The expression of endothelial nitric-oxide synthase is controlled by a cell-specific histone code

Epigenetic DNA Methylation and Protein Homocysteinylation: Key Players in Hypertensive Renovascular Damage

Hypertension has been a threat to the health of people, the mechanism of which, however, remains poorly understood. It is clinically related to loss of nephron function, glomerular sclerosis, or necrosis, resulting in renal functional declines. The mechanisms underlying hypertension's development and progression to organ damage, including hypertensive renal damage, remain to be fully elucidated. As a developing approach, epigenetics has been postulated to elucidate the phenomena that otherwise cannot be explained by genetic studies. The main epigenetic hallmarks, such as DNA methylation, histone acetylation, deacetylation, noncoding RNAs, and protein N-homocysteinylation have been linked with hypertension. In addition to contributing to endothelial dysfunction and oxidative stress, biologically active gases, including NO, CO, and H2S, are crucial regulators contributing to vascular remodeling since their complex interplay conducts homeostatic functions in the renovascular system. Importantly, epigenetic modifications also directly contribute to the pathogenesis of kidney damage via protein N-homocysteinylation. Hence, epigenetic modulation to intervene in renovascular damage is a potential therapeutic approach to treat renal disease and dysfunction. This review illustrates some of the epigenetic hallmarks and their mediators, which have the ability to diminish the injury triggered by hypertension and renal disease. In the end, we provide potential therapeutic possibilities to treat renovascular diseases in hypertension.

Spatiotemporal Nitric Oxide Modulation via Electrochemical Platform to Profile Tumor Cell Response

Nitric oxide (NO) is a gaseous molecule intricately implicated in oncologic processes, encompassing the modulation of angiogenesis and instigating apoptosis. Investigation of the antitumor effects of NO is currently underway, necessitating a detailed understanding of its cellular-level reactions. Regulating the behavior of radical NO species has been a significant challenge, primarily due to its instability in aqueous environments by rapid O2-induced degradation. In this study, we devised an electrochemical platform to investigate the cellular responses to reactive gaseous molecules. Our designed platform precisely controlled the NO flux and diffusion rates of NO to tumor cells. COMSOL Multiphysics calculations based on diffusion and reaction kinetics were conducted to simulate the behavior of electrochemically generated NO. We discerned that the effective radius, NO flux, and electrolysis duration are pivotal factors governing cellular response by NO.

Exploring the pathogenesis of pulmonary vascular disease

Pulmonary hypertension (PH) is a complex cardiopulmonary disorder impacting the lung vasculature, resulting in increased pulmonary vascular resistance that leads to right ventricular dysfunction. Pulmonary hypertension comprises of 5 groups (PH group 1 to 5) where group 1 pulmonary arterial hypertension (PAH), results from alterations that directly affect the pulmonary arteries. Although PAH has a complex pathophysiology that is not completely understood, it is known to be a multifactorial disease that results from a combination of genetic, epigenetic and environmental factors, leading to a varied range of symptoms in PAH patients. PAH does not have a cure, its incidence and prevalence continue to increase every year, resulting in higher morbidity and mortality rates. In this review, we discuss the different pathologic mechanisms with a focus on epigenetic modifications and their roles in the development and progression of PAH. These modifications include DNA methylation, histone modifications, and microRNA dysregulation. Understanding these epigenetic modifications will improve our understanding of PAH and unveil novel therapeutic targets, thus steering research toward innovative treatment strategies.

Epigenetics of hypertension as a risk factor for the development of coronary artery disease in type 2 diabetes mellitus

Hypertension, a multifaceted cardiovascular disorder influenced by genetic, epigenetic, and environmental factors, poses a significant risk for the development of coronary artery disease (CAD) in individuals with type 2 diabetes mellitus (T2DM). Epigenetic alterations, particularly in histone modifications, DNA methylation, and microRNAs, play a pivotal role in unraveling the complex molecular underpinnings of blood pressure regulation. This review emphasizes the crucial interplay between epigenetic attributes and hypertension, shedding light on the prominence of DNA methylation, both globally and at the gene-specific level, in essential hypertension. Additionally, histone modifications, including acetylation and methylation, emerge as essential epigenetic markers linked to hypertension. Furthermore, microRNAs exert regulatory influence on blood pressure homeostasis, targeting key genes within the aldosterone and renin-angiotensin pathways. Understanding the intricate crosstalk between genetics and epigenetics in hypertension is particularly pertinent in the context of its interaction with T2DM, where hypertension serves as a notable risk factor for the development of CAD. These findings not only contribute to the comprehensive elucidation of essential hypertension but also offer promising avenues for innovative strategies in the prevention and treatment of cardiovascular complications, especially in the context of T2DM.

Functional role of Ash2l in oxLDL induced endothelial dysfunction and atherosclerosis

Endothelial injury and dysfunction in the artery wall fuel the process of atherosclerosis. As a key epigenetic regulator, Ash2l (Absent, small, or homeotic-Like 2) is involved in regulating vascular injury and its complications. However, the role of Ash2l in atherosclerosis has not yet been fully elucidated. Here, we found increased Ash2l expression in high-cholesterol diet-fed ApoE-/- mice and oxidized LDL (oxLDL) treated endothelial cells (ECs). Furthermore, Ash2l promoted the scavenger receptors transcription by catalyzing histone H3 lysine 4 (H3K4) trimethylation at the promoter region of transcription factor peroxisome proliferator-activated receptor-γ (PPARγ) and triggered the activation of the pro-inflammatory nuclear factor-kappa B (NF-κB) by enhancing interaction between CD36 and toll-like receptor 4 (TLR4). Meanwhile, enhanced expression of scavenger receptors drove more oxLDL uptake by ECs. In vivo studies revealed that ECs-specific Ash2l knockdown reduced atherosclerotic lesion formation and promoted fibrous cap stability in the aorta of ApoE-/- mice, which was partly associated with a reduced endothelial activation by suppressing scavenger receptors and the uptake of lipids by ECs. Collectively, our findings identify Ash2l as a novel regulator that mediates endothelial injury and atherosclerosis. Targeting Ash2l may provide valuable insights for developing novel therapeutic candidates for atherosclerosis.

Effect of lead exposure on histone modifications: A review

Lead at any levels can result in detrimental health effects affecting various organ systems. These systematic manifestations under Pb exposure and the underlying probable pathophysiological mechanisms have not been elucidated completely. With advancements in molecular research under Pb exposure, epigenetics is one of the emerging field that has opened many possibilities for appreciating the role of Pb exposure in modulating gene expression profiles. In terms of epigenetic alterations reported in Pb toxicity, DNA methylation, and microRNA alterations are extensively explored in both experimental and epidemiological studies, however, the understanding of histone modifications under Pb exposure is still in its infant stage limited to experimental models. In this review, we aim to present a synoptic view of histone modifications explored in relation to Pb exposure attempting to bring out this potential lacunae in research. The scarcity of studies associating histone modifications with Pb toxicity, and the paucity of their validation in human cohort further emphasizes the strong research potential of this field. We summarize the review by presenting our hypotheses regarding the involvement of these histone modification in various diseases modalities associated with Pb toxicity.

NOS3 and CTH gene mutations as new molecular markers for detection of lung adenocarcinoma

Gene mutations can contribute to lung adenocarcinoma (LUAD) development, metastasis, and therapy. This study aims to identify mutations in the endothelial nitric oxide synthase (eNOS or NOS3) and cystathionine γ-lyase (CSE or CTH) genes that are connected to LUAD symptoms. Two gene polymorphisms were identified using Sanger sequencing in 31 LUAD patients' formalin-fixed paraffin-embedded (FFPE) tissues. Epidermal growth factor receptor (EGFR) mutation and programmed death-ligand 1 (PD-L1) expression were examined in 110 LUAD patients using real-time polymerase chain reaction and immunohistochemistry. Mutations in the selected genes were retrieved from the gnomAD database for all cancer types and the Mutagene and COSMIC databases for LUAD patients. The GeneMANIA prediction server was used to predict the interaction between the studied genes. Poorly and moderately differentiated tumours predominated, with pT3 N2 Mx being the most prevalent stage. Polymorphism data showed 189 NOS3 gene mutations and 34 CTH gene mutations. In 110 LUAD patients, 14 (12.73%) were PD-L1 positive and expressed 50% or more protein. Eight (7.27%) samples included EGFR mutations, including two deletions and two point mutations in exon 19, four point mutations in exon 21. In gnomAD, 4012 NOS3 mutations and 1214 CTH mutations are present. In the Mutagene and COSMIC databases, the NOS3 gene had 295 and 93 mutations, whereas the CTH gene had 61 and 36. According to the GeneMANIA prediction server, 10 genes are related to NOS3, eight with CTH, 15 with EGFR, and 5 with PD-L1. This study is the first to identify several previously unknown mutations in LUAD patients' NOS3 and CTH genes, with potential therapeutic implications.

The role of physics in multiomics and cancer evolution

Complex interactions between the physical environment and phenotype of a tumour, and genomics, transcriptomics, proteomics and epigenomics, are increasingly known to have a significant influence on cancer development, progression and evolution. For example, mechanical stress can alter both genome maintenance and histone modifications, which consequently affect transcription and the epigenome. Increased stiffness has been linked to genetic heterogeneity and is responsible for heterochromatin accumulations. Stiffness thereby leads to deregulation in gene expression, disrupts the proteome and can impact angiogenesis. Several studies have shown how the physics of cancer can influence diverse cancer hallmarks such as resistance to cell death, angiogenesis and evasion from immune destruction. In this review, we will explain the role that physics of cancer plays in cancer evolution and explore how multiomics are being used to elucidate the mechanisms underpinning them.

Epigenetic Signatures in Arterial Hypertension: Focus on the Microvasculature

Systemic arterial hypertension (AH) is a multifaceted disease characterized by accelerated vascular aging and high cardiometabolic morbidity and mortality. Despite extensive work in the field, the pathogenesis of AH is still incompletely understood, and its treatment remains challenging. Recent evidence has shown a deep involvement of epigenetic signals in the regulation of transcriptional programs underpinning maladaptive vascular remodeling, sympathetic activation and cardiometabolic alterations, all factors predisposing to AH. After occurring, these epigenetic changes have a long-lasting effect on gene dysregulation and do not seem to be reversible upon intensive treatment or the control of cardiovascular risk factors. Among the factors involved in arterial hypertension, microvascular dysfunction plays a central role. This review will focus on the emerging role of epigenetic changes in hypertensive-related microvascular disease, including the different cell types and tissues (endothelial cells, vascular smooth muscle cells and perivascular adipose tissue) as well as the involvement of mechanical/hemodynamic factors, namely, shear stress.

Diabetes and Its Cardiovascular Complications: Potential Role of the Acetyltransferase p300

Diabetes has been shown to accelerate vascular senescence, which is associated with chronic inflammation and oxidative stress, both implicated in the development of endothelial dysfunction. This condition represents the initial alteration linking diabetes to related cardiovascular (CV) complications. Recently, it has been hypothesised that the acetyltransferase, p300, may contribute to establishing an early vascular senescent phenotype, playing a relevant role in diabetes-associated inflammation and oxidative stress, which drive endothelial dysfunction. Specifically, p300 can modulate vascular inflammation through epigenetic mechanisms and transcription factors acetylation. Indeed, it regulates the inflammatory pathway by interacting with nuclear factor kappa-light-chain-enhancer of activated B cells p65 subunit (NF-κB p65) or by inducing its acetylation, suggesting a crucial role of p300 as a bridge between NF-κB p65 and the transcriptional machinery. Additionally, p300-mediated epigenetic modifications could be upstream of the activation of inflammatory cytokines, and they may induce oxidative stress by affecting the production of reactive oxygen species (ROS). Because several in vitro and in vivo studies shed light on the potential use of acetyltransferase inhibitors, a better understanding of the mechanisms underlying the role of p300 in diabetic vascular dysfunction could help in finding new strategies for the clinical management of CV diseases related to diabetes.

Progress in molecular biology and translational science: Epigenetics in cardiovascular health and disease

Conrad Waddington's epigenetics landscape has provided a metaphorical framework for how cells progress from undifferentiated states to one of several discrete, distinct, differentiated cell fates. The understanding of epigenetics has evolved over time, with DNA methylation being the most studied epigenetic modification, followed by histone modifications and non-coding RNA. Cardiovascular diseases (CVD) are leading contributors to death worldwide, with the prevalence of CVDs increasing across the last couple of decades. Significant amount of resources being poured into researching key mechanisms and underpinnings of the various CVDs. These molecular studies looked at the genetics, epigenetics as well as the transcriptomics of various cardiovascular conditions, aiming to provide mechanistic insights. It has paved the way for therapeutics to be developed and in recent years, epi-drugs for the treatment of CVDs. This chapter aims to cover the various roles of epigenetics in the context of cardiovascular health and disease. The following will be examined in detail: the developments in basic experimental techniques used to study epigenetics, the role of epigenetics in various CVDs (hypertension, atrial fibrillation, atherosclerosis, and heart failure), and current advances in epi-therapeutics, providing a holistic view of the current concerted efforts in advancing the field of epigenetics in CVDs.

Blood Vessels as a Key Mediator for Ethanol Toxicity: Implication for Neuronal Damage

Excessive intake of ethanol is associated with severe brain dysfunction, and the subsequent neurological and behavioral abnormalities are well-established social risks. Many research studies have addressed how ethanol induces neurological toxicity. However, the underlying mechanisms with which ethanol induces neurological toxicity are still obscure, perhaps due to the variety and complexity of these mechanisms. Epithelial cells are in direct contact with blood and can thus mediate ethanol neurotoxicity. Ethanol activates the endothelial cells of blood vessels, as well as lymphatic vessels, in a concentration-dependent manner. Among various signaling mediators, nitric oxide plays important roles in response to ethanol. Endothelial and inducible nitric oxide synthases (eNOS and iNOS) are upregulated and activated by ethanol and enhance neuroinflammation. On the other hand, angiogenesis and blood vessel remodeling are both affected by ethanol intake, altering blood supply and releasing angiocrine factors to regulate neuronal functions. Thus, ethanol directly acts on endothelial cells, yet the molecular target(s) on endothelial cells remain unknown. Previous studies on neurons and glial cells have validated the potential contribution of membrane lipids and some specific proteins as ethanol targets, which may also be the case in endothelial cells. Future studies, based on current knowledge, will allow for a greater understanding of the contribution and underlying mechanisms of endothelial cells in ethanol-induced neurological toxicity, protecting neurological health against ethanol toxicity.

EFFECTS OF PALM OIL DERIVED TOCOTRIENOL RICH FRACTION AND VITAMIN E ISOMERS ON BIOMARKERS OF EARLY ATHEROGENESIS IN STIMULATED HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS

This study was conducted to investigate the effects of tocotrienol rich fraction (TRF), α-TOC, and pure TCT isomers (α-. γ- & δ-TCT) on inflammation, endothelial activation, nuclear factor kappa B (NFκB), endothelial nitric oxide synthase (eNOS) and monocyte binding activity (MBA) in vitro. Human umbilical vein endothelial cells (HUVECs) were incubated with various concentrations of α-TOC, pure TCT isomers and TRF (0.3-10 µM) together with lipopolysaccharides (LPS) for 16 h. Culture medium and cells were collected and measured for the protein and gene expression of IL-6, TNF-α, NFκB, ICAM-1, VCAM-1, e-selectin, and eNOS. Monocyte binding activity (MBA) was measured by Rose Bengal staining. Area under the curve (AUC) analysis revealed that TRF and pure TCT particularly γ- and δ- isomers, showed better inhibition of inflammation and endothelial activation, MBA and greater eNOS increment than α-TOC. These suggest that TRF and pure TCT isomers have potential as preventive anti-atherogenic agents by attenuating the release of early biomarkers of atherogenesis which is better than α-TOC in LPS-stimulated human endothelial cells.   

Studying Epigenetics of Cardiovascular Diseases on Chip Guide

Epigenetics is defined as the study of inheritable changes in the gene expressions and phenotypes that occurs without altering the normal DNA sequence. These changes are mainly due to an alteration in chromatin or its packaging, which changes the DNA accessibility. DNA methylation, histone modification, and noncoding or microRNAs can best explain the mechanism of epigenetics. There are various DNA methylated enzymes, histone-modifying enzymes, and microRNAs involved in the cause of various CVDs (cardiovascular diseases) such as cardiac hypertrophy, heart failure, and hypertension. Moreover, various CVD risk factors such as diabetes mellitus, hypoxia, aging, dyslipidemia, and their epigenetics are also discussed together with CVDs such as CHD (coronary heart disease) and PAH (pulmonary arterial hypertension). Furthermore, different techniques involved in epigenetic chromatin mapping are explained. Among these techniques, the ChIP-on-chip guide is explained with regard to its role in cardiac hypertrophy, a final form of heart failure. This review focuses on different epigenetic factors that are involved in causing cardiovascular diseases.

HDAC1: an environmental sensor regulating endothelial function

The histone deacetylases (HDACs) are a family of enzymes that catalyse lysine deacetylation of both histone and non-histone proteins. Here, we review, summarize, and provide perspectives on the literature regarding one such HDAC, HDAC1, in endothelial biology. In the endothelium, HDAC1 mediates the effects of external and environmental stimuli by regulating major endothelial functions such as angiogenesis, inflammatory signalling, redox homeostasis, and nitric oxide signalling. Angiogenesis is most often, but not exclusively, repressed by endothelial HDAC1. The regulation of inflammatory signalling is more complex as HDAC1 promotes or suppresses inflammatory signalling depending upon the environmental stimuli. HDAC1 is protective in models of atherosclerosis where loss of HDAC1 results in increased cytokine and cell adhesion molecule (CAM) abundance. In other models, HDAC1 promotes inflammation by increasing CAMs and repressing claudin-5 expression. Consistently, from many investigations, HDAC1 decreases antioxidant enzyme expression and nitric oxide production in the endothelium. HDAC1 decreases antioxidant enzyme expression through the deacetylation of histones and transcription factors, and also regulates nitric oxide production through regulating both the expression and activity of nitric oxide synthase 3. The HDAC1-dependent regulation of endothelial function through the deacetylation of both histone and non-histone proteins ultimately impacts whole animal physiology and health.

Deacetylation of Caveolin-1 by Sirt6 induces autophagy and retards high glucose-stimulated LDL transcytosis and atherosclerosis formation

BACKGROUND

Atherosclerosis (AS) is the basis of diabetic macrovascular complications. The plasma low-density lipoprotein (LDL) particles transcytosis across endothelial cells (ECs) and deposition under the endothelium is the initiation step of AS. We previously reported that high glucose inhibits the autophagic degradation of Caveolin-1 and promote LDL transcytosis across ECs, which in turn accelerates atherosclerotic progression. Since Sirt6 is a chromatin-associated protein with deacetylation activity, whether it can regulate Caveolin-1 acetylation and regulating the autophagic degradation of Caveolin-1 remains elusive.

METHODS

Autophagy and histone acetylation were assessed in the umbilical cords of patients with gestational diabetes mellitus (GDM) by immunohistochemistry. An in vitro model of LDL transcytosis was established, and the role of Sirt6 in LDL transcytosis across endothelial cells was clarified. The effect of Sirt6 on the autophagic degradation of Caveolin-1 under hyperglycemic conditions was explored in a streptozotocin (STZ)-induced diabetic AS model established using the ApoE^-/- mice.

RESULTS

Caveolin-1 and acetylated histone H3 levels were significantly increased, while LC3B and Sirt6 were downregulated in the monolayer of the vascular wall from GDM and type 2 diabetes mellitus (T2DM) patients. Immunoprecipitation assays showed that Sirt6 interacts with Caveolin-1 and specifically mediated its acetylation levels. Immuno-electron microscopy (EM) further indicated that Sirt6 overexpression triggered the autophagic lysosomal degradation of Caveolin-1. ECs-specific overexpression of Sirt6 by adeno-associated viral vector serotype 9 (AAV9) induced autophagy, reduced Caveolin-1 expression, and ameliorated atherosclerotic plaque formation in STZ-induced diabetic ApoE^-/- mice.

CONCLUSION

Sirt6-mediated acetylation of Caveolin-1 activates its autophagic degradation and inhibits high glucose-stimulated LDL transcytosis. Thus, the Sirt6/Caveolin-1 autophagic pathway plays a crucial role in diabetic AS, and the overexpression or activation of Sirt6 is a novel therapeutic strategy.

Epigenetic Regulation of Endothelial Dysfunction and Inflammation in Pulmonary Arterial Hypertension

Once perceived as a disorder treated by vasodilation, pulmonary artery hypertension (PAH) has emerged as a pulmonary vascular disease with severe endothelial cell dysfunction. In the absence of a cure, many studies seek to understand the detailed mechanisms of EC regulation to potentially create more therapeutic options for PAH. Endothelial dysfunction is characterized by complex phenotypic changes including unchecked proliferation, apoptosis-resistance, enhanced inflammatory signaling and metabolic reprogramming. Recent studies have highlighted the role of epigenetic modifications leading to pro-inflammatory response pathways, endothelial dysfunction, and the progression of PAH. This review summarizes the existing literature on epigenetic mechanisms such as DNA methylation, histone modifications, and non-coding RNAs, which can lead to aberrant endothelial function. Our goal is to develop a conceptual framework for immune dysregulation and epigenetic changes in endothelial cells in the context of PAH. These studies as well as others may lead to advances in therapeutics to treat this devastating disease.

"Enhancing" mechanosensing: Enhancers and enhancer-derived long non-coding RNAs in endothelial response to flow

Endothelial cells (ECs), uniquely localized and strategically forming the inner lining of vascular wall, constitute the largest cell surface by area in the human body. The dynamic sensing and response of ECs to mechanical cues, especially shear stress, is crucial for maintenance of vascular homeostasis. It is well recognized that different flow patterns associated with atheroprotective vs atheroprone regions in the arterial tree, result in distinct EC functional phenotypes with differential transcriptome profiles. Mounting evidence has demonstrated an integrative and essential regulatory role of non-coding genome in EC biology. In particular, recent studies have begun to reveal the importance of enhancers and enhancer-derived transcripts in flow-regulated EC gene expression and function. In this minireview, we summarize studies in this area and discuss examples in support of the emerging importance of enhancers and enhancer(-derived) long non-coding RNAs (elncRNAs) in EC mechanosensing, with a focus on flow-responsive EC transcription. Finally, we will provide perspective and discuss standing questions to elucidate the role of these novel regulators in EC mechanobiology.

Endothelial Dysfunction Driven by Hypoxia-The Influence of Oxygen Deficiency on NO Bioavailability

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. The initial stage of CVDs is characterized by endothelial dysfunction, defined as the limited bioavailability of nitric oxide (NO). Thus, any factors that interfere with the synthesis or metabolism of NO in endothelial cells are involved in CVD pathogenesis. It is well established that hypoxia is both the triggering factor as well as the accompanying factor in cardiovascular disease, and diminished tissue oxygen levels have been reported to influence endothelial NO bioavailability. In endothelial cells, NO is produced by endothelial nitric oxide synthase (eNOS) from L-Arg, with tetrahydrobiopterin (BH₄) as an essential cofactor. Here, we discuss the mechanisms by which hypoxia affects NO bioavailability, including regulation of eNOS expression and activity. What is particularly important is the fact that hypoxia contributes to the depletion of cofactor BH₄ and deficiency of substrate L-Arg, and thus elicits eNOS uncoupling-a state in which the enzyme produces superoxide instead of NO. eNOS uncoupling and the resulting oxidative stress is the major driver of endothelial dysfunction and atherogenesis. Moreover, hypoxia induces impairment in mitochondrial respiration and endothelial cell activation; thus, oxidative stress and inflammation, along with the hypoxic response, contribute to the development of endothelial dysfunction.

Novel insights for the role of nitric oxide in placental vascular function during and beyond pregnancy

More than 30 years have passed since endothelial nitric oxide synthesis was described using the umbilical artery and vein endothelium. That seminal report set the cornerstone for unveiling the molecular aspects of endothelial function. In parallel, the understanding of placental physiology has gained growing interest, due to its crucial role in intrauterine development, with considerable long-term health consequences. This review discusses the evidence for nitric oxide (NO) as a critical player of placental development and function, with a special focus on endothelial nitric oxide synthase (eNOS) vascular effects. Also, the regulation of eNOS-dependent vascular responses in normal pregnancy and pregnancy-related diseases and their impact on prenatal and postnatal vascular health are discussed. Recent and compelling evidence has reinforced that eNOS regulation results from a complex network of processes, with novel data concerning mechanisms such as mechano-sensing, epigenetic, posttranslational modifications, and the expression of NO- and l-arginine-related pathways. In this regard, most of these mechanisms are expressed in an arterial-venous-specific manner and reflect traits of the fetal systemic circulation. Several studies using umbilical endothelial cells are not aimed to understand placental function but general endothelial function, reinforcing the influence of the placenta on general knowledge in physiology.

The link among microbiota, epigenetics, and disease development

The microbiome is a community of various microorganisms that inhabit or live on the skin of humans/animals, sharing the body space with their hosts. It is a sort of complex ecosystem of trillions of commensals, symbiotic, and pathogenic microorganisms, including trillions of bacteria, archaea, protozoa, fungi, and viruses. The microbiota plays a role in the health and disease status of the host. Their number, species dominance, and viability are dynamic. Their long-term disturbance is usually accompanied by serious diseases such as metabolic disorders, cardiovascular diseases, or even cancer. While epigenetics is a term that refers to different stimuli that induce modifications in gene expression patterns without structural changes in the inherited DNA sequence, these changes can be reversible or even persist for several generations. Epigenetics can be described as cell memory that stores experience against internal and external factors. Results from multiple institutions have contributed to the role and close interaction of both microbiota and epigenetics in disease induction. Understanding the mechanisms of both players enables a better understanding of disease induction and development and also opens the horizon to revolutionary therapeutic approaches. The present review illustrates the roles of diet, microbiome, and epigenetics in the induction of several chronic diseases. In addition, it discusses the application of epigenetic data to develop diagnostic biomarkers and therapeutics and evaluate their safety for patients. Understanding the interaction among all these elements enables the development of innovative preventive/therapeutic approaches for disease control.

The Role of Histone Protein Acetylation in Regulating Endothelial Function

Endothelial cell (EC), consisting of the innermost cellular layer of all types of vessels, is not only a barrier composer but also performing multiple functions in physiological processes. It actively controls the vascular tone and the extravasation of water, solutes, and macromolecules; modulates circulating immune cells as well as platelet and leukocyte recruitment/adhesion and activation. In addition, EC also tightly keeps coagulation/fibrinolysis balance and plays a major role in angiogenesis. Therefore, endothelial dysfunction contributes to the pathogenesis of many diseases. Growing pieces of evidence suggest that histone protein acetylation, an epigenetic mark, is altered in ECs under different conditions, and the acetylation status change at different lysine sites on histone protein plays a key role in endothelial dysfunction and involved in hyperglycemia, hypertension, inflammatory disease, cancer and so on. In this review, we highlight the importance of histone acetylation in regulating endothelial functions and discuss the roles of histone acetylation across the transcriptional unit of protein-coding genes in ECs under different disease-related pathophysiological processes. Since histone acetylation changes are conserved and reversible, the knowledge of histone acetylation in endothelial function regulation could provide insights to develop epigenetic interventions in preventing or treating endothelial dysfunction-related diseases.

In Vivo Function of Flow-Responsive Cis-DNA Elements of eNOS Gene: A Role for Chromatin-Based Mechanisms

BACKGROUND

eNOS (endothelial nitric oxide synthase) is an endothelial cell (EC)-specific gene predominantly expressed in medium- to large-sized arteries where ECs experience atheroprotective laminar flow with high shear stress. Disturbed flow with lower average shear stress decreases eNOS transcription, which leads to the development of atherosclerosis, especially at bifurcations and curvatures of arteries. This prototypic arterial EC gene contains 2 distinct flow-responsive cis-DNA elements in the promoter, the shear stress response element (SSRE) and the KLF (Krüppel-like factor) element. Previous in vitro studies suggested their positive regulatory functions on flow-induced transcription of EC genes including eNOS. However, the in vivo function of these cis-DNA elements remains unknown.

METHODS

Insertional transgenic mice with a mutation at each flow-responsive cis-DNA element were generated using a murine eNOS promoter-β-galactosidase reporter by linker-scanning mutagenesis and compared with episomal-based mutations in vitro. DNA methylation at the eNOS proximal promoter in mouse ECs was assessed by bisulfite sequencing or pyrosequencing.

RESULTS

Wild type mice with a functional eNOS promoter-reporter transgene exhibited reduced endothelial reporter expression in the atheroprone regions of disturbed flow (n=5). It is surprising that the SSRE mutation abrogated reporter expression in ECs and was associated with aberrant hypermethylation at the eNOS proximal promoter (n=7). Reporter gene silencing was independent of transgene copy number and integration position, indicating that the SSRE is a critical cis-element necessary for eNOS transcription in vivo. The KLF mutation demonstrated an integration site-specific decrease in eNOS transcription, again with marked promoter methylation (n=8), suggesting that the SSRE alone is not sufficient for eNOS transcription in vivo. In wild type mice, the native eNOS promoter was significantly hypermethylated in ECs from the atheroprone regions where eNOS expression was markedly repressed by chronic disturbed flow, demonstrating that eNOS expression is regulated by flow-dependent DNA methylation that is region-specific in the arterial endothelium in vivo.

CONCLUSIONS

We report, for the first time, that the SSRE and KLF elements are critical flow sensors necessary for a transcriptionally permissive, hypomethylated eNOS promoter in ECs under chronic shear stress in vivo. Moreover, eNOS expression is regulated by flow-dependent epigenetic mechanisms, which offers novel mechanistic insight on eNOS gene regulation in atherogenesis.

Nitric Oxide Synthase Inhibitors into the Clinic at Last

The 1998 Nobel Prize in Medicine and Physiology for the discovery of nitric oxide, a nitrogen containing reactive oxygen species (also termed reactive nitrogen or reactive nitrogen/oxygen species) stirred great hopes. Clinical applications, however, have so far pertained exclusively to the downstream signaling of cGMP enhancing drugs such as phosphodiesterase inhibitors and soluble guanylate cyclase stimulators. All clinical attempts, so far, to inhibit NOS have failed even though preclinical models were strikingly positive and clinical biomarkers correlated perfectly. This rather casts doubt on our current way of target identification in drug discovery in general and our way of patient stratification based on correlating but not causal biomarkers or symptoms. The opposite, NO donors, nitrite and enhancing NO synthesis by eNOS/NOS3 recoupling in situations of NO deficiency, are rapidly declining in clinical relevance or hold promise but need yet to enter formal therapeutic guidelines, respectively. Nevertheless, NOS inhibition in situations of NO overproduction often jointly with enhanced superoxide (or hydrogen peroxide production) still holds promise, but most likely only in acute conditions such as neurotrauma (Stover et al., J Neurotrauma 31(19):1599-1606, 2014) and stroke (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019). Conversely, in chronic conditions, long-term inhibition of NOS might be too risky because of off-target effects on eNOS/NOS3 in particular for patients with cardiovascular risks or metabolic and renal diseases. Nitric oxide synthases (NOS) and their role in health (green) and disease (red). Only neuronal/type 1 NOS (NOS1) has a high degree of clinical validation and is in late stage development for traumatic brain injury, followed by a phase II safety/efficacy trial in ischemic stroke. The pathophysiology of NOS1 (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016) is likely to be related to parallel superoxide or hydrogen peroxide formation (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 114(46):12315-12320, 2017; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019) leading to peroxynitrite and protein nitration, etc. Endothelial/type 3 NOS (NOS3) is considered protective only and its inhibition should be avoided. The preclinical evidence for a role of high-output inducible/type 2 NOS (NOS2) isoform in sepsis, asthma, rheumatic arthritis, etc. was high, but all clinical development trials in these indications were neutral despite target engagement being validated. This casts doubt on the role of NOS2 in humans in health and disease (hence the neutral, black coloring).

The Safety of Pharmacological and Surgical Treatment of Diabetes in Patients with Diabetic Retinopathy-A Review

BACKGROUND

Diabetes mellitus (DM) is a non-infectious pandemic of the modern world; it is estimated that in 2045 it will affect 10% of the world's population. As the prevalence of diabetes increases, the problem of its complications, including diabetic retinopathy (DR), grows. DR is a highly specific neurovascular complication of diabetes that occurs in more than one third of DM patients and accounts for 80% of complete vision loss cases in the diabetic population. We are currently witnessing many groundbreaking studies on new pharmacological and surgical methods of treating diabetes.

AIM

The aim of the study is to assess the safety of pharmacological and surgical treatment of DM in patients with DR.

MATERIAL AND METHODS

An analysis of the data on diabetes treatment methods currently available in the world literature and their impact on the occurrence and progression of DR.

RESULTS

A rapid decrease in glycaemia leads to an increased occurrence and progression of DR. Its greatest risk accompanies insulin therapy and sulfonylurea therapy. The lowest risk of DR occurs with the use of SGLT2 inhibitors; the use of DPP-4 inhibitors and GLP-1 analogues is also safe. Patients undergoing pancreatic islet transplants or bariatric surgeries require intensive monitoring of the state of the eye, both in the perioperative and postoperative period.

CONCLUSIONS

It is of utmost importance to individualize therapy in diabetic patients, in order to gradually achieve treatment goals with the use of safe methods and minimize the risk of development and progression of DR.

Factors Associated with Primary Hypertension in Pediatric Patients: An Up-to-Date

BACKGROUND

Arterial hypertension in children is considered a common alteration nowadays, mainly because obesity is a growing worldwide problem closely related to increased blood pressure. Childhood hypertension can be classified as primary or secondary, depending on the etiology. Primary or essential hypertension still has its pathophysiology not fully elucidated, and there is no consensus in the literature on most underlying mechanisms. In this review, genetic and environmental factors, including sodium and potassium intake, socioeconomic status, ethnicity, family structure, obesity, sedentary lifestyle, prematurity and low birth weight, prenatal and postnatal exposures are highlighted.

OBJECTIVE

The present study aimed to perform an update on primary hypertension in childhood, providing clinicians and researchers an overview of the current state of the literature regarding the influence of genetic and environmental factors.

METHODS

This integrative review searched for articles on genetic and environmental factors related to primary hypertension in pediatric patients. The databases evaluated were PubMed and Scopus.

RESULTS

The studies have provided insights regarding many genetic and environmental factors, in addition to their association with the pathophysiology of primary hypertension in childhood. Findings corroborated the idea that primary hypertension is a multifactorial disease. Further studies in the pediatric population are needed to elucidate the underlying mechanisms.

CONCLUSION

The study of primary hypertension in pediatrics has utmost importance for the adoption of preventive measures and the development of more efficient treatments, therefore reducing childhood morbidity and the incidence of cardiovascular diseases and other health consequences later in life.

Application of FRET Biosensors in Mechanobiology and Mechanopharmacological Screening

Extensive studies have shown that cells can sense and modulate the biomechanical properties of the ECM within their resident microenvironment. Thus, targeting the mechanotransduction signaling pathways provides a promising way for disease intervention. However, how cells perceive these mechanical cues of the microenvironment and transduce them into biochemical signals remains to be answered. Förster or fluorescence resonance energy transfer (FRET) based biosensors are a powerful tool that can be used in live-cell mechanotransduction imaging and mechanopharmacological drug screening. In this review, we will first introduce FRET principle and FRET biosensors, and then, recent advances on the integration of FRET biosensors and mechanobiology in normal and pathophysiological conditions will be discussed. Furthermore, we will summarize the current applications and limitations of FRET biosensors in high-throughput drug screening and the future improvement of FRET biosensors. In summary, FRET biosensors have provided a powerful tool for mechanobiology studies to advance our understanding of how cells and matrices interact, and the mechanopharmacological screening for disease intervention.

Probing the epigenetic signatures in subjects with coronary artery disease

Depletion of S-adenosyl methionine and 5-methyltetrahydrofolate; and elevation of total plasma homocysteine were documented in CAD patients, which might modulate the gene-specific methylation status and alter their expression. In this study, we have aimed to delineate CAD-specific epigenetic signatures by investigating the methylation and expression of 11 candidate genes i.e. ABCG1, LIPC, PLTP, IL-6, TNF-α, CDKN2A, CDKN2B, F2RL3, FGF2, P66 and TGFBR3. The methylation-specific PCR and qRT-PCR were used to assess the methylation status and the expression of candidate genes, respectively. CAD patients showed the upregulation of IL-6, TNF-α, CDKN2A, CDKN2B, F2RL3, FGF2, P66, and TGFBR3. Hypomethylation of CDKN2A loci was shown to increase risk for CAD by 1.79-folds (95% CI 1.22-2.63). Classification and regression tree (CART) model of gene expression showed increased risk for CAD with F2RL3 > 3.4-fold, while demonstrating risk reduction with F2RL3 < 3.4-fold and IL-6 < 7.7-folds. This CAD prediction model showed the excellent sensitivity (0.98, 95% CI 0.88-1.00), specificity (0.91, 95% CI 0.86-0.92), positive predictive value (0.82, 95% CI 0.75-0.84), and negative predictive value (0.99, 95% CI 0.94-1.00) with an overall accuracy of 92.8% (95% CI 87.0-94.1%). Folate and B₁₂ deficiencies were observed in CAD cases, which were shown to contribute to hypomethylation and upregulation of the prime candidate genes i.e. CDKN2A and F2RL3. Early onset diabetes was associated with IL-6 and TNF-α hypomethylation and upregulation of CDKN2A. The expression of F2RL3 and IL-6 (or) hypomethylation status at CDKN2A locus are potential biomarkers in CAD risk prediction. Early epigenetic imprints of CAD were observed in early onset diabetes. Folate and B₁₂ deficiencies are the contributing factors to these changes in CAD-specific epigenetic signatures.

The Epigenetic Profile of Tumor Endothelial Cells. Effects of Combined Therapy with Antiangiogenic and Epigenetic Drugs on Cancer Progression

Tumors require a constant supply of nutrients to grow which are provided through tumor blood vessels. To metastasize, tumors need a route to enter circulation, that route is also provided by tumor blood vessels. Thus, angiogenesis is necessary for both tumor progression and metastasis. Angiogenesis is tightly regulated by a balance of angiogenic and antiangiogenic factors. Angiogenic factors of the vascular endothelial growth factor (VEGF) family lead to the activation of endothelial cells, proliferation, and neovascularization. Significant VEGF-A upregulation is commonly observed in cancer cells, also due to hypoxic conditions, and activates endothelial cells (ECs) by paracrine signaling stimulating cell migration and proliferation, resulting in tumor-dependent angiogenesis. Conversely, antiangiogenic factors inhibit angiogenesis by suppressing ECs activation. One of the best-known anti-angiogenic factors is thrombospondin-1 (TSP-1). In pathological angiogenesis, the balance shifts towards the proangiogenic factors and an angiogenic switch that promotes tumor angiogenesis. Here, we review the current literature supporting the notion of the existence of two different endothelial lineages: normal endothelial cells (NECs), representing the physiological form of vascular endothelium, and tumor endothelial cells (TECs), which are strongly promoted by the tumor microenvironment and are biologically different from NECs. The angiogenic switch would be also important for the explanation of the differences between NECs and TECs, as angiogenic factors, cytokines and growth factors secreted into the tumor microenvironment may cause genetic instability. In this review, we focus on the epigenetic differences between the two endothelial lineages, which provide a possible window for pharmacological targeting of TECs.

Epigenetic-sensitive pathways in personalized therapy of major cardiovascular diseases

The complex pathobiology underlying cardiovascular diseases (CVDs) has yet to be explained. Aberrant epigenetic changes may result from alterations in enzymatic activities, which are responsible for putting in and/or out the covalent groups, altering the epigenome and then modulating gene expression. The identification of novel individual epigenetic-sensitive trajectories at single cell level might provide additional opportunities to establish predictive, diagnostic and prognostic biomarkers as well as drug targets in CVDs. To date, most of studies investigated DNA methylation mechanism and miRNA regulation as epigenetics marks. During atherogenesis, big epigenetic changes in DNA methylation and different ncRNAs, such as miR-93, miR-340, miR-433, miR-765, CHROME, were identified into endothelial cells, smooth muscle cells, and macrophages. During man development, lipid metabolism, inflammation and homocysteine homeostasis, alter vascular transcriptional mechanism of fundamental genes such as ABCA1, SREBP2, NOS, HIF1. At histone level, increased HDAC9 was associated with matrix metalloproteinase 1 (MMP1) and MMP2 expression in pro-inflammatory macrophages of human carotid plaque other than to have a positive effect on toll like receptor signaling and innate immunity. HDAC9 deficiency promoted inflammation resolution and reverse cholesterol transport, which might block atherosclerosis progression and promote lesion regression. Here, we describe main human epigenetic mechanisms involved in atherosclerosis, coronary heart disease, ischemic stroke, peripheral artery disease; cardiomyopathy and heart failure. Different epigenetics mechanisms are activated, such as regulation by circular RNAs, as MICRA, and epitranscriptomics at RNA level. Moreover, in order to open new frontiers for precision medicine and personalized therapy, we offer a panoramic view on the most innovative bioinformatic tools designed to identify putative genes and molecular networks underlying CVDs in man.

Histone methylation and vascular biology

The vasculature not only transports oxygenated blood, metabolites, and waste products but also serves as a conduit for hormonal communication between distant tissues. Therefore, it is important to maintain homeostasis within the vasculature. Recent studies have greatly expanded our understanding of the regulation of vasculature development and vascular-related diseases at the epigenetic level, including by protein posttranslational modifications, DNA methylation, and noncoding RNAs. Integrating epigenetic mechanisms into the pathophysiologic conceptualization of complex and multifactorial vascular-related diseases may provide promising therapeutic approaches. Several reviews have presented detailed discussions of epigenetic mechanisms not including histone methylation in vascular biology. In this review, we primarily discuss histone methylation in vascular development and maturity, and in vascular diseases.

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.

Sensitive and quantitative method to evaluate DNA methylation of the positive regulatory domains (PRDI, PRDII) and cAMP response element (CRE) in human endothelial nitric oxide synthase promoter

Nitric oxide plays a prominent role in the cardiovascular system and much attention has been devoted in the last years on deciphering the regulation of human endothelial nitric oxide synthase (eNOS) expression. Epigenetic-based mechanisms have a key role in the eNOS expression and their pathologic perturbations may have profound effects on the steady state RNA levels in the endothelium. The human eNOS promoter lacks a canonical TATA box and it does not contain a proximal CpG island. A differentially DNA methylated region (DMR) in the native eNOS proximal promoter is involved in gene expression regulation. Here we describe a quantitative, sensitive and cost-effective method that, relying on a novel normalization strategy, allows the quantification of DNA methylation status of the positive regulatory domains (PRDI, PRDII) and cAMP response element (CRE) in human eNOS promoter. This technique will enable to explore the functional relevance of DNA methylation perturbations of eNOS promoter both under pathological and physiological conditions.

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.

Epigenetic regulation of intercellular communication in the heart

The myocardium is a highly structured tissue consisting of different cell types including cardiomyocytes, endothelial cells, fibroblasts, smooth muscle cells, inflammatory cells, and stem cells. Microvascular endothelial cells are the most abundant cell type in the myocardium and play crucial roles during cardiac development, in normal adult myocardium, and during myocardial diseases such as heart failure. In the last decade, epigenetic changes have been described regulating cellular function in almost every cell type in the organism. Here, we review recent evidence on different epigenetic changes that regulate intercellular communication in normal myocardium and during myocardial diseases, including cardiac remodeling. Epigenetic changes influence many intercellular communication signaling systems, including the nitric oxide, angiotensin, and endothelin signaling systems. In this review, we go beyond discussing classic endothelial function (for instance nitric oxide secretion) and will discuss epigenetic regulation of intercellular communication.

The impact of epigenetics on cardiovascular disease

Mortality and morbidity from cardiovascular diseases (CVDs) represents a huge burden to society. It is recognized that environmental factors and individual lifestyles play important roles in disease susceptibility, but the link between these external risk factors and our genetics has been unclear. However, the discovery of sequence-independent heritable DNA changes (epigenetics) have helped us to explain the link between genes and the environment. Multiple diverse epigenetic processes, including DNA methylation, histone modification, and the expression of non-coding RNA molecules affect the expression of genes that produce important changes in cellular differentiation and function, influencing the health and adaptability of the organism. CVDs such as congenital heart disease, cardiomyopathy, heart failure, cardiac fibrosis, hypertension, and atherosclerosis are now being viewed as much more complex and dynamic disorders. The role of epigenetics in these and other CVDs is currently under intense scrutiny, and we can expect important insights to emerge, including novel biomarkers and new approaches to enable precision medicine. This review summarizes the recent advances in our understanding of the role of epigenetics in CVD.

LncRNAs and epigenetic regulation of vascular endothelium: genome positioning system and regulators of chromatin modifiers

Epigenetic mechanisms regulate the cell type-specific expression of endothelial-enriched genes. A major question has been how chromatin modifiers without inherent sequence specificity can be targeted to genomic coordinates. Recently, long noncoding RNAs (lncRNAs) have emerged as candidates for specifying genomic positioning for chromatin modifiers. However, lncRNAs function by a number of mechanisms in both the nucleus and the cytoplasm. Recent studies indicate the existence of endothelial-enriched lncRNAs. This review discusses lncRNA regulation in endothelial cells with a focus on four recently described nuclear-enriched lncRNAs: MANTIS, LEENE, STEEL, and GATA6-AS. This emerging work on these lncRNAs contributes to our understanding of epigenetic regulation in the vascular endothelium with links to important themes in endothelial biology, including angiogenesis and shear stress.

Generation of a nitric oxide signaling pathway in mesenchymal stem cells promotes endothelial lineage commitment

Enhancing differentiation of mesenchymal stem cells (MSCs) to endothelial cells may improve their ability to vascularize tissue and promote wound healing. This study describes a novel role for nitric oxide (NO) in reprogramming MSCs towards an endothelial lineage and highlights the role of Wnt signaling and epigenetic modification by NO. Rat MSCs were transduced with lentiviral vectors expressing endothelial nitric oxide synthase (pLV-eNOS) and a mutated caveolin gene (pLV-CAV-1^F92A ) to enhance NO generation resulting in increased in vitro capillary tubule formation and endothelial marker gene expression. An exogenous source of NO could also stimulate CD31 expression in MSCs. NO was associated with an arterial-specific endothelial gene expression profile of Notch1, Dll4, and Hey2 and significantly reduced expression of venous markers. Wnt signaling associated with NO was evident through increased gene expression of Wnt3a and β-catenin protein, and expression of the endothelial marker Pecam-1 could be significantly reduced by treatment with the Wnt signaling inhibitor Dkk-1. The role of NO as an epigenetic modifier was evident with reduced gene expression of the methyltransferase, DNMT1, and bisulfite sequencing of the endothelial Flt1 promoter region in NO-producing MSCs showed significant demethylation compared to control cells. Finally, subcutaneous implantation of NO-producing MSCs seeded in a biomaterial scaffold (NovoSorb®) resulted in survival of transplanted cells and the formation of blood vessels. In summary, this study describes, NO as a potent endothelial programming factor which acts as an epigenetic modifier in MSCs and may provide a novel platform for vascular regenerative therapy.

Epigenetic modification: a regulatory mechanism in essential hypertension

Essential hypertension (EH) is a multifactorial disease of the cardiovascular system that is influenced by the interplay of genetic, epigenetic, and environmental factors. The molecular dynamics underlying EH etiopathogenesis is unknown; however, earlier studies have revealed EH-associated genetic variants. Nevertheless, this finding alone is not sufficient to explain the variability in blood pressure, suggesting that other risk factors are involved, such as epigenetic modifications. Therefore, this review highlights the potential contribution of well-defined epigenetic mechanisms in EH, specifically, DNA methylation, post-translational histone modifications, and microRNAs. We further emphasize global and gene-specific DNA methylation as one of the most well-studied hallmarks among all epigenetic modifications in EH. In addition, post-translational histone modifications, such as methylation, acetylation, and phosphorylation, are described as important epigenetic markers associated with EH. Finally, we discuss microRNAs that affect blood pressure by regulating master genes such as those implicated in the renin-angiotensin-aldosterone system. These epigenetic modifications, which appear to contribute to various cardiovascular diseases, including EH, may be a promising research area for the development of novel future strategies for EH prevention and therapeutics.

New Therapeutic Implications of Endothelial Nitric Oxide Synthase (eNOS) Function/Dysfunction in Cardiovascular Disease

The Global Burden of Disease Study identified cardiovascular risk factors as leading causes of global deaths and life years lost. Endothelial dysfunction represents a pathomechanism that is associated with most of these risk factors and stressors, and represents an early (subclinical) marker/predictor of atherosclerosis. Oxidative stress is a trigger of endothelial dysfunction and it is a hall-mark of cardiovascular diseases and of the risk factors/stressors that are responsible for their initiation. Endothelial function is largely based on endothelial nitric oxide synthase (eNOS) function and activity. Likewise, oxidative stress can lead to the loss of eNOS activity or even “uncoupling” of the enzyme by adverse regulation of well-defined “redox switches” in eNOS itself or up-/down-stream signaling molecules. Of note, not only eNOS function and activity in the endothelium are essential for vascular integrity and homeostasis, but also eNOS in perivascular adipose tissue plays an important role for these processes. Accordingly, eNOS protein represents an attractive therapeutic target that, so far, was not pharmacologically exploited. With our present work, we want to provide an overview on recent advances and future therapeutic strategies that could be used to target eNOS activity and function in cardiovascular (and other) diseases, including life style changes and epigenetic modulations. We highlight the redox-regulatory mechanisms in eNOS function and up- and down-stream signaling pathways (e.g., tetrahydrobiopterin metabolism and soluble guanylyl cyclase/cGMP pathway) and their potential pharmacological exploitation.

Endothelial NOS: perspective and recent developments

Endothelial NOS (eNOS), and its product NO, are vital components of the control of vasomotor function and cardiovascular homeostasis. In the present review, we will take a deep dive into eNOS enzymology, function and mechanisms regulating endothelial NO. The mechanisms regulating eNOS and NO synthesis discussed here include alterations to transcriptional, post-translational modifications and protein-protein regulations. Also, we will discuss the phenotypes associated with various eNOS mutants and the consequences of a disrupted eNOS/NO cascade, highlighting the importance of eNOS function and vascular homeostasis. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

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.

Persistent pulmonary hypertension alters the epigenetic characteristics of endothelial nitric oxide synthase gene in pulmonary artery endothelial cells in a fetal lamb model

Decreased expression of endothelial nitric oxide synthase (eNOS), a key mediator of perinatal transition, characterizes persistent pulmonary hypertension of the newborn (PPHN) in neonates and a fetal lamb model; the mechanisms are unclear. We investigated whether increased DNA CpG methylation at the eNOS promoter in estrogen response elements (EREs) and altered histone code together contribute to decreased eNOS expression in PPHN. We isolated pulmonary artery endothelial cells (PAEC) from fetal lambs with PPHN induced by prenatal ductus arteriosus constriction from 128 to 136 days gestation or gestation-matched twin controls. We measured right ventricular systolic pressure (RVSP) and Fulton index and determined eNOS expression in PAEC in control and PPHN lambs. We determined DNA CpG methylation by pyrosequencing and activity of ten eleven translocase demethylases (TET) by colorimetric assay. We quantified the occupancy of transcription factors, specificity protein 1 (Sp1), and estrogen receptors and density of four histone marks around Sp1 binding sites by chromatin immunoprecipitation (ChIP) assays. Fetal lambs with PPHN developed increased RVSP and Fulton index. Levels of eNOS mRNA and protein were decreased in PAEC from PPHN lambs. PPHN significantly increased the DNA CpG methylation in eNOS promoter and decreased TET activity in PAEC. PPHN decreased Sp1 occupancy and density of the active mark, lysine 12 acetylation of histone 4, and increased density of the repression mark, lysine 9 trimethylation of histone 3 around Sp1 binding sites in eNOS promoter. These results suggest that epigenetic modifications are primed to decrease Sp1 binding at the eNOS gene promoter in PPHN.

Role of Nitric Oxide and Hydrogen Sulfide in Ischemic Stroke and the Emergent Epigenetic Underpinnings

Nitric oxide (NO) and hydrogen sulfide (H₂S) are the key gasotransmitters with an imperious role in the maintenance of cerebrovascular homeostasis. A decline in their levels contributes to endothelial dysfunction that portends ischemic stroke (IS) or cerebral ischemia/reperfusion (CI/R). Nevertheless, their exorbitant production during CI/R is associated with exacerbation of cerebrovascular injury in the post-stroke epoch. NO-producing nitric oxide synthases are implicated in IS pathology and their activity is regulated, inter alia, by various post-translational modifications and chromatin-based mechanisms. These account for heterogeneous alterations in NO production in a disease setting like IS. Interestingly, NO per se has been posited as an endogenous epigenetic modulator. Further, there is compelling evidence for an ingenious crosstalk between NO and H₂S in effecting the canonical (direct) and non-canonical (off-target collateral) functions. In this regard, NO-mediated S-nitrosylation and H₂S-mediated S-sulfhydration of specific reactive thiols in an expanding array of target proteins are the principal modalities mediating the all-pervasive influence of NO and H₂S on cell fate in an ischemic brain. An integrated stress response subsuming unfolded protein response and autophagy to cellular stressors like endoplasmic reticulum stress, in part, is entrenched in such signaling modalities that substantiate the role of NO and H₂S in priming the cells for stress response. The precis presented here provides a comprehension on the multifarious actions of NO and H₂S and their epigenetic underpinnings, their crosstalk in maintenance of cerebrovascular homeostasis, and their "Janus bifrons" effect in IS milieu together with plausible therapeutic implications.