Global gene expression signatures in response to citrate-coated silver nanoparticles exposure

Silver nanoparticles (AgNPs) are widely used in medical and commercial products for their unique antibacterial functions. However, the impact of AgNPs on human neural development is not well understood. To investigate the effect of AgNPs on human neural development, various doses of 20 nm citrate-coated AgNP (AgSC) were administered to human embryonic stem cell derived neural progenitors during the neuronal differentiation. Immunofluorescence staining with neuronal progenitor markers SOX2 (sex determining region Y-box 2) and Nestin (VI intermediate filament protein) showed that AgSC inhibited rosette formation, neuronal progenitor proliferation, and neurite outgrowth. Furthermore, AgSC promoted astrocyte activation and neuronal apoptosis. These adverse effects can be partially recovered with ascorbic acid. A genome-wide transcriptome analysis of both AgSC treated and untreated samples indicated that the most up-graduated genes were a group of Metallothionein (1F, 1E, 2A) proteins, a metal-binding protein that plays an essential role in metal homeostasis, heavy metal detoxification, and cellular anti-oxidative defence. The most significantly down-regulated genes were neuronal differentiation 6 (NEUROD6) and fork head box G1 (FOXG1). GO analyse indicated that the regulation of cholesterol biosynthetic process, neuron differentiation, synapse organization and pattern specification, oliogenesis, and neuronal apoptosis were the most impacted biological processes. KEGG pathway analyse showed that the most significantly impacted pathways were C5 isoprenoid, axon guidance, Notch, WNT, RAS-MAPK signalling pathways, lysosome, and apoptosis. Our data suggests that AgSCs interfered with metal homeostasis and cholesterol biosynthesis which induced oxidative stress, inhibited neurogenesis, axon guidance, and promoted apoptosis. Supplementation with ascorbic acid could act as an antioxidant to prevent AgSC-mediated neurotoxicity.