OBJECTIVETo investigate the effects of hydroquinone (HQ) on expression of Polymerase eta (Pol eta) and DNA damage in human hepatic cells (L-02), and to explore the role and possible mechanism of Pol eta involved in the process of DNA damage-tolerance.

METHODSAfter L-02 hepatic cells were exposed to HQ with various concentrations (0, 5, 10, 20, 40, 80 and 160 micromol/L) for 24 h, cell survival rate was detected by MTT assay; DNA impairment was detected by single cell gel electrophoresis (SCGE); Real-time fluorescent quantitative PCR and Western blotting methods were used to measure the expression of Pol eta at the mRNA and protein level in L-02 hepatic cells exposed to HQ with various concentrations (0, 5, 10, 20, 40, 80 and 160 micromol/L).

RESULTSMTT assay showed that HQ with concentrations from 0 to 80 micromol/L had little effect on the survival rate of L-02 (P>0.05); whereas the survival rate of the group of 160 micromol/Lwas significantly higher than that of the control (P<0.01) after being treated with HQ for 24 h; the higher dose of HQ presented, the more degrees of DNA damage were produced. It was found that HQ in a low concentration (1-80 micromol/L) could induce the expression of Pol eta which was in proportion to the increasements of HQ concentration; the expression levels of mRNA and protein were reached to the maximum when treated with 80 micromol/L; the expression of Pol eta decreased (the relative quantity values were 2.32 +/- 0.16 and 1.20 respectively) once the concentration of HQ exceeded 160 micromol/L as compared with the group of 80 micromol/L, but it was higher than that of the control.

CONCLUSIONThis study suggested that Pol eta might involve in the process of DNA damage-tolerance induced by HQ in the hepatic cells.

Cell Survival ; drug effects ; Cells, Cultured ; DNA Damage ; drug effects ; DNA Repair ; DNA-Directed DNA Polymerase ; metabolism ; Hepatocytes ; drug effects ; metabolism ; Humans ; Hydroquinones ; adverse effects ; Mutagens

The defect or block of apoptosis is an important factor involved in the drug resistance of tumor cells. Blm gene plays a great role in DNA damage and repair. This study was aimed to explore the relationship of blm gene expression with cell cycle and apoptosis after Jurkat DNA damage. The apoptosis rate and change of cell cycle were detected by flow cytometry, the expression level of blm mRNA in Jurkat cells was determined by semi-quantitative RT-PCR. The results indicated that after induction with 0.4 g/L of mitomycin C (MMC) for 24 hours the apoptosis rate of Jurkat cells were (11.42±0.013)%, and (66.08±1.60)% Jurkat cells were arrested in G2/M phase. After induction for 48 hours, the apoptosis rate of Jurkat cells declined from (11.42±0.013)% to (8.08±0.27)%, and cell count of Jurkat cells arrested in G2/M phase decreased from (66.08±1.60)% to (33.96±1.05)%. When induced with 0.4 g/L of MMC for 24 hours, the apoptosis rate of fibroblasts and the percentage of fibroblasts in G2/M, G0-G1 and S phase all showed no significant change until 48 hours. The range of apoptosis rate and the change of cell percentage in three phases were significantly different between Jurkat cells and fibroblasts (p<0.01). Expression level of blm mRNA in Jurkat cells was remarkably higher than that in normal fibroblasts (p<0.01), at 48 hours expression level of blm mRNA was remarkably higher than that at 24 hours. The 2 groups showed clear difference of blm mRNA expression after treated by MMC (p<0.01). It is concluded that the blm gene may play a significant role in repair of DNA damage of Jurkat cells after MMC induction. Abnormal expression of blm is correlated to the drug resistance of leukemia cells.
Apoptosis ; Cell Cycle ; DNA Damage ; drug effects ; DNA Repair ; drug effects ; Humans ; Jurkat Cells ; Mitomycin ; pharmacology ; RecQ Helicases ; genetics

OBJECTIVETo investigate the cyto-genotoxicity of cigarette smoke condensates (CSCs) in human peripheral blood lymphocytes with different assays in vitro.

METHODSHuman lymphocytes were exposed to particle matter of cigarette smoke combined with or without S9 mixtures at doses of 25, 50, 75, 100 and 125 microg/ml for 3 h. The cytotoxicity induced by CSCs was detected by CCK-8 assay. The DNA damage, DNA repair (repair time: 30, 60, 90, 120 and 240 min, respectively) and the somatic cell mutations induced by 75 microg/ml CSCs were measured by comet assay, hprt gene and TCR gene mutation tests, respectively.

RESULTSCCK-8 assay indicated that the cell viability decreased with CSCs doses. At the doses of 100, 125 microg/ml, the cell viability of CSCs +S9 group was significantly higher than that of CSCs -S9 group (P < 0.05, P < 0.01). In comet assay, DNA damage significantly increased in a dose-dependent manner, as compared with controls (P < 0.01). Moreover, there was significant difference between -S9 group and +S9 group (P < 0.05, P < 0.01). The Mf-TCR at each dose group was significantly higher than that of controls (P < 0.05, P < 0.01). The Mf-hprt at high-dose groups were significantly higher than that of controls (P < 0.01), and significant difference of Mf-TCR and Mf-hprt at high doses of CSCs between -S9 group and +S9 group (P < 0.05, P < 0.01). The DNA damage induced by CSCs +S9 or CSCs -S9 could be repaired, but DNA repair speed was different between -S9 group and +S9 group (P < 0.05, P < 0.01).

CONCLUSIONCSCs may induce cyto-genotoxicity in human peripheral blood lymphocytes in vitro, but S9 mix could reduce the toxicity of CSCs and impact DNA repair speed.

Cells, Cultured ; Comet Assay ; DNA Damage ; drug effects ; DNA Repair ; drug effects ; Humans ; Lymphocytes ; drug effects ; Male ; Mutation ; Tobacco Smoke Pollution ; adverse effects ; Young Adult

OBJECTIVETo study the role of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in silica-induced DNA double-strand break repair in human embryo lung fibroblasts (HELF).

METHODSTwo stable transfectants, HELF transfected with DNA-PKcs siRNA (HELF-PKcs) and with negative control siRNA (HELF-NC), were established. HELF cells were treated with 0, 25, 50, 100, 200, 300 and 400 microg/ml silica for 12 h and with 200 microg/ml silica for different times (0, 1, 2, 6, 12 and 24 h). HELF-PKcs and HELF-NC were treated with 200 microg/ml silica for 0, 12 and 24 h. The expression levels of DNA-PKcs and phosphor-H2AX (H2AX) were determined by Western blot. DNA double strand breaks were measured by neutral comet assay.

RESULTSAfter treatment with different doses of silica for 12 h, the levels of H2AX and the percentages of tail DNA increased in concentration-dependent manner. After treatment with 200 microg/ml silica for different times, the levels of H2AX increased in a time-dependent manner. The percentages of tail DNA increased significantly at 6 h, and reaching maximum at 12 h and then decreasing at 24 h. The expression level of DNA-PKcs was suppressed in HELF-PKcs. After treatment with silica at 12 h, the level of H2AX was lower in HELF-PKcs than in HELF-NC, and the percentages of tail DNA increased obviously in both HELF-PKcs and HELF-NC compared with non-treated cells, but no significant difference was found in the percentages of tail DNA between them. The percentages of tail DNA decreased markedly in silica-treated HELF-NC and was significantly lower than in HELF-PKcs at 24 h (P < 0.05).

CONCLUSIONSilica can induce DNA double strand breaks in human embryo lung fibroblasts. DNA-PKcs might play a major role in silica-induced DNA double strand break repair. Silica-induced histone H2AX phosphorylation was dependent on DNA-PKcs.

Cell Line ; DNA Breaks, Double-Stranded ; drug effects ; DNA Repair ; DNA-Activated Protein Kinase ; genetics ; metabolism ; Fibroblasts ; drug effects ; physiology ; Histones ; metabolism ; Humans ; Phosphorylation ; Silicon Dioxide ; pharmacology ; Transfection

OBJECTIVETo explore the molecular biological mechanism of acupuncture and moxibustion for relieving myelosuppression and increasing white blood cells.

METHODSTwo hundred and twenty-four clean male Kunming mice were randomly divided into a control group, a model group, an acupuncture group and a moxibustion group, 56 mice in each group. The model of myelosuppression was made with Cyclophosphamide. In the acupuncture group and the moxibustion group, acupoints "Dazhui" (GV 14), "Geshu" (BL 17), "Shenshu" (BL 23) and "Zusanli" (ST 36) were used for treatment with acupuncture and moxibustion, respectively, while, in the control group and the model group, there were no treatment carried out except catching and fixing. The changes of bone marrow cell DNA pol beta and XPD between the 2nd and 7th day were examined with immunohistochemical method.

RESULTSAcupuncture and moxibustion markedly up-regulated the expression of bone marrow cell DNA pol beta and XPD, and promoted the base excision repair and nucleotide excision repair, which leads to the relieving Cyclophosphamide-induced myelosuppression and increasing the number of white blood cells.

CONCLUSIONFor acupuncture and moxibustion, one of the bone major mechanisms in relieving post-chemotherapy myelosuppression, protecting hemopoietic function and increasing the white blood cells is that it can promote the repair of the bone marrow cell DNA excision and protect hemopoietic cells from injury by chemical drugs.

Acupuncture Therapy ; Animals ; Bone Marrow Cells ; enzymology ; Cyclophosphamide ; pharmacology ; DNA Damage ; drug effects ; DNA Repair ; DNA Repair Enzymes ; genetics ; metabolism ; Gene Expression ; drug effects ; Male ; Mice ; Moxibustion ; Random Allocation

OBJECTIVETo understand benzo[a]pyrene (B[a]P) mediated cellular responses, and to provide clues to explore molecular mechanism of mutagenesis and carcinogenesis induced by B[a]P.

METHODSTwo-dimensional electrophoresis (2-DE) was used to investigate the protein expression levels of FL cells after B[a]P exposure, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) combined with database search was applied to identify the differentially expressed proteins.

RESULTStatistical analysis showed that the volumes of 47 protein spots were altered after B[a]P treatment (P<0.05) and 23 proteins were successfully identified, including zinc finger proteins, SWI/SNF related protein, Bromo domain containing domain and other proteins.

CONCLUSIONThese affected proteins may be involved in the cellular responses to B[a]P exposure, and may mediate the B[a]P induced mutagenesis and carcinogenesis.

Amnion ; chemistry ; cytology ; drug effects ; Benzo(a)pyrene ; toxicity ; Cells, Cultured ; DNA Repair ; Electrophoresis, Gel, Two-Dimensional ; Humans ; Proteomics ; Zinc Fingers

The p53 tumor suppressor has long been envisaged to preserve genetic stability by the induction of cell cycle checkpoints and apoptosis. More recently, p53 has been implicated to play roles in DNA repair responses to genotoxic stresses. UV-damage and the damage caused by certain chemotherapeutics including cisplatin and nitrogen mustards are known to be repaired by the nucleotide excision repair (NER) pathway which is reportedly regulated by p53 and its downstream genes. There are evidences to suggest that the base excision repair (BER) induced by the base-damaging agent methyl methanesulfonate (MMS) is partially deficient in cells lacking functional p53. This result suggests that the activity of BER might be also dependent on the p53 status. In this review, we discuss the possibilities that p53 regulates BER as well as NER; these are one of the most significant potentials of p53 tumor suppressor for repairing the vast majority of DNA damages that is incurred from various environmental stresses.
Animals ; Antineoplastic Agents/pharmacology ; DNA/drug effects ; *DNA Damage ; DNA Repair/*physiology ; Humans ; Mice ; Protein p53/*physiology ; Research Support, Non-U.S. Gov't

Benzene is an established leukotoxin and leukemogen in humans. We have previously reported that exposure of workers to benzene and to benzene metabolite hydroquinone in cultured cells induced DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to mediate the cellular response to DNA double strand break (DSB) caused by DNA-damaging metabolites. In this study, we used a new, small molecule, a selective inhibitor of DNA-PKcs, 2-(morpholin-4-yl)-benzo[h]chomen-4-one (NU7026), as a probe to analyze the molecular events and pathways in hydroquinone-induced DNA DSB repair and apoptosis. Inhibition of DNA-PKcs by NU7026 markedly potentiated the apoptotic and growth inhibitory effects of hydroquinone in proerythroid leukemic K562 cells in a dose-dependent manner. Treatment with NU7026 did not alter the production of reactive oxygen species and oxidative stress by hydroquinone but repressed the protein level of DNA-PKcs and blocked the induction of the kinase mRNA and protein expression by hydroquinone. Moreover, hydroquinone increased the phosphorylation of Akt to activate Akt, whereas co-treatment with NU7026 prevented the activation of Akt by hydroquinone. Lastly, hydroquinone and NU7026 exhibited synergistic effects on promoting apoptosis by increasing the protein levels of pro-apoptotic proteins Bax and caspase-3 but decreasing the protein expression of anti-apoptotic protein Bcl-2. Taken together, the findings reveal a central role of DNA-PKcs in hydroquinone-induced hematotoxicity in which it coordinates DNA DSB repair, cell cycle progression, and apoptosis to regulate the response to hydroquinone-induced DNA damage.
Apoptosis ; drug effects ; physiology ; Benzene ; toxicity ; Catalysis ; Chromones ; pharmacology ; DNA Damage ; drug effects ; genetics ; DNA Repair ; drug effects ; physiology ; DNA-Activated Protein Kinase ; antagonists & inhibitors ; metabolism ; Humans ; K562 Cells ; Morpholines ; pharmacology ; Protein Subunits

BACKGROUNDThe accumulation of free radicals and advanced glycation end products (AGEs) in cell plays a very important role in replicative senescence. Aminoguanidine (AG) has potential antioxidant effects and decreases AGE levels. This study aimed to investigate its effect on replicative senescence in vitro.

METHODSThe effects of aminoguanidine on morphology, replicative lifespan, cell growth and proliferation, AGEs, DNA damage, DNA repair ability and telomere length were observed in human fetal lung diploid fibroblasts (2BS).

RESULTSAminoguanidine maintained the non-senescent phenotype of 2BS cells even at late population doubling (PD) and increased cumulative population doublings by at least 17 - 21 PDs. Aminoguanidine also improved the potentials of growth and proliferation of 2BS cells as detected by the MTT assay. The AGE levels of late PD cells grown from early PD in DMEM containing aminiguanidine decreased significantly compared with those of late PD control cells and were similar to those of young control cells. In addition, the cells pretreated with aminoguanidine had a significant reduction in DNA strand breaks when they were exposed to 200 micromol/L H(2)O(2) for 5 minutes which indicated that the compound had a strong potential to protect genomic DNA against oxidative stress. And most of the cells exposed to 100 micromol/L H(2)O(2) had much shorter comet tails and smaller tail areas after incubation with aminoguanidine-supplemented DMEM, which indicated that the compound strongly improved the DNA repair abilities of 2BS cells. Moreover, PD55 cells grown from PD28 in 2 mmol/L or 4 mmol/L aminoguanidine retain telomere lengths of 7.94 kb or 8.12 kb, which was 0.83 kb or 1.11 kb longer than that of the control cells.

CONCLUSIONAminoguanidine delays replicative senescence of 2BS cells and the senescence-delaying effect of aminoguanidine appear to be due to its many biological properties including its potential for proliferation improvement, its inhibitory effect of AGE formation, antioxidant effect, improvement of DNA repair ability and the slowdown of telomere shortening.

Cell Proliferation ; drug effects ; Cells, Cultured ; Cellular Senescence ; drug effects ; DNA Damage ; DNA Repair ; Diploidy ; Dose-Response Relationship, Drug ; Female ; Fibroblasts ; drug effects ; Glycation End Products, Advanced ; analysis ; Guanidines ; pharmacology ; Humans ; Hydrogen Peroxide ; toxicity ; Telomere

OBJECTIVE: To explore the effect and possible mechanism of catechin microcapsulation on the repair of DNA damage in glumreular mesangial cells (GMCs) induced by H2O2. METHODS: According to H2O2 concentration, the experiment GMCs were divided into 6 groups: a control group, 50 micromol/L group, 100 micromol/L group, 150 micromol/L group, 200 micromol/L group and 250 micromol/L group. Each group was sub-divided into 3 groups: 6 h group, 12 h group and 24 h group, in order to determining the optimum dose and the best time of detecting the DNA damage in GMCs. The cultured cells were divided into 8 groups as follows: the NS control group, the H2O2 group, the catechin groups (the final concentrations were 10.0, 15.0, and 20.0 mg/L respectively) and the various catechin microcapsulation groups (the final concentrations were 10.0, 15.0, and 20.0 mg/L respectively). At the end of the experiment, hydroxy radical (OH), malonydialdehyde (MDA) and total superoxide dismutase (tSOD) concentration of supernadant in GMCs were determined by biochemistry assay, the repair of DNA damage in GMCs were detected by single cell gel electrophoresis assay. RESULTS: (1)At 6th h, H2O2 of 100 micromoL/L could cause the DNA damage of GMCs, and H2O2 of 150 micromol/L could result in DNA damage significantly. (2) No difference was found in the comet span of GMCs DNA in the catechin group and catechin microcapsulation group of different concentrations, while the DNA comet tail-long in the catechin microcapsulation group was shorter than that of the catechin group(all P(s)<0.05), and the fluorescence intensity of tail in the catechin microcapsulation group was lower than that of the catechin group(all P(s)<0.01). (3)When the concentration of catechin was 10.0 mg/L, no statistical significance was obtained in the concentration of dOH-, MDA and tSOD between the catechin microcapsulation group and the catechin group; while dOH- and MDA concentrations were lower, and the tSOD was higher in the catechin microcapsulation group than that in the catechin group when the concentration of catechin was 15.0 mg/L and 20.0 mg/L(all P(s)<0.05). CONCLUSION Catechin microcapsulation can enhance the GMCs ability of repairing DNA damage,which may be due to elevating the capacity of its anti-oxidation by catechin microcapsulation.
Animals ; Capsules ; Catechin ; pharmacology ; Cells, Cultured ; Comet Assay ; DNA Damage ; drug effects ; DNA Repair ; drug effects ; Dose-Response Relationship, Drug ; Hydrogen Peroxide ; toxicity ; Hydroxyl Radical ; metabolism ; Malondialdehyde ; metabolism ; Mesangial Cells ; drug effects ; metabolism ; pathology ; Rats ; Superoxide Dismutase ; metabolism