Osmotin attenuates amyloid beta-induced memory impairment, tau phosphorylation and neurodegeneration in the mouse hippocampus

The pathological hallmarks of Alzheimer’s disease (AD) include amyloid beta (Aβ) accumulation, neurofibrillary tangle formation, synaptic dysfunction and neuronal loss. In this study, we investigated the neuroprotection of novel osmotin, a plant protein extracted from Nicotiana tabacum that has been considered to be a homolog of mammalian adiponectin. Here, we observed that treatment with osmotin (15 μg/g, intraperitoneally, 4 hr) at 3 and 40 days post-intracerebroventricular injection of Aβ(1-42) significantly ameliorated Aβ(1-42)-induced memory impairment in mice. These results revealed that osmotin reverses Aβ(1-42) injection-induced synaptic deficits, Aβ accumulation and BACE-1 expression. Treatment with osmotin also alleviated the Aβ(1-42)-induced hyperphosphorylation of the tau protein at serine 413 through the regulation of the aberrant phosphorylation of p-PI3K, p-Akt (serine 473) and p-GSK3β (serine 9). Moreover, our western blots and immunohistochemical results indicated that osmotin prevented Aβ(1-42)-induced apoptosis and neurodegeneration in the Aβ(1-42)-treated mice. Furthermore, osmotin attenuated Aβ(1-42)-induced neurotoxicity in vitro. To our knowledge, this study is the first to investigate the neuroprotective effect of a novel osmotin against Aβ(1-42)-induced neurotoxicity. Our results demonstrated that this ubiquitous plant protein could potentially serve as a novel, promising, and accessible neuroprotective agent against progressive neurodegenerative diseases such as AD.