The Human Preproendothelin-1 Gene

Elevated levels of c-jun and c-fos transcripts in the aged rat liver

Age-associated increases of transcript levels of several genes were studied using aged rat liver. Northern hybridization showed marked increases of c-jun, c-fos, and glutathione S-transferase P (GST-P) in 24-month-old rats. These genes have the 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-responsive element called TRE in their structures. Thus, TRE seems to be involved in important age-associated changes of gene expression.

Cloning and functional expression of human cDNA for the ETB endothelin receptor

We report the cloning of human cDNA encoding an ETB (non-isopeptide-selective) subtype of the endothelin receptor. The predicted amino acid sequence of the human ETB endothelin receptor was 87.8% and 62.9% identical with the previously cloned rat ETB and ETA receptors, respectively. COS cells transiently transfected with the cloned cDNA expressed specific, high-affinity binding sites for endothelin isopeptides and responded to the peptides with a transient increase of [Ca2+]i; endothelin-1 and endothelin-3 exhibited approximately equal potencies both in displacing 125I-labeled endothelin-1 binding and in eliciting [Ca2+]i transients. The ETB receptor mRNAs were expressed in various human tissues and also in the intact porcine aortic intimal cells ex vivo.

cDNA cloning, sequence analysis and tissue distribution of a precursor for vasoactive intestinal contractor (VIC)

A full-length cDNA encoding preprovasoactive intestinal contractor (PPVIC) has been cloned. From the deduced 160 amino acid PPVIC, the mature VIC is predicted to be produced via a 37 residue intermediate, big VIC. The PPVIC also contains a VIC-like peptide of 16 amino acids structurally related to to the amino-terminal residues of VIC and flanked by pairs of dibasic amino acids, putative processing sites. RNA blot hybridization with PPVIC cDNA confirmed the PPVIC gene to be expressed in the small and large intestinal tract in a tissue specific manner.

Phorbol dibutyrate stimulates the release of diffusible endothelium-derived vasoconstrictor factor(s) from canine femoral arteries

The purpose of this study was to analyze the effect of the tumor-promoting phorbol ester 12,13-dibutyrate (PDBu) on the synthesis/release of nonprostanoid endothelium-derived vasoactive factors. In bioassay experiments (in the presence of 10(-5) M indomethacin), infusion of PDBu (10(-9)-10(-7) M) through a femoral artery (donor) segment with endothelium evoked further, concentration-dependent contraction of superfused canine coronary artery bioassay rings without endothelium (already contracted with 10(-7) M PDBu). Removal of the endothelium from the donor segment abolished further contractions of the bioassay ring to 10(-9) M PDBu and significantly depressed the contractile responses to 10(-9) and 10(-7) M PDBu infused through the donor segment. The inactive phorbol ester 4 alpha-phorbol 12,13-didecanoate had no effect on vascular preparations mounted in the bioassay system. Selective exposure of the bioassay tissue to 10(-7) M PDBu completely inhibited its responsiveness to basally released endothelium-derived relaxing factor. These data indicate that PDBu stimulates the release of a diffusible and bioassayable vasoconstrictor mediator(s) from the endothelium of canine femoral arteries.

Endothelins: vasoconstrictor effects and localization in canine cerebral arteries

1. The vascular effects of endothelin and localization of endothelin-like immunoreactivity were characterized in isolated cerebral arteries of dogs. 2. Endothelin-like immunoreactivity was detected in a few populations of endothelial cells of dog basilar artery. 3. Endothelin-1, endothelin-2 and endothelin-3 contracted isolated ring preparations of cerebral arteries in a dose-dependent manner independently of the presence of endothelium. The ED50 values (and 95% confidence intervals) for the contraction were 411 pM (242-697 pM) and 478 pM (295-776 pM) for endothelin-1 and endothelin-2, respectively. Endothelin-3 induced vascular contraction at a higher concentration (ED50 = 26.5 nM, 95% confidence interval = 15.7-45.7 nM). 4. The increases in tone induced by endothelin-1 and endothelin-2 did not return to the resting level after repeated washings, while a rinse with Krebs solution reversed the vasoconstrictor response to endothelin-3. The endothelins did not cause any vasodilator response in arteries precontracted with uridine 5'-triphosphate even in the presence of intact endothelial cells. 5. NiCl2 (1 mM) attenuated the contractions induced by endothelin-3 (10-300 nM) and those to relatively low doses (1 nM) but not higher doses (10-100 nM) of endothelin-1 and endothelin-2. The contractions in response to endothelin-1, endothelin-2 and endothelin-3 were greatly attenuated in Ca(2+)-free solutions although high concentrations of endothelin-1 and endothelin-2 still evoked contractions. 6. These results suggest that the vasoconstriction induced by endothelin-3 and lower doses of endothelin-1 and endothelin-2, largely depends on the influx of Ca2+ ions. The apparent insensitivity to Ni2+ shows that additional distinct mechanisms also operate in the vasconstrictor responses to high concentrations of endothelin-1 and endothelin-2. 7. The presence of endothelin-like immunoreactivity in endothelial cells suggests that endothelin is a potential endogenous spasmogen.

Cytokine stimulated endothelin release from endothelial cells

Endothelin release from bovine endothelial cells of the aorta, pulmonary artery, and retinal microvessels was measured in response to various cytokines. Transforming growth factor beta (0.05-5 ng/ml) was found to be a potent stimulator (3-4 fold increase) of endothelin secretion in all three cell types. Tumour necrosis factor alpha (0.1-10 ng/ml) and interferon gamma (8-800 U/ml) had a small (1.5-2 fold increase) but significant effect on endothelin secretion from endothelial cells of large vessels but not the retinal microvessels. Interleukin-1 beta, Interleukin-6 and interleukin-8 at various doses did not affect endothelin secretion. These effects were observed at various time points from 6-24 hrs and indicate that of the cytokines tested, only transforming growth factor beta has a potent effect on endothelin release from endothelial cells of different organs.

Cytokine-induced release of endothelin-1 from porcine renal epithelial cell line

To elucidate the mechanism by which endothelin-1 (ET-1) is released from renal epithelial cells, we have investigated the effects of several compounds on release of ET-1-like immunoreactivity (LI) from LLCPK1 cell line. Thrombin, transforming growth factor-beta, cytokines (tumor necrotizing factor-alpha, interleukin-1 beta), and phorbol ester stimulated ET-1-LI release in a time- and dose-dependent manner. The cytokine-induced ET-1-LI release was not affected by indomethacin. Northern blot analysis using cDNA for porcine preproET-1 as a probe revealed a single major band corresponding to the size of ET-1 mRNA in LLCPK1. These data indicate that the preproET-1 gene is also expressed in renal epithelial cells and the release of ET-1 from renal cells is regulated by the similar mechanism to that from endothelial cells.

Endothelin: a novel peptide in the posterior pituitary system

Endothelin (ET), originally characterized as a 21-residue vasoconstrictor peptide from endothelial cells, is present in the porcine spinal cord and may act as a neuropeptide. Endothelin-like immunoreactivity has now been demonstrated by immunohistochemistry in the paraventricular and supraoptic nuclear neurons and their terminals in the posterior pituitary of the pig and the rat. The presence of ET in the porcine hypothalamus was confirmed by reversed-phase high-pressure liquid chromatography and radioimmunoassay. Moreover, in situ hybridization demonstrated ET messenger RNA in porcine paraventricular nuclear neurons. Endothelin-like immunoreactive products in the posterior pituitary of the rat were depleted by water deprivation, suggesting a release of ET under physiological conditions. These findings indicate that ET is synthesized in the posterior pituitary system and may be involved in neurosecretory functions.

Expression and regulation of endothelin precursor mRNA in avascular human amnion

Posttranslational processing of preproendothelin in endothelial cells gives rise to endothelin, a 21 amino acid polypeptide that is a potent vasoconstrictor. Endothelin production is believed to be mediated principally by transcriptional mechanisms. Previously, preproendothelin mRNA expression has been detected only in vascular endothelial tissue and cells. In this study, we found that preproendothelin mRNA is expressed in an avascular human tissue, namely, amnion, an extraembryonic fetal membrane. Preproendothelin mRNA was not detected in avascular chorion laeve tissue (also an extraembryonic fetal membrane), in the highly vascularized fetal trophoblast, or in maternal uterine tissues. Furthermore, we found that preproendothelin gene expression is retained in human amnion cells maintained in primary monolayer culture. Using the amnion cells in primary monolayer culture to investigate the regulation of preproendothelin mRNA expression, we found that epidermal growth factor (EGF) and interleukin-1 (IL-1) act to stimulate preproendothelin mRNA levels; in addition, the induction of preproendothelin mRNA by either of these agents is enhanced upon simultaneous treatment with cycloheximide. These findings are indicative that preproendothelin gene expression in amnion is regulated positively by EGF and IL-1 and that inhibition of protein synthesis leads to superinduction of preproendothelin mRNA. In human umbilical cord endothelial cells, neither IL-1 nor EGF stimulate preproendothelin mRNA expression but inhibition of protein synthesis does lead to increased levels of preproendothelin mRNA. The amnion, therefore, provides a useful system for expansion of our understanding of the tissue specific expression and regulation of preproendothelin mRNA.