Beta-Amyloid and Its Asp7 Isoform: Morphological and Aggregation Properties and Effects of Intracerebroventricular Administration.

BACKGROUND/OBJECTIVES: One of the hallmarks of Alzheimer's disease (AD) is the accumulation of aggregated beta-amyloid (Aβ) protein in the form of senile plaques within brain tissue. Senile plaques contain various post-translational modifications of Aβ, including prevalent isomerization of Asp7 residue. The Asp7 isomer has been shown to exhibit increased neurotoxicity and induce amyloidogenesis in brain tissue of transgenic mice. The toxicity of Aβ peptides may be partly mediated by their structure and morphology. In this respect, in this study we analyzed the structural and aggregation characteristics of the Asp7 isoform of Aβ and compared them to those of synthetic Aβ. We also investigated the effects of intracerebroventricular (i.c.v.) administration of these peptides, a method often used to induce AD-like symptoms in rodent models.

METHODS

Atomic force microscopy (AFM) was conducted to compare the morphological and aggregation properties of Aβ and Asp7 iso-Aβ. The effects of i.c.v. stereotaxic administration of the proteins were assessed via behavioral analysis and reactive oxygen species (ROS) estimation in vivo using a scanning ion-conductance microscope with a confocal module.

RESULTS

AFM measurements revealed structural differences between the two peptides, most notably in their soluble toxic oligomeric forms. The i.c.v. administration of Asp7 iso-Aβ induced spatial memory deficits in rats and elevated oxidative stress levels in vivo, suggesting a potential of ROS in the pathogenic mechanism of the peptide.

CONCLUSIONS

The findings support the further investigation of Asp7 iso-Aβ in translational research on AD and suggest its involvement in neurodegenerative processes.