The Journal of Toxicological Sciences
Online ISSN : 1880-3989
Print ISSN : 0388-1350
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Review
  • Patrice Bélanger, Christine R. West, Mark T. Brown
    Volume 43 (2018) Issue 1 Pages 1-10
    Released: February 08, 2018
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    Therapeutic agents commonly used in the management of chronic pain have limited effectiveness and may be associated with issues of dependence and tolerability. Thus, a large unmet medical need exists for the development of safe and effective therapeutics for treatment of chronic pain. A novel approach includes identification of intracellular signals involved in the pain transduction pathway, such as nerve growth factor (NGF). Monoclonal antibodies targeting NGF, such as tanezumab, fulranumab and fasinumab, have been investigated for the treatment of chronic pain conditions. Due to unexpected joint adverse events in clinical studies and concerns about sympathetic nervous system toxicity in animals, these agents were placed on 2 separate partial clinical holds, which were subsequently lifted after rigorous evaluations were conducted to understand how inhibition of NGF impacts safety. To share learnings regarding the rigorous evaluation of clinical and nonclinical safety data which contributed to the removal of these partial clinical holds, this article reviews the rationale for developing agents that target NGF as potential treatments for chronic pain, describes nonclinical and clinical studies of these agents, and describes strategies used to evaluate whether inhibition of NGF has negative effects on joint or sympathetic nervous system safety.

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Original Article
  • Minoru Yoshida, Jin-Yong Lee, Masahiko Satoh, Chiho Watanabe
    Volume 43 (2018) Issue 1 Pages 11-17
    Released: February 08, 2018
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    This study examined the effects on neurobehavioral function of exposure to low-level mercury vapor (Hg0), methylmercury (MeHg) in female mice and the combination of Hg0 and MeHg during postnatal development. Postnatal mice were exposed to Hg0 at a mean concentration of 0.188 mg/m3 Hg0 and supplied with food containing 3.85 μg/g of MeHg from day 2 to day 28 after delivery. The combined exposure group was exposed to both Hg0 and MeHg, using the same procedure. When their offspring reached the age of 11 weeks, behavioral analyses were performed. The behavioral effects in mice were evaluated based on locomotive activity and rate of center entries in the open field (OPF), learning activity in the passive avoidance response (PA) and spatial learning ability in the radial maze (RM). Total locomotive activity in the OPF significantly decreased in the Hg0, MeHg and combined exposure groups compared with the control group. The proportion of entries to central area in the OPF was significantly higher in the combined exposure group than in the control group, while those in the Hg0 or MeHg exposure group did not differ from the control group. Other behavioral tests did not reveal significant differences among the groups. Behavioral anomalies were more distinctive after combined exposure compared to Hg0 or MeHg exposure alone. The brain Hg concentration of offspring, immediately after exposure, was highest in the combined exposure group, exceeding 2 μg/g, followed by the MeHg and Hg0 exposure groups. Thus, the enhancement of neurobehavioral effects in the combined exposure group was associated with higher brain mercury concentration.

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Letter
  • Hisaka Kurita, Tatsuya Hasegawa, Yoshiyuki Seko, Hisamitsu Nagase, Mak ...
    Volume 43 (2018) Issue 1 Pages 19-24
    Released: February 08, 2018
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    Cadmium (Cd) is an environmental pollutant present in contaminated water, food and soil. Cd adversely affects fetal development. We exposed pregnant mice to daily oral doses of 5 and 10 mg/kg Cd and examined fetal growth. It was demonstrated that the exposure to Cd (10 mg/kg) during gestation caused fetal growth retardation (FGR). Investigation of the ubiquitin-proteasome system in fetal livers of mice exposed to gestational Cd revealed increased polyubiquitinated protein accumulation, contrasting with decreased levels of monoubiquitin protein. Moreover, the expression level of Ubc (encoding polyubiquitin C protein) was significantly decreased in 5 and 10 mg/kg Cd-treated groups in comparison with the control group. Therefore, we propose that decrease of monoubiquitin level and accumulation of polyubiquitinated protein in the fetal liver may be important factors in Cd-induced FGR.

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Letter
  • Yasuhiro Ishihara, Nami Ikeda-Ishihara, Chihaya Koriyama, Noriaki Kaki ...
    Volume 43 (2018) Issue 1 Pages 25-31
    Released: February 08, 2018
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    Many different types of chemicals are used in industry, and occupational allergies are becoming a serious problem in the field of industrial hygiene. In this study, we employed a novel enzyme-linked immunosorbent assay (ELISA) with partial peptides of human serum albumin (HSA) to quantify chemical-specific immunoglobulin G (IgG) in serum for evaluating exposure to chemicals. When HSA partial peptides containing lysine residues were mixed with formaldehyde (FA) or phthalic anhydride (PA), almost all lysine residues were lost. Mass spectrometry revealed that PA and FA formed imine and tertiary amine, respectively, with lysine residues in the peptides. Thus, we used FA- or PA-peptide adducts as an artificial antigen to detect FA- and PA-specific IgGs in serum. The concentrations of FA- and PA-specific IgGs in workers at plants utilizing plastic resins were significantly higher than those in general subjects. This method can estimate exposure levels to chemicals and thus be expected to contribute to the diagnosis of allergies in workers and to the prevention of health hazards due to harmful chemicals.

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Original Article
  • Limeng Wang, Zhihua Yang, Long Xu, Xiujie Pan, Xingyu Liu, Junwei Zhao ...
    Volume 43 (2018) Issue 1 Pages 33-44
    Released: February 08, 2018
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    Crotonaldehyde is a ubiquitous air pollutant in the environment. It is reported to be harmful to the biosystems in vivo and in vitro. The exposure to crotonaldehyde irritates the mucous membranes and induces edema, hyperemia, cell necrosis, inflammation, and acute respiratory distress syndrome in the lungs. However, the effects of crotonaldehyde on the immune system have not been reported. In the present study, 6-8 weeks old male Wistar rats were exposed to crotonaldehyde by intratracheal instillation at doses of 4, 8, and 16 μL/kg body weight (b.w.). The general damage in the animals was investigated; the cell counting and the biochemical analysis in the peripheral blood were tested. Furthermore, we investigated the functions of alveolar macrophages (AMs), the alterations of the T-lymphocyte subsets, and the cell composition in the bronchoalveolar lavage fluid (BALF). We found that the activities of the animals were changed after exposure to crotonaldehyde, the cellular ratios and the biochemical components in the peripheral blood were altered, the ratio of mononuclear phagocytes decreased, and the ratios of lymphocytes and granulocytes elevated significantly in BALF. Meanwhile, crotonaldehyde altered the ratio of the T-lymphocyte subsets, and the phagocytic rates and indices of AMs increased obviously. In conclusion, crotonaldehyde induces dysfunction of immune system in male Wistar rats.

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Original Article
  • Kaoru Toyoda, Yusuke Suzuki, Kyotaka Muta, Taku Masuyama, Kochi Kakimo ...
    Volume 43 (2018) Issue 1 Pages 45-58
    Released: February 08, 2018
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    Diabetic nephropathy (DN) is one of the complications of diabetes and is now the most common cause of end-stage renal disease. Fructose is a simple carbohydrate that is present in fruits and honey and is used as a sweetener because of its sweet taste. Fructose has been reported to have the potential to progress diabetes and DN in humans even though fructose itself does not increase postprandial plasma glucose levels. In this study, we investigated the effects of high fructose intake on the kidney of the Spontaneously Diabetic Torii (SDT) rats which have renal lesions similar to those in DN patients and compared these with the effects in normal SD rats. This study revealed that a 4-week feeding of the high fructose diet increased urinary excretion of kidney injury makers for tubular injury and accelerated mainly renal tubular and interstitial lesions in the SDT rats but not in normal rats. The progression of the nephropathy in the SDT rats was considered to be related to increased internal uric acid and blood glucose levels due to the high fructose intake. In conclusion, high fructose intake exaggerated the renal lesions in the SDT rats probably due to effects on the tubules and interstitium through metabolic implications for uric acid and glucose.

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Letter
  • Masahiro Iwaki, Toshiro Niwa, Yukiko Nakamura, Atsushi Kawase, Hiroshi ...
    Volume 43 (2018) Issue 1 Pages 59-63
    Released: February 08, 2018
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    The relative contribution of cytochrome P450 (CYP) isoforms responsible for carvedilol (CAR) oxidation in rats were evaluated in order to compare with that of reported human CYPs responsible for the metabolism of CAR enantiomers. The depletion of CAR enantiomers by recombinant CYPs and the effects of CYP-selective inhibitors on the depletion catalyzed by rat liver microsomes (RLM) was determined. Quinine (rat CYP2D inhibitor) markedly inhibited the metabolism of both R- and S-CAR by RLM. The metabolism of S-CAR was inhibited more than that of R-CAR by furafylline, (a CYP1A2 inhibitor, 53.5% vs 11.3%), α-naphthoflavone (a CYP1A2 inhibitor, 64.5% vs 33.6%), and ketoconazole (a CYP3A inhibitor, 87.1% vs 51.2%). Among the CYPs examined, CYP2D2 showed the highest metabolic activities against both the enantiomers. R-CAR was mainly metabolized by CYP2D2 and CYP3A2. CYP2C11 and CYP3A1, in addition to CYP2D2 and CYP3A2 showed higher metabolic activities against S-CAR than that against R-CAR. These results suggest that CYP2D2 predominantly catalyzed R-CAR metabolism, whereas CYP2D2 and CYP3A1/2 catalyzed S-CAR metabolism in rats.

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Original Article
  • Satoshi Kitaoka, Jo Hatogai, Ryuki Iimura, Yuka Yamamoto, Konomi Oba, ...
    Volume 43 (2018) Issue 1 Pages 65-74
    Released: February 08, 2018
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    The use of midazolam in early stages of pregnancy has resulted in a high incidence of birth defects; however, the underlying reason is unknown. We investigated expression changes of the CYP3A molecular species and focused on its midazolam metabolizing activity from the foetal period to adulthood. CYP3A16 was the only CYP3A species found to be expressed in the liver during the foetal period. However, CYP3A11 is upregulated in adult mice, but has been found to be downregulated during the foetal period and to gradually increase after birth. When CYP3A16 expression was induced in a microsomal fraction of cells used to study midazolam metabolism by CYP3A16, its activity was suppressed. These results showed that the capacity to metabolize midazolam in the liver during the foetal period is very low, which could hence result in a high incidence of birth defects associated with the use of midazolam during early stages of pregnancy.

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