Induction of Alzheimer's disease pathology by early-life stress

BackgroundAlzheimers disease (AD), a progressive neurodegenerative disorder, is a serious social problem. Recently, several early-life factors have been associated with an increased risk of a clinical diagnosis of AD. MethodsWe investigated the involvement of early-life stress in AD pathogenesis using heterozygous the amyloid precursor protein (APP) mutant mice (AppNL-G-F/wt) and wild-type (Appwt/wt) mice. Maternal separation was used as an animal paradigm for early-life stress. Object location and fear conditioning tests were performed to measure cognitive functions, in addition to biochemical tests. Immunohistochemical analyses were performed after the behavioral tests. ResultsWe found that maternal-separated Appwt/wt mice showed narrowing of vessels and decreased pericyte coverage of capillaries in prefrontal cortex, while maternal-separated AppNL-G-F/wt mice additionally showed impairment of cognitive function, and earlier formation of A{beta} plaques and disruption of the blood-brain barrier. Severe activation of microglia was detected in the maternal-separated AppNL-G-F/wt mice and maternal-separated Appwt/wt mice. At the early stage, morphological changes and inflammatory responses were observed in the microglia of the maternal-separated AppNL-G-F/wt mice and maternal-separated Appwt/wt mice, as well as morphological changes in the microglia of the non-maternal-separated AppNL-G-F/wt mice. ConclusionsMicroglia activation induced by maternal separation in combination with the APP mutation may impairs the vascular system, leading to AD progression. These findings therefore suggest that maternal separation causes early induction of AD pathology via angiopathy.