APOE and neurodegenerative disease: In regard to neurodegenerative diseases, as an increased nuclear translocation of HDAC4 in ApoE4 carrier astrocytes was associated with the downregulation of NHE6 expression, broad-spectrum HDAC inhibitors (like sodium valproate) were able to increase NHE6 expression, normalize endosomal pH, and mitigate Aβ clearance defects in ApoE4 astrocytes [28].