Aortic Endothelial Cells Research Articles

#1293 Endothelial calcification induced by high-phosphate is characterized by mesenchymal and osteoblastic transdifferentiation

Abstract Background and Aims Chronic kidney disease (CKD) is a prevalent condition that affects millions of people. Patients with CKD have an increased cardiovascular risk, mostly due to vascular calcification (VC). By now, it's quite clear how, in vitro and in vivo, vascular smooth muscle cells (VSMCs) actively participate to VC. In contrast to the wide studies on VSMCs, the role of endothelial cells (ECs) has been poorly investigated. It's known that ECs have a dynamic nature and following particular stimuli they can trans-differentiate and acquire several different phenotypes through the endothelial-to-mesenchymal transition (EndMT). Methods Human aortic ECs (HAECs) were challenged, in an in vitro calcification model, with 2, 2.5, 3, 3.5 mM Pi for up to 7 days. Early morphological changes, gene expression and cell migration were evaluated. Afterwards calcium deposition, genes and protein expression and ultrastructural changes were analyzed. Results High-Pi, at a concentration of 3 mM, is able to induce EC calcium deposition. Calcification is dependent on calcium influx without influencing Pit-1 expression. During the first days of high-Pi treatment ECs change their morphology from cobblestone to spindle shape acquiring motility, as demonstrated by the 24% increased closure in the scratch wound test. EndMT master genes such as SNAIL and TWIST resulted up-regulated at day 3 together with an increased protein expression of mesenchymal markers such as N-Cadherin, α-SMA, SM22α, FSP-1 and Fibronectin. Starting from day 5 high-Pi induces osteoblastic differentiation with RUNX2 and BMP2 mRNA up-regulation up to day 7, osteopontin increased protein expression and positive Alcian Blu staining. In calcified ECs mesenchymal and endothelial markers, such as α-SMA, SM22α, FSP-1 and Fibronectin or vWF progressively decrease. Finally, uremic serum is able to exacerbate in vitro calcification, compared to healthy serum characterized by an increase in both mesenchymal and osteoblastic mastergene such as TWIST and RUNX2. Conclusions Our data demonstrate that in vitro high-Pi induces the EndMT process and similar osteoblastic trans-differentiation suggesting a potential role of endothelium in VC. The relevancy of endothelial calcification is suggested by the calcification exacerbation induced by uremic compared to healthy sera.

Mitochondria targeted esculetin administration improves insulin resistance and hyperglycemia-induced atherosclerosis in db/db mice.

The development and progression of hyperglycemia (HG) and HG-associated atherosclerosis are exacerbated by mitochondrial dysfunction due to dysregulated mitochondria-derived ROS generation. We recently synthesized a novel mitochondria-targeted esculetin (Mito-Esc) and tested its dose-response therapeutic efficacy in mitigating HG-induced atherosclerosis in db/db mice. In comparison to simvastatin and pioglitazone, Mito-Esc administration resulted in a considerable reduction in body weights and improved glucose homeostasis, possibly by reducing hepatic gluconeogenesis, as indicated by a reduction in glycogen content, non-esterified free fatty acids (NEFA) levels, and fructose 1,6-bisphosphatase (FBPase) activity. Interestingly, Mito-Esc treatment, by regulating phospho-IRS and phospho-AKT levels, greatly improved palmitate-induced insulin resistance, resulting in enhanced glucose uptake in adipocytes and HepG2 cells. Also, and importantly, Mito-Esc administration prevented HG-induced atheromatous plaque formation and lipid accumulation in the descending aorta. In addition, Mito-Esc administration inhibited the HG-mediated increase in VACM, ICAM, and MAC3 levels in the aortic tissue, as well as reduced the serum pro-inflammatory cytokines and markers of senescence. In line with this, Mito-Esc significantly inhibited monocyte adherence to human aortic endothelial cells (HAECs) treated with high glucose and reduced high glucose-induced premature senescence in HAECs by activating the AMPK-SIRT1 pathway. In contrast, Mito-Esc failed to regulate high glucose-induced endothelial cell senescence under AMPK/SIRT1-depleted conditions. Together, the therapeutic efficacy of Mito-Esc in the mitigation of hyperglycemia-induced insulin resistance and the associated atherosclerosis is in part mediated by potentiating the AMPK-SIRT1 axis. KEY MESSAGES: Mito-Esc administration significantly mitigates diabetes-induced atherosclerosis. Mito-Esc improves hyperglycemia (HG)-associated insulin resistance. Mito-Esc inhibits HG-induced vascular senescence and inflammation in the aorta. Mito-Esc-mediated activation of the AMPK-SIRT1 axis regulates HG-induced endothelial cell senescence.

Lipid Variability Induces Endothelial Dysfunction by Increasing Inflammation and Oxidative Stress.

This study investigates the impact of fluctuating lipid levels on endothelial dysfunction. Human aortic and umbilical vein endothelial cells were cultured under varying palmitic acid (PA) concentrations: 0, 50, and 100 μM, and in a variability group alternating between 0 and 100 μM PA every 8 hours for 48 hours. In the lipid variability group, cells were exposed to 100 μM PA during the final 8 hours before analysis. We assessed inflammation using real-time polymerase chain reaction, Western blot, and cytokine enzyme-linked immunosorbent assay (ELISA); reactive oxygen species (ROS) levels with dichlorofluorescin diacetate assay; mitochondrial function through oxygen consumption rates via XF24 flux analyzer; and endothelial cell functionality via wound healing and cell adhesion assays. Cell viability was evaluated using the MTT assay. Variable PA levels significantly upregulated inflammatory genes and adhesion molecules (Il6, Mcp1, Icam, Vcam, E-selectin, iNos) at both transcriptomic and protein levels in human endothelial cells. Oscillating lipid levels reduced basal respiration, adenosine triphosphate synthesis, and maximal respiration, indicating mitochondrial dysfunction. This lipid variability also elevated ROS levels, contributing to a chronic inflammatory state. Functionally, these changes impaired cell migration and increased monocyte adhesion, and induced endothelial apoptosis, evidenced by reduced cell viability, increased BAX, and decreased BCL2 expression. Lipid variability induce endothelial dysfunction by elevating inflammation and oxidative stress, providing mechanistic insights into how lipid variability increases cardiovascular risk.

Transcriptional synergy in human aortic endothelial cells is vulnerable to combination p300/CBP and BET bromodomain inhibition

Combinatorial signaling by proinflammatory cytokines synergizes to exacerbate toxicity to cells and tissue injury during acute infections. To explore synergism at the gene-regulatory level, we investigated the dynamics of transcription and chromatin signaling in response to dual cytokines by integrating nascent RNA imaging mass spectrometry, RNA sequencing, amplification-independent mRNA quantification, assay for transposase-accessible chromatin using sequencing (ATAC-seq), and transcription factor profiling. Costimulation with interferon-gamma (IFNγ) and tumor necrosis factor alpha (TNFα) synergistically induced a small subset of genes, including the chemokines CXCL9, -10, and -11. Gene induction coincided with increased chromatin accessibility at non-coding regions enriched for p65 and STAT1 binding sites. To discover coactivator dependencies, we conducted a targeted chemogenomic screen of transcriptional inhibitors followed by modeling of inhibitor dose-response curves. These results identified high efficacy of either p300/CREB-binding protein (CBP) or bromodomain and extra-terminal (BET) bromodomain inhibitors to disrupt induction of synergy genes. Combination p300/CBP and BET bromodomain inhibition at half-maximal inhibitory concentrations (subIC50) synergistically abrogated IFNγ/TNFα-induced chemokine gene and protein levels.

Senescence of endothelial cells promotes phenotypic changes in adventitial fibroblasts: possible implications for vascular aging.

Aging is the most important risk factor for the development of cardiovascular diseases. Senescent cells release plethora of factors commonly known as the senescence-associated secretory phenotype, which can modulate the normal function of the vascular wall. It is currently not well understood if and how endothelial cell senescence can affect adventitial niche. The aim of this study was to characterize oxidative stress-induced endothelial cells senescence and identify their paracrine effects on the primary cell type of the adventitia, the fibroblasts. Human aortic endothelial cells (HAEC) were treated with hydrogen peroxide to induce premature senescence. Mass spectrometry analysis identified several proteomic changes in senescent HAEC with top upregulated secretory protein growth differentiation factor 15 (GDF-15). Treatment of the human adventitial fibroblast cell line (hAdv cells) with conditioned medium (CM) from senescent HAEC resulted in alterations in the proteome of hAdv cells identified in mass spectrometry analysis. Majority of differentially expressed proteins in hAdv cells treated with CM from senescent HAEC were involved in the uptake and metabolism of lipoproteins, mitophagy and ferroptosis. We next analyzed if some of these changes and pathways might be regulated by GDF-15. We found that recombinant GDF-15 affected some ferroptosis-related factors (e.g. ferritin) and decreased oxidative stress in the analyzed adventitial fibroblast cell line, but it had no effect on erastin-induced cell death. Contrary, silencing of GDF-15 in hAdv cells was protective against this ferroptotic stimuli. Our findings can be of importance for potential therapeutic strategies targeting cell senescence or ferroptosis to alleviate vascular diseases.

CCL4 contributes to aging related angiogenic insufficiency through activating oxidative stress and endothelial inflammation

Aging is a natural process associated with chronic inflammation in the development of vascular dysfunction. We hypothesized that chemokine C-C motif ligands 4 (CCL4) might play a vital role in aging-related vascular dysfunction. Circulating CCL4 was up-regulated in elderly subjects and in aged animals. CCL4 inhibition reduced generation of reactive oxygen species (ROS), attenuated inflammation, and restored cell functions in endothelial progenitor cells from elderly subjects and in aged human aortic endothelial cells. CCL4 promoted cell aging, with impaired cell functioning, by activating ROS production and inflammation. CCL4 knockout mice and therapeutic administration of anti-CCL4 neutralizing antibodies exhibited vascular and dermal anti-aging effects, with improved wound healing, via the down-regulation of inflammatory proteins and the activation of angiogenic proteins. Altogether, our findings suggested that CCL4 may contribute to aging-related vascular dysfunction via activating oxidative stress and endothelial inflammation. CCL4 may be a potential therapeutic target for vascular protections during aging.

Protective Effects of Polysaccharide of Atractylodes Macrocephala Koidz against Porcine Aortic Valve Endothelial Cells Damage Induced by di (2-ethylhexyl) Phthalate.

The activation, injury, and dysfunction of endothelial cells are considered to be the initial key events in the development of atherosclerosis. Di (2-ethylhexyl) phthalate (DEHP), a prevalent organic pollutant, can cause damage to multiple organs. Polysaccharide of Atractylodes macrocephala Koidz (PAMK) is a bioactive compound extracted from A. macrocephala Koidz with various biological activities. This study investigates the protective effects of PAMK on porcine aortic valve endothelial cells (PAVEC) damaged by DEHP. PAVECs treated with DEHP alone or with PAMK showed reduced cell apoptosis and death in PAMK-pretreated cells. PAMK up-regulated Bcl-2 expression and down-regulated Bax protein, suppressing apoptosis. Flow cytometry analysis demonstrated that PAMK protected PAVECs from DEHP-induced damage. These findings suggest that PAMK inhibits cell apoptosis and protects against DEHP damage in endothelial cells.

Mexenone protects mice from LPS-induced sepsis by EC barrier stabilization

Blood vessels permit the selective passage of molecules and immune cells between tissues and circulation. Uncontrolled inflammatory responses from an infection can increase vascular permeability and edema, which can occasionally lead to fatal organ failure. We identified mexenone as a vascular permeability blocker by testing 2,910 compounds in the Clinically Applied Compound Library using the lipopolysaccharide (LPS)-induced vascular permeability assay. Mexenone suppressed the LPS-induced downregulation of junctional proteins and phosphorylation of VE-cadherin in Bovine Aortic Endothelial Cells (BAECs). The injection of mexenone 1 hr before LPS administration completely blocked LPS-induced lung vascular permeability and acute lung injury in mice after 18hr. Our results suggest that mexenone-induced endothelial cell (EC) barrier stabilization could be effective in treating sepsis patients.

MiR-148a-3p/SIRT7 Axis Relieves Inflammatory-Induced Endothelial Dysfunction.

In endothelial cells, miR-148a-3p is involved in several pathological pathways, including chronic inflammatory conditions. However, the molecular mechanism of miR-148a-3p in endothelial inflammatory states is, to date, not fully elucidated. To this end, we investigated the involvement of miR-148a-3p in mitochondrial dysfunction and cell death pathways in human aortic endothelial cells (teloHAECs) treated with interleukin-6 (IL-6), a major driver of vascular dysfunction. The results showed that during IL6-activated inflammatory pathways, including increased protein levels of sirtuin 7 (SIRT7) (p < 0.01), mitochondrial stress (p < 0.001), and apoptosis (p < 0.01), a decreased expression of miR-148a-3p was observed (p < 0.01). The employment of a miR-148a mimic counteracted the IL-6-induced cytokine release (p < 0.01) and apoptotic cell death (p < 0.01), and ameliorated mitochondria redox homeostasis and respiration (p < 0.01). The targeted relationship between miR-148a-3p and SIRT7 was predicted by a bioinformatics database analysis and validated via the dual-luciferase reporter assay. Mechanistically, miR-148a-3p targets the 3' untranslated regions of SIRT7 mRNA, downregulating its expression (p < 0.01). Herein, these in vitro results support the role of the miR-148a-3p/SIRT7 axis in counteracting mitochondrial damage and apoptosis during endothelial inflammation, unveiling a novel target for future strategies to prevent endothelial dysfunction.

Ion channel Piezo1 activation aggravates the endothelial dysfunction under a high glucose environment

BackgroundVasculopathy is the most common complication of diabetes. Endothelial cells located in the innermost layer of blood vessels are constantly affected by blood flow or vascular components; thus, their mechanosensitivity plays an important role in mediating vascular regulation. Endothelial damage, one of the main causes of hyperglycemic vascular complications, has been extensively studied. However, the role of mechanosensitive signaling in hyperglycemic endothelial damage remains unclear.MethodsVascular endothelial-specific Piezo1 knockout mice were generated to investigate the effects of Piezo1 on Streptozotocin-induced hyperglycemia and vascular endothelial injury. In vitro activation or knockdown of Piezo1 was performed to evaluate the effects on the proliferation, migration, and tubular function of human umbilical vein endothelial cells in high glucose. Reactive oxygen species production, mitochondrial membrane potential alternations, and oxidative stress-related products were used to assess the extent of oxidative stress damage caused by Piezo1 activation.ResultsOur study found that in VECreERT2;Piezo1flox/flox mice with Piezo1 conditional knockout in vascular endothelial cells, Piezo1 deficiency alleviated streptozotocin-induced hyperglycemia with reduced apoptosis and abscission of thoracic aortic endothelial cells, and decreased the inflammatory response of aortic tissue caused by high glucose. Moreover, the knockout of Piezo1 showed a thinner thoracic aortic wall, reduced tunica media damage, and increased endothelial nitric oxide synthase expression in transgenic mice, indicating the relief of endothelial damage caused by hyperglycemia. We also showed that Piezo1 activation aggravated oxidative stress injury and resulted in severe dysfunction through the Ca2+-induced CaMKII-Nrf2 axis in human umbilical vein endothelial cells. In Piezo1 conditional knockout mice, Piezo1 deficiency partially restored superoxide dismutase activity and reduced malondialdehyde content in the thoracic aorta. Mechanistically, Piezo1 deficiency decreased CaMKII phosphorylation and restored the expression of Nrf2 and its downstream molecules HO-1 and NQO1.ConclusionIn summary, our study revealed that Piezo1 is involved in high glucose-induced oxidative stress injury and aggravated endothelial dysfunction, which have great significance for alleviating endothelial damage caused by hyperglycemia.

Abstract 3010: Inhibition Of Endothelial Cell-Mediated Efferocytosis Promotes Abdominal Aortic Aneurysm Formation

Introduction: Aortic wall inflammation and vascular smooth muscle (VSMC) apoptosis can lead to accumulation of apoptotic cells and debris during abdominal aortic aneurysm (AAA) formation. We hypothesize that dysregulation of MerTK receptor-mediated efferocytosis (clearance of apoptotic cell debris) by endothelial cells (ECs) can significantly contribute to aortic inflammation and vascular remodeling in AAA pathogenesis. Methods: Single-cell RNA sequencing of human AAA tissue from a published dataset (PMID: 33779682) was evaluated for cells of the aortic wall (VSMC/EC) identified via SingleR and cell-specific marker s. Differentially expressed genes (DEGs) were identified via edgeR using the QL F-test and efferocytosis-related genes (ERGs) were recognized using a list of 141 ERGs curated from GeneCards. MerTK expression was assessed in human aortic tissue and ECs via western blot and immunofluorescence. PKH67-labelled apoptotic VSMCs were overlayed on ECs to assess efferocytosis activity and visualized via confocal microscopy. In a murine elastase AAA model, endothelial-specific MerTK knockout ( Cdh5 Cre-ERT2 / MerTK fl/fl ) and littermate male mice were analyzed on postoperative day 14 for aortic diameter. Statistical analyses were performed by Welch’s T-test and p&lt;0.05 was considered statistically significant. Results: ERGs (ANXA2, PHACTR1, PPARG, ADAM9, CD14, IL6) were differentially expressed (p&lt;0.05, log 2 FC &gt; |1|) between aortic wall cells of human AAAs and control. Human AAA tissue displayed a significant increase in MerTK protein compared to controls (1±0.1 vs. 1.51±0.4, n=6/group, p=0.01). The expression of MerTK in aortic ECs was confirmed by western blot and immunofluorescence(n=3). Pharmacologic inhibition of MerTK using UNC5293, a specific MerTK inhibitor, attenuated EC-mediated efferocytosis of apoptotic VSMCs (qualitative data; 10 images/group n=4). Importantly, EC-specific MerTK -/- mice had a significant increase in aortic diameter compared to littermate controls (155±40.4 vs. 103±30.9%, n=5-6/group, p=0.04) on day 14. Conclusion: EC-mediated efferocytosis can be regulated by MerTK to mediate AAA formation. Ongoing studies will delineate mechanisms of EC-MerTK signaling in AAA formation.

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 1005: Hypertriglyceridemia Promotes Aortic Aneurysm Formation And Rupture In Angiotensin Ii Infused Mice

Plasma total cholesterol (TC) and triglyceride (TG) are reported to be positively associated with the risk of abdominal aortic aneurysm (AAA). Our group discovered that hypercholesterolemia augments angiotensin II-induced AAA in mice. We also found that remnants of triglyceride-rich lipoproteins (TRLs) may be crucial for AngII-induced AAA. Recently, it was reported that hypertriglyceridemia (HTG) caused by inducible lipoprotein lipase deficiency (iLpl-/-) results in uptake and accumulation of TRL lipid in aortic endothelial cells in vivo. Based upon these findings, we hypothesized that HTG stimulates AAA formation. Methods: Adult male and female Lplf/f.beta-actin-Mer/Cre/Mer 1/0 and Lplf/f mice were administered 75 mg/kg/day tamoxifen for 5 consecutive days. Mice were fed either a standard diet (SD) throughout the study or a Western-type diet (WD) starting 1 wk after the completion of tamoxifen administration and continuing for a total of 5 wks. Mini osmotic pumps were implanted in mice 2 wks after completion of tamoxifen administration and delivered saline or AngII at 1,000 ng/kg/min for 4 wks. Results: AngII infused and SD fed iLpl-/- versus Lplf/f mice had elevated plasma TG and TC levels but similar abdominal aortic external diameter and AAA incidence. Since the SD was low in fat, a high fat WD was then fed to AngII-infused mice. Plasma TG and TC were increased in female iLpl-/- versus Lplf/f mice. However, plasma lipid concentrations could not be measured in male iLpl-/- because 10 of 11 animals had died from aortic rupture. In contrast, none of the male Lplf/f mice died and only 4 of 11 had abdominal aortic dilation. Female compared to male iLpl-/- mice were protected from AngII-induced aortic rupture (1/11 died) and only 1 of 9 females had abdominal aortic dilation. To eliminate the possibility that HTG alone caused aortic rupture in male mice, the study was repeated with the addition of saline infusion. In agreement with the first study, AngII plus WD lead to death by aortic rupture in all male iLpl-/- mice (9/9). In contrast, iLpl-/- male mice infused with saline had markedly greater survival (1/5 died of unknown cause). Conclusions: HTG causes aortic aneurysm development in AngII-infused male iLpl-/- mice. Thus, treating HTG could reduce AAA risk.

Novel Role of Endothelial CD47 in the Regulation of Pathogenesis of Coronary Artery Disease

Background: The anti-phagocytic molecule CD47 is upregulated in atherosclerotic plaques of patients with CVD. However, the role of endothelial cell-specific expression of CD47 in the pathogenesis and progression of atherosclerosis has not yet been fully defined. Kojima et.al. described atheroprotective effect of anti-CD47 antibody by enhancing efferocytosis in atherosclerosis. In this study, we determined whether endothelial cell-specific CD47 regulates efferocytosis in atherosclerosis. Methods: Endothelial cell-specific, tamoxifen-inducible CD47knockout (CD47iECKO) mice were injected with a single dose of AAV-mutant PCSK9 via the tail vein. Susceptibility to atherosclerosis was evaluated in cross sections of the aortic sinus in mice fed Western Diet for 12 weeks. Using single-cell RNA sequencing and in vitro efferocytosis assays, we investigated the role of CD47 in regulating efferocytosis in an atherosclerotic mouse model. Results: Endothelial cell-specific deletion of CD47 led to a significant plaque reduction in the aortic sinus of athero-CD47iECKO mice. Cluster analysis and gene expression profiles of 20,000 aortic endothelial cells from athero-control and athero-CD47iECKO mice identified 10 major cell types from the integrated data: endothelial cells, vascular smooth muscle cells, fibroblasts, immune cells (B cells, T cells, macrophage), erythrocytes, oligodendrocytes cells, Schwann cells, and pericytes. After Western Diet intake, in the CD47iECKO group, a subpopulation of endothelial cells as well as fibroblasts, T-cells, B-cells, resident aortic macrophages, erythrocytes, oligodendrocytes, and pericytes were increased, while vascular smooth muscle cell numbers decreased. Using an in vitro efferocytosis assay on isolated primary endothelial cells from control and CD47iECKO mice, we observed CD47 deletion induced engulfment of apoptotic Jurkat cells, which had been exposed to BAY11-7082 (NF-κB inhibitor) to stimulate the apoptotic attributes. Quantitative PCR analyses showed that CD47 deletion increases the expression of efferocytosis receptor FasL, CX3CL1, Gpr132, MerTK, Scarb1, Sirpa, TSP1, and HMGB1. Conclusion: Our study indicates that genetic deletion of CD47 in endothelial cells attenuates atheroma progression by enhancing efferocytosis. This study also reveals phenotypic heterogenicity of endothelial cells at the single cell level during atherogenesis and provides a deeper understanding of endothelial cell biology in atherosclerosis that may facilitate the development of novel therapeutic interventions for this cardiovascular disease. NIH, AHA. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 1047: Cerebral Cavernous Malformation 2 Knockout Hinders Murine Atherosclerosis And Lowers Vascular Inflammation

Introduction: Genome-wide association studies (GWAS) have identified &gt;300 loci associated with coronary artery disease (CAD). The chr7p13 locus harbors several variants associated with decreased CAD risk, which are within the exon or the potential regulatory element of cerebral cavernous malformation 2 (CCM2, odds ratio = 0.95, p=1.53e-08). While CCM2 has been studied in venous endothelial cells (ECs) in the context of cerebral cavernous malformation, the role of CCM2 in aortic ECs and coronary atherosclerosis remains unknown. Methods and Results: To test whether CCM2 regulates atherosclerosis development, CCM2 heterozygous knockout (CCM2 +/-) mice and their control littermates (CCM2 +/+) were injected with AAV-PCKS9-D377Y and subjected to a high-fat, high cholesterol diet for 12 weeks. Atherosclerotic lesions were quantified at three different aortic sites (aortic root, minor aortic arch, and the brachiocephalic artery). Notably, heterozygous CCM2 knockout mice exhibited reduced atherosclerosis lesion in the aortic root in male mice (p=0.03), but not in female mice. Next, we sought to understand the mechanism by which CCM2 regulates the development of atherosclerosis. Single cell RNA-seq was conducted using aorta from CCM2 +/- mice and CCM2 +/+ mice. Gene set enrichment analysis on the EC population suggested that CCM2 heterozygous knockout suppressed inflammation pathways especially the TNF-alpha signaling pathway. Concordantly, after 12-weeks of high-fat, high cholesterol diet, the number of monocytes in the aorta were decreased in CCM2 +/- mice when compared to CCM2 +/+ mice. Furthermore, in vitro, ECs lacking CCM2 showed impaired THP-1 monocyte adhesion (p=0.001) and decreased expression of MCP-1 (p=3e-4). Conclusions: Our findings suggest that CCM2 heterozygous knockout hinders the development of atherosclerosis. This is likely achieved by lowering MCP-1 expression and decreasing monocyte recruitment. Further investigations are being conducted to functionally identify the causal variant in the CCM2 locus, specifically under disease-relevant stimuli, to further our understanding of CCM2’s potential as a diagnostic and therapeutic target in CAD.

Abstract 3067: Chronic Knockout Of The ETS Transcription Factor ERG Promotes Loss Of Endothelial Cell Identity And Endothelial Cell Dysfunction In An Aortic Endothelial Cell Model Relevant For Atherosclerosis

Background: The ETS transcription factor ERG is a key endothelial cell (EC) transcription factor. ERG represses vascular inflammation and is downregulated in chronic inflammatory diseases (e.g. liver fibrogenesis, atherosclerosis). Previously, transient ERG knock-down has been associated with endothelial-mesenchymal transition (EndMT) and EC dysfunction; however, the mechanisms underlying EndMT and the EC dysfunction associated with chronic ERG loss have not been elucidated in an atherosclerosis-relevant model. We hypothesize that chronic ERG knockout (KO) in telomerase-immortalized human aortic ECs (teloHAECs) induces EndMT and contributes to EC dysfunction underlying vascular dysregulation in atherosclerosis. Methods: TeloHAECs with CRIPSR/Cas9-mediated deletion of ERG were used. Chromatin accessibility and gene expression in ERG KO and wildtype (WT) teloHAECs were assessed using ATAC-seq (n=2) and RNA-seq (n=5-6). TOBIAS and diffTF were used to identify enriched motifs by footprinting (P&lt;0.05) and to profile TF activity (FDR&lt;0.05), respectively. ERG-mediated EC dysfunction was investigated using immunofluorescence (IF; n=3), western blot (WB; n=3), and a timelapse migration assay (n=3). Results: There were ~ 21,000 differentially accessible chromatin peaks between ERG KO and WT ECs. Integrated analysis of chromatin accessibility and gene expression demonstrated increased activity of TGFβ-SMAD and IL-1β signaling constituents and classical EndMT transcription factors. Loss of ERG downregulated EC genes (e.g., CLDN5 , TIE1 ) and protein expression (e.g., CDH5, vWF) and upregulated mesenchymal genes (e.g., ACTA2 , FSP1 ) and protein distribution (e.g., FN1, COL1A1). Investigation of EC-dysfunction phenotypes revealed increased migration and proliferation in ERG KO teloHAEC - with the percentage of Ki67 positive ECs increasing from 14% to 49% (P&lt;0.05, n=3). Conclusion: ERG KO in cultured aortic ECs markedly impacts chromatin accessibility and gene expression and induces EC identity loss, migration, and proliferation, providing mechanistic insight into the role of ERG in vascular dysfunction in atherosclerosis.

Abstract 1078: A Cross-species Platform And Phosphoproteomics Analysis To Mitigate Vegfri-induced Hypertension And Endothelial Dysfunction

Introduction: Vascular endothelial growth factor receptor inhibitors (VEGFRis) are a class of tyrosine kinase inhibitors (TKIs) used to treat human and canine cancers, but these drugs also cause hypertension (HTN) and endothelial cell (EC) dysfunction. Purpose: We combined phosphoproteomic analysis in ECs with a cross-species in-vitro and in-vivo approach to identify mitigating therapies for VEGFRi-induced EC dysfunction and HTN. Methods and Results: We developed a sorafenib-induced HTN mouse model showing increased blood pressure, mesenteric resistance vessel EC dysfunction (decreased phosphorylation of Ser1177 on endothelial nitric oxide synthase [p-eNOS], increased endothelin-1 [ET-1]), and renal glomerular endotheliosis. Human umbilical vein ECs were treated with VEGFR TKIs, non-VEGFR TKIs, and cardiovascular drugs. Phosphoproteomic mass spectrometry and a marker selection algorithm identified a 14-phosphopeptide signature differentiating VEGFR TKIs from non-VEGFR TKIs. The signature peptide RBM17 pS222 increased with VEGFRi treatment in human, canine, and mouse aortic ECs, correlating with reduced p-eNOS. By screening for cardiovascular drugs that reverse the VEGFRi phosphoproteomic signature, we found alpha-adrenergic antagonists, particularly doxazosin, had the most anti-correlated signatures. Doxazosin prevented VEGFRi-induced EC dysfunction in primary aortic ECs across species. In mice, doxazosin reversed sorafenib-induced EC dysfunction in resistance vessels without affecting blood pressure or renal glomerular endotheliosis. Conversely, lisinopril reduced HTN and glomerular endotheliosis but not EC dysfunction. Preliminary results from our clinical trial in canine cancer patients confirmed that toceranib induced HTN and showed that both doxazosin and lisinopril significantly lowered blood pressure in dogs with cancer and VEGFRi-induced HTN. Conclusion: Our study demonstrates the utility of phosphoproteomics and cross-species analysis in identifying EC-protective effects of doxazosin in VEGFRi-induced HTN. Our mouse data suggest distinct mechanisms for VEGFRi-induced EC dysfunction and HTN, potentially involving renal glomerular damage.

Abstract 3122: The Role Of Oct4 In Endothelial Cell Sexual Dimorphism And Angiogenesis

Background: Biological sex differences play a critical role in vascular diseases. Using endothelial ( EC ) lineage tracing atherosclerotic mice and cultured mouse and human aortic EC, we recently found that female EC have lower angiogenic potential, higher expression of pro-inflammatory genes and intracellular ROS, and worse mitochondria functions than male EC. However, the mechanisms responsible for this EC sexual dimorphism are still unknown. We previously identified the pluripotency factor OCT4 as a critical regulator of EC characteristics, including angiogenic potential, ROS accumulation, and mitochondrial functions. Therefore, this study aimed to test whether OCT4 is responsible for sex-dependent differences in EC in vivo and in vitro . Methods: We used male and female EC-specific tamoxifen-inducible OCT4 knockout and EC-lineage tracing (EC-OCT4 KO) mice to study the role of OCT4 in non-atherosclerotic conditions leading to pro-inflammatory angiogenesis, such as hind-limb ischemia and skin injury models. Male and female mouse aortic EC (MAEC) were isolated from EC-OCT4 KO and wild-type littermate mice for in vitro experiments. We performed BrdU assay, EC tube formation in Matrigel (in vitro angiogenesis), wound scratch assay, and angiogenic proteome profile array to evaluate angiogenic potential. Results: Compared to wild-type mice, EC-OCT4 KO male mice exhibited accelerated blood flow recovery and wound healing after hind-limb ischemia and skin injury. However, EC-OCT4 KO female mice showed no difference in blood flow recovery and delayed skin wound healing compared to control mice. In vitro , although male and female OCT4-KO MAEC had higher angiogenic potential than control, the phenotype in female EC was less pronounced. Mechanistically, we found that male OCT4 KO MAEC express higher levels of monocyte cytokine protein 1 ( MCP1 ). Furthermore, the inhibition of MCP1 in male OCT4 KO MAEC, but not in female cells, led to significant decreases in cell migration, proliferation, and endothelial tube formation in Matrigel. Conclusions: Our data indicate that OCT4-dependent mechanisms contribute to the sex differences observed in EC, suggesting a novel biological role for pluripotency signaling in vascular pathologies and homeostasis.

Kidney Stem Cell Reprogramming Drives Spontaneous Hypertension via Exosomes

The spontaneously hypertensive rat (SHR) is a commonly used animal model for studying primary hypertension. However, the precise mechanism of these rats developing hypertension remains to be defined. Here, we have first demonstrated that kidney stem cell reprogramming is a driver for the development of hypertension in SHR rats. In this study, we treated 5-week-old SHR rats with WKY-kidney stem cell-derived exosomes (WKY-Exo) and 5-week-old WKY rats with SHR-Exo, respectively, via i.p. injections. Notably, WKY-Exo effectively blocked the development of hypertension and arterial stiffening in SHRs. It is fascinating that WKY rats developed hypertension and arterial stiffening due to treatment of SHR-Exo. We confirmed that both WKY- and SHR-Exo were up taken into aortic endothelial and smooth muscle cells after i.p. delivery of CD63/GFP-labelled exosomes. We demonstrated that WKY-Exo can improve vascular functions and arterial compliance of SHR rats as evidenced by preventing the development of arterial stiffness and restoring renal artery endothelial function. We also demonstrated that the vascular functions were impaired in WKY rats after SHR-Exo treatment. Furthermore, our data show that expression of Elastin, Emilin1, and Myh11 was significantly downregulated in the aorta of SHR rats, which can be repaired by WKY-Exo treatment. SHR-Exo decreased expression of Elastin and Emilin1 without affecting Myh11 in the aorta of WKY rats, suggesting that Elastin and Emilin1 deficiency could contribute to arterial stiffening leading to the development of spontaneous hypertension. Proteomic analysis reveals the enrichment of protein-protein interaction network for elastic fiber assembling, blood vessel development, and regulation of angiogenesis in WKY-Exo vs SHR-Exo. In conclusion, our data first demonstrates that kidney stem cell reprograming is a driver for the development of spontaneous hypertension in SHR rats. WKY-KSCs-derived exosome contains a proteome profile promoting arterial repair, which may provide a therapeutic means to prevent and treat primary hypertension. NIH. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 3061: Sigma1 Receptor Protein: A Novel Player In Pcsk9/Western Diet-Induced Atherosclerosis And Vascular Endothelial Inflammation

Background: Atherosclerosis is a metabolic disorder characterized by hyperlipidemia and chronic inflammation that is initiated by endothelial dysfunction and altered lipid homeostasis. Sigma1 receptor (Sigmar1) is a ubiquitously expressed chaperone protein known to have a role in lipid metabolism and ER-mitochondrial lipid transport. Although studies showed a correlation between Sigmar1 inhibition and induction of inflammation, the role of Sigmar1 in regulating vascular inflammation during atherosclerosis remained unknown. Hypothesis: Absence of Sigmar1 will accelerate the development and progression of atherosclerosis by inducing endothelial inflammation and mitochondrial dysfunction. Methods and Results: We used a hypercholesterolemia model induced by AAV8-PCSK9 injection followed by 12 weeks of western diet (WD) in wildtype (Wt) and global Sigmar1 knockout (Sigmar1 -/- ) mice to determine the role of Sigmar1 in diet-induced atherosclerosis. We also used human aortic endothelial cells (HAEC) and CRISPR-Cas9 mediated Sigmar1 knockout HAECs (HAEC hKO ) to delineate the molecular mechanisms in vitro . Sigmar1 protein level was notably decreased in the human and mouse atherosclerotic tissues and in HAECs treated with inflammatory trigger, LPS+IFNγ. We observed increased atherosclerotic plaque area in aorta by en face analysis in Sigmar1 -/- mice compared to Wt mice subjected to PCSK9/WD model. LPS+IFNγ treated HAEC hKO showed significant upregulation of EC adhesion molecules (VCAM1, ICAM1) and activated nuclear factor NFκB expressions than the control HAEC hWT . Since mitochondrial dysfunction and elevated reactive oxygen species (ROS) generation play a role in inflammation and diseases, and Sigmar1 is known to regulate mitochondrial function, we wanted to dissect the contribution of EC-Sigmar1 in vascular inflammation. Both lack of Sigmar1 and LPS+IFNγ stimuli significantly reduced mitochondrial respiration in HAEC hKO cells and induced ROS production along with the induction of inflammation. Conclusion: So, lack of Sigmar1 leads to increased atherosclerotic plaque area in mice in response to PCSK9/WD suggesting a novel protective role for Sigmar1 in the development and progression of atherosclerosis and vascular inflammation.