Aβ impairs bone vascular homeostasis in APP/PS1 mice via disrupting the mitochondrial fission-efferocytosis axis in macrophages

Alzheimer's disease (AD) is associated with progressive bone loss, but the underlying mechanisms remain unclear. This study focused on how Amyloid-β (Aβ) disrupted bone vascular homeostasis by impairing macrophage efferocytosis in APP/PS1 mice. We found that Aβ accumulation in bone tissue impaired MerTK-mediated macrophage efferocytosis and promoted excessive accumulation of apoptotic endothelial cells (ECs). Mechanistically, Aβ triggered excessive mitochondrial fission via GSK-3β-mediated DRP1 phosphorylation, resulting in elevated Reactive Oxygen Species (ROS) and subsequent ADAM17 activation. ADAM17 cleaved MerTK, a critical efferocytosis receptor, impairing apoptotic cells (ACs) clearance. Pharmacological inhibition of GSK-3β (LiCl and TDZD-8) or mitochondrial fission (Mdivi-1) restored MerTK expression, improved efferocytosis, and reduced inflammatory cytokine release (such as TNF-α, IL-6), while enhancing vascular endothelial growth factors (VEGFs). In vivo, LiCl treatment ameliorated bone loss and vascular dysfunction in APP/PS1 mice. These findings revealed that Aβ disrupted the mitochondrial fission-efferocytosis axis in macrophages, contributing to AD-related bone pathology, and highlighted GSK-3β as a potential therapeutic target for preserving bone vascular homeostasis in AD.