Apolipoprotein D in the aging brain and in Alzheimer's dementia

Apolipoprotein D (apoD) levels were examined in the temporal cortex as well as an assessment of the location of apoD positive cells within the brain b y immunohistochemical and biochemical methods in young control (YC), aged c ontrol (AC), and Alzheimer's demented (AD) probands. Scattered apoD positiv e astrocytes and oligodendrocytes were found throughout the white matter by immunohistochemistry. ApoD immunoreactivity was also observed in the cereb ellar oligodendrocytes of the YC group. There was faint positive apoD stain ing in scattered cortical astrocytes and a few neurons in the same group. I n contrast, some of the AC and all of the AD probands had intense and frequ ent apoD immunostained cortical astrocytes and pyramidal neurons. The corti cal senile plaques and neurofibrillary tangles were apoD immunonegative. No quantitative differences were found between the cortical apoD levels in th e AC and AD groups, determined by immunoblotting. ApoD detected in the brai n tissue was different in molecular weight (29 kDaI) from that seen in CSF or in the serum (32 kDaI). Our results indicate apoD is present in the huma n brain, especially in glial cells, and has increased abundance in the elde rly and AD subjects.