Chemokine receptor 7 knockout attenuates atherosclerotic plaque development

Identification of biomarkers for abdominal aortic aneurysm in Behçet's disease via mendelian randomization and integrated bioinformatics analyses

Behçet's disease (BD) is a complex autoimmune disorder impacting several organ systems. Although the involvement of abdominal aortic aneurysm (AAA) in BD is rare, it can be associated with severe consequences. In the present study, we identified diagnostic biomarkers in patients with BD having AAA. Mendelian randomization (MR) analysis was initially used to explore the potential causal association between BD and AAA. The Limma package, WGCNA, PPI and machine learning algorithms were employed to identify potential diagnostic genes. A receiver operating characteristic curve (ROC) for the nomogram was constructed to ascertain the diagnostic value of AAA in patients with BD. Finally, immune cell infiltration analyses and single-sample gene set enrichment analysis (ssGSEA) were conducted. The MR analysis indicated a suggestive association between BD and the risk of AAA (odds ratio [OR]: 1.0384, 95% confidence interval [CI]: 1.0081-1.0696, p = 0.0126). Three hub genes (CD247, CD2 and CCR7) were identified using the integrated bioinformatics analyses, which were subsequently utilised to construct a nomogram (area under the curve [AUC]: 0.982, 95% CI: 0.944-1.000). Finally, the immune cell infiltration assay revealed that dysregulation immune cells were positively correlated with the three hub genes. Our MR analyses revealed a higher susceptibility of patients with BD to AAA. We used a systematic approach to identify three potential hub genes (CD247, CD2 and CCR7) and developed a nomogram to assist in the diagnosis of AAA among patients with BD. In addition, immune cell infiltration analysis indicated the dysregulation in immune cell proportions.

Macrophage Anti-inflammatory Behaviour in a Multiphase Model of Atherosclerotic Plaque Development

Atherosclerosis is an inflammatory disease characterised by the formation of plaques, which are deposits of lipids and cholesterol-laden macrophages that form in the artery wall. The inflammation is often non-resolving, due in large part to changes in normal macrophage anti-inflammatory behaviour that are induced by the toxic plaque microenvironment. These changes include higher death rates, defective efferocytic uptake of dead cells, and reduced rates of emigration. We develop a free boundary multiphase model for early atherosclerotic plaques, and we use it to investigate the effects of impaired macrophage anti-inflammatory behaviour on plaque structure and growth. We find that high rates of cell death relative to efferocytic uptake results in a plaque populated mostly by dead cells. We also find that emigration can potentially slow or halt plaque growth by allowing material to exit the plaque, but this is contingent on the availability of live macrophage foam cells in the deep plaque. Finally, we introduce an additional bead species to model macrophage tagging via microspheres, and we use the extended model to explore how high rates of cell death and low rates of efferocytosis and emigration prevent the clearance of macrophages from the plaque.

Plasma levels of CCL21, but not CCL19, independently predict future coronary events in a prospective population-based cohort

BACKGROUND AND AIMS

The homeostatic chemokines CCL21 and CCL19 have been explored as biomarkers in cardiovascular disease prediction in patients with established cardiovascular disease, but associations between these chemokines and first-time coronary event incidence have not been investigated before. Here, we explored associations between CCL21 or CCL19 and first-time incident coronary events in the general population-based Malmö Diet and Cancer cohort with two decades of follow-up.

METHODS

CCL21 and CCL19 levels in plasma were analysed with ELISA and proximity extension assay and associations with disease incidence were explored with conditional logistic regression in a nested case-control cohort (CCL21; n = 676) and with Cox regression in a population-based cohort (CCL19; n = 4636).

RESULTS

High CCL21 levels in plasma were associated with incident first-time coronary events independently of traditional risk factors (odds ratio of 2.64 with 95% confidence interval 1.62-4.31, p < 0.001, comparing the highest versus the lowest tertile of CCL21), whereas CCL19 was not. CCL19 was, however, associated with incident heart failure, as well as increased all-cause, cardiovascular and cancer mortality independently of age and sex.

CONCLUSIONS

Even though CCL21 and CCL19 both signal through CCR7, these chemokines may not be interchangeable as disease predictors and CCL21 could be used for prediction of future coronary events in individuals without any previous coronary heart disease history.

The Amino Acid Homoarginine Inhibits Atherogenesis by Modulating T-Cell Function

BACKGROUND

Amino acid metabolism is crucial for inflammatory processes during atherogenesis. The endogenous amino acid homoarginine is a robust biomarker for cardiovascular outcome and mortality with high levels being protective. However, the underlying mechanisms remain elusive. We investigated the effect of homoarginine supplementation on atherosclerotic plaque development with a particular focus on inflammation.

METHODS

Female ApoE-deficient mice were supplemented with homoarginine (14 mg/L) in drinking water starting 2 weeks before and continuing throughout a 6-week period of Western-type diet feeding. Control mice received normal drinking water. Immunohistochemistry and flow cytometry were used for plaque- and immunological phenotyping. T cells were characterized using mass spectrometry-based proteomics, by functional in vitro approaches, for example, proliferation and migration/chemotaxis assays as well as by super-resolution microscopy.

RESULTS

Homoarginine supplementation led to a 2-fold increase in circulating homoarginine concentrations. Homoarginine-treated mice exhibited reduced atherosclerosis in the aortic root and brachiocephalic trunk. A substantial decrease in CD3⁺ T cells in the atherosclerotic lesions suggested a T-cell-related effect of homoarginine supplementation, which was mainly attributed to CD4⁺ T cells. Macrophages, dendritic cells, and B cells were not affected. CD4⁺ T-cell proteomics and subsequent pathway analysis together with in vitro studies demonstrated that homoarginine profoundly modulated the spatial organization of the T-cell actin cytoskeleton and increased filopodia formation via inhibition of Myh9 (myosin heavy chain 9). Further mechanistic studies revealed an inhibition of T-cell proliferation as well as a striking impairment of the migratory capacities of T cells in response to relevant chemokines by homoarginine, all of which likely contribute to its atheroprotective effects.

CONCLUSIONS

Our study unravels a novel mechanism by which the amino acid homoarginine reduces atherosclerosis, establishing that homoarginine modulates the T-cell cytoskeleton and thereby mitigates T-cell functions important during atherogenesis. These findings provide a molecular explanation for the beneficial effects of homoarginine in atherosclerotic cardiovascular disease.

Targeting the chemokine network in atherosclerosis

Chemokines and their receptors represent a potential target for immunotherapy in chronic inflammation. They comprise a large family of cytokines with chemotactic activity, and their cognate receptors are expressed on all cells of the body. This network dictates leukocyte recruitment and activation, angiogenesis, cell proliferation and maturation. Dysregulation of chemokine and chemokine receptor expression as well as function participates in many pathologies including cancer, autoimmune diseases and chronic inflammation. In atherosclerosis, a lipid-driven chronic inflammation of middle-sized and large arteries, chemokines and their receptors participates in almost all stages of the disease from initiation of fatty streaks to mature atherosclerotic plaque formation. Atherosclerosis and its complications are the main driver of mortality and morbidity in cardiovascular diseases (CVD). Hence, exploring new fields of therapeutic targeting of atherosclerosis is of key importance. This review gives an overview of the recent advances on the role of key chemokines and chemokine receptors in atherosclerosis, addresses chemokine-based biomarkers at biochemical, imaging and genetic level in human studies, and highlights the clinial trials targeting atherosclerosis.

Gene Expression Analysis Suggests Immunological Changes of Peripheral Blood Monocytes in the Progression of Patients With Coronary Artery Disease

Objectives

To analyze the gene expression profile of peripheral blood monocytes in different stages of coronary artery disease (CAD) by transcriptome sequencing, and to explore potential genes and pathway involved in CAD pathogenesis.

Methods

According to the screening of coronary angiography and quality control of blood samples, eight intermediate coronary lesion patients were selected, then eight patients with acute myocardial infarction, and eight patients with normal coronary angiography were matched by age and gender. Transcriptomics sequencing was conducted for the peripheral blood monocytes of these 24 samples by using the Illumina HiSeq high-throughput platform. Then, differentially expressed genes (DEGs) were analyzed. Gene Ontology (GO) functional annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation, and protein-protein interaction (PPI) network were applied to annotate the potential functions of DEGs.

Results

Compared with the normal coronary angiography group, we identified a total of 169 DEGs in the intermediate coronary lesion group, which were significantly enriched in 59 GO terms and 17 KEGG pathways. Compared with the normal coronary angiography group, we found a total of 2,028 DEGs, which were significantly enriched in 311 GO terms and 20 KEGG pathways in the acute myocardial infarction group. The cross-comparison between normal versus intermediate coronary lesion group, and normal versus acute myocardial infarction group included 98 differential genes with 65 up regulated and 33 down regulated genes, which were significantly enriched in 46 GO terms and 10 KEGG pathways. During the progression of CAD, there was a significant up-regulated expression of CSF3, IL-1A, CCR7, and IL-18, and down-regulated expression of MAPK14. Besides GO items such as inflammatory response was significantly enriched, KEGG analysis showed the most remarkable enrichments in IL-17 signaling pathway and cytokine-cytokine receptor interactions.

Conclusions

Transcriptomics profiles vary in patients with different severity of CAD. CSF3, IL-1A, CCR7, IL-18, and MAPK14, as well as IL-17 signaling pathway and cytokine and cytokine receptor interaction signaling pathway related with inflammatory response might be the potential biomarker and targets for the treatment of coronary artery disease.

Inflammatory Cell Recruitment in Cardiovascular Disease

Atherosclerosis, the main underlying pathology for myocardial infarction and stroke, is a chronic inflammatory disease of middle-sized to large arteries that is initiated and maintained by leukocytes infiltrating into the subendothelial space. It is now clear that the accumulation of pro-inflammatory leukocytes drives progression of atherosclerosis, its clinical complications, and directly modulates tissue-healing in the infarcted heart after myocardial infarction. This inflammatory response is orchestrated by multiple soluble mediators that enhance inflammation systemically and locally, as well as by a multitude of partially tissue-specific molecules that regulate homing, adhesion, and transmigration of leukocytes. While numerous experimental studies in the mouse have refined our understanding of leukocyte accumulation from a conceptual perspective, only a few anti-leukocyte therapies have been directly validated in humans. Lack of tissue-tropism of targeted factors required for leukocyte accumulation and unspecific inhibition strategies remain the major challenges to ultimately translate therapies that modulate leukocytes accumulation into clinical practice. Here, we carefully describe receptor and ligand pairs that guide leukocyte accumulation into the atherosclerotic plaque and the infarcted myocardium, and comment on potential future medical therapies.

Inflammatory Chemokines in Atherosclerosis

Atherosclerosis is a long-term, chronic inflammatory disease of the vessel wall leading to the formation of occlusive or rupture-prone lesions in large arteries. Complications of atherosclerosis can become severe and lead to cardiovascular diseases (CVD) with lethal consequences. During the last three decades, chemokines and their receptors earned great attention in the research of atherosclerosis as they play a key role in development and progression of atherosclerotic lesions. They orchestrate activation, recruitment, and infiltration of immune cells and subsequent phenotypic changes, e.g., increased uptake of oxidized low-density lipoprotein (oxLDL) by macrophages, promoting the development of foam cells, a key feature developing plaques. In addition, chemokines and their receptors maintain homing of adaptive immune cells but also drive pro-atherosclerotic leukocyte responses. Recently, specific targeting, e.g., by applying cell specific knock out models have shed new light on their functions in chronic vascular inflammation. This article reviews recent findings on the role of immunomodulatory chemokines in the development of atherosclerosis and their potential for targeting.

Local M-CSF (Macrophage Colony-Stimulating Factor) Expression Regulates Macrophage Proliferation and Apoptosis in Atherosclerosis

OBJECTIVE

Previous studies have shown that deficiency of M-CSF (macrophage colony-stimulating factor; or CSF1 [colony stimulating factor 1]) dramatically reduces atherosclerosis in hyperlipidemic mice. We characterize the underlying mechanism and investigate the relevant sources of CSF1 in lesions. Approach and Results: We quantitatively assessed the effects of CSF1 deficiency on macrophage proliferation and apoptosis in atherosclerotic lesions. Staining of aortic lesions with markers of proliferation, Ki-67 and bromodeoxyuridine, revealed around 40% reduction in CSF1 heterozygous (Csf1+/-) as compared with WT (wild type; Csf1+/+) mice. Similarly, staining with a marker of apoptosis, activated caspase-3, revealed a 3-fold increase in apoptotic cells in Csf1+/- mice. Next, we determined the cellular sources of CSF1 contributing to lesion development. Cell-specific deletions of Csf1 in smooth muscle cells using SM22α-Cre (smooth muscle protein 22-alpha-Cre) reduced lesions by about 40%, and in endothelial cells, deletions with Cdh5-Cre (VE-cadherin-Cre) reduced lesions by about 30%. Macrophage-specific deletion with LysM-Cre (lysozyme M-Cre), on the other hand, did not significantly reduce lesions size. Transplantation of Csf1 null (Csf1-/-) mice bone marrow into Csf1+/+ mice reduced lesions by about 35%, suggesting that CSF1 from hematopoietic cells other than macrophages contributes to atherosclerosis. None of the cell-specific knockouts affected circulating CSF1 levels, and only the smooth muscle cell deletions had any effect on the percentage monocytes in the circulation. Also, Csf1+/- mice did not exhibit significant differences in Ly6Chigh/Ly6Clow monocytes as compared with Csf1+/+.

CONCLUSIONS

CSF1 contributes to both macrophage proliferation and survival in lesions. Local CSF1 production by smooth muscle cell and endothelial cell rather than circulating CSF1 is the primary driver of macrophage expansion in atherosclerosis.

T cell subsets and functions in atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall and the primary underlying cause of cardiovascular disease. Data from in vivo imaging, cell-lineage tracing and knockout studies in mice, as well as clinical interventional studies and advanced mRNA sequencing techniques, have drawn attention to the role of T cells as critical drivers and modifiers of the pathogenesis of atherosclerosis. CD4+ T cells are commonly found in atherosclerotic plaques. A large body of evidence indicates that T helper 1 (TH1) cells have pro-atherogenic roles and regulatory T (Treg) cells have anti-atherogenic roles. However, Treg cells can become pro-atherogenic. The roles in atherosclerosis of other TH cell subsets such as TH2, TH9, TH17, TH22, follicular helper T cells and CD28null T cells, as well as other T cell subsets including CD8+ T cells and γδ T cells, are less well understood. Moreover, some T cells seem to have both pro-atherogenic and anti-atherogenic functions. In this Review, we summarize the knowledge on T cell subsets, their functions in atherosclerosis and the process of T cell homing to atherosclerotic plaques. Much of our understanding of the roles of T cells in atherosclerosis is based on findings from experimental models. Translating these findings into human disease is challenging but much needed. T cells and their specific cytokines are attractive targets for developing new preventive and therapeutic approaches including potential T cell-related therapies for atherosclerosis.

Homeostatic Chemokines and Prognosis in Patients With Acute Coronary Syndromes

BACKGROUND

The chemokines CCL19 and CCL21 are up-regulated in atherosclerotic disease and heart failure, and increased circulating levels are found in unstable versus stable coronary artery disease.

OBJECTIVES

The purpose of this study was to evaluate the prognostic value of CCL19 and CCL21 in acute coronary syndrome (ACS).

METHODS

CCL19 and CCL21 levels were analyzed in serum obtained from ACS patients (n = 1,146) on the first morning after hospital admission. Adjustments were made for GRACE (Global Registry of Acute Coronary Events) score, left ventricular ejection fraction, pro-B-type natriuretic peptide, troponin I, and C-reactive protein levels.

RESULTS

The major findings were: 1) those having fourth quartile levels of CCL21 on admission of ACS had a significantly higher long-term (median 98 months) risk of major adverse cardiovascular events (MACE) and myocardial infarction in fully adjusted multivariable models; 2) high CCL21 levels at admission were also independently associated with MACE and cardiovascular mortality during short-time (3 months) follow-up; and 3) high CCL19 levels at admission were associated with the development of heart failure.

CONCLUSIONS

CCL21 levels are independently associated with outcome after ACS and should be further investigated as a promising biomarker in these patients.

Deletion of Ppard in CD11c+ cells attenuates atherosclerosis in ApoE knockout mice

Ppardδ, one of the lipid-activated nuclear receptor expressed in many cell types to activate gene transcription, also regulates cellular functions other than lipid metabolism. The mechanism regulating the function of antigen-presenting cells during the development of atherosclerosis is not fully understood. Here we aimed to study the involvement of PPARδ in CD11c⁺ cells in atherosclerosis. We used the Cre-loxP approach to make conditional deletion of Ppard in CD11c⁺ cells in mice on Apoe^-/- background, which were fed with high cholesterol diet to develop atherosclerosis. Ppard deficiency in CD11c⁺ cells attenuated atherosclerotic plaque formation and infiltration of myeloid-derived dendritic cells (DCs) and T lymphocytes. Reduced lesion was accompanied by reduced activation of dendritic cells, and also a reduction of activation and differentiation of T cells to Th1 cells. In addition, DC migration to lymph node was also attenuated with Ppard deletion. In bone marrow-derived DCs, Ppard deficiency reduced palmitic acid-induced upregulation of co-stimulatory molecules and pro-inflammatory cytokine IL12 and TNFα. Our results indicated PPARδ activation by fatty acid resulted in the activation of myeloid DCs and subsequent polarization of T lymphocytes, which contributed to atherosclerosis in Apoe^-/- mice. These findings also reveal the potential regulatory role of PPARδ in antigen presentation to orchestrate the immune responses during atherosclerosis.

Lymphatic Migration of Immune Cells

Lymphatic vessels collect interstitial fluid that has extravasated from blood vessels and return it to the circulatory system. Another important function of the lymphatic network is to facilitate immune cell migration and antigen transport from the periphery to draining lymph nodes. This migration plays a crucial role in immune surveillance, initiation of immune responses and tolerance. Here we discuss the significance and mechanisms of lymphatic migration of innate and adaptive immune cells in homeostasis, inflammation and cancer.

Semaphorins and Their Receptors: From Axonal Guidance to Atherosclerosis

Semaphorins are a large family of secreted, transmembrane, or GPI-anchored proteins initially identified as axon guidance cues signaling through their receptors, neuropilins, and plexins. Emerging evidence suggests that beyond the guidance, they also function in a broad spectrum of pathophysiological conditions, including atherosclerosis, a vascular inflammatory disease. Particular semaphorin members have been demonstrated to participate in atherosclerosis via eliciting endothelial dysfunction, leukocyte infiltration, monocyte-macrophage retention, platelet hyperreactivity, and neovascularization. In this review, we focus on the role of those semaphorin family members in the development of atherosclerosis and highlight the mechanistic relevance of semaphorins to atherogenesis.

Lysosome signaling controls the migration of dendritic cells

Dendritic cells (DCs) patrol their environment by linking antigen acquisition by macropinocytosis to cell locomotion. DC activation upon bacterial sensing inhibits macropinocytosis and increases DC migration, thus promoting the arrival of DCs to lymph nodes for antigen presentation to T cells. The signaling events that trigger such changes are not fully understood. We show that lysosome signaling plays a critical role in this process. Upon bacterial sensing, lysosomal calcium is released by the ionic channel TRPML1 (transient receptor potential cation channel, mucolipin subfamily, member 1), which activates the actin-based motor protein myosin II at the cell rear, promoting fast and directional migration. Lysosomal calcium further induces the activation of the transcription factor EB (TFEB), which translocates to the nucleus to maintain TRPML1 expression. We found that the TRPML1-TFEB axis results from the down-regulation of macropinocytosis after bacterial sensing by DCs. Lysosomal signaling therefore emerges as a hitherto unexpected link between macropinocytosis, actomyosin cytoskeleton organization, and DC migration.

Liver X Receptor Nuclear Receptors Are Transcriptional Regulators of Dendritic Cell Chemotaxis

The liver X receptors (LXRs) are ligand-activated nuclear receptors with established roles in the maintenance of lipid homeostasis in multiple tissues. LXRs exert additional biological functions as negative regulators of inflammation, particularly in macrophages. However, the transcriptional responses controlled by LXRs in other myeloid cells, such as dendritic cells (DCs), are still poorly understood. Here we used gain- and loss-of-function models to characterize the impact of LXR deficiency on DC activation programs. Our results identified an LXR-dependent pathway that is important for DC chemotaxis. LXR-deficient mature DCs are defective in stimulus-induced migration in vitro and in vivo Mechanistically, we show that LXRs facilitate DC chemotactic signaling by regulating the expression of CD38, an ectoenzyme important for leukocyte trafficking. Pharmacological or genetic inactivation of CD38 activity abolished the LXR-dependent induction of DC chemotaxis. Using the low-density lipoprotein receptor-deficient (LDLR^-/-) LDLR^-/- mouse model of atherosclerosis, we also demonstrated that hematopoietic CD38 expression is important for the accumulation of lipid-laden myeloid cells in lesions, suggesting that CD38 is a key factor in leukocyte migration during atherogenesis. Collectively, our results demonstrate that LXRs are required for the efficient emigration of DCs in response to chemotactic signals during inflammation.

Dendritic cells in atherosclerosis: Functions in immune regulation and beyond

Chronic inflammation drives the development of atherosclerosis. Dendritic cells (DCs) are known as central mediators of adaptive immune responses and the development of immunological memory and tolerance. DCs are present in non-diseased arteries, and accumulate within atherosclerotic lesions where they can be localised in close vicinity to T cells. Recent work has revealed important functions of DCs in regulating immune mechanisms in atherogenesis, and vaccination strategies using DCs have been explored for treatment of disease. However, in line with a phenotypical and functional overlap with plaque macrophages vascular DCs were also identified to engulf lipids, thus contributing to lipid burden in the vessel wall and initiation of lesion growth. Furthermore, a function of DCs in regulating cholesterol homeostasis has been revealed. Finally, phenotypically distinct plasmacytoid dendritic cells (pDCs) have been identified within atherosclerotic lesions. This review will dissect the multifaceted contribution of DCs and pDCs to the initiation and progression of atherosclerosis and the experimental approaches utilising DCs in therapeutic vaccination strategies.

HVC1 ameliorates hyperlipidemia and inflammation in LDLR-/- mice

Background

HVC1 consists of Coptidis Rhizoma (dried rhizome of Coptischinensis), Scutellariae Radix (root of Scutellariabaicalensis), Rhei Rhizoma (rhizome of Rheum officinale), and Pruni Cortex (cortex of Prunusyedoensis Matsum). Although the components are known to be effective in various conditions such as inflammation, hypertension, and hypercholesterolemia, there are no reports of the molecular mechanism of its hypolipidemic effects.

Methods

We investigated the hypolipidemic effect of HVC1 in low-density lipoprotein receptor-deficient (LDLR^−/−) mice fed a high-cholesterol diet for 13 weeks. Mice were randomized in to 6 groups: ND (normal diet) group, HCD (high-cholesterol diet) group, and treatment groups fed HCD and treated with simvastatin (10 mg/kg, p.o.) or HVC1 (10, 50, or 250 mg/kg, p.o.).

Results

HVC1 regulated the levels of total cholesterol, triglyceride (TG), low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol in mouse serum. In addition, it regulated the transcription level of the peroxisome proliferator-activated receptors (PPARs), sterol regulatory element-binding proteins (SREBP)-2, 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, lipoprotein lipase (LPL), apolipoprotein B (apo B), liver X receptor (LXR), and inflammatory cytokines (IL-1β, IL-6, and TNF-α). Furthermore, HVC1 activated 5′ adenosine monophosphate-activated protein kinase (AMPK).

Conclusion

Our results suggest that HVC1 might be effective in preventing high-cholesterol diet-induced hyperlipidemia by regulating the genes involved in cholesterol and lipid metabolism, and inflammatory responses.

CCR7-CCL19/CCL21 Axis is Essential for Effective Arteriogenesis in a Murine Model of Hindlimb Ischemia

Background

In order to identify factors that stimulate arteriogenesis after ischemia, we followed gene expression profiles in two extreme models for collateral artery formation over 28 days after hindlimb ischemia, namely “good‐responding” C57BL/6 mice and “poor‐responding” BALB/c mice.

Methods and Results

Although BALB/c mice show very poor blood flow recovery after ischemia, most known proarteriogenic genes were upregulated more excessively and for a longer period than in C57BL/6 mice. In clear contrast, chemokine genes Ccl19, Ccl21a, and Ccl21c and the chemokine receptor CCR7 were upregulated in C57BL/6 mice 1 day after hindlimb ischemia, but not in BALB/C mice. CCL19 and CCL21 regulate migration and homing of T lymphocytes via CCR7. When subjecting CCR7^−/−/LDLR^−/− mice to hindlimb ischemia, we observed a 20% reduction in blood flow recovery compared with that in LDLR^−/− mice. Equal numbers of α‐smooth muscle actin–positive collateral arteries were found in the adductor muscles of both mouse strains, but collateral diameters were smaller in the CCR7^−/−/LDLR^−/−. Fluorescence‐activated cell sorter analyses showed that numbers of CCR7⁺ T lymphocytes (both CD4⁺ and CD8⁺) were decreased in the spleen and increased in the blood at day 1 after hindlimb ischemia in LDLR^−/− mice. At day 1 after hindlimb ischemia, however, numbers of activated CD4⁺ T lymphocytes were decreased in the draining lymph nodes of LDLR^−/− mice compared with CCR7^−/−/LDLR^−/− mice.

Conclusions

These data show that CCR7‐CCL19/CCL21 axis facilitates retention CD4⁺ T lymphocytes at the site of collateral artery remodeling, which is essential for effective arteriogenesis.

Modulation of Chemokine Receptor Function by Cholesterol: New Prospects for Pharmacological Intervention

Chemokine receptors are seven transmembrane-domain receptors belonging to class A of G-protein-coupled receptors (GPCRs). The receptors together with their chemokine ligands constitute the chemokine system, which is essential for directing cell migration and plays a crucial role in a variety of physiologic and pathologic processes. Given the importance of orchestrating cell migration, it is vital that chemokine receptor signaling is tightly regulated to ensure appropriate responses. Recent studies highlight a key role for cholesterol in modulating chemokine receptor activities. The steroid influences the spatial organization of GPCRs within the membrane bilayer, and consequently can tune chemokine receptor signaling. The effects of cholesterol on the organization and function of chemokine receptors and GPCRs in general include direct and indirect effects (Fig. 1). Here, we review how cholesterol and some key metabolites modulate functions of the chemokine system in multiple ways. We emphasize the role of cholesterol in chemokine receptor oligomerization, thereby promoting the formation of a signaling hub enabling integration of distinct signaling pathways at the receptor-membrane interface. Moreover, we discuss the role of cholesterol in stabilizing particular receptor conformations and its consequence for chemokine binding. Finally, we highlight how cholesterol accumulation, its deprivation, or cholesterol metabolites contribute to modulating cell orchestration during inflammation, induction of an adaptive immune response, as well as to dampening an anti-tumor immune response.

Dendritic cell migration in health and disease

Dendritic cells (DCs) are potent and versatile antigen-presenting cells, and their ability to migrate is key for the initiation of protective pro-inflammatory as well as tolerogenic immune responses. Recent comprehensive studies have highlighted the importance of DC migration in the maintenance of immune surveillance and tissue homeostasis, and also in the pathogenesis of a range of diseases. In this Review, we summarize the anatomical, cellular and molecular factors that regulate the migration of different DC subsets in health and disease. In particular, we focus on new insights concerning the role of migratory DCs in the pathogenesis of diseases of the skin, intestine, lung, and brain, as well as in autoimmunity and atherosclerosis.

CCR7 Maintains Nonresolving Lymph Node and Adipose Inflammation in Obesity

Accumulation of immune cells in adipose tissue promotes insulin resistance in obesity. Although innate and adaptive immune cells contribute to adipose inflammation, the processes that sustain these interactions are incompletely understood. Here we show that obesity promotes the accumulation of CD11c(+) adipose tissue immune cells that express C-C chemokine receptor 7 (CCR7) in mice and humans, and that CCR7 contributes to chronic inflammation and insulin resistance. We identified that CCR7(+) macrophages and dendritic cells accumulate in adipose tissue in close proximity to lymph nodes (LNs) (i.e., perinodal) and visceral adipose. Consistent with the role of CCR7 in regulating the migration of immune cells to LNs, obesity promoted the accumulation of CD11c(+) cells in LNs, which was prevented by global or hematopoietic deficiency of Ccr7 Obese Ccr7(-/-) mice had reduced accumulation of CD8(+) T cells, B cells, and macrophages in adipose tissue, which was associated with reduced inflammatory signaling. This reduction in maladaptive inflammation translated to increased insulin signaling and improved glucose tolerance in obesity. Therapeutic administration of an anti-CCR7 antibody phenocopied the effects of genetic Ccr7 deficiency in mice with established obesity. These results suggest that CCR7 plays a causal role in maintaining innate and adaptive immunity in obesity.

Polymorphism in the chemokine receptor 7 gene (CCR7) is associated with previous myocardial infarction in patients undergoing elective coronary angiography

Coronary artery disease (CAD) remains a major cause of death in developed countries. Both environmental and, less known, genetic factors contribute to progression of CAD to myocardial infarction (MI). Immune system is activated in patients with CAD through dendritic cells (DCs), which present plaque antigens to T lymphocytes. Production of proinflammatory cytokines by activated T cells contributes to plaque rupture in MI. Chemokine receptor 7 (CCR7) on DCs is required for their chemotaxis from plaque to lymph nodes. This makes possible an interaction of DCs with T lymphocytes and initiation of specific immune response. We hypothesized that single nucleotide polymorphisms (SNPs) in CCR7 gene locus are associated with previous MI in patients with CAD. To test this hypothesis, we genotyped six SNPs from the CCR7 gene locus in 300 consecutive patients, admitted for elective coronary angiography. We performed univariate-, multivariate- (including potential confounders) and haplotype-based tests of association of SNPs with previous MI and results of angiography. Allele A of rs17708087 SNP was associated with previous MI. This association remained significant after adjustment for age, sex, smoking, hypercholesterolaemia and drugs used by patients (odds ratio 2.13, 95% confidence interval: 1.13-3.86). Therefore, we conclude that CCR7 gene locus harbours a polymorphism that modifies risk of MI in patients with CAD. Replication of this association could be sought in a prospective cohort of initially healthy individuals.

Linking CD11b (+) Dendritic Cells and Natural Killer T Cells to Plaque Inflammation in Atherosclerosis

Atherosclerosis remains the leading cause of death and disability in our Western society. To investigate whether the dynamics of leukocyte (sub)populations could be predictive for plaque inflammation during atherosclerosis, we analyzed innate and adaptive immune cell distributions in blood, plaques, and lymphoid tissue reservoirs in apolipoprotein E-deficient (ApoE^−/−) mice and in blood and plaques from patients undergoing endarterectomy. Firstly, there was predominance of the CD11b⁺ conventional dendritic cell (cDC) subset in the plaque. Secondly, a strong inverse correlation was observed between CD11b⁺ cDC or natural killer T (NKT) cells in blood and markers of inflammation in the plaque (including CD3, T-bet, CCR5, and CCR7). This indicates that circulating CD11b⁺ cDC and NKT cells show great potential to reflect the inflammatory status in the atherosclerotic plaque. Our results suggest that distinct changes in inflammatory cell dynamics may carry biomarker potential reflecting atherosclerotic lesion progression. This not only is crucial for a better understanding of the immunopathogenesis but also bares therapeutic potential, since immune cell-based therapies are emerging as a promising novel strategy in the battle against atherosclerosis and its associated comorbidities. The cDC-NKT cell interaction in atherosclerosis serves as a good candidate for future investigations.

Regulation of atherosclerotic plaque inflammation

The immune reactions that regulate atherosclerotic plaque inflammation involve chemokines, lipid mediators and costimulatory molecules. Chemokines are a family of chemotactic cytokines that mediate immune cell recruitment and control cell homeostasis and activation of different immune cell types and subsets. Chemokine production and activation of chemokine receptors form a positive feedback mechanism to recruit monocytes, neutrophils and lymphocytes into the atherosclerotic plaque. In addition, chemokine signalling affects immune cell mobilization from the bone marrow. Targeting several of the chemokines and/or chemokine receptors reduces experimental atherosclerosis, whereas specific chemokine pathways appear to be involved in plaque regression. Leukotrienes are lipid mediators that are formed locally in atherosclerotic lesions from arachidonic acid. Leukotrienes mediate immune cell recruitment and activation within the plaque as well as smooth muscle cell proliferation and endothelial dysfunction. Antileukotrienes decrease experimental atherosclerosis, and recent observational data suggest beneficial clinical effects of leukotriene receptor antagonism in cardiovascular disease prevention. By contrast, other lipid mediators, such as lipoxins and metabolites of omega-3 fatty acids, have been associated with the resolution of inflammation. Costimulatory molecules play a central role in fine-tuning immunological reactions and mediate crosstalk between innate and adaptive immunity in atherosclerosis. Targeting these interactions is a promising approach for the treatment of atherosclerosis, but immunological side effects are still a concern. In summary, targeting chemokines, leukotriene receptors and costimulatory molecules could represent potential therapeutic strategies to control atherosclerotic plaque inflammation.

MIF and CXCL12 in Cardiovascular Diseases: Functional Differences and Similarities

Coronary artery disease (CAD) as part of the cardiovascular diseases is a pathology caused by atherosclerosis, a chronic inflammatory disease of the vessel wall characterized by a massive invasion of lipids and inflammatory cells into the inner vessel layer (intima) leading to the formation of atherosclerotic lesions; their constant growth may cause complications such as flow-limiting stenosis and plaque rupture, the latter triggering vessel occlusion through thrombus formation. Pathophysiology of CAD is complex and over the last years many players have entered the picture. One of the latter being chemokines (small 8-12 kDa cytokines) and their receptors, known to orchestrate cell chemotaxis and arrest. Here, we will focus on the chemokine CXCL12, also known as stromal cell-derived factor 1 (SDF-1) and the chemokine-like function chemokine, macrophage migration-inhibitory factor (MIF). Both are ubiquitously expressed and highly conserved proteins and play an important role in cell homeostasis, recruitment, and arrest through binding to their corresponding chemokine receptors CXCR4 (CXCL12 and MIF), ACKR3 (CXCL12), and CXCR2 (MIF). In addition, MIF also binds to the receptor CD44 and the co-receptor CD74. CXCL12 has mostly been studied for its crucial role in the homing of (hematopoietic) progenitor cells in the bone marrow and their mobilization into the periphery. In contrast to CXCL12, MIF is secreted in response to diverse inflammatory stimuli, and has been associated with a clear pro-inflammatory and pro-atherogenic role in multiple studies of patients and animal models. Ongoing research on CXCL12 points at a protective function of this chemokine in atherosclerotic lesion development. This review will focus on the role of CXCL12 and MIF and their differences and similarities in CAD of high risk patients.

Cytokines in atherosclerosis: Key players in all stages of disease and promising therapeutic targets

Atherosclerosis, a chronic inflammatory disorder of the arteries, is responsible for most deaths in westernized societies with numbers increasing at a marked rate in developing countries. The disease is initiated by the activation of the endothelium by various risk factors leading to chemokine-mediated recruitment of immune cells. The uptake of modified lipoproteins by macrophages along with defective cholesterol efflux gives rise to foam cells associated with the fatty streak in the early phase of the disease. As the disease progresses, complex fibrotic plaques are produced as a result of lysis of foam cells, migration and proliferation of vascular smooth muscle cells and continued inflammatory response. Such plaques are stabilized by the extracellular matrix produced by smooth muscle cells and destabilized by matrix metalloproteinase from macrophages. Rupture of unstable plaques and subsequent thrombosis leads to clinical complications such as myocardial infarction. Cytokines are involved in all stages of atherosclerosis and have a profound influence on the pathogenesis of this disease. This review will describe our current understanding of the roles of different cytokines in atherosclerosis together with therapeutic approaches aimed at manipulating their actions.

Lymphocyte migration into atherosclerotic plaque

Adaptive immunity is involved in the pathogenesis of atherosclerosis, but the recruitment of T and B lymphocytes to atherosclerotic lesions is not as well studied as that of monocytes. In this review, we summarize the current understanding of the role of lymphocyte subsets in the pathogenesis of atherosclerosis and discuss chemokines and chemokine receptors involved in lymphocyte homing to atherosclerotic lesions. We review evidence for involvement of the chemokines CCL5, CCL19, CCL21, CXCL10, and CXCL16 and macrophage migration inhibitory factor in lymphocyte homing in atherosclerosis. Also, we review the role of their receptors CCR5, CCR6, CCR7, CXCR3, CXCR6, and CXCR2/CXCR4 and the role of the L-selectin in mouse models of atherosclerosis.

Increased CCL19 and CCL21 levels promote fibroblast ossification in ankylosing spondylitis hip ligament tissue

Background

It is well-documented that both chemokine (C-C motif) ligand 19 (CCL19) and 21 (CCL21) mediate cell migration and angiogenesis in many diseases. However, these ligands’ precise pathological role in ankylosing spondylitis (AS) has not been elucidated. The objective of this study was to examine the expression of CCL19 and CCL21 (CCL19/CCL21) in AS hip ligament tissue (LT) and determine their pathological functions.

Methods

The expression levels of CCL19, CCL21 and their receptor CCR7 in AS (n = 31) and osteoarthritis (OA, n = 21) LT were analyzed via real-time polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). The expression of CCL19, CCL21 and CCR7 in AS ligament fibroblasts was also detected. The proliferation of ligament fibroblasts was measured via a cell counting kit-8 (CCK8) assay after exogenous CCL19/CCL21 treatment. Additionally, the role of CCL19/CCL21 in osteogenesis was evaluated via RT-PCR and enzyme-linked immunosorbent assay (ELISA) in individual AS fibroblast cultures. Furthermore, the expression of the bone markers alkaline phosphatase (ALP), osteocalcin (OCN), collagenase I (COL1), integrin-binding sialoprotein (IBSP) and the key regulators runt-related transcription factor-2 (Runx-2) and osterix were investigated. Moreover, the CCL19/CCL21 levels in serum and LT were measured via ELISA.

Results

The mRNA levels of CCL19/CCL21 in AS hip LT were significantly higher than that in OA LT, and IHC analysis revealed a similar result. Exogenous CCL19/CCL21 treatment did not affect the proliferation of ligament fibroblasts but significantly up-regulated the expression of bone markers, including ALP and OCN, and the key regulators Runx-2 and osterix. In addition, the serum levels of CCL19/CCL21 were apparently elevated in AS patients compared to healthy controls (HC), and the expression of the two chemokines correlated significantly in AS patients.

Conclusions

CCL19 and CCL21, two chemokines displaying significantly associated expression in serum, indicating a synergistic effect on AS pathogenesis, may function as promoters of ligament ossification in AS patients.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-316) contains supplementary material, which is available to authorized users.

The omega-3 fatty acid docosahexaenoic acid favorably modulates the inflammatory pathways and macrophage polarization within aorta of LDLR(-/-) mice

The omega-3 fatty acid docosahexaenoic acid (DHA) has potent anti-atherogenic properties but its mechanisms of action at the vascular level remain poorly explored. Knowing the broad range of molecular targets of omega-3 fatty acids, microarray analysis was used to open-mindedly evaluate the effects of DHA on aorta gene expression in LDLR(-/-) mice and better understand its local anti-atherogenic action. Mice were fed an atherogenic diet and received daily oral gavages with oils rich in oleic acid or DHA. Bioinformatics analysis of microarray data first identified inflammation and innate immunity as processes the most affected by DHA supplementation within aorta. More precisely, several down-regulated genes were associated with the inflammatory functions of macrophages (e.g., CCL5 and CCR7), cell movement (e.g., ICAM-2, SELP, and PECAM-1), and the major histocompatibility complex (e.g., HLA-DQA1 and HLA-DRB1). Interestingly, several genes were identified as specific biomarkers of macrophage polarization, and their changes suggested a preferential orientation toward a M2 reparative phenotype. This observation was supported by the upstream regulator analysis highlighting the involvement of three main regulators of macrophage polarization, namely PPARγ (z-score = 2.367, p = 1.50 × 10(-13)), INFγ (z-score = -2.797, p = 2.81 × 10(-14)), and NFκB (z-score = 2.360, p = 6.32 × 10(-9)). Moreover, immunohistological analysis of aortic root revealed an increased abundance of Arg1 (+111 %, p = 0.01), a specific biomarker of M2 macrophage. The present study showed for the first time that DHA supplementation during atherogenesis is associated with protective modulation of inflammation and innate immunity pathways within aorta putatively through the orientation of plaque macrophages toward a M2 reparative phenotype.

Mechanisms that regulate macrophage burden in atherosclerosis

Mononuclear phagocytes (MPs) relevant to atherosclerosis include monocytes, macrophages, and dendritic cells. A decade ago, studies on macrophage behavior in atherosclerotic lesions were often limited to quantification of total macrophage area in cross-sections of plaques. Although technological advances are still needed to examine plaque MP populations in an increasingly dynamic and informative manner, innovative methods to interrogate the biology of MPs in atherosclerotic plaques developed in the past few years point to several mechanisms that regulate the accumulation and function of MPs within plaques. Here, I review the evolution of atherosclerotic plaques with respect to changes in the MP compartment from the initiation of plaque to its progression and regression, discussing the roles that recruitment, proliferation, and retention of MPs play at these different disease stages. Additional work in the future will be needed to better distinguish macrophages and dendritic cells in plaque and to address some basic unknowns in the field, including just how cholesterol drives accumulation of macrophages in lesions to build plaques in the first place and how macrophages as major effectors of innate immunity work together with components of the adaptive immune response to drive atherosclerosis. Answers to these questions are sought with the goal in mind of reversing disease where it exists and preventing its development where it does not.

Contribution of homeostatic chemokines CCL19 and CCL21 and their receptor CCR7 to coronary artery disease

OBJECTIVE

Our aim was to identify the role of the homeostatic chemokines CCL19 and CCL21 and their common receptor CCR7 in atherogenesis and to study the relationships between CCL19, CCL21, and CCR7 gene variants and coronary artery disease in a Chinese Han population.

APPROACH AND RESULTS

Immunohistochemical analysis of samples with atherosclerosis of various stages showed increased CCL19, CCL21, and CCR7 expression in atherosclerotic coronary plaques compared with nonatherosclerotic controls. Expression levels increased in positive correlation with coronary lesion stage. Cell adhesion assays confirmed that CCL19 promoted monocyte adhesion, which was induced by CCR7, to human umbilical vein endothelial cells, an effect partially antagonized by atorvastatin. After the human umbilical vein endothelial cells were treated with CCR7-neutralizing antibody, both CCL19- and CCL21-induced monocyte to human umbilical vein endothelial cell migration and CCL19-induced monocyte to human umbilical vein endothelial cell adhesion were abolished. The associations between genetic variants of CCL19, CCL21, CCR7, and coronary artery disease in a Chinese Han population were determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The following single nucleotide polymorphisms were associated with coronary artery disease: CCL19 rs2227302, CCL21 rs2812377, and CCR7 rs588019. Individuals with the CCL19 rs2227302 T allele or CCL21 rs2812377 G allele had higher plasma CCL19 levels than those with C/C genotype and higher CCL21 levels than those with T/T genotype in both case and control subjects.

CONCLUSION

CCL19/CCL21-CCR7 is a novel homeostatic chemokine system that modulates human monocyte adhesion and migration, promoting atherogenesis. It is associated with coronary artery disease risk in Chinese Han individuals. These data suggest that the CCL19/CCL21-CCR7 axis plays an important role in atherosclerosis progression.

MiR-142-3p attenuates the migration of CD4⁺ T cells through regulating actin cytoskeleton via RAC1 and ROCK2 in arteriosclerosis obliterans

The migration of CD4⁺ T cells plays an important role in arteriosclerosis obliterans (ASO). However, the molecular mechanisms involved in CD4⁺ T cell migration are still unclear. The current study is aimed to determine the expression change of miR-142-3p in CD4⁺ T cells from patients with ASO and investigate its role in CD4⁺ T cell migration as well the potential mechanisms involved. We identified by qRT-PCR and in situ hybridization that the expression of miR-142-3p in CD4⁺ T cells was significantly down-regulated in patients with ASO. Chemokine (C-X-C motif) ligand 12 (CXCL12), a common inflammatory chemokine under the ASO condition, was able to down-regulate the expression of miR-142-3p in cultured CD4⁺ T cells. Up-regulation of miR-142-3p by lentivirus-mediated gene transfer had a strong inhibitory effect on CD4⁺ T cell migration both in cultured human cells in vitro and in mouse aortas and spleens in vivo. RAC1 and ROCK2 were identified to be the direct target genes in human CD4⁺ T cells, which are further confirmed by dual luciferase assay. MiR-142-3p had strong regulatory effects on actin cytoskeleton as shown by the actin staining in CD4⁺ T cells. The results suggest that the expression of miR-142-3p is down-regulated in CD4⁺ T cells from patients with ASO. The down-regulation of miR-142-3p could increase the migration of CD4⁺ T cells to the vascular walls by regulation of actin cytoskeleton via its target genes, RAC1 and ROCK2.

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

BACKGROUND

We have previously shown that the homeostatic chemokine CXCL13 is up-regulated in monocytes in atherosclerosis, mediating anti-apoptotic and anti-inflammatory effects.

OBJECTIVE

To investigate the regulation of CXCL13s receptor, CXCR5.

METHODS/PATIENTS

In 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).

RESULTS

Our 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.

CONCLUSION

Our findings suggest that platelet-mediated signaling through CXCR5 may be active in vivo during plaque destabilization, potentially representing a counteracting mechanism to inflammation.

Increased levels of CCR7 ligands in carotid atherosclerosis: different effects in macrophages and smooth muscle cells

AIMS

The homeostatic chemokines, CCL19 and CCL21 and their receptor CCR7, have recently been linked to atherogenesis. We investigated the expression of CCL19/CCL21/CCR7 in carotid atherosclerosis as well as the ability of these chemokines to modulate lipid accumulation in macrophages and vascular smooth muscle cell (SMC) phenotype.

METHODS AND RESULTS

Our major findings were: (i) patients with carotid atherosclerosis (n = 158) had increased plasma levels of CCL21, but not of CCL19, compared with controls (n = 20), with particularly high levels in symptomatic (n = 99) when compared with asymptomatic (n = 59) disease. (ii) Carotid plaques showed markedly increased mRNA levels of CCL21 and CCL19 in symptomatic (n = 14) when compared with asymptomatic (n = 7) patients, with CCR7 localized to macrophages and vascular SMC (immunohistochemistry). (iii) In vitro, CCL21, but not CCL19, increased the binding of modified LDL and promoted lipid accumulation in THP-1 macrophages. (iv) CCL19, but not CCL21, increased proliferation and release and activity of matrix metalloproteinase (MMP) 1 in vascular SMC. (v) The differential effects of CCL19 and CCL21 in macrophages and SMC seem to be attributable to divergent signalling pathways, with CCL19-mediated activation of AKT in SMC- and CCL21-mediated activation of extracellular signal-regulated kinase 1/2 in macrophages.

CONCLUSION

CCL19 and CCL21 are up-regulated in carotid atherosclerosis. The ability of CCL21 to promote lipid accumulation in macrophages and of CCL19 to induce proliferation and MMP-1 expression in vascular SMC could contribute to their pro-atherogenic potential.

Chemokines in atherosclerosis: proceedings resumed

Chemokines play important roles in atherosclerotic vascular disease. Expressed by not only cells of the vessel wall but also emigrated leukocytes, chemokines were initially discovered to direct leukocytes to sites of inflammation. However, chemokines can also exert multiple functions beyond cell recruitment. Here, we discuss novel and recently emerging aspects of chemokines and their involvement in atherosclerosis. While reviewing newly identified roles of chemokines and their receptors in monocyte and neutrophil recruitment during atherogenesis and atheroregression, we also revisit homeostatic functions of chemokines, including their roles in cell homeostasis and foam cell formation. The functional diversity of chemokines in atherosclerosis warrants a clear-cut mechanistic dissection and stage-specific assessment to better appreciate the full scope of their actions in vascular inflammation and to identify pathways that harbor the potential for a therapeutic targeting of chemokines in atherosclerosis.

Protective effect of the ultra-filtration extract from Xin Mai Jia on human aortic smooth muscle cell injury induced by hydrogen peroxide

The aim of the present study was to explore whether an ultra-filtration extract from Xin Mai Jia (XMJ), a Chinese medicinal formulation, has a protective effect on human aortic smooth muscle cell (HASMC) injury models induced by hydrogen peroxide (H₂O₂), and to consider the mechanism and efficacy of the therapeutic action of XMJ on atherosclerosis. HASMCs were injured by H₂O₂ and then exposed to various concentrations of XMJ. The morphological changes, growth, proliferation, migration and cytokine release of HASMCs were detected using 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT), an enzyme-linked immunosorbent assay and a scratch adhesion test. H₂O₂ significantly promoted the proliferation of HASMCs. The ultra-filtration extract from XMJ was observed to significantly attenuate the morphological changes of injured HASMCs, reduce the expression levels of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), interleukin (IL)-1, IL-6 and nuclear factor (NF)-κB, and increase the expression levels of matrix metalloproteinase (MMP)-2 and tissue inhibitor of metalloproteinase (TIMP). XMJ has clear anti-inflammatory and antioxidant effects, and significantly inhibits the proliferation and migration of HASMCs.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

No detection of Helicobacter pylori in atherosclerotic plaques in end stage renal disease patients undergoing kidney transplantation

Chronic infection known to be a predisposing factor for the development of atherosclerosis. Several studies have found a possible role of Helicobacter pylori in the pathogenesis of atherosclerosis. The aim of this study was to investigate the presence of H. pylori in atherosclerotic plaques in iliac arteries in 25 end stage renal disease (ESRD) patients undergoing kidney transplantation. Esophagogastroduodenoscopy was performed in all patients before transplantation. Biopsy specimens obtained from gastric antrum were sent for pathologic evaluation. Gastric H. pylori infection was confirmed by microscopic assessment and rapid urease test. Arterial specimens were obtained from iliac arteries during kidney transplantation. Presence of H. pylori DNA in atherosclerotic plaques and healthy vessel samples was evaluated by the polymerase chain reaction (PCR). The mean age of patients was 44.1 ± 22.6 years. Risk factors in patients with atherosclerosis were hypertension (68%), diabetes mellitus (20%), hyperlipidemia (20%), positive family history (16%). Atherosclerotic plaques were found in 21 (84%) patients. PCR analysis did not detect H. pylori in any case. There was a significant relationship of atherosclerosis with hypertension (P = 0.006) but not with diabetes mellitus and hyperlipidemia (P = 0.5). There was no significant relationship between atherosclerosis and gastric H. pylori infection (P = 0.6). This study revealed no association between the presence of H. pylori as a pathogen of vessel walls and atherosclerosis in ESRD.

A myriad of functions and complex regulation of the CCR7/CCL19/CCL21 chemokine axis in the adaptive immune system

The chemokine receptor CCR7 and its ligands CCL19 and CCL21 control a diverse array of migratory events in adaptive immune function. Most prominently, CCR7 promotes homing of T cells and DCs to T cell areas of lymphoid tissues where T cell priming occurs. However, CCR7 and its ligands also contribute to a multitude of adaptive immune functions including thymocyte development, secondary lymphoid organogenesis, high affinity antibody responses, regulatory and memory T cell function, and lymphocyte egress from tissues. In this survey, we summarise the role of CCR7 in adaptive immunity and describe recent progress in understanding how this axis is regulated. In particular we highlight CCX-CKR, which scavenges both CCR7 ligands, and discuss its emerging significance in the immune system.

The role of the vascular dendritic cell network in atherosclerosis

A complex role has been described for dendritic cells (DCs) in the potentiation and control of vascular inflammation and atherosclerosis. Resident vascular DCs are found in the intima of atherosclerosis-prone vascular regions exposed to disturbed blood flow patterns. Several phenotypically and functionally distinct vascular DC subsets have been described. The functional heterogeneity of these cells and their contributions to vascular homeostasis, inflammation, and atherosclerosis are only recently beginning to emerge. Here, we review the available literature, characterizing the origin and function of known vascular DC subsets and their important role contributing to the balance of immune activation and immune tolerance governing vascular homeostasis under healthy conditions. We then discuss how homeostatic DC functions are disrupted during atherogenesis, leading to atherosclerosis. The effectiveness of DC-based "atherosclerosis vaccine" therapies in the treatment of atherosclerosis is also reviewed. We further provide suggestions for distinguishing DCs from macrophages and discuss important future directions for the field.

Lipoteichoic acid isolated from Lactobacillus plantarum suppresses LPS-mediated atherosclerotic plaque inflammation

Chronic inflammation plays an important role in atherogenesis. Experimental studies have demonstrated the accumulation of monocytes/macrophages in atherosclerotic plaques caused by inflammation. Here, we report the inhibitory effects of lipoteichoic acid (LTA) from Lactobacillus plantarum (pLTA) on atherosclerotic inflammation. pLTA inhibited the production of proinflammatory cytokines and nitric oxide in lipopolysaccharide (LPS)-stimulated cells and alleviated THP-1 cell adhesion to HUVEC by down-regulation of adhesion molecules such as intracellular adhesion molecule-1 (ICAM-I), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. The inhibitory effect of pLTA was mediated by inhibition of NF-κB and activation of MAP kinases. Inhibition of monocyte/macrophage infiltration to the arterial lumen was shown in pLTA-injected ApoE(-/-) mice, which was concurrent with inhibition of MMP-9 and preservation of CD31 production. The antiinflammatory effect mediated by pLTA decreased expression of atherosclerotic markers such as COX-2, Bax, and HSP27 and also cell surface receptors such as TLR4 and CCR7. Together, these results underscore the role of pLTA in suppressing atherosclerotic plaque inflammation and will help in identifying targets with therapeutic potential against pathogen-mediated atherogenesis.

Emerging role of chemokine receptor 7 in atherosclerosis

The CC chemokine receptor 7 (CCR7) and its ligands CCL19 and CCL21 essentially contribute to both immunity and tolerance by directing T cells and antigen-presenting dendritic cells (DCs) to and within lymph organs. In the pathogenesis of atherosclerosis, the accumulation of cholesterol in the subendothelial space of the vessel wall represents the initial step of plaque development in which DCs acquire and process low-density lipoprotein cholesterol as antigen in the vessel wall and then migrate to draining lymph nodes and present this antigen to naive T cells. Deletion of CCR7 receptor in murine atherosclerosis not only results in a reduced atherosclerotic plaque content but also leads to a disturbed entry and exit of T cells within the inflamed vessel wall. These observations are consistent with the notion that CCR7-dependent T cell priming in secondary lymphoid organs and CCR7-dependent recirculation of T cells between secondary lymphoid organs and inflamed tissue is pivotal for atherosclerotic plaque development and may represent an interesting target for innovative immune-modulatory therapy.