Components Of Endothelin System Research Articles

The role of the endothelin system in the pathogenesis of eye diseases

The endothelin system (ES) plays a complex role in the pathogenesis of various eye diseases as a local regulator of vascular tone as well as many other physiological processes. Components of ES - endothelins and their receptors - can be found nearly in all cellular structures of the eye, their concentration increases in the presence of many eye diseases. In glaucoma, ES is involved in the mechanisms of eye hypertension by influencing the secretion and outflow of aqueous humor. The increase of endothelin level leads to the decrease of perfusion pressure, hypoxia, astrocyte proliferation, increase of density and rigidity of lamina cribrosa, apoptosis of neural cells, and has a profibrogenic effect. In retinal pathology, increase of endothelins disturbs autoregulation of retinal blood vessels changing the neurovascular interactions, breaks intercellular contacts in the retina, promotes neoangiogenesis. In diabetic retinopathy, ES contributes to the development of microangiopathy and proliferative vitreoretinopathy. The review discusses the possibility of correcting ES activity in the eye with medications by influencing its synthesis, cleavage and receptor binding.

Nephron prorenin receptor deficiency alters renal medullary endothelin-1 and endothelin receptor expression.

The endothelin (ET) and prorenin/renin/prorenin receptor (PRR) systems have opposing physiological effects on collecting duct (CD) salt and water reabsorption. It is unknown if the CD ET and renin/PRR systems interact, hence we examined the effects of deleting CD renin or nephron PRR on CD ET system components. PRR knockout (KO) mice were polyuric and had markedly increased urinary ET-1 and inner medullary CD (IMCD) ET-1 mRNA. PRR KO mice had greatly increased IMCD ETA receptor mRNA and protein, while ETB mRNA and protein were decreased. Water loaded wild-type mice with similar polyuria as PRR KO mice had modestly increased urinary ET-1 excretion and inner medullary ET-1 mRNA, while inner medullary ETA and ETB mRNA or protein expression were unaffected. In contrast to PRR KO, CD prorenin/renin KO did not alter ET system components. Taken together, these results suggest that the nephron PRR is involved in regulating CD ET system expression, but this effect may be independent of CD-derived renin.

Altered endothelin expression in granulosa-lutein cells of women with polycystic ovary syndrome

AimsTo examine the levels of endothelin system components in granulosa lutein cells (GLCs) of women with PCOS and compare them to normally ovulating women undergoing In Vitro Fertilization (IVF).Polycystic ovary syndrome (PCOS) is one of the most common endocrine-metabolic disorders in women of reproductive age. Endothelins are locally produced by endothelial and granulosa cells of the preovulatory follicle. Abnormal expression or production of endothelins may be a contributing factor in PCOS pathogenesis. Main methodsFollicular aspirates containing GLCs were obtained from PCOS and normally ovulating patients undergoing oocyte retrieval during the IVF cycle. RNA was extracted and endothelin system components were quantified using real-time PCR. GLCs were cultured in basal media for 7days, and then challenged with various luteinizing agents (luteinizing hormone, hCG, or forskolin) for 24h. Key findingsIn GLCs from women with PCOS, Endothelin-1 mRNA expression was elevated (2.2-fold) as compared with normally ovulating women, whereas endothelin-2 mRNA was reduced (1.8-fold). ET receptors and endothelin-converting enzyme showed the same expression levels in the two groups. In vitro modeling showed that although the steroidogenic response was preserved in GLC, endothelin expression levels were not exhibited in vitro in their original pattern. SignificanceDysregulation of ovarian endothelin expression may induce a pathologic ovulation pattern characteristic of PCOS.

Expression pattern of endothelin system components and localization of smooth muscle cells in the human pre-ovulatory follicle

Whether ovarian follicular rupture involves contractile activity or not has been debated for decades. Recently, study in the rodents has indicated that an endogenously produced potent vasoconstrictive peptide, endothelin-2 (EDN2), may induce follicular constriction immediately prior to ovulation. This study was aimed to systematically characterize the human ovarian endothelin system and localize smooth muscle cells to assess the possible involvement of contractile activity in human ovulation. This is a prospective experimental study. Study subjects were 20 women aged 20-38 years who underwent IVF owing to tubal or male factors. Expression patterns of messenger RNAs (mRNAs) for EDN1, EDN2, EDN3, endothelin-converting enzyme-1 (ECE1 and ECE2), endothelin receptor A (ET(A)) and ET(B) in the granulosa cells (GCs) and cumulus cells and endothelin peptide concentration in the pre-ovulatory follicles were measured at 36 h after hCG injection. In addition, localization of ovarian smooth muscle cells and endothelin receptor expression were determined in normal (non-IVF patient) ovaries. Pre-ovulatory follicles express mRNA for EDN1 and EDN2, ECE1, ECE2, ET(A) and ET(B), but not EDN3, contain highly concentrated endothelin peptides (105.9 pg/ml) and are surrounded by theca externa that are made mostly of multicell layer non-vascular smooth muscle cells. ET(A) expression is localized in the smooth muscle cells of theca externa, theca interna and GC, whereas ET(B) expression is confined to theca interna. Pre-ovulatory follicles contain highly concentrated endothelins and are surrounded by non-vascular smooth muscle cells that express endothelin receptor, suggesting involvement of endothelin-induced contractile action in ovulation in the human ovary.

Enhanced Expressions of Endothelin-Converting Enzyme and Endothelin Receptors in Human Colonic Tissues of Crohn’s Disease

Endothelin-1, a powerful vasoconstrictor, forms the endothelin system together with endothelin-converting enzyme and endothelin type A and type B receptors. These endothelin system components are considered to participate in inflammatory and wound healing responses. Previous reports have suggested a role for the endothelin-1 in the pathology of Crohn’s disease. In the present study, we immunohistochemically investigated the expressions of the endothelin system components in affected human intestinal tissues of Crohn’s disease. Eighteen surgical specimens of colonic tissue obtained from patients with Crohn’s disease and 12 normal colonic tissues as controls were examined. Frozen tissue sections cut from the samples were subjected to the immunohistochemical single and double staining. The endothelin system components were expressed mainly in the muscular layers and blood vessels. In diseased colonic tissues, inflammatory infiltration and fibrotic tissue reactions with marked smooth muscle cell proliferation were frequently seen, and were closely associated with increased expressions of the endothelin system components. These results strongly suggest that endothelin-converting enzyme and endothelin type A and type B receptors collectively play a role in the inflammatory and fibrogenic processes of Crohn’s disease. Especially, submucosal smooth muscle proliferation, a histological hallmark of strictures, may be attributable to the upregulated endothelin system.

Effect of eicosapentaenoic acid on the different endothelin system components in endothelin-1-induced hypertrophied cardiomyocytes.

The cardiovascular benefit of fish oil, including eicosapentaenoic acid (EPA), in humans and experimental animals has been reported. The role of endothelin-1 (ET-1) in cardiac hypertrophy is well known. Endothelin-1 stimulates prepro-ET-1 mRNA expression in cardiomyocytes, and the autocrine/paracrine system of ET-1 is important for cardiomyocyte hypertrophy. Although many studies link EPA to cardiac protection, the effect of EPA on cardiac hypertrophy has yet to be clarified. Recently, we demonstrated that ET-1-induced cardiomyocytic change could be prevented by pretreatment with EPA. The present study investigated the changes of different components of the ET system at the mRNA level in ET-1-administered cardiomyocytes, and examined the effect of EPA pretreatment. Ventricular cardiomyocytes were isolated from 2-day-old Sprague-Dawley rats, cultured in Dulbecco's modified Eagle's medium and Ham F12 supplemented with 0.1% fatty acid-free bovine serum albumin for 3 days. At Day 4 of culture, the cardiomyocytes were divided into 3 groups: control group, ET-1-treated (0.1 nM) group, and ET-1-treated group pretreated with EPA (10 microM). Twenty-four hours after treatment, the gene expressions of different components of the endothelin system in three experimental groups were evaluated by real-time polymerase chain reaction. Prepro-ET-1 mRNA expression was 53% upregulated in ET-1-induced hypertrophied cardiomyocytes and suppressed in the EPA-pretreated group. Endothelin-converting enzyme-1 (ECE-1) was also increased in ET-1-administered cardiomyocytes by 42% compared with the control group and was reversed in the EPA-pretreated group. The two receptors of ET system, ET(A) and ET(B), tended to be increased in the ET-1-treated group, but no statistical significance was seen among study groups. Endothelin-1 increased prepro-ET-1 and ECE-1 mRNA expression in hypertrophied-neonatal cardiomyocytes, and this was reversed with EPA pretreatment. Thus, EPA may play a crucial role in the regression of ET-1-induced cardiomyocyte hypertrophy, partly through the suppression of ET-1 and ECE-1 expression.

Expression of the hepatic endothelin system in human cirrhotic livers.

It is considered that endothelin-1 participates in the development of liver cirrhosis and it has been recognized that every component of the endothelin system is upregulated in cirrhotic livers. However, the expression pattern of this system, including interaction between its components, is not fully understood in human livers. In this study, the expression pattern of the endothelin system was examined. Immunohistochemical analysis for endothelin-1, endothelin receptors and endothelin-converting enzyme was performed in 16 cirrhotic and 17 normal human liver tissues. Peptides, proteins, and RNAs extracted from the livers were also investigated using quantitative assays for the components of the hepatic endothelin system. Hepatic endothelin-1 levels were significantly higher in cirrhotic livers (0.084 +/- 0.052 pg/mg wet liver) than in normal livers (0.041 +/- 0.032 pg/mg; p < 0.01), and were closely related to the severity of liver fibrosis and portal hypertension. Immunoreactivity for endothelin-1, endothelin receptors, and endothelin-converting enzyme was detected mainly in fibrous areas and in the hepatic vasculature, and was enhanced in cirrhosis. Although there was a negative correlation between the expression of receptor mRNA and the hepatic endothelin-1 level, the amounts of the mRNAs were greater in cirrhotic livers than in normal livers. However, expression of endothelin-converting enzyme in cirrhotic livers was increased at the protein level but was relatively reduced at the mRNA level. These findings suggest that the hepatic endothelin system is activated in human cirrhotic livers in association with worsening of the disease, but that the regulation of the components of this system in this disorder is complex.

Endothelin system: the double-edged sword in health and disease.

The endothelin system consists of two G-protein-coupled receptors, three peptide ligands, and two activating peptidases. Its pharmacological complexity is reflected by the diverse expression pattern of endothelin system components, which have a variety of physiological and pathophysiological roles. In the vessels, the endothelin system has a basal vasoconstricting role and participates in the development of diseases such as hypertension, atherosclerosis, and vasospasm after subarachnoid hemorrhage. In the heart, the endothelin system affects inotropy and chronotropy, and it mediates cardiac hypertrophy and remodeling in congestive heart failure. In the lungs, the endothelin system regulates the tone of airways and blood vessels, and it is involved in the development of pulmonary hypertension. In the kidney, it controls water and sodium excretion and acid-base balance, and it participates in acute and chronic renal failure. In the brain, the endothelin system modulates cardiorespiratory centers and the release of hormones. More advanced functional analysis of the endothelin system awaits not only additional pharmacological studies using highly specific endothelin antagonists but also the generation of genetically altered rodent models with conditional loss-of-function and gain-of-function manipulations.

Involvement of the Endothelin System in Experimental Critical Hind Limb Ischemia

Endothelin- (ET-1) is involved in the pathogenesis of several ischemic diseases. We investigated the hypotheses that ET-1 is involved in the pathogenesis of experimental critical hind limb ischemia and that ET-1 receptor antagonists have a protective effect. Critical hind limb ischemia was achieved by exclusion of the femoral artery and embolization of collateral vessels in rats. The induction of endothelin system components by ischemia was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) (mRNAs) and immunoassay (peptides) in the plasma and ischemic muscles 5 hr (H5), 5 days (D5) and 14 days (D14) after ischemia. Two groups of rats received 100 mg/kg/day of either Bosentan, a mixed ET(A/B) receptor antagonist (n = 12), or LU 135252, a selective ET(A) receptor antagonist (n = 9), and a control group without treatment (n = 12) served as control. Muscle blood flow and ischemia were monitored in the ischemic limb by laser Doppler and phosphorylase activity, respectively. The procedure induced an 80% decrease in muscle blood flow and complete suppression of phosphorylase activity without necrosis. At day 14, the tissue blood flow remained reduced by 70% and phosphorylase activity was suppressed completely. There was up-regulation of preproendothelin-1, preproET-3, endothelin converting enzyme-1, and ET(A). ET(B) receptor mRNAs in ischemic muscle at day 5 and day 14 was accompanied by an increase in muscle concentration of ET-1 at day 5, without significant changes in plasma endothelin. Treatment with Bosentan and LU 135252 increased tissue blood flow and reduced muscle ischemia at day 14. Tissue production of ET- 1 is up-regulated in experimental critical hind limb ischemia. Inhibition of the endothelin system by a mixed ET(A/B) receptor antagonist may protect, at least in part, against muscle injury.

The endothelin system in human and monkey ovaries: in situ gene expression of the different components.

The endothelin system is composed of three endothelin isoforms (ET-1, ET-2, and ET-3), the endothelin receptors ETA and ETB, and the endothelin-converting enzyme (ECE). Besides having a major vasoactive role, endothelins have roles in different cell types at a local level. We investigated the presence of the different components of the endothelin system in primate ovaries. Human ovaries and gonadotropin-stimulated monkey ovaries were studied using immunohistochemistry for endothelin, and in situ hybridization with probes for ET-1, ET-2, ET-3, ETA and ETB receptors, and ECE. ET-1 and ETA receptors were detected in endothelial cells and vascular smooth muscle cells, respectively, in stromal vessels adjacent to follicles and corpora lutea. ETB receptors and ET-1 were found in the endothelial cells of capillaries of corpora lutea. ECE was present in internal theca cells of secondary, de Graaf, atretic follicles, and in luteinized granulosa cells of the corpora lutea. The endothelin system components are present in or around the follicles of human and monkey ovaries. Although the components are not expressed in the same cell types, they are synthesized, mainly in follicles, by cells that are in close proximity. Thus, the endothelin system could act in a paracrine manner. ECE expression in steroid-producing cells changes its compartmentalization during follicle maturation.