Preproendothelin-1 mRNA Research Articles

Endothelin converting enzyme-1 gene expression in the kidney of spontaneously hypertensive rats.

Abnormal renal handling of water and sodium is implicated in the pathogenesis of hypertension in spontaneously hypertensive rats (SHR). Alteration of renal endothelin-1 synthesis is also reported in SHR. Endothelin-1, a potent vasoconstrictor and regulator of sodium reabsorption in the nephron, has a pathophysiological potential in the development of hypertension. Because synthesis of bioactive endothelin-1 requires endothelin converting enzyme-1 (ECE-1), we investigated whether renal ECE-1 gene expression is altered in the kidney of SHR. Kidneys from both 4- and 12-week-old SHR and age-matched Wistar-Kyoto rats (WKY) were studied. ECE-1 mRNA in microdissected nephron segments was assessed by reverse transcription-competitive polymerase chain reaction, and ECE-1 protein level by Western blot. In 4-week-old SHR, ECE-1 mRNA was significantly increased in the proximal straight tubule, medullary thick ascending limb, cortical thick ascending limb, and inner medullary collecting duct. ECE-1 protein level was increased in both the outer and inner medulla. In 12-week-old SHR, ECE-1 gene expression was significantly increased in the proximal straight tubule, medullary thick ascending limb, and also in the glomeruli. Glomerular preproendothelin-1 mRNA expression was not different between the two strains at both 4 and 12 weeks. We conclude that high ECE-1 gene expression in the nephron, via increase of endothelin-1 synthesis, may promote sodium retention that contributes to the development and/or maintenance of hypertension in SHR.

Transient, isopeptide-specific induction of myocardial endothelin-1 mRNA in congestive heart failure in rats.

Increased myocardial expression of preproendothelin-1 (ppET-1) mRNA has been associated with congestive heart failure (CHF) in rats. However, the time course and isoform pattern of ppET mRNA induction and the cellular localization of ET in failing hearts are unknown. Thus our aim was to investigate myocardial ppET mRNA expression in CHF rats during the first 6 wk after induction of myocardial infarction. Furthermore, performing immunohistochemical analysis, we also investigated the origin and localization of immunoreactive endothelin (ET) in different regions of the failing heart. Ribonuclease protection assays revealed a marked increase in ppET-1 mRNA levels in rat myocardial tissues during CHF. The induction of ppET-1 mRNA was isopeptide specific and transient. The most substantial upregulation was observed in the infarcted area, where maximal expression of ppET-1 mRNA was observed after 7 days (25-fold increase, P < 0.05). However, a marked and statistically significant induction of ppET-1 mRNA was also observed in the nonischemic myocardium. Immunohistochemical analysis revealed ET-1-like immunoreactivity in cardiomyocytes, vascular endothelial cells, macrophages, and proliferating fibroblasts. Thus immunohistochemistry revealed the structural basis for the dramatic upregulation of the myocardial ET system in the infarcted region, suggesting a role for ET in the healing process after myocardial infarction. However, the global upregulation of ppET-1 mRNA in the heart also suggests an autocrine/paracrine regulatory mechanism in the nonischemic myocardium during CHF.

Characterization of endothelin receptors in human varicose veins

Experiments were designed to characterize endothelin receptors in human varicose veins. Three groups of veins were studied: (1) varicose vein (VV) tributaries of the greater saphenous vein from patients who were undergoing vein stripping for primary varicosity; (2) greater saphenous veins (SVs) from the same patients; and (3) greater saphenous veins from patients without varicosity who were undergoing arterial reconstruction (control). Veins were either cut into rings and suspended in organ chambers for measurement of isometric force, prepared for receptor binding of membrane proteins, or were prepared for measurement of preproendothelin mRNA by reverse transcriptase-polymerase chain reaction (RT-PCR). Endothelin-1 (10(-11) to 10(-7) mol/L) produced similar concentration-dependent contractions in rings with or without endothelium. Maximal tensions were significantly greater in control veins compared with either SVs or VVs. Sarafotoxin S6c (10(-11) to 3 x 10(-7) mol/L), which is selective for the endothelin-B receptor, also produced concentration-dependent increases in tension in all veins. Sarafotoxin S6c responses in VVs were shifted significantly rightward compared with either SVs or control. Maximal tensions to sarafotoxin S6c also were significantly greater in control veins compared with either SVs or VVs. In receptor binding studies, the number of binding sites as defined by competitive inhibition of 125I-endothelin-1 by endothelin-1 was less in VVs than control veins. Competitive inhibition of 125I-endothelin-1 with endothelin-3 (both A and B receptors) or sarafotoxin S6c (B receptors only) suggests that the difference in receptor number between varicose and nonvaricose veins is attributable to differences in the endothelin-B receptor subtype. Binding affinities were not significantly different for either of the receptor subtypes in all veins studied. Preproendothelin mRNA as quantitated by RT-PCR tended to be higher in VVs compared with either SVs or control veins. Decreased contractions to endothelin-1 in both varicose and saphenous veins of patients with primary varicosity may be associated with a decrease in the number of receptors. These receptors may be downregulated in response to increased production of endothelin-1, which is regulated at the transcriptional level.

Increased Lung Preproendothelin-1 mRNA and Decreased Endothelin B Receptor mRNA Expression After Chronic Pulmonary Hypertension in the Ovine Fetus.• 113

Endothelin-1 (ET-1), a potent vasoconstrictor and smooth muscle mitogen, is produced from its precursor, preproendothelin-1 (ppET-1), by ET converting enzyme (ECE-1) activity. In the fetal lung, the effects of ET-1 are also dependent upon stimulation of ET A and B receptors, which mediate vasoconstriction and vasodilation, respectively. Past studies have suggested that ET-1 contributes to high pulmonary vascular resistance (PVR) in an experimental model of perinatal pulmonary hypertension due to chronic ligation of the ductus arteriosus (DA). Physiologic studies in this model have demonstrated altered ET A and ET B activities after DA ligation, but little is known about mechanisms contributing to these changes in ET-1 activity. To further study the role of ET-1 in pulmonary hypertension after DA ligation, we studied lung mRNA expression of ppET-1, ECE-1, and the ET A and ET B receptors in normal and hypertensive fetal lambs. Total RNA was isolated from whole lung tissue in normal late gestation fetuses (135±3 days; 147 days = term) and from animals with pulmonary hypertension after DA ligation for 8 days(134±4 days). DA ligation increased right ventricular hypertrophy(0.56±0.02 vs 0.85±0.05, right ventricle / left ventricle + septum, p<0.05). Northern blot analysis was performed using cDNA probes and was normalized to the signal for 18s rRNA. We found a 71±24% increase in steady state ppET-1 mRNA (p<0.05) and a 62±5% decrease in ET B mRNA expression in DA ligation (p<0.05). ECE-1 and ET A receptor mRNA expression did not change. We conclude that chronic intrauterine pulmonary hypertension from DA ligation increases steady state ppET-1 mRNA and decreases ET B receptor mRNA without changing ECE-1 mRNA or ET A receptor mRNA expression. These findings suggest that both increased ET-1 production and decreased ET B receptor expression favor increased vasoconstrictor tone and contribute to high PVR in experimental neonatal pulmonary hypertension.

Inhibition of vascular contraction by intracisternal administration of preproendothelin-1 mRNA antisense oligoDNA in a rat experimental vasospasm model.

To clarify the role of endothelin-1 (ET-1) in the etiology of hemolysate-induced contraction of vessels, the authors introduced antisense oligoDNA for preproendothelin-1 (ppET-1) messenger RNA in a rat model of vasospasm. Phosphorothioate antisense oligoDNAs for ppET-1 were injected into the cisterna magna. Fluorescein isothiocyanate-labeled phosphorothioate antisense oligoDNAs were proven by fluorescence chasing to be incorporated into the vascular wall. Striking inhibitory effects of experimental vasospasm were observed in the basilar artery (BA) in which the oligoDNAs were injected. The vascular contraction was significantly inhibited by oligoDNAs after 20 minutes of hemolysate exposure, which suggested that ET synthesis started approximately 20 minutes after hemolysate stimulation. Expression of ppET-1 in the BA in which the spasm was inhibited was markedly suppressed at the transcription level. The results indicate that ET-1 may play an important role in hemolysate-induced vasoconstriction in rats. In addition, the antisense approach in the cerebrospinal fluid might be a useful tool for preventing cerebral vasospasm.

Pulmonary hypertension caused by congestive heart failure is ameliorated by long-term application of an endothelin receptor antagonist Increased expression of endothelin-1 messenger ribonucleic acid and endothelin-1-like immunoreactivity in the lung in congestive heart failure in rats

Objectives. The purpose of this study was to investigate whether 1) endothelin-1, a potent vasoconstrictor peptide, is involved in progression of pulmonary hypertension caused by congestive heart failure (CHF); and 2) whether long-term treatment with BQ-123, an endothelin receptor antagonist, ameliorates pulmonary hypertension caused by CHF.Background. Congestive heart failure accompanies pulmonary hypertension, and the severity of pulmonary hypertension is an important determinant of prognosis. Although we reported that production of endothelin-1 is increased in the failing heart in rats with CHF, it is not known whether production of endothelin-1 in the lung is altered by CHF.Methods. Congestive heart failure was induced by coronary artery ligation in rats. Expression of preproendothelin-1 messenger ribonucleic acid (mRNA) in the lung and kidney was determined. Endothelin-1 staining (immunoreactivity) in the lung was studied by immunohistochemical analysis. Effects of long-term BQ-123 treatment on the rats were studied.Results. Two weeks postoperatively, CHF accompanied by pulmonary hypertension developed in the rats (CHF rats). Expression of preproendothelin-1 mRNA in the lung was markedly higher in the CHF rats than in the sham-operated rats, whereas that in the kidney did not differ between the two groups. Endothelin-1 staining on the pulmonary vascular endothelial cells was more intense in the CHF rats. BQ-123 treatment over a 2-week period in the CHF rats greatly reduced right ventricular systolic pressure and central venous pressure, but it did not affect blood pressure or left ventricular contractility (peak positive first derivative of left ventricular pressure) in these rats.Conclusions. Long-term BQ-123 treatment greatly ameliorated pulmonary hypertension in the CHF rats. The present study suggests that endothelin-1 plays an important role in the progression of pulmonary hypertension caused by CHF and that an endothelin receptor antagonist may be a new therapeutic agent for CHF-induced pulmonary hypertension.

Increased concentrations of endothelin-1 messenger RNA in tissues and endothelin-1 peptide in plasma in septic pigs: modulation by betamethasone.

To study the expression of preproendothelin-1 messenger RNA (mRNA) in tissue after Escherichia coli lipopolysaccharide challenge and to evaluate the possible effects of betamethasone both regarding endothelin-1 production as well as hemodynamic and vascular effects during E. coli lipopolysaccharide infusion in pigs in vivo. Prospective trial. Laboratory at a university medical center. Ten domestic pigs, weighing 18 to 25 kg. Anesthetized pigs were given continuous infusions of E. coli lipopolysaccharide (15 micrograms/kg/hr for 3 hrs), with or without prior treatment with betamethasone (0.5 mg/kg im 12 hrs before the start of the surgical preparation and 0.5/kg iv at the start of the preparation). The E. coli lipopolysaccharide infusion evoked the characteristic cardiovascular changes observed in septic shock: decreased mean arterial pressure and cardiac output; increased heart rate and increased pulmonary vascular resistance. Large increases in both arterial plasma concentrations of endothelin-1-like immunoreactivity, as well as preproendothelin-1 mRNA concentrations in tissues, were also observed during the E. coli lipopolysaccharide infusion. Treatment with betamethasone significantly attenuated the E. coli lipopolysaccharide-induced increase in endothelin-1 plasma concentrations, whereas the increased mRNA concentrations were only slightly affected. Furthermore, betamethasone treatment also affected cardiovascular parameters, with significant attenuation of the E. coli lipopolysaccharide-induced increase in heart rate and a higher cardiac output after 60 mins of the E. coli lipopolysaccharide infusion. The urine production, which was markedly decreased during the E. coli lipopolysaccharide infusion, was significantly higher in the betamethasone-treated group compared with the control group. The present results indicate that the increased concentrations of endothelin-1-like immunoreactivity that are observed in septic shock may have negative effects on both cardiovascular parameters as well as renal function, which is in agreement with a possible role for endothelin-1 in the pathogenesis of septic shock.

Expression of endothelin precursor genes in human trophoblast in culture

We have shown previously the presence of immunoreactive endothelin in cultured trophoblastic cells from human term placenta as well as in the trophoblast-conditioned medium. To confirm whether or not the differentiated syncytiotrophoblast is a site for endothelin synthesis, we investigated, by reverse transcription and polymerase chain reaction, the expression of the three preproendothelin genes in 3-day cultured trophoblast. While no endothelin-2 precursor mRNA was detected, preproendothelin-1 mRNA was found to be expressed by the trophoblast. The endothelin-3 precursor gene was also expressed, but at low level and it was detected only after Southern blotting and oligonucleotide hybridization. The ability of trophoblast in culture to express the endothelin precursor genes supports the idea that, in human term placenta, villous syncytiotrophoblast that lines the intervillous space containing maternal blood acts as an endothelial layer.

Plasmin stimulates expression of endothelin-1 mRNA and endothelin-1 release in vascular endothelial cells

Incubation of cultured porcine aortic endothelial cells (ECs) with plasmin resulted in a significant and concentration-dependent increase in endothelin-1 (ET-1 ) release from the cells. This increasing effect was completely inhibited by aprotinin but not by tranexamic acid, thereby suggesting that the plasmin-induced stimulation of ET-1 release requires the catalytic site but not the lysine binding site, in plasmin molecule. Plasmin stimulated the expression of prepro ET-1 mRNA in ECs. Actinomycin D chase experiments suggested that enhanced stability of ET-1 mRNA could not account for the above plasmin-induced stimulation. It is likely that plasmin potentiates the endothelial ET-1 production, probably by the stimulation of ET-1 gene transcription. It remains to be seen whether the endothelial ET-1 production is enhanced after the thrombolytic therapy.

Endothelial and epithelial sources of endothelin-1 in sheep bronchi.

Airway smooth muscle tone and growth is regulated by endothelin-1 (ET-1), but the sources of ET-1 in the airway wall have not been clearly defined. We therefore wished to estimate the relative contributions of the epithelium and endothelium to ET-1 production in the bronchi (mean ID 1.7-4.9 mm) of mature normal sheep. Morphometric assessment of bronchial cross-sections revealed a number of epithelial cells three times greater than endothelial cells by direct cell count. In contrast, the overall cell surface density was five to six times greater, and the airway smooth muscle-centered cell surface density was three to four times greater for endothelial cells than for epithelial cells. The expression of preproendothelin-1 mRNA was detected in cultured aortic endothelial cells (as a substitute for bronchial endothelial cells) but not in cultured bronchial epithelial cells, and the former secreted seven times more immunoreactive ET-1 than the latter. These findings show that topographically the endothelium is better positioned for the regulation of ovine bronchial smooth muscle than the epithelium. Furthermore, the findings suggest greater constitutive ET-1 secretion by cultured endothelium than by epithelium.

Elevation of endothelin biosynthesis in human endothelial cells with mycoplasma infection.

The effects of mycoplasma infection on the biosynthesis of endothelin-1 (ET-1) in cultured human vascular endothelial cell lines were examined to understand regulatory mechanisms of ET-1 biosynthesis and causes of angiopathy due to mycoplasma infection. The growth of normal endothelial cells from the umbilical cord vein and of an immortal endothelial cell line transfected with prepro ET-1 cDNA was decreased, while the secretion of ET-1 into the culture medium was enhanced by mycoplasma infection. However, the rate of ET-1 production in these cell cultures was much higher at the growing phase than at the stationary phase. Immunocytochemical studies with anti-ET-1 antibody and an autoradiographic examination of the labeled nuclei with 3H-TdR revealed that mycoplasma infection induced an elevation of ET-1 production in both S and non-S phase cells. The expression of prepro ET-1 mRNA as examined by in situ hybridization and by RNase protection assay was not altered by mycoplasma infection. Thus, the biosynthesis of ET-1 in vascular endothelial cells may be regulated at the posttranscriptional level.

ET A receptor-mediated role of endothelin in the kidney of doca-salt hypertensive rats

Renal effects of FR139317, an endothelin ET A receptor antagonist, were examined using anesthetized normotensive and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The intravenous bolus injection of FR139317 (10 mg/kg) produced a slight decrease in mean blood pressure (MAP; −13%) in the control rats and this hypotension was accompanied by a moderate renal vasodilation (renal vascular resistance: RVR; −12%). In the DOCA-salt hypertensive rat, FR139317 had a more pronounced hypotensive effect (MAP; −26%) accompanied by a potent renal vasodilation (RVR; −33%). FR 139317 significantly increased renal blood flow only in the DOCAsalt rats. In contrast, FR139317 produced a significant decrease in urine flow and urinary sodium excretion only in control rats. Northern blot analysis revealed that the renal prepro endothelin-1 (ET-1) mRNA level was significantly increased in DOCA-salt hypertensive rats. Thus, it seems likely that endogenous ET-1 is responsible for the maintenance of DOCA-salt-induced hypertension. We also suggest that at least in part, ET-1 and £ta receptors are involved in renal hemodynamic abnormalities in DOCA-salt-induced hypertension. The augmentation of renal ET-1 production may possibly have a function in the development and maintenance of DOCA-salt-induced hypertension.

Endothelin-1 and its binding sites are upregulated in pressure overload cardiac hypertrophy.

The purpose of this study was to determine whether endothelin and endothelin receptors play an important role in the development of cardiac hypertrophy due to pressure overload in vivo. Cardiac hypertrophy was produced by placing a constricting clip around the suprarenal abdominal aorta of rats. Hemodynamic parameters and plasma and ventricular concentrations of endothelin-1 (ET-1) were measured in control unoperated rats, and 30 min, 2 and 6 h, and 1 and 8 days after operation in pressure overload rats and sham-operated rats. The density and dissociation constant of ET-1 binding sites were also measured in control rats and 1 and 8 days after pressure overload and sham operation. Additionally, in situ mRNA hybridization for preproendothelin-1 (preproET-1) mRNA was performed to determine which cells were responsible for increased ET-1 levels. Ventricular ET-1 levels increased markedly on day 8 of pressure overload, whereas plasma ET-1 levels increased transiently only 30 min after operation, quickly returning to control level. In addition, ventricular ET-1 levels on day 8 showed a significant positive correlation with the degree of cardiac hypertrophy. In situ mRNA hybridization revealed that cardiac myocytes expressed preproET-1 mRNA in hypertrophied hearts in vivo. In accord with the elevation of ventricular ET-1 levels, the density of ET-1 binding sites was increased significantly, without affecting their binding affinity, on day 8 of pressure overload. These data are compatible with the hypothesis that increases in locally produced ET-1 and the density of ET-1 binding sites have an important relationship with the development of cardiac hypertrophy in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Salt Loading on the Cardiac and Renal Preproendothelin-1 mRNA Expression in Stroke-Prone Spontaneously Hypertensive Rats

Endothelin-1 is a potent vasoactive peptide which may play a role in the regulation of vascular resistance through its autocrine/paracrine effects. We have investigated the influence of salt loading on the renal and cardiac production of endothelin-1 in stroke prone spontaneously hypertensive rats, a classical model of hypertension. The results show that the dietary salt intake did not change systolic blood pressure nor the renal expression of the preproendothelin-1 mRNA but increased cardiac expression of the endothelin-1 gene transcript and a concomitant ventricular hypertrophy.

Endothelin-1 expression in myenteric neurons cultured from rat small intestine

Endothelin is a potent vasoactive peptide. More recently, endothelin-1 (ET-1) has been found in neural tissues such as spinal cord, brain and peripheral ganglion cells. Inagaki (Gastroenterology 101 (1991) 47) reported evidence of ET-1-like immunoreactivity in enteric neurons, but there are no reports of ET-1 peptide or mRNA expression specifically in myenteric neurons. Using a primary culture of myenteric neurons, we set out to evaluate ET-1 peptide and mRNA expression. Myenteric neurons were cultured using a dissection and enzyme dispersion technique. ET-1 reactivity was localized to neurons and ET-1 levels from cells and media were assayed by radioimmunoassay under a variety of media conditions or with depolarizing buffer or veratridine (75 μM). Prepro ET-1 mRNA expression was determined by Northern analysis of total RNA utilizing a rat ET-1 cDNA. ET-1 immunoreactivity was observed almost exclusively in myenteric neurons. Cells contained 0.78 pg/μg protein and did not vary with variations in media conditions. Basal release/secretion into media occurred but was not enhanced by depolarizing media or veratridine. High levels of ET-1 mRNA expression were identified. These results of high level constitutive expression of ET-1 linked with previous reports of ET-1 modulation of cholinergic intestinal smooth muscle contraction suggest a neuromodulatory role.

Involvement of transforming growth factor-beta 1 for platelets-induced stimulation of endothelin-1 production.

1. Possible mechanisms by which platelets stimulate the production of endothelin-1 (ET-1) in vascular endothelial cells (EC) were investigated. 2. A supernatant of platelets stimulated the expression of prepro ET-1 mRNA, followed by an increased secretion of ET-1 from cultured EC. These responses were markedly enhanced by pretreatment of the platelets with thrombin, at a concentration which did not influence the ET-1 production in EC. A platelet suspension, separated from cultured EC by a permeable nylon membrane, also markedly stimulated the ET-1 secretion from EC. 3. Endothelin-1 production enhanced by the platelet supernatant, with or without thrombin pretreatment, correlated with the active transforming growth factor-beta 1 (TGF-beta 1) concentrations in the supernatant. The supernatant-induced increase in ET-1 secretion from the EC was markedly suppressed by TGF-beta 1 neutralizing antibody. 4. We tentatively conclude that platelets stimulate the endothelial ET-1 production by releasing a bioactive diffusible substance, mainly TGF-beta 1.

The control of endothelin-1 secretion

1. The human endothelin-1 (ET-1) gene, which is located on chromosome 6, contains cis-regulatory elements in the 5′-flanking region including the TPA-responsive element, nuclear factor 1 binding element and GATA motif. 2. The expression of preproendothelin-1 (PPET-1) mRNA is regulated by a mechanism involving receptor mediated mobilization of intracellular Ca 2+ and activation of protein kinase C in endothelial cells. 3. Activation of protein kinase C results in the synthesis of c-Jun protein and the rapid dephosphorylation of c-Jun protein. Consequently, the binding activity of c-Jun protein to the TPA-responsive element increases, and this causes the induction of PPET-1 mRNA. 4. The microtubular system seems to play some important roles in ET-1 secretion, especially in the process of transferring the synthesized ET-1 to the cell surface of the endothelial cells. 5. The secretion of ET-1 from endothelial cells is also regulated by intracellular Ca 2+ released from the Ca 2+ store and by Ca 2+-calmodulin complex. The phosphorylation of the myosin light chain, elicited by myosin light chain kinase and activated by Ca 2+-calmodulin complex, facilitates the formation of filamentous myosin and actin which probably participate in ET-1 secretion especially in transporting the ET-1-containing vesicles towards the cell membrane in the stimulated endothelial cells. 6. Many cultured cells, other than endothelial cells, also secrete ET-1 into the culture medium and this secretion can be stimulated by a variety of agents.

Increased endothelin-1 production in fibroblasts derived from patients with systemic sclerosis.

To determine whether fibroblasts from patients with systemic sclerosis (SSc) produce excessive amounts of endothelin-1 (ET-1), which is recognised as having vasoconstrictive properties and as having a potent mitogenic effect on fibroblasts. Dermal fibroblasts were removed from 11 patients with SSc and from five normal controls (NC). The assay of ET-1 protein was measured by an ELISA that used two anti-ET-1 antibodies. The gene expression of prepro ET-1 mRNA was evaluated by a reverse-transcriptase polymerase chain reaction (RT-PCR) method. Levels of ET-1 protein were significantly higher in SSc fibroblast cultures than in those of normal fibroblasts (p < 0.01). The expression of prepro ET-1 mRNA was also higher in SSc fibroblasts than in normal fibroblasts. The addition of interleukin-1 beta (IL-1 beta) increased the production of ET-1 by fibroblasts. The findings indicate that the overproduction of ET-1 is a novel abnormal function in SSc fibroblasts, and that ET-1 induced by fibroblasts may play a role in the fibrosis and Raynaud's phenomenon of SSc.

Endotoxin and pro-inflammatory cytokines stimulate endothelin-1 expression and release by airway epithelial cells.

Endothelin is a potent bronchoconstrictor peptide first identified as a novel vasoconstrictor produced by vascular endothelial cells. Recent reports suggest that airway epithelial cells are also capable of releasing this active peptide. To investigate the regulatory mechanism of endothelin expression, we studied the effects of endotoxin and pro-inflammatory cytokines such as interleukin-1 and tumour necrosis factor on the expression and release of endothelin-1 by airway epithelial cells. Both endotoxin and the cytokines stimulated endothelin-1 release by human bronchial epithelial cells. Northern blot analysis showed increased expression of preproendothelin-1 mRNA by these factors. These results suggested that airway epithelial cells might play a role in the local airway smooth muscle tone through the production of endothelin, which might be upregulated by inflammatory products in the airways.

Contribution of endogenous endothelin-1 to the progression of cardiopulmonary alterations in rats with monocrotaline-induced pulmonary hypertension.

Endothelin-1 (ET-1) is known to have potent contractile and proliferative effects on vascular smooth muscle cells and is known to induce myocardial cell hypertrophy. We studied the pathophysiological role of endogenous ET-1 in rats with monocrotaline-induced pulmonary hypertension. Four-week-old rats were given a single subcutaneous injection of 60 mg/kg monocrotaline (MCT rats) or saline (control rats) and were killed after 6, 10, 14, 18, and 25 days. In the MCT rats, right ventricular systolic pressure progressively increased and right ventricular hypertrophy developed in a parallel fashion. The venous plasma ET-1 concentration also progressively increased, and this increase preceded the development of pulmonary hypertension. The isolated pulmonary artery exhibited a significantly weaker response to ET-1 in the MCT rats on day 25 but not on days 6 and 14. In the MCT rats, the expression of prepro ET-1 mRNA as measured by Northern blot analysis significantly increased in the heart on days 18 and 25, whereas it gradually decreased in the lungs. The peptide level of ET-1 in the lungs also significantly decreased in the pulmonary hypertensive stage. The expression of prepro ET-1 mRNA had increased by day 6 only in the kidneys. Continuous infusion of BQ-123, a selective ETA receptor antagonist, by an osmotic minipump (14.3 mg per day per rat for 18 days) significantly inhibited the progression of both pulmonary hypertension (right ventricular systolic pressure, 77.8 +/- 4.2 [mean +/- SEM] mm Hg [n = 10] versus 52.3 +/- 2.4 mm Hg [n = 7]; P < .01) and right ventricular hypertrophy (right ventricle/[left ventricle +/- septum], 0.56 +/- 0.03 [n = 10] versus 0.41 +/- 0.02 [n = 7]; P < .01). Histological examination revealed that BQ-123 also effectively prevented pulmonary arterial medial thickening. The inhibition of right ventricular hypertrophy by BQ-123 may be partly ascribed to the blockade of excessive stimulation of the heart by ET-1, in addition to the prevention of pulmonary hypertension. The present findings suggest that endogenous ET-1 contributes to the progression of cardiopulmonary alterations in rats with MCT-induced pulmonary hypertension.