Increase of placental sensitivity to melatonin and the alteration to its local synthesis in hypertensive syndromes in pregnancy

Abstract

Objective: To evaluate the relation between hypertensive syndromes and melatonin, and its possible protective role against lesions due to hypertension. Methods: Placentas were classified into gestational hypertension (GH), chronic hypertension (CH), pre-eclampsia (PE) and pre-eclampsia superimposed on chronic hypertension, and morphologically examined by hematoxylin–eosin and periodic acid Schiff methods. Immunohistochemistry was performed to detect tryptophan hydroxylase (TH) and melatonin receptor 1A (MR-1A). Results: MR-1A expression was higher in all types of hypertensive syndromes in pregnancy (HSP), mainly in cases with GH, in Caesarean section delivery, preterm placentas and in the cases with alterations in the placental morphology, particularly those presenting inflammation. The expression of TH was higher in cases with CH when compared with the control. This expression was lower in primigestas, in the cases of inflammation and with PE. Conclusions: HSP therapies should be considered and studied, especially in the cases of HSP associated with PE, in which the placenta is more sensitive as it has more receptors, but its synthesis ability is reduced. As for GH and CH, the possible benefits should be evaluated, since the local placental ability to produce melatonin still exists.