The expression of phospholipase A2 and lipocortins (annexins) I, II and V in human fetal membranes and placenta in association with labour

Annexin A1/Formyl Peptide Receptor Pathway Controls Uterine Receptivity to the Blastocyst

Embryo implantation into the uterine wall is a highly modulated, complex process. We previously demonstrated that Annexin A1 (AnxA1), which is a protein secreted by epithelial and inflammatory cells in the uterine microenvironment, controls embryo implantation in vivo. Here, we decipher the effects of recombinant AnxA1 in this phenomenon by using human trophoblast cell (BeWo) spheroids and uterine epithelial cells (Ishikawa; IK). AnxA1-treated IK cells demonstrated greater levels of spheroid adherence and upregulation of the tight junction molecules claudin-1 and zona occludens-1, as well as the glycoprotein mucin-1 (Muc-1). The latter effect of AnxA1 was not mediated through IL-6 secreted from IK cells, a known inducer of Muc-1 expression. Rather, these effects of AnxA1 involved activation of the formyl peptide receptors FPR1 and FPR2, as pharmacological blockade of FPR1 or FPR1/FPR2 abrogated such responses. The downstream actions of AnxA1 were mediated through the ERK1/2 phosphorylation pathway and F-actin polymerization in IK cells, as blockade of ERK1/2 phosphorylation reversed AnxA1-induced Muc-1 and claudin-1 expression. Moreover, FPR2 activation by AnxA1 induced vascular endothelial growth factor (VEGF) secretion by IK cells, and the supernatant of AnxA1-treated IK cells evoked angiogenesis in vitro. In conclusion, these data highlight the role of the AnxA1/FPR1/FPR2 pathway in uterine epithelial control of blastocyst implantation.

Effects of reproductive season on embryo development in the buffalo

Interest in buffalo farming is increasing worldwide due to the critical role played by buffaloes as sources of animal protein in tropical and subtropical environments. However, reproductive seasonality negatively affects the profitability of buffalo farming. Buffaloes tend to be short-day breeders, with seasonality patterns increasing with greater distances from the Equator. Although ovarian cyclic activity may occur throughout the year, seasonal anoestrus and cycles in calving and milk production are recorded. When buffaloes are forced to mate during the unfavourable season, to meet market demand, they may undergo a higher incidence of embryo mortality. This review addresses the effects of the reproductive season on embryo development in the buffalo, analysing the different factors involved in determining embryo mortality during the unfavourable season, such as impaired luteal function, oocyte competence and sperm quality. The review then focuses on strategies to control the photoperiod-dependent annual fluctuations in conception and embryo mortality in the female buffalo.

Assessment of the cellular localisation of the annexin A2/S100A10 complex in human placenta

The AnxA2/S100A10 complex has been implicated in various placental functions but although the localisation of these proteins individually has been studied, there is no information about the localisation of their complex in situ at the cellular level. Using the proximity ligation technique, we have investigated the in situ localisation of AnxA2/S100A10 complex in the placenta and have compared this with the location patterns of the individual proteins. High levels of expression of AnxA2/S100A10 complexes were observed in the amniotic membrane and in blood vessel endothelial cells. Lower levels were detected in the brush border area of the syncytium and in the trophoblasts. Immunohistochemical analysis of AnxA2 and S100A10 individually revealed broadly similar patterns of localisation. The brush border staining pattern suggests that in this location at least some of the AnxA2 is not in complex with S100A10. The formal location of the AnxA2/S100A10 complex is compatible with a role in cell-cell interaction, intracellular transport and secretory processes and regulation of cell surface proteases, implying contributions to membrane integrity, nutrient exchange, placentation and vascular remodelling in different parts of the placenta. Future applications will allow specific assessment of the association of the complex with pathophysiological disorders.

Endogenous annexin A1 (AnxA1) modulates early-phase gestation and offspring sex-ratio skewing

Annexin A1 (AnxA1) is a glucocorticoid-regulated anti-inflammatory protein secreted by phagocytes and other specialised cells. In the endocrine system, AnxA1 controls secretion of steroid hormones and it is abundantly expressed in the testis, ovaries, placenta and seminal fluid, yet its potential modulation of fertility has not been described. Here, we observed that AnxA1 knockout (KO) mice delivered a higher number of pups, with a higher percentage of female offsprings. This profile was not dependent on the male features, as sperm from KO male mice did not present functional alterations, and had an equal proportion of Y and X chromosomes, comparable to wild type (WT) male mice. Furthermore, mismatched matings of male WT mice with female KO yielded a higher percentage of female pups per litter, a phenomenon which was not observed when male KO mice mated with female WT animals. Indeed, AnxA1 KO female mice displayed several differences in parameters related to gestation including (i) an arrested estrous cycle at proestrus phase; (ii) increased sites of implantation; (iii) reduced pre- and post-implantation losses; (iv) exacerbated features of the inflammatory reaction in the uterine fluid during implantation phase; and (v) enhanced plasma progesterone in the beginning of pregnancy. In summary, herein we highlight that AnxA1 pathway as a novel determinant of fundamental non-redundant regulatory functions during early pregnancy.

Label-free proteomic analysis of placental proteins during Toxoplasma gondii infection

Toxoplasma gondii is a ubiquitous, obligate intracellular parasite capable of crossing the placental barrier and causing spontaneous abortion, preterm labor, or significant disease in the surviving neonate. To better understand molecular mechanisms underlying abnormal pregnancy outcomes caused by T. gondii, placental proteins extracted from T. gondii-infected and -uninfected mice were comparatively analyzed using label-free liquid chromatography-tandem mass spectrometry. Significant difference was observed in the expression of 58 out of 792 proteins in infected placentas (p<0.05) compared with that in uninfected placentas. Quantitative real-time polymerase chain reaction, western blotting, and immunohistochemical staining were used to validate the results of the proteomic analysis. Some placental proteins differentially expressed in infected and uninfected mice were found to be associated with several different biological processes of pregnancy, particularly with trophoblast invasion and placental development. The results provide possible novel insights into the molecular mechanisms for abnormal pregnancy outcomes associated with T. gondii infection.

SIGNIFICANCE

In order to further explore the mechanisms of abnormal pregnant outcomes caused by T. gondii infection, we first applied label-free proteomic technology to analyze the differentially expressed host placental proteins with T. gondii infection. The results showed that some differential proteins are associated with trophoblast invasion and placenta development. The findings provide a systemic view of the altered placental proteins and help to declare the molecular mechanisms of abnormal pregnancy outcomes caused by T. gondii infection.

Anti-inflammatory prostaglandins for the prevention of preterm labour

Preterm birth occurs in 10-12% of pregnancies and is the primary cause of neonatal mortality and morbidity. Tocolytic therapies have long been the focus for the prevention of preterm labour, yet they do not significantly improve neonatal outcome. A direct causal link exists between infection-induced inflammation and preterm labour. As inflammation and infection are independent risk factors for poor neonatal outcome, recent research focus has been shifted towards exploring the potential for anti-inflammatory strategies. Nuclear factor kappa B (NFκB) is a transcription factor that controls the expression of many labour-associated genes including PTGS2 (COX2), prostaglandins (PGs) and the oxytocin receptor (OXTR) as well as key inflammatory genes. Targeting the inhibition of NFκB is therefore an attractive therapeutic approach for both the prevention of preterm labour and for reducing neonatal exposure to inflammation. While PGs are considered to be pro-labour and pro-inflammatory, the cyclopentenone PG 15-deoxy-Δ(12,14)PGJ2 (15d-PGJ2) exhibits anti-inflammatory properties via the inhibition of NFκB in human amniocytes, myocytes and peripheral blood mononuclear cells in vitro. 15d-PGJ2 also delays inflammation-induced preterm labour in the mouse and significantly increases pup survival. This review examines the current understanding of inflammation in the context of labour and discusses how anti-inflammatory PGs may hold promise for the prevention of preterm labour and improved neonatal outcome.

Regulation of sPLA2-IID in Human Decidua: Insights Into the Complexity of the Prostaglandin Pathway in Labor

Prostaglandins are implicated in the labor process, yet the precise role and regulation of the prostaglandin pathway remains to be elucidated. The first step in the pathway is cleavage of membrane phospholipids by phospholipase A₂ (PLA₂). Previous work demonstrated upregulation of secretory PLA₂ (sPLA₂)-IIA with labor in human myometrium, and recent evidence shows that there are numerous PLA₂ isoforms. The present study investigates the potential of additional sPLA₂ isoforms during pregnancy and labor. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemistry were used to determine sPLA₂ expression and localization. Results show the presence of sPLA₂-IID in amnion, chorion, placenta, decidua, and myometrium. Expression of sPLA₂-IID in decidua was significantly decreased in term labor compared to nonlabor patients, whereas no significant labor-associated changes were observed in other gestational tissues. Secretory PLA₂-IID was localized within chorion fibroblasts, placenta trophoblasts, decidual cells, and in myometrial smooth muscle cells. In primary decidual cell cultures, interleukin (IL) 10 (IL-10) increased sPLA₂-IID messenger RNA (mRNA) expression, while IL-1β had no effect on sPLA₂-IID mRNA expression. In conclusion, decreased expression of sPLA₂-IID in the decidua at labor indicates that it is unlikely to contribute to increased prostaglandin production during labor. However, increased expression of sPLA₂-IID, induced by IL-10, suggests that sPLA₂-IID may play an important anti-inflammatory role at the maternal-fetal interface. Nevertheless, precise functions of sPLA₂-IID within the human uterus remain to be determined.

Molecular regulators of resolution of inflammation: potential therapeutic targets in the reproductive system

Inflammatory processes are central to reproductive events including ovulation, menstruation, implantation and labour, while inflammatory dysregulation is a feature of numerous reproductive pathologies. In recent years, there has been much research into the endogenous mechanisms by which inflammatory reactions are terminated and tissue homoeostasis is restored, a process termed resolution. The identification and characterisation of naturally occurring pro-resolution mediators including lipoxins and annexin A1 has prompted a shift in the field of anti-inflammation whereby resolution is now observed as an active process, triggered as part of a normal inflammatory response. This review will address the process of resolution, discuss available evidence for expression of pro-resolution factors in the reproductive tract and explore possible roles for resolution in physiological reproductive processes and associated pathologies.

Proteomic analysis of the major cellular proteins of bovine trophectoderm cell lines derived from IVP, parthenogenetic and nuclear transfer embryos: Reduced expression of annexins I and II in nuclear transfer-derived cell lines

Trophectoderm cell lines were established from 8-day in vitro-cultured embryos of cattle derived from fertilization (IVF), somatic cell nuclear transfer (NT), or parthenogenetic activation (P) of in vitro-matured oocytes and from five 8-day-old in vivo (V) embryos. The most abundant cellular proteins of 5 V-, 16 NT-, 12 P-, and 16 IVF-derived cell lines were compared by 2D-gel electrophoresis and mass spectrometry; that is, the unaltered thiourea/urea extract of each cell culture was analyzed. Common protein spots (n=118) were examined, and 95% were identified with significant scores from protein and gene database searches. Of the proteins detected and identified, actin and cytokeratin-8 were found to be the most abundant. Other prominent cellular proteins were metabolic enzymes such as aldose reductase, phosphoglycerate mutase, enolase, triosephosphate isomerase, cytoskeletal interacting proteins transgelin and stratifin, anti-oxidant proteins peroxiredoxin 1 and anti-oxidant protein 2, and the calcium-dependent lipid-binding proteins annexins I and II. In comparative analysis of the 2D-gels, the NT-derived trophectoderm had less annexins I and II in comparison to the IVF- and P-derived trophectoderm. Because annexins I and II are abundant in the placenta and have functions important to the maintenance of placentation, the down-regulation of the annexin genes in the cultured NT trophectoderm may be related to the frequent failures of NT pregnancies.

Secretory and cytosolic phospholipase A2 activities and expression are regulated by oxytocin and estradiol during labor

The release of arachidonic acid from membrane glycerophospholipids through the action of phospholipases (PLs) is the first step in the biosynthesis of prostaglandins (PGs). In reproductive tissues, the most important PLs are cytosolic PLA2(cPLA2) and types IIA and V of the secretory isoform (sPLA2). The aim of this work was to investigate the role of ovarian steroid hormones and oxytocin (OT) in the regulation of rat uterine PLA2activity and expression during pregnancy and labor. The activity of sPLA2increased near labor, whereas cPLA2activity augmented towards the end of gestation. The levels of sPLA2IIA and cPLA2mRNA showed an increase before labor (P<0.05, day 21), whereas sPLA2V mRNA was not regulated during pregnancy. The administration of atosiban (synthetic OT antagonist) together with tamoxifen (antagonist of estrogen receptors) was able to decrease cytosolic and secretory PLA2activities, diminish the expression of sPLA2IIA and cPLA2, as well as decrease PGF2αproduction before the onset of labor (P<0.01). The ovarian steroid did not affect PLA2during pregnancy. Collectively, these findings indicate that in the rat uterus, both 17β-estradiol and OT could be regulating the activity and the expression of the secretory and the cytosolic isoforms of PLA2, thus controlling PGF2αsynthesis prior to the onset of labor.

Global gene expression analysis and regulation of the principal genes expressed in bovine placenta in relation to the transcription factor AP-2 family

BACKGROUND

Cell-cell communication is an important factor in feto-maternal units during placentogenesis. The placenta produces pivotal hormones and cytokines for communication between cotyledonary villi and the maternal caruncle. Gene expression in bovine placenta throughout pregnancy was comprehensively screened by a cDNA microarray, and we searched for a common transcription factor in a gene cluster that showed increasing expression throughout gestation in cotyledonary villi and caruncle.

METHODS

Placentomal tissues (villi and caruncle) were collected from Day 25 to Day 250 of gestation for microarray analysis. Global gene expression profiles were analyzed using the k-means clustering method. A consensus sequence cis-element that may control up-regulated genes in a characteristic cluster was examined in silico. The quantitative expression and localization of a specific transcription factor were investigated in each tissue using quantitative real-time RT-PCR and in situ hybridization.

RESULTS

The microarray expression profiles were classified into ten clusters. The genes with most markedly increased expression became concentrated in cluster 2 as gestation proceeded. Cluster 2 included placental lactogen (CSH1), pregnancy-associated glycoprotein-1 (PAG1), and sulfotransferase family 1E estrogen-preferring member 1 (SULT1E1), which were mainly detected in giant trophoblast binucleate cells (BNC). Consensus sequence analysis identified transcription factor AP-2 binding sites in some genes in this cluster. Quantitative real-time RT-PCR analysis confirmed that high level expression of transcription factor AP-2 alpha (TFAP2A) was common to cluster 2 genes during gestation. In contrast, the expression level of another AP-2 family gene, transcription factor AP-2 beta (TFAP2B), was extremely low over the same period. Another gene of the family, transcription factor AP-2 gamma (TFAP2C), was expressed at medium level compared with TFAP2A and TFAP2B. In situ hybridization showed that TFAP2A, TFAP2B and TFAP2C mRNAs were localized in trophoblast cells but were expressed by different cells. TFAP2A was expressed in cotyledonary epithelial cells including BNC, TFAP2B was specifically expressed in BNC, and TFAP2C in mononucleate cells.

CONCLUSION

We detected gestational-stage-specific gene expression profiles in bovine placentomes using a combination of microarray and in silico analysis. In silico analysis indicated that the AP-2 family may be a consensus regulator for the gene cluster that characteristically appears in bovine placenta as gestation progresses. In particular, TFAP2A and TFAP2B may be involved in regulating binucleate cell-specific genes such as CSH1, some PAG or SULT1E1. These results suggest that the AP-2 family is a specific transcription factor for clusters of crucial placental genes. This is the first evidence that TFAP2A may regulate the differentiation and specific functions of BNC in bovine placenta.

Molecular and biochemical mechanisms of preterm labour

Parturition involves the synchronization of myometrial activity and structural changes of the cervix, leading to regular co-ordinated uterine contractions and cervical dilatation and effacement. The biochemical events involved in parturition resemble an inflammatory reaction, with growing evidence pointing to a crucial role for pro-inflammatory cytokines and prostaglandins in labour. There is accumulating evidence that there are common mediators involved in the regulation of 'labour-associated proteins', and that, in each case, an increase or decrease in gene expression mediates changes in their concentration. It is possible, therefore, that targeting these common mediators may represent newer strategies for the prevention of preterm labour. Our aim is to review the mechanical and biochemical mechanisms that may be involved in the processes of term and preterm labour. Specifically, we will consider the regulation of some of the 'labour-associated proteins', chemotactic cytokines, prostaglandins and enzymes of the prostaglandin biosynthetic pathway and the oxytocin receptor.

Transcriptional regulation of genes for enzymes of the prostaglandin biosynthetic pathway

Numerous studies over the years have demonstrated changes in prostaglandin (PG) levels in intrauterine tissues in association with labour, and PG administration has long been used to induce delivery. While it is now widely accepted that PGs play a major role in human parturition, the complex regulation of their levels is still being elucidated, with the focus on the transcriptional control of the enzymes responsible for the various steps in PG biosynthesis and catabolism.

Phospholipase A2 isozymes in pregnancy and parturition

Mammalian cells contain several structurally different phospholipase (PLA2) enzymes that exhibit distinct localisation, function and mechanisms of regulation. PLA2 isozymes have been postulated to play significant roles in the parturition process. Both secretory and cytosolic PLA2 isozymes have been identified in human gestational tissues, and there is differential expression of these PLA2 isozymes in human fetal membranes and placenta obtained at preterm and term. The aims of this commentary are: (1) to review recent data concerning the expression, role and regulation of PLA2 isozymes in human gestational tissues; and (2) to present novel data demonstrating the regulation of PLA2 isozymes in human gestational tissues by nuclear factor-kappa B (NF-kappaB) and peroxisome proliferator-activated receptor (PPAR)-g.

Type II phospholipase A2 in preterm human gestational tissues

Maternal genital tract infections and the associated inflammatory response may contribute to the onset of many cases of preterm labour. Type II phospholipase A(2)(PLA2) hydrolyses glycerophospholipids, releasing free fatty acid for conversion into potent biological mediators, such as prostaglandins, which play a significant role in both the onset and progression of human labour and the activation of inflammatory reactions. The aim of this study was to quantify immunoreactive (ir) Type II PLA2 in placenta, amnion and choriodecidua collected from women delivering prematurely or due to histological chorioamnionitis, and to compare levels to those at term. Tissues were assayed for ir Type II PLA2 by ELISA and expressed as ng/mg tissue protein. Ir Type II PLA2 tissue content was significantly higher in preterm (n=26) amnion and choriodecidua, but not in the placenta when compared to tissues obtained at term (n=42). When the data were stratified with respect to labour status, ir Type II PLA2 content was significantly higher in the preterm not-in-labour group (NIL, n=17) than the preterm in labour group (IL, n=9) in the amnion. When the NIL group was analysed with respect to membrane rupture, women who had spontaneously ruptured membranes (n=6) expressed significantly greater ir Type II PLA2 than those that had intact membranes (n=11) in both the amnion and choriodecidua but not in the placenta. No significant difference was observed between the preterm IL group (n=9) and the group with histological chorioamnionitis (n=14). The data obtained in this study support a role for Type II PLA2 in association with spontaneous rupture of membranes.

Differential regulation in human amnion epithelial and fibroblast cells of prostaglandin E(2) production and prostaglandin H synthase-2 mRNA expression by dexamethasone but not tumour necrosis factor-alpha

Previous studies have identified both pro-inflammatory cytokines and glucocorticoids as positive regulators of amnion prostaglandin (PG) biosynthesis. The stimulatory effects of dexamethasone (Dex), a glucocorticoid agonist, on prostaglandin endoperoxide H synthase (PGHS)-2 mRNA expression and PG biosynthesis in amnion have been attributed to an atypical response by the mesenchymal cells of the amnion. The objective of this study was to confirm previous findings concerning cell type-dependant Dex-induced upregulation of PGHS-2 mRNA expression and PG production using separated amnion cell populations, in comparison with the effects of the pro-inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha). Amnion cells from placentae delivered at term by caesarian section were isolated by tryptic digestion and epithelial cells were then separated from mesenchymal cells by differential absorption onto plastic. After 24-72 h, the two cell populations were passaged and sub-cultured. Cells were treated with Dex (10(-9)-10(-6) m) or TNF-alpha (0.1-50 ng/ml) or media alone. Thereafter, PGE(2)production was determined and PGHS-2 mRNA content analysed by a competitive quantitative RT-PCR method established and validated for this study. PGE(2)production in fibroblast-enriched cultures was increased to 310+/-41 per cent (mean+/-sem, n=4 wells per treatment point) of control in the presence of 10(-8) m Dex. Conversely, PGE(2)production in Dex-treated amnion epithelial cells was decreased to 67+/-24 per cent of control. Altered PGE(2)biosynthesis was accompanied by the upregulation of PGHS-2 mRNA in amnion fibroblasts but not in epithelial cells. TNF-alpha increased PG output and PGHS-2 expression independent of cell type. Glucocorticoids therefore appear to have opposing effects on PG biosynthesis in the two major cellular components of the human amnion.

Localization of type II phospholipase A2 messenger RNA and immunoactivity in human placenta and fetal membranes

Although Type II phospholipase A2 (PLA2) immunoactivity has been identified in homogenates of human placenta and fetal membranes, there is a paucity of information concerning the sites of synthesis of this secreted PLA2 isozyme. The aim of this study, therefore, was to establish the cellular localization of Type II PLA2 messenger RNA (mRNA) in human term placental and fetal membranes by in situ hybridization. In addition, the co-localization of immunoreactive Type II PLA2 in gestational tissues was determined, and the effect of labour status and pre-eclampsia on immunolabelling intensity were established. Type II PLA2 mRNA was identified in all tissue sections examined and was localized principally in placental villous vasculature and mesenchymal elements of placenta, chorion and amnion. Within the vasculature, Type II PLA2 mRNA was associated with smooth muscle cells. Immunoreactive Type II PLA2 was identified in the fibroblast and spongy layers of the amnion, the fibroblast and reticular layer of the chorion, and in the mesenchymal core and trophoblasts of placental villi. Immunolabelling staining intensity was greater in placenta and chorion than that observed in amnion, however, staining intensity was unaffected by labour status. Pre-eclampsia was associated with increased immunolabelling for Type II PLA2 in placenta but not fetal membranes. The data obtained clearly established that Type II PLA2 is synthesized by multiple cell types within human gestational tissues and co-localization of Type II PLA2 mRNA and immunoreactive protein has been established. The role of Type II PLA2 in gestational tissue phospholipid metabolism and, in particular, in vascular and mesenchymal elements, has yet to be established. Possible roles for this isozyme may include, the provision of substrate for eicosanoid synthesis, maintaining cell membrane phospholipid asymmetry and prevention of clot formation within the placental vascular bed.

New insights into the mode of action of anti-inflammatory drugs

The discovery of a second cyclooxygenase has provided fresh impetus to the search for new anti-inflammatory drugs. The second enzyme is effectively absent from healthy tissues but its levels rise dramatically during inflammation. It can be induced in migratory cells by bacterial lipopolysaccharide, cytokines and growth factors. The constitutive cyclooxygenase-1 (COX-1) can thus be considered a "housekeeping" enzyme, in contrast to cyclooxygenase-2 (COX-2) which is activated by tissue damage. Both enzymes have a molecular weight of around 70 kDa and similar Km and Vmax values for their reaction with arachidonic acid. Several non steroid anti-inflammatory drugs which have more than 1,000 fold selectivity for COX-2 over COX-1 are in the early stages of drug development.