Oxidative Stress during the Progression of β-Amyloid Pathology in the Neocortex of the Tg2576 Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia, characterized by progressive neurodegeneration. Pathogenetic mechanisms, triggered by beta-amyloid (A beta) accumulation, include oxidative stress, derived from energy homeostasis deregulation and involving mitochondria and peroxisomes. We here addressed the oxidative stress status and the elicited cellular response at the onset and during the progression of A beta pathology, studying the neocortex of Tg2576 model of AD. Age-dependent changes of oxidative damage markers, antioxidant enzymes, and related transcription factors were analysed in relation to the distribution of A beta peptide and oligomers, by a combined molecular/morphological approach. Nucleic acid oxidative damage, accompanied by defective antioxidant defences, and decreased PGC1 alpha expression are already detected in 3-month-old Tg2576 neurons. Conversely, PPAR alpha is increased in these cells, with its cytoplasmic localization suggesting nongenomic, anti-inflammatory actions. At 6 months, when intracellular A beta accumulates, PMP70 is downregulated, indicating impairment of fatty acids peroxisomal translocation and their consequent harmful accumulation. In 9-month-old Tg2576 neocortex, A beta oligomers and acrolein deposition correlate with GFAP, GPX1, and PMP70 increases, supporting a compensatory response, involving astroglial peroxisomes. At severe pathological stages, when senile plaques disrupt cortical cytoarchitecture, antioxidant capacity is gradually lost. Overall, our data suggest early therapeutic intervention in AD, also targeting peroxisomes.