Amnion cell biosynthesis of interleukin-8: regulation by inflammatory cytokines

Pathophysiological Implication of Pattern Recognition Receptors in Fetal Membranes Rupture: RAGE and NLRP Inflammasome

Preterm prelabor ruptures of fetal membranes (pPROM) are a pregnancy complication responsible for 30% of all preterm births. This pathology currently appears more as a consequence of early and uncontrolled process runaway activation, which is usually implicated in the physiologic rupture at term: inflammation. This phenomenon can be septic but also sterile. In this latter case, the inflammation depends on some specific molecules called “alarmins” or “damage-associated molecular patterns” (DAMPs) that are recognized by pattern recognition receptors (PRRs), leading to a microbial-free inflammatory response. Recent data clarify how this activation works and which receptor translates this inflammatory signaling into fetal membranes (FM) to manage a successful rupture after 37 weeks of gestation. In this context, this review focused on two PRRs: the receptor for advanced glycation end-products (RAGE) and the NLRP7 inflammasome.

Acute chorioamnionitis and funisitis: definition, pathologic features, and clinical significance

Acute inflammatory lesions of the placenta consist of diffuse infiltration of neutrophils at different sites in the organ. These lesions include acute chorioamnionitis, funisitis, and chorionic vasculitis and represent a host response (maternal or fetal) to a chemotactic gradient in the amniotic cavity. While acute chorioamnionitis is evidence of a maternal host response, funisitis and chorionic vasculitis represent fetal inflammatory responses. Intraamniotic infection generally has been considered to be the cause of acute chorioamnionitis and funisitis; however, recent evidence indicates that "sterile" intraamniotic inflammation, which occurs in the absence of demonstrable microorganisms induced by "danger signals," is frequently associated with these lesions. In the context of intraamniotic infection, chemokines (such as interleukin-8 and granulocyte chemotactic protein) establish a gradient that favors the migration of neutrophils from the maternal or fetal circulation into the chorioamniotic membranes or umbilical cord, respectively. Danger signals that are released during the course of cellular stress or cell death can also induce the release of neutrophil chemokines. The prevalence of chorioamnionitis is a function of gestational age at birth, and present in 3-5% of term placentas and in 94% of placentas delivered at 21-24 weeks of gestation. The frequency is higher in patients with spontaneous labor, preterm labor, clinical chorioamnionitis (preterm or term), or ruptured membranes. Funisitis and chorionic vasculitis are the hallmarks of the fetal inflammatory response syndrome, a condition characterized by an elevation in the fetal plasma concentration of interleukin-6, and associated with the impending onset of preterm labor, a higher rate of neonatal morbidity (after adjustment for gestational age), and multiorgan fetal involvement. This syndrome is the counterpart of the systemic inflammatory response syndrome in adults: a risk factor for short- and long-term complications (ie, sterile inflammation in fetuses, neonatal sepsis, bronchopulmonary dysplasia, periventricular leukomalacia, and cerebral palsy). This article reviews the definition, pathogenesis, grading and staging, and clinical significance of the most common lesions in placental disease. Illustrations of the lesions and diagrams of the mechanisms of disease are provided.

The contribution of the immune system to parturition

The immune system plays a central role before and during parturition, including the main physiological processes of parturition: uterine contractions and cervical ripening. The immune system comprises white blood cells and their secretions. Polymorphonuclear cells and macrophages invade the cervical tissue and release compounds, such as oxygen radicals and enzymes, which break down the cervical matrix to allow softening and dilatation. During this inflammatory process, white blood cells undergo chemotaxis, adherence to endothelial cells, diapedesis, migration and activation. Factors that regulate white blood cell invasion and secretion include cytokines such as tumour necrosis factor and interleukins. Glucocorticoids, sex hormones and prostaglandins, affect cytokine synthesis. They also modulate the target cells, resulting in altered responses to cytokines. On the other hand, the immune system has profound effects on the hormonal system and prostaglandin synthesis. In animals, nitric oxide has marked effects on uterine quiescence during gestation. At the same time, it plays an important role in regulating the vascular tone of uterine arteries and has anti-adhesive effects on leukocytes. Cytokines are found in amniotic fluid, and in maternal and foetal serum at term and preterm. Several intrauterine cells have been shown to produce these cytoldnes. Since neither white blood cells, cytokines nor nitric oxide seem to be the ultimate intermediate for human parturition, the immune system is an additional but obligatory and underestimated component in the physiology of delivery. Scientists, obstetricians and anaesthesiologists must thus be aware of these processes.

Possible roles of proinflammatory and chemoattractive cytokines produced by human fetal membrane cells in the pathology of adverse pregnancy outcomes associated with influenza virus infection

Pregnant women are at an increased risk of influenza-associated adverse outcomes, such as premature delivery, based on data from the latest pandemic with a novel influenza A (H1N1) virus in 2009-2010. It has been suggested that the transplacental transmission of influenza viruses is rarely detected in humans. A series of our study has demonstrated that influenza virus infection induced apoptosis in primary cultured human fetal membrane chorion cells, from which a factor with monocyte differentiation-inducing (MDI) activity was secreted. Proinflammatory cytokines, such as interleukin (IL)-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-β, were identified as a member of the MDI factor. Influenza virus infection induced the mRNA expression of not only the proinflammatory cytokines but also chemoattractive cytokines, such as monocyte chemoattractant protein (MCP)-1, regulated on activation, normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1β, IL-8, growth-regulated oncogene (GRO)-α, GRO-β, epithelial cell-derived neutrophil-activating protein (ENA)-78, and interferon inducible protein (IP)-10 in cultured chorion cells. These cytokines are postulated to associate with human parturition. This paper, therefore, reviews (1) lessons from pandemic H1N1 2009 in pregnancy, (2) production of proinflammatory and chemoattractive cytokines by human fetal membranes and their functions in gestational tissues, and (3) possible roles of cytokines produced by human fetal membranes in the pathology of adverse pregnancy outcomes associated with influenza virus infection.

Surfactant protein-A as an anti-inflammatory component in the amnion: implications for human pregnancy

The mechanism of mouse parturition is thought to involve myometrial infiltration by amniotic fluid (AF) macrophages, activated by surfactant protein-A (SP-A). In humans, the concentration of AF SP-A decreases during labor, and no fetal macrophages are found in the myometrium after labor. Therefore, it appears that the mechanisms of labor in mice and humans are different. We investigated a potential role for SP-A in human pregnancy and parturition by examining SP-A expression patterns in AF and amnion. High molecular mass (>250 kDa) oligomeric SP-A was increased in AF with advancing gestation. Interestingly, these oligomers were more abundant in placental amnion before labor at term, while they increased primarily in reflected amnion during labor (p < 0.05). Immunoblotting showed a binding of high molecular mass SP-A in AF to amnion. In C57BL/6 mice, oligomeric SP-A was also readily detected in AF from E15 onwards, but not in amnion. Macrophage density in mice myometrium did not change with advancing gestational age. Microarray analysis of human amnion explants incubated with SP-A revealed a molecular signature of inhibited cytokine-cytokine receptor interaction with downregulation of IL-1beta, CXCL2, and CXCL5 mRNA expression. The findings in this study strongly suggest that SP-A signals amniotic anti-inflammatory response via AF during pregnancy. We propose that an SP-A interaction among AF, placental amnion, and reflected amnion is a unique mechanism for immunoregulation in human pregnancy akin to that established in lung biology. However, AF SP-A and fetal macrophages by themselves do not seem to be exclusive effectors of parturition in humans.

Exodus-1 (CCL20): evidence for the participation of this chemokine in spontaneous labor at term, preterm labor, and intrauterine infection

AIM

CCL20, also known as MIP-3 alpha, is a chemokine that participates in chemotaxis of immature dendritic cells, effector/memory T-cells, and B-lymphocytes. The objectives of this study were to determine whether CCL20 can be detected in amniotic fluid (AF) and if AF concentration of this chemokine changes with advancing gestational age, parturition (term and preterm), and intra-amniotic infection/inflammation (IAI).

METHODS

A cross-sectional study was conducted including the following groups: (1) mid-trimester of pregnancy (n=65); (2) term not in labor (TNL; n=22); (3) term in labor (TIL; n=47); (4) spontaneous preterm labor (PTL) who delivered at term (n=57); (5) spontaneous PTL without IAI who delivered preterm (n=71); and (6) spontaneous PTL with IAI (n=38). AF CCL20 concentrations were determined using ELISA.

RESULTS

(1) The median AF CCL20 concentration in TNL was higher than that of mid-trimester patients; (2) Women in spontaneous labor at term had a higher median AF concentration of CCL20 than patients at term not in labor; (3) Patients with spontaneous PTL and IAI had a significantly higher median AF concentration of CCL20 than those without IAI who delivered preterm and those who delivered at term. Moreover, women with spontaneous PTL without IAI who delivered preterm had a significantly higher median AF concentration than those with PTL who subsequently delivered at term.

CONCLUSIONS

(1) CCL20 is a physiologic constituent of AF and its concentration increases as term approaches; (2) spontaneous labor (term and preterm) in the absence of IAI is associated with increased bioavailability of AF CCL20 suggesting that an increase in CCL20 is part of the common pathway of human parturition; (3) patients with IAI had dramatic elevations in the AF CCL20 concentrations suggesting that this chemokine participates in the host response to infection or other stimuli associated with intra-amniotic infection.

Secretion of bioactive interleukin-6 and tumor necrosis factor-alpha proteins from primary cultured human fetal membrane chorion cells infected with influenza virus

Influenza virus infection during pregnancy is implicated in one of the causes of premature delivery, abortion and stillbirth. Pro-inflammatory cytokines, such as interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha produced by fetal membranes, are postulated to facilitate premature delivery. We investigated the secretion of IL-6 and TNF-alpha from primary cultured human fetal membrane chorion and amnion cells infected with influenza virus at protein and bioactivity levels in order to understand the pathology of premature delivery during influenza virus infection. Concentrations of IL-6 and TNF-alpha proteins were significantly increased in culture supernatants of chorion cells by influenza virus infection. Culture supernatants of the virus-infected chorion cells stimulated the proliferation of IL-6-sensitive 7-TD-1 cells and induced the cytolysis of TNF-alpha-sensitive L929 cells, both activities of which were inhibited by the addition of respective antibody, whereas no such phenomena were observed in amnion cells. The results demonstrated that only chorion cells secreted significant amounts of bioactive IL-6 and TNF-alpha proteins responding to influenza virus infection. The present study suggests a possibility that the secretion of bioactive IL-6 and TNF-alpha proteins from fetal membrane chorion cells is implicated in the pathogenesis of premature delivery during influenza virus infection.

Effect of amniotic fluid upon prostaglandin E2 and I2 production by cultured human myometrial cells

OBJECTIVE

Our goal was to study the effect of amniotic fluid obtained at 16 and 39 weeks of gestation in normal human pregnancies upon prostaglandin production by human myometrial cells in culture.

STUDY DESIGN

Amniotic fluid, sampled either at 16 weeks, during amniocentesis, or at 39 weeks, during caesarean section before labor, was fractionated by molecular-weight and then incubated with human myometrial cells in culture. We then used radioimmunoassay to measure PGE(2) and PGI(2) production.

RESULTS

The "3-30 kDa" fraction of amniotic fluid sampled at 16 weeks significantly inhibited PGE(2) and PGI(2) production by human myometrial cells. When amniotic fluid was sampled at 39 weeks, it stimulated both PGE(2) and PGI(2) production, and the ">30 kDa" fraction increased levels of PGE(2) considerably more than of PGI(2) (420.0+/-88.0 ng/10(6)cells versus 188.2+/-21.4 ng/10(6)cells, P<0.001).

CONCLUSION

Amniotic fluid contains substances whose effects in cultured myometrial cells vary according to gestational age and type of prostaglandin. These data suggest that the fetus plays a role in the regulation of myometrial activity during pregnancy.

Testing for risk of preterm delivery

Four discrete mechanisms for the pathogenesis of PTD have been described but they share a final common pathway. Moreover, although the mechanisms have distinct clinical characteristics, they are not mutually exclusive. As an example, triplet gestations are more likely to be associated with periconceptional intrauterine manipulations predisposing to infection, as well as fetal growth restriction, decidual hemorrhage, and pathologic uterine distention. An improved understanding of these pathologic pathways has led to the development of new tests to predict PTD. Use of multiple markers (eg, serum CRH, salivary E3, cervical IL-6, TAT, and fFN) holds promise for implementing targeted interventions to prevent PTD.

The interrelationship of maternal stress, endocrine factors and inflammation on gestational length

Preterm birth rates continue to rise in the United States despite the advent of tocolytic agents and the identification of risk factors for preterm birth, such as vaginal infection and a shortened cervix. Although improvement in gestational-age-related survival of preterm infants has occurred as a result of the use of antenatal corticosteroids, neonatal surfactant therapy, and regionalization of perinatal care, there has been no reduction in the incidence of preterm birth. Recently, investigators have appreciated that the etiology of preterm birth is heterogeneous, perhaps accounting for one reason for the failure of current interventions to improve pregnancy outcome. Both abnormal maternal hormonal homeostasis and intrauterine inflammatory responses appear to contribute to a significant proportion of the cases of preterm birth, and the interaction of the maternal endocrine and immunologic systems may contribute to the pathophysiology of this condition. An important modulator of endocrine and immune function is perceived emotional and social stress. Maternal stress has been strongly associated with preterm birth, but the links between maternal stress and resultant aberrations of maternal endocrine and immune function remain difficult to quantify and investigate. However, new insights into the role of perceived maternal stress on gestational length suggest that specific interventions to alleviate stress could contribute to an increase in gestational length and a decrease in the risk for preterm birth. This review addresses the role of maternal stress on the regulation of maternal hormone and inflammatory responses and how aberrations in these systems may lead to preterm birth.

Cytokines, prostaglandins and parturition--a review

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

Cytokines of the placenta and extra-placental membranes: biosynthesis, secretion and roles in establishment of pregnancy in women

Virtually all known cytokines have been demonstrated to be expressed in the placenta and associated fetal and maternal membranes during normal gestation. In addition to playing their traditional roles as modulators of immunological function, cytokines derived from the placenta and extraplacental membranes, together with other locally-derived growth factors, appear to be implicated in various aspects of implantation and placental development. Imbalances in the intrauterine cytokine milieu around the time of implantation and invasion may play a causative role in disorders associated with early pregnancy failure, and are also associated with the abnormal trophoblast development seen in gestational trophoblastic disease. Cytokines thus appear to be an important component of a paracrine/autocrine communication network operating within the feto-maternal interface to ensure the successful establishment of pregnancy.

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

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

Intra-amniotic endotoxin: chorioamnionitis precedes lung maturation in preterm lambs

The inflammatory and lung maturational effects of intra-amniotic exposure to endotoxin were assessed in fetal lambs. Five hours to 25 days after intra-amniotic injection of endotoxin, preterm lambs were delivered at 119-125 days gestation. Intra-amniotic endotoxin caused an inflammatory cell infiltration in amnion/chorion at 5 h, which persisted for 25 days. At 5-15 h after endotoxin, amnion/chorion cytokine mRNAs increased [12- to 26-fold for interleukin (IL)-1beta, IL-6, and IL-8 mRNA and 3-fold for tumor necrosis factor-alpha mRNA]. At 1-2 days after endotoxin, lung cytokine mRNAs increased 6- to 49-fold. Endotoxin caused modest changes in peripheral white blood cell counts and no significant cytokine mRNA responses in fetal liver, placenta, or jejunum. Lung maturation, as characterized by increased lung volumes and alveolar saturated phosphatidylcholine, occurred at 7 days and persisted for 25 days after endotoxin. We conclude that exposure to a single dose of intra-amniotic endotoxin causes inflammation and increases in cytokine mRNA in amnion/chorion and the fetal lung before lung maturation, consistent with the hypothesis that proinflammatory cytokines signal lung maturation.

Expression of interleukin-8 in human metastatic endometrial carcinoma cells and its regulation by inflammatory cytokines

In the present study, we analyzed the expression of a multifunctional cytokine, interleukin-8 (IL-8), in metastatic endometrial carcinoma cells. Our data demonstrate that human serous papillary endometrial adenocarcinoma (SPEC) and human endometrial adenocarcinoma (HEC) cells expressed steady-state IL-8-specific mRNA transcript and secreted IL-8 protein. The levels of IL-8 mRNA in SPEC-2 cells established from stage IV serous papillary adenocarcinoma were three-fold higher as compared to endometrial adenocarcinoma cells, HEC-1 A, established from stage IA endometrial cancer. Further, we observed higher levels of IL-8 mRNA and protein expression in the metastatic variants of SPEC-2 and HEC-1A cells as compared to the parent cell lines, demonstrating that IL-8 expression was associated with metastatic potential. Further, the treatment of endometrial carcinoma cells with inflammatory cytokines, IL-1beta and tumor necrosis factor-alpha (TNF-alpha), demonstrated that IL-1beta and TNF-alpha induced IL-8 expression in endometrial cancer cells. IL-1beta was a more potent inducer of IL-8 expression than TNF-alpha in our studies. These data demonstrate that constitutive and induced IL-8 expression in endometrial carcinoma cells might be an important regulatory mechanism of tumor growth and metastasis.

Effects of intrauterine IL-6 and IL-8 on the expression of surfactant apoprotein mRNAs in the fetal rat lung

OBJECTIVE

The purpose of this study was to investigate the effect of interleukin-6 (IL-6) and interleukin-8 (IL-8), whose concentrations are elevated with chorioamnionitis, on the expression of surfactant apoprotein mRNAs in fetal rat lung.

STUDY DESIGN

We employed an animal model in which we were able to administer substances continuously into the cavity between the fetal membranes and endometrium using a miniosmotic pump. Lipopolysaccharide (LPS), IL-6, or IL-8 was administered to timed pregnant rats for 3 days (day 16-19), and fetal lung expression of surfactant apoprotein mRNAs for SP (surfactant apoprotein)-A, SP-B, and SP-C was evaluated by Northern blot hybridization.

RESULTS

Continuous administration of LPS increased the expression of each surfactant apoprotein mRNA, but the expression of mRNAs was not dose-dependent. On the other hand, continuous IL-6 or IL-8 administration increased the expression of each surfactant apoprotein mRNA in a dose-dependent manner.

CONCLUSION

Fetal lung maturation may be promoted by either IL-6 or IL-8 produced in response to chorioamnionitis.

The distribution of receptors for the pro-inflammatory cytokines interleukin (IL)-6 and IL-8 in the developing human fetus

Interleukin-6 receptor alpha (IL-6R) and interleukin-8 receptor (IL-8RB) are widely expressed in adult human and murine tissues. Little is known about the expression of these receptors and the function of their ligands in the developing human fetus.

OBJECTIVES

To determine the tissue distribution and cellular expression of IL-6R and IL-8RB in the developing human fetus.

METHODS

Reverse transcription-PCR and immunohistochemical staining were performed on brain, spinal cord, eye, heart, lung, liver, spleen, adrenal, kidney, intestine, and placenta from fetuses of 8 and 16+/-2 weeks post-conception.

RESULTS

IL-6R and IL-8RB mRNA were detected in all tissues tested at both time points. Immunoreactivity to anti-IL-6R antibody was present on neurons, and in neuropil of the brain, as well as in bone marrow, bronchi, hepatocytes, zona glomerulosa of the adrenal, glomerular cells in kidney, spleen, and placental trophoblasts. Cell-specific expression for IL-8RB in the central nervous system was localized to specific groups of neurons and astrocytes in the brain and spinal cord, including the neural retina. In somatic organs IL-8RB was detected in bone marrow, myocardiocytes, bronchiolar epithelial cells, hepatocytes, cells of the zona glomerulosa and the zona fasciculata of the adrenal, the collecting system of the kidney, enterocytes of the bowel and in placental cells.

CONCLUSION

The widespread expression of these cytokine receptors suggests a nonhematopoietic role for their ligand in the developing fetus.

Markers of risk for preterm delivery

Clinical and experimental evidence indicate that PTD results from four primary pathogenic mechanisms: activation of the maternal or fetal HPA axis; amniochorionic-decidual or systemic inflammation; decidual hemorrhage; and, pathologic distention of the myometrium. Each of these four pathways has a distinct epidemiological and clinical profile, and unique biochemical and biophysical pathways initiating parturition, but shares a common final biochemical pathway involving myometrial activation and stimulation, and enhanced genital tract protease activity promoting PPROM and cervical change. Traditional methods of predicting women at risk relying on obstetrical history or symptoms and epidemiological risk factors are neither sensitive nor specific. Recent approaches to predicting PTD, including sonographic measurement of cervical length and biochemical assays for hCG, cytokines, fFN, MMPs, estrogens, and CRH, are more sensitive than traditional methods. Moreover, given the heterogeneous, interactive etiopathogeneses of PTD, multiple biochemical markers should not only increase sensitivity and specificity, but also permit the detection of the relative contribution of each pathogenesis to the overall risk of PTD.

Interleukin-8 potentiates the effect of interleukin-1-induced uterine contractions

The aim of this research was to study the effect of exogenous interleukin (IL)-8, IL-1 and IL-8 + IL-1 on uterine contractions in rabbits. Four equal groups of non-pregnant rabbits (n = 24) were investigated using either placebo or experimental drugs in the form of vaginal suppositories. The suppositories contained human recombinant IL-8 (200 ng), IL-1 (200 ng), IL-8 (200 ng) + IL-1 (200 ng) or vehicle Witepsol base, 500 microliters). Subsequently, the plasma concentration of prostaglandin (PG) E2 was estimated 3 h after the last dose of treatment. Neutrophil infiltration in the endometrial tissue was studied with anti-rabbit RT2 staining. Suppositories with IL-1 and IL-8 + IL-1 produced contractile responses with increased frequency (P < 0.003, P < 0.0005) and amplitude (P < 0.0001) in vivo, compared with vehicle. IL-1 and IL-8 + IL-1 also caused similar contractile effects with increased frequency (P < 0.01, P < 0.0007) and amplitude (P < 0.0001) in an in-vitro experiment than vehicle. The frequency and amplitude of uterine contractions were more significant with IL-8 + IL-1 than that of IL-1, both in vivo (P < 0.002, P < 0.05) and in vitro (P < 0.005, P < 0.01). IL-8 did not induce any contractions. Prostaglandin concentration was increased approximately 8-fold with IL-8 + IL-1 (P < 0.0001) and 2.5-fold with IL-1 treatment (P < 0.0001). Neutrophil numbers were significantly increased with IL-8 + IL-1 > IL-8 > IL-1 (P < 0.002, P < 0.0003 and P < 0.008) compared with vehicle. Our data suggest that IL-8 stimulates IL-1-induced uterine contractions through PGE2 production and could be an important process during labour and delivery.

Immunoendocrinology of preterm labor: the link between corticotropin-releasing hormone and inflammation

Preterm labor is the final common pathway after several potential insults to the uterus or fetus. The preterm labor syndrome may be precipitated by several different pathophysiologic events, including intrauterine infection, uterine ischemia, uterine overdistention, hormonal disturbances, and other problems. Intrauterine infections (both clinically evident and subclinical) are associated with increased amniotic fluid concentrations of proinflammatory cytokines, and gestational tissues and the fetus are potential sources of these cytokines. In addition to culture-proven intrauterine infection, there may be an "intrauterine inflammatory response syndrome" that could account for cases of preterm labor in which no infectious organism can be identified. Because the immunologic and endocrinologic systems regulate each other extensively, there is potential for corticotropin-releasing hormone to regulate inflammatory responses and vice versa. The cytokine interleukin 1 stimulates production of corticotropin-releasing hormone, and corticotropin-releasing hormone in turn regulates cytokine production by immune effector cells. Because maternal stress is associated with preterm birth, abnormalities in the regulation of corticotropin-releasing hormone and the production of inflammatory cytokines may be a mechanism that could form the pathophysiologic basis for this association.

Pre-term labor: an intra-uterine inflammatory response syndrome?

Emerging concepts of sepsis suggest that the host response to an infectious stimulus results in some cases of uncontrolled release of inflammatory cytokines leading to signs of sepsis. Systemic inflammatory response syndrome (SIRS) has been suggested as a diagnosis when no etiologic organism can be found. Infection may account for up to 30% of cases of pre-term labor, and may either be clinically-evident or sub-clinical. Inflammatory cytokines can be detected in elevated concentrations in the amniotic fluid and plasma of women with pre-term labor, and human gestational tissues are potentially rich sources of inflammatory cytokines, as found in in vivo and in vitro studies. Also, maternal decidua and fetal membranes produce mRNA for inflammatory cytokines in the setting of infection-associated pre-term labor and normal term labor. Notably, anti-inflammatory cytokines, such as interleukin-10 (IL-10) do not appear to be present in substantial quantities in these pathophysiologic and physiologic conditions. Animal models indicate that pre-term labor can be stimulated by bacteria, bacterial cell wall products, and inflammatory cytokines such as IL-1 and tumor necrosis factor. These findings suggest that: (1) infectious stimuli may result in the liberation of inflammatory cytokines from gestational tissues leading inevitably to pre-term labor and delivery; (2) inhibition of this process may either be overcome or abrogated, and (3) the mechanisms regulating cytokine production in maternal and fetal tissues are disturbed. Thus, pre-term labor associated with sub-clinical infection may result in a dysregulated local inflammatory response, in which the maternal host response causes an 'intra-uterine inflammatory response syndrome' leading to pre-term labor and delivery.

Differential secretion of chemokines from peripheral blood in pregnant compared with non-pregnant women

The maintenance of a normal pregnancy is dependent on the delicate interaction between the endocrine and the immune systems. Cytokines are thought to play a key role in pregnancy by way of local modulation of the immune system at the level of peripheral leukocytes. This study examined the potential of peripheral venous blood cultures from pregnant women throughout gestation and from non-pregnant women to produce the chemokines monocyte chemotactic protein-1 (MCP-1), interleukin-8 (IL-8) and RANTES. Significantly (P = < 0.001), higher levels of MCP-1 were released from peripheral blood cultures from pregnant women at term than during the first trimester or from women who were not pregnant. This could not be accounted for by differences in differential blood counts. Significantly higher levels (P = < 0.05) of MCP-1 were released from PBMC preparations from pregnant compared with non-pregnant women. No 'rebound' increase in MCP-1 was observed on withdrawing progesterone support to the PBMC preparations. MCP-1 was secreted predominately from CD14+ cells with those from pregnant women producing more than those from non-pregnant women. There was no statistical difference in release of IL-8 or RANTES from either peripheral blood or PBMC preparations from pregnant or non-pregnant women. IL-8 and RANTES were secreted from CD14+ and CD14- cells, respectively. The hypothesis proposed is that the monocytes are fundamentally different in pregnancy and that measurement of MCP-1 has the potential to act as a marker of pregnancy status.

Regulation of interleukin (IL)-6 and IL-8 production in an amnion-derived cell line by cytokines, growth factors, glucocorticoids, and phorbol esters

PROBLEM

To determine whether amnion cells produce interleukin (IL)-6 and -8 and thus may contribute to the high concentrations of these cytokines in amniotic fluid at term.

METHOD OF STUDY

Amnion-derived WISH cells were treated in culture with stimuli over 16 hr, and IL-6 and IL-8 concentrations in the conditioned media were measured by enzyme-linked immunosorbent assay or bioassay (IL-6 only).

RESULTS

IL-8 production was approximately 5-fold higher than that of IL-6 under basal and stimulated conditions. Significant (by Dunnett's test after analysis of variance) stimulation of production of both cytokines was achieved by IL-1 beta (> 0.2 ng/ml), TNF alpha (> 10 ng/ml), and the phorbol ester, phorbol 12-myristate 13-acetate (> 2 nM), over a 16-hr culture period. Epidermal growth factor at 10 ng/ml induced a small increase in production of IL-8, but not of IL-6, whereas bacterial lipopolysaccharide had minimal effects on production of either cytokine. Basal and cytokine-stimulated IL-6 and IL-8 production was inhibited by dexamethasone at concentrations equal to or greater than 1 nM.

CONCLUSION

These findings suggest that amnion may be a significant contributor to the IL-6 and IL-8 content of amniotic fluid, and that WISH cells may be a suitable model for the study of cytokine production by amnion epithelial cells.

Interleukin-8 in urine: a new diagnostic parameter for intra-amniotic infection after premature rupture of the membranes

Interleukin-8 (IL-8), a 72 amino acid peptide secreted by cells of the immune system and of the amnion, chorion and decidua, was measured in women in late pregnancy. IL-8 was detected in the urine of 91 of 104 women with premature rupture of the fetal membranes, with values exceeding 1000 ng/L in cases of severe intra-amniotic infection. Women with urinary tract infections were excluded. The routine measurement of IL-8 in urine, together with C-reactive protein in serum, thus provides a low risk and technically simple approach to the assessment of intra-amniotic infection.

Interleukin-10 inhibition of interleukin-6 in human amniochorionic membrane: transcriptional regulation

OBJECTIVE

Our purpose was to study the regulatory effects of recombinant interleukin-10 on interleukin-6 messenger ribonucleic acid and protein production by human fetal membranes.

STUDY DESIGN

Amniochorionic membranes were collected from women undergoing elective cesarean section. Membranes were maintained in an organ explant system and stimulated with media containing lipopolysaccharide (50 ng/ml) and various amounts of recombinant interleukin-10 (10, 50, 100 ng/ml). Experiments were conducted in a dose- and time-dependent manner. Transcription and translation of interleukin-6 were monitored with quantitative reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Interleukin-10 stimulation of amniochorionic membranes in culture produced a dose-dependent decrease in the production of interleukin-6 messenger ribonucleic acid and protein. Quantitative polymerase chain reaction was used to document a decrease in interleukin-6 messenger ribonucleic acid, which paralleled the decrease in peptide levels as detected with enzyme-linked immunosorbent assay. The interleukin-10 effect was present only when tissue was concurrently stimulated with lipopolysaccharide. Interleukin-10 inhibition could not be produced in the absence of lipopolysaccharide stimulation.

CONCLUSION

Addition of interleukin-10 to culture media leads to transcriptional regulation of interleukin-6, which results in decreased production of both messenger ribonucleic acid and protein by human amniochorionic membranes. The decrease in interleukin-6 is a dose-dependent effect of interleukin-10. This finding may have important implications with respect to a possible role for interleukin-10 or an interleukin-10 stimulatory factor in the management of preterm labor associated with the presence of inflammatory cytokines.

Stretching of fetal membranes increases the concentration of interleukin-8 and collagenase activity

OBJECTIVE

The aim of this study was to determine whether stretching of fetal membranes can increase interleukin-8 concentration and collagenase activity.

STUDY DESIGN

Strips of whole fetal membranes, amnion, or muscles of the lower uterine segment were stretched for 2 or 4 hours. Interleukin-8 and collagenase activity were measured in homogenized control and stretched samples. Immunohistochemical staining for interleukin-8 was carried out.

RESULTS

The interleukin-8 concentration increased significantly after the whole fetal membranes were stretched for 2 and 4 hours (p <0.0007 and 0.001, respectively). Also, stretching of amnion and muscles of the lower uterine segment for 2 and 4 hours increased the concentration of interleukin-8 significantly (p <0.0007 after 2 and 4 hours, respectively). Collagenase activity was significantly increased after stretching of amnion, amniochorion, and muscles of the lower uterine segment for 4 hours (p <0.0007, 0.006, and 0.0007, respectively). After stretching, samples were darkly stained for interleukin-8 compared with control nonstretched samples.

CONCLUSION

Stretching of amnion, amniochorion, and muscles of the lower uterine segment increased interleukin-8 production and collagenase activity.

Amniochorion: a source of interleukin-8

PROBLEM

Preterm labor and premature rupture of the membranes are major complications of pregnancy. We have reported the possible role of amniochorionic membrane in the production of inflammatory cytokines and the early onset of labor. This study was conducted to detect the expression of IL-8 mRNA and peptide production in cultured fetal membranes.

METHOD

Amniochorionic membranes were collected from women undergoing elective cesarean section at term. Membranes were cultured in an organ explant system and the expression of IL-8 was studied over a 10-day period by RT-PCR and in situ hybridization. IL-8 peptide localization was accomplished using immunocytochemistry.

RESULTS

Constitutive expression of IL-8 mRNA in cultured fetal membranes was demonstrated in both amniotic and chorionic leave cells. mRNA and peptide for IL-8 was homogeneously distributed throughout the amniotic and chorionic cells.

CONCLUSION

Human amniochorionic membrane is a source of IL-8 mRNA and peptide.

Expression of TNF-alpha and TNFR p55 in cultured amniochorion

PROBLEM

Preterm labor and PROM are major complications of pregnancy. We have reported the possible role of amniochorionic membrane as it relates to the production of cytokines and the early onset of labor. Amniochorion is capable of responding to an infectious process with the production of IL-6 and IL-1 beta. Here we examine the expression of TNF-alpha and TNFR in amniochorion.

METHOD

Amniochorionic membranes were collected and maintained in an organ explant system. Samples were frozen and/or fixed for RT-PCR, in situ hybridization, and immunocytochemistry.

RESULTS

RT-PCR demonstrated mRNA for TNF-alpha and in situ hybridization localized mRNA in chorion and amnion. Immunocytochemistry demonstrated TNF-alpha peptide in amnion but not in chorion. Immunocytochemical localization of TNFR indicates presence of that peptide in both amnion and chorion.

CONCLUSIONS

We conclude that the fetal membranes are sources of TNF-alpha and TNFR, supporting our previous work indicating that fetal membranes are active participants in the response to intraamniotic infection.

Interleukin 8 modulates interleukin-1 beta, interleukin-6 and tumor necrosis factor-alpha release from normal human mononuclear cells

Recombinant human interleukin 8 (IL-8) enhanced the release of inflammatory cytokines including interleukin 1 beta (IL-1 beta), interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) from normal human mononuclear cells in a dose-related manner (from 1 ng/ml to 10 ng/ml with a maximal effect at 5 ng/ml) when the cells incubated with IL-8 for 24 h. This cytokine-releasing activity of IL-8 is temperature-dependent and required protein synthesis since low temperature (4 degrees C) and cycloheximide (100 micrograms/ml) minimized the cytokine release from MNC. However, when IL-8 concentration was greater than 20 ng/ml, the cytokine release was suppressed. For further investigating the subcellular mechanism of the adverse effect of high dose IL-8 (20 ng/ml) in cytokine synthesis, human mononuclear cells (1 x 10(6)/ml) were stimulated with PHA (1 microgram/ml) in the presence of 20 ng/ml IL-8 for 3 days. We found not only [3H]thymidine incorporation of MNC was tremendously inhibited but DNA fragmentation appeared. Subsequently, the cell cycle of PHA-stimulated MNC retarded in the phase of G0/G1. These results suggest that in low concentration (5-10 ng/ml) IL-8 not only activated neutrophil phagocytosis but facilitated the release of inflammatory cytokines from mononuclear cells. Higher dose of IL-8 (more than 20 ng/ml) conversely suppressed these cytokine release from damaged cells by its cytotoxic effect. This newly found cytokine-releasing activity of IL-8 may play a role in the modulation of inflammation.

Neurotrophic effects of amnion explants co-cultured with rat mesencephalon

We investigated amnion-derived neurotrophic effects on embryonic day 14 rat mesencephalic (E14M) explants in co-culture. E14M explants showed extensive neurite outgrowth directed toward amnion tissue. Tyrosine hydroxylase immunocytochemistry, western immunoblot and [3H]dopamine uptake studies revealed significant neurotrophic effects on E14M dopaminergic neurons over 14 days in culture. Thus, amnion tissue appears to have potent neurotrophic effects for embryonic mesencephalic dopaminergic neurons in vitro.

The presence of cervical and vaginal fetal fibronectin predicts preterm delivery in an inner-city obstetric population

OBJECTIVE

It has previously been shown that fibronectin bearing a specific oncofetal domain is present at the chorionic-decidual interface and that its release into cervical and vaginal secretions accurately predicts preterm delivery in patients with uterine contractions. This study examines whether serial assessment of cervical and vaginal fetal fibronectin allows for the prediction of preterm delivery in symptom-free patients derived from an inner-city, general obstetric population.

STUDY DESIGN

Cervical and vaginal samples were obtained from 429 consenting patients who received routine prenatal care between 24 and 37 weeks' gestation. A sensitive immunoassay was used to quantitate cervical and vaginal fetal fibronectin levels, and clinicians were blinded to fetal fibronectin results. Post hoc receiver operating characteristic curve analysis was used to determine which sample site (cervical or vaginal), fetal fibronectin concentration, and number of consecutive positive samples optimized screening efficacy. Logistic regression was employed to determine whether fetal fibronectin was an independent predictor of preterm delivery.

RESULTS

The spontaneous preterm delivery rate was 11% (49/429). Among the 326 patients sampled within 28 days of delivery, receiver operating characteristic curve analysis indicated that the presence of a single cervical fetal fibronectin value > 60 ng/ml between 24 and 36 weeks' gestation predicted preterm delivery with a sensitivity of 73%, a specificity of 72%, and positive and negative predictive values of 25% and 95%, respectively. A vaginal fetal fibronectin value > 50 ng/ml predicted preterm delivery with a sensitivity of 68%, a specificity of 80%, and positive and negative predictive values of 30% and 95%, respectively. Cervical and vaginal fetal fibronectin predicted preterm deliveries resulting from both membrane rupture and preterm labor with intact membranes. A positive fetal fibronectin result preceded preterm delivery by 3.4 (+/- 3.2) weeks. Stepwise logistic regression demonstrated that cervical and vaginal fetal fibronectin levels were independent predictors of preterm delivery with adjusted odds ratios of 8.9 (95% confidence interval 3.6 to 22.1) and 6.0 (95% confidence interval 2.6 to 13.7), respectively.

CONCLUSIONS

Among patients undergoing monthly cervical and vaginal sampling between 24 and 36 weeks' gestation, the presence of fetal fibronectin is a sensitive and specific predictor of preterm delivery.

Cytokines in reproduction

A growing body of evidence indicates that, in addition to the hormones of hypothalamic, pituitary and gonadal origin, autocrine/paracrine regulators play important roles in the reproductive functions. Cytokines, originally known as immunoregulatory proteins, may affect the neuroendocrine events of reproduction, ovarian/testis function, endometrium, the developing embryo, placenta and parturition. Cytokines can modulate and mediate the actions of hormones at their target cells and, in the opposite way, hormones may regulate the production and action of cytokines at three different levels: cytokine secretion, cytokine receptor expression and cellular responses. Cytokines may also function in an endocrine manner affecting distant targets. As many of the cyclic changes that occur in the ovary and endometrium during the normal menstrual cycle are similar to those associated with the inflammatory and regenerative processes, it is likely that cytokines are involved in these reactions. Furthermore, cytokines secreted by endometrial white blood cells may influence embryo development and trophoblast growth and may play a fundamental role in the mechanisms of immunological reproductive failure. Cytokines have also been implicated in the mechanisms responsible for the onset of parturition.

New approaches to the prediction of preterm delivery

Current approaches to the detection of patients at risk for preterm delivery (PTD) have focused on the diagnosis of preterm labor. However, these approaches are complicated by treatment biases and our inability to convincingly differentiate preterm labor from Braxton-Hicks contractions. Moreover, preterm labor with intact membranes accounts for only one-half of all spontaneous PTDs since uterine contractions follow preterm premature rupture of the membranes (PROM) in an additional 50% of cases. Clinical dogma holds that the prevention of PTD requires the early detection of at risk patients. However, clinical indicators of PTD risk including cervical change, uterine contractions, vaginal bleeding, maternal demographic featuers and obstetrical history have poor sensitivity and/or specificity. Fortunately, an improved understanding of the association between preterm parturition and cervical, chorionic and decidual extracellular matrix degradation has led to a number of promising new biochemical indices of the proteolytic processes leading to PTD. These include measurement of serum collagenase activity and assessment of cervico-vaginal granulocyte elastase and oncofetal fibronectin levels. It remains to be seen, however, whether an improved detection of patients at risk will lead to a reduction in the occurrence of PTD.