Modulation of decidual stromal cell activity by interleukin-1 beta and interleukin-6

Bradykinin stimulates interleukin-6 and interleukin-8 secretion of human decidua derived cells

Cytokines are known to participate in the process of parturition within a paracrine network in fetal membranes. Bradykinin can also contribute to this process, increasing the release of eicosanoids from decidua cells. In this study, we present evidence for a cross-link between bradykinin and the cytokines. Short and long term cultures of human decidua cells were incubated for 4 h and 24 h with and without bradykinin. IL-6 and IL-8 were determined in the supernatants by ELISA. Results show a large interindividual variability in the basal secretion of IL-6 and IL-8 and a clear increase in the secretion of both ILs in response to bradykinin. By this amplifying effect on cytokine secretion, bradykinin can initiate local and systemic effects of amniochorionitis.

Decidual adenylate cyclase and prostaglandin production in vitro

Human decidua contains an active adenylate cyclase, and a number of studies indicate that adenylate cyclase is functionally linked to increased in vitro prostaglandin synthesis. Increased decidual prostaglandin synthesis is associated with parturition, and therefore activation of adenylate cyclase may be involved in the control of human parturition. In this study, third trimester human decidual cells were preincubated for no more than 24 h prior to stimulation with a number of reagents which increase cellular cyclic AMP levels. Forskolin rapidly increased intracellular and extracellular cyclic AMP levels, but there was no increase in prostaglandin E2 biosynthesis during incubations ranging from 5 min up to 24 h. Dibutyryl cyclic AMP or 8-bromo-cyclic AMP were also without effect on PGE2 production, which suggests that the adenylate cyclase was not linked to the mechanisms regulating prostaglandin production. Cholera toxin increased basal cyclic AMP and PGE2 synthesis, and was without effect on IL-1 beta-stimulated PGE2 levels. PGE2 synthesis was increased by 24 h culture with IL-1 beta in all the cell preparations, indicating that the cells were biologically active, and that the lack of effect of changes in cyclic AMP synthesis on PGE2 levels could not be attributed to a defect in the prostaglandin synthetic pathway. Our findings did not agree with earlier work which showed that changes in cyclic AMP were correlated with changes in PGE2 production by human decidual cells. It is clear that in the previous studies the decidual cells were preincubated for 4-7 days prior to stimulation, in contrast with 24 h in our investigation.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-1 beta-stimulated prostaglandin synthesis by human decidual cells is independent of protein kinase C

Basal prostaglandin E2 (PGE2) synthesis by human decidual cells was stimulated by phorbol myristate acetate (PMA) which activates protein kinase C. Staurosporine, which is an inhibitor of protein kinase C in most systems, also increased basal PGE2 synthesis. Further work is needed to explain this finding, as another inhibitor of protein kinase C, H7, inhibited PGE2 production under similar culture conditions. Interleukin-1 beta (IL-1 beta)-stimulated PGE2 synthesis was potentiated by coincubation with PMA or staurosporine, indicating that IL-1 beta and protein kinase C increase decidual PGE2 synthesis through different mechanisms. Desensitization of the decidual cells for 24 h with PMA did not affect IL-1 beta-stimulated PGE2 synthesis. The complex roles of protein kinase C in regulating decidual prostaglandin synthesis require further investigation, but it is clear that the effects of IL-1 beta are not mediated by protein kinase C.

An endogenous inhibitor of prostaglandin synthesis in human decidua

Human first trimester decidual tissue has been reported to contain an inhibitor of cyclo-oxygenase enzyme, but a careful reading of the literature indicates that the inhibitor may be human albumin. Our own studies also showed that high levels of albumin were present in samples from homogenised decidual tissues. We therefore digested the tissue to obtain isolated cells and washed them extensively to minimise contamination with blood. Homogenates of such cells did not bind arachidonic acid, and inhibited cyclo-oxygenase enzyme-1 (COX-1) activity. The cellular factor inhibited COX-1 at concentrations of 60-100 micrograms protein/ml, and was therefore more potent than human albumin (0.5-2.0 mg/ml). The inhibitory activity was lost after heat treatment (100 degrees C for 10 mins) and after digestion with trypsin or papain, but was resistant to mercaptoethanol and urea. Preliminary data indicated that the protein had a molecular weight > 30 kD.

Augmentation of fetal granulopoiesis with chorioamnionitis during the second trimester of gestation

Chorioamnionitis is a major hazard to pregnancy in the second trimester. It affects the fetomaternal unit, causing febrile illness in the mother. The fetus eventually is expelled because uterine contractions can no longer be suppressed after a certain stage of the disease. To determine the effects of chorioamnionitis on the fetus we examined fetal hematopoiesis, which is, for the most part, located extramedullarily during the second trimester of gestation. The study was performed morphometrically on sections of fetal tissues; the results are given as an increase of cells per square millimeter. In chorioamnionitis the fetuses (n = 18) showed increased granulopoiesis in the parenchyma of the liver (x12), in the spleen (x 5), in the portal triads of the liver (x3), and in the bone marrow (x1.35). Erythropoiesis and total hematopoiesis were reduced in all compartments. Inflammatory disease in the mother other than chorioamnionitis did not alter fetal hematopoiesis (n = 13). Under normal conditions fetal liver granulopoiesis is at a very low level within the sinusoids, but an early and substantial increase can be seen most easily in this location during infection; chorioamnionitis can thus be diagnosed from the fetal liver alone. Alterations in fetal hematopoiesis might be caused by cytokines generated at the fetomaternal interface during chorioamnionitis.

Evidence for decidual modulation of contractile function in the pregnant rat uterus

This study tested the hypothesis that the decidua of pregnant uterus modulates contractile behavior of the underlying myometrium. Isometric contractile function was measured in transverse rings of pregnant rat uterus with or without the decidua. Observations were made of spontaneous contractions after in vitro isolation, and also of contractile responses to oxytocin and prostaglandin F2 alpha (PGF2 alpha) after the tissues had ceased spontaneous mechanical activity. The amplitude and frequency of spontaneous uterine contractions progressively declined after in vitro isolation; during this period, amplitude of spontaneous contractions was greater in the presence of the decidua, whereas contraction frequency was similar in the decidua-intact and decidua-removed tissues. Reinsertion of donor decidua reproduced contractile characteristics of intact tissue. PGF2 alpha and oxytocin stimulated myometrial contractions, but contraction frequency was greater in the absence than in the presence of the decidua. Depending upon the stimulus, the decidua seems able to express both excitatory and inhibitory factors which can selectively modulate either strength or frequency of uterine contractions.

The "interleukin 1 receptor antagonist" is a partial agonist of prostaglandin synthesis by human decidual cells

In many systems the interleukin-1 receptor antagonist opposes the effects of interleukin-1 beta. We considered that it might block interleukin-1 beta-stimulated prostaglandin production from human decidual cells. Very high levels of interleukin-1 receptor antagonist (> 1000 pg/ml) had limited inhibitory effects on IL-1 beta-stimulated PGE2 synthesis, and lower levels of antagonist (< 1000 pg/ml) increased the effects of IL-1 beta. Low concentrations of the antagonist alone (1-100 pg/ml) increased basal PGE2 production, whereas higher levels (10-100 ng/ml) had less effect. It seems, therefore, that in human decidua the "antagonist" is more accurately described as a partial agonist. It has been suggested that the IL-1 receptor antagonist could be used to inhibit decidual prostaglandin synthesis and thereby prevent preterm labor, but this report shows that caution should be exercised before using the receptor antagonist.