Eukaryotic elongation factor 2 kinase regulates foam cell formation via translation of CD36

Eukaryotic elongation factor 2 kinase (eEF2K) is an atypical protein kinase that controls protein synthesis in cells under stress. Although well studied in cancer, less is known about its roles in chronic inflammatory diseases. Here, we examined its regulation of macrophage cholesterol handling in the context of atherosclerosis. eEF2K mRNA expression and protein activity were upregulated in murine bone marrow-derived macrophages (BMDMs) exposed to oxidized low-density lipoprotein cholesterol (oxLDL). When incubated with oxLDL, BMDMs from eEF2K knockout (Eef2k^-/- ) mice formed fewer Oil Red O⁺ foam cells than Eef2k^+/+ BMDMs (12.5% ± 2.3% vs. 32.3% ± 2.0%, p < .01). Treatment with a selective eEF2K inhibitor, JAN-384, also decreased foam cell formation for C57BL/6J BMDMs and human monocyte-derived macrophages. Disabling eEF2K selectively decreased protein expression of the CD36 cholesterol uptake receptor, mediated by a reduction in the proportion of translationally active Cd36 mRNA. Eef2k^-/- mice bred onto the Ldlr^-/- background developed aortic sinus atherosclerotic plaques that were 30% smaller than Eef2k^+/+ -Ldlr^-/- mice after 16 weeks of high cholesterol diet (p < .05). Although accompanied by a reduction in plaque CD36⁺ staining (p < .05) and lower CD36 expression in circulating monocytes (p < .01), this was not associated with reduced lipid content in plaques as measured by oil red O staining. Finally, EEF2K and CD36 mRNA levels were higher in blood mononuclear cells from patients with coronary artery disease and recent myocardial infarction compared to healthy controls without coronary artery disease. These results reveal a new role for eEF2K in translationally regulating CD36 expression and foam cell formation in macrophages. Further studies are required to explore therapeutic targeting of eEF2K in atherosclerosis.

Heart Failure with Reduced Ejection Fraction-Does Sex Matter?

PURPOSE OF REVIEW

There is an increasing recognition of the importance of sex in susceptibility, clinical presentation, and outcomes for heart failure. This review focusses on heart failure with reduced ejection fraction (HFrEF), unravelling differences in biology, clinical and demographic features and evidence for diagnostic and therapeutic strategies. This is intended to inform clinicians and researchers regarding state-of-the-art evidence relevant to women, as well as areas of unmet need.

RECENT FINDINGS

Females are well recognised to be under-represented in clinical trials, but there have been some improvements in recent years. Data from the last 5 years reaffirms that women presenting with HFrEF women are older and have more comorbidities like hypertension, diabetes and obesity compared with men and are less likely to have ischaemic heart disease. Non-ischaemic aetiologies are more likely to be the cause of HFrEF in women, and women are more often symptomatic. Whilst mortality is less than in their male counterparts, HFrEF is associated with a bigger impact on quality of life in females. The implications of this for improved prevention, treatment and outcomes are discussed. This review reveals distinct sex differences in HFrEF pathophysiology, types of presentation, morbidity and mortality. In light of this, in order for future research and clinical medicine to be able to manage HFrEF adequately, there must be more representation of women in clinical trials as well as collaboration for the development of sex-specific management guidelines. Future research might also elucidate the biochemical foundation of the sex discrepancy in HFrEF.

Association of Global Coagulation Profiles With Cardiovascular Risk Factors and Atherosclerosis: A Sex Disaggregated Analysis From the BioHEART-CT Study

Background

Although the association between dysregulated coagulation and atherosclerosis is well recognized, individual assays have been of minimal value in understanding disease susceptibility. Here we investigated the association of global coagulation profiles with coronary artery disease with consideration of sex differences.

Methods and Results

The study included patients from the BioHEART‐CT (The BioHEART Study: Assessing Patients With Suspected Cardiovascular Disease for New Disease Markers and Risk Factors) biobank who had computed tomography coronary angiograms scored for coronary artery calcium score (CACS) and Gensini score. The cohort included 206 adult patients who were referred for clinically indicated computed tomography coronary angiography and had a median of 2 major cardiac risk factors; 50% were women and the average age was 62.6 years (±9.9 years). The overall hemostatic potential (OHP) and calibrated automated thrombography generation assays were performed on platelet‐poor plasma. CACS and Gensini score in men were significantly correlated in bivariate analysis with measures from the OHP assay, and regression models predicting disease severity by CACS or Gensini score were improved by adding the OHP assay variables in men but not in women. The calibrated automated thrombography generation assay demonstrated a more hypercoagulable profile in women than in men. The OHP assay showed hypercoagulable profiles in women with hyperlipidemia and men with obesity.

Conclusions

The OHP assay identified hypercoagulable profiles associated with different risk factors for each sex and was associated with CACS and Gensini score severity in men, emphasizing the associations between increased fibrin generation and reduced fibrinolysis with cardiac risk factors and early atherosclerosis.

Registration Information

www.anzctr.org.au. Identifier: ACTRN12618001322224.

Bench-to-Bedside in Vascular Medicine: Optimizing the Translational Pipeline for Patients With Peripheral Artery Disease

Peripheral arterial disease is a growing worldwide problem with a wide spectrum of clinical severity and is projected to consume >$21 billion per year in the United States alone. While vascular researchers have brought several therapies to the clinic in recent years, few of these approaches have leveraged advances in high-throughput discovery screens, novel translational models, or innovative trial designs. In the following review, we discuss recent advances in unbiased genomics and broader omics technology platforms, along with preclinical vascular models designed to enhance our understanding of disease pathobiology and prioritize targets for additional investigation. Furthermore, we summarize novel approaches to clinical studies in subjects with claudication and ischemic ulceration, with an emphasis on streamlining and accelerating bench-to-bedside translation. By providing a framework designed to enhance each aspect of future clinical development programs, we hope to enrich the pipeline of therapies that may prevent loss of life and limb for those with peripheral arterial disease.

HDL Improves Cholesterol and Glucose Homeostasis and Reduces Atherosclerosis in Diabetes-Associated Atherosclerosis

BACKGROUND AND AIMS

Apolipoprotein A-I (ApoA-I), the main component of high-density lipoprotein (HDL), not only promotes reverse cholesterol transport (RCT) in atherosclerosis but also increases insulin secretion in pancreatic β-cells, suggesting that interventions which raise HDL levels may be beneficial in diabetes-associated cardiovascular disease (CVD). Previously, we showed that TNF-related apoptosis-inducing ligand (TRAIL) deletion in Apolipoprotein Eknockout (Apoe-/- ) mice results in diabetes-accelerated atherosclerosis in response to a "Western" diet. Here, we sought to identify whether reconstituted HDL (rHDL) could improve features of diabetes-associated CVD in Trail-/-Apoe-/- mice.

METHODS AND RESULTS

Trail-/-Apoe-/- and Apoe-/- mice on a "Western" diet for 12 weeks received 3 weekly infusions of either PBS (vehicle) or rHDL (containing ApoA-I (20 mg/kg) and 1-palmitoyl-2-linoleoyl phosphatidylcholine). Administration of rHDL reduced total plasma cholesterol, triglyceride, and glucose levels in Trail-/-Apoe-/- but not in Apoe-/- mice, with no change in weight gain observed. rHDL treatment also improved glucose clearance in response to insulin and glucose tolerance tests. Immunohistological analysis of pancreata revealed increased insulin expression/production and a reduction in macrophage infiltration in mice with TRAIL deletion. Furthermore, atherosclerotic plaque size in Trail-/-Apoe-/- mice was significantly reduced associating with increased expression of the M2 macrophage marker CD206, suggesting HDL's involvement in the polarization of macrophages. rHDL also increased vascular mRNA expression of RCT transporters, ABCA1 and ABCG1, in Trail-/-Apoe-/- but not in Apoe-/- mice. Conclusions. rHDL improves features of diabetes-associated atherosclerosis in mice. These findings support the therapeutic potential of rHDL in the treatment of atherosclerosis and associated diabetic complications. More studies are warranted to understand rHDL's mechanism of action.

FXYD1 Is Protective Against Vascular Dysfunction

[Figure: see text].

Single-Cell Immune Profiling in Coronary Artery Disease: The Role of State-of-the-Art Immunophenotyping With Mass Cytometry in the Diagnosis of Atherosclerosis

Coronary artery disease remains the leading cause of death globally and is a major burden to every health system in the world. There have been significant improvements in risk modification, treatments, and mortality; however, our ability to detect asymptomatic disease for early intervention remains limited. Recent discoveries regarding the inflammatory nature of atherosclerosis have prompted investigation into new methods of diagnosis and treatment of coronary artery disease. This article reviews some of the highlights of the important developments in cardioimmunology and summarizes the clinical evidence linking the immune system and atherosclerosis. It provides an overview of the major serological biomarkers that have been associated with atherosclerosis, noting the limitations of these markers attributable to low specificity, and then contrasts these serological markers with the circulating immune cell subtypes that have been found to be altered in coronary artery disease. This review then outlines the technique of mass cytometry and its ability to provide high-dimensional single-cell data and explores how this high-resolution quantification of specific immune cell subpopulations may assist in the diagnosis of early atherosclerosis in combination with other complimentary techniques such as single-cell RNA sequencing. We propose that this improved specificity has the potential to transform the detection of coronary artery disease in its early phases, facilitating targeted preventative approaches in the precision medicine era.

A "Western Diet" promotes symptoms of hepatic steatosis in spontaneously hypertensive rats

Systemic hypertension, characterized by elevated blood pressure ≥140/90 mm Hg, is a major modifiable risk factor for cardiovascular disease. Hypertension also associates with non-alcoholic fatty liver disease (NAFLD), which is becoming common due to a modern diet and lifestyle. The aim of the present study was to examine whether a high-fat "Western" diet had effects on hypertension and associated NAFLD. Normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were placed on a normal chow or high-fat diet for 8 weeks; blood pressure was measured fortnightly and body weight recorded weekly. As expected, SHR had elevated blood pressure compared to WKY. Diet did not influence blood pressure. Compared to SHR, WKY rats gained more weight, associating with increased white adipose tissue weight. Normotensive rats also had higher plasma cholesterol and triglycerides in response to a "Western" diet, with no changes in plasma glucose levels. Neither strain developed atherosclerosis. Interestingly, high-fat diet-fed SHR had increased liver weight, associating with a significant level of hepatic lipid accumulation not observed in WKY. Further, they exhibited hepatocellular ballooning and increased hepatic inflammation, indicative of steatohepatitis. These findings suggest that a high-fat "Western" diet promotes features of NAFLD in SHR, but not WKY rats. Importantly, the high-fat diet had no effect on blood pressure.

The novel P2X7 receptor antagonist PKT100 improves cardiac function and survival in pulmonary hypertension by direct targeting of the right ventricle

In pulmonary hypertension (PH) a proinflammatory milieu drives pulmonary vascular remodeling, maladaptive right ventricular (RV) remodeling, and right-sided heart failure. There is an unmet need for RV-targeted pharmaco-therapies to improve mortality. Targeting of the P2X7 receptor (P2X7R) reduces pulmonary pressures; however, its effects on the RV are presently unknown. We investigated the effect of P2X7 receptor (P2X7R) inhibition on the pulmonary vasculature and RV remodeling using the novel P2X7R antagonist PKT100. C57BL/6 mice were administered intratracheal bleomycin or saline and treated with PKT100 (0.2 mg·kg^-1·day^-1) or DMSO vehicle. RV was assessed by right heart catheterization and echocardiography, 21 days posttreatment. Cytokines in serum and bronchoalveolar lavage fluid (BALF) were analyzed by ELISA and flow cytometry. Lungs and hearts were analyzed histologically for pulmonary vascular and RV remodeling. Focused-PCR using genes involved in RV remodeling was performed. Right ventricular systolic pressure (RVSP) was elevated in bleomycin-treated mice (30.2 ± 1.1; n = 7) compared with control mice (23.5 ± 1.0; n = 10; P = 0.008). PKT100 treatment did not alter RVSP (32.4 ± 1.8; n = 9), but it substantially improved survival (93% vs. 57% DMSO). There were no differences between DMSO and PKT100 bleomycin mice in pulmonary inflammation or remodeling. However, RV hypertrophy was reduced in PKT100 mice. Bleomycin decreased echocardiographic surrogates of RV systolic performance, which were significantly improved with PKT100. Four genes involved in RV remodeling (RPSA, Rplp0, Add2, and Scn7a) were differentially expressed between DMSO and PKT100-treated groups. The novel P2X7R inhibitor, PKT100, attenuates RV hypertrophy and improves RV contractile function and survival in a mouse model of PH independently of effects on the pulmonary vasculature. PKT100 may improve ventricular response to increased afterload and merits further investigation into the potential role of P2X7R antagonists as direct RV-focused therapies in PH.NEW & NOTEWORTHY This study demonstrates the therapeutic potential for right-sided heart failure of a novel inhibitor of the P2X7 receptor (P2X7R). Inflammatory signaling and right ventricular function were improved in a mouse model of pulmonary fibrosis with secondary pulmonary hypertension when treated with this inhibitor. Importantly, survival was also improved, suggesting that this inhibitor, and other P2X7R antagonists, could be uniquely effective in right ventricle (RV)-targeted therapy in pulmonary hypertension. This addresses a major limitation of current treatment options, where the significant improvements in pulmonary pressures ultimately do not prevent mortality due to RV failure.

Plaque Calcification

Vascular calcification (VC) is strongly associated with all-cause mortality and is an independent predictor of cardiovascular events. Resulting from its complex, multifaceted nature, targeted treatments for VC have not yet been developed. Lipoproteins are well characterized in the pathogenesis of atherosclerotic plaques, leading to the development of plaque regressing therapeutics. Although their roles in plaque progression are well documented, their roles in VC, and calcification of a plaque, are not well understood. In this review, early in vitro data and clinical correlations suggest an inhibitory role for HDL (high-density lipoproteins) in VC, a stimulatory role for LDL (low-density lipoprotein) and VLDL (very low-density lipoprotein) and a potentially causal role for Lp(a) (lipoprotein [a]). Additionally, after treatment with a statin or PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitor, plaque calcification is observed to increase. With the notion that differing morphologies of plaque calcification associate with either a more stable or unstable plaque phenotype, uncovering the mechanisms of lipoprotein-artery wall interactions could produce targeted therapeutic options for VC.

Associations of ABCG1-mediated cholesterol efflux capacity with coronary artery lipid content assessed by near-infrared spectroscopy

Background

Although high-density lipoprotein (HDL) has atheroprotective properties, the association of HDL functionality with coronary plaques remains unclear.

Methods

We investigated the association between HDL-mediated cholesterol efflux capacity (CEC) and coronary lipid burden in 74 patients who underwent near-infrared spectroscopy (NIRS) imaging for acute coronary syndrome (ACS) or stable ischemic symptoms. We measured baseline HDL-mediated CEC, distinguishing the specific pathways, and stratified patients according to their median CEC values. Coronary lipid burden was assessed as lipid core burden index (LCBI) using NIRS at baseline (n=74) and on serial imaging (n=47).

Results

Patients with baseline ATP-binding cassette transporter G1 (ABCG1)-mediated CEC > median had a greater baseline LCBI {74 [20, 128] vs. 32 [5, 66]; P=0.04} or change in LCBI {-30 [-89, 0] vs. -3 [-16, 0]; P=0.048}. In addition to a negative association between baseline LCBI and change in LCBI (standardized β=-0.31; P=0.02), multivariable analysis demonstrated a significant interaction effect between clinical presentation of coronary artery disease (CAD) and baseline ABCG1-mediated CEC on change in LCBI (P=0.003), indicating that baseline ABCG1-mediated CEC was inversely associated with change in LCBI in patients with ACS (standardized β=-0.79, P=0.003), but not in those with stable ischemic symptoms (P=0.52).

Conclusions

In this study, ABCG1-mediated CEC, but not ATP-binding cassette transporter A1 and scavenger receptor B type I, was associated with regression of coronary artery lipid content, especially in patients with high-risk phenotype. Further studies are required to determine the roles of ABCG1 pathway in the development coronary plaques.

Translating Evidence of HDL and Plaque Regression

Considerable evidence from preclinical and population studies suggests that HDLs (high-density lipoproteins) possess atheroprotective properties. Reports from HDL infusion studies in animals and early clinical imaging trials reported evidence of plaque regression. These findings have stimulated further interest in developing new agents targeting HDL. However, the results of more recent imaging studies in the setting of high-intensity statin use have been disappointing. As the concept of plaque changes with HDL therapeutics evolves and imaging technology to evaluate these effects advances, there will become increasing opportunity to determine the effects of HDL agents on atherosclerotic plaque (Graphic Abstract).

Abstract 660: Elevated Calcium Drives Inflammatory-Driven Angiogenesis

Background: Peripheral arterial disease (PAD) is characterised by accelerated arterial calcification and impairment in angiogenesis, both of which can influence cardiovascular clinical outcomes. Studies implicate calcification as a driver of PAD, however, the mechanisms by which calcification modulates angiogenesis remain poorly understood. This study assessed the effect of high calcium on angiogenesis both in vitro and in vivo .

Methods: Human Coronary Artery Endothelial Cells (EC) were cultured and treated with calcification medium (CM) (CaCl 2 2.7mM, Na 2 PO 4 2.0mM) for 24 h. Angiogenic assays of proliferation, migration and tubulogenesis were conducted, and immunoblotting assessed angiogenic regulatory proteins. In vivo studies employed a calcification model with 8-12-week-old male OPG -/- and wildtype (C57BL6/J, control) mice which underwent hind-limb ischaemia (HLI) surgery. Blood flow reperfusion was assessed by Laser Doppler Perfusion Imaging (LDPI). Calcium assay assessed calcium levels in blood serum of the C57BL6/J and OPG -/- mice.

Results: CM significantly reduced EC tubulogenesis and viability (34% and 58% p<0.05) but increased migration (p<0.0001) over 24h. There was a significant increase in the protein levels of angiogenic regulators VEGFA (p<0.0001) and HIF-1α (p<0.0001). CM also significantly increased NF-κB (P65) nuclear protein, a key mediator of inflammatory-driven angiogenesis. qRT-PCR showed upregulation of osteoinductive factor Bone Morphogenetic protein (BMP2), and transcription factor Runx2 mRNA expression, both involved in osteogenesis and calcification. Blood serum calcium levels were significantly increased in OPG deficient mice. LDPI found there was significantly reduced blood-flow reperfusion in OPG -/- mice at days 6 (0.03±0.01 vs 0.32±0.05 p<0.01) and day 10 (0.08±0.01 vs 0.35±0.05 p<0.01) post HLI induction, compared to controls.

Conclusion: This is the first demonstration that high-levels of calcium impair ischaemia-driven angiogenesis in vivo and cause inflammation in ECs that suppresses tubule formation in vitro , despite upregulation of key angiogenic regulators VEGFA and HIF-1α. These findings have implications for the development of therapies that can suppress calcification in PAD.

Abstract 169: Lipoproteins and their Modified Forms Regulate Smooth Muscle Cell Calcification

Background: Vascular calcification (VC), alongside atherogenic lipoprotein profiles, have been correlated with poor cardiovascular outcome, however there is a paucity of literature exploring the relationship between the two regarding VC progression. We therefore aim to examine the roles of lipoprotein species and their oxidised forms on both medial and intimal VC.

Methods: Human aortic smooth muscle cells (HAoSMC) were pre-treated with 200 μg/ml high (HDL), low (LDL) and very low (VLDL) density lipoproteins for 24 hours before treating cells with a calcification medium (CM; Ca 2.7mM, PO 4 2.0 mM). Cells were harvested using an alizarin red (ARS) calcification assay, or at various time points for qPCR analysis. In parallel, in vivo studies using apolipoprotein E knock-out mice were fed an atherogenic diet for 40 weeks and received reconstituted HDL (rHDL) infusions containing apoA-I (20mg/kg) and 1-palmitoyl-2-linoleoyl phosphatidylcholine during the final 4 weeks of the study. Tissues were harvested and stained for plaque assessment (H&E) and calcium deposits (ARS).

Results: Pre-treatment of HAoSMC with rHDL inhibited calcification (43.9%, p<0.001), whereas ox-rHDL removed its protective effects. Likewise, ox-LDL (77.1%, p<0.05) also upregulated calcium deposition and interestingly ox-VLDL significantly decreased calcification (70.5%, p<0.05) with their native counterparts having no effects. PCR measures of calcification markers Runx2, RANKL and alkaline phosphatase show a time-dependent increase in expression as calcification occurs. In animal studies, no change in weight gain, cholesterol or triglyceride levels were observed with treatment. In addition, rHDL infusions did not alter plaque size however ARS staining of the brachiocephalic artery demonstrated a significant reduction (6.58%, p<0.05) in calcification present in the atherosclerotic plaque.

Conclusions: This study is the first to demonstrate the effects of lipoproteins on VC in vitro and the effects of rHDL on in vivo VC. Somewhat in accordance to the roles of lipoproteins in atherosclerosis, HDL and ox-VLDL show a reduction of calcification, where-as ox-LDL enhances calcification of HAoSMC.

High-Density Lipoprotein Infusions

High-density lipoproteins (HDLs) have presented an attractive target for development of new therapies for cardiovascular prevention on the basis of epidemiology and preclinical studies demonstrating their protective properties. Development of HDL mimetics provides an opportunity to administer functional HDL. However, clinical trials have produced variable results, with no evidence to date that they reduce cardiovascular events. This article reviews development programs of HDL mimetics.

VEGFR2 is activated by high-density lipoproteins and plays a key role in the proangiogenic action of HDL in ischemia

High-density lipoproteins augment hypoxia-induced angiogenesis by inducing the key angiogenic vascular endothelial growth factor A (VEGFA) and total protein levels of its receptor 2 (VEGFR2). The activation/phosphorylation of VEGFR2 is critical for mediating downstream, angiogenic signaling events. This study aimed to determine whether reconstituted high-density lipoprotein (rHDL) activates VEGFR2 phosphorylation and the downstream signaling events and the importance of VEGFR2 in the proangiogenic effects of rHDL in hypoxia. In vitro, rHDL increased VEGFR2 activation and enhanced phosphorylation of downstream, angiogenic signaling proteins ERK1/2 and p38 MAPK in hypoxia. Incubation with a VEGFR2-neutralizing antibody attenuated rHDL-induced phosphorylation of VEGFR2, ERK1/2, p38 MAPK, and tubule formation. In a murine model of ischemia-driven neovascularization, rHDL infusions enhanced blood perfusion and augmented capillary and arteriolar density. Infusion of a VEGFR2-neutralizing antibody ablated those proangiogenic effects of rHDL. Circulating Sca1⁺/CXCR4⁺ angiogenic progenitor cell levels, important for neovascularization in response to ischemia, were higher in rHDL-infused mice 3 d after ischemic induction, but that did not occur in mice that also received the VEGFR2-neutralizing antibody. In summary, VEGFR2 has a key role in the proangiogenic effects of rHDL in hypoxia/ischemia. These findings have therapeutic implications for angiogenic diseases associated with an impaired response to tissue ischemia.-Cannizzo, C. M., Adonopulos, A. A., Solly, E. L., Ridiandries, A., Vanags, L. Z., Mulangala, J., Yuen, S. C. G., Tsatralis, T., Henriquez, R., Robertson, S., Nicholls, S. J., Di Bartolo, B. A., Ng, M. K. C., Lam, Y. T., Bursill, C. A., Tan, J. T. M. VEGFR2 is activated by high-density lipoproteins and plays a key role in the proangiogenic action of HDL in ischemia.

Anacetrapib as a potential cardioprotective strategy

Cholesteryl ester transfer protein (CETP) facilitates movement of esterified cholesterol between high-density lipoproteins (HDLs) and apolipoprotein B-containing lipoproteins. By virtue of their ability to raise HDL cholesterol and lower low-density lipoprotein cholesterol, pharmacological inhibitors of CETP have received considerable attention as potential new agents in cardiovascular prevention. While early studies of CETP inhibitors have demonstrated a lack of clinical efficacy and potential toxicity, development of the potent CETP inhibitor, anacetrapib, has moved forward, with emerging evidence suggesting a role in reducing cardiovascular events. The experience with anacetrapib and its potential for use in clinical practice are reviewed here.

Abstract 315: Calcium Dose Dependently Influences Endothelial Cell Angiogenesis

Background: Peripheral artery disease (PAD) is a progressive occlusive disease of the arteries and a vascular complication in diabetes. Vascular calcification (VC) is implicated as a potential driver of PAD, and although the exact mechanisms are unclear, the site and location of calcification within the arterial wall contributes greatly. Long considered a passive process, VC is now recognised as a tightly regulated active process balancing the promotion and inhibition of calcification in the arterial wall. There is little evidence however, to demonstrate the effect of calcification on endothelial cell angiogenesis. This study sought to investigate the effects of calcium as a known inducer of calcification on in vitro angiogenesis.

Methods: Human Coronary Artery Endothelial Cells were cultured and treated with increasing calcium concentrations (CaCl 2 2.45-3.3 mM) for 24h. Proliferation, migration and tubule formation assays were conducted and real-time PCR assessed angiogenic and osteogenic genes. Alkaline phosphotase (ALP) activity was measured in supernatants following treatment.

Results: High concentrations of calcium reduced cell proliferation with a corresponding increase in ALP production suggesting release of osteogenic stimuli adversely affects cell viability. Mid-range concentrations of calcium induced a significant increase in cell migration (1.0 vs 2.4±0.3, p<0.05) while higher concentrations elicited no effect. Calcium treatment demonstrated a dose response where mid-range concentrations increased gene expression of hypoxia-inducible factor-1α (>500 fold), and fibroblast growth factor-2 (>150 fold). This increase corresponded with a decrease (1.0 vs 15.02±4.24; p<0.0001) in osteoprotegerin (OPG) at mid-range calcium with a significant increase at the highest concentration (1.0 vs 342±13.27; p<0.01) illustrating calcium-induced expression of OPG, a known protective gene in VC, may also regulate angiogenesis.

Conclusion: This is the first demonstration investigating the effects of calcium on endothelial cell angiogenesis. These findings suggest that calcium can directly affect genes involved in regulating angiogenesis, and could therefore provide an opportunity to develop potential treatments.

Infusional high-density lipoproteins therapies as a novel strategy for treating atherosclerosis

High-density lipoproteins (HDL) have received considerable interest as a target for the development of novel anti-atherosclerotic agents beyond conventional approaches to lipid lowering. While a number of approaches have focused on modifying remodeling and expression pathways implicated in the regulation of HDL levels, an additional approach involves simply infusions of delipidated HDL. Several groups have advanced HDL infusions to clinical development with intriguing signs suggesting potentially favorable impacts at the level of the artery wall. The findings of early studies of infusional HDL therapies will be reviewed.

Clinical trials with cholesteryl ester transfer protein inhibitors

PURPOSE OF REVIEW

Inhibition of cholesteryl ester transfer protein (CETP) has received considerable interest by virtue of its favorable effects on atherogenic and protective lipid parameters. The impact of CETP inhibitors in large clinical outcome trials will be reviewed.

RECENT FINDINGS

Population and genetic studies demonstrate that low CETP activity associates with lower rates of cardiovascular events. Inhibiting CETP activity in animal models has a favorable impact on experimental atherosclerosis. Although the first CETP inhibitor to advance to an outcome trial proved to have adverse clinical effects and the next agent, a more modest inhibitor, was clinically futile, there continues to be immense interest in the potential to develop nontoxic, potent CETP inhibitors to reduce cardiovascular risk.

SUMMARY

The current status of CETP inhibitors in the context of large outcomes trials will be reviewed.

Inducing apolipoprotein A-I synthesis to reduce cardiovascular risk: from ASSERT to SUSTAIN and beyond

Increasing attention has focused on efforts to promote the biological activities of high-density lipoproteins (HDL) in order to reduce cardiovascular risk. Targeting apolipoprotein A-I (apoA-I), the major protein carried on HDL particles, represents an attractive approach to promoting HDL by virtue of its ability to increase endogenous synthesis of functional HDL particles. A number of pharmacological strategies that target apoA-I, including upregulation of its production with the bromodomain and extraterminal (BET) protein inhibitor RVX-208, development of short peptide sequences that mimic its action, and administration as a component of reconstituted HDL particles, have undergone clinical development. The impact of these approaches on cardiovascular biomarkers will be reviewed.

Insulin promotes vascular smooth muscle cell proliferation and apoptosis via differential regulation of tumor necrosis factor-related apoptosis-inducing ligand

BACKGROUND

Insulin regulates glucose homeostasis but can also promote vascular smooth muscle (VSMC) proliferation, important in atherogenesis. Recently, we showed that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) stimulates intimal thickening via accelerated growth of VSMCs. The aim of the present study was to determine whether insulin-induced effects on VSMCs occur via TRAIL.

METHODS

Expression of TRAIL and TRAIL receptor in response to insulin and glucose was determined by polymerase chain reaction. Transcriptional activity was assessed using wild-type and site-specific mutations of the TRAIL promoter. Chromatin immunoprecipitation studies were performed. VSMC proliferation and apoptosis was measured.

RESULTS

Insulin and glucose exposure to VSMC for 24 h stimulated TRAIL mRNA expression. This was also evident at the transcriptional level. Both insulin- and glucose-inducible TRAIL transcriptional activity was blocked by dominant-negative specificity protein-1 (Sp1) overexpression. There are five functional Sp1-binding elements (Sp1-1, Sp1-2, Sp-5/6 and Sp1-7) on the TRAIL promoter. Insulin required the Sp1-1 and Sp1-2 sites, but glucose needed all Sp1-binding sites to induce transcription. Furthermore, insulin (but not glucose) was able to promote VSMC proliferation over time, associated with increased decoy receptor-2 (DcR2) expression. In contrast, chronic 5-day exposure of VSMC to 1 µg/mL insulin repressed TRAIL and DcR2 expression, and reduced Sp1 enrichment on the TRAIL promoter. This was associated with increased cell death.

CONCLUSIONS

The findings of the present study provide a new mechanistic insight into how TRAIL is regulated by insulin. This may have significant implications at different stages of diabetes-associated cardiovascular disease. Thus, TRAIL may offer a novel therapeutic solution to combat insulin-induced vascular pathologies.

Acute high-density lipoprotein therapies

PURPOSE OF REVIEW

Increasing interest has focused on the strategies that target the atheroprotective properties of HDL in order to reduce cardiovascular risk. The potential impact of strategies to acutely promote HDL functionality will be reviewed.

RECENT FINDINGS

Population and animal studies suggest that HDLs have a protective impact on atherosclerotic plaque. However, the failure of recent clinical trials of HDL cholesterol-raising agents has raised concerns that this may not be a viable strategy to reduce cardiovascular risk. Increasing attention has highlighted the importance of the functional quality, as opposed to quantity, of HDL with evidence of impaired HDL function in the setting of acute coronary syndromes (ACSs). The finding that infusing HDL in patients with recent acute ischemic events promotes the rapid regression of coronary atherosclerosis suggests a potentially useful strategy for ACS patients, although this remains to be fully established in large clinical outcome trials.

SUMMARY

Infusing HDL has favorable effects on coronary atherosclerosis in ACS patients, suggesting a potentially beneficial therapeutic strategy to acutely promote HDL functionality.

Abstract 103: HDL Improves Cholesterol and Glucose Homeostasis and Reduces Atherosclerosis in TRAIL-/-ApoE-/- mice

Background and Aims: Atherosclerosis is characterized by the infiltration and accumulation of monocytes in the arterial wall, combined with elevated plasma low density lipoprotein (LDL) and triglycerides, and low levels of high density lipoprotein (HDL). Apolipoprotein A-I (apoA-I), the main HDL apolipoprotein, is not only athero-protective but can also increase insulin secretion from pancreatic β-cells. Our laboratory recently demonstrated that in response to a ‘western’ diet TNF-related apoptosis-inducing ligand (TRAIL)-deficiency accelerated plaque development in ApoE-/- mice, and promoted features of diabetes typical to those observed in humans. We sought to determine whether reconstituted HDL (rHDL) could improve TRAIL-dependent disease.

Methods and Results: TRAIL-/-ApoE-/- and ApoE-/- mice on a ‘western’ diet for 12 w received 3 weekly infusions of either PBS (vehicle) or rHDL (20 mg/kg apoA-I, 1-palmitoyl-2-linoleoyl phosphatidylcholine) in the final 2 weeks of feeding prior to euthanasia. While no change in weight gain was observed, administration of rHDL significantly reduced plasma cholesterol, triglyceride and glucose levels, and improved glucose clearance and insulin sensitivity in TRAIL-/-ApoE-/- mice. Notably, rHDL treatment significantly attenuated atherosclerotic plaque size in brachiocephalic arteries of TRAIL-/-ApoE-/-, but not in ApoE-/- mice. rHDL-treated TRAIL-deficient mice also displayed elevated aortic mRNA expression of the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. This was associated with significantly increased expression of the pan macrophage marker F4/80 and the M2 marker CD206, suggesting that the rHDL stimulated polarization towards an M2 phenotype. Immunohistological analysis of the rHDL-treated TRAIL-/-ApoE-/- pancreata revealed increased insulin expression and reduced macrophage infiltration relative to ApoE-/- pancreata.

Conclusions: This is the first demonstration of rHDL improving atherosclerosis and rescuing features of diabetes which are dependent on TRAIL. Understanding how rHDL may be beneficial in TRAIL-dependent disease could identify new strategies in the treatment of atherosclerosis and associated diabetic complications.

TRAIL-deficiency accelerates vascular calcification in atherosclerosis via modulation of RANKL

The osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) cytokine system, not only controls bone homeostasis, but has been implicated in regulating vascular calcification. TNF–related apoptosis-inducing ligand (TRAIL) is a second ligand for OPG, and although its effect in vascular calcification in vitro is controversial, its role in vivo is not yet established. This study aimed to investigate the role of TRAIL in vascular calcification in vitro using vascular smooth muscle cells (VSMCs) isolated from TRAIL^−/− and wild-type mice, as well as in vivo, in advanced atherosclerotic lesions of TRAIL^−/−ApoE^−/− mice. The involvement of OPG and RANKL in this process was also examined. TRAIL dose-dependently inhibited calcium-induced calcification of human VSMCs, while TRAIL^−/− VSMCs demonstrated accelerated calcification induced by multiple concentrations of calcium compared to wild-type cells. Consistent with this, RANKL mRNA was significantly elevated with 24 h calcium treatment, while OPG and TRAIL expression in human VSMCs was inhibited. Brachiocephalic arteries from TRAIL^−/−ApoE^−/− and ApoE^−/− mice fed a high fat diet for 12 w demonstrated increased chondrocyte-like cells in atherosclerotic plaque, as well as increased aortic collagen II mRNA expression in TRAIL^−/−ApoE^−/− mice, with significant increases in calcification observed at 20 w. TRAIL^−/−ApoE^−/− aortas also had significantly elevated RANKL, BMP-2, IL-1β, and PPAR-γ expression at 12 w. Our data provides the first evidence that TRAIL deficiency results in accelerated cartilaginous metaplasia and calcification in atherosclerosis, and that TRAIL plays an important role in the regulation of RANKL and inflammatory markers mediating bone turn over in the vasculature.

Sp1, acetylated histone-3 and p300 regulate TRAIL transcription: mechanisms of PDGF-BB-mediated VSMC proliferation and migration

We recently reported that TNF-related apoptosis-inducing ligand (TRAIL) is important in atherogenesis, since it can induce vascular smooth muscle cell (VSMC) proliferation and arterial thickening following injury. Here we show the first demonstrate that TRAIL siRNA reduces platelet-derived growth factor-BB (PDGF-BB)-stimulated VSMC proliferation and migration. PDGF-BB-inducible VSMC proliferation was completely inhibited in VSMCs isolated from aortas of TRAIL(-/-) mice; whereas inducible migration was blocked compared to control VSMCs. TRAIL transcriptional control mediating this response is not established. TRAIL mRNA, protein and promoter activity was increased by PDGF-BB and subsequently inhibited by dominant-negative Sp1, suggesting that the transcription factor Sp1 plays a role. Sp1 bound multiple Sp1 sites on the TRAIL promoter, including two established (Sp1-1 and -2) and two novel Sp1-5/6 and -7 sites. PDGF-BB-inducible TRAIL promoter activity by Sp1 was mediated through these sites, since transverse mutations to each abolished inducible activity. PDGF-BB stimulation increased acetylation of histone-3 (ac-H3) and expression of the transcriptional co-activator p300, implicating chromatin remodelling. p300 overexpression increased TRAIL promoter activity, which was blocked by dominant-negative Sp1. Furthermore, PDGF-BB treatment increased the physical interaction of Sp1, p300 and ac-H3, while chromatin immunoprecipitation studies revealed Sp1, p300 and ac-H3 enrichment on the TRAIL promoter. Taken together, our studies demonstrate for the first time that PDGF-BB-induced TRAIL transcriptional activity requires the cooperation of Sp1, ac-H3 and p300, mediating increased expression of TRAIL which is important for VSMC proliferation and migration. Our findings have the promising potential for targeting TRAIL as a new therapeutic for vascular proliferative disorders.

The apolipoprotein A-I mimetic peptide, ETC-642, reduces chronic vascular inflammation in the rabbit

BACKGROUND

High-density lipoproteins (HDL) and their main apolipoprotein, apoA-I, exhibit anti-inflammatory properties. The development of peptides that mimic HDL apolipoproteins offers a promising strategy to reduce inflammatory disease. This study aimed to compare the anti-inflammatory effects of ETC-642, an apoA-I mimetic peptide, with that of discoidal reconstituted HDL (rHDL), consisting of full-length apoA-I complexed with phosphatidylcholine, in rabbits with chronic vascular inflammation.

RESULTS

New Zealand White rabbits (n = 10/group) were placed on chow supplemented with 0.2% (w/w) cholesterol for 6-weeks. The animals received two infusions of saline, rHDL (8 mg/kg apoA-I) or ETC-642 (30 mg/kg peptide) on the third and fifth days of the final week. The infusions of rHDL and ETC-642 were able to significantly reduce cholesterol-induced expression of intracellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the thoracic aorta (p < 0.05). When isolated rabbit HDL was pre-incubated with human coronary artery endothelial cells (HCAECs), prior to stimulation with TNF-α, it was found that HDL from ETC-642 treated rabbits were more effective at inhibiting the TNF-α-induced increase in ICAM-1, VCAM-1 and p65 than HDL isolated from saline treated rabbits (p < 0.05). There were, however, no changes in HDL lipid composition between treatment groups.

CONCLUSIONS

Infusion of ETC-642 causes anti-inflammatory effects that are comparable to rHDL in an animal model of chronic vascular inflammation and highlights that apoA-I mimetic peptides present a viable strategy for the treatment of inflammatory disease.

Anti-inflammatory effects of apolipoprotein A-I in the rabbit

OBJECTIVE

Infusions of apoA-I in the lipid-free form or as a constituent of discoidal reconstituted high-density lipoproteins, (A-I)rHDL, markedly inhibit acute vascular inflammation in normocholesterolemic New Zealand White (NZW) rabbits. This effect is apparent even when apoA-I is administered 24h prior to the inflammatory insult. The present study asks if this benefit is related to an improved anti-inflammatory capacity of the high-density lipoprotein (HDL) fraction, or to increased arterial expression of genes that inhibit inflammation.

METHODS AND RESULTS

The ability of apoA-I to increase the anti-inflammatory capacity of HDL was assessed by infusing normocholesterolemic NZW rabbits with saline, lipid-free apoA-I or (A-I)rHDL. The infused apoA-I incorporated rapidly into the rabbit HDL fraction. The animals were sacrificed at 5 or 360 min post-infusion and plasma was collected. HDL were isolated by ultracentrifugation and incubated with cytokine-activated cultured human coronary artery endothelial cells. HDL from animals sacrificed at 5 min post-apoA-I infusion had a slightly enhanced anti-inflammatory capacity relative to HDL from the saline-infused animals. The anti-inflammatory capacity of HDL from the animals sacrificed at 360 min post-apoA-I infusion was comparable to that of HDL from the saline-infused animals. The effect of (A-I)rHDL infusions on arterial 3β-hydroxysteroid-Δ24 reductase (DHCR24) and endothelial adhesion molecule expression was investigated in cholesterol-fed NZW rabbits. Relative to animals infused with saline, (A-I)rHDL infusions decreased aortic VCAM-1 and ICAM-1 protein expression by 73 and 54%, respectively (p<0.05), and increased DHCR24 mRNA levels by 56% (p<0.0001).

CONCLUSION

ApoA-I inhibits vascular inflammation in NZW rabbits, at least in part, by increasing DHCR24 expression.