonmolecular Imaging of Macrophages in Atherosclerosis.

Atherosclerosis is a major cause of ischemic heart disease, and the increasing medical burden associated with atherosclerotic cardiovascular disease has become a major public health concern worldwide. Macrophages play an important role in all stages of the dynamic progress of atherosclerosis, from its initiation and lesion expansion increasing the vulnerability of plaques, to the formation of unstable plaques and clinical manifestations. Early imaging can identify patients at risk of coronary atherosclerotic disease and its complications, enabling preventive measures to be initiated. Recent advances in molecular imaging have involved the noninvasive and semi-quantitative targeted imaging of macrophages and their related molecules in vivo, which can detect atheroma earlier and more accurately than conventional imaging. Multimodal imaging integrates vascular structure, function, and molecular imaging technology to achieve multi-dimensional imaging, which can be used to comprehensively evaluate blood vessels and obtain clinical information based on anatomical structure and molecular level. At the same time, the rapid development of nonmolecular imaging technologies, such as intravascular imaging, which have the unique advantages of having intuitive accuracy and providing rich information to identify macrophage inflammation and inform targeted personalized treatment, has also been seen. In this review, we highlight recent methods and research hotspots in molecular and nonmolecular imaging of macrophages in atherosclerosis that have enormous potential for rapid clinical application.

Macrophage Plasticity and Atherosclerosis Therapy.

Atherosclerosis is a chronic disease starting with the entry of monocytes into the subendothelium and the subsequent differentiation into macrophages. Macrophages are the major immune cells in atherosclerotic plaques and are involved in the dynamic progression of atherosclerotic plaques. The biological properties of atherosclerotic plaque macrophages determine lesion size, composition, and stability. The heterogenicity and plasticity of atherosclerotic macrophages have been a hotspot in recent years. Studies demonstrated that lipids, cytokines, chemokines, and other molecules in the atherosclerotic plaque microenvironment regulate macrophage phenotype, contributing to the switch of macrophages toward a pro- or anti-atherosclerosis state. Of note, M1/M2 classification is oversimplified and only represent two extreme states of macrophages. Moreover, M2 macrophages in atherosclerosis are not always protective. Understanding the phenotypic diversity and functions of macrophages can disclose their roles in atherosclerotic plaques. Given that lipid-lowering therapy cannot completely retard the progression of atherosclerosis, macrophages with high heterogeneity and plasticity raise the hope for atherosclerosis regression. This review will focus on the macrophage phenotypic diversity, its role in the progression of the dynamic atherosclerotic plaque, and finally discuss the possibility of treating atherosclerosis by targeting macrophage microenvironment.

Autophagy blockage promotes the pyroptosis of ox-LDL-treated macrophages by modulating the p62/Nrf2/ARE axis.

Atherosclerosis, a chronic comprehensive cardiovascular disease, is characterized by the lipid infiltration, formation of foam cells derived from macrophages and inflammation in the vessel wall. Substantial evidence confirms that the activity of autophagic bodies plays a pivot role in regulating cell deaths, but the mechanisms of autophagy to regulate the pyroptosis of macrophages in atherosclerosis remain unclear. In our study, we explored that ox-LDL decreased the cell viability and destroyed the integrity of cell membrane, resulting in the pyroptosis of THP-1 derived macrophages in a dose-dependent manner. Western blotting, qRT-PCR and ELISA also showed that chloroquine (CQ) could up-regulate the expression of p62 through impairing autophagy and induce the pyroptosis of macrophages treated by ox-LDL, as evidenced by the decrease of cell viability and membrane integrity, and the increase of pro-caspase-1, GSDMD, and proinflammatory factors IL-1β and IL-18. Further researches demonstrated that Nrf2, a nuclear factor activated by p62, was linked to macrophage pyroptosis. Overactivating or suppressing Nrf2/ARE signaling would correspondingly aggravate or alleviate pyroptosis, in which the level of p62 was regulated by Nrf2 feedback. Then, bioinformatic analysis verified that there was a close interaction between p62, Nrf2/ARE signaling proteins and pyroptosis-related proteins. Taken together, our results show that blocking autophagy promotes the pyroptosis of ox-LDL-treated macrophages via the p62/Nrf2/ARE axis, providing a novel therapeutic target for atherosclerosis.

Novel insights: Dynamic foam cells derivedfrom the macrophage in atherosclerosis.

Atherosclerosis can be regarded as a chronic disease derivedfrom the interaction between disordered lipoproteins and an unsuitable immune response. The evolution of foam cells is not only a significant pathological change in the early stage of atherosclerosisbut also a key stagein the occurrence and development of atherosclerosis. The formation of foam cells is mainly caused by the imbalance among lipids uptake, lipids treatment, and reverse cholesterol transport. Although a large number of studies have summarized the source of foam cells and the mechanism of foam cells formation, we propose anew ideaabout foam cells in atherosclerosis. Rather than an isolated microenvironment,the macrophage multiple lipiduptake pathways, lipidinternalization, lysosome, mitochondria, endoplasmic reticulum, neutral cholesterol ester hydrolase (NCEH), acyl-coenzyme A-cholesterol acyltransferase (ACAT), and reverse cholesterol transport are mutually influential, andforma dynamic process under multi-factor regulation. The macrophage takes on different uptake lipidstatuses depending on multiple uptake pathways and intracellular lipids, lipid metabolites versus pro-inflammatory factors. Except for NCEH and ACAT, the lipid internalization of macrophages also depends on multicellular organelles including the lysosome, mitochondria, and endoplasmic reticulum, which are associated with each other. A dynamic balance between esterification and hydrolysis of cholesterol for macrophages isessential for physiology and pathology. Therefore, we propose that the foam cell in the process of atherosclerosis may be dynamicunder multi-factor regulation, and collate thisstudy to provide a holistic and dynamic idea ofthe foam cell.

Targeting Macrophages in Atherosclerosis.

Atherosclerosis (AS) is an important pathological basis for the occurrence of Coronary Atherosclerotic Disease (CAD), stroke and other adverse cardiovascular events. AS is an inflammatory disease, and macrophages are the main inflammatory cells in AS lesions, playing a leading role in the formation of atherosclerotic plaques and the development and regression of AS. Various proinflammatory and anti-inflammatory factors act on macrophages to regulate AS. Pro-inflammatory factors recruit monocytes to accumulate in the inflammatory site and promote the transformation of monocytes to macrophages. A large number of aggregated macrophages secrete various inflammatory mediators to promote AS. Pro-inflammatory factors can induce the polarization of M1-type macrophages to start and maintain inflammation, promote the accumulation of lipids in macrophages, and accelerate the formation of foam cells. Anti-inflammatory factors can not only induce M2-type macrophages polarization, promote tissue remodeling and repair, and reduce the occurrence of AS, but also promote the metabolism of fatty acid oxidation and oxidative phosphorylation of macrophages, regulate lipid metabolism, stabilize plaques, and induce the transformation of helper T cells of type 1/2 (Th1/Th2) to Th2 cells, thus reducing inflammation. This review summarizes the effect and underlying regulatory mechanism of macrophages in the development of AS, which can provide new ideas for the diagnosis and treatment of AS targeting macrophages.

ZBTB20 Positively Regulates Oxidative Stress, Mitochondrial Fission, and Inflammatory Responses of ox-LDL-Induced Macrophages in Atherosclerosis.

Atherosclerosis (AS) is one of the most serious and common cardiovascular diseases affecting human health. AS is featured by the accumulation of plaques in vessel walls. The pathophysiology of AS is relevant in the low-density lipoprotein (LDL) uptake by macrophages, as well as the conversion of macrophages to foam cells. However, the mechanisms about how macrophages regulate AS have not been fully elucidated. In this study, we aimed to illuminate the roles of ZBTB20 and to excavate the underlying regulative mechanisms of ZBTB20 in AS. The microarray analysis revealed that ZBTB20 was a hub gene in the oxidative stress and inflammatory responses induced by oxidized LDL (ox-LDL) in AS. Correspondingly, our validation studies showed that ZBTB20 increased in either the human atherosclerotic lesion or the ox-LDL-stimulated macrophages. Moreover, the knockdown of ZBTB20 decreased M1 polarization, suppressed the proinflammatory factors, inhibited mitochondrial fission, and reduced the oxidative stress level of macrophages induced by ox-LDL. The mechanistic studies revealed that the ZBTB20 knockdown suppressed NF-κB/MAPK activation and attenuated the mitochondrial fission possibly via regulating the nucleus translocation of NRF2, a pivotal transcription factor on redox homeostasis. Our in vivo studies showed that the sh-ZBTB20 adenovirus injection could reduce the progression of AS in apolipoprotein E-deficient (ApoE−/−) mice. All in all, these results suggested that ZBTB20 positively regulated the oxidative stress level, mitochondrial fission, and inflammatory responses of macrophages induced by ox-LDL, and the knockdown of ZBTB20 could attenuate the development of AS in ApoE−/− mice.

Role of macrophages in atherosclerosis

Atherosclerosis is a chronic inflammatory state, which arise from the imbalance in lipid metabolism. Over the last decade, studies have showing the association of macrophages with this maladaptive immune response. Macrophages differentiated from monocytes and populate at the growing atherosclerotic lesions. At the lesion site by accumulating lipid they actively participate in the formation of atherosclerotic plaque. These plaques are very susceptible to rupture which can lead to myocardial infarction or stroke. In future more studies are needed to classify different macrophage populations according to their phenotypic and functional characteristics to identify their roles in the pathogenesis of atherosclerosis. This review highlights several aspects of macrophages activation, diversity, recruitment, and foam cell formation in atherosclerosis.
 Asian J. Med. Biol. Res. September 2020, 6(3): 366-374

Editorial introductions

Current Opinion in Lipidology was launched in 1990. It is part of a successful series of review journals whose unique format is designed to provide a systematic and critical assessment of the literature as presented in the many primary journals. The field of lipidology is divided into six sections that are reviewed once a year. Each section is assigned a Section Editor, a leading authority in the area, who identifies the most important topics at that time. Here we are pleased to introduce the Section Editor for this issue. Section Editor Mohamad NavabMohamad NavabMohamad Navab is a Faculty and a co-project leader at David Geffen school of medicine, University of California Los Angeles. He obtained his PhD in biochemistry from Columbia University, in 1976. Subsequently, he served as an Assistant Professor and Head of Clinical Labs at the National University School of Medicine in Tehran, Iran. He started his research and teaching first at the UCLA Cancer Center in 1981 and subsequently at the Division of Cardiology at UCLA where he has been since 1983. Prof. Navab has received research support from NIH and has served as grant reviewer for the National Heart, Lung & Blood Institute at NIH and the American Heart Association. He serves on the editorial board and advisory board of a dozen scientific journals. Prof. Navab has authored or been a coauthor for 203 papers indexed at PubMed and has presented 171 invited national and international medical lectures. Menno de WintherMenno de WintherMenno de Winther is a Professor of vascular immune cell biology at the AMC of the Amsterdam-University Medical Centers, Amsterdam, Netherlands. Prof. de Winther graduated in biology at Utrecht University, Netherlands, and obtained his PhD in 1999 at Leiden University, Netherlands with a thesis on macrophage scavenger receptors in atherosclerosis. After completing the PhD, he was a postdoc in Oxford University, UK and Maastricht University, Netherlands and became a principal investigator studying the role of macrophages in cardiovascular disease. In 2011, Prof. de Winther was appointed as a Professor of vascular immune cell biology at the Academic Medical Center of the University of Amsterdam. Using cellular and animal models for disease, his group studies the molecular regulation of macrophages in inflammatory disease. His research particularly focuses on the transcriptional regulation of monocytes and macrophages in atherosclerosis, characterizing environmental factors (e.g. dyslipidemia, metabolic triggers, cytokines) that drives signaling pathways influencing cellular function in disease. Prof. de Winther's group was the first to define the role of the transcription factor NF-κB in atherosclerosis and more recently identified the epigenetic enzyme HDAC3 a major regulator of macrophage gene programs in atherosclerosis. Significant efforts in his group are now running on further delineating epigenetic pathways in atherosclerostic diseases. His group thrives on a combination of human and mouse cell- and animal models combined with patient studies through close interactions with the clinic. Dr de Winther is an established investigator of the Netherlands Heart Foundation and together with Dr Glass (UCSD) is currently coordinating a Leducq Transatlantic Network on epigenetics in atherosclerosis.

Biomimetic 3D Models for Investigating the Role of Monocytes and Macrophages in Atherosclerosis.

Atherosclerosis, the inflammation of artery walls due to the accumulation of lipids, is the most common underlying cause for cardiovascular diseases. Monocytes and macrophages are major cells that contribute to the initiation and progression of atherosclerotic plaques. During this process, an accumulation of LDL-laden macrophages (foam cells) and an alteration in the extracellular matrix (ECM) organization leads to a local vessel stiffening. Current in vitro models are carried out onto two-dimensional tissue culture plastic and cannot replicate the relevant microenvironments. To bridge the gap between in vitro and in vivo conditions, we utilized three-dimensional (3D) collagen matrices that allowed us to mimic the ECM stiffening during atherosclerosis by increasing collagen density. First, human monocytic THP-1 cells were embedded into 3D collagen matrices reconstituted at low and high density. Cells were subsequently differentiated into uncommitted macrophages (M0) and further activated into pro- (M1) and anti-inflammatory (M2) phenotypes. In order to mimic atherosclerotic conditions, cells were cultured in the presence of oxidized LDL (oxLDL) and analyzed in terms of oxLDL uptake capability and relevant receptors along with their cytokine secretomes. Although oxLDL uptake and larger lipid size could be observed in macrophages in a matrix dependent manner, monocytes showed higher numbers of oxLDL uptake cells. By analyzing major oxLDL uptake receptors, both monocytes and macrophages expressed lectin-like oxidized low-density lipoprotein receptor-1 (LOX1), while enhanced expression of scavenger receptor CD36 could be observed only in M2. Notably, by analyzing the secretome of macrophages exposed to oxLDL, we demonstrated that the cells could, in fact, secrete adipokines and growth factors in distinct patterns. Besides, oxLDL appeared to up-regulate MHCII expression in all cells, while an up-regulation of CD68, a pan-macrophage marker, was found only in monocytes, suggesting a possible differentiation of monocytes into a pro-inflammatory macrophage. Overall, our work demonstrated that collagen density in the plaque could be one of the major factors driving atherosclerotic progression via modulation of monocyte and macrophages behaviors.

New Classification of Macrophages in Plaques: a Revolution.

Macrophages play vital roles in the development of atherosclerosis in responding to lipid accumulation and inflammation. Macrophages were classified as inflammatory (M1) and alternatively activated (M2) macrophage types based on results of in vitro experiments. On the other hand, the composition of macrophages in vivo is more complex and remains unresolved. This review summarizes the transcriptional variations of macrophages in atherosclerosis plaques that were discovered by single-cell RNA sequencing (scRNA-seq) to better understand their contribution to atherosclerosis. ScRNA-seq provides a more detailed transcriptional landscape of macrophages in atherosclerosis, which challenges the traditional view. By mining the data of GSE97310, we discovered the transcriptional variations of macrophages in LDLR-/- mice that were fed with high-fat diet (HFD) for 11 and 20weeks. Cells were represented in a two-dimensional tSNE plane and clusters were identified and annotated via Seurat and SingleR respectively, which were R toolkits for single-cell genomics. The results showed that in healthy conditions, Trem2hi (high expression of triggering receptors expressed on myeloid cells 2)-positive, inflammatory, and resident-like macrophages make up 68%, 18%, and 6% of total macrophages respectively. When mice were fed with HFD for 11weeks, Trem2hi, monocytes, and monocyte-derived dendritic cells take possession of 40%, 18%, and 17% of total macrophages respectively. After 20weeks of HFD feeding, Trem2hi, inflammatory, and resident-like macrophages occupied 12%, 37%, and 35% of total macrophages respectively. The phenotypes of macrophages are very different from the previous studies. In general, Trem2hi macrophages are the most abundant population in healthy mice, while the proportion of monocytes increases after 11weeks of HFD. Most importantly, inflammatory and resident-like macrophages make up 70% of the macrophage populations after 20weeks of HFD. These strongly indicate that inflammatory and resident-like macrophages promote the progression of atherosclerosis plaques.

The hematopoietic transcription factor GATA2 is a novel regulator of apoptotic cell clearance by macrophages in atherosclerosis

Abstract Atherosclerosis is an inflammatory disease involving formation of lipid-rich lesions within the arteries. Macrophages clear apoptotic cells that accumulate within these lesions. Defective apoptotic cell clearance is a hallmark of advanced atherosclerotic disease, yet mechanisms that drive this defect are poorly understood. In this study, we identify the hematopoietic transcription factor GATA2 as a novel regulator of macrophage-mediated apoptotic cell clearance. Macrophages were isolated by laser capture microdissection from atherosclerotic lesions in aortic tissue obtained from patients undergoing open heart surgery. Gene expression profiling was performed on these macrophages by microarray, with macrophages derived from peripheral blood monocytes used as a control. We found approximately 3,000 genes to be differentially expressed in aortic punch macrophages, with enrichment in pathways involved in apoptotic cell clearance. In particular, we identified upregulation of GATA2. Mutations in GATA2 have previously been associated with increased risk of coronary artery disease and we found that overexpression of GATA2 in vitro resulted in decreased ability of macrophages to both internalize and degrade apoptotic cells. Conversely, GATA2 downregulation is sufficient to abrogate oxLDL-induced defective apoptotic cell clearance. Atherosclerotic macrophages exhibit dysregulated expression of genes involved in apoptotic cell clearance and upregulation of GATA2. Recapitulation of GATA2 overexpression is sufficient to impair apoptotic cell clearance in vitro. To our knowledge, we are the first to identify a potential role for GATA2 in driving defective apoptotic cell clearance in atherosclerosis.

Desmosterol, an intermediate of cholesterol biosynthesis, modulates B cell activation and functions

Abstract Introduction Atherosclerosis is a disease of large/medium size vessels attributed to a hyperlipidemic environment and a low-grade chronic inflammation. Normally, macrophages uptake modified low-density lipoprotein (mLDL), resulting in excess intracellular desmosterol, an immediate precursor to cholesterol, which promotes anti-inflammatory signaling. In contrast, mLDL uptake by macrophages in atherosclerosis produces foam cells that play an atherogenic role. While it has been previously shown that B cells can uptake mLDL, it remains unclear how mLDL uptake modulates B cell phenotype. Methods Murine B cells were treated with 1 mM of desmosterol for 12/24 hrs, cholesterol efflux genes were analyzed using qPCR. CFSE-labeled splenocytes were incubated with LPS/BAFF, treated with 1 mM of desmosterol for 72 hrs, and analyzed via FACS. B cells isolated from transgenic mice ooverexpressing DHCR24, a dehydrocholesterol reductase, were analyzed for desmosterol content by lipidomics, Ca2+ flux by FACS, and DNP-Ficoll induced Igs production in vivo by ELISA. Results Desmosterol uptake results in an increased expression of cholesterol efflux genes and attenuated B cell proliferation. Overexpression of DHCR24 leads to a decreased intracellular desmosterol, hyper-response of B cells shown by increased Ca2+. DNP-Ficoll immunization of B cell-deficient mice populated with either DHCR24- or WT B cells induce more anti-IGM specific Abs in the DHCR24-B cell recipients. Conclusions These results suggest desmosterol is synthesized and sensed by B cells, and its accumulation regulates B cell activation thresholds in vitro and in vivo. These novel data offer new insights for B cell biology and atherosclerosis pathology.

Orientin suppresses oxidized low-density lipoproteins induced inflammation and oxidative stress of macrophages in atherosclerosis.

Atherosclerosis is a main reason for peripheral vascular disease. The present study aims to investigate the effects of macrophage foam cells which is an initial part in atherosclerosis. RAW 264.7 were treated with 80 μg/mL oxidized low-density lipoproteins (ox-LDL) to mimic atherosclerosis in vitro. Orientin, a flavonoid from plants, inhibited ox-LDL induced TNFα, IL-6, IL-1β expression increase. In addition, Orientin also can inhibit the emergence of ox-LDL-induced lipid droplets. The scavenger receptor CD 36 of ox-LDL was significantly downregulated after the treatment of orientin. Inhibition of ROS generation and increasing of eNOS expression by Orientin treatment was used to show the alteration of oxidative stress. Moreover, the expression levels of Angiopoietin-like 2 (angptl2) and NF-κB were significantly upregulated after cells induced by ox-LDL, whereas orientin significantly reversed the effects of ox-LDL. Orientin inhibited ox-LDL-induced inflammation and oxidative stress, and CD36 may be the key regulator during Orientin action.

Correlates and Predictors of Cerebrospinal Fluid Cholesterol Efflux Capacity from Neural Cells, a Family of Biomarkers for Cholesterol Epidemiology in Alzheimer's Disease.

Basic research has implicated intracellular cholesterol in neurons, microglia, and astrocytes in the pathogenesis of Alzheimer's disease (AD), but there is presently no assay to access intracellular cholesterol in neural cells in living people in the context of AD. To devise and characterize an assay that can access intracellular cholesterol and cholesterol efflux in neural cells in living subjects. We modified the protocol for high-density lipoprotein cholesterol efflux capacity (CEC) from macrophages, a biomarker that accesses cholesterol in macrophages in atherosclerosis. To measure cerebrospinal fluid (CSF) CECs from neurons, microglia, and astrocytes, CSF was exposed to, correspondingly, neuronal, microglial, and astrocytic cholesterol source cells. Human neuroblastoma SH-SY5Y, mouse microglial N9, and human astroglial A172 cells were used as the cholesterol source cells. CSF samples were screened for contamination with blood. CSF CECs were measured in a small cohort of 22 individuals. CSF CECs from neurons, microglia, and astrocytes were moderately to moderately strongly correlated with CSF concentrations of cholesterol, apolipoprotein A-I, apolipoprotein E, and clusterin (Pearson's r = 0.53-0.86), were in poor agreement with one another regarding CEC of the CSF samples (Lin's concordance coefficient rc = 0.71-0.76), and were best predicted by models consisting of, correspondingly, CSF phospholipid (R2 = 0.87, p < 0.0001), CSF apolipoprotein A-I and clusterin (R2 = 0.90, p < 0.0001), and CSF clusterin (R2 = 0.62, p = 0.0005). Characteristics of the CSF CEC metrics suggest a potential for independent association with AD and provision of fresh insight into the role of cholesterol in AD pathogenesis.