Treadmill exercise ameliorates symptoms of Alzheimer disease through suppressing microglial activation-induced apoptosis in rats

Alzheimer disease (AD) is a most common form of dementia and eventually causes impairments of learning ability and memory function. In the present study, we investigated the effects of treadmill exercise on the symptoms of AD focusing on the microglial activation-induced apoptosis. AD was made by bilateral intracerebroventricular injection of streptozotocin. The rats in the exercise groups were made to run on a treadmill once a day for 30 min during 4 weeks. The distance and latency in the Morris water maze task and the latency in the step-down avoidance task were increased in the AD rats, in contrast, treadmill exercise shortened these parameters. The numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive and caspase-3-positive cells in the hippocampal dentate gyrus were decreased in the AD rats, in contrast, treadmill exercise suppressed these numbers. Expressions of glial fibrillary acidic protein (GFAP) and cluster of differentiation molecule 11B (CD11b) in the hippocampal dentate gyrus were increased in the AD rats, in contrast, treadmill exercise suppressed GFAP and CD11b expressions. Bax expression was increased and Bcl-2 expression was decreased in the hippocampus of AD rats, in contrast, treadmill exercise decreased Bax expression and increased Bcl-2 expression. The present results demonstrated that treadmill exercise ameliorated AD-induced impairments of spatial learning ability and short-term memory through suppressing apoptosis. The antiapoptotic effect of treadmill exercise might be ascribed to the inhibitory effect of treadmill exercise on microglial activation.