Expression of cyclooxygenase types 1 and 2 in human fetal membranes at term

The hormonal control of parturition

Parturition is a complex physiological process that must occur in a reliable manner and at an appropriate gestation stage to ensure a healthy newborn and mother. To this end, hormones that affect the function of the gravid uterus, especially progesterone (P4), 17β-estradiol (E2), oxytocin (OT), and prostaglandins (PGs), play pivotal roles. P4 via the nuclear P4 receptor (PR) promotes uterine quiescence and for most of pregnancy exerts a dominant block to labor. Loss of the P4 block to parturition in association with a gain in prolabor actions of E2 are key transitions in the hormonal cascade leading to parturition. P4 withdrawal can occur through various mechanisms depending on species and physiological context. Parturition in most species involves inflammation within the uterine tissues and especially at the maternal-fetal interface. Local PGs and other inflammatory mediators may initiate parturition by inducing P4 withdrawal. Withdrawal of the P4 block is coordinated with increased E2 actions to enhance uterotonic signals mediated by OT and PGs to promote uterine contractions, cervix softening, and membrane rupture, i.e., labor. This review examines recent advances in research to understand the hormonal control of parturition, with focus on the roles of P4, E2, PGs, OT, inflammatory cytokines, and placental peptide hormones together with evolutionary biology of and implications for clinical management of human parturition.

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.

Up-regulation of cytosolic prostaglandin E synthase in fetal-membrane and amniotic prostaglandin E2 accumulation in labor

Prostaglandin E2 (PGE2) is known to have important roles in labor, but the detailed mechanism underlying the spontaneous human labor remains unknown. Here, we examined the involvement of prostaglandin biosynthetic enzymes and transporter in the accumulation of PGE2 in amniotic fluid in human labor. PGE2 and its metabolites were abundant in amniotic fluid in deliveries at term in labor (TLB), but not at term not in labor (TNL). In fetal-membrane Transwell assays, levels of PGE2 production in both maternal and fetal compartments were significantly higher in the TLB group than the TNL group. In fetal-membrane, the mRNA level of PTGES3, which encodes cytosolic prostaglandin E synthase (cPGES), was significantly higher in TLB than in TNL, but the mRNA levels of the other PGE2-synthase genes were not affected by labor. Moreover, the mRNA level of PTGS2, which encodes cyclooxygenase-2 (COX-2) in the amnion was significantly higher in TLB than in TNL. Western blot analyses revealed that the levels of COX-1 and COX-2 were comparable between the two groups, however, the level of cPGES was relatively higher in TLB than in TNL. COXs, cPGES, and prostaglandin transporter (SLCO2A1) proteins were all expressed in both chorionic trophoblasts and amniotic epithelium. These findings suggest that COXs, cPGES and SLCO2A1 contribute to PGE2 production from fetal-membrane in labor.

Anoctamin 1 antagonism potentiates conventional tocolytic-mediated relaxation of pregnant human uterine smooth muscle

BACKGROUND

Currently available tocolytic agents are not effective treatment for preterm labor beyond 48 h. A major reason is the development of maternal side effects which preclude the maintenance of an effective steady-state drug concentration. One strategy that can mitigate these side effects is utilizing synergistic drug combinations to reduce the drug concentrations necessary to elicit a clinical effect. We have previously shown that three anoctamin 1 (ANO1) antagonists mediate potent relaxation of precontracted human uterine smooth muscle (USM). In this study, we aimed to determine whether a combination of sub-relaxatory doses of tocolytic drugs in current clinical use [the L-type voltage-gated calcium channel (VGCC) blocker, nifedipine (NIF); and the β2-adrenergic (β2AR) agonist, terbutaline (TRB)] will potentiate USM relaxation with two ANO1 antagonists [benzbromarone (BB) and MONNA (MN)].

OBJECTIVE

This study sought to examine the synergistic potency and mechanistic basis of two ANO1 antagonists with currently available tocolytic drugs. Functional endpoints assessed included relaxation of pre-contracting pregnant human USM tissue, inhibition of intracellular calcium release, and reduction of spontaneous transient inward current (STIC) recordings in human uterine smooth muscle cells.

METHODS

Human myometrial strips and primary human USM cells were used in organ bath and calcium flux experiments with different combinations of sub-threshold doses of ANO1 antagonists and terbutaline or nifedipine to determine if ANO1 antagonists potentiate tocolytic drugs.

RESULTS

The combination of sub-threshold doses of two ANO1 antagonists and current tocolytic drugs demonstrate a significant degree of synergy to relax human pregnant USM compared to the effects achieved when these drugs are administered individually.

CONCLUSION

A combination of sub-threshold doses of VGCC blocker and β2AR agonist with ANO1 antagonists potentiates relaxation of oxytocin-induced contractility and calcium flux in human USM ex vivo. Our findings may serve as a foundation for novel tocolytic drug combinations.

PGE2 vs PGF2α in human parturition

Prostaglandin E2 (PGE2) and F2α (PGF2α) are the two most prominent prostanoids in parturition. They are involved in cervical ripening, membrane rupture, myometrial contraction and inflammation in gestational tissues. Because multiple receptor subtypes for PGE2 and PGF2α exist, coupled with diverse signaling pathways, the effects of PGE2 and PGF2α depend largely on the spatial and temporal expression of these receptors in intrauterine tissues. It appears that PGE2 and PGF2α play different roles in parturition. PGE2 is probably more important for labor onset, while PGF2α may play a more important role in labor accomplishment, which may be attributed to the differential effects of PGE2 and PGF2α in gestational tissues. PGE2 is more powerful than PGF2α in the induction of cervical ripening. In terms of myometrial contraction, PGE2 produces a biphasic effect with an initial contraction and a following relaxation, while PGF2α consistently stimulates myometrial contraction. In the fetal membranes, both PGE2 and PGF2α appear to be involved in the process of membrane rupture. In addition, PGE2 and PGF2α may also participate in the inflammatory process of intrauterine tissues at parturition by stimulating not only neutrophil influx and cytokine production but also cyclooxygenase-2 expression thereby intensifying their own production. This review summarizes the differential roles of PGE2 and PGF2α in parturition with respect to their production and expression of receptor subtypes in gestational tissues. Dissecting the specific mechanisms underlying the effects of PGE2 and PGF2α in parturition may assist in developing specific therapeutic targets for preterm and post-term birth.

Cooperative effects of sequential PGF2α and IL-1β on IL-6 and COX-2 expression in human myometrial cells†

The change from the state of pregnancy to the state of parturition, which we call uterine transitioning, requires the actions of inflammatory mediators and results in an activated uterus capable of performing the physiology of labor. Interleukin (IL)-1β and prostaglandin (PG)F2α are two key mediators implicated in preparing the uterus for labor by regulating the expression of uterine activation proteins (UAPs) and proinflammatory cytokines and chemokines. To investigate this process, primary human myometrial smooth muscle cells (HMSMC) isolated from the lower segment of women undergoing elective cesarean sections at term (not in labor) were used to test the inflammatory cytokine and UAP outputs induced by PGF2α and IL-1β alone or in sequential combinations. PGF2α and IL-1β regulate mRNA abundance of the PGF2α receptor FP, the IL-1 receptor system, interleukin 6, and other UAPs (OXTR, COX2), driving positive feedback interactions to further amplify their own proinflammatory effects. Sequential stimulation of HMSMC by PGF2α and IL-1β in either order results in amplified upregulation of IL-6 and COX-2 mRNA and protein, compared to their effects individually. These profound increases were unique to myometrium and not observed with stimulation of human fetal membrane explants. These results suggest that PGF2α and IL-1β act cooperatively upstream in the birth cascade to maximize amplification of IL-6 and COX-2, to build inflammatory load and thereby promote uterine transition. Targeting PGF2α or IL-1β, their actions, or intermediates (e.g. IL-6) would be an effective therapeutic intervention for preterm birth prevention or delay.

Cyclooxygenase inhibitors for treating preterm labour: What is the molecular evidence? 1

Preterm birth (<37 weeks of gestation) significantly increases the risk of neonatal mortality and morbidity. As many as half of all preterm births occur following spontaneous preterm labour. Since in such cases there are no known reasons for the initiation of labour, treatment of preterm labour (tocolysis) has sought to stop labour contractions and delay delivery. Despite some success, the use of cyclooxygenase (COX) inhibitors is associated with maternal/fetal side effects, and possibly increased risk of preterm birth. Clinical use of these drugs predates the collection of molecular and biochemical evidence in vitro, examining the expression and activity of COX enzymes in pregnant uterine tissues with and without labour. Such evidence is important to the rationale that COX enzymes are, or are not, appropriate targets for the tocolysis. The current study systematically searched existing scientific evidence to address the hypothesis that COX expression/activity is increased with the onset of human labour, in an effort to determine whether there is a rationale for the use of COX inhibitors as tocolytics. Our review identified 44 studies, but determined that there is insufficient evidence to support or refute a role of COX-1/-2 in the onset of preterm labour that supports COX-targeted tocolysis.

Anoctamin Channels in Human Myometrium: A Novel Target for Tocolysis

BACKGROUND

Spontaneous preterm labor leading to preterm birth is a significant obstetric problem leading to neonatal morbidity and mortality. Current tocolytics are not completely effective and novel targets may afford a therapeutic benefit.

OBJECTIVE

To determine whether the anoctamin (ANO) family, including the calcium-activated chloride channel ANO1, is present in pregnant human uterine smooth muscle (USM) and whether pharmacological and genetic modulation of ANO1 modulates USM contraction.

METHODS

Reverse transcription-polymerase chain reaction (RT-PCR), quantitative RT-PCR, and immunohistochemical staining were done to determine which members of the ANO family are expressed in human USM. Uterine smooth muscle strips were studied in an organ bath to determine whether ANO1 antagonists inhibit oxytocin-induced USM contractions. Anoctamin 1 small interfering RNA (siRNA) knockdown was performed to determine its effect on filamentous-/globular (F/G)-actin ratio, a measurement of actin polymerization's role in promoting smooth muscle contraction.

RESULTS

Messenger RNA (mRNA) encoding all members of the ANO family (except ANO7) are expressed in pregnant USM tissue. Anoctamin 1 mRNA expression was decreased 15.2-fold in pregnant USM compared to nonpregnant. Anoctamin 1 protein is expressed in pregnant human USM tissue. Functional organ bath studies with pregnant human USM tissue demonstrated that the ANO1 antagonist benzbromarone attenuates the force and frequency of oxytocin-induced contractions. In human USM cells, siRNA knockdown of ANO1 decreases F-/G-actin ratios.

CONCLUSION

Multiple members of the ANO family, including the calcium-activated chloride channel ANO1, are expressed in human USM. Antagonism of ANO1 by pharmacological inhibition and genetic knockdown leads to an attenuation of contraction in pregnant human USM. Anoctamin 1 is a potentially novel target for tocolysis.

Gestational tissue inflammatory biomarkers at term labor: A systematic review of literature

Parturition at term is characterized by inflammatory overload in both feto-maternal tissues. Despite the large number of individual studies on changes in inflammatory biomarkers linked to labor, a comprehensive profile of them in each of the uterine compartments is not available to better understand their mechanistic contributions to labor. This systematic review investigated the pro- and anti-inflammatory biomarkers reported in intra-uterine tissues (amnion, chorion, decidua, placenta, and myometrium) at term labor. We conducted a systematic review of studies on pro- and anti-inflammatory biomarkers (mRNA and/or protein) reported in feto-maternal tissues during normal human term labor, published in English (1980-2016), in 3 electronic data bases. From a total of 3712 citations, 172 were included for final review. Each tissue expresses a unique set of biomarkers at the time of term labor, but there is significant overlap between tissues. All tissues had IL-6, IL-8, IL-1β, COX-2, PGE-2, TNF-α, and hCAP18 in common at term labor. Common and unique inflammatory biomarkers are expressed in various feto-maternal compartments at term labor. Increase in pro-inflammatory markers in all gestational tissue signifies their harmonious functional role in promoting labor. Anti-inflammatory markers at term labor are hardly reported.

The Promise of Prostaglandins: Have They Fulfilled Their Potential as Therapeutic Targets for the Delay of Preterm Birth?

OBJECTIVE

The elucidation some 30 years ago by Sir Mont Liggins that the activation of the hypothalamic-pituitary-adrenal-placental axis in fetal sheep led to elevated maternal prostaglandin (PG) concentrations and the initiation of labor provided hope that targeting PG synthesis or action would lead to effective tocolysis and lowering of the human preterm birth rate. This was the "promise of PGs."

METHODS AND RESULTS

Although early trials showed that nonsteroidal anti-inflammatory drugs (NSAIDs), which inhibit PG H synthase (PGHS), delayed preterm birth by 48 hours, other trials revealed an association between NSAIDs and adverse fetal effects, including oligohydramnios, patent ductus arteriosus, necrotizing enterocolitis, intraventricular hemorrhage, and persistent pulmonary hypertension of the newborn (PPHN). Hope was revived when studies in the mid 1990s demonstrated that much of the PGs synthesized by intrauterine tissues at preterm labor were derived from the inducible isoenzyme PGHS-2. Unfortunately, administration of specific PGHS-2 inhibitors led to the same adverse fetal effects displayed by the mixed PGHS-1 and -2 NSAIDs, causing interest in the promise of PGs to wane. This led to the development of new strategies for specific PG inhibition or antagonism. One of these is the application of a specific PGF2alpha receptor blocker, Theratechnologies (THG)113.31. THG113.31 decreases the in vitro contractile activity of mouse, sheep, and human myometrium in response to exogenous PGF2alpha, delays lipopolysaccharide (LPS)-induced preterm birth in mice, and lowers uterine electromyographic activity and delays preterm birth in sheep administered RU486. There have been no observable maternal or fetal side effects with its use.

CONCLUSION

By developing new strategies based on other therapeutic targets, the promise of PGs may once again offer hope for delaying preterm birth.

Leukocyte Density and Proinflammatory Mediator Expression in Regional Human Fetal Membranes and Decidua Before and During Labot at Term

OBJECTIVES

The region of fetal membranes overlying the cervix, known as the zone of altered morphology (ZAM), is considered to be the principle site of membrane inflammatory activity and extracellular matrix remodelling. We wished to quantify the relative contribution of each area of fetal membranes to the inflammatory process of parturition. Specifically, we aimed to quantify and compare (1) leukocyte densities in three regions of fetal membranes and decidua before and during spontaneous labor at term, and (2) mRNA expression of interleukin (IL)-1beta, IL-6, IL-8, cyclo-oxygenase type 1 (COX-1), and COX-2 in three regions of fetal membranes and decidua before and during spontaneous labor at term.

METHODS

Biopsies of fetal membranes and decidua were obtained from pregnant women delivered by cesarean section at term both before and during spontaneous labor (n = 8 both groups). Fetal membranes were sampled from three areas, the ZAM, midzone (MZ), and periplacental (PP) regions. Leukocytes were identified by immunohistochemistry and their density quantified. Inflammatory mediator expression was quantified using TaqMan technology (Applied Biosystems, Foster City, CA).

RESULTS

There was a significantly greater density of leukocytes in (1) the PP region of membranes compared with the ZAM, and (2) the decidua compared with amnion, amniotic connective tissue, and chorion. IL-1beta, IL-6, and IL-8 mRNA expression was significantly greater in all regions following spontaneous labor compared with nonlaboring tissues. There were no regional differences in cytokine expression within the fetal membranes. Choriodecidua expressed significantly more IL-1beta mRNA than amnion. Amnion expressed more COX-2 mRNA than choriodecidua.

CONCLUSIONS

All regions of fetal membranes and decidua contribute to the inflammatory process of human parturition; however, their relative contributions differ in magnitude. Although the ZAM may be specifically important for membrane rupture, it does not appear to play a key or exclusive role in the other inflammatory processes of parturition. When studying fetal membranes, it is relevant to identify and define the area sampled for consistency and comparison with other studies.

The inwardly rectifying K+ channel KIR7.1 controls uterine excitability throughout pregnancy

Abnormal uterine activity in pregnancy causes a range of important clinical disorders, including preterm birth, dysfunctional labour and post-partum haemorrhage. Uterine contractile patterns are controlled by the generation of complex electrical signals at the myometrial smooth muscle plasma membrane. To identify novel targets to treat conditions associated with uterine dysfunction, we undertook a genome-wide screen of potassium channels that are enriched in myometrial smooth muscle. Computational modelling identified Kir7.1 as potentially important in regulating uterine excitability during pregnancy. We demonstrate Kir7.1 current hyper-polarizes uterine myocytes and promotes quiescence during gestation. Labour is associated with a decline, but not loss, of Kir7.1 expression. Knockdown of Kir7.1 by lentiviral expression of miRNA was sufficient to increase uterine contractile force and duration significantly. Conversely, overexpression of Kir7.1 inhibited uterine contractility. Finally, we demonstrate that the Kir7.1 inhibitor VU590 as well as novel derivative compounds induces profound, long-lasting contractions in mouse and human myometrium; the activity of these inhibitors exceeds that of other uterotonic drugs. We conclude Kir7.1 regulates the transition from quiescence to contractions in the pregnant uterus and may be a target for therapies to control uterine contractility.

Umbilical cord prostaglandins in term and preterm parturition

OBJECTIVE

Prostaglandins (PGs) are considered the universal mediators of parturition. Amniotic fluid PGE2 and PGF2α concentrations increase before the onset of spontaneous labor at term, as well as during labor. This study was conducted to determine if the concentrations of umbilical cord PGE2 and PGF2α change with advancing gestational age, spontaneous labor at term, and preterm labor (with and without funisitis).

METHODS

Umbilical cord (UC) tissue samples were obtained from women (N = 158) with singleton pregnancies in the following groups: (1) term deliveries without labor (TNL; n = 20); (2) term deliveries with labor (TIL; n = 20); (3) spontaneous preterm deliveries (sPTD) with (n = 20) and without acute funisitis (n = 20); and (4) preeclampsia without labor (n = 78). The concentrations of PGs were determined in different locations of the UC. PGE2 and PGF2α were measured by specific immunoassays. Non-parametric statistics were used for analysis.

RESULTS

(1) In spontaneous preterm deliveries, the median UC PGE2 concentration was higher in cases with funisitis than in those without funisitis (233.7 pg/µg versus 87.4 pg/µg of total protein, p = 0.001); (2) the median UC PGE2 concentration in sPTD with funisitis was also higher than that obtained from samples who had undergone labor at term (233.7 pg/µg versus 116.1 pg/µg of total protein, p = 0.03); (3) the UC PGE2 and PGF2α concentration increased as a function of advancing gestational age before 36 weeks (PGE2: ρ = 0.59, p < 0.001; PGF2α: ρ = 0.39, p = 0.01), but not after 36 weeks (PGE2: ρ = -0.1, p = 0.5; PGF2α: ρ = -0.2, p = 0.2); (4) the median UC concentrations of PGE2 and PGF2α at term was similar in samples obtained from women with and without labor (PGE2: TNL 133.7 pg/µg versus TIL 116.1 pg/µg of total protein, p = 0.9; PGF2α: TNL 8.4 pg/µg versus TIL 8.1 pg/µg of total protein, p = 0.7); and (5) there was no correlation between UC PG concentration and gestational age at term pregnancy (PGE2: ρ = 0.01, p = 0.9; PGF2α: ρ = 0.07, p = 0.7).

CONCLUSIONS

(1) PGE2 concentrations in the UC are higher in the presence of acute funisitis than in the absence of this lesion; (2) spontaneous labor at term was not associated with a change in the UC concentration of PGE2 and PGF2α; and (3) the UC concentrations of PGE2 and PGF2α increased as a function of gestational age. We propose that UC PGs act as inflammatory mediators generated in the context of fetal systemic inflammation.

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.

Prostaglandin pathway gene expression in human placenta, amnion and choriodecidua is differentially affected by preterm and term labour and by uterine inflammation

Background

Elucidation of the biochemical pathways involved in activation of preterm and term human labour would facilitate the development of effective management and inform judgements regarding the necessity for preterm tocolysis and post-term induction. Prostaglandins act at all stages of human reproduction, and are potentially activators of labour.

Methods

Expression of 15 genes involved in prostaglandin synthesis, transport and degradation was measured by qPCR using tissue samples from human placenta, amnion and choriodecidua at preterm and full-term vaginal and caesarean delivery. Cellular localisation of eight prostaglandin pathway proteins was determined by immunohistochemistry.

Results

Expression of prostaglandin pathway genes was differentially affected by factors including gestational age at delivery, and the incidence and duration of labour. Chorioamnionitis/deciduitis was associated with upregulation of PTGS2 (prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclooxygenase)), along with the inflammatory genes IL8 (interleukin 8), S100A8 (S100 calcium binding protein A8) and TLR2 (toll-like receptor 2), in amnion and choriodecidua, and with downregulation of CBR1 (carbonyl reductase 1) and HPGD (hydroxyprostaglandin dehydrogenase 15-(NAD)) in choriodecidua. Protein localisation differed greatly between the various maternal and fetal cell types.

Conclusions

Preterm and term labour are associated with distinct prostaglandin pathway expression profiles; inflammation provokes specific changes, unrelated to the presence of labour; spontaneous and induced term labour are indistinguishable.

Effect of propofol on prostaglandin E2 production and prostaglandin synthase-2 and cyclooxygenase-2 expressions in amniotic membrane cells

PURPOSE

Surgery during pregnancy can be a cause of preterm labor or birth, possibly resulting from anesthetic agents or direct effects of surgery. This study was aimed to investigate the effect of propofol on uterine contractility by examining prostaglandin E2 (PGE2) production and the expression of PGE synthase 2 (PGES2) and cyclooxygenase-2 (COX-2) in amniotic membrane cells.

METHODS

Amniotic membranes were collected from healthy full-term women who underwent cesarean section at 37-40 weeks of gestation. The amniotic cells were cultured in α-modified-Eagle's medium with 10% fetal bovine serum for 24 h at 5% CO2 in a 37 °C incubator. Then, various doses of propofol (0.01-10 μg/ml) were used for treatment for 3 h. PGE2 concentrations in conditioned media were evaluated using ELISA. PGES2 and COX-2 expression were examined using RT-PCR and Western blot. Cell viability and apoptosis were examined by MTT, ATP assays, and the TUNEL method.

RESULTS

PGE2 production significantly decreased at 0.1 and 1.0 μg/ml propofol concentrations compared to controls. COX-2 and PGES2 mRNA expression was decreased in a dose-dependent manner with a significant difference at 0.1 μg/ml propofol compared to controls. The protein expression of COX-2 showed a similar result to mRNA expression, but protein expression of PGES2 was not significantly decreased. No effect of propofol was found in cell viability.

CONCLUSIONS

This study showed that propofol reduced the production of PGE2 and the expression of COX-2 and PGES2 without affecting cell viability.

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.

Cyclic AMP increases COX-2 expression via mitogen-activated kinase in human myometrial cells

Cyclic AMP (cAMP) is the archetypal smooth muscle relaxant, mediating the effects of many hormones and drugs. However, recently PGI₂, acting via cAMP/PKA, was found to increase contraction-associated protein expression in myometrial cells and to promote oxytocin-driven myometrial contractility. Cyclo-oxygenase-2 (COX-2) is the rate-limiting enzyme in prostaglandin synthesis, which is critical to the onset and progression of human labour. We have investigated the impact of cAMP on myometrial COX-2 expression, synthesis and activity. Three cAMP agonists (8-bromo-cAMP, forskolin and rolipram) increased COX-2 mRNA expression and further studies confirmed that this was associated with COX-2 protein synthesis and activity (increased PGE₂ and PGI₂ in culture supernatant) in primary cultures of human myometrial cells. These effects were neither reproduced by specific agonists nor inhibited by specific inhibitors of known cAMP-effectors (PKA, EPAC and AMPK). We then used shRNA to knockdown the same effectors and another recently described cAMP-effector PDZ-GEF_1-2, without changing the response to cAMP. We found that MAPK activation mediated the cAMP effects on COX-2 expression and that PGE₂ acts through EP-2 to activate MAPK and increase COX-2. These data provide further evidence in support of a dual role for cAMP in the regulation of myometrial function.

Nuclear factor kappa B activation occurs in the amnion prior to labour onset and modulates the expression of numerous labour associated genes

BACKGROUND

Prior to the onset of human labour there is an increase in the synthesis of prostaglandins, cytokines and chemokines in the fetal membranes, particular the amnion. This is associated with activation of the transcription factor nuclear factor kappa B (NFκB). In this study we characterised the level of NFκB activity in amnion epithelial cells as a measure of amnion activation in samples collected from women undergoing caesarean section at 39 weeks gestation prior to the onset of labour.

METHODOLOGY/PRINCIPAL FINDINGS

We found that a proportion of women exhibit low or moderate NFκB activity while other women exhibit high levels of NFκB activity (n = 12). This activation process does not appear to involve classical pathways of NFκB activation but rather is correlated with an increase in nuclear p65-Rel-B dimers. To identify the full range of genes upregulated in association with amnion activation, microarray analysis was performed on carefully characterised non-activated amnion (n = 3) samples and compared to activated samples (n = 3). A total of 919 genes were upregulated in response to amnion activation including numerous inflammatory genes such cyclooxygenase-2 (COX-2, 44-fold), interleukin 8 (IL-8, 6-fold), IL-1 receptor accessory protein (IL-1RAP, 4.5-fold), thrombospondin 1 (TSP-1, 3-fold) and, unexpectedly, oxytocin receptor (OTR, 24-fold). Ingenuity Pathway Analysis of the microarray data reveal the two main gene networks activated concurrently with amnion activation are i) cell death, cancer and morphology and ii) cell cycle, embryonic development and tissue development.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that assessment of amnion NFκB activation is critical for accurate sample classification and subsequent interpretation of data. Collectively, our data suggest amnion activation is largely an inflammatory event that occurs in the amnion epithelial layer as a prelude to the onset of labour.

Labor and inflammation increase the expression of oxytocin receptor in human amnion

The oxytocin/oxytocin receptor (OXT/OXTR) system plays an important role in the regulation of parturition. The amnion is a major source of prostaglandins and inflammatory cytokine synthesis, which increase both before and during labor. Amnion is a noncontractile tissue; therefore, the role played by OXT/OXTR in this tissue will be fundamentally different from the role played in myometrial contractions. In the present study, we demonstrate increased OXTR mRNA and protein concentrations in human amnion epithelial cells associated with the onset of labor. We show that incubation of primary human amnion epithelial cells with IL1B results in a rapid, transient up-regulation of OXTR mRNA expression, which peaks in prelabor samples after 6 h. Incubation of prelabor amnion epithelial cells with OXT results in a marked increase of prostaglandin E(2) synthesis, and we demonstrate that OXT activates the extracellular signal-regulated protein kinase signal transduction pathway to stimulate up-regulation of cyclo-oxygenase 2 in human amnion epithelial cells. The increased ability of human amnion to produce prostaglandins in response to OXT treatment suggests a complementary role for the OXT/OXTR system in the activation of human amnion and the onset of labor.

Expression and regulation of prostaglandin receptors in the human placenta and fetal membranes at term and preterm

Prostaglandins (PGs) play an important role in parturition in many species, including humans. The present study examined the distribution of PG receptor subtypes (EP1-4 and FP) in intrauterine tissues at term and preterm birth. Placentas and fetal membranes were collected from patients at term in labour (n = 12) or not in labour (n = 12). Preterm tissue was collected from three different groups of patients: (1) idiopathic preterm labour (PTL) without chorioamnionitis or betamethasone (BM) treatment (n = 9), (2) idiopathic PTL that received BM with no chorioamnionitis (PTL-BM; n = 9) and (3) pregnancies that were complicated with chorioamnionitis and had no BM (PTL-CHA; n = 6). EP1-4 and FP receptors were localised and levels of expression were determined by western blot analysis. All EP receptors and FP were localised to the amnion, placenta and choriodecidua. Moreover, isolated amnion mesenchymal, amnion epithelial, chorion trophoblast and syncytiotrophoblast cells in primary culture also expressed PG receptors. A significant increase was observed in EP1, EP3 and FP expression in placenta, chorion and amnion with labour. Maternal betamethasone treatment increased EP1, EP3 and FP receptor protein expression and chorioamnionitis decreased expression in all the receptor subtypes. These changes in PG receptors in the fetal membranes are consistent with the development of a feed-forwards cascade mediated through PG action that may contribute to the birth process.

Characterization of the transcriptome of chorioamniotic membranes at the site of rupture in spontaneous labor at term

OBJECTIVE

The purpose of this study was to compare the transcriptome between the site of membrane rupture and the chorioamniotic membranes away from the site of rupture.

STUDY DESIGN

The transcriptome of amnion and chorion (n=20 each) from and distal to the site of rupture from women with spontaneous labor and vaginal delivery at term after spontaneous rupture of membranes was profiled with Illumina HumanHT-12 microarrays. Selected genes were validated with the use of quantitative reverse transcription-polymerase chain reaction.

RESULTS

Six hundred seventy-seven genes were differentially expressed in the chorion between the rupture and nonrupture sites (false discovery rate<0.1; fold change>1.5). Quantitative reverse transcription-polymerase chain reaction confirmed the differential expression in 10 of 14 genes. Enriched biological processes included anatomic structure development, cell adhesion and signal transduction. Extracellular matrix-receptor interaction was the most impacted signaling pathway.

CONCLUSION

The transcriptome of fetal membranes after spontaneous rupture of membranes in term labor is characterized by region- and tissue-specific differential expression of genes that are involved in signature pathways, which include extracellular matrix-receptor interactions.

Experience of the use of nimesulide, a cyclo-oxygenase-2 selective prostaglandin synthesis inhibitor, in the prevention of preterm labour in 44 high-risk cases

We report pregnancy outcome and fetal side effects in women at high risk of second trimester loss and early preterm delivery treated with nimesulide. This was a prospective observational study of 44 women treated with nimesulide from 17 to 32 weeks. All women underwent weekly ultrasound scans for AFI, Doppler studies of the ductus arteriosus and transvaginal assessment of cervical length. Outcome data were collected. Oligohydramnios occurred in 54% of cases; this returned to normal in all cases on discontinuation of treatment. There were no cases of constriction of the ductus arteriosus. Thirty-nine women took home a live baby. The mean gestation at delivery was 33 weeks and 1 day and the mean birth weight was 2105 g. Nimesulide appeared to have a significant benefit in women at high risk of preterm delivery with no long-term harmful effects on the fetus if monitored closely with an intensive ultrasound scanning regimen. Randomised placebo controlled trials are required to assess fully the benefit of COX-2 selective and specific prostaglandin synthesis inhibitors.

Nuclear factor-kappa B regulates inducible prostaglandin E synthase expression in human amnion mesenchymal cells

The human amnion is a major intrauterine source of prostaglandin (PG) E(2), a potent mediator of uterine contractions and cervical ripening. During parturition, inflammatory cytokines promote PGE(2) production through increased prostaglandin-endoperoxide synthase-2 (PTGS2, also known as cyclooxygenase-2) expression. This is mediated, in part, through activation of the transcription factor nuclear factor kappa B (NFkappaB). Prostaglandin E synthase (PTGES, also known as microsomal PGE synthase-1) acts downstream of PTGS2 and is inducibly expressed in most systems. We hypothesized that NFkappaB might regulate cytokine-induced PTGES expression in amnion cells. With amnion mesenchymal cells, we found that proinflammatory cytokines coordinately upregulated PTGS2 and PTGES mRNA expression. In parallel, increased expression of the PTGS2 and PTGES proteins was observed. In comparison, the expression of two other PGE synthases (PTGES2 and PTGES3) was unmodified. PTGES induction was blocked both in the presence of pharmacological NFkappaB inhibitors and following adenovirus-mediated overexpression of a dominant-negative NFkappaB pathway protein. In cells transiently transfected with a luciferase reporter bearing a portion (-597/+33) of the human PTGES gene promoter, interleukin-1beta (IL1B) produced a moderate increase in luciferase activity; this effect was abrogated in the presence of an indirect NFkappaB inhibitor (MG-132). Finally, a kappaB-like regulatory element was identified that, when mutated, markedly attenuated IL1B-responsive PTGES promoter activity. In conclusion, our results support a role for NFkappaB in cytokine-induced PTGES expression in amnion mesenchymal cells in vitro. By coordinately regulating PTGS2 and PTGES, NFkappaB may contribute to an inducible PGE(2) biosynthesis pathway during human parturition.

Pharmacological prevention of prematurity

The acute treatment of premature labour is successful for delaying delivery for short periods of time. Acute tocolysis does not have a significant impact on perinatal outcome. This is likely to be because the process leading to labour occurs over a longer timeframe and therefore therapies instigated as preventative measures are more likely to be successful in delaying delivery. Identification of women at risk of preterm birth is essential to ensure therapies are targeted appropriately. Risk assessments for prediction include previous obstetric history, previous episode of threatened preterm labour, fetal fibronectin status and cervical length. Several groups of pharmacological agents have been studied for the prophylactic treatment of preterm labour. There is no evidence to support the use of tocolytics such as beta-mimetics and oxytocin receptor antagonists. Current studies of calcium channel blockers are too small to draw final conclusions. Non-steroidal anti-inflammatory drugs are associated with side effects on the fetal renal system and ductus arteriosus, making them suitable only for long term use in pregnancy with close ultrasound surveillance. Antibiotics used early in pregnancy in women with abnormal vaginal flora may reduce the risk of preterm birth; however, in women with other risk factors for preterm birth, metronidazole may be associated with an increased risk. The use of progesterone in women with a history of very early preterm labour is likely to be beneficial for preventing preterm labour.

Preterm labour. Biochemical and endocrinological preparation for parturition

Preterm delivery is a common obstetric problem occurring in about 1 in 10 of all births. Preterm babies have a high risk of morbidity and mortality. Such births account for 75% of all major neonatal problems. At the other end of the spectrum, prolonged pregnancy is also a subject of concern because it too is associated with increased fetal morbidity and mortality. Despite extensive research, the mechanisms that control the length of human pregnancy and signal the onset of labour have not been fully determined. This chapter will discuss basic principles in the biology of parturition and the regulation of contraction-associated proteins including the oxytocin receptor. The major pathways regulating contractions and the transcriptional regulation of the main genes that are known to be involved in the onset of labour and parturition will be examined. Some new potentially therapeutic strategies for the biochemical management of preterm labour will be discussed.

Hypothetical role of prostaglandins in the onset of preterm labor after fetal surgery

Preterm labor is one of the most important factors limiting the advancement of fetal surgery programs. While prostaglandins (PGs) have long been indicated as the key factor in the initiation of labor in humans, there is significant evidence showing that the chorionic membrane acts as a powerful barrier between the decidua/myometrium and amniotic PGs during normal pregnancy. After either open or endoscopic fetal surgery the imperfect, non-hermetical closure of the chorion permits leakage of PGs from the amnionic sac, allowing them to reach the decidua and myometrium. The surgical wound in the chorionic barrier could be the major factor involved in preterm labor and delivery after human fetal surgery.

Myometrial prostaglandin E2 synthetic enzyme mRNA expression: spatial and temporal variations with pregnancy and labour

We have investigated the hypothesis that the expression of the enzymes involved in PGE(2) synthesis in the human uterus is co-ordinated. We have studied (i) the mRNA expression of the enzymes involved in PGE(2) synthesis [phospholipases (cPLA(2) and sPLA(2)), prostaglandin H synthase (PGHS)-2 and PG E synthases (PGES-1 and -2)] and their relationship to the expression of inflammatory cytokines in samples of myometrium obtained from pregnant women undergoing caesarean section (LSCS) either before or after the onset of labour at or before term; and (ii) the effect of IL-1beta, IL-6, TNF-alpha, PGE(2) and stretch on PGE(2) enzyme mRNA expression. We found that cPLA(2), sPLA(2) and PGHS-2 mRNA expression were greater in labour samples; cPLA(2), sPLA(2), PGHS-2, PGES-1 and -2 mRNA expression were greater in lower- than upper-segment samples; and there was no effect of gestational age. PGHS-2 mRNA levels correlated with those of PGES-1, cPLA(2), IL-1beta and IL-8; PGES-1 mRNA levels correlated with those of IL-1beta, IL-8 and cPLA(2). In primary cultures of uterine myocytes, cPLA(2) mRNA expression was increased by IL-1beta and IL-6; PGHS-2 mRNA expression was increased by IL-1beta, PGE(2) and stretch; and PGES-1 mRNA expression was increased by IL-1beta only. These data show that labour is associated with increased expression of the enzymes involved in PGE(2) synthesis and their expression is greater in the lower uterine segment. The presence of associations between the levels of PGE(2) enzyme mRNA expression and the effects of IL-1beta suggest that their expression is co-ordinated and that IL-1beta is the responsible factor.

Constriction of the ductus arteriosus by selective inhibition of cyclooxygenase-1 and -2 in near-term and preterm fetal rats

We studied the transplacental ductal constrictive effects of a selective cyclooxygenase (COX)-1 inhibitor (SC560), six selective COX-2 inhibitors including rofecoxib, and a non-selective COX inhibitor (indomethacin). Each drug was administered to the pregnant rats, and fetal ductus arteriosus (DA) was studied with a whole-body freezing method. The inner diameter ratio of the DA to the main pulmonary artery (DA/PA) was 1.02+/-0.03 (mean+/-S.E.M.) in controls. Every drug constricted the DA dose-dependently. In preterm rats on the 19th day of gestation, 10mg/kg of SC560, rofecoxib and indomethacin caused ductal constriction, with DA/PA reduced to 0.76+/-0.02, 0.80+/-0.03 and 0.75+/-0.02, respectively. In near-term on the 21st day, 10mg/kg of them caused ductal constriction, with DA/PA to 0.74+/-0.04, 0.26+/-0.02 and 0.33+/-0.05. In conclusion, both COX-1 and COX-2 selective inhibitors constrict fetal DA. They are not better alternatives for the fetus than non-selective COX inhibitors for tocolysis.

Increased susceptibility of ethanol-treated gastric mucosa to naproxen and its inhibition by DA-9601, an Artemisia asiatica extract

AIM

To examine the effect of DA-9601, a new gastroprotective agent, on the vulnerability of ethanol-treated rat's stomach to naproxen (NAP).

METHODS

Male Sprague-Dawley rats were pretreated with 1 mL of 50% ethanol twice a day for 5 d and then NAP (50 mg/kg) was administered. DA-9601 was administered 1 h before NAP. Four hours after NAP, the rats were killed to examine gross injury index (mm2), histologic change and to determine mucosal levels of malondialdehyde (MDA), prostaglandin E2 (PGE2), glutathione (GSH) and myeloperoxidase (MPO).

RESULTS

Pretreatment of ethanol significantly increased NAP-induced gastric lesions, as well as an increase in MDA and MPO. On the contrary, mucosal PGE2 and GSH contents were decreased dramatically by ethanol pretreatment, which were aggravated by NAP. DA-9601 significantly reduced NAP-induced gastric injury grossly and microscopically, regardless of pretreatment with ethanol. DA-9601 preserved, or rather, increased mucosal PGE2 and GSH in NAP-treated rats (P<0.05), with reduction in mucosal MDA and MPO levels.

CONCLUSION

These results suggest that repeated alcohol consumption renders gastric mucosa more susceptible to NSAIDs though, at least in part, reduction of endogenous cytoprotectants including PGE2 and GSH, and increase in MPO activation, and that DA-9601, a new gastroprotectant, can reduce the increased vulnerability of ethanol consumers to NSAIDs-induced gastric damage via the mechanism in which PGE2 and GSH are involved.

The role of CCAAT/enhancer-binding protein beta in the transcriptional regulation of COX-2 in human amnion

Human labour is associated with increased prostaglandin synthesis within the uterus by the action of the inducible type-2 cyclo-oxygenase enzyme (COX-2). A major source of prostaglandin is the fetal membranes, in particular the amnion, in which expression of COX-2 increases in late pregnancy and with labour. The COX-2 gene promoter contains several putative transcription factor binding sites including those for NF-kappaB, AP-1 and C/EBP and therefore has the features of a rapid response gene. We have previously shown that, in amnion, the NF-kappaB DNA-binding sites in the COX-2 promoter are essential for gene expression and that there is an increase in NF-kappaB activity in amnion with the onset of labour. In this study, we demonstrate that in primary human amnion cells, CCAAT/enhancer-binding protein beta (C/EBPbeta) DNA-binding sites are crucial for the function of the COX-2 gene promoter. Three potential C/EBPbeta DNA-binding sites were identified within the COX-2 promoter which were shown to bind to C/EBPbeta but not to C/EBPalpha, C/EBPdelta, CREB (cAMP responsive element modulator) or CREM. Luciferase reporter constructs with site-directed mutagenesis of the three C/EBPbeta sites in the COX-2 promoter showed reduced expression of luciferase in transient transfection studies. However, comparison of C/EBPbeta protein levels and their DNA-binding activity from cells obtained before and after labour showed no significant differences. This suggests that although C/EBPbeta plays an essential constitutive role in the expression of COX-2, C/EBPbeta may not be directly involved in its regulation in association with human labour.

Novel targeting of cyclooxygenase-2 (COX-2) pre-mRNA using antisense morpholino oligonucleotides directed to the 3' acceptor and 5' donor splice sites of exon 4: suppression of COX-2 activity in human amnion-derived WISH and myometrial cells

Increased expression of cyclooxygenase-2 (COX-2) has been implicated in the onset of both term and preterm labor. In this context, both selective and nonselective COX-2 inhibitors have been used in clinical trials to determine their efficacy in delaying preterm labor. However, recent evidence indicates that these tocolytics may have potentially adverse fetal and maternal side effects. Therefore, the development of more specific and nontoxic agents to inhibit COX-2 needs to be considered. We have evaluated whether antisense morpholino oligonucleotides have therapeutic potential in inhibiting COX-2 by specifically targeting both the 3' and 5' acceptor and donor sites of exon 4 of COX-2's pre-mRNA sequence. Confocal microscopy on "live" cells illustrated high levels of penetrance of antisense morpholino oligonucleotides using the Endo-Porter formula (Gene-Tools, LLC, Philomath, OR), with delivery efficiencies of 82 and 78%, respectively, in amnion-derived WISH and myometrial cells. Substantial inhibition by the morpholino oligonucleotides of COX-2 expression, induced by lipopolysaccharide administration, was observed at both the mRNA and protein levels. Loss of enzymic activity of COX-2 was confirmed using a sensitive COX enzyme activity assay, which reflects the rate of conversion of arachidonic acid to prostaglandin H2. Our results indicate that antisense morpholino oligonucleotides significantly inhibit expression and activity of this enzyme in in vitro cultures of amnion-WISH and myometrial cells. The potential thus exists that a similar approach can be mimicked in vivo to produce a highly specific and nontoxic strategy to inhibit COX-2 activity with its subsequent effects on the better management of preterm labor and other inflammatory conditions.

The role of nuclear factor kappa B in human labour

Preterm birth remains the leading cause of perinatal mortality and morbidity, largely as a result of a poor understanding of the precise mechanisms controlling labour onset in humans. Inflammation has long been recognised as a key feature of both preterm and term labour, with an influx of inflammatory cells into the uterus and elevated levels of pro-inflammatory cytokines observed during parturition. Nuclear factor kappa B (NF-κB) is a transcription factor family classically associated with inflammation. Accumulating evidence points to a role for NF-κB in the physiology and pathophysiology of labour. NF-κB activity increases with labour onset and is central to multiple prolabour pathways. Premature or aberrant activation of NF-κB may thus contribute to preterm labour. The current understanding of NF-κB in the context of human labour is discussed here.

TOCOX--a randomised, double-blind, placebo-controlled trial of rofecoxib (a COX-2-specific prostaglandin inhibitor) for the prevention of preterm delivery in women at high risk

OBJECTIVE

To assess the safety and efficacy of the long term prophylactic use of rofecoxib (a COX-2-specific inhibitor) in women at high risk of preterm delivery.

DESIGN

A randomised, double-blind, placebo-controlled trial.

SETTING

Queen Charlotte's and Chelsea Hospital, London and Guys and St Thomas' Hospitals, London.

POPULATION

Ninety-eight singleton pregnancies at high risk of preterm labour.

METHODS

Treatment from 16 to 32 weeks. Weekly ultrasound surveillance.

MAIN OUTCOME MEASURES

Fetal renal function and ductus arteriosus blood flow changes. Preterm delivery rates and neonatal outcome.

RESULTS

Rofecoxib caused a reduction in hourly fetal urine production rates (-34%, 95% CI -13 to -50%, P = 0.004) and amniotic fluid index (-2.2, 95% CI -3.2 to -1.2, P < 0.001). This effect did not increase with time on treatment and reversed in all cases on discontinuation of treatment. Rofecoxib had an effect on the ductus arteriosus, increasing maximum systolic velocity (0.1 m/s, 95% CI 0.03-0.16, P = 0.02) and minimum diastolic velocity (0.007 m/s, 95% CI 0.0007-0.013, P= 0.03). This effect increased with time on treatment but was reversed with discontinuation of treatment and had no long term clinical sequelae. There was no difference in preterm delivery rates <30 weeks (28% on placebo vs 33% on rofecoxib, Mantel-Haensel [M-H]-adjusted risk 1.11, 95% CI 0.67-1.87). There were more deliveries <37 weeks in those on rofecoxib (40%vs 67%, M-H-adjusted risk 1.59, 95% CI 1.09-2.32). Rates of preterm prelabour rupture of membranes (PPROM) were higher in those on rofecoxib (RR 2.5, 95% CI 1.3-4.7).

CONCLUSION

Rofecoxib has a significant but reversible effect on fetal renal function and the ductus arteriosus. It does not reduce the incidence of early preterm delivery <30 weeks and is associated with an increased risk of delivery before 37 weeks in women at high risk.

Placental expression of enzymes regulating prostaglandin synthesis and degradation

OBJECTIVE

The purpose of this study was to characterize placental expression of the prostaglandin synthase enzymes cyclooxygenase (COX) -1 and -2 and prostaglandin dehydrogenase (PGDH, a degrading enzyme).

STUDY DESIGN

Forty-one women between 20 and 37 weeks' gestation and 39 matched term controls with either spontaneous labor or premature rupture of membranes were enrolled in a prospective case-control study. The relative amounts of placental RNAs at delivery were determined using real-time polymerase chain reaction (PCR).

RESULTS

Placental COX-1 RNA decreased with advancing gestational age at delivery (R(2) = 0.13, P = .001), and increased by 43% when chorioamnionitis was present (P = .006). Among patients presenting at term, oxytocin use was associated with 30% lower expression of COX-1 (P = .01). COX-2 and PGDH were not associated with these variables.

CONCLUSION

Placental COX-1 RNA at delivery decreases with advancing gestational age and with oxytocin use at term. Thus, expression of placental COX-1 is not constitutive. Placental expression of COX-2 and PGDH do not correlate with gestational age, chorioamnionitis, or oxytocin use.

Effect of maternal administration of selective cyclooxygenase (COX)-2 inhibitors on renal size, growth factors, proteinases, and COX-2 secretion in the fetal rabbit

BACKGROUND

Selective cyclooxygenase (COX)-2 inhibitors are currently being considered for management of preterm labor. COX-2 is an important regulator of fetal renal growth and function. Its inhibition may lead to congenital oligonephropathy.

OBJECTIVES

We investigated whether maternal administration of a selective COX-2 inhibitor would adversely affect fetal renal growth.

METHODS

Three groups of timed pregnant rabbits at 13 days gestation were examined. Group 1 received oral celecoxib (30 mg/kg/day) from 13 to 20 days gestation (Cel-A); group 2 received celecoxib from 13 to 28 days gestation (Cel-B), and group 3 received equivalent volumes of the vehicle from 13 to 28 days gestation. The fetuses were delivered by cesarean section at 29 days gestation. The kidneys were weighed and analyzed for vascular endothelial growth factor (VEGF) and its soluble receptors, matrix metalloproteinase (MMP)-2 and -9, tissue inhibitor of metalloproteinase (TIMP)-1 and -2, COX-2, and total cellular protein levels. Sections from the cortex and medulla were assessed histologically.

RESULTS

Fetal kidney size was unaffected. VEGF levels were elevated in the Cel-B group. Soluble VEGF receptors, MMP-2, TIMP-1 and COX-2 levels remained unchanged. MMP-9 levels were suppressed in both treated groups, which resulted in significantly lower MMP-9/TIMP-1 ratios. Although TIMP-2 secretion was enhanced in the Cel-B group, MMP-2/TIMP-2 ratios were unaffected. No significant histological changes were detected.

CONCLUSIONS

We conclude that maternal administration of therapeutic doses of celecoxib does not adversely affect fetal renal growth. MMP-9 is increased in various nephropathies, but may also have protective effects therefore its suppression by COX-2 inhibitors needs further study.

Molecular and biochemical mechanisms of preterm labour

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

Labour is associated with increased expression of type-IIA secretory phospholipase A2 but not type-IV cytosolic phospholipase A2 in human myometrium

Human labour is associated with increased prostaglandin synthesis within the uterus. The aim of this study was to examine the expression of the type-IV cytosolic phospholipase A2 (cPLA2-IV) and the type IIA secretory phospholipase A2 (sPLA2-IIA) in myometrium in association with labour onset at term and preterm deliveries. These enzymes are important for the release of the prostaglandin precursor, arachidonic acid, from phospholipid membrane stores. RT-PCR was used to determine differences in gene expression between non-labour and labour groups. Expression of sPLA2-IIA in human myometrium was significantly increased with pregnancy, and with labour, both at term and preterm. Expression of cPLA2-IV in myometrium was not significantly altered with respect to pregnancy or labour. Immunohistochemical analysis demonstrated differences in the spatial localization of cPLA2-IV and sPLA2-IIA protein in upper and lower segment myometrium. cPLA2-IV was predominantly in vascular endothelial cells, while sPLA2-IIA was observed in vascular, endothelial and smooth muscle cells. In addition, sPLA2-IIA showed a distinct nuclear or perinuclear localization in myometrial smooth muscle cells of the lower segment. We postulate that the increased expression of sPLA2-IIA rather than cPLA2-IV in the myometrium may play a role in the onset and/or maintenance of human parturition.

Comparison of effects of cyclooxygenase inhibitors on myometrial contraction and constriction of ductus arteriosus in rats

The aim of this study was to compare the tocolytic effect of a selective cyclooxygenase-2 inhibitor, DFU (5,5-dimethyl-3(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone), indomethacin and nimesulide on myometrial strips isolated from rats in both lipopolysaccharide-induced preterm labour and term labour. We also compared the constrictor effects of DFU and indomethacin on the fetal ductus arteriosus. Myometrial strips were obtained from preterm and term labour Wistar albino rats and were mounted in organ baths for the recording of isometric tension. DFU, nimesulide and indomethacin significantly inhibited KCl-, oxytocin-, prostaglandin E(2)- and prostaglandin F(2 alpha)-stimulated contractions of myometrial strips isolated from rats in preterm and term labour. The E(max) value of indomethacin was significantly lower than those for DFU and nimesulide (P<0.05), with no change-log (10) EC(50) values. There was no significant difference between in -log (10) EC(50) and E(max) values of DFU and nimesulide for any of the tissues (P>0.05). In addition, there was no significant difference between -log (10) EC(50) and E(max) values for each of these three agents in myometrial tissues isolated from rats in preterm and term labour (P>0.05). Fetal ductus arteriosus was significantly constricted by DFU (10 or 100 mg/kg) in preterm and term rats, although DFU (10 or 100 mg/kg)-induced constriction ratios were significantly lower than those for indomethacin (P<0.05). These data demonstrate that DFU, a specific cyclooxygenase-2 inhibitor, could be considered as a new therapeutic agent for preterm labour. However, careful attention should be given to constriction of the fetal ductus arteriosus.

An EP4 receptor agonist prevents indomethacin-induced closure of rat ductus arteriosus in vivo

Indomethacin exerts a strong tocolytic effect by suppressing uterine contractions mediated by prostaglandins. However, indomethacin also induces in utero closure of fetal ductus arteriosus (DA), leading to serious neonatal consequences. Using rats, we tested the effect of an agonist for a subtype of prostaglandin E2 receptor (EP4), ONO-AE1-437 and its prodrug ONO-4819, as a DA dilator during indomethacin treatment. In vitro, ONO-AE1-437 exhibited a potent dilatory effect on DA against O(2)- and indomethacin-induced contractions in a concentration-dependent manner. In vivo, rat dams were given indomethacin (10 mg/kg, p.o.) alone or with ONO-4819 (0.3 micrograms/kg/h, s.c.) on d 21 of gestation and pups were delivered 4 h later through cesarean section to evaluate the ratio of diameter of DA to that of pulmonary artery. Pups from dams with no drug had DA/PA ratio of 0.9 +/- 0.05, whereas those from dams with indomethacin alone had a decreased ratio of 0.2 +/- 0.03. When ONO-4819 was co-administered to the dams, the ratio recovered significantly to 0.7 +/- 0.06. The administration of ONO-4819 to the dams did not induce any increase in the uterine activity. These results suggest that administration of an EP4 agonist in addition to indomethacin might prevent adverse reactions of indomethacin on fetal DA without restricting its tocolytic effects.

Rofecoxib Versus Magnesium Sulfate to Arrest Preterm Labor: A Randomized Trial

OBJECTIVE

To compare oral rofecoxib with intravenous magnesium sulfate as a tocolytic.

METHODS

This was a randomized study of patients who were between 22 and 34 weeks of gestation with preterm labor. Patients were randomly assigned to receive either daily oral rofecoxib (50 mg) or intravenous magnesium sulfate for a maximum of 48 hours. Outcome variables included delay of delivery for 48 hours and the incidence of side effects. Data were analyzed by using the Student t test, Mann-Whitney U test, chi(2) test, and repeated-measures analysis of variance. Sample size calculations were based on previous studies of tocolytic efficacy.

RESULTS

Two hundred fourteen patients were randomly assigned (105 received rofecoxib and 109 received magnesium sulfate). Delivery was delayed for 48 hours in 95 (90.4%) and 96 (88%) of the patients in the rofecoxib and magnesium sulfate groups, respectively (relative risk 0.97; 95% confidence interval 0.89, 1.06). To show a statistically significant benefit in delay of delivery past 48 hours, a total of 2,686 patients would be required in each group. There was no difference between the groups over the course of the study in cervical dilatation, amniotic fluid index, or cervical length by vaginal ultrasonography. The median hospital days on the original admission were also similar at 2 for both groups (P =.10). There was a higher reported incidence of maternal side effects in the magnesium sulfate group (relative risk 1.81; 95% confidence interval 1.07, 3.06). There was no difference in the incidence of neonatal side effects.

CONCLUSION

There was no difference between oral rofecoxib and intravenous magnesium sulfate in arresting preterm labor.

Transcriptional regulation of genes for enzymes of the prostaglandin biosynthetic pathway

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

Topographical specialization of prostaglandin function in late pregnancy and at parturition in the baboon

Prostaglandins play key central roles in both the maintenance of pregnancy and parturition. Extensive data exist from studies in human pregnancy but the needs of clinical management and the inability to conduct carefully controlled perturbation studies in human pregnancy make it necessary to obtain information from nonhuman primate models. We have used the pregnant baboon to evaluate production, metabolism and receptor mediated actions of prostaglandins in late gestation to demonstrate that expression of key genes is tightly controlled in enzyme-specific, gestation age-specific, tissue-specific and uterine region-specific fashion.

Changes of lipocalin-type prostaglandin D synthase level during pregnancy

AIM

Prostaglandin D (PGD), synthesized by lipocalin-type prostaglandin D synthase (L-PGDS), has marked effects on a number of biological processes, including the prevention of platelet aggregation and the relaxation of vascular smooth muscle. The aim of the study presented here was to examine the significance of L-PGDS in human pregnancy.

METHODS

We measured the concentration of plasma L-PGDS in pregnant and non-pregnant women, and the concentration of L-PGDS in the umbilical cord blood, amniotic fluid and urine of newborns by enzyme-linked immunoabsorbent assay. To determine the localization of L-PGDS, we performed immunohistochemical analysis. To evaluate the usefulness of diagnosis of rupture of membranes (ROM), we determined the concentration of L-PGDS in cervicovaginal secretions.

RESULTS

Pregnant women and non-pregnant women had similar L-PGDS concentrations (0.57 +/- 0.13 microg/mL vs 0.53 +/- 0.07 microg/mL). Umbilical cord blood, amniotic fluid and newborn urine contained higher L-PGDS concentrations (1.87 +/- 0.73 microg/mL, 2.62 +/- 0.86 microg/mL, 6.31 +/- 4.62 microg/mL, respectively) than maternal blood. The concentration of L-PGDS in amniotic fluid from 19 weeks onward was significantly greater than that at 15-18 weeks (3.201 +/- 0.384 microg/mL, n = 6 vs 1.735 +/- 0.477 microg/mL, n = 4; P < 0.05). Immunohistochemistry revealed that the amniotic cells of the placenta expressed L-PGDS. The sources of L-PGDS in amniotic fluid are fetus urine and amniotic cells. The concentration of L-PGDS in cervicovaginal secretions with rupture of membrane (ROM) were significantly higher than those without ROM.

CONCLUSION

The measurement of L-PGDS in cervicovaginal fluid was useful in the detection of ROM during pregnancy.