Plasma, not extracellular vesicles, disrupts the blood-brain barrier in eclampsia

Abstract Background Eclampsia is a severe complication of preeclampsia involving blood-brain barrier (BBB) disruption. While small extracellular vesicles (sEVs) contribute to endothelial dysfunction in preeclampsia, their role in eclampsia remains unclear. Magnesium sulfate (MgSO₄), the standard treatment, may mitigate BBB injury. We examined the effects of plasma and plasma-derived sEVs from women with eclampsia on BBB integrity and the potential modulatory role of MgSO₄. Methods Plasma and plasma-sEVs were isolated from women with normotensive pregnancies (n=18), preeclampsia (n=19), preeclampsia with organ complications (n=17), and eclampsia (n=20). An in vitro BBB model based on the culture of human brain endothelial cells was used to evaluate electrical resistance (TEER), Dextran 70 kDa permeability, and cytoskeletal alterations in the presence of women’s plasmas or plasma-sEVs. The uptake of fluorescently labeled sEVs in the absence or pretreatment (-3 h) with MgSO₄, and sEVs cargo of relevant proteins involved in BBB regulation, were analyzed. Results Plasma from women with eclampsia disrupted the BBB, with marked reductions in TEER and increased permeability compared to normotensive controls, preeclampsia, and preeclampsia with organ complications. In contrast, plasma-sEVs of women with eclampsia caused less BBB impairment than plasma-sEVs from normotensive controls or preeclampsia, correlating with reduced sEVs uptake by brain endothelial cells. Lower levels of eNOS and TNF-α in eclampsia-derived sEVs compared to normotensive controls were founnd. MgSO₄ treatment further diminished sEVs uptake. Conclusions Plasma, rather than sEVs, appears to drive BBB disruption in eclampsia. MgSO₄ may influence these effects by reducing sEVs uptake and altering their protein cargo.