Oxidative stress and activation of H2A.X in lung alveolar epithelial cells (A549) by nanoparticulate carbon black.

Fine airborne particulate matter enter the respiratory system, induce oxidative stress and initiate DNA damage. The aim of our study was the estimation of cell viability, oxidative stress, DNA damage, cell cycle alterations and activation of histone H2A.X. Experiments were done on lung alveolar epithelial (A549) cells grown for 24 h with 200 µg mL-1 coarse carbon black (CB), or nanoparticulate CB (NPCB). Neither CB nor glutathione depletion altered cell viability, growth rates, and H2A.X expression while NPCB decreased cell viability, increased oxidative stress and DNA damage. The cell cycle was blocked at G0/G1. NPCB but not CB increased expression and activation of H2A.X at mRNA and protein levels. Co-expression data point to γH2A.X as a major NPCB target, and show the interdependence of γH2A.X and oxidative stress. We conclude, that NPCB increases γ-H2A.X expression in A549 cells at mRNA and protein levels and stimulates H2A.X (Ser139), phosphorylation, associated with oxidative stress, the DNA damage response and G1 cell cycle arrest.

Assessing the cytotoxicity of aerosolized carbon black and benzo[a]pyrene with controlled physical and chemical properties on human lung epithelial cells.

Atmospheric particulate matter (PM) is a complex mixture of hazardous particles containing hundreds of inorganic and organic species. Organic components, such as carbon black (CB) and benzo[a]pyrene (BaP), are known to exhibit diverse genotoxic and carcinogenic effects. The toxicity of CB and polycyclic aromatic hydrocarbons has been well studied, however the combined toxicity is much less understood. A spray-drying system was used to control the size and chemical composition of PMs. PMs were prepared by loading BaP on three different sized CBs (0.1 µm, 2.5 µm, and 10 µm) to obtain BaP-unloaded CB (CB0.1, CB2.5, and CB10) and BaP-loaded CB (CB0.1-BaP, CB2.5-BaP, and CB10-BaP). We analyzed cell viability, levels of oxidative stress, and pro-inflammatory cytokines using human lung cells (A549 epithelial cells). Cell viability decreased when exposed to all PMs (PM0.1, PM2.5, and PM10), regardless of the presence of BaP. The increase in PM size due to BaP-adsorption to CB resulted in insufficient toxic effects on human lung cells compared to CB alone. Smaller CBs reduced cell viability, leading to reactive oxygen species formation, which can cause damage to cellular structures deliver more harmful substances. Additionally, small CBs were predominant in inducing the expression of pro-inflammatory cytokines in A549 epithelial cells. These results indicate that the size of CB is a key factor that immediately affects the inflammation of lung cells, compared to the presence of BaP.

Chronic exposure to carbon black ultrafine particles reprograms macrophage metabolism and accelerates lung cancer.

Chronic exposure to airborne carbon black ultrafine (nCB) particles generated from incomplete combustion of organic matter drives IL-17A-dependent emphysema. However, whether and how they alter the immune responses to lung cancer remains unknown. Here, we show that exposure to nCB particles increased PD-L1+ PD-L2+ CD206+ antigen-presenting cells (APCs), exhausted T cells, and Treg cells. Lung macrophages that harbored nCB particles showed selective mitochondrial structure damage and decreased oxidative respiration. Lung macrophages sustained the HIF1α axis that increased glycolysis and lactate production, culminating in an immunosuppressive microenvironment in multiple mouse models of non-small cell lung cancers. Adoptive transfer of lung APCs from nCB-exposed wild type to susceptible mice increased tumor incidence and caused early metastasis. Our findings show that nCB exposure metabolically rewires lung macrophages to promote immunosuppression and accelerates the development of lung cancer.

Effects of FW2 Nanoparticles Toxicity in a New In Vitro Pulmonary Vascular Cells Model Mimicking Endothelial Dysfunction.

Several epidemiological studies have revealed the involvement of nanoparticles (NPs) in respiratory and cardiovascular mortality. In this work, the focus will be on the effect of manufactured carbon black NPs for risk assessment of consumers and workers, as human exposure is likely to increase. Since the pulmonary circulation could be one of the primary targets of inhaled NPs, patients suffering from pulmonary hypertension (PH) could be a population at risk. To compare the toxic effect of carbon black NPs in the pulmonary circulation under physiologic and pathological conditions, we developed a new in vitro model mimicking the endothelial dysfunction and vascular dynamics observed in vascular pathology such as PH. Human pulmonary artery endothelial cells were cultured under physiological conditions (static and normoxia 21% O2) or under pathological conditions (20% cycle stretch and hypoxia 1% O2). Then, cells were treated for 4 or 6 h with carbon black FW2 NPs from 5 to 10 µg/cm2. Different endpoints were studied: (i) NPs internalization by transmission electronic microscopy; (ii) oxidative stress by CM-H2DCFDA probe and electron paramagnetic resonance; (iii) NO (nitrites and nitrates) production by Griess reaction; (iv) inflammation by ELISA assay; and (v) calcium signaling by confocal microscopy. The present study characterizes the in vitro model mimicking endothelial dysfunction in PH and indicates that, under such pathological conditions, oxidative stress and inflammation are increased along with calcium signaling alterations, as compared to the physiological conditions. Human exposure to carbon black NPs could produce greater deleterious effects in vulnerable patients suffering from cardiovascular diseases.

Black soot exposure induced hypothalamic and testicular oxidative stress and apoptosis in male rats.

Air pollution constitutes the largest cause of environmental risks today. At present, no scientific publication linking environmental black soot and derangement in the hypothalamus and testis of rats exists. This study investigated the effect of black soot exposure on hypothalamic and testicular functions of male rats exposed to black soot for 4, 8 and 12 weeks respectively. The hypothalamus and testis were processed for biochemical analysis. Results show that black soot exposure for 4, 8 and 12 weeks significantly (p < .05) increased oxidative stress markers both in the testis and in the hypothalamus of rats. Also, black soot exposure significantly (p < .05) decreased the alkaline phosphatase, acid phosphatase as well as lactate dehydrogenase activities in the testis. Furthermore, the result demonstrated an upregulation of the protein expression of caspase-3, an indication of increased apoptosis which led to the disruption of the histological architecture of the hypothalamus and testis. Taken together, black soot exposure induced hypothalamic and testicular oxidative stress and apoptosis in male rats.

Carbon black nanoparticles induce HDAC6-mediated inflammatory responses in 16HBE cells.

Long-term inhalation of carbon black nanoparticles (CBNPs) leads to pulmonary inflammatory diseases. Histone deacetylase 6 (HDAC6) has been identified as an important regulator in the development of inflammatory disorders. However, the direct involvement of HDAC6 in CBNPs-induced pulmonary inflammatory responses remains unclear. To explore whether HDAC6 participates in CBNPs-induced pulmonary inflammation, human bronchial epithelial cell line (16HBE cells) was transfected with HDAC6 small interference RNA (siRNA) and then exposed to CBNPs at concentrations of 0, 25, and 50 µg/ml for 24 h. Intracellular HDAC6 and intraflagellar transport protein 88 (IFT88) mRNA and protein were determined by real-time polymerase chain reaction and Western blot, respectively. The secretions of inflammatory cytokines including interleukin (IL)-8, tumor necrosis factor (TNF)-α, IL-6, and IL-1ß were measured by enzyme-linked immunosorbent assay. CBNPs induced a significant increase in the expressions of IL-8 and IL-6, accompanied by a high level of intracellular HDAC6 mRNA when compared with a blank control group (p < 0.05). However, there were no significant changes in the levels of TNF-α secretion, intracellular HDAC6 and IFT88 protein induced by CBNPs (p > 0.05). The HDAC6 mRNA expression was significantly suppressed in HDAC6 siRNA-transfected cells (p < 0.05). The secretions of IL-8, TNF-α, and IL-6 were significantly less in HDAC6 siRNA-transfected cells than that in normal 16HBE cells with exposure to 25 or 50 µg/ml of CBNPs, but intracellular IFT88 mRNA expression was markedly increased in HDAC6 siRNA-transfected cells when compared with normal 16HBE cells exposed to 50 µg/ml of CBNPs (all p < 0.05). Downregulation of the HDAC6 gene inhibits CBNPs-induced inflammatory responses in bronchial epithelial cells, partially through regulating IFT88 expression. It is suggested that CBNPs may trigger inflammatory responses in bronchial epithelial cells by an HDAC6/IFT88-dependent pathway.

Carbon content in airway macrophages and genomic instability in Chinese carbon black packers.

Carbon black (CB) particulates as virtually pure elemental carbon can deposit deep in the lungs of humans. International Agency for Research on Cancer classified CB as a Group 2B carcinogen due to inconclusive human evidence. A molecular epidemiological study was conducted in an established cohort of CB packers (CBP) to assess associations between CB exposure and genomic instability in peripheral lymphocytes using cytokinesis-block micronucleus assay (CBMN). Carbon content in airway macrophages (CCAM) was quantified as a bio-effective dosimeter for chronic CB exposure. Dose-response observed in CBPs was compared to that seen in workers exposed to diesel exhaust. The association between CB exposure status and CBMN endpoints was identified in 85 CBPs and 106 non-CBPs from a 2012 visit and replicated in 127 CBPs and 105 non-CBPs from a 2018 visit. The proportion of cytoplasm area occupied by carbon particles in airway macrophages was over fivefold higher in current CBPs compared to non-CBPs and was associated with CBMN endpoints in a dose-dependent manner. CB aerosol and diesel exhaust shared the same potency of inducing genomic instability in workers. Circulatory pro-inflammatory factors especially TNF-α was found to mediate associations between CB exposure and CBMN endpoints. In vitro functional validation supported the role of TNF-α in inducing genomic instability. An estimated range of lower limits of benchmark dose of 4.19-7.28% of CCAM was recommended for risk assessment. Chronic CB exposure increased genomic instability in human circulation and this provided novel evidence supporting its reclassification as a human carcinogen.

Soybeans Grown with Carbonaceous Nanomaterials Maintain Nitrogen Stoichiometry by Assimilating Soil Nitrogen to Offset Impaired Dinitrogen Fixation.

Engineered nanomaterials (ENMs) can enter agroecosystems because of their widespread use and disposal. Within soil, ENMs may affect legumes and their dinitrogen (N2) fixation, which are critical for food supply and N-cycling. Prior research focusing on end point treatment effects has reported that N2-fixing symbioses in an important food legume, soybean, can be impaired by ENMs. Yet, it remains unknown how ENMs can influence the actual amounts of N2 fixed and what plant total N contents are since plants can also acquire N from the soil. We determined the effects of one already widespread and two rapidly expanding carbonaceous nanomaterials (CNMs: carbon black, multiwalled carbon nanotubes, and graphene; each at three concentrations) on the N economy of soil-grown soybeans. Unlike previous studies, this research focused on processes and interactions within a plant-soil-microbial system. We found that total plant N accumulation was unaffected by CNMs. However, as shown by 15N isotope analyses, CNMs significantly diminished soybean N2 fixation (by 31-78%). Plants maintained N stoichiometry by assimilating compensatory N from the soil, accompanied by increased net soil N mineralization. Our findings suggest that CNMs could undermine the role of legume N2 fixation in supplying N to agroecosystems. Maintaining productivity in leguminous agriculture experiencing such effects would require more fossil-fuel-intensive N fertilizer and increase associated economic and environmental costs. This work highlights the value of a process-based analysis of a plant-soil-microbial system for assessing how ENMs in soil can affect legume N2 fixation and N-cycling.

Ambient black carbon particles reach the fetal side of human placenta.

Particle transfer across the placenta has been suggested but to date, no direct evidence in real-life, human context exists. Here we report the presence of black carbon (BC) particles as part of combustion-derived particulate matter in human placentae using white-light generation under femtosecond pulsed illumination. BC is identified in all screened placentae, with an average (SD) particle count of 0.95 × 104 (0.66 × 104) and 2.09 × 104 (0.9 × 104) particles per mm3 for low and high exposed mothers, respectively. Furthermore, the placental BC load is positively associated with mothers' residential BC exposure during pregnancy (0.63-2.42 µg per m3). Our finding that BC particles accumulate on the fetal side of the placenta suggests that ambient particulates could be transported towards the fetus and represents a potential mechanism explaining the detrimental health effects of pollution from early life onwards.

Prolonged exposure to carbon nanoparticles induced methylome remodeling and gene expression in zebrafish heart.

Growing black carbon (BC) emission has become one of the major urgent environmental issues facing human beings. Usually, BC or BC-containing carbon nanoparticles (CNPs) were recognized as non-directly toxic components of atmospheric particulate matter. However, epidemiology studies have provided much evidence of the associations of exposure of particulate-containing carbon particles with cardiovascular diseases. There are still no related studies to support the epidemiological conclusions. Hence, in this article we exposed adult zebrafish to CNPs for 60 days, and then explored the heart location and potential adverse effects on cardiac tissues of these nanosized carbon particles. Our results first showed direct visualization of cardiac endothelial uptake and heart deposition of CNPs in zebrafish. In addition, CNPs caused significant ultrastructural alterations in myocardial tissue and induced the expression of inflammatory cytokines in a dose-dependent manner, resulting in sub-endocardial inflammation and cell apoptosis. Moreover, our data demonstrated the perturbations caused by CNPs on DNA methylation, suggesting that DNA methylome remodeling might play a critical role in CNP-induced cardiotoxicity in zebrafish heart. Therefore, this study not only proved a laboratory link between CNP exposure and cardiotoxicity in vivo, but also indicated a possible toxicity mechanism involved.

Aerosol mixing state matters for particles deposition in human respiratory system.

Aerosol particles emitted from various human activities deteriorate air quality and are suggested to increase public health risk. Numerous studies have emphasized the relationship between the mass and/or number concentration of aerosols (or commonly known as particulate matter (PM)) in the atmosphere and the incidence of respiratory and cardiovascular diseases, while very few have examined the deposition efficiency of inhaled particles in the respiratory tract. We present the first examination of particles deposition based on, detailed simulation of aerosol physico-chemical properties by a recently developed particle-resolved aerosol model and the mixing state dependent hygrosocpic growth and deposition computed at particle-level by deposition model. Furthermore, we elucidate the impact of mixing state on deposition efficiency by using a recently introduced aerosol mixing state index. We find that without considering mixing-state-dependent hygroscopic growth of particles leads to overestimation of deposition efficiency; whereas considering an average mixing state leads to underestimation of 5% to 20% of soot particle deposition efficiency in human alveoli. We conclude that aerosol mixing state, which evolves during the interaction between atmospheric chemistry and meteorology, is important for the comprehensive evaluation of air quality and its implication to public health requires further investigation.

Oxidized Carbon Black: Preparation, Characterization and Application in Antibody Delivery across Cell Membrane.

Modulating biomolecular networks in cells with peptides and proteins has become a promising therapeutic strategy and effective biological tools. A simple and effective reagent that can bring functional proteins into cells can increase efficacy and allow more investigations. Here we show that the relatively non-toxic and non-immunogenic oxidized carbon black particles (OCBs) prepared from commercially available carbon black can deliver a 300 kDa protein directly into cells, without an involvement of a cellular endocytosis. Experiments with cell-sized liposomes indicate that OCBs directly interact with phospholipids and induce membrane leakages. Delivery of human monoclonal antibodies (HuMAbs, 150 kDa) with specific affinity towards dengue viruses (DENV) into DENV-infected Vero cells by OCBs results in HuMAbs distribution all over cells' interior and effective viral neutralization. An ability of OCBs to deliver big functional/therapeutic proteins into cells should open doors for more protein drug investigations and new levels of antibody therapies and biological studies.

Agglomeration Determines Effects of Carbonaceous Nanomaterials on Soybean Nodulation, Dinitrogen Fixation Potential, and Growth in Soil.

The potential effects of carbonaceous nanomaterials (CNMs) on agricultural plants are of concern. However, little research has been performed using plants cultivated to maturity in soils contaminated with various CNMs at different concentrations. Here, we grew soybean for 39 days to seed production in soil amended with 0.1, 100, or 1000 mg kg-1 of either multiwalled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), or carbon black (CB) and studied plant growth, nodulation, and dinitrogen (N2) fixation potential. Plants in all CNM treatments flowered earlier (producing 60% to 372% more flowers when reproduction started) than the unamended controls. The low MWCNT-treated plants were shorter (by 15%) with slower leaf cover expansion (by 26%) and less final leaf area (by 24%) than the controls. Nodulation and N2 fixation potential appeared negatively impacted by CNMs, with stronger effects at lower CNM concentrations. All CNM treatments reduced the whole-plant N2 fixation potential, with the highest reductions (by over 91%) in the low and medium CB and the low MWCNT treatments. CB and GNPs appeared to accumulate inside nodules as observed by transmission electron microscopy. CNM dispersal in aqueous soil extracts was studied to explain the inverse dose-response relationships, showing that CNMs at higher concentrations were more agglomerated (over 90% CNMs settled as agglomerates >3 µm after 12 h) and therefore proportionally less bioavailable. Overall, our findings suggest that lower concentrations of CNMs in soils could be more impactful to leguminous N2 fixation, owing to greater CNM dispersal and therefore increased bioavailability at lower concentrations.

Energy Transfer Mechanisms during Molecular Delivery to Cells by Laser-Activated Carbon Nanoparticles.

Previous studies have shown that exposure of carbon black nanoparticles to nanosecond pulsed near-infrared laser causes intracellular delivery of molecules through hypothesized transient breaks in the cell membrane. The goal of this study is to determine the underlying mechanisms of sequential energy transfer from laser light to nanoparticle to fluid medium to cell. We found that laser pulses on a timescale of 10 ns rapidly heat carbon nanoparticles to temperatures on the order of 1200 K. Heat is transferred from the nanoparticles to the surrounding aqueous medium on a similar timescale, causing vaporization of the surrounding water and generation of acoustic emissions. Nearby cells can be impacted thermally by the hot bubbles and mechanically by fluid mechanical forces to transiently increase cell membrane permeability. The experimental and theoretical results indicate that transfer of momentum and/or heat from the bubbles to the cells are the dominant mechanisms of energy transfer that results in intracellular uptake of molecules. We further conclude that neither thermal expansion of the nanoparticles nor a carbon-steam chemical reaction play a significant role in the observed effects on cells, and that acoustic pressure appears to be concurrent with, but not essential to, the observed bioeffects.

Indoor particulate matter exposure is associated with increased black carbon content in airway macrophages of former smokers with COPD.

INTRODUCTION: Exposure to fine particulate matter (PM2.5) is associated with worse morbidity in individuals with COPD. Inhaled PM is phagocytosed by airway macrophages (AM), and black carbon measured in AM may serve as a biomarker of air pollution exposure. As there is little data on how indoor PM exposure may influence AM black carbon content in those with respiratory disease, we investigated the association of indoor PM2.5 concentration to AM black carbon content in adults with COPD. METHODS: Former smokers (>10 pack-years smoking history, quit date >1 year prior to enrollment) older than 40 years of age with moderate-severe COPD were eligible. Indoor air PM2.5 concentrations were measured over 5-7 days at baseline, 3 month, and 6 month intervals. Sputum induction was performed during clinic visits concordant with home monitoring. A total of 50 macrophages per sputum specimen were photographed and quantified using appropriate software by trained staff blinded to PM concentrations. Longitudinal analyses using generalized estimating equations were used to assess the relationship between indoor PM exposure and AM black carbon content. RESULTS: Participants (n=20) were older (mean (SD) age 67 (4) years), predominantly Caucasian (85%) and male (70%), with an average smoking history of 52 pack-years and mean (SD) quit date of 13 (9) years prior to enrollment. The majority of daily time was reported to be spent indoors (>23h). Mean indoor PM2.5 concentration was 12.8 (13.5)µg/m(3). The mean area of black carbon quantified in airway macrophages was 1.2 (0.7)µm(2). In multivariate cross-sectional and longitudinal analyses, each 10µg/m(3) increase in indoor PM2.5 was significantly associated with a 0.26µm(2) and 0.19µm(2) increase in airway macrophage black carbon total area, respectively (p<0.05). CONCLUSION: Higher indoor PM2.5 concentration is associated with an increase in black carbon content of AM in individuals with COPD. These data support the potential for AM black carbon content to be a useful non-invasive biomarker of exposure to indoor PM.

Diesel exhaust particle exposure in vitro impacts T lymphocyte phenotype and function.

BACKGROUND: Diesel exhaust particles (DEP) are major constituents of ambient air pollution and their adverse health effect is an area of intensive investigations. With respect to the immune system, DEP have attracted significant research attention as a factor that could influence allergic diseases interfering with cytokine production and chemokine expression. With this exception, scant data are available on the impact of DEP on lymphocyte homeostasis. Here, the effects of nanoparticles from Euro 4 (E4) and Euro 5 (E5) light duty diesel engines on the phenotype and function of T lymphocytes from healthy donors were evaluated. METHODS: T lymphocytes were isolated from peripheral blood obtained from healthy volunteers and subsequently stimulated with different concentration (from 0.15 to 60 µg/ml) and at different time points (from 24 h to 9 days) of either E4 or E5 particles. Immunological parameters, including apoptosis, autophagy, proliferation levels, mitochondrial function, expression of activation markers and cytokine production were evaluated by cellular and molecular analyses. RESULTS: DEP exposure caused a pronounced autophagic-lysosomal blockade, thus interfering with a key mechanism involved in the maintaining of T cell homeostasis. Moreover, DEP decreased mitochondrial membrane potential but, unexpectedly, this effect did not result in changes of the apoptosis and/or necrosis levels, as well as of intracellular content of adenosine triphosphate (ATP). Finally, a down-regulation of the expression of the alpha chain of the interleukin (IL)-2 receptor (i.e., the CD25 molecule) as well as an abnormal Th1 cytokine expression profile (i.e., a decrease of IL-2 and interferon (IFN)-γ production) were observed after DEP exposure. No differences between the two compounds were detected in all studied parameters. CONCLUSIONS: Overall, our data identify functional and phenotypic T lymphocyte parameters as relevant targets for DEP cytotoxicity, whose impairment could be detrimental, at least in the long run, for human health, favouring the development or the progression of diseases such as autoimmunity and cancer.

Induction of platelet aggregation after a direct physical interaction with diesel exhaust particles.

BACKGROUND: There is a proven link between exposure to traffic-derived particulate air pollution and the incidence of platelet-driven cardiovascular diseases. It is suggested that inhalation of small, nanosized particles increases cardiovascular risk via toxicological and inflammatory processes and translocation of nanoparticles into the bloodstream has been shown in experimental models. We therefore investigated the ability of diesel exhaust particles (DEP) to interact physically and functionally with platelets. METHODS: The interaction of DEP and carbon black (CB) with platelets was examined by transmission electron microscopy (TEM), whereas the functional consequences of exposure were assessed by measuring in vitro and in vivo platelet aggregation via established methods. RESULTS: Both DEP and CB were internalized and seen in proximity with the open canalicular system in platelets. DEP induced platelet aggregation in vitro whereas CB had no effect. DEP induced Ca(2+) release, dense granule secretion and surface P-selectin expression, but not toxicologic membrane disruption. Low concentrations of DEP potentiated agonist-induced platelet aggregation in vitro and in vivo. CONCLUSIONS: DEP associate physically with platelets in parallel with a Ca(2+) -mediated aggregation response displaying the conventional features of agonist-induced aggregation. The ability of DEP to enhance the aggregation response to platelet stimuli would be expected to increase the incidence of platelet-driven cardiovascular events should they be inhaled and translocate into the blood. This study provides a potential mechanism for the increased thrombotic risk associated with exposure to ambient particulate air pollution.

Does carbon black disaggregate in lung fluid? A critical assessment.

Carbon black is an industrially produced particulate form of nearly pure elemental carbon. The basic building blocks of carbon black are (1) primary particles, minute pieces of matter with defined physical boundaries; (2) aggregates, collections of strongly bound or fused particles; and (3) agglomerates, collections of weakly bound aggregates. Industrial carbon black is produced within a closed reactor where the primary particles form aggregates, which become the indivisible entities of carbon black. These aggregates then form agglomerates, which are the typical form of carbon black in commerce. Carbon black is often used in in vitro and in vivo particle toxicology investigations as a reference nanoparticle. The toxicology studies often report the sizes of the primary particles but rarely the sizes of the aggregates or agglomerates. It appears in many cases that there is a limited understanding of the fact that carbon black typically does not exist as primary particles but instead exists as aggregates and agglomerates. Moreover, many toxicology studies manipulate carbon black particles in order to disperse them so that the form of carbon black used in these toxicology studies may be substantially different from the form that may be encountered in the workplace environment. Since the main exposure route for carbon black is inhalation, the question arose as to whether inhaled carbon black may deagglomerate or disaggregate to either smaller aggregates or primary particles when in contact with lung fluids. This question relates to the concern that there may be additional hazards of smaller particles, such as their ability to translocate to tissues and organs beyond the lung and the ability to pass through the blood-brain barrier. The purpose of this assessment is to review the existing literature for evidence as to whether carbon black deagglomerates or disaggregates into smaller aggregates or primary particles when in contact with lung fluid. On the basis of a review of the physical characteristics of commercial carbon black and various toxicology studies, it appears that commercially produced carbon black in contact with lung fluid is unlikely to deagglomerate or disaggregate into smaller aggregates or primary particles.

Citrullination of proteins: a common post-translational modification pathway induced by different nanoparticles in vitro and in vivo.

AIM: Rapidly expanding manufacture and use of nanomaterials emphasize the requirements for thorough assessment of health outcomes associated with novel applications. Post-translational protein modifications catalyzed by Ca(2+)-dependent peptidylargininedeiminases have been shown to trigger immune responses including autoantibody generation, a hallmark of immune complexes deposition in rheumatoid arthritis. Therefore, the aim of the study was to assess if nanoparticles are able to promote protein citrullination. MATERIALS & METHODS: Human A549 and THP-1 cells were exposed to silicon dioxide, carbon black or single-walled carbon nanotubes. C57BL/6 mice were exposed to respirable single-walled carbon nanotubes. Protein citrullination, peptidylargininedeiminases activity and target proteins were evaluated. RESULTS: The studied nanoparticles induced protein citrullination both in cultured human cells and mouse lung tissues. Citrullination occurred via the peptidylargininedeiminase-dependent mechanism. Cytokeratines 7, 8, 18 and plectins were identified as intracellular citrullination targets. CONCLUSION: Nanoparticle exposure facilitated post-translational citrullination of proteins.