Increased amyloidogenic secretion in cerebellar granule cells undergoing apoptosis

Chromosome missegregation and trisomy 21 mosaicism in Alzheimer's disease

A connection between Alzheimer's disease (AD) and Down syndrome (trisomy 21) is indicated by the fact that all Down syndrome individuals develop Alzheimer's disease neuropathology by the 4th decade of life. Previous studies have examined the frequency of aneuploidy and other chromosomal defects in cells from familial Alzheimer's disease (FAD) patients, with varying results. To investigate the possibility that a specific type of aneuploidy--trisomy 21 mosaicism--may contribute to Alzheimer's disease, we used quantitative fluorescence in situ hybridization to measure the number of trisomy 21 cells in primary fibroblast cultures from AD and unaffected subjects. The 27 AD cultures, including 15 that were derived from individuals carrying FAD mutations in presenilin 1 or 2, exhibited a significant approximately twofold increase in the number of trisomy 21 cells compared to 13 control cultures. A small double-hybridization experiment suggested that the aneuploidy in AD cells was not limited to chromosome 21 but extended at least to chromosome 18 as well. In a parallel study, the endogenous presenilin proteins in fibroblasts were localized to the centrosomes, the nuclear envelope, and its associated interphase kinetochores. Together these results indicate that the presenilin proteins may be involved in mitosis and that FAD mutations in the presenilin genes may predispose to chromosome missegregation (nondisjunction). The data reported here also suggest that trisomy 21 mosaicism may contribute to other forms of AD that are not caused by a presenilin mutation.

TNFalpha plus IFNgamma induce the production of Alzheimer beta-amyloid peptides and decrease the secretion of APPs

The appearance of inflammatory markers associated with amyloid plaques indicates a state of chronic inflammation in Alzheimer's disease (AD). Multiple epidemiological studies also suggest that patients taking anti-inflammatory drugs have a decreased risk of developing AD. Here we present evidence that inflammatory cytokines can alter the metabolism of the beta-amyloid precursor protein (betaAPP). We show that the combination of tumor necrosis factor alpha and interferon gamma triggers the production of beta-amyloid peptides and inhibits the secretion of soluble APPs by human neuronal and extraneuronal cells. The results demonstrate a new mechanism by which inflammatory components can exacerbate the fundamental pathology in AD.

Neuronal apoptosis in rats is accompanied by rapid impairment of cellular respiration and is prevented by scavengers of reactive oxygen species

Apoptosis of cerebellar granule cells induced by potassium withdrawal is accompanied by a very rapid decrease in both cell and mitochondrial respiration supported by glucose and succinate, respectively. The respiratory control ratio, which is an index of oxidative phosphorylation and therefore reflects the ability of mitochondria to produce ATP, is reduced by 50% within the first 2 h after the beginning of apoptosis, insulin-like growth factor I (IGF-I), actinomicin D or cycloheximide, previously reported to inhibit apoptosis, fully prevent the impairment of cellular respiration while scavengers of reactive oxygen species partially inhibit apoptosis and restore cellular respiration.