Fundamental Toxicological Sciences

2022 - Vol. 9 No. 6

2022 - Vol. 9

Original Article
Pharmaceutical concentrations and antimicrobial activity using hypersusceptible Escherichia coli lacking TolC component of multidrug efflux system in the Ayase River in Japan Vol.9, No.6, p.187-196
Tsuyoshi Murahashi , Jun-ichi Yamagishi , Kunihiko Nishino , Reika Takada , Takumi Sekine , Yoshikazu Matsuda , Toshiyuki Higuchi
Released: November 30, 2022
Abstract Full Text PDF[1M]

The pharmaceutical concentrations and antimicrobial activity in the Ayase River were investigated. The water sources of the Ayase River are agricultural wastewater and effluent from septic tanks during the irrigation season and effluent from a sewage treatment plant and septic tanks during the non-irrigation season. Acetaminophen, bezafibrate, carbamazepine, clarithromycin, and diphenhydramine levels were in the range of 1.9–495 ng/L. During the irrigation season, pharmaceutical concentrations were higher downstream than upstream due to the inflow of agricultural wastewater in upstream areas. However, during the non-irrigation season, since most of the water sources were effluent from a sewage treatment plant and septic tanks, pharmaceutical concentrations were extremely high from upstream to downstream. The pharmaceutical concentrations during the non-irrigation season were at the same levels as those downstream of the Arakawa River, which was polluted by the effluent from Japan’s largest sewage treatment plant. This extremely high pharmaceutical concentration in the non-irrigated season was found only in the Ayase River but not in the nearby Nakagawa and Furutone rivers, which are both urban water sources. The maximum concentration of clarithromycin in the Ayase River was higher than the predicted no-effect concentration for green algae, indicating that the water from the Ayase River may affect aquatic organisms. Antimicrobial activity analysis in the Ayase River using hypersusceptible Escherichia coli lacking the TolC component of the multidrug efflux system revealed that the river water had antimicrobial activity, suggesting potential risks, such as bactericidal action and development of antibiotic resistance in river water.

Original Article
Role of cytoplasmic acetyltransferases, NAA60 and HAT1, in cellular protection against genotoxic agents Vol.9, No.6, p.179-186
Pasjan Satrimafitrah , Hideki Nishitoh , Yasunari Takami
Released: November 09, 2022
Abstract Full Text PDF[3M]

Histone acetyltransferases (HATs) are separated into two types. Type A HATs act on nucleosomal histones and thus primarily function in transcriptional regulation, while cytoplasmic HATs (type B) are known as enzymes that modify free histones before their assembly into chromatin, and may also function outside the nucleus. N-alpha-acetyltransferase 60 (NAA60) is the most recently discovered type B HATs, which are also known as N-terminal acetyltransferases (NATs) and are found only in multicellular eukaryotes. NAA60 localizes to the Golgi complex and possesses a unique ability to catalyze the acetylation of membrane-anchored proteins at the N-terminus and free histones at the lysine side chains, the biological significance of which remains unclear. To investigate the cellular functions of NAA60 and its relation to other cytoplasmic HATs, Hat1, we generated NAA60- or HAT1-deficient cells and NAA60/HAT1-double deficient cells using a chicken B lymphocyte leukemia DT40 cell line. Although NAA60-deficient cells did not show any impairment in cell growth and showed a slight sensitivity to DNA damage agents, NAA60/HAT1-double deficient cells exhibited an additive increase in sensitivity to methyl methanesulfonate (MMS) and 4-nitroquinoline 1-oxide (4-NQO) when compared to HAT1-deficient cells, which were previously reported to be moderately sensitive to these agents. These results predict that each type B HATs might contribute differently in regulation of repair of chemical induced DNA lesions.

Assessment of genotoxicity of 2-[2-(acetylamino)-4-[bis(2-hydroxyethyl)amino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-6) in zebrafish (Danio rerio) using the comet assay and micronucleus test Vol.9, No.6, p.173-178
Yuya Deguchi , Tomoyasu Toyoizumi , Hiroaki Nagaoka , Shuichi Masuda
Released: November 09, 2022
Abstract Full Text PDF[1M]

This study aimed to evaluate the genotoxicity of 2-[2-(acetylamino)-4-[bis(2-hydroxyethyl)amino]-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-6) in fish. Adult zebrafish (Danio rerio) were exposed to PBTA-6 solution of 0.3 to 10 mg/L for 96 hr. Genotoxicity was evaluated using alkaline single-cell gel electrophoresis (comet assay) and micronucleus (MN) tests on blood and gills. Although PBTA-6 showed no positive response to MN induction, it caused a concentration-dependent increase in DNA damage. Fish exposed to PBTA-6 (10 mg/L) for 96 hr followed by a 96 hr recovery period in tap water were also examined; DNA damage decreased to the level before treatment within 96 hr. To compare the cytochrome P450 (CYP) activity in different tissues, CYP1A (ethoxyresorufin-O-deethylase; EROD and methoxyresorufin-O-demethylase; MROD) and CYP2B (penthoxyresorufin-O-depentylase; PROD and benzyloxyresorufin-O-debenzylase; BROD) activities were analyzed in liver and gill microsomes. The results showed that PBTA-6 markedly induced PROD activity in gills and caused DNA damage, but the results show that this damage could be reverted if the exposed fish are returned to tap water.

Induction of CYP3A4 mRNA by cooked food-derived carcinogenic heterocyclic aromatic amines in human HPL-A3 cells Vol.9, No.6, p.167-172
Masashi Sekimoto , Natsuki Yamashita , Seiichiro Maeda , Masakuni Degawa
Released: October 28, 2022
Abstract Full Text PDF[1021K]

The effects of six cooked food-derived heterocyclic carcinogenic amines (HCAs), including 2-amino-9H-pyrido[2,3-b]indole acetate (AαC) and its 3-methyl derivative (MeAαC), on cytochrome P450 3A (CYP3A) induction were examined using a human hepatoblastoma cell-derived HPL-A3 cell line, previously established for a luciferase-reporter gene assay for the detection of a CYP3A4 inducer. AαC and MeAαC, but not the four other HCAs, enhanced luciferase activity. Quantitative RT-PCR further confirmed the significant induction of CYP3A4 mRNA by AαC and MeAαC. Since CYP3A4 gene expression is primarily regulated by the pregnane X receptor (PXR) and occasionally by other receptors, such as the aryl hydrocarbon receptor and vitamin D receptor, the effects of siRNAs for these regulator genes on AαC- and MeAαC-mediated increases in luciferase activity were investigated further. PXR siRNA, but not other siRNAs, significantly reduced AαC- and MeAαC-induced luciferase activities. These results demonstrate for the first time that AαC and MeAαC, among the six HCAs tested, increase CYP3A4 mRNA via PXR activation in human hepatoblastoma-derived HPL-A3 cells.