Apocynin inhibits placental TLR4/NF-κB signaling pathway and ameliorates preeclampsia-like symptoms in rats

•Apocynin ameliorated the imbalance of sFlt-1 and PIGF in serum and placenta.•Apocynin attenuated serum and placental inflammatory and inhibited placental TLR4/NF-κB signaling.•Apocynin dose-dependently decreased systolic blood pressure and proteinuria during gestation and pups alive rate. We aimed to investigate the potency of apocynin in ameliorating preeclampsia and explore the underlying mechanisms. Preeclampsia model was constructed in rats by administering 200 mg/kg/day L-NAME. Apocynin was given orally in drinking water. Systolic blood pressure and proteinuria were monitored during treatment. Survival rate rate of the pups and placental weight were assessed. Serum sFlt-1, PIGF, IL-6 and placental TLR4 levels were measured using ELISA or qRT-PCR. Apocynin dose-dependently decreased systolic blood pressure and proteinuria during gestation. Survival rate of the pups and placental weight were improved by apocynin treatment. Apocynin ameliorated the imbalance of sFlt-1 and PIGF in serum and placenta of rats with preeclampsia. Apocynin attenuated serum inflammatory cytokine expression and placental inflammation most likely due to downregulation of the placental TLR4/NF-kB pathway in L-NAME treated rats. Apocynin potently ameliorates the L-NAME-induced preeclampsia, which is achieved by re-balancing the sFlt-1 and PIGF levels, attenuating inflammation, and inhibiting TLR4/NF-κB p65 signaling.