Alzheimer's disease (AD) is a progressive neurodegenerative disease which is clinically characterized by memory loss and cognitive decline caused by protein misfolding and aggregation. Imbalance between free radicals and the antioxidant system is a prominent and early feature in the neuropathology of AD. Selenium (Se), a vital trace element with excellent antioxidant potential, is preferentially retained in the brain in Se-limited conditions and has been reported to provide neuroprotection through resisting oxidative damage. In this paper, we studied for the first time the potential of Ebselen, a lipid-soluble selenium compound with GPx-like activity, in the treatment of cognitive dysfunction and neuropathology of triple-transgenic AD (3 × Tg-AD) mice, AD model cell, and primary culture. We demonstrated that Ebselen inhibited oxidative stress in both AD model cells and mouse brains with increasing GPx and SOD activities and meanwhile reduced p38 mitogen-activated protein kinases activities. By decreasing the expression of amyloid precursor protein and β-secretase, Ebselen reduced the levels of Aβ in AD neurons and mouse brains, especially the most toxic oligomeric form. Besides, mislocation of phosphorylated tau in neurons and phosphorylation levels of tau protein at Thr231, Ser396, and Ser404 residues were also inhibited by Ebselen, probably by its regulatory roles in glycogen synthase kinase 3β and protein phosphatase 2A activity. In addition, Ebselen mitigated the decrease of synaptic proteins including synaptophysin and postsynaptic density protein 95 in AD model cells and neurons. Consequently, the spatial learning and memory of 3 × Tg-AD mice were significantly improved upon Ebselen treatment. This study provides a potential novel therapeutic approach for the prevention of AD.
Keywords: Alzheimer’s disease (AD); Amyloid-β; Ebselen; Oxidative stress; Tau.