Abstract: Alzheimer’s disease (AD) is a neurodegenerative disorder with progressive memory loss in dementia. Gold nanoparticles (AuNPs) were reported beneficial for human neural stem cells (hNSCs) treated with Amyloid-beta (Aβ), but the neuroprotective mechanisms still are unknown. Cell Counting Kit-8 (CCK-8) was performed to detect hNSCs viability. The content of interleukin 6 (IL-6) and tumour necrosis factor-alpha (TNF-α) was analyzed by enzyme-linked immunosorbent (ELISA) assay. Immunocytochemistry was carried out to determinate Tuj-1 and glial fibrillary acidic protein (GFAP). The reactive oxygen species (ROS) and JC-1 assay kits were performed to detect ROS generation and mitochondrial membrane potential. miRNA array was used to systematically detect the differential miRNAs. Dual-luciferase reporter assay was applied to verify the targeting relationship between miR-21-5p and the suppressor of cytokine signalling 6(SOCS6). Quantitative PCR (qPCR) and Western blot assessments were also used to detect related gene expression intracellularly or in the supernatant. The pro-inflammation IL-6 and TNF-α were significantly decreased in the AuNPs co-treatment group. AuNPs could ameliorate neural stem cell differentiation inhibition due to Aβ accumulation. AuNPs co-treatment repressed the high expression of total tau (T-tau), phosphorylated tau (P-tau), and Aβ protein caused by the Aβ treatment. The apoptosis rate of hNSCs induced by Aβ was inhibited by AuNPs co-treatment and the expression of proteins associated with apoptosis was also reduced in AuNPs co-treatment group. Aβ-induced decreased mitochondrial membrane potential and mitochondria in the hNSCs were damaged, while AuNPs co-treatment showed a protective effect on mitochondrial membrane potential. Co-treatment with AuNPs significantly increased dynamin-related protein 1 (DRP1), nuclear respiratory factor 1 (NRF1), and mitochondrial transcription factor A (TFAM) mRNA levels. AuNPs may improve mitochondrial function impairment due to Aβ by elevating mitochondrial membrane potential, upregulating regulators of mitochondrial biogenesis, and inhibiting ROS production. hNSCs transfected with miR-21-5p inhibitor reversed AuNPs mediated cytoprotection induced by Aβ. miR-21-5p was involved in AuNPs protecting against Aβ-induced cell toxicity by reduced mitochondrial function. Overexpression of miR-21-5p contributes to enhancing the effect of cytoprotection of AuNPs. MiR-21-5p direct targeting SOCS6 and overexpression SOCS6 exerted opposite effects on hNSCs compared with miR-21-5p mimic. AuNPs can protect hNSCs from Aβ injury and decrease mitochondrial damage by regulating the miR-21-5p/SOCS6 pathway.

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