Misoprostol Reverse Hippocampal Neuron Cyclooxygenase-2 Downstream Signaling Imbalance in Aluminum-Overload Rats

Although COX-2 inhibition in animal models of neurodegenerative diseases has shown neuroprotection, recent studies have revealed some serious side effects (ulcers, bleeding, fatal cerebrovascular diseases etc.) and the limited benefits of COX-2 inhibitors. A more focused approach is necessary to explore the therapeutic effect of the COX downstream signaling pathway in neurological research. The aim of this study was to explore the alterations of the PGES-PGE(2)-EP signal pathway and the effect of misoprostol on neurodegeneration by chronic aluminum-overload in rats. Adult rats were treated by intragastric administration of aluminum gluconate. The PGE(2) content and expression of PGES and EPs in the hippocampi of rats were detected using ELISA, q-PCR and Western blot analysis, respectively. The content of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) in the rat hippocampi were also detected. The misoprostol treatment dose-dependently improved spatial learning and memory function as well as healing after hippocampal neuron damage induced by chronic aluminum-overload in rats. Meanwhile, the administration of misoprostol resulted in a decrease in the PGE2 level and down-regulation of the mPGES-1, EP(2) and EP(4) expression levels, while there was a dose-dependent up-regulation of EP3 expression. These results suggest that misoprostol possesses a neuroprotective property, and the mechanism involves affecting the EP3 level and reducing the endogenous production of PGE(2) through a negative feedback mechanism, increasing the EP(3) expression level, decreasing the EP(2) and EP(4) expression levels, and rebuilding the mPGES-1-PGE(2)-EP(1-4) signal pathway balance. In this way, misoprostol has a counteractive effect on oxidant stress and inflammation in the central nervous system. The PGES-PGE(2)-EPs signaling pathway is a potential therapeutic strategy for treating neurodegeneration in patients.