Mutagenesis by chemical agents in V79 chinese hamster cells: a review and analysis of the literature. A report of the Gene-Tox Program

Pyrene-polyethylene glycol-modified multi-walled carbon nanotubes: Genotoxicity in V79-4 fibroblast cells

The genotoxicity of pyrene-polyethylene glycol-modified multi-walled carbon nanotubes (MWCNT-PyPEG), engineered as a nanoplatform for bioapplication, was evaluated. Toxicity was assessed in hamster lung fibroblast cells (V79-4). MTT and Cell Titer Blue methods were used to evaluate cell viability. Genotoxicity was measured by the comet assay and the cytokinesis-block micronucleus cytome (CBMN-Cyt) assay, and fluorescence in situ hybridization (FISH) was used to test induction of structural chromosome aberrations (clastogenic activity) and/or numerical chromosome changes (aneuploidogenic activity). Exogenous metabolic activation enzymes were used in the CBMN-Cyt and FISH tests. Only with metabolic activation, the hybrids caused chromosomal damage, by both clastogenic and aneugenic processes.

Cytotoxicity and action mechanisms of polycyclic aromatic hydrocarbons by a miniature electrochemical detection system

The effects of six polycyclic aromatic hydrocarbons (PAHs) on the activity of V79 cells were studied by using a miniature electrochemical system based on graphene oxide quantum dots and multiwall carbon nanotubes modified anodized screen printed carbon electrode. The cytotoxicity sequence of PAHs on V79 cells was different with guanine/xanthine (G/X), adenine (A), hypoxanthine (HX), and the end product of purine nucleotide catabolism, uric acid (UA), as biomarkers. The IC₅₀ values measured with UA as the biomarker were the lowest, indicating that UA in cells was more sensitive to PAHs. The cytotoxicity sequence with G/X as the biomarker was the same as that of the MTT assay: pyrene > phenanthrene > benzo[a]pyrene > fluoranthene > fluorene > naphthalene. The cytotoxicity sequences measured by different biomarkers varied, which related to different structures that may influence the expression of the cellular aryl hydrocarbon receptor, gap junctional intercellular communication, and p53 protein. PAHs with different structures played varied roles in cell development and differentiation. Additionally, the electrochemical method was more sensitive than the MTT assay. The miniature electrochemical system enabled the simultaneous detection of four signals in cells, providing more information for multi-parameter evaluation and toxic mechanism study of PAHs and other pollutants.

Using a high-throughput method in the micronucleus assay to compare animal-free with rat-derived S9

This study presents a high-throughput (HTP) micronucleus assay in multi-well plates with an automated evaluation for risk assessment applications. The evaluation of genotoxicity via the micronucleus assays according to international guidelines ISO 21427-2 with Chinese hamster (Cricetulus griseus) V79 cells was the starting point to develop our methodology. A drawback of this assay is that it is very time consuming and cost intensive. Our HTP micronucleus assay in a 48-well plate format allows for the simultaneous assessment of five different sample-concentrations with additional positive, negative and solvent controls with six technical replicates each within a quarter of the time required for the equivalent evaluation using the traditional slide method. In accordance with the 3R principle, animal compounds should be replaced with animal-free alternatives. However, traditional cell culture-based methods still require animal derived compounds like rat-liver derived S9-fraction, which is used to simulate the mammalian metabolism in in vitro assays that do show intrinsic metabolization capabilities. In the present study, a recently developed animal-free biotechnological alternative (ewoS9R) was investigated in the new high-throughput micronucleus assay. In total, 12 different mutagenic or genotoxic chemicals were investigated to assess the potential use of the animal-free metabolization system (ewoS9R) in comparison to a common rat-derived product. Out of the 12 compounds, one compound did not induce micronuclei in any treatment and 2 substances showed a genotoxic potential without the need for a metabolization system. EwoS9R demonstrated promising potential for future applications as it shows comparable results to the rat-derived S9 for 6 of the 9 pro-genotoxic substances tested. The remaining 3 substances (2-Acetamidofluorene, Benzo[a]pyrene, Cyclophosphamide) were only metabolized by rat-derived S9. A potential explanation is that ewoS9R was investigated with an approx. 10-fold lower enzyme concentration and was only optimized for CYP1A metabolization that may be improved with a modified production procedure. Future applications of ewoS9R go beyond the micronucleus assay, but further research is necessary.

Ultrasonic therapy modulates the expression of genes related to neovascularization and inflammation in fibroblasts

Abstract Introduction: In the rehabilitation of musculoskeletal injuries, ultrasound is widely used in clinical practice. Objective: To evaluate the effects of pulsed ultrasonic therapy on the viability and modulation of genes involved in inflammation (IL-6) and neovascularization (VEGF) processes of L929 fibroblast cells. Methods: For irradiation with ultrasound the cells were subdivided into groups: G1 (without irradiation), G2 (0.3 W/cm2-20%) and G3 (0.6 W/cm2-20%), with periods of treatment at 24, 48 and 72 hours. The cell viability assay was analyzed by the MTT method and gene modulation was analyzed by RT-qPCR method. Results: After the comparative analysis between groups, only G2 and G3 (48-hour) presented statistically significant differences in relation to the control. In relation to the gene expression, the selection of the groups analyzed was delimited according to the comparative analysis of the values obtained by the MTT test. After the achievement of RT-qPCR, it could be observed that in G2 the amount of VEGF gene transcripts increased by 1.125-fold compared to endogenous controls, and increased 1.388-fold in G3. The IL-6 gene, on the other hand, had its transcripts reduced in both G2 (5.64x10-9) and G3 (1.91x10-6). Conclusion: Pulsed ultrasound in L929 fibroblasts showed a significant biostimulatory effect in the 48-hour period, with increased cell viability, and the same effect in the modulation of gene expression related the neovascularization and inflammation, mediating the acceleration of the tissue repair cascade.

Inhibition of Angiogenesis by Treatment with Cold Atmospheric Plasma as a Promising Therapeutic Approach in Oncology

Background: Cold atmospheric plasma (CAP) is increasingly used in the field of oncology. Many of the mechanisms of action of CAP, such as inhibiting proliferation, DNA breakage, or the destruction of cell membrane integrity, have been investigated in many different types of tumors. In this regard, data are available from both in vivo and in vitro studies. Not only the direct treatment of a tumor but also the influence on its blood supply play a decisive role in the success of the therapy and the patient’s further prognosis. Whether the CAP influences this process is unknown, and the first indications in this regard are addressed in this study. Methods: Two different devices, kINPen and MiniJet, were used as CAP sources. Human endothelial cell line HDMEC were treated directly and indirectly with CAP, and growth kinetics were performed. To indicate apoptotic processes, caspase-3/7 assay and TUNEL assay were used. The influence of CAP on cellular metabolism was examined using the MTT and glucose assay. After CAP exposure, tube formation assay was performed to examine the capillary tube formation abilities of HDMEC and their migration was messured in separate assays. To investigate in a possible mutagenic effect of CAP treatment, a hypoxanthine-guanine-phosphoribosyl-transferase assay with non malignant cell (CCL-93) line was performed. Results: The direct CAP treatment of the HDMEC showed a robust growth-inhibiting effect, but the indirect one did not. The MMT assay showed an apparent reduction in cell metabolism in the first 24 h after CAP treatment, which appeared to normalize 48 h and 72 h after CAP application. These results were also confirmed by the glucose assay. The caspase 3/7 assay and TUNEL assay showed a significant increase in apoptotic processes in the HDMEC after CAP treatment. These results were independent of the CAP device. Both the migration and tube formation of HDMEC were significant inhibited after CAP-treatment. No malignant effects could be demonstrated by the CAP treatment on a non-malignant cell line.

Toxicity, Clastogenicity and Genotoxicity of Theophylline and Pentoxifylline in Mammalian Cells Cultured In Vitro

— As part of a developmental study on theophylline and pentoxifylline, these drugs were tested for possible cytotoxic, mutagenic and clastogenic effects on V79 hamster cells and human lymphocytes cultured in vitro. After the short-term treatment of V79 cells with theophylline and pentoxifylline, the cells were relatively resistant to the toxic effects of these methylxanthines. Generally, only high concentrations of theophylline or pentoxifylline had toxic effects on exposed V79 cells. Short-term treatment of V79 cells with theophylline or pentoxifylline did not induce 6-thioguanine resistant mutations in either the presence or absence of S9 fractions. However, in the absence of an S9 fraction, elevated levels of single-strand breaks in DNA were induced. Both methylxanthines caused clastogenic effects in human lymphocytes and hamster V79 cells after long-term exposure. We suggest that theophylline and pentoxifylline are clastogenic but not genotoxic, and that the molecular mechanism for the induction of single-strand breaks in DNA and the induction of chromosomal aberrations in cells treated with theophylline and pentoxifylline is not the induction of lesions in the DNA but the inhibition of DNA chain elongation.

Gene (HPRT) and chromosomal (MN) mutations of nickel metal powder in V79 Chinese hamster cells

Nickel metal is a naturally occurring element used in many industrial and consumer applications. Human epidemiological data and animal cancer bioassays indicate that nickel metal is not likely to be a human carcinogen. Yet, nickel metal is classified as a suspected human carcinogen (CLP) and possibly carcinogenic to humans (IARC). There are no reliable studies on the potential for nickel metal to induce gene and micronucleus (MN) mutations. To fill these datagaps and increase our understanding of the mechanisms underlying the lack of nickel metal carcinogenicity, gene and micronucleus mutation studies were conducted with nickel metal powder (N36F) in V79 Chinese Hamster cells following OECD 476 and 487 guidelines, respectively, under GLP. Gene mutation at the hprt locus was tested, with and without metabolic activation, after 4-h treatment with 0.05-2.5 mM nickel metal powder. Cytokinesis-block MN frequency following exposure to 0.25-1.5 mM nickel metal was tested after 4-h treatment, with and without metabolic activation, followed by a 24-h treatment without metabolic activation. In the gene mutation assay, there were modest increases in hprt mutants observed at some test concentrations, not exceeding 2.2-fold, which were either within the historical control values and/or showed no concentration-response trend. The positive controls showed increases of at least 7-fold. Likewise, no increases in the MN frequency exceeding 1.5-fold were observed with nickel metal, with no concentration-response trends. Taking these results together, it can be concluded that nickel metal is non-mutagenic and does not cause gene nor chromosomal mutations.

The development and prevalidation of an in vitro mutagenicity assay based on MutaMouse primary hepatocytes, Part II: Assay performance for the identification of mutagenic chemicals

As demonstrated in Part I, cultured MutaMouse primary hepatocytes (PHs) are suitable cells for use in an in vitro gene mutation assay due to their metabolic competence, their "normal" phenotype, and the presence of the MutaMouse transgene for reliable mutation scoring. The performance of these cells in an in vitro gene mutation assay is evaluated in this study, Part II. A panel of 13 mutagenic and nonmutagenic compounds was selected to investigate the performance of the MutaMouse PH in vitro gene mutation assay. The nine mutagens represent a range of classes of chemicals and include mutagens that are both direct-acting and requiring metabolic activation. All the mutagens tested, except for ICR 191, elicited significant, concentration-dependent increases in mutant frequency (MF) ranging from 2.6- to 14.4-fold over the control. None of the four nonmutagens, including two misleading, or "false," positives (i.e., tertiary butylhydroquinone [TBHQ] and eugenol), yielded any significant increases in MF. The benchmark dose covariate approach facilitated ranking of the positive chemicals from most (i.e., 3-nitrobenzanthrone [3-NBA], benzo[a]pyrene [BaP], and aflatoxin B1 [AFB1]) to least (i.e., N-ethyl-N-nitrosourea [ENU]) potent. Overall, the results of this preliminary validation study suggest that this assay may serve as a complimentary tool alongside the standard genotoxicity test battery. This study, alongside Part I, illustrates the promise of MutaMouse PHs for use in an in vitro gene mutation assay, particularly for chemicals requiring metabolic activation. Environ. Mol. Mutagen. 60:348-360, 2019. © 2019 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.

Cytogenotoxic effects of venlafaxine hydrochloride on cultured human peripheral blood lymphocytes

The potential genotoxic effect of venlafaxine hydrochloride (venlafaxine), an antidepressant drug-active ingredient, was investigated by using in vitro chromosome aberrations (CAs) and cytokinesis-block micronucleus (CBMN) assays in human peripheral blood lymphocytes (PBLs). Mitotic index (MI) and cytokinesis-block proliferation index (CBPI) were also calculated to determine the cytotoxicity of this active drug. For this aim, the human PBLs were treated with 25, 50, and 100 µg/ml venlafaxine for 24 h and 48 h. The results of this study showed that venlafaxine significantly induced the formation of structural CA and MN for all concentrations (25, 50, and 100 µg/ml) and treatment periods (24 h and 48 h) when compared with the negative and the solvent control (except 25 µg/ml at 48 h for MN). In addition, the increases in the percentage of structural CA and MN were concentration-dependent for both treatment times. With regard to cell cycle kinetics, venlafaxine significantly decreased the MI at all concentrations, and also CBPI at the higher concentrations for both treatment times as compared to the control groups. The present results indicate for the first time that venlafaxine had significant clastogenic and cytotoxic effects at the tested concentrations (25, 50, and 100 µg/ml) in the human PBLs, in vitro; therefore, its excessive and careless use may pose a potential risk to human health.

Development of bioassay system for evaluation of materials for personal protective equipment (PPE) against toxic effects of ionizing radiations

Health effects caused by ionizing radiations raise considerable concern among general public and radiation workers. To estimate ability of personal protective equipment (PPE) materials that reduce toxic effects of ionizing radiations, we developed an experimental bioassay system using Chinese Hamster V79 cells. The system developed here distinguished the biological effectiveness of X-ray that was significantly affected by elements composed of shielding materials. Survival of the cells exposed to sub-lethal dose of X-ray was enhanced more than 2 times when the X-ray was filtrated by a lead plate. Also filtration of the X-ray with a tungsten plate enhanced the cell survival more than three times. These results suggested the colony assay system developed here was useful for examination of the biological effectiveness of X-ray and the ability of PPE materials reducing the toxic effects caused by ionizing radiations.

A Novel Strategy to Predict Carcinogenicity of Antiparasitics Based on a Combination of DNA Lesions and Bacterial Mutagenicity Tests

Genotoxicity and carcinogenicity testing of pharmaceuticals prior to commercialization is requested by regulatory agencies. The bacterial mutagenicity test was considered having the highest accuracy of carcinogenic prediction. However, some evidences suggest that it always results in false-positive responses when the bacterial mutagenicity test is used to predict carcinogenicity. Along with major changes made to the International Committee on Harmonization guidance on genotoxicity testing [S2 (R1)], the old data (especially the cytotgenetic data) may not meet current guidelines. This review provides a compendium of retrievable results of genotoxicity and animal carcinogenicity of 136 antiparasitics. Neither genotoxicity nor carcinogenicity data is available for 84 (61.8%), while 52 (38.2%) have been evaluated in at least one genotoxicity or carcinogenicity study, and only 20 (14.7%) in both genotoxicity and carcinogenicity studies. Among 33 antiparasitics with at least one old result in in vitro genotoxicity, 15 (45.5%) are in agreement with the current ICH S2 (R1) guidance for data acceptance. Compared with other genotoxicity assays, the DNA lesions can significantly increase the accuracy of prediction of carcinogenicity. Together, a combination of DNA lesion and bacterial tests is a more accurate way to predict carcinogenicity.

Genotoxic effects of the carbamate insecticide Pirimor-50® in Vicia faba root tip meristems and human lymphocyte culture after direct application and treatment with its metabolic extracts

The aim of the study was to evaluate genotoxic effects of Pirimor-50®, a pirimicarb-based formulation (50 % active ingredient), in human lymphocyte cultures and Vicia faba root meristems. Furthermore, the objective was to examine a combined influence of insecticide treatment with mammalian microsomal S9 and vegetal S10 metabolic fractions or S10 mix metabolic transformation extracts (after Vicia faba primary roots treatment with Pirimor-50®). We used sister chromatid exchange assay-SCE and measured cell cycle progression and proliferation (proportion of M1-M3 metaphases and replication index ratio-RI). Two processes were used for plant promutagen activation: in vivo activation-Pirimor-50® was applied for 4 h to the plant and then S10 mix was added to lymphocytes; and, in vitro activation-lymphocytes were treated with Pirimor-50® and S10 or S9 for 2 h. Direct treatment induced significantly higher SCE frequencies in meristems at 0.01 mg mL-1. In lymphocytes, significantly higher SCE was at 1 mg mL-1 with decrease in RI and M1-M3 metaphase proportions at 0.5 mg mL-1 and cell division stop at 2.5 mg mL1. S10 mix lymphocyte treatment showed significantly elevated SCE values at 2-2.5 mg mL-1, with cell death at 3 mg mL-1. Lymphocyte treatment with Pirimor-50® together with S9 or S10 showed slightly elevated SCE frequency but had a significant influence on RI decrease, with lowest values in S9 treatment. Since no data are available on the genotoxicity of Pirimor-50®, this study is one of the first to evaluate and compare its direct effect in two bioassays, animal and vegetal, and also the effect of plant and animal metabolism on its genotoxic potential.

Investigation of toxicity and mutagenicity of cold atmospheric argon plasma

Cold atmospheric argon plasma is recognized as a new contact free approach for the decrease of bacterial load on chronic wounds in patients. So far very limited data are available on its toxicity and mutagenicity on eukaryotic cells. Thus, the toxic/mutagenic potential of cold atmospheric argon plasma using the MicroPlaSter β^® , which has been used efficiently in humans treating chronic and acute wounds, was investigated using the XTT assay in keratinocytes and fibroblasts and the HGPRT (hypoxanthine guanine phosphoribosyl transferase) assay with V79 Chinese hamster cells. The tested clinical parameter of a 2 min cold atmospheric argon plasma treatment revealed no relevant toxicity on keratinocytes (viability: 76% ± 0.17%) and on fibroblasts (viability: 81.8 ± 0.10) after 72 hr as compared to the untreated controls. No mutagenicity was detected in the HGPRT assay with V79 cells even after repetitive CAP treatments of 2-10 min every 24 hr for up to 5 days. In contrast, UV-C irradiation of V79 cells, used as a positive control in the HGPRT test, led to DNA damage and mutagenic effects. Our findings indicate that cold atmospheric plasma using the MicroPlaSter β^® shows negligible effects on keratinocytes and fibroblasts but no mutagenic potential in the HGPRT assay, indicating a new contact free safe technology. Environ. Mol. Mutagen. 58:172-177, 2017. © 2017 Wiley Periodicals, Inc.

The Induction of Gene Mutations and Micronuclei by Oxiranes and Siloranes in Mammalian Cells in vitro

Oxiranes and siloranes are candidate molecules for the development of composite materials with low shrinkage. Since some of these molecules are highly reactive, they could lead to adverse biological effects from underlying genetic mechanisms. Therefore, we analyzed the formation of micronuclei (chromosomal aberrations) and the induction of gene mutations (HPRT assay) in mammalian cells. The numbers of micronuclei induced by the oxirane di(cyclohexene-epoxidemethyl)ether (Eth-Ep) at low concentrations (10 μM) were about five-fold higher than controls. The related compound epoxy cyclohexyl methyl-epoxy cyclo-hexane carboxylate (Est-Ep) was less effective. The activity of diglycidylether of bisphenol A (BADGE) was even lower but similar to the most reactive silorane, di-3,4-epoxy cyclohexylmethyl-dimethyl-silane (DiMe-Sil). No induction of micronuclei was detected in the presence of a rat liver homogenate (S9). Est-Ep and Eth-Ep also induced gene mutations. Our analyses indicated low mutagenic potentials of siloranes; however, some oxiranes induced strong effects at two genetic endpoints.

Origanum majorana Essential Oil Lacks Mutagenic Activity in the Salmonella/Microsome and Micronucleus Assays

The present study aimed to investigate the in vitro mutagenic activity of Origanum majorana essential oil. The most abundant compounds identified by GC-MS were γ-terpinene (25.73%), α-terpinene (17.35%), terpinen-4-ol (17.24%), and sabinene (10.8%). Mutagenicity was evaluated by the Salmonella/microsome test using the preincubation procedure on TA98, TA97a, TA100, TA102, and TA1535 Salmonella typhimurium strains, in the absence or in the presence of metabolic activation. Cytotoxicity was detected at concentrations higher than 0.04 μL/plate in the absence of S9 mix and higher than 0.08 μL/plate in the presence of S9 mix and no gene mutation increase was observed. For the in vitro mammalian cell micronucleus test, V79 Chinese hamster lung fibroblasts were used. Cytotoxicity was only observed at concentrations higher than or equal to 0.05 μg/mL. Moreover, when tested in noncytotoxic concentrations, O. majorana essential oil was not able to induce chromosome mutation. The results from this study therefore suggest that O. majorana essential oil is not mutagenic at the concentrations tested in the Salmonella/microsome and micronucleus assays.

Quinolone Amides as Antitrypanosomal Lead Compounds with In Vivo Activity

Human African trypanosomiasis (HAT) is a major tropical disease for which few drugs for treatment are available, driving the need for novel active compounds. Recently, morpholino-substituted benzyl amides of the fluoroquinolone-type antibiotics were identified to be compounds highly active against Trypanosoma brucei brucei Since the lead compound GHQ168 was challenged by poor water solubility in previous trials, the aim of this study was to introduce structural variations to GHQ168 as well as to formulate GHQ168 with the ultimate goal to increase its aqueous solubility while maintaining its in vitro antitrypanosomal activity. The pharmacokinetic parameters of spray-dried GHQ168 and the newly synthesized compounds GHQ242 and GHQ243 in mice were characterized by elimination half-lives ranging from 1.5 to 3.5 h after intraperitoneal administration (4 mice/compound), moderate to strong human serum albumin binding for GHQ168 (80%) and GHQ243 (45%), and very high human serum albumin binding (>99%) for GHQ242. For the lead compound, GHQ168, the apparent clearance was 112 ml/h and the apparent volume of distribution was 14 liters/kg of body weight (BW). Mice infected with T. b. rhodesiense (STIB900) were treated in a stringent study scheme (2 daily applications between days 3 and 6 postinfection). Exposure to spray-dried GHQ168 in contrast to the control treatment resulted in mean survival durations of 17 versus 9 days, respectively, a difference that was statistically significant. Results that were statistically insignificantly different were obtained between the control and the GHQ242 and GHQ243 treatments. Therefore, GHQ168 was further profiled in an early-treatment scheme (2 daily applications at days 1 to 4 postinfection), and the results were compared with those obtained with a control treatment. The result was statistically significant mean survival times exceeding 32 days (end of the observation period) versus 7 days for the GHQ168 and control treatments, respectively. Spray-dried GHQ168 demonstrated exciting antitrypanosomal efficacy.

Measurements of Deposition, Lung Surface Area and Lung Fluid for Simulation of Inhaled Compounds

Modern strategies in drug development employ in silico techniques in the design of compounds as well as estimations of pharmacokinetics, pharmacodynamics and toxicity parameters. The quality of the results depends on software algorithm, data library and input data. Compared to simulations of absorption, distribution, metabolism, excretion, and toxicity of oral drug compounds, relatively few studies report predictions of pharmacokinetics and pharmacodynamics of inhaled substances. For calculation of the drug concentration at the absorption site, the pulmonary epithelium, physiological parameters such as lung surface and distribution volume (lung lining fluid) have to be known. These parameters can only be determined by invasive techniques and by postmortem studies. Very different values have been reported in the literature. This review addresses the state of software programs for simulation of orally inhaled substances and focuses on problems in the determination of particle deposition, lung surface and of lung lining fluid. The different surface areas for deposition and for drug absorption are difficult to include directly into the simulations. As drug levels are influenced by multiple parameters the role of single parameters in the simulations cannot be identified easily.

Manool, a Salvia officinalis diterpene, induces selective cytotoxicity in cancer cells

Manool, a diterpene isolated from Salvia officinalis, was evaluated by the XTT colorimetric assay for cytotoxicity and selectivity against different cancer cell lines: B16F10 (murine melanoma), MCF-7 (human breast adenocarcinoma), HeLa (human cervical adenocarcinoma), HepG2 (human hepatocellular carcinoma), and MO59J, U343 and U251 (human glioblastoma). A normal cell line (V79, Chinese hamster lung fibroblasts) was used to compare the selectivity of the test substance. Manool exhibited higher cytotoxic activity against HeLa (IC50 = 6.7 ± 1.1 µg/mL) and U343 (IC50 = 6.7 ± 1.2 µg/mL) cells. In addition, in the used experimental protocols, the treatment with manool was significantly more cytotoxic for different tumor cell lines than for the normal cell line V79 (IC50 = 49.3 ± 3.3 µg/mL), and showed high selectivity. These results suggest that manool may be used to treat cancer without affecting normal cells.

Antischistosomal and Cytotoxic Effects of the Essential Oil of Tetradenia riparia (Lamiaceae)

This paper reports on the antischistosomal and cytotoxic effects of the essential oil obtained from Tetradenia riparia leaves (TR-EO). At concentrations of 50 and 100 μg/mL, TR-EO killed all the worms after 120 and 24 h of incubation, respectively. At a concentration equal to or higher than 50 μg/mL, this oil also separated the coupled pairs and decreased the adult worm motor activity after incubation periods higher than 72 h. In addition, at 120 h of incubation, TR-EO slightly decreased the number of eggs produced by Schistosoma mansoni adult worms and significantly reduced the percentage of developed eggs, in a dose-dependent manner. XTT-colorimetric assays showed that the tested TR-EO concentrations were not considerably cytotoxic to V79 cells (IC50 = 253.5 μg/mL). The effects of TR-EO on egg development were noteworthy; therefore, this essential oil deserves further investigation to identify the chemical constituents that elicit activity against S. mansoni.

Evaluation of repeated dose micronucleus assays of the liver using N-nitrosopyrrolidine: a report of the collaborative study by CSGMT/JEMS.MMS

The repeated dose liver micronucleus (RDLMN) assay has the potential to detect liver carcinogens, and can be integrated into a general toxicological study. To assess the performance of the assay, N-nitrosopyrrolidine (NPYR), a genotoxic hepatocarcinogen, was tested in 14- or 28-day RDLMN assays. NPYR was orally administered to rats at a daily dose of 25, 50 or 100 mg/kg. One day after the last administration, a portion of the liver was removed and hepatocyte micronucleus (MN) specimens were prepared by the new method recently established by Narumi et al. In addition, a bone marrow MN assay and a histopathological examination of the liver were conducted. The detection of Phospho-Histone H3 was performed by immunohistochemistry to evaluate the proliferation rate of hepatocytes. The results showed significant increase in the number of micronucleated hepatocytes and Phospho-Histone H3-positive cells from the lowest dose in both 14- and 28-day RDLMN assays. On the other hand, the bone marrow MN assay yielded a negative result, which was in accordance with the existing report of the bone marrow MN assay using mice. Upon histopathological examination, inflammatory lesions and hypertrophy were noted, which may explain the increase in the hepatocyte proliferation and the enhancement of MN induction by NPYR. Our findings indicate that the RDLMN assay could be a useful tool for comprehensive risk assessment of carcinogenicity by providing information on both genotoxicity and histopathology when integrated into a general repeat dosing toxicity assay.

Mutagenic potential of the isoflavone irilone in cultured V79 cells

After consumption of red clover-based dietary supplements, plasma concentrations of the isoflavone irilone (IRI) equal that of the well-investigated daidzein. Since some isoflavones are genotoxic, the potential of IRI to induce mutations was investigated. Gene mutations were determined by hypoxanthine-guanine phosphoribosyltransferase (HPRT) assay and sequencing of mutant cDNA, chromosome and genome mutations by micronucleus assay complemented by immunochemical staining of centromere proteins and microtubules in cultured V79 cells. Cell proliferation was monitored by electronic cell counting, flow cytometry and fluorescence microscopy. IRI did not affect the mutant frequency in the Hprt locus but altered the mutation spectrum by increasing the proportion of deletions and decreasing that of base pair substitutions. Induction of chromosome mutations was supported by a slight but significant increase in the number of micronucleated cells containing chromosomal fragments despite activation of three cell cycle checkpoints possibly interfering with micronuclei formation. Moreover, IRI exhibited a strong aneugenic potential characterized by disrupted mitotic spindles, mitotic arrest, and asymmetrical cell divisions leading to chromosome loss, nuclear fragmentation as well as mitotic catastrophe. Thus, IRI might be another isoflavone to be taken into account in safety assessment of dietary supplements.

Genotoxic and biochemical changes in Baccharis trimera induced by coal contamination

The processing and combustion of coal in thermal power plants release anthropogenic chemicals into the environment. Baccharis trimera is a common plant used in folk medicine that grows readily in soils degraded by coal mining activities. This shrub bioaccumulates metals released into the environment, and thus its consumption may be harmful to health. The purpose of this study was to investigate the phytochemical profile, antioxidant capacity (DPPH), genotoxic (comet assay) and mutagenic potential (CBMN-cyt) in V79 cells of B. trimera aqueous extracts in the coal-mining region of Candiota (Bt-AEC), and in Bagé, a city that does not experience the effects of exposure to coal (Bt-AEB, a reference site). In the comet assay, only Bt-AEC was genotoxic at the highest doses (0.8mg/mL and 1.6mg/mL), compared to the control. For extracts from both areas, mutagenic effects were observed at higher concentrations compared to the control. The cell damage parameters were significantly high in both extracts; however, more striking values were observed for Bt-AEC, up to the dose of 0.8mg/mL. In chemical analysis, no variation was observed in the contents of flavonoids and phenolic compounds, neither the antioxidant activity, which may suggest that DNA damage observed in V79 cells was induced by the presence of coal contaminants absorbed by the plant.

Carbamates: A study on genotoxic, cytotoxic, and apoptotic effects induced in Chinese hamster ovary (CHO-K1) cells

In vitro effects of the carbamates pirimicarb and zineb and their formulations Aficida® (50% pirimicarb) and Azzurro® (70% zineb), respectively, were evaluated in Chinese hamster ovary (CHO-K1) cells. Whereas the cytokinesis-blocked micronucleus cytome assay was employed to test for genotoxicity, MTT, neutral red (NR), and apoptosis evaluation were used as tests for estimating cell viability and succinic dehydrogenase activity, respectively. Concentrations tested were 10-300 μg/ml for pirimicarb and Aficida®, and 1-50 μg/ml for zineb and Azzurro®. All compounds were able to increase the frequency of micronuclei. A marked reduction in the nuclear division index was observed after treatment with 5 μg/ml of zineb and Azzurro® and 10 μg/ml of Azzurro®. Alterations in the cellular morphology not allowing the recognition of binucleated cells exposed to 300 μg/ml pirimicarb and Aficida® as well as 10-50 μg/ml zineb and Azzurro®. All four compounds induced inhibition of both cell viability and succinic dehydrogenase activity and trigger apoptosis in CHO-K1 cells, at least when exposed for 24 h. The data herein demonstrate the genotoxic and cytotoxic effects exerted by these carbamates and reveal the potential risk factor of these pesticides, still extensively used worldwide, for both human health and the environment.

Carboxylated short single-walled carbon nanotubes but not plain and multi-walled short carbon nanotubes show in vitro genotoxicity

Long carbon nanotubes (CNTs) resemble asbestos fibers due to their high length to diameter ratio and they thus have genotoxic effects. Another parameter that might explain their genotoxic effects is contamination with heavy metal ions. On the other hand, short (1-2 µm) CNTs do not resemble asbestos fibers, and, once purified from contaminations, they might be suitable for medical applications. To identify the role of fiber thickness and surface properties on genotoxicity, well-characterized short pristine and carboxylated single-walled (SCNTs) and multi-walled (MCNTs) CNTs of different diameters were studied for cytotoxicity, the cell's response to oxidative stress (immunoreactivity against hemoxygenase 1 and glutathione levels), and in a hypoxanthine guanine phosphoribosyltransferase (HPRT) assay using V79 chinese hamster fibroblasts and human lung adenocarcinoma A549 cells. DNA repair was demonstrated by measuring immunoreactivity against activated histone H2AX protein. The number of micronuclei as well as the number of multinucleated cells was determined. CNTs acted more cytotoxic in V79 than in A549 cells. Plain and carboxylated thin (<8 nm) SCNTs and MCNTs showed greater cytotoxic potential and carboxylated CNTs showed indication for generating oxidative stress. Multi-walled CNTs did not cause HPRT mutation, micronucleus formation, DNA damage, interference with cell division, and oxidative stress. Carboxylated, but not plain, SCNTs showed indication for in vitro DNA damage according to increase of H2AX-immunoreactive cells and HPRT mutation. Although short CNTs presented a low in vitro genotoxicity, functionalization of short SCNTs can render these particles genotoxic.

Effect of low-level laser therapy on the gene expression of collagen and vascular endothelial growth factor in a culture of fibroblast cells in mice

Low-level laser therapy treatment (LLLT) is widely used in rehabilitation clinics with the aim of accelerating the process of tissue repair; however, the molecular bases of the effect of LLLT have not been fully established. The aim of the present study was to evaluate the influence of the exposure of different doses of LLLT on the expression of collagen genes type I alpha 1 (COL1α1) and vascular endothelial growth factor (VEGF) in the fibroblast cells of mice (L929) cultivated in vitro. Fibroblast cells were irradiated with a Gallium-Arsenide laser (904 nm) every 24 h for 2 consecutive days, stored in an oven at 37 °C, with 5% CO2 and divided into 3 groups: G1-control group, G2-irradiated at 2 J/cm(2), and G3-irradiated at 3 J/cm(2). After irradiation, the total RNA was extracted and used in the complementary DNA (cDNA) synthesis. The gene expression was analyzed by real-time polymerase chain reaction. The cells irradiated in G2 exhibited a statistically significant growth of 1.78 in the expression of the messenger RNA (mRNA) of the COL1α1 gene (p = 0.036) in comparison with G1 and G3. As for the VEGF gene, an increase in expression was observed in the two irradiated groups in comparison with the control group. There was an increase in expression in G2 of 2.054 and G3 of 2.562 (p = 0.037) for this gene. LLLT (904 nm) had an influence on the expression of the genes COL1α1 (2 J/cm(2)) and VEGF (2 e 3 J/cm(2)) in a culture of the fibroblast cells of mice.

Genotoxicity evaluation of Mequindox in different short-term tests

Quinoxaline-1,4-dioxides (QdNOs) are the potent heterocyclic N-oxides with interesting biological properties such as antibacterial, anticandida, antitubercular, anticancer and antiprotozoal activities. Here, we tested and compared the mequindox (MEQ) for mutagenic abilities in a battery of different short term tests according to OECD guidelines. When compared with the controls, a strong mutagenicity of MEQ and carbadox (CBX) was observed with an approximate concentration-effect relationship in Salmonella reverse mutation test, chromosome aberration test, unscheduled DNA synthesis assay and HGPRT gene mutation test, in the absence and presence of S(9)-mix. In in vivo micronucleus test, CBX produced significant increase in the proportion of micronucleus formation than MEQ in mice bone marrow cells. From these results, we can conclude that MEQ had a strong genotoxic potential to mammalian cells in vitro as well as in vivo and its mutagenicity is slightly higher than CBX. Our results, for the 1st time, discuss the genotoxic potential of MEQ. These results not only confirm the earlier findings about CBX but also extend the knowledge and awareness about the genotoxic risk of QdNO derivatives.

Cytotoxic and mutagenic effects of anti- and syn-benzo[a]pyrene diol epoxide in human lymphocytes

Cytotoxicity and mutagenicity were measured in human lymphocytes after treatment in vitro with anti- or syn-benzo[a]pyrene diolepoxide, two diastereoisomer metabolites of benzo[a]pyrene. These compounds were incubated with resting and cycling lymphocytes to determine the inhibition of cell proliferation induced by phytohemoagglutinin and interleukin2 at different times after treatment. Anti-benzo[a]pyrene diolepoxide was more cytotoxic than the syn-adduct under all conditions, and its effect on cell growth was more marked in cycling lymphocytes. In contrast, neither of the compounds induced alteration of the ATP intracellular pool. Cytotoxic effects of anti- and syn-benzo[a]pyrene diolepoxide were also assessed by determining the cloning efficiency. Both compounds affected the cloning efficiency in human lymphocytes and the effect of anti-benzo[a]pyrene was particularly marked. Mutagenic potency of anti- and syn-benzo[a]pyrene diolepoxide at the hgprt locus was measured both in the V79 cell line and in human lymphocytes by selection of mutant cells in medium containing 6-thioguanine. Both compounds increased the mutant frequency in comparison with the control and anti-benzo[a]pyrene diolepoxide was more active than the syn-metabolite.

A critique of methods to measure cytotoxicity in mammalian cell genotoxicity assays

Various methods have been used to estimate cytotoxicity in mammalian cell genotoxicity assays since their introduction more than four decades ago, and although there is no agreement on whether any single method is optimal, there is now a better appreciation of their limitations. Methods based on aspects of cellular function are inevitably inaccurate unless some estimate of cell number is included, and those using some measure of cell proliferation give different results depending on the mathematical model used. Although it would be desirable, it is not possible to provide a universal measure of cytotoxicity because the phenomenon is so complex. There is some flexibility in the limits of cytotoxicity proposed in regulatory guidelines, and it can be argued these could be even less precise. Also, to make valid comparisons of the performance of different test systems, novel or established, it would seem essential to use similar measures of cytotoxicity.

The effects of sodium diethyldithiocarbamate in fibroblasts V79 cells in relation to cytotoxicity, antioxidative enzymes, glutathione, and apoptosis

Sodium diethyldithiocarbamate (DETC) is the main metabolite of disulfiram. Recently, we reported that mechanism of disulfiram cytotoxicity in V79 cells might be partially connected with thiol redox-state imbalance. Here, we examined the effect of DETC on the level of intracellular glutathione (GSH), protein oxidation (measured as PC—protein carbonyl content), lipid peroxidation (measured as TBARS—thiobarbituric acid reactive substances), antioxidant enzymatic defense, as well as on apoptosis. We used V79 Chinese hamster fibroblasts cells with and without modulated glutathione (GSH) level by N-acetyl-l-cysteine (NAC). We showed that treatment with DETC at concentrations that cause a moderate increase in thiol-state imbalance but not cell death stimulates oxidative stress measured as increased level of PC and TBARS, adaptive response of GSH-related enzymes and apoptosis. Our results show that cellular effects of DETC are partially attributable to the initial redox cellular state, since the increase of GSH level by NAC pre-treatment prevented the observed changes.

Increased risk of lung cancer associated with a functionally impaired polymorphic variant of the human DNA glycosylase NEIL2

Human NEIL2, one of five oxidized base-specific DNA glycosylases, is unique in preferentially repairing oxidative damage in transcribed genes. Here we show that depletion of NEIL2 causes a 6-7-fold increase in spontaneous mutation frequency in the HPRT gene of the V79 Chinese hamster lung cell line. This prompted us to screen for NEIL2 variants in lung cancer patients' genomic DNA. We identified several polymorphic variants, among which R103Q and R257L were frequently observed in lung cancer patients. We then characterized these variants biochemically, and observed a modest decrease in DNA glycosylase activity relative to the wild type (WT) only with the R257L mutant protein. However, in reconstituted repair assays containing WT NEIL2 or its R257L and R103Q variants together with other DNA base excision repair (BER) proteins (PNKP, Polβ, Lig IIIα and XRCC1) or using NEIL2-FLAG immunocomplexes, an ~5-fold decrease in repair was observed with the R257L variant compared to WT or R103Q NEIL2, apparently due to the R257L mutant's lower affinity for other repair proteins, particularly Polβ. Notably, increased endogenous DNA damage was observed in NEIL2 variant (R257L)-expressing cells relative to WT cells. Taken together, our results suggest that the decreased DNA repair capacity of the R257L variant can induce mutations that lead to lung cancer development.

Preclinical genotoxicology of nor-β-lapachone in human cultured lymphocytes and Chinese hamster lung fibroblasts

Nor-β-lapachone has shown several biological properties. Regarding cytotoxic activity against cancer cell lines, it has been recognized as an important prototype. However, quinonoid drugs present a major challenge because of their toxicity. In this study, we evaluated the cytotoxicity and genetic toxicity of nor-β-lapachone in human lymphocytes and HL-60 leukemia cells and murine V79 fibroblasts, to shed some light on its selectivity toward cancer cells. As measured by MTT test, exposure of V79 cells to nor-β-lapachone resulted in a weak cytotoxicity (IC(50) = 13.41 μM), and at a concentration up to 21.9 μM, no cytotoxic effect was observed in lymphocytes, while in HL-60 cells, nor-β-lapachone elicited significantly greater cytotoxicity (IC(50) = 1.89 μM). Cultures coexposed to GSH-OEt showed an increased viability, which may indicate a neutralization of ROS generated by quinonoid treatment. In fact, only the highest concentrations of nor-β-lapachone (10 or 20 μM) caused an increase in oxidative stress in nontumor levels cells as measured by TBARS and nitrite/nitrate detection. This was accompanied by an alteration in intracellular thiol content. However, NAC pre-exposure restored the redox equilibrium of the cells and the concentration of thiol levels to control values. Nor-β-lapachone at 2.5 and 5 μM failed to induce DNA damage in nontumor cells, but at the highest concentrations tested, it induced single and double DNA strand breaks and increased the frequency of chromosomal aberrations. Interestingly, these damages were prevented by NAC pretreatment or exacerbated by prior exposure to the GSH-depleting agent 1-bromoheptane. In electrochemical experiments, nor-β-lapachone at the same concentrations as those used in genotoxic tests did not damage DNA directly, but at the highest concentration tested (200 μM), it caused a very weak DNA interaction. Corroborating electrochemical data, oxidative modifications of DNA bases were observed, as checked by DNA repair enzymes EndoIII and FPG, which reinforced the indirect actions caused by nor-β-lapachone through ROS generation and not via DNA intercalation. The DNA repair capacities were higher for nontumor cells than for leukemia cells, which may be related to the selective cytoxicity of nor-β-lapachone toward cancer cells. Our data suggest that ROS play an important role in nor-β-lapachone toxicity and that its DNA-damaging effect occurs only at concentrations several times higher than that needed for its antiproliferative effect on cancer cells.

A core in vitro genotoxicity battery comprising the Ames test plus the in vitro micronucleus test is sufficient to detect rodent carcinogens and in vivo genotoxins

In vitro genotoxicity testing needs to include tests in both bacterial and mammalian cells, and be able to detect gene mutations, chromosomal damage and aneuploidy. This may be achieved by a combination of the Ames test (detects gene mutations) and the in vitro micronucleus test (MNvit), since the latter detects both chromosomal aberrations and aneuploidy. In this paper we therefore present an analysis of an existing database of rodent carcinogens and a new database of in vivo genotoxins in terms of the in vitro genotoxicity tests needed to detect their in vivo activity. Published in vitro data from at least one test system (most were from the Ames test) were available for 557 carcinogens and 405 in vivo genotoxins. Because there are fewer publications on the MNvit than for other mammalian cell tests, and because the concordance between the MNvit and the in vitro chromosomal aberration (CAvit) test is so high for clastogenic activity, positive results in the CAvit test were taken as indicative of a positive result in the MNvit where there were no, or only inadequate data for the latter. Also, because Hprt and Tk loci both detect gene-mutation activity, a positive Hprt test was taken as indicative of a mouse-lymphoma Tk assay (MLA)-positive, where there were no data for the latter. Almost all of the 962 rodent carcinogens and in vivo genotoxins were detected by an in vitro battery comprising Ames+MNvit. An additional 11 carcinogens and six in vivo genotoxins would apparently be detected by the MLA, but many of these had not been tested in the MNvit or CAvit tests. Only four chemicals emerge as potentially being more readily detected in MLA than in Ames+MNvit--benzyl acetate, toluene, morphine and thiabendazole--and none of these are convincing cases to argue for the inclusion of the MLA in addition to Ames+MNvit. Thus, there is no convincing evidence that any genotoxic rodent carcinogens or in vivo genotoxins would remain undetected in an in vitro test battery consisting of Ames+MNvit.

Assessment of the cytotoxicity and genotoxicity of haloacetic acids using microplate-based cytotoxicity test and CHO/HGPRT gene mutation assay

Haloacetic acids (HAAs) are the second most prevalent class of disinfection byproducts found in drinking water. The implications of HAAs presence in drinking water are a public health concern due to their potential mutagenic and carcinogenic effects. In the present study, we examined the cytotoxic and genotoxic effects of six common HAAs using a microplate-based cytotoxicity test and a hypoxanthine-guanine phosphoribosyltransferase (HGPRT) gene mutation assay in Chinese hamster ovary K1 (CHO-K1) cells. We found that their chronic cytotoxicities (72h exposure) to CHO-K1 cells varied, and we ranked their levels of toxicity in the following descending order: iodoacetic acid (IA)>bromoacetic acid (BA)>dibromoacetic acid (DBA)>chloroacetic acid (CA)>dichloroacetic acid (DCA)>trichloroacetic acid (TCA). The toxicity of IA is 1040-fold of that of TCA. All HAAs except TCA were shown to be mutagenic to CHO-K1 cells in the HGPRT gene mutation assay. The mutagenic potency was compared and ranked as follows: IA>DBA>BA>CA>DCA>TCA. There was a statistically significant correlation between cytotoxicity and mutagenicity of the HAAs in CHO-K1 cells. The microplate-based cytotoxicity assay and HGPRT gene mutation assay were suitable methods to monitor the cytotoxicity and genotoxicity of HAAs, particularly for comparing the toxic intensities quantitatively.

Protective effect of N-acetyl-L-cysteine against disulfiram-induced oxidative stress and apoptosis in V79 cells

This work investigated the effect of N-acetyl-L-cysteine (NAC) on disulfiram (DSF) induced oxidative stress in Chinese hamster fibroblast cells (V79). An increase in oxidative stress induced by DSF was observed up to a 200 μM concentration. It was evidenced by a statistically significant increase of both GSH(t) and GSSG levels, as well as elevated protein carbonyl (PC) content. There was no increase in lipid peroxidation (measured as TBARS). DSF increased CAT activity, but did not change SOD1 and SOD2 activities. Analysis of GSH related enzymes showed that DSF significantly increased GR activity, did not change Se-dependent GPx, but statistically significantly decreased non-Se-dependent GPx activity. DSF showed also pro-apoptotic activity. NAC alone did not produce any significant changes, besides an increase of GSH(t) level, in any of the variables measured. However, pre-treatment of cells with NAC ameliorated DSF-induced changes. NAC pre-treatment restored the viability of DSF-treated cells evaluated by Trypan blue exclusion assay and MTT test, GSSG level, and protein carbonyl content to the control values as well as it reduced pro-apoptotic activity of DSF. The increase of CAT and GR activity was not reversed. Activity of both GPx was significantly increased compared to their values after DSF treatment. In conclusion, oxidative properties are at least partially attributable to the cellular effects of disulfiram and mechanisms induced by NAC pre-treatment may lower or even abolish the observed effects. These observations illustrate the importance of the initial cellular redox state in terms of cell response to disulfiram exposure.

Protective effect of rosmarinic acid on V79 cells evaluated by the micronucleus and comet assays

Rosmarinic acid (RA) is a naturally occurring phenolic compound, which contributes to the beneficial and health-promoting effects of herbs, spices and medicinal plants. RA has shown several biological activities, such as hepatoprotective, anti-inflammatory, antiangiogenic, antitumor, antidepressant, antineurodegenerative, HIV-1 inhibitory and antioxidant effects. The aim of this study was to investigate the ability of RA to prevent chemically induced chromosome breakage or loss and primary DNA damage using the micronucleus and comet assays with V79 cells, respectively. The chemotherapeutic agent doxorubicin (DXR; 0.5 microg ml(-1)) was used as the DNA-damaging agent. The cultures were treated with different concentrations of RA (0.28, 0.56 and 1.12 mm) alone or in combination with DXR. The results showed that RA exerted no genotoxic effect, but significantly reduced the frequency of micronuclei and the extent of DNA damage induced by DXR at the three concentrations tested. The antioxidant activity of RA might be involved in the reduction of DXR-induced DNA damage observed in the present study.