Enhancement by endothelin-1 of microvascular permeability via the activation of ETA receptors

Sufentanil ameliorates oxygen‑glucose deprivation/reoxygenation‑induced endothelial barrier dysfunction in HCMECs via the PI3K/Akt signaling pathway

Ischemic heart disease, a chronic myocardial damage disease caused by coronary artery ischemia, is the leading cause of death worldwide. The aim of the present study was to explore the efficacy of sufentanil in myocardial ischemia/reperfusion (I/R) injury. Oxygen and glucose deprivation/reoxygenation (OGD/R) was utilized to induce human cardiac microvascular endothelial cells (HCMECs) to simulate myocardial I/R injury in vitro. The Cell Counting Kit-8 assay was used to detect the effects of sufentanil on HCMECs and OGD/R-induced HCMECs. The TUNEL, lactate dehydrogenase (LDH) activity, immunofluorescence and in vitro permeability assays, were used to assess apoptosis, LDH activity, VE-cadherin protein expression levels and endothelial barrier function in OGD/R-induced HCMECs, respectively. Moreover, western blotting was performed to assess the protein expression levels of apoptosis, endothelial barrier function and phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)-related proteins. The results demonstrated that sufentanil had no significant influence on the viability of HCMECs but increased the viability of OGD/R-induced HCMECs in a dose-dependent manner. Furthermore, sufentanil inhibited cell apoptosis and permeability of OGD/R-induced HCMECs but enhanced the protein expression levels of tight junction proteins, including ZO-1, Occludin, VE-cadherin and Claudin-5. Sufentanil was also demonstrated to activate the PI3K/Akt signaling pathway. In addition, the use of LY294002, an inhibitor of the PI3K/Akt signaling pathway, partially abolished the protective effects of sufentanil on apoptosis, permeability and tight junction protein expression levels. These results indicated that sufentanil ameliorated OGD/R-induced endothelial barrier dysfunction in HCMECs, potentially via the PI3K/Akt signaling pathway. The present study therefore suggested that sufentanil may serve as a novel therapeutic option for the improvement of myocardial I/R injury.

Remifentanil pretreatment ameliorates H/R-induced cardiac microvascular endothelial cell dysfunction by regulating the PI3K/Akt/HIF-1α signaling pathway

Restoration of blood supply through medical or surgical intervention is a commonly adopted method for acute myocardial ischemia, but is also a trigger for cardiac ischemia/reperfusion injury. Studies have shown that remifentanil (REM) displays cardioprotective effects. In this study, the effects of REM on HCMEC viability were examined before and after the induction of H/R using Cell Counting Kit-8 assays. Wound healing and Matrigel angiogenesis assays were performed to assess HCMEC migration and angiogenesis, respectively. Commercial kits and western blotting were used to determine the endothelial barrier function of H/R-stimulated HCMECs with or without REM treatment. The expression of PI3K/Akt/hypoxia-inducible factor-1α (HIF-1α) pathway-related proteins was detected by western blotting. After pre-treatment with PI3K/Akt, the effects of REM on H/R-induced HCMEC injury were examined. We found that pre-treatment with REM displayed no impact on HCMEC viability under normal conditions but noticeably improved cell viability following H/R. The migratory abilities and tube-like structure formations of H/R-stimulated HCMECs were both enhanced by REM in a concentration-dependent manner. REM also decreased the permeability of H/R-stimulated HCMECs and upregulated the expression of tight junction proteins. Furthermore REM increased the expression of PI3K/Akt/HIF-1α signaling-related proteins in HCMECs. Inhibition of PI3K/Akt rescued REM-enhanced HCMEC function under H/R condition. Therefore, the present study demonstrated that REM pretreatment ameliorated H/R-induced HCMEC dysfunction by regulating the PI3K/Akt/HIF-1α signaling pathway.

Quercetin attenuates zymosan-induced arthritis in mice

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by articular lesions, recruitment of inflammatory cells and increased levels of pro-inflammatory cytokine. The intra-articular administration of zymosan is an experimental model that promotes inflammatory parameters resembling RA. Therefore, this model was used to investigate the efficacy of quercetin as a treatment of articular inflammation. Treatment with quercetin dose-dependently reduced zymosan-induced hyperalgesia, articular edema and the recruitment of neutrophils to the knee joint cavity. Histological analysis confirmed that quercetin inhibited zymosan-induced arthritis. The treatment with quercetin also inhibited zymosan-induced depletion of reduced glutathione (GSH) levels, TNFα and IL-1β production, and gp91^phox, prepro-endothelin-1 (preproET-1), and cyclooxygenase-2 mRNA expression. These molecular effects of quercetin were related to the inhibition of the nuclear factor kappa-B and induction of Nuclear factor erythroid 2- related factor (Nrf2)/home oxygenase (HO-1) pathway. Thus, quercetin exerted anti-inflammatory, analgesic and antioxidant effects in experimental arthritis, suggesting quercetin is a possible candidate for arthritis treatment.

New Insights into the Role of Inflammation in the Pathogenesis of Atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipids, smooth muscle cell proliferation, cell apoptosis, necrosis, fibrosis, and local inflammation. Immune and inflammatory responses have significant effects on every phase of atherosclerosis, and increasing evidence shows that immunity plays a more important role in atherosclerosis by tightly regulating its progression. Therefore, understanding the relationship between immune responses and the atherosclerotic microenvironment is extremely important. This article reviews existing knowledge regarding the pathogenesis of immune responses in the atherosclerotic microenvironment, and the immune mechanisms involved in atherosclerosis formation and activation.

Endothelin-1 overexpression exacerbate experimental allergic encephalomyelitis

BACKGROUND

Multiple sclerosis (MS) is a CNS inflammatory demyelinating disorder. T helper 1 (Th1) and T helper 17 (Th17) cells are important in MS immunopathogenesis. Level of endothelin-1 (ET-1), a potent vasoconstrictor, is increased in sera of MS patients. We studied the role of ET-1 in experimental allergic encephalomyelitis (EAE), a MS animal model.

METHODS

EAE is induced in transgenic mice overexpressing endothelial ET-1 (TET-1), transgenic mice overexpressing astrocytic ET-1 (GET-1) and non-transgenic (NTg) mice by immunization with myelin oligodendrocyte glycoprotein (MOG)35-55 peptide. EAE scores, spinal cord histology, serum proinflammatory cytokines levels, and proinflammatory cytokines production from splenocytes of ET-1 transgenic and NTg mice with EAE were studied.

RESULTS

ET-1 transgenic mice developed more severe EAE than NTg with increased inflammation and demyelination in spinal cord. The mean maximum EAE scores for GET-1, TET-1 and NTg mice with EAE were 4.84, 4.31 and 4.05 respectively (p<0.05). Serum levels of IL-6, IL-17A, IFN-γ and TNF-α were higher in ET-1 transgenic than NTg mice with EAE (p<0.05) while serum IL-4 levels were similar. mRNA levels of IL-6, IL-17A, IFN-γ and TNF-α from cultured splenocytes were higher in ET-1-transgenic than NTg mice with EAE (p<0.05) while IL-4 mRNA levels were similar. Consistently, levels of IL-6, IL-17A, IFN-γ and TNF-α in culture media of splenocytes were higher in ET-1 transgenic than NTg mice with EAE (p<0.05) while IL-4 levels were similar.

CONCLUSIONS

Mice with endothelial or astrocytic ET-1 overexpression developed more severe EAE with increased splenic lymphocyte production of Th1 and Th17 proinflammatory cytokines.

Concentration-related effects of nitric oxide and endothelin-1 on human trabecular meshwork cell contractility

The contractility status of trabecular meshwork (TM) cells influences aqueous humor outflow resistance and intraocular pressure. Using human TM cells as a model, the goal of the present study was to examine concentration-response relationships of two prototypical molecules, nitric oxide (NO) and endothelin-1 (ET-1), known to differentially influence vascular smooth muscle contractility. Efficacy of ET-1, two NO donors (DETA-NO and SNP) and a cGMP analog (8-Br-cGMP) were assessed using two complementary methods: functionally in a gel contraction assay and biochemically using a myosin light chain phosphorylation assay. The NO donors DETA-NO and SNP dose dependently relaxed cultured human TM cells (EC50 for DETA-NO = 6.0 ± 2.4 μM, SNP = 12.6 ± 8.8 μM), with maximum effects at 100 μM. Interestingly, at concentrations of NO donors above 100 μM, the relaxing effect was lost. Relaxation caused by DETA-NO (100 μM) was dose dependently blocked by the soluble guanylate cyclase specific inhibitor ODQ (IC50 = 460 ± 190 nM). In contrast to the NO donors, treatment of cells with the cGMP analog, 8-Br-cGMP produced the largest relaxation (109.4%) that persisted at high concentrations (EC50 = 110 ± 40 μM). ET-1 caused a dose-dependent contraction of human TM cells (EC50 = 1.5 ± 0.5 pM), with maximum effect at 100 pM (56.1%) and this contraction was reversed by DETA-NO (100 μM). Consistent with functional data, phosphorylation status of myosin light chain was dose dependently reduced with DETA-NO, and increased with ET-1. Together, data show that TM cells rapidly change their contractility status over a wide dynamic range, well suited for the regulation of outflow resistance and intraocular pressure.

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.

Regulation of blood pressure and salt homeostasis by endothelin

Endothelin (ET) peptides and their receptors are intimately involved in the physiological control of systemic blood pressure and body Na homeostasis, exerting these effects through alterations in a host of circulating and local factors. Hormonal systems affected by ET include natriuretic peptides, aldosterone, catecholamines, and angiotensin. ET also directly regulates cardiac output, central and peripheral nervous system activity, renal Na and water excretion, systemic vascular resistance, and venous capacitance. ET regulation of these systems is often complex, sometimes involving opposing actions depending on which receptor isoform is activated, which cells are affected, and what other prevailing factors exist. A detailed understanding of this system is important; disordered regulation of the ET system is strongly associated with hypertension and dysregulated extracellular fluid volume homeostasis. In addition, ET receptor antagonists are being increasingly used for the treatment of a variety of diseases; while demonstrating benefit, these agents also have adverse effects on fluid retention that may substantially limit their clinical utility. This review provides a detailed analysis of how the ET system is involved in the control of blood pressure and Na homeostasis, focusing primarily on physiological regulation with some discussion of the role of the ET system in hypertension.

Contribution of insulin resistance to vascular dysfunction

Insulin is a vascular hormone, able to influence vascular cell responses. In this review, we consider the insulin actions on vascular endothelium and on vascular smooth muscle cells (VSMC) both in physiological conditions and in the presence of insulin resistance. In particular, we focus the relationships between activation of insulin signalling pathways of phosphatidylinositol-3 kinase (PI3-K) and mitogen-activated protein kinase (MAPK) and the different vascular actions of insulin, with a particular attention to the insulin ability to activate the pathway nitric oxide (NO)/cyclic GMP/PKG via PI3-K, owing to the peculiar relevance of NO in vascular biology. We also discuss the insulin actions mediated by the MAPK pathway (such as endothelin-1 synthesis and secretion and VSMC proliferation and migration) and by the interactions between the two pathways, both in insulin-sensitive and in insulin-resistant states. Finally, we consider the influence of free fatty acids, cytokines and endothelin on vascular insulin resistance.

Endothelins modulate inflammatory reaction in zymosan-induced arthritis: participation of LTB4, TNF-alpha, and CXCL-1

Endothelins (ETs) are involved in inflammatory events, including pain, fever, edema, and cell migration. ET-1 levels are increased in plasma and synovial membrane of rheumatoid arthritis (RA) patients, but the evidence that ETs participate in RA physiopathology is limited. The present study investigated the involvement of ETs in neutrophil accumulation and edema formation in the murine model of zymosan-induced arthritis. Intra-articular (i.a.) administration of selective ET(A) or ET(B) receptor antagonists (BQ-123 and BQ-788, respectively; 15 pmol/cavity) prior to i.a. zymosan injection (500 microg/cavity) markedly reduced knee-joint edema formation and neutrophil influx to the synovial cavity 6 h and 24 h after stimulation. Histological analysis showed that ET(A) or ET(B) receptor blockade suppressed zymosan-induced neutrophil accumulation in articular tissue at 6 h. Likewise, dual blockade of ET(A)/ET(B) with bosentan (10 mg/kg, i.v.) also reduced edema formation and neutrophil counts 6 h after zymosan stimulation. Pretreatment with BQ-123 or BQ-788 (i.a.; 15 pmol/cavity) also decreased zymosan-induced TNF-alpha production within 6 h, keratinocyte-derived chemokine/CXCL1 production within 24 h, and leukotriene B(4) at both time-points. Consistent with the demonstration that ET receptor antagonists inhibit zymosan-induced inflammation, i.a. injection of ET-1 (1-30 pmol/cavity) or sarafotoxin S6c (0.1-30 pmol/cavity) also triggered edema formation and neutrophil accumulation within 6 h. Moreover, knee-joint synovial tissue expressed ET(A) and ET(B) receptors. These findings suggest that endogenous ETs contribute to knee-joint inflammation, acting through ET(A) and ET(B) receptors and modulating edema formation, neutrophil recruitment, and production of inflammatory mediators.

Phosphoramidon, an endothelin-converting enzyme inhibitor, attenuates lipopolysaccharide-induced acute lung injury

Phosphoramidon blocks the formation of endothelin-1 (ET-1), a proinflammatory mediator implicated in the pathogenesis of a variety of lung diseases. To determine whether phosphoramidon can ameliorate pulmonary inflammation, our laboratory undertook a series of experiments involving treatment of hamsters with either intraperitoneal (i.p.) or aerosolized phosphoramidon prior to induction of acute lung injury by intratracheal administration of lipopolysaccharide (LPS). The results indicate that phosphoramidon significantly reduces LPS-induced pulmonary inflammation as measured by lung histology, neutrophil content of bronchoalveolar lavage (BAL) fluid, percent tumor necrosis factor receptor 1 (TNFR1)-labeled BAL macrophages, and alveolar septal cell apoptosis. In additional experiments, i.p. administration of a novel endothelin A receptor anatgonist (HJP272) similarly decreased BAL neutrophils, whereas i.p. administration of either ET-1, or its precursor peptide, "big" ET-1, had the opposite effect. These findings support further evaluation of phosphoramidon and other ET-1 suppressors as potential treatments for human inflammatory lung disease.

Endothelin-1 level in epithelial lining fluid of patients with acute respiratory distress syndrome

BACKGROUND AND OBJECTIVES

Endothelin-1 (ET-1), a potent vasoconstrictor peptide produced by endothelial cells, has been implicated in the dysfunction of various organs. To determine the role of ET-1 in acute lung injury (ALI) and ARDS, ET-1 levels were measured in epithelial lining fluid (ELF) and plasma obtained from patients with ALI/ARDS.

METHODS

A cross-sectional study of patients with ALI/ARDS in the intensive care unit of two university hospitals was performed. Patients with ALI/ARDS underwent bronchoscopic microsampling to collect ELF on the day of onset of the disease. Patients who underwent bronchoscopy to examine a small peripheral pulmonary nodule served as controls.

RESULTS

In the 23 patients with ALI/ARDS, the ET-1 level in ELF was significantly greater than that in plasma (P < 0.001). In contrast, ET-1 was not detectable in the ELF from six of the seven control subjects. The albumin concentration of ELF, used as a marker of endothelial and epithelial permeability, correlated with the ET-1 level in ELF (P < 0.001). The oxygenation index (PaO(2)/FiO(2)) was also correlated with ET-1 concentration in ELF (P < 0.001).

CONCLUSION

In patients with ALI/ARDS, ET-1 is produced mainly in the lung and is associated not only with pulmonary vasoconstriction but also the development of permeability oedema, leading to the impairment of oxygenation.

Effects of the dual endothelin receptor antagonist tezosentan and hypertonic saline/dextran on porcine endotoxin shock

AIM

To evaluate the haemodynamic effects of the dual endothelin receptor antagonist tezosentan, both alone and combined with hypertonic saline/dextran (HSD), on porcine endotoxin shock, with focus on cardiopulmonary circulation. The effects on gas exchange and short-term survival were also studied.

METHODS

A prospective, randomized experimental study was carried out. Thirty-two anaesthetized pigs underwent pulmonary and carotid artery catheterization. Following haemodynamic stabilization and baseline measurements, endotoxaemia was induced by an Escherichia coli-endotoxin infusion over 180 min and the animals observed another 120 min. After 60 min of endotoxaemia, directly before intervention, animals were randomized into four groups: a tezosentan group, an HSD group, a combined tezosentan/HSD group and a control group. The consequent haemodynamic effects and blood gas results were recorded.

RESULTS

The endotoxin infusion reduced mean arterial blood pressure from 111 +/- 14 (mean +/- standard deviation) to 77 +/- 27 mmHg and cardiac index from 126.9 +/- 27.2 to 109.3 +/- 22.6 mL min(-1) kg(-1) within 90 min in the control group. In addition, endotoxin simultaneously increased mean pulmonary artery pressure from 24 +/- 17 to 38 +/- 19 mmHg and reduced arterial oxygenation from 18.9 +/- 2.0 to 12.2 +/- 5.3 kPa. Tezosentan, alone and combined with HSD, reversed the pulmonary hypertension and prevented the reduction in cardiac index and arterial oxygenation, resulting in reduced metabolic acidosis. Additionally, in the tezosentan group, the mean arterial blood pressure was reduced to the same level as in controls, an effect not prevented by the addition of HSD. It was found that all three interventions improved survival rates.

CONCLUSION

Tezosentan, alone and in combination with HSD, improved cardiac index and arterial oxygenation. The addition of HSD to tezosentan treatment did not improve the endotoxin-induced hypotension, but beneficial effects on microcirculation and systemic oxygenation were seen despite low perfusion pressure, as indicated by increased SvO(2) and reduced metabolic acidosis.

The relationship between serum endothelin (ET)-1 and wheezing status in the children with Mycoplasma pneumoniae pneumonia

Although Mycoplasma pneumoniae infection is known to be associated with acute wheezing and the exacerbation of asthma, the mechanism by which this pathogen contributes to the development of wheeze-related symptoms is not fully understood. The aim of our study was to examine serum endothelin (ET)-1 and other cytokines in acute M. pneumoniae pneumonia and investigate if there is any relation between these inflammatory mediators and the occurrence of wheezing. We studied 53 patients, aged 3-13 yr, who admitted with pneumonia. These patients were divided into three groups: M. pneumoniae pneumonia with wheeze (n=23) and without wheeze (n=19), and the patients without the evidence of M. pneumoniae infection (n=11). Age-matched controls (n=10) were also studied. The serum concentrations of ET-1, interleukin (IL)-5 and IL-18 were measured using ELISA kits in patient groups and controls. The patients with M. pneumoniae pneumonia had significantly higher serum ET-1 than those without evidence of M. pneumoniae infection. In the presence of M. pneumoniae pneumonia, ET-1 concentrations were significantly higher in the patients with wheeze than those without wheeze. IL-5 and IL-18 in each patient group were higher compared to controls. However, no significant between-group difference was observed. Total serum IgE levels were significantly higher in the patients with M. pneumoniae pneumonia and wheeze than in those without wheeze. A positive correlation was observed between serum ET-1 and total IgE in the patients with M. pneumoniae pneumonia and wheeze. Our results may suggest a role of ET-1 in the occurrence of acute wheezing or exacerbation of asthma associated with M. pneumoniae pneumonia.

Insulin resistance and atherosclerosis

The epidemic of obesity in the developed world over the last two decades is driving a large increase in type 2 diabetes and consequentially setting the scene for an impending wave of cardiovascular morbidity and mortality. It is only now being recognized that the major antecedent of type 2 diabetes, insulin resistance with its attendant syndrome, is the major underlying cause of the susceptibility to type 2 diabetes and cardiovascular disease. In metabolic tissues, insulin signaling via the phosphatidylinositol-3-kinase pathway leads to glucose uptake so that in insulin resistance a state of hyperglycemia occurs; other factors such as dyslipidemia and hypertension also arise. In cardiovascular tissues there are two pathways of insulin receptor signaling, one that is predominant in metabolic tissues (mediated by phosphatidylinositol-3-kinase) and another being a growth factor-like pathway (mediated by MAPK); the down-regulation of the former and continued activity of the latter pathway leads to atherosclerosis. This review addresses the metabolic consequences of the insulin resistance syndrome, its relationship with atherosclerosis, and the impact of insulin resistance on processes of atherosclerosis including insulin signaling in cells of the vasculature.

Outcome of pregnancies complicated by severe ovarian hyperstimulation syndrome (OHSS): a follow-up beyond the second trimester

The main aim of this study was to assess the obstetric complications for those pregnancies that are complicated by ovarian hyperstimulation syndrome (OHSS) and continue beyond the first trimester. We checked also for other related serious events that occurred during the first trimester.

METHODS

We included only patients whose pregnancies continued beyond the first trimester and compared them with IVF-treated patients displaying moderate ovarian response.

RESULTS

We studied 165 patients with OHSS (101 singletons and 64 twins) and 156 IVF control patients (85 singletons and 71 twins). Two serious complications, gestational diabetes mellitus (GDM) and pregnancy-induced hypertension (PIH), were noted in both groups. However, the incidence of these two complications did not differ significantly between the groups. In the OHSS group, GDM presented with an incidence of 9.9% for singletons and 9.4% for twins, and 12.9% and 7.0%, respectively, for the control group. PIH presented as 6.9% for singletons and 10.9% for twins in the OHSS group, and 8.2% and 7.0%, respectively, for the control groups. During the first trimester laparoscopies for suspected ovarian torsion were performed in 13 patients, and in 10 patients the diagnosis were confirmed.

CONCLUSIONS

Although patients with OHSS-complicated pregnancies previously reported a relatively high risk of GDM and PIH, the occurrence rates do not differ from a matched control group of normally responding patients who conceived after IVF.

Characterization of endothelin-1 and nitric oxide generating systems in corpus luteum-derived endothelial cells

Endothelium-derived endothelin-1 (ET-1) and nitric oxide (NO) are pivotal regulators of corpus luteum (CL) function. To have a better insight into their synthesis and action, members of the ET system (ET-1, ET converting enzyme (ECE-1) isoforms a–d, ETAand ETBreceptors) along with NO synthase (NOS) isoforms – endothelial (e)NOS and inducible (i)NOS – were quantified in CL-derived endothelial cells (CLEC). The expression of these genes in microvascular CLEC, obtained by lectin-coated magnetic beads, was compared with cells removed from the luteal microenvironment and maintained in culture for different durations, and with endothelial cells (EC) derived from a large blood vessel (i.e. bovine aortic endothelial cells, BAEC). The profile of gene expression in the different EC types was determined by quantitative real-time PCR. Freshly isolated EC from mid-cycle CL exhibited high ET-1 receptor expression (both ETAand ETB), low ET-1 synthesizing ability (both prepro (pp) ET-1 and ECE-1), but elevated iNOS – the high throughput NOS isoform. The distinct phenotype of CLEC was lost soon after an overnight culture. ETAand ETBreceptor levels declined, ppET-1 levels increased while iNOS was reduced. These changes were extenuated during long-term culture of CLEC. The general pattern of gene expression in BAEC and long-term cultured CLEC was similar yet some differences, reminiscent of freshly isolated CLEC, remained: ECE-1c, ETBreceptor and NOS isoforms were expressed differently in BAEC as compared with lines of CLEC.

This study suggests that the luteal microenvironment is necessary to sustain the selective phenotype of its resident endothelial cells. The inverse relationship between ppET-1 and iNOS observed in freshly isolated CLEC and in cultured cells is physiologically significant and suggests that ET-1 and NO may modulate the production of each other.

Endothelin-1 decreases microvessel permeability after endothelial activation

BACKGROUND

Endothelin-1 (ET-1) is a potent vasoconstrictor that is released during shock and sepsis. We hypothesized that ET-1 plays a role in the modulation of the elevated microvascular permeability state of the activated endothelium.

METHODS

Hydraulic permeability (Lp) was measured using the modified Landis micro-occlusion technique. The effect of different ET-1 doses on Lp was determined by obtaining paired measures of Lp at baseline and after the vessels were perfused with ET-1 at doses of 2.0 pg/mL (n = 6), 20 pg/mL (n = 6), 200 pg/mL (n = 6), or 2,000 pg/mL (n = 6). To evaluate the effects of ET-1 in the activated endothelium, additional vessels were perfused with either 10 micromol/L adenosine triphosphate (ATP) (n = 6) or 1 nmol/L bradykinin (n = 6). The vessels were then perfused with 200 pg/mL ET-1 followed by the final L determination.

RESULTS

ET-1 significantly decreased Lp at doses of 20 pg/mL (p = 0.03), 200 pg/mL (p = 0.03), and 2,000 pg/mL (p = 0.01). Endothelial activation with ATP and bradykinin increased Lp to 4.21 +/- 0.39 (p < 0.0001) and 2.72 +/- 0.24 (p = 0.001), respectively. ET-1 significantly decreased the Lp to 1.99 +/- 0.48 after activation with ATP (p = 0.004). ET-1 also decreased the Lp to 1.10 +/- 0.19 after activation with bradykinin (p = 0.001). Units for Lp are x10(-7) cm x s(-1) x cm H2O(-1).

CONCLUSION

In this model, ET-1 attenuated the increase in microvascular permeability that can be seen in inflamed vessels. In addition to its vasopressor function, ET-1 may be of benefit in pathophysiologic states by decreasing third-space fluid loss. This receptor-mediated function of ET-1 may be amenable to pharmacologic manipulation.

Endothelin A but not endothelin B receptor blockade reduces capillary permeability in severe experimental pancreatitis

INTRODUCTION

Microcirculatory disorders, in particular increased capillary permeability (CapPerm), contribute to the multiple organ dysfunction syndrome in severe acute pancreatitis (AP). Endothelin receptor antagonists (ET-RA) have been shown to stabilize capillary leakage and improve organ function in AP.

AIM

To find out which endothelin receptor subtype (ET-A or ET-B) mediates the changes in CapPerm.

METHODOLOGY

Severe AP was induced in rats by intraductal bile salt infusion and i.v. cerulein. Animals were randomized to receive (1) saline; (2) selective ET-A-RA (LU-135252; 30 mg/kg); (3) selective ET-B-RA (A-192621); (4) nonselective ET-RA (LU-135252; 120 mg/kg); or (5) combined ET-A/B-RA (30 mg/kg LU-135252 + A-192621). Capillary blood flow (CBF) and CapPerm in the pancreas and colon and leukocyte rolling in mesenteric venules were determined.

RESULTS

Selective ET-A-RA increased CBF and decreased CapPerm in the pancreas and colon by 90-147% and reduced leukocyte rolling in AP but had no effect in healthy controls. Selective ET-B-RA increased pancreatic CBF (2.3 +/- 0.03 versus 2.1 +/- 0.04 nL/min) and enhanced CapPerm in the pancreas and colon by 24-35% in healthy controls but had no effect in AP. Blockade of both receptors produced effects similar to but less pronounced than those of selective ET-A-RA.

CONCLUSIONS

Blockade of ET-A and ET-B receptors has different effects on CapPerm in healthy animals and those with AP. This may explain the inconclusive results reported with nonselective ET-RA. In severe AP, blockade of ET-A but not ET-B receptors reduces CapPerm.

Endothelin-1 and atherosclerosis: potential complications associated with endothelin-receptor blockade

Atherosclerotic vascular disease remains the single most prevalent cause of death and morbidity in the western world. Endothelin-1 (ET-1) is a potent vasoconstrictor peptide that also possesses mitogenic activity on many cell types, including vascular smooth muscle cells. Raised plasma and tissue levels of ET-1 have been described in atherosclerosis in animal models and in man, suggesting that this peptide plays a pathophysiological role in this condition. Two main ET-1 receptors have been cloned (ET(A) and ET(B)). Mixed ET(A/B) and receptor subtype selective antagonists are now available. Since ET-1 is generally believed to be a 'pathophysiological peptide', we discuss the therapeutic potential of ET-1 antagonists in atherosclerosis and consider whether, at certain sites in this process, ET-1 may play a beneficial role. In such situations ET antagonism may be undesirable.

Pathogenesis of portal hypertensive gastropathy: a clinical and experimental review

Portal hypertensive gastropathy (PHG) is recognized as a clinical entity in portal hypertension, but the pathogenesis of PHG is still unclear. Therefore, we reviewed the current state of knowledge concerning the portal hypertensive gastric mucosa and hypothesized the pathogenesis of PHG. Elevated portal pressure can induce changes of local hemodynamics, thus causing congestion in the upper stomach and gastric tissue damage. These changes may then activate cytokines and growth factors, such as tumor necrosis factor alpha, which are substances that activate endothelial constitutive nitric oxide synthase and endothelin 1 in the portal hypertensive gastric mucosa. Overexpressed nitric oxide synthase produces an excess of nitric oxide, which induces hyperdynamic circulation and peroxynitrite overproduction. The overproduction of peroxynitrite, together with endothelin overproduction may cause an increased susceptibility of gastric mucosa to damage. When combined with the characteristics of impaired mucosal defense and healing, these factors may together produce PHG in patients with portal hypertension.

Comparison of the contractile and calcium-increasing properties of platelet-activating factor and endothelin-1 in the rat mesenteric artery and vein

In the present study, the properties of endothelin-1 (ET-1) and platelet-activating factor (PAF) in inducing contraction and increased intracellular-free calcium level in rat mesenteric arteries and veins were studied. Furthermore, measurements of cytosolic ([Ca](c)) and nuclear ([Ca](n)) Ca(2+) were performed by confocal microscopy. PAF, at a concentration of 1 microM, and the selective ET(B) agonists, IRL-1620 and sarafotoxin S6C (100 nM), induced a marked constriction and increase in [Ca](i) in the mesenteric vein but not in the artery. On the other hand, endothelin-1 (1 - 100 nM) induced a significant concentration-dependent nifedipine-insensitive increase in tension and [Ca](i) in both arteries and veins. Those responses to endothelin-1 were significantly reduced by the ET(A) receptor antagonist, BQ-123 (10(-6) M), on both types of vessels, whereas the selective ET(B) receptor antagonist, BQ-788, inhibited only the venous responses. The mixed ET(A)/ET(B) receptor antagonist, SB 209670, reduced the ET-1-induced venous responses to the same level of that found in presence of BQ-123 or BQ-788. However, concomitant applications of BQ-123 and BQ-788 reduced the vasoconstriction below to that induced by ET(A) or ET(B) blockade without further affecting [Ca](i). PAF and the selective ET(B) agonists IRL-1620, induced a sustained increase of [Ca](c) and [Ca](n) solely in venous cells and ET-1 in both arterial and venous smooth muscle cells. Thus, PAF increases total intracellular calcium concentration and tension on the smooth muscle cells from venous origin only. Furthermore, ET-1-induced vasoactive as well as [Ca](i) and [Ca](n) increasing effects are mediated by distinct receptors on venous and arterial smooth muscles.

Endothelin-1 reduces microvascular fluid permeability through secondary release of prostacyclin in cat Skeletal muscle

The aim of the study was to analyze effects of various plasma concentrations of the vasoconstrictor endothelin-1 on microvascular fluid permeability and on transcapillary fluid exchange. We also analyzed whether the permeability-reducing substance prostacyclin is involved in the permeability effects of endothelin-1, as prostacylin is suggested to be released via ET(B) receptor stimulation. The study was performed on an autoperfused cat calf muscle preparation, and a capillary filtration coefficient (CFC) technique was used to estimate variations in microvascular fluid permeability (conductivity). Intraarterial infusion of endothelin-1 in low doses (5 and 10 ng/min/100 g muscle) caused transcapillary absorption, whereas higher doses (20-40 ng/min/100 g) induced filtration despite further vasoconstriction. Low-dose endothelin-1 had no significant effect on CFC, while CFC was reduced to at most 55% of baseline at higher doses (P < 0.01). Simultaneous local intraarterial infusion of the prostacyclin synthesis inhibitor tranylcypromine restored CFC to 114% of baseline (P < 0.01) and further increased vascular resistance. A low, non-vasodilator dose of prostacyclin given intravenously counteracted the tranylcypromine effect on CFC. The decreased CFC induced by a high dose of endothelin-1 was counteracted by the ET(B) receptor antagonist BQ-788 with no change in vascular resistance (P < 0.05). We conclude that the decreased CFC following high doses of endothelin-1 can be attributed to a decrease in microvascular hydraulic conductivity, mediated by secondary release of prostacylin via stimulation of the ET(B) receptor. Endothelin-1 may induce edema through postcapillary vasoconstriction.

Timing of nitric oxide donor supplementation determines endothelin-1 regulation and quality of lung preservation for transplantation

Nitroglycerin (NTG) given to donor lungs improves lung preservation for transplantation, but the mechanism(s) underlying this therapeutic benefit remain incompletely understood. Furthermore, it is not known whether the therapeutic window of opportunity for NTG administration is temporally-restricted. Because endothelin-1 (ET-1), a potent vasoconstrictor, and nitric oxide (NO) are reciprocally regulated in vitro, we hypothesized that early administration of the NO donor NTG may suppress ET-1 and thereby improve lung preservation. Using an isogeneic rat left lung transplantation model, four groups were studied (n = 12 transplant/group): (1) NTG given during flush/ preservation (Early NTG); (2) NTG given in the ex vivo flush (Late NTG); (3) No NTG; and (4) a nonselective ET-receptor antagonist (PD156252) given during flush/preservation. Early NTG decreased vascular tone in lung grafts measured ex vivo as well as in vivo following lung transplantation, and resulted in improved survival (100%) and gas exchange (pO2 209 +/- 19 mm Hg) compared with Late (17%, 62 +/- 16 mm Hg) or No NTG (25%, 59 +/- 9 mm Hg) (P < 0.05 for Early NTG versus all other groups for both survival and pO2). PD156252 was associated with an intermediate level of survival (50%) and function (104 +/- 23 mm Hg). Transplanted lung graft ET-1 mRNA, measured by Northern blotting and in situ hybridization, and protein, measured by Western blotting and immunohistochemistry, were suppressed only with Early NTG (P < 0.05 versus all other groups). Post-transplantation benefits of NTG are restricted to lung grafts which received NTG during the early harvest and immersion periods, and are coincident with suppression of graft ET-1 expression. When viewed in the context of improved graft survival and function with ET-1 receptor blockade, these data suggest that early administration of NTG to donor lungs improves primary graft function, in part, by suppressing graft ET-1 expression.

Intrathecal administration of endothelin-1 receptor antagonist ameliorates autoimmune encephalomyelitis in Lewis rats

The role of endothelin-1 (ET-1) in the development of experimental autoimmune encephalomyelitis (EAE) was studied by the blocking the action of ET-1 with a receptor antagonist, BQ-123. Intrathecal administration of BQ-123 significantly ameliorated EAE progression at the peak stage of EAE (p<0.05). By immunohistochemistry, ED-1-positive macrophages in EAE lesions were identified as major producers of ET-1, whereas the immunoreactivity of ET-1 on brain cells, such as astrocytes, was dramatically increased in accordance with the progression of EAE. This study points to a putative pro-1nflammatory role for ET-1 in the pathogenesis of EAE. One possible application for the ET-1 receptor antagonist might be helpful in the therapy of autoimmune neurological disorders.

The endothelin system in septic and endotoxin shock

The view of the endothelium as a passive barrier has gradually changed as a number of endothelium-derived substances have been discovered. Substances like nitric oxide, prostaglandins and endothelins have potent and important properties, involving not only the circulation as such but also the response to stimuli like inflammation and trauma. The endothelin system, discovered in 1988, has not only strong vasoconstrictor properties, but also immunomodulating, endocrinological and neurological effects exerted through at least two types of receptors. Septic shock, a condition with high mortality, is associated with vast cardiovascular changes, organ dysfunction with microcirculatory disturbances and dysoxia. In the experimental setting, endotoxaemia resembles these changes and is, as well as septic shock, accompanied by a pronounced increase in plasma endothelin levels. The pathophysiology in septic and endotoxin shock remains to be fully elucidated, but several studies indicate that endothelial dysfunction is one contributing mechanism. Activation of the endothelin system is associated with several pathological conditions complicating septic shock, such as acute respiratory distress syndrome, cardiac dysfunction, splanchnic hypoperfusion and disseminated intravascular coagulation. Through the development of both selective and nonselective endothelin receptor antagonists, the endothelin system has been the object of a large number of studies during the last decade. This review highlights systematically the findings of previous studies in the area. It provides strong indications that the endothelin system, apart from being a marker of vascular injury, is directly involved in the pathophysiology of septic and endotoxin shock. Interventions with endothelin receptor antagonists during septic and endotoxin shock have so far only been done in animal studies but the results are interesting and promising.

Endothelin-1 changes polymorphonuclear leukocytes' deformability and CD11b expression and promotes their retention in the lung

Endothelin (ET)1 influences polymorphonuclear leukocyte (PMN)- endothelial cell interactions. The aim of this study was to examine the effect of ET-1 on factors that influence PMN-endothelial interaction and retention in the lung both in vitro and in vivo. In vitro, high concentration of ET-1 (> or = 10(-8) M) rapidly increased PMN F-actin content (10(-7) M: 58 +/- 6% increase, P<0.01), whereas lower concentration of ET-1 (< or = 10(-9) M) caused a small but consistent decrease in F-actin content (10(-10) M: 6.9+/-1.5% decrease, P< 0.01). Preincubation of PMNs with the nitric oxide donor sodium nitroprusside (SNP) inhibited the F-actin content increase by 10(-7) M of ET-1 (P<0.01), and enhanced the F-actin content decrease by 10(-10) M of ET-1 (P<0.01). Preincubation of PMNs with Nomega-nitro-L-arginine methylester prevented the F-actin content decrease by 10(-10) M of ET-1. ET-1 (10(-7) M) reduced the deformability of PMNs (P<0.01), which was inhibited by preincubation of PMNs with SNP (P<0.05). ET-1 (10(-9) to 10(-7) M) increased CD11b expression of PMNs (P<0.01), which was inhibited by preincubation of PMNs with SNP. In vivo studies showed that the retention of PMNs treated with ET-1 increased from 45+/-8 to 70+/-5% compared with naive PMNs during their first pass through the lung (P<0.05). We conclude that ET-1 changes the F-actin content, the deformability, and the CD11b expression of PMNs in a dose-dependent fashion and that this leads to increased PMN sequestration in pulmonary microvessels.

Basal release of endothelin-1 and the influence of the ETB receptor on single vessel hydraulic permeability

BACKGROUND

Endothelin-1 (ET-1) has a direct permeability decreasing effect on the microvasculature. The present study was designed to test the hypothesis that this effect is mediated via the endothelin B (ETB) receptor located on the microvascular endothelium and to determine whether basal microvascular permeability is dependent on constitutive release of ET-1. To isolate the direct effect of ET-1, experiments were conducted under conditions in which hydraulic and oncotic pressures were controlled.

METHODS

Postcapillary venules in the rat mesentery were perfused in situ, and paired measurements of hydraulic permeability (Lp) were obtained using the modified Landis micro-occlusion method. Lp measured after a 15-minute perfusion with the ETB receptor blocker BQ-788 (1 micromol/L) was compared with measures of Lp obtained after perfusion with a combined mixture of BQ-788 and ET-1 (80 pmol/L) (n = 6). In addition, the effect of basal endogenous ET-1 was tested by measuring the effects of BQ-788 perfusion on Lp (n = 6).

RESULTS

Units for Lp are mean +/- SE x 10(-8) cm x s(-1) cm H2O(-1). ETB receptor blockade prevented any decrease in Lp induced by ET-1 (BQ-788 alone = 7.9 +/- 0.7; BQ-788 + ET-1 = 8.2 +/- 0.8;p = 0.5). Under basal conditions and in the absence of exogenous ET-1, ETB receptor blockade led to a significant increase in Lp from 6.8 +/- 0.9 to 9.7 +/- 1.2 (p = 0.001).

CONCLUSION

Decreases in microvascular permeability in single postcapillary venules after the administration of ET-1 are mediated via the ETB receptor. Constitutive release of ET-1 from the microvascular endothelium also plays a role in maintaining basal levels of permeability. These findings suggest important roles for ET-1 in maintaining and modulating microvascular permeability.

Endothelin-1-induced ET(A) receptor-mediated nociception, hyperalgesia and oedema in the mouse hind-paw: modulation by simultaneous ET(B) receptor activation

Endothelin-1 causes ET(A) receptor-mediated enhancement of capsaicin-induced nociception in mice. We have assessed if this hyperalgesic effect of endothelin-1 is also accompanied by other pro-inflammatory effects, namely nociception and oedema, and characterized the endothelin ET receptors involved. Intraplantar (i. pl.) hind-paw injection of endothelin-1 (0.3 - 30 pmol) induced graded nociceptive responses (accumulated licking time: vehicle, 20. 5+/-3.3 s; endothelin-1 at 30 pmol, 78.1+/-9.8 s), largely confined to the first 15 min. Endothelin-1 (1 - 10 pmol) potentiated ipsilateral capsaicin-induced (0.1 microgram, i.pl.; at 30 min) nociception (vehicle, 40.2+/-2.6 s; endothelin-1 at 10 pmol, 98.4+/-5.8 s, but 30 pmol was inactive), and caused oedema (increase in paw weight 5 min after capsaicin: vehicle, 46.3+/-2.3 mg; endothelin-1 at 30 pmol, 100.3+/-6.1 mg). Selective ET(B) receptor agonists sarafotoxin S6c (up to 30 pmol) and IRL 1620 (up to 100 pmol) were inactive, whereas endothelin-3 (up to 30 pmol) induced only modest oedema. ET(A) receptor antagonists BQ-123 (1 nmol, i.pl. ) or A-127722-5 (6 micromol kg(-1), i.v.) prevented all effects of endothelin-1 (10 pmol), but the ET(B) receptor antagonist BQ-788 (1 or 10 nmol, i.pl.) was ineffective. BQ-788 (10 nmol, i.pl.) unveiled hyperalgesic effects of 30 pmol endothelin-1 and endothelin-3. Sarafotoxin S6c (30 pmol, i.pl.) did not modify endothelin-1-induced (10 pmol) nociception or oedema, but abolished hyperalgesia. Thus, endothelin-1 triggers ET(A) receptor-mediated nociception, hyperalgesia and oedema in the mouse hind-paw. Simultaneous activation of ET(B) receptors by endothelin-1 or selective agonists can limit the hyperalgesic, but not the nociceptive or oedematogenic, effects of the peptide.

Effect of endothelin and endothelin receptor blockade on capillary permeability in experimental pancreatitis

BACKGROUND

Capillary leakage with fluid loss into the third space contributes to many of the early systemic complications in severe acute pancreatitis. There has been increasing interest in endothelin as one of the factors affecting capillary permeability.

AIM

To elucidate further the role of endothelin in the development of capillary leakage in acute pancreatitis by investigating the effect of exogenous endothelin administration and endothelin receptor blockade in sham operated animals and two models of acute pancreatitis.

METHODS

Determination of capillary permeability in the pancreas and colonic mucosa by quantifying extravasation of fluorescein labelled dextran using a novel computer assisted video image analysis system.

RESULTS

Pancreatic and colonic capillary permeability increased stepwise from mild to severe acute pancreatitis. Endothelin increased pancreatic and colonic capillary permeability in healthy animals and animals with mild acute pancreatitis but had no additional adverse effect in severe acute pancreatitis. Endothelin receptor blockade decreased pancreatic capillary permeability in sham operated rats but had no effect on the colon. In mild and severe acute pancreatitis, endothelin receptor blockade stabilised increased capillary permeability in both the pancreas and colon.

CONCLUSIONS

Endothelin plays an important role in mediating capillary permeability in the pancreas. In severe pancreatitis, it increases capillary permeability even outside the pancreas, thereby contributing to capillary leakage. Endothelin receptor blockade significantly reduces capillary permeability in acute pancreatitis both in and outside the pancreas, suggesting a therapeutic approach to counteract capillary leakage in severe acute pancreatitis.

Endothelins and the lung

Since endothelins were discovered by Yanasigawa in 1988 it has been recognised that they may have an important role in lung pathophysiology. Despite their biological importance as vasoconstrictors the physiological role of endothelin has not yet been defined within the lungs. This review explores their role in acute and chronic disease. During acute inflammation and ischaemia-reperfusion injury cytokines may induce release of endothelin. This is important in the realm of acute lung injury and during surgical procedures such as cardiopulmonary operations including lung resections and transplantation. Complications of surgery including primary organ failure resulting in poor gas exchange as well as increased pulmonary vascular resistance have been linked to the presence of excessive endothelin. Endothelin may have an important role in transplantation biology. The complex process leading to successful lung transplantation includes optimising the donor with brain death, harvesting the lungs, managing acute and chronic rejection, and protecting the vital organs from toxic effects of immunosuppressants. During chronic disease processes, the mitotic action of endothelin may be important in vascular and airway remodelling by means of smooth muscle cell proliferation. We also explore recent advances in drug development, animal models and future directions for research.

Endothelins and asthma

In the decade since endothelin-1 (ET-1) and related endogenous peptides were first identified as vascular endothelium-derived spasmogens, with potential pathophysiological roles in vascular diseases, there has been a significant accumulation of evidence pointing to mediator roles in obstructive respiratory diseases such as asthma. Critical pieces of evidence for this concept include the fact that ET-1 is an extremely potent spasmogen in human and animal airway smooth muscle and that it is synthesised in and released from the bronchial epithelium. Importantly, symptomatic asthma involves a marked enhancement of these processes, whereas asthmatics treated with anti-inflammatory glucocorticoids exhibit reductions in these previously elevated indices. Despite this profile, a causal link between ET-1 and asthma has not been definitively established. This review attempts to bring together some of the evidence suggesting the potential mediator roles for ET-1 in this disease.

Clinical aspects of ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS) is characterized by massive transudation of protein-rich fluid (mainly albumin) from the vascular space into the peritoneal pleural and to a lesser extent to the pericardial cavities. The intensity of the syndrome is related to the degree of the follicular response in the ovaries to the ovulation inducing agents. OHSS is still a threat to every patient undergoing ovulation induction. The pathophysiology of OHSS is of extreme importance in the face of the increased use of ovulation induction agents as well as the development of sophisticated assisted reproductive techniques. The correlation found between plasma cytokine activities and the severity of OHSS suggests that plasma cytokines may be involved in the pathogenesis of OHSS and may serve as a means of monitoring the syndrome during the acute phase and throughout convalescence. The interactions between cytokine and non-cytokine mediators of the syndrome, such as the renin-angiotensin system and vascular endothelial growth factor were recently clarified. Awareness of possible mechanisms and factors in the pathophysiology of OHSS will hopefully provide opportunities to design specific treatment regimens effective for both prevention and treatment of this potentially fatal iatrogenic condition. Among IVF patients with severe and critical OHSS, pregnancy rates, multiple gestations, miscarriage, preterm premature rupture of the membranes, prematurity, and low birth weight rates are significantly higher than those reported previously for pregnancies after assisted conception. The incidence of other obstetrical complications, as well as congenital malformations and Cesarean section rates are not significantly different.

Involvement of the endothelin receptor subtype A in neuronal pathogenesis after traumatic brain injury

Endothelin-1 (ET-1) is a 21 amino acid peptide that has been closely linked to cerebral vasospasm and more recently to oxidative stress after traumatic brain injury. In this study, we have examined the effects of the endothelin receptor subtype A antagonist, Ro 61-1790, on acute cortical neuronal injury and delayed neuronal death in the cerebellum after mild traumatic brain injury. Rats were administered Ro 61-1790 or vehicle for 24 h after injury and euthanized at 1 day, 3 days, or 7 days. Heat shock protein70 (HSP70), a marker of neuronal stress/injury, was immunolocalized in the cortex. Induction of heme oxygenase-1 (HO-1) and enhanced immunoexpression of the complement C3bi receptor, both of which are indicators of cerebellar glial reactivity, and Purkinje cell loss were evaluated in the cerebellum. There was maximal induction of HSP70 in cortical neurons at 24 h postinjury in all animals. Drug treated animals showed significantly fewer HSP70 labeled cortical neurons at this time point. There were fewer reactive glia in the cerebellum of drug treated animals as compared to vehicle controls at 3 days postinjury. However, at 7 days postinjury glial reactivity and Purkinje cell loss were similar in both groups. These findings demonstrate that Ro 61-1790, when administered for the first 24 h postinjury, limits acute neuronal injury in the cortex, transiently influences glial reactivity in the cerebellum, and does not attenuate delayed Purkinje cell death. The latter finding may reflect the duration of infusion of the drug.

Increased pulmonary vascular permeability and oedema induced by intrathecally injected endothelins in rat

The intrathecal (i.t.) injection of endothelins to conscious rats was found to cause respiratory arrest. To gain some insights into this central phenomenon, peripheral vascular permeability and lung oedema were measured after i.t. and i.v. injections of these peptides. When injected at T-8 spinal cord level, endothelin-1 (65 and 650 pmol) and endothelin-3 (650 pmol) enhanced vascular permeability in the lungs by 22-fold and 7-fold, respectively, and caused sudden death at the highest dose. Less prominent increases (between 1.4- and 2.2-fold) of vascular permeability were observed in other tissues (trachea, kidney, ears, skin of hind paws and back skin) with endothelin-1. Endothelin-1 (650 pmol) caused a similar increase (27-fold) in lung vascular permeability when injected at T-2, although the response was significantly less (P < 0.05) if injected at the L-4 (15-fold) spinal cord level. Only endothelin-1 produced lung oedema when injected at the T-2 or T-8 level. In contrast, intravenous injection of endothelins-1 and -3 (650 pmol) did not produce lung oedema and the lung vascular permeability was increased by only 1.4-1.6-fold and all rats survived. The prior i.t. injection of 6.5 nmol BQ-123 (cyclo[D-Trp, D-Asp, L-Pro, D-Val, L-Leu]), a selective endothelin ET(A) receptor antagonist, prevented the increases of lung vascular permeability and oedema and the mortality induced by i.t. endothelin-1 (650 pmol). Whereas i.v. treatment with phentolamine (2 mg/kg) or pentolinium (25 mg/kg + 50 mg/kg per h x 15 min) abolished the lung vascular permeability changes evoked by endothelin-1 (650) pmol), atropine (1 mg/kg), NG-nitro-L-arginine (50 mg/kg) or indomethacin (5 mg/kg) had no effect. Moreover, the effects of endothelin-1 were attenuated in capsaicin pretreated rats (125 mg/kg, 10 days earlier) and almost abolished in rats subjected to sympathectomy with 6-hydroxydopamine (100 mg/kg, 24-48 h earlier). All these treatments except atropine and NG-nitro-L-arginine prevented the endothelin-1-induced lung oedema and reduced the lethality by around 50%. These results suggest that the increases of pulmonary vascular permeability and oedema induced by i.t. endothelin-1 are due to an intense pulmonary vasoconstriction mediated by alpha-adrenoceptors following the release of catecholamines in response to the activation of endothelin ET(A) receptor in the spinal cord. This central phenomenon seems to be reflexogenic, including the involvement of primary afferent C-fibers and spinal cord ascending fibers to the brain. Thus, endothelin-1 could play a role in neurogenic pulmonary oedema through a central mechanism.

Overexpression of endothelin-1 mRNA and protein in portal hypertensive gastric mucosa of rats: a key to increased susceptibility to damage?

BACKGROUND

Portal hypertension predisposes gastric mucosa to increased injury by various noxious factors. Because endothelin-1 (ET-1) is a potent vasoconstrictor that enhances gastric mucosal injury, we examined ET-1 expression in the portal hypertensive (PHT) gastric mucosa and its possible role in increased mucosal susceptibility to damage.

METHODS

In gastric specimens of PHT or sham-operated rats, ET-1 mRNA expression was studied by S1-nuclease protection assay and ET-1 protein by enzyme immunoassay and immunostaining. We also determined the extent of ethanol-induced gastric mucosal necrosis in PHT and sham-operated rats after administering either a placebo or FR 139317, a selective ETA receptor antagonist.

RESULTS

In PHT stomachs ET-1 mRNA expression and protein concentration were significantly increased compared with sham-operated controls: mRNA expression (ET-1/glyceraldehyde-3-phosphate-dehydrogenase ratio), 0.54 +/- 0.18 versus 0.30 +/- 0.08; protein concentration, 7.36 +/- 2.21 pg/mg versus 3.93 +/- 0.40 pg/mg, respectively; both p < 0.01. Immunofluorescence signal of ET-1 protein was predominantly localized to endothelia of gastric mucosal and submucosal vessels. In PHT stomachs FR 139317 significantly reduced mucosal necrosis (percentage of necrotic area, from 24.9 +/- 5.9% to 10.8 +/- 4.0%; p < 0.01), although it had no effect on sham-operated controls.

CONCLUSIONS

Portal hypertension activates the ET-1 gene with overexpression of ET-1 protein in the gastric mucosa. Protection of PHT gastric mucosa by ETA receptor antagonist against damage indicates that overexpression of ET-1 plays an important role in increased susceptibility of PHT gastric mucosa to injury.

Endothelial dysfunction in diabetes mellitus

In the present study, we examined the pattern of Evan's blue (EB) extravasation over time and we verified the effect of two inhibitors of aldose reductase (sorbinil and ARI 509) as well as aminoguanidine, which modulate nitric oxide (NO) production, on streptozotocin-induced capillary extravasation abnormalities in the upper bronchi, heart, kidney, duodenum, pancreas, skeletal muscle and skin. Albumin extravasation was measured using the EB technique (20 mg/kg). On the third day, a transient decrease in EB leakage was observed in the lung (-49%), heart (-29%) and skeletal muscle (-64%). These early changes in EB were transient, and values returned to normal there after. Later on, EB extravasation was significantly enhanced in the skin (+358, +680, +580, +525 and +365, respectively, at 2, 4, 5, 6 and 7 weeks of diabetes), the duodenum (+101, +160, +92, +124 and +76%), the upper bronchus (+70, +113, +70, +41 and +25%) and the pancreas (+43, +102, +46, +15 and +78%). In the kidney, the increase of EB extravasation was significant at 2 weeks (26%), and from 5 to 7 weeks (+12, +22, +36%). The chronic treatment of diabetic rats with aminoguanidine normalized capillary permeability in most tissues, suggesting that NO is involved in the development of endothelium dysfunction in this streptozotocin-induced diabetic model. Treatment with aldose reductase inhibitors selectively normalized EB extravasation in the kidney.

Evidence for ETA and ETB receptors in rat skin and an investigation of their function in the cutaneous microvasculature

1. The relative contribution of ETA and ETB receptors in the response of rat skin to endothelins was investigated by use of the selective ETB agonist IRL-1620 and the selective ETA antagonist BQ-123. 2. Binding data suggest the presence of ETA and ETB receptors as preincubation with [Ala3,11,18Nle7]-endothelin-1 reduced ET-1 binding by approximately 40%. 3. Intradermal injection of endothelin-1 (ET-1, 1-10 pmol/site) and ET-3 (3-100 pmol/site) induced a dose-dependent decrease in local blood flow assessed by 133Xe clearance at test sites in rat skin. 4. The endothelin analogue [Ala3,11,18Nle7]-ET-1 (30-1000 pmol/site) induced significant vasoconstriction (P < 0.05) at the highest doses used and the selective ETB receptor agonist, IRL-1620 [Suc[Glu9,Ala11,15] endothelin (8-21)], (0.01-100 pmol/site) acted in a potent manner to induce a significant (P < 0.01) dose-dependent decrease in 133Xe clearance. 5. Co-injection with the selective ETA receptor antagonist, BQ-123 (1 nmol/site), completely abolished the vasoconstriction to ET-1 and partially to ET-3, but had no effect on IRL-1620-induced vasoconstriction. In addition, IRL-1620 responses were not altered at sites treated with submaximal doses of a nitric oxide synthase inhibitor or a prostaglandin synthase inhibitor. 6. ET-1 and IRL-1620 (100 fmol-1 pmol/site) did not induce oedema formation as measured by [125I]-albumin accumulation in the presence or absence of the vasodilator, calcitonin gene-related peptide (CGRP). ET-1 (1-3 pmol/site) inhibited substance P-induced oedema formation and this effect,suggested to be secondary to a vasoconstrictor effect, was significantly reversed by BQ-123 (1 nmol/site).7. The findings in this study indicate that there are ETA and ETB receptors in rat skin and agents which activate either receptor act to mediate a decrease in cutaneous blood flow, but have no effect on increased microvascular permeability.

Immunolocalization of endothelin in the traumatized spinal cord: relationship to blood-spinal cord barrier breakdown

The purpose of this study was to determine the relationship between endothelin-1 (ET-1), a prominent vasoactive agent, and the breakdown of the blood-spinal cord barrier along the axis of the cord after a moderate spinal cord injury. In the first study rats (n = 10) were euthanized 24 h after spinal cord injury and compared to sham (n = 5) and unoperated (n = 10) controls. Endothelin and immunoglobulins (IgG) were immunolocalized in adjacent sections of spinal cord using semiquantitative immunocytochemical techniques. In the second study animals were pretreated with the endothelin antagonist Bosentan (n = 6) or vehicle (n = 6) prior to spinal cord injury. Animals were euthanized at 24 h postinjury. Ten minutes prior to euthanasia animals were given horseradish peroxidase (HRP) intravenously. After perfusion fixation sections of cord were prepared for quantitative HRP histochemistry. After spinal cord injury there was enhanced staining for endothelin along the axis of the cord that correlated with the anatomical pattern of barrier breakdown to IgG. In those animals that were pretreated with Bosentan, there was a significant reduction in barrier breakdown along the axis of the injured cord as compared to those animals that received vehicle only. Taken together, this data implicate involvement of endothelin in the axial pattern of barrier breakdown after spinal cord injury.

Endothelin receptor in microvessels isolated from human meningiomas: quantification with radioluminography

1. We characterized specific 125I-endothelin-1 (125I-ET-1) binding sites in microvessels isolated from human meningiomas, using an in vitro quantitative receptor autoradiographic technique coupled to a radioluminographic imaging plate system. 2. This newly developed and highly sensitive method revealed high-affinity ET receptors present in pellet sections of the microvessels from all the meningiomas studied, regardless of histological subtypes (dissociation constant, 1.2 +/- 0.3 nM; maximum binding capacity, 185 +/- 56 fmol/mg; means +/- SE for nine tumors). 3. In five cases of meningiomas, ET-3 competed for 125I-ET-1 binding to microvessels from those tumors with a low affinity [50% inhibiting concentration (IC50) of 1.6 +/- 0.4 x 10(-6) M], and a selective ETB receptor agonist, sarafotoxin S6c, up to 10(-6) M, did not displace ET binding from the sections. 4. In the sections of microvessels from four other tumors, biphasic competition curves were obtained in the case of incubation in the presence of increasing concentrations of ET-3, with an IC50 of 1.1 +/- 0.2 x 10(-9) M for the high-affinity component and 1.6 +/- 0.3 x 10(-6) M for the low-affinity component, respectively. In addition, S6c competed for ET binding to those sections (IC50 = 2.3 +/- 0.2 x 10(-10) M) and 10(-6) M S6c displaced 30% of the control, corresponding to the high-affinity component of competition curves obtained in the presence of ET-3. 5. Our results suggest that (a) capillaries in human meningiomas express a large number of high-affinity ETA (non-ETB) receptors with a small proportion of ETB receptors, and (b) ET may have a role in neovascularization, tumor blood flow, and/or function of the blood-tumor barrier in meningioma tissues by interacting with specific receptors present on the surface of the endothelium.

Actions of endothelins and sarafotoxin 6c in the rat isolated perfused lung

1. Endothelin (ET) receptors within the vasculature and airways were studied in a rat perfused lung model in which pulmonary perfusion pressure (PPP), pulmonary inflation pressure (PIP) and lung weight were continuously monitored. 2. The vascular potencies of ETs (ET-1 > ET-2 > ET-3) suggest an action via ETA receptors. This was confirmed by use of the antagonist, BQ123 (2 microM). The vasoconstrictor effects of sarafotoxin 6c (SX6C) also indicated the presence of ETB receptors. 3. Lung weight increases induced by ETs appeared to be a consequence of their vasoconstrictor potencies. The mixed ET receptor antagonist, bosentan (5 microM), markedly attenuated the responses of ET-1 and SX6C on PPP and lung weight, further implicating activation of both ETA and ETB receptors in these responses. 4. Endothelin-1 (ET-1) induced an accumulation of albumin-bound Evans blue dye in orthogradely perfused lungs. Retrograde perfusion attenuated the extravasation and increase in lung weight due to ET-1 but significantly augmented those induced by SX6C. 5. The bronchoconstrictor actions of ETs (ET-1 = ET-2 = ET-3) and SX6C suggest this is an ETB-mediated response. However SX6C was more potent than ETs and the dose-response curve was significantly steeper and achieved a higher maximum. 6. Indomethacin did not affect the vascular or bronchial responses to ET-1 or SX6C. 7. These findings indicate that rat pulmonary vasculature contains both ETA and ETB receptors. Retrograde perfusion suggests that ETB receptors are located arterially whereas ETA receptors are predominantly venous in distribution. Differences in the bronchoconstrictor potency of SX6C (compared to ETs) and the antagonism by bosentan may indicate ETB receptor heterogeneity in the airways.

Effect of allergen provocation on inflammatory cell profile and endothelin-like immunoreactivity in guinea-pig airways

The effect of allergen challenge on the number of leucocytes and the concentration of endothelin 1-like immunoreactivity (ET-LI) in bronchoalveolar lavage fluid (BALF) was investigated in guinea-pigs sensitized to Ascaris suum. The animals were twice exposed to allergen aerosol. All animals responded to the second challenge with bronchoconstriction. Twelve hours later, a significant increase in the number of eosinophilic granulocytes in BALF, compared to unsensitized and unprovoked control animals, was noted. Twenty-four hours after provocation, there was also an elevation of ET-LI concentration and content of neutrophils. During the first day post-challenge, the ET-LI values were moderately correlated to the eosinophil levels. One week after challenge, the ET-LI level and the neutrophil count did not differ from corresponding values in control animals whereas the number of eosinophils remained elevated. Pretreatment with dexamethasone before the second allergen challenge did not consistently affect the parameters studied during the first 24 h. Bronchoconstriction induced by carbachol aerosol affected significantly neither the ET-LI concentration nor the number of inflammatory cells in BALF. It is concluded that the allergen-induced inflammation in the guinea-pig airways causes an elevation in the ET-LI concentration in BALF and that this is moderately correlated to the influx of eosinophils during the first 24 h.

Increased capillary permeability induced by human follicular fluid: a hypothesis for an ovarian origin of the hyperstimulation syndrome

OBJECTIVE

To examine the effect of follicular fluid (FF) and peritoneal fluid (PF) from patients undergoing assisted reproductive technology procedures on endothelial barrier function. This was determined in vitro by measuring the permeability of filter-grown bovine aortic endothelial cell monolayers to a permeability marker.

DESIGN

Endothelial cells obtained from bovine thoracic arotas were treated with collagenase solution and plated on millicell filters, on which they formed confluent monolayers. Flux rate was determined at 60 minutes by measuring the radioactive tracer (3H mannitol) permeating from the apical to the basolateral part of the filter. Fifty-eight samples of FF and PF, both from stimulated and natural cycles were analyzed and grouped according to the number of eggs retrieved. Follicular fluid and PF samples from natural cycles were used as controls.

RESULTS

There was an augmentation in the permeability rate of both FF and PF from patients undergoing controlled ovarian hyperstimulation (COH) who responded with an increasing number of eggs compared with controls (51% and 39%, respectively). When analyzing samples from patients who responded with a low number of oocytes, no significant increase was observed.

CONCLUSIONS

It is known that in OHSS, the increase in capillary permeability is related to the administration of gonadotropins, and is believed to be mediated by a vasoactive substance of ovarian origin. In this study, FF and PF from patients undergoing COH showed a significant increase in the permeability rate through endothelial cells in vitro. Based on these findings, it could be hypothesized that if the same events took place in vivo, the isolation of this factor from ovarian source could be of significant importance to elucidate the pathogenesis of OHSS.

Effects of endothelin receptor antagonists on bradykinin-induced increases in macromolecular efflux

The goal of this study was to determine the effects of endothelin receptor antagonists on agonist-induced increases in macromolecular extravasation in the hamster cheek pouch in vivo. We used intravital fluorescent microscopy and fluorescein isothiocyanate dextran (FITC-dextran; mol wt = 70 K) to examine extravasation from postcapillary venules in response to bradykinin and endothelin before and following application of inhibitors of endothelin receptors (ETAB and ETA). Increases in extravasation of macromolecules were quantitated by counting the number of venular leaky sites. Bradykinin (0.5 and 1.0 microM) and endothelin-1 (0.01 and 0.1 nM) produced a dose-related increase in the number of venular leaky sites and superfusion of PD 142893 (ETAB antagonist), and PD 147953 and BQ-123 (ETA antagonists) significantly decreased bradykinin- and endothelin-induced responses. Addition of calcium to the superfusate restored bradykinin-induced increases in venular leaky sites in the presence of endothelin receptor antagonism. Thus, the findings of the present study suggest that endothelin receptor antagonists abrogate bradykinin- and endothelin-induced increases in macromolecular efflux from postcapillary venules. The mechanism for the effects of endothelin receptor antagonists appears to be related to inhibition of the ETA receptor which, in turn, alters the mobilization of calcium across venular endothelium.