APP Knock-In Mice Produce E22P-Aβ Exhibiting an Alzheimer’s Disease-like Phenotype with Dysregulation of Hypoxia-Inducible Factor Expression

Abstract

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that requires further pathological elucidation to establish effective treatment strategies. We previously showed that amyloid β (Aβ) toxic conformer with a turn at positions 22–23 is essential for forming highly toxic oligomers. In the present study, we evaluated phenotypic changes with aging in AD model AppNL-P-F/NL-P-F (NL-P-F) mice with Swedish mutation (NL), Iberian mutation (F), and mutation (P) overproducing E22P-Aβ, a mimic of toxic conformer utilizing the knock-in technique. Furthermore, the role of the toxic conformer in AD pathology was investigated. NL-P-F mice produced soluble toxic conformers from an early age. They showed impaired synaptic plasticity, glial cell activation, and cognitive decline, followed by the accumulation of Aβ plaques and tau hyperphosphorylation. In addition, the protein expression of hypoxia-inducible factor (HIF)-1α was increased, and gene expression of HIF-3α was decreased in NL-P-F mice. HIF dysregulation due to the production of soluble toxic conformers may be involved in AD pathology in NL-P-F mice. This study could reveal the role of a highly toxic Aβ on AD pathogenesis, thereby contributing to the development of a novel therapeutic strategy targeting the toxic conformer.

Chronic Treatment with Aβ42 with a Toxic Conformer and LPS Induces Inflammatory Responses in BV-2 Microglia with Dysregulation of Hypoxia-Inducible Factor Expression

“…[1][2][3][4] APP NL-P-F/NL-P-F mice (NL-P-F mice) with the overproducing E22P-Aβ42 showed glial activation and dysregulation of hypoxia-inducible factor (HIF) expression in the pathogenesis and development of AD-like phenotypes. 5,6) NL-P-F mice also exhibited increased HIF-1α protein and decreased HIF-3α mRNA expression level in hippocampus. 6) HIF-3α forms heterodimers with HIF-1α but has no transcriptional activity and represses downstream gene expression in the HIF-1α pathway.…”

“…5,6) NL-P-F mice also exhibited increased HIF-1α protein and decreased HIF-3α mRNA expression level in hippocampus. 6) HIF-3α forms heterodimers with HIF-1α but has no transcriptional activity and represses downstream gene expression in the HIF-1α pathway. 7) This suggests that increased gene transcriptional activity of HIF-1α pathway via decreased HIF-3α expression level is involved in the phenotypic changes of AD in NL-P-F mice.…”

“…17) The primer sequences of Interleukin-6 (IL-6), HIF-3α, and Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) used for PCR were based on previous studies. 6,17) Western Blot BV-2 microglia were lysed in radioimmunoprecipitation assay buffer (50 mM Tris-HCl [pH 7.6], 50 mM NaCl, 1% Nonidet P40 Substitute, 0.5% sodium deoxycholate, and 0.1% sodium dodecyl sulfate (SDS)) with 1% protease inhibitor cocktail (FUJIFILM Wako Pure Chemical Corporation) and 1 mM phenylmethylsulphonyl fluoride on ice. A Western blot experiment was then conducted as previously described with minor modifications.…”

“…Chronic Treatment with E22P-Aβ42 and LPS Decreases HIF-1α Protein and HIF-3α mRNA in BV-2 Microglia We previously reported that mice producing E22P-Aβ42 exhibited the increased expression of HIF-1α and decreased expression of HIF-3α with phenotypic changes which are associated with AD. 6) Therefore, we examined the expression of HIF molecules. The simultaneous treatment of E22P-Aβ42 and LPS significantly decreased HIF-1α protein and HIF-3α mRNA expression levels (Figs.…”

“…7) This suggests that increased gene transcriptional activity of HIF-1α pathway via decreased HIF-3α expression level is involved in the phenotypic changes of AD in NL-P-F mice. 6) Microglia play a central role in neuroinflammation in AD. 8) Therefore, an activation of inflammatory responses in microglia may be a potential target for E22P-Aβ42.…”