Interleukin-1 beta induces cyclooxygenase-2 in cultured human decidual cells

Maternal Whole Blood Gene Expression at 18 and 28 Weeks of Gestation Associated with Spontaneous Preterm Birth in Asymptomatic Women

The heterogeneity of spontaneous preterm birth (SPTB) requires an interdisciplinary approach to determine potential predictive risk factors of early delivery. The aim of this study was to investigate maternal whole blood gene expression profiles associated with spontaneous preterm birth (SPTB, <37 weeks) in asymptomatic pregnant women. The study population was a matched subgroup of women (51 SPTBs, 114 term delivery controls) who participated in the All Our Babies community based cohort in Calgary (n = 1878). Maternal blood at 17–23 (sampling time point 1, T₁) and 27–33 weeks of gestation (T₂) were collected. Total RNA was extracted and microarray was performed on 326 samples (165 women). Univariate analyses determined significant clinical factors and differential gene expression associated with SPTB. Thirteen genes were validated using qRT-PCR. Three multivariate logistic models were constructed to identify gene expression at T₁ (Model A), T₂ (Model B), and gene expression fold change from T₁ to T₂ (Model C) associated with SPTB. All models were adjusted for clinical factors. Model C can predict SPTB with 65% sensitivity and 88% specificity in asymptomatic women after adjusting for history of abortion and anaemia (occurring before T₂). Clinical data enhanced the sensitivity of the Models to predict SPTB. In conclusion, clinical factors and whole blood gene expression are associated with SPTB in asymptomatic women. An effective screening tool for SPTB during pregnancy would enable targeted preventive approaches and personalised antenatal care.

Inflammatory gene regulatory networks in amnion cells following cytokine stimulation: translational systems approach to modeling human parturition

A majority of the studies examining the molecular regulation of human labor have been conducted using single gene approaches. While the technology to produce multi-dimensional datasets is readily available, the means for facile analysis of such data are limited. The objective of this study was to develop a systems approach to infer regulatory mechanisms governing global gene expression in cytokine-challenged cells in vitro, and to apply these methods to predict gene regulatory networks (GRNs) in intrauterine tissues during term parturition. To this end, microarray analysis was applied to human amnion mesenchymal cells (AMCs) stimulated with interleukin-1β, and differentially expressed transcripts were subjected to hierarchical clustering, temporal expression profiling, and motif enrichment analysis, from which a GRN was constructed. These methods were then applied to fetal membrane specimens collected in the absence or presence of spontaneous term labor. Analysis of cytokine-responsive genes in AMCs revealed a sterile immune response signature, with promoters enriched in response elements for several inflammation-associated transcription factors. In comparison to the fetal membrane dataset, there were 34 genes commonly upregulated, many of which were part of an acute inflammation gene expression signature. Binding motifs for nuclear factor-κB were prominent in the gene interaction and regulatory networks for both datasets; however, we found little evidence to support the utilization of pathogen-associated molecular pattern (PAMP) signaling. The tissue specimens were also enriched for transcripts governed by hypoxia-inducible factor. The approach presented here provides an uncomplicated means to infer global relationships among gene clusters involved in cellular responses to labor-associated signals.

Thrombin and interleukin-1beta regulate HOXA10 expression in human term decidual cells: implications for preterm labor

CONTEXT

Preterm delivery is commonly caused by intraamniotic infection with expression of proinflammatory cytokines (IL-1beta) or by abruption resulting in generation of decidual thrombin. Although human parturition is not preceded by overt progesterone withdrawal, progesterone resistance likely leads to labor. The uteri of Hoxa10(-/-) mice demonstrate progesterone resistance; several genes, including prostaglandin receptors, are inappropriately regulated in response to progesterone.

OBJECTIVE

We hypothesized that IL-1beta or thrombin would decrease HOXA10 expression, contributing to the progestin-resistant environment. We analyzed expression of HOX genes and their regulation by IL-1beta or thrombin in decidual cells.

DESIGN AND SETTING

We conducted an in vitro experiment at an academic medical center.

INTERVENTION

Term decidual cells were treated with estradiol (E(2)) or E(2) plus medroxyprogesterone acetate followed by addition of thrombin or IL-1beta.

MAIN OUTCOME MEASURE

HOX mRNA was evaluated by microarray and confirmed by quantitative RT-PCR. Protein expression was detected using immunohistochemistry and Western analysis.

RESULTS

HOXA9, HOXA10, and HOXA11 were expressed in decidual cells and regulated by IL-1beta and thrombin. HOXA10 was further analyzed because of its association with progesterone responsiveness. After E(2) treatment, IL-1beta and thrombin decreased HOXA10 mRNA by 94 and 81%, respectively. After E(2) plus medroxyprogesterone acetate treatment, IL-1beta and thrombin resulted in an 86 and 72% decrease in HOXA10 mRNA, respectively. A similar decrease was noted in HOXA10 protein expression.

CONCLUSION

The expression of HOXA10 protein at term indicates that it may have a role in maintaining decidual cell phenotype and pregnancy. The dramatic decrease of HOXA10 in response to IL-1beta or thrombin may contribute to progestin resistance in preterm labor, mimicking progesterone resistance seen in Hoxa10(-/-) mice.

Immunohistochemical localization of leukemia inhibitory factor, interleukins 1 and 6 at the primary implantation site in the rhesus monkey

Blastocyst implantation and placentation involve localized inflammatory type of responses at and around the site of nidation. In the present study, the likely involvement of inflammatory cytokines, namely, leukemia inhibitory factor (LIF), interleukins 1 alpha and 1 beta (IL-1alpha and IL-1beta) and IL-6 at the primary implantation site of the rhesus monkey was examined immunocytochemically during lacunar (n=6) and villous (n=8) stages of gestation. Trophoblast cells and extraembryonic mesenchymal cells were immunopositive for LIF and IL-1alpha. The distribution of IL-1beta and IL-6 in trophoblast cells was low in lacunar stage samples, however, a higher degree of immunopositivity for IL-6 was observed in villous stage samples. Decidual cells were immunopositive for all the cytokines studied. In lacunar stage samples, plaque cells adjacent to implanted nidus were immunopositive for all the cytokines examined, and the degree of their immunoprecipitation increased, except that of IL-1beta, during the villous stage. Luminal and glandular epithelial cells were immunopositive for LIF, IL-1alpha, IL-1beta and IL-6 in lacunar and in villous stage samples. LIF immunopositivity was detected in endothelial cells of blood vessels within and below chorionic plate and cytotrophoblast shell, while vascular smooth muscle cells were positive for all the cytokines studied. The temporo-spatial characteristics of LIF, IL-1alpha, IL-1beta and IL-6 protein expressions in primary implantation sites of the rhesus monkey suggest that these pro-inflammatory cytokines play specific roles in regulating trophoblast cell proliferation, differentiation, invasion and associated maternal tissue remodelling during early gestation.

Expression of cyclooxygenase-2 in embryonic and fetal tissues during organogenesis and late pregnancy

BACKGROUND

Cyclooxygenase (COX) catalyzes the committed step in prostaglandin biosynthesis and exists as two related but unique isoforms, COX-1 (constitutive) and COX-2 (inducible). Prostaglandins (PGs) are known to have many important functions in reproduction, such as placentation and decidualization. Studies with the COX-1 and COX-2 knockout mice have demonstrated that COX-2, but not COX-1, is crucial for normal ovulation, implantation, and decidualization, suggesting that COX-2-derived PGs are important during the initial stages of pregnancy. Although the COX-2 knockout mice did not exhibit any abnormalities at birth, relatively little information exists with regard to the expression of COX-2 in the fetus during development.

METHODS

In order to understand the role of COX-2 throughout pregnancy, we characterized the cell type and the temporal expression of inducible COX-2 throughout embryonic and fetal development in the rat (n = 22) by immunohistochemistry and in situ hybridization.

RESULTS

High levels of COX-2 expression were seen in decidualized uterine tissue on gestation days 7-13 and then in the fetal membranes on gestation days 17-20. Cyclooxygenase-2 expression was not detectable in any tissues from developing embryos during gestation days 7-13, but was observed in the fetal growth period (gestation days 15-20) in the skin, heart, cartilage, and the kidney.

CONCLUSIONS

No COX-2 expression was seen in fetal tissues at days 7-13 of gestation, but was seen in various tissues at days 15-17 of gestation. These observations suggest that COX-2 may be important in mid to late pregnancy through an effect on fetal organ growth, but not in the organogenetic phase of fetal development.

Autocrine/paracrine regulation of apoptosis in epithelial cells by prostaglandin E2

This study was designed to investigate the effect of IL-1alpha-induced up-regulation of cyclooxygenase-2 (COX-2) on prostaglandin E(2) (PGE(2)) secretion and the subsequent phenotypic effects of PGE(2) on epithelial cells. The effect of IL-1alpha on COX-2 expression was investigated in the T24 bladder epithelial cell line following treatment with 0, 0.05, 0.5, 1 or 10 ng/ml IL-1alpha for 1, 2, 4 or 6 h. Quantitative PCR confirmed up-regulation of expression of COX-2 with maximal expression observed following treatment with 0.5 ng/ml IL-1alpha for 1 h. Co-treatment of the cells with 0.5 ng/ml IL-1alpha in the presence or absence of 100 ng/ml IL-1 receptor antagonist (RA) abolished the up-regulation in COX-2 expression confirming that the effect of IL-1alpha is mediated via its membrane-bound receptors. Treatment with 0.5 ng/ml IL-1alpha resulted in a time-dependent increase in PGE(2) secretion with maximal secretion detected at 24 and 48 h after stimulation with IL-1alpha. Co-treatment of the cells with IL-1alpha and IL-1RA or the COX-2 enzyme inhibitor NS398 abolished the IL-1alpha mediated secretion of PGE(2). Treatment of T24 cells with 100 nM PGE(2) resulted in a significant elevation in cAMP generation confirming the expression of functional PGE(2) receptors. Finally, the effect of exogenous treatment with PGE(2) on apoptosis of T24 cells was assessed using cell death detection ELISA. T24 cells were treated with camptothecin to induce apoptosis in the presence or absence of 50 or 100 nM PGE(2) or 10 microM forskolin. Treatment of T24 cells with increasing doses of camptothecin alone resulted in a significant increase in the induction of apoptosis (P<0.01). However, co-treatment of the cells with 50 or 100 nM PGE(2) or 10 microM forskolin resulted in the inhibition of induction of the apoptotic pathway by camptothecin. These data demonstrate that PGE(2) inhibits apoptosis of epithelial cells possibly via cAMP-dependent pathway.

Hormonal regulation of PGE2 and COX-2 production in rabbit uterine cervical fibroblasts

Prostaglandins (PGs) cause uterine contraction to initiate labor at term. We investigated the effect of progesterone and 17beta-estradiol on the production of PGE2 in rabbit uterine cervical fibroblasts. When the cervical fibroblasts were treated with interleukin-1alpha (IL-1alpha), the level of PGE2 was augmented in a time- and dose-dependent manner. The IL-1alpha-augmented PGE2 level was almost completely suppressed by progesterone and 17beta-estradiol at the physiological concentration (0.01 microM), whereas a slight decrease in the basal level of PGE2 was observed in the cervical fibroblasts treated with both hormones at a pharmacological concentration (1 microM). In addition, the level of PGE2 augmented by IL-1alpha was due to the increase of cyclooxygenase (COX) activity, which was inhibited by progesterone and 17beta-estradiol as well as by indomethacin and a specific COX-2 inhibitor, NS-398, but not by the well-known COX-1 inhibitor, aspirin. Furthermore, progesterone and 17beta-estradiol suppressed the IL-1alpha-augmented COX-2 production but not the constitutive production of COX-1 in rabbit uterine cervical fibroblasts. These results suggest that progesterone and 17beta-estradiol prevent the initiation of labor by inhibiting PGE2 production after the suppression of COX-2 production during pregnancy in the rabbit.

Expression of cyclooxygenase-2 and prostanoid receptors by human myometrium

Prostanoids play an important role in the regulation of parturition. All reproductive tissues, including fetal membranes, decidua, and myometrium, have the capacity to synthesize prostanoids, and fetal membranes have been shown to express elevated levels of cyclooxygenase-2 (Cox-2) at the onset of labor. We have now investigated the expression of Cox-2 in human myometrium. Myometrial samples collected from women in labor during lower segment cesarean section expressed 15-fold higher levels of Cox-2 messenger ribonucleic acid (mRNA) compared to myometrial specimens collected from women not in labor, as detected by Northern blot analysis. Immunohistochemical detection of Cox-2 protein showed cytoplasmic staining in the smooth muscle cells of the myometrium. Cultured myometrial cells expressed low levels of Cox-2 mRNA under baseline conditions, but interleukin-1beta (IL-1beta) caused a 17-fold induction of expression of the Cox-2 transcript after incubation for 6 h. IL-1beta also induced expression of biologically active Cox-2 protein, as detected by immunofluorescence, Western blot analysis, and measuring the conversion of arachidonic acid to prostanoids in the presence and absence of a Cox-2-selective inhibitor, NS-398. PGE2 receptor subtype EP2 mRNA was expressed in cultured myometrial smooth muscle cells, whereas transcripts for EP1, EP3, EP4, FP, and IP were low or below the detection limit as measured by Northern blot analysis. However, IL-1beta stimulated expression of EP4 receptor mRNA. Our data suggest that expression of Cox-2 transcript is elevated at the onset of labor in myometrial smooth muscle cells, which may depend on induction by cytokines. As, in addition to Cox-2, the expression of prostanoid receptors is regulated, not only the production of prostanoids, but also responsiveness to them, may be modulated.

Oxytocin signaling in human myometrium is impaired by prolonged exposure to interleukin-1

Intra-amniotic infection leads to preterm labor and is associated with the local release of inflammatory cytokines by fetal membranes, resulting in the production of uterotonic prostaglandins. Oxytocin, however, also plays a key role in the initiation of labor. Short-term exposure of myometrium to interleukin (IL)-1 enhances oxytocin signaling and contractility. With intrauterine infection, however, myometrium is exposed to inflammatory cytokines for prolonged periods. The present study was conducted to demonstrate that myometrial oxytocin signaling is significantly impaired following prolonged exposure to IL-1. Myometrial cells were treated with IL-1 for 24 h. Oxytocin-stimulated inositol trisphosphate (IP(3)) production was measured in tritiated myoinositol-loaded myometrial cells. Arachidonic acid (AA) release was measured in tritiated AA-loaded myometrial cells. Increases in intracellular calcium were measure with fluo-3. Prostaglandin (PG) F(2alpha) and 6-keto-PGF(1alpha) were measured by ELISA assay. Prolonged exposure of myometrial cells to IL-1 resulted in a significant reduction in oxytocin-mediated signaling as measured by IP(3) production and AA release, as well as a decrease in intracellular calcium. Prolonged exposure of myometrial cells to IL-1, however, resulted in enhanced PG release. Oxytocin may not contribute significantly to the labor-inducing action of IL-1 in the setting of preterm labor with prolonged infection.

Spontaneous and induced release of prostaglandins, interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha by placental tissue from normal and preeclamptic pregnancies

PROBLEM

The objective of this study was to clarify the role of the main proinflammatory cytokines (interleukin [IL]-1, IL-6, tumor necrosis factor [TNF]-alpha) in the pathogenesis of preeclampsia and how these cytokines affect one another and the production of prostaglandins (PGs).

METHOD OF STUDY

The concentrations of cytokines and PGs in supernatants of placental tissue from preeclamptic and normal women were determined by enzyme-linked immunosorbent assay.

RESULTS

The concentrations of the PGs from unstimulated preeclamptic placental tissue were significantly higher compared to the concentrations of PGs from normal unstimulated placental tissue. Significant levels of IL-1beta were observed only in the supernatants of preeclamptic placental tissue. Of interest, an increase in TNF-alpha production was detected in the supernatants of IL-1-stimulated preeclamptic placental tissue.

CONCLUSIONS

The overproduction of TNF-alpha may be related not only to the effect of a stimulant like IL-1beta, but mainly to the lack of mechanisms down-regulating the production of TNF-alpha.

Key enzymes of prostaglandin biosynthesis and metabolism. Coordinate regulation of expression by cytokines in gestational tissues: a review

Preterm labor is frequently associated with ascending intrauterine infection, accompanied by leukocytes infiltration and enhanced local production of cytokines and other inflammatory mediators. The resulting amplification of the inflammatory response, and of prostanoid production in particular, is postulated to be a principal mechanism of infection-driven preterm labor. In this review the effects of pro- and anti-inflammatory cytokines are discussed with respect to the expression of enzymes involved in three key steps of prostanoid biosynthesis and metabolism: liberation of arachidonic acid (AA), conversion of AA to bioactive prostanoids, and prostanoid catabolism. We suggest that by exerting coordinate actions on all three key steps, through multiple molecular mechanisms, inflammatory cytokines acutely up-regulate prostanoid production in intrauterine tissues.

Production of prostanoids via increased cyclo-oxygenase-2 expression in human amnion cells in response to low molecular weight hyaluronic acid fragment

Increased concentrations of hyaluronic acid (HA) have been found in serum and at uterine cervix at term. In its native form, HA exists as a high molecular weight (MW) polymer, but during parturition a lower MW HA fragment accumulates. The aim of this study was to investigate the regulatory mechanisms responsible for increased amnion prostanoid production and cyclo-oxygenase (COX) expression in response to HA. Human term amnion cells in culture were exposed to native HA polymer (MW 2.2x106) and its fragment (MW 3.5x104). We have determined levels of prostanoids, prostaglandins E2 and F2alpha, in conditioned media using specific immunoassays. Expression of COX-1 and COX-2 was examined with Western blot. Results were analyzed for statistical significance with Mann-Whitney U-test. Human amnion cells treated with HA fragment (100 nmol/l) produced significantly more PGE2 (2.3+/-0.21 (mean+/-S.D.) pg/106 cells/24 h) than controls (0.34+/-0.03) or high MW HA-treated cells (1.2+/-0.21). Protein levels of COX-2, but not COX-1, were substantially increased in amnion cells treated with HA fragment. HA fragment-mediated prostanoid production is markedly diminished by pretreatment with indomethacin. Our results indicate that HA fragment, rather than physiologic native HA polymer, induces amnion cell-derived prostanoid production via increased COX-2 expression. COX-2-mediated prostanoid production is likely a key physiologic event in HA fragment-mediated cervical ripening and the labor onset.

Coordinate expression of inducible nitric oxide synthase and cyclooxygenase-2 genes in uterine tissues of endotoxin-treated pregnant mice

OBJECTIVES

Our purpose was to investigate the relationship between expression of cyclooxygenase-2 and inducible nitric oxide synthase genes after labor induction with bacterial lipopolysaccharide in a murine model of preterm parturition.

STUDY DESIGN

Pregnant C57B1/6 mice were given Escherichia coli lipopolysaccharide (20 micrograms per mouse) by intraperitoneal injection on day 16 of gestation, and the animals were followed up for signs of labor. Control mice received an equivalent volume of 0.9% saline solution. The latency from lipopolysaccharide injections until appearance of the first pup was recorded. Two separate groups of mice were given either aminoguanidine or indomethacin (5 mg/kg intragastric) 24 hours before induction of preterm labor. In a separate set of experiments mice were treated with lipopolysaccharide as described and were killed at intervals from 0.5 to 72 hours and intrauterine tissues (uterus, placenta, and fetal membranes) were removed and snap frozen in liquid nitrogen. Total protein and ribonucleic acid were extracted for Western and Northern blot analysis of cyclooxygenase-2 and inducible nitric oxide synthase protein and messenger ribonucleic acid, respectively.

RESULTS

Northern blots from uterine, placental, and fetal membrane tissues of lipopolysaccharide- and saline solution-treated mice revealed that cyclooxygenase-2 and inducible nitric oxide synthase messenger ribonucleic acid transcripts were rapidly (within 0.5 to 2 hours) up-regulated after lipopolysaccharide administration but were unchanged in mice injected with saline solution. Immunoblot analysis with isoform-specific antibodies revealed that both enzymes were expressed in uterus, placenta, and fetal membranes in a coordinated fashion with peak expression seen at 6 to 8 hours. Although the steady-state accumulation of messenger ribonucleic acid transcripts encoding cyclooxygenase-2 and inducible nitric oxide synthase peaked at 6 hours and declined to baseline by 16 hours after injection with lipopolysaccharide, expression of cyclooxygenase-2 and inducible nitric oxide synthase was sustained through the period when premature delivery was observed. Nitric oxide-dependent cyclooxygenase-2 and inducible nitric oxide synthase expression was demonstrated by the elimination of accumulation of both messenger ribonucleic acid transcripts in mice pretreated with aminoguanidine before injection with lipopolysaccharide.

CONCLUSIONS

These data indicate that nitric oxide synthesis may be a prerequisite for subsequent stimulation of cyclooxygenase-2 and inducible nitric oxide synthase gene expression. Taken together, the data suggest that cyclooxygenase-2 and inducible nitric oxide synthase are expressed in a coordinated manner in the uterus of endotoxin-challenged pregnant mice and that their enzymatic products may contribute to the signaling of uterine activity or cervical changes culminating in expulsion of the fetus.

Tumor necrosis factor-alpha promotes sustained cyclooxygenase-2 expression: attenuation by dexamethasone and NSAIDs

Prostaglandin (PG) release is characteristic of most inflammatory diseases. The committed step in the formation of free arachidonic acid into PG products is catalyzed by cyclooxygenase (COX, prostaglandin H2 synthase, PGHS), which exists as two genetically distinct isoforms. COX-1 is constitutively expressed and produces PGs and thromboxane A2 during normal physiologic activities, while COX-2 is an inducible enzyme stimulated by growth factors, lipopolysaccharide, and cytokines during inflammation or cell injury. Proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) released into the amniotic fluid in the setting of infection have been proposed to signal amnion and decidual cells to produce PGs that may culminate in preterm labor. However, since the molecular control of this phenomenon has not been established, this study used amnion-derived WISH cells to determine if TNF-alpha promoted the formation of PGs through COX-2 activity. Treatment of WISH cells with TNF-alpha (0.1 ng/mL-100 ng/mL) caused a dose-dependent increase in COX-2 expression and the subsequent biosynthesis of PGE2 that persisted for at least 48 hrs. In contrast, COX-1 mRNA and protein levels were unaltered by TNF-alpha treatment as determined by RT-PCR and immunoblot analysis, respectively. TNF-alpha-stimulated COX-2 expression and the subsequent formation of PGE2 were inhibited by dexamethasone (0.1 microM). In addition, indomethacin (1 microM) and the novel COX-2-selective inhibitor, NS-398 (IC50 approximately 1.1 x 10(-9) M), attenuated TNF-alpha-elicited PGE2 production. Results presented here demonstrate that TNF-alpha elicits prolonged and regulatable induction of COX-2 in WISH cells, while COX-1 is constitutively expressed and unchanged in response to TNF-alpha stimulation.

Interleukin-1 receptor antagonist blocks interleukin-1-induced expression of cyclooxygenase-2 in endometrium

OBJECTIVE

Our purpose was to test the hypothesis that the interleukin-1 receptor antagonist can inhibit interleukin-1-induced prostaglandin production and de novo expression of the inducible cyclooxygenase-2 isoform in a human endometrial epithelial cell line.

STUDY DESIGN

A continuous line of human endometrial epithelial cells was established from a hysterectomy specimen from a nonmalignant uterus. Cells were maintained as a monolayer culture in medium 199 supplemented with 10% fetal bovine serum and 50 micrograms/ml gentamicin. Cultures were treated with cytokines (interleukin-1 alpha or interleukin-1 beta, interleukin-1 receptor antagonist, or tumor necrosis factor-alpha), and media were collected for analysis of prostaglandin E2 and prostaglandin F2 alpha) by radioimmunoassay, whereas cells were harvested for ribonucleic acid and protein extractions and subsequent Northern blot or Western blot analyses, respectively.

RESULTS

When endometrial cells were incubated with interleukin-1 alpha or interleukin-1 beta, each cytokine was shown to stimulate the production of prostaglandin E2 and prostaglandin F2 alpha in a time- and dose-dependent fashion, with interleukin-1 alpha being far more potent than interleukin-1 beta. Interleukin-1 receptor antagonist inhibited interleukin-1 alpha- and interleukin-1 beta-induced prostaglandin formation, with 50% inhibitory concentration values of 30 ng/ml for prostaglandin E2 and 90 ng/ml for prostaglandin F2 alpha. When Northern blots of interleukin-1 alpha-treated cells were probed with a complementary deoxyribonucleic acid fragment specific for either cyclooxygenase-1 or cyclooxygenase-2, rapid de novo induction of cyclooxygenase-2 messenger ribonucleic acid was observed; however, cyclooxygenase-1 expression was constant regardless of interleukin-1 alpha concentration or incubation time. Coincubation of cells with interleukin-1 alpha (10 ng/ml) and cycloheximide caused superinduction of cyclooxygenase-2 messenger ribonucleic acid but had no effect on the expression of cyclooxygenase-1 messenger ribonucleic acid. Actinomycin D completely abolished interleukin-1 alpha-induced cyclooxygenase-2 messenger ribonucleic acid expression, suggesting that the cytokine caused transcriptional activation of the cyclooxygenase-2 gene. Experiments were conducted to examine whether interleukin-1 receptor antagonist could suppress interleukin-1-induced cyclooxygenase-2 expression. Cells were preincubated for 30 minutes with interleukin-1 receptor antagonist and then challenged with interleukin-1 alpha. Northern and Western analyses revealed that interleukin-1 receptor antagonist blocked interleukin-1 alpha-induced expression of cyclooxygenase-2 messenger ribonucleic acid transcripts and the subsequent appearance of cyclooxygenase-2 protein. Interleukin-1 receptor antagonist had no effect on the constitutive expression of cyclooxygenase-1 messenger ribonucleic acid and protein. Interleukin-1 receptor antagonist failed to alter prostaglandin E2 formation in response to tumor necrosis factor-alpha, indicating that the antagonist is specific for interleukin-1 family cytokines. Finally, interleukin-1 receptor antagonist acted as a partial agonist in some experiments in that relatively high concentrations (> 100 ng/ml) caused a modest increase in prostaglandin E2 and F2 alpha production.

CONCLUSIONS

These data indicate that interleukin-1 receptor antagonist is a potent inhibitor of interleukin-1-induced arachidonic acid metabolism and could possibly serve as an endogenous or exogenous modulator of interleukin-1 action in the endometrial epithelium.