ESTETROL AND ITS NEUROPROTECTIVE EFFECT IN NEONATAL HYPOXIC-ISCHEMIC ENCEPHALOPATHY

Perinatal hypoxic-ischemic encephalopathy (HIE) occurs in 1-8 cases per live 1000 births. Brain hypoxia and ischemia due to systemic hypoxemia and reduced cerebral blood flow (CBF) are the primary causes of neonatal HIE accompanied by gray and white matter injuries occurring in neonates. About 20% of affected newborns die in the postnatal period, and an additional 25% will sustain childhood disabilities. So far no medical treatment provides important neuroprotection against HIE. Studies of new neuroprotective agents in animal models of HIE may provide important information pertinent to the development of treatments for this pathological condition.
Estetrol (E4) is a recently described estrogen with four hydroxyl-groups that is synthesized exclusively during pregnancy by the human fetal liver. It has important antioxidative activity. In this study, in vitro we defined antioxidative effect of E4 on primary hippocampal cell cultures, taken from newborn rat pups, before/after induction of oxidative stress. To examine oxidative stress and cell viability, lactate dehydrogenase (LDH) activity and cell survival (MTS) assays were performed on primary neuronal cell cultures. To study the neuroprotective and therapeutic effects of E4 in vivo neonatal HIE model of 7-day-old newborn rat pups was used. Rat pups body temperatures were examined along with their body and brain weights. Brains were studied at the level of the hippocampus and cortex. Intact cell counting and expressions of markers for neuronal cell viability (microtubule-associated protein-2 (MAP-2)), neurogenesis (doublecortin (DCX)) and angiogenesis (vascular-endothelial growth factor (VEGF)) were evaluated by histo- and immunohistochemistry. The serum levels of brain damage markers (S100B and glial fibrillary acidic protein (GFAP)) were measured by ELISA. Our results demonstrate for the first time that E4 has a significant neuroprotective and therapeutic effects. Also, E4 has powerful antioxidative and cell survival properties in vitro. It decreases the early gray matter loss and promotes neuro- and angiogenesis in vivo. Estetrol treatment has no effects on body weight, brain weight or body temperature. Taken together, E4 might become an important safe and physiological substance to treat neonatal HIE.