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Objective To establish an experimental model for the study of α-particle-induced bystander effect of DNA damage and investigate the characteristics of bystander DNA double-strand break (DSB).Methods The red fluorescence fusion protein of HsBrkl-RFP was used to mark the cytoplasm of one cell line to distinguish the irradiated target cells (HFS-RFP) and the non-irradiated bystander cells (HFS) in the co-culture cellular model.After α-particle irradiation,cellular DSB and its repair kinetics were analyzed by the immunofluorescence staining of γH2AX and laser confocal microscope observation.Results A bystander studying model was established by co-culturing human HFS-RFP cells with its partner HSF cells.After 0.1 Gy or 0.2 Gy α-particle irradiation,the similar kinetics of γH2AX foci production and abatement were observed in both irradiated HFS-RFP cells and non-irradiated bystander HFS cells,in which the highest level of γH2AX foci was detected at 1 h post-irradiation.The second peak of γH2AX foci formation appeared at 8 h post-irradiation,which possibly indicates the occurrence of secondary DSB.However,the production of secondary DSB in the bystander cells was weaker than that in the irradiated cells.Conclusions The cell co-culture model can be used for bystander effect investigation.Bystander DSB can be effectively induce by irradiation and the secondary breakage of DNA DSB in the bystander cells may relative to the consequential biochemical processing of clustered DNA damage.
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Objective To evaluate the radioprotective effect of vanillin derivative VND3207 on DNA damage induced by different LET ionizing radiation.Methods The plasmid DNA in liquid was irradiated by 60Co γ-rays, proton or 7Li heavy ion with or without VND3207.The conformation changes of plasmid DNA were assessed by agarose gel electrophoresis and the quantification was done using gel imaging system.Results The DNA damage induced by proton and 7Li heavy ion was much more serious as compared with that by 60Co γ-rays, and the vanillin derivative VND3207 could efficiently decrease the DNA damage induced by all three types of irradiation sources, which was expressed as a significantly reduced ratio of open circular form (OC) of plasmid DNA.The radioprotective effect of VND3207 increased with the increasing of drug concentration.The protective efficiencies of 200 μmol/L VND3207 were 85.3% (t =3.70,P =0.033), 73.3% (t = 10.58, P =0.017)and 80.4% (t =8.57,P =0.008)on DNA damage induction by 50 Gy of γ-rays, proton and 7Li heavy ion, respectively.It seemed that the radioprotection of VND3207 was more effective on DNA damage induced by high LET heavy ion than that by proton.Conclusions VND3207 has a protective effect against the genotoxicity of different LET ionizing radiation, especially for γ-rays and 7 Li heavy ion.
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Objective To investigate the dose-response pattern on the inducible expression of PIG3 mRNA in normal human lymphoblastoid AHHI cells by 60Co γ-rays,and its possibility for developing novel radiation biodosimeter.Methods Laser confocal fluorescent microscopy was used to detect the γ-H2AX foci,a biomarker of DNA double-strand break.After irradiation with 0,1,2,4,6,8 and 10 Gy of 60Coγ- rays,AHH-1 cells were harvested at 4,10 and 24 h post-irradiation,and subjected to total RNA extraction and detection of PIG3 mRNA expression by quantitative real-time PCR.Results PIG3 protein foci were formed in the nuclei at 30 min after irradiation,and a part of these PIG3 foci were colocalized with γH2AX foci.After irradiation,PIG3 mRNA level was enhanced with the increased time of postirradiation,and remained an increased level at least till 24 h.The radiation-inducible expression of PIG3 mRNA was demonstrated in a dose-dependent manner.The dose-dependent range at 4 h post-irradiation was 0 - 6 Gy,and at 10 h and 24 h was 0 - 10 Gy.Conclusions PIG3 involves in the cellular response to DNA double-strand break.The dose-dependent inducible response of PIG3 mRNA expression might provide a valuable candidate for developing a novel radiation biodosimeter.
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Objective To investigate the effect of Tip60 on the cellular radiosensitivity,and to explore the related mechanism.Methods siRNA and anacardic acid (AA,an inhibitor of Tip60 acetyltransferase) were used to inhibit Tip60 expression and its acetyltransferase activity,respectively.Radiosensitivity was analyzed by colony-forming ability assay.γ-H2AX foci were detected to analyze the DNA double-strand break (DSB).Immunoprecipitation was used to determine the interaction of proteins.Results siRNA-mediated silencing of Tip60 led to enhanced sensitivity of U2OS cells at 1,2 Gy after γ-ray irradiation,but had no significant effect at 4 Gy post-irradiation ( t =3.364,3.979,P ＜ 0.05 ).γ-H2AX foci detection indicated that Tip60 silencing resulted in a decreased capability of DNA doublestrand break repair at 1,4 and 8 h after irradiation( t =3.875,3.183 and 3.175,respectively,P ＜ 0.05 ).The interaction of Tip60 and DNA-PKcs was prompted by ionizing radiation.Anacardic acid largely abrogated the phosphorylation of DNA-PKcs at T2609 site induced by irradiation.Conclusions Tip60plays a role in the cellular response to ionizing radiation-induced DNA damage through,at least in part,interacting with DNA-PKcs and regulating its phosphorylation.
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Objective To provide more convincing evidences and experimental data for exploring vanillin derivative BVAN08,6-bromine-5-hydroxy-4-methoxy-benzaldehyde,as a new anticancer drug,and to investigate the effect on the growth,radiosensitization of human glioma cell line U-251 and the relative mechanism.Methods The effect of BVAN08 on cell proliferation of U-251 and radiosensitivity to 60Co γ-rays (irradiation dose rate 2.3 Gy/min) were analyzed with MTT and colony-forming ability assay.Change in cellular morphology was observed by using light microscope.Change in cell cycle and apoptosis was detected with flow cytometry.The autophagy was observed by using TEM (irradiation dose rate is transmission electron microscope).DNA-PKcs protein level was detected through Western blot analysis.Results BVAN08 exhibited a dose- and time-dependent inhibition on the proliferation of U-251 cells during the concentration range of 10-100 mol/L (t = 1.83-3.07,P ＜ 0.05).IC50 at 48 h and 72 h after administration with BVAN08 were 55.3 and 52.7 mol/L,respectively.Obvious G2/M arrest was induced in U-251 cells after 4 h administration with BVAN08,and reached peak at 12 h.The G2/M population reached 63.3% in U-251 cells after 12 h administration of 60 μmol/L BVAN08 and kept increasing with the time,while both apoptosis and autophagic cell death were induced.The most effective radiosensitization time for BVAN08 treatment was 12 h before irradiation.The enhancement ratio of radiosensitivity was 3.14 for 20 μmol/L of BVAN08 12 h before 2 Gy irradiation.Conclusions BVAN08 can nduce apoptosis as well as autophygic cell death of U-251 cells,and sensitize U-251 cells.The mechanism of its radiosensitizing effect might be associated with the induction of G2/M arrest and inhibition of DNA-PKcs expression.BVAN08 seemed to be a romising radiosensitizing anticancer drug.
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Objective To investigate the effects of dexamethasone on absorption of lung edema in rabbits with seawater drowning-induced acute lung injury.Methods Seawater(4 ml/kg body weight)was instilled into the lower trachea of ventilated and anesthetized rabbits.These rabbits were assigned randomly to receive intravenous injection of 1 mg/ kg body weight of dexamethasone(dexamethasone group,DG)or 2 ml of normal saline(control group,CG).Lung edema was measured by extravascular lung water index(EVLWI)using a gravimetric method.Three hours after treatment, epithelial Na~+ channel subunit-?(?-ENaC)mRNA and Na~+/K~+-adenosine triphosphatase subunit-?l(NKA-?l) protein abundances in lung tissues were respectively measured by reverse transcriptase-polymerase chain reaction and Western blotting,and NKA activity was measured by monitoring the release of inorganic phosphate(Pi)from adenosine triphosphate(ATP).Results The DG's EVLWI was significantly lower than the CG's[(0.508?0.089)vs.(0.648?0.102),P＜0.05)],but the DG's NKA activity,?-ENaC mRNA and NKA-?l protein abundances were significantly higher than the CG's,correspondingly(P＜0.05).Conclusions With up-regulation of the NKA activity and expressions of?-ENaC and NKA-?l,dexamethasone treatment could promote the absorption of lung edema in rabbits with seawater drowing-induced acute lung injury.