Coordinated expression of caspase 8, 3 and 7 mRNA in temporal cortex of Alzheimer disease:: Relationship to formic acid extractable Aβ42 levels

Recent studies support the hypothesis that Alzheimer disease (AD)-associated amyloid-beta protein (AP) may induce apoptosis mediated by a caspase cascade. To assess whether mRNA levels of caspase-3, 7, 8 and 9 change in AD brain, and whether these changes correlate with neurofibrillary tangles, A beta(40) or A beta(42) protein levels or senile plaques, 25 AD and 21 non-demented control brains were examined. Elevated mRNA levels of caspases-7 and 8 measured by a quantitative PCR method were observed in the AD temporal neocortex as compared to the control brains. No significant differences were noticed in levels of caspases-3 or 9 between AD and control brains. Multiple regression analysis demonstrated that, within subjects, the mRNA levels of caspase-8 strongly correlated with both caspse-3 and caspase-7 independently of postmortem interval. Further, there was a strong positive correlation of caspase-8 levels with formic acid extractable A beta(42) levels. Our results suggest that the transcriptional activation of key components of the apoptotic cascade correlates with accumulation of A beta(42). Thus, a principal caspase pathway from caspase-8 to caspase-3 and/or 7 may contribute to neuron loss in AD brain.