Beta secretase 1-dependent amyloid precursor protein processing promotes excessive vascular sprouting through NOTCH3 signaling

Abstract

Amyloid beta peptides (Aβ) proteins play a key role in vascular pathology in Alzheimer's Disease (AD) including impairment of the blood brain barrier and aberrant angiogenesis.Although previous work has demonstrated a pro-angiogenic role of Aβ, the exact mechanisms by which amyloid precursor protein (APP) processing and endothelial angiogenic signalling cascades interact in AD remain a largely unsolved problem. Here, we report that increased endothelial sprouting in human-APP transgenic mouse (TgCRND8) tissue is dependent on β-secretase (BACE1) processing of APP. Higher levels of Aβ processing in TgCRND8 tissue coincides with decreased NOTCH3/JAG1 signalling, overproduction of endothelial filopodia and increased numbers of vascular pericytes. Using a novel in vitro approach to study sprouting angiogenesis in TgCRND8 organotypic brain slice cultures (OBSCs), we find that BACE1 inhibition normalises excessive endothelial filopodia formation and restores NOTCH3 signalling. These data present the first evidence for the potential of BACE1 inhibition as an effective therapeutic target for aberrant angiogenesis in AD. SignificanceIn this study, we show that targeting amyloid beta processing provides an opportunity to selectively target tip cell filopodia-driven angiogenesis and develop therapeutic targets for vascular dysfunction related to aberrant angiogenesis in AD. Our data provide the first evidence for a safe level of BACE1 inhibition that can normalize excess angiogenesis in AD, without inducing vascular deficits in healthy tissue. Our findings may pave the way for the development of new angiogenesis dependent therapeutic strategies in Alzheimer's Disease.

The probable role of tissue plasminogen activator/neuroserpin axis in Alzheimer’s disease: a new perspective

“…It has been reported that a progressive increase of Aβ level during AD neuropathology is correlated with the overproduction of PAI-1 with subsequent reduction of plasmin and tPA levels and activities [55]. In turn, the reduction of plasmin and tPA activities promotes Aβ accumulation by reducing Aβ clearance [56].…”