5-Hydroxyeicosatetraenoic acid and human parturition

5-Hydroxyeicosatetraenoic acid (5-HETE) is an arachidonic acid (AA) metabolite derived from the lipoxygenase pathway which is capable of inducing uterine contractions. The purpose of this study was to determine a). whether 5-HETE concentrations in amniotic fluid increase before or after the onset of labor and b). whether acetylsalicylic acid (ASA) could modulate the production of 5-HETE by human amnion cells. 5-HETE concentrations are increased in amniotic fluid before the onset of labor. Furthermore, ASA treatment as expected inhibited PGE2, but also significantly increased 5-HETE production by amnion cells. 5-HETE concentrations on average increased by greater than 2.5 fold (p < 0.001) in amniotic fluid prior to spontaneous labor when compared with samples obtained from the same patients earlier in gestation and therefore may be important in mechanisms regulating the onset of labor. ASA provokes an increase in 5-HETE biosynthesis by amnion cells: control media 2.60 +/- 1.5, ASA treatment alone 5.17 +/- 0.20, IL-1 beta alone 6.39 +/- 2.1, and ASA + IL-1 beta 8.95 +/- 1.2 (mean +/- SEM) picograms per microgram protein per 16 hours. These findings may explain in part why cyclooxygenase inhibitors are not always successful in treating women with preterm labor.

Regulation of fetal fibronectin production in human amnion cells

OBJECTIVE

We evaluated the role of human amnion in the production of fetal fibronectin and assessed the regulation of fetal fibronectin production by inflammatory products and cytokines.

METHODS

Human amnion cells were grown in culture. At confluence, the cell were incubated with and without lipopolysaccharide, interleukin-1 beta, tumor necrosis factor-alpha, and interleukin-6. Fetal fibronectin production was measured in the supernatant fluid using an enzyme-linked immunosorbent assay technique.

RESULTS

Unstimulated amnion cells produced fetal fibronectin, and production was increased by lipopolysaccharide, interleukin-1 beta, tumor necrosis factor-alpha, and interleukin-6.

CONCLUSION

Human amnion cells in vitro produce fetal fibronectin in substantial quantities. This production is stimulated by inflammatory products and mediators that are considered to be important in the initiation of some cases of preterm labor.

The induction of cyclooxygenase-2 (COX-2) in intact human amnion tissue by interleukin-4

Infection is a major cause of preterm labor. Amniotic fluid from women in preterm labor associated with intrauterine infection contains increased concentrations of cytokines. The mechanism underlying this association may be a cytokine-mediated stimulation of amnion cell prostaglandin production. The biosynthesis of prostaglandins from arachidonic acid is regulated by the enzyme cyclooxygenase which exists in two forms; the constitutive form (COX-1) and the other mitogen inducible (COX-2). The purpose of this study was to evaluate the effect of the cytokine interleukin-4 (IL-4) on cyclooxygenase activity and PGE2 production in amnion. Amnion tissue was taken at caesarean section from term women not in labor and immediately incubated for 2 hours in media containing concentrations of IL-4 ranging from 1 to 100 ng/ml. An increase in both COX-2 enzyme and prostaglandin E2 (PGE2) production was observed for all concentrations of IL-4 greater than 25 ng/ml (P < 0.05, n = 8). No change in COX-1 was observed. Our data suggest that the cytokine IL-4 may be involved in the pathogenesis of premature labor by inducing COX-2 in amnion tissue resulting in increased production of PGE2 and subsequent myometrial activity.

Induction of both cytosolic phospholipase A2 and prostaglandin H synthase-2 by interleukin-1 beta in WISH cells in inhibited by dexamethasone

In previous studies we have shown that IL-1 beta induced both PGE2 release and total cellular cPLA2 activity and cPLA2 protein synthesis in human amnion-derived WISH cells. In this study, the effect of IL-1 beta on cPLA2 and PGHS-2 mRNA expression was investigated. Using RT-PCR, we found that IL-1 beta (0.1 ng/ml) coordinately induced both cPLA2 and PGHS-2 mRNA expression within 2 hours. The synthetic glucocorticoid dexamethasone (10(-10)-10(-6)M) inhibited IL-1 beta-induced cPLA2 and PGHS-2 mRNA expression activity and protein synthesis and PGE2 release in a concentration dependent manner. In the absence of IL-1 beta, dexamethasone alone (10(-6)M) inhibited basal cPLA2 activity, mRNA expression and protein synthesis. In addition, cycloheximide (5 micrograms/ml) apparently superinduced, but actinomycin D (2 micrograms/ml) inhibited IL-1 beta-induced cPLA2 and PGHS-2 mRNA expression suggesting that both are immediate early genes and a transcriptional mechanism is involved in the induction of both cPLA2 and PGHS-2 mRNA by IL-1 beta.

Stimulation of prostaglandin E2 synthesis by interleukin-1beta is amplified by interferons but inhibited by interleukin-4 in human amnion-derived WISH cells

Human amnion-derived WISH cells synthesize little prostaglandin E2 at the basal state. However, the cells were stimulated greatly to synthesize prostaglandin E2 by interleukin-1beta in a dose-dependent manner. Stimulation by interleukin-1beta was synergistically increased by pretreatment of the cells with interferon alpha or gamma, which alone were inactive. Synergism by interferons was dose-dependent. Stimulation by interleukin-1beta, on the contrary, was inhibited by preincubation of the cells with interleukin-4. Inhibition by interleukin-4 was also dose-dependent. Regulation of prostaglandin E2 synthesis by cytokines was further examined at the m-RNA level of cyclooxygenase-2. Quantitative reverse transcription-polymerase chain reaction indicated that the m-RNA level was not increased by interferon-gamma but was synergistically increased by interferon-gamma plus interleukin-1beta. Furthermore, the m-RNA level increased by interleukin-1beta was attenuated by interleukin-4. These results indicate that regulation of interleukin-1beta-stimulated prostaglandin E2 synthesis by interferons and interleukin-4 is controlled at the m-RNA level of cyclooxygenase-2.

Macrophage inflammatory protein-I alpha regulates prostaglandin E2 and interleukin-6 production by human gestational tissues in vitro

OBJECTIVE

To determine if the inflammatory cytokine macrophage inflammatory protein-1 alpha (MLP-1 alpha) stimulates the production of prostaglandin E2 (PGE2) and interleukin-6 (IL-6) by human gestational tissues.

METHODS

Human decidual cells, chorion cells, and amnion cells were isolated from term placentas of women with normal pregnancies, and primary cultures of each cell line were established. In various concentrations, MIP-1 alpha was then applied to each cell culture for 16 hours at 37C, and culture supernatants were assayed for PGE2 and IL-6.

RESULTS

After incubation with MIP-1 alpha, decidual cells produced increased amounts of both IL-6 (P < .05) but not PGE2. When subjected to similar conditions, chorion cells produced increased amounts of both IL-6 and PGE2 (P < .05). Conversely, amnion cells produced increased amounts of only PGE2 in response to increasing concentrations of MIP-1 alpha (P < .05).

CONCLUSION

Maternal and fetal gestational tissues differentially respond to MIP-1 alpha with regard to PGE2 and IL-6 production; MIP-1 alpha may play a role in both the initiation and propagation of the inflammatory response associated with intrauterine infection.

The activity of azithromycin on the infectivity of Chlamydia trachomatis in human amniotic cells

The effects of azithromycin on the infectivity and growth of Chlamydia trachomatis were investigated in primary human amniotic epithelial cells. Infection was prevented when cultures were exposed to the drug 6 h after inoculation and growth was completely inhibited when the drug was added to cultures 24, 48, 72 h or 7 days after infection. The same inhibition was observed at 0.5, 1.0 and 5.0 mg/L. Ultrastructural observations depicted interruption in the growth cycle of the chlamydia and ghost-like envelopes were present in the near empty inclusions. Azithromycin is effective in inhibiting chlamydial growth no matter when treatment is initiated after infection.

Changes in prostaglandin synthesis and metabolism associated with labour, and the influence of dexamethasone, RU 486 and progesterone

The objective was to compare the changes in prostaglandin synthesis and metabolism occurring within the fetal membranes that are associated with the onset of parturition and to study the effect of steroid hormones on prostaglandin metabolism. A tissue explant study was made of discs of amnion and chorion obtained from 24 pregnant women at 37-42 weeks' gestation following spontaneous labour and delivery (12 women) and elective caesarean section (12 women). Significantly more prostaglandin E2 (PGE2) and PGF2 alpha were synthesized by amnion obtained following spontaneous labour than elective caesarean section. Arachidonic acid stimulated both PGE2 and PGF2 alpha synthesis by amnion in both groups. Phorbol myristoyl acetate stimulated PGE2 synthesis in both groups. There was no difference between the groups in the capacity of the chorion to metabolize prostaglandins. Mifepristone (RU 486) reduced the metabolism of added PGE2 following spontaneous labour, while dexamethasone and progesterone had no effect on prostaglandin metabolism. In conclusion, the increase in concentration of PGE2 and PGF2 alpha associated with the onset of spontaneous labour is the result of an increase in synthesis rather than a reduction in metabolism. There was no decrease in metabolism to account for the increase in prostaglandin concentrations and, with the exception of mifepristone, metabolism was not altered by the addition of steroid hormones.

Nuclear microanalysis of the monovalent ion distribution in the human amnion. I. Effect of magnesium

The effect of the addition of MgCl2 on the Na+, K+, and Cl- concentration and distribution in epithelial and compact layers of the human amniotic membrane was investigated using the Bordeaux nuclear microprobe. Particle-induced X-ray emission and Rutherford backscattering spectrometry techniques were used to provide quantitative measurements. In physiological medium (Hanks' solution), the monovalent ion concentrations were identical in both layers. The addition of Mg2+ ions in Hanks' solution induced a decrease of, K+, and Cl- concentration in both layers and, Na+ concentration in the compact layer. The results obtained from nuclear microanalysis might be explained from electrophysiological data which indicate that the addition of Mg2+ ions results in an increase in the cellular, paracellular and exchanger ion pathways.

Comparative studies of Ca N-acetylhomotaurinate and Ca N-acetyltaurinate. II. Preventive and opposing actions of the acute ethanol depletive effect on the ionic transfer through the isolated human amnion

Ethanol reduces the ionic paraplacental transfer through the human amnion. This effect is exerted on the cationic paracellular pathway, the coupling between two adjacent epithelial cells, the monovalent cation pump and the antiport system. In this study, the preventive and opposing actions of two taurine and homotaurine derivatives (Ca N-acetyltaurinate: ATACa, Ca N-acetylhomotaurinate: AOTACa) were observed. One the maternal side, ATACa and AOTACa demonstrated protective actions on cationic paracellular pathways and on the Na/K-ATPase pump with AOTACa only. On the fetal side, the effect of ATACa was limited to the sodium paracellular pathway. This effect was total at 5 mM. On the maternal side, ATACa and AOTACa exhibited an opposing action on the same components of the conductance. But on the fetal side, ATACa increased the ethanol effect and AOTACa exerted an antagonistic effect on the cation pump only. These results indicate that two closely related molecules may have different effects on a membranous ethanol model.

Interleukin-1 beta induces the synthesis and activity of cytosolic phospholipase A2 and the release of prostaglandin E2 in human amnion-derived WISH cells

The objective of this study was to examine the expression and activity of cytosolic phospholipase A2 (cPLA2) in relation to prostaglandin E2 (PGE2) synthesis in human amnion-derived WISH cells in response to stimulation by interleukin-1 beta (IL-1 beta). cPLA2 activity was characterized by sensitivity to heat and acid treatment, stability to dithiothreitol, and inhibition by the specific inhibitor, arachidonyl trifluoromethyl ketone (AACOCF3). Treatment of WISH cells with IL-1 beta (0.01-1 ng/mL) for up to 24 h resulted in a significant increase in PGE2 release in a concentration- and time-dependent manner accompanied by increases both in total cellular cPLA2 activity and in cPLA2 protein levels detected by Western blot analysis. The parallel increase in total cellular cPLA2 activity and cPLA2 protein level indicates that IL-1 beta may induce the synthesis of cPLA2. Incubation of the cells with 10 microM AACOCF3 for 24 h significantly inhibited IL-1 beta-induced PGE2 production strongly suggesting that cPLA2 mediates IL-1 beta-induced PGE2 formation. In unstimulated cells, there is appreciable total cellular cPLA2 activity and protein, but these cells produce low amounts of PGE2 until stimulated by IL-1 beta, suggesting that cPLA2 translocation from cytosol to the membrane is necessary for its bioactivity. In contrast to IL-1 beta, treatment with phorbol ester (12-O-tetradecanoyl phorbol-13-acetate, TPA, 10(-10)-10(-6)M) for 24 h significantly inhibited total cellular cPLA2 activity in a concentration-dependent manner. The amount of total cellular cPLA2 protein seen on Western blot remained unchanged following TPA treatment. These data suggest that in WISH cells, IL-1 beta induces both translocation to the membrane and de novo synthesis of cPLA2 protein to sustain prostaglandin (PG) synthesis. In contrast, TPA may only cause cPLA2 translocation but no increase in cPLA2 protein synthesis, resulting in limited PG synthesis. Our results provide a mechanism for the effect of IL-1 beta on prostaglandin synthesis in human amnion cells and provide support for a role of cPLA2 in the mechanism initiating human parturition.

Comparative studies of Ca N-acetylhomotaurinate and Ca N-acetyltaurinate. I. Effects on the ionic transfer through the isolated human amnion

The effects of two taurine and homotaurine derivatives (Ca N-acetyltaurinate: ATACa and Ca N-acetylhomotaurinate: AOTACa) were studied on the ionic transfer through a membranous model: the human isolated amniotic membrane. The ionic transfer was evaluated by measurements of the various components (cellular and paracellular) of the total conductance across the membrane. AOTACa influenced all the components of the total ionic conductance without flux ratio modifications and the general action scheme was a biphasic effect: decrease conductance with low concentrations and increase conductance with high concentrations. This effect might be important in the case of lower or higher supplementation. ATACa only interfered with some conductance components and this action was predominantly monophasic (decreased or increased conductance). This study indicates differential actions between two closely related molecules on a membranous model.

[The modification of Bacillus intermedius ribonuclease by urea derivatives]

The results of the "Bacillus intermedius" RNAase modification by urea derivatives are presented. The modifiers synthesized for that purpose were the following: N-(4-chlorbenzoyl)-N'-benzolsulfonyl urea (M1) and N-(4-chlorbenzoyl)carbomoyl-epsilon-aminocapronic acid (M2). It was shown that RNAase modified by M2 stimulated the cell general metabolism by the test of the cell absorption of neutral red and had a more marked ability to disrupt RNA of the cell plasmatic membranes in comparison to that of the native enzyme.

[Dietetic factors and premature rupture of fetal membranes. Effect of vitamin C on collagen degradation in the chorioamnion]

Some studies have shown an association between vitamin C disposability (Vit C), and the development of premature rupture of membranes (RPM). However, vitamin C role in the metabolism of collagen upon chorioamnion tissue, has not been analyzed. In this study the effect of modulation with different vit C concentrations in culture cells derived from human amnion, was analyzed. Vit C concentrations were used in order to cover physiological range (29.0 micrograms/ml). After stimulation the cells media were analyzed for enzymatic activity of metalloproteinases with extracellular matrix (MMP), and relative quantity of MMP-1, MMP-2 and MMP-9, was quantified, by immune transference, using monospecific polyclonal antibodies. The activity, as well as protein decreased in amniotic cells media, in a direct way as to vit C concentration, so, at the highest used concentrations (100 micrograms/ml), the least MMP activity/quantity, was obtained. These results show a finding not described until now, which permits to establish a direct connection between vit C availability and increase in collagen degradation. According to results, the less availability of vit C, the greater degradation of collagen, which should lead to a mechanical support loss and eventual fetal membranes rupture.

Role of neutrophils in mediating human epithelial cell detachment from native basement membrane

Epithelial cell detachment from underlying basement membrane is a feature of diseases of many organs. In the lungs it is seen in disorders as diverse as bronchiectasis, allograft rejection, and asthma. The potential for different leukocytes to induce this change is not clear. In asthma both eosinophils and neutrophils are found in affected tissues, but the capacity of each of these types of cells to induce detachment of native epithelial cells from basement membrane requires clarification. Although eosinophils damage rather than detach human epithelial cells, the effects of neutrophils on epithelial cells naturally attached to basement membrane have not previously been described. Using the human amnion in vitro model, we tested the hypothesis that neutrophils have the capacity to detach intact human epithelial cells from basement membrane. The data indicate that increasing concentrations of neutrophils are able to detach epithelial cells from their underlying basement membrane. Detachment was increased when the neutrophils were activated in situ with tetradecanoyl phorbol acetate and after longer incubation periods. Platelet activating factor and opsonized zymosan showed similar boosting effects, whereas activated complement and formyl-methyl-leucyl-phenylalanine did not. Physical contact of the neutrophils with the epithelial cells was required to induce detachment. Detachment could be inhibited by glutathione and by soybean trypsin inhibitor, an inhibition pattern similar to cathepsin G and trypsin, but not collagenase, in this system. We conclude that neutrophils are capable of detaching human epithelial cells from basement membrane, which in part involves the release of chymotrypsin-like serine proteases, probably in conjunction with oxidants, and that this detachment can be inhibited.

[Antimutagenic protection of the human genetic system in acute intoxication]

The results of clinical studies and model experiments have shown that human genome damages are widely spread in patients with acute intoxication. For neutralization of the negative effects, biologically active compounds-antimutagens, alpha-tocopherol, and new plant mutagen were used. The application of antimutagens has been found to increase the level of genetic damages induced by acute intoxication.

The controversial role of cAMP on amnionic prostaglandin release: effect of adenylate cyclase inhibition

The suggested role of cAMP in the regulation of amnionic prostaglandin release was investigated using two adenylate cyclase inhibitors, MDL 12330A and SQ 22536. These substances exhibited a dose-dependent inhibitory effect on both amnionic enzyme and cAMP levels, but they did not influence prostaglandin E (PGE) release. In addition forskolin and IBMX (3-isobutyl-1-methylxanthine), two drugs known to increase cAMP levels, did not affect PGE output, while dibutyryl cyclic cAMP showed a dose-dependent inhibitory effect. On the basis of our data, the suggested role of amnionic adenylate cyclase in triggering prostaglandin release is not confirmed, and the pathway of phospholipase A2 activation at the onset of labor remains to be elucidated.

Inhibitor effects on the ionic exchanges through the human amniotic epithelial cell membranes

Direct measurements of cell podocyte/or microvillous membrane ionic exchanges were performed on the membranes of isolated human amniotic epithelial cells. The ionic exchanges were determined from the measures of cellular input conductances. The effects of various inhibitors: ouabain, amiloride, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), 4'4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), quinidine, barium, manganese were analyzed. This study shows that the ionic exchanges through the epithelial cells are regulated by the presence of Na+,K+,Cl- channels, Na+/H(+)-Cl-/HCO3- antiports, (Na-K)ATPase and Na+/Ca(2+)-Na+/Mg2+ exchangers on the 2 faces of the cells and of a Na(+)-K(+)-2Cl- cotransport on the membrane facing the amniotic cavity only.

Induction of interleukin-1 receptor antagonist in rhesus monkeys after intraamniotic infection with group B streptococci or interleukin-1 infusion

OBJECTIVE

Interleukin-1 receptor antagonist is a natural inhibitor of interleukin-1, a cytokine implicated in the initiation of preterm labor after intraamniotic infection. The effects of intraamniotic infection and interleukin-1 infusion on the appearance of interleukin-1 receptor antagonist in amniotic fluid and fetal and maternal plasma were assessed with a monkey model.

STUDY DESIGN

On day 130 of pregnancy four chronically catheterized rhesus macaques received intraamniotic inoculations of group B streptococci, three monkeys received intraamniotic infusions of recombinant human interleukin-1 beta, and three monkeys received buffered saline solution infusions. At timed intervals samples of amniotic fluid, fetal plasma, and maternal plasma were assayed for interleukin-1 beta and interleukin-1 receptor antagonist by immunoassays. Uterine activity was continuously monitored by intraamniotic pressure catheters and by electromyographic activity.

RESULTS

Interleukin-1 receptor antagonist, but not interleukin-1 beta, was present in the amniotic fluids of all monkeys before intervention. Infection induced the appearance of interleukin-1 beta and an increase in interleukin-1 receptor antagonist in the amniotic fluid. Interleukin-1 beta infusion resulted in a similar increase in the intraamniotic concentration of interleukin-1 receptor antagonist. Both infection and interleukin-1 beta infusion were followed by the transient appearance of interleukin-1 receptor antagonist in the plasma of all fetuses. The subsequent decrease in plasma levels was paralleled by increased amniotic fluid levels of interleukin-1 receptor antagonist. Interleukin-1 beta and interleukin-1 receptor antagonist were not detected in maternal plasma. Both infection and interleukin-1 infusion induced preterm labor in all treated animals.

CONCLUSIONS

Interleukin-1 receptor antagonist is a normal component of monkey amniotic fluid. Intraamniotic infection or the appearance of interleukin-1 beta in the amniotic fluid results in increased production of interleukin-1 receptor antagonist. Under physiologic conditions interleukin-1 receptor antagonist in amniotic fluid may inhibit interleukin-1-induced preterm labor.

Relaxin (hRLX-2)-induced weakening of human fetal membranes in vitro

We examined the effect of human relaxin (hRLX-2) on the biomechanical properties of human fetal membranes in vitro. Intact chorioamniotic membranes were obtained from twelve elective cesarean sections before the onset of labor. Membrane strips with a fixed width were biomechanically tested after incubation for 20 h with hRLX-2 in concentrations of 10(-7) mol/l and 10(-9) mol/l. Incubation with hRLX-2 (10(-9) mol/l) changed the load-strain values as the membrane stiffness was decreased by 19% when compared with controls: median 2.45 N (range, 0.81-4.31) versus 3.03 N (1.28-5.46), P = 0.02 (Mann-Whitney test). For description of the membrane material as such, the stress-strain values were calculated by dividing the load-strain values with the cross sectional area of the membranes. Incubation with hRLX-2 (10(-9) mol/l) decreased the tensile strength of the membranes by 30%-0.817 N/mm2 (0.282-1.139) vs. 0.575 N/mm2 (0.101-1.150), P = 0.03--and reduced the elastic modulus by 31%--2.26 N/mm2 (0.82-5.08) versus 1.57 N/mm2 (0.51-3.71), P = 0.002. Less pronounced effects were found after incubation with hRLX (10(-7) mol/l). No quantitative or qualitative changes of the membrane collagen were found after relaxin incubation. Although the mechanism for rupture of the fetal membranes remains unknown, the present results suggest that relaxin might be involved in the process leading to rupture of the membranes.

Prostaglandin production during spontaneous labor and after treatment with RU486 in pregnant rhesus macaques

The production of prostaglandins from amnion, chorion, decidua, and myometrium was studied in a superfusion system to determine the level of prostaglandin production during late pregnancy, during spontaneous labor, and after in vivo treatment with RU486. Tissues were divided into three groups: those from pregnant control animals, those from animals receiving RU486 (20 mg/kg/day for 3 days) in vivo, and those from animals in spontaneous term labor. Tissues were collected at cesarean section and placed in the superfusion system. After a 30-min equilibration period, fractions of media were collected after passing through the tissue chambers and were assayed for prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2). The results showed a significant increase in PGF2 alpha from decidua of animals treated with RU486 compared to pregnant controls (pregnant: 3.01 +/- 0.45 ng/g/min; RU486: 4.45 +/- 0.28 ng/g/min; p < 0.05). There was a dramatic increase in PGE2 production by amnion from animals in spontaneous labor but not after RU486 treatment (pregnant: 0.21 +/- 0.06 ng/g/min; RU486: 0.56 +/- 0.09 ng/g/min; spontaneous labor: 5.83 +/- 0.43 ng/g/min; p < 0.01). We conclude that while progesterone is important for maintaining uterine quiescence during pregnancy, progesterone receptor blockade by RU486 does not lead to an increase in PGE2 production by amnion as is shown during normal spontaneous labor.

Arginine vasopressin antagonism of oxytocin-stimulated PGE2 release from rabbit amnion cells and the activities of thioanalogs of oxytocin and arginine vasopressin

Using rabbit amnion membranes devoid of arginine vasopressin receptors, we have shown that arginine vasopressin acts as a partial agonist and oxytocin antagonist. We examined peptides with modifications in position 8 to determine the basis for partial agonism/antagonism. The 8-thioanalog of oxytocin had about 40% of oxytocin activity in eliciting PGE2 release by amnion cells and a corresponding 40% affinity for oxytocin binding sites on amnion membranes. Arginine vasotocin, which has arginine at the position 8 and about 90% homology with arginine vasopressin also acted as a full agonist. These results suggest that determination of the oxytocin antagonist activity of arginine vasopressin is largely dependent on the amino acid at position 3. We also synthesized the 8-thioanalog of arginine vasopressin, which had a very low affinity for arginine vasopressin binding sites in rat liver (V1 receptors) and rat kidney medulla (V2 receptors) membranes. These findings suggest that arginine vasopressin receptors are much more sensitive to modifications of the peptide bond between positions 8 and 9 than are oxytocin receptors.

Interleukin-1 receptor antagonist (IL-1ra) production by human amnion, chorion, and decidua

PROBLEM

This study was conducted to determine whether (1) conditioned media from unstimulated primary cultures of human amnion, chorion, or decidua contain detectable concentrations of IL-1ra in vitro, and (2) bacterial endotoxin (LPS), tumor necrosis factor-alpha (TNF-alpha), or IL-1-beta (IL-1 beta) stimulate amnion, chorion, or decidua to produce increased amounts of IL-1ra.

METHOD

Placentae were obtained from women at term with intact membranes before the onset of labor. Amnion, chorion, and decidual cells were isolated by standard procedures and grown to confluence. Cells were then cultured in quadruplicate for 16 h in tissue culture medium supplemented with 10% fetal calf serum or, additionally, with various concentrations of Escherichia coli LPS, TNF-alpha, or IL-1 beta. Culture supernatants were collected, and concentrations of IL-1ra were quantitated by a sensitive and specific enzyme-linked immunosorbent assay for IL-1ra.

RESULTS

Results showed that primary cultures of amnion and chorion from 4 of 9 and decidua from 10 of 12 placentae had detectable rates of production of IL-1ra (ranges: 0.08-6.5, 0.42-12.1, and 1.55-96.5 pg IL-1ra/microgram protein/16 h, respectively). In addition, LPS (10-1,000 ng/ml) and IL-1 beta (0.1-10 ng/ml), but not TNF-alpha (0.01-100 ng/ml), stimulated decidual cells to release/secrete increased amounts of IL-1ra compared with media alone (range: 2.5-400 pg IL-1ra/microgram protein/16 h, P < 0.0001). In contrast, neither LPS, TNF-alpha, or IL-1 beta could stimulate amnion or chorion to release/secrete IL-1ra.

CONCLUSIONS

These results indicate (1) that amnion, chorion, and predominantly decidua, can release or secrete IL-1ra in vitro, and (2) that LPS and IL-1 beta can stimulate decidual cells to produce increased amounts of IL-1ra.

Transforming growth factor-beta stimulates, and glucocorticoids and epidermal growth factor inhibit brain natriuretic peptide secretion from cultured human amnion cells

We previously reported the massive secretion of brain natriuretic peptide (BNP) from human amnion cells and suggested the possible role of BNP in the maintenance of human pregnancy. In this study, to elucidate the regulatory mechanism of BNP secretion from amnion cells, we measured the BNP level in the culture medium of amnion cells by RIA after incubation in the presence of various substances. Among the agents examined, cortisol (1 x 10(-7) to 1 x 10(-6) mol/L), dexamethasone (1 x 10(-8) to 1 x 10(-6) mol/L), and epidermal growth factor (EGF; 2 x 10(-11) to 2 x 10(-8) mol/L) inhibited BNP secretion from the cultured amnion cells in a dose-dependent manner. By contrast, transforming growth factor-beta (TGF beta; 4 x 10(-11) to 4 x 10(-9) mol/L) caused a 3- to 5-fold increase in BNP secretion. TGF beta-augmented BNP secretion was abolished by the addition of cortisol or EGF to the culture medium. Moreover, in this study, we revealed the presence of bioactive TGF beta in human amniotic fluid (approximately 4 x 10(-10) mol/L). The present finding of tight regulation of BNP secretion from amnion cells by cortisol, EGF and TGF beta, all at the concentrations physiologically present in human amniotic fluid, implies a physiological role of BNP secretion from amnion cells in the pregnant uterus.