Assessment of Metal Nanoparticle Agglomeration, Uptake, and Interaction Using High-Illuminating System

In the present study, an ultrahigh-resolution system was applied as a simple and convenient technique to characterize the extent of metal nanoparticle agglomeration in solution and to visualize nanoparticle agglomeration, uptake, and surface interaction in three cell phenotypes under normal culture conditions. The experimental results demonstrated that silver (25, 80, 130 nm); aluminum (80 nm); and manganese (40 nm) particles and agglomerates were effectively internalized by rat liver cells (BRL 3A), rat alveolar macrophages (MACs), and rat neuroendocrine cells (PC-12). Individual and agglomerated nanoparticles were observed within the cells and agglomerates were observed on the cell surface membranes. The particles were initially dispersed in aqueous or physiological balanced salt solutions and agglomeration was observed using the Ultra Resolution Imaging (URI) system. Different methods, such as sonication and addition of surfactant (0.1% sodium dodecyl sulfate [SDS]) reduced agglomeration. Due to effects of SDS itself on cell viability, the surfactant could not be directly applied during cell exposure. Therefore, following addition of 0.1% SDS, the particles were washed twice with ultrapure water, which reduced agglomeration even further. Reducing the agglomeration of the nanoparticles is important for studying their uptake and in applications that benefit from individual nanoparticles such as diagnostics. In summary, this study demonstrates a simple technique to characterize the extent of nanoparticle agglomeration in solution and visualize nanoparticle (40 nm and larger) uptake and interaction with cells. Additionally, an example application of nanoparticle labeling onto the surface and neurite extensions of murine neuroblastoma cells (N2A) is presented as a potential imaging tool.

High-Throughput Screening for Positive Allosteric Modulators Identified Potential Therapeutics against Acetylcholinesterase Inhibition

The current standard of care for treatment of organophosphate (OP) poisoning includes pretreatment with the weak reversible acetylcholinesterase (AChE) inhibitor pyridostigmine bromide. Because this drug is an AChE inhibitor, similar side effects exist as with OP poisoning. In an attempt to provide a therapeutic capable of mitigating AChE inhibition without such side effects, high-throughput screening was performed to identify a compound capable of increasing the catalytic activity of AChE. Herein, two such novel positive allosteric modulators (PAMs) of AChE are presented. These PAMs increase AChE activity threefold, but they fail to upshift the apparent IC50 of a variety of OPs. Further development and optimization of these compounds may lead to pre- and/or postexposure therapeutics with broad-spectrum efficacy against pesticide and nerve agent poisoning. In addition, they could be used to complement the current therapeutic standard of care to increase the activity of uninhibited AChE, potentially increasing the efficacy of current therapeutics in addition to altering the therapeutic window.

Quantitative proteomic analysis of the brainstem following lethal sarin exposure

The brainstem represents a major tissue area affected by sarin organophosphate poisoning due to its function in respiratory and cardiovascular control. While the acute toxic effects of sarin on brainstem-related responses are relatively unknown, other brain areas e.g., cortex or cerebellum, have been studied more extensively. The study objective was to analyze the guinea pig brainstem toxicology response following sarin (2×LD50) exposure by proteome pathway analysis to gain insight into the complex regulatory mechanisms that lead to impairment of respiratory and cardiovascular control. Guinea pig exposure to sarin resulted in the typical acute behavior/physiology outcomes with death between 15 and 25min. In addition, brain and blood acetylcholinesterase activity was significantly reduced in the presence of sarin to 95%, and 89%, respectively, of control values. Isobaric-tagged (iTRAQ) liquid chromatography tandem mass spectrometry (LC-MS/MS) identified 198 total proteins of which 23% were upregulated, and 18% were downregulated following sarin exposure. Direct gene ontology (GO) analysis revealed a sarin-specific broad-spectrum proteomic profile including glutamate-mediated excitotoxicity, calcium overload, energy depletion responses, and compensatory carbohydrate metabolism, increases in ROS defense, DNA damage and chromatin remodeling, HSP response, targeted protein degradation (ubiquitination) and cell death response. With regards to the sarin-dependent effect on respiration, our study supports the potential interference of sarin with CO2/H(+) sensitive chemoreceptor neurons of the brainstem retrotrapezoid nucleus (RTN) that send excitatory glutamergic projections to the respiratory centers. In conclusion, this study gives insight into the brainstem broad-spectrum proteome following acute sarin exposure and the gained information will assist in the development of novel countermeasures.

Lack of association between human plasma oxytocin and interpersonal trust in a Prisoner's Dilemma paradigm

Expanding interest in oxytocin, particularly the role of endogenous oxytocin in human social behavior, has created a pressing need for replication of results and verification of assay methods. In this study, we sought to replicate and extend previous results correlating plasma oxytocin with trust and trustworthy behavior. As a necessary first step, the two most commonly used commercial assays were compared in human plasma via the addition of a known quantity of exogenous oxytocin, with and without sample extraction. Plasma sample extraction was found to be critical in obtaining repeatable concentrations of oxytocin. In the subsequent trust experiment, twelve samples in duplicate, from each of 82 participants, were collected over approximately six hours during the performance of a Prisoner’s Dilemma task paradigm that stressed human interpersonal trust. We found no significant relationship between plasma oxytocin concentrations and trusting or trustworthy behavior. In light of these findings, previous published work that used oxytocin immunoassays without sample extraction should be reexamined and future research exploring links between endogenous human oxytocin and trust or social behavior should proceed with careful consideration of methods and appropriate biofluids for analysis.

Dynamic characteristics of silver nanoparticles in physiological fluids: toxicological implications

The field of nanotoxicology has made tremendous progress identifying novel and potentially adverse biological effects following nanomaterial (NM) exposure. However, one facet yet to be satisfactorily explored is how a physiological environment modifies NM physicochemical properties, thus introducing novel complexities associated with solid phase material exposures. In this study, artificial alveolar, lysosomal, and interstitial fluids were used to identify environmental-specific modulations to the properties and behavior of hydrocarbon-coated (Ag-HC) and polysaccharide-coated (Ag-PS) silver NMs. As inhalation is a common route of exposure, an alveolar macrophage cell model with deposition dosages representing approximately 2.5 months and 10 years of occupational exposure (0.5 and 25 ng/mL, respectively) were employed. Following dispersion in the artificial fluids, the Ag-HC and Ag-PS NMs demonstrated significant alterations to morphology, aggregation patterns, and particle reactivity. However, the Ag-PS also demonstrated a loss of particle coating, which elicited increased cytotoxicity, phagocytosis, and inflammation not associated with the original Ag-PS. This study demonstrated that in a physiological system NMs undergo considerable modulation, introducing a scenario where the toxicity of NMs may increase over time due to internal bioconditions. These findings highlight the critical influence that the dynamic and insoluble nature of NMs have on bioeffects and the importance of characterizing this behavior.

Potential new therapeutic modality revealed through agent-based modeling of the neuromuscular junction and acetylcholinesterase inhibition

Background

One of the leading causes of death and illness within the agriculture industry is through unintentionally ingesting or inhaling organophosphate pesticides. OP intoxication directly inhibits acetylcholinesterase, resulting in an excitatory signaling cascade leading to fasciculation, loss of control of bodily fluids, and seizures.

Methods

Our model was developed using a discrete, rules-based modeling approach in NetLogo. This model includes acetylcholinesterase, the nicotinic acetylcholine receptor responsible for signal transduction, a single release of acetylcholine, organophosphate inhibitors, and a theoretical novel medical countermeasure. We have parameterized the system considering the molecular reaction rate constants in an agent-based approach, as opposed to apparent macroscopic rates used in differential equation models.

Results

Our model demonstrates how the cholinergic crisis can be mitigated by therapeutic intervention with an acetylcholinesterase activator. Our model predicts signal rise rates and half-lives consistent with in vitro and in vivo data in the absence and presence of inhibitors. It also predicts the efficacy of theoretical countermeasures acting through three mechanisms: increasing catalytic turnover of acetylcholine, increasing acetylcholine binding affinity to the enzyme, and decreasing binding rates of inhibitors.

Conclusion

We present a model of the neuromuscular junction confirming observed acetylcholine signaling data and suggesting that developing a countermeasure capable of reducing inhibitor binding, and not activator concentration, is the most important parameter for reducing organophosphate (OP) intoxication.

Electronic supplementary material

The online version of this article (doi:10.1186/1742-4682-11-42) contains supplementary material, which is available to authorized users.

Porcine brain microvessel endothelial cells show pro-inflammatory response to the size and composition of metallic nanoparticles

The purpose of the current studies was to determine if systemic exposure of various metallic nanoparticles differing in size and composition [silver (Ag-NPs, 25, 40 and 80 nm), copper-oxide (Cu-NPs, 40 and 60 nm) or gold (Au-NPs, 3 and 5 nm)] can induce the release of pro-inflammatory mediators that influence the restrictive nature of the blood-brain barrier (BBB) in vitro. Confluent porcine brain microvessel endothelial cells (pBMECs) (8-12 days) were treated with various metallic nanoparticles (15 μg/ml). Extracellular concentrations of pro-inflammatory mediators (IL-1β, TNFα and PGE2) were evaluated using ELISA. pBMECs were cultured in standard 12-well Transwell® inserts, and permeability was evaluated by measuring the transport of fluorescein across the pBMEC monolayers. PGE2 release following Cu-NP exposure was significantly increased when compared to the control. Similar results were observed for Ag-NPs but not Au-NPs. The secretion of TNFα and IL-1β was observed for both Cu-NPs and Ag-NPs but not in response to Au-NPs. The post-treatment time profiles of TNFα and IL-1β revealed that the IL-1β response was more persistent. The permeability ratios (exposure/control) were significantly greater following exposure to Cu-NPs or Ag-NPs, compared to Au-NPs. Together, these data suggest that the composition and size of NPs can cause significant pro-inflammatory response that can influence the integrity of the BBB.

Spheres vs. rods: the shape of gold nanoparticles influences aggregation and deposition behavior

The influence of shape on nanomaterial aggregation and deposition was systematically studied with poly-acrylic acid (PAA) coated uniform-sized gold nanospheres (AuNSs) and nanorods (AuNRs). Time resolved dynamic light scattering was employed to study their aggregation kinetics in a wide range of mono- and di-valent electrolyte conditions. Results indicated that PAA coated AuNSs have higher aggregation propensity compared to anisotropic PAA coated AuNRs, as observed through critical coagulation concentration (CCC). The CCC values were estimated as 50 mM NaCl and 1.8 mM CaCl(2) for AuNS, which showed substantial increase to 250 mM NaCl and 7 mM CaCl(2) for anisotropic AuNRs. Though electrokinetic behavior showed similar surface potential for the spherical and rod-shaped materials, the geometric differences between the samples have likely resulted in unique conformation of the PAA coatings, leading to different magnitudes of steric hindrances and hence yielding the observed aggregation behavior. The deposition kinetics was monitored using the quartz crystal microbalance with dissipation technique. AuNRs showed relatively slower deposition compared to AuNSs for low electrolytes concentrations. With the increase in electrolyte concentration, the differences in deposition rates between spheres and rods diminished. The results from this study showed that the shape of nanomaterials can influence interfacial properties and result in unique aggregation and deposition behavior under typical aquatic conditions.

Novel platform development using an assembly of carbon nanotube, nanogold and immobilized RNA capture element towards rapid, selective sensing of bacteria

This study examines the creation of a nano-featured biosensor platform designed for the rapid and selective detection of the bacterium Escherichia coli. The foundation of this sensor is carbon nanotubes decorated with gold nanoparticles that are modified with a specific, surface adherent ribonucleiuc acid (RNA) sequence element. The multi-step sensor assembly was accomplished by growing carbon nanotubes on a graphite substrate, the direct synthesis of gold nanoparticles on the nanotube surface, and the attachment of thiolated RNA to the bound nanoparticles. The application of the compounded nano-materials for sensor development has the distinct advantage of retaining the electrical behavior property of carbon nanotubes and, through the gold nanoparticles, incorporating an increased surface area for additional analyte attachment sites, thus increasing sensitivity. We successfully demonstrated that the coating of gold nanoparticles with a selective RNA sequence increased the capture of E. coli by 189% when compared to uncoated particles. The approach to sensor formation detailed in this study illustrates the great potential of unique composite structures in the development of a multi-array, electrochemical sensor for the fast and sensitive detection of pathogens.

Effects of copper nanoparticles on rat cerebral microvessel endothelial cells

AIM

The purpose of the current study was to determine whether copper nanoparticles (Cu-NPs) can induce the release of proinflammatory mediators that influence the restrictive characteristics of the blood-brain barrier.

MATERIAL & METHODS

Confluent rat brain microvessel endothelial cells (rBMECs) were treated with well-characterized Cu-NPs (40 or 60 nm). Cytotoxicity of the Cu-NPs was evaluated by cell proliferation assay (1.5-50 µg/ml). The extracellular concentrations of proinflammatory mediators (IL-1β, IL-2, TNF-α and prostaglandin E(2)) were evaluated by ELISA.

RESULTS

The exposure of Cu-NPs at low concentrations increases cellular proliferation of rBMECs, by contrast, high concentrations induce toxicity. Prostaglandin E(2) release was significantly increased (threefold; 8 h) for Cu-NPs (40 and 60 nm). The extracellular levels of both TNF-α and IL-1β were significantly elevated following exposure to Cu-NPs. The P-apparent ratio, as an indicator of increased permeability of rBMEC was approximately twofold for Cu-NPs (40 and 60 nm).

CONCLUSION

These data suggest that Cu-NPs can induce rBMEC, proliferation at low concentrations and/or induce blood-brain barrier toxicity and potential neurotoxicity at high concentrations.

A pseudo MS3 approach for identification of disulfide-bonded proteins: uncommon product ions and database search

It has previously been reported that disulfide and backbone bonds of native intact proteins can be concurrently cleaved using electrospray ionization (ESI) and collision-induced dissociation (CID) tandem mass spectrometry (MS/MS). However, the cleavages of disulfide bonds result in different cysteine modifications in product ions, making it difficult to identify the disulfide-bonded proteins via database search. To solve this identification problem, we have developed a pseudo MS(3) approach by combining nozzle-skimmer dissociation (NSD) and CID on a quadrupole time-of-flight (Q-TOF) mass spectrometer using chicken lysozyme as a model. Although many of the product ions were similar to those typically seen in MS/MS spectra of enzymatically derived peptides, additional uncommon product ions were detected including c(i-1) ions (the i(th) residue being aspartic acid, arginine, lysine and dehydroalanine) as well as those from a scrambled sequence. The formation of these uncommon types of product ions, likely caused by the lack of mobile protons, were proposed to involve bond rearrangements via a six-membered ring transition state and/or salt bridge(s). A search of 20 pseudo MS(3) spectra against the Gallus gallus (chicken) database using Batch-Tag, a program originally designed for bottom up MS/MS analysis, identified chicken lysozyme as the only hit with the expectation values less than 0.02 for 12 of the spectra. The pseudo MS(3) approach may help to identify disulfide-bonded proteins and determine the associated post-translational modifications (PTMs); the confidence in the identification may be improved by incorporating the fragmentation characteristics into currently available search programs.

Doxycycline hydrogels as a potential therapy for ocular vesicant injury

PURPOSE

The goals of this study were (1) to compare the injury at the basement membrane zone (BMZ) of rabbit corneal organ cultures exposed to half mustard (2 chloroethyl ethyl sulfide, CEES) and nitrogen mustard with that of in vivo rabbit eyes exposed to sulfur mustard (SM); (2) to test the efficacy of 4 tetracycline derivatives in attenuating vesicant-induced BMZ disruption in the 24-h period postexposure; and (3) to use the most effective tetracycline derivative to compare the improvement of injury when the drug is delivered as drops or hydrogels to eyes exposed in vivo to SM.

METHODS

Histological analysis of hematoxylin and eosin–stained sections was performed; the ultrastructure of the corneal BMZ was evaluated by transmission electron microscopy; matrix metalloproteinase-9 was assessed by immunofluorescence; doxycycline as drops or a hydrogel was applied daily for 28 days to eyes exposed in vivo to SM. Corneal edema was assessed by pachymetry and the extent of neovascularization was graded by length of longest vessel in each quadrant.

RESULTS

Injury to the BMZ was highly similar with all vesicants, but varied in degree of severity. The effectiveness of the 4 drugs in retaining BMZ integrity did not correlate with their ability to attenuate matrix metalloproteinase-9 expression at the epithelial–stromal border. Doxycycline was most effective on organ cultures; therefore, it was applied as drops or a hydrogel to rabbit corneas exposed in vivo to SM. Eyes were examined at 1, 3, 7, and 28 days after exposure. At 7 and 28 days after SM exposure, eyes treated with doxycycline were greatly improved over those that received no therapy. Corneal thickness decreased somewhat faster using doxycycline drops, whereas the hydrogel formulation decreased the incidence of neovascularization.

CONCLUSIONS

Corneal cultures exposed to 2-chloroethyl ethyl sulfide and nitrogen mustard were effective models to simulate in vivo SM exposures. Doxycycline as drops and hydrogels ameliorated vesicant injury. With in vivo exposed animals, the drops reduced edema faster than the hydrogels, but use of the hydrogels significantly reduced neovascularization. The data provide proof of principle that a hydrogel formulation of doxycycline as a daily therapy for ocular vesicant injury should be further investigated.

Surface charge of gold nanoparticles mediates mechanism of toxicity

Recently gold nanoparticles (Au NPs) have shown promising biological and military applications due to their unique electronic and optical properties. However, little is known about their biocompatibility in the event that they come into contact with a biological system. In the present study, we have investigated whether modulating the surface charge of 1.5 nm Au NPs induced changes in cellular morphology, mitochondrial function, mitochondrial membrane potential (MMP), intracellular calcium levels, DNA damage-related gene expression, and of p53 and caspase-3 expression levels after exposure in a human keratinocyte cell line (HaCaT). The evaluation of three different Au NPs (positively charged, neutral, and negatively charged) showed that cell morphology was disrupted by all three NPs and that they demonstrated a dose-dependent toxicity; the charged Au NPs displayed toxicity as low as 10 µg ml(-1) and the neutral at 25 µg ml(-1). Furthermore, there was significant mitochondrial stress (decreases in MMP and intracellular Ca2+ levels) following exposure to the charged Au NPs, but not the neutral Au NPs. In addition to the differences observed in the MMP and Ca2+ levels, up or down regulation of DNA damage related gene expression suggested a differential cell death mechanism based on whether or not the Au NPs were charged or neutral. Additionally, increased nuclear localization of p53 and caspase-3 expression was observed in cells exposed to the charged Au NPs, while the neutral Au NPs caused an increase in both nuclear and cytoplasmic p53 expression. In conclusion, these results indicate that surface charge is a major determinant of how Au NPs impact cellular processes, with the charged NPs inducing cell death through apoptosis and neutral NPs leading to necrosis.

Brain microvessel endothelial cells responses to gold nanoparticles: In vitro pro-inflammatory mediators and permeability

This report examined blood-brain barrier (BBB) related proinflammatory mediators and permeability changes in response to various sized gold nanoparticles (Au-NPs) (3, 5, 7, 10, 30 and 60 nm) in vitro using primary rat brain microvessel endothelial cells (rBMEC). The Au-NPs were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and laser Doppler velocimetry (LDV). The accumulation of Au-NPs was determined spectrophotometrically. The rBMEC cytotoxicity of Au-NPs was evaluated by cell proliferation assay (XTT) (concentration range 0.24-15.63 μg/cm², for 24 h). The time-dependent changes (0, 2, 4 and 8 h) of several proinflammatory mediators (IL-1β, IL-2, TNFα and PGE₂) were evaluated by ELISA. The smaller Au-NPs (3-7 nm) showed higher rBMEC accumulation compared to larger Au-NPs (10-60 nm), while only moderate decreased cell viability was observed with small Au-NPs (3 nm) at high concentrations (≥ 7.8 μg/cm²). Even though slight changes in cell viability were observed with small Au-NPs, the basal levels of the various proinflammatory mediators remained unchanged with all treatments except LPS (positive control). rBMEC morphology appeared unaffected 24 h after exposure to Au-NPs with only mild changes in fluorescein permeability indicating BBB integrity was unaltered. Together, these data suggest the responses of the cerebral microvasculature to Au-NPs have a significant relationship with the Au-NPs unique size-dependent physiochemical properties.

Metal-based nanoparticles and their toxicity assessment

Nanoparticles (NPs) can potentially cause adverse effects on organ, tissue, cellular, subcellular, and protein levels due to their unusual physicochemical properties (e.g., small size, high surface area to volume ratio, chemical composition, crystallinity, electronic properties, surface structure reactivity and functional groups, inorganic or organic coatings, solubility, shape, and aggregation behavior). Metal NPs, in particular, have received increasing interest due to their widespread medical, consumer, industrial, and military applications. However, as particle size decreases, some metal-based NPs are showing increased toxicity, even if the same material is relatively inert in its bulk form (e.g., Ag, Au, and Cu). NPs also interact with proteins and enzymes within mammalian cells and they can interfere with the antioxidant defense mechanism leading to reactive oxygen species generation, the initiation of an inflammatory response and perturbation and destruction of the mitochondria causing apoptosis or necrosis. As a result, there are many challenges to overcome before we can determine if the benefits outweigh the risks associated with NPs.

Comparative study of the clastogenicity of functionalized and nonfunctionalized multiwalled carbon nanotubes in bone marrow cells of Swiss-Webster mice

The development of nanotechnologies may lead to environmental release of nanomaterials that are potentially harmful to human health. Among the nanomaterials, multiwalled carbon nanotubes (MWCNTs) are already commercialized in various products which can be in direct contact with populations. However, few studies address their potential toxicity. Although a few reports on the cytotoxicity of carbon nanotubes (CNTs) have been published, very little is known about their toxicity or genotoxicity in mammalian cells. We have for the first time compared the clastogenic/genotoxic potential of functionalized and nonfunctionalized MWCNTs in bone marrow cells of Swiss-Webster mice; using mitotic index (MI), chromosome aberrations (CA), micronuclei (MN) formation, and DNA damage in leukocytes as toxicologic endpoints. Six groups of five male mice, each weighing ∼30 ± 2 g, were administered intraperitoneally, once a day for five days with doses of 0.25, 0.5, 0.75, mg/kg body weight (BW) of functionalized and nonfunctionalized MWCNTs. Four vehicle control groups (negative) and a positive control group (carbon black) were also made of 5 mice each. Chromosome and micronuclei from bone marrow cells and comet slides from leukocytes were examined following standard protocols. The results demonstrated that MWCNTs exposure significantly increased (P < 0.05) the number of structural chromosomal aberrations, the frequency of micronucleated cells and the level of DNA damage, and decreased the mitotic index in treated groups compared to control groups. MWCNTs were shown to be toxic at sufficiently high concentrations, however purified functionalized MWCNTs had a higher clastogenic/genotoxic potential compared to nonfunctionalized form of MWCNT. The results of our study suggest that exposure to MWCNT has the potential to cause genetic damage. Hence, careful monitoring should be done with respect to designing/synthesizing biocompatible carbon nanomaterials. Further characterization of their systemic toxicity, genotoxicity and carcinogenicity is also essential.

Silver nanoparticle induced blood-brain barrier inflammation and increased permeability in primary rat brain microvessel endothelial cells

The current report examines the interactions of silver nanoparticles (Ag-NPs) with the cerebral microvasculature to identify the involvement of proinflammatory mediators that can increase blood-brain barrier (BBB) permeability. Primary rat brain microvessel endothelial cells (rBMEC) were isolated from adult Sprague-Dawley rats for an in vitro BBB model. The Ag-NPs were characterized by transmission electron microscopy (TEM), dynamic light scattering, and laser Doppler velocimetry. The cellular accumulation, cytotoxicity (6.25-50 μg/cm(3)) and potential proinflammatory mediators (interleukin [IL]-1β, IL-2, tumor necrosis factor [TNF] α, and prostaglandin E(2) [PGE(2)]) of Ag-NPs (25, 40, or 80 nm) were determined spectrophotometrically, cell proliferation assay (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) and ELISA. The results show Ag-NPs-induced cytotoxic responses at lower concentrations for 25 and 40 nm when compared with 80-nm Ag-NPs. The proinflammatory responses in this study demonstrate both Ag-NPs size and time-dependent profiles, with IL-1B preceding both TNF and PGE(2) for 25 nm. However, larger Ag-NPs (40 and 80 nm) induced significant TNF responses at 4 and 8 h, with no observable PGE(2) response. The increased fluorescein transport observed in this study clearly indicates size-dependent increases in BBB permeability correlated with the severity of immunotoxicity. Together, these data clearly demonstrate that larger Ag-NPs (80 nm) had significantly less effect on rBMEC, whereas the smaller particles induced significant effects on all the end points at lower concentrations and/or shorter times. Further, this study suggests that Ag-NPs may interact with the cerebral microvasculature producing a proinflammatory cascade, if left unchecked; these events may further induce brain inflammation and neurotoxicity.

Silver nanoparticles disrupt GDNF/Fyn kinase signaling in spermatogonial stem cells

Silver nanoparticles (Ag-NPs) are being utilized in an increasing number of fields and are components of antibacterial coatings, antistatic materials, superconductors, and biosensors. A number of reports have now described the toxic effects of silver nanoparticles on somatic cells; however, no study has examined their effects on the germ line at the molecular level. Spermatogenesis is a complex biological process that is particularly sensitive to environmental insults. Many chemicals, including ultrafine particles, have a negative effect on the germ line, either by directly affecting the germ cells or by indirectly acting on the somatic cells of the testis. In the present study, we have assessed the impact of different doses of Ag-NPs, as well as their size and biocompatible coating, on the proliferation of mouse spermatogonial stem cells (SSCs), which are at the origin of the germ line in the adult testis. At concentrations >OR= 10 microg/ml, Ag-NPs induced a significant decline in SSCs proliferation, which was also dependent on their size and coating. At the concentration of 10 microg/ml, reactive oxygen species production and/or apoptosis did not seem to play a major role; therefore, we explored other mechanisms to explain the decrease in cell proliferation. Because glial cell line-derived neurotrophic factor (GDNF) is vital for SSC self-renewal in vitro and in vivo, we evaluated the effects of Ag-NPs on GDNF-mediated signaling in these cells. Although the nanoparticles did not reduce GDNF binding or Ret receptor activity, our data revealed that already at a concentration of 10 microg/ml, silver nanoparticles specifically interact with Fyn kinase downstream of Ret and impair SSC proliferation in vitro. In addition, we demonstrated that the particle coating was degraded upon interaction with the intracellular microenvironment, reducing biocompatibility.

Metformin, independent of AMPK, inhibits mTORC1 in a rag GTPase-dependent manner

Dysfunctional mTORC1 signaling is associated with a number of human pathologies owing to its central role in controlling cell growth, proliferation, and metabolism. Regulation of mTORC1 is achieved by the integration of multiple inputs, including those of mitogens, nutrients, and energy. It is thought that agents that increase the cellular AMP/ATP ratio, such as the antidiabetic biguanides metformin and phenformin, inhibit mTORC1 through AMPK activation of TSC1/2-dependent or -independent mechanisms. Unexpectedly, we found that biguanides inhibit mTORC1 signaling, not only in the absence of TSC1/2 but also in the absence of AMPK. Consistent with these observations, in two distinct preclinical models of cancer and diabetes, metformin acts to suppress mTORC1 signaling in an AMPK-independent manner. We found that the ability of biguanides to inhibit mTORC1 activation and signaling is, instead, dependent on the Rag GTPases.

Preparation of cells for assessing ultrastructural localization of nanoparticles with transmission electron microscopy

We describe the use of transmission electron microscopy (TEM) for cellular ultrastructural examination of nanoparticle (NP)-exposed biomaterials. Preparation and imaging of electron-transparent thin cell sections with TEM provides excellent spatial resolution (approximately 1 nm), which is required to track these elusive materials. This protocol provides a step-by-step method for the mass-basis dosing of cultured cells with NPs, and the process of fixing, dehydrating, staining, resin embedding, ultramicrotome sectioning and subsequently visualizing NP uptake and translocation to specific intracellular locations with TEM. In order to avoid potential artifacts, some technical challenges are addressed. Based on our results, this procedure can be used to elucidate the intracellular fate of NPs, facilitating the development of biosensors and therapeutics, and provide a critical component for understanding NP toxicity. This protocol takes approximately 1 week.

Expression changes of dopaminergic system-related genes in PC12 cells induced by manganese, silver, or copper nanoparticles

Nanoparticles have received a great deal of attention for producing new engineering applications due to their novel physicochemical characteristics. However, the broad application of nanomaterials has also produced concern for nanoparticle toxicity due to increased exposure from large-scale industry production. This study was conducted to investigate the potential neurotoxicity of manganese (Mn), silver (Ag), and copper (Cu) nanoparticles using the dopaminergic neuronal cell line, PC12. Selective genes associated with the dopaminergic system were investigated for expression changes and their correlation with dopamine depletion. PC12 cells were treated with 10 microg/ml Mn-40 nm, Ag-15 nm, or Cu-90 nm nanoparticles for 24 h. Cu-90 nanoparticles induced dopamine depletion in PC12 cells, which is similar to the effect induced by Mn-40 shown in a previous study. The expression of 11 genes associated with the dopaminergic system was examined using real-time RT-PCR. The expression of Txnrd1 was up-regulated after the Cu-90 treatment and the expression of Gpx1 was down-regulated after Ag-15 or Cu-90 treatment. These alterations are consistent with the oxidative stress induced by metal nanoparticles. Mn-40 induced a down-regulation of the expression of Th; Cu-90 induced an up-regulation of the expression of Maoa. This indicates that besides the oxidation mechanism, enzymatic alterations may also play important roles in the induced dopamine depletion. Mn-40 also induced a down-regulation of the expression of Park2; while the expression of Snca was up-regulated after Mn-40 or Cu-90 treatment. These data suggest that Mn and Cu nanoparticles-induced dopaminergic neurotoxicity may share some common mechanisms associated with neurodegeneration.

Influence of engineered nanoparticles from metals on the blood-brain barrier permeability, cerebral blood flow, brain edema and neurotoxicity. An experimental study in the rat and mice using biochemical and morphological approaches

Influence of nanoparticles on brain function following in vivo exposures is not well known. Depending on the magnitude and intensity of nanoparticle exposure from the environment, food and/or water source, neuronal function could be affected and may lead to neurotoxicity and neuropathology. This hypothesis was examined in present investigation using systemic or intracerebroventricular administration of engineered nanoparticles from metals, i.e., Al, Ag and Cu (approximately equal to 50 to 60 nm) on neurotoxicity in rats and mice. Intraperitoneal (50 mg/kg), intravenous (30 mg/kg), intracarotid (2.5 mg/kg) or intracerebroventricular administration (20 microg) of nanoparticles significantly altered the blood-brain barrier (BBB) function to Evans blue and radioiodine in several regions of the brain and spinal cord at 24 h after their administration. Marked decreases in local cerebral blood flow (CBF) and pronounced brain edema was seen in regional areas associated with BBB leakage. Neuronal cell injuries, glial cell activation, heat shock protein (HSP) upregulation and loss of myelinated fibers are quite common in effected brain areas. The observed pathological changes were most pronounced in mice compared to rats. Exposures to Cu and Ag nanoparticles showed most marked effects on brain pathology when administered into systemic circulation or into the brain ventricular spaces as compared to Al nanoparticles. Our results are the first to show that nanoparticles from metals are able to induce selective and specific neurotoxicity that depends on the type of metals, route of administration and the species used.

Chronic treatment with nanoparticles exacerbate hyperthermia induced blood-brain barrier breakdown, cognitive dysfunction and brain pathology in the rat. Neuroprotective effects of nanowired-antioxidant compound H-290/51

The possibility that chronic exposure of nanoparticles may alter stress reaction and brain pathology following hyperthermia was examined in a rat model. Engineered nanoparticles from Ag or Cu (approximately equal to 50-60 nm) were administered (30 mg/kg, i.p.) once daily for 1 week in young male rats. On the 8th day these animals were subjected to 4 h heat stress at 38 degrees C in a BOD incubator. In these animals stress symptoms, blood-brain barrier (BBB) permeability, cognitive and motor functions and brain pathology were examined. Subjection of nanoparticle treated rats to heat stress showed exacerbation of stress symptoms i.e., hyperthermia, salivation and prostration and exhibited greater BBB disruption, brain edema formation, impairment of cognitive and motor functions and brain damage compared to normal animals. This enhanced brain pathology in heat stress was most marked in animals that received Ag nanoparticles compared to Cu treatment. Treatment with antioxidant compound H-290/51 either 30 min or 60 min after heat stress did not alter hyperthermia induce brain pathology in nanoparticle treated rats. Whereas, administration of nanowired-H-290/51 after 30 min or 60 min heat stress markedly attenuated BBB disruption, sensory motor function and brain pathology. These results suggest that chronic nanoparticles treatment exacerbate hyperthermia induced brain pathology that is significantly attenuated by nanowired but not normal H-290/51 compound. Taken together, our observations suggest that nano-wired drug delivery of H-290/51 is a promising approach to induce neuroprotection in hyperthermia induced brain pathology, not reported earlier.

Enhanced detection method for corneal protein identification using shotgun proteomics

Background

The cornea is a specialized transparent connective tissue responsible for the majority of light refraction and image focus for the retina. There are three main layers of the cornea: the epithelium that is exposed and acts as a protective barrier for the eye, the center stroma consisting of parallel collagen fibrils that refract light, and the endothelium that is responsible for hydration of the cornea from the aqueous humor. Normal cornea is an immunologically privileged tissue devoid of blood vessels, but injury can produce a loss of these conditions causing invasion of other processes that degrade the homeostatic properties resulting in a decrease in the amount of light refracted onto the retina. Determining a measure and drift of phenotypic cornea state from normal to an injured or diseased state requires knowledge of the existing protein signature within the tissue. In the study of corneal proteins, proteomics procedures have typically involved the pulverization of the entire cornea prior to analysis. Separation of the epithelium and endothelium from the core stroma and performing separate shotgun proteomics using liquid chromatography/mass spectrometry results in identification of many more proteins than previously employed methods using complete pulverized cornea.

Results

Rabbit corneas were purchased, the epithelium and endothelium regions were removed, proteins processed and separately analyzed using liquid chromatography/mass spectrometry. Proteins identified from separate layers were compared against results from complete corneal samples. Protein digests were separated using a six hour liquid chromatographic gradient and ion-trap mass spectrometry used for detection of eluted peptide fractions. The SEQUEST database search results were filtered to allow only proteins with match probabilities of equal or better than 10^-3 and peptides with a probability of 10^-2 or less with at least two unique peptides isolated within the run along with default Xcorr values. These parameters resulted in the identification of over 350 proteins, including over 225 new proteins not previously detected in the cornea by mass spectrometry. In addition, corneal layer separation resulted in identification of nearly every protein that was identified in the complete cornea assay. The epithelium and endothelium each revealed many unique proteomes specific to each layer. In the endothelium, the protein olfactomedin-like 3 was identified for the first time in the cornea by this analysis. Olfactomedin-3 is a neuronal expressed protein also known as optimedin that stimulates formation of cell adherent and cell-cell tight junctions and its expression modulates cytoskeleton organization and cell migration. However, the function of this protein in rabbit corneal endothelium is currently unknown.

Conclusion

This manuscript presents a description of a more comprehensive proteomic profile for mammalian cornea compared to past methods. The use of simple dissection procedures of the tissue and the application of long chromatographic gradients, many more proteins can be identified.

Expression of genes related to oxidative stress in the mouse brain after exposure to silver-25 nanoparticles

Nanoparticles are small scale substances (<100 nm) used in biomedical applications, electronics, and energy production. Increased exposure to nanoparticles being produced in large-scale industry facilities elicits concerns for the toxicity of certain classes of nanoparticles. This study evaluated the effects of silver-25 nm (Ag-25) nanoparticles on gene expression in different regions of the mouse brain. Adult-male C57BL/6N mice were administered (i.p.) 100mg/kg, 500 mg/kg or 1,000 mg/kg Ag-25 and sacrificed after 24h. Regions from the brain were rapidly removed and dissected into caudate nucleus, frontal cortex and hippocampus. Total RNA was isolated from each of the three brain regions collected and real-time RT-PCR analysis was performed using Mouse Oxidative Stress and Antioxidant Defense Arrays. Array data revealed the expression of genes varied in the caudate nucleus, frontal cortex and hippocampus of mice when treated with Ag-25. The data suggest that Ag-25 nanoparticles may produce neurotoxicity by generating free radical-induced oxidative stress and by altering gene expression, producing apoptosis and neurotoxicity.

DNA damage response to different surface chemistry of silver nanoparticles in mammalian cells

Silver nanoparticles (Ag NPs) have recently received much attention for their possible applications in biotechnology and life sciences. Ag NPs are of interest to defense and engineering programs for new material applications as well as for commercial purposes as an antimicrobial. However, little is known about the genotoxicity of Ag NPs following exposure to mammalian cells. This study was undertaken to examine the DNA damage response to polysaccharide surface functionalized (coated) and non-functionalized (uncoated) Ag NPs in two types of mammalian cells; mouse embryonic stem (mES) cells and mouse embryonic fibroblasts (MEF). Both types of Ag NPs up-regulated the cell cycle checkpoint protein p53 and DNA damage repair proteins Rad51 and phosphorylated-H2AX expression. Furthermore both of them induced cell death as measured by the annexin V protein expression and MTT assay. Our observations also suggested that the different surface chemistry of Ag NPs induce different DNA damage response: coated Ag NPs exhibited more severe damage than uncoated Ag NPs. The results suggest that polysaccharide coated particles are more individually distributed while agglomeration of the uncoated particles limits the surface area availability and access to membrane bound organelles.

Can silver nanoparticles be useful as potential biological labels?

Silver (Ag) nanoparticles have unique plasmon-resonant optical scattering properties that are finding use in nanomedical applications such as signal enhancers, optical sensors, and biomarkers. In this study, we examined the chemical and biological properties of Ag nanoparticles of similar sizes, but that differed primarily in their surface chemistry (hydrocarbon versus polysaccharide), in neuroblastoma cells for their potential use as biological labels. We observed strong optical labeling of the cells in a high illumination light microscopy system after 24 h of incubation due to the excitation of plasmon resonance by both types of Ag nanoparticle. Surface binding of both types of Ag nanoparticle to the plasma membrane of the cells was verified with scanning electron microscopy as well as the internalization and localization of the Ag nanoparticles into intracellular vacuoles in thin cell sections with transmission electron microscopy. However, the induction of reactive oxygen species (ROS), degradation of mitochondrial membrane integrity, disruption of the actin cytoskeleton, and reduction in proliferation after stimulation with nerve growth factor were found after incubation with Ag nanoparticles at concentrations of 25 µg ml(-1) or greater, with a more pronounced effect produced by the hydrocarbon-based Ag nanoparticles in most cases. Therefore, the use of Ag nanoparticles as potential biological labels, even if the surface is chemically modified with a biocompatible material, should be approached with caution.

Characterization of nanomaterial dispersion in solution prior to in vitro exposure using dynamic light scattering technique

The need to characterize nanoparticles in solution before assessing the in vitro toxicity is a high priority. Particle size, size distribution, particle morphology, particle composition, surface area, surface chemistry, and particle reactivity in solution are important factors which need to be defined to accurately assess nanoparticle toxicity. Currently, there are no well-defined techniques for characterization of wet nanomaterials in aqueous or biological solutions. Previously reported nanoparticle characterization techniques in aqueous or biological solutions have consisted of the use of ultra-high illumination light microscopy and disc centrifuge sedimentation; however, these techniques are limited by the measurement size range. The current study focuses on characterizing a wide range of nanomaterials using dynamic light scattering (DLS) and transmission electron microscopy, including metals, metal oxides, and carbon-based materials, in water and cell culture media, with and without serum. Cell viability and cell morphology studies were conducted in conjunction with DLS experiments to evaluate toxicological effects from observed agglomeration changes in the presence or absence of serum in cell culture media. Observations of material-specific surface properties were also recorded. It was also necessary to characterize the impact of sonication, which is implemented to aid in particle dispersion and solution mixture. Additionally, a stock solution of nanomaterials used for toxicology studies was analyzed for changes in agglomeration and zeta potential of the material over time. In summary, our results demonstrate that many metal and metal oxide nanomaterials agglomerate in solution and that depending upon the solution particle agglomeration is either agitated or mitigated. Corresponding toxicity data revealed that the addition of serum to cell culture media can, in some cases, have a significant effect on particle toxicity possibly due to changes in agglomeration or surface chemistry. It was also observed that sonication slightly reduces agglomeration and has minimal effect on particle surface charge. Finally, the stock solution experienced significant changes in particle agglomeration and surface charge over time.

Cellular interaction of different forms of aluminum nanoparticles in rat alveolar macrophages

Nanomaterials, with dimensions in the 1-100 nm range, possess numerous potential benefits to society. However, there is little characterization of their effects on biological systems, either within the environment or on human health. The present study examines cellular interaction of aluminum oxide and aluminum nanomaterials, including their effect on cell viability and cell phagocytosis, with reference to particle size and the particle's chemical composition. Experiments were performed to characterize initial in vitro cellular effects of rat alveolar macrophages (NR8383) after exposure to aluminum oxide nanoparticles (Al2O3-NP at 30 and 40 nm) and aluminum metal nanoparticles containing a 2-3 nm oxide coat (Al-NP at 50, 80, and 120 nm). Characterization of the nanomaterials, both as received and in situ, was performed using transmission electron microscopy (TEM), dynamic light scattering (DLS), laser Doppler velocimetry (LDV), and/or CytoViva150 Ultra Resolution Imaging (URI)). Particles showed significant agglomeration in cell exposure media using DLS and the URI as compared to primary particle size in TEM. Cell viability assay results indicate a marginal effect on macrophage viability after exposure to Al2O3-NP at doses of 100 microg/mL for 24 h continuous exposure. Al-NP produced significantly reduced viability after 24 h of continuous exposure with doses from 100 to 250 microg/mL. Cell phagocytotic ability was significantly hindered by exposure to 50, 80, or 120 nm Al-NP at 25 microg/mL for 24 h, but the same concentration (25 microg/mL) had no significant effect on the cellular viability. However, no significant effect on phagocytosis was observed with Al2O3-NP. In summary, these results show that Al-NP exhibit greater toxicity and more significantly diminish the phagocytotic ability of macrophages after 24 h of exposure when compared to Al2O3-NP.

Are Diamond Nanoparticles Cytotoxic?

Finely divided carbon particles, including charcoal, lampblack, and diamond particles, have been used for ornamental and official tattoos since ancient times. With the recent development in nanoscience and nanotechnology, carbon-based nanomaterials (e.g., fullerenes, nanotubes, nanodiamonds) attract a great deal of interest. Owing to their low chemical reactivity and unique physical properties, nanodiamonds could be useful in a variety of biological applications such as carriers for drugs, genes, or proteins; novel imaging techniques; coatings for implantable materials; and biosensors and biomedical nanorobots. Therefore, it is essential to ascertain the possible hazards of nanodiamonds to humans and other biological systems. We have, for the first time, assessed the cytotoxicity of nanodiamonds ranging in size from 2 to 10 nm. Assays of cell viability such as mitochondrial function (MTT) and luminescent ATP production showed that nanodiamonds were not toxic to a variety of cell types. Furthermore, nanodiamonds did not produce significant reactive oxygen species. Cells can grow on nanodiamond-coated substrates without morphological changes compared to controls. These results suggest that nanodiamonds could be ideal for many biological applications in a diverse range of cell types.

The Interaction of Manganese Nanoparticles with PC-12 Cells Induces Dopamine Depletion

This investigation was designed to determine whether nano-sized manganese oxide (Mn-40 nm) particles would induce dopamine (DA) depletion in a cultured neuronal phenotype, PC-12 cells, similar to free ionic manganese (Mn(2+)). Cells were exposed to Mn-40 nm, Mn(2+) (acetate), or known cytotoxic silver nanoparticles (Ag-15 nm) for 24 h. Phase-contrast microscopy studies show that Mn-40 nm or Mn(2+) exposure did not greatly change morphology of PC-12 cells. However, Ag-15 nm and AgNO(3) produce cell shrinkage and irregular membrane borders compared to control cells. Further microscopic studies at higher resolution demonstrated that Mn-40 nm nanoparticles and agglomerates were effectively internalized by PC-12 cells. Mitochondrial reduction activity, a sensitive measure of particle and metal cytotoxicity, showed only moderate toxicity for Mn-40 nm compared to similar Ag-15 nm and Mn(2+) doses. Mn-40 nm and Mn(2+) dose dependently depleted DA and its metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), while Ag-15 nm only significantly reduced DA and DOPAC at concentrations of 50 mug/ml. Therefore, the DA depletion of Mn-40 nm was most similar to Mn(2+), which is known to induce concentration-dependent DA depletion. There was a significant increase (> 10-fold) in reactive oxygen species (ROS) with Mn-40 nm exposure, suggesting that increased ROS levels may participate in DA depletion. These results clearly demonstrate that nanoscale manganese can deplete DA, DOPAC, and HVA in a dose-dependent manner. Further study is required to evaluate the specific intracellular distribution of Mn-40 nm nanoparticles, metal dissolution rates in cells and cellular matrices, if DA depletion is induced in vivo, and the propensity of Mn nanoparticles to cross the blood-brain barrier or be selectively uptaken by nasal epithelium.

Microarray Analysis of Mouse Ear Tissue Exposed to Bis-(2-chloroethyl) Sulfide: Gene Expression Profiles Correlate with Treatment Efficacy and An Established Clinical Endpoint

Bis-(2-chloroethyl) sulfide (sulfur mustard; SM) is a potent alkylating agent. Three treatment compounds have been shown to limit SM damage in the mouse ear vesicant model: dimercaprol, octyl homovanillamide, and indomethacin. Microarrays were used to determine gene expression profiles of biopsies taken from mouse ears after exposure to SM in the presence or absence of treatment compounds. Mouse ears were topically exposed to SM alone or were pretreated for 15 min with a treatment compound and then exposed to SM. Ear tissue was harvested 24 h after exposure for ear weight determination, the endpoint used to evaluate treatment compound efficacy. RNA extracted from the tissues was used to generate microarray probes for gene expression profiling of therapeutic responses. Principal component analysis of the gene expression data revealed partitioning of the samples based on treatment compound and SM exposure. Patterns of gene responses to the treatment compounds were indicative of exposure condition and were phenotypically anchored to ear weight. Pretreatment with indomethacin, the least effective treatment compound, produced ear weights close to those treated with SM alone. Ear weights from animals pretreated with dimercaprol or octyl homovanillamide were more closely associated with exposure to vehicle alone. Correlation coefficients between gene expression level and ear weight revealed genes involved in mediating responses to both SM exposure and treatment compounds. These data provide a basis for elucidating the mechanisms of response to SM and drug treatment and also provide a basis for developing strategies to accelerate development of effective SM medical countermeasures.

In vitro cytotoxicity of nanoparticles in mammalian germline stem cells

Gametogenesis is a complex biological process that is particularly sensitive to environmental insults such as chemicals. Many chemicals have a negative impact on the germline, either by directly affecting the germ cells, or indirectly through their action on the somatic nursing cells. Ultimately, these effects can inhibit fertility, and they may have negative consequences for the development of the offspring. Recently, nanomaterials such as nanotubes, nanowires, fullerene derivatives (buckyballs), and quantum dots have received enormous national attention in the creation of new types of analytical tools for biotechnology and the life sciences. Despite the wide application of nanomaterials, there is a serious lack of information concerning their impact on human health and the environment. Thus, there are limited studies available on toxicity of nanoparticles for risk assessment of nanomaterials. The purpose of this study was to assess the suitability of a mouse spermatogonial stem cell line as a model to assess nanotoxicity in the male germline in vitro. The effects of different types of nanoparticles on these cells were evaluated by light microscopy, and by cell proliferation and standard cytotoxicity assays. Our results demonstrate a concentration-dependent toxicity for all types of particles tested, whereas the corresponding soluble salts had no significant effect. Silver nanoparticles were the most toxic while molybdenum trioxide (MoO(3)) nanoparticles were the least toxic. Our results suggest that this cell line provides a valuable model with which to assess the cytotoxicity of nanoparticles in the germ line in vitro.

In vitro toxicity of nanoparticles in BRL 3A rat liver cells

This study was undertaken to address the current deficient knowledge of cellular response to nanosized particle exposure. The study evaluated the acute toxic effects of metal/metal oxide nanoparticles proposed for future use in industrial production methods using the in vitro rat liver derived cell line (BRL 3A). Different sizes of nanoparticles such as silver (Ag; 15, 100 nm), molybdenum (MoO(3); 30, 150 nm), aluminum (Al; 30, 103 nm), iron oxide (Fe(3)O(4); 30, 47 nm), and titanium dioxide (TiO(2); 40 nm) were evaluated for their potential toxicity. We also assessed the toxicity of relatively larger particles of cadmium oxide (CdO; 1 microm), manganese oxide (MnO(2); 1-2 microm), and tungsten (W; 27 microm), to compare the cellular toxic responses with respect to the different sizes of nanoparticles with different core chemical compositions. For toxicity evaluations, cellular morphology, mitochondrial function (MTT assay), membrane leakage of lactate dehydrogenase (LDH assay), reduced glutathione (GSH) levels, reactive oxygen species (ROS), and mitochondrial membrane potential (MMP) were assessed under control and exposed conditions (24h of exposure). Results showed that mitochondrial function decreased significantly in cells exposed to Ag nanoparticles at 5-50 microg/ml. However, Fe(3)O(4), Al, MoO(3) and TiO(2) had no measurable effect at lower doses (10-50 microg/ml), while there was a significant effect at higher levels (100-250 microg/ml). LDH leakage significantly increased in cells exposed to Ag nanoparticles (10-50 microg/ml), while the other nanoparticles tested displayed LDH leakage only at higher doses (100-250 microg/ml). In summary the Ag was highly toxic whereas, MoO(3) moderately toxic and Fe(3)O(4), Al, MnO(2) and W displayed less or no toxicity at the doses tested. The microscopic studies demonstrated that nanoparticle-exposed cells at higher doses became abnormal in size, displaying cellular shrinkage, and an acquisition of an irregular shape. Due to toxicity of silver, further study conducted with reference to its oxidative stress. The results exhibited significant depletion of GSH level, reduced mitochondrial membrane potential and increase in ROS levels, which suggested that cytotoxicity of Ag (15, 100 nm) in liver cells is likely to be mediated through oxidative stress.

Microarray analysis of gene expression in murine skin exposed to sulfur mustard

The chemical warfare agent sulfur mustard [bis-(2-chloroethyl)-sulfide; SM] produces a delayed inflammatory response followed by blister formation in skin of exposed individuals. Studies are underway evaluating the efficacy of pharmacological compounds to protect against SM skin injury. Microarray analysis provides the opportunity to identify multiple transcriptional biomarkers associated with SM exposure. This study examined SM-induced changes in gene expression in skin from mice cutaneously exposed to SM using cDNA microarrays. Ear skin from five mice, paired as SM-exposed right ear and dichloromethane vehicle-exposed left ear at six dose levels (0.005, 0.01, 0.02, 0.04, 0.08, and 0.16 mg; 6 mM to 195 mM range), was harvested at 24 h post-exposure. SM-induced gene expression was analyzed using cDNA microarrays that included 1,176 genes. Genes were selected on the basis of all mice (N=5) in the same dose group demonstrating a > or =2-fold increase or decrease in gene expression for the SM-exposed tissue compared to the dichloromethane vehicle control ear tissue at all six SM doses. When skin exposed to all six concentrations of SM was compared to controls, a total of 19 genes within apoptosis, transcription factors, cell cycle, inflammation, and oncogenes and tumor suppressors categories were found to be upregulated; no genes were observed to be downregulated. Differences in the number and category of genes that were up- or down-regulated in skin exposed to low (0.005-0.01 mg) and high (0.08-0.16 mg) doses of SM were also observed. The results of this study provide a further understanding of the molecular responses to cutaneous SM exposure, and enable the identification of potential diagnostic markers and therapeutic targets for treating SM injury.

Time- and dose-dependent analysis of gene expression using microarrays in sulfur mustard-exposed mice

The chemical warfare agent sulfur mustard (SM) produces blister formation with a severe inflammatory reaction in skin of exposed individuals. The development of efficacious countermeasures against SM vesication requires an understanding of the cellular and molecular mechanism of SM-induced tissue injury. This study examined SM-induced alterations in gene expression using Atlas Mouse 5K DNA microarrays (5002 genes) to identify transcriptional events associated with SM skin injury. Mice (N=3) were exposed topically to SM (0.04, 0.08, and 0.16 mg; 48.8, 97.5, and 195 mM) on the inner surface of the right ear and skin tissues were harvested at 1.5, 3, 6, and 12 h. Genes were selected based on the three mice in the same dose group demonstrating a > or =2-fold increase or decrease in gene expression for the SM-exposed tissue when compared to the dichloromethane vehicle control ear at all three doses and four time points. At the 0.04 mg SM dose, the genes observed were primarily involved in inflammation, apoptosis, and cell cycle regulation. Exposure to 0.08 mg SM increased the expression of genes related to inflammation and cell cycle regulation. Exposure to 0.16 mg SM led to a total of six genes that were changed at all observed time periods; however, these genes do not appear to be directly influential in biological mechanisms such as inflammation, apoptosis, and cell cycle regulation as was observed at the lower SM doses of 0.04 and 0.08 mg. These functional categories have been observed in previous studies utilizing both in vivo and in vitro model systems of SM-induced dermal injury, suggesting that molecular mechanisms associated with inflammation, apoptosis, and cell cycle regulation may be appropriate targets for developing prophylactic/therapeutic treatments for SM skin injury.

An inhibitor of p38 MAP kinase downregulates cytokine release induced by sulfur mustard exposure in human epidermal keratinocytes

Sulfur mustard (2,2'-dichlorodiethyl sulfide, SM) is a potent alkylating agent that induces skin vessication after cutaneous exposure. Previous work has revealed that SM induces the production of inflammatory cytokines, including IL-8, IL-6, TNF-alpha, and IL-1beta, in keratinocytes. The p38 MAP kinase (MAPK14) signaling pathway is activated via phosphorylation in response to cellular stress and has been implicated in the upregulation of cytokines in response to stress. We investigated the role of p38 MAP kinase in inflammatory cytokine upregulation following SM exposure. A dose response study in cultured human epidermal keratinocytes (HEK) revealed increasing phosphorylation of p38 MAP kinase in response to increasing concentrations of SM. A time course at the 200 microM exposure revealed that p38 MAP kinase phosphorylation is induced by 15 min post-exposure, peaks at 30 min and is sustained at peak levels until 8 h post-exposure. Phosphorylation of the upstream kinase MKK3/6 was also detected. Assay of the SM-exposed HEK culture media for cytokines revealed that exposure to 200 microM SM increased IL-8, IL-6, TNF-alpha, and IL-1beta. When cells exposed to 200 microM SM were treated with the p38 MAP kinase inhibitor SB203580, the levels of IL-8, IL-6, and TNF-alpha and IL-1beta were significantly decreased when compared with cells that were untreated. These results show that p38 MAP kinase plays a role in SM-induced cytokine production in HEK and suggest that inhibiting this pathway may alleviate the profound inflammatory response elicited by cutaneous SM exposure.

Sulfur mustard induces the formation of keratin aggregates in human epidermal keratinocytes☆1Current address: University of Texas at Austin, Cell & Molecular Biology, 1 University Station C0930, Austin, TX 78712-0253, USA

The vesicant sulfur mustard is an alkylating agent that has the capacity to cross-link biological molecules. We are interested in identifying specific proteins that are altered upon sulfur mustard exposure. Keratins are particularly important for the structural integrity of skin, and several genetically inherited blistering diseases have been linked to mutations in keratin 5 and keratin 14. We examined whether sulfur mustard exposure alters keratin biochemistry in cultured human epidermal keratinocytes. Western blotting with specific monoclonal antibodies revealed the formation of stable high-molecular-weight "aggregates" containing keratin 14 and/or keratin 5. These aggregates begin to form within 15 min after sulfur mustard exposure. These aggregates display a complex gel electrophoresis pattern between approximately 100 and approximately 200 kDa. Purification and analysis of these aggregates by one- and two-dimensional gel electrophoresis and mass spectrometry confirmed the presence of keratin 14 and keratin 5 and indicate that at least some of the aggregates are composed of keratin 14-keratin 14, keratin 14-keratin 5, or keratin 5-keratin 5 dimers. These studies demonstrate that sulfur mustard induces keratin aggregation in keratinocytes and support further investigation into the role of keratin aggregation in sulfur mustard-induced vesication.

Cytokine, chemokine, and matrix metalloproteinase response after sulfur mustard injury to weanling pig skin

Cutaneous exposure to sulfur mustard [bis(2-chloroethyl) sulfide; SM] produces a delayed inflammatory skin response and severe tissue injury. Pig skin has organ similarities to human skin that is characterized by the content and types of epidermal lipids, the density of hair follicles and presence of sweat glands, which together afford penetration of topically applied compounds, complex inflammatory responses, and subsequent wound healing. The goal of this study was to identify in vivo proinflammatory biomarkers of the SM porcine skin injury within 72 h after SM challenge, using the weanling pig model. Changes in gene expression of inflammatory mediators were examined at 3, 6, 24, 48, and 72 h, using subtraction library analyses and by quantitation of selected transcripts by reverse transcription-polymerase chain reaction (RT-PCR). Sequence analysis of subtraction libraries identified up-regulation of IL-8 at 24, 48, and 72 h. No other specific proinflammatory gene transcripts were isolated from the libraries. Specific transcript RT-PCR analysis showed increased production of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8 (IL-8), and matrix metalloproteinase-9 (MMP-9, gelatinase B) mRNA levels in response to SM exposure. Tumor necrosis factor-alpha (TNF-alpha) expression was only slightly increased and no change in the levels of expression was observed for monocyte chemoattractant protein-1 and MMP-2. This study identifies the main proinflammatory mediators involved in SM-induced skin injury in a weanling pig model. The results suggest transcriptional activity in the inflammatory response proteins IL-8, IL-6, IL-1beta, and MMP-9 and modest changes in TNF-alpha that together produce inflammation and contribute to the pathogenesis of SM dermatotoxicity. Therefore, drugs preventing SM-induced inflammation should be prime candidates for medical intervention to lessen collateral inflammation associated with tissue destruction.

Army medical laboratory telemedicine: role of mass spectrometry in telediagnosis for chemical and biological defense

An army medical field laboratory presently has the capability of performing standard protocols developed at the US Army Medical Research Institute of Chemical Defense for verification of nerve agent or sulfur mustard exposure. The protocols analyze hydrolysis products of chemical warfare agents using gas chromatography/mass spectrometry. Additionally, chemical warfare agents can produce alkylated or phosphorylated proteins following human exposure that have long biological half-lives and can be used as diagnostic biomarkers of chemical agent exposure. An analytical technique known as matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS) currently is being examined for its potential to analyze these biomarkers. The technique is capable of detecting large biomolecules and modifications made to them. Its fast analysis time makes MALDI-TOF/MS technology suitable for screening casualties from chemical or biological attacks. Basic operation requires minimal training and the instrument has the potential to become field-portable. The limitation of the technique is that the generated data may require considerable expertise from knowledgeable personnel for consultation to ensure correct interpretation. The interaction between research scientists and field personnel in the acquisition of data and its interpretation via advanced digital telecommunication technologies can enhance rapid diagnosis and subsequently improve patient care in remote areas.