Protective roles of isoastilbin against Alzheimer's disease via Nrf2-mediated antioxidation and anti-apoptosis

By analyzing the L-glutamic acid (L-Glu)-induced apoptosis of PC12 cells and an AlCl3 combined with D-galactose (D-gal)-developed Alzheimer's disease (AD) mouse model, the protective effects of isoastilbin (IAB) against AD were systematically investigated in the present study. Pre-incubation with IAB for 3 h prior to treatment with 25 mM L-Glu decreased cell viability and inhibited apoptosis, suppressed the accumulation of intracellular reactive oxygen species, and restored mitochondrial membrane potential in PC12 cells induced by L-Glu. In mice with AD, the reduced escape latency time in the water maze test, suppressed chronic movement in the center area of an open field test and enhanced ability to seek hidden food in a Y maze test indicated that abnormal behaviors had improved after 28 days of treatment with IAB. Furthermore, IAB reduced the deposition of amyloid (A) and the expression of phosphorylated-Tau in the mouse brain and enhanced the serum levels of A. IAB ameliorated the oxidative stress via modulating the levels of associated enzymes and improved the functioning of the central cholinergic system, as indicated by an increase in acetylcholine and choline acetyltransferase concentrations. The expression levels of acetylcholine esterase were reduced in the mouse brain in response to IAB pre-treatment. In cells and brain tissue, IAB regulated the expression levels of pro- and anti-apoptotic proteins and enhanced the nuclear levels of NF-E2p45-related factor 2 (Nrf2); subsequently, IAB further enhanced the expression of superoxide dismutase 1, catalase, and heme oxygenase-1 and -2. The findings of the present study indicated that the protection of IAB against AD is at least partially associated with its antioxidation and anti-apoptotic properties.