Full- versus Sub-Regional Quantification of Amyloid-Beta Load on Mouse Brain Sections

Multi-omics delineate growth factor network underlying exercise effects in an Alzheimer's mouse model

INTRODUCTION

Physical exercise is a primary defense against age-related cognitive decline and Alzheimer's disease (AD).

METHODS

We conducted single-nucleus transcriptomic and chromatin accessibility analyses (snRNA-seq and snATAC-seq) on the hippocampus of mice carrying mutations in the amyloid precursor protein gene (APPNL-G-F) following prolonged voluntary wheel-running exercise.

RESULTS

Exercise mitigates amyloid-induced changes in transcriptome and chromatin accessibility through cell type-specific regulatory networks converging on growth factor signaling, particularly the epidermal growth factor receptor (EGFR) signaling. The beneficial effects of exercise on neurocognition can be blocked by pharmacological inhibition of EGFR and its downstream PI3K signaling. Exercise leads to elevated levels of heparin-binding EGF (HB-EGF), and intranasal administration of HB-EGF enhances memory function in sedentary APPNL-G-F mice.

DISCUSSION

These findings offer a panoramic delineation of cell type-specific hippocampal transcriptional networks activated by exercise and suggest EGFR signaling as a druggable contributor to exercise-induced memory enhancement to combat AD-related cognitive decline.

HIGHLIGHTS

snRNA-seq and snATAC-seq analysis of APPNL-G-F mice after prolonged wheel-running. Exercise counteracts amyloid-induced transcriptomic and accessibility changes. Networks converge on the activation of EGFR and insulin signaling. Pharmacological inhibition of EGFR and PI3K blocked cognitive benefits of exercise. Intranasal HB-EGF administration enhances memory in sedentary APPNL-G-F mice.

Multi-omics delineate growth factor network underlying exercise effects in an Alzheimer's mouse model

Physical exercise represents a primary defense against age-related cognitive decline and neurodegenerative disorders like Alzheimer's disease (AD). To impartially investigate the underlying mechanisms, we conducted single-nucleus transcriptomic and chromatin accessibility analyses (snRNA-seq and ATAC-seq) on the hippocampus of mice carrying AD-linked NL-G-F mutations in the amyloid precursor protein gene (APPNL-G-F) following prolonged voluntary wheel-running exercise. Our study reveals that exercise mitigates amyloid-induced changes in both transcriptomic expression and chromatin accessibility through cell type-specific transcriptional regulatory networks. These networks converge on the activation of growth factor signaling pathways, particularly the epidermal growth factor receptor (EGFR) and insulin signaling, correlating with an increased proportion of immature dentate granule cells and oligodendrocytes. Notably, the beneficial effects of exercise on neurocognitive functions can be blocked by pharmacological inhibition of EGFR and the downstream phosphoinositide 3-kinases (PI3K). Furthermore, exercise leads to elevated levels of heparin-binding EGF (HB-EGF) in the blood, and intranasal administration of HB-EGF enhances memory function in sedentary APPNL-G-F mice. These findings offer a panoramic delineation of cell type-specific hippocampal transcriptional networks activated by exercise and suggest EGF-related growth factor signaling as a druggable contributor to exercise-induced memory enhancement, thereby suggesting therapeutic avenues for combatting AD-related cognitive decline.

Efficacy and Safety of a Brain-Penetrant Biologic TNF-α Inhibitor in Aged APP/PS1 Mice

Tumor necrosis factor alpha (TNF-α) plays a vital role in Alzheimer's disease (AD) pathology, and TNF-α inhibitors (TNFIs) modulate AD pathology. We fused the TNF-α receptor (TNFR), a biologic TNFI that sequesters TNF-α, to a transferrin receptor antibody (TfRMAb) to deliver the TNFI into the brain across the blood-brain barrier (BBB). TfRMAb-TNFR was protective in 6-month-old transgenic APP/PS1 mice in our previous work. However, the effects and safety following delayed chronic TfRMAb-TNFR treatment are unknown. Herein, we initiated the treatment when the male APP/PS1 mice were 10.7 months old (delayed treatment). Mice were injected intraperitoneally with saline, TfRMAb-TNFR, etanercept (non-BBB-penetrating TNFI), or TfRMAb for ten weeks. Biologic TNFIs did not alter hematology indices or tissue iron homeostasis; however, TfRMAb altered hematology indices, increased splenic iron transporter expression, and increased spleen and liver iron. TfRMAb-TNFR and etanercept reduced brain insoluble-amyloid beta (Aβ) 1-42, soluble-oligomeric Aβ, and microgliosis; however, only TfRMAb-TNFR reduced Aβ peptides, Thioflavin-S-positive Aβ plaques, and insoluble-oligomeric Aβ and increased plaque-associated phagocytic microglia. Accordingly, TfRMAb-TNFR improved spatial reference memory and increased BBB-tight junction protein expression, whereas etanercept did not. Overall, despite delayed treatment, TfRMAb-TNFR resulted in a better therapeutic response than etanercept without any TfRMAb-related hematology- or iron-dysregulation in aged APP/PS1 mice.