Regulation of gene expression in mouse trophoblast cells by interferon-gamma

Oncostatin M and STAT3 Signaling Pathways Support Human Trophoblast Differentiation by Inhibiting Inflammatory Stress in Response to IFNγ and GM-CSF

Interleukin-6 (IL-6) superfamily cytokines play critical roles during human pregnancy by promoting trophoblast differentiation, invasion, and endocrine function, and maintaining embryo immunotolerance and protection. In contrast, the unbalanced activity of pro-inflammatory factors such as interferon gamma (IFNγ) and granulocyte-macrophage colony-stimulating factor (GM-CSF) at the maternal-fetal interface have detrimental effects on trophoblast function and differentiation. This study demonstrates how the IL-6 cytokine family member oncostatin M (OSM) and STAT3 activation regulate trophoblast fusion and endocrine function in response to pro-inflammatory stress induced by IFNγ and GM-CSF. Using human cytotrophoblast-like BeWo (CT/BW) cells, differentiated in villous syncytiotrophoblast (VST/BW) cells, we show that beta-human chorionic gonadotrophin (βhCG) production and cell fusion process are affected in response to IFNγ or GM-CSF. However, those effects are abrogated with OSM by modulating the activation of IFNγ-STAT1 and GM-CSF-STAT5 signaling pathways. OSM stimulation enhances the expression of STAT3, the phosphorylation of STAT3 and SMAD2, and the induction of negative regulators of inflammation (e.g., IL-10 and TGFβ1) and cytokine signaling (e.g., SOCS1 and SOCS3). Using STAT3-deficient VST/BW cells, we show that STAT3 expression is required for OSM to regulate the effects of IFNγ in βhCG and E-cadherin expression. In contrast, OSM retains its modulatory effect on GM-CSF-STAT5 pathway activation even in STAT3-deficient VST/BW cells, suggesting that OSM uses STAT3-dependent and -independent mechanisms to modulate the activation of pro-inflammatory pathways IFNγ-STAT1 and GM-CSF-STAT5. Moreover, STAT3 deficiency in VST/BW cells leads to the production of both a large amount of βhCG and an enhanced expression of activated STAT5 induced by GM-CSF, independently of OSM, suggesting a key role for STAT3 in βhCG production and trophoblast differentiation through STAT5 modulation. In conclusion, our study describes for the first time the critical role played by OSM and STAT3 signaling pathways to preserve and regulate trophoblast biological functions during inflammatory stress.

The Role of Interferon (IFN)-γ in Extravillous Trophoblast Cell (EVT) Invasion and Preeclampsia Progression

The involvement of the immune system in pregnancy is a controversial subject. The functions of T helper (Th) 1 and Th2 cells have been proposed, that Th1 cytokines promoting allograft rejection may impair pregnancy, whereas Th2-type cytokines suppressing Th1 responses improve allograft tolerance and hence embryonic survival. Maternal-fetal tolerance begins in the uterus; therefore, optimal adaptation to the fetus is the result of a complex interference. The invasion of extravillous trophoblast cells (EVTs) into the decidua and the inner third of the myometrium is essential for a healthy pregnancy. The mechanisms that influence trophoblast invasion are unknown; however, cytokines from uterine natural killer (uNK) cells, NKT cells, macrophages, and T cells appear to be involved. All these cells are major sources of interferon gamma (IFN-γ). Recent studies have shown that IFN-γ can inhibit EVT invasion via a mechanism dependent on an increase in EVT apoptosis and a decrease in matrix metalloproteinases (MMPs). Regarding controversies in this context, this study aimed to comprehensively review the role of IFN-γ and IFN-γ-producing cells in EVT invasion, successful pregnancy, and preeclampsia.

The level pro-inflammatory and anti-inflammatory biomarkers in patients with chronic mechanical low back pain under pulse radiofrequency therapy

Low back pain is a frequent and recurrent condition, often with a non-specific cause. Conventional treatment methods are generally insufficient in the treatment of chronic low back pain. The aim of the study was to estimate the level of IFN, IL-1, IL-6 (proinflammatory), IL-10, IL-4 (anti-inflammatory) and VEGF proteins in the serum of patients with chronic mechanical low back pain under Pulse radiofrequency (PRF) therapy. The study was carried out on 40 patients 20-60 years old, diagnosed with chronic low back pain for at least 4 months, primary complaint on lumbosacral low back pain, pain intensity VAS (visual analog scale) score of 5 and above, not responding well to conservative treatment (analgesic drugs, physiotherapy, etc.). Therapeutic Radiofrequency applications were carried out with an RF generator (RFG 3C Plus, Radionics). Blood samples were taken 1 day before interventional treatment (control), then 1 day (group1) and 15 days (group 2) after. The serum level of IFN, IL-1, IL-6, IL-10, IL-4 and VEGF l was analyzed with ELISA test. It was shown that as a result of PRF treatment the level of IL-1 was decreased while the levels of IL-4 and IL-6 were increased. It was concluded that the increase in serum levels of proinflammatory cytokines may be correlated with the severity of pain and that the increase in the level of anti-inflammatory cytokines reduces pain by reducing inflammation. Keywords: chronic low back pain, cytokines, radiofrequency therapy

Stromal Cell-Derived Factor (SDF) 2 and the Endoplasmic Reticulum Stress Response of Trophoblast Cells in Gestational Diabetes Mellitus and In vitro Hyperglycaemic Condition

BACKGROUND AND AIM

The endoplasmic reticulum (ER) stress response and the unfolded protein response (UPR) are essential cellular mechanisms to ensure the proper functioning of ER in adverse conditions. However, activation of these pathways has also been associated with insulin resistance and cell death in pathological conditions such as diabetes mellitus. In the present study, we investigated whether stromal cell-derived factor 2 (SDF2)-an ER stress-responsive factor-is related to ER response in placental cells exposed to maternal gestational diabetes mellitus (GDM) or to a hyperglycaemic in vitro condition.

OBJECTIVE

The study aimed to investigate the role of SDF2 in BeWo cells , a trophoblast cell line originating from choriocarcinoma , and in placental tissue under hyperglycaemic conditions.

METHODS

Protein levels of SDF2 and UPR factors, glucose-related protein 78 (GRP78) and eukaryotic initiation factor 2 alpha (elF2 alpha) were evaluated in the placentae of pregnant women diagnosed with GDM and treated by diet-control (insulin was added when necessary). The mRNA expression of SDF2 and UPR factors CHOP and sXBP1 were assessed in cultured BeWo cells challenged with glucose and treated with or without insulin.

RESULTS

SDF2 expression was increased in the placentae of GDM women treated with diet. However, its values were similar to those of normoglycemic controls when the GDM women were treated with insulin and diet. BeWo cells cultured with high glucose and insulin showed decreased SDF2 expression, while high glucose increased CHOP and sXBP1 expression, which was then significantly reverted with insulin treatment.

CONCLUSION

Our findings extend the understanding of ER stress and SDF2 expression in placentae exposed to hyperglycaemia, highlighting the relevance of insulin in reducing the levels of ER stress factors in placental cells. Understanding the effect of ER stress partners such as SDF2 on signalling pathways involved in gestation, complicated by hyperglycaemia, is pivotal for basic biomedical research and may lead to new therapeutic possibilities.

Changing the paradigm of IFN-γ at the interface between innate and adaptive immunity: Macrophage-derived IFN-γ

IFN-γ plays a critical role in the immune response to bacterial infections. It is established that IFN-γ is mainly produced by NK/ILC1 cells and T cells, and most of papers have rejected the biologic reality of alternative sources for more than 20 years. Here, we are proposing to revisit this dogma and discuss the role of macrophage-derived IFN-γ in bacterial infections. Our hypothesis is based on a panel of publications and is recently revived by our results on placenta, a chimeric organ in which the immune response is tailored to protect the fetus from mother's immune response. The culture of purified placental macrophages is associated with a production of IFN-γ that may contribute to fetal protection from bacterial infections before eliciting a Th1-like immune response potentially pathogenic for pregnancy. Hence, macrophage IFN-γ may be a novel actor of early crosstalk between innate and adaptive immunity in the context of host defense against bacterial infections.

Efeito do hipotireoidismo materno na expressão espaço-temporal de mediadores imunológicos e população de células natural killers na decídua e na glândula metrial de ratas

RESUMO Estudou-se o efeito do hipotireoidismo materno na expressão espaço-temporal de mediadores imunológicos e na população de células natural killers (NK) na decídua e na glândula metrial de ratas durante a gestação. Avaliou-se a detecção imunoistoquímica de interferon γ (IFNγ), do fator inibidor de migração (MIF), da interleucina 15 (IL15), do óxido nítrico sintase induzível (iNOS), a marcação com lectina DBA para evidenciação das células NK uterinas DBA+ e a expressão gênica de Ifnγ e Nos2. O hipotireoidismo aumentou o iNOS aos sete dias, a IL15 e o MIF aos 10 e 12 dias, o IFNγ e o MIF aos 14 DG e a expressão dos transcritos gênicos para iNos aos 12 e 19 dias e para Ifnγ aos 14 DG. O hipotireoidismo reduziu a imunomarcação de MIF e lectina DBA aos sete dias, lectina DBA aos 10 e 14 DG, IFNγ aos 12 dias, e a expressão de Ifnγ aos 10 e 19 DG e de iNOS aos 12, 14 e 19 DG, bem como reduziu seus transcritos gênicos aos 10 e 14 DG. Conclui-se que o hipotireoidismo compromete o perfil imunológico na interface materno-fetal ao longo da gestação, particularmente por reduzir o fator anti-inflamatório iNOS e a população de células uNK DBA+.

Antiviral Inflammation during Early Pregnancy Reduces Placental and Fetal Growth Trajectories

Many viruses are detrimental to pregnancy and negatively affect fetal growth and development. What is not well understood is how virus-induced inflammation impacts fetal-placental growth and developmental trajectories, particularly when inflammation occurs in early pregnancy during nascent placental and embryo development. To address this issue, we simulated a systemic virus exposure in early pregnant rats (gestational day 8.5) by administering the viral dsRNA mimic polyinosinic:polycytidylic acid (PolyI:C). Maternal exposure to PolyI:C induced a potent antiviral response and hypoxia in the early pregnant uterus, containing the primordial placenta and embryo. Maternal PolyI:C exposure was associated with decreased expression of the maternally imprinted genes Mest, Sfrp2, and Dlk1, which encode proteins critical for placental growth. Exposure of pregnant dams to PolyI:C during early pregnancy reduced fetal growth trajectories throughout gestation, concomitant with smaller placentas, and altered placental structure at midgestation. No detectable changes in placental hemodynamics were observed, as determined by ultrasound biomicroscopy. An antiviral response was not evident in rat trophoblast stem (TS) cells following exposure to PolyI:C, or to certain PolyI:C-induced cytokines including IL-6. However, TS cells expressed high levels of type I IFNR subunits (Ifnar1 and Ifnar2) and responded to IFN-⍺ by increasing expression of IFN-stimulated genes and decreasing expression of genes associated with the TS stem state, including Mest IFN-⍺ also impaired the differentiation capacity of TS cells. These results suggest that an antiviral inflammatory response in the conceptus during early pregnancy impacts TS cell developmental potential and causes latent placental development and reduced fetal growth.

The potential contribution of stromal cell-derived factor 2 (SDF2) in endoplasmic reticulum stress response in severe preeclampsia and labor-onset

Endoplasmic reticulum (ER) stress occurs when the protein folding machinery in the cell is unable to cope with newly synthesized proteins, which results in an accumulation of misfolded proteins in the ER lumen. In response, the cell activates a cellular signaling pathway known as the Unfolded Protein Response (UPR), aiming to restore cellular homeostasis. Activation and exacerbation of the UPR have been described in several human pathologies, including cancer and neurological disorders, and in some gestational diseases such as preeclampsia and gestational diabetes. This review explores the participation of stromal cell-derived factor 2 (SDF2) in UPR pathways, shows new information and discusses its exacerbation regarding protein expression in severe preeclampsia and labor, both of which are associated with ER stress.

Chemokine (C-C motif) ligand 25 expressed by trophoblast cells and leukocytes bearing its receptor Ccr9: An alliance during embryo implantation?

PROBLEM

We hypothesized that trophoblast expression of Ccl25 attracts a specific leukocyte cell population to the implantation site for local regulation.

METHOD OF STUDY

Mice blastocysts, ectoplacental cones, and decidua at gestational days 3.5-7.5 were evaluated for Ccl25 and Ccr9 expressions. Peripheral availability and characterization of Ccr9+ leukocytes were determined by flow cytometry. Leukocyte chemotaxis was assessed in the presence of Ccl25 recombinant protein and embryos using antisense oligomers (ODNs) to Ccl25 and Ccr9 neutralizing antibody.

RESULTS

Ccl25 was expressed by embryonic cells, whereas Ccr9 expression was strong at the maternal compartment and in PBMC. Immunolocalization confirmed this expression. In vitro, chemotaxis assays showed that the embryonic Ccl25 signals to Ccr9+ PBMCs. Maternal Ccr9+α4β7+ monocytes switch from an anti-inflammatory phenotype (F4/80+11b+Ly6C-TGF-β+ cells, pre-implantation) to an inflammatory profile (F4/80+11b+Ly6C+TNF-α+ cells, post-implantation).

CONCLUSION

Our data support the establishment of a CCL25/CCR9-axis at the maternal-fetal interface in mice, which may be involved in immune regulatory mechanisms during embryo implantation.

Stromal Cell-Derived Factor 2: A Novel Protein that Interferes in Endoplasmic Reticulum Stress Pathway in Human Placental Cells

Endoplasmic reticulum (ER) stress results from changes in ER homeostasis and folding of proteins. ER stress initiates cellular adaptive mechanisms to rescue cell homeostasis or, if that does not work, to elicit apoptosis. We have previously shown that mouse SDF2 is sublocalized in the ER, is ubiquitously expressed, and shows strong similarities with stromal cell-derived factor (SDF) 2L1 and SDF2-like from Arabidopsis, ER proteins involved in chaperone network and protein folding. Thus, we hypothesized that SDF2 plays a role in the ER stress and unfolded protein response. In this study, we investigated the possible role of SDF2 in the human placenta. Expression of SDF2 was present throughout gestation and was expressed by several cell types. Second-trimester cytotrophoblast cells (CTBs) in the differentiation process, monitored through chorionic gonadotropin production, showed upregulation of SDF2 protein. SDF2 expression, however, was significantly diminished in placentas from neonates small for gestational age and in hypoxic in vitro conditions (P ≤ 0.001, 2% O2), suggesting a link with cellular stress. ER stress-induced cells-CTB and BeWo-also showed SDF2 downregulation in different time points, emphasizing this relationship. SDF2 downregulation was also followed by an increase in binding immunoglobulin protein (BiP) expression, an ER protein-associated chaperone acting as a sensor for misfolded proteins and an ER stress cell survival marker. In line with this, SDF2 siRNA resulted in significant anticipation of BiP expression. Downregulation of SDF2 also interfered with C/EBP homologous protein expression, one of the highest inducible genes during ER stress. These findings suggest that SDF2 may be an important regulatory factor by which trophoblast cells can control cell survival under ER stress. In conclusion, this study identifies a novel factor with the ability to interfere with ER stress proteins, which may contribute to the understanding of ER stress associated with placental-related diseases of pregnancy.

Tumorigenic factor CRIPTO-1 is immunolocalized in extravillous cytotrophoblast in placenta creta

CRIPTO-(CR)1 is a protein associated with tumorigenesis and metastasis. Here we demonstrate that CR-1 expression in normal and creta placentas is associated with various degrees of uterine invasion. Cytokeratin (CK) and CR-1 protein expression was visualized by immunohistochemical staining of formalin-fixed, paraffin-embedded placental specimens (control placentas, n = 9; accreta, n = 6; increta, n = 10; percreta, n = 15). The pattern of extravillous trophoblast (EVT) cell morphology was distinctive in creta placentas: densely-compacted cell columns and large star-shaped cells with a typically migratory phenotype, not common among third trimester control placentas. Quantification revealed higher CR-1 immunoreactivities in accreta (P = 0.001), increta (P = 0.0002), and percreta placentas (P = 0.001) than in controls. In contrast to controls, there was a significant positive relationship between CR-1 and CK reactivity in all creta placentas (accreta, P = 0.02; increta, P = 0.0001, and percreta, P = 0.025). This study demonstrated CR-1 expression in the placental bed, its increased expression in creta placentas, and EVT cells as the main CR-1-producing cell type. Morphological examination revealed an immature and invasive trophoblast profile in creta placentas, suggesting impairment of the trophoblast differentiation pathway. These findings provide important new insights into the pathophysiology of abnormal creta placentation and its gestational consequences.

The role of interferons in early pregnancy

The interferons (IFNs) form part of the large family of glycoproteins known as cytokines. They are secreted by host cells as a line of defence against pathogens and certain tumours. IFNs affect cell proliferation and differentiation and also play a very important role in the functioning of the immune system. Miscarriage in both humans has been associated with higher levels of IFN, particularly IFN-γ. However, this cytokine is evidently vital in successful murine pregnancies since it is involved in maintaining the decidual layer in addition to remodelling of the vasculature in the uterus. The effects of IFN on human pregnancies are more difficult to study. Hence, there is still a lot more to be discovered in the hope of reaching a definite conclusion regarding the impact of IFN.

Expression of interferon-γ in decidual natural killer cells from women with hypertensive disorder complicating pregnancy

AIM

Hypertensive disorder complicating pregnancy (HDCP) is one of the most frequent and serious pregnancy-related diseases, which is closely related to disorders of the maternal immune system, especially the local immune microenvironment of the maternal-fetal interface. Uterine decidual natural killer (dNK) cells are the major immune cells in the maternal-fetal interface and they play an important role in establishing and maintaining a normal pregnancy. The aim of this study was to investigate the phenotype and function of dNK cells from women with HDCP.

MATERIAL AND METHODS

Decidual tissues were collected from women with normal pregnancy (normal control group, n = 15 cases) and HDCP (HDCP group, n = 20 cases), respectively. The mononuclear cells were extracted from tissues and flow cytometry (FCM) was utilized to sort out dNK cells. The phenotypes of dNK cells (CD56(bright)CD16⁻CD3⁻ vs CD56(dim)CD16⁺CD3⁻) were detected by FCM. After being co-cultured with Phorbol 12-myristate 13-acetate, ionomycin and monensin, the expression level of interferon (IFN)-γ in the dNK cells was detected by FCM.

RESULTS

The phenotypes of dNK cells from the two groups were dominated by the CD56(bright)CD16⁻CD3⁻ subset, with no significant statistical difference (P < 0.05). The expression level of IFN-γ in the dNK cells from women with HDCP was on a lower trend than those from women with normal pregnancy, having significant statistical difference (P = 0.000 < 0.05).

CONCLUSIONS

Our results indicated that although the phenotype of dNK cells from women with HDCP is of no difference, their functions are abnormal. Impaired cell function leads to a lower expression level of IFN-γ and this may account for one of the pathogeneses of HDCP.

Expression of angiogenic factors in placenta of stressed rats

The aim of the present study was to analyse the influence of stress on pregnant rats, particularly in terms of maternal, placental and fetal weight, placental morphology and placental gene expression of the angiogenic factors Vegfa and Pgf and their receptors. The parameters were evaluated on gestation Day 20. Maternal, fetal and placental weights were statistically lower in stressed animals than controls, suggesting abnormalities in gestational physiology. Morphologically the placentas of rats subjected to stress were reduced in size and weight, with few glycogen cells and a significant increase in the number of apoptotic cells. Stress caused an increase in placental gene expression of Vegfa (P<0.05) and a reduction in Pgf, Flt1 and Kdr expression (P<0.05). It has been suggested that increased VEGF is associated with vasodilatation and hypotension, but in this model persistent hypertension was present. This study suggests that the limited hypotensive Vegfa response to stress-induced hypertension could result from reduced expression of Flt1/Kdr disrupting specific VEGF pathways. These findings may elucidate one of the multiple possible factors underlying how stress modulates placental physiology, and could aid the understanding of stress-induced gestational disorders.

NADPH oxidase as an important source of reactive oxygen species at the mouse maternal-fetal interface: putative biological roles

Oxygen derivatives that comprise the large family of reactive oxygen species (ROS) are actively involved in placental biology. They are generated at the maternal-fetal interface at the level of decidual, trophoblast and mesenchymal components. In normal conditions, ROS produced in low concentrations participate in different functions as signalling molecules, regulating activation of redox-sensitive transcription factors and protein kinases involved in cell survival, proliferation and apoptosis, hence much of cell functioning. Physiological ROS generation is also associated with such defence mechanisms as phagocytosis and microbiocidal activities. In mice, particularly but not exclusively, trophoblast cells phagocytose intensively during implantation and post-implantation periods and express enzymic machinery to address a ROS-producing response to changes in the environment. The cells directly associated with ROS production are trophoblast giant cells, which mediate each and every relationship with the maternal organism. In this review, the production of ROS by the implanting mouse trophoblast is discussed, focusing on NADPH oxidase expression, regulatory mechanisms and similarities with NOX2 from phagocytes. Some of the current controversies are assessed by attempting to integrate data from studies in human trophoblast and mouse models.

Reactive oxygen species-triggered trophoblast apoptosis is initiated by endoplasmic reticulum stress via activation of caspase-12, CHOP, and the JNK pathway in Toxoplasma gondii infection in mice

Toxoplasma gondii infection in pregnant women may result in abortion or in fetal teratogenesis; however, the underlying mechanisms are still unclear. In this paper, based on a murine model, we showed that maternal infection with RH strain T. gondii tachyzoites induced elevated production of reactive oxygen species (ROS), local oxidative stress, and subsequent apoptosis of placental trophoblasts. PCR array analysis of 84 oxidative stress-related genes demonstrated that 27 genes were upregulated at least 2-fold and that 9 genes were downregulated at least 2-fold in the T. gondii infection group compared with levels in the control group. The expression of NADPH oxidase 1 (Nox1) and glutathione peroxidase 6 (Gpx6) increased significantly, about 25-fold. The levels of malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) increased significantly with T. gondii infection, and levels of glutathione (GSH) decreased rapidly. T. gondii infection increased the early expression of endoplasmic reticulum stress (ERS) markers, followed by cleavage of caspase-12, activation of ASK1/JNK, and increased apoptosis of trophoblasts, both in vivo and in vitro. The apoptosis of trophoblasts, the activation of caspase-12 and the ASK1/JNK pathway, and the production of peroxides were dramatically inhibited by pretreatment with N-acetylcysteine (NAC). The upregulation of Nox1 was contact dependent and preceded the increase in levels of ERS markers and the activation of the proapoptosis cascade. Thus, we concluded that apoptosis in placental trophoblasts was initiated predominantly by ROS-mediated ERS via activation of caspase-12, CHOP, and the JNK pathway in acute T. gondii infection. Elevated ROS production is the central event in T. gondii-induced apoptosis of placental trophoblasts.

Tumor necrosis factor receptor subfamily 9 (Tnfrsf9) gene is expressed in distinct cell populations in mouse uterus and conceptus during implantation period of pregnancy

Tumor necrosis factor receptor subfamily 9 (TNFRSF9) plays a potentially important general role in immune function. Tnfrsf9 gene expression has previously been characterized in late pregnant mouse uterus and placenta. However, little is known about its expression in the uterus during the implantation phase of early pregnancy. We have assessed the levels and localization of Tnfrsf9 expression in the mouse uterus and conceptus during implantation. Relative Tnfrsf9 mRNA levels were significantly higher in implantation than in non-implantation site tissue on days 6.5-8.5 of pregnancy. This increase did not depend on the presence of the conceptus, as mRNA levels were not significantly different between pregnant implantation sites and artificially induced deciduomas. Localization by in situ hybridization revealed a subpopulation of endothelial and uterine natural killer cells expressing Tnfrsf9 in the endometrium during implantation. In the developing conceptus, primary trophoblast giant and ectoplacental cells expressed Tnfrsf9 on days 6.5-8.5, followed by expression in the trophoblast giant cell layers surrounding the conceptus on day 9.5 of pregnancy. Two main splice forms of Tnfrsf9 mRNA exist and encode proteins with distinct biological functions; both mRNA splice forms were present in uterine and conceptus tissues as determined by reverse transcription with the polymerase chain reaction. Thus, both membrane and soluble forms of Tnfrsf9 are expressed in specific cell types of the uterus and conceptus during the progression of implantation in mice and possibly have an important function in this process.

Histone deacetylases inhibit IFN-gamma-inducible gene expression in mouse trophoblast cells

Trophoblast cells are the first cells to differentiate from the developing mammalian embryo, and they subsequently form the blastocyst-derived component of the placenta. IFN-gamma plays critical roles in activating innate and adaptive immunity, as well as apoptosis. In mice, IFN-gamma is produced in the pregnant uterus, and is essential for formation of the decidual layer of the placenta and remodeling of the uterine vasculature. Responses of mouse trophoblast cells to IFN-gamma appear to be selective, for IFN-gamma activates MHC class I expression and enhances phagocytosis, but fails to activate either MHC class II expression or apoptosis in these cells. To investigate the molecular basis for the selective IFN-gamma responsiveness of mouse trophoblast cells, IFN-gamma-inducible gene expression was examined in the trophoblast cell lines SM9 and M-11, trophoblast stem cells, and trophoblast stem cell-derived giant cells. IFN-gamma-inducible expression of multiple genes, including IFN regulatory factor-1 (IRF-1), was significantly reduced in trophoblast cells compared with fibroblast cells. Decreased IRF-1 mRNA expression in trophoblast cells was due to a reduced rate of IRF-1 transcription relative to fibroblast cells. However, no impairment of STAT-1 tyrosine phosphorylation or DNA-binding capacity was observed in IFN-gamma-treated mouse trophoblast cells. Importantly, histone deacetylase (HDAC) inhibitors significantly enhanced IFN-gamma-inducible gene expression in trophoblast cells, but not fibroblasts. Our collective studies demonstrate that IFN-gamma-inducible gene expression is repressed in mouse trophoblast cells by HDACs. We propose that HDAC-mediated inhibition of IFN-gamma-inducible gene expression in mouse trophoblast cells may contribute to successful pregnancy by preventing activation of IFN-gamma responses that might otherwise facilitate the destruction of the placenta.

Interferon gamma in successful pregnancies

Interferon gamma (IFNG) is a proinflammatory cytokine secreted in the uterus during early pregnancy. It is abundantly produced by uterine natural killer cells in maternal endometrium but also by trophoblasts in some species. In normal pregnancies of mice, IFNG plays critical roles that include initiation of endometrial vasculature remodeling, angiogenesis at implantation sites, and maintenance of the decidual (maternal) component of the placenta. In livestock and in humans, deviations in these processes are thought to contribute to serious gestational complications, such as fetal loss or preeclampsia. Interferon gamma has broader roles in activation of innate and adaptive immune responses to viruses and tumors, in part through upregulating transcription of genes involved in cell cycle regulation, apoptosis, and antigen processing/presentation. Despite this, rodent and human trophoblast cells show dampened responses to IFNG that reflect the resistance of these cells to IFNG-mediated activation of major histocompatibility complex (MHC) class II transplantation antigen expression. Lack of MHC class II antigens on trophoblasts is thought to facilitate survival of the semiallogeneic conceptus in the presence of maternal lymphocytes. This review describes the dynamic roles of IFNG in successful pregnancy and briefly summarizes data on IFNG in gestational pathologies.

INTERFEROME: the database of interferon regulated genes

INTERFEROME is an open access database of types I, II and III Interferon regulated genes (http://www.interferome.org) collected from analysing expression data sets of cells treated with IFNs. This database of interferon regulated genes integrates information from high-throughput experiments with annotation, ontology, orthologue sequences from 37 species, tissue expression patterns and gene regulatory information to enable a detailed investigation of the molecular mechanisms underlying IFN biology. INTERFEROME fulfils a need in infection, immunity, development and cancer research by providing computational tools to assist in identifying interferon signatures in gene lists generated by high-throughput expression technologies, and their potential molecular and biological consequences.