Maternal engineered nanomaterial inhalation during gestation alters the fetal transcriptome.

BACKGROUND: The integration of engineered nanomaterials (ENM) is well-established and widespread in clinical, commercial, and domestic applications. Cardiovascular dysfunctions have been reported in adult populations after exposure to a variety of ENM. As the diversity of these exposures continues to increase, the fetal ramifications of maternal exposures have yet to be determined. We, and others, have explored the consequences of ENM inhalation during gestation and identified many cardiovascular and metabolic outcomes in the F1 generation. The purpose of these studies was to identify genetic alterations in the F1 generation of Sprague-Dawley rats that result from maternal ENM inhalation during gestation. Pregnant dams were exposed to nano-titanium dioxide (nano-TiO2) aerosols (10 ± 0.5 mg/m3) for 7-8 days (calculated, cumulative lung deposition = 217 ± 1 µg) and on GD (gestational day) 20 fetal hearts were isolated. DNA was extracted and immunoprecipitated with modified chromatin marks histone 3 lysine 4 tri-methylation (H3K4me3) and histone 3 lysine 27 tri-methylation (H3K27me3). Following chromatin immunoprecipitation (ChIP), DNA fragments were sequenced. RNA from fetal hearts was purified and prepared for RNA sequencing and transcriptomic analysis. Ingenuity Pathway Analysis (IPA) was then used to identify pathways most modified by gestational ENM exposure. RESULTS: The results of the sequencing experiments provide initial evidence that significant epigenetic and transcriptomic changes occur in the cardiac tissue of maternal nano-TiO2 exposed progeny. The most notable alterations in major biologic systems included immune adaptation and organismal growth. Changes in normal physiology were linked with other tissues, including liver and kidneys. CONCLUSIONS: These results are the first evidence that maternal ENM inhalation impacts the fetal epigenome.

Engineered nanoparticle exposure and cardiovascular effects: the role of a neuronal-regulated pathway.

Human and animal studies have confirmed that inhalation of particles from ambient air or occupational settings not only causes pathophysiological changes in the respiratory system, but causes cardiovascular effects as well. At an equal mass lung burden, nanoparticles are more potent in causing systemic microvascular dysfunction than fine particles of similar composition. Thus, accumulated evidence from animal studies has led to heightened concerns about the potential short- and long-term deleterious effects of inhalation of engineered nanoparticles on the cardiovascular system. This review highlights the new observations from animal studies, which document the adverse effects of pulmonary exposure to engineered nanoparticles on the cardiovascular system and elucidate the potential mechanisms involved in regulation of cardiovascular function, in particular, how the neuronal system plays a role and reacts to pulmonary nanoparticle exposure based on both in vivo and in vitro studies. In addition, this review also discusses the possible influence of altered autonomic nervous activity on preexisting cardiovascular conditions. Whether engineered nanoparticle exposure serves as a risk factor in the development of cardiovascular diseases warrants further investigation.

The influence of inhaled multi-walled carbon nanotubes on the autonomic nervous system.

BACKGROUND: Heart rate and cardiovascular function are regulated by the autonomic nervous system. Heart rate variability (HRV) as a marker reflects the activity of autonomic nervous system. The prognostic significance of HRV in cardiovascular disease has been reported in clinical and epidemiological studies. The present study focused on the influence of inhaled multi-walled carbon nanotubes (MWCNTs) on autonomic nervous system by HRV analysis. METHODS: Male Sprague-Dawley rats were pre-implanted with a telemetry device and kept in the individual cages for recovery. At week four after device implantation, rats were exposed to MWCNTs for 5 h at a concentration of 5 mg/m(3). The real-time EKGs were recorded by a telemetry system at pre-exposure, during exposure, 1 day and 7 days post-exposure. HRV was measured by root mean square of successive differences (RMSSD); the standard deviation of inter-beat (RR) interval (SDNN); the percentage of successive RR interval differences greater than 5 ms (pNN5) and 10 ms (pNN10); low frequency (LF) and high frequency (HF). RESULTS: Exposure to MWCNTs increased the percentage of differences between adjacent R-R intervals over 10 ms (pNN10) (p < 0.01), RMSSD (p < 0.01), LF (p < 0.05) and HF (p < 0.01). CONCLUSIONS: Inhalation of MWCNTs significantly alters the balance between sympathetic and parasympathetic nervous system. Whether such transient alterations in autonomic nervous performance would alter cardiovascular function and raise the risk of cardiovascular events in people with pre-existing cardiovascular conditions warrants further study.

Evaluation of the Pulmonary Toxicity of Ambient Particulate Matter From Camp Victory, Iraq.

Anecdotal reports in the press and epidemiological studies suggest that deployment to Iraq and Afghanistan may be associated with respiratory diseases and symptoms in U.S. military personnel and veterans. Exposures during military operations were complex, but virtually all service members were exposed to high levels of respirable, geogenic dust. Inhalation of other dusts has been shown to be associated with adverse health effects, but the pulmonary toxicity of ambient dust from Iraq has not been previously studied. The relative toxicity of Camp Victory dust was evaluated by comparing it to particulate matter from northern Kuwait, a standard U.S. urban dust, and crystalline silica using a single intratracheal instillation in rats. Lung histology, protein levels, and cell counts were evaluated in the bronchoalveolar lavage fluid 1-150 d later. The Iraq dust provoked an early significant, acute inflammatory response. However, the level of inflammation in response to the Iraq dust, U.S. urban dust, and Kuwait dust rapidly declined and was nearly at control levels by the end of the study At later times, animals exposed to the Iraq, U.S. urban, or Kuwait dusts showed increased small airway remodeling and emphysema compared to silica-exposed and control animals without evidence of fibrosis or premalignant changes. The severity and persistence of pulmonary toxicity of these three dusts from the Middle East resemble those of a U.S. urban dust and are less than those of silica. Therefore, Iraq dust exposure is not highly toxic, but similar to other poorly soluble low-toxicity dusts.

ROS evaluation for a series of CNTs and their derivatives using an ESR method with DMPO.

Carbon nanotubes (CNTs) are important materials in advanced industries. It is a concern that pulmonary exposure to CNTs may induce carcinogenic responses. It has been recently reported that CNTs scavenge ROS though non-carbon fibers generate ROS. A comprehensive evaluation of ROS scavenging using various kinds of CNTs has not been demonstrated well. The present work specifically investigates ROS scavenging capabilities with a series of CNTs and their derivatives that were physically treated, and with the number of commercially available CNTs. CNT concentrations were controlled at 0.2 through 0.6 wt%. The ROS scavenging rate was measured by ESR with DMPO. Interestingly, the ROS scavenging rate was not only influenced by physical treatments, but was also dependent on individual manufacturing methods. Ratio of CNTs to DMPO/ hydrogen peroxide is a key parameter to obtain appropriate ROS quenching results for comparison of CNTs. The present results suggest that dangling bonds are not a sole factor for scavenging, and electron transfer on the CNT surface is not clearly determined to be the sole mechanism to explain ROS scavenging.

Cell permeability, migration, and reactive oxygen species induced by multiwalled carbon nanotubes in human microvascular endothelial cells.

Multiwalled carbon nanotubes (MWCNT) have elicited great interest in biomedical applications due to their extraordinary physical, chemical, and optical properties. Intravenous administration of MWCNT-based medical imaging agents and drugs in animal models was utilized. However, the potential harmful health effects of MWCNT administration in humans have not yet been elucidated. Furthermore, to date, there are no apparent reports regarding the precise mechanisms of translocation of MWCNT into target tissues and organs from blood circulation. This study demonstrates that exposure to MWCNT leads to an increase in cell permeability in human microvascular endothelial cells (HMVEC). The results obtained from this study also showed that the MWCNT-induced rise in endothelial permeability is mediated by reactive oxygen species (ROS) production and actin filament remodeling. In addition, it was found that MWCNT promoted cell migration in HMVEC. Mechanistically, MWCNT exposure elevated the levels of monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule 1 (ICAM-1) in HMVEC. Taken together, these results provide new insights into the bioreactivity of MWCNT, which may have implications in the biomedical application of MWCNT in vascular targeting, imaging, and drug delivery. The results generated from this study also elucidate the potential adverse effects of MWCNT exposure on humans at the cellular level.

Cell permeability, migration, and reactive oxygen species induced by multiwalled carbon nanotubes in human microvascular endothelial cells.

Multiwalled carbon nanotubes (MWCNT) have elicited great interest in biomedical applications due to their extraordinary physical, chemical, and optical properties. Intravenous administration of MWCNT-based medical imaging agents and drugs in animal models was utilized. However, the potential harmful health effects of MWCNT administration in humans have not yet been elucidated. Furthermore, to date, there are no apparent reports regarding the precise mechanisms of translocation of MWCNT into target tissues and organs from blood circulation. This study demonstrates that exposure to MWCNT leads to an increase in cell permeability in human microvascular endothelial cells (HMVEC). The results obtained from this study also showed that the MWCNT-induced rise in endothelial permeability is mediated by reactive oxygen species (ROS) production and actin filament remodeling. In addition, it was found that MWCNT promoted cell migration in HMVEC. Mechanistically, MWCNT exposure elevated the levels of monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule 1 (ICAM-1) in HMVEC. Taken together, these results provide new insights into the bioreactivity of MWCNT, which may have implications in the biomedical application of MWCNT in vascular targeting, imaging, and drug delivery. The results generated from this study also elucidate the potential adverse effects of MWCNT exposure on humans at the cellular level.

Pulmonary and cardiovascular responses of rats to inhalation of a commercial antimicrobial spray containing titanium dioxide nanoparticles.

Our laboratory has previously demonstrated that application of an antimicrobial spray product containing titanium dioxide (TiO(2)) generates an aerosol of titanium dioxide in the breathing zone of the applicator. The present report describes the design of an automated spray system and the characterization of the aerosol delivered to a whole body inhalation chamber. This system produced stable airborne levels of TiO(2) particles with a median count size diameter of 110 nm. Rats were exposed to 314 mg/m(3) min (low dose), 826 mg/m(3) min (medium dose), and 3638 mg/m(3) min (high dose) of TiO(2) under the following conditions: 2.62 mg/m(3) for 2 h, 1.72 mg/m(3) 4 h/day for 2 days, and 3.79 mg/m(3) 4 h/day for 4 days, respectively. Pulmonary (breathing rate, specific airway resistance, inflammation, and lung damage) and cardiovascular (the responsiveness of the tail artery to constrictor or dilatory agents) endpoints were monitored 24 h post-exposure. No significant pulmonary or cardiovascular changes were noted at low and middle dose levels. However, the high dose caused significant increases in breathing rate, pulmonary inflammation, and lung cell injury. Results suggest that occasional consumer use of this antimicrobial spray product should not be a hazard. However, extended exposure of workers routinely applying this product to surfaces should be avoided. During application, care should be taken to minimize exposure by working under well ventilated conditions and by employing respiratory protection as needed. It would be prudent to avoid exposure to children or those with pre-existing respiratory disease.

Multi-walled carbon nanotube-induced gene expression in the mouse lung: association with lung pathology.

Due to the fibrous shape and durability of multi-walled carbon nanotubes (MWCNT), concerns regarding their potential for producing environmental and human health risks, including carcinogenesis, have been raised. This study sought to investigate how previously identified lung cancer prognostic biomarkers and the related cancer signaling pathways are affected in the mouse lung following pharyngeal aspiration of well-dispersed MWCNT. A total of 63 identified lung cancer prognostic biomarker genes and major signaling biomarker genes were analyzed in mouse lungs (n=80) exposed to 0, 10, 20, 40, or 80µg of MWCNT by pharyngeal aspiration at 7 and 56days post-exposure using quantitative PCR assays. At 7 and 56days post-exposure, a set of 7 genes and a set of 11 genes, respectively, showed differential expression in the lungs of mice exposed to MWCNT vs. the control group. Additionally, these significant genes could separate the control group from the treated group over the time series in a hierarchical gene clustering analysis. Furthermore, 4 genes from these two sets of significant genes, coiled-coil domain containing-99 (Ccdc99), muscle segment homeobox gene-2 (Msx2), nitric oxide synthase-2 (Nos2), and wingless-type inhibitory factor-1 (Wif1), showed significant mRNA expression perturbations at both time points. It was also found that the expression changes of these 4 overlapping genes at 7days post-exposure were attenuated at 56days post-exposure. Ingenuity Pathway Analysis (IPA) found that several carcinogenic-related signaling pathways and carcinogenesis itself were associated with both the 7 and 11 gene signatures. Taken together, this study identifies that MWCNT exposure affects a subset of lung cancer biomarkers in mouse lungs.

Genotoxicity of carbon nanofibers: are they potentially more or less dangerous than carbon nanotubes or asbestos?

The production of carbon nanofibers and nanotubes (CNF/CNT) and their composite products is increasing globally. CNF are generating great interest in industrial sectors such as energy production and electronics, where alternative materials may have limited performance or are produced at a much higher cost. However, despite the increasing industrial use of carbon nanofibers, information on their potential adverse health effects is limited. In the current study, we examine the cytotoxic and genotoxic potential of carbon-based nanofibers (Pyrograf®-III) and compare this material with the effects of asbestos fibers (crocidolite) or single-walled carbon nanotubes (SWCNT). The genotoxic effects in the lung fibroblast (V79) cell line were examined using two complementary assays: the comet assay and micronucleus (MN) test. In addition, we utilized fluorescence in situ hybridization to detect the chromatin pan-centromeric signals within the MN indicating their origin by aneugenic (chromosomal malsegregation) or clastogenic (chromosome breakage) mechanisms. Cytotoxicity tests revealed a concentration- and time-dependent loss of V79 cell viability after exposure to all tested materials in the following sequence: asbestos>CNF>SWCNT. Additionally, cellular uptake and generation of oxygen radicals was seen in the murine RAW264.7 macrophages following exposure to CNF or asbestos but not after administration of SWCNT. DNA damage and MN induction were found after exposure to all tested materials with the strongest effect seen for CNF. Finally, we demonstrated that CNF induced predominantly centromere-positive MN in primary human small airway epithelial cells (SAEC) indicating aneugenic events. Further investigations are warranted to elucidate the possible mechanisms involved in CNF-induced genotoxicity.

Mechanisms of pulmonary toxicity and medical applications of carbon nanotubes: Two faces of Janus?

Nanotechnology is an emerging science involving manipulation of materials at the nanometer scale. There are several exciting prospects for the application of engineered nanomaterials in medicine. However, concerns over adverse and unanticipated effects on human health have also been raised. In fact, the same properties that make engineered nanomaterials attractive from a technological and biomedical perspective could also make these novel materials harmful to human health and the environment. Carbon nanotubes are cylinders of one or several coaxial graphite layer(s) with a diameter in the order of nanometers, and serve as an instructive example of the Janus-like properties of nanomaterials. Numerous in vitro and in vivo studies have shown that carbon nanotubes and/or associated contaminants or catalytic materials that arise during the production process may induce oxidative stress and prominent pulmonary inflammation. Recent studies also suggest some similarities between the pathogenic properties of multi-walled carbon nanotubes and those of asbestos fibers. On the other hand, carbon nanotubes can be readily functionalized and several studies on the use of carbon nanotubes as versatile excipients for drug delivery and imaging of disease processes have been reported, suggesting that carbon nanotubes may have a place in the armamentarium for treatment and monitoring of cancer, infection, and other disease conditions. Nanomedicine is an emerging field that holds great promise; however, close attention to safety issues is required to ensure that the opportunities that carbon nanotubes and other engineered nanoparticles offer can be translated into feasible and safe constructs for the treatment of human disease.

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

Hard metal or cemented carbide consists of a mixture of tungsten carbide (WC) (85%) and metallic cobalt (Co) (5-15%). WC-Co is considered to be potentially carcinogenic to humans. However, no comparison of the adverse effects of nano-sized WC-Co particles is available to date. In the present study, we compared the ability of nano- and fine-sized WC-Co particles to form free radicals and propensity to activate the transcription factors, AP-1 and NF-kappaB, along with stimulation of mitogen-activated protein kinase (MAPK) signaling pathways in a mouse epidermal cell line (JB6 P(+)). Our results demonstrated that nano-WC-Co generated a higher level of hydroxyl radicals, induced greater oxidative stress, as evidenced by a decrease of GSH levels, and caused faster JB6 P(+) cell growth/proliferation than observed after exposure of cells to fine WC-Co. In addition, nano-WC-Co activated AP-1 and NF-kappaB more efficiently in JB6(+/+) cells as compared to fine WC-Co. Experiments using AP-1-luciferase reporter transgenic mice confirmed the activation of AP-1 by nano-WC-Co. Nano- and fine-sized WC-Co particles also stimulated MAPKs, including ERKs, p38, and JNKs with significantly higher potency of nano-WC-Co. Finally, co-incubation of the JB6(+/+) cells with N-acetyl-cysteine decreased AP-1 activation and phosphorylation of ERKs, p38 kinase, and JNKs, thus suggesting that oxidative stress is involved in WC-Co-induced toxicity and AP-1 activation.

Oxidative stress and inflammatory response in dermal toxicity of single-walled carbon nanotubes.

Single-walled carbon nanotubes (SWCNT) represent a novel material with unique electronic and mechanical properties. The extremely small size ( approximately 1 nm diameter) renders their chemical and physical properties unique. A variety of different techniques are available for the production of SWCNT; however, the most common is via the disproportionation of gaseous carbon molecules supported on catalytic iron particles (high-pressure CO conversion, HiPCO). The physical nature of SWCNT may lead to dermal penetration following deposition on exposed skin. This dermal deposition provides a route of exposure which is important to consider when evaluating SWCNT toxicity. The dermal effects of SWCNT are largely unknown. We hypothesize that SWCNT may be toxic to the skin. We further hypothesize that SWCNT toxicity may be dependent upon the metal (particularly iron) content of SWCNT via the metal's ability to interact with the skin, initiate oxidative stress, and induce redox-sensitive transcription factors thereby affecting/leading to inflammation. To test this hypothesis, the effects of SWCNT were assessed both in vitro and in vivo using EpiDerm FT engineered skin, murine epidermal cells (JB6 P+), and immune-competent hairless SKH-1 mice. Engineered skin exposed to SWCNT showed increased epidermal thickness and accumulation and activation of dermal fibroblasts which resulted in increased collagen as well as release of pro-inflammatory cytokines. Exposure of JB6 P+ cells to unpurified SWCNT (30% iron) resulted in the production of ESR detectable hydroxyl radicals and caused a significant dose-dependent activation of AP-1. No significant changes in AP-1 activation were detected when partially purified SWCNT (0.23% iron) were introduced to the cells. However, NFkappaB was activated in a dose-dependent fashion by exposure to both unpurified and partially purified SWCNT. Topical exposure of SKH-1 mice (5 days, with daily doses of 40 microg/mouse, 80 microg/mouse, or 160 microug/mouse) to unpurified SWCNT caused oxidative stress, depletion of glutathione, oxidation of protein thiols and carbonyls, elevated myeloperoxidase activity, an increase of dermal cell numbers, and skin thickening resulting from the accumulation of polymorphonuclear leukocytes (PMNs) and mast cells. Altogether, these data indicated that topical exposure to unpurified SWCNT, induced free radical generation, oxidative stress, and inflammation, thus causing dermal toxicity.

Nanoparticle inhalation impairs endothelium-dependent vasodilation in subepicardial arterioles.

Exposure to fine particulate matter (PM, mean aerodynamic diameter

Increased accumulation of neutrophils and decreased fibrosis in the lung of NADPH oxidase-deficient C57BL/6 mice exposed to carbon nanotubes.

Single-walled carbon nanotubes (SWCNT) have been introduced into a large number of new technologies and consumer products. The combination of their exceptional features with very broad applications raised concerns regarding their potential health effects. The prime target for SWCNT toxicity is believed to be the lung where exposure may occur through inhalation, particularly in occupational settings. Our previous work has demonstrated that SWCNT cause robust inflammatory responses in rodents with very early termination of the acute phase and rapid onset of chronic fibrosis. Timely elimination of polymorphonuclear neutrophils (PMNs) through apoptosis and their subsequent clearance by macrophages is a necessary stage in the resolution of pulmonary inflammation whereby NADPH oxidase contributes to control of apoptotic cell death and clearance of PMNs. Thus, we hypothesized that NADPH oxidase may be an important regulator of the transition from the acute inflammation to the chronic fibrotic stage in response to SWCNT. To experimentally address the hypothesis, we employed NADPH oxidase-deficient mice which lack the gp91(phox) subunit of the enzymatic complex. We found that NADPH oxidase null mice responded to SWCNT exposure with a marked accumulation of PMNs and elevated levels of apoptotic cells in the lungs, production of pro-inflammatory cytokines, decreased production of the anti-inflammatory and pro-fibrotic cytokine, TGF-beta, and significantly lower levels of collagen deposition, as compared to C57BL/6 control mice. These results demonstrate a role for NADPH oxidase-derived reactive oxygen species in determining course of pulmonary response to SWCNT.

Individualized survival and treatment response predictions for breast cancers using phospho-EGFR, phospho-ER, phospho-HER2/neu, phospho-IGF-IR/In, phospho-MAPK, and phospho-p70S6K proteins.

The development and progression of breast cancer involves the activation of numerous protein kinases, and the change in phosphorylation is a hallmark of protein kinase activation. In this study, we identified a comprehensive profile to predict individual breast cancer patients' survival and treatment responses using the Random Committee algorithm. The profile incorporated a subset of phosphorylated signal protein expressions and several selected clinical factors of breast cancer. The parameters of our profile were identified by supervised feature selection algorithms, Gain Ratio Attribute Evaluation and Relief. The results showed that the overall accuracy of survival prediction reached 92.3% for individual breast cancer patients with the use of the expression profiles of phospho-EGFR, phospho-ER, phospho-HER2/neu, phospho-IGFIR/In, phospho-MAPK, and phospho-p70S6K plus the selected clinical factors. The results also indicated that the overall accuracy of treatment response prediction was 92.6% with the use of the level of phospho-EGFR, phospho-ER, phospho-HER2/neu, phospho-MAPK, and phospho-p70S6K plus the selected clinical information. The prediction system combines multiple signal protein activation profiles and relevant clinical information, and provides a unique guideline to aid individualized decision-making in the clinical management of breast cancer.

Mechanistically identified suitable biomarkers of exposure, effect, and susceptibility for silicosis and coal-worker's pneumoconiosis: a comprehensive review.

Clinical detection of silicosis is currently dependent on radiological and lung function abnormalities, both late manifestations of disease. Markers of prediction and early detection of pneumoconiosis are imperative for the implementation of timely intervention strategies. Understanding the underlying mechanisms of the etiology of coal workers pneumoconiosis (CWP) and silicosis was essential in proposing numerous biomarkers that have been evaluated to assess effects following exposure to crystalline silica and/or coal mine dust. Human validation studies have substantiated some of these proposed biomarkers and argued in favor of their use as biomarkers for crystalline silica- and CWP-induced pneumoconiosis. A number of "ideal" biological markers of effect were identified, namely, Clara cell protein-16 (CC16) (serum), tumor necrosis factor-alpha (TNF-alpha) (monocyte release), interleukin-8 (IL-8) (monocyte release), reactive oxygen species (ROS) measurement by chemiluminescence (neutrophil release), 8-isoprostanes (serum), total antioxidant levels measured by total equivalent antioxidant capacity (TEAC), glutathione, glutathione peroxidase activity, glutathione S-transferase activity, and platelet-derived growth factor (PDGF) (serum). TNF-alpha polymorphism (blood cellular DNA) was identified as a biomarker of susceptibility. Further studies are planned to test the validity and feasibility of these biomarkers to detect either high exposure to crystalline silica and early silicosis or susceptibility to silicosis in gold miners in South Africa.

Direct and indirect effects of single walled carbon nanotubes on RAW 264.7 macrophages: role of iron.

Single-walled carbon nanotubes (SWCNT), nano-cylinders with an extremely small diameter (1-2 nm) and high aspect ratio, have unique physico-chemical, electronic and mechanical properties and may exhibit unusual interactions with cells and tissues, thus necessitating studies of their toxicity and health effects. Manufactured SWCNT usually contain significant amounts of iron that may act as a catalyst of oxidative stress. Because macrophages are the primary responders to different particles that initiate and propagate inflammatory reactions and oxidative stress, we utilized two types of SWCNT: (1) iron-rich (non-purified) SWCNT (26 wt.% of iron) and (2) iron-stripped (purified) SWCNT (0.23 wt.% of iron) to study their interactions with RAW 264.7 macrophages. Ultrasonication resulted in predominantly well-dispersed and separated SWCNT strands as evidenced by scanning electron microscopy. Neither purified nor non-purified SWCNT were able to generate intracellular production of superoxide radicals or nitric oxide in RAW 264.7 macrophages as documented by flow-cytometry and fluorescence microscopy. SWCNT with different iron content displayed different redox activity in a cell-free model system as revealed by EPR-detectable formation of ascorbate radicals resulting from ascorbate oxidation. In the presence of zymosan-stimulated RAW 264.7 macrophages, non-purified iron-rich SWCNT were more effective in generating hydroxyl radicals (documented by EPR spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide, DMPO) than purified SWCNT. Similarly, EPR spin-trapping experiments in the presence of zymosan-stimulated RAW 264.7 macrophages showed that non-purified SWCNT more effectively converted superoxide radicals generated by xanthine oxidase/xanthine into hydroxyl radicals as compared to purified SWCNT. Iron-rich SWCNT caused significant loss of intracellular low molecular weight thiols (GSH) and accumulation of lipid hydroperoxides in both zymosan-and PMA-stimulated RAW 264.7 macrophages. Catalase was able to partially protect macrophages against SWCNT induced elevation of biomarkers of oxidative stress (enhancement of lipid peroxidation and GSH depletion). Thus, the presence of iron in SWCNT may be important in determining redox-dependent responses of macrophages.

Interaction between primary alveolar macrophages and primary alveolar type II cells under basal conditions and after lipopolysaccharide or quartz exposure.

Intercellular communications between alveolar macrophages (AM) and alveolar epithelial type II (TII) cells have been suggested to be important in cellular responses. The main objective of this study was to improve our understanding of the interactions between AM and TII cells that might occur in the lung. In the present investigation, this interaction was studied under different interaction conditions (transwell or mixed coculture) and different exposure conditions (basal, lipopolysaccharide [LPS] exposure, or silica exposure). Studies also attempted different approaches to identify specific mediator(s) involved in this interaction. The following findings were made: (1) Surfactant released from TII cells appears to exert an inhibitory effect on AM activity. (2) Basal transwell coculture conditions are better than mixed coculture conditions to study AM/TII cell interactions, since the inhibitory effect of the surfactant in the transwell coculture is minimized. (3) AM/TII cell interaction is dependent on cell culture (transwell vs mixed) and exposure conditions. (4) Oxidants, tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, prostaglandins, and leukotrienes probably do not independently affect the AM/TII intercellular interaction; instead, they appear to indirectly modulate the complex pathways of AM/TII communication.

Lung dosimetry and risk assessment of nanoparticles: evaluating and extending current models in rats and humans.

Risk assessment of occupational exposure to nanomaterials is needed. Human data are limited, but quantitative data are available from rodent studies. To use these data in risk assessment, a scientifically reasonable approach for extrapolating the rodent data to humans is required. One approach is allometric adjustment for species differences in the relationship between airborne exposure and internal dose. Another approach is lung dosimetry modeling, which provides a biologically-based, mechanistic method to extrapolate doses from animals to humans. However, current mass-based lung dosimetry models may not fully account for differences in the clearance and translocation of nanoparticles. In this article, key steps in quantitative risk assessment are illustrated, using dose-response data in rats chronically exposed to either fine or ultrafine titanium dioxide (TiO2), carbon black (CB), or diesel exhaust particulate (DEP). The rat-based estimates of the working lifetime airborne concentrations associated with 0.1% excess risk of lung cancer are approximately 0.07 to 0.3 mg/m3 for ultrafine TiO2, CB, or DEP, and 0.7 to 1.3 mg/m3 for fine TiO2. Comparison of observed versus model-predicted lung burdens in rats shows that the dosimetry models predict reasonably well the retained mass lung burdens of fine or ultrafine poorly soluble particles in rats exposed by chronic inhalation. Additional model validation is needed for nanoparticles of varying characteristics, as well as extension of these models to include particle translocation to organs beyond the lungs. Such analyses would provide improved prediction of nanoparticle dose for risk assessment.