Endothelin ET _A receptor blockade restores NO-mediated endothelial function and inhibits atherosclerosis in apolipoprotein E-deficient mice

Abstract

This study investigated whether endothelin-1 (ET-1), a potent vasoconstrictor, which also stimulates cell proliferation, contributes to endothelial dysfunction and atherosclerosis. Apolipoprotein E (apoE)-deficient mice and C57BL͞6 control mice were treated with a Western-type diet to accelerate atherosclerosis with or without ET A receptor antagonist LU135252 (50 mg͞kg͞d) for 30 wk. Systolic blood pressure, plasma lipid profile, and plasma nitrate levels were determined. In the aorta, NO-mediated endotheliumdependent relaxation, atheroma formation, ET receptorbinding capacity, and vascular ET-1 protein content were assessed. In apoE-deficient but not C57BL͞6 mice, severe atherosclerosis developed within 30 wk. Aortic ET-1 protein content (P < 0.0001) and binding capacity for ET A receptors was increased as compared with C57BL͞6 mice. In contrast, NO-mediated, endothelium-dependent relaxation to acetylcholine (56 ؎ 3 vs. 99 ؎ 2%, P < 0.0001) and plasma nitrate were reduced (57.9 ؎ 4 vs. 93 ؎ 10 mol͞liter, P < 0.01). Treatment with the ET A receptor antagonist LU135252 for 30 wk had no effect on the lipid profile or systolic blood pressure in apoE-deficient mice, but increased NO-mediated endothelium-dependent relaxation (from 56 ؎ 3 to 93 ؎ 2%, P < 0.0001 vs. untreated) as well as circulating nitrate levels (from 57.9 ؎ 4 to 80 ؎ 8.3 mol͞liter, P < 0.05). Chronic ET A receptor blockade reduced elevated tissue ET-1 levels comparable with those found in C57BL͞6 mice and inhibited atherosclerosis in the aorta by 31% without affecting plaque morphology or ET receptor-binding capacity. Thus, chronic ET A receptor blockade normalizes NO-mediated endothelial dysfunction and reduces atheroma formation independent of plasma cholesterol and blood pressure in a mouse model of human atherosclerosis. ET A receptor blockade may have therapeutic potential in patients with atherosclerosis.Diseases related to atherosclerosis such as myocardial infarction and stroke account for the majority of deaths in industrialized countries (1). In patients with cardiovascular risk factors such as hypercholesterolemia, hypertension, or aging (2, 3), endothelial dysfunction precedes the development of atherosclerosis and predisposes to the development of structural vascular changes (1, 4). The endothelium releases vasoactive mediators such as NO and endothelin (ET-1), both of which are importantly involved in the regulation of vascular tone (5, 6) and structure (7,8). Endothelial NO synthase (9-11) converts L-arginine into NO and L-citrulline (12) and its expression (13), and the release of NO (14) is reduced in atherosclerosis. In experimental atherosclerosis, inhibition of the L-arginine͞NO pathway accelerates lesion progression in hypercholesterolemic rabbits (15-17) and low density lipoprotein (LDL) receptor-deficient mice (18). Furthermore, superoxide release in atherosclerosis inactivates NO resulting in formation of peroxynitrite (19,20), the production of which is further enhanced by cholesterol (21).In patients with coronary a...

Cardioprotective effect of an endothelin receptor antagonist during ischaemia/reperfusion in the severely atherosclerotic mouse heart

“…This appears to be in contrast to previous reports demonstrating impaired endothelium-dependent vasorelaxation and reduced concentration of NO derived from the aorta of the atherosclerotic mouse (Barton et al, 1998;Jiang et al, 2000;Scalia et al, 2001). However, in the isolated whole heart preparation, it cannot be determined whether the released NO X is derived from the coronary vessels or the myocardium.…”

“…It is therefore of pathophysiological and therapeutic importance to elucidate whether ET receptor antagonism protects the myocardium in a situation of severe atherosclerosis with endothelial dysfunction, as is the situation in patients with acute myocardial infarction. The apolipoprotein E/LDL receptor-deficient mouse is an atherosclerotic mouse model characterised by endothelial dysfunction due to impaired response to the endothelium-dependent vasodilatator acetylcholine and increased expression of ET-1 and ET receptors (Barton et al, 1998;Jiang et al, 2000;Kobayashi et al, 2000;d'Uscio et al, 2002). Therefore, this model is useful to investigate whether cardioprotection is achieved under severely atherosclerotic conditions.…”

“…Chronic treatment of apolipoprotein E-deficient mice with a selective ET A receptor antagonist restored NOmediated endothelial function and reduced elevated tissue ET-1 levels (Barton et al, 1998;d'Uscio et al, 2002). More importantly, it has been shown that selective ET A receptor antagonism improves endothelium-dependent vasodilatation in patients with atherosclerosis (Bohm et al, 2002b).…”

“…In atherosclerotic arteries, the production of ET is enhanced and the vasoconstrictor response to exogenous ET-1 is more pronounced (Jiang et al, 2000). Pharmacological blockade of ET receptors results in improved endothelium-dependent vasodilatation in atherosclerotic mice (Barton et al, 1998) and in patients with atherosclerosis (Bohm et al, 2002b).…”

Acute Pressor Response to Psychosocial Stress Is Dependent on Endothelium‐Derived Endothelin‐1

“…Recent genome‐wide association studies have implicated the ET A receptor as a genetic determinant of coronary artery disease,54, 55 carotid atherosclerosis,54 large‐artery stroke,55 and peripheral artery disease,56 suggesting a role of this receptor in atherogenesis across diverse arterial systems. These findings are supported by clinical and preclinical studies that suggest a direct role of the ET A receptor on the development of atherosclerosis 57, 58, 59, 60, 61. Recently, Gupta and colleagues demonstrated in a separate genome‐wide association study project that a single‐nucleotide polymorphism common in 5 vascular diseases, including coronary artery disease, promotes exaggerated endothelium‐derived ET‐1 and higher plasma ET‐1 62.…”