Delay of preterm birth in sheep by THG113.31, a prostaglandin F2alpha receptor antagonist

Effect of maternal oxytocin on umbilical venous and arterial blood flows during physiological-based cord clamping in preterm lambs

BACKGROUND

Delayed umbilical cord clamping (UCC) after birth is thought to cause placental to infant blood transfusion, but the mechanisms are unknown. It has been suggested that uterine contractions force blood out of the placenta and into the infant during delayed cord clamping. We have investigated the effect of uterine contractions, induced by maternal oxytocin administration, on umbilical artery (UA) and venous (UV) blood flows before and after ventilation onset to determine whether uterine contractions cause placental transfusion in preterm lambs.

METHODS AND FINDINGS

At ~128 days of gestation, UA and UV blood flows, pulmonary arterial blood flow (PBF) and carotid arterial (CA) pressures and blood flows were measured in three groups of fetal sheep during delayed UCC; maternal oxytocin following mifepristone, mifepristone alone, and saline controls. Each successive uterine contraction significantly (p<0.05) decreased UV (26.2±6.0 to 14.1±4.5 mL.min-1.kg-1) and UA (41.2±6.3 to 20.7 ± 4.0 mL.min-1.kg-1) flows and increased CA pressure and flow (47.1±3.4 to 52.8±3.5 mmHg and 29.4±2.6 to 37.3±3.4 mL.min-1.kg-1). These flows and pressures were partially restored between contractions, but did not return to pre-oxytocin administration levels. Ventilation onset during DCC increased the effects of uterine contractions on UA and UV flows, with retrograde UA flow (away from the placenta) commonly occurring during diastole.

CONCLUSIONS

We found no evidence that amplification of uterine contractions with oxytocin increase placental transfusion during DCC. Instead they decreased both UA and UV flow and caused a net loss of blood from the lamb. Uterine contractions did, however, have significant cardiovascular effects and reduced systemic and cerebral oxygenation.

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.

Prostaglandin FP receptor antagonists: discovery, pharmacological characterization and therapeutic utility

In contrast to the availability of potent and selective antagonists of several prostaglandin receptor types (including DP₁ , DP₂ , EP and TP receptors), there has been a paucity of well-characterized, selective FP receptor antagonists. The earliest ones included dimethyl amide and dimethyl amine derivatives of PGF_2α , but these have failed to gain prominence. The fluorinated PGF_2α analogues, AL-8810 and AL-3138, were subsequently discovered as competitive and non-competitive FP receptor antagonists respectively. Non-prostanoid structures, such as the thiazolidinone AS604872, the D-amino acid-based oligopeptide PDC31 and its peptidomimic analogue PDC113.824 came next, but the latter two are allosteric inhibitors of FP receptor signalling. AL-8810 has a sub-micromolar in vitro potency and ≥2 log unit selectivity against most other PG receptors when tested in several cell- and tissue-based functional assays. Additionally, AL-8810 has demonstrated therapeutic efficacy as an FP receptor antagonist in animal models of stroke, traumatic brain injury, multiple sclerosis, allodynia and endometriosis. Consequently, it appears that AL-8810 has become the FP receptor antagonist of choice. LINKED ARTICLES: This article is part of a themed section on Eicosanoids 35 years from the 1982 Nobel: where are we now? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.8/issuetoc.

Pharmacokinetics, safety and tolerability of OBE022, a selective prostaglandin F2α receptor antagonist tocolytic: A first-in-human trial in healthy postmenopausal women

AIMS

Preterm birth remains a significant risk for later disability. The selective inhibition of the prostaglandin F_2α receptor has significant advantages for a tocolytic. The prodrug OBE022 and its metabolite OBE002 are novel prostaglandin F_2α receptor antagonists under development for treating preterm labour.

METHODS

We performed a prospective, first in human, Phase I, dose escalation, placebo-controlled, randomized trial at a clinical trial site in the UK. Placebo, single ascending doses of 10, 30, 100, 300, 1000 or 1300 mg, and multiple ascending doses over 7 days of 100, 300 or 1000 mg day^-1 ; were administered to postmenopausal female volunteers. Food interaction was additionally evaluated.

RESULTS

Subjects tolerated OBE022 well at all single and multiple doses. No clinically relevant changes in safety parameters were shown and there were no serious adverse events. Observations showed that prodrug OBE022 was readily absorbed and rapidly converted into its equally active stable metabolite OBE002. The plasma level of OBE002 rose with increasing doses, reaching exposure levels that were anticipated to be clinically relevant within 1 h following administration. There was no clinically significant food interaction, with peak exposures reduced to 80% and area under the curve staying bioequivalent. The mean half-life of OBE002 ranged between 8 and 11 h following administration of a single dose and 22-29 h after multiple doses.

CONCLUSIONS

Administration of OBE022 was safe and had favourable pharmacokinetic characteristics and no clinically relevant interaction with food. Our results allow further investigation of OBE022 in preterm labour patients.

How do Spondias mombin L (Anacardiaceae) leaves extract increase uterine smooth muscle contractions to facilitate child birth in parturient women?

Background

Spondias mombin L. (Anacardiaceae) leaves were used in Togolese folk to treat dystocia, expel placenta and manage post-partum hemorrhage during child birth.

Objectives

This study aimed to establish how the extract of S. mombin leaves increase uterine smooth muscle contractions relevant to its traditional use to facilitate child birth.

Methods

Tests were performed on uterus muscle strips from Sprague-Dawley rats. Central portion of uterine horns were dissected, cleaned of surrounding fat and loose connective tissue, and cut longitudinally into strips which were placed in the organ bath for isometric tension record in presence of different substances.

Results

S. mombin leaves extract increased uterine spontaneous contractions. This effect was reduced by indomethacin (2 × 10-6 M), yohimbine (2 × 10-6 M) and 2-aminoethoxydiphenyl borate (2-APB) (5 × 10-5 M), but not by atropine (3.45 × 10-8 M) and cholesterol (2.5 mg/ml).

Conclusion

The pharmacological justification for the traditional use of S. mombin leaves to treat dystocia and expel placenta was that its hydro-ethanolic extract induced prostaglandins release, α2-adrenoceptors stimulation, calcium release from internal stores and lifted inhibitory effect of cholesterol on uterine contractions in order to increase uterine smooth muscle contractions.

OBE022, an Oral and Selective Prostaglandin F2α Receptor Antagonist as an Effective and Safe Modality for the Treatment of Preterm Labor

Preterm birth is the major challenge in obstetrics, affecting ∼10% of pregnancies. Pan-prostaglandin synthesis inhibitors [nonsteroidal anti-inflammatory drugs (NSAIDs)] prevent preterm labor and prolong pregnancy but raise concerns about fetal renal and cardiovascular safety. We conducted preclinical studies examining the tocolytic effect and fetal safety of the oral prodrug candidate OBE022 [(S)-2-amino-3-methyl-butyric acid (S)-3-{[(S)-3-(biphenyl-4-sulfonyl)-thiazolidine-2-carbonyl]-amino}-3-(4-fluoro-phenyl)-propyl ester] and its parent OBE002 [(S)-3-(biphenyl-4-sulfonyl)-thiazolidine-2-carboxylic acid [(S)-1-(4-fluoro-phenyl)-3-hydroxy-propyl]-amide], both potent and highly selective antagonist of the contractile prostaglandin F_2α (PGF_2α ) receptor (FP). Efficacy of OBE022 and OBE002, alone and in combination with other tocolytics, was assessed in human tissues and pregnant animal models for inhibition of uterine contraction and delay of parturition. Selective safety of OBE022 and/or OBE002, compared with NSAID indomethacin, was assessed on renal function, closure of the ductus arteriosus, and inhibition of platelet aggregation. In in vitro studies, OBE002 inhibited spontaneous, oxytocin- and PGF_2α -induced human myometrial contractions alone and was more effective in combination with atosiban or nifedipine. In in vivo studies, OBE022 and OBE002 reduced spontaneous contractions in near-term pregnant rats. In pregnant mice, OBE022 delayed RU486 [(8S,11R,13S,14S,17S)-11-[4-(dimethylamino)phenyl]-17-hydroxy-13-methyl-17-prop-1-ynyl-1,2,6,7,8,11,12,14,15,16-decahydrocyclopenta[a]phenanthren-3-one] -induced parturition and exerted synergistic effects in combination with nifedipine. OBE022 and/or OBE002 did not show the fetal side effects of ductus arteriosus constriction, impairment of kidney function, or inhibition of platelet aggregation observed with indomethacin. Orally active OBE022 and OBE002 exhibits potent tocolytic effects on human tissues ex vivo and animal models in vivo without causing the adverse fetal side effects seen with indomethacin. Selectively targeting the FP receptor in combination with existing tocolytics may be an effective strategy for preventing or delaying preterm delivery.

Gestation Related Gene Expression of the Endocannabinoid Pathway in Rat Placenta

Mammalian placentation is a vital facet of the development of a healthy and viable offspring. Throughout gestation the placenta changes to accommodate, provide for, and meet the demands of a growing fetus. Gestational gene expression is a crucial part of placenta development. The endocannabinoid pathway is activated in the placenta and decidual tissues throughout pregnancy and aberrant endocannabinoid signaling during the period of placental development has been associated with pregnancy disorders. In this study, the gene expression of eight endocannabinoid system enzymes was investigated throughout gestation. Rat placentae were obtained at E14.25, E15.25, E17.25, and E20, RNA was extracted, and microarray was performed. Gene expression of enzymes Faah, Mgll, Plcd4, Pld1, Nat1, Daglα, and Ptgs2 was studied (cohort 1, microarray). Biological replication of the results was performed by qPCR (cohort 2). Four genes showed differential expression (Mgll, Plcd4, Ptgs2, and Pld1), from mid to late gestation. Genes positively associated with gestational age were Ptgs2, Mgll, and Pld1, while Plcd4 was downregulated. This is the first comprehensive study that has investigated endocannabinoid pathway gene expression during rat pregnancy. This study provides the framework for future studies that investigate the role of endocannabinoid system during pregnancy.

Synthesis of azabicycloalkanone amino acid and azapeptide mimics and their application as modulators of the prostaglandin F2α receptor for delaying preterm birth

Premature birth (<37 weeks gestation) is the major cause of perinatal mortality and morbidity and has been steadily increasing worldwide. Towards the rational design of more effective therapeutic agents for inhibiting uterine contractions and prolonging gestation (a so-called tocolytic drug), our team has targeted the prostaglandin F2α receptor (FP) employing a peptidomimetic approach designed to provide modulators of this novel target. We identified first a lead peptide (PDC113) (1) based on the sequence of the second extracellular loop of FP on the basis that the loop itself might modulate receptor activation. Systematic study of the structure−activity relationships of 1 generated hypotheses concerning the conformation and side-chains responsible for activity that led to the synthesis of PDC113.31 (2), a potent all d-amino acid peptide, which has successfully completed Phase 1b clinical trials. Employing indolizidinone amino acids, peptide mimics were developed that served to probe the mechanism of FP modulation. For example, PDC113.824 (9) was shown to allosterically regulate FP activity contingent on the presence of prostaglandin F2α by a mechanism implicating biased signalling. Although attempts to understand the turn geometry responsible for the activity of 9 by replacement of its indolizidin-2-one moiety with other azabicycloalkanones failed to produce biologically active analogs, employment of aza-aminoacyl-proline analogs resulted in a series of FP modulators exhibiting distinct effects on different G protein-mediated signalling pathways. Our program has thus contributed novel probes for understanding the chemical biology of FP as well as new therapeutic agents with promise for inhibiting uterine contractions and preventing preterm birth.

PG F(2α) Receptor: A Promising Therapeutic Target for Cardiovascular Disease

Prostaglandins (PGs), a group of key lipid mediators, are involved in numerous physiological and pathological processes including inflammation and cardiovascular homeostasis. Each PG acts on its specific and distinct cell surface G protein-coupled receptors (GPCRs) or peroxisome proliferator-activated receptors (PPARs). Prostaglandin F(2α) receptor (FP) is required for female reproductive function such as luteolysis and parturition. It has recently been implicated in blood pressure regulation, atherosclerosis and other inflammation-related disorders. The emerging role of FP in cardiovascular diseases is highlighted and potential therapeutic translation is discussed in the current review.

Labour is associated with decreased expression of the PGF2alpha receptor (PTGFR) and a novel PTGFR splice variant in human myometrium but not decidua

The prostaglandin F(2α) receptor (PTGFR) is believed to play a role in the process of parturition. The main support for this comes from animal studies; however, in humans, the evidence is less clear. The gene coding for PTGFR may be subject to alternative splicing to generate alternate variants with different signalling pathways. We have determined regional (upper versus lower segment) and labour-associated expression of PTGFR mRNA and a recently identified splice variant of PTGFR in human myometrium and decidua. We also examined the effect of the inflammatory cytokine interleukin-1β (IL-1β) on PTGFR mRNA expression in a model of cultured human myometrial smooth muscle cells. We identified a PTGFR transcript variant 2 (PTGFR-v2) generated by alternate splicing in human myometrium and decidua. The PTGFR-v2 contains an additional 71 base pair exon, which results in a truncated protein at 297 amino acids compared with the PTGFR transcript variant 1 (PTGFR-v1) at 359 amino acids. In contrast to our hypothesis, we demonstrate that PTGFR-v1 and PTGFR-v2 mRNA expression is not significantly higher in upper segment compared with lower segment paired samples. We also show a labour-associated decrease in PTGFR-v1 and PTGFR-v2 mRNA expression in lower segment myometrial samples. IL-1β-stimulated mRNA expression of both PTGFR variants in a distinct time-dependent manner in myometrial cell cultures. We suggest that the role of the PTGFR in the human uterus requires further validation prior to pursuing it as a target for the treatment of preterm labour. In addition, the presence of distinct variants suggests further levels of gene regulation within the pregnant uterus.

The intrauterine to intra-arterial pressure ratio: a new parameter for the study of uterine contractility physiology

The objective of the study was to examine the uterine contractions and the arterial perfusion pressure changes after application of oxytocin, endothelin 1, prostaglandins PGE(1), PGE(2) and PGF(2alpha), in order to identify the substance with the greatest intrauterine pressure (IUP)/intra-arterial pressure (IAP) ratio, which means the substance most suitable for inducing uterine contractility without raising the systemic vascular pressure. Increasing doses of oxytocin, endothelin 1, PGE(1), PGE(2) and PGF(2alpha) were applied as bolus injection through the uterine artery of perfused swine uteri and the intrauterine and intra-arterial pressure rises were recorded. All substances showed a significant cervicofundic pressure gradient and, with the exception of PGF(2alpha), the uterine peristalsis moved towards the cervix uteri. The perfusion pressure after application of oxytocin, PGE(1), PGE(2) and PGF(2alpha) reached a maximum value and started to decrease, whereas endothelin 1 caused a continuous increase in the perfusion pressure. Endothelin 1 showed the lowest IUP/IAP ratio and oxytocin the greatest. In conclusion, the IUP/IAP ratio provides a promising new parameter for the study of uterine contractility physiology. Besides oxytocin, PGE(2) and PGF(2alpha) emerged as the best candidate substances to improve uterine contractility without raising the intra-arterial pressure.

Prostanoid receptor antagonists: development strategies and therapeutic applications

Identification of the primary products of cyclo-oxygenase (COX)/prostaglandin synthase(s), which occurred between 1958 and 1976, was followed by a classification system for prostanoid receptors (DP, EP(1), EP(2) ...) based mainly on the pharmacological actions of natural and synthetic agonists and a few antagonists. The design of potent selective antagonists was rapid for certain prostanoid receptors (EP(1), TP), slow for others (FP, IP) and has yet to be achieved in certain cases (EP(2)). While some antagonists are structurally related to the natural agonist, most recent compounds are 'non-prostanoid' (often acyl-sulphonamides) and have emerged from high-throughput screening of compound libraries, made possible by the development of (functional) assays involving single recombinant prostanoid receptors. Selective antagonists have been crucial to defining the roles of PGD(2) (acting on DP(1) and DP(2) receptors) and PGE(2) (on EP(1) and EP(4) receptors) in various inflammatory conditions; there are clear opportunities for therapeutic intervention. The vast endeavour on TP (thromboxane) antagonists is considered in relation to their limited pharmaceutical success in the cardiovascular area. Correspondingly, the clinical utility of IP (prostacyclin) antagonists is assessed in relation to the cloud hanging over the long-term safety of selective COX-2 inhibitors. Aspirin apart, COX inhibitors broadly suppress all prostanoid pathways, while high selectivity has been a major goal in receptor antagonist development; more targeted therapy may require an intermediate position with defined antagonist selectivity profiles. This review is intended to provide overviews of each antagonist class (including prostamide antagonists), covering major development strategies and current and potential clinical usage.

Emerging tocolytics: challenges in designing and testing drugs to delay preterm delivery and prolong pregnancy

The global rate of preterm delivery (before 37 completed weeks of pregnancy) is increasing and there are no effective means available to prevent this rise. Prematurity is the principal cause of neonatal mortality and a major cause of pediatric morbidity and long-term disability. Current strategies to prolong pregnancy are based on inhibiting the mechanisms that effect uterine smooth muscle (myometrium) contractions in women who are in preterm labor. Most drugs in this group were developed for other purposes. Newer strategies are designed to maintain a state of uterine quiescence and pregnancy, preventing the myometrium from initiating contractions and entering preterm labor. Again, it may be possible to use existing drugs for pregnancy maintenance. Several financial and practical barriers exist for developing completely new drugs to delay labor. Designing clinical trials to test tocolytics is complicated, as the health of two patients must be considered and the nature of preterm birth and its outcomes are different at early preterm labor (< 28 weeks) and late preterm labor (34 - 36 weeks).

Differences in muscarinic-receptor agonist-, oxytocin-, and prostaglandin-induced uterine contractions

OBJECTIVE

To investigate the contractile response of the perfused swine uterus to various receptor pathways (oxytocin, prostaglandins, and muscarine).

DESIGN

An extracorporeal perfusion model of the swine uterus was used that keeps the uterus in a functional condition and is appropriate for the study of physiologic questions.

INTERVENTION(S)

Oxytocin-, prostaglandin-, and carbachol-induced uterine contractility and peristalsis were assessed using an intrauterine double-chip microcatheter.

SETTING

University hospital.

MAIN OUTCOME MEASURE(S)

Intrauterine pressure profiles.

RESULT(S)

A dose-dependent increase in intrauterine pressure (IUP) in the isthmus uteri and corpus uteri was observed after the administration of prostaglandin F(2alpha) (PGF(2alpha)) and oxytocin, which reached a plateau after further stimulation. A dose-dependent increase in IUP in the isthmus uteri and corpus uteri was also observed after the administration of prostaglandin E(1) (PGE(1)) and prostaglandin E(2) (PGE(2)), with a plateau in IUP in the middle-concentration range and a decrease during the further course of stimulation. After administration of PGE(1), PGE(2), and PGF(2alpha), different directions of contraction waves were also observed. Carbachol also showed a unique contractility pattern, with isolated, very powerful, dose-dependent contractions with an IUP gradient, suggesting directed transport from the upper region to the lower region.

CONCLUSION(S)

This study demonstrated that oxytocin, the prostaglandins, and carbachol modulate contractility in nonpregnant swine uteri in a characteristic way, resulting in different contractility patterns.

Inflammatory processes in preterm and term parturition

A role for the pro-inflammatory cytokines interleukin (IL)-1beta, IL-6, IL-8 and tumor necrosis factor alpha (TNF-alpha) is evident in term and preterm delivery, and this is independent of the presence of infection. All uterine tissues progress through a staged transformation near the end of pregnancy that leads from relative uterine quiescence and maintenance of pregnancy to the activation of the uterus that prepares it for the work of labour and production of stimulatory molecules that trigger the onset of labour and delivery. The uterus is activated by pro-inflammatory cytokines through stimulation of the expression and production of uterine activation proteins (UAPs). One of these actions is the stimulation of prostaglandin (PG) synthesis. Particularly important for labour is PGF(2alpha) and its receptor, PTGFR. In addition, pro-inflammatory cytokines are able to increase the synthesis of matrix metalloproteinases (MMPs), vascular endothelial growth factor (VEGF) and the progesterone receptor C isoform, which leads to decreased tissue progesterone responsiveness. Some of these effects are replicated by PGF(2alpha), suggesting that it may act via its receptor to amplify the direct actions of cytokines. In turn, VEGF may enhance leukocyte recruitment to the uterus, and MMP-9 may promote activation of inactive pro-form cytokines. Pro-inflammatory cytokines also decrease the activity of 11beta-hydroxysteroid dehydrogenase, which likely increases intrauterine cortisol concentrations. In turn, cortisol may drive PG synthesis. Together these feed-forward mechanisms activate the uterus, trigger the production of uterine contractile stimulants and lead to labour and delivery.

Parturition and recruitment of macrophages in cervix of mice lacking the prostaglandin F receptor

Parturition does not occur in transgenic mice lacking the prostaglandin F receptor (Ptgfr(-/-)) because luteolysis is forestalled and progesterone production persists. Ovariectomy of pregnant Ptgfr(-/-) mice leads to a decline in circulating progesterone and delivery of live pups. The objective of the present study was to test the hypothesis that immigration of macrophages and increased innervation of the cervix of Ptgfr(-/-) mice was associated with ripening and parturition. The cervix of pregnant Ptgfr(-/-) mice was studied on Days 15-21 after breeding; additional groups were ovariectomized on Day 19 of pregnancy, and the cervix obtained on Day 20 of pregnancy before birth or the next day at about 24 h after birth. On Days 18-19 of pregnancy, macrophage numbers and nerve fiber density increased more than 3-fold compared with findings in nonpregnant or Day 15 or 21 pregnant Ptgfr(-/-) mice. The magnitude and time course of these changes were comparable to those found in wild-type controls that delivered on Day 19 after breeding. Thus, the mechanism regulating macrophage immigration, innervation, and cervical remodeling in Ptgfr(-/-) mice with delayed parturition is similar to wild-type controls that deliver at term. By contrast, ovariectomy forestalled the decrease in cervical macrophages in Ptgfr(-/-) mice. By Day 21 after breeding, macrophage numbers more than double those after ovariectomy, relative to those found in pregnant Ptgfr(-/-) mice, whereas nerve fiber density was the same regardless of birth. Density of collagen structure in these mice directly matched macrophage traffic in the cervix. The findings indicate that the prostaglandin F(2alpha) receptor and progesterone withdrawal are a necessary part of the final common pathway for ripening of the cervix and the process of parturition.

Pathological interactions with the timing of birth and uterine activation

The physiological processes that regulate the onset of parturition and birth are slowly being elucidated, and the points at which pathology can intervene are becoming more apparent. The data support the view that multiple pathways lead to myometrial activation. The clinical corollary is that combinations of tocolytics that operate via different mechanisms may be more effective than single agents. It may also be necessary to divide preterm labour into groups based on underlying mechanisms and to tailor therapy accordingly.

Arrest of preterm labor in rat and mouse by an oral and selective nonprostanoid antagonist of the prostaglandin F2alpha receptor (FP)

OBJECTIVE

The purpose of this study was to assess the tocolytic effect of AS604872, an orally active, potent, and selective prostanoid prostaglandin F2alpha receptor (FP) antagonist.

STUDY DESIGN

Compound AS604872 was characterized and tested for its ability to block uterine contraction and delay preterm parturition in rodent models.

RESULTS

AS604872 inhibited spontaneous uterine contractions in pregnant rat near term. In pregnant mouse, AS604872 delayed parturition induced by either the antiprogesterone RU-486 or the endotoxin lipopolysaccharide. Pups from treated mothers were delivered alive. The efficacy of AS604872 was superior to the beta-mimetic drug ritodrine. Combination of AS604872 and ritodrine showed an additive inhibitory effect on spontaneous uterine contractions in rat.

CONCLUSION

A selective antagonist of the FP receptor suppresses uterine contractility and delays labor. Our findings identify a new potential modality for the pharmacological management of preterm labor.

Tocolytic effect of a selective FP receptor antagonist in rodent models reveals an innovative approach to the treatment of preterm labor

Background

Management of preterm labor by tocolysis remains an unmet medical need. Prostaglandins play a major role in regulation of uterine activity and in molecular mechanisms of human labor and parturition. There is some circumstantial evidence that prostaglandin F2α by action through the prostaglandin receptor subtype FP is effective in key events during labor uterine contraction, rupture of membranes and cervical dilation. This role of FP is briefly reviewed. In this study, we tested the hypothesis that an orally active and selective FP antagonist may arrest labor and delay parturition in animal models.

Methods

We examined the effects of a small molecule selective antagonist of the FP receptor (AS604872) in inhibition of spontaneous uterine contraction in pregnant rat near term. We tested AS604872 for its ability to delay preterm birth in a mouse model in which the anti-progestin agent RU486 triggered parturition.

Results

By oral or intravenous dosing AS604872 reduced markedly and dose-dependently the spontaneous uterine contractions in late-term pregnant rats at gestational days 19–21. In pregnant mice, AS604872 delayed the preterm birth caused by RU486 administration. The effect was dose-dependent with a significant increase in the mean delivery time of 16 and 33 hours at oral doses of 30 mg/kg and 100 mg/kg, respectively, in the case of labor triggered at gestational day 14. In both models AS604872 appeared more effective than the β-agonist ritodrine.

Conclusion

The tocolytic activity displayed by a selective FP receptor antagonist supports a key role for the FP receptor in the pathophysiology of premature birth and demonstrates the therapeutic potential of an FP antagonist for the treatment of preterm labor cases in which uterine hyperactivity plays a dominant role.

The Interleukin 1beta-Induced Expression of Human Prostaglandin F2alpha Receptor Messenger RNA in Human Myometrial-Derived ULTR Cells Requires the Transcription Factor, NFkappaB1

The molecular mechanisms that regulate the expression of genes involved in parturition are poorly understood. The mRNA expression of the prostaglandin F(2alpha) receptor (PTGFR), a uterine activating gene, is increased at labor and is required for uterine contractile activity in numerous animal models, although the signaling pathways responsible for this increased expression have not been identified. Proinflammatory cytokines have been proposed to regulate the expression of the uterine activating genes via activation of the nuclear transcription factor, NFkappaB, and initiate labor. However, it is uncertain whether uterine PTGFR is regulated this way. In this report, we demonstrate for the first time that treatment of immortalized human myometrial-derived ULTR cells with the proinflammatory cytokine IL1beta causes an increase in PTGFR mRNA levels. Furthermore, IL1beta treatment increased the nuclear levels of the RELA subunit of NFkappaB and increased binding of RELA to the NFkappaB DNA-binding site. Inhibition of NFkappaB activation with either the proteasome inhibitor MG132 or phenethyl caffeiate reduced PTGFR mRNA levels, which indicates that this transcription factor is important for basal transcription. Furthermore, this inhibition prevented IL1beta induction ofPTGFRmRNA, which confirms that NFkappaB is required for the IL1beta-induced increase inPTGFR. These results are consistent with the proposal that proinflammatory cytokines directly regulate uterine activation genes and that the transcription factor NFkappaB is involved in both basal and IL1beta-stimulated transcription of the PTGFR gene.

Uterine contractility in response to different prostaglandins: results from extracorporeally perfused non-pregnant swine uteri

BACKGROUND

Prostaglandins (PGs) are important stimulators of uterine contractility. Limited data are available at present on the effects of different PGs on uterine contractility, measured using intraluminal pressure changes in the complete uterus. The goal of this study was to assess dynamic changes in uterine contractility and peristalsis in response to PGs in comparison with the effects of oxytocin administration.

METHODS

An extracorporeal perfusion model of swine uteri was used, which keeps the uterus in a functional condition, and is appropriate for the study of physiological questions. Oxytocin- and PG-induced uterine contractility and peristalsis were assessed using an intrauterine double-chip microcatheter.

RESULTS

A dose-dependent increase in intrauterine pressure (IUP) in the isthmus uteri (P < 0.001) and the corpus uteri (P < 0.001) was observed after the administration of PGF(2alpha) and oxytocin, which reached a plateau after further stimulation. A dose-dependent increase in IUP in the isthmus uteri (P < 0.001) and the corpus uteri (P < 0.001) was also observed after the administration of PGE(1) and PGE(2), with a plateau in IUP in the middle-concentration range and a decrease in the course of further stimulation. PGE(2) caused significantly more contractions starting in the corpus uteri and moving to the isthmus uteri (P = 0.008). The direction of most contractions caused by PGE(1), PGE(2) and oxytocin differed from that of PGF(2alpha).

CONCLUSIONS

This study demonstrates that the PGs tested modulate contractility in non-pregnant swine uteri in a characteristic way, resulting in different contractility patterns.