Genotoxicity of nano/microparticles in in vitro micronuclei, in vivo comet and mutation assay systems

Exposure to microcrystallized cellulose affects the health of tadpoles and sheds light on the threat these materials pose to amphibians

The increasing use of cellulose-based materials (CBMs) has provided beneficial applications in different sectors. However, its release into environments may represent an ecological risk, therefore demanding that ecotoxicological studies be conducted to understand the risks (current and future) of CBM pollution. Thus, we evaluated the possible effects of microcrystalline cellulose (CMs) in Physalaemus cuvieri tadpoles. After seven days of exposure to CMs (at 58.29 and 100 mg/L), the animals were subjected to behavioral evaluation, and different biomarkers (biometric and biochemical) were evaluated. Although our data do not point to a neurotoxic effect of CMs (inferred by the absence of behavioral changes and changes in AChE and BChE activity), animals exposed to CMs showed differences in body condition. Furthermore, we noticed an increase in the frequency of erythrocyte nuclear abnormalities and DNA damage, which were correlated with the ingestion of CMs. We noticed that the antioxidant activity of tadpoles exposed to CMs (inferred by SOD, CAT, and DPPH radical scavenging activity) was insufficient to control the increase in ROS and MDA production. Furthermore, exposure to CMs induced a predominant Th2-specific immune response, marked by suppressed IFN-γ and increased IL-10 levels, with a consequent reduction in NO levels. Principal component analysis and IBRv-2 indicate, in general, a primarily more toxic response to animals exposed to the highest CM concentration. Therefore, our study evidence that CMs affect the health of P. cuvieri tadpoles and sheds light on the threat these materials pose to amphibians.

An In Vitro Model to Assess Early Immune Markers Following Co-Exposure of Epithelial Cells to Carbon Black (Nano)Particles in the Presence of S. aureus: A Role for Stressed Cells in Toxicological Testing

The exposure of human lung and skin to carbon black (CB) is continuous due to its widespread applications. Current toxicological testing uses 'healthy' cellular systems; however, questions remain whether this mimics the everyday stresses that human cells are exposed to, including infection. Staphylococcus aureus lung and skin infections remain prevalent in society, and include pneumonia and atopic dermatitis, respectively, but current in vitro toxicological testing does not consider infection stress. Therefore, investigating the effects of CB co-exposure in 'stressed' infected epithelial cells in vitro may better approximate true toxicity. This work aims to study the impact of CB exposure during Staphylococcus aureus infection stress in A549 (lung) and HaCaT (skin) epithelial cells. Physicochemical characterisation of CB confirmed its dramatic polydispersity and potential to aggregate. CB significantly inhibited S. aureus growth in cell culture media. CB did not induce cytokines or antimicrobial peptides from lung and skin epithelial cells, when given alone, but did reduce HaCaT and A549 cell viability to 55% and 77%, respectively. In contrast, S. aureus induced a robust interleukin (IL)-8 response in both lung and skin epithelial cells. IL-6 and human beta defensin (hβD)-2 could only be detected when cells were stimulated with S. aureus with no decreases in cell viability. However, co-exposure to CB (100 µg/mL) and S. aureus resulted in significant inhibition of IL-8 (compared to S. aureus alone) without further reduction in cell viability. Furthermore, the same co-exposure induced significantly more hβD-2 (compared to S. aureus alone). This work confirms that toxicological testing in healthy versus stressed cells gives significantly different responses. This has significant implications for toxicological testing and suggests that cell stresses (including infection) should be included in current models to better represent the diversity of cell viabilities found in lung and skin within a general population. This model will have significant application when estimating CB exposure in at-risk groups, such as factory workers, the elderly, and the immunocompromised.

Recent Advances in Kaolinite Nanoclay as Drug Carrier for Bioapplications: A Review

Advanced functional two-dimensional (2D) nanomaterials offer unique advantages in drug delivery systems for disease treatment. Kaolinite (Kaol), a nanoclay mineral, is a natural 2D nanomaterial because of its layered silicate structure with nanoscale layer spacing. Recently, Kaol nanoclay is used as a carrier for controlled drug release and improved drug dissolution owing to its advantageous properties such as surface charge, strong biocompatibility, and naturally layered structure, making it an essential development direction for nanoclay-based drug carriers. This review outlines the main physicochemical characteristics of Kaol and the modification methods used for its application in biomedicine. The safety and biocompatibility of Kaol are addressed, and details of the application of Kaol as a drug delivery nanomaterial in antibacterial, anti-inflammatory, and anticancer treatment are discussed. Furthermore, the challenges and prospects of Kaol-based drug delivery nanomaterials in biomedicine are discussed. This review recommends directions for the further development of Kaol nanocarriers by improving their physicochemical properties and expanding the bioapplication range of Kaol.

In vivo genotoxicity assessment of a multiwalled carbon nanotube in a mouse ex vivo culture

Background

Multiwalled carbon nanotubes (MWCNTs) are suspected lung carcinogens because their shape and size are similar to asbestos. Various MWCNT types are manufactured; however, only MWNT-7 is classified into Group 2B by The International Agency for Research on Cancer. MWNT-7’s carcinogenicity is strongly related to inflammatory reactions. On the other hand, inconsistent results on MWNT-7 genotoxicity have been reported. We previously observed no significant differences in both Pig-a (blood) and gpt (lung) mutant frequencies between MWNT-7-intratracheally treated and negative control rats. In this study, to investigate in vivo MWNT-7 genotoxicity on various endpoints, we attempted to develop a lung micronucleus assay through ex vivo culture targeting the cellular fraction of Clara cells and alveolar Type II (AT-II) cells, known as the initiating cells of lung cancer. Using this system, we analyzed the in vivo MWNT-7 genotoxicity induced by both whole-body inhalation exposure and intratracheal instillation. We also conducted an erythrocyte micronucleus assay using the samples obtained from animals under intratracheal instillation to investigate the tissue specificity of MWNT-7 induced genotoxicities.

Results

 We detected a significant increase in the incidence of micronucleated cells derived from the cellular fraction of Clara cells and AT-II cells in both MWNT-7-treated and positive control groups compared to the negative control group under both whole-body inhalation exposures and intratracheal instillation. Additionally, the erythrocyte micronucleus assay detected a significant increase in the incidence of micronucleated reticulocytes only in the positive control group.

Conclusions

Our findings indicated that MWNT-7 was genotoxic in the lungs directly exposed by both the body inhalation and intratracheal instillation but not in the hematopoietic tissue.

Systematic review on primary and secondary genotoxicity of carbon black nanoparticles in mammalian cells and animals

Carbon black exposure causes oxidative stress, inflammation and genotoxicity. The objective of this systematic review was to assess the contributions of primary (i.e. direct formation of DNA damage) and secondary genotoxicity (i.e., DNA lesions produced indirectly by inflammation) to the overall level of DNA damage by carbon black. The database is dominated by studies that have measured DNA damage by the comet assay. Cell culture studies indicate a genotoxic action of carbon black, which might be mediated by oxidative stress. Many in vivo studies originate from one laboratory that has investigated the genotoxic effects of Printex 90 in mice by intra-tracheal instillation. Meta-analysis and pooled analysis of these results demonstrate that Printex 90 exposure is associated with a slightly increased level of DNA strand breaks in bronchoalveolar lavage cells and lung tissue. Other types of genotoxic damage have not been investigated as thoroughly as DNA strand breaks, although there is evidence to suggest that carbon black exposure might increase the mutation frequency and cytogenetic endpoints. Stratification of studies according to concurrent inflammation and DNA damage does not indicate that carbon black exposure gives rise to secondary genotoxicity. Even substantial pulmonary inflammation is at best only associated with a weak genotoxic response in lung tissue. In conclusion, the review indicates that nanosized carbon black is a weak genotoxic agent and this effect is more likely to originate from a primary genotoxic mechanism of action, mediated by e.g., oxidative stress, than inflammation-driven (secondary) genotoxicity.

In Vitro Genotoxicity Evaluation of an Antiseptic Formulation Containing Kaolin and Silver Nanoparticles

Worldwide antimicrobial resistance is partly caused by the overuse of antibiotics as growth promoters. Based on the known bactericidal effect of silver, a new material containing silver in a clay base was developed to be used as feed additive. An in vitro genotoxicity evaluation of this silver-kaolin clay formulation was conducted, which included the mouse lymphoma assay in L5178Y TK+/− cells and the micronucleus test in TK6 cells, following the principles of the OECD guidelines 490 and 487, respectively. As a complement, the standard and Fpg-modified comet assays for the evaluation of strand breaks, alkali labile sites and oxidative DNA damage were also performed in TK6 cells. The formulation was tested without metabolic activation after an exposure of 3 h and 24 h; its corresponding release in medium, after the continuous agitation of the silver-kaolin for 24 h was also evaluated. Under the conditions tested, the test compound did not produce gene mutations, chromosomal aberrations or DNA damage (i.e., strand breaks, alkali labile sites or oxidized bases). Considering the results obtained in the present study, the formulation seems to be a promising material to be used as antimicrobial in animal feed.

Exposure to carbon black nanoparticles during pregnancy aggravates lipopolysaccharide-induced lung injury in offspring: an intergenerational effect

Carbon black nanoparticles (CBNPs) are one of the most frequently used nanoparticles. Exposure to CBNPs during pregnancy (PrE to CBNPs) can directly induce inflammation, lung injury, and genotoxicity in dams and results in abnormalities in offspring. However, whether exposure to CBNPs during pregnancy enhances the susceptibility of offspring to environmental stimuli remains unknown. To address this issue, in this study, we intranasally treated pregnant mice with mock or CBNPs from gestational day (GD) 9 to GD18, and F1 and F2 offspring were normally obtained. By intratracheal instillation of mice with lipopolysaccharide (LPS) to trigger a classic animal model for acute lung injury, we intriguingly found that after LPS treatment, F1 and F2 offspring after exposure during pregnancy to CBNPs both exhibited more pronounced lung injury symptoms, including more degenerative histopathological changes, vascular leakage, elevated MPO activity, and activation of inflammation-related signaling transduction, compared with F1 and F2 offspring in the mock group, suggesting PrE to CBNPs would aggravate LPS-induced lung injury in offspring, and this effect was intergenerational. We also observed that PrE to CBNPs upregulated the mRNA expression of DNA methyltransferases (Dnmt) 1/3a/3b and DNA hypermethylation in both F1 and F2 offspring, which might partially account for the intergenerational effect. Together, our study demonstrates for the first time that PrE to CBNPs can enhance sensitivity to LPS in both F1 and F2 offspring, and this intergenerational effect may be related to DNA hypermethylation caused by CBNPs.

Toxicity, mutagenicity and trace metal constituent of Termitomyces schimperi (Pat.) R. Heim (Lyophyllaceae) and kaolin, a recipe used traditionally in cancer management in Cote d'Ivoire

ETHNOPHARMACOLOGICAL RELEVANCE

Some local communities in Cote d'Ivoire use the mushroom Termitomyces schimperi combined with kaolin (TSK) to manage various cancers in patients. However, there is a paucity of data on toxicity, mutagenicity and trace metal constituent of TSK.

AIM OF THE STUDY

We sought to investigate the acute and sub-chronic toxicities, mutagenic potential, and trace metal constituents of TSK.

MATERIALS AND METHODS

To assess acute toxicity, single doses (1000, 3000 and 5000 mg/kg) of aqueous extract of TSK were administrated per os to Sprague Dawley (SD) rats on Day 1. The rats were then monitored for 13 consecutive days. Sub-chronic toxicity was evaluated by daily administration of 200 and 500 mg/kg of the extract per os for 90 consecutive days. SD rats used as control received distilled water. Signs of toxicity, changes in body weight and mortality were monitored. After the aforementioned monitoring processes, rats were sacrificed and blood collected for full blood count and biochemistry analysis. Animal organs were also collected for histopathological examination. The mutagenic potential of the aqueous extract of TSK (10000 μg/mL) on TA98 Salmonella typhimurium was estimated. Additionally, energy-dispersive X-ray fluorescence (ED-XRF) method was employed to determine trace metal constituents of TSK.

RESULTS

Single-dose administration of 5000 mg/kg of TSK did not cause any death in the SD rats; thus, LD50 was above 5000 mg/kg. Administration of 1000 and 3000 mg/kg of the aqueous extract of TSK did not cause any significant change in behaviour and body weight of SD rats during the 14-day monitoring period. However, the mean corpuscular volume and the mean corpuscular haemoglobin concentration increased significantly (p < 0.01) among rats administered 1000 and 3000 mg/kg of TSK. There was a significant increase (p < 0.0001) in alanine transaminase levels in rats administered 1000 and 3000 mg/kg of TSK extract compared with control. Conversely, there was a significant decrease (p=0.0122) in serum creatine level among rats administered 1000 and 3000 mg/kg of TSK extract compared with control. After 14 days, there were minimal changes with isolated organs of TSK-treated and control rats. Furthermore, 90-day treatment with extract of TSK caused no significant change in parameters assessed. TSK induced frameshift gene mutation in S. typhimurium before (p < 0.05) and after metabolic activation (p < 0.001). Elemental analysis of TSK revealed the presence of toxic (aluminium) or potentially toxic (silver, rabidium, titanium and zirconium) elements.

CONCLUSIONS

The aqueous extract of TSK showed no toxicity (acute and sub-chronic) at doses tested. These findings are consistent with the absence of heavy metals (i.e., cadmium) and potentially toxic elements (i.e., uranium) in TSK samples analysed. TSK showed some level of mutagenic potential. Further mutagenic and chronic toxicity studies on TSK are required.

A critical review on genotoxicity potential of low dimensional nanomaterials

Low dimensional nanomaterials (LDNMs) have earned attention among researchers as they exhibit a larger surface area to volume and quantum confinement effect compared to high dimensional nanomaterials. LDNMs, including 0-D and 1-D, possess several beneficial biomedical properties such as bioimaging, sensor, cosmetic, drug delivery, and cancer tumors ablation. However, they threaten human beings with the adverse effects of cytotoxicity, carcinogenicity, and genotoxicity when exposed for a prolonged time in industry or laboratory. Among different toxicities, genotoxicity must be taken into consideration with utmost importance as they inherit DNA related disorders causing congenital disabilities and malignancy to human beings. Many researchers have performed NMs' genotoxicity using various cell lines and animal models and reported the effect on various physicochemical and biological factors. In the present work, we have compiled a comparative study on the genotoxicity of the same or different kinds of NMs. Notwithstanding, we have included the classification of genotoxicity, mechanism, assessment, and affecting factors. Further, we have highlighted the importance of studying the genotoxicity of LDNMs and signified the perceptions, future challenges, and possible directives in the field.

Kaolinite group minerals: Applications in cancer diagnosis and treatment

The clay minerals are characterized as important minerals due to their specific properties. One of the most important groups of the clay minerals is the kaolinite's group minerals due to their morphology, availability and range of potential applications. Halloysite and kaolinite are investigated here for their pharmaceutical applications and especially for their potential in cancer treatment. This review study is focusing on the potential applications of the kaolinite's group minerals in cancer diagnosis and monitoring, cancer treatment, the avoidance of metastasis, and the relief of cancer pains. Anticancer drug-loaded formulations based on these minerals show high potential for the treatment of various types of cancer as they have been shown to exhibit high anticancer activity in cancer cell lines and cancer animal models, high biocompatibility, low side effects, and high drug bioavailability.

The Puzzling Potential of Carbon Nanomaterials: General Properties, Application, and Toxicity

Being a member of the nanofamily, carbon nanomaterials exhibit specific properties that mostly arise from their small size. They have proved to be very promising for application in the technical and biomedical field. A wide spectrum of use implies the inevitable presence of carbon nanomaterials in the environment, thus potentially endangering their whole nature. Although scientists worldwide have conducted research investigating the impact of these materials, it is evident that there are still significant gaps concerning the knowledge of their mechanisms, as well as the prolonged and chronic exposure and effects. This manuscript summarizes the most prominent representatives of carbon nanomaterial groups, giving a brief review of their general physico-chemical properties, the most common use, and toxicity profiles. Toxicity was presented through genotoxicity and the activation of the cell signaling pathways, both including in vitro and in vivo models, mechanisms, and the consequential outcomes. Moreover, the acute toxicity of fullerenol, as one of the most commonly investigated members, was briefly presented in the final part of this review. Thinking small can greatly help us improve our lives, but also obliges us to deeply and comprehensively investigate all the possible consequences that could arise from our pure-hearted scientific ambitions and work.

Genotoxicity of micro- and nano-particles of kaolin in human primary dermal keratinocytes and fibroblasts

INTRODUCTION

Kaolin is a clay mineral with the chemical composition Al2Si2O5(OH)4. It is an important industrial material, and is also used as a white cosmetic pigment. We previously reported that fine particles of kaolin have genotoxic potency to Chinese hamster ovary CHO AA8 cells, and to the lungs of C57BL/6 J and ICR mice. In the present study, we evaluated the genotoxicity of different particle sizes of kaolin using primary normal human diploid epidermal keratinocytes and primary normal human diploid dermal fibroblasts, in addition to a CHO AA8 cell line.

FINDINGS

After 6-h treatment with kaolin micro- and nano-particles of particle sizes 4.8 μm and 0.2 μm (200 nm), respectively, the frequencies of micronucleated cells increased in a dose-dependent manner. The frequency increased 3- to 4-fold by exposure to the particles at 200 μg/mL (i.e., 31.4 μg/cm2) in all cells tested. Two-way ANOVA revealed a significant main effect of particle size, and the nano-particles tended to have a higher potency of micronucleus (MN) induction. However, the cell type did not significantly affect the MN frequencies. In addition, one-hour treatment with the kaolin particles increased DNA damage in a dose-dependent manner in a comet assay. The %tail DNA was increased 8- to 20-fold by exposure to the particles at 200 μg/mL, for all cells tested. The kaolin nano-particles had higher DNA-damaging potency than the micro-particles. Furthermore, treatment with kaolin particles dose-dependently increased the production of reactive oxygen species (ROS) in all cells. Again, we observed that kaolin nano-particles induced more ROS than the micro-particles in all cells.

CONCLUSION

Kaolin particles demonstrated genotoxicity in primary normal human diploid epidermal keratinocytes and fibroblasts as well as in CHO AA8 cells. Although no significant difference was observed among these three types of cells, fine particles of kaolin tended to have higher genotoxic potency than coarse particles. Since studies on its genotoxicity to skin have been scarce, the findings of the present study could contribute to safety evaluations of kaolin particles when used as a white cosmetic pigment.

Cytogenotoxic effects of fullerene C60 in the freshwater teleostean fish, Anabas testudineus (Bloch, 1792)

In recent years, carbon nanomaterials, including fullerene C₆₀ is regarded as the building block in nanotechnology because of its widespread use in medicine, industry, cosmetics and commercial products. Despite the special properties, several reports have raised public health concerns due to the unknown and practically unexplored toxic effects of nanomaterials. However, there have been relatively few studies regarding the genotoxic responses of fullerene C₆₀in vivo. Genotoxic effects of DMSO-solublized C₆₀ nanomaterial suspension at sublethal concentrations (5 and 10 mg/L) were investigated on adult freshwater fish, Anabas testudineus using micronucleus and comet assays. An assessment of micronucleus induction showed severe cytoplasmic and nuclear abnormalities in erythrocytes, gill and liver cells. Abnormalities in cytoplasm were identified as formation of sticky cells, vacuolated cytoplasm, cytoplasmic degeneration, echinocyte, acanthocyte, anisochromatic cells and abnormal erythrocyte membrane. The nuclear abnormalities included micronucleus, binucleated cells, nuclear buds, irregular nucleus, vacuolated, notched and serrated nucleus in the erythrocytes compared to the control groups. Similarly, significant increase (P < 0.05) in micronucleus frequencies were observed in gill and liver cells. The high frequency of micronucleus was observed in the gill cells followed by liver and erythrocytes, respectively, at both sublethal concentrations, and the severity was duration and concentration-dependent. In comet assay, significant increase (P < 0.05) in DNA damage was observed using the comet parameter, percent tail DNA. The highest level of comet damage with grade 3 was observed in blood, gill and liver cells on increase in duration and concentration when compared to the respective control groups. Thus the results revealed that fullerene C₆₀ nanomaterials may pose risk to aquatic organisms, especially fish, by the induction of genotoxicity. Further studies are warranted to provide new insights on the mechanisms and consequences of C₆₀ nanomaterials interactions with biological membranes.

Toxicity of Zero- and One-Dimensional Carbon Nanomaterials

The zero (0-D) and one-dimensional (1-D) carbon nanomaterials have gained attention among researchers because they exhibit a larger surface area to volume ratio, and a smaller size. Furthermore, carbon is ubiquitously present in all living organisms. However, toxicity is a major concern while utilizing carbon nanomaterials for biomedical applications such as drug delivery, biosensing, and tissue regeneration. In the present review, we have summarized some of the recent findings of cellular and animal level toxicity studies of 0-D (carbon quantum dot, graphene quantum dot, nanodiamond, and carbon black) and 1-D (single-walled and multi-walled carbon nanotubes) carbon nanomaterials. The in vitro toxicity of carbon nanomaterials was exemplified in normal and cancer cell lines including fibroblasts, osteoblasts, macrophages, epithelial and endothelial cells of different sources. Similarly, the in vivo studies were illustrated in several animal species such as rats, mice, zebrafish, planktons and, guinea pigs, at various concentrations, route of administrations and exposure of nanoparticles. In addition, we have described the unique properties and commercial usage, as well as the similarities and differences among the nanoparticles. The aim of the current review is not only to signify the importance of studying the toxicity of 0-D and 1-D carbon nanomaterials, but also to emphasize the perspectives, future challenges and possible directions in the field.

Genotoxicity Assessment of Nanomaterials: Recommendations on Best Practices, Assays, and Methods

Nanomaterials (NMs) present unique challenges in safety evaluation. An international working group, the Genetic Toxicology Technical Committee of the International Life Sciences Institute's Health and Environmental Sciences Institute, has addressed issues related to the genotoxicity assessment of NMs. A critical review of published data has been followed by recommendations on methods alterations and best practices for the standard genotoxicity assays: bacterial reverse mutation (Ames); in vitro mammalian assays for mutations, chromosomal aberrations, micronucleus induction, or DNA strand breaks (comet); and in vivo assays for genetic damage (micronucleus, comet and transgenic mutation assays). The analysis found a great diversity of tests and systems used for in vitro assays; many did not meet criteria for a valid test, and/or did not use validated cells and methods in the Organization for Economic Co-operation and Development Test Guidelines, and so these results could not be interpreted. In vivo assays were less common but better performed. It was not possible to develop conclusions on test system agreement, NM activity, or mechanism of action. However, the limited responses observed for most NMs were consistent with indirect genotoxic effects, rather than direct interaction of NMs with DNA. We propose a revised genotoxicity test battery for NMs that includes in vitro mammalian cell mutagenicity and clastogenicity assessments; in vivo assessments would be added only if warranted by information on specific organ exposure or sequestration of NMs. The bacterial assays are generally uninformative for NMs due to limited particle uptake and possible lack of mechanistic relevance, and are thus omitted in our recommended test battery for NM assessment. Recommendations include NM characterization in the test medium, verification of uptake into target cells, and limited assay-specific methods alterations to avoid interference with uptake or endpoint analysis. These recommendations are summarized in a Roadmap guideline for testing.

Cellular pathways affected by carbon nanopowder-benzo(α)pyrene complex in human skin fibroblasts identified by proteomics

One of the crucial and unsolved problems of the airborne carbon nanoparticles is the role played by the adsorbed environmental pollutants on their toxicological effect. Indeed, in the urban areas, the carbon nanoparticles usually adsorb some atmospheric contaminants, whose one of the leading representatives is the benzo(α)pyrene. Herein, we used the proteomics to investigate the alteration of toxicological pathways due to the carbon nanopowder-benzo(α)pyrene complex in comparison with the two contaminants administered alone on human skin-derived fibroblasts (hSDFs) exposed for 8 days in semi-static conditions. The preliminary confocal microscopy observations highlighted that carbon-nanopowder was able to pass through the cell membranes and accumulate into the cytoplasm both when administered alone and with the adsorbed benzo(α)pyrene. Proteomics revealed that the effect of carbon nanopowder-benzo(α)pyrene complex seems to be related to a new toxicological behavior instead of simple additive or synergistic effects. In detail, the cellular pathways modulated by the complex were mainly related to energy shift (glycolysis and pentose phosphate pathway), apoptosis, stress response and cellular trafficking.

Impacts of fullerene C60 and virgin olive oil on cadmium-induced genotoxicity in rats

Currently, cadmium is considered to be one of the major environmental pollutants. Environmentally, cadmium is released in various forms e.g. oxide, chloride and sulphide. The aim of the present study was to examine the genotoxic impact of fullerene nanoparticles C₆₀ (C₆₀) and virgin olive oil (VOO) on cadmium chloride (CdCl₂)-induced genotoxicity in rats. To evaluate these effects on DNA damage and chromosomal frequency, 25 albino rats were randomly assigned to 5 groups (n=5 per group): Group 1 served as a control; Group 2 received a single intraperitoneal dose of CdCl₂ (3.5mg/kg); Group 3 animals were treated with C₆₀ (4mg/kg, orally) every other day for 20days; Group 4 received a single intraperitoneal dose of CdCl₂ (3.5mg/kg) and an oral dose of C₆₀ (4mg/kg); and Group 5 received a single intraperitoneal dose of CdCl₂ (3.5mg/kg) and oral doses of VOO every other day for 20 consecutive days. Genotoxic and anti-genotoxic effects of C₆₀ and VOO were evaluated in the liver, kidney and bone marrow using molecular and cytogenetic assays. As expected, CdCl₂ and C₆₀ administration was associated with band number alterations in both liver and kidney; however, C₆₀ pretreatment recovered to approximately basal number. Surprisingly, C₆₀ and VOO significantly attenuated the genotoxic effects caused by CdCl₂ in livers and kidneys. In bone marrow, in addition to a reduction in the chromosomal number, several chromosomal aberrations were caused by CdCl₂. These chromosomal alterations were also reversed by C₆₀ and VOO. In conclusion, molecular and cytogenetic studies showed that C₆₀ and VOO exhibit anti-genotoxic agents against CdCl₂-induced genotoxicity in rats. Further studies are needed to investigate the optimal conditions for potential biomedical applications of these anti-genotoxic agents.

Establishment of an in vivo simulating co-culture assay platform for genotoxicity of multi-walled carbon nanotubes

Engineered nanomaterials (ENM) are now used in a wide variety of fields, and, thus, their safety should urgently be assessed and secured. It has been suggested that inflammatory responses via the phagocytosis of ENM by macrophages is a key mechanism for their genotoxicity. The present study was conducted to establish a mechanism‐based assay to evaluate the genotoxicity of ENM under conditions simulating an in vivo situation, featuring a co‐culture system of murine lung resident cells (GDL1) and immune cells (RAW264.7). GDL1 were cultured with or without RAW264.7, exposed to a multi‐walled carbon nanotube (MWCNT), and then analyzed for mutagenicity and underlying mechanisms. Mutation frequencies induced in GDL1 by the MWCNT were significantly greater with the co‐existence of RAW264.7 than in its absence. Mutation spectra observed in GDL1 co‐cultured with RAW264.7 were different from those seen in GDL1 cultured alone, but similar to those observed in the lungs of mice exposed to the MWCNT in vivo. Inflammatory cytokines, such as IL‐1β and TNF‐α, were produced from RAW264.7 cells treated with the MWCNT. The generation of reactive oxygen species and the formation of 8‐oxodeoxyguanosine in GDL1 exposed to the MWCNT were greater in the co‐culture conditions than in the single culture conditions. Based on these findings, it is indicated that inflammatory responses are involved in the genotoxicity of MWCNT, and that the presently established, novel in vitro assay featuring a co‐culture system of tissue resident cells with immune cells is suitable to evaluate the genotoxicity of ENM.

Cobalt nanoparticles induce lung injury, DNA damage and mutations in mice

BACKGROUND

We and other groups have demonstrated that exposure to cobalt nanoparticles (Nano-Co) caused oxidative stress and inflammation, which have been shown to be strongly associated with genotoxic and carcinogenic effects. However, few studies have reported Nano-Co-induced genotoxic effects in vivo. Here, we propose that Nano-Co may have high genotoxic effects due to their small size and high surface area, which have high capacity for causing oxidative stress and inflammation.

METHODS

gpt delta transgenic mice were used as our in vivo study model. They were intratracheally instilled with 50 μg per mouse of Nano-Co. At day 1, 3, 7 and 28 after exposure, bronchoalveolar lavage (BAL) was performed and the number of neutrophils, CXCL1/KC level, LDH activity and concentration of total protein in the BAL fluid (BALF) were determined. Mouse lung tissues were collected for H&E staining, and Ki-67, PCNA and γ-H2AX immunohistochemical staining. 8-OHdG level in the genomic DNA of mouse lungs was determined by an OxiSelect™ Oxidative DNA Damage ELISA Kit, and mutant frequency and mutation spectrum in the gpt gene were also determined in mouse lungs at four months after Nano-Co exposure by 6-TG selection, colony PCR, and DNA sequencing.

RESULTS

Exposure of mice to Nano-Co (50 μg per mouse) resulted in extensive acute lung inflammation and lung injury which were reflected by increased number of neutrophils, CXCL1/KC level, LDH activity and concentration of total protein in the BALF, and infiltration of large amount of neutrophils and macrophages in the alveolar space and interstitial tissues. Increased immunostaining of cell proliferation markers, Ki-67 and PCNA, and the DNA damage marker, γ-H2AX, was also observed in bronchiolar epithelial cells and hyperplastic type II pneumocytes in mouse lungs at day 7 after Nano-Co exposure. At four months after exposure, extensive interstitial fibrosis and proliferation of interstitial cells with inflammatory cells infiltrating the alveolar septa were observed. Moreover, Nano-Co caused increased level of 8-OHdG in genomic DNA of mouse lung tissues. Nano-Co also induced a much higher mutant frequency as compared to controls, and the most common mutation was G:C to T:A transversion, which may be explained by Nano-Co-induced increased formation of 8-OHdG.

CONCLUSION

Our study demonstrated that exposure to Nano-Co caused oxidative stress, lung inflammation and injury, and cell proliferation, which further resulted in DNA damage and DNA mutation. These findings have important implications for understanding the potential health effects of nanoparticle exposure.

Influence of Nanotoxicity on Human Health and Environment: The Alternative Strategies

Currently, nanotechnology revolutionizing both scientific and industrial community due to their applications in the fields of medicine, environmental protection, energy, and space exploration. Despite of the evident benefits of nanoparticles, there are still open questions about the influence of these nanoparticles on human health and environment. This is one of the critical issues that have to be addressed in the near future, before massive production of nanomaterials. Manufactured nanoparticles, which are finding ever-increasing applications in industry and consumer products fall into the category of emerging contaminants with ecological and toxicological effects on populations, communities and ecosystems. The existing experimental knowledge gave evidence that inhaled nanoparticles are less efficiently separated than larger particles by the macrophage clearance mechanisms and these nanoparticles are known to translocate through the lymphatic, circulatory and nervous systems to many tissues and organs, including the brain. In this review we highlight adverse impacts of nanoparticles on human and the environment with special emphasis on green nanoscience as a sustainable alternative.

Effect of physicochemical character differences on the genotoxic potency of kaolin

BACKGROUND

Kaolin is white clay mineral with the chemical composition Al2Si2O5(OH)4, and many varieties of kaolins having different crystal structures are utilized in industrial, cosmetic and medical fields. To evaluate the effect of physicochemical character differences on the genotoxicity of kaolin, two types of kaolin, kaolin-S with smooth, sphere-shaped crystals, and kaolin-P with clusters of thin pseudohexagonal plates, were used in the study.

RESULTS

ICR mice were intratracheally instilled with the kaolins (0.05 and 0.2 mg/mouse), and comet assay was performed on their lungs. Both kaolins showed DNA damage in the lungs of the mice, however the DNA damaging potency was much higher with kaolin-P than that with kaolin-S. In order to clarify the mechanisms for the different genotoxic potency, we examined the incorporation rate and ROS generation of these two types of kaolin in alveolar epithelial A549 and macrophage-like RAW264 cells, using flow cytometric (FCM) analysis. Kaolin-P showed a higher incorporation rate into the mammalian cells and ROS generation than that of kaolin-S. Especially, RAW264 cells aggressively incorporated kaolins, and generated ROS, whereas almost no ROS generation was observed in A549 cells. In addition, inflammatory cytokines were quantified, using the ELISA method, to understand further genotoxic potency differences of kaolins. Concentrations of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the media were increased by exposure to both kaolins, but in the case of kaolin-P, these inflammatory cytokines were significantly elevated. Based on these findings, differences of genotoxic potency may contribute to incorporation rates into immune cells. Furthermore, it is likely that immune cells and epithelial cells might closely interact with each other for the appearance of genotoxocity in vivo. In order to clarify the interaction between epithelial and immune cells, A549 and RAW264 were co-cultured and RAW264 cells only were exposed to kaolins, then subsequently A549 was applied to FCM analysis and comet assay. DNA damage observed in the A549 cells markedly increased in the presence of kaolin-exposed RAW264 cells compared to the single culture.

CONCLUSION

From these observations, it is suggested that mechanisms of kaolin genotoxicity against epithelial cells are through the activation of macrophage cells. Therefore, it is thought that interactions between epithelial and immune cells would be very important for evaluation of the genotoxicity of fine particulate matter. We also showed here that co-culture models of epithelial and immune cells could be used as suitable models for evaluation of lung genotoxicity of fine particulate matter, including nanomaterials, as in vivo mimicking systems.

Occupational exposure to photocopiers and their toners cause genotoxicity

Photocopier machines are inevitable office equipment, but they are also sources of air pollution. Millions of people across the world are involved in the operation and maintenance of photocopiers. We aimed to evaluate the potential genotoxic effects of exposure to photocopiers in photocopier operators and maintenance personnel by Comet assay. This study involved 50 photocopier operators, 61 maintenance personnel and 52 controls. Both the photocopier exposed groups exhibited significantly increased DNA damage when compared to controls. Cumulative exposure to photocopiers was the most significant contributor for genotoxicity ( p < 0.001). Genotoxicity among photocopier maintenance personnel may be due to the presence of carbon black, iron, silicon, magnetite and the high levels of other elements in the photocopier toners. Genotoxicity among photocopier operators might be due to exposure to high levels of particulate matter and volatile organic compounds emitted by photocopiers during operation. Research is essential to improve toner manufacturing processes and chemical composition of toners to reduce genotoxicity. Clean technologies are the need of the day to cut down on particulate matter and volatile organic compound emissions from photocopiers.

Absence of in vivo mutagenicity of multi-walled carbon nanotubes in single intratracheal instillation study using F344 gpt delta rats

Introduction

It is known that fibrous particles of micrometer length, such as carbon nanotubes, which have same dimensions as asbestos, are carcinogenic. Carcinogenicity of nanomaterials is strongly related to inflammatory reactions; however, the genotoxicity mechanism(s) is unclear. Indeed, inconsistent results on genotoxicity of multi-walled carbon nanotubes (MWCNTs) have been shown in several reports. Therefore, we analyzed the in vivo genotoxicity induced by an intratracheal instillation of straight MWCNTs in rats using a different test system—the Pig-a gene mutation assay—that can reflect the genotoxicity occurring in the bone marrow. Since lungs were directly exposed to MWCNTs upon intratracheal instillation, we also performed the gpt assay using the lungs.

Findings

We detected no significant differences in Pig-a mutant frequencies (MFs) between the MWCNT-treated and control rats. Additionally, we detected no significant differences in gpt MFs in the lung between the MWCNT-treated and control rats.

Conclusions

Our findings indicated that a single intratracheal instillation of MWCNTs was non-mutagenic to both the bone marrow and lung of rats.

[Study on the Relationship between the Inhalable Fine Particulate Matter of Xuanwei Coal Combustion and Lung Cancer]

背景与目的

云南省宣威地区是中国乃至世界肺癌的高发区，肺癌已成为制约当地社会经济发展和影响社会民生的重要因素。煤炭是当地主要的生活燃料，燃煤是当地室内污染的主要来源。本研究探讨云南宣威不同肺癌发病率地区烟煤燃烧过程中可吸入细颗粒物(fine particulate matter, PM2.5)产出情况，以及不同地区PM2.5成分异同。探讨吸入细颗粒物与当地肺癌高发的关系。

方法

收集宣威市来宾镇老林煤矿C1煤层、宝山镇虎场煤矿K7煤层、文兴镇太平煤矿M30煤层的煤矿进行燃烧试验。收集室内的空气中的PM2.5进行称重，元素分析，用电子显微镜观察其形态，对比三种PM2.5异同。对宣威地区的肺癌患者的术后标本进行电子显微镜观察。

结果

室内空气中的PM2.5浓度分别为C1煤(8.244±1.460)mg/m³，K7煤(5.066±0.984)mg/m³，K7煤(5.071±1.460)mg/m³；三组空气中PM2.5浓度两两比较差异有统计学意义(Ρ=0.029)。C1煤层中滤膜上的杂质有(Silicon, Si)和氧(Oxygen, O)元素富集，三组滤膜上均发现了碳(Carbon, C)，硫(Sulfur, S)的聚集，在部分的滤膜上可见游离的二氧化硅(SiO₂)，部分滤膜上有铝(Aluminium, Al)、钙(Calcium, Ca)元素的聚集。C1煤层与其他煤层相比所产生颗粒物形态不规则，成团块状，杂质较多。在部分的宣威来宾地区的肺癌患者术后标本中，发现纳米级细颗粒的杂质。

结论

C1煤与K7和M30煤燃烧产生的PM2.5不同，PM2.5的成分可能与当地肺癌高发相关。

Case studies putting the decision-making framework for the grouping and testing of nanomaterials (DF4nanoGrouping) into practice

Case studies covering carbonaceous nanomaterials, metal oxide and metal sulphate nanomaterials, amorphous silica and organic pigments were performed to assess the Decision-making framework for the grouping and testing of nanomaterials (DF4nanoGrouping). The usefulness of the DF4nanoGrouping for nanomaterial hazard assessment was confirmed. In two tiers that rely exclusively on non-animal test methods followed by a third tier, if necessary, in which data from rat short-term inhalation studies are evaluated, nanomaterials are assigned to one of four main groups (MGs). The DF4nanoGrouping proved efficient in sorting out nanomaterials that could undergo hazard assessment without further testing. These are soluble nanomaterials (MG1) whose further hazard assessment should rely on read-across to the dissolved materials, high aspect-ratio nanomaterials (MG2) which could be assessed according to their potential fibre toxicity and passive nanomaterials (MG3) that only elicit effects under pulmonary overload conditions. Thereby, the DF4nanoGrouping allows identifying active nanomaterials (MG4) that merit in-depth investigations, and it provides a solid rationale for their sub-grouping to specify the further information needs. Finally, the evaluated case study materials may be used as source nanomaterials in future read-across applications. Overall, the DF4nanoGrouping is a hazard assessment strategy that strictly uses animals as a last resort.

Applications of the comet assay in particle toxicology: air pollution and engineered nanomaterials exposure

Exposure to ambient air particles is associated with elevated levels of DNA strand breaks (SBs) and endonuclease III, formamidopyrimidine DNA glycosylase (FPG) and oxoguanine DNA glycosylase-sensitive sites in cell cultures, animals and humans. In both animals and cell cultures, increases in SB and in oxidatively damaged DNA are seen after exposure to a range of engineered nanomaterials (ENMs), including carbon black, carbon nanotubes, fullerene C60, ZnO, silver and gold. Exposure to TiO2 has generated mixed data with regard to SB and oxidatively damaged DNA in cell cultures. Nanosilica does not seem to be associated with generation of FPG-sensitive sites in cell cultures, while large differences in SB generation between studies have been noted. Single-dose airway exposure to nanosized carbon black and multi-walled carbon nanotubes in animal models seems to be associated with elevated DNA damage levels in lung tissue in comparison to similar exposure to TiO2 and fullerene C60. Oral exposure has been associated with augmented DNA damage levels in cells of internal organs, although the doses have been typically very high. Intraveneous and intraperitoneal injection of ENMs have shown contradictory results dependent on the type of ENM and dose in each set of experiments. In conclusion, the exposure to both combustion-derived particles and ENMs is associated with increased levels of DNA damage in the comet assay. Particle size, composition and crystal structure of ENM are considered important determinants of toxicity, whereas their combined contributions to genotoxicity in the comet assay are yet to be thoroughly investigated.

Approach to using mechanism-based structure activity relationship (SAR) analysis to assess human health hazard potential of nanomaterials

With the increasing use and development of engineered nanoparticles in electronics, consumer products, pesticides, food and pharmaceutical industries, there is a growing concern about potential human health hazards of these materials. A number of studies have demonstrated that nanoparticle toxicity is extremely complex, and that the biological activity of nanoparticles will depend on a variety of physicochemical properties such as particle size, shape, agglomeration state, crystal structure, chemical composition, surface area and surface properties. Nanoparticle toxicity can be attributed to nonspecific interaction with biological structures due to their physical properties (e.g., size and shape) and biopersistence, or to specific interaction with biomolecules through their surface properties (e.g., surface chemistry and reactivity) or release of toxic ions. The toxic effects of most nanomaterials have not been adequately characterized and currently, there are many issues and challenges in toxicity testing and risk assessment of nanoparticles. Based on the possible mechanisms of action and available in vitro and in vivo toxicity database, this paper proposes an approach to using mechanism-based SAR analysis to assess the relative human health hazard/risk potential of various types of nanomaterials.

DNA damage following pulmonary exposure by instillation to low doses of carbon black (Printex 90) nanoparticles in mice

We previously observed genotoxic effects of carbon black nanoparticles at low doses relative to the Danish Occupational Exposure Limit (3.5 mg/m(3)). Furthermore, DNA damage occurred in broncho-alveolar lavage (BAL) cells in the absence of inflammation, indicating that inflammation is not required for the genotoxic effects of carbon black. In this study, we investigated inflammatory and acute phase response in addition to genotoxic effects occurring following exposure to nanoparticulate carbon black (NPCB) at even lower doses. C57BL/6JBomTac mice were examined 1, 3, and 28 days after a single instillation of 0.67, 2, 6, and 162 µg Printex 90 NPCB and vehicle. Cellular composition and protein concentration was evaluated in BAL fluid as markers of inflammatory response and cell damage. DNA strand breaks in BAL cells, lung, and liver tissue were assessed using the alkaline comet assay. The pulmonary acute phase response was analyzed by Saa3 mRNA real-time quantitative PCR. Instillation of the low doses of NPCB induced a slight neutrophil influx one day after exposure. Pulmonary exposure to small doses of NPCB caused an increase in DNA strand breaks in BAL cells and lung tissue measured using the comet assay. We interpret the increased DNA strand breaks occurring following these low exposure doses of NPCB as DNA damage caused by primary genotoxicity in the absence of substantial inflammation, cell damage, and acute phase response.

Manufactured nanomaterials: categorization and approaches to hazard assessment

Nanotechnology offers enormous potential for technological progress. Fortunately, early and intensive efforts have been invested in investigating toxicology and safety aspects of this new technology. However, despite there being more than 6,000 publications on nanotoxicology, some key questions still have to be answered and paradigms need to be challenged. Here, we present a view on the field of nanotoxicology to stimulate the discussion on major knowledge gaps and the critical appraisal of concepts or dogma. First, in the ongoing debate as to whether nanoparticles may harbour a specific toxicity due to their size, we support the view that there is at present no evidence of 'nanospecific' mechanisms of action; no step-change in hazard was observed so far for particles below 100 nm in one dimension. Therefore, it seems unjustified to consider all consumer products containing nanoparticles a priori as hazardous. Second, there is no evidence so far that fundamentally different biokinetics of nanoparticles would trigger toxicity. However, data are sparse whether nanoparticles may accumulate to an extent high enough to cause chronic adverse effects. To facilitate hazard assessment, we propose to group nanomaterials into three categories according to the route of exposure and mode of action, respectively: Category 1 comprises nanomaterials for which toxicity is mediated by the specific chemical properties of its components, such as released ions or functional groups on the surface. Nanomaterials belonging to this category have to be evaluated on a case-by-case basis, depending on their chemical identity. Category 2 focuses on rigid biopersistent respirable fibrous nanomaterials with a specific geometry and high aspect ratio (so-called WHO fibres). For these fibres, hazard assessment can be based on the experiences with asbestos. Category 3 focuses on respirable granular biodurable particles (GBP) which, after inhalation, may cause inflammation and secondary mutagenicity that may finally lead to lung cancer. After intravenous, oral or dermal exposure, nanoscaled GBPs investigated apparently did not show 'nanospecific' effects so far. Hazard assessment of GBPs may be based on the knowledge available for granular particles. In conclusion, we believe the proposed categorization system will facilitate future hazard assessments.

Magnetite Nanoparticles Induce Genotoxicity in the Lungs of Mice via Inflammatory Response

Nanomaterials are useful for their characteristic properties and are commonly used in various fields. Nanosized-magnetite (MGT) is widely utilized in medicinal and industrial fields, whereas their toxicological properties are not well documented. A safety assessment is thus urgently required for MGT, and genotoxicity is one of the most serious concerns. In the present study, we examined genotoxic effects of MGT using mice and revealed that DNA damage analyzed by a comet assay in the lungs of imprinting control region (ICR) mice intratracheally instilled with a single dose of 0.05 or 0.2 mg/animal of MGT was approximately two- to three-fold higher than that of vehicle-control animals. Furthermore, in gpt delta transgenic mice, gpt mutant frequency (MF) in the lungs of the group exposed to four consecutive doses of 0.2 mg MGT was significantly higher than in the control group. Mutation spectrum analysis showed that base substitutions were predominantly induced by MGT, among which G:C to A:T transition and G:C to T:A transversion were the most significant. To clarify the mechanism of mutation caused by MGT, we analyzed the formation of DNA adducts in the lungs of mice exposed to MGT. DNA was extracted from lungs of mice 3, 24, 72 and 168 h after intratracheal instillation of 0.2 mg/body of MGT, and digested enzymatically. 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and lipid peroxide-related DNA adducts were quantified by stable isotope dilution liquid chromatography-mass spectrometry (LC-MS/MS). Compared with vehicle control, these DNA adduct levels were significantly increased in the MGT-treated mice. In addition to oxidative stress- and inflammation related-DNA adduct formations, inflammatory cell infiltration and focal granulomatous formations were also observed in the lungs of MGT-treated mice. Based on these findings, it is suggested that inflammatory responses are probably involved in the genotoxicity induced by MGT in the lungs of mice.

Genotoxicity and reactive oxygen species production induced by magnetite nanoparticles in mammalian cells

We examined the genotoxicity of magnetite nanoparticles (primary particle size: 10 nm) on human A549 and Chinese hamster ovary (CHO) AA8 cells. Six hours' treatment with the particles dose-dependently increased the frequency of micronuclei (MN) in the A549 and CHO AA8 cells up to 5.2% and 5.0% at a dose of 200 µg/ml (34 µg/cm²), respectively. In A549 cells, treatment with the nano-particles (2 µg/ml) for 1 hr induced H2AX phosphorylation, which is suggestive of DNA double strand breaks (DSB). Treating CHO AA8 cells with 2 µg/ml (0.34 µg/cm²) magnetite for 1 hour resulted in a five times higher frequency of sister chromatid exchange (SCE) than the control level. We detected reactive oxygen species (ROS) in CHO cells treated with the particles. These findings indicate that magnetite nano-particles induce ROS in mammalian cells, leading to the direct or indirect induction of DSB, followed by clastogenic events including MN and SCE.

Intraperitoneal exposure to nano/microparticles of fullerene (C₆₀) increases acetylcholinesterase activity and lipid peroxidation in adult zebrafish (Danio rerio) brain

Even though technologies involving nano/microparticles have great potential, it is crucial to determine possible toxicity of these technological products before extensive use. Fullerenes C₆₀ are nanomaterials with unique physicochemical and biological properties that are important for the development of many technological applications. The aim of this study was to evaluate the consequences of nonphotoexcited fullerene C₆₀ exposure in brain acetylcholinesterase expression and activity, antioxidant responses, and oxidative damage using adult zebrafish as an animal model. None of the doses tested (7.5, 15, and 30 mg/kg) altered AChE activity, antioxidant responses, and oxidative damage when zebrafish were exposed to nonphotoexcited C₆₀ nano/microparticles during 6 and 12 hours. However, adult zebrafish exposed to the 30 mg/kg dose for 24 hours have shown enhanced AChE activity and augmented lipid peroxidation (TBARS assays) in brain. In addition, the up-regulation of brain AChE activity was neither related to the transcriptional control (RT-qPCR analysis) nor to the direct action of nonphotoexcited C₆₀ nano/microparticles on the protein (in vitro results) but probably involved a posttranscriptional or posttranslational modulation of this enzymatic activity. Taken together these findings provided further evidence of toxic effects on brain after C₆₀ exposure.

Evaluation of immunohistochemical markers to detect the genotoxic mode of action of fine and ultrafine dusts in rat lungs

Data on local genotoxicity after particle exposure are crucial to resolve mechanistic aspects such as the impact of chronic inflammation, types of DNA damage, and their role in lung carcinogenesis. We established immunohistochemical methods to quantify the DNA damage markers poly(ADP-ribose) (PAR), phosphorylated H2AX (γ-H2AX), 8-hydroxyguanosine (8-OH-dG), and 8-oxoguanine DNA glycosylase (OGG1) in paraffin-embedded tissue from particle-exposed rats. The study was based on lungs from a subchronic study that was part of an already published carcinogenicity study where rats had been intratracheally instilled with saline, quartz DQ12, amorphous silica (Aerosil(®) 150), or carbon black (Printex(®) 90) at monthly intervals for 3 months. Lung sections were stained immunohistochemically and markers were quantified in alveolar lining cells. Local genotoxicity was then correlated with already defined endpoints, i.e. mean inflammation score, bronchoalveolar lavage parameters, and carcinogenicity. Genotoxicity was most pronounced in quartz DQ12-treated rats, where all genotoxicity markers gave statistically significant positive results, indicating considerable genotoxic stress such as occurrence of DNA double-strand breaks (DSB), and oxidative damage with subsequent repair activity. Genotoxicity was less pronounced for Printex(®) 90, but significant increases in γ-H2AX- and 8-OH-dG-positive nuclei and OGG1-positive cytoplasm were nevertheless detected. In contrast, Aerosil(®) 150 significantly enhanced only 8-OH-dG-positive nuclei and oxidative damage-related repair activity (OGG1) in cytoplasm. In the present study, γ-H2AX was the most sensitive genotoxicity marker, differentiating best between the three types of particles. The mean number of 8-OH-dG-positive nuclei, however, correlated best with the mean inflammation score at the same time point. This methodological approach enables integration of local genotoxicity testing in subchronic inhalation studies and makes immunohistochemical detection, in particular of γ-H2AX and 8-hydroxyguanine, a very promising approach for local genotoxicity testing in lungs, with prognostic value for the long-term outcome of particle exposure.

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.

Quantification of particle-induced inflammatory stress response: a novel approach for toxicity testing of earth materials

BACKGROUND

Reactive oxygen species (ROS) are vital regulators of many cellular functions in the body. The intracellular ROS concentration is highly regulated by a balance between pro-oxidants and anti-oxidants. A chronic excess of pro-oxidants leads to elevated ROS concentrations and inflammation, possibly initiating or enhancing disease onset. Mineral-induced generation of ROS, the role of minerals in upregulating cellular ROS, and their role in the development of several occupational diseases are now widely recognized. However, there is no standard protocol to determine changes in ROS production in cells after exposure to mineral dust or earth materials in general. In this study, a new method for determining the degree of cellular toxicity (i.e., cytotoxicity) of particles is described that will help bridge the gap in knowledge.

RESULTS

By measuring the production of ROS and the viability of cells, an inflammatory stress response (ISR) indicator is defined. This approach normalizes the ROS upregulation with respect to the number of viable cells at the time of measurement. We conducted experiments on a series of minerals and soils that represent materials that are inert (i.e., glass beads, anatase, and a soil with low trace element content), moderately reactive (i.e., soil with high trace element content), and highly reactive (i.e., pyrite). Inert materials generated the lowest ISR, averaging 350% compared to the control. Acid washed pyrite produced the highest ISR (1,100 fold higher than the control). The measurements conducted as a function of time showed a complex response. Most materials showed an increase in ISR with particle loading.

CONCLUSIONS

The amount of cellularly generated ROS and cell viability combined provide a better understanding of particle-induced oxidative stress. The results indicate that some earth materials may solicit an initial burst of ROS, followed by a second phase in which cell viability decreases and ROS production increases, leading to a high ISR value. Hence, measurements conducted over a range of particle loading combined with multiple data measurements up to 24 hours can provide new insights in the possible effect of exposure to earth materials on human health.

Investigations on cytotoxic and genotoxic effects of laser printer emissions in human epithelial A549 lung cells using an air/liquid exposure system

Exposure to emissions from laser printers during the printing process is commonplace worldwide, both in the home and workplace environment. In the present study, cytotoxic and genotoxic effects of the emission from five low to medium-throughput laser printers were investigated with respect to the release of ozone (O(3) ), volatile organic compounds (VOC), particulate matter (PM), and submicrometer particles (SMP) during standby and operation. Experiments were conducted in a 1 m(3) emission chamber connected to a Vitrocell® exposure system. Cytotoxicity was determined by the WST-1 assay and genotoxicity by the micronucleus test in human A549 lung cells. The five laser printers emitted varying but generally small amounts of O(3) , VOC, and PM. VOC emissions included 13 compounds with total VOC concentrations ranging from 95 to 280 μg/m(3) (e.g., 2-butanone, hexanal, m,p-xylene, and o-xylene). Mean PM concentrations were below 2.4 μg/m(3). SMP number concentration levels during standby ranged from 9 to 26 particles/cm(3). However, three of the printers generated a 90 to 16 × 10(3) -fold increase of SMP during the printing process (maximum 294,460 particles/cm(3)). Whereas none of the printer emissions were found to cause cytotoxicity, emissions from two printers induced formation of micronuclei (P < 0.001), thus providing evidence for genotoxicity. As yet, differences in biological activity cannot be explained on the basis of the specific emission characteristics of the different printers. Because laser printing technology is widely used, studies with additional cytogenetic endpoints are necessary to confirm the DNA-damaging potency and to identify emission components responsible for genotoxicity.

Carbon black nanoparticle instillation induces sustained inflammation and genotoxicity in mouse lung and liver

Background

Widespread occupational exposure to carbon black nanoparticles (CBNPs) raises concerns over their safety. CBNPs are genotoxic in vitro but less is known about their genotoxicity in various organs in vivo.

Methods

We investigated inflammatory and acute phase responses, DNA strand breaks (SB) and oxidatively damaged DNA in C57BL/6 mice 1, 3 and 28 days after a single instillation of 0.018, 0.054 or 0.162 mg Printex 90 CBNPs, alongside sham controls. Bronchoalveolar lavage (BAL) fluid was analyzed for cellular composition. SB in BAL cells, whole lung and liver were assessed using the alkaline comet assay. Formamidopyrimidine DNA glycosylase (FPG) sensitive sites were assessed as an indicator of oxidatively damaged DNA. Pulmonary and hepatic acute phase response was evaluated by Saa3 mRNA real-time quantitative PCR.

Results

Inflammation was strongest 1 and 3 days post-exposure, and remained elevated for the two highest doses (i.e., 0.054 and 0.162 mg) 28 days post-exposure (P < 0.001). SB were detected in lung at all doses on post-exposure day 1 (P < 0.001) and remained elevated at the two highest doses until day 28 (P < 0.05). BAL cell DNA SB were elevated relative to controls at least at the highest dose on all post-exposure days (P < 0.05). The level of FPG sensitive sites in lung was increased throughout with significant increases occurring on post-exposure days 1 and 3, in comparison to controls (P < 0.001-0.05). SB in liver were detected on post-exposure days 1 (P < 0.001) and 28 (P < 0.001). Polymorphonuclear (PMN) cell counts in BAL correlated strongly with FPG sensitive sites in lung (r = 0.88, P < 0.001), whereas no such correlation was observed with SB (r = 0.52, P = 0.08). CBNP increased the expression of Saa3 mRNA in lung tissue on day 1 (all doses), 3 (all doses) and 28 (0.054 and 0.162 mg), but not in liver.

Conclusions

Deposition of CBNPs in lung induces inflammatory and genotoxic effects in mouse lung that persist considerably after the initial exposure. Our results demonstrate that CBNPs may cause genotoxicity both in the primary exposed tissue, lung and BAL cells, and in a secondary tissue, the liver.

Nanoparticles: Is Toxicity a Concern?

Nanotechnology involving manipulation of atoms and molecules at the nanoscale is one of the frontier areas of research in modern science. During the last few years, nanotechnology has witnessed breakthroughs in the fields of medicine, environment, therapeutics, drug development and biotechnology. This is due to the unique properties of nanomaterials (e.g. chemical, mechanical, optical, magnetic, and biological) which make them desirable for commercial and medical applications. Considering the theory and practice of using nanoparticles, nanotechnology has a great potential in improving treatment of various disorders and in vitro diagnostics. However, there is not much information available on the toxicity of nanoparticles in relation to human health. Toxic effect of nanomaterials on humans is the primary concern of the health industry. Nanomaterials are able to cross biological membranes and access cells, tissues and organs that larger-sized particles normally cannot. Nanomaterials can gain access to the blood stream via inhalation or ingestion. This may lead to both genotoxicity and biochemical toxicity. In this review we try to show which types, sizes and concentrations of nanoparticles are safe for human use and this will help in developing diagnostic, prognostic and therapeutic models using nanoparticles.