MPO and Parkinson disease: In the CNS, highly expressed MPO were observed in both CSF and postmortem brain tissues from patients with AD and PD 48,49, while the origin of central MPO is still debated: 1) Studies have suggested that microglia, astrocytes, and neurons in the CNS can release MPO (58, 59), therefore high expression of MPO in the CNS may not solely be attributed to neutrophils; 2)Smyth et al.