Assessment of the toxicity and carcinogenicity of double-walled carbon nanotubes in the rat lung after intratracheal instillation: a two-year study

Background

Considering the expanding industrial applications of carbon nanotubes (CNTs), safety assessment of these materials is far less than needed. Very few long-term in vivo studies have been carried out. This is the first 2-year in vivo study to assess the effects of double walled carbon nanotubes (DWCNTs) in the lung and pleura of rats after pulmonary exposure.

Methods

Rats were divided into six groups: untreated, Vehicle, 3 DWCNT groups (0.12 mg/rat, 0.25 mg/rat and 0.5 mg/rat), and MWCNT-7 (0.5 mg/rat). The test materials were administrated by intratracheal-intrapulmonary spraying (TIPS) every other day for 15 days. Rats were observed without further treatment until sacrifice.

Results

DWCNT were biopersistent in the rat lung and induced marked pulmonary inflammation with a significant increase in macrophage count and levels of the chemotactic cytokines CCL2 and CCL3. In addition, the 0.5 mg DWCNT treated rats had significantly higher pulmonary collagen deposition compared to the vehicle controls. The development of carcinomas in the lungs of rats treated with 0.5 mg DWCNT (4/24) was not quite statistically higher (p = 0.0502) than the vehicle control group (0/25), however, the overall incidence of lung tumor development, bronchiolo-alveolar adenoma and bronchiolo-alveolar carcinoma combined, in the lungs of rats treated with 0.5 mg DWCNT (7/24) was statistically higher (p < 0.05) than the vehicle control group (1/25). Notably, two of the rats treated with DWCNT, one in the 0.25 mg group and one in the 0.5 mg group, developed pleural mesotheliomas. However, both of these lesions developed in the visceral pleura, and unlike the rats administered MWCNT-7, rats administered DWCNT did not have elevated levels of HMGB1 in their pleural lavage fluids. This indicates that the mechanism by which the mesotheliomas that developed in the DWCNT treated rats is not relevant to humans.

Conclusions

Our results demonstrate that the DWCNT fibers we tested are biopersistent in the rat lung and induce chronic inflammation. Rats treated with 0.5 mg DWCNT developed pleural fibrosis and lung tumors. These findings demonstrate that the possibility that at least some types of DWCNTs are fibrogenic and tumorigenic cannot be ignored.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00469-8.

Palmitoyl piperidinopiperidine, a novel derivative of 10‑hydroxy‑2‑decenoic acid, as a potent and selective anticancer agent against human colon carcinoma cell lines

The present study, to the best of our knowledge, is the first systematic study of the inhibitory effects of palmitoyl piperidinopiperidine (PPI; Japan Patent no. 5597427), on colon carcinogenesis. PPI exhibited marked growth inhibitory activity in several human colon carcinoma cell lines, with IC50 values of approximately 0.5‑2.2 µM. In silico docking analysis indicated that PPI could bind to the SH2 domain of signal transducer and activator of transcription 3 (STAT3). PPI markedly inhibited the transcriptional activity of the SW837 cell line. Flowcytometric analysis demonstrated that PPI induced an increase in the number of cells in the G1 phase of the cell cycle, and induced sub‑G1 fractions of cells at a higher concentration level of PPI. In the HT29 and SW837 cells, western blot analyses exhibited that in whole cell lysates, PPI induced a marked decrease in the expression levels of p‑STAT3, but not in the levels of STAT3 in these cells. PPI also induced a marked decrease in the expression levels of both STAT3 and p‑STAT3 in the chromatin fraction. In addition, PPI affected the protein expression levels of cyclin D1, p53, Bcl‑2, Bcl‑xL and vascular endothelial growth factor (VEGF). In the HT29 cells, PPI induced a marked and dose‑dependent increase in the expression levels of Bax, cleaved caspase‑3, cleaved caspase‑7, cleaved caspase‑8, cleaved caspase‑9 and cleaved poly (ADP‑ribose) polymerase (PARP). In animal model systems, PPI inhibited the growth of implanted carcinoma cells, and also induced a significant decrease in the multiplicity of colonic aberrant crypt foci. In addition, a marked and dose‑dependent inhibition of angiogenesis of the chick chorioallantoic membrane was observed. As regards the possible molecular mechanisms, it is suggested that the inhibition of STAT3 by PPI may affect the function of molecules that are related to apoptosis, angiogenesis and cell cycle progression, eventually contributing to the PPI‑induced growth inhibitory effects.

Evaluation of a biomarker for the diagnosis of pancreas cancer using an animal model

Many approaches have been taken to identify new biomarkers of pancreatic ductal carcinoma (PDC). Since animal models can be sampled under controlled conditions, better standardization is possible compared with heterogeneous human studies. Transgenic rats with conditional activation of oncogenic RAS in pancreatic tissue develop PDC that closely resembles the biological and histopathological features of human PDC. Using this model, we evaluated the usefulness of leucine-rich α2-glycoprotein-1 (LRG-1) as a serum marker. In this study, we found that LRG-1 was overexpressed in rat PDC compared with normal pancreas tissue of the control rats. Serum levels of LRG-1 were also significantly higher in rats bearing PDC than in controls. Importantly, chronic pancreatitis in male Wistar Bonn/Kobori rats, which is a widely accepted as a model of chronic pancreatitis, did not cause serum levels of LRG-1 to become elevated. These results strongly support serum LRG-1 as a candidate biomarker for noninvasive diagnosis of PDC. Our models of pancreas cancer provide a useful strategy for evaluation of candidate markers applicable to human cancer.

Therapeutic and Preventive Effects of Osteoclastogenesis Inhibitory Factor on Osteolysis, Proliferation of Mammary Tumor Cell and Induction of Cancer Stem Cells in the Bone Microenvironment

Background: We examined the effects of recombinant human osteoclastogenesis inhibitory factor (hOCIF) on osteolysis, proliferation of mammary tumor cells, and induction of cancer stem cells (CSCs) in the tumor-bone and tumor-subcutaneous microenvironments (TB- and TS-microE). Methods: Mouse mammary tumor cells were transplanted onto the calvaria or into a subcutaneous lesion of female mice, creating a TB-microE and a TS-microE, and the mice were then treated with hOCIF. To investigate the preventive effects of hOCIF, mice were treated with hOCIF before tumor cell implantation onto the calvaria (Pre), after (Post), and both before and after (Whole). The number of CSCs and cytokine levels were evaluated by IHC and ELISA assay, respectively. Results: hOCIF suppressed osteolysis, and growth of mammary tumors in the TB-microE, but not in the TS-microE. In the Pre, Post, and Whole groups, hOCIF suppressed osteolysis, and cell proliferation. hOCIF increased mouse osteoprotegrin (mOPG) levels in vivo, which suppressed mammary tumor cell proliferation in vitro. These preventive effects were observed in the dose-dependent. hOCIF did not affect the induction of CSCs in either microenvironment. Conclusion: While receptor activator of NF-κB ligand (RANKL) targeting therapy may not affect the induction of CSCs, RANKL is a potential target for prevention as well as treatment of breast cancer bone metastasis.

Chronic in Vivo Function of a New Ventricular Assist Device: The Extracorporeal Pulsatile Assist Device (Epad)

An extracorporeal pulsatile assist device (EPAD) is a valveless, single-chambered, pneumatically-actuated blood pump composed of a graft conduit, connecting ring, bladder, and blowmolded housing. This allows a simple and quick surgical procedure and is easily actuated with a conventional intraaortic balloon pumping console if desired. To evaluate in vivo pump functions, the EPAD was tested in calves as a left ventricular assist device for 6-24 days. The EPAD was well synchronized to the natural heart beat up to 130 bpm in the counterpulsation mode with mild systemic heparinization (active clotting time: 200-250 seconds). Heart rate, coronary flow and cardiac output were not significantly changed by on-off testing. However, the pump showed promising diastolic augmentation (10.8% increase in the diastolic pressure time index) in these chronic animal experiments.

Abstract 182: A new anticancer agent derived from decenoic acid for the treatment of colon cancer

The final goal of the current study is to create a promising lead compound that targets human colon carcinoma. After discovering in vitro antiproliferative activity of a naturally occurring compound, 10-hydroxy-2-decenoic acid, we designed and synthesized over 150 derivatives. The initial screening resulted in the discovery of three primary lead compounds, we then proceeded with modifications in side chain and eventually obtained a second-generation lead compound, named PPI (patented in 2014), whose IC50 was 0.3 μM. We focused on the transcription factor STAT3 that is able to drive carcinogenesis, apoptosis, and angiogenesis-related genes. In silico docking simulation exhibited that PPI can bind to SH2 domain of STAT3, suggesting that this drug blocks dimerization of STAT3, thereby PPI inactivates function of STAT3. PPI inhibited transcriptional activity of STAT3 when SW480, SW837, and HT29 human colon carcinoma cells were treated with 3.7 to 5 μM PPI for 24h. Flowcytometry analysis indicated that when HT29 cells were treated with 1 μM PPI, the percentage of cells in G1 increased by 5% and this was associated with a concomitant decrease of cells in the S and G2-M phases of the cell cycle. The results indicate that PPI causes carcinoma cells to arrest in the G1 phase. When HT29 cells were treated with 10 μM PPI, subG1 fraction and DNA fragmentation were seen, indicating induction of apoptosis. We then performed western blot analysis to determine whether treatment of carcinoma cells with PPI alters cellular levels of the G1 cell cycle control protein cyclin D1 and apoptosis/angiogenesis-related molecules. When HT29 cells were treated with PPI for 24 to 48h, there was a marked decrease in the levels of expression of the Bcl-2, Bcl-xL, and VEGF proteins and a marked increase in the levels of expression of the cleaved caspase 3, 7, 8, 9, and PARP proteins. PPI also inhibited expression levels and nuclear tanslocation of pSTAT3. To see if PPI exerts preventive effect on tumor promotion, F344 rats received sc injections of a carcinogen azoxymethane and then treated with soybean oil or PPI. There was a dose dependent decrease in multiplicity of aberrant crypt foci (ACF) in the colon. PPI inhibited the occurrence of larger ACF consisting of more than 4 aberrant crypts, indicating inhibitory effect of PPI on tumor promotion. In a mouse xenograft model, PPI decreased the size and number of blood vessels in the tumor. All mice survived without causing significant body weight loss during experiment. No histopathological abnormality was found in any of organ site. To confirm the effects of PPI on angiogenesis, we performed chorioallantoic membrane assays and found a dose-dependent decrease in average number of blood vessels. Inhibition of STAT3 by PPI may affect the function of molecules that are related to apoptosis, angiogenesis, and cell cycle progression and eventually contributes to PPI-induced growth inhibition.

Citation Format: Masumi Suzui, Saeko Ando, Harutoshi Matsumoto, Katsumi Fukamachi, Mitsuru Futakuchi, Naoki Yoshimi. A new anticancer agent derived from decenoic acid for the treatment of colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 182. doi:10.1158/1538-7445.AM2017-182

Abstract 2178: Growth inhibition of the crude extracts of Musa basjoo in human colon carcinoma cells

Musa basjoo (MB) is a tropical evergreen tree growing mainly in subtropical or tropical countries. MB has been used globally as a folk medicine such as antipyretic, diuretic, and hemostatic drugs for centuries but evidence-based biological activities and molecular mechanism of action of MB are unknown. Therefore, in the current study we examined whether the crude extracts of MB exert anticancer activity in HT29 and HCT116 human colon carcinoma cell lines. Dried leaves of MB samples were extracted with acetone or methanol. Crude extracts of MB were then dissolved in dimethylsulfoxide (DMSO) and used for the following experiments. Growth inhibition was determined by colony or MTT assays in these cell lines. Cells were treated with increasing concentrations (12.5 to 200 μg/mL in colony assays, 25 to 400 μg/mL in MTT assays) of acetone/methanol extracts of MB in DMEM/5%FBS. Untreated control cells were treated with DMSO alone. Crude extracts of MB inhibited the growth of cells with IC50 values of 118 µg/mL (acetone extract, HT29), 75 µg/mL (acetone extract, HCT116), &gt;200 µg/mL (methanol extract, HT29), 141 µg/mL (methanol extract, HCT116) in colony assays, and with IC50 values of 137 µg/mL (acetone extract, HT29), 73 µg/mL (acetone extract, HCT116), 240 µg/mL (methanol extract, HT29), 248 µg/mL (methanol extract, HCT116) in MTT assays. Acetone extract was used in the flowcytometry and western blot analyses because it showed stronger growth inhibition than methanol extract in both cell lines. Flowcytometry analysis indicated that when HT29 and HCT116 cells were treated with 100 µg/mL acetone extract of MB for 96h, the percentage of cells in G1 increased by 5.4% and this was associated with a concomitant decrease of cells in the S and G2-M phases of the cell cycle. Acetone extract of MB did not cause subG1 fraction in either HT29 or HCT116 cell lines. The results indicate that acetone extract of MB causes carcinoma cells to arrest in the G1 phase. We then performed western blot analysis to determine whether treatment of carcinoma cells with acetone extract of MB alters cellular levels of the G1 cell cycle control proteins cyclin D1, cdk4 and the cell cycle inhibitor protein p21CIP1. When HT29 and HCT116 cells were treated with 50 and 100 µg/mL acetone extract of MB for 96h, there was a marked decrease in the levels of expression of the cyclin D1 and cdk4 proteins and a marked increase in the levels of expression of the p21CIP1 protein. Thus, a decrease in cyclin D1 may cooperate with the induction of p21CIP1 to arrest cells in G1 and thereby further contribute to MB-induced growth inhibition. Taken together, the crude extracts of MB contain active component(s) that exert growth inhibition of human colon carcinoma cells. The current study is the first systematic examination of the anticancer activity of MB and may provide a novel approach to the chemoprevention and/or chemotherapy of human colon carcinoma.

Citation Format: Harutoshi Matsumoto, Saeko Ando, Katsumi Fukamachi, Mitsuru Futakuchi, Kazunori Kimura, Naoki Yoshimi, Masumi Suzui. Growth inhibition of the crude extracts of Musa basjoo in human colon carcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2178. doi:10.1158/1538-7445.AM2017-2178

Rapid Emergence of Mammary Preneoplastic and Malignant Lesions in Human c-Ha-ras Proto-Oncogene Transgenic Rats: Possible Application for Screening of Chemopreventive Agents

For comparison of mammary gland whole mounts with examination of 2 histologic sections of mammary gland, 56 Hras128 rats were intravenously injected with 50 mg/kg body weight of N-methyl- N-nitrosourea at 50 days of age and then sacrificed at days 5, 10, 15, 20, 25, and 56. Comparison of detection sensitivity between the whole mounts and histologic sections revealed no lesions apparent in whole mounts on day 10, although intraductal proliferation was clearly detected in histologic sections in 44% of treated rats. Proliferative lesions were first detected in whole mounts at a 44% incidence on day 15, while intraductal proliferations and atypical hyperplasias were apparent in the sections at 89% and 44% incidences, respectively. On day 20, atypical hyperplasias and small adenocarcinomas in histologic sections were found in almost all animals. In conclusion, examination of 2 histologic sections from mammary tissues was found to be practical for detection of small malignant lesions as early as 15 days after MNU injection, and suppressive effects of soy isoflavones were clearly evident within 20 days after carcinogen exposure. These results suggest that this model has practical utility for short-term screening of chemopreventive agents for mammary carcinogenesis.

Possible Application of Human c-Ha-ras Proto-Oncogene Transgenic Rats in a Medium-Term Bioassay Model for Carcinogens

With the aim of developing a medium-term assay for screening of environmental carcinogens, we exposed mammary carcinogen sensitive human c-Ha-ras proto-oncogene transgenic (Hras128) rats to various carcinogens, including compounds that do not normally induce mammary tumors. Seven-week-old Hras128 rats and wild-type littermates received administrations of 3-methylcholanthrene (3-MC), benzo[a]pyrene (B[a]P), anthracene, pyrene, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), dimethylarsinic acid (DMA), diethylnitrosamine (DEN) or azoxymethane (AOM) and were sacrificed at week 12 (females) (at week 10 for the 3-MC group) or week 20 (males). Female Hras128 rats receiving NNK, DEN, or DMA showed a significant increase in mammary tumor incidence and/or multiplicity compared to the respective values with olive oil or deionized distilled water (DDW) vehicles. In male Hras128 rats, a significant increase in mammary tumors was also observed in groups administered 3-MC, B[a]P, anthracene, IQ, and NNK. Mutations of transgenes were observed in codons 12 and/or 61 in the induced tumors by PCR-RFLP except in the DEN group in female and in the MeIQx group in male Hras128 rats. Thus various carcinogens, not necessarily limited to those normally targeting the breast, were found to induce mammary carcinomas in Hras128 rats, especially in females, pointing to potential use for medium-term screening.

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.

In vivo18F-fluorodeoxyglucose-positron emission tomography/computed tomography imaging of pancreatic tumors in a transgenic rat model carrying the human KRASG12V oncogene

A novel KRAS-mediated transgenic rat model has previously been demonstrated, in which animals develop multiple pancreatic ductal adenocarcinoma (PDAC) that is histologically similar to human PDAC within two weeks. Positron emission tomography (PET)/computed tomography (CT) is commonly used for the diagnosis and staging of PDAC in humans, and can be adopted for optimal use in animal experiments. The aim of the present study was to evaluate the carcinogenic process in a rat pancreatic carcinoma model using small-animal multimodality imaging systems. The utility of fluorodeoxyglucose (FDG)-PET/CT in detecting the location and size of PDAC during tumor development in the present transgenic rat model was assessed. A small animal multimodality PET/CT system and contrast-enhanced CT (CECT) system were used for the imaging analysis of KRAS^G12V male transgenic rats (n=6), which developed pancreatic tumors following the administration of an injection of Cre recombinase (Cre)-carrying adenovirus. Laparotomies performed at six weeks post-treatment revealed that all three (100%) Cre-expressing rats developed pancreatic tumors that were <2 mm in diameter, none of which were detected by ¹⁸F-FDG PET/CT or CECT. At eight weeks post-treatment, the pancreatic tumors were heterogeneously visualized by ¹⁸F-FDG-PET/CT and CECT in two of the three rats. Furthermore, the autopsies confirmed that all three rats had developed pancreatic tumors. These novel findings provide evidence that the FDG-PET/CT imaging system is a valuable tool for the evaluation of the carcinogenic process, and one which may aid in treatment and preventive methods for pancreatic tumors in mammalian models. A limitation associated with the early detection of PDACs warrants further investigation.

Chemokine (C-C motif) ligand 3 detection in the serum of persons exposed to asbestos: A patient-based study

Exposure to asbestos results in serious risk of developing lung and mesothelial diseases. Currently, there are no biomarkers that can be used to diagnose asbestos exposure. The purpose of the present study was to determine whether the levels or detection rate of chemokine (C-C motif) ligand 3 (CCL3) in the serum are elevated in persons exposed to asbestos. The primary study group consisted of 76 healthy subjects not exposed to asbestos and 172 healthy subjects possibly exposed to asbestos. The secondary study group consisted of 535 subjects possibly exposed to asbestos and diagnosed with pleural plaque (412), benign hydrothorax (10), asbestosis (86), lung cancer (17), and malignant mesothelioma (10). All study subjects who were possibly exposed to asbestos had a certificate of asbestos exposure issued by the Japanese Ministry of Health, Labour and Welfare. For the primary study group, levels of serum CCL3 did not differ between the two groups. However, the detection rate of CCL3 in the serum of healthy subjects possibly exposed to asbestos (30.2%) was significantly higher (P < 0.001) than for the control group (6.6%). The pleural plaque, benign hydrothorax, asbestosis, and lung cancer groups had serum CCL3 levels and detection rates similar to that of healthy subjects possibly exposed to asbestos. The CCL3 chemokine was detected in the serum of 9 of the 10 patients diagnosed with malignant mesothelioma. Three of the patients with malignant mesothelioma had exceptionally high CCL3 levels. Malignant mesothelioma cells from four biopsy cases and an autopsy case were positive for CCL3, possibly identifying the source of the CCL3 in the three malignant mesothelioma patients with exceptionally high serum CCL3 levels. In conclusion, a significantly higher percentage of healthy persons possibly exposed to asbestos had detectable levels of serum CCL3 compared to healthy unexposed control subjects.

Rat N-ERC/mesothelin as a marker for in vivo screening of drugs against pancreas cancer

Pancreatic ductal adenocarcinoma (PDA) is a highly lethal disease, which is usually diagnosed in an advanced stage. We have established transgenic rats carrying a mutated K-ras gene controlled by Cre/loxP activation. The animals develop PDA which is histopathologically similar to that in humans. Previously, we reported that serum levels of N-ERC/mesothelin were significantly higher in rats bearing PDA than in controls. In the present study, to determine whether serum levels of N-ERC/mesothelin correlated with tumor size, we measured N-ERC/mesothelin levels in rats bearing PDA. Increased serum levels of N-ERC/mesothelin correlated with increased tumor size. This result indicates an interrelationship between the serum level of N-ERC/mesothelin and tumor size. We next investigated the effect of chemotherapy on serum N-ERC/mesothelin levels. Rat pancreatic cancer cells were implanted subcutaneously into the flank of NOD-SCID mice. In the mice treated with 200 mg/kg gemcitabine, tumor weight and the serum level of N-ERC/mesothelin were significantly decreased compared to controls. These results suggest that serum N-ERC/mesothelin measurements might be useful for monitoring response to therapy.

Size- and shape-dependent pleural translocation, deposition, fibrogenesis, and mesothelial proliferation by multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNT) have a fibrous structure similar to asbestos, raising concern that MWCNT exposure may lead to asbestos-like diseases. Previously we showed that MWCNT translocated from the lung alveoli into the pleural cavity and caused mesothelial proliferation and fibrosis in the visceral pleura. Multiwalled carbon nanotubes were not found in the parietal pleura, the initial site of development of asbestos-caused pleural diseases in humans, probably due to the short exposure period of the study. In the present study, we extended the exposure period to 24 weeks to determine whether the size and shape of MWCNT impact on deposition and lesion development in the pleura and lung. Two different MWCNTs were chosen for this study: a larger sized needle-like MWCNT (MWCNT-L; l = 8 μm, d = 150 nm), and a smaller sized MWCNT (MWCNT-S; l = 3 μm, d = 15 nm), which forms cotton candy-like aggregates. Both MWCNT-L and MWCNT-S suspensions were administered to the rat lung once every 2 weeks for 24 weeks by transtracheal intrapulmonary spraying. It was found that MWCNT-L, but not MWCNT-S, translocated into the pleural cavity, deposited in the parietal pleura, and induced fibrosis and patchy parietal mesothelial proliferation lesions. In addition, MWCNT-L induced stronger inflammatory reactions including increased inflammatory cell number and cytokine/chemokine levels in the pleural cavity lavage than MWCNT-S. In contrast, MWCNT-S induced stronger inflammation and higher 8-hydroxydeoxyguanosine level in the lung tissue than MWCNT-L. These results suggest that MWCNT-L has higher risk of causing asbestos-like pleural lesions relevant to mesothelioma development.

A novel transgenic mouse model carrying human Tribbles related protein 3 (TRB3) gene and its site specific phenotype

Tribbles related protein 3 (TRB3) pseudokinase plays a crucial role in cell proliferation, migration and morphogenesis during development. In our recent study, an introduction of human TRB3 gene into mouse mammary tumor cells caused an increase of proliferation of tumor cells and their nuclear size. In the current study, to examine whether this gene causes de novo morphological changes in a specific organ site we have developed a novel variation of the transgenic mouse model that conditionally expresses human TRB3 (hTRB3) gene using Cre-recombinase (Cre)/loxP recombination system. By injecting hTRB3 transgene construct into pronuclei of mouse embryo, we eventually obtained four hTRB3 mice. The gene expression was controlled by infection of adenovirus-expressing Cre via the tail vein of hTRB3 mouse. In Cre-mediated hTRB3 mouse, expression of the hTRB3 protein was detected in the cytoplasm of hepatocytes in the liver. Expression of this protein was also seen in lymphocytes in the spleen, glomerular endothelial cells, and epithelial cells of collecting duct of the kidney. In hepatocytes of the hTRB3 mouse, nuclear size was significantly greater than that of the wild type mouse, indicating that hTRB3 can play a role at least in part in hepatic morphogenesis. The present animal model may provide a system for evaluation of de novo morphological changes induced by a specific transgene in a specific organ site.

Promotive effects of cell proliferation and chromosomal instability induced by tribbles-related protein 3 in mouse mammary tumor cells

Tribbles-related protein 3 (TRB3) has been shown to be a crucial modulator of tumorigenesis. However, the precise role and the functional morphology of TRB3 are not clearly understood. To elucidate these enigmas we established the cell line, M2TRB3, by introducing the human TRB3 gene and protein in Cl66M2 (M2) mouse mammary tumor cells. This cell line stably expressed the TRB3 gene and protein. After 72 h of cell culture, there was a 34% increase in the growth of M2TRB3 cells compared to the control M2 mock cells. The mean volume of the tumors originating from the M2TRB3 cells was significantly increased by 38% when compared to the mean volume of the M2 mock tumors, and the proliferating cell nuclear antigen (PCNA) labeling index in the M2TRB3 tumors was higher when compared to that of the M2 and M2 mock cells. In the tumor tissue samples, the mean diameter of nuclei in the M2TRB3 tumor cells (9.4±0.3 µm) showed a significant increase compared to that of the M2 mock tumor cells (7.0±0.2 µm). M2TRB3 cells also showed a marked increase in the population of tetraploid or octaploid nuclei compared to M2 mock cells bearing mainly either diploid or tetraploid nuclei. Western blot analysis revealed the overexpression of cyclin B1 and cyclin D1 in M2TRB3 cells when compared to that in the M2 mock cells. These novel findings provide further evidence that TRB3 promotes cell proliferation and chromosomal instability by causing polyploidization during development.

Abstract 3604: Evaluation of carcinogenic effect of multiwall carbon nanotubes on the rat lung at 2 and 52 weeks after pulmonary instillation

Multiwall carbon nanotubes (MWCNT) have recently been shown to contain fibers similar to asbestos in length and diameter. When these fibers are inhaled, MWCNT can induce pulmonary toxicity including inflammation, granuloma, fibrosis, and hyperplasia. Also, a characteristic shared with asbestos fibers has led to concern that environmental or occupational exposure to MWCNT might cause asbestos-like pulmonary diseases including carcinoma. To examine MWCNT's pulmonary toxicity, we used the intrapulmonary spraying (IPS) technique. Also, to examine the effects depending on its length of MWCNT, using a 25 μm-sieve it was separated into three fractions; the remaining (R), flow through (FT), and whole (W). Male F344 rats were treated with 0.5 mL of 250 mg/mL suspensions of each fraction of MWCNT eight times over a 14-day period by intrapulmonary spraying. Six hours after the last IPS, the rats were sacrificed and complete autopsy was done (short-term exp). Mean length of MWCNT was 2.6 μm (FT) and 4.2 μm (W). Length of the R fraction could not be measured because of its tangled up status. At 52 weeks after the start of the experiment, the remaining rats were sacrificed and complete autopsy was also done using a 25 μm-sieve. In the short-term exp, MWCNT were found mainly in focal granulomatous lesions in the alveoli and in alveolar macrophages. MWCNT were also seen in the mediastinal lymph nodes. Inflammatory cell infiltration and granuloma formation were seen in each fraction treatment group. Mean area of inflammatory cell infiltration was significantly increased in the FT fraction treatment group as compared to the other two fractions treatment groups and control group. In the long-term exp, MWCNT were detected in focal granulomatous/fibrous lesions in the alveoli and in alveolar macrophages. In the lung tissue of each fraction treatment group, mean area of granulomatous/fibrous lesions increased compared to the control group. In the lung tissue of the short-term exp, the levels of mRNA/protein expression of Csf3, IL6, Cxcl2, and Ccl4, which were highly expressed in a microarray analysis in primary cultured macrophages, were enhanced in each fraction treatment group compared to the control group. In the long-term exp, the levels of mRNA expression of Csf3 and IL6 were markedly low. mRNA expression of Cxcl2 and Ccl4 were almost same level as the control. IPS of MWCNT did not cause tumors in alveolar epithelial tissues. These results indicate that MWCNT cause inflammatory toxic effects on the rat lung at 2 and 52 weeks after instillation. The initial hypothesis of a carcinogenic activity of instilled MWCNT could not be verified in a 52-week bioassay system.

Citation Format: Masumi Suzui, Takamasa Numano, Mitsuru Futakuchi, Katsumi Fukamachi. Evaluation of carcinogenic effect of multiwall carbon nanotubes on the rat lung at 2 and 52 weeks after pulmonary instillation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3604. doi:10.1158/1538-7445.AM2013-3604

Abstract 3606: Effect of anatase type nanosized titanium dioxide particles on the rat lung and cultured macrophage

Nanosized titanium dioxide is mainly categorized into anatase type (anatase type nTiO2) and rutile type (rutile type nTiO2), and widely used in industry, commercial products and biosystems. Previous our report indicated that rutile type nTiO2 caused the growth of A549 human lung carcinoma cells, induction of macrophage, an increase of 8-hydroxydeoxyguanosine (8-OHdG) and overexpression of Macrophage inflammatory protein 1α(MIP1α). Furthermore, under ultraviolet irradiation, anatase type nTiO2 is 100 times more toxic than rutile type nTiO2 in vitro. In the present study, we compared the pulmonary toxic effects induced by anatase type nTiO2 and rutile type nTiO2. Female SD rats were treated with anatase type nTiO2 or rutile type nTiO2 by intrapulmonary spraying for 8 times over a two week period. Obvious lung inflammation foci were not observed in the rats treated with anatase type nTiO2 or rutile type nTiO2. Infiltration of alveolar macrophages was observed throughout the lung tissues and anatase type nTiO2 or rutile type nTiO2 particles were exclusively phagocytosed by alveolar macrophages. Treatment with both anatase type nTiO2 and rutile type nTiO2 also increased number of alveolar macrophage and the production of 8-OHdG in the lung tissue, with a littler higher in the rutile type nTiO2 treated group than in the anatase type nTiO2 treated group. Importantly, expression of MIP1α in the lung tissue treated with anatase type nTiO2 and rutile type nTiO2 as either mRNA level and protein level was significantly up-regulated compared with that of the control group, with significantly lower in the anatase type nTiO2 treated group than in the rutile type nTiO2 treated group. Similarly, anatase type nTiO2 induced significantly lower mRNA expression of MIP1α in primary alveolar macrophages (PAM) and protein level of MIP1α in the supernatants of PAM cell culture than rutile type nTiO2. Additionally, supernatants of PAM cell culture treated with anatase type nTiO2 had less effect on the growth of A549 cell than those treated with rutile type nTiO2. Conclusively, treatment with both anatase type nTiO2 and rutile type nTiO2 did not cause notable lung inflammation. Analysis of alveolar macrophage induction, production of 8-OHdG in the lung tissue, and MIP1α expression both in vivo in the lung and in vitro in PAM indicated that anatase type nTiO2 was less effective than rutile type nTiO2, partly due to low photocatalytic effect in the lung tissue.

Citation Format: Takamasa Numano, Jiegou Xu, Mitsuru Futakuchi, Katsumi Fukamachi, Fumio Furukawa, Masumi Suzui, Hiroyuki Tsuda. Effect of anatase type nanosized titanium dioxide particles on the rat lung and cultured macrophage. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3606. doi:10.1158/1538-7445.AM2013-3606

A novel reporter rat strain that expresses LacZ upon Cre-mediated recombination

The recent widespread application of Cre/loxP technology has resulted in a new generation of conditional animal models that can better recapitulate many salient features of human disease. These models benefit from the ability to monitor the expression and functionality of Cre protein. We have generated a conditional (Cre/loxP dependent) LacZ reporter rat (termed the LacZ541 rat) to monitor Cre in transgenic rats. When LacZ541 rats were bred with another transgenic rat line expressing Cre recombinase under the control of the CAG promoter, LacZ/Cre double transgenic embryos displayed ubiquitous expression of LacZ, and when LacZ541 rats were bred with transgenic rats expressing Cre/loxP-dependent oncogenic H- or K-ras, LacZ was expressed in the lesions resulting from the activation of the oncogene. The LacZ541 rat enables evaluation of the performance of Cre-expressing systems which are based upon transgenic rats or somatic gene transfer vectors and provides efficient and simple lineage marking.

Metabolomic and transcriptomic profiling of human K-ras oncogene transgenic rats with pancreatic ductal adenocarcinomas

Pancreatic ductal adenocarcinoma (PDAC) is one of the most debilitating malignancies in humans, and one of the reasons for this is the inability to diagnose this disease early in its development. To search for biomarkers that can be used for early diagnosis of PDAC, we established a rat model of human PDAC in which expression of a human K-ras(G12V) oncogene and induction of PDAC are regulated by the Cre/lox system. In the present study, transgenic rats bearing PDAC and control transgenic rats with normal pancreatic tissues were used for metabolomic analysis of serum and pancreatic tissue by non-targeted and targeted gas chromatography-mass spectrometry and transcriptomic analysis of pancreatic tissue by microarray. Comparison of the metabolic profiles of the serum and pancreatic tissue of PDAC-bearing and control rats identified palmitoleic acid as a metabolite, which was significantly decreased in the serum of PDAC-bearing animals. Transcriptomic analysis indicated that several transcripts involved in anaerobic glycolysis and nucleotide degradation were increased and transcripts involved in the trichloroacetic acid cycle were decreased. Other transcripts that were changed in PDAC-bearing rats were adenosine triphosphate citrate lyase (decreased: fatty acid biosynthesis), fatty acid synthase (increased: fatty acid biosynthesis) and arachidonate 5-lipoxygenase activating protein (increased: arachidonic acid metabolism). Overall, our results suggest that the decreased serum levels of palmitoleic acid in rats with PDAC was likely due to its decrease in pancreatic tissue and that palmitoleic acid should be investigated in human samples to assess its diagnostic significance as a serum biomarker for human PDAC.

Multi-walled carbon nanotubes translocate into the pleural cavity and induce visceral mesothelial proliferation in rats

Multi-walled carbon nanotubes have a fibrous structure similar to asbestos and induce mesothelioma when injected into the peritoneal cavity. In the present study, we investigated whether carbon nanotubes administered into the lung through the trachea induce mesothelial lesions. Male F344 rats were treated with 0.5 mL of 500 μg/mL suspensions of multi-walled carbon nanotubes or crocidolite five times over a 9-day period by intrapulmonary spraying. Pleural cavity lavage fluid, lung and chest wall were then collected. Multi-walled carbon nanotubes and crocidolite were found mainly in alveolar macrophages and mediastinal lymph nodes. Importantly, the fibers were also found in the cell pellets of the pleural cavity lavage, mostly in macrophages. Both multi-walled carbon nanotube and crocidolite treatment induced hyperplastic proliferative lesions of the visceral mesothelium, with their proliferating cell nuclear antigen indices approximately 10-fold that of the vehicle control. The hyperplastic lesions were associated with inflammatory cell infiltration and inflammation-induced fibrotic lesions of the pleural tissues. The fibers were not found in the mesothelial proliferative lesions themselves. In the pleural cavity, abundant inflammatory cell infiltration, mainly composed of macrophages, was observed. Conditioned cell culture media of macrophages treated with multi-walled carbon nanotubes and crocidolite and the supernatants of pleural cavity lavage fluid from the dosed rats increased mesothelial cell proliferation in vitro, suggesting that mesothelial proliferative lesions were induced by inflammatory events in the lung and pleural cavity and likely mediated by macrophages. In conclusion, intrapulmonary administration of multi-walled carbon nanotubes, like asbestos, induced mesothelial proliferation potentially associated with mesothelioma development.

RAS oncogenic signal upregulates EZH2 in pancreatic cancer

The neoplastic transformation by mutant RAS is thought to require remodeling of expression of an entire set of genes. However, the underlying mechanism for initiation of gene expression remodeling in tumorigenesis remains elusive. This study was aimed to define the oncogenic role of EZH2, a histone modifier protein that is induced by oncogenic mutant RAS, using pancreatic cancers of transgenic rats exogenously expressing human mutant RAS. Immunohistochemical observation of preneoplastic or cancerous lesions in the animal model suggested that upregulation of Ezh2 protein is an initiating event in pancreatic carcinogenesis. MEK-inhibition or Elk-1-knockdown downregulated EZH2, and MEK-inhibition or EZH2-knockdown restored expression of a tumor suppressor, RUNX3 in human and rat pancreatic cancer cells activated by the oncogenic RAS. Furthermore, Elk-1- or EZH2-knockdown inhibited growth of the cancer cells. These results strongly suggested that the oncogenic RAS upregulates EZH2 through MEK-ERK signaling, resulted in downregulation of tumor suppressors including RUNX3 in pancreatic carcinogenesis.

Serum level of expressed in renal carcinoma (ERC)/ mesothelin in rats with mesothelial proliferative lesions induced by multi-wall carbon nanotube (MWCNT)

Expressed in renal carcinoma (ERC)/mesothelin is a good biomarker for human mesothelioma and has been investigated for its mechanistic rationale during the mesothelioma development. Studies are thus ongoing in our laboratories to assess expression of ERC/mesothelin in sera and normal/proliferative/neoplastic mesothelial tissues of animals untreated or given potentially mesothelioma-inducible xenobiotics, by an enzyme-linked immunosorbent assay (ELISA) for N- and C-(terminal fragments of) ERC/mesothelin and immunohistochemistry for C-ERC/mesothelin. In the present paper, we intend to communicate our preliminary data, because this is the first report to show how and from what stage the ERC/mesothelin expression changes during the chemical induction of mesothelial proliferative/neoplatic lesions. Serum N-ERC/mesothelin levels were 51.4 +/- 5.6 ng/ml in control male Fischer 344 rats, increased to 83.6 +/- 11.2 ng/ml in rats given a single intrascrotal administration of 1 mg/kg body weight of multi-wall carbon nanotube (MWCNT) and bearing mesothelial hyperplasia 52 weeks thereafter, and further elevated to 180 +/- 77 ng/ml in rats similarly treated and becoming moribund 40 weeks thereafter, or killed as scheduled at the end of week 52, bearing mesothelioma. While C-ERC/mesothelin was expressed in normal and hyperplastic mesothelia, the protein was detected only in epithelioid mesothelioma cells at the most superficial layer. It is thus suggested that ERC/mesothelin can be used as a biomarker of mesothelial proliferative lesions also in animals, and that the increase of levels may start from the early stage and be enhanced by the progression of the mesothelioma development.

Abstract 2474: Increased PKC expression in diacylglycerol-induced mammary carcinogenesis in the human c-Ha-ras proto-oncogene transgenic rat

Protein kinase C (PKC) is implicated in cell proliferation and tumor promotion. PKC is activated by 1, 2-diacylglycerol (1, 2-DAG). An edible oil that includes 70% 1,3-DAG and 30% 1,2-DAG is commercially available in Japan, USA, and European countries. To examine whether the DAG oil enhances mammary carcinogenesis and to measure whether DAG affects the levels of PKC expression, we carried out this study with human c-Ha-ras proto-oncogene transgenic (Hras128) rats that are highly susceptible to mammary carcinogenesis. Hras128 rats (6-week-old) were randomly assigned into four experimental groups. DAG oil was administered to the rat as oral drops. Group 1 (G1): 0.5 mL triacylglyceraol (TAG) x2/week, Group 2 (G2): 0.5 mL DAG x2/week, Group 3 (G3): 0.5 mL TAG x1/week plus 0.5 mL DAG x1/week, Group 4 (G4): 0.5 mL DAG x1/2 weeks + 0.5 mL TAG x3/2 weeks. Experiment was terminated after 15 weeks. Mammary tumors were histologically identified as adenocarcinoma. Tumor incidence of G2 (77%) and G3 (77%) was significantly higher than G1 (22%). Tumor multiplicity of G2 (1.3 ± 1.1) was significantly higher than the other 3 groups (G1, 0.4 ± 1.0; G3, 0.9 ± 0.6; G4, 0.7 ± 1.0). In tumor samples, the mRNA expression levels of 6 PKC isoforms (α, δ, ε, η, λ, ν) increased compared to the adjacent normal tissues. In a parallel study, we also examined the levels of PKC expression in normal mammary tissues of Hras128 rats treated with either TAG or DAG oils alone for 4 weeks. The mRNA expression levels of 5 PKC isoforms (δ, ε, η, λ, θ) significantly increased in the DAG-treated normal tissues compared to the TAG-treated normal tissues. These findings provide evidence that treatment of Hras128 rats with DAG oil may promote mammary carcinogenesis by inducing expression of several PKC isoforms.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2474.

Enhancement of tongue carcinogenesis in Hras128 transgenic rats treated with 4-nitroquinoline 1-oxide

Transgenic rats carrying human c-Ha-ras proto-oncogene (Hras128 rats) have been shown to be highly susceptible to induction of tumors. We have found an early induction of tongue tumors in Hras128 rats treated with 4-nitroquinoline 1-oxide (4NQO). 4NQO was administered to the Hras128 and wild-type Sprague-Dawley (SD) rats for 4 and 8 weeks, respectively. The experiment was terminated at 14 (Hras128 rats) and 28 (SD rats) weeks. Either during or after treatment with 4NQO, dysplastic hyperplasia, papilloma and squamous cell carcinoma were found on the tongue of both Hras128 and wild-type rats, with a higher incidence and multiplicity in Hras128 rats. Treatment of the Hras128 rats with 4NQO significantly increased cell proliferation in the tumor compared to the control rats. In the tongue tumors of the Hras128 rats, there was a significant increase in the mRNA expression levels of cyclin D1 and COX2. To examine whether this experimental system is useful for screening of the candidate agents for cancer preventive effect, nimesulide, a selective COX2 inhibitor, was tested in the present model. Nimesulide significantly decreased total multiplicity of tongue lesions compared to the control rats. Treatment of Hras128 rats with nimesulide caused a significant decrease in the levels of mRNA expression of cyclin D1 and COX2 in the tumor. Therefore, the current 4NQO-induced Hras128 rat tongue carcinogenesis model provides a simple and rapid system for investigating carcinogenesis process and evaluating the effect of possible cancer preventive agents for human tongue cancer.

A medium-term, rapid rat bioassay model for the detection of carcinogenic potential of chemicals

The Ito Liver Model and the Ito Multi-organ Model are used in conjunction and constitute an efficient and rapid bioassay for the identification of both genotoxic and nongenotoxic carcinogenic chemicals. The Ito Liver Model is an 8-week bioassay system that uses the number and size of foci of hepatocytes positive for glutathione S-transferase placental form (GST-P) as the end-point marker. One hundred fifty-nine compounds were tested using the Ito Liver Model: 61 of 66 hepatocarcinogens tested positive, and 10 of 43 nonliver carcinogens were also positive. The false-positive detection of noncarcinogens was low; a single false-positive result was obtained from the 50 noncarcinogens tested. Since more than half of all known carcinogens are hepatocarcinogens in rodents, the initial 8-week bioassay is able to detect most carcinogens. The Ito Multi-organ Model is a 28-week bioassay system for the detection of carcinogens that were not identified by the Ito Liver Model. Results are evaluated by preneoplastic and neoplastic lesions in major organs. Forty-four compounds were tested using the Ito Multi-organ Model: 17 out of 17 liver carcinogens were positive, and 19 out of 22 (86%) nonliver carcinogens were positive. None of the five noncarcinogens tested positive.

Mature acinar cells are refractory to carcinoma development by targeted activation of Ras oncogene in adult rats

Pancreatic ductal adenocarcinoma (PDA) is one of the most debilitating malignancies in humans. A thorough understanding of the cytogenesis of this disease will aid in establishing successful treatments. We have developed an animal model which uses adult Hras(G12V) and Kras(G12V) transgenic rats in which oncogene expression is regulated by the Cre/loxP system and neoplastic lesions are induced by injection of adenovirus-expressing Cre recombinase. When adenovirus with Cre recombinase under the control of the CMV enhancer/chicken beta-actin (CAG) promoter (Ad-CAG-Cre) is injected into the pancreatic duct of these animals, pancreatic neoplasias develop. Pathologically, the origin of these lesions is duct, intercalated duct, and centroacinar cells, but not acinar cells. The present study was undertaken to test the effect of acinar cell-specific oncogenic ras expression. Adult transgenic rats were injected with adenovirus with Cre recombinase under the control of the acinar cell-specific promoters amylase (Ad-Amy-Cre) and elastase-1 (Ad-Ela-Cre) or under the control of the non-specific CAG promoter. Injection of either Ad-Amy-Cre or Ad-Ela-Cre into the pancreatic ducts of transgenic animals in which oncogenic Kras is tagged with hemagglutinin (HA), HA-Kras(G12V) rats resulted in expression of oncogenic ras in acinar cells but not in duct, intercalated duct, or centroacinar cells. Notably, injected animals did not develop any observable proliferative or neoplastic lesions. In marked contrast, injection of Ad-CAG-Cre resulted in pancreatic cancer development within 4 weeks. These results indicate that adult acinar cells are refractory to Ras oncogene activation and do not develop neoplasia in this model.

Comparative study of heart rate variability between healthy human subjects and healthy dogs, rabbits and calves

Several studies have been performed to assess heart rate variability (HRV) in several species such as humans, dogs, pigs, calves, rabbits and rats. However, haemodynamic parameters are totally different in each animal, and optimal animal models for studying HRV corresponding to human HRV are still unclear. The purpose of this study was to assess HRV in human subjects and to compare those HRV data with canine, bovine and rabbit HRV data. The heart rate in the human subjects (62.8 ± 7.4 bpm) was significantly lower than that in dogs (124.2 ± 18.8 bpm, P < 0.001), calves (73.4 ± 10.5 bpm, P < 0.05), and rabbits (217.3 ± 21.5 bpm, P < 0.001). The low-frequency waves (LF) (57.9 ± 65.8 ms2/Hz) and high-frequency waves (HF) (33.8 ± 49.1 ms2/Hz) in rabbits were significantly lower than human LF (1216.3 ± 1220.7 ms2/Hz, P < 0.05) and HF (570.9 ± 581.3 ms2/Hz, P < 0.05). Dogs and calves showed similar LF (991.1 ± 646.1 ms2/Hz and 547.0 ± 256.9 ms2/Hz, respectively), HF (702.1 ± 394.1 ms2/Hz and 601.0 ± 666.6 ms2/Hz, respectively) and LF/HF (2.0 ± 1.3 and 2.5 ± 1.9, respectively) when compared with the human data. The present study shows that dogs and calves revealed similar HRV values as those which relate to humans. Large deviation of the HRV values in rabbits compared with humans might be considered when conducting animal studies using those animals to reflect human clinical situations.

Toxicology of engineered nanomaterials - a review of carcinogenic potential

Nanotechnology has considerable socioeconomic potential. Benefits afforded by engineered nanoparticles (NP: defined as being less than 100 nm in diameter) are expected to be significant in fields such as plastics, energy, electronics, aerospace and medicine. However, NPs are being introduced into the market without adequate assessment of their potential toxicities. It is urgently important to conduct risk assessment of commercial NPs and establish a framework enabling risk management which is not subordinate to their commercial production. An overview of currently available carcinogenicity risk evaluation results of NP materials raises serious questions as to their safety. NP sized titanium dioxide (nTiO(2)) and carbon black (nCB) are carcinogenic to the lung of female rats, and the tumors preferentially include squamous cell morphology. Carbon nanotubes (CNT) induce mesotheliomas when applied intraperitoneally in rats and mice. Data for Fullerenes are insufficient to evaluate carcinogenic risk. Sub-chronic toxicity data indicate that, in general, NPs form aggregates and agglomerates and cause foreign body reactions at their applied sites with inflammatory cell, including macrophage, infiltration. These findings are similar to the biological effects of asbestos, a potent carcinogen, and indicate that careful assessment of NPs is indispensable.