Role of colony-stimulating factors in atherosclerosis

Colony stimulating factor 1 receptor (Csf1r) expressing cell ablation in mafia (macrophage-specific Fas-induced apoptosis) mice alters monocyte landscape and atherosclerotic lesion characteristics

Macrophage infiltration and accumulation in the atherosclerotic lesion are associated with plaque progression and instability. Depletion of macrophages from the lesion might provide valuable insights into plaque stabilization processes. Therefore, we assessed the effects of systemic and local macrophage depletion on atherogenesis. To deplete monocytes/macrophages we used atherosclerosis-susceptible Apoe- /- mice, bearing a MaFIA (macrophage-Fas-induced-apoptosis) suicide construct under control of the Csf1r (CD115) promotor, where selective apoptosis of Csf1r-expressing cells was induced in a controlled manner, by administration of a drug, AP20187. Systemic induction of apoptosis resulted in a decrease in lesion macrophages and smooth-muscle cells. Plaque size and necrotic core size remained unaffected. Two weeks after the systemic depletion of macrophages, we observed a replenishment of the myeloid compartment. Myelopoiesis was modulated resulting in an expansion of CSF1Rlo myeloid cells in the circulation and a shift from Ly6chi monocytes toward Ly6cint and Ly6clo populations in the spleen. Local apoptosis induction led to a decrease in plaque burden and macrophage content with marginal effects on the circulating myeloid cells. Local, but not systemic depletion of Csf1r+ myeloid cells resulted in decreased plaque burden. Systemic depletion led to CSF1Rlo-monocyte expansion in blood, possibly explaining the lack of effects on plaque development.

The contribution of matrix metalloproteinases and their inhibitors to the development, progression, and rupture of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) account for up to 8% of deaths in men aged 65 years and over and 2.2% of women. Patients with AAAs often have atherosclerosis, and intimal atherosclerosis is generally present in AAAs. Accordingly, AAAs are considered a form of atherosclerosis and are frequently referred to as atherosclerotic aneurysms. Pathological observations advocate inflammatory cell infiltration alongside adverse extracellular matrix degradation as key contributing factors to the formation of human atherosclerotic AAAs. Therefore, macrophage production of proteolytic enzymes is deemed responsible for the damaging loss of ECM proteins, especially elastin and fibrillar collagens, which characterise AAA progression and rupture. Matrix metalloproteinases (MMPs) and their regulation by tissue inhibitors metalloproteinases (TIMPs) can orchestrate not only ECM remodelling, but also moderate the proliferation, migration, and apoptosis of resident aortic cells, alongside the recruitment and subsequent behaviour of inflammatory cells. Accordingly, MMPs are thought to play a central regulatory role in the development, progression, and eventual rupture of abdominal aortic aneurysms (AAAs). Together, clinical and animal studies have shed light on the complex and often diverse effects MMPs and TIMPs impart during the development of AAAs. This dichotomy is underlined from evidence utilising broad-spectrum MMP inhibition in animal models and clinical trials which have failed to provide consistent protection from AAA progression, although more encouraging results have been observed through deployment of selective inhibitors. This review provides a summary of the supporting evidence connecting the contribution of individual MMPs to AAA development, progression, and eventual rupture. Topics discussed include structural, functional, and cell-specific diversity of MMP members; evidence from animal models of AAA and comparisons with findings in humans; the dual role of MMPs and the requirement to selectively target individual MMPs; and the advances in identifying aberrant MMP activity. As evidenced, our developing understanding of the multifaceted roles individual MMPs perform during the progression and rupture of AAAs, should motivate clinical trials assessing the therapeutic potential of selective MMP inhibitors, which could restrict AAA-related morbidity and mortality worldwide.

Peptide-Based Vaccine against Breast Cancer: Recent Advances and Prospects

Breast cancer is considered the second-leading cancer after lung cancer and is the most prevalent cancer among women globally. Currently, cancer immunotherapy via vaccine has gained great attention due to specific and targeted immune cell activity that creates a potent immune response, thus providing long-lasting protection against the disease. Despite peptides being very susceptible to enzymatic degradation and poor immunogenicity, they can be easily customized with selected epitopes to induce a specific immune response and particulate with carriers to improve their delivery and thus overcome their weaknesses. With advances in nanotechnology, the peptide-based vaccine could incorporate other components, thereby modulating the immune system response against breast cancer. Considering that peptide-based vaccines seem to show remarkably promising outcomes against cancer, this review focuses on and provides a specific view of peptide-based vaccines used against breast cancer. Here, we discuss the benefits associated with a peptide-based vaccine, which can be a mainstay in the prevention and recurrence of breast cancer. Additionally, we also report the results of recent trials as well as plausible prospects for nanotechnology against breast cancer.

Blockade of IL-6 signaling alleviates atherosclerosis in Tet2-deficient clonal hematopoiesis

Clonal hematopoiesis (CH) increases the risk of atherosclerotic cardiovascular disease possibly due to increased plaque inflammation. Human studies suggest that limitation of interleukin-6 (IL-6) signaling could be beneficial in people with large CH clones, particularly in TET2 CH. Here we show that IL-6 receptor antibody treatment reverses the atherosclerosis promoted by Tet2 CH, with reduction of monocytosis, lesional macrophage burden and macrophage colony-stimulating factor 1 receptor (CSF1R) expression. IL-6 induces expression of Csf1r in Tet2-deficient macrophages through enhanced STAT3 binding to its promoter. In mouse and human Tet2-deficient macrophages, IL-6 increases CSF1R expression and enhances macrophage survival. Treatment with the CSF1R inhibitor PLX3397 reversed accelerated atherosclerosis in Tet2 CH mice. Our study demonstrates the causality of IL-6 signaling in Tet2 CH accelerated atherosclerosis, identifies IL-6-induced CSF1R expression as a critical mechanism and supports blockade of IL-6 signaling as a potential therapy for CH-driven cardiovascular disease.

Macrophage-specific autophagy-related gene HSPB8 is involved in the macrophage polarization in atherosclerosis

BACKGROUND

Atherosclerosis (AS) is a chronic inflammatory disease, as a main cause leading to vascular diseases worldwide. Although increasing studies have focused on macrophages in AS, the exact relating mechanism is still largely unclear. Our study aimed to explore the pathogenic role and diagnostic role of macrophage autophagy related genes (MARGs) in AS.

METHODS

All datasets were downloaded from Gene Expression Omnibus database and Human Autophagy Database. The differential expression analysis and cross analysis were performed to identify candidate MARGs. GO and KEGG enrichment analyses were conducted to obtain the functional information. Moreover, we analyzed the correlation between target gene and macrophage polarization in AS. The correlation between target gene and plaque instability, different stages of AS were also analyzed.

RESULTS

Compared with normal samples, a total of 575 differentially expressed genes (DEGs) were identified in AS samples. A total of 12 overlapped genes were obtained after cross-analysis of the above 575 DEGs and autophagy related genes (ARGs). Then, 10 MARGs were identified in AS samples, which were significantly enriched in 22 KEGG pathways and 61 GO terms. The expression of HSPB8 was significantly down-regulated in atherosclerotic samples compared with normal samples (with largest fold change). Meanwhile, the proportion of M-CSF in low HSPB8 expression AS group was higher than high expression AS group. Furthermore, the expression of HSPB8 was negatively correlated with most inflammatory factors.

CONCLUSION

The downregulation of MARG HSPB8 probably involves in the M2 macrophage polarization in AS samples. HSPB8 is a promising diagnostic marker for AS patients.

Bioinformatic identification of potential biomarkers and therapeutic targets in carotid atherosclerosis and vascular dementia

Background

Vascular disease is the second most common cause of dementia. The prevalence of vascular dementia (VaD) has increased over the past decade. However, there are no licensed treatments for this disease. Carotid atherosclerosis (CAS) is highly prevalent and is the main cause of ischemic stroke and VaD. We studied co-expressed genes to understand the relationships between CAS and VaD and further reveal the potential biomarkers and therapeutic targets of CAS and VaD.

Methods

CAS and VaD differentially expressed genes (DEGs) were identified through bioinformatic analysis Gene Expression Omnibus (GEO) datasets GSE43292 and GSE122063, respectively. Furthermore, a variety of target prediction methods and network analysis approaches were used to assess the protein-protein interaction (PPI) networks, the Gene Ontology (GO) terms, and the pathway enrichment for DEGs, and the top 7 hub genes, coupled with corresponding predicted miRNAs involved in CAS and VaD, were assessed as well.

Result

A total of 60 upregulated DEGs and 159 downregulated DEGs were identified, of which the top 7 hub genes with a high degree of connectivity were selected. Overexpression of these hub genes was associated with CAS and VaD. Finally, the top 7 hub genes were coupled with corresponding predicted miRNAs. hsa-miR-567 and hsa-miR-4652-5p may be significantly associated with CAS and VaD.

Biflavonoids from Ginkgo biloba leaves as a novel anti-atherosclerotic candidate: Inhibition potency and mechanistic analysis

BACKGROUND

Ginkgo biloba L. is one of the oldest trees on earth, and its leaves have been used since ages as herbal medicine to treat cerebrovascular disorders. It is worth noting that in addition to the widely concerned flavonoids and terpenoids, it also contains various thus far neglected biflavonoids. In fact, biflavonoids are flavonoids consisting of apigenin or its derivatives as monomeric scaffold, and are linked via C-C or C-O-C bond.

PURPOSE

Based on the structural similarity of flavonoids, we hypothesized that biflavonoids may play a potential role in the treatment of cerebrovascular diseases. Here, we describe the effectiveness and underlying mechanisms for prevention and treatment of atherosclerosis (AS) by biflavonoids.

STUDY DESIGN AND METHODS

Four main biflavonoids in Ginkgo biloba leaves were screened by oleic acid-induced lipid production in HepG2 cells. The non-covalent effects of biflavonoids on the potential targets of atherosclerosis were screened by reverse targeting and molecular dynamics simulation. The interactions between biflavonoids and potential targets were evaluated by an exogenous cell model, which verified the consistency of the simulation results.

CONCLUSION

Among all four biflavonoids, ginkgetin significantly inhibited oleic acid-induced lipid production in HepG2 cells and reduced total cholesterol and triglyceride levels. The interaction of ginkgetin with CDK2 through π-alkyl and hydrogen bonds increased the binding of molecules and proteins. Ginkgetin arrested the cells in the G1-S phase, which significantly inhibited abnormal cell growth which closely related to the occurrence and development of atherosclerosis. Biflavonoids could be a promising natural medicine for the treatment of atherosclerosis.

miR-223 Exerts Translational Control of Proatherogenic Genes in Macrophages

A significant burden of atherosclerotic disease is driven by inflammation. Recently, microRNAs (miRNAs) have emerged as important factors driving and protecting from atherosclerosis. miR-223 regulates cholesterol metabolism and inflammation via targeting both cholesterol biosynthesis pathway and NF_kB signaling pathways; however, its role in atherosclerosis has not been investigated. We hypothesize that miR-223 globally regulates core inflammatory pathways in macrophages in response to inflammatory and atherogenic stimuli thus limiting the progression of atherosclerosis.

MicroRNAs and Efferocytosis: Implications for Diagnosis and Therapy

About 10-100 billion cells are generated in the human body in a day, and accordingly, 10-100 billion cells predominantly die for maintaining homeostasis. Dead cells generated by apoptosis are also rapidly engulfed by macrophages (Mθs) to be degraded. In case of the inefficient engulfment of apoptotic cells (ACs) via Mθs, they experience secondary necrosis and thus release intracellular materials, which display damage-associated molecular patterns (DAMPs) and result in diseases. Over the last decades, researchers have also reflected on the significant contribution of microRNAs (miRNAs) to autoimmune diseases through the regulation of Mθs functions. Moreover, miRNAs have shown intricate involvement with completely adjusting basic Mθs functions, such as phagocytosis, inflammation, efferocytosis, tumor promotion, and tissue repair. In this review, the mechanism of efferocytosis containing "Find-Me", "Eat-Me", and "Digest-Me" signals is summarized and the biogenesis of miRNAs is briefly described. Finally, the role of miRNAs in efferocytosis is discussed. It is concluded that miRNAs represent promising treatments and diagnostic targets in impaired phagocytic clearance, which leads to different diseases.

Lipid-Laden Macrophages and Inflammation in Atherosclerosis and Cancer: An Integrative View

Atherosclerotic arterial plaques and malignant solid tumors contain macrophages, which participate in anaerobic metabolism, acidosis, and inflammatory processes inherent in the development of either disease. The tissue-resident macrophage populations originate from precursor cells derived from the yolk sac and from circulating bone marrow-derived monocytes. In the tissues, they differentiate into varying functional phenotypes in response to local microenvironmental stimulation. Broadly categorized, the macrophages are activated to polarize into proinflammatory M1 and anti-inflammatory M2 phenotypes; yet, noticeable plasticity allows them to dynamically shift between several distinct functional subtypes. In atherosclerosis, low-density lipoprotein (LDL)-derived cholesterol accumulates within macrophages as cytoplasmic lipid droplets thereby generating macrophage foam cells, which are involved in all steps of atherosclerosis. The conversion of macrophages into foam cells may suppress the expression of given proinflammatory genes and thereby initiate their transcriptional reprogramming toward an anti-inflammatory phenotype. In this particular sense, foam cell formation can be considered anti-atherogenic. The tumor-associated macrophages (TAMs) may become polarized into anti-tumoral M1 and pro-tumoral M2 phenotypes. Mechanistically, the TAMs can regulate the survival and proliferation of the surrounding cancer cells and participate in various aspects of tumor formation, progression, and metastasis. The TAMs may accumulate lipids, but their type and their specific roles in tumorigenesis are still poorly understood. Here, we discuss how the phenotypic and functional plasticity of macrophages allows their multifunctional response to the distinct microenvironments in developing atherosclerotic lesions and in developing malignant tumors. We also discuss how the inflammatory reactions of the macrophages may influence the development of atherosclerotic plaques and malignant tumors, and highlight the potential therapeutic effects of targeting lipid-laden macrophages in either disease.

Neutralization of S100A4 induces stabilization of atherosclerotic plaques: role of smooth muscle cells

AIMS

During atherosclerosis, smooth muscle cells (SMCs) accumulate in the intima where they switch from a contractile to a synthetic phenotype. From porcine coronary artery, we isolated spindle-shaped (S) SMCs exhibiting features of the contractile phenotype and rhomboid (R) SMCs typical of the synthetic phenotype. S100A4 was identified as a marker of R-SMCs in vitro and intimal SMCs, in pig and man. S100A4 exhibits intra- and extracellular functions. In this study, we investigated the role of extracellular S100A4 in SMC phenotypic transition.

METHODS AND RESULTS

S-SMCs were treated with oligomeric recombinant S100A4 (oS100A4), which induced nuclear factor (NF)-κB activation. Treatment of S-SMCs with oS100A4 in combination with platelet-derived growth factor (PDGF)-BB induced a complete SMC transition towards a pro-inflammatory R-phenotype associated with NF-κB activation, through toll-like receptor-4. RNA sequencing of cells treated with oS100A4/PDGF-BB revealed a strong up-regulation of pro-inflammatory genes and enrichment of transcription factor binding sites essential for SMC phenotypic transition. In a mouse model of established atherosclerosis, neutralization of extracellular S100A4 decreased area of atherosclerotic lesions, necrotic core, and CD68 expression and increased α-smooth muscle actin and smooth muscle myosin heavy chain expression.

CONCLUSION

We suggest that the neutralization of extracellular S100A4 promotes the stabilization of atherosclerotic plaques. Extracellular S100A4 could be a new target to influence the evolution of atherosclerotic plaques.

Macrophage Plasticity and Atherosclerosis Therapy

Atherosclerosis is a chronic disease starting with the entry of monocytes into the subendothelium and the subsequent differentiation into macrophages. Macrophages are the major immune cells in atherosclerotic plaques and are involved in the dynamic progression of atherosclerotic plaques. The biological properties of atherosclerotic plaque macrophages determine lesion size, composition, and stability. The heterogenicity and plasticity of atherosclerotic macrophages have been a hotspot in recent years. Studies demonstrated that lipids, cytokines, chemokines, and other molecules in the atherosclerotic plaque microenvironment regulate macrophage phenotype, contributing to the switch of macrophages toward a pro- or anti-atherosclerosis state. Of note, M1/M2 classification is oversimplified and only represent two extreme states of macrophages. Moreover, M2 macrophages in atherosclerosis are not always protective. Understanding the phenotypic diversity and functions of macrophages can disclose their roles in atherosclerotic plaques. Given that lipid-lowering therapy cannot completely retard the progression of atherosclerosis, macrophages with high heterogeneity and plasticity raise the hope for atherosclerosis regression. This review will focus on the macrophage phenotypic diversity, its role in the progression of the dynamic atherosclerotic plaque, and finally discuss the possibility of treating atherosclerosis by targeting macrophage microenvironment.

Cholesterol loading suppresses the atheroinflammatory gene polarization of human macrophages induced by colony stimulating factors

In atherosclerotic lesions, blood-derived monocytes differentiate into distinct macrophage subpopulations, and further into cholesterol-filled foam cells under a complex milieu of cytokines, which also contains macrophage-colony stimulating factor (M-CSF) and granulocyte-macrophage-colony stimulating factor (GM-CSF). Here we generated human macrophages in the presence of either M-CSF or GM-CSF to obtain M-MØ and GM-MØ, respectively. The macrophages were converted into cholesterol-loaded foam cells by incubating them with acetyl-LDL, and their atheroinflammatory gene expression profiles were then assessed. Compared with GM-MØ, the M-MØ expressed higher levels of CD36, SRA1, and ACAT1, and also exhibited a greater ability to take up acetyl-LDL, esterify cholesterol, and become converted to foam cells. M-MØ foam cells expressed higher levels of ABCA1 and ABCG1, and, correspondingly, exhibited higher rates of cholesterol efflux to apoA-I and HDL2. Cholesterol loading of M-MØ strongly suppressed the high baseline expression of CCL2, whereas in GM-MØ the low baseline expression CCL2 remained unchanged during cholesterol loading. The expression of TNFA, IL1B, and CXCL8 were reduced in LPS-activated macrophage foam cells of either subtype. In summary, cholesterol loading converged the CSF-dependent expression of key genes related to intracellular cholesterol balance and inflammation. These findings suggest that transformation of CSF-polarized macrophages into foam cells may reduce their atheroinflammatory potential in atherogenesis.

Febuxostat, a Xanthine Oxidase Inhibitor, Decreased Macrophage Matrix Metalloproteinase Expression in Hypoxia

Macrophages in the atheroma region produce matrix metalloproteinases (MMPs) and decrease plaque stability. Tissue oxygen tension decreases in the arterial wall of the atherosclerotic region. Hypoxia inducible factor (HIF)-1α plays a critical role in the transcriptional activation of hypoxia inducible genes. However, the precise roles of HIF-1α independent pathways in hypoxic responses are largely unknown. Xanthine oxidase (XO) is an enzyme that utilizes molecular oxygen and produces reactive oxygen species (ROS). Here, we show that ROS derived from XO increases MMP-3, -10, and -13 expression in murine macrophages. We found that the transcript levels of macrophage MMP-3, -10, and -13 were increased in hypoxic conditions. Hypoxia induced MMP expression in HIF-1α deficient macrophages. N-acetylcysteine (NAC) or febuxostat, an XO inhibitor, suppressed MMP expression in murine macrophages. Febuxostat decreased the incidence of plaque rupture in apolipoprotein-E-deficient mice. Our results indicate that febuxostat stabilized atherosclerotic plaque via suppressing the activities of macrophage MMP-9 and -13. Febuxostat administration is a potential therapeutic option in the management of atherosclerotic patients.

Galectin-3 Identifies a Subset of Macrophages With a Potential Beneficial Role in Atherosclerosis

OBJECTIVE

Galectin-3 (formerly known as Mac-2), encoded by the LGALS3 gene, is proposed to regulate macrophage adhesion, chemotaxis, and apoptosis. We investigated the role of galectin-3 in determining the inflammatory profile of macrophages and composition of atherosclerotic plaques. Approach and Results: We observed increased accumulation of galectin-3-negative macrophages within advanced human, rabbit, and mouse plaques compared with early lesions. Interestingly, statin treatment reduced galectin-3-negative macrophage accrual in advanced plaques within hypercholesterolemic (apolipoprotein E deficient) Apoe-/- mice. Accordingly, compared with Lgals3+/+:Apoe-/- mice, Lgals3-/-:Apoe-/- mice displayed altered plaque composition through increased macrophage:smooth muscle cell ratio, reduced collagen content, and increased necrotic core area, characteristics of advanced plaques in humans. Additionally, macrophages from Lgals3-/- mice exhibited increased invasive capacity in vitro and in vivo. Furthermore, loss of galectin-3 in vitro and in vivo was associated with increased expression of proinflammatory genes including MMP (matrix metalloproteinase)-12, CCL2 (chemokine [C-C motif] ligand 2), PTGS2 (prostaglandin-endoperoxide synthase 2), and IL (interleukin)-6, alongside reduced TGF (transforming growth factor)-β1 expression and consequent SMAD signaling. Moreover, we found that MMP12 cleaves macrophage cell-surface galectin-3 resulting in the appearance of a 22-kDa fragment, whereas plasma levels of galectin-3 were reduced in Mmp12-/-:Apoe-/- mice, highlighting a novel mechanism where MMP12-dependent cleavage of galectin-3 promotes proinflammatory macrophage polarization. Moreover, galectin-3-positive macrophages were more abundant within plaques of Mmp12-/-:Apoe-/- mice compared with Mmp12+/+:Apoe-/- animals.

CONCLUSIONS

This study reveals a prominent protective role for galectin-3 in regulating macrophage polarization and invasive capacity and, therefore, delaying plaque progression.

Inflammation and its resolution in atherosclerosis: mediators and therapeutic opportunities

Atherosclerosis is a lipid-driven inflammatory disease of the arterial intima in which the balance of pro-inflammatory and inflammation-resolving mechanisms dictates the final clinical outcome. Intimal infiltration and modification of plasma-derived lipoproteins and their uptake mainly by macrophages, with ensuing formation of lipid-filled foam cells, initiate atherosclerotic lesion formation, and deficient efferocytotic removal of apoptotic cells and foam cells sustains lesion progression. Defective efferocytosis, as a sign of inadequate inflammation resolution, leads to accumulation of secondarily necrotic macrophages and foam cells and the formation of an advanced lesion with a necrotic lipid core, indicative of plaque vulnerability. Resolution of inflammation is mediated by specialized pro-resolving lipid mediators derived from omega-3 fatty acids or arachidonic acid and by relevant proteins and signalling gaseous molecules. One of the major effects of inflammation resolution mediators is phenotypic conversion of pro-inflammatory macrophages into macrophages that suppress inflammation and promote healing. In advanced atherosclerotic lesions, the ratio between specialized pro-resolving mediators and pro-inflammatory lipids (in particular leukotrienes) is strikingly low, providing a molecular explanation for the defective inflammation resolution features of these lesions. In this Review, we discuss the mechanisms of the formation of clinically dangerous atherosclerotic lesions and the potential of pro-resolving mediator therapy to inhibit this process.

Ubiquitin Carboxyl Terminal Hydrolase L1 Attenuates TNF-α-Mediated Vascular Smooth Muscle Cell Migration Through Suppression of NF-κB Activation

Ubiquitin carboxyl terminal hydrolase L1 (UCH-L1) is one of the deubiquitinating enzymes in the ubiquitin-proteasome system. It has been shown that UCH-L1 could markedly decrease neointima formation through suppressing vascular smooth muscle cell (VSMC) proliferation in the balloon-injured rat carotid. However, whether UCH-L1 plays roles in VSMC migration remains to be determined. In this study, the primary VSMCs were isolated from aortic media of rats and TNF-α to was used to induce VSMC migration. Using a modified Boyden chamber and wound healing assay, it was found that TNF-α can dose and time-dependently induce VSMC migration with a maximal effect at 10 ng/mL. Moreover, UCH-L1 expression increased gradually with the prolonged induction time at 10 ng/mL of TNF-α. UCH-L1 content in VSMC was then modulated by recombinant adenoviruses expressing UCH-L1 or RNA interference to evaluate its roles in cell migration. The results showed that over-expression of UCH-L1 attenuated VSMC migration, while knockdown of it enhanced cell migration significantly no matter whether TNF-α treatment or not. Finally, the effect of UCH-L1 on NF-κB activation was demonstrated by NF-κB nuclear translocation and DNA binding activity, and the levels of IL-6 and IL-8 in cell culture media were examined by ELISA. It was showed that UCH-L1 over-expression inhibited NF-κB activation and decrease IL-6 and IL-8 levels, while knockdown of it enhanced NF-κB activation and increase IL-6 and IL-8 levels during TNF-α treatment. These data suggest that UCH-L1 can inhibit TNF-α-induced VSMCs migration, and this kind of effect may partially due to its suppression role in NF-κB activation.

Macrophages in vascular inflammation and atherosclerosis

Atherosclerosis is characterized by lipid accumulation and chronic inflammation of the arterial wall, and its main complications-myocardial infarction and ischemic stroke-together constitute the first cause of death worldwide. Accumulation of lipid-laden macrophage foam cells in the intima of inflamed arteries has long been recognized as a hallmark of atherosclerosis. However, in recent years, an unexpected complexity in the mechanisms of macrophage accumulation in lesions, in the protective and pathogenic functions performed by macrophages and how they are regulated has been uncovered. Here, we provide an overview of the latest developments regarding the various mechanisms of macrophage accumulation in lesion, the major functional features of lesion macrophages, and how the plaque microenvironment may affect macrophage phenotype. Finally, we discuss how best to apprehend the heterogeneous ontogeny and functionality of atherosclerotic plaque macrophages and argue that moving away from a rigid nomenclature of arbitrarily defined macrophage subsets would be beneficial for research in the field.

MicroRNA-181b Controls Atherosclerosis and Aneurysms Through Regulation of TIMP-3 and Elastin

Supplemental Digital Content is available in the text.

Rationale:

Atherosclerosis and aneurysms are leading causes of mortality worldwide. MicroRNAs (miRs) are key determinants of gene and protein expression, and atypical miR expression has been associated with many cardiovascular diseases; although their contributory role to atherosclerotic plaque and abdominal aortic aneurysm stability are poorly understood.

Objective:

To investigate whether miR-181b regulates tissue inhibitor of metalloproteinase-3 expression and affects atherosclerosis and aneurysms.

Methods and Results:

Here, we demonstrate that miR-181b was overexpressed in symptomatic human atherosclerotic plaques and abdominal aortic aneurysms and correlated with decreased expression of predicted miR-181b targets, tissue inhibitor of metalloproteinase-3, and elastin. Using the well-characterized mouse atherosclerosis models of Apoe^−/− and Ldlr^−/−, we observed that in vivo administration of locked nucleic acid anti-miR-181b retarded both the development and the progression of atherosclerotic plaques. Systemic delivery of anti-miR-181b in angiotensin II–infused Apoe^−/− and Ldlr^−/− mice attenuated aneurysm formation and progression within the ascending, thoracic, and abdominal aorta. Moreover, miR-181b inhibition greatly increased elastin and collagen expression, promoting a fibrotic response and subsequent stabilization of existing plaques and aneurysms. We determined that miR-181b negatively regulates macrophage tissue inhibitor of metalloproteinase-3 expression and vascular smooth muscle cell elastin production, both important factors in maintaining atherosclerotic plaque and aneurysm stability. Validation studies in Timp3^−/− mice confirmed that the beneficial effects afforded by miR-181b inhibition are largely tissue inhibitor of metalloproteinase-3 dependent, while also revealing an additional protective effect through elevating elastin synthesis.

Conclusions:

Our findings suggest that the management of miR-181b and its target genes provides therapeutic potential for limiting the progression of atherosclerosis and aneurysms and protecting them from rupture.

Associations Between Macrophage Colony-Stimulating Factor and Monocyte Chemotactic Protein 1 in Plasma and First-Time Coronary Events: A Nested Case-Control Study

BACKGROUND

Myeloid cells play a central role in atherosclerosis. We investigated the associations between the plasma levels of growth factors and chemokines that regulate myeloid cell homeostasis and function and the risk of first-time acute coronary events in middle-aged persons.

METHODS AND RESULTS

We measured baseline plasma levels of macrophage colony-stimulating factor; monocyte chemotactic protein 1; C-C motif chemokine ligands 3, 4, and 20; C-X-C motif chemokine ligands 1, 6, and 16; and C-X3-C motif chemokine ligand 1 in 292 participants who had a coronary event during follow-up and 366 controls matched for age, sex, and time of inclusion who remained event free. Study participants were recruited from the Malmö Diet and Cancer Study population cohort and had no previous history of coronary artery disease. We found a strong independent negative association between macrophage colony-stimulating factor and incident coronary events in a forward stepwise Cox proportional hazards model including all biomarkers alongside the classic Framingham risk factors (age, sex, smoking, total cholesterol, high-density lipoprotein cholesterol, systolic blood pressure), diabetes mellitus, and medication. Conversely, monocyte chemotactic protein 1 had the strongest independent positive association with the outcome. The addition of macrophage colony-stimulating factor and monocyte chemotactic protein 1 significantly improved the predictive ability of a model including traditional risk factors alone (C statistic 0.81 [95% CI 0.78-0.84] versus 0.67 [95% CI 0.63-0.71]; net reclassification index 0.52 [0.42-0.62]; P<0.001). The combined model led to a 54% net downclassification of participants who did not have a coronary event during follow-up and was particularly effective in the intermediate-risk group.

CONCLUSIONS

High levels of macrophage colony-stimulating factor and low levels of monocyte chemotactic protein 1 in plasma characterize middle-aged persons at low risk to develop clinically manifested coronary artery disease.

Protein kinase A inhibition of macrophage maturation is accompanied by an increase in DNA methylation of the colony-stimulating factor 1 receptor gene

Macrophage colony-stimulating factor 1 (CSF-1) plays a critical role in the differentiation of mononuclear phagocytes from bone marrow precursors, and maturing monocytes and macrophages exhibit increased expression of the CSF-1 receptor, CSF1R. The expression of CSF1R is tightly regulated by transcription factors and epigenetic mechanisms. We previously showed that prostaglandin E2 and subsequent activation of protein kinase A (PKA) inhibited CSF1R expression and macrophage maturation. Here, we examine the DNA methylation changes that occur at the Csf1r locus during macrophage maturation in the presence or absence of activated PKA. Murine bone marrow cells were matured to macrophages by incubating cells with CSF-1-containing conditioned medium for up to 6 days in the presence or absence of the PKA agonist 6-bnz-cAMP. DNA methylation of Csf1r promoter and enhancer regions was assayed by bisulphite pyrosequencing. DNA methylation of Csf1r decreased during normal macrophage maturation in concert with an increase in Csf1r mRNA expression. Treatment with the PKA agonist inhibited Csf1r mRNA and protein expression, and increased DNA methylation at the Csf1r promoter. This was associated with decreased binding of the transcription factor PU.1 to the Csf1r promoter. Treatment with the PKA agonist inhibited the responsiveness of macrophages to CSF-1. Levels of endogenous PKA activity decreased during normal macrophage maturation, suggesting that attenuation of this signalling pathway contributes to the increase in CSF1R expression during macrophage maturation. Together, these results demonstrate that macrophage maturation is accompanied by Csf1r hypomethylation, and illustrates for the first time the ability of PKA to increase Csf1r DNA methylation.

Extracellular Release and Signaling by Heat Shock Protein 27: Role in Modifying Vascular Inflammation

Heat shock protein 27 (HSP27) is traditionally viewed as an intracellular chaperone protein with anti-apoptotic properties. However, recent data indicate that a number of heat shock proteins, including HSP27, are also found in the extracellular space where they may signal via membrane receptors to alter gene transcription and cellular function. Therefore, there is increasing interest in better understanding how HSP27 is released from cells, its levels and composition in the extracellular space, and the cognate cell membrane receptors involved in effecting cell signaling. In this paper, the knowledge to date, as well as some emerging paradigms about the extracellular function of HSP27 is presented. Of particular interest is the role of HSP27 in attenuating atherogenesis by modifying lipid uptake and inflammation in the plaque. Moreover, the abundance of HSP27 in serum is an emerging new biomarker for ischemic events. Finally, HSP27 replacement therapy may represent a novel therapeutic opportunity for chronic inflammatory disorders, such as atherosclerosis.

Metalloproteinase production from macrophages - a perfect storm leading to atherosclerotic plaque rupture and myocardial infarction

What is the topic of this review? The review discusses how in atherosclerotic plaques, a combination of inflammatory mediators together with loss of anti inflammatory factors is most likely to be responsible for the excess of MMP over TIMP expression that causes plaque rupture and myocardial infarction. What advances does it highlight? Regulation of matrix metalloproteinases (MMPs) and tissue inhibitors of MMP (TIMPs) is divergent between human and mouse macrophages. There is prostaglandin E₂ -dependent and -independent regulation. Inflammatory cytokines act through distinct (albeit overlapping) signalling pathways to elicit different patterns of MMP and TIMP expression. Transcriptional and epigenetic regulation occurs. Matrix metalloproteinases (MMPs) produced from macrophages contribute to plaque rupture, atherothrombosis and myocardial infarction. New treatments could emerge from defining the mediators and underlying mechanisms. In human monocytes, prostaglandin E₂ (PGE₂ ) stimulates MMP production, and inflammatory mediators such as tumour necrosis factor α, interleukin-1 and Toll-like receptor ligands can act either through or independently of PGE₂ . Differentiation of human monocytes to non-foamy macrophages increases constitutive expression of MMP-7, -8, -9, -14 and -19 and tissue inhibitor of MMP (TIMP)-1 to -3 through unknown, PGE₂ -independent mechanisms. Human macrophages express more MMP-1, -7 and -9 and TIMP-3 and less MMP-12 and -13 than mouse macrophages. Inflammatory mediators working through activator protein-1 and nuclear factor-κB transcription factor pathways upregulate MMP-1, -3, -10, -12 and -14 in human macrophages (MMP-9, -12 and -13 in mice), and studies with plaque tissue sections and isolated foam cells confirm this conclusion in vivo. Classical activation with granulocyte-macrophage colony-stimulating factor upregulates MMP-12, whereas interferon-γ upregulates MMP-12, -14 and -25 and downregulates TIMP-3 in human but not mouse macrophages. Alternative activation with interleukin-4 markedly stimulates the expression of only MMP-12 in humans and MMP-19 in mice. The anti-inflammatory cytokines interleukin-10 and transforming growth factor-β decrease production of several MMPs. Epigenetic upregulation of MMP-14 during foam cell formation or by granulocyte-macrophage colony-stimulating factor occurs by decreasing miRNA-24. A 'perfect storm' caused by a combination of these mechanisms is most likely to promote MMP-mediated macrophage invasion, tissue destruction and atherosclerotic plaque rupture.

G-CSF Predicts Cardiovascular Events in Patients with Stable Coronary Artery Disease

Granulocyte-colony-stimulating-factor (G-CSF) induces mobilization of progenitor cells but may also exert pro-inflammatory and pro-thrombotic effects. Treatment with recombinant G-CSF after acute myocardial infarction is currently under examination and has been associated with in-stent restenosis. However, it is not known whether plasma levels of endogenous G-CSF are also associated with an increased cardiovascular risk. Therefore we included 280 patients with angiographically proven stable coronary artery disease. G-CSF was measured by specific ELISA and patients were followed for a median of 30 months for the occurrence of major adverse cardiovascular events (MACE: death, myocardial infarction, re-hospitalization). Those with cardiac events during follow-up showed significant higher G-CSF levels (32.3 pg/mL IQR 21.4-40.5 pg/mL vs. 24.6 pg/mL IQR 16.4-34.9 pg/mL; p<0.05) at baseline. Patients with G-CSF plasma levels above the median had a 2-fold increased risk for MACE (p<0.05). This was independent from established cardiovascular risk factors. In addition, G-CSF above the median was a predictor of clinical in-stent restenosis after implantation of bare-metal stents (6.6% vs. 19.4%; p<0.05) but not of drug-eluting stents (7.7% vs. 7.6%; p = 0.98). This data suggests that endogenous plasma levels of G-CSF predict cardiovascular events independently from established cardiac risk factors and are associated with increased in-stent restenosis rates after implantation of bare metal stents.

Expression characteristics of neutrophil and mononuclear-phagocyte related genes mRNA in the stable angina pectoris and acute myocardial infarction stages of coronary artery disease

Objective

To investigate expression differences of neutrophil and mononuclear phagocyte related gene mRNAs among acute myocardial infarction (AMI), stable angina (SA) and control groups, and then discuss their expression characteristics in the stable angina pectoris (SAP) and AMI stages of coronary artery disease (CAD).

Methods

Whole Human Genome Oligo Microarrays were applied to assess the differential expression characteristics of neutrophil and mononuclear phagocyte related mRNAs in patients with AMI (n = 20), SA (n = 20) and controls (n = 20).

Results

(1) Almost all colony-stimulating factors (CSF) and their receptors related mRNAs was up-regulated in AMI and SA groups compared with the control group, and the expression of granulocyte-macrophage colony stimulating factor receptor (GM-CSFR) and granulocyte colony stimulating factor receptor (G-CSFR) mRNAs in the AMI group was significantly up-regulated compared with the other two groups (P < 0.01). (2) The expression of mRNAs related to monocyte chemoattractant protein-1 (MCP-1), CCR2 (MCP-1 receptor) and CXCR2 (IL-8 receptor) was significantly up-regulated (P < 0.01) in AMI group compared with SA and control groups. IL-8 mRNA expression in the AMI group was clearly higher than the controls (P < 0.05). (3) All mRNAs expression related to opsonic receptors (IgG FcR and C3bR/C4bR) was significantly up-regulated in AMI group compared with SA and control group (P < 0.01), and the SA group showed an upward trend compared with controls. (4) Most pattern recognition receptor (PRR)-related mRNAs expression was up-regulated in AMI group compared with SA and control groups. Most toll-like receptor (TLR) mRNAs expression was significantly up-regulated (P < 0.01) than the SA and control groups; macrophage scavenger receptor (MSR) mRNA was significantly up-regulated in AMI group compared with the control group (P < 0.01), and the SA group showed an upward trend compared with the controls.

Conclusions

The expression of most neutrophil and mononuclear-macrophage function related genes mRNAs was significantly up-regulated by stages during the progression of CAD, suggesting that the adhesive, chemotactic and phagocytic functions of neutrophil and mononuclear-macrophage were strengthened in the occurrence and development of coronary atherosclerosis and AMI. This also showed a stepped upward trend as the disease progressed.

Regulation of Csf1r and Bcl6 in Macrophages Mediates the Stage-Specific Effects of MicroRNA-155 on Atherosclerosis

Objective—

The function of microRNAs is highly context and cell type dependent because of their highly dynamic expression pattern and the regulation of multiple mRNA targets. MicroRNA-155 (miR-155) plays an important role in the innate immune response by regulating macrophage function; however, the effects of miR-155 in macrophages on atherosclerosis are controversial. We hypothesized that the stage-dependent target selection of miR-155 in macrophages determines its effects on atherosclerosis.

Approach and Results—

The expression of miR-155 increased in lesional macrophages of apolipoprotein E–deficient mice between 12 and 24 weeks of a high-cholesterol diet. Mir155 knockout in apolipoprotein E–deficient mice enhanced lesion formation, increased the lesional macrophage content, and promoted macrophage proliferation after 12 weeks of the high-cholesterol diet. In vitro, miR-155 inhibited macrophage proliferation by suppressing colony-stimulating factor-1 receptor, which was upregulated in lesional macrophages of Mir155 –/– apolipoprotein E–deficient mice. By contrast, Mir155 deficiency reduced necrotic core formation and the deposition of apoptotic cell debris, thereby preventing the progression of atherosclerosis between 12 and 24 weeks of the high-cholesterol diet. miR-155 inhibited efferocytosis in vitro by targeting B-cell leukemia/lymphoma 6 and thus activating RhoA (ras homolog gene family, member A). Accordingly, B-cell leukemia/lymphoma 6 was upregulated in lesional macrophages of Mir155 –/– apolipoprotein E–deficient mice after 24 weeks, but not after 12 weeks of the high-cholesterol diet.

Conclusions—

Our findings demonstrate a stage-specific role of miR-155 in lesion formation. miR-155 suppressed macrophage proliferation by targeting colony-stimulating factor-1 receptor in early and impaired efferocytosis by downregulating B-cell leukemia/lymphoma 6 in advanced atherosclerosis. Therefore, targeting the interaction between miR-155 and B-cell leukemia/lymphoma 6 may be a promising approach to inhibit the progression of atherosclerosis.

Dual Role of GM-CSF as a Pro-Inflammatory and a Regulatory Cytokine: Implications for Immune Therapy

Granulocyte macrophage colony stimulating factor (GM-CSF) is generally recognized as an inflammatory cytokine. Its inflammatory activity is primarily due its role as a growth and differentiation factor for granulocyte and macrophage populations. In this capacity, among other clinical applications, it has been used to bolster anti-tumor immune responses. GM-CSF-mediated inflammation has also been implicated in certain types of autoimmune diseases, including rheumatoid arthritis and multiple sclerosis. Thus, agents that can block GM-CSF or its receptor have been used as anti-inflammatory therapies. However, a review of literature reveals that in many situations GM-CSF can act as an anti-inflammatory/regulatory cytokine. We and others have shown that GM-CSF can modulate dendritic cell differentiation to render them "tolerogenic," which, in turn, can increase regulatory T-cell numbers and function. Therefore, the pro-inflammatory and regulatory effects of GM-CSF appear to depend on the dose and the presence of other relevant cytokines in the context of an immune response. A thorough understanding of the various immunomodulatory effects of GM-CSF will facilitate more appropriate use and thus further enhance its clinical utility.

Conjugated linoleic acid induces an atheroprotective macrophage MΦ2 phenotype and limits foam cell formation

Background

Atherosclerosis, the underlying cause of heart attack and strokes, is a progresive dyslipidemic and inflammatory disease where monocyte-derived macrophage cells play a pivotal role. Although most of the mechanisms that contribute to the progression of atherosclerosis have been identified, there is limited information on those governing regression. Conjugated linoleic acid (CLA) is a group of isomers of linoleic acid that differ in the position and/or geometry of their double bonds. We have previously shown that a specific CLA blend (80:20 cis-9,trans-11:trans-10,cis-12-CLA) induces regression of pre-established atherosclerosis in vivo, via modulation of monocyte/macrophage function. However, the exact mechanisms through which CLA mediates this effect remain to be elucidated.

Methods

Here, we address if CLA primes monocytes towards an anti-inflammatory MΦ2 macrophage and examine the effect of individual CLA isomers and the atheroprotective blend on monocyte-macrophage differentiation, cytokine generation, foam cell formation and cholesterol metabolism in human peripheral blood monocyte (HPBMC)-derived macrophages.

Results

cis-9,trans-11-CLA and the atheroprotective 80:20 CLA blend regulates expression of pro-inflammatory mediators and modulates the inflammatory cytokine profile of macrophages and foam cells. In addition, cis-9,trans-11-CLA and CLA blend primes HPBMCs towards an anti-inflammatory MΦ2 phenotype, characterised by increased scavenger receptor (CD36) and efflux protein (ABCA-1) expression. Furthermore, this altered macrophage phenotype impacts on foam cell formation, inhibiting ox-LDL accumulation and promoting cholesterol efflux via both PPARγ and LXRα dependent pathways.

Conclusion

The data increases the understanding of the pathways regulated by CLA in atheroprotection, namely, inhibiting the progressive acquisition of a pro-inflammatory macrophage phenotype.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-015-0060-9) contains supplementary material, which is available to authorized users.

rhCSF3 accelerates the proliferation of human melanocytes in culture through binding CSF3R and the expression of CSF3R transcripts

Melanogenic paracrine and autocrine cytokine networks have recently been discovered in vitro between melanocytes and other types of skin cells. Granulocyte colony-stimulating factor receptor (CSF3R) controls the survival, proliferation and differentiation of many kinds of cells, including neutrophils. To understand the function of CSF3R and recombinant human granulocyte colony-stimulating factor (rhCSF3) on melanocyte proliferation, this study compared the expression of CSF3R and the effects of rhCSF3 in primary human melanocytes, neutrophils and HEL 92.1.7 cells. The results show that CSF3R is localized in the cytoplasm and on cell membranes of melanocytes and neutrophils. The percentage of CSF3R(+) melanocytes was higher than CSF3R(+) HEL 92.1.7 cells, but was lower than CSF3R(+) neutrophils. Both CSF3R mRNA and CSF3R protein levels in melanocytes were higher than in HEL 92.1.7 cells, but were lower than in neutrophils. Treatment with rhCSF3 increased the proliferation of human melanocytes, but not their tyrosinase activity. Transcripts of CSF3R in human melanocytes, M14, A375 melanoma and A431 squamous cell carcinoma cells were also detected. Expression of the CSF3R V3 transcript was lower in melanocytes than in M14, A375 melanoma and A431 squamous cell carcinoma cells. In conclusion, rhCSF3 can promote melanocyte proliferation through CSF3R without affecting tyrosinase activity.

Small high-density lipoprotein is associated with monocyte subsets in stable coronary artery disease

Objective: High-density lipoprotein (HDL) particles are heterogeneous in structure and function and the role of HDL subfractions in atherogenesis is not well understood. It has been suggested that small HDL may be dysfunctional in patients with coronary artery disease (CAD). Monocytes are considered to play a key role in atherosclerotic diseases. Circulating monocytes can be divided into three subtypes according to their surface expression of CD14 and CD16. Our aim was to examine whether monocyte subsets are associated with HDL subfractions in patients with atherosclerosis. Methods: We included 90 patients with angiographically stable CAD. Monocyte subsets were defined as classical monocytes (CD14++CD16-; CM), intermediate monocytes (CD14++CD16+; IM) and non-classical monocytes (CD14+CD16++; NCM). HDL subfractions were measured by electrophoresis on polyacrylamide gel. Results: Serum levels of small HDL correlated with circulating pro-inflammatory NCM and showed an inverse relationship to circulating CM independently from other lipid parameters, risk factors, inflammatory parameters or statin treatment regime, respectively. IM were not associated with small HDL. In particular, patients with small HDL levels in the highest tertile showed dramatically increased levels of NCM (14.7 ± 7% vs. 10.7 ± 5% and 10.8 ± 5%; p = 0.006) and a decreased proportion of CM (79.3 ± 7% vs. 83.7 ± 6% and 83.9 ± 6%; p = 0.004) compared to patients in the two lower tertiles. In contrast, intermediate HDL, large HDL and total HDL were not associated with monocyte subset distribution. Conclusion: Small HDL levels are associated with pro-inflammatory NCM and inversely correlated with CM. This may suggest that small HDL could have dysfunctional anti-inflammatory properties in patients with established CAD.

•

Small HDL levels are associated with non-classical monocytes in stable CAD.

•

Classical monocytes are inversely associated with small HDL levels.

•

Associations are independent of other lipid parameters, risk factors, inflammatory parameters or statin treatment regime.

•

Inflammatory markers do not vary according to small HDL levels.

Cyclin-dependent kinase 9 may as a novel target in downregulating the atherosclerosis inflammation (Review)

Inflammation is a key component of atherosclerosis. Genes coding for inflammatory or anti-inflammatory molecules are considered good candidates for estimating the risk of developing atherosclerosis. Cyclin-dependent kinase 9 (CDK9), the kinase of positive transcription elongation factor b (P-TEFb), is crucial in the cell cycle and apoptosis. Previous studies have focused on its inhibition of immune cells for the resolution of inflammation. Considering the effects of inflammation in the pathogenicity of atherosclerosis, decreasing inflammation through the inhibition of CDK9 may be useful for the prognosis of atherosclerosis. The aim of this review was to examine whether inhibition of the CDK9 monocyte may affect the process of inflammation by acting on the cytokine secretion and interacting with endothelial cells (ECs). Thus, CDK9 may be a novel target for the diagnosis and therapy of atherosclerosis.

MicroRNA-24 regulates macrophage behavior and retards atherosclerosis

OBJECTIVE

Our recent studies have highlighted membrane type-1 matrix metalloproteinase (MMP)-14 as a selective marker for an invasive subset of macrophages potentially related to atherosclerotic plaque progression. Moreover, colony stimulating factors (CSF) may exert divergent effects on macrophage MMP expression, possibly through microRNAs. We, therefore, aim to identify and test the pathophysiological role of microRNAs, which modulate macrophage MMP-14 expression in atherosclerotic plaque progression.

APPROACH AND RESULTS

Compared with macrophage CSF-differentiated macrophages, granulocyte/macrophage CSF-matured macrophages exhibited reduced MMP-14 mRNA levels but increased protein expression and activity, which resulted in heightened macrophage invasion. MicroRNA-24, identified to target MMP-14, was accordingly increased in macrophage CSF compared with granulocyte/macrophage CSF macrophages. Silencing microRNA-24 in macrophage CSF macrophages significantly increased MMP-14 expression and enhanced their invasive capacity, mimicking granulocyte/macrophage CSF macrophages, and suggesting that granulocyte/macrophage CSF modulates MMP-14 protein expression and subsequent macrophage invasion in a microRNA-24-dependent manner. In human coronary atherosclerotic plaques, increased MMP-14 protein expression in foam cell macrophages was associated with lesions exhibiting histological characteristics associated with an unstable phenotype. Furthermore, microRNA-24 expression in these atherosclerotic plaques was inversely related to MMP-14 protein expression. Moreover, stable plaques contained higher microRNA-24 levels than unstable plaques, and microRNA-24 colocalized with foam cell macrophages that exhibited low MMP-14 protein expression. Finally, in atherosclerotic mice (apolipoprotein E-deficient), microRNA-24 inhibition increased plaque size and macrophage MMP-14 expression.

CONCLUSIONS

Taken together, our data demonstrates that downregulation of microRNA-24 promotes an invasive macrophage subset and plays a novel regulatory role in MMP-14 proteolytic activity and, therefore, plaque stability, highlighting its therapeutic potential.

Galectin-8 elicits pro-inflammatory activities in the endothelium

Galectins (Gals), a family of mammalian lectins, play diverse roles under physiological and pathological conditions. Here, we analyzed the tandem-repeat Gal-8 synthesis, secretion and effects on the endothelium physiology. Gal-8M and Gal-8L isoforms were secreted under basal conditions by human microvascular endothelial cells (HMEC-1). However, expression and secretion of the Gal-8M isoform, but not Gal-8L, were increased in response to bacterial lipopolysaccharide (LPS) stimulus and returned to control values after LPS removal. Similarly, cell surface Gal-8 exposure was increased after stimulation with LPS. To evaluate Gal-8 effects on the endothelium physiology, HMEC-1 cells were incubated in the presence of recombinant Gal-8M. Pretreated HMEC-1 cells became proadhesive to human normal platelets, indicating that Gal-8 actually activates endothelial cells. This effect was specific for lectin activity as it was prevented by the simultaneous addition of lactose, but not by sucrose. Endothelial cells also increased their exposition of von Willebrand factor after Gal-8 treatment, which constitutes another feature of cell activation that could be, in turn, responsible for the observed platelet adhesion. Several pro-inflammatory molecules were abundantly produced by Gal-8 stimulated endothelial cells: CXCL1 (GRO-α), GM-CSF, IL-6 and CCL5 (RANTES), and in a lower degree CCL2 (MCP-1), CXCL3 (GRO-γ) and CXCL8 (IL-8). In agreement, Gal-8M induced nuclear factor kappa B phosphorylation. Altogether, these results not only confirm the pro-inflammatory role we have already proposed for Gal-8 in other cellular systems but also suggest that this lectin is orchestrating the interaction between leukocytes, platelets and endothelial cells.

Understanding the role of B cells in atherosclerosis: potential clinical implications

Atherosclerosis is a progressive inflammatory disease of the medium to large arteries that is the largest contributor to cardiovascular disease. B-cell subsets have been shown in animal models of atherosclerosis to have both atherogenic and atheroprotective properties. In this review, we highlight the research that developed our understanding of the role of B cells in atherosclerosis both in humans and mice. From this we discuss the potential clinical impact B cells could have both as diagnostic biomarkers and as targets for immunotherapy. Finally, we recognize the inherent difficulty in translating findings from animal models into humans given the differences in both cardiovascular disease and the immune system between mice and humans, making the case for greater efforts at addressing the role of B cells in human atherosclerosis.

Is there a role for treating inflammation in moyamoya disease?: a review of histopathology, genetics, and signaling cascades

Moyamoya disease is a slowly progressing steno-occlusive condition affecting the cerebrovasculature. Affecting the terminal internal carotid arteries (ICA) and there branches, bilaterally, a resulting in a fine vascular network in the base of the brain to allow for compensation of the stenosed vessels. While there is obvious evidence of the involvement of inflammatory proteins in the condition, this has historically not been acknowledged as a causal factor. Here we describe the fundamental histopathology, genetics, and signaling cascades involved in moyamoya and debate whether these factors can be linked as causal factor for the condition or whether they are simply a secondary result of the ischemia described in the condition. A particular focus has been placed on the multitude of signaling cascades linked to the condition as these are viewed as having the greatest therapeutic potential. As such we hope to draw some novel insight into potential diagnostic and therapeutic inflammatory targets in the condition.