Quantitative production of prostaglandin E2 and its metabolites by human fetal membranes

The production of interleukin-1beta from human fetal membranes is not obligatory for increased prostaglandin output

Bacterial endotoxin increased the expression of mRNA (maximal after 4 hr) for interleukin-1beta (IL-1beta) and the release of mature protein from intact human fetal membranes. In contrast, the change in expression of mRNA for type 2 cyclo-oxygenase (COX-2) was biphasic, with peaks after 0.5-1 hr and after 8 hr of culture. An antibody to IL-1beta was without effect after 4 hr of culture, inhibited endotoxin-stimulated prostaglandin E2 (PGE2) production after 8 hr of culture, and caused a parallel decrease in the expression of mRNA for COX-2. We conclude that endotoxin induced the expression of COX-2 through IL-1beta-independent and IL-1beta-dependent mechanisms, and these differences are time dependent. Corticotrophin-releasing hormone (CRH) or platelet-activating factor (PAF) also increased the expression of mRNA for IL-1beta and the release of IL-1beta from some, but not all, fetal membranes. The antibody to IL-1beta did not affect CRH-stimulated or PAF-stimulated PGE2 production or COX-2 expression. We conclude that CRH and PAF can induce the expression of IL-1beta, but this is not obligatory for increased PGE2 release, and the effect of these stimuli on COX-2 expression is a direct, IL-1beta-independent effect.

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

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

Prostaglandin-endoperoxide H synthase-2 expression and activity increases with term labor in human chorion

We investigated the changes in prostaglandin-endoperoxide H synthase (PGHS) specific activity and the levels and distribution of PGHS-1 and PGHS-2 mRNA in chorion collected at term before the onset of labor (CS) and after term labor and delivery (SL). PGHS specific activity and PGHS-2 mRNA abundance were higher in chorion collected after SL compared with that obtained at CS (P < 0.001); there was no difference in the levels of PGHS-1 mRNA between CS and SI, tissues. The increase in PGHS specific activity at SL was significantly correlated with PGHS-2 mRNA expression (P < 0.05) but not with PGHS-1 mRNA levels. In situ hybridization indicated that the pervasiveness of staining for PGHS-1 mRNA throughout full-thickness membranes did not change with labor onset; however, a greater number of cells expressed PGHS-2 in SL tissues. Our results demonstrate a selective increase in PGHS-2 expression and activity in chorion trophoblasts and mesenchymal cells with term labor onset. These observations are similar to those concerning amnion and imply that a concerted mechanism may exist in the fetal membranes to induce PGHS-2 expression at labor.

Effects of interleukin-6 and tumor necrosis factor-alpha on prostaglandin production by cultured human fetal membranes

In this study we investigated the effects of the cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) on prostaglandin production by cultured human fetal membranes. These cytokines stimulate prostaglandin synthesis by isolated components of human fetal membranes, but their effects on the intact tissue comprising amnion, chorion and decidua were not known. TNF-alpha added to the maternal side of the membrane activated decidual production of PGF2 alpha but had no effects on synthesis of PGE2 or PGE2 metabolites. Addition of TNF-alpha to the fetal side of the membrane increased production of PGE2 by amnion and PGE2 metabolites from chorion. The addition of IL-6 to the fetal or the maternal side of the membrane increased production of PGE2 from amnion and PGE2m from chorion, suggesting that IL-6 might pass through the fetal membrane. IL-6 had no effect on decidual PGF2 alpha production. These results suggest that TNF-alpha may be involved in labor by increasing decidual prostaglandin synthesis, whereas IL-6 is less likely to have a role.

The effects of interleukins 1 alpha and 1 beta on prostaglandin production by cultured human fetal membranes

The effects of IL-1 alpha and IL-1 beta on cultured human fetal membranes were studied. These cytokines are known to regulate prostaglandin synthesis by the separated components of the fetal membranes (amnion, chorion and decidua), but their effects on intact tissue are unknown. IL-1 alpha increased PGE2 levels on the fetal side of the membrane, indicating increased production of prostaglandin from the amnion, but had little effect on levels of PGE2 on the maternal side of the membrane. Low levels of IL-1 beta (0.1-1.0 ng/ml) increased PGE2 levels on the fetal side of the membrane, and also increased the production of PGE2 metabolites and PGF2 alpha, suggesting that this cytokine stimulated the decidua as well as the amnion. High concentrations of both cytokines appeared able to stimulate prostaglandin production by the side of the membrane opposing that to which they were added, but it is not clear whether this was mediated by factors released by the stimulated membrane, or by direct transfer of small quantities of cytokines through the membrane. Taken together, these results indicate that IL-1 beta was a potent stimulator of the synthesis of prostaglandins by decidua and by amnion, whereas IL-1 alpha only stimulated the amnion.

Transfer and metabolism of platelet-activating factor by fetal membranes, amnion and chorio-decidua

OBJECTIVE

To determine the metabolism of 3H-Platelet-activating factor (3H-PAF) during transfer through human fetal membranes.

DESIGN

3H-PAF was added to the fetal side of cultured intact fetal membranes, amnion and chorio-decidua obtained from three pregnancies ending in elective caesarean section.

MAIN OUTCOME MEASURES

Radioactivity was measured on both sides of the tissue, and in the tissue itself. In some experiments, the metabolism of 3H-PAF was assessed by thin-layer chromatography.

RESULTS

Very little 3H-PAF crossed the intact fetal membrane (< 2%) during 24 h of culture. Most of the 3H-PAF which accumulated in the membrane was converted to a range of metabolites in the chorio-decidua.

CONCLUSIONS

These results suggest that PAF in amniotic fluid may not reach the decidua, and therefore is unlikely to be involved in the control of prostaglandin production from this tissue.

Effects of platelet-activating factor on prostaglandin E2 production by intact fetal membranes

OBJECTIVE

The hypothesis tested in this study is that platelet-activating factor increases prostaglandin E2 synthesis from fetal membranes.

STUDY DESIGN

Fetal membrane disks obtained before or after labor were incubated with or without platelet-activating factor for time periods of up to 24 hours. The production of prostaglandin E2 and its inactive metabolites was determined by specific radioimmunoassays.

RESULTS

Platelet-activating factor (1 to 10 mumol/L) stimulated the production of prostaglandin E2 and its metabolites by intact fetal membranes and chorion-decidua threefold to fourfold after 24 hours of incubation. Platelet-activating factor had far greater effects on the production of prostaglandin E2 by intact fetal membranes obtained after the onset of labor, such that prostaglandin E2 production was increased by tenfold to 100-fold.

CONCLUSION

These results suggest that platelet-activating factor mainly stimulates prostaglandin E2 production by the chorion-decidua before labor and that it may act in synergism with other stimulatory factors present in the fetal membranes during labor.