Accumulation of Intraneuronal β-Amyloid 42 Peptides Is Associated with Early Changes in Microtubule-Associated Protein 2 in Neurites and Synapses
Figure 1
Aβ42 peptide accumulation and MAP2 reduction in Tg2576 mouse brains with aging.
(A) Aggregation-state specificity of Aβ42 antibody (AB5078P) using gel electrophoresis and Western blot. The sample in the Western blot is in vitro aggregated synthetic Aβ1–42 polypeptide. The Aβ42 antibody prominently detected Aβ1–42 monomers and some low molecular weight oligomers (M/LMW) but not high molecular weight (HMW) oligomers (right lane). In contrast, Aβ antibody 6E10 detected M/LMW and HMW Aβ1–42 oligomers (left lane). (B) M/LMW Aβ42 peptides and MAP2 immunofluorescence in rostral CA1 hippocampal subregions. Tg2576 mouse brains were double labeled with antibodies against M/LMW Aβ42 (green) and MAP2 (red). Accumulation of M/LMW Aβ42 peptides correlated with reduced MAP2-immunoreactivity in CA1 with aging in Tg2576 mice between 2 and 17-months of age. MAP2 reduction was especially apparent in CA1 stratum lacunosum-moleculare (SLM, asterisks) and some reduction was also observed in the stratum radiatum (SR). MAP2 reduction was remarkable at the site where amyloid plaques were formed (arrows). Abbreviations: SO, stratum oriens; PCL, pyramidal cell layer; SR, stratum radiatum; SLM, stratum lacunosum-moleculare. Scale bar: 80 µm. (C) Representative images of the SR of the CA1 region of hippocampus demonstrated reduced MAP2 immunoperoxidase staining with aging (2, 9 and 18 months of age) in Tg2576 compared to wild-type mouse brains. Scale bar: 50 µm. (D) Quantification of MAP2-immunoreactivity in the SR of the hippocampal CA1 region revealed an age-related decrease in Tg2576 with aging at 9–11 and 17–18 months compared to at 2–3 months. Ratio of MAP2-immunoreactivity in the SR region of Tg2576 divided by that of wild-type mice were calculated at 2–3, 9–11, and 17–18 month-old mice, respectively. The ratio was standardized to 100% for MAP2-immunoreactivity of wild-type mouse. A comparison was performed between 2–3 months and 9–11 months, and 2–3 months and 17–18 months of age (Student's t test, * denotes significance: p<0.05).