ATM磷酸化速率调控p53动力学的分岔分析

压力后细胞内p53的不同动力学决定不同的细胞命运。本文基于包含ATM(Ataxia Telangiectasia Mutated)感应模块和PDCD5(Programmed Cell Death 5)调控p53-Mdm2(Murine Double Minute 2)振子的基因调控网络,利用分岔分析,探讨了在不同PDCD5表达水平下,ATM磷酸化速率对p53动力学的影响。结果显示,参数的变化可使系统产生平衡点的鞍结分岔,霍普夫分岔,同宿分岔,鞍结同宿分岔以及极限环的鞍结分岔,这些分岔使p53呈现单稳态,双稳态和三稳态的动力学。该研究表明PDCD5表达水平和ATM磷酸化速率对p53动力学有重要的影响,对了解压力后细胞命运起到一定理论指导作用。

七氟烷对大鼠肺缺血再灌注损伤中ATM的影响

目的七氟烷(Sev)通过抗氧化应激保护肺缺血再灌注(I/R),自动磷酸化蛋白(ATM)激酶可通过蛋白激酶(PK)C调控核因子E2相关因子(Nrf2)激活的抗氧化应激通路,探讨ATM激酶是否参与Sev的保护机制。方法 SD大鼠分为Sham组,肺I/R组,ATM抑制剂KU-55933组(KU组),Sev组,Sev和KU-55933联用组(Sev/KU组),其中Sev组为再灌注过程中吸入两次Sev,KU组为缺血前静脉注射KU-55933。再灌注后用免疫印迹法检测肺组织p-ATM、γ-H2AX、PKC水平和肺组织细胞核Nrf2水平,化学法检测血浆丙二醛(MDA)水平和超氧化物歧化酶(SOD)活性及测量肺部湿/干重比(W/D)。结果 Sev后处理对肺I/R起保护作用,可见p-ATM、γ-H2AX、PKC、Nrf2升高及MDA下降和SOD水平上升,然而,KU-55933处理阻碍了Sev的保护作用。结论ATM参与了Sev后处理诱导的PKC/Nrf2升高及抗凋亡过程,因此推测,激活抗氧化酶有利于Sev对肺I/R的保护。

γ射线诱导人淋巴细胞损伤及磷酸化组蛋白H2AX和ATM表达

目的探讨人外周血经不同剂量”℃0 γ射线照射后淋巴细胞损伤情况，以及与磷酸化的H2AX、ATM表达的关系。方法永生化淋巴细胞及人新鲜外周血淋巴细胞经0-8Gy ^60Co γ射线照射后0.5h，分别采用Westernblot和流式细胞术检测磷酸化ATM和1-H2AX的表达情况，并通过CB微核法检测受照射后人外周血淋巴细胞微核验证细胞损伤程度。结果流式细胞检测发现人外周血淋巴细胞照射后0.5h，,γ-H2AX表达的剂量效应关系呈线性平方模式，其拟合曲线为：Y=3.96＋11.29D-0.45D。，而相同方法检测磷酸化ATM蛋白的表达未见明显变化。Westernblot检测结果表明，照射后0．5h，各受照射组磷酸化ATM表达在0．1～8Gy范围内具有呈剂量依赖性增高的趋势。人外周血淋巴细胞微核结果显示，γ射线照射后DNA损伤情况明显加重，随吸收剂量的增加，微核细胞率明显增多。结论”Co γ射线可诱导DNA双链断裂，随着吸收剂量的增加，微核率明显增加，磷酸化的H2AX、ATM表达水平亦明显增高，本研究为辐射损伤及辐射事故生物剂量估算领域的研究提供了理论依据。

Relationship of HepG2 cell sensitivity to continuous low dose-rate irradiation with ATM phosphorylation

Objective: To investigate the change of ATM phosphorylation in HepG2 cells and its effect on HepG2 cell survival under a continuous low dose-rate irradiation. Methods: HepG2 cells were exposed to equivalent doses of irradiation deliv- ered at either a continuous low dose-rate (7.76 cGy/h) or a high dose-rate (4500 cGy/h). The ATM phosphorylated proteins and surviving fraction of HepG2 cell after low dose-rate irradiation were compared with that after equivalent doses of high dose-rate irradiation. Results: The phosphorylation of ATM protein was maximal at 0.5 Gy irradiation delivered at either a high dose-rate or a continuous low dose-rate. As the radiation dose increased, the phosphorylation of ATM protein decreased under continuous low dose-rate irradiation. However, the phosphorylation of ATM protein was remained stable under high dose-rate irradiation. When the phosphorylation of ATM protein under continuous low dose-rate irradiation was equal to that under high dose-rate irradiation, there was no significant difference in the surviving fraction of HepG2 cells between two ir- radiation methods (P > 0.05). When the phosphorylation of ATM protein significantly decreased after continuous low dose-rate irradiation compared with that after high dose-rate irradiation, increased amounts of cell killing was found in low dose-rate irradiation (P < 0.01). Conclusion: Continuous low dose-rate irradiation increases HepG2 cells radiosensitivity compared with high dose-rate irradiation. The increased amounts of cell killing following continuous low dose-rate exposures are associated with reduced ATM phosphorylated protein.