Key enzymes of prostaglandin biosynthesis and metabolism. Coordinate regulation of expression by cytokines in gestational tissues: a review

In vitro selenium supplementation suppresses key mediators involved in myometrial activation and rupture of fetal membranes

Spontaneous preterm birth, which can affect up to 20% of all pregnancies, is the greatest contributor to perinatal morbidity and mortality. Infection is the leading pathological cause of spontaneous preterm birth. Infection activates the maternal immune system, resulting in the upregulation of pro-inflammatory and pro-labor mediators that activate myometrial contractions and rupture of fetal membranes. Anti-inflammatory agents therefore have the potential for the prevention of spontaneous preterm birth. Selenium, an essential micronutrient, has been shown to be a potent anti-inflammatory regulator. Notably, clinical and epidemiological studies have suggested a link between selenium and preterm birth. Thus, the aim of this study was to assess the effect of selenite (an inorganic form of selenium) on the expression of pro-inflammatory and pro-labor mediators in human gestational tissues. Human fetal membranes and myometrium were pre-incubated with or without selenite before incubation with the bacterial product lipopolysaccharide (LPS) to stimulate inflammation associated with preterm birth. Selenite blocked LPS-induced expression of pro-inflammatory cytokines and chemokines and enzymes involved in remodelling of myometrium and degradation of fetal membranes. Of note, selenite also suppressed myometrial activation induced by inflammation as evidenced by a decrease in LPS-induced prostaglandin signalling and myometrial cell contractility. These effects of selenite were mediated by the MAPK protein ERK as selenite blunted LPS induced activation of ERK. In conclusion, selenite suppresses key mediators involved in inflammation induced activation of mediators involved in active labor in human fetal membranes and myometrium. These findings support recent clinical studies demonstrating selenium supplementation is associated with decreased incidence of spontaneous preterm birth.

Cytokines and pregnancy: Potential regulation by histone deacetylases

Cytokines are important regulators of pregnancy and parturition. Aberrant expression of proinflammatory cytokines during pregnancy contributes towards preterm labor, pre-eclampsia, and gestational diabetes mellitus. The regulation of cytokine expression in human cells is highly complex, involving interactions between environment, transcription factors, and feedback mechanisms. Recent developments in epigenetic research have made tremendous advancements in exploring histone modifications as a key epigenetic regulator of cytokine expression and the effect of their signaling molecules on various organ systems in the human body. Histone acetylation and subsequent deacetylation by histone deacetylases (HDACs) are major epigenetic regulators of protein expression in the human body. The expression of various proinflammatory cytokines, their role in normal and abnormal pregnancy, and their epigenetic regulation via HDACs will be discussed in this review.

The Role(s) of Eicosanoids and Exosomes in Human Parturition

The roles that eicosanoids play during pregnancy and parturition are crucial to a successful outcome. A better understanding of the regulation of eicosanoid production and the roles played by the various end products during pregnancy and parturition has led to our view that accurate measurements of a panel of those end products has exciting potential as diagnostics and prognostics of preterm labor and delivery. Exosomes and their contents represent an exciting new area for research of movement of key biological factors circulating between tissues and organs akin to a parallel endocrine system but involving key intracellular mediators. Eicosanoids and enzymes regulating their biosynthesis and metabolism as well as regulatory microRNAs have been identified within exosomes. In this review, the regulation of eicosanoid production, abundance and actions during pregnancy will be explored. Additionally, the functional significance of placental exosomes will be discussed.

Resolution of inflammation: a new therapeutic frontier

Dysregulated inflammation is a central pathological process in diverse disease states. Traditionally, therapeutic approaches have sought to modulate the pro- or anti-inflammatory limbs of inflammation, with mixed success. However, insight into the pathways by which inflammation is resolved has highlighted novel opportunities to pharmacologically manipulate these processes - a strategy that might represent a complementary (and perhaps even superior) therapeutic approach. This Review discusses the state of the art in the biology of resolution of inflammation, highlighting the opportunities and challenges for translational research in this field.

New insights into the resolution of inflammation

The goal of treating chronic inflammatory diseases must be to inhibit persistent inflammation and restore tissue function. To achieve this we need to improve our understanding of the pathways that drive inflammation as well as those that bring about its resolution. In particular, resolution of inflammation is driven by a complex set of mediators that regulate cellular events required to clear inflammatory cells from sites of injury or infection and restore homeostasis. Indeed, it may be argued that dysfunctional resolution may underpin the aetiology of some chronic inflammatory disease and that a novel goal in treating such diseases is to develop drugs based on the mode of endogenous pro-resolution factors in order to drive on-going inflammation down a pro-resolution pathway. And while we are improving our understanding of the resolution of acute and chronic inflammation, much remains to be discovered. Here we will discuss the key endogenous checkpoints necessary for mounting an effective yet limited inflammatory response and the crucial biochemical pathways necessary to prevent its persistence and trigger its resolution. In doing so, we will provide an update on what is known about resolution of acute inflammation, in particular its link with adaptive immunity.

Tetrabromobisphenol A activates inflammatory pathways in human first trimester extravillous trophoblasts in vitro

Tetrabromobisphenol A (TBBPA) is a widely used flame retardant. Despite the presence of TBBPA in gestational tissues and the importance of proper regulation of inflammatory networks for successful pregnancy, there is no prior study on the effects of TBBPA on inflammatory responses in gestational tissues. The present study aimed to investigate TBBPA activation of inflammatory pathways, specifically cytokine and prostaglandin production, in the human first trimester placental cell line HTR-8/SVneo. TBBPA enhanced release of interleukin (IL)-6, IL-8, and prostaglandin E2 (PGE2), and suppressed TGF-β release in HTR-8/SVneo cells. The lowest effective concentration was 10 μM TBBPA. A commercial immune response PCR array revealed increased expression of genes involved in inflammatory pathways stimulated by TBBPA in HTR-8/SVneo cells. Because proper regulation of inflammatory mediators in the gestational compartment is necessary for normal placental development and successful pregnancy, further investigation on the impact of TBBPA-stimulated responses on trophoblast function is warranted.

Expression of the prostaglandin F synthase AKR1B1 and the prostaglandin transporter SLCO2A1 in human fetal membranes in relation to spontaneous term and preterm labor

BACKGROUND

Human labor is a complex series of cellular and molecular events that occur at the materno-fetal and uterine levels. Many hypotheses have been proposed for the initiation of human labor, one hypothesis suggests that maturation of the fetus releases a signal in the amniotic fluid that will be transmitted to myometrium via the fetal membranes and initiate uterine contractions. There is strong evidence that prostaglandins (PGs) play a central role in initiation and progression of human labor.

OBJECTIVES

In this study we intended to investigate the expression of prostaglandin F synthase and the prostaglandin transporter in the human fetal membranes and to explore the relationship between cytokines and PGs in the mechanism of human labor.

METHODS

We used fetal membranes obtained before labor at term and after spontaneous labor at term or preterm to identify the changes in prostaglandin F synthase (AKR1B1) and human prostaglandin transporter (SLCO2A1) proteins in relation to parturition. Using fetal membranes explants we tested the effect of cytokines (interleukin-1 and tumor necrosis factor alpha) on PG production and the concomitant changes in cyclooxygenase-2 (PTGS2), AKR1B1 and SLCO2A1 expression.

RESULTS

Expression of PTGS2 and AKR1B1 was upregulated in the fetal membranes in association with term labor while SLCO2A1 was downregulated with advancing gestation and during term labor. Before labor, IL-1 increased the expression of PTGS2, however during labor TNF upregulated PTGS2 and AKR1B1 proteins.

CONCLUSIONS

The prostaglandin F synthase AKR1B1 is upregulated while prostaglandin transporter is downregulated during term labor. The amnion is more responsive than choriodecidua to stimulation with pro-inflammatory cytokines. The mechanisms of term and preterm labor are different.

Vitamin D regulates contractile profile in human uterine myometrial cells via NF-κB pathway

OBJECTIVE

Infection triggers inflammation that, in turn, enhances the expression of contractile-associated factors in myometrium and increases the risk of preterm delivery. In this study, we assessed vitamin D regulation of inflammatory markers, contractile-associated factors, steroid hormone receptors, and NFκB pathway proteins in human uterine myometrial smooth muscle (UtSM) cells that were cultured in an inflammatory environment.

STUDY DESIGN

Inflammatory environment was simulated for UtSM cells by coculturing them with monocyte lineage (THP1) cells. We measured the expression of inflammatory markers, contractile-associated factors, steroid hormone receptors, and NFκB pathway proteins in UtSM cells that were cultured with THP1 cells in the presence and absence of vitamin D by real time polymerase chain reaction and Western blot analysis.

RESULTS

Monocytes secreted monocyte inflammatory protein-1α and -1β, interleukin (IL)-1β and 6, and tumor necrosis factor-α into the conditioned medium. In the UtSM cells that had been cocultured with THP1 cells, there was a significant (P < .05) increase in the expression of inflammatory markers IL-1β, -6, and -13 and tumor necrosis factor-α; the contractile-associated factors connexin-43, Cox-2, and prostaglandin F2α receptor; the estrogen receptor α, and progesterone receptors A and B. Vitamin D treatment of cocultures decreased (P < .05) the expression of inflammatory markers and contractile-associated factors in UtSM cells. Similarly, vitamin D decreased estrogen receptor α and progesterone receptors A-to-B ratio in UtSM cells that were cocultured with THP1 cells. In addition, vitamin D treatment significantly (P < .05) decreased monocyte-induced p-IκBα in cytosol and NFκB-p65 in the nucleus and increased IκBα in cytosol in UtSM cells.

CONCLUSION

Our results suggest that vitamin D treatment decreases inflammation-induced cytokines and contractile-associated factors in the uterine myometrial smooth muscle cells through the NFκB pathway.

Myometrial immune cells contribute to term parturition, preterm labour and post-partum involution in mice

This study aimed to determine the mechanism of uterine activation during labour, both term (TL) and preterm (PTL). We hypothesized that the peripheral leucocytes are recruited to uterine tissues by locally produced cytokines where they contribute to the initiation of parturition. Mouse uteri were collected (i) during gestation, TL and post-partum (PP), (ii) during PTL initiated by intrauterine infusion of LPS (125 μg) or (iii) injection of the progesterone receptor antagonist RU486 and analysed for multiple cytokine expression levels by real-time polymerase chain reaction (RT-PCR) and 23-plex Cytokine assay or enzymatically dispersed for assessment of immune cell populations. Markers of myeloid cell differentiation (Gr1, Neu7/4 and F4/80) were evaluated by FACS to define tissue macrophages (Macs), monocytes (M) and neutrophils (N) and by immunohistochemistry to detect tissue Macs and N. Our results indicate that: (1) Macs were elevated in mouse myometrium before TL (P < 0.05) followed by an increase in M and N; these changes were accompanied by an increase in multiple pro-inflammatory cytokines/chemokines genes. The expression of corresponding proteins increased PP. (2) TL and RU486-PTL models showed similar gene/protein expression profiles, (3) LPS-PTL was characterized by strong pro-inflammatory response and massive influx of N in myometrial tissues showing a pattern different from TL and RU486-PTL, (4) The PP period appears similar in all three models, with elevated myometrial cytokine levels and high infiltration of immune cells. We concluded that leucocytes infiltrate myometrium around the time of parturition implicating their potential role in labour activation (both term and preterm) and major role in PP uterine involution.

Vitamin D elicits anti-inflammatory response, inhibits contractile-associated proteins, and modulates Toll-like receptors in human myometrial cells

Infection during pregnancy triggers inflammation, which can increase myometrial contractions and the risk of premature labor and delivery. In this study, we assessed the effects of vitamin D, an anti-inflammatory ligand on cytokines, chemokines, toll-like receptors, and contractile-associated proteins on immortalized human myometrial smooth muscle (UtSM) cells stimulated with lipopolysaccharide (LPS), a bacterial endotoxin, or interleukin (IL)-1β and measured Toll-like receptor (TLR)-10 expression in pregnant myometrial tissues. A superarray analysis revealed downregulation of the chemokines monocyte chemoattractant protein (MCP)-1, Chemokine (C-X-C motif) ligand (CXCL)-10, CXCL-11, and chemokine (C-X3-C motif) ligand (CX3CL)-1; the proinflammatory cytokines IL-13 and tumor necrosis factor (TNF)-α; the TLR-4 and -5 and triggering receptor expressed on myeloid cells (TREM)-2 and upregulation of the anti-inflammatory cytokine IL-10, as well as Toll interacting protein (TOLLIP) and TREM-1 in vitamin D-treated UtSM cells. In the presence of LPS, vitamin D caused dose-dependent decreases in the messenger RNA expression of MCP-1, IL-1β, IL-13, TNF-α, TLR-4, and TLR-5, the contractile-associated proteins connexin 43, the oxytocin receptor, and the prostaglandin receptor but caused increases in IL-10 and TLR-10 in UtSM cells. The TLR-10 expression was higher in human myometrial tissue obtained from women at term not in labor compared to labor. Vitamin D also attenuated IL-1β-induced MCP-1, IL-6, connexin 43, cyclooxygenase (COX)-2, and prostaglandin receptor expression. Western analysis showed that vitamin D decreased MCP-1, TLR-4, and connexin 43 in the presence of LPS and decreased connexin 43 in the presence of IL-1β. Our results suggest that vitamin D can potentially decrease infection-induced increases in cytokines and contractile-associated proteins in the myometrium.

Toll-like receptors in pregnancy disorders and placental dysfunction

The Toll receptor was originally identified as a regulator of embryogenesis in Drosophila. Toll-like receptors (TLRs) in mammals recognize infectious agents and other danger signals. Activation of TLRs on trophoblast influences immune cell recruitment, cytokine secretion, and decidual responses to invading pathogens during pregnancy. Importantly, biological effects of TLR signal transduction at multiple maternal-fetal interfaces may contribute to several pregnancy pathologies associated with placental dysfunction, including pre-eclampsia, intrauterine growth restriction, and preterm labor. We herein discuss mechanisms by which TLRs regulate the maternal immune response during normal and abnormal gestation, and we highlight recent data that assign a role to TLRs in the pathophysiology of selected pregnancy-associated complications.

All Our Babies Cohort Study: recruitment of a cohort to predict women at risk of preterm birth through the examination of gene expression profiles and the environment

Background

Preterm birth is the leading cause of perinatal morbidity and mortality. Risk factors for preterm birth include a personal or familial history of preterm delivery, ethnicity and low socioeconomic status yet the ability to predict preterm delivery before the onset of preterm labour evades clinical practice. Evidence suggests that genetics may play a role in the multi-factorial pathophysiology of preterm birth. The All Our Babies Study is an on-going community based longitudinal cohort study that was designed to establish a cohort of women to investigate how a women's genetics and environment contribute to the pathophysiology of preterm birth. Specifically this study will examine the predictive potential of maternal leukocytes for predicting preterm birth in non-labouring women through the examination of gene expression profiles and gene-environment interactions.

Methods/Design

Collaborations have been established between clinical lab services, the provincial health service provider and researchers to create an interdisciplinary study design for the All Our Babies Study. A birth cohort of 2000 women has been established to address this research question. Women provide informed consent for blood sample collection, linkage to medical records and complete questionnaires related to prenatal health, service utilization, social support, emotional and physical health, demographics, and breast and infant feeding. Maternal blood samples are collected in PAXgene™ RNA tubes between 18-22 and 28-32 weeks gestation for transcriptomic analyses.

Discussion

The All Our Babies Study is an example of how investment in clinical-academic-community partnerships can improve research efficiency and accelerate the recruitment and data collection phases of a study. Establishing these partnerships during the study design phase and maintaining these relationships through the duration of the study provides the unique opportunity to investigate the multi-causal factors of preterm birth. The overall All Our Babies Study results can potentially lead to healthier pregnancies, mothers, infants and children.

Isoprostanes 8-iPF2alpha-III: risk markers of premature rupture of fetal membranes?

AIMS

Isoprostanes may serve as sensitive and specific markers of in vivo oxidative stress intensity. We wanted to determine, whether or not isoprostane concentration may be considered as a risk marker of premature rupture of fetal membranes (PROM).

METHODS

On the basis of the presence of PROM and gestational maturity, a total of 128 patients were divided into: (1) preterm PROM (pPROM) group; (2) PROM at term group; (3) control preterm (C1) group and (4) control at term (C2) group. The concentrations of 8-iPF(2alpha)-III were determined using the enzyme-linked immunosorbent assay method.

RESULTS

The mean free isoprostane concentrations, examined in amniotic fluid and maternal plasma in the PROM at term patients were significantly higher than in C2 individuals (p < 0.01). The mean concentrations of free 8-iPF(2alpha)-III measured in blood plasma from women in the C1 group were significantly lower than in patients from the pPROM, PROM at term and C2 groups (p < 0.001, p < 0.00001 and p < 0.00001, respectively).

CONCLUSION

The measurement of free isoprostane concentration in maternal plasma and amniotic fluid may be considered as a laboratory marker of a PROM-risk pregnancy.

Tissue-specific cytokine release from human extra-placental membranes stimulated by lipopolysaccharide in a two-compartment tissue culture system

BACKGROUND

The extra-placental gestational membranes secrete cytokines in response to bacteria and other infectious agents, with potentially adverse consequences for pregnancy. The present study used lipopolysaccharide (LPS) as a prototype endotoxin to investigate the pattern of stimulated cytokine release from the amniotic and choriodecidual sides of full-thickness human gestational membranes in a two-compartment tissue culture system.

METHODS

Gestational membranes were collected from healthy non-laboring caesarean deliveries at term. Full-thickness membranes from each placenta were cut into pieces, mounted on Transwell frames, and placed in culture wells to create a two-compartment culture with the gestational membranes serving as the barrier between compartments. The LPS (100 ng/ml) was added to the amniotic, choriodecidual or both chambers of the culture, and cytokines were assayed in the medium of the amniotic and choriodecidual chambers after 8 h of LPS exposure. Cytokine concentrations were analyzed by two-way analysis of variance for effects of treatment and side specificity of cytokine release from the membranes.

RESULTS

LPS exposure on the choriodecidual side of the membranes significantly increased TNF-alpha, IL-6, IL-10 and IL-8 in the choriodecidual compartment, whereas TNF-alpha was the only cytokine observed to increase in the amniotic compartment. When LPS treatment was to the amniotic side of the membranes, there were significant increases in TNF-alpha and IL-6 in the amniotic compartment as well as increased concentrations of TNF-alpha, IL-6 and IL-8 in the choriodecidual compartment; however, there were no statistically significant differences for IL-10 in either compartment. No statistically significant differences were observed for IL-1beta, TGF-beta or IL-4 concentrations in response to LPS, regardless of the exposure modality.

CONCLUSION

The amnion and choriodecidua exhibited distinct patterns of response to LPS with evidence of inflammatory signaling across the layers of the gestational membranes. These results suggest a complicated network of signaling within the gestational membranes, in which cytokine- and tissue-specific responses to inflammatory stimulation may have important implications for maintaining pregnancy in the challenge of microbial invasion of the uterine compartment.

Diversity in cytokine response to bacteria associated with preterm birth by fetal membranes

OBJECTIVE

This study compared cytokine and prostaglandin (PG) responses by fetal membranes stimulated with 4 different bacterial species associated with preterm birth (PTB).

STUDY DESIGN

Fetal membranes (n = 13 from normal term cesarean sections [not in labor]) in an organ explant system were stimulated with heat-killed Ureaplasma parvum, Gardanerella vaginalis, Escherichia coli, group B Streptococcus (GBS), or lipopolysaccharide (LPS). Cytokines (interleukin [IL]-1beta, IL-6, IL-8, IL-10, tumor necrosis factor [TNF]-alpha, and interferon-gamma) and PG (PGF(2alpha) and PGE(2)) concentrations were quantitated and compared.

RESULTS

LPS and E coli increased all cytokine and PG productions compared with controls. Cytokine profiles were similar after G vaginalis and GBS stimulation. G vaginalis increased PGE(2), whereas GBS increased PGF(2alpha). U parvum demonstrated the mildest response with only IL-10 and TNF-alpha concentrations being higher with no detectible effect on PGs.

CONCLUSION

Fetal membrane cytokine signatures of 4 different bacteria associated with PTB are distinct, suggesting that infection as a potential cause of PTB is not homogeneous in its presentation.

Polybrominated diphenyl ethers in human gestational membranes from women in southeast Michigan

Polybrominated diphenyl ethers (PBDEs) have been incorporated into many consumer products as flame retardants. Due to their persistence and ability to bioaccumulate, PBDEs are ubiquitous in human blood and breast milk samples from industrialized nations. Although there exists a potential for environmental pollutants such as PBDEs to adversely impact birth outcomes and perinatal health, reports of PBDE levels in human reproductive tissues are limited. The aim of the current study is to evaluate the total levels and congener-specific profiles of PBDEs from human extraplacental gestational membranes. Gestational membranes from five term pregnancies were obtained from nonlaboring caesarian deliveries at the University of Michigan Women's Hospital Birth Center. Duplicate samples were extracted and analyzed by GC-MS for twenty-one PBDE congeners. Total PBDE loading was 17.4 +/- 3.9 pg/g tissue (5.62 +/- 1.28 ng/g lipid). Seventy-eight percent of the total measurable PBDE loading was due to BDEs 47, 49, 99, 100, and 153, with measured values of 3.63, 3.15, 3.05, 1.74, and 1.90 pg/g tissue (1170, 1018, 983, 561, and 612 pg/g lipid), respectively. The remaining 28% comprised BDEs 17, 28, 66, 71, 85, and 154. No octa-, nona-, or deca-BDEs were identified. Although previously unreported in the human gestational compartment BDE 49 comprised 17% of the total PBDE level. This work establishes baseline accumulated levels of PBDEs in gestational membranes of women in Southeast Michigan.

Activation of TLR3 in the trophoblast is associated with preterm delivery

PROBLEM

Toll-like receptors (TLRs) recognize conserved sequences on the surface of pathogens and trigger effector cell functions. Previously, we described the expression of TLR3 by human trophoblast and their ability to respond to (Poly[I:C]). Here we evaluate the effect of Poly[I:C] on mouse pregnancy and characterize the local and systemic response.

METHOD OF STUDY

C57B/6 wild type (wt) and TLR3 knockout (TLR3KO) mice were treated with Poly[I:C] at 16.5 dpc and pregnancy outcome recorded. Morphologic changes, cytokines and chemokines levels in blood and utero-placental tissue were determined. NF-kappaB pathway was evaluated in vivo and in vitro.

RESULTS

Poly[I:C] in C57B/6 wt mice caused preterm delivery within 24 hr (4.5 mg/kg). No effect was observed in TLR3KO mice. In addition, we observed local (placenta) and systemic (serum) response characterized by increased production of proinflammatory cytokines and chemokines. The NF-kappaB pathway was activated by Poly[I:C] in human and mice trophoblast cells.

CONCLUSION

We report that Poly[I:C] induces preterm delivery via TLR3-dependent manner. Furthermore, we demonstrate that the trophoblast is able to recognize Poly[I:C] through TLR3 and respond to viral infection, modulating the immune system at the feto-maternal interface.

Novel cyclooxygenase-catalyzed bioactive prostaglandin F2alpha from physiology to new principles in inflammation

Prostaglandin F2alpha (PGF2alpha), a foremost stable vasoactive cyclooxygenase (COX)-catalyzed prostaglandin, regulates a number of key physiological functions such as luteolysis, ovarian function, luteal maintenance of pregnancy, and parturition as a constitutive part of ongoing reproductive processes of the body. It has recently been implicated in the regulation of intricate pathophysiological processes, such as acute and chronic inflammation, cardiovascular and rheumatic diseases. Since the discovery of a second isoform of COXs, it has been shown that PGF2alpha can be formed in vivo from arachidonic acid through both isoforms of COXs, namely cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Being synthesized in various parts of the body, it metabolizes instantly to a number of rather inactive metabolites mainly in the lungs, liver, kidney, and efficiently excretes into the urine. 15-Keto-dihydro-PGF2alpha, a major stable metabolite of PGF2alpha that reflects in vivo PGF2alpha biosynthesis, is found in larger quantities than its parent compound in the circulation and urine in basal physiological conditions, with short-lived pulses during luteolysis, induced termination of pregnancy and parturition, and is increased in tissues and various body fluids during acute, sub-chronic, and severe chronic inflammation. Further, the close relationship of PGF2alpha with a number of risk factors for atherosclerosis indicates its major role in inflammation pathology. This review addresses multiple aspects of PGF2alpha in addition to its emerging role in physiology to inflammation.

Developmental regulation of prostacyclin synthase and prostacyclin receptors in the ovine uterus and conceptus during the peri-implantation period

This study documents the expression of prostacyclin (PGI2) synthase (PTGIS) and PGI2 receptors in the trophoblast and uterus of the ewe at the time of maternal recognition of pregnancy (i.e. days 7, 9, 12, 14 and 17). The membrane receptor for PGI2 (PTGIR) and the nuclear receptors, i.e. peroxisome proliferator-activated receptors (PPAR) and their heterodimer partners the retinoid X receptors (RXR), were analysed. In the endometrium, PTGIS transcript and protein were expressed at day 9 of pregnancy and levels declined from days 12 to 17. Immunohistochemistry and in situ hybridization indicated that PTGIS was mainly located in the luminal epithelium of the endometrium. Endometrial PTGIR, PPARA, PPARG and RXRG expression was regulated during the peri-implantation period whereas PPARD, RXRA and RXRB were consistently expressed. In the trophoblast, PTGIS transcript levels rose as development progressed and peaked at day 17. PTGIR and PPARA transcripts peaked before day 12 and then declined and became nearly undetectable by day 17, whereas PPARD and PPARG transcript levels rose steadily from days 12 to 17. Because the PPARs and the RXRs display different expression profiles, we suggest that different heterodimers may form and support distinct functions as development proceeds. Our results also underline the importance of PTGIS and PPARD in the trophoblast and PTGIR in the uterus, suggesting that PGI2 is of both uterine and trophoblastic origin and is involved in a complex signalling pathway at around the time of implantation in the ewe.

IL-1β Treatment Does not Co-ordinately Up-regulate mPGES-1 and COX-2 mRNA Expression, but Results in Higher Degree of Cellular and Intracellular Co-localization of their Immunoreactive Proteins in Human Placenta Trophoblast Cells

PGE2 is involved in initiation and progression of labor in many species. Biosynthesis of PGE2 is mediated by cyclooxygenases (COX) and prostaglandin E synthases (PGES). mPGES-1 and COX-2 form an inducible pathway for PGE2 production in many cell systems. In this study we investigated whether mPGES-1 is involved in cytokine induced PGE2 biosynthesis in human trophoblast cells. We have evaluated the cellular and intracellular co-localization of mPGES-1 and COX-2, as well as cPGES and COX-1 in human trophoblast cells by dual immunofluorescent staining. The effect of IL-1beta on mPGES-1 and COX-2 co-localization, such as would occur with infection, and the regulatory effects of pro-inflammatory cytokines IL-1beta and TNF-alpha on transcriptional activity of mPGES-1 and COX-2 in these cells were also studied. We found that in cultured unstimulated trophoblasts, some cells expressed predominantly either mPGES-1 or COX-2, though there were cells co-expressing both enzymes. With IL-1beta treatment, mPGES-1 and COX-2 became more consistently co-localized. mPGES-1 was not transcriptionally co-induced with COX-2 by the cytokine treatment. We conclude that mPGES-1 is not involved in the inducible COX-2 mediated pathway for PGE2 biosynthesis at the transcriptional level, however, the treatment with IL-1beta results in a higher degree of co-ordination of the mPGES-1 and COX-2 protein immunolocalization, eliciting PGE2 synthesis.

An automated multistep high-throughput screening assay for the identification of lead inhibitors of the inducible enzyme mPGES-1

Prostaglandin E2 synthase (mPGES-1), the enzyme which catalyzes the synthesis of PGE2, is induced during the inflammatory response. For this reason, mPGES-1 could be a potential therapeutic target. A high-throughput screening assay was developed to identify potential inhibitors of mPGES-1. The assay consisted of a 30-s mPGES-1 enzymatic reaction followed by the detection of PGE2 by enzyme immunoassay (EIA). The enzymatic reaction was performed in a batch mode because the instability of the substrate (10 min) limited the number of plates assayed within a working day. The detection of the product by EIA was performed on 3 instruments requiring 14 different steps for complete automation. The authors describe here the optimization and implementation of a 2-part assay on a Thermo CRS robotic system. More than 315,000 compounds were tested, and a hit rate of 0.84% was obtained for this assay. Although the entire assay required multiple steps, the assay was successfully miniaturized and automated for a high-throughput screening campaign.

Mechanisms underlying "functional" progesterone withdrawal at parturition

Progesterone is a major factor maintaining uterine quiescence throughout pregnancy. In most species, peripheral progesterone levels decline before initiation of labor, and treatments that inhibit progesterone synthesis or action cause termination of pregnancy and/or premature deliveries. These findings suggest that progesterone withdrawal is required for activation of myometrial contractions. However, in humans, circulating progesterone levels remain elevated until birth, which leads to the notion that a "functional" progesterone withdrawal occurs before parturition. The apparent loss of progesterone sensitivity at term could be a consequence of several different mechanisms including: (1) the catabolism of progesterone in the uterus into inactive compounds; (2) alterations in progesterone receptor (PR) isoform ratios; (3) changes in cofactor protein levels affecting PR transactivation; and (4) inflammation-induced trans-repression of PR by nuclear factor kappaB. All of these mechanisms are potentially capable of decreasing uterine progesterone responsiveness at term, thus enabling the expression of pathways that originally were blocked by progesterone in early pregnancy. However, the specific uterine genes whose transcription is directly controlled by PR, and thus affected by "functional" progesterone withdrawal, remain to be identified.

Nanomolar and micromolar effects of 15-deoxy-delta 12,14-prostaglandin J2 on amnion-derived WISH epithelial cells: differential roles of peroxisome proliferator-activated receptors gamma and delta and nuclear factor kappa B

15-Deoxy delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), an activator of peroxisome proliferator-activated receptor (PPAR)-gamma and -delta, is a prostanoid metabolite with anti-inflammatory actions. In intrauterine tissues, proinflammatory cytokines and prostaglandins have been identified as playing key roles in the maintenance of pregnancy and the onset of labor. We investigated and compared the early (<3 h) effects of 15d-PGJ(2) with rosiglitazone (PPAR-gamma ligand) and 2-methyl-4-((4-methyl-2-(4-trifluoromethylphenyl)-1,3-thiazol-5-yl)-methylsulfanyl)phenoxy-acetic acid (GW501516) (PPAR-delta ligand) on interleukin (IL)-1beta-induced prostaglandin and cytokine production by amnion-derived WISH cells. We show that 15d-PGJ(2) exerts differential effects depending on concentration. At low concentrations (<0.1 microM), 15d-PGJ(2) inhibited IL-1beta-stimulated prostaglandin E(2) (PGE(2)) but not cytokine (IL-6/IL-8) production or cyclooxygenase-2 (COX-2) expression. This effect was attenuated by a PPAR-gamma inhibitor [2-chloro-5-nitro-N-phenyl-benzamide (GW9662)], by transfection with a dominant-negative PPAR construct, and was reproduced by the PPAR-gamma ligand rosiglitazone. At higher concentrations (1-10 microM), 15d-PGJ(2) inhibited IL-1beta-stimulated PGE(2) and cytokine production and COX-2 expression, and this effect was not blocked by GW9662. Rosiglitazone at high concentrations (1-10 microM) stimulated PGE(2) production in the absence or presence of the dominant-negative PPAR. The PPAR-delta ligand GW501516 also inhibited IL-1beta-stimulated PGE(2) production but only at high concentrations (1 microM). IL-1beta-induced nuclear factor-kappaB (NF-kappaB) DNA binding activity was significantly inhibited by 15d-PGJ(2) (10 microM) and GW501516 (1 microM) but increased with 10 microM rosiglitazone. We conclude that 1) at low concentrations, 15d-PGJ(2) acts through a PPAR-gamma signaling pathway; b) at higher concentrations, its actions are mediated most likely through other pathways such as activation of PPAR-delta and/or inhibition of NF-kappaB; and 3) rosiglitazone exerts PPAR-independent effects at high concentrations (>1 microM).

Markedly elevated levels of inflammatory cytokines in maternal serum and peritoneal washing during arrested labor

BACKGROUND

The role of inflammatory cytokines in the pathophysiology of arrested labor is currently unknown. We measured levels of inflammatory cytokines in maternal serum and peritoneal washings in arrested first stage of labor to assess the possible involvement of these mediators in this obstetric disorder.

METHODS

This was a prospective, case-control study involving 15 women who underwent cesarean section for arrested cervical dilatation (group I), 15 controls who were operated during active labor for nonreassuring fetal heart-rate tracing (group II) and 15 controls who were operated electively (group III). Blood samples were drawn from all women shortly before the operation. The presence of peritoneal fluid was assessed and peritoneal washings were obtained during the operation. All samples were assayed for the inflammatory cytokines interleukin (IL)-1beta, IL-6, IL-8 and soluble IL-2 receptor (sIL-2R) by solid-phase enzyme-linked immunosorbent assay (ELISA).

RESULTS

All women from group I and one patient (6.7%) from group II had some degree of peritoneal fluid accumulation, while none from group III had any. Serum samples from group I contained significantly higher IL-1beta, IL-6, IL-8 and IL-2R levels than both control groups. Peritoneal washings from group I contained significantly higher IL-1beta, IL-6 and IL-8 but similar IL-2R levels.

CONCLUSIONS

Arrested first stage of labor is associated with peritoneal fluid accumulation and increased levels of inflammatory cytokines in both serum and peritoneal fluids. Inflammatory cytokines may therefore be involved in the pathophysiology of arrested labor.

Prostaglandins and the myometrium and cervix

Prostaglandins have long been thought to play important roles in the mechanism of parturition. Here we review the involvement of prostaglandins in myometrial and cervical functions with emphasis on human labor and birth. In addition, the cellular sources of prostaglandins as well as their interactions with various other endocrine, paracrine and physical factors, such as oxytocin, corticotropin releasing hormone, nitric oxide, platelet activating factor, cytokines, endothelin and stretch are also addressed together with their potential role in the molecular reorganization of cervical structure associated with labor and delivery. Finally, the premier role of progesterone in pregnancy maintenance and parturition is juxtaposed with the proposed "fine-tuning", modulatory role of prostaglandins and the above listed factors in the regulation of parturition.

Nuclear prostaglandin receptors: role in pregnancy and parturition?

The key regulatory role of prostanoids [prostaglandins (PGs) and thromboxanes (TXs)] in the maintenance of pregnancy and initiation of parturition has been established. However, our understanding of how these events are fine-tuned by the recruitment of specific signaling pathways remains unclear. Whereas, initial thoughts were that PGs were lipophilic and would easily cross cell membranes without specific receptors or transport processes, it has since been realized that PG signaling occurs via specific cell surface G-protein coupled receptors (GPCRs) coupled to classical adenylate cyclase or inositol phosphate signaling pathways. Furthermore, specific PG transporters have been identified and cloned adding a further level of complexity to the regulation of paracrine action of these potent bioactive molecules. It is now apparent that PGs also activate nuclear receptors, opening the possibility of novel intracrine signaling mechanisms. The existence of intracrine signaling pathways is further supported by accumulating evidence linking the perinuclear localization of PG synthesizing enzymes with intracellular PG synthesis. This review will focus on the evidence for a role of nuclear actions of PGs in the regulation of pregnancy and parturition.

Prostaglandin synthases: recent developments and a novel hypothesis

Cells are continuously exposed to cues, which signal cell survival or death. Fine-tuning of these conflicting signals is essential for tissue development and homeostasis, and defective pathways are linked to many disease processes, especially cancer. It is well established that prostaglandins (PGs), as signalling molecules, are important regulators of cell proliferation, differentiation and apoptosis. PG production has been a focus of many researchers interested in the mechanisms of parturition. Previously, investigators have focussed on the committed step of PG biosynthesis, the conversion by prostaglandin H synthase (PGHS; also termed cyclo-oxygenase, COX) of arachidonic acid (AA) (substrate) to PGH2, the common precursor for biosynthesis of the various prostanoids. However, recently the genes encoding the terminal synthase enzymes involved in converting PGH2 to each of the bioactive PGs, including the major uterotonic PGs, PGE2 (PGE synthase) and PGF2alpha (PGF synthase), have been cloned and characterized. This review highlights how the regulation of the expression and balance of key enzymes can produce, from a single precursor, prostanoids with varied and often opposing effects.

Expression of membrane prostaglandin E synthase in human placenta and fetal membranes and effect of labor

Initiation and maintenance of labor in humans is associated with an increase in prostaglandin synthesis by intrauterine tissues. The objective of the present study was to characterize the distribution of membrane-bound PGES (mPGES) protein and mPGES mRNA in human placenta, fetal membranes, and decidua at term and to determine whether any changes occurred with labor. Immunoreactive mPGES was found to be highly concentrated in amnion epithelial cells and the chorion laeve trophoblasts, with lower levels in the mesenchymal layers. The enzyme was at very low levels or undetectable in the decidual tissue. Much lower levels of mPGES protein and mRNA were found in placenta than in fetal membranes. mPGES was associated with the syncytiotrophoblast and in cells surrounding blood vessels. The expression of mPGES mRNA did not change with labor in full membranes or placenta, but Western analysis showed an increase in mPGES protein in chorion laeve and a decrease in mPGES protein in placenta during labor, with no change in the amnion. The differences in expression found among placenta, chorion, and amnion before and after labor would indicate that this enzyme is differentially regulated in these tissues at this time.

Cytokines, prostaglandins and parturition--a review

The elaboration of cytokines, chemokines and immunomodulatory proteins in the placenta and gestational membranes has been extensively investigated in the context of both normal and abnormal pregnancy and delivery. Patterns of expression of cytokines in the foetal membranes and decidua suggest that inflammatory activation occurs modestly with term labour, but much more robustly in preterm delivery, particularly in the presence of intrauterine infection. Enhanced chemokine expression, particularly evident in deliveries with an infected amniotic cavity, is presumably responsible for recruiting infiltrating leukocytes into the membranes thereby amplifying the inflammatory process and hastening membrane rupture and delivery. Anti-inflammatory cytokines suppress inflammatory reactions in the placenta, but under some circumstances may act in a pro-inflammatory fashion in the membranes. Intracellular signalling by cytokines is modulated by proteins such as SOCS (Silencer Of Cytokine Signalling)-1, -2 and -3. Changes in the abundance of these proteins occur with term labour, implicating them as modulators of cytokine actions around the time of parturition. Prostaglandins, released by the membranes in response to stretch and the actions of pro-inflammatory cytokines, act not only upon the myometrium and cervix, but may also exert paracrine/autocrine effects on cell viability and matrix protein integrity. The localization and regulation of prostanoid isomerases, responsible for converting PGH(2) (derived from prostaglandin H synthase-1 and -2) to bioactive prostanoids, are being studied in these tissues, particularly in the context of cytokine interactions. Although the gestational tissues are known to be sources of PGD(2), PGJ(2) and its derivatives, the regulation of production of these prostaglandins has yet to be studied in any detail and their actions, which may include apoptosis and suppression of inflammation, remain poorly defined. A more complete understanding of these aspects of cytokine-prostaglandin interactions in pregnancy and parturition will, no doubt, unfold as current studies come to fruition.

Mechanisms of term and preterm birth

Labour at term and preterm results from activation and then stimulation of the myometrium. Activation can occur through mechanical stretch of the uterus, and by endocrine pathways resulting from increased activity of the fetal hypothalamic-pituitary-adrenal axis. In women and in experimental animals, cortisol likely contributes to increased prostaglandin production in fetal tissues through up-regulation of the type 2 prostaglandin H2, synthase-2 (PGHS-2) and down-regulation of 15-OH prostaglandin dehydrogenase. Cortisol increases expression of prostaglandin dehydrogenase in the chorion by reversing the stimulatory effect of progesterone, and may represent "progesterone withdrawal" in the primate. By competing with progesterone inhibition, cortisol also increases expression of placental corticotropin-releasing hormone. Other agents, such as pro-inflammatory cytokines, similarly up-regulate PGHS-2 and decrease expression of prostaglandin dehydrogenase. Oxytocin, produced locally within the intrauterine tissues, is also thought to be involved in parturition, and there is a marked increase in oxytocin receptor expression at term. There are thus several mechanisms by which labour at term or preterm may be initiated. These different mechanisms need to be considered in the development of strategies for the detection and management of women in preterm labour. Ongoing studies are investigating the use of oxytocin receptor antagonists, PGHS-2 inhibitors, and nitric oxide to prevent or regulate preterm labour. The presence of fibronectin in vaginal secretions, and elevated maternal serum levels of corticotropin-releasing hormone, estrogens, and cytokines have been examined as possible markers of preterm labour. However, at the present time, we do not have the ability to accurately predict or diagnose preterm labour, nor do we have specific or efficient methods to inhibit labour once it has started.

Efficacy and specificity of non-steroidal anti-inflammatory drugs for the inhibition of cytokine-stimulated prostaglandin E(2) secretion by amnion-derived WISH cells

Prostaglandin H synthase-2 (PGHS-II) specific inhibitors have been proposed as a potential treatment in the prevention of preterm birth. We examined the efficacy of PGHS inhibitors on basal and cytokine-stimulated prostaglandin (PG) production by the amnion-like WISH cell line. WISH cells were treated with interleukin (IL)-1 beta and tumour necrosis factor (TNF)-alpha in the presence or absence of indomethacin, etodolac, 5,5-dimethy-3-(3-fluorophenyl)-4-(4-methlysulphonyl) phenyl-2 (5H)-furanone (DFU) or nimesulide (1.6-1000 nM) for 16 h. PG production was then measured using radioimmunoassay. Nimesulide and DFU were the most selective non-steroidal anti-inflammatory drugs (NSAIDs) of IL-beta-stimulated PG production in these studies with an a IC(50)(basal)/IC(50)(stimulated) ratio of, respectively, 142.2 and 113.8, followed by etodolac (25.3) and indomethacin (2.2). Similar results were obtained when cells were stimulated with TNF-alpha. The results of this study suggest that PGHS-II-selective NSAIDs may be effective in the prevention of cytokine-driven amnion PG production associated with preterm labour.

Cytokines of the placenta and extra-placental membranes: roles and regulation during human pregnancy and parturition

Summary In an earlier, companion, review, we concluded that cytokines produced by the placenta and associated membranes are likely to be involved in control of the processes of implantation and placental development (Bowen et al., 2002). In this review, we discuss evidence that cytokines continue to be part of a paracrine/autocrine regulatory network in the placenta and membranes throughout the mid and late stages of gestation. Cytokines are involved in regulation of placental growth during these later stages of pregnancy and also function to protect the fetus from pathological organisms. The evidence, while not entirely consistent, suggests that production of certain cytokines within the extraplacental membranes is altered during normal term parturition, whereas in the villous placenta evidence of labour-associated changes is much more equivocal. Roles for cytokines have been postulated in many facets of parturition, including expulsion of the fetus by uterine contractions, membrane rupture, and dilation of the cervix. Imbalances and disruptions to the cytokine milieu have been implicated in a number of diseases of pregnancy involving abnormalities of both placental growth/establishment and initiation of parturition. Cytokine secretion induced by intrauterine infection is associated with increased occurrence or severity of some neonatal diseases. This wealth of data supports the view that cytokines are an integral part of a functional regulatory/communication network operating within the placental-maternal unit during normal gestation.

Effects of tumor necrosis factor-alpha on secretion of prostaglandins E2 and F2alpha in bovine endometrium throughout the estrous cycle

To determine the physiological significance of tumor necrosis factor-alpha (TNFalpha) in the regulation of endometrial prostaglandin (PG) release in cattle, we investigated the effects of TNFalpha on the secretion of PGE2 and PGF2alpha by bovine endometrium during the estrous cycle. Bovine uteri were classified into six stages (estrus: Day 0, early luteal 1: Days 2 to 3, early luteal 11: Days 5 to 6, mid-luteal: Days 8 to 12, late luteal: Days 15 to 17 and follicular: Days 19 to 21). After 1 h of pre-incubation, endometrial tissues (20 to 30 mg) were exposed to 0 or 0.6 nM TNFalpha for 4 h. The PGE2 concentrations in the medium were higher in the luteal stages than in the follicular stage and in estrus. In contrast, PGF2alpha concentrations were higher in the follicular stage and in estrus than in the luteal stages. The ratio of the basal concentrations of PGE2 and PGF2alpha (PGE2/PGF2alpha ratio) was higher in the luteal stages than in the follicular stage and in estrus. Although TNFalpha stimulated both PGE2 and PGF2alpha secretion during the entire period of the estrous cycle, the level of stimulation of TNFalpha on PGE2 output by the bovine endometrium does not show the same cyclical changes as that shown on PGF2alpha output. The stimulation of TNFalpha resulted in a decrease in the PGE2/PGF2alpha ratio only in the late luteal stage. Furthermore, TNFalpha stimulated PGE2 secretion in stromal, but not epithelial cells. The overall results suggest that TNFalpha is a potent regulator of endometrial PGE2 secretion as well as PGF2alpha secretion during the entire period of estrous cycle, and that TNFalpha plays different roles in the regulation of secretory function of bovine endometrium at different phases of the estrous cycle.

Glucocorticoid regulation of human and ovine parturition: the relationship between fetal hypothalamic-pituitary-adrenal axis activation and intrauterine prostaglandin production

Birth in many animal species and in humans is associated with activation of hypothalamic-pituitary-adrenal function in the fetus and the increased influence of glucocorticoids on trophoblast cells of the placenta and fetal membranes. We suggest that in ovine pregnancy glucocorticoids directly increase fetal placental prostaglandin production, and indirectly increase prostaglandin production by maternal uterine tissues through the stimulation of placental estradiol synthesis. The events of ovine parturition are compared with those of human parturition. In the latter, we suggest similar direct effects of glucocorticoids on prostaglandin synthesis and metabolism in fetal membranes and similar indirect effects mediated by glucocorticoid-stimulated increases in intrauterine corticotropin-releasing hormone expression.

Cytokine-induced coordinate expression of enzymes of prostaglandin biosynthesis and metabolism: 15-hydroxyprostaglandin dehydrogenase

The effects of pro-inflammatory cytokines on 15-hydroxyprostaglandin dehydrogenase (PGDH) expression and prostaglandin (PG) metabolizing activity were investigated in placental tissue. Treatment of trophoblast cells in primary culture with interleukin-1beta (IL-1beta) or tumour necrosis factor-alpha (TNF-alpha) resulted in decreased prostaglandin metabolizing activity. This was assessed both by determining the ratio of production of prostaglandins to their metabolites, and by Northern blot analysis of PGDH mRNA abundance. Dexamethasone had similar inhibitory effect. We hypothesize that proinflammatory cytokines act to enhance prostaglandin actions through coordinated effects on activities of enzymes of both prostaglandin biosynthesis and metabolism, perhaps in concert with effects on receptor function.