Epigenetic regulation of endothelial-cell-mediated vascular repair

HOXA9 versus HOXB9; particular focus on their controversial role in tumor pathogenesis

The Homeobox (HOX) gene family is essential to regulating cellular processes because it maintains the exact coordination required for tissue homeostasis, cellular differentiation, and embryonic development. The most distinctive feature of this class of genes is the presence of the highly conserved DNA region known as the homeobox, which is essential for controlling their regulatory activities. Important players in the intricate process of genetic regulation are the HOX genes. Many diseases, especially in the area of cancer, are linked to their aberrant functioning. Due to their distinctive functions in biomedical research-particularly in the complex process of tumor advancement-HOXA9 and HOXB9 have drawn particular attention. HOXA9 and HOXB9 are more significant than what is usually connected with HOX genes since they have roles in the intricate field of cancer and beyond embryonic processes. The framework for a focused study of the different effects of HOXA9 and HOXB9 in the context of tumor biology is established in this study.

Phosphoproteomic profiling identifies DNMT1 as a key substrate of beta IV spectrin-dependent ERK/MAPK signaling in suppressing angiogenesis

βIV-spectrin is a membrane-associated cytoskeletal protein that maintains the structural stability of cell membranes and integral proteins such as ion channels and transporters. Its biological functions are best characterized in the brain and heart, although recently we discovered a fundamental new role in the vascular system. Using cellular and genetic mouse models, we reported that βIV-spectrin acts as a critical regulator of developmental and tumor-associated angiogenesis. βIV-spectrin was shown to selectively express in proliferating endothelial cells (EC) and suppress VEGF/VEGFR2 signaling by enhancing receptor internalization and degradation. Here we examined how these events impact the downstream kinase signaling cascades and target substrates. Based on quantitative phosphoproteomics, we found that βIV-spectrin significantly affects the phosphorylation of epigenetic regulatory enzymes in the nucleus, among which DNA methyltransferase 1 (DNMT1) was determined as a top substrate. Biochemical and immunofluorescence results showed that βIV-spectrin inhibits DNMT1 function by activating ERK/MAPK, which in turn phosphorylates DNMT1 at S717 to impede its nuclear localization. Given that DNMT1 controls the DNA methylation patterns genome-wide, and is crucial for vascular development, our findings suggest that epigenetic regulation is a key mechanism by which βIV-spectrin suppresses angiogenesis.

Inhibition of endothelial histone deacetylase 2 shifts endothelial-mesenchymal transitions in cerebral arteriovenous malformation models

Cerebral arteriovenous malformations (AVMs) are the most common vascular malformations worldwide and the leading cause of hemorrhagic strokes that may result in crippling neurological deficits. Here, using recently generated mouse models, we uncovered that cerebral endothelial cells (ECs) acquired mesenchymal markers and caused vascular malformations. Interestingly, we found that limiting endothelial histone deacetylase 2 (HDAC2) prevented cerebral ECs from undergoing mesenchymal differentiation and reduced cerebral AVMs. We found that endothelial expression of HDAC2 and enhancer of zeste homolog 1 (EZH1) was altered in cerebral AVMs. These alterations changed the abundance of H4K8ac and H3K27me in the genes regulating endothelial and mesenchymal differentiation, which caused the ECs to acquire mesenchymal characteristics and form AVMs. This investigation demonstrated that the induction of HDAC2 altered specific histone modifications, which resulted in mesenchymal characteristics in the ECs and cerebral AVMs. The results provide insight into the epigenetic impact on AVMs.

Molecular Insights into the Relationship Between Platelet Activation and Endothelial Dysfunction: Molecular Approaches and Clinical Practice

Platelets are one of the coagulation cells. When platelet activation occurs, many mediators are released and affect endothelial cells (ECs) and lead to endothelial dysfunction (ED). ED plays an important role in the pathogenesis of many diseases, including cardiovascular disease (CVD). Platelet are of important factors in ED. The release of mediators by platelets causes the stimulation of inflammatory pathways, oxidative stress, and apoptosis, which ultimately result in ED.On the other hand, platelet activation in CVD patients can be associated with a bad prognosis. Platelet activation can increase the level of markers such as p-selectin in the serum. Also, in this study, we have discussed the role of platelet as a diagnostic factor, as well as its use as a treatment option. In addition, we discussed some of the molecular pathways that are used to target platelet activation.

Lysine-Specific Demethylase 4D Is Critical for the Regulation of the Cell Cycle and Antioxidant Capacity in Goat Fibroblast Cells

Oxidative damage to skin fibroblast cells is a causative factor in many skin diseases. Previous studies have reported that lysine-specific demethylase 4D (Kdm4d) is involved in DNA replication, but its role on antioxidant capacity remains unclear. In the present study, we used goat fibroblast cells (GFCs) as the research model and identified 504 up-regulated and 1013 down-regulated genes following the knockdown of Kdm4d, respectively. The down-regulated genes of this enzyme were found to be enriched in the cell cycle, DNA replication, mitotic processes, and the oxidative phosphorylation pathway, as previously revealed from gene ontology (GO), Kyoto encyclopedia of genes and genomes (KEGG), and gene set enrichment analysis (GSEA), suggesting vital roles of the Kdm4d enzyme in the cell cycle and in antioxidant regulation. To this end, we found the cell proliferation rate was significantly decreased after the knockdown of Kdm4d. Moreover, both the mRNA and protein expression levels of superoxide dismutase 2 (SOD2), one of the major antioxidant enzymes, was decreased, while the reactive oxygen species (ROS) level was significantly increased in Kdm4d knocked-down cells. In addition, the expression of γH2A histone family member X (γH2AX) increased significantly, indicating the presence of DNA double-strand breaks after the knockdown of the Kdm4d enzyme. In conclusion, the knockdown of Kdm4d inhibited DNA replication and the cell cycle, repressed the expression of SOD2, and increased the generation of ROS, which led to the production of DNA damage in GFCs. Our data will be helpful for understanding the mechanism underlying antioxidant capacity regulation in fibroblast cells.

Epigenetic Mechanisms Involved in Inflammaging-Associated Hypertension

PURPOSE OF REVIEW

This review summarizes the involvement of inflammaging in vascular damage with focus on the epigenetic mechanisms by which inflammaging-induced hypertension is triggered.

RECENT FINDINGS

Inflammaging in hypertension is a complex condition associated with the production of inflammatory mediators by the immune cells, enhancement of oxidative stress, and tissue remodeling in vascular smooth muscle cells and endothelial cells. Cellular processes are numerous, including inflammasome assembly and cell senescence which may involve mitochondrial dysfunction, autophagy, DNA damage response, dysbiosis, and many others. More recently, a series of noncoding RNAs, mainly microRNAs, have been described as possessing epigenetic actions on the regulation of inflammasome-related hypertension, emerging as a promising therapeutic strategy. Although there are a variety of pharmacological agents that effectively regulate inflammaging-related hypertension, a deeper understanding of the epigenetic events behind the control of vessel deterioration is needed for the treatment or even to prevent the disease onset.

Research progress in endothelial cell injury and repair

Endothelial cells, which are important metabolic and endocrine cells, play an important role in regulating vascular function. The occurrence and development of various cardiovascular and cerebrovascular diseases are associated with endothelial dysfunction. However, the underlying mechanism of vascular endothelial injury is not fully understood. It has been reported that the mechanism of endothelial injury mainly involves inflammation and oxidative stress. Moreover, endothelial progenitor cells are regarded as important contributors in repairing damaged endothelium. Multiple interventions (including chemical drugs and traditional Chinese medicines) exert endothelial protection by decreasing the release of inducing factors, suppressing inflammation and oxidative stress, and preventing endothelial cell senescence.

Epi-Drugs in Heart Failure

Unveiling the secrets of genome’s flexibility does not only foster new research in the field, but also gives rise to the exploration and development of novel epigenetic-based therapies as an approach to alleviate disease phenotypes. A better understanding of chromatin biology (DNA/histone complexes) and non-coding RNAs (ncRNAs) has enabled the development of epigenetic drugs able to modulate transcriptional programs implicated in cardiovascular diseases. This particularly applies to heart failure, where epigenetic networks have shown to underpin several pathological features, such as left ventricular hypertrophy, fibrosis, cardiomyocyte apoptosis and microvascular dysfunction. Targeting epigenetic signals might represent a promising approach, especially in patients with heart failure with preserved ejection fraction (HFpEF), where prognosis remains poor and breakthrough therapies have yet to be approved. In this setting, epigenetics can be employed for the development of customized therapeutic approaches thus paving the way for personalized medicine. Even though the beneficial effects of epi-drugs are gaining attention, the number of epigenetic compounds used in the clinical practice remains low suggesting that more selective epi-drugs are needed. From DNA-methylation changes to non-coding RNAs, we can establish brand-new regulations for drug targets with the aim of restoring healthy epigenomes and transcriptional programs in the failing heart. In the present review, we bring the timeline of epi-drug discovery and development, thus highlighting the emerging role of epigenetic therapies in heart failure.

Epigenetic remodeling in heart failure with preserved ejection fraction

PURPOSE OF REVIEW

In this review, we critically address the role of epigenetic processing and its therapeutic modulation in heart failure with preserved ejection fraction (HFpEF).

RECENT FINDINGS

HFpEF associates with a poor prognosis and the identification of novel molecular targets and therapeutic approaches are in high demand. Emerging evidence indicates a key involvement of epigenetic signals in the regulation of transcriptional programs underpinning features of HFpEF. The growing understanding of chromatin dynamics has led to the development of selective epigenetic drugs able to reset transcriptional changes thus delaying or preventing the progression toward HFpEF. Epigenetic information in the setting of HFpEF can be employed to: (i) dissect novel epigenetic networks and chromatin marks contributing to HFpEF; (ii) unveil circulating and cell-specific epigenetic biomarkers; (iii) build predictive models by using computational epigenetics and deep machine learning; (iv) develop new chromatin modifying drugs for personalized management of HFpEF.

SUMMARY

Acquired epigenetic signatures during the lifetime can contribute to derail molecular pathways involved in HFpEF. A scrutiny investigation of the individual epigenetic landscape will offer opportunities to develop personalized epigenetic biomarkers and therapies to fight HFpEF in the decades to come.

The BET Protein Inhibitor Apabetalone Rescues Diabetes-Induced Impairment of Angiogenic Response by Epigenetic Regulation of Thrombospondin-1

Aims: Therapeutic modulation of blood vessel growth holds promise for the prevention of limb ischemia in diabetic (DM) patients with peripheral artery disease (PAD). Epigenetic changes, namely, posttranslational histone modifications, participate in angiogenic response suggesting that chromatin-modifying drugs could be beneficial in this setting. Apabetalone (APA), a selective inhibitor of bromodomain (BRD) and bromodomain and extraterminal containing protein family (BET) proteins, prevents bromodomain-containing protein 4 (BRD4) interactions with chromatin thus modulating transcriptional programs in different organs. We sought to investigate whether APA affects angiogenic response in diabetes. Results: Compared with vehicle, APA restored tube formation and migration in human aortic endothelial cells (HAECs) exposed to high-glucose (HG) levels. Expression profiling of angiogenesis genes showed that APA prevents HG-induced upregulation of the antiangiogenic molecule thrombospondin-1 (THBS1). ChIP-seq and chromatin immunoprecipitation (ChIP) assays in HG-treated HAECs showed the enrichment of both BRD4 and active marks (H3K27ac) on THBS1 promoter, whereas BRD4 inhibition by APA prevented chromatin accessibility and THBS1 transcription. Mechanistically, we show that THBS1 inhibits angiogenesis by suppressing vascular endothelial growth factor A (VEGFA) signaling, while APA prevents these detrimental changes. In diabetic mice with hind limb ischemia, epigenetic editing by APA restored the THBS1/VEGFA axis, thus improving limb vascularization and perfusion, compared with vehicle-treated animals. Finally, epigenetic regulation of THBS1 by BRD4/H3K27ac was also reported in DM patients with PAD compared with nondiabetic controls. Innovation: This is the first study showing that BET protein inhibition by APA restores angiogenic response in experimental diabetes. Conclusions: Our findings set the stage for preclinical studies and exploratory clinical trials testing APA in diabetic PAD. Antioxid. Redox Signal. 36, 667-684.

Endothelial Dysfunction in Hypertension: Current Concepts and Clinical Implications

Endothelium plays a fundamental role in the cardiovascular system, forming an interface between blood and adjacent tissues by regulating the vascular tone through the synthesis of nitric oxide, prostaglandins and other relaxing factors. Endothelial dysfunction is characterized by vasoconstriction, cell proliferation and shifting toward a proinflammatory and prothrombic state. In hypertension endothelial dysfunction may be involved in the initiation and development of vascular inflammation, vascular remodeling, and atherosclerosis and is independently associated with increased cardiovascular risk. Different conditions such as impaired vascular shear stress, inflammation and oxidative stress, activation of the renin angiotensin system have been described as important pathophysiological mechanisms involved in the development of endothelial dysfunction. The release of extracellular vesicles by neighboring cells in the vascular wall has emerged as an important regulator of endothelial function and with potential antihypertensive properties and beneficial effects by counteracting the hypertension mediated organ damage. Furthermore, macrovesicles are emerging as an innovative therapeutic approach for vascular protection, allowing the delivery of bioactive molecules, such as miRNA and drugs interacting with the renin angiotensin system. In this review we summarize the available evidence about the pathophysiological implications of endothelial dysfunction in cardiovascular diseases, focusing on hypertension and its sequelae, and the potential innovative therapeutic strategies targeting the endothelium with the aim to improve vascular function and remodeling.

Ischemia Modified Albumin and miR-126 Play Important Role in Diagnosis of Posterior Circulation Transient Ischemic Attack and Prediction of Secondary Cerebral Infarction

Background

Transient ischemic attack (TIA) is a super warning for cerebral infarction stroke, thus probe of sensitive biomarker for TIA diagnosis and prognosis can contribute to make an optimal intervention plan.

Objective

This study was conducted to explore the value of ischemic modified albumin (IMA) and microRNA-12miR-126 on the diagnosis of posterior circulation TIA and the prediction of secondary cerebral infarction.

Study Design

This study was conducted as a longitudinal prospective research.

Methods

The levels of serum IMA and miR-126 at 3h, 6h and 12h after TIA onset were analyzed in 106 patients, then the predictive value of IMA and miR-126 for secondary cerebral infarction were tested.

Results

A significant increase of serum IMA and a decrease of miR-126 were observed after TIA onset (P = 0.000),simultaneously a significant negative correlation was found between serum IMA for 3 h and miR-126 for 12 hr=-0.401, P = 0.000. Both IMA and miR-126 were significant associated with the secondary cerebral infarction.

Conclusion

Early detection of IMA and miR-126 is of great value in diagnosing posterior circulation TIA and predicting the secondary cerebral infarction.

Valproic Acid Decreases Endothelial Colony Forming Cells Differentiation and Induces Endothelial-to-Mesenchymal Transition-like Process

Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor is a widely used anticonvulsant drug. VPA is also under clinical evaluation to be employed in anticancer therapy, as an antithrombotic agent or a molecule to be used in the stem cells expansion protocols. Since endothelial colony forming cells (ECFC) has been identified as the human postnatal vasculogenic cells involved in thrombotic disorders and serve as a promising source of immature cell for vascular repair, objectives of the present study were to determine how VPA contributes to ECFC commitment and their angiogenic properties. We examined the effect of VPA on ECFC obtained from cord blood by evaluating colony number, proliferation, migration and their sprouting ability in vitro, as well as their in vivo vasculogenic properties. VPA inhibited endothelial differentiation potential from of cord blood derived stem cells associated with decreased proliferation and sprouting activity of cultured ECFC. VPA treatment significantly decreased the vessel-forming ability of ECFC transplanted together with mesenchymal stem cells (MSC) in Matrigel implants in nude mice model. Surprisingly, a microscopic evaluation revealed that VPA induces marked morphological changes from a cobblestone-like EC morphology to enlarged spindle shaped morphology of ECFC. RT-qPCR and a CD31/CD90 flow cytometry analysis confirmed a phenotypic switch of VPA-treated ECFC to mesenchymal-like phenotype. In conclusion, the pan-HDAC inhibitor VPA described for expansion of hematopoietic stem cells and very small embryonic like stem cells cannot be successfully employed for differentiation of endothelial lineage committed ECFC into functional endothelial cells. Our data also suggest that VPA based therapeutics may induce endothelial dysfunction associated with fibrosis that might induce thrombosis recurrence or venous insufficiency.

Leveraging clinical epigenetics in heart failure with preserved ejection fraction: a call for individualized therapies

Described as the 'single largest unmet need in cardiovascular medicine', heart failure with preserved ejection fraction (HFpEF) remains an untreatable disease currently representing 65% of new heart failure diagnoses. HFpEF is more frequent among women and associates with a poor prognosis and unsustainable healthcare costs. Moreover, the variability in HFpEF phenotypes amplifies complexity and difficulties in the approach. In this perspective, unveiling novel molecular targets is imperative. Epigenetic modifications-defined as changes of DNA, histones, and non-coding RNAs (ncRNAs)-represent a molecular framework through which the environment modulates gene expression. Epigenetic signals acquired over the lifetime lead to chromatin remodelling and affect transcriptional programmes underlying oxidative stress, inflammation, dysmetabolism, and maladaptive left ventricular remodelling, all conditions predisposing to HFpEF. The strong involvement of epigenetic signalling in this setting makes the epigenetic information relevant for diagnostic and therapeutic purposes in patients with HFpEF. The recent advances in high-throughput sequencing, computational epigenetics, and machine learning have enabled the identification of reliable epigenetic biomarkers in cardiovascular patients. Contrary to genetic tools, epigenetic biomarkers mirror the contribution of environmental cues and lifestyle changes and their reversible nature offers a promising opportunity to monitor disease states. The growing understanding of chromatin and ncRNAs biology has led to the development of several Food and Drug Administration approved 'epidrugs' (chromatin modifiers, mimics, anti-miRs) able to prevent transcriptional alterations underpinning left ventricular remodelling and HFpEF. In the present review, we discuss the importance of clinical epigenetics as a new tool to be employed for a personalized management of HFpEF.

FOXC2 Autoregulates Its Expression in the Pulmonary Endothelium After Endotoxin Stimulation in a Histone Acetylation-Dependent Manner

The innate immune response of pulmonary endothelial cells (EC) to lipopolysaccharide (LPS) induces Forkhead box protein C2 (FOXC2) activation through Toll Like Receptor 4 (TLR4). The mechanisms by which FOXC2 expression is regulated in lung EC under LPS stimulation remain unclear. We postulated that FOXC2 regulates its own expression in sepsis, and its transcriptional autoregulation directs lymphatic EC cell-fate decision. Bioinformatic analysis identified potential FOXC2 binding sites in the FOXC2 promoter. In human lung EC, we verified using chromatin immunoprecipitation (ChIP) and luciferase assays that FOXC2 bound to its own promoter and stimulated its expression after LPS stimulation. Chemical inhibition of histone acetylation by garcinol repressed LPS-induced histone acetylation in the FOXC2 promoter region, and disrupted LPS-mediated FOXC2 binding and transcriptional activation. CRISPR/dCas9/gRNA directed against FOXC2-binding-element (FBE) suppressed LPS-stimulated FOXC2 binding and autoregulation by blocking FBEs in the FOXC2 promoter, and repressed expression of lymphatic EC markers. In a neonatal mouse model of sterile sepsis, LPS-induced FOXC2 binding to FBE and FOXC2 expression in lung EC was attenuated with garcinol treatment. These data reveal a new mechanism of LPS-induced histone acetylation-dependent FOXC2 autoregulation.

Epigenetics in blood-brain barrier disruption

The vessels of the central nervous system (CNS) have unique barrier properties. The endothelial cells (ECs) which comprise the CNS vessels contribute to the barrier via strong tight junctions, specific transporters, and limited endocytosis which combine to protect the brain from toxins and maintains brain homeostasis. Blood-brain barrier (BBB) leakage is a serious secondary injury in various CNS disorders like stroke, brain tumors, and neurodegenerative disorders. Currently, there are no drugs or therapeutics available to treat specifically BBB damage after a brain injury. Growing knowledge in the field of epigenetics can enhance the understanding of gene level of the BBB and has great potential for the development of novel therapeutic strategies or targets to repair a disrupted BBB. In this brief review, we summarize the epigenetic mechanisms or regulators that have a protective or disruptive role for components of BBB, along with the promising approaches to regain the integrity of BBB.

Endothelial Reprogramming by Disturbed Flow Revealed by Single-Cell RNA and Chromatin Accessibility Study

Disturbed flow (d-flow) induces atherosclerosis by regulating gene expression in endothelial cells (ECs). For further mechanistic understanding, we carried out a single-cell RNA sequencing (scRNA-seq) and scATAC-seq study using endothelial-enriched single cells from the left- and right carotid artery exposed to d-flow (LCA) and stable-flow (s-flow in RCA) using the mouse partial carotid ligation (PCL) model. We find eight EC clusters along with immune cells, fibroblasts, and smooth muscle cells. Analyses of marker genes, pathways, and pseudotime reveal that ECs are highly heterogeneous and plastic. D-flow induces a dramatic transition of ECs from atheroprotective phenotypes to pro-inflammatory cells, mesenchymal (EndMT) cells, hematopoietic stem cells, endothelial stem/progenitor cells, and an unexpected immune cell-like (EndICLT) phenotypes. While confirming KLF4/KLF2 as an s-flow-sensitive transcription factor binding site, we also find those sensitive to d-flow (RELA, AP1, STAT1, and TEAD1). D-flow reprograms ECs from atheroprotective to proatherogenic phenotypes, including EndMT and potentially EndICLT.

Therapeutic Potential of Endothelial Colony-Forming Cells in Ischemic Disease: Strategies to Improve their Regenerative Efficacy

Cardiovascular disease (CVD) comprises a range of major clinical cardiac and circulatory diseases, which produce immense health and economic burdens worldwide. Currently, vascular regenerative surgery represents the most employed therapeutic option to treat ischemic disorders, even though not all the patients are amenable to surgical revascularization. Therefore, more efficient therapeutic approaches are urgently required to promote neovascularization. Therapeutic angiogenesis represents an emerging strategy that aims at reconstructing the damaged vascular network by stimulating local angiogenesis and/or promoting de novo blood vessel formation according to a process known as vasculogenesis. In turn, circulating endothelial colony-forming cells (ECFCs) represent truly endothelial precursors, which display high clonogenic potential and have the documented ability to originate de novo blood vessels in vivo. Therefore, ECFCs are regarded as the most promising cellular candidate to promote therapeutic angiogenesis in patients suffering from CVD. The current briefly summarizes the available information about the origin and characterization of ECFCs and then widely illustrates the preclinical studies that assessed their regenerative efficacy in a variety of ischemic disorders, including acute myocardial infarction, peripheral artery disease, ischemic brain disease, and retinopathy. Then, we describe the most common pharmacological, genetic, and epigenetic strategies employed to enhance the vasoreparative potential of autologous ECFCs by manipulating crucial pro-angiogenic signaling pathways, e.g., extracellular-signal regulated kinase/Akt, phosphoinositide 3-kinase, and Ca²⁺ signaling. We conclude by discussing the possibility of targeting circulating ECFCs to rescue their dysfunctional phenotype and promote neovascularization in the presence of CVD.

Growth Factors and Small-molecule Compounds in Derivation of Endothelial Lineages from Dental Stem Cells

INTRODUCTION

Incorporating fully assembled microvascular networks into bioengineered dental pulp constructs can significantly enhance functional blood flow and tissue survival upon transplantation. Endothelial cells (ECs), cellular building blocks of vascular tissue, play an essential role in the process of prevascularization. However, obtaining sufficient ECs from a suitable source for translational application is challenging. Dental stem cells (DSCs), which exhibit a robust proliferative ability and immunocompatibility because of their autologous origin, could be a promising alternative cell source for the derivation of endothelial lineages. Under specific culture conditions, DSCs differentiate into osteo/odontogenic, adipogenic, chondrogenic, and neurogenic cell lineages.

METHODS

Recently, a new approach has been developed to directly reprogram cells using chemical cocktails and growth factors. Compared with the traditional reprogramming approach based on the forced expression of exogenous transcription factors, the chemical strategy avoids the risk associated with lentiviral transduction while offering a more viable methodology to drive cell lineage switch. The aim of this review was to unveil the concept of the use of small-molecule compounds and growth factors modulating key signaling pathways to derive ECs from DSCs.

RESULTS

In addition, our preliminary study showed that stem cells from the apical papilla could be induced into EC-like cells using small-molecule compounds and growth factors. These EC-like cells expressed endothelial specific genes (CD31 and VEGFR2) and proteins (CD31, VEGF receptor 2, and vascular endothelial cadherin) as well as gave rise to vessel-like tubular structures in vitro.

CONCLUSIONS

Our preliminary results suggest that chemical reprogramming might offer a novel way to generate EC-like cells from dental stem cells.

The Role of Pi, Glutamine and the Essential Amino Acids in Modulating the Metabolism in Diabetes and Cancer

Purpose

Re-examine the current metabolic models.

Methods

Review of literature and gene networks.

Results

Insulin activates Pi uptake, glutamine metabolism to stabilise lipid membranes. Tissue turnover maintains the metabolic health. Current model of intermediary metabolism (IM) suggests glucose is the source of energy, and anaplerotic entry of fatty acids and amino acids into mitochondria increases the oxidative capacity of the TCA cycle to produce the energy (ATP). The reduced cofactors, NADH and FADH2, have different roles in regulating the oxidation of nutrients, membrane potentials and biosynthesis. Trans-hydrogenation of NADH to NADPH activates the biosynthesis. FADH2 sustains the membrane potential during the cell transformations. Glycolytic enzymes assume the non-canonical moonlighting functions, enter the nucleus to remodel the genetic programmes to affect the tissue turnover for efficient use of nutrients. Glycosylation of the CD98 (4F2HC) stabilises the nutrient transporters and regulates the entry of cysteine, glutamine and BCAA into the cells. A reciprocal relationship between the leucine and glutamine entry into cells regulates the cholesterol and fatty acid synthesis and homeostasis in cells. Insulin promotes the Pi transport from the blood to tissues, activates the mitochondrial respiratory activity, and glutamine metabolism, which activates the synthesis of cholesterol and the de novo fatty acids for reorganising and stabilising the lipid membranes for nutrient transport and signal transduction in response to fluctuations in the microenvironmental cues. Fatty acids provide the lipid metabolites, activate the second messengers and protein kinases. Insulin resistance suppresses the lipid raft formation and the mitotic slippage activates the fibrosis and slow death pathways.

The State of Art of Regenerative Therapy in Cardiovascular Ischemic Disease: Biology, Signaling Pathways, and Epigenetics of Endothelial Progenitor Cells

Ischemic heart disease is currently a major cause of mortality and morbidity worldwide. Nevertheless, the actual therapeutic scenario does not target myocardial cell regeneration and consequently, the progression toward the late stage of chronic heart failure is common. Endothelial progenitor cells (EPCs) are bone marrow-derived stem cells that contribute to the homeostasis of the endothelial wall in acute and chronic ischemic disease. Calcium modulation and other molecular pathways (NOTCH, VEGFR, and CXCR4) contribute to EPC proliferation and differentiation. The present review provides a summary of EPC biology with a particular focus on the regulatory pathways of EPCs and describes promising applications for cardiovascular cell therapy.

Vascular Remodeling in Moyamoya Angiopathy: From Peripheral Blood Mononuclear Cells to Endothelial Cells

The pathophysiological mechanisms of Moyamoya angiopathy (MA), which is a rare cerebrovascular condition characterized by recurrent ischemic/hemorrhagic strokes, are still largely unknown. An imbalance of vasculogenic/angiogenic mechanisms has been proposed as one possible disease aspect. Circulating endothelial progenitor cells (cEPCs) have been hypothesized to contribute to vascular remodeling of MA, but it remains unclear whether they might be considered a disease effect or have a role in disease pathogenesis. The aim of the present study was to provide a morphological, phenotypical, and functional characterization of the cEPCs from MA patients to uncover their role in the disease pathophysiology. cEPCs were identified from whole blood as CD45^dimCD34⁺CD133⁺ mononuclear cells. Morphological, biochemical, and functional assays were performed to characterize cEPCs. A significant reduced level of cEPCs was found in blood samples collected from a homogeneous group of adult (mean age 46.86 ± 11.7; 86.36% females), Caucasian, non-operated MA patients with respect to healthy donors (HD; p = 0.032). Since no difference in cEPC characteristics and functionality was observed between MA patients and HD, a defective recruitment mechanism could be involved in the disease pathophysiology. Collectively, our results suggest that cEPC level more than endothelial progenitor cell (EPC) functionality seems to be a potential marker of MA. The validation of our results on a larger population and the correlation with clinical data as well as the use of more complex cellular model could help our understanding of EPC role in MA pathophysiology.

Histone methylation and demethylation are implicated in the transient and sustained activation of the interleukin-1β gene in murine macrophages

Macrophages play a crucial role in the development of atherosclerosis. To explore the mechanism by which macrophages attain a proinflammatory phenotype for a sustained period, we stimulated macrophages with lipopolysaccharide (LPS) and interferon-γ (IFN-γ) and measured the interleukin-1β (IL-1β) expression. The IL-1β expression increased transiently, and its expression lasted for, at least, 1 week after the cessation of LPS and IFN-γ stimulation. At the promoter region of the IL-1β gene, the demethylation of histone H3 lysine 27 (H3K27) was significantly induced for 1 week after transient stimulation with LPS and IFN-γ. The expression of H3K27 demethylases ubiquitously transcribed tetratricopeptide repeat, X chromosome (UTX) and jumonji domain-containing 3 (JMJD3) increased significantly for 1 week after transient stimulation with LPS and IFN-γ. When the UTX expression was inhibited by using small interfering RNA (siRNA) for UTX, the IL-1β expression was significantly suppressed in both transient and sustained phases, whereas siRNA for JMJD3 significantly inhibited only the sustained phase of the IL-1β expression. These results suggested that H3K27 demethylation was implicated in the transient and sustained increase in the IL-1β expression after LPS and IFN-γ stimulation.

When Good Guys Turn Bad: Bone Marrow's and Hematopoietic Stem Cells' Role in the Pathobiology of Diabetic Complications

Diabetes strongly contributes to the development of cardiovascular disease, the leading cause of mortality and morbidity in these patients. It is widely accepted that hyperglycemia impairs hematopoietic stem/progenitor cell (HSPC) mobilization from the bone marrow (BM) by inducing stem cell niche dysfunction. Moreover, a recent study demonstrated that type 2 diabetic patients are characterized by significant depletion of circulating provascular progenitor cells and increased frequency of inflammatory cells. This unbalance, potentially responsible for the reduction of intrinsic vascular homeostatic capacity and for the establishment of a low-grade inflammatory status, suggests that bone BM-derived HSPCs are not only victims but also active perpetrators in diabetic complications. In this review, we will discuss the most recent literature on the molecular mechanisms underpinning hyperglycemia-mediated BM dysfunction and differentiation abnormality of HSPCs. Moreover, a section will be dedicated to the new glucose-lowering therapies that by specifically targeting the culprits may prevent or treat diabetic complications.

Early Programming of Adult Systemic Essential Hypertension

Cardiovascular diseases are being included in the study of developmental origins of health and disease (DOHaD) and essential systemic hypertension has also been added to this field. Epigenetic modifications are one of the main mechanisms leading to early programming of disease. Different environmental factors occurring during critical windows in the early stages of life may leave epigenetic cues, which may be involved in the programming of hypertension when individuals reach adulthood. Such environmental factors include pre-term birth, low weight at birth, altered programming of different organs such as the blood vessels and the kidney, and living in disadvantageous conditions in the programming of hypertension. Mechanisms behind these factors that impact on the programming include undernutrition, oxidative stress, inflammation, emotional stress, and changes in the microbiota. These factors and their underlying causes acting at the vascular level will be discussed in this paper. We also explore the establishment of epigenetic cues that may lead to hypertension at the vascular level such as DNA methylation, histone modifications (methylation and acetylation), and the role of microRNAs in the endothelial cells and blood vessel smooth muscle which participate in hypertension. Since epigenetic changes are reversible, the knowledge of this type of markers could be useful in the field of prevention, diagnosis or epigenetic drugs as a therapeutic approach to hypertension.

UTX/KDM6A Deletion Promotes Recovery of Spinal Cord Injury by Epigenetically Regulating Vascular Regeneration

The regeneration of the blood vessel system post spinal cord injury (SCI) is essential for the repair of neurological function. As a significant means to regulate gene expression, epigenetic regulation of angiogenesis in SCI is still largely unknown. Here, we found that Ubiquitously Transcribed tetratricopeptide repeat on chromosome X (UTX), the histone H3K27 demethylase, increased significantly in endothelial cells post SCI. Knockdown of UTX can promote the migration and tube formation of endothelial cells. The specific knockout of UTX in endothelial cells enhanced angiogenesis post SCI accompanied with improved neurological function. In addition, we found regulation of UTX expression can change the level of microRNA 24 (miR-24) in vitro. The physical binding of UTX to the promotor of miR-24 was indicated by chromatin immunoprecipitation (ChIP) assay. Meanwhile, methylation sequencing of endothelial cells demonstrated that UTX could significantly decrease the level of methylation in the miR-24 promotor. Furthermore, miR-24 significantly abolished the promoting effect of UTX deletion on angiogenesis in vitro and in vivo. Finally, we predicted the potential target mRNAs of miR-24 related to angiogenesis. We indicate that UTX deletion can epigenetically promote the vascular regeneration and functional recovery post SCI by forming a regulatory network with miR-24.

Therapeutic targets for endothelial dysfunction in vascular diseases

Vascular endothelial cells are located on the surface of the blood vessels. It has been recognized as an important barrier to the regulation of vascular homeostasis by regulating the blood flow of micro- or macrovascular vessels. Indeed, endothelial dysfunction is an initial stage of vascular diseases and is an important prognostic indicator of cardiovascular and metabolic diseases such as atherosclerosis, hypertension, heart failure, or diabetes. Therefore, in order to develop therapeutic targets for vascular diseases, it is important to understand the key factors involved in maintaining endothelial function and the signaling pathways affecting endothelial dysfunction. The purpose of this review is to describe the function and underlying signaling pathway of oxidative stress, inflammatory factors, shear stress, and epigenetic factors in endothelial dysfunction, and introduce recent therapeutic targets for the treatment of cardiovascular diseases.

Cysteine Glutathionylation Acts as a Redox Switch in Endothelial Cells

Oxidative post-translational modifications (oxPTM) of receptors, enzymes, ion channels and transcription factors play an important role in cell signaling. oxPTMs are a key way in which oxidative stress can influence cell behavior during diverse pathological settings such as cardiovascular diseases (CVD), cancer, neurodegeneration and inflammatory response. In addition, changes in oxPTM are likely to be ways in which low level reactive oxygen and nitrogen species (RONS) may contribute to redox signaling, exerting changes in physiological responses including angiogenesis, cardiac remodeling and embryogenesis. Among oxPTM, S-glutathionylation of reactive cysteines emerges as an important regulator of vascular homeostasis by modulating endothelial cell (EC) responses to their local redox environment. This review summarizes the latest findings of S-glutathionylated proteins in major EC pathways, and the functional consequences on vascular pathophysiology. This review highlights the diversity of molecules affected by S-glutathionylation, and the complex consequences on EC function, thereby demonstrating an intricate dual role of RONS-induced S-glutathionylation in maintaining vascular homeostasis and participating in various pathological processes.

Epigenetics: The master control of endothelial cell fate in cancer

The development of new blood vessels from pre-existing vasculature is called angiogenesis. The growth of tumors depends on a network of supplying vessels that provide them with oxygen and nutrients. Pro-angiogenic factors that are secreted by tumors will trigger the sprouting of nearby existing blood vessels towards themselves and therefore researchers have developed targeted therapy towards these pro-angiogenic proteins to inhibit angiogenesis. However, certain pro-angiogenic proteins tend to bypass the inhibition. Thus, instead of targeting these expressed proteins, research towards angiogenesis inhibition had been focused on a deeper scale, epigenetic modifications. Epigenetic regulatory mechanisms are a heritable change in a sequence of stable but reversible gene function modification yet do not affect the DNA primary sequence directly. Methylation of DNA, modification of histone and silencing of micro-RNA (miRNA)-associated gene are currently considered to initiate and sustain epigenetic changes. Recent findings on the subject matter have provided an insight into the mechanism of epigenetic modifications, thus this review aims to present an update on the latest studies.

Can Epigenetics of Endothelial Dysfunction Represent the Key to Precision Medicine in Type 2 Diabetes Mellitus?

In both developing and industrialized Countries, the growing prevalence of Type 2 Diabetes Mellitus (T2DM) and the severity of its related complications make T2DM one of the most challenging metabolic diseases worldwide. The close relationship between genetic and environmental factors suggests that eating habits and unhealthy lifestyles may significantly affect metabolic pathways, resulting in dynamic modifications of chromatin-associated proteins and homeostatic transcriptional responses involved in the progression of T2DM. Epigenetic mechanisms may be implicated in the complex processes linking environmental factors to genetic predisposition to metabolic disturbances, leading to obesity and type 2 diabetes mellitus (T2DM). Endothelial dysfunction represents an earlier marker and an important player in the development of this disease. Dysregulation of the endothelial ability to produce and release vasoactive mediators is recognized as the initial feature of impaired vascular activity under obesity and other insulin resistance conditions and undoubtedly concurs to the accelerated progression of atherosclerotic lesions and overall cardiovascular risk in T2DM patients. This review aims to summarize the most current knowledge regarding the involvement of epigenetic changes associated with endothelial dysfunction in T2DM, in order to identify potential targets that might contribute to pursuing “precision medicine” in the context of diabetic illness.

EZH2 inhibitor DZNep modulates microglial activation and protects against ischaemic brain injury after experimental stroke

Enhancer of zeste homolog-2 (EZH2), a histone methyltransferase, has been recognized to play a pivotal role in regulating the immune response in various diseases. However, its role in the inflammatory response induced by ischaemic stroke remains to be further investigated. The aim of this study was to determine the role of EZH2 in microglia-associated inflammation in ischaemic stroke and to further detect the effects of the EZH2 inhibitor, 3-deazaadenosine A (DZNep), in ischaemic brain injury. Here, we found that both in vivo ischemic/reperfusion (I/R) injury and in vitro oxygen-glucose deprivation (OGD) treatment induced a marked upregulation of EZH2 in microglia. The administration of the EZH2 inhibitor DZNep improved behavioural performance and reduced the infarct volume in mice after experimental stroke. Furthermore, we showed that DZNep blocked pro-inflammatory (CD86⁺) microglial activation and triggered anti-inflammatory (CD206⁺) microglial polarization in experimental stroke. Pro-inflammatory cytokines such as IL-1β, IL-6, TNF-α and CXCL10 were also significantly downregulated by DZNep. In addition, it was found that DZNep blocked the phosphorylation of signal transducer and activator of transcription 3 (STAT3) in microglia, which was increased by I/R injury and OGD. Collectively, we demonstrated that EZH2 is implicated in regulating microglial activation and exacerbates neurological deficits after ischaemic stroke, probably via activating STAT3, and that the EZH2 inhibitor DZNep can exert neuroprotective effects after ischaemic stroke.

Air pollution and stroke. A new modifiable risk factor is in the air

Evidence from epidemiological studies has demonstrated that outdoor air pollution is now a well-known major problem of public health, mainly in low and middle income countries. Contrasting with myocardial infarction, there are few data on the association of air pollution and stroke.

METHODS

We propose a narrative literature review of the effects and the underlying biological mechanisms of short- and long-term exposure to air pollutants on stroke risk and mortality, using the following key-words: stroke, cerebrovascular events, ischemic and haemorrhage stroke, transient ischaemic attack, mortality, air pollution and air pollutants.

RESULTS

Twenty-one papers were selected. Air pollution, of which whose small particulate matter are the most toxic, contributes to about one-third of the global burden of stroke. We can identify vulnerable patients with classical neuro-vascular risk factors or a prior history of stroke or transient ischemic attack or persons living in low-income countries. Biological mechanisms of this new morbid association are discussed.

CONCLUSION

Air pollution should be recognized as a silent killer inducing stroke whose mortality rates remain elevated by its role as a new modifiable neurovascular risk factor, needing public health policies.

Panobinostat, a histone deacetylase inhibitor, rescues the angiogenic potential of endothelial colony-forming cells in moyamoya disease

PURPOSE

Moyamoya disease (MMD) is one of the most common causes of pediatric stroke. We found defective angiogenic function and downregulation of retinaldehyde dehydrogenase 2 (RALDH2) in MMD endothelial colony-forming cells (ECFCs). Downregulation of RALDH2 mRNA was caused by decreased binding of acetyl-histone H3 (Ac-H3) to the RALDH2 promoter. In this study, we evaluated the feasibility of using a histone deacetylase (HDAC) inhibitor, panobinostat, to upregulate RALDH2 expression and restore the angiogenic potential of MMD ECFCs.

METHODS

ECFCs from healthy normal controls and patients with MMD were isolated and characterized. After panobinostat treatment, western blot, tube formation, and chromatin immunoprecipitation (ChIP) assays were conducted in vitro. A matrigel plug assay was performed in vivo.

RESULTS

Panobinostat increased the levels of Ac-H3 and Ac-H4 in both normal and MMD ECFCs but was much more effective in MMD ECFCs. Increased expression of RALDH2 by panobinostat was observed only in MMD ECFCs. Panobinostat increased the tube formation of both normal and MMD ECFCs in vitro and in vivo, but the effect was greater with MMD ECFCs.

CONCLUSIONS

We demonstrated that panobinostat increases the angiogenic ability of MMD ECFCs by regulating RALDH2 acetylation. Our results suggest that panobinostat might be a potent therapeutic option for MMD patients.

Proteomics based identification of KDM5 histone demethylases associated with cardiovascular disease

Background

The increased prevalence of cardiovascular disease (CVD) indicates a demand for novel therapeutic approaches. Proteome analysis of vascular tissues from animal models and humans with CVD could lead to the identification of novel druggable targets.

Methods

LC-MS/MS analysis of thoracic aortas from three mouse models of non-diabetic and diabetic (streptozotocin (STZ)-induced) atherosclerosis followed by bioinformatics/pathway analysis was performed. Selected findings were confirmed by proteomics analysis of human vessels from patients with CVD as well as in vitro studies (migration, proliferation, angiogenesis assays) using endothelial (HUVEC) cells.

Findings

Comparative tissue proteomics of low density lipoprotein receptor deficient (Ldlr−/−) and diabetic Ldlr−/− (Ldlr−/−STZ) with wild type (WT) animals led to the identification of 284 differentially expressed proteins in both models. Among them, 177 proteins were also differentially expressed in diabetic apolipoprotein E deficient (ApoE−/−STZ) mice, suggesting expression changes associated with atherosclerosis independent of the model used. These proteins recapitulated the hallmarks of atherosclerosis. Comparison of these findings with differentially expressed proteins in human vessels with CVD enabled shortlisting of six commonly dysregulated proteins. Among them, lysine-specific demethylase 5D (KDM5D) exhibited pronounced overexpression accompanied by a reduction in the protein levels of its substrate, the trimethylated lysine 4 of histone H3 (H3K4me3), in patients with CVD. Functional interference studies applying a KDM5 inhibitor on HUVEC reduced cell proliferation, migration and tube-forming ability in vitro.

Interpretation

This high-throughput proteomics strategy identified KDM5 histone demethylases being potentially involved in CVD, possibly by affecting H3K4 methylation.

Fund

[SysVasc, HEALTH-2013 603288], [ERA-CVD PROACT: ANR-17-ECVD-0006, 01KL1805], [FRM, DEQ20170336759].

Recent Advances in Endothelial Colony Forming Cells Toward Their Use in Clinical Translation

The term “Endothelial progenitor cell” (EPC) has been used to describe multiple cell populations that express endothelial surface makers and promote vascularisation. However, the only population that has all the characteristics of a real “EPC” is the Endothelial Colony Forming Cells (ECFC). ECFC possess clonal proliferative potential, display endothelial and not myeloid cell surface markers, and exhibit pronounced postnatal vascularisation ability in vivo. ECFC have been used to investigate endothelial molecular dysfunction in several diseases, as they give access to endothelial cells from patients in a non-invasive way. ECFC also represent a promising tool for revascularization of damaged tissue. Here we review the translational applications of ECFC research. We discuss studies which have used ECFC to investigate molecular endothelial abnormalities in several diseases and review the evidence supporting the use of ECFC for autologous cell therapy, gene therapy and tissue regeneration. Finally, we discuss ways to improve the therapeutic efficacy of ECFC in clinical applications, as well as the challenges that must be overcome to use ECFC in clinical trials for regenerative approaches.

Endothelial cell regulation through epigenetic mechanisms: Depicting parallels and its clinical application within an intra-islet microenvironment

The intra-islet endothelial cells (ECs), the building blocks of islet microvasculature, govern a number of cellular and pathophysiological processes associated with the pancreatic tissue. These cells are key to the angiogenic process and essential for islet revascularization after transplantation. Understanding fundamental mechanisms by which ECs regulate the angiogenic process is important as these cells maintain and regulate the intra-islet environment facilitated by a complex signaling crosstalk with the surrounding endocrine cells. In recent years, many studies have demonstrated the impact of epigenetic regulation on islet cell development and function. This review will present an overview of the reports involving endothelial epigenetic mechanisms particularly focusing on histone modifications which have been identified to play a critical role in governing EC functions by modifying the chromatin structure. A better understanding of epigenetic mechanisms by which these cells regulate gene expression and function to orchestrate cellular physiology and pathology is likely to offer improved insights on the functioning and regulation of an intra-islet endothelial microvascular environment.

Next-generation sequencing approaches for the study of genome and epigenome toxicity induced by sulfur mustard

Sulfur mustard (SM) is an extensive nucleophilic and alkylating agent that targets different tissues. The genotoxic property of SM is the most threatening effect, because it is associated with detrimental inflammations and susceptibility to several kinds of cancer. Moreover, SM causes a wide variety of adverse effects on DNA which result in accumulation of DNA adducts, multiple mutations, aneuploidies, and epigenetic aberrations in the genome. However, these adverse effects are still not known well, possibly because no valid biomarkers have been developed for detecting them. The advent of next-generation sequencing (NGS) has provided opportunities for the characterization of these alterations with a higher level of molecular detail and cost-effectivity. The present review introduces NGS approaches for the detection of SM-induced DNA adducts, mutations, chromosomal structural variation, and epigenetic aberrations, and also comparing and contrasting them with regard to which might be most advantageous.

Endothelial cell senescence in aging-related vascular dysfunction

Increased cardiovascular disease in aging is partly a consequence of the vascular endothelial cell (EC) senescence and associated vascular dysfunction. In this contest, EC senescence is a pathophysiological process of structural and functional changes including dysregulation of vascular tone, increased endothelium permeability, arterial stiffness, impairment of angiogenesis and vascular repair, and a reduction of EC mitochondrial biogenesis. Dysregulation of cell cycle, oxidative stress, altered calcium signaling, hyperuricemia, and vascular inflammation have been implicated in the development and progression of EC senescence and vascular disease in aging. A number of abnormal molecular pathways are associated with these underlying pathophysiological changes including Sirtuin 1, Klotho, fibroblast growth factor 21, and activation of the renin angiotensin-aldosterone system. However, the molecular mechanisms of EC senescence and associated vascular impairment in aging are not completely understood. This review provides a contemporary update on molecular mechanisms, pathophysiological events, as well functional changes in EC senescence and age-associated cardiovascular disease. This article is part of a Special Issue entitled: Genetic and epigenetic regulation of aging and longevity edited by Jun Ren & Megan Yingmei Zhang.

Endothelial Progenitor Cells: New Targets for Therapeutics for Inflammatory Conditions With High Cardiovascular Risk

Over the past decade, we have witnessed an exponential growth of interest into the role of endothelial progenitor cells (EPCs) in cardiovascular disease. While the major thinking revolves around EPC angiogenic repair properties, we have used a hypothesis-driven approach to discover disease-related defects in their characteristics and based on these findings, have identified opportunities for functional enhancement, which offer an exciting avenue for translation into clinical intervention. In this review, we focus on two groups; circulating myeloid angiogenic cells (MACs) and late outgrowth endothelial colony forming cells (ECFCs), and will discuss the unique properties and defects of each population, as new insights have been gained into the potential function of each sub-type using current techniques and multiomic technology. We will discuss their role in inflammatory disorders and alterations in mitochondrial function. In addition, we share key insights into the glycocalyx, and propose this network of membrane-bound proteoglycans and glycoproteins, covering the endothelium warrants further investigation in order to clarify its significance in ECFC regulation of vascularization and angiogenesis and ultimately for potential translational therapeutic aspects.

A review of epidemiological research on stroke and dementia and exposure to air pollution

Background

Outdoor air pollution is now a well-known risk factor for morbidity and mortality, and is increasingly being identified as a major risk factor for stroke.

Methods

A narrative literature review of the effects of short and long-term exposure to air pollution on stroke and dementia risk and cognitive functioning.

Results

Ten papers on stroke and 17 on dementia were selected. Air pollution, and in particular small particulate matter, contributes to about one-third of the global stroke burden and about one-fifth of the global burden of dementia. It particularly affects vulnerable patients with other vascular risk factors or a prior history of stroke in low- and medium-income countries. New pathophysiological mechanisms of the cause-effect associations are suggested.

Conclusion

Air pollution should be considered as a new modifiable cerebrovascular and neurodegenerative risk factor. This massive worldwide public health problem requires environmental health policies able to reduce air pollution and thus the stroke and dementia burden.

Investigation of circle of Willis variants and hemodynamic parameters in twins using transcranial color-coded Doppler sonography

Morphological and hemodynamic variations of the circle of Willis (CW) may have an important impact on cerebrovascular events. However, the environmental and genetic influence remains unclear. For this reason we studied the variations and hemodynamic parameters of the CW in twins using transcranial color-coded sonography (TCCS). Sixty-four twins, 19 monozygotic (MZ) and 13 dizygotic (DZ) pairs from the Italian Twin Registry (average age 45.0 ± 13.7 years) underwent TCCS and risk factor assessment. We examined CW morphology and recorded peak systolic velocity (PSV), end-diastolic velocity (EDV) and pulsatility index (PI). Raw heritability was determined for hemodynamic parameters, whereas concordance and discordance rates were calculated for CW morphological variants. A normal CW anatomy was observed in the majority of MZ and DZ twins (76.5% and 92.3%, respectively). The most frequent variant was a missing anterior cerebral artery (ACA). There was no significant difference in the prevalence of most CW variants depending on the zigosity. Concordance rates were low regarding the presence of variant CW anatomy both in MZ and DZ groups (0.14 and 0.00, respectively). Women had a significantly higher PI in vertebral arteries (VA) and in the right ACA (p = 0.01, p = 0.02 and p < 0.01, respectively). An inverse correlation was observed between hemodynamic parameters and age. Morphological variants of the CW do not seem to be heritable; they are most likely determined by environmental factors. In contrast, hemodynamic parameters of the CW are moderately heritable and this might have implications in the management and prevention of cerebrovascular diseases.

Epigenetic Activation of Pro-angiogenic Signaling Pathways in Human Endothelial Progenitors Increases Vasculogenesis

Human endothelial colony-forming cells (ECFCs) represent a promising source of adult stem cells for vascular repair, yet their regenerative capacity is limited. Here, we set out to understand the molecular mechanism restricting the repair function of ECFCs. We found that key pro-angiogenic pathways are repressed in ECFCs due to the presence of bivalent (H3K27me3/H3K4me3) epigenetic marks, which decreases the cells' regenerative potential. Importantly, ex vivo treatment with a combination of epigenetic drugs that resolves bivalent marks toward the transcriptionally active H3K4me3 state leads to the simultaneous activation of multiple pro-angiogenic signaling pathways (VEGFR, CXCR4, WNT, NOTCH, SHH). This in turn results in improved capacity of ECFCs to form capillary-like networks in vitro and in vivo. Furthermore, restoration of perfusion is accelerated upon transplantation of drug-treated ECFCs in a model of hindlimb ischemia. Thus, ex vivo treatment with epigenetic drugs increases the vascular repair properties of ECFCs through transient activation of pro-angiogenic signaling pathways.

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Pro-angiogenic pathways are maintained in a poised state in ECFCs

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Epigenetic drugs resolve bivalently marked genes toward an active state in ECFCs

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Treatment with epigenetic drugs activates multiple pro-angiogenic pathways in ECFCs

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Ex vivo treatment with epigenetic drugs increases ECFC-mediated vasculogenesis

Modulating putative endothelial progenitor cells for the treatment of endothelial dysfunction and cardiovascular complications in diabetes

Diabetes induces a decrease in the number and function of different pro-angiogenic cell types generically designated as putative endothelial progenitor cells (EPC), which encompasses cells from myeloid origin that act in a paracrine fashion to promote angiogenesis and putative "true" EPC that contribute to endothelial replacement. This not only compromises neovasculogenesis in ischemic tissues but also impairs, at an early stage, the reendotheliziation process at sites of injury, contributing to the development of endothelial dysfunction and cardiovascular complications. Hyperglycemia, insulin resistance and dyslipidemia promote putative EPC dysregulation by affecting the SDF-1/CXCR-4 and NO pathways and the p53/SIRT1/p66Shc axis that contribute to their mobilization, migration, homing and vasculogenic properties. To optimize the clinical management of patients with hypoglycemic agents, statins and renin-angiotensin system inhibitors, which display pleiotropic effects on putative EPC, is a first step to improve their number and angiogenic potential but specific strategies are needed. Among them, mobilizing therapies based on G-CSF, erythropoietin or CXCR-4 antagonism have been developed to increase putative EPC number to treat ischemic diseases with or without prior cell isolation and transplantation. Growth factors, genetic and pharmacological strategies are also evaluated to improve ex vivo cultured EPC function before transplantation. Moreover, pharmacological agents increasing in vivo the bioavailability of NO and other endothelial factors demonstrated beneficial effects on neovascularization in diabetic ischemic models but their effects on endothelial dysfunction remain poorly evaluated. More experiments are warranted to develop orally available drugs and specific agents targeting p66Shc to reverse putative EPC dysfunction in the expected goal of preventing endothelial dysfunction and diabetic cardiovascular complications.

Physical exercise and epigenetic adaptations of the cardiovascular system

During the last decade, epigenetics became one of the fastest growing research fields in numerous clinical and basic science disciplines. Evidence suggests that chromatin modifications (e.g., histone modifications and DNA methylation) as well as the expression of micro-RNA molecules play a crucial role in the pathogenesis of several cardiovascular diseases. On the one hand, they are involved in the development of general risk factors like chronic inflammation, but on the other hand, epigenetic modifications are conducive to smooth muscle cell, cardiomyocyte, and endothelial progenitor cell proliferation/differentiation as well as to extracellular matrix processing and endothelial function (e.g., endothelial nitric oxide synthase regulation). Therefore, epigenetic medical drugs have gained increased attention and provided the first promising results in the context of cardiovascular malignancies. Beside other lifestyle factors, physical activity and sports essentially contribute to cardiovascular health and regeneration. In this review we focus on recent research proposing physical activity as a potent epigenetic regulator that has the potential to counteract pathophysiological alterations in almost all the aforementioned cardiovascular cells and tissues. As with epigenetic medical drugs, more knowledge about the molecular mechanisms and dose-response relationships of exercise is needed to optimize the outcome of preventive and rehabilitative exercise programs and recommendations.