Structural Organization and Chromosomal Assignment of the Gene Encoding Endothelin

Endothelin-1 RS5370 gene polymorphism in primary nephrotic syndrome: A case-control study

INTRODUCTION

Primary nephrotic syndrome (NS) is a common glomerular disease in children. We assessed the genotypes and frequency of the rs5370 allelic variant of the EDN1 gene in children with primary NS.

PATIENTS AND METHODS

We conducted a case-control study in Mansoura University Children's Hospital, Egypt between December 2015 and January 2018. We recruited 50 patients with steroid-sensitive NS (SSNS) and 50 patients with steroid-resistant NS (SRNS) in addition to 100 healthy controls. The patients underwent clinical evaluations and tests including measurement of serum albumin, cholesterol, creatinine and urea levels and a 24-h urinary protein test. We used polymerase chain reaction methods to assess the genotypes of rs5370 variants of the EDN1 gene (GG, GT and TT) and alleles (T and G) in the groups under study.

RESULTS

The most frequent genotype of the EDN1 gene at the locus of interest in the control group was the GT genotype (88%; P=.001) while the GG genotype was more frequent in the NS group compared to the control group (P=.02). We did not find statistically significant differences between the NS and control groups in regard to the EDN1 rs5370 alleles (P=.69). The GG genotype was more frequent in the SSNS group compared to the SRNS and control groups (P=.03). When we compared allele frequencies between the control, SSNS and SRNS groups, we did not find significant differences (P=.89). The GT genotype was associated with normal blood pressure in children with NS (P=.007), while the GG genotype was associated with hypertension (P<.001). We did not find statistically significant differences in renal histopathology or serum cholesterol levels based on the genotype.

CONCLUSIONS

The GG genotype at the rs5370 locus of the EDN1 gene may be associated with an increased risk of primary NS and a better response to steroid therapy.

In vivo assessment of a single adenine mutation in 5'UTR of Endothelin-1 gene in paediatric cases with severe pulmonary hypertension: an observational study

Objective

Endothelin-1 plays an important role in the pathogenesis of severe pulmonary hypertension. The + 139 ‘A’, adenine insertion variant in 5′UTR of edn1 gene has been reported to be associated with increased expression of Endothelin-1 in vitro. The aim of present study was to explore the association of this variant with the circulating levels of Endothelin-1 in vivo using archived DNA and plasma samples from 38 paediatric congenital heart disease (cyanotic and acyanotic) patients with severe pulmonary hypertension.

Results

The plasma Endothelin-1 levels were highly varied ranging from 1.63 to75.16 pg/ml. The + 139 ‘A’ insertion variant in 5′UTR of edn1 was seen in 8 out of 38 cases with only one acyanotic sample demonstrating homozygosity of inserted ‘A’ allele at + 139 site (4A/4A genotype). The plasma Endothelin-1 levels in children with homozygous variant 3A/3A genotype were comparable in cyanotic and acyanotic groups. Lone 4A/4A acyanotic sample had ET-1 levels similar to the median value of ET-1 associated with 3A/3A genotype and was absent in cyanotic group presumably due to deleterious higher ET-1 levels. The discussed observations, limited by the small sample size, are suggestive of homozygous adenine insertion variant posing a risk in cyanotic babies with Severe Pulmonary Hypertension.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05609-5.

[Endothelin-1 rs5370 gene polymorphism in primary nephrotic syndrome: A case-control study]

INTRODUCTION

Primary nephrotic syndrome (NS) is a common glomerular disease in children. We assessed the genotypes and frequency of the rs5370 allelic variant of the EDN1 gene in children with primary NS.

PATIENTS AND METHODS

We conducted a case-control study in Mansoura University Children's Hospital, Egypt, between December 2015 and January 2018. We recruited 50 patients with steroid-sensitive NS (SSNS) and 50 patients with steroid-resistant NS (SRNS) in addition to 100 healthy controls. The patients underwent clinical evaluations and tests including measurement of serum albumin, cholesterol, creatinine and urea levels and a 24-hour urinary protein test. We used polymerase chain reaction methods to assess the genotypes of rs5370 variants of the EDN1 gene (GG, GT and TT) and alleles (T and G) in the groups under study.

RESULTS

The most frequent genotype of the EDN1 gene at the locus of interest in the control group was the GT genotype (88%; P=.001) while the GG genotype was more frequent in the NS group compared to the control group (P=.02). We did not find statistically significant differences between the NS and control groups in regard to the EDN1 rs5370 alleles (P=.69). The GG genotype was more frequent in the SSNS group compared to the SRNS and control groups (P=.03). When we compared allele frequencies between the control, SSNS and SRNS groups, we did not find significant differences (P=.89). The GT genotype was associated with normal blood pressure in children with NS (P=.007), while the GG genotype was associated with hypertension (P<.001). We did not find statistically significant differences in renal histopathology or serum cholesterol levels based on the genotype.

CONCLUSIONS

The GG genotype at the rs5370 locus of the EDN1 gene may be associated with an increased risk of primary NS and a better response to steroid therapy.

Characterisation of preproendothelin-1 derived peptides identifies Endothelin-Like Domain Peptide as a modulator of Endothelin-1

Endothelin-1 (ET-1) is involved in the pathogenesis of cardiac and renal diseases, and in the progression of tumour growth in cancer, but current diagnosis and treatment remain inadequate. Peptides derived from the 212 amino acid precursor preproendothelin-1 (ppET-1) may have utility as biomarkers, or cause biological effects that are unaffected by endothelin receptor antagonists. Here, we used specific immunoassays and LC-MS/MS to identify NT-proET-1 (ppET-1_[18–50]), Endothelin-Like Domain Peptide (ELDP, ppET-1_[93–166]) and CT-proET-1 (ppET-1_[169–212]) in conditioned media from cultured endothelial cells. Synthesis of these peptides correlated with ET-1, and plasma ELDP and CT-proET-1 were elevated in patients with chronic heart failure. Clearance rates of NT-proET-1, ELDP and CT-proET-1 were determined after i.v. injection in anaesthetised rats. CT-proET-1 had the slowest systemic clearance, hence providing a biological basis for it being a better biomarker of ET-1 synthesis. ELDP contains the evolutionary conserved endothelin-like domain sequence, which potentially confers biological activity. On isolated arteries ELDP lacked direct vasoconstrictor effects. However, it enhanced ET-1 vasoconstriction and prolonged the increase in blood pressure in anaesthetised rats. ELDP may therefore contribute to disease pathogenesis by augmenting ET-1 responses.

Association of Endothelin-1 rs5370 G>T gene polymorphism with the risk of nephrotic syndrome in children

Background:

Primary nephrotic syndrome (NS) is a common kidney disease in children. Objectives: The present study was aimed to investigate whether rs5370 G>T (lys198Asn) genetic variant of endothelin-1 (ET-1) is involved in the susceptibility to NS.

Patients and Methods:

This case-control study was performed on 138 patients with NS and 150 healthy children. Genomic DNA was extracted from whole blood using salting out method. Polymorphism of the ET-1 rs5370 G>T (lys198Asn) polymorphism detected by T-ARMS-PCR as well as PCR-RFLP method.

Results:

The results showed that the genotype and allelic frequencies of the ET-1 rs5370 G>T variant were not significantly different between cases and controls. Furthermore, subgroup analysis showed that rs5370 G>T variant was not associated with gender of patients. In NS patients the genotype was not associated with cholesterol, triglyceride, total protein and albumin levels.

Conclusions:

In conclusion, our findings indicate that ET-1 rs5370 G>T is not associated with NS. Further studies with larger sample sizes and different ethnicities are required to validate our findings.

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.

Antivascular therapy for multidrug-resistant ovarian tumors by macitentan, a dual endothelin receptor antagonist

Endothelin receptors (ETRs) are often overexpressed in ovarian tumors, which can be resistant to conventional therapies. Thus, we investigated whether blockage of the ETR pathways using the dual ETR antagonist macitentan combined with taxol or cisplatinum can produce therapy for orthotopically growing multidrug-resistant (MDR) human ovarian carcinoma. In several studies, nude mice were injected in the peritoneal cavity with HeyA8-MDR human ovarian cancer cells. Ten days later, mice were randomized to receive vehicle (saline), macitentan (oral, daily), taxol (intraperitoneal, weekly), cisplatinum (intraperitoneal, weekly), macitentan plus taxol, or macitentan plus cisplatinum. Moribund mice were killed, and tumors were collected, weighed, and prepared for immunohistochemical analysis. The HeyA8-MDR tumors did not respond to taxol, cisplatinum, or macitentan administered as single agents. In contrast, combination therapy with macitentan and taxol or macitentan and cisplatinum significantly decreased the tumor incidence and weight and significantly increased the survival of mice and their general condition. Multiple immunohistochemical analyses revealed that treatment with macitentan and macitentan plus taxol or cisplatinum inhibited the phosphorylation of ETRs, decreased the levels of pVEGFR2, pAkt, and pMAPK in tumor cells after 2 weeks of treatment and induced a first wave of apoptosis in tumor-associated endothelial cells followed by apoptosis in surrounding tumor cells. Our study shows that ovarian cancer cells, which express the endothelin axis and are multidrug resistant, are exquisitely sensitive to treatment with a dual ET antagonist and can be resensitized to both taxol and cisplatinum. This combined therapy led to a significant reduction in tumor weight.

Human lymphatic filariasis: genetic polymorphism of endothelin-1 and tumor necrosis factor receptor II correlates with development of chronic disease

BACKGROUND

Hydrocele and elephantiasis are 2 clinically very diverse and often mutually exclusive chronic manifestations of human bancroftian filariasis. Plasma levels of endothelin-1 (ET-1), a major angiogenic factor, and tumor necrosis factor receptors (TNFRs) that regulate host inflammation have been associated with development of chronic filariasis, although their genetic basis are not known.

METHODS

We studied polymorphisms of ET-1 (Ala288Ser) and TNFR-II (Met196Arg) genes by means of the polymerase chain reaction confronting 2 pairs primers method and restriction fragment length polymorphism, respectively. Plasma ET-1 level was measured by enzyme-linked immunosorbent assay.

RESULTS

Met196Arg genotype frequency of TNFR-II polymorphism was significantly greater in hydrocele patients, compared with elephantiasis patients (OR, 4.34 [95% CI, 2.04-9.20]). Conversely, a significantly high prevalence of the Ala288Ser mutation of ET-1 was observed in elephantiasis patients, compared with hydrocele cases (OR, 2.15 [95% CI, 1.13-4.10]). Decreased plasma ET-1 levels associated significantly with Ala288Ser mutation in the study population. A combined analysis indicated a 23-fold higher risk for developing elephantiasis in individuals with TNFR-II (Met196Met) and ET-1 mutants (Ala288Ser + Ser288Ser).

CONCLUSIONS

ET-1 (Ala288Ser) and TNFR-II (Met196Arg) polymorphisms are associated with development of one or the other form of chronic disease in bancroftian filariasis.

Macitentan (ACT-064992), a tissue-targeting endothelin receptor antagonist, enhances therapeutic efficacy of paclitaxel by modulating survival pathways in orthotopic models of metastatic human ovarian cancer

Potential treatments for ovarian cancers that have become resistant to standard chemotherapies include modulators of tumor cell survival, such as endothelin receptor (ETR) antagonist. We investigated the therapeutic efficacy of the dual ETR antagonist, macitentan, on human ovarian cancer cells, SKOV3ip1 and IGROV1, growing orthotopically in nude mice. Mice with established disease were treated with vehicle (control), paclitaxel (weekly, intraperitoneal injections), macitentan (daily oral administrations), or a combination of paclitaxel and macitentan. Treatment with paclitaxel decreased tumor weight and volume of ascites. Combination therapy with macitentan and paclitaxel reduced tumor incidence and further reduced tumor weight and volume of ascites when compared with paclitaxel alone. Macitentan alone occasionally reduced tumor weight but alone had no effect on tumor incidence or ascites. Immunohistochemical analyses revealed that treatment with macitentan and macitentan plus paclitaxel inhibited the phosphorylation of ETRs and suppressed the survival pathways of tumor cells by decreasing the levels of pVEGFR2, pAkt, and pMAPK. The dose of macitentan necessary for inhibition of phosphorylation correlated with the dose required to increase antitumor efficacy of paclitaxel. Treatment with macitentan enhanced the cytotoxicity mediated by paclitaxel as measured by the degree of apoptosis in tumor cells and tumor-associated endothelial cells. Collectively, these results show that administration of macitentan in combination with paclitaxel prevents the progression of ovarian cancer in the peritoneal cavity of nude mice in part by inhibiting survival pathways of both tumor cells and tumor-associated endothelial cells.

Transcriptional targeting of tumor endothelial cells for gene therapy

It is well known that angiogenesis plays a critical role in the pathobiology of tumors. Recent clinical trials have shown that inhibition of angiogenesis can be an effective therapeutic strategy for patients with cancer. However, one of the outstanding issues in anti-angiogenic treatment for cancer is the development of toxicities related to off-target effects of drugs. Transcriptional targeting of tumor endothelial cells involves the use of specific promoters for selective expression of therapeutic genes in the endothelial cells lining the blood vessels of tumors. Recently, several genes that are expressed specifically in tumor-associated endothelial cells have been identified and characterized. These discoveries have enhanced the prospectus of transcriptionally targeting tumor endothelial cells for cancer gene therapy. In this manuscript, we review the promoters, vectors, and therapeutic genes that have been used for transcriptional targeting of tumor endothelial cells, and discuss the prospects of such approaches for cancer gene therapy.

No effect of a Taql polymorphism in DNA at the endothelin I (EDN1) locus on normal blood pressure level or variability

Endothelin is a peptide reported to be one of the most potent vasoconstrictors known. Presumably, endothelin could play a role in the physiological regulation of blood pressure in healthy or hypertensive people. We have studied a normal restriction fragment length polymorphism (RFLP) at the endothelin-I (EDN1) locus detected with the restriction enzyme TaqI. In three different series comprising 166, 120 and 207 unrelated individuals, we found no evidence for association between genotype in this polymorphism and level of systolic or diastolic blood pressure. In two series of 156 and 117 monozygotic (MZ) twin pairs, respectively, there was no difference between genotypes in within-pair variation in systolic or diastolic blood pressure. Thus neither "level gene" nor "variability gene" effects of normal genes at the EDN1 locus could be detected with the polymorphism analyzed, in healthy population samples.

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.

A mouse model of Waardenburg syndrome type IV resulting from an ENU-induced mutation in endothelin 3

A line of mutant mice (114-CH19) exhibiting white spotting and preweaning lethality was identified during an N-ethyl-N-nitrosourea (ENU) mutagenesis screen. The trait segregated as a semidominant bellyspot with reduced penetrance. Homozygous mutant mice showed preweaning lethality, and exhibited white spotting over the majority of the body surface, with pigmented patches remaining around the pinnae, eyes and tail. Linkage analysis localized 114-CH19 on mouse chromosome 2, suggesting endothelin 3 (Edn3) as a candidate gene. Sequence analysis of Edn3 identified a G > A transversion that encodes an arginine to histidine substitution (R96H). This mutation is predicted to disrupt furin-mediated proteolytic cleavage of pro-endothelin that is necessary to form biologically active EDN3. This mutation is novel among human and mouse EDN3 mutants, is the first reported EDN3 ENU mutant, and is the second reported EDN3 point mutation. This study demonstrates the power of using ENU mutagenesis screens to generate new animal models of human disease, and expands the spectrum of EDN3 mutant alleles.

Structural analysis of the unique insecticidal activity of novel mungbean defensin VrD1 reveals possibility of homoplasy evolution between plant defensins and scorpion neurotoxins

A variety of evolutionarily related defensin molecules is found in plants and animals. Plant gamma-thionins and scorpion neurotoxins, for instance, may be categorized in this functional group, although each class recognizes a distinct receptor binding site. Such molecules are also categorized into the superfamily of cysteine-rich proteins. Plant defensins were generally believed to be involved in antimicrobial or antifungal mechanisms and, unlike scorpion toxins, little is known about whether these molecules are also endowed with the function of insect resistance. We have previously reported the isolation of a cDNA encoding a small cysteine-rich protein designated VrD1 (VrCRP) from a bruchid-resistant mungbean, which is apparently the first discovered plant defensin exhibiting in vitro and in vivo both insecticidal and antifungal activities. Our previous data also successfully demonstrated that VrD1 is toxic to E. coli and able to completely arrest the growth of Sf-21 insect cells at low concentration. However, the molecular and structural basis of this unique insecticidal activity of VrD1 is not clear. Therefore, in the present study, we use structural approach and phylogenic analysis to investigate the evolutionary and functional relations for such unique insecticidal activity. From our results, it is suggested that VrD1, in addition to gamma-thionins and several amylase inhibitors, is highly homologous to scorpion toxins, especially the short toxins. Moreover, based on the observation from our homology structures, VrD1 may utilize a newly found cluster of basic residues to achieve its insecticidal function, whereas all the other plant gamma-thionins were known to use a previously identified basic cluster conserved for gamma-thionins. Considering the general feature of short scorpion toxins to act on insect cell membranes with K(+)- or Cl(-)-channels as molecular targets, our analysis of interaction and recognition modes provides reasonable correlations between this newly found basic cluster and the insecticidal activity of VrD1, which is also comprehended as a possible link for "homoplasy evolution" between plant and animal defensin molecules.

Modulating effect of a selective endothelin A receptor antagonist on pulmonary endothelin system protein expression in experimental diaphragmatic hernia

BACKGROUND/PURPOSE

Previously, we reported that perinatal administration of atrasentan, a selective endothelin A receptor (ETA) antagonist, provided a beneficial effect on the cardiopulmonary profile under short-term conditions in newborn lambs with surgically induced congenital diaphragmatic hernia (CDH). We hypothesized that changes in the hemodynamic profile that we observed at birth in treated animals could be influenced by pulmonary modulation of the endothelin (ET) system.

METHODS

The effect of atrasentan on protein expression levels of ETs and ET receptors (ETA and ETB receptor) was investigated by immunohistochemistry in lung tissues of untreated control (n = 3), treated control (n = 6), untreated CDH (n = 6), and treated CDH newborn lambs (n = 8).

RESULTS

Right lung tissue of treated control lambs showed significantly higher ETA protein expression levels in both vascular adventitia and airway epithelia when compared with that of untreated control lambs (P < .05). In contrast, protein expression levels of ETA and ETB receptor were significantly lower in the vascular smooth muscle cells among other tissue subcompartments of the right lung of treated CDH newborn lambs vs CDH lambs (P < .02 and P = .005, respectively).

CONCLUSIONS

We speculate that rapid pulmonary modulation of ET system protein expression levels by atrasentan results from an indirect effect possibly dependent on ventilation and/or perfusion. In CDH groups, this could contribute to the beneficial effect of the treatment.

Polymorphisms in Genes of the Endothelin System and Cerebral Small-Vessel Disease

Background and Purpose— Endothelial dysfunction has been implicated in the pathogenesis of cerebral small-vessel disease (SVD). Endothelin (ET), released by the endothelium, plays a crucial role in vasoconstriction in the cerebral circulation and could contribute to the pathogenesis of cerebral SVD. Circulating ET levels may not reflect vascular production of endothelin-1 (ET-1), most of which is abluminal. Studying genetic associations, particularly of functional polymorphisms that alter activity of the ET system, is an attractive method of determining whether ET plays a role in SVD pathogenesis. We determined whether genetic variants in components of the ET system are a risk factor for cerebral SVD.

Methods— Three hundred SVD patients and 600 community controls were genotyped. Polymorphisms in the ET-1 gene (K198N), the ET receptor type A (ET A ), (−231 G > A and +1222 C > T ), and the ET type B (ET B ) receptor (G57S and L277L) were genotyped. Polymorphisms were studied both individually and as haplotypes. With brain imaging, cases were subtyped into those with lacunar infarct without leukoaraiosis and those with leukoaraiosis.

Results— No significant differences were observed between SVD cases and controls for any individual single-nucleotide polymorphism or the ET A haplotype. There were no differences between cases with isolated lacunar infarct or with lacunar infarct and leukoaraiosis.

Conclusions— This study, in a well-phenotyped population, does not support a role for genetic variation in the ET system as a risk factor for cerebral SVD.

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

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

Techniques: Cardiovascular pharmacology and drug discovery in the 21st century

The latter half of the 20th century has been characterized by pharmacologists as the 'age of the receptor', an era in which the bioassay, that stalwart of classical pharmacology, has played a seminal role in identifying novel cardiovascular medicines. In this article, we ask what, if anything, has changed in the pharmacologist's approach to discovering novel cardiovascular drugs on this, the 25th anniversary of the inaugural publication of Trends in Pharmacological Sciences.

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.

The Lack of Relationship between an Endothelin-1 Gene Polymorphism (Ala288Ser) and Incidence of Hypertension: A Retrospective Cohort Study among Japanese Workers

BACKGROUND

Some case-control association studies revealed the relationship between some endothelin-1 (ET-1) gene polymorphisms and blood pressure. Because no report was available about the relationship between any ET-1 gene polymorphism and incidence of hypertension, we examined the relationship between novel ET-1 gene polymorphism (G862T / Ala288Ser in exon 5) and incidence of hypertension by a retrospective cohort study.

METHODS

The subjects were Japanese workers at a company in Shimane Prefecture in Japan. The polymorphism with genome DNA extracted from the blood of the workers was analyzed using the polymerase chain reaction confronting two pair primers method. According to the results of two regular health checkups with a 6-year interval, the study population was divided into two groups by blood pressure and antihypertensive treatment in 1998, after excluding people who had hypertension in 1992.

RESULTS

There were 133 (93 males and 40 females) incidences of hypertension observed among the study population of 922 (540 males and 382 females). In the univariate analysis, odds ratios of Ala/Ser and Ser/Ser against Ala/Ala were 0.98 (95% confidence interval [CI]): 0.7-1.4) and 0.79 (95% CI: 0.4-1.6), respectively. In the multivariate analysis adjusted for sex, age, body mass index, serum total cholesterol, fasting blood sugar, and smoking and drinking habits, odds ratios for Ala/Ser and Ser/Ser against Ala/Ala were 0.97 (95% CI: 0.7-1.4) and 0.75 (95% CI: 0.4-1.5), respectively.

CONCLUSIONS

The ET-1 gene polymorphism in this study did not seem to be associated with the incidence of hypertension among the Japanese workers.

Nitric oxide decreases endothelin-1 secretion through the activation of soluble guanylate cyclase

The use of exogenous nitric oxide (NO) has been shown to alter the regulation of other endothelially derived mediators of vascular tone, such as endothelin-1 (ET-1). However, the interaction between NO and ET-1 appears to be complex and remains incompletely understood. One of the major actions of NO is the activation of soluble guanylate cyclase (sGC) with the subsequent generation of cGMP. Therefore, we undertook this study to test the hypothesis that NO regulates ET-1 production via the activation of the sGC/cGMP pathway. The results obtained indicated that the exposure of primary cultures of 4-wk-old ovine pulmonary arterial endothelial cells (4-wk PAECs) to the long-acting NO donor DETA NONOate induced both a dose- and time-dependent decrease in secreted ET-1. This decrease in ET-1 secretion occurred in the absence of changes in endothelin-converting enzyme-1 or sGC expression but in conjunction with a decrease in prepro-ET-1 mRNA. The changes in ET-1 release were inversely proportional to the cellular cGMP content. Furthermore, the NO-independent activator of sGC, YC-1, or treatment with a cGMP analog also produced significant decreases in ET-1 secretion. Conversely, pretreatment with the sGC inhibitor ODQ blocked the NO-induced decrease in ET-1. Therefore, we conclude that exposure of 4-wk PAECs to exogenous NO decreases secreted ET-1 resulting from the activation of sGC and increased cGMP generation.

Endothelin-1 gene Lys198Asn polymorphism and blood pressure reactivity

The Lys198Asn polymorphism of the endothelin-1 gene has been associated with increased blood pressure levels in several studies involving European and Australian adults. The purpose of the present study was to examine the potential moderating influence of ethnicity, obesity, and socioeconomic status on associations between the ET-1/Lys198Asn polymorphism and hemodynamic function at rest and during two laboratory stressors (video game, forehead cold) in a sample of 161 black and 213 white American normotensive young adults (mean age, 18.5+/-2.7 years). Carrier status of the T allele was not associated with resting blood pressure or total peripheral resistance index. However, carriers of the T allele showed greater diastolic blood pressure increases to the video game (P<0.04), particularly among those who were obese (P<0.02). Carrier status also interacted with socioeconomic status such that T allele carriers who came from lower socioeconomic status backgrounds exhibited the greatest increases in systolic blood pressure to the video game challenge (P<0.05). In conclusion, the findings point out the importance of examining the impact of genetic polymorphisms on blood pressure control phenotypes within the context of potentiating environmental factors.

A role for increased mRNA stability in the induction of endothelin-1 synthesis by lipopolysaccharide

An association exists between infection and cardiovascular diseases, including atherosclerosis, stroke and myocardial infarction. This may involve endothelin-1 (ET-1) which has been implicated in these and other vascular pathologies. ET-1 synthesis is controlled primarily by the level of its mRNA and numerous stimuli, including infection, lead to elevated ET-1 levels. Here, we have investigated the regulation of ET-1 release and preproET-1 (ppET-1) mRNA in bovine aortic endothelial cells by lipopolysaccharide (LPS). ET-1 release from bovine aortic endothelial cells was stimulated by LPS and reporter gene assays implicated LPS-induced ppET-1 transcription. However, changes in transcription were modest compared to increases in ET-1 synthesis. Therefore, ppET-1 mRNA levels were measured by real-time reverse transcription-polymerase chain reaction. The effect of LPS on ppET-1 mRNA levels was more marked than on transcription (1.2-fold increase in transcription vs. 5.5-fold increase in ppET-1 mRNA). Analysis of ppET-1 mRNA stability by real-time reverse transcription-polymerase chain reaction showed that LPS increased its half-life by approximately 2-fold. Thus, upregulated ppET-1 mRNA and hence increased ET-1 synthesis may be due to both increased transcription and reduced mRNA degradation. These effects of LPS on mRNA stability may be a key mechanism in vascular pathologies through which many proteins are induced in response to infection.

The endothelin axis: emerging role in cancer

Collectively, the endothelins and their receptors--referred to as the endothelin (ET) axis--have key physiological functions in normal tissue, acting as modulators of vasomotor tone, tissue differentiation, development, cell proliferation and hormone production. Based on new data, the ET axis also functions in the growth and progression of various tumours. Preliminary results from clinical trials, such as those with atrasentan--an ET(A)-receptor antagonist--in prostate cancer, are encouraging. The place of ET-receptor antagonists in cancer therapy for a range of malignancies merits further investigation.

PreproEndothelin-1 Expression in Human Mesangial Cells: Evidence for a p38 Mitogen-Activated Protein Kinase/Protein Kinases-C—Dependent Mechanism

Abstract. Endothelin-1 (ET-1) has been implicated in the pathogenesis of renal inflammation. This study investigated the mechanisms underlying the synergistic upregulation of preproET-1 gene expression in human mesangial cells after co-stimulation with thrombin and tumor necrosis factor α (TNFα). Whereas thrombin induced a moderate upregulation of preproET-1 mRNA, co-stimulation with TNFα resulted in a strong and protracted upregulation of this mRNA species. Thrombin+TNFα-induced upregulation of preproET-1 expression was found to require p38 mitogen-activated protein kinase and protein kinases C, whereas activation of extracellular signal-regulated kinase, c-Jun-N-terminal kinase, or intracellular Ca2+ release were not required. Actinomycin D chase experiments suggested that enhanced stability of preproET-1 mRNA did not account for the increase in transcript levels. PreproET-1 promoter analysis demonstrated that the 5′-flanking region of preproET-1 encompassed positive regulatory elements engaged by thrombin. Negative modulation of thrombin-induced activation exerted by the distal 5′ portion of preproET-1 promoter (-4.4 kbp to 204 bp) was overcome by co-stimulation with TNFα, providing a possible mechanism underlying the synergistic upregulation of preproET-1 expression by these two agonists. In conclusion, human mesangial cell expression of preproET-1 may be increased potently in the presence of two common proinflammatory mediators, thereby providing a potential mechanism for ET-1 production in inflammatory renal disease.

Endothelins: vasoactive modulators of renal function in health and disease

Vasoactive autocoids with directly opposing actions on the renal vasculature, glomerular function, and in salt and water homeostasis have been demonstrated in the kidney. In the renal cortex, endothelin (ET)-1 and angiotensin-II cause vasoconstriction, decreasing renal blood flow, and glomerular filtration rate, whereas bradykinin and atrial natriuretic peptide cause vasodilation and increase glomerular capillary permeability. ET-1 causes vasoconstriction of the afferent and efferent arteries and outer medullary descending vasa recta, thereby decreasing vasa recta and papillary blood flow, while bradykinin has the opposite effect. ET-1 stimulates cell proliferation, increasing the expression of several genes, including collagenase, prostaglandin endoperoxidase synthase, and platelet-derived growth factor. ET-1 promotes natriuresis via the ET-B receptor, causing down-regulation of the epithelial Na(+) channel in the renal tubule. Thus, ETs affect three major aspects of renal physiology: vascular and mesangial tone, Na(+) and water excretion, and cell proliferation and matrix formation.

Involvement of Rho GTPases in the transcriptional inhibition of preproendothelin-1 gene expression by simvastatin in vascular endothelial cells

Endothelial dysfunction is characterized by an impaired vasodilatory response to endothelial agonists as well as by alterations in adhesion and coagulation processes. 3-Hydroxy-3-methylglutaryl-CoA reductase inhibitors (statins) have been shown to be useful in the reversal of endothelial dysfunction, an effect that may be independent of the reduction in cholesterol levels. Both the L-arginine-nitric oxide-cGMP and endothelin pathways are involved in the regulation of vascular tone. Here, we show that the basal transcription rate of the preproendothelin-1 gene was decreased by simvastatin (10 micromol/L) in bovine aortic endothelial cells. Transfection studies with the preproendothelin-1 gene promoter showed that mevalonate (100 micromol/L) was able to prevent the inhibitory effect mediated by simvastatin. Protein geranylgeranylation, but not farnesylation, proved to be crucial for a correct expression of the preproendothelin-1 gene. The C3 exotoxin from Clostridium botulinum that selectively inactivates Rho GTPases, the processing of which involves geranylgeranylation, reproduced the inhibitory effect of simvastatin on the expression of preproendothelin-1. Overexpression of dominant-negative mutants of RhoA and RhoB led to a significant reduction in the preproendothelin-1 promoter activity, whereas the expression of wild-type and constitutively active forms of these proteins resulted in an increase, in support that Rho proteins are required for the basal expression of the preproendothelin-1 gene. Finally, we show that the Rho-dependent activation of the preproendothelin-1 gene transcription was inhibited by simvastatin. Thus, the control of vascular tone and proliferative response mediated by endothelin-1 is regulated at multiple levels, among which the Rho proteins play an essential role.

Functional parathyroid hormone receptors are present in an umbilical vein endothelial cell line

Acute parathyroid hormone exposure induces vascular smooth muscle relaxation. In contrast, continuous infusion of parathyroid hormone leads to vasoconstriction and an elevation of blood pressure. Despite the known effects of parathyroid hormone on vascular smooth muscle, possible direct effects on the vascular endothelium have not previously been investigated. Using a human umbilical vein endothelial cell line, we found that parathyroid hormone increased both intracellular calcium and cellular cAMP content in these endothelial cells. Furthermore, exposure of these cells to increasing concentrations of parathyroid hormone stimulated both [(3)H]thymidine incorporation and endothelin-1 secretion. Parathyroid hormone/parathyroid hormone-related peptide receptor mRNA could be detected at low levels in these cells. In summary, these data demonstrate that endothelium-derived cells contain functional parathyroid hormone receptors. The potential physiological role of these receptors remains to be determined.

Differential transcriptional regulation of endothelin-1 by immunosuppressants FK506 and cyclosporin A

Calcineurin antagonists FK506 and CsA, administered to treat organ allograft rejection, exert specific effects on renal vasoconstriction and nephrotoxicity, possibly due to endogenous vasoconstrictor release such as ET-1. We investigated contribution of FK506 and CsA on regulation of prepro ET-1 gene transcription in HUVEC. To conclude on transcriptional regulation, ET-1 mRNA levels were quantified by Northern blot analysis upon stimulation with calcineurin antagonists, and newly transcribed luciferase gene, placed under the control of the rat ET-1 promoter, was quantified by reporter gene assays, where luciferase activity reflects ET-1 promoter activation. Calcium fluorometry was employed to examine calcium dependency of ET-1 promoter-dependent gene transcription. Northern blot analysis shows differential induction of prepro ET-1 mRNA in favour of CsA over FK506. Likewise, luciferase assays demonstrate stronger ET-1 promoter-dependent stimulation of the reporter gene by CsA than by FK506. Transcription of prepro ET-1 gene upon stimulation with both calcineurin antagonists is regulated by intracellular calcium levels. Lack of extra- or intracellular calcium prevents ET-1 promoter-dependent gene transcription and ET-1 mRNA induction. These observations demonstrate that calcineurin antagonists FK506 and CsA differ in quality to induce transcription of prepro ET-1 in HUVEC via calcium-dependent nuclear signalling events. To examine the contribution of ET-1 in nephrotoxicity upon CsA and FK506 immunosuppression the availability of endothelin receptor antagonists or endothelin converting enzyme inhibitors is required.

Exposure of endothelial cells to recombinant human erythropoietin induces nitric oxide synthase activity

BACKGROUND

Anemic patients with chronic renal failure receiving recombinant human erythropoietin (rHuEPO) therapy frequently develop hypertension through an unknown mechanism. We hypothesize that EPO receptors (EPORs) on endothelial cells (ECs) in various sites of vasculature may mediate the activities of nitric oxide synthase (NOS) and/or the release of endothelin-1 (ET-1), contributing to blood pressure changes. We tested this hypothesis using primary cultures of ECs obtained from human coronary artery (HCAEC), pulmonary artery (HPAEC), dermis (HDEC), and umbilical vein (HUVEC).

METHODS

EPORs were measured by 125I-EPO binding. The effect of EPO on EPOR, ET-1, and NOS mRNA levels was assessed by quantitative reverse transcription-polymerase chain reaction. Cellular NOS activity and ET-1 release into the medium was measured by the NOSdetect assay and by radioimmunoassay kits.

RESULTS

Short-term (4 h) treatment with EPO (4 U/mL) did not change the number or affinity of EPOR per cell. Neither were there any changes in the amount of EPOR, ET-1, and NOS transcripts (cDNA/microg of mRNA) nor in ET-1 release and NOS activity. In HUVEC only, 24-hour exposure to EPO caused a threefold increase in NOS transcript. In other cells, EPO treatment for six days increased NOS activity by twofold to fourfold.

CONCLUSIONS

We show that upon extended exposure, EPO induces NOS activity but does not affect ET-1 release. These findings indicate that the hypertensive effect of EPO is not likely to be caused by a direct effect on ECs.

The renoprotective potential of endothelin receptor antagonists

The endothelin system has been identified as having a substantial role in renal failure, both acute and chronic. Beside its well characterised haemodynamic effects, its mitogenic and pro-fibrotic properties have gained increased interest in the pathophysiology of chronic renal failure. This review outlines the role of endothelin in the pathogenesis of various renal diseases with a special focus on the potential of blocking this system with endothelin receptor antagonists. So far, most data were derived from animal models, but they provide strong evidence that endothelin receptor antagonists may represent a powerful therapeutic strategy in ameliorating the course of acute and chronic renal failure.

Endothelin and the central and peripheral nervous systems: a decade of endothelin research

1. During the past decade, extensive investigation of the endothelin (ET) system, primarily characterized by its potent vasoactive peptide element ET-1, has suggested a prominent role for this humoral agent and its isopeptides in cardiovascular and neural regulation. 2. Major elements of this system, including its peptide isoforms, converting enzymes involved in their formation and metabolism, as well as multiple receptor subtypes, have been localized within various components of the cardiovascular system and the central and peripheral nervous systems. 3. An understanding of the possible roles for the ET system in neural regulation and development has progressed over the past several years; most notable is the influence of ET on the central control of cardiovascular function and sympathetic tone. 4. The present concentrated review of ET and the central and peripheral nervous systems is presented to introduce the other papers within this symposium by briefly describing the presence and influence of components of this unique peptide system within pertinent physiological structures involved in cardiovascular, adrenal, sympathetic and enteric developmental function.

Cyclosporin A induces prepro endothelin-1 gene transcription in human endothelial cells

Cyclosporin A employed in treatment of organ allograft rejection, is associated with hypertension possibly due to endothelin-1. We studied transcriptional regulation of endothelin-1 by cyclosporin A in human endothelial cells using cell transfection experiments and reporter gene assays. Human umbilical vein endothelial cells were established expressing a fusion gene of the coding sequence of the firefly luciferase gene, placed under the control of the rat endothelin-1 promoter. Luciferase assays demonstrate 2.8-fold stimulation of the reporter gene by cyclosporin A (P < 0.01), and Northern blot analysis shows induction of prepro endothelin-1 mRNA. Transcription is tightly repressed in the absence of the immunosuppressant, its regulation occurs Ca(2+)-dependent. Lack of extra- or intracellular Ca2+ prevents cyclosporin A-dependent endothelin-1 gene transcription and mRNA induction. These data demonstrate transcriptional regulation of endothelin-1 over a range of several orders of magnitude in human umbilical vein endothelial cells by cyclosporin A via Ca(2+)-dependent mechanisms. They support the critical role of endothelin- in cyclosporin A-associated hypertension.

Endothelins and asthma

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

Homocysteine decreases endothelin-1 production by cultured human endothelial cells

Hyperhomocysteinemia is believed to be responsible for the development of vascular disease via several mechanisms, including the impairment of endothelial-cell functionality. In-vitro studies have demonstrated that homocysteine decreases the production or bioavailability of vasodilator autacoids, such as prostacyclin and NO. Here, we show that the treatment of human endothelial cells with noncytotoxic homocysteine concentrations leads to a dose-dependent decrease in both the secretion of the vasoconstrictor agent endothelin-1 (ET-1) and the level of its mRNA. Homocysteine had an inhibitory effect at pathophysiological (0.1 and 0.5 mmol.L(-1)) and pharmacological noncytotoxic (1.0 and 2.0 mmol.L(-1)) concentrations. Mean percentage variation from control for ET-1 production was -36. 2 +/- 18.9% for 0.5 mmol.L(-1) homocysteine and -41.5 +/- 26.8% for 1.0 mmol.L(-1) homocysteine, after incubation for 8 h. Mean percentage variation from control for steady-state mRNA was -17.3 +/- 7.1% for 0.5 mmol.L(-1) homocysteine and -46.0 +/- 10.1 for 1.0 mmol.L(-1) homocysteine, after an incubation time of 2 h. ET-1 production was also reduced by incubation with various other thiol compounds containing free thiol groups, but not by incubation with thiol compounds with no free thiol group. Co-incubation of cells with homocysteine and the sulfhydryl inhibitor N-ethylmaleimide prevented the effect of homocysteine on ET-1 production, confirming a sulfhydryl-dependent mechanism. Based on the reciprocal feedback mechanism controlling the synthesis of vasoactive mediators, these preliminary data suggest a mechanism by which homocysteine may selectively impair endothelium-dependent vasodilation by primary inhibition of ET-1 production.

The Lys198Asn polymorphism in the endothelin-1 gene is associated with blood pressure in overweight people

There is accumulating evidence that endothelin-1 plays an important role in vascular pathophysiology. Our objective was to examine whether molecular variations at the endothelin-1 locus were involved in susceptibility to myocardial infarction and variation in blood pressure. The entire coding sequence and 1.4 kb of the 5' flanking region were screened. Five polymorphisms were detected, which were genotyped in the ECTIM (Etude Cas-Témoin de l'Infarctus du Myocarde) Study, a multicenter study comparing 648 male patients who had survived a myocardial infarction and 760 population-based controls. The polymorphisms were not associated with myocardial infarction, nor did they contribute to blood pressure levels in the population at large. However, a G/T polymorphism predicting an Lys/Asn change (ET1/C198) strongly interacted (P<0.001) with body mass index in the determination of blood pressure levels. There was a steeper increase of blood pressure with body mass index in carriers of the T allele than in GG homozygotes. As a consequence, the T allele was associated with an increase of blood pressure in overweight subjects (body mass index >/=26 kg/m2), while no significant effect was observed in lean subjects (body mass index <26 kg/m2). To determine whether this finding could be replicated, the ET1/C198 was genotyped in the Glasgow Heart Scan Study, a population-based study including 619 men and 663 women. Subjects homozygous for the T allele had higher resting blood pressure levels than others (P<0.05). A similar interaction between the T allele and body mass index was observed on the maximum blood pressure achieved during a treadmill exercise test (P<0.001). In conclusion, results from 2 independent studies suggest that the ET1/C198 polymorphism is associated with blood pressure levels in overweight people.

Gene expression of the renal endothelin system in renal transplant recipients on cyclosporine A based immunosuppression

BACKGROUND

Immunosuppressive therapy based on cyclosporine A (CsA) is potentially nephrotoxic, and each dose of CsA is followed by a transient increase in plasma endothelin (ET)-1. The aim of this study was to investigate the effect of CsA based immunosuppressive therapy on renal gene expression of the ET(A) and ET(B) receptor subtypes and preproET-1 in human transplant needle biopsies.

METHODS

Twelve living donor renal transplant recipients, median age 51.5 years (range 24-63 years) were included in the study. Immunosuppressive therapy consisted of CsA, azathioprine, and prednisolone. Baseline renal cortical needle biopsies from the living donor kidneys were obtained just before nephrectomy. Follow-up biopsies were obtained from the same transplanted kidneys after 2-6 weeks of immunosuppressive therapy. We used a quantitative, competitive reverse transcriptase polymerase chain reaction assay to measure renal ET(A) and ET(B) receptor subtype mRNAs as well as preproET-1 mRNA levels in each of the biopsies.

RESULTS

The renal ET system was not significantly altered by CsA-based immunosuppressive therapy. Median ET(A) mRNA level was 185 (range 35-244) at baseline, and 120 (11-189) amol/microg total RNA after CsA based immunosuppressive therapy (P=0.11). ET(B) mRNA level was 506 (209-1411) at baseline, and 463 (267-1609) amol/microg total RNA at follow-up (P=0.44) and preproET-1 mRNA level was 160 (112-392) before and 221 (187-361) amol/microg total RNA after immunosuppressive therapy based on CsA (P=0.58).

CONCLUSION

This study indicates that 2-6 weeks of CsA-based immunosuppression neither significantly influences renal gene expression of the ET(A) or ET(B) receptor subtypes nor preproET-1 in living donor renal transplant kidneys.

The expression of endothelin-1 and endothelin-converting enzyme-1 (ECE-1) are independently regulated in bovine aortic endothelial cells

The endopeptidase called endothelin-converting enzyme-1 (ECE-1) is thought to play a physiological role in endothelin-1 (ET-1) biosynthesis. For human ECE-1, differential splicing of messenger RNA (mRNA) results in the synthesis of three isoforms, termed ECE-1a, ECE-1b, and ECE-1c. The isoform(s) responsible for the hydrolysis of the biosynthetic intermediate big ET-1 in endothelial cells have yet to be assigned. To investigate whether the expression of mRNAs for preproET-1 and ECE-1 are regulated in parallel, a variety of conditions were used to compare levels of ET-1 synthesis by bovine aortic endothelial cells (BAECs) with levels of mRNA for preproET-1, ECE-1a, ECE-1c, and the combined ECE-1 isoforms (ECE-1a/b/c). Stimulation of BAECs with tumor necrosis factor-alpha or transforming growth factor-beta increased ET-1 synthesis, and treatment of BAECs with 2-chloroadenosine or staurosporine caused concentration-dependent reductions in ET-1 synthesis. Estimates of mRNA levels by reverse transcription-polymerase chain reaction (RT-PCR) with linear cycling conditions showed changes in preproET-1 expression to correlate well with ET-1 secretion. In contrast, RT-PCR analysis of ECE-1 expression by using primer pairs to measure ECE-1a, ECE-1c, or all the ECE-1 isoforms simultaneously showed no correlation between their mRNA levels and those of preproET-1. This indicates that under the conditions investigated, expression of ECE-1 is not coordinated with ET-1 synthesis in BAECs.

Membrane potential modulators: a thread of scarlet from plants to humans

The preservation along evolution of specific core motifs in proteins of diverse functions and taxonomic origins pinpoints a possible developmental advantage at the structural level. Such a preservation was observed in a group of membrane potential modulators including plant gamma-thionins, scorpion toxins, insect and scorpion defensins, bee venom apamin and MCD peptide, snake sarafotoxins, and human endothelins. These substances are short polypeptides of various lengths and nonhomologous sequences that affect organisms of distant phyla. Despite the structural differences, comparative analysis reveals commonality at three levels: 1) effect on membrane potential; 2) a common cysteine-stabilized alpha-helical (CSH) motif; and 3) similar gene organization (except for insect defensins), i.e., an intron that splits a codon toward the end of the leader sequence. We thus propose that these modulators, divided into two groups differing in their CSH motif orientation, have either diverged from two independent ancestors or have evolved by gene diversification via exon shuffling and subsequent modifications. To enforce protein synthesis through the secretory pathway and enable disulfide bond formation and secretion, insertion sites downstream of preexisting leader sequences have been a prerequisite. What seems advantageous for evolution, may also be exploited in attempts to 'accelerate evolution' by protein design using the conserved CSH core as a suitable scaffold for reshaping molecular exteriors.

Upregulation of endothelin-1 production by lysophosphatidic acid in rat aortic endothelial cells

Addition of lysophosphatidic acid (LPA) to rat aorta-derived endothelial cells significantly induced preproendothelin-1 (preproET-1) mRNA expression. PreproET-1 mRNA levels reached a plateau within 1 h after the addition of 0.5 microM LPA and declined after 2 h. The induction was superinduced by cycloheximide and was blocked by actinomycin D. Suramin, an LPA receptor antagonist, abolished the induction of preproET-1 mRNA by LPA. Protein kinase C inhibitors, H7 and bisindolylmaleimide, were able to block the induction. Transient transfection experiment revealed that the elevated preproET-1 mRNA was a result of the activation of ET-1 gene activity. Electrophoretic mobility shift assay revealed that LPA stimulated the binding of AP-1. The secreted level of ET-1 was elevated 2.3-fold after 12 h of stimulation with LPA. Our results suggest that the upregulation of preproET-1 by LPA may serve to augment and prolong the vasoconstriction action of LPA.

Quantification of mRNA levels of endothelin receptor subtypes and preproEndothelin-1 in renal needle biopsies by competitive reverse transcriptase polymerase chain reaction

The vasoconstrictive peptide endothelin-1 (ET-1) is an autocrine/paracrine peptide of putative pathophysiological importance in renal transplant medicine. The aim of the present study was to develop a method for analysis of gene expression of the renal endothelin system in humans. Only small amounts of tissue are available from renal cortical needle biopsies. Thus, in the present study we developed a quantitative assay based on the competitive reverse transcriptase polymerase chain reaction (RT-PCR) technology. We quantified endothelin A (ET(A)) and B (ET(B)) receptor subtype mRNAs and preproET-1 mRNA levels in renal cortex biopsies obtained before nephrectomy of healthy kidney donors. Mean (+/- SEM) mRNA levels of the ET(A) and ET(B) receptor subtypes in 26 living donors were 212 +/- 23 and 368 +/- 56 amol/microg total RNA, respectively. The preproET-1 mRNA level in 19 living donors was 213 +/- 28 amol/microg total RNA. The inter-assay coefficient of variation (CV) for the assay was 10%; the intra-assay CV was 6-13%. The competitive RT-PCR assay described provides an accurate tool for gene expression investigation of the human endothelin system in renal cortical needle biopsies.

The endothelin system in cardiovascular physiology and pathophysiology

Endothelin-1, a member of a novel family of regulatory peptides, is the most potent vasoconstrictor and pressor substance known. Endothelin-1 is a 21-amino-acid endothelium-derived peptide causing uniquely sustained vasoconstriction. In addition, endothelin-1 has pronounced effects on the coronary, renal and cerebral circulations, enhances responses to other vasoconstrictors, and is comitogenic. Recent studies have shown that the endothelins are essential for normal fetal development, and that endothelin-1 plays an important physiological role in the regulation of basal vascular tone and blood pressure in healthy humans. There is now also a wealth of evidence suggesting that endothelin-1 is a key mediator in a range of cardiovascular diseases associated with sustained vasoconstriction, such as chronic heart failure, and with vasospasm, such as subarachnoid haemorrhage. In addition, endothelin-1 appears to act in opposition to nitric oxide to promote the atherosclerotic process. There are a large number of oral and intravenously active endothelin antagonists entering clinical development and a number of clinical studies, particularly with endothelin receptor antagonists, are now under way. Such studies are beginning to define the role of the endothelins in cardiovascular disease and to confirm the potential of the endothelin system as an important new therapeutic target.

Vascular endothelial growth factor induces heparin-binding epidermal growth factor-like growth factor in vascular endothelial cells

Although several cytokines and growth factors have been shown to regulate vascular endothelial growth factor (VEGF) production, little is known about how VEGF may regulate growth factors that have known mitogenic and chemotactic actions on mesenchymal cells (which are involved in the maturation of the angiogenic process). We investigated the effect of VEGF on heparin-binding epidermal growth factor-like growth factor (HB-EGF) expression in human umbilical vein endothelial cells. HB-EGF mRNA was induced by 8-fold after 2 h of VEGF stimulation, and it returned to base line within 6 h. VEGF did not alter the half-life of HB-EGF mRNA (55 min). Nuclear run-on experiments showed a 4.9-fold increase in HB-EGF gene transcription within 2 h of VEGF stimulation, and Western analysis demonstrated an associated increase in cellular HB-EGF protein. We found that platelet-derived growth factor-BB (PDGF-BB) mRNA was also induced 3-fold after 5 h of VEGF stimulation, whereas neither endothelin 1 nor transforming growth factor-beta1 was regulated by VEGF. Finally, conditioned medium from VEGF-stimulated endothelial cells produced an increase in DNA synthesis in vascular smooth muscle cells, and this effect was blocked by a neutralizing antibody to PDGF. The induction of HB-EGF and PDGF-BB expression in endothelial cells may represent the mechanism by which VEGF recruits mesenchymal cells to form the medial and adventitial layers of arterioles and venules during the course of angiogenesis.

Airway hyperresponsiveness to methacholine in mutant mice deficient in endothelin-1

Endothelin-1 (ET-1) has recently been reported to have a potential pathophysiologic role in bronchial asthma. In the current study, we hypothesized whether ET-1 and a gene encoding ET-1 might be involved in airway hyperresponsiveness (AHR), which is a major feature of bronchial asthma. To test this hypothesis, we investigated airway responsiveness in ET-1(+/-) heterozygous knockout mice, which genetically produce lower levels of ET-1, and in ET-1(+/+) wild-type mice. Airway responsiveness was assessed through the concentration of an agonist required to double lung resistance (EC200 RL). Unexpectedly, airway responsiveness to methacholine was markedly enhanced in ET-1(+/-) heterozygous mice as compared with ET-1(+/+) wild-type mice (EC200 RL: 1.8 +/- 0.1 versus 21.6 +/- 5.6 mg/ml, p < 0.002). Pretreatment with the nitric oxide (NO) synthase inhibitor Ng-monomethyl-L-arginine (L-NMMA) significantly enhanced methacholine responsiveness in ET-1(+/+) wild-type mice, but not in ET-1(+/-) heterozygous mice. Meanwhile, there was no difference between ET-1(+/-) heterozygous mice and the wild-type mice in airway responsiveness to 5-hydroxytryptamine (5-HT). In sensitized mice, no significant differences in responsiveness to antigen were observed between the two groups. These findings suggest that the gene encoding ET-1 may be potentially involved in the etiology of airway hyperreactivity, and that the decrease in ET-1 concentration is associated with AHR to methacholine. In mice, ET-1 as well as NO may have a significant role in the homeostasis of airway physiology.