Prostaglandin concentrations in amniotic fluid of women with intra-amniotic infection and preterm labor

Prematurity, subclinical intraamniotic infection, and fetal biophysical parameters: is there a correlation?

Objective: This prospective study was undertaken to examine the effects of subclinical intraamniotic infection on fetal behavioral patterns.

Methods: Amniotic fluid was obtained from four groups of patients (n = 99): group 1, patients with preterm premature rupture of the fetal membranes (PPROM) without infection; group 2, patients with PPROM and infection; group 3, patients with preterm labor (PTL) and without infection; and group 4, patients with PTL and infection. Fetal biophysical profiles were obtained on admission to the labor suite. Amniotic fluid was analyzed for the presence of microorganisms and endotoxin to confirm intraamniotic infection; cytokines interleukin (IL)-1β, IL-6, and IL-8 were also assayed.

Results: We found no association between low scores for biophysical parameters and subclinical infection in patients with PPROM or PTL.

Conclusions: We could not demonstrate that upon a patient's admission to the labor hall absent fetal breathing and absent fetal movement, as well as reactivity, correlate with subclinical intraamniotic infection. Elevated cytokines, i.e. IL-1β, IL-6, and IL-8 were associated with subclinical chorioamnionitis.

Isobaric labeling and tandem mass spectrometry: a novel approach for profiling and quantifying proteins differentially expressed in amniotic fluid in preterm labor with and without intra-amniotic infection/inflammation

OBJECTIVE

Examination of the amniotic fluid (AF) proteome has been previously attempted to identify useful biomarkers in predicting the outcome of preterm labor (PTL). Isobaric Tag for Relative and Absolute Quantitation (iTRAQ) labeling allows direct ratiometric comparison of relative abundance of identified protein species among multiplexed samples. The purpose of this study was to apply, for the first time, the combination of iTRAQ and tandem mass spectrometry to identify proteins differentially regulated in AF samples of women with spontaneous PTL and intact membranes with and without intra-amniotic infection/inflammation (IAI).

METHODS

A cross-sectional study was designed and included AF samples from patients with spontaneous PTL and intact membranes in the following groups: (1) patients without IAI who delivered at term (n = 26); (2) patients who delivered preterm without IAI (n = 25); and (3) patients with IAI (n = 24). Proteomic profiling of AF samples was performed using a workflow involving tryptic digestion, iTRAQ labeling and multiplexing, strong cation exchange fractionation, and liquid chromatography tandem mass spectrometry. Twenty-five separate 4-plex samples were prepared and analyzed.

RESULTS

Collectively, 123,011 MS(2) spectra were analyzed, and over 25,000 peptides were analyzed by database search (X!Tandem and Mascot), resulting in the identification of 309 unique high-confidence proteins. Analysis of differentially present iTRAQ reporter peaks revealed many proteins that have been previously reported to be associated with preterm delivery with IAI. Importantly, many novel proteins were found to be up-regulated in the AF of patients with PTL and IAI including leukocyte elastase precursor, Thymosin-like 3, and 14-3-3 protein isoforms. Moreover, we observed differential expression of proteins in AF of patients who delivered preterm in the absence of IAI in comparison with those with PTL who delivered at term including Mimecan precursor, latent-transforming growth factor beta-binding protein isoform 1L precursor, and Resistin. These findings have been confirmed for Resistin in an independent cohort of samples using ELISA. Gene ontology enrichment analysis was employed to reveal families of proteins participating in distinct biological processes. We identified enrichment for host defense, anti-apoptosis, metabolism/catabolism and cell and protein mobility, localization and targeting.

CONCLUSIONS

(1) Proteomics with iTRAQ labeling is a profiling tool capable of revealing differential expression of proteins in AF; (2) We discovered 82 proteins differentially expressed in three clinical subgroups of premature labor, 67 which were heretofore unknown. Of particular importance is the identification of proteins differentially expressed in AF from women who delivered preterm in the absence of IAI. This is the first report of the positive identification of biomarkers in this subgroup of patients.

Metabolomics in premature labor: a novel approach to identify patients at risk for preterm delivery

OBJECTIVE

Biomarkers for preterm labor (PTL) and delivery can be discovered through the analysis of the transcriptome (transcriptomics) and protein composition (proteomics). Characterization of the global changes in low-molecular weight compounds which constitute the 'metabolic network' of cells (metabolome) is now possible by using a 'metabolomics' approach. Metabolomic profiling has special advantages over transcriptomics and proteomics since the metabolic network is downstream from gene expression and protein synthesis, and thus more closely reflects cell activity at a functional level. This study was conducted to determine if metabolomic profiling of the amniotic fluid can identify women with spontaneous PTL at risk for preterm delivery, regardless of the presence or absence of intraamniotic infection/inflammation (IAI).

STUDY DESIGN

Two retrospective cross-sectional studies were conducted, including three groups of pregnant women with spontaneous PTL and intact membranes: (1) PTL who delivered at term; (2) PTL without IAI who delivered preterm; and (3) PTL with IAI who delivered preterm. The first was an exploratory study that included 16, 19, and 20 patients in groups 1, 2, and 3, respectively. The second study included 40, 33, and 40 patients in groups 1, 2, and 3, respectively. Amniotic fluid metabolic profiling was performed by combining chemical separation (with gas and liquid chromatography) and mass spectrometry. Compounds were identified using authentic standards. The data were analyzed using discriminant analysis for the first study and Random Forest for the second.

RESULTS

(1) In the first study, metabolomic profiling of the amniotic fluid was able to identify patients as belonging to the correct clinical group with an overall 96.3% (53/55) accuracy; 15 of 16 patients with PTL who delivered at term were correctly classified; all patients with PTL without IAI who delivered preterm neonates were correctly identified as such (19/19), while 19/20 patients with PTL and IAI were correctly classified. (2) In the second study, metabolomic profiling was able to identify patients as belonging to the correct clinical group with an accuracy of 88.5% (100/113); 39 of 40 patients with PTL who delivered at term were correctly classified; 29 of 33 patients with PTL without IAI who delivered preterm neonates were correctly classified. Among patients with PTL and IAI, 32/40 were correctly classified. The metabolites responsible for the classification of patients in different clinical groups were identified. A preliminary draft of the human amniotic fluid metabolome was generated and found to contain products of the intermediate metabolism of mammalian cells and xenobiotic compounds (e.g. bacterial products and Salicylamide).

CONCLUSION

Among patients with spontaneous PTL with intact membranes, metabolic profiling of the amniotic fluid can be used to assess the risk of preterm delivery in the presence or absence of infection/inflammation.

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.

Amniotic fluid prostaglandin F2 increases even in sterile amniotic fluid and is an independent predictor of impending delivery in preterm premature rupture of membranes

OBJECTIVE

To determine whether amniotic fluid (AF) concentration of prostaglandins (PGs) increases in patients with intra-amniotic inflammation and/or proven AF infection in preterm PROM, and can predict impending delivery.

METHODS

AF PGF2a concentrations were determined by ELISA in 140 singleton pregnancies with preterm premature rupture of membranes (PROM) (< or =35 weeks). AF was cultured for aerobic and anaerobic bacteria, and genital mycoplasmas. Intra-amniotic inflammation was defined as an elevated AF matrix metalloproteinase-8 concentration (>23 ng/ml). Results. (1) Patients with intra-amniotic inflammation and a negative AF culture had a significantly higher median AF PGF2a than those without intra-amniotic inflammation and with a negative culture (p < 0.001); (2) However, there was no difference in the median AF PGF2a between patients with intra-amniotic inflammation with a negative culture and those with culture-proven AF infection (p > 0.1); (3) Patients with an elevated AF PGF2a had a significantly shorter interval-to-delivery than those with a low AF PGF2a (< or =170 pg/mL) (p < 0.001); (4) An elevated AF PGF2a (< or =170 pg/mL) concentration was a significant predictor of the duration of pregnancy after adjusting for gestational age and AF inflammation/infection (p < 0.005). Conclusions. AF PGF2a (> or =170 pg/mL) concentration increased in patients with intra-amniotic inflammation regardless of AF culture results. Moreover, an elevated AF PGF2a concentration was an independent predictor of impending delivery in preterm PROM.

Preterm prelabour amniorrhexis

Preterm delivery occurs in less than 10% of pregnancies but accounts for more than 60% of all neonatal deaths. Approximately one third of preterm deliveries are associated with preterm prelabour amniorrhexis and in a high proportion of such cases the underlying cause may be ascending infection from the lower genital tract. The causes of neonatal death in pregnancies with amniorrhexis are prematurity, pulmonary hypoplasia and sepsis. In the management of pregnancies with preterm prelabour amniorrhexis it is essential to distinguish between those with and without intrauterine infection. If there is no infection at presentation it is unlikely that this will develop and in such cases there is no benefit from hospitalisation, bed rest, prophylactic tocolytics or antibiotics. The group with evidence of intrauterine infection go into spontaneous labour within a few days of amniorrhexis; in this group the main determinant for the appropriate management is the gestation at amniorrhexis.

Evidence of the involvement of caspase-1 under physiologic and pathologic cellular stress during human pregnancy: a link between the inflammasome and parturition

OBJECTIVE

Caspase-1 is a component of the NALP3 inflammasome, a cytosolic multiprotein complex that mediates the processing of pro-inflammatory caspases and cytokines. The inflammasome represents the first line of defense against cellular stress and is a crucial component of innate immunity. Caspase-1 is the enzyme responsible for the cleavage and activation of interleukin (IL)-1 beta, which is a potent pro-inflammatory cytokine, and plays a central role in the mechanisms leading to labor (preterm and term) particularly in the context of intrauterine infection/inflammation. In addition, caspase-1 cleaves IL-18 and IL-33. The objectives of this study were to determine whether there is a relationship between amniotic fluid concentrations of caspase-1 and gestational age, parturition (term and preterm), and intra-amniotic infection/inflammation (IAI).

STUDY DESIGN

A cross-sectional study was conducted including 143 pregnant women in the following groups: (1) mid-trimester of pregnancy (n = 18); (2) term not in labor (n = 25); (3) term in labor (n = 28); (4) preterm labor (PTL) who delivered at term (n = 23); (5) PTL without IAI who delivered preterm (n = 32); (6) PTL with IAI who delivered preterm neonates (n = 17). Caspase-1 concentrations in amniotic fluid were determined by a specific and sensitive immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) Caspase-1 was detected in amniotic fluid of women at term, but in none of the mid-trimester samples. (2) Patients in labor at term had a significantly higher median amniotic fluid concentration of caspase-1 than women at term not in labor (term in labor: 10.5 pg/mL, range 0.0-666.0 vs. term not in labor: 5.99 pg/mL, range 0.0-237.4; p < 0.05). (3) Among patients with spontaneous PTL, those with IAI (median 41.4 pg/mL, range 0.0-515.0) had a significantly higher median amniotic fluid caspase-1 concentration than those without IAI who delivered preterm (median 0.0 pg/mL, range 0.0-78.4) and than those who delivered at term (median 0.0 pg/mL, range 0.0-199.5); p < 0.001 for both comparisons.

CONCLUSIONS

(1) The presence and concentration of caspase-1 in the amniotic fluid varies as a function of gestational age. (2) Women with spontaneous labor at term had a higher median caspase-1 amniotic fluid concentration than women at term without labor. This suggests that the inflammasome may be activated in spontaneous parturition at term. Since most women with labor do not have intra-amniotic infection, we propose that cellular stress during labor accounts for activation of the inflammasome. (3) Preterm labor associated with infection/inflammation was also associated with a high concentration of caspase-1, suggesting that infection may induce caspase-1 production and activation of the inflammasome. (4) The sequential activation of the inflammasome and caspase-1, leading to interleukin-1 beta processing and secretion, is a candidate pathway leading to the activation of the common pathway of parturition.

Eicosanoids and preterm labour

Products of arachidonic acid metabolism (eicosanoids, e.g. some prostaglandins and leukotrienes) have important roles in the maintenance of pregnancy, and certain diseases of pregnancy such as pregnancy-induced hypertension and the machanism(s) of parturition both at term and before term. The volume of literature describing these last relationships dictates that the present review has to be focused rather than global in nature. Only studies of preterm labour in women and the use of human tissues will be discussed in detail despite the limitations in experimental designs that are imposed on such studies. Emphasis will be placed on studies of cyclo-oxygenase and to a lesser extant lipoxygenase pathways of arachidonic acid metabolism mentioning only briefly the pathways for catabolism of these eicosanoids. It should be noted also that eicosanoids from the epoxygenase pathways and those not derived from arachidonic acid will not be discussed here. The review of literature will not be comprehensive but rather selective in order to focus on specific issues of importance or controversy. In developing concepts of regulation I have emphasized studies with amnion since this tissue has received most attention experimentally. The significance of the eicosanoids in the mechanisms of labour at term and before will be described primarily in a section in which I have attempted to deleneate those regulatory mechanisms that are considered most significant in, or specific to, pregnancy and parturition. Studies of labour at term will be freely interspersed with studies specific to preterm labour since the latter are limited, and we need a ‘strandard’ for comparison; moreover, results from one series of studies helps the development of concepts for the other. Finally, the reader is directed to several excellent reviews that concentrate on areas not emphasized in this review.1–7

Plasma protein Z concentrations in pregnant women with idiopathic intrauterine bleeding and in women with spontaneous preterm labor

OBJECTIVES

Preterm parturition has been associated with decidual vascular disorders and excessive thrombin generation. The objective of this study was to examine maternal plasma concentrations of protein Z in normal pregnancies, as well as in those presenting with spontaneous preterm labor (PTL) and intrauterine bleeding during pregnancy.

STUDY DESIGN

A cross-sectional study was designed to include patients with preterm labor and intact membranes and those with idiopathic intrauterine bleeding during pregnancy. Protein Z plasma concentrations were measured in the following groups: (1) normal pregnant women (n = 71); (2) patients at term with (n = 67) and without labor (n = 88); (3) patients with spontaneous PTL before 34 weeks who were classified into: (a) PTL with intra-amniotic infection/inflammation (IAI; n = 35), (b) PTL without IAI (n = 54), and (c) patients with PTL who delivered at term (n = 49); and (4) patients with idiopathic intrauterine bleeding in the second and third trimester who were divided into: (a) subsequent spontaneous PTL and delivery, and (b) term delivery. Maternal plasma protein Z concentration was measured by a specific and sensitive immunoassay. Moreover, the amniotic fluid concentration of protein Z was determined in a subset of patients with preterm labor (n = 30).

RESULTS

(1) There was no correlation between maternal plasma protein Z concentration and gestational age in normal pregnant women. (2) The mean maternal plasma concentration of protein Z was significantly lower in women during spontaneous labor at term than in those not in labor (mean 2.15 microg/mL (95% CI 2.01-2.29) vs. mean 2.45+/-0.52 microg/mL (95% CI 2.34-2.56), respectively; p = 0.001). (3) Women with PTL without IAI who delivered preterm had a significantly lower mean protein Z concentration than normal pregnant women (mean 2.12 mug/mL (95% CI 1.98-2.26) vs. mean 2.39 microg/mL (95% CI 2.28-2.5); p = 0.008). (4) Of interest, PTL with IAI was not associated with lower plasma concentrations of protein Z, nor were those with PTL who delivered at term (p > 0.05 for each). (5) No differences were found in the maternal plasma concentrations of anti-protein Z antibodies between normal pregnancies and those with spontaneous PTL. (6) Patients with idiopathic intrauterine bleeding who had spontaneous PTL and delivery had a significantly lower mean plasma protein Z concentration than those who delivered at term (mean 1.24 microg/mL (95% CI 1.08-1.4) vs. mean 1.49+/-0.47 microg/mL (95% CI 1.33-1.65), respectively; p = 0.03). (7) Amniotic fluid was found to contain immunoreactive protein Z.

CONCLUSIONS

(1) Patients with PTL leading to preterm delivery in the absence of IAI had a significantly lower plasma concentration of protein Z than those with normal pregnancies. (2) Patients with idiopathic intrauterine bleeding and subsequently spontaneous PTL and delivery had a significantly lower plasma concentration of protein Z than those with idiopathic intrauterine bleeding who delivered at term. (3) Protein Z was present in the amniotic fluid of patients with PTL. Collectively, these observations suggest that a subgroup of patients with PTL have a hemostatic disorder that involves bleeding/thrombosis as a mechanism of disease.

Mechanisms of progesterone action in inhibiting prematurity

Progesterone is a steroid hormone that plays an integral role in each step of human pregnancy. In early pregnancy, progesterone produced by the corpus luteum is critical to the maintenance of early pregnancy until the placenta takes over this function at 7 to 9 weeks of gestation, hence its name (pro-gestational steroid hormone). The role of progesterone in later pregnancy, however, is less clear. It has been proposed that progesterone may be important in maintaining uterine quiescence in the latter half of pregnancy by limiting the production of stimulatory prostaglandins and inhabiting the expression of contraction-associated protein genes within the myometrium. Although systemic progesterone withdrawl may not correlate directly with the onset of labour in humans, there is increasing evidence to suggest that progesterone exerts its influence indirectly via a 'functional' withdrawl at the level of the uterus. The molecular mechanisms by which progesterone is able to maintain uterine quiescence and prevent preterm birth in some high-risk women are not clear. Six putative mechanisms have been proposed in the literature by both US and other investigators and are explored in this review.

The role and regulation of the nuclear factor kappa B signalling pathway in human labour

Within the discipline of reproductive biology, our understanding of one of the most fundamental biological processes is lacking--the cellular and molecular mechanisms that govern birth. This lack of understanding limits our ability to reduce the incidence of labour complications. The incidence of labour complications including: preterm labour; cervical incompetence; and post-date pregnancies has not diminished in decades. The key to improving the management of human labour and delivery is an understanding of how the multiple processes that are requisite for a successful labour and delivery are coordinated to achieve a timely birth. Processes of human labour include the formation of: contraction associated proteins; inflammatory mediators (e.g. cytokines); uterotonic phospholipid metabolites (e.g. prostaglandins); and the induction of extracellular matrix (ECM) remodelling. Increasingly, it is becoming evident that labour onset and birth are the result of cross-talk between multiple components of an integrated network. This hypothesis is supported by recent data implicating various upstream regulatory pathways in the control of key labour-associated processes, including the activity of enzymes involved in the formation of prostaglandins and extracellular matrix remodelling, and mediators of inflammation. Clearly, the biochemical pathways involved in the formation of these mediators represent potential sites for intervention that may translate to therapeutic interventions to delay or prevent preterm labour and delivery. Available data strongly implicate the nuclear factor-kappaB (NF-kappaB) family as candidate upstream regulators of multiple labour-associated processes. Not only do these data warrant further detailed analysis of the involvement of these pathways in the process of human labour but also promise new insights into the key mechanisms that trigger birth and the identification of new therapeutic interventions that will improve the management of labour.

Timing of Neutrophil Activation and Expression of Proinflammatory Markers Do Not Support a Role for Neutrophils in Cervical Ripening in the Mouse1

The mechanisms that facilitate remodeling of the cervix in preparation for and during parturition remain poorly understood. In the current study, we have evaluated the timing of inflammatory cell migration in cervix through comparisons between wild-type mice and steroid 5alpha-reductase type 1 null mice (Srd5a1-/-), which fail to undergo cervical ripening due to insufficient local progesterone metabolism. The timing of migration and distribution of macrophages, monocytes, and neutrophils were examined using cervices from wild-type and Srd5a1-/- mice before Day 15 (d15) and during cervical ripening (late d18), and postpartum (d19). Neutrophil numbers were quantitated by cell counts and activity was estimated by measurement of myeloperoxidase activity. The mRNA and/or protein expression of neutrophil chemoattractants, CXCL2 and CXCL1, and other proinflammatory and adhesion molecules, including IL1A, IL1B, TNF, CCL11, CCL5, CCL3, ITGAM, and ICAM1, were measured in cervices collected before, during, and after birth. The effect of neutrophil depletion on parturition was tested. Tissue macrophages, myeloperoxidase activity, and expression of proinflammatory molecules are not increased within the cervix until after birth. Neutrophil numbers do not change after birth and neutrophil depletion before term has no effect on timing or success of parturition. These results suggest that cervical ripening does not require neutrophils. Moreover, neutrophil activation and a general inflammatory response are not initiated within the cervix until shortly after parturition. The timing of inflammatory cell migration and activation in pregnant cervix suggest a role for these cells in postpartum remodeling of the cervix rather than in the initiation of cervical ripening at parturition.

Evidence for a role of phosphodiesterase 4 in lipopolysaccharide-stimulated prostaglandin E2 production and matrix metalloproteinase-9 activity in human amniochorionic membranes

Chorioamniotic infection is a leading cause of preterm premature rupture of fetal membranes (amnion and chorion). Bacterial infection induces an inflammatory response characterized by elevated production of proinflammatory cytokines; the latter activate the production of both PGs that stimulate uterine contractions, and matrix metalloproteinases (MMPs) that degrade the extracellular matrix of the chorioamniotic membranes. The inflammatory response is under the control of cAMP content, which is partly regulated by phosphodiesterases (PDE). In this study, we investigated the role of the PDE4 family in the inflammatory process triggered by LPS in a model of amniochorionic explants. We found that PDE4 family is the major cAMP-PDE expressed in human fetal membranes and that PDE4 activity is increased by LPS treatment. Selective inhibition of PDE4 activity affected LPS signaling, because PDE4 inhibitors (rolipram and/or cilomilast) reduced the release of the proinflammatory cytokine TNF-alpha and increased the release of the anti-inflammatory cytokine IL-10. PDE4 inhibition reduced cyclooxygenase-2 protein expression and PGE(2) production and also modulated MMP-9, a key mediator of the membrane rupture process, by inhibiting pro-MMP-9 mRNA expression and pro-MMP-9 activity. These results demonstrate that the PDE4 family participates in the regulation of the inflammatory response associated with fetal membrane rupture during infection. The PDE4 family may be an appropriate pharmacological target for the management of infection-induced preterm delivery.

Uteroglobin inhibits prostaglandin F2alpha receptor-mediated expression of genes critical for the production of pro-inflammatory lipid mediators

Prematurity is one of the leading causes of infant mortality. It may result from intrauterine infection, which mediates premature labor by stimulating the production of inflammatory lipid mediators such as prostaglandin F2alpha (PGF2alpha). The biological effects of PGF2alpha are mediated via the G protein-coupled receptor FP; however, the molecular mechanism(s) of FP signaling that mediates inflammatory lipid mediator production remains unclear. We reported previously that in the human uterus, a composite organ in which fibroblast, epithelial, and smooth muscle cells are the major constituents, an inverse relationship exists between the levels of PGF2alpha and a steroid-inducible anti-inflammatory protein, uteroglobin. Here we report that, in NIH 3T3 fibroblasts and human uterine smooth muscle cells, FP signaling is mediated via multi-kinase pathways in a cell type-specific manner to activate NF-kappaB, thus stimulating the expression of cyclooxygenase-2. Cyclooxygenase-2 is a critical enzyme for the production of prostaglandins from arachidonic acid, which is released from membrane phospholipids by phospholipase A2, the expression of which is also stimulated by PGF2alpha. Most importantly, uteroglobin inhibits FP-mediated NF-kappaB activation and cyclooxygenase-2 gene expression by binding and most likely by sequestering PGF2alpha into its central hydrophobic cavity, thereby preventing FP-PGF2alpha interaction and suppressing the production of inflammatory lipid mediators. We propose that uteroglobin plays important roles in maintaining homeostasis in organs that are vulnerable to inadvertent stimulation of FP-mediated inflammatory response.

Possible interplay between vitamin C deficiency and prolactin in pregnant women with premature rupture of membranes: facts and hypothesis

The precise etiologic mechanisms involved in the premature rupture of membranes (PROM) during pregnancy, the main cause of preterm delivery worldwide, are unknown. Previous studies have shown that: (a) the rupture of chorioamniotic membranes is related to an imbalance between synthesis and degradation of collagen induced by the overexpression/activity of various matrix metalloproteinases (MMP); (b) during human labor and delivery the expression of prolactin receptors (PRL-R) increases in chorioamniotic membranes, decidua and placenta; (c) prolactin (PRL) can influence the synthesis of prostaglandins, the expression of some MMP (MMP-2, MMP-9 and decysin) and tissue inhibitors of MMP in general; (d) vitamin C deficiency induces the expression/activity of extracellular MMP and is considered a risk factor for PROM; and (e) vitamin C potentiates the dopamine-mediated inhibition of PRL in rats. The present hypothesis proposes that a decreased hypothalamic dopaminergic tone-and thus an increased synthesis/release of pituitary PRL - is induced by vitamin C deficiency below a critical threshold (<18 microg/10(8) leukocytes) and that both factors, in turn, would cause upregulation of the expression/activity of several MMP. The increased PRL concentrations (acting like a Th1-type cytokine) along with the overexpression of other proinflammatory cytokines would induce a premature switch from a favorable Th2-type immune response to a noxious Th1-type immune response in the intrauterine environment. This change, in conjunction with the upregulation of MMP-2 and MMP-9, would cause a premature imbalance between synthesis/degradation of collagen in chorioamniotic membranes (an "anticipation" of the normal parturition cascade?), which favors extracellular matrix degradation, proposed as the most relevant event in the genesis of PROM. This hypothesis represents a new dimension in the study of the etiology of PROM.

Fetal endoscopic surgery: indications and anaesthetic management

Fetal intervention for certain life-threatening conditions has progressed from being primarily experimental in nature to the standard of care in certain circumstances. While surgical techniques have advanced over the past few years, the anaesthetic goals for these interventions have remained the same; namely, minimizing maternal and fetal risk as well as maximizing the chances of a successful fetal intervention and optimize the conditions necessary to carry the fetus to term gestation. Fetal endoscopic techniques allow access to the fetus without the need for a hysterotomy incision, thus improving the chances of controlled post-operative tocolysis and term gestation after fetal intervention. This procedure, however, is not without associated risks to both fetus and mother. This chapter will address the fetal diseases that may benefit from fetoscopic intervention, the rationale behind why maternal and fetal anaesthesia is required, the various anaesthetics used for these cases and specific considerations of both maternal and fetal physiology that aid in the determination of the best anaesthetic technique for individual cases. Methods of intra-operative fetal monitoring and fetal resuscitation will also be discussed.

Placental lesions caused by experimental infection of Sprague-Dawley rats with Mycoplasma pulmonis

PROBLEM

Sprague-Dawley (SD) rats infected during pregnancy with Mycoplasma pulmonis display adverse pregnancy outcomes that are similar to those observed in women with chorioamnionitis and may provide a good model system for this disease. The placental lesions caused by this microorganism, however, have not been thoroughly characterized.

METHOD OF STUDY

Rats were infected with 10(7) colony-forming units (CFU) M. pulmonis or vehicle control on gestation day (gd) 14 and were euthanized on gd 16-18. Tissues were fixed in 10% neutral buffered formalin, embedded in paraffin, sectioned at 4 microm, and stained with hematoxylin and eosin (H & E). The slides were coded and examined by a blinded pathologist using light microscopy.

RESULTS

Infection with M. pulmonis was associated with necrosis of trophoblast giant cells at gd 18. Significantly more neutrophils were observed in the decidual region of the apex of the placenta in M. pulmonis infected animals. The vast majority of neutrophils, however, were observed in the decidua in the lateral regions of the placenta and in the adjacent endometrium.

CONCLUSIONS

Infection of SD rats with M. pulmonis resulted in histological placentitis similar to that described in deciduitis of humans and represents a good model system for investigations into the pathophysiology of intrauterine infection. The influx of neutrophils seems to migrate from the endometrium towards the lateral regions of the placenta near Reichert's membrane and the divergence of the parietal yolk sac.

Prostaglandin endoperoxide H synthase inhibitors and other tocolytics in preterm labour

Preterm delivery (<37 weeks of gestation) is the major obstetrical complication in developed countries, yet attempts to delay labour and prolong pregnancy have largely been unsuccessful. One of the many reasons it is so difficult to prevent preterm birth is that the nature of preterm labour changes as a function of gestational age, maternal lifestyle factors or infection, to list a few of the reasons. The inhibitors of prostaglandin endoperoxide H synthase (PGHS), known as the Non-steroidal Antiinflammatory Drugs, have been viewed with interest as tocolytics with promising effectiveness under most conditions of preterm labour. Three isoforms of PGHS exist; the first two, PGHS-1 and -2, have been studied for their catalytic activity, X-ray crystallographic structure, and physiological roles in the adult and the foetus. Mixed inhibitors and isoform-specific inhibitors of PGHS have been developed, and their roles in delaying preterm labour are examined and compared to other tocolytics.

Effects of endotoxin and macrophage-related cytokines on the contractile activity of the gravid murine uterus

Immune cell trafficking and activity are implicated in the parturition process, but little is known about the role of macrophages in control of uterine contractility at term. In the present study, we tested the hypothesis that endotoxin (lipopolysaccharide [LPS]) enhances uterine contractile activity through a mechanism that involves activation of resident macrophages. Various uterotonins and anti-inflammatory mediators were added to a standard muscle bath preparation that contained strips of uterus from Day 15 pregnant C3H/HeN mice. Spontaneous and agonist-induced contractile activity was enhanced following LPS treatment. LPS increased amplitude but not frequency of contractions. Addition of anti-inflammatory cytokines, interleukin 10 or transforming growth factor beta, to suppress macrophage activation did not block LPS-induced increases in contractility. By contrast, indomethacin given to block prostaglandin production suppressed the LPS-induced increase in amplitude of contractions. These findings suggest that an inflammatory response, possibly mediated by activation of macrophages and prostaglandins, participates in the regulation of amplitude but not frequency of contractile activity by the murine uterus before onset of parturition.

The role of prostaglandins in the initiation of parturition

Parturition is composed of five separate but integrated physiological events: fetal membrane rupture, cervical dilatation, myometrial contractility, placental separation and uterine involution. Prostaglandins (PGs) have central roles in each of these, but the most studied is myometrial contraction. Elevated uterine PGs or the enhanced sensitivity of the myometrium to PGs leads to contractions and labour. The regulator of PG synthesis is the mRNA expression of PGHS-2. Cytokines are important stimulators of this gene expression, and cortisol and other factors may be as well. This enzyme is an important therapeutic target in the prevention of preterm labour. Some preterm births occur without an elevation of uterine PGs, even though they are delayed by non-steroidal anti-inflammatory drugs (NSAIDs), suggesting enhanced myometrial sensitivity to PGs. The PGF(2alpha) receptor, FP, is emerging as a central component of uterine sensitivity and may prove to be involved with preterm birth and a reasonable target for tocolysis.

A systematic approach to the management of preterm labor

Preterm birth occurs in 7% to 12% of all deliveries, but accounts for over 85% of all perinatal morbidity and mortality. Although the ability of obstetric care providers to identify women at risk for preterm delivery has improved, the overall incidence of preterm birth has remained unchanged for the past 30 years. Preterm birth remains the single greatest challenge for physician-researchers in the field of maternal-fetal medicine in the 21st century. This article reviews in detail the current state of the literature as regards the etiology, pathophysiology, prevention, and treatment of premature labor and preterm birth. A better understanding of the molecular mechanisms responsible for the process of labor, both at term and preterm, will improve our ability to identify and manage women at risk of premature delivery.

Testing a sociomedical model for preterm delivery

The study purpose was to contribute to the development of a model for preterm birth that brings together social, psychosocial and biomedical factors. The three research questions were: (a) Which social and psychosocial factors influence the risk of preterm delivery? (b) Are the effects of social and psychosocial factors independent? (c) Do the biomedical factors identified and measured here explain the effect of social and psychosocial factors? The sample comprised 739 low-income black non-Hispanic women. Interviews were conducted after delivery, and medical records were abstracted. Nearly a quarter of the women delivered preterm (23.5%). Two social factors strongly predicted risk of preterm delivery: inadequacy of time and money for non-essentials. The effect of both was stronger than expected from each alone and was partially mediated by psychosocial factors. Several psychosocial factors also predicted preterm delivery risk but only stress and locus of control were independent predictors. With the inclusion of biomedical factors, stress (OR = 1.86, P = 0.005) and locus of control (OR = 1.75, P = 0.007) continued to be strongly associated with preterm delivery. The effect of inadequate resources for non-essentials was no longer significant, suggesting mediation. These strong effects of social and psychosocial factors should be examined in future studies.

Effect of lipopolysaccharide on uterine contractions and prostaglandin production in pregnant rats

OBJECTIVE

Our aim was to evaluate the effect of lipopolysaccharide on prostaglandin production and on contraction of isolated myometrial strips from preterm pregnant rats.

STUDY DESIGN

Pregnant Wistar rats on day 17 of gestation were killed 3 hours after intraperitoneal injection of lipopolysaccharide (1.5 mg/kg) or vehicle, with or without pretreatment with indomethacin (5 mg/kg administered intraperitoneally) 1 hour beforehand. Concentrations of endotoxin in maternal serum and amniotic fluid, prostaglandin F2alpha and prostaglandin E2 in amniotic fluid, and progesterone in maternal serum were determined. Longitudinal uterine strips were prepared, placed in organ chambers with Krebs-Ringer solution, aerated with 95% oxygen and 5% carbon dioxide (37 degrees C, pH approximately 7.4), and equilibrated at 1g passive tension. Concentration-contraction relationships to oxytocin were determined. Samples of bathing solution were collected 10 minutes after the concentration of oxytocin was maximal. Prostaglandins and progesterone were measured by radioimmunoassay and endotoxin was measured by the Endospecy (Seikagaku Kogyo, Tokyo, Japan) kit.

RESULTS

Lipopolysaccharide treatment significantly increased the levels of prostaglandin F2alpha and prostaglandin E2 in amniotic fluid. Treatment with lipopolysaccharide inhibited the production and release of prostaglandin F2alpha and prostaglandin E2 that were activated by oxytocin in uterine strips and increased the sensitivity of strips to the contractile effect of oxytocin. Indomethacin did not affect the basal or the lipopolysaccharide-activated levels of endotoxin in serum and amniotic fluid and exerted a counteraction on lipopolysaccharide-induced increases in concentrations of prostaglandin F2alpha and prostaglandin E2 in amniotic fluid. Indomethacin counteracted oxytocin-activated production and release of prostaglandin F2alpha and prostaglandin E2 in uterine tissues after lipopolysaccharide administration without changing the sensitivity of uterine strips to oxytocin. Concentrations of progesterone were not changed after lipopolysaccharide, indomethacin, or their combined application, which suggests that the changes described were not associated with alterations in the levels of the hormone.

CONCLUSIONS

The activation of the uterine contractile system by prostaglandin and oxytocin during intra-amniotic infection may be one of the causes of preterm delivery. A combination of an oxytocin receptor antagonist and an inhibitor of cyclooxygenase may be beneficial in prevention or treatment of preterm labor.

The regulation of prostaglandin output from term intact fetal membranes by anti-inflammatory cytokines

Prostaglandins are some of the main mediators which control parturition, and their production by intrauterine tissues can be up-regulated by pro-inflammatory cytokines. Anti-inflammatory cytokines may oppose these effects, and in this study we have investigated how two such cytokines affected fetal membrane function. Interleukin-10 (IL-10) inhibited the output of prostaglandin E2 (PGE2) from intact fetal membranes under basal and lipopolysaccharide (LPS)-stimulated conditions, and there was a parallel decrease in the expression of mRNA for COX-2. IL-10 also inhibited the production of interleukin-1beta (IL-1beta) and the expression of mRNA for IL-1beta, indicating that this cytokine has a broad anti-inflammatory effect. Transforming growth factor-beta1 (TGF-beta1), which is generally considered to be anti-inflammatory had opposite effects on PGE2 production, in that it increased the output of PGE2 for up to 8 hr. TGF-beta1 increased levels of type-2 cyclo-oxygenase (COX-2) and cytosolic phospholipase A2 (cPLA2) protein, and also activated the cPLA2 enzyme present; the profile of effects is similar to that of the pro-inflammatory cytokine IL-1beta, and was not expected. Combinations of TGF-beta1 with IL-1beta also increased PGE2 output and caused appropriate changes in prostaglandin pathway enzymes, whereas TGF-beta1 and IL-1alpha had more limited effects. Further studies are needed to establish the physiological significance of these findings, but TGF-beta1 does not seem to act as an inhibitory cytokine in intact fetal membranes at term.

Maternal serum interleukin 1, 2, 6, 8 and interleukin-2 receptor levels in preterm labor and delivery

OBJECTIVE

To determine the concentrations of maternal serum interleukins (ILs) 1, 2, 6, 8 and IL-2 receptors (IL-2R) in patients in their second and third trimesters of pregnancy and in preterm labor and delivery without evidence of chorioamnionitis.

STUDY DESIGN

The study was conducted in La Paz Maternal Hospital, Madrid. Maternal serum IL concentrations were measured in 103 gravidas during preterm labor and delivery. The Mann-Whitney U test was used for analysis.

RESULTS

Women in preterm labor and delivery had significantly higher median IL-2R concentration. Women who responded to tocolysis had significantly lower serum concentrations of IL-6. IL-2R and IL-6 serum concentrations predict delivery in 48 h and before 34 weeks gestation.

CONCLUSIONS

Compared with non-laboring gravidas, those in idiopathic preterm labor or delivery had significantly higher concentrations of maternal serum IL-2R. Both IL-6 and IL-2R may predict failure of tocolysis. IL-2 does not seem to play an important role in pregnancy.

Regulation of cyclooxygenase-2 expression by phosphatidate phosphohydrolase in human amnionic WISH cells

Prostaglandins are known to play a key role in the initiation of labor in humans, but the mechanisms governing their synthesis in amnion are largely unknown. In this study, we have examined the regulatory pathways for prostaglandin E(2) (PGE(2)) production during protein kinase C-dependent activation of human WISH cells. In these cells, PGE(2) synthesis appears to be limited not by free arachidonic acid availability but by the expression levels of cyclooxygenase-2 (COX-2). Concomitant with the cells being able to synthesize and secrete PGE(2), we detected significant elevations of both COX-2 protein and mRNA levels. Specific inhibition of COX-2 by NS-398 totally ablated PGE(2) synthesis. All of these responses were found to be strikingly dependent on an active phosphatidate phosphohydrolase 1 (PAP-1). Inhibition of PAP-1 activity by three different strategies (i.e. use of bromoenol lactone, propranolol, and ethanol) resulted in inhibition of COX-2 expression and hence of PGE(2) production. These data unveil a novel signaling mechanism for the regulation of PGE(2) production via regulation of COX-2 expression and implicate phosphatidate phosphohydrolase 1 as a key regulatory component of eicosanoid metabolic pathways in the amnion.

Trajectories of fetal loss in the czech republic

Using data for 555,038 pregnancies conceived in the Czech Republic in 1987-1990, we show that pronounced differences in fetal survival in the middle trimester of pregnancy by marital status, educational level, and labor force attachment become much smaller at full term; survival differences by age at conception and number of previous deliveries show relatively constant proportional hazards throughout gestation. Social inequalities in postpartum life chances have been documented previously, but we show that similar inequalities exist before birth.

The nuclear transcription factor NF-kappaB mediates interleukin-1beta-induced expression of cyclooxygenase-2 in human myometrial cells

OBJECTIVE

Up-regulation of prostaglandin production by gestational tissues in the setting of intrauterine infection has been implicated as an important contributor to preterm labor and parturition. In this study we investigated the possible role of the nuclear transcription factor NF-kappaB in interleukin-1 signaling, leading to the expression of cyclooxygenase 2 and prostaglandin production in human myometrial cell cultures.

STUDY DESIGN

Human myometrial smooth muscle cells from an immortalized line were used as a model system between passages 20 and 35. Growth-arrested cell cultures were stimulated with human recombinant interleukin 1, and the activation of NF-kappaB was assessed by the degradation of the inhibitory protein IkappaB-alpha (Western analysis), as well as by nuclear binding of NF-kappaB by using an electrophoretic mobility shift assay. The abundance of cyclooxygenase-2 messenger ribonucleic acid and protein was measured by Northern and Western analyses, whereas prostaglandin (prostaglandin I(2 ) and prostaglandin E(2 )) production was determined by specific radioimmunoassays.

RESULTS

Within 15 minutes of stimulation with interleukin 1, 90% of IkappaB-alpha was degraded. This was temporally associated with nuclear translocation and binding of NF-kappaB. Within 30 minutes, cyclooxygenase 2 messenger ribonucleic acid appeared, with steady-state levels increasing up to 4 hours. This was followed by an up to 80-fold increase in cyclooxygenase 2 protein and a corresponding time-dependent increase in prostaglandin production. When IkappaB-alpha degradation was blocked with calpain I inhibitor, NF-kappaB translocation, cyclooxygenase 2 messenger ribonucleic acid and protein expression, and prostaglandin synthesis were also inhibited.

CONCLUSION

Stimulation of human myometrial cells with interleukin 1 leads to rapid activation of the transcription factor NF-kappaB, which is functionally linked to the expression of cyclooxygenase 2 messenger ribonucleic acid, protein, and prostaglandin synthesis.

Phospholipase A2: its usefulness in laboratory diagnostics

Phospholipase A2 (PLA2) is an enzyme that catalyzes the hydrolysis of membrane phospholipids. This article reviews the source and structure of PLA2, the involvement of the enzyme in various biological and pathological phenomena, and the usefulness of PLA2 assays in laboratory diagnostics. Of particular importance is the role of PLA2 in the cellular production of mediators of inflammatory response to various stimuli. Assays for PLA2 activity and mass concentration are discussed, and the results of enzyme determinations in plasma from patients with different pathological conditions are presented. The determination of activity and mass concentration in plasma is particularly useful in the diagnosis and prognosis of pancreatitis, multiple organ failure, septic shock, and rheumatoid arthritis. A very important result is the demonstration that PLA2 is an acute phase protein, like CRP. Indeed, there is a close correlation between PLA2 mass concentration and CRP levels in several pathological conditions. Although the determination of C-reactive protein is much easier to perform and is routinely carried out in most clinical laboratories, the assessment of PLA2 activity or mass concentration has to be considered as a reliable approach to obtain a deeper understanding of some pathological conditions and may offer additional information concerning the prognosis of several disorders.

Stimulation of prostaglandin production from intact human fetal membranes by bacteria and bacterial products

The addition of live or sonicated Escherichia coli, or endotoxin from E. coli increased the release of prostaglandins (PG) on both sides of intact human fetal membranes after 24 h of incubation, indicating that live bacteria were not required to activate prostaglandin production. Time-course studies showed that the levels of PGE2 and PGF2alpha on the fetal side of the membrane were increased 6 h after the addition of endotoxin, whereas levels on the maternal side increased within 1-2 h. These changes were independent of the side to which the endotoxin was added, indicating that a stimulatory factor passes through the fetal membranes. This factor is not endotoxin, which did not cross the membranes, and further studies are required to identify this endogenous stimulus. Prostaglandin metabolite levels were either unaffected or increased by endotoxin, indicating that the main effect is at the level of increased prostaglandin biosynthesis rather than decreased metabolism.

15-hydroxyprostaglandin dehydrogenase: implications in preterm labor with and without ascending infection

There is evidence that intrauterine infection, which stimulates PG synthesis may play a role in the pathogenesis of some preterm labor. Local tissue concentrations of PGs are controlled not only by the rate of synthesis, but also by catabolism, which is regulated by 15-hydroxyprostaglandin dehydrogenase (PGDH). We hypothesized that a decrease of PGDH activity could contribute to an increase in PG output at the time of preterm labor (PTL) especially in association with infection. We measured PGDH activity with a zero order kinetic enzymatic assay, PGDH messenger ribonucleic acid by in situ hybridization and PGDH distribution and localization with immunohistochemistry in human placenta and fetal membranes from women at term before (n = 10) or after (n = 16) labor compared to preterm labor at less than 36 weeks without (n = 16) and with (n = 11) chorioamnionitis. PGDH activity in chorion was significantly lower in PTL than at term and was further reduced when PTL was associated with inflammation. Immunoreactive PGDH and PGDH messenger ribonucleic acid localized predominantly to chorionic trophoblasts at term and were reduced in PTL women with or without infection. These effects were not observed in the placenta. Loss of PGDH with infection was associated with infiltration of chorion by polymorphonuclear leukocytes, resulting in a compromised structural integrity, although the amniotic epithelium was generally intact. We conclude that a reduction in PGDH in the human fetal membranes may occur in some cases of preterm labor and may contribute to an increase in net PG accumulation and drive to myometrial contractility.

Pathogenesis of preterm labor and preterm premature rupture of membranes associated with intraamniotic infection

We have proposed a model in which the initiation of human parturition in the presence of infection is controlled by the host. Systemic maternal infections such as pyelonephritis or localized infections such as deciduitis can trigger parturition by the activation of the monocyte and macrophage system in peripheral blood and human decidua. Preterm labor and preterm PROM can, according to this, be considered events that occur when the intrauterine or maternal environment is hostile and threaten the survival of the fetal-maternal pair. From this point of view, the initiation of preterm labor may have survival value. Why does intrauterine infection result in preterm labor in some cases and PROM in others? It is possible that regulation of different components of the host response has an important role to play in determining clinical presentation. Thus, if preferential activation of the host response leads to the secretion of uterotonic agents (i.e., prostaglandins), preterm labor will result. On the other hand, if the activation of the host response results predominantly in the production of proteases (i.e., leukocyte elastase and MMPs), patients are more likely to experience PROM. Preterm labor and preterm PROM can be considered expressions of the same basic phenomenon: activation of the host-defense macrophage system. Although we have provided evidence that infection is an important factor in the pathogenesis of these conditions, preterm parturition should be considered as a syndrome with multiple causes.

Screening for bacterial vaginosis and cervicitis aimed at preventing premature delivery

OBJECTIVE

We performed screening and treatment of bacterial vaginosis and cervicitis during pregnancy for prevention of premature delivery. The incidence and the etiology of lower genital tract infections and premature delivery were examined to elucidate the effectiveness and problems of this trial.

METHODS

Three hundred sixty-five pregnant women who attended the obstetrical outpatient clinic in our hospital were included as subjects. The screening was done at prenatal-care visits around the 10th, 20th, and 30th gestational weeks.

RESULTS

Fifty-eight women were diagnosed as bacterial vaginosis and 54 women were successfully treated. Thirty-five women were diagnosed as cervicitis and all were cured. Nine women (2.5%) delivered before the 37th gestational week and 1 women delivered before the 35th gestational week because of cervical incompetence.

CONCLUSIONS

The treatment of bacterial vaginosis and cervicitis may prevent microbes in the lower genital tract from penetrating the intrauterine cavity and thereby reduce the incidence of premature delivery.

Cytokines concentrations in the cervical mucus of pregnant women

OBJECTIVE

Interleukin-1 alpha, interleukin-1 beta, interleukin-6 and interleukin-8 in specimens of cervical mucus were assayed to assess defense mechanisms against infection in the cervical canal during pregnancy.

METHODS

Two hundred and thirty-nine pregnant women who attended the obstetrics outpatient clinic in our hospital were included as subjects. Cervical mucus was collected with a newly developed collection swab, and cytokines and granulocyte elastase in the samples of cervical mucus were quantified using enzyme immunoassay kits. The 1-factor ANOVA, the Kruskal-Wallis test, and scheffé's F were used for statistical analysis.

RESULTS

Interleukin-1 alpha, interleukin-1 beta and interleukin-8 levels rose significantly as the concentrations of granulocyte elastase increased. High concentrations of interleukin-1 alpha (75.36 +/- 19.93 pg/ml), interleukin-1 beta (1005.29 +/- 238.75 pg/ml) and interleukin-8 (4822.4 +/- 633.2 pg/ml) were found in the specimens from the group of high granulocyte elastase levels.

CONCLUSIONS

These cytokines might be involved in defense mechanisms against ascending infection from the vagina.

Application of a new perchloric acid treatment method to measure endotoxin in both amniotic fluid and cord blood by an endotoxin-specific chromogenic Limulus test in intra-amniotic infection

Endotoxin in both amniotic fluid and cord blood was measured to detect intra-amniotic fetal infection. Both amniotic fluid and cord blood plasma were pretreated by a perchloric acid treatment, and the endotoxin level was measured by Endospecy test. Cut off values for endotoxin in amniotic fluid and cord blood were 8.5 pg/mL and 7.6 pg/mL, respectively. Escherichia coli intra-amniotic infection caused respiratory distress syndrome (RDS)-mimicking pneumonia. Abnormally high values of endotoxin in both amniotic fluid and cord blood were detected. Intra-amniotic infection caused by Gram-positive bacteria (group B streptococci, Enterococcus fecalis) was shown to be endotoxin negative in both amniotic fluid and cord blood. In cases of negative amniotic fluid culture, measurement of the value of endotoxin in the amniotic fluid is useful in identifying intra-amniotic fetal infection.

Interleukin-1 beta intra-amniotic infusion induces tumor necrosis factor-alpha, prostaglandin production, and preterm contractions in pregnant rhesus monkeys

OBJECTIVE

To describe the temporal and quantitative consequences of intra-amniotic interleukin-1 beta infusion in a nonhuman primate model.

METHODS

On days 128-138 of gestation (term 167 days), four chronically instrumented rhesus monkeys (Macaca mulatta) underwent serial intra-amniotic infusions of 2, 5, and 10-20 micrograms recombinant human interleukin-1 beta. Each infusion was for 2 hours, and subsequent infusions were at least 48 hours later. Amniotic fluid was sampled serially both before and after infusion for interleukin-1 beta, tumor necrosis factor-alpha (TFN-alpha), and prostaglandin (PG) E2 and F2 alpha by specific assays, and uterine activity in each monkey was recorded continuously.

RESULTS

Intra-amniotic concentrations of interleukin-1 beta rose dramatically after infusion. This rise was rapidly followed by the appearance of TNF-alpha in the amniotic cavities of all animals, with maximal levels reached 5 hours after the initiation of the infusion. Both interleukin-1 beta and TNF-alpha were rapidly cleared from the amniotic fluid and returned to baseline levels by 24-48 hours. Increases in PGE2 and F2 alpha paralleled those of the two cytokines but remained elevated for the duration of the experiments. The stimulation of uterine contractility from a pre-infusion level of 200 mmHg. seconds/hour to 6000 mmHg. seconds/hour occurred an average of 6-10 hours after interleukin-1 beta infusion. These stimulations were transient, usually abating by 22 hours after infusion, and did not result in frank labor.

CONCLUSION

In the rhesus monkey, intra-amniotic infusion of interleukin-1 beta rapidly induces production of intra-amniotic TNF-alpha as well as PGE2 and F2 alpha, followed by uterine contractility. Uterine activity diminishes as cytokine levels return to pre-infusion levels, even in the presence of elevated intraamniotic PG levels. Tumor necrosis factor-alpha may act synergistically with interleukin-1 beta in the pathophysiology of cytokine-related preterm labor.

Intrauterine infection and the effects of inflammatory mediators on prostaglandin production by myometrial cells from pregnant women

OBJECTIVE

Our purpose was to evaluate the effects of known stimulants of prostaglandin production on cultured myometrial cells from women in labor with and without intrauterine infection.

STUDY DESIGN

Myometrial segments were obtained from 16 patients between 33 and 40 weeks' gestation who had been in labor for > or = 8 hours at cesarean delivery; 8 patients had clinical chorioamnionitis and 8 did not. Myometrial cells were isolated and grown in culture. Incubations were conducted with interleukin-1 beta, tumor necrosis factor-alpha, or epidermal growth factor. Prostaglandin E2, prostaglandin F2 alpha, and 6-keto-prostaglandin F1 alpha (the stable metabolite of prostacyclin) were measured by radioimmunoassay, and cellular protein was determined.

RESULTS

Cultured human myometrial cells from patients with and without prior intrauterine infection produced prostaglandins in response to interleukin-1 beta, tumor necrosis factor-alpha, and epidermal growth factor at a significantly increased rate (p<0.05 vs controls at and above 10 ng/ml of interleukin-1 beta, tumor necrosis factor-alpha, and epidermal growth factor). The major prostaglandin produced in response to each stimulant was 6-keto-prostaglandin F1 alpha; however, this response was attenuated in cells from patients with intrauterine infection.

CONCLUSIONS

Cultured human myometrial cells from patients with and without prior intrauterine infection respond to known stimulants of prostaglandin production. Prior intrauterine infection has no effect on baseline prostaglandin production, but the amount of prostacyclin produced as a response to cellular stimulants is decreased with prior intrauterine infection. This effect may have a role in regulating myometrial function in intrauterine infection.

Prolactin concentrations in preterm and term pregnancy and labour

Maternal plasma and amniotic fluid (AF) were obtained for measurement of prolactin concentrations from: 1) 20 patients with preterm labor and intact membranes who delivered within one week of amniocentesis; 2) 20 patients with preterm labor who responded to tocolysis and delivered at term; 3) 20 women at term who were not in labor and 4) from 20 women in active labor at term. No significant differences were found between: 1) maternal plasma prolactin concentrations in women with preterm labor who delivered prematurely and those who delivered at term (155 ng/ml vs 176.5 ng/ml); 2) patients at term who were not in labor (188 ng/ml) and those who were in labor (155 ng/ml); 3) AF prolactin concentrations in the two preterm labor groups (1987.5 vs 1282.5 ng/ml) and 4) AF prolactin concentration in the two term groups (562 ng/ml vs 701 ng/ml). Prolactin concentrations were generally significantly higher preterm than at term. We concluded that no significant changes in maternal plasma and amniotic fluid prolactin levels were found in preterm and term parturition.

Interleukin-1 beta independently stimulates production of prostaglandin E2 and cyclic AMP from human decidual cells

Interleukin-1 beta (IL-1 beta) increased the production of cyclic AMP and prostaglandin E2 (PGE2) by cultured human decidual cells during 24 h of stimulation, but not over short incubation times (< 6 h). At concentrations of IL-1 beta ranging from 1 to 100 pg/ml, there were parallel changes in cyclic AMP and PGE2 levels, but 1000 pg of IL-1 beta/ml inhibited cyclic AMP production while still stimulating PGE2 synthesis. The possible link between cyclic AMP and PGE2 was therefore studied further. Inhibition of IL-1 beta-stimulated PGE2 synthesis by indomethacin and direct addition of PGE2 had no effect on cyclic AMP levels, indicating that PGE2 did not increase cyclic AMP production by human decidual cells and confirming the independent synthesis of cyclic AMP and PGE2. The increase in cyclic AMP production induced by IL-1 beta is dependent on protein synthesis, but it is not known which component of the adenylate cyclase is increased. A phosphodiesterase inhibitor potentiated the effects of IL-1 beta on cyclic AMP synthesis, indicating that the cytokine may increase cyclic AMP metabolism. We suggest that high concentrations of IL-1 beta activate phosphodiesterase activity more than adenylate cyclase, which gives rise to the low levels of cyclic AMP noted above. IL-1 beta also decreased forskolin-stimulated cyclic AMP production, which again indicates increased cyclic AMP metabolism. Since most concentrations of IL-1 beta alone increased cyclic AMP levels, this stimulation must out-weigh the increase in metabolism apparent in the presence of forskolin, phosphodiesterase inhibitor or high levels of interleukin. It is clear that IL-1 beta increased decidual PGE2 production independently of cyclic AMP, and that other second messenger must mediate the action of this cytokine.

A model of intrauterine infection and preterm delivery in mice

OBJECTIVE

Our purpose was to determine whether intrauterine bacterial inoculation leads to preterm delivery in mice.

STUDY DESIGN

Fifty-four female CD-1 mice at 75% of the length of the gestational period (14.5 days) received either an intrauterine bacterial inoculum of 2 to 10 x 10(3) Escherichia coli (n = 33), an intraperitoneal bacterial inoculum (n = 7), or an intrauterine injection of a sterile solution (n = 14).

RESULTS

Delivery within 48 hours of surgery occurred in 91% of mice after intrauterine bacteria, in 0% after intraperitoneal bacteria, and in 7% after sterile intrauterine injection (p < 0.001). Intrauterine bacterial inoculation produced systemic infection (i.e., recovery of organisms from culture of the heart) in 50% of animals post partum. Intraperitoneal bacteria and intrauterine saline solution injections resulted in systemic infection rates of 20% and 0%, respectively, 48 hours after surgery. Five of seven animals injected with bacteria into the uterus had histologic evidence of metritis, mild in all cases. Intrauterine bacterial inoculation resulted in induction of ribonucleic acid transcripts for tumor necrosis factor-alpha, interleukin-1 alpha, interleukin-1 beta, and cyclooxygenase-2.

CONCLUSIONS

Intrauterine inoculation with Escherichia coli in mice leads to preterm delivery and the local induction of factors known to be involved in human preterm labor with infection. The observation that intraperitoneal bacterial inoculation does not result in preterm delivery suggests that in this model labor is the product of a local (uterine) stimulus.

Bacterial lipopolysaccharide-mediated fetal death. Production of a newly recognized form of inducible cyclooxygenase (COX-2) in murine decidua in response to lipopolysaccharide

Maternal infection is a cause of spontaneous abortion and preterm labor in humans, but the pathophysiology is unclear. We hypothesized that eicosanoids play an important role in infection-driven pregnancy loss. To investigate this hypothesis, we administered lipopolysaccharide (LPS) to pregnant C3H/HeN mice and found that LPS administration caused fetal death in a dose-dependent fashion. Pretreatment with indomethacin significantly decreased the proportion of fetal death from 83% to < 25% in mice injected with 10 micrograms of LPS. Also, decidual explants from LPS-treated mice produced significantly more inflammatory eicosanoids, including prostaglandins E2 and F2 alpha and thromboxane B2, than controls. We investigated the regulatory mechanisms responsible for increased decidual prostanoid production in response to LPS. Western and Northern blots demonstrated that decidual protein and mRNA levels of a recently recognized highly inducible form of cyclooxygenase, COX-2, were substantially increased in mice treated with LPS. Induction of COX-2 was rapid: mRNA was detected 30 min after LPS injection. In contrast, another form of cyclooxygenase, COX-1, was only minimally induced in response to LPS. Our data indicate that LPS induces decidual prostanoid production via increased COX-2 expression. Since LPS-mediated fetal death is markedly diminished by pretreatment with indomethacin, COX-2-mediated eicosanoid production is likely a key pathophysiologic event in LPS-mediated fetal death.

Interleukin-1 beta-stimulated PGE2 production from early first trimester human decidual cells is inhibited by dexamethasone and progesterone

Cytokines are known to increase the production of prostaglandins by human decidual cells, but negative regulators have not been identified. We have examined the effects of dexamethasone and progesterone on prostaglandin (PG) E2 synthesis by cultured human first trimester decidual cells. The numbers of cyclooxygenase (COX) enzyme positive cells were visualised by immunocytochemistry, using antibodies specific for COX-1 and COX-2. Interleukin-1 beta stimulated the production of prostaglandins E2 and F2 alpha dose-dependently, and this was associated with increased numbers of COX-2 positive cells. Progesterone (10(-7)-10(-6) M) and dexamethasone (10(-7)-10(-6) M) inhibited basal and interleukin-1 beta-stimulated prostaglandin production, and decreased the numbers of COX-2 positive cells. Neither interleukin-1 beta nor the steroids affected numbers of COX-1 positive cells. COX-2 seems to be the main enzyme controlling the synthesis of PGE2 by human decidual cells, and may be negatively regulated by progesterone.

An experimental model for intraamniotic infection and preterm labor in rhesus monkeys

OBJECTIVE

Our purpose was to describe the temporal and quantitative relationship between intraamniotic infection and preterm labor in a nonhuman primate model.

STUDY DESIGN

On day 130 of gestation (term 167 days) four chronically instrumented rhesus monkeys (Macaca mulatta) were infected with an intraamniotic inoculation of 10(6) colony-forming units of group B streptococci. Four additional noninfected monkeys were followed up to spontaneous parturition as controls. Amniotic fluid was serially sampled in all monkeys both before and after inoculation for bacterial growth, tumor necrosis factor-alpha, interleukin-1 beta, interleukin-6, prostaglandin E2, and prostaglandin F2 alpha, and uterine activity was continuously recorded.

RESULTS

Increases in uterine contractility occurred 28 hours (range 14 to 40 hours) after inoculation and were preceded by increases in amniotic fluid cytokines and prostaglandins. Intraamniotic concentrations of tumor necrosis factor-alpha, interleukin-6, and interleukin-1 beta all rose dramatically 9, 15, and 18 hours after infection and 10 to 20 hours before increases in uterine contractility. In spontaneous parturition only interleukin-6 concentrations rose moderately (from 0.1 to 1.2 ng/ml). Increases in prostaglandin E2 and prostaglandin F2 alpha paralleled those of the cytokines. Peak prostaglandin concentrations in intraamniotic infection exceeded by severalfold concentrations seen in spontaneous parturition (16,046 pg/ml vs 2765 pg/ml for prostaglandin E2, p < 0.05; and 5547 pg/ml vs 708 pg/ml for prostaglandin F2 alpha, p < 0.05). In spite of intraamniotic none of the monkeys were febrile or had peripheral leukocytosis at the onset of labor.

CONCLUSION

In the rhesus monkey, after intraamniotic infection, there is a predictable and sequential increase in amniotic fluid tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6, followed by increases in prostaglandin E2 and prostaglandin F2 alpha. These increases all occur before an increase in uterine contractility and before clinical signs of infection. Our data provide evidence for a cause-and-effect relationship between intraamniotic infection and preterm labor and support the utility of measuring interleukin-6 or other cytokines in the diagnosis of intraamniotic infection.

The value of amniotic fluid interleukin-6 determination in patients with preterm labor and intact membranes in the detection of microbial invasion of the amniotic cavity

OBJECTIVES

Our purpose was to (1) determine the value of amniotic fluid interleukin-6 determination in the detection of microbial invasion of the amniotic cavity and (2) compare interleukin-6 to other rapid tests in the evaluation of preterm labor.

STUDY DESIGN

Amniotic fluid interleukin-6 was determined quantitatively by enzyme-linked immunosorbent assay in 91 amniotic fluid specimens obtained by amniocentesis in 89 patients with preterm labor. Amniotic fluid cultures for aerobes, anaerobes, and mycoplasma species were performed. Receiver-operator characteristic curve analysis, logistic regression analysis, and Cox's proportional-hazards model were used to explore the relationship between several explanatory and outcome variables. Diagnostic index values of interleukin-6, glucose level, Gram stain, leukocyte esterase, and limulus amebocyte lysate assay for prediction of a positive amniotic fluid culture, preterm delivery, clinical infection, and neonatal sepsis were calculated.

RESULTS

The prevalence of positive amniotic fluid cultures was 13% (12/89). The median interleukin-6 concentration in patients with positive cultures was 241.8 ng/ml, in contrast to 0.291 ng/ml in patients with negative cultures (p. < 0.005). Sensitivity and specificity of an interleukin-6 level > or = 6.17 ng/ml was 75% and 79%, in contrast to that of glucose, < or = 12 mg/dl (83% and 86%) for a positive amniotic fluid culture and sensitivity (p = 0.26, z test). All patients with an interleukin-6 level > 6.17 ng/ml were delivered preterm, in contrast to 85.2% of patients with a glucose level < or = 12 mg/dl. When all rapid tests and clinical parameters were considered simultaneously in the logistic model, only interleukin-6 maintained a significant relationship to preterm birth (odds ratio 35, p = 0.003). Cox's proportional analysis demonstrated a strong relationship between interleukin-6 and the amniocentesis-to-delivery interval after clinical variables were controlled for (hazard ratio 3.01, p < 0.00001).

CONCLUSION

Amniotic fluid interleukin-6 determination may be a useful adjunct to our armamentarium of rapid tests to exclude infection and predict delivery in patients with preterm labor and intact membranes.