C3 and Parkinson disease: The complement C3-positive astrocytes were increased in the ventral midbrain of the intrastriatal α-synuclein preformed fibril (PFF)-injected mice, and C3 secreted from astrocytes could induce the degeneration of dopaminergic neurons, suggesting the potential involvement of complement and coagulation cascades in dopaminergic neurodegeneration in PD (Ma et al., 2021).