Chinese Hamster Lung Fibroblasts Research Articles

BRCA2 protects mammalian cells from heat shock

Purpose: Heat shock induces DNA double-strand breaks (DSBs) in mammalian cells. Mammalian cells are capable of repairing DSBs by utilising the homologous recombination (HR) pathway. Breast cancer susceptibility gene 2 (BRCA2) is known to regulate the HR pathway. Here, we investigate the role of BRCA2 in repairing DNA damage induced by heat shock.Materials and methods: Chinese hamster lung fibroblast cell lines and human tongue squamous cell carcinoma SAS cells were used. RAD51 foci formation assay was used as an HR indicator. Heat sensitivity was analysed with colony forming assays. Phosphorylated histone H2AX (γH2AX) intensity, which correlates with the number of DSBs, was analysed with flow cytometry.Results: RAD51 foci appeared with heat shock, and the number of cells with RAD51 foci was maximal at about 4 h after heat shock. Heat-induced RAD51 foci co-localised with γH2AX foci. BRCA2-deficient cells were sensitive to heat when compared to their parental wild-type cells. Heat-induced γH2AX was higher in BRCA2-deficient cells compared to parental cells. In SAS cells, cells transfected with BRCA2-siRNA were more sensitive to heat than cells transfected with negative control siRNA. Apoptotic bodies increased in number more rapidly in BRCA2-siRNA transfected cells than in cells transfected with negative control siRNA when cells were observed at 48 h after a heat treatment. In addition, cells deficient in BRCA2 were incapable of activating heat-induced G2/M arrest.Conclusion: BRCA2 has a protecting role against heat-induced cell death. BRCA2 might be a potential molecular target for hyperthermic cancer therapy.

In vitro genotoxicity of airborne Ni-NP in air-liquid interface.

Studies using advanced toxicological methods enabling in vitro conditions that are more realistic are currently needed for understanding the risks of pulmonary exposure to airborne nanoparticles. Owing to the carcinogenicity of certain nickel compounds, the increased production of nickel nanoparticles (Ni‐NPs) raises occupational safety concerns. The aim of this study was to investigate the genotoxicity of airborne Ni‐NPs using a recently developed air–liquid interface exposure system. The wild‐type Chinese hamster lung fibroblast cell line (V79) was used and cytotoxicity, DNA damage and mutagenicity were studied by testing colony forming efficiency, alkaline DNA unwinding and HPRT mutation assays, respectively. Additionally, co‐exposure to a PARP‐1 inhibitor was performed to test possible involvement of base excision repair (BER) in repair of Ni‐induced DNA damage. The results showed that cell viability was reduced significantly (to 45% and 46%) after 48 hours Ni‐NP exposure at concentrations of 0.15 and 0.32 μg cm−2. DNA damage was significantly increased after Ni‐NP exposure in the presence of the BER inhibitor indicating that Ni‐NP‐induced DNA damages are subsequently repaired by BER. Furthermore, there was no increased HPRT mutation frequency following Ni‐NP exposure. In conclusion, this study shows that Ni‐NP treatment of lung fibroblasts in an air–liquid interface system that mimics real‐life exposure, results in increased DNA strand breaks and reduced cellular viability. These DNA lesions were repaired with BER in an error‐free manner without resulting in mutations. This study also underlines the importance of appropriate quantification of the actual exposure concentrations during air–liquid interface exposure studies.

Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Discovery of potent 2,4-difluoro-linker poly(ADP-ribose) polymerase 1 inhibitors with enhanced water solubility and in vivo anticancer efficacy.

Poly (ADP-ribose) polymerase 1 (PARP1) is overexpressed in a variety of cancers, especially in breast and ovarian cancers; tumor cells that are deficient in breast cancer gene 1/2 (BRCA1/2) are highly sensitive to PARP1 inhibition. In this study, we identified a series of 2,4-difluorophenyl-linker analogs (15-55) derived from olaparib as novel PARP1 inhibitors. Four potent analogs 17, 43, 47, and 50 (IC50=2.2-4.4 nmol/L) effectively inhibited the proliferation of Chinese hamster lung fibroblast V-C8 cells (IC50=3.2-37.6 nmol/L) in vitro, and showed specificity toward BRCA-deficient cells (SI=40-510). The corresponding hydrochloride salts 56 and 57 (based on 43 and 47) were highly water soluble in pH=1.0 buffered salt solutions (1628.2 μg/mL, 2652.5 μg/mL). In a BRCA1-mutated xenograft model, oral administration of compound 56 (30 mg·kg-1·d-1, for 21 d) exhibited more prominent tumor growth inhibition (96.6%) compared with the same dose of olaparib (56.3%); in a BRCA2-mutated xenograft model, oral administration of analog 43 (10 mg·kg-1·d-1, for 28 d) significantly inhibited tumor growth (69.0%) and had no negative effects on the body weights. Additionally, compound 56 exhibited good oral bioavailability (F=32.2%), similar to that of olaparib (F=45.4%). Furthermore, the free base 43 of the hydrochloride salt 56 exhibited minimal hERG inhibition activity (IC50=6.64 μmol/L). Collectively, these data demonstrate that compound 56 may be an excellent drug candidate for the treatment of cancer, particularly BRCA-deficient tumors.

Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Effect of Methotrexate and Omega-3 Combination on Cytogenetic Changes of Bone Marrow and Some Enzymatic Antioxidants: An Experimental Study

Cellular Response to Exponentially Increasing and Decreasing Dose Rates: Implications for Treatment Planning in Targeted Radionuclide Therapy.

The treatment of cancer using targeted radionuclide therapy is of interest to nuclear medicine and radiation oncology because of its potential for killing tumor cells while minimizing dose-limiting toxicities to normal tissue. The ionizing radiations emitted by radiopharmaceuticals deliver radiation absorbed doses over protracted periods of time with continuously varying dose rates. As targeted radionuclide therapy becomes a more prominent part of cancer therapy, accurate models for estimating the biologically effective dose (BED) or equieffective dose (EQD2α/β) will become essential for treatment planning. This study examines the radiobiological impact of the dose rate increase half-time during the uptake phase of the radiopharmaceutical. MDA-MB-231 human breast cancer cells and V79 Chinese hamster lung fibroblasts were irradiated chronically with 662 keV γ rays delivered with time-varying dose rates that are clinically relevant. The temporal dose-rate patterns were: 1. acute, 2. exponential decrease with a half-time of 64 h (Td = 64 h), 3. initial exponential increase to a maximum (half time Ti = 2, 8 or 24 h) followed by exponential decrease (Td = 64 h). Cell survival assays were conducted and surviving fractions were determined. There was a marked reduction in biological effect when Ti was increased. Cell survival data were tested against existing dose-response models to assess their capacity to predict response. Currently accepted models that are used in radiation oncology overestimated BED and EQD2α/β at low-dose rates and underestimated them at high-dose rates. This appears to be caused by an adaptive response arising as a consequence of the initial low-dose-rate phase of exposure. An adaptive response function was derived that yields more accurate BED and EQD2α/β values over the spectrum of dose rates and absorbed doses delivered. Our experimental data demonstrate a marked increase in cell survival when the dose-rate-increase half-time is increased, thereby suggesting an adaptive response arising as a consequence of this phase of exposure. We have modified conventional radiobiological models used in the clinic for brachytherapy and external beams of radiation to account for this phenomenon and facilitate their use for treatment planning in targeted radionuclide therapy.

Cellular Repair of DNA-DNA Cross-Links Induced by 1,2,3,4-Diepoxybutane.

Xenobiotic-induced interstrand DNA–DNA cross-links (ICL) interfere with transcription and replication and can be converted to toxic DNA double strand breaks. In this work, we investigated cellular responses to 1,4-bis-(guan-7-yl)-2,3-butanediol (bis-N7G-BD) cross-links induced by 1,2,3,4-diepoxybutane (DEB). High pressure liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI+-MS/MS) assays were used to quantify the formation and repair of bis-N7G-BD cross-links in wild-type Chinese hamster lung fibroblasts (V79) and the corresponding isogenic clones V-H1 and V-H4, deficient in the XPD and FANCA genes, respectively. Both V-H1 and V-H4 cells exhibited enhanced sensitivity to DEB-induced cell death and elevated bis-N7G-BD cross-links. However, relatively modest increases of bis-N7G-BD adduct levels in V-H4 clones did not correlate with their hypersensitivity to DEB. Further, bis-N7G-BD levels were not elevated in DEB-treated human clones with defects in the XPA or FANCD2 genes. Comet assays and γ-H2AX focus analyses conducted with hamster cells revealed that ICL removal was associated with chromosomal double strand break formation, and that these breaks persisted in V-H4 cells as compared to control cells. Our findings suggest that ICL repair in cells with defects in the Fanconi anemia repair pathway is associated with aberrant re-joining of repair-induced double strand breaks, potentially resulting in lethal chromosome rearrangements.

Safety evaluation of Chlorella sorokiniana strain CK-22 based on an in vitro cytotoxicity assay and a 13-week subchronic toxicity trial in rats

The genus Chlorella contains unicellular green algae that have been used as food supplements. The purpose of this work was to evaluate the safety of the Chlorella sorokiniana strain CK-22 using powdered preparation (CK-22P) both by in vitro and in vivo assays. These included an experiment for cytotoxicity using Chinese hamster lung fibroblasts (V79 cells) and a 13-week repeated-dose oral toxicity trial using Wistar rats. The cytotoxicity was evaluated by MTT assay of a hot water extract (Hw-Ex) and 80% ethanol extract (Et-Ex) of CK-22P, and no effect on cell viability was observed. The 50% viability inhibitory effect (IC50) value for Hw-Ex and Et-Ex were estimated as greater than 73 and 17 μg/ml, respectively. In the subchronic toxicity test, pelleted rodent diet containing 0%, 2.5%, 5% or 10% CK-22P was given to Wistar rats (ten animals/sex/groups) for 13 weeks. During the experimental period, no CK-22P treatment-induced differences in general condition, body weight gain, food and water consumption, ophthalmology, urinalysis, hematology, clinical chemistry, gross pathology, organ weights, histopathology, or animal death were observed. The no-observed-adverse-effect levels (NOAEL) were estimated to be 5.94 g/kg body-weight/day for males and 6.41 g/kg body-weight/day for females.

Antigenotoxic properties of Paliurus spina-christi Mill fruits and their active compounds

BackgroundPaliurus spina-christi Mill. (PS) fruits are widely used for different medical purposes in Turkey. Like in many medicinal herbs the studies concerning their activity, the activities of PS are also not well clarified. The aim of this study is to evaluate the antigenotoxicity of the compounds isolated and identified from the extracts of PS fruits.MethodsThe active compounds were separated, isolated, and determined by chromatographic methods and their structural elucidation was performed by Nuclear Magnetic Resonance (NMR) methods. The compounds were obtained from either ethyl acetate (EA) or n-butanol extracts. The cytotoxicities of the compounds using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the antigenotoxic activities of the compounds using the alkaline single cell gel electrophoresis techniques (comet assay) were evaluated in Chinese hamster lung fibroblast (V79) cell lines.ResultsThe isolated major compounds were identified as (+/−) catechins and gallocatechin from EA fraction and rutin from n-butanol fraction of PS fruits. Their chemical structures were identified by 1H-NMR, 13C-NMR, HMBC, and HMQC techniques. Half-maximal inhibitory concentration of catechins, gallocatechin, and rutin were found to be 734 μg/mL, 220 μg/mL, and 1004 μg/mL, respectively. The methanolic extract of PS (1-100 μg/mL) alone did not induce DNA single-strand breaks while catechins (1-100 μg/mL), gallocatechin (1-50 μg/mL), and rutin (1-50 μg/mL) significantly reduced H2O2-induced DNA damage.ConclusionIt has been suggested that PS fruits and their compounds catechins, gallocatechin and rutin may have beneficial effects in oxidative DNA damage. It seems that PS fruits may be used in protection of the disorders related to DNA damage.

Genotoxicity testing of sodium formononetin-3′-sulphonate (Sul-F) by assessing bacterial reverse mutation, chromosomal aberrations and micronucleus tests

As part of a safety evaluation, we evaluated the potential genotoxicity of sodium formononetin-3′-sulphonate (Sul-F) using bacterial reverse mutation assay, chromosomal aberrations detection, and mouse micronucleus test. In bacterial reverse mutation assay using five strains of Salmonella typhimurium (TA97, TA98, TA100, TA102 and TA1535), Sul-F (250, 500, 1000, 2000, 4000 μg/plate) did not increase the number of revertant colonies in any tester strain with or without S9 mix. In a chromosomal assay using Chinese hamster lung fibroblast (CHL) cells, there were no increases in either kind of aberration at any dose of Sul-F (400, 800, and 1600 μg/mL) treatment groups with or without S9 metabolic activation. In an in vivo bone marrow micronucleus test in ICR mice, Sul-F at up to 2000 mg/kg (intravenous injection) showed no significant increases in the incidence of micronucleated polychromatic erythrocytes, and the proportion of immature erythrocytes to total erythrocytes. The results demonstrated that Sul-F does not show mutagenic or genotoxic potential under these test conditions.

Impact of anatase titanium dioxide nanoparticles on mutagenic and genotoxic response in Chinese hamster lung fibroblast cells (V-79): The role of cellular uptake

The unique physico-chemical properties of nano crystalline anatase titanium dioxide nanoparticles (TiO2 NPs) render them with different biological and chemical activities. Hence, it is widely used in industrial and consumer applications. Previous studies have shown the genotoxicity of TiO2 NPs. However, there is a paucity of data regarding mutagenicity of these NPs. In the present study, the cellular uptake, sub-cellular localization, cytotoxicity and short term DNA interaction of TiO2 NPs (1–100 μgmL−1) of diameter ranging from 12 to 25 nm on mammalian lung fibroblast cells (V-79) has been studied. The flow cytometric analysis and electron micrographs of V-79 monolayer showed the internalization of TiO2 NPs in the cytoplasm with the confirmation of elemental composition through SEM/EDX analysis. TEM analysis also showed TiO2 NPs induced ultra-structural changes such as swollen mitochondria and nuclear membrane disruption in V-79 cells. TiO2 NPs generated free radicals, which induced indirect mutagenic and genotoxic responses. Apart from measuring the genotoxicity by Comet assay, the mutagenic potential of TiO2 NPs in V-79 cells was evaluated by mammalian HGPRT gene forward mutation assay, showing a 2.98- fold increase in 6TGR HGPRT mutant frequency (*p < 0.05, **p < 0.01, ***p < 0.001) by culture plate method, which is an early indicator of potential carcinogenicity. Hence, TiO2 NPs should be closely monitored and there should be a judicious use and disposal of NPs.

The Phosphorylation of the Na+‐H+ Exchanger Isoform I (NHE1) and Its Role in the Regulation of Cell Proliferation and Migration

The hallmarks of cancer are a collection of phenotypic changes that define cancer development and progression. Two of these hallmarks, sustaining proliferative growth and the activation of invasion and metastasis are regulated in part through the phosphorylation of the Na+‐H+ Exchanger Isoform 1 (NHE1) in response to changes in the tumor microenvironment. NHE1 is a transmembrane protein that exchanges one extracellular Na+ for one intracellular H+. The rate of transport activity can be altered through the phosphorylation of the cytoplasmic regulatory domain of the protein. Here we evaluate the role of NHE1 bring phosphorylated by five distinct protein kinases in seven defined locations. These kinases and the locations they phosphorylate are: 1) Pyk2 at both S602 and S605, 2) AKT at S648, 3) ROCK at T653, 4) RSK at S703, and 5) ERK at both S770 and S771. To evaluate the role of these phosphorylation sites in the regulation of cell proliferation and migration, we have created a series of Chinese hamster lung fibroblast cell lines expressing human NHE1. The PSN cells line expresses normal human NHE1 while the PSN‐7A cell line expresses human NHE1 with all seven of phosphorylation sites mutated to an alanine, thus removing that ability for NHE1 to be phosphorylated at these locations. Additionally, we have created PSN‐T653A which have the Rock phosphorylation site mutated to an alanine as well as a PSN‐7A‐T653 cell line which has the T653 site added back into the PSN‐7A mutants. We will present data on the production of PSN‐7A and PSN‐7A‐T653 cell lines and evaluate the impact of these mutations on cell proliferation and migrating in an effort to evaluate the role of Rock phosphorylation of NHE1 in these cellular functions.

Inhibition of Sodium Hydrogen Exchanger 1 Palmitoylation is Associated with Suppression of Cell Migration

The sodium hydrogen exchanger isoform 1 (NHE1) is involved in many cellular processes including regulation of intracellular pH, coordination of cell migration, control of cell volume, and anchoring protein interactions at the cell membrane. NHE1 is integral plasma membrane protein with 12 transmembrane spanning domains that exchanges an intracellular proton for an extracellular sodium ion. NHE1 is implicated in neoplastic transformation leading to tumorgenesis where the exchanger localizes to the leading edge of migrating cells initiating forward movement of cells indicating a potential role for NHE1 in cancer progression. NHE1 is regulated by many factors including multiple protein‐protein interactions and a number of phosphorylation events. Recent reports indicate that many proteins identified to play key roles in cancer are regulated by palmitoylation. S‐palmitoylation is a dynamic and reversible posttranslational modification, in which the protein undergoes cycles of palmitoylation and depalmitoylation, catalyzed by palmitoyl acyltransferases (PATs) and acyl protein thioesterases (APTs), respectively. Palmitoylation is known to regulate protein trafficking, membrane microlocalization and protein‐protein interactions. These findings prompted us to investigate the presence of this modification on NHE1 using acyl‐biotinyl exchange (ABE), an in vitro assay for post‐hoc detection of endogenous palmitoylation, which revealed that NHE1 is palmitoylated. To further evaluate the nature of NHE1 palmitoylation we treated Chinese hamster lung fibroblasts expressing human NHE1 (PSN) with the irreversible PAT inhibitor 2‐bromopalmitate (2BP). We found 2BP suppresses NHE1 palmitoylation in both a time and dose dependent manner. Additionally, PSN cell migration assessed using electric cell‐substrate impedance sensing was inhibited by 2BP in a manner consistent with the degree of inhibition of NHE1 palmitoylation. These results suggest that palmitoylation may regulate NHE1 function and its role in modulating cell migration.Support or Funding InformationNational Institutes of Health grants DA 031991 (JDF), DA13147 and 5P20‐104360 (RAV), P30‐GM103329 (UND), P20‐GM12345 (UND)

Dedicated high dose rate 192Ir brachytherapy radiation fields for in vitro cell exposures at variable source-target cell distances: killing of mammalian cells depends on temporal dose rate fluctuation

Afterloading brachytherapy is conducted by the stepwise movement of a radioactive source through surgically implanted applicator tubes where at predefined dwell positions calculated dwell times optimize spatial dose delivery with respect to a planned dose level. The temporal exposure pattern exhibits drastic fluctuations in dose rate at a given coordinate and within a single treatment session because of the discontinuous and repeated source movement into the target volume. This could potentially affect biological response. Therefore, mammalian cells were exposed as monolayers to a high dose rate 192Ir source by utilizing a dedicated irradiation device where the distance between a planar array of radioactive source positions and the plane of the cell monolayer could be varied from 2.5 mm to 40 mm, thus varying dose rate pattern for any chosen total dose.The Gammamed IIi afterloading system equipped with a nominal 370 GBq (10 Ci) 192-Ir source was used to irradiate V79 Chinese hamster lung fibroblasts from both confluent and from exponential growth phase with dose up to 12 Gy (at room temperature, total exposure not exceeding 1 h). For comparison, V79 cells were also exposed to 6 MV x-rays from a clinical linear accelerator (dose rate of 2.5 Gy min−1). As biological endpoint, cell survival was determined by standard colony forming assay. Dose measurements were conducted with a diamond detector (sensitive area 7.3 mm2), calibrated by means of 60Co radiation. Additionally, dose delivery was simulated by Monte Carlo calculations using the EGSnrc code system. The calculated secondary electron fluence spectra at the cell location did not indicate a significant change of radiation quality (i.e. higher linear energy transfer) at the lower distances.Clonogenic cell survival curves obtained after brachytherapy exhibited an altered biological response compared to x-rays which was characterized by a significant reduction of the survival curve shoulder when dose rate fluctuations were high. Therefore, also for the time scale of the present investigation, cellular effects of radiation are not invariant to the temporal pattern in dose rate. We propose that with high dose rate variation the cells activate less efficiently their DNA damage response than after continuous irradiation.

Antioxidant and cytoprotective effects of morin against hydrogen peroxide-induced oxidative stress are associated with the induction of Nrf-2-mediated HO-1 expression in V79-4 Chinese hamster lung fibroblasts

Natural phytochemicals of plant origin, including flavonoids, have been found to be potent antioxidants providing beneficial effects against oxidative stress-related diseases. The present study was carried out to investigate the antioxidant properties of morin, a flavonoid originally isolated from the flowering plants of the Moraceae family. Superoxide dismutase (SOD)‑like activity and 2,2'‑azino‑bis‑(3‑ethylbenzothiazoline‑6‑sulfonic acid) (ABTS•+) radical scavenging activity were determined. We also investigated the cytoprotective effects of morin against hydrogen peroxide (H2O2)‑induced DNA damage and apoptosis in V79‑4 Chinese hamster lung fibroblasts. Our results demonstrated that morin had strong scavenging effects against ABTS•+ radicals with enhanced SOD activity, which varied in a dose-dependent manner. Morin was found to reduce H2O2‑induced intracellular reactive oxygen species generation and nuclear DNA damage, and it recovered cell viability damaged by H2O2 via inhibition of mitochondrial dysfunction‑mediated apoptosis. Notably, the treatment of V79‑4 cells with morin markedly enhanced the expression of heme oxygenase‑1 (HO‑1) but not quinone oxidoreductase-1, which was associated with the increased expression and phosphorylation of nuclear factor-erythroid2-related factor2 (Nrf2) and the downregulation of Kelch‑like ECH‑associated protein1 expression. Based on our findings, we conclude that morin effectively ameliorated oxidative stress‑induced DNA damage through intrinsic free radical scavenging activity and activation of the Nrf2/HO-1 pathway.

Adverse and beneficial effects in Chinese hamster lung fibroblast cells following radiofrequency exposure.

In this study, the effect of radiofrequency (RF) exposure to 1950 MHz, Universal Mobile Telecommunication System signal, was investigated in Chinese hamster lung fibroblast cell line (V79). Genotoxic and cytotoxic effects of 20-h exposure at specific absorption rate (SAR) values from 0.15 W/kg to 1.25 W/kg were measured by means of cytokinesis-block micronucleus (MN) assay. Exposure was carried out blinded under strictly controlled conditions of dosimetry and temperature. The effect of RF exposure alone at four SAR values was tested, that is, 0.15, 0.3, 0.6, and 1.25 W/kg. A statistically significant increase in MN frequency was found in cultures exposed to 0.15 and 0.3 W/kg (P < 0.05) compared to sham-exposed ones, in the absence of cytotoxicity. SAR values of 0.6 and 1.25 W/kg did not exert any effect. Moreover, to evaluate the ability of RF to exert protective effects with respect to a chemical mutagen, cell cultures were also pre-exposed for 20 h at 0.3 or 1.25 W/kg, and then treated with 500 ng/ml of mitomycin-C (MMC). A significant reduction in the frequency of MN was detected in cultures pre-exposed to 1.25 W/kg compared to cultures treated with MMC alone (P < 0.05), indicating induction of adaptive response. Such a decrease was not induced by pre-exposure at 0.3 W/kg SAR. Taken together, our results indicated that V79 is a sensitive cell model to evidence either adverse or beneficial effects of RF exposure, depending on experimental conditions applied. Bioelectromagnetics. 38:245-254, 2017. © 2017 Wiley Periodicals, Inc.

Magnesium stearate, a widely-used food additive, exhibits a lack of in vitro and in vivo genotoxic potential.

Magnesium stearate is widely used in the production of dietary supplement and pharmaceutical tablets, capsules and powders as well as many food products, including a variety of confectionery, spices and baking ingredients. Although considered to have a safe toxicity profile, there is no available information regarding its potential to induce genetic toxicity. To aid safety assessment efforts, magnesium sulfate was evaluated in a battery of tests including a bacterial reverse mutation assay, an in vitro chromosome aberration assay, and an in vivo erythrocyte micronucleus assay. Magnesium stearate did not produce a positive response in any of the five bacterial strains tested, in the absence or presence of metabolic activation. Similarly, exposure to magnesium stearate did not lead to chromosomal aberrations in CHL/IU Chinese hamster lung fibroblasts, with or without metabolic activation, or induce micronuclei in the bone marrow of male CD-1 mice. These studies have been used by the Japanese government and the Joint FAO/WHO Expert Committee on Food Additives in their respective safety assessments of magnesium stearate. These data indicate a lack of genotoxic risk posed by magnesium stearate consumed at current estimated dietary exposures. However, health effects of cumulative exposure to magnesium via multiple sources present in food additives may be of concern and warrant further evaluation.

In vitro protective effects of botryosphaeran, a (1 → 3;1 → 6)-β-d-glucan, against mutagens in normal and tumor rodent cells

Botryosphaeran (BOT) is an exocellular β-d-glucan (carbohydrate biopolymer) of the (1→3;1→6)-linked type produced by Botryosphaeria rhodina MAMB-05. The cytotoxic, mutagenic, genotoxic, and protective effects of this substance were evaluated in Chinese hamster lung fibroblasts (V79) and rat hepatocarcinoma cells (HTC) by the micronucleus test (MN) and the comet assay. BOT was not genotoxic in either cell line; it decreased the clastogenic effects of doxorubicin, H2O2, and benzo[a]pyrene. These results indicate that BOT may have potential as a therapeutic agent.

Protective Effect of an Isoflavone, Tectorigenin, Against Oxidative Stress-induced Cell Death via Catalase Activation.

BackgroundIsoflavones are biologically active compounds that occur naturally in a variety of plants, with relatively high levels in soybean. Tectorigenin, an isoflavone, protects against hydrogen peroxide (H2O2)-induced cell damage. However, the underlying mechanism is unknown.MethodsThe MTT assay was performed to determine cell viability. Catalase activity was assessed by determining the amount of enzyme required to degrade 1 μM H2O2. Protein expression of catalase, phospho-extracellular signal-regulated kinase (ERK), IκB-α, and NF-κB were evaluated by Western blot analysis. A mobility shift assay was performed to assess the DNA-binding ability of NF-κB. Transient transfection and a NF-κB luciferase assay were performed to assess transcriptional activity.ResultsTectorigenin reduced H2O2-induced death of Chinese hamster lung fibroblasts (V79-4). In addition, tectorigenin increased the activity and protein expression of catalase. Blockade of catalase activity attenuated the protective effect of tectorigenin against oxidative stress. Furthermore, tectorigenin enhanced phosphorylation of ERK and nuclear expression of NF-κB, while inhibition of ERK and NF-κB attenuated the protective effect of tectorigenin against oxidative stress.ConclusionsTectorigenin protects cells against oxidative damage by activating catalase and modulating the ERK and NF-κB signaling pathway.

Cell electrotransfection and viability dependence on electrotransfection and viability dependence on electoporation medium

Electroporation is a physical method that uses electric fields to increase membrane permeability. The method is widely used for intracellular drug and gene delivery. In this study we aimed to investigate the importance of the medium for efficiency of cell electrotransfection and viability following the application of electric field pulses. The experiments were performed using 2 different cell lines: Chinese hamster ovary (CHO) and Chinese hamster lung fibroblast (DC-3F) and 2 different electroporation media: SMEM (medium conductivity equal to 1.3 S/m) and laboratory-made low-conductivity (0.1 S/m) electroporation (EP) medium. Cells suspended in these media were supplemented with plasmid (10 µg/ml) encoding luciferase and then were treated with 1, 5, or 10 high-voltage (1200 V/cm, 100 µs, at 1 Hz) pulses. Transfection efficiency was determined by luciferase activity 24 h after cell treatment, while cell viability was determined by clonogenic assay. Results showed significant differences between cell lines and used electroporation media. CHO transfection was higher when electroporation was performed in low conductivity EP medium. Low transfection efficiency in SMEM medium resulted from low viability. In contrast, transfection efficiency of DC-3F cells was higher in SMEM. Possible mechanisms governing these differences are discussed.