The Journal of Toxicological Sciences
Online ISSN : 1880-3989
Print ISSN : 0388-1350
ISSN-L : 0388-1350
Volume 44 , Issue 2
Showing 1-6 articles out of 6 articles from the selected issue
Original Article
  • Tadashi Hirata, Young-Man Cho, Isamu Suzuki, Takeshi Toyoda, Jun-ichi ...
    2019 Volume 44 Issue 2 Pages 73-81
    Published: 2019
    Released: February 05, 2019
    JOURNALS FREE ACCESS FULL-TEXT HTML

    To investigate the chemopreventive mechanisms of 4-Methylthio-3-butenyl isothiocyanate (MTBITC), we analyzed cell viability, cell cycle distribution, and expression levels for cell cycle and apoptosis-related proteins in MTBITC-treated malignant esophageal KYSE510 cells, with and without the reactive oxygen species (ROS) scavenger N-acethyl-L-Cysteine (NAC). MTBITC dose-dependently reduced cell viability and Bcl2 protein expression, while it induced cleavages of caspase-3, caspase-9, and PARP-1, suggesting that reduced cell viability occurred through the mitochondrial apoptotic pathway in KYSE510 cells. In cell cycle distribution analysis, MTBITC (20-40 µM) induced cell cycle arrest at G2/M phase. Furthermore, MTBITC induced Chk1 and Akt phosphorylations and decreased p27 protein expression. Both apoptotic- and cell cycle-related changes induced by MTBITC treatment were abolished by NAC. These results suggest that MTBITC has chemopreventive potential for esophageal carcinogenesis by elimination of cancer cells via induction of mitochondrial apoptotic cell death, G2/M cell cycle arrest, and ROS production.

Original Article
  • Hiromasa Tsuyama, Hitomi Fujishiro, Seiichiro Himeno, Daigo Sumi
    2019 Volume 44 Issue 2 Pages 83-92
    Published: 2019
    Released: February 05, 2019
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    Immunological functions are disturbed in humans who have been chronically exposed to arsenic via contaminated groundwater. Little is known about the specific mechanisms underlying the impairment of immunological defense system caused by arsenic. The activation of macrophage cells upon infection with bacteria and viruses plays important roles in the defense against these pathogens. Here we show that exposure to arsenite (As(III)) suppresses nitric oxide (NO) production in murine RAW264.7 macrophage cells stimulated with lipopolysaccharide (LPS) and poly(I:C), the compounds mimicking bacterial and viral infection, respectively. As(III) suppressed the LPS- or poly(I:C)-evoked induction of inducible NO synthase (iNOS) without affecting the transactivation of NF-κB. As the interferon (IFN)-β/STAT1 pathway is also involved in the induction of iNOS in addition to NF-κB, we examined the effects of As(III) on the expression and secretion of IFN-β, the expression of the components of IFN-α/β receptor, the phosphorylation of STAT1, and the levels of cytokines involved in STAT1 activation. The results showed that the expression and secretion of IFN-β were specifically suppressed by As(III) treatment in RAW264.7 cells stimulated with LPS or poly(I:C). These results suggest that As(III) suppresses the expression and secretion of IFN-β, leading to the reduced STAT1 activation and consequently the reduced iNOS induction in macrophage cells. Our data suggest an important role of the arsenic-induced suppression of IFN-β on the disturbances in immunological defense against both bacteria and viruses.

Original Article
  • Takeshi Tanaka, Kota Nakajima, Yasunori Masubuchi, Yuko Ito, Satomi Ki ...
    2019 Volume 44 Issue 2 Pages 93-105
    Published: 2019
    Released: February 05, 2019
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    Maternal exposure to 3,3′-iminodipropionitrile (IDPN) affects hippocampal neurogenesis in mouse offspring, with biphasic disruption, which facilitates neurogenesis during exposure and reduces the broad range of the granule cell lineage population at the adult stage. The present study investigated the epigenetically hypermethylated and downregulated genes related to the IDPN-induced disrupted neurogenesis. Mated female mice were treated with IDPN at 0 or 1200 ppm in drinking water from gestational day 6 to postnatal day (PND) 21 on weaning. The hippocampal dentate gyrus of male offspring on PND 21 was subjected to methyl-capture sequencing and real-time reverse transcription-PCR analyses, followed by validation analyses on DNA methylation. Three genes, Edc4, Kiss1 and Mrpl38, were identified as those showing promoter-region hypermethylation and transcript downregulation, with Mrpl38 sustaining the changes through PND 77. Immunohistochemically, MRPL38, a mitochondrial ribosomal protein, revealed an irreversible decrease in the number of immunoreactive interneurons in the dentate gyrus hilar region, suggesting a causal relationship with the long-lasting effect on neurogenesis by the impaired migration due to mitochondrial dysfunction of interneurons, which regulate the differentiation and survival of granule cell lineages. Downregulation of Edc4 may also be responsible for decreased neurogenesis on PND 77 owing to a mechanism involving interleukin-6 downregulation via processing body dysfunction. Downregulation of Kiss1 may be responsible for the facilitation of neurogenesis during IDPN-exposure due to decreased glutamatergic neurotransmission and also for suppressed neurogenesis on PND 77 due to decreased expression of immediate-early genes, which play a crucial role in the maintenance of cell differentiation or plasticity.

Letter
  • Kana Unuma, Toshihiko Aki, Ayaka Yamashita, Ayaka Yoshikawa, Koichi Ue ...
    2019 Volume 44 Issue 2 Pages 107-112
    Published: 2019
    Released: February 05, 2019
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    Inhalation of toxic gases is dangerous to humans; experiments using toxic gases themselves are also hazardous to researchers. Gas-releasing molecules are widely used as alternatives to toxic gases, but their impacts on the whole body remain to be examined. To investigate responses during hydrogen sulfide (H2S) poisoning, rats (Sprague-Dawley, male, 8-week-old) were intraperitoneally (i.p.) administered H2S donor, NaHS, and sacrificed 24 hr after the administration. The main histopathological finding commonly observed in NaHS-administered rat heart, liver, brain, and lung was congestion. In addition, inflammation and accumulation of mucopolysaccharides were observed in bronchioles of the lung. Immunoblot analysis indicated increasing trend of NF-κB activation, and real-time PCR analysis showed increasing tendency of TNFα and IL-1β, as well as MUC1 and 5B, in NaHS-administered rat lung. Immunohistochemistry by use of anti-MUC1 and 5B antibodies confirmed enhanced mucosal secretion from bronchial epithelium. Moreover, administration of TNFα or IL-1β to A549 lung epithelial cells resulted with enhanced expressions of MUC1 and 5B. This report shows bronchitis and respiratory mucosal secretion in animal model of H2S intoxication, which is created by i.p. administration of a H2S donor, through NF-κB-TNFα/IL-1β-ΜUC1/5B pathway.

Original Article
  • Tomoya Fujie, Taro Yamamoto, Chika Yamamoto, Toshiyuki Kaji
    2019 Volume 44 Issue 2 Pages 113-120
    Published: 2019
    Released: February 05, 2019
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    Although cytotoxicity of inorganic metals has been well investigated, little is known about the cytotoxicity of organic-inorganic hybrid molecules. The cytotoxicity of zinc complexes was evaluated using a culture system of vascular endothelial cells. We found that bis(1,4-dihydro-2-methyl-1-phenyl-4-thioxo-3-pyridiolato)zinc(II), termed Zn-06, exhibited strong cytotoxicity in vascular smooth muscle cells, epithelial cells, fibroblastic cells, and vascular endothelial cells. This study showed that the tetracoordinate structure of the Zn-06 molecule, which contains two sulfur and two oxygen atoms attached to the zinc atom, facilitated its accumulation within vascular endothelial cells whereas the whole structure of the zinc complex was involved in its cytotoxicity in the cells. The present data suggest that a part of the structure, especially the binding site of the metal atom, was responsible for accumulation of zinc complexes, and the entire structure is responsible for their cytotoxicity in vascular endothelial cells.

Original Article
  • Qingshu Li, Chunxia Gao, Hong Deng, Quancai Song, Li Yuan
    2019 Volume 44 Issue 2 Pages 121-131
    Published: 2019
    Released: February 05, 2019
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    Benzo(α)pyrene (BaP) possesses a forceful hepatotoxicity, and is ubiquitous in foods and ambient air. Our previous study found that BaP induced pyroptotic and autophagic death in HL-7702 human liver cells; the relevant mechanisms, however, remain unknown. This work was therefore to unravel the effects of the PI3K/Akt signaling pathway on pyroptotic and autophagic death triggered by BaP. Cells were treated with or without LY294002 (PI3K/Akt inhibitor) and IGF-1 (PI3K/Akt activator) before BaP exposure, and the results showed that compared with the control, the protein expression of p-Akt was markedly decreased by BaP (p < 0.05). IGF-1 did not subvert this inhibitive effect of BaP, while LY294002 enhanced it. Furthermore, the protein expression of pyroptosis (Cleaved Caspase-1, NO, IL-1β, IL-18), as well as LDH and the relative electrical conductivity were significantly augmented by BaP. The levels of these indices were increased by LY294002 pretreatment, and decreased by IGF-1. Similarly, LY294002 enhanced BaP-induced increase in the key protein expression of autophagy (Beclin-1 and LC3II), while IGF-1 weakened it. Finally, the phosphorylation of FOXO4 was clearly (p < 0.01) inhibited by BaP, and LY294002 suppressed this inhibitive effect of BaP, while IGF-1 strengthened it. In conclusion, BaP was able to induce pyroptotic and autophagic death via blocking the PI3K/Akt signaling pathway in HL-7702 liver cells.

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