The Prevention of Fatal Tauopathy in a Mouse Model of Alzheimer Disease by Blocking BCL2.

Abstract

A major goal in Alzheimer disease (AD) research is the reduction of the abnormal tau burden. Using multispectral analyses on brain tissues from humans who died of AD it was documented that neurons with hyperphosphorylated tau protein accumulate many proteins of the BCL2 family, including those that block cell turnover (eg, BCL2, MCL1, BCLXL) and those that promote cell turnover (eg, NOXA, PUMA, BAK, BAX). A mouse model of AD with the humanized hyperphosphorylated tau protein was used to test the hypothesis that shifting this balance to a pro-cell turnover milieu would reduce the tau burden with concomitant clinical improvement. Here, we show that a mouse model of AD with death at 11 to 15 months due to CNS tauopathy had a marked reduction in the tau burden after treatment with the FDA-approved drug venetoclax, which blocks BCL2. The reduction of the number of target neurons positive for hyperphosphorylated tau protein after venetoclax treatment in the brain and spinal cord neurons was 94.5% as determined by immunohistochemistry and 98.1% as documented with the modified Bielchowsky stain. The venetoclax treatment began after documented neurofibrillary tangles (NFTs) were evident and there was a concomitant reduction in neuroinflammation. The treated mice were robust until sacrificed at 13 months as compared with the untreated mice that showed unequivocal evidence of brain and spinal cord damage both clinically and at autopsy. We conclude that otherwise inexorable abnormal tau protein deposition, even after initiation, can be prevented by a drug that blocks one anti-cell turnover protein abundant in the NFTs of human AD.