Circulating platelet-derived and placenta-derived microparticles expose Flt-1 in preeclampsia.
Lok CAR., Böing AN., Sargent IL., Sooranna SR., van der Post JAM., Nieuwland R., Sturk A.
BACKGROUND: Flt-1 is secreted by various cells and elevated concentrations are present in preeclampsia affecting vascular function. Microparticles from these cells may expose Flt-1. We evaluated whether Flt-1 is microparticle-associated in preeclampsia, and established the origin of Flt-1-exposing microparticles. METHODS: The concentration of Flt-1 was measured in samples from preeclamptic patients, pregnant and nonpregnant women by enzyme-linked immunosorbent assay. Microparticles were analyzed by flow cytometry. Western blot determined the different forms of Flt-1. RESULTS: Noncell bound Flt-1 was elevated in preeclampsia compared to controls. A fraction (5%) was associated with microparticles in preeclampsia. Flt-1-exposing microparticles were increased in preeclampsia compared to normotensive pregnancy (p = 0.02). Full-length Flt-1, was identified in microparticles of platelet and placental origin. CONCLUSION: Full-length Flt-1 is associated with platelet and placenta-derived microparticles. Possibly, the presentation of Flt-1 on the membrane of a microparticle might alter its function, particularly if it acts in synergism with other exposed vasoactive molecules.