DNA damage in tissue-resident macrophages leads to age-related neurodegeneration

Abstract Neurodegenerative disorders are a growing challenge for the elderly yet their etiology remains elusive. Here, we show that persistent DNA damage in tissue-resident macrophages carrying an ERCC1-XPF DNA repair defect leads to cerebellar ataxia in mice. We find that cytoplasmic chromatin fragments accumulate in the brain microglia of progeroid and naturally aged mice stimulating a type-I Interferon (IFN-I) response and are then packaged in extracellular vesicles (EVs) leading to Purkinje cell death and neurodegeneration in Er1CX/− animals. To reduce neuroinflammation, we developed an EV-based strategy to deliver recombinant DNase I specifically in inflamed Er1CX/− microglia in vivo. Our approach rapidly removes dsDNAs from the cytoplasm of microglial cells and in secreted EVs; it alleviates the IFN-I response, decreases Purkinje cell death and delays the onset of neuronal decline in Er1CX/− animals. Thus, brain microglia causally contribute to neurodegeneration allowing for the development of promising therapeutic strategies against age-related neuroinflammation.