Melissa J. Mulla

Antiphospholipid antibodies induce a pro-inflammatory response in first trimester trophoblast via the TLR4/MyD88 pathway

Problem  Women with antiphospholipid antibodies (aPL) are at risk for recurrent miscarriage, pre‐eclampsia, and pre‐term labor. aPL target the placenta directly by binding to beta2‐glycoprotein I (β2GPI) expressed on the surface of trophoblast cells. The objective of this study was to determine the effects of aPL on trophoblast function and the mechanisms involved.

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

Citation Carroll TY, Mulla MJ, Han CS, Brosens JJ, Chamley LW, Giles I, Pericleous C, Rahman A, Sfakianaki AK, Paidas MJ, Abrahams VM. Modulation of trophoblast angiogenic factor secretion by antiphospholipid antibodies is not reversed by heparin. Am J Reprod Immunol 2011; 66: 286–296

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.

Uric acid induces trophoblast IL-1β production via the inflammasome: implications for the pathogenesis of preeclampsia.

Citation 
Mulla MJ, Myrtolli K, Potter J, Boeras C, Kavathas PB, Sfakianaki AK, Tadesse S, Norwitz ER, Guller S, Abrahams VM. Uric acid induces trophoblast IL‐1β production via the inflammasome: implications for the pathogenesis of preeclampsia. Am J Reprod Immunol 2010; 65: 542–548

ORIGINAL ARTICLE: Antiphospholipid Antibodies Limit Trophoblast Migration by Reducing IL-6 Production and STAT3 Activity

Citation Mulla MJ, Myrtolli K, Brosens JJ, Chamley LW, Kwak‐Kim JY, Paidas MJ, Abrahams VM. Antiphospholipid antibodies limit trophoblast migration by reducing IL‐6 production and STAT3 activity. Am J Reprod Immunol 2010

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.

A role for uric acid and the Nalp3 inflammasome in antiphospholipid antibody-induced IL-1β 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 (β2GPI) expressed on the trophoblast. We recently demonstrated in human first trimester trophoblast cells that anti-β2GPI antibodies (Abs) induce the secretion of IL-1β in a Toll-like receptor 4 (TLR4)-dependent manner. IL-1β secretion requires processing of pro-IL-1β 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-1β production in trophoblast via the inflammasome. Using a human first trimester trophoblast cell line, we demonstrated that a mouse anti-β2GPI mAb and human polyclonal aPL-IgG induce IL-1β processing and secretion, which was partially blocked upon caspase-1 inhibition. Nalp3 and ASC knockdown also attenuated anti-β2GPI Ab-induced IL-1β secretion. Furthermore, aPL stimulated the production of uric acid in a TLR4-dependent manner; and inhibition of uric acid prevented aPL-induced IL-1β 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-1β 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.

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

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.

Nod1, but not the ASC inflammasome, contributes to induction of IL-1β secretion in human trophoblasts after sensing of Chlamydia trachomatis.

Chlamydia trachomatis (Ct) is an obligate intracellular bacterial pathogen. Previously, we showed that infection of human trophoblast cells by Ct triggers the secretion of the pro-inflammatory cytokine, interleukin (IL)-1β. The aim of this study was to understand the innate immune pathways involved in trophoblast production of IL-1β after Ct infection. The approach we took was to inhibit the expression or function of the key Toll-like receptors (TLRs), Nod-like receptors, and inflammasome components that have been associated with chlamydia infection. In this study, we report that Ct-induced trophoblast IL-1β secretion is associated with the transcription of IL-1β mRNA, the translation and processing of pro-IL-1β, and the activation of caspase-1. In addition, we demonstrate that Ct-induced IL-1β production and secretion by the trophoblast is independent of TLR2, TLR4, MyD88, and the Nalp3/ASC inflammasome. Instead we report, for the first time, the importance of Nod1 for mediating trophoblast IL-1β secretion in response to a Ct infection.

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-1&bgr;, growth-regulated oncogene-&agr;, 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-&agr; 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-1&bgr;, 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-1&bgr; 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. LEVEL OF EVIDENCE: II