Basic and therapeutic relevance of endothelin-mediated regulation

Potential biological targets for bioassay development in drug discovery of Sturge-Weber syndrome

Sturge-Weber Syndrome (SWS) is a neurocutaneous disease with clinical manifestations including ocular (glaucoma), cutaneous (port-wine birthmark), neurologic (seizures), and vascular problems. Molecular mechanisms of SWS pathogenesis are initiated by the somatic mutation in GNAQ. Therefore, no definite treatments exist for SWS and treatment options only mitigate the intensity of its clinical manifestations. Biological assay design for drug discovery against this syndrome demands comprehensive knowledge on mechanisms which are involved in its pathogenesis. By analysis of the interrelated molecular targets of SWS, some in vitro bioassay systems can be allotted for drug screening against its progression. Development of such platforms of bioassay can bring along the implementation of high-throughput screening of natural or synthetic compounds in drug discovery programs. Regarding the fact that study of molecular targets and their integration in biological assay design can facilitate the process of effective drug discovery; some potential biological targets and their respective biological assay for SWS drug discovery are propounded in this review. For this purpose, some biological targets for SWS drug discovery such as acetylcholinesterase, alkaline phosphatase, GABAergic receptors, Hypoxia-Inducible Factor (HIF)-1α and 2α are suggested.

Chronic thromboembolic pulmonary hypertension

Chronic pulmonary thromboembolic disease is an important cause of severe pulmonary hypertension, and as such is associated with significant morbidity and mortality. The prognosis of this condition reflects the degree of associated right ventricular dysfunction, with predictable mortality related to the severity of the underlying pulmonary hypertension. Left untreated, the prognosis is poor. Pulmonary endarterectomy is the treatment of choice to relieve pulmonary artery obstruction in patients with chronic thromboembolic pulmonary hypertension and has been remarkably successful. Advances in surgical techniques along with the introduction of pulmonary hypertension-specific medication provide therapeutic options for the majority of patients afflicted with the disease. However, a substantial number of patients are not candidates for pulmonary endarterectomy due to either distal pulmonary vascular obstruction or significant comorbidities. Therefore, careful selection of surgical candidates in expert centres is paramount. The current review focuses on the diagnostic approach to chronic thromboembolic pulmonary hypertension and the available surgical and medical therapeutic options.

Endothelin-1 and its role in the pathogenesis of infectious diseases

Endothelins are potent regulators of vascular tone, which also have mitogenic, apoptotic, and immunomodulatory properties (Rubanyi and Polokoff, 1994; Kedzierski and Yanagisawa, 2001; Bagnato et al., 2011). Three isoforms of endothelin have been identified to date, with endothelin-1 (ET-1) being the best studied. ET-1 is classically considered a potent vasoconstrictor. However, in addition to the effects of ET-1 on vascular smooth muscle cells, the peptide is increasingly recognized as a pro-inflammatory cytokine (Teder and Noble, 2000; Sessa et al., 1991). ET-1 causes platelet aggregation and plays a role in the increased expression of leukocyte adhesion molecules, the synthesis of inflammatory mediators contributing to vascular dysfunction. High levels of ET-1 are found in alveolar macrophages, leukocytes (Sessa et al., 1991) and fibroblasts (Gu et al., 1991). Clinical and experimental data indicate that ET-1 is involved in the pathogenesis of sepsis (Tschaikowsky et al., 2000; Goto et al., 2012), viral and bacterial pneumonia (Schuetz et al., 2008; Samransamruajkit et al., 2002), Rickettsia conorii infections (Davi et al., 1995), Chagas disease (Petkova et al., 2000, 2001), and severe malaria (Dai et al., 2012; Machado et al., 2006; Wenisch et al., 1996a; Dietmann et al., 2008). In this minireview, we will discuss the role of endothelin in the pathogenesis of infectious processes.

The kallikrein-kinin system in experimental Chagas disease: a paradigm to investigate the impact of inflammatory edema on GPCR-mediated pathways of host cell invasion by Trypanosoma cruzi

Chronic chagasic myocarditis (CCM) depends on Trypanosoma cruzi persistence in the myocardium. Studies of the proteolytic mechanisms governing host/parasite balance in peripheral sites of T. cruzi infection revealed that tissue culture trypomastigotes (TCTs) elicit inflammatory edema and stimulate protective type-1 effector T cells through the activation of the kallikrein-kinin system. Molecular studies linked the proinflammatory phenotype of Dm28c TCTs to the synergistic activities of tGPI, a lipid anchor that functions as a Toll-like receptor 2 (TLR2) ligand, and cruzipain, a kinin-releasing cysteine protease. Analysis of the dynamics of inflammation revealed that TCTs activate innate sentinel cells via TLR2, releasing CXC chemokines, which in turn evoke neutrophil/CXCR2-dependent extravasation of plasma proteins, including high molecular weight kininogen (HK), in parasite-laden tissues. Further downstream, TCTs process surface bound HK, liberating lysyl-BK (LBK), which then propagates inflammatory edema via signaling of endothelial G-protein-coupled bradykinin B₂ receptors (BK₂R). Dm28 TCTs take advantage of the transient availability of infection-promoting peptides (e.g., bradykinin and endothelins) in inflamed tissues to invade cardiovascular cells via interdependent signaling of BKRs and endothelin receptors (ETRs). Herein we present a space-filling model whereby ceramide-enriched endocytic vesicles generated by the sphingomyelinase pathway might incorporate BK₂R and ETRs, which then trigger Ca²⁺-driven responses that optimize the housekeeping mechanism of plasma membrane repair from cell wounding. The hypothesis predicts that the NF-κB-inducible BKR (BK₁R) may integrate the multimolecular signaling platforms forged by ceramide rafts, as the chronic myocarditis progresses. Exploited as gateways for parasite invasion, BK₂R, BK₁R, ET_AR, ET_BR, and other G protein-coupled receptor partners may enable persistent myocardial parasitism in the edematous tissues at expense of adverse cardiac remodeling.

Trypanosoma cruzi invades host cells through the activation of endothelin and bradykinin receptors: a converging pathway leading to chagasic vasculopathy

BACKGROUND AND PURPOSE

Independent studies in experimental models of Trypanosoma cruzi appointed different roles for endothelin-1 (ET-1) and bradykinin (BK) in the immunopathogenesis of Chagas disease. Here, we addressed the hypothesis that pathogenic outcome is influenced by functional interplay between endothelin receptors (ET(A)R and ET(B)R) and bradykinin B(2) receptors (B(2)R).

EXPERIMENTAL APPROACH

Intravital microscopy was used to determine whether ETR/B(2)R drives the accumulation of rhodamine-labelled leucocytes in the hamster cheek pouch (HCP). Inflammatory oedema was measured in the infected BALB/c paw of mice. Parasite invasion was assessed in CHO over-expressing ETRs, mouse cardiomyocytes, endothelium (human umbilical vein endothelial cells) or smooth muscle cells (HSMCs), in the presence/absence of antagonists of B(2)R (HOE-140), ET(A)R (BQ-123) and ET(B)R (BQ-788), specific IgG antibodies to each GPCRs; cholesterol or calcium-depleting drugs. RNA interference (ET(A)R or ET(B)R genes) in parasite infectivity was investigated in HSMCs.

KEY RESULTS

BQ-123, BQ-788 and HOE-140 reduced leucocyte accumulation in HCP topically exposed to trypomastigotes and blocked inflammatory oedema in infected mice. Acting synergistically, ET(A)R and ET(B)R antagonists reduced parasite invasion of HSMCs to the same extent as HOE-140. Exogenous ET-1 potentiated T. cruzi uptake by HSMCs via ETRs/B(2)R, whereas RNA interference of ET(A)R and ET(B)R genes conversely reduced parasite internalization. ETRs/B(2)R-driven infection in HSMCs was reduced in HSMC pretreated with methyl-β-cyclodextrin, a cholesterol-depleting drug, or in thapsigargin- or verapamil-treated target cells.

CONCLUSIONS AND IMPLICATIONS

Our findings suggest that plasma leakage, a neutrophil-driven inflammatory response evoked by trypomastigotes via the kinin/endothelin pathways, may offer a window of opportunity for enhanced parasite invasion of cardiovascular cells.

Infection-associated vasculopathy in experimental chagas disease pathogenic roles of endothelin and kinin pathways

Acting at the interface between microcirculation and immunity, Trypanosoma cruzi induces modifications in peripheral tissues which translate into mutual benefits to host/parasite balance. In this chapter, we will review evidence linking infection-associated vasculopathy to the proinflammatory activity of a small subset of T. cruzi molecules, namely GPI-linked mucins, cysteine proteases (cruzipain), surface glycoproteins of the trans-sialidase family and/or parasite-derived eicosanoids (thromboxane A(2)). Initial insight into pathogenesis came from research in animal models showing that myocardial fibrosis is worsened as result of endothelin upregulation by infected cardiovascular cells. Paralleling these studies, the kinin system emerged as a proteolytic mechanism that links oedematogenic inflammation to immunity. Analyses of the dynamics of inflammation revealed that tissue culture trypomastigotes elicit interstitial oedema in peripheral sites of infection through synergistic activation of toll-like 2 receptors (TLR2) and G-protein-coupled bradykinin receptors, respectively, engaged by tGPI (TLR2 ligand) and kinin peptides (bradykinin B2 receptors (BK(2)R) ligands) proteolytically generated by cruzipain. Further downstream, kinins stimulate lymph node dendritic cells via G-protein-coupled BK(2)R, thus converting these specialized antigen-presenting cells into T(H)1 inducers. Tightly regulated by angiotensin-converting enzyme, the intact kinins (BK(2)R agonists) may be processed by carboxypeptidase M/N, generating [des-Arg]-kinins, which activates BK(1)R, a subtype of GPCR that is upregulated by cardiovascular cells during inflammation. Ongoing studies may clarify if discrepancies between proinflammatory phenotypes of T. cruzi strains may be ascribed, at least in part, to variable expression of TLR2 ligands and cruzipain isoforms.

Natriuretic peptides in cardiovascular diseases

The natriuretic peptide family comprises atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP), dendroaspis natriuretic peptide (DNP), and urodilatin. The activities of natriuretic peptides and endothelins are strictly associated with each other. ANP and BNP inhibit endothelin-1 (ET-1) production. ET-1 stimulates natriuretic peptide synthesis. All natriuretic peptides are synthesized from polypeptide precursors. Changes in natriuretic peptides and endothelin release were observed in many cardiovascular diseases: e.g. chronic heart failure, left ventricular dysfunction and coronary artery disease.

Chronically impaired endothelial vasoreactivity following oversized endovascular introducer sheath placement in porcine iliac arteries: implications for endovascular therapy

The conventional endovascular aortic aneurysm procedure entails the placement of oversized introducer sheaths in relatively normal ileofemoral arteries to allow the delivery and deployment of endovascular prosthesis. Endoluminal manipulation with passage of oversized endoluminal devices can lead to endothelial denudation, resulting in impaired cellular function. The purpose of this study was to assess the time course of endothelial function with vasoreactivity following oversized endovascular sheath insertion ranging from 1 day to 16 weeks in normal porcine iliac arteries. Following oversized introducer sheath placement in bilateral iliac arteries, vasoreactivity was tested using both endothelium-dependent and -independent vasodilators. Intravascular ultrasonography showed a significant reduction in the luminal area at 12 and 16 weeks. This was similarly supported by morphometric analysis, which showed increased medial thickness with an elevated intima to media ratio at the same time course. Endothelium-dependent relaxation to bradykinin, calcium ionophore A23187, serotonin, and adenosine diphosphate all uniformly displayed attenuated endothelial dysfunction at all time points when compared with the control group. In contrast, endothelium-independent relaxation showed a decreased vasoresponsiveness at 4 weeks. In conclusion, this study underscored the detrimental and chronic endothelial dysfunction in a normal artery caused by oversized introducer sheath placement. Chronically impaired endothelial function may play a role leading to iliofemoral artery thrombosis or late occlusion, which were well-recognized adverse events following endovascular aneurysm procedures. Our study underscores the importance of appropriate patient selection to minimize potential sheath oversize and endograft device miniaturization to avoid vessel wall injury and maintain vasoreactivity.

Plasma endothelin-1 levels in septic patients

Dysfunction of the vascular endothelium (ET) causes an increase in serum ET-1 concentration, as observed in septic patients. It was assumed that in this patient population the ET-1 level correlates with the degree of sepsis severity, including the level of organ dysfunction and, in particular, the level of circulatory dysfunction. The aim of the present study was to assess the relationship between levels of ET-1 and levels of N-terminal brain natriuretic propeptide (NT-proBNP), procalcitonin (PCT), and C-reactive protein (CRP), as well as the Sepsis-related Organ Failure Assessment (SOFA) score in septic patients. PCT and CRP were used to estimate the level of sepsis severity; the SOFA score was used to estimate multiorgan dysfunction; and NT-proBNP was used as a marker of cardiac dysfunction. Twenty patients with sepsis and severe sepsis were included in the study. Blood serum ET-1, NT-proBNP, PCT, and CRP concentrations were determined at specific time intervals, and the SOFA score was calculated. Mean ET-1, NT-proBNP, PCT, and CRP concentrations were 8.39 pg/ml +/- 6.39 pg/mL, 140.80 pg/mL +/- 84.65 pg/mL, 22.32 ng/mL +/- 97.41 ng/mL, and 128.51 mg/L +/- 79.05 mg/L, respectively. Correlation between ET-1 levels and levels of NT-proBNP, PCT, and CRP was .3879 (P < .001), .358 (P < .001), and .225 (P = .011), respectively. Mean SOFA score was 6.31 pts +/- 3.75 pts. Correlation between the ET-1 levels and SOFA score was .470 (P < .001). Six patients (30%) died during the observation period of 28 days. ET-1 levels correlate with levels of NT-proBNP, PCT, and CRP, as well as the SOFA score in septic patients.

A Novel Pathway Involving Progesterone Receptor, Endothelin-2, and Endothelin Receptor B Controls Ovulation in Mice

The steroid hormone progesterone (P) plays a pivotal role during ovulation. Mice lacking P receptor (Pgr) gene fail to ovulate due to a defect in follicular rupture. The P receptor (PGR)-regulated pathways that modulate ovulation, however, remain poorly understood. To identify these pathways, we performed gene expression profiling using ovaries from mice subjected to gonadotropin-induced superovulation in the presence and in the absence of CDB-2914, a synthetic PGR antagonist. Prominent among the genes that were down-regulated in response to CDB-2914 was endothelin (ET)-2, a potent vasoactive molecule. ET-2 mRNA was transiently induced in mural granulosa cells of the preovulatory follicles immediately preceding ovulation. This induction was absent in the ovaries of PGR null mice, indicating a critical role of this receptor in ET-2 expression. To investigate the functional role of ET-2 during ovulation, we employed selective antagonists of endothelin receptors, ETR-A and ETR-B. Mice treated with an ETR-B antagonist exhibited a dramatic (&gt;85%) decline in the number of released oocytes. Strong expression of ETR-B was observed in the mural and cumulus granulosa cells of the preovulatory follicles as well as in the capillaries lining the inner border of the theca interna. We also identified cGMP-dependent protein kinase II, a previously reported PGR-regulated gene, as a downstream target of ET-2 during ovulation. Collectively, our studies uncovered a unique pathway in which ET-2, produced by PGR in mural granulosa cells, acts in a paracrine or autocrine manner on multiple cell types within the preovulatory follicle to control the final events leading to its rupture.

Hemodynamic and Clinical Correlates of Endothelin-1 in Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

In non-thromboembolic pulmonary hypertension, endothelin (ET)-1 levels are increased and correlate with the hemodynamic severity of the disease. Whether such correlations exist in chronic thromboembolic pulmonary hypertension (CTEPH) is unknown, nor whether ET-1 levels correlate with hemodynamic outcome after pulmonary endarterectomy (PEA).

METHODS AND RESULTS

ET-1 levels were determined by ELISA. ET-levels were increased in 35 CTEPH patients (1.62+/-0.21 pg/ml) compared with healthy controls (n=11: 0.75+/-0.06 pg/ml, p<0.02). ET-1 levels correlated (all p<0.0001) with mean pulmonary artery pressure (mPAP) (r=0.70), cardiac index (r=-0.76), total pulmonary resistance (r=0.72), mixed venous oxygen saturation (r=-0.87), and the distance walked in the 6-min walk test (r=-0.59; p<0.005; n=23). Three months after PEA, ET-1 levels had decreased (p<0.002), and were similar between patients with and without residual pulmonary hypertension (p=0.4). Preoperative ET-1 levels, however, were higher in patients with bad postoperative outcome; that is, patients who either died because of persistent pulmonary hypertension or had residual pulmonary hypertension after PEA (2.68+/-0.48 pg/ml, and 1.13+/-0.15 pg/ml, respectively; p<0.002). The levels also correlated with hemodynamic outcome after PEA (mPAP: r=0.67, p<0.0001). By receiver-operator characteristic curve analysis, ET-1>1.77 pg/ml detected a bad postoperative outcome with a sensitivity and specificity of 79% and 85%, respectively, and a likelihood ratio of 5.2.

CONCLUSION

ET-1 levels in CTEPH closely correlated with the hemodynamic and clinical severity of disease in a large cohort of patients. Preoperative ET-1 levels may be useful for better identification of patients at risk for persistent pulmonary hypertension after PEA.

Flow inhibits inward remodeling in cannulated porcine small coronary arteries

The mechanisms of flow-induced vascular remodeling are poorly understood, especially in the coronary microcirculation. We hypothesized that application of flow in small coronary arteries in organoid culture would cause a nitric oxide (NO)-mediated dilation and inhibit inward remodeling. We developed an organoid culture setup to drive a flow through cannulated arterioles at constant luminal pressure via a pressure gradient between the pipettes. Subepicardial porcine coronary arterioles with diameter at full dilation and 60 mmHg ( D0) of 168 ± 10 (SE) μm were cannulated. Vessels treated with Nω-nitro-l-arginine (l-NNA) to block NO production and untreated vessels were pressurized at 60 mmHg for 3 days with and without flow. Endothelium-dependent dilation to 10−7M bradykinin was preserved in all groups. Tone was significantly less in vessels cultured under flow conditions in the last half of the culture period. Untreated and l-NNA-treated vessels regulated their diameter to yield shear stresses of 10.3 ± 2.1 and 14.0 ± 2.4 (SE) dyn/cm2, respectively (not significantly different). Without l-NNA, passive pressure-diameter curves at the end of the culture period revealed inward remodeling in the control group [to 92.3 ± 1.3% of D0(SE)] and no remodeling in the vessels cultured under flow conditions (100.2 ± 1.3% of D0); with l-NNA, the group subjected to flow showed inward remodeling (92.1 ± 2.5% of D0). We conclude that pressurized coronary resistance arteries could be maintained in culture for several days with flow. Vessels cultured under flow conditions remained more dilated when NO synthesis was blocked. Inward remodeling occurred in vessels cultured under no-flow conditions and was inhibited by flow-dependent NO synthesis.

Expression of endothelin-1 system in a pig model of endotoxic shock

Endothelin (ET)-1 is a potent vasoconstrictive peptide and it is involved in the pathogenesis of septic shock. Blockade of ET-1 receptors abolishes the LPS-induced pulmonary hypertension and worsens the LPS-dependent systemic hypotension, but the role of ET-1 in sepsis remains uncertain. To determine the role of ET-1 in cardiovascular and respiratory derangement in a porcine model of endotoxemic shock we evaluated ET-1 plasma levels and ET-1 mRNA and protein levels in lung, liver, and heart as well as Endothelin Converting Enzyme-1, ET(A) and ET(B) receptors mRNA in the same tissues. Twelve piglets were randomised to sham operated or to LPS-treated (40 microg/kg/h for 4 h) groups. During the experiment, respiratory and circulatory parameters have been recorded and blood samples collected. At the end of the experiment the animals were sacrificed and tissue samples collected for real-time quantitative PCR and ELISA test. LPS infusion evokes a large increase in ET-1 plasma concentration, and in tissues mRNA levels, associated with an increase in pulmonary arterial pressure, as well as in pulmonary and systemic vascular resistances, and a decrease in stroke volume. LPS infusion caused also a derangement of respiratory mechanics, evidenced by an increase in resistance and a decrease in compliance of the respiratory system. ET(A) and ET(B) receptor mRNA levels were markedly decreased in liver and lung and slightly increased in heart, evidencing that ET receptor subtypes were differentially regulated in the major organs of endotoxin treated pigs. In conclusion our data show the presence of a continuative and differentially regulated stimulating mechanism of ET-1 expression during pig endotoxaemia as well as a fundamental role of ET-1 system in the cardiovascular and respiratory derangement.

Urinary ET-1, AVP and sodium in premature infants treated with indomethacin and ibuprofen for patent ductus arteriosus

The relative potency and interrelationship between vasoactive and natriuretic mediators are thought to be important in the transition from fetal to neonatal life. The relationship between urinary vasoactive factors and sodium excretion has not been adequately addressed in premature infants receiving indomethacin and ibuprofen for therapy of patent ductus arteriosus. Excretion rates of AVP, ET-1 and sodium were measured in premature infants with RDS receiving indomethacin or ibuprofen. Forty-four RDS premature infants (<34-week gestation) with PDA received either ibuprofen (n=22) in an initial dose of 10 mg/kg followed by two doses of 5 mg/kg each after 24 and 48 h or 3 doses at 12-h intervals of indomethacin (n=24), 0.2 mg/kg, infused continuously over a period of 15 min. Urinary ET-1, AVP and sodium excretion were measured before and after treatment. Indomethacin treatment caused a significant decrease in urinary ET-1 and AVP excretion (UET-1/Ucr 0.14+/-0.01 vs. 0.10+/-0.05 fenton/mmol; P<0.05; 24.42+/-6.18 vs. 12.63+/-3.06 pg/mmol; P<0.05, respectively), along with a significant reduction in urinary sodium (92.1+/-36.1 vs. 64.8+/-35.6 mmol/l; P<0.01), fractional excretion of sodium (6.8+/-37.1 vs. 4.5+/-37.1%; P<0.01) and urinary osmolality (276.2+/-103.9 vs. 226.4+/-60.3 mOsmol/kg; P<0.05). Ibuprofen treatment caused a significant decrease in urinary AVP (UAVP/Ucr 24.5+/-3.4 vs. 16.3+/-2.04 pg/mmol; P<0.01), along with a significant decrease in urinary sodium (78.0+/-8.4 vs. 57.0+/-8.0 mmol/l; P<0.05) and in fractional excretion of sodium (7.5+/-1.3 vs. 3.9+/-3.0%; P<0.05), while it did not modify urinary ET-1 excretion. The association of renal ET-1 and AVP activity with sodium excretion in premature infants treated with indomethacin and ibuprofen supports the hypothesis that these factors may play a role in the physiologic changes in sodium excretion.

Sturge-Weber syndrome: altered blood vessel fibronectin expression and morphology

Sturge-Weber syndrome presents with vascular malformations of the brain, skin, and eye. Fibronectin has potent effects on angiogenesis, vessel remodeling, and vessel innervation density. To determine fibronectin expression in the blood vessels of Sturge-Weber syndrome brain and skin tissue and to quantify the density and circumference of Sturge-Weber syndrome blood vessels by type compared with controls, we performed in situ hybridization for fibronectin messenger ribonucleic acid (RNA) expression on six Sturge-Weber syndrome cortical brain samples, six epilepsy brain samples, skin from two port-wine stain skin lesions, and two normal skin samples from two subjects with Sturge-Weber syndrome. Fibronectin messenger RNA was expressed in blood vessels and endothelial cells in the parenchyma of both Sturge-Weber syndrome and control brain tissues and in skin samples. Fibronectin expression was significantly reduced by 23% in the Sturge-Weber syndrome meningeal vessels compared with the epilepsy controls (P < .01). Fibronectin expression was significantly increased by 19% in the Sturge-Weber syndrome parenchymal vessels compared with the epilepsy controls (P < .05). No difference was found in the expression of fibronectin in port-wine stain skin blood vessels. The density of leptomeningeal blood vessels in the Sturge-Weber syndrome brain tissue samples was 45% greater than in the epilepsy samples (P < .05). Blood vessel circumference was significantly decreased in the Sturge-Weber syndrome meningeal vessels compared with the controls (27%; P < .05). When blood vessels from different brain regions were compared, fibronectin expression was decreased in Sturge-Weber syndrome meningeal vessels and was increased in the parenchymal vessels. Altered blood vessel fibronectin expression in Sturge-Weber syndrome could contribute to abnormal vascular structure and function in this disorder.

Role of endothelin 1 in the pathogenesis of chronic chagasic heart disease

On the basis of previous observations, endothelin 1 (ET-1) has been suggested as contributing to the pathogenesis of Chagasic cardiomyopathy. Therefore, ET-1flox/flox;alpha-MHC-Cre(+) mice in which the ET-1 gene was deleted from cardiac myocytes and ET-1flox/flox;Tie 2 Cre(+) mice in which the ET-1 gene was deleted from endothelial cells were infected with Trypanosoma cruzi. Genetic controls for these cell-specific ET-1 knockout mice were used. Ninety percentage of all mice survived acute infection with the Brazil strain and were evaluated 130 days postinfection. Inflammation and fibrosis were observed in all infected mice; however, fibrosis was reduced in ET-1flox/flox;alpha-MHC-Cre(+) mice. Cardiac magnetic resonance imaging revealed that infection resulted in a significant increase in right ventricular internal diameter (RVID) in all mice except ET-1flox/flox;alpha-MHC-Cre(+) mice; i.e., RVID was not changed in infected ET-1flox/flox;alpha-MHC-Cre(+) mice. Echocardiography of the left ventricle demonstrated increased left ventricular end-diastolic diameter, reduced fractional shortening, and decreased relative wall thickness in infected mice. However, the magnitude of the changes was significantly less in ET-1flox/flox;alpha-MHC-Cre(+) mice compared to other groups. These data provide further evidence of a role for ET-1, particularly cardiac myocyte-derived ET-1, in the pathogenesis of chronic Chagasic cardiomyopathy.

Ursodeoxycholic acid reduces increased circulating endothelin 2 in primary biliary cirrhosis

BACKGROUND

Endothelins and nitric oxide regulate sinusoidal blood flow and the perfusion of the peribiliary vascular plexus.

AIMS

To study the serum and hepatic vein concentration of ET-1, ET-2, ET-3 and nitric oxide in patients with primary biliary cirrhosis and the effect of ursodeoxycholic acid treatment.

METHODS

Endothelins and nitrites/nitrates were measured in serum and hepatic vein blood in primary biliary cirrhosis and viral cirrhotic patients prior and after ursodeoxycholic acid therapy and in serum in controls. Endothelins were measured with commercial enzyme-linked immunosorbent assays and nitrites/nitrates with a modification of Griess reaction.

RESULTS

The ET-1 and ET-3 levels were similar in patients and controls. Primary biliary cirrhosis patients had the highest serum ET-2 (P < 0.001) compared with other groups. Nitrites/nitrates was increased in primary biliary cirrhosis (P < 0.05) compared with normal. ET-2 and nitric oxide were similar in all primary biliary cirrhosis stages. Ursodeoxycholic acid significantly decreased ET-2 in all stages (I and II: P < 0.05 and III and IV: P < 0.01) and increased nitric oxide (P < 0.05) in early primary biliary cirrhosis. Hepatic vein ET-1 and ET-3 were higher in viral cirrhosis patients, but only in primary biliary cirrhosis a significant difference for ET-1 and ET-3 between hepatic and peripheral veins was found.

CONCLUSIONS

Increased ET-2 is an early defect in primary biliary cirrhosis that is significantly reduced by the ursodeoxycholic acid treatment. The possibility of a more generalized endothelial cell dysfunction in primary biliary cirrhosis requires further investigation.

Chronic endothelin A receptor blockade in lambs with increased pulmonary blood flow and pressure

Endothelin receptor blockade is an emerging therapy for pulmonary hypertension. However, hemodynamic and structural effects and potential changes in endogenous nitric oxide (NO)-cGMP and endothelin-1 signaling of chronic endothelin A receptor blockade in pulmonary hypertension secondary to congenital heart disease are unknown. Therefore, the objectives of this study were to determine hemodynamic and structural effects and potential changes in endogenous NO-cGMP and endothelin-1 signaling of chronic endothelin A receptor blockade in a lamb model of increased pulmonary blood flow following in utero placement of an aortopulmonary shunt. Immediately after spontaneous birth, shunt lambs were treated lifelong with either an endothelin A receptor antagonist (PD-156707) or placebo. At 4 wk of age, PD-156707-treated shunt lambs (n = 6) had lower pulmonary vascular resistance and right atrial pressure than placebo-treated shunt lambs (n = 8, P < 0.05). Smooth muscle thickness or arterial number per unit area was not different between the two groups. However, the number of alveolar profiles per unit area was increased in the PD-156707-treated shunt lambs (190.7 +/- 5.6 vs. 132.9 +/- 10.0, P < 0.05). Plasma endothelin-1 and cGMP levels and lung NOS activity, cGMP, eNOS, preproendothelin-1, endothelin-converting enzyme-1, endothelin A, and endothelin B receptor protein levels were similar in both groups. We conclude that chronic endothelin A receptor blockade attenuates the progression of pulmonary hypertension and augments alveolar growth in lambs with increased pulmonary blood flow.

Physiology of the endothelium

In the past, the endothelium was considered to be inert, described as a 'layer of nucleated cellophane', with only non-reactive barrier properties, such as presentation of a non-thrombogenic surface for blood flow and guarding against pro-inflammatory insults. However, it is now becoming clear that endothelial cells actively and reactively participate in haemostasis and immune and inflammatory reactions. They regulate vascular tone via production of nitric oxide, endothelin and prostaglandins and are involved in the manifestations of atherogenesis, autoimmune diseases and infectious processes. They produce and react to various cytokines and adhesion molecules and it is now clear that they can mount anti- and pro-inflammatory and protective responses depending on environmental conditions and are key immunoreactive cells. Endothelial dysfunction or activation also contributes to a variety of disease states.

Age-related endothelial dysfunction : potential implications for pharmacotherapy

Aging per se is associated with abnormalities of the vascular wall linked to both structural and functional changes that can take place at the level of the extracellular matrix, the vascular smooth muscle and the endothelium of blood vessels. Endothelial dysfunction is generally defined as a decrease in the capacity of the endothelium to dilate blood vessels in response to physical and chemical stimuli. It is one of the characteristic changes that occur with age, independently of other known cardiovascular risk factors. This may account in part for the increased incidence of cardiovascular events in elderly people that can be reversed by restoring endothelial function. A better understanding of the mechanisms involved and the aetiopathogenesis of this process will help in the search for new therapeutic agents.Age-dependent alteration of endothelium-dependent relaxation seems to be a widespread phenomenon both in conductance and resistance arteries from several species. In the course of aging, there is an alteration in the equilibrium between relaxing and contracting factors released by the endothelium. Hence, there is a progressive reduction in the participation of nitric oxide and endothelium-derived hyperpolarising factor associated with increased participation of oxygen-derived free radicals and cyclo-oxygenase-derived prostanoids. Also, the endothelin-1 and angiotensin II pathways may play a role in age-related endothelial dysfunction. The use of drugs acting at different levels of these signalling cascades, including antioxidant therapy, lipid-lowering drugs and estrogens, seems to be promising.

Pathophysiology of Sturge-Weber syndrome

Sturge-Weber syndrome is a neurocutaneous disorder classically presenting with a facial port-wine stain, vascular eye abnormalities, and an ipsilateral occipital leptomeningeal angioma. Children with Sturge-Weber syndrome often develop progressive neurologic problems. Data on the pathophysiology of Sturge-Weber syndrome are briefly reviewed. The embryologic, genetic, and pathologic considerations are discussed, as are theories regarding the mechanisms of the degenerative brain changes. Sturge-Weber syndrome likely results from an early embryologic malformation of vascular development affecting the development of the nearby skin, eye, and brain structures. Studies suggest that complex molecular interactions contribute to the abnormal development and function of blood vessels in Sturge-Weber syndrome. Neurologic deterioration in Sturge-Weber syndrome is likely secondary to impaired blood flow to the brain and is worsened by the presence of seizures. Insights from related areas are discussed, and future research studies are suggested.

Endothelin-converting enzyme-1 (ECE-1) is a downstream target of the homeobox transcription factor Nkx2-5

The homeobox transcription factor Nkx2-5 and the zinc metalloprotease endothelin-converting enzyme-1 (ECE-1) are essential for cardiac development. Here, we demonstrate for the first time a functional link between Nkx2-5 and ECE-1. In transiently transfected rat H9c2 cardiomyoblasts, the alternative promoters specific for ECE-1a, ECE-1b, and ECE-1c are activated by Nkx2-5 coexpression. Lack of a consensus sequence for Nkx2-5 binding within the ECE-1c promoter and mutational analyses of Nkx2-5 consensus sequences identified in the ECE-1a and ECE-1b promoters, respectively, reveal an indirect mechanism of activation that is supported by gel shift assays. Furthermore, we have evidence of an additional direct activation mechanism of the ECE-1b promoter by Nkx2-5. With the use of RNase protection assay, Northern blot, and real-time PCR, the activating effect of Nkx2-5 on mRNA expression of ECE-1 isoforms was confirmed in the chromatin context of H9c2 and endothelial EA.hy926 cells, respectively, by stable Nkx2-5 overexpression. The interaction presented in this work provides a possible explanation for distinct phenotypic aspects of patients carrying mutations in the Nkx2-5 gene and may also be of significance for the pathophysiology of heart failure.