Probing amyloid beta-induced cell death using a fluorescence-peptide conjugate in Alzheimer's disease mouse model

With the increasing worldwide incidence of Alzheimer's disease (AD), there is a critical need for the discovery of more effective diagnostic methods. However, development of diagnostic tools in AD has been hindered by obstacles such as the absence of exact biomarkers. Apoptosis caused by amyloid-β (Aβ) plays an important role in AD pathology; therefore, provides an attractive biological target for the diagnosis of AD. The present study aimed to evaluate the potential of small peptide, named ApoPep-1 (Apoptosis-targeting peptide-1) as a new apoptosis imaging agent in AD. The fluorescein-conjugated ApoPep-1, but not the control peptide, targeted apoptotic cells in the brain of amyloid precursor protein (APP)/presenilin 1 (PS1) mice. We also observed fluorescence signals during in vivo imaging of apoptotic cells using ApoPep-1, and fluorescence levels increased in an age-dependent manner in APP/PS1 mice. Ex vivo imaging of isolated brains in APP/PS1 mice further confirmed the targeting of ApoPep-1 to apoptotic cells. The fluorescein-labeled ApoPep-1 co-localized with brain cells such as neurons, astrocytes, and microglia, all of which undergo apoptosis in the APP/PS1 mice brain. These findings demonstrate that ApoPep-1 can target apoptotic brain cells, and be used for experimental investigations relevant to apoptosis in AD.