Increased Myeloperoxidase in the Placenta and Circulation of Women With Preeclampsia

Myeloperoxidase (MPO) is a hemoprotein normally released from activated monocytes and neutrophils. Traditionally viewed as a microbicidal enzyme, MPO also induces low-density lipoprotein oxidation, activates metalloproteinases, and oxidatively consumes endothelium-derived NO. The elevated plasma MPO level is a risk factor for myocardial events in patients with coronary artery disease. Patients with preeclampsia display evidence of the inflammation and endothelial dysfunction associated with oxidative stress in the circulation, vasculature, and placenta. We hypothesized that MPO levels in the circulation and placental extracts from women with preeclampsia would be greater than levels in women with normal pregnancies. Placental extracts were prepared from placental villous biopsies from preeclamptic (n=27) and control (n=43) placentas. EDTA plasma samples were obtained from gestationally age-matched preeclamptic and control normal pregnancies. MPO concentrations were measured by ELISA. Immunohistochemistry was used to determine MPO localization in the placenta. MPO levels in placental extracts from women with preeclampsia were significantly higher than the levels in normal control subjects (546±62 versus 347±32 ng/mL; P=0.025). MPO was found in the floating villi and basal plate of placentas with a greater staining in the basal plates from preeclampsia placentas compared with normal pregnancies. Plasma MPO levels were 3-fold higher in patients with preeclampsia compared with normal control subjects (36.6±7.6 versus 11.0±3.1 ng/mL; P=0.003). In conclusion, MPO levels are significantly increased in the circulation and placenta of women with preeclampsia. We speculate that MPO may contribute to the oxidative damage reported in the endothelium and placenta of women with preeclampsia.