S100 beta expression in Alzheimer's disease: relation to neuropathology in brain regions.

S100 beta levels in tissue homogenates and distribution of S100 beta-containing activated astrocytes were examined by S100 beta-specific ELISA and immunohistochemistry, respectively, in brain regions exhibiting many, some, few, or no neuritic plaques in Alzheimer's disease (AD). Compared to samples collected at similar postmortem intervals from control patients of similar ages, S100 beta levels were elevated in specific brain regions from AD patients, and the overexpression of S100 beta correlated relatively well with the pattern of regional involvement by neuritic plaques. The largest increases in S100 beta levels were in hippocampus and temporal lobe, followed by frontal lobe and pons, with no elevation in occipital lobe or cerebellum. Immunohistochemical analysis showed S100 beta localization primarily in activated astrocytes surrounding neuritic plaques. These results demonstrate that S100 beta overexpression is brain region-specific and related to astrocyte activation and suggest that elevation of S100 beta above some threshold is related to the degree of neuropathological involvement of different brain regions in AD.