Gene Profiling in Atherosclerosis Reveals a Key Role for Small Inducible Cytokines

Exploratory Study of Differentially Expressed Genes of Peripheral Blood Monocytes in Patients with Carotid Atherosclerosis

BACKGROUND

The abundance of circulating monocytes is closely associated with the development of atherosclerosis in humans.

OBJECTIVE

This study aimed to further research into diagnostic biomarkers and targeted treatment of carotid atherosclerosis (CAS).

METHODS

We performed transcriptomics analysis through weighted gene co-expression network analysis (WGCNA) of monocytes from patients in public databases with and without CAS. Differentially expressed genes (DEGs) were screened by R package limma. Diagnostic molecules were derived by the least absolute shrinkage and selection operator (LASSO) and support vector machine recursive feature elimination (SVM-RFE) algorithms. NetworkAnalyst, miRWalk, and Star- Base databases assisted in the construction of diagnostic molecule regulatory networks. The Drug- Bank database predicted drugs targeting the diagnostic molecules. RT-PCR tested expression profiles.

RESULTS

From 14,369 hub genes and 61 DEGs, six differentially expressed monocyte-related hub genes were significantly associated with immune cells, immune responses, monocytes, and lipid metabolism. LASSO and SVM-RFE yielded five genes for CAS prediction. RT-PCR of these genes showed HMGB1 was upregulated, and CCL3, CCL3L1, CCL4, and DUSP1 were downregulated in CAS versus controls. Then, we constructed and visualized the regulatory networks of 9 transcription factors (TFs), which significantly related to 5 diagnostic molecules. About 11 miRNAs, 19 lncRNAs, and 39 edges centered on four diagnostic molecules (CCL3, CCL4, DUSP1, and HMGB1) were constructed and displayed. Eleven potential drugs were identified, including ibrutinib, CTI-01, roflumilast etc. Conclusion: A set of five biomarkers were identified for the diagnosis of CAS and for the study of potential therapeutic targets.

Mural cell-derived chemokines provide a protective niche to safeguard vascular macrophages and limit chronic inflammation

Maladaptive, non-resolving inflammation contributes to chronic inflammatory diseases such as atherosclerosis. Because macrophages remove necrotic cells, defective macrophage programs can promote chronic inflammation with persistent tissue injury. Here, we investigated the mechanisms sustaining vascular macrophages. Intravital imaging revealed a spatiotemporal macrophage niche across vascular beds alongside mural cells (MCs)-pericytes and smooth muscle cells. Single-cell transcriptomics, co-culture, and genetic deletion experiments revealed MC-derived expression of the chemokines CCL2 and MIF, which actively preserved macrophage survival and their homeostatic functions. In atherosclerosis, this positioned macrophages in viable plaque areas, away from the necrotic core, and maintained a homeostatic macrophage phenotype. Disruption of this MC-macrophage unit via MC-specific deletion of these chemokines triggered detrimental macrophage relocalizing, exacerbated plaque necrosis, inflammation, and atheroprogression. In line, CCL2 inhibition at advanced stages of atherosclerosis showed detrimental effects. This work presents a MC-driven safeguard toward maintaining the homeostatic vascular macrophage niche.

In Vitro Anti-Inflammatory and Vasculoprotective Effects of Red Cell Extract from the Black Sea Urchin Arbacia lixula

Sea urchins have emerged as an important source of bioactive compounds with anti-inflammatory and antioxidant properties relevant to human health. Since inflammation is a crucial pathogenic process in the development and progression of atherosclerosis, we here assessed the potential anti-inflammatory and vasculoprotective effects of coelomic red-cell methanolic extract of the black sea urchin Arbacia lixula in an in vitro model of endothelial cell dysfunction. Human microvascular endothelial cells (HMEC-1) were pretreated with A. lixula red-cell extract (10 and 100 μg/mL) before exposure to the pro-inflammatory cytokine tumor necrosis factor (TNF)-α. The extract was non-toxic after 24 h cell treatment and was characterized by antioxidant power and phenol content. The TNF-α-stimulated expression of adhesion molecules (VCAM-1, ICAM-1) and cytokines/chemokines (MCP-1, CCL-5, IL-6, IL-8, M-CSF) was significantly attenuated by A. lixula red-cell extract. This was functionally accompanied by a reduction in monocyte adhesion and chemotaxis towards activated endothelial cells. At the molecular level, the tested extract significantly counteracted the TNF-α-stimulated activation of the pro-inflammatory transcription factor NF-κB. These results provide evidence of potential anti-atherosclerotic properties of A. lixula red-cell extract, and open avenues in the discovery and development of dietary supplements and/or drugs for the prevention or treatment of cardiovascular diseases.

Cathepsin S (CTSS) activity in health and disease - A treasure trove of untapped clinical potential

Amongst the lysosomal cysteine cathepsin family of proteases, cathepsin S (CTSS) holds particular interest due to distinctive properties including a normal restricted expression profile, inducible upregulation and activity at a broad pH range. Consequently, while CTSS is well-established as a member of the proteolytic cocktail within the lysosome, degrading unwanted and damaged proteins, it has increasingly been shown to mediate a number of distinct, more selective roles including antigen processing and antigen presentation, and cleavage of substrates both intra and extracellularly. Increasingly, aberrant CTSS expression has been demonstrated in a variety of conditions and disease states, marking it out as both a biomarker and potential therapeutic target. This review seeks to contextualise CTSS within the cysteine cathepsin family before providing an overview of the broad range of pathologies in which roles for CTSS have been identified. Additionally, current clinical progress towards specific inhibitors is detailed, updating the position of the field in exploiting this most unique of proteases.

Role of the CCL2-CCR2 axis in cardiovascular disease: Pathogenesis and clinical implications

The CCL2-CCR2 axis is one of the major chemokine signaling pathways that has received special attention because of its function in the development and progression of cardiovascular disease. Numerous investigations have been performed over the past decades to explore the function of the CCL2-CCR2 signaling axis in cardiovascular disease. Laboratory data on the CCL2-CCR2 axis for cardiovascular disease have shown satisfactory outcomes, yet its clinical translation remains challenging. In this article, we describe the mechanisms of action of the CCL2-CCR2 axis in the development and evolution of cardiovascular diseases including heart failure, atherosclerosis and coronary atherosclerotic heart disease, hypertension and myocardial disease. Laboratory and clinical data on the use of the CCL2-CCR2 pathway as a targeted therapy for cardiovascular diseases are summarized. The potential of the CCL2-CCR2 axis in the treatment of cardiovascular diseases is explored.

Targeting the CCL2-CCR2 axis for atheroprotection

Decades of research have established atherosclerosis as an inflammatory disease. Only recently though, clinical trials provided proof-of-concept evidence for the efficacy of anti-inflammatory strategies with respect to cardiovascular events, thus offering a new paradigm for lowering residual vascular risk. Efforts to target the inflammasome-interleukin-1β-interleukin-6 pathway have been highly successful, but inter-individual variations in drug response, a lack of reduction in all-cause mortality, and a higher rate of infections also highlight the need for a second generation of anti-inflammatory agents targeting atherosclerosis-specific immune mechanisms while minimizing systemic side effects. CC-motif chemokine ligand 2/monocyte-chemoattractant protein-1 (CCL2/MCP-1) orchestrates inflammatory monocyte trafficking between the bone marrow, circulation, and atherosclerotic plaques by binding to its cognate receptor CCR2. Adding to a strong body of data from experimental atherosclerosis models, a coherent series of recent large-scale genetic and observational epidemiological studies along with data from human atherosclerotic plaques highlight the relevance and therapeutic potential of the CCL2-CCR2 axis in human atherosclerosis. Here, we summarize experimental and human data pinpointing the CCL2-CCR2 pathway as an emerging drug target in cardiovascular disease. Furthermore, we contextualize previous efforts to interfere with this pathway, scrutinize approaches of ligand targeting vs. receptor targeting, and discuss possible pathway-intrinsic opportunities and challenges related to pharmacological targeting of the CCL2-CCR2 axis in human atherosclerotic disease.

Pharmacological Targeting of the CCL2/CCR2 Axis for Atheroprotection: A Meta-Analysis of Preclinical Studies

BACKGROUND

The CCL2 (CC-chemokine ligand 2)/CCR2 (CC-chemokine receptor 2) axis governs monocyte recruitment to atherosclerotic lesions. Genetic and epidemiological studies show strong associations of CCL2 levels with atherosclerotic disease. Still, experimental studies testing pharmacological inhibition of CCL2 or CCR2 in atheroprone mice apply widely different approaches and report variable results, thus halting clinical translation.

METHODS

We systematically searched the literature for studies employing pharmacological CCL2/CCR2 blockade in atheroprone mice and meta-analyzed their effects on lesion size and morphology.

RESULTS

In a meta-analysis of 14 studies testing 11 different agents, CCL2/CCR2 blockade attenuated atherosclerotic lesion size in the aortic root or arch (g=-0.75 [-1.17 to -0.32], P=6×10^-4; N=171/171 mice in experimental/control group), the carotid (g=-2.39 [-4.23 to -0.55], P=0.01; N=24/25), and the femoral artery (g=-2.38 [-3.50 to -1.26], P=3×10^-5; N=10/10). Furthermore, CCL2/CCR2 inhibition reduced intralesional macrophage accumulation and increased smooth muscle cell content and collagen deposition. The effects of CCL2/CCR2 inhibition on lesion size correlated with reductions in plaque macrophage accumulation, in accord with a prominent role of CCL2/CCR2 signaling in monocyte recruitment. Subgroup analyses showed comparable efficacy of different CCL2- and CCR2-inhibitors in reducing lesion size and intralesional macrophages. The quality assessment revealed high risk of detection bias due to lack of blinding during outcome assessment, as well as evidence of attrition and reporting bias.

CONCLUSIONS

Preclinical evidence suggests that pharmacological targeting of CCL2 or CCR2 might lower atherosclerotic lesion burden, but the majority of existing studies suffer major quality issues that highlight the need for additional high-quality research.

Multi-omics approaches for revealing the complexity of cardiovascular disease

The development and progression of cardiovascular disease (CVD) can mainly be attributed to the narrowing of blood vessels caused by atherosclerosis and thrombosis, which induces organ damage that will result in end-organ dysfunction characterized by events such as myocardial infarction or stroke. It is also essential to consider other contributory factors to CVD, including cardiac remodelling caused by cardiomyopathies and co-morbidities with other diseases such as chronic kidney disease. Besides, there is a growing amount of evidence linking the gut microbiota to CVD through several metabolic pathways. Hence, it is of utmost importance to decipher the underlying molecular mechanisms associated with these disease states to elucidate the development and progression of CVD. A wide array of systems biology approaches incorporating multi-omics data have emerged as an invaluable tool in establishing alterations in specific cell types and identifying modifications in signalling events that promote disease development. Here, we review recent studies that apply multi-omics approaches to further understand the underlying causes of CVD and provide possible treatment strategies by identifying novel drug targets and biomarkers. We also discuss very recent advances in gut microbiota research with an emphasis on how diet and microbial composition can impact the development of CVD. Finally, we present various biological network analyses and other independent studies that have been employed for providing mechanistic explanation and developing treatment strategies for end-stage CVD, namely myocardial infarction and stroke.

Monocyte-Chemoattractant Protein-1 Levels in Human Atherosclerotic Lesions Associate With Plaque Vulnerability

[Figure: see text].

Role of myeloid-derived chemokine CCL5/RANTES at an early stage of atherosclerosis

One of the hallmarks of atherosclerosis is ongoing accumulation of macrophages in the artery intima beginning at disease onset. Monocyte recruitment contributes to increasing macrophage abundance at early stages of atherosclerosis. Although the chemokine CCL5 (RANTES) has been studied in atherosclerosis, its role in the recruitment of monocytes to early lesions has not been elucidated. We show that expression of Ccl5 mRNA, as well as other ligands of the CCR5 receptor (Ccl3 and Ccl4), is induced in the aortic intima of Ldlr^-/- mice 3 weeks after the initiation of cholesterol-rich diet (CRD)-induced hypercholesterolemia. En face immunostaining revealed that CCL5 protein expression is also upregulated at 3 weeks of CRD. Blockade of CCR5 significantly reduced monocyte recruitment to 3-week lesions, suggesting that chemokine signaling through CCR5 is critical. However, we observed that Ccl5-deficiency had no effect on early lesion formation and CCL5-blockade did not affect monocyte recruitment in Ldlr^-/- mice. Immunostaining of the lesions in Ldlr^-/- mice and reciprocal bone marrow transplantation (BMT) of Ccl5^+/+ and Ccl5^-/- mice revealed that CCL5 is expressed by both myeloid and endothelial cells. BMT experiments were carried out to determine if CCL5 produced by distinct cells has functions that may be concealed in Ccl5^-/-Ldlr^-/- mice. We found that hematopoietic cell-derived CCL5 regulates monocyte recruitment and the abundance of intimal macrophages in 3-week lesions of Ldlr^-/- mice but plays a minor role in 6-week lesions. Our findings suggest that there is a short window in early lesion formation during which myeloid cell-derived CCL5 has a critical role in monocyte recruitment and macrophage abundance.

Promoting plaque stability by gene silencing of monocyte chemotactic protein-3 or overexpression of tissue factor pathway inhibitor in ApoE-/- mice

Chemokines may promote the formation and instability of atherosclerotic plaque, which is the most common cause of acute coronary syndrome. The aim of this study was to clarify the function of monocyte chemotactic protein-3 (MCP-3) in the stability of atherosclerotic plaque, to determine the role of tissue factor pathway inhibitor (TFPI) on the development and stability of atherosclerotic plaques, and to further elucidate the anti-atherosclerotic mechanism of TFPI with the emphasis on chemokine MCP-3. We constructed an adenovirus-mediated shRNA against mouse MCP-3 (Ad-MCP-3-shRNA) and an adenovirus-containing TFPI (Ad-TFPI), and tranferred them in a model of vulnerable plaque in ApoE-/- mice respectively. Here, we reported that MCP-3-shRNA and TFPI could both reduce the plaque area and decrease the content of lipids and macrophages, on the contrary, the fibrous cap thickness and content of collagen and smooth muscle cells were increased. In addition, the expression of MCP-3 and CC chemokine receptor 2 (CCR2) was decreased by TFPI transfer. These data provide the first in vivo evidence that MCP-3 is a major contributor to the unstability of atherosclerotic plaque and TFPI may exert its anti-atherosclerotic effects and promote stabilisation of plaque at least partly through inhibiting MCP-3/CCR2 pathway, which may be a new therapeutic method for atherosclerosis.

Circulating Monocyte Chemoattractant Protein-1 and Risk of Stroke: Meta-Analysis of Population-Based Studies Involving 17 180 Individuals

Rationale: Proinflammatory cytokines have been identified as potential targets for lowering vascular risk. Experimental evidence and Mendelian randomization suggest a role of MCP-1 (monocyte chemoattractant protein-1) in atherosclerosis and stroke. However, data from large-scale observational studies are lacking. Objective: To determine whether circulating levels of MCP-1 are associated with risk of incident stroke in the general population. Methods and Results: We used previously unpublished data on 17 180 stroke-free individuals (mean age, 56.7±8.1 years; 48.8% men) from 6 population-based prospective cohort studies and explored associations between baseline circulating MCP-1 levels and risk of any stroke, ischemic stroke, and hemorrhagic stroke during a mean follow-up interval of 16.3 years (280 522 person-years at risk; 1435 incident stroke events). We applied Cox proportional-hazards models and pooled hazard ratios (HRs) using random-effects meta-analyses. After adjustments for age, sex, race, and vascular risk factors, higher MCP-1 levels were associated with increased risk of any stroke (HR per 1-SD increment in ln-transformed MCP-1, 1.07; 95% CI, 1.01-1.14). Focusing on stroke subtypes, we found a significant association between baseline MCP-1 levels and higher risk of ischemic stroke (HR, 1.11 [1.02-1.21]) but not hemorrhagic stroke (HR, 1.02 [0.82-1.29]). The results followed a dose-response pattern with a higher risk of ischemic stroke among individuals in the upper quartiles of MCP-1 levels as compared with the first quartile (HRs, second quartile: 1.19 [1.00-1.42]; third quartile: 1.35 [1.14-1.59]; fourth quartile: 1.38 [1.07-1.77]). There was no indication for heterogeneity across studies, and in a subsample of 4 studies (12 516 individuals), the risk estimates were stable after additional adjustments for circulating levels of IL (interleukin)-6 and high-sensitivity CRP (C-reactive protein). Conclusions: Higher circulating levels of MCP-1 are associated with increased long-term risk of stroke. Our findings along with genetic and experimental evidence suggest that MCP-1 signaling might represent a therapeutic target to lower stroke risk.Visual Overview: An online visual overview is available for this article.

Inhibitors of DAG metabolism suppress CCR2 signalling in human monocytes

BACKGROUND AND PURPOSE

CCL2 is an inflammatory chemokine that stimulates the recruitment of monocytes into tissue via activation of the GPCR CCR2.

EXPERIMENTAL APPROACH

Freshly isolated human monocytes and THP-1 cells were used. Fura-2 loaded cells were used to measure intracellular Ca²⁺ responses. Transwell migration to measure chemotaxis. siRNA-mediated gene knock-down was used to support pharmacological approaches.

KEY RESULTS

CCL2 evoked intracellular Ca²⁺ signals and stimulated migration in THP-1 monocytic cells and human CD14⁺ monocytes in a CCR2-dependent fashion. Attenuation of DAG catabolism in monocytes by inhibiting DAG kinase (R59949) or DAG lipase (RHC80267) activity suppressed CCL2-evoked Ca²⁺ signalling and transwell migration in monocytes. These effects were not due to a reduction in the number of cell surface CCR2. The effect of inhibiting DAG kinase or DAG lipase could be mimicked by addition of the DAG analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG) but was not rescued by application of exogenous phosphatidylinositol 4,5-bisphosphate. Suppressive effects of R59949, RHC80267, and OAG were partially or fully reversed by Gö6983 (pan PKC isoenzyme inhibitor) but not by Gö6976 (PKCα and PKCβ inhibitor). RNAi-mediated knock-down of DAG kinase α isoenzyme modulated CCL2-evoked Ca²⁺ responses in THP-1 cells.

CONCLUSIONS AND IMPLICATIONS

Taken together, these data suggest that DAG production resulting from CCR2 activation is metabolised by both DAG kinase and DAG lipase pathways in monocytes and that pharmacological inhibition of DAG catabolism or application suppresses signalling on the CCL2-CCR2 axis via a mechanism dependent upon a PKC isoenzyme that is sensitive to Gö6983 but not Gö6976.

Accelerated atherosclerosis development in C57Bl6 mice by overexpressing AAV-mediated PCSK9 and partial carotid ligation

Studying the role of a particular gene in atherosclerosis typically requires a time-consuming and often difficult process of generating double knockouts or transgenics on ApoE^-/- or LDL receptor (LDLR)^-/- background. Recently, it was reported that adeno-associated-virus-8 (AAV8)-mediated overexpression of PCSK9 (AAV8-PCSK9) rapidly induced hyperlipidemia. However, using this method in C57BL6 wild-type (C57) mice, it took ~3 months to develop atherosclerosis. Our partial carotid ligation model is used to rapidly develop atherosclerosis by inducing disturbed flow in the left common carotid artery within 2 weeks in ApoE^-/- or LDLR^-/- mice. Here, we combined these two approaches to develop an accelerated model of atherosclerosis in C57 mice. C57 mice were injected with AAV9-PCSK9 or AAV9-luciferase (control) and high-fat diet was initiated. A week later, partial ligation was performed. Compared to the control, AAV-PCSK9 led to elevated serum PCSK9, hypercholesterolemia, and rapid atherosclerosis development within 3 weeks as determined by gross plaque imaging, and staining with Oil-Red-O, Movat's pentachrome, and CD45 antibody. These plaque lesions were comparable to the atherosclerotic lesions that have been previously observed in ApoE^-/- or LDLR^-/- mice that were subjected to partial carotid ligation and high-fat diet. Next, we tested whether our method can be utilized to rapidly determine the role of a particular gene in atherosclerosis. Using eNOS^-/- and NOX1^-/y mice on C57 background, we found that the eNOS^-/- mice developed more advanced lesions, while the NOX1^-/y mice developed less atherosclerotic lesions as compared to the C57 controls. These results are consistent with the previous findings using double knockouts (eNOS^-/-_ApoE^-/- and NOX1^-/y_ApoE^-/-). AAV9-PCSK9 injection followed by partial carotid ligation is an effective and time-saving approach to rapidly induce atherosclerosis. This accelerated model is well-suited to quickly determine the role of gene(s) interest without generating double or triple knockouts.

Crossroads between peripheral atherosclerosis, western-type diet and skeletal muscle pathophysiology: emphasis on apolipoprotein E deficiency and peripheral arterial disease

Atherosclerosis is a chronic inflammatory process that, in the presence of hyperlipidaemia, promotes the formation of atheromatous plaques in large vessels of the cardiovascular system. It also affects peripheral arteries with major implications for a number of other non-vascular tissues such as the skeletal muscle, the liver and the kidney. The aim of this review is to critically discuss and assimilate current knowledge on the impact of peripheral atherosclerosis and its implications on skeletal muscle homeostasis. Accumulating data suggests that manifestations of peripheral atherosclerosis in skeletal muscle originates in a combination of increased i)-oxidative stress, ii)-inflammation, iii)-mitochondrial deficits, iv)-altered myofibre morphology and fibrosis, v)-chronic ischemia followed by impaired oxygen supply, vi)-reduced capillary density, vii)- proteolysis and viii)-apoptosis. These structural, biochemical and pathophysiological alterations impact on skeletal muscle metabolic and physiologic homeostasis and its capacity to generate force, which further affects the individual's quality of life. Particular emphasis is given on two major areas representing basic and applied science respectively: a)-the abundant evidence from a well-recognised atherogenic model; the Apolipoprotein E deficient mouse and the role of a western-type diet and b)-on skeletal myopathy and oxidative stress-induced myofibre damage from human studies on peripheral arterial disease. A significant source of reactive oxygen species production and oxidative stress in cardiovascular disease is the family of NADPH oxidases that contribute to several pathologies. Finally, strategies targeting NADPH oxidases in skeletal muscle in an attempt to attenuate cellular oxidative stress are highlighted, providing a better understanding of the crossroads between peripheral atherosclerosis and skeletal muscle pathophysiology.

Preclinical evaluation of a novel polyphosphazene surface modified stent

BACKGROUND

Treatment options for patients with coronary artery disease at high risk for bleeding complications are limited. The aim of the current preclinical study was to evaluate neointimal coverage, endothelial recovery, inflammation and thrombogenicity in a novel thin-strut (71μm thickness) Cobalt Chromium (CoCr) stent modified with a nano-thin Polyzene®-F (PzF) surface coating.

METHODS AND RESULTS

Twenty-eight single PzF nano-coated stents and 20 bare metal control stents (BMS) were implanted in the coronary arteries of 24 pigs, with scheduled 5- (n=5), 28- (n=13), and 90-day (n=6) follow-up in addition to overlapping configuration (n=6 each), examined at 28-days. Histomorphometric analysis showed significantly lower neointimal thickness in PzF nano-coated stents than BMS controls at both 28- and 90-days (p=0.023 and 0.005) and reduced inflammation (p=0.06 and 0.13). Endothelial coverage over luminal surfaces at all time points was similar between nano-coated stents and BMS controls. We conducted supplementary in-vitro experiments using human monocytes and an ex-vivo swine carotid-jugular arterio-venous shunt model to better understand the healing properties afforded by the PzF nano-coating. Overall, the PzF-nano-coating showed reduced monocyte adhesion and thrombus formation compared to the un-coated controls.

CONCLUSIONS

Stents modified with a nano-thin PzF-coating implanted in healthy swine indicate favorable vascular healing properties shown by reduced neointimal hyperplasia and inflammation, along with resistance to thrombus formation in an ex-vivo shunt model over unmodified stents.

Transcriptional Profiling of Foam Cells Reveals Induction of Guanylate-Binding Proteins Following Western Diet Acceleration of Atherosclerosis in the Absence of Global Changes in Inflammation

Background

Foam cells are central to two major pathogenic processes in atherogenesis: cholesterol buildup in arteries and inflammation. The main underlying cause of cholesterol deposition in arteries is hypercholesterolemia. This study aimed to assess, in vivo, whether elevated plasma cholesterol also alters the inflammatory balance of foam cells.

Methods and Results

Apolipoprotein E–deficient mice were fed regular mouse chow through the study or were switched to a Western‐type diet (WD) 2 or 14 weeks before death. Consecutive sections of the aortic sinus were used for lesion quantification or to isolate RNA from foam cells by laser‐capture microdissection (LCM) for microarray and quantitative polymerase chain reaction analyses. WD feeding for 2 or 14 weeks significantly increased plasma cholesterol, but the size of atherosclerotic lesions increased only in the 14‐week WD group. Expression of more genes was affected in foam cells of mice under prolonged hypercholesterolemia than in mice fed WD for 2 weeks. However, most transcripts coding for inflammatory mediators remained unchanged in both WD groups. Among the main players in inflammatory or immune responses, chemokine (C‐X‐C motif) ligand 13 was induced in foam cells of mice under WD for 2 weeks. The interferon‐inducible GTPases, guanylate‐binding proteins (GBP)3 and GBP6, were induced in the 14‐week WD group, and other GBP family members were moderately increased.

Conclusions

Our results indicate that acceleration of atherosclerosis by hypercholesterolemia is not linked to global changes in the inflammatory balance of foam cells. However, induction of GBPs uncovers a novel family of immune modulators with a potential role in atherogenesis.

Critical role of the C5a-activated neutrophils in high-fat diet-induced vascular inflammation

Exceed and chronic high-fat diet (HFD) contributes to the diagnosis and development of atherosclerosis, obesity, and metabolic syndrome. However, the key molecular component(s) triggered by HFD responsible for initiating vascular inflammation remain unknown. We observed that feeding HFD for 4 weeks is sufficient to induce leukocyte recruitment in the femoral artery of wild-type mice. Neutrophil- and monocyte-depletion analyses confirmed the preferential recruitment of neutrophils in these mice. Protein analysis of sera from HFD-fed mice revealed a marked elevation of complement component C5a levels. Exogenous C5a alone induced leukocyte recruitment, which was abolished by a C5a-receptor antagonist. We also examined the role of neutrophil-derived MCP-1 in accumulation of leukocytes in the artery. These results demonstrated a previously unrecognized role for C5a and neutrophils in the early onset of HFD-induced vascular inflammation. Further study may help in elucidating a novel regulatory pathway to control diet-induced inflammation such as that in case of atherosclerosis.

Relationship of Genetic Polymorphisms of the Chemokine, CCL5, and Its Receptor, CCR5, with Coronary Artery Disease in Taiwan

The chemokine receptor CCR5 polymorphism, which confers resistance to HIV infection, has been associated with reduced risk of cardiovascular disease. However, the association of the chemokine, CCL5, and its receptor, CCR5, polymorphism and coronary artery disease (CAD) in the Taiwanese has not been studied. In this study, 483 subjects who received elective coronary angiography were recruited from Chung Shan Medical University Hospital. CCL5-403 and CCR5-59029 were determined by polymerase chain reaction-restriction fragment length polymorphism. We found that CCL5-403 with TT genotype frequencies was significantly associated with the risk of CAD group (odds ratio = 3.063 and p = 0.012). Moreover, the frequencies of CCR5-59029 with GG or GA genotype were higher than AA genotype in acute coronary syndrome individuals (odds ratio = 1.853, CI = 1.176–2.921, p = 0.008). In conclusion, we found that CCL5-403 polymorphism may increase genetic susceptibility of CAD. CCL5-403 or CCR5-59029 single nucleotide polymorphism may include genotype score and it may predict cardiovascular event.

High MIP-1β Levels in Plasma Predict Long-Term Immunological Nonresponse to Suppressive Antiretroviral Therapy in HIV Infection

BACKGROUND

HIV-infected patients who fail to reconstitute their CD4 T-cell counts during suppressive antiretroviral therapy (ART) have increased risk of both AIDS-related and non-AIDS-related morbidity and mortality. Improved understanding of immunological nonresponse (INR) is necessary to enable earlier clinical intervention.

METHODS

In a cohort of 112 HIV-infected patients starting ART, we performed a serial analysis of 32 plasma-soluble markers, assessed by multiplex cytokine and enzyme immunoassay. Samples were drawn pre-ART and during the first 3 years of treatment, with a final observation time of 8.4 years (interquartile range, 7.0-10.7 years) on ART. Long-term INR (LT-INR) was defined as failure to reach a CD4 T-cell count >350 cells per microliter. Marker stability was evaluated by parallel analysis of samples from ART-naïve and HIV-seronegative controls.

RESULTS

Baseline CD4 T-cell counts predicted subsequent LT-INR (n = 15) [odds ratio, 1.10 (95% confidence interval: 1.01 to 1.19) pr. 10 cells/μL reduction in CD4 count, P = 0.030] in the cohort as a whole, but not in patients with baseline CD4 counts <200 cells per microliter (n = 78). LT-INR was best characterized by elevated plasma levels of the CC chemokine macrophage inflammatory protein 1β (MIP-1β), both at baseline (pre-ART) and during ART. In patients with baseline CD4 counts <200 cells per microliter, baseline MIP-1β predicted LT-INR [odds ratio 1.23 (95% confidence interval: 1.02 to 1.47) per 10 pg/mL increase in MIP-1β, P = 0.029].

CONCLUSIONS

Elevated pre-ART levels of MIP-1β identified LT-INR patients who started ART at CD4 counts <200. INR was characterized by persistently high MIP-1β during suppressive ART. Thus, MIP-1β may be of use for early identification of LT-INR.

Inflammation in coronary artery disease

Coronary artery disease (CAD) is the leading cause of death in the United States. Although CAD was formerly considered a lipid accumulation-mediated disease, it has now been clearly shown to involve an ongoing inflammatory response. Advances in basic science research have established the crucial role of inflammation in mediating all stages of CAD. Today, there is convincing evidence that multiple interrelated immune mechanisms interact with metabolic risk factors to initiate, promote, and ultimately activate lesions in the coronary arteries. This review aims to provide current evidence pertaining to the role of inflammation in the pathogenesis of CAD and discusses the impact of inflammatory markers and their modification on clinical outcomes.

Chemokines as effector and target molecules in vascular biology

Chemokines are key mediators of inflammation. In pathological tissues, the main roles of chemokines are to regulate leucocyte accumulation through the activation of oriented cell migration and the activation of limited programs of gene transcription. Through these activities, chemokines exert many crucial functions, including the regulation of angiogenesis. The 'chemokine system' is tightly regulated at several levels, such as the post-transcriptional processing of ligands, the regulation of the expression and function of the receptors and through the expression of molecules known as 'atypical chemokine receptors', proteins that function as chemokine scavenging and presenting molecules. Several experimental evidence obtained in vitro, in animal models and in human studies, has defined a crucial role of chemokines in cardiovascular diseases. An intense area of research is currently exploring the possibility to develop new effective therapeutic strategies through the identification of chemokine receptor antagonists.

Activation of an innate immune receptor, Nod1, accelerates atherogenesis in Apoe-/- mice

Atherosclerosis is essentially a vascular inflammatory process in the presence of an excess amount of lipid. We have recently reported that oral administration of a nucleotide-binding oligomerization domain (Nod)-1 ligand, FK565, induced vascular inflammation in vivo. No studies, however, have proven the association between Nod1 and atherosclerosis in vivo. To investigate a potential role of NOD1 in atherogenesis, we orally administered FK565 to apolipoprotein E knockout (Apoe(-/-)) mice for 4 wk intermittently and performed quantification of atherosclerotic lesions in aortic roots and aortas, immunohistochemical analyses, and microarray-based gene expression profiling of aortic roots. FK565 administration accelerated the development of atherosclerosis in Apoe(-/-) mice, and the effect was dependent on Nod1 in non-bone marrow origin cells by bone marrow transplantation experiments. Immunohistochemical studies revealed the increases in the accumulation of macrophages and CD3 T cells within the plaques in aortic roots. Gene expression analyses of aortic roots demonstrated a marked upregulation of the Ccl5 gene during early stage of atherogenesis, and the treatment with Ccl5 antagonist significantly inhibited the acceleration of atherosclerosis in FK565-administered Apoe(-/-) mice. Additionally, as compared with Apoe(-/-) mice, Apoe and Nod1 double-knockout mice showed reduced development of atherosclerotic lesions from the early stage as well as their delayed progression and a significant reduction in Ccl5 mRNA levels at 9 wk of age. Data in the present study show that the Nod1 signaling pathway in non-bone marrow-derived cells contributes to the development of atherosclerosis.

Implementation strategies of Systems Medicine in clinical research and home care for cardiovascular disease patients

Insights from the "-omics" science have recently emphasized the need to implement an overall strategy in medical research. Here, the development of Systems Medicine has been indicated as a potential tool for clinical translation of basic research discoveries. Systems Medicine also gives the opportunity of improving different steps in medical practice, from diagnosis to healthcare management, including clinical research. The development of Systems Medicine is still hampered however by several challenges, the main one being the development of computational tools adequate to record, analyze and share a large amount of disparate data. In addition, available informatics tools appear not yet fully suitable for the challenge because they are not standardized, not universally available, or with ethical/legal concerns. Cardiovascular diseases (CVD) are a very promising area for translating Systems Medicine into clinical practice. By developing clinically applied technologies, the collection and analysis of data may improve CV risk stratification and prediction. Standardized models for data recording and analysis can also greatly broaden data exchange, thus promoting a uniform management of CVD patients also useful for clinical research. This advance however requires a great organizational effort by both physicians and health institutions, as well as the overcoming of ethical problems. This narrative review aims at providing an update on the state-of-art knowledge in the area of Systems Medicine as applied to CVD, focusing on current critical issues, providing a road map for its practical implementation.

P2Y₆ receptor inhibition perturbs CCL2-evoked signalling in human monocytic and peripheral blood mononuclear cells

The chemokine CCL2 serves to target circulating monocytes and other leukocytes to tissue during innate immune responses, and modulates the progression of chronic inflammatory disease through activation of the receptor CCR2. Here, we show that co-activation of the P2Y₆ purinergic receptor (encoded by P2RY₆) occurs when THP-1 cells and human peripheral blood mononuclear cells sense CCL2 through CCR2. Furthermore, P2Y₆ receptor activation accounts for ∼80% of the intracellular Ca²⁺ signal evoked by CCL2. Scavenging extracellular nucleotides with apyrase caused a fourfold reduction in THP-1 sensitivity to CCL2, whereas inhibition of CD39-like ectonucleotidases potentiated CCL2-evoked Ca²⁺ responses. Pharmacological inhibition of P2Y₆ impaired CCL2-evoked Ca²⁺ signalling and chemotaxis in peripheral blood mononuclear cells and THP-1 cells. Furthermore, stable P2Y₆ receptor knockdown (of twofold) in THP-1 cells impaired CCL2-evoked Ca²⁺ signalling, chemotaxis and adhesion to TNFα-treated HUVECs. We demonstrate that THP-1 cells rapidly secrete ATP during signalling downstream of the CCL2-CCR2 axis and suggest this might act as a mechanism for P2Y₆ receptor co-activation following CCL2 activation of the CCR2 receptor. The discovery that P2Y₆ receptor mediates leukocyte responsiveness to CCL2 represents a new mechanism by which to modulate CCL2 signals.

Effects of estradiol on transcriptional profiles in atherosclerotic iliac arteries in ovariectomized cynomolgus macaques

OBJECTIVE

This study aimed to assess the in vivo effects of estradiol treatment on arterial gene expression in atherosclerotic postmenopausal female monkeys.

METHODS

Eight ovariectomized cynomolgus monkeys were fed atherogenic diets for 6.5 years. The left iliac artery was biopsied before randomization to the estradiol group (human equivalent dose of 1 mg/d, n = 4) or the vehicle group (n = 4) for 8 months. The right iliac artery was obtained at necropsy. Transcriptional profiles in pretreatment versus posttreatment iliac arteries were compared to assess the responses of atherosclerotic arteries to estradiol.

RESULTS

Iliac artery plaque size did not differ between the estradiol group and the placebo group at baseline or during the treatment period. Nevertheless, estradiol treatment was associated with increased expression of 106 genes and decreased expression of 26 genes in the iliac arteries. Estradiol treatment increased the expression of extracellular matrix genes, including the α1 chain of type I collagen, the α2 chain of type VI collagen, and fibulin 2, suggestive of an increase in the proportion or phenotype of smooth muscles or fibroblasts in lesions. Also increased were components of the insulin-like growth factor pathway (insulin-like growth factor 1, insulin-like growth factor binding protein 4, and insulin-like growth factor binding protein 5) and the Wnt signaling pathway (secreted frizzled-related protein 2, secreted frizzled-related protein 4, low-density lipoprotein receptor-related protein 6, and Wnt1-inducible signaling pathway protein 2).

CONCLUSIONS

Estradiol treatment of monkeys with established atherosclerosis affected iliac artery gene expression, suggesting changes in the cellular composition of lesions. Moreover, it is probable that the presence of atherosclerotic plaque affected the gene expression responses of arteries to estrogen.

Effects of equol on gene expression in female cynomolgus monkey iliac arteries

BACKGROUND AND AIMS

To examine effects of equol, the soy phytoestrogen metabolite, on gene expression in the monkey iliac artery.

METHODS AND RESULTS

A high fat/high cholesterol diet was fed to eight ovariectomized cynomolgus monkeys for 6.5 years. After biopsy of the left iliac artery, the animals were randomized to two treatment groups for 8 months; the treatment groups were equol (23.7 mg/100 g diet, n = 4) and vehicle (n = 4). The right iliac artery was removed at necropsy. Gene expression in the iliac arteries in response to equol was determined by DNA microarray. Comparison of atherosclerotic lesions and plasma lipids at pre-versus post-equol treatment time points and in vehicle versus equol treatment groups did not identify any significant differences. Despite the lack of effect of equol on these parameters, 59 genes were down-regulated and 279 were up-regulated in response to equol. Comparison of these data to previous work identified 10 genes regulated in opposite directions by equol compared to presence of atherosclerosis plaque (Menopause 2011; 18:1087-1095) and 55 genes differentially expressed in the same direction in response to both equol and estradiol (Eyster et al., Menopause 2014;21:143-152.).

CONCLUSIONS

Similar responses of genes to both equol and estradiol may reflect the extent to which equol serves as a natural selective estrogen receptor modulator in the arteries. Opposite responses of 10 genes to equol versus the presence of atherosclerosis implicates those genes in the potential protective effects of equol in arteries.

Affinity improvement of a therapeutic antibody by structure-based computational design: generation of electrostatic interactions in the transition state stabilizes the antibody-antigen complex

The optimization of antibodies is a desirable goal towards the development of better therapeutic strategies. The antibody 11K2 was previously developed as a therapeutic tool for inflammatory diseases, and displays very high affinity (4.6 pM) for its antigen the chemokine MCP-1 (monocyte chemo-attractant protein-1). We have employed a virtual library of mutations of 11K2 to identify antibody variants of potentially higher affinity, and to establish benchmarks in the engineering of a mature therapeutic antibody. The most promising candidates identified in the virtual screening were examined by surface plasmon resonance to validate the computational predictions, and to characterize their binding affinity and key thermodynamic properties in detail. Only mutations in the light-chain of the antibody are effective at enhancing its affinity for the antigen in vitro, suggesting that the interaction surface of the heavy-chain (dominated by the hot-spot residue Phe101) is not amenable to optimization. The single-mutation with the highest affinity is L-N31R (4.6-fold higher affinity than wild-type antibody). Importantly, all the single-mutations showing increase affinity incorporate a charged residue (Arg, Asp, or Glu). The characterization of the relevant thermodynamic parameters clarifies the energetic mechanism. Essentially, the formation of new electrostatic interactions early in the binding reaction coordinate (transition state or earlier) benefits the durability of the antibody-antigen complex. The combination of in silico calculations and thermodynamic analysis is an effective strategy to improve the affinity of a matured therapeutic antibody.

Pharmacogenomics in the development and characterization of atheroprotective drugs

Atherosclerosis is the main cause of cardiovascular disease (CVD) and can lead to stroke, myocardial infarction, and death. The clinically available atheroprotective drugs aim mainly at reducing the levels of circulating low-density lipoprotein (LDL), increasing high-density lipoprotein (HDL), and attenuating inflammation. However, the cardiovascular risk remains high, along with morbidity, mortality, and incidence of adverse drug events. Pharmacogenomics is increasingly contributing towards the characterization of existing atheroprotective drugs, the evaluation of novel ones, and the identification of promising, unexplored therapeutic targets, at the global molecular pathway level. This chapter presents highlights of pharmacogenomics investigations and discoveries that have contributed towards the elucidation of pharmacological atheroprotection, while opening the way to new therapeutic approaches.

Increased circulating CC chemokine levels in the metabolic syndrome are reduced by low-dose atorvastatin treatment: evidence from a randomized controlled trial

OBJECTIVE

Central obesity and insulin resistance are key components of the metabolic syndrome, which is associated with an increased risk of cardiovascular disease. In obesity, CC chemokines, such as monocyte chemotactic protein-1 (MCP-1), macrophage inhibitory protein-1β (MIP-1β) and eotaxin-1 and their respective receptors, are critically involved in peripheral monocyte activation and adipose tissue infiltration. The aim of the current study was to examine whether low-dose atorvastatin (10 mg/d) treatment modulated serum levels of CC chemokines in metabolic syndrome subjects.

MATERIALS AND METHODS

Serum levels of MCP-1, eotaxin-1, MIP-1β, C reactive protein (CRP) and interleukin-6 (IL-6) were measured in lean control and metabolic syndrome subjects at baseline, and following a 6-week randomized placebo-controlled clinical trial of atorvastatin (10 mg/d). Peripheral CD14(+) monocytes were isolated and mRNA levels of MCP-1, MIP-1 β and CCR5 determined.

RESULTS

Serum MCP-1 (P = 0·02), eotaxin-1 (P = 0·02) and MIP-1β (P = 0·03), CRP (P < 0·001) and IL-6 (P = 0·006) were significantly increased in metabolic syndrome in comparison with lean controls. Furthermore, CD14(+) peripheral monocyte mRNA expression of the chemokine receptor, CCR5, of which MIP-1β and eotaxin-1 are ligands, was increased two-fold in the metabolic syndrome group (P = 0·03). In addition to the expected improvements in lipid profile, atorvastatin treatment significantly reduced circulating eotaxin-1 (P < 0·05), MIP-1β (P < 0·05) levels and CD14(+) peripheral monocyte CCR5 mRNA expression (P = 0·02).

CONCLUSION

These results support a model whereby atorvastatin treatment, by inhibiting CD14(+) monocyte CCR5 expression, may inhibit monocyte trafficking, reduce chronic inflammation and, thus, lower circulating levels of CC chemokines.

CC chemokine receptors and chronic inflammation--therapeutic opportunities and pharmacological challenges

Chemokines are a family of low molecular weight proteins with an essential role in leukocyte trafficking during both homeostasis and inflammation. The CC class of chemokines consists of at least 28 members (CCL1-28) that signal through 10 known chemokine receptors (CCR1-10). CC chemokine receptors are expressed predominantly by T cells and monocyte-macrophages, cell types associated predominantly with chronic inflammation occurring over weeks or years. Chronic inflammatory diseases including rheumatoid arthritis, atherosclerosis, and metabolic syndrome are characterized by continued leukocyte infiltration into the inflammatory site, driven in large part by excessive chemokine production. Over years or decades, persistent inflammation may lead to loss of tissue architecture and function, causing severe disability or, in the case of atherosclerosis, fatal outcomes such as myocardial infarction or stroke. Despite the existence of several clinical strategies for targeting chronic inflammation, these diseases remain significant causes of morbidity and mortality globally, with a concomitant economic impact. Thus, the development of novel therapeutic agents for the treatment of chronic inflammatory disease continues to be a priority. In this review we introduce CC chemokine receptors as critical mediators of chronic inflammatory responses and explore their potential role as pharmacological targets. We discuss functions of individual CC chemokine receptors based on in vitro pharmacological data as well as transgenic animal studies. Focusing on three key forms of chronic inflammation--rheumatoid arthritis, atherosclerosis, and metabolic syndrome--we describe the pathologic function of CC chemokine receptors and their possible relevance as therapeutic targets.

Regulation of atherogenesis by chemokines and chemokine receptors

Atherosclerosis is a chronic inflammatory and metabolic disorder affecting large- and medium-sized arteries, and the leading cause of mortality worldwide. The pathogenesis of atherosclerosis involves accumulation of lipids and leukocytes in the intima of blood vessel walls creating plaque. How leukocytes accumulate in plaque remains poorly understood; however, chemokines acting at specific G protein-coupled receptors appear to be important. Studies using knockout mice suggest that chemokine receptor signaling may either promote or inhibit atherogenesis, depending on the receptor. These proof of concept studies have spurred efforts to develop drugs targeting the chemokine system in atherosclerosis, and several have shown beneficial effects in animal models. This study will review key discoveries in basic and translational research in this area.

Inflammatory serum proteome pattern in mice fed a high-fat diet

To investigate the influence of diet on serum protein pattern, mice were fed for 8 weeks either control chow or a high-fat diet (containing 21 % w/w milk fat and 0.2 % w/w cholesterol); sera were collected and analyzed by 2-DE. The main positive acute-phase reactant proteins, haptoglobin and hemopexin, were significantly up-regulated in animals receiving the high-fat diet. Data on all other proteins also pointed to an inflammatory condition in these animals. The largest change in concentration was observed for carboxylesterase N, a circulating enzyme seldom connected with lipid metabolism in earlier reports. These observations agree with the notion of a link between diet-induced hyperlipidemia and the inflammatory component of its cardiovascular sequels in humans, but the effects in the experimental animals are massive and obviously affect most of the major serum proteins.

Ribosomal protein L17, RpL17, is an inhibitor of vascular smooth muscle growth and carotid intima formation

BACKGROUND

Carotid intima-media thickening is associated with increased cardiovascular risk in humans. We discovered that intima formation and cell proliferation in response to carotid injury is greater in SJL/J (SJL) in comparison with C3HeB/FeJ (C3H/F) mice. The purpose of this study was to identify candidate genes contributing to intima formation.

METHODS AND RESULTS

We performed microarray and bioinformatic analyses of carotid arteries from C3H/F and SJL mice. Kyoto Encyclopedia of Genes and Genomes analysis showed that the ribosome pathway was significantly up-regulated in C3H/F in comparison with SJL mice. Expression of a ribosomal protein, RpL17, was >40-fold higher in C3H/F carotids in comparison with SJL. Aortic vascular smooth muscle cells from C3H/F grew slower in comparison to SJL. To determine the role of RpL17 in vascular smooth muscle cell growth regulation, we analyzed the relationship between RpL17 expression and cell cycle progression. Cultured vascular smooth muscle cells from mice, rats, and humans showed that RpL17 expression inversely correlated with growth as shown by decreased cells in S phase and increased cells in G(0)/G(1). To prove that RpL17 acted as a growth inhibitor in vivo, we used pluronic gel delivery of RpL17 small interfering RNA to C3H/F carotid arteries. This resulted in an 8-fold increase in the number of proliferating cells. Furthermore, following partial carotid ligation in SJL mice, RpL17 expression in the intima and media decreased, but the number of proliferating cells increased.

CONCLUSIONS

RpL17 acts as a vascular smooth muscle cell growth inhibitor (akin to a tumor suppressor) and represents a potential therapeutic target to limit carotid intima-media thickening.

Novel Therapy for Atherosclerosis Using Recombinant Immunotoxin Against Folate Receptor β-Expressing Macrophages

Background

Folate receptor β (FRβ) is induced during macrophage activation. A recombinant immunotoxin consisting of the truncated Pseudomonas exotoxin A (PE38) conjugated to an anti-FRβ antibody (anti–FRβ-PE38) has been reported to kill activated macrophages in inflammatory diseases. To elucidate the effect of an immunotoxin targeting FRβ on atherosclerosis, we determined the presence of FRβ-expressing macrophages in atherosclerotic lesions and administered the FRβ immunotoxin in apolipoprotein E–deficient mice.

Methods and Results

The FRβ-expressing macrophages were observed in atherosclerotic lesions of apolipoprotein E–deficient mice. At 15 or 35 weeks of age, the apolipoprotein E–deficient mice were divided into 3 groups and were intravenously administered 0.1 mg/kg of anti–FRβ-PE38 (immunotoxin group), 0.1 mg/kg of PE38 (toxin group), or 0.1 mL of saline (control group) every 3 days, for a total of 5 times for each age group. The mice were analyzed at 21 or 41 weeks of age. Treatment with the immunotoxin resulted in 31% and 22% reductions in atherosclerotic lesions of the 21- and 41-week-old mice, respectively (P<0.05). Administration of immunotoxin reduced the numbers of FRβ- and tumor necrosis factor-α–expressing macrophages, reduced cell proliferation, and increased the number of apoptotic cells (P<0.05). Real-time polymerase chain reaction demonstrated that the expression of FRβ and tumor necrosis factor-α mRNA was significantly decreased in the immunotoxin group (P<0.05).

Conclusions

These results suggest that FRβ-expressing macrophages exist in the atherosclerotic lesions of apolipoprotein E–deficient mice and that FRβ immunotoxin administration reduces the progression of atherosclerotic lesions in younger and older individuals. The recombinant FRβ immunotoxin targeting activated macrophages could provide a novel therapeutic tool for atherosclerosis. (J Am Heart Assoc. 2012;1:e003079 doi: 10.1161/JAHA.112.003079.)

Structural basis for high selectivity of anti-CCL2 neutralizing antibody CNTO 888

Human CC chemokine ligand 2 (CCL2), also known as monocyte chemoattractant protein-1 (MCP-1), is a member of the β chemokine family whose actions are mediated through the G-protein-coupled receptor CCR2. Binding of CCL2 to its receptor CCR2 triggers calcium mobilization and chemotaxis. CCL2 is implicated in the pathogenesis of certain inflammatory diseases and cancer. CNTO 888, a neutralizing human anti-CCL2 antibody, was derived by antibody phage display. The antibody binds human CCL2 with high affinity (K(D)=22 pM) and inhibits CCL2 binding to its receptor. The crystal structure of the CNTO 888 Fab alone and in complex with the monomeric form of CCL2 (P8A variant) was determined at 2.6 Å and 2.8 Å resolution, respectively. CNTO 888 recognizes a conformational epitope encompassing residues 18-24 and 45-51 that overlaps the mapped receptor binding site. The epitope of CNTO 888 does not overlap with the dimerization site of CCL2, and thus its inhibitory activity is not expected to result from interference with the oligomeric state of CCL2. Comparison of the X-ray-determined epitopes of CNTO 888 and another CCL2-neutralizing antibody, 11K2, provides insight into the molecular basis of antibody selectivity and functional inhibition.

Gene expression signatures differ with extent of atherosclerosis in monkey iliac artery

OBJECTIVE

The aim of this study was to evaluate global gene expression patterns in the common iliac arteries of monkeys with a varied extent of atherosclerosis.

METHODS

The left common iliac artery was removed from ovariectomized cynomolgus monkeys (n = 12) after 6.5 years of consuming a diet containing fat and cholesterol at levels comparable with those consumed in Western populations. Arterial gene expression was analyzed using DNA microarray and real-time reverse transcription-polymerase chain reaction.

RESULTS

Significant differential expression of 986 genes was observed in iliac arteries containing moderate to large atherosclerotic plaques compared with normal/minimally affected reference group arteries. Atherosclerosis-associated genes included cytokines, chemokines, components of signal transduction pathways, and transcriptional activators and repressors, as well as other functional categories. Real-time reverse transcription-polymerase chain reaction confirmed a differential expression of genes chosen from a variety of functional categories. Specifically, the expression of genes for estrogen receptor-1, claudin 11, and brain heart protocadherin 7 was reduced, whereas the expression of genes for apolipoprotein E, growth differentiation factor 15, superoxide dismutase-2, SET domain bifurcated 2, phospholipase A2 group IIA, phospholipase A2 group VII, and ring finger protein 149 was increased in atherosclerotic arteries.

CONCLUSIONS

The gene expression environment in arteries containing atherosclerotic plaques is profoundly different from that of relatively unaffected arteries and reflects the cellular and molecular complexity of atherosclerosis and associated arterial remodeling processes.

Chemokines: established and novel targets in atherosclerosis

In their role as small chemotactic cytokines, chemokines are crucial mediators and regulators of leukocyte trafficking during immune surveillance and inflammation. Their involvement in the development and progression of inflammatory diseases has been subject of intense investigation. Concordantly, the chemokine system has been explored in search for therapeutic targets to prevent or treat inflammatory disorders, such as atherosclerosis. Targeting the chemokine system offers various entry points for a causative treatment of this widespread and chronic illness. Although this approach has encountered some setbacks, several innovative compounds are currently in an advanced stage of development. In this review, the current standing of this dynamic field is highlighted and the potential advantages and drawbacks of particular strategies are discussed.

Platelets in atherosclerosis

Beyond obvious functions in haemostasis and thrombosis, platelets are considered to be essential in proinflammatory surroundings such as atherosclerosis, allergy, rheumatoid arthritis and even cancer. In atherosclerosis, platelets facilitate the recruitment of inflammatory cells towards the lesion sites and release a plethora of inflammatory mediators, thereby enriching and boosting the inflammatory milieu. Platelets do so by interacting with endothelial cells, circulating leukocytes (monocytes, neutrophils, dendritic cells, T-cells) and progenitor cells. This cross-talk enforces leukocyte activation, adhesion and transmigration. Furthermore, platelets are known to function in innate host defense through the release of antimicrobial peptides and the expression of pattern recognition receptors. In severe sepsis, platelets are able to trigger the formation of neutrophil extracellular traps (NETs), which bind and clear pathogens. The present antiplatelet therapies that target key pathways of platelet activation and aggregation therefore hold the potential to modulate platelet-derived immune functions by reducing cellular interactions of platelets with other immune components and by reducing the secretion of inflammatory proteins into the milieu. The objective of this review is to update and discuss the current perceptions of the platelet immune constituents and their prospect as therapeutic targets in an atherosclerotic setting.

Chemokine receptor CCR5: from AIDS to atherosclerosis

There is increasing recognition of an important contribution of chemokines and their receptors in the pathology of atherosclerosis and related cardiovascular disease. The chemokine receptor CCR5 was initially known for its role as a co-receptor for HIV infection of macrophages and is the target of the recently approved CCR5 antagonist maraviroc. However, evidence is now emerging supporting a role for CCR5 and its ligands CCL3 (MIP-1α), CCL4 (MIP-1β) and CCL5 (RANTES) in the initiation and progression of atherosclerosis. Specifically, the CCR5 deletion polymorphism CCR5delta32, which confers resistance to HIV infection, has been associated with a reduced risk of cardiovascular disease and both CCR5 antagonism and gene deletion reduce atherosclerosis in mouse models of the disease. Antagonism of CCL5 has also been shown to reduce atherosclerotic burden in these animal models. Crucially, CCR5 and its ligands CCL3, CCL4 and CCL5 have been identified in human and mouse vasculature and have been detected in human atherosclerotic plaque. Not unexpectedly, CC chemokines have also been linked to saphenous vein graft disease, which shares similarity to native vessel atherosclerosis. Distinct roles for chemokine-receptor systems in atherogenesis have been proposed, with CCR5 likely to be critical in recruitment of monocytes to developing plaques. With an increased burden of cardiovascular disease observed in HIV-infected individuals, the potential cardiovascular-protective effects of drugs that target the CCR5 receptor warrant greater attention. The availability of clinically validated antagonists such as maraviroc currently provides an advantage for targeting of CCR5 over other chemokine receptors.

A new monocyte chemotactic protein-1/chemokine CC motif ligand-2 competitor limiting neointima formation and myocardial ischemia/reperfusion injury in mice

OBJECTIVES

A nonagonist monocyte chemotactic protein-1 (MCP-1/CCL2) mutant (PA508) with increased affinity for glycosaminoglycans and thus competing with CCL2 was evaluated as a candidate for preventing neointima formation or myocardial ischemia/reperfusion injury.

BACKGROUND

Myocardial infarction (MI) remains a major cause of death worldwide despite improved interventional and therapeutic options. Therefore, the discovery of drugs that limit restenosis after intervention and post-MI damage remains an important challenge.

METHODS

The function of PA508 was assessed in functional assays in vitro and in mouse models of wire-induced neointima formation and experimental MI.

RESULTS

PA508 was functionally inactive in CC chemokine receptor 2 (CCR2) binding and calcium influx but inhibited monocyte chemotaxis or transendothelial migration toward CCL2, suggesting that it interferes with CCL2 presentation. In wild-type but not CCR2-deficient mice, PA508 reduced inflammatory leukocyte recruitment without affecting differential leukocyte counts, CCL2 levels, organ function, or morphology, indicating that it specifically attenuates the CCL2-CCR2 axis. Compared with vehicle, daily intraperitoneal injection of PA508 significantly (p < 0.05, n = 5) reduced neointimal plaque area and mononuclear cell infiltration in carotid arteries of hyperlipidemic apolipoprotein E-deficient mice while increasing smooth muscle cell content. In C57Bl/6J mice that underwent myocardial ischemia/reperfusion, treatment with PA508 significantly reduced infarction size, monocyte infiltration, and collagen and myofibroblast content in the infarction area and preserved heart function compared with vehicle (p < 0.05, n = 4 to 8).

CONCLUSIONS

Here we demonstrate that administration of a rationally designed CCL2 competitor reduced inflammatory monocyte recruitment, limited neointimal hyperplasia, and attenuated myocardial ischemia/reperfusion injury in mice and could therefore be envisioned as a combined therapeutic approach for restenosis and MI.

Chemokines as therapeutic targets for atherosclerotic plaque destabilization and rupture

Chemokines are instrumental in the initiation and progression of atherosclerosis. Recent advances in genomic technologies and the recognition of atherosclerosis as an inflammatory disease have given great impetus to studies addressing the relevance of chemokines for the clinically manifest stages of atherosclerosis and acute cardiovascular syndromes. In this paper, we will review the current status of these studies, highlighting those chemokines that have already been associated with plaque destabilization and rupture. We will recapitulate recent epidemiologic, genomic, histopathological and experimental support for the prominent role of particular chemokines in acute cardiovascular syndromes. Collectively, these data underpin the potential of chemokines as biomarkers and/or therapeutic targets, but also expose the lacunae in our understanding of the precise function of chemokines in the atherosclerosis-related disorders and in the efficacy of chemokine-targeted clinical trials.

Platelet CD40L mediates thrombotic and inflammatory processes in atherosclerosis

CD40 ligand (CD40L), identified as a costimulatory molecule expressed on T cells, is also expressed and functional on platelets. We investigated the thrombotic and inflammatory contributions of platelet CD40L in atherosclerosis. Although CD40L-deficient (Cd40l(-/-)) platelets exhibited impaired platelet aggregation and thrombus stability, the effects of platelet CD40L on inflammatory processes in atherosclerosis were more remarkable. Repeated injections of activated Cd40l(-/-) platelets into Apoe(-/-) mice strongly decreased both platelet and leukocyte adhesion to the endothelium and decreased plasma CCL2 levels compared with wild-type platelets. Moreover, Cd40l(-/-) platelets failed to form proinflammatory platelet-leukocyte aggregates. Expression of CD40L on platelets was required for platelet-induced atherosclerosis as injection of Cd40l(-/-) platelets in contrast to Cd40l(+/+) platelets did not promote lesion formation. Remarkably, injection of Cd40l(+/+), but not Cd40l(-/-), platelets transiently decreased the amount of regulatory T cells (Tregs) in blood and spleen. Depletion of Tregs in mice injected with activated Cd40l(-/-) platelets abrogated the athero-protective effect, indicating that CD40L on platelets mediates the reduction of Tregs leading to accelerated atherosclerosis. We conclude that platelet CD40L plays a pivotal role in atherosclerosis, not only by affecting platelet-platelet interactions but especially by activating leukocytes, thereby increasing platelet-leukocyte and leukocyte-endothelium interactions.