These data demonstrate that obesity augments prostanoid-dependent vasoconstriction and markedly increases vascular thromboxane receptor gene expression. These changes are likely to promote the development of vascular disease, hypertension and thrombosis associated with obesity.

No abstract

Abstract-In the C57BL/6J mice model, we investigated whether obesity affects the function or expression of components of the tissue renin-angiotensin system and whether endothelin (ET)-1 contributes to these changes. ACE activity (nmol ⅐ L His-Leu ⅐ mg protein Ϫ1 ) was measured in lung, kidney, and liver in control (receiving standard chow) and obese animals treated for 30 weeks with a high-fat, low cholesterol diet alone or in combination with LU135252, an orally active ET A receptor antagonist. ACE mRNA expression was measured in the kidney, and the effects of LU135252 on purified human ACE were determined. Aortic and renal tissue ET-1 protein content was measured, and the vascular contractility to angiotensin II was assessed. Obesity was associated with a tissue-specific increase in ACE activity in the kidney (55Ϯ4 versus 33Ϯ3 nmol/L) but not in the lung (34Ϯ2 versus 32Ϯ2 nmol/L). Long-term LU135252 treatment completely prevented this activation (13.3Ϯ0.3 versus 55Ϯ4 nmol/L, PϽ0.05) independent of ACE mRNA expression, body weight, or renal ET-1 protein but did not affect pulmonary or hepatic ACE activity. Obesity potentiated contractions in response to angiotensin II in the aorta (from 6Ϯ2% to 33Ϯ5% KCl) but not in the carotid artery (4Ϯ1% to 3.6Ϯ1% KCl), an effect that was completely prevented with LU135252 treatment (6Ϯ0.4% versus 33Ϯ5% KCl). No effect of LU135252 on purified ACE was observed. Thus, obesity is associated with the activation of renal ACE in vivo independent of its mRNA expression and enhanced vascular contractility to angiotensin II. These effects are regulated by ET in an organ-specific manner, providing novel mechanisms by which ET antagonists may exert organ protection.

Objective-The EphB ligand ephrinB2 has been identified as a critical determinant of arterial endothelial differentiation and as a positive regulator of invading endothelial cells during angiogenesis. This study was aimed at identifying determinants of endothelial cell ephrinB2 expression. Methods and Results-Arteriovenous asymmetrical endothelial cell ephrinB2 expression in vivo is lost on transfer into culture with aortic endothelial cells becoming partially ephrinB2-negative and saphenous vein endothelial cells becoming partially ephrinB2-positive. Contact with smooth muscle cells and angiogenic stimulation by vascular endothelial growth factor lead to an increased endothelial cell ephrinB2 expression. Quiescent, smooth musclecontacting endothelial cells express ephrinB2 uniformly on their luminal surface. In contrast, monolayer endothelial cells translocate ephrinB2 to interendothelial cell junctions, which is strongly enhanced by EphB4-Fc-mediated receptor body activation. Junctional ephrinB2 colocalizes and coimmunoprecipitates with CD31. Conclusions-This study identifies distinct regulatory mechanisms of endothelial ephrinB2 expression and cellular distribution in quiescent and activated endothelial cells. The data demonstrate that endothelial cell ephrinB2 expression is controlled by microenvironmental determinants rather than being an intrinsic endothelial cell differentiation marker.

Endothelial cells are constantly exposed to high or low shear stress in arteries and veins by the flowing blood. Angiopoietin-2 (Ang-2) is acting as a critical regulator of vessel maturation and endothelial cell quiescence. In this study, flow-dependent regulation of Ang-2 was analyzed in vitro and in vivo. Ang-2 mRNA, protein expression and release was upregulated by 24 h of low (1 dyne/cm(2)), but downregulated by high flow (30 dyne/cm(2)) in human endothelial cells. Increased endothelial NO synthase expression and NO formation was not affecting regulation of Ang-2 by low or high flow. Low and high flow increased VEGF-A expression. Inhibition of VEGFR-2 prevented upregulation of Ang-2 by low flow, but not downregulation of Ang-2 by high flow. Furthermore, upregulation of Ang-2 by VEGF was reduced by application of high flow. Forkhead box O (FOXO) transcription factor FOXO1 has been shown to regulate Ang-2 expression in endothelial cells. FOXO1 binding activity was reduced by high flow. Nuclear localization of transcription factor FOXO1 was not changed by low flow, but reduced by high flow. In vivo, Ang-2 was higher expressed in veins compared to arteries. Arterial ligation augmented Ang-2 expression in distal arterial low flow areas. Our results support a VEGF-dependent induction of Ang-2 in low flow areas, and FOXO1-dependent downregulation of Ang-2 in high flow areas. These data suggest a new mechanism of flow-dependent regulation of vessel stability and differentiation.

No abstract

The endothelium controls blood flow and pressure by releasing several vasoactive factors, among them the vasodilator nitric oxide (NO) and the potent vasoconstrictor endothelin-1 (ET-1). Although increased NO levels have been found in excessive erythrocytosis, little is known concerning ET-1 expression in this condition. Thus, we examined the endothelin system in transgenic mice that due to constitutive overexpression of erythropoietin (Epo) reached hematocrit levels of approximately 80%. Surprisingly, despite generalized vasodilatation, polycythemic mice exhibited a two- to fivefold elevation in ET-1 mRNA levels in aorta, liver, heart, and kidney. In line with this, increased expression of ET-1 protein was detected in the pulmonary artery by immunohistochemical analysis. Compared with their wild-type littermates, aortic rings of Epo transgenic animals exhibited a marked reduction in vascular reactivity to ET-1 and big ET-1, but this effect was abrogated upon preincubation with the NO synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME). Pretreatment of polycythemic mice with the ET(A) receptor antagonist darusentan for 3 wk significantly prolonged their survival upon acute exposure to L-NAME. Taken together, these results demonstrate for the first time that excessive erythrocytosis induces a marked activation of the tissue endothelin system that results in increased mortality upon blockade of NO-mediated vasodilatation. Because ETA antagonism prolonged survival after acute blockade of NO synthesis, endothelin may be regarded as a contributor to the adverse cardiovascular effects of erythrocytosis and may thus represent a new target in the treatment of cardiovascular disease associated with erythrocytosis.

Background-Statins and angiotensin type 1 (AT 1 ) receptor blockers reduce cardiovascular mortality and morbidity. In the Endothelial Protection, AT 1 blockade and Cholesterol-Dependent Oxidative Stress (EPAS) trial, impact of independent or combined statin and AT 1 receptor blocker therapy on endothelial expression of anti-atherosclerotic and proatherosclerotic genes and endothelial function in arteries of patients with coronary artery disease were tested.