Abstract
Nanoparticles are particles between 1 and 100 nanometers in size able to highly deposit in body organs by circulatory system. Silver nanoparticles (AgNPs) have antibacterial characteristics, and currently are applied in Ag-containing clothes, cosmetics, wound dressing, air-freshener sprays, water disinfectant, sunscreens, hygiene products and food containers. Human would suffer health risk due to the widespread usage of AgNPs. AgNPs can cross through blood brain barrier (BBB) to enter into the brain and central nervous system (CNS), and might induce inflammatory response for the progression of neurodegenerative disease such as Alzheimer’s disease (AD). This study investigated the potential effects of 3-5 nm AgNPs on gene expression of inflammation and neurodegenerative disorder in murine brain ALT astrocytes, microglial BV-2 cells and neuron N2a cells. ALT, BV-2 and N2a cells respectively regulate cell behavior, inflammatory response and signal transduction. The results found AgNPs can cross the cell membrane of N2a cells detectable under a polarizing microscope, and obviously increase interleukin-1β (IL-1β) secretion. Additionally, immunofluorescence images showed amyloid-β (Aβ) plaques for pathological feature of AD deposited in neural cells after AgNPs exposure. ALT and BV-2 cells mainly corresponded to the increased gene expression of C-X-C motif chemokine 13 (CXCL13), macrophage receptor with collagenous structure (MARCO) and glutathione synthetase (GSS) for inflammatory response and oxidative stress after 5, 10 and 12.5 µg/mL AgNPs exposure. AgNPs exposure induced the gene expression of amyloid precursor protein (APP), and reduced amyloid-degrading enzyme neprilysin (NEP) and Aβ transporter low-density lipoprotein receptor (LDLR) underlying the potential effect on Aβ deposition in ALT, BV-2 and N2a cells. In the analysis of Phalanx Mouse OneArray® chip data, Kyoto Encyclopedia of Genes and Genomes (KEGG) database and Cytoscape software were used to identify the alternation of gene expression in various pathways for neural cells exposed AgNPs. In focal adhesion pathway regulating cell behavior and growth signaling, AgNPs might induce the gene expression of ras protein-specific guanine nucleotide-releasing factor 1 (RasGRF1) and reduce the downstream B-cell lymphoma 2 (BCL2) gene potentially to cause cell death. AgNPs exposure would reduce the gene expression of three-prime repair exonuclease 1 (TREX1) and decrease interferon regulatory factor 7 (IRF7) to release inflammatory related cytokines in cytosolic DNA sensing for inflammation and cellular activation. In MAPK pathway relevant to cellular response and cell cycle, AgNPs could induce growth arrest and DNA-damage-inducible alpha (GADD45α) gene overexpression and reduce downstream protein tyrosine phosphatase receptor-type R (PTPRR) gene to interfere with neuron growth and differentiation, cerebellum motor coordination and balance skills. The findings of this study presented AgNPs exposure decreased presenilin-1 (PSEN1) and presenilin-2 (PSEN2) gene expression in dose-dependent manners to disrupt calcium homeostasis and presynaptic dysfunction for AD development. In exposure to AgNPs, the three mouse neural cells were all involved in the immune response to induce interferon regulatory factor 1 (IRF1) gene expression underlying inflammatory cytokine release and DNA damage. This study found that AgNPs can enter mouse neural cells to evoke inflammation and accelerate the Aβ plague formation. AgNPs exposure obviously altered the gene expression of inflammatory response, oxidative stress, cell behavior, cytokines release, cell cycle, immune effect and AD related genes. These findings suggested that AgNPs exposure potentially caused neurodegenerative disease progression.