Citations

Abstract—Hypercholesterolemia is associated with increased circulating and tissue endothelin-1 immunoreactivity, decreased nitric oxide (NO) activity, and altered endothelial function. We tested the hypothesis that chronic endothelin receptor antagonism preserves endothelial function and increases NO in experimental porcine hypercholesterolemia. Pigs were randomized to 3 groups: Group 1, a 2% high-cholesterol (HC) diet alone (n=7); group 2, RO-48-5695, a combined endothelin receptor antagonist, and an HC diet (n=8); and group 3, ABT-627, a selective endothelin-A receptor antagonist, and an HC diet (n=8). Coronary epicardial and arteriolar endothelial function was determined by a dose-response relaxation to bradykinin (10−11to 10−6mol/L),in all groups and in pigs maintained on a normal diet. Plasma total oxidized products of NO (NOx) were determined by chemiluminescence at baseline and after 12 weeks. Bradykinin-stimulated coronary epicardial and arteriolar relaxation in group 1 was attenuated compared with normal-diet controls. This relaxation was normalized with endothelin receptor antagonism. Plasma NOxdecreased after 12 weeks in group 1 (−74.8±5.5%). This decrease was attenuated in the endothelin receptor antagonist groups (group 2, −28.2±15.0%; group 3, −38.9±20.6%). Chronic endothelin receptor antagonism preserves coronary endothelial function and increases NO in hypercholesterolemia. This study supports a role of endothelin-1 in the regulation of NO activity and suggests a possible therapeutic role for endothelin receptor antagonists in hypercholesterolemia.

Abstract —Apoptosis is an active form of cell death that is intricately regulated and distinct from necrosis. Data suggest that apoptosis may play a role in the pathophysiology of coronary atherosclerotic disease. Anatomic evidence of apoptosis has been observed in coronary atherosclerosis, restenosis, and transplant arteriopathy, accompanied by an increase in biochemical and genetic markers of apoptosis. Vasoactive substances such as nitric oxide and angiotensin II also regulate vascular smooth muscle cell apoptosis; vasodilating factors may induce apoptosis, whereas vasoconstricting factors may inhibit apoptosis. The aim of this article is to review key points regarding the detection of apoptosis, its regulation, and its possible role in the pathogenesis of coronary artery disease.

Abstract —Endothelin (ET) may mediate the enhanced coronary vasoconstriction associated with hypercholesterolemia. We hypothesized that short-term inhibition of ET receptors attenuates the coronary epicardial vasoconstrictor response to acetylcholine in experimental hypercholesterolemia. ET-1 (group I, n=5; 5 ng · kg −1 · min −1 ) and acetylcholine (group III, n=7; 10 −6 to 10 −4 mol/L) were given by intracoronary infusion in pigs. ET-1 and acetylcholine were also infused with the specific ETA-receptor blocker FR-139317 (5 μg · kg −1 · min −1 ; group II, n=6; group IV, n=6). Acetylcholine was also infused with the combined ET-receptor blocker, bosentan (0.5 mg/kg plus 1 mg · kg −1 · h −1 , group V, n=5). The ETB-receptor agonist sarafotoxin 6c (5 ng · kg −1 · min −1 ; n=4) was also infused. The percentage change in coronary artery diameter (%ΔCAD) to the infusions was measured at baseline and after 10 weeks of high-cholesterol diet in all animals. Sarafotoxin 6c mildly reduced %ΔCAD at baseline and 10 weeks (−10±2% and −12±3%, respectively). FR-139317 did not attenuate the epicardial vasoconstrictor response to ET-1 at baseline (%ΔCAD −18±8% for group I versus −12±6% for group II; P =NS) but did at 10 weeks (%ΔCAD −77±14% for group I versus −14±6% for group II; P <.05). FR-139317 did not affect the response to acetylcholine at baseline (%ΔCAD 5±2% for group III versus 7±3% for group IV, P =NS) or at 10 weeks (%ΔCAD −23±12% for group III versus −19±7% for group IV; P =NS). Bosentan did not affect the response to acetylcholine at baseline or 10 weeks. Short-term ET-receptor inhibition in experimental hypercholesterolemia attenuated the enhanced coronary epicardial vasoconstrictor effects of ET-1 but not acetylcholine-induced coronary epicardial vasoconstriction, suggesting that acetylcholine-induced coronary epicardial vasoconstriction may not be mediated by ET receptors.

Abstract The coronary vasoconstrictor effects of endothelins, mediated by both endothelin ETA and ETB receptors, may be differentially altered in pathophysiological states associated with endothelial dysfunction and elevated endothelin levels. Experimental hypercholesterolemia is associated with coronary endothelial dysfunction and increased circulating endothelin concentrations. These studies were designed to test the hypothesis that experimental hypercholesterolemia is characterized by a differentially altered coronary contractile response to ETA- and ETB-receptor stimulation, in vitro. Pigs were fed either a normal or a high-cholesterol diet for 10 to 13 weeks. Changes in the intraluminal diameter of pressurized small coronary arteries (<481±25 μm in diameter) to cumulative concentrations (10 −10 to 10 −6 mol/L) of endothelin-1 (ET-1), and sarafotoxin 6c (S6c), a specific ETB-receptor agonist, were measured using a video dimension analyzer. The maximal contraction attained with ET-1 was greater than with S6c in both normal (86±7% versus 47±7%, P =.001) and hypercholesterolemic (77±6% versus 37±7%, P <.001) pigs. At 10 −10 mol/L, vessels from hypercholesterolemic pigs manifested greater contraction to both ET-1 (23±6% versus 8±3%, P =.02) and S6c (17±5% versus 4±2%, P =.02). Incubation of arteries from hypercholesterolemic pigs with BQ-788 (ETB-receptor antagonist), but not FR-139317 (ETA-receptor antagonist), altered the contractile response to ET-1 at 10 −10 mol/L. Removal of the endothelium abolished the difference in response to S6c between normal and hypercholesterolemic pigs. These studies demonstrate that experimental hypercholesterolemia is characterized by enhanced coronary vasoconstriction to endothelins in vitro, the mechanism of which is mediated mainly through the ETB receptor. Thus, the ETB receptor has a role in regulation of coronary artery tone in both the steady-state and pathophysiological states.

Percutaneous transluminal renal stenting (PTRS) does not consistently improve renal function in patients with atherosclerotic renovascular disease, but the mechanisms underlying irreversible kidney injury have not been fully elucidated. We hypothesized that renal dysfunction after PTRS is linked to ongoing renal microvascular (MV) remodeling. Pigs were studied after 10 wk of atherosclerosis and renal artery stenosis (ARAS), ARAS treated with PTRS 4 wk earlier, and normal controls ( n = 10 each). Renal blood flow (RBF) and glomerular filtration rate (GFR) were studied using multidetector computer tomography. Renal microvascular architecture (micro-CT), angiogenic activity, oxidative stress, and fibrosis were evaluated ex vivo. Four weeks after PTRS, blood pressure was normalized. However, GFR and RBF remained similarly decreased in untreated ARAS and ARAS+PTRS ( P < 0.05 vs. normal). MV rarefaction was unaltered after revascularization, and the spatial density of outer cortical microvessels correlated with residual GFR. Interstitial fibrosis and altered expression of proangiogenic and profibrotic factors persisted after PTRS. Tubulointerstitial injury in ARAS persisted 4 wk after mechanically successful PTRS, and vessel loss correlated with residual renal dysfunction. MV loss and fibrosis in swine ARAS might account for persistent renal dysfunction after PTRS and underscore the need to assess renal parenchymal disease before revascularization.

Coronary artery disease is a leading cause of death. Hypertension (HT) increases the incidence of cardiac events, but its effect on cardiac adaptation to coexisting coronary artery stenosis (CAS) is unclear. We hypothesized that concurrent HT modulates microvascular function in chronic CAS and aggravates microvascular remodeling and myocardial injury. Four groups of pigs ( n = 6 each) were studied: normal, CAS, HT, and CAS+HT. CAS and HT were induced by placing local irritant coils in the left circumflex coronary artery and renal artery, respectively. Six weeks later multidetector computerized tomography (CT) was used to assess systolic and diastolic function, microvascular permeability, myocardial perfusion, and responses to adenosine in the “area at risk.” Microvascular architecture, inflammation, and fibrosis were then explored in cardiac tissue. Basal myocardial perfusion was similarly decreased in CAS and CAS+HT, but its response to adenosine was significantly more attenuated in CAS. Microvascular permeability in CAS+HT was greater than in CAS and was accompanied by amplified myocardial inflammation, fibrosis, and microvascular remodeling, as well as cardiac systolic and diastolic dysfunction. On the other hand, compared with normal, micro-CT-derived microvascular (20–200 μm) transmural density decreased in CAS but not in HT or CAS+HT. We conclude that the coexistence of early renovascular HT exacerbated myocardial fibrosis and vascular remodeling distal to CAS. These changes were not mediated by loss of myocardial microvessels, which were relatively preserved, but possibly by exacerbated myocardial inflammation and fibrosis. HT modulates cardiac adaptive responses to CAS and bears cardiac functional consequences.

Background— Endothelin (ET-1) is one of the most potent vasoconstrictors and plays a seminal role in the pathogenesis of atherosclerosis. The present study was designed to test the hypothesis that long-term treatment with an endothelin-A (ET A ) receptor antagonist improves coronary endothelial function in patients with early coronary atherosclerosis. Methods and Results— Forty-seven patients with multiple cardiovascular risk factors, nonobstructive coronary artery disease, and coronary endothelial dysfunction were randomized in a double-blind manner to either the ET A receptor antagonist atrasentan (10 mg) or placebo for 6 months. Coronary endothelium-dependent vasodilation was examined by infusing acetylcholine (10 −6 to 10 −4 mol/L) in the left anterior descending coronary artery. N G -monomethyl- l -arginine was administered to a subgroup of patients. Endothelium-independent coronary flow reserve was examined by use of intracoronary adenosine and nitroglycerin. Baseline characteristics and incidence of adverse effects were similar between the 2 groups. There was a significant improvement in percent change of coronary blood flow in response to acetylcholine at 6 months from baseline in the atrasentan group compared with the placebo group (39.67%, 95% confidence interval 23.23% to 68.21%, versus −2.22%, 95% confidence interval −27.37% to 15.28%; P <0.001). No significant difference in the percent change of coronary artery diameter or change in coronary flow reserve was demonstrated. Coronary blood flow, coronary artery diameter, and the effect of N G -monomethyl- l -arginine were similar between the groups at baseline and at 6 months. Conclusions— This study demonstrates that 6-month treatment with atrasentan improves coronary microvascular endothelial function and supports the role of the endogenous endothelin system in the regulation of endothelial function in early atherosclerosis in humans. Clinical Trial Registration Information— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00271492.

Atherosclerotic renal artery stenosis (ARAS) is increasingly identified in patients with end-stage renal disease. Renal function in ARAS patients deteriorates more frequently than in nonatherosclerotic renal artery stenosis (RAS). This study was designed to test the hypothesis that atherosclerosis modifies the relationship between single-kidney hemodynamics and function and the severity of stenosis. The degree of unilateral RAS in domestic pigs (4 normal, 26 RAS, and 22 ARAS) was correlated with renal function and hemodynamics evaluated by 64-slice multidetector computerized tomography before and after endothelium-dependent challenge with ACh. The degree of stenosis and increase in mean arterial pressure were similar in RAS and ARAS. Stenotic single-kidney volume, blood flow, glomerular filtration rate, and cortical perfusion were lower than normal in both RAS and ARAS, but only in RAS correlated inversely with increasing degree of stenosis ( r = −0.62, r = −0.49, r = −0.51, and r = −0.46, respectively, P < 0.05 for all). Basal tubular fluid concentration capacity and stenotic cortical perfusion response to ACh were both blunted only in ARAS. This study shows that atherosclerosis modulates the impact of a stenosis in the renal artery on stenotic kidney hemodynamics, function, and tubular dynamics. These observations underscore the direct intrarenal effect of atherogenic factors on the kidneys.