Mechanical pressure and stretch release endothelin-1 from human atherosclerotic coronary arteries in vivo

Effects of chronic administration of L-arginine on vasoactive responses induced by endothelin-1 and its plasma level in streptozotocin-induced diabetic rats

To investigate the mechanism underlying increased endothelin-1 (ET-1) release in diabetic rats, we administered L-arginine chronically to streptozotocin (STZ)-induced diabetic rats. The plasma concentrations of glucose, ET-1 and NOx (NO2- + NO3-) were all significantly raised at 10 weeks after the STZ injection. Chronic administration of L-arginine resulted in a significantly higher plasma NOx concentration and a significantly lower plasma ET-1 level at 10 weeks compared with the untreated diabetic group. ET-1 induced a biphasic vasodilator/vasoconstrictor response in the perfused isolated mesenteric arterial beds from all groups. The vasodilatation was significantly greater in diabetic rats than in age-matched controls. Chronic oral L-arginine administration had no significant effect on the enhanced ET-1-induced vasodilatation seen in the untreated diabetic rats. The vasoconstrictions induced by ET-1 and methoxamine were significantly attenuated in STZ-diabetic rats. The attenuated vasoconstrictor response to ET-1, but not that to methoxamine, was further attenuated by chronic treatment with L-arginine. We conclude that since chronic L-arginine administration not only reduced the increase in plasma ET-1 levels but also further attenuated the ET-1-induced vasoconstriction without affecting the change in vasodilatation, chronic L-arginine administration could be valuable for the treatment of the symptoms of diabetic mellitus related to ET-1.

Endothelin A receptor antagonist LU 135252 inhibits hypercholesterolemia-induced, but not deendothelialization-induced, atherosclerosis in rabbit arteries

RATIONALE AND OBJECTIVES

The purpose of the study was to test the capability of the endothelin A receptor antagonist LU 135252 to reduce neointimal formation in rabbits after balloon denudation with and without the presence of hypercholesterolemia.

METHODS

Twenty-eight male New Zealand White rabbits underwent balloon denudation of the infrarenal aorta. The animals were randomly assigned to 1 of the 4 groups. After balloon denudation, group 1 (n = 6) and 2 (n = 7) received a standard diet, and group 3 (n = 8) and 4 (n = 7) were fed a 0.5% cholesterol diet. All interventional procedures were performed while the rabbits were under general anesthesia. One week prior to intervention treatment with LU 135252 was started in group 2 and 4. After 6 weeks the animals were killed for morphometric and histological analysis.

RESULTS

Rabbits in all treatment groups developed neointimal hyperplasia. By additional systemic treatment with LU 135252, the mean neointima to media ratio was significantly reduced only in the hypercholesterolemic animals of group 4 (neointimal to media ratio area of group 3 vs group 4: 2.07 +/- 0.62 vs 1.41 +/- 0.45, P < 0.05). ET receptor blockade in group 2 and 4 did not have an effect on plasma levels of cholesterol, very low-density lipoprotein-, high-density lipoprotein-, and low-density lipoprotein-cholesterol.

CONCLUSION

LU 135252 was efficient in reducing lipid induced atherosclerotic changes but was ineffective in inhibiting restenosis induced by balloon denudation.

Inhibition of endothelin-converting enzyme for protection against neointimal proliferation following balloon angioplasty of the rat carotid artery

Clinical success of percutaneous transluminal coronary angioplasty is limited by restenosis within months of the initial intervention. A number of vasoactive mediators and growth factors have been reported to participate in this process. The aim of the present experiments was to examine the effects of nonselective neutral endopeptidase (NEPi)/endothelin-converting enzyme (ECEi) inhibitors against neointimal proliferation (NIP) following balloon angioplasty of the left carotid artery of Sprague-Dawley rats with the right vessel serving as the uninjured control. The rats were divided in several groups: group 1, nontreated (vehicle); group 2, treated with a selective NEPi i.p.; groups 3-7, treated with nonselective NEPi/ECEi either i.p., s.c., i.v., or p.o. at various doses. After 2 weeks, cross-sectional histopathological and morphometrical examination of the left carotids revealed a severe NIP in vehicle-treated angioplastic rats compared with the control uninjured right carotid of the same rats. The selective NEPi CGS 24592 had no significant effect on restenosis, nor did the dual NEPi/ECEi CGS 26303 at 5 mg x kg(-1) x day(-1) i.p. Both s.c and i.v. NEPi/ECEi treatment (10 mg x kg(-1) x day(-1) b.i.d. s.c. or 10 mg x kg(-1) x day(-1) i.v.) reduced NIP by up to 35%. The prodrug CGS 26393 (p.o.) also attenuated NIP by 23%. Plasma concentrations of these compounds correlated with the degree of inhibition. These data support the participation of the endothelin system in the rat model of balloon angioplasty and suggest that selective ECEi may be effective.

Reciprocal regulation of endothelin-1 and nitric oxide: relevance in the physiology and pathology of the cardiovascular system

The endothelium plays a crucial role in the regulation of cardiovascular structure and function by releasing several mediators in response to biochemical and physical stimuli. These mediators are grouped into two classes: (1) endothelium-derived constricting factors (EDCFs) and (2) endothelium-derived relaxing factors (EDRFs), the roles of which are considered to be detrimental and beneficial, respectively. Endothelin-1 (ET-1) and nitric oxide (NO) are the prototypes of EDCFs and EDRFs, respectively, and their effects on the cardiovascular system have been studied in depth. Numerous conditions characterized by an impaired availability of NO have been found to be associated with enhanced synthesis of ET-1, and vice versa, thereby suggesting that these two factors have a reciprocal regulation. Experimental studies have provided evidence that ET-1 may exert a bidirectional effect by either enhancing NO production via ETB receptors located in endothelial cells or blunting it via ETA receptors prevalently located in the vascular smooth muscle cells. Conversely, NO was found to inhibit ET-1 synthesis in different cell types. In vitro and in vivo studies have started to unravel the molecular mechanisms involved in this complex interaction. It has been clarified that several factors affect in opposite directions the transcription of preproET-1 and NO-synthase genes, nuclear factor-KB and peroxisome proliferator-activated receptors playing a key role in these regulatory mechanisms. ET-1 and NO interplay seems to have a great relevance in the physiological regulation of vascular tone and blood pressure, as well as in vascular remodeling. Moreover, an imbalance between ET-1 and NO systems may underly the mechanisms involved in the pathogenesis of systemic and pulmonary hypertension and atherosclerosis.

Oestrogen attenuates coronary vasoconstriction after angioplasty: role of endothelin-1

BACKGROUND AND AIMS

There were controversies as to whether endothelin-1 is released after coronary angioplasty. We sought to determine whether endothelin-1 is released after coronary angioplasty and whether oestrogen administration can affect coronary vasomotor tone by reducing endothelin-1 concentrations.

METHODS

The study was designed to prospectively investigate 24 consecutive patients scheduled for elective coronary angioplasty. Patients were randomized into two groups according to whether they did not (group 1, n = 12) or did (group 2, n = 12) have intracoronary treatment with oestrogen. Quantitative coronary angiography was monitored at baseline, immediately after successful angioplasty, and 15 min after the last deflation. Blood samples for measuring the levels of endothelin-1 were drawn from the ascending aorta and the coronary sinus simultaneously before angioplasty and 15 min after balloon dilatation.

RESULTS

The diameters of the coronary artery at the dilated segments were significantly reduced 15 min after dilation compared with those immediately after dilation in group 1 from 3.20 +/- 0.22 to 2.30 +/- 0.23 mm (P < 0.001), respectively. The vasoconstriction was significantly blunted in group 2. The endothelin-1 levels from the coronary sinus rose significantly, by 29%, 15 min after angioplasty in group 1, which was attenuated after administering oestrogen. Significant correlation was found between the changes of coronary vasomotion of the dilated segment and endothelin-1 levels (r = 0.70, P = 0.01).

CONCLUSION

Endothelin-1 is released into the coronary circulation after angioplasty, and this vasoactive substance may contribute to the occurrence of vasoconstriction. The vasoconstriction is attenuated by oestrogen by reducing the endothelin-1 levels. This finding provided a new strategy to treat coronary vasoconstriction after angioplasty.

Stimulated release of endothelin-converting enzyme is simultaneous with tissue-type plasminogen activator and decrease in coronary heart disease

OBJECTIVE

During the process of atherosclerosis the endothelium changes both structurally and functionally. We examined whether shedding of endothelin-converting enzyme (ECE), a metalloprotease responsible for endothelin production, is concomitant with tissue-type plasminogen activator (t-PA), and how atherosclerosis affects ECE release.

DESIGN

Fourteen healthy volunteers and 24 patients with angiographically verified coronary heart disease (CHD) were investigated. ECE and t-PA releases were measured by a provocation test (20-min venous occlusion).

RESULTS

Serum ECE activities were comparable in both groups before the venous occlusion test (in CHD patients 205 +/- 24 vs in healthy controls 204 +/- 40 pmol/ml/h, p = NS). However, delta-ECE (= the difference between, after, and before the venous occlusion test) was significantly lower in CHD patients than in controls (203 +/- 36 vs 338 +/- 43 pmol/ml/h, p = 0.02, respectively). Delta-t-PA was similar in both groups (22.3 +/- 4.4 vs 14.5 +/- 4.6 ng/ml, p = NS, respectively). Furthermore, t-PA and ECE values correlated in the CHD group in all pre-, post-venous occlusion test, and delta-venous occlusion test values (r = 0.56, p = 0.009; r = 0.62, p = 0.003; r = 0.54, p = 0.01, respectively).

CONCLUSION

Vascular ECE release can be stimulated, and it is concomitant with t-PA release. A common location in endothelium may explain this simultaneous shedding. However, ECE levels do not rise in patients with CHD as markedly as in healthy patients. Atherosclerosis may explain reduced shedding of ECE.

Decoy oligodeoxynucleotide against activator protein-1 reduces neointimal proliferation after coronary angioplasty in hypercholesterolemic minipigs

OBJECTIVES

We sought to demonstrate, in an appropriate animal model, that co-medication with a transcription factor-blocking agent limits restenosis after percutaneous transluminal coronary angioplasty (PTCA).

BACKGROUND

Enhanced synthesis in the vessel wall of endothelin-1 (ET-1), a powerful co-mitogen for vascular smooth muscle cells, appears to be one mechanism that promotes restenosis after PTCA. Deformation-induced expression of prepro-ET-1 is governed by the transcription factor, activator protein-1 (AP-1).

METHODS

An anti-AP-1 decoy oligodeoxynucleotide (dODN) strategy was devised in which the dODN-containing solution (20 nmol) was administered locally through a Dispatch catheter into the coronary arteries of hypercholesterolemic minipigs at the time of PTCA (AVE-GFX stent).

RESULTS

Treatment with an AP-1 dODN, mimicking the consensus binding site of the transcription factor, significantly reduced neointimal formation in the coronary arteries of hypercholesterolemic minipigs (n = 10 to 12), compared with vehicle-treated coronary arteries, after four weeks of follow-up (neointimal area 2.64 +/- 0.33 vs. 4.81 +/- 1.04 mm(2) [mean +/- SEM]; p < 0.05). This effect was maintained after eight weeks (neointimal area 2.04 +/- 0.22 mm(2); n = 3) and correlated with a reduction in both nuclear translocation of AP-1 and ET-1 synthesis in the vessel wall 48 h after PTCA (n = 4). In contrast, an AP-1 mutant dODN, to which the transcription factor does not bind, showed no effect on neointimal formation at either time point (n = 3 to 7). Moreover, a consensus dODN directed against CCAAT/enhancer binding protein (C/EBP), another deformation-sensitive transcription factor, did not significantly affect neointimal formation after four weeks (n = 3).

CONCLUSIONS

These findings demonstrate the feasibility, efficacy and specificity of the anti-AP-1 dODN approach to the treatment of restenosis, which principally but not exclusively targets deformation-induced ET-1 synthesis in the vessel wall. Provided that these findings can be extrapolated to the situation of patients with coronary artery disease, the observed extent of the inhibitory effect of the AP-1 dODN treatment suggests that this co-medication may greatly reduce the incidence of in-stent restenosis.

New insight and therapeutic strategies in cardiovascular disease and focus on endothelial target: endothelin-1 and angina

This paper aims to demonstrate that there is currently sufficient evidence to suggest that endothelin-1 (ET-1) may play a role in angina and be associated with myocardial ischaemia. In order to demonstrate the potential role of ET-1 in angina, this paper examines three main factors: (i) that endothelin-1 can cause the pathophysiological states associated with myocardial ischaemia and angina; (ii) that ET-1 is over-expressed in humans and in animal models of myocardial ischaemia, which is associated with angina; and (iii) that modification of the ET-1 system is associated with an improvement in myocardial ischaemia and angina.

Endothelin receptor antagonists and cardiovascular diseases of aging

Our understanding of the role of the endothelin system in human cardiovascular physiology and pathophysiology has evolved very rapidly since the initial description of its constituent parts in 1988. Endothelin-1 (ET-1) is the predominant endothelin isoform in the human cardiovascular system and has potent vasoconstrictor, mitogenic and antinatriuretic properties which have implicated it in the pathophysiology of a number of cardiovascular diseases. The effects of ET-1 have been shown to be mediated by 2 principal endothelin receptor subtypes: ET(A) and ET(B). The development of a range of peptidic and nonpeptidic endothelin receptor antagonists represents an exciting breakthrough in human cardiovascular therapeutics. Two main classes of endothelin receptor antagonist have been developed for possible human therapeutic use: ET(A)-selective and nonselective antagonists. Extensive laboratory and clinical research with these agents has highlighted their promise in various cardiovascular diseases. Randomised, placebo-controlled clinical trials have yielded very encouraging results in patients with hypertension and chronic heart failure with more preliminary data suggesting a possible role in the treatment and prevention of atherosclerosis and stroke. Much more research is needed, however, before endothelin receptor antagonists can be considered for clinical use.

The effect of endothelin-1 on nuclear factor kappa B in macrophages

Nuclear factor kappaB (NF-kappaB) is a transcriptional factor which may be pivotal in the pathogenesis of atherosclerosis. Endothelin-1 (ET-1) is a peptide with proatherogenic properties. We hypothesized that ET-1 may act through activation of NF-kappaB and degradation of IkappaB-alpha, the cytosolic inhibitor of NF-kappaB activation, to create an atherogenic environment. The human monocytic cell line THP-1 was stimulated with ET-1 +/- the ET antagonist, BQ788 and the proteosome inhibitor, PSI. LPS was used as a positive control. Gel shift assays for NF-kappaB activity and Western blot analysis for IkappaB-alpha were performed. Both LPS and ET-1 led to activation of NF-kappaB in nuclear extracts [3.4 +/- 0.45 (LPS) and 2.9 +/- 0.26 (ET-1) fold increase in Arbitrary Densitometric Units (ADU) compared with negative control (P < 0.005 in both cases)]. In the presence of the ETB antagonist, BQ788, NF-kappaB activation was attenuated and not different from control (1.7 +/- 0.24 fold DU compared with negative control; P = NS). In addition, both LPS and ET-1 mediated NF-kappaB activation were attenuated by preincubation with the proteosome inhibitor, PSI (1.3 +/- 0.58 and 1.1 +/- 0.3 fold increase in ADU compared with negative control respectively). Both LPS and ET-1 led to a decrease in the amount of IkappaB-alpha present in the THP-1 cytoplasmic extracts (2.1 +/- 1.5% and 54 +/- 15.7% of ADU vs negative control (P < 0.05). NF-kappaB is activated by ET-1 in human THP-1 monocytes. This data supports a role for the ETs in the development of inflammation in the vessel wall in atherosclerosis.

Limitation of coronary reserve after successful angioplasty is prevented by oral pretreatment with an alpha1-adrenergic antagonist

Coronary vasoconstriction that occurs after percutaneous transluminal coronary angioplasty (PTCA) is abolished by intracoronary phentolamine. An impairment of coronary vasodilator reserve (CVR) has been observed < or = 7 days after successful PTCA. To ascertain whether pretreatment with the alpha1-adrenergic receptor blocker doxazosin could prevent the limitation of CVR after PTCA, we carried out a randomised, double-blind, controlled study on 26 patients with significant (> 75%) single vessel disease undergoing PTCA. Twelve patients received doxazosin 4 mg daily in addition to their standard treatment, while 14 patients received matching placebo, starting 11 days before PTCA. Myocardial blood flow (MBF) at baseline and after i.v. dipyridamole (0.56 mg/kg) was measured within 5 days after PTCA using positron emission tomography (PET) with oxygen-15-labelled water. Angioplasty was successful in all patients with a residual stenosis < or = 35%. At PET scanning, hemodynamic parameters were comparable in the two groups. In the territory subtended by the dilated artery, CVR was significantly higher in patients treated with doxazosin compared with those receiving placebo (2.78 +/- 0.1.21 vs. 1.95 +/- 0.68; p < 0.01). Conversely, CVR in the remote territories subtended by angiographically normal arteries was similar in the two groups (2.53 +/- 0.92 and 2.48 +/- 0.80, respectively; p = NS). Treatment with oral doxazosin in addition to standard antianginal therapy can prevent the impairment of CVR frequently observed despite successful PTCA.

Release of endothelin 1 and angiotensin II induced by percutaneous transluminal coronary angioplasty

Endothelial injury plays critical roles in acute and chronic complications after percutaneous transluminal coronary angioplasty (PTCA). We investigated coronary endothelial injury and the release of vasoactive substances induced by PTCA. We examined 44 patients with ischemic heart disease who underwent elective PTCA to isolated stenotic lesions in left coronary arteries. Eleven patients received balloon angioplasty (BA), 14 percutaneous transluminal rotational atherectomy (PTRA), and 19 stent implantation. Blood samples were drawn from the coronary sinus immediately before and after as well as 4 hr and 24 hr after PTCA. Plasma levels of endothelin (ET) 1, angiotensin (ANG) II, von Willebrand factor (vWF), and thrombomodulin (TM) were measured. Seven control subjects who underwent diagnostic coronary angiography (CAG) were used as controls. In all patients, ET-1 levels in the coronary sinus blood significantly increased immediately after PTCA. ANG II levels and vWF activity showed significant increases 4 hr after PTCA. Changes in levels of these markers were similar among the BA, PTRA, and stent groups. TM levels were elevated in all groups of patients, including those simply undergoing diagnostic CAG. Changes in ET-1, ANG II, and vWF levels in the coronary sinus reflect coronary endothelial injury induced by PTCA.

Stretch-induced endothelin B receptor-mediated apoptosis in vascular smooth muscle cells

Growing evidence suggests that a pressure-induced increase in the synthesis of endothelin (ET-1) is involved in arterial remodeling and, as a consequence, in the manifestation of chronic hypertension. To study potential stretch-induced changes in gene expression and their functional consequences, we have cultured rat aortic smooth muscle cells (raSMC) and porcine aortic endothelial cells (PAEC) on flexible elastomer membranes. The cells were periodically stretched (up to 20% elongation, 0.5 Hz, 6 h) and the expression of prepro-ET-1 and that of the endothelin A and B receptors (ET(A)-R and ET(B)-R) were analyzed by semi-quantitative RT-PCR analysis and ELISA (ET-1). In contrast to PAEC where ET-1 synthesis was up-regulated up to eightfold on exposure to cyclic stretch, ET-1 synthesis in raSMC was decreased by more than 80% under these conditions. ET(A) R -mRNA expression in stretched raSMC declined to 50% whereas ET(B) R -mRNA levels were increased up to 10-fold. One functional consequence of this apparent shift in receptor abundance was an apoptosis-promoting action of exogenous ET-1 (10 nM), as judged by the appearance of subdiploid peaks during FACS analysis, caspase-3 activation and chromatin condensation. This ET-1-induced apoptosis appeared to be ET(B)-R mediated, as it was completely suppressed by the ET(B)-R antagonist BQ 788 but not by the ET(A)-R antagonist BQ 123. Moreover, raSMC derived from homozygous spotting lethal rats, which lack a functional ET(B)-R, showed no signs of apoptosis after exposure to cyclic strain and exogenous ET-1. These findings suggest a central role for the endothelin system in the onset of hypertension-induced remodeling in conduit arteries, which may proceed via an initial stretch-induced apoptosis of the smooth muscle cells.

Activated nuclear factor-kappaB is present in the coronary vasculature in experimental hypercholesterolemia

BACKGROUND

Experimental hypercholesterolemia (HC) is characterized by a decrease in nitric oxide (NO) bioavailability and cellular proliferation. Nuclear factor-kappaB (NF-kappaB) is a transcriptional factor which plays a coordinating role in inflammation and cellular proliferation and may be involved in early atherosclerosis. We examined whether activated NF-kappaB was present in experimental hypercholesterolemia in the coronary vasculature in association with a decrease in NO bioavailability.

METHODS

A total of 14 juvenile domestic crossbred pigs were placed on a HC diet and six pigs on a normal diet for 10-12 weeks. A monoclonal antibody to the activated form of the p65 subunit of NF-kappaB was used to detect immunoreactivity in coronary artery sections. Coronary tissue homogenates were analyzed for activated NF-kappaB and endothelial nitric oxide synthase (eNOS) using Western blotting. In vitro coronary endothelium-dependent relaxation was performed in response to bradykinin, as a measure of NO bioavailability.

RESULTS

Intimal staining for activated NF-kappaB was present in 12/14 HC pigs as compared with 0/6 controls (P<0.001). Confocal microscopy confirmed the presence of NF-kappaB in the nucleus of intimal cells although the majority of the staining was cytoplasmic. In the HC group, Western blotting revealed an increase in activated NF-kappaB in the vessel wall compared to the normal group, in association with a decrease in the presence of eNOS protein and an attenuated vasorelaxation response to bradykinin.

CONCLUSION

This study suggests a potential role for activation of NF-kappaB, in association with a decrease in NO bioavailability, in the initial stages of atherosclerosis in the coronary vasculature.

Endothelin-1 release from atherosclerotic plaque after percutaneous transluminal coronary angioplasty in stable angina pectoris and single-vessel coronary artery disease

To assess the effects of percutaneous transluminal coronary angioplasty on endothelin-1 (ET-1) release, we assessed ET-1 concentrations at different sites of the coronary circulation in patients submitted to elective procedures. ET-1 levels immediately downstream from the plaque and ET-1 aortocoronary gradient increased significantly after the procedure, which was related to mechanical wall stress in patients only receiving balloons, but not in those undergoing stent percutaneous transluminal coronary angioplasty. No changes were found in the coronary sinus; these results suggest ET-1 release from the plaque rather than an ischemia/reperfusion-related production from the distal myocardium.

Prolonged blockade of endothelin ET(A) receptors decreases vascular reactivity in the aorta of spontaneously hypertensive rats in vitro

We investigated the effect of prolonged endothelin-1 type A (ET(A)) receptors blockade on the constrictor response to phenylephrine and the dilator response to acetylcholine (ACh) in isolated aortic rings from normotensive [Wistar-Kyoto (WKY)] rats and spontaneously hypertensive rats (SHRs). Animals were treated for 2 weeks with the ET(A)-receptor blocker LU135252 (50 mg/kg/day; n = 8). LU135252 treatment did not affect blood pressure in both strains. In isolated aortic segments, dilation to ACh and contractions to phenylephrine were decreased only in SHRs. Nitric oxide (NO) synthesis blockade (L-NAME, 0.1 mM) inhibited 90+/-11% (WKY rats) and 76+/-8% (SHRs) of ACh-induced dilation. Cyclooxygenases blockade (indomethacin, 10 microM) had no effect in both strains. Endothelium-derived hyperpolarizing factor(s) (EDHF) blockade (KCl, 20 mM) suppressed the remaining ACh-induced dilation in both strains. Treatment with LU135252 significantly decreased NO-dependent dilation, as compared with controls [70+/-8% vs. 90+/-11% (WKY rats) and 54+/-6% vs. 76+/-8% (SHRs) of total dilation; p<0.05]. On the other hand, EDHF-dependent dilation was significantly higher in the LU135252 groups [29+/-5% vs. 10+/-3% (WKY rats) and 44+/-7% vs. 19+/-4% (SHRs) of total dilation; p<0.05]. Thus prolonged ET(A)-receptor blockade decreased the responsiveness to phenylephrine and ACh in SHR aortas and changed the proportion of dilator agents in ACh-induced dilation.

Differential roles of endothelin-1 in the development of secondary pulmonary hypertension in patients with left heart failure with or without acute exacerbation

BACKGROUND

The aim of this study was to investigate the contribution of endothelin-1 (ET-1) to the development of secondary pulmonary hypertension (PH) in patients with left heart failure (HF).

METHODS AND RESULTS

The subjects were 40 patients with left HF with (group 1; n = 20) and without (group 2; n = 20) acute exacerbation. Before treatment, the ET-1 level in the pulmonary capillary wedge region was three times greater in patients of group 2 than group 1, although there was no significant difference in mean pulmonary artery pressure (mPAP) or pulmonary vascular resistance index (PVRI) between the two groups. Also, the ET-1 level significantly correlated with mPAP and PVRI for both groups, but with different slopes of the regression lines. After treatment of group 1, the extent of reduction in the ET-1 level significantly correlated with that in mPAP and in PVRI, whereas the ET-1 level itself correlated with mPAP, with the regression lines approximating those of group 2.

CONCLUSIONS

Our findings suggest that ET-1 may have differential roles in the development of secondary PH in patients with left HF with or without acute exacerbation.

Chronic endothelin-1-induced changes in vascular reactivity in rat resistance arteries and aorta

The role of endothelin-1 in vascular homeostasis is not yet clearly established. We investigated the responses to phenylephrine and acetylcholine in rat mesenteric resistance artery and aorta mounted in vitro in myographs after a 2-week treatment with endothelin-1 (5 pmol kg(-1) min(-1), n = 8). Systolic arterial blood pressure increased in endothelin-1-treated rats (171 +/- 7 mmHg vs. 196 +/- 6 mmHg, P < 0.05). In the aorta, chronic endothelin-1 significantly increased the dilator response to acetylcholine (maximal dilatation: 76 +/- 3 vs. 86 +/- 3% in control, P < 0.05). Acetylcholine-induced dilatation was decreased by nitric oxide (NO) synthase inhibition with NG-nitro-L-arginine methyl ester (L-NAME 100 micromol/l) and partly restored by cyclooxygenases inhibition (indomethacin, 10 micromol/l). In endothelin-1-treated rats, L-NAME-sensitive acetylcholine dilatation was lower than in the control, but dilator cyclooxygenase product(s) were found instead of constrictor cyclooxygenase product(s). In mesenteric resistance arteries chronic endothelin-1 increased the participation of cyclooxygenase products in acetylcholine-induced dilatation from 10 +/- 2 to 19 +/- 3%. In both types of arteries, phenylephrine-induced contraction was not affected by chronic endothelin-1. Thus chronic endothelin-1 increased the participation of dilator cyclooxygenase product(s) in acetylcholine-induced dilatation in the aorta and the mesenteric resistance arteries.

Chronic blockade of endothelin ETA receptors improves flow dependent dilation in resistance arteries of hypertensive rats

OBJECTIVE

Flow (shear stress)-induced dilation (FD) is attenuated in hypertension. Flow triggers the release by endothelial cells of dilators, such as NO or cyclo-oxygenase (COX) derivatives and constrictor factors such as endothelin-1 (ET-1) which might be involved in several cardiovascular diseases. We hypothesized that ET-1 might play a functional role in FD and participate in the endothelial dysfunction in hypertension.

METHODS

We investigated the effect of chronic treatment with the ETA receptor blocker LU135252 (50 mg/kg/day) for 2 weeks on the dilator response to flow in normotensive (Wistar-Kyoto; WKY) or hypertensive (SHR, n = 7 or 8 per group) rats.

RESULTS

Systolic arterial pressure was not significantly affected by chronic ETA receptor blockade in both strains. In mesenteric resistance arteries (diameter: approximately 100 microns), isolated in vitro, FD was lower and myogenic tone higher in SHR than in WKY rats. Chronic ETA receptor blockade increased FD by 73% (7.5 +/- 1.5 to 13.0 +/- 2.7 microns dilation with a flow-rate of 150 microliters/min) in SHR (no effect in WKY). The participation of NO to FD was increased in SHR and the participation of dilator COX product(s) (blocked by indomethacin 10 mumol/l) to FD was significantly increased in SHR and in WKY. In control rats FD was improved by acute ETA receptor blockade in WKY rats (18.5 +/- 2.0 to 23.2 +/- 1.8 microns dilation to flow-rate of 150 microliters/min) and significantly more in SHR (6.0 +/- 1.8 to 15.1 +/- 1.6 microns). Acetylcholine-induced dilation was also improved by chronic ETA receptor blockade (no effect of an acute blockade). Myogenic and phenylephrine-induced tone were not affected by chronic or acute ETA receptor blockade. The improvement of endothelium-dependent dilation was not related to a change in blood pressure.

CONCLUSION

Chronic ETA receptor blockade increased flow-induced dilation in SHR possibly by suppressing flow-induced ETA stimulation and by improving the release of dilator products by the endothelium.

Influence of non-insulin-dependent diabetes mellitus on plasma endothelin-1 levels in patients with advanced atherosclerosis

Endothelin-1 (ET-1) is an endothelium-derived vasoactive peptide with mitogen properties. Increased circulating ET-1 levels were found in patients with atherosclerosis as well as in patients with non-insulin-dependent diabetes mellitus (NIDDM) suggesting a role in the pathogenesis of these disorders. The aim of the present study was to ascertain the influence of the NIDDM on plasma ET-1 levels in patients with advanced atherosclerotic lesions. The circulating ET-1 levels were measured in 16 NIDDM patients (68.4 +/- 8.4 years) with macroangiopathy and in ten patients (65.3 +/- 11 years) with atherosclerosis without NIDDM. Twenty-two healthy subjects (43.1 +/- 18.3 years) served as controls. Circulating ET-1 levels were higher in NIDDM patients (6.8 +/- 2.8 pg/mL) than both controls (3.1 +/- 1 pg/mL; p < 0.001) and patients with vascular disease but without NIDDM (4.7 +/- 1.6 pg/mL; p < 0.04). No significant relationship was found between age and ET-1 concentrations, and no differences were noted between men and women in the control group. This study demonstrated that circulating ET-1 levels are increased in patients with atherosclerosis and that those with NIDDM showed the highest ET-1 levels. These observations strongly support a role for ET-1 in the pathogenesis of atherosclerosis and also suggest that this peptide may be involved in the development of atherosclerotic lesions in the NIDDM. We speculated that chronic exposure to hyperinsulinemia and hypertriglyceridemia in the diabetic patients could account for the increased ET-1 levels found in these patients.

Cardiac release and kinetics of endothelin after uncomplicated percutaneous transluminal coronary angioplasty

This study was designed to assess the release kinetics of endothelin after percutaneous transluminal coronary angioplasty (PTCA) and to prove the coronary endothelium as the source of the endothelin release. Twenty-seven patients with single-vessel coronary artery disease underwent PTCA. Endothelin, troponin T, myoglobin, and creatine phosphokinase paired blood samples were withdrawn from the coronary sinus and a peripheral vein before the balloon maneuver and at 1, 5, 10, 30, 45 minute(s), and at 1, 2, 3, 6, 12, and 24 hour(s) after the last balloon maneuver. Myocardial ischemia was monitored by means of cardiac lactate metabolism and 12-lead electrocardiogram. Thirteen patients who underwent a diagnostic cardiac catheterization served as a control group. In the left coronary artery, PTCA (n = 19) endothelin concentrations increased from 4.1 pg/ml as a common mean baseline level before intervention to 13.9 +/- 2.6 pg/ml (mean +/- SD) in the coronary sinus and 7.9 +/- 2.2 pg/ml (mean +/- SD) in the peripheral vein at 1 minute after the intervention (p <0.001). The levels remained elevated for 3 hours with higher coronary sinus than peripheral venous concentrations due to persistent cardiac endothelin release. PTCA of the right coronary artery (n = 8) also led to an instantaneous endothelin increase from a mean concentration of 4.4 before intervention to 8.3 pg/ml after intervention with identical coronary sinus and peripheral venous levels (p <0.001). Endothelin levels gradually decreased to normal within 6 hours. No patient developed a measurable myocardial ischemia or a myocardial infarction. In the control group all parameters remained unchanged. Uncomplicated PTCA was followed by a significant cardiac endothelin release that seems to indicate endothelial injury and not myocardial ischemia.

Expression of endothelial factors after arterial injury in the rat

Endothelin-1 (ET-1) and nitric oxide (NO) are potent vasoactive factors known to play a role in vascular remodeling. This study assessed the temporal expression of endothelial NO synthase (eNOS), preproET-1, and ETA and ETB receptor mRNAs in the rat carotid artery after balloon injury using quantitative competitive reverse transcription-polymerase chain reaction (qcRT-PCR) and the ribonuclease protection assay (RPA). Levels of ET-1 increased sharply after arterial injury, peaking (5.1-fold) at 2 days. This was associated with a dramatic increase in the expression of ETB (63-fold) and ETA (158-fold) receptor mRNA, peaking at days 1 and 2, respectively. Expression of eNOS was not detectable immediately after balloon injury, consistent with complete denudation, but reappeared after day 2 and increased to preinjury levels by day 14. The recovery of eNOS expression mirrored the return of ET-1 and ET receptor expression to baseline levels. The results confirm profound upregulation of the ET system in this model of arterial injury and suggest a critical role for eNOS expression and re-endothelialization in the normalization of ET-1 and ET receptor expression during the recovery phase, events that may be important in long-term arterial patency.

Endothelin-1 and endothelin-converting enzyme-1 gene regulation by shear stress and flow-induced pressure

Hemodynamic forces have been shown to modulate the expression of endothelin (ET-1) and endothelin-converting enzyme (ECE-1) in endothelial cells. We have subjected E.A. hy 926 cells in culture to steady fluid shear stress with and without flow-induced pressure. The effect of combining these two mechanical forces on the expression of genes in the ET system was studied and the changes were compared to the mRNA levels in static culture. Analysis of total RNA by Northern blot analysis and RNAse protection showed that steady shear stress induced ET-1 gene expression three- to fourfold in this system. The same condition had little to no effect on altering expression of ECE-1 isoforms. A range of flow-induced pressure (80-160 mm Hg) was not able to further augment ET-1 or ECE-1 gene expression. Overall, with the mechanical environment studied, we have been able to detect a predominant contribution of shear stress to altering the ET-1 gene in our system. Furthermore, this induction was independent of an alteration of ECE-1 gene levels, suggesting that these two genes have a different pattern of regulation by the same stimuli in this cell type.