γ-H2AX foci as indication for the DNA damage in erythrocytes of medaka (Oryzias latipes) intoxicated with 4-nonylphenol

Low Dose-Rate Irradiation of Gamma-Rays-Induced Cytotoxic and Genotoxic Alterations in Peripheral Erythrocytes of p53-Deficient Medaka (Oryzias latipes)

Morphological alterations and nuclear abnormalities in fish erythrocytes have been used in many studies as bioindicators of environmental mutagens including ionizing radiation. In this study, adult Japanese medaka (Oryzias latipes) were irradiated with gamma rays at a low dose rate (9.92 μGy/min) for 7 days, giving a total dose of 100 mGy; and morphological alterations, nuclear abnormalities, and apoptotic cell death induced in peripheral erythrocytes were investigated 8 h and 7 days after the end of the irradiation. A variety of abnormalities, such as tear-drop cell, crenated cell, acanthocyte, sickled cell, micronucleated cell, eccentric nucleus, notched nucleus, and schistocyte, were induced in the peripheral erythrocytes of the wild-type fish, and a less number of abnormalities and apoptotic cell death were induced in the p53-deficient fish. These results indicate that low dose-rate chronic irradiation of gamma rays can induce cytotoxic and genotoxic effects in the peripheral erythrocytes of medaka, and p53-deficient medaka are tolerant to the gamma-ray irradiation than the wild type on the surface.

Genotoxic activity of endocrine disrupting compounds commonly present in paper mill effluents

In the present study we evaluated cytotoxic and genotoxic activities of endocrine disrupting compounds (EDCs), including dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA), and nonylphenol (NP), which have been previously identified in effluents from two paper mills with different paper production technologies (virgin or recycled fibres). Moreover, we evaluated genotoxic activity of the effluents from these two paper mills and compared it to the activity of artificial complex mixtures consisting of the seven EDCs at concentrations detected in corresponding paper mill effluents. None of the EDCs was genotoxic in Salmonella typhimurium (SOS/umuC assay), while all induced DNA damage in human hepatocellular carcinoma (HepG2) cells (comet assay). After 4 h of exposure genotoxic effects were determined at concentrations ≥ 1 μg/L for BBP and DEHP, ≥10 μg/L for DMP, DEP, DBP, and BPA, and ≥100 μg/L for NP, while after 24 h of exposure DNA damage occurred at ≥10 μg/L for DBP, BPA and NP, and ≥100 μg/L for DMP, DEP, BBP and DEHP. The effluents and corresponding artificial mixtures of EDCs from paper mill that uses virgin fibres did not induce DNA damage in HepG2 cells, while the effluents and corresponding artificial mixtures for the paper mill that uses recycled fibres were genotoxic. Genotoxic activity of effluents was significantly higher compared to corresponding artificial mixtures suggesting the presence of further unknown compounds contributing to the effect. Wastewater monitoring based on chemical analysis is limited to determination of targeted compounds and does not take into account possible interactions between chemicals in mixtures. Therefore, it alone cannot provide an adequate information on potential toxic effects required for the assessment of genotoxic activity of real environmental samples and their potential threats to the environment and human health.

Recent advances in γH2AX biomarker-based genotoxicity assays: A marker of DNA damage and repair

The phosphorylation of histone variant H2AX and formation of γH2AX is a primary response to the DNA double-strand breaks (DSBs). Detection of γH2AX is a robust and sensitive tool for diagnosis of DNA damage and repair in pre-clinical drug discovery investigations. In addition, the replication stress also leads to the formation of γH2AX and cell death and so γH2AX can serve as a surrogate marker of drug-induced cytotoxicity. Recent advances in genomic research offer an opportunity to detect γH2AX as a specific biomarker for quantitative analysis of DNA damages and repair using high content screening technology and quantitative imaging analysis. The proposed approaches identify a wide range of genetic disorders and are applied in combination with other assays in drug discovery and also for the evaluation of the efficacy of various developmental drugs. In the current review, we provide recent insights into the potential of γH2AX biomarker as a powerful tool in genotoxicity analyses for the monitoring and managing of cancer diseases.

Iso-suillin-induced DNA damage leading to cell cycle arrest and apoptosis arised from p53 phosphorylation in A549 cells

Extensive investigations have revealed that iso-suillin, a secondary metabolite isolated from Suillus flavus, could induce cell cycle arrest and apoptosis in human chronic myeloid leukemia K562 cells, human hepatocellular carcinoma SMMC-7721 cell line, and human small cell lung cancer H446 cell line in vitro. In the present study, human lung cancer A549 cells were used to reveal the mechanism of iso-suillin's effects on lung adenocarcinoma, which were detected both in vitro and in vivo. Results showed that iso-suillin potently inhibited A549 cell proliferation through an early G1 arrest. Iso-suillin also induced A549 cell apoptosis in vitro. Phosphorylation of p53 at serines 15 and 20 may be one of the pivotal factors for cell cycle arrest and apoptosis after treatment of iso-suillin in A549 cells. Moreover, in an A549 xenograft model, tumor growth and progression could be inhibited by iso-suillin. Body weight change and some vital organs toxicity was also roughly examined, no significant toxic effects of iso-suillin were shown (at a dose of 5 mg/kg for each administration). The in vitro and in vivo anti-tumor effects implied that iso-suillin may act as a tumor growth inhibitor, and its induction of p53 phosphorylation is pivotal for cell cycle arrest and apoptosis in A549 cells.