The human endothelin family: three structurally and pharmacologically distinct isopeptides predicted by three separate genes

Pathophysiological effects of androgens on the female vascular system

Sex hormones and their respective receptors affect vascular function differently in men and women, so it is reasonable to assume they play a role in the sex differences in cardiovascular disease states. This review focuses on how the effects of testosterone on arterial vessels impact the female vasculature. In women with androgen-excess polycystic ovary syndrome, and in transgender men, testosterone exposure is associated with high blood pressure, endothelial dysfunction, and dyslipidemia. These relationships suggest that androgens may exert pathophysiological effects on the female vasculature, and these effects on the female vasculature appear to be independent from other co-morbidities of cardiovascular disease. There is evidence that the engagement of androgens with androgen receptor induces detrimental outcomes in the female cardiovascular system, thereby representing a potential causative link with sex differences and cardiovascular regulation. Gender affirming hormone therapy is the primary medical intervention sought by transgender people to reduce the characteristics of their natal sex and induce those of their desired sex. Transgender men, and women with androgen-excess polycystic ovary syndrome both represent patient groups that experience chronic hyperandrogenism and thus lifelong exposure to significant medical risk. The study of testosterone effects on the female vasculature is relatively new, and a complex picture has begun to emerge. Long-term research in this area is needed for the development of more consistent models and controlled experimental designs that will provide insights into the impact of endogenous androgen concentrations, testosterone doses for hormone therapy, and specific hormone types on function of the female cardiovascular system.

Retinal Physiology and Circulation: Effect of Diabetes

In this article, we present a discussion of diabetes and its complications, including the macrovascular and microvascular effects, with the latter of consequence to the retina. We will discuss the anatomy and physiology of the retina, including aspects of metabolism and mechanisms of oxygenation, with the latter accomplished via a combination of the retinal and choroidal blood circulations. Both of these vasculatures are altered in diabetes, with the retinal circulation intimately involved in the pathology of diabetic retinopathy. The later stages of diabetic retinopathy involve poorly controlled angiogenesis that is of great concern, but in our discussion, we will focus more on several alterations in the retinal circulation occurring earlier in the progression of disease, including reductions in blood flow and a possible redistribution of perfusion that may leave some areas of the retina ischemic and hypoxic. Finally, we include in this article a more recent area of investigation regarding the diabetic retinal vasculature, that is, the alterations to the endothelial surface layer that normally plays a vital role in maintaining physiological functions. © 2020 American Physiological Society. Compr Physiol 10:933-974, 2020.

Sleeve gastrectomy ameliorates endothelial function and prevents lung cancer by normalizing endothelin-1 axis in obese and diabetic rats

BACKGROUND

Previous evidence has implied that obesity is an independent risk factor for developing cancer. Being closely related to obesity, type 2 diabetes mellitus provides a suitable environment for the formation and metastasis of tumors through multiple pathways. Although bariatric surgeries are effective in preventing and lowering the risk of various types of cancer, the underlying mechanisms of this effect are not clearly elucidated.

AIM

To uncover the role and effect of sleeve gastrectomy (SG) in preventing lung cancer in obese and diabetic rats.

METHODS

SG was performed on obese and diabetic Wistar rats, and the postoperative transcriptional and translational alterations of the endothelin-1 (ET-1) axis in the lungs were compared to sham-operated obese and diabetic rats and age-matched healthy controls to assess the improvements in endothelial function and risk of developing lung cancer at the postoperative 4^th, 8^th, and 12^th weeks. The risk was also evaluated using nuclear phosphorylation of H2A histone family member X as a marker of DNA damage (double-strand break).

RESULTS

Compared to obese and diabetic sham-operated rats, SG brought a significant reduction to body weight, food intake, and fasting blood glucose while improving oral glucose tolerance and insulin sensitivity. In addition, ameliorated levels of gene and protein expression in the ET-1 axis as well as reduced DNA damage indicated improved endothelial function and a lower risk of developing lung cancer after the surgery.

CONCLUSION

Apart from eliminating metabolic disorders, SG improves endothelial function and plays a protective role in preventing lung cancer via normalized ET-1 axis and reduced DNA damage.

Homology modeling, molecular dynamics and virtual screening of endothelin-A receptor for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease of pulmonary arteries, causing serious shortness of breath and right ventricular failure with high mortality. Numerous studies have verified that the symptoms of PAH could be attenuated effectively with endothelin-A receptor (ETAR) antagonists. Unfortunately, the 3D structure of ETAR has not been released, making it difficult to understand the interactions between ETAR and its antagonists. In this study, computational methods including homology modeling, molecular docking and molecular dynamics simulations were performed to build the structure of ETAR and predict the binding patterns of ETAR with its two antagonists. Based on these results, virtual screening study was implemented against Traditional Chinese Medicine (TCM) database to identify novel natural ETAR antagonists. Six compounds with best binding energies were screened out and two of them were found to bind steadily with ETAR validated through molecular dynamics simulations and MM-GBSA calculation, indicating that they were potential antagonists of ETAR. In a word, our research provided a deep exploration into the interaction between ETAR and its antagonists, which could promote the development of novel therapy against PAH.[Formula: see text]Communicated by Ramaswamy H. Sarma.

Endothelin-1 Serum Concentration is Lower in Children and Adolescents with High Myopia, a Preliminary Study

The aim of this study is to evaluate the levels of enothelin-1 (ET-1) in children and adolescents with high myopia and its association with the axial length of the eye and the presence of myopic retinal degeneration. The cross-sectional study was carried out in 57 patients with high myopia and 29 control subjects. Serum concentrations of ET-1 were measured using enzyme-linked immunosorbent assay (ELISA) kit. A significantly lower concentration of ET-1 in highly myopic patients compared to controls was found (1.47 (0.91; 1.87) vs. 1.94 (1.1; 2.69) pg/mL, p = 0.005). In patients with high myopia, a weak negative correlation between ET-1 concentration and the longest axial length out of the two eyes was found (r = −0.255, p = 0.0558). Further analysis revealed statistically significant differences in ET-1 concentration between patients with the axial length of the eye > 26 and ≤ 26 mm (p < 0.041) and patients with the axial length of the eye > 26 mm and controls (p < 0.001). ET-1 expression is disturbed in highly myopic children and adolescents. Lower ET-1 concentration in patients with the axial length of the eye > 26 mm may co-occur with high myopia and should be considered a risk factor in the pathophysiology of high myopia progression.

Mouse connective tissue mast cell proteases tryptase and carboxypeptidase A3 play protective roles in itch induced by endothelin-1

Background

Itch is an unpleasant sensation that can be debilitating, especially if it is chronic and of non-histaminergic origin, as treatment options are limited. Endothelin-1 (ET-1) is a potent endogenous vasoconstrictor that also has the ability to induce a burning, non-histaminergic pruritus when exogenously administered, by activating the endothelin A receptor (ET_AR) on primary afferents. ET-1 is released endogenously by several cell-types found in the skin, including macrophages and keratinocytes. Mast cells express ET_ARs and can thereby be degranulated by ET-1, and mast cell proteases chymase and carboxypeptidase A3 (CPA3) are known to either generate or degrade ET-1, respectively, suggesting a role for mast cell proteases in the regulation of ET-1-induced itch. The mouse mast cell proteases (mMCPs) mMCP4 (chymase), mMCP6 (tryptase), and CPA3 are found in connective tissue type mast cells and are the closest functional homologs to human mast cell proteases, but little is known about their role in endothelin-induced itch.

Methods

In this study, we evaluated the effects of mast cell protease deficiency on scratching behavior induced by ET-1. To investigate this, mMCP knock-out and transgenic mice were injected intradermally with ET-1 and their scratching behavior was recorded and analyzed.

Results

CPA3-deficient mice and mice lacking all three proteases demonstrated highly elevated levels of scratching behavior compared with wild-type controls. A modest increase in the number of scratching bouts was also seen in mMCP6-deficient mice, while mMCP4-deficiency did not have any effect.

Conclusion

Altogether, these findings identify a prominent role for the mast cell proteases, in particular CPA3, in the protection against itch induced by ET-1.

Synthesis and Molecular Modelling Studies of New 1,3-Diaryl-5-Oxo-Proline Derivatives as Endothelin Receptor Ligands

The synthesis of seventeen new 1,3-diaryl-5-oxo-proline derivatives as endothelin receptor (ETR) ligands is described. The structural configuration of the new molecules was determined by analyzing selected signals in proton NMR spectra. In vitro binding assays of the human ET_A and ET_B receptors allowed us to identify compound 31h as a selective ET_AR ligand. The molecular docking of the selected compounds and the ET_A antagonist atrasentan in the ET_AR homology model provided insight into the structural elements required for the affinity and the selectivity of the ET_AR subtype.

CASIN and AMD3100 enhance endothelial cell proliferation, tube formation and sprouting

Endothelial dysfunction is prominent in atherosclerosis, hypertension, diabetes, peripheral and cardiovascular diseases, and stroke. Novel therapeutic approaches to these conditions often involve development of tissue-engineered veins with ex vivo expanded endothelial cells. However, high cell number requirements limit these approaches to become applicable to clinical applications and highlight the requirement of technologies that accelerate expansion of vascular-forming cells. We have previously shown that novel small molecules could induce hematopoietic stem cell expansion ex vivo. We hypothesized that various small molecules targeting hematopoietic stem cell quiescence and mobilization could be used to induce endothelial cell expansion and angiogenesis due to common origin and shared characteristics of endothelial and hematopoietic cells. Here, we have screened thirty-five small molecules and found that CASIN and AMD3100 increase endothelial cell expansion up to two-fold and induce tube formation and ex vivo sprouting. In addition, we have studied how CASIN and AMD3100 affect cell migration, apoptosis and cell cycle of endothelial cells. CASIN and AMD3100 upregulate key endothelial marker genes and downregulate a number of cyclin dependent kinase inhibitors. These findings suggest that CASIN and AMD3100 could be further tested in the development of artificial vascular systems and vascular gene editing technologies. Furthermore, these findings may have potential to contribute to the development of alternative treatment methods for diseases that cause endothelial damage.

Increased Endothelin-1 Mrna Expression in Peripheral Blood Monocytes of Dialysis Patients

Objective

To compare plasma endothelin (ET)-1 level and ET-1 mRNA level in peripheral blood monocytes of patients undergoing hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD).

Design

Endothelin-1 mRNA level in peripheral blood monocytes and plasma ET -1 level were studied in 30 HD patients, 15 CAPD patients, 20 chronic renal failure patients not being dialyzed, and 20 normal healthy controls. Hemodialysis patients were dialyzed three times per week with a bicarbonate dialysate. Different types of dialyzer membrane, viz., cellulose triacetate, cuprophane, poly-sulfone, polyacrylonitrile, and ethylenevinylalcohol were used in 8,6,6,5, and 5 patients, respectively. Continuous ambulatory peritoneal dialysis patients were dialyzed with four daily exchanges of a 2-L dialysate containing glucose at a concentration of 1.5% to 2.5%.

Results

Higher levels of ET -1 mRNA in monocytes were observed in HD patients than in CAPD patients (p < 0.01), chronic renal failure patients (p < 0.01), or normal healthy controls (p < 0.001). The level of ET -1 mRNA in monocytes at the end of HD was not significantly higher than that at the start of HD. ln addition, these mRNA levels in HD patients showed littledifference with different types of dialysis membrane. Plasma ET -1 level in HD patients (10.2 ± 2.4 pg/mL) was also higher than that in CAPD patients (7.8 ± 1.6 pg/mL, p < 0.01), in chronic renal failure patients (4.8 ± 1.2 pg/mL, p < 0.01), or in normal controls (2.6 ± 0.8 pg/mL, p < 0.001).

Conclusion

Dialysis itself did not significantly affect ET -1 mRNA levels in monocytes. Chronic stimulation of peripheral blood monocytes may be associated with higher levels of ET -1 mRNA and plasma ET -1 in HD patients than in CAPD patients.

Disulfide-Driven Cyclic Peptide Synthesis of Human Endothelin-2 with a Solid-Supported Npys-Cl

We report here the synthesis of human endothelin-2, a peptide of 21 amino acid residues with two disulfide bonds, based on the novel idea of a disulfide-driven cyclic peptide synthesis (DdCPS). This synthesis has two steps: (1) a one-pot solid-phase disulfide ligation of two different sulfur-containing peptide fragments using an Npys-Cl resin and (2) intramolecular cyclization of the disulfide peptide via amide bond formation using a thioester ligation. Human endothelin-2 was obtained in a total yield of 2.2% with two such DdCPS procedures and subsequent deprotection and HPLC purification. This strategy is the basis of a new solid-phase assisted practical synthesis of cyclic disulfide peptides.

Endothelin: 30 Years From Discovery to Therapy

Discovered in 1987 as a potent endothelial cell-derived vasoconstrictor peptide, endothelin-1 (ET-1), the predominant member of the endothelin peptide family, is now recognized as a multifunctional peptide with cytokine-like activity contributing to almost all aspects of physiology and cell function. More than 30 000 scientific articles on endothelin were published over the past 3 decades, leading to the development and subsequent regulatory approval of a new class of therapeutics-the endothelin receptor antagonists (ERAs). This article reviews the history of the discovery of endothelin and its role in genetics, physiology, and disease. Here, we summarize the main clinical trials using ERAs and discuss the role of endothelin in cardiovascular diseases such as arterial hypertension, preecclampsia, coronary atherosclerosis, myocardial infarction in the absence of obstructive coronary artery disease (MINOCA) caused by spontaneous coronary artery dissection (SCAD), Takotsubo syndrome, and heart failure. We also discuss how endothelins contributes to diabetic kidney disease and focal segmental glomerulosclerosis, pulmonary arterial hypertension, as well as cancer, immune disorders, and allograft rejection (which all involve ET_A autoantibodies), and neurological diseases. The application of ERAs, dual endothelin receptor/angiotensin receptor antagonists (DARAs), selective ET_B agonists, novel biologics such as receptor-targeting antibodies, or immunization against ET_A receptors holds the potential to slow the progression or even reverse chronic noncommunicable diseases. Future clinical studies will show whether targeting endothelin receptors can prevent or reduce disability from disease and improve clinical outcome, quality of life, and survival in patients.

Endothelins (EDN1, EDN2, EDN3) and their receptors (EDNRA, EDNRB, EDNRB2) in chickens: Functional analysis and tissue distribution

Endothelins (EDNs) and their receptors (EDNRs) are reported to be involved in the regulation of many physiological/pathological processes, such as cardiovascular development and functions, pulmonary hypertension, neural crest cell proliferation, differentiation and migration, pigmentation, and plumage in chickens. However, the functionality, signaling, and tissue expression of avian EDN-EDNRs have not been fully characterized, thus impeding our comprehensive understanding of their roles in this model vertebrate species. Here, we reported the cDNAs of three EDN genes (EDN1, EDN2, EDN3) and examined the functionality and expression of the three EDNs and their receptors (EDNRA, EDNRB and EDNRB2) in chickens. The results showed that: 1) chicken (c-) EDN1, EDN2, and EDN3 cDNAs were predicted to encode bioactive EDN peptides of 21 amino acids, which show remarkable degree of amino acid sequence identities (91-95%) to their respective mammalian orthologs; 2) chicken (c-) EDNRA expressed in HEK293 cells could be preferentially activated by chicken EDN1 and EDN2, monitored by the three cell-based luciferase reporter assays, indicating that cEDNRA is a functional receptor common for both cEDN1 and cEDN2. In contrast, both cEDNRB and cEDNRB2 could be activated by all three EDN peptides with similar potencies, indicating that both receptors can function as common receptors for the three EDNs and share functional similarity. Moreover, activation of three EDNRs could stimulate intracellular calcium, MAPK/ERK, and cAMP/PKA signaling pathways. 3) qPCR assay revealed that cEDNs and cEDNRs are widely, but differentially, expressed in adult chicken tissues. Taken together, our data establishes a clear molecular basis to uncover the physiological/pathological roles of EDN-EDNR system in birds and helps to reveal the conserved actions of EDN-EDNR signaling across vertebrates.

A Review of the Actions of Endogenous and Exogenous Vasoactive Substances during the Estrous Cycle and Pregnancy in Rats

Vascular endothelium plays a key role in regulating cardiovascular homeostasis by controlling the vascular tone. Variations in sex hormones during the reproductive cycle of females affect the homeostasis of the cardiovascular system. Also, the evidence shows that estrogens show a cardioprotective effect. On this basis, this study describes some vascular responses induced by vasoactive substances during the estrous cycle in rats. We obtained the information available on this topic from the online databases that included scientific articles published in the Web of Science, PubMed, and Scielo. Many investigations have evaluated the vasoactive response of substances such as acetylcholine and norepinephrine during the estrous cycle. In this review, we specifically described the vascular response to vasoactive substances in rats during the estrous cycle, pregnancy, and in ovariectomized rats. In addition, we discussed the existence of different signaling pathways that modulate vascular function. The knowledge of these effects is relevant for the optimization and development of new treatments for some vascular pathologies.

Androgens drive microvascular endothelial dysfunction in women with polycystic ovary syndrome: role of the endothelin B receptor

KEY POINTS

Polycystic ovary syndrome (PCOS) is a complex syndrome with cardiovascular risk factors, including obesity and insulin resistance. PCOS is also associated with high androgens, increases the risk of cardiovascular dysfunction in women. Due to the complexity of PCOS, had it has been challenging to isolate specific causes of the cardiovascular dysfunction. Our measure of cardiovascular dysfunction (endothelial dysfunction) was most profound in lean women with PCOS. The endothelin-1-induced vasodilation in these PCOS subject, was dependent on the ET_B R but was not NO-dependent. We also demonstrated oestrogen administration improved endothelial function in lean and obese women with PCOS likely because oestrogen increased NO availability. Our studies indicate a primary role for androgens in cardiovascular dysfunction in PCOS.

ABSTRACT

Endothelin-1 (ET-1) is an indicator of endothelial injury and dysfunction and is elevated in women with androgen excess polycystic ovary syndrome (AE-PCOS). The endothelin B receptor (ET_B R) subtype mediates vasodilatation, but is blunted in women with PCOS. We hypothesized that androgen drives endothelial dysfunction in AE-PCOS women and oestradiol (EE) administration reverses these effects. We assessed microvascular endothelial function in women with (7 lean and 7 obese) and without AE-PCOS (controls, 6 lean, 7 obese). Only obese AE-PCOS women were insulin resistant (IR). We evaluated cutaneous vascular conductance (%CVC_max ) with laser Doppler flowmetry during low dose intradermal microdialysis ET-1 perfusions (1, 3, 4, 5 and 7 pmol) with either lactated Ringer solution alone, or with ET_B R (BQ-788), or nitric oxide (NO) inhibition (l-NAME). Log[ET-1]-%maxCVC dose-response curves demonstrated reduced vasodilatory responses to ET-1 in lean AE-PCOS (logED₅₀ , 0.59 ± 0.08) versus lean controls (logED₅₀ , 0.49 ± 0.09, P < 0.05), but not compared to obese AE-PCOS (logED₅₀ , 0.65 ± 0.09). ET_B R inhibition decreased ET-1-induced vasodilatation in AE-PCOS women (logED₅₀ , 0.64 ± 0. 22, P < 0.05). This was mechanistically observed at the cellular level, with ET-1-induced, DAF-FM-measurable endothelial cell NO production, which was abrogated by dihydrotestosterone in an androgen receptor-dependent manner. EE augmented the cutaneous vasodilating response to ET-1(logED₅₀ 0.29 ± 0.21, 0.47 ± 0.09, P < 0.05 for lean and obese, respectively). Androgens drive endothelial dysfunction in lean and obese AE-PCOS. We propose that the attenuated ET-1-induced vasodilatation in AE-PCOS is a consequence of androgen receptor-mediated, suppressed ET_B R-stimulated NO production, and is reversed with EE.

Expression of endothelin type B receptors in uterine artery smooth muscle cells from pregnant Guinea pigs

INTRODUCTION

It is well established that upregulation of endothelin type B (ET_B) receptors in vascular smooth muscle cells plays a role in pathophysiological artery remodeling as response to ischemia and atherosclerosis. This study aimed to investigate the ET_B receptors function and localization under normal physiological remodeling. Specifically, in the guinea pig uterine arteries during pregnancy.

METHODS

Uterine artery contractility was assessed with sarafotoxin 6c and endothelin-1 in wire-myography in uterine arteries from non-pregnant and pregnant guinea pigs at gestational day 37 ± 5. Localization of ET_B receptors, proliferation marker Ki-67, and SMC differentiation marker SM22α in uterine arteries were investigated with immunohistochemistry.

RESULTS

Uterine arteries from pregnant guinea pigs showed significantly increased ET_B receptor-mediated vasoconstriction compared to uterine arteries from non-pregnant and to coronary arteries from pregnant guinea pigs (p < 0.001), suggesting that ET_B-receptor upregulation in uterine artery SMCs is a normal physiological mechanism taking place during remodeling. Furthermore, uterine arteries from pregnant guinea pigs showed enhanced expression of ET_B receptors, high density of Ki-67 positive SMCs and sparse SM22α staining in SMCs localized in the outer layer of the vessel wall.

DISCUSSION

Our results suggest that ET_B receptors are expressed in dedifferentiated proliferating SMCs of uterine arteries in pregnant guinea pigs. This study provides novel insight into the function and expression of ET_B receptors in uterine vascular remodeling during pregnancy.

Identification of New Potential Therapies for Colitis Amelioration Using an Appendicitis-Appendectomy Model

The appendix contains copious lymphoid tissue and is constantly exposed to gut flora. Appendicitis followed by appendectomy (AA), when done at a young age, prevents or significantly ameliorates inflammatory bowel diseases (IBDs) in later life. Inflammatory bowel disease comprises Crohn's disease and ulcerative colitis. Our unique murine AA model is the only existing experimental model of AA. Herein, the appendiceal pathology closely resembles the pathological features of human appendicitis. Our AA model protects against experimental colitis in an age-, bacteria- and antigen-dependent manner. Appendicitis-appendectomy performed in the most proximal colon curbs T helper 17 (Th17) cell activity, diminishes autophagy, modulates interferon activity-associated molecules, and suppresses endothelin vasoactivity-mediated immunopathology in the most distal colon. These changes induced by AA contribute to limiting colitis pathology. Manipulating and modulating various aspects of these pathways, pathophysiology, and molecular interactions will assist the development of novel therapeutic options to manage IBD. Competitive inhibition of the Th17 cell recruitment factor CCL20 or the chemokine CCL17 with antibodies, combinatorial peptides, or small molecules may limit colitic pathology. The chemokines CCL5 and CXCL11 could be investigated as potential therapies. Inhibition of the autophagy-associated molecules VPS15, LAMP2, LC3A, XBP1, or ULK1 may decrease colitic pathology. Curtailing endothelin-activity may decrease colitic impact. The antiproliferative, immunomodulatory molecules IFIT1, IFIT2, IFIT3, and IFI44 may have direct therapeutic value in ameliorating colitis. The molecules IRF4, IRF8, IRF2BP1, IFRD1, and IFRD2 are potentially good target molecules to competitively inhibit towards curbing colitis.

Thick Ascending Limb Sodium Transport in the Pathogenesis of Hypertension

The thick ascending limb plays a key role in maintaining water and electrolyte balance. The importance of this segment in regulating blood pressure is evidenced by the effect of loop diuretics or local genetic defects on this parameter. Hormones and factors produced by thick ascending limbs have both autocrine and paracrine effects, which can extend prohypertensive signaling to other structures of the nephron. In this review, we discuss the role of the thick ascending limb in the development of hypertension, not as a sole participant, but one that works within the rich biological context of the renal medulla. We first provide an overview of the basic physiology of the segment and the anatomical considerations necessary to understand its relationship with other renal structures. We explore the physiopathological changes in thick ascending limbs occurring in both genetic and induced animal models of hypertension. We then discuss the racial differences and genetic defects that affect blood pressure in humans through changes in thick ascending limb transport rates. Throughout the text, we scrutinize methodologies and discuss the limitations of research techniques that, when overlooked, can lead investigators to make erroneous conclusions. Thus, in addition to advancing an understanding of the basic mechanisms of physiology, the ultimate goal of this work is to understand our research tools, to make better use of them, and to contextualize research data. Future advances in renal hypertension research will require not only collection of new experimental data, but also integration of our current knowledge.

Targeting Endothelin-1 Receptor/β-Arrestin-1 Axis in Ovarian Cancer: From Basic Research to a Therapeutic Approach

Recent studies imply a key role of endothelin-1 receptor (ET-1R), belonging to the largest family of G protein-coupled receptors (GPCR), in the regulation of a plethora of processes involved in tumorigenesis and metastatic progression. β-arrestin-1 (β-arr1) system has been recognized as a critical hub controlling GPCR signaling network, directing the GPCR's biological outcomes. In ovarian cancer, ET-1R/β-arr1 axis enables cancer cells to engage several integrated signaling, and represents an actionable target for developing novel therapeutic approaches. Preclinical research studies demonstrate that ET-1R blockade by the approved dual ET_AR/ET_BR antagonist macitentan counteracts β-arr1-mediated signaling network, and hampers the dialogue among cancer cells and the tumor microenvironment, interfering with metastatic progression and drug response. In light of major developments in the ET-1R signaling paradigm, this review article discusses the emerging evidence of the dual ET-1R antagonist treatment in cancer, and outlines our challenge in preclinical studies warranting the repurposing of ET-1R antagonists for the design of more effective clinical trials based on combinatorial therapies to overcome, or prevent, the onset of drug resistance.

Endothelins and Sarafotoxins: Peptides of Similar Structure and Different Function

Endothelins are endogenous vasoactive peptides that are considered among the most potent vasoconstrictor substances known. In addition to their vascular effects, endothelins and their receptors have been shown to be present in many organs and share plenty physiological and pathophysiological functions. Sarafotoxins are natural substances from the venom of snakes genus Atractaspis, structurally and pharmacologically near to endothelins. The current minireview focuses on the chemical and molecular aspects of endothelins and sarafotoxins, and their receptors in physiological and pathophysiological processes.

Endothelin and the heart in health and diseases

Endothelin-1 (ET-1), a 21-amino acid peptide, was initially identified in 1988 as a potent vasoconstrictor and pressor substance isolated from the culture supernatant of porcine aortic endothelial cells. From human genomic DNA analysis, two other family peptides, ET-2 and ET-3, were found. They showed different effects and distribution, suggesting that each peptide may play separate roles in different organs. In the heart, ET-1 also causes positive inotropic and chronotropic responses and hypertrophic activity of the cardiomyocytes. ETs act via activation of two receptor subtypes, ET_A and ET_B receptors, both of which are coupled to various GTP-binding proteins depending on cell types. Endogenous ET-1 may be involved in progression of various cardiovascular diseases. ET antagonists are currently used clinically in the treatment for patients with pulmonary hypertension, and are considered to have further target diseases as heart failure, cardiac hypertrophy and other cardiac diseases, renal diseases, systemic hypertension, and cerebral vasospasm.

Maternal high-fat diet programs cerebrovascular remodeling in adult rat offspring

Maternal environmental factors such as diet have consequences on later health of the offspring. We found that maternal high-fat diet (HFD) exposure renders adult offspring brain more susceptible to ischemic injury. The present study was further to investigate whether HFD consumption during rat pregnancy and lactation influences the cerebral vasculature in adult male offspring. Besides the endothelial damage observed in the transmission electron microscopy, the MCAs of offspring from fat-fed dams fed with control diet (HFD/C) also displayed increased wall thickness and media/lumen ratio, suggesting that cerebrovascular hypertrophy or hyperplasia occurs. Moreover, smaller lumen diameter and elevated myogenic tone of the MCAs over a range of intralumenal pressures indicate inward cerebrovascular remodeling in HFD/C rats, with a concomitant increase in vessel stiffness. More importantly, both wire and pressure myography demonstrated that maternal HFD intake also enhanced the MCAs contractility to ET-1, accompanied by increases in ET types A receptor (ET_AR) but not B (ET_BR) density in the arteries. Furthermore, ET_AR antagonism but not ET_BR antagonism restored maternal HFD-induced cerebrovascular dysfunction in adult offspring. Taken together, maternal diet can substantially influence adult offspring cerebrovascular health, through remodeling of both structure and function, at least partially in an ET-1 manner.

Clinicopathological Significance of the ET Axis in Human Oral Squamous Cell Carcinoma

The interaction between cancer cells and the surrounding microenvironment in malignant tumor tissue is known to be closely associated with cancer cell invasion and proliferation. Endothelin (ET) present in the microenvironment surrounding tumors has been reported to play a role in cancer cell invasion and proliferation by binding to receptors on the cell membrane of cancer cells. Here, we immunohistologically detected the expression of ET-1 and its receptor ET_AR in oral squamous cell carcinoma (OSCC) and evaluated the association between the expression of each as well as their co-expression (ET-axis expression) and clinicopathological factors. A significant difference was observed between the invasion pattern as a parameter of cancer cell malignancy and the expressions of ET-1 and ET_AR. The survival rates were significantly lower among the patients who were strongly positive for ET-1 and the ET_AR-positive patients compared to negative patients. There was also a significant difference between ET-axis expression and the degree of histological differentiation and mode of invasion, and the survival rate of the positive cases was significantly lower than that of the negative cases. Our findings suggested that ET-axis assessments are important for assessing the malignancy of cancer cells and predicting the prognoses of OSCC patients.

The C9ORF72 Gene, Implicated in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia, Encodes a Protein That Functions in Control of Endothelin and Glutamate Signaling

A GGGGCC repeat expansion in the C9ORF72 (C9) gene is the most common known cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Several mechanisms have been proposed to account for its toxicity, including the possibility that reduced C9 protein levels contribute to disease. To investigate this possibility, we examined the effects of reduced C9 levels in several cell systems. We first showed that C9 knockdown (KD) in U87 glioblastoma cells results in striking morphological changes, including vacuolization and alterations in cell size. Unexpectedly, RNA analysis revealed changes in expression of many genes, including genes involved in endothelin (EDN) signaling and immune system pathways and multiple glutamate cycling genes (e.g., EAAT2), which were verified in several cell models, including astrocytes and brain samples from C9-positive patients. Consistent with deregulation of the glutamate cycling genes, elevated intracellular glutamate was detected in both KD cells and patient astrocytes. Importantly, levels of mRNAs encoding EDN1 and its receptors, known to be elevated in ALS, were sharply increased by C9 KD, likely resulting from an observed activation of NF-κB signaling and/or a possible role of a C9 isoform in gene control.

A novel neuroregenerative approach using ET(B) receptor agonist, IRL-1620, to treat CNS disorders

Endothelin B (ET(B)) receptors present in abundance the central nervous system (CNS) have been shown to have significant implications in its development and neurogenesis. We have targeted ET(B) receptors stimulation using a highly specific agonist, IRL-1620, to treat CNS disorders. In a rat model of cerebral ischemia intravenous administration IRL-1620 significantly reduced infarct volume and improved neurological and motor functions compared to control. This improvement, in part, is due to an increase in neuroregeneration. We also investigated the role of IRL-1620 in animal models of Alzheimer's disease (AD). IRL-1620 improved learning and memory, reduced oxidative stress and increased VEGF and NGF in Abeta treated rats. IRL-1620 also improved learning and memory in an aged APP/PS1 transgenic mouse model of AD. These promising findings prompted us to initiate human studies. Successful chemistry, manufacturing and control along with mice, rat and dog toxicological studies led to completion of a human Phase I study in healthy volunteers. We found that a dose of 0.6 microg/kg of IRL-1620 can be safely administered, three times every four hours, without any adverse effect. A Phase II clinical study with IRL-1620 has been initiated in patients with cerebral ischemia and mild to moderate AD.

Interaction between platelets and endothelium: from pathophysiology to new therapeutic options

Platelets were traditionally considered to purely have a role in the maintenance of haemostasis. Recently their role in vasomotor function, inflammation and atherosclerosis has been very well-recognized. Endothelium which was originally considered as a simple passive barrier, it is now viewed as an organ whose normal functioning is crucial for maintaining vascular health. When endothelial balance is disturbed, vascular disease initiates. Platelet interactions with endothelium have an important contribution in this process. Low-grade inflammation, endothelial dysfunction, and platelet hyper-reactivity are all independently associated with an increased risk of cardiovascular events. Older antiplatelet agents like aspirin and clopidogrel and newer more potent agents like prasugrel and ticagrelor have been proven effective in all the clinical spectrum of coronary artery disease patients. Current antiplatelet medications and especially newer generation P2Y12 inhibitor ticagrelor, offer clinical benefits not only due to their well-recognized antithrombotic effect, but also via the attenuation of platelet inflammatory action, impediment of P2Y12 activation effects in other cells and through other complex and sometimes undefined pathways. Future research is expected to better define platelet-endothelium interactions and the multiple impact of current antiplatelet therapy on them.

Pharmacological Potential of Endothelin Receptors Agonists and Antagonists

Endothelins are potent predominantly vasoconstricting agents that act as local autocrine and paracrine mediators. Endothelin-1 is the most potent and sustained vasoconstrictor and pressor substance yet identified. Abnormalities of the endothelin system occur in a range of diseases associated with vasoconstriction, vasospasm, and vascular hypertrophy. ET receptor antagonists were until recently regarded as drugs of great promise in patients with congestive heart failure, pulmonary hypertension and others. The aim of this article is a survey of compounds that affect the endothelin receptors and clinical trials with these agents.

News from the endothelin-3/EDNRB signaling pathway: Role during enteric nervous system development and involvement in neural crest-associated disorders

The endothelin system is a vertebrate-specific innovation with important roles in regulating the cardiovascular system and renal and pulmonary processes, as well as the development of the vertebrate-specific neural crest cell population and its derivatives. This system is comprised of three structurally similar 21-amino acid peptides that bind and activate two G-protein coupled receptors. In 1994, knockouts of the Edn3 and Ednrb genes revealed their crucial function during development of the enteric nervous system and melanocytes, two neural-crest derivatives. Since then, human and mouse genetics, combined with cellular and developmental studies, have helped to unravel the role of this signaling pathway during development and adulthood. In this review, we will summarize the known functions of the EDN3/EDNRB pathway during neural crest development, with a specific focus on recent scientific advances, and the enteric nervous system in normal and pathological conditions.

Retrobulbar hemodynamics and aqueous humor levels of endothelin-1 in exfoliation syndrome and exfoliation glaucoma

Background

Endothelin-1 (ET-1) is the most potent vasoconstrictor in the body. There are reports in the literature correlating plasma levels of ET-1 and its impact on retrobulbar hemodynamics. This study evaluates aqueous humor levels of ET-1 and retrobulbar hemodynamics in patients with exfoliation syndrome (XFS) and exfoliation glaucoma (XFG).

Patients and methods

Patients scheduled for cataract surgery were included. Patients were allocated to non-exfoliation non-glaucoma group (controls), XFG and XFS groups. Peak systolic velocity (PSV), end diastolic velocity, and resistivity index of the ophthalmic artery (OA), short posterior ciliary arteries, and central retinal artery (CRA) were determined preoperatively using color Doppler imaging. Aqueous humor samples obtained at the beginning of cataract surgery were analyzed with enzyme-linked immunosorbent assay.

Results

Sixty-nine participants of similar age were included (controls: n=24, XFG: n=22, XFS: n=23). Multiple regression analysis showed that ET-1, OA-PSV, OA-resistivity index, CRA-PSV, and CRA-end diastolic velocity were influenced by group but not by sex or age. ET-1 for the XFG group (15.93±2.8 pg/mL) was significantly higher than for the XFS (8.92±2.7 pg/mL) and control (8.44±2.6 pg/mL) groups. The difference in ET-1 titers between the control and XFS groups was not statistically significant. All four hemodynamic parameters affected by group status significantly correlated with ET-1 levels in eyes with XFS. In eyes with XFG, two of the four hemodynamic parameters significantly correlated with ET-1 levels. In control eyes, no correlation between ET-1 and hemodynamic parameters affected by group status was detected.

Conclusion

ET-1 aqueous levels in eyes with XFG were significantly higher than those of age-matched controls. Reduced blood flow and increased vascular resistivity were detected in the OA and the CRA in eyes with XFG/XFS. ET-1 levels in eyes with XFG/XFS exhibit a significant correlation with hemodynamic parameters that indicate reduced perfusion.

Maternal cardiovascular and endothelial function from first trimester to postpartum

Objective

To explore noninvasively the complex interactions of the maternal hemodynamic system throughout pregnancy and the resulting after-effect six weeks postpartum.

Methods

Eighteen women were tested beginning at the 12^th week of gestation at six time-points throughout pregnancy and six weeks postpartum. Heart rate, heart rate variability, blood pressure, pulse transit time (PTT), respiration, and baroreceptor sensitivity were analyzed in resting conditions. Additionally, hemoglobin, asymmetric and symmetric dimethylarginine and Endothelin (ET-1) were obtained.

Results

Heart rate and sympathovagal balance favoring sympathetic drive increased, the vagal tone and the baroreflex sensitivity decreased during pregnancy. Relative sympathetic drive (sympathovagal balance) reached a maximum at 6 weeks postpartum whereas the other variables did not differ compared to first trimester levels. Postpartum diastolic blood pressure was higher compared to first and second trimester. Pulse transit time and endothelial markers showed no difference throughout gestation. However, opposing variables PTT and asymmetric dimethylarginine (ADMA) were both higher six weeks postpartum.

Conclusions

The sympathetic up regulation throughout pregnancy goes hand in hand with a decreased baroreflex sensitivity. In the postpartum period, the autonomic nervous system, biochemical endothelial reactions and PTT show significant and opposing changes compared to pregnancy findings, indicating the complex aftermath of the increase of blood volume, the changes in perfusion strategies and blood pressure regulation that occur in pregnancy.

Endothelial cells and endothelin‑1 promote the odontogenic differentiation of dental pulp stem cells

It has been established that dental pulp stem cells (DPSCs) serve an important role in the restoration and regeneration of dental tissues. DPSCs are present in blood vessels and also exist in the vessel microenvironment in vivo and have a close association with endothelial cells (ECs). The present study aimed to evaluate the influence of ECs and their secretory product endothelin-1 (ET-1) on the differentiation of DPSCs. In the present study, cells were divided into four groups: i) a DPSC-only control group; ii) a DPSC with ET-1 administration group; iii) a DPSC and human umbilical vein endothelial cell (HUVEC) direct co-culture group; and iv) a DPSC and HUVEC indirect co-culture group using a Transwell system. Reverse transcription-quantitative polymerase chain reaction was used to detect the expression of the odontoblastic differentiation-associated genes, including dentin sialoprotein (DSP) and dentin matrix acidic phosphoprotein 1 (DMP-1) at days 4, 7, 14 and 21. Alizarin Red S staining, immunofluorescence and western blot analyses were also conducted to assess the differentiation of the DPSCs in each group. The highest expression levels of odontoblastic differentiation-associated genes were observed on day 7 and in the two co-culture groups were increased compared with the DPSC-only and DPSC + ET-1 culture groups at all four time points. However, expression levels in the DPSC + ET-1 group were not downregulated as notably as in the co-culture groups on days 14 and 21. The Transwell group exhibited the greatest ability for odontoblastic differentiation compared with the other groups according to staining with Alizarin Red S, immunofluorescence and western blot analysis results. According to the results of the present study, the culture solution with HUVECs affected the differentiation of DPSCs. In addition, ET-1 may promote the odontoblastic differentiation of DPSCs.

Endothelin A Receptors Expressed in Renal Blood Vessels of Renal Transplant Patients Are Connected With Acute Tubular Necrosis or Antibody-Mediated Rejection

BACKGROUND

The role of non-HLA antibodies named antiendothelin A receptor antibodies is potentially significant but not established. The significance of the endothelin A receptor (ETAR) and its expression in renal biopsy has not been defined. We decided to evaluate the presence and relevance of ETARs in renal transplant biopsy for cause. The aim of our study was to evaluate the immunoreactivity of the ETAR and its significance in patients who had a renal transplant biopsy due to deterioration of transplant function (biopsy for cause) with detailed characterization of staining in small and intermediate arteries of renal transplant biopsies.

METHODS

Immunohistochemical expression of ETARs was analyzed in 162 renal transplant biopsies. Microscopic evaluation of ETAR expression (polyclonal antibody) was performed on paraffin sections. ETAR expression was analyzed in renal blood vessels (small and intermediate arteries) based on three-step scale.

RESULTS

We analyzed 154 patients who had renal allograft biopsy between 6 days and 24 years (median 597 days) after transplantation. Positive staining of ETAR in small and intermediate arteries was noticed in 9 patients. Among these patients, 4 had early biopsies (<3 months after transplantation), all developed acute tubular necrosis, and 1 developed additionally acute humoral rejection. Further, 4 patients had late biopsy (1-8 years after transplantation) and all developed characteristics of antibody mediated rejection. Lastly, 1 patient had no characteristic changes in the biopsy 4 months after transplantation. Graft loss 1 year after biopsy was higher in patients who were ETAR-positive but statistical significance was not achieved.

CONCLUSIONS

The expression of endothelin receptors in renal blood vessels (small and intermediate arteries) seems to be important in diagnosis of damage during acute tubular necrosis and antibody-mediated rejection.

A potential regulatory region near the EDN3 gene may control both harness racing performance and coat color variation in horses

The Swedish-Norwegian Coldblooded trotter and the heavier North-Swedish draught horse both descend from the North-Swedish horse, but the Coldblooded trotters have been selected for racing performance while the North-Swedish draught horse is mainly used for agricultural and forestry work. By comparing the genomes of Coldblooded trotters, North-Swedish draught horses and Standardbreds for a large number of single-nucleotide polymorphisms (SNPs), the aim of the study was to identify genetic regions that may be under selection for racing performance. We hypothesized that the selection for racing performance, in combination with unauthorized crossbreeding of Coldblooded trotters and Standardbreds, has created regions in the genome where the Coldblooded trotters and Standardbreds are similar, but differ from the North-Swedish draught horse. A fixation index (Fst) analysis was performed and sliding window Delta Fst values were calculated across the three breeds. Five windows, where the average Fst between Coldblooded trotters and Standardbreds was low and the average Fst between Coldblooded trotters and North-Swedish draught horses was high, were selected for further investigation. Associations between the most highly ranked SNPs and harness racing performance were analyzed in 400 raced Coldblooded trotters with race records. One SNP showed a significant association with racing performance, with the CC genotype appearing to be negatively associated. The SNP identified was genotyped in 1915 horses of 18 different breeds. The frequency of the TT genotype was high in breeds typically used for racing and show jumping while the frequency of the CC genotype was high in most pony breeds and draught horses. The closest gene in this region was the Endothelin3 gene (EDN3), a gene mainly involved in melanocyte and enteric neuron development. Both functional genetic and physiological studies are needed to fully understand the possible impacts of the gene on racing performance.

Cardiomyokines from the heart

The heart is regarded as an endocrine organ as well as a pump for circulation, since atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were discovered in cardiomyocytes to be secreted as hormones. Both ANP and BNP bind to their receptors expressed on remote organs, such as kidneys and blood vessels; therefore, the heart controls the circulation by pumping blood and by secreting endocrine peptides. Cardiomyocytes secrete other peptides besides natriuretic peptides. Although most of such cardiomyocyte-derived peptides act on the heart in autocrine/paracrine fashions, several peptides target remote organs. In this review, to overview current knowledge of endocrine properties of the heart, we focus on cardiomyocyte-derived peptides (cardiomyokines) that act on the remote organs as well as the heart. Cardiomyokines act on remote organs to regulate cardiovascular homeostasis, systemic metabolism, and inflammation. Therefore, through its endocrine function, the heart can maintain physiological conditions and prevent organ damage under pathological conditions.

Multiple signaling pathways convey central and peripheral signals to regulate pituitary function: Lessons from human and non-human primate models

The anterior pituitary gland is a key organ involved in the control of multiple physiological functions including growth, reproduction, metabolism and stress. These functions are controlled by five distinct hormone-producing pituitary cell types that produce growth hormone (somatotropes), prolactin (lactotropes), adrenocorticotropin (corticotropes), thyrotropin (thyrotropes) and follicle stimulating hormone/luteinizing hormone (gonadotropes). Classically, the synthesis and release of pituitary hormones was thought to be primarily regulated by central (neuroendocrine) signals. However, it is now becoming apparent that factors produced by pituitary hormone targets (endocrine and non-endocrine organs) can feedback directly to the pituitary to adjust pituitary hormone synthesis and release. Therefore, pituitary cells serve as sensors to integrate central and peripheral signals in order to fine-tune whole-body homeostasis, although it is clear that pituitary cell regulation is species-, age- and sex-dependent. The purpose of this review is to provide a comprehensive, general overview of our current knowledge of both central and peripheral regulators of pituitary cell function and associated intracellular mechanisms, focusing on human and non-human primates.

Pulmonary vascular development in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a rare congenital anomaly characterised by a diaphragmatic defect, persistent pulmonary hypertension (PH) and lung hypoplasia. The relative contribution of these three elements can vary considerably in individual patients. Most affected children suffer primarily from the associated PH, for which the therapeutic modalities are limited and frequently not evidence based. The vascular defects associated with PH, which is characterised by increased muscularisation of arterioles and capillaries, start to develop early in gestation. Pulmonary vascular development is integrated with the development of the airway epithelium. Although our knowledge is still incomplete, the processes involved in the growth and expansion of the vasculature are beginning to be unravelled. It is clear that early disturbances of this process lead to major pulmonary growth abnormalities, resulting in serious clinical challenges and in many cases death in the newborn. Here we provide an overview of the current molecular pathways involved in pulmonary vascular development. Moreover, we describe the abnormalities associated with CDH and the potential therapeutic approaches for this severe abnormality.

The Role of Big Endothelin-1 in Colorectal Cancer

Introduction

Changes in liver blood flow caused by an unknown splanchnic vasoconstrictor have been noted in colorectal cancer patients with liver metastases. This prospective study was performed to assess whether plasma levels of big endothelin-1 (big ET-1) were raised in patients with colorectal cancer.

Methods

Plasma samples from peripheral vein of patients who underwent surgery for primary colorectal cancer (n=60) and those with known colorectal liver metastases (n=45) for a period of 15 months were taken prior to treatment and compared to age- and sex-matched controls (n=20). Plasma samples were analysed by using a single-step sandwich enzyme immunoassay. Immunohistochemistry and in situ hybridisation were also performed on tumour sections to investigate the expression of ET-1 by cancer cells.

Results

The median (range) plasma concentration of big ET-1 in controls was 2.1 pg/mL (1.2–13.4 pg/mL). The median (range) plasma concentration of big ET-1 in colorectal cancer patients with no overt hepatic metastases was 3.8 pg/mL (1.2–15.8 pg/mL), p=0.002, and the median (range) plasma concentration of big ET-1 in colorectal cancer patients with hepatic metastases was 5.2 pg/mL (1.7–30 pg/mL), p=0.0001; both were significantly elevated compared to the control group. A significant difference in immunostaining for big ET-1 was noted between paired normal colonic mucosa (median score-1) and tumour sections (median score-3), p=0.01.

Conclusion

This study has demonstrated elevated concentrations of big ET-1 in colorectal cancer patients, especially in those with hepatic metastases. Upregulation of ET activity in colorectal cancer could be inferred by the increased immunostaining of big ET-1 in cancer cells. Therefore, plasma big ET-1 levels should be evaluated as a potential tumour marker for the identification of hepatic metastases at an earlier stage.

Prognostic Significance of Elevated Endothelin-1 Levels in Patients with Colorectal Cancer

Background

Prognostic factors from clinical, laboratory and pathological data of patients with colorectal cancer are essential to identify high-risk groups to whom beneficial adjuvant therapy could be given. Endothelin-1, a growth factor, has been associated with the development and spread of solid tumours. This prospective study was performed to determine whether preoperative plasma big ET-1 levels might be useful as a prognostic indicator in patients with colorectal carcinoma.

Method

Sixty-five consecutive patients with colorectal cancer confirmed by biopsy were included prospectively into this study over a 12-month period. Plasma samples from a peripheral vein were obtained prior to surgery. Univariate analysis of survival using age (< or > 70 years), sex, Dukes’ stage (A&B versus C), tumour size (< or > 50 mm), vascular invasion and plasma big ET-1 levels was performed and significant factors were then analysed with the Cox regression model.

Results

Three variables, age, Dukes’ tumour stage and plasma big ET-1 levels, were found to have prognostic significance (p<0.05). Factors associated with a poorer prognosis were age >70 years (p=0.02), Dukes’ C tumours (p=0.04) and plasma big ET-1 levels >4.2 pg/mL (p=0.02). The Cox regression model identified the same three variables as having independent prognostic value for overall survival.

Conclusion

Preoperative plasma big ET-1 levels may be useful in predicting overall survival in patients with colorectal cancer. Plasma big ET-1 levels may be useful in the selection of high-risk lymph node-negative patients with colorectal cancer for adjuvant therapy.

Endothelin-1 is a Novel Prognostic Factor in Non-Small Cell Lung Cancer

Endothelin-1 (ET-1) is a potent vasoactive peptide and a hypoxia-inducible angiogenic growth factor associated with the development and growth of solid tumours. This study evaluated the expression of big endothelin-1 (big ET-1), a stable precursor of ET-1, and ET-1 in non-small cell lung cancer (NSCLC). Big ET-1 expression was evaluated in paraffin-embedded tissue sections from 10 NSCLC tumours using immunohistochemistry and in situ hybridisation. The production of big ET-1 and ET-1 was studied in six established NSCLC cell lines. The plasma concentrations of big ET-1 were measured in 30 patients with proven NSCLC prior to chemotherapy by means of a sandwich enzyme-linked immunoassay and compared to levels in 20 normal controls. Big ET-1 immunostaining was detected in the cancer cells of all tumours studied. Using in situ hybridisation, tumour cell big ET-1 mRNA expression was demonstrated in all samples. All six NSCLC cell lines expressed ET-1, with big ET-1 being detected in three. The median big ET-1 plasma level in patients with NSCLC was 5.4 pg/mL (range 0–22.7 pg/mL) and was significantly elevated compared to median big ET-1 plasma levels in controls, 2.1 pg/mL (1.2–13.4 pg/mL) (p=0.0001). Furthermore, patients with plasma big ET-1 levels above the normal range (upper tertile) had a worse outcome (p=0.01). In conclusion, big ET-1/ET-1 is expressed by resected NSCLC specimens and tumour cell lines. Plasma big ET-1 levels are elevated in NSCLC patients compared to controls with levels >7.8 pg/mL being associated with a worse outcome. The development of selective ET-1 antagonists such as Atrasentan indicates that ET-1 may be a therapeutic target in NSCLC.

miR-210 and GPD1L regulate EDN2 in primary and immortalized human granulosa-lutein cells

Endothelin-2 (EDN2), expressed at a narrow window during the periovulatory period, critically affects ovulation and corpus luteum (CL) formation. LH (acting mainly via cAMP) and hypoxia are implicated in CL formation; therefore, we aimed to elucidate how these signals regulate EDN2 using human primary (hGLCs) and immortalized (SVOG) granulosa-lutein cells. The hypoxiamiR, microRNA-210 (miR-210) was identified as a new essential player in EDN2 expression. Hypoxia (either mimetic compound-CoCl₂, or low O₂) elevated hypoxia-inducible factor 1A (HIF1A), miR-210 and EDN2 Hypoxia-induced miR-210 was suppressed in HIF1A-silenced SVOG cells, suggesting that miR-210 is HIF1A dependent. Elevated miR-210 levels in hypoxia or by miR-210 overexpression, increased EDN2 Conversely, miR-210 inhibition reduced EDN2 levels, even in the presence of CoCl₂, indicating the importance of miR-210 in the hypoxic induction of EDN2 A molecule that destabilizes HIF1A protein, glycerol-3-phosphate dehydrogenase 1-like gene-GPD1L, was established as a miR-210 target in both cell types. It was decreased by miR-210-mimic and was increased by miR-inhibitor. Furthermore, reducing GPD1L by endogenously elevated miR-210 (in hypoxia), miR-210-mimic or by GPD1L siRNA resulted in elevated HIF1A protein and EDN2 levels, implying a vital role for GPD1L in the hypoxic induction of EDN2 Under normoxic conditions, forskolin (adenylyl cyclase activator) triggered changes typical of hypoxia. It elevated HIF1A, EDN2 and miR-210 while inhibiting GPD1L Furthermore, HIF1A silencing greatly reduced forskolin's ability to elevate EDN2 and miR-210. This study highlights the novel regulatory roles of miR-210 and its gene target, GPD1L, in hypoxia and cAMP-induced EDN2 by human granulosa-lutein cells.

Physiology of blood pressure relevant to managing hypertension in pregnancy

PURPOSE

Pregnancy causes physiological changes in maternal organ systems, and blood pressure (BP) is one of the variables affected. This review is focusing on the physiology of BP relevant to the management of hypertension in pregnancy.

MATERIALS AND METHODS

A detailed literature search was performed using electronic databases (including WorldCat, PubMed, MEDLINE, Google Scholar) to retrieve and review reports related to physiology of BP in pregnancy.

RESULTS

During pregnancy, there is vasodilation caused by mediators such as increased levels of progesterone and nitric oxide. The vasodilation leads to a reduction in vascular resistance, BP, and renal blood flow. In compensation, the following postulated events occur: activation of renin-angiotensin-aldosterone axis, resetting of osmotic threshold for thirst, and an increase in the production of vasopressin. Sodium and water conservation ensue to increase the total body water, end-diastolic volume, cardiac output, and BP. The increase in cardiac output incompletely compensates for the decreased vascular resistance, and BP therefore decreases in midpregnancy and returns to prepregnancy level toward term.

CONCLUSIONS

An understanding of the physiological changes in BP is essential for appropriate management of pregnancy-related hypertension.

Biomarkers in Pulmonary Vascular Disease: Gauging Response to Therapy

Biomarkers are increasingly being investigated in the treatment of pulmonary vascular disease. In particular, the signaling pathways targeted by therapies for pulmonary arterial hypertension provide biomarkers that potentially can be used to guide therapy and to assess clinical response as an alternative to invasive procedures such as right-sided cardiac catheterization. Moreover, the growing use of combination therapy for both the initial and subsequent treatment of pulmonary arterial hypertension highlights the need for biomarkers in this treatment approach. Currently approved therapies for pulmonary arterial hypertension target 3 major signaling pathways: the nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate pathway, the endothelin pathway, and the prostacyclin pathway. Although the main biomarker used in practice and evaluated in clinical trials is N-terminal pro-brain natriuretic peptide, other putative biomarkers include the endogenous nitric oxide (NO) synthase inhibitor asymmetric dimethylarginine, NO metabolites including S-nitrosothiols and nitrite, exhaled NO, endothelins, cyclic guanosine monophosphate, cyclic adenosine monophosphate, and atrial natriuretic peptide. This review describes accessible biomarkers, related to the actual molecules targeted by current therapies, for measuring and predicting response to the individual pulmonary arterial hypertension treatment classes as well as combination therapy.

Anti-hypertensive and cardioprotective effects of a novel apitherapy formulation via upregulation of peroxisome proliferator-activated receptor-α and -γ in spontaneous hypertensive rats

Ventricular remodeling is associated with many heart diseases, and ventricular remodeling induced by hypertension can be fatal independent of hypertension. In this study, we prepared a novel apitherapy formulation, designated Bao-Yuan-Ling (BYL), which contained propolis, royal jelly, and bee venom, to treat spontaneous hypertensive rats (SHRs). We then evaluated the pharmacology of BYL and the potential mechanisms through which BYL affects hypertension and ventricular remodeling. We found that BYL treatment could reduce blood pressure in SHRs. Thereafter, we found that BYL treatment reduced serum levels of angiotensin II, endothelin 1, and transforming growth factor-β and improved the myocardial structure. Moreover, the results of quantitative real-time polymerase chain reaction indicated that BYL treatment could upregulate the mRNA expression of peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ. Thus, we could conclude that BYL had hypotensive and cardioprotective effects in SHRs, potentially through improvement of myocardial energy metabolism.

High endothelin-converting enzyme-1 expression independently predicts poor survival of patients with esophageal squamous cell carcinoma

Patients with esophageal squamous cell carcinoma have poor survival and high recurrence rate, thus an effective prognostic biomarker is needed. Endothelin-converting enzyme-1 is responsible for biosynthesis of endothelin-1, which promotes growth and invasion of human cancers. The role of endothelin-converting enzyme-1 in esophageal squamous cell carcinoma is still unknown. Therefore, this study investigated the significance of endothelin-converting enzyme-1 expression in esophageal squamous cell carcinoma clinically. We enrolled patients with esophageal squamous cell carcinoma who provided pretreated tumor tissues. Tumor endothelin-converting enzyme-1 expression was evaluated by immunohistochemistry and was defined as either low or high expression. Then we evaluated whether tumor endothelin-converting enzyme-1 expression had any association with clinicopathological findings or predicted survival of patients with esophageal squamous cell carcinoma. Overall, 54 of 99 patients with esophageal squamous cell carcinoma had high tumor endothelin-converting enzyme-1 expression, which was significantly associated with lymph node metastasis ( p = 0.04). In addition, tumor endothelin-converting enzyme-1 expression independently predicted survival of patients with esophageal squamous cell carcinoma, and the 5-year survival was poorer in patients with high tumor endothelin-converting enzyme-1 expression ( p = 0.016). Among patients with locally advanced and potentially resectable esophageal squamous cell carcinoma (stage II and III), 5-year survival was poorer with high tumor endothelin-converting enzyme-1 expression ( p = 0.003). High tumor endothelin-converting enzyme-1 expression also significantly predicted poorer survival of patients in this population. In patients with esophageal squamous cell carcinoma, high tumor endothelin-converting enzyme-1 expression might indicate high tumor invasive property. Therefore, tumor endothelin-converting enzyme-1 expression could be a good biomarker to identify patients with worse survival and higher risks of recurrence, who might benefit from the treatment by endothelin-converting enzyme-1 inhibitor.

Current status of the role of endothelins in regulating ovarian follicular function: A review

Endothelins (EDN) are a group of vasoactive 21 amino acid peptides reported to play roles in steroidogenesis, folliculogenesis, and ovulation. EDN1, EDN2 and EDN3 have all been shown to affect granulosa cell (GC) function in a variety of mammalians species. Herewithin, the role of EDN in regulating steroidogenesis and ovarian follicular development is reviewed, focusing on the localization and function of EDN and their receptors in ovarian follicular function emphasizing species differences. For example, in single ovulating species such as humans and cattle, in the presence of trophic hormones such as FSH and IGF1, EDN1 and EDN2 significantly inhibited GC estradiol production in 2 of 4 studies, while no effect was observed for GC progesterone production in 2 of 4 studies. In contrast, EDN1 exhibited inhibitory effects on progesterone production by GC in 3 of 3 studies in pigs and 3 of 4 studies in rats. Also, EDN1 inhibited GC estradiol production in 4 of 5 studies in rats. Altogether, these results indicate that EDN are produced by ovarian follicles and are involved in the regulation of steroidogenesis of GC of several mammalian species including humans, cattle, pigs and rats, but that these effects may vary with species and culture condition.

Biology of Microglia in the Developing Brain

Microglia exist in different morphological forms in the developing brain. They show a small cell body with scanty cytoplasm with many branching processes in the grey matter of the developing brain. However, in the white matter such as the corpus callosum where the unmyelinated axons are loosely organized, they appear in an amoeboid form having a round cell body endowed with copious cytoplasm rich in organelles. The amoeboid cells eventually transform into ramified microglia in the second postnatal week when the tissue becomes more compact with the onset of myelination. Microglia serve as immunocompetent macrophages that act as neuropathology sensors to detect and respond swiftly to subtle changes in the brain tissues in pathological conditions. Microglial functions are broadly considered as protective in the normal brain development as they phagocytose dead cells and sculpt neuronal connections by pruning excess axons and synapses. They also secrete a number of trophic factors such as insulin-like growth factor-1 and transforming growth factor-β among many others that are involved in neuronal and oligodendrocyte survival. On the other hand, microglial cells when activated produce a plethora of molecules such as proinflammatory cytokines, chemokines, reactive oxygen species, and nitric oxide that are implicated in the pathogenesis of many pathological conditions such as epilepsy, cerebral palsy, autism, and perinatal hypoxic-ischemic brain injury. Although many studies have investigated the origin and functions of the microglia in the developing brain, in-depth in vivo studies along with analysis of their transcriptome and epigenetic changes need to be undertaken to elucidate their full potential be it protective or neurotoxic. This would lead to a better understanding of their roles in the healthy and diseased developing brain and advancement of therapeutic strategies to target microglia-mediated neurotoxicity.

SCF-KIT signaling induces endothelin-3 synthesis and secretion: Thereby activates and regulates endothelin-B-receptor for generating temporally- and spatially-precise nitric oxide to modulate SCF- and or KIT-expressing cell functions

We demonstrate that SCF-KIT signaling induces synthesis and secretion of endothelin-3 (ET3) in human umbilical vein endothelial cells and melanoma cells in vitro, gastrointestinal stromal tumors, human sun-exposed skin, and myenteric plexus of human colon post-fasting in vivo. This is the first report of a physiological mechanism of ET3 induction. Integrating our finding with supporting data from literature leads us to discover a previously unreported pathway of nitric oxide (NO) generation derived from physiological endothelial NO synthase (eNOS) or neuronal NOS (nNOS) activation (referred to as the KIT-ET3-NO pathway). It involves: (1) SCF-expressing cells communicate with neighboring KIT-expressing cells directly or indirectly (cleaved soluble SCF). (2) SCF-KIT signaling induces timely local ET3 synthesis and secretion. (3) ET3 binds to ETBR on both sides of intercellular space. (4) ET3-binding-initiated-ETBR activation increases cytosolic Ca²⁺, activates cell-specific eNOS or nNOS. (5) Temporally- and spatially-precise NO generation. NO diffuses into neighboring cells, thus acts in both SCF- and KIT-expressing cells. (6) NO modulates diverse cell-specific functions by NO/cGMP pathway, controlling transcriptional factors, or other mechanisms. We demonstrate the critical physiological role of the KIT-ET3-NO pathway in fulfilling high demand (exceeding basal level) of endothelium-dependent NO generation for coping with atherosclerosis, pregnancy, and aging. The KIT-ET3-NO pathway most likely also play critical roles in other cell functions that involve dual requirement of SCF-KIT signaling and NO. New strategies (e.g. enhancing the KIT-ET3-NO pathway) to harness the benefit of endogenous eNOS and nNOS activation and precise NO generation for correcting pathophysiology and restoring functions warrant investigation.

Associations of genetic variants of endothelin with cardiovascular complications in patients with renal failure

BACKGROUND

Cardiovascular (CV) complications are the main cause of death in end-stage renal disease (ESRD) patients. The high CV risks are attributable to the additive effects of multiple factors. Endothelin (EDN) is a potent vasoconstrictor and plays a role in regulating vascular homeostasis. However, whether variants of the EDN gene are associated with risks of CV events is not known. We conducted a study to investigate associations of variants of the EDN gene with CV events in ESRD patients.

METHODS

A cohort of 190 ESRD patients was recruited, and 19 tagged single-nucleotide polymorphisms within the EDN gene family were selected for genotyping through a TaqMan assay. Data on clinical characteristics and hospitalizations for CV events were collected. Associations of genetic variants of the EDN gene with CV events were analyzed.

RESULTS

In this cohort, 62% (n = 118) of patients were hospitalized for a CV event. The EDN1 rs4714384 (CC/TC vs. TT) polymorphism was associated with an increased risk of a CV event after multiple testing (p < 0.001). Further functional exploration showed that it was a quantitative trait locus which may significantly alter gene expression in the tibial artery.

CONCLUSIONS

EDN1 rs4714384 is very likely an important biomarker of CV events in ESRD patients.