SIRT5 Represses Neurotrophic Pathways and Aβ Production in Alzheimer's Disease by Targeting Autophagy.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in elderly individuals and characterized by impaired cognition and accumulation of β-amyloid (Aβ). Activating autophagy to clear Aβ is a plausible approach for AD treatment. The levels of Aβ and autophagy signaling factors in APP695/PS1-dE9 transgenic (APP/PS1) mice were detected by immuno histological analysis, real-time PCR, and the western blotting assay. The progression of AD was determined by Aβ levels, activated neurons (MAP2+), and microglia (Iba-1+). The learning ability was measured using a Morris water maze. Reactive oxygen species (ROS) production, malondialdehyde (MDA) levels, and mitochondrial superoxide dismutase (SOD) activity were checked to determine oxidative stress. AD mice exhibited impaired autophagy and a decreased level of SIRT5. SIRT5 overexpression promoted autophagy, manifested by elevated Becn1 and ratio of LC3b-II/I, as well as suppressed oxidative stress. The SIRT5-ameliorated neuron damage was correlated with suppressed activation of microglia and astrocytes. Elevated SIRT5 expression decreased the inflammation in AD brains and neurons. Inhibition of autophagy abolished the protective role of SIRT5 in neurons during AD. Our findings suggested that SIRT5 overexpression could ameliorate the progression of AD both in vitro and in vivo through activating autophagy. We presented ectopic expression of SIRT5 as a promising therapeutic approach for AD.