Monocyte recruitment and foam cell formation in atherosclerosis

Suppression of microRNA-155 exerts an anti-inflammatory effect on CD4+ T cell-mediated inflammatory response in the pathogenesis of atherosclerosis

In the current study, we aimed to investigate the effects of miR-155 on CD4+ T cell-mediated immune response in the pathogenesis of atherosclerosis. CD34+ hematopoietic stem cells, CD4+ T lymphocytes, endothelial cells (ECs), and vascular smooth muscle cells (VSMCs) were harvested from the same donor. Knockdown of miR-155 in the CD4+ T cells was achieved by lentiviral transfection, whereas control RNA-transfected or untransfected lymphocytes were used as controls. The transfected CD4+ T cells were activated by incubating with oxidized low-density lipoprotein-treated dendritic cells. The proliferative capacities, phenotype distribution, and cytokine secretion profiles of the activated CD4+ T cells from different groups were evaluated. The activated lymphocytes were used to treat ECs co-cultivated with VSMCs. The ability of the CD4+ T cells to induce the apoptosis of the ECs and to promote the proliferation of the VSMCs was investigated. Inhibition of miR-155 was found to significantly reduce the proliferation rate of the transfected CD4+ T cells. CD4+ T lymphocytes transfected with the miR-155 inhibitor showed increased populations of T helper type 2 and regulatory T cells, as well as more production of anti-inflammatory cytokines. MiR-155 knockdown was also shown to significantly hamper the ability to CD4+ T cells to induce EC apoptosis and to promote the growth of VSMCs. Our data suggested that inhibition of miR-155 in CD4+ T cells could slow down the formation of atherosclerotic plaques. These results lay the groundwork for future research on the therapeutic potential of miR-155 against atherosclerosis-associated cardiovascular diseases.

Targeting Dysfunctional Vascular Endothelial Cells Using Immunoliposomes Under Flow Conditions

Introduction

Atherosclerosis (ATH), the build up of fat in the arteries, is a principal cause of heart attack and stroke. Drug instability and lack of target specificity are major drawbacks of current clinical therapeutics. These undesirable effects can be eliminated by site-specific drug delivery. The endothelial surface over ATH lesions has been shown to overexpress vascular cell adhesion molecule1 (VCAM1), which can be used for targeted therapy.

Methods

Here, we report the synthesis, characterization, and development of anti VCAM1-functionalized liposomes to target cells overexpressing VCAM1 under static and flow conditions. Liposomes were composed of dioleoyl-phosphatidylcholine, sphingomyelin, cholesterol, and distearoyl-phosphatidylethanolamine-polyethylene glycol-cyanur (31.67:31.67:31.67:5 mol%). VCAM1 expression in endothelial cells was induced by lipopolysaccharide (LPS) treatment.

Results

Characterization study revealed that liposomes were negatively charged (- 7.7 ± 2.6 mV) with an average diameter of 201.3 ± 3.3 nm. Liposomes showed no toxicity toward THP-1 derived macrophages and endothelial cells. Liposomes were able to target both fixed and non-fixed endothelial cells, in vitro, with significantly higher localization observed in non-fixed conditions. To mimic biological and physiologically-relevant conditions, liposome targeting was also examined under flow (4 dyn/cm²) with or without erythrocytes (40% v/v hematocrit). Liposomes were able to target LPS-treated endothelial cells under dynamic culture, in the presence or absence of erythrocytes, although targeting efficiency was five-fold lower in flow compared to static conditions.

Conclusions

This liposomal delivery system showed a significant improvement in localization on dysfunctional endothelium after surface functionalization. We conclude that VCAM1-functionalized liposomes can target and potentially deliver therapeutic compounds to ATH regions.

TRPV4 is a regulator in P. gingivalis lipopolysaccharide-induced exacerbation of macrophage foam cell formation

Porphyromonas gingivalis (P.g), a major causative agent of periodontitis, has been linked to atherosclerosis, a chronic inflammatory vascular disease. Recent studies have suggested a link between periodontitis and arterial stiffness, a risk factor for atherosclerosis. However, the mechanisms by which P.g infection contributes to atherogenesis remain elusive. The formation of lipid-laden macrophage "foam cells" is critically important to development and progression of atherosclerosis. We have obtained evidence that TRPV4 (transient receptor potential channel of the vanilloid subfamily 4), a mechanosensitive channel, is a regulator of macrophage foam cell formation both in response to P.g-derived lipopolysaccharide (PgLPS) or to an increase in matrix stiffness. Importantly, we found that TRPV4 activity (Ca²⁺ influx) was increased in response to PgLPS. Genetic deletion or chemical antagonism of TRPV4 channels blocked PgLPS-triggered exacerbation of oxidized LDL (oxLDL)-mediated foam cell formation. Mechanistically, we found that (1) TRPV4 regulated oxLDL uptake but not its cell surface binding in macrophages; (2) reduced foam cell formation in TRPV4 null cells was independent of expression of CD36, a predominant receptor for oxLDL, and (3) co-localization of TRPV4 and CD36 on the macrophage plasma membrane was sensitive to the increased level of matrix stiffness occurring in the presence of PgLPS. Altogether, our results suggest that TRPV4 channels play an essential role in P.g-induced exacerbation of macrophage foam cell generation through a mechanism that modulates uptake of oxLDL.

Principal component analysis of adipocytokines and insulin associate with risk factors of cardiovascular diseases

OBJECTIVES

Obesity plays an important role in the development of chronic diseases like cardiovascular diseases and diabetes. The possible underlying mechanism for this connection is that adipose tissue secretes an array of chemical messenger adipokines proinflammatory cytokines (tumor necrosis factor-alpha, interleukin-6, and interleukin-1-beta). This study aimed to investigate the linkage between adipocytokines and insulin with the cardiovascular disease risk, with particular reference to the adipokines galectin-3, plasminogen activator inhibitor-1, and interleukin-1-beta, C-reactive protein, and monocyte chemoattractant protein.

RESULT

Two patterns were identified. The first pattern was galectin-3, plasminogen activator inhibitor-1 and interleukin-1-beta and the second one was C-reactive protein, insulin and monocyte chemoattractant protein-1. The second pattern was strongly associated with the higher scores for resting metabolic rate, diastolic blood pressure, homeostasis model insulin resistance index, lipid profile (except low density lipoprotein, total cholesterol), and body composition parameters (except fat free mass index and waist hip ratio), while negatively associated with age and high density lipoprotein level (all p < 0.05). The first pattern was, however, significantly associated with body fat mass, obesity degree percentage, waist circumference, fat mass index, and waist hip ratio (p < 0.05 for all). This is a retrospective study. Ethics approval (IR.TUMS.VCR.REC.1395.1597).

HOTTIP knockdown inhibits cell proliferation and migration via regulating miR-490-3p/HMGB1 axis and PI3K-AKT signaling pathway in ox-LDL-induced VSMCs

AIMS

Atherosclerosis (AS) is a common cardiovascular disease with complicated pathogenesis. Long non-coding RNAs (lncRNAs) have been reported to be associated with AS progression. We aimed to explore the role and underlying mechanism of HOXA transcript at the distal tip (HOTTIP) in AS.

MATERIALS AND METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the expression of HOTTIP, miR-490-3p and high mobility group B 1 (HMGB1) in AS patients' sera and oxidized low-density lipoprotein (ox-LDL) induced human aortic vascular smooth muscle cells (HA-VSMCs). Cell Counting Kit-8 (CCK-8) assay and transwell assay were conducted to evaluate the proliferation and migration of HA-VSMCs, respectively. Western blot assay was carried out to determine the levels of proliferating cell nuclear antigen (PCNA), matrix metalloprotein 2 (MMP2), MMP9 and HMGB1. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted to verify the targeting association between HOTTIP and miR-490-3p, as well as miR-490-3p and HMGB1.

KEY FINDINGS

HOTTIP and HMGB1 were upregulated and miR-490-3p was downregulated in the sera of AS patients and ox-LDL-stimulated HA-VSMCs. HOTTIP knockdown suppressed ox-LDL induced proliferation and migration in HA-VSMCs. MiR-490-3p was identified as a target of HOTTIP and HOTTIP overexpression abolished the inhibition on cell proliferation and migration mediated by miR-490-3p in ox-LDL-induced HA-VSMCs. Moreover, miR-490-3p inhibition promoted cell proliferation and migration by directly targeting HMGB1 in ox-LDL-induced HA-VSMCs. Besides, HOTTIP knockdown repressed the activation of PI3K-AKT signaling pathway.

SIGNIFICANCE

HOTTIP knockdown suppressed cell proliferation and migration by regulating miR-490-3p/HMGB1 axis and PI3K-AKT pathway in ox-LDL-induced HA-VSMCs.

Selective Recruitment of Monocyte Subsets by Endothelial N-Glycans

Monocyte rolling, adhesion, and transmigration across the endothelium are mediated by specific interactions between surface adhesion molecules. This process is fundamental to innate immunity and to inflammatory disease, including atherosclerosis, where monocyte egress into the intimal space is central to formation of fatty plaques. Monocytes are a heterogeneous population of three distinct subsets of cells, all of which play different roles in atherosclerosis progression. However, it is not well understood how interactions between different monocyte subsets and the endothelium are regulated. Furthermore, it is appreciated that endothelial adhesion molecules are heavily N-glycosylated, but beyond regulating protein trafficking to the cell surface, whether and if so how these N-glycans contribute to monocyte recruitment is not known. This review discusses how changes in endothelial N-glycosylation may impact vascular and monocytic inflammation. It will also discuss how regulating N-glycoforms on the endothelial surface may allow for the recruitment of specific monocyte subsets to sites of inflammation, and how further understanding in this area may lead to the development of glyco-specific therapeutics in the treatment of cardiovascular disease.

Recent discoveries in dendritic cell tolerance-inducing pharmacological molecules

Dendritic cells (DCs) represent one of the most important biological tools for cellular immunotherapy purposes. There are an increasing number of phase I and II studies, where regulatory or tolerogenic DCs (TolDCs) are utilized as negative vaccines, with the aim of inducing tolerogenic outcomes in patients with various autoimmune or chronic-inflammatory diseases, as well as in transplant settings. The induction of tolerogenic properties in DCs can be achieved by altering their activation state toward expression of immunosuppressive elements and/or by achieving resistance to maturation, which leads to insufficient co-stimulatory signal delivery and inability to efficiently present antigens. In the past, one of the most efficient ways to induce DC tolerance has been the application of selected pharmacological agents which actively induce a tolerogenic transcription program or inhibit major pro-inflammatory transcription factors such as Nf-κB. Important examples include immunosuppressants such as different corticosteroids, vitamin D₃, rapamycin and others. The quality of TolDCs induced by different approaches is becoming a vital issue and recent evidence suggests substantial heterogeneity between variously-generated TolDCs as evidenced by their transcriptomic profile and function. The possibility of various "flavors" of TolDCs encourages future research in discovery of Tol-DC inducing agents to enrich various ways of DC manipulation. This would enable a broader range of tools to manipulate DC toward specific characteristics desirable in different disease settings. In recent years, several novel small molecules have been identified with the capacity to promote DC tolerogenic characteristics. In this review, we will present and discuss these novel findings and also highlight novel understandings of tolerogenic mechanisms by which DC tolerogenicity is induced by already established agents.

Lysophosphatidylcholine Induces NLRP3 Inflammasome-Mediated Foam Cell Formation and Pyroptosis in Human Monocytes and Endothelial Cells

Foam cells are specialized lipid-loaded macrophages derived from monocytes and are a key pathological feature of atherosclerotic lesions. Lysophosphatidylcholine (LPC) is a major lipid component of the plasma membrane with a broad spectrum of proinflammatory activities and plays a key role in atherosclerosis. However, the role of LPC in lipid droplet (LD) biogenesis and the modulation of inflammasome activation is still poorly understood. In the present study, we investigated whether LPC can induce foam cell formation through an analysis of LD biogenesis and determined whether the cell signaling involved in this process is mediated by the inflammasome activation pathway in human endothelial cells and monocytes. Our results showed that LPC induced foam cell formation in both types of cells by increasing LD biogenesis via a NLRP3 inflammasome-dependent pathway. Furthermore, LPC induced pyroptosis in both cells and the activation of the inflammasome with IL-1β secretion, which was dependent on potassium efflux and lysosomal damage in human monocytes. The present study described the IL-1β secretion and foam cell formation triggered by LPC via an inflammasome-mediated pathway in human monocytes and endothelial cells. Our results will help improve our understanding of the relationships among LPC, LD biogenesis, and NLRP3 inflammasome activation in the pathogenesis of atherosclerosis.

Gut Microbiota-Dependent Marker TMAO in Promoting Cardiovascular Disease: Inflammation Mechanism, Clinical Prognostic, and Potential as a Therapeutic Target

Cardiovascular disease (CVD) is the leading cause of death worldwide, especially in developed countries, and atherosclerosis (AS) is the common pathological basis of many cardiovascular diseases (CVDs) such as coronary heart disease (CHD). The role of the gut microbiota in AS has begun to be appreciated in recent years. Trimethylamine N-oxide (TMAO), an important gut microbe-dependent metabolite, is generated from dietary choline, betaine, and L-carnitine. Multiple studies have suggested a correlation between plasma TMAO levels and the risk of AS. However, the mechanism underlying this relationship is still unclear. In this review, we discuss the TMAO-involved mechanisms of atherosclerotic CVD from the perspective of inflammation, inflammation-related immunity, cholesterol metabolism, and atherothrombosis. We also summarize available clinical studies on the role of TMAO in predicting prognostic outcomes, including major adverse cardiovascular events (MACE), in patients presenting with AS. Finally, since TMAO may be a novel therapeutic target for AS, several therapeutic strategies including drugs, dietary, etc. to lower TMAO levels that are currently being explored are also discussed.

Immune-Inflammatory Responses in Atherosclerosis: The Role of Myeloid Cells

Inflammation plays a key role in the initiation and progression of atherosclerosis and can be caused by multiple agents, including increased concentration of circulating low-density lipoprotein (LDL) cholesterol. Areas of the arterial wall affected by atherosclerosis are enriched with lymphocytes and dendritic cells (DCs). Atherosclerotic plaques contain a variety of proinflammatory immune cells, such as macrophages, DCs, T cells, natural killer cells, neutrophils and others. Intracellular lipid accumulation in atherosclerotic plaque leads to formation of so-called foam cells, the cytoplasm of which is filled with lipid droplets. According to current understanding, these cells can also derive from the immune cells that engulf lipids by means of phagocytosis. Macrophages play a crucial role in the initial stages of atherogenesis by engulfing oxidized LDL (oxLDL) in the intima that leads to their transformation to foam cells. Dying macrophages inside the plaque form a necrotic core that further aggravates the lesion. Proinflammatory DCs prime differentiation of naïve T cells to proinflammatory Th1 and Th17 subsets. In this review, we discuss the roles of cell types of myeloid origin in atherosclerosis-associated inflammation.

Immunobiology of Atherosclerosis: A Complex Net of Interactions

Cardiovascular disease is the leading cause of mortality worldwide, and atherosclerosis the principal factor underlying cardiovascular events. Atherosclerosis is a chronic inflammatory disease characterized by endothelial dysfunction, intimal lipid deposition, smooth muscle cell proliferation, cell apoptosis and necrosis, and local and systemic inflammation, involving key contributions to from innate and adaptive immunity. The balance between proatherogenic inflammatory and atheroprotective anti-inflammatory responses is modulated by a complex network of interactions among vascular components and immune cells, including monocytes, macrophages, dendritic cells, and T, B, and foam cells; these interactions modulate the further progression and stability of the atherosclerotic lesion. In this review, we take a global perspective on existing knowledge about the pathogenesis of immune responses in the atherosclerotic microenvironment and the interplay between the major innate and adaptive immune factors in atherosclerosis. Studies such as this are the basis for the development of new therapies against atherosclerosis.

Salmonella-Infected Aortic Aneurysm: Investigating Pathogenesis Using Salmonella Serotypes

Salmonella infection is most common in patients with infected aortic aneurysm, especially in Asia. When the aortic wall is heavily atherosclerotic, the intima is vulnerable to invasion by Salmonella, leading to the development of infected aortic aneurysm. By using THP-1 macrophage-derived foam cells to mimic atherosclerosis, we investigated the role of three Salmonella enterica serotypes – Typhimurium, Enteritidis, and Choleraesuis – in foam cell autophagy and inflammasome formation. Herein, we provide possible pathogenesis of Salmonella-associated infected aortic aneurysms. Three S. enterica serotypes with or without virulence plasmid were studied. Through Western blotting, we investigated cell autophagy induction and inflammasome formation in Salmonella-infected THP-1 macrophage-derived foam cells, detected CD36 expression after Salmonella infection through flow cytometry, and measured interleukin (IL)-1β, IL-12, and interferon (IFN)-α levels through enzyme-linked immunosorbent assay. At 0.5 h after infection, plasmid-bearing S. Enteritidis OU7130 induced the highest foam cell autophagy – significantly higher than that induced by plasmid-less OU7067. However, plasmid-bearing S. Choleraesuis induced less foam cell autophagy than did its plasmid-less strain. In foam cells, plasmid-less Salmonella infection (particularly S. Choleraesuis OU7266 infection) led to higher CD36 expression than did plasmid-bearing strains infection. OU7130 and OU7266 infection induced the highest IL-1β secretion. OU7067-infected foam cells secreted the highest IL-12p35 level. Plasmid-bearing S. Typhimurium OU5045 induced a higher IFN-α level than did other Salmonella serotypes. Salmonella serotypes are correlated with foam cell autophagy and IL-1β secretion. Salmonella may affect the course of foam cells formation, or even aortic aneurysm, through autophagy.

The Effects of Dietary Polyphenols on Circulating Cardiovascular Disease Biomarkers and Iron Status: A Systematic Review

The prevalence of cardiovascular disease (CVD) is rising worldwide, remaining the major cause of death in developed countries. Polyphenols have been shown to have cardioprotective properties; however, their impact on iron bioavailability and potential impact on other aspects of health is unclear. A systematic review was undertaken to evaluate the current status of the relationship between habitual polyphenol consumption, iron status, and circulating biomarkers of CVD. Following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2009 guidelines, searches were performed across 5 electronic databases (PubMed, Cochrane Library, Scopus, Web of Science, and CINAHL) to identify randomized controlled trials which investigated the effects of polyphenol consumption on inflammatory markers, serum lipid profile, and iron absorption and bioavailability. In total, 1174 records were identified, with only 7 studies meeting the inclusion criteria. The selected studies involved 133 participants and used a variety of foods and supplements, including olive oil and cherries, rich in polyphenols including hydroxytyrosol, quercetin, and resveratrol, as well as catechin enriched drinks. The duration of the studies ranged from between 56 and 145 days, with total polyphenolic content of the food items and supplements ranging from 45 to 1015 mg (per 100 g). Polyphenols did not appear to interfere with iron status, and most studies reported improvements in inflammatory markers and lipid profile. While these results are promising, the limited number of studies and considerable heterogeneity across the interventions support the need for more extensive trials assessing the relationship between polyphenol intake, iron bioavailability, and CVD risk.

The three members of the Vav family proteins form complexes that concur to foam cell formation and atherosclerosis

During foam cell formation and atherosclerosis development, the scavenger receptor CD36 plays critical roles in lipid uptake and triggering of atherogenicity via the activation of Vav molecules. The Vav family includes three highly conserved members known as Vav1, Vav2, and Vav3. As Vav1 and Vav3 were found to exert function in atherosclerosis development, it remains thus to decipher whether Vav2 also plays a role in the development of atherosclerosis. In this study we found that Vav2 deficiency in RAW264.7 macrophages significantly diminished oxidized LDL uptake and CD36 signaling, demonstrating that each Vav protein family member was required for foam cell formation. Genetic disruption of Vav2 in ApoE-deficient C57BL/6 mice significantly inhibited the severity of atherosclerosis. Strikingly, we further found that the genetic deletion of each member of the Vav protein family by CRISPR/Cas9 resulted in a similar alteration of transcriptomic profiles of macrophages. The three members of the Vav proteins were found to form complexes, and genetic ablation of each single Vav molecule was sufficient to prevent endocytosis of CD36. The functional interdependence of the three Vav family members in foam cell formation was due to their indispensable roles in transcriptomic programing, lipid uptake, and activation of the JNK kinase in macrophages.

Atorvastatin Blocks Advanced Glycation End Products Induced Reduction in Macrophage Cholesterol Efflux Mediated With ATP-Binding Cassette Transporters G 1

BACKGROUND

There is accumulating evidence that the AGEs-RAGE interaction plays an important role in accelerated atherosclerosis in diabetes. Our previous study showed that the AGEs-RAGE axis can reduce the cholesterol efflux of THP-1 macrophages through suppression of the expression of ABCG1 and that statins can inhibit the expression of RAGE. However, the role of statins in recovering the cholesterol efflux of macrophages reduced by AGEs has not been assessed.Methods and Results:ApoE^-/-mice and THP-1 macrophages were both treated by AGEs or AGEs combined with anti-RAGE antibody (only in THP-1 cells), ALT711 and atorvastatin separately. Cholesterol efflux of THP-1 macrophages and murine peritoneal macrophages was tested by fluorescence microplate technique. RT-PCR and western blot analysis were used to measure the expression of RAGE and molecules included in cholesterol efflux. After co-incubating with atorvastatin and AGEs, reduction in lipid accumulation in THP-1 macrophages and improvement of lesions complexity occurred compared with treating by AGEs only. Atorvastatin increased cholesterol efflux and ABCG1 expression of macrophages, which were reduced by AGEs, and decreased the expression of RAGE at the same time.

CONCLUSIONS

This study demonstrated that atorvastatin can recover the deleterious ABCG1-mediated cholesterol efflux induced by AGEs in THP-1 macrophages and murine peritoneal macrophages by downregulating RAGE expression. It may contribute to the protective action of atorvastatin in diabetic subjects with atherosclerosis.

Treponema pallidum enhances human monocyte migration and invasion by dysregulating the MMP/TIMP balance

Although the infiltration of monocytes into local lesions is an obvious pathological manifestation in the pathogenesis of syphilis, little is known about the role of metalloproteinase (MMP)/tissue inhibitor of metalloproteinases (TIMP) imbalance in the migration/invasion of THP-1 cells induced by Treponema pallidum (T. pallidum). The influence of T. pallidum on the invasion and migration of THP-1 cells was evaluated. Changes in the MMP/TIMP balance and the mechanisms underlying the involvement of the MAPK and NF-κB signaling pathways in this process were explored. T. pallidum induced the migration/invasion of THP-1 cells and the mRNA and protein expression of MMP-1, MMP-9 and TIMP-1. The mRNA expression of TIMP-2 was reduced, and the protein expression of TIMP-2 was not changed. The MMP-1/TIMP-1, MMP-1/TIMP-2, MMP-9/TIMP-1 and MMP-9/TIMP-2 ratios were increased. Inhibition of JNK, MEK/ERK, p38 MAPK and NF-κB significantly decreased the MMP/TIMP ratio and ultimately suppressed the migration/invasion of THP-1 cells. These findings revealed that MMP/TIMP imbalances induced by T. pallidum enhanced THP-1 cell migration and invasion via MAPK and NF-κB signaling pathway activation, which revealed a novel step in syphilis pathophysiology.

Lonicera caerulea Berry Polyphenols Activate SIRT1, Enhancing Inhibition of Raw264.7 Macrophage Foam Cell Formation and Promoting Cholesterol Efflux

Lonicera caerulea berry polyphenols (LCBP) are known to reduce cholesterol accumulation. Currently, it is unknown whether LCBP can activate Sirtuin 1 (SIRT1) to regulate the formation of RAW264.7 macrophage foam cells. In this study, the effect of LCBP on lipid accumulation in macrophages was evaluated. Fluorescently labeled ox-LDL and 25-NBD cholesterol were used to detect the ox-LDL uptake and cholesterol outflow rate from macrophages. Gene silencing was performed using siRNA to detect changes in the expression of the ATP-binding cassette transporter A1 (ABCA1), sterol regulatory element-binding protein 2 (SREBP2), and SIRT1 proteins using Western blotting, and changes in the expression of miR-33 were detected by real-time polymerase chain reaction. The results showed that treatment with 80 μg/mL LCBP significantly inhibited the accumulation of lipids in RAW264.7 macrophages induced by ox-LDL and reduced intracellular cholesterol levels by activating SIRT1 to enhance the expression of ABCA1, a cholesterol efflux gene, but not independent effect. Of the three key LCBP components investigated, chlorogenic acid was found to activate SIRT1 and regulate the expression of the cholesterol-related factors ABCA1, SREBP2, and miR-33; cyanidin-3-glucoside and catechins were effective to a lesser extent. Our results suggest a novel hypolipidemic mechanism of LCBP.

Moxibustion at CV4 alleviates atherosclerotic lesions through activation of the LXRα/ABCA1 pathway in apolipoprotein-E-deficient mice

Objectives:

To investigate the anti-atherogenic effect of moxibustion and whether it is mediated through the reverse cholesterol transport process.

Methods:

8-week-old male apolipoprotein E deficient (ApoE^−/− knockout) mice were randomly divided into two groups (n=10 per group): atherosclerosis (AS) and AS plus moxibustion (AS+M). C57BL/6J mice of the same background (n=10) were selected as controls. Mice in the AS+M group received indirect moxibustion with an ignited moxa stick held over CV4. Mice of the AS and control groups were restrained in the same holder with an unlit moxa stick held over CV4. All treatments were performed for 20 min per day, 6 days per week for 12 weeks. After the treatment, the mice were euthanased and their serum lipids were measured. The aortic roots and thoracic aortas were collected for haematoxylin and eosin and red oil O staining, respectively, to analyse the atherosclerotic lesions. Expression of adenosine triphosphate binding cassette (ABCA)A1/G1 and liver X receptor α (LXRα) in the thoracic aorta were examined with Western blotting.

Results:

The moxibustion-treated (AS+M) mice showed a significantly lower plaque area percentage in the aortic root and thoracic aorta, and higher expression of LXRα and ABCA1 in the thoracic aorta compared with the AS mice. No significant differences were found in average lipid area percentage in the thoracic aorta, or ABCG1 expression in the thoracic aorta, between mice in the AS+M and AS groups.

Conclusion:

Moxibustion treatment at CV4 suppressed the progression of atherosclerotic lesions in ApoE^−/− mice. The anti-atherogenic effect of moxibustion may be achieved by: (1) regulation of lipid metabolism, and thus prevention of lipid accumulation; and (2) upregulation of LXRα- and ABCA1-mediated cholesterol efflux in the lesion area.

Biologic roles of the ABH and Lewis histo-blood group antigens part II: thrombosis, cardiovascular disease and metabolism

The ABH and Lewis antigens were among the first of the human red blood cell polymorphisms to be identified and, in the case of the former, play a dominant role in transfusion and transplantation. But these two therapies are largely twentieth-century innovations, and the ABH and related carbohydrate antigens are not only expressed on a very wide range of human tissues, but were present in primates long before modern humans evolved. Although we have learned a great deal about the biochemistry and genetics of these structures, the biological roles that they play in human health and disease are incompletely understood. This review and its companion, which appeared in a previous issue of Vox Sanguinis, will focus on a few of the biologic and pathologic processes which appear to be affected by histo-blood group phenotype. The first of the two reviews explored the interactions of two bacteria with the ABH and Lewis glycoconjugates of their human host cells, and described the possible connections between the immune response of the human host to infection and the development of the AB-isoagglutinins. This second review will describe the relationship between ABO phenotype and thromboembolic disease, cardiovascular disease states, and general metabolism.

12(S)-Hydroxyeicosatetraenoic acid downregulates monocyte-derived macrophage efferocytosis: New insights in atherosclerosis

The involvement of 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), a 12-lipooxygenase product of arachidonic acid, has been suggested in atherosclerosis. However, its effect on macrophage functions is not completely understood, so far. The uptake of apoptotic cells (efferocytosis) by macrophages is an anti-inflammatory process, impaired in advanced atherosclerotic lesions. This process induces the release of the anti-inflammatory cytokine interleukin-10 (IL-10), and it is regulated by Rho-GTPases, whose activation involves the isoprenylation, a modification inhibited by statins. We assessed 12-HETE levels in serum of coronary artery disease (CAD) patients, and explored 12(S)-HETE in vitro effect on monocyte-derived macrophage (MDM) efferocytosis. Sixty-four CAD patients and 24 healthy subjects (HS) were enrolled. Serum 12-HETE levels were measured using a tandem mass spectrometry method. MDMs, obtained from a spontaneous differentiation of adherent monocytes, were treated with 12(S)-HETE (10-50 ng/mL). Efferocytosis and RhoA activation were evaluated by flow cytometry. IL-10 was measured by ELISA. CAD patients showed increased 12-HETE serum levels compared to HS (665.2 [438.1-896.2] ng/mL and 525.1 [380.1-750.1] ng/mL, respectively, p < 0.05) and reduced levels of IL-10. MDMs expressed the 12(S)-HETE cognate receptor GPR31. CAD-derived MDMs displayed defective efferocytosis vs HS-MDMs (9.4 [7.7-11.3]% and 11.1 [9.6-14.1]% of MDMs that have engulfed apoptotic cells, respectively, p < 0.01). This reduction is marked in MDMs obtained from patients not treated with statin (9.3 [7.4-10.6]% statin-free CAD vs HS, p = 0.01; and 9.9 [8.6-11.6]% statin-treated CAD vs HS, p = 0.07). The in vitro treatment of MDMs with 12(S)-HETE (20 ng/mL) induced 20% decrease of efferocytosis (p < 0.01) and 71% increase of RhoA activated form (p < 0.05). Atorvastatin (0.1 μM) counteracted these 12(S)-HETE-mediated effects.These results show a 12(S)-HETE pro-inflammatory effect and suggest a new potential contribution of this mediator in the development of atherosclerosis.

Upregulated Sphingosine 1-Phosphate Receptor 1 Expression in Human and Murine Atherosclerotic Plaques

PURPOSE

Dysregulation of sphingosine 1-phosphate receptor 1 (S1PR1) signaling contributes to inflammation-related pathophysiological changes in cardiovascular diseases including atherosclerosis (AS). S1PR1-targeting compounds significantly reduce lesion size in murine models of AS. Therefore, characterization of S1PR1 expression in vitro and in vivo in atherosclerotic plaque could enable mechanistic studies and inform S1PR1 targeted therapies.

PROCEDURES

H&E staining and immunostaining studies were performed on variably diseased human femoral endarterectomy plaque specimens, as well as mouse aortic sections from ApoE^-/- mice maintained on a high-fat diet (AS mice). In vitro autoradiography study in human femoral plaques was used to confirm the tracer specificity. Micro positron emission tomography (PET) and ex vivo autoradiography studies were conducted in AS mice and their controls using a S1PR1-specific radioligand [¹¹C]TZ3321 for in vivo and ex vivo quantification of S1PR1 expression in mouse aortic plaques.

RESULTS

Increased S1PR1 expression was observed in areas of human femoral endarterectomy plaque specimens with foam cell accumulation compared with control tissue; in vitro autoradiography study indicated that SEW2781, a S1PR1 compound was able to reduce the uptake of [¹¹C]TZ3321 by 56 %. S1PR1 levels were also upregulated in AS mouse aortic plaques. MicroPET data showed the aorta-to-blood tracer uptake ratio in AS mice was approximately 20 % higher than that in controls. Autoradiographic study also revealed elevated tracer accumulation in AS mouse aorta.

CONCLUSIONS

Upregulated S1PR1 expression in human and mouse atherosclerotic plaques was successfully identified by immunostaining and radioligand-based methods. This data demonstrates that [¹¹C]TZ3321 PET provides great promise in imaging S1PR1 expression in atherosclerotic plaques.

ATP-Responsive Low-Molecular-Weight Polyethylenimine-Based Supramolecular Assembly via Host-Guest Interaction for Gene Delivery

In this work, we report on an ATP-responsive low-molecular-weight polyethylenimine (LMW-PEI)-based supramolecular assembly. It formed via host-guest interaction between PEI (MW = 1.8 kDa)-α-cyclodextrin (α-CD) conjugates and PEI_1.8k-phenylboronic acid (PBA) conjugates. The host-guest interaction between PEI_1.8k-α-CD and PEI_1.8k-PBA was confirmed by the 2D-NOESY chromatogram experiment and competition test. The ATP-responsive property of the supramolecular assembly was evaluated by a series of ATP-triggered degradation and siRNA release studies in terms of fluorescence resonance energy transfer, agarose gel electrophoresis assay, and the time course monitoring of the particle size and morphology. Confocal laser scanning microscopy confirmed the intracellular disassembly of the supramolecular polymer and the release of siRNA. The supramolecular assembly showed high buffering capability and was capable of protecting siRNA from RNase degradation. It had high cytocompatibility according to in vitro cytotoxicity and hemolysis assays. LMW-PEI-based supramolecular assembly facilitated cellular entry of siRNA via energy-dependent endocytosis. Moreover, the assembly/SR-A siRNA polyplexes at N/P ratio of 30 was most effective in knocking down SR-A mRNA and inhibiting uptake of modified LDL. Taken together, this work shows that ATP-responsive LMW-PEI-based supramolecular assembly is a promising gene vector and has potential application in treating atherosclerosis.

Inhibition of perilipin 2 expression reduces pro-inflammatory gene expression and increases lipid droplet size

Our lab previously demonstrated that triglyceride-rich lipoprotein (TGRL) lipolysis products induce lipid droplet formation and pro-inflammatory gene expression in monocytes. We hypothesized that the inhibition of perilipin 2 expression in THP-1 monocytes would reduce lipid droplet formation and suppress pro-inflammatory gene expression induced by TGRL lipolysis products. In the current study, we use microarray analysis to identify gene expression altered by TGRL lipolysis products in THP-1 monocytes. We confirmed the expression of selected genes by quantitative reverse transcription PCR and characterized lipid droplet formation in these cells after exposure to TGRL lipolysis products. Using siRNA inhibition of perilipin 2 expression, we examined the role of perilipin 2 in the response of THP-1 monocytes to TGRL lipolysis products. We found that perilipin 2 siRNA increased the intracellular triglyceride content, increased the size of lipid droplets, and reduced pro-atherogenic and pro-inflammatory gene expression. We saw a reduction of serum/glucocorticoid kinase 1, v-maf musculoaponeurotic fibrosarcoma oncogene homolog F (avian), chemokine (C-C motif) ligand 3, and interleukin 8 gene expression induced by TGRL lipolysis products. This study supports previous findings that reduction of perilipin 2 expression is protective against atherogenesis, while finding an unexpected increase in lipid droplet size with reduced perilipin 2 expression.

Increased ROS production and DNA damage in monocytes are biomarkers of aging and atherosclerosis

Background

New evidence demonstrates that aging and dyslipidemia are closely associated with oxidative stress, DNA damage and apoptosis in some cells and extravascular tissues. However, in monocytes, which are naturally involved in progression and/or resolution of plaque in atherosclerosis, this concurrence has not yet been fully investigated. In this study, we evaluated the influence of aging and hypercholesterolemia on serum pro-inflammatory cytokines, oxidative stress, DNA damage and apoptosis in monocytes from apolipoprotein E-deficient (apoE^−/−) mice compared with age-matched wild-type C57BL/6 (WT) mice. Experiments were performed in young (2-months) and in old (18-months) male wild-type (WT) and apoE^−/− mice.

Results

Besides the expected differences in serum lipid profile and plaque formation, we observed that atherosclerotic mice exhibited a significant increase in monocytosis and in serum levels of pro-inflammatory cytokines compared to WT mice. Moreover, it was observed that the overproduction of ROS, led to an increased DNA fragmentation and, consequently, apoptosis in monocytes from normocholesterolemic old mice, which was aggravated in age-matched atherosclerotic mice.

Conclusions

In this study, we demonstrate that a pro-inflammatory systemic status is associated with an impairment of functionality of monocytes during aging and that these parameters are fundamental extra-arterial contributors to the aggravation of atherosclerosis. The present data open new avenues for the development of future strategies with the purpose of treating atherosclerosis.

Disordered haematopoiesis and cardiovascular disease: a focus on myelopoiesis

Cardiovascular (CV) diseases (CVD) are primarily caused by atherosclerotic vascular disease. Atherogenesis is mainly driven by recruitment of leucocytes to the arterial wall, where macrophages contribute to both lipid retention as well as the inflammatory milieu within the vessel wall. Consequently, diseases which present with an enhanced abundance of circulating leucocytes, particularly monocytes, have also been documented to accelerate CVD. A host of metabolic and inflammatory diseases, such as obesity, diabetes, hypercholesteraemia, and rheumatoid arthritis (RA), have been shown to alter myelopoiesis to exacerbate atherosclerosis. Genetic evidence has emerged in humans with the discovery of clonal haematopoiesis of indeterminate potential (CHIP), resulting in a disordered haematopoietic system linked to accelerated atherogenesis. CHIP, caused by somatic mutations in haematopoietic stem and progenitor cells (HSPCs), consequently provide a proliferative advantage over native HSPCs and, in the case of Tet2 loss of function mutation, gives rise to inflammatory plaque macrophages (i.e. enhanced interleukin (IL)-1β production). Together with the recent findings of the CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcomes Study) trial that revealed blocking IL-1β using Canakinumab reduced CV events, these studies collectively have highlighted a pivotal role of IL-1β signalling in a population of people with atherosclerotic CVD. This review will explore how haematopoiesis is altered by risk-factors and inflammatory disorders that promote CVD. Further, we will discuss some of the recent genetic evidence of disordered haematopoiesis in relation to CVD though the association with CHIP and suggest that future studies should explore what initiates HSPC mutations, as well as how current anti-inflammatory agents affect CHIP-driven atherosclerosis.

Foam cell formation: A new target for fighting atherosclerosis and cardiovascular disease

During atherosclerosis, the gradual accumulation of lipids into the subendothelial space of damaged arteries results in several lipid modification processes followed by macrophage uptake in the arterial wall. The way in which these modified lipoproteins are dealt with determines the likelihood of cholesterol accumulation within the monocyte-derived macrophage and thus its transformation into the foam cell that makes up the characteristic fatty streak observed in the early stages of atherosclerosis. The unique expression of chemokine receptors and cellular adhesion molecules expressed on the cell surface of monocytes points to a particular extravasation route that they can take to gain entry into atherosclerotic site, in order to undergo differentiation into the phagocytic macrophage. Indeed several GWAS and animal studies have identified key genes and proteins required for monocyte recruitment as well cholesterol handling involving lipid uptake, cholesterol esterification and cholesterol efflux. A re-examination of the previously accepted paradigm of macrophage foam cell origin has been called into question by recent studies demonstrating shared expression of scavenger receptors, cholesterol transporters and pro-inflammatory cytokine release by alternative cell types present in the neointima, namely; endothelial cells, vascular smooth muscle cells and stem/progenitor cells. Thus, therapeutic targets aimed at a more heterogeneous foam cell population with shared functions, such as enhanced protease activity, and signalling pathways, mediated by non-coding RNA molecules, may provide greater therapeutic outcome in patients. Finally, studies targeting each aspect of foam cell formation and death using both genetic knock down and pharmacological inhibition have provided researchers with a clearer understanding of the cellular processes at play, as well as helped researchers to identify key molecular targets, which may hold significant therapeutic potential in the future.

ZIP8 induces monocyte adhesion to the aortas ex-vivo by regulating zinc influx

Monocytes recruited and adhering to the inflamed arteries are crucial for atherosclerosis development. Here, we report the role of zinc (Zn²⁺) homeostasis in monocyte adhesion and recruitment. By comparing the expression levels of Zn²⁺ transporters between non-adhering and adhering monocytes, we found that the Zn²⁺ importer ZIP8 was specifically upregulated in monocytes adhering to the aortas ex-vivo. Although the overexpression of ZIP8 increased the absorption of Zn²⁺, Fe²⁺ and Cd²⁺ in monocytes, only Zn²⁺ supplementation was demonstrated capable of promoting the adhesion of monocytes to endothelial monolayers in vitro. In addition, we confirmed the role of ZIP8-dependent Zn²⁺ influx in promoting monocyte adhesion to the aortas ex-vivo. More importantly, the enforced expression of ZIP8 increased monocyte adhesion and recruitment to the nascent atherosclerotic lesions in ApoE^-/- mice. Overall, our results suggest that the Zn²⁺ influx in monocytes regulated by ZIP8 is a novel factor determining their adhesion and recruitment to atherosclerotic lesions, and that targeting ZIP8 or Zn²⁺ homeostasis may represent a novel strategy to interfere these activities.

Lowering the n-6/n-3 PUFAs ratio inhibits the formation of THP-1 macrophage-derived foam cell

Background

The balance between n-6 and n-3 PUFAs is an important determinant in the risk for cardiovascular disease. The study was to investigate the influence of the n-6 and n-3 PUFAs ratio on the formation of THP-1 monocyte-derived foam cells and explore the probable mechanism of anti-atherosclerosis.

Methods

THP-1 monocyte cells were cultured with PMA and ox-LDL to establish a foam-cell model, while treated with different ratios of n-6 to n-3 PUFAs for 48 h. The cholesterol of foam cells was measured by a cholesterol assay kit. The levels of IL-6 and TNFα in supernatant were detected with ELISA methods. The expressions of CD36, ABCA1, ACAT1, PPARγ and LXRα mRNA were detected with real-time PCR.

Results

Compared with the foam cell model group, the low and middle ratio of n-6 to n-3 PUFAs groups decreased the intracellular concentration of cholesterol (P < 0.01), but the high n-6/n-3 PUFAs ratio did not. Fatty acids decreased the level of IL-6 and TNFα in supernatant in a ratio-dependent manner. Fatty acids treatment also decreased the expressions of CD36、ACTA1、PPARγ、LXRα mRNA in a ratio-dependent manner.

Conclusions

Lowering the ratios of n-6 to n-3 PUFAs can decrease the secretion of inflammatory cytokines then reduce the expressions of CD36 and ACAT1 mRNA. As well, it can decrease the expressions of CD36 mRNA through the PPARγ pathway. This leads to less cholesterol ingestion into the cells and decreased synthesis of cholesteryl ester, which inhibits the formation of the foam cells, further preventing the occurrence and development of atherosclerosis.

The CD44-HA axis and inflammation in atherosclerosis: A temporal perspective

Cardiovascular disease (CVD) due to atherosclerosis is a disease of chronic inflammation at both the systemic and the tissue level. CD44 has previously been implicated in atherosclerosis in both humans and mice. This multi-faceted receptor plays a critical part in the inflammatory response during the onset of CVD, though little is known of CD44's role during the latter stages of the disease. This review focuses on the role of CD44-dependent HA-dependent effects on inflammatory cells in several key processes, from disease initiation throughout the progression of atherosclerosis. Understanding how CD44 and HA regulate inflammation in atherogenesis is key in determining the utility of the CD44-HA axis as a therapeutic target to halt disease and potentially promote disease regression.

Metformin ameliorates the progression of atherosclerosis via suppressing macrophage infiltration and inflammatory responses in rabbits

AIMS

The present study aimed to investigate the possible effects of metformin on the progression of atherosclerosis in a rabbit model.

MAIN METHODS

Rabbits were randomly divided into three groups (n = 10): the control (Ctrl) group (fed with a chow diet), and two experimental groups, the AS group and the Met group (both received an atherogenic diet). After 2 weeks of acclimatization, the rabbits in the AS and Met groups were given a placebo and metformin, respectively, daily by gavage for 10 weeks. Plasma lipids and inflammatory cytokines were measured. The aorta was isolated for histological and immunohistochemical analysis. In vitro, human umbilical vein endothelial cells (HUVECs) were treated with metformin, and monocyte adhesion and adhesion molecule expression were measured.

KEY FINDINGS

Metformin reduced plasma inflammatory cytokine levels but did not alter lipid content. Compared with that in the AS group, the atherosclerosis burden in the Met group was significantly decreased. The lesional macrophage content was reduced, but the lesional collagen content was not affected in the metformin-treated rabbits, compared with the corresponding levels in the non-treated controls. Furthermore, the aortic mRNA expression levels of adhesion molecules and inflammatory cytokines in the Met group were also significantly reduced compared with those in the AS group. Metformin treatment reduced monocyte adhesion to endothelial cells (ECs) and adhesion molecule expression, and inhibited rabbit monocyte differentiation into macrophages and the macrophage inflammatory response.

SIGNIFICANCE

Our results suggest that metformin impeded the progression of atherosclerosis, possibly by suppressing macrophage infiltration and inflammatory responses.

Copper sulfide nanoparticles as a photothermal switch for TRPV1 signaling to attenuate atherosclerosis

Atherosclerosis is characterized by the accumulation of lipids within the arterial wall. Although activation of TRPV1 cation channels by capsaicin may reduce lipid storage and the formation of atherosclerotic lesions, a clinical use for capsaicin has been limited by its chronic toxicity. Here we show that coupling of copper sulfide (CuS) nanoparticles to antibodies targeting TRPV1 act as a photothermal switch for TRPV1 signaling in vascular smooth muscle cells (VSMCs) using near-infrared light. Upon irradiation, local increases of temperature open thermo-sensitive TRPV1 channels and cause Ca²⁺ influx. The increase in intracellular Ca²⁺ activates autophagy and impedes foam cell formation in VSMCs treated with oxidized low-density lipoprotein. In vivo, CuS-TRPV1 allows photoacoustic imaging of the cardiac vasculature and reduces lipid storage and plaque formation in ApoE^-/^- mice fed a high-fat diet, with no obvious long-term toxicity. Together, this suggests CuS-TRPV1 may represent a therapeutic tool to locally and temporally attenuate atherosclerosis.

Progression and Characterization of the Accelerated Atherosclerosis in Iliac Artery of New Zealand White Rabbits: Effect of Simvastatin

OBJECTIVE

Although atherosclerosis is described in New Zealand White rabbit's iliac artery, yet details of time-dependent atherosclerosis progression are not well known. Further, a well characterized accelerated model of atherosclerosis is also required for the screening of candidate drugs to target specific steps of atherosclerosis development. The present study extensively characterizes the time-dependent plaque composition and functional responses of the atherosclerosis in rabbit iliac artery and its modification by simvastatin.

METHODS

Atherosclerosis was induced with a combination of balloon injury and atherogenic diet (AD) (1% cholesterol, 6% peanut oil) in rabbit's iliac artery. Atherosclerosis progression was evaluated on days 8, 10, 15, 21, 35, and 56 after AD feeding. The plaque characterization was done using histology, real-time reverse transcription-polymerase chain reaction, and vasoreactivity experiments. The standard anti-hyperlipidemic drug, simvastatin (5 mg·kg·d), was used to investigate its effect on atherosclerotic changes.

RESULTS

Plasma lipids were elevated in a progressive manner after AD feeding from days 8 to 56. Similarly, arterial lipids, Monocyte Chemoattractant Protein-1 (MCP-1) level along with infiltration of macrophages in the lesion area were also increased from day 15 onward. This resulted in a significant increase in the plaque area and intimal-medial thickness ratio in contrast to normal animals. Inflammatory milieu was observed with a significant increase in expression of pro-inflammatory regulators like MCP-1, Tumor Necrosis Factor-α (TNF-α) and Vascular Cell Adhesion Molecule-1 (VCAM-1), whereas anti-inflammatory cytokine interleukin 10 decreased as disease progressed. Endothelial dysfunction was also observed, specifically Acetylcholine (ACh)-induced vasorelaxation was reduced from day 8 onward, whereas the phenylephrine-induced vasoconstriction response was progressively reduced from day 15 in the iliac artery. Ground substances including proteoglycans, α-actin, and collagen content along with metalloproteinase-9 and Tissue inhibitor of metalloproteinases-1 (TIMP-1) inhibitors were significantly augmented at later time points, day 21 onward. Simvastatin treatment for 35 days, at a dose having no significant effect on plasma lipid levels, significantly reduced atherosclerotic progression as evident by reduced macrophage content, inflammatory burden, and extracellular matrix component like proteoglycans and metalloproteinase-9.

CONCLUSIONS

The authors observed that AD feeding with balloon injury in the rabbit iliac artery accelerated the progression of atherosclerosis and exhibited predominant features of type III human lesion within 8 weeks (56 days). Simvastatin treatment for 35 days exhibited anti-atherosclerotic efficacy without significantly lowering the circulating lipids. The current study thus provides an insight into the time-dependent atherosclerotic progression in rabbit iliac artery and highlights its utility for anti-atherosclerotic evaluation of the candidate drugs.

Cigarette Smoking and Adipose Tissue: The Emerging Role in Progression of Atherosclerosis

Smoking is an established risk factor for atherosclerosis through several underlying pathways. Moreover, in the development of atherosclerotic plaque formation, obesity, defined as excess fat mass accumulation, also plays a vital role in dyslipidemia and insulin resistance. Substantial evidence shows that cigarette smoking induces multiple pathological effects in adipose tissue, such as differentiation of adipocytes, lipolysis, and secretion properties in adipose tissue. Therefore, there is an emerging speculation in which adipose tissue abnormality induced by smoking or nicotine is likely to accelerate the progression of atherosclerosis. Herein, this review aims to investigate the possible interplay between smoking and adipose tissue dysfunction in the development of atherosclerosis.

Regulation of pro- and anti-atherogenic cytokines

Despite advances in prevention and treatment, vascular diseases continue to account for significant morbidity and mortality in the developed world. Incidence is expected to worsen as the number of patients with common co-morbidities linked with atherosclerotic vascular disease, such as obesity and diabetes, continues to increase, reaching epidemic proportions. Atherosclerosis is a lipid-driven vascular inflammatory disease involving multiple cell types in various stages of inflammation, activation, apoptosis, and necrosis. One commonality among these cell types is that they are activated and communicate with each other in a paracrine fashion via a complex network of cytokines. Cytokines mediate atherogenesis by stimulating expression of numerous proteins necessary for induction of a host of cellular responses, including inflammation, extravasation, proliferation, apoptosis, and matrix production. Cytokine expression is regulated by a number of transcriptional and post-transcriptional mechanisms. In this context, proteins that control and fine-tune cytokine expression can be considered key players in development of atherosclerosis and also represent targets for rational drug therapy to combat this disease. This review will describe the cellular and molecular mechanisms that drive atherosclerotic plaque progression and present key cytokines that participate in this process. We will also describe RNA binding proteins that mediate cytokine mRNA stability and regulate cytokine abundance. Identification and characterization of the cytokines and proteins that regulate their abundance are essential to our ability to identify therapeutic approaches to ameliorate atherosclerotic vascular disease.

Human induced pluripotent stem cell‑derived mesenchymal stem cells alleviate atherosclerosis by modulating inflammatory responses

The transplantation of mesenchymal stem cells (MSCs) has been a reported method for alleviating atherosclerosis (AS). Because the availability of bone marrow‑derived MSCs (BM‑MSCs) is limited, the authors used this study to explore the use of a new type of MSC, human induced pluripotent stem cell‑derived MSCs (iPSC‑MSCs), to evaluate whether these cells could alleviate AS. iPSC‑MSCs were intravenously administered to ApoE knock out mice fed on a high‑fat diet (HFD) for 12 weeks. It was reported that systematically administering iPSC‑MSCs clearly reduced the size of plaques. In addition, the numbers of macrophages and lipids in plaques were lower in the HFD + iPSC‑MSCs group than in the HFD group. Furthermore, iPSC‑MSCs attenuated AS‑associated inflammation by decreasing the levels of inflammatory cytokines, such as tumor necrosis factor‑α and interleukin‑6, in serum. In addition, the expression of Notch1 was higher in the HFD group, and injecting iPSC‑MSCs reversed this effect. In conclusion, the current study provides the first evidence indicating that iPSC‑MSCs may be a new optional MSC‑based strategy for treating AS.

H2O2-responsive and plaque-penetrating nanoplatform for mTOR gene silencing with robust anti-atherosclerosis efficacy

The mammalian target of rapamycin (mTOR) that controls autophagy and lipid metabolism is pivotal for atherosclerosis initiation and progression. Although blocking the mTOR function with rapamycin and its analogs may stimulate autophagy and consequently attenuate lipid storage and atherosclerotic lesions, only limited success has been achieved in clinical applications due to the unsatisfactory efficacy and safety profiles. In this study, we engineered a cerium oxide nanowire (CeO₂ NW)-based RNA interference (RNAi) oligonucleotide delivery nanoplatform for the effective silencing of mTOR and treatment of atherosclerosis. This nanoplatform is composed of the following three key components: (i) a stabilin-2-specific peptide ligand (S2P) to improve plaque targeting and penetration; (ii) polyethylene glycosylation (PEGylation) to extend in vivo circulation time; and (iii) a high aspect ratio CeO₂ core to facilitate endosome escape and ensure "on-demand" release of the RNAi payloads through competitive coordination of cytosolic hydrogen peroxide (H₂O₂). Systemic administration of the nanoplatforms efficiently targeted stabilin-2-expressing plaque and suppressed mTOR expression, which significantly rescued the impaired autophagy and inhibited the atherosclerotic lesion progression in apolipoprotein E-deficient (ApoE^-/^-) mice fed with a high-fat diet. These results demonstrated that this H₂O₂-responsive and plaque-penetrating nanoplatform can be a potent and safe tool for gene therapy of atherosclerosis.

P-Selectin and ICAM-1 synergy in mediating THP-1 monocyte adhesion in hemodynamic flow is length dependent

The tightly orchestrated recruitment of monocytes, whose progeny are critical to the progression and resolution of various physiological and pathophysiological processes, is implicated in the time course, severity, and resolution of pathology. Using a microfluidic-based cell adhesion assay integrating spatiotemporal analyses and micropatterning of adhesive proteins, we interrogated the effects of adhesive molecule presentation length, which varies in vivo with disease and stage, on THP-1 monocyte cell rolling versus firm adhesion mediated by P-selectin and/or ICAM-1 in hemodynamic flow. Our results indicate that co-presentation of P-selectin and ICAM-1 substantially decreases the length of adhesive substrate required to sustain adhesion in flow and that P-selectin functions synergistically with ICAM-1 to substantially enhance THP-1 firm adhesion. This synergy was found to furthermore correlate with diminished cell rolling velocities and length-enhanced secondary cell capture. Our results suggest pathophysiological ramifications for local remodeling of the inflamed microvascular microenvironment in directing the efficiency of monocyte trafficking.

TRPV4 calcium-permeable channel is a novel regulator of oxidized LDL-induced macrophage foam cell formation

Cardiovascular disease is the number one cause of death in United States, and atherosclerosis, a chronic inflammatory arterial disease, is the most dominant underlying pathology. Macrophages are thought to orchestrate atherosclerosis by generating lipid-laden foam cells and by secreting inflammatory mediators. Emerging data support a role for a mechanical factor, e.g., matrix stiffness, in regulation of macrophage function, vascular elasticity, and atherogenesis. However, the identity of the plasma membrane mechanosensor and the mechanisms by which pro-atherogenic signals are transduced/maintained are unknown. We have obtained evidence that TRPV4, an ion channel in the transient receptor potential vanilloid family and a known mechanosensor, is the likely mediator of oxidized low-density lipoprotein (oxLDL)-dependent macrophage foam cell formation, a critical process in atherogenesis. Specifically, we found that: i) genetic ablation of TRPV4 or pharmacologic inhibition of TRPV4 activity by a specific antagonist blocked oxLDL-induced macrophage foam cell formation, and ii) TRPV4 deficiency prevented pathophysiological range matrix stiffness or scratch-induced exacerbation of oxLDL-induced foam cell formation. Mechanistically, we found that: i) plasma membrane localization of TRPV4 was sensitized to the increasing level of matrix stiffness, ii) lack of foam cell formation in TRPV4 null cells was not due to lack of expression of CD36, a major receptor for oxLDL, and iii) TRPV4 channel activity regulated oxLDL uptake but not its binding on macrophages. Altogether, these findings identify a novel role for TRPV4 in regulating macrophage foam cell formation by modulating uptake of oxLDL. These findings suggest that therapeutic targeting of TRPV4 may provide a selective approach to the treatment of atherosclerosis.

Oxidized Low-Density Lipoprotein Loading of Macrophages Downregulates TLR-Induced Proinflammatory Responses in a Gene-Specific and Temporal Manner through Transcriptional Control

Hypercholesterolemia is a key risk factor for atherosclerosis and leads to the uptake of native and oxidized low-density lipoprotein (oxLDL) by macrophages (Mϕs) and foam cell formation. Inflammatory processes accompany Mϕ foam cell formation in the artery wall, yet the relationship between Mϕ lipid loading and their response to inflammatory stimuli remains elusive. We investigated proinflammatory gene expression in thioglycollate-elicited peritoneal Mϕs, bone marrow-derived Mϕs and dendritic cells, and RAW264.7 cells. Loading with oxLDL did not induce peritoneal Mϕ apoptosis or modulate basal-level expression of proinflammatory genes. Upon stimulation of TLR4, the rapid induction of IFN-β was inhibited in cells loaded with oxLDL, whereas the induction of other proinflammatory genes by TLR4 (LPS), TLR3 (polyriboinosinic-polyribocytidylic acid), TLR2 (Pam₃CSK₄), and TLR9 (CpG) remained comparable within the first 2 h. Subsequently, the expression of a subset of proinflammatory genes (e.g., IL-1β, IL-6, CCL5) was reduced in oxLDL-loaded cells at the level of transcription. This phenomenon was partially dependent on NF erythroid 2-related factor 2 (NRF2) but not on nuclear liver X receptors α and β (LXRα,β), peroxisome proliferator-activated receptor-γ (PPARγ), and activating transcription factor 3 (ATF3). LPS-induced NF-κB reporter activity and intracellular signaling by NF-κB and MAPK pathways were comparable in oxLDL-loaded Mϕs, yet the binding of p65/RelA (the prototypic NF-κB family member) was reduced at IL-6 and CCL5 promoters. This study revealed that oxLDL loading of Mϕs negatively regulates transcription at late stages of TLR-induced proinflammatory gene expression and implicates epigenetic mechanisms such as histone deacetylase activity.

AG1296 enhances plaque stability via inhibiting inflammatory responses and decreasing MMP-2 and MMP-9 expression in ApoE-/- mice

BACKGROUND

Atherosclerosis is a chronic process that progresses to unstable plaques. Plaque rupture leads to deleterious consequences such as acute coronary syndrome, thrombosis and stroke. AG1296 is a potent tyrosine kinase inhibitor which is able to block PDGF-PDGFR signaling pathway. This study aims to assess the effect of AG1296 on plaque stability and explore the potential mechanisms.

METHODS

Atherosclerotic plaques were induced in carotid arteries in ApoE-/- mice by perivascular collar placement. All mice were randomly divided into PBS and AG1296 groups. 3 weeks after the surgery, the carotid arteries were harvested for histological analysis.

RESULTS

In AG1296 group, plaque area decreased by 41.5% (p = 0.0041) and the contents of macrophages and lipids decreased by 43.5% (p = 0.0003) and 35.6% (p = 0.0032) respectively. The contents of smooth muscle cells increased by 22.3% (p = 0.0214) in AG1296 group. Vulnerable index decreased by 48.3% (p = 0.0002). The inflammation factors IL-6 and TNF- alpha decreased by 49.0% (p = 0.0008) and 51.8% (p < 0.0001) and matrix metalloproteinases MMP-2 and MMP-9 decreased by 54.1% (p = 0.0004) and 37.1% (p < 0.0001) in AG1296 group. M1 macrophage markers (MCP-1) were downregulated by 30.3% (p = 0.0007) and M2 macrophage markers (ARG-1) were increased by 55.2% (p = 0.0009) in AG1296 group.

CONCLUSION

AG1296 inhibited the atherosclerotic plaque progression and enhanced plaque stability by inhibiting inflammatory responses, reducing the expression of matrix metalloproteinases and promoting macrophages from proinflammatory phenotype to anti-inflammatory phenotype.

AMP-activated protein kinase α1 promotes atherogenesis by increasing monocyte-to-macrophage differentiation

Monocyte-to-macrophage differentiation, which can be initiated by physiological or atherogenic factors, is a pivotal process in atherogenesis, a disorder in which monocytes adhere to endothelial cells and subsequently migrate into the subendothelial spaces, where they differentiate into macrophages and macrophage-derived foam cells and cause atherosclerotic lesions. However, the monocyte-differentiation signaling pathways that are activated by atherogenic factors are poorly defined. Here we report that the AMP-activated protein kinase α1 (AMPKα1) in monocytes promotes atherosclerosis by increasing monocyte differentiation and survival. Exposure of monocytes to oxidized low-density lipoprotein, 7-ketocholesterol, phorbol 12-myristate 13-acetate, or macrophage colony-stimulated factor (M-CSF) significantly activated AMPK and promoted monocyte-to-macrophage differentiation. M-CSF-activated AMPK is via M-CSF receptor-dependent reactive oxygen species production. Consistently, genetic deletion of AMPKα1 or pharmacological inhibition of AMPK blunted monocyte-to-macrophage differentiation and promoted monocyte/macrophage apoptosis. Compared with apolipoprotein E knock-out (ApoE^-/-) mice, which show impaired clearing of plasma lipoproteins and spontaneously develop atherosclerosis, ApoE^-/-/AMPKα1^-/- mice showed reduced sizes of atherosclerotic lesions and lesser numbers of macrophages in the lesions. Furthermore, aortic lesions were decreased in ApoE^-/- mice transplanted with ApoE^-/-/AMPKα1^-/- bone marrow and in myeloid-specific AMPKα1-deficient ApoE^-/- mice. Finally, rapamycin treatment, which abolished delayed monocyte differentiation in ApoE^-/-/AMPKα1^-/- mice, lost its atherosclerosis-lowering effects in these mice. Mechanistically, we found that AMPKα1 regulates FoxO3-dependent expression of both LC3 and ULK1, which are two important autophagy-related markers. Rapamycin treatment increased FoxO3 activity as well as LC3 and ULK1 expressions in macrophages from AMPKα1^-/- mice. Our results reveal that AMPKα1 deficiency impairs autophagy-mediated monocyte differentiation and decreases monocyte/macrophage survival, which attenuates atherosclerosis in ApoE^-/- mice in vivo.

Monocyte Subsets Coregulate Inflammatory Responses by Integrated Signaling through TNF and IL-6 at the Endothelial Cell Interface

Two major monocyte subsets, CD14⁺CD16⁻ (classical) and CD14^+/dimCD16⁺ (nonclassical/intermediate), have been described. Each has different functions ascribed in its interactions with vascular endothelial cells (EC), including migration and promoting inflammation. Although monocyte subpopulations have been studied in isolated systems, their influence on EC and on the course of inflammation has been ignored. In this study, using unstimulated or cytokine-activated EC, we observed significant differences in the recruitment, migration, and reverse migration of human monocyte subsets. Associated with this, and based on their patterns of cytokine secretion, there was a difference in their capacity to activate EC and support the secondary recruitment of flowing neutrophils. High levels of TNF were detected in cocultures with nonclassical/intermediate monocytes, the blockade of which significantly reduced neutrophil recruitment. In contrast, classical monocytes secreted high levels of IL-6, the blockade of which resulted in increased neutrophil recruitment. When cocultures contained both monocyte subsets, or when conditioned supernatant from classical monocytes cocultures (IL-6^hi) was added to nonclassical/intermediate monocyte cocultures (TNF^hi), the activating effects of TNF were dramatically reduced, implying that when present, the anti-inflammatory activities of IL-6 were dominant over the proinflammatory activities of TNF. These changes in neutrophil recruitment could be explained by regulation of E-selectin on the cocultured EC. This study suggests that recruited human monocyte subsets trigger a regulatory pathway of cytokine-mediated signaling at the EC interface, and we propose that this is a mechanism for limiting the phlogistic activity of newly recruited monocytes.