Significant Upregulation of Alzheimer's β‐Amyloid Levels in a Living System Induced by Extracellular Elastin Polypeptides

Abstract

Alzheimer's disease (AD) is a neurodegenerative disorder and the primary cause of age‐related dementia. The etiology of AD is complex and has not been completely elucidated. Herein, we report that treatment with elastin‐like polypeptides (ELPs), a component of the brain extracellular matrix (ECM), significantly increased the levels of AD‐related amyloid‐β peptides (Aβ) both in vitro and in vivo. Regarding the molecular mechanism(s), the upregulation of Aβ levels was related to increased proteolytic processing of the amyloid precursor protein. Furthermore, nesting tests demonstrated that the ELP‐treated animals showed significant neurobehavioral deficits with cognitive impairment. These results suggest that the elastin is associated with AD‐related pathological and behavioral changes. This finding presents a new aspect for Alzheimer's amyloidosis event and provides a great promise in developing ELP‐based model systems to better understand the pathogenesis of AD.

Extracellular Elastin Molecule Modulates Alzheimer’s Aβ Dynamics In Vitro and In Vivo by Affecting Microglial Activities

“…The T t of ELP90 was quantitatively evaluated using protein solutions at concentrations of 50, 100, and 200 μg•mL −1 , respectively. 33 The T t for the group with a concentration of 200 μg•mL −1 was ∼37°C, whereas the T t increased to higher than 37°C when the solution was 100 or 50 μg•mL −1 . The T t for ELP90 solutions was shown to be concentrationdependent, with an increased temperature at lower concentrations.…”

“…It is speculated that this may be based on the compensatory effects of the increased synthesized APP by cells, which is consistent with our previous findings. 33 To elucidate the possible mechanism responsible for the effects on the Aβ levels and microglial phagocytosis, we carried out the fluorescence assay with GFP-ELP90, a recombinant protein generated by genetic fusion of green fluorescent protein (GFP) to the N-terminal of ELP90 for additional fluorescent functionality (Supporting Information Figure S3). Intracellular fluorescence of HMC3 cells treated with the GFP-ELP90 sample was observed when incubated for 3 h and subjected to immunocytochemistry (ICC) analysis (Figure 2d).…”

“…hamster ovary cell model that stably expresses the V717F human APP mutation. 33,39 Cells were incubated with PBS (control) and 100 μg•mL −1 of GFP-ELP90. Nucleus in blue fluorescence and APP in red (immunofluorescence was labeled by 22C11).…”

“…The protocols for polypeptide production were the same as previously described. 33 Simplistically, protein was enriched by Ni-sepharose chromatography, followed by anion-exchange chromatography to remove endotoxin. Protein was lyophilized and stored at −80°C.…”

“…In our previous study, the levels of AD-related Aβ peptides was strongly elevated by elastin-like polypeptide (ELP) both in vitro and in vivo, which can be possibly attributed to the overexpression of γ-secretases when dosing with ELP. 33 However, the relationship of ELPs to other major players in AD pathology, such as microglia, remains elusive. Herein, we demonstrate that a recombinant ELP, derived from ECM native elastin, plays a previously unrecognized role in microglial activation.…”