Heterogeneity of endothelial dysfunction in hypertension

The endothelium may play a role as a target and mediator of hypertension. Due to its anatomical position, it is very exposed to mechanical forces; as a source of vasoactive material it may participate in increasing peripheral vascular resistance and in promoting local ischaemia in the heart and brain. Morphological and functional changes in the endothelium occur in experimental and human hypertension. However, the severity of the defect and the mechanisms involved among vascular beds and models of hypertension are heterogeneous. Endothelium-dependent relaxations are impaired in the aorta, carotid artery and in cerebral and mesenteric arterioles in hypertension. In the coronary circulation the defect is less pronounced. The mechanisms involve a reduced formation of nitric oxide, an enhanced production of prostaglandin H2 and an impaired responsiveness of vascular smooth muscle to nitric oxide. The role of endothelin in hypertension is controversial; circulating levels appear unaltered except in the presence of renal failure or atherosclerosis. The local vascular production of endothelin, however, may still be increased. The potentiating effects of threshold concentrations of endothelin on the vasoconstrictor response to noradrenalin are enhanced in hypertension. Thus, subtle and distinct endothelial function defects occur in hypertension, but not all vascular beds are similarly affected and different mechanisms contribute. Endothelial dysfunction may contribute to increased peripheral resistance, tissue ischaemia and cardiovascular complication

Endothelium-derived relaxing and contracting factors: potential role in coronary artery disease

Endothelial cells can release substances which profoundly affect vascular tone and platelet function. The inhibitory substances include endothelium-derived relaxing factor (EDRF or nitric oxide), prostacyclin and probably an endothelium-derived hyperpolarizing factor. Endothelin is a potent vasoconstrictor peptide released from endothelial cells. Under certain conditions, the endothelium can also produce angiotensin II, thromboxane A2 and a cyclooxygenase-dependent endothelium-derived contracting factor. In normal arteries, the effects of EDRF appear to dominate. In diseased arteries, the release and action of EDRF is impaired and that of endothelium-derived contracting factors is increased. Hyperlipidaemia, atherosclerosis and hypertension reduce endothelium-dependent relaxations. Hypoxia inhibits the release of EDRF and prolonged ischaemia severely impairs the response. Regenerated endothelium at sites of mechanical injury exhibits selective defects in response to aggregating platelets. The more effective release of EDRF in arterial compared with venous bypass grafts further suggests an involvement of the factor in preventing vascular occlusion. Therapeutic interventions with specific drugs and diets can augment the impaired endothelium-dependent relaxation of diseased arteries. Thus, functional changes of the endothelium in coronary artery disease may be an important factor in the development of vasospasm, ischaemia and thrombosi

Imbalance of Endothelium-derived Relaxing and Contracting Factors: A New Concept in Hypertension?

The endothelium has a strategical anatomical position between the circulating blood and vascular smooth muscle cells. It has recently been recognized that endothelial cells play an important regulatory role in the circulation. The cells metabolize or activate vasoactive hormones (ie, norepi-nephrine, serotonin, bradykinin, angiotensin II), produce substances involved in coagulation and can release endothelium-derived relaxing factors and contracting factors. Nitric oxide and prostacyclin are vasodilators and inhibitors of platelet function. Endothelin is the most potent vasoconstrictor substance known. Thus, the endothelium can profoundly affect platelet adhesion and aggregation, vascular smooth muscle tone and possibly also vascular smooth muscle growth. Under physiological conditions, endothelium-derived relaxing factors appear to dominate. In contrast, in hypertensive and atherosclerotic arteries the release of endothelium-derived relaxing factors and/or the responsiveness of vascular smooth muscle cells to the relaxing factors is reduced, while that of endothelium-derived contracting factors is augmented. This imbalance of endothelium-derived relaxing and contracting factors may be important in the pathogenesis of hypertension and its cardiovascular complications. Am J Hypertens 1990;3:317-33

Maintenance of vascular integrity: Role of nitric oxide and other bradykinin mediators

In the blood-vessel wall, the endothelium plays a key functional role by generating several substances that modulate vascular smooth muscle tone, as well as growth, and platelet function. This review focuses on the role of the endothelial L-arginine/nitric oxide signal transduction pathway in the maintenance of vascular integrity. Functional alterations of this pathway may be important in cardiovascular disease, because depressed activity of this protective mechanism leads to impaired relaxation and is also associated with reduced antithrombotic properties of the endothelial layer. Many of the beneficial effects of ACE inhibitor therapy may be mediated through their ability to enhance the physiological roles of nitricoxid

Darusentan, a selective endothelin A receptor antagonist, for the oral treatment of resistant hypertension

Resistant hypertension is defined as failure to lower blood pressure to target when a patient adheres to the maximum tolerated doses of three antihypertensive drugs including a diuretic. Notwithstanding the wide availability of several antihypertensive agents and the continued recommendation of dietary and lifestyle modifications, the prevalence of resistant hypertension remains high and is expected to increase thus underscoring the need for potential new treatment modalities in resistant hypertension. Endothelin-1 is a long-lasting potent vasoconstrictor and plays a key role in cardiovascular haemostasis. Endothelin mediates its biological activity in humans through the endothelin A and B receptors. The clinical experience and the evidence for therapy with darusentan in resistant systemic hypertension are reviewed. The leading journals that publish basic science and clinical research in the area of cardiovascular diseases and PubMed were scanned. While results from early clinical studies suggested that darusentan might emerge as new treatment option in patients with resistant hypertension, results from recent studies suggests that darusentan appears unlikely to find its way in the armamentarium for treatment of resistant hypertension

The gradient flow running coupling with twisted boundary conditions

We study the gradient flow for Yang-Mills theories with twisted boundary conditions. The perturbative behavior of the energy density $\langle E(t)\rangle$ is used to define a running coupling at a scale given by the linear size of the finite volume box. We compute the non-perturbative running of the pure gauge $SU(2)$ coupling constant and conclude that the technique is well suited for further applications due to the relatively mild cutoff effects of the step scaling function and the high numerical precision that can be achieved in lattice simulations. We also comment on the inclusion of matter fields.Comment: 27 pages. LaTe