Expression and Cellular Localization of CXCR4 and CXCL12 in Human Carotid Atherosclerotic Plaques

Identification of common mechanisms and biomarkers for dermatomyositis and atherosclerosis based on bioinformatics analysis

BACKGROUND

Dermatomyositis (DM) manifests as an autoimmune and inflammatory condition, clinically characterized by subacute progressive proximal muscle weakness, rashes or both along with extramuscular manifestations. Literature indicates that DM shares common risk factors with atherosclerosis (AS), and they often co-occur, yet the etiology and pathogenesis remain to be fully elucidated. This investigation aims to utilize bioinformatics methods to clarify the crucial genes and pathways that influence the pathophysiology of both DM and AS.

METHOD

Microarray datasets for DM (GSE128470, GSE1551, GSE143323) and AS (GSE100927, GSE28829, GSE43292) were retrieved from the Gene Expression Omnibus (GEO) database. The weighted gene co-expression network analysis (WGCNA) was used to reveal their co-expressed modules. Differentially expression genes (DEGs) were identified using the "limma" package in R software, and the functions of common DEGs were determined by functional enrichment analysis. A protein-protein interaction (PPI) network was established using the STRING database, with central genes evaluated by the cytoHubba plugin, and validated through external datasets. Immune infiltration analysis of the hub genes was conducted using the CIBERSORT method, along with Gene Set Enrichment Analysis (GSEA). Finally, the NetworkAnalyst platform was employed to examine the transcription factors (TFs) responsible for regulating pivotal crosstalk genes.

RESULTS

Utilizing WGCNA analysis, a total of 271 overlapping genes were pinpointed. Subsequent DEG analysis revealed 34 genes that are commonly found in both DM and AS, including 31 upregulated genes and 3 downregulated genes. The Degree Centrality algorithm was applied separately to the WGCNA and DEG collections to select the 15 genes with the highest connectivity, and crossing the two gene sets yielded 3 hub genes (PTPRC, TYROBP, CXCR4). Validation with external datasets showed their diagnostic value for DM and AS. Analysis of immune infiltration indicates that lymphocytes and macrophages are significantly associated with the pathogenesis of DM and AS. Moreover, GSEA analysis suggested that the shared genes are enriched in various receptor interactions and multiple cytokines and receptor signaling pathways. We coupled the 3 hub genes with their respective predicted genes, identifying a potential key TF, CBFB, which interacts with all 3 hub genes.

CONCLUSION

This research utilized comprehensive bioinformatics techniques to explore the shared pathogenesis of DM and AS. The three key genes, including PTPRC, TYROBP, and CXCR4, are related to the pathogenesis of DM and AS. The central genes and their correlations with immune cells may serve as potential diagnostic and therapeutic targets.

Top Five Stories of the Cellular Landscape and Therapies of Atherosclerosis: Current Knowledge and Future Perspectives

Atherosclerosis (AS) is characterized by impairment and apoptosis of endothelial cells, continuous systemic and focal inflammation and dysfunction of vascular smooth muscle cells, which is documented as the traditional cellular paradigm. However, the mechanisms appear much more complicated than we thought since a bulk of studies on efferocytosis, transdifferentiation and novel cell death forms such as ferroptosis, pyroptosis, and extracellular trap were reported. Discovery of novel pathological cellular landscapes provides a large number of therapeutic targets. On the other side, the unsatisfactory therapeutic effects of current treatment with lipid-lowering drugs as the cornerstone also restricts the efforts to reduce global AS burden. Stem cell- or nanoparticle-based strategies spurred a lot of attention due to the attractive therapeutic effects and minimized adverse effects. Given the complexity of pathological changes of AS, attempts to develop an almighty medicine based on single mechanisms could be theoretically challenging. In this review, the top stories in the cellular landscapes during the initiation and progression of AS and the therapies were summarized in an integrated perspective to facilitate efforts to develop a multi-targets strategy and fill the gap between mechanism research and clinical translation. The future challenges and improvements were also discussed.

CircMETTL14(11)S upregulated METTL14 and induced CXCR4 to aggravate endothelial inflammation and atherosclerosis

Endothelial inflammatory response can induce a variety of cardiovascular diseases, including atherosclerosis (AS). As a member of the m6A methyltransferase family, methyltransferase like 14 (METTL14) was reported to propel endothelial inflammation and aggravate AS. In this study, qRT-PCR and western blot analyses were performed to detect the RNA and protein levels of genes. To analyze the cyclic structure and localization of circMETTL14(11)S, agarose gel electrophoresis, subcellular fractionation and FISH assays were conducted. The role of circMETTL14(11)S on endothelial inflammation was exposed by monocyte adhesion assay. Luciferase reporter, chromatin immunoprecipitation (ChIP), pull-down and RNA binding protein immunoprecipitation (RIP) assays were conducted to explore the mechanism of circMETTL14(11)S on endothelial inflammation and AS. We found that circMETTL14(11)S (hsa_circ_0125169) expressed highly in TNF-α-induced endothelial inflammation and positively regulated the expression of METTL14 in human umbilical vein endothelial cells (HUVECs). CircMETTL14(11)S facilitated endothelial inflammation of HUVECs by METTL14. Based on the nuclear location, circMETTL14(11)S was found to activate METTL14 transcription via cooperating with SRY-box transcription factor 2 (SOX2). METTL14 accelerated the m6A methylation and stabilization of C-X-C motif chemokine receptor 4 (CXCR4) mRNA. Further, the facilitation of circMETTL14(11)S/METTL14/CXCR4 on TNF-α-induced endothelial inflammation of HUVECs was verified. Collectively, circMETTL14(11)S/METTL14/CXCR4 axis aggravated endothelial inflammation and AS.

DEL-1 suppression attenuates atherosclerosis by modulating macrophagic GSK-3β/CEBP-β signaling pathway

OBJECTIVE

The study aims to investigate the effect of developmental endothelial locus-1(DEL-1) expression in atherosclerotic plaque formation and its mechanism.

METHODS

Human left coronary arteries were collected to detect the DEL-1 expression. The ApoE-/- mice were used to establish the atherosclerosis mice model. The left coronary artery and mouse aorta were stained with HE, Oil Red O, and Movat staining. The DEL-1 levels, chemokines CXC chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1alpha (SDF-1α), pathway protein glycogen synthase kinase-3β (GSK-3β), CCAAT enhanced binding protein β (C/EBPβ), and downstream inflammatory factors (C-X-C motif chemokine 2 (MIP-2or CXCL2), macrophage inflammatory protein-1alpha (MIP-1α or CCL3),Tumor Necrosis Factor alpha (TNF-α) were detected by immunoblotting and immunohistochemistry. Pearson correlation coefficient was used to analyze the correlation between DEL-1 gene expression and inflammatory factors in the lesion group and the correlation between DEL-1 gene expression and structure-related indexes.

RESULTS

Compared with Control group(CON), the intravascular plaque area was widened, accompanied by narrowed lumens. The number of plaque foam cells was significantly increased in the high fat and high cholesterol (AS group) or AAV9-eGFP group (P < 0.05). Compared to CON, the enhanced fluorescence intensity of DEL-1 with CD68 in the AS or AAV9-eGFP groups. Diminished fluorescence of DEL-1 with CD68 expression in AAV9-CXCR4 group compared to AS group or AAV9-eGFP group. The DEL-1 and its downstream proteins in AS group or AAV9-eGFP group were mainly accumulated in the macrophage cytoplasm. The DEL-1 expression level was significantly and positively correlated with plaque area, lumen stenosis, plaque foam cell count, TNFα, CXCL2, and CCL3 levels.

CONCLUSION

DEL-1 inhibition decreases macrophagic inflammatory factors involved in atherosclerotic plaque formation.

CXCR4 - a possible serum marker for risk stratification of abdominal aortic aneurysms

Background: Abdominal aortic aneurysm (AAA) rupture is still associated with a mortality rate of 80-90%. Imaging techniques or molecular fingerprinting for patient-specific risk stratification to identify pending rupture are still lacking. The chemokine (C-X-C motif) receptor (CXCR4) activation by CXCL12 ligand has been identified as a marker of inflammation and atherosclerosis, associated with AAA. Both are highly expressed in the aortic aneurysm wall. However, it is still unclear whether different expression levels of CXCR4 and CXCL12 can distinguish ruptured AAAs (rAAA) from intact AAAs (iAAA). Patients and methods: Abdominal aortic tissue samples (rAAA: n=29; iAAA: n=54) were excised during open aortic repair. Corresponding serum samples from these patients (n=9 from rAAAs; n=47 from iAAA) were drawn pre-surgery. Healthy aortic tissue samples (n=8) obtained from adult kidney donors during transplantation and serum samples from healthy adult volunteers were used as controls (n=5 each). Results: CXCR4 was mainly expressed in the media of the aneurysmatic tissue. Focal positive staining was also observed in areas of inflammatory infiltrates within the adventitia. In tissue lysates, no significant differences between iAAA, rAAA, and healthy controls were observed upon ELISA analysis. In serum samples, the level of CXCR4 was significantly increased in rAAA by 4-fold compared to healthy controls (p=0.011) and 3.0-fold for rAAA compared to iAAA (p<0.001). Furthermore a significant positive correlation between aortic diameter and serum CXCR4 concentration was found for both, iAAA and rAAA (p=0.042). Univariate logistic regression analysis showed that increased CXCR4 serum concentrations were associated with AAA rupture (OR: 4.28, 95% CI: 1.95-12.1, p=0.001). Conclusions: CXCR4 concentration was significantly increased in serum of rAAA patients and showed a significant correlation with an increased aortic diameter. The level of CXCR4 in serum was associated with a more than 4-fold risk increase for rAAA and thus could possibly serve as a biomarker in the future. However, further validation in larger studies is required.

Human Cytomegalovirus Infection and Cardiovascular Disease: Current Perspectives

Infections with human cytomegalovirus (HCMV) are often asymptomatic in healthy adults but can be severe in people with a compromised immune system. While several studies have demonstrated associations between cardiovascular disease in older adults and HCMV seropositivity, the underlying mechanisms are unclear. We review evidence published within the last 5 years establishing how HCMV can contribute directly and indirectly to the development and progression of atherosclerotic plaques. We also discuss associations between HCMV infection and cardiovascular outcomes in populations with a high or very high burden of HCMV, including patients with renal or autoimmune disease, transplant recipients, and people living with HIV.

Zedoarondiol inhibits atherosclerosis by regulating monocyte migration and adhesion via CXCL12/CXCR4 pathway

Atherosclerosis (AS) is an essential pathological changes of ischemic cardio-cerebrovascular disease, and monocyte migration and adhesion to endothelial cells are the critical pathological process in AS. Our previous studies demonstrated a beneficial effect of zedoarondiol in AS, but whether the mechanism is associated with monocyte migration and adhesion to endothelial cells remains unclear. In this study, we investigated whether the anti-atherosclerotic effects of zedoarondiol were associated with decreasing migration and adhesion of monocytes. The oil red O staining demonstrated that zedoarondiol ameliorated AS plaques in en face aorta and aortic root of apolipoprotein E gene knocked (apoE^-/-) mice. In vitro, zedoarondiol decreased human monocytic macrophage-like cell line (THP-1) monocytes migration and adhesion to endothelial cells. Single-cell RNA sequencing analysis (scRNA-seq) in mice indicated that zedoarondiol decreased monocytes adhesion to endothelial cells by regulating CXC chemokine ligand 12/CXC chemokine receptor 4 (CXCL12/CXCR4) pathway, which was verified by Western blot of THP-1 monocytes；zedoarondiol also decreased the expressions of phosphoinositide 3-kinase (PI3K), protein kinase B (AKT) and nuclear factor-kappa B (NF/κB), the downstream proteins of CXCL12/CXCR4 pathway. In conclusion, zedoarondiol ameliorated AS plaque and inhibited monocyte migration and adhesion to endothelial cells via regulating CXCL12/CXCR4 pathway, suggesting that zedoarondiol might be a new promising drug for AS.

Accuracy of PET quantification in [68Ga]Ga-pentixafor PET/MR imaging of carotid plaques

AIM

The aim of this study was to evaluate and correct for partial-volume-effects (PVE) on [68Ga]Ga-Pentixafor uptake in atherosclerotic plaques of the carotid arteries, and the impact of ignoring bone in MR-based attenuation correction (MR-AC).

METHODS

Twenty [68Ga]Ga-pentixafor PET/MR examinations including a high-resolution T2-TSE MR of the neck were included in this study. Carotid plaques located at the carotid bifurcation were delineated and the anatomical information was used for partial-volume-correction (PVC). Mean and max tissue-to-background ratios (TBR) of the [68Ga]Ga-Pentixafor uptake were compared for standard and PVC-PET images. A potential influence of ignoring bone in MR-AC was assessed in a subset of the data reconstructed after incorporating bone into MR-AC and a subsequent comparison of standardized-uptake values (SUV).

RESULTS

In total, 34 atherosclerotic plaques were identified. Following PVC, mean and max TBR increased by 77 and 95%, respectively, when averaged across lesions. When accounting for bone in the MR-AC, SUV of plaque changed by 0.5%.

CONCLUSION

Quantitative readings of [68Ga]Ga-pentixafor uptake in plaques are strongly affected by PVE, which can be reduced by PVC. Including bone information into the MR-AC yielded no clinically relevant effect on tracer quantification.

Macrophage-Specific IGF-1 Overexpression Reduces CXCL12 Chemokine Levels and Suppresses Atherosclerotic Burden in Apoe-Deficient Mice

OBJECTIVE

IGF-1 (insulin-like growth factor 1) exerts pleiotropic effects including promotion of cellular growth, differentiation, survival, and anabolism. We have shown that systemic IGF-1 administration reduced atherosclerosis in Apoe^-/- (apolipoprotein E deficient) mice, and this effect was associated with a reduction in lesional macrophages and a decreased number of foam cells in the plaque. Almost all cell types secrete IGF-1, but the effect of macrophage-derived IGF-1 on the pathogenesis of atherosclerosis is poorly understood. We hypothesized that macrophage-derived IGF-1 will reduce atherosclerosis. Approach and Results: We created macrophage-specific IGF-1 overexpressing mice on an Apoe^-/- background. Macrophage-specific IGF-1 overexpression reduced plaque macrophages, foam cells, and atherosclerotic burden and promoted features of stable atherosclerotic plaque. Macrophage-specific IGF1 mice had a reduction in monocyte infiltration into plaque, decreased expression of CXCL12 (CXC chemokine ligand 12), and upregulation of ABCA1 (ATP-binding cassette transporter 1), a cholesterol efflux regulator, in atherosclerotic plaque and in peritoneal macrophages. IGF-1 prevented oxidized lipid-induced CXCL12 upregulation and foam cell formation in cultured THP-1 macrophages and increased lipid efflux. We also found an increase in cholesterol efflux in macrophage-specific IGF1-derived peritoneal macrophages.

CONCLUSIONS

Macrophage IGF-1 overexpression reduced atherosclerotic burden and increased features of plaque stability, likely via a reduction in CXCL12-mediated monocyte recruitment and an increase in ABCA1-dependent macrophage lipid efflux.

Emerging Roles of the Atypical Chemokine Receptor 3 (ACKR3) in Cardiovascular Diseases

Chemokines, and their receptors play a crucial role in the pathophysiology of cardiovascular diseases (CVD). Chemokines classically mediate their effects by binding to G-protein-coupled receptors. The discovery that chemokines can also bind to atypical chemokine receptors (ACKRs) and initiate alternative signaling pathways has changed the paradigm regarding chemokine-related functions. Among these ACKRs, several studies have highlighted the exclusive role of ACKR3, previously known as C-X-C chemokine receptor type 7 (CXCR7), in CVD. Indeed, ACKR3 exert atheroprotective, cardioprotective and anti-thrombotic effects through a wide range of cells including endothelial cells, platelets, inflammatory cells, fibroblasts, vascular smooth muscle cells and cardiomyocytes. ACKR3 functions as a scavenger receptor notably for the pleiotropic chemokine CXCL12, but also as a activator of different pathways such as β-arrestin-mediated signaling or modulator of CXCR4 signaling through the formation of ACKR3-CXCR4 heterodimers. Hence, a better understanding of the precise roles of ACKR3 may pave the way towards the development of novel and improved therapeutic strategies for CVD. Here, we summarize the structural determinant characteristic of ACKR3, the molecules targeting this receptor and signaling pathways modulated by ACKR3. Finally, we present and discuss recent findings regarding the role of ACKR3 in CVD.

Role and implications of the CXCL12/CXCR4/CXCR7 axis in atherosclerosis: still a debate

Atherosclerosis is one of the leading causes of mortality and morbidity worldwide. Chemokines and their receptors are implicated in the pathogenesis of atherosclerosis. CXCL12 is a member of the chemokine family exerting a myriad role in atherosclerosis through its classical CXCR4 and atypical ACKR3 (CXCR7) receptors. The modulatory and regulatory functional spectrum of CXCL12/CXCR4/ACKR3 axis in atherosclerosis spans from proatherogenic, prothrombotic and proinflammatory to atheroprotective, plaque stabilizer and dyslipidemia rectifier. This diverse continuum is executed in a wide range of biological units including endothelial cells (ECs), progenitor cells, macrophages, monocytes, platelets, lymphocytes, neutrophils and vascular smooth muscle cells (VSMCs) through complex heterogeneous and homogenous coupling of CXCR4 and ACKR3 receptors, employing different downstream signalling pathways, which often cross-talk among themselves and with other signalling interactomes. Hence, a better understanding of this structural and functional heterogeneity and complex phenomenon involving CXCL12/CXCR4/ACKR3 axis in atherosclerosis would not only help in formulation of novel therapeutics, but also in elucidation of the CXCL12 ligand and its receptors, as possible diagnostic and prognostic biomarkers.Key messagesThe role of CXCL12 per se is proatherogenic in atherosclerosis development and progression.The CXCL12 receptors, CXCR4 and ACKR3 perform both proatherogenic and athero-protective functions in various cell typesDue to functional heterogeneity and cross talk of CXCR4 and ACKR3 at receptor level and downstream pathways, regional boosting with specific temporal and spatial modulators of CXCL12, CXCR4 and ACKR3 need to be explored.

In Vivo Targeting of CXCR4-New Horizons

Given its pre-eminent role in the context of tumor cell growth as well as metastasis, the C-X-C motif chemokine receptor 4 (CXCR4) has attracted a lot of interest in the field of nuclear oncology, and clinical evidence on the high potential of CXCR4-targeted theranostics is constantly accumulating. Additionally, since CXCR4 also represents a key player in the orchestration of inflammatory responses to inflammatory stimuli, based on its expression on a variety of pro- and anti-inflammatory immune cells (e.g., macrophages and T-cells), CXCR4-targeted inflammation imaging has recently gained considerable attention. Therefore, after briefly summarizing the current clinical status quo of CXCR4-targeted theranostics in cancer, this review primarily focuses on imaging of a broad spectrum of inflammatory diseases via the quantification of tissue infiltration with CXCR4-expressing immune cells. An up-to-date overview of the ongoing preclinical and clinical efforts to visualize inflammation and its resolution over time is provided, and the predictive value of the CXCR4-associated imaging signal for disease outcome is discussed. Since the sensitivity and specificity of CXCR4-targeted immune cell imaging greatly relies on the availability of suitable, tailored imaging probes, recent developments in the field of CXCR4-targeted imaging agents for various applications are also addressed.

Imaging Inflammation in Patients and Animals: Focus on PET Imaging the Vulnerable Plaque

Acute coronary syndrome (ACS) describes a range of conditions associated with the rupture of high-risk or vulnerable plaque. Vulnerable atherosclerotic plaque is associated with many changes in its microenvironment which could potentially cause rapid plaque progression. Present-day PET imaging presents a plethora of radiopharmaceuticals designed to image different characteristics throughout plaque progression. Improved knowledge of atherosclerotic disease pathways has facilitated a growing number of pathophysiological targets for more innovative radiotracer design aimed at identifying at-risk vulnerable plaque and earlier intervention opportunity. This paper reviews the efficacy of PET imaging radiotracers ¹⁸F-FDG, ¹⁸F-NaF, ⁶⁸Ga-DOTATATE, ⁶⁴Cu-DOTATATE and ⁶⁸Ga-pentixafor in plaque characterisation and risk assessment, as well as the translational potential of novel radiotracers in animal studies. Finally, we discuss our murine PET imaging experience and the challenges encountered.

Impact of cholesterol on proinflammatory monocyte production by the bone marrow

AIM

Preclinical work indicates that low-density lipoprotein cholesterol (LDL-C) not only drives atherosclerosis by directing the innate immune response at plaque level but also augments proinflammatory monocyte production in the bone marrow (BM) compartment. In this study, we aim to unravel the impact of LDL-C on monocyte production in the BM compartment in human subjects.

METHODS AND RESULTS

A multivariable linear regression analysis in 12 304 individuals of the EPIC-Norfolk prospective population study showed that LDL-C is associated with monocyte percentage (β = 0.131 [95% CI: 0.036-0.225]; P = 0.007), at the expense of granulocytes (β = -0.876 [95% CI: -1.046 to -0.705]; P < 0.001). Next, we investigated whether altered haematopoiesis could explain this monocytic skewing by characterizing CD34+ BM haematopoietic stem and progenitor cells (HSPCs) of patients with familial hypercholesterolaemia (FH) and healthy normocholesterolaemic controls. The HSPC transcriptomic profile of untreated FH patients showed increased gene expression in pathways involved in HSPC migration and, in agreement with our epidemiological findings, myelomonocytic skewing. Twelve weeks of cholesterol-lowering treatment reverted the myelomonocytic skewing, but transcriptomic enrichment of monocyte-associated inflammatory and migratory pathways persisted in HSPCs post-treatment. Lastly, we link hypercholesterolaemia to perturbed lipid homeostasis in HSPCs, characterized by lipid droplet formation and transcriptomic changes compatible with increased intracellular cholesterol availability.

CONCLUSIONS

Collectively, these data highlight that LDL-C impacts haematopoiesis, promoting both the number and the proinflammatory activation of circulating monocytes. Furthermore, this study reveals a potential contributory role of HSPC transcriptomic reprogramming to residual inflammatory risk in FH patients despite cholesterol-lowering therapy.

Single systemic transfer of a human gene associated with exceptional longevity halts the progression of atherosclerosis and inflammation in ApoE knockout mice through a CXCR4-mediated mechanism

Aims

Here, we aimed to determine the therapeutic effect of longevity-associated variant (LAV)-BPIFB4 gene therapy on atherosclerosis.

Methods and results

ApoE knockout mice (ApoE^−/−) fed a high-fat diet were randomly allocated to receive LAV-BPIFB4, wild-type (WT)-BPIFB4, or empty vector via adeno-associated viral vector injection. The primary endpoints of the study were to assess (i) vascular reactivity and (ii) atherosclerotic disease severity, by Echo-Doppler imaging, histology and ultrastructural analysis. Moreover, we assessed the capacity of the LAV-BPIFB4 protein to shift monocyte-derived macrophages of atherosclerotic mice and patients towards an anti-inflammatory phenotype. LAV-BPIFB4 gene therapy rescued endothelial function of mesenteric and femoral arteries from ApoE^−/− mice; this effect was blunted by AMD3100, a CXC chemokine receptor type 4 (CXCR4) inhibitor. LAV-BPIFB4-treated mice showed a CXCR4-mediated shift in the balance between Ly6C^high/Ly6C^low monocytes and M2/M1 macrophages, along with decreased T cell proliferation and elevated circulating levels of interleukins IL-23 and IL-27. In vitro conditioning with LAV-BPIFB4 protein of macrophages from atherosclerotic patients resulted in a CXCR4-dependent M2 polarization phenotype. Furthermore, LAV-BPIFB4 treatment of arteries explanted from atherosclerotic patients increased the release of atheroprotective IL-33, while inhibiting the release of pro-inflammatory IL-1β, inducing endothelial nitric oxide synthase phosphorylation and restoring endothelial function. Finally, significantly lower plasma BPIFB4 was detected in patients with pathological carotid stenosis (>25%) and intima media thickness >2 mm.

Conclusion

Transfer of the LAV of BPIFB4 reduces the atherogenic process and skews macrophages towards an M2-resolving phenotype through modulation of CXCR4, thus opening up novel therapeutic possibilities in cardiovascular disease.

Association of SDF1 and MMP12 with Atherosclerosis and Inflammation: Clinical and Experimental Study

BACKGROUND

Atherosclerosis is the main etiology of cardiovascular diseases (CVD), associated to systemic inflammation. Matrix metalloproteinases (MMPs) are related to atherosclerosis progression through the SDF1/CXCR4 axis promoting macrophages recruitment within the vascular wall. The goal was to assess new circulatory inflammatory markers in relation to atherosclerosis.

METHODS

Measurement of SDF1, MMP12 and CRP in blood samples of 298 prospective patients with cardiovascular risk. To explore atherosclerosis progression, CXCR4/SDF1 axis and MMP12 expression were determined by RT-qPCR and by immunohistochemistry in the aorta of accelerated and delayed atherosclerosis mice models (Apoe-/- and Apoe-/-Mmp10-/-).

RESULTS

SDF1, MMP12 and CRP were elevated in patients with clinical atherosclerosis, but after controlling by confounding factors, only SDF1 and CRP remained increased. Having high levels of both biomarkers showed 2.8-fold increased risk of presenting clinical atherosclerosis (p = 0.022). Patients with elevated SDF1, MMP12 and CRP showed increased risk of death in follow-up (HR = 3.2, 95%CI: 1.5-7.0, p = 0.004). Gene and protein expression of CXCR4 and MMP12 were increased in aortas from Apoe-/- mice.

CONCLUSIONS

The combination of high circulating SDF1, MMP12 and CRP identified patients with particular inflammatory cardiovascular risk and increased mortality. SDF1/CXCR4 axis and MMP12 involvement in atherosclerosis development suggests that they could be possible atherosclerotic targets.

Association of the increased circulating CD62LloCXCR4hi neutrophil count with carotid atherosclerosis

Introduction. The role of neutrophils in the initiation and progression of atherosclerosis as well as in the development of its complications has received scientific attention only in the recent years. Today, there is growing evidence to support a role of the CXCL12/CXCR4 axis in sustained inflammation during different chronic inflammatory diseases by retaining neutrophils at inflammatory sites.The aim of the study is to assess the diagnostic and prognostic significance of circulating CD62LloCXCR4 hi neutrophils in patients with carotid atherosclerosis.Materials and methods. A total of 75 patients (52% of men and 48% of women) aged 40 to 64 years were examined. None of them were diagnosed with atherosclerotic cardiovascular diseases. All the patients underwent carotid artery duplex scanning. The flow cytometry and CD16, CD11b, CD62L, CD182 (CXCR2) and CD184 (CXCR4) conjugated monoclonal antibodies were used for phenotyping and differentiation of neutrophil subpopulations.Results. Atherosclerotic plaques in carotid arteries were detected in 72% of the patients; most of the patients were diagnosed with stenosis development in more than one of the carotid arteries (CA). The elevated levels of circulating CXCR4h neutrophils were associated with the levels of total cholesterol (r = 0.377; p = 0.001), low-density lipoprotein (LDL) cholesterol (r = 0.293; p = 0.014) and triglycerides (r = 0.388; p = 0.003). The study revealed direct correlation between the circulating CXCR4 hi neutrophil count and the cumulative percentage of CA stenosis (r = 0.300; p = 0.011), including the number of stenosed CA (r = 0.291; p = 0.034). It was also found that CXCR4 hi neutrophil counts demonstrated a statistically significant increase along with the increased number of stenosed CA (p = 0.025). The ROC analysis findings show that the elevated CXCR4 hi neutrophil counts ≥260 cells/μL made it possible to diagnose stenotic lesion of 4 CAs with a sensitivity of 71.4% and specificity reaching 76.6%.Conclusion. In patients with carotid atherosclerosis, the increased count of circulating CD62LloCXCR4 hi neutrophils was associated with the increased number of stenosed CAs, while no significant changes were observed in the other examined subpopulations of neutrophil granulocytes. The increased CD62LloCXCR4 hi neutrophil count made it possible to diagnose stenotic lesion of 4 CAs with a sufficient sensitivity and specificity.

Autoradiographical assessment of inflammation-targeting radioligands for atherosclerosis imaging: potential for plaque phenotype identification

PURPOSE

Many radioligands have been developed for the visualization of atherosclerosis by targeting inflammation. However, interpretation of in vivo signals is often limited to plaque identification. We evaluated binding of some promising radioligands in an in vitro approach in atherosclerotic plaques with different phenotypes.

METHODS

Tissue sections of carotid endarterectomy tissue were characterized as early plaque, fibro-calcific plaque, or phenotypically vulnerable plaque. In vitro binding assays for the radioligands [111In]In-DOTATATE; [111In]In-DOTA-JR11; [67Ga]Ga-Pentixafor; [111In]In-DANBIRT; and [111In]In-EC0800 were conducted, the expression of the radioligand targets was assessed via immunohistochemistry. Radioligand binding and expression of radioligand targets was investigated and compared.

RESULTS

In sections characterized as vulnerable plaque, binding was highest for [111In]In-EC0800; followed by [111In]In-DANBIRT; [67Ga]Ga-Pentixafor; [111In]In-DOTA-JR11; and [111In]In-DOTATATE (0.064 ± 0.036; 0.052 ± 0.029; 0.011 ± 0.003; 0.0066 ± 0.0021; 0.00064 ± 0.00014 %Added activity/mm2, respectively). Binding of [111In]In-DANBIRT and [111In]In-EC0800 was highest across plaque phenotypes, binding of [111In]In-DOTA-JR11 and [67Ga]Ga-Pentixafor differed most between plaque phenotypes. Binding of [111In]In-DOTATATE was the lowest across plaque phenotypes. The areas positive for cells expressing the radioligand's target differed between plaque phenotypes for all targets, with lowest percentage area of expression in early plaque sections and highest in phenotypically vulnerable plaque sections.

CONCLUSIONS

Radioligands targeting inflammatory cell markers showed different levels of binding in atherosclerotic plaques and among plaque phenotypes. Different radioligands might be used for plaque detection and discerning early from vulnerable plaque. [111In]In-EC0800 and [111In]In-DANBIRT appear most suitable for plaque detection, while [67Ga]Ga-Pentixafor and [111In]In-DOTA-JR11 might be best suited for differentiation between plaque phenotypes.

Association of Pericardiac Adipose Tissue With Coronary Artery Disease

BACKGROUND AND AIM

Coronary artery disease (CAD) poses a worldwide health threat. Compelling evidence shows that pericardial adipose tissue (PAT), a brown-like adipose adjacent to the external surface of the pericardium, is associated with CAD. However, the specific molecular mechanisms of PAT in CAD are elusive. This study aims to characterize human PAT and explore its association with CAD.

METHODS

We acquired samples of PAT from 31 elective cardiac surgery patients (17 CAD patients and 14 controls). The transcriptome characteristics were assessed in 5 CAD patients and 4 controls via RNA-sequencing. Cluster profile R package, String database, Cytoscape were applied to analyze the potential pathways and PPI-network key to DEGS, whereas the hubgenes were predicted via Metascape, Cytohubba, and MCODE. We use Cibersort, ENCORI, and DGIDB to predict immunoinfiltration, mRNA-miRNA target gene network, and search potential drugs targeting key DEGs. The predictable hubgenes and infiltrating inflammatory cells were validated in 22 patients (12 CAD samples and 10 control samples) through RT-qPCR and immunohistochemistry.

RESULTS

A total of 147 different genes (104 up-regulated genes and 43 down-regulated genes) were identified in CAD patients. These different genes were associated with immunity and inflammatory dysfunction. Cibersort analysis showed monocytes and macrophages were the most common subsets in immune cells, whereas immunohistochemical results revealed there were more macrophages and higher proportion of M1 subtype cells in PAT of CAD patients. The PPI network and module analysis uncovered several crucial genes, defined as candidate genes, including Jun, ATF3, CXCR4, FOSB, CCl4, which were validated through RT-qPCR. The miRNA-mRNA network implicated hsa-miR-185-5p as diagnostic targets and drug-gene network showed colchicine, fenofibrate as potential therapeutic drugs, respectively.

CONCLUSION

This study demonstrates that PAT is mainly associated with the occurrence of CAD following the dysfunction of immune and inflammatory processes. The identified hubgenes, predicted drugs and miRNAs are promising biomarkers and therapeutic targets for CAD.

Targeting Platelet in Atherosclerosis Plaque Formation: Current Knowledge and Future Perspectives

Besides their role in hemostasis and thrombosis, it has become increasingly clear that platelets are also involved in many other pathological processes of the vascular system, such as atherosclerotic plaque formation. Atherosclerosis is a chronic vascular inflammatory disease, which preferentially develops at sites under disturbed blood flow with low speeds and chaotic directions. Hyperglycemia, hyperlipidemia, and hypertension are all risk factors for atherosclerosis. When the vascular microenvironment changes, platelets can respond quickly to interact with endothelial cells and leukocytes, participating in atherosclerosis. This review discusses the important roles of platelets in the plaque formation under pro-atherogenic factors. Specifically, we discussed the platelet behaviors under disturbed flow, hyperglycemia, and hyperlipidemia conditions. We also summarized the molecular mechanisms involved in vascular inflammation during atherogenesis based on platelet receptors and secretion of inflammatory factors. Finally, we highlighted the studies of platelet migration in atherogenesis. In general, we elaborated an atherogenic role of platelets and the aspects that should be further studied in the future.

Distinct systemic cytokine networks in symptomatic and asymptomatic carotid stenosis

Inflammatory processes are crucial in atherosclerosis and atherothrombosis. This study aimed to identify a cytokine-pattern that is associated with plaque-vulnerability or symptomatic state in comprehensively investigated patients with symptomatic (sCS) and asymptomatic carotid stenosis (aCS). Twenty-two patients with sCS and twenty-four patients with aCS undergoing carotid endarterectomy (CEA) were considered. A cytokine-panel was measured in plasma-specimens prior to surgery and at a 90 day follow-up. Doppler-ultrasound detecting microembolic signals (MES) in the ipsilateral middle cerebral artery was performed. Carotid plaques were analysed regarding histopathological criteria of plaque-vulnerability and presence of chemokine receptor CXCR4. Correction for multiple comparisons and logistic regression analysis adjusting for vascular risk factors, grade of stenosis, antithrombotic and statin pretreatment were applied. In sCS-patients higher plasma-levels of Fractalkine (CX₃CL1), IFN-α2, IL-1β, IL-2, IL-3, IL-7 were found compared to aCS-patients. CXCR4-expression on inflammatory cells was more evident in sCS- compared to aCS-plaques and was associated with vulnerability-criteria. In contrast, plasma-cytokine-levels were not related to CXCR4-expression or other vulnerability-criteria or MES. However, in both groups distinct inter-cytokine correlation patterns, which persisted at follow-up and were more pronounced in the sCS-group could be detected. In conclusion, we identified a distinct cytokine/chemokine-network in sCS-patients with elevated and closely correlated mediators of diverse functions.

Designed CXCR4 mimic acts as a soluble chemokine receptor that blocks atherogenic inflammation by agonist-specific targeting

Targeting a specific chemokine/receptor axis in atherosclerosis remains challenging. Soluble receptor-based strategies are not established for chemokine receptors due to their discontinuous architecture. Macrophage migration-inhibitory factor (MIF) is an atypical chemokine that promotes atherosclerosis through CXC-motif chemokine receptor-4 (CXCR4). However, CXCR4/CXCL12 interactions also mediate atheroprotection. Here, we show that constrained 31-residue-peptides ('msR4Ms') designed to mimic the CXCR4-binding site to MIF, selectively bind MIF with nanomolar affinity and block MIF/CXCR4 without affecting CXCL12/CXCR4. We identify msR4M-L1, which blocks MIF- but not CXCL12-elicited CXCR4 vascular cell activities. Its potency compares well with established MIF inhibitors, whereas msR4M-L1 does not interfere with cardioprotective MIF/CD74 signaling. In vivo-administered msR4M-L1 enriches in atherosclerotic plaques, blocks arterial leukocyte adhesion, and inhibits atherosclerosis and inflammation in hyperlipidemic Apoe-/- mice in vivo. Finally, msR4M-L1 binds to MIF in plaques from human carotid-endarterectomy specimens. Together, we establish an engineered GPCR-ectodomain-based mimicry principle that differentiates between disease-exacerbating and -protective pathways and chemokine-selectively interferes with atherosclerosis.

Immunotherapy for cardiovascular disease

The outcomes of the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) trial have unequivocally proven that inflammation is a key driver of atherosclerosis and that targeting inflammation, in this case by using an anti-interleukin-1β antibody, improves cardiovascular disease (CVD) outcomes. This is especially true for CVD patients with a pro-inflammatory constitution. Although CANTOS has epitomized the importance of targeting inflammation in atherosclerosis, treatment with canakinumab did not improve CVD mortality, and caused an increase in infections. Therefore, the identification of novel drug targets and development of novel therapeutics that block atherosclerosis-specific inflammatory pathways and exhibit limited immune-suppressive side effects, as pursued in our collaborative research centre, are required to optimize immunotherapy for CVD. In this review, we will highlight the potential of novel immunotherapeutic targets that are currently considered to become a future treatment for CVD.

New Insights for BPIFB4 in Cardiovascular Therapy

Aging is the most relevant risk factor for cardiovascular diseases which are the main cause of mortality in industrialized countries. In this context, there is a progressive loss of cardiovascular homeostasis that translates in illness and death. The study of long living individuals (LLIs), which show compression of morbidity toward the end of their life, is a valuable approach to find the key to delay aging and postpone associate cardiovascular events. A contribution to the age-related decline of cardiovascular system (CVS) comes from the immune system; indeed, it is dysfunctional during aging, a process described as immunosenescence and comprises the combination of several processes overpowering both innate and adaptative immune system. We have recently discovered a longevity-associated variant (LAV) in bactericidal/permeability-increasing fold-containing family B member 4 (BPIFB4), which is a secreted protein able to enhance endothelial function through endothelial nitric oxide synthase (eNOS) activation and capable to protect from hypertension, atherosclerosis, diabetic cardiopathy, frailty, and inflammaging. Here, we sum up the state of the art of the mechanisms involved in the main pathological processes related to CVD (atherosclerosis, aging, diabetic cardiopathy, and frailty) and shed light on the therapeutic effects of LAV-BPIFB4 in these contexts.

TLR2/CXCR4 coassociation facilitatesChlamydia pneumoniaeinfection-induced atherosclerosis

Toll-like receptor 2 (TLR2) and C-X-C motif chemokine receptor 4 (CXCR4) have both been shown to be involved in atherosclerosis. We demonstrate for the first time the presence of TLR2/CXCR4 coassociation during C. pneumoniae infection-induced atherosclerosis. Amazingly, blocking of both TLR2 and CXCR4 significantly retards and even almost reverses this infection-induced atherosclerosis. Our work reveals new mechanisms about C. pneumoniae infection-induced atherosclerosis and identifies potential new therapeutic targets for the prevention and treatment of atherosclerosis.

In silico analysis of the molecular regulatory networks in peripheral arterial occlusive disease

BACKGROUND

Peripheral arterial occlusive disease (PAOD) is a global public health concern that decreases the quality of life of the patients and can lead to disabilities and death. The aim of this study was to identify the genes and pathways associated with PAOD pathogenesis, and the potential therapeutic targets.

METHODS

Differentially expressed genes (DEGs) and miRNAs related to PAOD were extracted from the GSE57691 dataset and through text mining. Additionally, bioinformatics analysis was applied to explore gene ontology, pathways and protein-protein interaction of those DEGs. The potential miRNAs targeting the DEGs and the transcription factors (TFs) regulating miRNAs were predicted by multiple different databases.

RESULTS

A total of 59 DEGs were identified, which were significantly enriched in the inflammatory response, immune response, chemokine-mediated signaling pathway and JAK-STAT signaling pathway. Thirteen genes including IL6, CXCL12, IL1B, and STAT3 were hub genes in protein-protein interaction network. In addition, 513 miRNA-target gene pairs were identified, of which CXCL12 and PTPN11 were the potential targets of miRNA-143, and IL1B of miRNA-21. STAT3 was differentially expressed and regulated 27 potential target miRNAs including miRNA-143 and miRNA-21 in TF-miRNA regulatory network.

CONCLUSION

In summary, inflammation, immune response and STAT3-mediated miRNA-target genes axis play an important role in PAOD development and progression.

Extracellular ubiquitin levels are increased in coronary heart disease and associated with the severity of the disease

Aim: This study aimed to evaluate concentration of plasma extracellular ubiquitin (UB) in coronary heart disease (CHD) patients and its correlation with the disease severity.Methods: Levels of UB and stromal cell-derived factor-1a (SDF-1a) were measured in 60 healthy controls and 67 CHD cases. Coronary atherosclerosis was assessed with Gensini scoring system. Spearman correlation was used to evaluate the correlation between UB and low-density lipoprotein cholesterol (LDL-C), C-reactive protein (CRP), creatine kinase-MB (CK-MB), cardiac troponin I (cTnI) or SDF-1a. The receiver-operating characteristic (ROC) curve was established to assess the predictive value of UB.Results: Plasma UB levels were significantly higher in CHD patients than in controls (p < .0001), and the levels in those with acute myocardial infarction (AMI) were higher than stable angina pectoris (SAP) and unstable angina pectoris (UAP) groups (both p < .01). UB was also positively correlated with Gensini score, CRP, CK-MB and cTnI in CHD. ROC analysis of UB showed that the area under the curve (AUC) were 0.711 (95%CI, 0.623-0.799) and 0.778 (95%CI, 0.666-0.890) for CHD and acute coronary syndrome (ACS), respectively. Plasma SDF-1a levels were elevated in CHD patients but showed no significant correlation with UB concentration or the severity of the disease.Conclusion: Plasma UB concentration was increased in CHD and the change of UB levels may reflect the progression of CHD.

Current and novel radiopharmaceuticals for imaging cardiovascular inflammation

Cardiovascular disease (CVD) remains the leading cause of death worldwide despite advances in diagnostic technologies and treatment strategies. The underlying cause of most CVD is atherosclerosis, a chronic disease driven by inflammatory reactions. Atherosclerotic plaque rupture could cause arterial occlusion leading to ischemic tissue injuries such as myocardial infarction (MI) and stroke. Clinically, most imaging modalities are based on anatomy and provide limited information about the on-going molecular activities affecting the vulnerability of atherosclerotic lesion for risk stratification of patients. Thus, the ability to differentiate stable plaques from those that are vulnerable is an unmet clinical need. Of various imaging techniques, the radionuclide-based molecular imaging modalities including positron emission tomography and single-photon emission computerized tomography provide superior ability to noninvasively visualize molecular activities in vivo and may serve as a useful tool in tackling this challenge. Moreover, the well-established translational pathway of radiopharmaceuticals may also facilitate the translation of discoveries from benchtop to clinical investigation in contrast to other imaging modalities to fulfill the goal of precision medicine. The relationship between inflammation occurring within the plaque and its proneness to rupture has been well documented. Therefore, an active effort has been significantly devoted to develop radiopharmaceuticals specifically to measure CVD inflammatory status, and potentially elucidate those plaques which are prone to rupture. In the following review, molecular imaging of inflammatory biomarkers will be briefly discussed.

Infection and Inflammation Imaging: Beyond FDG

This review discusses nuclear imaging of inflammation using molecular probes beyond fluoro-d-glucose, is structured by cellular targets, and focuses on those tracers that have been successfully applied clinically.

IGFBP6 Is Downregulated in Unstable Carotid Atherosclerotic Plaques According to an Integrated Bioinformatics Analysis and Experimental Verification

Aims: To investigate the differentially expressed genes (DEGs) and molecular interaction in unstable atherosclerotic carotid plaques.

Methods: Gene expression datasets GSE41571, GSE118481, and E-MTAB-2055 were analyzed. Co-regulated DEGs in at least two datasets were analyzed with the enrichment of Gene Ontology Biological Process (GO-BP), Kyoto Encyclopedia of Genes and Genomes (KEGG), protein-protein interaction (PPI) networks, interrelationships between miRNAs/transcriptional factors, and their target genes and drug-gene interactions. The expression of notable DEGs in human carotid artery plaques and plasma was further identified.

Results: The GO-BP enrichment analysis revealed that genes associated with inflammatory response, and extracellular matrix organization were altered. The KEGG enrichment analysis revealed that upregulated DEGs were enriched in the tuberculous, lysosomal, and chemokine signaling pathways, whereas downregulated genes were enriched in the focal adhesion and PI3K/Akt signaling pathway. Collagen type I alpha 2 chain (COL1A2), adenylate cyclase 3 (ADCY3), C-X-C motif chemokine receptor 4 (CXCR4), and TYRO protein tyrosine kinase binding protein (TYROBP) might play crucial roles in the PPI networks. In drug–gene interactions, colony-stimulating factor-1 receptor had the most drug interactions. Insulin-like growth factor binding protein 6 (IGFBP6) was markedly downregulated in unstable human carotid plaques and plasma. Under a receiver operating characteristic curve analysis, plasma IGFBP6 had a significant discriminatory power (AUC, 0.894; 95% CI, 0.810–0.977), with a cutoff value of 142.08 ng/mL.

Conclusions: The genes COL1A2, ADCY3, CXCR4, and TYROBP are promising targets for the prevention of unstable carotid plaque formation. IGFBP6 may be an important biomarker for predicting vulnerable plaques.

Foam cells promote atherosclerosis progression by releasing CXCL12

BACKGROUND

Atherosclerosis (AS) is a chronic inflammatory disease that contributes to multiple cardiovascular diseases (CVDs), and foam cell formation plays important roles in the progression of AS. There is an urgent need to identify new molecular targets for treating AS, and thereby improve the quality of life and reduce the financial burden of individuals with CVD.

METHODS

An in vitro model of AS was generated by treating THP-1 cells and human aortic vascular smooth muscle cells (HA-VSMCs) with oxidized low-density lipoproteins (ox-LDLs). HA-VSMC proliferation and foam cell formation were detected by the MTT assay and Oil Red O staining. C-X-C motif chemokine 12 (CXCL12) expression was suppressed by siRNA. An AS rat model was established by feeding rats a high-fat diet and vitamin D2 for 3 weeks. Histopathology examinations were conducted by Hematoxylin and Eosin (H&E) staining and the levels ionized calcium-binding adapter molecule 1 (IBA1) and α smooth muscle actin (α-SMA) expression were determined by ELISA assays and immunohistochemistry.

RESULTS

An in vitro model of AS was established with THP-1 cells. CXCL12 expression in the model THP-1 cells was significantly increased when compared with its expression in control cells. Suppression of CXCL12 expression reduced the progression of AS in the cell model. Moreover, CXCL12 promoted AS in the in vivo rat model.

CONCLUSION

Our results suggest that CXCL12 plays an important role in promoting the progression of AS. Furthermore, inhibition of CXCL12 might suppress the development of AS by inhibiting HA-VSMC proliferation and their transformation to foam cells.

Foam Cell-Derived CXCL14 Muti-Functionally Promotes Atherogenesis and Is a Potent Therapeutic Target in Atherosclerosis

CXC chemokine family has been related to atherogenesis for long. However, the relationship between CXCL14 and atherogenesis is still unclear. This study preliminarily detected CXCL14 expression at foam cells in atherosclerosis specimens by immunohistochemistry. In vitro foam cells were derived from THP-1 after phorbol-12-myristate-13-acetate (PMA) and oxidized low-density lipoprotein (ox-LDL) stimulation. Immunoblotting and qPCR convinced CXCL14 expression variation during foam cell formation. We further demonstrated that ox-LDL regulated CXCL14 expression by AP-1. AP-1 could bind to CXCL14 promoter and up-regulate CXCL14 mRNA expression. Besides, CXCL14 promoted THP-1 migration, macrophage lipid phagocytosis, and smooth muscle cell migration as well as proliferation mainly via the ERK1/2 pathway. Additionally, a CXCL14 peptide-induced immune therapy showed efficacy in ApoE^-/- mouse model. In conclusion, our study demonstrated that CXCL14 is highly up-regulated during foam cell formation and promotes atherogenesis in various ways. CXCL14 may be a potent therapeutic target for atherosclerosis.

CXCL12 promotes atherosclerosis by downregulating ABCA1 expression via the CXCR4/GSK3β/β-cateninT120/TCF21 pathway

CXC chemokine ligand 12 (CXCL12) is a member of the CXC chemokine family and mainly acts on cell chemotaxis. CXCL12 also elicits a proatherogenic role, but the molecular mechanisms have not been fully defined yet. We aimed to reveal if and how CXCL12 promoted atherosclerosis via regulating lipid metabolism. In vitro, our data showed that CXCL12 could reduce ABCA1 expression, and it mediated cholesterol efflux from THP-1-derived macrophages to apoA-I. Data from the luciferase reporter gene and chromatin immunoprecipitation assays revealed that transcription factor 21 (TCF21) stimulated the transcription of ABCA1 via binding to its promoter region, which was repressed by CXCL12. We found that CXCL12 increased the levels of phosphorylated glycogen synthase kinase 3β (GSK3β) and the phosphorylation of β-catenin at the Thr120 position. Inactivation of GSK3β or β-catenin increased the expression of TCF21 and ABCA1. Further, knockdown or inhibition of CXC chemokine receptor 4 (CXCR4) blocked the effects of CXCL12 on TCF21 and ABCA1 expression and the phosphorylation of GSK3β and β-catenin. In vivo, the overexpression of CXCL12 in Apoe^-/- mice via lentivirus enlarged the atherosclerotic lesion area and increased macrophage infiltration in atherosclerotic plaques. We further found that the overexpression of CXCL12 reduced the efficiency of reverse cholesterol transport and plasma HDL-C levels, decreased ABCA1 expression in the aorta and mouse peritoneal macrophages (MPMs), and suppressed cholesterol efflux from MPMs to apoA-I in Apoe^-/- mice. Collectively, these findings suggest that CXCL12 interacts with CXCR4 and then activates the GSK-3β/β-catenin^T120/TCF21 signaling pathway to inhibit ABCA1-dependent cholesterol efflux from macrophages and aggravate atherosclerosis. Targeting CXCL12 may be a novel and promising strategy for the prevention and treatment of atherosclerotic cardiovascular diseases.

Imaging Inflammation in Atherosclerosis with CXCR4-Directed 68Ga-Pentixafor PET/CT: Correlation with 18F-FDG PET/CT

C-X-C motif chemokine receptor 4 (CXCR4) is expressed on the surface of various cell types involved in atherosclerosis, with a particularly rich receptor expression on macrophages and T cells. First pilot studies with ⁶⁸Ga-pentixafor, a novel CXCR4-directed PET tracer, have shown promise to noninvasively image inflammation within atherosclerotic plaques. The aim of this retrospective study was to investigate the performance of ⁶⁸Ga-pentixafor PET/CT for imaging atherosclerosis in comparison to ¹⁸F-FDG PET/CT. Methods: Ninety-two patients (37 women and 55 men; mean age, 62 ± 10 y) underwent ⁶⁸Ga-pentixafor and ¹⁸F-FDG PET/CT for staging of oncologic diseases. In these subjects, lesions in the walls of large arteries were identified using morphologic and PET criteria for atherosclerosis (n = 652). Tracer uptake was measured and adjusted for vascular lumen (background) signal by calculation of target-to-background ratios (TBRs) by 2 investigators masked to the other PET scan. On a lesion-to-lesion and patient basis, the TBRs of both PET tracers were compared and additionally correlated to the degree of arterial calcification as quantified in CT. Results: On a lesion-to-lesion basis, ⁶⁸Ga-pentixafor and ¹⁸F-FDG uptake showed a weak correlation (r = 0.28; P < 0.01). ⁶⁸Ga-pentixafor PET identified more lesions (n = 290; TBR ≥ 1.6, P < 0.01) and demonstrated higher uptake than ¹⁸F-FDG PET (1.8 ± 0.5 vs. 1.4 ± 0.4; P < 0.01). The degree of plaque calcification correlated negatively with both ⁶⁸Ga-pentixafor and ¹⁸F-FDG uptake (r = -0.38 vs. -0.31, both P < 0.00001). Conclusion: CXCR4-directed imaging of the arterial wall with ⁶⁸Ga-pentixafor PET/CT identified more lesions than ¹⁸F-FDG PET/CT, with only a weak correlation between tracers. Further studies to elucidate the underlying biologic mechanisms and sources of CXCR4 positivity, and to investigate the clinical utility of chemokine receptor-directed imaging of atherosclerosis, are highly warranted.

Targeting Chemokine Receptor CXCR4 and Translocator Protein for Characterization of High-Risk Plaque in Carotid Stenosis Ex Vivo

Background and Purpose- This pilot study aims to demonstrate the feasibility of targeting molecular characteristics of high-risk atherosclerotic plaque in symptomatic and asymptomatic carotid stenosis (CS), that is, upregulation of the translocator protein (TSPO) and the chemokine receptor type 4 (CXCR4), by means of molecular imaging. Methods- In a translational setting, specimens of carotid plaques of patients with symptomatic and asymptomatic CS obtained by carotid endarterectomy were analyzed for the presence of TSPO and CXCR4 by autoradiography, using the positron emission tomography tracers ¹⁸F-GE180 and ⁶⁸Ga-Pentixafor and evaluated by histopathology. In addition, ⁶⁸Ga-Pentixafor positron emission tomography/computed tomography was performed in a patient with high-grade CS. Results- Distinct patterns of upregulation of TSPO (¹⁸F-GE180 uptake) and CXCR4 (⁶⁸Ga-Pentixafor uptake) were identified in carotid plaque by autoradiography. The spatial distribution was associated with specific histological hallmarks that are established features of high-risk plaque: TSPO upregulation correlated with activated macrophages infiltration, whereas CXCR4 upregulation also corresponded to areas of intraplaque hemorrhage. ⁶⁸Ga-Pentixafor uptake was significantly higher in plaques of symptomatic compared with asymptomatic CS. Clinical positron emission tomography revealed marked ⁶⁸Ga-Pentixafor uptake in carotid plaque of a patient with high-grade CS. Conclusions- Clinical imaging of molecular signatures of high-risk atherosclerotic plaque is feasible and may become a promising diagnostic tool for comprehensive characterization of carotid disease. This methodology provides a platform for future studies targeting carotid plaque.

CXC chemokine ligand 12 (CXCL12) in atherosclerosis: An underlying therapeutic target

CXC chemokine ligand 12 (CXCL12) is a specific chemokine ligand and plays a significant role in cell chemotaxis. Upon binding to CXC chemokine receptor 4 (CXCR4) or CXCR7, CXCL12 can activate different signaling cascades to regulate cell proliferation, migration, and metabolism. CXCL12 exerts a pro-atherogenic action by aggravating multiple pathogenesis of atherogenesis, including dyslipidemia, inflammation, neointima hyperplasia, angiogenesis, and insulin resistance. Serum CXCL12 levels are also markedly increased in patients with atherosclerosis-associated disease. The present review focuses on recent advances in CXCL12 research in the pathogenesis of atherosclerosis together with its clinical values. This may provide insight into potential novel therapies for atherosclerosis.

G-Protein Coupled Receptor Targeting on Myeloid Cells in Atherosclerosis

Atherosclerosis, the underlying cause of the majority of cardiovascular diseases (CVDs), is a lipid-driven, inflammatory disease of the large arteries. Gold standard therapy with statins and the more recently developed proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have improved health conditions among CVD patients by lowering low density lipoprotein (LDL) cholesterol. Nevertheless, a substantial part of these patients is still suffering and it seems that 'just' lipid lowering is insufficient. The results of the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) have now proven that inflammation is a key driver of atherosclerosis and that targeting inflammation improves CVD outcomes. Therefore, the identification of novel drug targets and development of novel therapeutics that block atherosclerosis-specific inflammatory pathways have to be promoted. The inflammatory processes in atherosclerosis are facilitated by a network of immune cells and their subsequent responses. Cell networking is orchestrated by various (inflammatory) mediators which interact, bind and induce signaling. Over the last years, G-protein coupled receptors (GPCRs) emerged as important players in recognizing these mediators, because of their diverse functions in steady state but also and specifically during chronic inflammatory processes - such as atherosclerosis. In this review, we will therefore highlight a selection of these receptors or receptor sub-families mainly expressed on myeloid cells and their role in atherosclerosis. More specifically, we will focus on chemokine receptors, both classical and atypical, formyl-peptide receptors, the chemerin receptor 23 and the calcium-sensing receptor. When information is available, we will also describe the consequences of their targeting which may hold promising options for future treatment of CVD.

[68Ga]Pentixafor PET/MR imaging of chemokine receptor 4 expression in the human carotid artery

Purpose

Type 4 chemokine receptor (CXCR4) plays an important role in immune cell migration during the atherosclerosis progression. We aimed to evaluate [⁶⁸Ga]Pentixafor positron emission tomography (PET) in combination magnetic resonance imaging (MRI) for in vivo quantification of CXCR4 expression in carotid plaques.

Methods

Seventy-two patients with lymphoma were prospectively scheduled for whole body [⁶⁸Ga]Pentixafor PET/MRI with an additional T2-weighted carotid sequence. Volumes of interest (VOIs) were drawn along the carotid bifurcation regions, and the maximum tissue-to-blood ratios (TBR) of [⁶⁸Ga]Pentixafor uptake were calculated. Lesions were categorized into non-eccentric (n = 27), mild eccentric (n = 67), moderately (n = 41) and severely (n = 19) eccentric carotid atherosclerosis. A different cohort of symptomatic patients (n = 10) with carotid stenosis scheduled for thrombendarterectomy (TEA) was separately imaged with 3T MRI with dedicated plaque sequences (time of flight, T1-, and T2-weighted). MRI findings were correlated with histochemical assessment of intact carotid plaques.

Results

At hybrid PET/MRI, we observed significantly increased [⁶⁸Ga]Pentixafor uptake in mildly (mean TBR_max = 1.57 ± 0.27, mean SUV_max = 2.51 ± 0.39), moderately (mean TBR_max = 1.64 ± 0.37, mean SUV_max = 2.61 ± 0.55) and severely eccentric carotids (mean TBR_max = 1.55 ± 0.26, mean SUV_max = 2.40 ± 0.44) as compared to non-eccentric carotids (mean TBR_max = 1.29 ± 0.21, mean SUV_max = 1.77 ± 0.42) (p ≤ 0.05). Histological findings from TEA confirmed that prominent CXCR4 expression was localized within inflamed atheromas and preatheromas. Co-localization of cellular CXCR4 and CD68 expression in the plaque was observed by immunofluorescence staining.

Conclusions

In vivo evaluation of CXCR4 expression in carotid atherosclerotic lesions is feasible using [⁶⁸Ga]Pentixafor PET/MRI. In atherosclerotic plaque tissue, CXCR4 expression might be used as a surrogate marker for inflammatory atherosclerosis.

Imaging of chemokine receptor CXCR4 expression in culprit and nonculprit coronary atherosclerotic plaque using motion-corrected [68Ga]pentixafor PET/CT

Purpose

The chemokine receptor CXCR4 is a promising target for molecular imaging of CXCR4⁺ cell types, e.g. inflammatory cells, in cardiovascular diseases. We speculated that a specific CXCR4 ligand, [⁶⁸Ga]pentixafor, along with novel techniques for motion correction, would facilitate the in vivo characterization of CXCR4 expression in small culprit and nonculprit coronary atherosclerotic lesions after acute myocardial infarction by motion-corrected targeted PET/CT.

Methods

CXCR4 expression was analysed ex vivo in separately obtained arterial wall specimens. [⁶⁸Ga]Pentixafor PET/CT was performed in 37 patients after stent-based reperfusion for a first acute ST-segment elevation myocardial infarction. List-mode PET data were reconstructed to five different datasets using cardiac and/or respiratory gating. Guided by CT for localization, the PET signals of culprit and various groups of nonculprit coronary lesions were analysed and compared.

Results

Ex vivo, CXCR4 was upregulated in atherosclerotic lesions, and mainly colocalized with CD68⁺ inflammatory cells. In vivo, elevated CXCR4 expression was detected in culprit and nonculprit lesions, and the strongest CXCR4 PET signal (median SUV_max 1.96; interquartile range, IQR, 1.55–2.31) was observed in culprit coronary artery lesions. Stented nonculprit lesions (median SUV_max 1.45, IQR 1.23–1.88; P = 0.048) and hot spots in naive remote coronary segments (median SUV_max 1.34, IQR 1.23–1.74; P = 0.0005) showed significantly lower levels of CXCR4 expression. Dual cardiac/respiratory gating provided the strongest CXCR4 PET signal and the highest lesion detectability.

Conclusion

We demonstrated the basic feasibility of motion-corrected targeted PET/CT imaging of CXCR4 expression in coronary artery lesions, which was triggered by vessel wall inflammation but also by stent-induced injury. This novel methodology may serve as a platform for future diagnostic and therapeutic clinical studies targeting the biology of coronary atherosclerotic plaque.

Electronic supplementary material

The online version of this article (10.1007/s00259-018-4076-2) contains supplementary material, which is available to authorized users.