Preeclampsia is characterized by a systemic inflammatory response involving cytokines, chemokines, and anti-angiogenic factors such as sFLT-1. In many other inflammatory diseases related responses are triggered by toll-like receptor (TLR) stimulation. Therefore, we tested the hypothesis that TLR stimulation of a trophoblast cell line induces inflammatory mediator production and, in particular, production of the preeclampsia-related anti-angiogenic factor sFLT-1.We stimulated human first trimester extravillous trophoblast cells (HTR-8/SV neo cell line) with a variety of TLR ligands and measured downstream NF-kappaB and IRF signaling, inflammatory mediator (RANTES), and sFLT-1 mRNA expression and protein production.Of all TLR ligands, we found that TLR3 ligation with polyI:C resulted in the biggest response with 5.6-fold increased signaling via NF-kappaB and 5.8-fold increased signaling via IRF. RANTES mRNA expression increased 2900 fold and protein production increased 1600 fold in response to TLR3 ligation. sFLT-1 mRNA expression increased 1.7-fold and protein production increased 3.1-fold in response to TLR3 ligation. Inhibitors of the NF-kappaB and IRF signaling pathway decreased TLR3 ligation-induced sFLT-1 protein production by 31.8% and 24.9%, respectively.We conclude that trophoblast cells respond to TLR3 ligation by signaling through both NF-kappaB and IRF pathways resulting in expression of inflammatory mediators and, in particular, the preeclampsia-related anti-angiogenic factor sFLT-1.