Activation of NF-κB in placentas of women with preeclampsia

Placentas are oxidatively stressed during preeclampsia and produce more tumor necrosis factor α (TNFα) and more thromboxane than normal. Oxidative stress may cause these abnormalities by activating nuclear factor-κB (NF-κB). We measured the levels of activated NF-κB in normal and preeclamptic placentas and determined whether oxidative stress activates NF-κB in a trophoblast-like cell line.

We used immunohistochemistry to determine the percentage of the total tissue area that stained for the p65 subunit of NF-κB in placentas obtained from normal and preeclamptic pregnancies. In a second set of experiments, we used a reporter plasmid bearing the NF-κB binding site and transfected it into trophoblast-like cells. The cells were incubated with medium control, linoleic acid (LA), an oxidizing solution (Ox), or Ox enriched with LA (OxLA), TNFα, or OxLA plus TNFα for 20 h. Cell lysates were analyzed using a dual luciferase assay kit.

Placentas obtained from women with preeclampsia showed nearly a 10-fold increase in the extent of area stained for activated NF-κB as compared to normal placentas. In cell culture experiments, Ox and OxLA induced a threefold increase in NF-κB activation as compared to medium control or LA. TNFα induced a threefold increase in NF-κB activation. The combination of TNFα with OxLA caused a 10-fold increase in NF-κB activation.

Placental NF-κB is activated nearly 10-fold in preeclampsia. Oxidative stress causes NF-κB activation in a trophoblast-like cell line, which is enhanced by TNFα. These data suggest that oxidative stress is likely an important in vivo activator of placental NF-κB in preeclampsia.