Amyloidogenic and non-amyloidogenic pathways of amyloid precursor protein processing in oligodendrocytes

Abstract

Excessive accumulation of toxic amyloid-β (Aβ) species in the brain is a major pathological process triggering neurodegeneration in Alzheimer's disease (AD). Recent studies indicate that both neurons and glial cells, including oligodendrocyte lineages (OLs), contribute to brain homeostasis and affect AD pathology; however, the roles of oligodendrocyte precursor cells (OPCs) and oligodendrocytes (OLGs) in AD remain to be fully elucidated. This study examined Aβ production and related protein expression in primary cultured OLs. Primary cultured OLs produced Aβ40 and Aβ42 and expressed amyloid precursor protein (APP), β-secretase (BACE1) and γ-secretase (PS1) as well as α-secretase (ADAM10). OLGs express APP770 in addition to APP695. Treatment with a γ-secretase inhibitor reduced Aβ40 and Aβ42 production levels derived from OPCs/OLGs and suppressed OPC differentiation. Additionally, conditioned media from OLGs improved neuronal cell viability under oxidative stress and contained higher levels of sAPPα compared to OPCs. The neuroprotective effect of OLG was diminished by a sAPPα inhibitor, suggesting that OLG-derived sAPPα protects neurons under oxidative stress. These findings revealed that OLs produce pathogenic Aβ40/42 via the amyloidogenic pathway and secrete neuroprotective sAPPα via the non-amyloidogenic pathway. Elucidating the pathological shift from beneficial non-amyloidogenic to harmful amyloidogenic processes in OLs during AD onset and progression would provide crucial insights into novel therapeutic approaches.