Increased density of metallothionein I/II-immunopositive cortical glial cells in the early stages of Alzheimer's disease.

We have examined the possible role of metallothionein I/II (MT I/II) in Alzheimer's disease (AD), with a focus on the cellular localization of MT I/II relative to the astrocyte marker, glial fibrillary acidic protein (GFAP). In AD and preclinical AD cases, MT I/II immunolabeling was present in glial cells and did not show a spatial relationship with beta-amyloid plaques or neurofibrillary pathology. There was a six- to sevenfold increase in both MT I/II- and GFAP-labeled cells in the gray matter of AD cases, relative to non-AD cases. However, there was a threefold increase in MT I/II-immunoreactive cells, but not GFAP-labeled cells, in the gray matter of preclinical AD cases compared to non-AD cases. Therefore, the specific increase in MT I/II is associated with the initial stages of the disease process, perhaps due to oxidative stress or the mismetabolism of heavy metals.