PLAC1 Regulates the Occurrence of Fetal Growth Restriction by Inhibiting the Apoptosis of Trophoblast Cells

OBJECTIVE

Fetal growth restriction (FGR) refers to impaired and insufficient intrauterine growth potential caused by a variety of adverse factors and is a serious perinatal complication that leads to fetal or neonatal mortality and morbidity. FGR has numerous causes, and its pathogenesis has not been fully understood. Recently, increasing numbers of researchers have begun to focus on the placenta, the only link between the fetus and the mother. The placenta is a vital organ that plays key roles in fetal development. PLAC1 is a trophoblast-specific gene located on the X chromosome and is important for placental development. However, the biological role of PLAC1 in fetal growth restriction is not well understood. In this study, we investigated the changes in the expression of placental-specific protein 1(PLAC1) in the placentas of pregnant women with FGR and in the placentas of normal pregnancies. We also explored the regulation of PLAC1 in the growth of trophoblast cells.

METHODS

Western blotting was used to detect the expression of PLAC1 in FGR and in normal placenta tissues. Cell counting kit 8 (CCK-8), wound healing, and transwell assays were used to detect the effects of PLAC1 knockdown on trophoblast cell proliferation, migration, and invasion. Western blotting was used to detect the expression of PLAC1 under hypoxic conditions, and the cell viability and apoptosis of trophoblast cells in a low oxygen concentration after overexpression of PLAC1 were detected by CCK-8 and flow cytometry assay.

RESULTS

Compared with the placentas in the control group of normal pregnancies, the expression of PLAC1 in the placentas of the FGR group was significantly down-regulated (p<0.05). Knocking down PLAC1 by siRNA significantly inhibited the proliferation, migration, and invasion of trophoblast cells. After treatment with alow oxygen concentration, the expression of PLAC1 protein was significantly reduced (p<0.05). The overexpression of PLAC1 can reverse the cell viability of trophoblast cells (p<0.05) and inhibit apoptosis of trophoblast cells (p<0.05) in low oxygen concentration.

CONCLUSION

The expression of PLAC1 was reduced in fetal growth restriction and did not protect trophoblast cells from hypoxic damage, suggesting that PLAC1 may be an important regulator in the occurrence of fetal growth restriction.

Maternal metabolism affects endometrial expression of oxidative stress and FOXL2 genes in cattle

Intensive selection for milk production has led to reduced reproductive efficiency in high-producing dairy cattle. The impact of intensive milk production on oocyte quality as well as early embryo development has been established but few analyses have addressed this question at the initiation of implantation, a critical milestone ensuring a successful pregnancy and normal post-natal development. Our study aimed to determine if contrasted maternal metabolism affects the previously described sensory properties of the endometrium to the conceptus in cattle. Following embryo transfer at Day 7 post-oestrus, endometrial caruncular (CAR) and intercaruncular (ICAR) areas were collected at Day 19 from primiparous postpartum Holstein-Friesian cows that were dried-off immediately after parturition (i.e., never milked; DRY) or milked twice daily (LACT). Gene quantification indicated no significant impact of lactation on endometrial expression of transcripts previously reported as conceptus-regulated (PLET1, PTGS2, SOCS6) and interferon-tau stimulated (RSAD2, SOCS1, SOCS3, STAT1) factors or known as female hormone-regulated genes (FOXL2, SCARA5, PTGS2). Compared with LACT cows, DRY cows exhibited mRNA levels with increased expression for FOXL2 transcription factor and decreased expression for oxidative stress-related genes (CAT, SOD1, SOD2). In vivo and in vitro experiments highlighted that neither interferon-tau nor FOXL2 were involved in transcriptional regulation of CAT, SOD1 and SOD2. In addition, our data showed that variations in maternal metabolism had a higher impact on gene expression in ICAR areas. Collectively, our findings prompt the need to fully understand the extent to which modifications in endometrial physiology drive the trajectory of conceptus development from implantation onwards when maternal metabolism is altered.

PreImplantation Factor in endometriosis: A potential role in inducing immune privilege for ectopic endometrium

Endometriosis is a chronic inflammatory condition characterised by the growth of endometrial epithelial and stromal cells outside the uterine cavity. In addition to Sampson’s theory of retrograde menstruation, endometriosis pathogenesis is facilitated by a privileged inflammatory microenvironment, with T regulatory FoxP3⁺ expressing T cells (Tregs) being a significant factor. PreImplantation Factor (PIF) is a peptide essential for pregnancy recognition and development. An immune modulatory function of the synthetic PIF analog (sPIF) has been successfully confirmed in multiple animal models. We report that PIF is expressed in the epithelial ectopic cells in close proximity to FoxP3⁺ stromal cells. We provide evidence that PIF interacts with FoxP3⁺ cells and modulates cell viability, dependent on cell source and presence of inflammatory mediators. Our finding represent a novel PIF-based mechanism in endometriosis that has potential for novel therapeutics.

Food Intake Affects Sperm-Egg Fusion Through the GIP/PSG17 Axis in Mice

In addition to overeating, starvation also reduces fecundity in mammals. However, little is known about the molecular mechanisms linking food intake to fertility, especially in males. Gastric inhibitory polypeptide (GIP), which is released from intestinal K-cells after meal ingestion, stimulates insulin secretion from pancreatic β-cells through the action of incretin and has several extrapancreatic effects. Here, we identified GIP receptor (Gipr) expression in mouse spermatids. Microarray analysis revealed that pregnancy-specific glycoprotein 17 (Psg17), a potential CD9-binding partner, was significantly decreased in GIP receptor-knockout (Gipr-/-) testes. Glycosylphosphatidylinositol-anchored PSG17 was expressed on the surface of acrosome-reacted sperm, and Gipr-/- sperm led to a lower fertilization rate in vitro, compared with that of Gipr+/+ sperm, both in the absence and presence of the zona pellucida. Plasma GIP concentrations and Psg17 messenger RNA (mRNA) were immediately increased in the testis after a single meal, whereas ingestion of a chronic high-fat diet markedly decreased Gipr and Psg17 mRNA. These results suggest that reduced GIP signaling, by decreased GIP levels or the downregulation of Gipr, is associated with the reduction of fecundity due to starvation or overeating. Thus, proper regulation of GIP signaling in the testis could be a potential unique therapeutic target for male infertility in obese and diabetic individuals.

Angiogenic growth factors augment K-Cl cotransporter expression in erythroid cells via hypoxia-inducible factor-1α

The potassium chloride cotransporters (KCC) family of proteins are widely expressed and are involved in the transepithelial movement of potassium and chloride ions and the regulation of cell volume. KCC activity is high in reticulocytes, and contributes to the dehydration of sickle red blood cells. Because plasma levels of both vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) are elevated in sickle cell individuals, and VEGF has been shown to increase KCC expression in other cells, we hypothesized that VEGF and PlGF influence KCC expression in erythroid cells. Both VEGF and PlGF treatment of human erythroid K562 cells increased both mRNA and protein levels of KCC1, KCC3b, and KCC4. VEGF- and PlGF-mediated cellular signaling involved VEGF-R1 and downstream effectors, specifically, PI-3 kinase, p38 MAP kinase, mTOR, NADPH-oxidase, JNK kinase, and HIF-1α. VEGF and PlGF-mediated transcription of KCC3b and KCC4 involved hypoxia response element (HRE) motifs in their promoters, as demonstrated by promoter analysis, EMSA and ChiP. These results were corroborated in vivo by adenoviral-mediated overexpression of PlGF in normal mice, which led to increased expression of mKCC3 and mKCC4 in erythroid precursors. Our studies show that VEGF and PlGF regulate transcription of KCC3b and KCC4 in erythroid cells via activation of HIF-1α, independent of hypoxia. These studies provide novel therapeutic targets for regulation of cell volume in RBC precursors, and thus, amelioration of dehydration in RBCs in sickle cell disease.

ISGylation: a conserved pathway in mammalian pregnancy

Successful pregnancy includes remodeling and differentiation of the endometrium in response to sex steroid hormones, development of maternal immunotolerance to the implanting embryo, and modification of the local uterine environment by the embryo to suit its own needs. The major signal released by the ruminant conceptus during establishment of pregnancy is interferon-tau (IFNT) that stimulates the expression of many genes in the endometrium and ovary. One of these genes is called interferon stimulated gene 15 (ISG15), which encodes a ubiquitin homolog with a C-terminal Gly that becomes covalently attached to Lys residues on targeted proteins through an ATP-dependent multi-step enzymatic reaction called ISGylation. The conceptus-derived induction of endometrial ISGs also occurs in mouse and human deciduas and placenta, in response to pregnancy presumably through action of cytokines such as interleukins and type I IFN. Described herein is evidence to support the concept that ISGylation is a maternal response to the developing conceptus, implantation and placentation that is conserved across mammalian pregnancy. Although the precise role for ISG15 remains elusive during pregnancy, it is clear that up-regulation in response to pregnancy may impart a pre-emptive defense to infection or other environmental insults, and protection of the conceptus against inflammatory insults across species.

Placental growth factor as a new marker for predicting abnormal glucose challenge test results

BACKGROUND

To differentiate placental growth factor (PlGF) levels in pregnancies with normal and abnormal glucose challenge test (GCT) results.

METHODS

A total of 94 pregnant women underwent a 50 -g GCT as part of our routine antenatal screening protocol from September 2011 to January 2012. The patients were divided into three groups: (i) normal GCT, (ii) abnormal GCT and (iii) gestational diabetes mellitus (GDM) based on the screening results for gestational diabetes. The main outcome measure of the study was the relationship between PlGF and GCT results in non-diabetic pregnancies. The Kolmogorov-Smirnov test was used to check the normality of the variables' distributions. The Kruskal-Wallis and analysis of variance tests (Tukey's test) were used to analyze the qualitative parameters.

RESULTS

There were 53 (56.4%), 22 (23.4%) and 19 (20.2%) patients in the normal GCT, abnormal GCT and GDM groups, respectively. The PlGF level in the abnormal GCT group was 518 ± 307.6 pg/mL, which was the highest level in the study population, and there was a statistically significant difference compared with the other groups (p = 0.006). There were no statistically significant differences with respect to fetal birth weight among the three groups in our study.

CONCLUSION

PlGF can be used as a laboratory marker to predict which patients will have abnormal GCT results.

Placenta growth factor mediates angiogenesis in hypoxic pulmonary hypertension

Our previous studies have proved that hypoxia enhances the 15-lipoxygenase (15-LO) expression and increases endogenous 15-hydroxyeicosatetraenoic acid (15-HETE) production to promote pulmonary vascular remodeling and angiogenesis, while the mechanisms of how hypoxia regulates 15-LO expression in endothelium is still unknown. As placenta growth factor (PlGF) promotes pathological angiogenesis by acting on the growth, migration and survival of endothelial cells, there may be some connections between PlGF and 15-LO in hypoxia induced endothelial cells proliferation. In this study, we performed immunohistochemistry, pulmonary artery endothelial cells migration and bromodeoxyuridine incorporation to determine the role of PlGF in pulmonary remodeling induced by hypoxia. Our results showed that hypoxia up-regulated PlGF expression, which was mediated by 15-LO/15-HETE pathway. Furthermore, we found that PlGF had a positive feedback regulation with 15-LO expression and 15-HETE generation. The interaction in hypoxia between 15-HETE and PlGF created a PlGF-15-LO-15-HETE loop, leading to endothelial dysfunction. Thus, these findings suggest a new therapeutic agent in combination with the blockade of PlGF as well as 15-LO in hypoxic pulmonary hypertension.

Differential evolutionary fate of an ancestral primate endogenous retrovirus envelope gene, the EnvV syncytin, captured for a function in placentation

Syncytins are envelope genes of retroviral origin that have been co-opted for a role in placentation. They promote cell–cell fusion and are involved in the formation of a syncytium layer—the syncytiotrophoblast—at the materno-fetal interface. They were captured independently in eutherian mammals, and knockout mice demonstrated that they are absolutely required for placenta formation and embryo survival. Here we provide evidence that these “necessary” genes acquired “by chance” have a definite lifetime with diverse fates depending on the animal lineage, being both gained and lost in the course of evolution. Analysis of a retroviral envelope gene, the envV gene, present in primate genomes and belonging to the endogenous retrovirus type V (ERV-V) provirus, shows that this captured gene, which entered the primate lineage >45 million years ago, behaves as a syncytin in Old World monkeys, but lost its canonical fusogenic activity in other primate lineages, including humans. In the Old World monkeys, we show—by in situ analyses and ex vivo assays—that envV is both specifically expressed at the level of the placental syncytiotrophoblast and fusogenic, and that it further displays signs of purifying selection based on analysis of non-synonymous to synonymous substitution rates. We further show that purifying selection still operates in the primate lineages where the gene is no longer fusogenic, indicating that degeneracy of this ancestral syncytin is a slow, lineage-dependent, and multi-step process, in which the fusogenic activity would be the first canonical property of this retroviral envelope gene to be lost.

Syncytins are “new” genes encoding the envelope protein of captured endogenous retroviral elements. Their unambiguous status of “cellular gene” was recently demonstrated by knocking them out in genetically modified mice, showing their absolute requirement for placenta formation and embryo survival, via formation by cell–cell fusion of the feto-maternal syncytium interface. These genes are remarkable, as they are “necessary” for a basic function in placental mammals and yet they were acquired “by chance” on multiple occasions and independently in diverse mammalian species. We proposed that syncytins have been pivotal for the emergence of animals with a placenta from those laying eggs via the capture of a founding retroviral env gene, then subsequently replaced in the diverse mammalian lineages upon successive and independent germline infections by new retroviruses and co-optation of their env gene, each new gene providing its host with a positive selective advantage. This hypothesis would account for the diversity of the captured syncytins that can be currently found, concomitant with the diversity of placental architectures. A consequence of this paradigm is that evidence for “decaying syncytins” in eutherian mammals should exist, and this is precisely what we sought—and found—in this study.

Aberrant alteration of vascular endothelial growth factor-family signaling in human tubal ectopic pregnancy: what is known and unknown?

More than 98% of ectopic pregnancies occur in the Fallopian tube. Because many facets of tubal ectopic pregnancy remain unclear, prediction, prevention and treatment of tubal ectopic pregnancy are still a major clinical challenge. Compelling evidence suggests that angiogenic growth factors are involved in normal and abnormal implantation. While acknowledging the importance of an intrauterine pregnancy requires the development of a local blood supply and angiogenesis, we hypothesize that the hypoxic- and estrogen-dependent regulation of vascular endothelial growth factor/placental growth factor expression, secretion, and signaling pathways that are possibly involved in the pathophysiology of tubal ectopic pregnancy. Our hypothesis may also lead to a new therapeutic strategy for women with tubal ectopic pregnancy.

Cortisol and interferon tau regulation of endometrial function and conceptus development in female sheep

During early pregnancy in sheep, the elongating conceptus secretes interferon-τ (IFNT) and the conceptus as well as endometrial epithelia produce prostaglandins (PG) via PG synthase 2 (PTGS2) and cortisol via hydroxysteroid (11-β) dehydrogenase 1 (HSD11B1). Ovarian progesterone induces and PG and IFNT stimulates endometrial HSD11B1 expression and keto-reductase activity as well as many epithelial genes that govern trophectoderm proliferation, migration, and attachment during elongation. The primary aim of these studies was to test the hypothesis that HSD11B1-derived cortisol has a biological role in endometrial function and conceptus development during early pregnancy in sheep. In study 1, cyclic ewes received vehicle, cortisol, PF 915275 (PF; a selective inhibitor of HSD11B1), cortisol and PF, meloxicam (a selective inhibitor of PTGS2), cortisol and meloxicam, recombinant ovine IFNT, or IFNT and PF into the uterus from day 10 to day14 after estrus. Cortisol and IFNT stimulated endometrial HSD11B1 expression and activity, increased endometrial PTGS2 activity and the amount of PG in the uterine lumen, and up-regulated many conceptus elongation-related genes in the endometrium. Some effects of cortisol and IFNT were mediated by PTGS2-derived PG. In study 2, bred ewes received PF 915275 or recombinant ovine IFNT and into the uterus from day 10 to day 14 after mating. Inhibition of HSD11B1 activity in utero prevented conceptus elongation, whereas IFNT rescued conceptus elongation in PF-infused ewes. These results suggest that HSD11B1-derived cortisol mediates, in part, actions of ovarian progesterone and the conceptus on endometrial function and support the hypothesis that IFNT, PG, and cortisol coordinately regulate endometrial functions important for conceptus elongation and implantation during early pregnancy in sheep.

Mechanistic mammalian target of rapamycin (MTOR) cell signaling: effects of select nutrients and secreted phosphoprotein 1 on development of mammalian conceptuses

Morphological differentiation of uterine glands in mammals is a postnatal event vulnerable to adverse effects of endocrine disruptors. Exposure of ewe lambs to a progestin from birth to postnatal day 56 prevents development of uterine glands and, as adults, the ewes are unable to exhibit estrous cycles or maintain pregnancy. Uterine epithelia secrete proteins and transport nutrients into the uterine lumen necessary for conceptus development, pregnancy recognition signaling and implantation, including arginine and secreted phosphoprotein 1 (SPP1). Arginine can be metabolized to nitric oxide and to polyamines or act directly to activate MTOR cell signaling to stimulate proliferation, migration, and mRNA translation in trophectoderm cells. SPP1 binds αvβ3 and α5β1 integrins and induces focal adhesion assembly, adhesion and migration of conceptus trophectoderm cells during implantation. Thus, arginine and SPP1 mediate growth, migration, cytoskeletal remodeling and adhesion of trophectoderm essential for pregnancy recognition signaling and implantation.

Hypoxanthine-xanthine oxidase down-regulates GLUT1 transcription via SIRT1 resulting in decreased glucose uptake in human placenta

Appropriate foetal growth and development is dependent on adequate placental glucose uptake. Oxidative stress regulates glucose uptake in various tissues. The effect of oxidative stress on placental glucose transport is not known. Thus, the aim of this study was to determine the effect of oxidative stress on glucose uptake and glucose transporters (GLUTs) in human placenta. Human placenta was incubated in the absence or presence of 0.5 mM hypoxanthine+15 mU/ml xanthine oxidase (HX/XO) for 24 h. Gene and protein expressions of the GLUTs were analysed by quantitative RT-PCR and western blotting respectively. Glucose uptake was measured using radiolabelled ((14)C) glucose. HX/XO significantly decreased GLUT1 gene and protein expression and resultant glucose uptake. There was no effect of the antioxidants N-acetylcysteine, catalase and superoxide dismutase or the NF-κB inhibitor BAY 11-0782 on HX/XO-induced decrease in glucose uptake. However, HX/XO treatment significantly decreased both gene and protein expression of SIRT1. In the presence of the SIRT1 activator resveratrol, the decrease in GLUT1 expression and glucose uptake mediated by HX/XO was abolished. Collectively, the data presented here demonstrate that oxidative stress reduces placental glucose uptake and GLUT1 expression by a SIRT1-dependent mechanism.

Relationship between quantity of IFNT estimated by IFN-stimulated gene expression in peripheral blood mononuclear cells and bovine embryonic mortality after AI or ET

BACKGROUND

Interferon tau (IFNT), which is secreted into the uterine cavity during the maternal recognition period (MRP), is a key factor for establishment of pregnancy. The present study aims to clarify the relationship between the ability of a bovine conceptus to produce IFNT during the MRP and the conceptus's ability to establish pregnancy.

METHODS

In the first experiment, IFNT (0, 500, or 1000 micrograms) was administered into the uterine horn ipsilateral to the CL 16 or 17 d after standing estrus, and mRNA levels of IFN-stimulated gene 15-kDa protein (ISG15) and Mx2 in peripheral blood mononuclear cells (PBMCs) were determined. In the second experiment, we investigated ISG15 mRNA expression in PBMCs during the MRP in cattle after either artificial insemination (AI) or embryo transfer (ET).

RESULTS

Intrauterine administration of IFNT stimulated ISG15 and Mx2 gene expressions in PBMCs in cattle, and there was a positive correlation between the expressions of peripheral markers and the quantity of IFNT administered. In pregnant and normal interestrous interval (< 25 d) cattle (nIEI cattle), expression levels of the ISG15 gene showed similar patterns after AI and ET, and ISG15 mRNA expression was increased in pregnant cattle but unchanged in nIEI cattle. In contrast, ISG15 gene expression in extended interestrous interval (greater than or equal to 25 d) cattle (eIEI cattle) differed after ET compared with AI. In eIEI cattle after ET, ISG15 gene expression increased, such that the value on day 18 was intermediate between those of pregnant and nIEI cattle. In eIEI cattle after AI, ISG15 gene expression did not increase throughout the observation period.

CONCLUSIONS

The results of the current study indicate that the quantity of conceptus-derived IFNT can be estimated by measuring ISG15 mRNA levels in PBMCs from cattle. Using this approach, we demonstrate that ISG15 gene expression during the MRP in eIEI cattle differed after ET compared with AI. In addition, the modest increase in ISG15 gene expression in eIEI cattle after ET suggests that late embryo losses were due to delayed or insufficient growth of the conceptus during the MRP in cattle.

Early pregnancy induced expression of prostaglandin E2 receptors EP2 and EP4 in the ovine endometrium and regulated by interferon tau through multiple cell signaling pathways

Prostaglandin E2 (PGE(2)) plays pleiotropic roles at fetal-maternal interface during establishment of pregnancy. The objectives of the study were to: (i) determine regulation of PGE2 receptors EP1, EP2, EP3, and EP4 in the endometrium during the estrous cycle and early pregnancy; and (ii) understand endometrial epithelial and stromal cell-specific hormonal regulation of EP2 and EP4 in sheep. Results indicate that: (i) early pregnancy induces expression of EP2 and EP4 but not EP1 and EP3 proteins in the endometrium on days 12-16 compared to that of estrous cycle; (ii) intrauterine infusion of interferon tau (IFNT) increases expression of EP2 and EP4 proteins in endometrium; and (iii) IFNT activates distinct epithelial and stromal cell-specific JAK, EGFR, ERK1/2, AKT, or JNK signaling module to regulate expression of EP2 and EP4 proteins in the ovine endometrium. Our results indicate a role for EP2 and EP4-mediated PGE(2) signaling in endometrial functions and establishment of pregnancy in ruminants.

Galectins: guardians of eutherian pregnancy at the maternal-fetal interface

Galectins are multifunctional regulators of fundamental cellular processes. They are also involved in innate and adaptive immune responses, and play a functional role in immune-endocrine crosstalk. Some galectins have attracted attention in the reproductive sciences because they are highly expressed at the maternal-fetal interface, their functional significance in eutherian pregnancies has been documented, and their dysregulated expression is observed in the 'great obstetrical syndromes'. The evolution of these galectins has been linked to the emergence of eutherian mammals. Based on published evidence, galectins expressed at the maternal-fetal interface may serve as important proteins involved in maternal-fetal interactions, and the study of these galectins may facilitate the prediction, prevention, diagnosis, and treatment of pregnancy complications.

Loss or inhibition of stromal-derived PlGF prolongs survival of mice with imatinib-resistant Bcr-Abl1(+) leukemia

Imatinib has revolutionized the treatment of Bcr-Abl1(+) chronic myeloid leukemia (CML), but, in most patients, some leukemia cells persist despite continued therapy, while others become resistant. Here, we report that PlGF levels are elevated in CML and that PlGF produced by bone marrow stromal cells (BMSCs) aggravates disease severity. CML cells foster a soil for their own growth by inducing BMSCs to upregulate PlGF, which not only stimulates BM angiogenesis, but also promotes CML proliferation and metabolism, in part independently of Bcr-Abl1 signaling. Anti-PlGF treatment prolongs survival of imatinib-sensitive and -resistant CML mice and adds to the anti-CML activity of imatinib. These results may warrant further investigation of the therapeutic potential of PlGF inhibition for (imatinib-resistant) CML.

Involvement of human endogenous retroviral syncytin-1 in human osteoclast fusion

Generation of osteoclasts through fusion of mono-nucleated precursors is a key event of bone physiology and bone resorption is inefficient without osteoclast fusion. Several factors playing a critical role in the fusion process have already been recognized, but the factors involved in the actual fusion of the lipid bilayers of their cell membranes are still unknown. Syncytin-1 is a protein encoded by a human endogenous retroviral gene which was stably integrated into the human ancestor genome more than 24 million years ago. Upon activation, syncytin-1 is able to destabilize the lipid bilayer of the target cell and to force the merging of plasma membranes. This protein is a key player in the fusion of cytotrophoblasts. In the present study, syncytin-1 as well as its putative receptor ASCT2 was found to be expressed in differentiating osteoclasts in vitro, both on mRNA and protein level. This was documented through Q-PCR, Western blot and immunofluorescence analyses. These in vitro findings were confirmed by immunohistochemical stainings in human iliac crest biopsies. A syncytin-1 inhibitory peptide reduced the number of nuclei per osteoclast by 30%, as well as TRACP activity. From a mechanistic point of view, it is interesting that the distribution of syncytin-1 immunoreactivity on the cell surface parallels that of actin, another important player in cell fusion, and that cell-cell proximity induces particular patterns of distribution of syncytin-1 and actin in the respective cells. These complementary observations support a critical role of syncytin-1 in osteoclast fusion, which is of special interest in view of its well-known ability to force the merging of plasma membranes.

Involvement of miR-30c and miR-301a in immediate induction of plasminogen activator inhibitor-1 by placental growth factor in human pulmonary endothelial cells

PAI-1 (plasminogen activator inhibitor-1) is a key physiological inhibitor of fibrinolysis. Previously, we have reported PlGF (placental growth factor)-mediated transcriptional up-regulation of PAI-1 (SERPINE1) mRNA expression via activation of HIF-1α (hypoxia-inducible factor-1α) and AP-1 (activator protein-1) in HPMVECs (human pulmonary microvascular endothelial cells), which resulted in elevated PAI-1 in humans with SCA (sickle cell anaemia). In the present study, we have identified the role of post-transcriptional mechanism(s) of PlGF-mediated accumulation of PAI-1 mRNA in HPMVECs by examining the role of microRNAs (miRNAs/miRs) in PlGF-induced PAI-1 mRNA stability. Our results show reduced expression of miR-30c and miR-301a, but not of miR-99a, in response to PlGF, which have evolutionarily conserved binding sites in the 3'-UTR (3'-untranslated region) of PAI-1 mRNA. Transfection of anti-miR-30c or anti-miR-301a oligonucleotides resulted in increased PAI-1 mRNA levels, which were increased further with PlGF stimulation. Conversely, overexpression of pre-miR-30c or pre-miR-301a resulted in an attenuation of PlGF-induced PAI-1 mRNA and protein levels. Luciferase reporter assays using wild-type and mutant 3'-UTR constructs confirmed that the PAI-1 3'-UTR is indeed a direct target of miR-30c and miR-301a. Finally, plasma levels of miR-30c and miR-301a were significantly down-regulated in patients with SCA compared with normal controls. These results provide a post-transcriptional regulatory mechanism of PlGF-induced PAI-1 elevation.

PLAC1 (Placenta-specific 1): a novel, X-linked gene with roles in reproductive and cancer biology

Placenta-specific 1 (PLAC1) is a recently described X-linked gene with expression restricted primarily to cells derived from trophoblast lineage during embryonic development. PLAC1 localizes to a region of the X chromosome thought to be important in placental development although its role in this process has not been defined. This review summarizes our current understanding of its expression, regulation, and function. PLAC1 is expressed throughout human pregnancy by the differentiated trophoblast and localizes to membranous structures in the syncytiotrophoblast, including the microvillous plasma membrane surface. Recent studies have demonstrated that PLAC1 is also expressed by a wide variety of human cancers. Studies of the PLAC1 promoter regions indicate that its expression in both normal placenta and cancer cells is driven by specific interactions involving a combination of transcription factors. Although functional insight into PLAC1 in the normal trophoblast is lacking, preliminary studies suggest that cancer-derived PLAC1 has the potential to promote tumor growth and function. In addition, it also appears to elicit a specific immunologic response that may influence survival in some cancer patients, suggesting that it may provide a therapeutic target for the treatment of some cancers. We also discuss a potential role for PLAC1 as a biomarker predictive of specific pregnancy complications, such as preeclampsia.

Human Hsp10 and Early Pregnancy Factor (EPF) and their relationship and involvement in cancer and immunity: current knowledge and perspectives

This article is about Hsp10 and its intracellular and extracellular forms focusing on the relationship of the latter with Early Pregnancy Factor and on their roles in cancer and immunity. Cellular physiology and survival are finely regulated and depend on the correct functioning of the entire set of proteins. Misfolded or unfolded proteins can cause deleterious effects and even cell death. The chaperonins Hsp10 and Hsp60 act together inside the mitochondria to assist protein folding. Recent studies demonstrated that these proteins have other roles inside and outside the cell, either together or independently of each other. For example, Hsp10 was found increased in the cytosol of different tumors (although in other tumors it was found decreased). Moreover, Hsp10 localizes extracellularly during pregnancy and is often indicated as Early Pregnancy Factor (EPF), which is released during the first stages of gestation and is involved in the establishment of pregnancy. Various reports show that extracellular Hsp10 and EPF modulate certain aspects of the immune response with anti-inflammatory effects in patients with autoimmune conditions improving clinically after treatment with recombinant Hsp10. Moreover, Hsp10 and EPF are involved in embryonic development, acting as a growth factor, and in cell proliferation/differentiation mechanisms. Therefore, it becomes evident that Hsp10 is not only a co-chaperonin, but an active player in its own right in various cellular functions. In this article, we present an overview of various aspects of Hsp10 and EPF as they participate in physiological and pathological processes such as the antitumor response and autoimmune diseases.

Insulin-like growth factor binding protein-1 in the ruminant uterus: potential endometrial marker and regulator of conceptus elongation

Establishment of pregnancy in ruminants requires conceptus elongation and production of interferon-tau (IFNT), the pregnancy recognition signal that maintains ovarian progesterone (P4) production. These studies determined temporal and spatial alterations in IGF binding protein (IGFBP)-1 and IGFBP3 in the ovine and bovine uterus; effects of P4 and IFNT on their expression in the ovine uterus; and effects of IGFBP1 on ovine trophectoderm cell proliferation, migration, and attachment. IGFBP1 and IGFBP3 were studied because they are the only IGFBPs specifically expressed by the endometrial luminal epithelia in sheep. In sheep, IGFBP1 and IGFBP3 expression was coordinate with the period of conceptus elongation, whereas only IGFBP1 expression was coordinate with conceptus elongation in cattle. IGFBP1 mRNA in the ovine endometria was between 5- and 29-fold more abundant between d 12 and 16 of pregnancy compared with the estrous cycle and greater on d 16 of pregnancy than nonpregnancy in the bovine uterus. In sheep, P4 induced and IFNT stimulated expression of IGFBP1 but not IGFBP3; however, the effect of IFNT did not mimic the abundant increase observed in pregnant ewes. Therefore, IGFBP1 expression in the endometrium is regulated by another factor from the conceptus. IGFBP1 did not affect the proliferation of ovine trophectoderm cells in vitro but did stimulate their migration and mediate their attachment. These studies reveal that IGFBP1 is a common endometrial marker of conceptus elongation in sheep and cattle and most likely regulates conceptus elongation by stimulating migration and attachment of the trophectoderm.

Prenatal hypoxia causes a sex-dependent increase in heart susceptibility to ischemia and reperfusion injury in adult male offspring: role of protein kinase C epsilon

The present study tested the hypothesis that protein kinase C (PKC) epsilon plays a key role in the sex dichotomy of heart susceptibility to ischemia and reperfusion injury in adult offspring resulting from prenatal hypoxic exposure. Time-dated pregnant rats were divided between normoxic and hypoxic (10.5% O(2) on days 15-21 of gestation) groups. Hearts of 3-month-old progeny were subjected to ischemia and reperfusion (I/R) injury in a Langendorff preparation. Preischemic values of left ventricle (LV) function were the same between control and hypoxic animals. Prenatal hypoxia significantly decreased postischemic recovery of LV function and increased cardiac enzyme release and infarct size in adult male, but not female, rats. This was associated with significant decreases in PKC(epsilon) and phospho-PKC(epsilon) levels in the LV of the male, but not female, rats. The PKC(epsilon) translocation inhibitor peptide (PKC(epsilon)-TIP) significantly decreased phospho-PKC(epsilon) in control male rats to the levels found in the hypoxic animals and abolished the difference in I/R injury observed between the control and hypoxic rats. In females, PKC(epsilon)-TIP inhibited PKC(epsilon) phosphorylation and decreased postischemic recovery of LV function equally well in both control and hypoxic animals. PKC(epsilon)-TIP had no effect on PKCdelta activation in either male or female hearts. The results demonstrated that prenatal hypoxia caused an increase in heart susceptibility to ischemia and reperfusion injury in offspring in a sex-dependent manner, which was due to fetal programming of PKC(epsilon) gene repression resulting in a down-regulation of PKC(epsilon) function in the heart of adult male offspring.

TIP47, a lipid cargo protein involved in macrophage triglyceride metabolism

OBJECTIVE

Uptake of lipids by macrophages (MPhi) leads to lipid droplet accumulation and foam cell formation. The PAT family proteins are implicated in lipid droplet formation, but the precise function of the 47-kDa tail interacting protein (TIP47), a member of this family, is poorly defined. The present study was performed to determine the function of TIP47 in MPhi lipid metabolism.

METHODS AND RESULTS

Freeze-fracture cytochemistry demonstrates that TIP47 is present in the plasma membrane of MPhi and is aggregated into clusters when the cells are incubated with oleate. Suppression of adipophilin levels using siRNA knockdown leads to migration of TIP47 from a cytoplasmic pool to the lipid droplet. Further, reduction of TIP47 decreases triglyceride levels, whereas raising TIP47 levels by expression of EGFP-TIP47 shows the opposite effect.

CONCLUSION

Our results show that the TIP47 protein levels directly correlate with triglyceride levels. We propose that TIP47 may act as a carrier protein for free fatty acids and in this way participates in conversion of MPhi into foam cells.

Glycodelin in reproductive endocrinology and hormone-related cancer

Glycodelin is an endocrine-regulated glycoprotein that has significant effects on immune cells, apoptosis, reproduction, cell adhesion, differentiation and cancer. In reproduction, glycodelin contributes to capacitation and immunoprotection of spermatozoa, and it modulates sperm-oocyte binding, acrosome reaction and implantation. In endocrine-related cancer, the differentiation inducing effects of glycodelin are accompanied by growth restriction of malignant cells, decreased expression of oncogenes, increased expression of tumour suppressor genes and morphological reversion of the malignant phenotype. This review features these properties and clinical connections, highlighting the role of glycosylation in biological actions.

The tumor marker human placental protein 11 is an endoribonuclease

Human PP11 (placental protein 11) was previously described as a serine protease specifically expressed in the syncytiotrophoblast and in numerous tumor tissues. Several PP11-like proteins were annotated in distantly related organisms, such as worms and mammals, suggesting their involvement in evolutionarily conserved processes. Based on sequence similarity, human PP11 was included in a protein family whose characterized members are XendoU, a Xenopus laevis endoribonuclease involved in small nucleolar RNA processing, and Nsp15, an endoribonuclease essential for coronavirus replication. Here we show that the bacterially expressed human PP11 displays RNA binding capability and cleaves single stranded RNA in a Mn(2+)-dependent manner at uridylates, to produce molecules with 2',3'-cyclic phosphate ends. These features, together with structural and mutagenesis analyses, which identified the potential active site residues, reveal striking parallels to the amphibian XendoU and assign a ribonuclease function to PP11. This newly discovered enzymatic activity places PP11-like proteins in a completely new perspective.

FLT1 and its ligands VEGFB and PlGF: drug targets for anti-angiogenic therapy?

Less than 5 years ago, it was still not clear whether anti-angiogenic drugs would prove successful in the clinic. After numerous patients with cancer or age-related macular degeneration have been treated with these drugs, they have now become part of the standard range of therapeutic tools. Despite this milestone, anti-angiogenic therapy still faces a number of clinical hurdles, such as improving efficacy, avoiding escape and resistance, and minimizing toxicity. Hopefully, other agents with complementary mechanisms, such as those that target placental growth factor, will offer novel opportunities for improved treatment.

Is the trophoblast an immune regulator? The role of Toll-like receptors during pregnancy

In the early 1950s, Medawar recognized for the first time the unique immunology of the maternal/ fetal interface and its potential relevance for transplantation. In his original work, he described the fetal allograft analogy whereby the fetus may be viewed as a semi-allogeneic conceptus that has evaded rejection by the maternal immune system. Although numerous hypotheses have been proposed to prove this observation, none have demonstrated that the maternal immune system is antagonist to the invading trophoblast. In the present article, we have reviewed recent studies demonstrating the expression and function of Toll-like receptors (TLRs) in trophoblast cells, and, based on these data, we propose an alternative view for maternal/fetal immune interactions.

The molecular basis of VEGFR-1 signal transduction pathways in primary human monocytes

OBJECTIVE

Arteriogenesis, the growth of preexisting arterioles into functional arteries, is dependent on the proper function of monocytes. Likewise, wound healing is monocyte-dependent. The activation of vascular endothelial growth factor receptor-1 (VEGFR-1) in monocytes induces a chemotactic response, triggers the expression of tissue factor, and gene expression of cytokines and chemokines. Little is known about intracellular signaling pathways mediating the biological functions triggered by VEGFR-1 in primary monocytes.

METHODS AND RESULTS

Monocytes were isolated from peripheral venous blood of young healthy individuals using indirect magnetic labeling. Stimulation of monocytes with either vascular endothelial growth factor-A (VEGF-A) or placenta growth factor (PlGF-1) triggered VEGFR-1 autophosphorylation and phosphorylation of distinct downstream proteins: phosphatidylinositol-3 kinase (PI-3K), Akt, p38, and extracellular signal-regulated kinase-1/2 (ERK1/2). PI-3K appears to be a central regulator in VEGFR-1 signaling in monocytes as the activation of Akt, p38, and ERK1/2 are PI-3-K-dependent. In addition, Akt activation functions downstream of p38 kinase. VEGFR-1-mediated chemotaxis of monocytes is dependent on the activation of PI-3K, p38 kinase, Akt, and ERK1/2, when assessed in a modified Boyden chamber.

CONCLUSIONS

Both PlGF-1 and VEGF-A can activate VEGFR-1-dependent signaling pathways in primary human monocytes, leading to the activation of several intracellular signaling pathways. These pathways are critically involved in primary monocyte chemotaxis.

Interferon-tau, a Type 1 interferon involved in maternal recognition of pregnancy

Interferon-tau is a major product of ovine and bovine conceptuses during the period before the trophoblast makes firm attachment to the uterine wall and begins to form a placenta. Its primary function is in preventing a return to ovarian cyclicity and hence ensuring the pregnancy continues, although it undoubtedly has other roles in ensuring receptivity of the maternal endometrium. Despite having properties similar to those of other Type 1, IFN-tau is not virally inducible and functions in a constitutive process unrelated to pathogenesis. The genes for IFN-tau (IFNT), which are confined to ruminant ungulate species, would appear to be the most recently evolved mammalian Type 1 gene family and are primarily under the transcriptional control of Ets2 and signal transduction pathways that target that transcription factor. The IFNT provide an illustration of how a gene control region can be commandeered and then refined to provide a radically changed pattern of expression.

Influenza A virus transactivates the mouse envelope gene encoding syncytin B and its regulator, glial cells missing 1

Recently, two candidate analogs for human syncytin, denoted syncytins A and B, were identified in the murine genome. These were found to have expression patterns and functions similar to human syncytin. In addition, the identification of glial cells missing (GCM)-binding motifs in putative promoter regions of the mouse syncytins imply analogous regulation. Transcriptional modulation of syncytin by exogenous agents was recently suggested by studies reporting transactivation of syncytin in human cell lines following virus infections. The authors report that influenza A virus infection increased the levels of transcripts encoding Gcm1 and syncytin B, but not syncytin A, in NIH-3T3 cells as well as in mouse primary neurons or glia. Overexpression of human GCM1 in NIH-3T3 cells resulted in increased levels of transcripts encoding syncytin B but not syncytin A. Systemic administration of neurotropic influenza A virus resulted in a neuronal infection and increased levels of Gcm1-encoding transcripts in brains of young mice. The mouse may therefore be useful for studies on the expression and function of endogenous retroviral envelope genes and transcription factors regulating their expression in the placenta and brain during physiological or pathological conditions.

Intronic polyadenylation signal sequences and alternate splicing generate human soluble Flt1 variants and regulate the abundance of soluble Flt1 in the placenta

The gene FLT1 produces at least two transcripts from a common transcription start site: full-length Flt1 contains 30 exons encoding a membrane-bound VEGF receptor; soluble Flt1 (sFlt1) shares the first 13 exons but utilizes poly(A) signal sequences within intron 13 to create a transcript that lacks downstream exons. To address the mechanisms that regulate human sFlt1, we mapped the 3' end of sFlt1 mRNA and defined the full extent of its 3' untranslated region (UTR). We identified a 3.2 Kb sFlt1 transcript that is cleaved within an alternatively spliced exon downstream of exon 14 and is predicted to encode a C-terminal variant of sFlt1 with an unusual polyserine tail. sFlt1 mRNA cleavage sites within intron 13 were identified in human placenta and in vascular endothelium by ribonuclease protection assay (RPA). A proximal and two distal mRNA cleavage sites were identified by RPA downstream of consensus polyadenylation signals that create variant transcripts with a 3' UTR ranging from 30 bases to approximately 4 Kb. Northern blot analysis and 3' rapid amplification of cDNA ends (RACE) in placenta confirmed the existence of distal intronic sFlt1 cleavage sites that give rise to a sFlt1 transcript of approximately 7 Kb. The identity of the distal signal sequences were then confirmed by mutagenesis of putative signal elements in a polyadenylation reporter assay. We demonstrate the heterogeneity of human sFlt1 that arises from alternate splicing and from alternative polyadenylation directed by strong intronic poly(A) signal sequences leading to C-terminal variants and to an sFlt1 transcript with a large 3' UTR containing several AU rich elements and poly(U) regions that may regulate mRNA stability.

Arginase activity mediates reversible T cell hyporesponsiveness in human pregnancy

Complex regulation of T cell functions during pregnancy is required to ensure materno-fetal tolerance. Here we reveal a novel pathway for the temporary suppression of maternal T cell responses in uncomplicated human pregnancies. Our results show that arginase activity is significantly increased in the peripheral blood of pregnant women and remarkably high arginase activities are expressed in term placentae. High enzymatic activity results in high turnover of its substrate l-arginine and concomitant reduction of this amino acid in the microenvironment. Amino acid deprivation is emerging as a regulatory pathway of lymphocyte responses and we assessed the consequences of this enhanced arginase activity on T cell responses. Arginase-mediated l-arginine depletion induces down-regulation of CD3ζ, the main signalling chain of the TCR, and functional T cell hyporesponsiveness. Importantly, this arginase-mediated T cell suppression was reversible, as inhibition of arginase activity or addition of exogenous l-arginine restored CD3ζ chain expression and T cell proliferation. Thus, l-arginine metabolism constitutes a novel physiological mechanism contributing to the temporary suppression of the maternal immune response during human pregnancy.

ApoA-I-binding protein (AI-BP) and its homologues hYjeF_N2 and hYjeF_N3 comprise the YjeF_N domain protein family in humans with a role in spermiogenesis and oogenesis

The screening for additional human YjeF_N domain containing proteins beside the apolipoprotein A-I interacting protein (AI-BP), identified two other genes designated hYjeF_N2-15q23 (formerly human homologue of yeast edc3) and hYjeF_N3-19p13.11 comprising the human YjeF_N family. AI-BP is ubiquitously expressed, with a predominance of these tissues where the homologues were found to be restricted including brain, mammary gland, testes and ovaries. Immunohistochemistry of human testes and ovaries showed an expression of hYjeF_N3-19p13.11 only in Leydig cells and theca cells, respectively, indicating a role in steroid hormone metabolism. Interestingly, the protein was also strongly expressed in Leydig cell tumors and in thecofibromas. The identification of hYjeF_N2-15q23 in theca cells and granulosa cells in ovaries, in human spermatids of meiotic division part II and the apical membrane of Sertoli cells in testes suggest similar functions in oogenesis and sperm maturation which is strengthened by the identification of the spermatogenesis regulator HMGA1 as a conserved transcription factor. However, in contrast to AI-BP, both homologous proteins are unable to bind apoA-I. These results relate the human YjeF_N domain containing protein family to cholesterol processing and steroid hormone metabolism in spermiogenesis and oogenesis, and AI-BP may link this function to the HDL pathway.

Fusiogenic endogenous-retroviral syncytin-1 exerts anti-apoptotic functions in staurosporine-challenged CHO cells

Fusiogenic glycoprotein syncytin-1, expressed in human placenta, is a promising candidate for acquiring a basic knowledge of placental syncytialization. However, its cellular mode of action is unidentified. We investigated whether syncytin-1 may exert influence on apoptotic processes. Therefore, we incubated CHO cells after stable transfection with syncytin-1 (CHO-52) in the presence or absence of staurosporine (STS), a kinase inhibitor well characterized to induce apoptosis. When testing the phenotype of CHO-52 cells, we could demonstrate that the induction of apoptosis by STS was delayed over a period of up to 24 h. Furthermore, the cell death rate was decreased by approx 75% following transfection of syncytin-1 in CHO-52 compared to mock-treated cells. In detail, after 18h of incubation with 500 nM STS, 64 +/- 2% of CHO-52 cells were viable compared to 16 +/- 1% of CHO-mocks, after 24 h 43 +/- 3% vs 5 +/- 2%, respectively. CHO-52 cells exhibited a lower expression of active caspase 3 and anti-apoptotic Bcl-2 was found to be increased in CHO-52 cells at baseline and following STS treatment. Our study provides first evidence that syncytin-1 serves anti-apoptotic function under certain conditions. A lessened activation of caspase 3 and an increased expression of Bcl-2 are possible mechanisms.

[Immunological role of progesterone in the maintenance of pregnancy]

Progesterone is an essential hormone for pregnancy maintenance. This hormone acts by binding to its intracellular receptor or by rapid non-genomic actions to regulate a wide variety of biological functions in the feto-placental unit. Progesterone regulates blastocyst implantation and placental development by inducing immunosuppression through type Th2 cytokines secretion. This review summarizes current research about the role of progesterone as critical regulator of expression and secretion of cytokines by T-cell and other placental cells.

Analysis of the gene regulatory program induced by the homeobox transcription factor distal-less 3 in mouse placenta

Dlx3, a homeodomain transcription factor, is essential for placental development in the mouse. The Dlx3(-/-) mouse embryo dies at embryonic d 9.5-10 putatively due to placental failure. To develop a more comprehensive understanding of the gene profile regulated by Dlx3, microarray analysis was used to determine differences in gene expression within the placenta of Dlx3(+/+) and Dlx3(-/-) mice. Array analysis revealed differential expression of 401 genes, 33 genes in which signal to log ratio values of null/wild-type were lower than -0.5 or higher than 0.5. To corroborate these findings, quantitative real-time PCR was used to confirm differential expression for 11 genes, nine of which displayed reduced expression and two with enhanced expression in the Dlx3(-/-) mouse. Loss of Dlx3 resulted in a marked reduction (>60%) in mRNA expression of placental growth factor (Pgf), a member of the vascular endothelial growth factor family. Consistent with these results, Pgf secretion from placental explants tended to be reduced in the Dlx3(-/-) mice, compared with wild type. To investigate mechanisms of Dlx3 regulation of Pgf gene transcription, we cloned 5.2 kb of the Pgf 5' flanking sequence for use in reporter gene assays. Expression of the Pgf promoter luciferase reporter containing at least three Dlx3 binding sites was increased markedly by overexpression of Dlx3 supporting the conclusion that Dlx3 may have a direct effect on Pgf promoter activity. These studies provide a novel view of the transcriptome regulated by Dlx3 in mouse placenta. Dlx3 is specifically required for full expression and secretion of Pgf in vivo. Moreover, in vitro studies support the conclusion that Dlx3 is sufficient to directly modulate expression of the Pgf gene promoter in placental cells.

Role of placenta growth factor in malignancy and evidence that an antagonistic PlGF/Flt-1 peptide inhibits the growth and metastasis of human breast cancer xenografts

The angiogenic growth factor placenta growth factor (PlGF) is implicated in several pathologic processes, including the growth and spread of cancer. We found by immunohistochemistry that 36% to 60% and 65% of primary breast cancers express PlGF and its receptor Flt-1, respectively. These findings suggest that PlGF may be active in tumor growth and metastasis beyond its role in angiogenesis. It was found that exogenously added PlGF (2 nmol/L), in contrast to vascular endothelial growth factor (2 nmol/L), significantly stimulated in vitro motility and invasion of the human breast tumor lines MCF-7 and MDA-MB-231. A PlGF-2/Flt-1-inhibiting peptide, binding peptide 1 (BP1), that binds Flt-1 at or near the heparin-binding site was identified and synthesized. Both PlGF-stimulated motility and invasion were prevented by treatment with BP1 (P < 0.05), as well as by anti-PlGF antibody. Treatment of mice bearing s.c. MDA-MB-231 with BP1 (200 mug i.p., twice per week) decreased the number of spontaneous metastatic lung nodules by 94% (P < 0.02), whereas therapy of animals with orthotopic mammary fat pad tumors decreased pulmonary metastases by 82% (P < 0.02). These results indicate, for the first time, that PlGF stimulates the metastatic phenotype in these breast cancer cells, whereas therapy with a PlGF-2/Flt-1 heparin-blocking peptide reduces the growth and metastasis of human breast cancer xenografts.

Placental growth factor-1 and epithelial haemato-retinal barrier breakdown: potential implication in the pathogenesis of diabetic retinopathy

AIMS/HYPOTHESIS

Disruption of the retinal pigment epithelial (RPE) barrier contributes to sub-retinal fluid and retinal oedema as observed in diabetic retinopathy. High placental growth factor (PLGF) vitreous levels have been found in diabetic patients. This work aimed to elucidate the influence of PLGF-1 on a human RPE cell line (ARPE-19) barrier in vitro and on normal rat eyes in vivo.

METHODS

ARPE-19 permeability was measured using transepithelial resistance and inulin flux under stimulation of PLGF-1, vascular endothelial growth factor (VEGF)-E and VEGF 165. Using RT-PCR, we evaluated the effect of hypoxic conditions or insulin on transepithelial resistance and on PLGF-1 and VEGF receptors. The involvement of mitogen-activated protein kinase (MEK, also known as MAPK)/extracellular signal-regulated kinase (ERK, also known as EPHB2) signalling pathways under PLGF-1 stimulation was evaluated by western blot analysis and specific inhibitors. The effect of PLGF-1 on the external haemato-retinal barrier was evaluated after intravitreous injection of PLGF-1 in the rat eye; evaluation was by semi-thin analysis and zonula occludens-1 immunolocalisation on flat-mounted RPE.

RESULTS

In vitro, PLGF-1 induced a reversible decrease of transepithelial resistance and enhanced tritiated inulin flux. These effects were specifically abolished by an antisense oligonucleotide directed at VEGF receptor 1. Exposure of ARPE-19 cells to hypoxic conditions or to insulin induced an upregulation of PLGF-1 expression along with increased transcellular permeability. The PLGF-1-induced RPE cell permeability involved the MEK signalling pathway. Injection of PLGF-1 in the rat eye vitreous induced an opening of the RPE tight junctions with subsequent sub-retinal fluid accumulation, retinal oedema and cytoplasm translocation of junction proteins.

CONCLUSIONS/INTERPRETATION

Our results indicate that PLGF-1 may be a potential regulation target for the control of diabetic retinal and macular oedema.

Glycodelin: a molecule with multi-functions on spermatozoa

Glycodelin is a glycoprotein with three isoforms, namely glycodelin-S, glycodelin-A and glycodelin-F. They have similar protein core but different glycan side chains. Spermatozoa are exposed to these isoforms during their passage to the fertilization site. They first encounter glycodelin-S in the seminal plasma. Data suggest that glycodelin-S suppresses albumin-induced cholesterol loss and maintains the spermatozoa in an uncapacitated state before they enter into the cervical canal where glycodelin-S is removed. This allows albumin in the uterine cavity to initiate capacitation. In the fallopian tube, the spermatozoa are exposed to glycodelin-A and -F produced by the fallopian tube. Glycodelin-A is an endogenous glycoprotein that inhibits the binding of spermatozoa to the zona pellucida. Glycodelin-A may protect the spermatozoa from maternal immune attack by its immunosuppressive activity. Glycodelin-F is the main glycodelin isoform in the follicular fluid. Similar to glycodelin-A, it inhibits spermatozoa-zona pellucida binding. The biological significance of the anti-fertilization activity of glycodelin-A and -F remains to be established. Glycodelin-F also suppresses progesterone-induced acrosome reaction. This is important to prevent premature acrosome reaction when the spermatozoa are swimming through the cumulus mass towards the oocyte and become exposed to progesterone produced by the cumulus cells. In summary, different isoforms of glycodelin act in succession to modulate different aspects of sperm function, and thereby, contribute to the success of fertilization.

C-Terminal truncations of syncytin-1 (ERVWE1 envelope) that increase its fusogenicity

Syncytin-1, the envelope protein of ERVWE1, an endogenous retrovirus of the HERV-W family, plays an important role in regulating fusion of the placental trophoblast. At least one of its receptors is expressed on a variety of human cell types. Its ability to fuse cells makes it an attractive candidate molecule in gene therapy against cancer. We studied the relevance of sequences in the cytoplasmic tail of syncytin-1 for inducing cell-cell fusion. We generated a series of C-terminally truncated syncytin-1 variants. Sequences immediately adjacent to the transmembrane region of syncytin-1 were necessary for inducing optimal fusion, whereas the extreme C-terminus of syncytin-1 partially inhibited its fusogenicity. Two variants of syncytin-1, truncated after residues 483 and 515, were significantly hyperfusogenic compared to wild-type syncytin-1. Cellular and cell-surface expression levels of these two variant proteins were similar to those of wild-type syncytin-1. In testing the latter we found that only a very minor portion of recombinantly expressed cellular syncytin-1 was fully mature and expressed on the cell surface. Our results contribute to the understanding of the structure-function relationship of syncytin-1, and might have implications for the use of this molecule in gene therapy.

Eighteenth annual pezcoller symposium: tumor microenvironment and heterotypic interactions

This symposium was held in Trento, Italy, from June 27 to 29, 2006, and was co-chaired by Robert Weinberg and Enrico Mihich. The interactions between tumor cells and their microenvironment were discussed with particular emphasis on their molecular mechanisms. The roles of transforming growth factor beta signaling, urokinase, and matrix metalloproteinases in matrix remodeling; the effects of matrix-tumor interactions on cell proliferation and migration; the tumor-promoting effects of inflammation and of related host cell and cytokine functions; the signaling mechanisms affecting the biology of the stroma; and the mechanisms governing angiogenesis were discussed.

Glycodelin mediates the increase in vascular endothelial growth factor in response to oxidative stress in the endometrium

OBJECTIVE

We hypothesized that glycodelin stimulates vascular endothelial growth factor (VEGF) expression in response to oxidative stress.

STUDY DESIGN

EM42 (human endometrial epithelial cell line) and primary endometrial epithelial cells were subjected to oxidative stress with minimally oxidized low density lipoprotein (mLDL). Cells were also incubated with no LDL (control) or native LDL (nLDL). Each condition was incubated with and without glycodelin antibody. Glycodelin and VEGF protein and messenger RNA (mRNA) levels were analyzed. Primary cells were cultured with glycodelin peptide to evaluate the effect on VEGF protein and mRNA.

RESULTS

Glycodelin and VEGF protein and mRNA were higher for cells grown with mLDL (P < .05), while glycodelin antibody attenuated the increase in VEGF protein (P < .01). Glycodelin peptide increased VEGF mRNA and protein (P < .05).

CONCLUSION

Glycodelin may act as an autocrine factor within endometriotic implants to increase VEGF expression during oxidative stress.

Down syndrome candidate region 1 isoform 1 mediates angiogenesis through the calcineurin-NFAT pathway

Down syndrome candidate region 1 (DSCR1) is one of more than 50 genes located in a region of chromosome 21 that has been implicated in Down syndrome. DSCR1 can be expressed as four isoforms, one of which, isoform 4 (DSCR1-4), has recently been found to be strongly induced by vascular endothelial growth factor A (VEGF-A(165)) and to provide a negative feedback loop that inhibits VEGF-A(165)-induced endothelial cell proliferation in vitro and angiogenesis in vivo. We report here that another DSCR1 isoform, DSCR1-1L, is also up-regulated by VEGF-A(165) in cultured endothelial cells and is strongly expressed in several types of pathologic angiogenesis in vivo. In contrast to DSCR1-4, the overexpression of DSCR1-1L induced the proliferation and activation of the transcription factor NFAT in cultured endothelial cells and promoted angiogenesis in Matrigel assays in vivo, even in the absence of VEGF-A. Similarly, small interfering RNAs specific for DSCR1-1L and DSCR1-4 had opposing inhibitory and stimulatory effects, respectively, on these same functions. DSCR1-4 is thought to inhibit angiogenesis by inactivating calcineurin, thereby preventing activation and nuclear translocation of NFAT, a key transcription factor. In contrast, DSCR1-1L, regulated by a different promoter than DSCR1-4, activates NFAT and its proangiogenic activity is inhibited by cyclosporin, an inhibitor of calcineurin. In sum, DSCR1-1L, unlike DSCR1-4, potently activates angiogenesis and could be an attractive target for antiangiogenesis therapy.

Syncytin is involved in breast cancer-endothelial cell fusions

Cancer cells can fuse spontaneously with normal host cells, including endothelial cells, and such fusions may strongly modulate the biological behaviour of tumors. However, the underlying mechanisms are unknown. We now show that human breast cancer cell lines and 63 out of 165 (38%) breast cancer specimens express syncytin, an endogenous retroviral envelope protein, previously implicated in fusions between placental trophoblast cells. Additionally, endothelial and cancer cells are shown to express ASCT-2, a receptor for syncytin. Syncytin antisense treatment decreases syncytin expression and inhibits fusions between breast cancer cells and endothelial cells. Moreover, a syncytin inhibitory peptide also inhibits fusions between cancer and endothelial cells. These results are the first to show that syncytin is expressed by human cancer cells and is involved in cancer-endothelial cell fusions.