Allopurinol inhibits excess glucose-induced trophoblast IL-1ß and ROS production.

Pre-gestational diabetes is a risk factor for preeclampsia, a condition associated with inflammatory markers, a dysregulated angiogenic profile, and impaired placentation. Using an in vitro model, we previously reported that hyperglycemic levels of glucose induced a pro-inflammatory (IL-1ß, IL-8, RANTES, GRO-α), anti-angiogenic (sFlt-1) and anti-migratory profile in a human trophoblast cell line. The IL-1ß response to excess glucose was mediated by uric acid-induced activation of the NLRP3 inflammasome. Allopurinol is a xanthine oxidase inhibitor that inhibits uric acid and reactive oxygen species (ROS) production. Thus, we sought to test the effects of allopurinol on the IL-1ß and other inflammatory, angiogenic and migratory responses that are triggered in the trophoblast by excess glucose. Under excess glucose conditions, allopurinol significantly inhibited trophoblast secretion of inflammatory IL-1ß; caspase-1 activity; IL-8; RANTES; and GRO-α. Allopurinol also significantly inhibited excess glucose-induced trophoblast secretion of anti-angiogenic sFlt-1. The presence of IL1Ra significantly inhibited excess glucose-induced trophoblast IL-8 and GRO-α secretion but had no effect on RANTES or sFlt-1. Conversely, DPI, a ROS inhibitor, significantly inhibited excess glucose-induced trophoblast GRO-α and sFlt-1 secretion, but had no effect on IL-8 or RANTES. Together, our findings indicate that the xanthine oxidase inhibitor allopurinol inhibited excess glucose-induced trophoblast IL-1ß secretion. Additionally, through its inhibition of both IL-1ß and ROS production by the trophoblast, allopurinol reduced the additional pro-inflammatory and anti-angiogenic responses to excess glucose. Thus, allopurinol may be a candidate medication to prevent placental dysfunction and adverse pregnancy outcomes, such as preeclampsia, in pregnant women with diabetes.

Pathogenic Autoreactive T and B Cells Cross-React with Mimotopes Expressed by a Common Human Gut Commensal to Trigger Autoimmunity.

Given the immense antigenic load present in the microbiome, we hypothesized that microbiota mimotopes can be a persistent trigger in human autoimmunity via cross-reactivity. Using antiphospholipid syndrome (APS) as a model, we demonstrate cross-reactivity between non-orthologous mimotopes expressed by a common human gut commensal, Roseburia intestinalis (R. int), and T and B cell autoepitopes in the APS autoantigen ß2-glycoprotein I (ß2GPI). Autoantigen-reactive CD4+ memory T cell clones and an APS-derived, pathogenic monoclonal antibody cross-reacted with R. int mimotopes. Core-sequence-dependent anti-R. int mimotope IgG titers were significantly elevated in APS patients and correlated with anti-ß2GPI IgG autoantibodies. R. int immunization of mice induced ß2GPI-specific lymphocytes and autoantibodies. Oral gavage of susceptible mice with R. int induced anti-human ß2GPI autoantibodies and autoimmune pathologies. Together, these data support a role for non-orthologous commensal-host cross-reactivity in the development and persistence of autoimmunity in APS, which may apply more broadly to human autoimmune disease.

Role of NOD2 in antiphospholipid antibody-induced and bacterial MDP amplification of trophoblast inflammation.

Women with antiphospholipid antibodies (aPL) are at high risk for pregnancy complications, such as preeclampsia. We previously demonstrated that aPL recognizing ß2GPI promote an extravillous trophoblast pro-inflammatory, anti-migratory and anti-angiogenic profile similar to that seen in preeclampsia. Since preeclampsia in the absence of aPL may have an underlying infectious element, women with aPL may be at increased risk for preeclampsia or other adverse outcomes if an infection is present. Our objective was to determine the impact the common bacterial component, muramyl dipeptide (MDP), has on trophoblast responses to aPL. Herein, we report that bacterial MDP amplifies trophoblast IL-1ß expression, processing, and secretion in the presence of aPL through activation of NOD2. In the absence of MDP, NOD2 also mediates anti- ß2GPI antibody-induced trophoblast IL-1ß and VEGF secretion. Additionally, we report a role for extravillous trophoblast vimentin as a novel danger signal that contributes to the aPL-induced trophoblast IL-1ß production. Together our data indicate that NOD2 mediates trophoblast inflammatory and angiogenic responses to aPL alone, and mediates trophoblast inflammation in the presence of bacterial MDP. These findings suggest that a bacterial infection at the maternal-fetal interface may exacerbate the impact aPL have on trophoblast inflammation and, thus, on pregnancy outcome.

Excess glucose induce trophoblast inflammation and limit cell migration through HMGB1 activation of Toll-Like receptor 4.

PROBLEM: Hyperglycemia increases the risk of preeclampsia. Hyperglycemia induces a placental trophoblast inflammatory (IL-1ß, IL-6, IL-8), antiangiogenic (sFlt-1, sEndoglin), and anti-migratory profile. The IL-1ß response is mediated via inflammasome activation by the damage-associated molecular pattern (DAMP), uric acid. The objective of this study was to determine the role of high-mobility group box-1 (HMGB1), a DAMP that activates Toll-like receptor 4 (TLR4), in human first trimester trophoblast responses to hyperglycemia. The trophoblast response to excess glucose under different oxygen tensions was also investigated. METHOD OF STUDY: The human first trimester trophoblast cell line (Sw.71) was exposed to glucose mimicking normoglycemia (5 mmol/L) and hyperglycemia (10 mmol/L), either alone or with the TLR4 antagonist, LPS-RS; or the HMGB1 inhibitor, glycyrrhizin. Cells were also treated with glucose under hyperoxic (21% O2 ), normoxic (8% O2 ), and hypoxic (2% O2 ) conditions. Cell-free supernatants were assayed by ELISA and bioassays for inflammatory: IL-1ß, IL-6, and IL-8; inflammasome-associated: uric acid and caspase-1; angiogenic: sEndoglin, sFlt-1, and PlGF; and the DAMP, HMGB1. Cell migration was measured using a two-chamber colormetric assay. RESULTS: Excess glucose triggered a trophoblast sterile inflammatory IL-8 and antimigratory response through HMGB1 activation of TLR4. The IL-1ß and sFlt-1/PlGF response was TLR4-mediated, but HMGB1-independent, suggesting another DAMP may be involved. Hyperoxia rather than normoxia or hypoxia was a major driver of trophoblast dysfunction in response to excess glucose. CONCLUSION: The findings from this study indicate a novel mechanism by which hyperglycemia may impact trophoblast function, early placentation, and ultimately, pregnancy outcome.

Modulation of trophoblast function by concurrent hyperglycemia and antiphospholipid antibodies is in part TLR4-dependent.

PROBLEM: While diabetes and APS are individually associated with increased risk of poor perinatal outcomes, in particular preeclampsia, recent studies have demonstrated an association between concurrent aPL and diabetes leading to an increased risk of pregnancy morbidity. Hyperglycemia and aPL have independently been shown to alter human trophoblast function by inducing a pro-inflammatory, anti-angiogenic, and antimigratory response. However, little is known about the effects of concurrent hyperglycemia and aPL on trophoblast function. METHOD OF STUDY: A human first-trimester extravillous trophoblast cell line was exposed to glucose at 5 mmol/L (normoglycemia) or 25 mmol/L (hyperglycemia), all in the presence or absence of low-dose aPL or control IgG. For some experiments, the TLR4 antagonist, LPS-RS, was included. Cell culture supernatants were measured for inflammatory IL-1ß and IL-8, and angiogenic PlGF, sFlt-1, and sEndoglin by ELISA. Inflammasome-associated uric acid was measured using a bioassay; caspase-1 was measured using an activity assay. Trophoblast migration was quantified using a two-chamber colorimetric assay. RESULTS: Compared to excess glucose alone, combination excess glucose and low-dose aPL (a) further augmented trophoblast inflammatory IL-1ß, inflammasome-associated uric acid and caspase-1, and pro-angiogenic PlGF; (b) dampened trophoblast inflammatory IL-8, anti-angiogenic sEndoglin, and sFlt-1; and (c) further reduced trophoblast migration. CONCLUSION: Our findings indicate that while concurrent aPL and hyperglycemia are overall detrimental to trophoblast function, the presence of two simultaneous insults triggers some protective effects.

Antiphospholipid Antibodies Inhibit Trophoblast Toll-Like Receptor and Inflammasome Negative Regulators.

OBJECTIVE: Women with antiphospholipid antibodies (aPL) are at risk for pregnancy complications associated with poor placentation and placental inflammation. Although these antibodies are heterogeneous, some anti-ß2 -glycoprotein I (anti-ß2 GPI) antibodies can activate Toll-like receptor 4 (TLR-4) and NLRP3 in human first-trimester trophoblasts. The objective of this study was to determine the role of negative regulators of TLR and inflammasome function in aPL-induced trophoblast inflammation. METHODS: Human trophoblasts were not treated or were treated with anti-ß2 GPI aPL or control IgG in the presence or absence of the common TAM (TYRO3, AXL, and Mer tyrosine kinase [MERTK]) receptor ligand growth arrest-specific protein 6 (GAS6) or the autophagy-inducer rapamycin. The expression and function of the TAM receptor pathway and autophagy were measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), Western blotting, and enzyme-linked immunosorbent assay (ELISA). Antiphospholipid antibody-induced trophoblast inflammation was measured by qRT-PCR, activity assays, and ELISA. RESULTS: Anti-ß2 GPI aPL inhibited trophoblast TAM receptor function by reducing cellular expression of the receptor tyrosine kinases AXL and MERTK and the ligand GAS6. The addition of GAS6 blocked the effects of aPL on the TLR-4-mediated interleukin-8 (IL-8) response. However, the NLRP3 inflammasome-mediated IL-1ß response was not affected by GAS6, suggesting that another regulatory pathway was involved. Indeed, anti-ß2 GPI aPL inhibited basal trophoblast autophagy, and reversing this with rapamycin inhibited aPL-induced inflammasome function and IL-1ß secretion. CONCLUSION: Basal TAM receptor function and autophagy may serve to inhibit trophoblast TLR and inflammasome function, respectively. Impairment of TAM receptor signaling and autophagy by anti-ß2 GPI aPL may allow subsequent TLR and inflammasome activity, leading to a robust inflammatory response.

Antiphospholipid antibody-induced miR-146a-3p drives trophoblast interleukin-8 secretion through activation of Toll-like receptor 8.

STUDY QUESTION: What is the role of microRNAs (miRs) in antiphospholipid antibody (aPL)-induced trophoblast inflammation? SUMMARY ANSWER: aPL-induced up-regulation of trophoblast miR-146a-3p is mediated by Toll-like receptor 4 (TLR4), and miR-146a-3p in turn drives the cells to secrete interleukin (IL)-8 by activating the RNA sensor, TLR8. WHAT IS KNOWN ALREADY: Obstetric antiphospholipid syndrome (APS) is an autoimmune disorder characterized by circulating aPL and an increased risk of pregnancy complications. We previously showed that aPL recognizing beta2 glycoprotein I (ß2GPI) elicit human first trimester trophoblast secretion of IL-8 by activating TLR4. Since some miRs control TLR responses, their regulation in trophoblast cells by aPL and functional role in the aPL-mediated inflammatory response was investigated. miRs can be released from cells via exosomes, and therefore, miR exosome expression was also examined. A panel of miRs was selected based on their involvement with TLR signaling: miR-9; miR-146a-5p and its isomiR, miR-146a-3p; miR-155, miR-210; and Let-7c. Since certain miRs can activate the RNA sensor, TLR8, this was also investigated. STUDY DESIGN, SIZE, DURATION: For in vitro studies, the human first trimester extravillous trophoblast cell line, HTR8 was studied. HTR8 cells transfected to express a TLR8 dominant negative (DN) were also used. Plasma was evaluated from pregnant women who have aPL, either with or without systemic lupus erythematous (SLE) (n = 39); SLE patients without aPL (n = 30); and healthy pregnant controls (n = 20). PARTICIPANTS/MATERIALS, SETTING, METHODS: Trophoblast HTR8 wildtype and TLR8-DN cells were incubated with or without aPL (mouse anti-human ß2GPI mAb) for 48-72 h. HTR8 cells were also treated with or without aPL in the presence and the absence of a TLR4 antagonist (lipopolysaccharide from Rhodobacter sphaeroides; LPS-RS), specific miR inhibitors or specific miR mimics. miR expression levels in trophoblast cells, trophoblast-derived exosomes and exosomes isolated from patient plasma were measured by qPCR. Trophoblast IL-8 secretion was measured by ELISA. MAIN RESULTS AND THE ROLE OF CHANCE: aPL significantly increased trophoblast cellular and exosome expression of miR-146a-5p, miR-146a-3p, miR-155 and miR-210. aPL-induced up-regulation of trophoblast miR-146a-5p, miR-146a-3p and miR-210, but not miR-155, was inhibited by the TLR4 antagonist, LPS-RS. While inhibition or overexpression of miR-146a-5p had no effect on aPL-induced trophoblast IL-8 secretion, miR-146a-3p inhibition significantly reduced this response. aPL-induced trophoblast IL-8 secretion was inhibited by the presence of the TLR8-DN. In the absence of aPL, transfection of trophoblast cells with a miR-146a-3p mimic significantly increased IL-8 secretion and this was inhibited by the presence of the TLR8-DN. Patients with aPL and adverse pregnancy outcomes (APOs) expressed significantly higher levels of circulating miR-146a-3p compared with healthy pregnant controls with no pregnancy complications (P < 0.05). LIMITATIONS, REASONS FOR CAUTION: While the enrichment of miR-146a-3p in trophoblast-derived exosomes support the role of this miR acting in a paracrine or endocrine manner through exosome delivery, this has not been demonstrated. However, miR-146a-3p may also exert its pro-inflammatory effect intracellularly within the same trophoblast cell targeted by aPL. WIDER IMPLICATIONS OF THE FINDINGS: These findings provide a novel mechanism of trophoblast inflammation through miRs activating RNA-sensing receptors. Furthermore, circulating exosomal-associated miR-146a-3p in APS patients may serve clinically as a biomarker for related APOs. STUDY FUNDING/COMPETING INTERESTS: This study was supported in part by grants from the American Heart Association (#10GRNT3640032 to V.M.A.), the March of Dimes Foundation (Gene Discovery and Translational Research Grant #6-FY12-255 to V.M.A.), NICHD, NIH (R01HD049446 to V.M.A.), the Gina M. Finzi Memorial Student Summer Fellowship from the Lupus Foundation of America (to S.M.G.), and the Yale University School of Medicine Medical Student Fellowship (to S.M.G.). The authors declare no competing financial interests. TRIAL REGISTRATION NUMBER: N/A.

Interferon-α and angiogenic dysregulation in pregnant lupus patients who develop preeclampsia.

OBJECTIVE: To investigate whether an elevated interferon-α (IFNα) level early in pregnancy is associated with poor pregnancy outcomes and to examine the relationship of an elevated IFNα level to angiogenic imbalance. METHODS: Women were enrolled in a longitudinal case-control study of pregnant patients with lupus. Serum samples obtained monthly throughout pregnancy were assayed for IFNα and for the antiangiogenic factor soluble Flt-1 and the proangiogenic factor placenta growth factor (PlGF). Each of 28 patients with systemic lupus erythematosus (SLE) with a poor pregnancy outcome was matched to an SLE patient with an uncomplicated pregnancy and to a pregnant healthy control. The effects of IFNα and/or soluble Flt-1 on human endothelial cells and endothelial cell-trophoblast interactions were assessed. RESULTS: Compared to SLE patients with uncomplicated pregnancies, patients with preeclampsia had increased IFNα levels before clinical symptoms. Patients without autoimmune disease who developed preeclampsia did not have increased IFNα levels. In SLE patients with low IFNα levels, marked angiogenic imbalance (higher soluble Flt-1, lower PlGF, and higher soluble Flt-1:PlGF ratios) preceded maternal manifestations of preeclampsia, whereas in SLE patients with high IFNα levels, preeclampsia occurred without evidence of systemic angiogenic imbalance. Treatment of human endothelial cells with soluble Flt-1 induced expression of sFLT1 messenger RNA, and IFNα dramatically amplified responses to soluble Flt-1. In a model of spiral artery transformation, only the combination of IFNα and soluble Flt-1 disrupted the ability of trophoblast cells to remodel endothelial tube structures. CONCLUSION: Our findings identify a new mechanism by which IFNα induces an antiangiogenic milieu and increases the sensitivity of endothelial cells to soluble Flt-1, and suggest that elevated IFNα levels may contribute to the pathogenesis of preeclampsia in some pregnant patients with SLE.

Vitamin D reverses aPL-induced inflammation and LMWH-induced sFlt-1 release by human trophoblast.

PROBLEM: Women with antiphospholipid syndrome (APS) are at increased risk of recurrent pregnancy loss (RPL) and preeclampsia. Antiphospholipid antibodies (aPL) directly alter trophoblast function. Treatment with low molecular weight heparin (LMWH) reduces the risk of RPL but not preeclampsia. Moreover, LMWH stimulates trophoblast sFlt-1 release, an anti-angiogenic factor associated with preeclampsia. Since vitamin D deficiency is associated with APS and preeclampsia, this study sought to determine the effect of vitamin D on trophoblast function in the setting of aPL and LMWH. METHOD OF STUDY: A human first trimester trophoblast cell line (HTR8) and primary trophoblast cultures were treated with or without aPL in the presence and absence of vitamin D, LMWH or both. Trophoblast secretion of inflammatory cytokines and angiogenic factors were measured by ELISA. RESULTS: Vitamin D alone or in combination with LMWH attenuated the aPL-induced trophoblast inflammatory response in the HTR8 cells and primary cultures. While vitamin D did not have any impact on aPL-mediated modulation of angiogenic factors in the primary trophoblast, it significantly inhibited LMWH-induced sFlt-1 release. CONCLUSION: LMWH in combination with vitamin D may be more beneficial than single-agent therapy by preventing aPL-induced trophoblast inflammation and reversing LMWH-induced sFlt-1 secretion.

Aspirin-triggered lipoxin prevents antiphospholipid antibody effects on human trophoblast migration and endothelial cell interactions.

OBJECTIVE: Antiphospholipid antibodies (aPL) interfere with several physiologic functions of human trophoblasts, including reducing their ability to migrate, decreasing their production of angiogenic factors, and inducing an inflammatory response. This may provide the underlying mechanism by which aPL responses lead to recurrent pregnancy loss or preeclampsia in women with obstetric antiphospholipid syndrome (APS). Although treatment with heparin may reduce the rate of recurrent pregnancy loss, the risk of preeclampsia remains high. Therefore, alternative treatments are needed for the management of pregnant patients with APS. Since aspirin-triggered lipoxins (ATLs) have immune and angiogenic modulatory properties, the objective of this study was to determine the effects of the ATL 15-epi-lipoxin A4 on the function of aPL-altered human trophoblasts in the first trimester of pregnancy. METHODS: A first-trimester human trophoblast cell line (HTR8) was treated with mouse anti-human ß2 -glycoprotein I monoclonal antibodies (aPL) in the presence or absence of the ATL 15-epi-lipoxin A4 . Trophoblast migration and interactions with endometrial endothelial cells were measured using Transwell and coculture assays. Trophoblast secretion of cytokines and angiogenic factors was measured by enzyme-linked immunosorbent assay. RESULTS: Treatment of HTR8 cells with ATL reversed the aPL-induced decrease in trophoblast migration, an effect that appeared to be regulated through restoration of interleukin-6 production. Using a model of spiral artery transformation, aPL and sera from APS patients with pregnancy morbidity disrupted trophoblast-endothelial cell interactions, and treatment with ATL restored the stability of the cocultures. In contrast, ATL treatment did not resolve the proinflammatory and antiangiogenic responses of trophoblasts induced by aPL. CONCLUSION: These findings indicate that ATLs may have some benefits in terms of preventing the effects of aPL on trophoblast function, which raises the possibility of the use of ATLs as an adjuvant therapy in women with aPL.

Glucose and metformin modulate human first trimester trophoblast function: a model and potential therapy for diabetes-associated uteroplacental insufficiency.

PROBLEM: Diabetes confers an increased risk of preeclampsia, but its pathogenic role in preeclampsia is poorly understood. The objective of this study was to elucidate the effects of excess glucose on trophoblast function and whether any changes could be reversed by metformin. METHOD OF STUDY: The human first trimester trophoblast cell line (Sw.71) was treated with glucose at 5, 10, 25, and 50 mm, in the presence and absence of metformin. Trophoblast migration was quantified and supernatant cytokine, chemokine, and angiogenic factors measured. RESULTS: Increasing concentrations of glucose significantly increased trophoblast secretion of the inflammatory cytokines/chemokines: IL-1ß, IL-6, IL-8, GRO-α, RANTES, and G-CSF; significantly increased trophoblast secretion of the anti-angiogenic factors sFlt-1 and sEndoglin; and significantly decreased trophoblast migration. Excess glucose-induced trophoblast IL-1ß production was inhibited by disabling the Nalp3/ASC inflammasome. Metformin partially reduced the glucose-induced inflammatory response, but had no effect on the anti-angiogenic or antimigratory response. CONCLUSION: Excess glucose induced a pro-inflammatory, anti-angiogenic, and antimigratory state in first trimester trophoblast cells. Glucose-induced trophoblast IL-1ß secretion was mediated by the inflammasome. Glucose-induced inflammation was partially reversed by metformin. These findings demonstrate the pleiotropic effects of hyperglycaemia on the trophoblast, providing potential explanations for the strong link between diabetes and preeclampsia.

Low molecular weight heparin modulates maternal immune response in pregnant women and mice with thrombophilia.

PROBLEM: Thrombophilia is associated with pregnancy complications. Treatment with low molecular weight heparin (LMWH) improves pregnancy outcome, but the underlying mechanisms are not clear. METHODS OF STUDY: We analyzed Treg frequency in blood from thrombophilic pregnancies treated with LMWH (n = 32) or untreated (n = 33) and from healthy pregnancies (n = 39) at all trimesters. Additionally, we treated pregnant wild-type, heterozygous and homozygous factor-V-Leiden (FVL) mice with LMWH or PBS and determined Treg frequency, pro-/anti-inflammatory cytokine levels and Caspase-3-activity in placenta and decidua. RESULTS: Treg frequencies were increased in second and third trimester in LMWH-treated thrombophilic pregnancies compared to controls. Treg levels were comparable to those of normal pregnancies. Homozygous FVL mice had decreased decidual Tregs compared to wild-type mice. LMWH treatment normalized Tregs and was associated with increased decidual IL-10 mRNA. LMWH diminished Caspase-3-activity in mice of all genotypes. CONCLUSION: We demonstrated anti-apoptotic and anti-inflammatory effects of LMWH in pregnant FVL mice. LMWH increased Treg levels in mice and humans, which suggests benefits of LMWH treatment for thrombophilic women during pregnancy.

Effect of hydroxychloroquine on antiphospholipid antibody-induced changes in first trimester trophoblast function.

PROBLEM: Women with antiphospholipid syndrome (APS) are at risk for pregnancy complications. Antiphospholipid antibodies (aPL) alter trophoblast function by triggering an inflammatory cytokine response; modulating angiogenic factor secretion; and inhibiting migration. While patients with APS are often treated with hydroxychloroquine (HCQ), its effect on trophoblast function is poorly understood. METHOD OF STUDY: A human first trimester trophoblast cell line was treated with or without antihuman ß2GPI mAbs in the presence or absence of HCQ. Supernatants were analyzed by ELISA. Cell migration was measured using a colormetric assay. RESULTS: Antiphospholipid antibodies-induced trophoblast IL-8, IL-1 ß, PlGF, and sEndoglin secretion were not altered by HCQ. aPL-induced inhibition of trophoblast migration was partially reversed by HCQ, even though HCQ significantly increased secretion of pro-migratory IL-6 to greater than baseline. aPL-induced upregulation of TIMP2 appears to inhibit trophoblast migration; the inability of HCQ to prevent aPL-induced TIMP2 may explain why migration was only partially restored. CONCLUSION: Hydroxychloroquine reversed the aPL-inhibition of trophoblast IL-6 secretion and partially limited aPL-inhibition of cell migration. Thus, some form of combination therapy that includes HCQ may be beneficial to pregnant APS patients.

A role for uric acid and the Nalp3 inflammasome in antiphospholipid antibody-induced IL-1ß production by human first trimester trophoblast.

Women with antiphospholipid syndrome (APS) are at risk of recurrent pregnancy loss and obstetrical disorders, such as preeclampsia and intrauterine growth restriction (IUGR). Antiphospholipid antibodies (aPL) directly target the placenta by binding beta2-glycoprotein I (ß2GPI) expressed on the trophoblast. We recently demonstrated in human first trimester trophoblast cells that anti-ß2GPI antibodies (Abs) induce the secretion of IL-1ß in a Toll-like receptor 4 (TLR4)-dependent manner. IL-1ß secretion requires processing of pro-IL-1ß and this is mediated by the inflammasome, a complex of Nalp3, apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1. The objective of this study was to determine if aPL induce IL-1ß production in trophoblast via the inflammasome. Using a human first trimester trophoblast cell line, we demonstrated that a mouse anti-ß2GPI mAb and human polyclonal aPL-IgG induce IL-1ß processing and secretion, which was partially blocked upon caspase-1 inhibition. Nalp3 and ASC knockdown also attenuated anti-ß2GPI Ab-induced IL-1ß secretion. Furthermore, aPL stimulated the production of uric acid in a TLR4-dependent manner; and inhibition of uric acid prevented aPL-induced IL-1ß production by the trophoblast. These findings demonstrate that aPL, via TLR4 activation, induce a uric acid response in human trophoblast, which in turn activates the Nalp3/ASC inflammasome leading to IL-1ß processing and secretion. This novel mechanism may account for the inflammation at the maternal-fetal interface, which causes placental dysfunction and increases the risk of adverse pregnancy outcome in patients with APS.

Cutting-edge report: TLR10 plays a role in mediating bacterial peptidoglycan-induced trophoblast apoptosis.

PROBLEM: 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. METHOD OF STUDY: 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. RESULTS: 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. CONCLUSION: 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.

Pravastatin does not prevent antiphospholipid antibody-mediated changes in human first trimester trophoblast function.

STUDY QUESTION: What is the effect of pravastatin on antiphospholipid antibody (aPL) modulation of human first trimester trophoblast function? SUMMARY ANSWER: Pravastatin does not prevent the effects of aPL on human first trimester trophoblast cell function. WHAT IS KNOWN ALREADY: Antiphospholipid syndrome (APS) is associated with recurrent pregnancy loss and late pregnancy complications, such as pre-eclampsia, owing to direct targeting of the placenta by aPL. While treatment with heparin reduces the rate of pregnancy loss, the risk for severe pre-eclampsia remains high. Thus, there is a need to find alternative treatments for the prenatal management of patients with APS. Statins have recently been shown to prevent aPL-mediated fetal loss in mice but their effects on a human pregnancy model of APS have not yet been studied. DESIGN, DATA COLLECTION, METHODS: The human first trimester trophoblast cell line, HTR8, and human first trimester trophoblast primary cultures were incubated with or without a mouse anti-human beta 2 glycoprotein I (ß(2)GPI) monoclonal antibody in the presence or absence of pravastatin. Cytokine and angiogenic factor secretion were measured by enzyme-linked immunosorbent assay and multiplex analysis. Cell migration was measured using a colorimetric two-chamber migration assay. MAIN FINDINGS: Using the human first trimester trophoblast cell line, HTR8, pravastatin significantly augmented, compared with no treatment, aPL-dependent secretion of interleukin (IL)-8 (P< 0.05), IL-1ß (P< 0.05) and soluble endoglin (P< 0.01) but had no effect on aPL-induced up-regulation of vascular endothelial growth factor, placenta growth factor or growth-related oncogene alpha secretion. Furthermore, pravastatin alone limited basal HTR8 cell migration (P< 0.01), and did not mitigate the adverse effect of aPL on trophoblast migration. Pravastatin also had no impact on the secretion of pro-inflammatory cytokines and angiogenic factors by primary human first trimester trophoblast cells exposed to aPL. LIMITATIONS AND WIDER IMPLICATIONS OF THE FINDINGS: While our in vitro findings suggest that pravastatin may not be effective in preventing pregnancy complications in patients with APS, the in vivo condition may be more complex, and thus, more studies are needed to determine the effectiveness of pravastatin in the prevention of aPL-associated pregnancy complications in humans. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the American Heart Association.

Immune cell activation by trophoblast-derived microvesicles is mediated by syncytin 1.

Envelope glycoproteins of human endogenous retrovirus (HERV), such as syncytin 1 (HERV-W), are highly expressed in the placenta and some family members have immunomodulatory properties. Placental microvesicles (MV), which are shed into the maternal circulation during pregnancy, have been demonstrated to induce immune cell activation. Therefore, the aim of this study was to investigate the immunological properties of the highly expressed placental HERV-W protein, syncytin 1, and its potential involvement in placental MV modulation of immune cell activity. The MV shed from first trimester, normal term and pre-eclamptic term placentas, and from the BeWo trophoblast cell line, all contain syncytin 1. Recombinant syncytin 1 and syncytin 1-positive BeWo trophoblast MV both induced peripheral blood mononuclear cell (PBMC) activation, indicated through production of cytokines and chemokines. Reducing syncytin 1 content in BeWo MV inhibited PBMC activation. Recombinant syncytin 1 and syncytin-1-positive BeWo MV dampened PBMC responses to lipopolysaccharide challenge. Our findings suggest that syncytin 1 is shed from the placenta into the maternal circulation in association with MV, and modulates immune cell activation and the responses of immune cells to subsequent lipopolysaccharide stimulation. These studies implicate placental MV-associated HERV in fetal regulation of the maternal immune system.

Aspirin and heparin effect on basal and antiphospholipid antibody modulation of trophoblast function.

OBJECTIVE: Low molecular weight (LMW) heparin, with or without aspirin (acetylsalicylic acid [ASA]), is used to prevent complications in antiphospholipid syndrome in pregnancy. Our objective was to elucidate the actions of low-dose LMW heparin and ASA on basal and antiphospholipid antibody-induced modulation of trophoblast function. METHODS: The human first-trimester trophoblast cell line (HTR-8) was treated with or without antiphospholipid antibody in the presence of no medication, low-dose LMW heparin, low-dose ASA, or combination therapy. Interleukin (IL)-6, IL-8, IL-1ß, growth-regulated oncogene-α, vascular endothelial growth factor (VEGF), placental growth factor, soluble FMS-like tyrosine kinase-1, and soluble endoglin were measured in the supernatant. Cell migration was performed using a two-chamber assay. RESULTS: Low molecular weight heparin improved basal trophoblast migration and induced potent increases in growth-regulated oncogene-α and soluble FMS-like tyrosine kinase-1. Aspirin did not affect basal function. Combined therapy promoted migration but did not reverse the LMW heparin-induced soluble FMS-like tyrosine kinase-1 effect. Antiphospholipid antibody increased IL-8, IL-1ß, growth-regulated oncogene-alpha, VEGF, placental growth factor, and soluble endoglin secretion, while decreasing cell migration and IL-6 and soluble FMS-like tyrosine kinase-1 secretion. The antiphospholipid antibody-induced cytokine changes were best reversed with LMW heparin, with partial reversal of IL-8 and IL-1ß upregulation. The antiphospholipid antibody-induced angiogenic changes were worsened by LMW heparin, with increased soluble FMS-like tyrosine kinase-1 secretion. The therapies did not reverse antiphospholipid antibody-induced decrease in migration. CONCLUSION: In the absence of antiphospholipid antibodies, LMW heparin induces potentially detrimental proinflammatory and antiangiogenic profile in the trophoblast. In the presence of antiphospholipid antibodies, single-agent LMW heparin may be the optimal therapy to counter trophoblast inflammation, but also induces an antiangiogenic response. These findings may explain the inability of current therapies to consistently prevent adverse outcomes.

Nod1 activation by bacterial iE-DAP induces maternal-fetal inflammation and preterm labor.

There is a strong association between infection and prematurity; however, the underlying mechanisms remain largely unknown. Nod1 and Nod2 are intracellular pattern recognition receptors that are activated by bacterial peptides and mediate innate immunity. We previously demonstrated that human first-trimester trophoblasts express Nod1 and Nod2, which trigger inflammation upon stimulation. This study sought to determine the expression and function of Nod1 and Nod2 in third-trimester trophoblasts, and to characterize the in vivo effects of Nod1 activation on pregnancy outcome. Human term placental tissues and isolated term trophoblast expressed Nod1, but not Nod2. Activation of Nod1 by its agonist, bacterial γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP), in term trophoblast cultures induced a proinflammatory cytokine profile, characterized by elevated levels of secreted IL-6, GRO-α, and MCP-1, when compared with the control. However, these cytokines were not upregulated in response to Nod2 stimulation with bacterial MDP. Administration of high-dose bacterial iE-DAP to pregnant C57BL/6J mice on embryonic day 14.5 triggered preterm delivery within 24 h. iE-DAP at a lower dose that did not induce prematurity, reduced fetal weight, altered the cytokine profile at the maternal-fetal interface, and induced fetal inflammation. Thus, functional Nod1 is expressed by trophoblast cells across gestation and may have a role in mediating infection-associated inflammation and prematurity. This study demonstrates that pattern recognition receptors, other than the TLRs, may be implicated or involved in infection-associated preterm labor.

Modulation of trophoblast angiogenic factor secretion by antiphospholipid antibodies is not reversed by heparin.

PROBLEM Women with antiphospholipid antibodies (aPL) are at risk of miscarriage and pre-eclampsia, obstetrical disorders associated with reduced trophoblast invasion and spiral artery transformation. aPL target the placenta by binding beta(2) -glycoprotein I (ß(2) GPI) on the trophoblast. In this study, we determined whether aPL alter the trophoblast secretion of angiogenic factors and evaluated the effect of low molecular weight heparin (LMWH) on this response. METHOD OF STUDY First-trimester trophoblast was treated with anti-ß(2) GPI antibodies with or without LMWH. Angiogenic factor secretion was measured by enzyme-linked immunosorbent assay. RESULTS Trophoblast cells produced more vascular endothelial growth factor (VEGF), placenta growth factor (PlGF), and soluble endoglin following exposure to anti-ß(2) GPI Abs, and this occurred in both a MyD88-dependent and MyD88-independent manner. LMWH was unable to reverse the effects of the anti-ß(2) GPI Abs on trophoblast VEGF secretion, but enhanced PlGF. Strikingly, LMWH upregulated soluble fms-like tyrosine kinase receptor-1 (sFlt-1) secretion independently of aPL. CONCLUSION This study demonstrates that aPL perturb the secretion of trophoblast angiogenic factors. LMWH does not reverse this effect but exacerbates sFlt-1 secretion, a potent anti-angiogenic factor. These findings may help to explain why women with antiphospholipid syndrome, who are treated with heparin to prevent early pregnancy loss, remain at increased risk of developing late obstetrical complications, such as pre-eclampsia.