Imipramine, in Part through Tumor Necrosis Factor α Inhibition, Prevents Cognitive Decline and β-Amyloid Accumulation in a Mouse Model of Alzheimer's Disease

Abstract

Alzheimer's disease (AD), the most common form of dementia in the older people, is a multifactoral pathology, characterized by cognitive deficits, increase in cerebral deposition of the beta-amyloid (Abeta) peptide, neurofibrillary tangles, and neurodegeneration. Studies currently support a central role of neuroinflammation, through production of proinflammatory cytokines including excess tumor necrosis factor alpha (TNF-alpha) in the pathogenesis of AD, especially in Abeta-induced cognitive deficits. Imipramine, a tricyclic antidepressant, has potent anti-inflammatory and neuroprotective effects. This study investigates the effect of imipramine on alterations of long-term and short-term memories, TNF-alpha expression, and amyloid precursor protein (APP) processing induced by intracerebroventricular injection of Abeta25-35 in mice. Mice were treated with imipramine (10 mg/kg i.p. once a day for 13 days) from the day after the Abeta25-35 injection. Memory function was evaluated in the water-maze (days 10-14) and Y-maze (day 9) tests. TNF-alpha levels and APP processing were examined in the frontal cortex and the hippocampus (day 14). Imipramine significantly prevented memory deficits caused by Abeta25-35 in the water-maze and Y-maze tests, and inhibited the TNF-alpha increase in the frontal cortex. Moreover, imipramine decreased the elevated levels of Abeta both in frontal cortex and hippocampus with different modulations of APP and C-terminal fragments of APP. So, imipramine prevents memory impairment through its intrinsic property to inhibit TNF-alpha and Abeta accumulation and may represent a potential candidate for AD treatment.