Is there a link between the presence of AQPs in placental EVs and the mechanism of action of magnesium sulfate to prevent seizures in preeclampsia?

SZPILBARG NATALIA; SIERRA, MATÍAS; BERTON, MAGALÍ; FERNANDEZ, NAZARENA; MEDINA, YOLLYSETH; DAMIANO ALICIA E

Chillan

Congreso; Reunion del Grivas 2022; 2022

Grivas

Preeclampsia is a complication of pregnancy that affects between 3 and 8% of women worldwide. One of the most characteristic manifestations in the most severe cases, and particularly in those that lead to eclampsia, are cerebral alterations, such as edema. It is believed that in these cases, what occurs is damage to the blood-brain barrier (BBB), which increases its permeability.Although the mechanisms are still unknown, other authors have pointed out that extracellular vesicles (EVs) could be related to seizures in women with eclampsia and that this effect is reversed with magnesium sulfate.In addition, AQP9 expressed in the brain has been linked to seizures in eclampsia.Our laboratory studies the alterations that AQPs undergo in preeclampsia, and we have previously described that AQP9 is significantly increased in these placentas. In addition, we demonstrated that AQP9 could participate in lactate transport, necessary to counteract the stress suffered by the preeclamptic placenta, but it would be nitrated and not functional in preeclampsia.It has been reported that the presence of AQPs in EVs could be related to pathological states in different organs.The hypothesis of this work is that AQP9 is found in placental EVs that are delivered to systemic circulation in pregnancy. When the placenta is stressed, the changes of this AQP at the trophoblast level are reflected in the content of circulating EVs, with the possibility of generating an impact at the brain level related to seizures in patients with eclampsia. Treatment with magnesium sulfate is known to improve the clinical picture, and we postulate that a possible mechanism could be the reduction of stress through the normalization of AQP9 levels in placenta, EVs and brain.In this work, placental explants were cultured in the presence of peroxynitrite and in hypoxia and hypoxia/reoxygenation (H/R) conditions to induce nitrative and oxidative stress, with and without the addition of MgSO4. The molecular expression of AQP9 was studied in these conditions.In addition, explants were cultured with CoCl2 to induce syncytiotrophoblast stress. In this case, culture supernatants were obtained and a protocol of differential centrifugations, filtration and ultracentrifugation was performed to obtain EVs smaller than 220nm. AQP9 expression was analyzed in this fraction.Finally, plasmas from pregnant women at term were analyzed to obtain circulating EVs to analyze the presence of AQP9.The results showed that AQP9 increases with syncytiotrophoblast stress and recovers to normal levels with magnesium sulfate in explants. Furthermore, it increases in EVs from explants cultured with CoCl2. Finally, we confirmed that AQP9 is present in EVs from pregnant women at term.In conclusion, in this work we observed that the alterations in AQP9 expression observed in preeclamptic placentas may be associated with increased oxidative and nitrative stress. In this context, magnesium sulfate restored the expression of AQP9 in human trophoblast, suggesting that this treatment may have a protective role in attenuating placental stress. In addition, AQP9 was found in EVs from plasma of pregnant women in the third trimester, and its expression was increased in EVs from supernatants of CoCl2-treated explants to induce syncytiotrophoblast stress.Further studies are needed to confirm whether, in preeclampsia, the stress suffered by the placenta translates into an increase of AQP9 in EVs of placental origin that are released into circulation, whether these EVs are related to the seizures of eclampsia, and, finally, whether the improvement observed in patients treated with magnesium sulfate is based on a mechanism via normalization of AQP9.