Effects of silver nanoparticles on the interactions of neuron‐ and glia‐like cells: Toxicity, uptake mechanisms, and lysosomal tracking
2017
Hsiao, I‐Lun | Hsieh, Yi‐Kong | Chuang, Chun‐Yu | Wang, Chu‐Fang | Huang, Yuh‐Jeen
Silver nanoparticles (AgNPs) are commonly used nanomaterials in consumer products. Previous studies focused on its effects on neurons; however, little is known about their effects and uptake mechanisms on glial cells under normal or activated states. Here, ALT astrocyte‐like, BV‐2 microglia and differentiated N2a neuroblastoma cells were directly or indirectly exposed to 10 nm AgNPs using mono‐ and co‐culture system. A lipopolysaccharide (LPS) was pretreated to activate glial cells before AgNP treatment for mimicking NP exposure under brain inflammation. From mono‐culture, ALT took up the most AgNPs and had the lowest cell viability within three cells. Moreover, AgNPs induced H₂O₂ and NO from ALT/activated ALT and BV‐2, respectively. However, AgNPs did not induce cytokines release (IL‐6, TNF‐α, MCP‐1). LPS‐activated BV‐2 took up more AgNPs than normal BV‐2, while the induction of ROS and cytokines from activated cells were diminished. Ca²⁺‐regulated clathrin‐ and caveolae‐independent endocytosis and phagocytosis were involved in the AgNP uptake in ALT, which caused more rapid NP translocation to lysosome than in macropinocytosis and clathrin‐dependent endocytosis‐involved BV‐2. AgNPs directly caused apoptosis and necrosis in N2a cells, while by indirect NP exposure to bottom chamber ALT or BV‐2 in Transwell, more apoptotic upper chamber N2a cells were observed. Cell viability of BV‐2 also decreased in an ALT–BV‐2 co‐culturing study. The damaged cells correlated to NP‐mediated H₂O₂ release from ALT or NO from BV‐2, which indicates that toxic response of AgNPs to neurons is not direct, but indirectly arises from AgNP‐induced soluble factors from other glial cells.
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