Reduced Endothelin-2 and Hypoxic Signaling Pathways in Granulosa-Lutein Cells of PCOS Women

Granulosa-lutein cells (GLCs) from PCOS women display reduced HIF-1α and EDN2 levels, suggesting their role in PCOS etiology. Here, we investigated the mechanisms involved in aberrant EDN2 expression in PCOS, and its association with HIF-1α. Various HIF-1α-dependent factors were studied in GLCs from PCOS and compared to normally ovulating women. MicroRNA-210 (miR-210), its target genes (SDHD and GPD1L), and HIF-1α-responsive genes (EDN2 and VEGFA) differed in GLCs from PCOS, compared with those of healthy women. Levels of miR-210—designated hypoxiamiR—and EDN2 were reduced in the PCOS GLCs; concomitantly, GPD1L and SDHD levels were elevated. Cultured GLCs retained low EDN2 expression and had low HIF-1α levels, providing evidence for a disrupted hypoxic response in the PCOS GLCs. However, VEGFA expression was elevated in these cells. Next, miR-210 levels were manipulated. miR-210-mimic stimulated EDN2 twice as much as the miR-NC-transfected cells, whereas miR-210-inhibitor diminished EDN2, emphasizing the importance of hypoxiamiR for EDN2 induction. Intriguingly, VEGFA transcripts were reduced by both miR-210-mimic and -inhibitor, demonstrating that EDN2 and VEGFA are distinctly regulated. Disrupted hypoxic response in the GLCs of periovulatory follicles in PCOS women may play a role in ovulation failure, and in the reduced fertility prevalent in this syndrome.

Core Binding Factor β Expression in Ovarian Granulosa Cells Is Essential for Female Fertility

Core binding factor β (CBFβ) is a non-DNA-binding partner of all RUNX proteins and critical for transcription activity of CBF transcription factors (RUNXs/CBFβ). In the ovary, the expression of Runx1 and Runx2 is highly induced by the luteinizing hormone (LH) surge in ovulatory follicles, whereas Cbfb is constitutively expressed. To investigate the physiological significance of CBFs in the ovary, the current study generated two different conditional mutant mouse models in which granulosa cell expression of Cbfb and Runx2 was reduced by Cre recombinase driven by an Esr2 promoter. Cbfbgc-/- and Cbfbgc-/- × Runx2gc+/- mice exhibited severe subfertility and infertility, respectively. In the ovaries of both mutant mice, follicles develop normally, but the majority of preovulatory follicles failed to ovulate either in response to human chorionic gonadotropin administration in pregnant mare serum gonadotropin-primed immature animals or after the LH surge at 5 months of age. Morphological and physiological changes in the corpus luteum of these mutant mice revealed the reduced size, progesterone production, and vascularization, as well as excessive lipid accumulation. In granulosa cells of periovulatory follicles and corpora lutea of these mice, the expression of Edn2, Ptgs1, Lhcgr, Sfrp4, Wnt4, Ccrl2, Lipg, Saa3, and Ptgfr was also drastically reduced. In conclusion, the current study provided in vivo evidence that CBFβ plays an essential role in female fertility by acting as a critical cofactor of CBF transcription factor complexes, which regulate the expression of specific key ovulatory and luteal genes, thus coordinating the ovulatory process and luteal development/function in mice.

Biomarkers for Diabetic Retinopathy - Could Endothelin 2 Be Part of the Answer?

Purpose

The endothelins are a family of three highly conserved and homologous vasoactive peptides that are expressed across all organ systems. Endothelin (Edn) dysregulation has been implicated in a number of pathophysiologies, including diabetes and diabetes-related complications. Here we examined Edn2 and endothelin receptor B (Endrb) expression in retinae of diabetic mouse models and measured serum Edn2 to assess its biomarker potential.

Materials and Methods

Edn2 and Ednrb mRNA and Edn2 protein expression were assessed in young (8wk) and mature (24wk) C57Bl/6 (wild type; wt), Kimba (model of retinal neovascularisation, RNV), Akita (Type 1 diabetes; T1D) and Akimba mice (T1D plus RNV) by qRT-PCR and immunohistochemistry. Edn2 protein concentration in serum was measured using ELISA.

Results

Fold-changes in Edn2 and Ednrb mRNA were seen only in young Kimba (Edn2: 5.3; Ednrb: 6.0) and young Akimba (Edn2: 7.9, Ednrb: 8.8) and in mature Kimba (Edn2:9.2, Ednrb:11.2) and mature Akimba (Edn2:14.0, Ednrb:17.5) mice. Co-localisation of Edn2 with Müller-cell-specific glutamine synthetase demonstrated Müller cells and photoreceptors as the major cell types for Edn2 expression in all animal models. Edn2 serum concentrations in young Kimba, Akita and Akimba mice were not elevated compared to wt. However, in mature mice, Edn2 serum concentration was increased in Akimba (6.9pg/mg total serum protein) compared to wt, Kimba and Akita mice (3.9, 4.6, and 3.8pg/mg total serum protein, respectively; p<0.05).

Conclusions

These results demonstrated that long-term hyperglycaemia in conjunction with VEGF-driven RNV increased Edn2 serum concentration suggesting Edn2 might be a candidate biomarker for vascular changes in diabetic retinopathy.

Expression of Endothelins and Their Receptors in Nonmelanoma Skin Cancers

Background:

Endothelins are paracrine peptides with growth-promoting and vasoactive functions for a variety of cell types. Elevated activation of the endothelin signaling pathway induces cell proliferation and/or survival and is implicated in a variety of malignancies. Increased endothelin 1 was described in solar lentigines in previous reports, raising the possibility that the endothelin pathway may be of significance in keratinocyte proliferation-related disorders. However, detailed investigation on endothelins in skin malignancies is lacking.

Objectives:

This study aims to survey the expression of endothelins and their receptors in keratinocyte-derived benign and malignant tumors of the skin and to test the effects of endothelin inhibitors on the growth and survival of cultured keratinocytes.

Methods:

Quantitative polymerase chain reaction was used to measure the level of gene transcription of three endothelins (ET-1, −2, and −3) and two endothelin receptors (ETRA and ETRB). The genes with significant messenger ribonucleic acid (mRNA) expression abnormalities were confirmed with immunohistochemical analysis to examine expression differences at the protein levels. To analyze the effect of endothelin inhibitors on the keratinocyte growth and survival, keratinocytes were cultured in the presence of various concentrations of endothelin inhibitors and subjected to tetrazolium bromide assay to quantify the cell numbers over time.

Results:

ET-1 mRNA was found to be significantly up-regulated in seborrheic keratosis and basal cell carcinoma. However, no significant expression increase was found in actinic keratosis, Bowen's disease, or squamous cell carcinoma. Immunohistochemical analysis of ET-1 peptide confirmed increased expression. In cultured keratinocytes, peptide inhibitors of the endothelin pathway resulted in a marked reduction in cell survival.

Conclusion:

The endothelin signaling pathway, especially ET-1, is activated in basoloid keratinocyte neoplasms of the skin, such as basal cell carcinoma and seborrheic keratosis. Blockade of this pathway can reduce cell survival in vitro. Therefore, endothelin inhibitors potentially offer a novel method for the treatment of some keratinocyte-derived skin tumors.

In vivo imaging reveals an essential role of vasoconstriction in rupture of the ovarian follicle at ovulation

Rupture of the ovarian follicle releases the oocyte at ovulation, a timed event that is critical for fertilization. It is not understood how the protease activity required for rupture is directed with precise timing and localization to the outer surface, or apex, of the follicle. We hypothesized that vasoconstriction at the apex is essential for rupture. The diameter and blood flow of individual vessels and the thickness of the apical follicle wall were examined over time to expected ovulation using intravital multiphoton microscopy. Vasoconstriction of apical vessels occurred within hours preceding follicle rupture in wild-type mice, but vasoconstriction and rupture were absent in Amhr2(cre/+)SmoM2 mice in which follicle vessels lack the normal association with vascular smooth muscle. Vasoconstriction is not simply a response to reduced thickness of the follicle wall; vasoconstriction persisted in wild-type mice when thinning of the follicle wall was prevented by infusion of protease inhibitors into the ovarian bursa. Ovulation was inhibited by preventing the periovulatory rise in the expression of the vasoconstrictor endothelin 2 by follicle cells of wild-type mice. In these mice, infusion of vasoconstrictors (either endothelin 2 or angiotensin 2) into the bursa restored the vasoconstriction of apical vessels and ovulation. Additionally, infusion of endothelin receptor antagonists into the bursa of wild-type mice prevented vasoconstriction and follicle rupture. Processing tissue to allow imaging at increased depth through the follicle and transabdominal ultrasonography in vivo showed that decreased blood flow is restricted to the apex. These results demonstrate that vasoconstriction at the apex of the follicle is essential for ovulation.

Endothelin-2-mediated protection of mutant photoreceptors in inherited photoreceptor degeneration

Expression of the Endothelin-2 (Edn2) mRNA is greatly increased in the photoreceptors (PRs) of mouse models of inherited PR degeneration (IPD). To examine the role of Edn2 in mutant PR survival, we generated Edn2^−/− mice carrying homozygous Pde6b^rd1 alleles or the Tg(RHO P347S) transgene. In the Edn2^−/− background, PR survival increased 110% in Pde6b^rd1/rd1 mice at post-natal (PN) day 15, and 60% in Tg(RHO P347S) mice at PN40. In contrast, PR survival was not increased in retinal explants of Pde6b^rd1/rd1; Edn2^−/− mice. This finding, together with systemic abnormalities in Edn2^−/− mice, suggested that the increased survival of mutant PRs in the Edn2^−/− background resulted at least partly from the systemic EDN2 loss of function. To examine directly the role of EDN2 in mutant PRs, we used a scAAV5-Edn2 cDNA vector to restore Edn2 expression in Pde6b^rd1/rd1; Edn2^−/− PRs and observed an 18% increase in PR survival at PN14. Importantly, PR survival was also increased after injection of scAAV5-Edn2 into Pde6b^rd1/rd1 retinas, by 31% at PN15. Together, these findings suggest that increased Edn2 expression is protective to mutant PRs. To begin to elucidate Edn2-mediated mechanisms that contribute to PR survival, we used microarray analysis and identified a cohort of 20 genes with >4-fold increased expression in Tg(RHO P347S) retinas, including Fgf2. Notably, increased expression of the FGF2 protein in Tg(RHO P347S) PRs was ablated in Tg(RHO P347S); Edn2^−/− retinas. Our findings indicate that the increased expression of PR Edn2 increases PR survival, and suggest that the Edn2-dependent increase in PR expression of FGF2 may contribute to the augmented survival.

Generating embryonic stem cells from the inbred mouse strain DBA/2J, a model of glaucoma and other complex diseases

Mouse embryonic stem (ES) cells are derived from the inner cell mass of blastocyst stage embryos and are used primarily for the creation of genetically engineered strains through gene targeting. While some inbred strains of mice are permissive to the derivation of embryonic stem cell lines and are therefore easily engineered, others are nonpermissive or recalcitrant. Genetic engineering of recalcitrant strain backgrounds requires gene targeting in a permissive background followed by extensive backcrossing of the engineered allele into the desired strain background. The inbred mouse strain DBA/2J is a recalcitrant strain that is used as a model of many human diseases, including glaucoma, deafness and schizophrenia. Here, we describe the generation of germ-line competent ES cell lines derived from DBA/2J mice. We also demonstrate the utility of DBA/2J ES cells with the creation of conditional knockout allele for Endothelin-2 (Edn2) directly on the DBA/2J strain background.

Induction of endothelin-2 expression by luteinizing hormone and hypoxia: possible role in bovine corpus luteum formation

The pattern and regulation of endothlin-2 (EDN2) expression and its putative roles in bovine ovaries were investigated. EDN2 mRNA was determined in corpus luteum (CL) and during folliculoluteal transition induced by GnRH in vivo. EDN2 was elevated only in the early CL and was not present in older CL. In the young CL, EDN2 mRNA was identified mainly in luteal cells but not endothelial cells that expressed the EDN1 gene. Similarly, in preovulatory follicles, EDN2 was expressed in the granulosa cells (GCs) and not in the vascular theca interna. LH and hypoxia are two major stimulants of CL formation. Therefore, GCs were cultured with bovine LH, under hypoxic conditions. GCs incubated with bovine LH resulted in increased EDN2 mRNA 42 h later. CoCl2, a hypoxia-mimicking agent, elevated EDN2 in GCs in a dose-dependent manner. Incubation of the human GC line (Simian virus 40 large T antigen) under low oxygen tension (1%) augmented EDN2 6 and 24 h later. In these two cell types, along with EDN2, hypoxia augmented VEGF. EDN2 induced in GCs changes that characterize the developing CL: cell proliferation as well as up-regulation of vascular endothelial growth factor and cyclooxygenase-2 (mRNA and protein levels). Human chorionic gonadotropin also up-regulated these two genes. Small interfering RNA targeting EDN-converting enzyme-1 effectively reduced its mRNA levels. This treatment, expected to lower the mature EDN2 peptide production, inhibited VEGF mRNA levels and GC numbers. Together these data suggest that elevated EDN2 in the early bovine CL, triggered by LH surge and hypoxia, may facilitate CL formation by promoting angiogenesis, cell proliferation, and differentiation.

The ovarian endothelin network: an evolving story

The endothelin (ET) system consists of three ET isopeptides, several converting enzyme isoforms and two G-protein-coupled receptors, ETA and ETB, which are linked to multiple signaling pathways. Less than 20 years after the initial detection of ET-1 in granulosa cells, the ovarian ET network continues to expand with the discovery of new members and functions. ETs influence a broad range of essential reproductive processes, such as ovulation, steroidogenesis and luteolysis. Therefore, a more comprehensive understanding of the ovarian ET network might provide new strategies for controlling reproduction. This review presents up-to-date findings on the ET network in the ovary.

Gene Expression Analysis of Photoreceptor Cell Loss inBbs4-Knockout Mice Reveals an Early Stress Gene Response and Photoreceptor Cell Damage

PURPOSE

To identify and characterize gene expression changes associated with photoreceptor cell loss in a Bbs4-knockout mouse model of retinal degeneration.

METHODS

Differential gene expression in the eyes of 5-month-old Bbs4(-/-) mice undergoing retinal degeneration were analyzed using gene microarrays (Affymetrix, Santa Clara, CA). Elevated ocular transcripts were confirmed by Northern blotting of RNA from Bbs4(-/-) and three additional mouse models of Bardet-Biedl Syndrome (BBS). TUNEL assays and transmission electron microscopy were used to study cell death and photoreceptor morphology in these mice.

RESULTS

Three hundred fifty-four probes were differentially expressed in Bbs4(-/-) eyes compared with controls using a twofold cutoff. Numerous vision-related transcripts decreased because of photoreceptor cell loss. Increased expression of the stress response genes Edn2, Lcn2, Serpina3n, and Socs3 was noted at 5 months of age and as early as postnatal week 4 in the eyes of four BBS mouse model strains. A burst of apoptotic activity in the photoreceptor outer nuclear layer at postnatal week 2 and highly disorganized outer segments by postnatal weeks 4 to 6 was observed in all four strains.

CONCLUSIONS

The specific loss of photoreceptors in Bbs4(-)(/)(-) mice allows us to identify a set of genes that are preferentially expressed in photoreceptors compared with other cell types found in the eye and is a valuable resource in the continuing search for genes involved in retinal disease. The molecular and morphologic changes observed in young BBS animal model eyes implies that BBS proteins play a critical, early role in establishing the correct structure and function of photoreceptors.

Endothelin-2 induces oviductal contraction via endothelin receptor subtype A in rats

Proper function of the oviduct is critical to reproductive success with regulated contraction and relaxation facilitating transportation of the germ cells to the site of fertilization. Endothelin-2 (EDN2) is a potent vasoconstrictor produced by granulosa cells of the preovulatory follicle at the time of ovulation; however, whether this gonadotropin surge-induced peptide played a role in facilitating germ cell transportation by inducing oviductal contraction was unknown. The objectives of these experiments were (1) to determine whether the endothelin receptor system was present in the oviduct, (2) to test the hypothesis that EDN2 induces oviductal contraction via a specific endothelin receptor subtype, (3) to determine, as a possible alternate source of the ligand, whether mRNA for EDN2 was expressed in cumulus-oocyte complexes (COCs) within the oviduct, and (4) to determine whether EDN2 could overcome prostaglandin E(2) (PGE(2))-induced oviductal relaxation. Microarray and real-time PCR analysis indicated that mRNA for both the endothelin receptor subtypes (ET(A) and ET(B)) was present in the oviduct, whereas immunohistochemical examination revealed that ET(A) protein was the dominant isoform, present in the luminal epithelial cells of the oviduct. Real-time PCR analysis demonstrated that mRNA for EDN2 was expressed in COCs after ovulation. Isometric tension analysis indicated that EDN2 was a potent oviductal constrictor and that the contractile effect of EDN2 was mediated by the ET(A) and not the ET(B) receptor subtype. The oviductal contraction induced by EDN2 also reversed oviductal relaxation induced by PGE(2). In summary, ET(A) receptor-specific EDN2-induced contraction as a facilitator of oviductal function suggests a novel pathway involved in germ cell transport and hence mammalian fertility.

High doses of ultraviolet-C irradiation increases vasoactive intestinal contractor/endothelin-2 expression in keratinocytes of the newborn mouse epidermis

We examined the expression profiles of vasoactive intestinal contractor/endothelin-2 (VIC/ET-2) at both gene and peptide level in skin irradiated with different ultraviolet wavelengths. We found that VIC/ET-2 gene expression is sensitive only to ultraviolet-C (UVC) irradiation and has an immediate response. These results provide direct evidence that high doses of UVC irradiation induce an increase in gene expression and protein production of VIC/ET-2 and endothelin (ET) receptors in a dose-dependent manner in epidermal keratinocytes. We suggest that VIC/ET-2 can play an essential role in the maintenance, protection and hyperpigmentation of the epidermis exposed to UVC irradiation from artificial or natural sources.

Fifteen polymorphisms in endothelin-1, endothelin-2 and endothelin-receptor-A genotyped by four duplex assays and seven simple assays on a LightCycler using hybridization probes

Endothelins (EDNs) are peptides, produced by various tissues, with potent vasoactive and mitogenic properties. Endothelin actions are mediated via specific G protein-coupled receptors of two subtypes, endothelin-receptor-A (EDNRA) and endothelin-receptor-B (EDNRB). Some polymorphisms of the EDN1, EDN2 and EDNRA genes may influence susceptibility to vascular diseases. Thus, genotyping for polymorphisms of these genes may represent a tool for predicting individual susceptibility to vascular diseases. Here, we report 11 fluorescence resonance energy transfer (FRET) assays for the detection of 15 polymorphisms, because the assays used in previous studies (allele-specific PCR and restriction fragment-length polymorphism assays) for some of these polymorphisms are laborious and time-consuming. The newly developed assays are fast and work without expensive ready-to-use mixtures.

Endothelin-2 in ovarian follicle rupture

The ovulatory process is activated by a surge of LH, a pituitary gonadotropin, which initiates a cohort of dramatic changes in biochemical, physical, and gene expression in the ovary, leading to follicle rupture and oocyte release. Here we report the identification of endothelin-2 (EDN2) as a last moment-trigger of follicle rupture. In the ovary, EDN2 is exclusively and transiently expressed in the granulosa cells immediately before ovulation. Administration of EDN2 to the ovarian tissue induced rapid contraction, whereas addition of tezosentan, an endothelin receptor antagonist, diminishes the EDN2 effect. In vivo, treatment of tezosentan before ovulation substantially decreases gonadotropin-induced superovulation. As a target tissue of EDN2 action, we identified a layer of smooth muscle cells in the follicular wall of each follicle. Taken together, our data indicate that EDN2 induces follicular rupture by constricting periovulatory follicles.

The genomic response to retinal disease and injury: evidence for endothelin signaling from photoreceptors to glia

Regardless of proximal cause, photoreceptor injury or disease almost invariably leads to the activation of Muller cells, the principal glial cells in the retina. This observation implies the existence of signaling systems that inform Muller cells of the health status of photoreceptors. It further suggests that diverse types of photoreceptor damage elicit a limited range of biochemical responses. Using the mouse retina, we show by microarray, RNA blot, and in situ hybridization that the genomic responses to both light damage and inherited photoreceptor degeneration involve a relatively small number of genes and that the genes activated by these two insults overlap substantially with one another and with the genes activated by retinal detachment. Among the induced transcripts, those coding for endothelin2 (Edn2) are unusual in that they are localized to photoreceptors and are also highly induced in all of the tested models of photoreceptor disease or injury. Acute light damage also leads to a >10-fold increase in endothelin receptor B (Ednrb) in Muller cells 24 h after injury. These observations suggest that photoreceptor-derived EDN2 functions as a general stress signal, that EDN2 signals to Muller cells by binding to EDNRB, and that Muller cells can increase their sensitivity to EDN2 as part of the injury response.

Expression of a neuropeptide, endothelin-1 in pons and medulla of prenatal and perinatal mouse brains

Endothelin-1 (ET-1), a potent vasoconstrictor, is widely distributed in the central nervous system. This article demonstrates the spatio-temporal expression of mouse preproendothelin-1 (mPPET-1) gene in pre- and perinatal mouse brain by in situ hybridization using a probe specific for mPPET-1. mPPET-1 mRNA expression was first observed in medulla at embryonic age 11.5 (E11.5) and the level became increasingly stronger toward later stages of development. At E18.5 and postnatal day 0.5 (D0.5), mPPET-1 mRNA was found in discrete nucleus group in ventrolateral medulla. mPPET-1 mRNA was also detected in thalamic reticular nucleus at E16.5, E18.5, and D0.5. These results showed that mPPET-1 mRNA is present in neurons of central cardiorespiratory region and drastically increased during the transition from episodic fetal breathing to continuous postnatal respiration (E18.5 to D0.5), implicating the important role of ET-1 in central cardiorespiratory control regulating the onset of respiration during this critical period.

Differential expression of endothelin-2 along the mouse intestinal tract

Endothelin (ET)-2, an ET family peptide, is highly expressed in intestine. However, the specific distribution and function of ET-2 remain unknown. We elucidated the expression profile and localization of ET-2 in mouse gastrointestinal tract. Real-time PCR analysis revealed that ET-2 gene expression in the gastrointestinal tract of healthy animals was relatively high in the colon. Immunohistochemical analysis revealed ET-2-like immunoreactivity mainly in epithelial cells of the mucosa throughout the intestinal tract of healthy animals. Intracellularly, ET-2 was concentrated close to the basement membrane of intestinal epithelial cells. A weak ET-2-like immunoreactivity was also localized to some neurofibers and the myenteric plexus of the muscle layer, coexpressing with vasoactive intestinal peptide. ET-2-like immunoreactivity was also detected at Brunner's glands of the duodenum and follicle-associated epithelium of Peyer's patch. In contrast, ET-1-like immunoreactivity was uniformly distributed in epithelial cells. In dextran sulfate sodium (DSS)-induced colitis, colonic ET-2 was upregulated during the late stage of DSS treatment. These results suggest that in intestinal epithelial cells ET-2 could be secreted into the lamina propria and the dome region in Peyer's patch, and that it might modulate immune cells in these sites for mucosal defense.

Cobalt chloride induces neurite outgrowth in rat pheochromocytoma PC-12 cells through regulation of endothelin-2/vasoactive intestinal contractor

We investigated whether endothelin-2/vasoactive intestinal contractor (ET-2/VIC) gene expression, upregulated by hypoxia in cancer cells, was associated with differentiation in neuronal cells. RT-PCR analysis, morphological observations, and immunostaining revealed that CoCl2, a hypoxic mimetic agent, at 200 microM increased expression of the ET-2/VIC gene, decreased expression of the ET-1 gene, and induced neurite outgrowth in PC-12 rat pheochromocytoma cells. These effects induced by 200 microM CoCl2 were completely inhibited by the antioxidant N-acetyl cysteine at 20 mM. In addition, CoCl2 increased the level of intracellular reactive oxygen species (ROS) at an early stage. Furthermore, interleukin (IL)-6 gene expression was upregulated upon the differentiation induced by CoCl2. These results suggest that expression of ET-2/VIC and ET-1 mediated by ROS may be associated with neuronal differentiation through the regulation of IL-6. When the cells were treated with 500 microM CoCl2 for 24 hr, however, ET-2/VIC gene expression disappeared, IL-6 gene expression was downregulated, and necrosis was subsequently induced in the PC-12 cells.

cDNA cloning, sequence analysis and organ distribution of horse preproendothelin-2

We cloned and characterized horse preproendothelin-2 (PPET-2) cDNA from intestinal tissue. The cDNA encoded 178 amino acids of the PPET-2 polypeptide, in which a 21-amino-acid mature endothelin-2 peptide and a 16-amino acid endothelin-2-like peptide were found. For the open reading frame the correspondence of horse PPET-2 cDNA with those of the ferret, human, dog, mouse and rat was 85.1%, 84.9%, 82.1%, 77.8% and 77.2%, respectively. Analysis of the organ distribution of PPET-2 mRNA by reverse transcription-polymerase chain reaction demonstrated that the kidney, stomach and small intestine are major sites of expression of the PPET-2 gene. Surprisingly, the mRNA is not detected in the large intestine, where high expression is demonstrated in the mouse and rat. This difference may result from the underlying functional differences of the large intestine between a herbivore (horse) and an omnivore (mouse and rat).

A role for endothelin-2 and its receptors in breast tumor cell invasion

We have studied the role of endothelins (ET-1, ET-2 and ET-3) and ET receptors (ET-RA and ET-RB) in the invasive capacity of breast tumor cells, which express ET-1 and ET-2 as well as ET-RA and ET-RB. Of five human breast tumor cell lines tested, all expressed mRNAs for ET-1, ET-2, and ET-RB. ET-RA mRNA was expressed by four of five tumor cell lines. Breast tumor cells migrated toward ET-1 and ET-2 but not toward ET-3. Chemotaxis involved signaling via both receptors, and a pertussis toxin-sensitive p42/p44 mitogen-activated protein kinase (MAPK)-mediated pathway that could be inhibited by MAPK kinase (MEK)1/2 antagonists. Chemotaxis toward ETs did not involve p38 or stress-activated protein kinase (SAPK)/Jun N-terminal kinase (JNK) and was not inhibited by hypoxia. Incubation of tumor cells with ET-2 also increased chemotaxis toward the chemokines CXCL12 and CCL21. As well as inducing chemotaxis of tumor cells, ET-1 and ET-2 increased tumor cell invasion through Matrigel. Furthermore, stimulation of macrophage/tumor cell cocultures with ETs led to increased matrix metalloproteinase (MMP)-2 and -9 production by macrophages and a marked increase in invasion of tumor cells. Antagonism of either ET-RA or ET-RB decreased the invasion seen in ET-stimulated cocultures, as did a broad-spectrum MMP inhibitor. Immunohistochemical staining of human breast tumor sections showed increased ET and ET receptor protein expression by tumor cells in invasive ductal carcinoma compared with normal breast tissue or ductal carcinoma in situ. Furthermore, tumor cell ET and receptor expression was stronger at the invasive margin of invasive ductal carcinomas, in the lymphovascular space, and in lymph node metastases. ET expression often colocalized with ET-RB expression in all neoplastic tissue indicating a possible autocrine action of ETs. We suggest that expression of ETs and their receptors by human breast tumors, particularly in conjunction with a high macrophage infiltrate, may have a role in the progression of breast cancer and the invasion of tumor cells.

Endothelin-2 down-regulation occurs in parallel with the anti-proliferative effect of dimethylsulfoxide in BeWO human choriocarcinoma cell line

Endothelins exhibit growth regulating properties in many cell types, and there is now considerable evidence that they play a critical pathophysiological role in human diseases such as carcinogenesis. In the choriocarcinoma cell lines JEG-3, JAR and BeWO, we demonstrate by RT-PCR that prepro endothelin (ET)-1 and prepro ET-2 mRNA were expressed, whereas prepro ET-3 was never expressed. Only ET-1 and ET-2 peptides were identified by HPLC/RIA analyses in culture media from these three choriocarcinoma cell lines. In the BeWO line, the cellular growth measured as the cell count and DNA content decreased with increasing concentrations of dimethyl sulfoxide (DMSO; range 0.5-3%). The expression of prepro ET-2 was also suppressed by DMSO, whereas no change was noticed inprepro ET-1 mRNA. All these effects were reversible when DMSO was replaced by 15% foetal calf serum. These effects of DMSO which are correlated to ET-2 down regulation in dividing BeWO cells suggest a role for this endothelin isoform in trophoblast proliferation.

[A search for genetic loci responsible for emotional stress-induced arterial hypertension in the ISIAH rats]

Hypertension is a widespread human disease caused by a complex interaction of a series of the genetic factors with both each other and the environmental conditions. In this study we aimed at determining the candidate genetic loci responsible for hypertension in the ISIAH rats and studying the dynamics of the relevant genetic and physiological mechanisms in rat ontogeny. The candidate genetic loci were identified from association of the microsatellite markers linked to these loci with arterial hypertension in rat F2 hybrids exposed to stress. Two populations of F2 hybrids of different age (3-4 and 6 months) were obtained by crossing hypertensive ISIAH and normotensive WAG rats. We present the results of cosegregation analysis for the following loci: the gene for the Na+, K(+)-ATPase alpha 1 subunit isoform (Atp1a1), the endothelin-2 gene (Edn2), the low affinity nerve growth factor receptor gene (Lngfr), and a region of chromosome 10 marked with the D10Rat58 microsatellile located 3 cM away of the aldolase C gene (AldC). The results obtained allowed us to localize the genes responsible for the stress-induced arterial hypertension in the ISIAH rats to the Atp1a1 locus (P < 0.05), chromosome 2 and to the Lngfr gene locus (P < 0.05), chromosome 10. The association of hypertensive status with the Lngfr gene was found only in young ISIAH rats whereas in adult rats of this line, hypertension was associated with the Atp1a1 locus.

Mechanical stress triggers selective release of fibrotic mediators from bronchial epithelium

Transforming growth factor-beta (TGF-beta) and endothelin (ET) are found in elevated amounts in the airways of individuals with asthma. The cellular source of these peptides and their role in mediating the airway fibrosis of chronic asthma are unknown. In response to mechanical stresses similar to those occurring in vivo during airway constriction, bronchial epithelial cells increase the steady-state level of mRNA for both ET-1 and ET-2, followed by increased release of ET protein. Mechanical stress also enhances release of TGF-beta2 from a preformed cell-associated pool. TGF-beta2 and ET act individually and, more importantly, synergistically to promote fibrotic protein synthesis in reporter fibroblasts. To confirm the role of these intermediates in stress-induced fibrosis, conditioned medium from mechanically stressed bronchial epithelial cells was shown to elicit fibrotic protein synthesis in reporter fibroblasts; this effect was significantly inhibited by combined treatment with ET receptor antagonists and a neutralizing antibody to TGF-beta2. These data are consistent with a primary pathogenic role for mechanical stress-induced release of both TGF-beta2 and ET in the subepithelial fibrosis that characterizes chronic asthma.

Vasoactive intestinal contractor/endothelin-2 gene expression in the murine central nervous system

Vasoactive intestinal contractor (VIC) is a member of the endothelin (ET) family. We have investigated the regional distribution of VIC/ET-2 and of ET-1 gene expression in the adult murine brain and pituitary gland. We used real-time quantitative reverse transcription-linked polymerase chain reaction. VIC/ET-2 gene expression was observed at high levels in the pituitary gland and medulla oblongata in both the mouse and rat. Moderate to low levels of expression were observed in other brain regions. On the contrary, ET-1 gene expression was quite low in the pituitary gland in comparison with the levels observed in the cerebral cortex, striatum, and midbrain. Cold injury to the mouse cerebral cortex caused a significant decrease in VIC/ET-2 gene expression in this structure, whilst expression of the ET-1 gene was increased. These results suggest that VIC/ET-2 may have certain physiological roles that differ from those of ET-1 in the brain and pituitary gland.

Expression of endothelins in human cardiogenesis

Genetic disruption of endothelin (ET) 1, endothelin-converting enzyme (ECE) 1, and endothelin receptor A (ET(A)) in "knockout" or mutant mouse models result in defects in branchial arch derived craniofacial tissues and in cardiac outflow and great vessel structures. Interestingly, certain types of human congenital cardiovascular malformations such as Catch 22 syndrome and type B interruption of the aortic arch strongly resemble defects seen in knockout animal models. To better address the exact involvement of the ET system in heart formation we explored the spatiotemporal pattern of expression of the components of the ET system during critical phases of cardiogenesis in the human embryo (3-6 weeks of development; Carnegie stages 10-17) by in situ hybridization. We detected high ET-1 mRNA expression in endocardial cells lining the heart outflow tract in the region where the future aortic valves will form. No hybridization signal corresponding to pre-pro-ET-3 was observed in the heart. At the same location, the underlying myocytes express ET(A) mRNA. Whereas a functional role of ET in the valve formation can be proposed because of the simultaneous presence of all the components of the endothelin system (ET-1/ECE-1/ET(A)), this seems not to be the case for the formation of the ventricular septum where endocardial cells do not express ET-1, and only a weak ET(A) hybridization signal was detected in the surrounding myocardium. An abnormal hemodynamism indirectly due to valve malformation may be the indirect cause of this septal defect. The results of this study suggest an important role for the ET system in the formation of certain anatomical structures of the developing human heart.

Increased gene expression of endothelin-1 and vasoactive intestinal contractor/endothelin-2 in the mammary gland of lactating mice

In an attempt to understand the roles of endothelin-1 (ET-1) and vasoactive intestinal contractor/endothelin-2 (VIC/ET-2), we have studied the genes for both peptides to be expressed in the mammary gland of lactating mice. We observed through real-time PCR analysis that ET-1 and VIC/ET-2 gene expression gradually increase after parturition and that ET-1 gene expression is significantly higher than that of VIC/ET-2. The distribution of ET-1 peptide was found to be localized mainly in the epithelial cells of the mammary gland at 14th day of lactation. ET-1 gene expression increases significantly, parallel to the increase in beta-casein gene expression, in epithelial cell lines (HC11) of mouse mammary gland after hormonal stimulation by addition of dexamethazone and prolactin. The observed increase in ET-1 expression in differentiated epithelial cells suggests physiological roles for ET-1, including milk production and secretion in the mammary gland of lactating mice.

Expression of endothelin-1 and vasoactive intestinal contractor genes in mouse organs during the perinatal period

In an attempt to understand the significance of endothelin-1 (ET-1) and vasoactive intestinal contractor (VIC)/ET-2 peptides in organs during perinatal development, we performed quantitative analysis of ET-1 and VIC gene expression in mouse organs obtained from embryos at days 14 and 17 (E-14 and E-17) of pregnancy, neonates at days 0, 1, 3 and 7 after birth (N-0, -1, -3 and -7), and adult mice (10 weeks old). In intestine, VIC gene expression progressively increased between E-14 and N-1 (approximately 10-fold) and then remained constant into adulthood. ET-1 gene expression exhibited a one-step increase between E-17 and N-0, subsequently remaining constant. In lung, a sharp increase in ET-1 mRNA level (approximately 10-fold) was noticed between E-14 and N-0. The gene expression pattern of VIC, with a peak at N-0, was similar to that of ET-1 although the expression level of VIC was two to three orders of magnitudes lower than that of ET-1. Gene expression patterns of ET-1 and VIC remained nearly constant in brain, heart, liver and kidney throughout the period examined. Considering that the intestinal and pulmonary gene expression levels of both genes reached almost the same level as observed in adult soon after birth, we suggest that these peptides may be involved in the emergence and maintenance of intestinal and pulmonary functions vital after birth.

Endothelins may modulate invasion and proliferation of Ewing's sarcoma and neuroblastoma

Tumours of the Ewing's sarcoma (ES) family and neuroblastoma (NBL) were examined by reverse transcriptase-PCR for expression of mRNA for endothelin (ET) receptors ET-A and ET-B, and the ligands ET-1, ET-2 and ET-3. The effect of ET-1, ET-3, an ET-1-neutralizing antibody and ET-A receptor antagonist BQ-123 on cell proliferation was examined using an ELISA. Loss of ET-B receptor mRNA occurred in 57% of ES and 42% of NBL tumours. This appeared to be associated with the presence of metastatic disease and disease progression. ET-A receptor mRNA was expressed in all ES and 85% of NBL tumours, and in all ES and NBL cell lines examined. All ET ligands were detected in NBL cell lines, but only ET-1 and ET-2 were expressed in ES cell lines. Treatment of ES and NBL cells with ET-1 increased proliferation, but ET-3 had no effect. Incubation of ES and NBL cells with an ET-1-neutralizing antibody or BQ-123 decreased proliferation. The ET-3 ligand and ET-B receptor may be associated with migration and metastasis of ES and NBL, whereas ET-1 (acting through the ET-A receptor) may regulate their proliferation.

Effect of aging on gene expression rates of endothelin-1 and endothelin-2/vasoactive intestinal contractor in ethanol-induced gastric mucosal injury of the mouse

To elucidate the physiological roles of endothelin-1 (ET-1) and endothelin-2 (ET-2)/vasoactive intestinal contractor (VIC) in gastric injury of mice, we measured the gene expression rates of ET-1 and ET-2/VIC in gastric injury induced by ethanol in young (8 weeks) and old (>33 weeks) mice. Mice that were fasted for 24 h were injected with absolute ethanol intragastrically and killed after 1 or 4 h of ethanol exposure. The size of the gastric lesions increased gradually after ethanol exposure and was at its greatest after 4 h, in both young and old mice. The gene expression of ET-1 tended to increase after 1 h and to decrease by 4 h of ethanol exposure in both young and old mice. However, the gene expression of ET-2/VIC in young mice increased significantly after 1 and 4 h of ethanol exposure, whereas the gene expression of ET-2/VIC in the old mice did not change after ethanol exposure. Based on these results, we conclude that aging influences the gene expression of ET-2/VIC but not lesion size or gene expression of ET-1 in ethanol-induced gastric injury in the mouse. We therefore suggest that regulation of gene expression of these two genes differs during the course of aging.

Endothelin content, expression, and receptor type in normal and diseased human gallbladder

The aims of this study were to characterize the endothelin (ET) system in human gallbladder by determining (1) the tissue content of ET-1 and ET-2 by ELISA; (2) the expression of mRNA of the ET precursors preproendothelin-1, -2, and -3; and (3) mRNA expression for the ETA and ETB receptors. Median content of ET-1/2 was significantly reduced in severely inflamed gallbladders compared to gallbladders with mild inflammation. There was an inverse correlation between content of ET-1/2 and inflammation score. mRNA for preproendothelin-2 was highly expressed in all samples, whereas mRNA for preproendothelin-1 was present in negligible quantities and mRNA for preproendothelin-3 was undetectable. mRNA for ETA receptors was expressed in all samples analyzed, whereas mRNA for ETB receptors was expressed at a much lower level. This study demonstrates the presence of ET-1/2 in human gallbladder. ET-1/2 content is decreased with increasing degrees of histological inflammation. ET-2 is likely to be the physiologically significant endothelin isopeptide expressed and ETA receptors appear to predominate in the human gallbladder.

BMP-7 regulates chemokine, cytokine, and hemodynamic gene expression in proximal tubule cells

BACKGROUND

Proximal tubule epithelial cells (PTEC) play a central role in the response of the kidney to insult by virtue of their production of chemokines and cytokines that signal an inflammatory response. Bone morphogenic protein-7 (BMP-7/OP-1), a member of the transforming growth factor-beta (TGF-beta) superfamily, has previously been demonstrated to reduce macrophage infiltration and tissue damage in animal models of acute and chronic renal failure. The present study was designed to define the molecular mechanism of BMP-7 action in human PTEC.

METHODS

Expression of BMP-7 in the adult mouse kidney was determined indirectly through X-gal staining of heterozygous BMP-7/lacZ mice in combination with cell-type specific markers. Primary human PTEC were cultured in the presence of the pro-inflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), with and without BMP-7. RNA isolated from these two populations was then used to identify differentially regulated genes via gene-array analysis. Modulation of potential target genes was subsequently confirmed through ELISA and/or quantitative PCR.

RESULTS

Expression from the BMP-7/lacZ transgene was detected in the collecting duct, thick ascending limb, distal convoluted tubule, and podocytes within glomeruli. No expression was detected within PTEC; however, these cells were found to express mRNA for BMP receptors including, ActR-I, BMPR-IA, ActR-II, ActR-IIB, and BMPR-II. BMP-7 significantly reduced TNF-alpha stimulated increases in mRNA for the pro-inflammatory genes, interleukin-6 (IL-6) and interleukin-1beta (IL-1beta), and the chemoattractants monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) in primary human PTEC. In addition, BMP-7 also reduced the expression of mRNA for endothelin-2 (ET-2), a vasoconstrictor, and increased the expression of mRNA for heme oxygenase-1 (HO-1), a vasodilator, although the latter was not statistically significant. In experiments designed to examine MCP-1 and IL-6 protein levels in response to additional TGF-beta superfamily members, TGF-beta1 was unable to mimic the effects of BMP-7 in reducing IL-6 production. However, the closely related BMP-6 exhibited similar properties to those of BMP-7. Each of the factors reduced MCP-1 expression.

CONCLUSIONS

BMP-7 represses the basal and TNF-alpha-stimulated expression of the pro-inflammatory cytokines IL-6 and IL-1beta, the chemokines MCP-1 and IL-8, and the vasoconstrictor ET-2 in PTEC. This data are consistent with the in vivo observations that BMP-7 administration in a model of chronic and acute renal failure results in a reduction in the infiltration of macrophages in the renal interstitium. Taken together, these observations suggest that BMP-7 may be a novel therapeutic agent for kidney disorders involving inflammation and ischemic damage of PTEC.

Rapid quantification of murine endothelin-1 and vasoactive intestinal contractor gene expression levels by a real-time PCR system

A rapid quantitative analysis method for murine endothelin-1 (ET-1) and vasoactive intestinal contractor (VIC) gene expression levels was established using a real-time polymerase chain reaction (PCR). We designed primer pairs and TaqMan probes specific for murine prepro-ET-1 (PPET-1) and prepro-VIC (PPVIC) genes, based on the cDNA sequence region common to both mouse and rat. The dynamic range for detection in this system spanned 100000-fold of the starting molecule. The gene expression levels of PPET-1 and PPVIC were estimated as gene expression rates normalized by the expression of the house-keeping gene, glyceraldehyde-3-phosphate dehydrogenase. To examine the reproducibility of this assay system, we calculated the intra-assay and interassay coefficients of variation of the gene expression rate, which ranged from 16.2 to 55.0% and from 24.2 to 56. 5%, respectively. Using this system, we examined gene expression levels of PPET-1 and PPVIC in mouse tissues. PPET-1 gene expression was found in all tissues at relatively high levels, whereas high levels of PPVIC gene expression were observed only in stomach, intestine, uterus, and ovary. The gene expression patterns agreed well with those determined by RNase protection assay and conventional PCR. These results show that this new rapid method is accurate and reproducible.

Association between diastolic blood pressure and variants of the endothelin-1 and endothelin-2 genes

The genes for endothelin (ET) and their receptors are candidates for essential hypertension. Those for ET-1, ET-2 and the ET(A) receptor were selected for mutation scanning, and associated studies comparing untreated hypertensive patients and matched controls. A number of silent polymorphisms were found, resulting from a single nucleotide insertion or a single nucleotide substitution. There were no significant differences in the frequency of any one of these between the two groups. However, for ET-1 and ET-2 there were significant differences in the quantitative measurements of blood pressure and the number of variant alleles. The variants which we have found are likely to be in linkage disequilibrium with so far undiscovered variants in the regulatory regions of the genes.

The endothelin-2/vasoactive intestinal contractor gene: expression and promoter activity in PC12 rat pheochromocytoma cells

In order to understand the physiological roles of vasoactive intestinal contractor (VIC)/endothelin-2 (ET-2), we examined the expression of this peptide by specific reverse transcriptase polymerase chain reaction (RT-PCR) analysis and found that PC12 rat pheochromocytoma cells express the VIC gene. The 5'-flanking 1.0 kilo base pair (kb) region of the mouse VIC gene is sufficient to express a secreted alkaline phosphatase (SEAP) reporter gene in transiently transfected PC12 cells. The 1.0 kb promoter region may contain cis-acting elements that determine the rate of the VIC gene transcription in PC12 cells.

Quantitative analysis of endothelin-1 and vasoactive intestinal contractor/endothelin-2 gene expression in rats by real-time reverse transcriptase polymerase chain reaction

We established a real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) system for the analysis of rat endothelin-1 (ET-1) and vasoactive intestinal contractor (VIC)/ET-2 gene expression. We used this technique to examine the expression levels in rat in 16 different organs. ET-1 gene expression was observed in all organs examined, while VIC mRNA was detected in some organs such as heart, lung, ovary, stomach, and intestine. Ovary and intestine express both ET-1 and VIC mRNA at high levels, suggesting the importance of both peptides in these organs. In addition, we examined the gene expression levels in intestinal epithelial and mesenchymal tissues from rat fetuses at 16.5 and 19.5 days postcoitus (E16.5 and E19.5). We observed distinct differences in the temporal gene expression patterns for ET-1 and VIC in fetal intestinal epithelial tissue. In fetal mesenchymal tissue the expression level of ET-1 is significantly higher than that of VIC, and the levels of both genes remain unchanged over the time period observed. These findings suggest distinct biological roles and gene regulation mechanisms for ET-1 and VIC in intestinal epithelial and mesenchymal tissues.

Selective expression of endothelin 1 mRNA in rat retina

Endothelin is a potent vasoactive agent and three isoforms--endothelin 1 (ET-1), endothelin 2 (ET-2) and endothelin 3 (ET-3)-- have been found in ocular tissues. However its source has not been determined. Therefore we have investigated the ET mRNA in the rat retina using reverse transcriptase with polymerase chain reaction. For ET-1, three retina samples were positive. For ET-2 and ET-3, all samples were negative. ET-1 mRNA was abundantly expressed compared with ET-2 and ET-3 mRNA (p < 0.05). Our study provides direct evidence that ET-1 is abundantly synthesized in the rat retina. The ET-1 within the retina could contribute to the regulation of the retinal circulation through vessel contraction.

Placental endothelin gene expression and endothelin concentration in fetal fluids of the first trimester gestational sac

We have investigated the distribution of immunoreactive endothelins (irET) in fetal fluids and expression of ET precursor genes in villous tissue during the first trimester. Samples of maternal plasma (n = 6), coelomic fluid (n = 28), amniotic fluid (n = 23) and villous tissue (n = 3) were obtained from 30 pregnancies immediately before surgical termination at 7-12 weeks gestation. irET concentration was measured in plasma and fluids using two different radioimmunoassay kits, i.e. RPA 545 and RPA 555 and high performance liquid chromatography (HPLC). Total RNA was extracted and purified from villous tissue, reverse transcription and polymerase chain reaction (RT-PCR) were performed to evaluate the expression of ET-related genes. The irET concentration as evaluated by both kits was significantly higher (P<0.005) in maternal plasma than in coelomic or amniotic fluid and significantly higher (P<0.005) in coelomic fluid than in amniotic fluid using the RPA 555 kit. The profile of ET obtained by the HPLC- radioimmunoassay (RPA 555 kit) method confirmed significantly (P<0.005) higher ET concentration in coelomic than in amniotic fluid, although a similar distribution pattern for the three ET was observed in both embryonic fliud cavities. ET-3 was the predominant isoform in both fluids, reaching 19.4+/-2.0 pg/ml and 6.3+/-1.6 pg/ml in coelomic and amniotic fluid, respectively. Coelomic or amniotic fluid irET concentration did not change with gestational age irrespective of the kit used. RT-PCR demonstrated that first trimester placenta expresses the genes encoding for prepro-ET-1, -ET-2 and -ET-3. The similar ET distribution pattern in both fluid cavities could reflect their origin from the villous tissue and suggests that ET may play a role in the development of placenta and other fetal organs during organogenesis.

Regulation of ET: pulmonary release of ET contributes to increased plasma ET levels and vasoconstriction in CHF

Endothelin (ET) contributes to the increased systemic vascular resistance and elevated cardiac filling pressures seen in congestive heart failure (CHF). We investigated to what extent ET-mediated vasoconstriction in CHF occurs through an endocrine action of elevated plasma ET or by an autocrine/paracrine mechanism related to induction of vascular ET gene expression. Three weeks of pacing (225 beats/min) induced a marked release of ET-1 from the pulmonary circulation with a sixfold elevation of arterial plasma ET in CHF pigs compared with sham-operated pigs. Arterial plasma ET was the strongest and only independent predictor of systemic vascular resistance. In contrast, vascular preproET-1 and ET-receptor mRNA expression were unaltered or decreased in CHF pigs and did not correlate with indexes of vascular tone. However, myocardial preproET-1 mRNA expression increased twofold in CHF pigs. PreproET-2 and preproET-3 mRNAs were not detectable in cardiovascular tissues. In conclusion, plasma ET was markedly increased because of an augmented release from the pulmonary circulation during CHF, and arterial plasma ET correlated with systemic vascular resistance. The absence of ET induction in the peripheral vasculature suggests that ET increases vascular tone during CHF by an endocrine, not an autocrine/paracrine, mechanism.

Endothelin-2 synthesis is stimulated by the type-1 tumour necrosis factor receptor and cAMP: comparison with endothelin-converting enzyme-1 expression

ABSTRACT The synthesis of the vasoconstrictor peptide endothelin-2 (ET-2) is dependent on hydrolysis of the biologically inactive intermediate big ET-2 by an endothelin-converting enzyme (ECE). Here, mechanisms inducing ET-2 synthesis have been investigated using the human renal adenocarcinoma cell line (ACHN). Synthesis of ET-2 by ACHN cells was inhibited by phosphoramidon (IC(50( congruent with11 microM). To determine whether ET-2 synthesis occurs in parallel with the metallopeptidase ECE-1, a putative processing peptidase for big ET-2, changes in the levels of their mRNAs were compared by semi-quantitative RT-PCR under conditions causing the upregulation of ET-2 synthesis. Tumour necrosis factor-alpha (TNFalpha), forskolin and a cell-permeable cAMP analogue (dibutyryl cAMP) caused concentration-dependent increases in ET-2 synthesis. Combination of forskolin or dibutyryl cAMP with TNFalpha produced a significantly greater increase in ET-2 production than these agents alone, indicating that adenylate cyclase and TNFalpha induce ET-2 synthesis by separate signalling pathways. Studies using receptor selective TNFalpha mutants, (125(I-TNFalpha binding and TNF receptor mRNA showed that type-1 TNF receptors mediate the ET-2 response to TNFalpha. PreproET-2 mRNA levels were increased by TNFalpha at 1 h and 2 h, but returned to control levels at 4 h. Treatment with forskolin significantly increased preproET-2 mRNA levels after 1 h and 4 h. ACHN cells expressed ECE-1b and ECE-1c, but not the ECE-1a isoform of this peptidase. RT-PCR for the combined isoforms ECE-1b/c/d showed TNFalpha to increase mRNA levels at 2 h and 4 h. Forskolin had no effect on ECE-1b/c/d mRNA levels. Thus, expression of ET-2 and ECE-1b/c/d mRNAs in ACHN cells do not display the co-ordinated regulation observed with typical peptide prohormone processing enzymes and their substrates.

The prepro vasoactive intestinal contractor (VIC)/endothelin-2 gene (EDN2): structure, evolution, production, and embryonic expression

Murine vasoactive intestinal contractor (VIC) and its human analog endothelin-2 (ET2) are potent vasoactive hormones composed of 21 amino acids. To study the structural characteristics of the VIC/ET2 gene (HGMW-approved symbol EDN2), we isolated the full length of the mouse VIC gene. Sequence analysis indicates that a biologically active mature VIC peptide is produced from a 175-residue precursor protein; preproVIC (PPVIC). Several remarkable similarities of the PPVIC gene to the human preproendothelin-1 gene strongly suggest that the two genes have arisen from a common progenitor by gene duplication. Transfection of ACHN adenocarcinoma cells with the cDNA resulted in the production of VIC peptide. VIC production was increased by the deletion of the 3'-untranslated region, which contains an AU-rich mRNA destabilizing sequence. Increased PPVIC gene expression during the late embryonic stage suggests an important function in development. This study provides the basis for disruption and regulation analysis of the gene, which may lead to a better understanding of VIC/ET2's physiological significance.

Myocardial expression of endothelin-2 is altered reciprocally to that of endothelin-1 during ischemia of cardiomyocytes in vitro and during heart failure in vivo

We and other groups have reported that endothelin (ET)-1 expression in the heart is altered in the setting of heart diseases. We have also reported that myocardial ET-1 is involved in the progression of heart failure, and that an ET receptor antagonist improves long-term survival in heart failure (Nature 384: 353-355, 1996). However, the role of myocardial ET-2 in disease states are not known. To characterize the role of ET-2, we used a) the failing hearts of rats with heart failure caused by myocardial infarction, and b) primary cultured cardiomyocytes subjected to hypoxia. In the failing heart in vivo, ET-1 mRNA increased by 390% compared with that in the non-failing heart, while ET-2 mRNA drastically decreased by 88%. Thus, gene expression of ET-1 and ET-2 was reciprocally altered in the failing heart in vivo. In in vitro studies, reciprocal alterations in ET-1 and ET-2 gene expression were also observed in isolated primary cultured cardiomyocytes, subjected to hypoxia. Specifically, acute hypoxic stress induced a significant increase (360% of the basal level) in ET-2 mRNA expression compared with that in normoxic cells, whereas it decreased ET-1 mRNA expression by 62% in primary cultured cardiomyocytes. Although these two crucial conditions, i.e., heart failure in vivo and acute hypoxic stress in vitro, are pathophysiologically distinct from each other, reciprocal alteration of ET-1 and ET-2 gene expression was observed in both cases. To further investigate the regulatory mechanism of the altered gene expression, luciferase analysis was performed using primary cultured cardiomyocytes. ET-2 promoter, which is the 5'-flanking region of preproET-2 gene (5'ET-2), showed a marked increase in luciferase activity during acute hypoxia. In contrast, the luciferase activity of 5'ET-1 (ET-1 promoter) did not change in response to hypoxic stress. The present study suggests that there are transcriptionally distinct regulatory mechanisms for ET-1 and ET-2 expression in cardiomyocytes, and therefore this study may provide a new aspect of cardiac ET system that not only ET-1 but also ET-2 can be participated in the pathophysiological conditions.

Quantitative association between a newly identified molecular variant in the endothelin-2 gene and human essential hypertension

BACKGROUND

Essential hypertension is a multifactorial disease in which the genetic contribution is probably the result of a number of genes acting in combination. Recent work has incriminated endothelin-2 (ET2) as a candidate gene for human essential hypertension. This study sought to (i) determine the existence of any molecular variants in the ET2 gene; (ii) undertake an allelic-association study of any such variants found in a large group of well characterized hypertensive and control populations; and (iii) assess any quantitative relationship between the molecular variant and pretreatment blood presure.

METHODS

The ET2 gene was subjected to single strand conformation polymorphism (SSCP) analysis in order to identify novel molecular variants. Well-characterized subjects recruited from our local population were used in our association study. Two hundred and forty-four hypertensive patients with pre-treatment blood pressure (range 139/94-237/133 mmHg) were well matched with 228 controls from our local population of 30000 healthy subjects (range 96/62-160/85 mmHg). All subjects were Caucasian.

RESULTS

Polymerase chain reaction-SSCP identified a single A985G base change in 3'-UTR of the ET2 gene which was confirmed by direct sequencing. A restriction site for the enzyme BsmA1 was either created (+) or removed (-) with this polymorphism. Analysis of variance showed that the ET2 genotype was an independent predictor of pre-treatment diastolic blood pressure (DBP) in the hypertensive (P< 0.001) but not normotensive group with higher pressures tracking with the (-) allele. Other covariates such as age, sex, alcohol, cigarette smoking, body mass index and cholesterol showed no significant relationship with this genotype. The genotype frequencies for the hypertensive and control population were (-/-: -/+: +/+) 178 :58:8 and 168:55: 5, respectively (not significant). Subjects from the top and tail quartiles of measurement of blood pressure in both groups were selected for genotype and allele frequency comparison. Both genotype and allele differences were highly significant between the two extreme groups for DBP (genotype P< 0.001, alleles P< 0.01) distribution. A search for potential functional variants in linkage disequilibrium with A985G found one further variant in the 5'-UTR, C44T. Conditional haplotype probabilities in 214 chromosomes show that this polymorphism is not in linkage disequilibrium with the 3'-UTR. No other variants were found on a molecular screen of the transcribed portion of the ET2 gene.

CONCLUSION

This newly identified polymorphism of the ET2 gene tracked significantly in hypertensives when blood pressure was assessed as a quantitative trait. The difference in genotype and allele frequencies between the extremes of blood pressure suggest that the ET2 locus influences the severity rather than the initial development of hypertension.

Transgenic rats expressing the human ET-2 gene: a model for the study of endothelin actions in vivo

Previous studies have characterized the endothelin peptides (ET-1, ET-2, ET-3) as strong vasoconstrictors which are possibly involved in the pathogenesis of cardiovascular disease. Whereas ET-1 and ET-3 have been characterized using a number of approaches, little is known about the function of ET-2. The aim of this study was to define the role of ET-2 in physiology and pathophysiology using a transgenic approach. Transgenic rats expressing a genomic construct of the human ET-2 gene were generated by microinjection of fertilized oocytes from Sprague-Dawley rats. Two transgenic lines were generated, and one line was further characterized in detail. Studies on mRNA expression demonstrated that the transgene is expressed predominantly in kidney, gastrointestinal tract, adrenal gland, lung, and brain. Plasma endothelin levels were elevated 2-fold, and big-endothelin levels were elevated 2.5-fold. Despite these alterations blood pressure in transgenic rats remained normal. Further analysis of transgenic animals revealed that endothelin receptors were not downregulated, and that infusion of exogenous human ET-2 results in an enhanced blood pressure response. These observations suggest the presence of counterregulatory mechanisms influencing the effects of endothelin on blood pressure. One of these mechanisms may involve the nitric oxide system since infusion of an inhibitor of nitric oxide synthase resulted in a greater blood pressure response than in non-transgenic littermates. Despite unchanged blood pressure, alterations were observed in organ development and function, namely of hearts and kidneys, indicating an interference between transgene expression and growth processes. Male rats seem to be more susceptible to endothelin actions. These data show that the elevation in endothelin-2 expression in this transgenic model does not induce hypertension but leads to changes at the end-organ level. Normotension is most likely due to compensatory mechanisms such as increased nitric oxide formation.

Gene expression of vasoactive intestinal contractor/endothelin-2 in ovary, uterus and embryo: comprehensive gene expression profiles of the endothelin ligand-receptor system revealed by semi-quantitative reverse transcription-polymerase chain reaction analysis in adult mouse tissues and during late embryonic development

Vasoactive intestinal contractor (VIC)/endothelin-2 (ET-2) is a 21 amino acid intestinal peptide characterized as a potent vasoactive and intestinal smooth muscle-contracting compound. To investigate the physiological roles of VIC/ET-2 further, we characterized the specificity of VIC gene expression relative to that of other members of the endothelin (ET) ligand-receptor system in adult mouse tissues and during embryonic development. Gene expression of ET-1, ET-3, ETA and ETB was ubiquitous in almost all tissues we examined while gene expression of VIC was localized to certain tissues. A high level of VIC gene expression was observed in ovary and uterus. The gene expression of VIC, relative to that of glyceraldehyde-3-phosphate dehydrogenase, was approximately 2.0%, 0.4%, and 2.3% in ovary, uterus, and intestine respectively, and was approximately 1.6 and 7. 1 times higher than that of ET-1 in ovary and intestine respectively. Thus, VIC may have some physiological role in adult ovary and uterus as well as intestine. In embryonic development, VIC gene expression sharply increased between 11 and 15 days post coitus and decreased after birth, suggesting an involvement in the later stages of embryonic development.

Endothelin and endothelin receptors A and B in the human testis

Human testicular capillaries interconnect Leydig cells and seminiferous tubules. Microcirculation and blood flow are therefore essential for the maintenance of spermatogenesis. The expression and the localisation of ET (endothelin) and its receptors in testicular tissue, in seminiferous tubules and in human testicular capillaries were studied. ET-1 mRNA was detected in whole testicular tissue and in seminiferous tubules whereas isolated testicular capillaries were negative. Big ET-1 (Big endothelin 1) and ET peptides were localised in Leydig and Sertoli cells whereas interstitial and intramural capillaries (within the lamina propria) remained unstained. ET was also found in mature spermatids. ET-A (endothelin receptor A) mRNA was detected in seminiferous tubules and whole testicular tissue whereas testicular blood vessels were negative. ET-A immunostaining was displayed in Leydig and Sertoli cells and in spermatids. ET-B (endothelin receptor B) mRNA was detected in whole testicular tissue, seminiferous tubules and in testicular capillaries. ET-B peptide was prominent in Leydig cells, peritubular cells, endothelial cells and pericytes of interstitial and intramural capillaries as well as in vascular endothelial and smooth muscle cells. From these results we conclude that ET produced in Leydig and Sertoli cells can act in a paracrine manner via ET-B on the human testicular microvasculature and the peritubular cells. The presence of both ET-A and ET-B in Leydig cells and of ET-A in Sertoli cells leads to the assumption that ET could influence these cells as an autocrine factor.

Structure of human endothelin-2 gene and demonstration of common expression in human right atrial tissue

The endothelins (ET) are a group of three vasoactive peptides also known to be involved in vascular remodeling. ET1 is the most extensively studied, but recent evidence has highlighted the role of the little investigated ET2 gene as a potential candidate gene in regulating blood pressure. To allow the future role of this gene to be studied the structure of human ET2 was characterized and intron/exon boundaries were determined. With this structural information and using reverse-transcriptase PCR technology we show that the ET2 gene is commonly expressed in human right atrial tissue. This work will allow a more detailed assessment of the role of this physiologically important gene in human essential hypertension.

Mapping of candidate genes for hypertension by fluorescence in situ hybridization on the genome of transgenic rats and mice

Transgenic animals are new and important models for the study of candidate genes in hypertension research as well as in other fields of medicine. For detailed genetic characterization of the transgenic animals, and to account for the symptoms arising from the insertion of transgenes in the genome, it is essential to identify these insertion sites. In this study, the insertion sites of the transgenes of candidate genes for hypertension were identified by fluorescence in situ hybridization (FISH) after G-banding of the chromosomes in transgenic rats and mice. This technique combines high resolution G-banding and fluorescence in situ hybridization for the mapping of four different candidate genes in six different transgenic rats as well as three different mouse transgenic lines. The presented results will help to draw conclusions about the influence of the respective integration site on transgene expression.

Endothelin expression and responsiveness in human ovarian carcinoma cell lines

To elucidate the potential role of endothelins (ETs) as growth regulators in ovarian carcinoma cells in culture, expression of endothelins and their receptors were measured in two ovarian cancer cell lines (PEO4 and PEO14), together with the effect of the exogenous addition of endothelins on the growth of these cell lines in vitro. RT-PCR analysis of mRNA prepared from PEO4 and PEO14 indicated the presence of ET-1 and ET-3 mRNA. Immunoreactive ET-1-like peptide was found in media from cultures of both PEO4 (1.7 +/- 0.4 fmol/10(6) cells/72 h) and PEO14 (20.2 +/- 6.8 fmol/10(6) cells/72 h) cell lines. Radioligand binding studies using 125I-ET-1 and membrane fractions were consistent with PEO4 cells having two receptor sites of either high affinity (Kd = 0.065 nM, Bmax = 0.047 pmol/mg protein) or lower affinity sites (Kd = 0.49 nM, Bmax = 0.23 pmol/mg protein). Studies using membrane fractions of PEO14 cells indicated that this cell line has only a single lower affinity binding site (Kd = 0.56 nM, Bmax = 0.31 pmol/mg protein). However, RT-PCR analysis indicated the presence of mRNA from both ETA and ETB receptors in PEO4 and PEO14 cell lines. Exogenous addition of ETs to PEO4 and PEO14 cells at concentrations of 10(-10)-10(-7)M resulted in specific dose-dependent increases in cell number for ET-1 (with maximum effects at 10(-10) and 10(-9)M for PEO4 and PEO14, respectively) and ET-2 (maximum effects at 10(-8) and 10(-9)M for PEO4 and PEO14, respectively) but not for ET-3. Experiments on the growth of PEO14 cells using BQ123 (ETA-R) antagonist and "antisense" oligonucleotide against the ETA-R, in the absence of exogenous ETs, suggested that immunoreactive ET-1-like material secreted by PEO14 cells can affect their growth in an autocrine manner. These results would be consistent with ET-1 acting as a possible autocrine growth regulator in human ovarian carcinoma cells.

[Vasoactive intestinal contractor (VIC)/mouse ET-2 and VIC receptor: biological activity, gene expression, and specific receptor]

Using molecular biology techniques with the Endothelin (ET) cDNA as a probe, we discovered a novel peptide, vasoactive intestinal contractor (VIC). VIC differed from ET (= ET-1) in 3 amino acid residues. Synthetic VIC had in vivo pressor and in vitro vasoconstrictor activity such as that of ET. Northern blot analysis, however, indicated the VIC gene to be expressed in the intestine. Furthermore, VIC evoked stronger contractile response in ileum than ET. VIC may thus possibly be reasonably classified as a gut peptide. From the cDNA sequence analysis, the mature VIC is predicted to be produced via an intermediate from the deduced prepro VIC.