Comparative regulation of inhibin, activin and human chorionic gonadotropin production by placental trophoblast cells in culture

Redox regulation of cardiovascular inflammation - Immunomodulatory function of mitochondrial and Nox-derived reactive oxygen and nitrogen species

Oxidative stress is a major hallmark of cardiovascular diseases although a causal link was so far not proven by large clinical trials. However, there is a close association between oxidative stress and inflammation and increasing evidence for a causal role of (low-grade) inflammation for the onset and progression of cardiovascular diseases, which may serve as the missing link between oxidative stress and cardiovascular morbidity and mortality. With the present review we would like to highlight the multiple redox regulated pathways in inflammation, discuss the sources of reactive oxygen and nitrogen species that are of interest for these processes and finally discuss the importance of angiotensin II (AT-II) as a trigger of cardiovascular inflammation and the initiation and progression of cardiovascular diseases.

The endocrine function of human placenta: an overview

During pregnancy, several tightly coordinated and regulated processes take place to enable proper fetal development and gestational success. The formation and development of the placenta is one of these critical pregnancy events. This organ plays essential roles during gestation, including fetal nourishment, support and protection, gas exchange and production of several hormones and other mediators. Placental hormones are mainly secreted by the syncytiotrophoblast, in a highly and tightly regulated way. These hormones are important for pregnancy establishment and maintenance, exerting autocrine and paracrine effects that regulate decidualization, placental development, angiogenesis, endometrial receptivity, embryo implantation, immunotolerance and fetal development. In addition, because they are released into maternal circulation, the profile of their blood levels throughout pregnancy has been the target of intense research towards finding potential robust and reliable biomarkers to predict and diagnose pregnancy-associated complications. In fact, altered levels of these hormones have been associated with some pathologies, such as chromosomal anomalies or pre-eclampsia. This review proposes to revise and update the main pregnancy-related hormones, addressing their major characteristics, molecular targets, function throughout pregnancy, regulators of their expression and their potential clinical interest.

Polymorphisms in inhibin α gene promoter associated with male infertility

Inhibins play important roles in normal gonadal function, including regulation of proliferation, differentiation, and steroidogenesis of Leydig and Sertoli cells via paracrine and autocrine processes. In adult males, circulating inhibin levels are correlated with fertility by regulating the number of Sertoli cells, total sperm count, and testicular volume. Given this important role, inhibin-α subunit (INHA) is a strong candidate gene in male fertility. However, limited data regarding the association of polymorphisms of INHA with male fertility are available. This study was based on the hypothesis that polymorphisms in the promoter of INHA are associated with male fertility. Han Chinese patients with non-normozoospermia (n=153) and normozoospermia (n=72) from Northern China were screened, and genotypes were analyzed by polymerase chain reaction-restriction fragment length polymorphism after INHA promoter was amplified. Statistical analysis results revealed a significant difference in the allele frequency of INHA promoter between males with non-normozoospermia and normozoospermia. For c.-124G>A, males carrying c.-124GG genotype and c.-124GA genotype showed an increased risk of non-normozoospermic syndrome. For c.-16C>T polymorphism, no significant difference in allele frequency was observed between the two groups. Therefore, the haplotype AC possibly displayed a considerable reduced risk of non-normozoospermic syndrome.

INHA promoter polymorphisms are associated with premature ovarian failure

Inhibin is an important glycoprotein that is involved in folliculogenesis. INHA, the gene encoding the inhibin alpha subunit, was recently proposed as a candidate for premature ovarian failure (POF), a syndrome that leads to the cessation of ovarian function under the age of 40 years. 70 POF patients and 70 controls were screened for the previously identified INHA -16C>T transition mutation. The T allele was found in 31/70 (44.3%) of controls, but only 18/70 (25.7%) of POF patients. This result indicates that the T allele is significantly underrepresented in the POF patient population (Fisher's exact test, two-tail: P = 0.033). Sequence analysis of the INHA promoter in 50 POF patients and 50 controls identified a highly polymorphic imperfect TG repeat at approximately -300 bp, that consisted of four common haplotypes (A, B, C and D). The -16T allele is linked to the shortest repeat haplotype (haplotype C). Despite the association between haplotype C and POF, no significant difference was found between the promoter activity of a luciferase reporter construct containing haplotype C, and most of the other haplotypes tested. Interestingly, haplotype B failed to show any promoter activity. We conclude that the inheritance of specific INHA promoter haplotypes predispose to the development of premature ovarian failure.

The secretion and effect of inhibin A, activin A and follistatin on first-trimester trophoblasts in vitro

OBJECTIVE

The objectives of this study were to investigate the effect of activin A and follistatin on first-trimester cytotrophoblast invasion in culture and to study the secretion of inhibin A, activin A and follistatin by these cells in vitro.

DESIGN AND METHODS

Cytotrophoblasts were isolated from human placental chorionic villous tissue obtained from 6-8, 8-10 and 10-12 weeks gestation. Cells were cultured for 3 days on cell-culture inserts coated with gelatine for invasion studies and in 24-well culture plates for secretion studies. The effects of activin A (10 ng/ml), follistatin (100 ng/ml), interleukin 1beta (IL-1beta; 10 ng/ml) and epidermal growth factor (EGF; 10 ng/ml) on cytotrophoblast invasion were investigated using a non-radioactive invasion assay. Secretion of inhibin A, activin A and follistatin in the presence of EGF, IL-1beta, activin A and follistatin were measured using in-house ELISAs.

RESULTS AND CONCLUSION

Activin A, follistatin and EGF had a significant stimulatory effect on cytotrophoblast invasion from 6-10 weeks gestation. IL-1beta had a significant stimulatory effect at 8-10 weeks and a significant inhibitory effect on invasion at 10-12 weeks gestation. Follistatin also had a significant inhibitory effect on invasion at 10-12 weeks gestation. In the secretion study, activin A secretion at 8-10 weeks was significantly stimulated by IL-1beta and EGF. At 10-12 weeks, follistatin and EGF had a significant inhibitory effect on activin A secretion. Follistatin secretion was significantly increased in the presence of IL-1beta at 6-8 weeks gestation. Inhibin A secretion was not significantly altered by EGF, IL-1beta, activin A and follistatin. These results show that activin A promotes invasion of first-trimester cytotrophoblasts until 10 weeks gestation. There is a difference in the control of secretion of these proteins dependent on the gestation, suggesting that there is a tight regulation in the function of first-trimester trophoblasts depending on the gestational age.

Endocrine cell lines from the placenta

Cell-lines derived from human placenta and chorion have been used extensively to model the endocrine functions of human trophoblast. In general terms, the endocrine functions of the primary cells and tissues are at least partially replicated within the cell-lines, suggesting that they may be used as appropriate models. There are, however, two major provisos that compromise this generalisation. Firstly, the endocrine function of placenta represents a complex interaction between cytotrophoblast, syncytiotrophoblast and multiple regulators, so a single cell population digested from the normal environment is unlikely to represent this. Secondly, the characterisation of primary trophoblast populations and of cell-lines is incomplete, complicating the assignment of functions to trophoblast populations. Despite these difficulties, useful information has been obtained from the available cell-lines, regardless of whether they have arisen spontaneously, been transformed in vitro, or derived from cancers in vivo.

11β-Hydroxysteroid Dehydrogenase Inhibitor Carbenoxolone Stimulates Chorionic Gonadotropin Secretion from Human Term Cytotrophoblast Cells Differentiated In Vitro *

PROBLEM

To investigate the effect of altering local glucocorticoid concentration on human chorionic gonadotropin (hCG) production by cultured placental trophoblast cells.

METHOD OF STUDY

Human placental trophoblasts were isolated from fresh placentas. Cytotrophoblasts were purified and placed into 24-well multiplates. For cultivation Dulbecco's modified Eagle's medium (DMEM) with 15 mm HEPES and 15% FBS was used. 11beta-Hydroxysteroid dehydrogenase (11beta-HSD) activity and its inhibition by carbenoxolone (CE) were measured in cultured cells. Cultures were exposed to CE for 16-20 hr. Overnight production of hCG was measured by radioimmunoassay in control and treated cells.

RESULTS

The 11beta-HSD activity in these cultures was inhibited by nm concentrations of CE, the apparent Ki being 2.5 nm. Inhibition of 11beta-HSD activity with 0.1 nm CE resulted in 1.5-fold increase in the production of hCG.

CONCLUSIONS

Increasing local glucocorticoid concentration by the inhibition of 11beta-HSD results in higher hCG secretion, which in turn enhance cell differentiation.

Placental, maternal serum and amniotic fluid molecular weight forms of inhibin A and pro-alphaC

Previous studies have identified the presence of unidentified small molecular weight (mol wt) forms of inhibin and the pro-alphaC region of the inhibin alpha subunit in serum from women during late pregnancy. The aim of this study was to investigate if these gestational-related changes in mol wt forms arose from changing placental production. Pooled placental extracts, derived from normal healthy singleton pregnancies in the 1st, 2nd and 3rd trimesters of pregnancy, were fractionated by a combined immunoaffinity chromatography, preparative PAGE and electroelution procedure. Inhibin A, inhibin B and the pro-alphaC region of the inhibin alpha subunit were determined in the eluted fractions by specific ELISAs, with the profiles of immunoactivity characterized in terms of molecular size and percentage recovery. Inhibin B was undetectable in all samples. Mol wt peaks of 36k, 75K and 97K for inhibin A and 29k, 55K and 97K for pro-alphaC were detected in placental extracts across all three trimesters. The relative abundancy of small mol wt inhibin A forms (<30K) present in the placenta increased significantly in the third trimester placenta, increasing from 0.3 per cent in the first trimesters to 6 per cent in the third trimester (P=0.01, chi-squared test). The relative abundances of various mol wt forms of pro-alphaC was similar at all three gestations (P=0.67). In serum, small mol wt inhibin A and pro-alphaC forms accounted for 23.4 per cent and 37.4 per cent of inhibins, respectively, in the third trimester. These data suggest that the presence of small mol wt forms of both inhibin A and pro-alphaC in maternal serum is only partially attributed to placental production and/or secretion. We conclude that inhibin A and pro-alphaC inhibins in maternal serum are processed in late pregnancy by more than one mechanism to form low mol wt circulating forms of, as yet, undetermined structure.

Inhibin and activin production and subunit expression in human placental cells cultured in vitro

Inhibins and activins are dimeric proteins, with each subunit being one of three related protein subunits (alpha, betaA or betaB). The mRNA levels of these subunits were studied quantitatively during in-vitro differentiation of human cytotrophoblast cells into syncytium, using Northern blot analysis and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. The corresponding protein concentrations were determined by specific enzyme-linked immunosorbent assays for inhibin A, B, pro alphaC and activin A in cellular protein extracts and culture medium (n = 5). Immunofluorescence studies showed syncytium formation after 48 h. The alpha subunit was present before plating and increased at 48 h (P<0.001) while the betaA subunit was weak before plating and increased at 24 h. The betaB subunit was not detected. With respect to corresponding protein synthesis, inhibin A (alpha + betaA) had risen after 48 h in cellular protein extract and after 72 h in culture medium, while activin A (betaA + betaB) was detected after 24 h, with no significant variations in culture medium. There was a good correlation between inhibin A and alpha subunit expression (r = 0.736, P<0.001), as well as between activin A and betaA subunit expression (r = 0.755, P<0.001). This study showed that mRNA expression parallels protein synthesis of inhibin and activin in trophoblast cells. Inhibin A synthesis appears to be dependent on alpha subunit mRNA expression, rather than on the betaA subunit which controls activin A synthesis. This study has also shown that isolated cytotrophoblast cells do not produce dimeric inhibin. However, during the transformation of cytotrophoblast cells into syncytium, betaA subunit mRNA expression may be an indicator of cell aggregation, while alpha subunit mRNA expression may be an indicator of cell fusion.

Raised maternal serum inhibin A concentration at 10 to 14 weeks of gestation is associated with pre-eclampsia

Maternal serum inhibin A and free beta human chorionic gonadotrophin (beta-hCG) were measured in 759 chromosomally normal, pregnant women at 10-14 weeks of gestation. There were nine who subsequently developed pre-eclampsia and in these women the maternal serum inhibin A concentration was significantly higher than in the normotensive controls.

Production of inhibin forms by the fetal membranes, decidua, placenta and fetus at parturition

Inhibins are regulators of paracrine and endocrine function during pregnancy, but their intrauterine sites of secretion are not well established. In amniotic fluid, inhibin A-, inhibin B- and inhibin pro-alphaC-containing isoforms were present in high concentrations, whereas in maternal serum, inhibin A and pro-alphaC forms were present in high amounts, with low concentrations of inhibin B. In fetal cord serum, inhibin pro-alphaC was present in all samples, inhibin B was detectable in male but not female fetuses, with no detectable inhibin A in either sex. From cultured explants, both inhibin A and B were secreted by chorion laeve, whereas only inhibin A was secreted by placenta, with both tissues secreting inhibin pro-alphaC. Only low concentrations of both dimeric inhibins and pro-alphaC forms were secreted by decidua parietalis and amnion. The dual perfused placental cotyledon secreted both inhibin A and pro-alphaC into maternal perfusate, but only inhibin pro-alphaC into the fetal circulation and less than to the maternal side. We conclude that trophoblast is the predominant source of dimeric inhibins, but with markedly different secretion depending on its intrauterine location. There was a significant decrease in inhibin A and pro-alphaC in amniotic fluid collected at term active labour compared to elective Caesarean section (P < 0.001). This may reflect a local change in inhibin/activin processing at labour, likely in chorion laeve trophoblast cells, which may be important in the paracrine control of the feto-maternal communication required to maintain pregnancy and initiate labour.

Advance in the study of inhibin, activin and follistatin production in pregnant women

This review summarizes the new information on the studies of inhibin, activin, and follistatin production in the placenta during human pregnancy. Inhibin and activin exert suppressive and stimulatory effects, respectively, on the release of FSH in the pituitary. Follistatin is bound to inhibin and activin and indirectly modulates the FSH release. The placenta produces these three proteins. The serum levels of inhibin, activin, and follistatin are elevated in pregnant women and decrease after delivery. The trophoblast cells from term placenta secrete inhibin and activin in the primary cultures. The production and mRNA expression of inhibin and activin are regulated by several stimulatory and suppressive hormones and growth factors in placental tissues. cAMP, Ca2+, and protein kinase-C may be involved in intracellular signal transduction in trophoblasts. Activin receptors are present on placental cells. Follistatin inhibits the binding of activin to ActRII receptor. Abnormal levels of inhibin and activin in maternal serum are observed in problem pregnancies and gestational diseases. Inhibin, activin, and follistatin may play roles in the regulation of reproductive endocrinology in pregnant women and the embryo/fetal development.

Anti-inflammatory effects of interleukin-4, interleukin-10, and transforming growth factor-beta on human placental cells in vitro

PROBLEM

To determine the effects of anti-inflammatory cytokines on the production of inflammatory mediators by placental cells.

METHOD OF STUDY

Cells from term human placentas were isolated and cultured in vitro in the presence of anti-inflammatory cytokines interleukin (IL)-4, IL-10, and transforming growth factor (TGF)-beta. Their effects on the production of IL-8 and prostaglandin E2 (PGE2) were investigated under basal conditions and after stimulation with IL-1 beta and tumor necrosis factor (TNF)-alpha.

RESULTS

Both IL-10 and IL-4 inhibited IL-1 beta- and TNF-alpha-induced PGE2 production but had no significant effects on the production of PGE2 under basal conditions. TGF-beta 1 was without effect in stimulated cells, whereas under basal conditions TGF-beta 1 stimulated PGE2 production. Similar trends were seen for IL-8 production, with the exceptions that TGF-beta 1 decreased the TNF-alpha-induced production and IL-4 decreased basal IL-8 production.

CONCLUSIONS

The anti-inflammatory effects shown by IL-4, IL-10, and (to lesser extent) TGF-beta may play a role in ameliorating the potentially harmful effects of pro-inflammatory mediators in the feto-placental unit.

Regulation of activin-A production by human amnion, decidua and placenta in vitro by pro-inflammatory cytokines

Activin-betaA subunits are expressed by the human placenta and extraplacental membranes at term and preterm. The regulation of activin-A production by these tissues has not been characterized to date, however. To determine the effects on activin-A production of pro-inflammatory cytokines, amnion, decidual and placental cells were isolated by enzyme dispersion and treated in primary culture with interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha). Activin-A production (determined by ELISA) by amnion, decidual and placental cultures was 1.2 +/-0.27, 31.1+/-9.9, and 50.7+/-28.5 pg/microg protein/16 h, respectively (mean+/-SEM; n=5-7 experiments). Both IL-1beta and TNF-alpha stimulated activin-A production in a concentration-dependent fashion in all cultures; maximal stimulation was achieved at 0.25-1.0 ng/ml IL-1beta and 25-50 ng/ml TNF-alpha, respectively. In amnion, decidual and placental cultures IL-1beta stimulated activin-A production to 747+/-274, 190+/-11, and 254+/-60.2 per cent of controls, while TNF-alpha stimulated production to 312+/-81.5, 194+/-22.5, and 193+/-12.5 per cent, respectively (mean+/-SEM; n=5; P<0.05 by ANOVA). These studies show for the first time that pro-inflammatory cytokines are potent stimulators of activin-A production by intrauterine tissues. This may provide an explanation for the elevated concentrations of activin-A measured in the sera of some women in preterm labour.

Culture of syncytiotrophoblast for the study of human placental transfer. Part II: Production, culture and use of syncytiotrophoblast

The conditions necessary for producing syncytical syncytiotrophoblast are examined. Tissue disaggregation conditions, culture media composition, different extracellular matrices and the influence of placental gestational age are all assessed. The importance of evaluating the biochemical and functional differentiational state of the cells is also stressed. Evidence is summarized that syncytiotrophoblast in culture is morphologically and ultrastructurally very similar to syncytiotrophoblast in vivo, and what is so far known biochemically is largely consistent with what is known in vivo. Studies published to date on microvillous membrane uptake and release and relationships with intracellular metabolism using syncytiotrophoblast in conventional culture are outlined from the point of view of the advantages and potential of this model. The present state of development of the two-sided model is assessed, mentioning factors to be considered such as the supporting membrane to be used, accounting for passive diffusion and paracellular leak components of transport and dealing with quantitative effects in kinetic studies of the presence of the supporting membrane. It is concluded that satisfactory methods are now in place for preparing pure villous syncytial syncytiotrophoblast in culture from cytotrophoblast derived from term (but not early) placentae, suitable for studying microvillous membrane transport and relationships with intracellular metabolism. Cytotrophoblast from early gestational age placenta may require different conditions to form true syncytiotrophoblast. A two-sided model for studies of overall transfer, basal transport and basal control mechanisms is now available and possibly with some development should be a good model for such investigations.

Maternal serum inhibin-A and free beta-hCG concentrations in trisomy 21 pregnancies at 10 to 14 weeks of gestation

OBJECTIVE

To determine the relation between maternal serum inhibin-A and free beta-hCG concentrations in chromosomally normal pregnancies and to compare the two biochemical markers for their sensitivity in identifying trisomy 21 pregnancies.

SAMPLE

Inhibin-A and free beta-hCG were measured in maternal serum samples from 800 chromosomally normal singleton pregnancies at 10 to 14 weeks of gestation and 76 singleton pregnancies with fetal trisomy 21.

RESULTS

In the normal group maternal serum inhibin-A was significantly associated with both maternal weight and gestational age (F = 11.2, P < 0.0001). In pregnancies with trisomy 21 the maternal serum inhibin-A and free beta-hCG concentrations were significantly increased (mean difference inhibin = 0.51 SD, F = 18, P < 0.0001 and mean difference free beta-hCG = 1.13 SD, F = 80, P < 0.0001). For a 5% false positive rate, the sensitivity of maternal serum free beta-hCG in identifying pregnancies with trisomy 21 was 28.9% compared with 12.8% for maternal serum inhibin-A. Delta inhibin-A was significantly associated with delta-free beta-hCG (r = 0.345, P < 0.01) and the deviation from the normal mean for free beta-hCG was significantly greater than the deviation for inhibin-A (t = 4.0, P < 0.0001). For a 5% false positive rate, the sensitivity achieved by combining information from delta inhibin-A and delta free beta-hCG was similar to the sensitivity of free beta-hCG alone (30.3% compared with 28.9%).

CONCLUSION

At 10 to 14 weeks of gestation fetal trisomy 21 is associated with increased maternal serum inhibin-A and free beta-hCG levels. However, the degree of elevation of inhibin-A is less than that of free beta-hCG, and there is a significant association between levels of the two proteins. The sensitivity for trisomy 21 achieved with the combination of maternal serum inhibin-A and free beta-hCG is not significantly different from that achieved with maternal serum free beta-hCG alone.

Inhibin, activin and follistatin in the human placenta--a new family of regulatory proteins

The family of inhibin-related proteins has been investigated extensively in the last decade. It is composed of three members: inhibin, activin and follistatin. Inhibin and activin are chemically related, while follistatin acts as an activin-binding protein. Initially identified as regulators of pituitary follice stimulating hormone (FSH) secretion, inhibin, activin and follistatin have more recently been characterized as growth factors, embryo modulators and immune factors. Human placenta, amnion, chorion and maternal decidua express mRNAs for inhibin, activin and follistatin, and the presence of both immunoreactive and bioactive proteins has been demonstrated. The proteins are present in maternal and fetal circulation, and are measurable in amniotic fluid with changes related to gestational age and to the occurrence of gestational diseases. Various biological actions have been described in embryo and intrauterine tissues, which suggest a role for these proteins in the development of the gestational unit. However, several questions remain to be elucidated. The chemical forms of inhibin, activin and follistatin produced by human placenta and the mechanisms involved in the regulation of their secretion are largely unknown. The nature of the receptors for these proteins and the physiological implications of receptor activation have not yet been elucidated and this will require further investigation.

Serum concentrations of human chorionic gonadotrophin and immunoreactive inhibin in early pregnancy and recurrent miscarriage: a longitudinal study

Serum concentrations of immunoreactive inhibin (ir-inhibin) and human chorionic gonadotrophin (HCG) have been measured during the first trimester in a longitudinal study of pregnant women attending a recurrent miscarriage clinic. In 30 singleton pregnancies (Group 1) that continued successfully to term, the median concentration of ir-inhibin initially declined from 1,140 pg/mL at week 4-5 then rose back to comparable values between weeks 7 and 10 but to decline again to reach the significantly lower level of 840 pg/mL (p < 0.01) at week 15-16. Serum levels of HCG showed the classical profile of normal pregnancy reaching a median peak value of 65,600 IU/L (1st IRP) at week 8-9. In 7 pregnancies that miscarried but earlier had evidence on ultrasound of an active fetal heart, HCG levels in the first 9 weeks were consistently below the 10th percentile for Group 1 pregnancies (p < 0.001). Levels of ir-inhibin were also suppressed but to a lesser extent. In 6 of 7 a fetal pregnancies, HCG levels during the first 9 weeks were again markedly subnormal. The levels of ir-inhibin varied between high normal and subnormal. In none of the pregnancy groups was a correlation found between ir-inhibin and HCG concentrations. In a single pregnancy with an anencephalic fetus, while levels of ir-inhibin and HCG were not depressed, peak values were not reached until week 12. The study shows that the level of ir-inhibin in the maternal serum in early pregnancy is of little value as a prognostic indicator of pregnancy outcome. It confirms that a subnormal HCG level is a useful predictor of early pregnancy failure.