ORIGINAL ARTICLE: Antiphospholipid Antibodies Induce a Pro‐Inflammatory Response in First Trimester Trophoblast Via the TLR4/MyD88 Pathway

Abstract

Problem-Women with antiphospholipid antibodies (aPL) are at risk for recurrent miscarriage, preeclampsia and preterm labor. aPL target the placenta directly by binding to Beta 2 -Glycoprotein I (β 2 GPI) 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.Method of study-First trimester trophoblast were treated with anti-β 2 GPI monoclonal antibodies and patient-derived aPL, after which cell survival and function was evaluated.Results-We report that anti-β 2 GPI antibodies trigger an inflammatory response in trophoblast, characterized by increased secretion of IL-8, MCP-1, GRO-α and IL-1β, and that this occurs in a TLR-4/MyD88-dependent manner. At high concentrations, these antibodies also induce caspasemediated cell death. This was attenuated upon disabling of the MyD88 pathway, suggesting that anti-β 2 GPI-induced inflammatory mediators compromise trophoblast survival by acting in an autocrine/ paracrine manner. Enhanced IL-8, GRO-α and IL-1β secretion also occured when trophoblast were incubated with antibodies from patients with antiphospholipid syndrome. Heparin, which acts as a pro-survival factor in human trophoblast, attenuated the anti-β 2 GPI antibody-mediated cell death, and also the pro-inflammatory response, but only at high concentrations.Conclusions-These findings demonstrate that aPL triggers a placental inflammatory response via the TLR-4/MyD88 pathway, which in turn compromises trophoblast survival. Thus, the TLR-4/ MyD88 pathway may provide a new therapeutic target to improve pregnancy outcome in antiphospholipid syndrome patients.

The role of TLR4 in pathophysiology of antiphospholipid syndrome‐associated thrombosis and pregnancy morbidity

“…Both clinical and experimental observations suggest that pregnancy loss in these patients may involve an inflammatory response at the maternal-fetal interface, as well as disruption of normal trophoblast survival and function (Sebire et al, 2002;Bose et al, 2006;Redecha et al, 2007Redecha et al, , 2008. Mulla et al (2009) demonstrated for the first time that anti-b2GPI antibodies elicit a dose-dependent response in human first trimester trophoblast cells. They showed that antib2GPI antibodies at lower concentrations markedly triggered an inflammatory response in HTR8 trophoblast cells, characterized by increased secretion of IL8, MCP1, GROa and IL1B in a TLR4/MyD88-dependent manner, whereas at high concentrations, these antibodies induced cell death and apoptosis.…”

“…Recently, attention has been paid to different cell types, such as trophoblasts. Mulla et al (2009) demonstrated that aPL triggers a placental inflammatory response via the TLR4⁄MyD88 pathway and indicated the potential value of studies in these cells. Besides thrombosis and fetal loss, the clinical spectrum of APS is becoming more complex as additional clinical manifestations are attributed to the syndrome.…”

“…More accurate kinetic studies are required to assess whether aPLs can activate different signalling pathways. On the other hand, data have shown that anti-b2GPI antibodies trigger an inflammatory response in a TLR4/MyD88-dependent manner and caspasemediated cell death in trophoblasts in comparison with a pro-inflammatory and pro-coagulant phenotype in ECs and monocytes via the TLR4/MyD88 pathway (Sorice et al, 2007;Mulla et al, 2009;Allen et al, 2012). This finding emphasizes the fact that the same autoantibody population is apparently able to mediate different effects, indicating that vascular and obstetric APS are two conditions that are close but not the same.…”

“…Analysis of the fine epitope specificity of b2GPI-dependent aPL is still a limitation in most studies. Most of the experiments involving TLR4 used total IgG or IgM samples isolated from serum or plasma of APS patients containing a variety of different antibodies Mulla et al, 2009;Lambrianides et al, 2010), some studies used affinity-purified anti-b2GPI IgG rather than total IgG Sorice et al, 2007), and others used animal antibodies (Zhou et al, , 2012Allen et al, 2012). It is striking that these polyclonal IgG samples were obtained from very small numbers of individual patients.…”

“…Using in vitro experimental models, Mulla et al (2009) demonstrated that aPL induces a placental inflammatory response in first trimester trophoblasts via the TLR4/MyD88 pathway, which in turn compromises cell viability. However, one in vivo model of fetal loss does not support the capacity of TLR4 signalling.…”