Effects of Newly Synthesized Recombinant Human Amyloid-β Complexes and Poly-Amyloid-β Fibers on Cell Apoptosis and Cognitive Decline.

Abstract

The main pathological hallmark of Alzheimer's disease is the deposition of amyloid-beta (Aβ) peptides in the brain. Aβ has been widely used to mimic several aspects of Alzheimer's disease. However, several characteristics of amyloid-induced Alzheimer's disease pathology are not well established, especially in mice. The present study aimed to develop a new Alzheimer's disease model by investigating how Aβ can be effectively aggregated using prokaryotes and eukaryotes. To express the Aβ42 complex in HEK293 cells, we cloned the Aβ42 region in a tandem repeat and incorporated the resulting construct into a eukaryotic expression vector. Following transfection into HEK293 cells via lipofection, cell viability assay and western blotting analysis revealed that exogenous Aβ42 can induce cell death and apoptosis. In addition, recombinant His-tagged Aβ42 was successfully expressed in Escherichia coli BL21 (DE3) and not only readily formed Aβ complexes, but also inhibited the proliferation of SH-SY5Y cells and E. coli. For in vivo testing, recombinant His-tagged Aβ42 solution (3 μg/μl in 1× PBS containing 1 mM Ni²⁺) was injected stereotaxically into the left and right lateral ventricles of the brains of C57BL/6J mice (n = 8). Control mice were injected with 1× PBS containing 1 mM Ni²⁺ following the same procedure. Ten days after the sample injection, the Morris water maze test confirmed that exogenous Aβ caused an increase in memory loss. These findings demonstrated that Ni²⁺ is capable of complexing the 50-kDa amyloid and that intracerebroventricular injection of Aβ42 can lead to cognitive impairment, thereby providing improved Alzheimer's disease models.