Significance of Intratracheal Instillation Tests for the Screening of Pulmonary Toxicity of Nanomaterials

An Integrated Approach to Testing and Assessment to Support Grouping and Read-Across of Nanomaterials After Inhalation Exposure

Introduction: Here, we describe the generation of hypotheses for grouping nanoforms (NFs) after inhalation exposure and the tailored Integrated Approaches to Testing and Assessment (IATA) with which each specific hypothesis can be tested. This is part of a state-of-the-art framework to support the hypothesis-driven grouping and read-across of NFs, as developed by the EU-funded Horizon 2020 project GRACIOUS.

Development of Grouping Hypotheses and IATA: Respirable NFs, depending on their physicochemical properties, may dissolve either in lung lining fluid or in acidic lysosomal fluid after uptake by cells. Alternatively, NFs may also persist in particulate form. Dissolution in the lung is, therefore, a decisive factor for the toxicokinetics of NFs. This has led to the development of four hypotheses, broadly grouping NFs as instantaneous, quickly, gradually, and very slowly dissolving NFs. For instantaneously dissolving NFs, hazard information can be derived by read-across from the ions. For quickly dissolving particles, as accumulation of particles is not expected, ion toxicity will drive the toxic profile. However, the particle aspect influences the location of the ion release. For gradually dissolving and very slowly dissolving NFs, particle-driven toxicity is of concern. These NFs may be grouped by their reactivity and inflammation potency. The hypotheses are substantiated by a tailored IATA, which describes the minimum information and laboratory assessments of NFs under investigation required to justify grouping.

Conclusion: The GRACIOUS hypotheses and tailored IATA for respiratory toxicity of inhaled NFs can be used to support decision making regarding Safe(r)-by-Design product development or adoption of precautionary measures to mitigate potential risks. It can also be used to support read-across of adverse effects such as pulmonary inflammation and subsequent downstream effects such as lung fibrosis and lung tumor formation after long-term exposure.

Comparison of acute inhalation toxicity of sulfuric acid by the inhalation and intratracheal instillation methods

Recently, intratracheal instillation has been focused on as a simple, low-cost alternative to the inhalation method. In this study, intratracheal instillation of sulfuric acid, a typical acidic compound, was performed to compare the acute toxicity of acidic compounds that could cause damage to the respiratory system between intratracheal instillation and inhalation. Sulfuric acid was administered to male rats at doses of 0.7, 2, 7, 20, and 60 mg/kg by dividing the total dose into four doses. General condition and body weight were examined up to 14 days after administration, and macropathological and histopathological examinations were performed. The half-lethal dose was then estimated. All animals administered 20 and 60 mg/kg sulfuric acid and one animal administered 2 mg/kg sulfuric acid died within 4 h after administration. No abnormalities were observed in other animals. At 20 and 60 mg/kg, multiple red foci or diffuse red areas were macroscopically observed in the lungs. In these lesions, histopathologically, clefts between the mucosal epithelium and basement membrane and necrosis of the alveolar epithelium were observed. Deaths in these groups may have resulted from lung injury. No notable changes were observed in other animals. Therefore, the half-lethal dose of sulfuric acid by intratracheal instillation was estimated as 7-20 mg/kg. The acute toxicity by intratracheal instillation was evaluated with two-fold sensitivity since the exposure at the half-lethal sulfuric acid concentration in inhalation studies was calculated as 43.2 mg/kg.

Inter-laboratory comparison of pulmonary lesions induced by intratracheal instillation of NiO nanoparticle in rats: Histopathological examination results

OBJECTIVE

In this study, in order to investigate the usefulness of intratracheal instillation in assessing the pulmonary toxicity of nanomaterials, intratracheal instillation of nickel oxide-nanoparticles (NiO-NP) was performed.

METHODS

In this study, rats were administered test materials by intratracheal instillation at five different research institutions in order to assess the validity of using intratracheal instillation for hazard identification of nanomaterials. Eight-week-old male SD rats were administered NiO-NP dispersed in deionized water by a single intratracheal instillation at doses of 0 (vehicle control), 0.2, 0.67, and 2 mg/kg BW. Three days after instillation, histopathological examination of the lungs was performed.

RESULTS

NiO-NP was distributed in the vicinity of hilus of the lung and in the alveoli around the bronchioles. Histopathological changes such as degeneration/necrosis of macrophages, inflammation, and proliferation of type II pneumocyte in the lung were observed, and their severity corresponded with increasing dose. The histopathological observations of pulmonary toxicity were almost similar at each institution.

CONCLUSION

The similarity of the histopathological changes observed by five independent groups indicates that intratracheal instillation can be a useful screening method to detect the pulmonary toxicity of nanomaterials.

Lung toxicity of a vapor-grown carbon fiber in comparison with a multi-walled carbon nanotube in F344 rats

Carbon fibers have excellent physicochemical and electrical properties. Vapor-grown carbon fibers are a type of carbon fibers that have a multi-walled carbon tube structure with a high aspect ratio. The representative vapor-grown carbon fiber, VGCF^TM-H, is extremely strong and stable and has superior thermal and electrical conductivity. Because some high-aspect-ratio multi-walled carbon nanotubes (MWCNTs) have been reported to have toxic and carcinogenic effects in the lungs of rodents, we performed a 13-week lung toxicity study using VGCF^TM-H in comparison with one of MWCNTs, MWNT-7, in rats. Male and female F344 rats were intratracheally administered VGCF^TM-H at doses of 0.2, 0.4, and 0.8 mg/kg bw or MWNT-7 at doses of 0.4 and 0.8 mg/kg bw once a week for 8 weeks and then up to week 13 without treatment. The lung burden was equivalent in the VGCF^TM-H and MWNT-7 groups; however, the lung weight had increased and the inflammatory and biochemical parameters in the broncho-alveolar lavage fluid and histopathological parameters, including inflammatory cell infiltration, alveolar type II cells proliferation, alveolar fibrosis, pleural fibrosis, lung mesothelium proliferation, and diaphragm fibrosis, were milder in the VGCF^TM-H group than in the MWNT-7 group. In addition, the proliferating cell nuclear antigen (PCNA)-positive index in the visceral and pleural mesothelium was significantly higher in the MWNT-7 group than in the controls, but not in the VGCF^TM-H group. Thus, the results of this study indicate that the lung and pleural toxicities of VGCF^TM-H were less than those of MWNT-7.

TiO2 Nanoparticles Caused DNA Damage in Lung and Extra-Pulmonary Organs Through ROS-Activated FOXO3a Signaling Pathway After Intratracheal Administration in Rats

Introduction

Because of the increased production and application of manufactured Nano-TiO₂ in the past several years, it is important to investigate its potential hazards. TiO₂ is classified by IARC as a possible human carcinogen; however, the potential mechanism of carcinogenesis has not been studied clearly. The present study aimed to investigate the mechanism of DNA damage in rat lung and extra-pulmonary organs caused by TiO₂nanoparticles.

Methods

In the present study, SD rats were exposed to Nano-TiO₂ by intratracheal injection at a dose of 0, 0.2, or 1 g/kg body weight. The titanium levels in tissues were detected by ICP-MS. Western blot was used to detect the protein expression levels. The DNA damage and oxidative stress were detected by comet assay and ROS, MDA, SOD, and GSH-Px levels, respectively.

Results

The titanium levels of the 1 g/kg group on day-3 and day-7 were significantly increased in liver and kidney as well as significantly decreased in lung compared to day-1. ROS and MDA levels were statistically increased, whereas SOD and GSH-Px levels were statistically decreased in tissues of rats in dose-dependent manners after Nano-TiO₂ treatment. PI3K, p-AKT/AKT, and p-FOXO3a/FOXO3a in lung, liver, and kidney activated in dose-dependent manners. The levels of DNA damage in liver, kidney, and lung in each Nano-TiO₂ treatment group were significantly increased and could not recover within 7 days. GADD45α, ChK2, and XRCC1 in liver, kidney, and lung of rats exposed to Nano-TiO₂ statistically increased, which triggered DNA repair.

Conclusion

This work demonstrated that Ti could deposit in lung and enter extra-pulmonary organs of rats and cause oxidative stress, then trigger DNA damage through activating the PI3K-AKT-FOXO3a pathway and then promoting GADD45α, ChK2, and XRCC1 to process the DNA repair.

Effects of administering different vehicles via single intratracheal instillation on responses in the lung and pleural cavity of Crl:CD(SD) rats

Intratracheal instillation is the introduction of a substance directly into the trachea. Intratracheal instillation has been used to investigate the lung toxicity of several chemicals and requires the suspension or dissolution of test material in a vehicle for even dispersal throughout the lung. Importantly, the toxicities of vehicles used in intratracheal instillation studies are generally considered to be insignificant. Hence, evaluating the influence of different vehicles on the lung due to intratracheal instillation is crucial. We examined the toxic effects of pure water, saline, phosphate buffered saline (PBS), 0.5% Kolliphor^® P188 (KP188), 0.1% Tween 20 in saline, and 1.0% BSA in PBS. These vehicles were administered to male Crl:CD(SD) rats by a single intratracheal instillation. On day 3, broncho-alveolar lavage fluid (BALF) from the right lung was collected and processed for cell counting and biochemical analysis, while the left lung was used for histopathological examination. Accumulation of alveolar macrophages was observed in all vehicle-treated groups but was minimal in the group administered saline, somewhat higher in the groups administered pure water, PBS, 0.1% Tween 20, and 1% BSA, and notably higher in the group administered 0.5% KP188. The results from BALF analysis indicated that intratracheal instillation of 0.5% KP188 also induced alveolar damage. Additionally, administering pure water did not appear to cause tissue damage. Eosinophil infiltration in the interstitial regions was histopathologically observed. Altogether, the results of this study are helpful for the selection of appropriate vehicles for use in intratracheal instillation studies.

Carcinogenic effect of potassium octatitanate (POT) fibers in the lung and pleura of male Fischer 344 rats after intrapulmonary administration

Background

Potassium octatitanate fibers (K₂O•8TiO₂, POT fibers) are used as an asbestos substitute. Their physical characteristics suggest that respirable POT fibers are likely to be carcinogenic in the lung and pleura. However, previous 2-year inhalation studies reported that respired POT fibers had little or no carcinogenic potential. In the present study ten-week old male F344 rats were left untreated or were administered vehicle, 0.25 or 0.5 mg rutile-type nano TiO₂ (r-nTiO₂), 0.25 or 0.5 mg POT fibers, or 0.5 mg MWCNT-7 by intra-tracheal intra-pulmonary spraying (TIPS), and then observed for 2 years.

Results

There were no differences between the r-nTiO₂ and control groups. The incidence of bronchiolo-alveolar cell hyperplasia was significantly increased in the groups treated with 0.50 mg POT and 0.50 mg MWCNT-7. The overall incidence of lung tumors, however, was not increased in either the POT or MWCNT-7 treated groups. Notably, the carcinomas that developed in the POT and MWCNT-7 treated rats were accompanied by proliferative fibrous connective tissue while the carcinomas that developed in the untreated rats and the r-nTiO₂ treated rats were not (carcinomas did not develop in the vehicle control rats). In addition, the carcinoma that developed in the rat treated with 0.25 mg POT was a squamous cell carcinoma, a tumor that develops spontaneously in about 1 per 1700 rats. The incidence of mesothelial cell hyperplasia was 4/17, 7/16, and 10/14 and the incidence of malignant mesothelioma was 3/17, 1/16, and 2/14 in the 0.25 mg POT, 0.5 mg POT, and MWCNT-7 treated groups, respectively. Neither mesothelial cell hyperplasia nor mesothelioma developed in control rats or the rats treated with r-nTiO₂. Since the incidence of spontaneously occurring malignant mesothelioma in rats is extremely low, approximately 1 per 1000 animals (Japan Bioassay Research Center [JBRC] historical control data), the development of multiple malignant mesotheliomas in the POT and MWCNT-7 treated groups was biologically significant.

Conclusion

The incidence of pleural mesotheliomas in male F344 rats administered POT fibers and MWCNT-7 was significantly higher than the JBRC historical control data, indicating that the incidence of pleural mesothelioma in the groups administered POT fibers and MWCNT-7 fibers via the airway using TIPS was biologically significant. The incidence of type II epithelial cell hyperplasia and the histology of the carcinomas that developed in the POT treated rats also indicates that respirable POT fibers are highly likely to be carcinogenic in the lungs of male F344 rats.

Electronic supplementary material

The online version of this article (10.1186/s12989-019-0316-2) contains supplementary material, which is available to authorized users.

Update of occupational lung disease

Objective

Occupational Lung Disease is an oldest but still a biggest problem in occupational health.

Methods

Steering Committee members of the Japan Society for Occupational Health (JSOH) Occupational Lung Disease Study Group selected and summarized current topics on occupational lung diseases based on expert opinion, as informed by governmental regulation, public health concerns, and frequently discussed in related academic conferences.

Results

The topics included in this review are professional education in medical screening skills, 2014 update of Helsinki Criteria, respiratory diseases found in the earthquake and tsunami affected regions, newly recognized occupational lung diseases, and potential respiratory health hazards.

Discussions

Although occupational lung diseases seem to stay as one of the major concerns in occupational health, screening tools and control measures are standardized for the better prevention of the diseases. As this health problem usually occurs in where the most actively economically developing area is, the patients tend to increase in emerging economic powers with huge population.

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.