Vascular endothelial growth factor induced functional and morphologic signs of endothelial dysfunction in isolated arteries from normal pregnant women

Maternal systemic vascular dysfunction in a primate model of defective uterine spiral artery remodeling

Uterine spiral artery remodeling (UAR) is essential for placental perfusion and fetal development. A defect in UAR underpins placental ischemia disorders, e.g., preeclampsia, that result in maternal systemic vascular endothelial dysfunction and hypertension. We have established a model of impaired UAR by prematurely elevating maternal serum estradiol levels during the first trimester of baboon pregnancy. However, it is unknown whether this experimental paradigm is associated with maternal vascular endothelial dysfunction. Therefore, in the present study baboons were administered estradiol on days 25-59 of gestation to suppress UAR and maternal vascular function determined on day 165 (term = 184 days) peripherally and in skeletal muscle, which accounts for over 40% of body mass and 25% of resting systemic vascular resistance. Maternal serum sFlt-1 levels were 2.5-fold higher (P < 0.05), and skeletal muscle arteriolar endothelial nitric oxide synthase (eNOS) protein expression and luminal area, and skeletal muscle capillary density were 30-50% lower (P < 0.05) in UAR suppressed baboons. Coinciding with these changes in eNOS expression, luminal area, and capillary density, maternal brachial artery flow-mediated dilation and volume flow were 70% and 55% lower (P < 0.05), respectively, and mean arterial blood pressure 29% higher (P < 0.01) in UAR defective baboons. In summary, maternal vascular function was disrupted in a baboon model of impaired UAR. These results highlight the translational impact of this primate model and relevance to adverse conditions of human pregnancy underpinned by improper uterine artery transformation.NEW & NOTEWORTHY Maternal vascular dysfunction is a hallmark of abnormal human pregnancy, particularly early-onset preeclampsia, elicited by impaired UAR. The present study makes the novel discovery that maternal systemic vascular dysfunction was induced in a baboon experimental model of impaired UAR. This study highlights the translational relevance of this nonhuman primate model to adverse conditions of human pregnancy underpinned by defective UAR.

Endothelial glycocalyx restoration by growth factors in diabetic nephropathy

The endothelial glycocalyx (eGlx) constitutes the first barrier to protein in all blood vessels. This is particularly noteworthy in the renal glomerulus, an ultrafiltration barrier. Leakage of protein, such as albumin, across glomerular capillaries results in albumin in the urine (albuminuria). This is a hall mark of kidney disease and can reflect loss of blood vessel integrity in microvascular beds elsewhere. We discuss evidence demonstrating that targeted damage to the glomerular eGlx results in increased glomerular albumin permeability. EGlx is lost in diabetes and experimental models demonstrate loss from glomerular endothelial cells. Vascular endothelial growth factor (VEGF)A is upregulated in early diabetes, which is associated with albuminuria. Treatment with paracrine growth factors such as VEGFC, VEGF165b and angiopoietin-1 can modify VEGFA signalling, rescue albumin permeability and restore glomerular eGlx in models of diabetes. Manipulation of VEGF receptor 2 signalling, or a common eGlx biosynthesis pathway by these growth factors, may protect and restore the eGlx layer. This would help to direct future therapeutics in diabetic nephropathy.

Association of pregnancy-associated plasma protein A and vascular endothelial growth factor with pregnancy-induced hypertension

The present study aimed to evaluate changes of pregnancy-associated plasma protein A (PAPP-A) and vascular endothelial growth factor (VEGF) in pregnancy-induced hypertension (PIH). A total of 105 cases (observation group) with complete data that underwent delivery and suffered from PIH in The Affiliated Hospital of Xuzhou Medical University from February 2015 to February 2017 were retrospectively analyzed. The observation group was further divided into the mild observation and severe observation groups according to severity degree of the disease. Another 65 asymptomatic pregnant women were recruited as the healthy control group. Basic data, obstetric data, PAPP-A and VEGF and data of perinatal infants were compared and analyzed. The Logistic regression model was adopted to screen out risk factors for PIH. In the observation group, the rate of periodic antenatal care was lower, and there were more primigravidas and housewives, with lower education level and economic income (P<0.05). In the observation group, the occurrence rates of placental abruption as well as turbid and bloody amniotic fluid were higher than those in the healthy control group (P<0.05). The neonatal birth weight was lower in the observation group than that in the healthy control group, while the occurrence rates of neonatal department transfer, small for gestational age (SGA), neonatal asphyxia and survival rates of perinatal infants were higher (P<0.05). PAPP-A levels at 34-40 gestational weeks in the observation group were significantly higher than those in the healthy control group (P<0.05). VEGF levels were lower than those in the healthy control group (P<0.05). Multivariate analysis revealed that high PAPP-A value [odds ratio (OR)=3.736] and identity of housewife (OR=2.514) were risk factors for PIH, while high VEGF value (OR=5.258), non-primigravid (OR=2.173), higher economic income (OR=4.162) and periodic antenatal care (OR=1.201) were regarded as protective factors. Therefore, enhancement of gestational management, early discovery and early treatment are critical for improving the prognosis of pregnant women and infants.

VEGF-A inhibits agonist-mediated Ca2+ responses and activation of IKCa channels in mouse resistance artery endothelial cells

KEY POINTS

Prolonged exposure to vascular endothelial growth factor A (VEGF-A) inhibits agonist-mediated endothelial cell Ca²⁺ release and subsequent activation of intermediate conductance Ca²⁺ -activated K⁺ (IK_Ca ) channels, which underpins vasodilatation as a result of endothelium-dependent hyperpolarization (EDH) in mouse resistance arteries. Signalling via mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) downstream of VEGF-A was required to attenuate endothelial cell Ca²⁺ responses and the EDH-vasodilatation mediated by IK_Ca activation. VEGF-A exposure did not modify vasodilatation as a result of the direct activation of IK_Ca channels, nor the pattern of expression of inositol 1,4,5-trisphosphate receptor 1 within endothelial cells of resistance arteries. These results indicate a novel role for VEGF-A in resistance arteries and suggest a new avenue for investigation into the role of VEGF-A in cardiovascular diseases.

ABSTRACT

Vascular endothelial growth factor A (VEGF-A) is a potent permeability and angiogenic factor that is also associated with the remodelling of the microvasculature. Elevated VEGF-A levels are linked to a significant increase in the risk of cardiovascular dysfunction, although it is unclear how VEGF-A has a detrimental, disease-related effect. Small resistance arteries are central determinants of peripheral resistance and endothelium-dependent hyperpolarization (EDH) is the predominant mechanism by which these arteries vasodilate. Using isolated, pressurized resistance arteries, we demonstrate that VEGF-A acts via VEGF receptor-2 (R2) to inhibit both endothelial cell (EC) Ca²⁺ release and the associated EDH vasodilatation mediated by intermediate conductance Ca²⁺ -activated K⁺ (IK_Ca ) channels. Importantly, VEGF-A had no direct effect against IK_Ca channels. Instead, the inhibition was crucially reliant on the downstream activation of the mitogen-activated protein/extracellular signal-regulated kinase kinase 1/2 (MEK1/2). The distribution of EC inositol 1,4,5-trisphosphate (IP₃ ) receptor-1 (R1) was not affected by exposure to VEGF-A and we propose an inhibition of IP₃ R1 through the MEK pathway, probably via ERK1/2. Inhibition of EC Ca²⁺ via VEGFR2 has profound implications for EDH-mediated dilatation of resistance arteries and could provide a mechanism by which elevated VEGF-A contributes towards cardiovascular dysfunction.

Altered Endothelial Nitric Oxide Signaling as a Paradigm for Maternal Vascular Maladaptation in Preeclampsia

PURPOSE OF REVIEW

The goal of this review is to present the newest insights into what we view as a central failure of cardiovascular adaptation in preeclampsia (PE) by focusing on one clinically significant manifestation of maternal endothelial dysfunction: nitric oxide signaling. The etiology, symptoms, and current theories of the PE syndrome are described first, followed by a review of the available evidence, and underlying causes of reduced endothelial nitric oxide (NO) signaling in PE.

RECENT FINDINGS

PE maladaptations include, but are not limited to, altered physiological stimulatory inputs (e.g., estrogen; VEGF/PlGF; shear stress) and substrates (L-Arg; ADMA), augmented placental secretion of anti-angiogenic and inflammatory factors such as sFlt-1 and Eng, changes in eNOS (polymorphisms, expression), and reduced bioavailability of NO secondary to oxidative stress. PE is a complex obstetrical syndrome that is associated with maternal vascular dysfunction. Diminished peripheral endothelial vasodilator influence in general, and of NO signaling specifically, are key in driving disease progression and severity.

Endothelial maintenance in health and disease: Importance of sex differences

The vascular endothelium has emerged as more than just an inert monolayer of cells lining the vascular bed. It represents the interface between the blood stream and vessel wall, and has a strategic role in regulating vascular homeostasis by the release of vasoactive substances. Endothelial dysfunction contributes to the development and progression of cardiovascular disease. Recognition of sex-specific factors implicated in endothelial cell biology is important for the identification of clinically relevant preventive and/or therapeutic strategies. This review aims to give an overview of the recent advances in understanding the importance of sex specific observations in endothelial maintenance, both in healthy and diseased conditions. The female endothelium is highlighted in the context of polycystic ovary syndrome and pre-eclampsia. Furthermore, sex differences are explored in chronic kidney disease, which is currently appreciated as one of public health priorities. Overall, this review endorses integration of sex analysis in experimental and patient-oriented research in the exciting field of vascular biology.

Targeting growth factor supply in keratopathy treatment: comparison between maternal peripheral blood and cord blood as sources for the preparation of topical eye drops

BACKGROUND

Epitheliotrophic growth factors (GF) can be supplied topically to patients with severe keratopathy through a variety of blood-derived products. We compared GF content in adult peripheral blood serum (PB-S) and cord blood serum (CB-S) as potential sources of GF. To limit inter-individual variability the assessment was performed in maternal-child pairs at the time of delivery.

MATERIAL AND METHODS

The amounts of epidermal GF (EGF), insulin-like GF (IGF), transforming GF-beta (TGF-β), vascular endothelial GF (VEGF) in CB units collected from the umbilical vein and PB from mothers (each group n=30) were estimated by enzyme-linked immunosorbent assays. Obstetric characteristics and haematological data were recorded from the archives of the Emilia Romagna Cord Blood Bank. Statistical evaluations were performed by Wilcoxon's test and correlations between variables were determined using Spearman's (ρ) coefficient; p-values <0.05 were considered statistically significant.

RESULTS

EGF, TGF-β and VEGF levels were significantly higher in CB-S than in PB-S (median 1,254.4 vs 646.0 pg/mL, 51.3 vs 38.4 μg/mL and 686.8 vs 30 pg/mL, respectively; all p<0.0001) whereas IGF content was significantly higher in PB-S than in CB-S (159.9 vs 53.5 pg/mL, respectively; p<0.0001). In CB-S, the CD34(+) cell concentration appeared to be related to EGF, IGF and TGF-β levels whereas white blood cell count appeared to be related to EGF and TGF-β levels. VEGF levels showed no relation to the haematological parameters considered. Platelet counts were not related to GF level in either CB or PB.

DISCUSSION

The GF content in the two blood sources was different, with CB containing larger amounts. Each GF selectively regulates cellular processes involved in corneal healing, so the use of PB or CB should be targeted to supply specific GF on the basis of the type and severity of the keratopathy.

Quantitative characterization of endothelial cell morphologies depending on shear stress in different blood vessels of domestic pigs using a focused ion beam and high resolution scanning electron microscopy (FIB-SEM)

Microstructured surfaces mimicking the endothelial cell (EC) morphology is a new approach to improve the blood compatibility of synthetic vascular grafts. The ECs are capable of changing their shapes depending on different shear conditions. However, the quantitative correlation between EC morphology and shear stress has not yet been investigated statistically. The aim of this study was to quantitatively investigate the morphology of ECs in dependence on the shear stress. Blood flow rates in different types of natural blood vessels (carotid, renal, hepatic and iliac arteries) originated from domestic pigs were first measured in vivo to calculate the shear stresses. The EC morphologies were quantitatively characterized ex vivo by imaging with high resolution scanning electron microscopy (SEM) and cross-sectioning of the cells using a state-of-the-art focused ion beam (FIB). The relationships between EC geometrical parameters and shear stress were statistically analyzed and found to be exponential. ECs under high shear stress conditions had a longer length and narrower width, i.e. a higher aspect ratio, while the cell height was smaller compared to low shear conditions. Based on these results, suitable and valid geometrical parameters of microstructures mimicking EC can be derived for various shear conditions in synthetic vascular grafts to optimize blood compatibility.

Public health and components of particulate matter: the changing assessment of black carbon

In 2012, the WHO classified diesel emissions as carcinogenic, and its European branch suggested creating a public health standard for airborne black carbon (BC). In 2011, EU researchers found that life expectancy could be extended four to nine times by reducing a unit of BC, vs reducing a unit of PM2.5. Only recently could such determinations be made. Steady improvements in research methodologies now enable such judgments. In this Critical Review, we survey epidemiological and toxicological literature regarding carbonaceous combustion emissions, as research methodologies improved over time. Initially, we focus on studies of BC, diesel, and traffic emissions in the Western countries (where daily urban BC emissions are mainly from diesels). We examine effects of other carbonaceous emissions, e.g., residential burning of biomass and coal without controls, mainly in developing countries. Throughout the 1990s, air pollution epidemiology studies rarely included species not routinely monitored. As additional PM2.5. chemical species, including carbonaceous species, became more widely available after 1999, they were gradually included in epidemiological studies. Pollutant species concentrations which more accurately reflected subject exposure also improved models. Natural "interventions"--reductions in emissions concurrent with fuel changes or increased combustion efficiency; introduction of ventilation in highway tunnels; implementation of electronic toll payment systems--demonstrated health benefits of reducing specific carbon emissions. Toxicology studies provided plausible biological mechanisms by which different PM species, e.g, carbonaceous species, may cause harm, aiding interpretation of epidemiological studies. Our review finds that BC from various sources appears to be causally involved in all-cause, lung cancer and cardiovascular mortality, morbidity, and perhaps adverse birth and nervous system effects. We recommend that the US. EPA rubric for judging possible causality of PM25. mass concentrations, be used to assess which PM2.5. species are most harmful to public health.

IMPLICATIONS

Black carbon (BC) and correlated co-emissions appear causally related with all-cause, cardiovascular, and lung cancer mortality, and perhaps with adverse birth outcomes and central nervous system effects. Such findings are recent, since widespread monitoring for BC is also recent. Helpful epidemiological advances (using many health relevant PM2.5 species in models; using better measurements of subject exposure) have also occurred. "Natural intervention" studies also demonstrate harm from partly combusted carbonaceous emissions. Toxicology studies consistently find biological mechanisms explaining how such emissions can cause these adverse outcomes. A consistent mechanism for judging causality for different PM2.5 species is suggested.

Pathogenesis of pre-eclampsia: marinobufagenin and angiogenic imbalance as biomarkers of the syndrome

Pre-eclampsia (preE), a pregnancy disorder with the de novo onset of hypertension and proteinuria after 20 weeks of gestation, has multiple triggers that initiate pathophysiologic mechanisms. This review addresses translational aspects of preE by synthesizing information on preE pathogenesis, describing diagnostic biomarkers that predict disease, and suggesting strategies to lessen adverse outcomes. Key to this understanding is the role of cardiotonic bufodienolides, with marinobufagenin (MBG) as the prototype, and angiogenic factors in preE pathogenesis. Data from a rat model believed to mimic human preE show that urinary excretion of MBG increases before the onset of hypertension and proteinuria and that affected animals have an increased vascular leakage and blood brain barrier permeability. Angiogenic imbalance occurs with the onset of the syndrome in this model. Also, we report that MBG levels in preE patients exceed those in normal pregnancy and that angiogenic factors are altered in patients showing signs and symptoms of overt disease. In vitro administration of MBG inhibits cytotrophoblast function and triggers hyperpermeability in endothelial cell monolayers. We advance the hypotheses that MBG precedes preE; MBG causes disruption of tight junction proteins leading to vascular leak via activation of MAPK which triggers apoptotic mechanisms resulting in further endothelial dysfunction leading to edema with the release of angiogenic factors. This review provides new evidence about the role of MBG and vasoactive intermediates in preE pathogenesis including the neurologic sequela and may reveal new therapeutic targets for the prevention of preE complications.

Maternal levels of prostacyclin, thromboxane, ICAM, and VCAM in normal and preeclamptic pregnancies

PROBLEM

To evaluate whether impaired endothelial function and endothelial inflammatory response occur in parallel in the women with preeclampsia.

METHOD OF STUDY

Venous blood was drawn from normal (n=40) and severe preeclamptic (sPE) (n=40) pregnant women when they were admitted to the L&D Unit and 24 hrs after delivery. Plasma and serum samples were extracted and measured for 6-keto PGF1α and TXB(2) (stable metabolites of PGI2 and TXA2), and intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM) by ELISA. Data are analyzed by Mann-Whitney test and paired t-test. The statistical significance is set as P<0.05. Results  Plasma 6-keto PGF1α levels were significantly reduced at admission and 24hr after delivery in sPE compared to normal pregnant controls, P<0.01. The ratio of 6-keto PGF1α and TXB(2) was significant less in sPE than that in normal pregnant controls before delivery. There was no significant difference for ICAM and VCAM levels between normal and patients with sPE before and after delivery.

CONCLUSION

Maternal 6-keto PGF1α levels and the ratio of 6-keto PGF1α and TXB(2) were decreased in patients with sPE compared to normal pregnant controls. In contrast, maternal ICAM and VCAM levels were not different between the two groups. These data suggest that serum ICAM and VCAM levels may not be sensitive inflammatory biomarkers for preeclampsia.

Vascular Endothelial Growth Factor Induces Endothelin-1 Production via Matrix Metalloproteinase-2 Rather than Endothelin-Converting Enzyme-1

OBJECTIVE

To investigate the mechanism of vascular endothelial growth factor (VEGF)-induced endothelin-1 production in human umbilical vein endothelial cells (HUVECs).

METHODS

Endothelin-1 levels were measured in conditioned medium of women with preeclampsia HUVECs were treated with different concentrations of VEGF(165) and at various time intervals. Next, we measured endothelin-1 levels after HUVECs were also incubated with VEGF and endothelin-converting enzyme-1 (ECE-1) inhibitor or tissue inhibitors of matrix metalloproteinase-2 (TIMP-2). Additionally, the circulating levels of total and free VEGF, matrix metalloproteinase-2 (MMP-2), and endothelin-1 were measured in 20 preeclamptic patients and 20 healthy pregnant controls.

RESULTS

HUVECs treated with VEGF increased their endothelin-1 production in a concentration and time-dependent manner. The production of endothelin-1 was inhibited by TIMP-2, but not by the ECE-1 inhibitor. Total VEGF, MMP-2, and endothelin-1 concentrations were higher in preeclampsia and showed significant positive correlations between them.

CONCLUSION

These findings suggest that VEGF-induced endothelin-1 production might be mediated by MMP-2 rather than by ECE-1 upregulation.

Marinobufagenin causes endothelial cell monolayer hyperpermeability by altering apoptotic signaling

Marinobufagenin (MBG) is an endogenous mammalian cardiotonic steroid that is involved in the inhibition of the sodium pump Na(+)/K(+)-ATPase. Increased plasma levels of MBG have been reported in patients with preeclampsia. MBG increases microvascular barrier permeability in an animal model of preeclampsia. However, the mechanism by which MBG impairs endothelial permeability is unknown. We utilized rat lung microvascular endothelial cells (RLMEC) to examine alterations in MBG-induced monolayer permeability and the effect of MBG on the phosphorylation status of ERK1/2, Jnk, and p38. Apoptosis was evaluated by examining alterations in caspases 3/7, 8, and 9 and annexin-V staining. We also examined the effect of MBG on the endothelial adherens junctions of the RLMEC monolayer. MBG inhibited the proliferation, and increased the monolayer permeability, of RLMEC. These actions of MBG were attenuated by ERK, p38, and pan caspase inhibition. MBG significantly decreased the phosphorylation of ERK1/2 and activated the phosphorylation of Jnk and p38. MBG also significantly increased the expression of caspases 3/7, 8, and 9, indicating the activation of apoptosis. MBG-induced apoptosis signaling was not observed in cells pretreated with a p38 inhibitor. MBG treatment induced the disruption of endothelial cell junctions. This effect was prevented by a pan caspase inhibitor. In conclusion, 1) MBG induced an impairment of RLMEC proliferation; 2) the bufadienolide also caused endothelial hyperpermeability; and 3) these effects of MBG were mediated by the downregulation of ERK1/2, the upregulation of Jnk and p38, by the activation of apoptosis, and by the disruption of endothelial cell junctions.

Placenta-derived chymotrypsin-like protease (CLP) disturbs endothelial junctional structure in preeclampsia

Placenta-derived chymotrypsin-like protease may contribute to endothelial activation in preeclampsia. In this study, we determined if placenta-derived chymotrypsin-like protease could disturb endothelial junctional integrity to promote endothelial permeability in preeclampsia. Confluent endothelial cells were cocultured with placental trophoblasts or treated with preeclampsia placenta-conditioned medium. Endothelial junction protein vascular endothelial cadherin expression and distribution were examined by fluorescent staining of endothelial cells with or without depletion of chymotrypsin. The association of endothelial cell junction protein complex VE-cadherin/beta-catenin/p120 was examined by a combined immuno-precipitation and immuno-blotting assay. Our results showed that endothelial cells cocultured with preeclampsia trophoblasts or exposed to preeclampsia placental conditioned medium exhibited a discontinuous distribution and reduced expression of vascular endothelial cadherin at cell contact regions. Vascular endothelial cadherin and p120 were expressed in control endothelial cells, but reduced or lost in endothelial cells exposed to preeclampsia placental conditioned medium, suggesting that the junctional protein complex of VE-cadherin/beta-catenin/p120 was disrupted in endothelial cells exposed to preeclampsia placental conditioned medium. We also observed that removal of trophoblasts from the coculture system and depletion of the protease from the preeclampsia placental conditioned medium could restore the dysregulated endothelial junction protein expression and distribution. Chymotrypsin also induced a dose dependent increase in endothelial monolayer permeability. We conclude that chymotrypsin-like protease released by the placenta is at least one important mediator responsible for disrupting endothelial cell integrity and inducing endothelial permeability in preeclampsia.

Vascular endothelial growth factor in monochorionic twins with twin-twin transfusion syndrome

OBJECTIVE

The purpose of this study was to determine vascular endothelial growth factor (VEGF) concentrations in the donor and the recipient in monochorionic twin pregnancies with twin-twin transfusion syndrome (TTTS) and single pregnancies in order to investigate the involvement of VEGF in the pathophysiology of TTTS.

METHODS

Six twin pregnancies in 11 monochorionic twin pregnancies complicated with TTTS and 11 single control pregnancies were compared. Gestational age-matched fetal blood and placental samples were obtained at birth. Serum VEGF concentration in the umbilical vein was measured by an enzyme-linked immunoabsorbant assay. Tissue protein expression of VEGF was determined by using immunohistochemistry. Western blot analysis and scanning densitometry were used to quantify and compare the VEGF expression in the terminal villi.

RESULTS

Serum VEGF concentrations in the umbilical vein in both donors and recipients tended to be higher than those in the controls. Immunolocalization of VEGF in terminal villous placenta samples in both donors and recipients was mainly observed in the syncytiotrophoblastic layer and vascular endothelial cells with less intense staining in stromal cells. The expression of VEGF in the donor placenta increased significantly (p=0.006) compared to that in the control placenta, but the expression of VEGF in the recipients tended to be higher than in the controls.

CONCLUSION

Intrauterine circulatory imbalance may induce changes in VEGF expression and these alterations may be involved in both donor and recipient in the pathogenesis of TTTS, due to the maintenance of hemodynamic stability between the circulation of the twins.

Endothelium-derived hyperpolarizing factor in preeclampsia: heterogeneous contribution, mechanisms, and morphological prerequisites

We hypothesized that in preeclampsia (PE), contribution of endothelium-derived hyperpolarizing factor (EDHF) and the mechanism/s of its action differ from that in normal pregnancy (NP). We aimed to assess endothelial function and morphology in arteries from NP and PE with particular focus on EDHF. Arteries (≈200 μm) were dissected from subcutaneous fat biopsies obtained from women undergoing cesarean section. With the use of wire myography, responses to the endothelium-dependent agonist bradykinin (BK) were determined before and after inhibition of pathways relevant to EDHF activity. The overall responses to BK in arteries from PE ( n = 13) and NP ( n = 17) were similar. However, in PE, EDHF-mediated relaxation was reduced ( P < 0.05). All women within the PE group were divided into two subgroups: with more ( group 1) or less ( group 2) than 50% reduction of EDHF-typed responses after 18-α-glycyrrhetinic acid (an inhibitor of myoendothelial gap junctions, MEGJs). The division showed that 1) MEGJs are principally involved when the EDHF contribution is reduced; and 2) when the EDHF contribution is similar to that in NP, the H2O2 and/or cytochrome P-450 epoxygenase products of arachidonic acid (AA), along with MEGJs, confer EDHF-mediated relaxation. In contrast, MEGJs were the main pathway for EDHF in NP. The abundant presence of MEGJs in arteries from NP but deficiency of them in PE was observed using transmission electron microscopy. We conclude that PE is associated with heterogeneous contribution of EDHF, and the mechanism behind EDHF-typed responses is mediated either by MEGJs alone or in combination with H2O2 or cytochrome P-450 epoxygenase metabolites of AA.

Increased superoxide generation and decreased stress protein Hsp90 expression in human umbilical cord vein endothelial cells (HUVECs) from pregnancies complicated by preeclampsia

OBJECTIVE

Endothelial dysfunction is associated with increased oxidative stress in the vascular system in women with preeclampsia (PE), a hypertensive disorder occurring during human pregnancy. However, due to the nature of the disease, direct evidence of increased endothelial oxidative stress in the maternal vascular system at an in vivo situation is still lacking. We previously reported that primary cultured endothelial cells (ECs) from umbilical cords (HUVECs) from pregnancies complicated by PE exhibit phenotypic changes compared to those from normal pregnancies such as reduced eNOs expression associated with disorganized endothelial junction protein distribution and increased endothelial permeability. In this study, we sought to determine whether increased oxidative stress was also present in primary cultured HUVECs from women with PE.

METHODS

HUVECs were isolated from normal and PE pregnancies and EC oxidative stress was examined by superoxide generation using positive nuclear dihydroethidium (DHE) staining as an indicator. Since Hsp90 is believed to have protective effects on endothelial function, we also determined mRNA and protein expression for Hsp90. Using Hsp90 inhibitor geldanamycin (GA), we further determined the potential role of Hsp90 in superoxide generation, eNOs expression, and prostacyclin production of altered EC function associated with PE pregnancies.

RESULTS

We found that primary cultured ECs from PE pregnancies showed an increase in DHE positive cells, p < 0.01. Hsp90 protein expression was significantly decreased in ECs from PE compared with that from normal pregnancies, p < 0.05. Inhibition of Hsp90 by GA resulted in an increase in superoxide generation and a decrease in eNOs protein expression. Decreased prostacyclin production was also found in ECs treated with GA.

CONCLUSION

These in vitro HUVEC data suggest that increased endothelial oxidative stress may also occur in the fetal compartment during preeclampsia.

Effects of peroxynitrite and superoxide radicals on endothelial monolayer permeability: potential role of peroxynitrite in preeclampsia

OBJECTIVE

Increased endothelial permeability is associated with increased oxidative stress in the maternal vasculature in women with preeclampsia. This study was to determine if oxidative stress elicited by peroxynitrite could lead to an increase in endothelial permeability.

METHODS

Endothelial oxidative stress was produced by adding 3-morpholinosydnonimine (SIN-1, a peroxynitrite generator) to the cell culture. Confluent endothelial cells (ECs) grown in cell culture inserts were treated with SIN-1 at a concentration of 0.5 mM alone or in combination with MnTMPyP (a peroxynitrite scavenger) or superoxide dismutase (SOD). EC permeability was determined by measuring EC electrical resistance (ER) and horseradish peroxide (HRP) leakage. Data are presented as means +/- SE and analyzed by analysis of variance (ANOVA). Junctional protein expression and distribution for vascular endothelial (VE)-cadherin, occludin, and phosphorylated focal adhesion kinase (FAK) at tyrosine 397 [pY397] were examined by fluorescent staining of ECs.

RESULTS

First, ER was significantly reduced and HRP leakage was significantly increased in ECs treated with SIN-1 compared to those in control cells, ER: 26.97 +/- 1.41 versus 42.27 +/- 0.40 Omega.cm2, P <.01; HRP: 0.26 +/- 0.07 versus 0.02 +/- 0.01 OD 470 nm, P <.01, respectively. Second, cells treated with SIN-1 showed formation of gaps and disorganized VE-cadherin and occludin distribution at cell contact regions. FAK[pY397] expression was completely lost in cells treated with SIN-1. Finally, these functional and morphologic changes in ECs induced by SIN-1 were blocked in cells pretreated with MnTMPyP and SOD.

CONCLUSIONS

Disorganization of junctional proteins and dephosphorylation of FAK[pY397] may account for the increased endothelial permeability induced by oxidative stress associated with preeclampsia.

Investigating native coronary artery endothelium in situ and in cell culture by scanning force microscopy

The purpose of our studies is to better understand the morphology and functioning of the arteries and their changes in pathogenesis. The most frequently used imaging techniques are intravascular ultrasound, magnetic resonance imaging, and optical coherence tomography. These methods do not image cell-level structural details and only provide biomechanical properties indirectly. We present a new protocol for imaging the endothelial surface and measuring elastic properties of vascular tissue by scanning force microscopy. Full-thickness sections of native pig coronary arteries were prepared. In addition, cultured human umbilical vein endothelial cells were studied as an in vitro model system and for comparison. We encountered a variety of difficulties mostly due to the softness of vascular tissue which required significant adaptations of standard equipment: (i) a new specimen holder designed to stably immobilize the coronary arteries; (ii) a phase-contrast microscope incorporated for assessing the status of the cultured endothelial cells and positioning the scanning force microscope (SFM) tip at a site of interest; and (iii) a continuous exchange of the culture medium at 37 degrees C to assure viability of the cells in the SFM over extended times. We were thus able to investigate both fresh arterial tissue and living endothelial cells in a near-physiological environment. We present initial SFM images of vascular tissue at a spatial resolution similar to scanning electron microscopy, but which also provide a closer view of the bona fide structure of native tissue. Novel morphological features such as distinct granular particles were observed. Moreover, we report initial measurements of vascular tissue surface stiffness, obtained by indentation-type SFM.

Significance of vascular endothelial growth factor expression in renal tissue of patients with preeclamptic nephropathy

OBJECTIVE

It was the aim of this study to evaluate the distribution and expression of vascular endothelial growth factor (VEGF) in kidneys of patients with preeclamptic nephropathy and their relationship with clinical and pathological manifestations.

METHODS

From May 1993 to August 2004, 19 patients with a mean age of 28.1 +/- 4.53 years (range 23-40), diagnosed with preeclamptic nephropathy by renal biopsy, were enrolled in this study. Fifteen were nulliparous and 4 multipara. Their renal tissues were subjected to immunohistochemical staining by a four-layer peroxidase-antiperoxidase method using monoclonal anti-VEGF. Residual normal renal tissue obtained at nephrectomy served as control. The relationship between the expression pattern of VEGF and clinicopathological features was also investigated.

RESULTS

The expression of VEGF markedly increased in renal tissues of patients with preeclamptic nephropathy at the early stage of gestation termination in comparison with normal controls. However, over time, it gradually decreased and reached the level of normal controls (100 vs. 71.43 vs. 20%, p < 0.05). The degree of endothelial proliferation in the glomeruli was closely related to the expression of VEGF, which was stronger in patients with diffuse endothelial proliferation than in those with segment proliferation (p < 0.05). In addition, there was a proportional relationship between the expression of VEGF and the level of urinary protein excretion (p < 0.05).

CONCLUSION

The patients with preeclamptic nephropathy showed strong expressions of VEGF in glomeruli, which were closely associated with glomerular endothelial lesions and proteinuria, and over time, gradually weakened to normal level after gestation termination.

Maternal urine albumin excretion and pregnancy outcome

BACKGROUND

Vascular dysfunction has been hypothesized as a causal pathway for preeclampsia, impaired fetal growth, and early parturition. The relationship between increased urine albumin excretion (albuminuria), a marker of endothelial dysfunction, and preterm birth has not been fully evaluated.

METHODS

We conducted a nested case-control study of 404 pregnancies from 1998 to 2000 within the Pregnancy, Infection and Nutrition cohort. Cases consisting of live births delivered before 37 weeks of gestation (preterm birth, n = 111) were compared with term births from the same cohort (n = 293). Albumin-creatinine ratio (in milligrams per gram) was measured in urine collected around 27 weeks of gestation. We compared risks for preterm birth in mothers with albuminuria with albumin levels of 3 to 20 mg/g and greater than 20 mg/g relative to those with albumin levels less than 3 mg/g by using logistic regression.

RESULTS

Median albuminuria was albumin level of 2.7 and 4.3 mg/g for term and preterm births, respectively. Albuminuria was strongly associated with preterm birth in a dose-response fashion, with adjusted odds ratios of 1.9 (95% confidence interval, 1.1 to 3.1) and 4.7 (95% confidence interval, 1.7 to 12.6) for albuminuria with albumin of 3 to 20 mg/g and greater than 20 mg/g, respectively. The association was present for both spontaneous and medically induced preterm births, but the effect was decreased and the dose-response relationship was eliminated by excluding high-risk groups and those with pregnancy complications.

CONCLUSION

Low levels of albuminuria are associated with preterm birth. The mechanism underlying this association warrants additional exploration.

Angioarrestin: A unique angiopoietin-related protein with anti-angiogenic properties

The process of angiogenesis plays a pivotal role in embryogenesis, wound healing, and tumorigenesis through the growth of new blood vessels from pre-existing vasculature. Among the angiogenic factors recently identified as specific for vascular endothelium are the angiopoietins. In depth characterization of the angiopoietins has allowed investigators to better understand the molecular basis of blood vessel formation and vascular endothelial cell function. In this review, we describe angiopoietins and related family members, with particular emphasis on a recently identified protein known as angioarrestin. Our investigations clearly demonstrate that angioarrestin is an anti-angiogenic molecule. The effects of angioarrestin on tumor cell progression and specific aspects of the angiogenic cascade in in vitro models are further discussed.

Endothelial function in conduit and resistance arteries in men with coronary disease

The aims of this study were to determine whether non-invasive measurement of endothelial function in conduit arteries reflects that of subcutaneous resistance arteries measured in vitro and to examine whether there is an endothelial dysfunction also in resistance arteries in patients with a previous myocardial infarction. The brachial artery diameter responses to a hyperemic flow stimulus and an in vitro method, pressure myography, to directly evaluate flow-mediated responses in arteries obtained from biopsies of subcutaneous fat were measured in 25 patients with a previous myocardial infarction and in 8 aged matched healthy subjects. Flow-mediated dilatation of the brachial artery was more pronounced in the healthy group compared with the group with coronary disease, 5.1 +/- 2.5% and 2.6 +/- 2.1%, respectively (p < 0.05). The flow-mediated dilatation in subcutaneous arteries from CHD patients was significantly reduced compared to control subjects (e.g. percent change from initial preconstriction at maximum flow rate of 204 microl/min: 42 +/- 7% CHD (n = 25) versus 84 +/- 24% control (n = 8), ANOVA, p = 0.03). There was a significant correlation between flow-mediated dilatation of the brachial artery and maximum flow-mediated dilatation at microvascular level, (p < 0.01). In conclusion this study demonstrates endothelial dysfunction in both conduit and resistance circulation in patients after myocardial infarction compared to an aged-matched healthy control group. Furthermore, a significant and independent relationship between endothelial function by means of flow-mediated dilatation in large conduit arteries and resistance arteries was observed.