Functional analysis of the human endothelial nitric oxide synthase promoter. Sp1 and GATA factors are necessary for basal transcription in endothelial cells

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.

Salvia miltiorrhiza augments endothelial cell function for ischemic hindlimb recovery

Salvia miltiorrhiza (Salvia miltiorrhiza) root, as a traditional herb, is widely applied to pharmacotherapy for vascular system disease. In this study, we elucidate the therapy mechanism of Salvia miltiorrhiza by using a model of hindlimb ischemia. Blood perfusion measurement showed that intravenous administration of the Water Extract of Salvia miltiorrhiza (WES) could facilitate damaged hindlimb blood flow recovery and blood vessel regeneration. In vitro mRNA screen assay in cultured human umbilical vein endothelial cells (HUVECs) show that WES induced increased NOS3, VEGFA, and PLAU mRNA levels. Endothelial NOS (eNOS) promotor reporter analysis revealed that WES and the major ingredients danshensu (DSS) could enhance eNOS promoter activity. Additionally, we found that WES and its ingredients, including DSS, protocatechuic aldehyde (PAI), and salvianolic acid A (SaA), promoted HUVECs growth by the endothelial cell viability assays. A mechanistic approach confirmed that WES augments HUVECs proliferation through the activation of extracellular signal-regulated kinase (ERK) signal pathway. This study reveals that WES promotes ischemic remodeling and angiogenesis through its multiple principal ingredients, which target and regulate multiple sites of the network of the blood vessel endothelial cell regenerating process.

Lymphocyte-Specific Protein 1 Regulates Expression and Stability of Endothelial Nitric Oxide Synthase

Nitric oxide (NO), synthesized by endothelial nitric oxide synthase (eNOS), plays a critical role in blood pressure regulation. Genome-wide association studies have identified genetic susceptibility loci for hypertension in human lymphocyte-specific protein 1 (LSP1) gene. LSP1 is recognized as modulator of leukocyte extravasation, and endothelial permeability, however, the role of LSP1 in regulation of NO signaling within endothelial cells (ECs) remains unknown. The present study investigated the role of LSP1 in the regulation of eNOS expression and activity utilizing human macrovascular ECs in vitro and LSP1 knockout (KO) mice. In ECs, specific CRISPR-Cas9 genomic editing deleted LSP1 and caused downregulation of eNOS expression. LSP1 gain-of-function through adenovirus-mediated gene transfer was associated with enhanced expression of eNOS. Co-immunoprecipitation and confocal fluorescence microscopy revealed that eNOS and LSP1 formed a protein complex under basal conditions in ECs. Furthermore, LSP1 deficiency in mice promoted significant upregulation and instability of eNOS. Utilizing a mass-spectrometry-based bottom-up proteomics approach, we identified novel truncated forms of eNOS in immunoprecipitates from LSP1 KO aortae. Our experimental data suggest an important role of endothelial LSP1 in regulation of eNOS expression and activity within human ECs and murine vascular tissues.

Directed evolution of AAV accounting for long-term and enhanced transduction of cardiovascular endothelial cells in vivo

Cardiac endothelial cells (ECs) are important targets for cardiovascular gene therapy. However, the approach of stably transducing ECs in vivo using different vectors, including adeno-associated virus (AAV), remains unexamined. Regarding this unmet need, two AAV libraries from DNA shuffling and random peptide display were simultaneously screened in a transgenic mouse model. Cardiac ECs were isolated by cell sorting for salvage of EC-targeting AAV. Two AAV variants, i.e., EC71 and EC73, enriched in cardiac EC, were further characterized for their tissue tropism. Both of them demonstrated remarkably enhanced transduction of cardiac ECs and reduced infection of liver ECs in comparison to natural AAVs after intravenous injection. Significantly, persistent transgene expression was maintained in mouse cardiac ECs in vivo for at least 4 months. The EC71 vector was selected for delivery of the endothelial nitric oxide synthase (eNOS) gene into cardiac ECs in a mouse model of myocardial infarction. Enhanced eNOS activity was observed in the mouse heart and lung, which was correlated with partially improved cardiac function. Taken together, two AAV capsids were evolved with more efficient transduction in cardiovascular endothelium in vivo, but their endothelial tropism might need to be further optimized for practical application to cardiac gene therapy.

Epigenetic down-regulation of microRNA-126 in scleroderma endothelial cells is associated with impaired responses to VEGF and defective angiogenesis

Impaired angiogenesis in scleroderma (SSc) is a critical component of SSc pathology. MicroRNA‐126 (miR‐126) is expressed in endothelial cells (MVECs) where it regulates VEGF responses by repressing the negative regulators of VEGF, including the sprouty‐related protein‐1 (SPRED1), and phosphoinositide‐3 kinase regulatory subunit 2 (PIK3R2). MVECs were isolated from SSc skin and matched subjects (n = 6). MiR‐126 expression was measured by qPCR and in situ hybridization. Matrigel‐based tube assembly was used to test angiogenesis. MiR‐126 expression was inhibited by hsa‐miR‐126 inhibitor and enhanced by hsa‐miR‐126 Mimic. Epigenetic regulation of miR‐126 expression was examined by the addition of epigenetic inhibitors (Aza and TSA) to MVECs and by bisulphite genomic sequencing of DNA methylation of the miR‐126 promoter region. MiR‐126 expression, as well as EGFL7 (miR‐126 host gene), in SSc‐MVECs and skin, was significantly down‐regulated in association with increased expression of SPRED1 and PIK3R2 and diminished response to VEGF. Inhibition of miR‐126 in NL‐MVECs resulted in reduced angiogenic capacity, whereas overexpression of miR‐126 in SSc‐MVECs resulted in enhanced tube assembly. Addition of Aza and TSA normalized miR‐126 and EGFL7 expression levels in SSc‐MVECs. Heavy methylation in miR‐126/EGFL7 gene was noted. In conclusion, these results demonstrate that the down‐regulation of miR‐126 results in impaired VEGF responses.

A20/TNFAIP3 Increases ENOS Expression in an ERK5/KLF2-Dependent Manner to Support Endothelial Cell Health in the Face of Inflammation

Rationale: Decreased expression and activity of endothelial nitric oxide synthase (eNOS) in response to inflammatory and metabolic insults is the hallmark of endothelial cell (EC) dysfunction that preludes the development of atherosclerosis and hypertension. We previously reported the atheroprotective properties of the ubiquitin-editing and anti-inflammatory protein A20, also known as TNFAIP3, in part through interrupting nuclear factor-kappa B (NF-κB) and interferon signaling in EC and protecting these cells from apoptosis. However, A20's effect on eNOS expression and function remains unknown. In this study, we evaluated the impact of A20 overexpression or knockdown on eNOS expression in EC, at baseline and after tumor necrosis factor (TNF) treatment, used to mimic inflammation. Methods and Results: A20 overexpression in human coronary artery EC (HCAEC) significantly increased basal eNOS mRNA (qPCR) and protein (western blot) levels and prevented their downregulation by TNF. Conversely, siRNA-induced A20 knockdown decreased eNOS mRNA levels, identifying A20 as a physiologic regulator of eNOS expression. By reporter assays, using deletion and point mutants of the human eNOS promoter, and knockdown of eNOS transcriptional regulators, we demonstrated that A20-mediated increase of eNOS was transcriptional and relied on increased expression of the transcription factor Krüppel-like factor (KLF2), and upstream of KLF2, on activation of extracellular signal-regulated kinase 5 (ERK5). Accordingly, ERK5 knockdown or inhibition significantly abrogated A20's ability to increase KLF2 and eNOS expression. In addition, A20 overexpression in HCAEC increased eNOS phosphorylation at Ser-1177, which is key for the function of this enzyme. Conclusions: This is the first report demonstrating that overexpression of A20 in EC increases eNOS transcription in an ERK5/KLF2-dependent manner and promotes eNOS activating phosphorylation. This effect withstands eNOS downregulation by TNF, preventing EC dysfunction in the face of inflammation. This novel function of A20 further qualifies its therapeutic promise to prevent/treat atherosclerosis.

Sequence and haplotypes of ankyrin 1 gene (ANK1) and their association with carcass and meat quality traits in yak

Ankyrin 1 (ANK1) gene has been demonstrated to be a functional candidate gene for meat quality that helps to constitute and maintain the structure of the cell skeleton. In this study, three contiguous ANK1 regions from yak were analyzed using polymerase chain reaction-single-stranded conformational polymorphism (PCR-SSCP). As a result, nine single-nucleotide polymorphisms (SNPs) were identified, four of them in the coding region and three (c.179 C/A, c.250 G/C, and c.313 C/T) putatively resulting in amino acid changes (p. Ala 60 Glu, p. Asp 84 His, and p. Pro 105 Ser). Some SNPs in promoter region were located within or nearby the putative transcription factor binding sites, such as Sp1 and GATA, which might have an impact on the expression of the yak ANK1 gene. The presence of C₁-D₃ and C₁-A₃ were associated with an increased hot carcass weight (p = 0.0045) and a decreased drip loss rate (p = 0.0046). The presence of B₁-B₃, C₁-A₃ and C₁-D₃ had decreased Warner-Bratzler shear force (p = 0.0066, p = 0.0343 and p = 0.0004). The presence of one and two copies of B₁-B₃ and C₁-A₃ had decreased Warner-Bratzler shear force (p = 0.0005 and p = 0.0443), and C₁-A₃ had also decreased drip loss rate (p = 0.0164). These findings indicated that genetic variations of the ANK1 gene would be a preferable biomarker for the improvement of yak meat quality.

Ectopic release of nitric oxide modulates the onset of cardiac development in avian model

Heart development is one of the earliest developmental events, and its pumping action is directly linked to the intensity of development of other organs. Heart contractions mediate the circulation of the nutrients and signalling molecules to the focal points of developing embryos. In the present study, we used in vivo, ex vivo, in vitro, and in silico methods for chick embryo model to characterize and identify molecular targets under the influence of ectopic nitric oxide in reference to cardiogenesis. Spermine NONOate (SpNO) treatment of 10 μM increased the percentage of chick embryos having beating heart at 40th h of incubation by 2.2-fold (p < 0.001). In an ex vivo chick embryo culture, SpNO increased the percentage of embryos having beats by 1.56-fold (p < 0.05) compared with control after 2 h of treatment. Total body weight of SpNO-treated chick embryos at the Hamburger and Hamilton (HH) stage 29 was increased by 1.22-fold (p < 0.005). Cardiac field potential (FP) recordings of chick embryo at HH29 showed 2.5-fold (p < 0.001) increased in the amplitude, 3.2-fold (p < 0.001) increased in frequency of SpNO-treated embryos over that of the control group, whereas FP duration was unaffected. In cultured cardiac progenitors cells (CPCs), SpNO treatment decreased apoptosis and cell death by twofold (p < 0.001) and 1.7-fold (p < 0.001), respectively. Transcriptome analysis of chick embryonic heart isolated from HH15 stage pre-treated with SpNO at HH8 stage showed upregulation of genes involved in heart morphogenesis, heart contraction, cardiac cell development, calcium signalling, structure, and development whereas downregulated genes were enriched under the terms extracellular matrix, wnt pathway, and BMP pathway. The key upstream molecules predicted to be activated were p38 MAPK, MEF2C, TBX5, and GATA4 while KDM5α, DNMT3A, and HNF1α were predicted to be inhibited. This study suggests that the ectopic nitric oxide modulates the onset of cardiac development.

Shear Stress in Schlemm's Canal as a Sensor of Intraocular Pressure

Elevated intraocular pressure (IOP) narrows Schlemm’s canal (SC), theoretically increasing luminal shear stress. Using engineered adenoviruses containing a functional fragment of the shear-responsive endothelial nitric oxide synthase (eNOS) promoter, we tested effects of shear stress and elevated flow rate on reporter expression in vitro and ex vivo. Cultured human umbilical vein endothelial cells (HUVECs) and SC cells were transduced with adenovirus containing eNOS promoter driving secreted alkaline phosphatase (SEAP) or green fluorescent protein (GFP) and subjected to shear stress. In parallel, human anterior segments were perfused under controlled flow. After delivering adenoviruses to the SC lumen by retroperfusion, the flow rate in one anterior segment of pair was increased to double pressure. In response to high shear stress, HUVECs and SC cells expressed more SEAP and GFP than control. Similarly, human anterior segments perfused at higher flow rates released significantly more nitrites and SEAP into perfusion effluent, and SC cells expressed increased GFP near collector channel ostia compared to control. These data establish that engineered adenoviruses have the capacity to quantify and localize shear stress experienced by endothelial cells. This is the first in situ demonstration of shear-mediated SC mechanobiology as a key IOP-sensing mechanism necessary for IOP homeostasis.

The histone deacetylase inhibitor tubacin mitigates endothelial dysfunction by up-regulating the expression of endothelial nitric oxide synthase

Endothelial nitric oxide (NO) synthase (eNOS) plays a critical role in the maintenance of blood vessel homeostasis. Recent findings suggest that cytoskeletal dynamics play an essential role in regulating eNOS expression and activation. Here, we sought to test whether modulation of cytoskeletal dynamics through pharmacological regulation of histone deacetylase 6 (HDAC6)-mediated tubulin deacetylation affects eNOS expression and endothelial function in vitro and in vivo We found that tubulin acetylation inducer (tubacin), a compound that appears to selectively inhibit HDAC6 activity, dramatically increased eNOS expression in several different endothelial cell lines, as determined by both immunoblotting and NO production assays. Mechanistically, we found that these effects were not mediated by tubacin's inhibitory effect on HDAC6 activity, but rather were due to its ability to stabilize eNOS mRNA transcripts. Consistent with these findings, tubacin also inhibited proinflammatory cytokine-induced degradation of eNOS transcripts and impairment of endothelium-dependent relaxation in the mouse aorta. Furthermore, we found that tubacin-induced up-regulation in eNOS expression in vivo is associated with improved endothelial function in diabetic db/db mice and with a marked attenuation of ischemic brain injury in a murine stroke model. Our findings indicate that tubacin exhibits potent eNOS-inducing effects and suggest that this compound might be useful for the prevention or management of endothelial dysfunction-associated cardiovascular diseases.

Case-control study on the association between the GATA2 gene and premature myocardial infarction in the Iranian population

In recent decades, due to the high prevalence of coronary artery disease (CAD) and myocardial infarction (MI), numerous studies have attempted to elucidate genetic contributing factors in these complex disorders. A very interesting gene in this regard is GATA-binding protein 2 (GATA2), an important regulator of various gene expressions in vascular endothelial cells. Accordingly, the association of different GATA2 polymorphisms with CAD and MI has already been evaluated. Rs2713604 is a genetic marker whose association with CAD has not been reproduced in previous studies. Considering the importance of replicating the initial association, the present case-control study aimed to examine the association of this intronic variant with premature MI in a sample of the Iranian population. In this study, 193 participants from Jahrom Hospital (Jahrom, Iran) were consecutively recruited during a 1.5-year period, and, following blood sampling, genomic DNA was extracted. We then proceeded to genotype rs2713604 using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method and statistically analyzed the data. After adjustment for hyperlipidemia, hypertension, and type 2 diabetes mellitus, the results of the multivariate regression analysis showed no significant association between rs2713604 and premature MI. Interestingly, the risk allele (A-allele) of rs2713604 displayed a slightly higher frequency among controls compared to cases.

Targeted sequencing of linkage region in Dominican families implicates PRIMA1 and the SPATA7-PTPN21-ZC3H14-EML5-TTC8 locus in carotid-intima media thickness and atherosclerotic events

Carotid intima-media thickness (cIMT) is a subclinical marker for atherosclerosis. Previously, we reported a quantitative trait locus (QTL) for total cIMT on chromosome 14q and identified PRiMA1, FOXN3 and CCDC88C as candidate genes using a common variants (CVs)-based approach. Herein, we further evaluated the genetic contribution of the QTL to cIMT by resequencing. We sequenced all exons within the QTL and genomic regions of PRiMA1, FOXN3 and CCDC88C in Dominican families with evidence for linkage to the QTL. Unrelated Dominicans from the Northern Manhattan Study (NOMAS) were used for validation. Single-variant-based and gene-based analyses were performed for CVs and rare variants (RVs). The strongest evidence for association with CVs was found in PRiMA1 (p = 8.2 × 10⁻⁵ in families, p = 0.01 in NOMAS at rs12587586), and in the five-gene cluster SPATA7-PTPN21-ZC3H14-EML5-TTC8 locus (p = 1.3 × 10⁻⁴ in families, p = 0.01 in NOMAS at rs2274736). No evidence for association with RVs was found in PRiMA1. The top marker from previous study in PRiMA1 (rs7152362) was associated with fewer atherosclerotic events (OR = 0.67; p = 0.02 in NOMAS) and smaller cIMT (β = −0.58, p = 2.8 × 10⁻⁴ in Family). Within the five-gene cluster, evidence for association was found for exonic RVs (p = 0.02 in families, p = 0.28 in NOMAS), which was enriched among RVs with higher functional potentials (p = 0.05 in NOMAS for RVs in the top functional tertile). In summary, targeted resequencing provided validation and novel insights into the genetic architecture of cIMT, suggesting stronger effects for RVs with higher functional potentials. Furthermore, our data support the clinical relevance of CVs associated with subclinical atherosclerosis.

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.

Cavin-1 regulates caveolae-mediated LDL transcytosis: crosstalk in an AMPK/eNOS/ NF-κB/Sp1 loop

Caveolae are specialized lipid rafts structure in the cell membrane and critical for regulating endothelial functions, e.g. transcytosis of macromolecules like low density lipoprotein (LDL) etc. Specifically, the organization and functions of caveolae are mediated by structure protein (caveolin-1) and adapter protein (cavin-1). The pathogenic role of caveolin-1 is well studied; nevertheless, mechanisms whereby cavin-1 regulates signaling transduction remain poorly understood. The aim of this study was designed to explore the role of cavin-1 in caveolae-mediated LDL transcytosis across endothelial cells. We reported here that cavin-1 knockdown mediated by small interfering RNA (siRNA) caused a significant decrease of LDL transcytosis. Moreover, cavin-1 knockdown increased the activity of endothelial nitric oxide synthase (eNOS) and the production of nitric oxide (NO). Consequently, an eNOS inhibitor, N-Nitro-L-Arginine Methyl Ester (L-NAME), not only suppressed the activity of specificity protein (Sp1) and nuclear factor kappa B (NF-κB), but also inhibited both activities via activating adenosine 5‘-monophosphate- activated protein kinase (AMPK). In conclusion, we proposed an AMPK/eNOS/NF-κB/Sp1 circuit loop was formed to regulate caveolae residing proteins’ expression, e.g. LDL receptor (LDLR), caveolin-1, eNOS, thereby to regulate caveolae-mediated LDL transcytosis in endothelial cells.

Identification of a novel distal regulatory element of the human Neuroglobin gene by the chromosome conformation capture approach

Neuroglobin (NGB) is predominantly expressed in the brain and retina. Studies suggest that NGB exerts protective effects to neuronal cells and is implicated in reducing the severity of stroke and Alzheimer's disease. However, little is known about the mechanisms which regulate the cell type-specific expression of the gene. In this study, we hypothesized that distal regulatory elements (DREs) are involved in optimal expression of the NGB gene. By chromosome conformation capture we identified two novel DREs located -70 kb upstream and +100 kb downstream from the NGB gene. ENCODE database showed the presence of DNaseI hypersensitive and transcription factors binding sites in these regions. Further analyses using luciferase reporters and chromatin immunoprecipitation suggested that the -70 kb region upstream of the NGB gene contained a neuronal-specific enhancer and GATA transcription factor binding sites. Knockdown of GATA-2 caused NGB expression to drop dramatically, indicating GATA-2 as an essential transcription factor for the activation of NGB expression. The crucial role of the DRE in NGB expression activation was further confirmed by the drop in NGB level after CRISPR-mediated deletion of the DRE. Taken together, we show that the NGB gene is regulated by a cell type-specific loop formed between its promoter and the novel DRE.

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.

MicroRNA-Based Therapy of GATA2-Deficient Vascular Disease

BACKGROUND

The transcription factor GATA2 orchestrates the expression of many endothelial-specific genes, illustrating its crucial importance for endothelial cell function. The capacity of this transcription factor in orchestrating endothelial-important microRNAs (miRNAs/miR) is unknown.

METHODS

Endothelial GATA2 was functionally analyzed in human endothelial cells in vitro. Endogenous short interfering RNA-mediated knockdown and lentiviral-based overexpression were applied to decipher the capacity of GATA2 in regulating cell viability and capillary formation. Next, the GATA2-dependent miR transcriptome was identified by using a profiling approach on the basis of quantitative real-time polymerase chain reaction. Transcriptional control of miR promoters was assessed via chromatin immunoprecipitation, luciferase promoter assays, and bisulfite sequencing analysis of sites in proximity. Selected miRs were modulated in combination with GATA2 to identify signaling pathways at the angiogenic cytokine level via proteome profiler and enzyme-linked immunosorbent assays. Downstream miR targets were identified via bioinformatic target prediction and luciferase reporter gene assays. In vitro findings were translated to a mouse model of carotid injury in an endothelial GATA2 knockout background. Nanoparticle-mediated delivery of proangiogenic miR-126 was tested in the reendothelialization model.

RESULTS

GATA2 gain- and loss-of-function experiments in human umbilical vein endothelial cells identified a key role of GATA2 as master regulator of multiple endothelial functions via miRNA-dependent mechanisms. Global miRNAnome-screening identified several GATA2-regulated miRNAs including miR-126 and miR-221. Specifically, proangiogenic miR-126 was regulated by GATA2 transcriptionally and targeted antiangiogenic SPRED1 and FOXO3a contributing to GATA2-mediated formation of normal vascular structures, whereas GATA2 deficiency led to vascular abnormalities. In contrast to GATA2 deficiency, supplementation with miR-126 normalized vascular function and expression profiles of cytokines contributing to proangiogenic paracrine effects. GATA2 silencing resulted in endothelial DNA hypomethylation leading to induced expression of antiangiogenic miR-221 by GATA2-dependent demethylation of a putative CpG island in the miR-221 promoter. Mechanistically, a reverted GATA2 phenotype by endogenous suppression of miR-221 was mediated through direct proangiogenic miR-221 target genes ICAM1 and ETS1. In a mouse model of carotid injury, GATA2 was reduced, and systemic supplementation of miR-126-coupled nanoparticles enhanced miR-126 availability in the carotid artery and improved reendothelialization of injured carotid arteries in vivo.

CONCLUSIONS

GATA2-mediated regulation of miR-126 and miR-221 has an important impact on endothelial biology. Hence, modulation of GATA2 and its targets miR-126 and miR-221 is a promising therapeutic strategy for treatment of many vascular diseases.

Differential Expression of Endothelial Nitric Oxide Synthase in Coronary and Cardiac Tissue in Hypoxic Fetal Guinea Pig Hearts

OBJECTIVE

The purpose of the present study was to quantify the effect of chronic hypoxia on endothelial nitric oxide synthase (eNOS) gene and protein expression of fetal coronary artery segments and cardiac tissue of fetal guinea pig hearts.

METHODS

Time-mated pregnant guinea pigs (term = 65 days) were housed in room air (NMX, n = 6) or in a hypoxic chamber containing 10.5% O2 for 14 days (HPX14, n = 6). At near term (60 days gestation), fetuses were excised from anesthetized animals via hysterotomy and hearts were removed and weighed. Both coronary artery segments and cardiac ventricle were excised from the same hearts, frozen, and stored at -80 C until ready for study. eNOS mRNA was quantified using real-time polymerase chain reaction (PCR) based on SYBR Green I labeling (BioRad Laboratories, Hercules, CA) using eNOS primers obtained from GeneBank normalized to 18S. eNOS proteins were quantified by Western immunoblotting using eNOS antibody (1:200) and normalized to normoxic controls. eNOS cell-specific localization in the fetal guinea pig heart was performed by double immunofluorescence staining.

RESULTS

Both coronary artery endothelial cells (EC) and cardiomyocytes (CM) but not vascular smooth muscle cells of normoxic hearts exhibited positive immunostaining of eNOS protein. Chronic hypoxia significantly (P < .05) increased both eNOS mRNA and protein levels of coronary artery segments (by 210.6% and 51.4%, respectively) but decreased (P < .05) mRNA and protein of cardiac tissue (by 50.0% and 40.6%, respectively) in the same hearts.

CONCLUSIONS

Chronic fetal hypoxia, after 14 days, induces sustained changes in eNOS gene and eNOS protein expression that differ between coronary and cardiac tissue in the fetal guinea pig heart. This study suggests that while the functional roles of altered eNOS expression in hypoxic fetal hearts remain unclear, the site at which eNOS expression is altered may be important in the adaptive response of the fetal heart to hypoxia.

AP-1 Inhibition by SR 11302 Protects Human Hepatoma HepG2 Cells from Bile Acid-Induced Cytotoxicity by Restoring the NOS-3 Expression

The harmful effects of bile acid accumulation occurring during cholestatic liver diseases have been associated with oxidative stress increase and endothelial nitric oxide synthase (NOS-3) expression decrease in liver cells. We have previously reported that glycochenodeoxycholic acid (GCDCA) down-regulates gene expression by increasing SP1 binding to the NOS-3 promoter in an oxidative stress dependent manner. In the present study, we aimed to investigate the role of transcription factor (TF) AP-1 on the NOS-3 deregulation during GCDCA-induced cholestasis. The cytotoxic response to GCDCA was characterized by 1) the increased expression and activation of TFs cJun and c-Fos; 2) a higher binding capability of these at position -666 of the NOS-3 promoter; 3) a decrease of the transcriptional activity of the promoter and the expression and activity of NOS-3; and 4) the expression increase of cyclin D1. Specific inhibition of AP-1 by the retinoid SR 11302 counteracted the cytotoxic effects induced by GCDCA while promoting NOS-3 expression recovery and cyclin D1 reduction. NOS activity inhibition by L-NAME inhibited the protective effect of SR 11302. Inducible NOS isoform was no detected in this experimental model of cholestasis. Our data provide direct evidence for the involvement of AP-1 in the NOS-3 expression regulation during cholestasis and define a critical role for NOS-3 in regulating the expression of cyclin D1 during the cell damage induced by bile acids. AP-1 appears as a potential therapeutic target in cholestatic liver diseases given its role as a transcriptional repressor of NOS-3.

Dependence of Proximal GC Boxes and Binding Transcription Factors in the Regulation of Basal and Valproic Acid-Induced Expression of t-PA

Objective. Endothelial tissue-type plasminogen activator (t-PA) release is a pivotal response to protect the circulation from occluding thrombosis. We have shown that the t-PA gene is epigenetically regulated and greatly induced by the histone deacetylase (HDAC) inhibitor valproic acid (VPA). We now investigated involvement of known t-PA promoter regulatory elements and evaluated dependence of potential interacting transcription factors/cofactors. Methods. A reporter vector with an insert, separately mutated at either the t-PA promoter CRE or GC box II or GC box III elements, was transfected into HT-1080 and HUVECs and challenged with VPA. HUVECs were targeted with siRNA against histone acetyl transferases (HAT) and selected transcription factors from the Sp/KLF family. Results. An intact VPA-response was observed with CRE mutated constructs, whereas mutation of GC boxes II and III reduced the magnitude of the induction by 54 and 79% in HT-1080 and 49 and 50% in HUVECs, respectively. An attenuated induction of t-PA mRNA was observed after Sp2, Sp4, and KLF5 depletion. KLF2 and p300 (HAT) were identified as positive regulators of basal t-PA expression and Sp4 and KLF9 as repressors. Conclusion. VPA-induced t-PA expression is dependent on the proximal GC boxes in the t-PA promoter and may involve interactions with Sp2, Sp4, and KLF5.

Endothelial nitric oxide synthase: From biochemistry and gene structure to clinical implications of NOS3 polymorphisms

Nitric oxide (NO) is an important vasodilator with a well-established role in cardiovascular homeostasis. While mediator is synthesized from L-arginine by neuronal, endothelial, and inducible nitric oxide synthases (NOS1,NOS3 and NOS2 respectively), NOS3 is the most important isoform for NO formation in the cardiovascular system. NOS3 is a dimeric enzyme whose expression and activity are regulated at transcriptional, posttranscriptional,and posttranslational levels. The NOS3 gene, which encodes NOS3, exhibits a number of polymorphic sites including single nucleotide polymorphisms (SNPs), variable number of tandem repeats (VNTRs), microsatellites, and insertions/deletions. Some NOS3 polymorphisms show functional effects on NOS3 expression or activity, thereby affecting NO formation. Interestingly, many studies have evaluated the effects of functional NOS3 polymorphisms on disease susceptibility and drug responses. Moreover, some studies have investigated how NOS3 haplotypes may impact endogenous NO formation and disease susceptibility. In this article,we carried out a comprehensive review to provide a basic understanding of biochemical mechanisms involved in NOS3 regulation and how genetic variations in NOS3 may translate into relevant clinical and pharmacogenetic implications.

LPS Down-Regulates Specificity Protein 1 Activity by Activating NF-κB Pathway in Endotoxemic Mice

Background

Specificity protein (Sp) 1 mediates the transcription of a large number of constitutive genes encoding physiological mediators. NF-κB mediates the expression of hundreds of inducible genes encoding pathological mediators. Crosstalk between Sp1 and NF-κB pathways could be pathophysiologically significant, but has not been studied. This study examined the crosstalk between the two pathways and defined the role of NF-κB signaling in LPS-induced down-regulation of Sp1 activity.

Methods and Main Findings

Challenge of wild type mice with samonelia enteritidis LPS (10 mg/kg, i.p.) down-regulated Sp1 binding activity in lungs in a time-dependent manner, which was concomitantly associated with an increased NF-κB activity. LPS down-regulates Sp1 activity by inducing an LPS inducible Sp1-degrading enzyme (LISPDE) activity, which selectively degrades Sp1 protein, resulting in Sp1 down-regulation. Blockade of NF-κB activation in mice deficient in NF-κB p50 gene (NF-κB-KO) suppressed LISPDE activity, prevented Sp1 protein degradation, and reversed the down-regulation of Sp1 DNA binding activity and eNOS expression (an indicator of Sp1 transactivation activity). Inhibition of LISPDE activity using a selective LISPDE inhibitor mimicked the effects of NF-κB blockade. Pretreatment of LPS-challenged WT mice with a selective LISPDE inhibitor increased nuclear Sp1 protein content, restored Sp1 DNA binding activity and reversed eNOS protein down-regulation in lungs. Enhancing tissue level of Sp1 activity by inhibiting NF-κB-mediated Sp1 down-regulation increased tissue level of IL-10 and decreased tissue level of TNF- αin the lungs.

Conclusions

NF-κB signaling mediates LPS-induced down-regulation of Sp1 activity. Activation of NF-κB pathway suppresses Sp1 activity and Sp1-mediated anti-inflammatory signals. Conversely, Sp1 signaling counter-regulates NF-κB-mediated inflammatory response. Crosstalk between NF-κB and Sp1 pathways regulates the balance between pro- and anti-inflammatory cytokines.

The short and long of noncoding sequences in the control of vascular cell phenotypes

The two principal cell types of importance for normal vessel wall physiology are smooth muscle cells and endothelial cells. Much progress has been made over the past 20 years in the discovery and function of transcription factors that coordinate proper differentiation of these cells and the maintenance of vascular homeostasis. More recently, the converging fields of bioinformatics, genomics, and next generation sequencing have accelerated discoveries in a number of classes of noncoding sequences, including transcription factor binding sites (TFBS), microRNA genes, and long noncoding RNA genes, each of which mediates vascular cell differentiation through a variety of mechanisms. Alterations in the nucleotide sequence of key TFBS or deviations in transcription of noncoding RNA genes likely have adverse effects on normal vascular cell phenotype and function. Here, the subject of noncoding sequences that influence smooth muscle cell or endothelial cell phenotype will be summarized as will future directions to further advance our understanding of the increasingly complex molecular circuitry governing normal vascular cell differentiation and how such information might be harnessed to combat vascular diseases.

A novel NKX2.5 loss-of-function mutation associated with congenital bicuspid aortic valve

Bicuspid aortic valve (BAV) is the most common form of congenital cardiovascular defect in humans and is associated with substantial morbidity and mortality. Emerging evidence demonstrates that genetic risk factors play an important role in the pathogenesis of BAV. However, BAV is a genetically heterogenous disorder, and the genetic defects underpinning BAV in most patients remain to be identified. In the present study, the coding exons and flanking introns of the NKX2.5 gene, which encodes a homeodomain-containing transcription factor essential for the normal development of the aortic valve, were sequenced in 142 unrelated patients with BAV. The available relatives of the mutation carrier and 200 unrelated healthy subjects used as controls were also genotyped for NKX2.5. The functional characteristics of the mutation were delineated by using a dual-luciferase reporter assay system. As a result, a novel heterozygous NKX2.5 mutation, p.K192X, was identified in a family with BAV transmitted in an autosomal dominant pattern. The nonsense mutation was absent in 400 control chromosomes. Functional analyses revealed that the mutant NKX2.5 had no transcriptional activity compared with its wild-type counterpart. Furthermore, the mutation abolished the synergistic transcriptional activation between NKX2.5 and GATA5, another transcription factor crucial for the aortic valvular morphogenesis. In conclusion, this study is the first to link an NKX2.5 loss-of-function mutation to enhanced susceptibility to human BAV, providing novel insight into the molecular mechanism of BAV and suggesting potential implications for genetic counseling and clinical care of families presenting with BAV.

Histone deacetylase 5 interacts with Krüppel-like factor 2 and inhibits its transcriptional activity in endothelium

AIMS

Vascular endothelial dysfunction and inflammation are hallmarks of atherosclerosis. Krüppel-like factor 2 (KLF2) is a key mediator of anti-inflammatory and anti-atherosclerotic properties of the endothelium. However, little is known of the molecular mechanisms for regulating KLF2 transcriptional activation.

METHODS AND RESULTS

Here, we found that histone deacetylase 5 (HDAC5) associates with KLF2 and represses KLF2 transcriptional activation. HDAC5 resided with KLF2 in the nuclei of human umbilical cord vein endothelial cells (HUVECs). Steady laminar flow attenuated the association of HDAC5 with KLF2 via stimulating HDAC5 phosphorylation-dependent nuclear export in HUVEC. We also mapped the KLF2-HDAC5-interacting domains and found that the N-terminal region of HDAC5 interacts with the C-terminal domain of KLF2. Chromatin immunoprecipitation and luciferase reporter assays showed that HDAC5 through a direct association with KLF2 suppressed KLF2 transcriptional activation. HDAC5 overexpression inhibited KLF2-dependent endothelial nitric oxide synthesis (eNOS) promoter activity in COS7 cell and gene expression in both HUVECs and bovine aortic endothelial cells (BAECs). Conversely, HDAC5 silencing enhanced KLF2 transcription and hence eNOS expression in HUVEC. Moreover, we observed that the level of eNOS protein in the thoracic aorta isolated from HDAC5 knockout mice was higher, whereas expression of pro-inflammatory vascular cell adhesion molecule 1 was lower, compared with those of HDAC5 wild-type mice.

CONCLUSIONS

We reveal a novel role of HDAC5 in modulating the KLF2 transcriptional activation and eNOS expression. These findings suggest that HDAC5, a binding partner and modulator of KLF2, could be a new therapeutic target to prevent vascular endothelial dysfunction associated with cardiovascular diseases.

[Regulation of endothelial cell-specific Robo4 gene expression by DNA methylation and non-lineage specific transcription factors]

Studies of tissue-specific gene expression have suggested that tissue-specific transcription factors or tissue-specific combinations of non-cell-type-specific transcription factors regulate tissue-specific gene expression. Although the studies of endothelial cell (EC)-specific gene expression has identified several transcriptional activators such as SP1, ETS family proteins, and GATA proteins, their expression and combinations are not likely to be EC-specific. To investigate the mechanism of EC-specific gene expression, we analyzed the regulation mechanism of an EC-specific gene, Roundabout4 (Robo4). We identified the 3-kb Robo4 promoter and several transcription factors including SP1 and GABP that bind to the Robo4 promoter and promote Robo4 gene expression. However, we could not explain the mechanism for EC-specific Robo4 gene expression with only those factors because their expression and combination are not EC-specific. Therefore, we hypothesized the contribution of other mechanisms, especially epigenetic control, to Robo4 gene regulation and demonstrated the importance of DNA methylation for EC-specific Robo4 expression. In this review, we summarize our recent studies and discuss the novel regulation model of Robo4 gene expression by transcription factors and DNA methylation.

Identification and characterization of a novel porcine endothelial cell-specific Tie1 promoter

BACKGROUND

The use of a transgenic pig for xenotransplantation and as a cardiovascular disease model has caught much attention in the past decades. The vascular endothelial cell is the primary modification target for the application of genetically modified pigs in this field. However, the powerful porcine endothelial cell-specific promoter is still so rare that the mouse and human promoters are commonly used. In the study, the porcine Tie1 (sTie1) promoter was identified and characterized as a potential endothelial cell-specific promoter to generate a cardiovascular disease model.

METHODS

Tie1 promoters with different lengths of 5'-regulatory regions were cloned, and major putative DNA-binding motifs were mutated by site-directed mutagenesis. All fragments were ligated into the luciferase reporter system and were transiently transfected into endothelial cells to identify luciferase activity using a dual luciferase reporter assay.

RESULTS

The luciferase activities of sTie1 promoters with different lengths of the 5'-regulatory region were tested. Results showed that the luciferase activity of the 1234-bp sTie1 fragment was the strongest compared with that of others (P < 0.001). Site-directed mutagenesis in transcription-factor-binding sites, including Ets, GATA, and AP2, verified their key roles in regulating transcription, especially sites Ets (-103), GATA (-211), and AP2 (-3). The activities of Tie1 promoters from pig, human, and mouse were significantly different in pig iliac endothelial cells (PIECs) (P < 0.001), and the sTie1 promoter showed the highest activity. Moreover, sTie1 promoter activity could be detected in porcine embryo fibroblasts and skeletal muscle cells.

CONCLUSIONS

The sTie1 promoter shows a highly conserved sequence compared with the Tie1 promoters in human and mouse, but it has a greater activity in the porcine endothelial cell line than that of human and mouse promoters. Thus, sTie1 will be a valuable tool for generating a pig cardiovascular disease model.

An intronic miRNA regulates expression of the human endothelial nitric oxide synthase gene and proliferation of endothelial cells by a mechanism related to the transcription factor SP-1

OBJECTIVE

This study was to investigate the molecular mechanisms underlying the 27nt-miRNA-mediated regulation of expression of the endothelial nitric oxide synthase (eNOS) gene.

METHODS

Cell lines overexpressing 27nt-miRNA or its mutant were established by transfecting the miRNA expression vector into the endothelial cells. eNOS mRNA and protein expression were examined by RT-PCR and Western Blotting, respectively. Luciferase activity reporter system was used to study the target of 27nt-miRNA.

RESULTS

The results showed that overexpression of 27nt-miRNA significantly inhibited eNOS mRNA level and protein expression, and reduced the eNOS transcriptional efficiency. Such inhibitory effects of 27nt-miRNA were attenuated by the sequence mutations in 27nt-miRNA. Interestingly, the transcription factor SP-1 expression was reduced by 27nt-miRNA. Meanwhile, overxpression of SP-1 protein partially restored eNOS expression, and rescued the 27nt-miRNA-mediated reduction of endothelial cell proliferation. Moreover, certain sites in the SP-1 mRNA were found to be the direct target of 27nt-miRNA by a luciferase reporter system.

CONCLUSIONS

These results demonstrate that the 27nt-miRNA suppresses eNOS gene expression and SP-1 expression in vascular endothelial cells. The 27nt-miRNA directly target to SP-1 mRNA, thereby contributing to proliferation of endothelial cells.

MiR-492 impairs the angiogenic potential of endothelial cells

Endothelial cells growing in high glucose-containing medium show reduced cell proliferation and in vitro angiogenesis. Evidence suggests that the molecular pathways leading to these cellular responses are controlled by microRNAs, endogenous post-transcriptional regulators of gene expression. To identify the microRNAs and their targeted genes involved in the glucose responses, we performed the miRNA signature of Human Umbelical Vein Endothelial Cells (HUVECs) exposed and unexposed to high glucose. Among differentially expressed microRNAs, we analysed miR-492 and showed that its overexpression was able to reduce proliferation, migration and tube formation of HUVEC. These effects were accompanied by the down-regulation of eNOS, a key regulator of the endothelial cell function. We showed that eNOS was indirectly down-regulated by miR-492 and we discovered that miR-492 was able to bind mRNAs involved in proliferation, migration, tube formation and regulation of eNOS activity and expression. Moreover, we found that miR-492 decreased VEGF expression in HUVEC and impaired in vivo angiogenesis in a tumour xenograft model, suggesting a role also in modulating the secretion of pro-angiogenic factors. Taken together, the data indicate that miR-492 exerts a potent anti-angiogenic activity in endothelial cells and therefore miR-492 seems a promising tool for anti-angiogenic therapy.

Loss of Jak2 impairs endothelial function by attenuating Raf-1/MEK1/Sp-1 signaling along with altered eNOS activities

A number of inhibitors have been used to dissect the functional relevance of Jak2 in endothelial homeostasis, with disparate results. Given that Jak2 deficiency leads to embryonic lethality, the exact role of Jak2 in the regulation of postnatal endothelial function is yet to be fully elucidated. We generated a model in which Jak2 deficiency can be induced by tamoxifen in adult mice. Loss of Jak2 significantly impaired endothelium-dependent response capacity for vasodilators. Matrigel plug assays indicated a notable decrease in endothelial angiogenic function in Jak2-deficient mice. Studies in a hindlimb ischemic model indicated that Jak2 activity is likely to be a prerequisite for prompt perfusion recovery, based on the concordance of temporal changes in Jak2 expression during the course of ischemic injury and perfusion recovery. A remarkable delay in perfusion recovery, along with reduced capillary and arteriole formation, was observed in Jak2-deficient mice. Antibody array studies indicated that loss of Jak2 led to repressed eNOS expression. In mechanistic studies, Jak2 deficiency attenuated Raf-1/MEK1 signaling, which then reduced activity of Sp-1, an essential transcription factor responsible for eNOS expression. These data are important not only for understanding the exact role that Jak2 plays in endothelial homeostasis, but also for assessing Jak2-based therapeutic strategies in a variety of clinical settings.

Inactivation of Serum Response Factor Contributes To Decrease Vascular Muscular Tone and Arterial Stiffness in Mice

Rationale:

Vascular smooth muscle (SM) cell phenotypic modulation plays an important role in arterial stiffening associated with aging. Serum response factor (SRF) is a major transcription factor regulating SM genes involved in maintenance of the contractile state of vascular SM cells.

Objective:

We investigated whether SRF and its target genes regulate intrinsic SM tone and thereby arterial stiffness.

Methods and Results:

The SRF gene was inactivated SM-specific knockout of SRF (SRF SMKO ) specifically in vascular SM cells by injection of tamoxifen into adult transgenic mice. Fifteen days later, arterial pressure and carotid thickness were lower in SRF SMKO than in control mice. The carotid distensibility/pressure and elastic modulus/wall stress curves showed a greater arterial elasticity in SRF SMKO without modification in collagen/elastin ratio. In SRF SMKO , vasodilation was decreased in aorta and carotid arteries, whereas a decrease in contractile response was found in mesenteric arteries. By contrast, in mice with inducible SRF overexpression, the in vitro contractile response was significantly increased in all arteries. Without endothelium, the contraction was reduced in SRF SMKO compared with control aortic rings owing to impairment of the NO pathway. Contractile components (SM-actin and myosin light chain), regulators of the contractile response (myosin light chain kinase, myosin phosphatase target subunit 1, and protein kinase C–potentiated myosin phosphatase inhibitor) and integrins were reduced in SRF SMKO .

Conclusions:

SRF controls vasoconstriction in mesenteric arteries via vascular SM cell phenotypic modulation linked to changes in contractile protein gene expression. SRF-related decreases in vasomotor tone and cell-matrix attachment increase arterial elasticity in large arteries.

Chronic intermittent hypoxia down-regulates endothelial nitric oxide synthase expression by an NF-κB-dependent mechanism

OBJECTIVES

Patients with obstructive sleep apnea have an impaired endothelium-dependent vasodilator response. The mechanisms underlying this impairment remain unclear. We tested the hypothesis that chronic intermittent hypoxia (CIH) impairs endothelium-dependent vasodilatation by NF-κB-mediated down-regulation of endothelial nitric oxide synthase (eNOS) expression.

METHODS

Wild type (WT) mice and mice deficient in NF-κB p50 or TNF-α gene were exposed to sham or CIH. Aortic NF-κB activity and aortic expression of TNF-α were determined. Aortic and mesenteric artery levels of eNOS expression were examined and their correlation to endothelium-dependent vasodilator response in vitro and vasodepressor response in vivo were analyzed.

RESULTS

WT mice exposed to CIH for five to eight weeks showed significantly reduced eNOS protein expression in aortas and mesenteric arteries, associated with significantly blunted vasodilator and vasodepressor responses to acetylcholine, but not to sodium nitroprusside. CIH activated NF-κB, which preceded TNF-α up-regulation and eNOS down-regulation. NF-κB p50 gene deletion blocked NF-κB activation, inhibited TNF-α expression, prevented eNOS down-regulation and reversed the impaired endothelium-dependent vasodepressor response induced by CIH. TNF-α knockout prevented CIH-induced eNOS down-regulation and restored the endothelium-dependent vasodepressor response.

CONCLUSIONS

CIH exposure impairs endothelium-dependent vasodilator mechanism by stimulating NF-κB-mediated TNF-α generation, which in turn, down-regulates eNOS expression, resulting in an impaired endothelium-dependent vasodilatation.

Intracellular redox equilibrium is essential for the constitutive expression of AP-1 dependent genes in resting cells: studies on TGF-β1 regulation

The mechanisms involved in the continuous expression of constitutive genes are unclear. We hypothesize that steady state intracellular reactive oxygen species (ROS), which their levels are tightly maintained, could be regulating the expression of these constitutive genes in resting cells. We analyzed the regulation of an important constitutive gene, TGF-β1, after decreasing intracellular ROS concentration in human mesangial cells. Decreased intracellular hydrogen peroxide by catalase addition reduced TGF-β1 protein, mRNA expression and promoter activity. Furthermore, catalase decreased the basal activity of Activated Protein-1 (AP-1) that regulates TGF-β1 promoter activity. This effect disappeared when AP-1 binding site was removed. Similar results were observed with another protein containing AP-1 binding sites in its promoter, such as eNOS, but it was not the case in other constitutive genes without any AP-1 binding site, as COX1 or PKG1. The pharmacological inhibition of the different ROS synthesis sources by blocking NADPH oxidase, the mitochondrial respiratory chain or xanthine oxidase, or the use of human fibroblasts with genetically deficient mitochondrial activity, induced a similar, significant reduction of steady state ROS concentration as the one observed with catalase. Moreover, there was decreased TGF-β1 expression in all the cases excepting the xanthine oxidase blockade. These findings suggest a novel role for the steady state intracellular ROS concentration, where the compartmentalized, different systems involved in the intracellular ROS production, could be essential for the expression of constitutive AP1-dependent genes, as TGF-β1.

Induction of endothelial nitric oxide synthase expression by IL-17 in human vascular endothelial cells: implications for vascular remodeling in transplant vasculopathy

IL-17 is a signature cytokine of Th17 cells, a recently described subset of effector CD4 T cells implicated in the development of several pathologies. We have examined the role of IL-17 in regulating endothelial NO synthase (eNOS) expression in human vascular endothelial cells (ECs) because of the key role of eNOS in determining the pathological outcome of immune-mediated vascular diseases. In cultured ECs, IL-17 increased expression of eNOS, eNOS phosphorylation at Ser(1177), and NO production. The induction of eNOS expression by IL-17 was prevented by the pharmacological inhibition of NF-κB, MEK, and JNK, as well as by small interfering RNA-mediated gene silencing of these signaling pathways. The expression of IL-17 was then examined by immunohistochemistry in human arteries affected by transplant vasculopathy (TV), a vascular condition that is a leading reflection of chronic heart transplant rejection. IL-17 was expressed by infiltrating leukocytes in the intima of arteries with TV, and the majority of IL-17-positive cells were T cells. The number of IL-17-positive cells was not correlated with the intima/media ratio, but was negatively correlated with the amount of luminal occlusion. There was also a significant positive correlation between the number of IL-17-positive cells and the density of eNOS-expressing luminal ECs in arteries with TV. Altogether, these findings show that IL-17 induces the expression of eNOS in human ECs and that this may facilitate outward expansion of arteries afflicted with TV.

Genomewide association study using a high-density single nucleotide polymorphism array and case-control design identifies a novel essential hypertension susceptibility locus in the promoter region of endothelial NO synthase

Essential hypertension is a multifactorial disorder and is the main risk factor for renal and cardiovascular complications. The research on the genetics of hypertension has been frustrated by the small predictive value of the discovered genetic variants. The HYPERGENES Project investigated associations between genetic variants and essential hypertension pursuing a 2-stage study by recruiting cases and controls from extensively characterized cohorts recruited over many years in different European regions. The discovery phase consisted of 1865 cases and 1750 controls genotyped with 1M Illumina array. Best hits were followed up in a validation panel of 1385 cases and 1246 controls that were genotyped with a custom array of 14 055 markers. We identified a new hypertension susceptibility locus (rs3918226) in the promoter region of the endothelial NO synthase gene (odds ratio: 1.54 [95% CI: 1.37-1.73]; combined P=2.58 · 10(-13)). A meta-analysis, using other in silico/de novo genotyping data for a total of 21 714 subjects, resulted in an overall odds ratio of 1.34 (95% CI: 1.25-1.44; P=1.032 · 10(-14)). The quantitative analysis on a population-based sample revealed an effect size of 1.91 (95% CI: 0.16-3.66) for systolic and 1.40 (95% CI: 0.25-2.55) for diastolic blood pressure. We identified in silico a potential binding site for ETS transcription factors directly next to rs3918226, suggesting a potential modulation of endothelial NO synthase expression. Biological evidence links endothelial NO synthase with hypertension, because it is a critical mediator of cardiovascular homeostasis and blood pressure control via vascular tone regulation. This finding supports the hypothesis that there may be a causal genetic variation at this locus.

Successful allogeneic hematopoietic stem cell transplantation for GATA2 deficiency

We performed nonmyeloablative HSCT in 6 patients with a newly described genetic immunodeficiency syndrome caused by mutations in GATA2-a disease characterized by nontuberculous mycobacterial infection, monocytopenia, B- and NK-cell deficiency, and the propensity to transform to myelodysplastic syndrome/acute myelogenous leukemia. Two patients received peripheral blood stem cells (PBSCs) from matched-related donors, 2 received PBSCs from matched-unrelated donors, and 2 received stem cells from umbilical cord blood (UCB) donors. Recipients of matched-related and -unrelated donors received fludarabine and 200 cGy of total body irradiation (TBI); UCB recipients received cyclophosphamide in addition to fludarabine and TBI as conditioning. All patients received tacrolimus and sirolimus posttransplantation. Five patients were alive at a median follow-up of 17.4 months (range, 10-25). All patients achieved high levels of donor engraftment in the hematopoietic compartments that were deficient pretransplantation. Adverse events consisted of delayed engraftment in the recipient of a single UCB, GVHD in 4 patients, and immune-mediated pancytopenia and nephrotic syndrome in the recipient of a double UCB transplantation. Nonmyeloablative HSCT in GATA2 deficiency results in reconstitution of the severely deficient monocyte, B-cell, and NK-cell populations and reversal of the clinical phenotype. Registered at www.clinicaltrials.gov as NCT00923364.

Epigenetically coordinated GATA2 binding is necessary for endothelium-specific endomucin expression

GATA2 is well recognized as a key transcription factor and regulator of cell-type specificity and differentiation. Here, we carried out comparative chromatin immunoprecipitation with comprehensive sequencing (ChIP-seq) to determine genome-wide occupancy of GATA2 in endothelial cells and erythroids, and compared the occupancy to the respective gene expression profile in each cell type. Although GATA2 was commonly expressed in both cell types, different GATA2 bindings and distinct cell-specific gene expressions were observed. By using the ChIP-seq with epigenetic histone modifications and chromatin conformation capture assays; we elucidated the mechanistic regulation of endothelial-specific GATA2-mediated endomucin gene expression, that was regulated by the endothelial-specific chromatin loop with a GATA2-associated distal enhancer and core promoter. Knockdown of endomucin markedly attenuated endothelial cell growth, migration and tube formation. Moreover, abrogation of GATA2 in endothelium demonstrated not only a reduction of endothelial-specific markers, but also induction of mesenchymal transition promoting gene expression. Our findings provide new insights into the correlation of endothelial-expressed GATA2 binding, epigenetic modification, and the determination of endothelial cell specificity.

The role of the GATA2 transcription factor in normal and malignant hematopoiesis

Hematopoiesis involves an elaborate regulatory network of transcription factors that coordinates the expression of multiple downstream genes, and maintains homeostasis within the hematopoietic system through the accurate orchestration of cellular proliferation, differentiation and survival. As a result, defects in the expression levels or the activity of these transcription factors are intimately linked to hematopoietic disorders, including leukemia. The GATA family of nuclear regulatory proteins serves as a prototype for the action of lineage-restricted transcription factors. GATA1 and GATA2 are expressed principally in hematopoietic lineages, and have essential roles in the development of multiple hematopoietic cells, including erythrocytes and megakaryocytes. Moreover, GATA2 is crucial for the proliferation and maintenance of hematopoietic stem cells and multipotential progenitors. In this review, we summarize the current knowledge regarding the biological properties and functions of the GATA2 transcription factor in normal and malignant hematopoiesis.

Haem arginate infusion stimulates haem oxygenase-1 expression in healthy subjects

BACKGROUND AND PURPOSE

Haem oxygenase 1 (HO-1) is an inducible protein that plays a major protective role in conditions such as ischaemia-reperfusion injury and inflammation. In this study, we have investigated the role of haem arginate (HA) in human male subjects in the modulation of HO-1 expression and its correlation with the GT length polymorphism (GT(n)) in the promoter of the HO-1 gene.

EXPERIMENTAL APPROACH

In a dose-escalation, randomized, placebo-controlled trial, seven healthy male subjects with a homozygous short (S/S) and eight with a long (L/L) GT(n) genotype received intravenous HA. HO-1 protein expression and mRNA levels in peripheral blood monocytes, bilirubin, haptoglobin, haemopexin and haem levels were analysed over a 48 h observation period.

KEY RESULTS

We found that the baseline mRNA levels of HO-1 were higher in L/L subjects, while protein levels were higher in S/S subjects. HA induced a dose-dependent increase in the baseline corrected area under the curve values of HO-1 mRNA and protein over 48 h. The response of HO-1 mRNA was more pronounced in L/L subjects but the protein level was similar across the groups.

CONCLUSIONS AND IMPLICATION

HA is an effective inducer of HO-1 in humans irrespective of the GT(n) genotype. The potential therapeutic application of HA needs to be evaluated in clinical trials.

Vascular Endothelial Growth Factor Increases Endothelial Nitric Oxide Synthase Transcription In Huvec Cells

Although it is known that VEGF increases eNOS protein, the mechanisms responsible remain unclear. To determine if VEGF alters eNOS transcription, human umbilical vein endothelial cells were transfected with reporters under the control of the eNOS promoter and stimulated with VEGF₁₆₅. VEGF significantly increased eNOS-mRNA after 2 hours exposure. VEGF significantly increased eNOS reporter activity as early as one hour (268±32%), but this increase returned to baseline after 6 hours. Using deletion constructs, the VEGF response region was initially localized to within the -722/-494 region. GMSA indicated that VEGF increased DNA binding to both a cAMP-like and AP1-like response elements. Site-specific mutations and heterologous constructs indicated that the site centered at AP1-like site was both necessary and sufficient to meditate VEGF transcriptional activation. These results indicate that VEGF rapidly activates eNOS transcription prior to a rise eNOS-mRNA, an effect mediated by a cis-trans interaction localized to an AP1-like site within the eNOS promoter.

An endocardial pathway involving Tbx5, Gata4, and Nos3 required for atrial septum formation

In humans, septal defects are among the most prevalent congenital heart diseases, but their cellular and molecular origins are not fully understood. We report that transcription factor Tbx5 is present in a subpopulation of endocardial cells and that its deletion therein results in fully penetrant, dose-dependent atrial septal defects in mice. Increased apoptosis of endocardial cells lacking Tbx5, as well as neighboring TBX5-positive myocardial cells of the atrial septum through activation of endocardial NOS (Nos3), is the underlying mechanism of disease. Compound Tbx5 and Nos3 haploinsufficiency in mice worsens the cardiac phenotype. The data identify a pathway for endocardial cell survival and unravel a cell-autonomous role for Tbx5 therein. The finding that Nos3, a gene regulated by many congenital heart disease risk factors including stress and diabetes, interacts genetically with Tbx5 provides a molecular framework to understand gene-environment interaction in the setting of human birth defects.

VE-statin/egfl7 expression in endothelial cells is regulated by a distal enhancer and a proximal promoter under the direct control of Erg and GATA-2

Angiogenesis is the process by which new blood vessels arise from existing ones by the budding out of endothelial cell capillaries from the luminal side of blood vessels. Blood vessel formation is essential for organ development during embryogenesis and is associated with several physiological and pathological processes, such as wound healing and tumor development. The VE-statin/egfl7 gene is specifically expressed in endothelial cells during embryonic development and in the adult. We studied here the regulatory mechanisms that control this tissue-specific expression. RT-qPCR analyses showed that the specificity of expression of VE-statin/egfl7 in endothelial cells is not shared with its closest neighbor genes notch1 and agpat2 on the mouse chromosome 2. Chromatin-immunoprecipitation analysis of histone modifications at the VE-statin/egfl7 locus showed that the chromatin is specifically opened in endothelial cells, but not in fibroblasts at the transcription start sites. A 13 kb genomic fragment of promoter was cloned and analyzed by gene reporter assays which showed that two conserved regions are important for the specific expression of VE-statin/egfl7 in endothelial cells; a −8409/−7563 enhancer and the −252/+38 region encompassing the exon-1b transcription start site. The latter contains essential GATA and ETS-binding sites, as assessed by linker-scanning analysis and site-directed mutagenesis. An analysis of expression of the ETS and GATA transcription factors showed that Erg, Fli-1 and GATA-2 are the most highly expressed factors in endothelial cells. Erg and GATA-2 directly control the expression of the endogenous VE-statin/egfl7 while Fli-1 probably exerts an indirect control, as assessed by RNA interference and chromatin immunoprecipitation. This first detailed analysis of the mechanisms that govern the expression of the VE-statin/egfl7 gene in endothelial cells pinpoints the specific importance of ETS and GATA factors in the specific regulation of genes in this cell lineage.

Characterization of the human Activin-A receptor type II-like kinase 1 (ACVRL1) promoter and its regulation by Sp1

Background

Activin receptor-like kinase 1 (ALK1) is a Transforming Growth Factor-β (TGF-β) receptor type I, mainly expressed in endothelial cells that plays a pivotal role in vascular remodelling and angiogenesis. Mutations in the ALK1 gene (ACVRL1) give rise to Hereditary Haemorrhagic Telangiectasia, a dominant autosomal vascular dysplasia caused by a haploinsufficiency mechanism. In spite of its patho-physiological relevance, little is known about the transcriptional regulation of ACVRL1. Here, we have studied the different origins of ACVRL1 transcription, we have analyzed in silico its 5'-proximal promoter sequence and we have characterized the role of Sp1 in the transcriptional regulation of ACVRL1.

Results

We have performed a 5'Rapid Amplification of cDNA Ends (5'RACE) of ACVRL1 transcripts, finding two new transcriptional origins, upstream of the one previously described, that give rise to a new exon undiscovered to date. The 5'-proximal promoter region of ACVRL1 (-1,035/+210) was analyzed in silico, finding that it lacks TATA/CAAT boxes, but contains a remarkably high number of GC-rich Sp1 consensus sites. In cells lacking Sp1, ACVRL1 promoter reporters did not present any significant transcriptional activity, whereas increasing concentrations of Sp1 triggered a dose-dependent stimulation of its transcription. Moreover, silencing Sp1 in HEK293T cells resulted in a marked decrease of ACVRL1 transcriptional activity. Chromatin immunoprecipitation assays demonstrated multiple Sp1 binding sites along the proximal promoter region of ACVRL1 in endothelial cells. Furthermore, demethylation of CpG islands, led to an increase in ACVRL1 transcription, whereas in vitro hypermethylation resulted in the abolishment of Sp1-dependent transcriptional activation of ACVRL1.

Conclusions

Our results describe two new transcriptional start sites in ACVRL1 gene, and indicate that Sp1 is a key regulator of ACVRL1 transcription, providing new insights into the molecular mechanisms that contribute to the expression of ACVRL1 gene. Moreover, our data show that the methylation status of CpG islands markedly modulates the Sp1 regulation of ACVRL1 gene transcriptional activity.

Hydrogen peroxide decreases endothelial nitric oxide synthase promoter activity through the inhibition of Sp1 activity

We have previously shown that endothelial nitric oxide synthase (eNOS) promoter activity is decreased in endothelial cells in response to the addition of hydrogen peroxide (H(2)O(2)), and this involves, at least in part, the inhibition of AP-1 activity. Thus, the objective of this study was to determine if other cis-element(s) and transcription factor(s) are involved in the oxidant-mediated downregulation of eNOS. Our initial experiments indicated that although H(2)O(2) treatment increased eNOS mRNA levels in ovine pulmonary arterial endothelial cells (OPAECs), there was a significant decrease in the promoter activity of an eNOS promoter construct containing 840 bp of upstream sequence. However, a truncated promoter construct that lacked the AP-1 element (650 bp) was also inhibited by H(2)O(2). A similar effect was observed when the 650 bp human eNOS promoter construct was transfected into human PAECs. We also found that although exposure of the cells to PEG-catalase prevented the inhibitory effect on eNOS promoter activity, the hydroxyl radical scavenger, deferoxamine myslate, did not. Nor could we identify an increase in hydroxyl radical levels in cells exposed to H(2)O(2). Exposure of PAECs caused a significant increase in labile zinc levels in response to H(2)O(2). As the eNOS promoter has a cis-element for Sp1 binding, we evaluated the role of Sp1 in response to H(2)O(2). As previously reported, mutation of the Sp1 consensus lead to the complete loss of eNOS promoter activity, confirming the key role of Sp1 in regulating basal eNOS promoter activity. In addition, we found, using electrophoretic mobility and supershift assays, that H(2)O(2) decreased Sp1 binding. Finally, using chromatin immunoprecipitation analysis, we found a significant decrease in Sp1 binding to the eNOS promoter in vivo in response to treatment with H(2)O(2). Together, these data suggest that the inhibition of Sp1 activity, possibly through loss of zinc in the protein, plays a role in the H(2)O(2)-induced inhibition of eNOS promoter activity.

SENP1-mediated GATA1 deSUMOylation is critical for definitive erythropoiesis

Small ubiquitin-like modifier (SUMO) modification of proteins (SUMOylation) and deSUMOylation have emerged as important regulatory mechanisms for protein function. SENP1 (SUMO-specific protease) deconjugates SUMOs from modified proteins. We have created SENP1 knockout (KO) mice based on a Cre-loxP system. Global deletion of SENP1 (SENP1 KO) causes anemia and embryonic lethality between embryonic day 13.5 and postnatal day 1, correlating with erythropoiesis defects in the fetal liver. Bone marrow transplantation of SENP1 KO fetal liver cells to irradiated adult recipients confers erythropoiesis defects. Protein analyses show that the GATA1 and GATA1-dependent genes are down-regulated in fetal liver of SENP1 KO mice. This down-regulation correlates with accumulation of a SUMOylated form of GATA1. We further show that SENP1 can directly deSUMOylate GATA1, regulating GATA1-dependent gene expression and erythropoiesis by in vitro assays. Moreover, we demonstrate that GATA1 SUMOylation alters its DNA binding, reducing its recruitment to the GATA1-responsive gene promoter. Collectively, we conclude that SENP1 promotes GATA1 activation and subsequent erythropoiesis by deSUMOylating GATA1.

SPP1 promoter polymorphisms and glioma risk in a Chinese Han population

SPP1 was found to be significantly upregulated in many kinds of malignant tumors, including gliomas. Considering that gene polymorphisms have been implicated in the development of gliomas, we performed an association study between SPP1 functional promoter region polymorphisms and glioma risk in a Chinese population. We found significant evidence of an association between SPP1 promoter polymorphisms and glioma risk. For the -155_156insG variant, the -155_156GG allele was found to be significantly associated with an increased risk of glioma (P=0.020, odds ratio (OR)=1.202, 95% confidence interval (CI): 1.028-1.408). Individuals with the genotype containing the GG allele had a 1.372-fold increased risk (P=0.006, OR=1.372, 95% CI: 1.095-1.719). Further stratified analyses suggested that a significant association existed in adult glioma patients, male subjects and in cases without a family history of cancer. Alternatively, the study of single-nucleotide polymorphism -443C/T in a recessive model revealed that the genotype CC+CT significantly decreased the risk of glioma when compared with TT (P=0.023, OR=0.774, 95% CI: 0.621-0.966). After the analysis of haplotypes, the haplotype -155_156GG/-443T was represented at a significantly higher frequency in cases (P=0.029, OR=1.192, 95% CI: 1.018-1.395). Cellular assay indicated that the transcriptional activity of the SPP1 promoter containing the -155_156GG allele significantly increased in glioma cells. Thus, variants of the SPP1 promoter might influence the risk of glioma by regulating promoter activity. Further analyses are necessary to validate our observation in larger samples or in other ethnic groups.