Effects of the DNA repair inhibitors, cytosine arabinoside and 3-aminobenzamide, on the frequency of radiation-induced micronuclei, nuclear buds, and nucleoplasmic bridges.

BACKGROUND: Micronuclei (MN), nuclear bud (NBud), and nucleoplasmic bridge (NPB) are suggested as biomarkers for radiation exposure; however, they have not been extensively studied to understand the underlying mechanisms responsible for their formation. OBJECTIVES: To (1) validate NBud and NPB within the cytokinesis-blocked micronucleus (CBMN) assay as biomarkers for radiation exposure and (2) determine the effects of the DNA repair inhibitors, cytosine arabinoside (Ara C) and 3-aminobenzamide (3-AB) on radiation-induced MN, NBud, and NPB formation. METHODS: Human blood samples were irradiated with 0-3 Gy X-rays and subsequently treated with Ara C and 3-AB. CBMN and chromosome aberration assays were carried out to measure MN, NBud, and NPB and dicentric chromosomes, respectively. RESULTS: The frequency of radiation-induced MN, NBud, and NPB increased in a dose-dependent manner. The frequency of MN, NBud, and NPB was highly and positively correlated with the dicentric chromosome, a standard biomarker for biodosimetry (r > 0.98, p < 0.0001). Furthermore, Ara C increased the frequency of MN, NBud, and NPB, whereas 3-AB increased the frequency of MN and NPB, but not NBud. Further, the potentiating effect of Ara C on the frequency of MN, NBud, and NPB was greater than that of 3-AB. CONCLUSION: Our results validate NBuds and NPBs as independent valuable markers of radiation exposure. Additionally, we suggest that different mechanisms are likely involved in the formation of NBuds and NPBs following X-irradiation; however, additional studies are warranted to better understand the contribution of distinct DNA repair pathways to the formation of radiation-induced damages.

Subacute toxicity and toxicokinetics study of DHP107, an oral paclitaxel formulation with once-weekly dosing in mice.

DHP107, an oral formulation of paclitaxel, is effectively and systemically absorbed in intestinal endothelial cells. Although the in vivo efficacy of DHP107 has been reported, the potential toxicity of DHP107 has not been evaluated. Therefore, this study was conducted to evaluate the toxicity and toxicokinetics of DHP107 orally administered to ICR mice at 25, 50, and 100 mg/kg via once-weekly dosing for six weeks. DHP107-related clinical signs were observed in both sexes at 100 mg/kg. There were significant increases in the number of platelets and percentages of reticulocytes and basophils in male mice. Also in males, there was a significant decrease in the absolute and relative weights of testes, epididymides, kidneys, and heart. Relative spleen weights were significantly increased in males treated with doses ≥50 mg/kg which had histopathological correlates. These changes were reversible after a two-week recovery period with the exception of the findings in the reproductive organs. Systemic exposure to paclitaxel increased with DHP107 doses in single and multiple dosing with no marked differences between sexes. In conclusion, the target organs were determined to be the reproductive and hematopoietic organs in male mice, suggesting of sex difference and the NOAEL of DHP107 was established to be < 25 mg/kg for males and 50 mg/kg for females.

Therapeutic Effect of a Xeno-Free Three-Dimensional Stem Cell Mass in a Hind Limb Ischemia Model.

IMPACT STATEMENT: We describe an innovative method of culturing a three-dimensional cell mass (3DCM) of human adipose-derived stem cells (hASCs) in the xeno-free (XF) condition for the treatment of severe ischemic diseases. The majority of the mice injected with XF-3DCMs exhibited limb salvaging and displayed similar blood perfusion compared to normal limbs. In vivo tumorigenicity and toxicity analysis showed that XF-3DCMs did not transform into tumor cells and induce toxicity, respectively. Our results strongly suggest that XF-3DCMs can be effectively used for therapeutic applications and eliminate immunological reaction of animal-derived material contamination.

Tumorigenicity Evaluation of Umbilical Cord Blood-derived Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) have been identified in multiple types of tissue and exhibit characteristic self-renewal and multi-lineage differentiation abilities. However, the possibility of oncogenic transformation after transplantation is concerning. In this study, we investigated the tumorigenic potential of umbilical cord blood-derived MSCs (hUCB-MSCs) relative to MRC-5 and HeLa cells (negative and positive controls, respectively) both in vitro and in vivo. To evaluate tumorigenicity in vitro, anchorage-independent growth was assessed using the soft agar colony formation assay. hUCB-MSCs and MRC-5 cells formed few colonies, while HeLa cells formed a greater number of larger colonies, indicating that hUCB-MSCs and MRC-5 cells do not have anchorage-independent proliferation potential. To detect tumorigenicity in vivo, hUCB-MSCs were implanted as a single subcutaneous injection into BALB/c-nu mice. No tumor formation was observed in mice transplanted with hUCB-MSCs or MRC-5 cells based on macroand microscopic examinations; however, all mice transplanted with HeLa cells developed tumors that stained positive for a human gene according to immunohistochemical analysis. In conclusion, hUCB-MSCs do not exhibit tumorigenic potential based on in vitro and in vivo assays under our experimental conditions, providing further evidence of their safety for clinical applications.

Protective Effect of Onion Extract on Bleomycin-Induced Cytotoxicity and Genotoxicity in Human Lymphocytes.

Following one of the world's largest nuclear accidents, occured at Fukushima, Japan in 2011, a significant scientific effort has focused on minimizing the potential adverse health effects due to radiation exposure. The use of natural dietary antioxidants to reduce the risk of radiation-induced oxidative DNA damage is a simple strategy for minimizing radiation-related cancer rates and improving overall health. The onion is among the richest sources of dietary flavonoids and is an important food for increasing their overall intake. Therefore, we examined the effect of an onion extract on cyto- and geno-toxicity in human lymphocytes treated with bleomycin (BLM), a radiomimetic agent. In addition, we measured the frequency of micronuclei (MN) and DNA damage following treatment with BLM using a cytokinesis-blocked micronucleus assay and a single cell gel electrophoresis assay. We observed a significant increase in cell viability in lymphocytes treated with onion extract then exposed to BLM compared to cells treated with BLM alone. The frequency of BLM induced MN and DNA damage increased in a dose-dependent manner; however, when lymphocytes were pretreated with onion extract (10 and 20 µL/mL), the frequency of BLM-induced MN was decreased at all doses of BLM and DNA damage was decreased at 3 µg/mL of BLM. These results suggest that onion extract may have protective effects against BLM-induced cyto- and genotoxicity in human lymphocytes.

Radiation-induced changes in DNA methylation and their relationship to chromosome aberrations in nuclear power plant workers.

PURPOSE: We investigated the association between occupational radiation exposure and DNA methylation changes in nuclear power plant workers. We also evaluated whether radiation- induced DNA methylation alterations are associated with chromosome aberrations. MATERIALS AND METHODS: The study population included 170 radiation-exposed workers and 30 controls. We measured global, long interspersed nuclear element-1 (LINE-1), and satellite 2 methylation levels in blood leukocyte DNA. The analysis of chromosome aberrations was performed on peripheral lymphocytes. RESULTS: Global DNA methylation levels were lower in radiation-exposed workers than in controls. The methylation levels were negatively associated with the recent 1.5-year radiation dose in a multiple linear regression model (ß = - 0.0088, p ≤ 0.001); the levels increased proportionally with the total cumulative dose in radiation-exposed workers. LINE-1 methylation levels were higher in radiation-exposed workers than in controls and were significantly associated with the total cumulative radiation dose in a multiple linear regression model (ß = - 0.031, p = 0.035). Global DNA methylation levels were also correlated with chromosome aberrations among workers. Workers with low global methylation levels had a higher frequency of chromosome aberrations than did subjects with high global methylation levels. CONCLUSION: Occupational exposure to low-dose radiation could affect DNA methylation levels, and the radiation-induced DNA methylation alterations may be associated with chromosome aberrations.

Enhanced cytotoxic and genotoxic effects of gadolinium following ELF-EMF irradiation in human lymphocytes.

There are many studies of Gd nephrotoxicity and neurotoxicity, whereas research on cyto- and genotoxicity in normal human lymphocytes is scarce. It is important to investigate the effect of extremely low-frequency electromagnetic fields (ELF-EMF) on Gd toxicity, as patients are co-exposed to Gd and ELF-EMF generated by MRI scanners. We investigated the cytotoxicity and genotoixcity of Gd and the possible enhancing effect of ELF-EMF on Gd toxicity in cultured human lymphocytes by performing a micronuclei (MN) assay, trypan blue dye exclusion, single cell gel electrophoresis, and apoptosis analyses using flow cytometry. Isolated lymphocytes were exposed to 0.2-1.2 mM of Gd only or in combination with a 60-Hz ELF-EMF of 0.8-mT field strength. Exposing human lymphocytes to Gd resulted in a concentration- and time-dependent decrease in cell viability and an increase in MN frequency, single strand DNA breakage, apoptotic cell death, and ROS production. ELF-EMF (0.8 mT) exposure also increased cell death, MN frequency, olive tail moment, and apoptosis induced by Gd treatment alone. These results suggest that Gd induces DNA damage and apoptotic cell death in human lymphocytes and that ELF-EMF enhances the cytotoxicity and genotoxicity of Gd.

Cyto-/genotoxic effects of the ethanol extract of Chan Su, a traditional Chinese medicine, in human cancer cell lines.

ETHNOPHARMACOLOGICAL RELEVANCE: Chan Su, an ethanolic extract from skin and parotid venom glands of the Bufo bufo gargarizans Cantor, is widely used as a traditional Chinese medicine for cancer therapy. Although the anti-cancer properties of Chan Su have been investigated, no information exists regarding whether Chan Su has genotoxic effects in cancer cells. The aim of the present study was to examine the cyto-/genotoxic effect of Chan Su in human breast carcinoma (MCF-7 cells), human lung carcinoma (A-549 cells), human T cell leukemia (Jurkat T cells), and normal human lymphocytes. MATERIALS AND METHODS: Effects on the viability of MCF-7, A-549, Jurkat T cells, and normal lymphocytes were evaluated by Trypan blue exclusion assays. The DNA content in the sub-G1 region was detected by propidium iodide (PI) staining and flow cytometry. The genotoxicity of Chan Su was assessed by single-cell gel electrophoresis (comet assay) and the cytokinesis-block micronucleus assay (CBMN assay). RESULTS: Chan Su significantly inhibited the viability of MCF-7, A-549, and Jurkat T cells dose dependently, but had no effect on normal human lymphocytes. Apoptotic death of the cancer cells was evident after treatment. Chan Su also induced genotoxicity in a dose-dependent manner, as indicated by the comet and cytokinesis-block micronucleus assays. CONCLUSIONS: These findings suggest that Chan Su can induce apoptotic death of, and exert genotoxic effects on, MCF-7, A-549, and Jurkat T cells.

Selective Effects of Curcumin on CdSe/ZnS Quantum-dot-induced Phototoxicity Using UVA Irradiation in Normal Human Lymphocytes and Leukemia Cells.

Quantum dots (QDs) have received considerable attention due to their potential role in photosensitization during photodynamic therapy. Although QDS are attractive nanomaterials due to their novel and unique physicochemical properties, concerns about their toxicity remain. We suggest a combination strategy, CdSe/ZnS QDs together with curcumin, a natural yellow pigment from turmeric, to reduce QD-induced cytotoxicity. The aim of this study was to explore a potentially effective cancer treatment: co-exposure of HL-60 cells and human normal lymphocytes to CdSe/ZnS QDs and curcumin. Cell viability, apoptosis, reactive oxygen species (ROS) generation, and DNA damage induced by QDs and/or curcumin with or without ultraviolet A (UVA) irradiation were evaluated in both HL-60 cells and normal lymphocytes. In HL-60 cells, cell death, apoptosis, ROS generation, and single/double DNA strand breaks induced by QDs were enhanced by treatment with curcumin and UVA irradiation. The protective effects of curcumin on cell viability, apoptosis, and ROS generation were observed in normal lymphocytes, but not leukemia cells. These results demonstrated that treatment with QD combined with curcumin increased cell death in HL-60 cells, which was mediated by ROS generation. However, curcumin acted as an antioxidant in cultured human normal lymphocytes.

Cytotoxicity and genotoxicity induced by photothermal effects of colloidal gold nanorods.

Gold nanorods (Au NRs) that absorb near-infrared (NIR) light have great potential in the field of nanomedicine. Photothermal therapy (PTT), a very attractive cancer therapy in nanomedicine, combines nanomaterials and light. The aim of this study was to elucidate the molecular mechanism involved in Au NR-mediated cytotoxic, genotoxic, and other biological responses, in the presence or absence of NIR irradiation. Specifically, cell death mode, generation of reactive oxygen species, DNA damage, apoptotic gene expression, and cell morphological changes induced by Au NRs under NIR irradiation were evaluated in cancer cells. In human lung adenocarcinoma epithelial cells (A549 cells), mild necrosis via DNA damage was induced by NIR responsive Au NRs. Unlike in the cancer cells, cell viability of normal human lymphocyte was not affected by the combined treatment of Au NRs and NIR irradiation. This study delineates differential cytotoxic and genotoxic susceptibility of cancer and normal cells during photothermal treatment of Au NRs. In conclusion, our results suggest that the photothermal cyto-/genotoxic activity of Au NRs is an effective method for cancer therapy in human lung cancer cells.

Enhancement of cisplatin cytotoxicity by benzyl isothiocyanate in HL-60 cells.

Cis-diamminedichloroplatinum (II) (cisplatin) is one of the most widely used chemotherapeutic drugs, but its effectiveness is limited by tumor cell resistance and the severe side effects it causes. One strategy for overcoming this problem is the concomitant use of natural dietary compounds as therapeutic agents. Benzyl isothiocyanate (BITC) is a promising chemopreventive agent found in cruciferous vegetables and papaya fruits. The aim of this study was to investigate the effects of BITC on cisplatin-induced cytotoxicity in human promyelocytic leukemia cells and normal human lymphocytes. The combined treatment of HL-60 cells with BITC followed by cisplatin (BITC/cisplatin) caused a significant decrease in cell viability. BITC also increased apoptotic cell death compared to cisplatin treatment alone. In normal human lymphocytes, BITC did not enhance the cytotoxic effects of cisplatin. Cellular exposure to BITC/cisplatin increased reactive oxygen species (ROS) generation but decreased the total glutathione (GSH) level in HL-60 cells. Pretreatment of HL-60 cells with N-acetylcysteine or glutathione monoethyl ester effectively decreased BITC/cisplatin-induced cell death. The addition of the extracellular signal-regulated kinase (ERK) inhibitor PD98059 abolished BITC/cisplatin-induced apoptosis. Taken together, our results suggest that BITC enhances cisplatin-induced cytotoxicity through the generation of ROS, depletion of GSH, and ERK signaling in HL-60 cells.