FDA-preapproved drugs targeted to the translational regulation and processing of the amyloid precursor protein.

The 5′ untranslated region (5′UTR) of the transcript encoding the Alzheimer’s amyloid precursor protein (APP) is a key regulatory sequence that determines the amount of intracellular APP holoprotein present in brain derived cells. Using neuroblastoma cells (SY5Y) we developed a transfection based screen of a library of FDA drugs to identify compounds that limited APP luciferase reporter expression translated from the APP 5′UTR. Paroxetine (Paxil™), dimercaptopropanol, phenserine, desferrioxamine, tetrathiolmobdylate, and azithromycin were six leads that were subsequently found to also suppress APP holoprotein levels or to alter APP cleavage (azithromycin). Since APP holoprotein levels are proportionate to Aβ peptide output in many systems we tested the efficacy of paroxetine and dimercaptopropanol to limit Aβ secretion as measured by ELISA assays. Paroxetine and dimercaptopropanol limited Aβ peptide secretion from lens epithelial cells (B3 cells). Interestingly, paroxetine changed the steady-state levels of transferrin receptor mRNAs. These data suggested that this serotonin reuptake inhibitor (SSRI) provided extra pharmacological action to chelate interacellular iron or change the intracellular iron distribution. An altered iron distribution would be predicted to indirectly limit APP holoprotein expression and Aβ peptide secretion.