Inhibition by bosentan, an endothelin antagonist, of the hypersensitivity to Ca2+ channel activator evoked by salt-loading in basilar artery of stroke-prone spontaneously hypertensive rats

Aprocitentan and the endothelin system in resistant hypertension

Endothelin has emerged as a target for therapeutic intervention in systemic hypertension. As a vasoconstrictor, co-mitogenic agent, linking pulse pressure and vascular remodeling, and mediator of aldosterone and catecholamine release, endothelin is a key player in hypertension and end-organ damage. In 10-20% of the hypertensive population, the high blood pressure is resistant to administration of antihypertensive drugs of different classes in combination. Because endothelin is not targeted by the current antihypertensive drugs this may suggest that this resistance is due, in part at least, to a dependence on endothelin. This hypothesis is supported by the observation that this form of hypertension is often salt-sensitive, and that the endothelin system is stimulated by salt. In addition, the endothelin system is activated in subjects at risk of developing resistant hypertension, such as African-Americans or patients with obesity or obstructive sleep apnea. Aprocitentan is a novel, potent, dual endothelin receptor antagonist (ERA) currently in phase 3 development for the treatment of difficult-to-treat hypertension. This article discusses the research which underpinned the discovery of this ERA and the choice of its first clinical indication for patients with forms of hypertension which cannot be well controlled with classical antihypertensive drugs.

Calcium-channel modulators for cardiovascular disease

It is generally accepted that hypertension doubles the risk of cardiovascular disease, of which coronary heart disease is the most common and lethal. Hypertension is a predisposing factor for the development of stroke, peripheral arterial disease, heart failure and end-state renal disease. Atherosclerosis-causing coronary heart disease is related to the severity of hypertension. Inhibition of calcium entry reduces the active tone of vascular smooth muscle and produces vasodilatation. This pharmacological action has been the basis for the use of calcium-channel blockers (CCBs) for the management of hypertension. Other drug families may achieve this: diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin-receptor antagonists. Cardiovascular hypertrophy and atherosclerosis are major complications related to high blood pressure. Cardiac hypertrophy is considered as an independent risk factor associated with abnormalities of diastolic function and can result in heart failure. Atherosclerosis is associated with activation of innate immunity. Atherosclerosis is expressing itself not only as coronary heart disease, but as a cerebrovascular and peripheral arterial disease. By impairing physiological vasomotor function, atherosclerosis includes ultimately necrosis of myocardium. CCBs reduce blood pressure. Do they prevent the progress of the main complications of hypertension? This major question is the matter of the present paper.

Antioxidant effects and the therapeutic mode of action of calcium channel blockers in hypertension and atherosclerosis

Drugs currently known as calcium channel blockers (CCB) were initially called calcium antagonists because of their ability to inhibit calcium-evoked contractions in depolarized smooth muscles. Blocking the entry of calcium reduces the active tone of vascular smooth muscle and produces vasodilatation. This pharmacological property has been the basis for the use of CCBs in the management of hypertension and coronary heart disease. A major question is whether drugs reducing blood pressure have other effects that help prevent the main complications of hypertension, such as atherosclerosis, stroke, peripheral arterial disease, heart failure and end-state renal disease. Experimental studies that focus on this question are reviewed in the present paper.

New Insights into the Therapeutic Mechanism of Action of Calcium Channel Blockers in Salt-Dependent Hypertension: Their Interaction with Endothelin Gene Expression

It appears that the beneficial action of calcium channel blockers (CCBs) in hypertension may be related to short-term and long-term effects. This paper summarises pharmacological studies aiming to characterise those effects. The primary consequence of the short-term effects is the decrease of blood pressure related to a selective interaction of CCBs with calcium channels in hypertensive vessels. The long-term effects may additionally control the disease through prevention of end organ damage, accompanying the interaction of CCBs with the pathways, leading to the re-expression of embryonic genes and to the overactivation of type I collagen gene, which are amplified by a high-salt diet. ET-1 and tumour growth factor beta-1 could be among the main factors activating those pathways. The processes leading to overexpression of those factors and to tissue remodelling may be controlled by lacidipine, independent of the reduction of blood pressure.

Effect of nitro-L-arginine on electrical and mechanical responses to acetylcholine in the superior mesenteric artery from stroke-prone hypertensive rat

1. High salt diet is known to aggravate the vascular pathology in spontaneously hypertensive stroke-prone rats (SHR-SP). The aim of the present study was to assess the involvement of endothelial dysfunction in this effect. Contractile tension and membrane potential were simultaneously recorded in superior mesenteric artery rings of untreated and NaCl-loaded (1% NaCl in the drinking water) SHR-SP and normotensive Wistar Kyoto rats (WKY). 2. In unstimulated artery, hyperpolarization evoked by acetylcholine was not different in WKY and in NaCl-loaded WKY; it was reduced in SHR-SP and further reduced in NaCl-loaded SHR-SP. Hyperpolarization was unaffected by N(omega)-nitro-L-arginine (L-NA) but was abolished in high-KCl solution. 3. In noradrenaline-stimulated artery, ACh-evoked hyperpolarization and relaxation were not different in WKY and in SHR-SP. NaCl-treatment did not affect the responses to ACh in WKY but decreased maximum relaxation in SHR-SP from 93+/-2% to 72+/-7% of the contraction. In WKY, in NaCl-loaded WKY and in SHR-SP, L-NA similarly shifted the concentration-relaxation curve to ACh to the right and depressed its maximum but L-NA did not affect the hyperpolarization to ACh. In NaCl-loaded SHR-SP, L-NA blunted the effects of ACh on membrane potential and on contraction. 4. The NO donor SNAP abolished the depolarization and the contraction evoked by noradrenaline with the same potency in WKY and in untreated SHR-SP but was more potent in NaCl-loaded SHR-SP. 5. In KCl-contracted arteries the relaxations to ACh were not different in WKY and SHR-SP but NaCl-loaded SHR-SP were more sensitive to ACh. 6. The results showed that NaCl-rich diet markedly reduced the L-NA-resistant responses to ACh and increased the sensitivity to NO in SHR-SP.