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

The main pathological hallmark of Alzheimer's disease is the deposition of amyloid-beta (A beta) peptides in the brain. A beta 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 A beta can be effectively aggregated using prokaryotes and eukaryotes. To express the A beta 42 complex in HEK293 cells, we cloned the A beta 42 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 A beta 42 can induce cell death and apoptosis. In addition, recombinant His-tagged A beta 42 was successfully expressed in Escherichia coli BL21 (DE3) and not only readily formed A beta complexes, but also inhibited the proliferation of SH-SY5Y cells and E. coli. For in vivo testing, recombinant His-tagged A beta 42 solution (3 mu g/mu l in 1x 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 1x PBS containing 1 mM Ni2+ following the same procedure. Ten days after the sample injection, the Morris water maze test confirmed that exogenous A beta caused an increase in memory loss. These findings demonstrated that Ni2+ is capable of complexing the 50-kDa amyloid and that intracerebroventricular injection of A beta 42 can lead to cognitive impairment, thereby providing improved Alzheimer's disease models.