MPO and Parkinson disease: Several studies have demonstrated that reactive microglia expressing proinflammatory mediators are present in the midbrains of PD patients [48–50], while increasing evidence, including our own [24–26], has shown that activated microglia contribute to DA neuronal cell death through NADPH- [50] and MPO- [48] mediated oxidative stress and production of proinflammatory molecules (iNOS, TNF-α, and IL-1β) [51] in the MPTP mouse model of PD.