缺氧对Egr-1启动子辐射诱导活性的影响及机制的初步探讨

目的　探明缺氧对早期生长反应基因 1(earlygrowthresponsegene 1,Egr 1)启动子辐射诱导活性的影响及机制。方法　利用基因重组构建Egr 1启动子调控的荧光素酶报告质粒 ,脂质体介导转染肺癌A5 49细胞 ,在 0 .1%、0 .5 %、1%、2 .5 %、5 %等氧浓度下给转染细胞以 2、4、6、8、10Gyγ 线照射 ,观察照射后荧光素酶表达水平及过氧化氢产量变化 ;观察过氧化氢浓度对Egr 1启动子转录活性的影响。结果　成功构建了Egr 1启动子报告载体 ,转染A5 49细胞 ,发现当氧浓度 <2 .5 %时 ,Egr 1启动子活性明显低于常氧对照组 (P <0 .0 1) ,并随氧浓度的下降而降低。照射后的过氧化氢产量呈现类似的变化特征 ,结果还表明Egr 1启动子的活性与过氧化氢浓度密切相关。结论　缺氧 (O2 <2 .5 % )导致Egr 1启动子辐射诱导活性下降 ,可能与氧自由基产量减少有关。

Effects of cell hypoxia on radio-inducible activity of Egr-1 promoter and its mechanisms

Objective To investigate the effects of cell hypoxia on radio-inducible activity of early growth response gene-1 (Egr-1) promoter and its mechanisms. Methods The reporter vector of Egr-1 promoter was constructed by inserting the promoter sequence upstream the lucifearase gene in pGL3, which was then transfected into the lung adenocarcinoma A549 cell by liposome. The luciferase activity and H 2O 2 production were detected in the transfected cells exposed to doses of 2, 4, 6, 8, and 10 Gy radiation combined with the oxygen concentrations of 0.1%, 0.5%, 1%, 2.5%, and 5 %. The changes of luciferase activity in the transfected cells exposed to various concentrations of H 2O 2 were observed. Results The reporter vector of Egr-1 promoter was constructed successfully. The radio-inducible activity of Egr-1 promoter decreased significantly in the transfected cells exposed to oxygen concentration below 2.5% in a concentration-dependent manner, as compared with that in the normal control (P<0.01). The results showed that H 2O 2 production in the transfected cells exposed to the same intervention demonstrated similar alterations. The results also indicated that the radio-inducible activity of Egr-1 promoter was closely associated with H 2O 2 concentration. Conclusion Cell hypoxia (O 2<2.5%) can lead to decrease in radio-inducible activity of Egr-1 promoter, which might result from the reduction of oxygen free radicals formation following radiation.