Monocyte Atherosclerosis Research Articles

Monocyte Count as a Predictor of Major Adverse Limb Events in Aortoiliac Revascularization.

Background/Objectives: Atherosclerosis is a leading cause of death, especially in the developed world, and is marked by chronic arterial inflammation and lipid accumulation. As key players in its progression, monocytes contribute to plaque formation, inflammation, and tissue repair. Understanding monocyte involvement is crucial for developing better therapeutic approaches. The objective of this study is to assess the prognostic value of monocytes for limb-related outcomes following revascularization for complex aortoiliac lesions, thereby emphasizing the central role of monocytes in atherosclerosis. Methods: This prospective cohort study-enrolled patients who had undergone elective aortoiliac revascularization at two hospitals between January 2013 and December 2023. Patients with TASC II type D lesions were included, excluding those with aneurysmal disease. Demographic, clinical, and procedural data were gathered, and patients were monitored for limb-related outcomes. Preoperative complete blood counts were analyzed, and statistical analyses, including multivariable Cox regression, were conducted to identify predictors of major adverse limb events (MALE). Results: The study included 135 patients with a mean age of 62.4 ± 9.20 years and predominantly male (93%). Patients were followed for a median of 61 IQR [55.4-66.6] months. Smoking history (91%) was the most prevalent cardiovascular risk factor. Preoperative monocyte count >0.720 × 109/L was associated with worse 30-day limb-related outcomes (MALE: OR 7.138 95% CI: 1.509-33.764, p = 0.013) and long-term outcomes, including secondary patency (p = 0.03), major amputation (p = 0.04), and MALE (p = 0.039). Cox regression analysis confirmed an elevated monocyte count as an independent predictor of MALE (adjusted hazard ratio 2.149, 95% CI: 1.115-4.144, p = 0.022). Conclusions: This study demonstrated that patients with a higher absolute monocyte count may be more exposed to the risk of MALE in patients with aortoiliac TASC II type D lesions undergoing revascularization, with predictive accuracy in both the short and long term. Additionally, it was an independent predictor of major amputation. This new marker has the potential to serve as a cost-effective and easily available tool for risk stratification, helping identify patients at higher risk of MALE.

Abstract 3054: Proinflammatory Phenotypes And Role Of Ly-6c Low Monocytes In Atherosclerosis With Hypertriglyceridemia

Background: Monocytes play pivotal roles in atherosclerosis. Ly-6C low monocytes, also known as patrolling monocytes, become foamy in the circulation of mice with hyperlipidemia. However, the role of Ly-6C low monocytes in atherosclerosis with hypertriglyceridemia (HTG) remains to be determined. Aim: To examine the phenotypes and role of Ly-6C low monocytes in atherosclerosis in HTG. Method: Ldlr -/- ApoC3Tg (transgenic expression of human ApoC3) mice fed a western high-fat diet (WD) were used to examine the effects of HTG on monocyte lipid accumulation (foamy monocyte formation), phenotypes, and contributions to atherosclerosis. Results: Plasma triglycerides in Ldlr -/- ApoC3Tg mice were 5.1 times higher than in Ldlr -/- controls at 6 weeks on WD, correlating with more than twice the increase in aortic atherosclerosis (P<0.01). Consistently, Ly-6C low compared to Ly-6C high monocytes in Ldlr -/- mice had increased lipid accumulation and exhibited elevated levels of TNFα, IL-6, IL-1β, Plin2, and PPAR-γ. In Ldlr -/- ApoC3Tg mice, Ly-6C low (also CD11c + ) monocytes demonstrated even greater lipid accumulation and adhesion to VCAM-1 and had further elevations in levels of TNFα, IL-6, IL-1β, Plin2, and PPAR-γ than CD11c + (Ly-6C low ) monocytes in Ldlr -/- controls, indicating an enhanced inflammatory response and lipid accumulation under HTG. Furthermore, compared to Ldlr -/- control mice, Ldlr -/- ApoC3Tg mice had an increase in the level of SIRPα (a ligand of the “don’t-eat me” signal CD47) on Ly-6C low monocytes, indicative of impairment in efferocytosis and clearance of apoptotic cells. Additionally, nuclear c-Rel mRNA and protein levels were upregulated in Ly-6C low monocytes of Ldlr -/- ApoC3Tg mice compared to Ldlr -/- controls, suggesting activation of the NF-κB pathway in Ly-6C low monocytes by HTG. Finally, depletion of Ly-6C low monocytes reduced atherosclerosis by 45% (P<0.05) in Ldlr -/- ApoC3Tg mice, indicating a role of Ly-6C low monocytes in atherosclerosis in HTG. Conclusions: HTG accelerates atherogenesis in Ldlr -/- mice, possibly by increasing lipid accumulation and inflammatory phenotypic changes in monocytes, primarily CD11c + Ly-6C low monocytes.

The Entry and Egress of Monocytes in Atherosclerosis: A Biochemical and Biomechanical Driven Process.

In accordance with “the response to injury” theory, the entry of monocytes into the intima guided by inflammation signals, taking up cholesterol and transforming into foam cells, and egress from plaques determines the progression of atherosclerosis. Multiple cytokines and receptors have been reported to be involved in monocyte recruitment such as CCL2/CCR2, CCL5/CCR5, and CX3CL1/CX3CR1, and the egress of macrophages from the plaque like CCR7/CCL19/CCL21. Interestingly, some neural guidance molecules such as Netrin-1 and Semaphorin 3E have been demonstrated to show an inhibitory effect on monocyte migration. During the processes of monocytes recruitment and migration, factors affecting the biomechanical properties (e.g., the membrane fluidity, the deformability, and stiffness) of the monocytes, like cholesterol, amyloid-β peptide (Aβ), and lipopolysaccharides (LPS), as well as the biomechanical environment that the monocytes are exposed, like the extracellular matrix stiffness, mechanical stretch, blood flow, and hypertension, were discussed in the latter section. Till now, several small interfering RNAs (siRNAs), monoclonal antibodies, and antagonists for CCR2 have been designed and shown promising efficiency on atherosclerosis therapy. Seeking more possible biochemical factors that are chemotactic or can affect the biomechanical properties of monocytes, and uncovering the underlying mechanism, will be helpful in future studies.

Trained Circulating Monocytes in Atherosclerosis: Ex Vivo Model Approach.

Inflammation is one of the key processes in the pathogenesis of atherosclerosis. Numerous studies are focused on the local inflammatory processes associated with atherosclerotic plaque initiation and progression. However, changes in the activation state of circulating monocytes, the main components of the innate immunity, may precede the local events. In this article, we discuss tolerance, which results in decreased ability of monocytes to be activated by pathogens and other stimuli, and training, the ability of monocyte to potentiate the response to pathological stimuli, and their relation to atherosclerosis. We also present previously unpublished results of the experiments that our group performed with monocytes/macrophages isolated from atherosclerosis patients. Our data allow assuming the existence of relationship between the formation of monocyte training and the degree of atherosclerosis progression. The suppression of trained immunity ex vivo seems to be a perspective model for searching anti-atherogenic drugs.

Quantitative Protein Sulfenic Acid Analysis Identifies Platelet Releasate-Induced Activation of Integrin β2 on Monocytes via NADPH Oxidase.

Physiological stimuli such as thrombin, or pathological stimuli such as lysophosphatidic acid (LPA), activate platelets. The activated platelets bind to monocytes through P-selectin-PSGL-1 interactions but also release the contents of their granules, commonly called "platelet releasate". It is known that monocytes in contact with platelet releasate produce reactive oxygen species (ROS). Reversible cysteine oxidation by ROS is considered to be a potential regulator of protein function. In a previous study, we used THP-1 monocytic cells exposed to LPA- or thrombin-induced platelet releasate and a modified biotin switch assay to unravel the biological processes that are influenced by reversible cysteine oxidation. To gain a better understanding of the redox regulation of monocytes in atherosclerosis, we have now altered the modified biotin switch to selectively quantify protein sulfenic acid, a subpopulation of reversible cysteine oxidation. Using arsenite as reducing agent in the modified biotin switch assay, we were able to quantify 1161 proteins, in which more than 100 sulfenic acid sites were identified. Bioinformatics analysis of the quantified sulfenic acid sites highlighted the relevant, previously missed biological process of monocyte transendothelial migration, which included integrin β2. Flow cytometry validated the activation of LFA-1 (αLβ2) and Mac-1 (αMβ2), two subfamilies of integrin β2 complexes, on human primary monocytes following platelet releasate treatment. The activation of LFA-1 was mediated by ROS from NADPH oxidase (NOX) activation. Production of ROS and activation of LFA-1 in human primary monocytes were independent of P-selectin-PSGL-1 interaction. Our results proved the modified biotin switch assay to be a powerful tool with the ability to reveal new regulatory mechanisms and identify new therapeutic targets.

Matthias Nahrendorf: Healing Insights.

Born in Salzwedel, East Germany, Matthias Nahrendorf entered adulthood just as the Iron Curtain was lifting in Eastern Europe. He earned his medical degree and PhD in cardiovascular biology at Heidelberg University, and completed his residency plus fellowships in internal medicine and cardiovascular imaging at University of Wuerzburg. In 2004, a postdoctoral position at Massachusetts General Hospital’s Center for Molecular Imaging Research brought Nahrendorf to Boston. He is now a principal investigator at MGH’s Center for Systems Biology and director of the hospital’s Mouse Imaging Program. Nahrendorf, 45, is pursuing a deeper understanding of the consequences of ischemic injury, especially regarding how monocytes/macrophages impact acute healing and scar development,1–3 and how an imbalance in the process fuels prolonged inflammation and then heart failure. An associate professor of radiology at Harvard Medical School, Nahrendorf and his collaborators are also developing molecular imaging tools to noninvasively study regulators of heart failure biology and infarct healing processes.4–6 A long-term goal of the work is to devise new therapies for ischemic injury that reduce the action of inflammatory cells to what is necessary only to promote healthy healing, Nahrendorf says. If that could be achieved, “Ideally we wouldn’t have heart failure anymore.” I have one brother, he’s younger, and my parents. It was a pretty sheltered childhood. I grew up in Magdeburg, and the (Berlin) Wall came down when I was 18. Army service was compulsory in East Germany. So I spent one year in the army and then Germany reunited, so I was free to go wherever I wanted. My parents are both doctors. My dad is a cardiologist, my mom a pediatrician. I had a happy childhood. They were never telling me what to do. But I was obviously influenced by their jobs. They talked about …

Native LDL promotes differentiation of human monocytes to macrophages with an inflammatory phenotype.

Recruitment of monocytes in atherosclerosis is dependent upon increased levels of plasma lipoproteins which accumulate in the blood vessel wall. The extracellular milieu can influence the phenotype of monocyte subsets (classical: CD14++CD16-, intermediate: CD14+CD16+ and non-classical: CD14dimCD16++) and macrophages (M1 or M2) and consequently the initiation, progression and/or regression of atherosclerosis. However, it is not known what effect lipoproteins, in particular native low-density lipoproteins (nLDL), have on the polarisation of monocyte-derived macrophages. Monocytes were differentiated into macrophages in the presence of nLDL. nLDL increased gene expression of the inflammatory cytokines TNFα and IL-6 in macrophages polarised towards the M1 phenotype while decreasing the M2 surface markers, CD206 and CD200R and the anti-inflammatory cytokines TGFβ and IL-10. Compared to the classical and intermediate subsets, the non-classical subset-derived macrophages had a reduced ability to respond to M1 stimuli (LPS and IFNγ). nLDL enhanced the TNFα and IL-6 gene expression in macrophages from all monocyte subsets, indicating an inflammatory effect of nLDL. Further, the classical and intermediate subsets both responded to M2 stimuli (IL-4) with upregulation of TGFβ and SR-B1 mRNA; an effect, which was reduced by nLDL. In contrast, the non-classical subset failed to respond to IL-4 or nLDL, suggesting it may be unable to polarise into M2 macrophages. Our data suggests that monocyte interaction with nLDL significantly affects macrophage polarisation and that this interaction appears to be subset dependent.

Role of splenic monocytes in atherosclerosis.

This review relates recent findings that highlight the role of the spleen as an active donor of monocytes during inflammation, with a special focus on atherosclerosis. The contribution of hypercholesterolemia and monocytes/macrophages to atherosclerotic lesion formation is undisputable. The origin of plaque macrophages is, however, still a subject of debate as to whether they derive from local amplification of (resident) macrophages or from continuous recruitment and differentiation of monocytes. Recently, the spleen has emerged as an important reservoir of monocytes that contributes to lesion growth. The regulation of monocyte mobilization from the splenic compartment has, therefore, raised a keen interest in understanding the cellular and molecular mechanisms involved in this process. Impaired regulation of cholesterol metabolism increases the proliferation of hematopoietic stem and progenitor cells in both the bone marrow and the spleen. Recent findings identified the implication of angiotensin II, red pulp macrophages and B-lymphocytes as partners of monocyte expansion in, and mobilization from the spleen. Future studies will help in understanding the mechanisms of monocyte mobilization and its precise roles in atherosclerosis, and whether modulation of the splenic components may become a promising future direction in the prevention and treatment of cardiovascular diseases.

Heterogeneity of peripheral blood monocytes, endothelial dysfunction and subclinical atherosclerosis in patients with systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is characterized by increased cardiovascular morbidity and mortality. SLE patients have increased prevalence of subclinical atherosclerosis, although the mechanisms of this observation remain unclear. Considering the emerging role of monocytes in atherosclerosis, we aimed to investigate the relationship between subclinical atherosclerosis, endothelial dysfunction and the phenotype of peripheral blood monocytes in SLE patients. We characterized the phenotype of monocyte subsets defined by the expression of CD14 and CD16 in 42 patients with SLE and 42 non-SLE controls. Using ultrasonography, intima-media thickness (IMT) of carotid arteries and brachial artery flow-mediated dilation (FMD) as well as nitroglycerin-induced dilation (NMD) were assessed. Patients with SLE had significantly, but only modestly, increased IMT when compared with non-SLE controls (median (25th/75th percentile) 0.65 (0.60/0.71) mm vs 0.60 (0.56/0.68) mm; p < 0.05). Importantly, in spite of early atherosclerotic complications in the studied SLE group, marked endothelial dysfunction was observed. CD14dimCD16+proinflammatory cell subpopulation was positively correlated with IMT in SLE patients. This phenomenon was not observed in control individuals. Interestingly, endothelial dysfunction assessed by FMD was not correlated with any of the studied monocyte subsets. Our observations suggest that CD14dimCD16+monocytes are associated with subclinical atherosclerosis in SLE, although the mechanism appears to be independent of endothelial dysfunction.

Chemokines control mobilization, recruitment, and fate of monocytes in atherosclerosis.

Atherosclerosis is a chronic inflammatory disease of large arteries and, among others, characterized by continuous influx of monocytes into the subendothelial space, subsequent macrophage accumulation, and foam cell formation. Chemokines and their receptors tightly orchestrate monocyte trafficking and fate from birth to death. This brief review summarizes our current understanding of the interplay between monocytes and chemokines entertaining crucial processes in atherosclerosis development, progression, and regression.

A Cytofluorometric Study of Membrane Rafts in Human Monocyte Subsets in Atherosclerosis

The peripheral blood monocytes of atherosclerotic patients are pre-activated and have some of the features of tissue macrophages. Their adhesion to the endothelium is 1.5 times higher than that of monocytes from healthy subjects, and they express a number of receptors and antigens typical of tissue macrophages. Additionally, earlier we showed that the biosynthesis of gangliosides, whose main function is the formation of membrane rafts, is significantly activated in blood monocytes from atherosclerotic patients, as well as during the in vitro differentiation of normal monocytes into macrophages. In this study, we investigated the expression of membrane rafts on various monocyte subsets from healthy subjects and atherosclerotic patients. Based on flow cytometry results, the monocytes in the examined atherosclerotic patients were found to differ from those in healthy subjects by a twofold increase in the proportion of the intermediate subset (CD14(++)/CD16(+)) and by enhancement in the expression of the fractalkine receptor CX3CR1 on the intermediate and non-classical subsets (CD14(++)/CD16(+) and CD14(+)/CD16(++)) (2.3 and 1.8 times, respectively). This suggests a pre-activated state of monocytes in atherosclerotic patients. At the same time, the expression of the membrane raft marker on the monocyte subsets was similar in both studied groups. However, a study of the in vitro differentiation of monocytes into macrophages showed that the membrane raft expression increased 2 times as early as on the 1st day of culturing and 3 times on the 7th day compared to that in freshly isolated monocytes. Therefore, it is suggested that monocytes in atherosclerosis accumulate gangliosides that are used to form membrane rafts during the macrophage differentiation after the migration of monocytes into the arterial intima.

Activated platelets promote increased monocyte expression of CXCR5 through prostaglandin E2-related mechanisms and enhance the anti-inflammatory effects of CXCL13

BackgroundWe have previously shown that the homeostatic chemokine CXCL13 is up-regulated in monocytes in atherosclerosis, mediating anti-apoptotic and anti-inflammatory effects. ObjectiveTo investigate the regulation of CXCL13s receptor, CXCR5. Methods/patientsIn vitro studies in THP-1 and primary monocytes and studies of CXCR5 expression in thrombus material obtained at the site of plaque rupture during myocardial infarction (MI). ResultsOur major findings were: (i) toll-like receptor agonists and particularly β-adrenergic receptor activation and releasate from thrombin-activated platelets increased CXCR5 mRNA levels in monocytes. (ii) The platelet-mediated induction of CXCR5 involved prostaglandin E2/cAMP/protein kinase A-dependent as well as RANTES-dependent pathways with NFκB activation as a potential common down-stream mediator. (iii) Releasate from thrombin-activated platelets augmented the anti-inflammatory effects of CXCL13 in monocytes at least partly by enhancing the effects of CXCL13 on CXCR5 expression. (iv) We found strong immunostaining of CXCR5 in thrombus material obtained at the site of plaque rupture in patients with ST elevation MI (STEMI) and in unstable carotid lesions, co-localized with platelets. ConclusionOur findings suggest that platelet-mediated signaling through CXCR5 may be active in vivo during plaque destabilization, potentially representing a counteracting mechanism to inflammation.

165 SCAVENGER RECEPTORS MEDIATE UPTAKE OF MODIFIED LDL BY CIRCULATING BLOOD MONOCYTE SUBSETS: CONSEQUENCES FOR ATHEROSCLEROSIS.

A major risk factor for cardiovascular disease (CVD) is elevated LDL-cholesterol, which can undergo oxidative modification (mLDL). Experimental models show that mLDL in atherosclerotic prone vascular beds leads to increased...

Monocytes in atherosclerosis: subsets and functions

Chronic inflammation drives atherosclerosis, the leading cause of cardiovascular disease. Over the past two decades, data have emerged showing that immune cells are involved in the pathogenesis of atherosclerotic plaques. The accumulation and continued recruitment of leukocytes are associated with the development of 'vulnerable' plaques. These plaques are prone to rupture, leading to thrombosis, myocardial infarction or stroke, all of which are frequent causes of death. Plaque macrophages account for the majority of leukocytes in plaques, and are believed to differentiate from monocytes recruited from circulating blood. However, monocytes represent a heterogenous circulating population of cells. Experiments are needed to address whether monocyte recruitment to plaques and effector functions, such as the formation of foam cells, the production of nitric oxide and reactive oxygen species, and proteolysis are critical for the development and rupture of plaques, and thus for the pathophysiology of atherosclerosis, as well as elucidate the precise mechanisms involved.

Understanding the Essential Role of Monocytes in Atherosclerosis

Understanding the Essential Role of Monocytes in Atherosclerosis

The fate of monocytes in atherosclerosis.

Monocytes are the primary inflammatory cell type that infiltrates early atherosclerotic plaques. Their recruitment into plaques drives disease progression. Disease interventions that target monocytes could act at several points: alteration in the phenotype of circulating monocyte subpopulations; reduced recruitment of monocytes into plaques; alterations in the survival of monocyte-derived cells in atherosclerosis; and promotion of migratory egress from plaques to bring about resolution of the plaque inflammatory response. All of these points of intervention will be briefly discussed in this article.

The fate of monocytes in atherosclerosis

The fate of monocytes in atherosclerosis

Mo-W12:7 The opposing roles of monocytes in atherosclerosis

Mo-W12:7 The opposing roles of monocytes in atherosclerosis

Hematein Inhibits Tumor Necrotic Factor-α-Induced Vascular Cell Adhesion Molecule-1 and NF-κB-Dependent Gene Expression in Human Vascular Endothelial Cells

Monocyte adhesion to the endothelium via adhesion molecules is one of the earliest events in atherogenesis. It has been suggested that vascular cell adhesion molecule-1 (VCAM-1) plays a very important role in the recruitment of monocytes in atherosclerosis. The aim of our study was to evaluate whether hematein can influence the expression of VCAM-1 and the transcription of nuclear factor-κB (NF-κB)-dependent genes. Immunohistochemistry revealed that mouse aortic artery endothelial cells express VCAM-1 after feeding a high cholesterol diet for 8 weeks. Hematein dose dependently suppressed TNF-α-induced VCAM-1 in both surface (30.8%) and soluble protein (65%) production in HUVECs. The transcription level of VCAM-1 was measured by Northern blot analysis, and decreased VCAM-1 protein expression was associated with a reduction of VCAM-1 mRNA expression. Transient transfection study of NF-κB promoter construct and electrophoretic mobility shift assay suggested that hematein inhibited both NF-κB-dependent gene expression and NF-κB activation induced by TNF-α. Our results suggest that the down-regulation of VCAM-1 expression by hematein may in part be due to the inhibition of NF-κB-dependent gene expression.

Selective inhibition by probucol of vascular cell adhesion molecule-1 (VCAM-1) expression in human vascular endothelial cells

An early event in atherogenesis is the adhesion of monocytes to endothelium via adhesion molecules, such as VCAM-1 and intracellular adhesion molecule-1 (ICAM-1). It has been suggested that VCAM-1 plays a very important role in the recruitment of monocytes in atherosclerosis. Probucol is a potent inhibitor of atherosclerosis in animal models. However, the mechanism of its antiatherogenic effect is poorly understood. The aim of our study was to evaluate whether probucol can influence the expression of endothelial cell adhesion molecules and endothelial adhesiveness. The study was performed on cultured human umbilical vein endothelial cells (HUVEC). HUVEC were pretreated with probucol (50 μM) at different time periods before stimulation with TNFα (100 U ml −1) or IL-1β (100 U ml −1). The protein expression of VCAM-1 and ICAM-1 was measured by flow cytometry. VCAM-1 mRNA expression was measured by reverse transcription polymerase chain reaction (RT PCR). Probucol time dependently reduced agonist-induced VCAM-1 (≈45%, 48 h) surface protein and mRNA expression (≈40%, 48 h) in HUVEC, but not ICAM-1 surface protein expression. Decreased VCAM-1 expression was associated with reduction (≈40%) of adherence between cytokine-stimulated HUVEC and peripheral blood mononuclear leukocytes (PBMC). Our results suggest that the antiatherogenic effect of probucol may, in part, be due to a downregulation of VCAM-1 expression.