Lack of in vivo mutagenicity of carbendazim in the liver and glandular stomach of MutaMice.

BACKGROUND: Carbendazim (methyl 2-benzimidazolecarbamate, CASRN: 10605-21-7) exhibits spindle poisoning effects and is widely used as a fungicide. With respect to genotoxicity, carbendazim is deemed to be non-mutagenic in vitro, but it causes indicative DNA damage in vivo and chromosome aberrations in vitro and in vivo. In this study, we examined the mutagenicity of carbendazim in vivo. RESULTS: MutaMice were treated with carbendazim orally at doses of 0 (corn oil), 250, 500, and 1,000 mg/kg/day once a day for 28 days. A lacZ assay was used to determine the mutant frequency (MF) in the liver and glandular stomach of mice. MutaMice were administered up to the maximum dose recommended by the Organization for Economic Co-operation and Development Test Guidelines for Chemicals No. 488 (OECD TG488). The lacZ MFs in the liver and glandular stomach of carbendazim-treated animals were not significantly different from those in the negative control animals. In contrast, positive control animals exhibited a significant increase in MFs in both the liver and glandular stomach. CONCLUSIONS: Carbendazim is non-mutagenic in the liver and glandular stomach of MutaMice following oral treatment.

In vivo mutagenicity assessment of orally treated tert-butyl hydroperoxide in the liver and glandular stomach of MutaMouse.

BACKGROUND: tert-Butyl hydroperoxide (TBHP; CAS 75-91-2), a hydroperoxide, is mainly used as a polymerization initiator to produce polyethylene, polyvinyl chloride, and unsaturated polyester. It is a high-production chemical, widely used in industrial countries, including Japan. TBHP is also used as an additive for the manufacturing of food utensils, containers, and packaging (UCP). Therefore, there could be consumer exposure through oral intake of TBHP eluted from UCPs. TBHP was investigated in various in vitro and in vivo genotoxicity assays. In Ames tests, some positive results were reported with and/or without metabolic activation. As for the mouse lymphoma assay, the positive result was reported, regardless of the presence or absence of metabolic activation enzymes. The results of some chromosomal aberrations test and comet assay in vitro also demonstrated the genotoxic positive results. On the other hand, in in vivo tests, there are negative results in the bone marrow micronucleus test of TBHP-administered mice by single intravenous injection and the bone marrow chromosomal aberration test using rats exposed to TBHP for 5 days by inhalation. Also, about dominant lethal tests, the genotoxic positive results appeared. In contrast, there is little information about in vivo mutagenicity and no information about carcinogenicity by oral exposure. RESULTS: We conducted in vivo gene mutation assay using MutaMice according to the OECD Guidelines for the Testing of Chemicals No. 488 to investigate in vivo mutagenicity of TBHP through oral exposure. After repeated dosing for 28 days, there were no significant differences in the mutant frequencies (MFs) of the liver and glandular stomach up to 300 mg/kg/day (close to the maximum tolerable dose (MTD)). The positive and negative controls produced the expected responses. CONCLUSIONS: These findings show that orally administrated TBHP is not mutagenic in the mouse liver and glandular stomach under these experimental conditions.

Derivation of subacute guidance values for chemical contaminants of drinking water quality standard in Japan.

The concentration of chemicals in drinking water may transiently and accidently exceed the Drinking Water Quality Standard (DWQS). If the level of a contaminant is not expected to cause adverse effects for a limited period of exposure, immediate suspension of the water supply may not be necessary. Assessments should be conducted using subacute guidance values (SGVs). In this study, we assessed 26 chemicals for the DWQS to establish the SGVs. Principally, a key study was selected from subacute studies to derive a Subacute Reference Dose (saRfD). The SGV was calculated from the saRfD for adults (drinking water intakes: 40 mL/kg/day) and children (drinking water intakes: 150 mL/kg/day). No allocation factor was applied to derive the SGV. We established the SGV for 20 chemicals, which were 2-38 times higher than the corresponding DWQS. However, SGVs for six chemicals were the same as the corresponding DWQS. Therefore, immediate action will be required for these six accidental contaminants. Our established SGVs are useful for assessing accidental contamination.

In vivo mutagenicity assessment of styrene in MutaMouse liver and lung.

BACKGROUND: Styrene (CAS 100-42-5) is widely used as polystyrene and acrylonitrile-butadiene-styrene resin such as plastic, rubber, and paint. One of the primary uses of styrene is food utensils and containers, but a small amount of styrene transferred into food can be ingested by eating. Styrene is metabolized into styrene 7,8-oxide (SO). SO is mutagenic in bacteria and mouse lymphoma assays. It is clastogenic in cultured mammalian cells. However, styrene and SO are not clastogenic/aneugenic in rodents, and no rodent in vivo gene mutation studies were identified. METHODS: To investigate the mutagenicity of orally administered styrene, we used the transgenic rodent gene mutation assay to perform an in vivo mutagenicity test (OECD TG488). The transgenic MutaMouse was given styrene orally at doses of 0 (corn oil; negative control), 75, 150, and 300 mg/kg/day for 28 days, and mutant frequencies (MFs) were determined using the lacZ assay in the liver and lung (five male mice/group). RESULTS: There were no significant differences in the MFs of the liver and lung up to 300 mg/kg/day (close to maximum tolerable dose (MTD)), when one animal with extremely high MFs that were attributed to an incidental clonal mutation was omitted. Positive and negative controls produced the expected results. CONCLUSIONS: These findings show that styrene is not mutagenic in the liver and lung of MutaMouse under this experimental condition.

Initial hazard assessment of ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate: Genotoxicity tests and combined repeated-dose and reproductive/developmental toxicity screening in rats.

Ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate, used in laundry detergents, shampoos, and body soaps, is classified by the Japanese Chemical Substances Control Law as a priority assessment chemical substance for environmental effects. However, its toxicity data for human health are insufficient. This study evaluated this chemical under the Safety Examination of Existing Chemicals and Safety Programmes of the Ministry of Health, Labour and Welfare (MHLW). The MHLW conducted bacterial reverse mutation (Ames test), in vitro chromosomal aberration, and combined repeated-dose and reproductive/developmental toxicity screening tests. We performed a screening assessment of ethyl(dimethyl)(tetradecyl)ammonium ethyl sulfate for human health. The chemical showed a negative reaction in the Ames test and a positive reaction in the in vitro chromosomal aberration test with metabolic activation in rats. The combined repeated-dose and reproductive/developmental toxicity screening test showed significantly decreased food consumption at 50 mg/kg body weight/day, but no reproductive and developmental toxicity was observed. The no-observed-effect level of 15 mg/kg/day was obtained as a screening value. Therefore, this chemical was classified as hazard class 3, with a derived-no-effect level of 0.025 mg/kg/day. The results of this study will be useful for risk assessment of groups of structurally similar alkyl quaternary ammonium surfactants.

Initial hazard assessment of benzyl salicylate: In vitro genotoxicity test and combined repeated-dose and reproductive/developmental toxicity screening test in rats.

Benzyl salicylate is used as a fragrance ingredient and an ultraviolet light absorber, but its toxicity is unknown. Therefore, toxicity tests and hazard classification were conducted for screening assessment under the Japanese Chemical Substances Control Law. Benzyl salicylate was found to be non-genotoxic in vitro based on the chromosomal aberration test using Chinese hamster lung cells. However, the combined repeated-dose and reproductive/developmental screening toxicity test, in which male and female rats were administered benzyl salicylate by gavage at 0, 30, 100, or 300 mg/kg/day for 42 and 41-46 days, respectively, from 14 days before mating until postnatal Day 4, showed that repeated doses had major effects on the thymus, liver, epididymis, and femur at 100 and/or 300 mg/kg/day. Furthermore, although benzyl salicylate had no effect on the estrus cycle, fertility, corpus lutea, or implantation rate, embryonic resorption, offspring mortality, and neural tube defects were observed at 300 mg/kg/day, and the offspring had lower body weights at 30 and 100 mg/kg/day, suggesting teratogenicity similar to other salicylates. Based on the developmental toxicity, this chemical was classified as hazard class 2, with a lowest observed adverse effect level (LOAEL) of 30 mg/kg/day and a D-value of 0.003 mg/kg/day.

Initial hazard assessment of 4-benzylphenol, a structural analog of bisphenol F: Genotoxicity tests in vitro and a 28-day repeated-dose toxicity study in rats.

4-Benzylphenol (CAS No. 101-53-1), a structural analog of bisphenol F, has estrogenic activity in vitro and in vivo, as is the case with bisphenol F. 4-Benzylphenol is used in plastics and during organic synthesis. Since its safety is largely unknown, we conducted toxicity tests as part of screening risk assessment in an existing chemical safety survey program. Based on results of the Ames test and the chromosomal aberration test using Chinese hamster lung cells (OECD TG 471 and 473), 4-benzylphenol was determined to be non-genotoxic in vitro. In a 28-day repeated-dose toxicity study, Crl:CD (SD) rats were administrated 4-benzylphenol by gavage at 0, 30, 150, or 750 mg/kg/day (OECD TG 407). Consequently, body weight was lower in males at 750 mg/kg/day. In the liver, relative organ weights were increased in both sexes at 750 mg/kg/day, and centrilobular hepatocellular hypertrophy was observed in males at 150 and 750 mg/kg/day. In the forestomach, hyperkeratosis and hyperplasia of squamous cells were observed in males at 150 and 750 mg/kg/day, and in females at 750 mg/kg/day. Based on these results, we identified the NOAEL for 4-benzylphenol as 30 mg/kg/day, with a hazard assessment value (D-value) of 0.05 mg/kg/day corresponding to hazard class 3.

Modulation of the expression of bloom helicase by estrogenic agents.

We report that the expression of Bloom helicase (BLM) was up-regulated by 17beta-estradiol (E2) in estrogen receptor (ER)-positive mammary tumor MCF-7 cells, but was hardly modulated in ER-negative mammary tumor MDA-MB-231 cells. ER antagonist ICI182780 blocked the E2 effect on BLM expression in MCF-7 cells. From these results we conclude that ER participates in up-regulation of BLM expression in MCF-7 cells by means of E2. Similar results were obtained when MCF-7 cells were treated with bisphenol A (BPA), an endocrine-disrupting chemical having a weak estrogenic activity. The ER binding ability of BPA is estimated at 1/1000 of E2 ability, and in this study about 1000-times more BPA was needed for the same levels of estrogenic effect of E2. The expression of cell-cycle associated genes, cdc6, MCM5, MCM2, Myt1, PCNA and AuroraA were up-regulated by E2 and BPA treatment in MCF-7 cells accompanied by up-regulation of BLM. In this BLM promoter study, Sp1 elements in the upper region of BLM modulated transcription, but were not indispensable for E2 response. Our results suggested that up-regulation of BLM expression by E2 and BPA is ER-dependent and may be responsible for repair of DNA damage caused by the genotoxicity of these estrogenic agents.

Study of nateglinide in Japan: long-term treatment of patients with type 2 diabetes.

Nateglinide is an oral antidiabetic medication that acts through rapid, short-term stimulation of insulin production. This study undertook to identify the nature of any adverse effects of nateglinide and to assess its clinical efficacy in long-term use in clinical practice. Patients (n=1014) were recruited from centers in Japan and were followed over a 15-month treatment period. Pretreatment and posttreatment values were obtained for fasting blood glucose, postprandial blood glucose, hemoglobin A1c (HbA1c), triglycerides, and total cholesterol. All adverse reactions were noted, along with standard laboratory blood variables. The efficacy value was rated as 78.76% by the treating physicians; this was indicated by a postprandial glucose decrease of 53.2 mg/dL (from 223.8+/-61.1 mg/dL to 170.6+/-40.7 mg/dL), a fasting glucose decrease of 9.3 mg/dL (from 155.1+/- 40.0 mg/dL to 145.4+/-35.1 mg/dL), and an HbA1c decrease of 0.68% (from 7.51+/- 1.36% to 6.83+/-1.09%). In patients previously treated with sulfonylurea, a decrease in HbA1c was not observed. Changes in HbA1c had no association with age, body mass index (BMI), duration of diabetes, or concomitant disease. No change in BMI was noted after 15 months of nateglinide treatment. Adverse reactions occurred at an incidence of 10.07% (100/993 cases), with hypoglycemic symptoms being the most prevalent (1.91%). Adverse reactions were sometimes associated with extant renal dysfunction, a condition about which the physician had to be aware. No problems such as increased incidences of adverse reactions or deterioration in severity were detected in this long-term study. This study showed the efficacy and safety of long-term treatment with nateglinide of patients with diabetes from various backgrounds.

DNA damage caused by bisphenol A and estradiol through estrogenic activity.

Evidence exists that raises concern about genotoxic effects induced by estrogen: oxidative stress caused by estrogen-derived oxidants, DNA adducts formed by estrogen metabolites and estrogen-induced chromosomal aberration. Estrogen receptors (ER) participate in some of these genotoxic effects by estrogen. In this study, we showed the effects of bisphenol A (BPA), an endocrine-disrupting chemical eliciting weak estrogenic activity, and of 17beta-estradiol (E2), on DNA damage in ER-positive MCF-7 cells by Comet assay. Higher concentrations of BPA, more than 1000 times of E2, were needed to induce the same levels of effects by E2. Immunofluorescence microscopy showed that gammaH2AX, an early marker of DNA breaks, increased after treatment with E2 or BPA in MCF-7 cells. gammaH2AX foci colocalized with Bloom helicase, which is considered to be responsible for the repair of DNA damage after treatment with E2 or BPA. Interestingly, DNA damage was not as severe in ER-negative MDA-MB-231 cells as in MCF-7 cells. The ER antagonist ICI182780 blocked E2 and BPA genotoxic effects on MCF-7 cells. These results together suggest that BPA causes genotoxicity ER dependently in the same way as E2.

Postmarketing study of nateglinide in Japan: treatment of medication-naïve patients with type 2 diabetes.

Nateglinide is an oral antidiabetic medication (OAD) that acts through rapid, short-term stimulation of insulin production. This study was conducted to identify the nature of any adverse effects associated with nateglinide and to evaluate its clinical efficacy in patients with type 2 diabetes, with particular attention to hypoglycemia. Patients with type 2 diabetes who were OAD naïve (n=547), whose fasting blood glucose levels were 150 mg/dL or lower, and who had start-ed to take nateglinide alone were recruited from 139 centers in Japan with a 12-week observation period. The incidence of adverse reactions was 7.62%. Hypoglycemia accompanied by hypoglycemic symptoms was the most prevalent adverse event (2.10%; 11/525). Nine of 11 episodes required no therapeutic intervention. Severe hypoglycemia was recognized in only 1 case of diabetes complicated by serious renal dysfunction, for which nateglinide has been contraindicated in Japan. No subject experienced symptoms of nocturnal or prolonged hypoglycemia. After 12 weeks of nateglinide treatment, decreases were noted in hemoglobin A1c (0.82%), postprandial glucose (reduced by 59.4 mg/dL to 158.0 mg/dL), and fasting glucose (reduced by 11.7 mg/dL to 122.4 mg/dL). Nateglinide, which demonstrates limited risk of hypoglycemia and effectively controls blood glucose level, is regarded as a useful drug for the treatment of patients with type 2 diabetes.

Postmarketing surveillance study of nateglinide in Japan.

Nateglinide is an oral antidiabetic medication that acts through rapid, short-term stimulation of insulin production. This study was undertaken to identify the incidence and nature of adverse effects of nateglinide and to assess its efficacy in clinical practice. Patients (n = 3254) were recruited from 606 centers in Japan with a 12-week observation period. Pretreatment and posttreatment values were obtained for fasting blood glucose, postprandial blood glucose, hemoglobin A1c (HbA1c), triglycerides, cholesterol, and body mass index. All adverse events were reported, along with standard laboratory blood variables. The incidence of adverse events was 7.40%; hypoglycemia, including hypoglycemic symptoms, was reported as the most prevalent (1.62%). Adverse events were observed more frequently in patients with hepatic or renal dysfunction; no significant findings were noted in the remaining patient population. The efficacy rating determined by the treating physicians was 76.40%. HbA1c decreased by 0.81% from 7.70+/-1.53% to 6.89+/-1.22%, postprandial glucose decreased by 54.05 mg/dL from 228.91+/-73.69 mg/dL to 174.86+/-62.86 mg/dL, and fasting glucose decreased by 23.73 mg/dL from 164.15+/-51.42 mg/dL to 140.43+/-42.63 mg/dL. These effects were most marked in patients who were previously medication naïve or who had been diagnosed with diabetes for a short period. Mean body mass index decreased, and nateglinide was equally effective in obese patients. Nateglinide showed good therapeutic effect when used as the first choice in patients with a short duration of diabetes, and in those with no history of previous treatment. Moreover, nateglinide seemed to be useful for the treatment of elderly patients and obese patients.