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

Elucidating the role of chemokines in inflammaging associated atherosclerotic cardiovascular diseases

Age-related inflammation or inflammaging is a critical deciding factor of physiological homeostasis during aging. Cardiovascular diseases (CVDs) are exquisitely associated with aging and inflammation and are one of the leading causes of high mortality in the elderly population. Inflammaging comprises dysregulation of crosstalk between the vascular and cardiac tissues that deteriorates the vasculature network leading to development of atherosclerosis and atherosclerotic-associated CVDs in elderly populations. Leukocyte differentiation, migration and recruitment holds a crucial position in both inflammaging and atherosclerotic CVDs through relaying the activity of an intricate network of inflammation-associated protein-protein interactions. Among these interactions, small immunoproteins such as chemokines play a major role in the progression of inflammaging and atherosclerosis. Chemokines are actively involved in lymphocyte migration and severe inflammatory response at the site of injury. They relay their functions via chemokine-G protein-coupled receptors-glycosaminoglycan signaling axis and is a principal part for the detection of age-related atherosclerosis and related CVDs. This review focuses on highlighting the detailed intricacies of the effects of chemokine-receptor interaction and chemokine oligomerization on lymphocyte recruitment and its evident role in clinical manifestations of atherosclerosis and related CVDs. Further, the role of chemokine mediated signaling for formulating next-generation therapeutics against atherosclerosis has also been discussed.

Immune-Related Genes in the Pathogenesis of Atherosclerosis: Based on Sex Differences

Purpose

Atherosclerosis is still a global public problem with increasing incidence rate and mortality. It has been found that gender factors play an important role in the progression of atherosclerosis. However, few people explore gender related atherosclerosis at the level of genes and immune cells. The purpose of this study was to determine genetic and immune cell differences between male and female samples.

Patients and Methods

This study aims to identify differential genes between male and female samples in the GSE43292 dataset. The focus will be on identifying immune-related genes (IRGs) among these differentially expressed genes. Subsequently, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis will be employed to explore the enrichment of IRGs in biological processes, molecular functions, cellular components, and pathways. Furthermore, a protein-protein interaction (PPI) network for the IRGs will be constructed using Cytoscape software. To estimate the degree of immune cell infiltration, single-sample gene set enrichment analysis (ssGSEA) will be conducted. Moreover, the identified IRGs will be validated using GSE28829 dataset. Finally, we validated in atherosclerotic mice.

Results

Seven IRGs (CCL13, IL1RN, FPR2, S100A8, CCL19, CXCL1, CXCL8) were identified as being overexpressed in male atherosclerosis. GO and KEGG analysis revealed that these IRGs are primarily enriched in inflammatory response pathways, cytokine signaling pathways, and cytokine- cytokine receptor interactions. Notably, when compared to females, there was a significant infiltration of immune cells in male specimens. Importantly, all seven IRGs demonstrated high diagnostic value in GSE28829 dataset. The use of animal samples supports our results.

Conclusion

This study demonstrates the effectiveness of seven IRGs and reveal sex differences in atherosclerosis. Notably, there is a significant presence of immune cells within the atherosclerotic plaque of men compared to women. These findings have potential implications for the development of personalized treatment approaches targeting gender-related atherosclerosis.

Plasma homeostatic chemokines CCL19 and CCL21 and the prognosis of ischemic stroke in two Chinese prospective cohorts

BACKGROUND

The homeostatic chemokines CCL19 and CCL21 are involved in carotid plaque vulnerability and post-ischemic neuroinflammatory responses. This study aimed to examine the prognostic values of CCL19 and CCL21 in ischemic stroke.

METHODS

Plasma CCL19 and CCL21 were measured in 4483 ischemic stroke patients from two independent cohorts of CATIS (China Antihypertensive Trial in Acute Ischemic Stroke) and IIPAIS (Infectious Factors, Inflammatory Markers, and Prognosis of Acute Ischemic Stroke), and participants were followed up at 3 months after stroke. The primary outcome was the composite outcome of death or major disability. The associations of CCL19 and CCL21 levels with the primary outcome were examined.

RESULTS

In CATIS, multivariable-adjusted odds ratios of the primary outcome in the highest quartiles of CCL19 and CCL21 compared with the lowest quartiles were 2.06 and 2.62, respectively. In IIPAIS, odds ratios of the primary outcome in the highest quartiles of CCL19 and CCL21 were 2.81 and 2.78 compared with the lowest quartiles, respectively. In the pooled analysis of the two cohorts, odds ratios of the primary outcome associated with the highest quartiles of CCL19 and CCL21 were 2.24 and 2.66, respectively. Similar findings were observed in the analysis with major disability, death, and the composite outcome of death or cardiovascular events as the secondary study outcomes. Adding CCL19 and CCL21 to conventional risk factors significantly improved risk reclassification and discrimination for adverse outcomes.

CONCLUSIONS

Both CCL19 and CCL21 levels were independently associated with adverse outcomes within 3 months after ischemic stroke and should be further investigated for risk stratification and potential therapeutic targets of ischemic stroke.

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.

CCL21/CCR7 Axis Contributes to Trophoblastic Cell Migration and Invasion in Preeclampsia by Affecting the Epithelial Mesenchymal Transition via the ERK1/2 Signaling Pathway

Preeclampsia (PE) is a pregnancy-related disorder that is a leading cause of maternal death. The failure of spiral artery remodeling due to insufficient trophoblast migration and invasion is critical in the pathogenesis of PE. Recently, the CC motif chemokine ligand 21 (CCL21) has been widely linked to cancer cell invasion and migration. However, their potential mechanisms are still unknown. In this study, we found that CCL21 expression was significantly lower in the PE group than that in the control group. In vitro experiments revealed that recombinant CCL21 could promote trophoblast cell epithelial-to-mesenchymal transitions (EMTs) and improve migration and invasion. Furthermore, an inhibitor of the ERK1/2 signaling pathway inhibited the CCL21-induced EMT process. Finally, a PE mouse model was established using the NOS inhibitor L-NAME, and we obtained similar results, with downregulated CCL21 and EMT biomarkers and upregulated CCR7. Taken together, these findings suggest that the CCL21/CCR7 axis influences EMT by activating the ERK1/2 signaling pathway, thereby affecting trophoblast cell migration and invasion, which may play a crucial role in the pathogenesis of PE.

The commonness in immune infiltration of rheumatoid arthritis and atherosclerosis: Screening for central targets via microarray data analysis

Background

Although increasing evidence has reported an increased risk of atherosclerosis (AS) in rheumatoid arthritis (RA), the communal molecular mechanism of this phenomenon is still far from being fully elucidated. Hence, this article aimed to explore the pathogenesis of RA complicated with AS.

Methods

Based on the strict inclusion/exclusion criteria, four gene datasets were downloaded from the Gene Expression Omnibus (GEO) database. After identifying the communal differentially expressed genes (DEGs) and hub genes, comprehensive bioinformatics analysis, including functional annotation, co-expression analysis, expression validation, drug-gene prediction, and TF-mRNA-miRNA regulatory network construction, was conducted. Moreover, the immune infiltration of RA and AS was analyzed and compared based on the CIBERSORT algorithm, and the correlation between hub genes and infiltrating immune cells was evaluated in RA and AS respectively.

Results

A total of 54 upregulated and 12 downregulated communal DEGs were screened between GSE100927 and GSE55457, and functional analysis of these genes indicated that the potential pathogenesis lies in immune terms. After the protein-protein interaction (PPI) network construction, a total of six hub genes (CCR5, CCR7, IL7R, PTPRC, CD2, and CD3D) were determined as hub genes, and the subsequent comprehensive bioinformatics analysis of the hub genes re-emphasized the importance of the immune system in RA and AS. Additionally, three overlapping infiltrating immune cells were found between RA and AS based on the CIBERSORT algorithm, including upregulated memory B cells, follicular helper T cells and γδT cells.

Conclusions

Our study uncover the communal central genes and commonness in immune infiltration between RA and AS, and the analysis of six hub genes and three immune cells profile might provide new insights into potential pathogenesis therapeutic direction of RA complicated with AS.

Heteromerization between α1B -adrenoceptor and chemokine (C-C motif) receptor 2 biases α1B -adrenoceptor signaling: Implications for vascular function

Previously, we reported that chemokine (C-C motif) receptor 2 (CCR2) heteromerizes with α1B -adrenoceptor (α1B -AR) in leukocytes, through which α1B -AR controls CCR2. Whether such heteromers are expressed in human vascular smooth muscle cells (hVSMCs) is unknown. Bioluminescence resonance energy transfer confirmed formation of recombinant CCR2:α1b -AR heteromers. Proximity ligation assays detected CCR2:α1B -AR heteromers in hVSMCs and human mesenteric arteries. CCR2:α1B -AR heteromerization per se enhanced α1B -AR-mediated Gαq -coupling. Chemokine (C-C motif) ligand 2 (CCL2) binding to CCR2 inhibited Gαq activation via α1B -AR, cross-recruited β-arrestin to and induced internalization of α1B -AR in recombinant systems and in hVSMCs. Our findings suggest that CCR2 within CCR2:α1B -AR heteromers biases α1B -AR signaling and provide a mechanism for previous observations suggesting a role for CCL2/CCR2 in the regulation of cardiovascular function.

High Circulating Levels of the Homeostatic Chemokines CCL19 and CCL21 Predict Mortality and Disease Severity in COVID-19

BACKGROUND

Immune dysregulation is a major factor in the development of severe coronavirus disease 2019 (COVID-19). The homeostatic chemokines CCL19 and CCL21 have been implicated as mediators of tissue inflammation, but data on their regulation in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is limited. We thus investigated the levels of these chemokines in COVID-19 patients.

METHODS

Serial blood samples were obtained from patients hospitalized with COVID-19 (n = 414). Circulating CCL19 and CCL21 levels during hospitalization and 3-month follow-up were analyzed. In vitro assays and analysis of RNAseq data from public repositories were performed to further explore possible regulatory mechanisms.

RESULTS

A consistent increase in circulating levels of CCL19 and CCL21 was observed, with high levels correlating with disease severity measures, including respiratory failure, need for intensive care, and 60-day all-cause mortality. High levels of CCL21 at admission were associated with persisting impairment of pulmonary function at the 3-month follow-up.

CONCLUSIONS

Our findings highlight CCL19 and CCL21 as markers of immune dysregulation in COVID-19. This may reflect aberrant regulation triggered by tissue inflammation, as observed in other chronic inflammatory and autoimmune conditions. Determination of the source and regulation of these chemokines and their effects on lung tissue is warranted to further clarify their role in COVID-19.

CLINICAL TRIALS REGISTRATION

NCT04321616 and NCT04381819.

Immune-Associated Gene Signatures and Subtypes to Predict the Progression of Atherosclerotic Plaques Based on Machine Learning

Objective: Experimental and clinical evidence suggests that atherosclerosis is a chronic inflammatory disease. Our study was conducted for uncovering the roles of immune-associated genes during atherosclerotic plaque progression.

Methods: Gene expression profiling of GSE28829, GSE43292, GSE41571, and GSE120521 datasets was retrieved from the GEO database. Three machine learning algorithms, least absolute shrinkage, and selection operator (LASSO), random forest, and support vector machine–recursive feature elimination (SVM-RFE) were utilized for screening characteristic genes among atherosclerotic plaque progression- and immune-associated genes. ROC curves were generated for estimating the diagnostic efficacy. Immune cell infiltrations were estimated via ssGSEA, and immune checkpoints were quantified. CMap analysis was implemented to screen potential small-molecule compounds. Atherosclerotic plaque specimens were classified using a consensus clustering approach.

Results: Seven characteristic genes (TNFSF13B, CCL5, CCL19, ITGAL, CD14, GZMB, and BTK) were identified, which enabled the prediction of progression of atherosclerotic plaques. Higher immune cell infiltrations and immune checkpoint expressions were found in advanced-stage than in early-stage atherosclerotic plaques and were positively linked to characteristic genes. Patients could clinically benefit from the characteristic gene-based nomogram. Several small molecular compounds were predicted based on the characteristic genes. Two subtypes, namely, C1 immune subtype and C2 non-immune subtype, were classified across atherosclerotic plaques. The characteristic genes presented higher expression in C1 than in C2 subtypes.

Conclusion: Our findings provide several promising atherosclerotic plaque progression- and immune-associated genes as well as immune subtypes, which might enable to assist the design of more accurately tailored cardiovascular immunotherapy.

Inflammatory Mediators in Atherosclerotic Vascular Remodeling

Atherosclerotic vascular disease remains the most common cause of ischemia, myocardial infarction, and stroke. Vascular function is determined by structural and functional properties of the arterial vessel wall, which consists of three layers, namely the adventitia, media, and intima. Key cells in shaping the vascular wall architecture and warranting proper vessel function are vascular smooth muscle cells in the arterial media and endothelial cells lining the intima. Pathological alterations of this vessel wall architecture called vascular remodeling can lead to insufficient vascular function and subsequent ischemia and organ damage. One major pathomechanism driving this detrimental vascular remodeling is atherosclerosis, which is initiated by endothelial dysfunction allowing the accumulation of intimal lipids and leukocytes. Inflammatory mediators such as cytokines, chemokines, and modified lipids further drive vascular remodeling ultimately leading to thrombus formation and/or vessel occlusion which can cause major cardiovascular events. Although it is clear that vascular wall remodeling is an elementary mechanism of atherosclerotic vascular disease, the diverse underlying pathomechanisms and its consequences are still insufficiently understood.

Identification of potential biomarkers and pathways associated with carotid atherosclerotic plaques in type 2 diabetes mellitus: A transcriptomics study

Type 2 diabetes mellitus (T2DM) affects the formation of carotid atherosclerotic plaques (CAPs) and patients are prone to plaque instability. It is crucial to clarify transcriptomics profiles and identify biomarkers related to the progression of T2DM complicated by CAPs. Ten human CAP samples were obtained, and whole transcriptome sequencing (RNA-seq) was performed. Samples were divided into two groups: diabetes mellitus (DM) versus non-DM groups and unstable versus stable groups. The Limma package in R was used to identify lncRNAs, circRNAs, and mRNAs. Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, protein-protein interaction (PPI) network creation, and module generation were performed for differentially expressed mRNAs. Cytoscape was used to create a transcription factor (TF)-mRNA regulatory network, lncRNA/circRNA-mRNA co-expression network, and a competitive endogenous RNA (ceRNA) network. The GSE118481 dataset and RT-qPCR were used to verify potential mRNAs.The regulatory network was constructed based on the verified core genes and the relationships were extracted from the above network. In total, 180 differentially expressed lncRNAs, 343 circRNAs, and 1092 mRNAs were identified in the DM versus non-DM group; 240 differentially expressed lncRNAs, 390 circRNAs, and 677 mRNAs were identified in the unstable versus stable group. Five circRNAs, 14 lncRNAs, and 171 mRNAs that were common among all four groups changed in the same direction. GO/KEGG functional enrichment analysis showed that 171 mRNAs were mainly related to biological processes, such as immune responses, inflammatory responses, and cell adhesion. Five circRNAs, 14 lncRNAs, 46 miRNAs, and 54 mRNAs in the ceRNA network formed a regulatory relationship. C22orf34-hsa-miR-6785-5p-RAB37, hsacirc_013887-hsa-miR-6785-5p/hsa-miR-4763-5p/hsa-miR-30b-3p-RAB37, MIR4435-1HG-hsa-miR-30b-3p-RAB37, and GAS5-hsa-miR-30b-3p-RAB37 may be potential RNA regulatory pathways. Seven upregulated mRNAs were verified using the GSE118481 dataset and RT-qPCR. The regulatory network included seven mRNAs, five circRNAs, six lncRNAs, and 14 TFs. We propose five circRNAs (hsacirc_028744, hsacirc_037219, hsacirc_006308, hsacirc_013887, and hsacirc_045622), six lncRNAs (EPB41L4A-AS1, LINC00969, GAS5, MIR4435-1HG, MIR503HG, and SNHG16), and seven mRNAs (RAB37, CCR7, CD3D, TRAT1, VWF, ICAM2, and TMEM244) as potential biomarkers related to the progression of T2DM complicated with CAP. The constructed ceRNA network has important implications for potential RNA regulatory pathways.

Construction of the circRNA-miRNA-mRNA Regulatory Network of an Abdominal Aortic Aneurysm to Explore Its Potential Pathogenesis

Background

Abdominal aortic aneurysm (AAA) is a progressive cardiovascular disease, which is a permanent and localized dilatation of the abdominal aorta with potentially fatal consequence of aortic rupture. Dysregulation of circRNAs is correlated with the development of various pathological events in cardiovascular diseases. However, the function of circRNAs in abdominal aortic aneurysm (AAA) is unknown and remains to be explored. This study is aimed at determining the regulatory mechanisms of circRNAs in AAAs. This study was aimed at exploring the underlying molecular mechanisms of abdominal aortic aneurysms based on the competing endogenous RNA (ceRNA) regulatory hypothesis of circRNA, miRNA, and mRNA.

Methods

The expression profiles of circRNAs (GSE144431), miRNAs (GSE62179), and mRNAs (GSE7084, GSE57691, and GSE47472) in human tissue sample from the aneurysm group and normal group were obtained from the Gene Expression Omnibus database, respectively. The circRNA-miRNA-mRNA network was constructed by using Cytoscape 3.7.2 software; then, the protein-protein interaction (PPI) network was constructed by using the STRING database, and the hub genes were identified by using the cytoHubba plug-in. The circRNA-miRNA-hub gene regulatory subnetwork was formed to understand the regulatory axis of hub genes in AAAs.

Results

The present study identified 40 differentially expressed circRNAs (DECs) in the GSE144431, 90 differentially expressed miRNAs (DEmiRs) in the GSE62179, and 168 differentially expressed mRNAs (DEGs) with the same direction regulation (130 downregulated and 38 upregulated) in the GSE7084, GSE57691, and GSE47472 datasets identified regarding AAAs. The miRNA response elements (MREs) of three DECs were then predicted. Four overlapping miRNAs were obtained by intersecting the predicted miRNA and DEmiRs. Then, 17 overlapping mRNAs were obtained by intersecting the predicted target mRNAs of 4 miRNAs with 168 DEGs. Furthermore, the circRNA-miRNA-mRNA network was constructed through 3 circRNAs, 4 miRNAs, and 17 mRNAs, and three hub genes (SOD2, CCR7, and PGRMC1) were identified. Simultaneously, functional enrichment and pathway analysis were performed within genes in the circRNA-miRNA-mRNA network. Three of them (SOD2, CCR7, and PGRMC1) were suggested to be crucial based on functional enrichment, protein-protein interaction, and ceRNA network analysis. Furthermore, the expression of SOD2 and CCR7 may be regulated by hsa_circ_0011449/hsa_circ_0081968/hsa-let-7f-5p; the expression of PGRMC1 may be regulated by hsa_circ_0011449/hsa_circ_0081968-hsa-let-7f-5p/hsa-let-7e-5p.

Conclusion

In conclusion, the ceRNA interaction axis we identified may be an important target for the treatment of abdominal aortic aneurysms. This study provided further understanding of the potential pathogenesis from the perspective of the circRNA-related competitive endogenous RNA network in AAAs.

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.

The pathogenic importance of CCL21 and CCR7 in rheumatoid arthritis

Innate and adaptive immunity regulate the inflammatory and erosive phenotypes observed in rheumatoid arthritis (RA) patients. Hence, identifying novel pathways that participate in different stages of RA pathology will provide valuable insights concerning the mechanistic behavior of different joint leukocytes and the strategy to restrain their activity. Recent findings have revealed that CCL21 poses as a risk factor for RA and expression of its receptor, CCR7, on circulating monocytes is representative of the patient's disease activity score. Expression of CCR7 was found to be the hallmark of RA synovial fluid (SF) M1 macrophages (MФs) and its levels were potentiated in response to M1 mediating factors and curtailed by M2 mediators in naïve MФs. Intriguingly, although both CCR7 ligands, CCL19 and CCL21, are elevated in RA specimens, only CCL21 was predominately responsible for CCR7's pathological manifestation of RA. Unique subset of MФs differentiated in response to CCL21 stimulation, exhibited upregulation in Th17-polarizing monokines. Moreover, CCL21-activated monokines were capable of differentiating naïve T cells into joint Th17 cells, which also partook in RA osteoclastogenesis. Finally, to conserve chronic inflammation, SF CCL21 amplified RA neovascularization directly and indirectly by promoting RA FLS and MΦs to secrete proangiogenic factors, VEGF and IL-17. This review aims to shed light on the broad pathogenic impact of CCL21, linking immunostimulatory MФs with Th17 cells, while concurrently advancing RA bone destruction and neovascularization.

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.

The differential role of CR3 (CD11b/CD18) and CR4 (CD11c/CD18) in the adherence, migration and podosome formation of human macrophages and dendritic cells under inflammatory conditions

CR3 and CR4, the leukocyte specific β2-integrins, involved in cellular adherence, migration and phagocytosis, are often assumed to have similar functions. Previously however, we proved that under physiological conditions CR4 is dominant in the adhesion to fibrinogen of human monocyte-derived macrophages (MDMs) and dendritic cells (MDDCs). Here, using inflammatory conditions, we provide further evidence that the expression and function of CR3 and CR4 are not identical in these cell types. We found that LPS treatment changes their expression differently on MDMs and MDDCs, suggesting a cell type specific regulation. Using mAb24, specific for the high affinity conformation of CD18, we proved that the activation and recycling of β2-integrins is significantly enhanced upon LPS treatment. Adherence to fibrinogen was assessed by two fundamentally different approaches: a classical adhesion assay and a computer-controlled micropipette, capable of measuring adhesion strength. While both receptors participated in adhesion, we demonstrated that CR4 exerts a dominant role in the strong attachment of MDDCs. Studying the formation of podosomes we found that MDMs retain podosome formation after LPS activation, whereas MDDCs lose this ability, resulting in a significantly reduced adhesion force and an altered cellular distribution of CR3 and CR4. Our results suggest that inflammatory conditions reshape differentially the expression and role of CR3 and CR4 in macrophages and dendritic cells.

Symptomatic Carotid Atherosclerotic Plaques Are Associated With Increased Infiltration of Natural Killer (NK) Cells and Higher Serum Levels of NK Activating Receptor Ligands

A wide array of immune cells, including lymphocytes, is known to be present and to play a pathogenetic role in atherosclerotic lesions. However, limited information is currently available regarding the presence of Natural Killer (NK) cell subsets within vessel plaque, and more in general, regarding their role in human atherosclerosis. We evaluated the distribution of NK cells in human carotid atherosclerotic plaques, dissecting asymptomatic and symptomatic patients (identified as affected by stroke, transient ischemic attack, or amaurosis fugax within 6 months) with the aim of shedding light on the putative contribution of NK cells to the pathogenic process that leads to plaque instability and subsequent clinical complications. We observed that carotid plaques were consistently infiltrated by NK cells and, among them, CD56^brightperforin^low NK cells were abundantly present and displayed different markers of tissue residency (i.e., CD103 CD69 and CD49a). Interestingly, carotid atherosclerotic plaques of symptomatic patients showed a higher content of NK cells and an increased ratio between CD56^brightperforin^low NK cells and their CD56^dimperforin^high counterpart. NK cells isolated from plaques of symptomatic patients were also stronger producers of IFN-γ. Analysis of the expression of NK activating receptor ligands (including MICA/B, ULBP-3, and B7-H6) in atherosclerotic carotid plaques revealed that they were abundantly expressed by a HLA-DR⁺CD11c⁺ myeloid cell population resident in the plaques. Remarkably, sera of symptomatic patients contained significant higher levels of soluble ligands for NK activating receptors. Our observations indicate that CD56^bright NK cells accumulate within human atherosclerotic lesions and suggest a possible contribution of NK cells to the process determining plaque instability.

CCL21 as a Potential Serum Biomarker for Pulmonary Arterial Hypertension in Systemic Sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is a major cause of pulmonary arterial hypertension (PAH). Murine models indicate key roles for chemokines CCL19 and CCL21 and their receptor CCR7 in lung inflammation leading to PAH. The objective of this study was to assess the chemokine CCL19-CCL21 axis in patients with SSc-related PAH.

METHODS

Serum samples obtained from 2 independent prospective SSc cohorts (n = 326), patients with idiopathic PAH (n = 12), and healthy control subjects (n = 100) were analyzed for CCL19/CCL21 levels, by enzyme-linked immunosorbent assay. The levels were defined as either high or low, using the mean + 2 SD value in controls as the cutoff value. Risk stratification at the time of PAH diagnosis and PAH-related events were performed. Descriptive and Cox regression analyses were conducted.

RESULTS

CCL21 levels were higher in patients with SSc compared with controls and were elevated prior to the diagnosis of PAH. PAH was more frequent in patients with high CCL21 levels (≥0.4 ng/ml) than in those with low CCL21 levels (33.3% versus 5.3% [P < 0.001]). In multivariate analyses, CCL21 was associated with PAH (hazard ratio [HR] 5.1, 95% CI 2.39-10.76 [P < 0.001]) and occurrence of PAH-related events (HR 4.7, 95% CI 2.12-10.46, P < 0.001). Risk stratification at the time of PAH diagnosis alone did not predict PAH-related events. However, when risk at diagnosis was combined with high or low CCL21 level, there was a significant predictive effect (HR 1.3, 95% CI 1.03-1.60 [P = 0.027]). A high CCL21 level was associated with decreased survival (P < 0.001).

CONCLUSION

CCL21 appears to be a promising marker for predicting the risk of SSc-related PAH and PAH progression. CCL21 may be part of a dysregulated immune pathway linked to the development of lung vascular damage in SSc.

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.

Regulation of CCR7-dependent cell migration through CCR7 homodimer formation

The chemokine receptor CCR7 contributes to various physiological and pathological processes including T cell maturation, T cell migration from the blood into secondary lymphoid tissues, and tumor cell metastasis to lymph nodes. Although a previous study suggested that the efficacy of CCR7 ligand-dependent T cell migration correlates with CCR7 homo- and heterodimer formation, the exact extent of contribution of the CCR7 dimerization remains unclear. Here, by inducing or disrupting CCR7 dimers, we demonstrated a direct contribution of CCR7 homodimerization to CCR7-dependent cell migration and signaling. Induction of stable CCR7 homodimerization resulted in enhanced CCR7-dependent cell migration and CCL19 binding, whereas induction of CXCR4/CCR7 heterodimerization did not. In contrast, dissociation of CCR7 homodimerization by a novel CCR7-derived synthetic peptide attenuated CCR7-dependent cell migration, ligand-dependent CCR7 internalization, ligand-induced actin rearrangement, and Akt and Erk signaling in CCR7-expressing cells. Our study indicates that CCR7 homodimerization critically regulates CCR7 ligand-dependent cell migration and intracellular signaling in multiple cell types.

Recent advances on CD4+ T cells in atherosclerosis and its implications for therapy

Atherosclerosis is an arterial inflammatory disease and the primary cause of cardiovascular disease. T helper (Th) cells are an important part in atherosclerotic plaque as they can be either disease promoting or protective. A body of evidence points to a pro-atherosclerotic role of Th1 cells, whereas the role of Th2, Th17 and iNKT cells seems more complex and dependent on surrounding factors, including the developmental stage of the disease. Opposed to Th1 cells, there is convincing support for an anti-atherogenic role of Tregs. Recent data identify the plasticity of Th cells as an important challenge in understanding the functional role of different Th cell subsets in atherosclerosis. Much of the knowledge of Th cell function in atherosclerosis is based on findings from experimental models and translating this into human disease is challenging. Targeting Th cells and/or their specific cytokines represents an attractive option for future therapy against atherosclerosis, although the benefits and the risk of modulation of Th cells with these novel drug targets must first be carefully assessed.

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.

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.

Loss of Gadkin Affects Dendritic Cell Migration In Vitro

Migration is crucial for the function of dendritic cells (DCs), which act as outposts of the immune system. Upon detection of pathogens, skin- and mucosa-resident DCs migrate to secondary lymphoid organs where they activate T cells. DC motility relies critically on the actin cytoskeleton, which is regulated by the actin-related protein 2/3 (ARP2/3) complex, a nucleator of branched actin networks. Consequently, loss of ARP2/3 stimulators and upstream Rho family GTPases dramatically impairs DC migration. However, nothing is known yet about the relevance of ARP2/3 inhibitors for DC migration. We previously demonstrated that the AP-1-associated adaptor protein Gadkin inhibits ARP2/3 by sequestering it on intracellular vesicles. Consistent with a role of Gadkin in DC physiology, we here report Gadkin expression in bone marrow-derived DCs and show that its protein level and posttranslational modification are regulated upon LPS-induced DC maturation. DCs derived from Gadkin-deficient mice were normal with regards to differentiation and maturation, but displayed increased actin polymerization. While the actin-dependent processes of macropinocytosis and cell spreading were not affected, loss of Gadkin significantly impaired DC migration in vitro, however, in vivo DC migration was unperturbed suggesting the presence of compensatory mechanisms.

Differential ligand-signaling network of CCL19/CCL21-CCR7 system

Chemokine (C-C motif) receptor 7 (CCR7), a class A subtype G-Protein Coupled Receptor (GPCR), is involved in the migration, activation and survival of multiple cell types including dendritic cells, T cells, eosinophils, B cells, endothelial cells and different cancer cells. Together, CCR7 signaling system has been implicated in diverse biological processes such as lymph node homeostasis, T cell activation, immune tolerance, inflammatory response and cancer metastasis. CCL19 and CCL21, the two well-characterized CCR7 ligands, have been established to be differential in their signaling through CCR7 in multiple cell types. Although the differential ligand signaling through single receptor have been suggested for many receptors including GPCRs, there exists no resource or platform to analyse them globally. Here, first of its kind, we present the cell-type-specific differential signaling network of CCL19/CCL21-CCR7 system for effective visualization and differential analysis of chemokine/GPCR signaling.

Database URL:http:// www. netpath. org/ pathways? path_ id= NetPath_ 46.

Increased Eotaxin and MCP-1 Levels in Serum from Individuals with Periodontitis and in Human Gingival Fibroblasts Exposed to Pro-Inflammatory Cytokines

Periodontitis is a chronic inflammatory disease of tooth supporting tissues resulting in periodontal tissue destruction, which may ultimately lead to tooth loss. The disease is characterized by continuous leukocyte infiltration, likely mediated by local chemokine production but the pathogenic mechanisms are not fully elucidated. There are no reliable serologic biomarkers for the diagnosis of periodontitis, which is today based solely on the degree of local tissue destruction, and there is no available biological treatment tool. Prompted by the increasing interest in periodontitis and systemic inflammatory mediators we mapped serum cytokine and chemokine levels from periodontitis subjects and healthy controls. We used multivariate partial least squares (PLS) modeling and identified monocyte chemoattractant protein-1 (MCP-1) and eotaxin as clearly associated with periodontitis along with C-reactive protein (CRP), years of smoking and age, whereas the number of remaining teeth was associated with being healthy. Moreover, body mass index correlated significantly with serum MCP-1 and CRP, but not with eotaxin. We detected higher MCP-1 protein levels in inflamed gingival connective tissue compared to healthy but the eotaxin levels were undetectable. Primary human gingival fibroblasts displayed strongly increased expression of MCP-1 and eotaxin mRNA and protein when challenged with tumor necrosis factor-α (TNF-α and interleukin-1β (IL-1β), key mediators of periodontal inflammation. We also demonstrated that the upregulated chemokine expression was dependent on the NF-κΒ pathway. In summary, we identify higher levels of CRP, eotaxin and MCP-1 in serum of periodontitis patients. This, together with our finding that both CRP and MCP-1 correlates with BMI points towards an increased systemic inflammatory load in patients with periodontitis and high BMI. Targeting eotaxin and MCP-1 in periodontitis may result in reduced leukocyte infiltration and inflammation in periodontitis and maybe prevent tooth loss.

CCL19 and CCL21 modulate the inflammatory milieu in atherosclerotic lesions

Despite advances in the pharmacologic and interventional treatment of coronary artery disease, atherosclerosis remains the leading cause of death worldwide. Atherosclerosis is a chronic inflammatory disease, and elevated expression of CCL19 and CCL21 has been observed in ruptured lesions of coronary arteries of patients with myocardial infarction and carotid plaques of patients with ischemic symptoms, as well as in plasma of coronary artery disease patients. However, the exact role of CCL19 and CCL21 in atherosclerosis remains unknown. In order to identify CCL19 and CCL21 as a novel therapeutic target, we performed bone marrow transplantation as an immunomodulatory treatment concept. Bone marrow of plt/plt mice (lacking CCL19 and CCL21-Ser) was transplanted into atherogenic Ldlr(-/-) mice. The study demonstrated a significantly increased inflammatory cellular infiltration into the lesions of plt/plt/Ldlr(-/-) mice versus controls. Although the level of chemoattraction was increased, messenger ribonucleic acid and protein levels in thoracic aorta and serum of several proinflammatory cytokines (TNFα, IFNγ, IL-6, IL-12, and IL-17) were significantly reduced in plt/plt/Ldlr(-/-) versus control mice. Increased influx, accompanied by reduced activation of leukocytes in atherosclerotic lesion, was accompanied by increased plaque stability but unchanged lesion development. In conclusion, modulation of the chemokines CCL19 and CCL21 represents a potent immunoregulatory treatment approach, and thus represents a novel therapeutic target to stabilize atherosclerotic lesions.

Emerging regulators of vascular smooth muscle cell function in the development and progression of atherosclerosis

After a period of relative senescence in the field of vascular smooth muscle cell (VSMC) research with particular regards to atherosclerosis, the last few years has witnessed a resurgence, with extensive research re-assessing potential molecular mechanisms and pathways that modulate VSMC behaviour within the atherosclerotic-prone vessel wall and the atherosclerotic plaque itself. Attention has focussed on the pathological contribution of VSMC in plaque calcification; systemic and local mediators such as inflammatory molecules and lipoproteins; autocrine and paracrine regulators which affect cell-cell and cell to matrix contacts alongside cytoskeletal changes. In this brief focused review, recent insights that have been gained into how a myriad of recently identified factors can influence the pathological behaviour of VSMC and their subsequent contribution to atherosclerotic plaque development and progression has been discussed. An overriding theme is the mechanisms involved in the alterations of VSMC function during atherosclerosis.