Endothelial dysfunction and arterial stiffness in ischemic stroke: the role of sleep-disordered breathing

Sleep-disordered breathing (SDB) represents a risk factor for cardiovascular morbidity after a cerebral ischemic event (acute ischemic event, ischemic stroke, or transient ischemic attack). In the present study, endothelial function and arterial stiffness were analyzed in patients who experienced a postacute ischemic event with relation to SDB, sleep disruption, and nocturnal oxygenation parameters.

The prevalence of endothelial dysfunction in patients with and without coronary artery disease

Endothelial dysfunction (ED) is frequently present in patients presenting with acute or stable coronary artery disease (CAD), but it is also found in patients presenting with chest pain without angiographic coronary lesions.

Intravital microscopy reveals endothelial dysfunction in resistance arterioles in Angiotensin II-induced hypertension

It is known that hypertension is associated with endothelial dysfunction and that Angiotensin II (Ang II) is a key player in the pathogenesis of hypertension. We aimed to elucidate whether endothelial dysfunction is a specific feature of Ang II-mediated hypertension or a common finding of hypertension, independently of underlying etiology. We studied endothelial-dependent vasorelaxation in precapillary resistance arterioles and in various large-caliber conductance arteries in wild-type mice with Ang II-dependent hypertension (2-kidney 1-clip (2K1C) model) or Ang II-independent (volume overload) hypertension (1-kidney 1-clip model (1K1C)). Normotensive sham mice were used as controls. Aortic mechanical properties were also evaluated. Intravital microscopy of precapillary arterioles revealed a significantly impaired endothelium-dependent vasorelaxation in 2K1C mice compared with sham mice, as quantified by the ratio of acetylcholine (ACh)-induced over S-nitroso-N-acetyl-D,L-penicillamine (SNAP)-induced vasorelaxation (2K1C: 0.49±0.12 vs. sham: 0.87±0.11, P=0.018). In contrast, the ACh/SNAP ratio in volume-overload hypertension 1K1C mice was not significantly different from sham mice, indicating no specific endothelial dysfunction (1K1C: 0.77±0.27 vs. sham: 0.87±0.11, P=0.138). Mechanical aortic wall properties and endothelium-dependent vasorelaxation, assessed ex vivo in rings of large-caliber conductance (abdominal and thoracic aorta, carotid and femoral arteries), were not different between 2K1C, 1K1C and sham mice. Endothelial dysfunction is an early feature of Ang II- but not volume-overload-mediated hypertension. This occurs exclusively at the level of precapillary arterioles and not in conduit arteries. Our findings, if confirmed in clinical studies, will provide a better understanding of the pathophysiological mechanisms of hypertension.

Resting heart rate and incident heart failure and cardiovascular mortality in older adults: role of inflammation and endothelial dysfunction: the PROSPER study

Resting heart rate is a promising modifiable cardiovascular risk marker in older adults, but the mechanisms linking heart rate to cardiovascular disease are not fully understood. We aimed to assess the association between resting heart rate and incident heart failure (HF) and cardiovascular mortality, and to examine whether these associations might be attributable to systemic inflammation and endothelial dysfunction.

[Pulmonary hypertension and lung edema at high altitude. Role of endothelial dysfunction and fetal programming]

High altitude constitutes an exciting natural laboratory for medical research. While initially, the aim of high-altitude research was to understand the adaptation of the organism to hypoxia and find treatments for altitude-related diseases, over the past decade or so, the scope of this research has broadened considerably. Two important observations led to the foundation for the broadening of the scientific scope of high-altitude research. First, high-altitude pulmonary edema (HAPE) represents a unique model which allows studying fundamental mechanisms of pulmonary hypertension and lung edema in humans. Secondly, the ambient hypoxia associated with high-altitude exposure facilitates the detection of pulmonary and systemic vascular dysfunction at an early stage. Here, we review studies that, by capitalizing on these observations, have led to the description of novel mechanisms underpinning lung edema and pulmonary hypertension and to the first direct demonstration of fetal programming of vascular dysfunction in humans.

Histamine increases sphingosine kinase-1 expression and activity in the human arterial endothelial cell line EA.hy 926 by a PKC-alpha-dependent mechanism

Sphingosine 1-phosphate (S1P) is a potent mitogenic signal generated from sphingosine by the action of sphingosine kinases (SKs). In this study, we show that in the human arterial endothelial cell line EA.hy 926 histamine induces a time-dependent upregulation of the SK-1 mRNA and protein expression which is followed by increased SK-1 activity. A similar upregulation of SK-1 is also observed with the direct protein kinase C activator 12-O-tetradecanoylphorbol-13-acetate (TPA). In contrast, SK-2 activity is not affected by neither histamine nor TPA. The increased SK-1 protein expression is due to stimulated de novo synthesis since cycloheximide inhibited the delayed SK-1 protein upregulation. Moreover, the increased SK-1 mRNA expression results from an increased promoter activation by histamine and TPA. In mechanistic terms, the transcriptional upregulation of SK-1 is dependent on PKC and the extracellular signal-regulated protein kinase (ERK) cascade since staurosporine and the MEK inhibitor U0126 abolish the TPA-induced SK-1 induction. Furthermore, the histamine effect is abolished by the H1-receptor antagonist diphenhydramine, but not by the H2-receptor antagonist cimetidine. Parallel to the induction of SK-1, histamine and TPA stimulate an increased migration of endothelial cells, which is prevented by depletion of the SK-1 by small interfering RNA (siRNA). To appoint this specific cell response to a specific PKC isoenzyme, siRNA of PKC-alpha, -delta, and -epsilon were used to selectively downregulate the respective isoforms. Interestingly, only depletion of PKC-alpha leads to a complete loss of TPA- and histamine-triggered SK-1 induction and cell migration. In summary, these data show that PKC-alpha activation in endothelial cells by histamine-activated H1-receptors, or by direct PKC activators leads to a sustained upregulation of the SK-1 protein expression and activity which, in turn, is critically involved in the mechanism of endothelial cell migration.

Measures of endothelial dysfunction in plasma of patients with posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) confers an increased cardiovascular risk. In 14 otherwise healthy patients with PTSD and in 14 age- and gender-matched non-PTSD controls, we investigated whether the categorical diagnosis of PTSD and severity of PTSD symptom clusters (i.e. re-experiencing, avoidance, arousal, and overall score) would be associated with plasma concentrations of three markers of endothelial dysfunction [soluble tissue factor (sTF), von Willebrand factor (VWF), and soluble intercellular adhesion molecule (sICAM)-1]. Compared with controls, patients had significantly higher sTF; this difference became nonsignificant when controlling for psychological distress. VWF and sICAM-1 levels were not significantly different between patients and controls. In the entire sample virtually all PTSD symptom clusters correlated significantly and positively with sTF and VWF but not with sICAM-1. The correlation between symptoms of re-experiencing and sTF was significantly different between patients and controls. Controlling for symptoms of anxiety and depression (i.e. psychological distress) rendered most associations between PTSD symptom clusters and sTF nonsignificant, whereas controlling for age retained significance of associations with VWF. Posttraumatic stress showed a continuous relationship with sTF and VWF, with the former relationship being partly affected by psychological distress. This suggests one mechanism by which posttraumatic stress could contribute to atherosclerosis.

Human internal thoracic arteries from diabetic patients are resistant to endothelial dysfunction

The aim of this analysis was to compare vasoreactive properties of internal thoracic arteries (ITA) grafts from diabetic (DM) to those of non-diabetic (ND) patients. Ring segments of ITA, taken from patients undergoing coronary artery bypass grafting, were suspended in organ bath chambers filled with modified Krebs-Henseleit solution and contractile responses to potassium chloride (KCl), noradrenaline (NA), endothelin-1 (ET-l), and endothelium-dependent relaxant responses to acetylcholine (ACH) were recorded isometrically. The receptor-mediated agonists NA and ET-1 stimulated ITA from both groups within similar concentration ranges while ITA from DM patients proved to be significantly more sensitive to KCl than ITA from ND. Furthermore, maximal contractile responses indicated that KCl (3.79 +/- 0.30 g, n = 7 in DM and 2.50 +/- 0.23 g, n = 29 in ND, P < 0.05) evoked significantly higher responses in ITA from DM as compared to the ND control group while both NA and ET-l stimulated ITA from both groups with similar efficacies. Endothelium-dependent relaxant responses to ACH proved to be similar in both groups when expressed as percentages of the pre-existing tone. The present data support the contention that in comparison to ND controls arteries from DM patients are more sensitive to depolarization but endothelial dysfunction is less frequent in human ITA than expected from observations in systemic vascular beds.

Vascular dysfunction and reduced circulating endothelial progenitor cells in young healthy UK South Asian men

OBJECTIVES: The objective of this study was to examine determinants of excess coronary artery disease risk in UK South Asians, more prevalent in this population than UK Caucasians, by examining differences in risk factors, vascular function, and endothelial progenitor cells (EPCs). METHODS AND RESULTS: 24 South Asian and 25 Caucasian healthy age-matched nonsmoking men were studied. Vascular function was assessed by flow-mediated and GTN brachial artery dilatation and blood flow responses to infusion of ACh, SNP, and L-NMMA. EPC number and function were measured by flow cytometry (CD34, CD133, and KDR positive cells), and CFU/migration assays. Traditional risk factors and anthropometric measurements were similar in the groups. South Asians had higher fasting insulin levels (6.01 versus 3.62 microU/mL; P = 0.02). South Asians had lower FMD (6.9 versus 8.5%; P = 0.003), L-NMMA response (0.8 versus 1.3 mL/min/100 mL; P = 0.03), mean SNP response (9.5+/-0.6 versus 11.6+/-0.6; P = 0.02), EPC number (0.046+/-0.005% versus 0.085+/-0.009%; P = < 0.001), and CFU ability (CFU 4.29+/-1.57 versus 18.86+/-4.00; P = 0.005). EPC number was the strongest predictor of FMD. Ethnicity was the strongest predictor of EPC number. CONCLUSIONS: Healthy South Asian men are more insulin resistant, and demonstrate endothelial dysfunction and reduced EPC number and function compared with Caucasians. These abnormalities may contribute to their increased CAD risk.

Impaired endothelial progenitor cell function predicts age-dependent carotid intimal thickening

OBJECTIVES: We investigated whether qualitative or quantitative alterations of the endothelial progenitor cell (EPC) pool predict age-related structural vessel wall changes. BACKGROUND: We have previously shown that age-related endothelial dysfunction is accompanied by qualitative rather than quantitative changes of EPCs. Animal studies suggest that impaired EPC functions lead to accelerated arterial intimal thickening. METHODS: Intima-media thickness (IMT) was measured in the common carotid artery in our previously published groups of younger (25 +/- 1 years, n = 20) and older (61 +/- 2 years, n = 20) healthy non-smoking volunteers without arterial hypertension, hypercholesterolemia, and diabetes mellitus. Endothelial progenitor cells (EPCs, KDR(+)/CD34(+) and KDR(+)/CD133(+)) were counted in peripheral blood using flow cytometry. In ex vivo expanded EPCs, the function was determined as chemotaxis to VEGF, proliferation, and survival. RESULTS: We observed thicker IMT in older as compared to younger subjects (0.68 +/- 0.03 mm Vs. 0.48 +/- 0.02 mm, P < 0.001). Importantly, there were significant inverse univariate correlations between IMT, EPC chemotaxis, and survival (r = -0.466 P < 0.05; r = -0.463, P < 0.01). No correlation was observed with numbers of circulating EPCs. Multivariate regression analysis revealed that age, mean arterial pressure and migration of EPCs were independent predictors of IMT (R (2 )= 0.58). CONCLUSION: Impaired EPC function may lead to accelerated vascular remodeling due to chronic impairment of endothelial maintenance.

Methodological considerations and practical recommendations for the application of peripheral arterial tonometry in children and adolescents

Endothelial dysfunction is recognized as the primum movens in the development of atherosclerosis. Its crucial role in both cardiovascular morbidity and mortality has been confirmed. In the past, research was hampered by the invasive character of endothelial function assessment. The development of non-invasive and feasible techniques to measure endothelial function has facilitated and promoted research in various adult and paediatric subpopulations. To avoid user dependence of flow-mediated dilation (FMD), which evaluates nitric oxide dependent vasodilation in large vessels, a semi-automated, method to assess peripheral microvascular function, called peripheral arterial tonometry (Endo-PAT®), was recently introduced. The number of studies using this technique in children and adolescents is rapidly increasing, yet there is no consensus with regard to either measuring protocol or data analysis of peripheral arterial tonometry in children and adolescents. Most paediatric studies simply applied measuring and analysing methodology established in adults, a simplification that may not be appropriate. This paper provides a detailed description of endothelial function assessment using the Endo-PAT for researchers and clinicians. We discuss clinical and methodological considerations and point out the differences between children, adolescents and adults. Finally, the main aim of this paper is to provide recommendations for a standardised application of Endo-PAT in children and adolescents, as well as for population-specific data analysis methodology.

Mice generated by in vitro fertilization exhibit vascular dysfunction and shortened life span

Children conceived by assisted reproductive technologies (ART) display a level of vascular dysfunction similar to that seen in children of mothers with preeclamspia. The long-term consequences of ART-associated vascular disorders are unknown and difficult to investigate in healthy children. Here, we found that vasculature from mice generated by ART display endothelial dysfunction and increased stiffness, which translated into arterial hypertension in vivo. Progeny of male ART mice also exhibited vascular dysfunction, suggesting underlying epigenetic modifications. ART mice had altered methylation at the promoter of the gene encoding eNOS in the aorta, which correlated with decreased vascular eNOS expression and NO synthesis. Administration of a deacetylase inhibitor to ART mice normalized vascular gene methylation and function and resulted in progeny without vascular dysfunction. The induction of ART-associated vascular and epigenetic alterations appeared to be related to the embryo environment; these alterations were possibly facilitated by the hormonally stimulated ovulation accompanying ART. Finally, ART mice challenged with a high-fat diet had roughly a 25% shorter life span compared with control animals. This study highlights the potential of ART to induce vascular dysfunction and shorten life span and suggests that epigenetic alterations contribute to these problems.

Endothelial-specific deletion of connexin40 promotes atherosclerosis by increasing CD73-dependent leukocyte adhesion

Endothelial dysfunction is the initiating event of atherosclerosis. The expression of connexin40 (Cx40), an endothelial gap junction protein, is decreased during atherogenesis. In the present report, we sought to determine whether Cx40 contributes to the development of the disease.

Pulsatile shear and Gja5 modulate arterial identity and remodeling events during flow-driven arteriogenesis

In the developing chicken embryo yolk sac vasculature, the expression of arterial identity genes requires arterial hemodynamic conditions. We hypothesize that arterial flow must provide a unique signal that is relevant for supporting arterial identity gene expression and is absent in veins. We analyzed factors related to flow, pressure and oxygenation in the chicken embryo vitelline vasculature in vivo. The best discrimination between arteries and veins was obtained by calculating the maximal pulsatile increase in shear rate relative to the time-averaged shear rate in the same vessel: the relative pulse slope index (RPSI). RPSI was significantly higher in arteries than veins. Arterial endothelial cells exposed to pulsatile shear in vitro augmented arterial marker expression as compared with exposure to constant shear. The expression of Gja5 correlated with arterial flow patterns: the redistribution of arterial flow provoked by vitelline artery ligation resulted in flow-driven collateral arterial network formation and was associated with increased expression of Gja5. In situ hybridization in normal and ligation embryos confirmed that Gja5 expression is confined to arteries and regulated by flow. In mice, Gja5 (connexin 40) was also expressed in arteries. In the adult, increased flow drives arteriogenesis and the formation of collateral arterial networks in peripheral occlusive diseases. Genetic ablation of Gja5 function in mice resulted in reduced arteriogenesis in two occlusion models. We conclude that pulsatile shear patterns may be central for supporting arterial identity, and that arterial Gja5 expression plays a functional role in flow-driven arteriogenesis.

Mycophenolate acid inhibits endothelial NAD(P)H oxidase activity and superoxide formation by a Rac1-dependent mechanism

Endothelial dysfunction precedes hypertension and atherosclerosis and predicts cardiac allograft vasculopathy and death in heart transplant recipients. Endothelial overproduction of reactive oxygen species, such as superoxide anions produced by NAD(P)H oxidase, induces endothelial dysfunction. Because immunosuppressive drugs have been associated with increased reactive oxygen species production and endothelial dysfunction, we sought to elucidate the underlying mechanisms. Reactive oxygen species, release of superoxide anions, and NAD(P)H oxidase activity were studied in human umbilical vein endothelial cells and in polymorphonuclear neutrophils. Gp91ds-tat was used to specifically block NAD(P)H oxidase. Transcriptional activation of different subunits of NAD(P)H oxidase was assessed by real-time RT-PCR. Rac1 subunit translocation and activation were studied by membrane fractionation and pull-down assays. Calcineurin inhibitors significantly increased endothelial superoxide anions production because of NAD(P)H oxidase, whereas mycophenolate acid (MPA) blocked it. MPA also attenuated the respiratory burst induced by neutrophil NAD(P)H oxidase. Because transcriptional activation of NAD(P)H oxidase was not affected, but addition of guanosine restored endothelial superoxide anions formation after MPA treatment, we speculate that the inhibitory effect of MPA was mediated by depletion of cellular guanosine triphosphate content. This prevented activation of Rac1 and, thus, of endothelial NAD(P)H oxidase. Because all heart transplant recipients are at risk for cardiac allograft vasculopathy development, these differential effects of immunosuppressants on endothelial oxidative stress should be considered in the choice of immunosuppressive drugs.