Clozapine Improves Memory Impairment and Reduces Aβ Level in the Tg-APPswe/PS1dE9 Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive degenerative condition. In order to treat AD, the use of a "drug repositioning" or "repurposing" approach with potential disease-modifying compounds has been increased. The new generation antipsychotics are commonly used in AD and other dementias for the treatment of psychosis and behavioral symptoms, and several animal models have shown the effects of these potential disease-modifying compounds. In this study, we examined whether long-term clozapine treatment could reduce amyloid beta (A beta) deposition and cognitive impairment in transgenic mice of AD, Tg-APPswe/PS1dE9. AD mice were fed clozapine at 20 mg/kg/day for 3 months from 4.5 months of age. Intake of clozapine improved the A beta-induced memory impairment and suppressed A beta levels and plaque deposition in the brain of AD mice. Clozapine upregulated Trk, brain-derived neurotrophic factor, cyclin-dependent kinase-5, and p35 in the cortex and hippocampus of AD mice and activated AMP-activated protein kinase (AMPK). As a downstream effector of AMPK, beta-secretase expression was decreased by clozapine administration. Moreover, clozapine-phosphorylated synapsin I at Ser9 and Ser549 sites in the hippocampus and cortex of AD mice, which may be involved in synaptic strength. This study suggests that as one of candidate for multi-target approach of AD treatment, clozapine is proposed as a therapeutic drug for treatment of AD patients.