Primary Human Aortic Endothelial Cells Research Articles

The effect of CD38 inhibition in age-associated vascular dysfunction

Abstract Introduction Aging is characterized by age-related vascular dysfunction, mainly caused by endothelial dysfunction and arterial stiffness. Levels of nicotinamide adenine dinucleotide (NAD) decrease with aging and accordingly, NAD is thought to be involved in the progression of age-related vascular dysfunction. Recent studies reported the involvement of CD38 in NAD regulation; indeed, its inhibition significantly prolongs the lifespan of progeroid and aged mice. However, whether CD38 is involved in the progression of age-related vascular dysfunction remains to be investigated. Methods CD38 expression was investigated in aortic homogenates of young (12-16 weeks) and aged (18-24 months) C57BL/6 wild-type mice, as well as in vitro in young (passage 5-7) and senescent (passage 14-15) primary human aortic endothelial cells (HAECs). Ex vivo tension myograph experiments were performed on thoracic aortas isolated from aged C57BL/6 mice (22-24 months old) pre-incubated for 1 hour with CD38-specific inhibitor, 78c, or DMSO as control. The effect of CD38 inhibition was also observed in vitro in senescent HAECs. Results A significant upregulation of CD38 expression was detected in the aortas of aged mice compared to the young ones as well as in senescent HAECs compared to young cells. Ex vivo tension myograph experiments showed a significant increase in endothelium-dependent relaxation responses to acetylcholine upon CD38 inhibition. The improvement of endothelial function was prevented by the addition of endothelial nitric oxide synthase (eNOS) inhibitor (L-NAME), but not by the COXs inhibitor, indomethacin, indicating that the observed effect achieved by CD38 inhibition is eNOS dependent. The involvement of the eNOS pathway was further supported by the in vitro finding in HAECs of increased eNOS activation upon CD38 inhibition. Conclusion The herein-reported data suggests an involvement of CD38 in the development of age-related endothelial dysfunction. Further studies are ongoing to investigate the underlying molecular mechanisms as well as the effect of long-term CD38 inhibitor supplementation on the progression of age-related vascular dysfunction.

Sirt5 as a mediator of endothelial and vascular dysfunction: potential therapeutic target in aging-related vascular diseases

Abstract Background Aging is one of the most dominant cardiovascular (CV) risk factors. Sirt5 belongs to the lifespan-regulating sirtuin superfamily as a protein deacylase. However, its regulatory effects on vascular function and aging are yet unclear. Purpose We therefore aimed to investigate the roles of Sirt5 on endothelial and vascular function during aging, decipher the underlying mechanisms, and to explore its potential as a therapeutic target through in vivo and in vitro studies. Methods Aortic expression of Sirt5 were studied in C5BL/6 wild type (WT) mice during aging, followed by vascular functional and structural assessment in WT mice and Sirt5-overexpressing mice (Sirt5/Tg) using the established myograph system and histological staining respectively. Furthermore, the regulatory role of Sirt5 on endothelial function was investigated in senescent primary human aortic endothelial cells (HAECs, passages 13-15) by studying its interference with endothelial nitric oxide synthase (eNOS) expression and activity in knock-down experiments using siRNA. The therapeutic potential of Sirt5 inhibition was explored at the tissue level in myograph experiments. Results Aged WT mice had increased level of Sirt5 in aorta compared to the young ones. Overexpression of Sirt5 in vivo led to significantly reduced aortic endothelial-dependent relaxation and displayed thicker collagen deposition in the adventitia compared to aged WT controls. The reduction of vascular relaxing response in Sirt5/Tg mice was prevented by an addition of eNOS inhibitor (L-name), indicating that Sirt5 regulated vascular function through the eNOS pathway. In senescent HAECs, knock-down of Sirt5 markedly induced total eNOS expression and increased its activity (phospho-eNOS Ser1177), further confirming the regulatory role of Sirt5 on eNOS pathway. In line with the above, aorta from aged WT mice displayed improved endothelial function after pharmacological inhibition of Sirt5. Conclusion Vascular Sirt5 expression increases with age and contributes to aging-related endothelial dysfunction by downregulating the eNOS pathway. Thus, Sirt5 inhibition may represent a novel therapeutic approach to maintain vascular function during aging. Ongoing studies will investigate Sirt5 silencing in-vivo using RNA interference for its therapeutic potential to prevent aging-related vascular dysfunction.

Targeting the histone methyltransferase SETD7 rescues diabetes-induced impairment of angiogenic response by transcriptional repression of semaphorin 3G

Abstract Background Peripheral artery disease (PAD) is highly prevalent in patients with diabetes (DM) and associates with a high rate of limb amputation and poor prognosis. Surgical and catheter-based revascularization have failed to improve outcome in DM patients with PAD. Hence, a need exists to develop new treatment strategies able to promote blood vessel growth in this setting. Mono-methylation of histone 3 at lysine 4 (H3K4me1) - a specific epigenetic signature induced by the histone methyltransferase SETD7 - favours an open chromatin thus enabling gene transcription. Purpose To investigate whether SETD7-dependent epigenetic changes modulate angiogenic response in diabetes. Methodology Primary human aortic endothelial cells (HAECs) were exposed to normal glucose (NG, 5 mM) or high glucose (HG, 25 mM) concentrations for 48 hours. Unbiased gene expression profiling was performed by RNA sequencing (RNA-seq) followed by Ingenuity Pathway Analysis (IPA). In vitro assays, namely cell migration and tube formation were employed to study angiogenic properties in HAECs. SETD7 and H3K4me1 levels were investigated by Western blot and Chromatin immunoprecipitation (ChIP). Pharmacological blockade of SETD7 was achieved by using the highly selective inhibitor (R)-PFI-2. Mice with streptozotocin-induced diabetes were orally treated with (R)-PFI-2 or vehicle and underwent hindlimb ischemia by femoral artery ligation for 14 days. Blood flow recovery was analysed at 30 minutes, 7 and 14 days by laser Doppler imaging. Our experimental findings were also translated in gastrocnemius muscle samples from patients with and without diabetes. Results RNA-seq in HG-treated HAECs revealed a profound upregulation of the methyltransferase SETD7, an enzyme involved in mono-methylation of lysine 4 at histone 3 (H3K4me1). SETD7 upregulation in HG-treated HAECs was associated with increased H3K4me1 levels as well as with impaired endothelial cell migration and tube formation. Both SETD7 gene silencing and pharmacological inhibition by (R)PFI-2 rescued hyperglycemia-induced impairment of HAECs migration and tube formation, while SETD7 overexpression blunted the angiogenic response. RNA-seq and ChIP assays showed that SETD7-dependent H3K4me1 regulates the transcription of the angiogenesis inhibitor semaphorin-3G (SEMA-3G). Moreover, SEMA-3G overexpression blunted migration and tube formation in SETD7-depleted HAECs. In diabetic mice with hindlimb ischemia, treatment with (R)-PFI-2 improved limb vascularization and perfusion as compared to vehicle. Finally, SETD7/SEMA3G axis was upregulated in muscle specimens from T2D patients as compared to controls. Conclusion Targeting SETD7 represents a novel epigenetic-based therapy to boost neovascularization in diabetic patients with PAD.

Targeting the histone methyltransferase SETD7 rescues diabetes-induced impairment of angiogenic response by transcriptional repression of semaphorin 3G

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Swiss National Science Foundation (n. 310030_197557), the Swiss Heart Foundation (n. FF19045) Background Peripheral artery disease (PAD) is highly prevalent in patients with diabetes (DM) and associates with a poor prognosis (1). Revascularization strategies failed to improve outcome, highlighting the need to develop new strategies to promote blood vessel growth (2). Histone modifications have emerged as key modulators of gene expression (3), however their role in angiogenic response in DM remains poorly understood. The present study investigates the role of chromatin remodelling in DM-related impairment of angiogenic response. Methodology Primary human aortic endothelial cells (HAECs) were exposed to normal glucose (NG, 5 mM) or high glucose (HG, 25 mM) levels for 48 hours. Unbiased gene expression profiling was performed by RNA sequencing (RNA-seq). Cell migration and tube formation were employed to study angiogenic properties in HAECs. Levels of the histone methyltransferase SETD7 and its chromatin signature at histone 3 on lysine 4 (H3K4me1) were investigated by Western blot and chromatin immunoprecipitation (ChIP). Pharmacological blockade of SETD7 was achieved by using the selective inhibitor (R)-PFI-2 while the inactive enantiomer (S)-PFI-2 was used as a control. Mice with streptozotocin-induced DM were orally treated with (R)-PFI-2 or vehicle and underwent hindlimb ischemia by femoral artery ligation. Blood flow was analysed at 24 hours, 7 and 14 days by laser Doppler imaging. Our experimental findings were also translated in endothelial cells (ECs) and gastrocnemius muscle samples obtained from DM patients with PAD. Results RNA-seq in HG-treated HAECs unveiled the histone methyltransferase SETD7 as the top-ranking transcript. SETD7 upregulation was associated with increased H3K4me1 levels as well as with impaired HAECs migration and tube formation. Both SETD7 silencing and inhibition by (R)PFI-2 rescued hyperglycemia-induced impairment of HAECs migration and tube formation, while SETD7 overexpression blunted the angiogenic response. RNA-seq and ChIP assays showed that SETD7-induced H3K4me1 enables the transcription of the angiogenesis inhibitor semaphorin-3G (SEMA-3G) by increasing chromatin accessibility to PPARγ. Moreover, SEMA-3G overexpression mimicked the impairment of angiogenic response observed during hyperglycemia. In DM mice with hindlimb ischemia, (R)-PFI-2 improved limb perfusion by suppressing SEMA-3G. Finally, RNAseq in vascular specimens from DM patients with PAD confirmed the upregulation of SETD7/SEMA3G signalling, whereas SETD inhibition restored angiogenic properties in ECs from DM patients. Conclusion SETD7 is a novel epigenetic target to boost neovascularization in DM patients with PAD.

Atheroprotective WSS effects on human aortic endothelial cells in a new generation bioreactor

Abstract Funding Acknowledgements None. Background Luminal arterial endothelial cells are mainly aligned along the blood flow direction, whereas the in vitro endothelial cells (EC) showed heterogeneous distribution. In atherosclerosis the altered blood flow, acting on mechano-transduction, contributes to endothelial dysfunction and barrier disorganization. A low wall shear stress (WSS) has a pro-atherosclerotic effect, whilst elevated WSS is atheroprotective. Purposes Aim of this work is to study the primary human aortic EC cells (HAOEC) capability to acquire a distribution reminiscent of the luminal alignment under atheroprotective WSS using a prototypal new generation bioreactor. Methods We have developed a novel device compatible with culture inside standard sterile incubator, allowing to apply complex WSS patterns in controlled conditions. The bioreactor includes a sample housing and a parallel plate flow chamber and is controlled by a custom electronic interface actuating motor and pump. The cells were settled over PMMA supports and coating conditions were setup. Atheroprotective WSS patterns were tested. We compared HAOEC submitted to high flow (1.2 Pa for 24h) vs. ramps with different slopes (3h, 8h, 24h) followed by steady-state flow (1.2Pa for 24h, 48h). Viability and distribution of Acridine Orange-labelled HAOEC were assessed over bioreactor supports at both beginning and end of the experiments using fluorescence microscope. Hematoxylin/Eosin and Coomassie Blue staining were tested after the experiment to evaluate the shape and cell orientation (directionality FiJi plugin). Confocal microscopy on HAOEC labelled with Phalloidin–TRITC, anti-CD31/PECAM1-AlexaFluor488 and DAPI displayed the flow-related changes. Results HAOEC settled over naked sterile PMMA supports mainly detached under WSS, independently from the cell number. Coating with extracellular matrix components (i.e., human laminin, bovine fibronectin, chicken collagen type II, human collagen type I) showed the superiority of collagen type I to obtain homogeneously distributed, flow-resistant cell monolayers. In static condition, HAOEC on coated supports demonstrated ≥50% detachment within 24h, those submitted to a direct atheroprotective WSS of 1.2Pa almost completely detached. Consistently, to ramps with high slope (range 0.2-1,2Pa in 3h or 8h) followed by1.2Pa WSS corresponded 60%-90% cell detachment. Conversely, a 24h ramp (range 0.2-1,2Pa) followed by 24h or 48h of 1.2Pa WSS preserved the HAOEC monolayer adherence, and aligned cells were found. Microscopy comparative analysis of selected areas before/after WSS showed a partial spatial reorganization, with changes in the F-actin cytoskeleton and CD31 distribution. Conclusion We have optimized a protocol for studying HAOEC under atheroprotective WSS. In perspective further increasing the duration of the stimulus under constant WSS will achieve full alignment and provide a pseudo-physiologic model for multidirectional atherogenic WSS studies.

Abstract 2063: Endothelial Cell Scavenger Receptor Class B, Type I Expression Is Transcriptionally Controlled By HIF-1α

Background: Scavenger Receptor Class B, Type I (SR-BI), encoded by Scarb1, mediates LDL cholesterol transcytosis in endothelial cells (EC) to deliver circulating LDL into the subendothelial space to drive atherogenesis. Research Questions: It is unknown whether EC SR-BI expression is altered in atherosclerosis, and how EC SR-BI expression is regulated. Approach: Single cell RNAseq was performed on coronary arteries from 5 ischemic heart disease patients, in segments both with and without a grossly apparent atheroma. Transcription factor (TF) network analysis was done to reveal possible regulatory relationships between differentially-expressed genes (DEGs). The modulation of EC SR-BI was studied in primary human aortic EC (HAEC) and in vivo in mouse aortic EC. ChIP-seq, ChIP-qPCR and CRISPR-based mutagenesis were used to interrogate TF binding to the human Scarb1 gene. EC SR-BI expression was determined by immunoblotting and qPCR, and EC LDL transcytosis was studied in transwells using DiI-labeled LDL. Results: SR-BI expression was greater in EC in coronary segments with atheroma versus those without atheroma (p=0.003). TF networks for DEGs in atheroma versus non-atheroma EC, and for DEGs in EC with low versus high SR-BI revealed multiple TF with possible regulatory relationships with Scarb1. One TF in common was HIF-1α. In HAEC, an increase in HIF-1α with the HIF prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) caused upregulation of SR-BI mRNA and protein, and a parallel increase in LDL transcytosis that was entirely SR-BI-dependent. Expression of a constitutively-active HIF-1α variant also increased SR-BI and LDL transcytosis. ChIP-seq revealed a HIF-1α binding site in Scarb1 intron 1, and HIF-1α binding there increased 4-fold with DMOG. CRISPR deletion of the binding site fully prevented SR-BI upregulation by DMOG without affecting known HIF-1α target genes. In mice, 3d treatment with DMOG increased SR-BI in aortic EC. Conclusions: EC expression of SR-BI is upregulated with increasing atherosclerosis severity in human coronary artery. HIF-1α is upregulated in parallel, and HIF-1α causes the direct transcriptional upregulation of EC SR-BI leading to enhanced EC LDL transport. HIF-1α control of SR-BI in EC may be critical to atherogenesis.

Abstract 109: Estrogen Receptor Alpha Inhibition Of Mineralocorticoid Receptor In Endothelial Cells As A Mechanism Of Protection From Atherosclerosis Inflammation

Background: Atherosclerosis (athero) inflammation predicts plaque rupture, causing heart attack and stroke. Female protection from heart attack and stroke is lost with age, implicating estrogen, but by unclear mechanism. Our lab showed that the mineralocorticoid receptor (MR) is expressed in endothelial cells (ECs), where it drives plaque inflammation in male mice by inducing the NFkB-regulated adhesion molecule ICAM1. Females had less inflamed plaques, unchanged by EC-MR-knockout (KO). Hypothesis: We hypothesized that EC-estrogen receptor alpha (ER) protects females from plaque inflammation by inhibiting NFkB and EC-MR induction of ICAM1. Methods and Results: Mice with EC specific MR KO (EC-MR-KO), ER KO (EC-ER-KO), or EC KO of both receptors (DKO) were developed and crossed to the LDLR KO background. EC specific gene recombination of MR and/or ER was confirmed by genomic PCR of lung (rich in ECs) and compared to blood, revealing no recombination in leukocytes. Baseline athero risk factors were unchanged by genotype. Male and female mice of all KO lines and floxed Cre- littermate controls were fed high fat diet for 12 weeks resulting in increased body weight and cholesterol with no difference by genotype in athero risk factors. Aortic arches were digested for flow cytometry to quantify plaque inflammation, confirming less inflamed plaques in females versus males. EC-ER-KO increased plaque inflammation, while DKO prevented this increase in both sexes. Compared to controls, ICAM1 protein expression in the descending aorta was decreased by EC-MR-KO only in males. In both sexes, ICAM1 was increased by EC-ER-KO and unchanged by DKO. Females had increased aortic expression of IkB, the inhibitor of NFkB, compared to males and this was prevented by EC-ER-KO. In primary human aortic ECs (HAECs) in vitro , cells from females expressed significantly less ICAM1 protein compared to males. Conclusions: Female atherogenic mice have less inflamed plaques than males and female HAECs express less ICAM1. In vivo , EC-ER protects from plaque inflammation and suppresses ICAM1 in both sexes and IkB in females, and EC-MR is necessary for this atheroprotection. These data support the concept that EC-ER prevents inflammation by inhibiting NFkB and EC-MR-induced ICAM1 expression.

Identification of DNA methylation biomarkers for evaluating cardiovascular disease risk from epigenome profiles altered by low-dose ionizing radiation

BackgroundEnvironmental exposure, medical diagnostic and therapeutic applications, and industrial utilization of radionuclides have prompted a growing focus on the risks associated with low-dose radiation (< 100 mGy). Current evidence suggests that such radiation can induce epigenetic changes. Nevertheless, whether exposure to low-dose radiation can disrupt endothelial cell function at the molecular level is unclear. Because endothelial cells play crucial roles in cardiovascular health and disease, we aimed to investigate whether low-dose radiation could lead to differential DNA methylation patterns at the genomic level in endothelial cell (EC) lines.MethodsWe screened for changes in DNA methylation patterns in primary human aortic (HAECs) and coronary artery endothelial cells following exposure to low-dose ionizing radiation. Using a subset of genes altered via DNA methylation by low-dose irradiation, we performed gene ontology (GO) analysis to predict the possible biological network mediating the effect of low-dose radiation. In addition, we performed comprehensive validation using methylation and gene expression analyses, and ChIP assay to identify useful biomarkers among candidate genes for use in detecting low-dose radiation exposure in human primary normal ECs.ResultsLow-dose radiation is sufficient to induce global DNA methylation alterations in normal EC lines. GO analysis demonstrated that these hyper- or hypo-methylated genes were linked to diverse biological pathways. Our findings indicated a robust correlation between promoter hypermethylation and transcriptional downregulation of four genes (PGRMC1, UNC119B, RERE, and FNDC3B) in response to low-dose ionizing radiation in HAECs.ConclusionsBased on these findings, the identified genes can serve as potential DNA methylation biomarkers for the assessment of cardiovascular risk upon exposure to low-dose radiation.

Endothelial IL17RD promotes Western diet-induced aortic myeloid cell infiltration

The Interleukin-17 (IL17) family is a group of cytokines implicated in the etiology of several inflammatory diseases. Interleukin-17 receptor D (IL17RD), also known as Sef (similar expression to fibroblast growth factor) belonging to the family of IL17 receptors, has been shown to modulate IL17A-associated inflammatory phenotypes. The objective of this study was to test the hypothesis that IL17RD promotes endothelial cell activation and consequent leukocyte adhesion. We utilized primary human aortic endothelial cells and demonstrated that RNAi targeting of IL17RD suppressed transcript levels by 83 % compared to non-targeted controls. Further, RNAi knockdown of IL17RD decreased the adhesion of THP-1 monocytic cells onto a monolayer of aortic endothelial cells in response to IL17A. Additionally, we determined that IL17A did not significantly enhance the activation of canonical MAPK and NFκB pathways in endothelial cells, and further did not significantly affect the expression of VCAM-1 and ICAM-1 in aortic endothelial cells, which is contrary to previous findings. We also determined the functional relevance of our findings in vivo by comparing the expression of endothelial VCAM-1 and ICAM-1 and leukocyte infiltration in the aorta in Western diet-fed Il17rd null versus wild-type mice. Our results showed that although Il17rd null mice do not have significant alteration in aortic expression of VCAM-1 and ICAM-1 in endothelial cells, they exhibit decreased accumulation of proinflammatory monocytes and neutrophils, suggesting that endothelial IL17RD induced in vivo myeloid cell accumulation is not dependent on upregulation of VCAM-1 and ICAM-1 expression. We further performed proteomics analysis to identify potential molecular mediators of the IL17A/IL17RD signaling axis. Collectively, our results underscore a critical role for Il17rd in the regulation of aortic myeloid cell infiltration in the context of Western diet feeding.

Directional Endothelial Communication by Polarized Extracellular Vesicle Release.

Extracellular vesicles (EVs) contain bioactive cargo including miRNAs and proteins that are released by cells during cell-cell communication. Endothelial cells (ECs) form the innermost lining of all blood vessels, interfacing with cells in the circulation and vascular wall. It is unknown whether ECs release EVs capable of governing recipient cells within these 2 separate compartments. Given their boundary location, we propose ECs use bidirectional release of distinct EV cargo in quiescent (healthy) and activated (atheroprone) states to communicate with cells within the circulation and blood vessel wall. EVs were isolated from primary human aortic ECs (plate and transwell grown; ±IL [interleukin]-1β activation), quantified, visualized, and analyzed by miRNA transcriptomics and proteomics. Apical and basolateral EC-EV release was determined by miRNA transfer, total internal reflection fluorescence and electron microscopy. Vascular reprogramming (RNA sequencing) and functional assays were performed on primary human monocytes or smooth muscle cells±EC-EVs. Activated ECs increased EV release, with miRNA and protein cargo related to atherosclerosis. EV-treated monocytes and smooth muscle cells revealed activated EC-EV altered pathways that were proinflammatory and atherogenic. ECs released more EVs apically, which increased with activation. Apical and basolateral EV cargo contained distinct transcriptomes and proteomes that were altered by EC activation. Notably, activated basolateral EC-EVs displayed greater changes in the EV secretome, with pathways specific to atherosclerosis. In silico analysis determined compartment-specific cargo released by the apical and basolateral surfaces of ECs can reprogram monocytes and smooth muscle cells, respectively, with functional assays and in vivo imaging supporting this concept. Demonstrating that ECs are capable of polarized EV cargo loading and directional EV secretion reveals a novel paradigm for endothelial communication, which may ultimately enhance the design of endothelial-based therapeutics for cardiovascular diseases such as atherosclerosis where ECs are persistently activated.

Disturbed flow impairs MerTK-mediated efferocytosis in aortic endothelial cells during atherosclerosis.

Background: MER proto-oncogene tyrosine kinase (MerTK) is a key receptor for efferocytosis, a process for the clearance of apoptotic cells. MerTK is mainly expressed in macrophages and immature dendritic cells. There are very limited reports focused on MerTK biology in aortic endothelial cells (ECs). It remains unclear for the role of blood flow patterns in regulating MerTK-mediated efferocytosis in aortic ECs. This study was designed to investigate whether endothelial MerTK and EC efferocytosis respond to blood flow patterns during atherosclerosis. Methods: Big data analytics, RNA-seq and proteomics combined with our in vitro and in vivo studies were applied to reveal the potential molecular mechanisms. Partial carotid artery ligation combined with AAV-PCSK9 and high fat diet were used to set up acute atherosclerosis in 4 weeks. Results: Our data showed that MerTK is sensitive to blood flow patterns and is inhibited by disturbed flow and oscillatory shear stress in primary human aortic ECs (HAECs). The RNA-seq data in HAECs incubated with apoptotic cells showed that d-flow promotes pro-inflammatory pathway and senescence pathway. Our in vivo data of proteomics and immunostaining showed that, compared with WT group, MerTK-/- aggravates atherosclerosis in d-flow areas through upregulation of endothelial dysfunction markers (e.g. IL-1β, NF-κB, TLR4, MAPK signaling, vWF, VCAM-1 and p22phox) and mitochondrial dysfunction. Interestingly, MerTK-/-induces obvious abnormal endothelial thickening accompanied with decreased endothelial efferocytosis, promoting the development of atherosclerosis. Conclusions: Our data suggests that blood flow patterns play an important role in regulating MerTK-mediated efferocytosis in aortic ECs, revealing a new promising therapeutic strategy with EC efferocytosis restoration to against atherosclerosis.

STING inhibition enables efficient plasmid-based gene expression in primary vascular cells: A simple and cost-effective transfection protocol.

Plasmid transfection in cells is widely employed to express exogenous proteins, offering valuable mechanistic insight into their function(s). However, plasmid transfection efficiency in primary vascular endothelial cells (ECs) and smooth muscle cells (SMCs) is restricted with lipid-based transfection reagents such as Lipofectamine. The STING pathway, activated by foreign DNA in the cytosol, prevents foreign gene expression and induces DNA degradation. To address this, we explored the potential of STING inhibitors on the impact of plasmid expression in primary ECs and SMCs. Primary human aortic endothelial cells (HAECs) were transfected with a bicistronic plasmid expressing cytochrome b5 reductase 4 (CYB5R4) and enhanced green fluorescent protein (EGFP) using Lipofectamine 3000. Two STING inhibitors, MRT67307 and BX795, were added during transfection and overnight post-transfection. As a result, MRT67307 significantly enhanced CYB5R4 and EGFP expression, even 24 hours after its removal. In comparison, MRT67307 pretreatment did not affect transfection, suggesting the inhibitor's effect was readily reversible. The phosphorylation of endothelial nitric oxide synthase (eNOS) at Serine 1177 (S1177) by vascular endothelial growth factor is essential for endothelial proliferation, migration, and survival. Using the same protocol, we transfected wild-type and phosphorylation-incapable mutant (S1177A) eNOS in HAECs. Both forms of eNOS localized on the plasma membrane, but only the wild-type eNOS was phosphorylated by vascular endothelial growth factor treatment, indicating normal functionality of overexpressed proteins. MRT67307 and BX795 also improved plasmid expression in human and rat aortic SMCs. In conclusion, this study presents a modification enabling efficient plasmid transfection in primary vascular ECs and SMCs, offering a favorable approach to studying protein function(s) in these cell types, with potential implications for other primary cell types that are challenging to transfect.

(R,S)-Equol 7-β-D-glucuronide, but not other circulating isoflavone metabolites, modulates migration and tubulogenesis in human aortic endothelial cells targeting the VEGF pathway.

Current knowledge indicates that the consumption of isoflavone-rich foodstuffs can have a beneficial impact on cardiovascular health. To what extent these isoflavones act as the main actors of that benefit is less clear. Genistein (GEN), daidzein (DAZ), and the DAZ-derived microbial metabolite equol (Eq) exhibit antiangiogenic effects in vitro, but their low bloodstream concentrations make it difficult to rationalize the in vivo effects. Their derived phase-II metabolites (glucuronides and sulfates) are major metabolites found in plasma, but their role as antiangiogenic molecules remains unexplored. We aimed here to first assess the anti-angiogenic activities of the main circulating isoflavone metabolites (glucuronides and sulfates) and compare them with their corresponding free forms at physiological concentrations (0.1-10 μM). The effects of the conjugated vs. free forms on tubulogenesis, cell migration, and VEGF-induced signalling were investigated in primary human aortic endothelial cells (HAECs). While (R,S)-equol 7-β-D-glucuronide (Eq 7-glur) exerted dose-dependent inhibition of tubulogenesis and endothelial migration comparable to that exerted by the free forms (GEN, DAZ, and Eq), the rest of the phase-II conjugates exhibited no significant effects. The underlying molecular mechanisms were independent of the bFGF but related to the modulation of the VEGF pathway. Besides, the observed dissimilar cellular metabolism (conjugation/deconjugation) places the phase-II metabolites as precursors of the free forms; however, the question of whether this metabolism impacts their biological activity requires additional studies. These new insights suggest that isoflavones and their circulating metabolites, including Eq 7-glur, may be involved in cardiovascular health (e.g., targeting angiogenesis).

Development of an automated, high-throughput assay to detect angiotensin AT2-receptor agonistic compounds by nitric oxide measurements in vitro

Angiotensin AT2-receptor (AT2R) agonists have shown a wide range of protective effects in many preclinical disease models. However, the availability of AT2R-agonists is very limited due to the lack of high-throughput assays for AT2R-agonist identification. Therefore, we aimed to design and validate an assay for high-throughput screening of AT2R-agonist candidates. The assay is based on nitric oxide (NO) release measurements in primary human aortic endothelial cells (HAEC), in AT2R-transfected CHO cells (AT2R-CHO) or in non-transfected CHO cells (Flp-CHO) using the fluorescent probe DAF-FM diacetate. It is run in 96-well plates and fluorescence signals are semi-automatically quantified. The assay was tested for sensitivity (recognition of true positive results), selectivity (recognition of true negative results), and reliability (by calculating the repeatability coefficient (RC)). The high-throughput, semi-automated method was proven suitable, as the NO-releasing agents C21, CGP42112A, angiotensin-(1−7) and acetylcholine significantly increased NO release from HAEC. The assay is sensitive and selective, since the established AT2R-agonists C21, CGP42112A and angiotensin II significantly increased NO release from AT2R-CHO cells, while the non-AT2R-agonists angiotensin-(1−7) and acetylcholine had no effect. Assay reliability was shown by high-throughput screening of a library comprised of 40 potential AT2R-agonists, of which 39 met our requirements for reliability (RC ≤ 20% different from RC for C21). Our newly developed high-throughput method for detection of AT2R-agonistic activity was proven to be sensitive, selective, and reliable. This method is suitable for the screening of potential AT2R-agonists in future drug development programs.

Histone Mono-methylation by SETD7 Orchestrates Angiogenic Response in Diabetic Limb Ischemia

Abstract Background Peripheral artery disease (PAD) is highly prevalent in patients with diabetes (DM) and associates with a high rate of limb amputation and poor prognosis. Surgical and catheter-based revascularization have failed to improve outcome in DM patients with PAD. Hence, a need exists to develop new treatment strategies able to promote blood vessel growth in this setting. Mono-methylation of histone 3 at lysine 4 (H3K4me1) - a specific epigenetic signature induced by the histone methyltransferase SETD7 - favours an open chromatin thus enabling gene transcription. Purpose: To investigate whether SETD7-dependent epigenetic changes modulate angiogenic response in diabetes. Methodology: Primary human aortic endothelial cells (HAECs) were exposed to normal glucose (NG, 5 mM) or high glucose (HG, 25 mM) concentrations for 48 hours. Unbiased gene expression profiling was performed by RNA sequencing (RNA-seq) followed by Ingenuity Pathway Analysis (IPA). In vitro assays, namely cell migration and tube formation were employed to study angiogenic properties in HAECs. SETD7 and H3K4me1 levels were investigated by Western blot and Chromatin immunoprecipitation (ChIP). Pharmacological blockade of SETD7 was achieved by using the highly selective inhibitor (R)-PFI-2. Mice with streptozotocin-induced diabetes were orally treated with (R)-PFI-2 or vehicle and underwent hindlimb ischemia by femoral artery ligation for 14 days. Blood flow recovery was analysed at 30 minutes, 7 and 14 days by laser Doppler imaging. Our experimental findings were also translated in gastrocnemius muscle samples from patients with and without diabetes. Results RNA-seq in HG-treated HAECs revealed a profound upregulation of the methyltransferase SETD7, an enzyme involved in mono-methylation of lysine 4 at histone 3 (H3K4me1). SETD7 upregulation in HG-treated HAECs was associated with increased H3K4me1 levels as well as with impaired endothelial cell migration and tube formation. Both SETD7 gene silencing and pharmacological inhibition by (R)PFI-2 rescued hyperglycemia-induced impairment of HAECs migration and tube formation, while SETD7 overexpression blunted the angiogenic response. RNA-seq and ChIP assays showed that SETD7-dependent H3K4me1 regulates the transcription of the angiogenesis inhibitor semaphorin-3G (SEMA-3G, (Figure 1). Moreover, SEMA-3G overexpression blunted migration and tube formation in SETD7-depleted HAECs. In diabetic mice with hindlimb ischemia, treatment with (R)-PFI-2 improved limb vascularization and perfusion as compared to vehicle (Figure 2). Finally, SETD7/SEMA3G axis was upregulated in muscle specimens from T2D patients as compared to controls (Figure 2) Conclusion: Targeting SETD7 represents a novel epigenetic-based therapy to boost neovascularization in diabetic patients with PAD.

The effect of antibody-mediated PCSK9 inhibitor on bare-metal stent implantation outcome

Abstract Introduction Percutaneous coronary intervention (PCI) is the gold standard for the management of acute coronary syndrome, and has been benefited from advances in pharmacotherapy and device innovation. Nevertheless, in-stent restenosis and stent thrombosis remain serious complications following PCI procedure with stent implantation. Proprotein convertase subtilisin kexin type 9 (PCSK9) is an enzyme known for its role in plasma cholesterol homeostasis. Efficiently reducing plasma cholesterol, PCSK9 inhibition recently became a pivotal treatment strategy for hypercholesterolemia. However, the effect of PCSK9 inhibition on stent implantation outcomes remains uninvestigated. Methods Carotid artery bare-metal stent (BMS) implantation was performed on C57Bl/6 mice, which then a parallel assessment of various inflammatory mediators was performed. To inhibit PCSK9, alirocumab was administered weekly to antiplatelet-treated mice started before stent implantation. Six weeks after the stent implantation procedure, animals were harvested and histomorphometric analysis was performed on stented arteries. In vitro cell migration and cellular senescence were also assessed on alirocumab-treated primary human aortic endothelial (EC) and vascular smooth muscle cells (VSMC). Results Compared to sham intervention, stent implantation was associated with increased expression of several inflammatory mediators, including PCSK9. Interestingly, the increase in PCSK9 level was confirmed in the stented vascular tissue, but not in plasma (Fig 1A). Following alirocumab treatment, PCSK9 inhibition results in an increased intimal hyperplasia in the stented vascular segment of alirocumab-treated animals compared to controls (Fig 1B). In vitro, alirocumab promoted migration and inhibited the onset of senescence in primary human VSMC, while blunted the migration and increased the senescence of EC. Conclusion The results of this study demonstrated that antibody-based PCSK9 inhibition worsen bare-metal stent implantation outcome in mice. This observed effect is mediated, in part, by the differential effect on VSMC and EC senescence, thus promoting in-stent intimal hyperplasia while blunting vascular healing. The herein-reported data warrant additional investigations concerning the use of PCSK9 inhibitors in patients undergoing PCI with stent implantation.

Functional assay for assessment of agonistic or antagonistic activity of angiotensin AT2 receptor ligands reveals that EMA401 and PD123319 have agonistic properties

With the discovery of the protective arm of the renin-angiotensin system (RAS), interest has grown in protective RAS-related receptors such as the angiotensin AT2-receptor [AT2R] as potential new drug targets. While it is known that AT2R couple to Gi, it is also apparent that they do not signal via inhibition of adenylyl cyclase/decrease in cAMP, as do many Gi-coupled receptors. Thus, standard commercially-available assays cannot be applied to test for agonistic or antagonistic properties of AT2R ligands. This lack of standard assays has hampered the development of new drugs targeting the AT2R.Therefore, we aimed at developing a reliable, technically easy assay for the determination of intrinsic activity of AT2R ligands, primarily for distinguishing between AT2R agonists and antagonists. We found that measurement of NO release by DAF-FM fluorescence in primary human aortic endothelial cells (HAEC) or in AT2R-transfected CHO cells is a reliable assay for the characterization of AT2R ligands. While testing the assay, we made several novel findings, including: a) C21 is a full agonist at the AT2R (with the same efficacy as angiotensin II); b) C21 has no intrinsic activity at the receptor Mas; c) AT2R-transfected HEK-293 cells are unresponsive to AT2R stimulation; d) EMA401 and PD123319, which are commonly regarded as AT2R antagonists, are partial agonists at the AT2R.Collectively, we have developed and tested an assay based on the measurement and quantification of NO release in HAEC or in AT2R-CHO cells that is suitable for the characterisation of novel and established AT2R ligands.

Platelet factor 4 (PF4) induces cluster of differentiation 40 (CD40) expression in human aortic endothelial cells (HAECs) through the SIRT1/NF-κB/p65 signaling pathway.

PF4 is a pro-atherosclerotic molecule. Endothelial CD40, upon binding to its ligand CD40L, induces endothelial cell (EC) activation, which is a vital pathophysiological process in the initiation and progression of atherosclerosis. However, the relationship between PF4 and endothelial CD40 remains elusive. This study aims to investigate whether and how PF4 affects endothelial CD40 expression using primary HAECs. PF4 treatment down-regulated sirtuin 1 (SIRT1) expression but upregulated the expression of acetylated NF-κB p65 (Ac-p65) and CD40 in HAECs in a concentration- and time-dependent manner. Pretreatment with SIRT1 agonist (SRT1720 or RSV) or SIRT1-overexpressing lentivirus attenuated PF4-induced Ac-p65 and CD40 expression in HAECs, whereas preincubation with SIRT1 antagonist (NAM or EX527) or SIRT1 shRNA had the opposite effect. To investigate whether NF-κB/p65 signaling pathway modulates CD40 expression in PF4-treated HAECs, PDTC, a NF-κB inhibitor, and p65-shRNA were introduced. PDTC or p65-shRNA treatment down-regulated Ac-p65 expression in HAECs. PDTC or p65-shRNA preincubation suppressed CD40 expression in HAECs after PF4 treatment. To better determine whether SIRT1 regulates CD40 expression in PF4-treated HAECs via the NF-κB/p65 signaling pathway, p65-knockdown HAECs were preincubated with SIRT1 agonists before PF4 treatment. SIRT1 agonist preincubation further decreased CD40 expression in p65-knockdown HAECs treated with PF4. Moreover, PF4 treatment promoted p65 nuclear translocation in HAECs. The results of dual luciferase assay demonstrated that four NF-κB binding sites in the promoter of human CD40 gene were activated in PF4-treated HAECs. In conclusion, our findings suggest that PF4 treatment facilitates CD40 expression in HAECs through the SIRT1/NF-κB/p65 pathway.

Mapping the dynamic high-density lipoprotein synapse

Background and aimsHeterogeneous high-density lipoprotein (HDL) particles, which can contain hundreds of proteins, affect human health and disease through dynamic molecular interactions with cell surface proteins. How HDL mediates its long-range signaling functions and interactions with various cell types is largely unknown. Due to the complexity of HDL, we hypothesize that multiple receptors engage with HDL particles resulting in condition-dependent receptor-HDL interaction clusters at the cell surface. MethodsHere we used the mass spectrometry-based and light-controlled proximity labeling strategy LUX-MS in a discovery-driven manner to decode HDL-receptor interactions. ResultsSurfaceome nanoscale organization analysis of hepatocytes and endothelial cells using LUX-MS revealed that the previously known HDL-binding protein scavenger receptor B1 (SCRB1) is embedded in a cell surface protein community, which we term HDL synapse. Modulating the endothelial HDL synapse, composed of 60 proteins, by silencing individual members, showed that the HDL synapse can be assembled in the absence of SCRB1 and that the members are interlinked. The aminopeptidase N (AMPN) (also known as CD13) was identified as an HDL synapse member that directly influences HDL uptake into the primary human aortic endothelial cells (HAECs). ConclusionsOur data indicate that preformed cell surface residing protein complexes modulate HDL function and suggest new theragnostic opportunities.

Myeloperoxidase inhibition may protect against endothelial glycocalyx shedding induced by COVID-19 plasma

BackgroundSARS-CoV-2, the causative agent of COVID-19, is a threat to public health. Evidence suggests increased neutrophil activation and endothelial glycocalyx (EG) damage are independently associated with severe COVID-19. Here, we hypothesised that an increased level of blood neutrophil myeloperoxidase (MPO) is associated with soluble EG breakdown, and inhibiting MPO activity may reduce EG damage.MethodsAnalysing a subset of acute and convalescent COVID-19 plasma, 10 from severe and 15 from non-severe COVID-19 cases, and 9 from pre-COVID-19 controls, we determined MPO levels, MPO activity and soluble EG proteins (syndecan-1 and glypican-1) levels by enzyme-linked immunosorbent assay. In vitro primary human aortic endothelial cells were cultured with plasma untreated or treated with specific MPO inhibitors (MPO-IN-28, AZD5904) to determine EG shedding. We then investigated whether inhibiting MPO activity decreased EG degradation.ResultsIn COVID-19 plasma, MPO levels, MPO activity and levels of soluble EG proteins are significantly raised compared to controls, and concentrations increase in proportion to disease severity. Despite clinical recovery, protein concentrations remain significantly elevated. Interestingly, there is a trend of increasing MPO activity in convalescent plasma in both severe and non-severe groups. MPO levels and MPO activity correlate significantly with soluble EG levels and inhibiting MPO activity leads to reduced syndecan-1 shedding, in vitro.ConclusionsNeutrophil MPO may increase EG shedding in COVID-19, and inhibiting MPO activity may protect against EG degradation. Further research is needed to evaluate the utility of MPO inhibitors as potential therapeutics against severe COVID-19.