Alzheimer ß-amyloid peptides normal and abnormal localization

Alzheimer's disease (AD) neuropathology is characterized by accumulation of “senile” plaques (SPs) and neurofibrillary tangles (NFTs) in vulnerable brain regions. SPs are principally composed of aggregates of up to 42/43 amino acid ß-amyloid (Aß) peptides. The discovery of familial AD (FAD) mutations in the genes for the amyloid precursor protein (APP) and presenilins (PSs), all of which increase Aß42 production, support the view that Aß is centrally involved in the pathogenesis of AD. Aß42 aggregates readily, and is thought to seed the formation of fibrils, which then act as templates for plaque formation. Aß is generated by the sequential intracellular cleavage of APP by ßsecretase to generate the N-terminal end of Aß, and intramembranous cleavage by g-secretase to generate the C-terminal end. Cell biological studies have demonstrated that Aß is generated in the ER, Golgi, and endosomal/lysosomal system. A central question involving the role of Aß in AD concerns how Aß causes disease and whether it is extracellular Aß deposition and/or intracellular Aß accumulation that initiates the disease process. The most prevalent view is that SPs are composed of extracellular deposits of secreted Aß and that Aß causes toxicity to surrounding neurons as extracellular SP. The recent emphasis on the intracellular biology of APP and Aß has led some investigators to consider the possibility that intraneuronal Aß may directly cause toxicity. In this review we will outline current knowledge of the localization of both intracellular and extracellular Aß

Maternal separation differentially modulates early pathology by sex in 5xFAD Alzheimer’s disease-transgenic mice

Alzheimer’s disease (AD) is the most common neurodegenerative disease. Most cases of AD are considered idiopathic and likely due to a combination of genetic, environmental, and lifestyle-related risk factors. Despite occurring decades before the typical age of an AD diagnosis, early-life stress (ELS) has been suggested to have long-lasting effects that may contribute to AD risk and pathogenesis. Still, the mechanisms that underlie the role of ELS on AD risk remain largely unknown. Here, we used 5xFAD transgenic mice to study relatively short-term alterations related to ELS in an AD-like susceptible mouse model at 6 weeks of age. To model ELS, we separated pups from their dams for 3 h per day from postnatal day 2–14. Around 6 weeks of age, we found that maternally separated (MS) 5xFAD mice, particularly female mice, displayed increased amyloid-β-immunoreactivity in the anterior cingulate cortex (ACC) and basolateral amygdala (BLA). In anterior cingulate cortex, we also noted significantly increased intraneuronal amyloid-β-immunoreactivity associated with MS but only in female mice. Moreover, IBA1-positive DAPI density was significantly increased in relation to MS in ACC and BLA, and microglia in BLA of MS mice had significantly different morphology compared to microglia in non-MS 5xFAD mice. Cytokine analysis showed that male MS mice, specifically, had increased levels of neuroinflammatory markers CXCL1 and IL-10 in hippocampal extracts compared to non-MS counterparts. Additionally, hippocampal extracts from both male and female MS 5xFAD mice had decreased levels of synapse- and activity-related markers Bdnf, 5htr6, Cox2, and Syp in hippocampus. Lastly, we performed behavioral tests to evaluate anxiety- and depressive-like behavior and working memory but could not detect any significant differences between groups. Overall, we detected several sex-specific molecular and cellular alterations in 6-week-old adolescent 5xFAD mice associated with MS that may help explain the connection between ELS and AD risk