The use of silver nanoparticles is one of the fastest growing product categories in the nanotechnology industry, with a focus on antimicrobial activity. However, thus far, toxicity data for silver nanoparticles are limited. In this study, we investigated the cytotoxic effects of silver nanoparticles (Ag NPs) and the pathway by which they affect A549 lung epithelial cells. The effects of Ag NPs on cell survival, cell cycle progression, and mRNA and protein alterations of selected cell cycle- and apoptosis-related genes were studied using formazan dye and LDH release assays, flow cytometric analysis, semi-quantitative RT-PCR, and Western blot analysis. Ag NPs reduced cell viability, increased LDH release, and modulated cell cycle distribution through the accumulation of cells at G2/M and sub-G1 phases (cell death), with a concurrent decrease in cells at G1. Ag NP treatment increased Bax and Bid mRNA levels and downregulated Bcl-2 and Bcl-w mRNAs in a dose-dependent manner. Furthermore, Ag NPs altered the mRNA levels of protein kinase C (PKC) family members. In particular, ectopic overexpression of PKCζ led to the enhancement of cellular proliferation and reduced sensitivity to Ag NPs in A549 cells. Together, these results suggest that Ag NPs induce strong toxicity and G2/M cell cycle arrest by a mechanism involving PKCζ downregulation in A549 cells.
The increased use and disposal of silver nanoparticles (AgNPs) has led to their release from wastewater treatment plants into surface waters and concern over potential for negative effects in aquatic organisms. Investigations of the toxicity of AgNPs in fish have considered various species, exposure routes, and test end points; however, the toxicokinetics of total silver has not been studied in fish exposed to aqueous AgNPs. In this study, we investigated the toxicokinetics of total silver in common carp (Cayprinus carpio) exposed to AgNPs [0.62 ± 0.12 (mean ± standard deviation) mg L(-1)] for 7 days followed by a 2 week depuration period. During exposure and depuration, fish were sampled, tissues were excised (gills, brain, skeletal muscle, gastrointestinal tract, liver, and blood) and digested in acid, and total silver concentrations were analyzed by inductively coupled plasma-optical emission spectrometry. Total silver in tissues increased during the 7 day exposure, and mean concentrations were 5.61 mg/kg of liver, 3.32 mg/kg of gills, 2.93 mg/kg of gastrointestinal tract, 0.48 mg/kg of skeletal muscle, 0.14 mg/kg of brain, and 0.02 mg/kg of blood. Transmission electron microscopy energy-dispersive spectroscopy confirmed the presence of silver in the tissues. After depuration for 14 days, total silver returned to control levels in all tissues except liver (4.22 mg/kg), gastrointestinal tract (1.26 mg/kg), and gills (0.77 mg/kg).
Multiwall carbon nanotubes (MWCNTs) have many attractive properties with potential applications in various fields. Despite their usefulness, however, the associated waste can be hazardous to the environment. To examine adverse effects in aquatic environments, Oryzias latipes were exposed to MWCNTs dispersed in water for 14 days and apoptosis and antioxidant gene expression were observed. This work showed that in gills exposed to 100 mg/L MWCNTs for 4 days, there was significant p53, caspase-3 (Cas3), caspase-8 (Cas8), and caspase-9 (Cas9) gene expression relative to the controls, while catalase (CAT) and glutathione-S-transferase (GST) expression were reduced. At 14 days, CAT, GST, and metallothionein (MT) were induced significantly in the gills and Cas3, Cas8, and Cas9 were induced in the liver. No significant gene induction was seen in intestine. Intracellular reactive oxygen species (ROS) were increased significantly only at 14 days. Histologically, no apoptosis was observed with exposure to 100 mg/L MWCNTs for 21 days. The gills were more sensitive to MWCNT toxicity than the other organs. Males had higher apoptosis gene induction than females. These results demonstrated that MWCNTs could cause apoptosis in a manner influenced by tissue and gender in aqueous environments.
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