Soluble beta-amyloid leads to mitochondrial defects in amyloid precursor protein and tau transgenic mice

Background: Mitochondrial dysfunction has been identified in neurodegenerative disorders including Alzheimer's disease, where accumulation of P-amyloid (A beta) and oxidative stress seem to play central roles in the pathogenesis, by probably directly leading to mitochondrial dysfunction. Objective: In order to study the in vivo effect of A beta load during aging, we evaluated the mitochondrial function of brain cells from transgenic mice bearing either mutant amyloid precursor protein (tgAPP) or mutant amyloid precursor protein and mutant PSI (tgAPP/PS1) as well as from nontransgenic wild-type littermates. tgAPP mice exhibit onset of AP plaques at an age of 6 months, but the intracellular soluble A beta load is already increased at 3 months of age. In contrast, onset of A beta plaques starts at an age of 3 months in tgAPP/PS1 mice. In addition, we investigated the effects of different A beta preparations on mitochondrial function of brain cells from tau transgenic mice. Results: Of note, mitochondrial damage such as reduced mitochondrial membrane potential and ATP levels can already be detected in the brains from these mice before the onset of plaques. In agreement with our findings in tgAPP mice, soluble A beta induced mitochondrial dysfunction in brain cells from tau transgenic mice. Conclusion: Our results indicate that mitochondrial dysfunction is exacerbated by the presence of soluble A beta species as a very early event during pathogenesis. Copyright (c) 2008 S. Karger AG, Basel.