DNA damage response in resting and proliferating peripheral blood lymphocytes treated by camptothecin or X-ray

DNA damage response (DDR) in different cell cycle status of human peripheral blood lymphocytes (PBLs) and the role of H2AX in DDR were investigated. The PBLs were stimulated into cell cycle with phytohemagglutinin (PHA). The apoptotic ratio and the phosphorylation H2AX (S139) were flow cytometrically measured in resting and proliferating PBLs after treatment with camptothecin (CPT) or X-ray. The expressions of γH2AX, Bcl-2, caspase-3 and caspase-9 were detected by Western blotting. DDR in 293T cells was detected after H2AX was silenced by RNAi method. Our results showed that DNA double strand breaks (DSBs) were both induced in quiescent and proliferating PBLs after CPT or X-ray treatment. The phosphorylation of H2AX and apoptosis were more sensitive in proliferating PBLs compared with quiescent lymphocytes (P<0.05). The expression levels of anti-apoptotic proteins Bcl-2 were reduced and cleaved caspase-3 and caspase-9 were increased. No significant changes were observed in CPT-induced apoptosis in 293T cells between H2AX knocking down group and controls. It was concluded that proliferating PBLs were more vulnerable to DNA damage compared to non-stimulated lymphocytes and had higher apoptosis rates. γH2AX may only serve as a marker of DNA damage but exert no effect on apoptosis regulation.     

Apoptosis of matured T lymphocytes induced by mouse sertoli cells in cocultures in vitro

Objective: To study whether mouse sertoli cells can induce the apoptosis of matured T lymphocytes in cocultures in vitro. Methods: With TUNEL, DNA electrophoresis, eleetro-mierography and flow cytometry, we examined the apoptosis and its rates of mouse matured T lymphocytes in control group (T lymphocytes only), group A (T lymphocytes culture medium of sertoli cells), group B (T lymphocytes sertoli cells). Results: Under electro-micrography, chromatin condensation, karyopyknosis, karyorhexis and apoptotic body were observed in some T lymphocytes in 3 groups; some nucleuses were stained dark blue with TUNEL; a typical DNA ladder was found with DNA electrophoresis. The apoptotic rates of T lymphocytes in group A and B were significantly higher than that in control group (P＜0.01). The apoptotic rate of T lymphocytes in group B was significantly higher than that in group A (P＜0.01). Conclusion: In coculture condition in vitro,mouse sertoli cells can induce the apoptosis of matured T lymphocytes.     

Isolation and characterization of radiation-resistant lung cancer D6-R cell line

Objective To isolate an isogenic radioresistant cancer cell line after fractioned X-ray radiation and characterize the resistant cells. Methods D6 cells were exposed to repeated X-ray irradiation, and after a total dose of 5200 cGy in 8 fractions, a radioresistant monoclone D6-R was obtained. The radiosensitivity and drug sensitivity of the novel radioresistant D6-R cells, together with their parent D6 cells, were measured using clonogenic assay and MTT assay respectively. Cell cycle distribution was analyzed by flow cytometry. Fluorescence microscopy and flow cytometry were applied for apoptosis detection Comet assay was used for the detection of DNA damage and repair. Results D6-R cells showed higher and broader initial shoulder （D0=2.08 Gy, Dq=1.64 Gy, N=2.20） than the parent D6 cells （D0=1.84 Gy, Dq=0.34 Gy, N=1.20）. They were 1.65-fold more radioresistant than D6 cells in terms of SF2 （63% vs 38%） and were more resistant to ADM （3.15-fold） and 5-FU （3.86-fold） as compared with the latter. It was found that D6-R cells had higher fractions of cells in S phase （53.4% vs 37.8%） and lower fractions of cells in G1 （44.1% vs 57.2%） and G2-M phase （2.5% vs 5%）. There was no difference in radiation-induced apoptosis between D6-R and D6 cells. D6-R cells showed less initial DNA damage and increased capacity in DNA repair after irradiation, as compared with the parent cells. Conclusions D6-R cells have been isolated by exposing the parental D6 cells to repeated irradiation. The difference in cell cycle pattern together with the induction and repair of DNA damage might, at least partially, explain the mechanism of the radioresistance.     

Effect of prolonging interval time between coronary angiography and percutaneous coronary intervention on X-ray-induced DNA double-strand breaks in blood lymphocytes

Background It is desirable to minimize the risk of adverse radiation effects associated with percutaneous coronary intervention.The aim of this study was to determine the impact of prolonging the interval between coronary angiography and percutaneous coronary intervention on X-ray-induced DNA double-strand breaks in blood lymphocytes using γ-H2AX immunofluorescence microscopy.Methods Blood samples of eight patients were taken before the first exposure to ionizing radiation,10 minutes,20 minutes,30 minutes,1 hour,and 24 hours after the last exposure to determine the γ-H2AX foci repair kinetics.Fifty-eight patients undergoing percutaneous coronary intervention were randomized to an intermittent radiation exposure group and a continuous radiation exposure group.Blood samples were taken before coronary angiography and 15 minutes after the last exposure.By enumerating γ-H2AX foci,the impact of prolonging the interval on DNA double-strand breaks was investigated.Student t-test was used to compare the difference in DNA double-strand breaks between the two groups.Results An increase in foci was found in all patients received percutaneous coronary intervention.The maximum number of γ-H2AX foci was found 10-20 minutes after the end of the last exposure.There was no statistically significant difference between the two groups in γ-H2AX foci at baseline.On average there were （0.79±0.15） γ-H2AX foci induced by interventional X-rays per lymphocyte in the continuous radiation exposure group and （0.66±0.21） in the intermittent radiation exposure group after exposure （P〈0.05）.Conclusions A significant number of γ-H2AX foci develop following the percutaneous coronary intervention procedures.The number of X-ray-induced DNA double-strand breaks may be decreased by prolonging the interval time between coronary angiography and percutaneous coronary intervention to 30 minutes.     

Differential activation of mitogen-activated protein kinases by γ-irradi-ation in IEC-6 cells: Role of intracellular Ca~(2 )

Objective: To explore the effects of γ-irradiation on mitogen-activated protein kinases (MAPKs) and role of intracellular calcium in this event in intestinal epithelial cell line 6 (IEC-6 cells). Methods: After cultured rat IIEC-6 cells with or without the pretreatment of intracellular Ca2 chelator were exposed to Y-ir-radiation of 6 Gy, the total and phosphorylated MAPKs in the cells were determined with Western blotting and apoptosis was examined with flow cytometry. Activities of Extracellular signal-regulated protein kinase (ERK) and p38 MAPK were determined by using immuoprecipitation followed by Western blotting. Results: In response to γ-irradiation, phosphorylation of ERK was not significantly observed, while the levels of phosphorylated c-Jun NH2-terminal kinase (JNK) and p38 MAPK were increased in 30 min and reached the peak 2 h after exposure to 6 Gy γ-irradiation, though the cell viability was significantly lowered 12 h. On the other hand, no obvious changes were seen in the total protei     

Effect of Shenfu on the Expression of Bcl-2 and Bax of Intestinal Mucosal Epithelial Cells after Ischemic Reperfusion in Rats

Objective To study the effect of Shenfu on the expression of bax and bcl-2 in small intestinal mucosal epithelial cells after ischemic reperfusion injury and explore the effect of Shenfu on small intestinal mucosal epithelial cells apoptosis. Methods 36 SD rats were randomized into three groups, each consisting of 12 rats： Sham group （S group）, Ischemic reperfusion group （IR group）, Shenfu group （SF group）, Ischemic reperfusion models were made by ligated the superior menseneric artery for 1 hour followed by 2 hrs reperfusion. Histological mucosal damage in each group was graded according to Chiu＇s score. Immunohistochemistry detected the expression of bax and bcl-2, and obtained the optical density （OD） value using a color image pattern analysis system, and then calculated the ratio of bcl-2/bax. TUNEL method measured apoptotic intestinal mucosal epithelial cells, and calculated the apoptotic index. Results There were edema and epithelial impairment in part of villus and the integral was higher in SF group than S group （P〈0.05）, but lower than IR group （P〈0.01）. Compared IR group with S group and SF group, the average OD value of bcl-2 and bax had significant statistic difference （P〈0.01）, and the average OD value of bcl-2 in SF group was higher than in S group （P〈0.05）, meanwhile bcl-2/bax was significantly lower in IR group than in S group and SF group （P〈0.01）, but that was higher in SF group than in S group （P〈0.05）. Apoptotic index in IR group was significantly higher than that in other two groups （P〈0.01）, and that in SF group was higher than in S group （P〈0.05）. Conclusion Shenfu can enhance the expression of bcl-2, decrease the expression of bax, meanwhile increase the ratio of bcl-2/bax, inhibit small intestinal mucosal epithetlial cells apoptosis, and protect small intestine mucosal epithetlial after ischemic reperfusion.     

Differential activation of mitogen—activated protein kinases by γ—irradiation in IEC—6 cells：Role of intracelluklar Ca^2＋

Abstract Objective:To explore the effects of γ-irradiation on mitogen-activatedprotein kinases(MAPKs) and role intracellular calcium in this event in intestinal epithelial cell line 6(IEC-6 cells).Methods:After cultured rat IIEC-6 cells with or without the pretreatment of intracellular Ca^2 chelator were exposed to γ-ir-radiation of 6 Gy, the total and phosphorylated MAPKs in the cells were determined with Western blotting and apoptosis was examined with flow cytometry.Activities of Extracellular signal-regulated protein kinase (ERK) and p38 MAPK were determined by using immuoprecipitation followed by Western blotting.Results:In response to γ-irradiation,phosphorylation of ERK was not significantly observed ,while the levels of phos-phorylated c-Jun NH2-terminal kinase(JNK) and p38 MAPK were increased in 30 min and reached the peak 2h after exposure to 6Gy γ-irradiation,though the cell viability was significantly lowered 12h.On the other hand, no obvious changes were seen in the total protein levels of ERK, JNK and p38 MAPK.Chelation of in-tracellular Ca^2 almost completely suppressed the JNK and p38 MAPK phosphorylation induced by γ-irradiation is a potent activator for JNK and p38 MAPK, and Ca^2 mobilized from intracellular stores plays an important role in the activation of MAPKs and the induction of apoptosis in IEC-6 cells.     

EFFECT OF PLANT POLYSACCHARIDES ON T AND B LYMPHOCYTES IN NORMAL AND TUMOR TRANSPLANTED MICE

The effect of 24 plant polysaccharides on theperipheral T and B lymphocytes,thymus T lympho-cyte in normal mice and the peripheral T lymphocytein tumor transplanted mice was studied cytochemical-ly.The results showed that these polysaccharidesmight be classified into 3 groups:those increasingthe peripheral T,B lymphocytes and thymus Tlymphocyte,those lowering these cells,and thosewith no apparent effect on them.The number of polysaccharides with obviouseffect on the peripheral and thymus T lymphocytes,the connection between the thymus weight and theT lymphocyte percentage changes in normal miceand the correlation between the change of the peri-pheral T lymphocyte and the inhibitory effect ontumor growth in tumor transplanted mice are dis-cussed.     

Studies on the Induction of Cross—Resistance by Low Dose Radiation or by Low Concentrations of Chemicals

The cross-resistance induced by low-level radiation and low concentration of chemical mutagens was studied using human lymphocytes in vitro and mouse bone marrow cells and germ cells in vivo.The chemical mutagens used in these experiments included the MMC H2O2 and CP.The results reported here,in addition to those that have appeared in the literature,show the following reatures documented for the first time:(1)MMC as an adaptive treatment could also induce the adaptive response to radiation-induced cytogenetic damage;(2)esistance against MMC-induced damage could be induced by low dose radiation in vivo;(3)it is in mouse germ cells that low dose radiation or chemical mutagens could induce the cross-adaptation;(4) the cells pretreated by low dose X-rays could show the high resistance to H2O2-induced cytogenetic damage;(5)CP as D1 treat6ment could not induce the adaptive response to radiation and low dose radiation also could not induce the adaptive response to CP.     

Effects of magnesium sulfate on neuron apoptosis and expression of caspase- 3， bax and bcl-2 after cerebral ischemia-reperfusion injury

Objective To investigate the effects of magnesium sulfate on neuron apoptosis and the expressions of caspase-3,bax and bcl-2 after cerebral ischemia-reperfusion injury. Methods Thirty-six gerbils were randomly divided into three groups: Sham-operation group (So, n=12), ischemia-reperfusion group (I-R, n=12) and magnesium sulfate group (Ms, n=12). The neuron apoptosis was detected by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-fluorescence nick end labeling (TUNEL stain), and the protein expressions of caspase-3, bax and bcl-2 were detected by immunohistochemisty stain.Results Apoptotic neurons and the expressions of caspase-3 and bax were significantly increased in I-R and Ms groups, compared with those in So group. Apoptotic neurons and the expressions of bax and caspase-3 in Ms group were significantly less than those in I-R group. There was no significant difference in the expression of bcl-2 among three groups.Conclusions Magnesium sulfate decreases neuron apoptosis after cerebral ischemia-reperfusion injury, which may be related with the suppressed expressions of caspase-3 and bax.     

放疗对人肝癌HepG2细胞凋亡及细胞周期的影响

目的:探讨放疗对人肝癌HepG2细胞凋亡及细胞周期的影响。方法:采用6MV-X射线照射细胞,提取DNA进行琼脂糖凝胶电泳,观察细胞发生凋亡的情况,并采用免疫组织化学染色观察人肝癌细胞株中Bax和Bcl-2蛋白的表达。同时观察细胞周期改变情况。结果:照射后48h,2Gy、4Gy和6Gy出现明显DNA降解("梯形结构"),但对照组及8Gy和10Gy无"梯形结构"出现。Bax和Bcl-2蛋白的表达在时间和剂量之间存在交互作用(F=1.733,P=0.042;F=1.700,P=0.048)。4Gy照射剂量作用细胞48h后,HepG2细胞中Bax表达显著上调,而Bcl-2表达明显降低。4GyX线照射后培养6h,即可观察到G2/M期、S期阻滞,G2/M期阻滞峰值为正常的56倍,在6~48h阻滞"崩溃",细胞被释放,再度进入细胞周期或死亡。结论:6MV-X射线照射HepG2细胞,可诱使其产生凋亡,其机制可能通过促进Bax蛋白表达和抑制Bcl-2蛋白的表达来诱导肝癌细胞凋亡。4Gy照射引起的G2期阻滞释放可能与凋亡水平上调有关。     

四生汤对照射小鼠胸腺淋巴细胞凋亡和抗氧化能力的作用

目的探讨四生汤对受辐射小鼠胸腺淋巴细胞抗氧化能力及细胞凋亡的影响及作用机制。方法建立60Co（辐射强度为3Gy）对体外培养的小鼠胸腺淋巴细胞辐射损伤模型。实验设计分为5组：对照组,60Co模型组,高、中、低剂量四生汤组。MTT法检测细胞活性;酶生化法测定各组小鼠胸腺细胞胞浆超氧化物歧化酶（SOD）活性和丙二醛（MDA）含量;流式细胞仪测定小鼠胸腺淋巴细胞凋亡率,免疫细胞化学法检测各组Bcl-2和Bax的表达。结果在强度为3Gy60Co辐射情况下,1%-4%浓度范围内四生汤能显著提高小鼠胸腺淋巴细胞的活性;显著提高细胞浆中SOD活性,降低MDA含量;各四生汤组淋巴细胞凋亡率明显低于模型组（P〈0.01）;Bcl-2蛋白表达增强,Bax蛋白表达减弱。结论四生汤能提高体外培养的小鼠胸腺淋巴细胞活性,抑制60Co辐射诱导的淋巴细胞凋亡,其作用机制与四生汤提高抗氧化酶SOD活性,抑制脂质过氧化水平及调节凋亡因子Bcl-2与Bax之间的平衡有关。     

褪黑素对电离辐射诱导离体小鼠淋巴细胞凋亡的影响

目的：探讨褪黑素（melatonin,MLT）对电离辐射诱导的离体小鼠淋巴细胞凋亡的影响及其机制。 方法：采用流式细胞术（FCM）和荧光分光光度法分别检测小鼠胸腺和脾淋巴细胞凋亡小体百分率和DNA裂解率。 结果：电离辐射可诱导离体小鼠胸腺、脾淋巴细胞凋亡,在0.5~6.0 Gy范围内凋亡呈剂量依赖性增加。照射前预先加入2 mmol•L^-1MLT,细胞凋亡小体百分率和DNA裂解率与单纯照射组比较均显著降低,胸腺、脾淋巴细胞凋亡小体百分率分别降低为单纯照射组的86.25%和89.22%,DNA裂解率分别降低为单纯照射组的87.23%和89.16%。 结论：MLT在体外可减轻电离辐射诱导的小鼠淋巴细胞凋亡,对淋巴细胞损伤有防护作用。     

电离辐射对小鼠胸腺bcl-2蛋白表达及细胞凋亡的作用机制

目的:研究不同剂量X射线照射对小鼠胸腺bcl-2 蛋白表达及细胞凋亡的作用机制.方法:用免疫组织化学、图像分析技术及透射电镜技术分别检测小鼠胸腺bcl-2蛋白表达及细胞凋亡.结果:假照组胸腺实质内bcl-2蛋白表达主要分布于髓质,胸腺皮质内可有少量凋亡的胸腺细胞.2 Gy照射后4、8和12 h胸腺髓质内bcl-2表达减少,皮质内出现许多典型的凋亡细胞;0.075 Gy照射后bcl-2蛋白表达增多,皮质内凋亡细胞减少,且可见较多的细胞分裂像.结论:不同剂量电离辐射对胸腺细胞凋亡的影响与胸腺髓质内bcl-2蛋白表达水平有关.     

冷冻治疗对G422胶质瘤细胞凋亡的影响

目的 研究局部冷冻对G422胶质瘤细胞凋亡及其调控机制的影响。方法 建立小鼠脑胶质瘤动物模型,于冷冻治疗后6、12、24、48、72 h留取标本,用光镜、末端标记法(TUNEL)、DNA凝胶电泳检测细胞凋亡,用免疫组化技术检测凋亡相关基因bcl-2、bax的表达产物。结果G422胶质瘤经冷冻治疗后,冷冻灶中心区呈坏死改变,冷冻周边区出现凋亡的形态学改变,DNA呈“梯状”降解,冷冻后各时间点凋亡细胞数目均明显多于对照组(P<0.01)。bax表达阳性细胞数也多于对照组(P<0.05),而冷冻对bcl-2表达无明显影响。结论 除坏死外,诱导细胞凋亡可能是冷冻杀伤胶质瘤细胞的另一重要机制;这种细胞凋亡可能是通过上调bax基因的表达来实现。     

Effects of L-Tetrahydropalmatine on the Expressions of bcl-2 and bax in Rat after Acute Global Cerebral Ischemia and Reperfusion

Polygenesregulateapoptosis .bcl 2isananti apoptosisgene ,whilebaxisapro apoptosisgene .L Tetrahydropalmatine (L THP) ,akindofalkaloidextractedfromtraditionalChinesemedicineRhizomacorydalis,possessesanalgesic ,sedativeandhypnoticeffects.Recently ,ithasbeen…     

放疗对人肝癌细胞株Hep-G2中Bax和Bcl-2表达的影响

目的:探讨放疗对人肝癌细胞株Hep-G2中Bax和Bcl-2蛋白表达水平的影响.方法:6MV-X射线照射细胞,采用免疫组织化学染色观察人肝癌细胞株中Bax和Bcl-2的表达.结果:Bax和Bcl-2的表达在照射时间和照射剂量之间存在交互作用(F=1.733,P=0.042;F=1.700,P=0.048).4Gy照射剂量作用细胞48h后,Hep-G2细胞中Bax的表达达高峰、Bcl-2的表达至低谷.结论:放射线可能通过促进Bax表达和抑制Bcl-2表达诱导肝癌细胞凋亡.     

Cortical neuron apoptosis induced by beta-amyloid peptide and protective effect of panoxadiol in mice

OBJECTIVE: To investigate the apoptosis of cortical neurons induced by beta-amyloid peptide (Abeta(1-40)) and the protective effect of panoxadiol. METHODS: The Abeta(1-40) induced damage of primarily cultured mouse cortical neurons was examined with morphological observation, MTT assay, DNA agarose gel electrophoresis and Western-blot. RESULT: After 48 h treated with 12 mumol/L Abeta(1-40), the cortical neurons showed apoptotic characteristics: including decreased OD570 value in MTT assay, DNA cleavage fragment in electrophoresis and increased apoptotic cells. Western-blot showed that the expression of bcl-2 reduced significantly (P<0.05). Cell apoptosis was significantly attenuated in 40 mg/L panoxadiol treated group. CONCLUSION: Panoxadiol can protect cultured cortical neurons from apoptosis induced by Abeta(1-40) in mice.     

加强师资队伍建设是高校实施素质教育的重要保证

随着中国改革开放的不断发展和深入，特别是中国正式加入WTO之后，人才的需求量加大，人才的竞争更加激烈。