In this study we tested whether plasma from preeclamptic women contains factors that can activate endothelial cells in the presence of monocytes in vitro. Plasma from preeclamptic women (n=6), healthy pregnant women (n=6) and nonpregnant women (n=6) was incubated with mono-cultures and co-cultures of human umbilical vein endothelial cells (HUVEC) and monomac-6 monocytes. Reactive oxygen species (ROS) production and ICAM-1 expression were measured using flow cytometry. Whether scavenging of ROS by superoxide dismutase and catalase inhibited HUVEC ICAM-1 expression was also investigated. We found that in HUVEC co-cultured with monomac-6 cells but not in HUVEC cultured alone, ICAM-1 was upregulated after incubation with plasma from preeclamptic women but not plasma from non-pregnant women. Also in co-cultures, monomac-6 ICAM-1 was upregulated by plasma from preeclamptic women, while in both mono- and co-cultures monomac-6 ROS production was upregulated by plasma from pregnant and preeclamptic women, compared with plasma from non-pregnant women. Scavenging of ROS by superoxide dismutase and catalase resulted in a further upregulation of HUVEC ICAM-1 after incubation with plasma from preeclamptic women, compared with incubation without superoxide dismutase and catalase. These results show that endothelial cells in vitro are activated by plasma of preeclamptic women only if they are co-cultured with monocytes. This upregulation appeared not to be due to extracellular ROS production by monocytes or HUVEC, pointing to involvement of other mechanisms. Our data suggest that plasma of preeclamptic women activates monocytes, and that these monocytes subsequently activate endothelial cells.
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