NF-κB regulates a cassette of immune/inflammatory genes in human pregnant myometrium at term

SOX4 exerts contrasting regulatory effects on labor-associated gene promoters in myometrial cells

The uterine muscular layer, or myometrium, undergoes profound changes in global gene expression during its progression from a quiescent state during pregnancy to a contractile state at the onset of labor. In this study, we investigate the role of SOX family transcription factors in myometrial cells and provide evidence for the role of SOX4 in regulating labor-associated genes. We show that Sox4 has elevated expression in the murine myometrium during a term laboring process and in two mouse models of preterm labor. Additionally, SOX4 differentially affects labor-associated gene promoter activity in cooperation with activator protein 1 (AP-1) dimers. SOX4 exerted no effect on the Gja1 promoter; a JUND-specific activation effect at the Fos promoter; a positive activation effect on the Mmp11 promoter with the AP-1 dimers; and surprisingly, we noted that the reporter expression of the Ptgs2 promoter in the presence of JUND and FOSL2 was repressed by the addition of SOX4. Our data indicate SOX4 may play a diverse role in regulating gene expression in the laboring myometrium in cooperation with AP-1 factors. This study enhances our current understanding of the regulatory network that governs the transcriptional changes associated with the onset of labor and highlights a new molecular player that may contribute to the labor transcriptional program.

Integrative analysis of noncoding mutations identifies the druggable genome in preterm birth

Preterm birth affects ~10% of pregnancies in the US. Despite familial associations, identifying at-risk genetic loci has been challenging. We built deep learning and graphical models to score mutational effects at base resolution via integrating the pregnant myometrial epigenome and large-scale patient genomes with spontaneous preterm birth (sPTB) from European and African American cohorts. We uncovered previously unidentified sPTB genes that are involved in myometrial muscle relaxation and inflammatory responses and that are regulated by the progesterone receptor near labor onset. We studied genomic variants in these genes in our recruited pregnant women administered progestin prophylaxis. We observed that mutation burden in these genes was predictive of responses to progestin treatment for preterm birth. To advance therapeutic development, we screened ~4000 compounds, identified candidate molecules that affect our identified genes, and experimentally validated their therapeutic effects on regulating labor. Together, our integrative approach revealed the druggable genome in preterm birth and provided a generalizable framework for studying complex diseases.

Prostaglandin F2α requires activation of calcium-dependent signalling to trigger inflammation in human myometrium

Introduction

Preterm birth is one of the major causes of neonatal morbidity and mortality across the world. Both term and preterm labour are preceded by inflammatory activation in uterine tissues. This includes increased leukocyte infiltration, and subsequent increase in chemokine and cytokine levels, activation of pro-inflammatory transcription factors as NF-κB and increased prostaglandin synthesis. Prostaglandin F2α (PGF2α) is one of the myometrial activators and stimulators.

Methods

Here we investigated the role of PGF2α in pro-inflammatory signalling pathways in human myometrial cells isolated from term non-labouring uterine tissue. Primary myometrial cells were treated with G protein inhibitors, calcium chelators and/or PGF2α. Nuclear extracts were analysed by TranSignal cAMP/Calcium Protein/DNA Array. Whole cell protein lysates were analysed by Western blotting. mRNA levels of target genes were analysed by RT-PCR.

Results

The results show that PGF2α increases inflammation in myometrial cells through increased activation of NF-κB and MAP kinases and increased expression of COX-2. PGF2α was found to activate several calcium/cAMP-dependent transcription factors, such as CREB and C/EBP-β. mRNA levels of NF-κB-regulated cytokines and chemokines were also elevated with PGF2α stimulation. We have shown that the increase in PGF2α-mediated COX-2 expression in myometrial cells requires coupling of the FP receptor to both Gαq and Gαi proteins. Additionally, PGF2α-induced calcium response was also mediated through Gαq and Gαi coupling.

Discussion

In summary, our findings suggest that PGF2α-induced inflammation in myometrial cells involves activation of several transcription factors - NF-κB, MAP kinases, CREB and C/EBP-β. Our results indicate that the FP receptor signals via Gαq and Gαi coupling in myometrium. This work provides insight into PGF2α pro-inflammatory signalling in term myometrium prior to the onset of labour and suggests that PGF2α signalling pathways could be a potential target for management of preterm labour.

Is human labor at term an inflammatory condition?†

Parturition at term in normal pregnancy follows a predictable sequence of events. There is some evidence that a state of inflammation prevails in the reproductive tissues during labor at term, but it is uncertain whether this phenomenon is the initiating signal for parturition. The absence of a clear temporal sequence of inflammatory events prior to labor casts doubt on the concept that normal human labor at term is primarily the result of an inflammatory cascade. This review examines evidence linking parturition and inflammation in order to address whether inflammation is a cause of labor, a consequence of labor, or a separate but related phenomenon. Finally, we identify and suggest ways to reconcile inconsistencies regarding definitions of labor onset in published research, which may contribute to the variability in conclusions regarding the genesis and maintenance of parturition. A more thorough understanding of the processes underlying normal parturition at term may lead to novel insights regarding abnormal labor, including spontaneous preterm labor, preterm premature rupture of the fetal membranes, and dysfunctional labor, and the role of inflammation in each.

Inflammatory Amplification: A Central Tenet of Uterine Transition for Labor

In preparation for delivery, the uterus transitions from actively maintaining quiescence during pregnancy to an active parturient state. This transition occurs as a result of the accumulation of pro-inflammatory signals which are amplified by positive feedback interactions involving paracrine and autocrine signaling at the level of each intrauterine cell and tissue. The amplification events occur in parallel until they reach a certain threshold, ‘tipping the scale’ and contributing to processes of uterine activation and functional progesterone withdrawal. The described signaling interactions all occur upstream from the presentation of clinical labor symptoms. In this review, we will: 1) describe the different physiological processes involved in uterine transition for each intrauterine tissue; 2) compare and contrast the current models of labor initiation; 3) introduce innovative models for measuring paracrine inflammatory interactions; and 4) discuss the therapeutic value in identifying and targeting key players in this crucial event for preterm birth.

Is there an inflammatory stimulus to human term labour?

Inflammation is thought to play a pivotal role in the onset of term and some forms of preterm labour. Although, we recently found that myometrial inflammation is a consequence rather than a cause of term labour, there are several other reproductive tissues, including amnion, choriodecidua parietalis and decidua basalis, where the inflammatory stimulus to labour may occur. To investigate this, we have obtained amnion, choriodecidual parietalis and decidua basalis samples from women at various stages of pregnancy and spontaneous labour. The inflammatory cytokine profile in each tissue was determine by Bio-Plex Pro® cytokine multiplex assays and quantitative RT-PCR. Active motif assay was used to study transcription activation in the choriodecidua parietalis. Quantitative RT-PCR was use to study the pro-labour genes (PGHS-2, PGDH, OTR and CX43) in all of the tissues at the onset of labour and oxytocin (OT) mRNA expression in the choriodecidual parietalis and decidua basalis. Statistical significance was ascribed to a P value <0.05. In the amnion and choriodecidua parietalis, the mRNA levels of various cytokines decreased from preterm no labour to term no labour samples, but the protein levels were unchanged. The choriodecidua parietalis showed increase in the protein levels of IL-1β and IL-6 in the term early labour samples. In the amnion and decidua basalis, the protein levels of several cytokines rose in term established labour. The multiples of the median derived from the 19-plex cytokine assay were greater in term early labour and term established labour samples from the choriodecidua parietalis, but only in term established labour for myometrium. These data suggest that the inflammatory stimulus to labour may begin in the choriodecidua parietalis, but the absence of any change in prolabour factor mRNA levels suggests that the cytokines may act on the myometrium where we observed changes in transcription factor activation and increases in prolabour gene expression in earlier studies.

PKA and AKIP1 interact to mediate cAMP-driven COX-2 expression: A potentially pivotal interaction in preterm and term labour

Previously, we showed that cAMP increased COX-2 expression in myometrial cells via MAPK. Here, we have extended these observations, using primary myometrial cell cultures to show that the cAMP agonist, forskolin, enhances IL-1β-driven COX-2 expression. We then explored the role of A-kinase interacting protein (AKIP1), which modulates the effect of PKA on p65 activation. AKIP1 knockdown reversed the effect of forskolin, such that its addition inhibited IL-1β-induced COX-2 mRNA expression and reduced the IL-1β-induced increase in nuclear levels of p65 and c-jun. Forskolin alone and with IL-1β increased IκBα mRNA expression suggesting that in the context of inflammation and in the presence of AKIP1, cAMP enhances p65 activation. AKIP1 knockdown reversed these changes. Interestingly, AKIP1 knockdown had minimal effect on the ability of forskolin to repress either basal OTR expression or IL-1β-stimulated OTR mRNA expression. AKIP1 was up-regulated by IL-1β, but not stretch and was repressed by cAMP. The mRNA expression of AKIP1 increased in early labour in tandem with an increase in COX-2 mRNA and protein. AKIP1 protein levels were also increased with inflammation and stretch-induced preterm labour. Our results identify a second important cAMP effector-switch occurring at term in human myometrium and suggest that a hitherto unrecognized interaction may exist between AKIP1, NFκB and AP-1. These data add to the proposition that cAMP acts as a key regulator of human myometrial contractility.

Pro-inflammatory signals induce 20α-HSD expression in myometrial cells: A key mechanism for local progesterone withdrawal

Metabolism of progesterone (P4) by the enzyme 20α hydroxysteroid dehydrogenase (20α‐HSD) in myometrial cells is postulated to be a mechanism for P4 withdrawal, which occurs concomitant to uterine inflammation (physiologic or infection‐induced) and associated activation of transcription factors: NF‐кB and AP‐1, common to term and preterm labour. We found that 20α‐HSD protein is significantly increased in human myometrium during term labour, and in mouse uterus during term and preterm labour. Treatment of human myometrial cells with the pro‐inflammatory mediators, lipopolysaccharide (LPS, mimicking infection) and 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA, mimicking inflammation), induced 20α‐HSD gene expression and increased 20α‐HSD protein abundance. LPS treatment decreased P4 release into the culture medium and resulted in up‐regulation of GJA1 in the hTERT‐HM cells. The NF‐кB /AP‐1 transcription factors mediated effects of LPS and TPA on 20α‐HSD gene transcription. Both pro‐inflammatory stimuli induced 20α‐HSD promoter activity in LPS/TPA‐treated cells which was significantly attenuated by inhibition of NF‐кB (JSH: 20 µM) or AP‐1 signalling (T5224: 10 µM). Deletion of NF‐кB consensus sites abrogated LPS‐mediated promoter induction, while removal of AP‐1 sites reversed the TPA‐mediated induction of 20α‐HSD promoter. We conclude that inflammatory stimuli (physiologic or pathologic) that activate NF‐кB or AP‐1 induce 20α‐HSD transcription and subsequent local P4 withdrawal resulting in up‐regulation of GJA1 and activation of myometrium that precedes labour.

Transcriptional control of parturition: insights from gene regulation studies in the myometrium

The onset of labour is a culmination of a series of highly coordinated and preparatory physiological events that take place throughout the gestational period. In order to produce the associated contractions needed for foetal delivery, smooth muscle cells in the muscular layer of the uterus (i.e. myometrium) undergo a transition from quiescent to contractile phenotypes. Here, we present the current understanding of the roles transcription factors play in critical labour-associated gene expression changes as part of the molecular mechanistic basis for this transition. Consideration is given to both transcription factors that have been well-studied in a myometrial context, i.e. activator protein 1, progesterone receptors, oestrogen receptors, and nuclear factor kappa B, as well as additional transcription factors whose gestational event-driving contributions have been demonstrated more recently. These transcription factors may form pregnancy- and labour-associated transcriptional regulatory networks in the myometrium to modulate the timing of labour onset. A more thorough understanding of the transcription factor-mediated, labour-promoting regulatory pathways holds promise for the development of new therapeutic treatments that can be used for the prevention of preterm labour in at-risk women.

NF-κB and Its Regulators During Pregnancy

The transcriptional factor NF-κB is a nuclear factor involved in both physiological and pathological processes. This factor can control the transcription of more than 400 genes, including cytokines, chemokines, and their modulators, immune and non-immune receptors, proteins involved in antigen presentation and cell adhesion, acute phase and stress response proteins, regulators of apoptosis, growth factors, other transcription factors and their regulators, as well as different enzymes; all these molecules control several biological processes. NF-κB is a tightly regulated molecule that has also been related to apoptosis, cell proliferation, inflammation, and the control of innate and adaptive immune responses during onset of labor, in which it has a crucial role; thus, early activation of this factor may have an adverse effect, by inducing premature termination of pregnancy, with bad outcomes for the mother and the fetus, including product loss. Reviews compiling the different activities of NF-κB have been reported. However, an update regarding NF-κB regulation during pregnancy is lacking. In this work, we aimed to describe the state of the art around NF-κB activity, its regulatory role in pregnancy, and the effect of its dysregulation due to invasion by pathogens like Trichomonas vaginalis and Toxoplasma gondii as examples.

Transcription factors regulated by cAMP in smooth muscle of the myometrium at human parturition

Cyclic adenosine monophosphate (cAMP) contributes to maintenance of a quiescent (relaxed) state in the myometrium (i.e. uterine smooth muscle) during pregnancy, which most commonly has been attributed to activation of protein kinase A (PKA). PKA-mediated phosphorylation of cytosolic contractile apparatus components in myometrial smooth muscle cells (mSMCs) are known to promote relaxation. Additionally, PKA also regulates nuclear transcription factor (TF) activity to control expression of genes important to the labour process; these are mostly involved in actin-myosin interactions, cell-to-cell connectivity and inflammation, all of which influence mSMC transition from a quiescent to a contractile (pro-labour) phenotype. This review focuses on the evidence that cAMP modulates the activity of TFs linked to pro-labour gene expression, predominantly cAMP response element (CRE) binding TFs, nuclear factor κB (NF-κB), activator protein 1 (AP-1) family and progesterone receptors (PRs). This review also considers the more recently described exchange protein directly activated by cAMP (EPAC) that may oppose the pro-quiescent effects of PKA, as well as explores findings from other cell types that have the potential to be of novel relevance to cAMP action on TF function in the myometrium.

The potential therapeutic effects of curcumin on pregnancy complications: Novel insights into reproductive medicine

Pregnancy complications including preeclampsia, preterm birth, intrauterine growth restriction, and gestational diabetes are the main adverse reproductive outcomes. Excessive inflammation and oxidative stress play crucial roles in the pathogenesis of pregnancy disorders. Curcumin, the main polyphenolic compound derived from Curcuma longa, is mainly known by its anti-inflammatory and antioxidant properties. There are in vitro and in vivo reports revealing the preventive and ameliorating effects of curcumin against pregnancy complications. Here, we aimed to seek mechanisms underlying the modulatory effects of curcumin on dysregulated inflammatory and oxidative responses in various pregnancy complications.

Evolution of male pregnancy associated with remodeling of canonical vertebrate immunity in seahorses and pipefishes

Among vertebrates, pregnancy has evolved more than 150 times independently. A fundamental problem for pregnancy to evolve is inadvertent rejection of the embryo when being recognized as foreign tissue by the vertebrate’s adaptive immune system. We show that the unique evolution of male pregnancy in pipefishes and seahorses coincided with a genomic modification of one arm of the adaptive immune system. Our findings indicate a trade-off between immunological tolerance and embryo rejection to accompanying the emergence of male pregnancy. That syngnathids survive in an ocean of microbes despite their drastically modified immune defense suggests an unexpected immunological flexibility. Our results may improve the understanding of immune-deficiency diseases and call for a reassessment of vertebrate immunity.

A fundamental problem for the evolution of pregnancy, the most specialized form of parental investment among vertebrates, is the rejection of the nonself-embryo. Mammals achieve immunological tolerance by down-regulating both major histocompatibility complex pathways (MHC I and II). Although pregnancy has evolved multiple times independently among vertebrates, knowledge of associated immune system adjustments is restricted to mammals. All of them (except monotremata) display full internal pregnancy, making evolutionary reconstructions within the class mammalia meaningless. Here, we study the seahorse and pipefish family (syngnathids) that have evolved male pregnancy across a gradient from external oviparity to internal gestation. We assess how immunological tolerance is achieved by reconstruction of the immune gene repertoire in a comprehensive sample of 12 seahorse and pipefish genomes along the “male pregnancy” gradient together with expression patterns of key immune and pregnancy genes in reproductive tissues. We found that the evolution of pregnancy coincided with a modification of the adaptive immune system. Divergent genomic rearrangements of the MHC II pathway among fully pregnant species were identified in both genera of the syngnathids: The pipefishes (Syngnathus) displayed loss of several genes of the MHC II pathway while seahorses (Hippocampus) featured a highly divergent invariant chain (CD74). Our findings suggest that a trade-off between immunological tolerance and embryo rejection accompanied the evolution of unique male pregnancy. That pipefishes survive in an ocean of microbes without one arm of the adaptive immune defense suggests a high degree of immunological flexibility among vertebrates, which may advance our understanding of immune-deficiency diseases.

Oxidative stress - Related spontaneous preterm delivery challenges in causality determination, prevention and novel strategies in reduction of the sequelae

Spontaneous preterm birth (PTB) is one of the major complications of pregnancy and the main cause of neonatal mortality and morbidity. Despite the efforts devoted to the understanding of this obstetrical syndrome and improved medical care, there has been a tendency for the PTB rate to increase in the last decades globally. The costs of the screening for spontaneous PTB, its management, and treatment of the sequelae represent a major burden to the health service economy of high-income countries. In this scenario, it has been widely acknowledged that oxidative stress (OS) plays an important role in the pathogenicity of human disease in wide range of areas of medicine. There is an emerging evidence that an imbalance between pro-and-antioxidants may be associated with spontaneous PTB. However, there are still many controversies on the mechanisms by which OS are involved in the pathogenesis of prematurity. Moreover, the crucial question whether the OS is the cause or consequence of the disease is yet to be answered. The purpose of this article is to briefly summarize the current knowledge and controversies on oxidative stress-related spontaneous PTB and to give a critical approach on future perspectives on this topic as a classical example of translational medicine. Placenta-mediated pregnancy adverse outcome associated with OS leading to iatrogenic PTB (e.g. pre-eclampsia, intrauterine growth restriction, gestational diabetes) will not be discussed.

Delineating differential regulatory signatures of the human transcriptome in the choriodecidua and myometrium at term labor

Preterm deliveries remain the leading cause of neonatal morbidity and mortality. Current therapies target only myometrial contractions and are largely ineffective. As labor involves multiple coordinated events across maternal and fetal tissues, identifying fundamental regulatory pathways of normal term labor is vital to understanding successful parturition and consequently labor pathologies. We aimed to identify transcriptomic signatures of human normal term labor of two tissues: in the fetal-facing choriodecidua and the maternal myometrium. Microarray transcriptomic data from choriodecidua and myometrium following term labor were analyzed for functional hierarchical networks, using Cytoscape 2.8.3. Hierarchically high candidates were analyzed for their regulatory casual relationships using Ingenuity Pathway Analysis. Selected master regulators were then chemically inhibited and effects on downstream targets were assessed using real-time quantitative PCR (RT-qPCR). Unbiased network analysis identified upstream molecular components in choriodecidua including vimentin, TLR4, and TNFSF13B. In the myometrium, candidates included metallothionein 2 (MT2A), TLR2, and RELB. These master regulators had significant differential gene expression during labor, hierarchically high centrality in community cluster networks, interactions amongst the labor gene set, and strong causal relationships with multiple downstream effects. In vitro experiments highlighted MT2A as an effective regulator of labor-associated genes. We have identified unique potential regulators of the term labor transcriptome in uterine tissues using a robust sequence of unbiased mathematical and literature-based in silico analyses. These findings encourage further investigation into the efficacy of predicted master regulators in blocking multiple pathways of labor processes across maternal and fetal tissues, and their potential as therapeutic approaches.

Surfactant protein A suppresses preterm delivery induced by live Escherichia coli in mice

Preterm birth accounts for the majority of neonatal morbidity and mortality in the developed world. A significant proportion of cases of spontaneous preterm labor are attributable to infections within gestational tissues. Surfactant protein A (SP-A), a collectin produced in the fetal lung and other tissues, has been shown previously in mice to suppress preterm delivery due to intrauterine (IU) instillation of sterile proinflammatory substances. Here we report a powerful antilabor effect for SP-A after IU infection with live Escherichia coli. SP-A abolished preterm birth (rate reduced from 100% to 0%) when it was administered into the uterus simultaneously with bacterial infection, reducing it by 75% when administered intravenously at the same time as IU bacterial inoculation, and by 48% when administered intravenously 4 h after IU bacterial infection. This effect on preterm delivery was accompanied by a parallel benefit on fetal survival in utero. SP-A had no effect on bacterial growth but reversed several major consequences of infection, including increased production of inflammatory mediators and a shift in macrophage polarization to the M1 phenotype. These findings suggest that exogenous SP-A has potential use to counteract infection-induced labor by reversing its proinflammatory consequences.

Interaction between NF-κB and AP-1 and their intracellular localization at labor in human late pregnant myometrial cells in vivo and in vitro

Preterm birth (PTB) is the most important cause of neonatal morbidity and mortality next to congenital anomalies in the developed world. NF-κB and AP-1 were reported to play an important role in parturition initiation. However, the interaction relationship between the 2 molecules in labor initiation has not yet been reported.This study aimed to investigate the interaction between NF-κB and AP-1 and their intracellular translocation during labor in human late pregnant myometrial cells (HLPMCs).Co-immunoprecipitation (Co-IP), Western blot analysis, immunohistochemistry (IHC), and immunocytofluorescence (ICF) techniques were applied to explore the interaction between NF-κB and AP-1 and the alteration in their intracellular localization before and after labor onset.The protein expression levels of NF-κBp65 and AP-1(c-jun) in the natural labor group were observed significantly higher than that in the non-labor group. Pearson's correlation analysis showed a positive correlation between the protein expression of NF-κBp65 and AP-1(c-jun). Interactions were found between the 2 molecules in HLPMCs both in natural labor and non-labor group and were also found in primary culture HLPMCs before and after neuromedin B (NMB) stimulation. NF-κBp65 and AP-1(c-jun) were localized mainly in the cytoplasm before labor onset or NMB stimulation and were translocated into the nucleus upon labor initiation and NMB stimulation.These results demonstrated that upregulated protein expression of NF-κBp65 and AP-1(c-jun), the enhanced interaction between the 2 molecules, and their translocation to nucleus might be correlated to labor initiation.

The role of NFκB in the three stages of pregnancy - implantation, maintenance, and labour: a review article

The transcription factor nuclear factor kappa B (NFκB) controls the expression of over 400 genes, some of which are associated with reproductive events. During implantation, immune cells accumulate in the maternal-fetal interface; they secrete inflammatory mediators under the control of NFĸB, the level of which also rises. NFĸB is then downregulated to maintain gestation, but its level rises again before birth to manage prostaglandin, cytokine, and chemokine synthesis, and to stimulate uterine contraction. This review summarises the current state of knowledge about NFκB and its role in the molecular regulation of processes related to pregnancy development.

TWEETABLE ABSTRACT

This review examines the current state of knowledge about role of NFκB in the development of pregnancy.

Is myometrial inflammation a cause or a consequence of term human labour?

Myometrial inflammation is thought to have a pivotal role in the onset of term and some forms of preterm labour. This is based on the comparison of samples taken from women undergoing term elective CS prior to the onset of labour with those taken from women in established labour. Consequently, it is not clear whether myometrial inflammation is a cause or a consequence of labour. Our objective is to test the hypothesis that myometrial inflammation is a consequence of the onset of labour. To test this hypothesis, we have obtained myometrial samples from women at various stages of pregnancy and spontaneous labour and studied the activation of the AP-1 (c-Jun) and NFκB (p65) systems, cytokine mRNA expression and protein levels and inflammatory cell infiltration and activation. We found that the activation of p65 declined from preterm to term not in labour samples and thereafter increased in early and established labour. Cytokine mRNA expression and protein levels increased in established labour only. Using flow cytometry of myometrial tissue, we found that the number of neutrophils did increase with the onset of labour, but on tissue section, these were seen to be intravascular and not infiltrating into the myometrium. These data suggest that myometrial inflammation is a consequence rather than a cause of term labour.

Advances in the role of oxytocin receptors in human parturition

Oxytocin (OT) is a neurohypophysial hormone which has been found to play a central role in the regulation of human parturition. The most established role of oxytocin/oxytocin receptor (OT/OTR) system in human parturition is the initiation of uterine contractions, however, recent evidence have demonstrated that it may have a more complex role including initiation of inflammation, regulation of miRNA expression, as well as mediation of other non-classical oxytocin actions via receptor crosstalk with other G protein-coupled receptors (GPCRs). In this review we highlight both established and newly emerging roles of OT/OTR system in human parturition and discuss the expanding potential for OTRs as pharmacological targets in the management of preterm labour.

The Potential Functions of Small Heat Shock Proteins in the Uterine Musculature during Pregnancy

The small heat shock protein B (HSPB) family is comprised of eleven members with many being induced by physiological stressors. In addition to being molecular chaperones, it is clear these proteins also play important roles in cell death regulation, cytoskeletal rearrangements, and immune system activation. These processes are important for the uterine smooth muscle or myometrium during pregnancy as it changes from a quiescent tissue, during the majority of pregnancy, to a powerful and contractile tissue at labor. The initiation and progression of labor within the myometrium also appears to require an inflammatory response as it is infiltrated by immune cells and it produces pro-inflammatory mediators. This chapter summarizes current knowledge on the expression of HSPB family members in the myometrium during pregnancy and speculates on the possible roles of these proteins during myometrial programming and transformation of the myometrium into a possible immune regulatory tissue.

A Novel Role for SIRT3 in Regulating Mediators Involved in the Terminal Pathways of Human Labor and Delivery

Preterm birth remains the major cause of neonatal mortality and morbidity, mediated largely by an inflammatory process. The sirtuin (SIRT) family of cellular regulators has been implicated as key inhibitors of inflammation. We have previously reported a role for SIRT1, SIRT2, and SIRT6 in regulating inflammation-induced prolabor mediators. In this study, we determined the effect of term labor and pro-inflammatory cytokines on SIRT3, SIRT4, SIRT5, and SIRT7 expression in human myometrium. Functional studies were also used to investigate the effect of small interfering RNA (siRNA) knockdown of SIRTs in regulating inflammation-induced prolabor mediators. Western blot analysis and qRT-PCR were used to determine SIRT3, SIRT4, SIRT5, and SIRT7 mRNA and protein expression in human myometrium. Small interfering RNA knockdown of SIRT3 in myometrial primary cells determined its role in response to inflammatory stimuli IL1B and TNF. SIRT3 mRNA and protein expression levels were significantly lower in term laboring myometrium compared with term nonlaboring myometrium. There was no effect of labor on SIRT4, SIRT5 or SIRT7 protein expression. The pro-inflammatory cytokines IL1B and TNF significantly decreased levels of SIRT3 mRNA and protein expression. SIRT3 knockdown by siRNA significantly augmented IL1B- and TNF-stimulated IL6, CXCL8, and CCL2 mRNA expression and release; PTGS2 mRNA expression and subsequent PGF_2alpha release; the mRNA expression and secretion of the adhesion molecule ICAM1 and the extracellular matrix remodeling enzyme MMP9; and nuclear factor kappa B1 (NFkappaB1) transcriptional activity. In human myometrium, SIRT3 expression decreases with term labor and regulates the mediators involved in the terminal effector pathways of human labor and delivery through the NFkappaB1 pathway.

The role of sex steroid hormones in the pathophysiology and treatment of sarcopenia

Sex steroids influence the maintenance and growth of muscles. Decline in androgens, estrogens and progesterone by aging leads to the loss of muscular function and mass, sarcopenia. These steroid hormones can interact with different signaling pathways through their receptors. To date, sex steroid hormone receptors and their exact roles are not completely defined in skeletal and smooth muscles. Although numerous studies focused on the effects of sex steroid hormones on different types of cells, still many unexplained molecular mechanisms in both skeletal and smooth muscle cells remain to be investigated. In this paper, many different molecular mechanisms that are activated or inhibited by sex steroids and those that influence the growth, proliferation, and differentiation of skeletal and smooth muscle cells are reviewed. Also, the similarities of cellular and molecular pathways of androgens, estrogens and progesterone in both skeletal and smooth muscle cells are highlighted. The reviewed signaling pathways and participating molecules can be targeted in the future development of novel therapeutics.

The study of progesterone action in human myometrial explants

STUDY HYPOTHESIS

Myometrial explants represent a superior model compared with cell culture models for the study of human myometrial progesterone (P4) signalling in parturition.

STUDY FINDING

Gene expression analysis showed myometrial explants closely resemble the in vivo condition and the anti-inflammatory action of P4 is not lost with labour onset.

WHAT IS KNOWN ALREADY

Circulating P4 levels decline before the onset of parturition in most animals, but not in humans. This has led to the suggestion that there is a functional withdrawal of P4 action at the myometrial level prior to labour onset. However, to date, no evidence of a loss of P4 function has been provided, with studies hampered by a lack of a physiologically relevant model.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

Myometrial biopsies obtained at Caesarean section were dissected into explants after a portion was immediately snap frozen (t = 0). Microarray analysis was used to compare gene expression of t = 0 with paired (i) explants, (ii) passage 4 myometrial cell cultures or (iii) the hTERT myometrial cell line. Western blotting and chemokine/cytokine assays were used to study P4 signalling in myometrial explants.

MAIN RESULTS AND THE ROLE OF CHANCE

Gene expression comparison of t = 0 to the three models demonstrated that explants more closely resemble the in vivo status. At the protein level, explants maintain both P4 receptor (PR) and glucocorticoid receptor (GR) levels versus t = 0 whereas cells only maintain GR levels. Additionally, treatment with 1 µM P4 led to a reduction in interleukin-1 (IL-1) β-driven cyclooxygenase-2 in explants but not in cells. P4 signalling in explants was PR-mediated and associated with a repression of p65 and c-Jun phosphorylation. Furthermore, the anti-inflammatory action of P4 was maintained after labour onset.

LIMITATIONS/REASONS FOR CAUTION

There is evidence of basal inflammation in the myometrial explant model.

WIDER IMPLICATIONS OF THE FINDINGS

Myometrial explants constitute a novel model to study P4 signalling in the myometrium and can be used to further elucidate the mechanisms of P4 action in human labour.

LARGE SCALE DATA

Data deposited at http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?token=gvmpggkurbgxfqf&acc=GSE77830.

STUDY FUNDING AND COMPETING INTEREST

This work was supported by grants from the Joint Research Committee of the Westminster Medical School Research Trust, Borne (No. 1067412-7; a sub-charity of the Chelsea and Westminster Health Charity) and the Imperial NIHR Biomedical Research Centre. The views expressed are those of the author(s) and not necessarily those of the NHS or the Department of Health. The authors have no conflict of interest.

Mechanistic Differences Leading to Infectious and Sterile Inflammation

Inflammation is a physiologic component of pregnancy and parturition. Overwhelming intrauterine inflammatory load promotes quiescent feto-maternal tissues into a contractile phenotype. Like inflammation, oxidative stress is an inevitable component of both pregnancy and parturition. Pathologic activation of host innate immune response to adverse pregnancy conditions can lead to premature activation of inflammatory and oxidative stress. Inflammation and oxidative stress markers seen with both sterile and infectious inflammation are often similar; therefore, it is difficult to understand causality of conditions like spontaneous preterm birth. This review demonstrates potential mechanistic pathways of activation of sterile and infectious inflammation. We demonstrate the activation of two unique pathways of inflammation by factors that are well-documented proxies for oxidative stress (cigarette smoke extract) and infection (lipopolysaccharide). Sterile inflammation seen after exposure to an oxidative stress inducer is due to cellular elemental damage resulting in p38 mitogen-activated protein kinase (MAPK) induced cellular senescence. Infectious inflammation is through activation of transcription factor NF-κB and independent of oxidative stress-associated damages and p38 MAPK-induced senescence. Understanding the differences in the inflammatory pathway activation by various risk factors is important to design better screening, diagnostic and intervention strategies to reduce the risks of adverse pregnancy outcomes.

Sulfasalazine augments a pro-inflammatory response in interleukin-1β-stimulated amniocytes and myocytes

Preterm birth occurs in 10% of pregnancies and is a major cause of neonatal morbidity and mortality. The majority of cases of early preterm labour are associated with infection/inflammation, which places the fetal central nervous system at risk. Targeting immune activation is therefore an appealing therapeutic strategy for the prevention of preterm labour and neonatal brain injury. The expression of many labour-associated and inflammatory-response genes is controlled by the transcription factors nuclear factor-κB (NF-κB) and activator protein-1 (AP-1), which makes them therapeutic targets of interest. Sulfasalazine (SASP) has been shown to inhibit NF-κB and reduce lipopolysaccharide-induced cytokine concentrations in fetal membrane explants and reduce the rate of Escherichia coli-induced preterm labour in mice. Its effects upon AP-1 in the context of pregnancy are unknown. In this study the effect of SASP on interleukin-1β (IL-1β) -induced NF-κB and AP-1 activity, cytokine production and cyclo-oxygenase-2 (COX-2) expression was examined in amniocytes and myocytes. A supra-therapeutic concentration (5 mm) was required to inhibit IL-1β-induced NF-κB (P < 0·0001) in amniocytes and IL-1β-induced NF-κB (P < 0·01), AP-1 (P < 0·01) and COX-2 (P < 0·05) in myocytes. Despite inhibiting IL-1β-induced cytokines, a basal increase in IL-6 (P < 0·01), IL-8 (P < 0·0001) and tumour necrosis factor-α (TNF-α) (P < 0·001) was seen with 5 mm SASP in amniocytes, and significant cytotoxic effects were seen in myocytes. The therapeutic concentration of 0·015 mm had no inhibitory effects on pro-inflammatory mediators, but led to an augmented response to IL-1β-induced IL-6 (P < 0·01), IL-8 (P < 0·05) and TNF-α (P < 0·05) in amniocytes and IL-8 (P < 0·05) in myocytes. SASP is therefore an unlikely therapeutic candidate for the prevention of inflammation-induced preterm labour.

Progesterone and the Repression of Myometrial Inflammation: The Roles of MKP-1 and the AP-1 System

Progesterone (P4) maintains uterine quiescence during pregnancy and its functional withdrawal is associated with increased prostaglandin synthesis and the onset of labor. In primary human myometrial cells, the glucocorticoid receptor (GR) rather than the P4 receptor mediates P4 antagonism of IL-1β-induced cyclooxygenase-2 (COX-2) expression, the rate-limiting enzyme in prostaglandin synthesis. We now report that P4 also acts via GR to induce MAPK phosphatase (MKP)-1 and knockdown of MKP-1 impairs the ability of P4 to repress IL-1β-dependent COX-2 induction. Microarray analysis revealed that P4 repressed preferentially activator protein-1-responsive genes in response to IL-1β. Consistent with these observations, we found that the ability of P4 to reduce c-Jun activation was lost upon GR as well as MKP-1 knockdown. Interestingly, c-Jun levels in human myometrial cells declined upon GR and MKP-1 knockdown, which suggests the presence of an activator protein-1 feedback loop. This is supported by our observation that c-Jun levels declined after an initial rise in primary myometrial cells treated with phorbol 12-myrisatate 13-acetate, a potent activator of c-Jun N-terminal kinase. Finally, we show that MKP-1 is an intermediate in P4-mediated repression of some but not all IL-1β-responsive genes. For example, P4 repression of IL11 and IRAK3 was maintained upon MKP-1 knockdown. Taken together, the data show that P4 acts via GR to drive MKP-1 expression, which in turn inhibits IL-1β-dependent c-Jun activation and COX-2 expression.

Nuclear factor of activated T-cell isoform expression and regulation in human myometrium

BACKGROUND

During pregnancy, myometrial gene and protein expression is tightly regulated to accommodate fetal growth, promote quiescence and ultimately prepare for the onset of labour. It is proposed that changes in calcium signalling, may contribute to regulating gene expression and that nuclear factor of activated T-cell (NFAT) transcription factors (isoforms c1-c4) may be involved. Currently, there is little information regarding NFAT expression and regulation in myometrium.

METHODS

This study examined NFAT isoform mRNA expression in human myometrial tissue and cells from pregnant women using quantitative PCR. The effects of the Ca(2+) ionophore A23187 and in vitro stretch (25 % elongation, static strain; Flexercell FX-4000 Tension System) on NFAT expression were determined in cultured human myometrial cells.

RESULTS

Human myometrial tissue and cultured cells expressed NFATc1-c4 mRNA. NFATc2 gene expression in cultured cells was increased in response to 6 h stretch (11.5 fold, P < 0.001, n = 6) and calcium ionophore (A23187, 5 μM) treatment (20.6 fold, P < 0.001, n = 6). This response to stretch was significantly reduced (90 %, P < 0.001, n = 10) in the presence of an intracellular calcium chelator, BAPTA-AM (20 μM).

CONCLUSIONS

These data suggest that NFATc2 expression is regulated by intracellular calcium and in vitro stretch, and that the stretch response in human myometrial cells is dependent upon intracellular calcium signalling pathways. Our findings indicate a potentially unique role for NFATc2 in mediating stretch-induced gene expression per se and warrant further exploration in relation to the mechanisms promoting uterine smooth muscle growth in early pregnancy and/or labour.

Specific Lipopolysaccharide Serotypes Induce Differential Maternal and Neonatal Inflammatory Responses in a Murine Model of Preterm Labor

Intrauterine inflammation is recognized as a key mediator of both normal and preterm birth but is also associated with neonatal neurological injury. Lipopolysaccharide (LPS) is often used to stimulate inflammatory pathways in animal models of infection/inflammation-induced preterm labor; however, inconsistencies in maternal and neonatal responses to LPS are frequently reported. We hypothesized that LPS serotype-specific responses may account for a portion of these inconsistencies. Four different Escherichia coli LPS serotypes (O111:B4, O55:B5, O127:B8, and O128:B12) were administered to CD1 mice via intrauterine injection at gestational day 16. Although control animals delivered at term 60 ± 15 hours postinjection (p.i.), those administered with O111:B4 delivered 7 ± 2 hours p.i., O55:B5 delivered 10 ± 3 hours p.i., O127:B8 delivered 16 ± 10 hours p.i., and O128:B12 delivered 17 ± 2 hours p.i. (means ± SD). A correlation between the onset of preterm labor and myometrial activation of the inflammatory transcription factor, activator protein 1, but not NF-κB was observed. Specific LPS serotypes induced differential activation of downstream contractile and inflammatory pathways in myometrium and neonatal pup brain. Our findings demonstrate functional disparity in inflammatory pathway activation in response to differing LPS serotypes. Selective use of LPS serotypes may represent a useful tool for targeting specific inflammatory response mechanisms in these models.

Gestational tissue transcriptomics in term and preterm human pregnancies: a systematic review and meta-analysis

BACKGROUND

Preterm birth (PTB), or birth before 37 weeks of gestation, is the leading cause of newborn death worldwide. PTB is a critical area of scientific study not only due to its worldwide toll on human lives and economies, but also due to our limited understanding of its pathogenesis and, therefore, its prevention. This systematic review and meta-analysis synthesizes the landscape of PTB transcriptomics research to further our understanding of the genes and pathways involved in PTB subtypes.

METHODS

We evaluated published genome-wide pregnancy studies across gestational tissues and pathologies, including those that focus on PTB, by performing a targeted PubMed MeSH search and systematically reviewing all relevant studies.

RESULTS

Our search yielded 2,361 studies on gestational tissues including placenta, decidua, myometrium, maternal blood, cervix, fetal membranes (chorion and amnion), umbilical cord, fetal blood, and basal plate. Selecting only those original research studies that measured transcription on a genome-wide scale and reported lists of expressed genetic elements identified 93 gene expression, 21 microRNA, and 20 methylation studies. Although 30 % of all PTB cases are due to medical indications, 76 % of the preterm studies focused on them. In contrast, only 18 % of the preterm studies focused on spontaneous onset of labor, which is responsible for 45 % of all PTB cases. Furthermore, only 23 of the 10,993 unique genetic elements reported to be transcriptionally active were recovered 10 or more times in these 134 studies. Meta-analysis of the 93 gene expression studies across 9 distinct gestational tissues and 29 clinical phenotypes showed limited overlap of genes identified as differentially expressed across studies.

CONCLUSIONS

Overall, profiles of differentially expressed genes were highly heterogeneous both between as well as within clinical subtypes and tissues as well as between studies of the same clinical subtype and tissue. These results suggest that large gaps still exist in the transcriptomic study of specific clinical subtypes as well in the generation of the transcriptional profile of well-studied clinical subtypes; understanding the complex landscape of prematurity will require large-scale, systematic genome-wide analyses of human gestational tissues on both understudied and well-studied subtypes alike.

Oxytocin activates NF-κB-mediated inflammatory pathways in human gestational tissues

Human labour, both at term and preterm, is preceded by NF-κB-mediated inflammatory activation within the uterus, leading to myometrial activation, fetal membrane remodelling and cervical ripening. The stimuli triggering inflammatory activation in normal human parturition are not fully understood. We show that the neurohypophyseal peptide, oxytocin (OT), activates NF-κB and stimulates downstream inflammatory pathways in human gestational tissues. OT stimulation (1 pM-100 nM) specifically via its receptor (OTR) in human myometrial and amnion primary cells led to MAPK and NF-κB activation within 15 min and maximal p65-subunit nuclear translocation within 30 min. Both in human myometrium and amnion, OT-induced activation of the canonical NF-κB pathway upregulated key inflammatory labour-associated genes including IL-8, CCL5, IL-6 and COX-2. IKKβ inhibition (TPCA1; 10 µM) suppressed OT-induced NF-κB-p65 phosphorylation, whereas p65-siRNA knockdown reduced basal and OT-induced COX-2 levels in myometrium and amnion. In both gestational tissues, MEK1/2 (U0126; 10 µM) or p38 inhibition (SB203580; 10 µM) suppressed OT-induced COX-2 expression, but OT-induced p65-phosphorylation was only inhibited in amnion, suggesting OT activation of NF-κB in amnion is MAPK-dependent. Our data provide new insight into the OT/OTR system in human parturition and suggest that its therapeutic modulation could be a strategy for regulating both contractile and inflammatory pathways in the clinical context of term/preterm labour.

Oxidative stress damage as a detrimental factor in preterm birth pathology

Normal term and spontaneous preterm births (PTB) are documented to be associated with oxidative stress (OS), and imbalances in the redox system (balance between pro- and antioxidant) have been reported in the maternal-fetal intrauterine compartments. The exact mechanism of labor initiation either at term or preterm by OS is still unclear, and this lack of understanding can partially be blamed for failure of antioxidant supplementation trials in PTB prevention. Based on recent findings from our laboratory, we postulate heterogeneity in host OS response. The physiologic (at term) and pathophysiologic (preterm) pathways of labor are not mediated by OS alone but by OS-induced damage to intrauterine tissues, especially fetal membranes of the placenta. OS damage affects all major cellular elements in the fetal cells, and this damage promotes fetal cell senescence (aging). The aging of the fetal cells is predominated by p38 mitogen activated kinase (p38MAPK) pathways. Senescing cells generate biomolecular signals that are uterotonic, triggering labor process. The aging of fetal cells is normal at term. However, aging is premature in PTB, especially in those PTBs complicated by preterm premature rupture of the membranes, where elements of redox imbalances and OS damage are more dominant. We postulate that fetal cell senescence signals generated by OS damage are likely triggers for labor. This review highlights the mechanisms involved in senescence development at term and preterm by OS damage and provides insight into novel fetal signals of labor initiation pathways.

Slit2 is decreased after spontaneous labour in myometrium and regulates pro-labour mediators

Preterm birth, a global healthcare problem, is commonly associated with inflammation. As Slit2 plays an emerging role in inflammation, the purpose of this study was to determine the effect of Slit2 on labour mediators in human gestational tissues. Slit2 mRNA and protein expression were assessed using qRT-PCR and immunohistochemistry in foetal membranes and myometrium obtained before and after labour. Slit2 silencing was achieved using siRNA in primary myometrial cells. Pro-inflammatory and pro-labour mediators were evaluated by qRT-PCR, ELISA and gelatin zymography. Slit2 mRNA and protein expression were found to be significantly lower in myometrium after labour onset. There was no effect of term or preterm labour on Slit2 expression in foetal membranes. Slit2 mRNA expression was decreased in myometrium treated with LPS and IL-1β. Slit2 siRNA in myometrial cells increased IL-1β-induced pro-inflammatory cytokine gene expression and release (IL-6 and IL-8), COX-2 expression and prostaglandin PGE2 and PGF2α release, and MMP-9 gene expression and pro MMP-9 release. There was no effect of Slit2 siRNA on IL-1β-induced NF-κB transcriptional activity. Our results demonstrate that Slit2 is decreased in human myometrium after labour and our knock-down studies describe an anti-inflammatory effect of Slit2 in myometrial cells.

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.

Activator protein 1 is a key terminal mediator of inflammation-induced preterm labor in mice

Activation of uterine inflammatory pathways leads to preterm labor (PTL), associated with high rates of neonatal mortality and morbidity. The transcription factors nuclear factor κB (NFκB) and activator protein 1 (AP-1) regulate key proinflammatory and procontractile genes involved in normal labor and PTL. Here we show that NFκB activation normally occurs in the mouse myometrium at gestation day E18, prior to labor, whereas AP-1 and JNK activation occurs at labor onset. Where labor was induced using the progesterone receptor antagonist RU486, NFkB and AP-1/JNK activation both occurred at the time of labor (20 h compared to 60 h in DMSO-treated controls). Using an LPS (Escherichia coli: serotype O111)-induced PTL model that selectively activates AP-1 but not NFkB, we show that myometrial AP-1 activation drives production of cytokines (Il-6, Il-8, and Il-1β), metalloproteinases (Mmp3 and Mmp10), and procontractile proteins (Cox-2 and Cx43) resulting in PTL after 7 h. Protein levels of CX43 and IL-1β, and IL-1β cleavage, were increased following LPS-induced activation of AP-1. Inhibition of JNK by SP600125 (30 mg/kg) delayed PTL by 6 h (7.5 vs. 13.5 h P<0.05). Our data reveal that NFκB activation is not a functional requirement for infection/inflammation-induced preterm labor and that AP-1 activation is sufficient to drive inflammatory pathways that cause PTL.

EP2 receptor activates dual G protein signaling pathways that mediate contrasting proinflammatory and relaxatory responses in term pregnant human myometrium

Prostaglandin (PG) E2 (PGE(2)) plays a central role in the regulation of smooth muscle contractions. Classically, PGE(2) stimulates contractions via EP1 and EP3 receptors, whereas EP2 and EP4 maintain quiescence. Labor involves a change from myometrial quiescence to contractions with a shift from anti- to proinflammatory pathways. EP2, a Gαs-coupled receptor, is known to mediate its actions via cAMP signaling. However, we have recently shown that EP2 also activates the proinflammatory PG G/H synthase-2 (PGHS-2). Here, we identify the mechanism underlying the ability of EP2 to maintain uterine quiescence and activate a proinflammatory/prolabor response in term-pregnant human myometrium. Human myometrial biopsies for in vivo and in vitro studies were taken at cesarean section at term, before or after the onset of labor. Activation of EP2 increased intracellular levels of cAMP and reduced contractility. Contrastingly, EP2 stimulation increased levels of PGHS-2, membrane-associated PGE synthase-1, and PGE(2). This was entirely dependent on EP2-mediated activation of calcium signaling. Both calcium signaling and up-regulation of PGHS-2 were insensitive to the Gαi inhibitor pertussis toxin but inhibited by small interfering RNA knockdown of Gαq/11. There were no differences in EP2 mRNA or protein levels between upper or lower segment myometrium or between pre- and postlabor myometrium. However, in myocytes taken after the onset of labor, cAMP signaling was markedly attenuated, whereas activation of calcium and PGHS-2 was preserved. Overall, the dual coupling of EP2 to Gαs-cAMP and Gαq/11-calcium pathways underlies its ability to mediate contrasting functions in term pregnancy and the "switching" to a prolabor receptor.

SLIT3 is increased in supracervical human foetal membranes and in labouring myometrium and regulates pro-inflammatory mediators

PROBLEM

Inflammation is associated with preterm birth, a worldwide healthcare issue. SLIT3 has a role in inflammation, and thus, the purpose of this study was to determine the effect of SLIT3 on labour mediators in human gestational tissues.

METHOD OF STUDY

SLIT3 protein expression was performed using immunohistochemistry in foetal membranes and myometrium with no labour and after labour. Foetal membranes were also obtained from a distal site (DS) and supracervical site (overlying the cervix; SCS). SLIT3 gene silencing was achieved using siRNA in primary amnion and myometrial cells. Pro-inflammatory and pro-labour mediators were evaluated by qRT-PCR, ELISA and gelatin zymography.

RESULTS

SLIT3 expression was greater in foetal membranes from the SCS compared with DS and in myometrium after term spontaneous labour onset. SLIT3 siRNA in primary amnion and myometrial cells decreased IL-1β-induced pro-inflammatory cytokine gene expression and release (IL-6 and IL-8) and MMP-9 gene expression and release. In amnion cells, SLIT3 siRNA knockdown decreased IL-1β-induced COX-2 expression and prostaglandin PGE2 release. There was no effect of SLIT3 siRNA on IL-1β-induced NF-κB transcriptional activity.

CONCLUSION

Our results demonstrate that SLIT3 is increased with labour, and both our amnion and our myometrial studies describe a pro-inflammatory effect of SLIT3 in these tissues.

Corticotropin-releasing hormone interacts with interleukin-1β to regulate prostaglandin H synthase-2 expression in human myometrium during pregnancy and labor

CONTEXT

The onset of labor appears to involve the activation of myometrial inflammatory pathways, and transcription factors such as nuclear factor-κB (NF-κB) control expression of the contraction-associated proteins required to induce a procontractile phenotype. These responses might involve CRH, which integrates immune and neuroendocrine systems.

OBJECTIVES

In human myometrium we investigated cyclooxygenase 2 (PGHS2) expression and regulation by CRH and the proinflammatory cytokine IL-1β before and after labor.

DESIGN

Myometrial tissues obtained from pregnant women at term before (n = 12) or during labor (n = 10) and pathological cases of choriamnionitis-associated term labor (n = 5) were used to isolate primary myocytes and investigate in vitro, CRH effects on basal and IL-1β regulated p65 activation and PGHS2 expression.

RESULTS

In nonlaboring myometrial cells, CRH was unable to induce NF-κB nuclear translocation; however, it altered the temporal dynamics of IL-1β-driven NF-κB nuclear entry by initially delaying entry and subsequently prolonging retention. These CRH-R1-driven effects were associated with a modest inhibitory action in the early phase (within 2 hours) of IL-1β stimulated PGHS2 mRNA expression, whereas prolonged stimulation for 6-18 hours augmented the IL-1β effects. The early-phase effect required intact protein kinase A activity and was diminished after the onset of labor. The presence of chorioamnionitis led to exaggerated PGHS2 mRNA responses to IL-1β but diminished effects of CRH.

CONCLUSIONS

CRH is involved in the inflammatory regulation of PGHS2 expression before and during labor; these actions might be important in priming and preparing the myometrium for labor and cellular adaptive responses to inflammatory mediators.

The expression of the let-7 miRNAs and Lin28 signalling pathway in human term gestational tissues

INTRODUCTION

Labour and delivery are processes associated with inflammation within intrauterine and cervical tissues. The mechanisms that induce labour-associated changes and, in particular, the role of microRNAs (miRNAs) remain to be elucidated. MiRNAs are small non-coding RNAs that repress gene expression via mRNA degradation and translational repression. Let-7 miRNAs are negatively regulated by RNA-binding protein, Lin28, and both function downstream of NF-κB signalling. In non-gestational tissues, let-7 and Lin28 reportedy function as negative and positive regulators of IL-6 expression. We hypothesised that labour-associated inflammation involves the downregulation of let-7 miRNAs and upregulation of Lin28 expression.

AIM

To determine the expression of Lin28 protein and let-7 miRNA in human gestational tissue obtained before and after labour.

METHOD

Gestational tissues were collected from women at term by Caesarean section with and without labour and following normal vaginal delivery (n = 6 per group). Protein and RNA was extracted and Lin28 and let-7 miRNA expression was measured by Western blotting and real-time PCR.

RESULTS

The data obtained established that let-7 miRNA and Lin28 display tissue-specific expression: Lin28 was strongly expressed in the placenta and choriodecidua, but not measurable in amnion; and let-7b and -7c expression were significantly lower in choriodecidua compare to placenta and amnion, whereas the amnion expressed less let-7d and -7f than other tissues.

CONCLUSION

While the expression of Lin28 protein and let-7 miRNA did not vary significantly with labour onset and delivery, changes in their bioactivity and impact on nuclear signalling pathways in human gestational tissues remain to be established.

Interactions between inflammatory signals and the progesterone receptor in regulating gene expression in pregnant human uterine myocytes

The absence of a fall in circulating progesterone levels has led to the concept that human labour is associated with 'functional progesterone withdrawal' caused through changes in the expression or function of progesterone receptor (PR). At the time of labour, the human uterus is heavily infiltrated with inflammatory cells, which release cytokines to create a 'myometrial inflammation' via NF-κB activation. The negative interaction between NF-κB and PR, may represent a mechanism to account for 'functional progesterone withdrawal' at term. Conversely, PR may act to inhibit NF-κB function and so play a role in inhibition of myometrial inflammation during pregnancy. To model this inter-relationship, we have used small interfering (si) RNA-mediated knock-down of PR in human pregnant myocytes and whole genome microarray analysis to identify genes regulated through PR. We then activated myometrial inflammation using IL-1β stimulation to determine the role of PR in myometrial inflammation regulation. Through PR-knock-down, we found that PR regulates gene networks involved in myometrial quiescence and extracellular matrix integrity. Activation of myometrial inflammation was found to antagonize PR-induced gene expression, of genes normally upregulated via PR. We found that PR does not play a role in repression of pro-inflammatory gene networks induced by IL-1β and that only MMP10 was significantly regulated in opposite directions by IL-1β and PR. We conclude that progesterone acting through PR does not generally inhibit myometrial inflammation. Activation of myometrial inflammation does cause 'functional progesterone withdrawal' but only in the context of genes normally upregulated via PR.

Dietary phytophenols curcumin, naringenin and apigenin reduce infection-induced inflammatory and contractile pathways in human placenta, foetal membranes and myometrium

A tenet of contemporary obstetrics is that a significant proportion of preterm births involve bacterial infection. Bacterial endotoxin induces pro-inflammatory cytokines, prostaglandins and proteases via the pro-inflammatory pathway nuclear factor-κB (NF-κB), which plays a key role in initiating uterine contractions and rupture of foetal membranes. In non-gestational tissues, the phytophenols curcumin, naringenin and apigenin exert anti-inflammatory properties via inhibition of NF-κB. The aim of this study was to determine whether these treatments regulate pro-inflammatory and pro-labour mediators in human gestational tissues. Placenta, foetal membranes and myometrium were treated with curcumin, naringenin and apigenin in the presence of lipopolysaccharide (LPS) or interleukin (IL)-1β. In placenta and foetal membranes, all treatments significantly reduced LPS-stimulated release and gene expression of pro-inflammatory cytokines IL-6 and IL-8; placenta decreased cyclooxygenase (COX-2) mRNA expression, subsequent release of prostaglandins PGE2 and PGF2α and expression and activity of matrix-degrading enzyme matrix metalloproteinase (MMP)-9. In myometrial cells, all treatments attenuated IL-1β-induced COX-2 expression, release of PGE2 and PGF2α and expression and activity of MMP-9. Although naringenin significantly attenuated IL-1β-induced IL-6 and IL-8 mRNA expression and release, there was no effect of curcumin and apigenin. LPS-stimulated release of 8-isoprostane, a marker of oxidative stress, was attenuated by all treatments. NF-κB p65 DNA-binding activity was also decreased using these treatments. In conclusion, curcumin, naringenin and apigenin exert anti-inflammatory properties in human gestational tissues by inhibiting the transcriptional activity of NF-κB. Further studies should be undertaken to define a possible implication of these natural spices in the management of preterm labour and delivery.

The entry of fetal and amniotic fluid components into the uterine vessel circulation leads to sterile inflammatory processes during parturition

Pro-inflammatory cytokines play an important role during the process of human parturition. The focus of this review was to explore the contribution of biological, biochemical, and genetic changes in the onset of term labor. This article reviews the English-language literature on inflammatory, hormonal, and immunological factors in an effort to identify the molecular basis of human parturition. The majority of the genes and proteins up-regulated in parturition at term are related to four functional categories, mechanical stretch-mediated damage-associated molecular patterns (DAMPs) activation, response to immunity, induction of inflammatory signaling, and progressive uterine myometrial contractility and resultant term birth. Mechanical stretch could promote the entry of amniotic fluid components into the uterine vessel circulation that is the common physiologic mechanism at term prior to labor. The fetal or amniotic fluid-derived DAMPs could activate the immune system. The inflammatory mediators are produced by infiltrating activated leukocytes and by the reproductive tissues themselves such as myometrium, and subsequently lead to uterine contractions. This review supports the sterile inflammation hypothesis that there are at least two phases of human parturition: the initial wave of the entry of amniotic fluid components into uterine vasculatures would be followed by the second big wave of subsequent myometrial contraction.

Prostaglandin E2 represses interleukin 1 beta-induced inflammatory mediator output from pregnant human myometrial cells through the EP2 and EP4 receptors

Inflammatory mediators, including prostaglandins, cytokines, and chemokines, are strongly implicated in the mechanism of human labor, though their precise roles remain unknown. Here we demonstrate that interleukin 1 beta (IL-1beta) significantly increased the expression and release of interleukin-8 (CXCL8), monocyte chemotactic protein-1 (CCL2), and granulocyte macrophage colony-stimulating factor (CSF2) by primary human myometrial cells. However, this effect was repressed by prostaglandin E(2) (PGE(2)). As PGE(2) can activate four distinct PGE(2) receptors (EP(1), EP(2), EP(3), and EP(4)) to elicit various responses, we sought to define the EP receptor(s) responsible for this repression. Using selective EP receptor agonists and a selective EP(4) antagonist, we show that PGE(2) mediates the repression of IL-1beta-induced release of CXCL8, CCL2, and CSF2 via activation of the EP(2) and EP(4) receptors. The use of siRNA gene-specific knockdown further confirmed a role for both receptors. Real-time RT-PCR demonstrated that EP(2) was the most highly expressed of all four EP receptors at the mRNA level in human myometrial cells, and immunocytochemistry showed that EP(2) protein is abundantly present throughout the cells. Interestingly, PGE(2) does not appear to reduce mRNA expression of CXCL8, CCL2, and CSF2. Our results demonstrate that PGE(2) can elicit anti-inflammatory responses via activation of the EP(2) and EP(4) receptors in lower segment term pregnant human myometrial cells. Further elucidation of the EP receptor-mediated signaling pathways in the pregnant human uterus may be beneficial for optimizing the maintenance of pregnancy, induction of labor or indeed treatment of preterm labor.

NFκB and AP-1 drive human myometrial IL8 expression

The uterine expression of the chemokine IL8 increases dramatically with the onset of labour both at term and preterm. The IL8 promoter contains binding sites for the transcription factors nuclear factor-kappa B (NFκB), activator protein-1 (AP-1), and CCAAT/enhancer-binding protein (CEBP). In this study we investigated the roles of these transcription factors in IL1B regulation of the IL8 gene in human myometrium. Using chromatin immune precipitation (ChIP) assay, we showed that each of NFκB, CEBP, and AP-1 binds to the IL8 promoter upon IL1B stimulation. To examine the relative importance of each site in IL8 gene expression, site-directed mutagenesis of each of these sites was performed. We found that the NFκB site was essential for basal and IL1B-stimulated gene expression. Mutation of the AP-1 site reduced both basal and IL1B-stimulated expression but to a lesser extent. Mutation of the CEBP site had no effect upon basal expression but eliminated the IL1B response. Small interfering RNA (siRNA) silencing of NFκB abolished the IL8 response to IL1B significantly; siRNA against AP-1 reduced it to a lesser extent whilst knockdown of CEBP enhanced the response. Our data confirms a central and essential role for NFκB in regulation of IL8 in human myometrium.

Physiologic uterine inflammation and labor onset: integration of endocrine and mechanical signals

The mechanisms underlying the preparation of the uterus for labor are not fully understood. Our previous studies have shown that during pregnancy, the uterine muscle (myometrium) undergoes dramatic phenotypic modulation culminating in term labor. The current review will discuss the cellular mechanisms involved in the regulation of myometrial activity and its modulation by endocrine signals and by mechanical stimulation of the uterus by the growing fetus. In particular, the contribution of uterine inflammation to the onset of labor will be described. We provide evidence that increased production of cytokines/chemokines in pregnant myometrium is associated with uterine occupancy and regulated by progesterone, suggesting the integration of mechanical and endocrine signals. Myometrial cells can actively participate in the inflammatory process in the uterus through the release of multiple proinflammatory cytokines and chemokines, providing a strong signal for activation of immune cells, their subsequent infiltration into pregnant uterus, and the initiation of labor.

Neuromedin B and its receptor influence the activity of myometrial primary cells in vitro through regulation of Il6 expression via the Rela/p65 pathway in mice

The neuromedin B receptor (Nmbr) is an important physiological regulator of spontaneous activities and stress responses through different cascades as well as its autocrine and paracrine effects. Previous studies have revealed that neuromedin B (Nmb) and its receptor signal via the Rela (also known as p65)/Il6 pathway in a mouse model of pregnancy. This study investigated the mechanism of Nmbr signaling via the Rela/p65-Il6 pathway and regulation of the concentration of intracellular free calcium ([Ca(2+)](i)) during the onset of labor in primary mouse myometrial cell cultures isolated from mice in term labor. Data demonstrated Nmbr agonist-mediated upregulation of the DNA binding activity of Rela/p65, Il6 expression, and [Ca(2+)](i) in a concentration-dependent manner. Furthermore, a significant correlation was observed between DNA binding activity of Rela/p65 and Il6 expression. Moreover, this up-regulation was blocked by Nmbr and Rela/p65 knockdown, achieved by RNA interference (RNAi) technology. No significant differences were identified in the inhibition of Il6 expression as a result of Nmbr or Rela/p65 knockdown. However, significant differences were observed between the [Ca(2+)](i) in Rela/p65-specific group and that in the Nmbr-specific small interfering RNA (siRNA)-treated groups. These data demonstrated that the Nmb/Nmbr interaction in pregnant myometrial primary cells in vitro predominantly influenced uterine activity through regulation of Il6 expression via the Rela/p65 pathway, although the effects of Nmbr on [Ca(2+)](i) involved several pathways that remain to be elucidated.

Male gender promotes an increased inflammatory response to lipopolysaccharide in umbilical vein blood

OBJECTIVES

To establish gender-specific differences in maternal and fetal immune response in healthy human fetuses at term.

METHODS

Forty-five women with elective caesarean sections for uncomplicated singleton pregnancies were recruited for two studies. Using a multiplex biomarker immunoassay system, unstimulated maternal and fetal plasma concentrations of interleukin (IL)-1β, IL-1ra, IL-6, IL-8, macrophage inflammatory protein (MIP)-1α, and tumor necrosis factor (TNF)-α were measured from one study population. Lipopolysaccharide (LPS)-stimulated cytokine response was measured in a second study.

RESULTS

There were no significant gender differences in either maternal or fetal unstimulated plasma cytokine concentrations, but concentrations of the proinflammatory cytokines IL-1β and IL-6 were significantly greater in male fetal LPS-stimulated samples than in female fetal samples.

CONCLUSIONS

Blood of male fetuses mounts a larger pro-inflammatory response to lipopolysaccharide (LPS). This heightened response could be a critical pathway in promoting premature rupture of membranes (PPROM) and may be associated with life long differential gender response to infection.