Is there a link between the presence of AQP9 in placental EVs and the mechanism of action of magnesium sulfate to prevent seizures in preeclampsia?

SPILBARG, NATALIA; SIERRA, MATIAS; BERTÓN, MAGALI; FERNANDEZ, NAZARENA; MEDINA, YOLLYSETH; DAMIANO, ALICIA E.

Congreso; Annual Meeting GRIVAS; 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, it was pointed out that extracellular vesicles (EVs) could be related to seizures in women with eclampsia and that this effect is reversed by magnesium sulfate.In addition, brain AQP9 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. This is necessary to counteract the physiological stress of pregnancy. In preeclampsia, this stress increases but AQP9 is nitrated and not functional, enhancing the stress in the preeclamptic placenta.It has been reported that the presence of AQPs in EVs could be related to pathological states in different organs.Our hypothesis is that AQP9 is found in placental EVs that are delivered to the maternal circulation. When the placenta is stressed, the changes of this AQP in the trophoblast 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 220 nm. 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, 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 trophoblast cells, 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 after the induction of syncytiotrophoblast stress.Further studies are needed to confirm if the stress suffered by the preeclamptic placenta translates into an increase of AQP9 in EVs of placental origin released into maternal circulation and if these EVs are related to the seizures of eclampsia. Finally, more research will determine whether the improvement observed in patients treated with magnesium sulfate is based on a mechanism involving AQP9.