Prostaglandin E2 inhibits proliferation and migration of HTR-8/SVneo cells, a human trophoblast-derived cell line

Modelling lipid rafts formation through chemo-mechanical interplay triggered by receptor-ligand binding

Cell membranes, mediator of many biological mechanisms from adhesion and metabolism up to mutation and infection, are highly dynamic and heterogeneous environments exhibiting a strong coupling between biochemical events and structural re-organisation. This involves conformational changes induced, at lower scales, by lipid order transitions and by the micro-mechanical interplay of lipids with transmembrane proteins and molecular diffusion. Particular attention is focused on lipid rafts, ordered lipid microdomains rich of signalling proteins, that co-localise to enhance substance trafficking and activate different intracellular biochemical pathways. In this framework, the theoretical modelling of the dynamic clustering of lipid rafts implies a full multiphysics coupling between the kinetics of phase changes and the mechanical work performed by transmembrane proteins on lipids, involving the bilayer elasticity. This mechanism produces complex interspecific dynamics in which membrane stresses and chemical potentials do compete by determining different morphological arrangements, alteration in diffusive walkways and coalescence phenomena, with a consequent influence on both signalling potential and intracellular processes. Therefore, after identifying the leading chemo-mechanical interactions, the present work investigates from a modelling perspective the spatio-temporal evolution of raft domains to theoretically explain co-localisation and synergy between proteins' activation and raft formation, by coupling diffusive and mechanical phenomena to observe different morphological patterns and clustering of ordered lipids. This could help to gain new insights into the remodelling of cell membranes and could potentially suggest mechanically based strategies to control their selectivity, by orienting intracellular functions and mechanotransduction.

Multiple Roles of Prostaglandin E2 Receptors in Female Reproduction

Among prostaglandins, Prostaglandin E2 (PGE2) (PGE2) is considered especially important for decidualization, ovulation, implantation and pregnancy. Four major PGE2 receptor subtypes, EP1, EP2, EP3, EP4, as well as peroxisome proliferator-activated receptors (PPARs), mediate various PGE2 effects via their coupling to distinct signaling pathways. This review summarizes up-to-date literatures on the role of prostaglandin E2 receptors in female reproduction, which could provide a broad perspective to guide further research in this field. PGE2 plays an indispensable role in decidualization, ovulation, implantation and pregnancy. However, the precise mechanism of Prostaglandin E2 (EP) receptors in the female reproductive system is still limited. More investigations should be performed on the mechanism of EP receptors in the pathological states, and the possibility of EP agonists or antagonists clinically used in improving reproductive disorders.

Brominated diphenyl ether-47 differentially regulates cellular migration and invasion in a human first trimester trophoblast cell line

Polybrominated diphenyl ethers (PBDEs) are flame retardant compounds detected in human placenta and linked to adverse pregnancy outcomes. Impaired trophoblast migration and invasion during early pregnancy have been implicated as potential mechanisms of pregnancy disorders. The present study investigated the effect of BDE-47, a prevalent PBDE congener, on cell migration, invasion, and matrix metalloproteinase (MMP) expression in a human first trimester extravillous trophoblast cell line, HTR-8/SVneo. BDE-47 stimulated cell migration in HTR-SV/neo cells while decreasing invasion of cells into Matrigel. In addition, BDE-47 led to differential expression of MMP-1, -2, -3, and -9 at protein and mRNA levels. In summary, BDE-47 differentially regulated cellular migration and invasion with divergent changes in MMP expression in trophoblasts. Because proper regulation of trophoblast migration and invasion is critical for placental development and function, further research is warranted to determine if exposure to PBDEs disrupts trophoblast functions with increased risk for adverse pregnancy outcomes.

Gene expression and DNA methylation changes in BeWo cells dependent on tumor necrosis factor-α and insulin-like growth factor-I

Pregnant women with increased insulin resistance, characterized by elevated levels of tumor necrosis factor-alpha (TNF-α) and insulin-like growth factor-I (IGF-I), are at high risk of preeclampsia. We hypothesized that TNF-α and IGF-I affect the placentas and cause pathological changes leading to preeclampsia. To understand the genetic and epigenetic effects of TNF-α and IGF-I on trophoblast cells, gene expression microarray and DNA methylation array of BeWo cells stimulated by TNF-α (100 pg/ml, 100 ng/ml) and IGF-I (100 ng/ml) were conducted. Microarray analysis revealed the differential gene expression patterns in BeWo cells co-stimulated by TNF-α and IGF-I. Enrichment analysis identified the terms associated with NF-kappa B signaling pathways and arachidonic acid cascades such as PTGS2 and PTGER2. DNA methylation array revealed the distinct CpG methylation pattern in BeWo cells stimulated by high-TNF-α and IGF-I, while neither of them showed independent effects. Enrichment analysis identified the terms associated with major histocompatibility complex proteins. Integration of transcriptome and DNA methylome analyses identified three differentially expressed genes with significant DNA methylation change: C3, GP1BA, and NFKBIE, which are all possibly associated with pathogenesis of preeclampsia. In conclusion, co-stimulation of TNF-α and IGF-I induced the genetic and epigenetic changes associated with preeclampsia in BeWo cells. The results suggested that BeWo cells stimulated by TNF-α and IGF-I is a good in vitro model of preeclamptic placenta in pregnancy with increased insulin resistance.

Microbial metabolite deoxycholic acid controls Clostridium perfringens-induced chicken necrotic enteritis through attenuating inflammatory cyclooxygenase signaling

Necrotic enteritis (NE) caused by Clostridium perfringens infection has reemerged as a prevalent poultry disease worldwide due to reduced usage of prophylactic antibiotics under consumer preferences and regulatory pressures. The lack of alternative antimicrobial strategies to control this disease is mainly due to limited insight into the relationship between NE pathogenesis, microbiome, and host responses. Here we showed that the microbial metabolic byproduct of secondary bile acid deoxycholic acid (DCA), at as low as 50 µM, inhibited 82.8% of C. perfringens growth in Tryptic Soy Broth (P < 0.05). Sequential Eimeria maxima and C. perfringens challenges significantly induced NE, severe intestinal inflammation, and body weight (BW) loss in broiler chickens. These negative effects were diminished (P < 0.05) by 1.5 g/kg DCA diet. At the cellular level, DCA alleviated NE-associated ileal epithelial death and significantly reduced lamina propria cell apoptosis. Interestingly, DCA reduced C. perfringens invasion into ileum (P < 0.05) without altering the bacterial ileal luminal colonization. Molecular analysis showed that DCA significantly reduced inflammatory mediators of Infγ, Litaf, Il1β, and Mmp9 mRNA accumulation in ileal tissue. Mechanism studies revealed that C. perfringens induced (P < 0.05) elevated expression of inflammatory mediators of Infγ, Litaf, and Ptgs2 (Cyclooxygenases-2 (COX-2) gene) in chicken splenocytes. Inhibiting the COX signaling by aspirin significantly attenuated INFγ-induced inflammatory response in the splenocytes. Consistent with the in vitro assay, chickens fed 0.12 g/kg aspirin diet protected the birds against NE-induced BW loss, ileal inflammation, and intestinal cell apoptosis. In conclusion, microbial metabolic product DCA prevents NE-induced BW loss and ileal inflammation through attenuating inflammatory response. These novel findings of microbiome protecting birds against NE provide new options on developing next generation antimicrobial alternatives against NE.

Prostaglandin F2α stimulates adhesion, migration, invasion and proliferation of the human trophoblast cell line HTR-8/SVneo

INTRODUCTION

The amount of prostaglandin F_2α (PGF_2α) in the uterine lumen increases during the window of implantation in many mammals, including humans. We hypothesized that PGF_2α regulates processes related to human embryo implantation.

METHODS

The effect of PGF_2α was studied using an in vitro model of human extravillous trophoblast (EVT) cell line (HTR-8/SVneo). Adhesion, proliferation, invasion and migration assays, zymography for metalloproteinases (MMP) activity, and gene/protein expression analyses were applied. Doses of 100 nM and/or 1 μM of PGF_2α and fluprostenol were used. PGF_2α receptor (PTGFR), MMP9 and MMP2 proteins in the human first trimester placenta were localized by immunohistochemistry and immunofluorescence.

RESULTS

This study is the first reporting the expression of PTGFR protein in the first trimester placenta, as well as in HTR-8/SVneo cells. PGF_2α and fluprostenol increased HTR-8/SVneo cell proliferation and adhesion to extracellular matrix protein (P < 0.05). This effect was abolished by mitogen activated protein kinases (MAPK) inhibitor. PGF_2α induced phosphorylation of focal adhesion kinase and MAPK1/3 (P < 0.05). PGF_2α increased mRNA content and protein activity of MMP9, and gene and protein expression of interleukin-6 (P < 0.05). EVT cell migration and invasiveness were stimulated by PGF_2α (P < 0.05). The PGF_2α effect on cell invasion was reduced by inhibitors of MMP2, MMP9 and mTOR. In all experiments, the stimulatory effects of PGF_2α were diminished by using a PTGFR antagonist.

DISCUSSION

Our findings suggest a significant role for PGF_2α in mechanisms associated with implantation. PGF_2α acting by PTGFR in HTR-8/SVneo cells stimulates their adhesion and proliferation through the MAPK signaling pathway and increases invasiveness inducing MMP proteolytic activity and mTOR signaling.

Serum omega-3 fatty acids and treatment outcomes among women undergoing assisted reproduction

STUDY QUESTION

Are serum polyunsaturated fatty acids (PUFA) concentrations, including omega-3 (ω3-PUFA) and omega-6 (ω6-PUFA), related to ART outcomes?

SUMMARY ANSWER

Serum levels of long-chain ω3-PUFA were positively associated with probability of live birth among women undergoing ART.

WHAT IS KNOWN ALREADY

Intake of ω3-PUFA improves oocyte and embryo quality in animal and human studies. However, a recent cohort study found no relation between circulating ω3-PUFA levels and pregnancy rates after ART.

STUDY DESIGN SIZE, AND DURATION

This analysis included a random sample of 100 women from a prospective cohort study (EARTH) at the Massachusetts General Hospital Fertility Center who underwent 136 ART cycles within one year of blood collection.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Serum fatty acids (expressed as percentage of total fatty acids) were measured by gas chromatography in samples taken between Days 3 and 9 of a stimulated cycle. Primary outcomes included the probability of implantation, clinical pregnancy and live birth per initiated cycle. Cluster-weighted generalized estimating equation (GEE) models were used to analyze the association of total and specific PUFAs with ART outcomes adjusting for age, body mass index, smoking status, physical activity, use of multivitamins and history of live birth.

MAIN RESULTS AND ROLE OF CHANCE

The median [25th, 75th percentile] serum level of ω3-PUFA was 4.7% [3.8%, 5.8%] of total fatty acids. Higher levels of serum long-chain ω3-PUFA were associated with higher probability of clinical pregnancy and live birth. Specifically, after multivariable adjustment, the probability of clinical pregnancy and live birth increased by 8% (4%, 11%) and 8% (95% CI: 1%, 16%), respectively, for every 1% increase in serum long-chain ω3-PUFA levels. Intake of long-chain ω3-PUFA was also associated with a higher probability of life birth in these women, with RR of 2.37 (95% CI: 1.02, 5.51) when replacing 1% energy of long-chain ω3-PUFA for 1% energy of saturated fatty acids. Serum ω6-PUFA, ratios of ω6 and ω3-PUFA, and total PUFA were not associated with ART outcomes.

LIMITATIONS REASONS FOR CAUTION

The generalizability of the findings to populations not undergoing infertility treatment may be limited. The use of a single measurement of serum fatty acids to characterize exposure may lead to potential misclassification during follow up.

WIDER IMPLICATIONS OF THE FINDINGS

Serum ω3-PUFA are considered biomarkers of dietary intake. The association of higher serum long chain ω3-PUFA levels with improved ART outcomes suggests that increased intake of these fats be may be beneficial for women undergoing infertility treatment with ART.

STUDY FUNDING/COMPETING INTERESTS

NIH grants R01-ES009718 from the National Institute of Environmental Health Sciences, P30-DK046200 and T32-DK007703-16 from the National Institute of Diabetes and Digestive and Kidney Diseases, and L50-HD085359 from the National Institute of Child Health and Human Development, and the Early Life Nutrition Fund from Danone Nutricia US. Dr Rueda is involved in a patent 9,295,662, methods for enhancing, improving, or increasing fertility or reproductive function (http://patents.com/us-9295662.html). This patent, however, does not lead to financial gain for Dr Rueda, or for Massachusetts General Hospital. Dr Rueda does not own any part of the company nor does he have any equity in any fertility related company. As Dr Rueda is not a physician, he does not evaluate patients or prescribe medications. All other coauthors have no conflicts of interest to declare.

Omega-3 polyunsaturated fatty acids and IVF treatment

Omega-3 polyunsaturated fatty acids (PUFAs) are essential fatty acids, derived mostly from fish oil, that have a significant anti-inflammatory effect. Data from animal studies support their role in the reproductive mechanism, and recent human studies suggest a positive effect on sperm quality and natural conception. Their general role in human fertility, and specifically in IVF treatment, however, is not clear. A few small, prospective cohort studies have examined the relationship between serum PUFAs and outcome measures and success in IVF, with conflicting results. Some have demonstrated a better chance of live birth with increased levels of serum omega-3 PUFAs, whereas others have failed to show such a correlation, and the reasons for such differences are not clear. Moreover, no well-designed, published studies have assessing whether the administration of omega-3 PUFAs before IVF treatment can improve clinical pregnancy and live birth rates. The development of safe and well-tolerated pharmaceutical forms of the active omega-3 PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), mean that assessment of this question is now possible and future studies are warranted.

Prostaglandin E2 receptor 3 signaling is induced in placentas with unexplained recurrent pregnancy losses

Although an inflammatory microenvironment is required for successful implantation, an inflammatory overreaction is one of the causes of unexplained recurrent pregnancy losses (uRPL). Prostaglandin E₂ (PGE₂) plays a pivotal role in regulating immune balance during early pregnancy, and it can stimulate inflammatory reactions via prostaglandin E₂ receptor 3 (EP3). However, the role of PGE₂ receptor signaling in the uRPL remains unknown. We aimed to investigate whether EP3 signaling is involved in the mechanism of uRPL. Via immunohistochemistry we could show that the expression of cyclooxygenase-2, EP3 and G protein alpha inhibitor 1 (G_i1) was enhanced in the decidua of the uRPL group in comparison to the control group in first-trimester placentas. In vitro, we demonstrated that sulprostone (an EP1/EP3 agonist) inhibited the secretion of beta-hCG and progesterone in JEG-3 cells and the secretion of beta-hCG in HTR-8/SVneo cells while it induced the expression of plasminogen activator inhibitor type 1 in JEG-3 cells. In addition, PGE₂/sulprostone was able to stimulate the expression of G_i1, phosphorylated-extracellular signal-regulated kinases 1/2 (p-ERK1/2) and p53. L-798,106 (an EP3-specific antagonist) suppressed the expression of EP3 and p-ERK1/2 without affecting the secretion of beta-hCG. Elevated activation of EP3 signaling in first-trimester placentas plays an important role in regulating the inflammatory microenvironment, the hormone secretion of extravillous trophoblasts and the remodeling of extracellular matrix in the fetal-maternal interface. L-798,106 might be a 'potential therapeutic candidate' for the treatment of uRPL.

Mono-2-ethylhexyl phthalate inhibits human extravillous trophoblast invasion via the PPARγ pathway

Concerns over the adverse reproductive outcomes in human have been raised, more evidence including the underlying mechanism are required. Since extravillous trophoblast (EVT) invasion is an important physiological step during early development, the effects of mono-2-ethylhexyl phthalate (MEHP), the bioactive metabolite of DEHP, on EVT invasion were investigated using Matrigel-coated transwell chambers and cell line HTR-8/SVneo. In the transwell-based invasive assay, MEHP exposure inhibited EVT invasion as judged by decreased invasion index. Further analysis showed that MEHP exposure significantly inhibited the activity of matrix metalloproteinase-9 (MMP-9), which is an important positive regulator of EVT invasion. Meanwhile, the protein levels of tissue inhibitor matrix metalloproteinase-1 (TIMP-1), one key negative regulator of EVT invasion, were upregulated by MEHP treatment. Finally, inactivation of PPARγ pathway by either PPARγ inhibitors or PPARγ shRNA knockdown rescued the MEHP-induced inhibited invasion of HTR-8/SVneo cells, which is accompanied by the recovery of inhibited MMP-9 expression. The present study provides the evidence that MEHP exposure inhibits trophoblast invasion via PPARγ at concentrations comparable to those found in humans, which provides an insight in understanding the mechanisms of DEHP-associated early pregnancy loss.

Reactive Oxygen Stimulation of Interleukin-6 Release in the Human Trophoblast Cell Line HTR-8/SVneo by the Trichlorethylene Metabolite S-(1,2-Dichloro)-l-Cysteine

Trichloroethylene (TCE) is a common environmental pollutant associated with adverse reproductive outcomes in humans. TCE intoxication occurs primarily through its biotransformation to bioactive metabolites, including S-(1,2-dichlorovinyl)-l-cysteine (DCVC). TCE induces oxidative stress and inflammation in the liver and kidney. Although the placenta is capable of xenobiotic metabolism and oxidative stress and inflammation in placenta have been associated with adverse pregnancy outcomes, TCE toxicity in the placenta remains poorly understood. We determined the effects of DCVC by using the human extravillous trophoblast cell line HTR-8/SVneo. Exposure to 10 and 20 μM DCVC for 10 h increased reactive oxygen species (ROS) as measured by carboxydichlorofluorescein fluorescence. Moreover, 10 and 20 μM DCVC increased mRNA expression and release of interleukin-6 (IL-6) after 24-h exposure, and these responses were inhibited by the cysteine conjugate beta-lyase inhibitor aminooxyacetic acid and by treatments with antioxidants (alpha-tocopherol and deferoxamine), suggesting that DCVC-stimulated IL-6 release in HTR-8/SVneo cells is dependent on beta-lyase metabolic activation and increased generation of ROS. HTR-8/SVneo cells exhibited decreased mitochondrial membrane potential at 5, 10, and 20 μM DCVC at 5, 10, and 24 h, showing that DCVC induces mitochondrial dysfunction in HTR-8/Svneo cells. The present study demonstrates that DCVC stimulated ROS generation in the human placental cell line HTR-8/SVneo and provides new evidence of mechanistic linkage between DCVC-stimulated ROS and increase in proinflammatory cytokine IL-6. Because abnormal activation of cytokines can disrupt trophoblast functions necessary for placental development and successful pregnancy, follow-up investigations relating these findings to physiologic outcomes are warranted.

Protective effect of (±)α-tocopherol on brominated diphenyl ether-47-stimulated prostaglandin pathways in human extravillous trophoblasts in vitro

Brominated diphenyl ether (BDE)-47 is a prevalent flame retardant chemical found in human tissues and is linked to adverse pregnancy outcomes in humans. Because dysregulation of the prostaglandin pathway is implicated in adverse pregnancy outcomes, the present study investigates BDE-47 induction of prostaglandin synthesis in a human extravillous trophoblast cell line, HTR-8/SVneo, examining the hypothesis that BDE-47 increases generation of reactive oxygen species (ROS) to stimulate the prostaglandin response. Treatment with 20 μM BDE-47 significantly increased mRNA expression of prostaglandin-endoperoxide synthase 2 (PTGS2) at 4, 12 and 24 h, and 24-h treatment significantly increased cyclooxygenase (COX)-2 cellular protein expression and prostaglandin E2 (PGE2) concentration in culture medium. The BDE-47-stimulated PGE2 release was inhibited by the COX inhibitors indomethacin and NS398, implicating COX activity. Exposure to 20 μM BDE-47 significantly increased ROS generation as measured by carboxydichlorofluorescein fluorescence, and this response was blocked by cotreatment with the peroxyl radical scavenger (±)-α-tocopherol. (±)-α-Tocopherol cotreatment suppressed BDE-47-stimulated increases of PGE2 release without significant effects on COX-2 mRNA and protein expression, implicating a role for ROS in post-translational regulation of COX activity. Because prostaglandins regulate trophoblast functions necessary for placentation and pregnancy, further investigation is warranted of BDE-47 impacts on trophoblast responses.

Changes in Functional Activity of JEG-3 Trophoblast Cell Line in the Presence of Factors Secreted by Placenta

BACKGROUND AND AIMS

Cells in the maternal-fetal interface secrete cytokines that regulate proliferation, migration, and trophoblast invasion during the first trimester of pregnancy and the limitation of these processes during the third trimester. The aim of the study was to evaluate the influence of factors secreted by human placenta during the first and third trimester of pregnancy on cytokine receptor expression and proliferative and migratory activity of JEG-3 trophoblast cells.

METHODS

The research was conducted using the explant conditioned media of placentas obtained from healthy women with elective termination of pregnancy at 9-11 weeks and placentas of women whose pregnancy progressed without complications at 38-39 weeks. Assessment of surface molecule expression was performed using FACS Canto II flow cytometer (BD, USA). The proliferative activity of JEG-3 trophoblast cells was evaluated by dyeing with crystal violet vital dye. The migration activity of JEG-3 was evaluated using 24-well insert plates with polycarbonate inserts (pore size 8 microns).

RESULTS

Expression of CD116, CD118, CD119, IFNγ-R2, CD120b, CD183, CD192, CD295, EGFR, and TGFβ-R2 on JEG-3 was higher when the cells were incubated in the presence of the third trimester placental factors in comparison with the first trimester placental factors. Factors secreted by the placenta during the third trimester of pregnancy had more pronounced stimulatory effect on the proliferation and migration of trophoblast in comparison with baseline levels and with the effect of the first trimester placental factors.

CONCLUSIONS

The findings suggest that the behavior of trophoblasts in vitro might not be representative of in vivo behavior in the absence of additional local factors that influence the trophoblast in vivo.

Tetrabromobisphenol A activates inflammatory pathways in human first trimester extravillous trophoblasts in vitro

Tetrabromobisphenol A (TBBPA) is a widely used flame retardant. Despite the presence of TBBPA in gestational tissues and the importance of proper regulation of inflammatory networks for successful pregnancy, there is no prior study on the effects of TBBPA on inflammatory responses in gestational tissues. The present study aimed to investigate TBBPA activation of inflammatory pathways, specifically cytokine and prostaglandin production, in the human first trimester placental cell line HTR-8/SVneo. TBBPA enhanced release of interleukin (IL)-6, IL-8, and prostaglandin E2 (PGE2), and suppressed TGF-β release in HTR-8/SVneo cells. The lowest effective concentration was 10 μM TBBPA. A commercial immune response PCR array revealed increased expression of genes involved in inflammatory pathways stimulated by TBBPA in HTR-8/SVneo cells. Because proper regulation of inflammatory mediators in the gestational compartment is necessary for normal placental development and successful pregnancy, further investigation on the impact of TBBPA-stimulated responses on trophoblast function is warranted.

Protective effect of nuclear factor E2-related factor 2 on inflammatory cytokine response to brominated diphenyl ether-47 in the HTR-8/SVneo human first trimester extravillous trophoblast cell line

Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants, and BDE-47 is a prevalent PBDE congener detected in human tissues. Exposure to PBDEs has been linked to adverse pregnancy outcomes in humans. Although the underlying mechanisms of adverse birth outcomes are poorly understood, critical roles for oxidative stress and inflammation are implicated. The present study investigated antioxidant responses in a human extravillous trophoblast cell line, HTR-8/SVneo, and examined the role of nuclear factor E2-related factor 2 (Nrf2), an antioxidative transcription factor, in BDE-47-induced inflammatory responses in the cells. Treatment of HTR-8/SVneo cells with 5, 10, 15, and 20μM BDE-47 for 24h increased intracellular glutathione (GSH) levels compared to solvent control. Treatment of HTR-8/SVneo cells with 20μM BDE-47 for 24h induced the antioxidant response element (ARE) activity, indicating Nrf2 transactivation by BDE-47 treatment, and resulted in differential expression of redox-sensitive genes compared to solvent control. Pretreatment with tert-butyl hydroquinone (tBHQ) or sulforaphane, known Nrf2 inducers, reduced BDE-47-stimulated IL-6 release with increased ARE reporter activity, reduced nuclear factor kappa B (NF-κB) reporter activity, increased GSH production, and stimulated expression of antioxidant genes compared to non-Nrf2 inducer pretreated groups, suggesting that Nrf2 may play a protective role against BDE-47-mediated inflammatory responses in HTR-8/SVneo cells. These results suggest that Nrf2 activation significantly attenuated BDE-47-induced IL-6 release by augmentation of cellular antioxidative system via upregulation of Nrf2 signaling pathways, and that Nrf2 induction may be a potential therapeutic target to reduce adverse pregnancy outcomes associated with toxicant-induced oxidative stress and inflammation.

Diverse roles of prostaglandins in blastocyst implantation

Prostaglandins (PGs), derivatives of arachidonic acid, play an indispensable role in embryo implantation. PGs have been reported to participate in the increase in vascular permeability, stromal decidualization, blastocyst growth and development, leukocyte recruitment, embryo transport, trophoblast invasion, and extracellular matrix remodeling during implantation. Deranged PGs syntheses and actions will result in implantation failure. This review summarizes up-to-date literatures on the role of PGs in blastocyst implantation which could provide a broad perspective to guide further research in this field.

Autocrine and paracrine mechanisms of prostaglandin E₂ action on trophoblast/conceptus cells through the prostaglandin E₂ receptor (PTGER2) during implantation

The conceptus and endometrium secrete large amounts of prostaglandin E₂ (PGE₂) into the porcine uterine lumen during the periimplantation period. We hypothesized that PGE₂ acts on conceptus/trophoblast cells through auto- and paracrine mechanisms. Real-time RT-PCR analysis revealed that PGE₂ receptor (PTGER)2 mRNA was 14-fold greater in conceptuses/trophoblasts on days 14-25 (implantation and early placentation period) vs preimplantation day 10-13 conceptuses (P < .05). Similarly, expression of PTGER2 protein increased during implantation. Conceptus expression of PTGER4 mRNA and protein did not differ on days 10-19. PGE₂ stimulated PTGER2 mRNA expression in day 15 trophoblast cells through PTGER2 receptor signaling. PGE₂ elevated aromatase expression and estradiol-17β secretion by trophoblast cells. Moreover, PGE₂ and the PTGER2 agonist, butaprost, increased the adhesive capacity of both human HTR-8/SVneo trophoblast and primary porcine trophoblast cells to extracellular matrix. This PGE₂-induced alteration in trophoblast cell adhesion to extracellular matrix was abolished by incubation of these cells with AH6809 (PTGER2 antagonist), ITGAVB3-directed tetrapeptide arg-gly-asp-ser or integrin ITGAVB3 antibody. PGE₂ stimulated adhesion of porcine trophoblast cells via the estrogen receptor and MEK/MAPK signaling pathway. PGE₂ induced phosphorylation of MAPK1/MAPK3 through PTGER2 and up-regulated expression of cell adhesion proteins such as focal adhesion kinase and intercellular adhesion molecule-1. Our study indicates that elevated PGE₂ in the periimplantation uterine lumen stimulates conceptus PTGER2 expression, which in turn promotes trophoblast adhesion via integrins, and synthesis and secretion of the porcine embryonic signal estradiol-17β. Moreover, the mechanism through which PGE₂ increases trophoblast adhesion is not species specific because it is PTGER2- and integrin-dependent in both porcine and human trophoblast cells.

Mono-2-ethylhexyl phthalate induces oxidative stress responses in human placental cells in vitro

Di-2-ethylhexyl phthalate (DEHP) is an environmental contaminant commonly used as a plasticizer in polyvinyl chloride products. Exposure to DEHP has been linked to adverse pregnancy outcomes in humans including preterm birth, low birth-weight, and pregnancy loss. Although oxidative stress is linked to the pathology of adverse pregnancy outcomes, effects of DEHP metabolites, including the active metabolite, mono-2-ethylhexyl phthalate (MEHP), on oxidative stress responses in placental cells have not been previously evaluated. The objective of the current study is to identify MEHP-stimulated oxidative stress responses in human placental cells. We treated a human placental cell line, HTR-8/SVneo, with MEHP and then measured reactive oxygen species (ROS) generation using the dichlorofluorescein assay, oxidized thymine with mass-spectrometry, redox-sensitive gene expression with qRT-PCR, and apoptosis using a luminescence assay for caspase 3/7 activity. Treatment of HTR-8 cells with 180μM MEHP increased ROS generation, oxidative DNA damage, and caspase 3/7 activity, and resulted in differential expression of redox-sensitive genes. Notably, 90 and 180μM MEHP significantly induced mRNA expression of prostaglandin-endoperoxide synthase 2 (PTGS2), an enzyme important for synthesis of prostaglandins implicated in initiation of labor. The results from the present study are the first to demonstrate that MEHP stimulates oxidative stress responses in placental cells. Furthermore, the MEHP concentrations used were within an order of magnitude of the highest concentrations measured previously in human umbilical cord or maternal serum. The findings from the current study warrant future mechanistic studies of oxidative stress, apoptosis, and prostaglandins as molecular mediators of DEHP/MEHP-associated adverse pregnancy outcomes.

Effects of alcohol, lithium, and homocysteine on nonmuscle myosin-II in the mouse placenta and human trophoblasts

OBJECTIVE

Mouse embryonic exposure to alcohol, lithium, and homocysteine results in intrauterine growth restriction (IUGR) and cardiac defects. Our present study focused on the placental effects. We analyzed the hypothesis that expression of nonmuscle myosin (NMM)-II isoforms involved in cell motility, mechanosensing, and extracellular matrix assembly are altered by the 3 factors in human trophoblast (HTR8/SVneo) cells in vitro and in the mouse placenta in vivo.

STUDY DESIGN

After exposure during gastrulation to alcohol, homocysteine, or lithium, ultrasonography defined embryos exhibiting abnormal placental blood flow.

RESULTS

NMM-IIA/NMM-IIB are differentially expressed in trophoblasts and in mouse placental vascular endothelial cells under pathological conditions. Misexpression of NMM-IIA/NMM-IIB in the affected placentas continued stably to midgestation but can be prevented by folate and myoinositol supplementation.

CONCLUSION

It is concluded that folate and myoinositol initiated early in mouse pregnancy can restore NMM-II expression, permit normal placentation/embryogenesis, and prevent IUGR induced by alcohol, lithium, and homocysteine.

Review: Spatiotemporal dynamics of hCG/cAMP signaling and regulation of placental function

The pregnancy hormone human chorionic gonadotropin (hCG) is essential to sustain early pregnancy and involved in regulation of progesterone production, decidualization, and cytotrophoblast differentiation. It binds to and activates the G-protein coupled luteinizing hormone/hCG-receptor, activating the cAMP/protein kinase A (PKA) pathway which results in the phosphorylation of specific intracellular target proteins. Specificity in cAMP signaling is ensured by generation of localized pools of cAMP controlled by phosphodiesterases and by discrete spatial and temporal activation of PKA in supramolecular signaling clusters inside the cell organized by A-kinase-anchoring proteins. Here we discuss spatiotemporal regulation of PKA signaling in response to hCG controlling placental function.

H3N2 influenza A virus replicates in immortalized human first trimester trophoblast cell lines and induces their rapid apoptosis

PROBLEM

Epidemiological data suggested that pandemic influenza increased the risks of spontaneous abortion and premature labor, while seasonal influenza also increased the risk of schizophrenia in adolescence. However, their pathogenesis is so far unknown.

METHOD OF STUDY

The first trimester trophoblast cell lines, namely, Swan71 and HTR8 cells were challenged with A/Udorn/72 influenza virus (H3N2). At indicated time points, cells were examined for expression of influenza proteins. Viral replication in culture media, apoptosis and the expression of human leukocyte antigen (HLA)-G were also examined.

RESULTS

Intracellular localization of viral proteins was observed. Twenty-four hours after inoculation, virus was detected in culture media while most cells fell into apoptosis. During apoptosis, expression of HLA-G was unchanged.

CONCLUSION

We revealed replication of low pathogenic influenza virus in the first trimester trophoblast cell lines. Placental damages are likely to be induced by direct cytopathic effects of influenza virus and subsequent apoptosis rather than down regulation of HLA-G expression and subsequent rejection by maternal immune system.

Current concepts regarding the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating disease that predominantly affects premature neonates. The mortality associated with NEC has not changed appreciably over the past several decades. The underlying etiology of NEC remains elusive, although bacterial colonization of the gut, formula feeding, and perinatal stress have been implicated as putative risk factors. The disease is characterized by massive epithelial destruction, which results in gut barrier failure. The exact molecular and cellular mechanisms involved in this complex disease are poorly understood. Recent studies have provided significant insight into our understanding of the pathogenesis of NEC. Endogenous mediators such as prostanoids, cyclooxygenases, and nitric oxide may play a role in the development of gut barrier failure. Understanding the structural architecture of the gut barrier and the cellular mechanisms that are responsible for gut epithelial damage could lead to the development of novel diagnostic, prophylactic and therapeutic strategies in NEC.

Smurf2 participates in human trophoblast cell invasion by inhibiting TGF-beta type I receptor

Successful embryo implantation depends on the ability of the trophoblast cells to invade the endometrium and the receptivity of the endometrium. Unlike tumor invasion, trophoblast invasion is spatio-temporaly restricted. Transforming growth factor (TGF)-beta is a key inhibitory factor in the invasion of early trophoblast cells. Smad ubiquitination regulatory factor 2 (Smurf2), a HECT type E3 ubiquitin ligase, is an important regulator of the TGF-beta signaling pathway, targeting TGF-beta receptors and various Smads for proteasome-mediated degradation. In this context, we wished to determine whether Smurf2 has a physiological role during embryo implantation, especially in trophoblast invasion. We examined the spatio-temporal expression of Smurf2 in human placental villi and the function of Smurf2 in trophoblast cell migration and invasion in a model system involving a human extravillous trophoblast cell line, HTR-8/SVneo. Results from RT-PCR and immunohistochemical studies showed that expression of Smurf2 in placental villi was the highest during the first trimester and decreased as the pregnancy progressed. Overexpression of Smurf2 in HTR-8/SVneo cells reduced TGF-beta type I receptor levels, and enhanced cell migration and invasion. Conversely, RNA interference-mediated downregulation of Smurf2 resulted in a significant increase in TGF-beta type I receptor protein levels. However, the levels of Smad2, another potential target of Smurf2, remained unchanged. In conclusion, the present study suggests that Smurf2 promotes trophoblast cell migration and invasion, and this function may involve downregulation of TGF-beta type I receptor.

Lysophosphatidic acid signaling during embryo development in sheep: involvement in prostaglandin synthesis

We investigated the lysophosphatidic acid (LPA) pathway during early pregnancy in sheep. LPA was detected in the uteri of early-stage pregnant ewes. Using quantitative RT-PCR, the expression of autotaxin, the LPA-generating enzyme, was found in the endometrium and conceptus. In the latter autotaxin, transcript levels were low on d 12-14 and increased on d 15-16, in parallel with the level of LPA. Autotaxin was localized in the luminal epithelium and superficial glands of the endometrium and in trophectoderm cells of the conceptus. The expression of G protein-coupled receptors for LPA was also examined in the ovine conceptus. LPA receptor LPAR1 and LPAR3 transcripts were expressed during early pregnancy and displayed a peak on d 14, whereas the highest level of protein for both receptors was observed at d 17. LPAR1 was localized in cellular membranes and nuclear compartments of the trophectoderm cells, whereas LPAR3 was revealed only in membranes. LPA activated phosphorylation of the MAPK ERK1/2 in ovine trophectoderm-derived cells. Moreover, the bioactive lipid increased the proliferation of trophectoderm cells in culture, as shown by thymidine and bromodeoxyuridine incorporation. Furthermore, LPA induced changes to the organization of beta-actin and alpha-tubulin, suggesting a role for it in rearrangement of trophectoderm cells cytoskeleton. Because a link had previously been established between prostaglandin and LPA pathways, we analyzed the effect of LPA on prostaglandin synthesis. LPA induced an increase in the release of prostaglandin F2alpha and prostaglandin E2, with no significant modifications to cytosolic phospholipase A2alpha and prostaglandin synthase-2 expression. Taken together, our results suggest a new role for LPA-mediated signaling in the ovine conceptus at the time of implantation.

Somatostatin as a regulator of first-trimester human trophoblast functions

We have tested the hypothesis that human early trophoblast is a target for somatostatin (SRIF) regulatory actions. We report for the first time that SSTR2A and 2B transcripts and proteins are present in first-trimester human chorionic villi and the trophoblast-derived HTR-8/SVneo and JAR cells. In both cell lines, SSTR are functional since SRIF inhibits cyclic AMP pathway, stimulates arachidonic acid release and enhances cell proliferation. Moreover, in HTR-8/SVneo cells, considered a good model of first-trimester EVT, SRIF also enhances migration. An involvement of the cyclic AMP pathway in mediating SRIF effects on proliferation and migration is suggested. Our data support the idea that SRIF regulates early trophoblast functions mainly through an interaction with SSTR2.

Molecular signaling in necrotizing enterocolitis: regulation of intestinal COX-2 expression

Necrotizing enterocolitis (NEC) is the most common surgical emergency in premature infants. The underlying etiology of NEC remains unknown, although bacterial colonization of the gut, formula feeding, and perinatal stress have been implicated as putative risk factors. The disease is characterized by exuberant gut inflammation leading to ischemia and coagulation necrosis of the intestinal epithelium. The molecular and cellular mechanisms responsible for these pathologic changes are poorly understood. It has been shown that various exogenous and endogenous mediators such as lipopolysaccharide, inflammatory cytokines, platelet activating factor, and nitric oxide may play a role in the pathogenesis of NEC. Recent studies in our laboratory and others have established a link between NEC and activation of cyclooxygenase-2, the enzyme that catalyzes the rate-limiting step in the biosynthesis of prostanoids. The challenge is in defining the molecular signaling pathways leading to accumulation of these mediators early in the disease progression, before the onset of tissue necrosis and systemic sepsis. Identification and characterization of these pathways could lead to the development of novel treatment strategies to alleviate the morbidity and mortality associated with NEC.

Control of human trophoblast function

The trophoblast, i.e. the peripheral part of the human conceptus, exerts a crucial role in implantation and placentation. Both processes properly occur as a consequence of an intimate dialogue between fetal and maternal tissues, fulfilled by membrane ligands and receptors, as well as by hormone and local factor release. During blastocyst implantation, generation of distinct trophoblast cell types begins, namely the villous and the extravillous trophoblast, the former of which is devoted to fetal-maternal exchanges and the latter binds the placental body to the uterine wall. Physiological placentation is characterized by the invasion of the uterine spiral arteries by extravillous trophoblast cells arising from anchoring villi. Due to this invasion, the arterial structure is replaced by amorphous fibrinoid material and endovascular trophoblastic cells. This transformation establishes a low-resistance, high-capacity perfusion system from the radial arteries to the intervillous space, in which the villous tree is embedded. The physiology of pregnancy depends upon the orderly progress of structural and functional changes of villous and extravillous trophoblast, whereas a derangement of such processes can lead to different types of complications of varying degrees of gravity, including possible pregnancy loss and maternal life-threatening diseases. In this review we describe the mechanisms which regulate trophoblast differentiation, proliferation, migration and invasiveness, and the alterations in these mechanisms which lead to pathological conditions. Furthermore, based on the growing evidence that proper inflammatory changes and oxidative balance are needed for successful gestation, we explain the mechanisms by which agents able to influence such processes may be useful in the prevention and treatment of pregnancy disorders.