The Journal of Toxicological Sciences
Online ISSN : 1880-3989
Print ISSN : 0388-1350
ISSN-L : 0388-1350
Volume 43 , Issue 9
Showing 1-4 articles out of 4 articles from the selected issue
Original Article
  • Tetsuya Fujimoto, Shuji Aou
    2018 Volume 43 Issue 9 Pages 531-536
    Published: 2018
    Released: September 04, 2018
    JOURNALS FREE ACCESS FULL-TEXT HTML

    Perinatal exposure to bisphenol A (BPA) causes several alterations in brain function and behavior. In previous studies, we showed that prenatal treatment with low-level BPA impaired gender-specific behavior, enhanced depression-like behavior, and augmented behavioral responses to predator odor in rats. On this premise, we hypothesized that BPA-treated rats were more susceptible to predator odor stress. To test the potential neural mechanism underlying this effect, we conducted an electrophysiological study of neurons in the medial amygdala—a regional component of the olfactory pathway with high estrogen and androgen receptor expression, and thus a potential target of BPA—in rats exposed to BPA. Extracellular recordings were obtained during the presentation of 3 plant odors and 3 predator odorants. Odor-responsive neurons in BPA-exposed rats showed greater activity in response to fox odor than did those in control rats. This finding complements the results of our previous behavioral study in which BPA-exposed rats exhibited enhanced avoidance behavior in response to fox odor. Given the close relationship between olfactory signaling and the stress response system, we suspect that BPA modifies the olfactory pathway at the level of the medial amygdala and thus modulates the corresponding stress response.

Original Article
  • Masayo Hirao-Suzuki, Shuso Takeda, Takanobu Kobayashi, Katsuhito Kino, ...
    2018 Volume 43 Issue 9 Pages 537-543
    Published: 2018
    Released: September 04, 2018
    JOURNALS FREE ACCESS FULL-TEXT HTML

    There is adequate evidence for the carcinogenicity of cadmium (Cd). However, a significant unaddressed question remains as to how this metal actually causes malignant transformation (tumor initiation). Since it has been shown that Cd only has the weak direct interaction potential with DNA, the metal is recognized as an indirect genotoxicant and mutagen. Currently, Cd-mediated “epigenetic” modifications, such as changes in DNA methylation resulting in alteration in target gene expression, coupled with cancer progression, are the focus of mechanistic research. We have reported that the apolipoprotein E (ApoE) gene, a suppressor of cell invasion, is an early Cd target, and is involved in the malignant transformation of TRL 1215 rodent liver cells. Cd exposure suppresses ApoE expression which can be re-activated with 5-aza-2’-deoxycytidine, a DNA demethylating agent. In the present study, we sought direct evidence of Cd-induced DNA hypermethylation of the ApoE promoter region by performing bisulfite sequencing and real-time quantitative methylation-specific PCR. Our data clearly suggest that Cd can down-regulate the expression of ApoE via introduction of excess DNA methylation in the promoter region of ApoE during malignant transformation of TRL 1215 cells.

Original Article
  • Yongmin Xu, Dazhuang Sun, Chunqing Song, Rui Wang, Xuesong Dong
    2018 Volume 43 Issue 9 Pages 545-555
    Published: 2018
    Released: September 04, 2018
    JOURNALS FREE ACCESS FULL-TEXT HTML

    Objective : To investigate the protective effect and underlying mechanism of the superoxide dismutase mimic, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP), on paraquat (PQ)-induced lung alveolar epithelial-like cell injury. Methods : Lung alveolar epithelial-like cells (A549) were pretreated with 10 μM MnTMPyP for 1.5 hr and then cultured with or without PQ (750 uM) for 24 hr. Cell survival was determined using the MTT assay. Apoptosis, mitochondrial transmembrane potential, reactive oxygen species (ROS) production, and Ca2+ levels were measured using flow cytometry. Glutathione reductase activity (GR activity) and caspase-3 activation were determined using spectrophotometry. Expression of the apoptosis proteins, Bcl-2 and Bax, and the endoplasmic reticulum (ER) stress proteins, glucose regulatory protein 78 (Grp78) and C/EBP homologous protein (CHOP), was measured using Western blot analysis. Results : Cell viability, mitochondrial membrane potential, GR activity, and Bcl-2 expression were decreased, but apoptosis, ROS production, caspase-3 activity, cytoplasmic Ca2+ levels, and Bax, Grp78 and CHOP expression were all increased in the PQ group compared to the control group. There were no statistically significant changes in the MnTMPyP group. Cell viability, GR activity, mitochondrial membrane potential, and Bcl-2 protein expression were all increased, while apoptosis, ROS production, cytoplasmic Ca2+ levels, caspase-3 activity, and Bax, Grp78 and CHOP expression were all significantly reduced in the MnTMPyP group compared to PQ group. Conclusion : MnTMPyP effectively reduced PQ-induced lung epithelial-like cell injury, and the underlying mechanism is related to antagonism of PQ-induced oxidative stress.

Original Article
  • Shuji Ogawa, Hiroyuki Kuroda, Toshiko Kinomoto, Yoshihiro Kawabata, Ma ...
    2018 Volume 43 Issue 9 Pages 557-563
    Published: 2018
    Released: September 04, 2018
    JOURNALS FREE ACCESS FULL-TEXT HTML

    There is sometimes controversy over whether or not statistically significant responses produced in carcinogenicity studies have biologically significance. Ambiguous results from our previous two-year oral carcinogenicity study on acotiamide hydrochloride hydrate (acotiamide-HH), a prokinetic drug for functional dyspepsia, in rats made it unclear whether the drug may exhibit uterine carcinogenicity. To check this finding, we performed a second long-term carcinogenicity study using two identical control groups to more accurately evaluate uterine carcinogenesis by considering the incidence of spontaneous neoplasms. Female Fischer 344 rats were divided into three groups: the two control groups (control 1 and 2) were administered vehicle (0.5% w/v methylcellulose) and the acotiamide-HH-treated group was administered 2,000 mg/kg/day of acotiamide-HH by oral gavage for two years. Among all groups, the incidence of endometrial adenocarcinoma (EmA) was highest in the control 2 group, followed by the acotiamide-HH-treated group and the control 1 group. Moreover, acotiamide-HH did not affect the incidence of precursor lesions of EmA. In cases where an ambiguous difference is observed, the use of two control groups allows for a more informed interpretation of the findings in the drug-treated groups. The outcomes in this study strongly support the hypothesis that the increase in EmA in rats treated with acotiamide-HH in our previous study is unrelated to administration of the drug.

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