Blockade of endothelin receptors markedly reduces atherosclerosis in LDL receptor deficient mice: role of endothelin in macrophage foam cell formation

Association of Low-Density Lipoprotein Cholesterol Levels During Statin Treatment With Cardiovascular and Renal Outcomes in Patients With Moderate Chronic Kidney Disease

Background The benefit of low-density lipoprotein cholesterol (LDL-C) levels in chronic kidney disease populations remains unclear. This study evaluated the cardiovascular and renal outcomes in patients with stage 3 chronic kidney disease with different LDL-C levels during statin treatment. Methods and Results There were 8500 patients newly diagnosed as having stage 3 chronic kidney disease under statin treatment who were identified from the Chang Gung Research Database and divided into 3 groups according to their first LDL-C level after the index date: <70 mg/dL, 70 to 100 mg/dL, and >100 mg/dL. Inverse probability of treatment weighting was performed to balance baseline characteristics. Compared with the LDL-C ≥100 mg/dL group, the 70≤LDL-C<100 mg/dL group exhibited significantly lower risks of major adverse cardiac and cerebrovascular events (6.8% versus 8.8%; subdistribution hazard ratio [SHR], 0.76 [95% CI, 0.64-0.91]), intracerebral hemorrhage (0.23% versus 0.51%; SHR, 0.44 [95% CI, 0.25-0.77]), and new-onset end-stage renal disease requiring chronic dialysis (7.6% versus 9.1%; SHR, 0.82 [95% CI, 0.73-0.91]). By contrast, the LDL-C <70 mg/dL group exhibited a marginally lower risk of major adverse cardiac and cerebrovascular events (7.3% versus 8.8%; SHR, 0.82 [95% CI, 0.65-1.02]) and a significantly lower risk of new-onset end-stage renal disease requiring chronic dialysis (7.1% versus 9.1%; SHR, 0.76 [95% CI, 0.67-0.85]). Conclusions Among patients with stage 3 chronic kidney disease, statin users with 70≤LDL-C<100 mg/dL and with LDL-C <70 mg/dL had similar beneficial effect in the reduction of risks of major adverse cardiac and cerebrovascular events and new-onset end-stage renal disease compared with those with LDL-C >100 mg/dL. Moreover, the 70≤LDL-C<100 mg/dL group seemed to have a lowest risk of intracerebral hemorrhage, although the incidence was low.

Effects of Gold Nanoparticles Functionalized with Bioactive Compounds from Cornus mas Fruit on Aorta Ultrastructural and Biochemical Changes in Rats on a Hyperlipid Diet-A Preliminary Study

Cornus mas L. extract (CM) presents hypolipidemic, antioxidant and anti-inflammatory activity. Gold nanoparticles (AuNPs) are considered potent delivery systems and may be used to release pharmaceutical compounds at the level of injury. In our study, we used gold nanoparticles functionalized with bioactive compounds from Cornus mas L. (AuNPsCM) in an experimental model of a high-fat diet (HFD), and we assessed their effects on aorta wall but also in the serum, as compared to Cornus mas (CM) administration. Sprague Dawley female rats were fed for 9 months with an HFD. During the last month of the experiment, we randomly allocated the animals into three groups that received, by oral gavage: saline solution, CM solution (0.158 mg/mL polyphenols) or AuNPsCM solution (260 μg Au/kg/day), while a Control group received a standard diet and saline solution. At the end of the experiment, we performed an ultrasonography of the aorta and left ventricle and a histology and transmission electron microscopy of the aorta walls; we investigated the oxidative stress and inflammation in aorta homogenates and in serum and, in addition, the lipid profile. AuNPsCM presented better effects in comparison with the natural extract (CM) on lipid peroxidation (p < 0.01) and TNF-alpha (p < 0.001) in aorta homogenates. In serum, both CM and AuNPsCM decreased the triglycerides (p < 0.001) and C-reactive protein (CM, p < 0.01; AuNPsCM, p < 0.001) and increased the antioxidant protection (p < 0.001), in comparison with the HFD group. In intima, AuNPsCM produced ultrastructural lesions, with the disorganization of intima and subendothelial connective layer, whereas CM administration preserved the intima normal aspect, but with a thinned subendothelial connective layer. AuNPsCM oral administration presented certain antioxidant, anti-inflammatory and hypolipidemic effects in an experimental model of HFD, but with a negative impact on the ultrastructure of aorta walls, highlighted by the intima disorganization.

Roles of Macrophages in Atherogenesis

Atherosclerosis is a chronic inflammatory disease that may ultimately lead to local proteolysis, plaque rupture, and thrombotic vascular disease, resulting in myocardial infarction, stroke, and sudden cardiac death. Circulating monocytes are recruited to the arterial wall in response to inflammatory insults and differentiate into macrophages which make a critical contribution to tissue damage, wound healing, and also regression of atherosclerotic lesions. Within plaques, macrophages take up aggregated lipoproteins which have entered the vessel wall to give rise to cholesterol-engorged foam cells. Also, the macrophage phenotype is influenced by various stimuli which affect their polarization, efferocytosis, proliferation, and apoptosis. The heterogeneity of macrophages in lesions has recently been addressed by single-cell sequencing techniques. This article reviews recent advances regarding the roles of macrophages in different stages of disease pathogenesis from initiation to advanced atherosclerosis. Macrophage-based therapies for atherosclerosis management are also described.

Monitoring Endothelin-A Receptor Expression during the Progression of Atherosclerosis

Cardiovascular disease remains the most frequent cause of death worldwide. Atherosclerosis, an underlying cause of cardiovascular disease, is an inflammatory disorder associated with endothelial dysfunction. The endothelin system plays a crucial role in the pathogenesis of endothelial dysfunction and is involved in the development of atherosclerosis. We aimed to reveal the expression levels of the endothelin-A receptor (ET_AR) in the course of atherogenesis to reveal possible time frames for targeted imaging and interventions. We used the ApoE^−/− mice model and human specimens and evaluated ET_AR expression by quantitative rtPCR (qPCR), histology and fluorescence molecular imaging. We found a significant upregulation of ET_AR after 22 weeks of high-fat diet in the aortae of ApoE^−/− mice. With regard to translation to human disease, we applied the fluorescent probe to fresh explants of human carotid and femoral artery specimens. The findings were correlated with qPCR and histology. While ET_AR is upregulated during the progression of early atherosclerosis in the ApoE^−/− mouse model, we found that ET_AR expression is substantially reduced in advanced human atherosclerotic plaques. Moreover, those expression changes were clearly depicted by fluorescence imaging using our in-house designed ET_AR-Cy 5.5 probe confirming its specificity and potential use in future studies.

Assessment of Inflammation in Pulmonary Artery Hypertension by 68Ga-Mannosylated Human Serum Albumin

Rationale: Diagnosis and monitoring of patients with pulmonary artery hypertension (PAH) is currently difficult.Objectives: We aimed to develop a noninvasive imaging modality for PAH that tracks the infiltration of macrophages into the pulmonary vasculature, using a positron emission tomography (PET) agent, ⁶⁸Ga-2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) mannosylated human serum albumin (MSA), that targets the mannose receptor (MR).Methods: We induced PAH in rats by monocrotaline injection. Tissue analysis, echocardiography, and ⁶⁸Ga-NOTA-MSA PET were performed weekly in rats after monocrotaline injection and in those treated with either sildenafil or macitentan. The translational potential of ⁶⁸Ga-NOTA-MSA PET was explored in patients with PAH.Measurements and Main Results: Gene sets related to macrophages were significantly enriched on whole transcriptome sequencing of the lung tissue in PAH rats. Serial PET images of PAH rats demonstrated increasing uptake of ⁶⁸Ga-NOTA-MSA in the lung by time that corresponded with the MR-positive macrophage recruitment observed in immunohistochemistry. In sildenafil- or macitentan-treated PAH rats, the infiltration of MR-positive macrophages by histology and the uptake of ⁶⁸Ga-NOTA-MSA on PET was significantly lower than that of the PAH-only group. The pulmonary uptake of ⁶⁸Ga-NOTA-MSA was significantly higher in patients with PAH than normal subjects (P = 0.009) or than those with pulmonary hypertension by left heart disease (P = 0.019) (n = 5 per group).Conclusions: ⁶⁸Ga-NOTA-MSA PET can help diagnose PAH and monitor the inflammatory status by imaging the degree of macrophage infiltration into the lung. These observations suggest that ⁶⁸Ga-NOTA-MSA PET has the potential to be used as a novel noninvasive diagnostic and monitoring tool of PAH.

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

Background

Acute psychosocial stress provokes increases in circulating endothelin‐1 (ET‐1) levels in humans and animal models. However, key questions about the physiological function and cellular source of stress‐induced ET‐1 remain unanswered. We hypothesized that endothelium‐derived ET‐1 contributes to the acute pressor response to stress via activation of the endothelin A receptor.

Methods and Results

Adult male vascular endothelium‐specific ET‐1 knockout mice and control mice that were homozygous for the floxed allele were exposed to acute psychosocial stress in the form of cage switch stress (CSS), with blood pressure measured by telemetry. An acute pressor response was elicited by CSS in both genotypes; however, this response was significantly blunted in vascular endothelium‐specific ET‐1 knockout mice compared with control mice that were homozygous for the floxed allele. In mice pretreated for 3 days with the endothelin A antagonist, ABT‐627, or the dual endothelin A/B receptor antagonist, A‐182086, the pressor response to CSS was similar between genotypes. CSS significantly increased plasma ET‐1 levels in control mice that were homozygous for the floxed allele. CSS failed to elicit an increase in plasma ET‐1 in vascular endothelium‐specific ET‐1 knockout mice. Telemetry frequency domain analyses suggested similar autonomic responses to stress between genotypes, and isolated resistance arteries demonstrated similar sensitivity to α₁‐adrenergic receptor‐mediated vasoconstriction.

Conclusions

These findings specify that acute stress‐induced activation of endothelium‐derived ET‐1 and subsequent endothelin A receptor activation is a novel mediator of the blood pressure response to acute psychosocial stress.

Growth Hormone (GH) and Cardiovascular System

This review describes the positive effects of growth hormone (GH) on the cardiovascular system. We analyze why the vascular endothelium is a real internal secretion gland, whose inflammation is the first step for developing atherosclerosis, as well as the mechanisms by which GH acts on vessels improving oxidative stress imbalance and endothelial dysfunction. We also report how GH acts on coronary arterial disease and heart failure, and on peripheral arterial disease, inducing a neovascularization process that finally increases flow in ischemic tissues. We include some preliminary data from a trial in which GH or placebo is given to elderly people suffering from critical limb ischemia, showing some of the benefits of the hormone on plasma markers of inflammation, and the safety of GH administration during short periods of time, even in diabetic patients. We also analyze how Klotho is strongly related to GH, inducing, after being released from the damaged vascular endothelium, the pituitary secretion of GH, most likely to repair the injury in the ischemic tissues. We also show how GH can help during wound healing by increasing the blood flow and some neurotrophic and growth factors. In summary, we postulate that short-term GH administration could be useful to treat cardiovascular diseases.

TRAF3IP2 mediates high glucose-induced endothelin-1 production as well as endothelin-1-induced inflammation in endothelial cells

Hyperglycemia-induced production of endothelin (ET)-1 is a hallmark of endothelial dysfunction in diabetes. Although the detrimental vascular effects of increased ET-1 are well known, the molecular mechanisms regulating endothelial synthesis of ET-1 in the setting of diabetes remain largely unidentified. Here, we show that adapter molecule TRAF3 interacting protein 2 (TRAF3IP2) mediates high glucose-induced ET-1 production in endothelial cells and ET-1-mediated endothelial cell inflammation. Specifically, we found that high glucose upregulated TRAF3IP2 in human aortic endothelial cells, which subsequently led to activation of JNK and IKKβ. shRNA-mediated silencing of TRAF3IP2, JNK1, or IKKβ abrogated high-glucose-induced ET-converting enzyme 1 expression and ET-1 production. Likewise, overexpression of TRAF3IP2, in the absence of high glucose, led to activation of JNK and IKKβ as well as increased ET-1 production. Furthermore, ET-1 transcriptionally upregulated TRAF3IP2, and this upregulation was prevented by pharmacological inhibition of ET-1 receptor B using BQ-788, or inhibition of NADPH oxidase-derived reactive oxygen species using gp91ds-tat and GKT137831. Notably, we found that knockdown of TRAF3IP2 abolished ET-1-induced proinflammatory and adhesion molecule (IL-1β, TNF-α, monocyte chemoattractant protein 1, ICAM-1, VCAM-1, and E-selectin) expression and monocyte adhesion to endothelial cells. Finally, we report that TRAF3IP2 is upregulated and colocalized with CD31, an endothelial marker, in the aorta of diabetic mice. Collectively, findings from the present study identify endothelial TRAF3IP2 as a potential new therapeutic target to suppress ET-1 production and associated vascular complications in diabetes. NEW & NOTEWORTHY This study provides the first evidence that the adapter molecule TRAF3 interacting protein 2 mediates high glucose-induced production of endothelin-1 by endothelial cells as well as endothelin-1-mediated endothelial cell inflammation. The findings presented herein suggest that TRAF3 interacting protein 2 may be an important therapeutic target in diabetic vasculopathy characterized by excess endothelin-1 production.

Selective improvement of pulmonary arterial hypertension with a dual ETA/ETB receptors antagonist in the apolipoprotein E-/- model of PAH and atherosclerosis

Idiopathic pulmonary arterial hypertension (IPAH) is increasingly diagnosed in elderly patients who also have an increased risk of co-morbid atherosclerosis. Apolipoprotein E-deficient (ApoE^−/−) mice develop atherosclerosis with severe PAH when fed a high-fat diet (HFD) and have increased levels of endothelin (ET)-1. ET-1 receptor antagonists (ERAs) are used for the treatment of PAH but less is known about whether ERAs are beneficial in atherosclerosis. We therefore examined whether treatment of HFD-ApoE^−/− mice with macitentan, a dual ET_A/ET_B receptor antagonist, would have any effect on both atherosclerosis and PAH. ApoE^−/− mice were fed chow or HFD for eight weeks. After four weeks of HFD, mice were randomized to a four-week treatment of macitentan by food (30 mg/kg/day dual ET_A/ET_B antagonist), or placebo groups. Echocardiography and closed-chest right heart catheterization were used to determine PAH phenotype and serum samples were collected for cytokine analysis. Thoracic aortas were harvested to assess vascular reactivity using wire myography, and histological analyses were performed on the brachiocephalic artery and aortic root to assess atherosclerotic burden. Macitentan treatment of HFD-fed ApoE^−/− mice was associated with a beneficial effect on the PAH phenotype and led to an increase in endothelial-dependent relaxation in thoracic aortae. Macitentan treatment was also associated with a significant reduction in interleukin 6 (IL-6) concentration but there was no significant effect on atherosclerotic burden. Dual blockade of ET_A/ET_B receptors improves endothelial function and improves experimental PAH but had no significant effect on atherosclerosis.

Peri-interventional endothelin-A receptor blockade improves long-term outcome in patients with ST-elevation acute myocardial infarction

Endothelin (ET)-1 is a pro-fibrotic vasoconstrictive peptide causing microvascular dysfunction and cardiac remodelling after acute ST-elevation myocardial infarction (STEMI). It acts via two distinct receptors, ET-A and ET-B, and is involved in inflammation and atherogenesis. Patients with posterior-wall STEMI were randomly assigned to intravenous BQ-123 at 400 nmol/minute (min) or placebo over 60 min, starting immediately prior to primary percutaneous coronary intervention (n=54). Peripheral blood samples were drawn at baseline as well as after 24 hours and 30 days. Myeloperoxidase (MPO), as a marker of neutrophil activation and matrix metalloproteinase 9 (MMP-9), a marker of extracellular matrix degradation were measured in plasma. Clinical follow-up was conducted by an investigator blinded to treatment allocation over three years. During the median follow-up period of 3.6 years (interquartile range [IQR] 3.3–4.1) we observed a longer event-free survival in patients randomised to receive BQ-123 compared with patients randomised to placebo (mean 4.5 years (95% confidence interval: 3.9–5) versus mean 3 years (2.2–3.7), p=0.031). Patients randomised to ET-A receptor blockade demonstrated a greater reduction of MPO levels from baseline to 24 hours compared to placebo-treated patients (-177 ng/ml (IQR 103–274) vs –108 ng/ml (74–147), p=0.006). In addition, a pronounced drop in MMP-9 levels (-568 ng/ml (44–1157) vs –117 ng/ml (57–561), p=0.018) was observed. There was no significant difference in amino-terminal propetide of pro-collagen type III levels. In conclusion, short-term administration of BQ-123 leads to a reduction in MPO, as well as MMP-9 plasma levels and to a longer event-free survival in patients with STEMI.

ClinicalTrials.gov Identifier: NCT00502528

Estimation of Some Oxidative Stress Parameters and Blood Pressure After Administration of Endothelin-1 (ET-1) in Rats

The aim of the study was to investigate changes in the plasma antioxidative activity and in lipid peroxidation after administration of endothelin-1 (ET-1) and endothelin receptor blockers and additionally, to estimate blood pressure. The study was performed on male Wistar rats (n = 6 per group) divided into 4 groups which received: (1) saline, (2) endothelin-1 (ET-1) (3 μg/kg b.w.) + saline, (3) BQ123 (1 mg/kg) + ET-1 (3 μg/kg), and (4) BQ788 (3 mg/kg) + ET-1 (3 μg/kg b.w.). The endothelin receptor antagonist was injected intravenously 30 min before ET-1 administration. Blood pressure was monitored, and the blood was collected before the saline or ET-1 administration as well as 60 and 300 min after their administration. The antioxidative properties were examined by FRAP method (ferric reducing ability of plasma), and the concentration of lipid peroxidation products was examined by the reaction with thiobarbituric acid (TBARS). It was estimated that intravenous administration of endothelin receptor blocker ETA increases plasma antioxidative properties (p < 0.01) and parallelly decreases the process of lipid peroxidation (p < 0.05 vs. ET-1) and blood pressure (p < 0.05).

Effect of endothelin-1 and endothelin receptor blockade on the release of microparticles

BACKGROUND

Increased levels of endothelial cell microparticles (EMP) are known to reflect endothelial dysfunction (ED). In diabetes mellitus type 2 (T2DM), the expression of endothelin (ET)-1 is increased. As treatment with an ET-1 antagonist significantly inhibited atherosclerosis in animal models, we sought to investigate whether treatment with ET-1 antagonists affects EMP levels in vitro and in vivo in patients with T2DM.

MATERIALS AND METHODS

In vitro study: Human umbilical vein endothelial cells (HUVEC) were stimulated with ET-1 alone and ET-1 in combination with a dual ET-A and ET-B endothelin receptor blocker. In vivo study: Patients with T2DM were randomized to treatment with the ET receptor antagonist bosentan or placebo. After 4 weeks, the patients were re-examined and blood samples were obtained. EMP counts in supernatants and plasma samples were determined using flow cytometry.

RESULTS

In vitro study: In supernatants of ET-1-stimulated HUVECs, the increased release of EMP was reduced significantly by co-incubation with an ET-1 receptor antagonist (e.g. CD31+/CD42b-EMP decreased from 37·1% ± 2·8 to 31·5% ± 2·8 SEM, P = 0·0078). In vivo study: No changes in EMP levels in blood samples of patients with T2DM were found after 4 weeks of bosentan treatment (n = 36, P = ns).

CONCLUSIONS

Our in vitro results suggest that ET-1 stimulates the release of EMP from HUVECs via a receptor-dependent mechanism. Co-incubation with an endothelin receptor blocker abolished ET-1-dependent EMP release. However, treatment with bosentan for 4 weeks failed to alter EMP levels in patients with T2DM. Other factors seem to have influenced EMP release in patients with T2DM independent of ET-1 receptor-mediated mechanisms.

Skeletal Muscle Vascular Function: A Counterbalance of Insulin Action

Insulin is a vasoactive hormone that regulates vascular homeostasis by maintaining balance of endothelial-derived NO and ET-1. Although there is general agreement that insulin resistance and the associated hyperinsulinemia disturb this balance, the vascular consequences for hyperinsulinemia in isolation from insulin resistance are still unclear. Presently, there is no simple answer for this question, especially in a background of mixed reports examining the effects of experimental hyperinsulinemia on endothelial-mediated vasodilation. Understanding the mechanisms by which hyperinsulinemia induces vascular dysfunction is essential in advancing treatment and prevention of insulin resistance-related vascular complications. Thus, we review literature addressing the effects of hyperinsulinemia on vascular function. Furthermore, we give special attention to the vasoregulatory effects of hyperinsulinemia on skeletal muscle, the largest insulin-dependent organ in the body. This review also characterizes the differential vascular effects of hyperinsulinemia on large conduit vessels versus small resistance microvessels and the effects of metabolic variables in an effort to unravel potential sources of discrepancies in the literature. At the cellular level, we provide an overview of insulin signaling events governing vascular tone. Finally, we hypothesize a role for hyperinsulinemia and insulin resistance in the development of CVD.

Endothelin

The endothelins comprise three structurally similar 21-amino acid peptides. Endothelin-1 and -2 activate two G-protein coupled receptors, ETA and ETB, with equal affinity, whereas endothelin-3 has a lower affinity for the ETA subtype. Genes encoding the peptides are present only among vertebrates. The ligand-receptor signaling pathway is a vertebrate innovation and may reflect the evolution of endothelin-1 as the most potent vasoconstrictor in the human cardiovascular system with remarkably long lasting action. Highly selective peptide ETA and ETB antagonists and ETB agonists together with radiolabeled analogs have accurately delineated endothelin pharmacology in humans and animal models, although surprisingly no ETA agonist has been discovered. ET antagonists (bosentan, ambrisentan) have revolutionized the treatment of pulmonary arterial hypertension, with the next generation of antagonists exhibiting improved efficacy (macitentan). Clinical trials continue to explore new applications, particularly in renal failure and for reducing proteinuria in diabetic nephropathy. Translational studies suggest a potential benefit of ETB agonists in chemotherapy and neuroprotection. However, demonstrating clinical efficacy of combined inhibitors of the endothelin converting enzyme and neutral endopeptidase has proved elusive. Over 28 genetic modifications have been made to the ET system in mice through global or cell-specific knockouts, knock ins, or alterations in gene expression of endothelin ligands or their target receptors. These studies have identified key roles for the endothelin isoforms and new therapeutic targets in development, fluid-electrolyte homeostasis, and cardiovascular and neuronal function. For the future, novel pharmacological strategies are emerging via small molecule epigenetic modulators, biologicals such as ETB monoclonal antibodies and the potential of signaling pathway biased agonists and antagonists.

Vascular endothelium - Gatekeeper of vessel health

The vascular endothelium is an interface between the blood stream and the vessel wall. Changes in this single cell layer of the artery wall are believed of primary importance in the pathogenesis of vascular disease/atherosclerosis. The endothelium responds to humoral, neural and especially hemodynamic stimuli and regulates platelet function, inflammatory responses, vascular smooth muscle cell growth and migration, in addition to modulating vascular tone by synthesizing and releasing vasoactive substances. Compromised endothelial function contributes to the pathogenesis of cardiovascular disease; endothelial 'dysfunction' is associated with risk factors, correlates with disease progression, and predicts cardiovascular events. Therapies for atherosclerosis have been developed, therefore, that are directed towards improving endothelial function.

Reduction of adhesion molecule production and alteration of eNOS and endothelin-1 mRNA expression in endothelium by Euphorbia hirta L. through its beneficial β-amyrin molecule

The inflammatory reaction in large blood vessels involves up-regulation of vascular adhesion molecules such as endothelial cell selectin (E-selectin), soluble vascular cell adhesion molecule (sVCAM)-1, and soluble intercellular adhesion molecule (sICAM)-1. These vascular dysfunctions are associated with the development of atherosclerosis. β-Amyrin, an active component of Euphorbia hirta L., has potent anti-inflammatory effects. So far, its preventive effects against the expression of inflammatory mediator-induced adhesion molecules have not been investigated. Endothelial cells (SVEC4-10 cell line) were treated with 50% RAW conditioned media (i.e., normal SVEC4-10 culture media contains 50% of lipopolysaccharide-activated macrophage culture media) without or with β-amyrin (0.6 and 0.3 µM). The production levels of E-selectin, sICAM-1, and sVCAM-1 in the SVEC4-10 cells were measured with ELISA assay kits. Under the same treatment conditions, expression of endothelin (ET)-1 and endothelial type of NO synthase (eNOS) mRNA were analyzed by RT-PCR and agarose gel. With β-amyrin, the 50% RAW conditioned media-induced E-selectin, sICAM-1, and sVCAM-1 levels as well as ET-1 gene expression were all suppressed. β-Amyrin treatment also restored the 50% RAW conditioned media-suppressed eNOS mRNA expression. These data indicate that β-amyrin is potentially useful in preventing chronic inflammation-related vascular diseases.

Chlorella 11-peptide inhibits the production of macrophage-induced adhesion molecules and reduces endothelin-1 expression and endothelial permeability

The inflammation process in large vessels involves the up-regulation of vascular adhesion molecules such as endothelial cell selectin (E-selectin), intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) which are also known as the markers of atherosclerosis. We have reported that Chlorella 11-peptide exhibited effective anti-inflammatory effects. This peptide with an amino sequence Val-Glu-Cys-Tyr-Gly-Pro-Asn-Arg-Pro-Gln-Phe was further examined for its potential in preventing atherosclerosis in this study. In particular, the roles of Chlorella 11-peptide in lowering the production of vascular adhesion molecules, monocyte chemoattractant protein (MCP-1) and expression of endothelin-1 (ET-1) from endothelia (SVEC4-10 cells) were studied. The production of E-selectin, ICAM-1, VCAM-1 and MCP-1 in SVEC4-10 cells was measured with ELISA. The mRNA expression of ET-1 was analyzed by RT-PCR and agarose gel. Results showed that Chlorella 11-peptide significantly suppressed the levels of E-selectin, ICAM, VCAM, MCP-1 as well as ET-1 gene expression. The inhibition of ICAM-1 and VCAM-1 production by Chlorella 11-peptide was reversed in the presence of protein kinase A inhibitor (H89) which suggests that the cAMP pathway was involved in the inhibitory cause of the peptide. In addition, this peptide was shown to reduce the extent of increased intercellular permeability induced by combination of 50% of lipopolysaccharide (LPS)-activated RAW 264.7 cells medium and 50% normal SEVC cell culture medium (referred to as 50% RAW-conditioned medium). These data demonstrate that Chlorella 11-peptide is a promising biomolecule in preventing chronic inflammatory-related vascular diseases.

Endothelin-1 overexpression exacerbates atherosclerosis and induces aortic aneurysms in apolipoprotein E knockout mice

OBJECTIVE

Endothelin (ET)-1 plays a role in vascular reactive oxygen species production and inflammation. ET-1 has been implicated in human atherosclerosis and abdominal aortic aneurysm (AAA) development. ET-1 overexpression exacerbates high-fat diet-induced atherosclerosis in apolipoprotein E(-/-) (Apoe(-/-)) mice. ET-1-induced reactive oxygen species and inflammation may contribute to atherosclerosis progression and AAA development.

APPROACH AND RESULTS

Eight-week-old male wild-type mice, transgenic mice overexpressing ET-1 selectively in endothelium (eET-1), Apoe(-/-) mice, and eET-1/Apoe(-/-) mice were fed high-fat diet for 8 weeks. eET-1/Apoe(-/-) had a 45% reduction in plasma high-density lipoprotein (P<0.05) and presented ≥ 2-fold more aortic atherosclerotic lesions compared with Apoe(-/-) (P<0.01). AAAs were detected only in eET-1/Apoe(-/-) (8/21; P<0.05). Reactive oxygen species production was increased ≥ 2-fold in perivascular fat, media, or atherosclerotic lesions in the ascending aorta and AAAs of eET-1/Apoe(-/-) compared with Apoe(-/-) (P<0.05). Monocyte/macrophage infiltration was enhanced ≥ 2.5-fold in perivascular fat of ascending aorta and AAAs in eET-1/Apoe(-/-) compared with Apoe(-/-) (P<0.05). CD4(+) T cells were detected almost exclusively in perivascular fat (3/6) and atherosclerotic lesions (5/6) in ascending aorta of eET-1/Apoe(-/-) (P<0.05). The percentage of spleen proinflammatory Ly-6C(hi) monocytes was enhanced 26% by ET-1 overexpression in Apoe(-/-) (P<0.05), and matrix metalloproteinase-2 was increased 2-fold in plaques of eET-1/Apoe(-/-) (P<0.05) compared with Apoe(-/-).

CONCLUSIONS

ET-1 plays a role in progression of atherosclerosis and AAA formation by decreasing high-density lipoprotein, and increasing oxidative stress, inflammatory cell infiltration, and matrix metalloproteinase-2 in perivascular fat, vascular wall, and atherosclerotic lesions.

Long-term endothelin receptor antagonism attenuates coronary plaque progression in patients with early atherosclerosis

AIM

The purpose of the current study was to determine if long term treatment with an endothelin-A (ETA) receptor antagonist attenuates the progression of coronary plaques in patients with coronary endothelial dysfunction.

METHODS

Thirty-five patients with non-obstructive coronary disease and coronary endothelial dysfunction were randomized in a double blind manner to treatment with placebo or ETA receptor antagonist Atrasentan (10 mg) for six months. Endothelial function was assessed by the change in coronary blood flow and coronary artery diameter in response to intracoronary acetylcholine. Normalized mean total atheroma volume (TAVMEAN), percent atheroma volume (PAV) and changes of atheroma volume were assessed by intravascular ultrasound (IVUS) at baseline and 6-month follow-up.

RESULTS

In segments with coronary endothelial dysfunction, there was a significant decrease in normalized TAVMEAN and PAV at six months from baseline in the Atrasentan group compared to the placebo group median (IQR) -2.00 mm(3) (-7.28, 2.53.) vs 9.11 mm(3) (1.23, 14.05), p=0.0024 and 0.955% (-3.43, 1.70) vs 3.85% (-0.39, 14.59) p=0.010. There was no change in normalized TAV or PAV in the segments with normal endothelial function.

CONCLUSION

This study demonstrates that 6-month treatment with Atrasentan attenuates progression of coronary plaque in segments with endothelial dysfunction.

Arctium lappa ameliorates endothelial dysfunction in rats fed with high fat/cholesterol diets

Background

Arctium lappa L. (Asteraceae), burdock, is a medicinal plant that is popularly used for treating hypertension, gout, hepatitis, and other inflammatory disorders. This study was performed to test the effect of ethanol extract of Arctium lappa L. (EAL) seeds on vascular reactivity and inflammatory factors in rats fed a high fat/cholesterol diet (HFCD).

Method

EAL-I (100 mg·kg⁻¹/day), EAL-II (200 mg·kg⁻¹/day), and fluvastatin (3 mg·kg⁻¹/day) groups initially received HFCD alone for 8 weeks, with EAL supplementation provided during the final 6 weeks.

Results

Treatment with low or high doses of EAL markedly attenuated plasma levels of triglycerides and augmented plasma levels of high-density lipoprotein (HDL) in HFCD-fed rats. Chronic treatment with EAL markedly reduced impairments of acetylcholine (ACh)-induced relaxation of aortic rings. Furthermore, chronic treatment with EAL significantly lowered systolic blood pressure (SBP) and maintained smooth and flexible intimal endothelial layers in HFCD-fed rats. Chronic treatment with EAL suppressed upregulation of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and E-selectin in the aorta. Chronic treatment with EAL also suppressed increases in matrix metalloproteinase (MMP)-2 expression. These results suggested that EAL can inhibit HFCD-induced vascular inflammation in the rat model.

Conclusion

The present study provides evidence that EAL ameliorates HFCD-induced vascular dysfunction through protection of vascular relaxation and suppression of vascular inflammation.

Pathological Importance of the Endothelin-1/ET(B) Receptor System on Vascular Diseases

Activation of the endothelin (ET)-1/ET receptor system is involved in the development of vascular diseases such as atherosclerosis, vascular hypertrophy, and restenosis. Some issues still remain unresolved including whether ET receptor antagonists are expected to become the new therapeutic tools for the treatment of vascular diseases. One of the unresolved critical points is the functional role of ET receptor subtypes on each vascular disease, in particular the pathophysiological roles of the ET_B receptor. We recently demonstrated that selective inhibition of the ET_B receptor system showed harmful effects in the development of neointimal formation after vascular injury. However, there was no apparent difference in the therapeutic effects between a nonselective ET_A/ET_B receptor antagonist and selective ET_A receptor antagonist. These findings indicate that antagonism of the ET_A receptor system is essential for suppressing vascular remodeling, irrespective of the presence of ET_B-receptor-mediated actions, although the selective ET_B receptor antagonist worsens vascular remodeling. In addition, we found that ET receptor systems contribute to sex differences in the severity of vascular disease, thereby suggesting that the efficacy of ET receptor antagonists for vascular diseases may differ between sexes. In this paper, we outline the roles of the ET-1/ET_B receptor system on vascular diseases and its sex differences.

Cynanchum wilfordii ameliorates hypertension and endothelial dysfunction in rats fed with high fat/cholesterol diets

Hypercholesterolemia increases the incidence of atherosclerosis and its pathologic complications. This study was performed to test the effect of an ethanol extract of Cynanchum wilfordii (ECW) on vascular dysfunction in rats fed with high fat/cholesterol diets (HFCD). Male rats were fed a HFCD consisting of 7.5% cocoa butter and 1.25% cholesterol, with or without 100, 200 mg/day/kg ECW. Rats fed with HFCD increased body weight associated with an increase in plasma low-density lipoprotein (LDL) cholesterol level. Chronic ECW treatment in HFCD-fed rats lessened LDL cholesterol and triglyceride levels as well as elevated high-density lipoprotein (HDL) cholesterol. Chronic ECW treatment recovered the HFCD-induced increase in systolic blood pressure, maintained smooth and soft intima endothelial layers by the decrease of intima-media thickness. ECW significantly recovered the diet-induced decrease in vasorelaxation to acetylcholine, high-dose ECW apparently increased vasorelaxation response to sodium nitroprusside in rats fed with HFCD. ECW clearly restored the HFCD-induced reduction in endothelial nitric oxide (NO) synthase expression and Akt expression levels in aortic tissue, leading to improve endothelial function through an increase in endothelium-derived NO production. Furthermore, treatment of ECW significantly recovered the HFCD-induced decrease in aortic cGMP levels in rats. These findings suggest that ECW ameliorates hypertension and endothelial dysfunction via improvement of NO/cGMP signaling pathway in aortic tissue of rats fed with HFCD, suggesting a vascular protective role for this herb in the treatment and prevention of atherosclerotic vascular disease.

New perspectives on endothelin-1 in atherosclerosis and diabetes mellitus

Endothelin-1 (ET-1) is a vasoconstrictor, proinflammatory and proliferative endothelial cell-derived peptide that is of significant importance in the regulation of vascular function. It is involved in the development of endothelial dysfunction including important interactions with nitric oxide. The expression and functional effects of ET-1 and its receptors are markedly altered during development of cardiovascular disease. Increased production of ET-1 and its receptors mediate many pathophysiological events contributing to the development of atherosclerosis and vascular complications in diabetes mellitus. The present review focuses on the pathophysiological role of ET-1 and the potential importance of ET receptors as a therapeutic target for treatment of these conditions.

Activation of spleen tyrosine kinase is required for TNF-α-induced endothelin-1 upregulation in human aortic endothelial cells

Endothelin-1 (ET-1) promotes atherosclerosis. We tested whether spleen tyrosine kinase (Syk) mediates tumor necrosis factor-α (TNF-α)-induced ET-1 upregulation in human aortic endothelial cells (HAECs) and sought to identify the signal pathways involved. TNF-α-induced reactive oxygen species (ROS) activated Syk and phosphatidylinositol 3-kinase (PI3K), which was required for the activation of AP-1 and subsequent ET-1 gene transcription. ROS mediated c-Jun NH(2)-terminal kinase (JNK) is also required for AP-1 activation, but Syk and PI3K regulated AP-1 activation independently of JNK. Through regulation of ET-1 production, Syk could be implicated in atherosclerosis.

Improved endothelial dysfunction by Cynanchum wilfordii in apolipoprotein E(-/-) mice fed a high fat/cholesterol diet

Cynanchum wilfordii is used in traditional Chinese medicine with almost all parts of this plant considered beneficial for various vascular diseases. This study was performed to evaluate the effect of an ethanol extract of C. wilfordii (ECW) on vascular dysfunction in apolipoprotein E (apoE)(-/-) mice fed with high fat/cholesterol diets (HFCDs). The apoE(-/-) mice were fed HFCD consisting of 7.5% cocoa butter and 1.25% cholesterol, with or without 100 or 200 mg/day/kg ECW. Chronic ECW treatment significantly lessened the level of low-density lipoprotein (P<.05) and elevated that of high-density lipoprotein-cholesterol (P<.01). Chronic ECW treatment normalized the HFCD-induced increase in systolic blood pressure, maintained smooth and soft intimal endothelial layers, and decreased intima-media thickness in aortic sections of HFCD-fed apoE(-/-) mice. ECW significantly restored the diet-induced decrease in vasorelaxation response to acetylcholine; however, the response to sodium nitroprusside did not change. ECW clearly restored the HFCD-induced reduction in endothelial nitric oxide synthase expression levels in aortic tissue, leading to decreased vascular inflammation through an inhibition of cellular adhesion molecules such as E-selectin, vascular cell adhesion molecule-1, and intracellular adhesion molecule-1 as well as endothelin-1 (ET-1) expression. In conclusion, ECW ameliorates endothelial dysfunction via improvement of the nitric oxide/cyclic GMP signaling pathway in a diet/genetic model of hyperlipidemia. ECW also substantially inhibited the development of atherosclerosis, possibly by inhibiting ET-1, cell adhesion molecules, and lesion formation, suggesting a vascular protective role for this herb in the treatment and prevention of atherosclerotic vascular disease.

Endothelin-1 exacerbates lipid accumulation by increasing the protein degradation of the ATP-binding cassette transporter G1 in macrophages

Endothelin-1 (ET-1), a potent proatherogenic vasoconstrictive peptide, is known to promote macrophage foam cell formation via mechanisms that are not fully understood. Excessive lipid accumulation in macrophages is a major hallmark during the early stages of atherosclerotic lesions. Cholesterol homeostasis is tightly regulated by scavenger receptors (SRs) and ATP-binding cassette (ABC) transporters during the transformation of macrophage foam cells. The aim of this study was to investigate the possible mechanisms by which ET-1 affects lipid accumulation in macrophages. Our results demonstrate that oxidized low-density lipoprotein (oxLDL) treatment increases lipid accumulation in rat bone marrow-derived macrophages. Combined treatment with ET-1 and oxLDL significantly exacerbated lipid accumulation in macrophages as compared to treatment with oxLDL alone. The results of Western blotting show that ET-1 markedly decreased the ABCG1 levels via ET type A and B receptors and activation of the phosphatidylinositol 3-kinase pathway; however, ET-1 had no effect on the protein expression of CD36, SR-BI, SR-A, or ABCA1. In addition, real-time PCR analysis showed that ET-1 treatment did not affect ABCG1 mRNA expression. We also found that ET-1 decreases ABCG1 possibly due to the enhancement of the proteosome/calpain pathway-dependent degradation of ABCG1. Moreover, ET-1 significantly reduced the efficiency of the cholesterol efflux in macrophages. Taken together, these findings suggest that ET-1 may impair cholesterol efflux and further exacerbate lipid accumulation during the transformation of macrophage foam cells.

Differential roles of endothelin-1 in angiotensin II-induced atherosclerosis and aortic aneurysms in apolipoprotein E-null mice

Because both endothelin-1 (ET-1) and angiotensin II (AngII) are independent mediators of arterial remodeling, we sought to determine the role of ET receptor inhibition in AngII-accelerated atherosclerosis and aortic aneurysm formation. We administered saline or AngII and/or bosentan, an endothelin receptor antagonist (ERA) for 7, 14, or 28 days to 6-week- and 6-month-old apolipoprotein E-knockout mice. AngII treatment increased aortic atherosclerosis, which was reduced by ERA. ET-1 immunostaining was localized to macrophage-rich regions in aneurysmal vessels. ERA did not prevent AngII-induced aneurysm formation but instead may have increased aneurysm incidence. In AngII-treated animals with aneurysms, ERA had a profound effect on the non-aneurysmal thoracic aorta via increasing wall thickness, collagen/elastin ratio, wall stiffness, and viscous responses. These observations were confirmed in acute in vitro collagen sheet production models in which ERA inhibited AngII's dose-dependent effect on collagen type 1 α 1 (COL1A1) gene transcription. However, chronic treatment reduced matrix metalloproteinase 2 mRNA expression but enhanced COL3A1, tissue inhibitor of metalloproteinase 1 (TIMP-1), and TIMP-2 mRNA expressions. These data confirm a role for the ET system in AngII-accelerated atherosclerosis but suggest that ERA therapy is not protective against the formation of AngII-induced aneurysms and can paradoxically stimulate a chronic arterial matrix remodeling response.

Darbepoetin alfa suppresses tumor necrosis factor-α-induced endothelin-1 production through antioxidant action in human aortic endothelial cells: role of sialic acid residues

Recombinant human erythropoietin (r-HuEPO) is widely used to correct anemia in end-stage renal disease patients, who commonly suffer from atherosclerosis. Endothelin-1 (ET-1) has been implicated in the pathogenesis of atherosclerosis. Here, we tested whether darbepoetin alfa, a hypersialylated analogue of r-HuEPO, regulates tumor necrosis factor-α (TNF-α)-induced ET-1 production in human aortic endothelial cells, and sought to identify the signal pathways involved. Darbepoetin alfa attenuated TNF-α-induced ET-1 production. It also diminished TNF-α-induced reactive oxygen species (ROS) accumulation and subsequent activation of c-Jun NH2-terminal kinase (JNK), which regulates the DNA-binding activities of both AP-1 and NF-κB required for ET-1 gene transcription. Like a JNK inhibitor, darbepoetin alfa did not affect IκBα degradation or p65 nuclear translocation, but did inhibit mitogen- and stress-activated protein kinase 1 (MSK1) activation and attenuated p65 phosphorylation (serine 276), effects that may account for the reduction in NF-κB DNA-binding activity. Desialylation completely abolished darbepoetin alfa's inhibitory effects on TNF-α-induced ROS accumulation, MSK1 activation, and ET-1 gene expression, without affecting its stimulation of STAT5 activity. These data demonstrate that darbepoetin alfa suppresses TNF-α-induced ET-1 production through its antioxidant action and suggest that the sialic acid residues of darbepoetin alfa are essential for its antioxidant effect, possibly by scavenging ROS.

Endothelin-1 and diabetic complications: focus on the vasculature

Diabetes is not only an endocrine but also a vascular disease. Cardiovascular complications are the leading cause of morbidity and mortality associated with diabetes. Diabetes affects both large and small vessels and hence diabetic complications are broadly classified as microvascular (retinopathy, nephropathy and neuropathy) and macrovascular (heart disease, stroke and peripheral arterial disease) complications. Endothelial dysfunction, defined as an imbalance of endothelium-derived vasoconstrictor and vasodilator substances, is a common denominator in the pathogenesis and progression of both macro and microvascular complications. While the pathophysiology of diabetic complications is complex, endothelin-1 (ET-1), a potent vasoconstrictor with proliferative, profibrotic, and proinflammatory properties, may contribute to many facets of diabetic vascular disease. This review will focus on the effects of ET-1 on function and structure of microvessels (retina, skin and mesenteric arteries) and macrovessels (coronary and cerebral arteries) and also discuss the relative role(s) of endothelin A (ET(A)) and ET(B) receptors in mediating ET-1 actions.

Mycophenolic acid attenuates tumor necrosis factor-alpha-induced endothelin-1 production in human aortic endothelial cells

AIMS

Atherosclerotic cardiovascular disease is the major cause of morbidity and mortality in solid organ transplant recipients. Endothelin-1 (ET-1) is implicated in the pathogenesis of atherosclerosis and is one of the potential therapeutic targets. This study was conducted to evaluate the effect of mycophenolic acid (MPA), an immunosuppressant for the transplant recipients, on tumor necrosis factor-alpha (TNF-alpha)-induced ET-1 production in aortic endothelial cells.

METHODS AND RESULTS

In cultured human aortic endothelial cells, TNF-alpha increased ET-1 through AP-1 and NF-kappaB, whereas MPA attenuated it by reducing both AP-1 and NF-kappaB DNA-binding activities. TNF-alpha increased ET-1 via c-Jun NH2-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), but not extracellular signal-regulated kinase. N-acetylcysteine that downregulated TNF-alpha-induced reactive oxygen species (ROS) inhibited JNK activation, but not p38 MAPK. N-acetylcysteine, SP600125 (JNK inhibitor) and SB203580 (p38 MAPK inhibitor) attenuated TNF-alpha-induced DNA-binding activities of both AP-1 and NF-kappaB. MPA inhibited JNK and p38 MAPK activations as well as ROS generation. N-acetylcysteine, SP600125, SB203580 and MPA had no effect on either TNF-alpha-induced IkappaBalpha degradation or p65 nuclear translocation, but attenuated p65 Ser276 phosphorylation.

CONCLUSION

MPA attenuated TNF-alpha-induced ET-1 production through inhibitions of ROS-dependent JNK and ROS-independent p38 MAPK that regulated NF-kappaB as well as AP-1. These findings suggest that MPA could have an effect of amelioration of atherosclerosis.

Increased expression of vascular endothelin type B and angiotensin type 1 receptors in patients with ischemic heart disease

Background

Endothelin-1 and angiotensin II are strong vasoconstrictors. Patients with ischemic heart disease have elevated plasma levels of endothelin-1 and angiotensin II and show increased vascular tone. The aim of the present study was to examine the endothelin and angiotensin II receptor expression in subcutaneous arteries from patients with different degrees of ischemic heart disease.

Methods

Subcutaneous arteries were obtained, by biopsy from the abdomen, from patients undergoing coronary artery bypass graft (CABG) surgery because of ischemic heart disease (n = 15), patients with angina pectoris without established myocardial infarction (n = 15) and matched cardiovascular healthy controls (n = 15). Endothelin type A (ET_A) and type B (ET_B), and angiotensin type 1 (AT₁) and type 2 (AT₂) receptors expression and function were examined using immunohistochemistry, Western blot and in vitro pharmacology.

Results

ET_A and, to a lesser extent, ET_B receptor staining was observed in the healthy vascular smooth muscle cells. The level of ET_B receptor expression was higher in patients undergoing CABG surgery (250% ± 23%; P < 0.05) and in the patients with angina pectoris (199% ± 6%; P < 0.05), than in the healthy controls (100% ± 28%). The data was confirmed by Western blotting. Arteries from CABG patients showed increased vasoconstriction upon administration of the selective ET_B receptor agonist sarafotoxin S6c, compared to healthy controls (P < 0.05). No such difference was found for the ET_A receptors. AT₁ and, to a lesser extent, AT₂ receptor immunostaining was seen in the vascular smooth muscle cells. The level of AT₁ receptor expression was higher in both the angina pectoris (128% ± 25%; P < 0.05) and in the CABG patients (203% ± 41%; P < 0.05), as compared to the healthy controls (100% ± 25%). The increased AT₁ receptor expression was confirmed by Western blotting. Myograph experiment did however not show any change in vasoconstriction to angiotensin II in CABG patients compared to healthy controls (P = n.s).

Conclusion

The results demonstrate, for the first time, upregulation of ET_B and AT₁ receptors in vascular smooth muscle cells in ischemic heart disease. These receptors may play a role in the pathophysiology of ischemic heart disease and could provide important targets for pharmaceutical interventions.

Cigarette smoke-induced emphysema in A/J mice is associated with pulmonary oxidative stress, apoptosis of lung cells, and global alterations in gene expression

Cigarette smoking is the major risk factor for developing chronic obstructive pulmonary disease, the fourth leading cause of deaths in the United States. Despite recent advances, the molecular mechanisms involved in the initiation and progression of this disease remain elusive. We used Affymetrix Gene Chip arrays to determine the temporal alterations in global gene expression during the progression of pulmonary emphysema in A/J mice. Chronic cigarette smoke (CS) exposure caused pulmonary emphysema in A/J mice, which was associated with pronounced bronchoalveolar inflammation, enhanced oxidative stress, and increased apoptosis of alveolar septal cells. Microarray analysis revealed the upregulation of 1,190, 715, 260, and 246 genes and the downregulation of 1,840, 730, 442, and 236 genes in the lungs of mice exposed to CS for 5 h, 8 days, and 1.5 and 6 mo, respectively. Most of the genes belong to the functional categories of phase I genes, Nrf2-regulated antioxidant and phase II genes, phase III detoxification genes, and others including immune/inflammatory response genes. Induction of the genes encoding multiple phase I enzymes was markedly higher in the emphysematous lungs, whereas reduced expression of various cytoprotective genes constituting ubiquitin-proteasome complex, cell survival pathways, solute carriers and transporters, transcription factors, and Nrf2-regulated antioxidant and phase II-responsive genes was noted. Our data indicate that the progression of CS-induced emphysema is associated with a steady decline in the expression of various genes involved in multiple pathways in the lungs of A/J mice. Many of the genes discovered in this study could rationally play an important role in the susceptibility to CS-induced emphysema.

Endothelin-1 signalling in vascular smooth muscle: pathways controlling cellular functions associated with atherosclerosis

Atherosclerosis is the primary ischaemic vascular condition underlying a majority of cardiovascular disease related deaths. Endothelin-1 is a vasoactive peptide agent upregulated in atherosclerosis and in conjunction with its G protein-coupled receptors exerts diverse actions on all cells of the vasculature in particular vascular smooth muscle cells (VSMC). The effects of endothelin-1 include cell proliferation, migration and contraction, and the induction of extracellular matrix components and growth factors. VSMC as the major component of the neointima in atherosclerotic plaques accordingly play a key role in atherogenesis. In this review we examine classic and novel signalling pathways activated by endothelin-1 in VSMC (including phospholipase C, adenylate cyclase, Rho kinase, transactivation of receptor tyrosine kinases, mitogen activated protein kinase cascades and beta-arrestin) and their likely impact on the development and progression of atherosclerosis.

Contrasting actions of endothelin ET(A) and ET(B) receptors in cardiovascular disease

First identified as a powerful vasoconstrictor, endothelin has an extremely diverse set of actions that influence homeostatic mechanisms throughout the body. Two receptor subtypes, ET(A) and ET(B), which usually have opposing actions, mediate the actions of endothelin. ET(A) receptors function to promote vasoconstriction, growth, and inflammation, whereas ET(B) receptors produce vasodilation, increases in sodium excretion, and inhibit growth and inflammation. Potent and selective receptor antagonists have been developed and have shown promising results in the treatment of cardiovascular diseases such as pulmonary arterial hypertension, acute and chronic heart failure, hypertension, renal failure, and atherosclerosis. However, results are often contradictory and complicated because of the tissue-specific vasoconstrictor actions of ET(B) receptors and the fact that endothelin is an autocrine and paracrine factor whose activity is difficult to measure in vivo. Considerable questions remain regarding whether ET(A)-selective or nonselective ET(A)/ET(B) receptor antagonists would be useful in a range of clinical settings.

Contrasting actions of endothelin ET(A) and ET(B) receptors in cardiovascular disease

First identified as a powerful vasoconstrictor, endothelin has an extremely diverse set of actions that influence homeostatic mechanisms throughout the body. Two receptor subtypes, ET(A) and ET(B), which usually have opposing actions, mediate the actions of endothelin. ET(A) receptors function to promote vasoconstriction, growth, and inflammation, whereas ET(B) receptors produce vasodilation, increases in sodium excretion, and inhibit growth and inflammation. Potent and selective receptor antagonists have been developed and have shown promising results in the treatment of cardiovascular diseases such as pulmonary arterial hypertension, acute and chronic heart failure, hypertension, renal failure, and atherosclerosis. However, results are often contradictory and complicated because of the tissue-specific vasoconstrictor actions of ET(B) receptors and the fact that endothelin is an autocrine and paracrine factor whose activity is difficult to measure in vivo. Considerable questions remain regarding whether ET(A)-selective or nonselective ET(A)/ET(B) receptor antagonists would be useful in a range of clinical settings.

Tissue-engineered human vascular media produced in vitro by the self-assembly approach present functional properties similar to those of their native blood vessels

We have developed a tissue-engineering approach for the production of a completely biological blood vessel from cultured human cells. In the present study, we took advantage of this tissue-engineering method to demonstrate that it can be used to reproduce the subtle differences in the expression of receptors present on the media of native human blood vessels. Indeed, a small percentage (3 of 18) of native human umbilical cord veins (HUCVs) responded to endothelin, the most powerful vasopressor agent known to date, via both endothelin A (ET(A)) and endothelin B (ET(B)) receptor activation. In contrast, most HUCVs tested responded to ET via ET(A) receptor activation only. Tissue-engineered vascular media (TEVM) were next reconstructed by using vascular smooth muscle cells (VSMCs) isolated and cultured from HUCVs expressing both ET(A) and ET(B) receptors to determine the functional integrity of our TEVM model. The reconstructed TEVM presents an endothelin response similar to that of respective HUCVs from which VSMCs were isolated. Reverse transcriptase polymerase chain reaction on TEVM reconstructed in vitro correlated these vasocontractile profiles by showing the presence of messenger RNA for both ET(A) and ET(B) receptors. Taken together with recently published results on TEVM expressing only ET(A) receptor, these results show that our reconstructed TEVM present a similar ET response profile as the blood vessel from which the VSMCs were isolated and cultured. These findings indicate that subtle differences, such as receptor expression, are preserved in the reconstructed tissue. Therefore, our TEVM offers a valuable human in vitro model with which to study the functionality of human blood vessels, such as their vasoactive response, or to perform pharmacologic studies.

Caveolin-1-deficient aortic smooth muscle cells show cell autonomous abnormalities in proliferation, migration, and endothelin-based signal transduction

We previously showed that ablation of caveolin-1 (Cav-1) gene expression in mice promotes neointimal hyperplasia in vivo, a phenomenon normally characterized by smooth muscle cell (SMC) migration and proliferation. Whether these defects are cell autonomous, i.e., due to loss of Cav-1 within SMCs or loss of Cav-1 expression in other adjacent cell types in vivo, remains unknown. Cav-1 has been shown to associate with receptors for many vasoactive factors on the SMC surface. Therefore, Cav-1 might be an important regulator of SMC proliferation, migration, and signal transduction. To mechanistically dissect the role of Cav-1 in SMC signaling, we isolated SMCs from the aortas (AoSMCs) of Cav-1-deficient (Cav-1(-/-)) mice and characterized these cells with respect to their proliferation, migration, and Ca(2+) response to an important vasoactive factor, endothelin-1 (ET-1). 5-Bromo-2'-deoxyuridine incorporation and a wound-healing assay showed an increase in proliferation and migration rates in Cav-1(-/-) compared with wild-type (Cav-1(+/+)) AoSMCs. Cav-1(-/-) AoSMCs demonstrated upregulation of phosphorylated ERK1/2, cyclin D1, and proliferating cell nuclear antigen and reduced expression of the cyclin-dependent kinase inhibitor p27(Kip1). The Ca(2+) response was examined in the presence of ET-1 and assessed by confocal microscopy with the Ca(2+)-sensitive fluorescent probe fluo 3. When treated with ET-1, Cav-1(-/-) AoSMCs exhibited a faster and larger increase in free intracellular Ca(2+) than Cav-1(+/+) cells. The ET-1-induced response in Cav-1(-/-) cells was mediated by the ET(B) receptor, as shown using the ET(B) receptor antagonist BQ-788 and the ET(A) receptor antagonist BQ-123. In Cav-1(-/-) cells, ET(A) receptor expression was reduced and ET(B) receptor expression was upregulated. Therefore, Cav-1 ablation increased the ET-1-induced Ca(2+) response in SMCs by altering the type and expression level of the ET receptor (i.e., receptor isoform switching). These data suggest a novel regulatory role for Cav-1 in SMCs with respect to their proliferation, migration, and Ca(2+)-mediated signaling.

Contribution of vasoconstriction to the origin of atherosclerosis: a conceptual study

Research during the past century has clearly shown that endothelial injury (EI) and/or endothelial dysfunction (ED) are among the major events determining the onset of atherosclerosis. Included in the events that may elicit endothelial damage, vasoconstriction (VC) has received relatively little attention. This conceptual review attempts to show that in elastic and conduit arteries, VC is not only capable of producing EI/ED, but is also closely associated with many recognized proatherogenic stimuli. Of related interest is the observation that a number of suspected antiatherogenic stimuli oppose VC by their vasodilatory effects, lending further support to this relationship. In addition, recent developments in the knowledge of the molecular basis of VC (including the role of specific inhibitors) are discussed, and their potential for preventing lesion formation and thus becoming novel therapeutic alternatives against the onset of atherosclerosis are highlighted.

The role of endothelin-1 in myocarditis and inflammatory cardiomyopathy: old lessons and new insights

Endothelin-1 has emerged as an important participant in the pathophysiology of a variety of cardiovascular diseases, where it may act on endocrine, paracrine and autocrine bases. Here we review its regulated biosynthesis, receptor-mediated signaling, and functional consequences in the heart, with particular emphasis on cardiac development and disease. Exploring published data employing molecular genetic mouse models of endothelin dysregulation, we highlight its heretofore underappreciated role as a pro-inflammatory cytokine. We also present novel micro-array data from one such mouse model, which implicate the specific downstream pathways that may mediate endothelin-1's effects.Key words: endothelin-1, cardiac development, inflammation, transgenic mice, gene expression profiling.

In vitro biomarker discovery for atherosclerosis by proteomics

The purpose of this study was to identify in vitro and then prioritize a tractable set of protein biomarker candidates of atherosclerosis that may eventually be developed to measure the extent, progression, regression, and stability of atherosclerotic lesions. A study was conducted using an in vitro"foam cell" model based on the stimulation of differentiated THP1 cells with oxidized low-density lipoprotein (oxidized LDL) as compared with low-density lipoprotein (LDL). Analysis of the proteins contained in the cell supernatant using proteome scanning technology identified 59 proteins as being increased, 57 with no statistically measurable difference, and 17 decreasing in abundance following treatment with oxidized LDL, as compared with LDL. From the up-regulated list, proteins were prioritized based on their analytical confidence as well as their relevance to atherosclerosis pathways. Within the group of increased abundance, seven families of proteins were of particular interest: fatty acid-binding proteins, chitinase-like enzymes, cyclophilins, cathepsins, proteoglycans, urokinase-type plasminogen activator receptor, and a macrophage scavenger receptor.

Conditional Cardiac Overexpression of Endothelin-1 Induces Inflammation and Dilated Cardiomyopathy in Mice

Background— Myocardial expression of endothelin-1 (ET-1) and its receptors ET A and ET B is increased in heart failure. However, the role of ET-1 and its signaling pathways in the pathogenesis of myocardial diseases is unclear.

Methods and Results— Human ET-1 cDNA was placed downstream of a promoter responsive to a doxycycline (DOX)-regulated transcriptional activator (tTA). This line (ET + ) was bred with one harboring cardiac myocyte-restricted expression of tTA (αMHC-tTA). Myocardial ET-1 peptide levels were significantly increased in binary transgenic (BT, ET + /tTA + ) compared with nonbinary transgenic (NBT, ET + /tTA − ; ET − /tTA + ; ET − /tTA − ) or DOX-treated BT littermates (40.1±4.7 versus 2.6±1.2 fmol/mL, P <0.003). BT mice demonstrated progressive mortality between 5 and 11 weeks after DOX withdrawal, associated with left ventricular dilatation and contractile dysfunction (peak +dP/dT, 4673±468 versus 5585±658 mm Hg/s, P <0.05). An interstitial inflammatory infiltrate, including macrophages and T lymphocytes, was evident in the myocardium of BT mice, associated with sequential increases in nuclear factor-κB translocation and expression of tumor necrosis factor-α, interferon-γ, interleukin-1 and interleukin-6. Significant prolongation of survival was observed with the combined ET A /ET B antagonist LU420627 (n=8, P <0.05) in BT mice but not the ET A -selective antagonist LU135252 (n=5, P =0.9), consistent with an important role for ET B in this model.

Conclusions— These are the first data to demonstrate that cardiac overexpression of ET-1 is sufficient to cause increased expression of inflammatory cytokines and an inflammatory cardiomyopathy leading to heart failure and death.

Endothelin-1 in atherosclerosis and other vasculopathies

Atherosclerosis is a major risk factor for both myocardial infarction and stroke. A key aspect of this disease is the imbalance of vasoactive factors. In this concise review, we focus on the role of endothelin-1 in the atherosclerotic process and other vasculopathies. Previously, we have demonstrated that there is a correlation between the expression of endothelin and the underlying atherosclerotic lesion. Immunoreactivity was observed for both ET-1 and ECE-1 in endothelial cells, smooth muscle cells, and macrophages within lesions. Endothelin's role in atherosclerosis must extend from its varying physiological activities, including vasoconstriction, mitogenesis, neutrophil adhesion, and platelet aggregation, and hypertrophy, as well as its propensity to induce the formation of reactive oxygen species. We also discuss regulation of endothelin by angiotensin II, reactive oxygen species, thrombin, aging, and LDL in the cardiovascular system. Finally, we demonstrate the role of endothelin in pulmonary hypertension and transplant associated vasculopathy.

[New expansion of endothelin research: perspectives for clinical application of endothelin-receptor antagonists]

Three isopeptides of endothelin (ET-1, -2, and -3) exert various actions through stimulation of two sub-types of receptor (ETA and ETB). Vascular endothelial cells produce only ET-1. In addition to its powerful vasoconstrictor action, ET-1 has direct mitogenic actions on cardiovascular tissues, as well as comitogennic actions with a wide variety of growth factors and vasoactive substances. ET-1 also promotes the synthesis and secretion of growth factors and various substances, including extracellular constituents. These effects of endogenous ET-1 would naturally be thought to be concerned with the development and/or aggravation of chronic cardiovascular diseases; e.g., hypertension, pulmonary hypertension, vascular remodeling (stenosis, atherosclerosis), renal failure, and heart failure. A large number of peptide and orally active non-peptide endothelin receptor antagonists have been developed, and utilized to analyze physiological and pathophysiological roles of endogenous ET-1. These antagonists have been shown to exert excellent therapeutic effects in animal models of various kinds of diseases by either acute or chronic treatment. Therapeutic treatment of patients suffering from the above-mentioned cardiovascular diseases with ET-receptor antagonists have also been taking place, and bosentan (ETA/ETB antagonist) was recently approved by the FDA as a formal therapeutic drug for pulmonary hypertension. In this review, perspectives for therapeutic applicability of ET-receptor antagonists will be explored.

Peroxisome proliferator-activated receptor activators inhibit oxidized low-density lipoprotein-induced endothelin-1 secretion in endothelial cells

Endothelin is a potent vasoconstrictor peptide isolated from endothelial cells and it induces smooth muscle cell proliferation. Endothelin-1 secretion is increased in atheroma and induces deleterious effects such as vasospasm and atherosclerosis. Oxidized low-density lipoproteins (LDLs) induce atherosclerosis in the vascular wall, as well as endothelin-1 secretion in endothelial cells and are activators of both peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and PPAR-gamma. PPAR-alpha (fibric acids) and PPAR-gamma (glitazones) activators are used to treat dyslipoproteinemias and type 2 diabetes, respectively. Furthermore, these drugs induce numerous pleiotropic effects, such as inhibiting thrombin-induced endothelin-1 secretion in endothelial cells. This study shows that both PPAR-alpha (Wy 14643) and PPAR-gamma activation (rosiglitazone) partially inhibit oxidized LDL-induced protein kinase C activity and endothelin-1 secretion in endothelial cells at the transcriptional levels and suggests that synthetic PPAR activators are stronger PPAR activators than oxidized LDL. This study also suggests that fibrate and glitazone treatments should have beneficial effects on the vascular wall by reducing endothelin-1 secretion and the resulting vasospasm and atherosclerosis.

The therapeutic potential of endothelin-1 receptor antagonists and endothelin-converting enzyme inhibitors on the cardiovascular system

Clinical trials have established bosentan, an orally active non-selective endothelin (ET) receptor antagonist, as a beneficial treatment in pulmonary hypertension. Trials have also shown short-term benefits of bosentan in systemic hypertension and congestive heart failure. However, bosentan also increased plasma levels of ET-1, probably by inhibiting the clearance of ET-1 by endothelin type B (ET(B)) receptors, and this may mean its effectiveness is reduced with long-term clinical use. Preliminary data suggests that selective endothelin type A (ET(A)) receptor antagonists (BQ-123, sitaxsentan) may be more beneficial than the non-selective ET receptor antagonists in heart failure, especially when the failure is associated with pulmonary hypertension. Experimental evidence in animal disease models suggests that non-selective ET or selective ET(A) receptor antagonism may have a role in the treatment of atherosclerosis, restenosis, myocarditis, shock and portal hypertension. In animal models of myocardial infarction and/or reperfusion injury, non-selective ET or selective ET(A) receptor antagonists have beneficial or detrimental effects depending on the conditions and agents used. Thus clinical trials of the non-selective ET or selective ET(A) receptor antagonists in these conditions are not presently warranted. Several selective endothelin-converting enzyme inhibitors have been synthesised recently, and these are only beginning to be tested in animal models of cardiovascular disease, and thus the clinical potential of these inhibitors is still to be defined.