Neuritic plaques, a pathological hallmark in Alzheimer’s disease (AD) brains, comprise extracellular aggregates of amyloid-beta (Aβ) peptide and degenerating neurites that accumulate autolysosomes. We found that, in the brains of patients with AD and in AD mouse models, Aβ plaque-associated Olig2- and NG2-expressing oligodendrocyte progenitor cells (OPCs), but not astrocytes, microglia, or oligodendrocytes, exhibit a senescence-like phenotype characterized by the upregulation of p21/CDKN1A, p16/INK4/CDKN2A proteins, and senescence-associated β-galactosidase activity. Molecular interrogation of the Aβ plaque environment revealed elevated levels of transcripts encoding proteins involved in OPC function, replicative senescence, and inflammation. Direct exposure of cultured OPCs to aggregating Aβ triggered cell senescence. Senolytic treatment of AD mice selectively removed senescent cells from the plaque environment, reduced neuroinflammation, lessened Aβ load, and ameliorated cognitive deficits. Our findings suggest a role for Aβ-induced OPC cell senescence in neuroinflammation and cognitive deficits in AD, and a potential therapeutic benefit of senolytic treatments.

Intermittent food deprivation (fasting, IF) improves mood and cognition and protects neurons against excitotoxic degeneration in animal models of epilepsy and Alzheimer’s disease (AD). The mechanisms by which neuronal networks adapt to IF and how such adaptations impact neuropathological processes are unknown. We show that hippocampal neuronal networks adapt to IF by enhancing GABAergic tone, which is associated with reduced anxiety-like behaviors and improved hippocampus-dependent memory. These neuronal network and behavioral adaptations require the mitochondrial protein deacetylase SIRT3 as they are abolished in SIRT3-deficient mice and wild type mice in which SIRT3 is selectively depleted from hippocampal neurons. In the App NL-G-F mouse model of AD, IF reduces neuronal network hyperexcitability and ameliorates deficits in hippocampal synaptic plasticity in a SIRT3-dependent manner. These findings demonstrate a role for a mitochondrial protein deacetylase in hippocampal neurons in behavioral and GABAergic synaptic adaptations to IF.

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