Preeclampsia is a hypertensive disease of human pregnancy in which a factor from the placenta triggers systemic endothelial cell dysfunction in the maternal vasculature leading to hypertension. The nature of the placental trigger of preeclampsia is unknown. In all pregnancies cellular debris, called trophoblast debris, is extruded from the placental trophoblast into the maternal blood. In normal pregnancy, trophoblasts debris is apoptotic, but in preeclampsia it is hypothesized that the debris is produce by a more necrotic cell death which may make it one of the placental triggers of preeclampsia. Endothelial cells can phagocytose both apoptotic and necrotic trophoblast debris and phagocytosis of necrotic, but not apoptotic, trophoblast debris induces endothelial cell activation¹. How endothelial cells distinguish apoptotic and necrotic trophoblast debris is unknown. Macrophages recognize and respond to necrotic cellular material via the NALP-3 inflammasome. We investigated whether endothelial cells respond to necrotic trophoblast debris via the NALP-3 inflammasome.

Placental explants were obtained from first trimester placentae (n= 12) and cultured in Netwells. Trophoblast debris shed from the explants was harvested and rendered necrotic by a freeze-thaw cycle. The debris was added to monolayers of HMEC-1 endothelial cells. Expression of the components of the NALP-3 inflammasome was examined by qRT-PCR, immunocytochemistry and Western blotting.

Analysis by qRT-PCR showed that all three components of NALP3 inflammasome (NALP-3, the adaptor protein ASC and Caspase 1) were expressed in untreated HMEC-1 endothelial cells. Immunocytochemistry and Western blotting both confirmed expression of NALP-3. The mRNAs for both NALP3 and caspase-1 were increased in the HMEC-1 cells in response to necrotic trophoblast debris.

These results indicate that the NALP3 inflammasome complex might be the mechanism by which endothelial cells recognize and respond to necrotic trophoblast debris leading to endothelial cell activation. The identification of the response of the NALP-3 inflammasome in maternal endothelial cells to necrotic trophoblast debris may provide further insight into the pathogenesis of preeclampsia.