Changes of apoptosis-related proteins in hippocampus of SAM mouse in development and aging

Expression of Caspase and Bcl-2 proteins was examined in the hippocampus of senescence-accelerated mice (SAM, P8 and R1 strain) from E19 to 16 months of age. Immunoblotting analysis showed no upregulation of pro-apoptotic proteins (caspase-2L, -3, -6, -8, -9, and Bax) with age while all the anti-apoptotic proteins (caspase-2S, Bcl-2, and Bcl-XL) remained unchanged during aging. Terminal dUTP nick end labeling (TUNEL) and electron microscopy on the hippocampus of 3- and 16-month-old SAM revealed very few TUNEL positive cells in both groups. Morphometric study further showed neuronal loss in the hippocampus was not age-related. Our results suggest apoptosis and cell loss are minor events in the hippocampus of SAM mice and are unlikely to be the cause of functional decline during aging in SAM.