A product from human decidua inhibits prostaglandin production by human amnion

Fetal membranes inhibit prostaglandin but not oxytocin-induced uterine contractions

OBJECTIVE

Paracrine signaling in fetal membranes and uterus is hypothesized to play a role in the initiation of labor in women. Numerous fetal membrane signals that stimulate uterine contractions have been described. Recently, by means of the dual-chamber, fetal membrane, uterine muscle model we showed that fetal membranes inhibit spontaneous uterine contractions. This study was designed to test whether human fetal membranes can also inhibit agonist-induced uterine contractions.

STUDY DESIGN

A rat uterine muscle strip was mounted into the maternal side of a Plexiglas acrylic plastic chamber. Uterine contractions were recorded for 3 hours after the addition of either 50 nmol/L prostaglandin E2 or 0.1 nmol/L oxytocin to the maternal side of the chamber. During the first and third hours no fetal membranes were present (basal condition). At the beginning of the second hour fetal membranes were inserted into the chamber so that they divided the chamber into maternal and fetal compartments. The membranes were removed before the beginning of the third hour. The integrated force of uterine contractions during the second hour, when the muscle was exposed to fetal membranes, was compared with the basal condition (first and third hours) by repeated-measure analysis of variance.

RESULTS

Fetal membranes reversibly inhibited prostaglandin E2-induced uterine contractions by 22%. Fetal membranes did not inhibit oxytocin-induced uterine contractions.

CONCLUSION

Fetal membranes inhibit agonist-induced uterine contractions. The fetal membrane inhibitory system is agonist selective.

Interleukin-1 beta stimulates decidual stromal cell cyclo-oxygenase enzyme and prostaglandin production

The cytokine interleukin-1 (IL-1 beta) increased prostaglandin production by decidual stromal cells in culture in a time and dose dependent manner. Optimum conditions for stimulation were found to be for 24 hours at a concentration of 100 pg IL-1 beta/ml. An apparent increase in cyclo-oxygenase enzyme synthesis accompanied the increase in prostaglandin production, and both changes were inhibited by the protein synthesis inhibitor cycloheximide. This implicates protein synthesis in the stimulatory effects of IL-1 beta, which may be mediated through the increase in cyclo-oxygenase enzyme. A pre-incubation period of 72 hours was found to be necessary to observe the stimulatory effect of IL-1 beta on prostaglandin production, but this did not seem to be due to any change in the sensitivity of the cells to IL-1 beta; the increase in the number of cyclo-oxygenase positive cells was the same if IL-1 beta was added on day 1, day 2 or day 3 of culture, even though prostaglandin production was not stimulated on day 1 or day 2. Cycloheximide increased prostaglandin production on the first two days of culture and had no effect on the third day of culture. This was interpreted as indicating that a factor inhibiting cyclo-oxygenase activity was synthesised during the initial period of culture, which prevented any increase in prostaglandin production following the increase in enzyme synthesis.

Amnion cell prostaglandin E2 stimulatory activity in chorion laeve-conditioned medium

In this study we demonstrate the presence of a stimulant(s) to amnion cell prostaglandin (PG) E2 production in chorion-conditioned medium (CCM). The CCM induced a dose-dependent increase in amnion cell PGE2 production. This stimulatory activity was eliminated by heat and protease treatment. Maximal stimulation of amnion PGE2 by CCM did not occur until after 2 h of incubation, and treatment with cycloheximide (1 microgram/ml) effectively eliminated the ability of the amnion cells to respond to CCM. Additionally, CCM and arachidonic acid (2-40 microM) were synergistic in their stimulatory actions on amnion PGE2 production. CCM-treated amnion cells recover more quickly from acetylsalicylic acid pretreatment as compared to control. It is concluded that CCM contains a heat-labile protein which stimulates amnion cell PGE2 production by induction of prostaglandin endoperoxide synthase activity.

Bacterial endotoxin and tumor necrosis factor stimulate prostaglandin production by human decidua

The purpose of these studies was to determine the effect of bacterial endotoxin and tumor necrosis factor (TNF) on prostaglandin (PG) secretion by human decidua. Decidual explants were established from women undergoing elective cesarean sections before the onset of labor. Escherichia Coli endotoxin and purified human recombinant TNF (rh TNF) were incubated with decidual explants. PGF2 alpha and PGE2 biosynthesis was measured by radioimmunoassay. A significant increase in the release of all PGs into the media occurred in response to LPS and TNF. In the setting of an extraamniotic infection, bacterial and host secretory products (TNF) could trigger the onset of labor, activating the decidua to produce PGs.