Astrocyte senescence in an Alzheimer’s disease mouse model is mediated by TGF-β1 and results in neurotoxicity

Alterations in astrocyte function such as a pro-inflammatory phenotype are associated with Alzheimers disease (AD). We had shown impairments in the ability of aged astrocytes isolated from 5xFAD mice to clear and uptake amyloid-{beta} (A{beta}) as well as to support neuronal growth. Senescent cells accumulate with age and exhibit a senescence-associated secretory phenotype, which includes secretion of pro-inflammatory cytokines. In this study, we predicted that with age, astrocytes in 5xFAD mice would exhibit a cellular senescence phenotype that could promote neurodegeneration. We found an age-dependent increase in senescent astrocytes adjacent to A{beta} plaques in 5xFAD mice. Inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells reduced interelukin-6 secretion by senescent astrocytes and resulted in improved neuronal support. Moreover, senescent astrocytes exhibited an increase in the induction of the TGF-{beta}1-SMAD2/3 pathway, and inhibition of this pathway resulted in a reduction of cellular senescence. We also discovered that soluble A{beta}42 induced astrocyte senescence in young naive mice in a SMAD2/3-dependent manner. Our results suggest an important role of astrocyte senescence in AD and its role in mediating the neurotoxicity properties of astrocytes in AD and related neurodegenerative diseases.