Amyloid precursor protein derivatives differentially alter the microRNA cargo of astrocyte-derived extracellular vesicles

Abstract

Alterations to the protein and microRNA cargo of extracellular vesicles (EVs) occur in Alzheimer's disease (AD) and may contribute to disease progression. We previously showed that ingestion of amyloid-beta (Aβ) by both murine and human astrocytes leads to alterations to the protein cargo of EVs that induce significant neuronal impairment and apoptosis. Here, we hypothesised that pathological changes to the microRNA cargo of astrocyte-derived EVs (ADEVs) would also occur following exposure of astrocytes to Aβ, whereas treatment of astrocytes with the neuroprotective protein secreted amyloid precursor protein-alpha (sAPPα) would induce neuroprotective changes in microRNA expression in ADEVs. Primary murine astrocytes were treated with vehicle, 0.1 μM Aβ protofibrils (AβPF), 1 nM sAPPα, or 1 nM sAPPα in conjunction with 0.1 μM AβPF (sAPPα + AβPF). Differentially expressed microRNA in ADEVs were detected by RT-qPCR using highly sensitive TaqMan Advanced microRNA arrays representing 168 neurodegeneration-associated microRNA. ADEVs from AβPF-exposed astrocytes contained significantly higher amounts of let-7c-5p, miR-29a-3p and miR-34a-5p, while miR-99b-5p and miR-181d-5p were significantly increased in ADEVs from sAPPα- and sAPPα + AβPF-treated astrocytes, respectively. Bioinformatic analysis revealed that gene targets of microRNA upregulated in ADEVs following astrocytic exposure to either AβPF or sAPPα + AβPF were enriched in numerous pathways with known links to AD pathology, with gene targets of the sAPPα + AβPF group also enriched in immune system-related pathways. In contrast, gene targets of miR-99b-5p are known to directly target pathways that are involved in AD, suggesting that ADEVs secreted by sAPPα-treated astrocytes have neuroprotective potential.