Dynamics of β-Amyloid Reductions in Brain, Cerebrospinal Fluid, and Plasma of β-Amyloid Precursor Protein Transgenic Mice Treated with a γ-Secretase Inhibitor

Publisher Website
Google Scholar
Abstract
γ-Secretase inhibitors are one promising approach to the development of a therapeutic for Alzheimer's disease (AD). γ-Secretase inhibitors reduce brain β-amyloid peptide (Aβ), which is believed to be a major contributor in the etiology of AD. Transgenic mice overexpressing the human β-amyloid precursor protein (APP) are valuable models to examine the dynamics of Aβ changes with γ-secretase inhibitors in plaque-free and plaque-bearing animals. BMS-299897 2-[(1R)-1-[[(4-chlorophenyl)sulfony](2,5-difluorophenyl)amino]ethyl]-5-fluorobenzenepropanoic acid, a γ-secretase inhibitor, showed dose- and time dependent reductions of Aβ in brain, cerebrospinal fluid (CSF), and plasma in young transgenic mice, with a significant correlation between brain and CSF Aβ levels. Because CSF and brain interstitial fluid are distinct compartments in composition and location, this correlation could not be assumed. In contrast, aged transgenic mice with large accumulations of Aβ in plaques showed reductions in CSF Aβ in the absence of measurable changes in plaque Aβ in the brain after up to 2 weeks of treatment. Hence, CSF Aβ levels were a valuable measure of γ-secretase activity in the central nervous system in either the presence or absence of plaques. Transgenic mice were also used to examine potential side effects due to Notch inhibition. BMS-299897 was 15-fold more effective at preventing the cleavage of APP than of Notch in vitro. No changes in the maturation of CD8+ thymocytes or of intestinal goblet cells were observed in mice treated with BMS-299897, showing that it is possible for γ-secretase inhibitors to reduce brain Aβ without causing Notch-mediated toxicity.