Increased gene expression of the cardiac endothelin system in obese mice.

Obesity is a well-known risk factor of atherosclerosis and heart failure. In the human heart, a local endothelin system containing prepro-endothelin-1, endothelin-converting enzyme-1, and endothelin receptors A and B has been described. The endothelin system is activated in heart failure; however, the impact of obesity on the cardiac endothelin system is unknown. In this study, 18-week-old male C57BL/6 mice fed either a control diet or a high-fat diet for 10 weeks were analyzed. High-fat diet significantly increased the body weight of the animals and augmented low-density lipoprotein, high-density lipoprotein, and cholesterol plasma levels, compared to control. The animal groups showed no significant differences in left ventricular size or function (heart rate, ejection fraction, fractional shortening, left ventricular posterior wall thickness, cardiac output) after control or high-fat diet. We did not observe signs of cardiac hypertrophy or changes in markers of cardiac fibrosis in these heart samples. The cardiac expression of prepro-endothelin-1 mRNA, endothelin-converting enzyme-1 mRNA, and protein and endothelin receptors A and B mRNA was increased in 18-week-old obese C57BL/6 mice compared to animals with normal weight (p<0.05 vs. control). Furthermore, endothelin-1 plasma levels showed an increasing trend. In conclusion, an increased expression of genes of the endothelin system was observed in the hearts of 18-week-old mice after high-fat diet, possibly contributing to later cardiovascular complications of obesity.

ERK1/2 MAPKs and Wnt signaling pathways are independently involved in adipocytokine-mediated aldosterone secretion.

Obesity is one major risk factor for the development of arterial hypertension, and the development of obesity-related hypertension has been associated with increased plasma aldosterone levels. Our previous work shows a direct stimulatory effect of adipokines on aldosterone secretion from human adrenocortical cells, mediated via ERK1/2-dependent upregulation of steroid acute regulatory protein (StAR) activity. Recent evidence also indicates the involvement of the Wnt-signaling pathway in fat cell-mediated aldosterone secretion. Wnt-signaling molecules are secreted by adipocytes and regulate the activity of SF-1, a key transcription factor in adrenal steroidogenesis. The goal of this study was to investigate the cellular mechanisms of adipocyte-induced aldosterone secretion in detail, and to evaluate effects and possible interactions of the ERK1/2 MAPK- and the Wnt-signaling pathways on adipocyte-induced adreno-cortical aldosterone secretion. Our results show that, similar to adipocyte-conditioned medium (ACM), ß-catenin, which is an intracellular mediator of canonical Wnt-signaling, induced StAR promotor activity in human NCI-H295R adrenocortical cells, and ACM-induced StAR promotor activity depended on intact SF-1 binding sites. Wnt antagonist sFRP-1 inhibited adipokine-mediated StAR activity, but did not affect ERK1/2 MAPK activation. Accordingly, Wnt did not stimulate ERK1/2 phosphorylation in adrenocortical cells, indicating that ERK1/2 MAPK and Wnt signaling pathways are independently involved in adipocyte-mediated aldosterone secretion.

[LOX-1 receptor as a novel target in endothelial dysfunction and atherosclerosis]. / Der LOX-1-Rezeptor als neues Zielmolekül bei endothelialer Dysfunktion und Atherosklerose.

Atherosclerosis with its complications like heart attack and stroke, is the most frequent cause of death in the industrialized countries. Oxidized low-density lipoproteins (LDL) play a major role in the pathogenesis of atherosclerosis. Inhibition of cholesterol synthesis by statins has several protective effects but is not sufficient to prevent the uptake of oxidized LDL and the development of atherosclerotic plaques. For this reason a selective pharmacological inhibition of the uptake of oxidized LDL (oxLDL) in endothelial cells is an interesting therapeutic approach. An important novel target molecule is the endothelial lectin-like oxLDL receptor LOX-1. This receptor is able to take up both minimally and highly oxidized LDL. In addition it mediates endothelial phagocytosis of aged and apoptotic cells and plays a role in thrombocyte adhesion and in the interaction between bacterial proteins and endothelial cells in sepsis. LOX-1 is induced by proinflammatory cytokines, oxLDL, angiotensin II, endothelin-1 and arterial hypertension. LOX-1 increases endothelial dysfunction and atherosclerosis by endothelial uptake of oxLDL. This is the reason why LOX-1 has been considered as a novel link between hypertension and atherosclerosis. Transgenic overexpression of the LOX-1 receptor and high-fat diet induces intramyocardial vascular disease and endothelial dysfunction in resistance arteries. In contrast, genetic deletion of the LOX-1 gene reduces the development of atherosclerotic plaques. In the clinical context LOX-1 has been detected in the early phase of endothelial dysfunction and atherosclerosis in arteries of patients with coronary heart disease. Several novel data support a role of LOX-1 in the endothelial dysfunction in diabetic vascular and renal disease, hypercholesterolemia, obesity and preeclampsia. This makes the LOX-1 receptor a novel and interesting target molecule in endothelial dysfunction and atherosclerosis.

COUP-TFII is regulated by high glucose in endothelial cells.

Diabetes mellitus is an important risk factor for cardiovascular diseases. Clinical evidence supports a link between hyperglycemia, endothelial dysfunction, and vascular disorders. However, the precise molecular mechanisms causing endothelial dysfunction in diabetic patients remain unclear. An interesting novel mediator could be chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII), which plays an essential role in glucose metabolism. COUP-TFII is known to be expressed in venous endothelial cells. In this study, we show COUP-TFII expression in human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells. HUVECs express glucose transporters 1, 3, 6, and 10, and the insulin receptor. Insulin in combination with glucose activates protein kinase B (PKB or Akt) phosphorylation via phosphoinositide 3-kinase (PI3-kinase). Short-term (60-240 min) stimulation of HUVECs with high glucose increased COUP-TFII expression independent of insulin. Long-term (48 h) stimulation of HUVECs with high glucose augmented expression of the insulin receptor and E-selectin, but downregulated COUP-TFII protein expression. Downregulation of COUP-TFII by shRNA leads to downregulation of E-selectin and upregulation of eNOS and glucose transporters. Our data suggest that COUP-TFII is regulated by glucose in a time- and dose-dependent manner in endothelial cells. COUP-TFII might affect endothelial function in a diabetic background.

Analysis of murine vascular function in vivo by optical coherence tomography in response to high-fat diet.

In this study, we demonstrate the application of optical coherence tomography (OCT) as a contactless imaging technique to analyze vasodynamics in small blood vessels in vivo. The transluminal OCT imaging of vessels avoids micro traumata in the endothelium and circumvents surgical intervention. It can be performed in the intact perfused vessel and provides a new method to measure vascular function and dynamics in vivo. The resolution of 10 mum and the velocity of image acquisition are adequate to detect differences in the inner diameter, the maximal velocity, or the time to half-maximal diameter change of small vessels. We applied this new technology to study the vascular dynamics in small vessels of 6- and 20-week-old C57BL/6 mice in vivo. In addition, we determined by this technique the impact of a high-fat diet for 14 weeks on vascular function in 20-week-old animals. The diameter of the saphenous artery was increased under resting conditions, after vasoconstriction and after vasodilatation in 20-week-old animals on normal chow and high-fat diet, compared to 6-week-old animals. High-fat diet caused a significantly impaired vasoconstriction in the saphenous artery. The maximal velocity of diameter changes of the saphenous artery was determined by time-resolved OCT imaging. A significant reduction of this parameter was found during vasoconstriction in 20-week-old mice on high-fat diet, compared to 6-week-old animals. In conclusion, transluminal optical coherence tomography imaging is a novel and useful technique to analyze the impaired vasodynamics of small arteries in response to high-fat diet in vivo.

NAD(P)H oxidase and endothelial dysfunction.

The regulation of endothelial function plays an important role in the development and progression of metabolic and cardiovascular diseases. A critical determinant of endothelial function is the balance between nitric oxide and reactive oxygen species. Endothelium-derived NO availability can be limited by enhanced formation of reactive oxygen species. Major sources of reactive oxygen species in the vessel wall are NAD(P)H oxidase complexes. This review summarizes the impact of vascular NAD(P)H oxidase-derived reactive oxygen species on atherosclerosis and endothelial dysfunction. Changes in NAD(P)H oxidase expression and activity have clinical implications. Mutations in NAD(P)H oxidase subunits can lead to impaired oxidative burst in leukocytes and chronic granulomatous disease. In contrast, normalization of increased expression and activity of NAD(P)H oxidase in endothelial dysfunction and vascular disorders can be considered as a novel therapeutic strategy in the treatment of cardiovascular diseases.

Endothelin receptor B-mediated induction of c-jun and AP-1 in response to shear stress in human endothelial cells.

In vivo, endothelial cells are constantly exposed to shear stress by flowing blood. Short-term exposure of endothelial cells to shear stress has been shown to induce endothelin-1 release. It is currently unknown, however, whether this shear stress-dependent endothelin-1 release affects the expression and activity of transcription factors. In this study, primary cultures of human endothelial cells from the umbilical vein were exposed to laminar shear stress in a cone-and-plate viscometer. Laminar shear stress for 30 min induced a 2-fold increase in mRNA expression of c-jun , but not c-fos, in human endothelial cells. Blockade of endothelin receptor subtype B (ET B) with BQ788 prevented this shear stress-dependent induction of c-jun expression. The induction of c-jun by shear stress involved protein kinase C and endothelial NO synthase. In addition, exposure of endothelial cells to arterial laminar shear stress for 1 h increased the binding of transcription factor AP-1 to its consensus sequence by 1.7-fold in electrophoretic mobility shift assays. This induction was also mediated by an ET B-dependent pathway. Supershift analysis supports an AP-1 complex containing c-jun, but not c-fos, in human endothelial cells. In conclusion, our data suggest endothelin-1-mediated induction of c-jun expression and activation of AP-1 (possibly as a c-jun homodimer) by laminar shear stress in human endothelial cells.

Expression of human endothelin-converting enzyme isoforms: role of angiotensin II.

A key step in endothelin-1 (ET-1) synthesis is the proteolytic cleavage of big ET-1 by the endothelin-converting enzyme-1 (ECE-1). Four alternatively spliced isoforms, ECE-1a to ECE-1d, have been discovered; however, regulation of the expression of specific ECE-1 isoforms is not well understood. Therefore, we stimulated primary human umbilical vein endothelial cells (HUVECs) with angiotensin II (Ang II). Furthermore, expression of ECE-1 isoforms was determined in internal mammary arteries of patients undergoing coronary artery bypass grafting surgery. Patients had received one of 4 therapies: angiotensin-converting enzyme inhibitors (ACE-I), Ang II type 1 receptor blockers (ARB), HMG-CoA reductase inhibitors (statins), and a control group that had received neither ACE-I, ARB (that is, treatment not interfering in the renin-angiotensin system), nor statins. Under control conditions, ECE-1a is the dominant isoform in HUVECs (4.5+/-2.8 amol/microg RNA), followed by ECE-1c (2.7+/-1.0 amol/microg), ECE-1d (0.49+/-0.17 amol/microg), and ECE-1b (0.17+/-0.04 amol/microg). Stimulation with Ang II did not change the ECE-1 expression pattern or the ET-1 release. We found that ECE-1 mRNA expression was higher in patients treated with statins than in patients treated with ARB therapy (5.8+/-0.76 RU versus 3.0+/-0.4 RU), mainly attributed to ECE-1a. In addition, ECE-1a mRNA expression was higher in patients receiving ACE-I therapy than in patients receiving ARB therapy (1.68+/-0.27 RU versus 0.83+/-0.07 RU). We conclude that ECE-1a is the major ECE-1 isoform in primary human endothelial cells. Its expression in internal mammary arteries can be regulated by statin therapy and differs between patients with ACE-I and ARB therapy.

Low-density lipoproteins induce the renin-angiotensin system and their receptors in human endothelial cells.

Increased levels of low-density lipoproteins are well-established risk factors of endothelial dysfunction and the metabolic syndrome. In this study, we evaluated the effect of native low-density lipoprotein (nLDL) and oxidized LDL (oxLDL) on the expression of genes of the renin-angiotensin system (angiotensin-converting enzyme, ACE; angiotensin II type 1 receptor, AT(1)) and their receptors (low-density lipoprotein receptor: LDLR; lectin-like oxLDL receptor: LOX-1; toll-like receptor 4: TLR4) in primary cultures of human umbilical vein endothelial cells. ACE and AT(1) expressions were significantly increased after stimulation with nLDL and oxLDL. OxLDL receptor LOX-1 showed a maximum induction after 7 hours. Increased LOX-1 protein expression in response to oxLDL could be blocked by a LOX-1-specific antibody. TLR4 expression was increased by nLDL and oxLDL as well. We conclude that LDL and oxLDL can activate the renin-angiotensin system and their receptors LDLR, LOX-1, and TLR4 in human endothelial cells. These data suggest a novel link between hypercholesterolemia and hypertension in patients with the metabolic syndrome.

Pam3CSK4 and LTA-TLRs ligands associated with microdomains induce IL8 production in human adrenocortical cancer cells.

Bacterially derived ligands, Pam3CSK4 and LPS, can directly impact adrenal glands steroidogenesis through microdomain-related TLR1/2 and 4, respectively, and indirectly via immune cell-derived cytokines. The bilateral immunoadrenal relationship plays an important role in the proper functioning of both systems. CXC chemokine-dependent immune cell infiltration into adrenocortical carcinomas (ACC), which correlates with poor prognosis, is a common phenomenon. Recently, IL8 was identified in ACC and NCI-H295R cells, and was found to contribute to ACC tumour growth. The aim of this study was to clarify the role of different TLR ligands in IL8 production in NCI-H295R cells. This is the first study to demonstrate the expression of several TLRs including TLR1, 3, 6, 7 and 9 in human adrenocortical cells by using the RT-PCR approach. Only stimulation with TLR1/6 together with TLR2 ligands resulted in IL8 peptide and mRNA induction in a dose and time-dependent manner. Our data suggest that gram-positive bacteria-related TLR1/2/6 ligands might contribute to adrenal gland tumorigenesis via IL8 production.

Oxidative stress and endothelial dysfunction.

This review focuses on the role of vascular oxidative stress in the development and progression of endothelial dysfunction. We discuss different sources of oxidative stress in the vessel wall, oxidative stress and coagulation, the role of oxidative stress and vascular function in arteries and veins, the flow-dependent regulation of reactive oxygen species, the putative impact of oxidative stress on atherosclerosis, the interaction of angiotensin II, oxidative stress and endothelial dysfunction, and clinical implications.

Increased cardiac endothelial nitric oxide synthase expression in patients taking angiotensin-converting enzyme inhibitor therapy.

BACKGROUND: The efficacy of angiotensin-converting enzyme (ACE) inhibitors has been demonstrated in large clinical trials, but knowledge of the underlying mechanisms remains incomplete. Therefore, this study investigated the impact of ACE inhibitor therapy on cardiac nitric oxide (NO) synthases in patients with coronary artery disease (CAD) or heart failure. PATIENTS AND METHODS: The mRNA expression was quantified by standard calibrated competitive RT-PCR, protein expression by Western blotting and NOS activity by monitoring the conversion of [3H]arginine to [3H]citrulline during enzymatic formation of NO in tissue homogenates of myocardium of patients with, or without, ACE inhibitor treatment before elective coronary artery bypass grafting or heart transplantation. RESULTS: The mRNA expression (amol microg(-1) RNA) of endothelial NO synthase (eNOS) was higher (22.5 +/- 4.8, n = 23) in the atrial myocardium of patients taking ACE inhibitor treatment, before elective coronary artery bypass grafting, compared with patients not taking this therapy (8.9 +/- 0.7, n = 33, P < 0.0001). The ACE inhibitor therapy increased eNOS protein expression from [(9 +/- 0.7) relative units (RUs) to (12 +/- 0.9) RUs, P < 0.05, respectively] and cardiac NOS activity from 17.6 +/- 1.3 to 23.7 +/- 1.1 pmol mg protein(-1) min(-1) (P < 0.001, respectively). Inducible and neuronal NO synthase expression was not changed by the ACE inhibition. A similar up-regulation of eNOS by ACE inhibition was found in the left ventricles of patients with heart failure. The augmented endothelial NOS expression and activity was not the result of differences in clinical characteristics and concomitant therapy between the patient groups. CONCLUSION: Increased eNOS expression and activity might contribute to the beneficial effects of ACE inhibitor therapy in the treatment of CAD and heart failure.

Induction of NAD(P)H oxidase by oxidized low-density lipoprotein in human endothelial cells: antioxidative potential of hydroxymethylglutaryl coenzyme A reductase inhibitor therapy.

BACKGROUND: Elevated oxidative stress and superoxide anion formation in vascular cells could promote conversion of LDL to atherogenic oxidized LDL (oxLDL), contributing to endothelial dysfunction and atherosclerosis. As a major source of vascular superoxide anion formation, an endothelial NAD(P)H oxidase, similar to the leukocyte enzyme, has been identified. METHODS AND RESULTS: To elucidate functional differences between NAD(P)H oxidases of endothelial cells and leukocytes, DNA sequences of endothelial NAD(P)H oxidase subunits were determined. Gp91phox cDNA sequence showed no difference between the 2 cell types. Endothelial p67phox cDNA sequence revealed 2 known polymorphisms, which do not affect NAD(P)H oxidase function. Next, we analyzed relative mRNA expression of NAD(P)H subunits in human umbilical vein endothelial cells (HUVECs) and leukocytes using a common cRNA standard in competitive reverse transcription-polymerase chain reaction. NAD(P)H oxidase subunits p22phox and p47phox are expressed at a similar level in both cell types, whereas p67phox (2.5%) and gp91phox (1.1%) are expressed at a much lower level in endothelial cells than in leukocytes. Differences of gp91phox expression in leukocytes and HUVECs correlate with differences in superoxide release. Gp91phox mRNA and endothelial superoxide anion formation are induced in response to oxLDL in HUVECs. Furthermore, a lower gp91phox mRNA expression was found in internal mammary artery biopsy samples of patients with coronary artery disease treated with HMG-CoA reductase inhibitors before coronary bypass surgery. CONCLUSIONS: We conclude that oxLDL induces proatherosclerotic NAD(P)H oxidase expression and superoxide anion formation in human endothelial cells and an antioxidative potential of HMG-CoA reductase inhibition via reduction of vascular NAD(P)H oxidase expression.

Upregulation of vascular NAD(P)H oxidase subunit gp91phox and impairment of the nitric oxide signal transduction pathway in hypertension.

In this study we analyzed the role of vascular NAD(P)H oxidase in the generation of O(2)(-) and the endothelial impairment of NO signal transduction pathway in hypertension. In aortic rings of 15-month-old stroke-prone spontaneously hypertensive rats (SHR15) we found a 10-fold increased expression of NAD(P)H oxidase subunit gp91phox mRNA associated with a 3-fold increased production of O(2)(-) compared to age-matched Wistar rats (WIS15). Vasorelaxation studies in aortas of SHR15 showed a strongly diminished response to acetylcholine, NO-donor S-nitroso-N-acetyl-d,l-penicillamine, and organic nitrate glyceryl trinitrate compared to WIS15. Soluble guanylate cyclase (sGC) activity and sGC beta(1)-subunit protein expression was downregulated in aortas and lungs of SHR15. These data suggest an upregulation of vascular NAD(P)H oxidase and an impairment of the NO signal transduction pathway in hypertension.

Induction of the oxLDL receptor LOX-1 by endothelin-1 in human endothelial cells.

In this study, we analyzed the effect of endothelin-1 (ET-1) on expression of the lectin-like oxidized low-density lipoprotein (oxLDL) receptor-1 LOX-1 and on oxLDL uptake in primary cultures of human umbilical vein endothelial cells (HUVEC). LOX-1 mRNA was quantified by standard-calibrated competitive RT-PCR, LOX-1 protein expression by Western analysis and endothelial oxLDL uptake using DiI-labeled oxLDL. ET-1 induces LOX-1 mRNA expression, reaching its maximum after 1 h (160 +/- 14% of control, 100 nM ET-1, P < 0.05). This increased ET-1-mediated LOX-1 mRNA expression could be inhibited by endothelin receptor B antagonist BQ-788. In addition, ET-1 stimulates LOX-1 protein expression and oxLDL uptake in HUVEC. The augmented oxLDL uptake by ET-1 is mediated by endothelin receptor B, but not by protein kinases. These data support a new pathophysiological mechanism how locally and systemically increased ET-1 levels could promote LOX-1-mediated oxLDL uptake in human endothelial cells and the development and progression of endothelial dysfunction and atherosclerosis.

Increased expression of endothelin-1 and inducible nitric oxide synthase isoform II in aging arteries in vivo: implications for atherosclerosis.

We here report that aging increases expression of endothelin-1 and NO synthases in the vasculature and kidney of normotensive rats in vivo. Expression of preproendothelin-1 mRNA was quantified by RT-PCR and in situ hybridization, and endothelin-1 protein was determined by radioimmunoassay/HPLC. Vascular mRNA expression of NO synthase isoforms II and III was analyzed by RT-PCR. In young animals, vascular endothelin-1 protein was differentially expressed (aorta < renal artery < carotid artery) and increased with aging in all vascular beds (P < 0.05). In the intact aorta of aged rats, mRNA expression of preproendothelin-1, "inducible" NO synthase II, and endothelial cell NO synthase III gene was up-regulated (P < 0.05). Moreover, preproendothelin-1 mRNA expression increased in glomeruli and tubulointerstitial cells (P < 0.05). To our knowledge this is the first study demonstrating local vascular up-regulation of the trophic factor endothelin under physiological conditions. Activation of vascular endothelin and NO synthases may be important, pressure-independent factors contributing to structural and functional abnormalities of age-dependent diseases, including atherosclerosis.

[Reverse remodeling by surgery--fact or fiction?]. / "Reverse remodeling" durch Chirurgie induzierbar?

Mortality of chronic heart failure in industrial countries remains unacceptably high despite advances in medical therapy. Heart transplantation, the gold standard in the treatment of end-stage heart failure is reserved for only a few patients because of the shortage of donor hearts. Surgical alternatives to transplantation include dynamic cardiomyoplasty (CMP), mitral valve reconstruction, left ventricular reduction surgery (PLVR) and ventricular assist devices (VAD). Improved survival and objective physiologic improvement have not been documented for CMP in the treatment of dilative cardiomyopathy. Mitral valve reconstruction on the other hand shows promising results. PLVR is an innovative procedure in which the heart is surgically reduced in size and cardiac function is dramatically improved immediately after surgery. The presence of long-term effects is still unknown. VAD have been shown to be extremely effective as a short- and long-term "bridge" to heart transplantation. They are not approved for permanent support. A randomized trial in the U.S. is underway to compare the efficacy of these devices with the efficacy of medical therapy in NYHA functional class IV patients in quality of life, survival and costs.

Shear stress-dependent expression of apoptosis-regulating genes in endothelial cells.

Laminar shear stress exerts potent anti-apoptotic effects. Therefore, we analyzed the influence of laminar shear stress on the expression of apoptosis-regulating genes in human umbilical vein endothelial cells (HUVEC). Application of high levels of laminar shear stress (15 and 30 dyn/cm(2)) decreased the susceptibility of HUVEC to undergo apoptosis, whereas low shear stress (1 dyn/cm(2)) had no effect. These diminished signs of apoptosis were accompanied by a decreased mRNA expression of apoptosis-inducing Fas receptor. Furthermore, mRNA and protein expression of anti-apoptotic, soluble Fas isoform FasExo6Del and anti-apoptotic Bcl-x(L) were induced. Surprisingly, high shear stress also elevated mRNA and protein expression of pro-apoptotic Bak. The shear stress-induced up-regulation of Bcl-x(L) and Bak mRNA can be abrogated by inhibition of the endothelial NO synthase. We propose that altered expression of Bcl-x(L) and the Fas system is involved in the protective effect of laminar shear stress against apoptosis in human endothelial cells.

Deloading of the left ventricle by ventricular assist device normalizes increased expression of endothelin ET(A) receptors but not endothelin-converting enzyme-1 in patients with end-stage heart failure.

BACKGROUND: Ventricular assist devices (VAD) are implanted in patients with end-stage heart failure for bridging the time until heart transplantation, resulting in hemodynamic unloading of the failing heart, improved cardiac contractile and mitochondrial function, and reversal of cardiac hypertrophy. It is unknown whether VAD unloading may affect the cardiac endothelin (ET) system, which has been proposed as one of the putative pathomechanisms of heart failure. METHODS AND RESULTS: With the use of standard-calibrated, competitive reverse-transcription-polymerase chain reaction mRNA expression of components of the ET system was analyzed in left ventricular myocardium from nonfailing donor hearts, from failing hearts without and with ACE inhibitor therapy, and from patients with end-stage heart failure at the time of VAD implantation and 103+/-15 days after VAD implantation during removal with subsequent heart transplantation. ET receptor A (ET(A)) was markedly upregulated in failing human myocardium. This increased ET(A) expression was not affected by ACE inhibitor treatment but was normalized by VAD unloading. ET(A) expression before or after VAD implantation did not correlate with duration of VAD implantation or suppression of Pro-ANP mRNA. ET(B) mRNA expression was unaffected by heart failure or VAD. In contrast, increased ET-converting enzyme-1 mRNA and ET-1 peptide levels in failing myocardium were partially normalized by ACE inhibition but not by VAD unloading. CONCLUSIONS: We conclude that VAD implantation normalizes ET(A) expression in failing human left ventricular myocardium, probably as the result of the beneficial effects of VAD unloading.