Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia.It is estimated that there are currently about 18 million people worldwide suffering from Alzheimer's disease, and this number will double by 2 025 to 34 millions (http://www.alz.org). Enormous efforts have been taken to identify key molecular events underlying AD pathogenesis and seek for measures to postpone the onset and progression of,if not prevent the disease.