DEMONSTRATION OF SERINE PROTEASE INHIBITORS IN THE ALZHEIMER-TYPE DEMENTIA BRAINS

I examined the localization of α1-antichymotrypsin (ACT) mRNA and ACT immunoreactivity (ACT-IR) in 12 brains obtained from elderly autopsy cases, including 4 of Alzheimer-type dementia. I investigated the relationship between the ACTmRNA and ACT-IR and the extent of β or tau deposits. In the brains without plaques and tangles, there were no detectable ACTmRNA signals in the gray matter, and those in the white matter were weak. In these brains, ACT-IR was generally weak. The brains with fl-plaques but no tangles showed weak ACT mRNA expression in the astrocytes in both the gray and white matter. They also showed weak ACT-IR in the astrocytes. In the Alzheimer brains with both plaques and tangles, ACTmRNA was expressed intensely in a majority of the astrocytes in the white and gray matter. Some senile plaque-associated astrocytes expressed ACTmRNA. ACT-IR was abundant in the white matter astrocytes. Among protease inhibitors and proteases, only ACT was associated with β-plaques. ACT-IR and ACT mRNA expression in astrocytes was well-correlated with the extent of β and tau deposits. It can be assumed that ACT plays an important role in amyloidogenesis.