The FXYD1 protein plays a protective role against pulmonary hypertension and arterial remodeling via redox and inflammatory mechanisms

Pulmonary hypertension (PH) consists of a heterogenous group of diseases that culminate in increased pulmonary arterial pressure and right ventricular (RV) dysfunction. We sought to investigate the role of FXYD1, a small membrane protein that modulates Na+-K+-ATPase function, in the pathophysiology of PH. We mined online transcriptome databases to assess FXYD1 expression in PH. We characterized the effects of FXYD1 knockout (KO) in mice on right and left ventricular (RV and LV) function using echocardiography and measured invasive hemodynamic measurements under normal conditions and after treatment with bleomycin sulfate or chronic hypoxia to induce PH. Using immunohistochemistry, immunoblotting, and functional assays, we examined the effects of FXYD1 KO on pulmonary microvasculature and RV and LV structure and assessed signaling via endothelial nitric oxide synthase (eNOS) and inflammatory pathways. FXYD1 lung expression tended to be lower in samples from patients with idiopathic pulmonary arterial hypertension (IPAH) compared with controls, supporting a potential pathophysiological role. FXYD1 KO mice displayed characteristics of PH including significant increases in pulmonary arterial pressure, increased muscularization of small pulmonary arterioles, and impaired RV systolic function, in addition to LV systolic dysfunction. However, when PH was stimulated with standard models of lung injury-induced PH, there was no exacerbation of disease in FXYD1 KO mice. Both the lungs and left ventricles exhibited elevated nitrosative stress and inflammatory milieu. The absence of FXYD1 in mice results in LV inflammation and cardiopulmonary redox signaling changes that predispose to pathophysiological features of PH, suggesting FXYD1 may be protective.NEW & NOTEWORTHY This is the first study to show that deficiency of the FXYD1 protein is associated with pulmonary hypertension. FXYD1 expression is lower in the lungs of people with idiopathic pulmonary artery hypertension. FXYD1 deficiency results in both left and right ventricular functional impairment. Finally, FXYD1 may endogenously protect the heart from oxidative and inflammatory injury.

Sex, Endothelial Cell Functions, and Peripheral Artery Disease

Peripheral artery disease (PAD) is caused by blocked arteries due to atherosclerosis and/or thrombosis which reduce blood flow to the lower limbs. It results in major morbidity, including ischemic limb, claudication, and amputation, with patients also suffering a heightened risk of heart attack, stroke, and death. Recent studies suggest women have a higher prevalence of PAD than men, and with worse outcomes after intervention. In addition to a potential unconscious bias faced by women with PAD in the health system, with underdiagnosis, and lower rates of guideline-based therapy, fundamental biological differences between men and women may be important. In this review, we highlight sexual dimorphisms in endothelial cell functions and how they may impact PAD pathophysiology in women. Understanding sex-specific mechanisms in PAD is essential for the development of new therapies and personalized care for patients with PAD.

Endothelial cell dysfunction: Implications for the pathogenesis of peripheral artery disease

Peripheral artery disease (PAD) is caused by occluded or narrowed arteries that reduce blood flow to the lower limbs. The treatment focuses on lifestyle changes, management of modifiable risk factors and vascular surgery. In this review we focus on how Endothelial Cell (EC) dysfunction contributes to PAD pathophysiology and describe the largely untapped potential of correcting endothelial dysfunction. Moreover, we describe current treatments and clinical trials which improve EC dysfunction and offer insights into where future research efforts could be made. Endothelial dysfunction could represent a target for PAD therapy.

Associations between adipokines and atrial fibrillation: A systematic review and meta-analysis

AIMS

Although overweight and obesity are associated with increased risk of atrial fibrillation (AF), the underlying mechanisms are not well characterised. Recent data suggest that this link may be partly due to abnormal adipose tissue-derived cytokines or adipokines. However, this relationship is not well clarified. To evaluate the association between adipokines and AF in a systematic review and meta-analysis.

DATA SYNTHESIS

PubMed, Embase, and Web of Science Core Collection were searched from inception through 1^st March 2021. Studies were included if they reported any adipokine and AF, with their quality assessed using the Newcastle-Ottawa scale. Data were independently abstracted, with unadjusted and multivariable adjusted estimates pooled in a random-effects meta-analysis. Data are presented for overall prevalent or incident AF and AF subtypes (paroxysmal, persistent, or non-paroxysmal AF). A total of 34 studies, with 31,479 patients, were included. The following adipokines were significantly associated with AF in the pooled univariate data - apelin (risk ratio for prevalent AF: 0.05 [0.00-0.50], p = 0.01; recurrent AF: 0.21 [0.11-0.42], p < 0.01) and resistin (incident AF: 2.05 [1.02-4.1], p = 0.04; prevalent AF: 2.62 [1.78-3.85], p < 0.01). Pooled analysis of multivariable adjusted effect size estimates showed adiponectin as the sole independent predictor of AF incidence (1.14 [1.02-1.27], p = 0.02). Moreover, adiponectin was associated with non-paroxysmal AF (persistent AF: 1.45 [1.08-1.94, p = 0.01; non-paroxysmal versus paroxysmal AF: 3.14 [1.87-5.27, p < 0.01).

CONCLUSIONS

Adipokines, principally adiponectin, apelin, and resistin, are associated with the risk of atrial fibrillation. However, the association is not seen after multivariate adjustment, likely reflecting the lack of statistical power. Future research should investigate these relationships in larger prospective cohorts and how they can refine AF monitoring strategies.

PROSPERO ID

CRD42020208879.

3D-Printed Micro Lens-in-Lens for In Vivo Multimodal Microendoscopy

Multimodal microendoscopes enable co-located structural and molecular measurements in vivo, thus providing useful insights into the pathological changes associated with disease. However, different optical imaging modalities often have conflicting optical requirements for optimal lens design. For example, a high numerical aperture (NA) lens is needed to realize high-sensitivity fluorescence measurements. In contrast, optical coherence tomography (OCT) demands a low NA to achieve a large depth of focus. These competing requirements present a significant challenge in the design and fabrication of miniaturized imaging probes that are capable of supporting high-quality multiple modalities simultaneously. An optical design is demonstrated which uses two-photon 3D printing to create a miniaturized lens that is simultaneously optimized for these conflicting imaging modalities. The lens-in-lens design contains distinct but connected optical surfaces that separately address the needs of both fluorescence and OCT imaging within a lens of 330 µm diameter. This design shows an improvement in fluorescence sensitivity of >10x in contrast to more conventional fiber-optic design approaches. This lens-in-lens is then integrated into an intravascular catheter probe with a diameter of 520 µm. The first simultaneous intravascular OCT and fluorescence imaging of a mouse artery in vivo is reported.

The Effects of Exercise on Plaque Volume and Composition in a Mouse Model of Early and Late Life Atherosclerosis

Background

Exercise is associated with a less atherogenic lipid profile; however, there is limited research on the effect of exercise on atherosclerotic plaque composition and markers of plaque stability.

Methods

A total of 110 apolipoprotein (apo)E−/− mice were placed on a chow diet and randomly assigned to control or exercise for a period of 10 weeks, commencing either at 12 weeks of age (the early-stage atherosclerosis, EA group) or at 40 weeks of age (the late-stage atherosclerosis, LA group). At the end of the exercise period, blood was assayed for lipids. Histologic analysis of the aortic sinus was undertaken to assess plaque size and composition that includes macrophage content, monocyte chemoattractant protein (MCP)-1, matrix metalloproteinase-2 (MMP-2), and tissue inhibitors of metalloproteinase 1 and 2 (TIMP-1 and 2).

Results

A total of 103 mice (38 EA, 65 LA) completed the protocol. In the EA group, exercise reduced plasma total cholesterol (TC) (−16%), free cholesterol (−13%), triglyceride (TG) (−35%), and phospholipid (−27%) levels, when compared to sedentary control mice (p &lt; 0.01). In the EA group, exercise also significantly reduced plaque stenosis (−25%, p &lt; 0.01), and there were higher levels of elastin (3-fold increase, p &lt; 0.0001) and collagen (11-fold increase, p &lt; 0.0001) in plaques, compared to control mice. There was an increase in plaque MMP-2 content in the exercise group (13% increase, p &lt; 0.05) but no significant difference in macrophage or MCP-1 content. In the LA group, exercise reduced plaque stenosis (−18%, p &lt; 0.05), but there was no significant difference in plaque composition. There was no difference in macrophage, MCP-1, or MMP-2 content in the LA groups. TIMP-1 was lower with exercise in both the EA and LA groups (−59%, p &lt; 0.01 and −51%, p &lt; 0.01 respectively); however, there was no difference in TIMP-2 levels.

Conclusion

A 10-week exercise period reduces atherosclerotic plaque stenosis when commenced at both early- and late-stage atherosclerosis. Intervening earlier with exercise had a greater beneficial effect on lipids and plaque composition than when starting exercise at a later disease stage.

The Anti-inflammatory and Proangiogenic Properties of High-Density Lipoproteins: An Emerging Role in Diabetic Wound Healing

Significance: Prolonged inflammation and impaired angiogenesis are the two principal factors that prevent successful wound healing, which is exacerbated in people with diabetes. There is a significant need for new wound healing treatments that target both these factors simultaneously. This review discusses the emerging evidence that high-density lipoproteins (HDL) have pleiotropic wound healing benefits. Recent Advances: Numerous in vitro and in vivo studies have demonstrated the anti-inflammatory and proangiogenic effects of HDL. In endothelial cells, HDL mediate these effects through interaction with the scavenger receptor SR-BI, which activates the PI3K/Akt pathway, causing a decrease in inflammatory protein production and an increase in proangiogenic growth factors. In macrophages, HDL inhibit inflammation through suppression of the nuclear factor kappa B activation pathway. This review details the molecular disturbances that cause impaired wound healing in diabetes with a particular focus on inflammation and angiogenesis and the pathways in which HDL provide benefit. Critical Issues: Diabetic foot ulcers (DFUs) impose a major public health challenge worldwide. It is estimated that 20% patients with DFUs require amputation, which is accompanied by a significant social and economic burden. To date, there are no therapeutic agents with pleiotropic effects that actively improve wound healing, highlighting a therapeutic void for this complex disease.

Emerging Therapeutic Applications for Fumarates

Fumarates are successfully used for the treatment of psoriasis and multiple sclerosis. Their antioxidative, immunomodulatory, and neuroprotective properties make fumarates attractive therapeutic candidates for other pathologies. The exact working mechanisms of fumarates are, however, not fully understood. Further elucidation of the mechanisms is required if these drugs are to be successfully repurposed for other diseases. Towards this, administration route, dosage, and treatment timing, frequency, and duration are important parameters to consider and optimize with clinical paradigms in mind. Here, we summarize the rapidly expanding literature on the pharmacokinetics and pharmacodynamics of fumarates, including a discussion on two recently FDA-approved fumarates VumerityTM and BafiertamTM. We review emerging applications of fumarates, focusing on neurological and cardiovascular diseases.

A Nanoparticle-Based Affinity Sensor that Identifies and Selects Highly Cytokine-Secreting Cells

We developed a universal method termed OnCELISA to detect cytokine secretion from individual cells by applying a capture technology on the cell membrane. OnCELISA uses fluorescent magnetic nanoparticles as assay reporters that enable detection on a single-cell level in microscopy and flow cytometry and fluorimetry in cell ensembles. This system is flexible and can be modified to detect different cytokines from a broad range of cytokine-secreting cells. Using OnCELISA we have been able to select and sort highly cytokine-secreting cells and identify cytokine-secreting expression profiles of different cell populations in vitro and ex vivo. We show that this system can be used for ultrasensitive monitoring of cytokines in the complex biological environment of atherosclerosis that contains multiple cell types. The ability to identify and select cell populations based on their cytokine expression characteristics is valuable in a host of applications that require the monitoring of disease progression.

P731High-density lipoproteins rescue diabetes-impaired angiogenesis by restoring cellular metabolic reprogramming responses to hypoxia

Background

We have previously identified that high-density lipoproteins (HDL) rescue hypoxia-induced angiogenesis in diabetes, however the underlying mechanisms remain unknown. A central component of hypoxia-induced angiogenesis is the reprogramming of endothelial cell (EC) metabolism to improve tolerance of hypoxia at the site of injury/repair, including following myocardial infarction. Pyruvate dehydrogenase kinase 4 (PDK4) suppresses mitochondrial respiration in hypoxia to decrease oxygen consumption and preserve cell survival. Diabetes impairs this adaptation to hypoxia, causing cellular dysfunction and may underlie delayed angiogenic responses to ischaemia in hyperglycaemia.

Purpose

To determine the role of metabolic reprogramming in angiogenesis and diabetes and the effect of reconstituted HDL (rHDL).

Methods and results

Using an in vitro functional angiogenesis assay, siRNA-mediated knockdown of PDK4 impaired human coronary artery endothelial cell (HCAEC) tubulogenesis in hypoxia by 82% versus siScrambled controls (P<0.0001). HCAECs were treated with rHDL (20μM, apolipoproteinA-I + phosphatidylcholine) or PBS (vehicle) and exposed to glucose (5 or 25 mM, 72 h), then normoxia or hypoxia (1.2% O2, 6 h). PDK4 expression was increased by 65% in hypoxia versus the normoxia control (P<0.05). By contrast, in high glucose PDK4 expression failed to increase in response to hypoxia. Incubation with rHDL rescued this impairment and elevated PDK4 expression by 40% in hypoxia and in high glucose (P<0.01), versus the PBS control. In parallel, rHDL rescued high glucose-impaired tubulogenesis in hypoxia by 64% versus the PBS/normoxia control (P<0.001). We next used a murine model of diabetic wound healing that tracks angiogenesis in the wound bed. We found daily topical application of rHDL (50μg/wound/day) increased wound angiogenesis by 10% (as assessed by Laser Doppler perfusion imaging) and promoted CD31+ neovessel formation by 46% in diabetic wounds, supporting an increased rate of wound closure in diabetic animals of 30% (P<0.05). rHDL treated wounds from diabetic mice had a striking increase in PDK4 gene (180%) and protein expression (350%) in the early-mid stages (24 h and 3-day time points, P<0.05) post-wounding, when the angiogenic response to wound ischaemia is most important.

Conclusions

We have demonstrated that the key protein controlling the metabolic reprogramming response to hypoxia, PDK4, plays an important role in endothelial cell angiogenesis. We also show that the PDK4 and angiogenesis responses to hypoxia are impaired in high glucose and can be rescued by rHDL. In vivo we find that topical rHDL increases wound angiogenesis and PDK4 levels, explaining the enhanced rate of wound closure in diabetic mice and has implications for improving cardiovascular outcomes for diabetic patients following myocardial infarction.

Abstract 138: A Novel Cellular and Genetic Approach to Investigate the Cardioprotective Role Played by Endothelial Nitric Oxide Synthase in Myocardial Infarction

The loss of regenerative properties in adult cardiomyocytes (CMs) is directly linked to their inability to proliferate. Following an extensive ischaemic event in an aged heart, fibrotic scar formation is the only repair process and eventually heart failure develops. However, molecular and cellular cues in the neonatal heart support that cardiac regeneration is possible in presence of proliferating CMs. Based on previous studies demonstrating that endothelial nitric oxide synthase (eNOS) regulates proliferation in both endothelial cells (ECs) and CMs, we hypothesized that eNOS signaling could play a cardioprotective role. To test our hypothesis, we injected different combinations of co-cultured ECs and CMs in the LV muscle wall of MI mice (permanent LAD ligation). First, injected cells were isolated from either WT or KO eNOS neonatal mice and then co-cultured to form 3D vascularized cardiac spheroids (VCSs), which were eventually transplanted in adult MI mice on the day of the procedure. Control infarcted animals received media-only (vehicle). Other mice received a suspension of co-cultured VCSs in media as follows: i ) WT CMs and ECs; ii ) WT CMs and KO ECs; iii ) KO CMs and WT ECs. Following 28 days, injection of WT cells increased the ejection fraction (EF%) by 20% compared with control animals (61%±4% and 41%±11%, respectively). When eNOS was absent in either CMs or ECs, the EF% was 40%±5% and 46%±2%, respectively, suggesting that the eNOS-mediated protection is dependent on its presence in both cells. Histological analyses confirmed the presence of WT VCSs in MI mice, contributing to a thicker wall thickness compared to vehicle MI mice. No VCSs were observed in the LV wall when KO cells were injected. Therefore, our results strongly suggest that eNOS may play a major role via both an autocrine (CMs) and paracrine (ECs) mechanism. Current studies are focusing on further evaluating the mechanism(s) for this eNOS-mediated protective role. To our knowledge, this is the first study combining cellular and genetic approaches to evaluate the cardioprotective role of eNOS in the heart. A better understanding of this mechanisms may have significant impact for the development of improved molecular and cell therapeutics (including stem cells) for heart failure patients.

Induction of obesity impairs reverse cholesterol transport in ob/ob mice

Objectives

Obesity is an independent risk factor for cardiovascular disease. Reverse cholesterol transport (RCT) is an important cardioprotective mechanism. This study aimed to investigate RCT changes in a murine model of obesity.

Methods

Ob/ob and control mice were injected with [³H]-cholesterol-labelled macrophages and cholesterol accumulation quantified after 48 h. Ex vivo, cholesterol efflux and uptake were determined in hepatic and adipose tissues.

Results

Ob/ob mice had more labelled cholesterol in their plasma (86%, p<0.001), suggesting impaired RCT. SR-BI-mediated cholesterol efflux was elevated from ob/ob mice (serum, 33%; apoB-depleted plasma, 14%, p<0.01) and HDL-c were also higher (60%, p<0.01). Ex vivo it was found that cholesterol uptake was significantly lower into the livers and adipose tissue of ob/ob mice, compared to non-obese wildtype controls. Furthermore, ex vivo cholesterol efflux was reduced in ob/ob liver and adipose tissue towards apoA-I and HDL. Consistent with this, protein levels of SR-BI and ABCG1 were significantly lower in ob/ob hepatic and adipose tissue than in wildtype mice. Finally, labelled cholesterol concentrations were lower in ob/ob bile (67%, p<0.01) and faeces (76%, p<0.0001).

Conclusion

Obesity causes impairment in RCT due to reduced plasma cholesterol uptake and efflux by hepatocytes and adipocytes. A reduction in the capacity for plasma cholesterol clearance may partly account for increased CVD risk with obesity.

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.

Broad-Spectrum Inhibition of the CC-Chemokine Class Improves Wound Healing and Wound Angiogenesis

Angiogenesis is involved in the inflammation and proliferation stages of wound healing, to bring inflammatory cells to the wound and provide a microvascular network to maintain new tissue formation. An excess of inflammation, however, leads to prolonged wound healing and scar formation, often resulting in unfavourable outcomes such as amputation. CC-chemokines play key roles in the promotion of inflammation and inflammatory-driven angiogenesis. Therefore, inhibition of the CC-chemokine class may improve wound healing. We aimed to determine if the broad-spectrum CC-chemokine inhibitor “35K” could accelerate wound healing in vivo in mice. In a murine wound healing model, 35K protein or phosphate buffered saline (PBS, control) were added topically daily to wounds. Cohorts of mice were assessed in the early stages (four days post-wounding) and in the later stages of wound repair (10 and 21 days post-wounding). Topical application of the 35K protein inhibited CC-chemokine expression (CCL5, CCL2) in wounds and caused enhanced blood flow recovery and wound closure in early-mid stage wounds. In addition, 35K promoted neovascularisation in the early stages of wound repair. Furthermore, 35K treated wounds had significantly lower expression of the p65 subunit of NF-κB, a key inflammatory transcription factor, and augmented wound expression of the pro-angiogenic and pro-repair cytokine TGF-β. These findings show that broad-spectrum CC-chemokine inhibition may be beneficial for the promotion of wound healing.

The Vascular Endothelial Growth Factor Inhibitors Ranibizumab and Aflibercept Markedly Increase Expression of Atherosclerosis-Associated Inflammatory Mediators on Vascular Endothelial Cells

INTRODUCTION

Recent studies have suggested that the VEGF inhibitors, Ranibizumab and Aflibercept may be associated with an excess of cardiovascular events, potentially driven by increasing atheroma instability, leading to plaque rupture and clinical events. Inflammation plays a key role in the progression of atherosclerotic plaque and particularly conversion to an unstable phenotype. Here, we sought to assess the in vitro effects of these drugs on the expression of key inflammatory mediators on endothelial cells.

METHODS

Human coronary artery endothelial cells were co-incubated for 16h with Ranibizumab (0.11nM) or Aflibercept (0.45nM), as determined by each drug's peak serum concentration (Cmax). Expression at protein (ELISA) and gene (RT-PCR) level of inflammatory chemokines CCL2, CCL5 and CXC3L1 as well as gene expression for the cell adhesion molecules VCAM-1, ICAM-1 and the key NF-κb protein p65 was assessed. VEGF-A protein levels were also determined.

RESULTS

Both drugs significantly increased chemokine, cell adhesion molecule (CAM) and p65 expression, while decreasing VEGF-A protein secretion. At equivalent Cmax concentrations, Aflibercept was significantly more pro-inflammatory than Ranibizumab. Reduction of secreted VEGF-A levels significantly attenuated inflammatory effects of both drugs, whereas blockade of the VEGF-A receptor or silencing of VEGF-A gene synthesis alone had no effect, suggesting that binding of drug to secreted VEGF-A is crucial in promoting inflammation. Finally, blockade of Toll-like receptor 4 significantly reduced inflammatory effects of both drugs.

CONCLUSION

We demonstrated here, for the first time, that both drugs have potent pro-inflammatory effects, mediated via activation of Toll-like receptor 4 on the endothelial cell surface by drug bound to VEGF-A. Further studies are required to investigate whether these effects are also seen in vivo.

Colchicine Acutely Suppresses Local Cardiac Production of Inflammatory Cytokines in Patients With an Acute Coronary Syndrome

Background

Interleukin (IL)-1β, IL-18, and downstream IL-6 are key inflammatory cytokines in the pathogenesis of coronary artery disease. Colchicine is believed to block the NLRP3 inflammasome, a cytosolic complex responsible for the production of IL-1β and IL-18. In vivo effects of colchicine on cardiac cytokine release have not been previously studied. This study aimed to (1) assess the local cardiac production of inflammatory cytokines in patients with acute coronary syndromes (ACS), stable coronary artery disease and in controls; and (2) determine whether acute administration of colchicine inhibits their production.

Methods and Results

Forty ACS patients, 33 with stable coronary artery disease, and 10 controls, were included. ACS and stable coronary artery disease patients were randomized to oral colchicine treatment (1 mg followed by 0.5 mg 1 hour later) or no colchicine, 6 to 24 hours prior to cardiac catheterization. Blood samples from the coronary sinus, aortic root (arterial), and lower right atrium (venous) were collected and tested for IL-1β, IL-18, and IL-6 using ELISA. In ACS patients, coronary sinus levels of IL-1β, IL-18, and IL-6 were significantly higher than arterial and venous levels (P=0.017, <0.001 and <0.001, respectively). Transcoronary (coronary sinus-arterial) gradients for IL-1β, IL-18, and IL-6 were highest in ACS patients and lowest in controls (P=0.077, 0.033, and 0.014, respectively). Colchicine administration significantly reduced transcoronary gradients of all 3 cytokines in ACS patients by 40% to 88% (P=0.028, 0.032, and 0.032, for IL-1β, IL-18, and IL-6, respectively).

Conclusions

ACS patients exhibit increased local cardiac production of inflammatory cytokines. Short-term colchicine administration rapidly and significantly reduces levels of these cytokines.

Abstract 600: Aldosterone-Dependent Transfer of microRNA-Containing Exosomes Between Endothelial and Smooth Muscles Cells

Background: Aldosterone is a cardiovascular risk factor and recent research has demonstrated that aldosterone increases exocytosis from endothelial cells, which may be an important signalling mechanism. Exosomes are small extracellular particles that contribute to cell-to-cell communication. Once released from a host cell they can circulate in the blood and transfer their contents (e.g. miRNAs) to recipient cells. We aimed to examine the effect of aldosterone on: 1) exosome release from endothelial cells and 2) exosome trafficking of miRNA from endothelial cells to smooth muscle cells.

Methods and Results: Human coronary artery endothelial cells (HCAECs) were incubated with aldosterone (100nM) or vehicle for 1 or 18 hours. Exosomes were isolated from cell media via ultracentrifugation and then analyzed by nanoparticle-tracking (NanoSight). Aldosterone increased exosome concentration by 2.65-fold (1h; 19.1x10 10 particles/mL) or 3.25-fold (18h; 28.6x10 10 particles/mL) when compared to the time-point vehicle control (7.2x10 10 and 8.8x10 10 particles/mL, respectively). To test exosome paracrine trafficking, HCAECs were transfected with a c.elegans miRNA (cel-miR-39) and incubated adjacent to human coronary artery smooth muscle cells (HCASMCs) separated by a 0.4μm filter for 24 hour, with or without aldosterone. qRT-PCR analysis was used to measure cel-miR-39 expression in HCASMCs following incubation near transfected HCAECs, a confirmation of trafficking. Importantly, levels of cel-miR-39 in HCASMCs increased significantly (2.42±0.52 fold; p=0.02) in aldosterone-stimulated cells, compared to control. Blocking transcription with Dactinomycin had no effect on aldosterone-mediated trafficking (cel-miR-39 expression 2.07±0.61 fold; p>0.05). Finally, antagonizing the mineralocorticoid receptor (MR) with spironolactone had no effect on cel-miR-39 expression in HCASMCs (3.43±1.49 fold; p>0.05).

Conclusion: This study demonstrates that aldosterone increases exosome secretion from endothelial cells, leading to increased uptake of exosome-packaged microRNAs by smooth muscle cells, independent of transcription and the MR. Together, this represents a novel mechanism by which aldosterone contributes to vascular disease.

Abstract 566: Broad-Spectrum Chemokine Inhibition Blocks Inflammation-Induced Pathological Angiogenesis but Preserves Hypoxia-Driven Physiological Angiogenesis

Introduction: Angiogenesis is critical for survival and in the regenerative response to tissue hypoxia. An imbalance in its regulation causes excessive angiogenesis, exacerbating inflammatory diseases such as cancer and atherosclerosis. Chemokines from the CC-chemokine class are increasingly implicated in the regulation of inflammatory pathological angiogenesis but, in contrast, have a minimal role in hypoxia-driven physiological angiogenesis. Inhibition of CC-chemokines may therefore differentially regulate angiogenesis depending on the pathophysiological context. The ‘35K’ protein uniquely inhibits the CC chemokine class and does not affect chemokines from other classes.

Aim: To determine the effect of CC-chemokine inhibition with 35K on inflammation-induced angiogenesis and hypoxia-driven angiogenesis using human coronary artery endothelial cells (EC) in in vitro angiogenic functional assays.

Results: Matrigel tubule formation was strikingly inhibited (95.8%, p<0.001) by 35K (50nM) under the inflammatory stimuli of macrophage conditioned media. The addition of 35K also reduced inflammation-induced proliferation by 88.3% (p<0.001). Furthermore, we found the addition of 35K suppressed inflammation stimulated EC migration speed by 15.8% (p<0.05). By contrast, in hypoxia, 35K (50nM) reduced tubule formation by 45.2% (p<0.01), indicating a relative preservation of tubulogenesis in hypoxia compared to inflammation. Consistent with this, in hypoxia, 35K reduced proliferation by 43.8% (p<0.05). Moreover, the speed of EC migration was completely preserved under hypoxic conditions following the addition of 35K. Mechanistic studies supported our functional observations. Angiogenic growth factor, VEGF, was inhibited (53.4%) by 35K (200nM) under inflammatory conditions yet was augmented in hypoxia (31.5%). 35K also decreased key angiogenesis transcription factors, p65 (37.3%) and HIF-1α (87.3%) in inflammation.

Conclusion: Broad-spectrum chemokine inhibition by 35K blocks inflammation-induced angiogenic processes, whilst preserving hypoxia-driven angiogenesis. This may present as a therapeutic strategy to reduce pathological angiogenic disease, without the severe side effects of current therapies.

Tetrahydrobiopterin determines vascular remodeling through enhanced endothelial cell survival and regeneration

BACKGROUND

Endothelial cell (EC) survival and regeneration are important determinants of the response to vascular injury that leads to neointimal hyperplasia and accelerated atherosclerosis. Nitric oxide (NO) is a key regulator of EC and endothelial progenitor cell function, but the pathophysiological mechanisms that regulate endothelial NO synthase in endothelial regeneration remain unclear.

METHODS AND RESULTS

Endothelium-targeted overexpression of GTP cyclohydrolase (GCH) I increased levels of the endothelial NO synthase cofactor, tetrahydrobiopterin, in an EC-specific manner and reduced neointimal hyperplasia in experimental vein grafts in GCH/apolipoprotein E-knockout mice. These effects were mediated through enhanced donor-derived survival and recipient-derived repopulation of GCH transgenic ECs, revealed by tracking studies in Tie2-LacZ/GCH-Tg/apolipoprotein E-knockout recipient mice or donor grafts, respectively. Endothelial GCH overexpression increased endothelial NO synthase coupling and enhanced the proliferative capacity of ECs and circulating endothelial progenitor cell numbers after vascular injury.

CONCLUSIONS

These observations indicate that endothelial tetrahydrobiopterin availability modulates neointimal hyperplasia after vascular injury via accelerated EC repopulation and growth. Targeting tetrahydrobiopterin-dependent endothelial NO synthase regulation in the endothelium is a rational therapeutic target to enhance endothelial regeneration and reduce neointimal hyperplasia in vascular injury states.

Abstract 240: High-Density Lipoproteins Augment Hypoxia-Induced Angiogenic Regulation via Mediators in the HIF-1α Signaling Pathway

Background: Angiogenesis plays a critical role in tissue neovascularization in response to ischemia, particularly in collateral vessel development following myocardial infarction (MI). One of the key pathways involved in hypoxia-induced angiogenesis is the HIF-1α/VEGF pathway. High-density lipoproteins (HDL) are associated with improved survival and prognosis following MI, suggesting that it may play a role in hypoxia-induced angiogenic regulation. We assessed the hypothesis that HDL regulates the HIF-1α/VEGF pathway in vitro .

Methods: Human coronary artery endothelial cells (HCAECs) were pre-incubated with PBS (control) or reconstituted HDL (rHDL) for 24 hrs then subjected to either normoxic or hypoxic conditions for a further 6 hrs. Protein and gene expression of key mediators in the HIF-1α/VEGF pathway were investigated.

Results: As expected, hypoxia elevated HIF-1α protein levels (49%, p<0.05), which was augmented by a further 30% (p<0.05) in rHDL-treated HCAECs. Consistent with this, rHDL increased VEGF mRNA levels above hypoxia-induced increases (23%, p<0.05). Prolyl hydroxylases (PHD 1-3) hydroxylate HIF-1α, targeting it for degradation. rHDL pre-incubation inhibited hypoxia-induced increases in PHD2 and PHD3 levels (32% and 45%, respectively, p<0.05), indicating that rHDL may protect against HIF-1α degradation and explains the rHDL-induced elevation in HIF-1α protein levels. Furthermore, the mRNA levels of Siah-1 and Siah-2, which promote PHD degradation, were increased in rHDL-treated HCAECs (58% and 88% respectively, p<0.05). To determine the importance of Siah-1 and Siah-2 in the HDL-induced modulation of the HIF-1α/VEGF pathway, a siRNA knockdown approach was used. When cells had low levels of Siah-1 and -2, HDL’s ability to induce VEGF was completely attenuated.

Conclusion: In conclusion, we found that HDL is able to augment the HIF-1α/VEGF pathway through the stabilization of HIF-1α protein via a decrease in PHD2/3 and increase in Siah1/2. These findings suggest that rHDL may stimulate hypoxia-induced angiogenic regulation via the HIF-1α pathway, which may have implications for preventing ischemic injury following MI.

Abstract 388: TXNIP Knockdown Rescues Diabetes-Related Impairment in Endothelial Progenitor Cell-Mediated Angiogenesis

Introduction: Endothelial progenitor cell (EPC) participation in neovascularization of ischemic tissue is impaired in diabetes mellitus. Thioredoxin interacting protein (TXNIP) is strongly induced by glucose. TXNIP is overexpressed in tissues of diabetes sufferers and is associated with impaired angiogenesis. We hypothesized that gene-silencing of TXNIP in diabetic EPC would ameliorate impaired EPC angiogenic function.

Methods and results: EPC (CD34+/CD45+/KDR+) isolated from young Type 1 diabetes patients were markedly reduced, which was associated with induction of TXNIP and reduced expression of VEGF compared to age- and sex-matched healthy controls. We further found that high glucose (15-25 mmol/L) impaired EPC angiogenic processes in vitro, including cell proliferation, migration and vascular network formation. This was associated with induction of TXNIP and a reduction in VEGF. However, EPC transfected with siRNA to TXNIP were protected from high-glucose mediated impairment of angiogenic processes and had normal VEGF production. Next, diabetic and healthy EPC were treated with TXNIP siRNA and xenotransplanted into a normoglycemic Balb/c nude mouse model of unilateral hindlimb ischemia. Xenotransplanted diabetic EPC were associated with reductions in blood flow recovery (laser Doppler perfusion imaging) and increased tissue ischemia/amputations. However, gene silencing of TXNIP in diabetic EPC restored blood flow recovery, with reductions in tissue ischemia/amputations, to levels seen in mice xenotransplanted with healthy control EPC.

Conclusion: Hyperglycemia-mediated induction of TXNIP impairs EPC angiogenic function in vitro and in vivo. Inhibition of TXNIP in diabetic EPC rescues impaired angiogenesis, with implications for therapeutic modulation of diabetic vascular disease.

Evaluation of androgenic activity of nutraceutical-derived steroids using mammalian and yeast in vitro androgen bioassays

Androgenic steroids marketed online as nutraceuticals are a growing concern in sport doping. The inability of conventional mass spectrometry (MS)-based techniques to detect structurally novel androgens has led to the development of in vitro androgen bioassays to identify such designer androgens by their bioactivity. The objective of this study was to determine the androgenic bioactivity of novel steroidal compounds isolated from nutraceuticals using both yeast and mammalian cell-based androgen bioassays. We developed two new in vitro androgen bioassays by stably transfecting HEK293 and HuH7 cells with the human androgen receptor (hAR) expression plasmid together with a novel reporter gene vector (enhancer/ARE/SEAP). The yeast β-galactosidase androgen bioassay was used for comparison. Our new bioassay featuring the enhancer/ARE/SEAP construct (-S) displayed simpler assay format and higher specificity with lower sensitivity compared with the commonly used mouse mammary tumour virus (MMTV)-luciferase. The relative potencies (RP), defined as [EC(50)] of testosterone/[EC(50)] of steroid, of nutraceutical extracts in the yeast, HEK293-S, and HuH7-S, were 34, 333, and 80,000 for Hemapolin; 208, 250, and 80 for Furazadrol; 0.38, 10, and 106 for Oxyguno; 2.7, 0.28, and 15 for Trena; and 4.5, 0.1, and 0.4 for Formadrol, respectively. The wide discrepancies in rank RP of these compounds was reconciled into a consistent potency ranking when the cells were treated with meclofenamic acid, a nonselective inhibitor of steroid metabolizing enzymes. These findings indicate that steroids extracted from nutraceuticals can be converted in vitro into more or less potent androgens in mammalian but not in yeast cells. We conclude that the putative androgenic bioactivity of a new compound may depend on the bioassay cellular format and that mammalian cell bioassays may have an added benefit in screening for proandrogens but sacrifice specificity for sensitivity in quantitation.