Herbert Fluhr

Interferon-γ and tumor necrosis factor-α sensitize primarily resistant human endometrial stromal cells to Fas-mediated apoptosis

The subtle interaction between the implanting embryo and the maternal endometrium plays a pivotal role during the process of implantation. Human endometrial stromal cells (ESCs) express Fas and the implanting trophoblast cells secrete Fas ligand (FASLG, FasL), suggesting a possible role for Fas-mediated signaling during early implantation. Here we show that ESCs are primarily resistant to Fas-mediated apoptosis independently of their state of hormonal differentiation. Pre-treatment of ESCs with interferon (IFN)-γ and tumor necrosis factor (TNF)-α sensitizes them to become apoptotic upon stimulation of Fas by an agonistic anti-Fas antibody. Incubation of ESCs with the early embryonic signal human chorionic gonadotropin (hCG, CGB) does not influence their reaction to Fas stimulation. The sensitizing effect of IFN-γ and TNF-α was accompanied by a significant upregulation of Fas and FLICE-inhibitory protein (FLIP, CFLAR) expression in ESCs. Additionally, we observed an activation of caspase 3, caspase 8 and caspase 9 upon apoptotic Fas triggering. In summary, we demonstrate that IFN-γ and TNF-α sensitize primarily apoptosis-resistant ESCs to Fas-mediated cell death. This might be due to an upregulation of Fas expression, and apoptosis seems to be mediated by active caspase 3, caspase 8 and caspase 9. The observed pro-apoptotic effect of IFN-γ and TNF-α on ESCs could play an important role in the modulation of early implantation.

Heparin inhibits TNF-α signaling in human endometrial stromal cells by interaction with NF-κB

Heparins have been shown to be beneficial for the prevention of habitual miscarriages and repeated implantation failure, independently of their function as anticoagulants. The pro-inflammatory cytokine tumor necrosis factor (TNF)-α plays a role in the pathogenesis of these early pregnancy complications. Therefore, we examined the impact of heparin on TNF-α signaling in human endometrial stromal cells (ESCs) in vitro. Human ESCs were isolated from hysterectomy specimens and either used as undifferentiated cells or after decidualization in vitro. Cells were incubated with TNF-α, unfractionated heparin and signaling- and transporter-inhibitors. Interleukin (IL)-8 and -6 were measured using ELISAs and real-time RT-PCR. Nuclear factor of transcription (NF)-κB and its inhibitor IκBα were analyzed by in-cell western assays and confocal microscopy. Activation of NF-κB was determined in nuclear extracts using a specific transcription factor assay. Cellular internalization of heparin was detected by a heparin-uptake assay. Unfractionated heparin significantly suppressed the TNF-α-induced and NF-κB-mediated secretion and expression of IL-8 and -6 as well as other molecules in decidualized and undifferentiated human ESCs. Thereby heparin had no influence on the degradation of IκBα and the phosphorylation of NF-κB, but it inhibited the activity of NF-κB in the nucleus. An active heparin-uptake into the cells was the prerequisite for these heparin-effects. Unfractionated heparin is able to inhibit TNF-α/NF-κB-mediated inflammatory effects in the human endometrium independently of its classical function as an anticoagulant. These observations further underline on a molecular level the beneficial anti-inflammatory effects of heparin in women suffering from implantation disorders even in the absence of a thrombophilia.

Nonapoptotic effects of tumor necrosis factor–related apoptosis-inducing ligand on interleukin-6, leukemia inhibitory factor, interleukin-8, and monocyte chemoattractant protein 1 vary between undifferentiated and decidualized human endometrial stromal cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), which is known to exert death-inducing as well as nonapoptotic functions, has been shown to be expressed by the early trophoblast. Here we report that TRAIL has no apoptotic effects on human endometrial stromal cells, but differentially regulates cytokines and chemokines and might therefore play a role in the modulation of the cytokine milieu at the implantation site.

Non-apoptotic Fas-induced regulation of cytokines in undifferentiated and decidualized human endometrial stromal cells depends on caspase-activity

Fas has originally been described as a member of the death-receptor family, mediating apoptosis upon stimulation by Fas-ligand (FasL). However, Fas expressing human endometrial stromal cells (ESCs) are resistant to Fas-mediated apoptosis. Since the implanting embryo secretes FasL, we examined whether Fas mediates non-apoptotic effects in human ESCs in vitro. ESCs were isolated from hysterectomy specimens, decidualized using progesterone and 17β-estradiol and incubated with an activating anti-Fas antibody, recombinant FasL and a caspase-inhibitor. Leukemia inhibitory factor (LIF), interleukin (IL)-11, -6, -8, monocyte chemoattractant protein (MCP)-1 and RANTES (Regulated on Activation Normal T cell Expressed and Secreted) were measured using ELISA and real-time RT-PCR. Viability of ESCs was determined using an MTT assay. Caspase-activity was measured by luminescent assays. Activation of nuclear factor (NF)-κB was detected by in-cell western and transcription factor assays. LIF and IL-11 in undifferentiated and IL-8 in decidualized ESCs were up-regulated by non-apoptotic Fas-signaling. In contrast, IL-6, MCP-1 and RANTES were not regulated by Fas. Caspases were activated upon Fas-stimulation and the Fas-mediated effects on LIF, IL-11 and -8 were reversed by caspase-inhibition. The transcription factor NF-κB was not activated in ESCs after stimulation of Fas. These results suggest a differential regulatory role of caspase-dependent Fas-signaling at the feto-maternal interface during early implantation. Remarkably, this typical death machinery mediates non-apoptotic effects in the human endometrium rather than inducing apoptosis.

Constitutive activity of Erk1/2 and NF-κB protects human endometrial stromal cells from death receptor-mediated apoptosis

Apoptosis in the human endometrium plays an essential role for endometrial receptivity and early implantation. A dysbalance of pro- and anti-apoptotic events in the secretory endometrium seems to be involved in implantation disorders and consecutive pregnancy complications. However, little is known about the mechanisms regulating apoptosis-sensitivity in the human endometrium. Therefore this study was performed to identify molecular mechanisms underlying the resistance toward apoptosis in human endometrial stromal cells (ESCs). Human ESCs were isolated from hysterectomy specimens and used as undifferentiated cells or after decidualization in vitro. Cells were incubated with an activating anti-Fas antibody, tumor-necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), TNF-α and inhibitors of protein- and RNA-syntheses, a caspase-inhibitor and inhibitors of extracellular signal regulated kinase (Erk)1/2, nuclear factor (NF)-κB and Akt. Apoptosis was measured by flow cytometric detection of hypodiploid nuclei. Caspase-activity was detected by luminescencent assays. Several pro- and anti-apoptotic molecules and the activation of Erk1/2, NF-κB and Akt were analyzed by in-cell Western assays or flow cytometry. Inhibition of protein- and RNA-syntheses differentially sensitized human ESCs for death receptor-mediated apoptosis in a caspase-dependent manner, based on the up-regulation of the death receptors Fas and TRAIL-R2. The constitutive activity of Erk1/2 and NF-κB could be identified as a reason for the apoptosis-resistance of human ESCs. These results suggest the pro-survival signaling pathways Erk1/2 and NF-κB as key regulators of the sensitivity of human ESCs for death receptor-mediated apoptosis. The modulation of these pathways might play an important role in the physiology of implantation.

The molecular charge and size of heparins determine their impact on the decidualization of human endometrial stromal cells.

Heparin modulates the decidualization of human endometrial stromal cells (ESCs), but the molecular mechanisms behind these effects are still unknown. In the present study, we further specified this biological effect of heparin in human ESCs in vitro. ESCs were isolated from hysterectomy specimens, decidualized over 12 days using progesterone and 17β-estradiol and incubated with thrombin, factor Xa (FXa), unfractionated heparin, dextran sulfate, danaparoid or different low-molecular-weight heparins (LMWHs). Production of insulin-like growth factor (IGF)-I, prolactin (PRL) and IGF-binding protein (IGFBP)-1 by ESCs was measured using ELISAs. Like heparin, thrombin and FXa cause an increase in IGF-I in ESCs, suggesting an action of heparin independent from its anticoagulatory effects. This was supported by demonstrating the induction of the same effects on IGF-I, PRL and IGFBP-1 as heparin by dextran sulfate, a polysaccharide of similar size and charge as heparin, but without anticoagulatory properties. LMWHs with the same anti-FXa activity as heparin showed less pronounced effects on ESCs than heparin, whereas the very short pentasaccharide fondaparinux (17 kDa) had barely any effect, further supporting the primary role of molecular size and charge mediating these biological effects of heparin on ESCs. In conclusion, the effects of heparin on the decidualization of human ESCs seem to be independent of its anticoagulatory function, but rather depend on the charge and the size of this polysulfated glycosaminoglycan. Therefore, highly sulfated polysaccharides with a molecular weight >17 kDa might be an interesting pharmacological approach for the therapy of endometrial pathologies, e.g. the treatment of women suffering from recurrent miscarriage or repeated implantation failure.

Heparin inhibits interferon-γ signaling in human endometrial stromal cells by interference with the cellular binding of interferon-γ

OBJECTIVE To examine the impact of heparins on interferon-γ (IFN-γ) signaling in human endometrial stromal cells (ESCs) in vitro. DESIGN In vitro experiment. SETTING Research laboratory at a medical university center. PATIENT(S) Premenopausal women undergoing hysterectomy for benign reasons. INTERVENTION(S) The ESCs were isolated from hysterectomy specimens, decidualized in vitro using P and 17β-E(2), and incubated with recombinant IFN-γ, unfractionated heparin, and low molecular weight heparins (LMWHs). MAIN OUTCOME MEASURE(S) Interferon response factor 1 (IRF-1) and N-myc interactor (Nmi) messenger RNA (mRNA) were measured using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Phosphorylation of signal transducer and activator of transcription 1 (STAT-1) was detected by an in-cell Western assay, expression of the IFN-γ receptor by flow cytometry. Cell-bound IFN-γ was determined in lysates by an ELISA. RESULT(S) Heparin and LMWHs inhibit the IFN-γ-mediated induction of IRF-1, but not Nmi in undifferentiated and decidualized ESCs. The phosphorylation of signal transducer and activator of transcription 1 STAT-1 upon IFN-γ stimulation is inhibited as well. Heparin has no effect on the IFN-γ receptor in ESCs, but inhibits the binding of IFN-γ to the cells. CONCLUSION(S) Unfractionated heparin, as well as LMWHs, are able to inhibit IFN-γ signaling in human ESCs and therefore might be clinically interesting agents to modulate the actions of this proinflammatory cytokine at the implantation site.

The role of recent thymic emigrant-regulatory T-cell (RTE-Treg) differentiation during pregnancy

During pregnancy, regulatory T cells (Tregs) have a key role in maternal immune tolerance to the semi‐allogeneic fetus. Our previous results showed that the naive CD45RA+‐Treg pool is functionally improved in pregnant women compared with non‐pregnant women. Therefore, we examined the thymic output and differentiation of CD45RA+CD31+ recent thymic emigrant (RTE)‐Tregs during normal pregnancy and in the presence of preeclampsia. With the onset of pregnancy, the composition of the total CD4+CD127low+/−FoxP3+‐Treg pool changed in the way that its percentage of RTE‐ and CD45RA−CD31+‐memory Tregs decreased strongly, whereas that of the CD45RA+CD31−‐mature naive (MN)‐Tregs did not change and that of the CD45RA−CD31−‐memory Tregs increased complementary. Thereby, the ratio of RTE‐/MN‐Tregs decreased from 1.0 to 0.7 leading to a significant increase in the suppressive activity of the naive CD45RA+‐Treg pool. This effect was confirmed by re‐assembling separated RTE‐ and MN‐Tregs from non‐pregnant women in the ratio of pregnant women. The suppressive activity of both separated naive Treg subsets was equally high in non‐pregnant and pregnant women, but considerably reduced in preeclampsia patients, who showed significantly increased percentages of CD45RA−CD31+‐memory Tregs, but decreased percentages of RTE‐ and MN‐Tregs. Our results suggest a reduced thymic output of RTE‐Tregs during pregnancy, which causes a decrease in the ratio of RTE‐/MN‐Tregs and thus an increase in the differentiation of RTE‐Tregs towards CD45RA−CD31−‐memory Tregs. Presumably, this differentiation of RTE‐Tregs, which was impaired in preeclampsia patients, ensures the improved suppressive activity of the CD45RA+‐naive Treg pool and thus retains the maintenance of pregnancy.

Heparins modulate the IFN-γ-induced production of chemokines in human breast cancer cells

Heparins seem to improve survival in patients with advanced malignancies independently of their anticoagulatory function. As the treatment options in advanced and metastatic breast cancer are still very limited, heparins might be an interesting addition to the existing systemic therapies. The interferon (IFN)-γ-inducible chemokines CXCL9 and CXCL10 play an essential role in the regulation of the immune milieu in malignant tumours, thereby being interesting targets for an immunological intervention. We therefore wanted to test whether heparins have an impact on the chemokines CXCL9 and CXCL10 as well as the IFN-γ signalling in human breast cancer cells in vitro. The well-established cell lines BT-474, MCF-7, SK-BR-3 and MDA-MB-231 were incubated with IFN-γ, unfractionated heparin (UFH), different low molecular weight heparins (LMWHs) and the heparin-related polyanions danaparoid and dextran sulphate. The production of CXCL9 and CXCL10 was measured by ELISA and real-time RT-PCR, the phosphorylation of signal transducer and activator of transcription (STAT) 1 was detected by an in-cell western assay and the amount of cellular bound IFN-γ was analysed by a high sensitivity ELISA. We observed that IFN-γ induced CXCL9 and CXCL10 production in MCF-7, SK-BR-3 and MDA-MB-231 cells but not in BT-474. UFH dose dependently inhibited the effect of IFN-γ on the secretion and expression of CXCL9 and CXCL10. LMWHs and heparin-related compounds differentially modulated IFN-γ-effects—the results depended on their molecular size and charge, but were independent of their anticoagulatory properties. As a reason for these heparin effects, we could show that the IFN-γ-induced phosphorylation of STAT1 was modulated by heparins, caused by an interaction with the cellular binding of IFN-γ. In conclusion, these results support the significance of the immunomodulatory properties of heparins independently of their classical anticoagulatory function. Heparin-derived sulphated polysaccharides with distinct molecular properties might thus be interesting candidates for new therapeutic strategies in breast cancer.

Inverse regulation of the interferon-γ receptor and its signaling in human endometrial stromal cells during decidualization

OBJECTIVE To investigate whether human endometrial stromal cells (ESCs) express the interferon-gamma-receptor (IFN-gamma R) and whether the process of decidualization or human chorionic gonadotropin (hCG) regulate the IFN-gamma R and its signaling pathway. DESIGN In vitro experiment. SETTING Research laboratory at a medical university center. PATIENT(S) Premenopausal women undergoing hysterectomy for benign reasons. INTERVENTION(S) Isolation and incubation of ESCs from hysterectomy specimens with 17beta-estradiol, progesterone, recombinant hCG, and IFN-gamma as well as an IFN-gamma R-blocking antibody. MAIN OUTCOME MEASURE(S) We analyzed IFN-gamma R and the phosphorylation of signal transducer and activator of transcription 1 (STAT-1) by flow cytometry. We measured IFN-gamma R and interferon response factor 1 (IRF-1) mRNA using semiquantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR). RESULT(S) The IFN-gamma R is up-regulated in human ESCs during decidualization without affecting the phosphorylation of STAT-1. Stimulation of IRF-1 by IFN-gamma is reduced in decidualized ESCs. We found that hCG neither regulates the IFN-gamma R nor its signaling pathway. CONCLUSION(S) These results show an inverse regulation of the IFN-gamma R and its signaling response via STAT-1 and IRF-1 in human ESCs during decidualization. The early embryonic signal hCG has no effect on this process. This mechanism may finely modulate the reactivity of ESCs to IFN-gamma-mediated signals from immune cells at the implantation site.