Placentally derived prostaglandin E2 acts via the EP4 receptor to inhibit IL-2-dependent proliferation of CTLL-2 T cells

Amphiregulin orchestrates the paracrine immune-suppressive function of amniotic-derived cells through its interplay with COX-2/PGE2/EP4 axis

The paracrine crosstalk between amniotic-derived membranes (AMs)/epithelial cells (AECs) and immune cells is pivotal in tissue healing following inflammation. Despite evidence collected to date, gaps in understanding the underlying molecular mechanisms have hindered clinical applications. The present study represents a significant step forward demonstrating that amphiregulin (AREG) orchestrates the native immunomodulatory functions of amniotic derivatives via the COX-2/PGE2/EP4 axis. The results highlight the immunosuppressive efficacy of PGE2-dependent AREG release, dampening PBMCs' activation, and NFAT pathway in Jurkat reporter cells via TGF-β signaling. Moreover, AREG emerges as a key protein mediator by attenuating acute inflammatory response in Tg(lysC:DsRed2) zebrafish larvae. Notably, the interplay of diverse COX-2/PGE2 pathway activators enables AM/AEC to adapt rapidly to external stimuli (LPS and/or stretching) through a responsive positive feedback loop on the AREG/EGFR axis. These findings offer valuable insights for developing innovative cell-free therapies leveraging the potential of amniotic derivatives in immune-mediated diseases and regenerative medicine.

Protective effects of extracts from Acer truncatum leaves on SLS-induced HaCaT cells

Introduction:A. truncatum Bunge (Sapindaceae or formerly Aceraceae) is a tall deciduous tree native to China. Traditionally, the leaves of A. truncatum are decocted and used by Chinese Mongolians, Koreans, and Tibetans to treat skin itching, dry cracks, and other skin ailments, which indicates A. truncatum leaves may have a potential inhibitory effect on various skin inflammations.

Methods: To examine the protective effect against skin inflammations of A. truncatum leaf extract (ATLE), an in vitro dermatitis model was established using sodium dodecyl sulfate (SLS)-induced HaCaT cells. The anti-inflammatory effect of ATLE was evaluated by analyzing cell viability, apoptosis, reactive oxygen species (ROS), interleukin 6 (IL-6), and prostaglandin E2 (PGE2) levels.

Results: Orthogonal experiments showed that the pretreatment with ATLE can reduce the IL-6 levels, PGE2 levels, and apoptosis increased in SLS-stimulated HaCaT cells, which indicates that ATLE has positive efficacy for dermatitis. Furthermore, three flavonoid compounds kaempferol-3-O-α-L-rhamnoside, quercetin-3-O-α-L-rhamnopyranoside, kaempferol-3,7-di-O-α-L-rhamnoside, and 1,2,3,4,6-Penta-O-galloyl-β-D-glucopyranose (PGG) were isolated and identified. Among them, kaempferol-3,7-di-O-α-L-rhamnoside was isolated from this plant for the first time. These compounds have been proven to have an anti-inflammatory effect. They may contribute to the efficacy of A. truncatumin treating skin inflammation.

Discussion: The results revealed that ATLE has the potential to be used as an additive in various skin care products to prevent skin inflammations and may be incorporated in formulations for topical application as a therapeutic approach against dermatitis.

Cooperative inflammation: The recruitment of inflammatory signaling in marsupial and eutherian pregnancy

The evolution of viviparity in therian mammals, i.e. marsupials and "placental" mammals, occurred by retention of the conceptus in the female reproductive tract and precocious "hatching" from the shell coat. Both eutherian embryo implantation and the opossum embryo attachment reaction are evolutionarily derived from and homologous to a defensive inflammatory process induced after shell coat hatching. However, both lineages, marsupials and placental mammals, have modified the inflammatory response substantially. We review the induction, maintenance, and effects of inflammation throughout pregnancy, with special attention to the role of prostaglandins and the mucosal inflammatory response, both of which likely had roles in early mammalian viviparity. We propose that the key step was not only suppression of the inflammatory response after implantation in placental mammals, but also the transfer of the inflammatory cell-cell communication network to a different set of cell types than in generic inflammation. To support this conclusion we discuss evidence that pro-inflammatory signal production in the opossum is not limited to maternal cells, as expected in bona fide defensive inflammation, but also includes fetal tissues, in a process we term cooperative inflammation. The ways in which the inflammatory reaction was independently modified in these two lineages helps explain major life history differences between extant marsupials and eutherians.

Differential Expression of Prostaglandin E2 Receptors in Porcine Kidney Transplants

BACKGROUND

Acute rejection of a kidney allograft results from adaptive immune responses and marked inflammation. The eicosanoid prostaglandin E2 (PGE2) modulates the inflammatory response, is generated by cyclooxygenase 2 (COX-2), and binds to 1 of the 4 G protein-coupled E prostanoid cell surface receptors (EP1-4). Receptor activation results in in proinflammatory (EP1 and EP3) or anti-inflammatory (EP2 and EP4) responses. We theorized that expression of the components of the COX-PGE2-EP signaling pathway correlates with acute rejection in a porcine model of allogeneic renal transplantation.

METHOD

COX-2 enzyme and EP receptor protein expression were quantitated with western blotting and immunohistochemistry from allotransplants (n = 18) and autotransplants (n = 5). Linear regression analysis was used to correlate EP receptor expression with the Banff category of rejection.

RESULTS

Pigs with advanced rejection demonstrated significant increases in serum PGE2 metabolites, while pigs with less rejection demonstrated higher tissue concentrations of PGE2 metabolites. A significant negative correlation between COX-2 expression and Banff category of rejection (R = -0.877) was shown. Rejection decreased expression of EP2 and EP4. For both receptors, there was a significant negative correlation with the extent of rejection (R = -0.760 and R = -0.891 for EP2 and EP4, respectively). Rejection had no effect on the proinflammatory receptors EP1 and EP3.

CONCLUSION

Downregulation of COX-2 and the anti-inflammatory EP2 and EP4 receptors is associated with acute rejection in unmatched pig kidney transplants, suggesting that the COX-2-PGE2-EP pathway may modulate inflammation in this model. Enhancing EP2 and/or EP4 activity may offer novel therapeutic approaches to controlling the inflammation of acute allograft rejection.

Cardiosphere-derived cells suppress allogeneic lymphocytes by production of PGE2 acting via the EP4 receptor

Cardiosphere-derived cells (CDCs) are a cardiac progenitor cell population, which have been shown to possess cardiac regenerative properties and can improve heart function in a variety of cardiac diseases. Studies in large animal models have predominantly focussed on using autologous cells for safety, however allogeneic cell banks would allow for a practical, cost-effective and efficient use in a clinical setting. The aim of this work was to determine the immunomodulatory status of these cells using CDCs and lymphocytes from 5 dogs. CDCs expressed MHC I but not MHC II molecules and in mixed lymphocyte reactions demonstrated a lack of lymphocyte proliferation in response to MHC-mismatched CDCs. Furthermore, MHC-mismatched CDCs suppressed lymphocyte proliferation and activation in response to Concanavalin A. Transwell experiments demonstrated that this was predominantly due to direct cell-cell contact in addition to soluble mediators whereby CDCs produced high levels of PGE₂ under inflammatory conditions. This led to down-regulation of CD25 expression on lymphocytes via the EP4 receptor. Blocking prostaglandin synthesis restored both, proliferation and activation (measured via CD25 expression) of stimulated lymphocytes. We demonstrated for the first time in a large animal model that CDCs inhibit proliferation in allo-reactive lymphocytes and have potent immunosuppressive activity mediated via PGE₂.

Decidual stromal cell-derived PGE2 regulates macrophage responses to microbial threat

PROBLEM

Bacterial chorioamnionitis causes adverse pregnancy outcomes, yet host-microbial interactions are not well characterized within gestational membranes. The decidua, the outermost region of the membranes, is a potential point of entry for bacteria ascending from the vagina to cause chorioamnionitis. We sought to determine whether paracrine communication between decidual stromal cells and macrophages shaped immune responses to microbial sensing.

METHOD OF STUDY

Decidual cell-macrophage interactions were modeled in vitro utilizing decidualized, telomerase-immortalized human endometrial stromal cells (dTHESCs) and phorbol ester-differentiated THP-1 macrophage-like cells. The production of inflammatory mediators in response to LPS was monitored by ELISA for both cell types, while phagocytosis of bacterial pathogens (Escherichia coli and Group B Streptococcus (GBS)) was measured in THP-1 cells or primary human placental macrophages. Diclofenac, a non-selective cyclooxygenase inhibitor, and prostaglandin E₂ (PGE₂ ) were utilized to interrogate prostaglandins as decidual cell-derived paracrine immunomodulators. A mouse model of ascending chorioamnionitis caused by GBS was utilized to assess the colocalization of bacteria and macrophages in vivo and assess PGE₂ production.

RESULTS

In response to LPS, dTHESC and THP-1 coculture demonstrated enhancement of most inflammatory mediators, but a potent suppression of macrophage TNF-α generation was observed. This appeared to reflect a paracrine-mediated effect of decidual cell-derived PGE₂ . In mice with GBS chorioamnionitis, macrophages accumulated at sites of bacterial invasion with increased PGE₂ in amniotic fluid, suggesting such paracrine effects might hold relevance in vivo.

CONCLUSION

These data suggest key roles for decidual stromal cells in modulating tissue responses to microbial threat through release of PGE₂ .

Expression of prostaglandin receptors in Chlamydia trachomatis-infected recurrent spontaneous aborters

A study was undertaken to quantify the expression of prostaglandin (PG) receptors and find the effect of gestational age on expression of PG receptor genes in Chlamydia trachomatis-infected recurrent spontaneous aborters (RSA). Endometrial curettage tissue (ECT) was collected from 130 RSA (Group I) and 100 age-matched controls (Group II) at the Department of Obstetrics and Gynecology, Safdarjung Hospital, New Delhi (India). PCR was performed for diagnosis of C. trachomatis cryptic plasmid; mRNA expression of PG receptor genes was assessed by real-time PCR (q-PCR), while serum progesterone/estrogen levels were determined by respective commercial kits. Data were evaluated statistically. A total of 15.4 % RSA (GroupI) were diagnosed as C. trachomatis-positive (200 bp), whereas controls were uninfected. q-PCR showed significant upregulation (P<0.0001) of PGE2 (EP-1, EP-2, EP-3, EP-4), PGF2α (FP) and PGI2 (IP) receptors in Group I versus Group II. The expression of PG receptors increased significantly with advanced gestational age (P<0.002); however, only contractile receptors, EP-1, EP-3 and FP, were positively correlated with gestational age in Group-I. In infected RSA, mean serum progesterone level was significantly low (P<0.0001) while serum oestrogen was high (P<0.0001). Overall, the data suggest that increased expression of PG receptors, particularly contractile gene receptors (EP-1, EP-3, FP), with advanced gestational age and altered steroid levels could be a possible risk factor for abortion in Chlamydia-infected RSA.

Accumulation of cells expressing macrophage colony-stimulating factor receptor gene in the ovary of a pregnant viviparous fish, Neoditrema ransonnetii (Perciformes, Embiotocidae)

Macrophage colony-stimulating factor receptor (M-CSFR), a member of the group of type III protein tyrosine kinase receptors, is expressed primarily by monocyte/macrophage lineage cells. In order to describe the distribution of macrophages at the maternal-fetal interface in Neoditrema ransonnetii, a viviparous fish species, M-CSFR cDNA was sequenced. Two sequences were obtained: NrM-CSFR1 (4381 bp, encoding 980 amino acids), and NrM-CSFR2 (3573 bp, encoding 1016 amino acids). Both the genes were expressed in the ovary of pregnant females. In situ hybridization revealed that a number of cells that were positive for NrM-CSFR1 and/or NrM-CSFR2 populated the ovigerous lamellae of the ovary during pregnancy. Following parturition, M-CSFR-positive cells disappeared from the subepithelial region of ovigerous lamellae, and were localized in perivascular tissues. These results suggest the role of M-CSFR-positive cells, which appear to be macrophages, in N. ransonnetii during pregnancy.

Prostaglandin E2 Regulation of Macrophage Innate Immunity

Globally, maternal and fetal health is greatly impacted by extraplacental inflammation. Group B Streptococcus (GBS), a leading cause of chorioamnionitis, is thought to take advantage of the uterine environment during pregnancy in order to cause inflammation and infection. In this study, we demonstrate the metabolic changes of murine macrophages caused by GBS exposure. GBS alone prompted a delayed increase in lactate production, highlighting its ability to redirect macrophage metabolism from aerobic to anaerobic respiration. This production of lactate is thought to aid in the development and propagation of GBS throughout the surrounding tissue. Additionally, this study shows that PGE2 priming was able to exacerbate lactate production, shown by the rapid and substantial lactate increases seen upon GBS exposure. These data provide a novel model to study the role of GBS exposure to macrophages with and without PGE2 priming.

Regulatory T-cells in pregnancy: historical perspective, state of the art, and burning questions

In this review, we first revisit the original concept of "suppressor T-cells" in pregnancy, put it in a historical perspective, and then highlight the main data that licensed its resurrection and revision into the concept of "regulatory T-cells" (Tregs) in pregnancy. We review the evidence for a major role of Tregs in murine and human pregnancy and discuss Treg interactions with dendritic and uterine natural killer cells, other players of maternal-fetal tolerance. Finally, we highlight what we consider as the most important questions in the field.

T CD3+CD8+ lymphocytes are more susceptible for apoptosis in the first trimester of normal human pregnancy

Aims. Normal human pregnancy is a complex process of many immunoregulatory mechanisms which protect fetus from the activation of the maternal immune system. The aim of the study was to investigate the apoptosis of lymphocytes in peripheral blood of normal pregnant patients and healthy nonpregnant women. Methods. Sixty pregnant women and 17 nonpregnant women were included in the study. Lymphocytes were isolated and labeled with anti-CD3, anti-CD4, and anti-CD8 monoclonal antibodies. Apoptosis was detected by CMXRos staining and analyzed using the flow cytometric method. Results. We found significantly higher apoptosis of total lymphocytes in peripheral blood of pregnant patients when compared to healthy nonpregnant women. The percentage of apoptotic T CD3⁺CD8⁺ cells in the first trimester was significantly higher when compared to the third trimester of normal pregnancy. The ratio of T CD3⁺CD4⁺ : T CD3⁺CD8⁺ apoptotic lymphocytes was significantly lower in the first trimester when compared to other trimesters of pregnancy and to both of the phases of the menstrual cycle. Conclusions. The higher apoptosis of T CD3⁺CD8⁺ lymphocytes and the lower ratio of T CD3⁺CD4⁺ : T CD3⁺CD8⁺ apoptotic cells in the first trimester of normal pregnancy may suggest a higher susceptibility of T CD3⁺CD8⁺ cells for apoptosis as a protective mechanism at the early stage of pregnancy.

Prostaglandin E₂ down-regulates the expression of CD25 on bovine T cells, and this effect is mediated through the EP4 receptor

A crucial event in the initiation of an immune response is the activation of T cells, which requires IL-2 binding to its high-affinity IL-2 receptor for optimal signaling. The IL-2 receptor α-chain (CD25) is needed for the high affinity binding of IL-2 to effector cells and is potently induced after T cell activation. The aim of this research has been to determine whether prostaglandin E2 (PGE2) affects the CD25 expression on bovine T cells, and if it does, then which of the PGE2 receptor (EP) subtype(s) mediate(s) this effect. Herein, we report that exposure of peripheral blood mononuclear cells (PBMC) to PGE2 considerably reduces the percentage and absolute counts of CD25(+)CD4(+), CD25(+)CD8(+) and CD25(+)WC1(+) T cells, significantly increases the value of these parameters with respect of CD25(-)CD4(+), CD25(-)CD8(+) and CD25(-)WC1(+) T cells, and does not affect counts of the total populations of CD4(+), CD8(+) and WC1(+) T cells. These results indicate that PGE2 down-regulates the CD25 expression on bovine T cells. Moreover, we show that the selective blockade of EP4 receptor, but not EP1 and EP3 receptors, prevents this effect. Interestingly, the exposure of PBMC to a selective EP2 receptor agonist leads to a substantial increase in the percentage and absolute number of CD25(+)CD4(+), CD25(+)CD8(+) and CD25(+)WC1(+) T cells. In conclusions, the PGE2-induced down-regulation of CD25 expression on bovine CD4(+), CD8(+) and WC1(+) T cells should be considered as immunosuppressive and anti-inflammatory action, because these lymphocytes primarily represent effector cells and adequate CD25 expression is essential for their correct functioning. The PGE2-mediated down-regulation of the CD25 expression on bovine T cells is mediated via the EP4 receptor, although selective activation of the EP2 receptor up-regulates the CD25 expression on these cells. Thus, with respect to the effect of PGE2 on the CD25 expression on bovine T cells, EP4 receptor serves as an inhibitory receptor, whereas EP2 receptor functions as a stimulatory receptor. The fact that non-selective stimulation of EP receptors, i.e. triggered by PGE2, leads to weaker CD25 expression proves that inhibitory actions prevail over stimulatory ones. These results indicate the possibility of pharmacological manipulation of the CD25 expression on T cells via selective antagonists and agonists of EP2 and EP4 receptors.

Intrauterine group A streptococcal infections are exacerbated by prostaglandin E2

Streptococcus pyogenes (Group A Streptococcus; GAS) is a major cause of severe postpartum sepsis, a re-emerging cause of maternal morbidity and mortality worldwide. Immunological alterations occur during pregnancy to promote maternofetal tolerance, which may increase the risk for puerperal infection. PGE2 is an immunomodulatory lipid that regulates maternofetal tolerance, parturition, and innate immunity. The extent to which PGE2 regulates host immune responses to GAS infections in the context of endometritis is unknown. To address this, both an in vivo mouse intrauterine (i.u.) GAS infection model and an in vitro human macrophage-GAS interaction model were used. In C57BL/6 mice, i.u. GAS inoculation resulted in local and systemic inflammatory responses and triggered extensive changes in the expression of eicosanoid pathway genes. The i.u. administration of PGE2 increased the mortality of infected mice, suppressed local IL-6 and IL-17A levels, enhanced neutrophilic inflammation, reduced uterine macrophage populations, and increased bacterial dissemination. A role for endogenous PGE2 in the modulation of antistreptococcal host defense was suggested, because mice lacking the genes encoding the microsomal PGE2 synthase-1 or the EP2 receptor were protected from death, as were mice treated with the EP4 receptor antagonist, GW627368X. PGE2 also regulated GAS-macrophage interactions. In GAS-infected human THP-1 (macrophage-like) cells, PGE2 inhibited the production of MCP-1 and TNF-α while augmenting IL-10 expression. PGE2 also impaired the phagocytic ability of human placental macrophages, THP-1 cells, and mouse peritoneal macrophages in vitro. Exploring the targeted disruption of PGE2 synthesis and signaling to optimize existing antimicrobial therapies against GAS may be warranted.

EP4 and EP2 receptor activation of protein kinase A by prostaglandin E2 impairs macrophage phagocytosis of Clostridium sordellii

PROBLEM

Clostridium sordellii causes endometrial infections, but little is known regarding host defenses against this pathogen.

METHOD OF STUDY

We tested the hypothesis that the immunoregulatory lipid prostaglandin (PG) E2 suppresses human macrophage clearance of C. sordellii through receptor-induced increases in intracellular cyclic adenosine monophosphate (cAMP). The THP-1 macrophage cell line was used to quantify C. sordellii phagocytosis.

RESULTS

PGE2 increased cAMP levels, activated protein kinase A (PKA), and inhibited the class A scavenger receptor-dependent phagocytosis of C. sordellii. Activation of the EP2 and EP4 receptors increased intracellular cAMP and inhibited phagocytosis, with evidence favoring a more important role for EP4 over EP2. This was supported by EP receptor expression data and the use of pharmacological receptor antagonists. In addition, the PKA isoform RI appeared to be more important than RII in mediating the suppression of ingestion of C. sordellii.

CONCLUSION

The endogenous lipid mediator PGE2 impairs human innate immune responses against C. sordellii.

[Immunological analogies between ovarian cancer and pregnancy]

During pregnancy an environment allowing installation of tolerance toward the fetus is set up locally at the materno-fetal interface. Numerous effectors of immunity are involved in this tolerance (NK cell, T cell, Macrophages, dendritic cell). Specific mechanisms during pregnancy attract locally these immunological cells. In the decidua, they are educated toward tolerance. These mechanisms evolve during the pregnancy because at the end of the pregnancy, tolerance is broken to prepare and activate the labor. Ovarian tumors, after having surmounted the immunosurveillance, like trophoblast, chair the installation of a tolerance of their host facilitating the development of the disease. The blocking of these mechanisms of tolerance coupled with activation of mechanisms of defenses offer new perspectives in the treatment of the ovarian cancer. The authors suggest showing the analogies of the tolerance observed during ovarian cancer and pregnancy. The knowledge of the orchestration of the physiological mechanisms observed during pregnancy will offer new therapeutic targets.

Toll-like receptor-3 ligation-induced indoleamine 2, 3-dioxygenase expression in human trophoblasts

Indoleamine 2,3-dioxygenase (IDO) is an enzyme that degrades an essential amino acid, tryptophan, and plays a role in inhibiting the proliferation of T cells and intracellular pathogens. Inhibiting IDO in mice leads to fetal rejection, suggesting its significance in establishing pregnancy. Toll-like receptor 3 (TLR-3) is a key component of the innate immune system that recognizes viral double-stranded RNA and triggers immune reactions by producing type I interferon. Using a human trophoblast cell culture system, we studied the effect of TLR-3 ligation on IDO expression and function by treating trophoblasts with polyinosinic-polycytidylic acid [poly(I:C)] (a synthetic double stranded RNA, which mimics viral RNA). Real-time PCR and Western blot analysis revealed that IDO mRNA and protein expression was significantly induced by poly(I:C). The activity of IDO was also increased by poly(I:C) given that the L-kynurenine concentrations were elevated in conditioned media. Conditioned media from poly(I:C)-treated trophoblasts were found to inhibit the proliferation of human T cells significantly. Poly(I:C) was also shown to induce interferon (IFN)-β mRNA expression in trophoblasts. Recombinant human IFN-β increased IDO mRNA expression in trophoblasts more rapidly than poly(I:C). Pretreating with neutralizing antibody against IFN-β significantly suppressed IDO induction by poly(I:C). Collectively we have demonstrated that ligation of TLR-3 by poly(I:C) induces IDO expression in human first-trimester trophoblasts via an IFN-β-dependent pathway. These findings suggest that upon viral infection, trophoblasts induce IDO and in turn contribute to antimicrobial activity and maintenance of fetomaternal tolerance.

Postpartum group a Streptococcus sepsis and maternal immunology

Group A Streptococcus (GAS) is an historically important agent of puerperal infections and sepsis. The inception of hand-washing and improved hospital hygiene drastically reduced the incidence of puerperal sepsis, but recently the incidence and severity of postpartum GAS infections has been rising for uncertain reasons. Several epidemiological, host, and microbial factors contribute to the risk for GAS infection and mortality in postpartum women. These include the mode of delivery (vaginal versus cesarean section), the location where labor and delivery occurred, exposure to GAS carriers, the altered immune status associated with pregnancy, the genetic background of the host, the virulence of the infecting GAS strain, and highly specialized immune responses associated with female reproductive tract tissues and organs. This review will discuss the complicated factors that contribute to the increased susceptibility to GAS after delivery and potential reasons for the recent increase observed in morbidity and mortality.

The regulation of CD4+ T cell immune responses toward Th2 cell development by prostaglandin E2

As an important immune mediator, PGE2 plays an important role in the immune tolerance, autoimmune diseases, immune regulation and tumor immunotolerance. PGE2 is considered to be a promising candidate for the control of the immune diseases. To further understand the immuno-modulating effects of PGE2 on CD4+ T cells, in vitro investigation was conducted in the present study. The results showed that PGE2 inhibited the proliferation of T cells in vitro in a dose-dependent manner. Gene expression profiling showed that 1716 genes were down regulated and 73 genes were up regulated with a change of 1.5 fold. Several signal transduction pathways were involved, such as TNF-α and NF-kB signaling pathway, T cell receptor signaling pathway, IL-2 signaling pathway, and MAPK pathway. The results showed that PGE2 inhibited IFN-γ, TNF-α and IL-4 production by CD4+ T cells 24h after cell culture. A comparison between IFN-γ and IL-4 production showed that PGE2 enhanced the relative ratio of IL-4 to IFN-γ in CD4+ T cells culture, and regulated CD4+ T cells toward Th2 cell development. The results of the present study indicated that PGE2 has the potential to treat Th1-mediated inflammatory diseases by regulating CD4+ T cells toward Th2 cell immune response.

CD14+ monocytes promote the immunosuppressive effect of human umbilical cord matrix stem cells

Here, the effect of CD14(+) monocytes on human umbilical cord matrix stem cell (hUC-MSC)-mediated immunosuppression was studied in vitro. hUC-MSCs exerted a potent inhibitory effect on the proliferation and interferon-gamma (IFN-gamma) secretion capacities of CD4(+) and CD8(+) T cells in response to anti-CD3/CD28 stimulation. Transwell co-culture system revealed that the suppressive effect was primarily mediated by soluble factors. Addition of prostaglandin synthesis inhibitors (indomethacin or NS-398) almost completely abrogated the immunosuppression activity of hUC-MSCs, identifying prostaglandin E(2) (PGE(2)) as an important soluble mediator. CD14(+) monocytes were found to be able to enhance significantly the immunosuppressive effect of hUC-MSCs in a dose-dependent fashion. Moreover, the inflammatory cytokine IL-1beta, either exogenously added or produced by CD14(+) monocytes in culture, could trigger expression of high levels of PGE(2) by hUC-MSCs, whereas inclusion of the IL-1 receptor antagonist (IL-1RA) in the culture down-regulated not only PGE(2) expression, but also reversed the promotional effect of CD14(+) monocytes and partially restored CD4(+) and CD8(+) T cell proliferation and IFN-gamma secretion. Our data demonstrate an important role of monocytes in the hUC-MSC-induced immunomodulation, which may have important implications in future efforts to explore the clinical potentials of hUC-MSCs.

Tolerance to the foetal allograft?

In this review, we will detail the concept of tolerance and its history in reproductive immunology. We will then consider whether it applies to the foetal-maternal relationship and discuss the mechanisms involved in non-rejection of the foeto-placental unit.

Human umbilical cord mesenchymal stem cells hUC-MSCs exert immunosuppressive activities through a PGE2-dependent mechanism

Human umbilical-cord-derived mesenchymal stem cells (hUC-MSCs) constitute an attractive alternative to bone-marrow-derived MSCs for potential clinical applications because of easy preparation and lower risk of viral contamination. In this study, both proliferation of human peripheral blood mononuclear cells (hPBMCs) and their IFN-gamma production in response to mitogenic or allogeneic stimulus were effectively inhibited by hUC-MSCs. Co-culture experiments in transwell systems indicated that the suppression was largely mediated by soluble factor(s). Blocking experiments identified prostaglandin E(2) (PGE(2)) as the major factor, because inhibition of PGE(2) synthesis almost completely mitigated the immunosuppressive effects, whereas neutralization of TGF-beta, IDO, and NO activities had little effects. Moreover, the inflammatory cytokines, IFN-gamma and IL-1beta, produced by hPBMCs upon activation notably upregulated the expression of cyclooxygenase-2 (COX-2) and the production of PGE(2) by hUC-MSCs. In conclusion, our data have demonstrated for the first time the PGE(2)-mediated mechanism by which hUC-MSCs exert their immunomodulatory effects.

Role of cAMP in the promotion of colorectal cancer cell growth by prostaglandin E2

Background

Prostaglandin E2 (PGE2), a product of the cyclooxygenase (COX) reaction, stimulates the growth of colonic epithelial cells. It is inferred that the abrogation of prostaglandins' growth-promoting effects as a result of COX inhibition underlies the advantageous effects of non-steroidal anti-inflammatory drugs in colorectal carcinoma (CRC). Despite this appreciation, the underlying molecular mechanisms remain obscure since cell culture studies have yielded discrepant results regarding PGE2's mitogenicity.

Methods

We have employed several alternative approaches to score cell proliferation and apoptosis of 4 CRC cell lines exposed to PGE2 under various conditions. To investigate the role of cAMP in PGE2's functions, activation of the cAMP pathway was assessed at different levels (changes in cAMP levels and PKA activity) in cells subjected to specific manipulations including the use of specific inhibitors or prostanoid receptor-selective agonists/antagonists.

Results

Our data document that the dose-response curve to PGE2 is 'bell-shaped', with nano molar concentrations of PGE2 being more mitogenic than micro molar doses. Remarkably, mitogenicity inversely correlates with the ability of PGE2 doses to raise cAMP levels. Consistent with a major role for cAMP, cAMP raising agents and pertussis toxin revert the mitogenic response to PGE2. Accordingly, use of prostanoid receptor-selective agonists argues for the involvement of the EP3 receptor and serum deprivation of HT29 CRC cells specifically raises the levels of Gi-coupled EP3 splice variants.

Conclusion

The present data indicate that the mitogenic action of low PGE2 doses in CRC cells is mediated via Gi-proteins, most likely through the EP3 receptor subtype, and is superimposed by a second, cAMP-dependent anti-proliferative effect at higher PGE2 doses. We discuss how these findings contribute to rationalize conflictive literature data on the proliferative action of PGE2.

Respiratory Francisella tularensis live vaccine strain infection induces Th17 cells and prostaglandin E2, which inhibits generation of gamma interferon-positive T cells

Two key routes of Francisella tularensis infection are through the skin and airway. We wished to understand how the route of inoculation influenced the primary acute adaptive immune response. We show that an intranasal inoculation of the F. tularensis live vaccine strain (LVS) with a 1,000-fold-smaller dose than an intradermal dose results in similar growth kinetics and peak bacterial burdens. In spite of similar bacterial burdens, we demonstrate a difference in the quality, magnitude, and kinetics of the primary acute T-cell response depending on the route of inoculation. Further, we show that prostaglandin E(2) secretion in the lung is responsible for the difference in the gamma interferon (IFN-gamma) response. Intradermal inoculation led to a large number of IFN-gamma(+) T cells 7 days after infection in both the spleen and the lung. In contrast, intranasal inoculation induced a lower number of IFN-gamma(+) T cells in the spleen and lung but an increased number of Th17 cells in the lung. Intranasal infection also led to a significant increase of prostaglandin E(2) (PGE(2)) in the bronchoalveolar lavage fluid. Inhibition of PGE(2) production with indomethacin treatment resulted in increased numbers of IFN-gamma(+) T cells and decreased bacteremia in the lungs of intranasally inoculated mice. This research illuminates critical differences in acute adaptive immune responses between inhalational and dermal infection with F. tularensis LVS mediated by the innate immune system and PGE(2).

Induction of prostaglandin E2 synthesis and microsomal prostaglandin E synthase–1 expression in murine microglia by glioma-derived soluble factors

Object

Microglia are one of the members of monocyte/macrophage lineage in the central nervous system (CNS) and exist as ramified microglia in a normal resting state, but they are activated by various stimuli, such as tumors. Activated microglia induce immune responses in the CNS, but the precise functions of microglia in glioma microenvironments are not clear. It has been reported that glioma cells produce prostaglandin (PG)E2, which promotes the growth of tumor cells and possesses immunosuppressive activity. The authors previously reported that PGE2 production by peritoneal macrophages was enhanced by glioma-derived soluble factors, which induce an immunosuppressive state. In this study, they investigated PGE2 production by microglia treated with glioma cells and assessed the role of microglia in glioma microenvironments in the mouse.

Methods

Microglia and peritoneal macrophages were cultured in vitro with or without lipopolysaccharide, and tumor necrosis factor (TNF) and PGE2 in the culture supernatant were measured using L929 bioassay and enzyme immunoassay. The expression of mRNA was measured using reverse transcriptase polymerase chain reaction, and the protein expression was assayed with Western blotting. In some experiments glioma cells and conditioned glioma medium were added to the microglia cultures.

Results

Glioma cells studied in this report did not produce a significant amount of PGE2. However, the coculture of microglia with glioma cells or conditioned glioma medium led to the production of a large amount of PGE2. The enhancement of PGE2 production by microglia was more significant than that by peritoneal macrophages. The expression of cyclooxygenase (COX)–2 and particularly the expression of microsomal PGE synthase (mPGES)–1 (a terminal enzyme of the arachidonate cascade) in microglia were enhanced by conditioned glioma medium. The enhancement of mPGES-1 expression in microglia was more significant than that in peritoneal macrophages. The production of TNF was suppressed when culturing microglia with conditioned glioma medium, but this suppression was abrogated by the addition of a COX inhibitor (NS-398) and a PGE2 receptor (EP4) antagonist. Furthermore, TNF production was not suppressed in microglia from mPGES-1–deficient mice.

Conclusions

These results indicate that PGE2 production by microglia is enhanced by conditioned glioma medium, which induces an immunosuppressive state in the CNS. Therefore, the manipulation of microglia, from the standpoint of PGE2, provides investigators with an important strategy to induce an effective antiglioma immune response.

The Th1/Th2 paradigm: still important in pregnancy?

The enunciation of the T helper 1/T helper 2 (Th1/Th2) paradigm in pregnancy has represented a major step forward in our understanding of physiological and pathologic materno-foetal relationship. However, recent developments in studies of the implantation process and in the emergence of the uterine vascular bed and its control by natural killer cells and cytokines suggest that one must go beyond this hitherto useful scheme. In this review, we replace the emergence of the paradigm in its historical context and then emphasises what it does explain and what it no longer account for. A final reappraisal of the paradigm is suggested.

Francisella tularensis-infected macrophages release prostaglandin E2 that blocks T cell proliferation and promotes a Th2-like response

Francisella tularensis is a highly infectious bacterial pathogen, and is likely to have evolved strategies to evade and subvert the host immune response. In this study, we show that F. tularensis infection of macrophages alters T cell responses in vitro, by blocking T cell proliferation and promoting a Th2-like response. We demonstrate that a soluble mediator is responsible for this effect and identify it as PGE(2). Supernatants from F. tularensis-infected macrophages inhibited IL-2 secretion from both MHC class I and MHC class II-restricted T cell hybridomas, as well as enhanced a Th2-like response by inducing increased production of IL-5. Furthermore, the soluble mediator blocked proliferation of naive MHC class I-restricted T cells when stimulated with cognate tetramer. Indomethacin treatment partially restored T cell proliferation and lowered IL-5 production to wild-type levels. Macrophages produced PGE(2) when infected with F. tularensis, and treatment of infected macrophages with indomethacin, a cyclooxygenase-1/cyclooxygenase-2 inhibitor, blocked PGE(2) production. To further demonstrate that PGE(2) was responsible for skewing of T cell responses, we infected macrophages from membrane PGE synthase 1 knockout mice (mPGES1(-/-)) that cannot produce PGE(2). Supernatants from F. tularensis-infected membrane PGE synthase 1(-/-) macrophages did not inhibit T cell proliferation. Furthermore, treatment of T cells with PGE(2) recreated the effects seen with infected supernatant. From these data, we conclude that F. tularensis can alter host T cell responses by causing macrophages to produce PGE(2). This study defines a previously unknown mechanism used by F. tularensis to modulate adaptive immunity.

Specific Isolation of Placenta-Derived Exosomes from the Circulation of Pregnant Women and Their Immunoregulatory Consequences

PROBLEM

One immunoregulatory pathway receiving little attention is placental exosome release. In normal pregnancy, as factors linked with early immunomodulation decline, placental exosomes become critical in modulating T-cell activation, suppressing effector T cells by enhancing lymphocyte apoptosis and CD3-zeta loss.

METHOD OF STUDY

Placental exosomes were specifically isolated from the maternal peripheral circulation by a chromatographic/immunosorbent procedure. Exosomal suppression of T-cell signaling molecules on unfractionated T cells and T subsets was analyzed by Western immunoblot. The role of Fas ligand (FasL) was defined by use of Fas-blocking antibody.

RESULTS

While exosomes of lymphoid origin could be demonstrated in all women, placenta-derived exosomes were only identified in pregnant patients. Placental exosomes suppressed T-cell expression of CD3-zeta and JAK3, while inducing SOCS-2. This downregulation of CD3-zeta was partially reversed by pre-incubating T cells with ZB4 antibody. Using T subsets, the level of CD3-zeta on CD8+ cells was inhibited 1.43-fold more than in CD4+ cells. On CD4+ CD25+ cells, CD3-zeta was not significantly inhibited.

CONCLUSION

Placental exosomes suppressed T-cell signaling components; however, while exosomal FasL is an important contributor, it does not appear to be the sole mediator. The additional expression of PD-L1 may explain immunoregulatory consequences of exosomes with low or absent FasL.

No cancer in cancers: Evolutionary trade-off between successful viviparity and tumor escape from the adaptive immune system

Some invertebrate species including the king crab and king squid enjoy relatively long lives of up to 20 years. Nevertheless, there are few reports of malignancies among invertebrate animals while there are many such reports in lower vertebrates such as in fishes, amphibians, and reptiles. Viviparity is characteristic of most mammalian species, although it has been observed in both vertebrate and non-vertebrate species. As adaptive immune responses evolved among the cartilaginous fishes by virtue of gene duplication, all viviparous vertebrates cope with specific immune responses to reject the fetal allograft. The escape mechanisms employed by both human and animal malignancies share common properties, which are also employed by feto-placental units, such as the expression of non-classical major histocompatibility antigens (HLA-E, HLA-F, and HLA-G in humans), accumulation of regulatory T cells, Th2-directed immune responses, Fas/FasL- and/or PD-1/PD-L1-induced apoptosis, and the expression of indoleamine 2, 3 dioxygenase which starves the local tryptophan supply that is indispensable for an effective cytotoxic T cells response. In humans, a single cancer cell requires 1-10 years to develop into a clinically remarkable tumor. For cancer cells, the genes encoding the immunoregulatory mechanisms employed by feto-placental units could be of value for escaping the host immune system. Taken together, these observations support the author's hypothesis that the evolution of viviparity resulted in an evolutionary trade-off that may have increased susceptibility to malignancies.

Mechanisms underlying the relaxation response induced by bradykinin in the epithelium-intact guinea-pig trachea in vitro

In this study, we investigated some of the signalling pathways involved in bradykinin (BK)-induced relaxation in epithelium-intact strips of the guinea-pig trachea (GPT + E). BK induced time- and concentration-dependent relaxation of GPT + E. Similar responses were observed for prostaglandin E2 (PGE2) or the combination of subthreshold concentrations of BK plus PGE2. The nonselective cyclooxygenase (COX) inhibitors indomethacin or pyroxicam, or the selective COX-2 inhibitors DFU, NS 398 or rofecoxib, but not the selective COX-1 inhibitor SC 560, all abolished BK-induced relaxation. The tyrosine kinase inhibitors herbimycin A and AG 490 also abolished BK-induced relaxation in GPT + E. The nonselective nitric oxide synthase (NOS) inhibitor 7-NINA concentration-dependently inhibited BK effects. BK-induced relaxation was prevented by the selective antagonists for EP3 (L 826266), but not by EP1 (SC 19221), EP1/EP2 (AH 6809) or EP4 (L161982) receptor antagonists. Otherwise, the selective inhibitors of protein kinases A, G and C, mitogen-activated protein kinases, phospholipases C and A2, nuclear factor-kappaB or potassium channels all failed to significantly interfere with BK-mediated relaxation.BK caused a marked increase in PGE2 levels, an effect that was prevented by NS 398, HOE 140 or AG 490. COX-2 expression did not differ in preparations with or without epithelium, and it was not changed by BK stimulation. However, incubation with BK significantly increased the endothelial NOS (eNOS) and neuronal NOS (nNOS) expression, independent of the epithelium integrity. Our results indicate that BK-induced relaxation in GPT + E depends on prostanoids (probably PGE2 acting via EP3 receptors) and NO release and seems to involve complex interactions between kinin B2 receptors, COX-2, nNOS, eNOS and tyrosine kinases.

Prostaglandin E2 induces FOXP3 gene expression and T regulatory cell function in human CD4+ T cells

Naturally occurring CD4+CD25+ regulatory T cells (T reg) are pivotal in suppressing immune responses and maintaining tolerance. The identification of molecules controlling T reg differentiation and function is important in understanding host immune responses in malignancy and autoimmunity. In this study we show that PGE2 enhances the in vitro inhibitory function of human purified CD4+CD25+ T reg cells. Moreover, PGE2 induces a regulatory phenotype in CD4+CD25- T cells. PGE2-treated T cell-mediated inhibition of anti-CD3-stimulated lymphocyte proliferation did not require cell contact. Phenotypic analysis revealed that PGE2 diminished CD25 expression in both CD4+CD25dim T cells and CD4+CD25bright T reg cells. PGE2 exposure induced the T reg cell-specific transcription factor forkhead/winged helix transcription factor gene (FOXP3) in CD4+CD25- T cells and significantly up-regulated its expression in CD4+CD25+ T reg cells. Similarly, 24-h incubation with supernatants from cyclooxygenase-2-overexpressing lung cancer cells that secrete high levels of PGE2 significantly induced FOXP3 in CD4+CD25- T cells. Finally, PGE2 up-regulated FOXP3 at both mRNA and protein levels and enhanced FOXP3 promoter activity. This is the first report indicating that PGE2 can modulate FOXP3 expression and T reg function in human lymphocytes.

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

Normal placentation requires a highly coordinated control of proliferation, migration and invasiveness of extravillous trophoblast cells. Since prostaglandin E2 is a major prostanoid synthesized by intrauterine tissues and highly involved in pregnancy homeostasis, we examined the possibility that it modulates extravillous trophoblast cell functions. Here, we report the presence of mRNAs for prostaglandin E2 EP2 and EP4 receptor isoforms and of proteins in both first-trimester human chorionic villi and in the human trophoblast-derived HTR-8/SVneo cells. Moreover we found that: (i) this cell line releases prostaglandin E2 and the output is enhanced by interleukin-1beta; (ii) the prostanoid consistently inhibits serum- or epidermal growth factor-induced cell proliferation and also migration. An involvement of cAMP in the prostaglandin E2 antiproliferative action is suggested by the observation that the prostanoid greatly enhances cAMP level in HTR-8/SVneo cells and that forskolin inhibits cell proliferation; moreover the administration of prostaglandin E2 plus forskolin, a condition which evokes a synergistic enhancement of cAMP, induces a major impairment of cell growth. Provided that our data are applicable to the trophoblast tissue in vivo, we suggest that prostaglandin E2 exerts an important control on extravillous trophoblast cell functions, preventing an excessive proliferation and migration.

Expression of cyclooxygenase-2 in colorectal cancer and its clinical significance

AIM: To clarify the clinicopathologic significance of COX-2 expression in human colorectal cancer.

METHODS: A total of 128 surgically resected colorectal cancer specimens were immunohistochemically analyzed with the use of anti-COX-2, anti-VEGF and anti-MMP-2 antibodies. The relationship between the cyclooxygenase-2 expression in primary lesions of colorectal cancer and clinicopathologic parameters was evaluated by chi-square test.

RESULTS: Among 128 cases of colorectal cancer, 87 (67.9%) were positive for cyclooxygenase-2. The expression of cyclooxygenase-2 was significantly correlated with the depth of invasion, stage of disease, and metastasis (lymph node and liver). Patients in T3-T4, stages III-IV and with metastasis had much higher expression of cyclooxygenase-2 than ones in T1-T2, stages I-II and without metastasis (P<0.05). Among 45 cases of colorectal cancer with lymph node metastasis, the COX-2- positive rate was 86.7% (39/45) for primary lesions and diffuse cytoplasmic staining for COX-2 protein was detected in cancer cells in 100% of metastatic lesions of the lymph nodes. VEGF expression was detected in 49 tumors (38.3%), and VEGF expression was closely correlated with COX-2 expression. The positive expression rate of VEGF (81.6%) in the cyclooxygenase-2-positive group was higher than that in the cyclooxygenase-2- negative group (18.4%, P<0.05). MMP-2 expression was detected in 88 tumors (68.8%), and MMP-2 expression was closely correlated with COX-2 expression. The positive expression rate of MMP-2 (79.6%) in the positive COX-2 group was higher than that in the negative COX-2 group (20.4%, P<0.05).

CONCLUSION: Cyclooxygenase-2 may be associated with tumor progression by modulating the angiogenesis and cancer cell motility and invasive potential in colorectal cancer and it can be used as a possible biomarker.

Dialogue materno-fœtal et implantation embryonnaire humaine : des concepts qui évoluent

Multiple immunogical mechanisms allow fetal allograft tolerance. In this review, we first describe the maternal and embryological side in order to expose the dangers for the embryo enabling the development of materno-fetal strategies that will allow fetal survival and growth.

Possible involvement of inositol phosphoglycan-P in human parturition

Preterm labour is a major cause of neonatal morbidity and mortality but the pathophysiology that underlies preterm labour is unknown. Inositolphosphoglycans (IPGs) comprise a ubiquitous family of putative carbohydrate second messengers and they have been linked to the pathogenesis of various conditions, including diabetes and pre-eclampsia. Studying IPG-P levels in normal and pre-eclamptic pregnancies, we noticed a constant rise of urinary IPG-P levels in all women at the time of delivery. A prospective pilot study of urinary IPG-P levels in 23 non-labouring and labouring women with uncomplicated pregnancies has, therefore, been performed. Levels of urinary IPG-P were significantly higher in labour than in the non-labouring group (P<0.0001). These higher levels have been found in both spontaneous and induced labour. The clinical significance of this observation with particular reference to the onset of labour itself is discussed.

Cyclooxygenase-2 expression and angiogenesis in colorectal cancer

AIM: Cyclooxygenase-2 is involved in a variety of important cellular functions, including cell growth and differentiation, cancer cell motility and invasion, angiogenesis and immune function. However, the role of cyclooxygenase-2 as an angiogenic factor in colorectal cancer tissue is still unclear. We investigated the relationship between cyclooxygenase-2 and angiogenesis by analyzing the expression of cyclooxygenase-2 in colorectal cancer tissue, as well as its association with vascular endothelial growth factor (VEGF) and microvascular density (MVD).

METHODS: The expression of cyclooxygenase-2, VEGF, as well as MVD was detected in 128 cases of colorectal cancer by immunohistochemical staining. The relationship between the cyclooxygenase-2 and VEGF expression and MVD was evaluated. Our objective was to determine the effect of cyclooxygenase-2 on the angiogenesis of colorectal cancer tissue.

RESULTS: Among 128 cases of colorectal cancer, 87 were positive for cyclooxygenase-2 (67.9%), and 49 for VEGF (38.3%), respectively. The microvessel counts ranged from 23 to 142, with a mean of 51.7 (standard deviation, 19.8). The expression of cyclooxygenase-2 was correlated significantly with the depth of invasion, stage of disease, metastasis (lymph node and liver), VEGF expression and MVD. Patients in T3-T4, stage III-IV and with metastasis had much higher expression of cyclooxygenase-2 than patients in T1-T2, stage I-II and without metastasis (P < 0.05). The positive expression rate of VEGF (81.6%) in the cyclooxygenase-2 positive group was higher than that in the cyclooxygenase-2 negative group (18.4%, P < 0.05). Also, the microvessel count (56 ± 16) in cyclooxygenase-2 positive group was significantly higher than that in cyclooxygenase-2 negative group (43 ± 12, P < 0.05). The microvessel count in tumors with positive cyclooxygenase-2 and VEGF was the highest (60 ± 18, 41-142, P < 0.05), whereas that in tumors with negative cyclooxygenase-2 and VEGF was the lowest (39 ± 16, 23-68, P < 0.05).

CONCLUSION: Cyclooxygenase-2 may be associated with tumor progression by madulating the angiogenesis in colorectal cancer tissue and used as a possible biomarker.

Mechanisms of enhanced macrophage-mediated prostaglandin E2 production and its suppressive role in Th1 activation in Th2-dominant BALB/c mice

PGE(2) has been known to suppress Th1 responses. We studied the difference in strains of mice in PGE(2) production by macrophages and its relation to Th1 activation. Macrophages from BALB/c mice produced greater amounts of PGE(2) than those from any other strains of mice, including C57BL/6, after LPS stimulation. In accordance with the amount of PGE(2) produced, macrophage-derived IL-12 and T cell-derived IFN-gamma production were more strongly suppressed in BALB/c macrophages than in C57BL/6 macrophages. When macrophages were treated with indomethacin or EP4 antagonist, Th1 cytokines were more markedly increased in cells from BALB/c mice than in those from C57BL/6 mice. Although cyclooxygenase-2 was expressed similarly after LPS stimulation in these mouse strains, the release of arachidonic acid and the expression of type V secretory phospholipase A(2) mRNA were greater in BALB/c macrophages. However, exogenous addition of arachidonic acid did not reverse the lower production of PGE(2) by C57BL/6 macrophages. The expression of microsomal PGE synthase, a final enzyme of PGE(2) synthesis, was also greater in BALB/c macrophages. These results indicate that the greater production of PGE(2) by macrophages, which is regulated by secretory phospholipase A(2) and microsomal PGE synthase but not by cyclooxygenase-2, is related to the suppression of Th1 cytokine production in BALB/c mice.