Our findings also suggest that oxidative stress influences astrocytic Hbβ, as shown in our AD and PD models, similar to reduced brain Hbβ mRNA and protein levels in patients.41,45,52 Paradoxically, while Hbβ increases in the cerebrospinal fluid of mild cognitive impairment patients,53 acute H2O2 exposure in astrocytes increases Hbβ mRNA and opens its promoter regions (Supplementary Fig. 17e–g), suggesting its initial antioxidative role. Here, HBB is linked to Parkinson disease.