NLRP3 facilitates α-synuclein-induced dopaminergic neuronal senescence in a mouse model of Parkinson’s disease through SATB1/DNA damage/p21 signaling pathway

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by the selective loss of nigral dopaminergic neurons and abnormal accumulation of α-synuclein. Our recent study has shown that α-synuclein induces cellular senescence prior to the loss of dopaminergic neurons and the onset of motor dysfunction. Microglia are known to contribute to dopaminergic neurodegeneration, primarily through NLRP3-mediated neuroinflammatory mechanism or by facilitating the propagation of α- synuclein. In this study, we identified the cell type susceptible to α-synuclein-induced cellular senescence in the substantia nigra and investigated the specific role of microglia with a particular focus on the NLRP3 inflammasome. PD mouse model was established by bilateral microinjection of viaAAV2/9 vectors encoding human α-syn-A53T into the SNpc to overexpress human mutant α-synuclein-A53T. We showed that overexpression of α-synuclein-A53T (α-syn-A53T) for 1 week not only induced a pro- inflammatory phenotype in nigral microglia but also led to the acquisition of a senescent state in a subset of microglial cells. Depletion of microglia by administration of the CSF1R inhibitor PLX5622 (1200 ppm) in diet for 1 week significantly attenuated α- synuclein aggregation, iron dysregulation and cellular senescence in the substantia nigra of PD mouse model. Transcriptomic and immunostaining analyses revealed that α-syn-A53T promoted senescence in nigral dopaminergic neurons via the SATB1/DNA damage/p21 signaling pathway, evidenced by reduced SATB1 expression along with increased levels of γ-H2A.X and p21 in TH- positive dopaminergic neurons within the substantia nigra. Moreover, genetic knockout of NLRP3 effectively mitigated α-syn-A53T- induced cellular senescence in these neurons by suppressing the SATB1/DNA damage/p21 signaling pathway. These results highlight the critical role of microglia in promoting dopaminergic neuronal senescence and suggest that NLRP3 may serve as a promising therapeutic target for early intervention in PD to mitigate neuronal senescence and subsequent neurodegeneration.