Fundamental Toxicological Sciences

2023 - Vol. 10 No. 1

2023 - Vol. 10

mRNA expression profile of cytokines in rat primary alveolar macrophages treated with multiwalled carbon nanotube (MWCNT) Vol.10, No.1, p.27-30
Nahida Sultana , Katsumi Fukamachi , Jiegou Xu , Hiroyuki Tsuda , Masumi Suzui
Released: February 17, 2023
Abstract Full Text PDF[698K]

Multiwalled carbon nanotubes (MWCNT) are fiber-shaped nanomaterials that have a potential risk for cancer due to properties that are similar to asbestos. One type of nanotube called MWCNT-7 was categorized in Group 2B as possibly carcinogenic to humans by the International Agency for Research on Cancer. MWCNT-N, which is similar to MWCNT-7, is carcinogenic to the lung and pleura when administered to rats via the respiratory tract using intra-tracheal intra‐pulmonary spraying. Macrophages have an important role in the MWCNT induced pulmonary carcinogenicity. In this study, rat primary alveolar macrophages were employed to examine possible mechanism of carcinogenic effects of the MWCNT-N. MWCNT-N was fractionated into flow-through and retained fraction by passing it through a sieve with a pore size of 25 μm. Microarray analysis showed up-regulation of various cytokines in macrophages exposed to MWCNT-N. MWCNT-N strongly induced the expression of cytokines such as interleukin-6 (IL-6) in macrophages. In contrast, few cytokines were prominently down-regulated in macrophages treated with MWCNT-N. The sieve fractions did not have a significant effect on mRNA expression of cytokines in macrophages. These results provide useful information for understanding MWCNT-induced carcinogenicity via cytokine expression by macrophages.

DNA damage mediated by 4,4'-methylenebis(2-chloroaniline) cannot be detected via the DNA damage marker γH2AX: A case study Vol.10, No.1, p.21-25
Saho Kobayashi , Hiroki Kashiwagi
Released: February 15, 2023
Abstract Full Text PDF[1M]

DNA damage may be induced by both intrinsic and extrinsic factors, the latter involving chemical exposure at workplaces. Upon DNA damage induction, checkpoint kinases such as ATM and ATR, phosphorylate serine 139 of the histone H2AX generating γH2AX, to initiate the damage response pathway. This allows antibodies that act against post-translational modifications, such as γH2AX, to be used for detecting genotoxicity. The aromatic amine 4,4'-methylenebis(2-chloroaniline) (MOCA), which is utilized in industry to produce polyurethane resins, exhibits genotoxicity and induces cancers in animals, including rodents and humans. DNA damage, due to MOCA-induced toxicity during its metabolism, is believed to be first step towards carcinogenesis. However, we failed to detect γH2AX induction by MOCA in cellular systems via western blotting, even when electrophoresis-based methods clearly indicated that physical DNA damage had been induced. In the present study, we utilized RNA sequencing of MOCA-treated cells and controls to elucidate factors underlying the discrepancies observed between these two analytical systems. Our results indicated that H2AX mRNA expression was significantly downregulated; this finding partially clarified the inefficient induction of γH2AX. Although downregulation of γH2AX in the presence of MOCA witnessed in this study was quite unexpected, we believe that this finding prompts researchers to be cautious when screening for genotoxicity using γH2AX only, due to the possibility of genotoxicity being overlooked in some cases. Thus, it appears that a combined approach may be more suitable for detecting genotoxicity.

Original Article
Paternal exposure to methylphenidate induces ADHD-like behavioral phenotypes and altered gene expressions in mouse offspring Vol.10, No.1, p.7-20
Ryota Nakano , Asuka Kaizaki-Mitsumoto , Satoshi Numazawa
Released: February 01, 2023
Abstract Full Text PDF[2M]

Methylphenidate (MPH) is used as a first-line treatment for attention-deficit/hyperactivity disorder (ADHD). Because the onset of ADHD appears in early childhood and the incidence number is increasing, more patients could become adults with long-term use of MPH. In addition, few men would discontinue the medication during a fertile period. Recently, environmental factors such as diet and drug abuse have been reported to produce changes in the sperm epigenome and affect the health of the next generation. However, the effects of long-term administration of a psychostimulant such as MPH on the next generation is unknown. In this study, we examined the effects of paternal administration of MPH on the growth, behavior, and gene expression in offspring using a mouse model. Sires were subcutaneously administered MPH for 21 days and mated with naive dams. Upon reaching 6–7 weeks of age, offspring were subjected to spontaneous locomotor, elevated plus-maze, and passive avoidance tests. Additionally, RNA-seq and RT-qPCR were performed on the striatum. Paternal MPH exposure induced increased atomoxetine-sensitive impulsivity and decreased long-term memory function in the offspring. Enrichment analysis following RNA-seq revealed significant enrichment of terms involved in the nervous system. Gene expression levels of Snap25, Syt1, Drd2, Maoa, and Comt, which are associated with ADHD pathology, are altered in the striatum. These results suggest that continuous administration of MPH to male mice induces ADHD-like behavior and changes in the expression of genes involved in the nervous system in the brain of the next generation.

Toxicomics Report
PPAR gamma negatively regulates the expression of TRPM8 in normal epidermal cells but mutually regulate their expressions with TRPM8 by feed-back loop regulation in squamous carcinoma cells Vol.10, No.1, p.1-6
Tomofumi Fujino , Mizuki Nakamura , Saki Ohkawa
Released: January 13, 2023
Abstract Full Text PDF[1M]

TRPM8, non-selective cation channel of the transient receptor potential (TRP) superfamily, required for the transduction of moderate cold temperatures, regulates proliferation of epidermal cells in cyclin-dependent kinase inhibitor p21/Cip1-dependent manner. Given that downregulation of TRPM8 decreases p21/Cip1 level, increasing risk for carcinogenesis, and other TRP family is regulated by nuclear receptor peroxisome proliferator-activated receptor (PPAR) gamma, we examined whether TRPM8 expression was regulated by PPAR gamma. Knockdown assay and inhibition of PPAR gamma revealed that PPAR gamma negatively regulates the expression of TRPM8 in normal epidermal cells but positively regulates that in squamous carcinoma cells. Later restoration of decreased TRPM8 level in PPAR gamma antagonist-treated squamous carcinoma cells was attributed to feed-back loop regulation between TRPM8 and PPAR gamma using TRPM8 knockdown assay. Consisting with this finding, p21/Cip1 decrease by TRPM8 blocker, N-(4-Tertiarybutylphenyl)-4-(3-chloropyridin- 2-yl) tetrahydropyrazine-1 (2H)-carbox-amide (BCTC), was restored by additional BCTC treatment in squamous carcinoma cells.