Impairment of lysosomal and proteasomal protein-degradation in PS1/APP mice. A and B; Representative western blots and quantitative analysis (n=5 for each age and animal group) of the autophagic vesicle marker LC3 (A) and ubiquitinated proteins (B) performed using the same protein samples. An age-dependent accumulation of both LC3-II and ubiquitinated proteins were observed exclusively in PS1/APP samples. (C-D) Three different magnifications of LC3- (C) or ubiquitin- (D) immunolabeled hippocampal sections (counterstained with Congo red for Abeta plaques) of 6 and 18 months of age PS1/APP mice corroborated the age-dependent accumulation of both markers, associated with dystrophic neurites surrounding amyloid plaques (c1, c4, d1 and d4, panoramic views of immunostained hippocampus; c2, c5, d2 and d5, CA1 region, arrows indicate plaques covered by immunopositive dystrophies and inset in d2 shows immunolabeling in the pyramidal layer somata; c3, c6, d3 and d6, representative image of a congophilic plaque surrounded by dystrophic neurites, arrows point to positive dystrophies around a congophilic plaque indicated by an asterisk). Assays of lysosomal cathepsin B or D (E) and proteasomal chymotrypsin-like (F) enzymatic activities demonstrated the existence of a pronounced decrease in cathepsin B and D activities (since early ages in PS1/APP), whereas proteasome was affected only in aged tg mice. CA1, hippocampal subfield; DG, dentate gyrus; so, stratum oriens; sp, stratum pyramidale; sr, stratum radiatum; slm, stratum lacunoso-moleculare. Scale bars: 500 μm (c1/c4, d1/d4), 100 μm (c2/c5, d2/d5), 10 μm (c3/c5, d3/d5); 50 μm (d2, inset).