Publications by authors named "Masahiro Takeyoshi"

39 Publications

Registration status of skin sensitisation data derived from the Local Lymph Node Assay (LLNA): BrdU-ELISA in REACH.

Arch Toxicol 2021 Mar 22. Epub 2021 Mar 22.

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Tokyo, Japan.

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http://dx.doi.org/10.1007/s00204-021-03029-9DOI Listing
March 2021

Development of a new photosafety test method based on singlet oxygen generation detected using electron spin resonance.

J Appl Toxicol 2021 Feb 15;41(2):247-255. Epub 2020 Jul 15.

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Saitama, Japan.

Photosafety evaluations of chemicals used in consumer products, such as pharmaceuticals and cosmetics, are very important. Currently, two non-animal tests for photosafety evaluations, the in vitro 3T3 neutral red uptake phototoxicity test (NRU PT) and the reactive oxygen species (ROS) assay, are used to detect photoreactive chemicals. However, these two tests are difficult to apply to hydrophobic chemicals. In the present study, we attempted to develop a new photosafety test method, named the electron spin resonance-based photosafety test (ESR-PT), that would be applicable even to hydrophobic chemicals based on the detection of singlet oxygen generation after irradiation using ESR spectroscopy with 4-hydroxy-2,2,6,6-tetramethyl-piperidine as a spin trap reagent. To achieve a quantitative evaluation, the singlet oxygen formation (SOF) value, which can be calculated as the increment in relative intensity after irradiation of the test mixture normalized by the increment in relative intensity after irradiation of the vehicle control solution, was calculated. The performance of the ESR-PT was evaluated by testing all the proficiency chemicals of the ROS assay plus additional chemicals, including hydrophobic chemicals and chemicals that tested false negative in the 3T3-NRU PT and ROS assay. SOF values were successfully calculated for all the chemicals tested including the hydrophobic chemicals, and the accuracy of the ESR-PT using a tentative cutoff value of 2.8 against the photosafety information was 100%. Therefore, the SOF value could be an effective parameter for photosafety evaluations, suggesting that the newly developed ESR-PT is a promising non-animal test applicable even to hydrophobic chemicals.
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http://dx.doi.org/10.1002/jat.4040DOI Listing
February 2021

Applicability of the proposed GHS subcategorization criterion for LLNA:BrdU-ELISA (OECD TG442B) to the CBA/J strain mouse.

J Appl Toxicol 2020 10 5;40(10):1435-1439. Epub 2020 May 5.

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Shimotakano, Sugito-machi, Kitakatsushika-gun, Saitama, Japan.

The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is a hazard classification and communication system for providing information on the safe handling of chemicals worldwide. In this study, we evaluated the applicability of the newly proposed GHS subcategorization criterion for murine local lymph node assay:2-bromodeoxyuridine enzyme-linked immunosorbent assay (LLNA:BrdU-ELISA), Category 1A:EC1.6 ≤6%, Category 1B:EC1.6 >6%, to data derived from LLNA:BrdU-ELISA performed in the CBA/J strain mouse. Fifteen chemicals categorized in GHS hazard Category 1 sensitizers listed in the LLNA performance standard were tested by LLNA:BrdU-ELISA in the CBA/J strain mouse and were classified according to the new criterion. The results revealed that all of the GHS 1A or 1B category chemicals classified according to the EC3 values derived from radioisotopic LLNA (LLNA-RI) could be correctly assigned into the respective 1A and 1B categories using the newly proposed GHS subclassification criterion. In addition, analysis of the correlation between the reported EC3 values and EC1.6 values derived from the LLNA:BrdU-ELISA performed in the CBA/J strain mouse confirmed the existence of a strong correlation (r = 0.9076, P < .0001). These findings suggest that the newly proposed GHS subcategorization criterion for LLNA:BrdU-ELISA is potentially applicable for practical use in GHS subcategorization.
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http://dx.doi.org/10.1002/jat.3996DOI Listing
October 2020

α-Sens: The improved ARE-Nrf2-based sensitization screening assay using normalized transcriptional activity.

Toxicology 2020 06 23;439:152476. Epub 2020 Apr 23.

The United Graduate School of Veterinary Science, Yamaguchi University, Japan.

Two non-animal test methods, KeratinoSens™ and LuSens, have been approved by the Organization of Economic Cooperation and Development (OECD) test guidelines for evaluating the sensitization potential of chemicals, and been positioned as a method for appraising key event (KE)-2, namely, the keratinocyte response component of the Adverse Outcome Pathway (AOP) in sensitization process. However, these two methods require separate cytotoxicity tests to determine the concentrations to be tested in the main test. Therefore, we developed a simple and highly accurate KE-2 test method named α-Sens that uses the dual luciferase assay system and attempted a further application of luciferase-based determination of cell viability to calculate the normalized Antioxidant response element (ARE)-mediated transcriptional activity, named normalized ARE Activity (nAA), to evaluate the sensitizing potential of chemicals. A cell line carrying the ARE-inducible Firefly luciferase reporter gene and Thymidine kinase (TK) promoter-driven Renilla luciferase gene was established and used for the α-Sens. A total of 28 chemicals, consisting of 19 skin sensitizers and nine non-skin sensitizers were tested by this assay system. The α-Sens yielded an accuracy (%), sensitivity (%), and specificity (%) against corresponding values for local lymph node assay of 96.4 %, 95.0 %, and 100 %, respectively, and for human data of 100 % for all. The α-Sens gave clear positive results for phenyl benzoate and eugenol, chemicals for which KeratinoSens™ or LuSens yielded false-negative results, using a new parameter. Our results suggest that better prediction capacity could be achieved by using nAA as a classifier compared to other existing KE-2 test methods. In conclusion, the α-Sens is promising as a simple and highly accurate in vitro skin sensitization test method for evaluation of KE-2.
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http://dx.doi.org/10.1016/j.tox.2020.152476DOI Listing
June 2020

Proposal of GHS sub-categorization criteria for LLNA: BrdU-ELISA (OECD TG442B).

Regul Toxicol Pharmacol 2019 Oct 18;107:104409. Epub 2019 Jun 18.

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute (CERI), 1600, Shimotakano, Sugito-machi, Kitakatsushika-gun, Saitama, 3450043, Japan.

The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is a hazard classification and communication system for providing information on the safe handling of chemicals worldwide. While the GHS provides sub-categorization criteria for sensitizers when using the guinea pig maximization test/Buehler test (OECD TG406) and the standard radioisotopic LLNA (OECD TG429), the sub-categorization criteria for LLNA: BrdU-ELISA (OECD TG442B) are not currently provided. In this study, we re-analyzed the existing data of 32 sensitizers classified in the 1A or 1B categories of the GHS, and attempted to determine optimal criteria for GHS sub-categorization using LLNA: BrdU-ELISA. Consequently, the optimal criterion for the GHS sub-categorization was determined to be 6% when using EC1.6, showing the correct outcomes (%) for GHS 1A and GHS 1B category chemicals were 92.3 and 84.2 for all 32 chemicals, respectively. When excluding 2-mercaptobenzothiazole which may cause strain specific low response in this assay system, the correct outcomes (%) for GHS 1A chemicals was 100. Further work would be necessary, but the GHS sub-categorization criteria proposed in this study might be promising when using LLNA: BrdU-ELISA to provide information on the skin sensitization potency category of chemicals.
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http://dx.doi.org/10.1016/j.yrtph.2019.104409DOI Listing
October 2019

Effects of Soluble Tumor Necrosis Factor (TNF) on Antibody-Dependent Cellular Cytotoxicity of Therapeutic anti-TNF-α Antibody.

Immunol Invest 2019 Jul 20;48(5):441-450. Epub 2018 Dec 20.

a Chemicals Assessment and Research Center , Chemicals Evaluation and Research Institute , Saitama , Japan.

Anti-TNF antibodies are major therapeutics for rheumatoid arthritis and have been approved for marketing in many countries. Antibody-dependent cellular cytotoxicity (ADCC) is considered to be a potential mechanism of action of anti-TNF antibodies, since some anti-TNF antibodies have been confirmed to induce cytotoxic effects on TNF-producing cells via ADCC and complement-dependent cytotoxicity (CDC) in experiments. In this study, we established a new stable effector cell line expressing human FcγRIIIa, CD16:KHYG-1, and compared the performance of this cell line with that of peripheral blood mononuclear cells (PBMCs) in ADCC assays against CHO-derived target cells expressing protease-sensitive pro-TNF. Although an inhibitory effect of soluble TNF released from pro-TNF expressing cells on ADCC activity was seen, clear dose-responsive ADCC activities were observed even in the presence or absence of TNF-α converting enzyme (TACE) inhibitor. However, significant differences in the ADCC activities in the presence or absence of TACE inhibitor were only noted when CD16:KHYG-1 cells were used as the effector cells. Our findings indicate that soluble TNF may influence ADCC activity of anti-TNF antibody. Moreover, the fact that the influence was able to be detected only in the case using stable effector cell also suggests that the stable effector cell established this time enable highly accurate ADCC measurement.
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http://dx.doi.org/10.1080/08820139.2018.1549067DOI Listing
July 2019

New approach to predict photoallergic potentials of chemicals based on murine local lymph node assay.

J Appl Toxicol 2018 10 23;38(10):1316-1322. Epub 2018 May 23.

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Saitama, Japan.

Photoallergic dermatitis, caused by pharmaceuticals and other consumer products, is a very important issue in human health. However, S10 guidelines of the International Conference on Harmonization do not recommend the existing prediction methods for photoallergy because of their low predictability in human cases. We applied local lymph node assay (LLNA), a reliable, quantitative skin sensitization prediction test, to develop a new photoallergy prediction method. This method involves a three-step approach: (1) ultraviolet (UV) absorption analysis; (2) determination of no observed adverse effect level for skin phototoxicity based on LLNA; and (3) photoallergy evaluation based on LLNA. Photoallergic potential of chemicals was evaluated by comparing lymph node cell proliferation among groups treated with chemicals with minimal effect levels of skin sensitization and skin phototoxicity under UV irradiation (UV+) or non-UV irradiation (UV-). A case showing significant difference (P < .05) in lymph node cell proliferation rates between UV- and UV+ groups was considered positive for photoallergic reaction. After testing 13 chemicals, seven human photoallergens tested positive and the other six, with no evidence of causing photoallergic dermatitis or UV absorption, tested negative. Among these chemicals, both doxycycline hydrochloride and minocycline hydrochloride were tetracycline antibiotics with different photoallergic properties, and the new method clearly distinguished between the photoallergic properties of these chemicals. These findings suggested high predictability of our method; therefore, it is promising and effective in predicting human photoallergens.
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http://dx.doi.org/10.1002/jat.3643DOI Listing
October 2018

Applicability of an Integrated Testing Strategy consisting of in silico, in chemico and in vitro assays for evaluating the skin sensitization potencies of isocyanates.

Toxicology 2018 01 1;393:9-14. Epub 2017 Nov 1.

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute (CERI), 1-4-25 Koraku, Bunkyo-ku, Tokyo 112-0004, Japan.

The skin sensitization potential of chemicals has been traditionally assessed using regulatory accepted in vivo methods, such as guinea pig maximization test or mouse local lymph node assays (LLNAs). A huge effort to reduce and replace the use of animals for safety assessments of chemicals because of regulatory requirements and ethical issues is presently underway, and alternative non-animal methods have been greatly developed. So far, a few studies have investigated the sensitization potencies of isocyanates which is a group of highly reactive chemicals that are known to be occupational allergens. The present study evaluated nine commonly used isocyanates using an in vivo LLNA and assessed the applicability of an Integrated Testing Strategy (ITS) consisting of an in silico Derek Nexus prediction, an in chemico direct peptide reactivity assay (DPRA), and an in vitro human Cell Line Activation Test (h-CLAT) to isocyanates. All nine isocyanates were evaluated as positive using the LLNA, Derek Nexus and DPRA, whereas seven chemicals tested positive using the h-CLAT: hexamethylene diisocyanate tested negative, and 1,5-diisocyanatonaphthalene could not be examined because of a solubility issue. When assessed using the ITS, the positive/negative evaluations of skin sensitization hazard were consistent with those assessed using the LLNA for all nine chemicals. However, the potency prediction results of the ITS tended to be underestimated, compared with those of the LLNA. The data presented in this work provide insights into the performance of non-animal testing approaches for evaluating the skin sensitization potencies of isocyanates.
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http://dx.doi.org/10.1016/j.tox.2017.10.015DOI Listing
January 2018

Investigation of the early-response genes in chemical-induced renal carcinogenicity for the prediction of chemical carcinogenicity in rats.

J Toxicol Sci 2017 ;42(2):175-181

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute.

This study was designed to identify early-response genes of chemical-induced renal carcinogenicity for the prediction of chemical carcinogenicity in rats. We conducted a 28-day repeated-dose test in male Crl:CD (SD) rats with 12 carcinogens and 10 non-carcinogens as the training dataset, and five carcinogens and five non-carcinogens as the validation dataset. Renal gene expression profiles were analyzed by using a microarray. Fifteen candidate genes were selected from the gene expression profiles of the training dataset as genes that showed specific expression in response to carcinogens. To assess the prediction performance of the candidate genes for renal carcinogenicity, a prediction formula was developed on the basis of the gene expression data. When this formula was applied to the training dataset to check its predictive performance, all of the carcinogens and non-carcinogens were predicted correctly; the prediction formula was then applied to the validation dataset, and five carcinogens and four non-carcinogens were correctly predicted. However, 4-Hydroxy-m-phenylenediammonium dichloride (AMIDOL), a known non-renal carcinogen, was judged as positive. Therefore, the accuracy of the prediction formula for renal carcinogenicity was 100% for the training dataset and 90% for the validation dataset. Among the predictive genes, Hamp and Ranbp1 are known to be important for cell growth and cell cycle regulation, which are important events in carcinogenesis. Given our current limited knowledge of the genes responsible for renal carcinogenesis, the identification of candidate genes of chemical-induced renal carcinogenicity by use of this gene expression-based prediction method represents a promising advance in renal carcinogen identification.
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http://dx.doi.org/10.2131/jts.42.175DOI Listing
August 2017

Simpler alternative to CARCINOscreen(®) based on quantitative PCR (qPCR).

J Toxicol Sci 2016 ;41(3):383-90

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Japan (CERI).

Carcinogenicity of chemicals in our environment is one of the most important health hazards to humans. Recently, a microarray-based short-term prediction system for the hepatocarcinogenicity of chemicals, named CARCINOscreen(®), was developed. Although the system is a promising tool reported to have an ability to predict hepatocarcinogenicity in rats with 92.9% accuracy, it requires specialized equipment and skilled bioinformatics approaches for data analysis. Therefore, we attempted to develop a quantitative PCR (qPCR)-based system as an alternative to microarray-based CARCINOscreen(®). Finally, an optimized gene set consisting of four predictive genes (Abcb1b, Eprs, Map3K8, and Igh-6) was selected from among 3,150 combinations of candidate gene sets. The results of training- and validation-phase trials showed that the qPCR-based alternative to the microarray-based CARCINOscreen(®) could predict the hepatocarcinogenicity of chemicals in rats with 82.8%-86.4% accuracy. One of the predictive genes, Abcb1b, a member of the ATP-binding cassette protein superfamily and multi-drug resistance-associated protein, and the results of this study may indicate a close relation of this gene to the carcinogenicity of chemicals. The prediction performance of the qPCR-based CARCINOscreen(®), as well as its user-friendliness and cost efficiency, suggests that this method is promising for application to primary health hazard assessment. Thus, the qPCR-based CARCINOscreen(®) is considered as a promising tool for predicting the carcinogenicity of chemicals.
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http://dx.doi.org/10.2131/jts.41.383DOI Listing
April 2017

Identification of sheep red blood cell (SRBC) surface immune-responsive peptides detected by antisera from SRBC-immunized rats.

J Toxicol Sci 2016 Feb;41(1):13-6

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Japan.

To identify the sheep red blood cell (SRBC) surface immune-responsive peptides, immuno-reactive fraction of SRBC was detected by SDS-PAGE and western blot analysis with antisera from SRBC-immunized rats. Then the most intense immuno-reactive band on SDS-PAGE was subjected to nanoLC-ESI-MS/MS analysis, and 17 proteins were identified including membrane proteins of erythrocytes such as band 3 anion transport protein isoform 1 (Anion exchange protein 1; AE-1, CD233), Ammonium transporter Rh type A (Rh type A glycoprotein, CD241) and Ankyrin-1 (ANK-1), Spectrin beta chain. Among them, plasma protein AE-1 (CD233) and Rh type A glycoprotein (CD241) have transmembrane domain and correspond to extracellular region in their sequences. These extracellular regions of the plasma membrane proteins are supposed to be major immune-responsive peptides of SRBC in rats. These peptides are promising for the construction of an ELISA system which does not require the processing of SRBC membrane ghosts.
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http://dx.doi.org/10.2131/jts.41.13DOI Listing
February 2016

Differences in gene expression profiles in liver caused by different types of anesthesia: cases of CO2-O2 and isoflurane.

J Toxicol Sci 2015 Dec;40(6):829-36

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Japan (CERI).

Anesthesia is used for pain control and is necessary in toxicological studies. In this study, we examined the effects of anesthesia on gene expression profiles caused by different types of anesthesia. To elucidate the effects of anesthesia on gene expression profiles, DNA microarray analysis was performed with CO2-O2 anesthesia and isoflurane anesthesia, and gene expression profiles in the liver were analyzed. Consequently, a total of 209 probes out of 61,573 showed higher or lower expression levels in the isoflurane anesthesia group compared with CO2-O2 anesthesia. This is less than 0.34% of all probes, indicating that the effects of different types of anesthesia on gene expression profiles are limited. However, careful consideration should be taken in the cases of handling the disturbed genes using DNA microarray, especially in case of research on glutathione-related pathway under isoflurane anesthesia.
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http://dx.doi.org/10.2131/jts.40.829DOI Listing
December 2015

Applicability of a gene expression based prediction method to SD and Wistar rats: an example of CARCINOscreen®.

J Toxicol Sci 2015 Dec;40(6):805-7

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Japan (CERI).

Recently, the development of several gene expression-based prediction methods has been attempted in the fields of toxicology. CARCINOscreen® is a gene expression-based screening method to predict carcinogenicity of chemicals which target the liver with high accuracy. In this study, we investigated the applicability of the gene expression-based screening method to SD and Wistar rats by using CARCINOscreen®, originally developed with F344 rats, with two carcinogens, 2,4-diaminotoluen and thioacetamide, and two non-carcinogens, 2,6-diaminotoluen and sodium benzoate. After the 28-day repeated dose test was conducted with each chemical in SD and Wistar rats, microarray analysis was performed using total RNA extracted from each liver. Obtained gene expression data were applied to CARCINOscreen®. Predictive scores obtained by the CARCINOscreen® for known carcinogens were > 2 in all strains of rats, while non-carcinogens gave prediction scores below 0.5. These results suggested that the gene expression based screening method, CARCINOscreen®, can be applied to SD and Wistar rats, widely used strains in toxicological studies, by setting of an appropriate boundary line of prediction score to classify the chemicals into carcinogens and non-carcinogens.
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http://dx.doi.org/10.2131/jts.40.805DOI Listing
December 2015

Comparison of outcomes obtained in murine local lymph node assays using CBA/J or CBA/Ca mice.

J Appl Toxicol 2016 08 12;36(8):1011-4. Epub 2015 Oct 12.

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute (CERI), 1600, Shimotakano, Sugito-machi, Kitakatsushika-gun, Saitama, 345-0043, Japan.

CBA/J and CBA/Ca mice are the recommended strains for local lymph node assays (LLNAs). Here, we report quantitative and qualitative comparisons between both mouse strains to provide useful information for the strain selection of sensitization testing. LLNA was conducted, in accordance with Organisation for Economic Co-operation and Development Test Guideline No. 429, with CBA/J and CBA/Ca mice using five chemicals including typical contact sensitizers and non-sensitizers: 2,4-dinitrochlorobenzene (DNCB), isoeugenol, α-hexylcinnamic aldehyde (HCA), propylene glycol (PG), and hexane; then outcomes were compared based on the raw data (disintegrations per minute, DPM), stimulation index (SI) values, EC3 values and positive/negative decisions. Although a significant difference was noted between DPM values derived from each strain of mice, SI values exhibited no considerable difference. The EC3 values for DNCB in CBA/J and CBA/Ca mice were 0.04 and 0.03, those for isoeugenol were 1.4 and 0.9, and those for HCA were 7.7 and 6.0, respectively. All EC values derived from each test system were almost equivalent and were within the range of acceptance criteria of the ICCVAM performance standard for LLNA. Positive/negative outcomes for all test chemicals were consistent. In conclusion, no considerable differences were observed in the final outcomes derived from CBA/J and CBA/Ca mice in LLNA. Copyright © 2015 John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/jat.3250DOI Listing
August 2016

CARCINOscreen®: New short-term prediction method for hepatocarcinogenicity of chemicals based on hepatic transcript profiling in rats.

J Toxicol Sci 2014 ;39(5):725-34

Chemicals Assessment and Research Center, Chemicals Evaluation and Research Institute, Japan (CERI).

Carcinogenicity is one of the most serious toxic effects of chemicals, and highly accurate methods for predicting carcinogens are strongly desired for human health. Here, we developed a new prediction system named "CARCINOscreen®" for evaluating the carcinogenic potentials of chemicals using the gene expression profiles of liver tissues from rats after a 28-day repeated dose toxicity study.The prediction formula was generated using a support vector machine with predictive genes selected from 68 training chemical datasets; a predictive score was then calculated to predict the carcinogenic potentials of the tested chemicals. To ensure the accuracy of the prediction system, the chemicals were divided into three groups (Groups 1 to 3) according to the resulting hepatic gene expression profiles, and a prediction formula was generated for each group. The prediction system was capable of predicting the carcinogenicity of training carcinogens and non-carcinogens with an accuracy of 92.9% to 100%. The final prediction result was determined based on the maximum prediction value obtained with three independent prediction formulas to build up the CARCINOscreen®. The system was able to predict carcinogenicity accurately in 94.1% of the 68 training chemicals. An external validation trial was performed with 16 chemicals, consisting of various carcinogens targeting rat liver or other organs and non-carcinogens. The system identified 68.8% of all the chemicals and 100% of the rat liver carcinogens as carcinogens. Thus, the CARCINOscreen®, a novel system for predicting hepatocarcinogenicity, is a promising tool for the prediction of rat liver carcinogens.
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http://dx.doi.org/10.2131/jts.39.725DOI Listing
April 2015

Downregulation of immediate-early genes linking to suppression of neuronal plasticity in rats after 28-day exposure to glycidol.

Toxicol Appl Pharmacol 2014 Sep 8;279(2):150-62. Epub 2014 Jun 8.

Laboratory of Veterinary Pathology, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan. Electronic address:

We previously found that the 28-day oral toxicity study of glycidol at 200mg/kg/day in rats resulted in axonopathy in both the central and peripheral nervous systems and aberrations in the late-stage of hippocampal neurogenesis targeting the process of neurite extension. To capture the neuronal parameters in response to glycidol toxicity, these animals were subjected to region-specific global gene expression profiling in four regions of cerebral and cerebellar architectures, followed by immunohistochemical analysis of selected gene products. Expression changes of genes related to axonogenesis and synaptic transmission were observed in the hippocampal dentate gyrus, cingulate cortex and cerebellar vermis at 200mg/kg showing downregulation in most genes. In the corpus callosum, genes related to growth, survival and functions of glial cells fluctuated their expression. Immunohistochemically, neurons expressing gene products of immediate-early genes, i.e., Arc, Fos and Jun, decreased in their number in the dentate granule cell layer, cingulate cortex and cerebellar vermis. We also applied immunohistochemical analysis in rat offspring after developmental exposure to glycidol through maternal drinking water. The results revealed increases of Arc(+) neurons at 1000ppm and Fos(+) neurons at ≥300ppm in the dentate granule cell layer of offspring only at the adult stage. These results suggest that glycidol suppressed neuronal plasticity in the brain after 28-day exposure to young adult animals, in contrast to the operation of restoration mechanism to increase neuronal plasticity at the adult stage in response to aberrations in neurogenesis after developmental exposure.
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http://dx.doi.org/10.1016/j.taap.2014.05.017DOI Listing
September 2014

Expression alterations of genes on both neuronal and glial development in rats after developmental exposure to 6-propyl-2-thiouracil.

Toxicol Lett 2014 Aug 26;228(3):225-34. Epub 2014 Apr 26.

Laboratory of Veterinary Pathology, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo 183-8509, Japan. Electronic address:

The present study was performed to determine target gene profiles associated with pathological mechanisms of developmental neurotoxicity. For this purpose, we selected a rat developmental hypothyroidism model because thyroid hormones play an essential role in both neuronal and glial development. Region-specific global gene expression analysis was performed at postnatal day (PND) 21 on four brain regions representing different structures and functions, i.e., the cerebral cortex, corpus callosum, dentate gyrus and cerebellar vermis of rats exposed to 6-propyl-2-thiouracil in the drinking water at 3 and 10ppm from gestational day 6 to PND 21. Expression changes of gene clusters of neuron differentiation and development, cell migration, synaptic function, and axonogenesis were detected in all four regions. Characteristically, gene expression profiles suggestive of affection of ephrin signaling and glutamate transmission were obtained in multiple brain regions. Gene clusters suggestive of suppression of myelination and glial development were specifically detected in the corpus callosum and cerebral cortex. Immunohistochemically, immature astrocytes immunoreactive for vimentin and glial fibrillary acidic protein were increased, and oligodendrocytes immunoreactive for oligodendrocyte lineage transcription factor 2 were decreased in the corpus callosum. Immunoreactive intensity of myelin basic protein was also decreased in the corpus callosum and cerebral cortex. The hippocampal dentate gyrus showed downregulation of Ptgs2, which is related to synaptic activity and neurogenesis, as well as a decrease of cyclooxygenase-2-immunoreactive granule cells, suggesting an impaired synaptic function related to neurogenesis. These results suggest that multifocal brain region-specific microarray analysis can determine the affection of neuronal or glial development.
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http://dx.doi.org/10.1016/j.toxlet.2014.04.018DOI Listing
August 2014

Inter-laboratory validation of the modified murine local lymph node assay based on 5-bromo-2'-deoxyuridine incorporation.

J Appl Toxicol 2011 Jan;31(1):63-74

National Institute of Health Sciences, Tokyo, Japan.

The murine local lymph node assay (LLNA) is a well-established alternative to the guinea pig maximization test (GPMT) or Buehler test (BT) for the assessment of the skin sensitizing ability of a drug, cosmetic material, pesticide or industrial chemical. Instead of radioisotope using in this method, Takeyoshi M. et al. (2001) has developed a modified LLNA based on the 5-bromo-2'-deoxyuridine (BrdU) incorporation (LLNA:BrdU-ELISA). The LLNA:BrdU-ELISA is practically identical to the LLNA methodology excluding the use of BrdU, for which a single intraperitoneal injection of BrdU is made on day 4, and colorimetric detection of cell turnover. We conducted the validation study to evaluate the reliability and relevance of LLNA:BrdU-ELISA. The experiment involved 7 laboratories, wherein 10 chemicals were examined under blinded conditions. In this study, 3 chemicals were examined in all laboratories and the remaining 7 were examined in 3 laboratories. The data were expressed as the BrdU incorporation using an ELISA method for each group, and the stimulation index (SI) for each chemical-treated group was determined as the increase in the BrdU incorporation relative to the concurrent vehicle control group. An SI of 2 was set as the cut-off value for exhibiting skin sensitization activity. The results obtained in the experiments conducted for all 10 chemicals were sufficiently consistent with small variations in their SI values. The sensitivity, specificity, and accuracy of LLNA:BrdU-ELISA against those of GPMT/BT were 7/7 (100%), 3/3 (100%), and 10/10 (100%), respectively.
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http://dx.doi.org/10.1002/jat.1567DOI Listing
January 2011

Gene expression changes induced by type IV allergy-inducible chemicals in dendritic cells.

J Vet Med Sci 2008 Jul;70(7):673-80

Department of Veterinary Hygiene, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Japan.

In the present study, the changes of gene expression profile in dendritic cell (DC)-derived DC2.4 cells sensitized with two allergenic chemicals were analyzed by microarray analysis to develop a basis for an in vitro assessment system of type IV allergenic chemicals. Consequently, 26 genes were significantly up-regulated, and 53 were down-regulated in both groups. Interestingly, some of up-regulated genes were associated with the maturation process of DCs. A set of genes was further evaluated by real-time reverse transcription-polymerase chain reaction to identify the gene expression changes specifically induced by type IV allergy-inducible chemicals in DC2.4 cells, and 2 possible candidates, syndecan-1 (Sdc1) and smoothened (SMO) genes were identified. Thus, up-regulation of Sdc1 gene and down-regulation of SMO gene in DC2.4 cells may be diagnostic markers for the screening of type IV-allergenic chemicals.
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http://dx.doi.org/10.1292/jvms.70.673DOI Listing
July 2008

Interlaboratory validation of the modified murine local lymph node assay based on adenosine triphosphate measurement.

J Pharmacol Toxicol Methods 2008 Jul-Aug;58(1):11-26. Epub 2008 May 21.

Kyoto University School of Public Health, Japan.

Introduction: The murine local lymph node assay (LLNA) is a well-established alternative to the guinea pig maximization test (GPMT) or Buehler test (BT) for the assessment of the skin sensitizing ability of drugs and chemicals. Daicel Chemical Industries Ltd. has developed a modified LLNA based on the adenosine triphosphate (ATP) content (LLNA-DA). We conducted 2 interlaboratory validation studies to evaluate the reliability and relevance of LLNA-DA.

Methods: The experiment involved 17 laboratories, wherein 14 chemicals were examined under blinded conditions. In the first study, 3 chemicals were examined in 10 laboratories and the remaining 9 were examined in 3 laboratories. In the second study, 1 chemical was examined in 7 laboratories and the remaining 4 chemicals were examined in 4 laboratories. The data were expressed as the ATP content for each chemical-treated group, and the stimulation index (SI) for each chemical-treated group was determined as the increase in the ATP content relative to the concurrent vehicle control group. An SI of 3 was set as the cut-off value for exhibiting skin sensitization activity.

Results: The results of the first study obtained in the experiments conducted for the 3 chemicals that were examined in all the 10 laboratories and for 5 of the remaining 9 chemicals were sufficiently consistent with small variations in their SI values. The sensitivity, specificity, and accuracy of LLNA-DA against those of GPMT/BT were 7/8 (87.5%), 3/3 (100%), and 10/11 (90.9%), respectively. In the second study, all the 5 chemicals studied demonstrated acceptably small interlaboratory variations.

Discussion: In the first study, a large variation was observed for 2 chemicals; in the second study, this variation was small. It was attributed to the application of dimethylsulfoxide as the solvent for the metallic salts. In conclusion, these 2 studies provide good evidence for the reliability of the LLNA-DA.
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http://dx.doi.org/10.1016/j.vascn.2008.05.001DOI Listing
October 2008

Comprehensive identification of cytochrome p450 isoforms from solubility-based fractionated rat liver microsomes.

Drug Metab Lett 2007 Dec;1(4):281-6

Chemicals Assessment Center, Chemicals Evaluation and Research Institute, 1600, Shimo-Takano, Sugito-machi, Kitakatsushika-gun, Saitama 345-0043, Japan.

Cytochrome P450 isoforms from male rat liver microsomes were comprehensively identified using nano liquid chromatography tandem mass spectrometry (nanoLC-MS/MS). The enrichment of P450, an endomembrane-anchored heme protein, was achieved by solubility-based protein fractionation, and greatly improved the total number of identified P450 isoforms. LC-MS/MS analysis of fractions resulted in the identification of total 36 P450 isoforms. The combination of proteomic analysis and the solubility-based fractionation would provide powerful tool for the expression analysis of the superfamily proteins having great similarities between the amino acids sequences.
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http://dx.doi.org/10.2174/187231207783221394DOI Listing
December 2007

Skin sensitization potency of isoeugenol and its dimers evaluated by a non-radioisotopic modification of the local lymph node assay and guinea pig maximization test.

J Appl Toxicol 2008 May;28(4):530-4

Health Effect Research Section, Chemicals Assessment Center, Chemicals Evaluation and Research Institute (CERI-Japan), 1600, Shimotakano, Sugito-machi, Kitakatsushika-gun, Saitama 345-0043, Japan.

Allergic contact dermatitis is the serious unwanted effect arising from the use of consumer products such as cosmetics. Isoeugenol is a fragrance chemical with spicy, carnation-like scent, is used in many kinds of cosmetics and is a well-known moderate human sensitizer. It was previously reported that the dimerization of eugenol yielded two types of dimer possessing different sensitization potencies. This study reports the differences in skin sensitization potencies for isoeugenol and two types of dimer, beta-O-4-dilignol and dehydrodiisoeugenol (DIEG), as evaluated by the non-radioisotopic local lymph node assay (non-RI LLNA) and guinea pig maximization test. In the guinea pig maximization test, isoeugenol, beta-O-4-dilignol and DIEG were classified as extreme, weak and moderate sensitizers, respectively. As for the results of non-RI LLNA, the EC3 for isoeugenol, beta-O-4-dilignol and DIEG were calculated as 12.7%, >30% and 9.4%, respectively. The two types of isoeugenol dimer showed different sensitizing activities similar to the case for eugenol dimers. A reduction of sensitization potency achieved by dimerization may lead to developing safer cosmetic ingredients. Isoeugenol dimers are not currently used for fragrance chemicals. However, the dimerization of isoeugenol may yield a promising candidate as a cosmetic ingredient with low sensitization risk. The data may also provide useful information for the structure-activity relationship (SAR) in skin sensitization.
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http://dx.doi.org/10.1002/jat.1305DOI Listing
May 2008

Development of a monoclonal antibody-based sandwich ELISA for detection of guinea pig interleukin-2.

J Vet Med Sci 2006 Dec;68(12):1281-7

Department of Veterinary Hygiene, Faculty of Agriculture, Yamaguchi University, Yamaguchi, Japan.

Interleukin 2 (IL-2) is a T cell proliferation factor released by Th0- and Th1-type helper T cells and is an essential cytokine for immune responses. In the present study, recombinant glutathione S-transferase (GST)-guinea pig IL-2 (GPIL-2) fusion protein was prepared by Escherichia coli (E. coli) and by using this protein as an immunogen, monoclonal antibodies (mAbs) against GPIL-2 were produced to establish a basis for a research on immune responses in guinea pigs. Three stable hybridoma cell lines were established, and specific binding of each mAb to recombinant GPIL-2 produced by E. coli and insect cells infected with recombinant baculovirus was shown by enzyme linked immunosorbent assay (ELISA) and/or immunoblot analysis. Isotype analyses of these mAbs revealed that all three mAbs were IgG1 and had kappa chain. Furthermore, assessment of their epitopes by competition binding assay indicated that the mAbs obtained in this study bound to three different epitopes. Thus, a sandwich ELISA based on the two mAbs specific to different GPIL-2 epitopes was developed for detection of GPIL-2, which had a sensitivity threshold of about 0.3 ng/ml of GPIL-2.
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http://dx.doi.org/10.1292/jvms.68.1281DOI Listing
December 2006

Advantage of using CBA/N strain mice in a non-radioisotopic modification of the local lymph node assay.

J Appl Toxicol 2006 Jan-Feb;26(1):5-9

Hita Laboratory, Chemicals Evaluation and Research Institute, 3-822, Ishii-machi, Hita-shi, Oita 8770061, Japan.

The murine local lymph node assay (LLNA) is currently recognized as a stand-alone test method for determining the skin sensitizing potential of chemicals. It has been incorporated into the official test guidelines published by some authorities, including the OECD. To avoid the use of radioisotopes, efforts have been made recently to develop non-radioisotopic modifications of the LLNA. A non-radioisotopic modification of the LLNA was developed previously using 5-bromo-2'-deoxyuridine (BrdU) incorporation (non-RI LLNA). However, the non-RI LLNA was found to be somewhat less sensitive than the standard assay. This study reports the advantage of using mice of the CBA/N strain in the non-RI LLNA to improve the sensitivity of this method. The non-RI LLNA was performed using CBA/JN and CBA/N mice exposed to one of four confirmed skin sensitizers, 2,4-dinitrochlorobenzene (DNCB), eugenol (EG), isoeugenol (IEG) or alpha-hexylcinnamic aldehyde (HCA), and to one non-sensitizer, propylene glycol (PG). The EC3 values for DNCB, IEG, EG, HCA and PG were calculated to be 0.1%, 9.6%, 40.6%, 45.5% and >50% in CBA/JN mice and 0.08%, 1.9%, 10.7%, 20.3% and >50% in CBA/N mice, respectively. The EC3 values for DNCB, IEG, EG, HCA and PG in the standard LLNA using CBA/Ca mice and radioisotopes were reported elsewhere as being 0.08%, 1.3%, 13.0%, 8.0% and >50%, respectively. The EC3 values derived from the CBA/N mice in the non-RI LLNA were nearly equivalent to the EC3 values obtained using the standard radioisotopic LLNA with CBA/Ca mice. These data suggest that the use of CBA/N mice may provide a realistic opportunity to develop a version of the LLNA that does not have a requirement for the use of radioisotopes, but which nevertheless has sensitivity approaching, or comparable to, the standard method.
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http://dx.doi.org/10.1002/jat.1096DOI Listing
March 2006

Screening for androgen receptor activities in 253 industrial chemicals by in vitro reporter gene assays using AR-EcoScreen cells.

Toxicol In Vitro 2005 Sep;19(6):831-42

EcoScreen R&D Section, Endocrine Disrupting Chemical Analysis Center, Otsuka Life Science Initiative, Otsuka Pharmaceutical Co., Ltd., 224-18 Ebisuno Hiraishi, Kawauchi-cho, Tokushima 771-0195, Japan.

Recently, there has been great concern about the potential of industrial chemicals to act as endocrine disrupters. In this report, we conducted a pilot study to validate the use of AR-EcoScreen cells for tier 1 screening of androgen receptor (AR) agonist and antagonist activities. From 253 test compounds, we identified two AR agonists and nine antagonists. The two agonists, 2-tert-butylanthraquinone and benzoanthrone, were relatively weak (10% maximal activation of the positive control, 5alpha-dihydrotestosterone, at 2.54x10(-7) and 4.46x10(-6) M, respectively). The most potent antagonist was 3,3'-dichlorobenzidine dihydrochloride (IC50 = 2.28x10(-7) M). The order of the anti-androgenic activities was 3,3'-dichlorobenzidine dihydrochloride>4-diethylaminobenzaldehyde>4,4'-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bis[phenol]>2,4,6-trichlorophenylhydrazine = 4-(phenylpropyl)pyridine>2-hydroxy-4-methoxybenzophenone>2,2-bis(4-cyanophenyl)propane>4-methoxy-2-methyldiphenylamine = 2,4-diphenyl-4-methylpentene-1. These results suggest that AR-EcoScreen cell line has the potential to be used as a tool for the large scale tier 1 screening of chemicals for androgen receptor agonist and antagonist activity.
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http://dx.doi.org/10.1016/j.tiv.2005.04.009DOI Listing
September 2005

Changes in serum alpha2u-globulin levels in castrated male rats treated with testosterone propionate in a Hershberger assay.

J Appl Toxicol 2005 Mar-Apr;25(2):176-8

Hita Laboratory, Chemicals Evaluation and Research Institute, 3-822 Ishii-machi, Hita-shi, Oita 8770061, Japan.

The Hershberger assay has been proposed as a candidate screening test method for the detection of androgenic and anti-androgenic chemicals and is being validated presently under the test guideline programme of the Organization for Economic Cooperation and Development (OECD). Rat alpha2u-globulin is male rat-specific protein appearing in their serum and urine, and the protein is known to be induced by androgens. We investigated the usefulness of measuring serum alpha2u-globulin levels as a parameter for the androgenic activity of chemicals tested in the Hershberger assay. The serum alpha2u-globulin level was measured after the administration of testosterone propionate at dosages of 0, 20, 100 or 500 microg kg(-1) day(-1) for ten consecutive days in the castrated male rats. The ventral prostate, balbocavernosus/levator ani muscles, glans penis and Cowper's gland were collected and weighed. Although all the androgen-responsive organ weights were increased significantly at dosages of 100 and 500 microg kg(-1) day(-1), the serum alpha2u-globulin level was increased significantly only at a dosage of 500 microg kg(-1) day(-1). These results show that the serum alpha2u-globulin level may be a useful biomarker for detecting androgenic activity caused by test chemicals, but it is less sensitive than the organ weights of androgen-responsive tissues in the Hershberger assay.
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http://dx.doi.org/10.1002/jat.1038DOI Listing
July 2005

Novel approach for classifying chemicals according to skin sensitizing potency by non-radioisotopic modification of the local lymph node assay.

J Appl Toxicol 2005 Mar-Apr;25(2):129-34

Hita Laboratory, Chemicals Evaluation and Research Institute, 3-822 Ishii-machi, Hita-shi, Oita 8770061, Japan.

The murine local lymph node assay (LLNA) is currently recognized as a stand-alone sensitization test for determining the sensitizing potential of chemicals, and it has the advantage of yielding a quantitative endpoint that can be used to predict the sensitization potency of chemicals. The EC3 has been proposed as a parameter for classifying chemicals according to the sensitization potency. We previously developed a non-radioisotopic endpoint for the LLNA based on 5-bromo-2'-deoxyuridine (BrdU) incorporation (non-RI LLNA), and we are proposing a new procedure to predict the sensitization potency of chemicals based on comparisons with known human contact allergens. Nine chemicals (i.e. diphencyclopropenone, p-phenylenediamine, glutaraldehyde, cinnamicaldehyde, citral, eugenol, isopropyl myristate, propyleneglycol and hexane) categorized as human contact allergen classes 1-5 were tested by the non-RI LLNA with the following reference allergens: 2,4-dinitrochlorobenzene (DNCB) as a class 1 human contact allergen, isoeugenol as a class 2 human contact allergen and alpha-hexylcinnamic aldehyde (HCA) as a class 3 human contact allergen. Consequently, nine test chemicals were almost assigned to their correct allergen class. The results suggested that the new procedure for non-RI LLNA can provide correct sensitization potency data. Sensitization potency data are useful for evaluating the sensitization risk to humans of exposure to new chemical products. Accordingly, this approach would be an effective modification of LLNA with regard to its experimental design. Moreover, this procedure can be applied also to the standard LLNA with radioisotopes and to other modifications of the LLNA.
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http://dx.doi.org/10.1002/jat.1045DOI Listing
July 2005

Evaluation of a rapid in vitro androgen receptor transcriptional activation assay using AR-EcoScreen cells.

Toxicol In Vitro 2005 Apr 21;19(3):335-52. Epub 2005 Jan 21.

EcoScreen R&D Section, Endocrine Disrupting Chemical Analysis Center, Otsuka Life Science Initiative, Otsuka Pharmaceutical Co. Ltd., 224-18 Ebisuno Hiraishi, Kawauchi-cho, Tokushima 771-0195, Japan.

An accurate and reliable in vitro assay system has been needed for first tier screening of endocrine disrupting chemicals. For the purpose, we previously developed stable AR-EcoScreen cell lines to assess androgen receptor (AR)-mediated transcriptional activation. In this report, we evaluated AR-EcoScreen cell lines as the phase I of prevalidation study by determining the intra-laboratory reproducibility, assay stability, and overall protocol performance of AR-EcoScreen assays. Forty compounds recommended by the ICCVAM were tested for AR agonist and antagonist activity. The mean coefficient of variation (CV) for intra-assay reproducibility in the AR agonist assay was 4.35% for 5alpha-dihydrotestosterone (DHT), and that for the antagonist assay was 5.51% for hydroxyflutamide. The detection limit of the agonist assay was 2.3x10(-11) M for 5alpha-dihydrotestosterone. Furthermore, we examined the overall performance of the method by comparing the predicted result with the ICCVAM classification. Thus, the overall sensitivity, specificity, and accuracy of the agonist assay were 89%, 94%, and 91%, respectively. For the antagonist assay, these values were 94%, 100%, and 96%, respectively. In summary, we concluded that AR-EcoScreen method was ready to proceed to the phase II prevalidation study to asses the inter-laboratory variability and transfer of the protocol.
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http://dx.doi.org/10.1016/j.tiv.2004.10.008DOI Listing
April 2005

Differences in responsiveness of mouse strain against p-benzoquinone as assessed by non-radioisotopic murine local lymph node assay.

Exp Anim 2004 Apr;53(2):171-3

Hita Laboratory, Chemicals Evaluation and Research Institute, Japan, Oita, Japan.

The non-radioisotopic modification of murine local lymph node assay (LLNA) by using 5-bromo-2'-deoxyuridine (BrdU) was conducted to investigate the strain-related difference of the responsiveness of mice to p-benzoquinone (PBQ) with BALB/cAnN, CBA/JN and CD-1 mouse strains. Strain and dose related differences were analyzed by two-way analysis of variance (two-way ANOVA). CBA/JN was considered to be the highest responsive strain to PBQ, and interaction was detected between CD-1 and each of the other inbred strains. These results support the recommendation in the OECD test guideline 429 and the skin sensitization test guideline of US-EPA with regard to the selection of mouse strain for LLNA.
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http://dx.doi.org/10.1538/expanim.53.171DOI Listing
April 2004