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Chorioamnionitis, premature rupture of fetal membranes (FM), and subsequent preterm birth are associated with local infection and inflammation, particularly interleukin 1 beta (IL-1β) production. While bacterial infections are commonly identified, other microorganisms may play a role in the pathogenesis. Since viral pandemics, such as influenza, Ebola and Zika are becoming more common, and pregnant women are at increased risk of associated complications, this study evaluated the impact viral infection had on human FM innate immune responses. This study shows that a herpes viral infection of FMs sensitizes the tissue to low levels of bacterial lipopolysaccharide (LPS), giving rise to an exaggerated IL-1β response. Using an ex vivo human FM explant system and an in vivo mouse model of pregnancy, we report that the mechanism by which this aggravated inflammation arises is through the inhibition of the TAM receptor, MERTK, and activation of the inflammasome. The TAM receptor ligand, growth arrest specific 6 (GAS6), re-establishes the normal FM response to LPS by restoring and augmenting TAM receptor and ligand expression, and by preventing the exacerbated IL-1β processing and secretion. These findings indicate a novel mechanism by which viruses alter normal FM immune responses to bacteria, potentially giving rise to adverse pregnancy outcomes.

OBJECTIVE: Pregnancies in women with the antiphospholipid syndrome (APS) are frequently complicated by fetal loss and intrauterine growth restriction (IUGR). How circulating antiphospholipid antibodies (aPL) cause pregnancy complications in APS is poorly understood. We sought to determine if the LDL receptor family member apoE receptor 2 (apoER2) mediates trophoblast dysfunction and pregnancy complications induced by aPL. METHODS: Placental and trophoblast apoER2 expression was evaluated by immunohistochemistry and immunoblotting. Normal human IgG (NHIgG) and aPL were purified from healthy individuals and APS patients, respectively. The role of apoER2 in aPL-induced changes in trophoblast proliferation, migration and kinase activation was assessed using RNA interference in HTR-8/SVneo cells. The participation of apoER2 in aPL-induced pregnancy loss and IUGR was evaluated in pregnant apoER2(+/+) and apoER2(-/-) mice injected with aPL or NHIgG. RESULTS: We found that apoER2 is abundant in human and mouse placental trophoblasts, and in multiple trophoblast-derived cell lines including HTR-8/SVneo cells. ApoER2 and its interaction with the cell surface protein β2-glycoprotein I were required for aPL-induced inhibition of cultured trophoblast proliferation and migration. In parallel, aPL antagonism of Akt kinase activation by EGF in trophoblasts was mediated by apoER2. Furthermore, in a murine passive transfer model of pregnancy complications of APS, apoER2(-/-) mice were protected from both aPL-induced fetal loss and aPL-induced IUGR. CONCLUSION: ApoER2 plays a major role in the attenuation of trophoblast function by aPL, and the receptor mediates aPL-induced pregnancy complications in vivo in mice. ApoER2-directed interventions can now potentially be developed to combat the pregnancy complications associated with APS. This article is protected by copyright. All rights reserved.

There is a strong correlation between intrauterine bacterial infection and preterm labor. While inflammation is a common mechanism, certain pathogens may trigger placental apoptosis. TLR2 activation by gram-positive bacterial peptidoglycan (PDG) induces first-trimester trophoblast apoptosis and decreased IL-6 secretion. This is dependent upon the presence of TLR1 and the absence of TLR6 and both TLR2 coreceptors. As TLR10 is also a TLR2 coreceptor, the objective of this study was to determine its expression and function in the trophoblast.First-and third-trimester human placental tissue and isolated trophoblast were evaluated for TLR10 expression. A first-trimester human trophoblast cell line stably transfected with a TLR10 dominant negative (TLR10-DN) or vector control was treated with or without PDG and analyzed for apoptosis and IL-6.TLR10 was expressed by trophoblasts during the first and third trimesters of pregnancy. PDG-induced trophoblast caspase-3 activity was inhibited by the presence of the TLR10-DN. The presence of the TLR10-DN had no effect on PDG reduction in trophoblast IL-6 secretion.This study demonstrates that trophoblast TLR10 plays a role in promoting apoptosis triggered by gram-positive bacterial components and suggests that TLR10 may regulate the balance between trophoblast survival and cell death.

Chlamydia trachomatis and smoking are major risk factors for tubal ectopic pregnancy (EP), but the underlying mechanisms of these associations are not completely understood. Fallopian tube (FT) from women with EP exhibit altered expression of prokineticin receptors 1 and 2 (PROKR1 and PROKR2); smoking increases FT PROKR1, resulting in a microenvironment predisposed to EP. We hypothesize that C. trachomatis also predisposes to EP by altering FT PROKR expression and have investigated this by examining NFkappaB activation via ligation of the Toll-like receptor (TLR) family of cell-surface pattern recognition receptors. PROKR2 mRNA was higher in FT from women with evidence of past C. trachomatis infection than in those without (P < 0.05), and was also increased in FT explants and in oviductal epithelial cell line OE-E6/E7 infected with C. trachomatis (P < 0.01) or exposed to UV-killed organisms (P < 0.05). The ability of both live and dead organisms to induce this effect suggests ligation of a cell-surface-expressed receptor. FT epithelium and OE-E6/E7 were both found to express TLR2 and TLR4 by immunohistochemistry. Transfection of OE-E6/E7 cells with dominant-negative TLR2 or IkappaBalpha abrogated the C. trachomatis-induced PROKR2 expression. We propose that ligation of tubal TLR2 and activation of NFkappaB by C. trachomatis leads to increased tubal PROKR2, thereby predisposing the tubal microenvironment to ectopic implantation.

It is well established that intrauterine infections can pose a threat to pregnancy by gaining access to the placenta and fetus, and clinical studies have strongly linked bacterial infections with preterm labor. While Chlamydia trachomatis (C. trachomatis; Ct) can infect the placenta and decidua, little is known about its effects on trophoblast cell immune function. We have demonstrated that Ct infects trophoblast cells to form inclusions, and completes the life cycle within these cells by generating infectious elementary bodies. Moreover, infection with Ct leads to differential modulation of the trophoblast cell's production of cytokines and chemokines. Using two human first trimester trophoblast cell lines, Sw.71 and H8, the most striking feature we found was that Ct infection results in a strong induction of IL-1β secretion, and a concomitant reduction in MCP-1 (CCL2) production in both cell lines. In addition, we have found that Ct infection of the trophoblast results in the cleavage and degradation of NFκB p65. These findings suggest that the effect of a Chlamydia infection on trophoblast secretion of chemokines and cytokines involves both activation of innate immune receptors expressed by the trophoblast, and virulence factors secreted into the trophoblast by the bacteria. Such altered trophoblast innate immune responses may have a profound impact on the microenvironment of the maternal-fetal interface, and this could influence pregnancy outcome.