Biomedical subjects

W Gibb

Publications and source records attributed to W Gibb.

At least 19 recordsLinked to original sources

PubMed2006

The effect of tobacco exposure on the fetal hypothalamic-pituitary-adrenal axis.

OBJECTIVE: Our objective was to determine if maternal smoking is associated with programming of the fetal hypothalamic-pituitary-adrenal (HPA) axis. Cigarette smoking, which induces a state of hypoxia in the fetus, may promote in utero'programming' of the HPA axis. In utero, adaptations to the HPA axis, which become maladaptive later in life, have been hypothesised to contribute to the development of adult cardiovascular disease and metabolic disorders. DESIGN: This was a prospective cohort study of term infants. POPULATION AND SETTING: The study involved 104 infants born by elective caesarean section, 21 of whom were exposed to in utero tobacco and 83 were nonexposed. METHODS: Healthy women with healthy pregnancies were recruited if they were undergoing elective caesarean section. Maternal blood was drawn for cortisol and cotinine in the morning, and the umbilical blood was drawn immediately after delivery of the baby. MAIN OUTCOME MEASURES: Umbilical arterial cortisol and adrenocorticotropin hormone (ACTH) levels. RESULTS: ACTH levels were significantly elevated in smoke-exposed infants [17 (4-22) pmol/l versus 4 (2-11) pmol/l, respectively, P= 0.005], while cortisol levels were similar [182 (130-240) nmol/l versus 192 (127-265) nmol/l, respectively, P= 0.541]. CONCLUSIONS: For the first time, it was shown that infants exposed to in utero tobacco smoke have significantly elevated ACTH levels compared with nonexposed infants. The results of this study warrant further exploration of the effect of smoking on the neonatal HPA axis as a potential set up for 'programming'.

Adrenocorticotropic Hormone↗

PubMed2006

The pattern of glucocorticoid and estrogen receptors may explain differences in steroid dependency of intrauterine prostaglandin production at parturition in sheep.

BACKGROUND: We have recently described two distinct pathways of intrauterine prostaglandin (PG) synthesis: a cortisol-dependent/estradiol-independent mechanism within trophoblast tissue leading to elevations in fetal plasma PGE2, and an estradiol-dependent mechanism within maternal endometrium that leads to increased maternal plasma PGF2(2alpha). We hypothesized that the differential effects of cortisol and estradiol on intrauterine PGH synthase-II (PGHS-II) expression and PG production may be because of the tissue specific expression of the glucocorticoid and estradiol receptors (GR and ER, respectively) within the intrauterine tissues. In addition, we suggest that these two pathways of PG production are linked through the expression of P450(C17hydroxylase) (P450(C17)) and subsequent increase in placental estradiol synthesis. METHODS: To test the hypotheses, we infused singleton, chronically catheterized fetal sheep beginning at day 125 of gestation (term 147 to 150 days) with (1) cortisol (0.45 mg/mL; n = 5); (2) cortisol and 4-hydroxyandrostenedione, a P450(aromatase) inhibitor (4-OHA: 1.44 mg/h; n = 5); (3) saline (n = 5); or (4) saline and 4-OHA (n = 5). PGHS-II, ER alpha, ER beta, and GR alpha were localized using immunohistochemistry. ER alpha, ER beta, P450(C17), and GR alpha protein expressions were determined by Western blot analysis. Data were analyzed by analysis of variance (ANOVA) (P < or =.05). RESULTS: Fetal cortisol infusion in the presence or absence of a rise in placental estrogen synthesis increased placental expression of GR alpha; both PGHS-II and GR alpha localized to the uninucleate trophoblast cells of the placentome and were excluded from the maternal stroma and binucleate cells. Both forms of ER were excluded from the trophoblast tissue of the placentome. ER alpha, ER beta, and PGHS-II showed a similar pattern of distribution within the luminal epithelium of the endometrium; there were no alterations in the level of the ER in the presence of cortisol +/- 4-OHA. Placental P450(C17) protein expression was increased in the presence of a rise in fetal cortisol independent of changes in placental estrogen synthesis. CONCLUSIONS: We concluded that the differential effects of cortisol and estradiol on intrauterine PGHS-II expression and PG production may be due to the tissue-specific expression of the GR and ER within the intrauterine tissues. Glucocorticoid effects on trophoblast PG production may be mediated in a positive feed-forward manner. We further suggest that either cortisol or a cortisol-stimulated intermediate, like PGE2, increased P450(C17) expression, leading to a rise in placental estradiol synthesis and triggering maternal intrauterine tissue PG production.

Animals↗

PubMed2005

Expression of the multidrug resistance P-glycoprotein, (ABCB1 glycoprotein) in the human placenta decreases with advancing gestation.

The multidrug resistance p-glycoprotein (P-gp), encoded by the ABCB1 gene, is a plasma membrane protein that actively extrudes a wide variety of substances from cells. Preliminary studies in mice have shown that the ABCB1/P-gp can protect the fetus from a number of toxic substances. ABCB1/P-gp is expressed in the human placenta and is potentially capable of protecting the fetus from a large number of drugs and toxins, including herbicides and pesticides. The protein can also extrude various steroids including certain glucocorticoids and may therefore play an important role in regulating fetal access of glucocorticoids. The aim of the present study was to examine the expression profile and cellular localization of ABCB1/P-gp in human placenta throughout gestation. We hypothesized that there would be gestational age-related changes in the expression of the protein. ABCB1/P-gp mRNA was measured by Real-Time PCR using specific probes in tissues obtained from 6 weeks gestation to term. ABCB1/P-gp mRNA levels in placental tissue obtained at 6-10 weeks (n=5) and 24-35 weeks (n=5) were significantly higher than in tissues obtained at term (38-41 weeks gestation) by elective C-section (n=6) or following labor (n=6). The profile of ABCB1/P-gp protein levels, quantified using Western analysis, demonstrated a similar decrease with advancing gestation. At all gestational ages ABCB1/P-gp was localized by immunohistochemistry to the syncytiotrophoblast. In term tissues, it appeared to be localized to some areas of the villi and not others. Together, these data indicate that with advancing gestation there is a decrease in the level of ABCB1/P-gp in the human placenta indicating that the fetus may be more susceptible to toxic insults in the latter part of gestation. Further, the reduction in ABCB1/P-gp expression may contribute to the increased transfer of maternal cortisol to the fetus that is known to occur in late gestation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2003

Effects of cortisol and oestradiol on hepatic 11beta-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor proteins in late-gestation sheep fetus.

In the late-gestation sheep, increased fetal plasma cortisol concentration and placental oestradiol (E(2)) output contribute to fetal organ maturation, in addition to the onset of parturition. Both cortisol and E(2) are believed to regulate the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which interconverts bioactive 11-hydroxy glucocorticoids and their inactive 11-keto metabolites. 11beta-HSD1, abundantly expressed in fetal liver, operates primarily as a reductase enzyme to produce bioactive cortisol and thus regulates local hepatic glucocorticoid concentrations. Cortisol acts through the glucocorticoid receptor (GR) present in the liver. In this study, we examined the effects of cortisol and E(2) on hepatic 11beta-HSD1 and GR in the liver of chronically catheterized sheep fetuses treated with saline (n=5), cortisol (1.35 mg/h; n=5), saline+4-hydroxyandrostendione, a P450 aromatase inhibitor (4-OHA; 1.44 mg/h; n=5), or cortisol+4-OHA (n=5). Cortisol infusion resulted in increased plasma concentrations of fetal cortisol and E(2); concurrent administration of 4-OHA attenuated the increase in plasma E(2) concentrations. Using immunohistochemistry, we showed that fetal hepatocytes expressed both 11beta-HSD1 and GR proteins. Cortisol treatment increased GR in both cytosol and nuclei of hepatocytes; concurrent administration of 4-OHA was associated with distinct nuclear GR staining. Western blot revealed that cortisol, in the absence of increased E(2) concentrations, significantly increased concentrations of 11beta-HSD1 (34 kDa) and GR (95 kDa) proteins. 11beta-HSD1 enzyme activity was measured in the liver microsomal fraction in the presence of [(3)H]cortisone (10(-)(6) M) or [(3)H]cortisol (10(-)(6) M) and NADPH (reductase activity) or NADP(+) (dehydrogenase activity) respectively. 11beta-HSD1 reductase activity was significantly greater in the presence of cortisol. In summary, we found that, in sheep during late gestation, cortisol increased both 11beta-HSD1 and GR in the fetal liver, and these effects were accentuated in the absence of increased E(2).

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed2002

Mechanisms of term and preterm birth.

Labour at term and preterm results from activation and then stimulation of the myometrium. Activation can occur through mechanical stretch of the uterus, and by endocrine pathways resulting from increased activity of the fetal hypothalamic-pituitary-adrenal axis. In women and in experimental animals, cortisol likely contributes to increased prostaglandin production in fetal tissues through up-regulation of the type 2 prostaglandin H2, synthase-2 (PGHS-2) and down-regulation of 15-OH prostaglandin dehydrogenase. Cortisol increases expression of prostaglandin dehydrogenase in the chorion by reversing the stimulatory effect of progesterone, and may represent "progesterone withdrawal" in the primate. By competing with progesterone inhibition, cortisol also increases expression of placental corticotropin-releasing hormone. Other agents, such as pro-inflammatory cytokines, similarly up-regulate PGHS-2 and decrease expression of prostaglandin dehydrogenase. Oxytocin, produced locally within the intrauterine tissues, is also thought to be involved in parturition, and there is a marked increase in oxytocin receptor expression at term. There are thus several mechanisms by which labour at term or preterm may be initiated. These different mechanisms need to be considered in the development of strategies for the detection and management of women in preterm labour. Ongoing studies are investigating the use of oxytocin receptor antagonists, PGHS-2 inhibitors, and nitric oxide to prevent or regulate preterm labour. The presence of fibronectin in vaginal secretions, and elevated maternal serum levels of corticotropin-releasing hormone, estrogens, and cytokines have been examined as possible markers of preterm labour. However, at the present time, we do not have the ability to accurately predict or diagnose preterm labour, nor do we have specific or efficient methods to inhibit labour once it has started.

Evidence-Based Medicine↗

PubMed2002

Localization of nuclear factor-kappa B (NF kappa B) and inhibitory factor-kappa B (I kappa B) in human fetal membranes and decidua at term and preterm delivery.

The human fetal membranes and decidua are thought to be involved in the onset of human parturition. These tissues produce and respond to various cytokines, which may be involved in preterm labour and possibly term labour. They also show increasing production of prostaglandins (PGs) with advancing gestation and labour. The expression of PGHS-2, a rate limiting enzyme in PG synthesis, is increased in the fetal membranes at labour. The gene for PGHS-2 and many of the cytokine genes (e.g. TNFalpha, IL-1, IL-6) are stimulated by the transcription factor NF kappa B. This factor is composed of two subunits, p50 and p65, which are localized in the cytoplasm bound to I kappa B. When activated I kappa B is metabolized, and p50, p65 translocate to the nucleus to activate various genes. The purpose of the present study was to examine the tissue and cellular distribution of p65 and I kappa B in the human fetal membranes and decidua throughout gestation. Term tissues were obtained prior to labour by elective caesarean section (n=10) or following vaginal delivery (n=10) and 10 preterm tissues were obtained following labour prior to 37 weeks gestation. None of the tissues had any evidence of infection. The immunoreactive NF kappa B and I kappa B were localized in the tissues. p65 protein was found in the nucleus and cytoplasm of cells in the amnion, chorion laeve and decidua. In the amnion and chorion laeve, no changes occurred in subcellular localization with advancing gestation or term labour. However, in the decidua, there was a marked increase in the nuclear localization of i.r. p 65 in tissues obtained at term when compared with tissues delivered preterm. In the case of I kappa B, it was localized to the cytoplasm of cells in all tissues and there was an increase i.r. I kappa B in decidua at term compared to preterm but no change occurred in the amnion or chorion. The increase in nuclear localization of p65 in the decidua that occurs with advancing gestation, highlights the potential importance of this factor in the regulation of parturition related genes in this tissue.

Cell Nucleus↗

PubMed2002

Ontogeny and regulation of ovine placental prostaglandin E2 synthase.

Recent evidence suggests that ovine placental output of prostaglandin (PG) E2 rises through late gestation partly because of a direct effect of cortisol on PGH2 synthase 2 (PGHS-2) expression and activity within trophoblast tissue. Synthesis of PGE2 is also dependent, however, on PGE2 synthase (PGES), which converts PGH2 to PGE2. We hypothesized that PGES is expressed in the ovine placenta, and that, similar to PGHS-2, expression increases through gestation and is regulated positively by cortisol. Placental tissues from pregnant ewes in mid and late gestation, at term, and during early and active labor were analyzed to determine the gestational profile of PGES. The regulation of PGES expression was assessed in placental tissues from pregnant ewes in which intrafetal cortisol infusion was administered in late gestation, in the presence or absence of an aromatase inhibitor, to block the cortisol-stimulated rise in estradiol. Expression of PGES was analyzed by in situ hybridization, Western blot analysis, and immunohistochemistry. In the placentome, PGES localized to fetal trophoblast cells and endothelial cells in maternal blood vessels, consistent with its contribution to the rise in placental PGE2 output toward the onset of labor and with a role of PGE2 in the local regulation of uteroplacental blood flow, respectively. Expression of PGES mRNA and protein increased with gestation. However, there was no significant further change with labor or during cortisol infusion in the presence or absence of a rise in fetal plasma estradiol, in contrast to reported changes in PGHS-2. These results suggest that PGES is not coregulated with PGHS-2 in the sheep placenta at term. The progressive increase in PGES, however, likely contributes to the rise in circulating PGE2 in the fetus in late pregnancy.

Animals↗

PubMed2002

Expression of prostaglandin I(2) synthase, but not prostaglandin E synthase, changes in myometrium of women at term pregnancy.

Prostaglandins (PGs) act as potent uterotonins at the time of labor. Prostaglandin E synthase (PGES) is responsible for the formation of PGE(2), a uterotonin. PGI(2) is synthesized by the prostaglandin I synthase enzyme (PGIS) and contributes to relaxation in the lower uterine segment. We examined the expression of membrane-bound PGES and PGIS in myometrium from pregnant women during preterm and term labor. Tissues were collected from the lower uterine segment from preterm no labor, preterm labor, term no labor, and term labor patients and used for immunohistochemistry and Western blot analysis using specific antibodies. Immunoreactive (ir-) PGES and PGIS proteins were localized to the cytoplasm of myocytes of the myometrium and vascular smooth muscle cells. Ir-PGES was also detected in vascular endothelial cells. Western blot analyses revealed a predominant protein band of 180 kDa, and a second 16-kDa band for ir-PGES and 56-kDa band for ir-PGIS. There was no significant change in ir-PGES protein (180 or 16 kDa) or mRNA levels with preterm or term labor or gestational age. There was a significant decrease in PGIS mRNA and protein with advancing gestational age. We conclude that the gestational age decrease in the inhibitory PGIS is consistent with lessening of its influence in myometrium at the time of labor. The lack of change in PGES indicates that alterations at other points along the pathway of arachidonic acid metabolism may be of greater importance in affecting local changes in PGE(2).

Actins↗

PubMed2001

Glucocorticoid regulation of human and ovine parturition: the relationship between fetal hypothalamic-pituitary-adrenal axis activation and intrauterine prostaglandin production.

Birth in many animal species and in humans is associated with activation of hypothalamic-pituitary-adrenal function in the fetus and the increased influence of glucocorticoids on trophoblast cells of the placenta and fetal membranes. We suggest that in ovine pregnancy glucocorticoids directly increase fetal placental prostaglandin production, and indirectly increase prostaglandin production by maternal uterine tissues through the stimulation of placental estradiol synthesis. The events of ovine parturition are compared with those of human parturition. In the latter, we suggest similar direct effects of glucocorticoids on prostaglandin synthesis and metabolism in fetal membranes and similar indirect effects mediated by glucocorticoid-stimulated increases in intrauterine corticotropin-releasing hormone expression.

Adrenal Glands↗

PubMed2001

Understanding preterm labor.

Increased uterine contractility at term and preterm results from activation and then stimulation of the myometrium. Activation can be provoked by mechanical stretch of the uterus and by an endocrine pathway resulting from increased activity of the fetal hypothalamic-pituitary-adrenal (HPA) axis. In fetal sheep, increased cortisol output during pregnancy regulates prostaglandin H synthase type 2 (PGHS2) expression in the placenta in an estrogen-independent manner, resulting in increased levels of PGE2 in the fetal circulation. Later increases in maternal uterine expresssion of PGHS2 require elevations of estrogen and lead to increased concentrations of PGF2alpha in the maternal circulation. Thus, regulation of PGHS2 at term is differentially controlled in fetal (trophoblast) and maternal (uterine epithelium) tissue. This difference may reflect expression of the glucocorticoid receptor (GR), but not estrogen receptor (ER), in placental trophoblast cells. In women, cortisol also contributes to increased PG production in fetal tissues through upregulation of PGHS2 (amnion and chorion) and downregulation of 15-OH PG dehydrogenase (chorion trophoblasts). The effect of cortisol on chorion expression of PGDH reverses a tonic stimulatory effect of progesterone, potentially through a paracrine or autocrine action. We have interpreted this interaction as a reflection of "progesterone withdrawal" in the primate, in relation to birth. Other agents, such as proinflammatory cytokines, similarly upregulate PGHS2 and decrease expression of PGDH, indicating the presence of several mechanisms by which labor at term or preterm may be initiated. These different mechanisms need to be considered in the development of strategies for the detection and management of the patient in preterm labor.

Corticotropin-Releasing Hormone↗

PubMed2000

The characterization of human amnion epithelial and mesenchymal cells: the cellular expression, activity and glucocorticoid regulation of prostaglandin output.

The amnion, a single layer of epithelial cells (EC) overlying layers of mesenchymal cells (MC) has been identified as a source of intrauterine prostaglandins (PG). The objectives of the present study were: (1) to establish a technique for the isolation and culture of pure amnion EC and MC preparations, (2) to characterize the cellular expression of PGHS-II and PGHS activity within these separated amnion cells and (3) to characterize the pattern of glucocorticoid stimulation of these separated amnion cells. Term gestation human amnion was collected after elective caesarean section or vaginal delivery. A trypsin digestion was used to isolate EC and a mechanical digestion and collagenase dispersion was used to isolate MC. Following 48 or 96 h in culture, cells were incubated for 24 h in the presence or absence of 1 microm arachidonic acid and treated with cortisol (F: 10-1000 nm) or 1 microm dexamethasone (DEX). Cell types were identified by immunohistochemistry (IHC). Immunoreactive PGHS-II (ir-PGHS-II) and glucocorticoid receptor (ir-GR) were localized by IHC. PGHS activity was measured as PGE(2)output determined by radioimmunoassay. Mean PGE(2)production by MC at 72 h was 22-fold greater (P<0.05) and at 120 h was 32-fold greater (P<0.03) than PGE(2)output by EC. Administration of arachidonic acid stimulated a 5.0-fold increase in PGE(2)output (P<0.0002) by EC after 72 h and a 3.6-fold increase (P<0.05) after 120 h but did not alter MC PGE(2)output. Despite exogenous substrate, EC PGE(2)output remained significantly less than PGE(2)output by MC. There was no difference in PG production by EC and MC with the onset of labour. Ir-GR expression was found in both EC and MC. F and/or DEX with and without arachidonic acid (AA) stimulated PGE(2)output by EC. Only DEX and not F increased PGE(2)output by MC. These data suggest that relatively pure EC and MC preparations can be established from amnion. PG output and its regulation appears to differ within these two amnion cell types, dependent upon (1) substrate availability and (2) the regulation of PGHS activity.

Adult↗

PubMed2000

Fetal-to-maternal progression of prostaglandin H(2) synthase-2 expression in ovine intrauterine tissues during the course of labor.

We examined whether spontaneous parturition in sheep was associated with tissue-specific changes in prostaglandin H(2) synthase-2 (PGHS-2) expression and/or with altered expression of myometrial EP and FP receptors. Placental and uterine tissues were collected from three groups of chronically catheterized sheep in relation to term spontaneous labor: late pregnancy, not in labor; early labor; and active labor. Expression of PGHS-2 mRNA and protein was determined by in situ hybridization, Western blotting, and immunohistochemistry. Semiquantitative reverse transcription-polymerase chain reaction was used to assess the presence of and changes in prostaglandin (PG) receptor subtypes. In placenta, PGHS-2 mRNA and protein localized to trophoblast uninucleate cells and tended to increase with early labor. PGHS-2 mRNA and protein localized to endometrial epithelium and to myometrium, where PGHS-2 protein levels rose in active labor tissues. Concentrations of PGE(2) in fetal plasma rose progressively with labor, whereas 13,14-dihydro-15-keto-PGF(2alpha) in maternal plasma increased significantly only in active labor. Messenger RNA encoding four EP receptor subtypes and FP receptor were present in myometrium, but levels did not change with labor. We suggest that spontaneous labor in sheep is associated with a progressive increase in PGHS-2 expression in a temporal and tissue-specific manner from trophoblast to maternal tissues, rather than alteration in PG receptor gene expression.

Animals↗

PubMed2000

Endocrine and paracrine regulation of birth at term and preterm.

We have examined factors concerned with the maintenance of uterine quiescence during pregnancy and the onset of uterine activity at term in an animal model, the sheep, and in primate species. We suggest that in both species the fetus exerts a critical role in the processes leading to birth, and that activation of the fetal hypothalamic-pituitary-adrenal axis is a central mechanism by which the fetal influence on gestation length is exerted. Increased cortisol output from the fetal adrenal gland is a common characteristic across animal species. In primates, there is, in addition, increased output of estrogen precursor from the adrenal in late gestation. The end result, however, in primates and in sheep is similar: an increase in estrogen production from the placenta and intrauterine tissues. We have revised the pathway by which endocrine events associated with parturition in the sheep come about and suggest that fetal cortisol directly affects placental PGHS expression. In human pregnancy we suggest that cortisol increases PGHS expression, activity, and PG output in human fetal membranes in a similar manner. Simultaneously, cortisol contributes to decreases in PG metabolism and to a feed-forward loop involving elevation of CRH production from intrauterine tissues. In human pregnancy, there is no systemic withdrawal of progesterone in late gestation. We have argued that high circulating progesterone concentrations are required to effect regionalization of uterine activity, with predominantly relaxation in the lower uterine segment, allowing contractions in the fundal region to precipitate delivery. This new information, arising from basic and clinical studies, should further the development of new methods of diagnosing the patient at risk of preterm labor, and the use of scientifically based strategies specifically for the management of this condition, which will improve the health of the newborn.

Adrenal Glands↗

PubMed2000

Prostaglandin production at the onset of ovine parturition is regulated by both estrogen-independent and estrogen-dependent pathways.

A current hypothesis of ovine parturition proposes that fetal adrenal cortisol induces placental E2 production, which, in turn, triggers intrauterine PG production. However, recent evidence suggests that cortisol may directly increase PG production in trophoblast-derived tissues. To separate cortisol-dependent and estrogen-dependent PG production in sheep intrauterine tissues, we infused singleton, chronically catheterized fetuses beginning on day 125 of gestation (term, 147-150 days) with 1) cortisol (1.35 mg/h; n = 5); 2) cortisol and 4-hydroxyandrostendione, a P450aromatase inhibitor (4-OHA: 1.44 mg/h; n = 5); 3) saline (n = 5); or 4) saline and 4-OHA (n = 5). Fetal and maternal arterial blood samples were collected at 12-h intervals starting 24 h before infusion and continuing during treatment for 80 h or until active labor. Uterine contractility was measured by electromyogram recording of myometrial activity. Plasma E2, progesterone (P4), PGE2, and 13,14-dihydro- 15-keto-PGF2alpha were quantified by RIA. PGHS-II messenger RNA (mRNA) and protein expression were determined by in situ hybridization and Western blot analysis, respectively. Data were analyzed by ANOVA (P < or = 0.05). Labor-type uterine contractions were present after 68 h of cortisol infusion and had increased significantly by 80 h. Labor-type uterine contractions were induced after 68 h of cortisol plus 4-OHA infusion, but the contraction frequency remained less than that in the cortisol-treated animals. Fetal cortisol infusion increased fetal and maternal plasma E2 concentrations and decreased the maternal plasma P4 concentration significantly; concurrent 4-OHA infusion attenuated the increase in fetal and maternal plasma E2, but not the decrease in maternal plasma P4. The fetal plasma PGE2 concentration increased after both cortisol and cortisol plus 4-OHA infusion. The maternal plasma 13,14-dihydro-15-keto-PGF2alpha concentration rose after fetal cortisol infusion, but not after cortisol plus 4-OHA infusion. Placental trophoblast PGHS-II mRNA and protein expression were increased significantly after both cortisol and cortisol plus 4-OHA infusion. Endometrial PGHS-II mRNA and protein expression increased after cortisol infusion, but not after cortisol plus 4-OHA infusion. Plasma steroid and PG concentrations, uterine activity pattern, and intrauterine PGHS-II expression were not altered in either control group. We conclude that these data suggest distinct pathways of intrauterine PG synthesis: a cortisol-dependent/E2-independent mechanism within trophoblast tissue leading to elevations in fetal plasma PGE2, and an E2-dependent mechanism within maternal endometrium that leads to increased maternal plasma PGF2alpha and appears necessary for uterine activity and parturition.

Animals↗

PubMed2000

Localization of prostaglandin synthase type-1 (PGHS-1) mRNA and prostaglandin synthase type-2 (PGHS-2) mRNA in ovine myometrium and endometrium throughout gestation.

Increased prostaglandin production by tissues in the sheep uterus and placenta are thought to be important for the onset of parturition. In the sheep placenta, this is most likely due to increased expression of prostaglandin synthase type-2 (PGHS-2) rather than prostaglandin synthase type-1 (PGHS-1). However, there is no information concerning expression of PGHS isoenzymes in maternal uterine tissues during pregnancy. Therefore, the purpose of the present study was to examine the expression of PGHS-1 and PGHS-2 in the sheep myometrium and endometrium during late gestation using in situ hybridization and immunohistochemistry. Using (35)S-labelled oligonucleotide probes, which give specific hybridization signals in other tissues, we localized PGHS-2 mRNA to endometrial epithelium, and apparently to other cells in both endometrium and myometrium. This artefactual signal was still present with 100-fold excess unlabelled oligonucleotide probe and with sense probes, but was resolved with the use of (33)P-oligonucleotides. Using (33)P-labelled oligonucleotide probes we could not detect either PGHS-1 or PGHS-2 mRNA in myometrium, and found expression only of PGHS-2 mRNA in endometrium. PGHS-2 mRNA localized to the endometrial epithelium and was undetectable in glandular epithelium. The level of PGHS-2 expression rose significantly between days 80 and 85 of pregnancy and term, and this corresponded to the appearance of immunoreactive PGHS-2 protein, measured by immunohistochemistry, in the endometrial epithelium. Therefore we conclude that (33)P-labelled probes are preferred for detection of mRNAs encoding PGHS-2 in ovine uterine tissues. Expression of PGHS-2 mRNA is greater than that of PGHS-1, increases during gestation, and predominates in the endometrial epithelium, consistent with the site of PGHS-2 protein localization.

Animals↗

PubMed1999

Distribution of interleukin-1 receptors in term human fetal membranes and decidua.

Interleukin-1 (IL-1) is a dimorphic cytokine that acts on target cells through high-affinity receptors, type I and type II. It has been implicated in the onset of term and preterm labour with associated intrauterine infection. To define better the potential action of this cytokine in the human fetal membranes and decidua, the objective of this study was to define the type(s) of IL-1 receptors present in the tissues at term, examine the tissue and cellular distribution of the receptor(s) and determine if there were any changes in their expression or distribution with the onset of labour. Tissues were obtained following elective caesarean section (n=12) or normal labour delivery (n=11). Paraffin embedded and frozen sections were examined by immunohistochemistry and in situ hybridization for evidence of the type I and type II receptors and their corresponding mRNAs. In all tissues studied the type I receptor was localized mainly to the decidua and the type II receptor was localized to the decidua and scattered cells in the amnion-chorion mesenchymal layer. In situ hybridization localized type I receptor mRNAs and type II receptor mRNAs to the decidua. The type I and type II receptor protein in the decidua showed a similar pattern of staining as that found for CD-68, a macrophage marker. The pattern of receptor expression and distribution was unrelated to the mode of delivery. No evidence for the presence of the type I or type II receptor or their mRNAs in the amnion epithelial cells or chorion laeve trophoblast was found.

Cesarean Section↗

PubMed1998

Cellular specificity of interleukin-1beta-stimulated expression of type-2 prostaglandin H synthase in human amnion cell cultures.

Interleukin-1beta (IL-1beta) has been shown in numerous studies to increase prostaglandin output by cultures of human amnion cells. This is due to an increase in the expression of type-2 prostaglandin H synthase (PGHS-2), the inducible form of the enzyme, in these cultures. Amnion consists of an epithelial layer of cells and a subepithelial mesenchymal layer of cells. The purpose of the present study was to determine the cell-type(s) responsible for the IL-1beta-induced PGHS-2 expression in amnion cultures. Amnion was obtained at term after elective Cesarean section or vaginal delivery. Tissues were dispersed with collagenase, and cells were plated in multichamber culture slides and cultured for 7 days in media supplemented with 10% fetal bovine serum. Cell types were characterized with antisera to keratin (epithelial cells) and vimentin (mesenchymal cells). Cultures contained both cell types, and the proportion of these varied considerably from one culture to another. Cells were treated with various concentrations of IL-1beta for 6 or 24 h and were then fixed in 4% paraformaldehyde. The fixed cells were permeabilized with Triton and examined by immunohistochemistry for PGHS-2 protein using specific antisera, and PGHS-2 mRNA was localized by in situ hybridization using a specific oligonucleotide probe. The cell type(s) expressing PGHS-2 was characterized using double labeling with antisera to keratin (epithelial cell marker) and vimentin (mesenchymal cell marker). IL-1beta was found to increase expression of immunoreactive PGHS-2 and PGHS-2 mRNA. This increased expression was found to occur only in the vimentin-positive cells and not the epithelial cells. These results highlight the potential importance of the subepithelial cells in the mesenchymal layer of amnion in the formation of prostaglandins during pregnancy and possibly in preterm labor with infection.

Amnion↗

PubMed1998

The role of prostaglandins in human parturition.

Parturition is the process of giving birth, and the molecular mechanisms involved are still to be elucidated. Among the various factors involved prostaglandins appear to have an important role. They are synthesized within the human fetal membranes (amnion and chorion) and decidua and act to ripen the cervix, change membrane structure and contract the myometrium. Prostaglandin concentrations increase in amniotic fluid prior to myometrial contractions, and the activity of prostaglandin H synthase (PGHS) increases in the chorion laeve and amnion at labour. This increase is due to increased expression of the PGHS-2 isoenzyme rather than the PGHS-1 isoenzyme. In animal pregnancy, there is also an increase in the expression of the PGHS-2 isoenzyme, and in both human and animal pregnancies this increase appears to occur in the fetal tissues rather than in the maternal tissues. Prostaglandin metabolism also plays an important role in altering prostaglandin output by the human fetal membranes. Prostaglandin dehydrogenase (PGDH) activity decreases in certain cases of preterm labour, and at term it decreases in the area of the chorion laeve covering the cervix. This may allow active prostaglandins produced by the amnion and chorion to access the cervix and myometrium. Recent studies have indicated that glucocorticoids may be important in regulating prostaglandin formation within the human fetal membranes by increasing expression of PGHS-2 in the amnion and decreasing PGDH activity in the chorion. Prostaglandin formation is also important in infection-induced preterm labour and both phospholipase and PGHS-2 activities can be increased by various cytokines. Prostaglandins are important for the onset of both term and preterm parturition and their effects may result from changes in prostaglandin synthesis, prostaglandin metabolism and expression of various prostaglandin receptors.

Animals↗