Distribution of molybdenum in soft tissues and blood of rats after intratracheal instillation of molybdenum(IV) sulfide nano- and microparticles

There is still little literature data on the toxicity and safety of the commonly used molybdenum (Mo) disulfide which is present in the working as well as living environments. Thus, an experiment was carried out involving rats, with single and repeated intratracheal exposure (in the latter case, 7 administrations at 2-week intervals with the analysis performed after 90 days) to lower (1.5 mg Mo kg-1 b.w.) and higher (5 mg Mo kg-1 b.w.) doses of molybdenum(IV) sulfide nanoparticles (MoS2-NPs) and microparticles (MoS2-MPs). The analysis of Mo concentrations in the tail and heart blood as well as in soft tissues (lung, liver, spleen, brain), after mineralization and bioimaging, was meant to facilitate an assessment of its accumulation and potential effects on the body following short- and long-term exposure. The multi-compartment model with an exponential curve of Mo concentration over time with different half-lives for the distribution and elimination phases of MoS2-MPs and MoS2-NPs was observed. After 24 h of exposure, a slight increase in Mo concentration in blood was observed. Next, Mo concentration indicated a decrease in blood concentration from 24 h to day 14 (the Mo concentration before the second administration), below the pre-exposure concentration. The next phase was linear, less abrupt and practically flat, but with an increasing trend towards the end of the experiment. Significantly higher Mo concentrations in MoS2-NPs and MoS2-MPs was found in the lungs of repeatedly exposed rats compared to those exposed to a single dose. The analysis of Mo content in the liver and the spleen tissue showed a slightly higher concentration for MoS2-NPs compared to MoS2-MPs. The results for the brain were below the calculated detection limit. Results were consistent with results obtained by bioimaging technique.

An optimized protocol for the generation and monitoring of conditional orthotopic lung cancer in the KP mouse model using an adeno-associated virus vector compatible with biosafety level 1

BACKGROUND

The inducible Kras/p53 lung adenocarcinoma mouse model, which faithfully recapitulates human disease, is routinely initiated by the intratracheal instillation of a virus-based Cre recombinase delivery system. Handling virus-based delivery systems requires elevated biosafety levels, e.g., biosafety level 2 (BSL-2). However, in experimental animal research facilities, following exposure to viral vectors in a BSL-2 environment, rodents may not be reclassified to BSL-1 according to standard practice, preventing access to small animal micro-computed tomography (micro-CT) scanners that are typically housed in general access areas such as BSL-1 rooms. Therefore, our goal was to adapt the protocol so that the Cre-induced KP mouse model could be handled under BSL-1 conditions during the entire procedure.

RESULTS

The Kras-Lox-STOP-Lox-G12D/p53 flox/flox (KP)-based lung adenocarcinoma mouse model was activated by intratracheal instillation of either an adenoviral-based or a gutless, adeno-associated viral-based Cre delivery system. Tumor growth was monitored over time by micro-CT. We have successfully substituted the virus-based Cre delivery system with a commercially available, gutless, adeno-associated, Cre-expressing vector that allows the KP mouse model to be handled and imaged in a BSL-1 facility. By optimizing the anesthesia protocol and switching to a microscope-guided vector instillation procedure, productivity was increased and procedure-related complications were significantly reduced. In addition, repeated micro-CT analysis of individual animals allowed us to monitor tumor growth longitudinally, dramatically reducing the number of animals required per experiment. Finally, we documented the evolution of tumor volume for different doses, which revealed that individual tumor nodules induced by low-titer AAV-Cre transductions can be monitored over time by micro-CT.

CONCLUSION

Modifications to the anesthesia and instillation protocols increased the productivity of the original KP protocol. In addition, the switch to a gutless, adeno-associated, Cre-expressing vector allowed longitudinal monitoring of tumor growth under BSL-1 conditions, significantly reducing the number of animals required for an experiment, in line with the 3R principles.

Difference in carcinogenicities of two different vapor grown carbon fibers with different physicochemical characteristics induced by intratracheal instillation in rats

BACKGROUND

Carbon fibers are high aspect ratio structures with diameters on the submicron scale. Vapor grown carbon fibers are contained within multi-walled carbon tubes, with VGCF™-H commonly applied as a conductive additive in lithium-ion batteries. However, several multi-walled carbon fibers, including MWNT-7, have been reported to induce lung carcinogenicity in rats. This study investigated the carcinogenic potential of VGCF™-H fibers in F344 rats of both sexes with the vapor grown carbon fibers VGCF™-H and MWNT-7 over 2 years. The carbon fibers were administered to rats by intratracheal instillation at doses of 0, 0.016, 0.08, and 0.4 mg/kg (total doses of 0, 0.128, 0.64, and 3.2 mg/kg) once per week for eight weeks and the rats were observed for up to 2 years after the first instillation.

RESULTS

Histopathological examination showed the induction of malignant mesothelioma on the pleural cavity with dose-dependent increases observed at 0, 0.128, 0.64, and 3.2 mg/kg in rats of both sexes that were exposed to MWNT-7. On the other hand, only two cases of pleural malignant mesothelioma were observed in the VGCF™-H groups; both rats that received 3.2 mg/kg in male. The animals in the MWNT-7 groups either died or became moribund earlier than those in the VGCF™-H groups, which is thought related to the development of malignant mesothelioma. The survival rates were higher in the VGCF™-H group, and more carbon fibers were observed in the pleural lavage fluid (PLF) of the MWNT-7 groups. These results suggest that malignant mesothelioma is related to the transfer of carbon fibers into the pleural cavity.

CONCLUSIONS

The intratracheal instillation of MWNT-7 clearly led to carcinogenicity in both male and female rats at all doses. The equivocal evidence for carcinogenic potential that was observed in male rats exposed to VGCF™-H was not seen in the females. The differences in the carcinogenicities of the two types of carbon fibers are thought due to differences in the number of carbon fibers reaching the pleural cavity. The results indicate that the carcinogenic activity of VGCF™-H is lower than that of MWNT-7.

Intratracheally administered iron oxide nanoparticles induced murine lung inflammation depending on T cells and B cells

Iron oxide nanoparticles (Fe₂O₃ NPs), produced in track traffic system and a wide range of industrial production, poses a great threat to human health. However, there is little research about the mechanism of Fe₂O₃ NPs toxicity on respiratory system. Rag1^-/- mice which lack functional T and B cells were intratracheally challenged with Fe₂O₃ NPs, and interleukin (IL)-33 as an activator of group 2 innate lymphoid cells (ILC2s) to observe ILC2s changes. The lung inflammatory response to Fe₂O₃ NPs was alleviated in Rag1^-/- mice compared with wild type (WT) mice. Infiltration of inflammatory cells and collagen deposition in tissue, leukocyte numbers (neutrophils, macrophages and lymphocytes), cytokine levels, such as IL-6, IL-13 and thymic stromal lymphopoietin (TSLP), and expression of Toll-like receptor (TLR)2, TLR4, and downstream myeloid differentiation factor (MyD)88, nuclear factor (NF)-κB and tumor necrosis factor (TNF)-α were decreased in lungs. Fe₂O₃ NPs markedly elevated ILC2s compared with the control, but ILC2s numbers were much lower compared with IL-33 in both WT and Rag1^-/- mice. Furthermore, ILC2s amounts were strongly greater in Rag1^-/- mice than WT mice. Our results suggested that Fe₂O₃ NPs induced sub-chronic pulmonary inflammation, which is majorly dependent on T cells and B cells rather than ILC2s.

Mechanisms of pulmonary disease in F344 rats after workplace-relevant inhalation exposure to cross-linked water-soluble acrylic acid polymers

BACKGROUND

Recently in Japan, six workers at a chemical plant that manufactures resins developed interstitial lung diseases after being involved in loading and packing cross-linked water-soluble acrylic acid polymers (CWAAPs). The present study focused on assessing lung damage in rats caused by workplace-relevant inhalation exposure to CWAAP and investigated the molecular and cellular mechanisms involved in lung lesion development.

METHODS

Using a whole-body inhalation exposure system, male F344 rats were exposed once to 40 or 100 mg/m³ of CWAAP-A for 4 h or to 15 or 40 mg/m³ of CWAAP-A for 4 h per day once per week for 2 months (9 exposures). In a separate set of experiments, male F344 rats were administered 1 mg/kg CWAAP-A or CWAAP-B by intratracheal instillation once every 2 weeks for 2 months (5 doses). Lung tissues, mediastinal lymph nodes, and bronchoalveolar lavage fluid were collected and subjected to biological and histopathological analyses.

RESULTS

A single 4-h exposure to CWAAP-A caused alveolar injury, and repeated exposures resulted in regenerative changes in the alveolar epithelium with activation of TGFβ signaling. During the recovery period after the last exposure, some alveolar lesions were partially healed, but other lesions developed into alveolitis with fibrous thickening of the alveolar septum. Rats administered CWAAP-A by intratracheal instillation developed qualitatively similar pulmonary pathology as rats exposed to CWAAP-A by inhalation. At 2 weeks after intratracheal instillation, rats administered CWAAP-B appeared to have a slightly higher degree of lung lesions compared to rats administered CWAAP-A, however, there was no difference in pulmonary lesions in the CWAAP-A and CWAAP-B exposed rats examined 18 weeks after administration of these materials.

CONCLUSIONS

The present study reports our findings on the cellular and molecular mechanisms of pulmonary disease in rats after workplace-relevant inhalation exposure to CWAAP-A. This study also demonstrates that the lung pathogenesis of rats exposed to CWAAP-A by systemic inhalation was qualitatively similar to that of rats administered CWAAP-A by intratracheal instillation.

Toxicokinetic study following intratracheal instillation or oral gavage of two [7Be]-tagged carbon black samples

BACKGROUND

The toxicokinetic behaviour of nanostructured particles following pulmonary or oral deposition is of great scientific interest. In this toxicokinetic study, following the general principles of OECD TG 417, the systemic availability of carbon black, a nanostructured material consisting of agglomerated aggregates was characterised.

METHODS

Each of two grades of beryllium-7 labelled carbon black (Monarch® 1000, oxidized and Printex® 90; untreated) was administered either intratracheally or orally to adult rats. Independent of route, rats received a single dose of approximately 0.3 mg radiolabelled carbon black. A total of 12 rats were treated per grade and per exposure route: 4 females each for feces/urine/organs and serial blood kinetics; 4 males for organs. At necropsy, the complete suite of organs was analysed for females, but only the lungs, liver, kidney, reproductive organs for males.

RESULTS

In the pulmonarily exposed animals, ⁷Be-Monarch® 1000 and ⁷Be-Printex® 90 was detected in feces in the first 3 days after treatment at significant levels, i.e. 17.6% and 8.2%, respectively. In urine, small percentages of 6.7% and 0.4% were observed, respectively. In blood, radioactivity, representative of carbon black was within the background noise of the measurement method. At necropsy, 20 days post-instillation, both test items were practically exclusively found in lungs (75.1% and 91.0%, respectively) and in very small amounts (approximately 0.5%) in the lung-associated lymph nodes (LALN). In the other organs/tissues the test item was not detectable. BAL analyses indicated that carbon black particles were completely engulfed by alveolar macrophages. In orally exposed animals, 98% (⁷Be-Monarch® 1000) and 99% (⁷Be-Printex® 90) of the measured radioactivity was detected in feces. Excretion was complete within the first 3 days following treatment. 1.3% and 0.5% of measured activity was attributable to urine in animals that received ⁷Be-Monarch® 1000 and ⁷Be-Printex® 90, respectively. Radioactivity was absent in blood and other organs and tissues.

CONCLUSION

Radioactivity, representative of carbon black, was not detected beyond the experimentally defined limit of quantitation systemically after deposition in lungs or stomach in rats. Under these experimental conditions, the two CB samples were not shown to translocate beyond the lung or the GI tract into the blood compartment.

Sublethal pulmonary toxicity screening of silica nanoparticles in rats after direct intratracheal instillation

The present aimed to characterize the toxicity of silica nanoparticles in Sprague Dawley rats and determine the dose levels for a repeated-dose toxicity study. Silica nanoparticles (SiO2, 20 nm and 50 nm) were administered as a single intratracheal instillation of standardized SiO2 20 nm (low dose, 200 µg/mL; high dose, 400 µg/mL) and 50 nm (low dose, 200 µg/mL; high dose, 400 µg/mL). Each group consisted of five male rats. We documented the mortality rate, clinical signs, body weight, bronchoalveolar lavage fluid analysis, hematological values, serum chemistry values, organ weight, gross findings at necropsy, and histopathological assessments. Rats treated with 200 µg/mL and 400 µg/mL SiO2 50 nm exhibited a decreased mean corpuscular volume, while those treated with 400 µg/mL of SiO2 50 nm showed increases in absolute monocyte and absolute lymphocyte count as well as prothrombin time. In addition, rats treated with 400 µg/mL SiO2 20 nm and 50 nm presented reduced creatinine, alanine aminotransferase, and sodium levels. Therefore, a single intratracheal instillation of SiO2 20 nm and 50 nm elicited no toxicity up to a dose of 400 µg/mL, and the approximate lethal dose of this test substance exceeded 400 µg/mL in male Sprague Dawley rats under the present experimental conditions.

Two-year intermittent exposure of a multiwalled carbon nanotube by intratracheal instillation induces lung tumors and pleural mesotheliomas in F344 rats

BACKGROUND

A mounting number of studies have been documenting the carcinogenic potential of multiwalled carbon nanotubes (MWCNTs); however, only a few studies have evaluated the pulmonary carcinogenicity of MWCNTs in vivo. A 2-year inhalation study demonstrated that MWNT-7, a widely used MWCNT, was a pulmonary carcinogen in rats. In another 2-year study, rats administered MWNT-7 by intratracheal instillation at the beginning of the experimental period developed pleural mesotheliomas but not lung tumors. To obtain data more comparable with rats exposed to MWNT-7 by inhalation, we administered MWNT-7 to F344 rats by intratracheal instillation once every 4-weeks over the course of 2 years at 0, 0.125, and 0.5 mg/kg body weight, allowing lung burdens of MWNT-7 to increase over the entire experimental period, similar to the inhalation study.

RESULTS

Absolute and relative lung weights were significantly elevated in both MWNT-7-treated groups. Dose- and time-dependent toxic effects in the lung and pleura, such as inflammatory, fibrotic, and hyperplastic lesions, were found in both treated groups. The incidences of lung carcinomas, lung adenomas, and pleural mesotheliomas were significantly increased in the high-dose group compared with the control group. The pleural mesotheliomas developed mainly at the mediastinum. No MWNT-7-related neoplastic lesions were noted in the other organs. Cytological and biochemical parameters of the bronchoalveolar lavage fluid (BALF) were elevated in both treated groups. The lung burden of MWNT-7 was dose- and time-dependent, and at the terminal necropsy, the average value was 0.9 and 3.6 mg/lung in the low-dose and high-dose groups, respectively. The number of fibers in the pleural cavity was also dose- and time-dependent.

CONCLUSIONS

Repeated administration of MWNT-7 by intratracheal instillation over the 2 years indicates that MWNT-7 is carcinogenic to both the lung and pleura of rats, which differs from the results of the 2 carcinogenicity tests by inhalation or intratracheal instillation.

Histopathological changes in the lungs of rats instilled with Korean chrysotile

To evaluate the pulmonary toxicity of Korean chrysotile (KC), 1 or 2 mg of KC (low- and high-concentration groups, respectively) was instilled in the lungs of Sprague-Dawley rats by a single intratracheal instillation. The lungs were examined using a light microscope at several time points (5 days, 5 weeks, and 10 weeks). Up to 10 weeks after KC instillation, differences were observed in the pathological reactions and ultimately in lung recovery between the two groups. At 5 days after KC instillation, lung weight increased and severe bronchiolitis obliterans developed in proportion to the KC concentration administered. From 5 to 10 weeks after KC administration, the lung weight of the low-concentration group increased and bronchiolitis obliterans worsened. In the high-concentration group, the lung weight and the severity of bronchiolitis obliterans at 10 weeks after administration of KC declined compared to those at 5 weeks. In conclusion, the effects of KC on lung tissue were initially found to be more influenced by the amount of fiber, but over time, the effects were influenced by the residual fibrous material in the lung tissue and its biodurability.

Exposure effects of inhaled nickel nanoparticles on the male reproductive system via mitochondria damage

Nickel nanoparticles (Ni NPs) have a wide range of application prospects, however there is still a lack of their safety evaluation for the reproductive system. Nowadays, male reproductive health has been widely concerned for the increasing incidence of male infertility. To investigate the male reproductive toxicity induced by Ni NPs and its relation with the mitochondrial fission and mitophagy, male mice were administered with or without 5, 15, and 45 mg/kg of Ni NPs by intratracheal instillation. At the end of intervention, sex hormone level, sperm abnormality rate, pathological morphology of testis, cell apoptosis and the expression levels of Drp1, Pink1 and Parkin proteins in testis tissues were detected. The results indicated that the rate of sperm deformity and serum levels of reproductive hormones increased obviously with the increasing concentrations of Ni NPs. Testicular spermatogenic cells were damaged and the number of apoptotic cells increased significantly. Furthermore, the expressions of key proteins (Drp1, Pink1 and Parkin) related to mitochondrial fission/autophagy in testis tissues also increased after exposure to Ni NPs. Collectively, mitochondria damage may play an important role in male mice reproductive toxicity induced by the intratracheal instillation of Ni NPs.

No prominent toxicity of polyethylene microplastics observed in neonatal mice following intratracheal instillation to dams during gestational and neonatal period

Microplastics (MPs) have been recently recognized as a global environmental threat and its exposure as a risk factor to human health. Health effects through MPs exposure have been recently reported, especially through oral route of exposure. Since MPs could be exposed to humans through routes other than oral, this study was designed to evaluate whether MPs exposed through the inhalation route could be delivered to fetal mice and exhibit systemic toxicity. Polyethylene (PE) with 10-45 µm diameter were administered at 0 (distilled water, vehicle control), 6 (low administration), and 60 (high administration) µg/mouse/day to 3 pregnant dams per group from gestational day 9 to postnatal day (PND) 7 through intratracheal instillation. Dams and neonates were sacrificed at PND 7 and blood was collected. Various neonatal organs including brain, lung, heart, stomach, intestine, kidneys, and ovaries were collected for histopathological observation and weight measurement. No influence of PE-MPs administration was observed on the number of offsprings born, but the body and organs' weight were heavier overall in the high administration group of dams and neonates than the other groups with statistical significance achieved in the heart and spleen weight. Level of serum acetylcholinesterase and glutathione peroxidase activity was decreased in the high administration group of dams and neonates compared with the other groups. Lung was the organ with highest number of PE-MPs present in the both administration groups of dams, and PE-MPs were also detected in liver and intestine of the high administration dams. Whereas, PND7 neonates showed accountable numbers of PE-MPs only in kidneys of the high administration group. Overall, the present study indicates that PE-MPs instilled intratracheally could be delivered to neonates from dams. Even though adverse effects from PE-MPs exposure during pregnant and lactational period are less prominent on both dam and neonate, potential of second-generation toxicity could be considered for further investigation.

Intratracheally instillated diesel PM2.5 significantly altered the structure and composition of indigenous murine gut microbiota

A diverse and large community of gut microbiota reside in the intestinal tract of various organisms and play important roles in metabolism and immune homeostasis of its host. The disorders of microbiota-host interaction have been closely associated with numerous chronic inflammatory and metabolic diseases, including inflammatory bowel disease and type 2 diabetes. The accumulating evidence has shown that fine particulate matter (PM2.5) exposure contributes to the diabetes, atherosclerosis and inflammatory bowel diseases; however, few studies have explored the impact of inhaled diesel PM2.5 on gut microbiota in vivo. In this study, C57BL/6J mice were exposed to diesel PM2.5 for 14 days via intratracheal instillation, and colon tissues and feces were harvested for microbiota analysis. Using high-throughput sequencing technology, we observed that intratracheally instillated diesel PM2.5 significantly altered the gut microbiota diversity and community. At the phylum and genus levels, principal coordinate analysis (PCoA) and principal component analysis (PCA) indicated pronounced segregation of microbiota compositions, which were further confirmed by β diversity analysis. As the most affected phylum, Bacteroidetes was greatly diminished by diesel PM2.5. On the genus level, Escherichia, Parabacteroides, Akkermansia, and Oscillibacter were significantly elevated by diesel PM2.5 exposure. Our findings provided clear evidence that exposure to diesel PM2.5 via intratracheal instillation deteriorated the gastrointestinal (GI) tract and significantly altered the structure and composition of gut microbiota, which might subsequently contribute to the developmental abnormalities of inflammation, immunity and metabolism.

Biodistribution and pulmonary metabolic effects of silver nanoparticles in mice following acute intratracheal instillations

The respiratory tract is the route of entry for accidentally inhaled AgNPs, which can reach the lungs and redistribute to other main organs through systemic circulation. In the present work, we aimed to evaluate silver biodistribution and biological effects after 1 or 2 intratracheal instillations (IT) of two differently sized PVP-coated AgNPs (5 and 50 nm-3 mg/kg) and ionic silver (AgNO₃-1 mg/kg bw) in mice. Furthermore, nuclear magnetic resonance (NMR) metabolomics was applied to unveil pulmonary metabolic variations. Animals exposed to 5 nm AgNP (AgNP5) showed higher levels of ionic silver in organs, especially in the lung, spleen, kidney and liver, while animals exposed to 50 nm AgNP (AgNP50) showed higher levels of silver in the blood. Animals exposed to AgNP50 excreted higher amounts of silver than those exposed to AgNP5, which is consistent with higher tissue accumulation of silver in animals exposed to the latter. Lung metabolic profiling revealed several Ag-induced alterations in metabolites involved in different pathways, such as glycolysis and tricarboxylic acid (TCA) cycle, amino acid and phospholipid metabolism, and antioxidant defense. Notably, most of the metabolic changes observed after 1 IT were absent in animals subjected to 2 IT of AgNO₃, or reversed for AgNPs, suggesting adaptation mechanisms to cope with the initial insult and recover homeostasis. Graphical abstract.

Single intratracheal administration of cross-linked water-soluble acrylic acid polymer causes acute alveolo-interstitial inflammation and the subsequent fibrotic formation possibly via the TGF-β1 pathway in the lung of rats

In a Japanese chemical factory, a lung disease like pneumoconiosis appeared at a high rate among workers handling cross-linked water-soluble acrylic acid polymer (CWAAP). To our knowledge, no such case was known in the world until very recently. The present study was designed to elucidate the effect of single intratracheal CWAAP instillation on the lung of rats. The CWAAP group had a significant increase in relative lung weight accompanied by a significant elevation in the number of total cells, total protein concentrations, and myeloperoxidase concentrations in bronchoalveolar lavage fluid when compared to the control group. The histopathological study revealed acute lung inflammation with the destruction of alveoli. The factors promoting fibrosis, macrophages, TGF-β1, collagen and fibronectin vs. the factors suppressing fibrosis, matrix metalloproteinases were more powerfully driven in the CWAAP group, resultantly leading to fibrotic formation. In turn, we examined if acute lung inflammation and the subsequent fibrotic formation seen in the CWAAP group appeared in the other water-soluble polymer groups. Their histopathological findings were observed only in the polyacrylic acid sodium (PAAS), a monomer of CWAAP, group. The degree of inflammation and fibrogenesis was stronger in the CWAAP group than in the PAAS group. In conclusion, the present study demonstrated the induction of acute lung inflammation and the subsequent fibrotic formation by single intratracheal CWAAP instillation. The structural features of CWAAP that contains many carboxyl groups and cross-linked chains may be responsible for enhanced inflammation and fibrogenesis in the lung.

Assessment of acute toxicological effects of molybdenum(IV) disulfide nano- and microparticles after single intratracheal administration in rats

Despite growing applications of molybdenum(IV) sulfide (MoS₂) nano- and microparticles in their capacity as lubricants, data available on their safety are scarce. In this study the effect of MoS₂ nano- and microparticles after single intratracheal instillation in rats has been analyzed. MoS₂ suspensions were administered at the dose of 1.5 or 5 mg MoS₂/kg body weight. The analysis after 24 h and 7 days included: blood biochemical parameters, hematological parameters, bronchoalveolar lavage fluid (BALF) parameters with selected cytokines, a comet assay and histopathological examination. In the BALF cells isolated from animals exposed to both forms, numerous macrophages loaded with particles were observed. The hematological and biochemical parameters analyzed 24 h or 7 days after the exposure to both forms did not show any biologically meaningful changes. Comet assay results showed no genotoxic effect. The histopathological analysis of the lungs revealed inflammatory changes in the respiratory system of the treated animals, slightly stronger for the microsized form. The deposits of particles observed in the lung tissue up to 7 days after the instillation indicate their easy penetration through the epithelium and prolonged clearance. Concluding, no meaningful acute systemic effects were observed, however some pathological changes were noted in the lung tissue.

Biodistribution and histopathology studies of amphotericin B sodium deoxycholate sulfate formulation following intratracheal instillation in rat models

Aerosol inhalation of amphotericin B (AmB) can be a clinically compliant way to administer the drug directly to the pulmonary route for treatment as well as prophylaxis of invasive pulmonary aspergillosis (IPA). We report aerosol formulation of AmB using sodium deoxycholate sulfate (SDCS), a lipid carrier synthesized in-house using natural precursor deoxycholic acid. In vitro toxicity was determined by MTT assay. Biodistribution and histopathology in rats were evaluated in targeted organs including the lungs, kidneys, spleen, and liver. No toxicity was observed when lung and kidney cells treated with AmB-SDCS formulations up to 8 μg/mL and minimal toxicity at higher concentration 16 μg/mL, while the Fungizone®-like formulation induced toxicity to lung and kidney cells with viability decreasing from 86 to 41% and 100 to 49%, respectively, when compared with an equivalent concentration of AmB-SDCS. Renal and hepatic markers were raised for Fungizone®-like formulation-treated rats but not for AmB-SDCS formulations following 7 days of regular dosing by intratracheal instillation. AmB concentrations were highest in the lungs (5.4-8.3 μg/g) which were well above minimum inhibitory concentration (MIC) of all Aspergillus species. Plasma concentration was also above MIC (> 2 μg/mL) for all AmB-SDCS formulations in comparison with Fungizone®-like formulation. No evidence of abnormal histopathology was observed in the lungs, liver, spleen, and kidneys for all AmB-SDCS formulations but was observed for the group treated with Fungizone®-like formulation. It is concluded that AmB-SDCS formulations can be efficiently administered via intratracheal instillation with no evidence of toxicity and may find great value in the treatment as well as prophylaxis of IPA through inhalation route.

Particle characterization and toxicity in C57BL/6 mice following instillation of five different diesel exhaust particles designed to differ in physicochemical properties

Background

Diesel exhaust is carcinogenic and exposure to diesel particles cause health effects. We investigated the toxicity of diesel exhaust particles designed to have varying physicochemical properties in order to attribute health effects to specific particle characteristics. Particles from three fuel types were compared at 13% engine intake O₂ concentration: MK1 ultra low sulfur diesel (DEP13) and the two renewable diesel fuels hydrotreated vegetable oil (HVO13) and rapeseed methyl ester (RME13). Additionally, diesel particles from MK1 ultra low sulfur diesel were generated at 9.7% (DEP9.7) and 17% (DEP17) intake O₂ concentration. We evaluated physicochemical properties and histopathological, inflammatory and genotoxic responses on day 1, 28, and 90 after single intratracheal instillation in mice compared to reference diesel particles and carbon black.

Results

Moderate variations were seen in physical properties for the five particles: primary particle diameter: 15–22 nm, specific surface area: 152–222 m²/g, and count median mobility diameter: 55–103 nm. Larger differences were found in chemical composition: organic carbon/total carbon ratio (0.12–0.60), polycyclic aromatic hydrocarbon content (1–27 μg/mg) and acid-extractable metal content (0.9–16 μg/mg). Intratracheal exposure to all five particles induced similar toxicological responses, with different potency. Lung particle retention was observed in DEP13 and HVO13 exposed mice on day 28 post-exposure, with less retention for the other fuel types. RME exposure induced limited response whereas the remaining particles induced dose-dependent inflammation and acute phase response on day 1. DEP13 induced acute phase response on day 28 and inflammation on day 90. DNA strand break levels were not increased as compared to vehicle, but were increased in lung and liver compared to blank filter extraction control. Neutrophil influx on day 1 correlated best with estimated deposited surface area, but also with elemental carbon, organic carbon and PAHs. DNA strand break levels in lung on day 28 and in liver on day 90 correlated with acellular particle-induced ROS.

Conclusions

We studied diesel exhaust particles designed to differ in physicochemical properties. Our study highlights specific surface area, elemental carbon content, PAHs and ROS-generating potential as physicochemical predictors of diesel particle toxicity.

Pulmonary toxicity of silver vapours, nanoparticles and fine dusts: A review

Silver is used in a wide range of products, and during their production and use, humans may be exposed through inhalation. Therefore, it is critical to know the concentration levels at which adverse effects may occur. In rodents, inhalation of silver nanoparticles has resulted in increased silver in the lungs, lymph nodes, liver, kidney, spleen, ovaries, and testes. Reported excretion pathways of pulmonary silver are urinary and faecal excretion. Acute effects in humans of the inhalation of silver include lung failure that involved increased heart rate and decreased arterial blood oxygen pressure. Argyria-a blue-grey discoloration of skin due to deposited silver-was observed after pulmonary exposure in 3 individuals; however, the presence of silver in the discolorations was not tested. Argyria after inhalation seems to be less likely than after oral or dermal exposure. Repeated inhalation findings in rodents have shown effects on lung function, pulmonary inflammation, bile duct hyperplasia, and genotoxicity. In our evaluation, the range of NOAEC values was 0.11-0.75 mg/m³. Silver in the ionic form is likely more toxic than in the nanoparticle form but that difference could reflect their different biokinetics. However, silver nanoparticles and ions have a similar pattern of toxicity, probably reflecting that the effect of silver nanoparticles is primarily mediated by released ions. Concerning genotoxicity studies, we evaluated silver to be positive based on studies in mammalian cells in vitro and in vivo when considering various exposure routes. Carcinogenicity data are absent; therefore, no conclusion can be provided on this endpoint.

Airway exposure to TiO2 nanoparticles and quartz and effects on sperm counts and testosterone levels in male mice

Several types of engineered nanoparticles (ENP) have been shown to adversely affect male reproduction in rodent studies, but the airway route of exposure has been little investigated. This precludes adequate risk assessment of ENP exposure in occupational settings. Titanium dioxide nanoparticles (TiO₂ NP) have been shown to affect total sperm count in adult male mice after intravenous and oral administration. This study aimed to investigate whether also airway exposure would affect sperm counts in male mice. Mature C57BL/6J mice were intratracheally instilled with 63 μg of rutile nanosized TiO₂, once weekly for seven weeks. Respirable α-quartz (SRM1878a) was included at a similar dose level as a positive control for pulmonary inflammation. BALF cell composition showed neutrophil granulocyte influx as indication of pulmonary inflammation in animals exposed to TiO₂ NP and α-quartz, but none of the particle exposures affected weight of testes or the epididymis, sperm counts or plasma testosterone when assessed at termination of the study.

Oxidative effects of lungs in Wistar rats caused by long-term exposure to four kinds of China representative chrysotile

Chrysotile accounts for some 90% to 95% of all the asbestos used worldwide. Scientific evidences have shown that asbestos (including chrysotile) exposure is associated with increased rates of lung cancer, asbestosis, and mesothelioma. However, molecular mechanisms underlying the toxicity effects of chrysotile are not clear. This study evaluated the oxidative stress in chronic lung toxicity caused by the intratracheal instillation (IT) of four kinds China representative chrysotile once a month for 12 months in Wistar rats. These results indicated that chrysotile exposure led to an obvious increase in lung mass and slowed the growth of body mass. Inflammation and fibrosis were observed by hematoxylin-eosin (HE) staining. Exposure to chrysotile significantly increased the accumulation of reactive oxygen species (ROS) and the level of lipid peroxidation and decreased antioxidant capacity in lung tissues. Furthermore, 1-6-month chrysotile exposure activated heme oxygenase-1 (HO-1) and heat shock protein 70 (HSP70) expression, whereas 12-month exposure caused significant decreases of two-factor expression levels in XK and MN groups when compared to negative control group. Therefore, our results suggested that chronic chrysotile pulmonary injury in Wistar rats is triggered by oxidative damage. Meanwhile, the oxidative damage of MN and XK was stronger than that of SSX and AKS, and the difference of oxidative damage in four chrysotile could have been brought by its properties, morphology, chemical composition, and particle size. With all the above mentioned in view, we hope that the revealed data in the experiment could contribute to the progress of further researches on the toxicity and mechanism of chrysotile.

Pulmonary toxicity of two different multi-walled carbon nanotubes in rat: Comparison between intratracheal instillation and inhalation exposure

Multi-walled carbon nanotubes (MWCNTs), which vary in length, diameter, functionalization and specific surface area, are used in diverse industrial processes. Since these nanomaterials have a high aspect ratio and are biopersistant in the lung, there is a need for a rapid identification of their potential health hazard. We assessed in Sprague-Dawley rats the pulmonary toxicity of two pristine MWCNTs (the "long and thick" NM-401 and the "short and thin" NM-403) following either intratracheal instillation or 4-week inhalation in order to gain insights into the predictability and intercomparability of the two methods. The deposited doses following inhalation were lower than the instilled doses. Both types of carbon nanotube induced pulmonary neutrophil influx using both exposure methods. This influx correlated with deposited surface area across MWCNT types and means of exposure at two different time points, 1-3 days and 28-30 days post-exposure. Increased levels of DNA damage were observed across doses and time points for both exposure methods, but no dose-response relationship was observed. Intratracheal instillation of NM-401 induced fibrosis at the highest dose while lower lung deposited doses obtained by inhalation did not induce such lung pathology. No fibrosis was observed following NM-403 exposure. When the deposited dose was taken into account, sub-acute inhalation and a single instillation of NM-401 and NM-403 produced very similar inflammation and DNA damage responses. Our data suggest that the dose-dependent inflammatory responses observed after intratracheal instillation and inhalation of MWCNTs are similar and were predicted by the deposited surface area.

Usefulness of myeloperoxidase as a biomarker for the ranking of pulmonary toxicity of nanomaterials

BACKGROUND

In order to examine whether myeloperoxidase (MPO) can be a useful marker for evaluating the pulmonary toxicity of nanomaterials, we analyzed MPO protein in bronchoalveolar lavage fluid (BALF) samples obtained from previous examinations of a rat model. In those examinations we performed intratracheal instillation exposures (dose: 0.2-1.0 mg) and inhalation exposures (exposure concentration: 0.32-10.4 mg/m3) using 9 and 4 nanomaterials with different toxicities, respectively. Based on those previous studies, we set Nickel oxide nanoparticles (NiO), cerium dioxide nanoparticles (CeO2), multi wall carbon nanotubes with short or long length (MWCNT (S) and MWCNT (L)), and single wall carbon nanotube (SWCNT) as chemicals with high toxicity; and titanium dioxide nanoparticles (TiO2 (P90) and TiO2 (Rutile)), zinc oxide nanoparticles (ZnO), and toner with external additives including nanoparticles as chemicals with low toxicity. We measured the concentration of MPO in BALF samples from rats from 3 days to 6 months following a single intratracheal instillation, and from 3 days to 3 months after the end of inhalation exposure.

RESULTS

Intratracheal instillation of high toxicity NiO, CeO2, MWCNT (S), MWCNT (L), and SWCNT persistently increased the concentration of MPO, and inhalation of NiO and CeO2 increased the MPO in BALF. By contrast, intratracheal instillation of low toxicity TiO2 (P90), TiO2 (Rutile), ZnO, and toner increased the concentration of MPO in BALF only transiently, and inhalation of TiO2 (Rutile) and ZnO induced almost no increase of the MPO. The concentration of MPO correlated with the number of total cells and neutrophils, the concentration of chemokines for neutrophils (cytokine-induced neutrophil chemoattractant (CINC)-1 and heme oxygenase (HO)-1), and the activity of released lactate dehydrogenase (LDH) in BALF. The results from the receiver operating characteristics (ROC) for the toxicity of chemicals by the concentration of MPO proteins in the intratracheal instillation and inhalation exposures showed that the largest areas under the curves (AUC) s in both examinations occurred at 1 month after exposure.

CONCLUSION

These data suggest that MPO can be a useful biomarker for the ranking of the pulmonary toxicity of nanomaterials, especially at 1 month after exposure, in both intratracheal instillation and inhalation exposure.

Basic study of intratracheal instillation study of nanomaterials for the estimation of the hazards of nanomaterials

In order to examine the usefulness of intratracheal instillation of nanoparticles for the screening of the harmful effects of nanoparticles, we performed intratracheal instillation studies of nanomaterials on rats using different delivery devices and postures as a basic study. Multiwall carbon nanotubes (MWCNTs) with a geometric mean length and secondary diameter of 2.16 μm and 752 nm, respectively, were used as the nanomaterials. Male F344 rats were intratracheally exposed to 0.04 or 0.2 mg/rat of MWCNT, were dissected at 1 d and 3 d, and cell analyses of the bronchoalveolar lavage fluid (BALF) were analyzed. Two delivery devices were used for the intratracheal instillation of the MWCNTs: a gavage needle and a microsprayer aerolizer. Both induced neutrophil influx in the lung at 1 and 3 d, and there were no significant differences in neutrophil inflammation between the two delivery devices. The main distribution of pulmonary inflammation by both delivery devices was in the centrilobular spaces in the lung. Two postures were used: an angle of approximately 45 degrees and a standing posture on a board, both of which also induced pulmonary influx in BALF and pulmonary inflammation mainly in the centrilobular spaces, with no large difference in pulmonary inflammation between the two postures. Taken together, the differences in the delivery devices and postures of the rats in the intratracheal instillation did not affect the acute pulmonary toxicity of the nanomaterials.

Primary genotoxicity in the liver following pulmonary exposure to carbon black nanoparticles in mice

Background

Little is known about the mechanism underlying the genotoxicity observed in the liver following pulmonary exposure to carbon black (CB) nanoparticles (NPs). The genotoxicity could be caused by the presence of translocated particles or by circulating inflammatory mediators released during pulmonary inflammation and acute-phase response. To address this, we evaluated induction of pulmonary inflammation, pulmonary and hepatic acute-phase response and genotoxicity following exposure to titanium dioxide (TiO₂), cerium oxide (CeO₂) or CB NPs. Female C57BL/6 mice were exposed by intratracheal instillation, intravenous injection or oral gavage to a single dose of 162 μg NPs/mouse and terminated 1, 28 or 180 days post-exposure alongside vehicle control.

Results

Liver DNA damage assessed by the Comet Assay was observed after intravenous injection and intratracheal instillation of CB NPs but not after exposure to TiO₂ or CeO₂. Intratracheal exposure to NPs resulted in pulmonary inflammation in terms of increased neutrophils influx for all NPs 1 and 28 days post-exposure. Persistent pulmonary acute phase response was detected for all NPs at all three time points while only a transient induction of hepatic acute phase response was observed. All 3 materials were detected in the liver by enhanced darkfield microscopy up to 180 days post-exposure. In contrast to TiO₂ and CeO₂ NPs, CB NPs generated ROS in an acellular assay.

Conclusions

Our results suggest that the observed hepatic DNA damage following intravenous and intratracheal dosing with CB NPs was caused by the presence of translocated, ROS-generating, particles detected in the liver rather than by the secondary effects of pulmonary inflammation or hepatic acute phase response.

Electronic supplementary material

The online version of this article (10.1186/s12989-017-0238-9) contains supplementary material, which is available to authorized users.

Tissue Processing for Stereological Analyses of Lung Structure in Chronic Obstructive Pulmonary Disease

Quantitative data on lung structure, such as volume, surface area and length, are used for assessment of the functional performance of the lung during normal development and inflammatory-related diseases such as chronic obstructive pulmonary disorder (COPD), and carcinogenesis, in animal models. Stereology is considered as the gold standard to obtain quantitative data on lung structure, with a key advantage being to quantify irregular three-dimensional structures on the basis of measurement made on two-dimensional sections. Therefore, preservation of original tissue dimensions without shrinkage is vital for stereology.Three steps, fixation, sampling and embedding, are essential requirements to minimise tissue shrinkage to obtain theoretically unbiased estimates of stereological parameters of lung structures. Perfusion fixation by intratracheal instillation with 1.5% glutaraldehyde/1.5% formaldehyde at a pressure of 25 cm fluid column is considered as one of the best methods. A systematic uniform random sampling scheme is then applied to the fixed lung to ensure each and every part of the lung is analysed, irrespective of homogeneity or heterogeneity of the structural distribution. The sampled tissue sections are then embedded in glycol methacrylate to minimise further tissue shrinkage. Here we describe the accurate fixation, sampling and embedding for stereological methods to quantify lung structures in mice.

A 104-week pulmonary toxicity assessment of long and short single-wall carbon nanotubes after a single intratracheal instillation in rats

We compared long-term pulmonary toxicities after a single intratracheal instillation of two types of dispersed single-wall carbon nanotubes (SWCNTs), namely, those with relatively long or short linear shapes with average lengths of 8.6 and 0.55 µm, respectively. Both types of SWCNTs were instilled intratracheally in male F344 rats at 0.2 or 1.0 mg/kg (long SWCNTs) or 1.0 mg/kg (short SWCNTs). Pulmonary responses were characterized at 26, 52 and 104 weeks after a single instillation. Inflammatory changes, test substance deposition, test substance engulfment by macrophages, and alveolar wall fibrosis were observed in the lungs of almost all test rats at 52 and 104 weeks after short nanotube instillation. The incidences of these changes were much lower in the long nanotube-treated groups. In almost all rats of the long nanotube-treated groups, fibrosis and epithelium loss in the terminal bronchiole with test substance deposition were observed. These bronchiolar changes were not observed after administering short nanotubes. Both bronchiolo-alveolar adenoma and carcinoma were found in the negative-control group, the high-dose long-nanotube group, and the short-nanotube group at 104 weeks post-instillation, although the incidences were not statistically different. The genotoxicity of the SWCNTs was also evaluated by performing in vivo comet assays with lung cells obtained 26 weeks post-instillation. No significant changes in the percent tail deoxyribonucleic acid were found in any group. These findings suggested that most long SWCNTs were deposited at the terminal bronchioles and that a considerable amount of short SWCNTs reached the alveolus, resulting in chronic inflammatory responses, but no genotoxicity in the lungs.

Length effects of single-walled carbon nanotubes on pulmonary toxicity after intratracheal instillation in rats

We aimed to evaluate the effects of the length of single-walled carbon nanotubes (SWCNTs) on pulmonary toxicity in rats. Each rat received a single intratracheal instillation of short (S-) (average length of 0.40 μm) or long (L-) (average length of 2.77 μm) SWCNTs at a dose of 1 mg/kg and was observed for the next 6 months. Neither S- nor L-SWCNTs affected clinical signs, body weight, or autopsy findings. An increase in lung weight was observed after instillation of S- or L-SWCNTs; however, lung weights were slightly higher in the rats that were administered the S-SWCNTs. Distinct differences in bronchoalveolar lavage fluid (BALF) composition were observed between the S- and L-SWCNT-treated rats as early as 7 days after the intratracheal instillations of the SWCNTs. The S-SWCNTs caused persistent lung injury and inflammation during the 6-month observational period. However, the L-SWCNTs induced minimal lung injury and inflammation. Although the S- and L-SWCNTs changed BALF parameters and histopathological features of the lung, the magnitudes of the changes observed after the S-SWCNT treatment were greater than the respective changes observed after the L-SWCNT treatment. These findings indicate that the severity of the pulmonary toxicity caused after intratracheal instillation of SWCNT depends on the length of the SWCNTs. It appears that shorter SWCNTs induce greater pulmonary toxicity than longer SWCNTs do.

Review of toxicity studies of carbon nanotubes

OBJECTIVE

We reviewed studies on pulmonary, reproductive, and developmental toxicity caused by carbon nanotubes (CNTs). In paricular, we analyzed how CNT exposure affects the several processes of pulmonary toxicity, including inflammation, injury, fibrosis, and pulmonary tumors.

METHODS

In pulmonary toxicity, there are various processes, including inflammation, injury, fibrosis, respiratory tumor in the lungs, and biopersistence of CNTs and genotoxicity as tumor-related factors, to develop the respiratory tumor. We evaluated the evidence for the carcinogenicity of CNTs in each process. In the fields of reproductive and developmental toxicity, studies of CNTs have been conducted mainly with mice. We summarized the findings of reproductive and developmental toxicity studies of CNTs.

RESULTS

In animal studies, exposure to CNTs induced sustained inflammation, fibrosis, lung cancer following long-term inhalation, and gene damage in the lung. CNTs also showed high biopersistence in animal studies. Fetal malformations after intravenous and intraperitoneal injections and intratracheal instillation, fetal loss after intravenous injection, behavioral changes in offsprings after intraperitoneal injection, and a delay in the delivery of the first litter after intratracheal instillation were reported in mice-administered multi-walled carbon nanotubes (MWCNTs). Single-walled carbon nanotubes (SWCNTs) appeared to be embryolethal and teratogenic in mice when given by intravenous injection; moreover, the tubes induced death and growth retardation in chicken embryos.

CONCLUSION

CNTs are considered to have carcinogenicity and can cause lung tumors. However, the carcinogenicity of CNTs may attenuate if the fiber length is shorter. The available data provide initial information on the potential reproductive and developmental toxicity of CNTs.

Nanoparticle exposure reactivates latent herpesvirus and restores a signature of acute infection

Background

Inhalation of environmental (nano) particles (NP) as well as persistent herpesvirus-infection are potentially associated with chronic lung disease and as both are omnipresent in human society a coincidence of these two factors is highly likely. We hypothesized that NP-exposure of persistently herpesvirus-infected cells as a second hit might disrupt immune control of viral latency, provoke reactivation of latent virus and eventually lead to an inflammatory response and tissue damage.

Results

To test this hypothesis, we applied different NP to cells or mice latently infected with murine gammaherpesvirus 68 (MHV-68) which provides a small animal model for the study of gammaherpesvirus-pathogenesis in vitro and in vivo. In vitro, NP-exposure induced expression of the typically lytic viral gene ORF50 and production of lytic virus. In vivo, lytic viral proteins in the lung increased after intratracheal instillation with NP and elevated expression of the viral gene ORF50 could be detected in cells from bronchoalveolar lavage. Gene expression and metabolome analysis of whole lung tissue revealed patterns with striking similarities to acute infection. Likewise, NP-exposure of human cells latently infected with Epstein-Barr-Virus also induced virus production.

Conclusions

Our results indicate that NP-exposure of persistently herpesvirus-infected cells – murine or human – restores molecular signatures found in acute virus infection, boosts production of lytic viral proteins, and induces an inflammatory response in the lung – a combination which might finally result in tissue damage and pathological alterations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0181-1) contains supplementary material, which is available to authorized users.

Multiwalled carbon nanotubes intratracheally instilled into the rat lung induce development of pleural malignant mesothelioma and lung tumors

Multiwalled carbon nanotubes (MWCNT) have a fibrous structure and physical properties similar to asbestos and have been shown to induce malignant mesothelioma of the peritoneum after injection into the scrotum or peritoneal cavity in rats and mice. For human cancer risk assessment, however, data after administration of MWCNT via the airway, the exposure route that is most relevant to humans, is required. The present study was undertaken to investigate the carcinogenicity of MWCNT‐N (NIKKISO) after administration to the rat lung. MWCNT‐N was fractionated by passing it through a sieve with a pore size of 25 μm. The average lengths of the MWCNT were 4.2 μm before filtration and 2.6 μm in the flow‐through fraction; the length of the retained MWCNT could not be determined. For the present study, 10‐week‐old F344/Crj male rats were divided into five groups: no treatment, vehicle control, MWCNT‐N before filtration, MWCNT‐N flow‐through and MWCNT‐N retained groups. Administration was by the trans‐tracheal intrapulmonary spraying (TIPS) method. Rats were administered a total of 1 mg/rat during the initial 2 weeks of the experiment and then observed up to 109 weeks. The incidences of malignant mesothelioma and lung tumors (bronchiolo‐alveolar adenomas and carcinomas) were 6/38 and 14/38, respectively, in the three groups administered MWCNT and 0/28 and 0/28, respectively, in the control groups. All malignant mesotheliomas were localized in the pericardial pleural cavity. The sieve fractions did not have a significant effect on tumor incidence. In conclusion, administration of MWCNT to the lung in the rat induces malignant mesothelioma and lung tumors.

No involvement of alveolar macrophages in the initiation of carbon nanoparticle induced acute lung inflammation in mice

Background

Carbonaceous nanoparticles (CNP) represent a major constituent of urban particulate air pollution, and inhalation of high CNP levels has been described to trigger a pro-inflammatory response of the lung. While several studies identified specific particle characteristics driving respiratory toxicity of low-solubility and low-toxicity particles such as CNP, the major lung cell type, which initiates and drives that response, remains still uncertain. Since alveolar macrophages (AM) are known to effectively phagocytose inhaled particles and play a crucial role for the initiation of pulmonary inflammation caused by invading microbes, we aimed to determine their role for sterile stimuli such as CNP by profiling the primary alveolar cell compartments of the lung. We exposed C57BL/6 mice to 20 μg CNP by intratracheal instillation and comprehensively investigated the expression of the underlying mediators during a time span of 3 to 72 h in three different lung cell populations: CD45- (negative) structural cells, CD45+ (positive) leukocytes, and by BAL recovered cells.

Results

Bronchoalveolar lavage (BAL) analysis revealed an acute inflammatory response characterized by the most prominent culmination of neutrophil granulocytes from 12 to 24 h after instillation, which declined to basal levels by day 7. As early as 3 h after CNP exposure 50 % of the AM revealed particle laden. BAL concentrations and lung gene expression profiles of TNFα, and the neutrophil chemoattractants CXCL1,-2 and-5 preceded the neutrophil recruitment and showed highest levels after 12 h of CNP exposure, pointing to a significant activation of the inflammation-evoking lung cells at this point of time. AM, isolated from lungs 3 to 12 h after CNP instillation, however, did not show a pro-inflammatory signature. On the contrary, gene expression analysis of different lung cell populations isolated 12 h after CNP instillation revealed CD45-, mainly representing alveolar epithelial type II (ATII) cells as major producer of inflammatory CXCL cytokines. Particularly by CD45- cells expressed Cxcl5 proved to be the most abundant chemokine, being 12 h after CNP exposure 24 (±11) fold induced.

Conclusion

Our data suggests that AM are noninvolved in the initiation of the inflammatory response. ATII cells, which induced highest CXCL levels early on, might in contrast be the driver of acute neutrophilic inflammation upon pulmonary CNP exposure.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0144-6) contains supplementary material, which is available to authorized users.

Pulmonary toxicity of well-dispersed cerium oxide nanoparticles following intratracheal instillation and inhalation

We performed inhalation and intratracheal instillation studies of cerium dioxide (CeO₂) nanoparticles in order to investigate their pulmonary toxicity, and observed pulmonary inflammation not only in the acute and but also in the chronic phases. In the intratracheal instillation study, F344 rats were exposed to 0.2 mg or 1 mg of CeO₂ nanoparticles. Cell analysis and chemokines in bronchoalveolar lavage fluid (BALF) were analyzed from 3 days to 6 months following the instillation. In the inhalation study, rats were exposed to the maximum concentration of inhaled CeO₂ nanoparticles (2, 10 mg/m³, respectively) for 4 weeks (6 h/day, 5 days/week). The same endpoints as in the intratracheal instillation study were examined from 3 days to 3 months after the end of the exposure. The intratracheal instillation of CeO₂ nanoparticles caused a persistent increase in the total and neutrophil number in BALF and in the concentration of cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2, chemokine for neutrophil, and heme oxygenase-1 (HO-1), an oxidative stress marker, in BALF during the observation time. The inhalation of CeO₂ nanoparticles also induced a persistent influx of neutrophils and expression of CINC-1, CINC-2, and HO-1 in BALF. Pathological features revealed that inflammatory cells, including macrophages and neutrophils, invaded the alveolar space in both studies. Taken together, the CeO₂ nanoparticles induced not only acute but also chronic inflammation in the lung, suggesting that CeO₂ nanoparticles have a pulmonary toxicity that can lead to irreversible lesions.

Pulmonary toxicity of well-dispersed titanium dioxide nanoparticles following intratracheal instillation

In order to investigate the pulmonary toxicity of titanium dioxide (TiO₂) nanoparticles, we performed an intratracheal instillation study with rats of well-dispersed TiO₂ nanoparticles and examined the pulmonary inflammation and histopathological changes in the lung. Wistar Hannover rats were intratracheally administered 0.2 mg (0.66 mg/kg) and 1.0 mg (3.3 mg/kg) of well-dispersed TiO₂ nanoparticles (P90; diameter of agglomerates: 25 nm), then the pulmonary inflammation responses were examined from 3 days to 6 months after the instillation, and the pathological features were examined up to 24 months. Transient inflammation and the upregulation of chemokines in the broncho-alveolar lavage fluid were observed for 1 month. No respiratory tumors or severe fibrosis were observed during the recovery time. These data suggest that transient inflammation induced by TiO₂ may not lead to chronic, irreversible legions in the lung, and that TiO₂ nanoparticles may not have a high potential for lung disorder.

Pulmonary toxicity of well-dispersed titanium dioxide nanoparticles following intratracheal instillation

In order to investigate the pulmonary toxicity of titanium dioxide (TiO₂) nanoparticles, we performed an intratracheal instillation study with rats of well-dispersed TiO₂ nanoparticles and examined the pulmonary inflammation and histopathological changes in the lung. Wistar Hannover rats were intratracheally administered 0.2 mg (0.66 mg/kg) and 1.0 mg (3.3 mg/kg) of well-dispersed TiO₂ nanoparticles (P90; diameter of agglomerates: 25 nm), then the pulmonary inflammation responses were examined from 3 days to 6 months after the instillation, and the pathological features were examined up to 24 months. Transient inflammation and the upregulation of chemokines in the broncho-alveolar lavage fluid were observed for 1 month. No respiratory tumors or severe fibrosis were observed during the recovery time. These data suggest that transient inflammation induced by TiO₂ may not lead to chronic, irreversible legions in the lung, and that TiO₂ nanoparticles may not have a high potential for lung disorder.

Aggravating effect of natural sand dust on male reproductive function in mice

Purpose

Although adverse health effects of environment (such as cadmium, pesticides, diesel exhaust, etc.) on the male reproductive system have been suggested, there is little experimental evidence of such an effect of atmospheric sand dust. In the present study, the effects of sand dust (mineral particles) were investigated on the male reproductive system of mice.

Methods

Two types of sand dusts (Asian sand dust and Arizona sand dust) were intratracheally administered (0.1 mg/mouse 4 times every other week) to ICR male mice and then male reproductive organ weight, daily sperm production (DSP), histological analysis and serum testosterone level were measured.

Results

Histological examination showed that interstitial edema was produced by both sand dust types, and partial vacuolation of the seminiferous tubules was detected in the exposed mice. Moreover, exposure to these natural sand dusts significantly decreased DSP. On the other hand, there was no significant differences in serum testosterone concentration.

Conclusions

These results suggest that natural sand dust-exposure produced adverse effects on mouse male reproductive function.