Search

Transforming growth factor-β (TGF-β) is a well-known disease-related biomarker associated with fibrotic diseases, and initiation and progression of cancer in many organs. Therefore, quantitative and sensitive detection of TGF-β and similar biomarkers is crucial for patient treatment in the early stages of diagnosis. In many studies, the detection of TGF-β, an important profibrotic and cancer promoting cytokine, has been generally conducted by fluorescence or absorbance-based immunoassays. However, conventional methods for detecting TGF-β have problems including use of time-consuming sample pretreatment steps and multiple reagents for signal amplification and difficulty in real-time detection from living cells. Herein, we present a plasmon-based immunoassay for TGF-β using antibody-conjugated single gold nanoparticles that act as optically excellent intracellular and extracellular detection probes that do not require additional signal amplification. To detect TGF-β sensitively and selectively, we exploited the localized surface plasmon resonance (LSPR) property of antibody-conjugated plasmonic gold nanoparticles at a single particle level. By measuring the LSPR spectral shifts of the single plasmonic nanoprobes, TGF-β can be detected down to the picomolar level, which is comparable with the conventional methods but without significant interference from other proteins. The optimized plasmonic nanoprobes were applied to quantify and monitor the extracellular TGF-β level secreted from the cells under stress conditions, such as cancer, and exposure to toxic environments. Owing to the ease of cellular internalization of the nanoprobes, we directly image and detect increases in intracellular TGF-β levels in living cells under the given stress conditions without cell lysis. We envision that this strategy of using individual nanoparticles as sensors to monitor protein biomarkers in living cells could be applied for various biological assays and diagnosis.

An adverse outcome pathway (AOP) is a framework that organizes the mechanistic or predictive relationships between molecular initiating events (MIEs), key events (KEs), and adverse outcomes (AOs). Previously, we intensively investigated the molecular mechanism that underlies toxicity caused by AgNPs in the nematode Caenorhabditis elegans. Using transcriptomics, functional genetics, and various molecular/biochemical tools, we identified oxidative stress as the major mechanism underlying toxicity and reproduction failure as the outcome. With this information, here we conducted a case study of building an AOP to link oxidative stress with reproductive toxicity. To validate this AOP, we filled the gaps by conducting further experiments on its elements, such as NADPH oxidase, ROS formation, PMK-1 P38 MAPK activation, HIF-1 activation, mitochondrial damage, DNA damage, and apoptosis. The establishment of a causal link between the MIE and AO is critical for the construction of an AOP. Therefore, causal relationships between each KE and AO were verified by using functional genetic mutants of each KE. By combining these experimental data with our previously published results, we established causal relationships between the MIE, KEs, and AO using a Bayesian network (BN) model, culminating in an AOP entitled 'NADPH oxidase and P38 MAPK activation leading to reproductive failure in C. elegans ( https://aopwiki.org/aops/207)' . Overall, our approach shows that an AOP can be developed using existing data and further experiments can be conducted to fill the gaps between the MIE, KEs, and the AO. This study also shows that BN modeling has the potential to identify causal relationships in an AOP.

Titanium dioxide nanoparticles (TiO 2 NPs) are widely used nanoparticles, whose catalytic activity is mainly due to photoactivation. In this study, the toxicity of TiO 2 NPs was investigated on the nematode Caenorhabditis elegans, with and without UV activation. Comparative analyses across the four treatments revealed that UV-activated TiO 2 NPs led to significant reproductive toxicity through oxidative stress. To understand the underlying molecular mechanism, transcriptomics and metabolomics analyses were conducted, followed by whole-genome network-based pathway analyses. Differential expression analysis from microarray data revealed only 4 DEGs by exposure to TiO 2 NPs alone, compared to 3,625 and 3,286 DEGs by UV alone and UV-activated TiO 2 NPs, respectively. Pathway analyses suggested the possible involvement of the JAK/STAT and TGF-ß pathways in the phototoxicity of TiO 2 NPs, which correlated with the observation of increased gene expression of those pathways. Comparative analysis of C. elegans response across UV activation and TiO 2 NPs exposure was performed using loss-of-function mutants of genes in these pathways. Results indicated that the JAK/STAT pathway was specific to TiO 2 NPs, whereas the TGF-ß pathway was specific to UV. Interestingly, crosstalk between these pathways was confirmed by further mutant analysis. We consider that these findings will contribute to understand the molecular mechanisms of toxicity of TiO 2 NPs in the natural environment.

The properties, fate, and toxicity of silver nanoparticles (AgNPs) are readily modified in the environment. Thus, in order to predict the environmental impact of AgNPs, the toxicity test should be conducted to assess the interactions of AgNPs with environmental matrices. Dissolved organic matter (DOM) is known to mitigate AgNPs toxicity in natural systems, and it is also known that silver binds strongly to sulfur. Little is known, however, about the effect of sulfidation and to what extent it could compete with DOM in the sediment. We therefore investigated the effect of sulfide on a sediment dwelling organism, Chironomus riparius using ecotoxicity endpoints. We then investigated how sulfide and a combination of sulfide and DOM affect the toxicity of AgNPs in C. riparius. We also monitored the concentrations of silver in the water and sediment compartments, as well as in C. riparius tissue, in the presence and absence of sulfide. Finally, in order to investigate how sulfide and DOM affect the release of ions from AgNPs, we also monitored released Ag(+) in each treatment. In the presence of sulfide, AgNPs were found to be less toxic to C. riparius in acute and chronic endpoints than AgNPs alone, whereas DOM treatment did not modulate the toxicity of AgNPs. Sulfide treatment reduced the release of Ag(+) from AgNPs. Water-spiked AgNPs with sulfide were found to be more slowly incorporated into both sediment and larvae as compared to the AgNP alone. Overall, the results suggest that the presence of sulfide in sediment mitigates the ecotoxicity of AgNPs in C. riparius., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Although sediment is generally considered to be the major sink for nanomaterials in aquatic environments, few studies have addressed the ecotoxicity of nanomaterials in the presence of sediment. In the present study, the ecotoxicity of silver nanoparticles (AgNPs) with a range of organic coatings was examined in a freshwater sediment-dwelling organism, Chironomus riparius, using acute and chronic ecotoxicity endpoints, including molecular indicators. The toxicity of AgNPs coated with different organic materials, such as polyvinylpyrrolidone, gum arabic, and citrate, to C. riparius was compared with that of bare-AgNPs and AgNO3 (ionic silver). Total silver concentration was also measured to monitor the behavior of the AgNPs in water and sediment and to determine how ion dissolution affects the toxicity of all AgNPs. The coated- and bare-AgNPs caused DNA damage and oxidative stress-related gene expression. In addition, the bare-AgNPs and AgNO3 had a significant effect on development and reproduction. The surface coatings generally mitigated the toxicity of AgNPs to C. riparius, which can be explained by the reduced number of ions released from coated-AgNPs. Citrate-AgNPs caused the most significant alteration at the molecular level, but this did not translate to higher-level effects. Finally, comparing previously conducted studies on AgNP-induced gene expression without sediments, the authors show that the presence of sediment appears to mitigate the toxicity of AgNPs., (© 2015 SETAC.)

In our previous in vitro study of the toxicity on silver nanoparticles (AgNPs), we observed a dramatically higher sensitivity of Jurkat T cells to AgNPs than to Ag ions, and DNA damage and apoptosis were found to be involved in that toxicity. In this study, to understand underlying mechanism of different sensitivity of Jurket T cells to AgNPs and Ag ions, mRNA microarray and micro RNA microarray were concomitantly conducted on AgNPs and Ag ions exposed Jurkat T cells. Surprisingly only a small number of genes were differentially expressed by exposure to each of the silver (15 altered mRNA by AgNPs exposure, whereas 4 altered mRNA by Ag ions exposure, as determined 1.5-fold change as the cut-off value). miRNA microarray revealed that the expression of 63 miRNAs was altered by AgNPs exposure, whereas that of 32 miRNAs was altered by Ag ions exposure. An integrated analysis of mRNA and miRNA expression revealed that the expression of hsa-miR-219-5p, was negatively correlated with the expression of metallothionein 1F (MT1F) and tribbles homolog 3 (TRIB3), in cells exposed to AgNPs; whereas, the expression of hsa-miR-654-3p was negatively correlated with the expression of mRNA, endonuclease G-like 1 (EDGL1) in cells exposed to Ag ions. Network analysis were further conducted on mRNA-miRNA pairs, which revealed that miR-219-5p-MT1F and -TRIB3 pairs by AgNPs are being involved in various cellular processes, such as, oxidative stress, cell cycle and apoptosis, whereas, miR-654-3p and ENDOGL1 pair by Ag ions generated a much simpler network. The putative target genes of AgNPs-induced miR-504, miR-33 and miR-302 identified by Tarbase 6.0 are also found to be involved in DNA damage and apoptosis. These results collectively suggest that distinct epigenetic regulation may be an underlying mechanism of different sensitivity of Jurkat T cells to AgNPs and Ag ion. Further identification of putative target genes of DE miRNA by AgNPs and Ag ions may provide additional clues for the mechanism of differential toxicity. Overall results suggest that epigenetic mechanism is involved in toxicity of AgNPs and Ag ions in Jurkat T cells., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

This study examined the effects of polyvinylpyrrolidone (PVP) surface coating and size on the organismal and molecular toxicity of silver nanoparticles (AgNPs) on the nematode, Caenorhabditis elegans. The toxicity of bare AgNPs and 8 and 38 nm PVP-coated AgNPs (PVP8-AgNPs, PVP38-AgNPs) were compared. The toxicity of AgNO3 was also tested because ion dissolution and particle-specific effects are often important characteristics determining Ag nanotoxicity. Comparative toxicity across AgNO3 and the three different types of AgNPs was first evaluated using a C. elegans mortality test by a direct comparison of the LC50 values. Subsequently, mutant screening followed by oxidative stress, mitochondrial toxicity and DNA damage assays were carried out at equitoxic (LC10 and LC50) concentrations to further assess the toxicity mechanism of AgNO3 and AgNPs. AgNO3 and bare AgNPs had similar toxicities, whereas PVP coating reduced the toxicity of the AgNPs significantly. Of the PVP-AgNPs, the smaller NPs were more toxic. Different groups of mutants responded differently to AgNO3 and AgNPs, which indicates that their toxicity mechanism might be different. AgNO3 and bare AgNPs induced mitochondrial membrane damage. None of the silver materials tested caused detectable polymerase-inhibiting DNA lesions in either the nucleus or mitochondria as measured by a quantitative PCR assay, but AgNO3, bare AgNPs and PVP8-AgNPs induced oxidative DNA damage. These results show that coatings on the AgNPs surface and the particle size make a clear contribution to the toxicity of the AgNPs, and oxidative stress-related mitochondrial and DNA damage appear to be potential mechanisms of toxicity., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The large-scale use of silver nanoparticles (AgNPs) has raised concerns over potential impacts on the environment and human health. We previously reported that AgNP exposure causes an increase in reactive oxygen species, DNA damage, and induction of p38 MAPK and PMK-1 in Jurkat T cells and in Caenorhabditis elegans. To elucidate the underlying mechanisms of AgNP toxicity, here we evaluate the effects of AgNPs on oxidative DNA damage-repair (in human and C. elegans DNA glycosylases hOGG1, hNTH1, NTH-1, and 8-oxo-GTPases-hMTH1, NDX-4) and explore the role of p38 MAPK and PMK-1 in this process. Our comparative approach examined viability, gene expression, and enzyme activities in wild type (WT) and p38 MAPK knock-down (KD) Jurkat T cells (in vitro) and in WT and pmk-1 loss-of-function mutant strains of C. elegans (in vivo). The results suggest that p38 MAPK/PMK-1 plays protective role against AgNP-mediated toxicity, reduced viability and greater accumulation of 8OHdG was observed in AgNP-treated KD cells, and in pmk-1 mutant worms compared with their WT counterparts, respectively. Furthermore, dose-dependent alterations in hOGG1, hMTH1, and NDX-4 expression and enzyme activity, and survival in ndx-4 mutant worms occurred following AgNP exposure. Interestingly, the absence or depletion of p38 MAPK/PMK-1 caused impaired and additive effects in AgNP-induced ndx-4(ok1003); pmk-1(RNAi) mutant survival, and hOGG1 and NDX-4 expression and enzyme activity, which may lead to higher accumulation of 8OHdG. Together, the results indicate that p38 MAPK/PMK-1 plays an important protective role in AgNP-induced oxidative DNA damage-repair which is conserved from C. elegans to humans., (Copyright © 2013 Wiley Periodicals, Inc.)

Silver nanoparticles (AgNPs) have been widely used in commercial goods ranging from medical devices to home appliances. Their widespread application increase the risk related to their potential toxicity. Although several studies showed their acute hazardous effects on living animals, our understanding of chronic effects of AgNPs exposed by the environment we encounter in our everyday lives is still very limited. This is partly because of the lack of versatile animal model system for studying AgNPs effects on terrestrial animals including human. In this study, we used Drosophila model to study AgNPs toxicity in terrestrial animals, and found that long-term exposure of AgNPs, but not Ag ions, at low level (0.1 and 1μg/mL) significantly shortened the lifespan. By taking advantage of the power of Drosophila genetics, we also isolated a GAL4 enhancer trap line called M95, in which the expression of GAL4 is up-regulated in response to ingestion of AgNPs at concentrations as low as 0.1μg/mL. Interestingly M95 flies showed significantly increased tolerance to both AgNPs treatment and dry starvation probably due to up-regulation of JNK signaling. These findings suggest not only that M95 may be a very useful biomarker of AgNPs because of its high sensitivity and tolerance to AgNPs, but also that Drosophila may be a versatile terrestrial invertebrate model for studying the effects of AgNPs on human health., (Copyright © 2013 Elsevier B.V. All rights reserved.)

In the present study, nanotoxicity mechanism associated with silver nanoparticles (AgNPs) exposure was investigated on the nematode, Caenorhabditis elegans focusing on the hypoxia response pathway. In order to test whether AgNPs-induced hypoxia inducible factor-1 (HIF-1) activation was due to hypoxia or to oxidative stress, depletion of dissolved oxygen (DO) in the test media and a rescue effect using an antioxidant were investigated, respectively. The results suggested that oxidative stress was involved in activation of the HIF-1 pathway. We then investigated the toxicological implications of HIF-1 activation by examining the HIF-1 mediated transcriptional response. Of the genes tested, increased expression of the flavin containing monooxygenase-2 (FMO-2) gene was found to be the most significant as induced by AgNPs exposure. We found that AgNPs exposure induced FMO-2 activation in a HIF-1 and p38 MAPK PMK-1 dependent manner, and oxidative stress was involved in it. We conducted all experiments to include comparison of AgNPs and AgNO3 in order to evaluate whether any observed toxicity was due to dissolution or particle specific. The AgNPs and AgNO3 did not produce any qualitative differences in terms of exerting toxicity in the pathways observed in this study, however, considering equal amount of silver mass, in every endpoint tested the AgNPs were found to be more toxic than AgNO3. These results suggest that Ag nanotoxicity is dependent not only on dissolution of Ag ion but also on particle specific effects and HIF-1-FMO-2 pathway seems to be involved in it., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Silver nanoparticles (AgNPs) are extensively used in many commercial products because of their antimicrobial properties and they are therefore released into the environment from various products. A number of genes, especially those representing antioxidant and detoxification pathways, have potential application for studying mechanism of action of environmental pollutants at molecular level. In the present study, the stress responsive transcription of antioxidant and detoxification genes in response to AgNPs and Ag(+) ions exposure is studied in the ecotoxicologically important model species Chironomus riparius. The selected genes were superoxide dismutases (CuZnSOD and MnSOD), catalase (CAT), phospholipid hydroperoxide glutathione peroxidase 1 (PHGPx1), thioredoxin reductase 1 (TrxR1), and delta-3, sigma-4 and epsilon-1 classes of glutathione S-transferases (GSTs). The mRNA expression levels of each gene were determined after exposure of animals for 24h to three different AgNP and Ag(+) ion concentrations using Real-Time PCR method. Significant up-regulation of CuZnSOD and MnSOD was found after exposure to Ag(+) ions and AgNPs, respectively. The transcript levels of CAT, PHGPx1 and TrxR1 were significantly up-regulated only after exposure to AgNPs and no significant change was observed after exposure to Ag(+) ions. The expression levels of all the GSTs were more pronounced after exposure to AgNPs as compared to Ag(+) ions. The overall results suggest that AgNPs led to pronounced induction of genes related to oxidative stress and detoxification than Ag(+) ions., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In the present study, a toxic mechanism of silver nanoparticles (AgNPs) was investigated in the nematode, Caenorhabditis elegans, focusing on the involvement of oxidative stress in reproduction toxicity. Initially, AgNPs were tested as potential oxidative stress inducers, and increased formation of reactive oxygen species (ROS) was observed in AgNP-exposed C. elegans. Subsequently, the potential upstream signaling pathway activated in response to AgNP exposure was investigated, paying special attention to the C. elegans PMK-1 p38 mitogen-activated protein kinase (MAPK). Increased PMK-1 p38 MAPK gene and protein expressions were observed in C. elegans exposed to AgNPs. Expression of the p38-dependent transcription factor genes and glutathione S-transferase (GST) enzyme activity was also investigated in wildtype (N2) and pmk-1 mutant (km25) C. elegans exposed to AgNPs. The results indicated that AgNP exposure led to increased ROS formation, increased expression of PMK-1 p38 MAPK and hypoxia-inducible factor (HIF-1), GST enzyme activity, and decreased reproductive potential in wildtype (N2) C. elegans; whereas in the AgNP-exposed pmk-1 (km25) mutant, ROS formation and HIF-1 and GST activation were not observed, and decreased reproductive potential was rescued. These results suggest that oxidative stress is an important mechanism of AgNP-induced reproduction toxicity in C. elegans, and that PMK-1 p38 MAPK plays an important role in it. The results also suggest that GST and HIF-1 activation by AgNP exposure are PMK-1 p38 MAPK-dependent, and that both play an important role in the PMK-1 p38 MAPK-mediated defense pathway to AgNP exposure in C. elegans., (Copyright © 2011 SETAC.)

Chironomus riparius, a non-biting midge (Chironomidae, Diptera), is extensively used as a model organism in aquatic ecotoxicological studies, although little is known about its genome sequences. Ecdysteroids are steroid hormones that play an important role in development, growth, moulting of larva, and reproduction in Chironomus spp. The effect of ecdysteroids is mediated by their binding to the ecdysteroid receptor (EcR). To study the effect of environmental stressors, nonylphenol and silver nanoparticles (AgNPs), on the modulation of EcR mRNA, in this study, full length cDNA of C. riparius ecdysone receptor (CrEcR) was identified from the Expressed Sequence Tags (ESTs) database and expression of the corresponding mRNA was analyzed following exposure to nonylphenol and AgNPs. The CrEcR cDNA was 2548 base pairs (bp) in length, with a 5' untranslated region (UTR) of 242 bp and a 3' UTR of 684 bp. The open reading frame contains 1617 nucleotides, encoding 539 amino acids with a predicted molecular weight of 61 kDa and pI of 5.89, and revealed the presence of several domains associated with DNA binding, dimerization, ligand binding and transcriptional activation characteristic of steroid receptor family members. It was found that the expression level of CrEcR was significantly up-regulated on exposure to nonylphenol and significant up or down regulation was observed on exposure to AgNPs. These finding shows that nonylphenol as well as AgNPs could modulate the ecdysone nuclear receptor and may have significant implications in different developmental stages in C. riparius., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Although silver nanoparticles (AgNPs) have been reported to exert strong acute toxic effects on various cultured cells by inducing oxidative stress, the molecular mechanisms by which AgNPs-damaged cells are unknown. Because the endoplasmic reticulum (ER) may play an important role in the response to oxidative stress-induced damage and is quite sensitive to oxidative damage, we hypothesized that AgNPs may exert cytotoxic effects on cells by modulating ER stress. In our study, AgNPs resulted in cytotoxicity and apoptotic cell death when analyzing cell viability, DNA fragmentation and the apoptotic sub-G(1) population. Flow cytometry and confocal microscopy indicated that the cells were sensitive to AgNPs with respect to the induction of mitochondrial Ca(2+) overloading and enhancement of ER stress. AgNPs induced a number of signature ER stress markers, including phosphorylation of RNA-dependent protein kinase-like ER kinase (PERK) and its downstream eukaryotic initiation factor 2α, phosphorylation of inositol-requiring protein 1 (IRE1), splicing of ER stress-specific X-box transcription factor-1, cleavage of activating transcription factor 6 (ATF6) and up-regulation of glucose-regulated protein-78 and CCAAT/enhancer-binding protein-homologous protein (CHOP/GADD153). Down-regulation of PERK, IRE1 and ATF6 expression using siRNA significantly decreased AgNPs-induced the enhancement of ER stress. In addition, down-regulation of CHOP expression with siRNA CHOP attenuated AgNPs-induced apoptosis. Taken together, the present study supports an important role for the ER stress response in mediating AgNPs-induced apoptosis., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Recently, we reported that silver nanoparticles (AgNPs) induced reactive oxygen species (ROS) generation and the resultant oxidative stress contributes to the cell damage associated with AgNPs. 8-Oxoguanine (8-oxoG) is sensitive marker of ROS-induced DNA damage. 8-Oxoguanine DNA glycosylase 1 (OGG1) is an important DNA repair enzyme that recognizes and excises 8-oxoG. The aim of the present study was to examine the effect of AgNPs-induced oxidative stress on OGG1 and to elucidate mechanisms underlying AgNPs toxicity. AgNPs decreased OGG1 mRNA and protein expression, resulting in decreased OGG1 activity. Decreased OGG1 activity in AgNPs-treated cells led to increased 8-oxoG levels. The transcription factor NF-E2-related factor 2 (Nrf2) is an important factor in the inducible regulation of OGG1. AgNPs treatment decreased nuclear Nrf2 expression, translocation into nucleus, and transcriptional activity of Nrf2. Extracellular regulated kinase (ERK) and protein kinase B (PKB, AKT), which are upstream of Nrf2, contribute to OGG1 expression. AgNPs attenuated both active forms of ERK and AKT protein expression, resulting in suppression of Nrf2 and decrease of OGG1 expression. These studies demonstrate that down-regulation of Nrf2-mediated OGG1 in exposure to AgNPs occurs through ERK and AKT inactivation., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

A full-length ribosomal protein L15 cDNA from Chironomus riparius (CrRPL15) was identified from the Expressed Sequence Tag (EST) database developed vt 454 pyrosequencing, and expression of the corresponding mRNA was analyzed during different developmental stages and following exposure to Cadmium chloride (Cd) and Silver nanoparticles (AgNPs). The CrRPL15 cDNA contains an open reading frame (ORF) of 615 base pairs (bp) encoding a putative protein of 204 amino acids, with a high level of sequence similarity to RPL15 proteins from other species. The consensus sequence, GXXXXGKS, which is present in other RPL15 proteins, was also present in the putative CrRPL15 protein. The CrRPL15 transcript was present at all life stages, but was most abundant in the eggs. Expression of the CrRPL15 gene was significantly down-regulated in response to exposure to both Cd and AgNPs. In contrast, expression of the heat shock protein 70 (HSP70) gene, a general stress indicator, was significantly up-regulated., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Silver nanoparticles (AgNPs), which have well-known antimicrobial properties, are extensively used in various medical and general applications. Despite the widespread use of AgNPs, relatively few studies have been undertaken to determine the cytotoxic effects of AgNPs exposure. This study investigates possible molecular mechanisms underlying the cytotoxic effects of AgNPs. Here, we show that AgNPs-induced cytotoxicity was higher compared than that observed when AgNO(3) was used as a silver ion source. AgNPs induced reactive oxygen species (ROS) generation and suppression of reduced glutathione (GSH) in human Chang liver cells. ROS generated by AgNPs resulted in damage to various cellular components, DNA breaks, lipid membrane peroxidation, and protein carbonylation. Upon AgNPs exposure, cell viability decreased due to apoptosis, as demonstrated by the formation of apoptotic bodies, sub-G(1) hypodiploid cells, and DNA fragmentation. AgNPs induced a mitochondria-dependent apoptotic pathway via modulation of Bax and Bcl-2 expressions, resulting in the disruption of mitochondrial membrane potential (Δψ(m)). Loss of Δψ(m) was followed by cytochrome c release from the mitochondria, resulting in the activation of caspases 9 and 3. The apoptotic effect of AgNPs was exerted via the activation of c-Jun NH(2)-terminal kinase (JNK) and was abrogated by the JNK-specific inhibitor, SP600125 and siRNA targeting JNK. In summary, the results suggest that AgNPs cause cytotoxicity by oxidative stress-induced apoptosis and damage to cellular components., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

The eco- and genotoxicity of silver nanoparticles (AgNPs) was investigated in the fourth instar larvae of the aquatic midge, Chironomus riparius. AgNPs did not have acute toxicity in C. riparius, but did exhibited chronic toxicity on development (pupation and emergence failure) and reproduction. Genotoxicity also occurred in AgNPs exposed C. riparius. Differential Display PCR (DD-PCR), based on the Annealing Control Primer (ACP) technique, was conducted to investigate the underlying toxic mechanism, which identified altered gene expression in C. riparius after treatment with AgNPs. The possible toxicity mechanism of AgNPs in C. riparius involves the down regulation of the ribosomal protein gene (CrL15) affecting the ribosomal assembly and consequently, protein synthesis. Up regulation of the gonadotrophin releasing hormone gene (CrGnRH1) might lead to the activation of gonadotrophin releasing hormone mediated signal transduction pathways and reproductive failure. Up regulation of the Balbiani ring protein gene (CrBR2.2) may be an indication of the organism's protection mechanism against the AgNPs. The overall results suggest that the toxicity of AgNPs towards aquatic organisms should be thoroughly investigated to allow for their safe use, as they seem to exhibit important toxicity towards C. riparius., (Copyright © 2010 Elsevier B.V. All rights reserved.)

To identify potential harmful effects of silver nanoparticles (AgNPs) on human health, a comprehensive toxicity assay was conducted on human Jurkat T cells, using oxidative stress-related endpoint. The effect of Ag ions was also investigated and compared with that of AgNPs, as it is anticipated that Ag ions will be released from AgNPs, which may be responsible for their toxicity. Cell viability tests indicated high sensitivity of Jurkat T cells when exposed to AgNPs compared to Ag ions; however, both AgNPs and Ag ions induce similar levels of cellular reactive oxygen species during the initial exposure period and; after 24 h, they were increased on exposure to AgNPs compared to Ag ions, which suggest that oxidative stress may be an indirect cause of the observed cytotoxicity of AgNPs. AgNPs exposure activates p38 mitogen-activated protein kinase through nuclear factor-E2-related factor-2 and nuclear factor-kappaB signaling pathways, subsequently inducing DNA damage, cell cycle arrest and apoptosis. Selective toxicity of AgNPs on Jurkat T cells suggests that rigorous toxicity evaluation should be conducted using various different cell types and biological systems prior to the widespread use of AgNPs.

Cytotoxicity induced by silver nanoparticles (AgNPs) and the role that oxidative stress plays in this process were demonstrated in human hepatoma cells. Toxicity induced by silver (Ag(+)) ions was studied in parallel using AgNO(3) as the Ag(+) ion source. Using cation exchange treatment, we confirmed that the AgNP solution contained a negligible amount of free Ag(+) ions. Metal-responsive metallothionein 1b (MT1b) mRNA expression was not induced in AgNP-treated cells, while it was induced in AgNO(3)-treated cells. These results indicate that AgNP-treated cells have limited exposure to Ag(+) ions, despite the potential release of Ag(+) ions from AgNPs in cell culture. AgNPs agglomerated in the cytoplasm and nuclei of treated cells, and induced intracellular oxidative stress. AgNPs exhibited cytotoxicity with a potency comparable to that of Ag(+) ions in in vitro cytotoxicity assays. However, the toxicity of AgNPs was prevented by use of the antioxidant N-acetylcysteine, and AgNP-induced DNA damage was also prevented by N-acetylcysteine. AgNO(3) treatment induced oxidative stress-related glutathione peroxidase 1 (GPx1) and catalase expression to a greater extent than AgNP exposure, but treatment with AgNO(3) and AgNPs induced comparable superoxide dismutase 1 (SOD1) expression levels. Our findings suggest that AgNP cytotoxicity is primarily the result of oxidative stress and is independent of the toxicity of Ag(+) ions.

In the present study, the ecotoxicity of silver nanoparticles (AgNPs) was investigated in Caenorhabditis elegans using survival, growth, and reproduction, as the ecotoxicological endpoints, as well as stress response gene expression. Whole genome microarray was used to screen global changes in C. elegans transcription profiles after AgNPs exposure, followed by quantitative analysis of selected genes. The integration of gene expression with organism and population level endpoints was investigated using C. elegans functional genomics tools, to test the ecotoxicological relevance of AgNPs-induced gene expression. AgNPs exerted considerable toxicity in C. elegans, most clearly as dramatically decreased reproduction potential. Increased expression of the superoxide dismutases-3 (sod-3) and abnormal dauer formation protein (daf-12) genes with 0.1 and 0.5 mg/L of AgNPs exposures occurred concurrently with significant decreases in reproduction ability. Overall results of functional genomic studies using mutant analyses suggested that the sod-3 and daf-12 gene expressions may have been related to the AgNPs-induced reproductive failure in C. elegans and that oxidative stress may have been an important mechanism in AgNPs toxicity.