Size-dependent effects of tungsten carbide-cobalt particles on oxygen radical production and activation of cell signaling pathways in murine epidermal cells

Mechanistic Implications of Biomass-Derived Particulate Matter for Immunity and Immune Disorders

Particulate matter (PM) is a major and the most harmful component of urban air pollution, which may adversely affect human health. PM exposure has been associated with several human diseases, notably respiratory and cardiovascular diseases. In particular, recent evidence suggests that exposure to biomass-derived PM associates with airway inflammation and can aggravate asthma and other allergic diseases. Defective or excess responsiveness in the immune system regulates distinct pathologies, such as infections, hypersensitivity, and malignancies. Therefore, PM-induced modulation of the immune system is crucial for understanding how it causes these diseases and highlighting key molecular mechanisms that can mitigate the underlying pathologies. Emerging evidence has revealed that immune responses to biomass-derived PM exposure are closely associated with the risk of diverse hypersensitivity disorders, including asthma, allergic rhinitis, atopic dermatitis, and allergen sensitization. Moreover, immunological alteration by PM accounts for increased susceptibility to infectious diseases, such as tuberculosis and coronavirus disease-2019 (COVID-19). Evidence-based understanding of the immunological effects of PM and the molecular machinery would provide novel insights into clinical interventions or prevention against acute and chronic environmental disorders induced by biomass-derived PM.

Multigenerational Exposure to WCCo Nanomaterials-Epigenetics in the Soil Invertebrate Enchytraeus crypticus

It has become clear how important it is to assess longer term effects of (nano) materials in the environment given the current evidence showing how epigenetics drives response mechanisms. Here we studied global DNA methylation in standard soil invertebrate Enchytraeus crypticus over 224 days when exposed to nanostructured tungsten carbide cobalt (WCCo nanomaterials (NMs)) and to cobalt (CoCl₂) in a multigenerational experiment. In order to assess the transgenerational effect, we used a multigenerational (MG) test design consisting of four generations in spiked soil followed by two generations in clean soil. Results showed that MG exposure to WCCo NMs caused global DNA methylation to increase, which continued in unexposed generations and was associated with an increase in reproduction (phenotypic effect). In general, WCCo NMs caused more (and more consistent) methylation than CoCl₂.

PVP-stabilized tungsten oxide nanoparticles: pH sensitive anti-cancer platform with high cytotoxicity

Photochromic tungsten oxide (WO₃) nanoparticles stabilized by polyvinylpyrrolidone (PVP) were synthesized to evaluate their potential for biomedical applications. PVP-stabilized tungsten oxide nanoparticles demonstrated a highly selective cytotoxic effect on normal and cancer cells in vitro. WO₃ nanoparticles were found to induce substantial cell death in osteosarcoma cells (MNNG/HOS cell line) with a half-maximal inhibitory concentration (IC50) of 5 mg/mL, while producing no, or only minor, toxicity in healthy human mesenchymal stem cells (hMSc). WO₃ nanoparticles induced intracellular oxidative stress, which led to apoptosis type cell death. The selective anti-cancer effects of WO₃ nanoparticles are due to the pH sensitivity of tungsten oxide and its capability of reactive oxygen species (ROS) generation, which is expressed in the modulation of genes involved in reactive oxygen species metabolism, mitochondrial dysfunction, and apoptosis.

Genotoxicity of amorphous silica nanoparticles: Status and prospects

Amorphous silica nanoparticles (SNPs) are widely used in biomedical applications and consumer products. Little is known, however, about their genotoxicity and potential to induce gene expression regulation. Despite recent efforts to study the underlying mechanisms of genotoxicity of SNPs, inconsistent results create a challenge. A variety of factors determine particle-cell interactions and underlying mechanisms. Further, high-throughput studies are required to carefully assess the impact of silica nanoparticle physicochemical properties on induction of genotoxic response in different cell lines and animal models. In this article, we review the strategies available for evaluation of genotoxicity of nanoparticles (NPs), survey current status of silica nanoparticle gene alteration and genotoxicity, discuss particle-mediated inflammation as a contributing factor to genotoxicity, identify existing gaps and suggest future directions for this research.

Evaluation of Nrf2 with Exposure to Nanoparticles

Transcription factor Nrf2, nuclear factor (erythroid-derived 2)-like 2, is considered a master regulator of redox homeostasis and plays a central role in antioxidant and anti-inflammatory defence. It has been largely reported that oxidative stress is implicated in nanoparticle-induced toxicity with the involvement of Nrf2. Several basic methods for Nrf2 evaluation with exposure to nanoparticles are described in this chapter including real-time reverse transcription-polymerase chain reaction (RT-PCR), western blotting, immunofluorescence staining, electrophoretic mobility shift assay, DNase I footprinting, dimethylsulfate footprinting, protein pulse-chase analysis, and tert-butylhydroquinone treatment.

Comparative Assessment of Tungsten Toxicity in the Absence or Presence of Other Metals

Tungsten is a refractory metal that is used in a wide range of applications. It was initially perceived that tungsten was immobile in the environment, supporting tungsten as an alternative for lead and uranium in munition and military applications. Recent studies report movement and detection of tungsten in soil and potable water sources, increasing the risk of human exposure. In addition, experimental research studies observed adverse health effects associated with exposure to tungsten alloys, raising concerns on tungsten toxicity with questions surrounding the safety of exposure to tungsten alone or in mixtures with other metals. Tungsten is commonly used as an alloy with nickel and cobalt in many applications to adjust hardness and thermal and electrical conductivity. This review addresses the current state of knowledge in regard to the mechanisms of toxicity of tungsten in the absence or presence of other metals with a specific focus on mixtures containing nickel and cobalt, the most common components of tungsten alloy.

Cobalt and its compounds: update on genotoxic and carcinogenic activities

This article summarizes recent experimental and epidemiological data on the genotoxic and carcinogenic activities of cobalt compounds. Emphasis is on the respiratory system, but endogenous exposure from Co-containing alloys used in endoprostheses, and limited data on nanomaterials and oral exposures are also considered. Two groups of cobalt compounds are differentiated on the basis of their mechanisms of toxicity: (1) those essentially involving the solubilization of Co(II) ions, and (2) metallic materials for which both surface corrosion and release of Co(II) ions act in concert. For both groups, identified genotoxic and carcinogenic mechanisms are non-stochastic and thus expected to exhibit a threshold. Cobalt compounds should, therefore, be considered as genotoxic carcinogens with a practical threshold. Accumulating evidence indicates that chronic inhalation of cobalt compounds can induce respiratory tumors locally. No evidence of systemic carcinogenicity upon inhalation, oral or endogenous exposure is available. The scarce data available for Co-based nanosized materials does not allow deriving a specific mode of action or assessment for these species.

Tungsten: an Emerging Toxicant, Alone or in Combination

PURPOSE OF REVIEW

Tungsten is an emerging environmental toxicant, yet our understanding of the potential risks of exposure on human health is still limited.

RECENT FINDINGS

In this review, we will discuss populations most at risk of exposure to high concentrations of tungsten. In addition, we will highlight what is known about the toxicity profile of tungsten compounds, based on epidemiological, in vitro, and in vivo studies, focusing on bone, immune, pulmonary, and cancer outcomes. Of note, emerging evidence indicates that tungsten can augment the effects of other stimulants, stressors, and toxicants. Of particular importance may be tungsten-cobalt mixtures that seem to be more toxic than either metal alone. This is important because it means that we cannot just evaluate the toxicity of tungsten in isolation. Finally, we still have limited information of how many of the in vitro and in vivo findings translate to human populations, so it will be important to conduct epidemiology studies in highly exposed populations to adequately address the potential risks of tungsten exposure on human health. Together, we discuss recent findings that support further investigation into the toxicities of tungsten alone and in combination with other metals.

L-Ascorbic Acid Protected Against Extrinsic and Intrinsic Apoptosis Induced by Cobalt Nanoparticles Through ROS Attenuation

Currently, tissue damage induced by cobalt nanoparticles (CoNPs) and cobalt ions (Co²⁺) are the most serious syndrome in the patients with metal-on-metal hip prostheses. Therefore, an urgent need exists for the identification of the mechanisms and the development of therapeutic strategies to limit it. The purpose of this study was to explore the mechanism of this damage and to demonstrate if L-ascorbic acid (L-AA) could protect against the cell toxicities induced by CoNPs and Co²⁺ in vitro. With CoNPs and Co²⁺ treatment, cell viability was significantly decreased; the ROS (reactive oxygen species) level in mitochondria was dramatically increased in CoNPs treated cells, but cobalt ions could barely induce the ROS. Consistently, the level of cell apoptosis was increased with the upregulation of pro-apoptotic factors (caspases 8, 9, and 3, and Bax) and the downregulation of anti-apoptotic factor Bcl-2. Besides that, the levels of cytochrome c and AIF were increased and released from mitochondria into the cytoplasm. After the cells were pretreated with L-AA, the cell viability decreased by CoNPs was reversed and the ROS induced by CoNPs was suppressed. The level of cell apoptosis induced by CoNPs was decreased as well. But it could not reverse the effects induced by Co²⁺. These studies demonstrated that CoNPs induce extrinsic and intrinsic apoptotic pathways via generation of ROS, and L-AA could prevent the cytotoxicity by reducing the level of ROS. While Co²⁺ may induce cytotoxicity through other signals, it could not be protected by L-AA treatment.

Nanotoxicity: emerging concerns regarding nanomaterial safety and occupational hard metal (WC-Co) nanoparticle exposure

As the number of commercial and consumer products containing engineered nanomaterials (ENMs) continually rises, the increased use and production of these ENMs presents an important toxicological concern. Although ENMs offer a number of advantages over traditional materials, their extremely small size and associated characteristics may also greatly enhance their toxic potentials. ENM exposure can occur in various consumer and industrial settings through inhalation, ingestion, or dermal routes. Although the importance of accurate ENM characterization, effective dosage metrics, and selection of appropriate cell or animal-based models are universally agreed upon as important factors in ENM research, at present, there is no “standardized” approach used to assess ENM toxicity in the research community. Of particular interest is occupational exposure to tungsten carbide cobalt (WC-Co) “dusts,” composed of nano- and micro-sized particles, in hard metal manufacturing facilities and mining and drilling industries. Inhalation of WC-Co dust is known to cause “hard metal lung disease” and an increased risk of lung cancer; however, the mechanisms underlying WC-Co toxicity, the inflammatory disease state and progression to cancer are poorly understood. Herein, a discussion of ENM toxicity is followed by a review of the known literature regarding the effects of WC-Co particle exposure. The risk of WC-Co exposure in occupational settings and the updates of in vitro and in vivo studies of both micro- and nano-WC-Co particles are discussed.

In vitro inflammatory effects of hard metal (WC-Co) nanoparticle exposure

Identifying the toxicity of nanoparticles (NPs) is an important area of research as the number of nanomaterial-based consumer and industrial products continually rises. In addition, the potential inflammatory effects resulting from pulmonary NP exposure are emerging as an important aspect of nanotoxicity. In this study, the toxicity and inflammatory state resulting from tungsten carbide–cobalt (WC–Co) NP exposure in macrophages and a coculture (CC) of lung epithelial cells (BEAS-2B) and macrophages (THP-1) at a 3:1 ratio were examined. It was found that the toxicity of nano-WC–Co was cell dependent; significantly less toxicity was observed in THP-1 cells compared to BEAS-2B cells. It was demonstrated that nano-WC–Co caused reduced toxicity in the CC model compared to lung epithelial cell monoculture, which suggested that macrophages may play a protective role against nano-WC–Co-mediated toxicity in CCs. Nano-WC–Co exposure in macrophages resulted in increased levels of interleukin (IL)-1β and IL-12 secretion and decreased levels of tumor necrosis factor alpha (TNFα). In addition, the polarizing effects of nano-WC–Co exposure toward the M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophage phenotypes were investigated. The results of this study indicated that nano-WC–Co exposure stimulated the M1 phenotype, marked by high expression of CD40 M1 macrophage surface markers.

Synthesis of Co3O4 nanoparticles with block and sphere morphology, and investigation into the influence of morphology on biological toxicity

In the present study, cobalt oxide (Co₃O₄) magnetic nanoparticles with block and sphere morphologies were synthesized using various surfactants, and the toxicity of the particles was analyzed by monitoring biomarkers of nanoparticle toxicity in zebrafish. The use of tartarate as a surfactant produced highly crystalline blocks of Co₃O₄ nanoparticles with pores on the sides, whereas citrate lead to the formation of nanoparticles with a spherical morphology. Co₃O₄ structure, crystallinity, size and morphology were studied using X-ray diffractogram and field emission scanning electron microscopy. Following an increase in nanoparticle concentration from 1 to 200 ppm, there was a corresponding increase in nitric oxide (NO) generation, induced by both types of nanoparticles [Co₃O₄-NP-B (block), r=0.953; Co₃O₄-NP-S (sphere), r=1.140]. Comparative analyses indicated that both types of nanoparticle produced significant stimulation at ≥5 ppm (P<0.05) compared with a control. Upon analyzing the effect of nanoparticle morphology on NO generation, it was observed that Co₃O₄-NP-S was more effective compared with Co₃O₄-NP-B (5 and 100 ppm, P<0.05; 200 ppm, P<0.01). Exposure to both types of nanoparticles produced reduction in liver glutathione (GSH) activity with corresponding increase in dose (Co₃O₄-NP-B, r=-0.359; Co₃O₄-NP-S, r=-0.429). However, subsequent analyses indicated that Co₃O₄-NP-B was more potent in inhibiting liver GSH activity compared with Co₃O₄-NP-S. Co₃O₄-NP-B proved to be toxic at 5 ppm (P<0.05) and GSH activity was almost completely inhibited at 200 ppm. A similar toxicity was observed with both types of Co₃O₄-NPs against brain levels of acetylcholinesterase (AChE; Co₃O₄-NP-B, r=-0.180; Co₃O₄-NP-S, r=-0.230), indicating the ability of synthesized Co₃O₄-NPs to cross the blood-brain barrier and produce neuronal toxicity. Co₃O₄-NP-B showed increased inhibition of brain AChE activity compared with Co₃O₄-NP-S (1,5, and 10 ppm, P<0.05; 50, 100 and 200 ppm, P<0.01). These results suggested that the morphology of nanoparticle and surface area contribute to toxicity, which may have implications for their biological application.

The potential for chemical mixtures from the environment to enable the cancer hallmark of sustained proliferative signalling

The aim of this work is to review current knowledge relating the established cancer hallmark, sustained cell proliferation to the existence of chemicals present as low dose mixtures in the environment. Normal cell proliferation is under tight control, i.e. cells respond to a signal to proliferate, and although most cells continue to proliferate into adult life, the multiplication ceases once the stimulatory signal disappears or if the cells are exposed to growth inhibitory signals. Under such circumstances, normal cells remain quiescent until they are stimulated to resume further proliferation. In contrast, tumour cells are unable to halt proliferation, either when subjected to growth inhibitory signals or in the absence of growth stimulatory signals. Environmental chemicals with carcinogenic potential may cause sustained cell proliferation by interfering with some cell proliferation control mechanisms committing cells to an indefinite proliferative span.

Genotoxicity of tungsten carbide-cobalt (WC-Co) nanoparticles in vitro: mechanisms-of-action studies

We showed previously that tungsten carbide-cobalt (WC-Co) nanoparticles (NP) can be used as a nanoparticulate positive control in some in vitro mammalian genotoxicity assays. Here, we investigate the mechanisms of action involved in WC-Co NP genotoxicity in L5178Y mouse lymphoma cells and primary human lymphocytes, in vitro. Data from the micronucleus assay coupled with centromere staining and from the chromosome-aberration assay show the involvement of both clastogenic and aneugenic events. Experiments with the formamidopyrimidine DNA glycosylase (FPG)-modified comet assay showed a slight (non-significant) increase in FPG-sensitive sites in the L5178Y mouse lymphoma cells but not in the human lymphocytes. Electron paramagnetic resonance spin-trapping results showed the presence of hydroxyl radicals (•OH) in WC-Co NP suspensions, with or without cells, but with time-dependent production in the presence of cells. However, a significant difference in •OH production was observed between human lymphocytes from two different donors. Using H2O2, we showed that WC-Co NP can participate in Fenton-like reactions. Thus, •OH might be produced either via intrinsic generation by WC-Co NP or through a Fenton-like reaction in the presence of cells.

Altered gene transcription in human cells treated with Ludox® silica nanoparticles

Silica (SiO₂) nanoparticles (NPs) have found extensive applications in industrial manufacturing, biomedical and biotechnological fields. Therefore, the increasing exposure to such ultrafine particles requires studies to characterize their potential cytotoxic effects in order to provide exhaustive information to assess the impact of nanomaterials on human health. The understanding of the biological processes involved in the development and maintenance of a variety of pathologies is improved by genome-wide approaches, and in this context, gene set analysis has emerged as a fundamental tool for the interpretation of the results. In this work we show how the use of a combination of gene-by-gene and gene set analyses can enhance the interpretation of results of in vitro treatment of A549 cells with Ludox^® colloidal amorphous silica nanoparticles. By gene-by-gene and gene set analyses, we evidenced a specific cell response in relation to NPs size and elapsed time after treatment, with the smaller NPs (SM30) having higher impact on inflammatory and apoptosis processes than the bigger ones. Apoptotic process appeared to be activated by the up-regulation of the initiator genes TNFa and IL1b and by ATM. Moreover, our analyses evidenced that cell treatment with Ludox^® silica nanoparticles activated the matrix metalloproteinase genes MMP1, MMP10 and MMP9. The information derived from this study can be informative about the cytotoxicity of Ludox^® and other similar colloidal amorphous silica NPs prepared by solution processes.

Growth inhibition, cell-cycle alteration and apoptosis in stimulated human peripheral blood lymphocytes by multiwalled carbon nanotube buckypaper

AIM

This study was designed to investigate the cytotoxicity of multiwalled carbon nanotube buckypaper (BP) in stimulated human peripheral blood lymphocytes. Materials & methods & results: BP treatment led to a delay in the cell growth, as proven by a minor increase in the cell number over time relative to that seen in untreated cells, assessed by trypan blue, resazurin and neutral red assays. The analysis of cell-cycle profile, by propidium iodide staining, indicated that BP treatment blocked cell-cycle progression by arresting cells at the G0/G1 phase. Moreover, increased apoptosis was also recorded by Annexin V-fluorescein isothiocyanate/propidium iodide staining.

CONCLUSION

The results presented here demonstrate an inhibitor effect of BP on cell growth that was likely through cytostatic and cytotoxic events.

Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause "hard metal lung disease" but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure.

Responses of hepatic metallothioneins and apoptotic activity in Carassius auratus gibelio witness a release of cobalt and zinc from waterborne nanoscale composites

The main goal of this study was to evaluate the ability of fish Carassius auratus tissues to release cobalt (Co) and zinc (Zn) cations present in the applied Co- and Zn-containing nanoscale composites (NCs). Male fish was subjected to 14day long action of Co- and Zn-NCs, as well as of Co(2+) and Zn(2+) or polymeric substance (PS) used for the NC preparation and derived from the vinylpyrrolidone. 50μg∙L(-1) of Co and 100μg∙L(-1) of Zn were applied either as a salt or a nanocomposite. Both Co and Co-NC increased (3.1 and 2.3 times, respectively) concentration of total Co, metallothionein-related Co (3.7 and 6.6 times, respectively) and thiols (by 71 and 95%, respectively), and caspase-3 activity (2.2 and 3.7 times, respectively) in the fish liver. At the same time, Co and Co-NC decreased glutathione level (1.8 and 1.9 times, respectively) and activated vitellogenesis (5.1 and 9.9 times, respectively) in the fish liver. Both Zn and Zn-NC increased markedly concentrations of metallothionein-related Zn (2.4 and 2.9 times, respectively) and Cu (2.8 and 3.2 times, respectively), and decreased metallothionein-related thiol (2.5 and 4.2 times, respectively), oxyradical (by 30.4 and 44.2%, respectively), and caspase-3 (3.0 and 5.3 times, respectively) levels in the fish liver. These peculiarities are common for metal and metal-NC and witness a release of metal from NS in fish organism. The differences in the levels of DNA strand breaks, biotransformation enzymes and total Zn levels in the liver were dependent on the kind of exposure.

Intracellular signal modulation by nanomaterials

A thorough understanding of the interactions of nanomaterials with biological systems and the resulting activation of signal transduction pathways is essential for the development of safe and consumer friendly nanotechnology. Here we present an overview of signaling pathways induced by nanomaterial exposures and describe the possible correlation of their physicochemical characteristics with biological outcomes. In addition to the hierarchical oxidative stress model and a review of the intrinsic and cell-mediated mechanisms of reactive oxygen species (ROS) generating capacities of nanomaterials, we also discuss other oxidative stress dependent and independent cellular signaling pathways. Induction of the inflammasome, calcium signaling, and endoplasmic reticulum stress are reviewed. Furthermore, the uptake mechanisms can be of crucial importance for the cytotoxicity of nanomaterials and membrane-dependent signaling pathways have also been shown to be responsible for cellular effects of nanomaterials. Epigenetic regulation by nanomaterials, effects of nanoparticle-protein interactions on cell signaling pathways, and the induction of various cell death modalities by nanomaterials are described. We describe the common trigger mechanisms shared by various nanomaterials to induce cell death pathways and describe the interplay of different modalities in orchestrating the final outcome after nanomaterial exposures. A better understanding of signal modulations induced by nanomaterials is not only essential for the synthesis and design of safer nanomaterials but will also help to discover potential nanomedical applications of these materials. Several biomedical applications based on the different signaling pathways induced by nanomaterials are already proposed and will certainly gain a great deal of attraction in the near future.

Induction of miR-21-PDCD4 signaling by UVB in JB6 cells involves ROS-mediated MAPK pathways

Ultraviolet (UV) irradiation plays a major role in the development of human skin cancer. The present study examined the alterations of miR-21-PDCD4 signaling in a mouse epidermal cell line (JB6 P(+)) post exposure to UVB irradiation. The results showed that (1) UVB caused PDCD4 inhibition in JB6 cells; (2) exposure of cells to UVB caused a significant increase of miR-21, the upstream regulator of PDCD4, expression; (3) both inhibition of ERKs with U0126 and inhibition of p38 with SB203580 significantly reversed UVB-induced PDCD4 inhibition; (4) ROS scavenger, N-acetyl-l-cysteine reversed the inhibitory effect of UVB on PDCD4 expression. The above results suggested that UVB induced PDCD4 inhibition, which may be mediated through ROS, especially endogenous H2O2 and p38 and ERKs phosphorylation. Unraveling the complex mechanisms associated with these events may provide insights into the initiation and progression of UVB-induced carcinogenesis.

Apoptosis induced by tungsten carbide-cobalt nanoparticles in JB6 cells involves ROS generation through both extrinsic and intrinsic apoptosis pathways

In this study, apoptosis and related signaling induced by WC-Co nanoparticles were investigated in JB6 cells and rat lung macrophages. Electron spin resonance (ESR) and fluorescent staining indicated that both WC-Co nanoparticles and fine particles stimulated reactive oxygen species (ROS) generation. Catalase exhibited an inhibitory effect on WC-Co nanoparticle-induced ROS as well as mitochondrial membrane permeability damage. Further study indicated that WC-Co nanoparticles elicited higher cytotoxicity and apoptotic induction than fine particles. Western blot analysis showed activation of proapoptotic factors including Fas, Fas-associated protein with death domain (FADD), caspase 3, 8 and 9, BID and BAX. In addition, both cytochrome c and apoptosis-inducing factor (AIF) were upregulated and released from mitochondria to the cytoplasm. Our findings demonstrate that, on a mass basis, WC-Co nanoparticles exhibit higher cytotoxicity and apoptotic induction than fine particles. Apoptosis induced by WC-Co nanoparticles and fine particles involves both extrinsic and intrinsic apoptosis pathways.

Genotoxicity and carcinogenicity of cobalt-, nickel- and copper-based nanoparticles

The nanotechnology industry has matured and expanded at a rapid pace in the last decade, leading to the research and development of nanomaterials with enormous potential. The largest source of these nanomaterials is the transitional metals. It has been revealed that numerous properties of these nano-sized elements are not present in their bulk states. The nano size of these particles means they are easily transported into biological systems, thus, raising the question of their effects on the susceptible systems. Although advances have been made and insights have been gained on the effect of transitional metals on susceptible biological systems, there still is much ground to be covered, particularly with respect to our knowledge on the genotoxic and carcinogenic effects. Therefore, this review intends to summarize the current knowledge on the genotoxic and carcinogenic potential of cobalt-, nickel- and copper-based nanoparticles indicated in in vitro and in vivo mammalian studies. In the present review, we briefly state the sources, use and exposure routes of these nanoparticles and summarize the current literature findings on their in vivo and in vitro genotoxic and carcinogenic effects. Due to the increasing evidence of their role in carcinogenicity, we have also included studies that have reported epigenetic factors, such as abnormal apoptosis, enhanced oxidative stress and pro-inflammatory effects involving these nanoparticles.

Comparative evaluation of particle properties, formation of reactive oxygen species and genotoxic potential of tungsten carbide based nanoparticles in vitro

Tungsten carbide (WC) and cobalt (Co) are constituents of hard metals and are used for the production of extremely hard tools. Previous studies have identified greater cytotoxic potential of WC-based nanoparticles if particles contained Co. The aim of this study was to investigate whether the formation of reactive oxygen species (ROS) and micronuclei would help explain the impact on cultured mammalian cells by three different tungsten-based nanoparticles (WC(S), WC(L), WC(L)-Co (S: small; L: large)). The selection of particles allowed us to study the influence of particle properties, e.g. surface area, and the presence of Co on the toxicological results. WC(S) and WC(L)/WC(L)-Co differed in their crystalline structure and surface area, whereas WC(S)/WC(L) and WC(L)-Co differed in their cobalt content. WC(L) and WC(L)-Co showed neither a genotoxic potential nor ROS induction. Contrary to that, WC(S) nanoparticles induced the formation of both ROS and micronuclei. CoCl(2) was tested in relevant concentrations and induced no ROS formation, but increased the rate of micronuclei at concentrations exceeding those present in WC(L)-Co. In conclusion, ROS and micronuclei formation could not be associated with the presence of Co in the WC-based particles. The contrasting responses elicited by WC(S) vs. WC(L) appear to be due to large differences in crystalline structure.

Walterinnesia aegyptia venom combined with silica nanoparticles enhances the functioning of normal lymphocytes through PI3K/AKT, NFκB and ERK signaling

Background

The toxicity of snake venom varies over time in some species. The venom of newborn and small juvenile snakes appears to be more potent than adults of the same species, and a bite from a snake that has not fed recently, such as one that has just emerged from hibernation, is more dangerous than one that has recently fed due to the larger volume of venom injected. Therefore, the potency of a snake's venom is typically determined using the LD₅₀ or IC₅₀ tests. In the present study, we evaluated the anti-tumor potential of snake venom from Walterinnesia aegyptia (WEV) on the human breast carcinoma cell line MDA-MB-231, as well as its effect on the normal mice peripheral blood mononuclear cells (PBMCs).

Results

This venom was used alone (WEV) or in combination with silica nanoparticles (WEV+NP). The IC₅₀ values of WEV alone and WEV+NP in the MDA-MB-231 cells were determined to be 50 ng/ml and 20 ng/ml, respectively. Interestingly, at these concentrations, the venom did not affect the viability of normal human PBMCs. To investigate the in vivo effects of this venom further, three groups of mice were used (15 mice in each group): Group I was the control, Group II was subcutaneously injected with WEV, and Group III was injected with WEV+NP. Using flow cytometry and western blot analysis, we found that the blood lymphocytes of WEV-injected mice exhibited a significant increase in actin polymerization and cytoskeletal rearrangement in response to CXCL12 through the activation of AKT, NF-κB and ERK. These lymphocytes also showed a significant increase in their proliferative capacity in response to mitogen stimulation compared with those isolated from the control mice (P < 0.05). More importantly, in the WEV+NP-treated mice, the biological functions of normal lymphocytes were significantly (P < 0.05) enhanced in comparison with those of WEV-treated mice.

Conclusion

Our data reveal the unique biological effects of WEV, and we demonstrated that its combination with nanoparticles strongly enhanced these biological effects.

Luciferase reporter system for studying the effect of nanoparticles on gene expression

Nanotechnology exploits the fact that nanoparticles exhibit unique physicochemical properties, which are distinct from larger particles of the same composition. It follows that nanoparticles may also express distinct bioactivity and unique interactions with biological systems. Therefore, it is essential to assess the potential health risks of exposure to nanoparticles to allow development and implementation of prevention measures. One of the biggest challenges facing the field of nanotoxicology is the huge variety of different nanoparticle types possessing a variety of properties. Genetic Luciferase Reporter System or Reporter gene assay has become an invaluable tool in studies of gene expression. This is achieved by linking the firefly luciferase gene to a promoter sequence. Luciferase assays are quick, highly sensitive, have wide dynamic range, and are cheap to perform. Because of their simplicity and versatility, and because of the absence of endogenous luciferase activity in most cell types, this test can be applied for testing a large variety of nanomaterials for their pathogenic or carcinogenetic effects on a wide range of mammalian cells. This system is an ideal early-stage toxicology tool for screening nanomaterials. Here we describe the Genetic Luciferase Reporter System as the method for detecting alteration of gene expression in response to external stimuli (e.g., nanoparticles).

New perspectives for in vitro risk assessment of multiwalled carbon nanotubes: application of coculture and bioinformatics

Nanotechnology is a rapidly expanding field with wide application for industrial and medical use; therefore, understanding the toxicity of engineered nanomaterials is critical for their commercialization. While short-term in vivo studies have been performed to understand the toxicity profile of various nanomaterials, there is a current effort to shift toxicological testing from in vivo observational models to predictive and high-throughput in vitro models. However, conventional monoculture results of nanoparticle exposure are often disparate and not predictive of in vivo toxic effects. A coculture system of multiple cell types allows for cross-talk between cells and better mimics the in vivo environment. This review proposes that advanced coculture models, combined with integrated analysis of genome-wide in vivo and in vitro toxicogenomic data, may lead to development of predictive multigene expression-based models to better determine toxicity profiles of nanomaterials and consequent potential human health risk due to exposure to these compounds.

Inhibitory effect of tungsten carbide nanoparticles on voltage-gated potassium currents of hippocampal CA1 neurons

The effects of tungsten carbide nanoparticles (nano-WC) on the properties of voltage-dependent potassium currents and evoked action potentials were studied in the hippocampal CA1 pyramidal neurons of rats at the ages of postnatal days 10-14 using the whole-cell patch-clamp technique. The results indicated that: (1) the amplitudes of transient outward potassium current (I(A)) and delayed rectifier potassium current (I(K)) were significantly decreased by 10(-7) g/ml nano-WC, while the current-voltage curves of I(A) and I(K) were significantly decreased by nano-WC from +10 to +90 mV. (2) Nano-WC produced a depolarizing shift in the steady-state activation curve of I(A) and I(K) with increased slope factors, and delayed the recovery of I(A) from inactivation, but no significant effects were found on the inactivation of I(A). (3) Nano-WC prolonged the evoked action potential duration and lowered the firing rate. These results suggest that 10(-7) g/ml nano-WC can decrease the amplitudes of I(A) and I(K) currents by reducing the opening number of voltage-gated potassium channels and delaying the recovery of I(A) from inactivation, which indicate that nano-WC has the potential neurotoxicity.

The innate and adaptive immune response induced by alveolar macrophages exposed to ambient particulate matter

Emerging epidemiological evidence suggests that exposure to particulate matter (PM) air pollution increases the risk of cardiovascular events but the exact mechanism by which PM has adverse effects is still unclear. Alveolar macrophages (AM) play a major role in clearing and processing inhaled PM. This comprehensive review of research findings on immunological interactions between AM and PM provides potential pathophysiological pathways that interconnect PM exposure with adverse cardiovascular effects. Coarse particles (10 μm or less, PM(10)) induce innate immune responses via endotoxin-toll-like receptor (TLR) 4 pathway while fine (2.5 μm or less, PM(2.5)) and ultrafine particles (0.1 μm or less, UFP) induce via reactive oxygen species generation by transition metals and/or polyaromatic hydrocarbons. The innate immune responses are characterized by activation of transcription factors [nuclear factor (NF)-κB and activator protein-1] and the downstream proinflammatory cytokine [interleukin (IL)-1β, IL-6, and tumor necrosis factor-α] production. In addition to the conventional opsonin-dependent phagocytosis by AM, PM can also be endocytosed by an opsonin-independent pathway via scavenger receptors. Activation of scavenger receptors negatively regulates the TLR4-NF-κB pathway. Internalized particles are subsequently subjected to adaptive immunity involving major histocompatibility complex class II (MHC II) expression, recruitment of costimulatory molecules, and the modulation of the T helper (Th) responses. AM show atypical antigen presenting cell maturation in which phagocytic activity decreases while both MHC II and costimulatory molecules remain unaltered. PM drives AM towards a Th1 profile but secondary responses in a Th1- or Th-2 up-regulated milieu drive the response in favor of a Th2 profile.

Evaluation of iron oxide nanoparticle biocompatibility

Nanotechnology is an exciting field of investigation for the development of new treatments for many human diseases. However, it is necessary to assess the biocompatibility of nanoparticles in vitro and in vivo before considering clinical applications. Our characterization of polyol-produced maghemite γ-Fe₂O₃ nanoparticles showed high structural quality. The particles showed a homogeneous spherical size around 10 nm and could form aggregates depending on the dispersion conditions. Such nanoparticles were efficiently taken up in vitro by human endothelial cells, which represent the first biological barrier to nanoparticles in vivo. However, γ-Fe₂O₃ can cause cell death within 24 hours of exposure, most likely through oxidative stress. Further in vivo exploration suggests that although γ-Fe₂O₃ nanoparticles are rapidly cleared through the urine, they can lead to toxicity in the liver, kidneys and lungs, while the brain and heart remain unaffected. In conclusion, γ-Fe₂O₃ could exhibit harmful properties and therefore surface coating, cellular targeting, and local exposure should be considered before developing clinical applications.

Nanoparticles: molecular targets and cell signalling

Increasing evidence linking nanoparticles (NPs) with different cellular outcomes necessitate an urgent need for the better understanding of cellular signalling pathways triggered by NPs. Oxidative stress has largely been reported to be implicated in NP-induced toxicity. It could activate a wide variety of cellular events such as cell cycle arrest, apoptosis, inflammation and induction of antioxidant enzymes. These responses occur after the activation of different cellular pathways. In this context, three groups of MAP kinase cascades [ERK (extracellular signal-regulated kinases), p38 mitogen-activated protein kinase and JNK (c-Jun N-terminal kinases)] as well as redox-sensitive transcription factors such as NFκB and Nrf-2 were specially investigated. The ability of NPs to interact with these signalling pathways could partially explain their cytotoxicity. The induction of apoptosis is also closely related to the modulation of signalling pathways induced by NPs. Newly emerged scientific areas of research are the studies on interactions between NPs and biological molecules in body fluids, cellular microenvironment, intracellular components or secreted cellular proteins such as cytokines, growth factors and enzymes and use of engineered NPs to target various signal transduction pathways in cancer therapy. Recently published data present the ability of NPs to interact with membrane receptors leading to a possible aggregation of these receptors. These interactions could lead to a sustained modulation of specific signalling in the target cells or paracrine and even "by-stander" effects of the neighbouring cells or tissues. However, oxidative stress is not sufficient to explain specific mechanisms which could be induced by NPs, and these new findings emphasize the need to revise the paradigm of oxidative stress to explain the effects of NPs.