Interleukin 1 increases the production of endothelin-1 by cultured endothelial cells

Topical application of endothelin receptor a antagonist attenuates imiquimod-induced psoriasiform skin inflammation

Endothelin-1 (ET-1) is well known as the most potent vasoconstrictor, and can evoke histamine-independent pruritus. Recently, its involvement in cutaneous inflammation has begun to draw attention. The upregulation of ET-1 expression in the epidermis of human psoriasis patients has been reported. It was also demonstrated that ET-1 can stimulate dendritic cells to induce Th17/1 immune responses. However, the role of the interaction between ET-1 and ET-1 receptors in the pathogenesis of psoriasis remains elusive. Here, we investigated the effects of ET-1 receptor antagonist on imiquimod (IMQ) -induced psoriasiform dermatitis in mouse. Psoriasis-related cytokines such as IL-17A and TNF-α induced ET-1 expression in human keratinocytes. Topical application of selective endothelin A receptor (ETAR) antagonist ambrisentan significantly attenuated the development of IMQ-induced psoriasiform dermatitis and also significantly inhibited the histological inflammation and cytokine expression (TNF-α, IL-12p40, IL-12 p19, and IL-17) in the lesional skin of the mouse model. Furthermore, topical application of ambrisentan suppressed phenotypic and functional activation of dendritic cells in lymph nodes. Our findings indicate that the ET-1 and ETAR axis plays an important role in the pathogenesis of psoriasis and is a potential therapeutic target for treating psoriasis.

Interleukin-1 Receptor Antagonist Protects Newborn Mice Against Pulmonary Hypertension

Pulmonary hypertension secondary to bronchopulmonary dysplasia (BPD-PH) represents a major complication of BPD in extremely preterm infants for which there are currently no safe and effective interventions. The abundance of interleukin-1 (IL-1) is strongly correlated with the severity and long-term outcome of BPD infants and we have previously shown that IL-1 receptor antagonist (IL-1Ra) protects against murine BPD; therefore, we hypothesized that IL-1Ra may also be effective against BPD-PH. We employed daily injections of IL-1Ra in a murine model in which BPD/BPD-PH was induced by antenatal LPS and postnatal hyperoxia of 65% O₂. Pups reared in hyperoxia for 28 days exhibited a BPD-PH-like disease accompanied by significant changes in pulmonary vascular morphology: micro-CT revealed an 84% reduction in small vessels (4-5 μm diameter) compared to room air controls; this change was prevented by IL-1Ra. Pulmonary vascular resistance, assessed at day 28 of life by echocardiography using the inversely-related surrogate marker time-to-peak-velocity/right ventricular ejection time (TPV/RVET), increased in hyperoxic mice (0.27 compared to 0.32 in air controls), and fell significantly with daily IL-1Ra treatment (0.31). Importantly, in vivo cine-angiography revealed that this protection afforded by IL-1Ra treatment for 28 days is maintained at day 60 of life. Despite an increased abundance of mediators of pulmonary angiogenesis in day 5 lung lysates, namely vascular endothelial growth factor (VEGF) and endothelin-1 (ET-1), no difference was detected in ex vivo pulmonary vascular reactivity between air and hyperoxia mice as measured in precision cut lung slices, or by immunohistochemistry in alpha-smooth muscle actin (α-SMA) and endothelin receptor type-A (ET_A) at day 28. Further, on day 28 of life we observed cardiac fibrosis by Sirius Red staining, which was accompanied by an increase in mRNA expression of galectin-3 and CCL2 (chemokine (C-C motif) ligand 2) in whole hearts of hyperoxic pups, which improved with IL-1Ra. In summary, our findings suggest that daily administration of the anti-inflammatory IL-1Ra prevents the increase in pulmonary vascular resistance and the pulmonary dysangiogenesis of murine BPD-PH, thus pointing to IL-1Ra as a promising candidate for the treatment of both BPD and BPD-PH.

Role of cardiac inflammation in right ventricular failure

Right ventricular failure (RVF) is the main determinant of mortality in patients with pulmonary arterial hypertension (PAH). Although the exact pathophysiology underlying RVF remains unclear, inflammation may play an important role, as it does in left heart failure. Perivascular pulmonary artery and systemic inflammation is relatively well studied and known to contribute to the initiation and maintenance of the pulmonary vascular insult in PAH. However, less attention has been paid to the role of cardiac inflammation in RVF and PAH. Consistent with many other types of heart failure, cardiac inflammation, triggered by systemic and local stressors, has been shown in RVF patients as well as in RVF animal models. RV inflammation likely contributes to impaired RV contractility, maladaptive remodelling and a vicious circle between RV and pulmonary vascular injury. Although the potential to improve RV function through anti-inflammatory therapy has not been tested, this approach has been applied clinically in left ventricular failure patients, with variable success. Because inflammation plays a dual role in the development of both pulmonary vascular pathology and RVF, anti-inflammatory therapies may have a potential double benefit in patients with PAH and associated RVF.

The IL-1β Antibody Gevokizumab Limits Cardiac Remodeling and Coronary Dysfunction in Rats With Heart Failure

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Immediate IL-1β antibody gevokizumab administration reduces ischemia/reperfusion related infarct size.

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Immediate and late IL-1β antibody gevokizumab administration improves heart failure related left ventricular remodeling.

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IL-1β antibody gevokizumab improves heart failure related coronary dysfunction.

This study reports preclinical data showing that the interleukin (IL)-1β modulation is a new promising target in the pathophysiological context of heart failure. Indeed, in nondiabetic Wistar and diabetic Goto-Kakizaki rats with chronic heart failure induced by myocardial infarction, administration of the IL-1β antibody gevokizumab improves ‘surrogate’ markers of survival (i.e., left ventricular remodeling, hemodynamics, and function as well as coronary function). However, whether IL-1β modulation per se or in combination with standard treatments of heart failure improves long-term outcome in human heart failure remains to be determined.

A Genetic Variant Associated with Five Vascular Diseases Is a Distal Regulator of Endothelin-1 Gene Expression

Genome-wide association studies (GWASs) implicate the PHACTR1 locus (6p24) in risk for five vascular diseases, including coronary artery disease, migraine headache, cervical artery dissection, fibromuscular dysplasia, and hypertension. Through genetic fine mapping, we prioritized rs9349379, a common SNP in the third intron of the PHACTR1 gene, as the putative causal variant. Epigenomic data from human tissue revealed an enhancer signature at rs9349379 exclusively in aorta, suggesting a regulatory function for this SNP in the vasculature. CRISPR-edited stem cell-derived endothelial cells demonstrate rs9349379 regulates expression of endothelin 1 (EDN1), a gene located 600 kb upstream of PHACTR1. The known physiologic effects of EDN1 on the vasculature may explain the pattern of risk for the five associated diseases. Overall, these data illustrate the integration of genetic, phenotypic, and epigenetic analysis to identify the biologic mechanism by which a common, non-coding variant can distally regulate a gene and contribute to the pathogenesis of multiple vascular diseases.

Current understanding of sepsis: criticism and a proposal

The failure to improve outcome of septic patients may reflect flawed hypotheses pertaining to the pathogenesis of sepsis. Alternatively, it may represent the use of clinically irrelevant experimental animal models. To address these issues, an alternative hypothesis is proposed. It is suggested that leukocyte activation in sepsis is initiated by a priming effect of minuscule doses of endotoxin on leukocytes for enhanced responsiveness to minute doses of inflammatory mediators (or vice versa) as opposed to activation by overwhelming doses of endotoxin per se. The experimental impetus of this hypothesis has been provided by a novel rat model of sepsis precipitated by the co-administration of PAF and LPS at doses 1/1000 lower than those previously used to elicit sepsis in the same species.

Advanced glycation end products upregulate lysyl oxidase and endothelin-1 in human aortic endothelial cells via parallel activation of ERK1/2-NF-κB and JNK-AP-1 signaling pathways

Endothelial dysfunction involves deregulation of the key extracellular matrix (ECM) enzyme lysyl oxidase (LOX) and the vasoconstrictor protein, endothelin-1 (ET-1), whose gene expression can be modulated by the transcriptional activators nuclear factor kappa B (NF-κB) and activator protein-1 (AP-1). Advanced glycation end products (AGEs) present an aggravating factor of endothelial dysfunction which upon engagement to their receptor RAGE induce upregulation of mitogen-activated protein kinases (MAPKs), leading to NF-κB and AP-1 potentiation. We hypothesized that AGEs could induce NF-κΒ- and AP-1-dependent regulation of LOX and ET-1 expression via the AGE/RAGE/MAPK signaling axis. Western blot, real-time qRT-PCR, FACS analysis and electrophoretic mobility-shift assays were employed in human aortic endothelial cells (HAECs) following treatment with AGE-bovine serum albumin (AGE-BSA) to investigate the signaling pathway towards this hypothesis. Furthermore, immunohistochemical analysis of AGEs, RAGE, LOX and ET-1 expression was conducted in aortic endothelium of a rat experimental model exposed to high- or low-AGE content diet. HAECs exposed to AGE-BSA for various time points exhibited upregulation of LOX and ET-1 mRNA levels in a dose- and time-dependent manner. Exposure of HAECs to AGE-BSA also showed specific elevation of phospho(p)-ERK1/2 and p-JNK levels in a dose- and time-dependent fashion. AGE administration significantly increased NF-κΒ- and AP-1-binding activity to both LOX and ET-1 cognate promoter regions. Moreover, LOX and ET-1 overexpression in rat aortic endothelium upon high-AGE content diet confirmed the functional interrelation of these molecules. Our findings demonstrate that AGEs trigger NF-κΒ- and AP-1-mediated upregulation of LOX and ET-1 via the AGE/RAGE/MAPK signaling cascade in human endothelial cells, thus contributing to distorted endothelial homeostasis by impairing endothelial barrier function, altering ECM biomechanical properties and cell proliferation.

The role of the intestinal microcirculation in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) continues to be a devastating inflammatory disease of the newborn intestine. Despite advances in management, morbidity and mortality remain high. While it is clear that intestinal ischemia plays a large role in disease pathogenesis, attempts to link NEC to intestinal macrovascular derangement have been largely unsuccessful. More recently, there has been a concerted effort to characterize the pathologic changes of the intestinal microcirculation in response to intestinal injury, including NEC. This microcirculatory regulation is controlled by a balance of vasoconstrictor and vasodilator forces. Vasoconstriction is mediated primarily by endothelin-1 (ET-1), while vasodilation is mediated primarily by nitric oxide (NO). These chemical mediators have been implicated in many aspects of intestinal ischemic injury and NEC, with the balance shifting toward increased vasoconstriction associated with intestinal injury. With a proper understanding of these antagonistic forces, potential therapeutic avenues may result from improving this pathologic microcirculatory dysregulation.

Increased expression of endothelin-1 and endothelin receptor A in reflux esophagitis and Barrett's esophagus

Barrett's esophagus (BE) is considered a complication of the inflammation provoked by acid and bile reflux. Endothelin-1 (ET-1) expresses in various cells during inflammatory process. However, the role of ET-1 in human inflamed and uninflamed esophageal tissue is unknown. The present study aimed to examine the expression of ET-1 and its receptors in human reflux esophagitis (RE) and BE. Endoscopic biopsies of normal squamous epithelium (NSE) (n = 20), RE (n = 22), and long segment BE (n = 14) were obtained. The segmental degree of endoscopic and histopathological inflammation was graded, and immunohistochemistry and real-time quantitative polymerase chain reaction were used to determine the expression of ET-1 and endothelin receptor A (ET(A)R) and endothelin receptor B (ET(B)R). ET-1 and ET(A)R messenger RNA (mRNA) levels were higher in RE than in NSE (3.25 ± 1.78 vs. 1.10 ± 0.71, P = 0.000; 2.13 ± 1.06 vs. 1.12 ± 0.64, P = 0.001, respectively). In BE, relative ET-1 mRNA levels in the proximal segment were higher than in the distal segment (3.03 ± 1.83 vs. 1.16 ± 0.70, P = 0.004) and in normal esophageal epithelium (P = 0.002). There was no significantly difference of ET(A)R mRNA levels between the proximal segment and the distal segment (1.99 ± 1.28 vs. 1.14 ± 0.67, P = 0.072). ET(B)R mRNA expression was unaltered between the groups. Furthermore, immunohistochemistry demonstrated that ET-1 expression increased significantly in RE (51.18 ± 30.14) compared with those in NSE (21.10 ± 18.17, P = 0.000) and in distal BE segment (28.02 ± 24.92, P = 0.022). There were more ET-1 positive cells in proximal BE segment (50.07 ± 25.88) than in distal BE segment (P = 0.030) and in NSE (P = 0.001). ET-1 expression increased in a stepwise manner with the growing degree of inflammation, and there were significant differences between mild, moderate, and marked degree esophagitis (36.08 ± 27.84, 65.86 ± 11.82, 98.00 ± 8.49, P = 0.003, respectively). However, expression of receptors remained unchanged. This study demonstrates that over-expression of ET-1 and ET(A)R in esophagitis may be related to the inflammatory process. ET-1 may play a significant role in the progression of Barrett's metaplasia.

Refractoriness to the effect of endothelin-1 in porcine ciliary arteries

PURPOSE

Endothelin-1 (ET) is an important molecule in vascular physiology. After an acute stimulation with ET, vessels are to some extent temporarily refractory to further stimulation. However, few details are known about this phenomenon. The aim of our study was to verify the existence of refractoriness in ophthalmic ciliary arteries and, if present, to analyze its time course.

METHODS

Twenty freshly isolated porcine ciliary arteries were placed in a myograph system to measure isometric forces. Each vessel was stimulated with 10(-7) M ET twice. The experiment was performed in 5 groups of vessels, which differed in the time interval between the initial and the second stimulation with ET. The intervals were 15 min, 30 min, 1 h, 2 h, and 4 h, respectively.

RESULTS

The vasoconstrictive response to re-exposure to ET was time-dependently reduced. The response was lowest after 15 min (22% of baseline response), and then the sensitivity slowly recovered and was finally normal again after 4 h.

CONCLUSIONS

Our experiment with isolated porcine ophthalmic ciliary arteries revealed a refractoriness phase to ET after an acute stimulation with ET. This refractoriness was transient and disappeared after 4 h. The lowest response was observed in the group of vessels re-exposed 15 min after the first stimulation.

Turnour necrosis factor stimulates endothelin-1 gene expression in cultured bovine endothelial cells

We have studied the effect of human recombinant tumour necrosis factor-α (TNF-α) on gene expression and production of endothelin-1 in cultured bovine aortic endothelial cells. TNF-α (10 and 100 ng ml⁻¹) increased in a time dependent manner the preproendothelin-1 mRNA levels in respect to unstimulated endothelial cells. TNF-α induced endothelin-1 gene expression was associated with a parallel increase in the release of the corresponding peptide in the culture medium. These findings suggest that the enhanced synthesis and release of endothelin-1 occurring in conditions of increased generation of TNF, may act as a modulatory factor that counteracts the hypotensive effect and the excessive platelet aggregation and adhesion induced by TNF.

Cholinoceptor activation subserving the effects of interferon gamma on the contractility of rat ileum

Recombinant rat interferon γ stimulated the contractility of isolated rat ileum at doses of 4–12 units/ml. Muscarinic cholinoceptors were involved, as treatment of the tissue with atropine prevented the contractile response of the ileum. Furthermore, interferon γ increased the affinity of carbachol for the cholinoceptors and did not change its maximum effect. Neurogenic pathways were also involved since pretreatment of ileum with hexamethonium, hemicholinium or tetrodotoxin impaired the contractile effect of interferon γ. In contrast to the action of exogenous carbachol, the effects of interferon γ are indirect. They appear to involve a G protein regulating phosphoinositide turnover and cytoskeletal structures since they could not be induced in ileum strips that were pretreated with pertussis toxin, phospholipase C inhibitors (2-nitro-carboxyphenyl, NN-diphenyl carbamate and neomycin), cytochalasine B or colchicine.

The role of endothelin and endothelin antagonists in traumatic brain injury: a review of the literature

OBJECTIVES

To date, there is increasing evidence for the role of endothelins in the pathophysiological development of cerebral vasospasms associated with a variety of neurological diseases, e.g., stroke and subarachnoid hemorrhage. In contrast, only little is known regarding the role of endothelins in impaired cerebral hemodynamics after traumatic brain injury. Therapeutic work in blocking the endothelin system has led to the discovery of a number of antagonists potentially useful in restoring cerebral blood flow after traumatic brain injury, potentially reducing the detrimental effects of secondary brain injury. Therefore, the present work provides an overview of background topics such as structures and biosynthesis of endothelins, different types as well as potential mechanisms and sites of action. In addition, the role of age for the effects of endothelins on cerebral hemodynamics after traumatic brain injury is discussed.

RESULTS

Description of data supporting the role of the endothelins play in a host of neurological deficits.

CONCLUSIONS

Endothelin antagonists may be effective as novel treatments for various neuropathologies.

The significance of endothelin in platelet-activating factor-induced fetal growth restriction

The significance of endothelin-1 (ET-1) in platelet-activating factor (PAF)-induced fetal growth restriction (FGR) was evaluated in timed-pregnant rats receiving intravenous carbamyl-PAF (c-PAF; 0.5, 1.0, or 2.5 µg/kg per h) or vehicle, with or without ET-1 receptor A (ET(A)) antagonist (10 or 20 mg/kg per d) for 7 days beginning on gestation day 14. Tissues were collected on day 21. Carbamyl-PAF reduced fetal weights dose dependently. Placental weights were significantly reduced but not dose dependently. ET(A) antagonism prevented FGR at the 0.5, but not the 1.0 and 2.5 µg/kg per h c-PAF doses. Correspondingly, placental, but not uterine, preproET-1 messenger RNA (mRNA) expression (determined by reverse transcription-polymerase chain reaction) was increased at 0.5 µg/kg per h but not at higher c-PAF doses. In summary, c-PAF infusion results in fetal and placental growth restriction in the rat. At low doses of c-PAF, ET-1 is central to the pathophysiology of PAF-induced FGR. At higher c-PAF doses, FGR is induced by mechanisms other than ET-1 action.

Contribution of vascular cell-derived cytokines to innate and inflammatory pathways in atherogenesis

Inflammation is a central element of atherogenesis. Innate pathways contribute to vascular inflammation. However, the initial molecular process(es) starting atherogenesis remain elusive. The various risk factors, represented by particular compounds (activators), may cause altered cellular functions in the endothelium (e.g. vascular endothelial cell activation or -dysfunction), in invading cells (e.g. inflammatory mediator production) or in local vessel wall cells (e.g. inflammatory mediators, migration), thereby triggering the innate inflammatory process. The cellular components of innate immunology include granulocytes, natural killer cells and monocytes. Among the molecular innate constituents are innate molecules, such as the toll-like receptors or innate cytokines. Interleukin-1 (IL-1) and IL-6 are among the innate cytokines. Cytokines are potent activators of a great number of cellular functions relevant to maintain or commove homeostasis of the vessel wall. Within the vessel wall, vascular smooth muscle cells (SMCs) can significantly contribute to the cytokine-dependent inflammatory network by: (i) production of cytokines, (ii) response to cytokines and (iii) cytokine-mediated interaction with invading leucocytes. The cytokines IL-1 and IL-6 are involved in SMC-leucocyte interaction. The IL-6 effects are proposed to be mediated by trans-signalling. Dysregulated cellular functions resulting from dysregulated cytokine production may be the cause of cell accumulation, subsequent low-density lipoprotein accumulation and deposition of extracellular matrix (ECM). The deposition of ECM, increased accumulation of leucocytes and altered levels of inflammatory mediators may constitute an 'innate-immunovascular-memory' resulting in an ever-growing response to anew invasion. Thus, SMC-fostered inflammation, promoted by invading innate cells, may be a potent component for development and acceleration of atherosclerosis.

Enteral arginine does not increase superior mesenteric arterial blood flow but induces mucosal growth in neonatal pigs

Arginine is an essential amino acid in neonates synthesized by gut epithelial cells and a precursor for NO that regulates vasodilatation and blood flow. Arginine supplementation has been shown to improve intestinal integrity in ischemia-reperfusion models and low plasma levels are associated with necrotizing enterocolitis. We hypothesized that enteral arginine is a specific stimulus for neonatal intestinal blood flow and mucosal growth under conditions of total parenteral nutrition (TPN) or partial enteral nutrition (PEN). We first tested the dose dependence and specificity of acute (3 h) enteral arginine infusion on superior mesenteric artery (SMA) blood flow in pigs fed TPN or PEN. We then determined whether chronic (4 d) arginine supplementation of PEN increases mucosal growth and if this was affected by treatment with the NO synthase inhibitor, N(G)-nitro-l-arginine methyl ester (L-NAME). Acute enteral arginine infusion increased plasma arginine dose dependently in both TPN and PEN groups, but the plasma response was markedly higher (100-250%) in the PEN group than in the TPN group at the 2 highest arginine doses. Baseline SMA blood flow was 90% higher in the PEN (2.37 ± 0.32 L⋅kg(-1)⋅h(-1)) pigs than in the TPN pigs (1.23 ± 0.17 L⋅kg(-1)⋅h(-1)), but was not affected by acute infusion individually of arginine, citrulline, or other major gut fuels. Chronic dietary arginine supplementation in PEN pigs induced mucosal growth in the intestine, but this effect was not prevented by treatment with L-NAME. Intestinal crypt cell proliferation, protein synthesis, and phosphorylation of mammalian target of rapamycin and p70S6 kinase were not affected by dietary arginine. We conclude that partial enteral feeding, but not acute enteral arginine, increases SMA blood flow in the neonatal pig. Furthermore, supplementing arginine in partial enteral feeding modestly increases intestinal mucosal growth and was NO independent.

Current and emerging strategies for the treatment and management of systemic lupus erythematosus based on molecular signatures of acute and chronic inflammation

Lupus is a chronic, systemic inflammatory condition in which eicosanoids, cytokines, nitric oxide (NO), a deranged immune system, and genetics play a significant role. Our studies revealed that an imbalance in the pro- and antioxidants and NO and an alteration in the metabolism of essential fatty acids exist in lupus. The current strategy of management includes administration of nonsteroidal anti-inflammatory drugs such as hydroxychloroquine and immunosuppressive drugs such as corticosteroids. Investigational drugs include the following: 1) belimumab, a fully human monoclonal antibody that specifically recognizes and inhibits the biological activity of B-lymphocyte stimulator, also known as B-cell-activation factor of the TNF family; 2) stem cell transplantation; 3) rituximab, a chimeric monoclonal antibody against CD20, which is primarily found on the surface of B-cells and can therefore destroy B-cells; and 4) IL-27, which has potent anti-inflammatory actions. Our studies showed that a regimen of corticosteroids and cyclophosphamide, and methods designed to enhance endothelial NO synthesis and augment antioxidant defenses, led to induction of long-lasting remission of the disease. These results suggest that methods designed to modulate molecular signatures of the disease process and suppress inflammation could be of significant benefit in lupus. Some of these strategies could be vagal nerve stimulation, glucose-insulin infusion, and administration of lipoxins, resolvins, protectins, and nitrolipids by themselves or their stable synthetic analogs that are known to suppress inflammation and help in the resolution and healing of the inflammation-induced damage. These strategies are likely to be useful not only in lupus but also in other conditions, such as rheumatoid arthritis, scleroderma, ischemia-reperfusion injury to the myocardium, ischemic heart disease, and sepsis.

Platelets as initiators and mediators of inflammation at the vessel wall

Platelets are dynamic cells with activities that extend beyond thrombosis including an important role in initiating and sustaining vascular inflammation. A role for platelets has been described in many physiologic and pathophysiologic processes such as atherosclerosis, stem cell trafficking, tumor metastasis, and arthritis. Platelet activation at sites of an intact inflamed endothelium contributes to vascular inflammation and vascular wall remodeling. Platelets secrete a wide array of preformed and synthesized inflammatory mediators upon activation that can exert significant local and systemic effects. This review will focus on the role of platelet derived mediators in vascular inflammation and vascular wall remodeling.

Endothelin in the female vasculature: a role in aging?

Cardiovascular diseases are the leading cause of morbidity and mortality in the world. Aging is associated with an increased incidence of cardiovascular disease. Premenopausal women are relatively protected from vascular alterations compared with age-matched men, likely due to higher levels of the female sex hormones. However, these vasoprotective effects in women are attenuated after menopause. Thus, the vascular system in aging women is affected by both the aging process as well as loss of hormonal protection, positioning women of this age group at a high risk for cardiovascular diseases such as hypertension, myocardial infarction, and stroke. The endothelin system in general and endothelin-1 (ET-1) in particular plays an important role in the pathogenesis of vascular dysfunction associated with aging. Evidence suggests that the female sex steroids can interfere with the vascular expression and actions of ET-1 via several mechanisms, which may further contribute to pathological processes in the vasculature of aging women. In this review, we have summarized hormone-dependent vascular pathways whereby ET-1 may mediate the deleterious effects of aging in postmenopausal females.

Synergistic induction of endothelin-1 by tumor necrosis factor alpha and interferon gamma is due to enhanced NF-kappaB binding and histone acetylation at specific kappaB sites

Endothelin-1 (ET-1) is a potent vasoconstrictor and co-mitogen for vascular smooth muscle and is implicated in pulmonary vascular remodeling and the development of pulmonary arterial hypertension. Vascular smooth muscle is an important source of ET-1. Here we demonstrate synergistic induction of preproET-1 message RNA and release of mature peptide by a combination of tumor necrosis factor alpha (TNFalpha) and interferon gamma (IFNgamma) in primary human pulmonary artery smooth muscle cells. This induction was prevented by pretreatment with the histone acetyltransferase inhibitor anacardic acid. TNFalpha induced a rapid and prolonged pattern of nuclear factor (NF)-kappaB p65 subunit activation and binding to the native preproET-1 promoter. In contrast, IFNgamma induced a delayed activation of interferon regulatory factor-1 without any effect on NF-kappaB p65 nuclear localization or consensus DNA binding. However, we found cooperative p65 binding and histone H4 acetylation at distinct kappaB sites in the preproET-1 promoter after stimulation with both TNFalpha and IFNgamma. This was associated with enhanced recruitment of RNA polymerase II to the ATG start site and read-through of the ET-1 coding region. Understanding such mechanisms is crucial in determining the key control points in ET-1 release. This has particular relevance to developing novel treatments targeted at the inflammatory component of pulmonary vascular remodeling.

Aminaftone, a derivative of 4-aminobenzoic acid, downregulates endothelin-1 production in ECV304 Cells: an in vitro Study

BACKGROUND AND OBJECTIVE

Endothelin-1 (ET-1) plays a central role in the pathogenesis of several vascular diseases. Aminaftone is a drug used for the treatment of capillary disorders but which has a mechanism of action that is not fully understood. We investigated whether aminaftone may exert its effect by interfering with the production of ET-1.

METHODS

Human ECV304 endothelial cells were incubated with interleukin-1beta (IL-1beta) 100 IU/mL with or without the addition of increasing concentrations of aminaftone (2, 4 or 6 microg/mL). ET-1 concentrations in surnatants were quantified by enzyme immunoassay kit at 3, 6 and 12 hours. Pre-pro-endothelin-1 (PPET-1) gene expressions were also analysed by real-time polymerase chain reaction (RT-PCR) at the same time points. Endothelin-converting enzyme (ECE) activity was also determined.

RESULTS

Incubation with IL-1beta increased concentrations of ET-1 and PPET-1 relative gene expression. Incubation with aminaftone significantly reduced production of ET-1 in a concentration-dependent manner. A strong direct correlation was found between ET-1 concentrations and PPET-1 relative gene expression, but aminaftone did not influence ECE activity.

CONCLUSION

Aminaftone inhibits ET-1 production in cell cultures by interfering with transcription of the PPET-1 gene. These findings may account for the clinical efficacy of aminaftone in the treatment of capillary disorders and may encourage conduct of further clinical trials.

Vascular cells contribute to atherosclerosis by cytokine- and innate-immunity-related inflammatory mechanisms

Cardiovascular diseases are the human diseases with the highest death rate and atherosclerosis is one of the major underlying causes of cardiovascular diseases. Inflammatory and innate immune mechanisms, employing monocytes, innate receptors, innate cytokines, or chemokines are suggested to be involved in atherogenesis. Among the inflammatory pathways the cytokines are central players. Plasma levels of cytokines and related proteins, such as CRP, have been investigated in cardiovascular patients, tissue mRNA expression was analyzed and correlations to vascular diseases established. Consistent with these findings the generation of cytokine-deficient animals has provided direct evidence for a role of cytokines in atherosclerosis. In vitro cell culture experiments further support the suggestion that cytokines and other innate mechanisms contribute to atherogenesis. Among the initiation pathways of atherogenesis are innate mechanisms, such as toll-like-receptors (TLRs), including the endotoxin receptor TLR4. On the other hand, innate cytokines, such as IL-1 or TNF, or even autoimmune triggers may activate the cells. Cytokines potently activate multiple functions relevant to maintain or spoil homeostasis within the vessel wall. Vascular cells, not least smooth muscle cells, can actively contribute to the inflammatory cytokine-dependent network in the blood vessel wall by: (i) production of cytokines; (ii) response to these potent cell activators; and (iii) cytokine-mediated interaction with invading cells, such as monocytes, T-cells, or mast cells. Activation of these pathways results in accumulation of cells and increased LDL- and ECM-deposition which may serve as an 'immunovascular memory' resulting in an ever-growing response to subsequent invasions. Thus, vascular cells may potently contribute to the inflammatory pathways involved in development and acceleration of atherosclerosis.

The effects of endothelin receptor blockade by bosentan on the healing of a bowel anastomosis in an experimental Crohn's disease model

OBJECTIVE

It was previously described that endothelins may contribute to the pathogenesis of Crohn's disease. In this study, it was aimed to investigate the effects of endothelin receptor blockade by bosentan on the healing of a bowel anastomosis in an experimental Crohn's disease model.

MATERIAL AND METHODS

Twenty-eight Sprague-Dawley rats were divided into four groups. Groups I and II were used as sham-operated and control groups, respectively. Bowel inflammation induced by intrajejunal injection of iodoacetamide in groups III and IV. Rats in group IV were treated with oral preparation of bosentan 60 mg/kg/day. Three days after induction of the inflammation, partial resection of test loop and anastomosis was performed. Re-laparotomy was performed, anastomosis bursting pressures and peritonitis scores were measured, and tissue samples were obtained for the measurements of tissue hydroxylproline level and mucosal damage index 4 days later.

RESULTS

The mean mucosal damage index and peritonitis score of group IV were significantly lower, and the mean tissue hydroxyproline level and anastomotic bursting pressure of group IV were significantly higher than those of group III.

CONCLUSION

The blockade of endothelin receptors by bosentan decreases the severity of iodoacetamide induced intestinal inflammation, increases the wound healing in the inflamed intestinal tissue, and decreases the severity of peritonitis.

Interleukin-1beta, but not interleukin-6, enhances renal and systemic endothelin production in vivo

The inflammatory cytokines IL-1beta and IL-6 have been shown to stimulate production of endothelin-1 (ET-1) by several cell types in vitro, but their effects on renal ET-1 production in vivo are not known. To test whether IL-1beta and IL-6 stimulate renal ET-1 production and release in vivo, urine was collected from male C57BL/6 mice over 24-h periods at baseline and on days 7 and 14 of a 14-day subcutaneous infusion of IL-1beta (10 ng/h), IL-6 (16 ng/h), or vehicle. By day 14, plasma ET-1 was significantly increased by IL-1beta infusion (1.7 +/- 0.1 vs. 0.8 +/- 0.1 pg/ml for vehicle, P < 0.001). Compared with vehicle infusion, IL-1beta infusion induced significant increases in urinary ET-1 excretion rate and urine flow but did not affect conscious mean arterial pressure (telemetry). IL-1beta infusion significantly increased renal cortical and medullary IL-1beta content (ELISA) and prepro-ET-1 mRNA expression (quantitative real-time PCR). In contrast, 14 days of IL-6 infusion had no significant effect on plasma ET-1 or urinary ET-1 excretion rate. To determine whether IL-1beta stimulates ET-1 release via activation of NF-kappaB, inner medullary collecting duct (IMCD-3) cells were incubated for 24 h with IL-1beta, and ET-1 release and NF-kappaB activation were measured (ELISA). IL-1beta activated NF-kappaB and increased ET-1 release in a concentration-dependent manner. The effect of IL-1beta on ET-1 release could be partially inhibited by pretreatment of IMCD-3 cells with an inhibitor of NF-kappaB activation (BAY 11-7082). These results indicate that IL-1beta stimulates renal and systemic ET-1 production in vivo, providing further evidence that ET-1 participates in inflammatory responses.

The neonatal intestinal vasculature: contributing factors to necrotizing enterocolitis

Based on the demonstration of coagulation necrosis, it is clear that intestinal ischemia plays a role in the pathogenesis of necrotizing enterocolitis (NEC). Intestinal vascular resistance is determined by a dynamic balance between vasoconstrictive and vasodilatory inputs. In the newborn, this balance heavily favors vasodilation secondary to the copious production of endothelium-derived nitric oxide (NO), a circumstance which serves to ensure adequate blood flow and thus oxygen delivery to the rapidly growing intestine. Endothelial cell injury could shift this balance in favor of endothelin (ET)-1-mediated vasoconstriction, leading to intestinal ischemia and tissue injury. Evidence obtained from animal models and from human tissue collected from infants with NEC implicates NO and ET-1 dysregulation in the pathogenesis of NEC. Strategies focused on maintaining the delicate balance favoring vasodilation in the newborn intestinal circulation may prove to be useful in the prevention and treatment of NEC.

Endothelin-1-induced pain and hyperalgesia: a review of pathophysiology, clinical manifestations and future therapeutic options

Pain in patients with metastatic cancer contributes to increased suffering in those already burdened by their advancing illness. The causes of this pain are unknown, but are likely to involve the action of tumour-associated mediators and their receptors. In recent years, several chemical mediators have increasingly come to the forefront in the pathophysiology of cancer pain. One such mediator, endothelin-1 (ET-1), is a peptide of 21 amino acids that was initially shown to be a potent vasoconstrictor. Extensive research has revealed that members of the ET family are indeed produced by several epithelial cancerous tumours, in which they act as autocrine and/or paracrine growth factors. Several preclinical and clinical studies of various malignancies have suggested that the ET axis may represent an interesting contributor to tumour progression. In addition, evidence is accumulating to suggest that ET-1 may contribute to pain states both in humans and in other animals. ET-1 both stimulates nociceptors and sensitises them to painful stimuli. Selective stimulation of ET receptors has been implicated as a cause of inflammatory, neuropathic and tumoural pain. ET-1-induced pain-related behaviour seems to be mediated either solely by one receptor type or via both endothelin-A receptors (ETAR) and endothelin-B receptors (ETBR). Whereas stimulation of ETAR on nociceptors always elicits a pain response, stimulation of ETBR may cause analgesia or elicit a pain response, depending on the conditions. The administration of ETAR antagonists in the receptive fields of these nociceptors has been shown to ameliorate pain-related behaviours in animals, as well as in some patients with advanced metastatic prostate cancer. The identification of tumour-associated mediators that might directly or indirectly cause pain in patients with metastatic disease, such as ET-1, should lead to improved, targeted analgesia for patients with advanced cancer. In this review, we will describe the current status of the role of ET-1 in different types of painful syndromes, with special emphasis on its role in the pathophysiology of cancer pain. Finally, potential new treatment options that are based on the role of the ET axis in the pathophysiology of cancer are elaborated.

Examination of mRNA expression in rat hearts and lungs for analysis of effects of exposure to concentrated ambient particles on cardiovascular function

Epidemiological studies have suggested that fine particulate matter (f-PM) is associated with adverse effects on cardiovascular health. However, these effects on the cardiovascular system have not yet been fully elucidated. Using mRNA expression and correlation analyses, we designed the present study to elucidate (1) translocation of chemicals in inhaled f-PM to the heart, (2) induction of oxidative stress, one of the causes of cardiovascular diseases (CVDs), (3) mRNA expression related to CVDs, and (4) correlations among mRNA expression of various molecules and cardiovascular function. Wistar Kyoto male rats were exposed to concentrated ambient particles (CAPs, 0.6-1.5mg/m3) in Yokohama for 4 days (4.5h/day) or to filtered air for 3 days and CAPs for 1 day or to filtered air for 4 days. Messenger RNA expression and cardiovascular function were measured after the 4-day exposure. In samples of heart tissue, the mRNAs of cytochrome P450 (CYP) 1B1, a biomarker of exposure to chemicals; heme oxygenase-1 (HO-1), a marker of oxidative stress; and endothelin A (ET A) receptor, a receptor of vasoconstrictors, were up-regulated by CAPs; their levels were significantly correlated with the cumulative weight of CAPs in the exposure chamber. The up-regulation of ET A receptor mRNA was significantly correlated with the increase in HO-1 mRNA and weakly with the increase in mean blood pressure (Delta MBP). These results suggest the possibility that chemicals in CAPs might be translocated to the heart, where they induce oxidative stress and activate endothelin signaling, resulting in an increase in the blood pressure. The exposure to f-PM might thus affect cardiovascular function through activation of endothelin signaling.

Antivasospastic and antiinflammatory effects of caspase inhibitor in experimental subarachnoid hemorrhage

Object

Inflammation in the subarachnoid space and apoptosis of arterial endothelial cells have been implicated in the development of delayed cerebral vasospasm after subarachnoid hemorrhage (SAH). The authors investigated mechanisms of possible antivasospastic effects of N-benzyl-oxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK), a caspase inhibitor that can inhibit both inflammatory and apoptotic systems, in animal models of SAH.

Methods

Rabbits were assigned to three groups of eight animals each and were subjected to SAH by injection of blood into the cisterna magna. The experiments were performed in the following groups: SAH only, SAH + vehicle, and SAH + Z-VAD-FMK. The Z-VAD-FMK (1 mg) or vehicle (5% dimethyl sulfoxide) was intrathecally administered before SAH induction. Diameters of the basilar artery (BA) were measured on angiograms obtained before and 2 days after SAH. The BA diameter on Day 2 was expressed as a percentage of that before SAH. Interleukin (IL)–1β in the cerebrospinal fluid (CSF) was examined using Western blotting, and brains were immunohistochemically examined for caspase-1 and IL-1β. In a separate experiment, 20 rats were subjected to SAH and their brains were immunohisto-chemically assessed for caspase-1, IL-1β, and macrophages.

Results

In rabbits, Z-VAD-FMK significantly attenuated cerebral vasospasm (the BA diameter on Day 2 in SAH-only, SAH + vehicle, and SAH + Z-VAD-FMK groups was 66.6 ± 3.2%, 66.3 ± 3.7%, and 82.6 ± 4.9% of baseline, respectively), and suppressed IL-1β release into the CSF and also suppressed immunoreactivities of caspase-1 and IL-1β in macrophages infiltrating into the subarachnoid space. Immunoreactivities for caspase-1 and IL-1β were observed in immunohistochemically proven infiltrating macrophages in rats.

Conclusions

These results indicate that caspase activation may be involved in the development of SAH-induced vasospasm through inflammatory reaction.

Endothelin-1 activates ETA receptors to cause reflex scratching in BALB/c mice

BACKGROUND AND PURPOSE

Endothelin-1 (ET-1) is present in murine and human skin and causes itch (pruritus) when injected in humans. This behavioural study examined the scratch reflex evoked by ET-1 in mice.

EXPERIMENTAL APPROACH

An automated detector was used to determine whether ET-1 causes reflex scratching, the behavioural correlate of itching, in BALB/c mice. Selective agonists and antagonists were used to probe the ET receptor(s) involved.

KEY RESULTS

ET-1 evoked dose-related reflex scratching lasting up to 20 min following intradermal injection (0.1-100 ng; 0.04-40 pmol). The ED(50) for ET-1 induced scratching was 2.1 ng and desensitization occurred with cumulative dosing. High doses of the ET(B) receptor agonist IRL1620 (10 microg; 5.5 nmol), also caused scratching (ED(50) 1.3 microg, 0.7 nmol). The ET(A) receptor antagonist BQ123 significantly reduced scratching evoked by ET-1 and IRL 1620, suggesting that both agonists caused scratching via an ET(A) receptor-dependent mechanism. The ET(B) receptor antagonist BQ788 significantly reduced scratching evoked by IRL1620 but had no effect on scratching evoked by ET-1. This indicated that activation of ET(B) receptors by high doses of ET(B) agonist, but not ET-1, can trigger scratching.

CONCLUSION AND IMPLICATIONS

ET-1 is a potent endogenous activator of reflex scratching (itch). Mechanisms for ET-induced scratching are considered, including direct action of ET-1 on pruriceptive nerve endings and indirect actions via release of endogenous mediators such as histamine from mast cells. ET-1 and ET(A) receptors, possibly also ET(B) receptors, are potential targets for developing specific anti-pruritic drugs to treat pruritic skin disorders such as atopic dermatitis.

Endothelins Mediate Neutrophil Activation, ProMMP-9 Release and Endothelial Cell Detachment

Neutrophils isolated from human peripheral blood added to a monolayer of human endothelial cells (ECV-304 cell line) stimulated with LPS (100 ng ml(-1)) resulted in: (a) neutrophil activation, measured by spreading and release of leukotriene B(4) (LTB(4)); (b) neutrophil degranulation, measured by release of matrix pro-metalloproteinase-9 (proMMP-9) and (c) loss of the monolayer integrity due to detachment of the endothelial cells. Stimulation of endothelial cells with tumor necrosis factor-alpha (TNF-alpha 10 ng ml(-1)) or interleukin-1 (IL-1; 10 ng ml(-1)) induced a similar dose-dependent increase in the neutrophil activation and endothelial cell detachment. Pre-treatment of LPS-activated ECV-304 cells with [Phe22]BigET-1(19-37) (10(-9) M; an inhibitor of endothelin converting enzyme (ECE)) or addition of BQ-123 (10(-6) M; a selective endothelin A (ET(A)) receptor antagonist) to the co-cultures, significantly reduced neutrophil spreading (50-70% inhibition) as well as the levels of LTB(4) (70-100% inhibition) and proMMP-9 (40-50% inhibition) in the co-culture supernatants. In addition, the detachment of endothelial cells was also reduced (60-75% inhibition). Moreover, the exogenous addition of ET-1 (10(-9) M) to neutrophil suspensions induced neutrophil spreading and release of LTB(4) and proMMP-9. Taken together, these findings indicate that neutrophils added to stimulated endothelial cells in the co-culture system employed in this study, get activated by products of these cells and degranulate. In parallel, the detachment of endothelial cell monolayer from the culture plates, possibly by the action of neutrophil granule-derived gelatinases, is observed. Endothelins (ETs) produced by the endothelial cells are suggested to play an essential role in these phenomena.

HLA-B35 upregulates the production of endothelin-1 in HLA-transfected cells: a possible pathogenetic role in pulmonary hypertension

HLA-B35 is associated with an increased risk for developing isolated pulmonary hypertension (iPHT) in systemic sclerosis, but the mechanisms underlying this association have not been fully elucidated yet. Endothelin-1 (ET-1) is the main pathogenetic molecule implied in the development of iPHT; therefore, we sought to determine if ECV304 cells transfected with the HLA-B35 allele produce increased amounts of ET-1 after incubation with physiological concentrations of interleukin-1 beta (IL-1beta). ECV304 cells transfected with HLA-B*3501 and HLA-B*0801 polymorphic alpha chain or with pIRESneo2 were incubated with 100 U/ml of IL-1beta for 6, 12, 24, 36 and 48 h. ET-1 levels were determined using EIA kit (CAYMAN Chemical, Ann Arbor, MI) in supernatants from different cell cultures; the relative expression of the preproendothelin-1 (PPET-1) gene was also determined by reverse transcription-polymerase chain reaction. Cells expressing the HLA-B35 allele showed significantly increased levels of ET-1 at all the selected times compared with controls or HLA-B8-transfected cells. The relative expression of the PPET-1 gene was also increased in a proportionally direct manner. The HLA-B35 allele influences the production of ET-1 in HLA-B35-transfected ECV304 cells by promoting the expression of its precursor, PPET-1. Our results provide an explanation for the epidemiological association existing between iPHT and HLA-B35.

IL-1beta alters hemodynamics in newborn intestine: role of endothelin

Studies were carried out to determine the effects of IL-1beta on newborn intestinal hemodynamics. IL-1beta increased the release of ET-1 by primary endothelial cells in a dose-dependent manner; as well, it reduced expression of the endothelin (ET) type B (ET(B)) receptor on endothelial cells and increased expression of the ET type A (ET(A)) receptor on vascular smooth muscle cells. IL-1beta increased endothelial cell endothelial nitric oxide (NO) synthase (eNOS) expression but did not enhance eNOS activity as evidenced by release of NO(x) into conditioned medium in response to acetylcholine or shear stress. The effects of IL-1beta on flow-induced dilation were evaluated in terminal mesenteric arteries in vitro. Pretreatment with IL-1beta (1 ng; 4 h) significantly attenuated vasodilation in response to flow rates of 100 and 200 microl/min. This effect was mediated, in part, by the endothelin ET(A) receptor; thus selective blockade of ET(A) receptors with BQ610 nearly restored flow-induced dilation. In contrast, exogenous ET-1 only shifted the diameter-flow curve downward without altering the percent vasodilation in response to flow. The effects of IL-1beta on ileal oxygenation were then studied using in vivo gut loops. Intramesenteric artery infusion of IL-1beta upstream of the gut loop caused ileal vasoconstriction and reduced the arterial-venous O(2) difference across the gut loop; consequently, it reduced ileal oxygenation by 60%. This effect was significantly attenuated by pretreatment with BQ610. These data support a linkage between the proinflammatory cytokine IL-1beta and vascular dysfunction within the intestinal circulation, mediated, at least in part, by the ET system.

Endothelial function and its assessment

Endothelial dysfunction is a characteristic aspect of most of the conditions associated with atherosclerosis and is commonly found as an early feature in atherothrombotic vascular disease. An appreciation of the underlying mechanisms of endothelial function, as well as dysfunction, is essential as this has critical influence on the different methods in the assessment of endothelial function and effects of various treatments on its quantification. Furthermore, endothelial dysfunction is recognised as a type of 'target organ damage' in common cardiovascular conditions (e.g., hypertension) and the area is of increasing interest for new drug development, as therapies that modulate the endothelium will have added advantages; thus, for the development of new/experimental drugs, an awareness of ways to assess the endothelium is necessary. In this review, an overview of different methods including biochemical markers, and invasive and non-invasive tools, to determine endothelial function is presented as well as their clinical relevance. Furthermore, the effects of various treatments on endothelial dysfunction and their underlying mechanisms are elucidated.

Ischemia and necrotizing enterocolitis: where, when, and how

While it is accepted that ischemia contributes to the pathogenesis of necrotizing enterocolitis (NEC), three important questions regarding this role subsist. First, where within the intestinal circulation does the vascular pathophysiology occur? It is most likely that this event begins within the intramural microcirculation, particularly the small arteries that pierce the gut wall and the submucosal arteriolar plexus insofar as these represent the principal sites of resistance regulation in the gut. Mucosal damage might also disrupt the integrity or function of downstream villous arterioles leading to damage thereto; thereafter, noxious stimuli might ascend into the submucosal vessels via downstream venules and lymphatics. Second, when during the course of pathogenesis does ischemia occur? Ischemia is unlikely to the sole initiating factor of NEC; instead, it is more likely that ischemia is triggered by other events, such as inflammation at the mucosal surface. In this context, it is likely that ischemia plays a secondary, albeit critical role in disease extension. Third, how does the ischemia occur? Regulation of vascular resistance within newborn intestine is principally determined by a balance between the endothelial production of the vasoconstrictor peptide endothelin-1 (ET-1) and endothelial production of the vasodilator free radical nitric oxide (NO). Under normal conditions, the balance heavily favors NO-induced vasodilation, leading to a low resting resistance and high rate of flow. However, factors that disrupt endothelial cell function, eg, ischemia-reperfusion, sustained low-flow perfusion, or proinflammatory mediators, alter the ET-1:NO balance in favor of constriction. The unique ET-1-NO interaction thereafter might facilitate rapid extension of this constriction, generating a viscous cascade wherein ischemia rapidly extends into larger portions of the intestine.

Eyeing endothelins: a cellular perspective

Endothelin is an endogenous vasoactive peptide that is considered among the most potent vasoconstrictor substances known. In addition to its vascular effects, endothelins and their receptors have been shown to be present in the eye and to have a number of ocular actions that may be important for ocular homeostasis, but, in excess can be a potential contributor to ocular neuropathy in glaucoma. The current review focuses on the cellular and molecular aspects of endothelins and its receptors in the eye with an emphasis on its relationship to ocular function and its potential role in the etiology of glaucoma pathophysiology.

Role of the 3'-untranslated region of human endothelin-1 in vascular endothelial cells. Contribution to transcript lability and the cellular heat shock response

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide expressed in the vascular endothelium. Stringent control over ET-1 expression is achieved through a highly regulated promoter and rapid mRNA turnover. Since little is known about mechanisms governing ET-1 post-transcriptional regulation, and changes in ET-1 mRNA stability are implicated in disease processes, we characterized these pathways using a variety of functional approaches. We expressed human ET-1 and luciferase transcripts with or without a wild type ET-1 3'-untranslated region (3'-UTR) and found that the 3'-UTR had potent mRNA destabilizing activity. Deletion analysis localized this activity to two domains of the 3'-UTR we have termed destabilizing elements 1 and 2 (DE1 and DE2). Mutational studies revealed that DE1 functions as an AU-rich element (ARE) dependent on a 100-nucleotide region. This activity was further localized to a 10-nucleotide region at position 978-987 of the 3'-UTR. Depletion of AUF1 by RNA interference up-regulated ET-1 in endothelial cells suggesting AUF1-dependent regulation. Since AUF1 functions through the ubiquitin-proteasome pathway, we disrupted this pathway with heat shock and proteasome inhibitor in endothelial cells and observed stabilization of endogenous ET-1 mRNA. Chimeric transcripts bearing wild type ET-1 3'-UTRs were also stabilized in response to proteasome inhibition whereas DE1 mutants failed to respond. Taken together, these findings suggest a complex model of ARE-mediated mRNA turnover dependent on two 3'-UTR domains, DE1 and DE2. Furthermore, DE1 functions as an ARE directing mRNA half-life through the proteasome. Finally, this data provides evidence for a novel pathway of ET-1 mRNA stabilization by heat shock.

Investigation into the potential anti-inflammatory effects of endothelin antagonists in a murine model of experimental monosodium urate peritonitis

Endothelin (ET)-1 has been detected in many inflammatory pathologies, including rheumatoid arthritic patients, asthma, and ischemic-reperfusion injury. In this study, we have investigated the effect of a panel of different ET-1 antagonists displaying different selectivities for the receptors in a murine model of experimental inflammatory peritonitis. Systemic treatment of mice with the ETA antagonist C33H44N6O5, N-[N-[-N(hexahydro-1H-azepin-1-yl)carbonyl]-L-leucyl]-1-methyl-D-tryptophyl]-3-(2-pyridinyl)-D-alanine (FR139317) inhibited neutrophil accumulation. However, a greater degree of inhibition was observed with the ETB antagonist C34H51N5O7, N-cis-2,6-dimethylpiperidinocarbonyl-b-tBu-Ala-D-Trp(1-methoxycarbonyl)-D-Nle-OH (BQ-788) and the ET(A and B) antagonist C52H65N7O10, N-acetyl-alpha-[10,11-dihydro-5H-dibenzo-[a,d]cycloheptadien-5-yl]-D-Gly-Leu-Asp-lle-lle-Trp (PD145065); all these effects occurred without altering peripheral blood cell counts. Release of the CXC chemokine KC was significantly reduced by the FR139317 and PD145065 but not by BQ-788. Evaluation of the therapeutic potential of these antagonists showed that PD145065 inhibited neutrophil migration and KC release, whereas the others caused a nonsignificant reduction in these parameters. Parameters of endothelial cell activation showed that urate-stimulated interleukin-1beta release was inhibited by BQ-788 and PD145065 but not by FR139317, whereas ET-1 was only inhibited by the mixed antagonist. A different scenario was observed with respect to release of the CXC chemokine KC with FR139317 and PD145065 being effective, whereas with a marker of polymorphonuclear activation the ETA and mixed antagonist inhibited adhesion molecule expression. These data show that ET-1 antagonists elicit different mechanisms of actions in the way they display their antimigratory effects in a murine model of monosodium urate crystal peritonitis.

Involvement of endogenous endothelins in thermal and mechanical inflammatory hyperalgesia in mice

Endothelin receptors have been involved in inflammatory, neuropathic and tumoral pain. In the case of inflammatory hyperalgesia, some previous papers have pointed towards the involvement of ETB receptors, although the stimulation of ETA receptors seems to participate in the development of the inflammatory reaction. We have studied the effect of ETA and ETB receptor antagonists in the thermal and mechanical hyperalgesia induced in a model of acute (induced by carrageenan) and chronic (induced by complete Freund's adjuvant, CFA) inflammation in mice. The i.pl. administration of the selective ETA antagonist BQ-123 (1-10 nmol) antagonized the thermal hyperalgesia detected by the unilateral hot plate test, observed in both inflammatory models, whereas the i.pl. administration of the ETB selective antagonist BQ-788 (17.7 nmol) failed to modify this. In contrast, both BQ-123 (3-17.7 nmol) and BQ-788 (3-17.7 nmol) antagonized the mechanical hyperalgesia, as assessed by the Randall-Selitto test in carrageenan- and CFA-treated mice. Both BQ-123 and BQ-788 were able to antagonize the mechanical hyperalgesia induced by ET-1 (200 pmol; i.pl.) in the same dose range. Thus, ETA receptors are involved in both thermal and mechanical hyperalgesia whereas ETB receptors are only involved in mechanical hyperalgesia in these inflammatory models. In conclusion, the role of ETB receptors in inflammatory pain is further supported and new insights into the participation of ETA receptors in inflammatory hyperalgesia are given.

Increased expression of endothelin-1 and its mitogenic receptor ETA in human papillary thyroid carcinoma

OBJECTIVE

Since the isolation of endothelin-1 (ET-1) in 1988, there has been tremendous interest in the pathophysiological roles of ET-1 as a vasoconstrictive and mitogenic peptide. Whereas ET-1 is mainly released by vascular endothelial cells, it also proved to be produced by various tissues including the thyroid. Because of its mitogenic properties in malignancy and its role as an inflammatory modulator, ET-1 could be involved in thyroid carcinogenesis and thyroiditis.

DESIGN AND PATIENTS

Studies were performed in human thyroid samples obtained at the time of surgery from 39 men and women aged 15-72 years. Thyroid samples were classified in four groups according to conventional histology: normal thyroid (n = 7) papillary thyroid carcinoma (n = 12), Hashimoto's thyroiditis (n = 9) and benign nontoxic nodular goitres (n = 11). Immunohistochemistry and real-time quantitative polymerase chain reaction were used to determine the expression of ET-1 and its receptors (ETAR and ETBR).

RESULTS

ET-1 and ETAR mRNA levels were, respectively, 3.8 +/- 1.3 and 4.1 +/- 1.5 times greater (P < 0.001) in papillary thyroid carcinoma than in normal thyroid. Expression of ETBR was unaltered. In Hashimoto's thyroiditis, ET-1 and ETAR were also overexpressed (P < 0.005). Furthermore, immunohistochemistry demonstrated a greater percentage of ET-1-positive follicular cells in these conditions (P < 0.001). In nodular goitres, the expression was increased by 1.7 +/- 0.7 times (P < 0.05) but expression of receptors remained unchanged.

CONCLUSIONS

ET-1 and ETAR overexpression observed in thyroid carcinoma suggest a mitogenic role of ET-1 that theoretically could be countered by ETAR antagonists. ET-1 and ETAR overexpression in thyroiditis supports a role of ET-1 in the inflammatory process.

Secretion of interleukin-1beta by astrocytes mediates endothelin-1 and tumour necrosis factor-alpha effects on human brain microvascular endothelial cell permeability

Evidence suggests that endothelin-1 (ET-1) plays an essential role in brain inflammation. However, whether ET-1 contributes directly to blood-brain barrier (BBB) breakdown remains to be elucidated. Using an in vitro BBB model consisting of co-cultures of human primary astrocytes and brain microvascular endothelial cells (BMVECs), we first investigated the expression of ET-1 by BMVECs upon stimulation with tumour necrosis factor (TNF)-alpha, which plays an essential role in the induction and synthesis of ET-1 during systemic inflammatory responses. Increased ET-1 mRNA was detected in the human BMVECs 24 h after TNF-alpha treatment. This was correlated with an increase in ET-1 levels in the culture medium, as determined by sandwich immunoassay. Both TNF-alpha and ET-1 increased the permeability of human BMVECs to a paracellular tracer, sucrose, but only in the presence of astrocytes. The increase in BMVEC permeability by TNF-alpha was partially prevented by antibody neutralization of ET-1 and completely by monoclonal antibody against IL-1beta. Concomitantly, TNF-alpha induced IL-1beta mRNA expression by astrocytes in co-culture and this effect was partially prevented by ET-1 antibody neutralization. In parallel experiments, treatment of human primary astrocytes in single cultures with ET-1 for 24 h induced IL-1beta mRNA synthesis and IL-1beta protein secretion in the cell culture supernatant. Taken together, these results provide evidence for paracrine actions involving ET-1, TNF-alpha and IL-1beta between human astrocytes and BMVECs, which may play a central role in BBB breakdown during CNS inflammation.