We explored the functions and mechanisms of N-myc downstream-regulated gene 4 (NDRG4) in an amyloid beta 1-40 induced Alzheimer's disease cell model. The levels of total and phosphorylated Tau protein were significantly up-regulated and cell activity was decreased with increasing Aβ1-40 treatment in SH-SY5Y cells. The expression of NDRG4 mRNA and protein levels were significantly decreased that induced by Aβ1-40 in these cells. NDRG4 overexpression significantly alleviated Aβ1-40-induced SH-SY5Y apoptosis rates and caspases-3/7 activities. Equally, Reactive oxygen species, Mitochondrial membrane potential and Microscale malondialdehyde levels were significantly down-regulated, and Superoxide dismutase activity was increased by NDRG4 overexpression. BDNF protein level and phosphorylation levels of AKT and ERK1/2 were enhanced by NDRG4 overexpression. We also determined that the inhibitory effects of NDRG4 on cell apoptosis and Reactive oxygen species release were partially reversed by BDNF silencing, and by application of the PI3K specific inhibitor (LY294002) or ERK inhibitor (PD98059). These data indicate that NDRG4 attenuates Aβ1-40-induced cell apoptosis and Reactive oxygen species release release, as well as oxidative stress injury. These effects may be mediated through BDNF-induced PI3K/AKT and MEK/ERK pathways.
Keywords: Alzheimer's disease; BDNF; NDRG4; apoptosis; oxidative stress.