Co-localization of apolipoprotein E and β-amyloid in plaques and cerebral blood vessels of aged non-human primates

The regional, structural and cellular localization of apolipoprotein E (apoE) was examined in the brains of 15 non-human primates. The presence of both apoE and β-amyloid (Aβ) in tissue sections was visualized by dual-label fluorescent immunohistochemistry. Additionally, dual label studies of glial fibrillary acidic protein (GFAP) and Aβ were used to investigate the orientation of astrocytes to plaques, and apoE and GFAP dual labeling was used to determine whether astrocytes or other brain cells in monkeys were potential sources for brain apoE. ApoE immunoreactivity (IR) was associated with all plaques and cerebrovascular amyloid in five aged moneys. GFAP immunoreactive astrocytes were also observed in the neuropil surrounding some plaques, but apoE IR was not observed in the cell bodies of astrocytes in these five monkeys. These results support an early role for apoE in the development of plaques and cerebrovascular amyloid in the brains of non-human primates. Furthermore, the inability to detect apoE IR in the cell bodies of astrocytes in these monkeys does not support the hypothesis that plaque or blood vessel associated apoE is principally derived from astrocytes, however apoE labeling of certain neurons was readily observed. Additionally, we report that the basal ganglia of rhesus and long tailed macaques, similar to human basal ganglia, are targets for plaque formation. These findings also emphasize the value of non-human primates for investigating mechanisms of human neurodegenerative disorders, including Alzheimer's disease.