The γ-secretase inhibitor 2-[(1R)-1-[(4-chlorophenyl)sulfonyl](2,5-difluorophenyl) amino]ethyl-5-fluorobenzenebutanoic acid (BMS-299897) alleviates Aβ1-42 seeding and short-term memory deficits in the Aβ25-35 mouse model of Alzheimer's disease

Alzheimer's disease pathomimetic toxicity could be induced in mice within one week after the intracerebroventricular (i.c.v.) injection of an aggregated preparation of the highly toxic and endogenous Amyloid-β fragment Aβ(25-35). It was recently reported that Aβ(25-35) also provokes a modification of APP processing with accumulation of endogenous Aβ(1-42). We here analyzed whether a γ-secretase Inhibitor, BMS-299897, attenuated this Aβ(25-35)-induced Aβ(1-42) seeding and toxicity. The compound was administered at 0.1-1 nmol/mouse, concomittantly with Aβ(25-35) (9 nmol) in male Swiss mice. After one week, the contents in Aβ(1-42) and Aβ(1-40), and the levels in lipid peroxidation were analyzed in the mouse hippocampus. Mice were submitted to spontaneous alternation, passive avoidance and object recognition to analyze their short- and long-term memory abilities. Aβ(25-35) increased Aβ(1-42) content (+240%) but failed to affect Aβ(1-40). BMS-299897 blocked the increase in Aβ(1-42) content and decreased Aβ(1-40) levels significantly. The compound did not affect Aβ(25-35)-induced increase in hippocampal lipid peroxidation. Behaviorally, BMS-299897 blocked the Aβ(25-35)-induced deficits in spontaneous alternation or novel object recognition, using a 1h intertrial time interval. BMS-299896 failed to affect the passive avoidance impairments or novel object recognition, using a 24h intertrial time interval. These results confirmed that Aβ(25-35) injection provoked an accumulation in endogenous Aβ(1-42), an effect blocked by γ-secretase inhibition. This Aβ(1-42) accumulation marginally contributed to the toxicity or long-term memory deficits. However, since the seeded Aβ(1-42) affected short-term memory, the rapid Aβ(25-35) injection Alzheimer's disease model could be used to screen the activity of new secretase inhibitors.