Interferon tau regulates PGF2alpha release from the ovine endometrial epithelial cells via activation of novel JAK/EGFR/ERK/EGR-1 pathways

Effect of mastitis during early-stage pregnancy on the immunity levels and pregnancy function of goats

In this study, we investigated the effects of mammary inflammation induced by lipopolysaccharide (LPS) and Staphylococcus aureus (SA) infusions on pregnancy function during early pregnancy in goats. In Experiment 1, pregnant goats were subjected to an intramammary LPS infusion for 1 week from Days 60-66 after natural mating (n = 5), and in Experiment 2, they received intramammary infusions of either saline, LPS, or SA for 1 week from Days 45-51 after natural mating (n = 15). Blood was collected to determine the plasma cytokine, cortisol, 13,14-dihydro-15-keto-prostaglandin F2α (PGFM), and progesterone levels. Pregnancy length was significantly longer in the LPS-treated group than that for the saline-treated group of experiment 2. Cytokine levels (IL-1β, IL-8, Tumor necrosis factor-α: TNF-α) after LPS (in both Experiments 1 and 2) and SA (in Experiment 2) infusion were significantly higher compared with those before infusion. In Experiment 2, the SA-infused group showed significantly higher TNF-α concentrations than those in the saline group. Cortisol levels increased in both experiment 1 and 2 after LPS infusion, but not after saline and SA treatments. Furthermore, PGFM levels increased after LPS infusion in Experiment 1. In Experiment 2, LPS- and SA-infused goats showed significantly higher PGFM levels than those in the saline-infused goats. However, the progesterone levels decreased after LPS treatment in Experiment 1. Our results show that intramammary LPS infusion during the early stage of pregnancy in goats induces inflammatory cytokine and stress hormone production, which prolongs the pregnancy period.

Extracellular Vesicles Secreted by Pre-Hatching Bovine Embryos Produced In Vitro and In Vivo Alter the Expression of IFNtau-Stimulated Genes in Bovine Endometrial Cells

The embryo-maternal interaction occurs during the early stages of embryo development and is essential for the implantation and full-term development of the embryo. In bovines, the secretion of interferon Tau (IFNT) during elongation is the main signal for pregnancy recognition, but its expression starts around the blastocyst stage. Embryos release extracellular vesicles (EVs) as an alternative mechanism of embryo-maternal communication. The aim of the study was to determine whether EVs secreted by bovine embryos during blastulation (D5-D7) could induce transcriptomic modifications, activating IFNT signaling in endometrial cells. Additionally, it aims to assess whether the EVs secreted by embryos produced in vivo (EVs-IVV) or in vitro (EVs-IVP) have different effects on the transcriptomic profiles of the endometrial cells. In vitro- and in vivo-produced bovine morulae were selected and individually cultured for 48 h to collect embryonic EVs (E-EVs) secreted during blastulation. E-EVs stained with PKH67 were added to in vitro-cultured bovine endometrial cells to assess EV internalization. The effect of EVs on the transcriptomic profile of endometrial cells was determined by RNA sequencing. EVs from both types of embryos induced several classical and non-classical IFNT-stimulated genes (ISGs) and other pathways related to endometrial function in epithelial endometrial cells. Higher numbers of differentially expressed genes (3552) were induced by EVs released by IVP embryos compared to EVs from IVV (1838). Gene ontology analysis showed that EVs-IVP/IVV induced the upregulation of the extracellular exosome pathway, the cellular response to stimulus, and the protein modification processes. This work provides evidence regarding the effect of embryo origin (in vivo or in vitro) on the early embryo-maternal interaction mediated by extracellular vesicles.

Spatiotemporal endometrial transcriptome analysis revealed the luminal epithelium as key player during initial maternal recognition of pregnancy in the mare

During the period of maternal recognition of pregnancy (MRP) in the mare, the embryo needs to signal its presence to the endometrium to prevent regression of the corpus luteum and prepare for establishment of pregnancy. This is achieved by mechanical stimuli and release of various signaling molecules by the equine embryo while migrating through the uterus. We hypothesized that embryo's signals induce changes in the endometrial gene expression in a highly cell type-specific manner. A spatiotemporal transcriptomics approach was applied combining laser capture microdissection and low-input-RNA sequencing of luminal and glandular epithelium (LE, GE), and stroma of biopsy samples collected from days 10-13 of pregnancy and the estrous cycle. Two comparisons were performed, samples derived from pregnancies with conceptuses ≥ 8 mm in diameter (comparison 1) and conceptuses ≤ 8 mm (comparison 2) versus samples from cyclic controls. The majority of gene expression changes was identified in LE and much lower numbers of differentially expressed genes (DEGs) in GE and stroma. While 1253 DEGs were found for LE in comparison 1, only 248 were found in comparison 2. Data mining mainly focused on DEGs in LE and revealed regulation of genes related to prostaglandin transport, metabolism, and signaling, as well as transcription factor families that could be involved in MRP. In comparison to other mammalian species, differences in regulation of genes involved in epithelial barrier formation and conceptus attachment and implantation reflected the unique features of equine reproduction at the time of MRP at the molecular level.

Small extracellular vesicles derived from in vivo- or in vitro-produced bovine blastocysts have different miRNAs profiles-Implications for embryo-maternal recognition

In vivo- and in vitro-produced bovine embryos have different metabolic profiles and differences in gene transcription patterns. These embryos also have a distinct ability to establish and sustain early pregnancies. Small extracellular vesicles (sEVs) are secreted by embryos and carry bioactive molecules, such as miRNAs. We hypothesize that in vivo or in vitro-produced bovine hatched blastocysts on Day 9 and the sEVs secreted by them have different miRNA profiles. To address this hypothesis, embryos of both groups were placed in in vitro culture on Day 7. After 48 h, hatched embryos and hatched embryo-conditioned media (eCM) of both groups were collected. A total of 210 miRNAs were detected in embryos of both groups, of these 6 miRNAs were downregulated, while 7 miRNAs were upregulated in vitro group when compared to in vivo group. sEVs were isolated from eCM to determine miRNA profile. A total of 106 miRNAs were detected in both groups, including 14 miRNAs upregulated in sEVs from in vivo-eCM, and 2 miRNAs upregulated in sEVs from in vitro-eCM. These miRNAs express in embryos and sEVs secreted by them regulate early embryonic developmental and endometrial pathways, which can modify embryo-maternal communication during early pregnancy and consequently affect pregnancy establishment.

Progesterone stimulates histone citrullination to increase IGFBP1 expression in uterine cells

Peptidylarginine deiminases (PAD) enzymes were initially characterized in uteri, but since then little research has examined their function in this tissue. PADs post-translationally convert arginine residues in target proteins to citrulline and are highly expressed in ovine caruncle epithelia and ovine uterine luminal epithelial (OLE)-derived cell line. Progesterone (P4) not only maintains the uterine epithelia but also regulates the expression of endometrial genes that code for proteins that comprise the histotroph and are critical during early pregnancy. Given this, we tested whether P4 stimulates PAD-catalyzed histone citrullination to epigenetically regulate expression of the histotroph gene insulin-like growth factor binding protein 1 (IGFBP1) in OLE cells. 100 nM P4 significantly increases IGFBP1 mRNA expression; however, this increase is attenuated by pre-treating OLE cells with 100 nM progesterone receptor antagonist RU486 or 2 µM of a pan-PAD inhibitor. P4 treatment of OLE cells also stimulates citrullination of histone H3 arginine residues 2, 8, and 17 leading to enrichment of the ovine IGFBP1 gene promoter. Since PAD2 nuclear translocation and catalytic activity require calcium, we next investigated whether P4 triggers calcium influx in OLE cells. OLE cells were pre-treated with 10 nM nicardipine, an L-type calcium channel blocker, followed by stimulation with P4. Using fura2-AM imaging, we found that P4 initiates a rapid calcium influx through L-type calcium channels in OLE cells. Furthermore, this influx is necessary for PAD2 nuclear translocation and resulting citrullination of histone H3 arginine residues 2, 8, and 17. Our work suggests that P4 stimulates rapid calcium influx through L-type calcium channels initiating PAD-catalyzed histone citrullination and an increase in IGFBP1 expression.

Downregulated luteolytic pathways in the transcriptome of early pregnancy bovine corpus luteum are mimicked by interferon-tau in vitro

Background

Maintenance of the corpus luteum (CL) beyond the time of luteolysis is essential for establishing pregnancy. Identifying the distinct features of early pregnancy CL remains unresolved, hence we analyzed here the transcriptome of CL on day 18 pregnant (P) and non-pregnant (NP) cows using RNA-Seq. CL of P cows expressed ISGs, verifying exposure to the pregnancy recognition signal, interferon-tau (IFNT), whereas the CL of NP cows had elevated luteal progesterone levels, implying that luteolysis had not yet commenced.

Results

The DEGs, IPA, and metascape canonical pathways, along with GSEA analysis, differed markedly in the CL of P cows from those of NP cows, at the same day of the cycle. Both metascape and IPA identified similar significantly enriched pathways such as interferon alpha/beta, sonic hedgehog pathway, TNFA, EDN1, TGFB1, and PDGF. However, type-1 interferon and sonic hedgehog pathways were positively enriched whereas most of the enriched pathways were downregulated in the P compared to NP samples. Thirty-four % of these pathways are known to be elevated by PGF2A during luteolysis. Notably, selective DEGs in luteinized granulosa cells were modulated by IFNT in vitro in a similar manner to their regulation in the CL of P cows.

Conclusion

This study unraveled the unique transcriptomic signature of the IFNT-exposed, early pregnancy CL, highlighting the abundance of downregulated pathways known to be otherwise induced during luteolysis. These and IFNT-regulated in vitro pregnancy-specific DEGs suggest that IFNT contributes to the characteristics and maintenance of early pregnancy CL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07747-3.

Mechanisms for the establishment and maintenance of pregnancy: synergies from scientific collaborations

Research on the functions of interferon tau (IFNT) led to the theory of pregnancy recognition signaling in ruminant species. But IFNT does much more as it induces expression of interferon regulatory factor 2 (IRF2) in uterine luminal (LE), superficial glandular (sGE), but not glandular (GE) epithelia. First, IRF2 silences transcription of the estrogen receptor alpha gene and, indirectly, transcription of the oxytocin receptor gene to abrogate development of the luteolytic mechanism to prevent regression of the corpus luteum and its production of progesterone for establishing and maintaining pregnancy. Second, IRF2 silences expression of classical interferon-stimulated genes in uterine LE and sGE; however, uterine LE and sGE respond to progesterone (P4) and IFNT to increase expression of genes for transport of nutrients into the uterine lumen such as amino acids and glucose. Other genes expressed by uterine LE and sGE encode for adhesion molecules such as galectin 15, cathepsins, and cystatins for tissue remodeling, and hypoxia-inducible factor relevant to angiogenesis and survival of blastocysts in a hypoxic environment. IFNT is also key to a servomechanism that allows uterine epithelia, particularly GE, to proliferate and to express genes in response to placental lactogen and placental growth hormone in sheep. The roles of secreted phosphoprotein 1 are also discussed regarding its role in implantation in sheep and pigs, as well as its stimulation of expression of mechanistic target of rapamycin mRNA and protein which is central to proliferation, migration, and gene expression in the trophectoderm cells.

Hormone regulates endometrial function via cooperation of endoplasmic reticulum stress and mTOR-autophagy

In ruminant, the receptive endometrium and the elongation of the hatched blastocyst are required to complete the process of implantation. However, the mechanisms regulating goat endometrial function during the peri-implantation period of pregnancy are still unclear. In this study, EECs were treated with progesterone, estradiol, and interferon-tau (IFNT). We have found that endoplasmic reticulum (ER) stress was activated under hormones treatment. To identify the cellular mechanism of regulation of endometrial function, we investigated the effect of ER stress activator thapsigargin (TG) and inhibitor 4 phenyl butyric acid (4-PBA) on EECs. We found that TG, which activated the three branches of UPR, increased the expression of genes associated with promoting conceptus elongation and cellular attachment, significantly up-regulated the spheroid attachment rate and PGE₂ /PGF_2α ratio. 4-PBA pre-treatment inhibited UPR and inhibited promoting conceptus elongation and cellular attachment related genes, but the spheroid attachment rate and PGE₂ /PGF_2α ratio were not changed significantly. Moreover, knockdown of ATF6 via shATF6 promoted the conceptus elongation related genes, but increased the dissolution of the corpus luteum. Besides, blocking ATF6 attenuated autophagy by activating mammalian target of rapamycin (mTOR) pathway. Moreover, rapamycin (mTOR inhibitor) pre-treatment inhibited the expression of promoting conceptus elongation and increased PGE₂ /PGF_2α ratio. Taken together, our study indicated that physiological level of ER stress may contribute to early pregnancy success, and ATF6 signaling pathway cooperated with autophagy to regulate endometrial function by modulating mTOR pathway.

JAK3 and PI3K mediate bovine Interferon-tau stimulated gene expression in the blood neutrophils

Interferon tau, a 23 kDa trophoblast derived protein diffuses out from the uterus into the circulation and leads to the expression of IFNτ stimulated genes viz. ISG15 and OAS1 in blood neutrophils. The IFNτ pathway is species as well as tissue specific. To unsnarl the IFNτ downstream signaling pathway, the blood neutrophils were incubated simultaneously with 10 ng/ml of recombinant bovine interferon tau and the inhibitors of JAK2 (AG490), JAK3 (CP690550), p38 (SB202190), PI3K/Akt (LY294002), and MAPK/Erk (U0126) at specific doses for 4-hr duration. The IFNτ pathway was determined through real-time gene expression of ISG15 and OAS1; immunocytochemistry of ISG15; and Western blotting of ISG15, OAS1, pJAK3 and PI3K. The ISG15 and OAS1 expression decreased significantly (p < 0.001) in the presence of pJAK3 and PI3K inhibitors as compared to a positive control where only interferon tau was used. Immunocytochemistry revealed an attenuated ISG15 response while stimulating blood neutrophils with pJAK3 inhibitor (CP690550) and PI3K inhibitor (LY294002). Similarly, Western blot analysis of neutrophil protein fraction showed weak signals of ISG15, OAS1, pJAK3 and PI3K in the presence of pJAK3 and PI3K inhibitors. The expression profile, immunocytochemistry and western blot analysis revealed a JAK3 and PI3K mediated interferon-tau stimulated gene expression in blood neutrophils.

Paracrine and endocrine actions of interferon tau (IFNT)

This review focuses on the paracrine and endocrine actions of interferon tau (IFNT) during pregnancy recognition and establishment in ruminants. Pregnancy recognition involves the suppression of the endometrial luteolytic mechanism by the conceptus to maintain progesterone production by the corpus luteum (CL). The paracrine antiluteolytic effects of conceptus-derived IFNT inhibit upregulation of oxytocin receptors in the endometrial epithelia of the uterus, thereby preventing the production of luteolytic prostaglandin F2 alpha (PGF2α) pulses. In the endometrium, IFNT induces or upregulates a large number of classical IFN-stimulated genes (ISGs) and regulates expression of many other genes in a cell-specific manner that are likely important for conceptus elongation, implantation and establishment of pregnancy. Further, IFNT has endocrine effects on extrauterine cells and tissues. In sheep, IFNT induces luteal resistance to PGF2α, thereby ensuring survival of the CL for maintenance of pregnancy. The ISGs induced in circulating peripheral blood mononuclear cells by IFNT may also be useful as an indicator of pregnancy status in cattle. An increased knowledge of IFNT and ISGs is important to improve the reproductive efficiency in ruminants.

Interferon-tau promotes luteal endothelial cell survival and inhibits specific luteolytic genes in bovine corpus luteum

Interferon-tau (IFNT), a maternal recognition of pregnancy (MRP) signals in domestic ruminants, suppresses the release of luteolytic pulses of uterine prostaglandin F2a (PGF2a), thus extending the corpus luteum (CL) life span. We hypothesized that IFNT also exerts anti-luteolytic actions in bovine CL. To examine the direct effects of IFNT on bovine CL, luteal slices and enriched luteal endothelial cells (LECs) were utilized. We found that recombinant ovine IFNT (roIFNT) markedly elevates interferon-associated genes (STAT1, STAT2 and IRF9) and interferon-stimulated genes (ISGs: MX2, ISG15 and OAS1Y) in both models. Furthermore, IFNT time-dependently induced STAT1 phosphorylation in LECs without affecting total STAT1. roIFNT-stimulated viable LECs numbers and the knockdown of protein inhibitor of activated STAT1 (PIAS1) abolished this effect, suggesting that PIAS1 may mediate the proliferative effect of IFNT. IFNT significantly downregulated luteolytic genes such as TGFB1, thrombospondin-1 (THBS1), endothelin-1 (EDN1) and serpin family E member-1 (SERPINE1) in LECs. However, less robust effects were observed in luteal slices. Moreover, PGF2a alone induced THBS1, SERPINE1 and EDN1 mRNA in CL slices whereas in the presence of IFNT, THBS1 and SERPINE1 stimulation was abolished. Collectively, these results indicate that IFNT acts via STAT1- IRF9-dependent and independent pathways and affects diverse luteal functions. Most interestingly, this study suggests the existence of an anti-luteolytic effect of IFNT in bovine CL, namely, inhibiting key PGF2a-induced luteolytic genes. The proliferative effect of IFNT may constitute an additional mechanism that promotes luteal cell survival, thus, extending the luteal life span during early pregnancy in cows.

Effects of interferon tau on endometrial epithelial cells in caprine in vitro

Embryo attachment, a precondition of ruminant pregnancy, has been recognized to be related to apoptosis in endometrial epithelial cells (EECs). In ruminants, interferon tau (IFNT) is secreted by trophoblast of conceptus and works in a concentration-dependent style. To verify the function of IFNT in caprine embryo attachment, caprine EECs were dealt with IFNT at 0, 1, 10 and 100 ng/ml. In this study, IFNT arrested caprine EEC cell cycle in G2 phase and induced cell apoptosis at 1 ng/ml and 10 ng/ml of IFNT. Interestingly, pro-apoptotic protein FAS and PRβ together with anti-apoptotic proteins SP1 and IGF1R were all up-regulated at 1 ng/ml of IFNT. It demonstrated that IFNT at 1 ng/ml might induce caprine EEC apoptosis and keep a balance between apoptosis and proliferation. Furthermore, regulation of HOXA10, COX-2, PRL, PTEN and STAT3 pathway in caprine EECs was likely to be contributed by IFNT at 1 ng/ml to improve the chances for embryo attachment.

Chromium VI - Induced developmental toxicity of placenta is mediated through spatiotemporal dysregulation of cell survival and apoptotic proteins

Environmental contamination with hexavalent chromium (CrVI) is a growing problem both in the U.S and developing countries. CrVI is a heavy-metal endocrine disruptor; women working in Cr industries exhibit an increased incidence of premature abortion and infertility. The current study was designed to understand the mechanism of CrVI toxicity on placental cell survival/death pathways. Pregnant mothers were treated with or without CrVI (50ppmK₂Cr₂O₇) through drinking water from gestational day (GD) 9.5-14.5, and placentas were analyzed on GD 18.5. Results indicated that CrVI increased apoptosis of trophoblasts, vascular endothelium of the metrial glands and yolk sac epithelium through caspase-3 and p53-dependent pathways. CrVI increased apoptosis in labyrinth and basal zones in a caspase-3-independent manner via AIF, and through an ATM-p53-NOXA-PUMA-p27 network. CrVI downregulated cell survival proteins Bcl-2, Bcl-XL and XIAP in the placenta. CrVI disrupts placental histoarchitecture and increases cell death by spatiotemporal modulation of apoptotic signaling.

Novel concepts on the role of prostaglandins on luteal maintenance and maternal recognition and establishment of pregnancy in ruminants

In ruminants, the corpus luteum (CL) of early pregnancy is resistant to luteolysis. Prostaglandin (PG)E2 is considered a luteoprotective mediator. Early studies indicate that during maternal recognition of pregnancy (MRP) in ruminants, a factor(s) from the conceptus or gravid uterus reaches the ovary locally through the utero-ovarian plexus (UOP) and protects the CL from luteolysis. The local nature of the embryonic antiluteolytic or luteoprotective effect precludes any direct effect of a protein transported or acting between the gravid uterus and CL in ruminants. During MRP, interferon tau (IFNT) secreted by the trophoblast of the conceptus inhibits endometrial pulsatile release of PGF2α and increases endometrial PGE2. Our recent studies indicate that (1) luteal PG biosynthesis is selectively directed toward PGF2α at the time of luteolysis and toward PGE2 at the time of establishment of pregnancy (ESP); (2) the ability of the CL of early pregnancy to resist luteolysis is likely due to increased intraluteal biosynthesis and signaling of PGE2; and (3) endometrial PGE2 is transported from the uterus to the CL through the UOP vascular route during ESP in sheep. Intrauterine co-administration of IFNT and prostaglandin E2 synthase 1 (PGES-1) inhibitor reestablishes endometrial PGF2α pulses and regresses the CL. In contrast, intrauterine co-administration of IFNT and PGES-1 inhibitor along with intraovarian administration of PGE2 rescues the CL. Together, the accumulating information provides compelling evidence that PGE2 produced by the CL in response to endometrial PGE2 induced by pregnancy may counteract the luteolytic effect of PGF2α as an additional luteoprotective mechanism during MRP or ESP in ruminants. Targeting PGE2 biosynthesis and signaling selectively in the endometrium or CL may provide luteoprotective therapy to improve reproductive efficiency in ruminants.

Early pregnancy modulates survival and apoptosis pathways in the corpus luteum in sheep

The corpus luteum (CL) is a transient endocrine gland. Functional and structural demise of the CL allows a new estrous cycle. On the other hand, survival of CL and its secretion of progesterone are required for the establishment of pregnancy. Survival or apoptosis of the luteal cells is precisely controlled by interactions between survival and apoptosis pathways. Regulation of these cell signaling components during natural luteolysis and establishment of pregnancy is largely unknown in ruminants. The objective of the present study was to determine the regulation of survival and apoptosis signaling protein machinery in the CL on days 12, 14, and 16 of the estrous cycle and pregnancy in sheep. Results indicate that: i) expressions of p-ERK1/2, p-AKT, β-catenin, NFκB -p65, -p50, -p52, p-Src, p-β -arrestin, p-GSK3β, X-linked inhibitor of apoptosis protein (XIAP), and p-CREB proteins are suppressed during natural luteolysis; in contrast, their expressions are sustained or increased during establishment of pregnancy; ii) expressions of cleaved caspase-3, apoptosis inducing factor (AIF), c-Fos, c-Jun, and EGR-1 proteins are increased during natural luteolysis; in contrast, their expressions are decreased during establishment of pregnancy; and iii) expressions of Bcl-2, Bcl-XL, Bad, and Bax proteins are not modulated during natural luteolysis while expressions of Bcl2 and Bcl-XL proteins are increased during establishment of pregnancy in sheep. These proteomic changes are evident in both large and small luteal cells. These results together indicate that regression of the CL during natural luteolysis or survival of the CL during establishment of pregnancy is precisely controlled by distinct programmed suppression or activation of intraluteal cell survival and apoptosis pathways in sheep/ruminants.

Maternal organism and embryo biosensoring: insights from ruminants

In terms of contribution to pregnancy, the mother not only produces gametes, but also hosts gestation, whose progression in the uterus is conditioned by early events during implantation. In ruminants, this period is associated with elongation of the extra-embryonic tissues, gastrulation of the embryonic disk and cross-talk with the endometrium. Recent data have prompted the need for accurate staging of the bovine conceptus and shown that asynchrony between elongation and gastrulation processes may account for pregnancy failure. Data mining of endometrial gene signatures has allowed the identification of molecular pathways and new factors regulated by the conceptus (e.g. FOXL2, SOCS6). Interferon-tau has been recognised to be the major signal of pregnancy recognition, but prostaglandins and lysophospholipids have also been demonstrated to be critical players at the conceptus-endometrium interface. Interestingly, up-regulation of interferon-regulated gene expression has been identified in circulating immune cells during implantation, making these factors a potential source of non-invasive biomarkers for early pregnancy. Distinct endometrial responses have been shown to be elicited by embryos produced by artificial insemination, in vitro fertilisation or somatic cell nuclear transfer. These findings have led to the concept that endometrium is an early biosensor of embryo quality. This biological property first demonstrated in cattle has been recently extended and associated with embryo selection in humans. Hence, compromised or suboptimal endometrial quality can subtly or deeply affect embryo development, with visible and sometimes severe consequences for placentation, foetal development, pregnancy outcome and the long-term health of the offspring.

Conceptus elongation in ruminants: roles of progesterone, prostaglandin, interferon tau and cortisol

The majority of pregnancy loss in ruminants occurs during the first three weeks after conception, particularly during the period of conceptus elongation that occurs prior to pregnancy recognition and implantation. This review integrates established and new information on the biological role of ovarian progesterone (P4), prostaglandins (PGs), interferon tau (IFNT) and cortisol in endometrial function and conceptus elongation. Progesterone is secreted by the ovarian corpus luteum (CL) and is the unequivocal hormone of pregnancy. Prostaglandins (PGs) and cortisol are produced by both the epithelial cells of the endometrium and the trophectoderm of the elongating conceptus. In contrast, IFNT is produced solely by the conceptus trophectoderm and is the maternal recognition of pregnancy signal that inhibits production of luteolytic pulses of PGF_2α by the endometrium to maintain the CL and thus production of P4. Available results in sheep support the idea that the individual, interactive, and coordinated actions of P4, PGs, IFNT and cortisol regulate conceptus elongation and implantation by controlling expression of genes in the endometrium and/or trophectoderm. An increased knowledge of conceptus-endometrial interactions during early pregnancy in ruminants is necessary to understand and elucidate the causes of infertility and recurrent early pregnancy loss and provide new strategies to improve fertility and thus reproductive efficiency.

Interferon receptor signaling in malignancy: a network of cellular pathways defining biological outcomes

IFNs are cytokines with important antiproliferative activity and exhibit key roles in immune surveillance against malignancies. Early work initiated over three decades ago led to the discovery of IFN receptor activated Jak-Stat pathways and provided important insights into mechanisms for transcriptional activation of IFN-stimulated genes (ISG) that mediate IFN biologic responses. Since then, additional evidence has established critical roles for other receptor-activated signaling pathways in the induction of IFN activities. These include MAPK pathways, mTOR cascades, and PKC pathways. In addition, specific miRNAs appear to play a significant role in the regulation of IFN signaling responses. This review focuses on the emerging evidence for a model in which IFNs share signaling elements and pathways with growth factors and tumorigenic signals but engage them in a distinctive manner to mediate antiproliferative and antiviral responses.

Intrauterine coadministration of ERK1/2 inhibitor U0126 inhibits interferon TAU action in the endometrium and restores luteolytic PGF2alpha pulses in sheep

In ruminants, prostaglandin F2 alpha (PGF2alpha) is synthesized and released in a pulsatile pattern from the endometrial luminal epithelial (LE) cells during the process of luteolysis. Interferon tau (IFNT) is a Type 1 IFN secreted by the trophoblast cells of the developing conceptus. IFNT acts locally on endometrial LE cells to inhibit pulsatile releases of PGF2alpha and thus establish an endocrine environment for recognition of pregnancy. Cell signaling pathways through which IFNT stimulates expression of multiple genes or proteins in endometrial LE are largely unknown. Results of the present investigation indicate that intrauterine administration of IFNT inhibits pulsatile release of PGF2alpha, while coadministration IFNT and ERK 1/2 inhibitor U0126 restores luteolytic PGF2alpha pulses in sheep. IFNT increases phosphorylation of ERK1/2 proteins and increases its interaction with PGT proteins in endometrial LE. Blockade of ERK1/2 pathways inhibits IFNT action, decreases pERK1/2 and PGT protein interactions, and re-establishes the spatial expression of the oxytocin receptor protein completely and the estrogen receptor protein partially without modulating the expression of interferon regulatory factor-2 (IRF-2) protein in endometrial LE. IFNT does not decrease expression of COX-2, PGDH, or PGT protein in endometrial LE. Our results provide important new insights into IFNT signaling and the molecular endocrine control of PGF2alpha release at the time of establishment of pregnancy in ruminants. This novel IFNT-ERK1/2 signaling module needs to be explored in future studies to understand molecular and cellular mechanisms of IFNT action in endometrial LE in ruminants.

Intrauterine inhibition of prostaglandin transporter protein blocks release of luteolytic PGF2alpha pulses without suppressing endometrial expression of estradiol or oxytocin receptor in ruminants

In ruminants, prostaglandin F2 alpha (PGF2(alpha)) is synthesized and released in a pulsatile pattern from the endometria luminal epithelial (LE) cells during the process of luteolysis. Prostaglandin transporter (PGT) is a 12-transmembrane solute carrier organic anion transporter protein that facilitates transport of PGF2(alpha). The present study determined the effects of inhibition of PGT protein on pulsatile release of luteolytic PGF2(alpha) and the underlined cell-signaling mechanisms. The results indicate that intrauterine inhibition of the PGT protein inhibits the pulsatile release of PGF2(alpha) from the endometrium and maintains a functional corpus luteum. Surprisingly, inhibition of PGT-mediated luteolytic pulses is not associated with spatial regulation of estrogen and oxytocin receptors in the LE of the endometrium and is also not accompanied by decreased biosynthesis of PGF2(alpha) or increased catabolism of PGF2(alpha) by the endometrium. Importantly, PGT inhibitor increases expression of pERK1/2 proteins in the LE of the endometrium. Knock down of ERK1/2 genes in LE cells reverses the inhibitory effects of PGT inhibitor on release of PGF2(alpha). In conclusion, intrauterine inhibition of PGT inhibits the pulsatile release of PGF2(alpha) from the endometrium without modulating spatial expressions of estrogen and oxytocin receptor proteins and metabolism of PGF2(alpha) at the time of luteolysis. Activation of ERK1/2 pathways and interactions between ERK1/2 and PGT protein appear to be important cell-signaling mechanisms that control PGT-mediated efflux transport function. PGT emerges as an important final component in the luteolytic machinery that controls the release of luteolytic pulses of PGF2(alpha) from the endometrium in sheep.

Early pregnancy induced expression of prostaglandin E2 receptors EP2 and EP4 in the ovine endometrium and regulated by interferon tau through multiple cell signaling pathways

Prostaglandin E2 (PGE(2)) plays pleiotropic roles at fetal-maternal interface during establishment of pregnancy. The objectives of the study were to: (i) determine regulation of PGE2 receptors EP1, EP2, EP3, and EP4 in the endometrium during the estrous cycle and early pregnancy; and (ii) understand endometrial epithelial and stromal cell-specific hormonal regulation of EP2 and EP4 in sheep. Results indicate that: (i) early pregnancy induces expression of EP2 and EP4 but not EP1 and EP3 proteins in the endometrium on days 12-16 compared to that of estrous cycle; (ii) intrauterine infusion of interferon tau (IFNT) increases expression of EP2 and EP4 proteins in endometrium; and (iii) IFNT activates distinct epithelial and stromal cell-specific JAK, EGFR, ERK1/2, AKT, or JNK signaling module to regulate expression of EP2 and EP4 proteins in the ovine endometrium. Our results indicate a role for EP2 and EP4-mediated PGE(2) signaling in endometrial functions and establishment of pregnancy in ruminants.

The multidrug resistance-associated protein 4 (MRP4) appears as a functional carrier of prostaglandins regulated by oxytocin in the bovine endometrium

Prostaglandins (PG) are involved in several female reproductive processes, and their action is regulated at the levels of biosynthesis, catabolism, and signal transduction. Facilitated transport across cell membranes emerges as an additional checkpoint regulating PG action. We have already reported on the influx transporter solute carrier organic anion transporting polypeptide (SLCO2A1) [PG transporter (PGT)] in relation to PG action in the bovine endometrium. In the present study, we report on the functional expression and regulation of multidrug resistance-associated protein 4 (MRP4)/ATP-binding cassette carrier 4, an alternate PG transporter belonging to the ATP-binding cassette carrier (ABC) family. We have found that MRP4 protein was present throughout the estrous cycle and exhibited a pattern of expression similar to that of PGT with maximal expression during early-mid luteal phase in the bovine endometrium. Functional expression and regulation of MRP4 was studied in vitro using the newly developed bovine endometrial epithelial bEEL and stromal CSC cell lines. Oxytocin (OT) stimulated PGF2α production and MRP4 mRNA and protein in a time- and dose-dependent manner but had no effect on PGT. OT induced preferred accumulation of PG outside the cells and secretion toward the basolateral side of polarized bEEL cells grown on membrane inserts. MK-571 and indomethacin, two documented inhibitors of MRP4 activity, blocked preferred accumulation of PG, but interferon-τ and NS-398 had no effect on MRP4 expression or the direction of PG transport. Our results suggest that MRP4 is a functional PG carrier under the regulation of OT in the bovine endometrium.

ATP-binding cassette ABCC1 is involved in the release of sphingosine 1-phosphate from rat uterine leiomyoma ELT3 cells and late pregnant rat myometrium

Sphingosine 1-phosphate (S1P), a bioactive lipid generated by sphingosine kinases (SphK1/2), initiates different signalling pathways involved in physiological and pathological processes. We previously demonstrated that in rat myometrium at late (day 19) gestation, SphK1 increases the expression of COX2 via S1P generation and release. In rat uterine leiomyoma cells (ELT3), SphK1/S1P axis controls survival and proliferation. In the present study we demonstrate that PDBu activates SphK1 but not SphK2. SphK1 activation requires PKC and MAPK ERK1/2. S1P produced by PDBu is released in the medium. PDBu-induced S1P export is abolished by Ro-318220 and BIM (PKC inhibitors), by U0126 and PD98059 (MEK inhibitors), SKI-II (SphKI/2 inhibitor) and SphK1-siRNA, suggesting the involvement of PKC, ERK and SphK1 respectively. The release of S1P is insensitive to inhibitors of ATP Binding Cassette (ABC)A1 and ABCB1 transporters, but is abolished when ABCC1 transporters are inhibited by MK571 or down-regulated by ABCC1-siRNA. PDBu increases COX2 expression that is blocked by the inhibition of PKC, ERK1/2, SphK1, and when cells are treated with MK571 or transfected with ABCC1-siRNA. The induction of COX2 by the S1P release due to PDBu or by exogenous S1P involves S1P2 receptors coupled to Gi. In myometrium from rat at late gestation, the release of S1P is also strongly reduced when SphK and ABCC1 are inhibited. The data reveal that in rat leiomyoma cells and late pregnant rat myometrium, the release of S1P involves a similar signalling pathway and occurs through ABCC1.