Role of DNA methyltransferase 1 on the altered eNOS expression in human umbilical endothelium from intrauterine growth restricted fetuses

Epigenetic regulation by hypoxia, N-acetylcysteine and hydrogen sulphide of the fetal vasculature in growth restricted offspring: A study in humans and chicken embryos

Fetal growth restriction (FGR) is a common outcome in human suboptimal gestation and is related to prenatal origins of cardiovascular dysfunction in offspring. Despite this, therapy of human translational potential has not been identified. Using human umbilical and placental vessels and the chicken embryo model, we combined cellular, molecular, and functional studies to determine whether N-acetylcysteine (NAC) and hydrogen sulphide (H2S) protect cardiovascular function in growth-restricted unborn offspring. In human umbilical and placental arteries from control or FGR pregnancy and in vessels from near-term chicken embryos incubated under normoxic or hypoxic conditions, we determined the expression of the H2S gene CTH (i.e. cystathionine γ-lyase) (via quantitative PCR), the production of H2S (enzymatic activity), the DNA methylation profile (pyrosequencing) and vasodilator reactivity (wire myography) in the presence and absence of NAC treatment. The data show that FGR and hypoxia increased CTH expression in the embryonic/fetal vasculature in both species. NAC treatment increased aortic CTH expression and H2S production and enhanced third-order femoral artery dilator responses to the H2S donor sodium hydrosulphide in chicken embryos. NAC treatment also restored impaired endothelial relaxation in human third-to-fourth order chorionic arteries from FGR pregnancies and in third-order femoral arteries from hypoxic chicken embryos. This NAC-induced protection against endothelial dysfunction in hypoxic chicken embryos was mediated via nitric oxide independent mechanisms. Both developmental hypoxia and NAC promoted vascular changes in CTH DNA and NOS3 methylation patterns in chicken embryos. Combined, therefore, the data support that the effects of NAC and H2S offer a powerful mechanism of human translational potential against fetal cardiovascular dysfunction in complicated pregnancy. KEY POINTS: Gestation complicated by chronic fetal hypoxia and fetal growth restriction (FGR) increases a prenatal origin of cardiovascular disease in offspring, increasing interest in antenatal therapy to prevent against a fetal origin of cardiovascular dysfunction. We investigated the effects between N-acetylcysteine (NAC) and hydrogen sulphide (H2S) in the vasculature in FGR human pregnancy and in chronically hypoxic chicken embryos. Combining cellular, molecular, epigenetic and functional studies, we show that the vascular expression and synthesis of H2S is enhanced in hypoxic and FGR unborn offspring in both species and this acts to protect their vasculature. Therefore, the NAC/H2S pathway offers a powerful therapeutic mechanism of human translational potential against fetal cardiovascular dysfunction in complicated pregnancy.

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.

Nrf2 pre-recruitment at Enhancer 2 is a hallmark of H2 O2 -induced epigenetic transcriptional memory in the HMOX1 gene in human umbilical artery endothelial cells

Maternal obesity (MO) is a significant cause of increased cardiometabolic risk in offspring, who present endothelial dysfunction at birth. Alterations in physiologic and cellular redox status are strongly associated with altered gene regulation in arterial endothelium. However, specific mechanisms by which the pro-oxidant fetal environment in MO could modulate the vascular gene expression and function during the offspring's postnatal life are elusive. We tested if oxidative stress could reprogram the antioxidant-coding gene's response to a pro-oxidant challenge through an epigenetic transcriptional memory (ETM) mechanism. A pro-oxidant double-hit protocol was applied to human umbilical artery endothelial cells (HUAECs) and EA.hy 926 endothelial cell lines. The ETM acquisition in the HMOX1 gene was analyzed by RT-qPCR. HMOX1 mRNA decay was evaluated by Actinomycin-D treatment and RT-qPCR. To assess the chromatin accessibility and the enrichment of NRF2, RNAP2, and phosphorylation at serin-5 of RNAP2, at HMOX1 gene regulatory regions, were used DNase HS-qPCR and ChIP-qPCR assays, respectively. The CpG methylation pattern at the HMOX1 core promoter was analyzed by DNA bisulfite conversion and Sanger sequencing. Data were analyzed using two-way ANOVA, and p < 0.05 was statistically significant. Using a pro-oxidant double-hit protocol, we found that the Heme Oxygenase gene (HMOX1) presents an ETM response associated with changes in the chromatin structure at the promoter and gene regulatory regions. The ETM response was characterized by a paused-RNA Polymerase 2 and NRF2 enrichment at the transcription start site and Enhancer 2 of the HMOX1 gene, respectively. Changes in DNA methylation pattern at the HMOX1 promoter were not a hallmark of this oxidative stress-induced ETM. These data suggest that a pro-oxidant milieu could trigger an ETM at the vascular level, indicating a potential epigenetic mechanism involved in the increased cardiovascular risk in the offspring of women with obesity.

Methylation of eNOS in the rat penile corpus cavernosum under different pathological states and its relationship with erectile function

BACKGROUND

It has been shown that methylation in the promoter region of eNOS can downregulate eNOS expression resulting in the endothelial dysfunction. However, it is unclear whether low androgen levels and type 1 diabetes cause ED by methylating the promoter region of eNOS in the penile corpus cavernosum.

OBJECTIVE

To clarify the effects of type 1 diabetes and hypo-androgen status on the methylation level of the promoter region of the eNOS gene in penile cavernous tissue and their relationship with the erectile function.

METHODS

Fifty-eight eight-week-old male Sprague-Dawley rats were randomly divided into six groups (n = 6): sham operation group, castration group, castration+testosterone (cast+T) group, normoglycemia group, diabetic group, and diabetic+methyltransferase inhibitor (5-aza-dc, 1.5 mg/kg) group. The ICPmax/MAP, serum T, the concentration of nitric oxide (NO), the expression of DNMT1, DNMT3a, DNMT3b, and eNOS, and the methylation level of the eNOS promoter region in penile corpus cavernosum of rat were examined 4 weeks after surgery in the sham-operated group, the castration group, and the castration + testosterone replacement group. Those tests were examined after 6 weeks using of methylation inhibitors in the normoglycemic group, the diabetic group, and the diabetic + methylation inhibitor group.

RESULTS

ICPmax/MAP, DNMT1, DNMT3a, DNMT3b, eNOS, and NO levels were significantly lower in castrated rats than in sham and cast+T rats (P < 0.05). ICPmax/MAP, eNOS, and NO levels were lower, and DNMT1, DNMT3a, and DNMT3b expression levels were significantly increased in the diabetic group compared with the normoglycemic and diabetic+methyltransferase inhibitor groups (P < 0.05). There was no significant difference in the methylation level of the promoter region of eNOS in penile cavernous tissue of castrated rats compared with the sham group or the testosterone replacement group. The methylation level of the promoter region of eNOS in penile cavernous tissue was significantly higher in the diabetic group than in the normoglycemic group and diabetic+methyltransferase inhibitor group (P < 0.05).

CONCLUSION

Although low androgen status inhibited the level of methyltransferase in rat penile cavernous tissue, did not affect the level of methylation in the promoter region of eNOS. Hyperglycemia inhibits the NO level in the penile cavernous tissue and the erectile function of rats by upregulating the methyltransferase level in the penile cavernous tissue and the methylation level in the promoter region of eNOS. Methylation inhibitors can partly improve the erectile function in type 1 diabetic rats.

Endothelial dysfunction in preterm infants: The hidden legacy of uteroplacental pathologies

Millions of infants are born prematurely every year worldwide. Prematurity, particularly at lower gestational ages, is associated with high mortality and morbidity and is a significant global health burden. Pregnancy complications and preterm birth syndrome strongly impact neonatal clinical phenotypes and outcomes. The vascular endothelium is a pivotal regulator of fetal growth and development. In recent years, the key role of uteroplacental pathologies impairing endothelial homeostasis is emerging. Conditions leading to very and extremely preterm birth can be classified into two main pathophysiological patterns or endotypes: infection/inflammation and dysfunctional placentation. The first is frequently related to chorioamnionitis, whereas the second is commonly associated with hypertensive disorders of pregnancy and fetal growth restriction. The nature, timing, and extent of prenatal noxa may alter fetal and neonatal endothelial phenotype and functions. Changes in the luminal surface, oxidative stress, growth factors imbalance, and dysregulation of permeability and vascular tone are the leading causes of endothelial dysfunction in preterm infants. However, the available evidence regarding endothelial physiology and damage is limited in neonates compared to adults. Herein, we discuss the current knowledge on endothelial dysfunction in the infectious/inflammatory and dysfunctional placentation endotypes of prematurity, summarizing their molecular features, available biomarkers, and clinical impact. Furthermore, knowledge gaps, shadows, and future research perspectives are highlighted.

Endothelial Dysfunction in Pregnancy Complications

The endothelium, which constitutes the inner layer of blood vessels and lymphatic structures, plays an important role in various physiological functions. Alterations in structure, integrity and function of the endothelial layer during pregnancy have been associated with numerous gestational complications, including clinically significant disorders, such as preeclampsia, fetal growth restriction, and diabetes. While numerous experimental studies have focused on establishing the role of endothelial dysfunction in pathophysiology of these gestational complications, their mechanisms remain unknown. Numerous biomarkers of endothelial dysfunction have been proposed, together with the mechanisms by which they relate to individual gestational complications. However, more studies are required to determine clinically relevant markers specific to a gestational complication of interest, as currently most of them present a significant overlap. Although the independent diagnostic value of such markers remains to be insufficient for implementation in standard clinical practice at the moment, inclusion of certain markers in predictive multifactorial models can improve their prognostic value. The future of the research in this field lies in the fine tuning of the clinical markers to be used, as well as identifying possible therapeutic techniques to prevent or reverse endothelial damage.

Potential roles of imprinted genes in the teratogenic effects of alcohol on the placenta, somatic growth, and the developing brain

Despite several decades of research and prevention efforts, fetal alcohol spectrum disorders (FASD) remain the most common preventable cause of neurodevelopmental disabilities worldwide. Animal and human studies have implicated fetal alcohol-induced alterations in epigenetic programming as a chief mechanism in FASD. Several studies have demonstrated fetal alcohol-related alterations in methylation and expression of imprinted genes in placental, brain, and embryonic tissue. Imprinted genes are epigenetically regulated in a parent-of-origin-specific manner, in which only the maternal or paternal allele is expressed, and the other allele is silenced. The chief functions of imprinted genes are in placental development, somatic growth, and neurobehavior-three domains characteristically affected in FASD. In this review, we summarize the growing body of literature characterizing prenatal alcohol-related alterations in imprinted gene methylation and/or expression and discuss potential mechanistic roles for these alterations in the teratogenic effects of prenatal alcohol exposure. Future research is needed to examine potential physiologic mechanisms by which alterations in imprinted genes disrupt development in FASD, which may, in turn, elucidate novel targets for intervention. Furthermore, mechanistic alterations in imprinted gene expression and/or methylation in FASD may inform screening assays that identify individuals with FASD neurobehavioral deficits who may benefit from early interventions.

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.

Endothelial Progenitor Cells Dysfunctions and Cardiometabolic Disorders: From Mechanisms to Therapeutic Approaches

Metabolic syndrome (MetS) is a cluster of several disorders, such as hypertension, central obesity, dyslipidemia, hyperglycemia, insulin resistance and non-alcoholic fatty liver disease. Despite health policies based on the promotion of physical exercise, the reduction of calorie intake and the consumption of healthy food, there is still a global rise in the incidence and prevalence of MetS in the world. This phenomenon can partly be explained by the fact that adverse events in the perinatal period can increase the susceptibility to develop cardiometabolic diseases in adulthood. Individuals born after intrauterine growth restriction (IUGR) are particularly at risk of developing cardiovascular diseases (CVD) and metabolic disorders later in life. It has been shown that alterations in the structural and functional integrity of the endothelium can lead to the development of cardiometabolic diseases. The endothelial progenitor cells (EPCs) are circulating components of the endothelium playing a major role in vascular homeostasis. An association has been found between the maintenance of endothelial structure and function by EPCs and their ability to differentiate and repair damaged endothelial tissue. In this narrative review, we explore the alterations of EPCs observed in individuals with cardiometabolic disorders, describe some mechanisms related to such dysfunction and propose some therapeutical approaches to reverse the EPCs 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.

Specific arterio-venous transcriptomic and ncRNA-RNA interactions in human umbilical endothelial cells: A meta-analysis

Whether arterial-venous differences of primary endothelial cells commonly used for vascular research are preserved in vitro remains under debate. To address this issue, a meta-analysis of Affymetrix transcriptomic data sets from human umbilical artery (HUAECs) and vein (HUVEC) endothelial cells was performed. The meta-analysis showed 2,742 transcripts differentially expressed (false discovery rate <0.05), of which 78% were downregulated in HUVECs. Comparisons with RNA-seq data sets showed high levels of agreement and correlation (p < 0.0001), identifying 84 arterial-venous identity markers. Functional analysis revealed enrichment of key vascular processes in HUAECs/HUVECs, including nitric oxide- (NO) and hypoxia-related genes, as well as differences in miRNA- and ncRNA-mRNA interaction profiles. A proof of concept of these findings in primary cells exposed to hypoxia in vitro and in vivo confirmed the arterial-venous differences in NO-related genes and miRNAs. Altogether, these data defined a cross-platform arterial-venous transcript profile for cultured HUAEC-HUVEC and support a preserved identity involving key vascular pathways post-transcriptionally regulated in vitro.

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Transcriptional differences among HUAEC and HUVEC are preserved in culture

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These differences occur even after correcting for experimental conditions

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The heterogenous regulation affects NO- and hypoxia-related genes

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Cell-specific ncRNA/mRNA interactions are found

Developmental programming in human umbilical cord vein endothelial cells following fetal growth restriction

BACKGROUND

Fetal growth restriction (FGR) is associated with an increased susceptibility for various noncommunicable diseases in adulthood, including cardiovascular and renal disease. During FGR, reduced uteroplacental blood flow, oxygen and nutrient supply to the fetus are hypothesized to detrimentally influence cardiovascular and renal programming. This study examined whether developmental programming profiles, especially related to the cardiovascular and renal system, differ in human umbilical vein endothelial cells (HUVECs) collected from pregnancies complicated by placental insufficiency-induced FGR compared to normal growth pregnancies. Our approach, involving transcriptomic profiling by RNA-sequencing and gene set enrichment analysis focused on cardiovascular and renal gene sets and targeted DNA methylation assays, contributes to the identification of targets underlying long-term cardiovascular and renal diseases.

RESULTS

Gene set enrichment analysis showed several downregulated gene sets, most of them involved in immune or inflammatory pathways or cell cycle pathways. seven of the 22 significantly upregulated gene sets related to kidney development and four gene sets involved with cardiovascular health and function were downregulated in FGR (n = 11) versus control (n = 8). Transcriptomic profiling by RNA-sequencing revealed downregulated expression of LGALS1, FPR3 and NRM and upregulation of lincRNA RP5-855F14.1 in FGR compared to controls. DNA methylation was similar for LGALS1 between study groups, but relative hypomethylation of FPR3 and hypermethylation of NRM were present in FGR, especially in male offspring. Absolute differences in methylation were, however, small.

CONCLUSION

This study showed upregulation of gene sets related to renal development in HUVECs collected from pregnancies complicated by FGR compared to control donors. The differentially expressed gene sets related to cardiovascular function and health might be in line with the downregulated expression of NRM and upregulated expression of lincRNA RP5-855F14.1 in FGR samples; NRM is involved in cardiac remodeling, and lincRNAs are correlated with cardiovascular diseases. Future studies should elucidate whether the downregulated LGALS1 and FPR3 expressions in FGR are angiogenesis-modulating regulators leading to placental insufficiency-induced FGR or whether the expression of these genes can be used as a biomarker for increased cardiovascular risk. Altered DNA methylation might partly underlie FPR3 and NRM differential gene expression differences in a sex-dependent manner.

MiR-21-5p directly contributes to regulating eNOS expression in human artery endothelial cells under normoxia and hypoxia

Clinical conditions associated with hypoxia and oxidative stress, such as fetal growth restriction (FGR), results in endothelial dysfunction. Previous reports show that changes in eNOS expression under these conditions are tightly controlled by DNA methylation and histone posttranslational modifications. However, the contribution of an orchestrating epigenetic mechanism, such as miRNAs, on the NO-related genes expression has not been addressed. We aimed to determine the levels of miRNAs highly expressed in normal endothelial cells (EC), miR-21 and miR-126, in FGR human umbilical artery EC (HUAEC), and their effects on hypoxia-dependent regulation of both, NO-related and oxidative stress-related genes. Results were validated by transcriptome analysis of HUAEC cultured under chronic low oxygen conditions. Cultured FGR-HUAEC showed decreased hsa-miR-21, DDAH1, SOD1, and NRF2, but increased miR-126, NOX4, and eNOS levels, compared with controls. MiR-21-5p levels in FGR were associated with increased hg-miR-21 gene promoter methylation, with no changes in hg-miR-126 gene promoter methylation. HUAEC exposed to hypoxia showed a transient increase in eNOS and DDAH11, paralleled by decrease miR-21-5p levels, but no changes in miR-126-3p and the other genes under study. Transcriptome profiling showed an inverse relationship among miR-21 and several transcripts targeted by miR-21 in HUAEC exposed to hypoxia, meanwhile miR-21-5p-mimic decreased eNOS and DDAH1 transcripts stability, blocking their induction by hypoxia. Consequently, FGR programs a hypoxia-related miRNA that contributes to the regulation of the NO pathway, involving a direct effect of miR-21-5p on eNOS transcript stability, not previously reported. Moreover, hypoxia downregulates miR-21-5p, contributing to increasing the expression of NO-related genes in arterial endothelial cells.

Gasotransmitters in pregnancy: from conception to uterine involution

Gasotransmitters are endogenous small gaseous messengers exemplified by nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S or sulfide). Gasotransmitters are implicated in myriad physiologic functions including many aspects of reproduction. Our objective was to comprehensively review basic mechanisms and functions of gasotransmitters during pregnancy from conception to uterine involution and highlight future research opportunities. We searched PubMed and Web of Science databases using combinations of keywords nitric oxide, carbon monoxide, sulfide, placenta, uterus, labor, and pregnancy. We included English language publications on human and animal studies from any date through August 2018 and retained basic and translational articles with relevant original findings. All gasotransmitters activate cGMP signaling. NO and sulfide also covalently modify target protein cysteines. Protein kinases and ion channels transduce gasotransmitter signals, and co-expressed gasotransmitters can be synergistic or antagonistic depending on cell type. Gasotransmitters influence tubal transit, placentation, cervical remodeling, and myometrial contractility. NO, CO, and sulfide dilate resistance vessels, suppress inflammation, and relax myometrium to promote uterine quiescence and normal placentation. Cervical remodeling and rupture of fetal membranes coincide with enhanced oxidation and altered gasotransmitter metabolism. Mechanisms mediating cellular and organismal changes in pregnancy due to gasotransmitters are largely unknown. Altered gasotransmitter signaling has been reported for preeclampsia, intrauterine growth restriction, premature rupture of membranes, and preterm labor. However, in most cases specific molecular changes are not yet characterized. Nonclassical signaling pathways and the crosstalk among gasotransmitters are emerging investigation topics.

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.

Adult vascular dysfunction in foetal growth-restricted guinea-pigs is associated with a neonate-adult switching in Nos3 DNA methylation

AIM

Foetal growth restriction (FGR) is associated with endothelial dysfunction and cardiovascular diseases in adult subjects. Early vascular remodelling and epigenetic changes occurring on key endothelial genes might precede this altered vascular function. Further, it has been proposed that oxidative stress during development may determine some of these epigenetic modifications. To address this issue, we studied the in vivo and ex vivo vascular function and Nos3 promoter DNA methylation in arteries from eight-month-old guinea-pig born from control, FGR-treated and FGR-NAC-treated pregnancies.

METHODS

Femoral and carotid arteries in vivo vascular function were determined by Doppler, whilst ex vivo vascular function and biomechanical properties were assessed by wire myography. Levels of eNOS mRNA and site-specific DNA methylation in Nos3 promoter in aorta endothelial cells (AEC) were determined by qPCR and pyrosequencing respectively.

RESULTS

FGR adult showed an increased femoral vascular resistance (P < .05), stiffness (P < .05) and arterial remodelling (P < .01), along with an impaired NO-mediated relaxation (P < .001). These effects were prevented by maternal treatment with NAC. Endothelial-NOS mRNA levels were decreased in FGR adult compared with control and FGR-NAC (P < .05), associated with increased DNA methylation levels (P < .01). Comparison of Nos3 DNA methylation in AEC showed a differential methylation pattern between foetal and adult guinea-pigs (P < .05).

CONCLUSION

Altogether, these data suggest that adult vascular dysfunction in the FGR does not result from early changes in Nos3 promoter DNA methylation, but from an altered vessel structure established during foetal development.

Epigenetic Modulation in the Initiation and Progression of Pulmonary Hypertension

Pulmonary hypertension (PH) is a severe disease with multiple etiologies. In addition to genetics, recent studies have revealed the epigenetic modulation in the initiation and progression of PH. In this review, we summarize the epigenetic mechanisms in the pathogenesis of PH, specifically, DNA methylation, histone modifications, and microRNAs. We further emphasize the diagnostic and therapeutic potential of these epigenetic hallmarks in PH. Finally, we highlight the developmental reprogramming in adult-onset PH because of adverse perinatal exposures such as intrauterine growth restriction and extrauterine growth restriction. Therefore, epigenetic modifications provide promise for the therapy and prevention of PH.

Premature Vascular Aging in Guinea Pigs Affected by Fetal Growth Restriction

Cardiovascular risk associated with fetal growth restriction (FGR) could result from an early impaired vascular function. However, whether this effect results in premature vascular aging has not been addressed. We studied the ex vivo reactivity of carotid and femoral arteries in fetal (near term), adults (eight months-old) and aged (16 months-old) guinea pigs in normal (control) and FGR offspring. Additionally, an epigenetic marker of vascular aging (i.e., LINE-1 DNA methylation) was evaluated in human umbilical artery endothelial cells (HUAEC) from control and FGR subjects. Control guinea pig arteries showed an increased contractile response (KCl-induced) and a progressive impairment of NO-mediated relaxing responses as animals get older. FGR was associated with an initial preserved carotid artery reactivity as well as a later significant impairment in NO-mediated responses. Femoral arteries from FGR fetuses showed an increased contractility but a decreased relaxing response compared with control fetuses, and both responses were impaired in FGR-adults. Finally, FGR-HUAEC showed decreased LINE-1 DNA methylation compared with control-HUAEC. These data suggest that the aging of vascular function occurs by changes in NO-mediated responses, with limited alterations in contractile capacity. Further, these effects are accelerated and imposed at early stages of development in subjects exposed to a suboptimal intrauterine environment.

Maternal hyperglycemia and fetal cardiac development: Clinical impact and underlying mechanisms

Congenital heart disease (CHD) is the most common type of birth defect and is both a significant pediatric and adult health problem, in light of a growing population of survivors. The etiology of CHD has been considered to be multifactorial with genetic and environmental factors playing important roles. The combination of advances in cardiac developmental biology, which have resulted in the elucidation of molecular pathways regulating normal cardiac morphogenesis, and genome sequencing technology have allowed the discovery of numerous genetic contributors of CHD ranging from chromosomal abnormalities to single gene variants. Conversely, mechanistic details of the contribution of environmental factors to CHD remain unknown. Maternal diabetes mellitus (matDM) is a well-established and increasingly prevalent environmental risk factor for CHD, but the underlying etiologic mechanisms by which pregestational matDM increases the vulnerability of embryos to cardiac malformations remains largely elusive. Here, we will briefly discuss the multifactorial etiology of CHD with a focus on the epidemiologic link between matDM and CHD. We will describe the animal models used to study the underlying mechanisms between matDM and CHD and review the numerous cellular and molecular pathways affected by maternal hyperglycemia in the developing heart. Last, we discuss how this increased understanding may open the door for the development of novel prevention strategies to reduce the incidence of CHD in this high-risk population.

Human umbilical artery endothelial cells from Large-for-Gestational-Age newborn have increased antioxidant efficiency and gene expression

Obesity is a public health problem worldwide, and especially in women in reproductive age where more than one in three have obesity. Maternal obesity is associated with an increased maternal, placental, and newborn oxidative stress, which has been proposed as a central factor in vascular dysfunction in large-for-gestational-age (LGA) newborn. However, cellular and molecular mechanisms behind this effect have not been elucidated. Untreated human umbilical artery endothelial cells (HUAEC) from LGA (LGA-HUAEC) presented higher O₂ ^- levels, superoxide dismutase activity and heme oxygenase 1 messenger RNA (mRNA) levels, paralleled by reduced GSH:GSSG ratio and NRF2 mRNA levels. In response to an oxidative challenge (hydrogen peroxide), only HUAEC from LGA exhibited an enhanced Glutathione Peroxidase 1 (GPX1) expression, as well as a more efficient antioxidant machinery measured by the biosensor probe, HyPer. An open state of chromatin in the TSS region of GPX1 in LGA-HUAEC was evidenced by the DNase-HS assay. Altogether, our data indicate that LGA-HUAEC have an altered cellular and molecular antioxidant system. We propose that a chronic pro-oxidant intrauterine milieu, as evidenced in pregestational obesity, could induce a more efficient antioxidant system in fetal vascular cells, which could be maintained by epigenetic mechanism during postnatal life.

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.

Cardiovascular Programming During and After Diabetic Pregnancy: Role of Placental Dysfunction and IUGR

Intrauterine growth restriction (IUGR) is a condition whereby a fetus is unable to achieve its genetically determined potential size. IUGR is a global health challenge due to high mortality and morbidity amongst affected neonates. It is a multifactorial condition caused by maternal, fetal, placental, and genetic confounders. Babies born of diabetic pregnancies are usually large for gestational age but under certain conditions whereby prolonged uncontrolled hyperglycemia leads to placental dysfunction, the outcome of the pregnancy is an intrauterine growth restricted fetus with clinical features of malnutrition. Placental dysfunction leads to undernutrition and hypoxia, which triggers gene modification in the developing fetus due to fetal adaptation to adverse utero environmental conditions. Thus, in utero gene modification results in future cardiovascular programming in postnatal and adult life. Ongoing research aims to broaden our understanding of the molecular mechanisms and pathological pathways involved in fetal programming due to IUGR. There is a need for the development of effective preventive and therapeutic strategies for the management of growth-restricted infants. Information on the mechanisms involved with in utero epigenetic modification leading to development of cardiovascular disease in adult life will increase our understanding and allow the identification of susceptible individuals as well as the design of targeted prevention strategies. This article aims to systematically review the latest molecular mechanisms involved in the pathogenesis of IUGR in cardiovascular programming. Animal models of IUGR that used nutrient restriction and hypoxia to mimic the clinical conditions in humans of reduced flow of nutrients and oxygen to the fetus will be discussed in terms of cardiac remodeling and epigenetic programming of cardiovascular disease. Experimental evidence of long-term fetal programming due to IUGR will also be included.

Knowledge Gaps and Emerging Research Areas in Intrauterine Growth Restriction-Associated Brain Injury

Intrauterine growth restriction (IUGR) is a complex global healthcare issue. Concerted research and clinical efforts have improved our knowledge of the neurodevelopmental sequelae of IUGR which has raised the profile of this complex problem. Nevertheless, there is still a lack of therapies to prevent the substantial rates of fetal demise or the constellation of permanent neurological deficits that arise from IUGR. The purpose of this article is to highlight the clinical and translational gaps in our knowledge that hamper our collective efforts to improve the neurological sequelae of IUGR. Also, we draw attention to cutting-edge tools and techniques that can provide novel insights into this disorder, and technologies that offer the potential for better drug design and delivery. We cover topics including: how we can improve our use of crib-side monitoring options, what we still need to know about inflammation in IUGR, the necessity for more human post-mortem studies, lessons from improved integrated histology-imaging analyses regarding the cell-specific nature of magnetic resonance imaging (MRI) signals, options to improve risk stratification with genomic analysis, and treatments mediated by nanoparticle delivery which are designed to modify specific cell functions.

Arginine bioavailability and endothelin-1 system in the regulation of vascular function of umbilical vein endothelial cells from intrauterine growth restricted newborns

BACKGROUND AND AIMS

Intrauterine growth restriction (IUGR) is a major risk factor for perinatal morbidity and mortality, leading to long-term adverse cardiovascular outcomes. The present study aimed to investigate the potential mechanisms in IUGR-associated vascular endothelial dysfunction.

METHODS AND RESULTS

Human umbilical vein endothelial cells (HUVECs) were derived from IUGR or normal newborns. We found that the proliferation of IUGR-derived HUVECs was accelerated compared to those from normal subjects. Gene profiles related to vascular function including vasomotion, oxidative stress, and angiogenesis were dysregulated in IUGR-HUVECs. Compared with HUVECs from normal newborns, nitric oxide (NO) production was reduced, with imbalance between endothelial nitric oxide synthase (eNOS) and arginase-2 (Arg-2) in IUGR. Meanwhile, intracellular asymmetric dimethylarginine (ADMA) level was elevated with diminished dimethylarginine dimethylaminohydrolase 1 (DDAH1) expression in IUGR-HUVECs. Furthermore, endothelin-1 (ET-1) and hypoxia-inducible factor 1α (HIF-1α) expression were increased, and endothelin receptor type-B (ET_BR) was reduced in the IUGR group. IUGR-HUVECs exposed to hypoxia increased the ratio of ADMA to l-arginine, HIF-1α and protein arginine methyltransferase 1 (PRMT1) expression compared to controls.

CONCLUSIONS

The present study demonstrated that the reduction of NO bioavailability and release results from elevated Arg-2, accumulation of intracellular ADMA, and imbalance of ET-1 and ET_BR, further leading to IUGR-associated vascular endothelial dysfunction. Our study provides novel evidence on the mechanism underlying fetal programming associated with IUGR, which will serve as potential therapeutic targets in the prevention of adverse cardiovascular consequences in adulthood.

Guinea pig models for translation of the developmental origins of health and disease hypothesis into the clinic

Over 30 years ago Professor David Barker first proposed the theory that events in early life could explain an individual's risk of non-communicable disease in later life: the developmental origins of health and disease (DOHaD) hypothesis. During the 1990s the validity of the DOHaD hypothesis was extensively tested in a number of human populations and the mechanisms underpinning it characterised in a range of experimental animal models. Over the past decade, researchers have sought to use this mechanistic understanding of DOHaD to develop therapeutic interventions during pregnancy and early life to improve adult health. A variety of animal models have been used to develop and evaluate interventions, each with strengths and limitations. It is becoming apparent that effective translational research requires that the animal paradigm selected mirrors the tempo of human fetal growth and development as closely as possible so that the effect of a perinatal insult and/or therapeutic intervention can be fully assessed. The guinea pig is one such animal model that over the past two decades has demonstrated itself to be a very useful platform for these important reproductive studies. This review highlights similarities in the in utero development between humans and guinea pigs, the strengths and limitations of the guinea pig as an experimental model of DOHaD and the guinea pig's potential to enhance clinical therapeutic innovation to improve human health.

Interleukin-6 determines protein stabilization of DNA methyltransferases and alters DNA promoter methylation of genes associated with insulin signaling and angiogenesis

Individuals with type 2 diabetes (T2D) display vascular insulin resistance and decreased nitric oxide production leading to vasoconstriction and atherosclerosis. Soluble factors such as pro-inflammatory molecules, and various genetic and epigenetic mechanisms have been implicated to induce insulin resistance in vascular endothelial cells. Epigenetic mechanisms such as altered promoter DNA methylation have been demonstrated in development and progression of metabolic disorders and atherosclerosis. However, underlying precise epigenetic mechanisms regulating cross talk between insulin signaling genes and inflammation in vascular cells remains to be fully understood. Human endothelial cells when (a) treated with interleukin-6 (IL-6) and insulin together, (b) pretreated with IL-6, and (c) under hyperinsulinemic conditions led to a state of vascular insulin resistance resulting in decreased Akt/eNOS activation and subsequent stabilization of STAT3 phosphorylation. IL-6 abrogated insulin effects on angiogenesis in 3D spheroid and matrigel assays. IL-6-induced insulin resistance was associated with decreased activity of DNA methyltransferase isoforms and global DNA hypomethylation, which inversely correlated with S-phase of cell cycle. CpG microarray analysis in IL-6 treated endothelial cells revealed promoters associated hypo- and hypermethylation of 199 and 98 genes respectively. Promoter DNA methylation status of genes associated with insulin signaling and angiogenesis such as RPS6KA2, PIK3R2, FOXD3, EXOC7, MAP3K8, ITPKB, EPHA6, IGF1R, and FOXC2 were validated by bisulfite DNA sequencing. Concentration and time-dependent analysis revealed that IL-6 reduced DNMT1 and DNMT3B but not DNMT3A protein levels. Our data indicate a causal link between IL-6-induced changes in global and promoter-specific DNA methylation, due to reduced DNMT1 and DNMT3B protein levels leading to altered expression of critical genes involved in insulin signaling and angiogenesis.

Chronic hypoxia upregulates DNA methyltransferase and represses large conductance Ca2+-activated K+ channel function in ovine uterine arteries

Chronic hypoxia during gestation suppresses large-conductance Ca2+-activated K+ (BKCa) channel function and impedes uterine arterial adaptation to pregnancy. This study tested the hypothesis that chronic hypoxia has a direct effect in upregulating DNA methyltransferase (DNMT) and epigenetically repressing BKCa channel beta-1 subunit (KCNMB1) expression in uterine arteries. Resistance-sized uterine arteries were isolated from near-term pregnant sheep maintained at ∼300 m above sea level or animals acclimatized to high-altitude (3,801 m) hypoxia for 110 days during gestation. For ex vivo hypoxia treatment, uterine arteries from normoxic animals were treated with 21.0% O2 or 10.5% O2 for 48 h. High-altitude hypoxia significantly upregulated DNMT3b expression and enzyme activity in uterine arteries. Similarly, ex vivo hypoxia treatment upregulated DNMT3b expression and enzyme activity that was blocked by a DNMT inhibitor 5-aza-2'-deoxycytidine (5-Aza). Of importance, 5-Aza inhibited hypoxia-induced hypermethylation of specificity protein (SP) 1 binding site at the KCNMB1 promoter and restored transcription factor binding to the KCNMB1 promoter, resulting in the recovery of KCNMB1 gene expression in uterine arteries. Furthermore, 5-Aza blocked the effect of hypoxia and rescued BKCa channel activity and reversed hypoxia-induced decrease in BKCa channel-mediated relaxations and increase in myogenic tone of uterine arteries. Collectively, these results suggest that chronic hypoxia during gestation upregulates DNMT expression and activity, resulting in hypermethylation and repression of KCNMB1 gene and BKCa channel function, impeding uterine arterial adaptation to pregnancy.

Implication of Oxidative Stress in Fetal Programming of Cardiovascular Disease

Lifestyle and genetic background are well known risk factors of cardiovascular disease (CVD). A third contributing factor is suboptimal fetal development, due to nutrient or oxygen deprivation, placental insufficiency, or exposure to toxic substances. The fetus adapts to adverse intrauterine conditions to ensure survival; the immediate consequence is low birth weight (LBW) and the long-term effect is an increased susceptibility to develop CVD in adult life. This process is known as Developmental Origins of Health and Disease (DOHaD) or fetal programming of CVD. The influence of fetal life for the future cardiovascular health of the individual has been evidenced by numerous epidemiologic studies in populations suffering from starvation during intrauterine life. Furthermore, experimental animal models have provided support and enabled exploring the underlying mechanisms. Oxidative stress seems to play a central role in fetal programming of CVD, both in the response of the feto-placental unit to the suboptimal intrauterine environment and in the alterations of physiologic systems of cardiovascular control, ultimately leading to disease. This review aims to summarize current knowledge on the alterations in oxidative balance in response to fetal stress factors covering two aspects. Firstly, the evidence from human studies of the implication of oxidative stress in LBW induced by suboptimal conditions during intrauterine life, emphasizing the role of the placenta. In the second part we summarize data on specific redox alterations in key cardiovascular control organs induced by exposure to known stress factors in experimental animals and discuss the emerging role of the mitochondria.

Epigenetic Regulation and Its Therapeutic Potential in Pulmonary Hypertension

Recent advances in epigenetics have made a tremendous impact on our knowledge of biological phenomena and the environmental stressors on complex diseases. Understanding the mechanism of epigenetic reprogramming during the occurrence of pulmonary hypertension (PH) is important for advanced studies and clinical therapy. In this article, we review the discovery of novel epigenetic mechanisms associated with PH including DNA methylation, histone modification, and noncoding RNA interference. In addition, we highlight the role of epigenetic mechanisms in adult PAH resulting from undesirable perinatal environments-Extrauterine growth restriction (EUGR) and Intrauterine growth retardation (IUGR). Lastly, we give a comprehensive summary for the remaining challenges and discuss future methods of epigenetic targeted therapy for pulmonary hypertension.

The Mammalian Target of Rapamycin and DNA methyltransferase 1 axis mediates vascular endothelial dysfunction in response to disturbed flow

The earliest atherosclerotic lesions preferentially develop in arterial regions experienced disturbed blood flow, which induces endothelial expression of pro-atherogenic genes and the subsequent endothelial dysfunction. Our previous study has demonstrated an up-regulation of DNA methyltransferase 1 (DNMT1) and a global hypermethylation in vascular endothelium subjected to disturbed flow. Here, we determined that DNMT1-specific inhibition in arterial wall ameliorates the disturbed flow-induced atherosclerosis through, at least in part, targeting cell cycle regulator cyclin A and connective tissue growth factor (CTGF). We identified the signaling pathways mediating the flow-induction of DNMT1. Inhibition of the mammalian target of rapamycin (mTOR) suppressed the DNMT1 up-regulation both in vitro and in vivo. Together, our results demonstrate that disturbed flow influences endothelial function and induces atherosclerosis in an mTOR/DNMT1-dependent manner. The conclusions obtained from this study might facilitate further evaluation of the epigenetic regulation of endothelial function during the pathological development of atherosclerosis and offer novel prevention and therapeutic targets of this disease.

Epigenetic mechanisms underlying maternal diabetes-associated risk of congenital heart disease

Birth defects are the leading cause of infant mortality, and they are caused by a combination of genetic and environmental factors. Environmental risk factors may contribute to birth defects in genetically susceptible infants by altering critical molecular pathways during embryogenesis, but experimental evidence for gene-environment interactions is limited. Fetal hyperglycemia associated with maternal diabetes results in a 5-fold increased risk of congenital heart disease (CHD), but the molecular basis for this correlation is unknown. Here, we show that the effects of maternal hyperglycemia on cardiac development are sensitized by haploinsufficiency of Notch1, a key transcriptional regulator known to cause CHD. Using ATAC-seq, we found that hyperglycemia decreased chromatin accessibility at the endothelial NO synthase (Nos3) locus, resulting in reduced NO synthesis. Transcription of Jarid2, a regulator of histone methyltransferase complexes, was increased in response to reduced NO, and this upregulation directly resulted in inhibition of Notch1 expression to levels below a threshold necessary for normal heart development. We extended these findings using a Drosophila maternal diabetic model that revealed the evolutionary conservation of this interaction and the Jarid2-mediated mechanism. These findings identify a gene-environment interaction between maternal hyperglycemia and Notch signaling and support a model in which environmental factors cause birth defects in genetically susceptible infants.

Endothelial dysfunction in individuals born after fetal growth restriction: cardiovascular and renal consequences and preventive approaches

Individuals born after intrauterine growth restriction (IUGR) have an increased risk of perinatal morbidity/mortality, and those who survive face long-term consequences such as cardiovascular-related diseases, including systemic hypertension, atherosclerosis, coronary heart disease and chronic kidney disease. In addition to the demonstrated long-term effects of decreased nephron endowment and hyperactivity of the hypothalamic-pituitary-adrenal axis, individuals born after IUGR also exhibit early alterations in vascular structure and function, which have been identified as key factors of the development of cardiovascular-related diseases. The endothelium plays a major role in maintaining vascular function and homeostasis. Therefore, it is not surprising that impaired endothelial function can lead to the long-term development of vascular-related diseases. Endothelial dysfunction, particularly impaired endothelium-dependent vasodilation and vascular remodeling, involves decreased nitric oxide (NO) bioavailability, impaired endothelial NO synthase functionality, increased oxidative stress, endothelial progenitor cells dysfunction and accelerated vascular senescence. Preventive approaches such as breastfeeding, supplementation with folate, vitamins, antioxidants, L-citrulline, L-arginine and treatment with NO modulators represent promising strategies for improving endothelial function, mitigating long-term outcomes and possibly preventing IUGR of vascular origin. Moreover, the identification of early biomarkers of endothelial dysfunction, especially epigenetic biomarkers, could allow early screening and follow-up of individuals at risk of developing cardiovascular and renal diseases, thus contributing to the development of preventive and therapeutic strategies to avert the long-term effects of endothelial dysfunction in infants born after IUGR.

IL-10 expression in macrophages from neonates born from obese mothers is suppressed by IL-4 and LPS/INFγ

Obese women offspring have a higher risk of developing chronic diseases associated with an altered immune function. We aim to determine, in neonatal monocyte-derived macrophages, whether maternal obesity is associated with an altered expression and DNA methylation of pro- and anti-inflammatory genes, along with a higher pro-inflammatory response. Cord blood from newborns of obese (Ob) and lean (control) women were obtained at delivery. Monocytes were isolated and differentiated into macrophages, in which M1 (LPS/IFNγ) and M2 (IL-4) polarization were assayed. The mRNA levels for TNFα, IL-1β, IL-12A, IL-12B, IL-10, and IL-4R were quantified by qPCR and the DNA methylation of candidate genes determined by pyrosequencing.

RESULTS

Ob-monocytes had decreased levels of mRNA for pro-inflammatory cytokines IL-1β, IL-10, and IL-12B compared with controls. Conversely, Ob-macrophages showed increased levels of mRNA for TNFα, IL-4R, and IL-10 compared with controls. M1 response was comparable between both groups, characterized by an important induction of TNFα and IL-1β. In response to an M2 stimulus, control macrophages showed a decreased expression of inflammatory mediators while Ob-macrophages had an additional suppression of the anti-inflammatory mediator IL-10. Changes in IL-1β (monocytes) and IL-10 (macrophages) in Ob-monocytes were paralleled by changes in their promoter DNA methylation in fetal monocytes. These results suggest that monocyte-derived macrophages from obese newborns show a basal anti-inflammatory phenotype with an unbalanced response to M1 and M2 polarization stimuli. The presence of changes in DNA methylation of key inflammatory genes in neonatal monocytes suggests an intrauterine programing of immune function by maternal obesity.

Pregnancy as a critical window for blood pressure regulation in mother and child: programming and reprogramming

Pregnancy is a critical time for long-term blood pressure regulation in both mother and child. Pregnancies complicated by placental insufficiency, resulting in pre-eclampsia and intrauterine growth restriction, are associated with a threefold increased risk of the mother to develop hypertension later in life. In addition, these complications create an adverse intrauterine environment, which programmes the foetus and the second generation to develop hypertension in adult life. Female offspring born to a pregnancy complicated by placental insufficiency are at risk for pregnancy complications during their own pregnancies as well, resulting in a vicious circle with programmed risk for hypertension passing from generation to generation. Here, we review the epidemiology and mechanisms leading to the altered programming of blood pressure trajectories after pregnancies complicated by placental insufficiency. Although the underlying mechanisms leading to hypertension remain the subject of investigation, several abnormalities in angiotensin sensitivity, sodium handling, sympathetic activity, endothelial function and metabolic pathways are found in the mother after exposure to placental insufficiency. In the child, epigenetic modifications and disrupted organ development play a crucial role in programming of hypertension. We emphasize that pregnancy can be viewed as a window of opportunity to improve long-term cardiovascular health of both mother and child, and outline potential gains expected of improved preconceptional, perinatal and post-natal care to reduce the development of hypertension and the burden of cardiovascular disease later in life. Perinatal therapies aimed at reprogramming hypertension are a promising strategy to break the vicious circle of intergenerational programming of hypertension.

N-Acetylcysteine, a glutathione precursor, reverts vascular dysfunction and endothelial epigenetic programming in intrauterine growth restricted guinea pigs

KEY POINTS

Intrauterine growth restriction (IUGR) is associated with vascular dysfunction, oxidative stress and signs of endothelial epigenetic programming of the umbilical vessels. There is no evidence that this epigenetic programming is occurring on systemic fetal arteries. In IUGR guinea pigs we studied the functional and epigenetic programming of endothelial nitric oxide synthase (eNOS) (Nos3 gene) in umbilical and systemic fetal arteries, addressing the role of oxidative stress in this process by maternal treatment with N-acetylcysteine (NAC) during the second half of gestation. The present study suggests that IUGR endothelial cells have common molecular markers of programming in umbilical and systemic arteries. Notably, maternal treatment with NAC restores fetal growth by increasing placental efficiency and reverting the functional and epigenetic programming of eNOS in arterial endothelium in IUGR guinea pigs.

ABSTRACT

In humans, intrauterine growth restriction (IUGR) is associated with vascular dysfunction, oxidative stress and signs of endothelial programming in umbilical vessels. We aimed to determine the effects of maternal antioxidant treatment with N-acetylcysteine (NAC) on fetal endothelial function and endothelial nitric oxide synthase (eNOS) programming in IUGR guinea pigs. IUGR was induced by implanting ameroid constrictors on uterine arteries of pregnant guinea pigs at mid gestation, half of the sows receiving NAC in the drinking water (from day 34 until term). Fetal biometry and placental vascular resistance were followed by ultrasound throughout gestation. At term, umbilical arteries and fetal aortae were isolated to assess endothelial function by wire-myography. Primary cultures of endothelial cells (ECs) from fetal aorta, femoral and umbilical arteries were used to determine eNOS mRNA levels by quantitative PCR and analyse DNA methylation in the Nos3 promoter by pyrosequencing. Doppler ultrasound measurements showed that NAC reduced placental vascular resistance in IUGR (P < 0.05) and recovered fetal weight (P < 0.05), increasing fetal-to-placental ratio at term (∼40%) (P < 0.001). In IUGR, NAC treatment restored eNOS-dependent relaxation in aorta and umbilical arteries (P < 0.05), normalizing eNOS mRNA levels in EC fetal and umbilical arteries (P < 0.05). IUGR-derived ECs had a decreased DNA methylation (∼30%) at CpG -170 (from the transcription start site) and this epigenetic signature was absent in NAC-treated fetuses (P < 0.001). These data show that IUGR-ECs have common molecular markers of eNOS programming in umbilical and systemic arteries and this effect is prevented by maternal treatment with antioxidants.

Oxytocin, a main breastfeeding hormone, prevents hypertension acquired in utero: A therapeutics preview

Hypertension is a major risk factor for ischemic heart disease and stroke, leading causes of morbidity and death worldwide. Intrauterine growth restriction (IUGR), caused by an excess of glucocorticoid exposure to the fetus, produces an imbalance in oxidative stress altering many biochemical and epigenetic gene transcription processes exposing the fetus and neonate to the 'thrifty' phenotype and pervasive polymorphisms appearance damaging health, cognitive, and behavioral processes in later life. OT is a major regulator of oxidative stress radicals that plays a major role in neonatal maturation of the central nervous system and many peripheral tissues expressing oxytocin/oxytocin-receptor (OT/OTR) system in the early postnatal period. OT and OTR are damaged by IUGR and early stress. This review highlights the fact that hypertension is likely to be a legacy of preterm birth due to IUGR and failure to meet nutritional needs in early infancy when fed formula instead of breastfeeding or human milk.

Nitric oxide, the new architect of epigenetic landscapes

Nitric oxide (NO) is an endogenously produced signaling molecule with multiple regulatory functions in physiology and disease. The most studied molecular mechanisms underlying the biological functions of NO include its reaction with heme proteins and regulation of protein activity via modification of thiol residues. A significant number of transcriptional responses and phenotypes observed in NO microenvironments, however, still lack mechanistic understanding. Recent studies shed new light on NO signaling by revealing its influence on epigenetic changes within the cell. Epigenetic alterations are important determinants of transcriptional responses and cell phenotypes, which can relay heritable information during cell division. As transcription across the genome is highly sensitive to these upstream epigenetic changes, this mode of NO signaling provides an alternate explanation for NO-mediated gene expression changes and phenotypes. This review will provide an overview of the interplay between NO and epigenetics as well as emphasize the unprecedented importance of these pathways to explain phenotypic effects associated with biological NO synthesis.

In Utero Origins of Hypertension: Mechanisms and Targets for Therapy

The developmental origins of health and disease theory is based on evidence that a suboptimal environment during fetal and neonatal development can significantly impact the evolution of adult-onset disease. Abundant evidence exists that a compromised prenatal (and early postnatal) environment leads to an increased risk of hypertension later in life. Hypertension is a silent, chronic, and progressive disease defined by elevated blood pressure (>140/90 mmHg) and is strongly correlated with cardiovascular morbidity/mortality. The pathophysiological mechanisms, however, are complex and poorly understood, and hypertension continues to be one of the most resilient health problems in modern society. Research into the programming of hypertension has proposed pharmacological treatment strategies to reverse and/or prevent disease. In addition, modifications to the lifestyle of pregnant women might impart far-reaching benefits to the health of their children. As more information is discovered, more successful management of hypertension can be expected to follow; however, while pregnancy complications such as fetal growth restriction, preeclampsia, preterm birth, etc., continue to occur, their offspring will be at increased risk for hypertension. This article reviews the current knowledge surrounding the developmental origins of hypertension, with a focus on mechanistic pathways and targets for therapeutic and pharmacologic interventions.

5-Hydroxymethylcytosine-mediated alteration of transposon activity associated with the exposure to adverse in utero environments in human

Preeclampsia and gestational diabetes mellitus (GDM) are the most common clinical conditions in pregnancy that could result in adverse in utero environments. Fetal exposure to poor environments may raise the long-term risk of postnatal disorders, while epigenetic modifications could be involved. Recent research has implicated involvement of 5-hydroxymethylcytosine (5hmC), a DNA base derived from 5-methylcytosine, via oxidation by ten-eleven translocation (TET) enzymes, in DNA methylation-related plasticity. Here, we show that the TET2 expression and 5hmC abundance are significantly altered in the umbilical veins of GDM and preeclampsia. Genome-wide profiling of 5hmC revealed its specific reduction on intragenic regions from both GDM and preeclampsia compared to healthy controls. Gene Ontology analysis using loci bearing unique GDM- and preeclampsia-specific loss-of-5hmC indicated its impact on several critical biological pathways. Interestingly, the substantial alteration of 5hmC on several transposons and repetitive elements led to their differential expression. The alteration of TET expression, 5hmC levels and 5hmC-mediated transposon activity was further confirmed using established hypoxia cell culture model, which could be rescued by vitamin C, a known activator of TET proteins. Together, these results suggest that adverse pregnancy environments could influence 5hmC-mediated epigenetic profile and contribute to abnormal development of fetal vascular systems that may lead to postnatal diseases.

Markers of early endothelial dysfunction in intrauterine growth restriction-derived human umbilical vein endothelial cells revealed by 2D-DIGE and mass spectrometry analyses

Intrauterine growth restriction (IUGR) associates with fetal and placental vascular dysfunction, and increased cardiovascular risk later on life. We hypothesize that endothelial cells derived from IUGR umbilical veins present significant changes in the proteome which could be involved in the endothelial dysfunction associated to this conditions. To address this the proteome profile of human umbilical endothelial cells (HUVEC) isolated from control and IUGR pregnancies was compared by 2D-Differential In Gel Electrophoresis (DIGE) and further protein identification by MALDI-TOF MS. Using 2D-DIGE 124 spots were identified as differentially expressed between control and IUGR HUVEC, considering a cut-off of 2 fold change, which represented ∼10% of the total spots detected. Further identification by MALDI-TOF MS and in silico clustering of the proteins showed that those differentially expressed proteins between control and IUGR HUVEC were mainly related with cytoskeleton organization, proteasome degradation, oxidative stress response, mRNA processing, chaperones and vascular function. Finally Principal Component analysis of the identified proteins showed that differentially expressed proteins allow distinguishing between control and IUGR HUVEC based on their proteomic profile. This study demonstrates for the first time that IUGR-derived HUVEC maintained in primary culture conditions present an altered proteome profile, which could reflect an abnormal programming of endothelial function in this fetal condition.

Impact of oxidative stress during pregnancy on fetal epigenetic patterns and early origin of vascular diseases

Epidemiological studies have led scientists to postulate the developmental origins of health and disease hypothesis for noncommunicable diseases such as diabetes, cardiovascular diseases, hypertension, and obesity. However, the cellular and molecular mechanisms involved in the development of these diseases are not well understood. In various animal models, it has been observed that oxidative stress during pregnancy is associated with the early development of endothelial dysfunction in offspring. This phenomenon suggests that endothelial dysfunction may initiate in the uterus and could lead to increased risk of cardiovascular disease later in life. Currently, it is known that many of the fetal adaptive responses to environmental factors are mediated by epigenetic changes in the genome, especially by the degree of methylation in cytosines in the promoter regions of genes. These findings suggest that the establishment of a particular epigenetic pattern in the genome may be generated by oxidative stress.

Arginase-2 is cooperatively up-regulated by nitric oxide and histone deacetylase inhibition in human umbilical artery endothelial cells

Arginase-2 counteracts endothelial nitric oxide synthase (eNOS) activity in human endothelium, and its expression is negatively controlled by histone deacetylase (HDAC2). Conversely NO inhibits HDAC and previous studies suggest that arginase-2 is up-regulated by NO. We studied whether NO regulates arginase-2 expression in umbilical artery endothelial cells (HUAEC) increasing ARG2 promoter accessibility. HUAEC exposed to NOC-18 (NO donor, 1-100 μM, 0-24 h) showed an increase in arginase-2 but a decrease in eNOS mRNA levels in a time-dependent manner, with a maximal effect at 100 μM (24 h). Conversely NOS inhibition with L-NAME (100 μM) reduced arginase-2 mRNA and protein levels, an effect reverted by co-incubation with NOC-18. Treatment with TSA paralleled the effects of NO on arginase-2 and eNOS at mRNA and protein levels, with maximal effect at 10 μM. Co-incubation of NOC-18 (100 μM) with a sub-maximal concentration of TSA (1 μM) potentiated the increase in arginase-2 mRNA levels, whilst L-NAME prevented TSA-dependent arginase-2 induction. The effects on arginase-2 mRNA were paralleled by changes in chromatin accessibility, as well as increased levels of H3K9 and H4K12 acetylation, at ARG2 proximal (-579 to -367 and -280 to -73 bp from TSS) and core (-121 to +126 bp from TSS) promoter. Finally NO-dependent arginase-2 induction was prevented by pre-incubation for 10 min with the cysteine blocker MMTS (10 mM). These data showed for the first time that NO up-regulates arginase-2 expression in primary cultured human endothelial cells by an epigenetic-mediated mechanism increasing ARG2 promoter accessibility suggesting a negative regulatory loop for eNOS activity.