BCL2 and Alzheimer disease: BCL2 proteins are downregulated in AD, whereby Aβ plaques can evoke an imbalance in the protein levels of BCL2 family members.449,450 In vivo exposure of brains or ex vivo treatment of hippocampal slides with Aβ oligomers results in a decrease in BCL2 proteins and an increase in BIM, thereby triggering the activation of BAX and neuronal death.