Effects of silver nanoparticles on the interactions of neuron‐ and glia‐like cells: Toxicity, uptake mechanisms, and lysosomal tracking

Abstract

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 H O 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. Ca -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 H O 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.

Toxicity of metallic nanoparticles in the central nervous system

“…An analogous research of the absorption of Ag NPs showed less uptake by neuroblastoma N2a cells, as compared to ALT and BV-2 cells. In ALT cells prevailed phagocytosis and clathrin/caveolae independent endocytosis, while in BV-2 Ag NPs were taken mainly by micropinocytosis and clathrin-mediated endocytosis [75].…”

Nebulized jet-based printing of bio-electrical scaffolds for neural tissue engineering: a feasibility study

“…The printing parameters were as in table 5 for PAN+CNT samples (Ø nozzle =610 μm, s=50 mm min −1 , z=1.5 mm, p=1.25 bar). Specifically, three samples were printed at n=40 layers and three at n=1 layer to highlight the effect of the quantity of printed silver (Ø avg,particle size ∼100 nm) on cell viability, as mentioned in the literature [51,[54][55][56][57][58][59][60][61]. The samples were subjected to the same post-sintering process as for SI-AJ20X ink (180°for 1 h in a Heraeus oven), although a different ink-substrate wettability has to be considered.…”

“…Specifically, in biological solutions, the AgNP surface can be mainly oxidized by O 2 , activating the release of Ag + ions, which can interact with nucleic acids, lipid molecules and proteins, causing oxidative stress and damaging several cellular components [53]. On the other hand, to the best of our knowledge, most of the studies on in vitro cell cultures, report cytotoxicity of AgNP powders at various concentrations [51,[54][55][56][57][58][59][60][61], with a Ø avg particle size ≪ 100 nm, i.e. much smaller than the AgNP ink suspension used in our study (Ø avg,particle size ∼100 nm).…”

Synaptotagmin‐11 regulates the functions of caveolae and responds to mechanical stimuli in astrocytes

“…The BODIPY FL C5-LacCer complexed to BSA (LacCer, Molecular Probes, Eugene, OR, USA) uptake assay was modified from that previously described. [41][42][43] Briefly, cells were plated on coverslips and washed with HEPESbuffered minimal essential medium (HMEM+G) containing (in mM) 13.8 Hepes, 137 NaCl, 5.4 KCl, 2.0 glutamine, 0.4 KH 2 PO 4 , 0.18 Na 2 HPO 4 , 5.5 glucose, pH 7.4. Syt11-KO, or rescue astrocytes were then incubated with HMEM+G containing 100 nM LacCer for 30 minutes at 10°C.…”

“…The knockout efficiency reached 83.77% ± 6.52% at the protein level, while Cav1 and EHD2 remained largely unaffected and cavin1 was slightly downregulated ( Figure 1C). LacCer, a sphingolipid analog often used to indicate caveolae-mediated endocytosis, [41][42][43] was internalized in a time-dependent manner both in control and Syt11-KO astrocytes ( Figure 1D), while its uptake was markedly enhanced in KO cells. It was accelerated by ~1.5 times compared to control except at the 5-min time point (1.2-fold).…”